阅读说明：本技术 热敏记录材料 (Thermosensitive recording material ) 是由 纳迪娅·艾尔-卡扎兹 克拉斯·博克斯哈默 于 2019-01-31 设计创作，主要内容包括：本发明涉及一种热敏记录材料,所述热敏记录材料包含：基板；热敏记录层,所述热敏记录层包含N-(4-甲基苯基磺酰基)-N’-(3-(4-甲基苯基磺酰氧基)苯基)脲和/或N-[2-(3-苯基脲基)苯基]苯磺酰胺；和设置在基板和热敏记录层之间的中间层,所述中间层包含煅烧硅酸铝。本发明还涉及一种用于制造热敏记录材料的方法,以及一种煅烧硅酸铝在热敏记录材料的中间层中的应用。(The present invention relates to a thermosensitive recording material comprising: a substrate; a thermosensitive recording layer containing N- (4-methylphenylsulfonyl) -N' - (3- (4-methylphenylsulfonyloxy) phenyl) urea and/or N- [2- (3-phenylureido) phenyl ] benzenesulfonamide; and an intermediate layer disposed between the substrate and the thermosensitive recording layer, the intermediate layer containing calcined aluminum silicate. The invention also relates to a method for producing a heat-sensitive recording material and to the use of calcined aluminium silicate in an intermediate layer of a heat-sensitive recording material.)

1. a thermosensitive recording material comprising or consisting of:

a substrate having a front side and a back side opposite the front side,

-a heat-sensitive recording layer disposed on the front side of the mesh substrate, wherein the heat-sensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer

a) Is a compound of formula (I) shown below

Or

b) Is a compound of the formula (II) shown below

Or

c) Is a mixture comprising the compound of formula (I) and the compound of formula (II)

And

-an intermediate layer arranged between the substrate and the thermosensitive recording layer, the intermediate layer comprising calcined aluminum silicate, wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 50% to 90% by mass of the total mass of the solid fraction in the intermediate layer.

2. The thermosensitive recording material according to claim 1,

wherein the compound of formula (I) is present in the form of a crystalline modification at 3401 ± 20cm in the IR spectrum^-1With an absorption band.

3. The thermosensitive recording material according to claim 1 or 2,

wherein the calcined aluminum silicate is formed in the intermediate layer in a platelet-shaped manner.

4. The thermosensitive recording material according to claim 3,

wherein the small flake-shaped calcined aluminum silicate has an aspect ratio of 3 to 100, preferably 5 to 95, particularly preferably 10 to 90.

5. The thermosensitive recording material according to any of the preceding claims,

wherein the compound of formula (II) is present as a color developer, and the thermosensitive recording layer or the thermosensitive recording material does not include the compound of formula (I).

6. The thermosensitive recording material according to any one of claims 1 to 4,

wherein the compound of formula (I) is present as a color developer, and the thermosensitive recording layer or the thermosensitive recording material does not include the compound of formula (II).

7. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer contains a sensitizer.

8. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer contains a sensitizer, and the sensitizer is selected from: 1, 2-bis (3-methylphenoxy) ethane, 1, 2-diphenoxyethane, 1, 2-bis (m-methylphenoxy) ethane, 2- (2H-benzotriazol-2-yl) -p-cresol, 2,2 '-bis (4-methoxyphenoxy) diethyl ether, 4,4' -diallyloxydiphenylsulfone, 4-acetoacetophenone, 4-benzylbiphenyl, acetoacetanilide, benzyl 2-naphthyl ether, benzyl naphthyl ether, 4- (benzyloxy) benzyl benzoate, benzyl p-hydroxybenzoate, bis (4-chlorobenzyl) oxalate, bis (4-methoxyphenyl) ether, dibenzyl oxalate, dibenzyl terephthalate, dimethyl sulfone, diphenyl adipate, diphenylsulfone, ethylene bis stearamide, fatty acid anhydride, m-pentenyl, N-methylol stearamide, N-stearylurea, N-stearylstearamide, N- (2-hydroxyethyl) octadecanamide, N (hydroxymethyl) octadecanamide, p-benzylbiphenyl, phenylbenzenesulfonate, salicylanilide, stearamide, ethylene glycol m-tolyl ether and α, α' -diphenoxyxylene.

9. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer contains a sensitizer, and the sensitizer is 1, 2-diphenoxyethane or benzyl naphthalene ether.

10. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer has a Bekk smoothness determined according to DIN 53107:2016-05, the Bekk smoothness being from 100 to 1200 seconds, preferably from 150 to 1100 seconds.

11. The thermosensitive recording material according to any of the preceding claims,

wherein the mass per unit area of the intermediate layer is 4.0g/m²To 15.0g/m²In the range of (1), it is preferably 6.0g/m²To 12.0g/m²In the range of (1), particularly preferably 7.0g/m²To 10g/m²And the mass per unit area of the thermosensitive recording layer is in the range of 1.5g/m²To 6g/m²In the range of (1), it is preferably 2.0g/m²To 5.5g/m²In the range of (1), particularly preferably 2.0g/m²To 4.8g/m²Within the range of (1).

12. The thermosensitive recording material according to any of the preceding claims,

wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 60 to 89%, preferably 70 to 88%, based on the total mass of the solid fraction in the intermediate layer.

13. The thermosensitive recording material according to any of the preceding claims,

wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 65% to 75% by mass, based on the total mass of the solid fraction in the intermediate layer.

14. The thermosensitive recording material according to any of the preceding claims,

wherein the intermediate layer further comprises one or more components selected from the group consisting of: biocides, binders, dispersants, separating agents, defoamers, thickeners and optical brighteners.

15. The thermosensitive recording material according to any of the preceding claims,

wherein the intermediate layer comprises one or more dispersants.

16. The thermosensitive recording material according to claim 15,

wherein the dispersant is a sodium polyacrylate homopolymer.

17. The thermosensitive recording material according to any of the preceding claims,

wherein the middle layer contains styrene-butadiene latex, starch and methyl cellulose.

18. The thermosensitive recording material according to any of the preceding claims,

wherein the substrate is or comprises paper, synthetic paper, cardboard, or plastic film.

19. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer further comprises one or more components selected from the group consisting of: binders, sensitizers, pigments, dispersants, antioxidants, separating agents, defoamers, light stabilizers and optical brighteners.

20. The thermosensitive recording material according to any of the preceding claims,

wherein the thermosensitive recording layer is completely or partially covered with a protective layer.

21. The thermosensitive recording material according to any of the preceding claims,

wherein an adhesive layer is arranged on a back side of the substrate facing away from the front side of the substrate.

22. The thermosensitive recording material according to any of the preceding claims,

wherein a separation layer is provided on the thermosensitive recording layer, the separation layer being configured to be adhesive with respect to the binder layer.

23. The thermosensitive recording material according to claim 22,

wherein the separating layer comprises at least one compound containing organosiloxane groups or a wax.

24. A product, preferably a ticket for admission, air, train, boat or bus, lottery, parking, labeling, receipt, bank bill, self-adhesive label, medical and/or technical drawing paper, facsimile paper, security paper or bar code label, comprising a heat-sensitive recording material according to any of claims 1 to 23.

25. Use of the thermosensitive recording material according to any one of claims 1 to 23 as a bar-code label, a self-adhesive ticket, a self-adhesive admission ticket, a self-adhesive shopping ticket, a self-adhesive label, a self-adhesive admission ticket, an air ticket, a train ticket, a boat ticket or bus ticket, a lottery ticket, a parking ticket, a label, a receipt, a bank bill, medical or technical chart paper, facsimile paper or security paper.

26. A method for producing a thermosensitive recording material, preferably according to any one of claims 1 to 23, comprising the steps of:

-providing or manufacturing a substrate comprising a front side and a back side opposite to the front side,

-providing or producing a first coating composition, wherein the first coating composition comprises a calcined aluminium silicate,

-applying the first coating composition onto the front side of the substrate,

drying and/or crosslinking the applied first coating composition so that at least one intermediate layer is formed,

-providing or manufacturing a second coating composition, wherein the second coating composition comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer

a) Is a compound of formula (I) shown below

Or

b) Is a compound of the formula (II) shown below

Or

c) Is a mixture comprising said compound of formula (I) and said compound of formula (II),

-applying the second coating composition onto at least one of the intermediate layers,

-drying and/or crosslinking the applied second coating composition such that the thermosensitive recording layer is constituted.

27. A method for producing a thermosensitive recording material, preferably according to any one of claims 21 to 23, comprising the steps of:

-providing or manufacturing a thermosensitive recording material according to any of claims 1 to 20, wherein the manufacturing is preferably carried out according to the method of claim 26,

-providing or manufacturing a separation layer coating composition, wherein the separation layer coating composition comprises at least one organosiloxane group containing compound or wax,

-applying the separation layer coating composition onto the heat-sensitive recording layer or the second intermediate layer,

drying and/or crosslinking the applied release layer coating composition to form a release layer, which is configured to be adhesive to the binder.

28. Use of calcined alumino-silicate in an intermediate layer of a thermosensitive recording material, wherein the thermosensitive recording material comprises or consists of, in addition to the intermediate layer:

-a substrate, wherein the substrate has a front side and a back side opposite the front side,

and

-a heat-sensitive recording layer disposed on the front side of the mesh substrate, wherein the heat-sensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer

a) Is a compound of formula (I) shown below

Or

b) Is a compound of the formula (II) shown below

c) Is a mixture comprising said compound of formula (I) and said compound of formula (II),

and wherein the intermediate layer is provided between the substrate and the thermosensitive recording layer, and wherein a mass fraction of the calcined aluminum silicate in the intermediate layer is 65% to 75% by mass based on a total mass of a solid fraction in the intermediate layer.

Technical Field

The present invention relates to a thermosensitive recording material including: a substrate; the invention also relates to a method for producing a heat-sensitive recording material, and to the use of a calcined aluminium silicate in an intermediate layer of a heat-sensitive recording material.

Background

Thermosensitive recording materials have been known for many years and are very popular. This popularity is further due to the fact that its use is associated with the following advantages: the color-forming components are contained in the recording material itself, and a printer without toner and color cartridges can be used. Therefore, it is no longer necessary to purchase, store, replace, or replenish toner or color cartridges. This innovative technology has therefore been widely implemented on a large scale, especially in public transport and retail operations.

However, recently there has been an increasing thought on environmental compatibility, especially of specific (di) phenolic developers, also known as color acceptors, and partly also of the dye precursors with which they react to form a visually recognizable color upon the delivery of heat, which is no longer overlooked by industry and especially by commerce. Therefore, recently, for example, components which are well known and are excellently studied in natural science among color developers are known as

Bisphenol A, which is 2,2 bis (4-hydroxyphenyl) -propane, and

bisphenol S, which is 4,4' -dihydroxydiphenyl sulfone,

becoming increasingly the center of public criticism, and are sometimes replaced by:

■ N- (4-methylphenylsulfonyl) -N' - (3- (4-methylphenylsulfonyloxy) phenyl) urea, also known as Pergafast 201, sold by BASF SE,

■ 4-hydroxy-4' -isopropoxydiphenyl sulfone, also known as "D8", and

■ N- [2- (3-phenylureido) phenyl ] benzenesulfonamide, also known as "NKK".

In order to improve heat-sensitive recording materials, in particular when they are used as tickets or lottery tickets, with regard to their resistance to environmental influences such as heat, moisture and chemicals, the chemistry and manufacturing techniques on which such recording materials are produced have been developed.

In order to increase the resistance of the thermal prints obtainable on heat-sensitive recording materials (thermogenic recording) to water, aqueous alcohol solutions and plasticizers, DE 102004004204 a1 proposes a heat-sensitive recording material whose heat-sensitive recording layer has the usual dye precursors and a combination of phenolic and urea-urethane-based developers.

DE 102015104306 a1 describes a heat-sensitive recording material comprising a carrier substrate and a heat-sensitive color-forming layer which comprises at least one color former and at least one phenol-free developer, wherein for example N-phenyl-N ' - [ (phenylamino) sulfonyl ] urea, N- (4-methylphenyl) -N ' - [ (4-ethylphenylamino) sulfonyl ] urea, N- (4-ethoxycarbonylphenyl) -N ' - [ (4-ethoxycarbonylphenylamino) sulfonyl ] urea or structurally similar compounds are used as phenol-free developers.

In JP 2014-218062A heat-sensitive recording material having a heat-sensitive recording layer comprising at least one leuco dye and a developer on a support is described. A mixture of 4,4' -bis (3-toluenesulfonylureido) diphenylmethane and N- [2- (3-phenylureido) phenyl ] benzenesulfonamide is used as a developer.

A crystalline form of N- [2- (3-phenylureido) phenyl ] benzenesulfonamide and its use in recording materials is described in International patent application WO 2016/136203A 1. The crystalline forms are characterized by an X-ray powder diffraction pattern or a description of the diffraction reflections in the diffraction pattern and by the melting point, and are thus distinguished from other crystalline forms of the compounds. It is additionally mentioned that the crystal forms can likewise be distinguished from one another by absorption bands in the IR spectrum. It is also shown that different crystalline forms of the compound can give rise to different properties of the recording material manufactured with the compound.

The subject of US 2005/0148467 a1 is a heat-sensitive recording material comprising at least two components of a colour-forming system, one of which is of the chelate type and the other of which is a conventional leuco dye system, in order to constitute an irreversible printed image.

However, there is always a demand for other thermosensitive recording materials for various applications, which must be capable of being manufactured at low production costs due to high sales in a strongly competitive market, and further must have a simple configuration. Another challenge is that printed heat sensitive recording materials are subjected to a number of different environmental influences, such as moisture, heat or chemicals, in their typical application as tickets, admission tickets, parking tickets, etc.

Therefore, the thermosensitive recording material can come into contact with a large number of different substances during normal use, which may affect the resistance of the thermosensitive printing. In addition to water and organic solvents, these substances also include fats and oils which are contained, for example, in hand care products and are transferred to heat-sensitive recording materials when they are handled. Resistance, in particular to greases and oils, is therefore of great importance.

In addition to resistance to chemicals that may come into contact with the thermosensitive recording material, the thermosensitive recording material must also have high resistance to thermal influences and to light incidence. On the one hand, the thermosensitive recording material should be capable of energy-efficient and easy printing, in order to consume a small amount of energy, for example, in mobile applications. On the other hand, the printed image should remain after printing and, under the action of heat or light, should neither fade nor discolor the unprinted background, which would otherwise cause the printed matter to no longer be clearly readable. For example, in the case of a parking ticket that is stored after being printed on a windshield and then subjected to high temperature and direct sunlight in summer, thermal resistance and resistance against light are extremely important.

Also in the case of tickets, such as concert tickets or airline tickets, which are usually ordered long in advance, or in the case of receipts or proof of purchase required as proof of purchase within a long warranty period, long-term resistance of the thermosensitive recording material is very important. Especially if it has to be assumed that: the heat-sensitive recording material may come into contact with moisture, for example, by keeping the recording material used as a concert ticket, air ticket, or proof of purchase close to the body (e.g., in a pants pocket), and thus in contact with sweat, it must be ensured that: the recording material remains well readable even after contact with moisture.

Disclosure of Invention

Accordingly, there is a continuing need to improve the resistance of thermal printing to different environmental influences. It is therefore a main object of the present invention to provide a heat-sensitive recording material which has an improved resistance to environmental influences, such as sunlight and heat input, in the printed state and which, here, ideally has very good printability.

Another object is derived from the following description and claims.

The subject matter of the invention is defined in the appended claims and the following description.

The above object is achieved by a thermosensitive recording material including or consisting of:

a substrate having a front side and a back side opposite the front side,

a thermosensitive recording layer provided on a mesh substrate (Substrat), wherein the heat-sensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer

a) Is a compound of the formula (I)

Or

b) Is a compound of the following formula (II)

Or

c) Is a mixture comprising a compound of formula (I) and a compound of formula (II)

And

an intermediate layer arranged between the substrate and the thermosensitive recording layer, the intermediate layer comprising calcined aluminum silicate, wherein a mass fraction of the calcined aluminum silicate in the intermediate layer is 50 to 90% by mass based on a total mass of the solid fraction in the intermediate layer.

Surprisingly, it has been demonstrated that the thermosensitive recording material according to the present invention has improved light fastness to sunlight. In internal studies it has furthermore been demonstrated that the optical printing density or the stability of the printed thermosensitive recording material is improved. Another positive and unexpected effect is that the contrast between the printed area and the unprinted area (background) of the thermal recording material is also improved and has high stability.

Furthermore, it has surprisingly been demonstrated that in the case of the thermosensitive recording material according to the present invention, the dynamic print density can be improved, so that a higher print density (blackness) can be obtained with a specific amount of energy acting on the thermosensitive recording material.

It has also surprisingly been demonstrated that the maximum print density (Dmax) in the recording material according to the invention is higher, so that a darker black color of the printed area can be obtained.

Internal studies have also demonstrated that by using calcined aluminium silicates in the thermosensitive recording material according to the invention, soiling of the unprinted areas (e.g. "tailing" or "bleeding") of the printed image can be significantly reduced or even completely avoided, especially when compared to thermosensitive recording materials having organic hollow body pigments as pigments in the middle layer. Where "smear" describes smudges of the printed image in the process direction and "bleed" describes non-directional smudges of the printed image starting from the center point or center.

This result is excellent in this respect because it has been assumed so far that in order to improve the characteristics of the thermosensitive recording material, it is necessary to change or optimize the composition of the thermosensitive recording layer. For example, in the above-cited prior art, only the composition of the thermosensitive recording layer is changed in order to obtain improved characteristics. It has always been assumed so far: the composition of the intermediate layer has no influence on the properties of the thermosensitive recording layer located thereon, and the inorganic pigment is arbitrarily replaceable without significantly changing the properties of the thermosensitive recording layer or the resultant thermosensitive recording material. The improvement of the response property of the thermosensitive recording material is known only when a hollow body pigment is used in the intermediate layer. This can be explained by the following: the hollow body pigment containing air in its interior has a high heat reflection capacity, and the resulting intermediate layer is a good insulator. In this connection, an intermediate layer optimized with a hollow body pigment as a heat-reflective layer improves the response properties of the recording layer with respect to heat in a particularly targeted manner. It is now more surprising that the thermal recording material according to the present invention has a higher dynamic print density, a higher maximum print density (Dmax) and a higher light resistance than a material using a hollow body pigment instead of calcined aluminum silicate in the intermediate layer.

In some embodiments of the invention, it is advantageous if the compound of formula (I) is used as developer and the compound of formula (II) is not contained in the thermosensitive recording layer. Alternatively, it is advantageous in a further embodiment of the invention if the compound of the formula (II) is used as developer and the compound of the formula (I) is not contained in the thermosensitive recording layer.

If mixtures comprising compounds of the formula (I) and compounds of the formula (II) are used as developers, it has proven to be particularly advantageous if the compounds of the formula (I) are present in a crystalline form which is 3401. + -. 20cm in the IR spectrum^-1With an absorption band.

The combination of (a) the developer of formula (I), formula (II) or a mixture thereof used according to the invention and (B) the calcined aluminum silicate in the intermediate layer has a synergistic effect, which results in the production of a thermosensitive recording material having improved properties.

The compounds of the formula (I) are the known compounds N- [2- (3-phenylureido) phenyl ] benzenesulfonamide, which is described, for example, in EP2923851A 1. Which is sold under the name NKK.

The compound having the formula (II) is the known compound N- (4-methylphenylsulfonyl) -N' - (3- (4-methylphenylsulfonyloxy) phenyl) urea, which is sold under the name Pergafast 201 and is described, for example, in EP 1140515B 1. Pergafast 201 is currently the most commonly used phenolic-free developer.

It has been demonstrated in internal studies that: the compound of formula (I) can exist in two different crystalline forms. These two crystal forms have different physical properties, which have an influence on the thermosensitive recording material.

One crystalline form of the compound having formula (I) has a melting point of about 158 ℃, while a second crystalline form of the compound having formula (I) has a melting point of 175 ℃. In connection with thermosensitive recording materials, only compounds of the formula (I) have been described so far in the literature in the form of crystals having a melting point of about 158 ℃ (see, for example, EP2923851a1 paragraph [0084 ]). To date, the preparation and use of crystalline forms of the compound of formula (I) having a melting point of about 175 ℃ has not been described in the literature. Accordingly, it must be assumed that: even if the melting points are not explicitly mentioned in the corresponding literature, crystalline forms having a melting point of about 158 ℃ of the compounds of the formula (I) are always used. Crystalline forms of the compound of formula (I) having a melting point of 175 ℃ have also recently become commercially available.

Preferred according to the invention are thermosensitive recording materials in which the crystalline form of the compound of the formula (I) has a (preferably endothermic) transition at a temperature between 170 ℃ and 178 ℃, preferably between 173 ℃ and 177 ℃, particularly preferably between 174 ℃ and 176 ℃, determined by means of dynamic differential scanning calorimetry (DKK) at a heating rate of 10K/min.

The two crystal forms of the compound of formula (I) are also capable of absorbing in IRAre distinguished from each other in the spectrum. It is particularly characterized that, in the crystalline form used according to the invention of the compound of the formula (I), the absorption band in the IR spectrum is 3401. + -. 20cm^-1To (3). In the crystalline form of the compound of formula (I) having a melting point of about 158 deg.C, said band is absent, but at 3322 and 3229cm, respectively^-1There is a band.

According to the invention, preference is given to thermosensitive recording materials in which the compound of the formula (I) is present in the form of a crystalline modification in the IR spectrum at 3401. + -. 20cm^-1With an absorption band.

Internal studies have demonstrated that two crystalline forms of the compound of formula (I) can be used. However, the resulting thermosensitive recording materials have slightly different characteristics. Even if improvements in dynamic print density, maximum print density (Dmax) and light resistance can be achieved in the two crystal forms in the thermosensitive recording material according to the present invention, it has been confirmed that the compound of formula (I) is present at 3401 ± 20cm in the IR spectrum^-1The thermosensitive recording material having an absorption band or a crystalline form having a melting point of about 175 ℃ has slightly improved characteristics compared to a thermosensitive recording material in which the compound of formula (I) is present in another crystalline form.

However, internal studies have demonstrated that the recording materials in which the compounds of the formula (I) are present in the form of crystals of 3322 ± 5 and 3229 ± 5cm in the IR spectrum have a slightly improved stability with respect to fats and oils (lanolin), ethanol and when stored at 40 ℃ in high air humidity^-1Has two absorption bands or has a melting point of about 158 c. If high stability with respect to fats and oils, such as lanolin, and/or solvents, such as ethanol, or resistance under high air humidity is required, preference is given to using crystalline forms of the compounds of the formula (I) which are 3322. + -. 5 and 3229. + -.5 cm in the IR spectrum^-1Has two absorption bands or has a melting point of about 158 c.

In one embodiment of the thermosensitive recording material according to the present invention, a mixture of the compound of formula (I) and the compound of formula (II) is present as the developer.

It is known to the person skilled in the art that the combination of different developers, such as compounds of formula (I) or (II), often causes a deterioration of the properties of the thermosensitive recording material. Generally, the combination of two or more developers causes an undesirable change in color of the thermosensitive recording material, so that the thermosensitive recording material shows, for example, gray without improving the remaining characteristics here. Accordingly, the person skilled in the art provides, at the time of experimentation, a heat-sensitive recording material which has a high resistance in the printed state with respect to environmental influences, such as moisture, heat or chemicals, without taking into account that different developers are combined with one another and without conducting corresponding experiments. For this reason, the design of the solution according to the invention shown here is surprising, since in order to achieve the stated object, the person skilled in the art must first overcome a technical prejudice that the two developers should not be combined with one another.

In one embodiment of the present invention, the following thermosensitive recording materials are preferred according to the present invention, wherein the mass ratio between the compound of formula (I) and the compound of formula (II) is 0.5: 99.5 to 99.5: 0.5. in internal studies, it has been found that the positive influence of the corresponding compounds is not so pronounced at a mass fraction of the compounds of the formula (I) or (II) of less than 0.5%, based on the total mass of the compounds of the formula (I) and (II).

According to one embodiment of the present invention, thermosensitive recording materials are particularly preferred, wherein the mass ratio between the compound of formula (I) and the compound of formula (II) is from 35:65 to 65:35, preferably from 40:60 to 60:40, particularly preferably from 45:55 to 55: 45.

It has been demonstrated in internal studies that mixtures with a mass ratio between the compound of formula (I) and the compound of formula (II) of about 1: 1 or in the range defined above from 35:65 to 65:35, preferably from 40:60 to 60:40, particularly preferably from 45:55 to 55: 45. The heat-sensitive recording material comprising as developer mixture a mixture having the stated mass ratio, i.e. a mixture of compounds of the formulae (I) and (II) having an equal or approximately equal mass fraction, shows better properties than a heat-sensitive recording material in which the developer mixture is replaced by the same mass fraction only of compounds of the formulae (II) or (I).

It has been demonstrated in particular with regard to resistance at high temperatures (60 ℃): the mass ratio between the compound of formula (I) and the compound of formula (II) is 0.5: the printed images of 99.5 to 35:65 of the thermosensitive recording materials according to the present invention, after storage at 60 ℃ for 24 hours, were also reduced less than in the case of the thermosensitive recording materials in which the developer mixture was replaced by the compound of formula (I) in equal mass fractions. In part, the printed image of the thermosensitive recording material according to the present invention has a higher print density after storage at 60 ℃ for 24 hours than in the case of a thermosensitive recording material in which the developer mixture is replaced by the compound of formula (I) or (II) in equal mass fractions. The combination of the compound of the formula (I) with the compound of the formula (II) used according to the invention therefore has a synergistic effect which is unpredictable and, in turn, entirely surprising.

In a further embodiment of the invention, thermosensitive recording materials are preferred according to the invention in which the mass ratio between the compound of the formula (I) and the compound of the formula (II) is from 5:95 to 30:70, preferably from 15:85 to 25: 75.

It has been demonstrated in internal studies that mixtures having a mass ratio between the compound of formula (I) and the compound of formula (II) of about 20:80 or in the above-defined range of 5:95 to 30:70, preferably 15:85 to 25:75, have a synergistic effect with respect to improved resistance at 60 ℃ for at least 24 hours. The thermosensitive recording material having the mass ratio as the developer mixture shows better stability at 60 ℃ than the thermosensitive recording material in which the developer mixture is replaced with the compound of formula (II) or formula (I) alone at an equal mass fraction.

In a further embodiment of the invention, thermosensitive recording materials are preferred according to the invention in which the mass ratio between the compound of the formula (I) and the compound of the formula (II) is from 97:3 to 85:15, preferably 95:5 to 90: 10.

It has been demonstrated in internal studies that mixtures having the following mass ratios between the compound of the formula (I) and the compound of the formula (II) of about 93:7 or in the range defined above of 97:3 to 85:15, preferably 95:5 to 90:10, have particularly good properties with regard to resistance at 40 ℃ and high air humidity for at least 24 hours and improved resistance with respect to fats and oils, in particular lanolin. The thermosensitive recording material of the mixture having this mass ratio as the developer mixture shows better characteristics (moisture resistance or oil resistance) than the thermosensitive recording material in which the developer mixture is replaced with the compound of formula (II) or formula (I) alone at an equal mass fraction.

Commercially available lanolin is a mixture obtained, for example, according to the german pharmacopoeia 10(DAB 10) by melting together 65 parts by mass of wool wax, 20 parts by mass of water and 15 parts by mass of viscous paraffin. By kneading, a further 100 parts by mass of water can be added without the external properties changing. Wool wax (Lanolin, Adeps Lanae, INCI name: Lanolin, E913) is the secretion of the sebaceous glands of sheep. It is obtained by extraction of wool with isopropanol. The name Lanolin (Lanolin) is derived from latin langa ═ wool and oleum ═ oil.

Surprisingly it has been demonstrated that no greying of the unprinted recording material is observed in the thermosensitive recording material according to the invention, in which the mass ratio between the compound of formula (I) and the compound of formula (II) is from 99.5:0.5 to 65: 35. In particular, when the mass ratio between the compound of the formula (I) and the compound of the formula (II) is from 99:1 to 75:25, no associated ashing of the unprinted recording material occurs. Therefore, the mixing ratio is preferable.

Therefore, the characteristics of the resulting thermosensitive recording material are optimized for the purpose of use by adjusting the mixing ratio between the compound of formula (I) and the compound of formula (II) according to the expected influence exerted on the thermosensitive paper. Therefore, different requirements are placed on the thermosensitive recording material used as a parking ticket and on the material used as a concert ticket. The optimized properties can be even further improved by the combination of a mixture of compounds of formula (I) and formula (II) in the intermediate layer with calcined aluminium silicate.

In one embodiment of the thermosensitive recording material according to the present invention, the compound of formula (I) is present as the color developer, and the compound of formula (II) is absent.

It is preferred according to the invention that the heat-sensitive recording layer has a Bekk smoothness determined according to DIN 53107:2016-05 (heading: test of paper and board-smoothness determined according to the Bekk method) of from 100 to 1200 seconds, preferably from 150 to 1100 seconds.

Internal studies have confirmed that the thermosensitive recording material has particularly good properties if the thermosensitive recording layer is present as an outer layer and has a Bekk smoothness of 100 to 1200 seconds or preferably 150 to 1100 seconds. The thermal head of the thermal printer can be protected by the high smoothness of the thermal recording material, among other advantages. Further, the smooth thermosensitive recording material has particularly good touch and appearance, and can be printed particularly well.

As has been detailed hereinbefore, the thermosensitive recording material according to the present invention shows improved resistance against light and improved contrast with respect to the prior art. It has been confirmed herein that the thermosensitive recording material according to the present invention in which the compound of formula (I) is present as a developer has higher resistance against light, better contrast, and higher maximum print density (Dmax) than the thermosensitive recording material according to the present invention in which the compound of formula (II) is present as a developer.

It has also been confirmed that the thermosensitive recording material according to the present invention in which the compound of formula (I) is present as a color developer does not have any background fogging after storage at 90 ℃ for at least 24 hours.

In a preferred embodiment according to the invention, the calcined aluminum silicate is formed in the intermediate layer in the form of platelets. Internal studies comparing non-platelet-shaped aluminium silicates with platelet-shaped aluminium silicates have surprisingly shown that the use of platelet-shaped calcined aluminium silicates can lead to particularly good properties of heat-sensitive recording materials. When using small pieces of calcined aluminum silicate in the intermediate layer, the individual pieces of aluminum silicate are stacked one above the other in a staggered manner, so that a very compact layer structure results. Calcined aluminosilicates which are not platelet-shaped do not form such a layer structure. The non-platelet-shaped calcined aluminum silicate can be obtained, for example, by grinding the platelet-shaped calcined aluminum silicate or by adjusting the production parameters accordingly. Platelet-shaped (also referred to as flake-like or lamellar-like) is understood to mean particles whose diameter is significantly greater than their thickness.

In this context, it is particularly preferred according to the invention that the small-flake calcined aluminum silicate has a (preferably average) aspect ratioThe aspect ratio is 3 to 100, preferably 5 to 95, particularly preferably 10 to 90. In a preferred embodiment, the (preferably average) aspect ratio of the inorganic pigments is greater than 15. The Aspect ratio (also referred to as "Aspect ratio" or "Shape-factor") is the quotient between the diameter and thickness of the platelets of the inorganic pigment prior to mixing with the additional components. The aspect ratio is 15: the diameter of the tablet is 15 times greater than the thickness of the tablet.

In a preferred embodiment of the recording material according to the invention, 85 to 93% of the calcined aluminum silicate particles used for producing the intermediate layer have a particle size of 2 μm or less, as determined by X-ray granulometry.

Internal studies have demonstrated that the calcined alumino-silicate particles are particularly well suited for making interlayers used in accordance with the present invention.

In a preferred embodiment of the recording material according to the invention, the calcined aluminum silicate used has a brightness (also referred to as whiteness or luminosity) of greater than or equal to 85%, preferably greater than or equal to 90%, particularly preferably greater than or equal to 92%.

It is particularly advantageous for the oil absorption of the calcined aluminum silicate in the intermediate layer to be at least 80cm³/100gAnd more preferably 100cm³Per 100g, determined according to DIN EN ISO 787-5:1995-10 (title: general test method for pigments and fillers-part 5: determination of oil absorption (ISO 787-5: 1980); German version EN ISO 787-5: 1995).

It has surprisingly been found in internal studies that a high mass fraction of more than 50% of calcined aluminum silicate in the recording material according to the invention leads to particularly good properties.

According to the invention, the proportion by mass of the calcined aluminum silicate in the intermediate layer is preferably 60 to 89%, preferably 70 to 88%, based on the total mass of the solid proportion in the intermediate layer.

According to the invention, it is further preferred that the proportion by mass of the calcined aluminum silicate in the intermediate layer is 80 to 87%, preferably 83 to 87%, based on the total mass of the solid proportion in the intermediate layer.

Internal studies have demonstrated that the heat-sensitive recording materials have particularly good properties, in particular little or no soiling of the unprinted areas of the printed images, high resistance to sunlight and heat, high sensitivity and high maximum print density (Dmax), if the mass fraction of the calcined aluminium silicate lies within the limits set out above. A mass fraction of about 86% of the calcined aluminum silicate is found as optimum. When the mass fraction exceeds 90%, the smear of the printed image is no longer significantly reduced, whereas other characteristics of the thermosensitive recording material suddenly deteriorate. The deterioration of the characteristics can be explained as follows: on the one hand, the adhesion of the intermediate layer is greatly deteriorated. It has been found that when the calcined aluminum silicate is used in the intermediate layer in a mass proportion of more than 90%, the aluminum silicate particles are no longer sufficiently held together and peeling or tearing of the intermediate layer can occur. Such peeling can cause deterioration of the printed image and cause deposits on the print head. The deposition on the print head may cause damage to the print head or further deterioration of the printed image. Furthermore, a mass proportion of the calcined aluminum silicate in the intermediate layer of more than 90% leads to the binder of the thermosensitive recording layer being partially absorbed by the intermediate layer during the production of the thermosensitive recording material and no longer providing a bond for the thermosensitive recording layer due to the high open porosity of the intermediate layer. In order to compensate for such absorption of the binder, it is necessary to increase the binder content of the coating composition used for manufacturing the thermosensitive recording layer. However, such an increase in the binder content causes deterioration in printing sensitivity and maximum printing density.

In an alternative embodiment, it is particularly preferred according to the invention if the proportion by mass of the calcined aluminum silicate in the intermediate layer is 60 to 79%, preferably 65 to 75%, based on the total mass of the proportion by mass of solids in the intermediate layer.

In a preferred embodiment of the thermosensitive recording material according to the invention, no further organic or inorganic pigments are present, apart from the calcined aluminum silicate.

However, it can also be preferred in some embodiments that, in addition to the calcined aluminum silicate, further inorganic or organic pigments are present in the intermediate layer. In addition to the organic pigments, which are preferably present as organic hollow body pigments, the intermediate layer can also have further inorganic pigments, wherein the inorganic pigments are selected from the following list, either individually or in combination with one another: natural kaolinite, silica and in particular bentonite herein, calcium carbonate and aluminum-oxide-hydroxide and in particular boehmite herein.

Preferred according to the present invention are thermosensitive recording materials in which the intermediate layer further contains one or more components selected from the group consisting of: biocides, binders, dispersants, separating agents, defoamers, thickeners and optical brighteners.

Preferred according to the invention are thermosensitive recording materials in which the intermediate layer comprises, in addition to the calcined aluminosilicates and possibly in addition to further inorganic and/or organic pigments, at least one binder, preferably based on synthetic polymers, of which styrene-butadiene latex gives particularly good results. The use of synthetic binders with incorporation of at least one natural polymer, such as starch being particularly preferred, is a particularly suitable embodiment. It was also determined during the experiments that a binder-pigment ratio within the intermediate layer of between 3:7 and 1:9, in each case in mass fraction in the intermediate layer, is a particularly suitable embodiment.

In a particularly preferred embodiment, a mixture of styrene-butadiene latex and starch is used as the binder in the intermediate layer.

Internal studies have demonstrated that the combination consisting of styrene-butadiene latex and starch has a positive effect on the properties of the thermosensitive recording material. When a pure styrene-butadiene latex is used, a thermosensitive recording material having very high adhesion is obtained. However, the pores of the calcined aluminosilicates are blocked by the styrene-butadiene latex. The addition of starch surprisingly leads to: the interlayer still maintains a high open porosity. The combination of styrene-butadiene latex and starch thus results in an intermediate layer which has very good adhesion and at the same time maintains a high open porosity of the calcined aluminum silicate. The combination of styrene-butadiene latex and starch therefore leads to an intermediate layer which cannot be obtained with the aid of the binders used individually.

It has furthermore surprisingly been demonstrated that the properties of an intermediate layer comprising styrene-butadiene latex and starch can be further improved if the intermediate layer comprises methylcellulose and/or a dispersing assistant.

Styrene-butadiene latexes have significantly higher adhesion than polyvinyl alcohol and are therefore preferred. Eugenol-butadiene latex is additionally preferred, since it is insoluble in water and does not dissolve anymore when the heat-sensitive recording layer is applied after the intermediate layer has dried.

Preferred according to the present invention is a thermosensitive recording material wherein the mass per unit area of the intermediate layer is in the range of 4.0 to 15.0g/m²In the range of 6.0 to 12.0g/m, preferably²In the range of (1), particularly preferably from 7.0 to 10g/m²Within the range of (1).

Internal studies have shown that particularly good results can be achieved if the intermediate layer is formed relatively thick.

Preferred according to the present invention is a thermosensitive recording material in which the dye precursor is selected from derivatives of compounds composed of fluoran, phthalic acid amide, lactam, triphenylmethane, phenothiazine and spiropyran.

Internal studies have demonstrated that the dye precursors in combination with the developers or developer mixtures used according to the invention have particularly good properties.

A preferred thermosensitive recording material according to the present invention preferably has, as a dye precursor, a fluoran-type compound selected from: 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3 ' -methylphenylamino) fluoran (6 ' - (diethylamino) -3 ' -methyl-2 ' - (m-tolylamino) -3H-spiro [ isobenzofuran-1, 9 ' -xanthine ] -3-one, ODB-7), 3-di-n-pentylamino-6-methyl-7-anilinofluoran, 3- (diethylamino) -6-methyl-7- (3-methylphenylamino) fluoran, 3-di-n-butylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-xylylfluoran, 3-diethylamino-7- (2-carbonylmethoxyphenylamino) fluoran, 3-pyrrolidinyl-6-methyl-7-anilinofluoran, 3-pyrrolidinyl-6-methyl-7- (4-N-butylphenylamino) fluoran, 3-piperidinyl-6-methyl-7-anilinofluoran, 3-N-dibutylamine-6-methyl-7-anilinofluoran (ODB-2), 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluoran), 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofuranyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-4-tolyl) 6-methyl-7- (4-tolyl) fluoran and 3- (N-cyclopentyl-N-ethyl) amino-6-methyl-7-anilinofluoran.

Also preferred is a thermosensitive recording material according to the present invention, which contains the compound mentioned in paragraphs [0049] to [0052] of EP2923851A1 as a dye precursor.

Particularly preferred according to the present invention are thermosensitive recording materials in which the dye precursor is selected from: 3-N-di-N-butylamine-6-methyl-7-anilinofluoran (ODB-2) and 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran.

Preferred according to the present invention are thermosensitive recording materials in which the thermosensitive recording layer further contains one or more components selected from: binders, sensitizers, pigments, dispersants, antioxidants, separating agents, defoamers, light stabilizers and optical brighteners.

Preferred according to the present invention is a thermosensitive recording material in which the thermosensitive recording layer contains a sensitizer.

When a sensitizer is used, the sensitizer is first melted upon the delivery of heat during the printing process, and the melted sensitizer dissolves and/or lowers the melting temperature of the color former and developer present side by side in the thermosensitive recording layer so as to cause a color developing reaction. The sensitizer does not participate in the color development reaction itself.

A sensitizer is therefore understood to be a substance which serves to set the melting temperature of the thermosensitive recording layer and with which it is preferably possible to set a melting temperature of approximately 70 to 80 ℃ without the sensitizer itself taking part in the color-developing reaction.

According to the invention, as sensitizers, for example, fatty acid salts, fatty acid esters and fatty acid amides (e.g. zinc stearate, stearamide, palmitamide, oleamide, lauramide, ethylene and methylene bis stearamide, methylol stearamide) (preferably fatty acid amides each having a number of carbon atoms in the range of 16 to 24), fatty acid amide derivatives (e.g. N- (2-hydroxyethyl) octadecanamide, N- (hydroxymethyl) -octadecanamide), ethylene glycol m-toluyl ether, naphthalene derivatives, biphenyl derivatives, phthalates and terephthalates can be used.

Particularly preferred according to the present invention are thermosensitive recording materials wherein the sensitizer is selected from: 1, 2-bis (3-methylphenoxy) ethane, 1, 2-diphenoxyethane, 1, 2-bis (m-methylphenoxy) ethane, 2- (2H-benzotriazol-2-yl) -p-cresol, 2,2 '-bis (4-methoxyphenoxy) diethyl ether, 4,4' -diallyloxydiphenylsulfone, 4-acetoacetophenone, 4-benzylbiphenyl, acetoacetic anhydride, benzyl-2-naphthylmethyl ether, benzylnaphthyl ether, 4- (benzyloxy) benzyl benzoate, benzyl p-hydroxybenzoate, bis (4-chlorobenzyl) oxalate, bis (4-methoxyphenyl) ether, dibenzyl oxalate, dibenzyl terephthalate, dimethyl sulfone, diphenyl adipate, diphenylsulfone, ethylene bis stearamide, fatty acid anhydride, m-pentenyl, N-methylol stearamide, N-stearylurea, N-stearylstearamide, N- (2-hydroxyethyl) octadecanamide, N- (hydroxymethyl) octadecanamide, p-benzylbiphenyl, phenylbenzenesulfonate, salicylanilide, stearamide, ethylene glycol m-tolyl ether and α, α' -diphenoxyxylene, with particular preference given to ethylene glycol m-tolyl ether, benzyl naphthyl ether, diphenylsulfone, 1, 2-bis (m-methylphenoxy) ethane and 1, 2-diphenoxyethane.

In a particularly preferred embodiment of the thermosensitive recording material according to the invention, the thermosensitive recording layer contains 1, 2-diphenoxyethane, ethylene glycol m-tolyl ether or a mixture of 1, 2-diphenoxyethane and ethylene glycol m-tolyl ether as a sensitizer.

Internal studies have demonstrated that resistance to lanolin and heat resistance at 90 ℃ can be improved when 1, 2-diphenoxyethane is used as a sensitizer, compared to other sensitizers.

Also preferred is a thermosensitive recording material according to the present invention, which contains the compound mentioned in paragraphs [0059] to [0061] of EP2923851a1 as a sensitizer.

According to a first preferred embodiment, the sensitizers are used individually, i.e. not in combination with the other mentioned sensitizers in the above list, respectively. According to a second seemingly preferred embodiment, at least two sensitizers selected from the above list are incorporated into the thermosensitive recording layer.

Preferred according to the present invention is a thermosensitive recording material wherein the sensitizer has a melting point of 60 ℃ to 180 ℃, preferably 80 ℃ to 140 ℃.

Furthermore, in the thermosensitive recording material according to the present invention, the use of 4,4 '-diaminodiphenyl sulfone (4, 4' -DDS, dapsone) as an additional additive in the thermosensitive recording layer proved to be likely to be suitable. The use of 4,4' -diaminodiphenyl sulfone in thermal paper is described, for example, in WO 2014/143174a 1. In this case, the invention can then relate to a thermosensitive recording material in which 4,4' -diaminodiphenyl sulfone is contained in the thermosensitive recording layer, especially additionally as an additive.

Also preferred is a thermosensitive recording material wherein the thermosensitive recording layer comprises a binder, preferably a crosslinked or uncrosslinked binder, selected from the group consisting of: polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, a combination of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acrylate copolymer and film-forming acrylic copolymer.

The coating material for constituting the thermosensitive recording layer of the thermosensitive recording material according to the present invention preferably contains one or more crosslinking agents for the one or more binders in addition to the one or more binders. Preferred are crosslinking agents selected from the group consisting of: zirconium carbonate, polyamidoamine-chlorohydrin resin, boric acid, glyoxal, dihydroxybis (ammonium lactate) titanium (IV) (CASNO.65104-06-5; Tyzor LA) and glyoxal derivatives.

The thermosensitive recording layer of the thermosensitive recording material according to the present invention is formed of a coating material containing one or more binders and one or more crosslinking agents for the one or more binders, the thermosensitive recording material containing one or more binders in the thermosensitive recording layer, the binders being crosslinked by reaction with the one or more crosslinking agents, wherein the one or more crosslinking agents are selected from the group consisting of: zirconium carbonate, polyamidoamine-epichlorohydrin resin, boric acid, glyoxal, dihydroxybis (ammonium lactate) titanium (IV) (CAS) 65104-06-5; tyzor LA) and glyoxal derivatives. By "crosslinked adhesive" is herein understood a reaction product formed by reaction of the adhesive with one or more crosslinking agents.

Preferred according to the present invention is a thermosensitive recording material in which the mass per unit area of the thermosensitive recording layer is in the range of 1.5 to 6g/m²In the range of 2.0 to 5.5g/m, preferably²In the range of (1), particularly preferably from 2.0 to 4.8g/m²More preferably in the range of 2.5 to 3.5g/m²Within the range of (1).

Also preferred according to the invention are heat-sensitive recording materials in which the proportion by mass of the developer mixture in the heat-sensitive recording layer is from 35 to 15%, preferably from 31 to 19%, particularly preferably from 28 to 22%, based on the total solids proportion of the heat-sensitive recording layer.

In the recording materials according to the invention, it is additionally possible to use image stabilizers, dispersants, antioxidants, separating agents, defoamers, light stabilizers and brighteners, as are known in the art. Each component is generally used in an amount having a mass fraction of 0.01 to 15%, in particular 0.1 to 15%, preferably 1 to 10%, excluding defoamers, based on the total solids fraction of the thermosensitive recording layer. When defoaming agents are used in the formulations associated therewith, they can be present in the recording material according to the invention in an amount having a mass fraction of 0.03 to 0.05%, based on the total solids fraction of the thermosensitive recording layer.

According to the invention, preference is given to the thermosensitive recording material according to the invention being configured as a self-adhesive label. The use of self-adhesive labels is very common in a large number of applications. It is thus possible to provide and use for example stamps, parcel stickers, advertising labels, illustrations or price labels as self-adhesive labels. Printable labels are also widely used on a large scale in the retail industry for recording self-weighing products or in public transport, for example as luggage stickers.

Therefore, according to the present invention, preferred is a thermosensitive recording material in which an adhesive layer is provided on a back surface of the substrate facing away from the front surface of the substrate.

Self-adhesive labels are provided with an adhesive layer which enables the self-adhesive label to be applied to the desired application location. Until the self-adhesive label is used, the adhesive layer is typically covered by a separate release paper so that the adhesive layer is not contaminated or the self-adhesive label is not already adhered until the desired use. Especially in the case of pre-punched labels, it is preferred to use a separate release paper. In the case of an endless roll of labels, it is more favorable and more practical in its operation if the label has a coating on the front side which is adhesively structured relative to the adhesive layer on the rear side. In this case, the adhesive layer on the rear side is covered up to its use by a layer which is adhesively formed on the front side. Since the self-adhesive label thus serves as its own release paper, a separate release paper can be dispensed with, so that the removal of the release paper at the application position is dispensed with. This technique has proven useful, inter alia, in labels that are printed and used in the field. Storage of the label is almost impossible without a release paper or layer.

Preferred according to the present invention is a thermosensitive recording material in which a separation layer is provided on the thermosensitive recording layer, the separation layer being configured to be adhesive with respect to a binder layer, wherein the separation layer contains at least one organosiloxane group-containing compound or wax.

In the context of the present invention, a wax is understood to be a wax which is obtained by chemical modification of vegetable oils. The chemical modification can be, for example, partial or complete hydrogenation by means of metal catalysts, such as nickel and hydrogen, in which all or part of the double bonds of the oil are hydrogenated to single bonds. Unlike vegetable oils, the waxes do not exist in the liquid state at 20 ℃, but exist in the solid state. Thus, chemical modification of the vegetable oil causes an increase in the melting point.

Vegetable oil is understood to be fatty acid triglycerides obtained from plants or plant parts. Here, the oil is generally obtained by squeezing, extracting or refining the oil from the plant or plant part. The obtaining of oils is known to the person skilled in the art. If plant seeds are used to obtain oil, they are called oilseeds. The oil is present in the seeds in the form of lipids, which are their cell membranes and energy stores. A distinction is made between non-dry oils (e.g. olive oil), semi-dry oils (e.g. soybean oil or rapeseed oil) and dry oils (e.g. linseed oil or poppy oil) according to the fraction of unsaturated fatty acids in the oil. The term "drying" herein does not mean evaporation, but solidification of the oil due to oxidation and polymerization of the unsaturated fatty acids. It is preferred to use semi-dried and dried oils as the raw material for making the waxes used according to the invention.

Possible sources of vegetable oils are acai oil, algal oil, argan nut oil (from the fruit of argan nut trees), avocado oil (avocado pulp from avocado trees), babassu oil, cottonseed oil (seeds from cotton plants), borage oil or borage seed oil (seeds from borage plants), ash nut oil, cashew nut shell oil, thistle oil (also known as "safflower oil", seeds from safflower or safflower genera), peanut oil (peanut kernels from peanut plants), hazelnut oil (hazelnut from the hazelnut bush), sesame oil (seeds from edible hemp), jatropha oil (seeds from jatropha curcas), jojoba oil (actually liquid wax; seeds from jojoba bush), camellia oil (seeds from camellia oleifera, camellia oleifera or camellia, cocoa butter, coconut oil (fruit from coconut, cacao nutshell), pumpkin seed oil (also called seed oil; seed kernel from squash), linseed oil (ripe linseed oil from linseed), pseudolinseed oil (cruciferae seed from cruciferae), macadamia nut oil (nut from macadamia nut), corn germ oil (from corn germ), almond oil (almond oil from almond tree), mango butter (from mango), apricot kernel oil or almond oil (almond oil from almond kernel, i.e. apricot kernel or apricot kernel), poppy oil (from poppy seed), evening primrose oil, olive oil (pulp and kernel from olive, fruit of olive tree), palm oil (from palm pulp, oil palm fruit), palm kernel oil (from palm kernel, oil palm fruit), papaya oil, pistachio oil, pecan oil, perilla oil from seeds of perilla genus plant (perilla, sesame leaf), rapeseed oil (seed from rape, cruciferae), rice oil, castor oil (seed from castor bean), sea buckthorn oil (pulp from sea buckthorn berries, fruit from sea buckthorn shrubs), sea buckthorn seed oil (kernel from sea buckthorn berries, fruit from sea buckthorn shrubs), mustard oil (seed kernel from black mustard), black cumin oil (seed from fruit capsules of black cumin plants), sesame oil (seed from sesame plants), shea butter (seed from shea butter), soybean oil (bean from soybean), sunflower seed oil (seed kernel from sunflower), tung oil, walnut oil (kernel from nut of walnut tree), watermelon oil, grape seed oil (seed from grape or fruit of grape tree (grape), wheat germ oil (germ from wheat) and/or seed oil (wood from seed of libamon). This list, which should not be considered exclusive, shows the possibilities for obtaining vegetable oils that can be converted into the waxes used according to the invention.

It is preferred according to the invention that the wax is an oil-based wax, said wax being selected from the following list: palm oil, coconut oil, poppy oil, olive oil, linseed oil, soybean oil, sunflower oil, safflower oil and rapeseed oil; preferably, the vegetable oil-based wax is a soybean oil-based wax, i.e. a soybean oil wax or a soybean wax.

Preferred according to the invention are waxes having a melting point of more than 40 ℃, preferably more than 50 ℃, particularly preferably more than 60 ℃.

Internal studies have demonstrated that very good results can be obtained already when waxes with melting points higher than 20 ℃ are used. Surprisingly, however, it has been found that the resistance of the separating layer to mechanical loading can be increased when waxes having a melting point of more than 40 ℃ are used. In the case of a higher melting point of the wax, the resistance is further increased. Internal studies have also demonstrated that the optimum melting point of the wax is in the range of 60 to 80 ℃ as long as the separating layer should be used at a temperature between 6 ℃ and 30 ℃. If the separating layer is also to be used at higher temperatures, it may be expedient to use a wax with a higher melting point.

Preference is given according to the invention to separating layers in which the mass fraction of wax in the separating layer is from 6 to 98%, preferably from 20 to 90%, particularly preferably from 50 to 89%, based on the total mass of the separating layer.

In this case, it is preferred according to the invention that, in addition to the wax, a polymer binder, preferably a crosslinked or uncrosslinked binder, is additionally contained in the separating layer, said binder being selected from the group consisting of: starch, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer, combinations of polyvinyl alcohol and ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, silanol-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, modified polyethylene glycol, unmodified polyethylene glycol, alpha-isodecyl-omega-hydroxy-poly (oxy-1, 2-ethanediyl), styrene-butadiene-latex, styrene-acrylate polymers, acrylic acid copolymers, and mixtures thereof.

As long as the separating layer comprises an organosiloxane group-containing compound, it has been demonstrated in various studies carried out in connection with the invention that a mass per unit area of 0.5g/m is set for the separating layer²To 3g/m²Preferably 0.8g/m²To 1.85g/m²Particularly preferably 0.85g/m²To 1.35g/m²In the range of (1).

Here, the thermosensitive recording material is preferably produced such that, after coating of the coating composition comprising the organosiloxane group-containing compound, a part of the organosiloxane group-containing compound first remains on the thermosensitive recording layer and is here partially diffused or penetrated into the thermosensitive recording layer before crosslinking of the coating composition. Thus constituting a diffusion zone which improves the adhesion of the two layers. This achieves that the adhesively formed separating layer remains attached to the thermosensitive recording layer and does not detach.

In this case, according to the invention, the diffusion region is preferably formed by: at least a part of the compound containing an organosiloxane group diffuses from the coating composition comprising the compound containing an organosiloxane group flat into the upper region of the thermosensitive recording layer applied before application of the coating composition, which is oriented toward the coating composition, and wherein a mass fraction of 1.5 to 50% of the total amount of the compound containing an organosiloxane group diffuses into the upper region of the thermosensitive recording layer formed.

In order to influence the amount of the portion diffused into the thermosensitive recording layer, the binder and the pigment preferably incorporated into the thermosensitive recording layer play an important role. It has proved very helpful on the one hand and furthermore preferred that the heat-sensitive recording layer comprises at least one, preferably inorganic, pigment selected from the following list: natural kaolinite, calcined kaolinite, magnesium silicate hydrate (talc), calcium carbonate and silica (silicic acid).

It is particularly preferred here that the inorganic pigments in the thermosensitive recording layer are platelet-shaped, as is the case, for example, in kaolinite and talc. Therefore, kaolinite and talc are particularly preferable in the thermosensitive recording layer. It is particularly preferred that the inorganic, platelet-shaped pigments (especially kaolinite and talc) in the thermosensitive recording layer have an aspect ratio of from 5 to 100, preferably from 15 to 100, particularly preferably from 20 to 100. In a preferred embodiment, the aspect ratio of the inorganic pigment in the thermosensitive recording layer is greater than 20.

As regards the amount of pigment in the thermosensitive recording layer, a mass fraction in terms of the total mass of the thermosensitive recording layer in the range of 8 to 18% (atro (absolute dry)) is considered particularly suitable, which is narrowed downward by the risk of possible thermal head precipitation and is narrowed upward by gradually reducing the sensitivity with respect to the thermal head that causes the heat of the printed image.

It is considered preferable that the thermosensitive recording layer contains at least one hydrophilic binder due to the hydrophobic property of the organosiloxane group-containing compound in the separation layer, wherein the compound diffuses into the thermosensitive recording layer. Particularly preferred here are the following binders selected from the following list: ethylene-vinyl acetate copolymers, polyvinyl alcohol, styrene-butadiene latex, styrene-acrylate latex and starch.

Preferably, the polyvinyl alcohol used as binder for the thermosensitive recording layer has a degree of saponification of more than 99 Mol% and a viscosity of more than 7mPas, preferably more than 12mPas, particularly preferably more than 15mPas, measured on an aqueous solution having a concentration of 4% by mass at 20 ℃ in accordance with DIN 53015. Particular preference is given to polyvinyl alcohol (PVA)15-99 or a corresponding PVA which has a higher degree of saponification and/or a higher viscosity than PVA 15-99.

In a preferred embodiment of the invention, the binder of the thermosensitive recording layer is a crosslinked (self-crosslinked or externally crosslinked) and/or modified polyvinyl alcohol, wherein the modified polyvinyl alcohol is preferably a diacetone-modified polyvinyl alcohol, a silanol-modified polyvinyl alcohol or a carboxyl-modified polyvinyl alcohol, preferably a diacetone-modified polyvinyl alcohol or a silanol-modified polyvinyl alcohol.

In a preferred embodiment of the invention, it is preferred, in particular if non-self-crosslinking polyvinyl alcohols are used as binders, that the heat-sensitive recording layer comprises at least one crosslinking assistant selected from the following list: boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic dihydrazide, dimethylurea, melamine formaldehyde, used alone or in admixture with one another.

In the sense of the present invention, ethylene-vinyl acetate copolymers are suitable as the sole binder or in combination with polyvinyl alcohol as particularly preferred binders, which are incorporated in the thermosensitive recording layer in a range having a mass fraction of from 10 to 20%, based on the total mass of the thermosensitive recording layer.

In one embodiment of the thermosensitive recording material according to the present invention, the thermosensitive recording layer is completely or partially covered with a protective layer. By providing a protective layer covering the thermosensitive recording layer, the thermosensitive recording layer is also shielded from the outside or toward the carrier substrate of the next sublayer within the roll, so that it is protected from the outside.

In this case, in addition to protecting the thermosensitive recording layer disposed below the protective layer from environmental influences, such a protective layer generally has an additional positive effect of improving the printability of the thermosensitive recording material according to the present invention, especially in indigo printing, offset printing and flexographic printing. For this reason, it may be desirable for certain application cases that the thermosensitive recording material according to the present invention has a protective layer, although, due to the presence of the developer mixture as defined above in the thermosensitive recording layer of the thermosensitive recording material according to the present invention, the resistance of the thermosensitive print obtained on the thermosensitive recording material according to the present invention is sufficient, even without the protective layer, with respect to a substance selected from the group consisting of: water, alcohols, fats and oils, oils and mixtures thereof.

It is preferred according to the invention that the protective layer has a Bekk smoothness of 350 to 1500 seconds, preferably 400 to 1400 seconds, determined according to DIN 53107:2016-05 (heading: test of paper and board-determination of smoothness according to the Bekk method).

Internal studies have confirmed that the thermosensitive recording material has particularly good properties if the protective layer is present as the uppermost layer and has a Bekk smoothness of 350 to 1500 seconds or preferably 400 to 1400 seconds. The thermal head of the thermal printer can be protected by the high smoothness of the thermal recording material, among other advantages. Further, the smooth thermosensitive recording material has particularly good touch and appearance, and can be printed particularly well.

Preferably, the protective layer of the thermosensitive recording material according to the present invention comprises one or more crosslinked or uncrosslinked binders selected from the group consisting of: polyvinyl alcohol modified with carboxyl groups, polyvinyl alcohol modified with silanol groups, polyvinyl alcohol modified with diacetone, partially and completely saponified polyvinyl alcohol, and film-forming acrylic acid copolymers.

Preferably, the coating material used for constituting the protective layer of the thermosensitive recording material according to the present invention contains, if present, one or more crosslinking agents for the one or more binders in addition to the one or more binders. Preferably, the crosslinking agent is then selected from: boric acid, polyamines, epoxy resins, dialdehydes, formaldehyde oligomers, epichlorohydrin resins, adipic dihydrazide, melamine formaldehyde, urea, methylol urea, ammonium zirconium carbonate, polyamide epichlorohydrin resins, and dihydroxybis (ammonium lactate) titanium (IV) Tyzor LA (CAS No. 65104-06-5).

The protective layer of the thermosensitive recording material according to the present invention is formed of a coating material containing one or more binders and one or more crosslinking agents for the one or more binders, the thermosensitive recording material containing one or more binders in the protective layer, the binders being crosslinked by reaction with the one or more crosslinking agents, wherein the one or more crosslinking agents are selected from: boric acid, polyamine, epoxy resin, dialdehyde, formaldehyde oligomer, epichlorohydrin resin, adipic dihydrazide, melamine formaldehyde, urea, methylolurea, ammonium zirconium carbonate, polyamide epichlorohydrin resin and dihydroxybis (ammonium lactate) titanium (IV) Tyzor LA (CAS number: 65104-06-5). By "crosslinked adhesive" is herein understood a reaction product formed by reacting an adhesive with one or more crosslinking agents.

In a first embodiment variant, the protective layer which completely or partially covers the thermosensitive recording layer can be obtained from a coating material comprising one or more polyvinyl alcohols and one or more crosslinking agents. Preferably, the polyvinyl alcohol of the protective layer is modified by carboxyl groups or, in particular, silanol groups. It can also be preferred to use mixtures of different carboxyl-modified or silanol-modified polyvinyl alcohols. Such a protective layer has a high affinity with respect to printing inks used in offset printing processes, which are preferably UV-crosslinked. This decisively supports the requirement for excellent printability in offset printing.

The crosslinking agent or agents for the protective layer according to this embodiment variant are preferably selected from: boric acid, polyamine, epoxy resin, dialdehyde, formaldehyde oligomer, polyamine epichlorohydrin resin, adipic acid dihydrazide, melamine formaldehyde and dihydroxybis (ammonium lactate) titanium (IV) Tyzor LA (CAS number: 65104-06-5). Mixtures of different crosslinking agents are also possible.

Preferably, in the coating material for constituting the protective layer according to this embodiment modification, the mass ratio of the modified polyvinyl alcohol to the crosslinking agent is preferably in the range of 20:1 to 5:1, and particularly preferably in the range of 12:1 to 7: 1. It is particularly preferable that the ratio of the modified polyvinyl alcohol to the crosslinking agent is in the range of 100 mass fraction to 8 to 11 mass fraction.

Particularly good results can be achieved if the protective layer according to this embodiment variant additionally contains inorganic pigments. Here, the inorganic pigment is preferably selected from: silica, bentonite, boehmite, calcium carbonate, natural kaolinite, calcined kaolinite and mixtures of the abovementioned inorganic pigments.

Preferably, the protective layer according to this variant of embodiment is applied with a mass per unit area of 1.0g/m²To 6g/m²And particularly preferably in the range of 1.2g/m²To 3.8g/m²Within the range of (1). In this case, the protective layer is preferably formed as a single layer.

In a second embodiment variant, the coating material used to form the protective layer comprises a water-insoluble, self-crosslinking acrylic polymer, a crosslinking agent and a pigment component, the pigment component of the protective layer consisting of one or more inorganic pigments and being formed at least in 80% by mass fraction from highly pure, alkaline-prepared bentonite, the binder of the protective layer consisting of one or more water-insoluble, self-crosslinking acrylic polymers and the binder/pigment ratio being 7:1 to 9: 1.

the self-crosslinking acrylic polymer in the protective layer according to the second embodiment variant described herein is preferably chosen from: styrene-acrylate copolymers, copolymers containing acrylamide groups and consisting of styrene and acrylate, and copolymers based on acrylonitrile, methacrylamide and acrylate. The latter is preferred. As pigments, it is possible to incorporate alkaline-prepared bentonites, natural or precipitated calcium carbonates, kaolinites, silicic acids or aluminum hydroxides into the protective layer. Preferred cross-linking agents are selected from: cyclic urea, methylol urea, ammonium zirconium carbonate and polyamide epichlorohydrin resin.

By selecting as the binder a water-insoluble, self-crosslinking acrylic polymer and having a mass ratio to (i) the pigment of 7:1 to 9:1, and the mass ratio thereof to (ii) the crosslinking agent is greater than 5:1, the high environmental resistance of the thermosensitive recording material according to the present invention has been achieved when the protective layer has a relatively small mass per unit area. Such a mass ratio is therefore preferred.

The protective layer itself canCoating with conventional coating units, for which purpose it is furthermore possible to use coating pigments, preferably with a mass per unit area of from 1.0 to 4.5g/m²In the range of (1). In an alternative variant, the protective layer is printed. A protective layer that is curable by means of actinic radiation is particularly suitable in terms of processing technology and in terms of its technical properties. The term "actinic radiation" is understood to mean UV or ionizing radiation, such as an electron beam.

The appearance of the protective layer is decisively determined by the way of smoothing and the roll surfaces and their materials that influence the friction in the smoothing mechanism and the calender. In particular due to the existing market requirements, it is considered preferable that the roughness of the protective layer (printed surface roughness) is less than 1.5 μm (determined according to ISO standard 8791, part 4). It has proven particularly useful in the context of experimental work prior to the present invention to use a smoothing mechanism in which NipcoFlex or zone-regulated Nipco-P rolling is used, however, the present invention is not limited thereto.

Preferred according to the invention is a thermosensitive recording material wherein the substrate is or comprises paper, synthetic paper, cardboard, paperboard or plastic film.

Even if paper is not restricted to use as substrate, preferred in the sense of the present invention are paper and here in particular coating base paper without surface treatment, which has become popular on the market also in view of good environmental compatibility due to good recyclability. A coating base paper without surface treatment is understood to be a coating base paper which has not been treated in a size press or coating equipment. For the present invention, a film composed of, for example, polypropylene, polyolefin and paper coated with polyolefin is possible to the same extent as the mesh substrate, and such an embodiment is not exclusive.

In one embodiment of the present invention, the thermosensitive recording material includes or is constituted of:

-a substrate having a front side and a back side opposite the front side, wherein the substrate is or comprises paper,

-a thermosensitive recording layer disposed on the front side of the mesh substrate, wherein the thermosensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer is a compound of formula (II) shown below

And does not comprise the developer of formula (I) shown

And

an intermediate layer arranged between the substrate and the thermosensitive recording layer, the intermediate layer comprising calcined aluminum silicate, wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 60% to 75% based on the total mass of the solid fraction in the intermediate layer, wherein the calcined aluminum silicate is constituted in small pieces and has an aspect ratio of 5 to 95, wherein the intermediate layer comprises styrene-butadiene latex, starch and methyl cellulose,

wherein the thermosensitive recording layer contains 1, 2-diphenoxyethane and/or benzyl naphthalene ether, and wherein the mass per unit area of the intermediate layer is 4.0 to 15.0g/m²In the range of (1), preferably from 6.0 to 12.0g/m²In the range of (1), particularly preferably from 7.0 to 10g/m²And the mass per unit area of the thermosensitive recording layer is in the range of 1.5 to 6g/m²In the range of (1), preferably from 2.0 to 5.5g/m²In the range of (1), particularly preferably from 2.0 to 4.8g/m²Within the range of (1).

In one embodiment of the present invention, the thermosensitive recording material includes or is constituted of:

-a substrate having a front side and a back side opposite the front side, wherein the substrate is or comprises paper,

-a thermosensitive recording layer disposed on the front side of the mesh substrate, wherein the thermosensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer is a compound of formula (I) shown below

Wherein the compound of formula (I) is present in the form of a crystalline modification at 3401 ± 20cm in the IR spectrum^-1There is an absorption band in the region of the membrane,

and does not comprise the developer of formula (I) shown

And

an intermediate layer arranged between the substrate and the thermosensitive recording layer, the intermediate layer comprising calcined aluminum silicate, wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 60% to 75% based on the total mass of the solid fraction in the intermediate layer, wherein the calcined aluminum silicate is constituted in small pieces and has an aspect ratio of 5 to 95, wherein the intermediate layer comprises styrene-butadiene latex, starch and methyl cellulose,

wherein the thermosensitive recording layer contains 1, 2-diphenoxyethane and/or benzyl naphthalene ether, and wherein the mass per unit area of the intermediate layer is 4.0 to 15.0g/m²In the range of (1), preferably from 6.0 to 12.0g/m²In the range of (1), particularly preferably from 7.0 to 10g/m²And the mass per unit area of the thermosensitive recording layer is in the range of 1.5 to 6g/m²In the range of (1), preferably from 2.0 to 5.5g/m²In the range of (1), particularly preferably from 2.0 to 4.8g/m²Within the range of (1).

In one embodiment of the present invention, the thermosensitive recording material includes or is constituted of:

-a substrate having a front side and a back side opposite the front side, wherein the substrate is or comprises paper,

-a thermosensitive recording layer disposed on the front side of the mesh substrate, wherein the thermosensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer is a compound of formula (II) shown below

And the color developer of formula (I) shown

Wherein the compound of formula (I) is present in the form of a crystalline modification at 3401 ± 20cm in the IR spectrum^-1There is an absorption band in the region of the membrane,

and

an intermediate layer arranged between the substrate and the thermosensitive recording layer, the intermediate layer comprising calcined aluminum silicate, wherein the mass fraction of the calcined aluminum silicate in the intermediate layer is 60 to 75% by mass based on the total mass of the solid fraction in the intermediate layer, wherein the calcined aluminum silicate is constituted in small pieces and has an aspect ratio of 5 to 95, wherein the intermediate layer comprises styrene

Butadiene latex, starch and methyl cellulose,

wherein the thermosensitive recording layer contains 1, 2-diphenoxyethane and/or benzyl naphthalene ether, and wherein the mass per unit area of the intermediate layer is 4.0 to 15.0g/m²In the range of (1), preferably from 6.0 to 12.0g/m²In the range of (1), particularly preferably from 7.0 to 10g/m²And the mass per unit area of the thermosensitive recording layer is in the range of 1.5 to 6g/m²In the range of (1), preferably from 2.0 to 5.5g/m²In the range of (1), particularly preferably from 2.0 to 4.8g/m²In the range of (1).

Another aspect of the invention relates to a product, preferably a ticket for admission, TITO ticket (admission, discharge), air ticket, train ticket, boat ticket or bus ticket, lottery ticket, parking ticket, label, receipt, bank bill, self-adhesive label, medical and/or technical graphic paper, facsimile paper, security paper or bar code label, comprising a thermosensitive recording material according to the invention.

A further aspect of the invention is the use of the thermosensitive recording material according to the invention as a bar-code label, a self-adhesive ticket, a self-adhesive admission ticket, a self-adhesive shopping receipt, a self-adhesive label, a self-adhesive admission ticket, an admission ticket, a TITO ticket (admission ticket, ticketing), an air ticket, a train ticket, a boat ticket or bus ticket, a lottery ticket, a parking ticket, a label, a receipt, a bank bill, medical and/or technical chart paper, facsimile paper or security paper.

Another aspect of the present invention relates to a method for producing a thermosensitive recording material, preferably a thermosensitive recording material according to the present invention, comprising the steps of:

-providing or manufacturing a substrate comprising a front side and a back side opposite the front side,

-providing or producing a first coating composition, wherein the first coating composition comprises a calcined aluminium silicate,

applying a first coating composition onto the front side of the substrate,

drying and/or crosslinking the applied first coating composition so that at least one intermediate layer is formed,

-providing or manufacturing a second coating composition, wherein the second coating composition comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, the developer

a) Is a compound of formula (I) shown below

Or

b) Is a compound of the formula (II) shown below

Or

c) Is a mixture comprising a compound of formula (I) and a compound of formula (II)

-applying a second coating composition onto at least one intermediate layer,

-drying and/or crosslinking the applied second coating composition such that a thermosensitive recording layer is constituted. Preferred according to the invention is a process, wherein the process additionally comprises the following steps:

-providing or manufacturing a binder coating composition comprising at least one binder or binder precursor,

-applying the adhesive coating composition to the back side of the substrate opposite to the front side, and

if necessary, drying and/or crosslinking the applied adhesive coating composition to form the adhesive layer.

Preferred according to the invention is a process, wherein the process additionally comprises the following steps:

-providing or manufacturing an interlayer coating composition,

-applying an intermediate layer coating composition onto the heat-sensitive recording layer,

and

-drying and/or crosslinking the applied interlayer coating composition to constitute a second interlayer. Preferred according to the invention is a process, wherein the process additionally comprises the following steps:

-providing or manufacturing a protective layer coating composition,

-applying the protective layer coating composition onto the thermosensitive recording layer,

and

-drying and/or crosslinking the applied protective layer coating composition to constitute the protective layer.

Preferred according to the invention is a method, wherein the method additionally comprises the following steps:

-providing or manufacturing a separation layer coating composition, wherein the separation layer coating composition comprises at least one organosiloxane group containing compound or wax,

-applying the separation layer coating composition onto the heat-sensitive recording layer or the second intermediate layer,

drying and/or crosslinking the applied release layer coating composition to form a release layer, which is configured to be adhesive to the binder.

With regard to preferred embodiments and combinations of the coating compositions used in the method according to the invention, the statements made above for the thermosensitive recording material according to the invention apply accordingly (if appropriate in the sense of meaning), and vice versa.

In the context of the present invention and in keeping with the general understanding in the field of papermaking technology, the term "coating composition" denotes a coating material which comprises or consists of a pigment or a matrix pigment, a binder and additives, which is applied ("coated") to the paper surface or a layer already arranged thereon by means of a specific coating device in order to surface refine or modify the paper. The paper produced in this way is called "coated paper" and is excellent, for example, due to a better feel. Thus, the term "coating composition" is a generic concept in the paper industry for all coatable coatings, formulations and/or solvents used for treating, modifying or refining the surface of paper.

For applying the coating composition to the carrier substrate or the intermediate layer, different coating techniques are known to the person skilled in the art, for example: knife Coating, film press Coating, cast Coating, Curtain Coating ("curing Coating"), knife Coating, air brush Coating or spray Coating. All these known coating techniques are suitable for applying the coating composition according to the invention to a substrate, preferably paper, which comprises one or more pre-or intermediate coatings or which also does not comprise a pre-or intermediate coating.

Another aspect of the invention relates to the use of calcined aluminosilicates in an intermediate layer of a thermosensitive recording material, wherein, in addition to the intermediate layer, the thermosensitive recording material comprises or consists of:

a substrate, wherein the substrate has a front side and a back side opposite the front side,

and

-a heat-sensitive recording layer disposed on the front side of the mesh substrate, wherein the heat-sensitive recording layer comprises at least one dye precursor and at least one developer capable of reacting with the dye precursor, wherein the developer

a) Is a compound of formula (I) shown below

Or

b) Is a compound of the formula (II) shown below

Or

c) Is a mixture comprising a compound of formula (I) and a compound of formula (II),

and wherein the intermediate layer is provided between the substrate and the thermosensitive recording layer, and wherein a mass fraction of the calcined aluminum silicate in the intermediate layer is 50 to 90% by mass of a total mass of a solid fraction in the intermediate layer.

Within the scope of the present invention, it is preferred to simultaneously achieve a plurality of the above-identified preferred aspects; especially preferred is a combination of such an aspect and corresponding features, which combination is derived from the appended claims.

Drawings

Figures 1,2 and 3 are machine-created graphic replicas (fine graphs) of the original spectrum.

Detailed Description

FIG. 1 shows two crystal forms of the compound of formula (I) at about 4000 to 2000cm^-1Comparison of IR spectra in the wavenumber range of (a). Depicted in the upper part and denoted by a) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of 175 ℃. Depicted in the lower part and denoted by b) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of about 158 ℃.

FIG. 2 shows two crystalline forms of the compound of formula (I) at about 2400 to 400cm^-1Comparison of IR spectra in the wavenumber range of (a). Depicted in the upper part and denoted by a) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of 175 ℃. Depicted in the lower part and denoted by b) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of about 158 ℃.

Figure 3 shows a comparison of the IR spectra of two crystalline forms of the compound of formula (I). Depicted in the upper part and denoted by a) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of 175 ℃. Depicted in the lower part and denoted by b) is the IR spectrum of the crystalline form of the compound of formula (I) used according to the invention having a melting point of about 158 ℃.

The following examples and comparative examples further illustrate the invention:

example 1:

as a wire-like substrate, a mass per unit area of 64g/m was produced on a fourdrinier paper machine from bleached and ground hardwood and softwood cellulose with the addition of AKD glue as a pulp size and further customary additives in a mass fraction of 0.8% based on the total solids fraction (atro) of the pulp fed to the paper machine²The paper carrier of (1).

In paper manufacturing, three grades of solids content are distinguished for paper and cellulose: "atro" (absolute drying), "lutro" (air drying) and "otro" (oven drying). The description was made with "% atro", "% lutro", and "% otro", respectively. Wherein "atro" represents paper or cellulose with a water content of 0%. For "lutro", the "normal" (as is in principle necessary for paper) moisture content is used here as the basis for the calculation. Cellulose and wood pulp typically involve 90: a calculated mass of 100, i.e. 90 parts material, 10 parts water. After drying under defined, defined conditions, the state of the paper or cellulose is called "otro".

The unit area mass was 9g/m with a coating knife²Is applied to the front side and comprises the following components in percentage by mass:

83% of calcined aluminium silicate is used as pigment,

12% of styrene-butadiene latex as a binder,

2.5% of starch as a composite binder, and

2.5% of further auxiliaries (fungicide 0.05%, dispersant 0.35%, methyl cellulose 0.2%,

thickener 0.2%).

The unit area mass was 3.2g/m by means of a roller blade coating apparatus²Is applied to the intermediate layer comprising the calcined alumina silicate. According to the formulation described in table 1, the aqueous coating used for this purpose comprises the following components:

table 1:

further constituents of the thermosensitive recording layer, not specified in percentages and in parts by mass [% ] (atro) based on the total mass, also include dispersants, defoamers, optical brighteners, thickeners, waxes and crosslinkers.

After the application of the heat-sensitive recording layer, the heat-sensitive recording layer is dried and leveled, wherein here the coating is applied according to DIN 53107:2016-05 (title: test of paper and board-smoothness determined according to Bekk) measures a value of 500 Bekk/sec for the surface smoothness of the front side.

The produced web-shaped substrate with intermediate layer and thermosensitive recording layer was coated on the front side (on the thermosensitive recording layer) with a standard UV silicone system cured by free radicals by means of a checkered roll coating mechanism. The solventless, winning standard silicone system used for this purpose contained the formulation described in table 2. The coating weight of the silicone resin is about 1.2g/m²。

Table 2:

the batch with separating agent obtained in this way was cured with a UV lamp (80W/cm) under a protective gas atmosphere consisting of nitrogen.

A thermosensitive recording material according to the present invention is obtained in which the separation layer having the organosiloxane group-containing compound is not detached from the thermosensitive recording layer. The separation layer having the separating agent does not detach from the thermosensitive recording layer even after 30 days of storage. The recording material produced has good sensitivity.

Example 2:

example 1 was repeated, except that instead of N- (p-toluenesulfonyl) -N' -3- (p-toluenesulfonyloxyphenyl) urea (Pergafast 201(BASF)), the compound N- [2- (3-phenylureido) phenyl ] benzenesulfonamide (NKK) having a melting point of 178 ℃ was used as the color developer.

Example 3:

an adhesive layer was produced on the back surface of the substrate of the thermosensitive recording layer produced in example 1 by coating a polyacrylic resin adhesive.

The substrate is then rolled up so that the adhesive layer is located on the separation layer comprising the organosiloxane group-containing compound. Even after 30 days of storage, the respective sub-layers of the thermosensitive recording material can be developed without the separation layer having the separating agent coming off from the thermosensitive recording layer or without leaving residues of the adhesive layer on the separation layer having the separating agent.

Example 4:

an adhesive layer was produced on the back surface of the substrate of the thermosensitive recording layer produced in example 2 by coating a polyacrylate resin adhesive.

The web substrate is then rolled up so that the adhesive layer is on the separation layer comprising the organosiloxane group-containing compound. Even after 30 days of storage, the respective sub-layers of the thermosensitive recording material can be developed without the separation layer having the separating agent coming off from the thermosensitive recording layer or without leaving residues of the adhesive layer on the separation layer having the separating agent.

Comparative example 1:

example 1 was repeated except that a hollow body pigment (particle diameter: 1.5 μm) was used as the pigment in the intermediate layer instead of the calcined aluminum silicate.

Comparative example 2:

example 3 was repeated except that a hollow body pigment (particle diameter: 1.5 μm) was used as the pigment in the intermediate layer instead of the calcined aluminum silicate.

The sunlight resistance was determined from the thermosensitive recording materials in examples 1 and 2 and comparative example 2. The thermosensitive recording material in example 1 showed an improvement in stability (stability of image and contrast) of about 3% as compared with the thermosensitive recording material in comparative example 1, while the thermosensitive recording material in example 2 showed an improvement in stability (stability of image and contrast) of about 7% as compared with the thermosensitive recording material in comparative example 1. The results are plotted in fig. 4 and 5.

Determination of the resistance of the heat-sensitive recording material in daylight:

the sunlight resistance was determined from the thermosensitive recording materials in examples 1 and 2 and comparative example 2.

In order to measurably detect the sunlight resistance of thermal printing on the thermal recording materials according to examples 1 and 2 of the present invention and comparative example 1, thermal printing test specimens of black and white checkered design were respectively created on the thermal recording materials to be tested by means of a "thermal response testing system" apparatus of Atlantek model 400 of the company Global Media Instruments, LLC (usa), using a resolution of 300dpi and an energy per unit area of 16mJ/mm²The thermal head of (1).

After the creation of the thermal printing sample of black and white squares, the printing density was determined by means of a TECHKON spectrodensitometer, a spectral densitometer, at three points of the black colored area and the uncolored area, respectively, of the thermal printing sample after a rest time of more than 5 minutes. The average values are formed from the respective measured values of the black colored area and the uncolored area, respectively.

With the aid of fluorescent lamp at 21600kJ/m²The thermally printed sample was irradiated for 24 hours. At 24 hoursThereafter, the thermal paper print was taken out, and the print density was redetermined at three locations of the black colored area and the uncolored area of the thermal print sample by means of a TECHKON spectrodensometer-spectral densitometer. The average values are formed from the corresponding measured values of the black colored area and the uncolored area, respectively.

The resistance in% of the printed image corresponds to the quotient of the formed average of the print densities of the colored areas before and after storage under daylight lamp multiplied by 100.

The thermosensitive recording material in example 1 showed an improvement in stability (stability of image and contrast) of about 3% as compared with the thermosensitive recording material in comparative example 1, while the thermosensitive recording material in example 2 showed an improvement in stability (stability of image and contrast) of about 7% as compared with the thermosensitive recording material in comparative example 1. The results are plotted in fig. 4 and 5.

Resistance of the thermosensitive recording material was determined (at 90)℃The next hour):

in order to measurably detect the resistance of thermal printing on the thermal recording materials according to examples 1 and 2 of the present invention and comparative example 1, thermal printing test specimens of black and white square design were respectively created on the thermal recording materials to be tested by means of a "thermal response testing system" apparatus of Atlantek model 400 of the company Global Media Instruments, LLC (usa), using a thermal recording material with a resolution of 300dpi and an energy per unit area of 16mJ/mm²The thermal head of (1).

After the creation of the thermal printing sample of black and white squares, the printing density was determined by means of a TECHKON spectrodensitometer, a spectral densitometer, at three points of the black colored area and the uncolored area, respectively, of the thermal printing sample after a rest time of more than 5 minutes. The average values are formed from the respective measured values of the black colored area and the uncolored area, respectively.

The thermally printed samples were hung in an air conditioning cabinet at 90 ℃. After one hour, the thermal paper print was removed, cooled to room temperature, and the print density was redetermined at three locations each of the black colored area and the uncolored area of the thermal print coupon with the aid of a TECHKON spectrodensometer-spectrodensitometer. The average values are formed from the corresponding measured values of the black colored area and the uncolored area, respectively.

The resistance in% of the printed image corresponds to the quotient of the formed average values of the print densities of the colored areas before and after storage in the air-conditioning cabinet multiplied by 100.

The thermosensitive recording material in example 1 showed an improvement in image stability of about 1% compared to the thermosensitive recording material in comparative example 1, while the thermosensitive recording material in example 2 showed an improvement in background stability (stability of contrast) of about 7% compared to the thermosensitive recording material in comparative example 1. The results are plotted in fig. 6 and 7.

The recording material in example 2 showed no background fogging at all, compared with the thermosensitive recording materials in example 1 and comparative example 1. The background image remains absolutely white.

Determination of dynamic print density:

in order to detect the dynamic print density of thermal printing on the thermal recording materials according to examples 1 and 2 of the present invention and comparative example 1 in a measured manner, ten rectangles were printed on the thermal recording materials to be tested at respectively different energy inputs, respectively. The thermal print coupon was created with the help of a "thermal response testing system" device Model Atlantek Model 400 from the company Global Media Instruments, LLC (usa). Here, a resolution of 300dpi and energy per unit area of 3.22, 4.62, 6.07, 7.49, 8.88, 10.32, 11.74, 13.17, 14.57 and 16mJ/mm can be used²The thermal head of (1).

After the creation of the thermal printing coupon, the print density was determined by means of a TECHKON spectrodensometer, a spectral densitometer, at three locations of each black colored area of the thermal printing coupon, respectively, after a rest time of more than 5 minutes. The average values are formed from the corresponding measured values of the black colored areas.

Thermosensitive recording from examples 1 and 2 and comparative example 2The recording material determines the dynamic print density. At higher energies (from about 7 mJ/mm)²Starting from), the thermosensitive recording materials in examples 1 and 2 showed higher printing density (sensitivity) than the material in comparative example 2. Furthermore, the material is at higher energy (16 mJ/mm)²) A higher maximum print density (Dmax) and a higher print density are shown. The results are plotted in table 3 below and fig. 8.

Table 3: