阅读说明：本技术 自由基系粘接剂组合物、粘接剂层、偏振片和影像显示装置 (Radical adhesive composition, adhesive layer, polarizing plate and image display device ) 是由 金熹正 金东旭 权润京 于 2020-02-03 设计创作，主要内容包括：本申请涉及自由基系粘接剂组合物、粘接剂层、偏振片和影像显示装置。(The present application relates to a radical adhesive composition, an adhesive layer, a polarizing plate and an image display device.)

1. A radical adhesive composition which, after curing, has a glass transition temperature according to the Tan delta peak of 100 ℃ to 130 ℃,

the free radical adhesive composition has a storage modulus at 80 ℃ of 1000MPa to 2000MPa after curing,

contains 55 to 70 parts by weight of 2 or more kinds of polyfunctional acrylate compounds per 100 parts by weight of the total radical adhesive composition,

the multifunctional acrylate compound comprises more than 1 glass transition temperature T_gA polyfunctional acrylate compound at a temperature of 150 ℃ or higher,

30 to 60 parts by weight of the glass transition temperature T relative to 100 parts by weight of the total multifunctional acrylate compound_gA polyfunctional acrylate compound at a temperature of 150 ℃ or higher.

2. The radical adhesive composition according to claim 1, wherein the epoxy compound is contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total radical adhesive composition.

3. The radical adhesive composition according to claim 1, wherein the radical adhesive composition contains a photoacid generator.

4. The radical adhesive composition according to claim 3, wherein the photoacid generator is a photo cation initiator.

5. The radical adhesive composition according to claim 1, wherein the radical adhesive composition contains a radical polymerization initiator.

6. The radical adhesive composition according to claim 1, further comprising an additive for increasing adhesion.

7. The radical adhesive composition according to claim 6, wherein the additive for increasing adhesion is a silane coupling agent.

8. The radical adhesive composition according to claim 1, wherein a peel force of the radical adhesive composition is 2.5N/2cm or more.

9. The radical adhesive composition according to claim 1, wherein the radical adhesive composition has no peak of ether bond in IR spectrum after curing.

10. An adhesive layer comprising the radical adhesive composition according to any one of claims 1 to 9 or a cured product thereof.

11. A polarizing plate comprising:

a polarizer;

the adhesive layer according to claim 10, wherein the adhesive layer is provided on at least one surface of the polarizer; and

and a protective film provided on the adhesive layer.

12. The polarizing plate according to claim 11, wherein the adhesive layer has a thickness of 0.1 μm to 10 μm.

13. The polarizing plate according to claim 11, wherein the protective film is a cellulose-based film.

14. An image display device, comprising:

a display panel; and

the polarizing plate according to claim 11, which is provided on one or both surfaces of the display panel.

Technical Field

The specification claims priority of korean patent application No. 10-2019-0014850, which was filed on 8.2.2019 from the korean patent office, the entire contents of which are incorporated herein.

The present specification relates to a radical adhesive composition, an adhesive layer, a polarizing plate, and an image display device.

Background

The polarizing plate is generally used in the following structure: a structure in which a protective film is laminated on one surface or both surfaces of a polarizer made of polyvinyl alcohol (hereinafter referred to as PVA) based resin dyed with dichroic dye or iodine by an adhesive. Conventionally, triacetyl cellulose (hereinafter referred to as TAC) based films have been mainly used as polarizer protective films, but when such TAC films are used, there is a problem that they are easily deformed in a high-temperature and high-humidity environment. Therefore, protective films made of various materials have been developed in recent years as substitutes for TAC films, and for example, a method of using polyethylene terephthalate (PET), cycloolefin polymer (hereinafter, referred to as COP), acrylic film, or the like singly or in combination has been proposed.

In this case, as the adhesive for attaching the polarizer and the protective film, an aqueous adhesive mainly composed of an aqueous solution of a polyvinyl alcohol resin is used. However, the above-mentioned aqueous adhesive has a problem that the use thereof is limited depending on the film material because the adhesive strength is weak when an acrylic film or COP film, which is not TAC, is used as the protective film. In addition, the above-mentioned aqueous adhesive has a problem of poor adhesion due to the material, and when the materials of the protective films applied to both surfaces of the PVA element are different, a problem of curling (curl) of the polarizing plate due to the drying step of the aqueous adhesive, a problem of lowering initial optical properties, and the like occur. In addition, when the above-mentioned aqueous adhesive is used, a drying step is necessary, and in such a drying step, a difference in moisture permeability, thermal expansion, or the like occurs, which causes a problem of an increase in the fraction defective. As a means for solving the above-described problems, a means of using a nonaqueous adhesive instead of an aqueous adhesive has been proposed.

Therefore, it has been proposed to improve the reliability and yield of the polarizing plate by using a cationically polymerizable ultraviolet-curable adhesive instead of an aqueous adhesive.

The cationically polymerizable ultraviolet-curable adhesive has an epoxy compound as a main component, and has advantages of high curing density and high reliability. However, such cationic polymerization is carried out by a dark reaction (post-polymerization) after irradiation with ultraviolet rays and by a ring-opening reaction of epoxy rings, and in this case, there is a problem that the cationic polymerization is easily affected by humidity during curing and variation in the cured state is easily caused. Therefore, in order to exhibit a uniform cured state, not only the environmental humidity but also the water content of the PVA polarizer need to be strictly controlled.

The radical polymerizable ultraviolet curable adhesive is excellent in that the problem of the unevenness of the adhesive strength due to moisture as described above is relatively small. Since there is no inhibition of the curing reaction due to moisture, the reaction can be stably carried out by using the light energy without being inhibited by the moisture in the polarizer.

In addition, from the viewpoint of the reduction in thickness and durability of the polarizing plate, the thinner the thickness of the adhesive layer is, the more advantageous the adhesive is to have a low viscosity in order to satisfy such properties.

However, since the radical compound mainly uses a monofunctional group to maintain a low viscosity, the curing density and the adhesive strength are low, and it is difficult to expect a good margin in the subsequent process and reliability.

In consideration of the reliability of the polarizing plate under high temperature and high humidity, the higher the rigidity after curing of the adhesive layer, the smaller the degree of dimensional change under high temperature and high humidity, and hence the reduction of the fraction defective of the polarizer is facilitated.

In order to satisfy the properties of such adhesives, it is conceivable to use a polyfunctional monomer or a homopolymer having a high glass transition temperature, but in this case, the curing density is low and the adhesive strength is lowered.

Therefore, a series of experiments for realizing low viscosity characteristics and high rigidity after curing of the adhesive have been conducted, and as a result, the curing density of the radical compound can be appropriately adjusted to complete a highly reliable adhesive composition.

Disclosure of Invention

Technical subject

The present specification provides a radical adhesive composition, an adhesive layer, a polarizing plate and an image display device.

Means for solving the problems

One embodiment of the present disclosure provides a radical adhesive composition which, after curing, contains 55 to 70 parts by weight of 2 or more polyfunctional acrylate compounds based on 100 parts by weight of the total radical adhesive composition, and 1 or more of the polyfunctional acrylate compounds having a Glass Transition Temperature (T Transition Temperature, T) of 1 or more, based on the Glass Transition Temperature of Tan Delta (Tan Delta) peak of 100 to 130 ℃, and a Storage Modulus (Storage Modulus) of 1000 to 2000MPa at 80 ℃. (T Delta) peak of 100 to 130 ℃. (T Delta, Tan Delta, and the like)_g) Is 150 ℃ or higher, and contains 30 to 60 parts by weight of the Glass Transition Temperature (T) per 100 parts by weight of the total multifunctional acrylate compound_g) A polyfunctional acrylate compound at a temperature of 150 ℃ or higher.

Another embodiment of the present specification provides an adhesive layer containing the radical adhesive composition or a cured product thereof.

Another embodiment of the present specification provides a polarizing plate including: a polarizer; the adhesive layer is provided on at least one surface of the polarizer; and a protective film provided on the adhesive layer.

Another embodiment of the present disclosure provides an image display device including: and a polarizing plate provided on one or both surfaces of the display panel.

Effects of the invention

The radical adhesive composition according to one embodiment of the present description has a high glass transition temperature and a high storage modulus at high temperatures after curing, and thus can realize excellent heat resistance.

Drawings

Fig. 1 is a diagram showing an exemplary laminated structure of a polarizing plate according to an embodiment of the present description.

Fig. 2 is a diagram showing an exemplary laminated structure of a polarizing plate according to an embodiment of the present description.

101: first protective film

102: first adhesive layer

103: polarizer

104: second adhesive layer

105: second protective film

Detailed Description

The present specification will be described in more detail below.

In the present specification, when a part of "includes" a certain component is referred to, unless otherwise stated, it means that the other component may be further included without excluding the other component.

In the present specification, when it is stated that a certain member is "on" another member, it includes not only a case where the certain member is in contact with the other member but also a case where the other member exists between the two members.

In the present specification, Tan δ (loss tangent) refers to the ratio of storage modulus to loss modulus. Specifically, Tan δ (loss tangent) can be represented by the following formula.

Tan delta (loss tangent) ═ storage modulus/loss modulus

In the present specification, the glass transition temperature meansThe temperature at which the polymer substance changes from a hard solid state such as glass to a rubbery state having elasticity. Since the glass transition temperature is determined by the structural properties of the monomer, the polymer has a glass transition temperature specific to the kind of monomer to be polymerized. The lower the glass transition temperature, the more flexible the material, and the higher the glass transition temperature, the harder the material. Since the glass transition temperature cannot be measured by the monomer itself, the glass transition temperature is usually measured by polymerizing a homopolymer of the monomer. However, in the present specification, the glass transition temperature is determined based on the Tan δ (loss tangent) value. Corresponding to Tan delta having the maximum value (peak value) among Tan delta values according to temperature_{Maximum of}The temperature of (b) is the glass transition temperature.

One embodiment of the present invention relates to a radical adhesive composition, wherein after curing, a glass transition temperature of a Tan δ (loss tangent) peak is 100 ℃ or more and 130 ℃ or less, and a Storage Modulus (Storage Modulus) at 80 ℃ is 1000MPa or more and 2000MPa or less.

The adhesive composition further comprises 55 to 70 parts by weight of 2 or more kinds of polyfunctional acrylate compounds, and 1 or more kinds of the polyfunctional acrylate compounds have a Glass Transition Temperature (T) of 55 to 70 parts by weight based on 100 parts by weight of the total amount of the radical adhesive composition_g) Is 150 ℃ or higher, and contains 30 to 60 parts by weight of the Glass Transition Temperature (T) per 100 parts by weight of the total multifunctional acrylate compound_g) A polyfunctional acrylate compound at a temperature of 150 ℃ or higher.

When the radical adhesive composition is used for bonding a polarizer and a protective film, excellent adhesive force can be provided. The higher the storage modulus at high temperature after curing the radical adhesive composition, the more favorable the thermal shock property of the polarizing plate.

In one embodiment of the present specification, the temperature condition is 23 ℃ and the relative humidity is 23 ℃ when the radical adhesive composition is cured55% and a light quantity of 1000mJ/cm²。

In one embodiment of the present specification, the glass transition temperature of the radical adhesive composition according to the Tan δ (loss tangent) peak is 100 ℃ or higher and 130 ℃ or lower, and preferably 113 ℃ or higher and 130 ℃ or lower. When the glass transition temperature of the Tan δ (loss tangent) peak is in the above range, thermal deformation of the adhesive layer is hardly present in the temperature range for evaluating reliability, and thus high reliability can be ensured.

The radical adhesive composition is an adhesive composition comprising: the adhesive composition contains not less than 80 parts by weight and not more than 90 parts by weight of a radical polymerizable compound, does not contain a polymerizable compound other than a radical polymerizable compound, or contains a small amount, for example, less than 10 parts by weight, based on 100 parts by weight of the total radical adhesive composition. For example, since the compound having an epoxy functional group is a non-radical polymerizable cationic polymerizable material and is used in a small amount as an additive for imparting other functions than non-polymerizable properties, the compound does not have an ether bond peak (1080 cm) in the IR spectrum after curing as a result thereof^-1)。

In order to measure Tan.delta.the above-mentioned Tan.delta.was measured by first applying a radical adhesive composition to a release film and irradiating the release film with 1000mJ/cm at a temperature of 23 ℃ and a relative humidity of 55%²The light quantity of (b) was cured by light, and an adhesive film was produced. In this case, the adhesive film may have a thickness of 30 μm to 50 μm, for example, 30 μm. After removing the release film, a test piece manufactured in a size of length × width × thickness (5.3mm × 5mm × 30 μm) was heated from 0 ℃ to 150 ℃ at 5 ℃ by a Temperature sweep test (Temperature sweep test) (stress (Strain) 0.04%, Preload Force (Preload Force)0.05N, Force trace (Force Track) 125%, Frequency (Frequency)1Hz) using DMA Q800(TA instrument) to measure the storage modulus. Then, the Y axis on the graph obtained by the analysis tool is set as a numerical change of Tan δ (loss tangent), and Tan δ having the maximum value is set_{Maximum of}The temperature at (a) is defined as the glass transition temperature.

In one embodiment of the present specification, the storage modulus of the radical adhesive composition at 80 ℃ may be 1000MPa or more and 2000MPa or less, and preferably 1200MPa or more and 2000MPa or less. The storage modulus ranges above are storage moduli at 80 ℃, and storage moduli at temperatures other than 80 ℃ may have different values. When the storage modulus at 80 ℃ is in the above range, the polarizer protection performance including the adhesive layer between the polarizer and the protective film can be effectively realized. Specifically, the occurrence of cracks in the polarizer can be effectively suppressed under a severe environment such as thermal shock.

When the storage modulus at 80 ℃ is less than 1000Mpa, it is difficult to suppress shrinkage and expansion of the polarizer due to temperature during the evaluation of thermal shock, and cracks occur in the polarizer, and when the storage modulus at 80 ℃ exceeds 2000Mpa, the bending phenomenon of the polarizer may occur depending on the substrate laminated with the polarizer.

In the present specification, the above-mentioned crack may refer to a long crack portion of the polarizing plate in the MD (machine direction). For example, the length of the crack may be 0.01mm or more.

In order to measure the storage modulus, a release film was coated with the radical adhesive composition, and irradiated at a temperature of 23 ℃ and a relative humidity of 55% at 1000mJ/cm²The light quantity of (b) was cured by light, and an adhesive film was produced. In this case, the adhesive film may have a thickness of 30 μm to 50 μm, for example, 30 μm. After removing the release film, the storage modulus was measured by a Temperature sweep test (Temperature sweep test) (stress 0.04%, Preload Force 0.05N, Force Track 125%, Frequency 1Hz) using DMA Q800(TA instrument) and by raising the Temperature of a test piece manufactured in a size of length × width × thickness (5.3mm × 5mm × 30 μm) from 0 ℃ to 150 ℃ at 5 ℃.

In one embodiment of the present specification, the radical adhesive composition contains a radical polymerizable compound. The radical polymerizable compound may contain 2 or more kinds of polyfunctional acrylate compounds. When 2 or more kinds of polyfunctional acrylates are contained, a more suitable curing density can be achieved and a good adhesive force can be imparted as compared with a radical polymerizable compound containing 1 kind of polyfunctional acrylate. Therefore, when applied to a polarizer, the occurrence of cracks in the polarizer due to thermal shock can be prevented.

In one embodiment of the present specification, the total content of the polyfunctional acrylate compound is preferably about 55 to 70 parts by weight, or about 55 to 65 parts by weight, based on 100 parts by weight of the total radical adhesive composition.

When the total content of the above multifunctional acrylate compound satisfies the above range, a high storage modulus after curing can be ensured while maintaining good adhesion.

Examples of the polyfunctional acrylate compound include dipropylene glycol diacrylate, trimethylolpropane triacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, neopentyl glycol diacrylate, 3-methyl-1, 5-pentanediol diacrylate, 1, 6-hexanediol diacrylate, 1, 9-nonanediol diacrylate, dimethylol tricyclodecane diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate and [2- [1, 1-dimethyl-2 [ (1-oxoallyl) oxy ] acrylate]Ethyl radical]-5-ethyl-1, 3-bisAlk-5-yl]Methacrylic acid esters, etc., but are not limited thereto.

In one embodiment of the present specification, the radical adhesive composition includes a multifunctional acrylate compound having a glass transition temperature of 150 ℃.

In one embodiment of the present specification, the radical adhesive composition includes a multifunctional acrylate compound having a glass transition temperature of 170 ℃.

In one embodiment of the present specification, the radical adhesive composition includes a polyfunctional acrylate compound having a glass transition temperature of 250 ℃.

When the multifunctional acrylate compound with the glass transition temperature of more than 250 ℃ is contained, the glass transition temperature is higher based on Tan delta (loss tangent) peak, and the storage modulus at high temperature is higher.

In one embodiment of the present specification, the glass transition temperature of the multifunctional acrylate compound may be, for example, 400 ℃ or lower or 300 ℃ or lower.

Examples of the polyfunctional acrylate compound having a glass transition temperature of 150 ℃ or higher include dimethylol tricyclodecane diacrylate (Tg: 214 ℃) and [2- [1, 1-dimethyl-2 [ (1-oxoallyl) oxy ] group]Ethyl radical]-5-ethyl-1, 3-bisAlk-5-yl]Methacrylate (Tg: 180 ℃ C.), 9-bis [4- (2-acryloyloxyethoxy) phenylfluorene (Tg: 179 ℃ C.), and (trishydroxyethyl isocyanurate) triacrylate (Tg: 272 ℃ C.), but are not limited thereto.

The content of the multifunctional acrylate compound having a glass transition temperature of 150 ℃ or higher is preferably 15 to 40 parts by weight, 20 to 40 parts by weight, or 30 to 40 parts by weight, based on 100 parts by weight of the total of the radical adhesive composition.

In one embodiment of the present specification, the radical adhesive composition may include 2 kinds of multifunctional acrylate compounds. For example, a multifunctional acrylate compound having a glass transition temperature of 100 ℃ or more and less than 150 ℃ may be combined with a multifunctional acrylate compound having a glass transition temperature of 150 ℃ or more, or a multifunctional acrylate compound having a chain structure may be combined with a multifunctional acrylate compound having a ring-containing structure.

In one embodiment of the present specification, the radical adhesive composition may include dipropylene glycol diacrylate and tris (2-hydroxyethyl) isocyanurate triacrylate, or dipropylene glycol diacrylateAlcohol diacrylate and [2- [1, 1-dimethyl-2 [ (1-oxoallyl) oxy ] group]Ethyl radical]-5-ethyl-1, 3-bisAlk-5-yl]Methacrylate as the 2 kinds of polyfunctional acrylate compounds.

According to an embodiment of the present disclosure, the radical adhesive composition may further include a multifunctional acrylate compound. The amount of the polyfunctional acrylate compound is preferably about 0.01 to 25 parts by weight, or about 1 to 25 parts by weight, based on 100 parts by weight of the total amount of the radical adhesive composition. Examples of the polyfunctional acrylate compound include, but are not limited to, phenoxyethyl acrylate, benzyl acrylate, isobornyl acrylate, tetrahydrofuryl acrylate, isodecyl acrylate, and lauryl acrylate.

According to an embodiment of the present specification, the radical adhesive composition may contain a small amount of an epoxy compound as an additive, instead of the epoxy compound as a polymerizable compound. The content of the epoxy compound is 0.1 to 5 parts by weight, preferably 0.1 to 3 parts by weight, and more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the total of the radical adhesive composition.

Whether or not the radical adhesive composition contains an epoxy compound can be confirmed by measuring an IR spectrum. The epoxy adhesive composition containing an epoxy compound has an ether bond peak (1080 cm) in an IR spectrum due to an ether bond generated by the ring opening of an epoxy ring^-1) In contrast, the radical adhesive composition containing the acrylate compound has no peak of ether bond. Furthermore, at 1200cm^-1-1000cm^-1In the vicinity, 3 peaks were observed in the epoxy adhesive composition, but only 1 peak was observed in the radical adhesive composition.

As the radical polymerizable compound, a radical polymerizable compound having at least one hydrophilic functional group in a molecule can be used. The compound having at least one hydrophilic functional group improves compatibility with the substrate, thereby exerting an effect of improving compatibility between the surface of the substrate and the adhesive. In particular, when a polarizer is used, excellent adhesion of the adhesive between the substrate and the polarizer can be provided.

The radical polymerizable compound having the hydrophilic functional group is preferably 10 to 20 parts by weight, 13 to 20 parts by weight, or 15 to 20 parts by weight, based on 100 parts by weight of the total radical adhesive composition.

The radical polymerizable compound is not particularly limited as long as it can undergo radical polymerization by the presence of an unsaturated double bond between carbons in the molecule. In this case, the hydrophilic functional group is not particularly limited as long as it is a functional group capable of binding hydrogen, such as a hydroxyl group, a carboxyl group, a carbamate group, an amine group, or an amide group. For example, the radical polymerizable compound having the hydrophilic functional group may be a (meth) acrylate having 1 or more hydroxyl groups and an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. For example, the hydroxyl group-containing polyfunctional (meth) acrylate may be one or more selected from 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate, and these may be used alone or in a mixture of 2 or more.

According to an embodiment of the present disclosure, the radical adhesive composition may include 2 or more kinds of multifunctional acrylate compounds and 1 kind of radical polymerizable compound having a hydrophilic functional group.

According to another embodiment, the radical adhesive composition may include 2 or more kinds of multifunctional acrylate compounds, 1 kind of monofunctional acrylic compound, and 1 kind of radical polymerizable compound having a hydrophilic functional group.

According to an embodiment of the present disclosure, the radical adhesive composition may include a photoacid generator.

The photo-acid generator is a generator that generates an acid (H) by an active energy ray⁺) The compound of (4) as the photoacid generator which can be used in the present invention is, for example, preferably one containing iodineOnium salt (Iodonium salt) or Sulfonium salt (Sulfonium salt). As containing iodineSpecific examples of the photoacid generator of the salt (Iodonium salt) include (4-methylphenyl) [4- (2-methylpropyl) phenyl group]IodineHexafluorophosphate and diphenyl iodideHexafluorophosphate and diphenyl iodideHexafluoroantimonate and diphenyl iodideTetrafluoroborate and diphenyl iodideTetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodideHexafluorophosphate, bis (dodecylphenyl) iodideHexafluoroantimonate, bis (dodecylphenyl) iodideTetrafluoroborate and bis (dodecylphenyl) iodideTetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyl iodideHexafluorophosphate, 4-methylphenyl-4- (1-methylethyl) phenyliodideHexafluoroantimonate, 4-methylphenyl-4- (1-methylethyl) phenyliodideTetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodideTetrakis (pentafluorophenyl) borate, etc., but is not limited thereto. Specific examples of the photoacid generator containing a Sulfonium salt (Sulfonium salt) include diphenyl (4-phenylsulfide) phenylsulfinium hexafluoroantimonate, diphenyl (4-phenylsulfide) phenylsulfinium hexafluorophosphate, and (phenyl) [4- (2-methylpropyl) phenyl ] Sulfonium hexafluorophosphate]IodineHexafluorophosphate, (thiodi-4, 1-phenylene) bis (diphenylsulfonium) dioxaantimonate, and (thiodi-4, 1-phenylene) bis (diphenylsulfonium) dioxafluorophosphate, but are not limited thereto.

The content of the light generating agent may be about 0.5 to 15 parts by weight, preferably about 0.5 to 12 parts by weight, and more preferably about 0.5 to 10 parts by weight, based on 100 parts by weight of the total of the radical adhesive composition. When the photoacid generator satisfies the above content range, not only the curing of the adhesive can be smoothly achieved, but also it is advantageous to impart excellent resistance.

In one embodiment of the present specification, the radical adhesive composition includes a radical polymerization initiator. The radical polymerization initiator according to one embodiment of the present description is used to promote radical polymerizability and increase curing speed, and a radical polymerization initiator generally used in the art may be used without limitation.

For example, the polymerization initiator may be selected from 2, 4-diethylthioxanthone, diphenyl (2,4, 6-trimethylbenzoyl) -phosphine oxide, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-propanone, methylbenzoyl formate, oxy-phenyl-acetic acid-2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl ester, oxy-phenyl-acetic acid-2- [ 2-hydroxy-ethoxy ] -ethyl ester, methyl, More than 1 of alpha-dimethoxy-alpha-phenylacetophenone, 2-benzyl-2- (dimethylamino) 1- [4- (4-morpholinyl) phenyl ] -1-butanone, 2-methyl-1- [4- (methylthio) phenyl ] -2- (4-morpholinyl) -1-propanone and phenylbis (2,4, 6-trimethylbenzoyl).

According to an embodiment of the present specification, the content of the radical polymerization initiator is preferably 0.5 to 10 parts by weight, 1 to 5 parts by weight, or 2 to 4 parts by weight, relative to 100 parts by weight of the total radical adhesive composition. When the radical polymerization initiator is contained in the above range, the radical adhesive composition according to one embodiment of the present description has an effect that the adhesive can be smoothly cured.

In one embodiment of the present specification, the radical adhesive composition includes an additive for increasing the adhesive strength. The additive for increasing the adhesive strength is added to improve the adhesive strength by favorably polymerizing monomers contained in the adhesive composition. The kind of the additive for increasing the adhesive strength is not limited, and is preferably 5 to 25 parts by weight, 10 to 25 parts by weight, or 15 to 20 parts by weight, based on 100 parts by weight of the total of the radical adhesive composition.

According to an embodiment of the present disclosure, the additive for increasing the adhesive strength is a silane coupling agent. When the silane coupling agent is contained, the silane coupling agent can reduce the surface energy of the adhesive, thereby providing an effect of improving the wettability (wetting) of the adhesive. The silane coupling agent is not particularly limited, but preferably contains an epoxy compound, and examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane and 2- (3, 4-epoxycyclohexyl) -ethyltrimethoxysilane.

In one embodiment of the present specification, the peel force of the radical adhesive composition is 2.5N/2cm or more and 7N/2cm or less.

In one embodiment of the present specification, the protective film is used for supporting and protecting the polarizer, and for example, a cellulose-based film is used. The cellulose-based film is used by being pretreated by being immersed in a potassium hydroxide (KOH) solution.

In order to measure the peel force, the free radical adhesive composition was applied to a cellulose protective film prepared in advance by a pipette, the resultant was laminated on both surfaces of a polarizer (PVA element), the resultant adhesive layer was passed through a laminator (5m/min) under conditions set so that the final adhesive layer thickness became 1 to 2 μm, and then the surface on which the film was laminated was irradiated with 1000mJ/cm by a UV irradiation device (Metal halide lamp)²The polarizing plate was manufactured under the conditions of 20 ℃ temperature and 50% humidity.

The produced polarizing plate was left to stand at a temperature of 20 ℃ and a humidity of 70% for 1 day, cut into a sheet having a width of 20mm and a length of 100mm, and peeled at an angle of 90 degrees at a speed of 30m/min using a Texture Analyzer (Stable Micro Systems) apparatus (TA-XT Plus), to measure the peeling force between the polarizer and the substrate film.

According to an embodiment of the present specification, there is provided an adhesive layer formed using the radical adhesive composition.

The adhesive layer can be formed by a method known in the art. For example, it can be carried out by the following method: after a radical adhesive composition is applied to one surface of the polarizer or the protective film to form an adhesive layer, the polarizer and the protective film laminate are cured. In this case, the coating may be performed by a coating method known in the art, for example, spin coating, bar coating, roll coating, gravure coating, blade coating, and the like.

According to an embodiment of the present disclosure, the average thickness of the adhesive layer is greater than 0 μm and less than about 20 μm, greater than 0 μm and less than about 10 μm, and preferably about 0.1 μm to 10 μm or about 0.1 μm to 5 μm. This is because if the thickness of the adhesive layer is too thin, the uniformity and adhesion of the adhesive layer may be reduced, and if the thickness of the adhesive layer is too thick, the problem of wrinkling of the appearance of the polarizing plate may occur.

According to an embodiment of the present specification, there is provided a polarizing plate including: a polarizer; an adhesive layer formed on at least one surface of the polarizer by the radical adhesive composition; and a protective film provided on the adhesive layer.

According to fig. 1, a polarizing plate according to an embodiment of the present description includes: the polarizer 103 includes a first adhesive layer 102 and a first protective film 101 in this order on one surface of the polarizer.

In a polarizing plate according to another embodiment, as shown in fig. 2, a first protective film 101 and a second protective film 105 are provided on both surfaces of a polarizer 103 through a first adhesive layer 102 and a second adhesive layer 104, respectively, as a medium.

Alternatively, the adhesive layers 102 and 104 may be provided with the protective films 101 and 105 on both surfaces.

The polarizer is not particularly limited, and any polarizer known in the art, for example, a film made of polyvinyl alcohol (PVA) containing iodine or dichroic dye can be used. The polarizer may be manufactured by dyeing iodine or dichroic dye on a PVA film, but the manufacturing method thereof is not particularly limited. In this specification, the polarizer refers to a state not including a protective film, and the polarizing plate refers to a state including the polarizer and the protective film.

In one embodiment of the present specification, the protective film is used to support and protect the polarizer, and protective films of various materials generally known in the art, for example, cellulose-based films, Polyethylene terephthalate (PET) films, Cycloolefin polymer (COP) films, acrylic films, and the like may be used without limitation.

In one embodiment of the present specification, the protective film may be a cellulose-based film. In addition, in order to improve the adhesion, a process of performing corona treatment or water washing treatment with KOH solution on the surface of the cellulose-based film may be added.

According to an embodiment of the present disclosure, there is provided an image display device including: a display panel, and the polarizing plate provided on one or both surfaces of the display panel.

The display panel may be a liquid crystal panel, a plasma panel, and an organic light emitting panel.

Accordingly, the image display device may be a liquid crystal display device (LCD), a plasma display device (PDP), and an organic electroluminescent display device (OLED).

More specifically, the image display device may include a liquid crystal panel and polarizing plates provided on both surfaces of the liquid crystal panel, and at least one of the polarizing plates may be a polarizing plate including the polarizer according to one embodiment of the present specification. That is, the polarizing plate is a polarizing plate comprising a polyvinyl alcohol polarizer dyed with iodine and/or a dichroic dye, and a protective film provided on at least one surface of the polyvinyl alcohol polarizer, and is characterized by locally having a polarization-reduced region having a monomer transmittance of 80% or more in a wavelength region of 400nm to 800nm, the polarization-reduced region having an arithmetic average roughness (Ra) of 200nm or less, a degree of polarization of 10% or less, and a sag (sagging) of 10 μm or less.

In this case, the type of the liquid crystal panel included in the liquid crystal display device is not particularly limited. For example, without being limited to the kind thereof, the following may be applied: passive matrix panels such as TN (twisted nematic) type, STN (super twisted nematic) type, F (ferroelectric) type, or PD (polymer dispersed) type; panels in an active matrix system such as a two-terminal (two terminal) or three-terminal (three terminal); and well-known panels such as In-Plane Switching (IPS) panels and Vertical Alignment (VA) panels. In addition, the types of other structures constituting the liquid crystal display device, for example, the upper and lower substrates (for example, a color filter substrate or an array substrate) and the like are also not particularly limited, and the structures known in the art can be adopted without limitation.

Modes for carrying out the invention

The present invention will be described in detail below with reference to examples for specifically describing the invention. However, the embodiments according to the present description may be modified into various forms, and the scope of the present description is not to be construed as being limited to the embodiments described below. The embodiments of the present description are provided to more fully describe the present description to those skilled in the art.

< production example 1> production of radical adhesive composition

Examples 1 to 5 and comparative examples 1 to 3

A radical adhesive composition having a composition shown in table 1 below was produced in an amount of 104.8 parts by weight based on the total amount of the radical adhesive composition.

[ Table 1]

-DPGDA: dipropylene glycol diacrylate

-M370: tris (2-hydroxyethyl) isocyanurate triacrylate

-R-604: [2- [1, 1-dimethyl-2 [ (1-oxoallyl) oxy group]Ethyl radical]-5-ethyl-1, 3-bisAlk-5-yl]Methacrylic acid esters

-4-HBA: 4-hydroxybutyl acrylate

-TMPTA: trimethylolpropane triacrylate

-POEA: phenoxyethyl acrylate

-I250: (4-methylphenyl) [4- (2-methylpropyl) phenyl group]IodineHexafluorophosphates

-TPO: diphenyl (2,4, 6-trimethylbenzoyl) -phosphine oxide

-DETX: 2, 4-diethylthioxanthone

-KBM 403: (3-glycidoxypropyl) trimethoxysilane

< production example 2> production of polarizing plate

The radical adhesive composition is applied to a cellulose protective film (TAC1 or TAC2) which has been pretreated and saponified by a pipette, and the resultant is laminated on both surfaces of a polarizer (PVA element), and then passed through a laminator (5m/min) under conditions set so that the final adhesive layer thickness is 1 to 2 μm. Then, the surface on which the film was laminated was irradiated with 1000mJ/cm by a UV irradiation apparatus (Metal halide lamp)²Thereby manufacturing a polarizing plate. In this case, a polarizing plate was produced under conditions of a temperature of 20 ℃ and a humidity of 50%.

< Experimental example 1> measurement of glass transition temperature and storage modulus of radical adhesive composition

Coating the radical adhesive composition on a release film (PET film), and irradiating at 23 deg.C and 55% relative humidity with 1000mJ/cm²The light quantity of the light source is used for light curing, and the adhesive film with the thickness of 30-50 mu m is manufactured. After removing the release film, a test piece manufactured in a size of width × length × thickness (5.3mm × 5mm × 30 μm) was heated at 5 ℃ from 0 ℃ to 150 ℃ by a Temperature sweep test (Temperature sweep test) (stress 0.04%, Preload Force 0.05N, Force Track 125%, Frequency 1Hz) using DMA Q800(TA instrument) to measure the storage modulus, and the value measured at 80 ℃ was read. Then, the Y axis on the graph obtained by the analysis tool is set to Tan δThe value of (loss tangent) changes, and Tan.delta.with the maximum value is recorded_{Maximum of}The temperature of (c).

The measurement results according to the above experimental example 1 are shown in the following table 2.

[ Table 2]

< Experimental example 2> measurement of peeling force of radical adhesive composition

The polarizing plate produced as described above was left to stand at 20 ℃ and 70% humidity for 1 day, cut to a width of 20mm and a length of 100mm, and peeled at an angle of 90 degrees at a speed of 30m/min using a Texture Analyzer (Stable Micro Systems) apparatus (TA-XT Plus), to measure the peeling force between the polarizer and the base film. In this case, the peel force was expressed as "X", the peel force was expressed as "2.5N/2 cm" or more, the peel force was expressed as "O", the peel force was expressed as "2.0N/2 cm or more and less than 2.5N/2 cm" or less, the peel force was expressed as "X", the peel force was expressed as "1.0N/2 cm" or more and less than 2.0N/2cm "or less, and the peel force was expressed as" XX ".

< Experimental example 3> evaluation of tolerance

An adhesive film for adhesion to a glass substrate was attached to the polarizing plate produced using the compositions of examples 1 to 5 and comparative examples 1 to 3, and the polarizing plate was cut 150mm in the direction perpendicular to the absorption axis of the polarizer and 150mm in the direction of the absorption axis, and then laminated on a glass substrate (glass plating), and left to stand at room temperature for 24 hours. Then, the glass substrate was placed in a water bath at 60 ℃ for 24 hours and then taken out. The appearance of the sample was visually confirmed to confirm whether or not the film was discolored and peeled.

< Experimental example 4> thermal shock stability

An adhesive film for adhesion to a glass substrate was attached to the polarizing plate produced using the compositions of examples 1 to 5 and comparative examples 1 to 3, and the adhesive film was cut by 150mm in the direction perpendicular to the absorption axis of the polarizer and 150mm in the direction of the absorption axis, and then laminated on a glass substrate (glass plating), and after leaving it at-40 ℃ for 30 minutes, it was left again at 80 ℃ for 30 minutes, and this process was repeated 100 times. Then, whether the appearance of the polarizing plate is deformed or not was evaluated visually.

The case where the polarizing plate was not deformed in appearance was regarded as excellent, the case where cracks smaller than 1mm were generated in the cut portion was regarded as good, and the case where cracks of 1mm or more were generated was regarded as poor.

The results according to the above experimental examples 2 to 4 are shown in the following table 3.

[ Table 3]

As is apparent from the above tables 2 and 3, in the radical adhesive compositions according to the present invention (examples 1 to 5), the glass transition temperature after curing and the storage modulus at 80 ℃ were measured to be higher than those of the compositions of comparative examples 1 to 3, and the polarizing plates manufactured using the radical adhesive compositions of examples 1 to 5 were excellent in the peeling force, the high temperature resistance and the thermal shock resistance as compared with those of the compositions of comparative examples 1 to 3.

Specifically, when a radical adhesive composition in which 2 kinds of multifunctional acrylate compounds are contained in a polarizer in an amount of 55 parts by weight or more based on 100 parts by weight of the total radical adhesive composition and contains a multifunctional acrylate compound having a glass transition temperature of 150 ℃ or more is used for a polarizing plate, the composition has a peeling force of 2.5N/2cm or more, has excellent high-temperature resistance that causes no discoloration or film peeling at 60 ℃, and has no deformation in appearance or cracks of less than 1mm at the time of thermal shock (-40 → 80 ℃). In particular, the radical adhesive compositions of examples 1 to 4, which contained the polyfunctional acrylate compound having a glass transition temperature of 250 ℃ or higher, had higher glass transition temperatures after curing and higher storage moduli at 80 ℃.