阅读说明：本技术 白色调色剂 (White toner ) 是由 越智红一郎 千本裕也 宫阶智代 平佐崇 于 2019-01-08 设计创作，主要内容包括：本发明提供具有优异隐蔽性且不降低耐热污损性的白色调色剂。该白色调色剂的特征在于包括：含有粘结剂树脂和钛酸钙颗粒的调色剂颗粒,其中所述粘结剂树脂具有酸值,并且所述调色剂中的所述钛酸钙颗粒的含量在25质量％至80质量％的范围内。(The invention provides a white toner having excellent concealing properties without reducing hot offset resistance. The white toner is characterized by comprising: toner particles containing a binder resin and calcium titanate particles, wherein the binder resin has an acid value, and a content of the calcium titanate particles in the toner is in a range of 25 to 80 mass%.)

1. A white toner, characterized by comprising:

toner particles containing a binder resin and calcium titanate particles,

wherein

The binder resin has an acid value, an

The content of the calcium titanate particles in the toner is in the range of 25 to 80 mass%.

2. The white toner according to claim 1, wherein the acid value of the binder resin is in a range of 10mg KOH/g to 30mg KOH/g.

3. The white toner according to claim 1 or 2, wherein the surface alkali amount of the calcium titanate particles is in a range of 15 μmol/g or more.

4. The white toner according to any one of claims 1 to 3, wherein a weight average molecular weight of tetrahydrofuran solubles of the binder resin determined by gel permeation chromatography is in a range of 50,000 to 200,000.

5. The white toner according to any one of claims 1 to 4, wherein in a molecular weight distribution of tetrahydrofuran solubles of the binder resin determined by gel permeation chromatography, a content of a component having a molecular weight of 100 to 5,000 with respect to a total amount of the tetrahydrofuran solubles of the binder resin is in a range of 20 to 40 mass%.

6. The white toner according to any one of claims 1 to 5, wherein an average dispersed diameter of the calcium titanate particles in the toner particles is in a range of 200nm to 500 nm.

7. The white toner according to any one of claims 1 to 6, wherein the calcium titanate particles have a perovskite-type crystal structure.

8. The white toner according to any one of claims 1 to 7, wherein the binder resin comprises a polyester resin.

Technical Field

The present invention relates to a white toner for use in an image forming method of electrophotography.

Background

In recent years, with the development of image forming apparatuses such as copiers and printers, toners suitable for various media have been demanded. Among them, a technique has been developed to obtain a high value-added printed matter by using a special color toner such as a transparent toner or a white toner.

A white toner is important for forming a white image on a color paper and a transparent film, and in order to achieve strong concealment, a toner using a material having a high refractive index such as titanium oxide has been developed (patent document 1).

However, such special color toners are also required to satisfy demands for high speed, high image quality, long life, and energy saving. Hot offset resistance is particularly important for securing a fixing temperature range, and a technique of crosslinking a binder resin composition of a toner, for example, has been proposed as a means of improving the hot offset resistance (patent document 2).

Disclosure of Invention

Problems to be solved by the invention

In general, in order to form a white image using a white toner and to express sufficient white color, it is preferable to conceal the color of the underlying layer and make it unrecognizable. Since such image concealment is exhibited by light scattering in the image film, a material having a colorless pigment with a large difference in refractive index from the binder resin, that is, a high refractive index, is required. Further, in order to exhibit sufficient hiding properties, it is preferable to contain the above white pigment in a larger amount and with better dispersibility than other colors in the toner of the white toner.

It has been found that, as described in patent document 1, when a large amount of a white pigment such as titanium oxide is contained in the toner, since the relative amount of the binder resin is small compared to other color toners, the hot offset resistance of the toner during fixing at high temperatures is reduced.

As proposed in patent document 2, the toner viscosity can also be increased by crosslinking the binder resin composition of the toner. However, it has been found that in this case, the dispersibility of the white pigment is lowered, and the image concealment is lowered.

It is an object of the present invention to address these problems. That is, an object is to provide a white toner having excellent concealing properties without reducing hot offset resistance.

Means for solving the problems

As a result of intensive studies by the present inventors, both hiding properties and hot offset resistance can be achieved by using a white toner containing calcium titanate particles together with a binder resin having an acid value.

That is, the present invention relates to

A white toner, comprising:

toner particles containing a binder resin and calcium titanate particles,

wherein

The binder resin has an acid value, an

The content of the calcium titanate particles in the toner is in the range of 25 to 80 mass%.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a white toner having excellent concealing properties without reducing hot offset resistance can be provided.

Detailed Description

In the present invention, unless otherwise specifically indicated, the description of a numerical range such as "above X and below Y" or "X to Y" includes numerical values at the upper and lower limits of the range.

The toner of the present invention is a white toner, which includes: toner particles containing a binder resin and calcium titanate particles, wherein the binder resin has an acid value, and the content of the calcium titanate particles in the toner is in a range of 25 to 80 mass%.

By combining the calcium titanate particles with the binder resin having an acid value in the toner particles, both of the hot offset resistance and the hiding resistance can be achieved during image formation.

The reason why calcium titanate has such a special effect is considered as follows. The calcium titanate may generally have a perovskite-type crystal structure. Gas molecules and the like adsorb to calcium atoms on the particle surface of the crystal, and therefore sites having hydroxyl groups exist. When these sites coexist with the binder resin having a carboxyl group, they may appear as adsorption sites for the carboxyl group.

Since the calcium titanate particles and the binder resin form a morphology resembling a cross-linked structure through these adsorption sites, the viscosity of the toner particles at the time of fixing increases, and the hot offset resistance improves. Such an effect is peculiar to calcium titanate, and is considered to be due to the coordination state of calcium in the perovskite crystal structure, the improvement of the carboxyl group adsorption efficiency due to the specific ionic radius of calcium, and the like.

Since this method does not increase the viscosity of the binder resin itself, in addition, the dispersibility of the calcium titanate particles can be increased, and the concealing property of the white toner is not impaired even after the image formation.

In order to confirm whether the calcium titanate particles have a perovskite-type crystal structure, the peak pattern was analyzed by X-ray diffraction.

The binder resin used in the present invention is a binder resin having an acid value. In the case where there is no acid value, since there is no site for interaction with the calcium titanate particles, the heat offset resistance is not improved.

The acid value of the binder resin is preferably in the range of 5mgKOH/g to 40mgKOH/g, or more preferably in the range of 10mgKOH/g to 30mgKOH/g, or still more preferably in the range of 12mgKOH/g to 25 mgKOH/g. If the binder resin has an acid value of 5mgKOH/g or more, it can easily interact with calcium titanate, so that the heat offset resistance is easily improved. If it is 40mgKOH/g or less, the toner has good chargeability.

The weight average molecular weight of Tetrahydrofuran (THF) solubles of the binder resin as determined by Gel Permeation Chromatography (GPC) is preferably in the range of 50000 to 200000, or more preferably in the range of 100000 to 170000. If it is 50000 or more, a crosslinked structure is formed with the calcium titanate particles, and the hot offset resistance is easily improved. On the other hand, if it is 200000 or less, the dispersibility of the calcium titanate particles in the binder resin improves, and the concealing property is good.

In the molecular weight distribution of tetrahydrofuran solubles of the binder resin determined by GPC, the content of the component having a molecular weight of 100 to 5000 is preferably in the range of 20 to 40 mass%, or more preferably in the range of 23 to 35 mass%, based on the total mass of tetrahydrofuran solubles of the binder resin.

When the binder resin contains a specific amount of such a low-molecular weight component, the high-mobility component in the binder resin is effectively adsorbed to the surface of the calcium titanate particles, and the hot offset resistance is improved. The content of the component having a molecular weight of 100 to 5000 can be controlled by mixing a resin having many low molecular weight components having a molecular weight of 100 to 5000 as needed.

Known polymers can be used as the binder resin of the toner, and specifically the following polymers can be used.

Homopolymers of styrene and its substituted forms such as polystyrene, poly (p-chlorostyrene), and polyvinyltoluene; styrene-based copolymers such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene- α -chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, and styrene-acrylonitrile-indene copolymer; and polyvinyl chloride, phenol resins, natural resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethane resins, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumarone-indene resins, and petroleum-based resins. The binder resin may be used alone, or two or more thereof may be combined.

The binder resin preferably contains the polyester resin described above, and more preferably a polyester resin. The inclusion of the polyester resin makes it easier to disperse the calcium titanate particles and to obtain both the hot offset resistance and the concealing property as described above. The content of the polyester resin in the binder resin is preferably in the range of 50 to 100 mass%, or more preferably in the range of 85 to 100 mass%, or still more preferably in the range of 95 to 100 mass%.

The polyester resin is preferably a polycondensate of an alcohol component and an acid component. The following compounds are examples of monomers used to form the polyester resin.

Examples of the alcohol component include the following glycols.

Ethylene glycol, propylene glycol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, diethylene glycol, triethylene glycol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, 2-ethyl-1, 3-hexanediol, hydrogenated bisphenol A, bisphenol represented by the following formula (I) and derivatives thereof, and glycols represented by the following formula (II).

Trihydric or higher polyols such as 1,2, 3-propanetriol, trimethylolpropane, hexanetriol, pentaerythritol and the like can also be used as the alcohol component.

[C2]

(wherein R represents an ethylene group or a propylene group, X and Y are each an integer of 0 or more, and the average value of X + Y is 0 to 10.)

[C3]

(wherein R' represents:

x 'and y' are each an integer of 0 or more, and the average value of x '+ y' is 0 to 10. )

As the alcohol component, a bisphenol represented by formula (I) is preferable, and ethylene oxide adducts of bisphenol a such as polyoxypropylene (2.2) -2, 2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2, 2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2, 2-bis (4-hydroxyphenyl) propane, and polyoxypropylene (6) -2, 2-bis (4-hydroxyphenyl) propane are more preferable.

Examples of the acid component include the following dicarboxylic acids.

Benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride, or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or anhydrides thereof; succinic acid substituted with an alkyl group having a carbon number of 6 to 18 or an alkenyl group having a carbon number of 6 to 18 or an anhydride thereof; and unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, and itaconic acid, or anhydrides thereof.

Preferably, a polybasic acid of three or more members is used as the acid component. Examples thereof include 1,2, 4-benzenetricarboxylic acid (trimellitic acid), 1,2, 4-cyclohexanetricarboxylic acid, 1,2, 4-naphthalenetricarboxylic acid, pyromellitic acid and anhydrides thereof or lower alkyl esters thereof.

Among them, aromatic compounds which are also highly stable against environmental changes are preferred, and examples include 1,2, 4-benzenetricarboxylic acid and hydrides thereof.

The toner particles contain calcium titanate particles. The content of the calcium titanate particles in the toner is in the range of 25 to 80 mass%.

If the content is less than 25 mass%, the concealing property is insufficient, and if it exceeds 80 mass%, the charging property is lowered. The content of the calcium titanate particles in the toner is preferably in the range of 40 to 70 mass%.

The surface base amount (surface base amount) of the calcium titanate particles is preferably 10. mu. mol/g or more. If the surface alkali amount is 10. mu. mol/g or more, since the amount of hydroxyl groups is suitable for interaction with the carboxyl groups of the binder resin, the heat offset resistance can be easily improved.

The surface alkali amount is more preferably 15. mu. mol/g or more, or still more preferably 20. mu. mol/g or more. Although there is no particular upper limit, it is preferably 200. mu. mol/g or less, or still more preferably 150. mu. mol/g or less, or particularly 40. mu. mol/g or less. The surface alkali amount of the calcium titanate particles can be controlled by surface treatment with various organic or inorganic materials, or by changing the surface area thereof by pulverizing the particles, or the like.

The average dispersed diameter of the calcium titanate particles in the toner particles is preferably in the range of 200nm to 500nm, or more preferably in the range of 300nm to 480 nm. If the average dispersion diameter is within this range, good concealment is obtained. In the case of preparing the toner by, for example, a pulverization method or the like, the average dispersion diameter of the calcium titanate particles in the toner particles can be controlled by changing the shear rate at the time of melt-kneading with the resin.

Preferred embodiments of the present invention are described below.

< Release agent (wax) >

Waxes may also be used for the toner. Examples of waxes include the following:

hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline waxes, paraffin waxes, and fischer-tropsch waxes; hydrocarbon wax oxides such as polyethylene oxide wax (polyethylene oxide wax) and block copolymers thereof; waxes such as carnauba wax mainly composed of fatty acid esters; and partially or fully deoxygenated fatty acid esters such as deoxygenated carnauba wax.

Other examples include the following: saturated linear fatty acids such as palmitic acid, stearic acid and montanic acid; unsaturated fatty acids such as barbituric acid, eleostearic acid and parinaric acid (parinaric acid); saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauba alcohol, ceryl alcohol and myricyl alcohol; polyols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid and montanic acid with alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauba alcohol, ceryl alcohol and myricyl alcohol; fatty acid amides such as linoleamide, oleamide and lauramide; saturated fatty acid diamides such as methylene distearamide, ethylene dihexanamide, ethylene dilauramide and hexamethylene distearamide; unsaturated fatty acid amides such as ethylene diolamide, hexamethylene diolamide, N ' -dioleyladipamide (N, N ' -dioleyladipamide), and N, N ' -dioleylsebactamide; aromatic diamides such as m-xylene distearamide (m-xylene bisstearamide) and N, N '-distearyl isophthalamide (N, N' -distearyl isophthalamide); aliphatic metal salts (generally referred to as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esterification products of fatty acids such as behenic acid monoglyceride and polyhydric alcohols; and methyl ester compounds containing hydroxyl groups obtained by hydrogenation of plant-based oils and fats.

Of these waxes, hydrocarbon waxes such as paraffin wax and fischer-tropsch wax, and fatty acid ester waxes such as palm wax are preferable from the viewpoint of improving low-temperature fixability and hot offset resistance.

The content of the wax is preferably in the range of 1 to 20 parts by mass per 100 parts by mass of the binder resin.

< Charge control agent >

The toner may also contain a charge control agent, as necessary. The charge control agent contained in the toner may be a known charge control agent, and metal compounds of aromatic carboxylic acids are particularly preferable because they are colorless, provide a fast charging speed, and can stably maintain a fixed charge amount.

Examples of the negative charge control agent include salicylic acid metal compounds, naphthoic acid metal compounds, dicarboxylic acid metal compounds, high molecular compounds having sulfonic acid or carboxylic acid in the side chain, high molecular compounds having sulfonic acid salt or sulfonic acid ester in the side chain, high molecular compounds having carboxylic acid salt or carboxylic acid ester in the side chain, and boron compounds, urea compounds, silicon compounds, and calixarene compounds.

Examples of the positive charge control agent include quaternary ammonium salts, polymer compounds having such quaternary ammonium salts in side chains, guanidine compounds, and imidazole compounds.

The charge control agent may be added internally or externally to the toner particles. The addition amount of the charge control agent is preferably in the range of 0.2 parts by mass to 10 parts by mass per 100 parts by mass of the binder resin.

< inorganic Fine particles (Main external additive) >

The toner may further contain inorganic fine particles other than the calcium titanate particles as necessary. The inorganic fine particles may be internally added to the toner particles or mixed with the toner particles as an external additive. Inorganic fine powder such as silica, titanium oxide, or alumina is preferable as the external additive. The inorganic fine powder is preferably hydrophobized with a hydrophobizing agent such as a silane compound or a silicone oil or a mixture thereof.

To improve flowability, it will preferably be 50m²G to 400m²Inorganic fine powder of specific surface area/g as an external additive, while preferably having a specific surface area of 10m for stable durability²G to 50m²Inorganic fine powder of specific surface area/g. In order to improve both the fluidity and the stable durability, inorganic fine powders having specific surface areas within these ranges may be used together.

The external additive is preferably used in an amount of 0.1 to 10.0 parts by mass per 100 parts by mass of the toner particles. Mixing of the external additive with the toner particles can be accomplished using a known MIXER such as a HENSCHEL MIXER (HENSCHEL MIXER).

< method for producing toner >

The method for producing the toner is not particularly limited, and a known method such as an emulsion aggregation method, a pulverization method, or a suspension polymerization method can be used. In the emulsion aggregation method, toner particles are obtained by preparing a fine particle dispersion of a material containing toner particles, aggregating the fine particle dispersion to form aggregated particles, and melting and fusing the aggregated particles.

The following example using the pulverization method illustrates the manufacturing process of the toner.

In the raw material mixing step, as materials constituting the toner particles, for example, a binder resin, calcium titanate particles, and other components such as a release agent and a charge control agent as needed are weighed in specific amounts, compounded, and mixed. The mixing device may be exemplified by a double cone mixer, a V-type mixer, a drum type mixer, a high speed mixer (Supermixer), a Henschel mixer, a Nauta mixer (Nauta mixer), and a Mecano Hybrid (Nippon lake & Engineering Co., Ltd.), and the like.

The mixed material is then melt kneaded. The melt-kneading step may use a batch kneader such as a pressure kneader or a banbury mixer or may use a continuous kneader. Single and twin screw extruders are preferred, which have the advantage of providing continuous production. Examples thereof are a KTK twin screw extruder (Kobe Steel, Ltd.), a TEM twin screw extruder (Toshiba machine Co., Ltd.), a PCM Kneader (Ikegai Corp.), a twin screw extruder (KCK), a compound Kneader (Co-Kneader) (Buss), and a Kneadex (Nippon biscuit & Engineering Co., Ltd.).

The resin composition resulting from the melt-kneading may be rolled using, for example, a two-roll mill, and may be cooled using, for example, water in the cooling step.

The cooled resin composition is then pulverized to a desired particle size in a pulverization step. In the pulverization step, for example, coarse pulverization is performed using a grinder such as a crusher, a hammer Mill, or a grinder (feather Mill), followed by fine pulverization by, for example, using a pulverizer such as a Kryptron System (Kawasaki gravity Industries, Ltd.), Super Rotor (nisshin engineering Inc.), or Turbo Mill (Turbo Kogyo co., Ltd.) or using an air jet System.

Then, a classification product (toner particles) is obtained by classifying with a sieving apparatus or a classifier such as an inertial classification system such as Elbow Jet (nitttetsu Mining co., Ltd.) or the like or a centrifugal classification system such as turboplex (Hosokawa Micron Corporation), TSP Separator (Hosokawa Micron Corporation), Faculty (Hosokawa Micron Corporation) or the like as necessary.

The resulting toner particles can be used as toners as they are. The surface of the toner particles may also be externally treated with an external additive, as desired. As an external treatment method of the external additive, a predetermined amount of the classified toner particles and various well-known external additives are blended, and stirred and mixed using a mixing device such as a double cone mixer, a V-type mixer, a drum-type mixer, a high-speed mixer, a henschel mixer, a nauta mixer, MECHANOHYBRID (manufactured by Nippon Coke Industry co., ltd.) or nobita (manufactured by Hosokawa Micron Corporation) as an external addition device.

< measurement of acid value of resin >

The acid value is the amount of mg of potassium hydroxide required to neutralize acid components such as free fatty acids and resin acids contained in 1g of the sample. Measured according to the method of JIS K0070.

(1) Sample (I)

Solvent: immediately prior to use, the toluene-ethanol (2:1) mixture was neutralized with 0.1mol/L ethanolic potassium hydroxide solution using a phenolphthalein indicator.

Phenolphthalein solution: 1g of phenolphthalein was dissolved in 100mL of ethanol (95 vol%).

0.1mol/L ethanolic potassium hydroxide solution: 7.0g of potassium hydroxide are dissolved in the smallest possible amount of water, ethanol (95% by volume) is added to a total of 1 l, and the mixture is then left for 2 to 3 days and filtered. Standardization was carried out according to JIS K8006 (basic of Titration of Dual Reagent Content Testing) for the Content test of reagents.

(2) Operation of

1 to 20g of the resin was accurately weighed as a sample, 100mL of the above solvent and a few drops of the above phenolphthalein solution as an indicator were added, and the mixture was sufficiently shaken until the sample was completely dissolved. In the case of solid samples, dissolution was carried out by heating in a water bath. After cooling, titration was carried out with the aforementioned 0.1mol/L ethanol solution of potassium hydroxide, and the point at which the light pink color of the indicator lasted for 30 seconds was taken as the end point of neutralization.

(3) Calculation formula

The acid number was calculated by the following formula:

A＝B×f×5.611/S

a: acid value (mg KOH/g)

B: amount of 0.1mol/L Potassium hydroxide ethanol solution used (mL)

f: coefficient of 0.1mol/L potassium hydroxide ethanol solution

S: mass of sample (g)

(when measured with toner)

First, the external additive is removed from the toner by the following method.

A concentrated sucrose solution was prepared by adding 160g of sucrose (Kishida Chemical co., Ltd.) to 100mL of ion-exchanged water and boiling to dissolve.

A dispersion was prepared by placing 31g of the concentrated sucrose solution and 6mL of continon N (a 10 mass% aqueous solution of a neutral detergent of pH7 for washing precision measuring instruments, including a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, ltd.) in a centrifuge tube.

To the dispersion, 1.0g of toner was added, and the toner mass was broken with a doctor blade or the like.

The centrifuge tube was then shaken in a shaker. After shaking, the solution was transferred to a glass tube (50mL) for a swing rotor and separated in a centrifuge at 3500rpm for 30 minutes. By this operation, the external additive that has been removed from the toner particles is separated.

It was visually confirmed that the toner particles were completely separated from the aqueous solution, the toner particles were collected and filtered with a vacuum filter, and then dried in a dryer for 1 hour or more to obtain toner particles in which the external additive was separated.

The obtained toner particles were further dissolved in tetrahydrofuran, and insoluble matter was filtered off to obtain a dried matter to isolate the binder resin. Then, the acid value of the resin was measured by the above-mentioned method.

< determination of Structure of resin >

The structure of the resin was determined using the following method.

ECA-400(400MHz) using JEOL Ltd¹H-NMR and¹³C-NMR spectroscopy.

The assay was performed in a deuterated solvent containing tetramethylsilane as an internal standard substance at 25 ℃. The chemical shift value is shown as a ppm shift value (value) under the condition that 0 is used as the value of tetramethylsilane as an internal standard substance.

< measurement of weight average molecular weight and molecular weight distribution of resin >

The weight average molecular weight and molecular weight distribution of the binder resin and other resins were determined by Gel Permeation Chromatography (GPC) as follows.

First, the sample was dissolved in Tetrahydrofuran (THF) at room temperature over 24 hours. Then, the resulting solution was filtered with a solvent-resistant membrane filter (Maishori Disk, Tosoh Corporation) having a pore size of 0.2 μm to obtain a sample solution. The concentration of THF solubles in the sample solution was adjusted to about 0.8 mass%. The measurement was performed under the following conditions using the sample solution.

A unit: HLC8120 GPC (detector: RI) (Tosoh Corporation)

Column: shodex KF-801, 802, 803, 804, 805, 806, 807 (total 7) (Showa Denko K.K.)

Eluent: tetrahydrofuran (THF)

Flow rate: 1.0 mL/min

The furnace temperature: 40.0 deg.C

Sample injection amount: 0.10mL

Molecular weight calibration curves prepared using standard polystyrene resins (TSK standard polystyrenes F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500, Tosoh Corporation) were used to calculate the molecular weight of the samples.

In the measurement from the toner, the measurement may be performed after the binder resin is separated from the toner by the above-described method.

< content of calcium titanate particles >

The amount of calcium titanate particles contained in the toner particles is calculated as follows.

For the measurement apparatus, an Axios wavelength dispersive X-ray fluorescence spectrometer (Malvern panalytical Ltd) and accessory dedicated software SuperQ ver.4.0f (Malvern panalytical Ltd) for setting measurement conditions and analyzing measurement data were used. Rh was used as an anode of the X-ray tube and the measurement atmosphere was vacuum, the measurement diameter (collimator mask diameter) was 27mm and the measurement time was 10 seconds. In the detection, the light element is measured by a Proportional Counter (PC) and the heavy element is measured by a Scintillation Counter (SC).

For the test samples, 4g of the toner was placed in a special aluminum ring for compression, laid flat, and formed into pellets of about 2mm thickness and about 39mm diameter by pressing with a BRE-32 pastille former (Maekawa Testing Machine mfg. co., Ltd.) at 20MPa for 60 seconds.

The measurement was performed under the above-mentioned conditions, the elements were identified based on their peak positions in the obtained X-rays, and their concentrations were calculated from the count rate (unit: cps) which is the number of X-ray photons per unit time.

< amount of surface base of calcium titanate particles >

The surface alkali amount of the calcium titanate particles was calculated as follows.

Calcium titanate was added to 1/100mol/L hydrochloric acid-ethanol solution, sonicated at 25 ℃ for 1 hour, and centrifuged to obtain a supernatant. The supernatant was then subjected to potentiometric titration with 1/100mol/L potassium hydroxide-ethanol solution using an AT-510 automated potentiometric titrator (Kyoto Electronics manufacturing Co., Ltd.). The surface alkali amount of the calcium titanate particles was determined from the difference between the amount of potassium hydroxide used for titration of only 1/100mol/L hydrochloric acid-ethanol solution and the amount of potassium hydroxide used for titration of supernatant.

(when measured with toner)

First, the external additive is separated from the toner particles.

A concentrated sucrose solution was prepared by adding 160g of sucrose (Kishida Chemical co., Ltd.) to 100mL of ion-exchanged water and boiling to dissolve.

Then, 31g of the concentrated sucrose solution and 6mL of continon N (a 10 mass% aqueous solution of a neutral detergent of pH7 for washing precision measuring instruments including a nonionic surfactant, an anionic surfactant and an organic builder, manufactured by Wako Pure Chemical Industries, ltd.) were put in a centrifuge tube to prepare a dispersion.

1.0g of toner was added to the dispersion, and the toner mass was broken with a doctor blade or the like.

The centrifuge tube was then shaken in a shaker. After shaking, the solution was transferred to a glass tube (50ml) for a swing rotor and separated in a centrifuge at 3,500rpm for 30 minutes. By this operation, the external additive that has been removed from the toner particles is separated.

It was visually confirmed that the toner particles were completely separated from the aqueous solution, the toner particles were collected and filtered with a vacuum filter, and then dried in a dryer for 1 hour or more, to obtain toner particles from which the external additive had been separated.

Then, the soluble matters other than the calcium titanate particles in the resultant toner particles are dissolved with tetrahydrofuran, toluene, hexane, and the like. Then, it was filtered and redispersed in water, and the calcium titanate was collected by removing the remaining external additives by centrifugation, and the surface alkali amount was calculated by the above-mentioned surface alkali amount measuring method.

< measurement of average Dispersion diameter of calcium titanate particles by TEM Observation >

The average dispersion diameter of the calcium titanate particles in the toner particles was measured by a Transmission Electron Microscope (TEM) as follows.

An Os film (5nm) and a naphthalene film (20nm) as protective films were formed on the toner using an Osmium Plasma Coater (Filgen, inc., OPC80T), and then embedded with a D800 photocurable resin (JEOL Ltd.). Then, a 60nm thick toner particle section was prepared with an ultrasonic ultramicrotome (Leica Microsystems, UC7) at a cutting speed of 1 mm/s.

The circle equivalent diameter of calcium titanate particles measurable in a cross section of 20 randomly selected toner particles was determined, and the arithmetic average value was taken as the average dispersion diameter of the calcium titanate particles in the toner particles.