JP2001166124A - Color paste for color filter, method for producing same and color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of ionic impurities from a color filter and to suppress or prevent defective display by a liquid crystal display. SOLUTION: A pigment adopted by this invention has <=1,000 ppm copper ions in extraction with water. The method for producing a color filter in this invention includes a step for removing all or part of copper ions from a pigment dispersion and/or a color paste by ion exchange. A colored film comprising the produced color paste is disposed every color in a desired pattern shape by an arbitrary number of colors to obtain the color filter in this invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color paste for a color filter, a method of manufacturing a color paste for a color filter, and a color filter. The present invention relates to a method for producing a paste and a color paste, and a color filter for a liquid crystal display using the color paste.

[0002]

2. Description of the Related Art In order to color a liquid crystal display, a color filter in which pixels of three colors of R (red), G (green) and B (blue) are arranged in a line or mosaic on a transparent substrate. Used. For example, a TFT (thin film transistor) color liquid crystal display, which is widely used at present, is a panel in which liquid crystal is sealed between a transparent glass substrate on which a color filter is formed and a transparent glass substrate on which a TFT is formed. Composed of light sources. When light emitted from the backlight passes through the liquid crystal panel, an image is displayed by controlling the transmittance of the light by the voltage applied to the liquid crystal. Since each pixel needs to be similar to the chromaticity characteristics of the CRT phosphor, the pigments are selected to match the light transmission characteristics of the backlight and the liquid crystal display element, and two or more pigments are toned at a fixed ratio. Often used. For example, the color filter R
The (red) pixel is used by selecting two or more kinds of red, orange, and yellow pigments and toning them at a fixed ratio. Similarly G
(Green) pixels are also used by selecting two or more kinds of green, orange, and yellow pigments and toning them. The pigment is selected in consideration of such required chromaticity characteristics, and ionic impurities are not considered much. Generally, commercially available pigments contain many ionic impurities including alkali metals such as sodium, potassium, calcium, and barium. For ionic impurities, particularly sodium and potassium ions, see JP-A-7-1989.
No. 28 discloses a method for producing a color paste containing a total of 0.001 to 80 ppm of alkali metals, sodium and potassium, and a color paste for electronic industry in which all or a part of sodium and potassium are removed by an ion exchange method. ing. The present inventors have found that, among ionic impurities contained in the pigment, free copper contained in the pigment having a copper phthalocyanine skeleton has a relationship with display failure of the liquid crystal display.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a color paste in which specific ionic impurities are reduced and a method for producing the same. It is another object of the present invention to produce a color filter having excellent display performance by using the color paste.

[0004]

The object of the present invention is achieved by the following constitution. (1) A color paste for a color filter, wherein a pigment having a copper content of 1000 ppm or less when extracted with hydrochloric acid is used. (2) The color paste for a color filter according to the above (1), wherein the pigment is a pigment having a copper phthalocyanine skeleton. (3) A color filter comprising a step of removing all or a part of copper ions in a pigment dispersion from a pigment dispersion containing at least a pigment having a copper phthalocyanine skeleton and an organic solvent by an ion exchange method. Production method for color paste. (4) a pigment having at least a copper phthalocyanine skeleton;
A method for producing a color paste for a color filter, comprising a step of removing all or a part of copper ions in a color paste containing an organic solvent and a resin by an ion exchange method. (5) In a color filter having pixels composed of colored layers provided in a desired pattern for each color in an arbitrary number of colors, the colored layer is formed from the color paste described in any of (1) and (2) above. A color filter characterized by being a colored film. (6) A liquid crystal display device using the color filter according to (5).

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pigment used in the present invention is copper extracted with hydrochloric acid at 1000 pp by weight based on the pigment.
It is important that it is less than m. Particularly, a pigment having a copper phthalocyanine skeleton has copper in the molecular structure and usually contains copper as an impurity, and it is important to reduce the amount of free copper eluted. It is considered that copper ions and counter ions of copper ions are ionized in the liquid crystal and adversely affect the display performance of the liquid crystal display. The amount of copper ions extracted with hydrochloric acid is more preferably 800 ppm or less, and most preferably 600 ppm or less. In the present invention, the copper content is not the target, but the eluted free copper. As a method of obtaining such a pigment having a copper phthalocyanine skeleton, there is a method of washing the pigment as described later, but control in the pigment production step is important. That is, phthalic anhydride, urea, and cuprous chloride are used as raw materials for synthesizing a pigment having a copper phthalocyanine skeleton, and it is desirable to suppress the generation of impurity copper during the synthesis of the pigment.

Pigments having a copper phthalocyanine skeleton include pigment blue 15, 15: 1, 1 which is a blue pigment.
5: 2, 15: 3, 15: 4, 15: 6, 17, and Pigment Greens 7, 36, 37, and 38 which are green pigments. The present invention is particularly effective for green pigments among pigments having a copper phthalocyanine skeleton.

Specific examples of the pigment used for the color filter are listed, including the pigment having the copper phthalocyanine skeleton. Pigment Red 9, 9 as a red pigment
7, 122, 123, 144, 149, 166, 16
8, 177, 180, 190, 192, 215, 21
6, 224, etc., as a green pigment, Pigment Green 7, 10, 36, 37, 38, 47, etc., and as a blue pigment, Pigment Blue 15, 15: 1, 15: 2, 1
5: 3, 15: 4, 15: 6, 16, 17, 21, 2
2, 60, 64 and the like, and as yellow pigments, Pigment Yellow 13, 17, 20, 24, 83, 86, 93, 9
4, 95, 109, 110, 117, 125, 129,
137, 138, 139, 150, 153, 154, 1
66, 173 and the like as pigments such as Pigment Violet 19, 23, 29, 30, 32, 33, 36;
37, 38, etc., as the orange pigment, Pigment Orange 13, 31, 36, 38, 40, 42, 43, 51,
55, 59, 61, 64, 65, etc .; pigment blues 15, 16 as indigo pigments; and pigment reds 81, 122, 144, 146, 1 as red pigments.
69, 177 and Pigment Violet 19 can be employed. These pigments may be used alone,
Two or more types may be used in combination. If necessary, the pigment may be subjected to a surface treatment such as a rosin treatment, an acid group treatment, and a basic treatment.

[0008] The resin used in the present invention is for keeping the pigment dispersed therein, and is not particularly limited as long as it is generally used for a paste for a color filter, and any resin can be used. It is. For example, acrylic resin,
Alkyd resin, melamine resin, polyvinyl alcohol,
Various resins such as phenol resin, polyamide, polyamide imide, and polyimide can be used. In particular, a resin dissolved in an alkaline aqueous solution is desirable because the equipment can be simplified in the developing or etching step. Among resins that dissolve in an aqueous alkali solution, a resin having a carboxyl group is preferably used, and specifically, an acrylic resin and a polyimide are preferable in terms of solvent resistance. For polyimide,
Polyimide precursors are more preferred because they function as pigment dispersants. Further, from the viewpoint of heat resistance of the color filter, it is preferable to use polyimide.

In the present invention, the term "polyimide precursor" refers to a polyamic acid or a partially esterified polyamic acid. Polyimide precursor, by heat or chemical treatment,
Form an imide ring. The polyamic acid referred to here is represented by the following general formula (1).

[0010]

Embedded image

Here, R ₁ is a tetravalent organic group having 2 to 22 carbon atoms, R _{2 is a} divalent organic group having 1 to 22 carbon atoms, n is 1 and / or 2, and the weight average molecular weight is at least 2,000. Polymer.

Polyamic acid can be obtained by reacting a tetracarboxylic dianhydride with a diamine. As the tetracarboxylic dianhydride, for example, aliphatic or alicyclic ones can be used, and specific examples thereof include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,5-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-bicyclohexenetetracarboxylic dianhydride, 1,2,
4,5-cyclohexanetetracarboxylic dianhydride,
1,3,3a, 4,5,9b-Hexahydro-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-C] furan-1,3-dione and the like. When an aromatic compound is used, a polyimide precursor composition that can be converted into a polyimide having good heat resistance can be obtained.
4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride Anhydride, 4,4'-oxydiphthalic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3, 3 ', 4,4'-
Paraterphenyltetracarboxylic dianhydride, 3,3
', 4,4'-metaphenylphenyltetracarboxylic dianhydride. Also, if a fluorine-based material is used,
A polyimide precursor composition which can be converted into a polyimide having good transparency in a short wavelength region can be obtained, and specific examples thereof include 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride and the like. Is mentioned. The present invention is not limited to these, and one or more tetracarboxylic dianhydrides are used.

In the present invention, as the diamine, for example, an aliphatic or alicyclic diamine can be used. Specific examples thereof include ethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane,
4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexyl and the like can be mentioned. When an aromatic compound is used, a polyimide precursor composition that can be converted into a polyimide having good heat resistance can be obtained. Specific examples thereof include 4,4′-diaminodiphenyl ether and 3,4′-diaminodiphenyl ether. '-Diaminodiphenyl ether, 4,4'
-Diaminodiphenylmethane, 4,4'-diaminobenzanilide, 3,3'-diaminodiphenylmethane,
4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,5-
Diaminotoluene, 2,6-diaminotoluene, benzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, o-tolidine, 4,4 ″ -diaminoterphenyl, 1,5-diaminonaphthalene, 3, 3 '
-Dimethyl-4,4'-diaminodiphenylmethane,
4,4'-bis (4-aminophenoxy) biphenyl,
2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [ 4- (3-aminophenoxy) phenyl] sulfone and the like. Also,
When a fluorine-based material is used, a polyimide precursor composition that can be converted into a polyimide having good transparency in a short wavelength region can be obtained. As a specific example, 2,2-bis [4- ( 4-aminophenoxy) phenyl] hexafluoropropane and the like.

When siloxane diamine represented by bis-3- (aminopropyl) tetramethylsiloxane is used, the adhesion to an inorganic substrate can be improved. Siloxane diamine is usually 1 to 1 in all diamines.
Used in an amount of 20 mol%. If the amount of siloxane diamine is too small, the effect of improving the adhesiveness will not be exhibited, and if it is too large, the heat resistance will decrease. The present invention is not limited to these, and one or more diamines are used.

The synthesis of polyamic acid is generally carried out by reacting a diamine with a tetracarboxylic dianhydride in a polar organic solvent. At this time, the degree of polymerization of the obtained polyamic acid can be controlled by the mixing ratio of the diamine and the tetracarboxylic dianhydride. In addition, the present invention is also applicable to derivatives such as the above-mentioned esterified products of polyamic acid. Amide polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide and N, N-dimethylformamide are used as the solvent. Polyamic acid is preferably synthesized in a solvent containing lactones as a main component or lactones alone in order to enhance the dispersing effect of the pigment. Here, the solvent containing a lactone as a main component or a lactone alone means that the lactone is contained in 50% by weight or more. Examples of the solvent other than the lactones include methyl cellosolve, ethyl cellosolve, methyl carbitol, ethyl carbitol and the like in addition to the amide-based polar solvent.

Lactones are aliphatic cyclic esters and compounds having 3 to 12 carbon atoms. As specific examples, β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-
Examples include, but are not limited to, caprolactone. Particularly, γ-butyrolactone is preferred in view of the solubility of polyamic acid.

The color paste for a color filter of the present invention contains a pigment, an organic solvent and a resin. The organic solvent used in the present invention is not particularly limited, and a general organic solvent can be used. When polyimide is used as a component of the pixel matrix, it is preferable to use a polyimide precursor for the resin of the color paste, and it is preferable that the solvent used is a solvent that dissolves the polyimide precursor. Solvents for dissolving the polyimide precursor include N, N-dimethylacetamide, N, N
Polar organic solvents such as amides such as -dimethylformamide, lactones such as γ-butyrolactone, and pyrrolidones such as 2-pyrrolidone and N-methyl-2-pyrrolidone. In addition, usually, the polyimide precursor alone does not dissolve, an alcohol such as ethanol, butanol, isopropanol, cellosolves such as methyl cellosolve and ethyl cellosolve, and organic solvents such as propylene glycol derivatives such as propylene glycol monomethyl ether as a polyimide precursor. It can be used by mixing with a solvent that dissolves the body. In order to enhance the effect of dispersing the pigment, a solvent containing a lactone as a main component is preferable. The amount of the solvent used is not particularly limited, but is preferably an amount sufficient to dissolve the resin and an amount having an appropriate viscosity.

The color paste is prepared by directly dispersing the pigment in the resin solution using a disperser, or dispersing the pigment in water or an organic solvent using a disperser to prepare a pigment dispersion. Manufactured by a method of mixing with There is no particular limitation on the method of dispersing the pigment, and a ball mill,
Various methods such as a sand grinder, a three-roll mill, and a high-speed impact mill can be used.

The color paste of the present invention usually comprises a resin:
The pigment is produced in a range of 5: 5 to 8: 2 (weight ratio).

All of the copper ions in the pigment dispersion of the present invention are obtained by ion exchange from a pigment dispersion containing at least a pigment and an organic solvent and / or from a color paste containing at least a pigment, an organic solvent and a resin. A method of obtaining a color paste by removing a part thereof will be described. By using a cation exchange resin having a cation exchange group such as a sulfone group or a carboxylic acid, a cation exchange membrane, a cation exchange fiber or an inorganic cation exchanger, for example, zirconium phosphate, titanium phosphate, etc. Copper ions can be adsorbed or ion-exchanged from a pigment dispersion containing an organic solvent, a pigment dispersion containing a resin, or a color paste, and the amount thereof can be reduced.

An example of an ion exchange method using an ion exchange resin is as follows. A column is filled with a granular ion exchange resin, a pigment dispersion or a color paste is flowed into the column, and copper ions are adsorbed or ion-exchanged. Can be reduced. There is also a method in which a pigment dispersion or a color paste and a granular ion exchange resin are mixed and stirred, and then the ion exchange resin is removed by filtration or the like.
A method of simultaneously performing ion exchange while dispersing the pigment is preferable because the removal effect is large. For example, a mill-type disperser filled with ceramic beads such as alumina or zirconia can be directly connected to a column filled with a granular ion-exchange resin to simultaneously perform ion exchange while dispersing the pigment. In addition, ion exchange of the color paste is preferable because copper ions dissolved after the formation of the color paste can be removed from the pigment dispersion.

While the above has described examples of the ion exchange method using an ion exchange resin, the present invention is not limited to these individual methods, and any ion exchange method can be used.

In addition to the ion exchange method, there is a method of repeatedly washing the pigment with pure water or an organic solvent. For example, pure water and a pigment are mixed, stirred, and allowed to stand to precipitate the pigment. After removing the supernatant, and after adding pure water and stirring, the pigment is precipitated and the supernatant is removed. By repeating this several times and then drying, copper ions in the pigment can be reduced. Further, a method using a continuous extractor such as Soxhlet or a method such as dialysis can be used.

In the present invention, the anion is removed after or simultaneously with the step of removing all or a part of the copper ions in the pigment dispersion from the pigment dispersion containing at least the pigment and the organic solvent by an ion exchange method. A removal step may be included as appropriate.

Specifically, the anion exchange is carried out by using an anion exchange resin having an anion exchange group of a tertiary amino group and / or a quaternary ammonium group, an anion exchange membrane, an anion exchange fiber or an inorganic anion exchange fiber. By using an ion exchanger,
Anions can be adsorbed or ion-exchanged to reduce the amount.

For the purpose of improving the applicability of the color paste and the uniformity of the surface of the colored film or the dispersibility of the pigment, a surfactant may be added to the color paste of the present invention. it can.

The method of applying the color paste on the substrate includes a method of applying the color paste to the substrate by a spin coater, a per coater, a blade coater, a roll coater, a die coater, a screen printing method, etc., a method of dipping the substrate in the color paste, Various methods such as spraying a color paste on a substrate can be used.

As the substrate, a transparent substrate such as soda glass, non-alkali glass, borosilicate glass, and quartz glass is usually used, but is not particularly limited thereto. In the case of applying a color paste on a substrate, if the surface of the substrate is treated with an adhesion aid such as a silane coupling agent, the adhesion between the colored film and the substrate can be improved.

The thickness of the colored film formed using the color paste is not particularly limited, but is usually 0.1 to 10 μm.
m, preferably 0.5 to 5 μm. If the film thickness is too small, light absorption will be too small, and the optical characteristics as a color filter will not be satisfied. If the film thickness is too large, on the contrary, problems such as excessive absorption of light may occur, and the optical characteristics as a color filter may not be satisfied.

Next, an example of a method of manufacturing a color filter in the case of using polyimide as a resin component of a pixel matrix and using polyamic acid as a precursor thereof will be described.
After applying the color paste on the transparent substrate by the method described above, a polyimide precursor colored film is formed by air drying, heating drying, vacuum drying, or the like. In the case of heating and drying, use an oven, a hot plate, etc., at 50 to 180 ° C.
, More preferably 30 seconds to 3 at 80 to 120 ° C.
Do time. When the temperature is too low, the solvent does not readily evaporate. Conversely, when the temperature is too high, the solubility in the developer decreases. A pattern is formed on the thus obtained polyimide precursor colored film by ordinary wet etching.
First, a positive photoresist is applied on the polyimide precursor colored film to form a photoresist film. Subsequently, a mask is placed on the photoresist film, and ultraviolet light is irradiated using an exposure device. After the exposure, the photoresist coating and the polyimide precursor colored film are simultaneously etched with a positive photoresist alkaline developer. After the etching, the unnecessary photoresist film is removed.

Thereafter, the polyimide precursor colored film is converted into a polyimide colored film by performing a heat treatment. The heat treatment is usually performed in air, in a nitrogen atmosphere, or in a vacuum, at 150 to 450 ° C., preferably 1 to 450 ° C.
It is carried out continuously or stepwise at a temperature of 80 to 350 ° C, more preferably 200 to 320 ° C for 0.5 to 5 hours. The above steps are performed for three color pastes of R (red), G (green), B (blue) or Y (yellow), M (magenta), and C (cyan) and, if necessary, black color paste. Do.
A pigment having a copper phthalocyanine skeleton is also used for cyan.

A transparent protective film can be formed on the colored layer, if necessary. As the resin used for the transparent protective film, an epoxy resin, an acrylic resin, a urethane resin, a polyester resin, a polyimide resin, a polyolefin resin, and gelatin are preferably used. A resin having a heat resistance that can withstand such heat in a liquid crystal display device manufacturing process is preferable, and a resin having a resistance to an organic solvent used in a liquid crystal display device manufacturing device is preferable. Preferably, an epoxy resin or an acrylic resin is used.

As a method of applying the transparent protective film, a dip method, a roll coater method, a spinner method, a die coating method, a method using a wire bar, and the like are preferably used, as in the case of the colored paste. Heat and dry using a hot plate. At this time, vacuum drying and preliminary heating drying (semi-curing) may be performed as needed for the purpose of improving the leveling property. The semi-curing conditions vary depending on the resin, solvent and paste applied amount, but it is usually preferable to heat at 60 to 200 ° C. for 1 to 60 minutes. The curing conditions at the time of heating and drying are different depending on the resin. When a polyimide resin is obtained from the precursor, the curing condition is slightly different depending on the amount of application, but usually 200 to 300.
It is common to heat at 1C for 1 to 60 minutes.

An overcoat made of a transparent resin may be provided on the colored films of the three primary colors for the purpose of improving the flatness. On the other hand, there is a disadvantage in that the cost is increased due to an increase in the number of layers. The present invention is particularly effective when there is no overcoat covering the colored film. STN method, T
When the N method, the vertical alignment method, or the like is adopted, a transparent conductive film for driving a liquid crystal is formed on the colored film. A metal oxide thin film such as an ITO film is suitably used for the transparent conductive film.

A black matrix may be formed around a pixel in order to improve the contrast. In view of low reflectivity and environmental friendliness without using chromium, there are increasing examples of producing a black matrix with a black paste in which a light shielding material is dispersed in a resin. In some cases, a pigment is added to a black paste for a black matrix in order to flatten the spectrum and achieve neutral black.

The color filter of the present invention has the same effect not only in a transmissive liquid crystal display device having a backlight but also in a reflective liquid crystal display device which uses external light by reflecting it. Further, the present invention has an effect of reducing display defects even if a color filter is formed on either side of a transparent substrate sandwiching a liquid crystal. When a color filter is formed on the substrate side on which active elements such as TFTs are formed (color filter on array: COA), the active elements are provided under the colored layer in order to improve the aperture ratio and prevent a voltage drop due to the insulating film. And through the through hole formed in the colored layer,
In general, a transparent conductive film on a colored layer or a reflective electrode is electrically connected to an active element. In this configuration,
When a through hole is formed in a colored film, a pigment is easily formed on the inner wall of the through hole and exposed to the liquid crystal without being wrapped by the resin, and a voltage stress for driving the liquid crystal is applied, so that impurities are easily eluted. Further, the transparent conductive film serving as the pixel electrode is divided for each pixel, and a portion where the colored layer between the pixels is in direct contact with the liquid crystal is formed, so that the effect of the present invention is particularly large. Further, when a color filter is provided on the substrate on the side opposite to the substrate provided with the active elements, it is possible to cover the entire colored film with an overcoat made of a transparent resin and reduce elution of impurities from the pigment. However, in the case of COA, the fact that the above-mentioned through-hole portion cannot be covered with the overcoat is also one of the reasons why the effect of the present invention is great in COA.

The color liquid crystal display device of the present invention can be used for displaying personal computers, word processors, engineering workstations, navigation systems, televisions, videos and the like, and can also be used as a light modulation device.

[0038]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The specific method of the measuring method described in the examples is as follows.

(Measurement Method) Measurement of Free Copper Concentration 1 g of the pigment was placed in a container, 50 ml of hydrochloric acid was added thereto, and the container was sealed.
Ultrasonic waves were applied for 0 minutes. Next, the pigment was removed from the solution by a centrifuge to obtain an extract. This extract was analyzed by the atomic absorption method to determine the amount of copper atoms. The concentration was indicated by the weight ratio to the pigment used.

Display Quality A color paste to be evaluated is applied on a non-alkali glass, dried and cured. On top of this, a 0.1 μm thick I
After forming the TO film on the entire surface, by photosonography,
A hole having a diameter of 100 μm is formed in the ITO film. That is,
After a photoresist is applied on the ITO film and prebaked, the mask pattern is exposed, and the photoresist is immersed in a developer and developed. The sample is washed with water, post-baked, and immersed in an etching solution of ferric chloride: nitric acid = 1: 1 to form holes in the ITO film. The photoresist is stripped with a stripper, washed with water and dried. Separately, a substrate in which an ITO film is formed on the entire surface of non-alkali glass is prepared as a counter substrate. An alignment film is printed and rubbed on the substrate (colored layer substrate) to which the color paste is applied and the counter substrate to be aligned. After bonding these two substrates with a sealant into which a microrod is kneaded, TN liquid crystal is injected and the liquid crystal injection port is closed with a sealing agent. The liquid crystal cell thus obtained is driven in an atmosphere of 60 ° C. with a rectangular wave of ± 4 V, 30 Hz for 24 hours, and the display is observed between polarizing films arranged orthogonally. When impurities are eluted from the holes formed in the ITO film of the colored layer substrate and ionic impurities are generated, the threshold is lowered, so that the periphery of the holes appears darker than other parts in gray level display. It is desirable that the threshold voltage does not decrease due to ionic impurities.

Measurement of Voltage Holding Ratio The voltage holding ratio was measured as a measurement value related to the amount of ionic impurities eluted from the pigment into the liquid crystal. 15 μg of a solution in which the pigment was dispersed in isopropyl alcohol at a concentration of 1% was dropped and dried on the alkali-free glass having the ITO film pattern formed thereon. This glass substrate and another non-alkali glass substrate on which an ITO film pattern is formed are bonded with a sealing agent into which a microrod is kneaded, and then TN liquid crystal is injected, and the liquid crystal injection port is closed with a sealing agent. The liquid crystal cell thus obtained was subjected to ± 4 V, 30 H in an atmosphere of 60 ° C.
After driving for 24 hours with a rectangular wave of z, the voltage holding ratio is measured. Charging time 60μsec, voltage holding time 16.7m
Second, the liquid crystal cell temperature was set to 90 ° C. The maximum voltage holding ratio is 100%, and a larger value indicates a smaller ionic impurity elution amount.

Reference Example 1 Synthesis of Polymer Dispersant 161.93 g of 4,4'-diaminobenzanilide
3,3'-diaminodiphenyl sulfone 176.70
g, and 18.64 g of bis (3-aminopropyl) tetramethyldisiloxane with γ-butyrolactone 3266
g, N-methyl-2-pyrrolidone (622 g), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (439.09 g) was added, and the mixture was reacted at 70 ° C. for 3 hours. .22 g and then at 70 ° C.
For 1 hour and then a viscosity of 45 poise (25 ° C.)
A 17% solution (P-1) of a polymer dispersant was obtained.

Examples 1 and 2 and Comparative Examples 1 and 2 Four types of pigment green 36, which is a green pigment having a copper phthalocyanine skeleton, were prepared. When the green pigment was extracted with hydrochloric acid and copper was measured, the copper extracted from the green pigments A, B, C, and D was 550 ppm, 760 ppm, and 1 ppm, respectively.
It was 300 ppm and 1920 ppm. These differences are considered to reflect some differences in the pigment production process. 83.79 g of pigments A to D were weighed, 4.41 g of a dispersant “SOLSPERS” 12000 manufactured by Zeneca, 557 g of γ-butyrolactone, 323 g of 3-methoxy-5-methyl-1-butanol, and a polymer dispersant ( 494 g of P-1) was placed in a mill type disperser together with zirconia beads, and dispersed at 3000 rpm for 2 hours to obtain two kinds of dispersion liquids. 300 g of the dispersion and 156.3 g of the polymer dispersant (P-1) were added to γ-butyrolactone 19
8.3 g and a solution diluted with 185.3 g of 3-methoxy-3-methyl-1-butanol were mixed to obtain a green color paste. Using the colored layer substrate, 10 liquid crystal cells were prepared for each pigment, and the display quality was examined.
Table 1 shows the results.

[0044]

[Table 1]

As shown in Table 1, in Comparative Example 1 (Pigment C) and Comparative Example 2 (Pigment D) in which a large amount of copper was extracted, the voltage holding ratio was small and defective. In the gray level display due to the lowering of the threshold value, which is considered to be caused by the generation of impurities, many of the holes of the ITO film of the colored layer substrate were observed to be darker than their surroundings. It was big.

Example 3 In preparing a dispersion using the pigment C with the same composition as in Comparative Example 1, a mill type disperser filled with zirconia beads and a column filled with a cation exchange resin "DIAION" CR20 were used. They were connected by a pipe, and ion exchange was performed while dispersing the pigment. The dispersion was made into a color paste in the same manner as in Comparative Example 1. When the display quality was examined by assembling a liquid crystal cell using a colored layer substrate coated with the color paste on glass, 10% of the liquid crystal cells in which the hole portion of the ITO film of the colored layer substrate was observed to be darker than its surroundings were observed. Two of the cells,
An improvement was observed as compared with Comparative Example 1.

Example 4 A cation exchange resin "DIAION" CR20 was added to 500 g of a green color paste having the same composition as Comparative Example 1 and using Pigment C.
And stirred for 3 hours. The ion exchange resin was removed from the color paste by filtration. The color paste was applied to glass, dried and cured, and a liquid crystal cell was assembled using the colored layer substrate. The display quality was examined.
The number of the liquid crystal cells in which the hole portion of the TO film was darker than the periphery thereof was 2 out of 20 cells, which was an improvement as compared with Comparative Example 1.

Example 5, Comparative Example 3 Two kinds of pigment blue 15: 6, which are blue pigments having a copper phthalocyanine skeleton, were prepared. When the blue pigment was extracted with hydrochloric acid and copper was measured, the copper extracted from the blue pigments A and B was 520 ppm (Example 5) and 1220 pp, respectively.
m (Comparative Example 3). When the voltage holding ratios of the blue pigments A and B were measured, the blue pigment A was 44%, and the blue pigment B was 3%.
%, And the blue pigment B having a large amount of free copper had a small voltage holding ratio and was defective.

[0049]

According to the present invention, it is possible to suppress and prevent display defects of a liquid crystal display by reducing the amount of copper that is eluted in a free state among the coppers contained in the pigment. It is considered that copper ions and their counter ions are ionized in the liquid crystal, leading to display failure.

Claims (6)

[Claims] 1. A color paste for a color filter, wherein a pigment in which copper extracted with hydrochloric acid is 1000 ppm or less is employed. 2. The color paste for a color filter according to claim 1, wherein the pigment is a pigment having a copper phthalocyanine skeleton. 3. A method comprising the step of removing all or a part of copper ions of a pigment dispersion from a pigment dispersion containing at least a pigment having a copper phthalocyanine skeleton and an organic solvent by an ion exchange method. A method for producing a color paste for a color filter. 4. A process for removing all or a portion of copper ions in a color paste from a color paste containing at least a pigment having a copper phthalocyanine skeleton, an organic solvent and a resin by an ion exchange method. A method for producing a color paste for a color filter. 5. A color filter having pixels of a color layer provided in a desired pattern for each color in an arbitrary number of colors, wherein the color layer is made of the color paste according to claim 1. A color filter characterized by being a colored film. 6. A liquid crystal display device using the color filter according to claim 5.