JP2000056123A - Pigment for color filter and color paste, color filter, liquid crystal display device and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment and a color paste in which a material having possibility of causing display irregularity of a liq. crystal display device is reduced and to provide a liq. crystal display device hardly generating display irregularity. SOLUTION: A pigment for a color filter contains a compd. which has a cyanobenzen skeleton or ultra-violet absorptions at 2.2×102 nm, 2.6×102 nm and 2.9×102 nm at a concn. of <=10 ppm for the pigment, and a color paste is obtained by using the pigment. And the color paste for the color filter has a characteristics that the compd. which has the cyanobenzen skeleton or the ultra-violet absorptions at 2.2×102 nm, 2.6×102 nm and 2.9×102 nm, is contained at a concn. of <=0.5 ppm for the color paste. And production of the pigment for the color filter and the color paste include a purification treatment with an adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment for a color filter, a color paste for a color filter, and a method for producing the same. The present invention relates to color pastes and methods for producing them.

[0002]

2. Description of the Related Art A color liquid crystal display device (liquid crystal display) is composed of R (red), G (green), B (blue) or Y (red).
An image is displayed by changing the transmittance of each pixel using a color filter including three colors (yellow), M (magenta), and C (cyan) and a black matrix. The characteristics required for a color filter are mainly transmittance, contrast, and color purity, and pigments and color pastes used for the color filter are also prepared for the purpose. For example, for the R (red) pixel of the color filter, two or more kinds of red, orange, and yellow pigments are selected and used 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.

[0003]

The pigment is selected in consideration of the required chromaticity characteristics as described above, and the effects of additives and impurities other than the pigment itself on the display characteristics of the liquid crystal display element are deeply considered. It has not been. In general, commercially available pigments and color pastes include compounds for suppressing crystal growth and pigment derivatives for improving dispersibility.
It contains a dispersing aid and the like. Among these additives and impurities generated in the pigment manufacturing process, those that deteriorate the display characteristics of the liquid crystal display element are included.

An object of the present invention is to provide a pigment and a color paste in which substances causing display unevenness of a liquid crystal display element are reduced, and to provide a liquid crystal display element in which display unevenness hardly occurs.

[0005]

An object of the present invention is to provide a compound having a cyanobenzene skeleton or 2.2 × 10 ² nm,
This is achieved by a color filter pigment and a color filter color paste using the same, wherein the compound having ultraviolet absorption at × 10 ² nm and 2.9 × 10 ² nm has a concentration of 10 ppm or less based on the pigment. .

Another object of the present invention is to provide a compound having a cyanobenzene skeleton or a compound having ultraviolet absorption at 2.2 × 10 ² nm, 2.6 × 10 ² nm and 2.9 × 10 ² nm in an amount of 0.5 ppm with respect to the color paste. This is achieved by a color paste for a color filter, which has the following density.

Further, the object of the present invention is achieved by a color filter and a liquid crystal display device using the above color paste for a color filter.

The object of the present invention is attained by a method for producing a pigment for a color filter and a method for producing a color paste for a color filter, which comprises purifying with an adsorbent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The color paste for a color filter of the present invention contains at least a pigment, an organic solvent and a resin, and is usually produced in a range of resin: pigment = 5: 5 to 8: 2 (weight ratio). You. As the pigment used in the present invention, a general pigment can be used.In addition to selecting a pigment that matches the reduction of display unevenness which is the object of the present invention, light resistance,
Those excellent in heat resistance, chemical resistance and the like are desirable. Specific examples of typical pigments are indicated by color index numbers. Examples of yellow pigments include Pigment Yellow 20,
24, 83, 86, 93, 94, 109, 110, 11
7, 125, 129, 137, 138, 139, 14
7, 148, 153, 154, 166, 173 and the like. Examples of orange pigments include Pigment Orange 13, 31, 36, 38, 40, 42, 43, 51, 5
5, 59, 61, 64, 65 and the like. Examples of red pigments include Pigment Red 9, 97, 122,
123, 144, 149, 166, 168, 177, 1
90, 192, 215, 216, 224 and the like. Examples of purple pigments include Pigment Violet 1
9, 23, 29, 32, 33, 36, 37, 38 and the like. Pigment Blue 1 is an example of a blue pigment.
5 (15: 3, 15: 4, 15: 6, etc.), 21, 2
2, 60, 64 and the like. Examples of green pigments include pigments 7, 10, 36, 47, and the like.

The pigment may be treated with rosin if necessary.
Although those which have been subjected to a surface treatment such as an acidic group treatment or a basic group treatment may be used, those which meet the purpose of the present invention for reducing display unevenness are selected.

The present inventors have found that, among the impurities contained in the pigment and the color paste, a compound having a cyanobenzene skeleton has a serious adverse effect on the display characteristics of a liquid crystal display device. Here, the term “impurities” includes not only impurities generated in the pigment manufacturing process but also additives to the pigment and the color paste.

In the pigment of the present invention, it is important that the compound having a cyanobenzene skeleton is not more than 10 ppm by weight based on the pigment. It is more preferably at most 5 ppm, most preferably at most 2 ppm. The compound is soluble in the liquid crystal and 10 p
It has been clarified by the inventors of the present invention that the case where the content exceeds pm significantly affects the display unevenness of the liquid crystal display element. The compound having a cyanobenzene skeleton is
It is mainly a compound group represented by the following structural formula (1).
A compound having such a structure has ultraviolet absorption at 2.2 × 10 ² nm, 2.6 × 10 ² nm, and 2.9 × 10 ² nm in an acetonitrile-water mixed solvent. In particular, pigments having a phthalocyanine skeleton tend to contain a large amount of the compound, which greatly affects display unevenness of a liquid crystal display element, and thus the present invention is important.

[0013]

Embedded image (Including those in which some of the above compounds are substituted with halogen elements)

The pigments having a phthalocyanine skeleton include:
Pigment Blue 15 (15: 1, 15: 2, 15:
3, 15: 4, 15: 6), 16, 17, and Pigment Green 7, 36, 37, 38.

The method for producing the pigment of the present invention includes washing with water or an organic solvent, washing with an ion-exchange resin or the like, and recrystallization of the pigment after dissolving the pigment in sulfuric acid or the like. Washing using water or an organic solvent includes continuous or batch washing with a Soxhlet extractor or the like. Further, strengthening of washing with water, hot water or an organic solvent in a filter press device in the pigment production process is also effective. If the washing with the filter press is performed after the pigment is once dispersed in the dispersion, the effect of the washing can be enhanced. When cleaning is performed by raising the temperature of the cleaning solution,
The release of impurities from the pigment easily occurs, and the cleaning effect can be enhanced. When performing pigment washing, in an organic solvent,
It is effective to make the pigment finer or to apply it while applying ultrasonic waves. For example, while making the pigment finer with a disperser,
A method in which an organic solvent serving as a matrix is circulated in a column filled with an adsorbent, an ion-exchange resin, and the like is given. By going through these washing steps, it is possible to produce a color filter pigment having a reduced effect on display characteristics.

It is preferable to remove and purify the impurities by adsorbing them with an adsorbent because the cleaning effect is high. Washing using an adsorbent can be used by circulating a washing solution, and is also preferable in that a large amount of washing solution is not used.

As the adsorbent, natural zeolite, clay,
Acid clay, synthetic zeolite, silica gel, alumina, porous glass, natural activated carbon, synthetic activated carbon, resin adsorbent, chelate resin, ion exchange resin, etc. can be employed. The shape of the adsorbent is not particularly limited, and may be any of powdery, granular, fibrous, and processed and shaped products thereof. If necessary, a surface treatment such as a hydrophobic treatment, a hydrophilic treatment, a basic treatment, an acid treatment, a neutral treatment, and an attachment of a chemical agent may be used. The pore size distribution of the adsorbent preferably has a large distribution amount of 2 nm or less, and particularly preferably has a large distribution amount of 1.5 nm or less.
Among these adsorbents, activated carbon is particularly effective because it has adsorption sites of various sizes and can adsorb various types of impurities. The activated carbon used is desirably a high-hardness carbon fiber or an activated carbon fiber having excellent friction resistance in order to prevent the activated carbon from being mixed into the color paste.

The color paste of the present invention contains at least a pigment, an organic solvent and a resin, and the compound having a cyanobenzene skeleton is preferably 0.5 ppm or less, more preferably 0.1 ppm or less, based on the paste. It is even more desirable. When the compound is contained in an amount exceeding 0.5 ppm by weight with respect to the color paste, display unevenness of the liquid crystal display element is easily caused.

The color paste of the present invention can be produced by adding an organic solvent, a resin for dispersing and retaining the pigment, and an additive such as a surfactant to the pigment having undergone the above-mentioned washing process. A resin and an additive that match the reduction in display unevenness, which is the object of the present invention, are selected. Also, after adding an adsorbent, ion exchange resin, etc. to the color paste made of unwashed pigment to remove impurities in the paste,
By filtering, a color paste having a reduced effect on display characteristics can be manufactured.

The organic solvent used in the present invention is not particularly limited, and a general organic solvent can be used. When using polyimide as the resin of the present invention,
As the resin of the color paste, it is preferable to use a polyimide precursor, and the solvent used in this case is preferably a solvent that dissolves the polyimide precursor. Examples of the solvent for dissolving the polyimide precursor include amides such as N, N-dimethylacetamide and N, N-dimethylformamide, lactones such as γ-butyrolactone, and pyrrolidones such as 2-pyrrolidone and N-methyl-2-pyrrolidone. And polar organic solvents such as 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 resin used in the present invention is for dispersing and holding the pigment, and is not particularly limited as long as it is a resin generally used for a paste for a color filter, and any resin can be used. is there. 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 product obtained by esterifying a part thereof. Polyimide precursor, by heat or chemical treatment,
Form an imide ring. The polyamic acid mentioned here is represented by the following general formula (2).

[0023]

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,
It is a polymer having a weight average molecular weight of at least 2000.

The 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, for example, aliphatic or alicyclic diamines can be used as the diamine, and 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.
Use 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 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 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.

A surfactant can be added to the color paste of the present invention for the purpose of improving the applicability of the color paste and the uniformity of the surface of the colored film or for improving the dispersibility of the pigment. .

As a method of applying the color paste on the substrate, a method of applying the color paste to the substrate by a spin coater, a bar coater, a blade coater, a roll coater, a die coater, a screen printing method, or the like, or 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 a soda glass, an alkali-free glass, a borosilicate glass, a quartz glass, and a polymer film is generally 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 for 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 the color paste is applied on the transparent substrate by the method described above, a polyimide precursor colored film is formed by air drying, heat drying, vacuum drying, or the like. In the case of heating and drying, use an oven, hot plate, etc.
To 180 ° C, more preferably 80 to 120 ° C for 30 seconds to 3 hours. 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. When the above steps are performed for three color pastes of R (red), G (green), and B (blue) and, if necessary, a black color paste, a color filter for a liquid crystal display element can be manufactured.

Here, the formation of a colored film on a transparent substrate has been described. However, the present invention is also applicable to a so-called color filter-on-array in which a colored film is formed on a driving substrate such as a TFT, a MIM, and a segment electrode. The same applies. Further, the present invention is not limited to the type of the liquid crystal display element, and is applicable to any of a transmission type, a reflection type and a projection type liquid crystal display element. The use of the liquid crystal display element of the present invention is
The present invention is not particularly limited, and is used for a notebook PC monitor, a desktop monitor, a portable terminal, a vehicle monitor, a projection type liquid crystal display, and the like.

[0037]

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 measurement method described in the examples is as follows.

(Measurement of Impurity Concentration) As for the pigment, 50 g of the pigment is weighed and washed with 250 g of ethyl formate for 5 hours using a Soxhlet extractor which is a kind of a continuous extractor. Next, the obtained washing liquid is mixed with the same amount of purified water, and separated into a water phase and an ethyl formate phase using a separating funnel. The compound having a cyanobenzene skeleton is contained in the ethyl formate phase.
The solution of the ethyl formate phase is vacuum dried to obtain a pigment impurity component. The impurity component is dissolved in 25 g of acetonitrile, and the impurity component is separated using high-performance liquid chromatography for separation. For the measurement of high performance liquid chromatography, a mixed solvent of water and acetonitrile was used, and LC-10A manufactured by Shimadzu Corporation was used. The separation column was kept at 45 ° C. during the measurement, and “Inertsil ODS-2” manufactured by GL Science Co., Ltd. was used. The collected compound is put in a container which has been measured in advance, dried in vacuum, and the solvent component is removed. The container is weighed again to determine the amount of the separated impurities, and the concentration for the pigment is determined.

When the amount of impurities is too small to measure easily, a solution having a known concentration is diluted or concentrated, and a calibration curve is prepared using a spectrophotometer or high performance liquid chromatography. Next, the target solution is measured to determine the solution concentration.

The separated impurities were analyzed by UV spectrum (LC-10A manufactured by Shimadzu Corporation), IR spectrum (FTIR-8600PC manufactured by Shimadzu Corporation), NMR spectrum (DRX-500 manufactured by Bruker), mass spectrum (JMS-DX303 manufactured by JEOL Ltd.) and the like to identify the structure.

With respect to the color paste, the impurity concentration was measured as follows. Ethyl formate 5 in 100 g of paste
0 g is gently added to agglomerate the polymer component contained in the paste. The container is sealed, and the polymer and pigment components agglomerated are dispersed by an ultrasonic cleaner for 15 minutes, and heated in an oven at 60 ° C. for 5 hours. The dispersion is filtered using a 1 μm filter to remove solids. The filtered turbid solution is further completely removed of solids using a 0.2 μm filter, and then the solvent component is removed by a vacuum dryer. Again, 10 g of ethyl formate is added, and after filtration using a 0.2 μm syringe filter, the same amount of purified water is added, and the mixture is separated into an ethyl formate phase and an aqueous phase. The ethyl formate phase is analyzed using high performance liquid chromatography in the same manner as described above, and the concentration with respect to the paste is determined.

(Evaluation of Deterioration of Display Quality by Impurities) After forming an ITO film on non-alkali glass, an alignment film is printed and a rubbing treatment is performed. Extraction liquid obtained from the pigment using a Soxhlet extractor is subjected to separation treatment such as separation using a separation funnel and separation by high performance liquid chromatography, and then 10 μl is collected and dropped on the alignment film. I do. The concentration of the solution at that time is 50 g of ethyl formate per 10 g of the extract from the pigment. 90
Place in a clean oven at ゜ C to evaporate the solvent component. A non-alkali glass substrate on which an ITO film is separately prepared is used as a counter substrate, and the substrates are bonded to each other with a sealant into which micro rods are kneaded. TN compatible with 4V drive
Liquid crystal is injected and the liquid crystal injection port is closed with a sealing agent. The obtained liquid crystal cell is sandwiched between polarizing films arranged orthogonally.
V, 30Hz square wave is applied for 48 hours, then 2V,
A 30 Hz rectangular wave is applied and the display is observed. If impurities are eluted into the liquid crystal, when 2 V halftone display is performed,
The area around the drop site appears darker than the other areas.

The evaluation of the color paste is performed in a state where the color paste is applied on a non-alkali glass, dried and cured. A 0.1 μm thick I
After forming the TO film on the entire surface, by photolithography
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. These two substrates are bonded together with a sealing agent into which a microrod is kneaded, and then a TN liquid crystal capable of driving at 4 V is injected, and the liquid crystal injection port is closed with the sealing agent. The liquid crystal cell thus obtained was kept at 60 ° C., and ± 1 V, 30 Hz rectangular wave
After driving for 00 hours, 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, the peripheries of the holes appear darker in halftone display than other portions. This is the display unevenness,
The threshold voltage of the voltage-transmittance curve is lowered.

(Measurement of Voltage-Transmittance Curve) A liquid crystal cell which has been subjected to a rubbing treatment and into which liquid crystal has been injected is sandwiched between orthogonal polarizing films and arranged on a backlight. A voltage is applied to the liquid crystal cell using a function generator (3325A manufactured by Hewlett-Packard Company) using an AC rectangular wave of 30 Hz. By changing the applied voltage, the color luminance meter BM-5A
(Manufactured by Topcon Corporation), and the luminance of transmitted light is measured. 4
Using a TN liquid crystal compatible with V drive, when the luminance at an applied voltage of 4 V is 0 and the luminance at an applied voltage of 0 V is 100, a voltage at which the luminance becomes 50 is defined as a threshold voltage.

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.

Reference Example 2 Synthesis of oligomer dispersant 204.79 g of 3,3'-diaminodiphenyl sulfone
And 13.62 g of bis (3-aminopropyl) tetramethyldisiloxane were charged together with 3809 g of γ-butyrolactone, 59.98 g of pyromellitic dihydrate, 3,
295.6 g of 3 ', 4,4'-diphenylsulfonetetracarboxylic acid dihydrate was added and reacted at 60 ° C for 3 hours, and 98.22 g of 2-aminoanthraquinone was added.
Further, the reaction was carried out at 60 ° C. for 1 hour.
% Solution (O-1) was obtained.

Reference Example 3 Synthesis of Polyamic Acid 144.1 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dihydrate was combined with 1095 g of γ-butyrolactone and N-
Charged with 209 g of methyl-2-pyrrolidone,
95.1 g of 4'-diaminodiphenyl ether and 6.20 g of bis (3-aminopropyl) tetramethyldisiloxane were added and reacted at 70 ° C. for 3 hours, and 2.96 g of phthalic anhydride was added. For 1 hour to obtain a 16% solution of polyamic acid (PAA1).

Reference Example 4 Synthesis of polyamic acid 372.4 g of 3,3'-diaminodiphenyl sulfone
146.0 g of paraphenylenediamine and bis (3
-Aminopropyl) tetramethyldisiloxane 32.3
g in 5750 g of N-methyl-2-pyrrolidone,
After adding 873.9 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and reacting at 70 ° C. for 3 hours, adding 5.88 g of maleic anhydride and further adding 70 ° C.
For 1 hour, and a 20% solution of polyamic acid (PAA
2) was obtained.

Reference Example 5 50 g of a green pigment having a phthalocyanine skeleton, Pigment Green 36, was weighed, and washed with 250 g of ethyl formate for 5 hours using a Soxhlet extractor. Next, the ethyl formate solution was mixed with the same amount of purified water, and separated into a water phase and an ethyl formate phase using a separating funnel. The solution of the ethyl formate phase was separated using high performance liquid chromatography. The fractions separated into the respective components were freeze-dried and redissolved in 10 times the volume of ethyl formate of the sample solution injected into the high performance liquid chromatography. The re-dissolved solution obtained was dropped on the alignment film, and the display quality was examined. As a result, a compound having a cyanobenzene skeleton having ultraviolet absorption at 2.2 × 10 ² nm, 2.6 × 10 ² nm, and 2.9 × 10 ² nm in a water-acetonitrile mixed solvent (hereinafter referred to as Compound A)
In the liquid crystal cell in which the liquid crystal cell was dropped, the periphery of the dropped portion was observed to be darker when a halftone display was performed, and a large decrease (about 200 mV) was observed in the threshold voltage of the voltage-transmittance curve. On the other hand, in the liquid crystal cell in which the compound other than the compound A was dropped, the decrease in the threshold voltage was small (10 mV or less) or was not observed.

Example 1, Comparative Example 1 50 g of Pigment Green 36 (Pigment B) was weighed and washed with 250 g of ethyl formate for 5 hours using a Soxhlet extractor. Next, the ethyl formate solution was mixed with the same amount of purified water, and separated into a water phase and an ethyl formate phase using a separating funnel. The concentration of Compound A with respect to the pigment was 60 ppm. The display quality was examined by dropping a solution of the ethyl formate phase on the alignment film. As a result, when displaying halftones,
The periphery of the dropping site was observed darker, and a large decrease (about 200 mV) was observed in the threshold voltage of the voltage-transmittance curve (Comparative Example 1).

100 g of Pigment Green 36 is weighed, and 500 g of ethyl formate is added using a Soxhlet extractor.
For 5 hours. Next, the obtained pigment cake was dried in an oven at 80 ° C. and ground in an automatic mortar. Again, the pigment was added to a Soxhlet extractor using ethyl formate 500
g for 5 hours. Such a washing step was repeated five times to obtain a pigment with reduced impurities (Pigment A). The concentration of Compound A with respect to the pigment was determined to be 8 ppm. As a result of dropping the extract onto the alignment film in the same manner as in the case of Pigment B, the decrease in the threshold voltage was reduced to about 30 mV, and improvement was observed (Example 1).

Examples 2 and 3 100 g of Pigment Green 36 was weighed, 1900 g of γ-butyrolactone was added, and the mixture was dispersed together with zirconia beads in a mill-type dispersing machine. Dispersion 1 obtained
Activated carbon fiber "Cractive" grade 15 for 000g
25 g (Kuraray Chemical Co., Ltd.)
For 6 hours. 2 hours after the start of stirring, the dispersion 2
Of the obtained dispersion at 80 ° C. for 1 hour.
After vacuum drying for 2 hours, 10 g of the washed pigment was obtained (Pigment D). Also, 6 hours after the start of stirring, the dispersion 2
Of the obtained dispersion at 80 ° C. for 1 hour.
After vacuum drying for 2 hours, 10 g of the washed pigment was obtained (Pigment C). When the concentration of the compound A with respect to the pigment was determined, it was 1 ppm and 4 ppm for the pigments C and D.

10 g of each of the pigments C and D was added to ethyl formate 5
Washed with 0 g using a Soxhlet extractor for 5 hours.
Next, the obtained ethyl formate washing solution was mixed with the same amount of purified water to separate into an ethyl formate phase and an aqueous phase. The obtained solution of the ethyl formate phase was dropped on the alignment film, and the display quality was examined.
As a result, no decrease in the threshold voltage was observed for Pigment C (Example 2), and for Pigment D, the decrease in threshold voltage was 15 mV, both of which were small (Example 3).

Examples 4 and 5, Comparative Example 2 83.79 g of each of pigments B, C and D were weighed, and 4.41 of a dispersant "SOLSPERS" 12000 manufactured by Zeneca Co., Ltd. was used.
g, 557 g of γ-butyrolactone, 3-methoxy-3
323 g of -methyl-1-butanol, 494 g of the polymer dispersant (P-1), and zirconia beads were charged into a mill-type dispersing machine, and dispersed at 3000 rpm for 2 hours to obtain respective dispersions. 300 g of the dispersion and 156.3 g of the polymer dispersant (P-1) were mixed with γ-butyrolactone.
3 g, 3-methoxy-3-methyl-1-butanol 18
The solution was mixed with the solution diluted with 5.3 g to obtain green pastes B, C, and D containing pigments B, C, and D, respectively. The amount of compound A contained in pastes B, C and D was 1.2 p each.
pm, 0.05 ppm, and 0.3 ppm.

Each of pastes B, C and D was applied on a glass with a spinner so that the film thickness after curing became 1.5 μm, and then dried at 120 ° C. for 20 minutes. Then 2
The colored layer was formed by curing at 40 ° C. for 30 minutes. When the display quality was examined by assembling a liquid crystal cell using the colored layer substrate, in Paste B, a decrease in the threshold voltage considered to be due to the elution of impurities was observed around the ITO film hole of the colored layer substrate. When the tone display was performed, the ratio of the liquid crystal cells in which the periphery of the ITO hole was observed to be darker was 8 out of 10 cells (Comparative Example 2). On the other hand, in the colored layer substrate using the paste C, there is no liquid crystal cell in which the portion of the ITO hole is darker than its surroundings (Example 4), and in the colored layer substrate using the paste D, the ratio is 2 cells out of 10 cells. And an improvement was observed (Example 5).

Example 6 1000 g of the paste B described in Comparative Example 2 was kept at 50 ° C. and circulated for 5 hours through a column filled with 50 g of activated carbon fiber “Krakuti” grade 15 (manufactured by Kuraray Chemical Co., Ltd.). , Paste with impurities removed (paste E)
Was prepared. The amount of the compound A contained in the paste E is 0.
It was 1 ppm.

The paste was applied on glass by a spinner so that the film thickness after curing was 1.5 μm.
Dry at 0 ° C. for 20 minutes. Next, curing was performed at 240 ° C. for 30 minutes to form a colored layer. When the display quality was examined by assembling a liquid crystal cell using the colored layer substrate, the ratio of the liquid crystal cells in which the periphery of the ITO hole was observed to be darker when halftone display was performed was 3 out of 10 cells, The improvement was observed as compared with the paste B without the adsorption treatment.

[0058]

According to the present invention, the display unevenness of the liquid crystal display device can be reduced by reducing the specific impurities in the pigment and the color paste. Further, a method for producing a pigment and a color paste having a high refining effect by performing a refining treatment with an adsorbent is provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 7/004 505 G03F 7/004 505 F term (Reference) 2H025 AB13 AC01 AD03 DA31 FA15 FA40 2H048 AA05 BA45 BA47 BA48 BB33 BB42 2H091 FA02Y FB02 FB12 FC01 LA12 LA16

Claims (13)

[Claims] 1. A pigment for a color filter, wherein the compound having a cyanobenzene skeleton has a concentration of 10 ppm or less based on the pigment. 2. The pigment for a color filter according to claim 1, wherein the compound having a cyanobenzene skeleton is a compound group represented by the following structural formula (1). Embedded image (Including those in which some of the above compounds are substituted with halogen elements) (3) 2.2 × 10 ² nm, 2.6 × 10 ² nm and 2.9 × 10 ² nm
A pigment having an ultraviolet absorption at a concentration of 10 ppm or less with respect to the pigment. 4. The pigment for a color filter according to claim 1, wherein said pigment has a phthalocyanine skeleton. 5. A color paste for a color filter comprising at least a pigment, an organic solvent and a polymer, wherein the pigment is the pigment according to any one of claims 1 to 4. . 6. A color paste for a color filter containing at least a pigment, an organic solvent and a polymer, wherein the compound having a cyanobenzene skeleton has a concentration of 0.5 ppm or less based on the color paste. For color paste. 7. The color paste for a color filter according to claim 6, wherein the compound having a cyanobenzene skeleton is a compound group represented by the following structural formula (1). 8. A color filter color paste containing at least a pigment, an organic solvent and a polymer,
A color paste for a color filter, wherein the compound having ultraviolet absorption at 2 × 10 ² nm, 2.6 × 10 ² nm and 2.9 × 10 ² nm has a concentration of 0.5 ppm or less based on the color paste. 9. The color paste for a color filter according to claim 6, wherein said pigment has a phthalocyanine skeleton. 10. A color filter, wherein a color layer is formed using the color paste according to claim 5. 11. A liquid crystal display device using the color filter according to claim 10. 12. A method for producing a color filter pigment, which comprises purifying with an adsorbent. 13. A method for producing a color paste for a color filter, comprising purifying a color paste containing at least a pigment, an organic solvent and a resin with an adsorbent.