JP2002285068A - Pigment dispersion, color paste and color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment dispersion having good dispersion stability of the pigment, and to provide a color paste having good dispersion stability of the pigment and a color filter having a pixel excellent in transmittance, contrast and surface smoothness. SOLUTION: The pigment dispersion comprises a polymer having a basic group in a side chain. The color paste is prepared using the pigment dispersion. The color filter is prepared using the color paste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pigment dispersion, a color paste and a color filter.

[0002]

2. Description of the Related Art Color filters for liquid crystal display elements are
Red, green, and blue three color stripes, or dot-like colored patterns has a structure fabricated on a substrate,
As characteristics required for the colored pattern, good color characteristics such as color purity and transmittance are particularly required.

[0003] Usually, a coloring pattern of a color filter is obtained by a pigment dispersion method in which a pigment is dispersed in a resin. At that time, the pigment to be used is selected so as to match the backlight characteristics of the liquid crystal display device, and two or more kinds of pigments are often used by being toned at a fixed ratio. For example R (red) pixels of the color filters, red, orange, yellow pigment to select two or more, used in the color tone at a constant rate. Similarly, the G (green) pixel is also used by selecting two or more kinds of green, orange, and yellow pigments and toning them. The pigment is selected from the chromaticity characteristics required in this way, but depending on the pigment used, the combination of the pigment, and the toning ratio, the pigment is not stably dispersed, aggregates, and the transmittance of the pixel coating film, the contrast of This causes a decrease and an increase in the surface roughness, thereby deteriorating the display quality of the liquid crystal display device.

In order to solve such a problem, a resin such as rosin or modified rosin has been used as a pigment surface treating agent. However, such a surface treatment agent has a problem that it dissolves out in a dispersing solvent and causes aggregation instead, or it is colored by heating at the time of forming a coating film to lower color performance.

As another means, a method has been proposed in which a polymer having an imino group or an iminocarbonyl group in the main chain is added as a dispersant (Japanese Patent Laid-Open No. 10-120964). However, in this method, although a pigment dispersion liquid and a color paste having good dispersion stability can be obtained, there is a problem that the pigment cannot be sufficiently refined and only a low-contrast coating film can be obtained. .

As a means other than the above, a method of adding a pigment derivative as a dispersing agent (for example, Japanese Patent Publication No. 4-3841)
Has also been proposed. However, this method, a dispersing aid comprising one to express dispersion effect is adsorbed on the pigment surface, various devices for effectively adsorbed, ie need to optimize the dispersion conditions such as the selection of the dispersing solvent However, even with such a method, it was not possible to adsorb a sufficient amount of the pigment, and it was difficult to obtain the effect expected as a dispersing aid.

[0007]

[0008] The present invention, the conventional view of the art of the background is intended to St. provide a pigment dispersion having excellent dispersion stability of the pigment, with it, excellent dispersion stability of the pigment And a color filter having pixels excellent in transmittance, contrast, and surface smoothness.

[0008]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the pigment dispersion of the present invention is characterized by containing a polymer having a basic group in a side chain. Further, the color paste of the present invention is characterized by being prepared using such a pigment dispersion,
Further, the color filter of the present invention is characterized by being prepared using such a color paste.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pigment dispersion of the present invention is characterized by containing a polymer having a basic group in a side chain.

As the basic group, any basic substituent can be suitably used. Specifically, although not particularly limited, an amino group, an alkylamino group, an aromatic amino group, an aminoalkyl group, an alkylaminoalkyl group, an aromatic aminoalkyl group, a pyridyl group, a triazine group, a pyryl group, Indolyl, carbazolyl, imidazolyl, benzimidazolyl,
And a thiazolyl group and a benzthiazolyl group.
Among these, aromatic amino groups are particularly preferably used because they have a large effect on dispersion stability and can be easily introduced into a polymer.

In the present invention, the side chain may be roughly considered to be a short branch branched from the main chain (long branch) of a polymer which is substantially chained, as generally defined. . In order for the effects of the present invention to be fully exhibited, it is important that the side chains have a high degree of conformational freedom. For that purpose, it is essential that the molecular weight is not restricted by the branch. That is, as the side chain having a high degree of conformational freedom, the side chain (particularly, a basic group, especially, a central atom or an atomic group, for example,
The size of the second largest branch attached to the nitrogen atom, etc. (of course, the first largest branch is a part connected to the polymer main chain, and if it is a phenylamino group, the phenyl group is the second) It is small. The size is not particularly limited, but preferably has a molecular weight of 1000
Or less (more preferably the molecular weight is 500 or less, further preferably the molecular weight is 200 or less).

In the polymer having a basic group in the side chain according to the present invention, the number of the basic group is not particularly limited, but is preferably 1 group / molecule or more (more preferably 20 groups / molecule or more, More preferably, 50 groups / molecule or more)
It is. If the ratio is below the lower limit, the dispersion stability becomes poor, which may be undesirable. There is no particular upper limit, but it is preferably 10,000 groups / molecule or less.

Here, the polymer means a polymer, and includes a high molecular weight polymer having a weight average molecular weight of 5,000 or more and a low molecular weight polymer having a weight average molecular weight of 500 to 5,000. Although not particularly limited, the weight average molecular weight is preferably 500 to 100,000 (more preferably 1,000 to 50,000, and still more preferably 2,000 to 50,000).
000). When the value is below the lower limit of the numerical range, the dispersion stability becomes poor. On the other hand, when the value exceeds the upper limit, the developing property may be unfavorably reduced. The polymer or its molecular weight as used herein refers to a pigment dispersion or a color paste. For example, when a color filter is prepared, the acrylic polymer is mostly crosslinked, and in that case, the molecular weight cannot be measured. On the other hand, in the case of polyamic acid, the degree of molecular ring closure is generally about the same as in the case of a polyamic acid, and therefore, there are many examples in which the molecular weight is not much different from the state in which a pigment paste is formed and the state in which a color filter is formed.

Since the surface of a pigment that can be used for a color filter is generally acidic, the polymer having a basic group in the side chain of the present invention is adsorbed on the pigment surface by an acid-base interaction in a pigment dispersion. I do. The adsorbed polymer prevents the pigments from aggregating due to steric repulsion, so that the dispersion stability of the pigment is achieved. The advantage obtained by introducing the basic group into the side chain instead of the main chain is that the polymer does not reduce the degree of freedom of the main chain conformation when adsorbed on the pigment, so that the polymer can be efficiently adsorbed on the pigment surface. The point is that you can.

The main chain skeleton of the polymer is not particularly limited as long as it is soluble in a solvent and has excellent heat resistance, and any skeleton can be used. For example, although not particularly limited, polyacrylic acid derivatives, polyamides, polyamideimides, polyimides, polyamic acids, and the like can be given. Among these, polyamic acid is
Synthesis is easy, because it has the advantage of being converted to highly heat-resistant polyimide by heating in the manufacturing process of a color filter, can be particularly preferably used.

The above 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, but are not particularly limited to,
1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,5-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-bicyclohexenetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,3,3a, 4,4
5,9b-Hexahydro-5- (tetrahydro-2,5
- dioxo-3-furanyl) - such as naphtho [1,2-C] furan-1,3-dione can be cited. In addition, when an aromatic compound is used, a polyamic acid that can be converted into a polyimide having good heat resistance can be obtained, and specific examples thereof include 3,3 ′, 4,4′-benzophenonetetracarboxylic acid. Dianhydride, pyromellitic dianhydride, 3,4
9,10-perylenetetracarboxylic dianhydride, 3,3
', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3
', 4,4'-biphenyltetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-p-terphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-metaphenylphenyl carboxylic acid dianhydride. The present invention is tetracarboxylic dianhydride is used one or two or more without being limited thereto.

The diamine may be, for example, an aliphatic or alicyclic diamine. Specific examples thereof include, but are not limited to, ethylenediamine and 1,3-diaminocyclohexane. , 1,
4- diaminocyclohexane, 4,4'-diamino -
3,3'-dimethyldicyclohexylmethane, 4,4 '
- such as diamino-3,3'-dimethyl dicyclohexyl 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.
'-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 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.

Examples of the method for introducing the basic group into the polyamic acid include a method by reacting a tetracarboxylic dianhydride having the basic group and / or a diamine having the basic group, and synthesizing the polyamic acid. Later, a method of adding the basic group to the polyamic acid main chain skeleton by an appropriate reaction may be mentioned. Among them, the former method is more preferable because a polymer having a desired basic group can be easily synthesized.

The amount of the polymer having a basic group of the present invention is preferably 0.1 to 1000 wt.
%, More preferably 1 to 100 wt%, and still more preferably 2 to 50 wt%. If the addition amount is too small, the effect of dispersion stability is not exhibited, and if it is too large, the developability in producing a color filter is reduced. Method of addition, the addition of pre-pigment dispersion, may be any of addition after the pigment dispersion.

As the pigments usable in the present invention, specific examples of typical pigments are shown below by color index (CI) numbers, but are not limited thereto.

Examples of yellow pigments include Pigment Yellow (hereinafter abbreviated as PY) 12, 13, 17, 20, 24,
83, 86, 93, 95, 109, 110, 117, 1
25, 129, 137, 138, 139, 147, 14
8, 150, 153, 154, 166, 168, 185
And the like. Examples of orange pigments include Pigment Orange (hereinafter abbreviated as PO) 1
3, 36, 38, 43, 51, 55, 59, 61, 6
4, 65, 71, etc., and examples of red pigments include Pigment Red (hereinafter abbreviated as PR) 9, 48, 97, 122, 123, 144, 14
9, 166, 168, 177, 179, 180, 19
2,209,215,216,217,220,22
3, 224, 226, 227, 228, 240, 254
And the like. Pigment violet (hereinafter abbreviated as PV) 19, 2
3, 29, 30, 32, 37, 40, 50 and the like, and examples of blue pigments include Pigmentable (hereinafter abbreviated as PB) 15, 15: 3, 15:
4, 15: 6, 22, 60, 64 and the like, and examples of green pigments include pigment green (hereinafter abbreviated as PG) 7, 10, 36 and the like. in addition, examples of the black pigments can be used pigment black 7, carbon black, and titanium black.

When the present invention is used for a color filter for a liquid crystal display device, the above-mentioned pigments are selected and used so as to match the R (red), G (green), and B (blue) color characteristics of the LCD. If necessary, two or more kinds of pigments may be combined and toned. As an example of such toning, for example, in the case of R (red), PR-17
7 and PY-138, PR-254 and PY-13
8 combinations, PR-254 and PO-71 combinations, PR
-209 and PO-38, PR-209 and PO-
71 or PR-254 alone, PR-2
09 alone can be preferably used. In the case of G (green), PG-7 or PG-36 and the above-mentioned yellow pigment, for example, PY-17, PY-83, PY-138,
The combination of PY-139, PY-150 can be preferably used. More preferably, PG-36 and PY-1
7, a combination of PG-36 and PY-138, and a combination of PG-36 and PY-150 can provide G pixels with good color characteristics. If the B (blue), PB15: 6 alone, or PB15: 6
It can be preferably used a combination of PV23 when.

Next, a color paste using the pigment dispersion of the present invention will be described. Such a color paste, especially a color filter color paste, at least,
Pigments, resins, is made of a solvent.

The resin used for the color paste of the present invention is not particularly limited as long as it is a resin generally used for a color filter, and any resin can be used. For example, it is possible to use acrylic resins, alkyd resins, melamine resins, polyvinyl alcohol, polyamide, polyamideimide, polyimide, various resins such as a polyimide precursor. Among resins soluble in an alkaline aqueous solution, a photosensitive acrylic resin having a carboxyl group or a polyimide precursor is particularly preferable because a pattern can be easily formed by development or etching. Polyamide acid and its esterified product are preferably used as the polyimide precursor, and form an imide ring by heat or chemical treatment.

The solvent used for the color paste of the present invention is not particularly limited, and water and common organic solvents can be used. As the organic solvent, is not particularly limited, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and diethylene glycol monomethyl ether (poly) alkylene glycol ether polarity Solvent, N-methyl-2-pyrrolidone, N,
Amide polar solvents such as N-dimethylacetamide and N, N-dimethylformamide, β-propiolactone,
Lactones such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, and ε-caprolactone can be used. When polyimide is used as a component of the pixel matrix, the solvent used in the colorant composition is preferably a solvent that dissolves the polyimide precursor. As the solvent for dissolving the polyimide precursor, the polar organic solvents such as the amide-based polar solvents and the lactones are used. Further, an organic solvent such as ethanol, butanol, alcohols such as isopropanol, cellosolves such as methyl cellosolve and ethyl cellosolve, and propylene glycol derivatives such as propylene glycol monomethyl ether alone which does not dissolve the polyimide precursor alone is used as a polyimide precursor. Can be used as a mixture with a solvent that dissolves

The yield value of the color paste of the present invention is preferably 0.01 or less (more preferably 0.001 or less,
More preferably, it is 0.0001 or less. Exceeding the upper limit may cause coating unevenness and pigment aggregation.

The color paste is prepared by directly dispersing the pigment in the resin solution using a disperser, or using a disperser.
Water or by dispersing the pigment in an organic solvent, to prepare a pigment dispersion, then, is produced by a method of mixing the resin solution. The method for dispersing the pigment is not particularly limited, and various methods such as a ball mill, a sand grinder, a three-roll mill, and a high-speed impact mill can be employed.

In the above color paste, the resin component and the pigment are preferably in a weight ratio of 20:80 to 90:10,
More preferably, they are mixed in the range of 30:70 to 80:20, particularly preferably 40:60 to 70:30. If the amount of the resin component is too small, the adhesion of the colored film to the substrate becomes poor, and if the amount of the pigment is too small, the degree of coloration becomes a problem. The ratio of the solvent in the colorant composition is preferably 10 to 99.5 wt%, more preferably 50 to 98 wt%.

The pigments that can be used in the color paste of the present invention can be used alone or as a mixture of two or more, and may be used as a mixture with a generally known pigment dispersant. Examples of such pigment dispersants,
Although not particularly limited, for example, decanamide,
Dodecane amide, N-dodecyl hexadecane amide, N
- octadecyl propionitrile amides, N, N- dimethyl dodecanamide, N, amide compounds such as N- dihexyl acetamide, diethylamine, triethylamine, di-heptyl amine, dibutyl hexadecylamine, amine compounds such as aniline, monoethanolamine, diethanolamine, An amine compound having a hydroxyl group such as triethanolamine can be used. The amount of the pigment dispersant added to the color paste of the present invention is preferably 0.1 to 200 wt%, more preferably 1 to 200 wt%, based on the pigment.
５０50 wt%.

When the color paste contains a large amount of ionic impurities, when a liquid crystal display device is manufactured using a color filter manufactured from the color paste, impurities oozing into the liquid crystal adversely affect the driving of the liquid crystal, resulting in a display defect. There are cases. Therefore, it is preferable to remove ionic impurities from the color paste as much as possible. The method for removing ionic impurities is not particularly limited, but a method using an ion exchange resin is preferably employed. For example, by directly connecting a mill-type disperser filled with ceramic beads and a column filled with granular ion-exchange resin, ionic impurities can be removed simultaneously with the dispersion of the pigment.

A surfactant may be added to the color paste of the present invention for the purpose of improving the coatability of the color paste and the uniformity of the surface of the colored film or the dispersibility of the pigment. it can. The addition amount of the surfactant is, based on the pigment, preferably 0.001~10wt
%, More preferably 0.01 to 1 wt%. If the addition amount is too small, there is no effect of improving the coating properties, the uniformity of the colored film surface, or the dispersibility of the pigment, and if too large, on the contrary, the coating properties become poor or the aggregation of the pigment occurs. . Specific examples of such a surfactant include anionic surfactants such as ammonium lauryl sulfate and polyoxyethylene alkyl ether triethanolamine sulfate, cationic surfactants such as stearylamine acetate and lauryltrimethylammonium chloride, and lauryl dimethylamine oxide. And amphoteric surfactants such as laurylcarboxymethylhydroxyethylimidazolium betaine, and nonionic surfactants such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether and sorbitan monostearate. Such surfactants can be used alone or in combination of two or more. Such a surfactant can be added at any time during or before or after the pigment dispersion step. However, care must be taken since the dispersibility of the pigment may change depending on the time of addition.

Next, a color filter using the color paste of the present invention will be described.

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, etc. And various methods such as spraying the colorant composition onto the substrate. Typically the substrate, soda glass, alkali-free glass, borosilicate glass, or a transparent substrate such as quartz glass, silicon, gallium - although such a semiconductor substrate such as arsenic is used, is not particularly limited thereto. In the case where the colorant composition is applied on the 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 colored film formed by using the color paste of the present invention is used for a color filter of a liquid crystal display or an image pickup device, a light shielding film of an optical device, a coating film of an optical fiber, and the like. For example, an optical fiber coated with a colored film using a colorant composition can be used as an optical sensor at a high temperature. There is no particular limitation on the thickness of the colored film is preferably 0.1 to 10 [mu] m, more preferably 0.5 to 5 [mu] m. 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, conversely cause problems, such as absorption of light becomes too large, there is a possibility that the optical properties of the color filters is not satisfied. The optical properties usually have a desired chromaticity depending on the application, so that the pigment composition and the film thickness are adjusted to match the chromaticity to produce a colored film.

When used as a color filter for a liquid crystal display device, important characteristics of the colored film include contrast and surface roughness in addition to chromaticity. The contrast is preferably 800 or more, more preferably 1 in the state of a colored film.
It is desired that the number be 000 or more, more preferably 1200 or more. If the contrast is less than 800, the contrast of the display becomes too low, and the display characteristics may be deteriorated. The surface roughness is usually represented by a center line surface roughness (Ra), and is preferably 0.008 μm or less, more preferably 0.006 μm or less, and further preferably 0.004 μm or less. If the surface roughness (Ra) is larger than 0.008 μm, the orientation of the liquid crystal may be disturbed when a display is formed, and display characteristics may be poor.

Next, taking a color filter for a liquid crystal display device, which is a typical application of a color filter, as an example, production of a color filter using polyimide as a resin component of a pixel matrix and polyamic acid as a precursor thereof. An example of the method will be described.

After the colorant composition is applied on a 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 drying by heating, an oven, a hot plate or the like is used, preferably in the range of 50 to 180 ° C, more preferably in the range of 80 to 12 ° C.
Perform at 0 ° C. for 30 seconds to 3 hours. If the temperature is too low, the solvent does not easily evaporate, the temperature is too high, solubility in a 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 apparatus. After the exposure, the photoresist coating and the polyimide precursor colored film are simultaneously etched with a positive photoresist alkaline developer. After etching, the photoresist is stripped off film which has become unnecessary. Thereafter, the polyimide precursor colored film is converted into a polyimide colored film by performing a heat treatment. The heat treatment is preferably performed in air, in a nitrogen atmosphere, or in vacuum, preferably at 150 to 450 ° C.
More preferably 180 to 350 ° C., particularly preferably 2
It is performed continuously or stepwise at a temperature of 00 to 320 ° C. for 0.5 to 5 hours.

When the above steps are performed on the three colorant compositions of R (red), G (green), and B (blue) and, if necessary, the black colorant composition, a color filter for a liquid crystal display device can be obtained. Can be produced.

[0039]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The measuring methods described in the examples are as shown below. (Measurement method) <Contrast> The brightness of parallel Nicols and the brightness of parallel Nicols of a sample are measured with a color luminance meter (Topcon BM-5A) on a back light (Toppan BM-5A) in a field of view twice. The ratio between the luminance of the direct Nicol and the contrast was defined as the contrast.

<Surface roughness> A product made by Tokyo Seimitsu Co., Ltd.
The center line average roughness (Ra) was measured with Fucom 1500A.

<Chromaticity> MCPD-, manufactured by Otsuka Electronics Co., Ltd.
It was measured with a C light source at 2000 with a visual field twice.

The C light source is the International Commission on Illumination (CIE)
Is the standard light C defined. This is a color temperature of 6740 °
K, which is obtained by applying a specified filter to a gas-filled tungsten lamp that is lit according to a specified rule.
The nature of this light corresponds to daylight including blue sky light. 2
A degree field of view refers to a field of view ranging from 0 ° to 2 °. Then, the C light source and 2 ° field of view, the transmitted light when the light is transmitted in the C source to the measurement object, the optical axis of light of the C light source is through the measurement object perpendicular to the 0 ° and, when the measurement object has a base point, the permeate side, 0
This means that the transmitted light in the visual field within the range of ２2 ° is measured (transmitted light chromaticity measurement).

<Viscosity, Yield Value> Viscometer, model RE100L, manufactured by Toki Sangyo Co., Ltd.

Reference Example: Synthesis of polyamic acid 3,3'-diaminodiphenylsulfone 620.6
g, p-phenylenediamine 757.0 g, and bis (3-aminopropyl) tetramethyldisiloxane
12.4.3 g of γ-butyrolactone 11521 g,
Charged with 2033 g of N-methylpyrrolidone,
After adding 2795.1 g of 3 ′, 4,4′-biphenyltetracarboxylic dianhydride and reacting at 60 ° C. for 5 hours, 98.1 g of maleic anhydride was added and further 60
C. for 1 hour to obtain a polyamic acid solution (PA-1) having a viscosity of 50 cp.

SYNTHESIS EXAMPLE 1 3,3'-diaminodiphenylsulfone 9.44
g, 2,4-diaminodiphenylamine 7.57 g,
0.99 g of bis (3-aminopropyl) tetramethyldisiloxane was charged into 241 g of γ-butyrolactone, and 4,4′-oxydiphthalic dianhydride 24.32.
g, and reacted at 60 ° C. for 5 hours. Then, 0.16 g of maleic anhydride was added, and the mixture was further reacted at 60 ° C. for 1 hour. The polyamic acid solution having a phenylamino group in the side chain having a viscosity of 50 cp (PA -2) was obtained.

Synthesis Example 2 In place of 2,4-diaminodiphenylamine, 2,4-diaminodiphenylamine was used.
A polyamic acid solution (PA-3) having a viscosity of 50 cp and having a diphenylamino group in a side chain was obtained in the same manner as in Synthesis Example 1 except that diaminotriphenylamine was used.

Example 1 50.56 g of PG-36, 43.94 of PY-138
g, 70.0 g of polyamic acid (PA-2) and 1335.5 g of γ-butyrolactone were charged into a mill-type disperser filled with zirconia beads, and dispersed at 4000 rpm for 3 hours. Thus, a pigment dispersion having a solid content of 7% was obtained. The viscosity of this pigment dispersion is 7 centipoise (2
At 5 ° C.), yield value is very excellent flow properties 0.005 Pascal, even after 1 month storage at -20 ° C. was excellent in dispersion stability without change in flow characteristics. This pigment dispersion 40
To g, the polyamic acid (PA-1) to 20 g .gamma.-butyrolactone 38 g, 0.1% surfactant BYK361 (B
YK-Chemie Co., Ltd.) added γ- butyrolactone 2
The solution diluted with g was added and mixed to obtain a color paste. The viscosity of the color paste was 18.5 centipoise (25 ° C.), and the yield value was 0.0001 pascal, which was excellent in flow characteristics. Using this color paste, the chromaticity of finish on the glass substrate y. The coating is 0.56, after 10 minutes drying at 120 ° C., and heat-treated for 30 minutes at 270 ° C., was converted to polyimide. The G (green) coating film thus obtained had a transparent film surface, and exhibited excellent characteristics of surface roughness (Ra) of 0.002 μm and contrast of 1850.

Example 2 Polyamic acid (P) was used instead of polyamic acid (PA-2).
A pigment dispersion, a color paste, and a G (green) coating film were obtained in the same manner as in Example 1 except that A-3) was used. The viscosity of this pigment dispersion is 6.5 centipoise (25
° C), the yield value was 0.004 pascal, and the flow characteristics were very excellent. Even after storage at -20 ° C for 1 month, the flow characteristics did not change and the dispersion stability was excellent. The viscosity of the color paste was 18 centipoise (25 ° C.), and the yield value was 0.0001 pascal.
Further, this G (green) coating film has a transparent film surface, a surface roughness (Ra) of 0.002 μm, and a contrast of 1
900 excellent properties.

Comparative Example 1 Polyamic acid (P) was used instead of polyamic acid (PA-2).
A pigment dispersion, a color paste and a G (green) coating film were obtained in the same manner as in Example 1 except that A-1) was used. The viscosity of the pigment dispersion is 100 centipoise (25 ° C)
The yield value was 0.12 Pa and the flow characteristics were poor, and pigment aggregation occurred. Color viscosity of the paste is 80 centipoise (25 ° C.), yield value has poor flow properties and 0.05 Pascal yielded pigment aggregation. Further, the G (green) coating film is clouded due to the aggregation of the pigment, and the surface roughness (Ra)
0.020 μm, contrast 500, and poor characteristics.

Example 3 50.56 g of PR-177, 43.94 of PO-38
g, 70.0 g of polyamic acid (PA-2) and 1335.5 g of γ-butyrolactone were charged into a mill-type disperser filled with zirconia beads and dispersed at 3000 rpm for 3 hours. Thus, a pigment dispersion having a solid content of 7% was obtained. The viscosity of this pigment dispersion is 7 centipoise (25
° C), the yield value was 0.006 pascal and the flow characteristics were very excellent, and the flow characteristics did not change even after storage at -20 ° C for one month, and the dispersion stability was excellent. To 40 g of this dispersion,
20 g of polyamic acid (PA-1) was added to 38 g of γ-butyrolactone, and 0.1% surfactant BYK361 (BYK-
A solution diluted with 2 g of γ-butyrolactone added by Chemie was added and mixed to obtain a color paste. The viscosity of this color paste is 21 centipoise (25 ° C)
The yield value was 0.0011 Pascal and the flow characteristics were very excellent. Using this color paste, apply it on a glass substrate so that the finished chromaticity x becomes 0.58.
After drying at 20 ° C. for 10 minutes, heat treatment was performed at 270 ° C. for 30 minutes to convert to polyimide. The R (red) coating film thus obtained has a transparent film surface, and the surface roughness (Ra)
Excellent characteristics of 0.004 μm and contrast of 1000 were exhibited.

Example 4 Polyamic acid (P) was used instead of polyamic acid (PA-2).
A pigment dispersion, a color paste and an R (red) coating film were obtained in the same manner as in Example 3 except that A-3) was used.
The viscosity of this pigment dispersion is 7 centipoise (25 ° C.)
The yield value was as excellent as 0.005 Pascal and the flow characteristics were excellent. Even after storage at -20 ° C. for one month, the flow characteristics did not change and the dispersion stability was excellent. The viscosity of the color paste was 21 centipoise (25 ° C.), and the yield value was 0.00.
The flow characteristics at 1 Pascal were very good. Further, this R (red) coating film had a transparent film surface, and exhibited excellent properties such as a surface roughness (Ra) of 0.004 μm and a contrast of 1000.

Comparative Example 2 Polyamic acid (P) was used instead of polyamic acid (PA-2).
A pigment dispersion, a color paste and an R (red) coating film were obtained in the same manner as in Example 3 except that A-1) was used.
The viscosity of the pigment dispersion is 120 centipoise (25 ° C.)
The yield value was poor at 0.22 Pascal, which resulted in pigment aggregation. The viscosity of the color paste was 90 centipoise (25 ° C.), the yield value was 0.05 Pascal, the flow characteristics were poor, and pigment aggregation occurred. Further, the R (red) coating film is clouded due to the aggregation of the pigment, and has a surface roughness (Ra) of 0.0.
18 μm, contrast 400 and characteristics were also poor.

Example 5 94.5 g of PR-254, polyamic acid (PA-2)
70.0 g and 1335.5 g of γ-butyrolactone were charged into a mill-type disperser filled with zirconia beads,
It was dispersed at 3000 rpm for 3 hours. Thus, a pigment dispersion having a solid content of 7% was obtained. This pigment dispersion has a viscosity of 8 centipoise (25 ° C.) and a yield value of 0.004.
Very good Pascal and flow characteristics.
Even after storage for months, the flow characteristics did not change and the dispersion stability was excellent. To 40 g of this dispersion, polyamic acid (PA-1)
20 g was added to 38 g of γ-butyrolactone and 0.1% surfactant BYK361 (manufactured by BYK-Chemie) was added.
Adding and mixing the solution diluted with 2 g of butyrolactone,
A color paste was obtained. The viscosity of this color paste is 2
At 4 centipoise (25 ° C.), the yield value was 0.0009 Pascal and the flow characteristics were very good. Using this color paste, the finished chromaticity x is 0.5 on a glass substrate.
8 and dried at 120 ° C for 10 minutes.
Heat treatment was performed at 0 ° C. for 30 minutes to convert to polyimide. The R (red) coating film thus obtained had a transparent film surface, and exhibited excellent properties such as a surface roughness (Ra) of 0.004 μm and a contrast of 1050.

Example 6 Instead of polyamic acid (PA-2), polyamic acid (P
A pigment dispersion, a color paste and an R (red) coating film were obtained in the same manner as in Example 3 except that A-3) was used.
The viscosity of this pigment dispersion is 8 centipoise (25 ° C.)
The yield value was 0.003 pascal and the flow characteristics were very excellent. Even after storage at −20 ° C. for one month, the flow characteristics did not change and the dispersion stability was excellent. The viscosity of the color paste was 24 centipoise (25 ° C.), and the yield value was 0.00.
The flow characteristics were very good at 09 Pascal. The R (red) coating film had a transparent film surface, and exhibited excellent surface roughness (Ra) of 0.004 μm and excellent contrast of 1100.

Comparative Example 3 Polyamic acid (P) was used instead of polyamic acid (PA-2).
A pigment dispersion, a color paste and an R (red) coating film were obtained in the same manner as in Example 5 except that A-1) was used.
The viscosity of the pigment dispersion is 200 centipoise (25 ° C.)
The yield value was 0.59 Pascal and the flow characteristics were poor, causing pigment agglomeration. The viscosity of the color paste was 110 centipoise (25 ° C.), the yield value was 0.04 pascal, the flow characteristics were poor, and pigment aggregation occurred. Further, the R (red) coating film is clouded due to the aggregation of the pigment, and has a surface roughness (Ra) of 0.0.
15 μm, contrast 500 and characteristics were also poor.

[0056]

According to the present invention, a pigment dispersion having excellent pigment dispersion stability can be provided. Therefore, a color paste having excellent pigment dispersion stability, transmittance, contrast and surface smoothness can be provided. A color filter having pixels excellent in the color filter can be provided. Such a color filter is suitably used particularly for a liquid crystal display device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09B 67/46 C09B 67/46 B 4J038 C09C 3/10 C09C 3/10 C09D 179/08 C09D 179/08 Z 201/02 201/02 G02B 5/20 101 G02B 5/20 101 5/22 5/22 G02F 1/1335 505 G02F 1/1335 505 // B01F 17/22 B01F 17/22 17/52 17/52 F-term (Ref.) FF23 4J038 CE021 CG032 CG141 DA161 DD121 DH001 DH002 DJ021 DJ022 DJ031 DJ032 DJ051 DJ052 EA011 GA06 KA06 KA08 KA18 MA10 NA26

Claims (5)

[Claims] 1. A pigment dispersion comprising a polymer having a basic group in a side chain. 2. The pigment dispersion according to claim 1, wherein said basic group is an aromatic amino group. 3. The pigment dispersion according to claim 1, wherein the main chain skeleton of the polymer is a polyamic acid. 4. A color paste comprising a pigment, a resin and a solvent, obtained from the pigment dispersion according to claim 1. 5. A color filter obtained from the color paste according to claim 4.