JP3356932B2 - Color filter, manufacturing method thereof and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a color filter,
The present invention relates to a manufacturing method and a liquid crystal display device.

[0002]

2. Description of the Related Art A color filter for a liquid crystal display device is an essential component for colorizing a liquid crystal display device, and is manufactured by forming colored pixels on a glass or transparent plastic substrate. ing. The colored pixel is configured by arranging pixels of three primary colors of red (R), blue (B), and green (G) in a line, mosaic, or triangle shape, and has a size of about 100 μm.
Between each pixel, to increase the contrast of the pixels,
A light-shielding colored layer generally called a black matrix is formed, and is used for light-shielding a transistor and a wiring portion in a TFT driving method.

[0003] These black matrices are usually formed by etching a metal chromium vapor deposition film or a sputtering film. The width of the black matrix is several μm in a narrow place and about 100 μm in a wide place. On the other hand, R,
A method of patterning with light using each of the G and B photosensitive coloring pastes, or a method of jetting non-photosensitive ink to a predetermined position by an inkjet method and coloring, a screen on a substrate using a printing apparatus A method of coloring by printing, a method of coloring on a substrate on which a transparent electrode is formed by an electrodeposition method, and the like have been proposed.

When a conventional black matrix is used, ink overflows on the black matrix, and a flat pixel cannot be obtained. As measures against this, JP-A-4-123005, JP-A-4-123006, JP-A-4-123007 and JP-A-4-19.
As disclosed in Japanese Patent Application Laid-Open No. 5102 and the like, a method of manufacturing a color filter by an ink jet method or a printing method in which a silicone resin layer is formed on a photosensitive resin layer and ink repulsion is applied is described. However, in order to impart ink resilience on the black matrix of each pixel ink,
When the light-shielding layer photosensitive resin layer and the silicone resin layer are formed, problems such as an increase in the overall film thickness, complexity of the process, and the cost are large.

[0005] The present invention has been made in view of the above problems, and it is possible to more easily form a black matrix, and the black matrix has excellent light resistance, heat resistance, moisture resistance, etc. It is an object of the present invention to provide a low-cost liquid crystal display device with high image quality by providing a color filter comprising such a black matrix.

According to the present invention, there is provided a color filter comprising a plurality of colored pixels and a black matrix arranged between the colored pixels on a light transmitting substrate, wherein the black matrix is made of an inorganic oxidizing agent. There is provided a color filter formed by dispersing carbon black particles which have been subjected to a surface treatment and further neutralized with an inorganic or organic basic substance, in a binder resin dissolved in a polar solvent.

According to the present invention, the surface of the carbon black particles is treated with an inorganic oxidizing agent, neutralized with an inorganic or organic basic substance, and then dissolved in a polar solvent. A method for producing a color filter is provided, in which a donor liquid is prepared by dispersing the donor liquid in a binder resin, and the donor liquid is applied on a light-transmitting substrate to form a black matrix. Further, according to the present invention, there is provided a liquid crystal display device in which liquid crystal is sealed between a pair of substrates at least one of which is a light-transmitting substrate, and the color filter is provided on at least one of the substrates.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A color filter according to the present invention comprises a plurality of colored pixels and a black matrix formed on a light-transmitting substrate, and is used for, for example, a liquid crystal display device. Each colored pixel is usually 10
Although a black matrix having a width of about 0 μm and a line width of about 20 μm is provided between the colored pixels, the present invention is not limited to these widths. Each colored pixel is
A so-called stripe-shaped pixel arranged in a line or a colored pixel surrounded by a black matrix is arranged in a mosaic or triangle.

The light-transmitting substrate used in the present invention is not particularly limited as long as it has an appropriate light transmittance and strength and can function as a substrate, such as a transparent substrate or a translucent substrate. However, for example, glass, a plastic plate, a plastic film and the like can be mentioned.
The light-transmitting substrate may be coated / formed with a dyeable medium as described later.

The black matrix of the color filter of the present invention is formed of carbon black particles whose surface has been treated with an inorganic oxidizing agent. The particulate carbon black to be surface-treated is not particularly limited, and examples thereof include channel black, acetylene black,
Examples include oil furnace black and thermal black. Above all, channel black is
It is preferable because it has excellent surface treatment efficiency and degree of blackening. At this time, the carbon black particles preferably have a fine structure. Here, the fine structure is 0.01 to 0.0
Having an average particle size of about 5 μm, and 0.001 to 0.1
It means that particles having a particle size of about μm have a particle size distribution of about 50% or more, more preferably about 80% or more of all particles. When the particle size distribution is large, it is difficult to make the black matrix uniform and the degree of blackening is not improved. On the other hand, if the amount of ultrafine carbon black is large, purification during surface treatment,
There is a problem in drying, which is not preferable. In addition, these carbon black particles, even after performing the surface treatment described below,
Generally, the particle size distribution hardly changes.

As a method for treating the surface of carbon black particles with an inorganic oxidizing agent as described above, for example,
Disperse the carbon black particles in water, add an inorganic oxidizing agent, and heat to room temperature or about 80 ° C.
For about 60 minutes. As the inorganic oxidizing agent in this case, for example, at least one oxidizing agent selected from the group consisting of nitric acid, sulfuric acid, perchloric acid, hydrogen peroxide, potassium dichromate, permanganic acid and sodium permanganate Is mentioned. The concentration of the inorganic oxidizing agent at the time of the treatment can be appropriately adjusted depending on the type of the oxidizing agent used, but is preferably from a low concentration of about 0.05N to about 10N. Above all, when nitric acid having a relatively low concentration of about 0.1N to 1N is used, the obtained carbon black particles are preferably dispersed in a polar solvent such as water, and the degree of blackening is also sharp. .

As described above, the surface-treated carbon black particles have improved dispersibility in polar solvents, mainly water, and have improved stability over time, mainly in carbon dioxide gas, in the atmosphere. The carbon black particles used in the present invention are subjected to a surface treatment with an inorganic oxidizing agent as described above, and further, sodium hydroxide, barium hydroxide, ammonia, ethylamine, triethylamine, diethylamine, monoethanolamine, tributylamine. Or a solution containing an inorganic or organic basic substance, such as an aqueous solution. Among them, ammonia, diethylamine, triethylamine and the like are preferable. By this neutralization, it is considered that an alkali metal, an alkaline earth metal, ammonia, an amine, or the like can be adsorbed to a carbonyl group introduced to the surface of the carbon black particles by treating the carbon black particles with an oxidizing agent. The dispersion in the polar solvent becomes better, and the excess of the oxidizing agent used in the preceding surface treatment can be removed.Moreover, when a volatile substance is used as the basic substance, Can be removed by evaporating water and basic substances. The concentration of the basic solution for neutralization at this time can be appropriately adjusted depending on the type and concentration of the solution used in the previous oxidizing agent treatment, for example,
It can be used at about 0.1 to 3.0M.

As a method for forming a black matrix in the color filter of the present invention, a donor liquid is prepared by dispersing the above-mentioned carbon black in a binder resin optionally dissolved in a polar solvent. Can be performed by patterning the light-transmitting substrate. The binder resin is not particularly limited, and includes a resin that is soluble in a polar solvent and hardly softens even at 200 ° C. or higher. Specifically, acrylic resin, methacrylic resin, styrene resin, melamine resin, epoxy resin, phenoxy resin, aromatic polyamide resin,
A polyimide resin or the like is suitable. As the acrylic resin and methacrylic resin, for example, acrylic acid, methacrylic acid or an ester group thereof is introduced into a low molecular weight polymer such as a polyester resin, an epoxy resin, a polyurethane resin, an alkyd resin, and a silicone resin as a main resin component; or an oligomer. Prepolymer; a system in which a polyfunctional reactant having two or more acrylic acid or methacrylic acid groups or ester groups thereof in a single molecule is added as a crosslinking agent. In this case, it is effective to add a heat or a radical generator that generates radicals as a reaction initiator as necessary. A system in which a methylolated melamine is added as a crosslinking agent to a polymer having a hydroxyl group such as a phenol resin or an alkyd resin, or a substance which generates an acidic substance by light or heat as an initiator is also effective. These resins are preferably used in the form of a latex, and examples of a method of using the resin in a latex state include a method of adding a surfactant during or after the synthesis of the resin. A resin obtained by partially quaternizing a part of a copolymer resin containing a carboxyl group such as styrene: maleic anhydride or styrene: maleic anhydride half ester with ammonia triethylamine or the like can also be used as the binder resin.

The polar solvent includes water, methyl alcohol, ethyl alcohol, propyl alcohol and the like. The carbon black in the donor liquid is preferably dispersed in the binder resin at a weight ratio of 1: 100 to 100: 1, more preferably 1:10 to 1:
It is one. In general, as the amount of resin increases, the film thickness increases in order to obtain a required optical density, and conversely, as the amount of carbon black increases, the coating properties tend to deteriorate.

Conventionally, the donor liquid is patterned on the light-transmitting substrate by a direct patterning method, a patterning method using a photomask, or the like. Various methods known per se that have been used for the application can be mentioned. By using such a method, a black matrix can be easily formed. Specifically, there are the following methods.

A method of directly patterning on a light-transmitting substrate by using a donor liquid as an ink for ink-jet printing, and a method of directly patterning on a light-transmitting substrate by a printing method such as screen printing, stencil printing, offset printing, etc. When using this method, it is necessary to use a thickener, a partially crosslinked binder resin or a binder resin having a molecular weight exceeding 50,000 in combination to increase the viscosity of the donor.) Direct patterning using a flexible ink head that does not damage the light-transmitting substrate surface, a method of patterning by photolithography by imparting photosensitivity to the binder resin in the donor liquid, A method of patterning by a photoresist method without imparting photosensitivity to the liquid itself.

The black matrix in the color filter of the present invention is preferably formed with a film thickness of about 0.3 μm to 20 μm, and the film thickness is determined by an optimum value based on applicability, pattern resolution, optical density and the like. Can be. In the black matrix of the color filter of the present invention, the optical density value is preferably 0.5 to 4.0.
The range is about 0, more preferably about 2.0 to 4.0. Further, the ratio and the shape of the black matrix forming region and the non-forming region in the color filter of the present invention can be freely changed by adjusting the shape of a mask used for exposure, etc., depending on the function, use and the like. Note that the black matrix formed as described above has resilience to ink for forming a colored pixel described later by itself or a coating layer having a pattern of the same shape on the black matrix. Preferably, it is Ink resilience can be imparted by adding a substance having ink resilience to a resin, a solvent, or the like when forming the black matrix, as described below.

In the color filter of the present invention, colored pixels are formed together with the black matrix. The colored pixel is formed by being divided into, for example, three primary colors of red R, green G, and blue B using a known material or a dye by a method known in the art. As a method of forming a colored pixel, a known method such as an inkjet method, a printing method, a method of dyeing a dyeable medium formed using a photolithography method, a method of using a pigment-dispersed photosensitive composition, and an electrodeposition method Is mentioned.

For example, the following method is effective as a method for forming a colored pixel using an ink jet device.
Heads for three colors of R, G, and B are prepared, and minute ink droplets are ejected from each of the heads to color the colored pixel portions between the black matrices on the light transmitting substrate. As a coloring mechanism in this case, a dyeable ink may be used to dye the light-transmitting substrate itself or a dyeable medium formed on the light-transmitting substrate, and a resin, a dye or a pigment, and an ink solvent may be used. And then the resin may be thermally cured or photocured. In addition, when forming a dyeable medium on a light transmissive substrate, it is preferable to perform it before forming a black matrix. In addition, when the colored pixels are formed by the above-described inkjet method, even if a small amount of ink adheres to the black matrix, the amount of ink in the colored pixel portion becomes uneven, which causes color unevenness. Therefore, it is necessary to eject fine ink droplets so that no ink is deposited on the black matrix.

For this reason, it is important that the contact angle between the black matrix and the ink ejected from the ink jet device is large. As is well known, the contact angle between a liquid and a solid includes an advancing contact angle and a receding contact angle.For example, when fine irregularities exist on the surface of a black matrix or when the black matrix has an affinity for ink. When both a component having high resilience and a component having high resilience are contained, the receding contact angle may be small even if the advancing contact angle is large. In order to prevent the ink from adhering to the black matrix at all, it is particularly necessary that the receding contact angle of the ink is large. Specifically, when a color filter is produced using an oil-soluble inkjet ink or printing ink, the surface of each pixel must be exposed to water in order to prevent the ink from adhering to the black matrix.
It preferably has a receding contact angle of at least 60 °, more preferably at least 60 °. When a black matrix that satisfies this condition is used, the ink can be completely pushed into the colored pixel portion without adhering the ink. It should be noted that a large receding contact angle between the black matrix and the ink is also very effective when the pixel portion is colored using a flat type printing press using a waterless lithographic plate.

Further, the ink repellency can also be evaluated by the surface energy of a portion where ink adhesion is not desired.
For example, in order to prevent the ink from adhering to the black matrix at all, the surface energy of the black matrix or the coating layer formed thereon is 20 dyn / m2.
The following low energy is preferable. Further, it is preferable that a substance having a low surface energy is finely dispersed in the black matrix or the coating layer. Examples of low surface energy substances include, for example, fluorine-containing organic compounds,
And silicon-containing organic compounds.

In the color filter of the present invention, after the black matrix and the colored pixels are formed, for example, in the case of a color filter for a liquid crystal display element, in order to protect the color filter and to improve flatness, In order to prevent impurities from flowing into the liquid crystal layer existing adjacent to the color filter when assembled in the display element,
A transparent resin thin film may be formed on the surface. In addition, when forming the transparent resin thin film, if the above-described black matrix ink repellent coating layer becomes an obstacle,
The coating film may be peeled off in advance. Transparent resin thin film, for example, casein, gelatin, polyvinyl alcohol,
It can be formed by a known thin film forming method using (N-trimethoxysilylpropyl) polyethyleneimine or the like.

The color filter of the present invention can be suitably applied to all liquid crystal display devices such as an active drive type or a simple multiplex drive type transmissive liquid crystal display device or a reflective display type liquid crystal display device. Further, the color filter of the present invention includes a color plasma display (PDP),
The present invention can be widely applied to devices using a color filter such as an electroluminescent display (EL).

[0024]

EXAMPLES Examples of the color filter, the method of manufacturing the same, and the liquid crystal display device of the present invention will be specifically described below, but the present invention is not limited thereto. First, a specific method of chemical treatment of carbon black for a black matrix in the color filter of the present invention will be described.

(Surface Treatment of Carbon Black by Liquid Phase Oxidation) First, carbon black (Neospectra II:
Particles of 0.01 μm or less are contained in about 80% of all particles)
Was weighed in an amount of 10 g, added to 1 liter of 6N-HNO ₃ water, and heated and stirred at an internal temperature of 70 ° C. for 3 hours. Next, HNO ₃ water containing carbon black was filtered through a membrane filter, and then the filtered carbon black was filtered into acetic acid water (concentration: 0.2 N, volume 100 ml), pure water (1000 m2).
Washed in 1) and dried. The carbon black after the treatment was 10.2 g.

(Confirmation Reaction of Surface Carboxyl Group) 2 g of the surface-treated carbon black obtained above was weighed, added to 50 ml of a 0.1N NaHCO ₃ solution, and stirred at room temperature for 4 hours. Then, take 25 ml of the supernatant,
50 ml of 0.05N-HCl was added, and the mixture was boiled for 20 minutes while removing carbon dioxide from the system. Then 0.05
Back titration (phenolphthalein added) was performed with an N-NaOH solution. In addition, a blank test was performed at the same time, and the difference between the two was defined as the amount of carboxyl groups. As a result, in the blank test, 0.
40 mmol / g, 6.5 after treatment with basic solution
It was 1 mmol / g, and the presence of a carboxyl group on the surface of the carbon black particles was confirmed.

Examples 1 to 5 A 1% aqueous solution of gelatin was applied on a glass plate having a thickness of 2.5 mm with a spinner to form an undercoat layer having a thickness of 0.4 μm. Next, using a oxidizing agent shown in Table 1, a black matrix donor solution containing the following components containing carbon black surface-treated in the same manner as described above was printed in a desired pattern by a screen printing method. At 80 ° C. for about 5 minutes from the back surface of the glass plate to form a 2.0 μm-thick black matrix.

As a comparative example, a donor liquid for a black matrix containing untreated carbon black was prepared, and a black matrix was formed in the same manner. -Black matrix donor solution Surface-treated carbon black particles 10 parts by weight Styrene: maleic anhydride half-ester copolymer 15 parts by weight Ammonia additive (SMA-1440H) Alginate propylene glycol ester (thickener) 3 parts by weight part _{^{+ H 4 N - OOC-C}} 2 F 4 -COO - NH 4 + ( Hatsusui agent) 2 parts by weight of distilled water 60 parts by weight

[0029]

[Table 1]

Surface oxidation degree: amount of carboxyl group in 1 g of carbon black (mmol / g) Viscosity: Viscosity (CP) at 25 ° C. by B-type viscosity type Dispersion: Permeation by turbidimeter (integrating sphere type) Sex (pp
m) Next, an ink jet ejecting apparatus is used to form a pixel forming region of the ink repellent black matrix forming substrate,
Each of R, G, and B ink droplets was ejected to the corresponding position and colored. The ejected ink was as follows. (Red ink) Red pigment Pyrazolone red 5 parts by weight Surfactant "Newcol" 710F (manufactured by Nippon Emulsifier) 5 parts by weight Melamine resin "Sumitec Resin" M-3 (manufactured by Sumitomo Chemical) 10 parts by weight Curing agent ACX 0.3 parts by weight of water (manufactured by Sumitomo Chemical Co., Ltd.) 200 parts by weight of water (green ink) A green ink was prepared in the same manner as the red ink except that phthalocyanine green was used instead of pyrazolone red. (Blue ink) A blue ink was prepared in the same manner as the red ink except that a blue lake was used instead of pyrazolone red.

The ink jet-colored in this manner is applied to 12
By heating at 0 to 150 ° C. for 10 minutes or more, the melamine component in the ink was cured to form 1.5 μm-thick colored pixels. With respect to the color filter thus formed, the adhesion of the ink onto the black matrix and the receding contact angle between each colored pixel and the black matrix were measured by a microscope. Table 2 shows the results.

[0032]

[Table 2]

The dispersibility of the donor liquid using the untreated carbon black of Comparative Example 1 was extremely poor, and it was very difficult to form a black matrix. In addition, the optical density was small, the roughness of the black matrix surface was strong, the receding contact angle was not measurable, and it could not be used as a black matrix for color filters. On the other hand, as shown in Examples 1 to 5, even when the oxidizing agent used was treated at a very low concentration, the effect was sufficiently achieved, and it was found that the allowable range of the oxidizing agent concentration was wide.

(Examples 6 to 8) A black matrix was formed in the same manner as in the above example except that the carbon blacks shown in Table 3 were used as the surface-treated carbon blacks, and the characteristics were measured. , Optical density,
R, G, B, ink adhesion on black matrix,
It was found that there was no problem such as the receding contact angle and the color filter was excellent in display quality and flatness.

[0035]

[Table 3]

A liquid crystal display device in which such a color filter is used for an active drive type transmissive liquid crystal display device will be described with reference to FIGS. 1 and 2. FIG. The liquid crystal display panel 21 includes a TFT substrate 22 made of a transparent insulating substrate.
And the opposing substrate 23 are arranged to face each other, and are bonded together via a sealant 24 to seal the liquid crystal to form a liquid crystal layer 33, that is, a structure in which the liquid crystal layer 33 is sandwiched between the TFT substrate 22 and the opposing substrate 23. Has become.

On the TFT substrate 22, pixel electrodes 25 are formed in a matrix, and signal electrodes (source electrodes) 26 and scan electrodes (gate electrodes) 27 are formed.
Is formed. Near the intersection of the signal electrode 26 and the scanning electrode 27, a thin film transistor (TFT) 28
The TFT 28 has the pixel electrode 25
Is connected.

On the other hand, the common electrode 29
Are formed, and R corresponding to each pixel electrode 25 is formed.
(Red), G (green), B (blue) color filters 30,
A black matrix 31 for separating each pixel portion is formed. The black matrix 31 is provided to block light from entering the gaps between the pixel electrodes 25 and the TFT area.

The TFT substrate 22 and the counter substrate 23
In each of the embodiments, an alignment film 34 for aligning liquid crystal molecules in a predetermined direction is formed on a surface of each of the opposing surfaces in contact with the liquid crystal layer 33. Further, the alignment films 34 of both substrates 22 and 23,
On the surface opposite to the surface where
5, 35 are provided. Each pixel electrode 25 has R,
A pixel electrode 25r for displaying red, a pixel electrode 25g for displaying green, and a pixel electrode 2 for displaying blue corresponding to each of the G and B color filters 30.
5b, one pixel 32 is formed.

Each of the pixels 32 has a corresponding one of the pixel electrodes 25.
Is driven by the TFT 28 connected to the. That is,
The gate of each TFT 28 is connected to the scanning electrode 27, and each pixel electrode 25 is connected to the signal electrode 26 via the drain and source of the TFT 28. This allows each T
The FT 28 controls supply of an image signal to the pixel electrode 25,
The pixel electrodes 25 are independently driven.

In the liquid crystal display device having the liquid crystal display panel 21, the transmittance of the liquid crystal changes in accordance with the image signal supplied to each pixel electrode 25, thereby modulating the light incident from a backlight (not shown). By transmitting the color image, a color image is displayed.

[0042]

According to the present invention, the surface of carbon black particles having a fine structure is chemically treated with an inorganic oxidizing agent and optionally neutralized with an organic or inorganic basic substance. Thereby, when a black matrix of a color filter is formed by using this, it has a high-efficiency optical density, has excellent display quality and pixel flatness, and is stable to light, heat, temperature, etc. A color filter can be obtained.

Further, by using the above-described carbon black, a highly accurate color filter can be manufactured by a particularly simple method. Further, according to the present invention, by providing a color filter having excellent heat resistance, light resistance and moisture resistance, it is possible to realize an inexpensive liquid crystal display device having excellent color display performance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part showing a liquid crystal display device provided with a color filter of the present invention.

FIG. 2 is a schematic perspective view of a main part of the liquid crystal display device in FIG.

[Explanation of symbols]

 Reference Signs List 21 liquid crystal display panel 22 TFT substrate 23 counter substrate 24 sealant 25 pixel electrode 25r pixel electrode 25g for displaying red pixel electrode 25b for displaying green pixel electrode 26b for displaying blue 26 signal electrode (source electrode) 27 scanning electrode (gate electrode) 28 thin film transistor (TFT) 29 common electrode 30 color filter 31 black matrix 32 one pixel 33 liquid crystal layer 34 alignment film 35 polarizing plate

Continuation of front page (56) References JP-A-6-67421 (JP, A) JP-A-61-31470 (JP, A) JP-A-5-171056 (JP, A) JP-A-8-319444 (JP, A) JP-A-9-15403 (JP, A) JP-A-9-304760 (JP, A) JP-A-6-35188 (JP, A) JP-A-6-95434 (JP, A) 5-186704 (JP, A) JP-A-2-111885 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/20 101 G09F 9/30 349 C09C 1/48 C09C 1/56

Claims (6)

(57) [Claims] 1. A color filter comprising a plurality of colored pixels and a black matrix disposed between the colored pixels on a light transmitting substrate, wherein the black matrix is surface-treated with an inorganic oxidizing agent, Furthermore, a color filter formed by dispersing carbon black particles neutralized with an inorganic or organic basic substance in a binder resin dissolved in a polar solvent. 2. The color filter according to claim 1, wherein the inorganic oxidizing agent is nitric acid. 3. The color filter according to claim 1, wherein the carbon black particles are channel black particles. 4. The method according to claim 1, wherein the carbon black particles have a content of 0.001 to 0.001.
The color filter according to any one of claims 1 to 3, wherein the color filter has a particle size in a range of 0.1 µm, and the particles are 80% or more of all particles. 5. After treating the surface of carbon black particles with an inorganic oxidizing agent and further neutralizing with an inorganic or organic basic substance, the carbon black particles are dispersed in a binder resin dissolved in a polar solvent. A method for producing a color filter, wherein a black matrix is formed by preparing a donor liquid by applying the donor liquid on a light-transmitting substrate. 6. A liquid crystal is sealed between a pair of substrates, at least one of which is a light-transmitting substrate, and the color filter according to claim 1 is provided on at least one of the substrates. Characteristic liquid crystal display device.