JPH0570122B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a color filter that is suitable for being installed in a liquid crystal cell of a color liquid crystal display device, and includes twisted nematic (TN) type liquid crystal,
It also relates to a color filter for color separation in a color liquid crystal display device using a guest-host (GH) type liquid crystal. (Technical background of the invention and its problems) In contrast to CRTs (cathode ray tubes), which are said to already have satisfactory performance and price for conventional home use, but whose performance is being further improved, panel-type displays are Efforts have been made to satisfy the requirements in many ways, and the product has grown to account for approximately 20% of the market.
Panel-type displays include LEDs (light-emitting diodes), liquid crystals, fluorescent displays, EL (electroluminescent) displays, and plasma displays. It is aimed at applications that have not yet been penetrated. Among these panel-type displays, liquid crystal panels are TN-type liquid crystals, which have the major advantages of low voltage and low power consumption, making up for the difficulty of viewing due to strong viewing angle dependence, making them the mainstream for calculators, watches, games, etc. . Even in matrix displays, the number of rows, which are constrained by effective voltage dependence, viewing angle, temperature characteristics, etc., has been improved year by year.
A 128-line panel with 1/64 time division drive was put into practical use.
GH type liquid crystals are being put into practical use because the display color can be easily selected, the viewing angle is wide, there is little dependence on cell spacing or temperature, and the dichroism of the dye and the lifespan have been improved. In such a liquid crystal display device, a color filter method is particularly effective in providing full color and excellent color reproducibility. A color filter is provided inside or outside a liquid crystal cell, and utilizes the liquid crystal as an optical shutter to realize a full color display panel. When installed in a color filter liquid crystal cell,
It requires excellent properties in terms of transparency, light resistance, heat resistance, and chemical resistance. That is, in the liquid crystal cell manufacturing process, chemical resistance is required from the cleaning step, and heat resistance is required from the alignment film forming step, the transparent conductive film forming step, the liquid crystal sealing material forming step, and the like. However, organic filters that use dye-dyed polypeptides as the material for the filter layer, which are currently being used in color liquid crystal displays, have a heat resistance of 200%.
The temperature limit is around 10°C, and the chemical resistance is also poor, so there are many problems when used as a color filter for color liquid crystal display devices. (Purpose of the Invention) The present invention was realized after conducting various studies in order to compensate for the weaknesses of the above-mentioned dye-dyed organic filters. In addition, a color filter suitable for use in a liquid crystal display device is therefore provided. (Summary of the Invention) That is, the present invention provides a color filter having a colored layer mainly composed of a polyimide resin and an organic pigment on a substrate, and a protective layer interposed for each hue of the colored layer, The layer is formed by coating a substrate with a coloring composition whose main components are a polyimide precursor, an organic pigment, and a dispersion aid consisting of an organic dye derivative, and is formed by patterning with an alkaline solution. The color filter is characterized in that the protective layer is made of an acrylic resin thermoset at 200 to 300°C. (Detailed Description of the Invention) The color filter of the present invention will be explained below with reference to the drawings. FIG. 1 shows an example of a color liquid crystal display device using color filters. White light 1 emitted from a light source passes through a polarizing plate 2, a transparent substrate 3, a transparent pixel electrode 4, an alignment film 5, a liquid crystal 6, an alignment film 7,
The light passes through the colored layer 9 via the transparent common electrode 8 and is separated into three primary colors. In response to the electrical signals applied to the pixel electrodes 4 and the common electrode 8, the liquid crystal 6 is aligned, operates as an optical shutter by the action of the polarizing plate 11, and the electrical signals are converted into information as three primary color lights. The size of each color of the colored layer 9 is the same as that of the pixel electrode 4, and is on the order of several millimeters to several tens of microns to several hundred microns depending on various types of liquid crystal display devices, and can be made of materials capable of printing methods and photolithography. Is required. The configuration of the color filter of the present invention will be explained in more detail. As shown in FIG. 2, each colored layer has protective layers 15, 16,
17 is configured to be protected. In the case of a color liquid crystal display device, the colored layer consists of three colors: a red layer 12, a green layer 13, and a blue layer 14. Each colored layer is composed of a polyimide resin, a pigment, and a dispersion aid. This colored layer has the role of color-separating white light, and is required to have transparency, light resistance, heat resistance, and chemical resistance. The main component, polyimide resin, must be heat resistant, transparent, chemical resistant, patternable, and pigment-dispersible. Although polyimide alone has the above properties, it is difficult to disperse pigments, and it is necessary to add a dispersion aid to prevent pigment agglomeration and ensure uniform dispersion. The dispersion aid must also have heat resistance.
Derivatives of organic dyes, such as pigments or dyes, are very effective as dispersing aids for this purpose.
However, even if a polyimide resin having such a composition is coated, if the protective layers 15, 16, and 17 are not present, the polyimide resin has no solvent resistance, and coloring may occur during positive resist coating or positive resist film. Cracks occur in the layer, polyimide resin,
Transparency is lost. In addition, when the colored layer is patterned in one color and then patterned in several colors, that is, when coating with the second color polyimide resin, the first color layer may crack due to the solvent of the second color polyimide resin and lose its transparency. cormorant. Cracks also occur in the colored layer when coating an alignment film after patterning several colors. Furthermore, since polyimide resin is sensitive to alkaline solutions, a colored layer is left behind even when washed with alkaline solutions. The protective layers 15, 16, and 17 are required to improve solvent resistance and alkali resistance. This protective layer 1
Nos. 5, 16, and 17 require a composition that does not cause cracks in the polyimide resin during coating, and also requires transparency, heat resistance, chemical resistance, and light resistance. If a transparent polyimide resin is used as a protective layer, the polyimide resin of the colored layer will be soaked and cracks will occur when coating as a polyimide resin solution. When coating a resin as a protective layer, a solvent that does not attack the polyimide resin is required, and aromatic hydrocarbons and hexane-based solvents such as xylene and cyclohexanone are effective. Soluble in the solvent, transparent, heat resistant, chemical resistant,
Acrylic resin is effective as a light-resistant resin. Furthermore, it is advantageous that patterning is possible during lamination, and ultraviolet rays and acrylic resins that are sensitive to ultraviolet light are effective. Examples of resins that are considered to meet the above requirements include copolymers of glycidyl methane acrylate and cinnamate esters of glycidyl methacrylate, copolymers of glycidyl methacrylate and ethyl acrylate, and glycidyl methacrylate as a resin for improving heat resistance. There are copolymers of acrylate and styrene, glycidyl methacrylate and methacrylic acid chloride, etc. These acrylic resins are heat resistant up to at least 300°C and have chemical resistance to alkalis, acids, and solvents.Moreover, if they are heat-cured at a low temperature of about 200 to 300°C, they will not be filtered during heat curing. There is no fading of the organic pigments in the layer. moreover,
It is characterized by excellent transparency and low light absorption in the visible wavelength range of 400 to 700 nm. Furthermore, it is convenient if these acrylic resins have a photosensitive group that gives them the property of being polymerized and cured by exposure to ultraviolet light, since they can be partially cured by a photographic method and patterned by development. With the alkaline resin interposed as a protective layer,
For the first time, it becomes possible to provide colored layers of several colors on a transparent substrate. The polyimide resin used for the colored layer will be explained in more detail. The polyimide resin used in the colored layer of the present invention is generally obtained by a condensation reaction or an addition reaction of a polyimide precursor. Currently, commercially available polyimide precursors are mainly of the condensation reaction type, for example, by polymerizing tetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, etc. and aromatic diamine in a solvent, producing a polyamine acidic solution. , that is, a polyimide precursor is produced. The patterning of the polyimide resin is AZ-
Etching is carried out by using a photoresist such as 1350 (trade name, manufactured by Shippray, Inc., USA) or OFPR (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.), and etching the photoresist and polyimide resin together with a photoresist developer. This method heats the polyimide precursor coated on the substrate at 100°C to 150°C to semi-cure it.
A photoresist is coated on the polyimide precursor. The photoresist is exposed and developed with an alkaline solution. After development, the exposed polyimide precursor is semi-cured and therefore soluble in an alkaline solution, so the photoresist serves as a mask and is etched and patterned with an alkaline solution. For the alkaline solution, a strong alkaline solution such as tetramethylammonium hydroxide is used for photoresist AZ1350, and for photoresist OFPR,
Alkaline solutions such as sodium carbonate and sodium hydroxide are used. Another etching method is to heat the polyimide precursor until it is almost imidized, and then use a negative coat resist to etch the polyimide precursor with a mixed solution of hydrazine hydrate and ethylenediamine. Also, by vapor deposition using oxygen plasma, oxygen sputtering, etc.
There is also a method in which a metal film such as Mo or Cr is laminated and the polyimide film is dry etched using the metal film as a mask. The composition of the polyimide precursor of the present invention will be explained in more detail. The polyimide resin consists of a polyimide precursor, a pigment, and a dispersion aid in order to provide colored layers of each color. The role of the polyimide resin is to fix pigments of various colors on the substrate, to enable patterning of arbitrary shapes as required, and to form a transparent conductive film on the colored layer.
Pigments of each color have the role of separating white light into colors,
It must have excellent transparency, light resistance, and heat resistance. The primary particle size of the pigment is 0.3 microns or less,
It is preferably 0.1 micron or less, which is sufficiently small compared to the wavelength of visible light. An organic pigment is preferably used as a pigment with excellent transparency in the filter layer. The dispersion aid is added to prevent pigment agglomeration and to uniformly disperse the pigment in the polyimide resin. The dispersion aid also requires heat resistance. It has been found that derivatives of organic dyes, which are pigments or dyes, are very effective as dispersing aids for this purpose. The weight ratio of pigment to polyimide resin is usually preferably in the range of 3 to 0.05. Lowering the pigment ratio improves the properties as a filter, but
In order to obtain a predetermined optical density, it is necessary to increase the film thickness, which makes microfabrication difficult. Increasing the proportion of pigment significantly deteriorates the dispersibility and coating properties of the pigment. Therefore, the weight ratio of pigment to polyimide resin is preferably in the range of 0.5 to 3. The weight ratio of the dispersion aid to the pigment is preferably 0.01 to 0.2, but it is not necessarily limited to this value. Next, as pigments that can be used in the present invention, materials that are highly transparent and have excellent heat resistance, light resistance, and chemical resistance are shown below. All materials are indicated by color index (CI) numbers. CI Pigment Yellow 20, 24, 86, 93, 109,
110, 117, 125, 137, 138, 148, 153, 154,
166, 168 CI Pigment Orange 36, 43, 51, 55, 59,
61 CI Pigment Red 9, 97, 122, 123, 149,
168, 177, 180, 192, 215, 216, 220, 223,
224, 226, 227, 228, 240 CI Pigment Violet 19, 23, 29, 30,
37, 40, 50 CI Pigment Blue 15, 15:6, 22, 60, 64 CI Pigment Green 7, 36 CI Pigment Brown 23, 25, 26 CI Pigment Black 7 Next, the dispersion aid used in the present invention is an organic pigment. It is a derivative. Organic pigment derivatives are derivatives of organic pigments or dyes, such as azo,
Phthalocyanine series, quinacridone series, anthraquinone series, perinone series, thioindigo series, dioxazine series, isoindolinone series, quinophthalone series,
It is a triphenylmethane-based or metal complex salt-based organic dye compound having a substituent. The substituent is a substituent represented by the following general formula, such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a carbonamide group, or a sulfonamide group.

[Table] 〓 and heterocycles containing at least a nitrogen atom
The organic pigment and the parent organic pigment of the derivative are usually the same in terms of hue, but they do not necessarily have to be the same. As shown in FIG. 3, the structure of the color filter may include a black light shielding layer 19 interposed between the colored filter layers of each color. In this case, it is preferable to form the light-shielding layer 19 using a colored composition containing a black pigment such as carbon black by the above-mentioned etching means or printing means. Since the light-shielding layer 19 is also required to have heat resistance like the colored layer, it is preferable to use a layer in which a black pigment is dispersed in a heat-resistant resin layer such as polyimide. In addition, a black substance such as a metal or a metal compound, or a light-shielding substance may be formed by means such as vapor deposition. When a voltage is applied to both the common electrode 8 and the pixel electrode 4 in FIG. 1, an electric field is applied between the two electrodes, causing the liquid crystal 6 to align and act as a polarizer to act as a shutter for the white light 1. If thin film transistors are used, each pixel's red, green,
It functions as a switching element corresponding to the blue colored layer 9 to control the amount of light transmitted by each layer. Just like a color CRT, any color can be produced by mixing the three primary colors. It is also possible to provide the common electrode 8 on the colored layer directly on the substrate and to laminate the colored layer on the electrode, in which case it is necessary to pattern the protective layer as well. Incidentally, the color filter of the present invention can be fully used as a color stripe filter for an image pickup tube, and also as a color filter for a solid-state image sensor. The color filter according to the present invention will be described below based on Examples. (Example 1) 9.0 g and 0.9 g of pigment and dispersant were added to 90.1 g of polyimide precursor Semicofaine SP-910 manufactured by Toray Industries, Inc., and thoroughly kneaded with three rolls to produce red, green, and blue. Created a varnish. Pigments and dispersants are shown below. (For red filter) Pigment Liotogenredo GD (CI manufactured by Toyo Ink Mfg. Co., Ltd.)
A mixture of 6.75 g of Pigment Red 168) and 2.25 g of Lionogen Orange R (CI Pigment Orange 36 manufactured by Toyo Ink Manufacturing Co., Ltd.) Dispersion aid Compound of the following structural formula

[For green filter] Pigment Lionor Green 2YS (manufactured by Toyo Ink Manufacturing Co., Ltd.)
A mixture of 6.75 g of CI Pigment Green 36) and 2.25 g of Lionogen Yellow 3G (CI Pigment Yellow 154 manufactured by Toyo Ink Manufacturing Co., Ltd.) Dispersion aid The following copper phthalocyanine derivative CuPC [-SO ₂ N (C ₁₈ H ₃₇ ) ₂ 〕 ₂ (For blue filter) Pigment Lionor Blue ES (CI manufactured by Toyo Ink Manufacturing Co., Ltd.)
A mixture of 7.2 g of Pigment Blue 15:6) and 1.8 g of Lionogen Violet RL (Toyo Ink Manufacturing Co., Ltd. CI Pigment Violet 23) Dispersion aid Copper phthalocyanine derivatives listed below

[Chemical] Next, for 10g of red varnish, N-methyl-2
Add 2g of pyrrolidone (hereinafter referred to as NMP), stir thoroughly, and place on a glass substrate using a spinner.
Rotary coating was performed at 1500 rpm for 60 seconds, and after drying at 60°C for 15 minutes, prebaking was performed at 130°C for 60 minutes to form a red film. Next, a positive photoresist "OFPR" 25cp made by Tokyo Ohka was applied on the red film using a spinner at 2000 rpm, prebaked at 60°C for 60 minutes, pattern exposed with an ultra-high pressure mercury lamp, developed with an alkaline developer, and further developed. The red film was etched with a liquid and the red film was patterned, and then the unexposed areas of the "OFPR-" photoresist were peeled off with a mixed solution of xylene and N-butyl acetate in a ratio of 1:2.
A red colored layer was formed by heating and baking at 250°C for 30 minutes.
After that, Fuji Pharmaceutical “FVR”, an acrylic resin coating liquid,
Apply G-10” with a spinner at 1000rmp and heat at 60℃20
After drying for a minute, it was baked at 250°C for 30 minutes to form an intermediate protective film. Next, add 4g of NMP to 10g of green varnish, mix and stir, and apply on the FVR intermediate protective film.
The varnish was spin-coated at 2000 rpm for 60 seconds and treated in the same manner as the red varnish, patterned so as not to overlap with the red varnish to form a green colored layer. Then blue varnish
Add 2.5g of NMP to 10g, mix and stir, apply on the green coloring, apply on the baked FVR intermediate protective film, process in the same manner as the red varnish to form a blue coloring layer, and then apply the red layer. Apply FVR in the same way as
Cured at 250°C for 30 minutes. After forming the three colored layers and the protective layer FVR, an ITO film was formed by sputtering and baked at 300° C. for 1 hour to produce a color filter. (Example 2) Pigment and dispersant were added to 120 g of polyimide precursor "PIQ" manufactured by Hitachi Chemical Co., Ltd.
Red, green, and blue varnishes were created by adding 9.0g and 0.9g and making three rolls. The same pigment and dispersant as shown in Example 1 were used. An ITO film was formed on a glass substrate by sputtering and baked at 300°C for 1 hour. Thereafter, a solution in which 3 g of NMP was added to 10 g of blue varnish was spin-coated at 1800 rpm for 60 seconds, dried at 60°C for 15 minutes, and heated at 120°C for 30 minutes. An ITO film of 600 Å was sputtered on the blue film, heated at 120°C for 20 minutes, and 25 cp of “OFPR” was spin-coated on the ITO film at 2000 rpm, prebaked at 60°C for 60 minutes, and then exposed to pattern light.
Alkaline developed. The ITO film exposed by the development was etched with a 1.5% hydrochloric acid solution using OFPR as a mask, and the bottom layer, the blue film, was further etched with the aforementioned alkaline developer. After this,
The entire surface of the OFPR film is exposed, and the film is peeled off using an alkaline developer.
The entire exposed ITO film was etched with a 1.5% hydrochloric acid solution, leaving only the patterned blue film. Thereafter, the blue colored layer was baked at 250°C for 30 minutes,
On the blue colored layer, spin-coat the acrylic resin coating liquid "FVR, G-10" manufactured by Fuji Pharmaceutical at 1000 rpm and heat at 70℃.
Dry for 30 minutes. Thereafter, the pattern was exposed using an ultra-high pressure mercury lamp, developed with a solvent, and the edges were exposed. Applicable
The FVR membrane was dried at 60°C for 20 minutes and then heated at 250°C for 30 minutes to cure it. Next, add 2g of NMP to 10g of green varnish, mix and stir and apply on the FVR membrane.
Spin application at 1500 rpm for 60 seconds. After that, the same process as the blue varnish was performed to pattern the green colored layer and FVR layer. Furthermore, for 10g of red varnish
Add 4g of NMP, mix and stir, spin coat at 1000 rpm for 60 seconds on the FVR layer on top of the green colored layer, repeat the same process as above for the blue and green colored layers, pattern the FVR film in the same way, and layer the bottom layer. A color filter was manufactured by exposing the terminals of the ITO film. (Effects of the Invention) The present invention is a color filter as described above, and according to the present invention, a colored layer mainly made of polyimide resin, which has poor chemical resistance, especially chemical resistance, is provided with heat-resistant protection for each hue. Therefore, it has the durability required for the cleaning process with a solvent, the alignment film formation process, the transparent conductive film formation process, and the liquid crystal encapsulation sealing material formation process in the filter layer creation process. It satisfies chemical resistance and heat resistance. The obtained color filter is mainly composed of polyimide resin and organic pigment.
The color filter does not undergo discoloration or decomposition reactions even at high temperatures of approximately 200 to 300 degrees Celsius, and in combination with the heat-resistant protective film made of acrylic resin mentioned above, it is a color filter that can be applied to a wider range of applications including liquid crystal display devices. It has become so.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a full-color liquid crystal display device, FIG. 2 is a cross-sectional view showing an example of a color filter of the present invention, and FIG. FIG. DESCRIPTION OF SYMBOLS 1... White light, 2... Polarizing plate, 3... Transparent substrate, 4... Pixel electrode, 5... Alignment film, 6... Liquid crystal, 7... Alignment film, 8... Common electrode, 9... colored layer, 10... transparent substrate, 11... polarizing plate, 12,
13, 14... Colored layer, 15, 16, 17... Protective layer, 18... Substrate, 19... Light shielding layer.

Claims (1)

[Scope of Claims] 1. A color filter having a colored layer mainly composed of a polyimide resin and an organic pigment on a substrate, with a protective layer interposed for each hue of the colored layer, wherein the colored layer is on the substrate. It is formed by coating a coloring composition whose main components are a polyimide precursor, an organic pigment, and a dispersion aid consisting of an organic dye derivative, and is provided by patterning with an alkaline solution. and
In addition, the color filter is characterized in that the protective layer is made of an acrylic resin thermoset at 200 to 300°C. 2. The color filter according to claim 1, wherein the acrylic resin forming the protective layer is an ultraviolet curing resin. 3. A method for producing a color filter having a colored layer mainly composed of a polyimide resin and an organic pigment on a substrate, and a protective layer interposed for each hue of the colored layer, comprising: (a) a polyimide precursor on the substrate; (b) coating a photoresist thereon; (c) photoresist; (d) patterning the film provided in the steps (a) and (b) by developing with an alkaline solution;
a step of providing a colored layer; (e) a step of applying an acrylic resin coating solution that heat-cures at 200 to 300°C and heat-curing it to form a protective layer on the colored layer; at least the above steps (a) to (e); A method for manufacturing a color filter characterized by repeating a required number of colors.