JPH04301604A - Color filter and production thereof and liquid crystal display device formed by using this filter - Google Patents

Abstract

PURPOSE:To provide the color filter which is good in image contrast, is free from unequal colors, is large in area and is low in production cost and the process for producing this color filter and further the liquid crystal display device formed by using this filter. CONSTITUTION:The color filter is constituted by providing transparent electrodes 2 on a transparent substrate 1 and providing a transparent colored layer 5 consisting of the aggregate of the chain-form chromatic conductive high polymers oriented nearly perpendicularly to the transparent substrate 1 on these transparent electrode 2. The production of this color filter is executed by forming a thin film 4 of nitrile/butadiene rubber on the transparent electrodes 2, then immersing the substrate together with a counter electrode into a soln. contg. the monomer of the chromatic conductive high polymers and a supporting base and impressing a voltage between both electrodes to form the thin film of the colored conductive high polymers.

Description

[Detailed description of the invention]

[Object of the invention]

0002

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

0003

[Prior Art] Liquid crystal display devices, the demand for which has been increasing rapidly in recent years, and fluorescent discharge tubes that make up the pixels of large display devices used outdoors, are equipped with color filters that enable these devices to display color. It is used.

FIG. 3 shows an example of a color filter used in a color liquid crystal display device. In the same figure, this color filter 31 includes a black matrix 33 provided in a portion separating individual pixels on one surface of a transparent substrate 32, and a colored layer 34 formed in the pixel portion formed by this black matrix 33. On top of these, a transparent protective film 35,
It has a structure in which a transparent electrode 36 and an alignment film 37 are laminated in this order. In the color liquid crystal display device, the color filter 31 is disposed facing an array substrate 40 in which pixel electrodes 39 are formed on a transparent substrate 38 at positions corresponding to individual pixels, and a liquid crystal composition 41 is placed between them. While holding the
It has a structure in which polarizing plates 42 and 43 are integrally laminated on both sides.

By the way, the characteristics of a color liquid crystal display device are as follows.
Although it is known that the quality of the color filter greatly depends on the quality of the color filter, conventionally, a glass substrate or the like has been used for the transparent substrate 32 of the color filter 31, and the black matrix 33 is made by patterning a Cr thin film formed by sputtering. The pattern is formed by a method of photo-etching, or a method of forming a pattern by exposing a thin film formed by coating a black dye containing a photosensitizer. In addition, in the colored layer, three types of pigments corresponding to the three primary colors of R (red), G (green), and B (blue) are arranged in each pixel area, and each pigment is arranged in the pixel area. Methods used include dyeing methods, dye dispersion methods, pigment dispersion methods, printing methods, electrodeposition methods, and dye vapor deposition methods. Furthermore, acrylic resin, epoxy resin, etc. are used for the transparent protective film 35, and the transparent electrode 3
6 has I. T. O. (Indium Tin Oxid
e) A polyimide thin film is generally used for the alignment film 37.

[0006] However, there are still many points that need to be improved in the technology related to conventional color filters, and among them, the process of arranging the pigments has a large impact on the characteristics and manufacturing cost of the resulting color filter. As mentioned above, various methods are known, but each has its advantages and disadvantages.

That is, the dyeing method results in a colored layer that is poor in water resistance, chemical resistance, especially alkali resistance, and heat resistance. For this reason, for example, in order to reduce the resistivity when forming a transparent electrode, I. T. O. After forming thin films such as, heat treatment is performed, but it is not possible to raise the processing temperature high, and it is not possible to obtain transparent electrodes with sufficiently low resistivity, resulting in image contrast of display devices using this. decreases.

[0008] The dyeing and dispersion method improves water resistance and chemical resistance compared to the dyeing method, but heat resistance is not improved because it depends on the inherent properties of the dye, and in addition, it requires a large number of steps and requires expensive dispersion. The disadvantage is that the manufacturing cost is high because of the use of chemicals.

Although the pigment dispersion method has sufficient heat resistance and does not have the above-mentioned problems, it uses expensive organic pigments, and
Since this pigment goes through a process of once applying it to areas other than pixel areas, a large amount of pigment is required and the manufacturing cost is extremely high.

[0010] In the printing method, as the size of the color filter increases, the accuracy for accurately placing the dye in the pixel area becomes poor, so there is a limit to the printing size, and the surface smoothness of the printed pixels is inferior. There are some difficulties.

[0011] In principle, in the electrodeposition method, a transparent electrode is provided on a transparent substrate, and a colored layer is formed by disposing a dye on this electrode, so the heat resistance requirements are higher than those of the above-mentioned methods. On the other hand, when driving a liquid crystal display device, a colored layer must be sandwiched between a transparent electrode and an opposing electrode, and a voltage applied to it. Since the colored layer has extremely low conductivity, the voltage applied to the liquid crystal layer is low, resulting in a reduction in the contrast of the resulting image. In order to solve this problem, as shown in Japanese Patent Application Laid-Open No. 64-80984, a polymer film is formed on a transparent electrode by electrolytic polymerization, and then it is immersed in a solution containing a dye and a voltage is applied. However, this method requires two steps: forming the polymer membrane and dyeing the polymer membrane, resulting in high costs.

0012

[Problems to be Solved by the Invention] As described above, each of the conventional colored layer forming methods for color filters has its own drawbacks. However, the reality is that satisfactory properties and manufacturing costs have not yet been obtained.

[0013] By the way, if we summarize and examine the above-mentioned methods for forming colored layers, in the dyeing method, dye dispersion method, pigment dispersion method, and printing method, transparent electrodes are formed after forming a colored layer on a transparent substrate. There is. On the other hand, in the electrodeposition method, a colored layer is formed after forming a transparent electrode on a transparent substrate. The transparent electrode can be formed by any method such as I.D. using a sputtering method or the like. T. O. After forming a thin film such as, heat treatment is performed to lower the resistivity. therefore,
The former dyeing method requires heat resistance that can withstand the heat treatment temperature to obtain a transparent electrode with sufficiently low resistivity, but methods that use dyes do not allow the heat treatment temperature to be raised;
A transparent electrode with sufficiently low resistivity cannot be obtained, resulting in low image contrast. When a pigment is used, the heat resistance is sufficient, but as mentioned above, the manufacturing cost increases. In the printing method, there is a limit to the print size and the surface smoothness is poor. On the other hand, in the latter electrodeposition method, a colored layer is formed after forming the transparent electrode, so there is no problem in obtaining a transparent electrode with sufficiently low resistivity, but there is a colored layer that is an insulator on the transparent electrode. Therefore, the effective voltage applied to the liquid crystal layer decreases,
Image contrast decreases. Further, in the polymer membrane dyeing method which is an improvement on this electrodeposition method, the problem of manufacturing cost remains.

[0014] To summarize the above, it is desirable that the formation of the transparent electrode be performed before the formation of the colored layer, and
It is desirable that the colored layer formed on the transparent electrode does not reduce the effective voltage applied to the liquid crystal layer. Moreover,
The present invention was made based on such knowledge that it is desirable not to limit the formation area or increase the manufacturing cost, and the transparent electrode is formed before the colored layer is formed.
In addition, the above-mentioned problems of the prior art can be solved by making the colored layer formed on the transparent electrode so as not to reduce the effective voltage applied to the liquid crystal layer without restricting the formation area or increasing the manufacturing cost. It is an object of the present invention to provide a large-area, low-cost color filter with good image contrast and no color unevenness, a method for manufacturing the same, and a liquid crystal display device using the same. [
Structure of the invention]

[0015]

[Means for Solving the Problems] The color filter of the present invention has a transparent electrode on a transparent substrate, and on this transparent electrode, a chain-shaped colored conductive polymer is oriented almost perpendicularly to the transparent substrate. It is characterized by comprising a transparent colored layer consisting of an aggregate.

The method for manufacturing a color filter of the present invention further includes a step of forming a transparent electrode on a transparent substrate, a step of forming a thin film made of nitrile butadiene rubber on the transparent electrode, and a step of forming a thin film made of nitrile butadiene rubber on the transparent electrode. butadiene rubber
A transparent substrate with a thin film formed thereon is immersed together with a counter electrode in a solution containing a colored conductive polymer monomer and a supporting salt, and a voltage is applied between the transparent electrode and the counter electrode. The present invention is characterized by comprising the step of forming a colored conductive polymer thin film on the transparent electrode by passing it through the thin film made of nitrile butadiene rubber. Furthermore, the liquid crystal display device of the present invention has a transparent electrode on the color filter, that is, a transparent substrate, and a collection of chain-shaped colored conductive polymers oriented substantially perpendicularly to the transparent substrate on the transparent electrode. It is characterized by having a transparent colored layer consisting of the body.

Examples of the conductive polymer constituting the colored layer of the color filter of the present invention include thiophene derivatives such as thiophene, 3-methylthiophene, and 2-benzothiophene, and furan derivatives such as furan, 2-methylthiophene, and benzofuran. polymers whose monomers are 5-membered heterocyclic compounds, polymers whose monomers are aromatic amino compounds such as aniline, its derivatives, and diphenylamine, and monomers containing aromatic hydrocarbon compounds such as pyrene, azulene, and fluorene. Polymers containing vinyl compounds such as vinylcarbazole as monomers, polymers containing aromatic halogen compounds such as dibrompyridine and tetrabromoxylene as monomers, etc. The polymer is not particularly limited to the above, as long as it is a polymer with a structure having a double bond or triple bond in the molecule and has a color.

In the present invention, an I.I. T. O. A transparent electrode is formed by forming a film of , tin oxide, indium oxide, etc. by a sputtering method, a vacuum evaporation method, or the like.

[0019] In addition, in order to form a transparent colored layer consisting of an aggregate of chain-shaped colored conductive polymers oriented almost perpendicularly to the transparent substrate on this transparent electrode, first, nitrile butadiene rubber is coated on the transparent electrode. A thin film of - is formed by a method such as a spin coating method or a casting method. In addition, nitrile butadiene rubber has a structural formula shown by the following formula.

[0020]

[Chemical formula 1]

Next, as shown in FIG. 2, the transparent electrode 21
A transparent substrate 23 on which a thin film 22 made of and nitrile butadiene rubber is sequentially formed is heated in a solution (electrolytic polymerization solution) containing a colored conductive polymer monomer and a supporting salt as mentioned above.
By immersing a counter electrode 25, for example, an electrode made of platinum, etc., in 24, and applying a required voltage between both electrodes 21 and 25, a colored conductive conductive material is formed on the transparent electrode 21 through the thin film 22 made of nitrile butadiene rubber. The polymer is polymerized and precipitated. As a result, a transparent colored layer (not shown) consisting of an aggregate of chain-shaped colored conductive polymers oriented substantially perpendicularly to the transparent substrate 23 is finally formed. The transparent colored layer formed here has conductivity, for example, polythiophene has a conductivity of 102 Scm-1, and ponianiline has a conductivity of 10 Scm-1. In FIG. 2, 26 is a constant voltage power supply for applying a voltage between both electrodes 21 and 25, and 27 and 28 are a reference electrode and a potentiometer, respectively.

[0022] The above-mentioned supporting salt is not particularly limited, but it is desirable to select and use one type from those represented by chemical formulas such as LiClO4, LiBF4, and LiPF4. In addition, propylene carbonate is used as a solvent for dissolving the colored conductive polymer monomer and supporting salt.
Bonate, acetonitrile, water, etc. are used.

The absorption spectrum of the colored conductive polymer changes reversibly as it undergoes redox. Table 1 shows the colors that various colored conductive polymers have in the redox state, taking as an example a polymer having a thiophene derivative and an aniline derivative as monomers.

[0024]
[Table 1]
monomer
polymer color

oxidant
Reduced thiophene
Blue Red 3-methylthiophene
deep blue red
2-benzothiophene colorless
blue aniline green
Colorless Therefore, from among various conductive polymers, conductive polymers that have a desired color in either redox state are selected, and the monomers constituting these are used to prepare an electrolytic polymerization solution. By appropriately masking the electrode and forming a conductive polymer,
A color filter having a layer colored in a desired color at a desired position and in a desired shape can be manufactured.

[0025]

[Function] The color filter of the present invention has a structure in which a transparent electrode is provided on a transparent substrate, and a colored layer is provided on this transparent electrode, so that a sufficiently high heat treatment can be performed when forming the transparent electrode. It is possible to obtain good contrast in a display device using this.

Moreover, the colored layer is composed of an aggregate of chain-shaped colored conductive polymers oriented substantially perpendicularly to the transparent substrate, and has conductivity, so that in a display device using the colored layer, the liquid crystal layer It also does not reduce the effective voltage applied to.

Furthermore, in the manufacturing method of the present invention, the nitrile-butadiene rubber thin film is etched into a tubular shape in an electrolytic polymerization solution, and then a conductive polymer is electrolytically polymerized on the etched tubular portion, so that it becomes conductive. The polymer chains can be oriented almost perpendicularly to the transparent electrode and have uniform lengths, and a colored layer with excellent smoothness can be formed, making it possible to manufacture color filters with no uneven color. can. In addition, the length of the conductive polymer chain can be adjusted by adjusting the electrolysis time, current density, voltage, etc. By keeping these conditions constant, conductive polymer chains of uniform length can be produced even on large-area transparent substrates. A molecular chain, that is, a colored layer with a uniform thickness can be formed.

Furthermore, since the liquid crystal display device of the present invention uses the color filter described above, it has good contrast, no color unevenness, and high reliability.

[0029]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

First, as shown in FIG. 1, a glass substrate is used as the transparent substrate 1, and an I
．． T. O. by sputtering method to a thickness of 0.1 μm
A film was formed and heat treated to form a transparent electrode 2 with low resistivity. Next, on this transparent electrode 2, a 0.1 μm thick Cr
A thin film was formed by sputtering, and a positive resist (PMER P-40 manufactured by Tokyo Ohka Co., Ltd.) was applied on top of the thin film.
0) was applied to a thickness of 1 μm using a spinner, and a predetermined black pattern 3 was formed by sequentially performing exposure, development, etching, and resist removal. Subsequently, a nitrile butadiene rubber thin film 4 was formed thereon to a thickness of 0.5 μm by spin coating.

[0031] After that, a shielding plate (not shown) having an opening of a predetermined shape at a predetermined position corresponding to a part of the non-forming part of the black pattern 3 is superimposed and fixed on top of this. This was immersed in an electrolytic polymerization solution tank as shown in FIG. 2 above, with the transparent electrode 2 facing the platinum electrode and lithium electrode, which had been placed in advance as a counter electrode and a reference electrode, respectively. did. In addition, in the electrolytic polymerization solution bath, thiophene as a monomer to form a conductive polymer and LiClO4 as a supporting salt are contained in propylene carbonate as a solvent.
An electrolytic polymerization solution containing 0.1 mol/dm3 of each dissolved therein is stored.

In this state, a voltage is applied between the transparent electrode 2 and the counter electrode so that the transparent electrode potential becomes +0.75VvsLi/Li+, and a thickness of 0.5 μm is formed on the transparent electrode 2.
A thin film of polythiophene was formed and brought into a reduced state to obtain a transparent conductive polymer film colored red.

After that, the glass substrate on which the conductive polymer film was formed was taken out from the electrolytic polymerization solution tank and the shielding plate was removed. A transparent conductive polymer thin film 5a colored red in a predetermined shape was arranged.

Similarly, green and blue transparent conductive polymer films 5b and 5c were formed on the transparent electrode 2 to form a colored layer 5 having the three primary colors of red, green and blue. In addition, to form the green transparent conductive polymer film 5b, aniline is used as a monomer to form a conductive polymer and Li is used as a supporting salt in propylene carbonate as a solvent.
After forming a thin film using a solution in which 0.1 mol/dm3 of ClO4 was dissolved, the film was brought into an oxidized state and colored green. To form the blue transparent conductive polymer film 5c, 2-benzothiophene as a monomer for forming a conductive polymer and LiClO4 as a supporting salt are added in propylene carbonate as an electrolytic polymerization solution at 0.0.
After forming a thin film using a 1 mol/dm3 dissolved solution,
It was brought into a reduced state and colored blue.

After forming the colored layer 5 in this manner, a liquid obtained by dissolving acrylic resin in an organic solvent is applied thereon using a spinner to form a transparent protective film 6, and then a polyimide resin is screened on top of it. An alignment film 7 was formed by printing to produce a color filter.

The contrast ratio and in-plane color difference of the obtained color filter were examined and compared with those of color filters produced by conventional dyeing and pigment dispersion methods. The color filter of the example was superior to the conventional one, and the in-plane color difference was smaller than that of the conventional one, and had good characteristics. The above results are shown in Table 2.

[0037] Note that the contrast ratio here refers to the color
Place a deflection plate and a backlight behind the filter,
This is the ratio of the brightness of backlight light transmitted through a color filter when one deflection plate is placed in front and both deflection plates are combined in parallel and perpendicular directions.

[Table 2
]

Example Comparative example 1
Comparative example 2

(Dyeing method) (Pigment dispersion method) Contrast ratio Blue 1420 33
0 450
green
1050 320
420
red 1200
280 140
In-plane color difference
0.9 1.5
2.1 Next, a liquid crystal display device of the same type as the liquid crystal display device shown in FIG. 3 described above was manufactured using the above color filter. This will be explained below with reference to FIG.

[0039] That is, the color filter having the above configuration is
The color filter 31 shown in FIG. 3 is arranged opposite to an array substrate 40 in which a large number of predetermined pixel electrodes 39 are formed on a glass substrate 38, and a transformer 4-n- The pentylcyclohexyfluphenyl derivative compound was sandwiched and its periphery was sealed and fixed with a sealing agent 44 made of epoxy adhesive, and polarizing plates 42 and 43 were integrally laminated on both surfaces thereof. Note that the substrate spacing was 10 μm.

[0040] The liquid crystal display device thus obtained is as follows:
It had excellent contrast and good display quality without color unevenness.

[0041]

[Effects of the Invention] As explained above, according to the present invention,
A color filter that has a transparent electrode of low resistance and does not reduce the effective voltage of the liquid crystal layer can be obtained at low cost without any area limitations, and by using this color filter, A liquid crystal display device with excellent contrast and display quality without color unevenness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a color filter according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method for manufacturing a color filter according to the present invention.

FIG. 3 is a cross-sectional view showing a structural example of an active matrix liquid crystal display device using color filters.

[Explanation of symbols]

1, 21...Transparent substrate 2, 21...Transparent electrode 4, 22...Nitrile butadiene rubber thin film 5...
Colored transparent conductive polymer films 5a, 5b, 5c...
Red, green, and blue transparent conductive polymer films 25...Counter electrode 31...Color filter

Claims (3)

[Claims] 1. A transparent electrode is provided on a transparent substrate, and a transparent colored layer made of an aggregate of chain-shaped colored conductive polymers oriented substantially perpendicularly to the transparent substrate is provided on the transparent electrode. A color filter featuring 2. A step of forming a transparent electrode on a transparent substrate, a step of forming a thin film made of nitrile butadiene rubber on the transparent electrode, and a step of forming a thin film made of the transparent electrode and nitrile butadiene rubber. A transparent substrate is immersed together with a counter electrode in a solution containing a colored conductive polymer monomer and a supporting salt, and a voltage is applied between the transparent electrode and the counter electrode to form a colored conductive conductor on the transparent electrode. 1. A method for manufacturing a color filter, comprising the step of forming a thin film of a color polymer through the thin film made of the nitrile butadiene rubber. 3. A liquid crystal display device comprising the color filter according to claim 1.