JPH08286029A - Color filter and color liquid crystal display device using the same - Google Patents

Abstract

PURPOSE: To obtain a color filter which has polarizing power and is used as a component of a liquid crystal display device having high transmissivity by employing a polarizing element or plate that has a layer contg. optically active molecules and another layer contg. dichroic molecules as the constituent of the color filter. CONSTITUTION: This color filter consists of a polarizing element or plate which has a layer contg. optically active molecules and another layer that is in contact with this layer and contains dichroic molecules. This polarizing element is obtained by joining or dispersing the optically active molecules to or into the surface layer of a substrate beforehand, then irradiating the resulting optically active molecule layer with linearly polarized light having absorption wavelengths of the active molecules through a desired mask pattern to print a polarized light pattern in the layer and thereafter, adsorbing one or more than two kinds of dichroic molecules on this optically active molecule layer. As the optically active molecules, molecules each of which contains at least one nonaromatic double bond selected from C=C, C=N and N=N can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel color filter having a polarizing ability and a liquid crystal display device using the color filter.

[0002]

2. Description of the Related Art A color liquid crystal display device is a cathode ray tube (CR
T) Compared with color display devices, it is thinner and lighter, and the color reproducibility is being improved to a level comparable to that of other color display devices. By taking advantage of these features and arranging several panels, large display devices, multi-displays, etc. Has been applied to various display devices. A color filter method is a typical method for this full-color liquid crystal display device with excellent color reproducibility.This method uses a liquid crystal as an optical shutter by providing a color filter inside or outside the liquid crystal cell. is there. This color filter is generally formed by forming a pixel pattern of three primary colors of red, green and blue on a transparent substrate by a printing method, an electrodeposition method, a dyeing method and a pigment dispersion method.

At present, liquid crystal display elements are required to have low power consumption for OA / information device displays, particularly notebook personal computers. In order to reduce the power consumption of the liquid crystal display element, it is effective to improve the driving method, improve the efficiency of the backlight, and improve the transmittance of the liquid crystal display element. For that purpose, it is effective to improve the aperture ratio and the transmittance of the polarizing plate, but it is also important to improve the transmittance of the color filter. However, currently used color filters and polarizing plates cause a decrease in transmittance of liquid crystal display elements.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel color filter having a polarizing ability and a liquid crystal display device using the color filter.

[0005]

The present invention provides (1) a color filter comprising a polarizing element or a polarizing plate having a layer having a photoactive molecule and a layer containing a dichroic molecule in contact with the layer, (2) The color filter according to (1), wherein the layer containing a dichroic molecule is composed of pixel patterns of three primary colors of red, green and blue. (2) A color liquid crystal display device comprising the color filter of (2) above, a substrate, a liquid crystal layer and a polarizing plate. Regarding

The polarizing element or polarizing plate used in the present invention is described in, for example, WO95 / 07474.
Specifically, the color filter substrate and the liquid crystal cell substrate used in the present invention may be those capable of binding or coating photoactive molecules, for example, silica-based glass, a glass plate such as hard glass, a quartz plate, or the like. , ABS resin, acetal resin, (meth) acrylic resin, cellulose acetate,
Chlorinated polyether, ethylene-vinyl acetate copolymer, fluororesin, ionomer, methylpentene polymer, nylon, polyamide, polycarbonate, polyethylene terephthalate, polyester such as polybutylene terephthalate, polyimide, polyphenylene oxide, polyphenylene sulfide, polyallyl sulfone, Polyarylate, polyethylene, polypropylene, polystyrene,
Polysulfone, vinyl acetate resin, vinylidene chloride resin,
Plastic plates and sheets (films) of various materials such as AS resin, vinyl chloride resin, alkyd resin, allyl resin, amino resin, urea resin, melamine resin, epoxy resin, phenol resin, unsaturated polyester resin, silicone resin, polyurethane Used. These substrates may be not only flat but also curved.

The photoactive molecule used in the present invention is a molecule which undergoes a change in molecular axis orientation by linearly polarized light. The change in molecular axis orientation referred to here is a phenomenon in which the direction of the molecular axis changes after absorbing the light energy of linearly polarized light. As photoactive molecules for this purpose, C = C, C = N,
At least one double bond selected from N = N,
Molecules whose double bond is non-aromatic are effectively used. The wavelength of light absorbed by the photoactive molecule is not limited to that in the visible light region, and includes those in the ultraviolet and infrared regions that are not observed by the naked eye. When the layer of this photoactive molecule is irradiated with linearly polarized light including the wavelength range absorbed by the molecule, the molecular axis orientation is easily changed.

The phenomenon of molecular axis orientation change due to irradiation with linearly polarized light is interpreted as follows. That is, in the ground state of ethylene, which is the simplest molecule having a non-aromatic double bond, two carbon atoms and four hydrogen atoms are in the same plane, whereas in the photoexcited state, there are two pairs. HCH
It is well known that the planes formed by the atomic groups have a twisted structure orthogonal to each other. Similarly, in the photoactive molecule used in the present invention, the planarity formed by the above double bond disappears in the photoexcited state, and the molecular axis orientation change occurs in the process of returning to the ground state through the twisted structure caused thereby. It is estimated to be. Therefore, even if the molecular structure change based on the geometrical isomerization before and after the light irradiation is not caused, the molecular axis orientation change is advanced. For example, many azobenzene-based compounds having a non-aromatic N = N bond cause a photogeometric isomerization reaction from the trans form to the cis form by ultraviolet rays, but for longer wavelength light, the cis form to the trans form. It is well known that almost no photogeometric isomerization occurs because conversion to the body is prioritized. It is also known that the photoisomerization reaction may not be substantially observed in some cases because the change from the cis form to the trans form occurs rapidly thermally. A compound having a non-aromatic C = N bond can be converted into a geometric isomer by irradiation with light, but since it is unstable, it rapidly returns to its original thermodynamically stable structure. No photoisomerization is observed. Furthermore, most of the compounds having a non-aromatic C = C bond undergo a photogeometric isomerization reaction, but as with the case of azobenzene, light with a wavelength range suitable for isomerization from cis to trans isomers is used. , Substantially no geometric isomerization is observed. However, even when such an apparent photoisomerization reaction is not exhibited, the molecular axis orientation is easily changed by irradiation with linearly polarized light, and thus a compound having such a property can also be used as the photoactive molecule of the present invention. ..

Specific examples of the photoactive molecule used in the present invention are shown below. Examples of the non-aromatic compound having an N = N bond include aromatic azo compounds such as azobenzene, azonaphthalene, bisazo compounds and formazan, and further compounds having azoxybenzene as a basic skeleton.

Examples of the non-aromatic compound having a C = N bond include aromatic Schiff bases and aromatic hydrazones.

Examples of the non-aromatic compound having a C = C bond include polyene, stilbene, stilbazole, stilbazolium, cinnamic acid, indigo, thioindigo and hemithioindigo.

Further, the photogeometric isomer is unstable, so that the original structure is immediately returned to, and at room temperature, a compound in which a substantial photoisomerization reaction is not observed by irradiation of light, and further, the photogeometric isomerization reaction is not observed at all. Compounds not shown can also be used in the present invention, and examples thereof include cyanines and merocyanines.

Furthermore, C = C which is non-aromatic in the spiro ring
Other photoactive molecules, such as spiropyrans and spirooxazines, which are compounds having a bond or a C = N bond and which reversibly change the molecular structure upon irradiation with light can also be used. These are different from the above-mentioned molecular structures, but non-aromatic C = C bonds and C = N bonds contained in the molecule cause a reversible spiro ring opening / closing reaction by the action of light, It is considered that the axial orientation change occurs.

These photoactive molecules are listed as examples of the basic skeleton of the compound having a double bond group, and these skeletons have a methyl group, an ethyl group, a propyl group, a butyl group and a hexyl group. Alkyl groups such as, methoxy groups, ethoxy groups, propoxy groups, butoxy groups, and other alkoxy groups, allyl groups, allyloxy groups, cyano groups, methoxycarbonyl groups, ethoxycarbonyl groups, and other alkoxycarbonyl groups, hydroxy groups, dimethylamino groups , One or more substituents selected from a dialkylamino group such as a diethylamino group and a nitro group may be bonded. In particular, C ₁ -C which gives a structure similar to that of liquid crystal molecules
Preferred examples of the substituent include a ₆ alkyl group, a C _{1 to} C ₆ alkoxy group, a cyano group, and a C _{1 to} C ₆ alkoxycarbonyl group.

In the present invention, in order to provide a photoactive molecule layer which causes such a reversible molecular axis alignment change on a substrate, the photoactive molecule is physically or chemically added to the substrate surface depending on the surface characteristics of the substrate. There is a method of binding to the substrate, a method of preparing a polymer to which a photoactive molecule is bound or a polymer to which the photoactive molecule is added, and coating this on a substrate as a thin film. The photoactive molecule immobilized on the substrate surface, that is, the photoactive molecule bound to the substrate surface and the photoactive molecule bound polymer coated on the substrate as a thin film have the same orientation. The state is stable and preferable.

First, a method for binding a photoactive molecule to the substrate surface will be described. For this purpose, for example, if the substrate is silyl glass, the method used for liquid crystal alignment can be adopted (J. Cognard, “Molecular Crystals and Liquid Crystals”).
nd Liquid Crystals "Supplement 1 (1982), p. 1).

As a first method for binding the photoactive molecule to the surface of the substrate, a solution of the photoactive molecule having the above non-aromatic double bond group and the surface active group as described below dissolved in a solvent is used as the substrate. Examples include a method of coating the surface to adsorb and bond the photoactive molecule. Examples of surface active groups include carboxylic acid residues, malonic acid residues, carbamoyl groups, tetraalkylammonium groups, alkylpyridinium residues, alkylquinolinium residues, carboxylatochromium residues, ester residues, nitrile residues. Group, urea residue, amino group, hydroxyl group, betaine residue and the like. When the photoactive molecule is a liquid, it may be directly applied to the surface of the substrate.

As a second method, the Langmuir-Blodgett method can be employed in which the above-mentioned photoactive molecule having a surface active group is developed as a monomolecular layer on the water surface and at least one layer is transferred onto a substrate. For this purpose, surface active groups such as carboxyl group, carbamoyl group, amino group, ammonium group, tetraalkylammonium group,
Hydroxyl groups are preferred.

A third method is a method of binding a photoactive molecule to the surface of a substrate via a silyl group. Specifically, for example, a method of binding a photoactive molecule having a silyl group substituted with at least one halogen atom or an alkoxy group to the substrate surface, or a carboxyl group or a carboxyl group on the substrate surface treated with a silylating agent having an amino group. Examples thereof include a method of subjecting a photoactive molecule having an acrylic group to a condensation reaction or an addition reaction. In the former method, the silyl group is previously introduced into the photoactive molecule and the surface of the silica-based glass is treated.
Examples of the silyl group substituted with at least one halogen atom or an alkoxy group include a trichlorosilyl group,
Examples thereof include trimethoxysilyl group and triethoxysilyl group. In the latter method, examples of the silylating agent having an amino group include aminopropyltrichlorosilane, aminobutyltrichlorosilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane and the like. The operation of binding these photoactive molecules to the substrate surface may be carried out in the coexistence of another silylation treatment agent.
Examples of the silylation agent for this purpose, methyltriethoxysilane, dimethyldiethoxysilane, trimethylchlorosilane, ethyltriethoxysilane, diethyldiethoxysilane, propyltriethoxysilane, butyltriethoxysilane, butylmethyldiethoxysilane, Examples thereof include, but are not limited to, alkyl (poly) alkoxysilanes such as pentyltriethoxysilane and hexyltriethoxysilane.

As a fourth method, when the polymer substance forms the substrate itself or the substrate surface layer, the photoactive compound having a surface active group is adsorbed and bound to the substrate surface, or The photoactive molecule may be bound to the active group exposed on the surface of the molecule by a covalent bond. In the latter case, for example, when the polymer substance is polyvinyl alcohol, the photoactive molecule is bonded to the surface layer of the substrate by an acetal bond, an ester bond or a urethane bond.
For this purpose, for example, a photoactive molecule having a covalent bond-forming group such as a formyl group, a chloroformyl group, or an isocyanate group is prepared, and this is dissolved in a solvent that does not dissolve polyvinyl alcohol. May be soaked and reacted. In order to increase the treatment reaction rate, a catalyst acid such as p-toluenesulfonic acid may be added in the case of acetalization, and triethylamine or triethylamine in order to remove the acid generated in the reaction in the case of esterification or urethanization. A base such as pyridine may be added.

Next, a method for preparing a polymer to which a photoactive molecule is bound or a polymer to which a photoactive molecule is added and coating this as a thin film on a substrate will be described. First, a method for preparing a polymer to which a photoactive molecule is bound will be described. To attach the photoactive molecule to the side chain or main chain of the polymer,
Polymerize a monomer having a photoactive molecule, or
A photoactive molecule having a reactive residue suitable for its chemical structure is attached to a polymer substance.

In the former polymerization method, in particular, a photoactive molecule having a (meth) acryl group having radical polymerization ability is suitable as a monomer, and by polymerizing the photoactive molecule, a high-molecular compound having a photoactive molecule bonded to its side chain is used. The molecule is easily obtained. In the case of polymers such as polyesters, polyamides, polyimides and the like by polycondensation reaction and polyurethanes and other polyaddition reactions, a bifunctional monomer having a photoactive molecule may be prepared. Examples of the bifunctional monomer include vinyl cinnamate. The polymer compound having a photoactive molecule obtained by polymerization is a homopolymer obtained by polymerizing only a monomer having a photoactive molecule, or a copolymer obtained by polymerizing a monomer having a photoactive molecule and another monomer. Any of Other monomers include, for example, methyl (meth) acrylate,
Examples thereof include ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. By changing the use ratio of the monomer having the photoactive molecule and the other monomer, the binding amount of the photoactive molecule in the polymer can be adjusted. The usage ratio depends on the structure of the monomer, but is from 1: 0 to 1:10.
The range is 0, more preferably 1: 0 to 1:50.

In the latter case, when the photoactive molecule having a reactive residue suitable for its chemical structure is bound to the polymer substance, the above-mentioned fourth method can be used. Examples of the polymer to be used include, but are not limited to, polyvinyl alcohol, styrene-maleic anhydride copolymer, polyglycidyl methacrylate or its copolymer, and the like.

A spin coating method is preferable as a method for providing such a polymer thin film having a photoactive molecule in the main chain or side chain on the surface of the substrate. Further, this type of polymer may be provided on the substrate by the Langmuir-Blodgett method. Further, the substrate may be immersed in these polymer solutions for adsorption. A film thickness of 1 μm or less is sufficient.

A method of using a polymer to which a photoactive molecule is added will be described. This method is a method in which a photoactive molecule is dissolved or uniformly dispersed in a polymer in advance, and the photoactive molecule is applied in a thin film on the surface of the substrate. In this case, the polymer and the photoactive molecule must not dissolve in the solvent used for the solution of the dichroic molecule described below. As the polymer, for example, polyimides are particularly preferable because they are insoluble in solvents such as water and alcohols, but not limited thereto.

Next, the operation of irradiating the photoactive molecule layer provided on the substrate with linearly polarized light will be described. The wavelength of the polarized light to be irradiated is not particularly limited as long as it is a wavelength that is absorbed by the photoactive molecule, and may be not only visible light but also light in the ultraviolet or infrared region. As a light source, a mercury lamp, a xenon lamp, a fluorescent lamp, a chemical lamp, a helium-cadmium laser,
Any of an argon laser, a krypton laser, a helium-neon laser, a semiconductor laser, sunlight, or the like may be used, and it may be selected depending on an absorption wavelength region of a photoactive molecule, a light irradiation time, an irradiation area, or the like. Linearly polarized light may be obtained by combining light emitted from these light sources with a linearly polarizing element or a linearly polarizing plate. Examples of the polarizing element and the polarizing plate for this purpose include a prism element such as a Glan-Thompson prism and a polarizing element and a polarizing plate made of a polymer film obtained by dissolving or adsorbing dichroic molecules and stretching. Furthermore, the polarizing element (plate) manufactured by the present invention can also be used. The exposure energy of the linearly polarized light used here varies depending on the wavelength, the structure of the photoactive molecule, the bonding state, the irradiation temperature, etc., but is preferably in the range of 1 mJ / cm ² to 10 J / cm ² . When a laser is used as a light source, a polarizing element (plate) is not necessary if the laser beam itself is linearly polarized light.

In order to print the polarization pattern on the photoactive molecular layer, the photoactive molecular layer may be irradiated with linearly polarized light through a desired mask pattern. By diverging or condensing the linearly polarized light using a lens or the like, it is possible to greatly enlarge the pattern or, conversely, form an extremely fine pattern. When a laser is used as a light source and the laser beam itself is linearly polarized light, an extremely fine pattern can be freely drawn by combining with a polarization plane rotating element such as a Faraday element. Further, since the change of the molecular axis orientation of the photoactive molecule due to the linearly polarized light is reversible, the patterns can be freely overwritten by irradiating the linearly polarized light having a different polarization axis for each mask pattern. In addition, if one polarizing element (plate) having a complicated pattern is manufactured, the polarizing element (plate) having a complicated pattern, which was conventionally difficult, can be obtained by using the polarizing element (plate) as a mask pattern. A large number can be manufactured by a simple method of irradiation with linearly polarized light.

By adsorbing the dichroic molecule on the photoactive molecule layer having the molecular axes arranged in a certain direction thus obtained, that is, by providing the dichroic molecule layer on the photoactive molecule layer. , The molecular axis of the dichroic molecule is aligned in the alignment direction of the molecular axis of the photoactive molecule, that is, the direction defined by the polarization axis of the linearly polarized light irradiated on the photoactive molecule layer, and the polarization axis is fixed and polarized. The property as an element (plate) is exhibited.

The dichroic molecule used in the present invention is a compound exhibiting a polarization property by arranging in itself or in an aggregate in a certain direction, and for example, a compound having an aromatic ring structure is preferable. As the aromatic ring structure, in addition to benzene, naphthalene, anthracene, phenanthrene, thiazole, pyridine, pyrimidine, pyridazine,
Heterocycles such as pyrazine and quinoline, quaternary salts thereof, and condensed rings of these with benzene and naphthalene are particularly preferable. Further, it is preferable that hydrophilic substituents such as sulfonic acid group, amino group and hydroxyl group are introduced into these aromatic rings.

Examples of dichroic molecules include azo dyes,
Examples thereof include stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. Water-soluble compounds are preferable, but not limited thereto. Further, it is preferable that hydrophilic substituents such as sulfonic acid group, amino group and hydroxyl group are introduced into these dichroic molecules.

Since this dichroic molecule is used as a color filter, it is preferably a dye of three primary colors, and specific examples thereof include C.I. I. Direct
Red 39, C.I. I. Direct Red 7
9, C.I. I. Direct Red 81, C.I. I. D
direct Red 83, C.I. I. Direct R
ed 89, C.I. I. Acid Red 37, C.I. I. Direct Green 59, C.I. as blue color. I. Direct Blue 67, C.I. I.
Direct Blue 90 etc. are mentioned. The structures of typical ones of these dyes are shown below.

[0032]

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[0033]

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A method for anisotropically adsorbing these dichroic molecules to the photoactive molecule layer on the substrate irradiated with the linearly polarized light will be described below. The above-mentioned dichroic molecule alone or a mixture of two or more kinds is dissolved in a hydrophilic solvent such as water, methanol, ethanol or the like or a water-containing solvent thereof. The concentration is preferably 0.1 to 10 w / w%, more preferably 0.5 to 5 w /
It is about w%. A surfactant can also be added to this solution. As the surfactant, any of cationic, nonionic and anionic surfactants can be used, but nonionic surfactants are preferred. Next, the dichroic molecule solution is provided on the surface of the substrate by a photolithography method, a masking method, or the like to form a dichroic molecule layer including pixel patterns (color patterns) of three primary colors of red, green, and blue. Examples of the color pattern forming method include, but are not limited to, the above methods. The thickness of the dichroic molecular layer is preferably thin, from the viewpoint of improving the polarization characteristics, for example, 10 μm or less, particularly preferably 0.1 to 2 μm.

The substrate to which the solution of dichroic molecules is attached is dried to form a solid-state dichroic molecule layer, whereby the color filter of the present invention is obtained. The drying conditions vary depending on the type of solvent, the type of dichroic molecule, the amount of the solution of the dichroic molecule applied, the concentration of the dichroic molecule, etc., but the temperature is room temperature to 100 ° C., preferably room temperature to 5
0 ° C., humidity 20 to 80% RH, preferably 30 to 70
% RH is preferable.

The anisotropically adsorbed dichroic molecular layer thus prepared is in a solid state such as amorphous and crystalline, but since the dichroic molecular layer is usually inferior in mechanical strength, its surface is Is provided with a protective layer. This protective layer is usually a dichroic molecular layer coated with a transparent polymer film that is UV-curable, thermosetting and thermoplastic, or laminated with a transparent polymer film such as a polyester film or a cellulose acetate film. It is provided by a coating method such as a thing.

A color liquid crystal display device can be produced by using the color filter having a polarizing ability of the present invention.
FIG. 1 is shown as an example, but the structure of the liquid crystal display element is not limited to this.

[0038]

Industrial Applicability The polarizing element used in the present invention is prepared by previously binding or dispersing photoactive molecules on the surface layer of a substrate, and then irradiating linearly polarized light having a wavelength absorbed by the photoactive molecules. It is obtained by adsorbing one or more dichroic molecules on the layer. The reason why the polarizing element can be obtained by such a photochemical method is that the molecular axis of the dichroic molecule in the solid state is adsorbed on the photoactive molecule in which the molecular axis is aligned in a certain direction by linearly polarized light irradiation. This is considered to define the arrangement direction. By using the color filter having polarization ability of the present invention, it is possible to integrate the color filter and the polarizing plate, which is one of the causes of the decrease in the transmittance of the conventional liquid crystal display element, and the transmittance of the liquid crystal display element. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a schematic view of a color liquid crystal display device.

[Explanation of symbols]

 Figure 1 (1): Color filter substrate (2): Polarization color filter (3): Overcoat layer (4): Electrode (5): Liquid crystal layer (6): Electrode (7): Substrate (8): Polarizing plate

Claims (3)

[Claims] 1. A color filter comprising a polarizing element or a polarizing plate having a layer containing a photoactive molecule and a layer containing a dichroic molecule in contact with the layer. 2. The color filter according to claim 1, wherein the layer containing a dichroic molecule comprises a pixel pattern of three primary colors of red, green and blue. 3. A color liquid crystal display device comprising the color filter according to claim 2, a substrate, a liquid crystal layer and a polarizing plate.