JP4929715B2 - Liquid crystal display and color filter - Google Patents

Description

  The present invention relates to a liquid crystal display and a color filter used therefor, and more particularly to a liquid crystal display device using an inorganic EL exhibiting high luminance as a backlight.

 In a color liquid crystal display, a liquid crystal cell and a color filter are arranged between two polarizing plates, and the voltage applied to the electrodes of the liquid crystal cell is adjusted for each pixel, thereby allowing the first polarizing plate to pass through the backlight. Color display is enabled by controlling the polarization of light and controlling the amount of light transmitted through the second polarizing plate. Therefore, the emission spectrum of the backlight and the spectral characteristics of the color filter are important factors that determine the color characteristics of the color liquid crystal display device.

 Conventionally, pigment-dispersed color filters having excellent characteristics such as heat resistance and light resistance have been used as color filters, and fluorescent lamps having excellent color rendering properties have been widely used as backlights. In particular, a pigment dispersion type color filter is known which is formed of a coloring composition using a mixture of a dye and a copper phthalocyanine pigment for a blue pixel (see, for example, Patent Document 1).

 However, such a pigment-dispersed color filter has a trade-off relationship between color purity and light transmittance, and the brightness decreases as the color purity increases. For this reason, there is a problem in that sufficient brightness cannot be obtained with a conventional backlight.

In addition, the fluorescent lamp is thick and cannot be made flexible, and has a problem of low color purity. On the other hand, it is conceivable to use organic EL or inorganic EL as the backlight. However, since the organic EL is difficult to achieve both life and luminance, and the light amount is reduced to 1/10 due to deterioration, the backlight is used as the backlight. Is unsuitable. On the other hand, although inorganic EL has a long life, it has a low luminance and is difficult to use in combination with the color filter.
JP2001-124915

  The present invention has been made under the circumstances as described above, and an object thereof is to provide a liquid crystal display capable of displaying an image satisfying both high color purity and sufficient luminance.

  Another object of the present invention is to provide a color filter suitably used for such a liquid crystal display.

In order to solve the above-described problems, a first aspect of the present invention is a phosphor layer composed of YAG (yttrium, aluminum, garnet) yellow phosphor on a transparent substrate, a transparent electrode, an inorganic EL light emitting layer containing ZnS and GaAs. and a backlight sequentially laminated counter electrode, a color filter, a liquid crystal display comprising a liquid crystal device, the chromaticity of the color filter in the C light source, red, green, and for at least one color of blue , X> 0.67 for red, y <0.33, y> 0.71 for green, x> 0.14 for blue, and y <0.08 I will provide a.

  In such a liquid crystal display, the inorganic EL light emitting layer may be formed by a thin film forming method. The inorganic EL light emitting layer may be formed by forming particles containing ZnS and GaAs, dispersing them in a binder resin and a solvent, and applying the particles.

A second aspect of the present invention is a color filter used in the liquid crystal display according to the second aspect of the present invention, and includes a white inorganic EL including an inorganic EL light-emitting layer containing ZnS and GaAs and a yellow phosphor layer. The chromaticity when the element is used as the light source is x> 0.67 and y <0.33 for red, y> 0.71 for green, x> 0.14 for blue, and y <0.08. Provided is a color filter characterized by satisfying a condition.

  According to the liquid crystal display of the present invention, a combination of a backlight having an inorganic EL light emitting layer containing ZnS and GaAs and a color filter having a predetermined chromaticity satisfies both high color purity and sufficient luminance. The image to be displayed can be displayed. Moreover, according to the color filter of the present invention, a liquid crystal display that can display an image satisfying both high color purity and sufficient luminance is configured by combining with a backlight having an inorganic EL light emitting layer. be able to.

  The best mode for carrying out the invention will be described below.

  FIG. 1 is a cross-sectional view schematically showing a liquid crystal display according to an embodiment of the present invention. In FIG. 1, a pixel electrode 12 is formed on a glass substrate 10 among a pair of glass substrates 10 and 11 that are arranged to face each other, and a color filter 13 is formed on the glass substrate 11 to further protect the glass substrate 10. A common electrode 15 is formed via the film 14. A liquid crystal layer 16 is interposed between the glass substrates 10 and 11. A polarizing plate 17 and a backlight 18 are disposed outside the glass substrate 10, and a polarizing plate 19 is disposed outside the glass substrate 11.

  In the liquid crystal display according to one embodiment of the invention configured as described above, the backlight has a configuration as shown in FIG. That is, as shown in FIG. 2, a backlight is configured by sequentially laminating a phosphor layer 22, a transparent electrode 23, an inorganic EL light emitting layer 24, and a counter electrode 25 on a transparent substrate 21.

  Any material can be used as the transparent substrate 21 as long as it has translucency and has a certain level of strength. As such a thing, a glass plate, a plastic film, and a plastic sheet can be used, for example.

  As the phosphor layer 22, since the inorganic EL containing ZnS and GaAs emits blue light, a yellow phosphor can be used to obtain white light. Examples of the yellow phosphor include YAG (yttrium, aluminum, garnet). In addition, the emission spectrum of the backlight which combined blue light emission inorganic EL containing ZnS and GaAs, and YAG yellow fluorescent substance is shown in FIG.

As the transparent electrode 23, ITO can be used.
As the counter electrode 25, a metal such as Al or Mg can be used.
The inorganic EL containing ZnS and GaAs constituting the light emitting layer 24 can be produced by activating ZnS with an activator or coactivator and then reacting with GaAs in the presence of Mn. Copper can be used as the activator, and halogens such as Cl and Br can be used as the coactivator.

More specifically, it is obtained by mixing ZnS powder and an activator such as CuO ₄ and firing, then crushing the fired body, further adding GaAs powder, firing, washing, and drying. Can do. The firing temperature of the mixture of ZnS and GaAs is preferably about 300 to 1000 ° C. The mixing ratio of ZnS and GaAs is preferably 1: 9 to 9: 1.

  As a method of forming the inorganic EL light emitting layer 24 using the inorganic EL thus obtained, there are a vapor deposition method and a printing method.

  As the vapor phase method, an evaporation method, a CVD method, or a sputtering method can be used, but an evaporation method is preferable. Vapor deposition can be performed under conventionally known normal conditions. According to the vapor deposition method, an extremely high-brightness inorganic EL light-emitting layer can be obtained. The thickness of the inorganic EL light emitting layer formed by vapor deposition is preferably 0.01 to 5 μm, for example.

  The printing method is to print the ink containing the inorganic EL, and printing includes letterpress printing, offset printing and the like, and a method by letterpress printing using letterpress printing ink is preferable. The relief printing ink is obtained by dissolving the inorganic EL in a solvent together with a binder resin. The viscosity of the ink is preferably 15 to 50 mPas, for example. As the solvent, tetralin, cyclohexylbenzene, methyl benzoate, ethyl benzoate, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, or the like can be used. As the binder resin, for example, polystyrene, polyvinyl carbazole, or the like can be used. In addition, you may add surfactant, antioxidant, a ultraviolet absorber, etc. to ink as needed.

  The letterpress used for printing may be made of metal. However, when the printing medium is a brittle material, it is desirable that the printing medium be made of resin since cracks may occur in the printing medium due to pressing during printing. Further, the solvent contained in the ink is an oil-soluble organic solvent, and it is desirable to use a relief printing plate having a hydrophilic plate surface in order to prevent the printing plate from being swollen by this solvent and to accurately print the image line.

  Examples of such a water-developable curable photosensitive resin include a mixture of a hydrophilic polymer and a polymer having an unsaturated bond. Examples of the unsaturated bond include a vinyl bond, and examples of the compound having a vinyl bond include a methacrylate polymer. Moreover, what mixed the photoreaction initiator may be used. Examples of the photoreaction initiator include aromatic carbonyl compounds.

  The thickness of the inorganic EL light emitting layer formed by printing is preferably, for example, 0.1 to 50 μm.

  The color filter 13 used in the liquid crystal display according to the embodiment of the present invention has a chromaticity of at least one of red, green, and blue for the C light source, and x> 0.67, y <0.33 for red. For green, y> 0.71, for blue, x> 0.14, and y <0.08.

  Even when a white inorganic EL element including an inorganic EL light emitting layer containing ZnS and GaAs and a yellow phosphor layer is used as a light source, the chromaticity of such a white light source is at least one of red, green, and blue. For red, x> 0.67 and y <0.33, for green, y> 0.71, for blue, x> 0.14, and y <0.08.

  Specifically, such a color filter is composed of a mixture of a dye containing at least one of an oil-soluble dye, a disperse dye, and a basic dye and a copper phthalocyanine pigment as a blue pixel, and a mixture of the dye and the copper phthalocyanine pigment. A colored composition having a weight ratio of 10:90 to 50:50 can be used. As such a coloring composition, 80% by weight or more of the copper phthalocyanine pigment is C.I. What is I Pigment Blue 15: 6 can be used.

  Examples of pigments used for red pixels include C.I. Pigment Red 254 and C.I. As a pigment used for a green pixel, a mixture of I Pigment Red 177 is used as C.I. Pigment Green 36 and C.I. I Pigment Yellow 150 or C.I. Mixtures with I Pigment Yellow 139 can be used.

  Hereinafter, such a color filter will be described in more detail.

  The dye contained in the coloring composition includes at least one of an oil-soluble dye, a disperse dye, and a basic dye. One kind may be used alone, or two or three kinds may be mixed. Specific examples include oil-soluble dyes, disperse dyes, and basic dyes described in the color index. For example, C.I. I Solvent Blue 2, 5, 25, 44, 49, 73, C.I. I Solvent Violet 13, C.I. I Disperse Violet 26, 28, basic dyes include C.I. I Basic Violet 3, 14, 25, C.I. I Basic Blue 1, 5, 7, 26 and the like. The dyes exemplified above may be used alone or in combination.

  The mixing ratio of the dye and the pigment is in the range of 10:90 to 50:50 by weight. Preferably it is used at 20:80 to 40:60. When the mixing ratio of the dye is less than 10, the transparency is lowered, and when it exceeds 50, the heat resistance and the light resistance are lowered.

  As the copper phthalocyanine pigment, crystalline copper phthalocyanine pigments such as α-type, β-type, and ε-type can be used. Among them, since the maximum transmission wavelength is the shortest wavelength, ε-type copper phthalocyanine (CI Pigment Blue 15: 6) is preferably used. In particular, 80% by weight or more of copper phthalocyanine pigment is C.I. I. Pigment Blue 15: 6 is preferable. C. When the ratio of I Pigment 15: 6 is less than 80% by weight of the copper phthalocyanine pigment, the y value becomes large, and it becomes difficult to meet y = 0.06 of the EBU standard.

  Examples of the resin include a thermoplastic resin, a thermosetting resin, a photosensitive resin, and a monomer or oligomer that forms a coating film similar to the resin by curing with radiation, and these are used alone or in combination of two or more. be able to. When the composition is cured by ultraviolet irradiation, the color composition for color filter of the present invention is applied on a photoinitiator and a glass substrate so that the dry film thickness is 2 μm or less, preferably 1 to 2 μm. For example, a solvent or the like is added. When the thickness is 2 μm or more, there is a possibility that the thickness varies among the colors, the smoothness is lost between the colors, the orientation of the liquid crystal is disturbed, and the image quality is deteriorated.

  Examples of the thermoplastic resin include butyral resin, styrene-maleic acid copolymer, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyurethane resin, phenol resin, Examples include polyester resins, acrylic resins, alkyd resins, styrene resins, polyamide resins, rubber resins, cyclized rubbers, celluloses, polybutadiene, and polyimide resins. Moreover, as a thermosetting resin, an epoxy resin, a benzoguanamine resin, a melamine resin, a urea resin etc. are mentioned, for example.

  Photosensitive resins include (meth) acrylic compounds, cinnamic acid, etc. by intervening isocyanate groups, aldehyde groups, and epoxy groups in linear polymers having reactive substituents such as hydroxyl groups, carboxyl groups, and amino groups. A resin having a photocrosslinkable group introduced therein is used. In addition, a linear polymer containing an acid anhydride such as a styrene-maleic anhydride copolymer or an α-olefin-maleic anhydride copolymer is converted into a (meth) acrylic compound having a hydroxyl group such as hydroxyalkyl (meth) acrylate. Half-esterified polymers can also be used.

  As monomers and oligomers, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, cyclohexyl (meth) acrylate, polyethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa Various acrylic esters and methacrylic esters such as (meth) acrylate, tricyclodecanyl (meth) acrylate, melamine (meth) acrylate, epoxy (meth) acrylate, (meth) acrylic acid, styrene, vinyl acetate, (meth) Examples include acrylamide, N-hydroxymethyl (meth) acrylamide, and acrylonitrile.

  As photoinitiators, 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, diethoxyacetophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl Acetophenone photoinitiators such as ketones, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldimethyl Benzoin photoinitiators such as ketals, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl- Benzophenone photoinitiators such as' -methyldiphenyl sulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4,6-trichloro-s-triazine, 2-phenyl-4 , 6-Bis (trichloromethyl) -s-triazine, 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (tolyl) -4,6-bis (trichloromethyl) ) -S-triazine, 2-piphenyl-4,6-bis (trichloromethyl) -s-triazine, 2,4-bis (trichloromethyl) -6-styryl-s-triazine, 2- (4-methoxy-naphtho) -1-yl) -4,6-bis (trichloromethyl) -s-triazine, 2- (naphth-1-yl) -4,6-bi Triazine photoinitiators such as (trichloromethyl) -s-triazine, 2,4-trichloromethyl (piperonyl) -6-triazine, 2,4-trichloromethyl (4′-methoxystyryl) -6-triazine and carbazole A photoinitiator or an imidazole photoinitiator compound is used.

  The initiators are used alone or in combination of two or more. As the sensitizer, α-acyloxime ester, acylphosphine oxide, methylphenylglyoxylate, benzyl, 9,10-phenanthrenequinone, camphorquinone , Ethyl anthraquinone, 4,4′-diethylisophthalophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 4,4′-diethylaminobenzophenone I can do it.

  Solvents include cyclohexanone, ethyl cellosolve acetate, butyl cellosolve acetate, 1-methoxy-2-propyl acetate, diethylene glycol dimethyl ether, ethylbenzene, ethylene glycol diethyl ether, xylene, ethyl cellosolve, methyl-n-amyl ketone, propylene glycol monomethyl ether toluene, methyl ethyl ketone , Ethyl acetate, methanol, ethanol, isopropyl alcohol, butanol, isobutyl ketone, petroleum solvent and the like, and these are used alone or in combination.

  As described above, the liquid crystal display device according to an embodiment of the present invention includes a backlight including an inorganic EL light emitting layer containing ZnS and GaAs and a specific color exhibiting a predetermined chromaticity by combining the backlight. It is a combination of filters, and an image satisfying both high color purity and sufficient luminance can be displayed.

It is sectional drawing of the EL element which concerns on one Embodiment of this invention. It is sectional drawing of the EL element which concerns on one Embodiment of this invention. The characteristic view which shows the emission spectrum of the backlight which combined blue light emission inorganic EL and yellow fluorescent substance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,11 ... Glass substrate, 12 ... Pixel electrode, 13 ... Color filter, 14 ... Protective film, 15 ... Common electrode, 16 ... Liquid crystal layer, 17, 19 ... Polarizing plate, 18 ... backlight, 21 ... transparent substrate, 22 ... phosphor layer, 23 ... transparent electrode, 24 ... inorganic EL light emitting layer, 25 ... counter electrode.

Claims (4)

A phosphor layer made of YAG (yttrium aluminum garnet) yellow phosphor on a transparent substrate, a backlight inorganic EL light-emitting layer, and were successively laminated a counter electrode containing a transparent electrode, ZnS and GaAs, and the color filter, A liquid crystal display comprising a liquid crystal element , wherein the chromaticity of the color filter in the C light source is at least one of red, green and blue, x> 0.67 for red, A liquid crystal display characterized by satisfying the condition of y> 0.71 for green, x> 0.14 for blue, and y <0.08.   The liquid crystal display according to claim 1, wherein the inorganic EL light emitting layer is formed by a thin film forming method.   2. The liquid crystal display according to claim 1, wherein the inorganic EL light emitting layer is formed by forming particles containing ZnS and GaAs, dispersing the particles in a binder resin and a solvent, and applying the particles. The color filter used in the liquid crystal display according to any one of claims 1 to 3, wherein a white inorganic EL element including an inorganic EL light-emitting layer containing ZnS and GaAs and a yellow phosphor layer is used as a light source. The chromaticity is such that x> 0.67 and y <0.33 for red, y> 0.71 for green, x> 0.14 for blue, and y <0.08. Color filter to be used.

Images