JP2000275426A - Optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an aqueous binder allowing formation of a firm coating excellent in coating adequacy to provide an optical filter having a filter layer formed on a transparent support body, by including as the binder of the filter layer, gelatin having a specific range of viscosity of specific aqueous solution at a specific temperature. SOLUTION: This optical filter has at least a filter layer on a transparent support body. As a binder of the filter layer, gelatin where viscosity of 10 wt.% aqueous solution is in the range of 5-100 mPa.s at 25 deg.C is contained. Weight-average molecular weight of this gelatin used as the binder of the filter layer is in the range of 2000-50000. In addition, the filter layer is formed from an aqueous composition containing dye and the gelatin. Using a dye composition composed of the gelatin binder excellent in coating characteristic and pigment, the uniform filter layer without color nonuniformity is formed on the transparent support body, and thereby imparting a suitable color correction function to the optical filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical filter having a transparent support and a filter layer. In particular,
The present invention relates to a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode ray tube display (CRT), a fluorescent display tube, and a surface of an image display device such as a field emission display. The present invention relates to an optical filter attached for improving color reproducibility.

[0002]

2. Description of the Related Art A liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode ray tube display (CRT),
2. Description of the Related Art An image display device such as a fluorescent display tube or a field emission display displays a color image by a combination of light of three primary colors of red, blue and green in principle. However, it is very difficult (practically impossible) to make light for display ideal three primary colors. For example, in a plasma display panel (PDP), it is known that light emitted from the three primary color phosphors contains extra light (wavelength in the range of 500 to 620 nm). Therefore, it has been proposed to perform color correction using a filter that absorbs light of a specific wavelength in order to correct the color balance of display colors. Japanese Patent Application Laid-Open No. 58-153904 discloses color correction using a filter.
No. 61-188501, JP-A-3-231988,
Nos. 5-205564, 9-145918, 9-
306366, 10-26704, WO98 / 2
It is described in each publication of 3980.

Various methods have been disclosed for forming an optical filter. JP-A-61-188501, JP-A-5-205643, JP-A-9-145918 and JP-A-9-145918
In the optical filter described in each publication of 306366,
A dye or a pigment is added to the transparent support so that the support functions as a filter. JP-A-10-26704
In the optical filter described in the publication, a hard coat layer (surface hardened layer) provided between the transparent support and the antireflection layer
And the hard coat layer functions as a filter. In the optical filter described in JP-A-7-209510, a mixed solution of a dye and a metal alkoxide is applied, dried, and fired to function as a filter layer. Further, in the optical filter described in WO98 / 23980, a dye and a matrix polymer are dissolved and coated in an appropriate solvent to function as a filter layer. However, when color correction is performed by these methods, there is a problem that the luminance of the display is reduced and the color balance is reduced.

If the transparent support or the hard coat layer is colored, the transparent support or the hard coat layer functions as a filter. However, the types of dyes and pigments that can be added to the transparent support and the hard coat layer are very limited. The transparent support is made from plastic or glass (usually plastic). Dyes and pigments to be added to the transparent support are required to have extremely high heat resistance enough to withstand the temperature during the production of the support. The hard coat layer is generally a layer containing a cross-linked polymer, and the cross-linking reaction of the polymer is performed after application of the layer. Further, a method of forming a filter layer from a dye and a metal alkoxide also requires baking after application of the dye. Under these reaction conditions for crosslinking and baking, there are many dyes and pigments that fade. Dyes or pigments used for color correction are required to have various absorption spectrum characteristics depending on the type of image display device. If the types of dyes and pigments used for color correction are limited, it is difficult to perform appropriate correction.

[0005]

As a means for solving such a problem, WO 98/23980 discloses a method of forming a filter layer from a dye and a matrix polymer.
Issue. However, in this method, since the dye and the matrix polymer are dissolved in an appropriate solvent and applied, depending on the combination of the dye, the matrix polymer and the solvent used, the viscosity of the coating solution is high, and a streak or cissing-like coating is applied to the filter layer. Unevenness occurs and color unevenness occurs.
Even if the concentration of the dye and the matrix polymer is lowered by adding a solvent, it is necessary to increase the coating amount of the coating solution in order to achieve the required solid coating amount, and it is possible to avoid a drying load. Absent. Further, as a solvent for the coating solution, a safe aqueous system which does not require explosion-proof and recovery equipment is desired as compared with an organic solvent system.

Accordingly, an object of the present invention is to solve these problems, and it is possible to use a safe aqueous system as a solvent for a coating solution without the need for explosion-proof and recovery equipment, and to be compatible with a dye for color correction. An object of the present invention is to provide an optical filter in which a filter layer is formed on a transparent support using an aqueous binder which has good coatability and can form a strong film. It is another object of the present invention to provide an optical filter having an appropriate color correction function for a display image and free from color unevenness.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have formed a filter layer on a transparent support from a combination of a gelatin binder and a dye excellent in coatability, and used the optical layer as an optical film. The inventors have found that the object can be achieved, and have completed the present invention. That is,
The present invention is as follows. (1) An optical filter having at least a filter layer on a transparent support, which contains, as a binder of the filter layer, gelatin whose viscosity of a 10% by weight aqueous solution at 25 ° C. is in the range of 5 to 100 mPa · s. An optical filter, characterized in that: (2) The optical filter according to (1), wherein the weight average molecular weight of gelatin used as a binder for the filter layer is in the range of 2,000 to 50,000. (3) The filter according to (1), wherein the filter layer is formed from an aqueous composition containing a dye and the gelatin.
Or the optical filter according to (2). (4) The above-mentioned (1) to (1), wherein the dye contained in the filter layer is at least one kind of an aggregate of a dye selected from a cyanine dye or an oxonol dye.
The optical filter according to any one of (3). (5) The filter layer has a maximum light absorption of 560 nm or more.
The optical filter according to any one of (1) to (4), wherein the optical filter has a wavelength between 620 nm and a half width of 50 nm or less.

(6) The optical filter according to any one of (1) to (5), wherein the filter layer contains a gelatin crosslinking agent. (7) The optical filter as described in any of (1) to (6) above, wherein an antireflection layer including at least a low refractive index layer having a lower refractive index than the support is provided on the transparent support. . (8) The optical filter according to (7), further including a hard coat layer having a higher hardness than the support between the antireflection layer of the optical filter and the transparent support. (9) The optical filter according to any one of (1) to (8), wherein the filter layer is formed by wire bar coating. (10) The optical filter according to any one of (1) to (9), which is used for display on an image display device. (11) The optical filter according to any one of (1) to (10), which is used for displaying a plasma display panel (PDP). (12) A front plate for a plasma display panel (PDP), wherein the optical filter according to (11) is held on a surface. (13) A plasma display panel (PDP) display device, wherein the optical filter according to (1) to (8) is provided on at least one of a surface of a PDP module, a surface of a front plate, and a back surface of the front plate. .

The optical filter of the present invention is formed on a transparent support by using a coating composition comprising a gelatin binder having excellent coatability and a dye to form a uniform filter layer without color unevenness on an optical film. An appropriate color correction function can be provided. The present inventor has proposed an image display device (particularly a plasma display panel, hereinafter referred to as a PDP).
Research was also conducted on extra light (wavelengths of 500 to 620) included in the emission from the three primary color phosphors.
nm range), more precisely, a plurality of wavelength ranges (50 nm).
0 to 550 nm and 560 to 620 nm). Therefore, the wavelength is 500 to 550 nm.
It is more appropriate for the image display apparatus to perform the color correction for both wavelength ranges by dividing the range of the wavelength range from 560 to 620 nm. Therefore, in the optical filter of the present invention, a wavelength of 500
The absorption maximum is given in both the range of ５550 nm and the range of the wavelength of 560 to 620 nm. As a result, the optical filter of the present invention has an appropriate color correction function for an image display device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The optical filter of the present invention has a transparent support and a filter layer. The optical filter may further have an arbitrary layer (eg, a low refractive index layer, a medium refractive index layer, a high refractive index layer, a hard coat layer, and an undercoat layer). When the optical filter has a layer other than the transparent support and the filter layer, there is a preferred layer configuration (layer arrangement order). FIG. 1 is a schematic cross-sectional view illustrating a layer configuration of the optical filter. The embodiment shown in (a1) of FIG. 1 has a layer structure in the order of the filter layer (2), the transparent support (1), and the low refractive index layer (3). The transparent support (1) and the low refractive index layer (3) have a refractive index satisfying the following relationship. Refractive index of low refractive index layer <refractive index of transparent support In the embodiment shown in (a2) of FIG. 1, the filter layer (2), the transparent support (1), the hard coat layer (4), and the low refractive index layer ( It has a layer configuration in the order of 3). The embodiment shown in FIG. 1 (a3) is a filter layer (2), a transparent support (1), a hard coat layer (4), a high refractive index layer (5), and a low refractive index layer (3). Having a configuration. The transparent support (1), the low refractive index layer (3) and the high refractive index layer (5) have a refractive index satisfying the following relationship. The refractive index of the low refractive index layer <the refractive index of the transparent support <the refractive index of the high refractive index layer In the embodiment shown in FIG. 1 (a4), the filter layer (2), the transparent support (1), the hard coat layer ( 4), a middle refractive index layer (6), a high refractive index layer (5), and a low refractive index layer (3). The transparent support (1), the low refractive index layer (3), the high refractive index layer (5) and the medium refractive index layer (6)
It has a refractive index satisfying the following relationship. Refractive index of low refractive index layer <refractive index of transparent support <refractive index of medium refractive index layer <refractive index of high refractive index layer

The embodiment shown in FIG. 1 (b1) has a layer structure in the order of a transparent support (1), a filter layer (2), and a low refractive index layer (3). The relationship between the refractive index of the transparent support (1) and the refractive index of the low refractive index layer (3) is the same as that of (a1). FIG.
In the embodiment shown in (b2), the transparent support (1), the filter layer (2), the hard coat layer (4), and the low refractive index layer (3)
In the following order. The embodiment shown in (b3) of FIG. 1 has a transparent support (1), a filter layer (2), a hard coat layer (4), a high refractive index layer (5), and a low refractive index layer (3). Having a configuration. The relationship between the refractive indices of the transparent support (1), the low refractive index layer (3) and the high refractive index layer (5) is (a)
Same as 3). The mode shown in (b4) of FIG. 1 includes a transparent support (1), a filter layer (2), a hard coat layer (4), a medium refractive index layer (6), a high refractive index layer (5), and a low refractive index. It has a layer configuration in the order of layer (3). The relationship between the refractive indices of the transparent support (1), the low refractive index layer (3), the high refractive index layer (5) and the middle refractive index layer (6) is the same as that of (a4).

(Transparent support) Examples of the material forming the transparent support include cellulose esters (eg, diacetyl cellulose, triacetyl cellulose (TAC), propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose). Polyamide, polycarbonate, polyester (eg, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4'-dicarboxylate, poly Butylene terephthalate), polystyrene (eg, syndiotactic polystyrene), polyolefin (eg, polyethylene, polypropylene, polymethylpentene), polymethylmethacrylate , Syndiotactic polystyrene, polysulfone, polyethersulfone, polyetherketone, polyetherimide and polyoxyethylene. Triacetyl cellulose, polycarbonate and polyethylene terephthalate are preferred. The transmittance of the transparent support is preferably 80% or more,
More preferably, it is 86% or more. Haze is 2
%, More preferably 1% or less. The refractive index is preferably from 1.45 to 1.70. An infrared absorber or an ultraviolet absorber may be added to the transparent support. The amount of the infrared absorber added is preferably 0.01 to 20% by weight of the transparent support, more preferably 0.05 to 10% by weight. Further, as a slipping agent, particles of an inert inorganic compound may be added to the transparent support. Examples of inorganic compounds include S
iO ₂ , TiO ₂ , BaSO ₄ , CaCO ₃ ,
Includes talc and kaolin. The transparent support may be subjected to a surface treatment. Examples of surface treatment include chemical treatment,
Mechanical treatment, corona discharge treatment, flame treatment, ultraviolet irradiation treatment, high frequency treatment, glow discharge treatment, active plasma treatment,
Laser treatment, mixed acid treatment and ozone oxidation treatment are included. Glow discharge treatment, ultraviolet irradiation treatment, corona discharge treatment and flame treatment are preferred, and glow discharge treatment and ultraviolet treatment are more preferred. Further, an undercoat layer for strengthening the adhesion with the upper layer may be provided.

(Filter Layer) The thickness of the filter layer is preferably 0.5 to 15 μm. The filter layer has an absorption maximum in a wavelength range of 560 to 620 nm (between green and red). The transmittance at the absorption maximum in the wavelength range of 560 to 620 nm is preferably in the range of 5 to 50%. The absorption maximum in the wavelength range of 560 to 620 nm is set to selectively cut a sub-band that reduces the color purity of the red phosphor. In the PDP, unnecessary light emission near 595 nm emitted by excitation of neon gas is also cut. By separating the absorption maximum according to the present invention, light can be selectively cut without adversely affecting the color tone of the green phosphor. In order to further reduce the effect on the color tone of the green phosphor, it is preferable to sharpen the peak of the absorption spectrum. Specifically, the half width at the absorption maximum in the wavelength range of 560 to 620 nm is preferably 15 to 200 nm, and 30 to 2 nm.
00 nm, more preferably 40 to 100 nm.
Is more preferable, and most preferably 50 to 80 nm.

The filter layer has a thickness of 560 to 620 nm.
May have an absorption maximum in a wavelength range of 500 to 550 nm. The transmittance in the wavelength range of 500 to 550 nm is preferably in the range of 50 to 85%. The absorption maximum in the wavelength range of 500 to 550 nm is set to adjust the emission intensity of the green phosphor having high visibility. It is preferable that the emission region of the green phosphor be cut smoothly. The half width at the absorption maximum in the wavelength range of 500 to 550 nm (the width of the wavelength region showing half the absorbance at the absorption maximum) is preferably 30 to 300 nm, more preferably 40 to 300 nm. Preferably, it is more preferably 50 to 150 nm, and most preferably 60 to 150 nm.

Dye (dye or pigment, preferably dye)
Is used to impart the above absorption spectrum to the filter layer. Dyes having an absorption maximum in the wavelength range of 500 to 550 nm include squarylium, azomethine, cyanine, oxonol, azo, benzylidene,
Xanthene-based or merocyanine-based compounds are preferably used. Examples of the dye having an absorption maximum in the wavelength range of 500 to 550 nm are shown below.

[0016]

Embedded image

[0017]

Embedded image

[0018]

Embedded image

[0019]

Embedded image

As a dye having an absorption maximum in the wavelength range of 560 to 620 nm, a cyanine or oxonol compound is preferably used. These exhibit sharp absorption by dispersing in water to form aggregates.
Examples of dyes having an absorption maximum in the wavelength range of 560 to 620 nm are shown below.

[0021]

Embedded image

[0022]

Embedded image

In the filter layer, two or more kinds of dyes as described above can be used in combination. Further, the wavelength ranges from 500 to 550 nm and the wavelength ranges from 560 to 620.
Dyes having an absorption maximum in both the nm range can be used in the filter layer. For example, the above-mentioned cyanine-based and oxonol-based dyes have a molecular dispersion of 500 to 550.
Absorption in the nm range and 560-620 nm in aggregated state
Can have a sharp absorption in the range of When used in a state where such a dye is partially formed into an aggregate, a wavelength of 5
An absorption maximum can be obtained in both the range of 00 to 550 nm and the range of wavelength of 560 to 620 nm. Examples of such dyes are shown below.

[0024]

Embedded image

The filter layer preferably contains a polymer binder for controlling the stability and reflectance characteristics of the dye. In order to form a filter layer while forming an associated body, it is generally preferable to use gelatin which is generally known to have excellent protective colloid properties for dispersed particles. However, gelatin having a weight-average molecular weight of 100,000 or more extracted and purified by ordinary acid treatment or alkali treatment loses fluidity and gels at 25 ° C. even in an aqueous solution of about 10 wt%. In order to enable coating, it is necessary to raise the temperature of the coating solution or to lower the gelatin concentration of the coating solution, but the dye aggregate becomes unstable.

As the gelatin used for the binder of the present invention, the viscosity of a 10 wt% aqueous solution at 25 ° C. is 5 to 1%.
Gelatin having a viscosity of 00 mPa · s is preferable, and gelatin having a viscosity of 5 to 50 mPa · s is more preferable. If it is less than 5 mPa · s, wind unevenness is likely to occur during the drying process. Gelatin may be used alone or as a mixture of two or more kinds as long as it is within the above viscosity range. The viscosity was measured using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd.
It is performed under the condition of one rotor and 60 rpm.

The weight average molecular weight of the gelatin used in the binder of the present invention is preferably in the range of 2,000 to 50,000, more preferably in the range of 2,000 to 20,000. The average molecular weight is measured according to the molecular weight distribution measurement method by gel filtration described in the PAGI method (photographic gelatin test method). If the molecular weight is less than 2,000, the mechanical strength of drying is insufficient, and if it exceeds 20,000, gelation is easily caused, application becomes difficult, and both are unsuitable.

Specific examples of the gelatin of the present invention include # 8
60, # 880, # 881 (Nitta Gelatin Co., Ltd.)
Manufactured). These gelatins may be used alone, or may be used by blending two or more kinds as necessary.

An anti-fading agent may be added to the filter layer. Examples of anti-fading agents that function as dye stabilizers include hydroquinone derivatives (US Pat. No. 3,935,016).
Nos. 3,982,944), hydroquinone diether derivatives (described in U.S. Pat. No. 4,254,216 and JP-A-55-21004), phenol derivatives (described in JP-A-54-145530),
Derivatives of spiroindane or methylenedioxybenzene (UK Patent Publications Nos. 2077455 and 2062888)
And the derivatives of chroman, spirochroman or coumaran (U.S. Pat. Nos. 3,432,300 and 3,573,050).
Nos. 3574627 and 3764337 and JP-A Nos. 52-152225 and 53-20327.
Nos. 53-17729 and 61-90156), hydroquinone monoether or paraaminophenol derivatives (UK Patent 1347556,
Nos. 2066975 and JP-B-54-12
337, JP-A-55-6321) and bisphenol derivatives (described in US Pat. No. 3,700,455 and JP-B-48-31625).

In order to improve the stability of the dye to light or heat, a metal complex (described in US Pat. No. 4,245,018 and JP-A-60-97353) may be used as an anti-fading agent. In order to further improve the light fastness of the dye, a singlet oxygen quencher may be used as an anti-fading agent. Examples of the singlet oxygen quencher include a nitroso compound (described in JP-A-2-300288), a diimmonium compound (described in US Pat. No. 4,656,612), a nickel complex (described in JP-A-4-146189), and antioxidant. Agent (European Patent Publication 820057A1)
Description).

In addition, a matting agent, a surfactant, an antistatic agent, a coating aid and a hardener may be added to the filter layer.

(Undercoat layer) It is preferable to provide an undercoat layer between the transparent support and the filter layer. The undercoat layer is a layer containing a polymer having a glass transition temperature of 25 ° C. or lower,
The filter layer is formed as a layer having a rough surface or a layer containing a polymer having an affinity for the polymer of the filter layer. An undercoat layer is provided on the surface of the transparent support on which the filter layer is not provided, and the transparent support and the layers provided thereon (for example, an antireflection layer and a hard coat layer)
May be improved. The undercoat layer may be provided to improve the affinity between the optical filter and an adhesive for bonding the optical filter and the image forming apparatus. The thickness of the undercoat layer is preferably from 20 nm to 1000 nm, more preferably from 80 nm to 300 nm. An undercoat layer containing a polymer having a glass transition temperature of 25 ° C. or lower adheres the transparent support and the filter layer due to the tackiness of the polymer. Polymers having a glass transition temperature of 25 ° C. or lower can be obtained by polymerization or copolymerization of vinyl chloride, vinylidene chloride, vinyl acetate, butadiene, neoprene, styrene, chloroprene, acrylate, methacrylate, acrylonitrile or methyl vinyl ether. . The glass transition temperature is preferably 20 ° C or lower, more preferably 15 ° C or lower, and 10 ° C or lower.
C. or lower, more preferably 5C or lower, and most preferably 0C or lower. The undercoat layer having a rough surface adheres the transparent support and the filter layer by forming a filter layer on the rough surface. The undercoat layer having a rough surface can be easily formed by applying a polymer latex. The average particle size of the latex is preferably from 0.02 to 3 μm, and more preferably from 0.05 to 1 μm. Examples of polymers having an affinity for the binder polymer of the filter layer include acrylic resins, cellulose derivatives, gelatin, casein, starch, polyvinyl alcohol, soluble nylon, and polymer latex. Two or more undercoat layers may be provided. The undercoat layer may contain a solvent for swelling the transparent support, a matting agent, a surfactant, an antistatic agent, a coating aid and a hardener.

(Anti-Reflection Layer) An anti-reflection layer may be provided on the optical filter to give the optical filter an anti-reflection function. As the antireflection layer, a low refractive index layer is essential. The refractive index of the low refractive index layer is lower than the refractive index of the transparent support. The refractive index of the low refractive index layer is 1.20 to 1.55
And more preferably 1.30 to 1.55. The thickness of the low refractive index layer is 50 to 400.
nm, more preferably 50 to 200 nm. The low refractive index layer is a layer made of a fluoropolymer having a low refractive index (JP-A-57-34526,
JP-A-3-130103, JP-A-6-115023, JP-A-8-313702, and JP-A-7-168004), layers obtained by a sol-gel method (JP-A-5-208)
Nos. 811, 6-299091 and 7-168003
Or the layer containing fine particles (JP-B-60)
-59250, JP-A-5-13021, 6-56
478, 7-92306, and 9-288201). In the layer containing fine particles, voids can be formed in the low refractive index layer as microvoids between the fine particles or in the fine particles. The layer containing fine particles preferably has a porosity of 3 to 50% by volume, more preferably 5 to 35% by volume.

In order to prevent reflection in a wide wavelength range,
It is preferable to laminate a layer having a high refractive index (middle / high refractive index layer) in addition to the low refractive index layer. The refractive index of the high refractive index layer is preferably from 1.65 to 2.40, and is 1.7.
More preferably, it is 0 to 2.20. The refractive index of the middle refractive index layer is adjusted to be an intermediate value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably from 1.55 to 1.70. During·
The thickness of the high refractive index layer is preferably from 5 nm to 100 μm, more preferably from 10 nm to 10 μm, and most preferably from 30 nm to 1 μm. The haze of the middle / high refractive index layer is preferably 5% or less, more preferably 3% or less, and most preferably 1% or less. The middle / high refractive index layer can be formed using a polymer binder having a relatively high refractive index. Examples of high refractive index polymers include polystyrene, styrene copolymers, polycarbonates, melamine resins, phenolic resins, epoxy resins, and polyurethanes obtained by reacting cyclic (alicyclic or aromatic) isocyanates with polyols. . Polymers having other cyclic (aromatic, heterocyclic, alicyclic) groups,
A polymer having a halogen atom other than fluorine as a substituent also has a high refractive index. A polymer may be formed by a polymerization reaction of a monomer capable of radical curing by introducing a double bond.

In order to obtain a higher refractive index, inorganic fine particles may be dispersed in a polymer binder. The refractive index of the inorganic fine particles is preferably from 1.80 to 2.80. The inorganic fine particles are preferably formed from a metal oxide or sulfide. Examples of metal oxides or sulfides include titanium dioxide (eg, rutile, rutile / anatase mixed crystal, anatase, amorphous structure), tin oxide, indium oxide, zinc oxide, zirconium oxide, and zinc sulfide. Titanium oxide, tin oxide and indium oxide are particularly preferred. The inorganic fine particles contain oxides or sulfides of these metals as main components and may further contain other elements. The main component means a component having the largest content (% by weight) among the components constituting the particles. Examples of other elements include Ti, Zr, Sn, Sb, Cu, Fe, Mn,
Pb, Cd, As, Cr, Hg, Zn, Al, Mg, S
i, P and S are included. Inorganic materials that are film-forming and can be dispersed in solvents or are themselves liquid, such as alkoxides of various elements, salts of organic acids, coordination compounds (eg, chelate compounds) combined with coordination compounds, activity The middle / high refractive index layer can be formed using an inorganic polymer.

The anti-reflection layer can provide a surface with an anti-glare function (a function of scattering incident light on the surface to prevent a scene around the film from shifting to the film surface). For example, by forming fine irregularities on the surface of a transparent film, and forming an antireflection layer on the surface, or after forming the antireflection layer, by forming irregularities on the surface with an embossing roll, an anti-glare function is obtained. be able to.
The antireflection layer having an antiglare function is generally 3 to 3
Has a haze of 0%.

(Other Layers) The optical filter may be provided with a hard coat layer, a lubricating layer, an antistatic layer or an intermediate layer. The hard coat layer preferably contains a cross-linked polymer. The hard coat layer can be formed using an acrylic, urethane, or epoxy polymer, oligomer, or monomer (eg, an ultraviolet curable resin). The hard coat layer can also be formed from a silica-based material. A lubricating layer may be formed on the surface of the antireflection layer (low refractive index layer). The lubricating layer has a function of imparting lubricity to the surface of the low refractive index layer and improving scratch resistance.
The lubricating layer can be formed using polyorganosiloxane (eg, silicone oil), natural wax, petroleum wax, higher fatty acid metal salt, fluorine-based lubricant or a derivative thereof. The thickness of the lubricating layer is preferably from 2 to 20 nm.

The filter layer, undercoat layer, antireflection layer (medium-refractive-index layer, high-refractive-index layer, low-refractive-index layer), hard coat layer, lubricating layer, and other layers are formed by a general coating method. Can be. Examples of the coating method include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, and an extrusion coating method using a hopper (described in US Pat. No. 2,681,294). Is included. Two or more layers may be formed by simultaneous coating. The simultaneous coating method is described in U.S. Pat.
No. 941898, No. 3508947, No. 352652
No. 8 and Yuji Harazaki, "Coating Engineering"
253 (published by Asakura Shoten in 1973).

(Use of Optical Filter) The optical filter is applied to an image display device such as a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), and a cathode ray tube display (CRT). . When the low refractive index layer is provided, the low refractive index layer is disposed such that the surface on which the low refractive index layer is not provided faces the image display surface of the image display device. When the optical filter of the present invention is used as a filter of a plasma display panel (PDP), a particularly remarkable effect is obtained.
A plasma display panel (PDP) includes a gas, a glass substrate, an electrode, an electrode lead material, a thick film printing material, and a phosphor. There are two glass substrates, a front glass substrate and a rear glass substrate. An electrode and an insulating layer are formed on two glass substrates. A phosphor layer is further formed on the rear glass substrate. Assemble two glass substrates,
Meanwhile, gas is sealed. Plasma display panels (PDPs) are already commercially available. The plasma display panel is described in JP-A-5-205643 and JP-A-9-306366.

[0040]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should be understood that the scope of the present invention is not limited by these Examples. [Example 1] (Formation of undercoat layer) After both surfaces of a transparent polyethylene terephthalate film having a thickness of 100 µm were subjected to corona treatment,
A latex made of a styrene-butadiene copolymer was applied on one side to a thickness of 130 nm to form an undercoat layer.

(Formation of Second Undercoat Layer) On the undercoat layer,
A gelatin aqueous solution containing acetic acid and glutaraldehyde was applied to a thickness of 50 nm to form a second undercoat layer.

(Formation of Low Refractive Index Layer) Reactive Fluoropolymer (JN-7219, manufactured by Nippon Synthetic Rubber Co., Ltd.) 2.50
1.3 g of t-butanol was added to the resulting mixture, and the mixture was stirred at room temperature for 10 minutes and filtered with a 1 μm polypropylene filter.
The obtained coating liquid for a low refractive index layer was coated on a surface opposite to the undercoat surface of the transparent support with a dry film thickness of 1 using a bar coater.
It was applied to a thickness of 10 nm, dried at 120 ° C. for 30 minutes and cured to form a low refractive index layer.

(Formation of Filter Layer) Gelatin # 881
180 g of a 10 wt% aqueous solution of Nitta Gelatin Co., Ltd.
In addition, 0.05 g of dye (a1) and 0.0 g of dye (b6)
After dissolving 5 g and stirring at 25 ° C. for 30 minutes,
m with a polypropylene filter. The obtained coating solution for the filter layer was kept at 25 ° C., and was applied on the second undercoat layer with a wire bar so that the dry film thickness became 3.5 μm, and dried at 120 ° C. for 10 minutes to form a filter. Layers were formed to create an optical filter.

10 w of gelatin # 881 at 25 ° C.
The viscosity of the t% aqueous solution was 15 mPa · s. The viscosity was measured using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd.
o. This was performed under the conditions of one rotor and 60 rpm.

Comparative Example 1 (Formation of Filter Layer) Dye (a) was added to 180 g of a 10 wt% aqueous solution of gelatin # 810 (manufactured by Nitta Gelatin Co., Ltd.).
1) 0.05 g of the dye (b6) and 0.05 g of the dye (b6) were dissolved, stirred at 40 ° C. for 30 minutes, and filtered with a 30 μm polypropylene filter. The obtained coating solution for a filter layer was kept at 40 ° C., and was coated on the second undercoat layer with a wire bar so that the dry film thickness was 3.5 μm.
After drying at 120 ° C. for 10 minutes, a filter layer was formed to prepare an optical filter. Except for the filter layer, it was produced in the same manner as in Example 1.

10 w of gelatin # 810 at 25 ° C.
Since the t% aqueous solution gelled and completely lost the fluidity, the viscosity could not be measured.

Comparative Example 2 (Formation of Filter Layer) Dye (a) was added to 180 g of a 10 wt% aqueous solution of gelatin # 810 (manufactured by Nitta Gelatin Co., Ltd.).
1) 0.05 g of the dye (b6) and 0.05 g of the dye (b6) were dissolved, stirred at 30 ° C. for 30 minutes, and filtered with a 30 μm polypropylene filter. The obtained coating solution for a filter layer was kept at 30 ° C., and was coated on the second undercoat layer with a wire bar so that the dry film thickness was 3.5 μm.
After drying at 120 ° C. for 10 minutes, a filter layer was formed to prepare an optical filter. Except for the filter layer, it was produced in the same manner as in Example 1.

(Evaluation of Dye Particle Stability of Coating Liquid) The coating liquids prepared in Example 1 and Comparative Examples 1 and 2 were stored at the respective coating liquid temperatures, and after 3 hours, the dye particles in the coating liquid were removed. The condition was visually evaluated. The results are shown in Table 1.

[0049]

[Table 1]

(Evaluation of Filter Function) Plasma Display Panel (PDS4202J-H, Fujitsu Limited)
The film on the outermost surface of the front plate made of the above-mentioned product is peeled off, and instead, the optical filter (the side on which the low refractive index layer is not provided) prepared in Example 1, Comparative Examples 1 and 2 is attached with an adhesive. Was. The color unevenness of the optical filter and the displayed image were visually evaluated for white light and red light. The results are shown in Table 2.

[0051]

[Table 2]

As is clear from the above, the optical filter of the present invention has a viscosity of 10 wt% aqueous solution at 25 ° C. of 5%.
Low molecular weight gelatin in the range of ~ 100 mPa · s;
By the filter layer formed from the dye, a uniform optical filter without color unevenness was obtained, but the optical filter of each comparative example using a normal gelatin having a molecular weight of 100,000 or more is:
At room temperature, it was necessary to keep it warm as a coating solution because it gelled, and the pigment particles became unstable and were unsatisfactory in some properties.

[0053]

As described above, the optical filter of the present invention comprises a coating composition comprising a gelatin binder having excellent coating suitability and a pigment, and a filter layer having no uniform color unevenness on a transparent support. By forming, it became possible to give an appropriate color correction function to the optical film. The present inventor has also conducted research on an image display device (particularly, a PDP). As a result, extra light (wavelength in the range of 500 to 620 nm) included in light emission from the three primary color phosphors is more accurately determined at a plurality of wavelengths. It was found that it could be decomposed into regions (500-550 nm and 560-620 nm).
Therefore, the wavelength is in the range of 500 to 550 nm and the wavelength is 56
It is more appropriate to perform color correction in both wavelength regions by dividing the range from 0 to 620 nm, which is more appropriate for the image display device. Therefore, in the optical filter of the present invention, the absorption maximum is given to both the wavelength range of 500 to 550 nm and the wavelength range of 560 to 620 nm in the filter layer. As a result, the optical filter of the present invention,
It has an appropriate color correction function for the image display device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer configuration of an optical filter.

FIG. 2 is a graph showing the spectral transmittance of the optical filter prepared in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent support 2 Filter layer 3 Low refractive index layer 4 Hard coat layer 5 High refractive index layer 6 Medium refractive index layer

Claims (13)

[Claims] 1. An optical filter having at least a filter layer on a transparent support, wherein gelatin having a viscosity of a 10% by weight aqueous solution at 25 ° C. in the range of 5 to 100 mPa · s is used as a binder of the filter layer. An optical filter characterized by containing. 2. The optical filter according to claim 1, wherein the weight average molecular weight of gelatin used as a binder for the filter layer is in the range of 2,000 to 50,000. 3. The optical filter according to claim 1, wherein the filter layer is formed from an aqueous composition containing a dye and the gelatin. 4. The optical filter according to claim 1, wherein the dye contained in the filter layer is at least one aggregate of a dye selected from a cyanine-based dye and an oxonol-based dye. 5. The filter layer has a light absorption maximum of 56.
0 nm to 620 nm, the half width of which is 50 nm
The optical filter according to claim 1, wherein: 6. The optical filter according to claim 1, wherein the filter layer contains a gelatin crosslinking agent. 7. The optical filter according to claim 1, further comprising an antireflection layer including at least a low refractive index layer having a lower refractive index than the support on the transparent support. 8. The optical filter according to claim 7, further comprising a hard coat layer having higher hardness than the support between the antireflection layer of the optical filter and the transparent support. 9. The optical filter according to claim 1, wherein said filter layer is formed by wire bar coating. 10. The optical filter according to claim 1, wherein the optical filter is used for displaying on an image display device. 11. A plasma display panel (PD)
The optical filter according to any one of claims 1 to 8, which is used for P) display. 12. A front panel for a plasma display panel (PDP), wherein the optical filter according to claim 11 is held on a surface. 13. A plasma display panel (PDP) display device, wherein the optical filter according to claim 1 is provided on at least one of a surface of a PDP module, a surface of a front plate, and a back surface of the front plate.