JP2000266930A - Optical selective filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter capable of selectively cutting light of wavelength degrading color purity and correcting color balance by respectively specifying the range of maximum absorption and transmission factors in wavelength maximum. SOLUTION: An optical filter is used, which has stratiform construction of total six or more layers made of alternating laminated layer of two or more sorts of substances, absorption maximum in the range of 560-620 nm, and the transmission factor under 50% in the wavelength maximum. In this case, the filter layer is manufactured following to the well-known principle of multi-layer reflecting films, having construction of two or more layers of different refraction factors alternately laminated. The absorption maximum in the range of wavelength 560-620 nm is set for selectively cutting subband degading the color purity of a red fluorescent substance. In a plasma display panel(PDP), unnecessary emitted light in the vicinity of 585 nm discharged by excitation of neon gas is also cut.

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 three primary color phosphors contains extra light (wavelength is in a 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
No. 5,205,643, No. 9-145918, No. 9-306366, and No. 10-26704.

[0003]

However, many filters utilizing absorption by dyes or pigments have broad absorption half widths, and it is difficult to selectively cut off only light in a specific narrow wavelength range. Was often the case. In view of the above problems, the present inventors have conducted intensive studies and as a result, it has been found that a multilayer interference film in which layers having different optical refractive indices are alternately laminated gives a suitable result for this purpose.
Furthermore, it has been clarified that by controlling the optical refractive index and the thickness of the materials to be alternately laminated and the variation thereof, it is possible to control the wavelength of absorption and the half width thereof, which are the basic performances of the selective reflection filter. An object of the present invention is to provide an optical filter capable of selectively cutting light having a wavelength that reduces color purity and correcting the color balance, and to provide an image display device using the same. .

[0004]

The object of the present invention has been attained by the following optical filters (1) to (10), an image display device, and a plasma display panel. (1) An optical filter having a layered structure of a total of six or more layers composed of alternating layers of two or more kinds of substances, having an absorption maximum in the range of 560 to 620 nm, and transmitting at the maximum of the wavelength. An optical filter having a ratio of 50% or less. (2) 500 to 550 in addition to 560 to 620 nm
(1) The optical filter according to (1), which has an absorption maximum in a range of nm and has a transmittance of 30% or more at the maximum of the wavelength. (3) It has a layered structure of a total of six or more layers composed of alternating layers of two or more kinds of substances, has an absorption maximum in the range of 560 to 620 nm, and has a transmittance of 50% at the wavelength maximum. Having a layered structure of a total of four or more layers composed of the following selective reflection layer and alternate lamination of two or more substances,
(1) The optical filter according to (1), comprising a selective reflection layer having an absorption maximum in a range between 550 nm and 550 nm, and having a transmittance of 30% or more at the wavelength maximum. (4) 560 to layer including an absorption maximum between the range of 620nm is formed by alternating lamination of layers and the optical refractive index n ₂ layers of the optical refractive index _{n1, 1.03 <n 2 / n} 1 ≦ 1.3, (1), (2), (3)
Optical filter. (5) The optical filter according to (4), wherein the relationship of 1.38 ≦ n ₁ is satisfied. (6) alternately laminated variation of the layer thickness d ₁ of the optical refractive index n _1, the variation of the optical index of refraction n ₂ layer thickness d ₂ are each 3
0% or less, and 1120 ≦ n ₁ d ₁ + n ₂ d ₂ ≦ 12
The optical filter according to (4) or (5), which is within the range of 40. (7) The optical filter according to (1) to (6), having an adhesive, a filter layer, a support, and an antireflection layer. (8) The optical filter according to (1) to (7), which is used for displaying a plasma display panel (PDP). (9) A front panel for a PDP, wherein the optical filter according to (8) is held on a surface. (10) A PDP display device, wherein the optical filter according to (1) to (9) 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.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be illustrated by the following examples, but is not limited to these examples unless otherwise specified.

(Transparent Support) Examples of materials for 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 the inorganic _{compound, SiO 2, TiO 2, BaSO} 4, CaCO 3, 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 filter layer is formed in accordance with the principle of a known multilayer reflective film, and has a structure in which two or more layers having different refractive indexes are alternately laminated. The thickness of the filter layer is not particularly limited, but is preferably in the range of about 0.3 to 15 μm from the viewpoint of thickness accuracy and transparency. The filter layer has a wavelength of 560 to 6
It has an absorption maximum in the range of 20 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 from 10 to 50 nm, more preferably from 10 to 30 nm, and most preferably from 10 to 20 nm. When the half width is less than 10 nm, the absorption of unnecessary light due to the excitation of neon gas becomes substantially incomplete,
The effect is reduced.

The filter layer has a thickness of 560 to 620 n.
In addition to the range of m, the wavelength may have an absorption maximum in the range of 500 to 550 nm. Wavelength is 500 to 550
The transmittance in the range of 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. Wavelength 500 to 55
The half width at the absorption maximum in the range of 0 nm (the width of the wavelength region showing half the absorbance at the absorption maximum) is 30 to 3
The thickness is preferably 00 nm, more preferably 40 to 300 nm, further preferably 50 to 150 nm, and most preferably 60 to 150 nm.

[0009] In order to impart an absorption spectrum in the range of 560 to 620 nm to the transparent support, a total of six or more layered structures composed of alternately laminated two or more substances are required. Is not particularly limited.
For example, a method by coating such as multi-layer coating, multi-layer deposition, and multi-layer sputtering, or a method by press-bonding an injection-molded product such as a multi-layer parallel spinning method or a composite spinning method, and the like can be mentioned. Further, the multilayer coated product and the multilayer film-formed product can be oriented by biaxial stretching to adjust the refractive index in the plane direction.

In order to obtain sharp absorption in multilayer interference, it is preferable that the ratio of the refractive indices of the alternately laminated materials be closer to 1, but if it is too close, interference will not occur effectively. In order to improve the selective reflection in the above, a larger number of layers is required, which is not preferable in terms of manufacturing suitability and cost. In practice, the ratio of the refractive index of the alternately laminated layers is preferably 1.03 or more and 1.3 or less, and more preferably 1.04 or more and 1.2 or less.
It is more preferably at most 1.05, more preferably at least 1.05 and at most 1.1.

As the number of layers of the multilayer interference layer increases, the selective reflectivity increases. However, as the number of layers increases, the contribution of the variation in the average thickness of each layer and the variation in the thickness within the layer increase, and the suitability for manufacturing and cost increase. This is not preferred. Conversely, if the number of layers is too small, the selective reflectivity at a specific wavelength decreases,
Unnecessary light cannot be efficiently cut, which is not preferable. The actual total number of layers is preferably in the range of 4 to 800 layers, more preferably in the range of 6 to 200 layers, and even more preferably in the range of 6 to 50 layers.

The material used for forming the multilayer interference layer by coating or film formation is not particularly limited. Examples thereof include a water-soluble binder such as gelatin, polyacrylic acid, polyacrylamide and polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, and the like. Polyvinyl pyrrolidone, polystyrene, an organic solvent-soluble binder such as polyvinyl naphthalene, SBR, polyacrylate,
A water-dispersible latex such as polyvinylidene chloride can be used alone or as a mixture. The above materials are partially fluorinated or completely fluorinated to lower the refractive index (such as perfluoropropyl polyacrylate), and conversely, an aromatic ring or a hetero atom such as Br or S is introduced to introduce a refractive index. (Polyvinyl- (2,6) bromonaphthalene and the like) are known, and can be used to adjust the refractive index without any particular limitation. These materials include SiO ₂ (refractive index 1.4) for adjusting the refractive index.
4), organic or inorganic low refractive particles such as MgF ₂ (refractive index: 1.38), amorphous fluoropolymer particles (refractive index: 1.29 or more), CeF ₃ (refractive index: 1.63), Al ₂ O
₃ (refractive index 1.62), polystyrene (refractive index 1.5
8), organic or inorganic medium refractive particles such as polythiophene (refractive index 1.72), ZrO ₂ (refractive index 2.08), T
Organic or inorganic high refractive index fine particles such as iO ₂ (refractive index 2.42) and polyphenylene sulfide (refractive index 1.82) can be mixed.

It is also possible to orient the material by biaxially stretching the coated film or the melt-formed product to increase the refractive index in the plane direction. For example, polyethylene naphthalate has a refractive index of about 1.60, but a biaxially stretched film of about 4 times has a refractive index in the plane direction of about 1.75, and the refractive index can be adjusted by the degree of stretching. It is possible. However,
The refractive index actually developed differs depending on the stretching temperature, the stretching speed, as well as the stretching ratio, and thus cannot be unconditionally determined.

When the present selective reflection layer is formed by multi-layer deposition or multi-layer sputtering, the source may be MgF as in the case of ordinary vapor deposition or sputtering.
₂ , SiO ₂ , TiO ₂ , ZnO _{2 and the} like can be used. Alternatively, a target layer can be obtained by oxidizing or nitriding the layer in an oxygen or nitrogen atmosphere after vapor deposition or sputtering. Also, coating by fluoropolymer sputtering or polymer polymerization in situ is effective. However, if a fluorine-containing polymer is used, the adhesiveness between the upper and lower layers is deteriorated. Therefore, it is not suitable for actual use.
F ₂ is preferably used.

Since the absorption in the wavelength range of 500 to 550 nm does not need to be particularly sharp, it is also possible to provide absorption by a dye in addition to the above method. 500
As the dye having an absorption in the range of from 550 nm to 550 nm, a squarylium-based, azomethine-based, cyanine-based, oxonol-based, azo-based, benzylidene-based, xanthene-based, or merocyanine-based compound is preferably used. Specific examples of the dye having an absorption maximum in the wavelength range of 500 to 550 nm are shown below, but are not limited thereto.

[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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When the above dye is used to provide absorption at 500 to 550 nm, the filter layer can be formed with the dye alone, but may contain a polymer binder for controlling the stability and reflectance characteristics of the dye.

Gelatin is preferred as the matrix of the present invention, but in addition, acrylic, urethane, SBR
System, olefin system, vinylidene chloride system, vinyl acetate system,
A polyester or a copolymer thereof is preferably used. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized, or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is preferably from 5000 to 100000, more preferably from about 10,000 to 100,000 in number average molecular weight. If the molecular weight is too small, the film strength is insufficient, and if it is too large, the film-forming properties are poor, which is not preferable.

Specific examples of the polymer latex usable in the present invention are as follows. Latex of methyl methacrylate / ethyl acrylate / methacrylic acid copolymer, latex of methyl methacrylate / 2-ethylhexyl acrylate / styrene / acrylic acid copolymer, latex of styrene / butadiene / acrylic acid copolymer, latex of styrene / butadiene / divinylbenzene / methacrylic acid copolymer Latex of methyl methacrylate / vinyl chloride / acrylic acid copolymer, latex of vinylidene chloride / ethyl acrylate / acrylonitrile / methacrylic acid copolymer, and the like. Such polymers are also commercially available, and the following polymers can be used.

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).

(Undercoat layer) An undercoat layer may be provided between the transparent support and the filter layer. The undercoat layer is
It is formed as a layer containing a polymer having a glass transition temperature of 25 ° C. or lower, a layer having a rough surface on the filter layer side, 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 to improve the adhesion between the transparent support and a layer provided thereon (for example, an antireflection layer or a hard coat layer). Is also good. 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, 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 1.5
5, and more preferably 1.30 to 1.55. The thickness of the low refractive index layer is preferably 50 to 400 nm, and 50 to 200 nm.
Is more preferable. The low refractive index layer is a layer made of a fluorine-containing polymer having a low refractive index (JP-A-57-345).
No. 26, JP-A-3-130103, and JP-A-6-11502
3, No. 8-313702, and No. 7-168004), and a layer obtained by a sol-gel method (Japanese Unexamined Patent Application Publication No.
Nos. -2088811, 6-299091 and 7-16
No. 8003) or a layer containing fine particles (JP-B-60-59250, JP-A-5-13021, JP-A-6-56478, JP-A-7-92306, and 9-288).
No. 201). 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 the 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 high refractive index layer preferably has a refractive index of 1.65 to 2.40.
More preferably, it is 70 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. The thickness of the middle / 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. .
Other polymers having a cyclic (aromatic, heterocyclic, alicyclic) group and polymers having a halogen atom other than fluorine as a substituent also have 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.
An antireflection layer having an antiglare function generally has a haze of 3 to 30%.

(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 2 to 20 nm.

Filter layer (except for the case of vapor deposition, sputtering, spinning, etc.), undercoat layer, antireflection layer (medium refractive index layer, high refractive index layer, low refractive index layer), hard coat layer, lubricating layer, etc. Can be formed by a general coating method. 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. 41898, No. 3508947, No. 3526528
Issue specifications and Yuji Harazaki, "Coating Engineering" 2
It is described on page 53 (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. This plasma display panel is also called a PDP module. Plasma display panels (PDPs) are already commercially available. Regarding the plasma display panel, see Japanese Patent Application Laid-Open
No. 643 and No. 9-306366. The front plate referred to in the present invention is a transparent plate installed on the front of the plasma display panel and incorporated in a housing, and is sometimes called an “optical filter”.

[0040]

EXAMPLE 1 (Formation of Multilayer Interference Film) After a corona treatment was applied to both sides of a transparent polyethylene terephthalate film having a thickness of 100 μm, a titanium oxide thin film and an aluminum oxide thin film were alternately laminated by a vacuum deposition method. A transparent film having selective reflection was formed. The layer configuration of this reflective film is as follows.

Titanium oxide (94 nm) / aluminum oxide (112 nm) / titanium oxide (75 nm) / aluminum oxide (112 nm) / titanium oxide (75 nm) / aluminum oxide (112 nm) / titanium oxide (75n)
m) / aluminum oxide (112 nm) / titanium oxide (75 nm) / aluminum oxide (112 nm) / titanium oxide (75 nm) / aluminum oxide (112 nm)
/ Titanium oxide (94 nm) / aluminum oxide (112
nm) / polyethylene terephthalate film

When the spectral transmittance of the optical filter was examined, it had an absorption maximum at 590 nm, the transmittance at the absorption maximum was 25%, and the half width at the absorption maximum wavelength was 37 nm.

Example 2 (Formation of Multilayer Interference Film) After a corona treatment was applied to both sides of a transparent polyethylene terephthalate film having a thickness of 100 μm, a titanium oxide thin film and an aluminum oxide thin film were alternately laminated by a vacuum deposition method. A transparent film having selective reflection was formed. On this film, polyvinyl alcohol is applied as an intermediate layer so as to have a thickness of 1.0 μm, and titanium oxide and aluminum oxide are alternately laminated again by a vacuum evaporation method to form a transparent film having a desired selective reflection property. did.
The layer configuration of the formed film is shown below.

Silicon dioxide (161 nm) / aluminum oxide (112 nm) / silicon dioxide (161 nm) /
Aluminum oxide (112 nm) / silicon dioxide (16
1 nm) / aluminum oxide (112 nm) / silicon dioxide (161 nm) / aluminum oxide (112 nm)
/ Silicon dioxide (161 nm) / aluminum oxide (1
12 nm) / polyvinyl alcohol layer (1.0 μm) /
Titanium oxide (80 nm) / silicon dioxide (35 nm) /
Titanium oxide (105 nm) / silicon dioxide (35 nm)
/ Titanium oxide (105nm) / silicon dioxide (35n
m) / titanium oxide (180 nm) / polyethylene terephthalate film

When the spectral transmittance of the optical filter was examined, the optical filter had absorption maximums at 530 nm and 591 nm, and the transmittance at the absorption maximum was 69% at 530 nm and 59%.
The absorption maximum at 3 nm was 30%. In addition, 591 nm
Has a half width at an absorption maximum wavelength of 47 nm.

Example 3 (Formation of Undercoat Layer) After a corona treatment was applied to both sides of a transparent polyethylene terephthalate film having a thickness of 100 μm,
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, 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) To 180 g of a latex of polybutyl methacrylate (10% by weight dispersion),
Fine particles of titanium dioxide were mixed with 180 g of a latex of polybutyl methacrylate (10 wt% dispersion) to adjust the refractive index of the coating film to 1.51 and 1.62, respectively. The obtained coating liquid for a filter layer was alternately applied on the second undercoat layer in a total of 8 layers, and dried at 120 ° C. for 10 minutes to form a part of the filter layer. Further, to 180 g of a 10% by weight dispersion of gelatin, 0.01 of dye (a1) was added.
After dissolving 6 g and stirring at 40 ° C. for 30 minutes, 2 μm
Was filtered with a polypropylene filter. The obtained coating liquid for a filter layer is applied onto the second undercoat layer so that the dry film thickness becomes 3.5 μm, and dried at 120 ° C. for 10 minutes to form a filter layer, thereby forming an optical filter. did. The layer structure of the obtained filter is shown below.

Dye-mixed gelatin layer (3.5 μm) / polybutyl methacrylate latex (201 nm, a1
Layer) / polybutyl methacrylate latex layer mixed with titanium dioxide particles (180 nm, a2 layer) / a1 layer (201 n
m) / a2 layer (180 nm) / a1 layer (201 nm) /
a2 layer (180 nm) / a1 layer (201 nm) / a2 layer (180 nm) / undercoat layer / polyethylene terephthalate film / anti-reflection layer

Examination of the spectral transmittance of the optical filter revealed that the optical filter had absorption maximums at 530 nm and 593 nm, and the transmittance at the absorption maximum was 70% at 530 nm and 59%.
The absorption maximum at 3 nm was 25%. 593 nm
Was at 50 nm.

Comparative Example 1 (Formation of Filter Layer) 6.0 g of partially hydrolyzed polyvinyl acetate was dissolved in 160 g of isopropyl alcohol: water = 1: 1 (weight), and a commercially available dye (Hosperterm Pink E) 6. 0 g and 0.05 g of the dye (a1) were dissolved, stirred at 40 ° C. for 20 minutes, and filtered with a 2 μm polypropylene filter. The obtained coating liquid for a filter layer is applied onto the second undercoat layer so that the dry film thickness becomes 3.5 μm, and dried at 120 ° C. for 10 minutes to form a filter layer, thereby forming an optical filter. did.

When the spectral transmittance of the optical filter was examined, it had an absorption maximum at 530 nm and 570 nm, and the transmittance at the absorption maximum was 69% at 530 nm and 57% at 530 nm.
The absorption maximum at 0 nm was 65%.

(Evaluation of Filter Function) Plasma Display Panel (PDS4202J-H, Fujitsu Limited)
The film on the outermost surface of the front plate of the first embodiment is peeled off, and the optical filter (the surface on the side where the low refractive index layer is not provided) prepared in Examples 1 and 2 and Comparative Example 1 is attached with an adhesive instead. Was. Contrast,
The luminance (relative value to Example 1) was measured, and white light and red light were visually evaluated. Table 1 and 2
It is shown in the table.

Table 1 Characteristics of Filter Transmittance (%) Optical Filter 460 nm 620 nm Transmittance at Transmittance with Number of Half-width nm (Absorption at 560-620 nm) Example 1 89% 91% 37 Example 2 86 % 91% 47 Example 3 86% 90% 50 Comparative example 85% 76% 150

Table 2 Display Characteristics Optical Filter Contrast Brightness White Light Red Light Example 1 16: 1110 Slightly Green White Beautiful Red (Improved) (Improved) Example 2 15: 1 100 White (Improved) Beautiful Red (Improved) Example 3 15: 1 105 White (Improved) Beautiful Red (Improved) Comparative Example 1 12: 1 85 Magenta White containing a weak orange color Red (Slightly improved) No filter 10: 1 130 Green Tinged white orange-tinged red

As is clear from the results shown in Table 1, the contrast of the PDP and the tint of white light and red light can be significantly improved by using a filter having a sharp selective wavelength characteristic utilizing the principle of multilayer interference. . On the other hand, a filter using a pigment with a wide half-value width not only has a small effect of improving tint, but also reduces the intensity of blue or red that is actually required, causing color mismatch, and the range of decrease in luminance. And a large decrease in image quality is inevitable.

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[Procedure amendment]

[Submission date] April 27, 1999 (1999.4.2
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

(Filter layer) The filter layer is formed in accordance with the principle of a known multilayer reflective film, and has a structure in which two or more layers having different refractive indexes are alternately laminated. The thickness of the filter layer is not particularly limited, but is preferably in the range of about 0.1 μm to 5 cm from the viewpoint of thickness accuracy and transparency. More preferably, 1 μm to 1 cm
is there. The filter layer has an absorption maximum in the 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 5 to 5
It is preferably in the range of 0%. Wavelength 560-6
The absorption maximum in the range of 20 nm is set in order to selectively cut out the sub-band that reduces the color purity of the red phosphor. In the PDP, unnecessary light emission near 585 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 wavelength is 560 to 620 nm
The half width at the absorption maximum in the range of 1.5 to 200 nm
It is more preferably 20 to 100 nm, most preferably 22 to 80 nm. When the half width is less than 10 nm, the absorption of unnecessary light due to the excitation of neon gas becomes substantially incomplete, and the effect is reduced.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

The filter layer has a thickness of 560 to 620 n.
In addition to the range of m, the wavelength may have an absorption maximum in the range of 500 to 550 nm. Wavelength is 500 to 550
The transmittance in the range of nm is preferably in the range of 20 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. Wavelength 500 to 55
The half width at the absorption maximum in the range of 0 nm (the width of the wavelength region showing half the absorbance at the absorption maximum) is 30 to 3
The thickness is preferably 00 nm, more preferably 40 to 300 nm, further preferably 50 to 150 nm, and most preferably 60 to 150 nm.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

(Undercoat layer) An undercoat layer may be provided between the transparent support and the filter layer. The undercoat layer is
It is formed as a layer containing a polymer having a glass transition temperature of 60 ° C. or less and −60 ° C. or more , a layer having a rough surface on the filter layer side, 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 to improve the adhesion between the transparent support and a layer provided thereon (for example, an antireflection layer or a hard coat layer). Is also good. 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 from 20 nm to 1000
nm is preferable, and 80 nm to 300 nm is more preferable. The undercoat layer containing a polymer having a glass transition temperature of 60 ° C or lower and -60 ° C or higher adheres the transparent support and the filter layer due to the tackiness of the polymer. Glass transition temperature is 60 ℃
The polymer having a temperature of −60 ° C. or higher 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 less,
It is more preferably at most 10 ° C, more preferably at most 10 ° C, still more preferably at most 5 ° C, most preferably at most 0 ° C. 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 0.02 to 3 μm.
More preferably, the thickness is from 0.05 to 1 μm. Examples of the polymer having an affinity for the binder polymer of the filter layer include an acrylic resin, a cellulose derivative, gelatin,
Includes casein, starch, polyvinyl alcohol, soluble nylon and polymeric 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.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

(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 1.5
5, and more preferably 1.30 to 1.50 . The thickness of the low refractive index layer is preferably 50 to 400 nm, and 50 to 200 nm.
Is more preferable. The low refractive index layer is a layer made of a fluorine-containing polymer having a low refractive index (JP-A-57-345).
No. 26, JP-A-3-130103, and JP-A-6-11502
3, No. 8-313702, and No. 7-168004), and a layer obtained by a sol-gel method (Japanese Unexamined Patent Application Publication No.
Nos. -2088811, 6-299091 and 7-16
No. 8003) or a layer containing fine particles (JP-B-60-59250, JP-A-5-13021, JP-A-6-56478, JP-A-7-92306, and 9-288).
No. 201). 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 the fine particles preferably has a porosity of 3 to 50% by volume, more preferably 5 to 35% by volume.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

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 high refractive index layer preferably has a refractive index of 1.65 to 2.40.
More preferably, it is 70 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 1.50 to 1.90 . The thickness of the middle / 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. .
Other polymers having a cyclic (aromatic, heterocyclic, alicyclic) group and polymers having a halogen atom other than fluorine as a substituent also have 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.

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Claims (10)

[Claims] 1. An optical filter having a layered structure of a total of six or more layers composed of alternating layers of two or more substances,
An optical filter having an absorption maximum in the range of 560 to 620 nm and having a transmittance of 50% or less at the wavelength maximum. 2. The optical filter according to claim 1, which has an absorption maximum in a range of 500 to 550 nm in addition to 560 to 620 nm, and has a transmittance of 30% or more at the maximum of the wavelength. 3. It has a layered structure of a total of 6 or more layers composed of alternating layers of two or more substances, has an absorption maximum in the range of 560 to 620 nm, and has a transmittance at the wavelength maximum. It has a layered structure of a total of four or more layers consisting of a selective reflection layer of 50% or less and an alternate lamination of two or more kinds of substances, has an absorption maximum in the range of 500 to 550 nm, and 3. A selective reflection layer having a transmittance at a maximum of 30% or more.
An optical filter according to item 1. 4. The absorption pole in the range between 560 and 620 nm.
The layer having the large optical refractive index n₁Layer and optical refractive index n
_Two, And 1.03 <n _Two/ N₁≤
1.3, characterized in that it is in the range of 1.3.
Or the optical filter according to 3. 5. The optical filter according to claim 4, wherein a relationship of 1.38 ≦ n ₁ is satisfied. 6. An optical refractive index n alternately laminated.₁Layer thickness
d₁Of the optical refractive index n_TwoLayer thickness d_TwoVariation
Are each 30% or less, and 1120 ≦ n₁d ₁+ N_Twod
_Two5. The method according to claim 4, wherein the value is in the range of .ltoreq.1240.
Or the optical filter according to 5. 7. The optical filter according to claim 1, which has an adhesive, a filter layer, a support, and an antireflection layer. 8. A plasma display panel (PDP)
The optical filter according to claim 1, which is used for display. 9. A front panel for a PDP, wherein the optical filter according to claim 8 is held on the surface. 10. A 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.