JP2009237435A - Light-reflective film and backlight device for image display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-reflective film excelling in luminance uniformity with little degradation of luminance with the lapse of time even under long-time use in high-temperature conditions and capable of maintaining high-quality images over a long period of time. <P>SOLUTION: The light-reflective film is provided with an A-layer containing an ultraviolet absorbent, on at least one face of a white film formed of laminated structure of two or more layers. The thickness of the A-layer is 1.0 μm or less, and the thickness of a surface layer on the side, provided with the A-layer, of the white film is 0.001-20 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement of a white film used for a light reflecting member, and more particularly, a member used for a light reflecting plate of an edge light type and a direct type surface light source for a liquid crystal screen, a lamp reflector of a light source unit, and the like. Thus, the present invention relates to a light-reflective film that hardly changes in color tone even when used in a backlight for a long period of time, prevents contamination of the film due to electric resistance, and has excellent long-term stability.

  As an illumination device for a liquid crystal screen, a so-called edge light system in which light is introduced from a side surface of a light guide plate using a cold cathode ray tube as an illumination light source is widely used (see, for example, Patent Document 1). In this illumination method, in order to use light more efficiently, a reflector is provided around the cold cathode ray tube, and in order to efficiently reflect the light diffused from the light guide plate to the liquid crystal screen side, Is provided with a reflector. Thereby, the loss of light from the cold cathode ray tube is reduced, and the function of brightening the liquid crystal screen is provided. In addition, for large screens such as liquid crystal televisions, the direct light method has been adopted because it is not possible to increase the screen brightness with the edge light method. In this method, a cold cathode ray tube is provided in parallel at the lower part of the liquid crystal screen, and the cold cathode ray tubes are arranged in parallel on the reflector. The reflecting plate may be a flat plate or a cold cathode ray tube formed into a semicircular concave shape.

Reflectors and reflectors (generally referred to as surface light source reflecting members) used in such surface light sources for liquid crystal screens are required to have a high reflecting function, and conventionally, a film added with a white dye or a white pigment or a fine structure inside. A film containing various bubbles has been used alone, or a film in which these films are bonded to a metal plate, a plastic plate, or the like has been used (see, for example, Patent Document 2 and Patent Document 3). In recent years, the use of liquid crystal screens has been remarkably expanded, and these light reflecting films have been widely used in stationary personal computers, liquid crystal televisions, mobile phone displays, and various game machines. In accordance with such expansion of applications, it is desired to increase the brightness and definition of the screen, and the illumination light source has been improved by increasing the output and increasing the number of light source lamps. Furthermore, in order to meet the demands of long-time use on a large screen such as a liquid crystal television, higher brightness and durability are required, especially when using a direct light source, etc. Therefore, higher durability of the reflector is required. In this regard, in the case of a reflector or reflector using conventional films, the color tone changes (yellowing occurs) with deterioration of the film when used for a long time, the reflection characteristics deteriorate, and in turn pulls down the screen brightness. In order to prevent yellowing due to deterioration of the film itself, a method of adding a light stabilizer to the film and a coating layer containing the light stabilizer have been developed. (For example, refer to Patent Document 4 and Patent Document 5.)
JP-A-63-62104 (Claims (1) to (4)) JP-A-6-322153 ([Claim 1] to [Claim 4], [0009] to [0024] paragraphs) JP-A-7-118433 ([Claim 2], [0009] paragraph, [0014] paragraph) JP 2001-287327 A ([Claim 2], [0014] paragraphs) JP 2002-90515 A ([Claim 1] to [Claim 3], [0019] to [0033] paragraphs)

  However, when a layer containing an ultraviolet absorber is provided on the white base film by coating, a film thickness of a certain level or more is required to maintain durability, especially when it is composed only of an organic ultraviolet absorber. In this case, the thickness of the layer must be increased, but the higher the thickness, the higher the cost.

  Furthermore, in the light reflecting film used for the lamp reflector of the sidelight type backlight or the direct type backlight, the cold cathode ray tube and the film are close to each other and are in an environment where the heat from the light source is easily received. There were cases in which the degree of discoloration due to oxidation increased.

  An object of the present invention is to provide a light-reflective film capable of maintaining a high quality over a long period of time even when used for a long time under a high temperature condition, and a backlight device for image display using the same. It is.

As a result of intensive investigations aimed at solving the above-described problems in the prior art, the present inventors have reduced the cost by reducing the thickness of the A layer, and the side on which the A layer containing the ultraviolet absorber is provided. The present invention has been accomplished by finding that by reducing the thickness of the surface layer of the white film, it is possible to reduce the change in color tone due to the deterioration of the film over time and to reduce yellowing. That is, the present invention is characterized by the following configuration.
An A layer containing an ultraviolet absorber is provided on at least one side of a white film having a laminated structure of two or more layers, and the A layer has a thickness after drying of 1.0 μm or less, and the A layer The surface thickness of the white film on the side where the film is provided is 0.001 to 20 μm, and a backlight device for image display using the same is provided. According to a preferred embodiment of the present invention, the thickness of the surface layer is preferably in the range of 0.1 to 5 μm, and further, the initial color tone b0 measured from the surface side of the A layer side, and the UV irradiation described in the text The difference Δb = b1−b0 from the color tone b1 after 24 hours in the test is most preferably 5.0 or less. In addition, the ultraviolet absorber contained in the layer A is preferably a combination of an organic ultraviolet absorber and an inorganic ultraviolet absorber, or composed only of an inorganic ultraviolet absorber, and further, the white film has an internal structure. If it consists of a laminated film of two or more layers having a polyester layer containing fine bubbles as a main layer, it can be a light-reflective film that maintains high reflection and high brightness over a long period of time.

  The light reflective film of the present invention has little deterioration over time even when used under high temperature conditions, is excellent in average reflectance and luminance uniformity, and can maintain the image quality and brightness of a liquid crystal display or the like over a long period of time. it can.

  In the present invention, it is necessary to provide an A layer containing an ultraviolet absorber on at least one side of a white film having a laminated structure of two or more layers as a base material.

  The thickness of the A layer containing the ultraviolet absorber must be 1.0 μm or less, more preferably 0.02 to 0.8 μm, and most preferably 0.1 to 0.7 μm. When the thickness of the A layer is 1.0 μm or less, a high cost reduction effect by obtaining a thin film is obtained, and when the A layer is provided by coating during the formation of the base film, a good film forming property is obtained. The thickness unevenness and the coating defects are difficult, which is preferable. In addition, when the thickness of the A layer is 0.02 μm or more, the UV resistance performance of the A layer is further improved. Therefore, when used as a reflective material for a backlight of a liquid crystal display, discoloration of the film and long-term reflectance decrease are caused. It is effective to prevent. Therefore, when the thickness of the A layer is within this range, it is preferable that the durability of the A layer is sufficiently obtained and the luminance is not lowered.

  Moreover, in this invention, the white film used as a base material consists of a laminated structure of two or more layers, and the surface layer thickness by the side in which A layer is provided needs to be 0.001-20 micrometers, Preferably it is 0.05. ˜15 μm, more preferably 0.05 to 10 μm, and most preferably 0.1 to 5 μm. When the surface layer thickness is 0.001 μm or more, it is difficult for defects such as scratches and dents to be attached to the surface of the film when the film is handled. On the other hand, when the surface layer thickness is 20 μm or less, the layer that is easily affected by ultraviolet rays emitted from the cold cathode ray tube as the light source becomes thin when used as a surface light source reflecting member, and as a result, the color tone changes. There is little, and light reflectivity and a brightness are hard to fall. In particular, when the thickness of the surface layer is 5 μm or less, the thickness of the layer that deteriorates due to ultraviolet irradiation is very thin, so that the change in color tone of the base film itself is small, and further, the thickness of the A layer is reduced. It becomes possible, and it can be set as a lightweight and high-performance light-reflective film. Thus, if the surface layer thickness is in the range of 0.001 to 20 μm, a film having excellent light reflectivity can be obtained over a long period of time.

In the present invention, the difference Δb = b1−b0 between the initial color tone b0 measured from the A layer side and the color tone b1 after 24 hours in the UV irradiation test is preferably 5.0 or less, and more preferably 4.5. Hereinafter, it is most preferably 4.0 or less. When the Δb value is 5.0 or less, the change in reflectance between the initial color tone and after the UV irradiation test is small, and sufficient luminance can be obtained. In the present invention, the b value refers to a b value measured according to JIS Z-8722 using a spectroscopic color difference meter. In addition, the UV irradiation test in the present invention is a condition of temperature 60 ° C., humidity 50% RH, UV illuminance 100 mW / cm ² using a weather resistance promotion tester iSuper UV Tester SUV-W131 manufactured by Iwasaki Electric Co., Ltd. Under UV irradiation.

  Although the total thickness of the white film in this invention is not specifically limited, 50-500 micrometers is preferable and 100-300 micrometers is more preferable. A total thickness of 50 μm or more is preferable because the reflectance, whiteness, and color are good, and the film is easy to handle. On the other hand, if it is 500 micrometers or less, when it uses for a liquid crystal display etc. as a surface light source reflection member, it is easy to handle in terms of weight and thickness, and also the cost can be suppressed, which is preferable. Moreover, the ratio of the thickness of the surface layer portion / inner layer portion of the white film is not particularly limited, but is preferably 0.01 / 100 to 1/30, more preferably 0.1 / 100 to 1/50. . In the case of a three-layer composite film of surface layer portion / inner layer portion / surface layer portion, the ratio is expressed as the sum of both surface layer portions / inner layer portion. Furthermore, in the case of a three-layer composite film, the thicknesses of both surface layer portions may be the same, or the surface layer thickness of the white film on the A layer side may be decreased.

  As UV absorbers, organic UV absorbers such as hindered amines, salicylic acids, benzophenones, benzotriazoles, cyanoacrylates, triazines, benzoates, oxalate anilides, benzosakidinones, or inorganics such as sol-gels System ultraviolet absorbers can be used, and these can be used in combination. Specific examples of ultraviolet absorbers that can be suitably used are shown below, but of course not limited thereto.

(Organic UV absorber)
Hindered amines: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine Polycondensate.

  Salicylic acid type: pt-butylphenyl salicylate, p-octylphenyl salicylate.

  Benzophenone series: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2′-4,4′-tetrahydroxybenzophenone, 2,2 ′ -Dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane.

  Benzotriazole series: 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′) , 5'-di-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy- 3 ', 5'-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-t-octylphenol) benzotriazole, 2- (2'-hydroxy-3', 5 '-Di-t-amylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-ben Triazol-2-yl) phenol], 2 (2′hydroxy-5′-methacryloxyphenyl) -2H-benzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 "-tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5-acryloyloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methacrylic) Roxyethylphenyl) -2H-benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-acryloylethylphenyl) -5-chloro-2H-benzotriazole.

  Cyanoacrylate series: Ethyl-2-cyano-3,3'-diphenylacrylate.

  Other than the above: nickel bis (octylphenyl) sulfide, [2,2′-thiobis (4-tert-octylphenolate)]-n-butylamine nickel, nickel complex-3,5-di-t-butyl-4-hydroxy Benzyl phosphate monoethylate, nickel dibutyldithiocarbamate, 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate, 2,4-di-t-butyl Phenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, 2-ethoxy-2′-ethyl oxac acid bisanilide, 2- (4,6-diphenyl-1,3,5-triazine -2-yl) -5-[(hexyl) oxy] -phenol, 2,2 ′ (p-phenylene) di-3,1-benzoxazi -4-one 4H-3,1-benzoxazin-4-one, 2,2 '-(1,4-phenylene) bis-2,2'-(1,4-phenylene) bis [4H-3,1- Benzoxazin-4-one] 2,2 ′ (p-phenylene) di-3,1 benzoxazin-4-one.

(Inorganic UV absorber)
Titanium oxide, zinc oxide, cerium oxide alone, or titanium oxide, zinc oxide as a core layer (core) with alumina, zinc oxide, zirconium oxide, cobalt, etc. coated on the surface, or zinc carbonate, carbonic acid Calcium, magnesium carbonate, magnesium oxide, silica, talc, kaolin, lithium fluoride, calcium fluoride, barium sulfate, zinc sulfide, alumina, calcium phosphate, mica, etc. are used as the core layer (core), and titanium oxide and zinc oxide are formed on the surface. Coated.

  In the present invention, among the specific examples of the organic ultraviolet absorber, at least one of a hindered amine, benzophenone, and benzotriazole is preferably used, and more preferably used in combination. Moreover, when using an organic type ultraviolet absorber, in order to make formation of A layer easier, it is preferable to mix another resin component suitably. That is, the resin component and the organic ultraviolet absorber are dissolved or dispersed in an organic solvent, water, a mixture of two or more organic solvents, or an organic solvent / water mixture that can dissolve the resin component and the organic ultraviolet absorber, respectively. It is a preferable embodiment that the coating liquid is used. Of course, the resin component and the organic ultraviolet absorber separately dissolved or dispersed in an organic solvent, water, an organic solvent mixed solution, or an organic solvent / water mixed solution may be arbitrarily mixed and used. It is also a preferred embodiment that a copolymer of an organic ultraviolet absorber component and a resin component is used as it is as a coating material. Of course, the copolymer may be dissolved in an organic solvent, water, a mixture of two or more organic solvents, or an organic solvent / water mixture. The resin component to be mixed or copolymerized is not particularly limited. For example, polyester resin, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, Examples thereof include polystyrene resin, polyvinyl acetate resin, and fluorine resin. These resins may be used alone or in the form of two or more copolymers or a mixture.

  Among the above resin components, it is preferable to select and use an acrylic resin or a methacrylic resin, and it is more preferable to use an acrylic resin or a methacrylic resin copolymerized with an organic ultraviolet absorber component for the A layer. . In the case of copolymerization, it is preferable to copolymerize an acrylic monomer component or a methacryl monomer component with an organic ultraviolet absorber monomer component.

  As the organic ultraviolet agent monomer component, for example, a benzotriazole-based reactive monomer, a hindered amine-based reactive monomer, a benzophenone-based reactive monomer, or the like can be preferably used. The benzotriazole-based monomer is not particularly limited as long as it is a monomer having benzotriazole in the substrate skeleton and an unsaturated bond. For example, 2- (2′-hydroxy-5-acryloyloxyethylphenyl)- 2H-benzotriazole, 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-acryloylethylphenyl)- 5-chloro-2H-benzotriazole and the like can be mentioned. Similarly, the hindered amine-based reactive monomer and the benzophenone-based reactive monomer may be any monomer having hindered amine and benzophenone on the substrate skeleton and having an unsaturated bond, respectively. Examples of the hindered amine-based reactive monomer include bis (2,2,6,6-tetramethyl-4-piperidyl-5-acryloyloxyethylphenyl) sebacate, dimethyl succinate, 1- (2-hydroxyethyl) -4- Hydroxy-2,2,6,6-tetramethyl-5-acryloyloxyethylphenylpiperidine polycondensate, bis (2,2,6,6-tetramethyl-4-piperidyl-5-methacryloxyethylphenyl) sebacate, Dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethyl-5-methacryloxyethylphenylpiperidine polycondensate, bis (2,2,6,6-tetra Methyl-4-piperidyl-5-acryloylethylphenyl) sebacate, dimethyl succinate 1- (2 Hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethyl-5-acryloylethyl phenylpiperidine polycondensates, and the like. Examples of the benzophenone-based reactive monomer include 2-hydroxy-4-methoxy-5-acryloyloxyethylphenylbenzophenone, 2,2′-4,4′-tetrahydroxy-5-acryloyloxyethylphenylbenzophenone, 2, 2'-dihydroxy-4-methoxy-5-acryloyloxyethylphenylbenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-acryloyloxyethylphenylbenzophenone, 2-hydroxy-4-methoxy-5-methacryl Loxyethylphenylbenzophenone, 2,2′-4,4′-tetrahydroxy-5-methacryloxyethylphenylbenzophenone, 2,2′-dihydroxy-4-methoxy-5-acryloylethylphenylbenzophenone, 2,2 -, and the like-dihydroxy-4,4'-dimethoxy-5-acryloyl ethyl phenyl benzophenone.

  As an acrylic monomer component or a methacryl monomer component copolymerized with these organic ultraviolet absorber monomer components, or oligomer components thereof, alkyl acrylate, alkyl methacrylate (the alkyl group is methyl group, ethyl group, n-propyl group, Isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group, etc.), and monomers having a crosslinkable functional group, such as carboxyl group, methylol group, acid anhydride Examples thereof include monomers having a physical group, a sulfonic acid group, an amide group, a methylolated amide group, an amino group, an alkylolated amino group, a hydroxyl group, and an epoxy group. Furthermore, acrylonitrile, methacrylonitrile, styrene, butyl vinyl ether, maleic acid, itaconic acid and dialkyl esters thereof, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, alkoxysilanes having a vinyl group, It is good also as a copolymer with saturated polyester.

  The copolymerization ratio between these organic ultraviolet absorber monomer components and the monomers copolymerized is not particularly limited, and one or more of each can be copolymerized at an arbitrary ratio, but preferably Most preferably, the ratio of the organic ultraviolet absorber monomer component is 10% by weight or more, more preferably 20% by weight or more, and even more preferably 35% by weight or more based on the solid content of the A layer. Of course, a homopolymer of an organic ultraviolet absorber monomer component may be used. The molecular weight of these polymers is not particularly limited, but is usually 5,000 or more, preferably 10,000 or more, and more preferably 20,000 or more in terms of toughness of the coating layer. These polymers are used in a state dissolved or dispersed in an organic solvent, water, or an organic solvent / water mixture. In addition to these, commercially available hybrid UV-absorbing polymers such as “Udouble” (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) can also be used.

  Among the above specific examples of the inorganic ultraviolet absorber in the present invention, at least titanium oxide, zinc oxide, cerium oxide alone, or titanium oxide, zinc oxide as a core layer (core), on its surface, alumina, zinc oxide, It is preferable to use any one coated with zirconium oxide, and it is also preferable to use these in combination.

  In addition, fine particles are preferably used for the inorganic ultraviolet absorber, and the shape thereof is not particularly limited, such as spherical, square, hexagonal, needle-like, columnar, spindle-shaped, polyhedron, etc. Aggregates may also be used.

  The primary particle size of these inorganic ultraviolet absorbers is preferably 1 to 500 nm, more preferably 1 to 200 nm, and most preferably 1 to 100 nm. When the shape of the inorganic ultraviolet absorber is not a true sphere, the size of the longest side is regarded as the primary particle size. When the primary particle size of the inorganic ultraviolet absorber is less than 1 nm, the viscosity of the coating liquid may increase to become a gel, and when it exceeds 500 nm, the inorganic ultraviolet absorber is contained in the A layer. A portion having a rough distribution is generated, and the light resistance may be deteriorated.

  The form of the inorganic ultraviolet absorber used in the present invention is not particularly limited, and the powder may be used as it is, but an organic solvent, water, a mixture of two or more organic solvents, or an organic solvent / In a preferred embodiment, the resin component and the inorganic ultraviolet absorber are dispersed in a water mixture and used in a coating solution state. Of course, a resin component and an inorganic ultraviolet absorber separately dissolved or dispersed in an organic solvent, water, an organic solvent mixed solution, or an organic solvent / water mixed solution may be arbitrarily mixed and used. The resin component to be mixed with the inorganic ultraviolet absorber is not particularly limited. For example, polyester resin, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinyl chloride Examples thereof include vinylidene resin, polystyrene resin, polyvinyl acetate resin, and fluorine resin. These resins may be used alone or in the form of two or more copolymers or a mixture.

  In the present invention, the ultraviolet absorber contained in the layer A may be composed of only the organic ultraviolet absorbers listed above, but various organic ultraviolet absorbers and inorganic ultraviolet absorbers are selected and used in combination. Or it is a preferable form that it is comprised only with an inorganic type ultraviolet absorber from the point which improves light resistance performance more. Moreover, the addition ratio of the addition amount of the organic ultraviolet absorber and the addition amount of the inorganic ultraviolet absorber contained in the layer A is preferably in the range of 0/10 to 9/1 by weight, and more preferably 1/9. ~ 8/2 is preferred. At this time, when an organic ultraviolet absorber is a copolymer with a resin component, the addition amount including a resin component is said. Within such a range, good reflectance can be maintained even after the UV irradiation test.

  A layer containing the ultraviolet absorber in this invention can be provided by arbitrary methods. For example, methods such as gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating, and dipping can be used. Moreover, when hardening A layer after application | coating, the hardening method can take a well-known method. For example, thermosetting, a method using active rays such as ultraviolet rays, electron beams, radiation, or a combination of these methods can be applied. In the present invention, a heat curing method using a hot air oven is preferred. Furthermore, in the curing with a hot air oven, the method of increasing the drying temperature in stages, such as material preheating / constant rate drying / residual rate drying, does not leave the solvent in the A layer and the fine particles contained in the coating material Is effective for uniformly dispersing in the A layer. When it hardens | cures rapidly at high temperature, since solvent volatilization becomes intense and particle | grains aggregate, it is unpreferable. Moreover, it is preferable to use together hardening | curing agents, such as a crosslinking agent, for the coating film hardening in this invention. Moreover, as a method of providing an application layer, it may be applied during the production of a white base film (in-line coating), or may be applied onto the white film after completion of crystal orientation (off-line coating). In particular, in-line coating is preferable because of high production efficiency.

  The layer A containing the ultraviolet absorber may be provided directly on the white film as the base material. However, when the adhesiveness is insufficient, the easy-adhesion layer can be used as a corona discharge treatment or undercoat treatment of the white film. Is preferably provided. The easy adhesion layer may be provided within the white film production process (inline coating method), or may be separately applied after the white film is produced (offline coating method). The material to be applied to the subbing treatment is not particularly limited and may be appropriately selected. Suitable examples thereof include copolymer polyester resin, polyurethane resin, acrylic resin, methacrylic resin, and various coupling agents. .

  In the present invention, it is preferable to add organic and / or inorganic fine particles having no ultraviolet absorbing function in the A layer in order to prevent film blocking. Silica, alumina, calcium carbonate can be used as the inorganic fine particles, and silicone compounds, crosslinked styrene, crosslinked acryl, crosslinked melamine, and the like can be used as the organic particles, and spherical silica particles are preferable. The particle diameter of the organic and / or inorganic fine particles is not particularly limited, and is preferably used as long as the ratio of the thickness of the A layer to the particle diameter is in the range of 1/1 to 1/2. . When the ratio between the A layer and the particle diameter is less than 1/1, the particles are buried in the A layer, so that blocking occurs when the film provided with the A layer is rolled up, , Exceeding ½ is not preferable because particles fall off due to rubbing or the like. Within such a range, a good film can be wound.

In the light reflective film of the present invention, the surface specific resistance value of the light reflective film on the side provided with the A layer is preferably 1.0 × 10 ¹³ Ω / □ or less. More preferably, it is 1.0 * 10 < ⁷ > -1.0 * 10 < ¹² > ohm / square, More preferably, it is 1.0 * 10 < ⁸ > -1.0 * 10 < ¹¹ > ohm / square. If it exists in this range, contamination of the film surface by static electricity can be prevented, and high quality can be maintained over a long period of time. In addition, when providing A layer on both surfaces of a white film, the surface specific resistance value of the at least one surface side should just satisfy | fill the said range.

  Further, in order to satisfy the above surface specific resistance value, an antistatic agent is added to the easy adhesion layer provided as a subbing treatment of the A layer containing the ultraviolet absorber on at least one side of the base film, or the A It is preferable to add an antistatic agent directly to the layer.

  Examples of the antistatic material include, but are not limited to, a surfactant, an ionic conductive polymer, an electron conductive polymer, a conductive metal oxide, and metals. Specific examples of surfactants and ionic conductive polymers that are ionic conductive components include the following.

  Surfactants include cationic surfactants such as sulfonated compounds, N-acyl amino acids or salts thereof, anionic surfactants such as alkyl ether carboxylates, aliphatic amine salts, and aliphatic quaternary ammonium salts. , Amphoteric surfactants such as carboxybetaine, imidazolinium betaine, and aminocarboxylate. Among them, sulfonated compounds are preferably applied, and specifically sodium dodecylbenzenesulfonate, sodium stearylbenzenesulfonate, sodium octylbenzenesulfonate, potassium dodecylbenzenesulfonate, lithium dodecylbenzenesulfonate, lithium octylnaphthalenesulfonate, Sodium oxylnaphthalene sulfonate, sodium dodecyl naphthalene sulfonate, potassium dodecyl naphthalene sulfonate, sodium butyl sulfonate, sodium pentyl sulfonate, sodium hexyl sulfonate, sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, decyl sulfone Acid sodium, sodium undecyl sulfonate, sodium dodecyl sulfonate, Sodium Ridecyl sulfonate, Sodium tetradecyl sulfonate, Sodium tetradecyl sulfonate, Sodium pentadecyl sulfonate, Sodium hexadecyl sulfonate, Sodium heptadecyl sulfonate, Sodium octadecyl sulfonate, Potassium decyl sulfonate, Potassium dodecyl sulfonate And potassium octadecyl sulfonate.

  Examples of the ionic conductive polymer include polystyrene sulfonates and their low molecular weight compounds represented by polystyrene sulfonates such as alkali metal salts and ammonium salts thereof, alkyl phosphate ester salts and alkyl ether phosphate ester salts. Examples thereof include a phosphoric acid polymer compound copolymerized as a monomer and a polyacrylic acid ester having an ionic functional group.

Specific examples of the electron conductive polymer that is the electron conductive component include the following. Examples thereof include known conductive polymers such as polyacetylene derivatives, polyparaphenylene derivatives, polyparafinylene vinylene derivatives, polythiophene derivatives, polyaniline derivatives, polypyrrole derivatives, polyfuran derivatives, and polyazulene derivatives. Furthermore, a dopant component is added as an auxiliary component of the electron conductive polymer. For example, halogens such as Br ₂ , Cl ₂ , and I ₂ , Lewis acids such as BF ₃ , PF ₃ , SbF ₅ , and AsF ₅ , H ₂ Protonic acids such as SO ₄ , HClO ₄ , HCl, HF, CF ₃ SO _4, and low molecular weight dopants such as transition metal halides such as FeCl ₃ , MoCl ₃ , WCl ₃ , SnCl ₄ , MoF ₅ , polystyrene sulfonic acid derivatives Polymer type dopants such as

  In addition, examples of the conductive metal oxide include tin compounds such as ITO and ATO, titanium oxide, silica, indium oxide, tin oxide, zinc oxide, vanadium oxide, ruthenium oxide, tantalum oxide and the like whose surface is subjected to conductive treatment. Is mentioned.

  Further, it is formed by vapor deposition or coating of metals such as Al, Cr, Cd, Ti, Fe, Cu, In, Ni, Pd, Pt, Rh, Ag, Au, Ru, W, Sn, Zr, and Ir. The conductive layer can also be applied to the present invention.

  In the conductive layer provided on the white film in the present invention, a binder component such as a polyester resin, an acrylic resin, a urethane resin, an epoxy resin, a silicone resin, a phenol resin, and modified products thereof may be blended. At least one selected from a polyester resin, an acrylic resin urethane resin, and a modified product thereof can be preferably used from the viewpoint that adhesion with a coating can be imparted. These binder components are preferably used in a state of being dissolved or dispersed in water or an arbitrary solvent such as an organic solvent. In addition to these, a commercially available hybrid UV-absorbing polymer that already contains an antistatic agent, for example, “Udable” (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) can be used.

  The content of the antistatic agent contained in the A layer in the present invention is preferably 0.01% by weight or more and less than 20% by weight. When the content is less than 0.01% by weight, the antistatic performance is insufficient and the film may be contaminated, which is not preferable. When the content exceeds 20% by weight, the antistatic agent bleeds out from the A layer. May cause blocking, or may cause cracks in the A layer during the film stretching process during in-line coating. If the content of the antistatic agent contained in the A layer is within such a range, high reflection and high luminance can be maintained over a long period of time.

  In the light reflective film of the present invention, the average reflectance of light having a wavelength of 400 to 800 nm is preferably 95% or more, more preferably 98% or more, and particularly preferably 100% or more. If the average reflectance is 95% or more, a very high luminance can be obtained when mounted on the backlight of a liquid crystal display. In addition, the average reflectance of light having a wavelength of 400 to 800 nm defined in the present invention refers to an average value obtained by measuring a spectral reflectance in a range of 400 to 800 nm with a spectrophotometer at intervals of 10 nm. To do.

  In the present invention, organic and / or inorganic fine particles can also be added to the A layer from the viewpoint of increased light diffusibility and luminance uniformity. Silica, alumina, titanium oxide (rutile type, anatase type), zinc oxide, calcium carbonate, zeolite, kaolin, talc, etc. can be used as inorganic fine particles, and silicone compounds, crosslinked styrene, crosslinked acrylic are used as organic particles. Cross-linked melamine can be used. The particle diameter of the organic and / or inorganic fine particles is preferably 0.01 to 2 μm, and the particle diameter is 0.01 μm or more within a range where the ratio of the thickness of the layer A to the particle diameter is up to 1/2. If it exists, the effect of glossiness reduction is fully acquired, and if it is 2 micrometers or less, drop-off of a particle | grain does not occur easily and it is preferable. The content is preferably 60% by weight or less, more preferably 1 to 50% by weight, and most preferably 5 to 30% by weight with respect to the solid content of the A layer. If the content is within such a range, the effect of reducing the surface gloss is obtained, the coating is easy, and the particles are not easily dropped off, which is preferable.

  In the present invention, in order to prevent thermal oxidation of the film, a method of adding an antioxidant to the A layer is also preferable. For example, there are phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and organic metal salt-based antioxidants. The content of the antioxidant is preferably added in the range of 0.001 to 5.0% by weight, more preferably 0.1 to 3.0% by weight, most preferably 0 with respect to the solid content of the A layer. .3 to 2.0% by weight. If content of antioxidant exists in this range, the heat-resistant effect will be exhibited and the dispersion | distribution to a coating film will also be favorable.

  In the present invention, various additives can be added to the A layer having an ultraviolet absorber as long as the effects of the present invention are not impaired. Examples of the additive that can be used include a crosslinking agent, a fluorescent brightening agent, an organic lubricant, an antistatic agent, a nucleating agent, and a coupling agent.

  For example, it is more preferable to add a cross-linking agent to the A layer because the adhesion to the white base film is improved. Examples of the crosslinking agent include an isocyanate crosslinking agent, a silicone crosslinking agent, a polyolefin crosslinking agent, a melamine crosslinking agent, and an oxazoline crosslinking agent. Further, the content of the crosslinking agent in the A layer is preferably 30% by weight or less, more preferably 0.1 to 25% by weight, and most preferably 0.5 to 20% by weight. preferable. If it exists in this preferable range, the effect will be acquired sufficiently and it is preferable, without providing a film curl after providing A layer.

  Various additives can be added to the conductive layer provided on the white film in the present invention within a range not impairing the effects of the present invention. As the additive, for example, organic or inorganic fine particles, pigments, dyes, crosslinking agents, fluorescent brighteners, organic lubricants, antistatic agents, nucleating agents, coupling agents and the like can be used. The thickness of the conductive layer is preferably from 0.01 to 5 μm, more preferably from 0.05 to 3 μm. If it exists in this range, the effect can fully be exhibited.

  The content of the antistatic agent in the conductive layer provided on the white film or the A layer containing the ultraviolet absorber is preferably 50% by weight or less, more preferably 0.01 to 20% with respect to the coating weight after drying. It is preferable to be in the range of% by weight.

  The light-reflective film of the present invention comprises a light-reflective white film and an A layer provided on the surface thereof, and the white film has a high light reflectance and is not biased in color tone. A white polyester film containing fine bubbles inside is preferable. As such a white polyester film, those in which fine bubbles are contained in any layer and those contained in all layers can be used.

  Such a white polyester film containing fine bubbles inside the film is obtained by adding an organic or inorganic dye, fine particles, etc. to a thermoplastic polyester film; the polyester resin constituting the film is not a resin component. A compatible resin and / or organic or inorganic particles mixed and melt-extruded and then stretched in at least one direction to form fine bubbles inside; adding foamable particles to a polyester resin; There is no particular limitation as long as it has an apparent whiteness, such as one obtained by foaming by melt extrusion; one obtained by injecting a gas such as carbon dioxide into a polyester resin and then foaming by extrusion. Particularly in applications of the present invention, the polyester resin constituting the film is mixed with a resin that is incompatible with the resin component and / or organic or inorganic particles, as the reflectance is improved and the luminance is improved. Then, after being melt-extruded, it is preferably stretched in at least one direction to form fine bubbles therein. Further, a thermoplastic resin to which organic or inorganic fine particles are added is laminated on at least one side of a film in which fine bubbles are formed inside by a method such as co-extrusion, and further stretched, and finer bubbles are formed on the surface layer portion than the inner layer portion. A composite film formed with is particularly preferred.

  The polyester resin constituting the white base film has good dimensional stability and mechanical properties and hardly absorbs in the visible light region. Specific examples of the polyester resin include polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene-2,6-naphthalenedicarboxylate (hereinafter abbreviated as PEN), polypropylene terephthalate, polybutylene terephthalate, and poly-1,4. -Cyclohexylene dimethylene terephthalate and the like can be mentioned. Of course, these polyesters may be homopolymers or copolymers, but are preferably homopolymers. Examples of copolymer components in the case of a copolymer include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and diol components having 2 to 15 carbon atoms. Examples of these components include isophthalic acid. , Adipic acid, sebacic acid, phthalic acid, sulfonate group-containing isophthalic acid, and ester-forming compounds thereof, diethylene glycol, triethylene glycol, neopentyl glycol, polyalkylene glycol having a molecular weight of 400 to 20,000, and the like. .

  In these polyesters, various additives such as heat stabilizers, oxidation stabilizers, organic lubricants, organic and inorganic fine particles, light stabilizers, antistatic agents, nucleating agents, as long as the effects of the present invention are not impaired. A coupling agent or the like may be added.

  Hereinafter, as a preferred example of the present invention, a polyester film used as a base material for a white film will be described in detail. In order to exhibit the effects of the present invention more remarkably, it is necessary to use polyester as a base material and to contain fine bubbles inside the film. For this purpose, (1) a method in which a foaming agent is contained and foamed by heat during extrusion or film formation, or foamed by chemical decomposition, (2) a gas such as carbon dioxide gas or vaporizable at the time of extrusion or after extrusion A method of adding a substance and foaming, (3) A method of adding a thermoplastic resin incompatible with polyester, and then stretching it uniaxially or biaxially after melt extrusion, (4) Adding organic or inorganic fine particles Examples thereof include a method of stretching uniaxially or biaxially after melt extrusion. In the present invention, it is preferable to increase the reflective interface by forming fine bubbles. From this point, it is preferable to use the method (3) or (4).

Size of the bubbles obtained by the above method (cross-sectional area size in the thickness direction) is 0.5μm ² ~50μm ^2, preferably preferred because those 1 [mu] m ² 30 .mu.m ² of brightness enhancement. Further, the cross-sectional shape of the bubble may be either circular or elliptical. The number of these bubbles is not particularly limited, but there is a structure in which 10 or more bubbles exist in the thickness direction of the film (at this time, no matter which thickness direction is observed in the plane of the film, the number of bubbles is 10 It is preferable from the viewpoint of improving the reflectance, and more preferably 20 to 200. The number of these bubbles can be observed with an image of a scanning electron microscope S-2100A type (manufactured by Hitachi, Ltd.). That is, the light emitted from the light source is incident from the film surface when the reflector is used, and it is the most preferable form that all the incident light is reflected by the internal bubbles. Actually, there is also light passing through the film, and this part is lost, but in order to cover this, metal deposition such as aluminum or silver is performed on the film surface side opposite to the incident light side (light source side). It is preferable to apply. In order to reduce light loss of the film containing fine bubbles inside, it is preferable to provide a layer containing fine bubbles of organic or inorganic fine particles on the surface of the bubble-containing polyester film. This surface layer can be obtained by making polyester resin contain organic or inorganic fine particles, coextruding and compositing at the time of producing the internal bubble-containing film, and then stretching in at least one direction. Further, the bubbles in the surface layer portion are preferably smaller than the bubbles in the inner layer portion in terms of luminance. The ratio (the size of bubbles in the surface layer portion / the size of bubbles in the inner layer portion) is not particularly limited, but is preferably 0.05 to 0.8, more preferably 0.07 to 0.7, and most preferably 0. .1 to 0.6. The size of the bubbles can be controlled by the size of the added particles.

  Here, a polyester resin and an incompatible resin added to form bubbles, and organic or inorganic fine particles added to the inner layer portion and the surface layer portion will be described. The polyester resin and incompatible resin (hereinafter, abbreviated as incompatible resin) is a thermoplastic resin other than polyester and can be dispersed in the form of particles in the polyester. For example, polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, polystyrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, and fluorine resins are preferable. These may be homopolymers or copolymers, or two or more of them may be used in combination. In particular, a resin having a large difference in critical surface tension from polyester and being difficult to be deformed by heat treatment after stretching is preferred, and a polyolefin resin, particularly polymethylpentene is particularly preferred. The content of the incompatible resin in the white film is not particularly limited, and may be selected in consideration of breakage during film formation, brightness due to bubble formation with the incompatible resin as a core, and usually 3 to 35 weights. %, More preferably 4 to 30% by weight, and most preferably 5 to 25% by weight. Within such a preferable range, a sufficient brightness enhancement effect is obtained, and film breakage is less likely to occur during film formation, which is preferable.

  As the inorganic fine particles to be added to the inner layer part and / or the surface layer part, those capable of forming bubbles with itself as a nucleus are preferable. For example, calcium carbonate, magnesium carbonate, zinc carbonate, titanium oxide (anatase type, rutile type), oxidation Zinc, barium sulfate, zinc sulfide, basic lead carbonate, mica titanium, antimony oxide, magnesium oxide, calcium phosphate, silica, alumina, mica, talc, kaolin, etc. can be used. Silica, alumina, calcium carbonate, barium sulfate, etc. are preferable in terms of light diffusibility, and titanium oxide (anatase type, rutile type), zinc oxide, etc. having ultraviolet absorption ability are preferably used for improving light resistance. Furthermore, it is possible to use a combination of these fine particles, a light reflective film Highly preferred from the viewpoint of performance improvement. In the case of organic fine particles, those which are not melted by melt extrusion are preferable, and cross-linked fine particles such as cross-linked styrene and cross-linked acrylic are preferable in terms of improving luminance. The organic fine particles may be hollow, and may be used alone or in combination of two or more, and may be used in combination with the inorganic fine particles. The particle diameter of the fine particles is not particularly limited, but is desirably 0.01 to 15 μm, preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. When added to the surface layer portion, using fine particles having a particle diameter larger than the surface layer thickness is a preferable method in terms of increasing the surface irregularities of the film and improving the light diffusibility. Further, it is preferable to combine with the A layer containing a fine particle inorganic ultraviolet absorber because the surface gloss of the film is further lowered and a high-brightness light reflective film excellent in light diffusibility can be obtained.

  The content of the fine particles in the white film is preferably 1 to 30% by weight, more preferably 2 to 25% by weight, and most preferably 3 to 20% by weight. When the content is within such a preferable range, film tearing is less likely to occur during film formation, which is preferable.

  In the present invention, the specific gravity which is a measure of the bubble content of the white film containing bubbles is preferably from 0.1 to less than 1.3. When the specific gravity is less than 0.1, the mechanical strength as a film may be insufficient, or problems such as easy breakage and poor handleability may occur. On the other hand, when it exceeds 1.3, the bubble content is too low, the reflectance is lowered, and the luminance tends to be insufficient. In the present invention, the specific gravity of the white film is preferably in the range of 0.7 to 1.1 from the viewpoint of heat resistance, dimensional stability, long-term use stability, etc., and is mainly composed of polyester. Preferably it is.

  The light reflective film in the present invention preferably has a 60 ° gloss of 40% or less, more preferably 30% or less, and most preferably 20% or less. If the glossiness is within such a range, the light diffusibility is high, and it is very preferable because the display unevenness caused by the difference between the on-tube brightness of the cold cathode ray tube and the brightness between the tubes is reduced when incorporated in a direct type backlight. .

  The light-reflective film is a plate-like material that is incorporated into a surface light source for light reflection as described above. Specifically, the light-reflective film is a reflection plate for edge lights for liquid crystal screens, and a surface light source for direct type lights. It is used for a reflector, a reflector around a cold cathode ray tube, and the like, and the reflector is preferably higher in whiteness in terms of the color tone of the screen, and more preferably has a bluish color than yellow. Considering this point, it is preferable to add a fluorescent brightening agent to the white film as the base material. Commercially available fluorescent whitening agents may be used as appropriate, for example, “Ubitex” (registered trademark) (manufactured by Ciba-Gaigi), OB-1 (manufactured by Eastman), TBO (manufactured by Sumitomo Seika Co., Ltd.). ), “Kaycoal” (registered trademark) (manufactured by Nippon Soda Co., Ltd.), “Kayalite” (registered trademark) (manufactured by Nippon Kayaku Co., Ltd.), “Lycopua” (registered trademark), EGM (manufactured by Client Japan), etc. Can do. The content of the optical brightener in the white film is preferably 0.005 to 1% by weight, more preferably 0.007 to 0.7% by weight, and even more preferably 0.01 to 0.5% by weight. Most preferably. If it exists in this preferable range, the effect is fully acquired and it is preferable, without becoming yellowish. When the white film is a composite film, it is more effective to add the fluorescent brightening agent to the surface layer portion.

  Next, although an example is demonstrated about the manufacturing method of the light reflection film of this invention, it is not limited to this example.

  In the composite film forming apparatus provided with the extruder A and the extruder B, the extruder A includes a material in which 85 parts by weight of dried PET, 15 parts by weight of polymethylpentene, and 1 part by weight of polyethylene glycol having a molecular weight of about 4000 are mixed. Supply. To the extruder B, a material obtained by mixing 95 parts by weight of PET and 5 parts by weight of silica particles having an average particle size of about 5 μm is supplied. Of course, each component of the raw material supplied to the extruders A and B may be mixed in advance by a method such as pelletizing. Extruders A and B are heated to 280-300 ° C. and melt extruded. At this time, the raw material of the extruder A is combined so that the raw material of the extruder B is laminated on both surfaces. The extruded sheet is solidified on a cooling drum having a surface temperature of 10 to 60 ° C. At this time, in order to obtain a uniform sheet, it is preferable to apply static electricity to make it adhere to the drum. The cooled and solidified sheet is guided to a roll group heated to 70 to 120 ° C., stretched about 2 to 5 times in the longitudinal direction, and cooled with a roll group of 20 to 40 ° C. Further, the film is continuously guided to the tenter while being gripped by a clip, preheated to 90 to 120 ° C., and then stretched 3 to 6 times in the width direction. Subsequently, the film is led continuously to a zone heated to 180 to 230 ° C., subjected to heat treatment for about 3 to 20 seconds, and then cooled to 40 ° C. or lower to obtain a white film. On one side of the obtained white film, a predetermined ratio of an organic UV-absorbing compound, an inorganic UV-absorbing agent, a resin, an organic or inorganic fine particle having no UV-absorbing ability, an additive, etc. The coating liquid mixed in (1) is applied in-line or offline so that the coating thickness after drying is 0.02 to 1 μm, and is dried at 70 to 130 ° C.

  The light-reflective film of the present invention thus obtained has excellent initial luminance without generating bright lines and luminance non-uniformity, is less deteriorated even in long-term use, and can maintain the luminance of the liquid crystal screen. .

The methods used in the examples are described below.
[Measurement and evaluation method of characteristics]
(1) Layer A, thickness of white film A cross section of the film was magnified and photographed 500 to 5,000 times using a field emission scanning electron microscope “JSM-6700F” (manufactured by JEOL Ltd.). From the cross-sectional photograph, the lengths of the A layer and the surface layer and the inner layer of the white film were measured in the thickness direction, and the thickness was obtained by calculating back from the magnification. In determining the thickness, a total of five cross-sectional photographs arbitrarily selected from different measurement visual fields were used, and the average value was calculated.

(2) Average reflectance Using a spectrophotometer U-3410 (manufactured by Hitachi, Ltd.), the spectral reflectance in the range of 400 to 700 nm on the A layer side is measured at 10 nm intervals, and the average value is average reflected. Rate. The number of samples was n = 5, the average reflectance was measured, and the average value was calculated. The measuring unit used an integrating sphere (model number 130-0632) with a diameter of 60 mm, and a 10 ° inclined spacer was attached. Moreover, aluminum oxide (model number 210-0740) was used for the standard white plate. An average reflectance of 95% or higher is acceptable and 100% or higher is very good.

(3) b value measurement Using a spectroscopic color difference meter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the b value of the reflection mode on the A layer side was measured according to JIS Z-8722 (2000). The number of samples was n = 5, each b value was measured, and the average value was calculated. The sample measurement diameter was 30 mmφ.

(4) Backlight luminance and luminance uniformity Using a direct type backlight 181BLM07 (manufactured by NEC Corporation), measurement was performed according to the apparatus shown in FIG. The current film bonded in the backlight was peeled off, and the measurement sample 1 was pasted so that the A layer became the upper surface. In this state, the attached diffusion film 3 and the attached diffusion plate 4 are attached, the cold cathode ray tube 2 is turned on for 1 hour to stabilize the light source, and then the color luminance meter BM-7fast (Co., Ltd.) from the diffusion film 3 side. Luminance (cd / m ² ) was measured using TOPCON. The luminance was measured at 9 points which are the center points of a section obtained by dividing the backlight surface into 9 parts, and the luminance uniformity was obtained from the maximum value, minimum value and average value of the 9 points by the following formula. The number of samples was n = 3, the luminance uniformity of each was measured, and the average value was calculated. If the luminance uniformity is less than 5%, it is acceptable, and if it is less than 2.5%, it is very excellent.
Luminance uniformity (%) = (maximum value−minimum value) / (average value) × 100.

(5) Luminance unevenness The luminance is measured in the direction perpendicular to the cold cathode ray tube 2 at the center position in the longitudinal direction of the cold cathode ray tube 2 using a direct type backlight with the measurement sample set in the same manner as in (4). The luminance L1 at the position corresponding to the upper part of the cold cathode ray tube and the luminance L2 at the position corresponding to the center of the adjacent cold cathode ray tubes were respectively determined, and the luminance unevenness was determined by the following equation. The average value of the luminance measured at the top of each of the plurality of cold cathode ray tubes was L1, and the average value of the luminance at the position corresponding to the center of the adjacent cold cathode ray tubes was L2. The number of samples was n = 3, and each luminance unevenness was measured, and the average value was calculated. If the luminance unevenness is less than 10%, it is acceptable, and if it is less than 5%, it is very excellent.
Brightness unevenness (%) = 100−L2 / L1 × 100.

(6) Average reflectance and luminance after UV irradiation test A heat resistance test was performed under the following conditions using a weather resistance promotion tester iSuper UV Tester SUV-W131 manufactured by Iwasaki Electric Co., Ltd.
"UV irradiation test conditions"
The surface of the A layer side was irradiated with UV at a temperature of 60 ° C., a humidity of 50% RH, and a UV illuminance of 100 mW / cm ² . The processing time was 24 hours.

The average reflectance, b value, and luminance uniformity of the sample after UV treatment were measured according to the methods (2), (3), and (4). About b value, (DELTA) b value was computed from the following formula and the magnitude | size was determined. If the Δb value is 5.0 or less, it is acceptable, and if it is 4.0 or less, it is very excellent.
Δb = b1 (b after heat treatment) −b0 (b before heat treatment).

(7) Glossiness Using a digital variable glossiness meter UGV-5B (manufactured by Suga Test Instruments Co., Ltd.), the glossiness was measured according to JIS Z-8741 (1997) from the A layer side of the light reflective film. The measurement conditions were an incident angle = 60 ° and a light receiving angle = 60 °. The number of samples was n = 5, the glossiness of each was measured, and the average value was calculated.

(8) Surface specific resistance Surface ratio on the A layer side of a sample that was allowed to stand for 24 hours in an environment of 23 ° C. and 65% RH using a digital ultrahigh resistance / microammeter (R8340 / R8430A) manufactured by Advantest Corporation Resistance was measured. The applied voltage was 100V. The number of samples was n = 5, and each surface specific resistance value was measured, and the average value was calculated. If the surface specific resistance value (when the A layer is provided on both sides of the film, at least one surface specific resistance value on the A layer side) is 1.0 × 10 ¹³ Ω / □ or less, it is acceptable. It is very excellent if it is 0 × 10 ¹² Ω / □ or less.

(9) Contamination evaluation of film After leaving a sample for 30 days in an indoor environment at 25 ° C., 50% RH, and particles having a diameter of 1 μm or more of 1.0 × 10 ^{5 to} 5.0 × 10 ⁵ particles / cm ³ The average reflectance was measured according to (2). An average reflectance of 95% or higher is acceptable and 100% or higher is very good.

(10) Blocking test Place two sample films on top of each other, place a weight of 100 cm ³ and a weight of 500 g on it, and leave it in an indoor environment at 23 ° C. and 60% RH for 5 days. It was confirmed visually. The number of samples is n = 3, and when all the stacked films are removed, all the films are not adhered to each other.

(11) Particle diameter measurement Particles from an image obtained by magnifying the surface or cross section of the film 500 to 5,000 times using a field emission scanning electron microscope JSM-6700F (manufactured by JEOL Ltd.). Was measured, and the particle size was determined by calculating backward from the magnification. 100 particles randomly selected from a total of five cross-sectional photographs arbitrarily selected from different measurement fields were measured. In addition, when the shape of particle | grains was not a perfect sphere, the magnitude | size of the part which is the longest side was considered as a primary particle size, and the average value was computed.

  The present invention will be described with reference to the following examples and comparative examples, but is not particularly limited thereto.

Moreover, the detail of material AK of the coating liquid used by an Example and a comparative example is as follows.
A: Organic ultraviolet absorber water-based emulsion solution Hals hybrid “Udable” (registered trademark) UVEM084K-7 (manufactured by Nippon Shokubai Co., Ltd., 30 wt% solution, organic ultraviolet absorber-containing material)
B: Antistatic agent Pesresin A-212P (manufactured by Takamatsu Yushi Co., Ltd., 20% by weight solution, containing no organic ultraviolet absorber)
C: Acrylic solution Nicazole RX7013ED (manufactured by Nippon Carbide Industry Co., Ltd., 35% by weight solution, no organic UV absorber)
D: Titanium oxide fine particle aqueous dispersion RTIW15WT% -G0 (manufactured by CI Kasei Co., Ltd., 15% by weight solution)
E: Zinc oxide fine particle aqueous dispersion Maxlite ZS-032-W (manufactured by Showa Denko KK, 50 wt% solution)
F: Antistatic agent Versa TL_YE910 (manufactured by NSC Japan, 16 wt% solution)
G: Oxazoline-based curing agent Epocros WS500 (manufactured by Nippon Shokubai Co., Ltd., 39% by weight solution)
H: Melamine-based curing agent Nicarak MW12LF (manufactured by Sanwa Chemical Co., Ltd., 71 wt% solution)
I: Silica fine particle aqueous dispersion Spherica slurry PA1000 (manufactured by Catalytic Chemical Industry Co., Ltd., 10 wt% solution)
J: Silica fine particle aqueous dispersion Seahoster KE-W30 (manufactured by Nippon Shokubai Co., Ltd., 20% by weight solution)
K: Surfactant plus coat RY-2 (manufactured by Kyoyo Chemical Co., Ltd., 10 wt% solution).

Example 1
Raw materials having the following composition were supplied to a composite film forming apparatus having an extruder X and an extruder Y.
Extruder X: 85 parts by weight of PET vacuum-dried at 180 ° C. for 4 hours, 15 parts by weight of polymethylpentene, and 1 part by weight of polyethylene glycol having a molecular weight of 4000.
Extruder Y: 100 parts by weight of PET chip containing 5% by weight of silica particles having an average particle diameter of 1 μm and vacuum dried at 180 ° C. for 4 hours.

  Each raw material was melt-extruded at 290 ° C. from the extruders X and Y, and the molten raw material of the extruder X was merged into the inner layer, and the molten raw material of the extruder Y became both surface layers and extruded from the T-die into a sheet shape. . This sheet was cast on a mirror surface cooling drum having a surface temperature of 20 ° C. to obtain an unstretched sheet. This sheet was preheated with a group of rolls heated to 90 ° C., and stretched 3.4 times in the longitudinal direction at 95 ° C. After applying the following adjustment coating liquid on one side of the sheet in-line, the sheet edge is gripped with a clip, guided into a tenter heated to 105 ° C., preheated, and then continuously in an atmosphere at 120 ° C. The film was stretched 3.5 times in the width direction. Further, a heat treatment was continuously performed for 10 seconds in an atmosphere at 200 ° C. to obtain a film having a total thickness of 250 μm and a thickness structure of Y / X / Y (0.05 / 249.9 / 0.05). The coating thickness after drying of the coating film provided in-line was 1.0 μm. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had excellent characteristics.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 20% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 62.7 parts by weight Material G: 2.7 parts by weight Material I: 1.4 parts by weight Material K: 0.2 parts by weight Purified water: 33.2 parts by weight.

(Example 2)
A film was obtained in the same manner as in Example 1 except that the coating thickness after drying of the coating film provided using the following adjustment coating liquid was 0.4 μm. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had excellent characteristics.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 36.0 parts by weight Material D: 30.0 parts by weight Material G: 6.6 parts by weight Material J: 0.6 parts by weight Material K: 0.2 parts by weight Purified water: 26.8 parts by weight.

(Example 3)
The raw material of the extruder Y was vacuum-dried at 180 ° C. for 4 hours with 100 parts by weight of PET, the thickness of the white base film was Y / X / Y (2/246/2), and the following adjustment coating liquid was used. A film was obtained in the same manner as in Example 1 except that the coating thickness after drying of the coating film provided inline was 0.6 μm. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had initial luminance unevenness reduced and excellent light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 39.0 parts by weight Material D: 30.0 parts by weight Material G: 4.2 parts by weight Material I: 1.3 parts by weight Material K: 0.2 parts by weight Purified water: 25.5 parts by weight.

Example 4
The raw material of the extruder Y is 100 parts by weight of a PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and vacuum dried at 180 ° C. for 4 hours, and the thickness structure of the white base film is Y / X / Y A film was obtained in the same manner as in Example 1 except that the coating thickness after drying of the coating film provided inline was 0.6 μm using the following adjustment coating liquid. It was. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had initial luminance unevenness reduced and excellent light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 39.0 parts by weight Material D: 30.0 parts by weight Material G: 4.2 parts by weight Material I: 1.3 parts by weight Material K: 0.2 parts by weight Purified water: 25.5 parts by weight.

(Example 5)
As a raw material of the extruder Y, a PET chip containing 30 parts by weight of a PET chip containing 50% by weight of titanium oxide particles having an average particle diameter of 200 nm and 3% by weight of a fluorescent brightening agent OB-1 (manufactured by Eastman) 3 parts by weight, 67 parts by weight of PET chip and vacuum dried at 180 ° C. for 4 hours, the thickness of the white base film is Y / X / Y ′ (1/240/9), and the surface layer on the Y side A film was obtained in the same manner as in Example 3, except that the A layer was provided. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had the initial brightness unevenness further reduced and the light resistance was more excellent.

(Example 6)
As a raw material of the extruder Y, a PET chip containing 30 parts by weight of a PET chip containing 50% by weight of titanium oxide particles having an average particle diameter of 200 nm and 3% by weight of a fluorescent brightening agent OB-1 (manufactured by Eastman) 3 parts by weight, 67 parts by weight of PET chips containing 5% by weight of silica particles having an average particle size of 5 μm were vacuum-dried at 180 ° C. for 4 hours, and the thickness of the white base film was defined as Y / X / Y ′ (1/240/9) and a film was obtained in the same manner as in Example 3 except that the A layer was provided on the surface layer on the Y side. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film was excellent in initial luminance characteristics and very excellent in light resistance.

(Example 7)
As a raw material of the extruder Y, a PET chip containing 30 parts by weight of a PET chip containing 50% by weight of titanium oxide particles having an average particle diameter of 200 nm and 3% by weight of a fluorescent brightening agent OB-1 (manufactured by Eastman) Using 3 parts by weight of PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and 67 parts by weight, the white base film was made into Y / X / Y ( 15/220/15), and using the following adjustment coating liquid, a film was obtained in the same manner as in Example 1 except that the coating thickness after drying of the coating film provided inline was 1.0 μm. It was. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had excellent light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 20% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 36.0 parts by weight Material D: 48.0 parts by weight Material G: 4.7 parts by weight Material I: 1.4 parts by weight Material K: 0.2 parts by weight Purified water: 9.9 parts by weight.

(Example 8)
The raw material of the extruder Y is 100 parts by weight of a PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and vacuum dried at 180 ° C. for 4 hours, and the thickness structure of the white base film is Y / X / Y (2/246/2), and using the following adjustment coating liquid, the coating thickness after drying of the coating film provided in-line was 0.6 μm, and the addition ratio of the ultraviolet absorber was adjusted to the composition shown in Table 1. A film was obtained in the same manner as in Example 1 except that the change was made. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film was excellent in initial luminance characteristics and very excellent in light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material B: 36.0 parts by weight Material C: 10.3 parts by weight Material D: 30.0 parts by weight Material H: 3.6 parts by weight Material I: 1.3 parts by weight Material K: 0.2 parts by weight Purified water : 18.8 parts by weight.

Example 9
The raw material of the extruder Y is 100 parts by weight of a PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and vacuum dried at 180 ° C. for 4 hours, and the thickness structure of the white base film is Y / X / Y A film was obtained in the same manner as in Example 1 except that the coating thickness after drying of the coating film provided inline was 0.6 μm using the following adjustment coating liquid. It was. The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had excellent light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 36.0 parts by weight Material E: 9.0 parts by weight Material G: 6.6 parts by weight Material I: 1.3 parts by weight Material K: 0.2 parts by weight Purified water: 47.2 parts by weight.

(Example 10)
Raw materials having the following composition were supplied to a composite film forming apparatus having an extruder X and an extruder Y.
Extruder X: 85 parts by weight of PET vacuum-dried at 180 ° C. for 4 hours, 15 parts by weight of polymethylpentene, and 1 part by weight of polyethylene glycol having a molecular weight of 4000.
Extruder Y: 100 parts by weight of a PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and vacuum-dried at 180 ° C. for 4 hours.
The respective raw materials were melt-extruded at 290 ° C. from the extruders X and Y, merged so that the molten raw material of the extruder X and the molten raw material of the extruder Y became two layers, and extruded from a T-die into a sheet shape. This sheet was cast on a mirror surface cooling drum having a surface temperature of 20 ° C. to obtain an unstretched sheet. This sheet was preheated with a group of rolls heated to 90 ° C., and stretched 3.4 times in the longitudinal direction at 95 ° C. Thereafter, the end of the sheet was gripped with a clip, led into a tenter heated to 105 ° C., preheated, and then continuously stretched 3.5 times in the width direction in an atmosphere at 120 ° C. Further, a heat treatment was continuously performed for 10 seconds in an atmosphere at 200 ° C. to obtain a white base film having a total thickness of 250 μm and a thickness structure of Y / X (2/248).

  On the surface of layer B side of this white base film, the following adjustment coating solution was applied with a microgravure plate / kiss coat with a diameter of 100 mm so that the thickness after drying was 1.0 μm, and the drying was performed at 20 m / min. At 70 ° C./100° C./120° C. (each zone is 10 m). The composition of the film is as shown in Table 1. As shown in Table 2, the obtained film had excellent light resistance.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was 18% by weight, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material A: 36.0 parts by weight Material D: 30.0 parts by weight Material G: 6.6 parts by weight Material I: 1.3 parts by weight Material K: 0.2 parts by weight Purified water: 26.2 parts by weight.

(Comparative Example 1)
Raw materials having the following composition were supplied to a composite film forming apparatus having an extruder X and an extruder Y.
Extruder X: 85 parts by weight of PET vacuum-dried at 180 ° C. for 4 hours, 15 parts by weight of polymethylpentene, and 1 part by weight of polyethylene glycol having a molecular weight of 4000.
Extruder Y: 100 parts by weight of a PET chip containing 5% by weight of silica particles having an average particle diameter of 5 μm and vacuum-dried at 180 ° C. for 4 hours.
Each raw material was melt-extruded at 290 ° C. from the extruders X and Y, and the molten raw material of the extruder X was merged into the inner layer, and the molten raw material of the extruder Y became both surface layers and extruded from the T-die into a sheet shape. . This sheet was cast on a mirror surface cooling drum having a surface temperature of 20 ° C. to obtain an unstretched sheet. This sheet was preheated with a group of rolls heated to 90 ° C., and stretched 3.4 times in the longitudinal direction at 95 ° C. The end of the sheet was gripped with a clip, guided into a tenter heated to 105 ° C., preheated, and then continuously stretched 3.5 times in the width direction in an atmosphere at 120 ° C. Further, a heat treatment was continuously performed in an atmosphere at 200 ° C. for 10 seconds to obtain a film having a total thickness of 250 μm and a thickness structure of Y / X / Y (2/246/2). The composition of the film is as shown in Table 1. As a result of evaluating the obtained film as a light reflective film as it was, the initial characteristics were excellent, but the color tone change after the light resistance test was large, and the average reflectance was remarkably reduced.

(Comparative Example 2)
The thickness structure of the white base film is Y / X / Y (2/246/2), and further using the following adjustment coating liquid, the coating thickness after drying of the coating film provided inline is 0.04 μm, A film was obtained in the same manner as in Example 4 except that the addition ratio of the ultraviolet absorber was changed to the composition shown in Table 1. The composition of the film is as shown in Table 1. Although the obtained film was excellent in the initial characteristics, the color change after the light resistance test was large, and the average reflectance was remarkably lowered.

Coating solution: The following materials were mixed so that the solid content concentration of the coating solution was a 6 wt% solution, stirred for 10 minutes with a universal stirrer, and then filtered with a filter to prepare a coating solution.
Material C: 15.4 parts by weight Material F: 3.8 parts by weight Material K: 0.1 part by weight Purified water: 80.8 parts by weight

(Comparative Example 3)
A film was obtained in the same manner as in Example 4 except that the thickness of the white base film was Y / X / Y (23/204/23). The composition of the film is as shown in Table 1. Although the obtained film was excellent in the initial characteristics, the color change after the light resistance test was large, and the average reflectance was remarkably lowered.

  The present invention can be applied not only to the light-reflecting film of the edge-light type and direct-type liquid crystal screen but also to the light-reflecting film for outdoor electric decoration plates, etc., but the application range is limited to these. is not.

It is a longitudinal cross-sectional view which shows the outline of an apparatus structure for measuring the brightness | luminance of a surface light source.

Explanation of symbols

1 Measurement Sample 2 Cold Cathode Ray Tube 3 Diffusion Film 4 Diffusion plate

Claims (9)

An A layer containing an ultraviolet absorber is provided on at least one side of a white film having a laminated structure of two or more layers, and the thickness of the A layer is 1.0 μm or less, and the A layer of the white film The light-reflective film whose surface layer thickness of the side in which is provided is 0.001-20 micrometers. The light reflective film according to claim 1, wherein in the white film, the surface layer thickness is 0.1 to 5 μm. 3. The light reflection according to claim 1, wherein a difference Δb = b1−b0 between an initial color tone b0 measured from the A layer side and a color tone b1 after 24 hours in the UV irradiation test is 5.0 or less. Sex film. The light-reflective film according to any one of claims 1 to 3, wherein the ultraviolet absorber contained in the A layer is an organic ultraviolet absorber and an inorganic ultraviolet absorber, or an inorganic ultraviolet absorber. The addition ratio of the addition amount of the organic ultraviolet absorber and the addition amount of the inorganic ultraviolet absorber contained in the layer A is in a range of 0/10 to 9/1 by weight ratio. A light-reflective film according to claim 1. The light-reflective film according to any one of claims 1 to 5, wherein the inorganic ultraviolet absorber contained in the A layer is fine particles, and the primary particle size thereof is 1 to 500 nm. Inorganic or organic fine particles having no ultraviolet absorbing function are added to the A layer, and the ratio between the thickness of the A layer and the diameter of the fine particles is in a range of 1/1 to 1/2. Item 7. The light reflective film according to any one of Items 1 to 6. The light reflective film according to any one of claims 1 to 7, wherein the white film is composed of a laminated film of two or more layers including a polyester layer containing fine bubbles therein. The backlight apparatus for image displays containing the light reflective film in any one of Claims 1-8.

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