JP2008076764A - Optical film, polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having excellent UV absorptivity as well as excellent heat resistance and excellent optical transparency and preventing foaming, to provide a polarizing plate having less appearance defects by using the above optical film, and to provide a high-quality image display device using the polarizing plate. <P>SOLUTION: The optical film has a light transmittance of 15% or less at 380 nm in a thickness of 80 μm and is obtained by extruding a molding material having a resin component essentially comprising (meth)acrylic resin and an antioxidant by 0.02 parts by weight or more with respect to 100 parts by weight of the resin component, showing a weight reduction of 10% or less by heating at 300°C for 20 minutes. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film, a polarizing plate using the optical film, and an image display device such as a liquid crystal display device, an organic EL display device, and a PDP including at least one polarizing plate.

  In the liquid crystal display device, it is indispensable to dispose polarizing plates on both sides of the glass substrate on which the liquid crystal panel surface is formed because of the image forming method. In general, a polarizing plate is used in which a polarizer protective film is bonded to both surfaces of a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine with a polyvinyl alcohol adhesive.

  The optical film used as the polarizer protective film may require ultraviolet absorption performance for the purpose of preventing the liquid crystal and the polarizer from ultraviolet degradation. At present, an ultraviolet absorber is added to the polarizer protective film to provide ultraviolet absorption performance.

  As a resin component of an optical film used as a polarizer protective film, triacetyl cellulose has been generally used so far. However, triacetyl cellulose does not have sufficient heat and heat resistance, and when a polarizing plate using a triacetyl cellulose film as a polarizer protective film is used at high temperature or high humidity, the performance of the polarizing plate, such as the degree of polarization and the hue, decreases. There is a drawback. In addition, the triacetyl cellulose film produces a phase difference with respect to incident light in an oblique direction. Such a phase difference significantly affects viewing angle characteristics as the size of liquid crystal displays increases in recent years.

  Therefore, the use of a (meth) acrylic resin having high transparency and heat resistance as a material for a polarizer protective film that replaces conventional triacetyl cellulose has been studied.

  The (meth) acrylic resin generally has a problem that decomposition is accelerated at about 250 ° C. or more, and a (meth) acrylic monomer is generated. Therefore, so far, (meth) acrylic resins are generally molded at about 240 ° C. or lower (see Patent Documents 1 to 4).

  The optical film is required to have few appearance defects. Therefore, when a resin material mainly composed of (meth) acrylic resin is used as an optical film material, a molding material containing the resin material is extruded in order to remove foreign matters in the resin material that cause appearance defects. When molding an optical film, it is necessary to remove the foreign matter through a polymer filter. Thus, in order to pass a molding material containing a resin material mainly composed of (meth) acrylic resin through a polymer filter, it is necessary to sufficiently reduce the viscosity of the molding material containing (meth) acrylic resin. In order to sufficiently reduce the viscosity, it is necessary to increase the temperature of the (meth) acrylic resin when passing through the polymer filter.

However, as described above, when the temperature of the (meth) acrylic resin is increased, decomposition is promoted and a (meth) acrylic monomer is generated. The production of this monomer causes foaming during the molding of the optical film, and there is a problem that it cannot be used as an optical film.
JP 2005-82716 A JP 2004-2835 A JP-A-9-164638 JP-A-9-164638

  The object of the present invention is to provide an optical film having (1) excellent ultraviolet absorption ability, excellent heat resistance, excellent optical transparency, and extremely low foaming, (2) such An object of the present invention is to provide a polarizing plate using an optical film with few appearance defects, and (3) to provide a high-quality image display device using such a polarizing plate.

The optical film of the present invention is
An optical film having a light transmittance of 15% or less at 380 nm at a thickness of 80 μm,
A resin component containing a (meth) acrylic resin as a main component, and an antioxidant having a weight loss of 10% or less when heated at 300 ° C. for 20 minutes at 0.02 part by weight or more with respect to 100 parts by weight of the resin component Is obtained by molding by extrusion molding.

  In preferable embodiment, the temperature of the molding material at the time of the said extrusion molding is 250 degreeC or more.

  In preferable embodiment, the said antioxidant contains a phenolic antioxidant.

  In preferable embodiment, the said antioxidant contains 0.01 weight part or more of phenolic antioxidant and 0.01 weight part or more of thioether type | system | group antioxidant with respect to 100 weight part of said resin components.

  In preferable embodiment, the said antioxidant contains 0.01 weight part or more of phenolic antioxidant and 0.01 weight part or more of phosphorus antioxidant with respect to 100 weight part of said resin components.

  In a preferred embodiment, the molding material contains a triazole-based UV absorber and / or a triazine-based UV absorber having a weight loss of 10% or less when heated at 300 ° C. for 20 minutes.

  In a preferred embodiment, the (meth) acrylic resin is a (meth) acrylic resin having a lactone ring structure.

  According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate of the present invention includes the optical film of the present invention as a polarizer protective film.

  According to another aspect of the present invention, an image display device is provided. The image display device of the present invention includes at least one polarizing plate of the present invention.

  According to the present invention, it is possible to provide an optical film having excellent ultraviolet absorption ability, excellent heat resistance, excellent optical transparency, and extremely low foaming. In addition, a polarizing plate using such an optical film and having few appearance defects can be provided. Furthermore, a high-quality image display apparatus using such a polarizing plate can be provided.

  Such an effect includes, as a molding material at the time of extrusion molding, a resin component containing a (meth) acrylic resin as a main component and a specific antioxidant in a specific proportion amount or more with respect to the resin component. By using a molding material and making the light transmittance under a specific condition of the optical film obtained to be a specific amount or less, it is possible to express. Since the decomposition of the (meth) acrylic resin is suppressed by the antioxidant and the generation of radicals is suppressed, it is possible to prevent foaming and coloring caused by the radicals attacking the resin and various additives.

  In addition, the said specific antioxidant is an antioxidant which has the specific conditions "The weight loss in the heating for 20 minutes at 300 degreeC is 10% or less."

  By extruding under the above conditions, foaming in the finally obtained optical film can be sufficiently suppressed even when the molding temperature is 250 ° C. or higher.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

[A. Optical film)
[A-1. Resin material)
The optical film of the present invention is obtained by molding a molding material containing a resin component containing a (meth) acrylic resin as a main component by extrusion molding. That is, the optical film of the present invention contains (meth) acrylic resin as a main component.

  As said (meth) acrylic-type resin, Tg (glass transition temperature) becomes like this. Preferably it is 115 degreeC or more, More preferably, it is 120 degreeC or more, More preferably, it is 125 degreeC or more, Most preferably, it is 130 degreeC or more. The optical film of the present invention contains a (meth) acrylic resin having a Tg (glass transition temperature) of 115 ° C. or higher as a main component, so that, for example, when incorporated in a polarizing plate as a polarizer protective film, the optical film has durability. Can be excellent. The upper limit value of Tg of the (meth) acrylic resin is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

As said (meth) acrylic-type resin, arbitrary appropriate (meth) acrylic-type resins can be employ | adopted within the range which does not impair the effect of this invention. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  Specific examples of the (meth) acrylic resin include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. Examples of the resin include high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  In the present invention, a (meth) acrylic resin having a lactone ring structure is particularly preferable as the (meth) acrylic resin in that it has high heat resistance, high transparency, and high mechanical strength.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  The (meth) acrylic resin having a lactone ring structure preferably has a lactone ring structure represented by the following general formula (1).

（一般式（１）中、Ｒ^１、Ｒ^２およびＲ^３は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。なお、有機残基は酸素原子を含んでいても良い。）

(In the general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. good.)

  The content ratio of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, The amount is preferably 10 to 60% by weight, particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, heat resistance, solvent resistance, and surface hardness are poor. May be sufficient. If the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, the moldability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, the effects of the present invention may not be sufficiently exhibited.

  The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C., most preferably 140 ° C. or higher. When Tg is 115 ° C. or higher, for example, when incorporated in a polarizing plate as a polarizer protective film, it can be excellent in durability. The upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency is lowered and the optical film may not be used.

  The content of the (meth) acrylic resin in the optical film of the present invention is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 98%. 97% by weight. When the content of the (meth) acrylic resin in the optical film of the present invention is less than 50% by weight, the high heat resistance and high transparency inherent in the (meth) acrylic resin may not be sufficiently reflected. is there.

  The optical film of the present invention may contain a resin component other than the (meth) acrylic resin. As a resin component other than the (meth) acrylic resin, any appropriate resin component can be adopted as long as the effects of the present invention are not impaired.

  The content of the (meth) acrylic resin in the molding material used when molding the optical film of the present invention is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, and still more preferably 60 to 98%. % By weight, particularly preferably 70 to 97% by weight. When the content of the (meth) acrylic resin in the molding material used when molding the optical film of the present invention is less than 50% by weight, the (meth) acrylic resin originally has high heat resistance and high transparency. May not be sufficiently reflected.

  In the molding material used when molding the optical film of the present invention, a resin component other than the (meth) acrylic resin may be contained. As a resin component other than the (meth) acrylic resin, any appropriate resin component can be adopted as long as the effects of the present invention are not impaired.

[A-2. Antioxidant)
The optical film of the present invention is obtained by molding a molding material containing an antioxidant by extrusion molding.

  The amount of the antioxidant is 0.02 parts by weight or more, preferably 0.02 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and still more preferably 100 parts by weight of the resin component. 0.1 to 2.5 parts by weight. If the amount of the antioxidant is less than 0.02 parts by weight, decomposition of the resin component (particularly (meth) acrylic resin) may be accelerated. If the amount of the antioxidant is greater than 5 parts by weight, the optical properties of the resulting optical film may be degraded.

  The antioxidant has a weight loss of 10% or less when heated at 300 ° C. for 20 minutes. A method of measuring “weight loss by heating at 300 ° C. for 20 minutes” will be described later. The said antioxidant is so preferable that the weight loss in the heating for 20 minutes at 300 degreeC is small. The weight loss upon heating at 300 ° C. for 20 minutes is preferably 9% or less, more preferably 8% or less, still more preferably 6% or less, and particularly preferably 5% or less. When an antioxidant having a weight loss of greater than 10% when heated at 300 ° C. for 20 minutes is used, decomposition of the resin component (especially (meth) acrylic resin) is promoted during molding of the optical film, and foaming occurs. There is a possibility that it cannot be used as an optical film.

  The antioxidant preferably contains a phenolic antioxidant in order to further develop the effects of the present invention. Arbitrary appropriate phenolic antioxidants can be employ | adopted as a phenolic antioxidant. For example, n-octadecyl = 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl = 3- (3,5-di-t-butyl-4-hydroxyphenyl)- Acetate, n-octadecyl = 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl = 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl = 3,5-di T-butyl-4-hydroxyphenylbenzoate, neo-dodecyl = 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl = β (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, ethyl = α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl = α- (4- Droxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl = α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n-octylthio) ethyl = 3,5-di-tert-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl = 3,5-di-tert-butyl-4-hydroxy-phenylacetate, 2- (n-octadecylthio) Ethyl = 3,5-di-tert-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl = 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-hydroxyethyl) Thio) ethyl = 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol = bis- (3,5-di-t-butyl-4- Hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl = 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide-N, N-bis- [ethylene = 3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene = 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ], 2- (2-stearoyloxyethylthio) ethyl = 3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl = 7- (3-methyl-5- t-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol = bis- [3- (3,5-di-t-butyl-4 Hydroxyphenyl) propionate], ethylene glycol = bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol = bis- [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), glycerin-1-n-octadecanoate-2,3-bis -(3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 1 , 1,1-trimethylolethane-tris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propiyl Nate], sorbitol hexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) ) Propionate, 2-stearoyloxyethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t -Butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 3,9-bis [1,1-dimethyl-2- [β -(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro 5,5] - like undecane. For example, pentaerythritol-tetrakis- [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate may be used as a weight loss of 10% or less upon heating at 300 ° C. for 20 minutes. 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxa Spiro [5,5] -undecane.

  In order to further develop the effect of the present invention, the antioxidant is 0.01 parts by weight or more of phenol-based antioxidant and 0.01 parts by weight or more of thioether-based oxidation with respect to 100 parts by weight of the resin component. More preferably, an inhibitor is included. More preferably, it contains 0.025 parts by weight or more of a phenolic antioxidant and 0.025 parts by weight or more of a thioether-based antioxidant, and particularly preferably 0.05 parts by weight or more of a phenolic antioxidant. An antioxidant and 0.05 parts by weight or more of a thioether-based antioxidant.

  Any appropriate thioether antioxidant can be adopted as the thioether antioxidant. For example, pentaerythrityltetrakis (3-lauryl thiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipro Pionate is mentioned. As a thing whose weight loss in the heating for 20 minutes at 300 degreeC is 10% or less, pentaerythrityl tetrakis (3-lauryl thiopropionate) is mentioned, for example.

  In order to further develop the effect of the present invention, the antioxidant is 0.01 parts by weight or more of phenol-based antioxidant and 0.01 parts by weight or more of phosphorus-based oxidation with respect to 100 parts by weight of the resin component. More preferably, an inhibitor is included. More preferably, it contains 0.1 parts by weight or more of a phenolic antioxidant and 0.1 parts by weight or more of a phosphorus-based antioxidant, and particularly preferably 0.5 parts by weight or more of a phenolic oxidation. An antioxidant and 0.5 parts by weight or more of a phosphorus-based antioxidant.

  Arbitrary appropriate phosphorus antioxidant can be employ | adopted as a phosphorus antioxidant. For example, tris (2,4-di-t-butylphenyl) phosphite, 2-[[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3, 2] Dioxaphosphepin-6-yl] oxy] -N, N-bis [2-[[2,4,8,10-tetrakis (1,1 dimethylethyl) dibenzo [d, f] [1, 3,2] dioxaphosphin-6-yl] oxy] -ethyl] ethanamine, diphenyltridecyl phosphite, triphenyl phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl Phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, cyclic neopen Integrators Tri bis (2,6-di -t- butyl-4-methylphenyl) phosphite and the like. Examples of the weight loss of 10% or less upon heating at 300 ° C. for 20 minutes include cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methylphenyl) phosphite. Be

[A-3. (UV absorber)
The molding material for obtaining the optical film of the present invention preferably contains a triazole-based UV absorber and / or a triazine-based UV absorber whose weight loss upon heating at 300 ° C. for 20 minutes is 10% or less. A method of measuring “weight loss by heating at 300 ° C. for 20 minutes” will be described later. The triazole-based UV absorber and / or triazine-based UV absorber is preferably as small as possible when the weight loss upon heating at 300 ° C. for 20 minutes is small. The weight loss upon heating at 300 ° C. for 20 minutes is preferably 9% or less, more preferably 8% or less, still more preferably 6% or less, and particularly preferably 5% or less. When a triazole UV absorber and / or a triazine UV absorber having a weight loss greater than 10% when heated at 300 ° C. for 20 minutes is used, an optical film having sufficient UV absorbing ability may not be obtained. .

  As said ultraviolet absorber, arbitrary ultraviolet absorbers suitable for this invention can be selected, for example. For example, the ultraviolet absorber as described in Unexamined-Japanese-Patent No. 2001-72782 and Special Table 2002-543265 is mentioned. The melting point of the ultraviolet absorber is preferably 110 ° C. or higher, and more preferably 120 ° C. or higher. In the present invention, only one ultraviolet absorber may be used, or two or more ultraviolet absorbers may be used in combination. Examples of ultraviolet absorbers that can be preferably used in the present invention include triazole-based ultraviolet absorbers.

  The amount of the ultraviolet absorber used is preferably 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, still more preferably 3 to 7 parts by weight, particularly preferably 4 to 100 parts by weight based on 100 parts by weight of the resin component. 6 parts by weight. The triazine ultraviolet absorber preferably has a molecular weight of 400 or more. The triazole ultraviolet absorber preferably has a molecular weight of 400 or more.

  Examples of the triazole ultraviolet absorber include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3,5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazole-2- Yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzo Triazol-2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert Butylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6 -(3,4,5,6-tetrahydrophthalimidylmethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction products, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol.

  As the triazine-based ultraviolet absorber, for example, a compound having a 1,3,5-triazine ring can be preferably used. Specific examples include 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol.

  As the ultraviolet absorber whose weight loss upon heating at 300 ° C. for 20 minutes is 10% or less, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 1,3,3-tetramethylbutyl) phenol]. As a commercial item, "ADK STAB LA-31" (made by Asahi Denka Kogyo Co., Ltd.) is mentioned as a triazole type ultraviolet absorber, for example.

[A-4. Molding material]
The molding material used for obtaining the optical film of the present invention by extrusion molding contains the resin component and the antioxidant, and preferably further contains the ultraviolet absorber.

  The molding material used in the present invention may contain any appropriate other component as long as the effects of the present invention are not impaired. For example, it contains general compounding agents, specifically stabilizers, lubricants, processing aids, plasticizers, impact aids, retardation reducing agents, matting agents, antibacterial agents, antifungal agents, etc. Also good.

[A-5. Characteristics of optical film)
The optical film of the present invention preferably has a high light transmittance, and preferably has a low in-plane retardation Δnd and a thickness direction retardation Rth. The in-plane phase difference Δnd can be obtained by Δnd = (nx−ny) × d. The thickness direction retardation Rth can be obtained by Rth = (nx−nz) × d. Here, nx and ny are in-plane refractive indexes in the slow axis direction and the fast axis direction, respectively, and nz is the refractive index in the thickness direction. The slow axis direction refers to the direction in which the in-plane refractive index is maximum.

  The light transmittance at 380 nm in the thickness of 80 μm of the optical film of the present invention is 15% or less, preferably 12% or less, more preferably 10% or less, further preferably 8% or less, particularly preferably 6% or less, most Preferably it is 5% or less. When the light transmittance at 380 nm in the thickness of 80 μm of the optical film of the present invention exceeds 15%, there is a possibility that sufficient ultraviolet absorbing ability cannot be exhibited.

  YI in the thickness of 80 μm of the optical film of the present invention is preferably 1.27 or less, more preferably 1.25 or less, further preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the excellent optical transparency may not be exhibited. YI is obtained from tristimulus values (X, Y, Z) of colors obtained by measurement using, for example, a high-speed integrating sphere type spectral transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Research Laboratory). The following equation can be used.

  YI = [(1.28X−1.06Z) / Y] × 100

  The b value (a measure of hue according to Hunter's color system) at a thickness of 80 μm of the optical film of the present invention is preferably less than 1.5, more preferably 1.0 or less. When b value is 1.5 or more, there is a possibility that excellent optical transparency may not be exhibited due to coloring of the film. The b value is obtained by, for example, cutting an optical film sample into a 3 cm square and measuring the hue using a high-speed integrating sphere type spectral transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Research Laboratory). it can. Moreover, a hue can be evaluated by b value according to Hunter's color system.

  In the optical film of the present invention, the in-plane retardation Δnd is preferably 3.0 nm or less, more preferably 1.0 nm or less. If the in-plane retardation Δnd exceeds 3.0 nm, the effects of the present invention, in particular, excellent optical characteristics may not be exhibited. The thickness direction retardation Rth is preferably 5.0 nm or less, more preferably 3.0 nm or less. When the thickness direction retardation Rth exceeds 5.0 nm, the effects of the present invention, in particular, excellent optical characteristics may not be exhibited. When the optical film of the present invention is disposed between a polarizer and a liquid crystal cell, the above retardation is preferable.

In the optical film of the present invention, the moisture permeability is preferably 100 g / m ² · 24 hr or less, more preferably 60 g / m ² · 24 hr or less. If the moisture permeability exceeds 100 g / m ² · 24 hr, the moisture resistance may be inferior.

The optical film of the present invention preferably also has excellent mechanical strength. Tensile strength, in the MD direction, preferably 65N / mm ² or more, more preferably 70N / mm ² or more, more preferably 75N / mm ² or more, particularly preferably 80 N / mm ² or more, in the TD direction, preferably the 45N / mm ² or more, more preferably 50 N / mm ² or more, more preferably 55N / mm ² or more, and particularly preferably 60N / mm ² or more. The tensile elongation is preferably 6.5% or more, more preferably 7.0% or more, further preferably 7.5% or more, particularly preferably 8.0% or more in the MD direction, and preferably in the TD direction. Is 5.0% or more, more preferably 5.5% or more, still more preferably 6.0% or more, and particularly preferably 6.5% or more. When the tensile strength or tensile elongation is out of the above range, there is a possibility that excellent mechanical strength may not be exhibited.

  In the optical film of the present invention, the haze representing optical transparency is better as it is lower, preferably 5% or less, more preferably 3% or less, further preferably 1.5% or less, particularly preferably 1% or less. It is. When the haze is 5% or less, it is possible to visually give a good clear feeling to the film. When the haze is 1.5% or less, even when used as a lighting member such as a window, the visibility and the lighting performance are improved. Since both can be obtained, and even when used as a front plate of a display device, the display contents can be visually recognized well, and thus the industrial utility value is high.

  The thickness of the optical film of the present invention is preferably 10 to 250 μm, more preferably 15 to 200 μm, still more preferably 30 to 180 μm, and particularly preferably 40 to 160 μm. When the thickness of the optical film of the present invention is 20 μm or more, it has appropriate strength and rigidity, and handling properties are good during secondary processing such as laminating and printing. Further, the phase difference caused by the stress at the time of take-up can be easily controlled, and the film can be manufactured stably and easily. When the thickness of the optical film of the present invention is 200 μm or less, film winding is facilitated, and line speed, productivity, and controllability are facilitated.

  The optical film of the present invention can be used by being laminated on another substrate. For example, it can be laminated by multilayer extrusion molding including an adhesive resin layer or multilayer inflation molding on a substrate such as glass, a polyolefin resin, an ethylene vinylidene copolymer serving as a high barrier layer, or polyester. If the heat-fusibility is high, the adhesive layer may be omitted.

  The optical film of the present invention is suitable for use as a polarizer protective film. In addition to the use as a polarizer protective film, for example, building lighting members such as windows and carport roofing materials, vehicle lighting members such as windows, agricultural lighting members such as greenhouses, lighting members, front filters, etc. It can be used by laminating to display members, etc., and it has been used to make home appliance housings, vehicle interior members, interior building materials, wallpaper, decorative boards, entrance doors that have been conventionally coated with (meth) acrylic resin films. It can also be used by being laminated on window frames, baseboards, and the like.

[A-6. Optical film molding]
The optical film of the present invention can be obtained by extrusion molding (melt extrusion method such as T-die method or inflation method) of the molding material. Specifically, biaxial kneading using direct addition or a master batch method is preferably performed. As a kneading method, kneading is preferably performed using a TEM manufactured by Toshiba Machine.

  In the present invention, as described above, as a molding material at the time of extrusion molding, as described above, a resin component containing a (meth) acrylic resin as a main component, and a specific antioxidant of a specific proportion amount or more with respect to the resin component Even if the molding temperature is set to 250 ° C. or higher by using a molding material containing the above and by setting the light transmittance of the obtained optical film under a specific amount to a specific amount or less, it finally enters the optical film. The generation of foam can be sufficiently suppressed. Therefore, it is preferable to set the temperature so that the temperature of the molding material at the time of extrusion molding is 250 ° C. or higher. The temperature of the molding material at the time of extrusion molding is more preferably 250 to 300 ° C. If the temperature rises too much, decomposition of the (meth) acrylic resin may easily proceed.

  Extrusion molding does not require drying and scattering of the solvent in the adhesive used during processing, for example, the organic solvent in the adhesive for dry lamination, as in the dry lamination method. Excellent in productivity.

  As an example of a preferable embodiment of the molding method for obtaining the optical film of the present invention, a molding material is added to a twin-screw kneader and extruded at a molding temperature of 250 ° C. or more to produce resin pellets. The pellets are supplied to a single screw extruder connected to a T die and extruded at a die temperature of 250 ° C. or more to obtain an optical film. In the present invention, the thickness of the optical film obtained by extrusion molding is preferably 20 to 250 μm, more preferably 25 to 200 μm, still more preferably 30 to 180 μm, and particularly preferably 40 to 160 μm.

  The optical film in the present invention may be stretched by longitudinal stretching and / or lateral stretching.

  The stretching may be stretching by only longitudinal stretching (free end uniaxial stretching) or stretching by only lateral stretching (fixed end uniaxial stretching), but the longitudinal stretching ratio is 1.1 to 3.0 times, and the transverse stretching ratio. Is preferably a sequential stretching or simultaneous biaxial stretching of 1.1 to 3.0 times. In stretching only by longitudinal stretching (free end uniaxial stretching) and stretching only by lateral stretching (fixed end uniaxial stretching), the film strength increases only in the stretching direction, and the strength does not increase in the direction perpendicular to the stretching direction. There is a possibility that sufficient film strength as a whole cannot be obtained. The longitudinal stretching ratio is more preferably 1.2 to 2.5 times, and still more preferably 1.3 to 2.0 times. The transverse stretching ratio is more preferably 1.2 to 2.5 times, and still more preferably 1.4 to 2.5 times. When the longitudinal draw ratio and the transverse draw ratio are less than 1.1 times, the draw ratio is too low, and there is a possibility that there is almost no effect of stretching. When the longitudinal stretching ratio and the lateral stretching ratio exceed 3.0 times, stretch breakage is likely to occur due to the problem of the smoothness of the film end face.

  The stretching temperature is preferably Tg to (Tg + 30 ° C.) of the film to be stretched. If the stretching temperature is lower than Tg, the film may be broken. If the stretching temperature exceeds (Tg + 30 ° C.), the film may start to melt and paper passing may be difficult.

  When the optical film of the present invention is stretched by longitudinal stretching and / or lateral stretching, the optical film has excellent optical properties, is excellent in mechanical strength, and improves productivity and reworkability. The thickness of the optical film after stretching is preferably 10 to 80 μm, more preferably 15 to 60 μm.

[B. Polarizer〕
The polarizing plate of the present invention includes the optical film of the present invention as a polarizer protective film. Preferably, the polarizing plate includes a polarizer formed from a polyvinyl alcohol-based resin and the optical film of the present invention, and the polarizer is bonded to the optical film via an adhesive layer.

  One preferred embodiment of the polarizing plate of the present invention is that, as shown in FIG. 1, one surface of a polarizer 31 is bonded to the optical film 34 of the present invention via an adhesive layer 32 and an easy adhesion layer 33. Thus, the other surface of the polarizer 31 is bonded to the optical film 36 via the adhesive layer 35. The optical film 36 may be the optical film of the present invention, or may be any other appropriate optical film (polarizer protective film).

  As the polarizer formed from the polyvinyl alcohol-based resin, one obtained by dyeing a polyvinyl alcohol-based resin film with a dichroic substance (typically iodine, a dichroic dye) and uniaxially stretching is used. The polymerization degree of the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is preferably 100 to 5000, and more preferably 1400 to 4000. The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any suitable method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). . The thickness of the polarizer can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is typically 5 to 80 μm.

  As a method for producing a polarizer, any appropriate method can be adopted depending on the purpose, materials used, conditions, and the like. Typically, a method is employed in which the polyvinyl alcohol-based resin film is subjected to a series of production steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol-based resin film in a bath containing a solution used in each step. The order, frequency, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing with water, and drying can be appropriately set according to the purpose, materials used, conditions, and the like. For example, several processes may be performed simultaneously in one process, and a specific process may be omitted. More specifically, for example, the stretching process may be performed after the dyeing process, may be performed before the dyeing process, or may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. Further, for example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath (swelling bath) filled with water. By this treatment, dirt on the surface of the polyvinyl alcohol-based resin film and an anti-blocking agent can be washed, and unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based resin film. Glycerin, potassium iodide, or the like can be appropriately added to the swelling bath. The temperature of the swelling bath is typically about 20 to 60 ° C., and the immersion time in the swelling bath is typically about 0.1 to 10 minutes.

  The dyeing step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath (dye bath) containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. The dichroic substance is typically used at a ratio of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the solvent. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.02 to 20 parts by weight, more preferably 2 to 10 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium is mentioned. The temperature of the dyeing bath is typically about 20 to 70 ° C., and the immersion time in the dyeing bath is typically about 1 to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polyvinyl alcohol resin film in a treatment bath (crosslinking bath) containing a crosslinking agent. Arbitrary appropriate crosslinking agents can be employ | adopted as a crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These can be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. The crosslinking agent is typically used at a ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the solvent. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot often be obtained. When the concentration of the crosslinking agent exceeds 10 parts by weight, the stretching force generated in the film during stretching increases, and the resulting polarizing plate may shrink. The solution of the crosslinking bath preferably further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as those in the dyeing process. The temperature of the crosslinking bath is typically about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is typically about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polyvinyl alcohol-based resin film needs to be 5 times or more, preferably 5 to 7 times, and more preferably 5 to 6.5 times. When the cumulative draw ratio is less than 5 times, it may be difficult to obtain a polarizing plate with a high degree of polarization. When the cumulative draw ratio exceeds 7 times, the polyvinyl alcohol-based resin film (polarizer) may be easily broken. Arbitrary appropriate methods may be employ | adopted as a specific method of extending | stretching. For example, when the wet stretching method is adopted, the polyvinyl alcohol-based resin film is stretched at a predetermined magnification in a treatment bath (stretching bath). As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polyvinyl alcohol-based resin film subjected to the above-described various treatments in a treatment bath (water washing bath). An unnecessary residue of the polyvinyl alcohol-based resin film can be washed away by the water washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide or sodium iodide). The concentration of the iodide aqueous solution is preferably 0.1 to 10% by mass. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is typically 1 second to 1 minute. The water washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process can be adjusted suitably. For example, the water washing step includes a step of immersing the polymer film in an aqueous potassium iodide solution (0.1 to 10% by mass, 10 to 60 ° C.) for 1 second to 1 minute, and a step of rinsing with pure water.

  Any appropriate drying method (for example, natural drying, air drying, heat drying) may be employed as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., and the drying time is typically 1 to 10 minutes. A polarizer is obtained as described above.

  In the polarizing plate of this invention, the said polarizer is adhere | attached on the optical film of this invention through an adhesive bond layer.

  In the present invention, the optical film of the present invention and the polarizer are bonded via an adhesive layer formed from an adhesive. This adhesive layer is preferably a layer formed from a polyvinyl alcohol-based adhesive in order to develop stronger adhesiveness. The polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin and a crosslinking agent.

  The polyvinyl alcohol-based resin is not particularly limited. For example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; and a saponified product of a copolymer with a monomer having copolymerizability with vinyl acetate. Modified polyvinyl alcohol obtained by acetalization, urethanization, etherification, grafting, phosphoric esterification, etc. of polyvinyl alcohol. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins may be used alone or in combination of two or more.

  From the viewpoint of adhesiveness, the polyvinyl alcohol-based resin preferably has an average degree of polymerization of 100 to 3000, more preferably 500 to 3000, and an average degree of saponification of preferably 85 to 100 mol%, more preferably 90. ˜100 mol%.

  As the polyvinyl alcohol resin, a polyvinyl alcohol resin having an acetoacetyl group can be used. A polyvinyl alcohol-based resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable in terms of improving the durability of the polarizing plate.

  A polyvinyl alcohol-based resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto, and a polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. And the like. Moreover, the method of making diketene gas or liquid diketene contact directly to polyvinyl alcohol is mentioned.

  The degree of acetoacetyl group modification of the polyvinyl alcohol resin having an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. If it is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient, which is inappropriate. The degree of acetoacetyl modification is preferably 0.1 to 40 mol%, more preferably 1 to 20 mol%. When the degree of acetoacetyl modification exceeds 40 mol%, the number of reaction points with the cross-linking agent decreases, and the effect of improving water resistance is small. The degree of acetoacetyl modification is a value measured by NMR.

  As said crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. As the crosslinking agent, a compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene amine, hexamethylene diamine (hexamethylene diamine is preferred); tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylene propane tolylene Isocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate and isocyanates such as ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di Or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylo Epoxys such as rupropane triglycidyl ether, diglycidyl aniline, diglycidyl amine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleindialdehyde And dialdehydes such as phthaldialdehyde; amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde; sodium, potassium, magnesium Divalent metals such as calcium, aluminum, iron and nickel, or salts of trivalent metals and oxides thereof. Is to, melamine-based crosslinking agent is preferably, suitable in particular melamine.

  The amount of the crosslinking agent is preferably 0.1 to 35 parts by weight, more preferably 10 to 25 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. On the other hand, in order to further improve the durability, the crosslinking agent can be blended in a range of more than 30 parts by weight and 46 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin. In particular, when a polyvinyl alcohol-based resin containing an acetoacetyl group is used, it is preferable to use the crosslinking agent in an amount exceeding 30 parts by weight. Water resistance improves by mix | blending a crosslinking agent in the range of more than 30 weight part and 46 weight part or less.

  The polyvinyl alcohol-based adhesive further includes coupling agents such as silane coupling agents and titanium coupling agents, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and the like. A stabilizer or the like can also be blended.

  The optical film of the present invention can be subjected to an easy adhesion treatment for improving adhesion on the surface in contact with the polarizer. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment, and a method of forming an anchor layer, and these can be used in combination. Among these, a corona treatment, a method of forming an anchor layer, and a method of using these in combination are preferable.

  Examples of the anchor layer include a silicone layer having a reactive functional group. The material of the silicone layer having a reactive functional group is not particularly limited. For example, an isocyanate group-containing alkoxysilanol, an amino group-containing alkoxysilanol, a mercapto group-containing alkoxysilanol, a carboxy-containing alkoxysilanol, an epoxy group-containing Examples thereof include alkoxysilanols, vinyl-type unsaturated group-containing alkoxysilanols, halogen group-containing alkoxylanols, and isocyanate group-containing alkoxysilanols, and amino silanols are preferred. Furthermore, the adhesive force can be strengthened by adding a titanium-based catalyst or a tin-based catalyst for efficiently reacting the silanol. Moreover, you may add another additive to the silicone which has the said reactive functional group. Specifically, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins and other tackifiers, UV absorbers, antioxidants, heat stabilizers and other stabilizers may be used. Moreover, the layer which consists of what saponified cellulose acetate butyrate resin as an anchor layer is also mentioned.

  The silicone layer having the reactive functional group is formed by coating and drying by a known technique. The thickness of the silicone layer is preferably 1 to 100 nm, more preferably 10 to 50 nm after drying. During coating, silicone having a reactive functional group may be diluted with a solvent. The dilution solvent is not particularly limited, and examples thereof include alcohols. The dilution concentration is not particularly limited, but is preferably 1 to 5% by weight, more preferably 1 to 3% by weight.

  The adhesive layer is formed by applying the adhesive to either side or both sides of the optical film of the present invention and to either side or both sides of the polarizer. After laminating the optical film of the present invention and the polarizer, a drying process is performed to form an adhesive layer composed of a coated and dried layer. This can also be bonded after forming the adhesive layer. Bonding of the polarizer and the optical film of the present invention can be performed by a roll laminator or the like. The heating and drying temperature and drying time are appropriately determined according to the type of adhesive.

  The thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm, since it is not preferable in terms of the adhesiveness of the optical film of the present invention if the thickness after drying becomes too thick. is there.

  The optical film of the present invention can be bonded to the polarizer on both sides of the polarizer on one side of the optical film of the present invention.

  Moreover, the optical film of the present invention can be bonded to a polarizer by adhering to one side of the polarizer on one side of the optical film of the present invention and bonding the cellulosic resin to the other side.

  The cellulose resin is not particularly limited, but triacetyl cellulose is preferable in terms of transparency and adhesiveness. The thickness of the cellulosic resin is preferably 30 to 100 μm, more preferably 40 to 80 μm. When the thickness is less than 30 μm, the film strength is lowered and the workability is inferior. When the thickness is more than 100 μm, the light transmittance is significantly reduced in durability.

  The polarizing plate of the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to other members such as other optical films and liquid crystal cells can be provided on the side of the optical film of the present invention where the polarizer is not adhered.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is used as a base polymer. It can select suitably and can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance and heat resistance can be preferably used. In particular, an acrylic pressure-sensitive adhesive made of an acrylic polymer having 4 to 12 carbon atoms is preferable.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler or pigment made of glass fiber, glass beads, metal powder, other inorganic powders, a colorant, an antioxidant. An additive to be added to the pressure-sensitive adhesive layer such as an agent may be contained.

  Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  The attachment of the pressure-sensitive adhesive layer can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or a pressure-sensitive adhesive layer is formed on a separator according to the above, and the surface is applied to a polarizer protective film. The method of transferring to is included.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of the polarizing plate as a superposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers with a different composition, a kind, thickness, etc. in the front and back of a polarizing plate.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is preferably 1 to 40 μm, more preferably 5 to 30 μm, and particularly preferably 10 to 25 μm. When the thickness is less than 1 μm, the durability is deteriorated. When the thickness is more than 40 μm, floating or peeling due to foaming or the like is liable to occur, resulting in poor appearance.

  In order to improve the adhesion between the optical film of the present invention and the pressure-sensitive adhesive layer, an anchor layer may be provided between the layers.

  As the anchor layer, an anchor layer selected from polyurethane, polyester and polymers containing an amino group in the molecule is preferably used, and polymers containing an amino group in the molecule are particularly preferably used. Polymers containing amino groups in the molecule are good because the amino groups in the molecule exhibit interactions such as reaction or ionic interaction with carboxyl groups in the adhesive and polar groups in the conductive polymer. Adhesion is ensured.

  Examples of the polymer containing an amino group in the molecule include, for example, polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, and amino-containing groups such as dimethylaminoethyl acrylate shown as a copolymer monomer of the acrylic pressure-sensitive adhesive. Examples thereof include polymers of contained monomers.

  In order to impart antistatic properties to the anchor layer, an antistatic agent may be added. Antistatic agents for imparting antistatic properties include ionic surfactant systems, conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline, and metal oxide systems such as tin oxide, antimony oxide, and indium oxide. In particular, a conductive polymer system is preferably used from the viewpoint of optical characteristics, appearance, antistatic effect, and stability of the antistatic effect when heated and humidified. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used. This is because, when a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, it is possible to suppress deterioration of the optical film substrate due to an organic solvent during the coating process.

  In the present invention, each layer such as a polarizer, an optical film (polarizer protective film, etc.) or an adhesive layer forming the polarizing plate described above includes, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, Those having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a cyanoacrylate compound or a nickel complex salt compound may be used.

  The polarizing plate of the present invention may be provided on either the viewing side or the backlight side of the liquid crystal cell or on both sides, and is not limited.

  Next, the image display apparatus of the present invention will be described. The image display device of the present invention includes at least one polarizing plate of the present invention. Here, a liquid crystal display device will be described as an example, but it goes without saying that the present invention can be applied to any display device that requires a polarizing plate. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). Can be mentioned. FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. In the illustrated example, a transmissive liquid crystal display device will be described, but it goes without saying that the present invention is also applied to a reflective liquid crystal display device and the like.

  The liquid crystal display device 100 includes a liquid crystal cell 10, retardation films 20 and 20 ′ disposed across the liquid crystal cell 10, and polarizing plates 30 and 30 ′ disposed outside the retardation films 20 and 20 ′. A light guide plate 40, a light source 50, and a reflector 60 are provided. The polarizing plates 30 and 30 'are arranged so that their polarization axes are orthogonal to each other. The liquid crystal cell 10 includes a pair of glass substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium disposed between the substrates. One substrate 11 is provided with a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal ( Neither is shown). The other glass substrate 11 ′ is provided with a color layer constituting a color filter and a light shielding layer (black matrix layer) (both not shown). The distance (cell gap) between the substrates 11 and 11 ′ is controlled by the spacer 13. In the liquid crystal display device of the present invention, the polarizing plate of the present invention described above is employed as at least one of the polarizing plates 30 and 30 '.

  For example, in the case of the TN mode, in such a liquid crystal display device 100, when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 12 are arranged in a state where the polarization axis is shifted by 90 degrees. In such a state, incident light that is transmitted through only light in one direction by the polarizing plate is twisted 90 degrees by liquid crystal molecules. As described above, since the polarizing plates are arranged so that the polarization axes thereof are orthogonal to each other, the light (polarized light) reaching the other polarizing plate is transmitted through the polarizing plate. Therefore, when no voltage is applied, the liquid crystal display device 100 performs white display (normally white method). On the other hand, when a voltage is applied to such a liquid crystal display device 100, the arrangement of liquid crystal molecules in the liquid crystal layer 12 changes. As a result, the light (polarized light) that has reached the other polarizing plate cannot be transmitted through the polarizing plate, resulting in black display. An image is formed by switching such display for each pixel using an active element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, the percentages in the examples and comparative examples are based on weight. Evaluation was performed as follows.

<Mass average molecular weight>
Measurement was made in terms of polystyrene using Shodex GPC system-21H manufactured by Showa Denko K.K.

<Tg (Glass transition temperature, sometimes referred to as TG)>
The polymer is once dissolved in tetrahydrofuran, re-precipitated by adding it to excess hexane or toluene, and the precipitate taken out by filtration is dried under reduced pressure (1 mmHg (1.33 hPa), 3 hours or more). The resin obtained was measured using a DSC apparatus (DSC8230, manufactured by Rigaku Corporation). In addition, about Tg of the polarizer protective film, the sample cut finely according to the measurement cell size was produced, and it measured using the said sample as it was.

<Dealcoholization reaction rate (lactone cyclization rate)>
The dealcoholization reaction rate was determined based on the weight loss that occurred when all hydroxyl groups were dealcoholated as methanol from the polymer composition obtained by polymerization. From the 150 ° C. before the weight reduction began in dynamic TG measurement, It calculated | required from the weight reduction by the dealcoholization reaction to 300 degreeC before decomposition | disassembly started.

That is, in the dynamic TG measurement of the polymer having a lactone ring structure, the weight reduction rate between 150 ° C. and 300 ° C. is measured, and the obtained actual weight reduction rate is defined as (X). On the other hand, from the composition of the polymer, all the hydroxyl groups contained in the polymer composition are involved in the formation of the lactone ring, so that it becomes an alcohol and is dealcoholized. (Y) is the weight loss rate calculated on the assumption that the% dealcoholization reaction has occurred. The theoretical weight reduction rate (Y) is more specifically the molar ratio of raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material unit in the polymer composition. It can be calculated from the content of the monomer. These values (X, Y) are calculated from the dealcoholization formula:
1- (actual weight reduction rate (X) / theoretical weight reduction rate (Y))
Substituting into, the value is obtained and expressed in%, the dealcoholization reaction rate (lactone cyclization rate) is obtained.

<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg based on JIS-K6874.

<Total light transmittance>
The produced protective film sample was cut into a 3 cm square, and the total light transmittance was measured with “UV-VIS-NIR-SPECTROMETER UV3150” manufactured by Shimadzu Corporation.

<Weight loss upon heating at 300 ° C. for 20 minutes>
The weight loss during heating at 300 ° C. for 20 minutes was evaluated by the weight reduction rate when heated at 300 ° C. for 20 minutes in a nitrogen stream. About 5 to 10 mg of the sample was used, and measurement was performed in a nitrogen stream with a thermogravimetric analyzer (manufactured by Seiko Instruments Inc., TG / DTA6200). The temperature was raised to 300 ° C. at 10 ° C./min, and then held at 300 ° C. for 20 minutes. When the weight before treatment = M0, the weight after treatment = M1, and the weight reduction rate (%) = M, the following formula was used.

  M = (M1-M0) / M0

<Observation of foaming>
When the die temperature was extruded from a T die with a single screw extruder at 290 ° C., the resin extruded from the T die was observed, and the presence or absence of foaming was observed.
XX: Many foams having a diameter (long diameter in the case of an elliptical shape) of 0.5 mm or more are observed on the entire surface.
X: Foaming having a diameter (long diameter in the case of an elliptical shape) of 0.5 mm or more is observed on the entire surface.
○: Foaming of 0.5 mm or less is observed.
A: No foaming is observed visually.

<Method for evaluating UV absorption ability>
About the obtained optical film, the light transmittance of 380 nm was measured using Hitachi spectrophotometer U-4100 by Hitachi High-Technologies Corporation.

<Appearance evaluation of polarizing plate>
After the adhesive polarizing plate was cut to 25 mm × 50 mm, the release film was peeled off and attached to a glass plate via an adhesive layer to obtain an evaluation sample. This was put in an ultraviolet long life fade meter (manufactured by Suga Test Instruments Co., Ltd., model: U48HB) and irradiated with ultraviolet rays for 240 hours. After irradiation, a sample was taken out and the appearance was visually evaluated.

  ○: No change from the initial stage.

  X: Discoloration is seen compared with the initial stage.

Reference Example 1 Production of Polarizer A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, after being immersed in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide and further stretched to 5.5 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. It was immersed in a 5% by weight aqueous potassium iodide solution. Then, it dried for 3 minutes in 40 degreeC oven, and obtained the 30-micrometer-thick polarizer.

[Reference Example 2]: Production of lactone ring-containing acrylic resin In a 30 L reaction kettle equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe, 8000 g of methyl methacrylate (MMA) and 2000 g of 2- (hydroxymethyl) ) Methyl acrylate (MHMA), charged with 10,000 g of toluene, heated to 105 ° C. while passing through nitrogen, and refluxed, 10.0 g of tertiary amyl peroxyisononanoate (manufactured by Atofina Yoshitomi, (Trade name: Lupazole 570) was added, and at the same time, a solution consisting of 20.0 g of initiator and 100 g of toluene was added dropwise over 4 hours, and solution polymerization was performed under reflux (about 105 to 110 ° C.). Aged over time.

  To the obtained polymer solution, 10 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 110 ° C.) for 5 hours. A condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (Φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. By extrusion, a transparent lactone ring-containing acrylic resin pellet (A) was obtained.

  The lactone ring-containing acrylic resin pellet (A) had a lactone cyclization rate of 97.0%, a mass average molecular weight of 147700, a melt flow rate of 11.0 g / 10 min, and a Tg (glass transition temperature) of 130 ° C. .

[Example 1]
For 100 parts by weight of the lactone ring-containing acrylic resin pellet (A) obtained in Reference Example 2, 5 parts by weight of a triazole UV absorber (ADEKA, Adeka Stub LA-31), a phosphorus antioxidant ( 1 part by weight of ADEKA, PEP-36) and 1 part of phenolic antioxidant (Ciba Specialty Chemicals, IRGANOX1010) were mixed at 250 ° C. with a twin-screw kneader, and resin pellets were mixed. Produced.

  Each additive used was reduced in weight by heating at 300 ° C. for 20 minutes. Triazole UV absorber (ADEKA, ADK STAB LA-31) = 2.8%, Phosphorous antioxidant (ADEKA) , PEP-36) = 7.9%, phenolic antioxidant (Ciba Specialty Chemicals, IRGANOX 1010) = 4.2%.

  The obtained resin pellets were dried at 800 Pa (6 Torr) and 100 ° C. for 12 hours, and extruded from the T die at a die temperature of 290 ° C. with a single screw extruder to produce an optical film (1) having a thickness of 90 μm.

  The results are shown in Table 1.

[Example 2]
For 100 parts by weight of the lactone ring-containing acrylic resin pellets (A) obtained in Reference Example 2, 5 parts by weight of a triazole UV absorber (ADEKA, Adeka Stab LA-31), a thioether-based antioxidant ( Sumitomo Chemical Co., Ltd., Sumilizer TP-D) 0.8 parts by weight, phenolic antioxidant (Ciba Specialty Chemicals Co., Ltd., IRGANOX 1010) 0.8 parts by weight in a twin-screw kneader at 250 ° C. It mixed and produced the resin pellet.

  The weight loss of each additive used when heated at 300 ° C. for 20 minutes was as follows: triazole UV absorber (ADEKA, ADK STAB LA-31) = 2.8%, thioether antioxidant (Sumitomo Chemical Co., Ltd.) Manufactured, Sumilyzer TP-D) = 2.4%, phenolic antioxidant (Ciba Specialty Chemicals, IRGANOX 1010) = 4.2%.

  The obtained resin pellets were dried at 800 Pa (6 Torr) and 100 ° C. for 12 hours, and extruded from the T die at a die temperature of 290 ° C. with a single screw extruder to produce an optical film (2) having a thickness of 90 μm.

  The results are shown in Table 1.

[Comparative Example 1]
For 100 parts by weight of the lactone ring-containing acrylic resin pellet (A) obtained in Reference Example 2, 5 parts by weight of a triazole UV absorber (ADEKA, Adeka Stub LA-31), a phosphorus antioxidant ( 1 part by weight of Ciba Specialty Chemicals, IRGAFOS168) and 1 part of phenolic antioxidant (Ciba Specialty Chemicals, IRGANOX1010) are mixed at 250 ° C. with a biaxial kneader, and resin pellets Was made.

  The weight loss of each additive used after heating at 300 ° C. for 20 minutes was as follows: triazole UV absorber (ADEKA, ADK STAB LA-31) = 2.8%, phosphorus antioxidant (Ciba Specialty) Chemicals, IRGAFOS168) = 100%, phenolic antioxidant (Ciba Specialty Chemicals, IRGANOX1010) = 4.2%.

  The obtained resin pellets were dried at 800 Pa (6 Torr) and 100 ° C. for 12 hours, and extruded from the T die at a die temperature of 290 ° C. using a single-screw extruder to produce an optical film (C1) having a thickness of 90 μm.

  The results are shown in Table 1.

[Comparative Example 2]
For 100 parts by weight of the lactone ring-containing acrylic resin pellet (A) obtained in Reference Example 2, 5 parts by weight of a triazole UV absorber (ADEKA, Adeka Stub LA-31) was added to a biaxial kneader. Were mixed at 250 ° C. to prepare resin pellets.

  The weight loss of the additive used when heated at 300 ° C. for 20 minutes was triazole UV absorber (ADEKA, Adeka Stub LA-31) = 2.8%.

  The obtained resin pellets were dried at 800 Pa (6 Torr) and 100 ° C. for 12 hours, and extruded from the T die at a die temperature of 290 ° C. with a single-screw extruder to produce an optical film (C2) having a thickness of 90 μm.

  The results are shown in Table 1.

Example 3
(adhesive)
A polyvinyl alcohol adhesive aqueous solution prepared by adjusting an aqueous solution containing 20 parts by weight of methylolmelamine to 100 parts by weight of an acetoacetyl-modified polyvinyl alcohol resin (degree of acetylation 13%) to a concentration of 0.5% by weight It was adjusted.

(Preparation of polarizing plate)
The said film was bonded together on both surfaces of the polarizer obtained in Reference Example 1 using the polyvinyl alcohol-type adhesive agent. Each of the polyvinyl alcohol-based adhesives was applied to the acrylic resin surface side and dried at 70 ° C. for 10 minutes to obtain a polarizing plate.

(Adhesive)
As a base polymer, a solution (solid content 30) containing an acrylic polymer having a weight average molecular weight of 2 million consisting of a copolymer of butyl acrylate: acrylic acid: 2-hydroxyethyl acrylate = 100: 5: 0.1 (weight ratio) %) Was used. Viscosity adjustment of 4 parts of Coronate L manufactured by Nippon Polyurethane Co., Ltd., which is an isocyanate-based polyfunctional compound, to 100 parts of polymer solids and 0.5 part of an additive (KBM403, manufactured by Shin-Etsu Silicone) A solvent (ethyl acetate) was added to prepare an adhesive solution (solid content 12%). The adhesive solution was applied on a release film (polyethylene terephthalate substrate: Diafoil MRF38, manufactured by Mitsubishi Chemical Polyester Co., Ltd.) so that the thickness after drying was 25 μm, and then dried in a hot air circulation oven. An adhesive layer was formed.

(Polarizing plate anchor layer)
A polyethylenimine adduct of polyacrylic acid ester (trade name: Polyment NK380, manufactured by Nippon Shokubai Co., Ltd.) was diluted 50 times with methyl isobutyl ketone. This was coated and dried on the nylon resin side of the polarizing plate using a wire bar (# 5) so that the thickness after drying was 50 nm.

(Preparation of adhesive polarizing plate)
A release film having the pressure-sensitive adhesive layer formed thereon was bonded to the anchor layer of the polarizing plate to prepare a pressure-sensitive adhesive-type polarizing plate.

(Evaluation of polarizing plate)
The adhesion between the film and the polarizer and the appearance of the obtained polarizing plate were evaluated. Adhesiveness was good, and the polarizer and the film were integrated and no peeling occurred. Moreover, the evaluation result of the external appearance was ○.

  The optical film and polarizing plate of the present invention can be suitably used for various image display devices (liquid crystal display devices, organic EL display devices, PDPs, etc.).

It is sectional drawing which shows an example of the polarizing plate of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 11, 11 'Glass substrate 12 Liquid crystal layer 13 Spacer 20, 20' Retardation film 30, 30 'Polarizing plate 31 Polarizer 32 Adhesive layer 33 Easy adhesion layer 34 Optical film 35 Adhesive layer 36 Optical film 40 Conduction Light plate 50 Light source 60 Reflector 100 Liquid crystal display device

Claims (9)

An optical film having a light transmittance of 15% or less at 380 nm at a thickness of 80 μm,
A resin component containing a (meth) acrylic resin as a main component, and an antioxidant having a weight loss of 10% or less when heated at 300 ° C. for 20 minutes at 0.02 part by weight or more with respect to 100 parts by weight of the resin component An optical film obtained by molding a molding material containing   The optical film of Claim 1 whose temperature of the molding material at the time of the said extrusion molding is 250 degreeC or more.   The optical film of Claim 1 or 2 in which the said antioxidant contains a phenolic antioxidant.   The said antioxidant contains 0.01 weight part or more phenolic antioxidant and 0.01 weight part or more of thioether type antioxidant with respect to 100 weight part of said resin components. Optical film.   The said antioxidant contains 0.01 weight part or more phenolic antioxidant with respect to 100 weight part of said resin components, and 0.01 weight part or more of phosphorus antioxidant. Optical film.   The optical according to any one of claims 1 to 5, wherein the molding material contains a triazole-based UV absorber and / or a triazine-based UV absorber whose weight loss upon heating at 300 ° C for 20 minutes is 10% or less. the film.   The optical film according to any one of claims 1 to 6, wherein the (meth) acrylic resin is a (meth) acrylic resin having a lactone ring structure.   A polarizing plate comprising the optical film according to claim 1 as a polarizer protective film.   An image display device comprising at least one polarizing plate according to claim 8.

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