JP4895290B2 - Optical film manufacturing method, optical film, polarizing plate, and image display device - Google Patents

Description

  The present invention relates to an optical film manufacturing method, an optical film obtained by the manufacturing method, a polarizing plate using the optical film, and an image of a liquid crystal display device, an organic EL display device, a PDP, or the like including at least one polarizing plate. The present invention relates to a display device.

  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 polarizer protective film may be required to have ultraviolet absorption performance for the purpose of preventing the liquid crystal and the polarizer from being deteriorated by ultraviolet rays. As a resin component of an optical film used as a polarizer protective film, triacetyl cellulose has been generally used so far. At present, an ultraviolet absorber is added to a triacetyl cellulose film as a polarizer protective film to provide ultraviolet absorption performance.

  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 deteriorates. 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, a transparent thermoplastic resin having high moisture and heat resistance has been studied as a material for a polarizer protective film that replaces conventional triacetyl cellulose, and an ultraviolet absorber is added to such a thermoplastic resin to absorb ultraviolet rays. Optical films with performance have been reported (see Patent Documents 1 and 2). However, in order to manufacture such an optical film having high heat resistance, it is necessary to mold the film at a high temperature. Therefore, in order to avoid the ultraviolet absorber from decomposing at a high temperature, an ultraviolet absorber having a high heat resistance is used. It is necessary to use it. However, an ultraviolet absorber having high heat resistance has low compatibility with a transparent thermoplastic resin having high heat-and-moisture resistance, in particular, a (meth) acrylic resin. For this reason, it is obtained when a molding material containing a resin component containing a (meth) acrylic resin as a main component and an ultraviolet absorber is molded by extrusion molding at a relatively high temperature to produce an optical film. There is a problem that the ultraviolet absorber bleeds out on the optical film, resulting in an appearance defect, and a problem that production stability is lowered due to adhesion of the bleed-out ultraviolet absorber to the roll at the time of production.

Further, depending on the application (for example, mobile application), it is necessary to reduce the thickness of the optical film. However, a thin optical film tends to have insufficient ultraviolet absorbing ability. For this reason, it is necessary to add more ultraviolet absorbers than usual, and various problems resulting from the above bleed out will appear more remarkably.
JP-A-9-166711 JP 2004-45893 A

  The subject of this invention is (1) (meth) acrylic-type optical film which has the outstanding ultraviolet-ray absorption capability by addition of sufficient amount of high heat-resistant ultraviolet absorber, and also has the outstanding heat resistance and optical characteristics. In manufacturing, the bleed-out of the UV absorber on the optical film during extrusion molding is suppressed, which reduces the appearance defects of the optical film, and the UV absorber adheres to the roll during manufacturing. Providing an optical film production method capable of maintaining production stability by suppressing, (2) Providing an optical film with few appearance defects by such production method, (3) Providing such an optical film It is to provide a polarizing plate having few appearance defects, and (4) to provide a high-quality image display device using such a polarizing plate.

The method for producing the optical film of the present invention comprises:
A resin component containing a (meth) acrylic resin as a main component, and a weight reduction in heating at 300 ° C. for 20 minutes of 0.5 to 5.5 parts by weight with respect to 100 parts by weight of the resin component is 10% or less. A method for producing an optical film by molding a molding material containing an ultraviolet absorber by extrusion molding,
The resin component contains 0.1 to 20% by weight of a styrene polymer.

  In a preferred embodiment, the styrenic polymer is a copolymer containing 50 to 90% by weight of styrene monomer units.

  In a preferred embodiment, the styrenic polymer is a styrene / acrylonitrile copolymer.

  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 ultraviolet absorber contains at least 1 sort (s) chosen from a triazole type ultraviolet absorber and a triazine type ultraviolet absorber.

  According to another aspect of the present invention, an optical film is provided. The optical film of the present invention is obtained by the method for producing an optical film of the present invention.

  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, in the production of a (meth) acrylic optical film having an excellent ultraviolet absorbing ability and an excellent heat resistance and optical properties by adding a sufficient amount of an ultraviolet absorber having high heat resistance. , Suppresses bleed-out of UV absorber on the optical film during extrusion molding, thereby reducing the appearance defects of the optical film, and also suppresses UV absorber adhesion due to bleed-out to the roll during production. An optical film manufacturing method capable of maintaining production stability can be provided. In addition, such a manufacturing method can provide an optical film with few appearance defects. Furthermore, a polarizing plate using such an optical film and having few appearance defects can be provided. In addition, a high-quality image display device using such a polarizing plate can be provided.

  Such an effect is obtained by molding a molding material containing a resin component containing a (meth) acrylic resin as a main component and a sufficient amount of a heat-resistant UV absorber by extrusion molding. In producing an optical film, the resin component can be expressed by containing a specific range amount of a styrene polymer.

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

[A. Manufacturing method of optical film]
[A-1. Resin component)
The method for producing an optical film of the present invention is a method for producing an optical film by molding a molding material containing a resin component containing a (meth) acrylic resin as a main component by extrusion molding.

  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 may be used as the (meth) acrylic resin in terms of having 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, further preferably 130 ° C. or higher, particularly preferably 135 ° C. or higher, most preferably. Is 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 molding material is preferably 50 to 99.5% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 90%. 97% by weight. When the content of the (meth) acrylic resin in the molding material is less than 50% by weight, the high heat resistance and high transparency inherent in the (meth) acrylic resin may not be sufficiently reflected. When the content of the (meth) acrylic resin in the molding material exceeds 99.5% by weight, the content of the ultraviolet absorber described later in the molding material becomes insufficient, and thus the obtained optical film is There is a possibility that sufficient ultraviolet absorbing ability cannot be exhibited.

  The resin component containing the (meth) acrylic resin as a main component contains 0.1 to 20% by weight of a styrene polymer. The content of the styrenic polymer is preferably 1 to 18% by weight, more preferably 5 to 16% by weight.

  When the content of the styrenic polymer is out of the above range, when the optical film is produced, the ultraviolet absorber bleeds out on the obtained optical film, resulting in an appearance defect, There is a possibility that the production stability is lowered due to adhesion of the bleed-out ultraviolet absorber to the roll.

  Examples of the styrenic polymer include homopolymers of styrene monomers (polystyrene) and copolymers of styrene monomers and other copolymerizable monomers. Further, a modified product of these polymers may be used. Examples of the copolymer of a styrene monomer and another copolymerizable monomer include a styrene / maleic anhydride copolymer, a styrene / acrylonitrile copolymer, and a styrene / maleimide copolymer.

  The styrene polymer is preferably a copolymer containing 50 to 90% by weight of styrene monomer units. The ratio of the styrene monomer unit in the styrene polymer is more preferably 55 to 85% by weight, and still more preferably 60 to 80% by weight.

  In order to fully exhibit the effects of the present invention, a styrene / acrylonitrile copolymer is particularly preferable as the styrene polymer which is a copolymer containing 50 to 90% by weight of a styrene monomer unit.

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

[A-2. UV absorber)
The molding material contains 0.5 to 5.5 parts by weight of an ultraviolet absorber having a weight loss of 10% or less when heated at 300 ° C. for 20 minutes with respect to 100 parts by weight of the resin component. The content of the ultraviolet absorber in the molding material is preferably 1 to 5 parts by weight, more preferably 2 to 5 parts by weight, and further preferably 3 to 5 parts by weight with respect to 100 parts by weight of the resin component. is there.

  As the ultraviolet absorber, any appropriate ultraviolet absorber can be adopted as long as the object of the present invention can be achieved. Examples include benzotriazole-based UV absorbers, benzophenone-based UV absorbers, triazine-based UV absorbers, inorganic particle-based UV absorbers, and other organic UV absorbers. Moreover, the ultraviolet absorber as described in Unexamined-Japanese-Patent No. 2001-72782 and Special Table 2002-543265 is mentioned. The ultraviolet absorber is preferably a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, or a triazine ultraviolet absorber, and more preferably in the present invention, a benzotriazole ultraviolet absorber or a benzophenone ultraviolet absorber. Particularly preferred are benzotriazole ultraviolet absorbers. Only one type of ultraviolet absorber may be used, or two or more types may be used in combination.

  The melting point of the ultraviolet absorber is preferably 110 ° C. or higher, and more preferably 120 ° C. or higher.

  The ultraviolet absorber 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 ultraviolet absorber 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 ultraviolet absorber having a weight loss of greater than 10% when heated at 300 ° C. for 20 minutes is used, an optical film having sufficient ultraviolet absorbing ability may not be obtained.

  Examples of the benzotriazole 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)- Benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-t rt-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 / Examples include the reaction product of polyethylene glycol 300, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol. As a commercial item, "ADK STAB LA-31" (made by ADEKA) is mentioned, for example.

  Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, and bis (2-methoxy-4-). Hydroxy-5-benzoylphenylmethane).

  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.

  Examples of the inorganic particle-based ultraviolet absorber include zinc oxide nanoparticles. As a commercial item, "NANOBYK-3820" (made by BYK-Chemie) is mentioned, for example.

  Examples of other organic ultraviolet absorbers include oxalic acid anilide ultraviolet absorbers and malonic ester ultraviolet absorbers. Commercially available products include, for example, “Sanduboa VSU” (manufactured by Clariant) as an oxalic anilide-based UV absorber, and “Hostabin PR-25” and “Hostabin B-CAP” (both Clariant) as malonic ester-based UV absorbers. For example).

  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-3. Molding material]
The said molding material can contain arbitrary appropriate other components in the range which does not impair the effect of this invention. For example, general compounding agents, specifically, antioxidants, stabilizers, lubricants, processing aids, plasticizers, impact aids, phase difference reducing agents, matting agents, antibacterial agents, fungicides, etc. It may be included.

  Any appropriate method can be adopted as a method for preparing the molding material. For example, a direct addition method or a master batch method may be used. More specifically, a method in which the ultraviolet absorber is added to the styrene polymer is added to a resin component containing the (meth) acrylic resin as a main component, or the (meth) acrylic resin is added. A method in which a resin component contained as a main component is added to the styrenic polymer is added to the ultraviolet absorber. In order to improve the compatibility, a method of adding the above styrene polymer to which the ultraviolet absorber is added to a resin component containing the (meth) acrylic resin as a main component is preferable. The mixture obtained by adding the respective materials for preparing the molding material is preferably pre-blended with an appropriate mixer and then extruded and kneaded. Any appropriate kneader can be adopted as the kneader used for extrusion kneading. For example, a single screw extruder, a twin screw extruder, and a pressure kneader are mentioned. It is also preferable to use a TEM manufactured by Toshiba Machine. Alternatively, each material for preparing the molding material may be directly subjected to extrusion molding described later.

[A-4. Production method〕
In the method for producing an optical film of the present invention, the molding material is molded by extrusion molding. Preferably, the molding material obtained by the extrusion kneading is formed into a film by extrusion molding. Alternatively, each material for preparing the molding material may be directly subjected to extrusion molding.

  Any appropriate method can be adopted as the method of extrusion molding. Examples thereof include a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  The temperature of the molding material at the time of extrusion molding is preferably 250 ° C. or higher. More preferably, it is 250-300 degreeC, More preferably, it is 260-290 degreeC. When the temperature of the molding material at the time of extrusion molding is less than 250 ° C., the molding material containing a resin having high heat resistance may not be stably molded.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol , N-butanol, 2-butanol and other alcohol solvents; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, etc. Is mentioned. These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum type casting machine, a band type casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method. The forming temperature of the film when performing the melt extrusion method is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. More preferably, it is 250-300 degreeC.

  When film forming is performed by the T-die method, for example, a T-die is attached to the tip of a single-screw extruder or a twin-screw extruder, and the film extruded into a film shape at a die temperature of 250 ° C. or higher is taken up by a winding roll. Winding and roll film can be obtained. At this time, it is possible to adjust the temperature of the winding roll as appropriate and apply stretching in the extrusion direction to achieve a uniaxial stretching step. Moreover, it is also possible to add processes, such as sequential biaxial stretching and simultaneous biaxial stretching, by adding the process of extending | stretching a film in the direction perpendicular | vertical to an extrusion direction.

  According to the method for producing an optical film of the present invention, the bleeding out of the ultraviolet absorber onto the optical film during extrusion molding is suppressed, thereby reducing the appearance defect of the optical film, and the bleeding into the roll during production. The production stability can be maintained by suppressing the adhesion of the UV absorber due to the out.

[B. Optical film)
The optical film of the present invention is obtained by the method for producing an optical film of the present invention. 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 20% or less, preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, and particularly preferably 8% or less. . When the light transmittance at 380 nm in the thickness of 80 μm of the optical film of the present invention exceeds 20%, 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.

  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 stretching effect. When the longitudinal stretching ratio and the lateral stretching ratio exceed 3.0 times, stretching 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.

[C. 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.

  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 (hexamethylene diamine is particularly preferred); isocyanates such as isophorone diisocyanate; epoxies such as ethylene glycol diglycidyl ether; monoaldehydes such as formaldehyde; glyoxal and the like Dialdehydes; amino-formaldehyde resins such as methylol melamine; and divalent metals such as sodium, potassium, magnesium, calcium, aluminum, iron, nickel, and salts of trivalent metals and oxides thereof. As the cross-linking agent, a melamine-based cross-linking agent is preferable, and methylol melamine is particularly preferable.

  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.

  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. If the thickness is less than 30 μm, the film strength is lowered and workability is inferior.

  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 copolymerization monomer of the above-mentioned acrylic adhesive. Examples thereof include polymers of contained monomers.

  In order to impart antistatic properties to the anchor layer, an antistatic agent may be added.

  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.

[D. (Image display device)
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.

<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

<Method for evaluating UV absorption ability>
About the obtained optical film, the light transmittance of 380 nm was measured with the film thickness of 80 micrometers using Hitachi spectrophotometer U-4100 by Hitachi High-Technologies.

<Evaluation of occurrence of roll deposits>
When the surface of the cast roll of the optical film obtained by winding after the extrusion molding was cloudy white, it was judged that the roll deposit was generated, and when it was not white, it was judged that the roll deposit was not generated.
○: No roll adhering occurrence ×: Roll adhering occurrence

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.

[Example 1]
25.9 kg of polymethyl methacrylate, 3.0 kg of styrene / acrylonitrile copolymer (containing 76% by weight of styrene monomer unit), UV absorber (ADEKA, ADK STAB LA-31, 20 minutes at 300 ° C. Weight reduction by heating = 2.8%) 1.05 kg was added, kneaded using a twin screw extruder at 230 ° C, extruded using a single screw extruder at 270 ° C, and wound with a roll. . The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

[Example 2]
26.4 kg of polymethyl methacrylate, 3.0 kg of styrene / acrylonitrile copolymer (containing 76% by weight of styrene monomer unit), UV absorber (ADEKA, Adeka Stub LA-31, 20 minutes at 300 ° C. Weight reduction by heating = 2.8%) 0.6 kg was added, kneaded at 230 ° C. using a twin screw extruder, extruded at 270 ° C. using a single screw extruder, and wound with a roll. . The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

Example 3
24.0 kg of polymethyl methacrylate, 4.5 kg of styrene / acrylonitrile copolymer (containing 76% by weight of styrene monomer unit), UV absorber (ADEKA Corporation, ADK STAB LA-31, 20 minutes at 300 ° C. Weight reduction by heating = 2.8%) 1.5 kg was added, kneaded using a twin screw extruder at 230 ° C, extruded using a single screw extruder at 270 ° C, and wound with a roll. . The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

Example 4
52.8 kg of polymethylmethacrylate, 6.0 kg of styrene / acrylonitrile copolymer (containing 76% by weight of styrene monomer unit), UV absorber (Adeka, Adeka Stub LA-31, 20 minutes at 300 ° C. (Weight reduction by heating = 2.8%) 2.4 kg was added, kneaded at 230 ° C. using a twin screw extruder, extruded at 270 ° C. using a single screw extruder, and wound up with a roll. . The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

Example 5
An acrylic resin having a lactone ring structure described in JP-A-2005-146084, 52.8 kg, 6.0 kg of a styrene / acrylonitrile copolymer (containing 76% by weight of a styrene monomer unit), UV absorption 1.2 kg of an additive (ADEKA, Adeka Stub LA-31, weight loss by heating at 300 ° C. for 20 minutes = 2.8%), kneaded at 230 ° C. using a twin screw extruder, at 270 ° C. Extrusion molding was performed using a single screw extruder, and the product was wound up with a roll. The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

[Comparative Example 1]
To 29.4 kg of polymethyl methacrylate, 0.6 kg of an ultraviolet absorber (ADEKA, ADK STAB LA-31, weight loss by heating at 300 ° C. for 20 minutes = 2.8%) is added, and biaxial extrusion at 230 ° C. After kneading using a machine, extrusion molding was carried out at 270 ° C. using a single screw extruder and wound up with a roll. The optical film obtained was evaluated for light transmittance at 380 nm and the presence or absence of roll deposits on the cast roll of the obtained optical film. The results are shown in Table 1.

Example 6
(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 optical film obtained in Example 1 was bonded to both surfaces of the polarizer obtained in Reference Example 1 using a polyvinyl alcohol adhesive 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 pressure-sensitive adhesive solution was applied on a release film (polyethylene terephthalate substrate: Diafoil MRF38, manufactured by Mitsubishi Chemical Polyester) 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 one 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)
As a result of evaluating the appearance of the obtained polarizing plate, it was satisfactory without any defects.

  The optical film and polarizing plate obtained by the production method 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 (5)

A resin component containing a (meth) acrylic resin as a main component, and a weight reduction in heating at 300 ° C. for 20 minutes of 0.5 to 5.5 parts by weight with respect to 100 parts by weight of the resin component is 10% or less. A molding material containing an ultraviolet absorber is molded by extrusion molding, wound with a roll, and a method for producing an optical film,
The resin component contains 0.1 to 20% by weight of a styrene polymer ,
The molding material is prepared by previously preparing the styrene polymer added with the ultraviolet absorber and adding it to a resin component containing the (meth) acrylic resin as a main component.
Manufacturing method of optical film.   The manufacturing method of Claim 1 whose said styrene-type polymer is a copolymer containing 50 to 90 weight% of styrene monomer units.   The production method according to claim 1 or 2, wherein the styrene polymer is a styrene / acrylonitrile copolymer.   The manufacturing method of Claim 1 whose temperature of the molding material at the time of the said extrusion molding is 250 degreeC or more. The manufacturing method in any one of Claim 1 to 4 in which the said ultraviolet absorber contains at least 1 sort (s) chosen from a triazole type ultraviolet absorber and a triazine type ultraviolet absorber.

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