JP6601056B2 - Thermoplastic resin film - Google Patents

Description

The present invention relates to a thermoplastic resin film, and also relates to a stretched film and a polarizer protective film formed by stretching the film.

A liquid crystal display device is usually provided with a polarizing plate, and as a polarizing plate, usually for protecting the polarizer on at least one surface of a polarizer made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. The thing in which the polarizer protective film is arrange | positioned is used.

Liquid crystal display devices are often used in high-temperature environments such as the interior of automobiles, for example, and polarizers tend to shrink in high-temperature environments, so they have excellent heat resistance and suppress the shrinkage of polarizers. Thus, there is a demand for a polarizer protective film that does not easily shrink in a high temperature environment.

In general, as the polarizer protective film, a thermoplastic film is used as it is or a stretched film obtained by stretching a thermoplastic resin film is used. Patent Document 1 discloses a stretched film obtained by stretching a thermoplastic resin film comprising an acrylic copolymer having a (meth) acrylic acid monomer unit, a vinyl aromatic monomer unit, and a lactone ring monomer unit. Is used as a polarizer protective film, but the thermoplastic resin film described in Patent Document 1 may be easily broken by stretching, and there is room for improvement in handling properties during stretching. .

JP 2007-63541 A

In order to provide a thermoplastic resin film that has excellent heat resistance, does not easily shrink in a high-temperature environment, and is not easily broken by stretching, the inventors have intensively studied to arrive at the present invention.

The present invention includes the following.
[1] A resin (A) containing a methacrylic acid ester monomer unit and an aromatic vinyl monomer unit, and a resin (B) containing a methacrylic acid ester monomer unit and no aromatic vinyl monomer unit A thermoplastic resin film comprising a thermoplastic resin containing
Resin (A) is a resin in which the content of aromatic vinyl monomer units is 50% by weight or more with respect to 100% by weight of all monomer units constituting resin (A),
The resin (B) is a resin in which the content of the methacrylic acid ester monomer unit is 50% by weight or more with respect to 100% by weight of all the monomer units constituting the resin (B),
A thermoplastic resin film in which the ratio (W _B / W _A ) of the weight (W _B ) of the resin (B) to the content (W _A ) of the methacrylic acid ester monomer unit in the resin ( _A ) is greater than 1.
[2] The thermoplastic resin film according to [1], wherein the resin composition further contains rubber elastic particles.
[3] The thermoplastic resin according to [1] or [2], wherein the resin (A) further contains a cyclic acid anhydride monomer unit, and the melt mass flow rate of the resin composition is 1.2 g / 10 min or more. Resin film.
[4] A stretched film obtained by stretching the thermoplastic resin film according to any one of [1] to [3].
[5] A polarizer protective film comprising the thermoplastic resin film according to any one of [1] to [3] or the stretched film according to [4].
[6] A polarizing plate in which the polarizer protective film according to [5] is disposed on at least one surface of the polarizer.

ADVANTAGE OF THE INVENTION According to this invention, the thermoplastic resin film which is excellent in heat resistance, is hard to shrink | contract in a high temperature environment, and is hard to fracture | rupture by extending | stretching, and the stretched film formed by extending | stretching it can be provided. Moreover, the polarizer protective film which consists of such a thermoplastic resin film or a stretched film can be provided, and also the polarizing plate by which this polarizer protective film is arrange | positioned on one surface of a polarizer can also be provided.

It is a schematic explanatory drawing which shows the manufacturing method of the thermoplastic resin film which concerns on one Embodiment of this invention.

(Resin composition)
The thermoplastic resin film of the present invention comprises a resin composition, and the resin composition comprises a resin (A) containing a methacrylic acid ester monomer unit and an aromatic vinyl monomer unit;
It contains a resin (B) containing a methacrylic acid ester monomer unit and no aromatic vinyl monomer unit.

[Resin (A)]
Resin (A) which comprises a resin composition is resin containing a methacrylic acid ester monomer unit and an aromatic vinyl monomer unit.

A methacrylic acid ester monomer unit is a monomer unit derived from a methacrylic acid ester monomer. Examples of the methacrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, Examples thereof include C1-C8 alkyl or cycloalkyl ester monomers of methacrylic acid such as cyclohexyl methacrylate. Two or more methacrylate monomers may be used in combination. Especially, the C1-C7 alkylester monomer of methacrylic acid is preferable, and methyl methacrylate is more preferable at the heat resistance and transparency point of resin (A).

The content of the methacrylic acid ester monomer unit in the resin (A) is preferably 5% by weight to 40% by weight with respect to 100% by weight of all the monomer units constituting the resin (A). From the viewpoint of the transparency of the resin (A), 5% by weight to 35% by weight is more preferable, 10% by weight to 30% by weight is further preferable, and 15% by weight to 25% by weight is particularly preferable.

（式中、Ｒ^１およびＲ^２は、それぞれ独立して、水素原子、ハロゲン原子、ヒドロキシル基、アルコキシ基、ニトロ基または炭素数１〜１２のアルキル基を表わし、ｎは１〜３の整数を表わす。）
で表される単量体単位が挙げられる。 The aromatic vinyl monomer unit is a monomer unit derived from an aromatic vinyl monomer. In the present specification, the aromatic vinyl monomer means a monomer having a structure in which an unsubstituted vinyl group or a substituted vinyl group is bonded to an aromatic ring. Specific examples of the aromatic vinyl monomer unit include the following formula (1):

(Wherein R ¹ and R ² each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxy group, a nitro group or an alkyl group having 1 to 12 carbon atoms, and n represents an integer of 1 to 3) Represents.)
The monomer unit represented by these is mentioned.

As a halogen atom in Formula (1), a fluorine atom, a chlorine atom, and a bromine atom are mentioned. Examples of the alkyl group having 1 to 12 carbon atoms include linear or branched groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, and 2-ethylhexyl group. A branched alkyl group may be mentioned, an alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group is more preferable.

R ¹ is preferably a hydrogen atom or a methyl group. R ² is preferably a hydrogen atom, and n is preferably 1. R ¹ and R ² may be the same as or different from each other.

Examples of the aromatic vinyl monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2-methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, α-methylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro- α-methylstyrene, 4-bromo-α-methylstyrene, 4-tert-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2-chlorostyrene, 3- Chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, 2- Lomostyrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, β-bromostyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like. preferable. Two or more aromatic vinyl monomers may be used in combination.

The content of the aromatic vinyl monomer unit in the resin (A) is 50% by weight or more with respect to 100% by weight of all the monomer units constituting the resin (A). Since the thermoplastic resin film of the present invention contains such a resin (A), it becomes a thermoplastic resin film excellent in dimensional stability in a high temperature environment. The content of the aromatic vinyl monomer unit in the resin (A) is preferably from 50% by weight to the transparency, heat resistance and dimensional stability in a high temperature environment of the thermoplastic resin film of the present invention. 80% by weight, more preferably 55% by weight to 75% by weight, and still more preferably 60% by weight to 70% by weight.

（式中、Ｒ^３およびＲ^４は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１〜１２のアルキル基またはフェニル基を表わす。）
で表される環状酸無水物単量体単位が挙げられる。 The resin (A) preferably contains a cyclic acid anhydride monomer unit. The cyclic acid anhydride monomer unit is derived from a cyclic acid anhydride monomer. As a specific example of the cyclic acid anhydride monomer unit, the following formula (2)

(In the formula, R ³ and R ⁴ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or a phenyl group.)
The cyclic acid anhydride monomer unit represented by these is mentioned.

As a halogen atom and a C1-C12 alkyl group in Formula (2), the thing similar to what was mentioned above in Formula (1), respectively is mentioned.

R ³ and R ⁴ are preferably a hydrogen atom. R ³ and R ⁴ may be the same as or different from each other.

Examples of cyclic acid anhydride monomers include maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, dichloromaleic anhydride, bromomaleic anhydride, dibromomaleic anhydride, phenylmaleic anhydride and diphenylmaleic anhydride. Maleic anhydride is preferred. Two or more cyclic acid anhydride monomers may be used in combination.

The content ratio of the cyclic acid anhydride monomer unit in the resin (A) is 100% by weight of all the monomer units constituting the resin (A), and the transparency and heat resistance of the resin (A). In this respect, it is preferably 5 to 30% by weight, more preferably 10 to 25% by weight, and particularly preferably 10 to 20% by weight.

As long as the effect of the present invention is not impaired, the resin (A) is a monomer unit other than those described above, that is, a methacrylic acid ester monomer unit, an aromatic vinyl monomer unit, and a cyclic acid anhydride monomer unit. Monomer units may be included. The monomer unit other than the monomer unit described above is a monomer unit derived from a monomer that can be copolymerized with at least one of the monomers derived from the monomer unit described above. The monomer unit is preferably a monomer unit derived from a monomer derived from a monomer copolymerizable with all of the monomers derived from the above-described three types of monomer units. The content ratio of monomer units other than the monomer units described above is preferably 50% by weight or less, more preferably 100% by weight or less, more preferably 100% by weight of all monomer units constituting the resin (A). , 30% by weight or less, and more preferably 10% by weight or less.

The weight average molecular weight of the resin (A) is preferably 90,000 to 300,000 from the viewpoint of the handleability of the film during molding of the thermoplastic resin film of the present invention or when stretching the thermoplastic resin film of the present invention. More preferably, it is 100,000-250,000, More preferably, it is 110,000-200,000.

The resin (A) can be produced by polymerizing each monomer by a known method such as a bulk polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a casting polymerization method, By changing the amount of the monomer used, the content of each monomer unit in the resin (A) can be adjusted.

[Resin (B)]
The resin (B) constituting the resin composition is a resin containing a methacrylic acid ester monomer unit and no aromatic vinyl monomer unit.

Examples of the methacrylic acid ester monomer for deriving the methacrylic acid ester monomer unit include the same as those described above for the resin (A), and methyl methacrylate is preferred. Two or more methacrylate ester monomer units may be included.

It is preferable that the methacrylic acid ester monomer unit in the resin (A) and the methacrylic acid ester monomer unit in the resin (B) are the same.

The content ratio of the methacrylic acid ester monomer unit in the resin (B) is 50% by weight or more, preferably 70% by weight with respect to 100% by weight of all the monomer units constituting the resin (B). % Or more, more preferably 90% by weight or more, and still more preferably 95% by weight.

The resin (B) is a resin that does not contain an aromatic vinyl monomer unit, that is, a resin in which the content ratio of the aromatic vinyl monomer unit is 0 (zero) wt%, but the methacrylic acid ester monomer unit. And other monomer units that are not aromatic vinyl monomer units. Examples of other monomers include acrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and the like. Monomer;
Unsubstituted or substituted styrene monomers such as styrene, vinyl toluene, α-methyl styrene, chlorostyrene, bromostyrene and the like;
Unsaturated carboxylic acid monomers such as methacrylic acid and acrylic acid; unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile;
Cyclic acid anhydride monomers such as maleic anhydride;
Examples include cyclic imide monomers such as phenylmaleimide and cyclohexylmaleimide, and acrylate monomers are preferred.

The weight average molecular weight of the resin (B) is preferably 90,000 to 300,000 from the viewpoint of the handleability of the film during molding of the thermoplastic resin film of the present invention or when stretching the thermoplastic resin film of the present invention. More preferably, it is 100,000-250,000, More preferably, it is 110,000-200,000.

Resin (B) is a known method such as a bulk polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a casting polymerization method, etc. for a methacrylic acid ester monomer and other monomers as required. Can be produced by polymerization.

[Thermoplastic film of the present invention]
The thermoplastic resin film of this invention consists of a resin composition containing resin (A) and resin (B).

The thermoplastic resin film of the present invention has a ratio (W _B / W _A ) of the weight (W _B ) of the resin (B) to the content (W _A ) of the methacrylic acid ester monomer unit in the resin ( _A ). When the resin composition is larger than 1, W _B / W _A is larger than 1, so that it becomes a thermoplastic resin film that hardly breaks during stretching and has good handling properties. The ratio (W _B / W _A ) is more preferably 1.5 or more, and usually 30 or less.

The content of the resin (A) and the resin (B) in the resin composition constituting the thermoplastic resin film of the present invention, the resin (A) content of the methacrylic acid ester monomer units in the (W _A) Accordingly, the ratio (W _B / W _A ) is appropriately selected so as to satisfy the above ratio. For example, the content of the resin (A) relative to 100 parts by weight of the total amount of the resin (A) and the resin (B) is usually 10 Parts by weight to 80 parts by weight, preferably 20 parts by weight to 75 parts by weight, and the content of the resin (B) is usually 20 parts by weight to 90 parts by weight, preferably 25 parts by weight to 80 parts by weight.

The resin composition may contain elastic rubber particles in addition to the resin (A) and the resin (B). As the rubber elastic particles, commercially available rubber elastic particles can be used. For example, “Paraloid ^™ ” EXL series sold by Dow Chemical Company, “Kane Ace (registered trademark)” sold by Kaneka Corporation. ) ”Series,“ Metablene ”C series, E series, W series, S series, etc. sold by Mitsubishi Rayon Co., Ltd.

The particle diameter of the rubber elastic particles is, for example, 50 nm to 0.8 μm, preferably 0.1 μm to 0.5 μm. When the rubber elastic particles have a particle diameter of less than 50 nm, the fluidity tends to decrease when the resin composition is processed into a film. When the particle diameter exceeds 0.8 μm, the internal haze of the thermoplastic resin composition tends to increase. The particle diameter of rubber elastic particles can be measured as a number average molecular weight by observation with an electron microscope.

The content of the elastic rubber particles is usually 2 to 50 parts by weight, preferably 5 to 35 parts by weight, with respect to 100 parts by weight of the total amount of the resin (A) and the resin (B).

In the thermoplastic resin film of the present invention, the resin (A) and the resin (B) are mixed with W _B / W _A according to the content (W _A ) of the methacrylic acid ester monomer unit in the resin (A). Can be produced by forming the resin composition into a film by a melt extrusion molding method, for example, as shown in FIG. Moreover, it can also manufacture by the method of forming a resin composition into a film by the solution casting film forming method, the hot press method, etc. Especially, it is preferable to manufacture a thermoplastic resin film by a melt extrusion molding method.

The method for producing the thermoplastic resin film of the present invention by the melt extrusion molding method will be further described below. The resin (A) and the resin (B) are blended so that W _B / W _A is greater than 1, and if necessary, other components described later are added to obtain a resin composition, and then the obtained resin The composition is melt-kneaded by a single-screw or twin-screw extruder, and the molten resin is continuously extruded from a T-die into a film shape. Further, the extruded film-shaped molten resin is cooled with a pair of smooth surfaces. A long thermoplastic resin in an unstretched state by being sandwiched between rolls (first cooling roll and second cooling roll), further wound around a third cooling roll as necessary, and molded and cooled. A film can be produced. The method of blending the resin (A), the resin (B) and other components is not limited, and may be blended by a known method, a super mixer or a banbury mixer may be used, or a single or twin screw extruder. Melt kneading may be performed, or these may be combined. Moreover, a 1st cooling roll, a 2nd cooling roll, and a 3rd cooling roll may be comprised with a metal roll or a metal elastic roll, and may be comprised combining a metal roll and a metal elastic roll.

When the thermoplastic resin film of the present invention is a thermoplastic resin film containing the resin (A) and the resin (B) and further containing rubber elastic particles, the resin (A), the resin (B) and After the rubber elastic particles are blended to obtain a thermoplastic resin composition, it can be produced by forming a film by the melt extrusion molding method as described above. Moreover, it can also manufacture by the method of film-forming by the solution casting film-forming method, the hot press method, etc. A melt extrusion molding method is preferred.

When the thermoplastic resin film of the present invention is a thermoplastic resin film containing the resin (A) and the resin (B) and further containing rubber elastic particles, the thermoplastic resin of the present invention is obtained by a melt extrusion molding method. The method for producing a resin film will be further described below. The resin (A), the resin (B), and rubber elastic single particles are blended so that W _B / W _A is greater than 1, and if necessary, other components described later are added to obtain a resin composition, The obtained resin composition is melt-kneaded with a uniaxial or biaxial extruder, and the molten resin is continuously extruded into a film form from a T-die. It is long in an unstretched state by being sandwiched between cooling rolls (first cooling roll and second cooling roll) having a smooth surface, wound around a third cooling roll as necessary, and molded and cooled. A thermoplastic resin film can be produced. The blending method of the resin (A), the resin (B), the rubber elastic particles and other components is not limited, and may be blended by a known method, and a super mixer or a Banbury mixer may be used. It may be melt kneaded with a twin screw extruder or a combination thereof. Moreover, a 1st cooling roll, a 2nd cooling roll, and a 3rd cooling roll may be comprised with a metal roll or a metal elastic roll, and may be comprised combining a metal roll and a metal elastic roll.

The thermoplastic resin film of the present invention may contain components other than the resin (A) and the resin (B). Other components include light diffusing agents, matting agents, dyes, light stabilizers, UV absorbers, antioxidants, mold release agents, flame retardants, antistatic agents, and other resins (resin (A) and resin ( Resin other than B).

The thermoplastic film of the present invention preferably contains an ultraviolet absorber, more preferably an ultraviolet absorber having an absorption maximum at a wavelength of 200 to 320 nm (hereinafter referred to as ultraviolet absorber X), and an absorption at a wavelength of 320 to 400 nm. An ultraviolet absorber having a maximum (hereinafter referred to as ultraviolet absorber Y) is included.

Examples of the ultraviolet absorber X include a triazine ultraviolet absorber having an absorption maximum at a wavelength of 200 to 320 nm, a benzophenone ultraviolet absorber having an absorption maximum at a wavelength of 200 to 320 nm, and a benzotriazole ultraviolet having an absorption maximum at a wavelength of 200 to 320 nm. Examples thereof include an absorbent, a benzoate ultraviolet absorber having an absorption maximum at a wavelength of 200 to 320 nm, and a cyanoacrylate ultraviolet absorber having an absorption maximum at a wavelength of 200 to 320 nm.

Examples of the ultraviolet absorber X include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-). Ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-) Butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,6-diphenyl-4- (2- Hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, , 4-Diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3 , 5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-N-octyloxyphenyl) -1,3,5-triazine, 2- (4,6- Diphenyl-1,3,5-triazin-2-yl) -5- (2- (2-ethylhexanoyloxy) ethoxy) phenol,
2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 2, 2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone 2- (2-hydroxy-3,5-di -Tert-pentylphenyl) benzotriazole,
2,4-di-tert-butylphenyl 3 ′, 5′-di-tert-butyl-4′-hydroxybenzoate, 2,6-di-tert-butylphenyl 3 ′, 5′-di-tert-butyl- 4′-hydroxybenzoate, n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate,
Examples include 2-ethylhexyl 2-cyano-3,3-diphenyl acrylate and ethyl 2-cyano-3- (3,4-methylenedioxyphenyl) acrylate.

The ultraviolet absorber Y includes a triazine ultraviolet absorber having an absorption maximum at a wavelength of 320 to 400 nm, a benzophenone ultraviolet absorber having an absorption maximum at a wavelength of 320 to 400 nm, and a benzotriazole ultraviolet having an absorption maximum at a wavelength of 320 to 400 nm. An absorbent is mentioned.

Examples of the ultraviolet absorber Y include 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine,
2,2′-dihydroxy-4-methoxybenzophenone,
2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3-tert-butyl-5) -Methylphenyl) benzotriazole,
2- (2-hydroxy-3,5-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3- (3,4,5,6-tetrahydrophthalimidomethyl) -5 Methylphenyl) benzotriazole, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2-hydroxy -3-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3,5-di-tert-amylphenyl) -5-chlorobenzotriazole, and the like.

Two or more ultraviolet absorbers X may be used in combination, or two or more ultraviolet absorbers Y may be used in combination. The ultraviolet absorber X and the ultraviolet absorber Y having a similar structure may be used in combination, or the ultraviolet absorber X and the ultraviolet absorber Y having no similar structure may be used in combination. Ultraviolet absorbers that are easy to evaporate during melt extrusion molding and melt extrusion molding in that a thermoplastic resin film with excellent UV absorption ability is obtained with little contamination around the molding machine due to transpiration during film molding. It is preferable to use in combination with an ultraviolet absorber that is difficult to evaporate.

The ultraviolet absorbers X and Y each preferably have a molecular weight of 500 to 1000, and more preferably 550 to 700. If the average molecular weights of the UV absorbers X and Y are too small, they tend to evaporate during the formation of the polarizer protective film, and if the molecular weight is too large, the compatibility with the thermoplastic resin tends to decrease.

The ultraviolet absorbers X and Y each preferably have a molar extinction coefficient at the absorption maximum wavelength of 10 L / mol · cm or more, and more preferably 15 L / mol · cm or more. When the molar extinction coefficient at the wavelength of the absorption maximum of the ultraviolet absorbers X and Y is within the above predetermined range, the ultraviolet absorbing ability of the polarizer protective film becomes more excellent. The content of the ultraviolet absorber can be reduced.

A commercially available ultraviolet absorber may be used. As a commercially available triazine-based ultraviolet absorber, for example, “Kemisorb 102” (2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-N-octyloxyphenyl) manufactured by Chemipro Kasei Co., Ltd.) -1,3,5-triazine), “ADEKA STAB LAF70” (2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine, manufactured by ADEKA Corporation ), “Adekastab LA46” (2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (2- (2-ethylhexanoyloxy) ethoxy) phenol), and BASF “Tinuvin 1577” (2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3, manufactured by Japan Co., Ltd. 5-triazine).
As a commercially available benzotriazole ultraviolet absorber, for example, “ADEKA STAB LA31” (2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H— Benzotriazol-2-yl) phenol), “Kemisorb 279” (2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole) manufactured by Chemipro Kasei Co., Ltd. 2-yl) phenol) and “Sumisorb 200” (2- (2-hydroxy-5-methylphenyl) benzotriazole) manufactured by Sumika Chemtex Co., Ltd., and the like.

The glass transition temperature of the resin composition containing the resin (A) and the resin (B) is preferably 100 ° C. or higher, more preferably 115 ° C. or higher, and usually 180 ° C. or lower. The glass transition temperature means an extrapolated glass transition intermediate temperature obtained at a heating rate of 10 ° C./min by differential scanning calorimetry according to JIS K7121: 1987. When the glass transition temperature of the resin composition is lower than 100 ° C., when the thermoplastic film is used as a polarizer protective film, it becomes difficult to suppress the contraction of the polarizer in a high temperature environment, and the polarizing plate is deformed or polarized. The child protective film may be easily peeled off from the polarizer.

The melt mass flow rate (MFR) at 230 ° C. and 37.3 N of the resin composition is preferably 0.8 g / 10 min to 10 g / 10 min, more preferably 0.9 g / 10 min to 8 g / 10 min. More preferably, it is 1.0 g / 10 min to 6 g / 10 min. If the MFR is larger than this range, the stability of the discharge amount of the molten resin composition may be impaired when a thermoplastic resin film is produced by melt extrusion molding. If the MFR is smaller than this range, when a thermoplastic resin film is produced by melt extrusion molding, the molten resin composition does not spread uniformly in the T-die, and the thickness accuracy of the thermoplastic resin film decreases. Sometimes. MFR can be measured according to JIS K7210 under the conditions of a measurement temperature of 230 ° C. and a load of 37.3 N.

Further, when a resin (A) further containing a cyclic acid anhydride monomer unit is used, the MFR is 1.2 g / 10 min or more. It is preferable at the point which can suppress generation | occurrence | production of the bubble resulting from a unit.

The thickness of the thermoplastic resin film of the present invention is preferably 10 μm to 1000 μm, more preferably 20 μm to 500 μm, and still more preferably 20 μm to 300 μm.

The thermoplastic resin film of the present invention has a light transmittance at a wavelength of 260 nm converted to a film thickness of 40 μm, preferably 2% or less, and a light transmittance at a wavelength of 380 nm converted to a film thickness of 40 μm. , Preferably 5% or less.

The thermoplastic resin film of the present invention is preferably a film having a single layer structure, but may be a film having a multilayer structure of two or more layers as long as the effects of the present invention are not impaired. When the thermoplastic resin film is a multilayer film, each layer may be formed from a resin composition having the same composition, or may be formed from resin compositions having different compositions. Resin compositions with different compositions are those containing different types of resin, the same type of resin but different contents of each resin, the same type and content of resin, but other components In any case, including those with different.

[The stretched film of the present invention]
The stretched film of the present invention is a film formed by stretching the thermoplastic resin film of the present invention. Similar to the thermoplastic resin film of the present invention, the stretched film of the present invention is excellent in heat resistance, hardly shrinks in a high temperature environment, and is also excellent in mechanical strength because it is stretched.

Examples of the method for stretching the thermoplastic resin film of the present invention include a uniaxial stretching method and a biaxial stretching method. Of these, the biaxial stretching method is preferred. Examples of the biaxial stretching method include a sequential biaxial stretching method and a simultaneous biaxial stretching method. Examples of the stretching direction include a machine flow direction of the thermoplastic resin film, and a direction orthogonal to the machine flow direction and a direction oblique to the machine flow direction are also included. The draw ratio is preferably 1.1 to 3 times. In this specification, the machine flow direction is defined as the longitudinal direction, the stretching in the longitudinal direction is defined as the longitudinal stretching, the direction orthogonal to the machine flow direction is defined as the transverse direction, and the stretching in the transverse direction is defined as the transverse stretching. Further, the machine flow direction refers to a direction in which a resin composition is conveyed while being formed from a molten state to a film when a long thermoplastic resin film is produced by melt extrusion.

The stretched film of the present invention may be subjected to a surface treatment, and examples of the surface treatment include a hard coat treatment, an antiglare treatment and an antifouling treatment.

[Polarizer protective film]
Both the thermoplastic resin film of the present invention and the stretched film of the present invention are suitable as a polarizer protective film. The polarizer protective film is a film used for protecting the polarizer by being disposed on one surface of the polarizer. In addition to the polarizer protective film, the thermoplastic resin film of the present invention and the stretched film of the present invention are architectural daylighting members such as windows and carport roofing materials, vehicle daylighting members such as car windows, and agricultural daylighting members such as greenhouses. It may be laminated to display members such as lighting members, front filters, etc., and as a decorative film, a housing for home appliances, a vehicle interior member, a building material for interior, wallpaper, a decorative board, a front door, a window frame, You may laminate on a baseboard.

〔Polarizer〕
The polarizing plate of the present invention is a polarizing plate in which the polarizer protective film of the present invention is disposed on at least one surface of the polarizer. It is preferable that the polarizer protective film and the polarizer are bonded. Examples of the polarizer include known polarizers. The thickness of the polarizer is usually 5 μm to 40 μm.

When a polarizer protective film is disposed on one surface of the polarizer, a transparent resin film may be disposed on the other surface. It is preferable that the transparent resin film and the polarizer are bonded.
Examples of the transparent resin film include a triacetyl cellulose film, a polycarbonate film, a polyethylene terephthalate film, an acrylic resin film, a laminated film of an acrylic resin and a polycarbonate resin, and an olefin resin film.

The polarizer protective film and the polarizer of the present invention are preferably bonded with an adhesive. Prior to bonding, at least one of the bonding surfaces is preferably subjected to corona discharge treatment, plasma irradiation treatment, electron beam irradiation treatment, or other surface activation treatment. The polarizer protective film of the present invention was bonded to the polarizer with an adhesive as compared with a polarizer protective film comprising a resin containing a methacrylic acid ester monomer unit and no aromatic vinyl monomer unit. Sometimes it has excellent adhesive strength.

The adhesive can be arbitrarily selected and used from those that exhibit adhesive strength to each member. Typically, a water-based adhesive, that is, an active energy ray-curable adhesive containing an adhesive component dissolved in water or an adhesive component dispersed in water, or a component that cures upon irradiation with active energy rays is used. Can be mentioned. Among these, an active energy ray-curable adhesive is preferable from the viewpoint of productivity.

As the water-based adhesive, a composition using a polyvinyl alcohol resin or a urethane resin as a main component is preferable. When a polyvinyl alcohol-based resin is used as the main component of the aqueous adhesive, the polyvinyl alcohol-based resin includes partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol. Examples thereof include modified polyvinyl alcohol resins such as group-modified polyvinyl alcohol and amino group-modified polyvinyl alcohol. When using a polyvinyl alcohol-based resin as the adhesive component, the adhesive is often prepared as an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol resin in the adhesive aqueous solution is preferably 1 part by weight to 10 parts by weight, and more preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water.

In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to the water-based adhesive having a polyvinyl alcohol resin as a main component. Examples of water-soluble epoxy resins include polyamide polyamines obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a polycarboxylic acid such as adipic acid and epichlorohydrin. An epoxy resin etc. are mentioned. As the polyamide polyamine epoxy resin, a commercially available product may be used. For example, “Smilease Resin 6” manufactured by Taoka Chemical Co., Ltd.
50 ”and“ SUMIREZ RESIN 675 ”,“ WS-525 ”manufactured by Seiko PMC Co., Ltd., and the like. The addition amount of the curable component or the crosslinking agent is preferably 1 to 100 parts by weight, and more preferably 1 to 50 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. When the addition amount is small, the effect of improving the adhesiveness is reduced, while when the addition amount is large, the adhesive layer may become brittle.

When a urethane resin is used as the main component of the aqueous adhesive, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group can be given as an example of a suitable adhesive composition. The polyester ionomer type urethane resin here is a urethane resin having a polyester skeleton, and a small amount of ionic component (hydrophilic component) therein.
Is introduced. An ionomer type urethane resin is directly emulsified in water without using an emulsifier and becomes an emulsion, so that it is preferable as an aqueous adhesive.

In the case of using an activated energy ray-curable adhesive, a component that is cured by irradiation of an active energy ray constituting the adhesive (hereinafter, simply referred to as “curable component”) includes an epoxy compound, an okitacene compound, and an acrylic type. Compound etc. are mentioned. When a cationically polymerizable compound such as an epoxy compound or an okitacene compound is used, a cationic polymerization initiator is blended. Further, when a radical polymerizable compound such as an acrylic compound is used, a radical polymerization initiator is blended. Among these, an adhesive having an epoxy compound as one of the curable components is preferable, and an adhesive having an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocycle as one of the curable components is more preferable. Moreover, you may use an oxetane compound together.

As the epoxy compound, commercially available products may be used. For example, “Epicoat” series manufactured by Mitsubishi Chemical Corporation, “Epicron” series manufactured by DIC Corporation, “Epototo” series manufactured by Nippon Steel & Sumitomo Metal Corporation, ADEKA Corporation “Adeka Resin” series manufactured by Nagase ChemteX Corporation, “Denacol” series manufactured by Nagase ChemteX Corporation, “Dow Epoxy” series manufactured by Dow Chemical Co., “Tepic” manufactured by Nissan Chemical Industries, Ltd., and the like.
As the alicyclic epoxy compound in which the epoxy group is directly bonded to the saturated carbocyclic ring, a commercially available product may be used. For example, “Celoxide” series and “Cyclomer” series manufactured by Daicel Chemical Industries, Ltd., Dow -The “Syracure” series manufactured by Chemical Company, etc.
As the oxetane compound, commercially available products may be used, and examples thereof include “Aron Oxetane” series manufactured by Toagosei Co., Ltd., “ETERRNACOLL” series manufactured by Ube Industries, Ltd., and the like.

As the cationic polymerization initiator, commercially available products may be used. For example, “Kayacure” series manufactured by Nippon Kayaku Co., Ltd., “Syracure” series manufactured by Dow Chemical Co., Ltd., photoacid generator manufactured by San Apro Co., Ltd. “CPI” series, photo acid generators “TAZ”, “BBI” and “DTS” manufactured by Midori Chemical Co., Ltd., “Adekaoptomer” series manufactured by ADEKA Co., Ltd., “RHODORSIL” manufactured by Rhodia Series.

The active energy ray-curable adhesive can contain a photosensitizer as necessary. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured product layer can be further improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, anthracene compounds, halogen compounds, and photoreducible dyes.

Various additives can be blended with the active energy ray-curable adhesive within a range that does not impair the adhesiveness. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent. Furthermore, a curable component that cures by a reaction mechanism different from cationic polymerization can be blended within a range that does not impair the adhesion.

The active energy ray-curable adhesive may have the same composition or a different composition, but it is preferable that irradiation of active energy rays for curing both is performed simultaneously.

Examples of the active energy rays include X-rays, ultraviolet rays, and visible rays. Among these, ultraviolet rays are preferable from the viewpoints of ease of use, ease of preparation of the active energy ray-curable adhesive, stability, and curing performance. As an ultraviolet light source, for example, a low-pressure mercury lamp,
Examples include medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

An active energy ray-curable adhesive is applied to the polarizer or the polarizer protective film of the present invention to form a coating film, and the polarizer and the polarizer protective film of the present invention are overlapped through the formed coating film. By irradiating the active energy ray, the active energy ray-curable resin is cured, and the polarizer and the protective film of the present invention are bonded together to obtain the polarizing plate of the present invention.

1-50 micrometers is preferable and, as for the thickness of the adhesive bond layer obtained using an active energy ray hardening adhesive, 1-10 micrometers is more preferable. The thickness of an adhesive bond layer can be adjusted with the thickness of the coating film formed in a polarizer or the polarizer protective film of this invention.

The polarizing plate of the present invention can be bonded to a liquid crystal cell to form a liquid crystal panel used for a liquid crystal display device. It is preferable that the polarizing plate and the liquid crystal cell are bonded via an adhesive layer using an adhesive. This pressure-sensitive adhesive layer is generally formed of an acrylic pressure-sensitive adhesive having an acrylic resin mainly composed of an acrylate ester and an acrylic resin copolymerized with a functional group-containing acrylic monomer. A liquid crystal panel in which a polarizing plate is bonded to a liquid crystal cell via an adhesive layer can be used for a liquid crystal display device.

In the polarizing plate of the present invention, since the polarizer protective film is made of the thermoplastic resin of the present invention or the stretched film of the present invention, it has excellent heat resistance and can suppress the contraction of the polarizer even in a high temperature environment.

Hereinafter, the present invention will be described specifically by way of examples.

The extrusion apparatus used in Examples and Comparative Examples is the apparatus shown in FIG. 1, and the configuration thereof is as follows.
Extruder: Screw diameter 65 mm, single screw, vented extruder (manufactured by Toshiba Machine Co., Ltd.).
T-die: Multi-manifold die (manufactured by Hitachi Zosen) with a width of 800 mm and a lip interval of 1 mm
1st cooling roll: metal elastic roll 2nd cooling roll: metal roll 3rd cooling roll: metal roll

The metal elastic roll has a 2 mm thick stainless steel thin film with one side mirrored so as to cover the outer periphery of the shaft roll made of stainless steel so that the mirror finished surface is the outer surface of the roll. It is a metal elastic roll having an outer diameter of 250 mm, in which a fluid made of heat transfer oil is sealed between the metal thin film. The metal roll is a spiral roll made of stainless steel having a mirror-finished surface and having an outer diameter of 250 mm.

[Thermoplastic resin]
The thermoplastic resins used in Examples 1 to 6 and Comparative Examples 1 to 5 are shown below. The weight average molecular weight Mw and the number average molecular weight Mn of each resin were determined by gel permeation chromatography (GPC) measurement. In addition, the weight average molecular weight Mw and the number average molecular weight Mn of resin A1, resin A2, and resin C were calculated | required in polystyrene conversion. The weight average molecular weight Mw and the number average molecular weight Mn of the resin B1 were determined in terms of polymethyl methacrylate.

Resin A1: A resin comprising a methyl methacrylate monomer unit, a styrene monomer unit and a maleic anhydride monomer unit, prepared by copolymerizing methyl methacrylate, styrene and maleic anhydride Using.
The content of the methyl methacrylate monomer unit is 20% by weight and the content of the styrene monomer unit is 65% by weight with respect to a total of 100% by weight of all the monomer units constituting the resin A1, The content ratio of maleic anhydride monomer units was 15% by weight.
Moreover, the weight average molecular weight (Mw) of resin A1 was 150,000, the number average molecular weight (Mn) was 68,000, and Mw / Mn was 2.2.

Resin A2: a resin comprising a methyl methacrylate monomer unit, a styrene monomer unit and a maleic anhydride monomer unit, prepared by copolymerizing methyl methacrylate, styrene and maleic anhydride Using.
The content ratio of the methyl methacrylate monomer unit is 26% by weight and the content ratio of the styrene monomer unit is 57% by weight with respect to a total of 100% by weight of all the monomer units constituting the resin A2. The content ratio of the maleic anhydride monomer unit was 17% by weight.
The weight average molecular weight (Mw) of the resin A2 was 150,000, the number average molecular weight (Mn) was 66,000, and Mw / Mn was 2.3.

Resin C: a resin comprising a methyl methacrylate monomer unit, a styrene monomer unit and a maleic anhydride monomer unit, prepared by copolymerizing methyl methacrylate, styrene and maleic anhydride Using.
The content ratio of the methyl methacrylate monomer unit is 39% by weight and the content ratio of the styrene monomer unit is 47% by weight with respect to a total of 100% by weight of all the monomer units constituting the resin C. The content ratio of the maleic anhydride monomer unit was 14% by weight.
Resin C had a weight average molecular weight (Mw) of 220,000, a number average molecular weight (Mn) of 83,000, and Mw / Mn of 2.6.

Resin B1: A resin composed of a methyl methacrylate monomer unit and a methyl acrylate monomer unit, wherein methyl methacrylate and methyl acrylate are combined in a total of 100% by weight of all the monomer units constituting the resin B1. And blending so that the content ratio of the methyl methacrylate monomer unit is 97% by weight and the content ratio of the methyl acrylate monomer unit is 3% by weight, and after polymerization, the absorption maximum is 300 nm and 342 nm. An ultraviolet absorber “Sumisorb 200” (manufactured by Sumika Chemtex Co., Ltd.) having a concentration of 120 ppm was used, and the obtained resin composition was melt kneaded with a twin screw extruder.
The weight average molecular weight (Mw) of the resin B1 was 160,000, the number average molecular weight (Mn) was 85,000, and Mw / Mn was 1.9.

[Ultraviolet absorber]
The following X1, Y1, and Y2 are used as the UV absorber, and the UV absorber X1: UV absorber Y1: UV absorber Y2 (weight ratio) is 0.7: 0.6: 1.2. Used in combination.
UV absorber X1: UV absorber “Kemisorb 102” manufactured by Chemipro Kasei Co., Ltd. (absorption maximum: wavelength 280 nm, molar extinction coefficient: 68.3 L / mol · cm, weight average molecular weight: 508.9, triazine-based UV absorber)
UV absorber Y1: UV absorber “LAF70” manufactured by ADEKA Corporation (absorption maximum: wavelength 356 nm, molar extinction coefficient: 65.7 L / mol · cm, weight average molecular weight: 699.9, triazine UV absorber)
UV absorber Y2: UV absorber “ADEKA STAB LA31” manufactured by ADEKA Corporation (absorption maximum: wavelength 350 nm, molar extinction coefficient: 18.0 L / mol · cm, weight average molecular weight: 658, benzotriazole UV absorber)

Examples 1-6 and Comparative Examples 1-5
[Production of thermoplastic resin film]
The extruder, the T die, and the first to third cooling rolls were arranged as shown in FIG. Next, the resin composition obtained by mixing the resin A1, the resin A2 or the resin C, the resin B1 and the ultraviolet absorber at the ratio shown in Table 1 was melt-kneaded in an extruder, and each of them was T at a set temperature of 260 ° C. Supplied to the die.
A film-shaped molten resin extruded from a T-die is sandwiched between a first cooling roll and a second cooling roll arranged opposite to each other, wound around a third cooling roll, molded and cooled, and a thermoplastic resin film having a thickness of 120 μm. Got.
In addition, the surface temperature of the 1st cooling roll was 80 degreeC, the surface temperature of the 2nd cooling roll was 80 degreeC, and the surface temperature of the 3rd cooling roll was 100 degreeC. These temperatures are values obtained by actually measuring the surface temperature of each cooling roll.
The amount of resin A2, resin B1 and ultraviolet absorber used in 100 parts by weight of resin A2 and resin B1 in Example 6 is approximately 25 parts by weight of resin A2 and the amount of resin B1 used. About 75 parts by weight, and the amount of UV absorber used is about 2.5 parts by weight.

The MFR (measurement temperature 230 ° C., load 37.3 N) of each resin composition was measured according to JIS K7210. Moreover, the glass transition temperature of each resin composition was measured. The obtained results are shown in Table 2.

In order to evaluate the impact resistance of each of the obtained thermoplastic resin films, Charpy impact strength was measured by the following method, and in order to evaluate surface hardness, pencil hardness was measured by the following method. The results are shown in Table 3.
<Charpy impact strength>
According to JIS K7111-1, the obtained thermoplastic resin film was cut into a width of 10 mm and measured.
<Pencil hardness>
It measured according to JIS K5600.

[Production of stretched film]
The obtained thermoplastic resin films were each biaxially stretched to produce stretched films. First, each thermoplastic resin film was longitudinally stretched between two pairs of nip rolls provided before and after a hot-air circulating furnace. The furnace used was a furnace capable of setting the temperature by dividing it into four zones with an interval of 1 m. The first zone on the entrance side of the furnace is set to room temperature, the next second zone is set to the same temperature as the glass transition temperature (Tg) of the resin composition used for the production of the thermoplastic resin film, and the next third zone. And the fourth zone on the outlet side were set to temperatures 10 ° C. higher than Tg, respectively. By making the speed of the film passing through the nip roll on the inlet side 2 mm / min and the speed of the film passing through the nip roll on the outlet side 4.4 mm / min, the longitudinal stretch ratio is 2.2 times longer. A longitudinally stretched film was prepared.
Next, the produced longitudinally stretched film is cut so that the length in the longitudinal direction is 1 m to obtain a longitudinally stretched film having a length in the longitudinal direction of 1 m, and the length in the longitudinal direction is 1 m. The stretched film was introduced into a tenter transverse stretching machine and subjected to transverse stretching. The transverse stretching was performed in a hot air circulation furnace having a length of 4 m, and the furnace temperature was set to a temperature 10 ° C. higher than Tg. The speed passing through the furnace was 1 mm / min, and the draw ratio was 2 times. As described above, a biaxially stretched film having a longitudinal stretching ratio of 2.2 times and a transverse stretching ratio of 2 times was obtained. The thickness of the obtained biaxially stretched film was 40 μm.

<Handling properties>
The handling property at the time of extending | stretching of the thermoplastic film used for preparation of a stretched film was evaluated with the following method.
A longitudinally stretched film obtained by longitudinally stretching a thermoplastic resin film was cut to obtain 10 longitudinally stretched films having a length in the longitudinal direction of 1 m. About the obtained 10 longitudinally stretched films, each was laterally stretched to obtain 10 biaxially stretched films. In this longitudinal stretching and lateral stretching, when the number of films broken by stretching was zero, the handling property was judged to be good and evaluated as ◯, and when one or more films were broken, the handling property was poor. Judged and evaluated as x. The evaluation results are shown in Table 3.

[Production of polarizer]
A polyvinyl alcohol film having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm is immersed in pure water at 30 ° C., and then the weight ratio of iodine / potassium iodide / water is 0.00. It was immersed in an aqueous solution of 02/2/100 at 30 ° C. Then, it further immersed at 56.5 degreeC in the aqueous solution whose weight ratio of potassium iodide / boric acid / water is 12/5/100. The film after immersion was washed with pure water at 8 ° C. and then dried at 65 ° C. to obtain a polarizer in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was performed mainly in the steps of iodine staining and boric acid treatment, the total stretching ratio was 5.3 times, and the thickness of the obtained polarizer was 27 μm.

[Preparation of polarizing plate]
A biaxially stretched film as a protective film was applied to both sides of the resulting polarizer, and each of the bonded surfaces was subjected to corona treatment, and then an ultraviolet curable adhesive ("Aronix" manufactured by Toagosei Co., Ltd.) was applied. And it bonded by the bonding roll. Then, the ultraviolet-ray was irradiated and the said adhesive agent was hardened, and the polarizing plate was obtained. In addition, ultraviolet irradiation was performed so that the integrated light quantity in a wavelength range of 260 nm-320 nm might be 200 mJ / cm < ² >.

<Evaluation of mechanical strength in high temperature environment>
In order to evaluate the mechanical strength of the biaxially stretched film in a high temperature environment, the high temperature tensile elastic modulus at 80 ° C. of the biaxially stretched film was measured by the following method. The higher the value, the higher the strength of suppressing the shrinkage of the polarizing film in a high temperature environment when it is bonded to the polarizer, which is better.
The biaxially stretched film was cut into a rectangle with a longitudinal direction of 120 mm and a lateral direction of 25 mm with the longitudinal direction as the long side, and a tensile test was performed at 80 ° C. at a tensile speed of 5 mm / min in the longitudinal direction with a distance between chucks of 90 mm. . The high temperature tensile modulus was calculated from the slope of the stress-strain curve in the region where the tensile strength was 3 MPa to 6 MPa. The calculated results are shown in Table 3.

<Light transmittance evaluation>
The light transmittance at a wavelength of 260 nm and the light transmittance at a wavelength of 380 nm of the biaxially stretched film were measured using a spectrophotometer U-4100 manufactured by Hitachi High-Tech Fielding Co., Ltd. The results are shown in Table 3.

<Evaluation of shrinkage rate of polarizing plate>
From the produced polarizing plate, the length in the MD direction is 100 mm and the length in the TD direction is MD, where MD is the direction parallel to the stretching direction of the polarizing film, and TD is the direction perpendicular to the stretching direction of the polarizing film. A polarizing plate of 100 mm was cut out. The cut polarizing plate was placed in an oven set at 80 ° C. and held for 250 hours. The polarizing plate was taken out, the length in the MD direction and the length in the TD direction were each measured with a caliper, and the shrinkage in each of the MD direction and the TD direction was calculated according to the following formula. The results are shown in Table 4.
Shrinkage rate (%) = 100 × {100− (length after heating at 80 ° C. (mm))} / 100

<Evaluation of adhesive strength of polarizing plate>
The peel strength between the polarizing film and the protective film in the polarizing plate was evaluated by the method shown below.
The prepared polarizing plate was allowed to stand for 300 hours and then cut into a rectangle having a size of 200 mm × 25 mm. An acrylic pressure-sensitive adhesive layer was provided on the surface of one protective film, and the pressure-sensitive adhesive layer was attached to a glass plate. A cutter blade was inserted between the protective film provided with the pressure-sensitive adhesive layer and the polarizing film, and 30 mm was peeled off from the end in the length direction, and the peeled portion was grasped by a gripping portion of a testing machine. The test piece in this state is gripped and moved in an atmosphere of a temperature of 23 ° C. and a relative humidity of 55% in accordance with JIS K6854-2: 1999 “Adhesive—Peeling adhesive strength test method—Part 2: 180 degree peeling”. A 180 degree peeling test was performed at a speed of 300 mm / min, and an average peeling force over a length of 170 mm excluding 30 mm of the grip portion was obtained. The results are shown in Table 5.

〔Thermoplastic resin〕
The thermoplastic resins used in Examples 7 to 11 and Comparative Examples 6 to 8 are shown below. The weight average molecular weight Mw and the number average molecular weight Mn of each resin were determined by gel permeation chromatography (GPC) measurement. In addition, the weight average molecular weight Mw and the number average molecular weight Mn of the resin A3 and the resin A4 were obtained in terms of polystyrene. The weight average molecular weight Mw and number average molecular weight Mn of the resin B2 were determined in terms of polymethyl methacrylate.

Resin A1: The same resin A1 as used in Examples 1 to 3 was used.

Resin A3: a resin comprising a methyl methacrylate monomer unit, a styrene monomer unit and a maleic anhydride monomer unit, prepared by copolymerizing methyl methacrylate, styrene and maleic anhydride Using.
The content ratio of the methyl methacrylate monomer unit is 21% by weight and the content ratio of the styrene monomer unit is 57% by weight with respect to a total of 100% by weight of all the monomer units constituting the resin A3. The content of maleic anhydride monomer units is 22% by weight.
Resin A3 has a weight average molecular weight (Mw) of 193,000, a number average molecular weight (Mn) of 88,000, and Mw / Mn of 2.2.

Resin A4: a resin comprising a methyl methacrylate monomer unit, a styrene monomer unit and a maleic anhydride monomer unit, prepared by copolymerizing methyl methacrylate, styrene and maleic anhydride Using.
The content ratio of the methyl methacrylate monomer unit is 21% by weight and the content ratio of the styrene monomer unit is 57% by weight with respect to a total of 100% by weight of all the monomer units constituting the resin A4. The content of maleic anhydride monomer units is 22% by weight.
The weight average molecular weight (Mw) of the resin A4 was 127,000, the number average molecular weight (Mn) was 58,000, and Mw / Mn was 2.19.

Resin B1: The same resin B1 as that used in Examples 1 to 6 and Comparative Examples 3 to 5 was used.

Resin B2: A resin comprising a methyl methacrylate monomer unit and a methyl acrylate monomer unit, and methyl methacrylate and methyl acrylate are combined in a total of 100% by weight of all the monomer units constituting the resin B2. And blending so that the content ratio of the methyl methacrylate monomer unit is 99% by weight and the content ratio of the methyl acrylate monomer unit is 1% by weight. After polymerization, the absorption maximum is 300 nm and An ultraviolet absorbent “SUMISOB 200” having a thickness of 342 nm was blended so as to have a concentration of 100 ppm, and the obtained resin composition was melt kneaded with a twin screw extruder.
The weight average molecular weight (Mw) of the resin B2 was 101,000, the number average molecular weight (Mn) was 58,000, and Mw / Mn was 1.8.

[Rubber elastic particles]
As rubber elastic particles, the following rubber 1 and rubber 2 were used.
Rubber 1: “PARALOID ^™ EXL-2678” (butadiene rubber particles, powder form) manufactured by Dow Chemical Japan Co., Ltd. was used. This rubber 1 has a refractive index of 1.516 and a particle diameter of 200 nm.

Rubber 2: Kaneace M732 (butadiene rubber, powder form) manufactured by Kaneka Corporation was used. The refractive index of the rubber 2 is 1.515, and the particle diameter is 130 to 180 nm.

Examples 7-11 and Comparative Examples 6-8
[Production of thermoplastic resin film]
Resin A1, Resin A2, Resin A3, Resin A4, Resin B1, Resin B2, Rubber 1, Rubber 2 and UV absorber were mixed in the ratio shown in Table 6 to obtain a resin composition. As an ultraviolet absorber, only Y2 [Adeka Stab LA31] was used. Similarly to Examples 1-6 and Comparative Examples 1-5, the obtained resin composition was used to obtain a thermoplastic resin film using the extruder, T die, and first to third cooling rolls shown in FIG. At this time, the thickness of the thermoplastic resin film was as shown in Table 8.

Table 7 shows the measurement results of MFR and glass transition temperature of each resin composition, and Table 8 shows the Charpy impact strength of the obtained thermoplastic resin film. In addition, the bendability of the obtained thermoplastic resin film is “○” when the film sample is cut into 10 mm × 50 mm, the long side direction is bent in half, and the film is not broken, and the film is broken. Evaluated as “x”. The results are shown in Table 8.

<Evaluation of mechanical strength in high temperature environment 2>
As a second method for evaluating the mechanical strength of the thermoplastic resin film in a high temperature environment, the high temperature tensile elastic modulus at 80 ° C. of the thermoplastic resin film was measured by the following method.
The thermoplastic resin film was cut into a rectangle of 100 mm in the vertical direction and 25 mm in the horizontal direction with the extrusion direction as the long side, and a tensile test was performed at 80 ° C. at a tensile speed of 1 mm / min in the vertical direction with a distance between chucks of 50 mm. The high temperature tensile modulus was calculated from the slope of the stress-strain curve in the region where the tensile strength was 3 MPa to 6 MPa. The calculated results are shown in Table 8.

<Light transmittance evaluation 2>
As a second method for evaluating the light transmittance of the thermoplastic resin film, the light transmittance at a wavelength of 260 nm and the light transmittance at a wavelength of 380 nm are measured using a spectrophotometer UV-2450 manufactured by Shimadzu Corporation. It was measured. The results are shown in Table 8.

[Production of stretched film]
The thermoplastic resin films obtained in Examples 7 and 8 were biaxially stretched under the same conditions as in Examples 1 to 6 and Comparative Examples 1 to 5, respectively, to produce stretched films. The thickness of the obtained biaxially stretched film was 20 μm. The handling properties of the thermoplastic resin films of Examples 7 and 8 were all good. As a result of measuring the high-temperature tensile elastic modulus of the stretched film after stretching in the same manner as the thermoplastic resin film before stretching, the stretched film of Example 7 was 2090 MPa, and the stretched film of Example 8 was 1869 MPa.

[Production of Polarizer 2]
A polarizer 2 was produced in the same manner as the polarizer 1 except that the thickness of the polyvinyl alcohol film was changed to 60 μm and the total draw ratio was changed to 5.6 times. The thickness of the obtained polarizer 2 was 22 μm.

[Preparation of polarizing plate]
After applying the corona treatment to the bonding surfaces of the thermoplastic resin films of Examples 7 to 11 and Comparative Examples 6 to 8 on one side of the polarizer 2, an ultraviolet curable adhesive ("Aronix" manufactured by Toagosei Co., Ltd.) )) Is applied, and the other surface of the polarizer 2 is a biaxially stretched product of a cycloolefin resin, and a retardation film having a corona treatment preliminarily applied to a bonding surface, an epoxy compound as a main component. Then, another ultraviolet curable adhesive was applied and bonded as a thermoplastic resin film / polarizer / retardation film. Then, the ultraviolet-ray was irradiated and the said adhesive agent was hardened, and the polarizing plate was obtained. In addition, ultraviolet irradiation was performed so that the integrated light quantity in a wavelength range of 260 nm-320 nm might be 200 mJ / cm < ² >.

<Evaluation of shrinkage rate of polarizing plate 2>
In the obtained polarizing plate, the direction parallel to the stretching direction of the polarizing film is MD, and the direction perpendicular to the stretching direction of the polarizing film is TD. A polarizing plate having a length of 100 mm was cut out. The cut out polarizing plate was put into an oven at 80 ° C. and held for 250 hours. The dimensions before and after the oven were measured using a two-dimensional dimension measuring instrument “NEXIV VMR-12072” manufactured by Nikon Corporation. And the value calculated | required by the following formula | equation was made into shrinkage | contraction rate (%). Table 9 shows the measurement results.

この表６において、樹脂Ａ１、樹脂Ａ２、樹脂Ａ３、樹脂Ａ４、樹脂Ｂ１、樹脂Ｂ２、ゴム１、ゴム２および紫外線吸収剤（Ｙ２）の使用量は、「重量部」で示しており、表中では単位を「(部)」と示した。

In Table 6, the amounts used of Resin A1, Resin A2, Resin A3, Resin A4, Resin B1, Resin B2, Rubber 1, Rubber 2 and UV absorber (Y2) are shown in “parts by weight”. The unit was indicated as “(part)”.

Since the thermoplastic resin film of the present invention is excellent in heat resistance, hardly shrinks in a high temperature environment, and is not easily broken by stretching, a stretched film obtained by stretching it is useful as a protective film for a polarizer.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Die 3 Film-form molten resin 4 Cooling unit 5 1st cooling roll 6 2nd cooling roll 7 3rd cooling roll A Thermoplastic resin film

Claims (5)

A resin (A) comprising a methacrylic acid ester monomer unit , an aromatic vinyl monomer unit , and a cyclic acid anhydride monomer unit ;
A thermoplastic resin film comprising a resin composition comprising a resin (B) containing a methacrylate ester monomer unit and not containing an aromatic vinyl monomer unit,
Resin (A) is a resin in which the content of aromatic vinyl monomer units is 50% by weight or more with respect to 100% by weight of all monomer units constituting resin (A),
The resin (B) is a resin in which the content of the methacrylic acid ester monomer unit is 50% by weight or more with respect to 100% by weight of all the monomer units constituting the resin (B),
The content of methacrylic acid ester monomer units in the resin (A) the ratio _(W B / W _A) of the weight _{(W B)} of the resin (B) with respect to _{(W A)} is rather greater than 1,
A thermoplastic resin film having a melt mass flow rate of 1.2 g / 10 min or more of the resin composition . The thermoplastic resin film according to claim 1, wherein the resin composition further contains rubber elastic particles. The stretched film obtained by extending | stretching the thermoplastic resin film in any one of Claims 1-2 . Polarizer protective film made of a stretched film according to the thermoplastic resin film or claim 3 according to any one of claims 1 to 2. The polarizing plate by which the polarizer protective film of Claim 4 is arrange | positioned on the at least one surface of the polarizer.

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