JP2009292961A - Acrylic thermoplastic resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic thermoplastic resin film which is excellent in optical isotropy and transparency and superior in thermal shrinking property for lamination applications. <P>SOLUTION: The acrylic thermoplastic resin film satisfies following (i) to (v): (i) the thermal shrinkage in the MD direction is -0.15 to 0.15% when heated to 80°C; (ii) the thermal shrinkage in the MD direction is ≥1.5% when heated to 120°C; (iii) the thickness is 5-200 μm; (iv) the thickness-direction retardation Rth is -8 to 8 nm; and (v) the in-plane retardation Δnd is ≤8 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acrylic thermoplastic resin film that is industrially useful and excellent in heat resistance and optical isotropy, and particularly excellent in heat shrinkability.

  More specifically, for example, it is useful as a surface protection material for display materials such as flat display panels, interior materials and exterior materials for vehicles, electrical appliances, inner layers and exterior materials for building materials, and various films used for them. In particular, the present invention relates to an acrylic thermoplastic resin film that is useful as a material for a flat display panel such as a polarizer protective film because of its excellent heat resistance, optical isotropy, and heat shrinkability.

  Various polymer resin films, especially acrylic resin, polycarbonate, vinyl chloride, cyclic olefin, and other films are excellent in transparency and surface glossiness, so liquid crystal display sheets or films, optical materials such as light guide plates, and vehicles Used in a wide range of fields such as interior materials and exterior materials, exterior materials for vending machines, electrical appliances, inner layers for building materials and surface skins of exterior materials.

  Among these resin films, particularly with regard to liquid crystal display sheets or films, with the recent increase in accuracy of liquid crystal televisions, higher functionality is also required for optical films used for them. In particular, an acrylic resin film typified by PMMA is excellent in optical properties, and is often studied as an optical film. For example, a film having a glutaric anhydride unit represented by the following structural formula (1) is used. (Patent Documents 1 and 2).

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.)
Such an optical film is rarely used alone, and is usually used in combination with an optical film having other functions. Therefore, the amount of heat received when forming a hard coat layer or an antireflection film. This causes problems such as shrinkage and unstable dimensions. In order to solve such a problem, a method of stretching after obtaining an unstretched film by using a solution casting method or a melt casting method is disclosed (Patent Document 1).

  However, since the film and the coating layer itself used in the normal processing process also have heat shrinkability, the curling and heat shrinkage that occur only by making the heat shrinkage rate close to 0% cannot be completely suppressed. In addition, in the above method, since it is necessary to go through two steps of forming an unstretched sheet once and then applying it to a stretching apparatus in order to control the heat shrinkage rate, a large-scale apparatus is required and the cost is reduced. There is a problem of rising.

  Further, for example, the technique described in Patent Document 3 is disclosed as a method for producing a film having a large heat shrinkage. However, since this method does not allow temperature control, it is difficult to control the thickness unevenness of the optical film. In order to suppress curling, it is not possible to perform a slight heat gain control for each temperature.

  Moreover, in the technique described in Patent Document 4, a guide roll or a drawing roll having a different draw ratio is arranged next to the cooling roll as a manufacturing method for producing a simultaneous biaxially stretched film with good operability. Slight heat gain control cannot be performed for each temperature.

In the technique described in Patent Document 5, humidity curl is suppressed by drawing a cellulose acylate film with a cooling roll in order to obtain an unstretched optical film. Thermal shrinkage cannot be controlled and cannot be applied to amorphous resins.
International Publication No. 2005/105918 Pamphlet JP 2005-314534 A JP 2005-67081 A JP 2001-30352 A JP 2007-2216 A

  An object of the present invention is to provide an acrylic thermoplastic resin film that is excellent in optical isotropy and transparency and excellent in heat shrinkage characteristics in the processing stage in view of the problems of the conventional technology.

The acrylic resin film of the present invention for achieving the above object has the following structures [1] to [3] [1] An acrylic film satisfying the following (i) to (v) Thermoplastic resin film.

(I) Thermal contraction rate in MD direction at 80 ° C. is −0.15 to 0.15%
(Ii) Thermal shrinkage in MD direction when heated at 120 ° C. is 1.5% or more (iii) Thickness is 5 to 200 μm
(Iv) Thickness direction retardation Rth is −8 to 8 nm
(V) The in-plane retardation Δnd is 8 nm or less [2] The acrylic according to [1], including an acrylic resin (A) containing a glutaric anhydride unit represented by the following structural formula (1) -Based thermoplastic resin film.

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.)
[3] The acrylic thermoplastic resin film according to the above [1] or [2], wherein the film has a glass transition temperature of 110 ° C. or higher.

  According to the present invention, an acrylic thermoplastic resin that can exhibit high transparency and low heat shrinkage after processing and has excellent heat resistance and optical isotropy while having excellent handleability and workability. A film can be obtained.

  A preferred embodiment of the present invention will be described below.

  The thermoplastic resin that can be used in the present invention is not particularly limited as long as it is substantially transparent. For example, acrylic resin, polycarbonate, vinyl chloride, and alicyclic polyolefin are suitable, and particularly excellent in optical isotropy. From the viewpoint, an acrylic resin is preferably used (hereinafter, the acrylic resin used in the present invention may be referred to as an acrylic resin (A)).

  An acrylic resin is a resin obtained by polymerizing acrylic acid and its derivatives, and in the present invention, it is represented by the following general formula (1) in the molecule for the purpose of exhibiting heat resistance and optical isotropy. It is preferable to contain a glutaric anhydride unit.

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.)
The heat resistance of the resin film, such as the glass transition temperature (Tg) and the heat distortion temperature, is determined by the degree of freedom of the resin structure. For example, an aromatic material in which a rigid benzene ring is bonded by a rigid imide bond. Polyimide has a Tg of over 400 ° C. On the other hand, Tg of polymethacrylmethyl (PMMA), which is a flexible aliphatic polymer having a high degree of freedom, is less than 100 ° C. On the other hand, the acrylic resin having the above structure is preferable because it contains a glutaric anhydride unit having an alicyclic structure and can significantly improve heat resistance.

  In addition, a small phase difference is required for optical isotropic applications. Here, when an aromatic ring having many π electrons is introduced, the heat resistance is improved more than the introduction of an alicyclic structure, but at the same time, there is a problem that birefringence increases and a phase difference is easily developed. For this reason, it is most preferable to contain an alicyclic structure in order to improve heat resistance while maintaining optical isotropy.

  Examples of the alicyclic structure include a glutaric anhydride structure, a lactone ring structure, a norbornene structure, and a cyclopentane structure. For optical isotropy and heat resistance, the same effect can be obtained using any structure, but is it necessary to use expensive raw materials having these structures for the introduction of lactone ring structure, norbornene structure, cyclopentane structure, etc. Further, it is industrially disadvantageous because it is necessary to use an expensive raw material that becomes a precursor of these structures and to obtain a target structure through several steps of reaction. On the other hand, glutaric anhydride units are industrially very advantageous because they are obtained from a general acrylic raw material by one-step dehydration and / or dealcoholization reaction.

  Here, the optical isotropy application is an application in which optical isotropy is required inside the material, and specific examples thereof include a polarizing plate protective film, a lens, and an optical waveguide core. In a liquid crystal television, two polarizing plates are used with the two polarizing plates orthogonal or parallel, but when the polarizing plate protective film is not present or is optically isotropic, black is displayed in a state where the two polarizing plates are orthogonal, White is displayed when two polarizing plates are parallel. On the other hand, when the polarizing plate protective film is not optically isotropic, for example, dark purple is displayed instead of black when the two polarizing plates are orthogonal to each other, and yellow instead of white is displayed when the two polarizing plates are parallel. The This coloring varies depending on the anisotropy of the polarizing plate protective film. Ideally, the polarizing plate protective film does not exist optically, but is indispensable for the purpose of protecting the polarizer from external stress and moisture. In the case of a lens, the lens is intended to refract light at the interface, but it is necessary for light to travel uniformly within the lens. If the inside of the lens is not optically isotropic, there is a problem that the image is distorted. In the case of the optical waveguide core, if it is not optically isotropic, for example, there is a difference in the transmission speed between the horizontal wave signal and the vertical wave signal, which causes noise and interference problems. Other optical isotropic applications include prism sheet substrates, optical disk substrates, flat panel display substrates, and the like.

  Next, the manufacturing method of the acrylic resin containing a glutaric anhydride unit is explained in full detail.

  Unsaturated carboxylic acid monomer (i) and unsaturated carboxylic acid alkyl ester monomer (ii) which give the glutaric anhydride unit represented by the general formula (1) by the subsequent heating step, and other vinyls In the case where a monomer unit is included, the vinyl monomer (iii) providing the unit is polymerized to form a copolymer (a), and then the copolymer (a) is present in the presence of a suitable catalyst. It can be produced by heating in the absence or in the absence of an intramolecular cyclization reaction by dealcoholization and / or dehydration. In this case, the carboxyl group of the unsaturated carboxylic acid unit of 2 units is typically dehydrated by heating the copolymer (a), or the adjacent unsaturated carboxylic acid unit and unsaturated carboxylic acid alkyl ester unit. 1 unit of the glutaric anhydride unit is generated by the elimination of the alcohol.

  The unsaturated carboxylic acid monomer (i) used in this case is not particularly limited, and can be copolymerized with another vinyl compound (iii). The body can be used.

(However, R ³ represents hydrogen or an alkyl group having 1 to 5 carbon atoms.)
In particular, acrylic acid and methacrylic acid are preferable from the viewpoint of excellent thermal stability, and methacrylic acid is more preferable. These can be used alone or in combination of two or more thereof. The unsaturated carboxylic acid monomer (i) represented by the general formula (i) gives a carboxylic acid unit having a structure represented by the following general formula (i-2) when copolymerized.

(However, R ³ represents hydrogen or an alkyl group having 1 to 5 carbon atoms.)
As the unsaturated carboxylic acid alkyl ester monomer (ii), methyl methacrylate is preferable from the viewpoint of transparency and weather resistance of the resulting film. Further, other unsaturated carboxylic acid alkyl ester monomers can be used alone or in combination with methyl methacrylate. Although there is no restriction | limiting in particular as another unsaturated carboxylic acid alkylester monomer, As a preferable example, what is represented by the following general formula (ii) can be mentioned.

(Wherein, R ⁴ represents hydrogen or an aliphatic having 1 to 5 carbon atoms, or alicyclic hydrocarbon group, R ⁵ represents any substituent other than hydrogen.)
Among these, R ⁵ is particularly preferably an acrylate ester and / or a methacrylic ester having an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms or a hydrocarbon group having a substituent. The unsaturated carboxylic acid alkyl ester monomer represented by the general formula (ii) gives a carboxylic acid alkyl ester unit having a structure represented by the following general formula (ii-2) when copolymerized.

(Wherein, R ⁴ represents hydrogen or an aliphatic having 1 to 5 carbon atoms, or alicyclic hydrocarbon group, R ⁵ represents any substituent other than hydrogen.)
Preferable specific examples of the unsaturated carboxylic acid alkyl ester monomer (ii) other than methyl methacrylate include ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, ( T-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate , (Meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl, (meth) acrylic acid 2,3,4,5-tetrahydroxypentyl and the like. .

  Moreover, in manufacture of the acrylic resin (A) used by this invention, you may use another vinyl-type monomer (iii) in the range which does not impair the effect of this invention. Preferable specific examples of the other vinyl monomers (iii) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene and pt-butylstyrene. Aromatic vinyl monomers such as, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, styrene-p-glycidyl ether, p-glycidyl styrene, maleic anhydride, anhydrous Itaconic acid, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, aminoethyl acrylate, acrylic Propylaminoethyl methacrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine , P-aminostyrene, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, 2-styryl-oxazoline, etc., but transparency, birefringence, chemical resistance And a monomer that does not contain an aromatic ring is more preferably used. These may be used alone or in combination of two or more.

  As for the acrylic resin (A), radical polymerization can be basically carried out by using various polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc., but solution polymerization in terms of fewer impurities. It is particularly preferable to perform radical polymerization using bulk polymerization or suspension polymerization.

  The polymerization temperature is not particularly limited, but from the viewpoint of color tone, a monomer mixture containing an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid alkyl ester monomer is polymerized at a polymerization temperature of 95 ° C. or less. Is preferred. Furthermore, in order to further suppress the coloration after the heat treatment, a preferable polymerization temperature is 85 ° C. or less, and particularly preferably 75 ° C. or less. The lower limit of the polymerization temperature is not particularly limited as long as the polymerization proceeds, but is usually 50 ° C. or higher, preferably 60 ° C. or higher from the viewpoint of productivity considering the polymerization rate. For the purpose of improving the polymerization yield or the polymerization rate, it is possible to raise the polymerization temperature according to the progress of the polymerization. In this case, the upper limit temperature is preferably controlled to 95 ° C. or less, and the polymerization start temperature Is preferably performed at a relatively low temperature of 75 ° C. or lower. The polymerization time is not particularly limited as long as it is a sufficient time to obtain the required degree of polymerization, but is preferably in the range of 60 to 360 minutes, particularly preferably in the range of 90 to 180 minutes from the viewpoint of production efficiency.

  The acrylic resin (A) used for the acrylic resin film of the present invention preferably has a mass average molecular weight of 50,000 to 150,000. In the acrylic resin (A) having such a molecular weight, the copolymer (a) is previously controlled to a desired molecular weight, that is, a mass average molecular weight of 50,000 to 150,000 at the time of producing the copolymer (a). Can be achieved. When the mass average molecular weight exceeds 150,000, there is a tendency to color at the time of heat degassing in the subsequent step. On the other hand, when the mass average molecular weight is less than 50,000, the mechanical strength of the acrylic resin film tends to decrease.

  The molecular weight control method of the copolymer (a) is not particularly limited. For example, the addition amount of radical polymerization initiators such as azo compounds and peroxides, or alkyl mercaptans, carbon tetrachloride, carbon tetrabromide, dimethyl It can be controlled by the addition amount of a chain transfer agent such as acetamide, dimethylformamide, triethylamine or the like. In particular, a method of controlling the addition amount of the alkyl mercaptan as a chain transfer agent can be preferably used from the viewpoint of stability of polymerization, ease of handling, and the like.

  Examples of the alkyl mercaptan used in the present invention include n-octyl mercaptan, t-dodecyl mercaptan, n-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan and the like. Among them, t-dodecyl mercaptan, n-dodecyl mercaptan is preferably used.

  The amount of the alkyl mercaptan added is not particularly limited as long as it is controlled to the specific molecular weight of the present invention, but is usually 0.2 to 5.5 with respect to 100 parts by mass of the total amount of the monomer mixture. 0 parts by mass, preferably 0.3 to 4.0 parts by mass, more preferably 0.4 to 3.0 parts by mass.

  In the present invention, a method for producing a thermoplastic polymer containing glutaric anhydride units by heating the copolymer (a) and (i) dehydrating and / or (b) intramolecular cyclization reaction by dealcoholization. Although there is no restriction | limiting in particular, From the viewpoint of productivity, the method of manufacturing through the heated extruder which has a vent, and the method of manufacturing in the apparatus which can be heated and volatilized under an inert gas atmosphere or pressure reduction are preferable. In particular, when an intramolecular cyclization reaction is performed by heating in the presence of oxygen, the yellowness tends to deteriorate, so it is preferable to sufficiently replace the interior with an inert gas such as nitrogen. As a particularly preferable apparatus, for example, a single screw extruder equipped with a “unimelt” type screw, a twin screw, a three screw extruder, a continuous or batch kneader type kneader, etc. can be used. The machine can be preferably used. Moreover, it is more preferable that the apparatus has a structure capable of introducing an inert gas such as nitrogen into them. For example, as a method for introducing an inert gas such as nitrogen into a twin-screw extruder, a method of connecting a pipe of an inert gas stream of about 10 to 100 liters / minute from the upper part and / or the lower part of the hopper can be mentioned. .

  The temperature for the devolatilization by the above method is not particularly limited as long as it is a temperature at which an intramolecular cyclization reaction occurs due to (i) dehydration and / or (b) dealcoholization, but preferably in the range of 180 to 300 ° C. In particular, a range of 200 to 280 ° C. is preferable.

  In addition, the time for heating and devolatilization in this case is not particularly limited and can be appropriately set according to the desired copolymer composition, but is usually 1 minute to 60 minutes, preferably 2 minutes to 30 minutes, especially 3 to 3. A range of 20 minutes is preferred. In particular, the length / diameter ratio (L / D) of the extruder screw is preferably 40 or more in order to secure a heating time for allowing sufficient intramolecular cyclization reaction to proceed using an extruder. When an extruder with a small L / D is used, a large amount of unreacted unsaturated carboxylic acid units remain, so that the reaction proceeds again during the heat molding process, and there is a tendency for bubbles to be seen in the molded product and the color tone during molding retention. Tend to get worse.

  Furthermore, in the present invention, when the copolymer (a) is heated by the above method or the like, one or more of acid, alkali and salt compounds may be added as a catalyst for promoting the cyclization reaction to glutaric anhydride. it can. There is no restriction | limiting in particular in the addition amount, About 0.01-1 mass part is suitable with respect to 100 mass parts of copolymers (a). There are no particular restrictions on the types of these acids, alkalis, and salt compounds, and examples of the acid catalyst include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, phosphoric acid, phosphorous acid, phenylphosphonic acid, and methyl phosphate. It is done. Examples of the basic catalyst include metal hydroxides, amines, imines, alkali metal derivatives, alkoxides, ammonium hydroxide salts and the like. Furthermore, examples of the salt-based catalyst include metal acetates, metal stearates, metal carbonates, and the like. However, it is necessary to add in a range where the color possessed by the catalyst does not adversely affect the coloring of the thermoplastic polymer and the transparency is not lowered. Among them, the compound containing an alkali metal can be preferably used because it exhibits an excellent reaction promoting effect with a relatively small addition amount. Specifically, hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, alkoxide compounds such as sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide, and potassium phenoxide, lithium acetate And organic carboxylates such as sodium acetate, potassium acetate and sodium stearate, among which sodium hydroxide, sodium methoxide, lithium acetate and sodium acetate can be preferably used.

  The content of the glutaric anhydride unit represented by the general formula (1) in the acrylic resin (A) used in the present invention is 5-45 mol%, more preferably 10-40 mol%, most preferably 15- 25 mol%. When a glutaric anhydride unit is less than 5 mol%, a glass transition point (Tg) may fall and the heat resistance improvement effect may become small. Further, if the glutaric anhydride unit exceeds 45 mol%, the toughness may be deteriorated. Improvement in heat resistance and improvement in toughness are in a trade-off relationship and can be adjusted by the content of glutaric anhydride units. For this reason, it is preferable to employ | adopt arbitrary values for content of a glutaric anhydride unit within the range of 5-45 mol% according to a use.

  Examples of other components contained in the acrylic resin (A) include a methyl methacrylate unit and a methacrylic acid unit. The methyl methacrylate unit is preferably contained, and the content of the methyl methacrylate unit is From the viewpoint of optical isotropy and toughness, 55 to 95 mol% is preferable. Furthermore, from the viewpoint of hydrolysis resistance and optical isotropy of the acrylic resin (A), it is preferable that the sum of the content of methyl metal acrylate units and the content of glutaric anhydride units is 90 mol% or more. When the sum of the content of the methyl metal acrylate unit and the content of the glutaric anhydride unit is less than 90 mol%, the optical isotropy may be impaired or the hydrolysis resistance may deteriorate.

  In addition to the glutaric anhydride unit and the methyl methacrylate unit, a methacrylic acid unit that is a precursor of the glutaric anhydride unit may be included. When a methacrylic acid unit or a methyl methacrylate unit is adjacent to a methacrylic acid unit, dehydration or dealcoholization reaction may occur during heating in film forming or stretching process, which may cause foaming. Since the dehydration or dealcoholization reaction cannot occur if the product units are adjacent to each other, methacrylic acid units may be included.

A proton nuclear magnetic resonance ( ¹ H-NMR) measuring instrument is generally used for quantification of each component unit in the acrylic resin (A) used in the present invention. ^{In the 1} H-NMR method, for example, in the case of a copolymer consisting of a glutaric anhydride unit, methacrylic acid, and methyl methacrylate, the spectral assignment in a dimethyl sulfoxide heavy solvent is 0.5 to 1.5 ppm peak. Is hydrogen of α-methyl group of methacrylic acid, methyl methacrylate and glutaric anhydride ring compound, peak of 1.6 to 2.1 ppm is hydrogen of methylene group of polymer main chain, peak of 3.5 ppm is methyl methacrylate The carboxylic acid ester (—COOCH ₃ ) of hydrogen, the peak at 12.4 ppm can determine the copolymer composition from the carboxylic acid hydrogen of methacrylic acid and the integral ratio of the spectrum. In addition to the above, in the case of a copolymer containing styrene as another copolymer component, hydrogen of an aromatic ring of styrene is seen at 6.5 to 7.5 ppm, and the copolymer is similarly obtained from the spectral ratio. The composition can be determined.

  Moreover, the acrylic resin (A) used for this invention can contain an unsaturated carboxylic acid unit and / or other vinyl-type monomer units which can be copolymerized in an acrylic resin (A).

  The amount of unsaturated carboxylic acid units contained in the acrylic resin (A) used in the present invention is preferably 10 mol% or less, that is, 0 to 10 mol%, more preferably 0 to 5 mol%, most preferably 0 to 0 mol%. It is preferably 1 mol%, and more preferably not present. When the unsaturated carboxylic acid unit exceeds 10 mol%, the colorless transparency and the residence stability tend to be lowered.

  The amount of other vinyl monomer units copolymerizable with the acrylic resin (A) is preferably 5 mol% or less, that is, in the range of 0 to 5 mol%, more preferably 0 to 3 mol%, Is preferably absent. In particular, when an aromatic vinyl monomer unit such as styrene is contained and the content exceeds the above range, colorless transparency, optical isotropy, and chemical resistance tend to decrease.

  In the present invention, the glass transition temperature (Tg) of the acrylic thermoplastic resin film is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, and further preferably 125 ° C. or higher. When Tg is less than 110 ° C., the heat resistance is inferior. For example, when processing a hard coat or the like on a film, problems such as poor flatness or increased curling due to shrinkage occur. In addition, when used inside the display, the image may be deteriorated due to a dimensional change due to internal heat or deterioration of flatness. Further, the upper limit of the glass transition point (Tg) is not particularly specified, but it is usually 200 ° C. or less because of problems in resin production and melt extrudability during film production.

  In the present invention, acrylic elastic particles (B) may be contained in the film. In this case, the content of the acrylic elastic particles (B) is 100 parts by mass of the total of the acrylic resin (A) and the acrylic elastic particles (B), and 5 to 50 parts by mass of the acrylic elastic particles (B). Preferably, it is 10-30 mass parts more preferably. When the acrylic elastic particle (B) is less than 5 parts by mass, the toughness of the film may be inferior or the haze may not be controlled to a desired value. Moreover, when acrylic elastic-body particle | grains (B) exceed 50 mass parts, heat resistance may become inadequate or it may become impossible to control a haze to a desired value.

  The acrylic elastic particles (B) are composed of a layer containing one or more rubbery polymers and one or more layers composed of different polymers, and these layers are adjacent to each other. Graft copolymer made by copolymerizing a monomer mixture composed of vinyl monomers in the presence of so-called core-shell type multilayer structure polymer (BM) and rubbery polymer. Combined (BG) etc. can be used preferably.

  As the core-shell type multilayer structure polymer (BM) used in the present invention, the number of layers constituting the core-shell type polymer (BM) is not particularly limited, and may be two or more layers, or three or more layers or Although it may be four layers or more, it is preferably a multilayer structure polymer having at least one rubber layer inside.

  In the above multilayer structure polymer (BM), the kind of the rubber layer is not particularly limited as long as it is composed of a polymer component having rubber elasticity. For example, a rubber composed of a polymer obtained by polymerizing an acrylic component, a silicone component, a styrene component, a nitrile component, a conjugated diene component, a urethane component or an ethylene component, a propylene component, an isobutene component, and the like can be given. Preferred rubbers include, for example, acrylic components such as ethyl acrylate units and butyl acrylate units, silicone components such as dimethylsiloxane units and phenylmethylsiloxane units, styrene components such as styrene units and α-methylstyrene units, acrylonitrile units, A rubber composed of a nitrile component such as a methacrylonitrile unit and a conjugated diene component such as a butanediene unit or an isoprene unit. A rubber composed of a combination of two or more of these components is also preferable. For example, (1) acrylic components such as ethyl acrylate units and butyl acrylate units and silicones such as dimethylsiloxane units and phenylmethylsiloxane units. Rubber composed of components, (2) rubber composed of acrylic components such as ethyl acrylate units and butyl acrylate units, and styrene components such as styrene units and α-methylstyrene units, (3) ethyl acrylate units and Rubber composed of acrylic components such as butyl acrylate units and conjugated diene components such as butanediene units and isoprene units, and (4) acrylic components such as ethyl acrylate units and butyl acrylate units, dimethylsiloxane units and phenylmethylsiloxanes Unit etc. Rubber composed of styrene component such as silicone component and styrene units and α- methyl styrene units and the like. In addition to these components, a rubber obtained by crosslinking a copolymer composed of a crosslinking component such as a divinylbenzene unit, an allyl acrylate unit, and a butylene glycol diacrylate unit is also preferable.

  In the above-mentioned multilayer structure polymer (BM), the type of layer other than the rubber layer is not particularly limited as long as it is composed of a polymer component having thermoplasticity, but it is more than the rubber layer. A polymer component having a high glass transition temperature is preferred. Polymers having thermoplastic properties include unsaturated carboxylic acid alkyl ester units, unsaturated carboxylic acid units, unsaturated glycidyl group-containing units, unsaturated dicarboxylic acid anhydride units, aliphatic vinyl units, and aromatic vinyls. Examples include polymers containing at least one unit selected from system units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units and other vinyl units. Among them, unsaturated carboxylic acids A polymer containing at least one unit selected from an alkyl ester unit, an unsaturated glycidyl group-containing unit, and an unsaturated dicarboxylic acid anhydride unit is preferable, and further, an unsaturated glycidyl group-containing unit and an unsaturated dicarboxylic acid A polymer containing at least one unit selected from anhydride-based units is more preferable.

  Although it does not specifically limit as a monomer used as the raw material of the said unsaturated carboxylic-acid alkylester type | system | group unit, (meth) acrylic-acid alkylester is used preferably. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, (meth) acrylic N-hexyl acid, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, stearyl (meth) acrylate, octadecyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, ( Chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3,4,5,6 (meth) acrylic acid -Pentahydroxyhexyl, 2,3,4,5-tetrahydroxypentyl (meth) acrylate, amino acid acrylate Examples include ethyl, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, and cyclohexylaminoethyl methacrylate, and from the viewpoint that the effect of improving impact resistance is large ( Methyl methacrylate is preferably used. These units can be used alone or in combination of two or more.

  The unsaturated carboxylic acid monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, maleic acid, and further a hydrolyzate of maleic anhydride. Acrylic acid is particularly excellent in terms of thermal stability. Methacrylic acid is preferable, and methacrylic acid is more preferable. These can be used alone or in combination.

  The monomer used as the raw material for the unsaturated glycidyl group-containing unit is not particularly limited, and is glycidyl (meth) acrylate, glycidyl itaconate, diglycidyl itaconate, allyl glycidyl ether, styrene-4-glycidyl ether. And 4-glycidylstyrene, and glycidyl (meth) acrylate is preferably used from the viewpoint that the effect of improving impact resistance is great. These units can be used alone or in combination of two or more.

  Examples of the monomer used as a raw material for the unsaturated dicarboxylic acid anhydride unit include maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, and aconitic anhydride, and the effect of improving impact resistance. From the standpoint of large, maleic anhydride is preferably used. These units can be used alone or in combination of two or more.

  Examples of the monomer that is a raw material for the aliphatic vinyl-based unit include ethylene, propylene, and butadiene. Examples of the monomer that is a raw material for the aromatic vinyl-based unit are styrene, α-methylstyrene, 1 -Vinyl naphthalene, 4-methyl styrene, 4-propyl styrene, 4-cyclohexyl styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene, 4- (phenylbutyl) styrene, halogenated styrene, etc. Acrylonitrile, methacrylonitrile, ethacrylonitrile, etc. are used as the raw material for the vinyl-based unit, and maleimide, N-methylmaleimide, N-ethylmaleimide are used as the monomer for the maleimide-based unit. N-propylmaleimide, N-isopropylmaleimide, Examples of monomers that can be used as raw materials for the unsaturated dicarboxylic acid units include maleic acid and maleic acid such as -cyclohexylmaleimide, N-phenylmaleimide, N- (p-bromophenyl) maleimide, and N- (chlorophenyl) maleimide. Monoethyl ester, itaconic acid, phthalic acid, and the like, which are monomers used as raw materials for the other vinyl units, include acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, N- Vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, p-aminostyrene, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, and 2-styrene Examples include ril-oxazoline, and these monomers can be used alone or in combination of two or more.

  In the multilayer structure polymer (BM) containing the rubber polymer, the type of the outermost layer is not particularly limited, and is an unsaturated carboxylic acid alkyl ester unit, an unsaturated carboxylic acid unit, Unsaturated glycidyl group-containing units, aliphatic vinyl units, aromatic vinyl units, vinyl cyanide units, maleimide units, unsaturated dicarboxylic acid units, unsaturated dicarboxylic anhydride units, and other vinyl units And at least one selected from polymers containing, for example, unsaturated carboxylic acid alkyl ester units, unsaturated carboxylic acid units, unsaturated glycidyl group-containing units, and unsaturated dicarboxylic anhydrides At least one selected from polymers containing units is preferred, and further, unsaturated carboxylic acid alkyl ester units, unsaturated polymers. Polymers containing carbon acid units are more preferable.

  Furthermore, in the present invention, when the outermost layer in the multilayer polymer (BM) is a polymer containing an unsaturated carboxylic acid alkyl ester unit and an unsaturated carboxylic acid unit, by heating, Similarly to the production of the acrylic resin (A) described above, the intramolecular cyclization reaction proceeds to produce a glutaric anhydride unit represented by the above general formula (1). Therefore, a multilayer structure polymer (BM) having a polymer containing an unsaturated carboxylic acid alkyl ester unit and an unsaturated carboxylic acid unit in the outermost layer is blended with the copolymer (a) described above, In the acrylic resin (A) that becomes a continuous phase (matrix phase) by heating and kneading under such conditions, the glutaric anhydride unit represented by the above general formula (1) is formed in the outermost layer. By dispersing the multilayer structure polymer (BM) having a polymer containing the polymer, a good dispersion state is possible without agglomeration, and the mechanical properties such as impact resistance are improved. It is considered that transparency can be expressed.

  That is, a monomer mixture containing an unsaturated carboxylic acid monomer and an unsaturated carboxylic acid alkyl ester monomer is copolymerized to obtain a copolymer (a), and then the copolymer (a) and acrylic elasticity After pre-blending the body particles (B), usually at 200 to 350 ° C., by uniformly melt-kneading with a single-screw or twin-screw extruder, the cyclization reaction of the copolymer (a) described above is performed, The acrylic elastic particles (B) can be blended. In this case, when a part of the acrylic elastic particles (B) contains a copolymer composed of an unsaturated carboxylic acid monomer unit and an unsaturated carboxylic acid alkyl ester monomer unit, the cyclization reaction thereof Can be done at the same time.

  The monomer used as the raw material for the unsaturated carboxylic acid alkyl ester unit herein is not particularly limited, but (meth) acrylic acid alkyl ester is preferred, and methyl (meth) acrylate is more preferred. Preferably used.

  Further, the monomer used as a raw material for the unsaturated carboxylic acid unit is not particularly limited, but (meth) acrylic acid is preferable, and methacrylic acid is more preferably used.

  As a preferred example of the multilayer structure polymer (BM) of the present invention, the core layer is butyl acrylate / styrene polymer, the outermost layer is methyl methacrylate / glutaric acid anhydride represented by the above general formula (1). A copolymer consisting of a physical unit, or a methyl methacrylate / glutaric anhydride unit represented by the above general formula (1) / methacrylic acid polymer, and the core layer is a dimethylsiloxane / butyl acrylate polymer. The outer layer is a methyl methacrylate polymer, the core layer is a butanediene / styrene polymer and the outermost layer is a methyl methacrylate polymer, and the core layer is a butyl acrylate polymer and the outermost layer is a methyl methacrylate polymer ("/" Indicates copolymerization). Furthermore, a preferable example is one in which either one or both of the rubber layer and the outermost layer is a polymer containing a glycidyl methacrylate unit. Among them, the core layer is butyl acrylate / styrene polymer, and the outermost layer is methyl methacrylate / a copolymer of glutaric anhydride units represented by the above general formula (1), or methyl methacrylate / the above general formula. In the resin composition, the glutaric anhydride unit represented by (1) / methacrylic acid polymer approximates the refractive index with the acrylic resin (A) that is the continuous phase (matrix phase), and It is possible to obtain a good dispersion state, and the transparency that can satisfy the demand for more advanced in recent years is expressed.

  As an average particle diameter of said multilayer structure polymer (BM), it is preferable to set it as 50-300 nm, More preferably, it is 100-200 nm. When the average particle size is less than 50 nm, the toughness may not be sufficiently improved, and when it exceeds 300 nm, the internal haze may be deteriorated.

  The average particle diameter of the rubbery polymer can be determined by measuring the diameter of 100 particles using an electron microscope and calculating the average value.

  In the above-mentioned multilayer structure polymer (BM), the mass ratio of the core and the shell is not particularly limited, but the core layer is 50 parts by mass or more with respect to 100 parts by mass of the entire multilayer structure polymer, It is preferably 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

  As said multilayer structure polymer, the commercial item which satisfy | fills the conditions mentioned above may be used, and it can also synthesize | combine and use it by a well-known method.

  Commercially available products of multilayer structure polymers include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., Ltd., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paraloid” manufactured by Kureha Chemical Co., Ltd. “Staffyroid” manufactured by Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd. and the like can be mentioned, and these can be used alone or in combination of two or more.

  Further, specific examples of the rubber-containing graft copolymer (BG) that can be used as the acrylic elastic particles (B) in the present invention include unsaturated carboxylic acid esters in the presence of the rubbery polymer. A monomer mixture comprising a monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith. And graft copolymers.

  The rubbery polymer used for the graft copolymer (B-G) is not particularly limited, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

  The graft copolymer (BG) used in the present invention is 10 to 80 parts by mass, preferably 20 to 70 parts by mass, more preferably 100 parts by mass of the rubbery polymer with respect to 100 parts by mass of the graft copolymer (BG). Is obtained by copolymerizing 20 to 90 parts by weight, preferably 30 to 80 parts by weight, more preferably 40 to 70 parts by weight of the above-mentioned monomer (mixture) in the presence of 30 to 60 parts by weight. When the ratio of the rubbery polymer is less than the above range or exceeds the above range, the impact strength and the surface appearance may be lowered.

  The graft copolymer (BG) may contain a non-grafted copolymer that is produced when a monomer mixture is graft copolymerized with a rubbery polymer. However, from the viewpoint of impact strength, the graft ratio is preferably 10 to 100%. Here, the graft ratio is a mass ratio of the grafted monomer mixture to the rubbery polymer. In addition, the intrinsic viscosity measured at 30 ° C. of the methylethylketone solvent of the ungrafted copolymer is not particularly limited, but 0.1 to 0.6 dl / g is a balance between impact strength and moldability. From the viewpoint of, it is preferably used.

  Although there is no restriction | limiting in particular in the methyl ethyl ketone solvent of the vinyl-type copolymer (BG) used in this invention, and the intrinsic viscosity measured at 30 degreeC, If it is 0.2-1.0 dl / g, impact strength and It is preferably used from the viewpoint of balance with molding processability, more preferably 0.3 to 0.7 dl / g.

  The acrylic thermoplastic resin film of the present invention has an in-plane retardation (Δnd) of 8 nm or less, preferably 5 nm or less, more preferably 2 nm or less. Further, the acrylic thermoplastic resin film of the present invention has a thickness direction retardation (Rth) of -8 to 8 nm, preferably -5 to 5 nm. When the absolute value of the in-plane retardation (Δnd) or thickness direction retardation (Rth) exceeds 8 nm, the optical isotropy deteriorates, so it is used for liquid crystal display applications such as polarizer protective films and optical disk protective films. If this occurs, problems such as unevenness in the screen and increased data error frequency may occur. In applications where optical isotropy is required, the absolute values of the in-plane retardation (Δnd) and the thickness direction retardation (Rth) are preferably small, but in reality, the lower limit is considered to be about 0.1 nm. In order to obtain an acrylic thermoplastic resin film having such optical isotropy, as described above, an alicyclic structure such as a glutaric anhydride structure, a lactone ring structure, a norbornene structure, or a cyclopentane structure is included in the resin. It is most preferable to contain them, and it is effective not to introduce an additive or a copolymer component that develops a phase difference, or to lower the draw ratio during film formation.

  It is preferable that the thermal shrinkage rate in the MD direction of the acrylic thermoplastic resin film of the present invention when heated at 80 ° C. is −0.15 to 0.15%. When the thermal shrinkage in the MD direction when heated at 80 ° C is greater than 0.15% or less than -0.15%, curling when heated to 80 ° C after bonding with other films in-line there's a possibility that.

  The thermal shrinkage rate in the MD direction of the acrylic thermoplastic resin film of the present invention when heated at 120 ° C. is preferably 1.50% or more. When the thermal shrinkage rate in the MD direction during heating at 120 ° C is less than 1.50%, when it is bonded inline with other film and heated to 120 ° C, follow the shrinkage rate of the bonded film. There is a possibility of curling. Conventionally, as a countermeasure against curling, there is a method of bringing the heat shrinkability close to 0, and there is also a technique for increasing the heat shrinkability in the MD direction with respect to the TD direction in consideration of inline processability. However, in recent years, heat resistance requirements of products used at high temperatures such as car navigation systems are increasing, and the importance of thermal characteristics at higher temperatures is increasing. However, in the past, attention was focused only on the temperature range of 80 ° C. to 100 ° C., which was insufficient for eliminating workability and curling. Therefore, the present invention has focused on solving such problems by controlling heat shrinkage under high temperature and heat shrinkage under low temperature conditions. In other words, when used in such applications, focusing on the temperature of 120 ° C where most materials begin to heat shrink, trying to design to heat shrink from that temperature, curling can be suppressed under a wide range of temperature conditions An extremely effective film could be obtained.

  The thermoplastic resin film in the present invention preferably has a single layer structure by a melt extrusion method. When using a solution casting method in which a resin is dissolved in a solvent to form a sheet, the film cannot be drawn, and the process becomes complicated, such as peeling and passing through stretching equipment to control heat recovery. May also rise. Moreover, when it is set as a composite layer structure, the intensity | strength between layers often becomes inadequate and problems, such as peeling, may arise.

  The thickness of the acrylic thermoplastic resin film of the present invention is desirably 5 to 200 μm. If the thickness is less than 5 μm, curling may occur or it may be difficult to protect the polarizer from moisture or the like. On the other hand, when the thickness exceeds 200 μm, the thickness of the entire polarizing plate increases. The film thickness is more preferably 15 μm or more and 80 μm or less, and most preferably 20 μm or more and 40 μm or less.

  As a method for forming the thermoplastic resin film of the present invention, an extruder type melt extrusion apparatus equipped with a single screw or a twin screw may be used by the T-die method. Preferably, a twin screw kneading extruder with L / D = 25 or more and 120 or less is preferable in order to prevent coloring.

The melt shear rate for producing the film of the present invention is preferably from 1,000 S ^{−1 to} 5,000 S ⁻¹ . Moreover, when melt-kneading using a melt-extrusion apparatus, it is preferable to perform the melt-kneading under reduced pressure or the melt-kneading under nitrogen stream from a viewpoint of coloring suppression. Casting method measures molten resin with a gear pump and then discharges it from a T die die, and on a cooled drum, the electrostatic application method as an adhesion means, the air chamber method, the air knife method, the press roll method, etc. It is preferable to closely cool and solidify to the cooling medium and rapidly cool to room temperature to obtain an unstretched film.

  In the present invention, the average residence time of the molten resin from the extruder outlet to the T-die outlet is preferably 30 minutes to 90 minutes. This is because the average residence time affects the wavy uneven shape formed on the surface. If the average residence time is less than 30 minutes, sufficient unevenness may not be formed and the handleability may deteriorate, and if it exceeds 90 minutes, foreign matter such as a melted resin degradation product or gelled product increases, and the film The quality of the product may deteriorate. In addition, the average residence time here is the time which remove | divided the molten resin filling mass calculated from the internal volume between an extruder exit and a nozzle | cap | die exit by the discharge amount.

  The temperature of the molten resin immediately after discharging the die for producing the film of the present invention is preferably a glass transition point (Tg) +50 to + 200 ° C., more preferably a glass transition point (Tg) +80 to + 150 ° C. When the temperature of the molten resin is less than the glass transition point (Tg) + 50 ° C., the polymer is cured before the resin is deposited, which may cause uneven thickness. When the temperature of the molten resin exceeds the glass transition point (Tg) + 200 ° C., defects due to the decomposition of the resin tend to increase.

  In order to produce the film of the present invention, it is preferable to draw a film immediately after discharging the die using a plurality of cooling rolls. When a film having a temperature of 100 to 140 ° C. is conveyed, the draw ratio of the roll to which the film is first adhered / the roll to which the film is later adhered is preferably 100.1% or more. When the draw ratio is less than 100.1%, the thermal contraction rate in the MD direction at 120 ° C. may be less than 1.50%. The upper limit of the draw ratio is not particularly specified, but the film is usually transported at 100 to 110% in order to avoid stretching the film and developing a retardation. When a film having a polymer temperature of 60 to 99 ° C. is conveyed, the draw ratio of the roll to which the film is first adhered / the roll to which the film is later adhered is preferably 99.5 to 99.9%. When the draw ratio exceeds 100% or less than 99.5%, the thermal shrinkage in the MD direction at 80 ° C. may exceed 0.15% or less than −0.15%.

  In addition, it is possible to apply the method of drawing the film through the oven at the target temperature of heat collection after cooling and solidification, and stretching it, but it is difficult to control the temperature and stretching point of the film, and the equipment is large. It is easy to become.

  In the molding process of the acrylic thermoplastic resin film of the present invention, the temperature of the cooling roll immediately after discharge of the die is preferably a glass transition point (Tg) of −60 ° C. or higher to + 80 ° C. When the temperature of the cooling roll 1 is less than the glass transition point (Tg) −60 ° C., the temperature of the molded film is too low, and there is a possibility that unevenness in MD direction thickness occurs on the film surface when the film is peeled off from the cooling roll. is there. Moreover, when the temperature of a cooling roll exceeds glass transition point (Tg) +80 degreeC, the planarity of a film-forming film may deteriorate.

  The film conveyance speed is preferably 5 to 80 m / min, more preferably 10 to 40 m / min.

  The acrylic thermoplastic resin film of the present invention obtained as described above can be suitably used for optical applications due to its excellent heat resistance, optical isotropy, and inline processability. Examples of the optical use here include members for display devices, and particularly, it can be suitably used for members used in flat panel displays such as liquid crystal displays, plasma displays, field emission displays, and electroluminescence displays. Also, various plastic substrates, lenses, polarizing plates, polarizing plate protective films, ultraviolet absorbing films, infrared absorbing films, electromagnetic wave shielding films, prism sheets, prism sheet base materials, Fresnel lenses, optical disk substrates, optical disk substrate protective films, conductive films Applications such as a light plate, a retardation film, a light diffusion film, a viewing angle widening film, a reflection film, an antireflection film, an antiglare film, a brightness enhancement film, a prism sheet, a conductive film for a touch panel can be exemplified, and in particular, its optical isotropy It is useful as a polarizing plate protective film.

[Measurement method of physical properties]
Hereinafter, the configuration and effects of the present invention will be described more specifically with reference to examples. Of course, the present invention is not limited to the following examples. Prior to the description of each example, various physical property measurement methods employed in the example will be described.

(1) Glass transition temperature (Tg)
After storing the film in a desiccator for 24 hours, about 10 mg of the sample is sealed in a hermetic pan and the temperature is increased at 20 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (TA Instrument Q100 type). Measured at temperature rate. The measurement was an average value of two times. As the glass transition temperature (Tg), the midpoint glass transition temperature (Tmg) of JIS K7121 (1987) is adopted.

(2) Haze The haze of the film at 23 ° C. was measured based on JIS K7105 (1981) 6.4 haze (cloudiness value). The measurement was performed 3 times and the average value was defined as haze.

(3) In-plane retardation (Δnd), thickness direction retardation (Rth)
An elliptical polarization measuring device (KOBRA-WPR) and a phase difference measuring device KOBRA-ΔND (software for KOBRA-WR) Ver. 1.21 was used. The measurement is performed in the simple N calculation mode of incident angle dependence measurement, using the low phase difference measurement method, with the slow axis as the tilt center axis and the incident angle of 40 ° (wavelength 590 nm). (Δnd) and thickness direction retardation (Rth) were obtained. The R0 value that is the phase difference at an incident angle of 0 ° was defined as the in-plane phase difference (Δnd). Moreover, the measurement was performed on a sample stored for 24 hours in a desiccator, and the average value of N = 5 times was defined as an in-plane retardation (Δnd) and a thickness direction retardation (Rth).

(4) Photoelastic coefficient (10 ⁻¹² m ² / N)
A sample having a short side of 1 cm and a long side of 7 cm was cut out. Using this sample, TRANSDUCER U3C1-5K manufactured by Shimadzu Corp., the upper and lower sides were sandwiched by 1 cm each, and a tension (F) of 1 kg / mm ² (9.81 × 10 ⁶ Pa) was applied in the long side direction. In this state, Re (nm) was measured using a polarizing microscope 5892 manufactured by Nikon Corporation. Sodium D line (589 nm) was used as a light source. These numerical values were applied to photoelastic coefficient = Re / (d × F) to calculate the photoelastic coefficient. The measurement was performed once.

(5) Thermal contraction rate during heating at 80 ° C. A sample having a long side of 320 mm and a short side of 10 mm was cut out and the length thereof was measured. Each sample was placed 1 cm above and below the chuck, and a load of 3 g was applied in the long side direction. In this state, the mixture was put in a gear oven manufactured by Nikon Corporation heated to 80 ° C. for 30 minutes. Thereafter, the processed length of the sample taken out was measured using a heat shrinkage automatic measuring device manufactured by Techno Needs Co., Ltd. The value of the length before and after heat treatment is the heat shrinkage rate = (distance between the marked lines of the untreated specimen -the distance between the marked lines of the specimen after the heat treatment) / the distance between the marked lines of the untreated specimen. The calculation was applied to × 100. The measurement was performed twice, and the average value was defined as the heat shrinkage rate.

(6) Thermal contraction rate during heating at 120 ° C. A sample having a long side of 120 mm and a short side of 10 mm was cut out and the length thereof was measured. Each sample was placed 1 cm above and below the chuck, and a load of 1.5 g was applied in the long side direction. In this state, it was put into a gear oven manufactured by Nikon Corporation heated to 120 ° C. for 30 minutes. Thereafter, the processed length of the sample taken out was measured using a heat shrinkage automatic measuring device manufactured by Techno Needs Co., Ltd. The value of the length before and after heat treatment is the heat shrinkage rate = (distance between the marked lines of the untreated specimen -the distance between the marked lines of the specimen after the heat treatment) / the distance between the marked lines of the untreated specimen. The calculation was applied to × 100. The measurement was performed twice, and the average value was defined as the heat shrinkage rate.

(7) Curl measurement at 80 ° C. Polyvinyl alcohol having a thickness of 75 μm and a polymerization degree of 2,400 was stretched 2.5 times while immersed in pure water at 30 ° C. for 1 minute. Next, the film was stretched 1.2 times while being immersed in a dyeing bath containing iodine and potassium iodide at 30 ° C. for 1 minute. Next, the film was stretched twice while immersed in a boric acid bath at 60 ° C. for 2 minutes. Furthermore, after being immersed in an aqueous solution having a potassium iodide concentration of 5 mass% at 30 ° C. for 5 seconds, it was dried at 35 ° C. for 5 minutes to obtain a polarizer. The thickness on one side of the polarizer using a PVA-based adhesive bonded triacetyl cellulose film moisture permeability 900g / m 2 / ^24h subjected to saponification treatment of 40 [mu] m, to form a laminate. At the time of bonding, the tension was controlled so that the resulting laminate was flat. The obtained laminate was dried at 50 ° C. for 5 minutes, and subsequently (that is, without winding up and storing the laminate), a PVA adhesive was used on the other surface of the polarizer. The acrylic resin film obtained in the invention was bonded and dried at 60 ° C. for 5 minutes and at 70 ° C. for 5 minutes to obtain a polarizing plate. At the time of pasting, the tension was controlled so that the resulting polarizing plate was flat. The obtained polarizing plate was cut out to a size of 10 cm × 10 cm and put into an oven at 80 ° C. for 10 min. It was placed on a horizontal table so that the convex side was on the lower side, and the distance of the portion farthest from the plane of the polarizing plate was measured. Evaluation was performed according to the following criteria.

  X: The maximum amount of warpage (floating from the plane) of the end of the film is 5 mm or more.

  (Circle): The maximum curvature amount (floating from a plane) of the edge part of a film is less than 5 mm.

(8) 120 ° C. Curl Measurement Polyvinyl alcohol having a thickness of 75 μm and a polymerization degree of 2,400 was stretched 2.5 times while immersed in pure water at 30 ° C. for 1 minute. Next, the film was stretched 1.2 times while being immersed in a dyeing bath containing iodine and potassium iodide at 30 ° C. for 1 minute. Next, the film was stretched twice while immersed in a boric acid bath at 60 ° C. for 2 minutes. Furthermore, after being immersed in an aqueous solution having a potassium iodide concentration of 5 mass% at 30 ° C. for 5 seconds, it was dried at 35 ° C. for 5 minutes to obtain a polarizer. The thickness on one side of the polarizer using a PVA-based adhesive bonded triacetyl cellulose film moisture permeability 900g / m 2 / ^24h subjected to saponification treatment of 40 [mu] m, to form a laminate. At the time of bonding, the tension was controlled so that the resulting laminate was flat. The obtained laminate was dried at 50 ° C. for 5 minutes, and subsequently (that is, without winding up and storing the laminate), a PVA adhesive was used on the other surface of the polarizer. The acrylic resin film obtained in the invention was bonded and dried at 60 ° C. for 5 minutes and at 70 ° C. for 5 minutes to obtain a polarizing plate. At the time of pasting, the tension was controlled so that the resulting polarizing plate was flat. The obtained polarizing plate was cut out to a size of 10 cm × 10 cm and put into an oven at 120 ° C. for 10 min. It was placed on a horizontal table so that the convex side was on the lower side, and the distance of the portion farthest from the plane of the polarizing plate was measured. Evaluation was performed according to the following criteria.

  X: The maximum amount of warpage (floating from the plane) of the end of the film is 5 mm or more.

  (Circle): The maximum curvature amount (floating from a plane) of the edge part of a film is less than 5 mm.

(9) Each component composition The film was melt | dissolved in acetone, this solution was centrifuged at 9,000 rpm for 30 minutes, and it isolate | separated into the acetone soluble component and the acetone insoluble component. The acetone-soluble component was dried under reduced pressure at 60 ° C. for 5 hours, and each component unit was quantified to identify each component composition of the acrylic resin.

Quantification of each component unit was performed by a proton nuclear magnetic resonance ( ¹ H-NMR) method. ^{In the 1} H-NMR method, for example, in the case of a copolymer consisting of a glutaric anhydride unit, methacrylic acid, and methyl methacrylate, the spectral assignment in a dimethyl sulfoxide heavy solvent is 0.5 to 1.5 ppm peak. Is hydrogen of α-methyl group of methacrylic acid, methyl methacrylate and glutaric anhydride ring compound, peak of 1.6 to 2.1 ppm is hydrogen of methylene group of polymer main chain, peak of 3.5 ppm is methyl methacrylate The carboxylic acid ester (—COOCH ₃ ) of hydrogen, the peak at 12.4 ppm can determine the copolymer composition from the carboxylic acid hydrogen of methacrylic acid and the integral ratio of the spectrum. In addition to the above, in the case of a copolymer containing styrene as another copolymer component, hydrogen of the aromatic ring of styrene is seen at 6.5 to 7.5 ppm, and the copolymer composition is similarly determined from the spectral ratio. Can be determined.

[Example]
(1) Preparation of acrylic resin 20 parts by mass of methyl methacrylate, 80 parts by mass of acrylamide, 0.3 part by mass of potassium persulfate, and 1,500 parts by mass of ion-exchanged water were charged into the reactor, and the reactor was replaced with nitrogen gas. The temperature was kept at 70 ° C. The reaction was continued until the monomer was completely converted to a polymer, and a methyl methacrylate / acrylamide copolymer suspension was obtained. A solution in which 0.05 part by mass of the methyl methacrylate / acrylamide copolymer suspension obtained by the above method was dissolved in 165 parts by mass of ion-exchanged water was supplied, and the system was replaced with nitrogen gas while stirring. . Next, the following raw material monomer mixture was added while stirring the reaction system, and the temperature was raised to 70 ° C. The time when the internal temperature reached 70 ° C. was set as the start of polymerization, and kept for 180 minutes to complete the polymerization. Thereafter, the reaction system was cooled, the polymer was separated, washed, and dried in accordance with ordinary methods to obtain a bead-shaped copolymer intermediate (a-1). The polymerization rate of this copolymer (a-1) was 98%, and the mass average molecular weight was 100,000.

Methacrylic acid: 27 parts by weight Methyl methacrylate: 73 parts by weight t-dodecyl mercaptan: 1.5 parts by weight 2,2′-azobisisobutyronitrile: 0.4 parts by weight Additive (lithium acetate) Intramolecular cyclization reaction was performed at a screw rotation speed of 100 rpm and a cylinder temperature of 290 ° C. while purging nitrogen from the hopper using a twin screw extruder (L / D = 44.5). Next, the foreign matter was filtered with a filter obtained by sintering and compressing stainless steel fibers having an average opening of 3 μm to obtain a pellet-shaped acrylic resin (A). The composition ratio of methyl methacrylate units in this acrylic resin (A) was 76 mol%, the composition ratio of methacrylic acid units was 2 mol%, and the composition ratio of glutaric anhydride units was 22 mol%.

(2) Preparation of Acrylic Elastic Particles 120 parts by weight of ionic water, 0.5 parts by weight of potassium carbonate, 0.5 parts by weight of dioctyl sulfosuccinate, and 0.005 parts by weight of potassium persulfate were stirred in a nitrogen atmosphere and then acrylic. 45 parts by mass of butyl acid, 15 parts by mass of styrene, and 3 parts by mass of allyl methacrylate (crosslinking agent) were charged. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a core layer (inner layer) polymer. Next, a mixture of 28 parts by weight of methyl methacrylate, 12 parts by weight of methacrylic acid and 0.005 part by weight of potassium persulfate was continuously added over 90 minutes, and the mixture was further maintained for 90 minutes to polymerize the shell layer (outer layer). The polymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered and dried to obtain acrylic elastic particles (B) having a two-layer structure (core-shell structure).

(3) Preparation of acrylic resin and acrylic elastic particle mixture 80 parts by mass of the above acrylic resin (A) and acrylic elastic particles (B) were blended at a composition ratio of 20 parts by mass, and a twin-screw extruder (L / D = 44). 5) was used for kneading at a screw speed of 200 rpm and a cylinder temperature of 280 ° C. to obtain a mixture in which acrylic elastic particles were dispersed in a pellet-like acrylic resin. The average particle diameter of the acrylic elastic particles measured with a transmission electron microscope was 180 nm.

(4) Production of film 80 parts by mass of the acrylic resin and acrylic elastic particles are blended at a composition ratio of 20 parts by mass, and a twin screw extruder (TEX30 (manufactured by Nippon Steel Co., Ltd., L / D = 44.5)) is used. Then, after kneading at a screw rotation speed of 200 rpm and a cylinder temperature of 280 ° C., foreign matter was filtered with a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm to obtain a pellet-like acrylic resin.

  Next, the pellets dried for 6 hours at 100 ° C. and 100 Pa were extruded with a vented 90 mmφ single screw extruder at a vent pressure of 5 kPa and an extrusion set temperature of 240 ° C., and the resin was measured via a gear pump. (Gear pump speed 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 250 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely in close contact with the cooling roll 1 having a surface temperature of 95 ° C., the temperature is similarly 95 ° C. and 95 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 20 μm was obtained. The draw ratio of each roll was 100.10, 100.00, and 99.70% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 was 115 degreeC, a cooling roll The temperature of the film peeled from 3 was 84 ° C. The characteristics of the obtained film are as shown in Table 2. The film had excellent heat resistance and optical isotropy, and was excellent in properties after workability.

[Example 2]
The procedure was as in Example 1 until the acrylic resin in the form of pellets was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 230 ° C., and the resin was measured via a gear pump (gear pump rotation Number 10.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 250 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely brought into close contact with the cooling roll 1 having a surface temperature of 137 ° C., similarly, the temperature is 120 ° C. and 115 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 31 μm was obtained. The draw ratio of each roll was 100.30, 100.02, 99.81% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 135 degreeC, a cooling roll The temperature of the film peeled from 3 was 99 ° C. The characteristics of the obtained film are as shown in Table 2. The film had excellent heat resistance and optical isotropy, and was excellent in properties after workability.

[Example 3]
The procedure was as in Example 1 until the pellet-shaped acrylic resin was charged into the single screw extruder, the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 245 ° C., and the resin was measured via a gear pump (gear pump rotation Number 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 260 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely in close contact with the cooling roll 1 having a surface temperature of 120 ° C., similarly, 120 ° C. and 115 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 20 μm was obtained. The draw ratio of each roll was 100.10, 100.00, 99.90% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 122 degreeC, a cooling roll The temperature of the film peeled from 3 was 91 ° C. The characteristics of the obtained film are as shown in Table 2. The film had excellent heat resistance and optical isotropy, and was excellent in properties after workability.

[Example 4]
The procedure was as in Example 1 until the acrylic resin in the form of pellets was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 230 ° C., and the resin was measured via a gear pump (gear pump rotation Number 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 250 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely brought into close contact with the cooling roll 1 having a surface temperature of 137 ° C., similarly, the temperature is 120 ° C. and 115 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 20 μm was obtained. The draw ratio of each roll was 100.30, 100.02, 99.81% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 132 degreeC, a cooling roll The temperature of the film peeled from 3 was 99 ° C. The characteristics of the obtained film are as shown in Table 2. The film had excellent heat resistance and optical isotropy, and was excellent in properties after workability.

[Comparative Example 1]
The procedure was as in Example 1 until the pellet-shaped acrylic resin was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 260 ° C., and the resin was measured via a gear pump (gear pump rotation Number 10.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 260 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely brought into close contact with the cooling roll 1 having a surface temperature of 105 ° C., similarly, 90 ° C. and 60 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 39 μm was obtained. The draw ratio of each roll was 100.30, 100.05, 99.20% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 153 degreeC, a cooling roll The temperature of the film peeled from 3 was 52 ° C. The properties of the obtained film are as shown in Table 2 and had excellent heat resistance and optical isotropy, but were inferior in properties after workability.

[Comparative Example 2]
The procedure was as in Example 1 until the pellet-shaped acrylic resin was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 260 ° C., and the resin was measured via a gear pump (gear pump rotation Number 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 260 ° C.)). The sheet-like resin melt-extruded is cooled using a film forming apparatus as shown in FIG. 1 so that one surface is completely brought into close contact with the cooling roll 1 having a surface temperature of 125 ° C., and then similarly 95 ° C. and 50 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 42 μm was obtained. The draw ratio of each roll was 100.00, 100.00, and 99.80% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 156 degreeC, a cooling roll The temperature of the film peeled from 3 was 79 ° C. The properties of the obtained film are as shown in Table 2 and had excellent heat resistance and optical isotropy, but were inferior in properties after workability.

[Comparative Example 3]
The procedure was as in Example 1 until the pellet-shaped acrylic resin was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 240 ° C., and the resin was measured via a gear pump (gear pump rotation Number 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 260 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely in close contact with the cooling roll 1 having a surface temperature of 95 ° C., the temperature is similarly 95 ° C. and 95 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 20 μm was obtained. The draw ratio of each roll was 100.00, 100.00, and 99.80% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 is 156 degreeC, a cooling roll The temperature of the film peeled from 3 was 82 ° C. The properties of the obtained film are as shown in Table 2 and had excellent heat resistance and optical isotropy, but were inferior in properties after workability.

[Comparative Example 4]
The procedure was as in Example 1 until the pellet-shaped acrylic resin was charged into the single screw extruder, and the acrylic resin was extruded at a vent pressure of 5 kPa and an extrusion set temperature of 240 ° C., and the resin was measured via a gear pump (gear pump rotation Number 8.0 rpm). Next, foreign matter was filtered through a filter obtained by sintering and compressing stainless steel fibers having an average opening of 7 μm, and then melt extruded through a die (T die (lip gap 0.8 mm, set temperature 260 ° C.)). After the melt-extruded sheet-like resin is cooled by using a film forming apparatus as shown in FIG. 1 so that one surface is completely brought into close contact with the cooling roll 1 having a surface temperature of 95 ° C., similarly, 90 ° C. and 60 ° C. The film was gradually cooled through the cooling rolls 2 and 3 in order, and then the film was nip-conveyed with the metal roll 4 and the rubber roll to relax. Then, the film was wound into a roll and an acrylic resin film having a thickness of 20 μm was obtained. The draw ratio of each roll was 100.10, 100.00, and 99.30% in the order of cooling roll 2 / cooling roll 1, cooling roll 3 / cooling roll 2, and metal roll 4 / cooling roll 3. About the temperature of the film in conveyance, when it measured 5 cm away from the film using the radiation thermometer (IT-314) made from ASONE, the temperature of the film between the cooling roll 1 and the cooling roll 2 was 115 degreeC, a cooling roll The temperature of the film peeled from 3 was 50 ° C. The properties of the obtained film are as shown in Table 2 and had excellent heat resistance and optical isotropy, but were inferior in properties after workability.

It is a general | schematic cross-sectional view which shows the cooling roll vicinity of the manufacturing apparatus of the acrylic thermoplastic resin film which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooling roll 2 Cooling roll 3 Cooling roll 4 Metal roll 5 Rubber roll 6 Film 7 Free roll 8 Free roll 9 Free roll 10 Cap

Claims (3)

An acrylic thermoplastic resin film that satisfies the following (i) to (v).
(I) Thermal contraction rate in MD direction at 80 ° C. is −0.15 to 0.15%
(Ii) Thermal shrinkage in MD direction when heated at 120 ° C. is 1.50% or more (iii) Thickness is 5 to 200 μm
(Iv) Thickness direction retardation Rth is −8 to 8 nm
(V) In-plane retardation Δnd is 8 nm or less The acrylic thermoplastic resin film of Claim 1 containing the acrylic resin (A) containing the glutaric anhydride unit represented by following Structural formula (1).

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.) The acrylic thermoplastic resin film according to claim 1 or 2, wherein the glass transition temperature of the film is 110 ° C or higher.

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