TWI835728B - Optical films, polarizing plates, and image display devices - Google Patents

Abstract

The present invention provides an optical film with high adhesion between a base film and a surface treatment layer. The optical film of the present invention includes a base film that is a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the base film, and the base film in the optical film is cut to 10 cm×10 cm. The dimensional change rate is -2.0%~0% when it is left standing at 100°C for 120 hours while being attached to the glass plate via an adhesive material.

Description

Optical film, polarizing plate, and image display device

The present invention relates to an optical film, a polarizing plate, and an image display device.

In recent years, an optical film having a functional layer (surface treatment layer) such as a hard coating layer, an anti-glare layer, and an anti-reflection layer formed on one side of a substrate film comprising an acrylic resin has been known (Patent Document 1). The surface treatment layer can be formed by coating a resin composition on one side of a substrate film and drying or curing it. Such an optical film can be used, for example, as a protective film for a polarizing element or a front panel of an image display device. Prior Art Document Patent Document Patent Document 1: Japanese Patent Publication No. 2016-218478

[Problem to be solved by the invention] However, in the step of drying the resin composition, the substrate film may be wrinkled due to heat shrinkage, resulting in a poor appearance. When the resin composition is dried at a low temperature to prevent the abnormality caused by heat shrinkage, there is a problem that the adhesion between the substrate film and the surface treatment layer becomes insufficient. The present invention is completed to solve the above-mentioned previous problems, and its main purpose is to provide an optical film with high adhesion between the substrate film and the surface treatment layer, a polarizing plate having such an optical film, and an image display device having such a polarizing plate. [Technical means for solving the problem] The optical film of the present invention comprises a substrate film as a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the substrate film, and the substrate film in the optical film has a dimensional change rate of -2.0% to 0% when it is cut into 10 cm×10 cm and bonded to a glass plate via an adhesive and left at 100°C for 120 hours. In one embodiment, the substrate film contains the acrylic resin and core-shell particles dispersed in the acrylic resin. In one embodiment, the substrate film contains 5 to 50 parts by weight of the core-shell particles relative to 100 parts by weight of the acrylic resin. In one embodiment, the acrylic resin has at least one selected from the group consisting of glutaric anhydride units, lactone ring units, maleic anhydride units, maleic anhydride units and glutaric anhydride units. In one embodiment, the surface treatment layer is a hardening layer of the resin composition coated on the substrate film. In one embodiment, the surface treatment layer is at least one selected from the group consisting of a hard coating layer, an anti-glare layer and an anti-reflection layer. According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate includes a polarizing element and a protective layer disposed on one side of the polarizing element, and the protective layer is the optical film. According to another aspect of the present invention, an image display device is provided. The image display device has the above-mentioned polarizing plate. [Effect of the invention] According to the present invention, by using the above-mentioned substrate film with a dimensional change rate of -2.0% to 0%, an optical film with high adhesion between the substrate film and the surface treatment layer, a polarizing plate having such an optical film, and an image display device having such a polarizing plate can be provided.

The following describes the embodiments of the present invention, but the present invention is not limited to the embodiments. A. Overall structure of optical film 1 is a schematic cross-sectional view of an optical film of one embodiment of the present invention. The optical film 100 includes a substrate film 10 and a surface treatment layer 20 formed on one side of the substrate film 10. The substrate film 10 is a stretched film containing an acrylic resin. When the substrate film 10 is cut into 10 cm×10 cm and attached to a glass plate via an adhesive and left at 100°C for 120 hours, the dimensional change rate along a specific direction is -2.0%~0%. The shape of the substrate film 10 is not particularly limited. For example, when the substrate film is in the shape of a strip or rectangle, the dimensional change rate can be measured by cutting the substrate film into 10 cm×10 cm along the long side direction and the short side direction (direction perpendicular to the long side direction) of the substrate film. The specific direction is typically the direction along each side of the substrate film cut into 10 cm×10 cm. In one embodiment, the substrate film 10 contains an acrylic resin and core-shell particles dispersed in the acrylic resin. In this case, the substrate film 10 preferably contains 5 to 50 parts by weight of the core-shell particles relative to 100 parts by weight of the acrylic resin. The acrylic resin preferably has at least one selected from the group consisting of glutaric anhydride units, lactone ring units, maleic anhydride units, maleic anhydride units and glutaric anhydride units. The surface treatment layer 20 is typically a hardening layer of a resin composition coated on the substrate film 10. The surface treatment layer 20 is preferably at least one selected from the group consisting of a hard coating layer, an anti-glare layer and an anti-reflection layer. By means of the above-mentioned optical film, shrinkage (especially shrinkage along the extension direction) in a state where the surface treatment layer is formed can be suppressed. As a result, the adhesion between the substrate film 10 and the surface treatment layer 20 can be improved. In particular, when the surface treatment layer 20 is formed by applying the resin composition on the substrate film 10 and drying and hardening the resin composition, sufficient adhesion between the substrate film 10 and the surface treatment layer 20 can be achieved even when the resin composition is dried at a low temperature. Therefore, the generation of wrinkles on the substrate film due to the heat when the resin composition is dried can be suppressed. B. Substrate film B-1. Characteristics of substrate film As described above, the substrate film is a stretched film containing an acrylic resin, and the dimensional change rate when the substrate film is cut into 10 cm×10 cm along the long side direction and the orthogonal direction of the substrate film and attached to a glass plate via an adhesive and left at 100°C for 120 hours is -2.0% to 2.0%. The above-mentioned dimensional change rate is preferably -1.8%~1.0%, more preferably -1.0%~0.0%, and particularly preferably -0.5%~0.0%. In one embodiment, the substrate film contains an acrylic resin and core-shell particles dispersed in the acrylic resin. The thickness of the substrate film is preferably 5 μm~150 μm, more preferably 10 μm~100 μm. The substrate film is preferably substantially optically isotropic. In this specification, the so-called "substantially optically isotropic" means that the in-plane phase difference Re(550) is 0 nm~10 nm and the phase difference Rth(550) in the thickness direction is -10 nm~+10 nm. The in-plane phase difference Re(550) is more preferably 0 nm~5 nm, further preferably 0 nm~3 nm, and particularly preferably 0 nm~2 nm. The phase difference Rth(550) in the thickness direction is preferably -5 nm to +5 nm, further preferably -3 nm to +3 nm, and particularly preferably -2 nm to +2 nm. If the Re(550) and Rth(550) of the substrate film are in such a range, adverse effects on display characteristics can be prevented when the optical film is applied to an image display device. Furthermore, Re(550) is the in-plane phase difference of the film measured at 23°C using light with a wavelength of 550 nm. Re(550) can be calculated by the formula: Re(550)=(nx-ny)×d. Rth(550) is the phase difference in the thickness direction of the film measured at 23°C using light with a wavelength of 550 nm. Rth(550) can be calculated by the formula: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the direction where the in-plane refractive index becomes the maximum (i.e., the retardation axis direction), ny is the refractive index in the direction orthogonal to the retardation axis (i.e., the advance axis direction) in the plane, nz is the refractive index in the thickness direction, and d is the thickness of the film (nm). The higher the light transmittance at 380 nm when the thickness of the substrate film is 30 μm, the better. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and further preferably 90% or more. If the light transmittance is in this range, the required transparency can be ensured. The light transmittance can be measured, for example, by a method in accordance with ASTM-D-1003. The lower the haze of the substrate film, the better. Specifically, the haze is preferably less than 5%, more preferably less than 3%, further preferably less than 1.5%, and particularly preferably less than 1%. If the haze is 5% or less, the film can be given a good sense of transparency. Furthermore, even when the optical film is used as a protective layer for the visual side polarizer of an image display device, the display content can be well visualized. When the thickness of the substrate film is 30 μm, the YI (Yellowness Index) is preferably 1.27 or less, more preferably 1.25 or less, further preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, there is a situation where the optical transparency becomes insufficient. Furthermore, the YI can be obtained, for example, by the following formula based on the three stimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere spectroscopic transmittance meter (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory). YI=[(1.28X-1.06Z)/Y]×100 When the thickness of the substrate film is 30 μm, the b value (the scale of hue according to the Hunter colorimetric system) is preferably less than 1.5, and more preferably less than 1.0. When the b value is greater than 1.5, there is a case where an undesirable color tone appears. In addition, the b value can be obtained by, for example, cutting the substrate film sample into 3 cm squares, measuring the hue using a high-speed integrating sphere spectroscopic transmittance meter (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory), and evaluating the hue according to the Hunter colorimetric system. The moisture permeability of the substrate film is preferably 300 g/m ²・24 hr or less, more preferably 250 g/m ²・24 hr or less, further preferably 200 g/m ²・24 hr or less, particularly preferably 150 g/m ²・24 hr or less, and most preferably 100 g/m ²・24 hr or less. If the moisture permeability of the substrate film is within this range, a polarizing plate having excellent durability and moisture resistance can be obtained when used as a protective layer of a polarizing element. The tensile strength of the substrate film is preferably 10 MPa or more and less than 100 MPa, more preferably 30 MPa or more and less than 100 MPa. When it is less than 10 MPa, there is a possibility that sufficient mechanical strength cannot be exhibited. If it exceeds 100 MPa, there is a possibility that processability becomes insufficient. The tensile strength can be measured, for example, in accordance with ASTM-D-882-61T. The tensile elongation of the substrate film is preferably 1.0% or more, more preferably 3.0% or more, and further preferably 5.0% or more. The upper limit of the tensile elongation is, for example, 100%. When the tensile elongation is less than 1%, the toughness may be insufficient. The tensile elongation can be measured, for example, in accordance with ASTM-D-882-61T. The tensile modulus of the substrate film is preferably 0.5 GPa or more, more preferably 1 GPa or more, and further preferably 2 GPa or more. The upper limit of the tensile modulus is, for example, 20 GPa. When the tensile modulus of the film is less than 0.5 GPa, sufficient mechanical strength may not be exhibited. The tensile modulus of the film can be measured, for example, in accordance with ASTM-D-882-61T. The base film may contain any appropriate additives depending on the purpose. Specific examples of additives include: ultraviolet absorbers; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and non-ionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; lubricants, etc. Additives can be added during the polymerization of the acrylic resin or during film formation. The type, amount, combination, and addition amount of the additive can be appropriately set depending on the purpose. B-2. Acrylic resin B-2-1. Composition of acrylic resin As the acrylic resin, any suitable acrylic resin can be used. Acrylic resins typically contain (meth) alkyl acrylate as a main component as a monomer unit. In this specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid. As the (meth) alkyl acrylate constituting the main skeleton of the acrylic resin, examples include linear or branched alkyl groups with 1 to 18 carbon atoms. These can be used alone or in combination. Furthermore, any suitable copolymer monomer can be introduced into the acrylic resin by copolymerization. The type, amount, copolymerization ratio, etc. of such copolymer monomers can be appropriately set depending on the purpose. The constituent components (monomer units) of the main skeleton of the acrylic resin are described below with reference to general formula (2). The acrylic resin preferably has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleic anhydride unit, and a glutaric anhydride unit. Acrylic resins having a lactone ring unit are described, for example, in Japanese Patent Publication No. 2008-181078, the description of which is cited in this specification as a reference. The glutarimide unit is preferably represented by the following general formula (1): [Chemical 1] In the general formula (1), ^R1 and ^R2 are independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and ^R3 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In the general formula (1), it is preferred that ^R1 and ^R2 are independently a hydrogen atom or a methyl group, and ^R3 is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group. It is more preferred that ^R1 is a methyl group, ^R2 is a hydrogen atom, and ^R3 is a methyl group. The above-mentioned alkyl (meth)acrylate is typically represented by the following general formula (2): [Chemical 2] In the general formula (2), ^R4 represents a hydrogen atom or a methyl group, and ^R5 represents a hydrogen atom, or an aliphatic or alicyclic alkyl group having 1 to 6 carbon atoms which may be substituted. Examples of the substituent include halogens and hydroxyl groups. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, and 2,3,4,5-tetrahydroxypentyl (meth)acrylate. In the general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, the most preferred (meth)acrylic acid alkyl ester is methyl acrylate or methyl methacrylate. The acrylic resin may contain only a single pentylimide unit, or may contain a plurality of pentylimide units with different R ¹ , R ² and R ³ in the general formula (1). The content ratio of the pentylimide unit in the acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, further preferably 2 mol% to 40 mol%, particularly preferably 2 mol% to 35 mol%, and most preferably 3 mol% to 30 mol%. If the content ratio is less than 2 mol%, the effects derived from the pentylene imide unit (e.g., higher optical properties, higher mechanical strength, excellent adhesion of polarizing elements, and thinning) may not be fully exerted. If the content ratio exceeds 50 mol%, for example, heat resistance and transparency may become insufficient. The acrylic resin may contain only a single (meth) alkyl ester unit, or may contain a plurality of (meth) alkyl ester units in which ^R4 and ^R5 in the general formula (2) are different. The content ratio of the (meth) alkyl acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, further preferably 60 mol% to 98 mol%, particularly preferably 65 mol% to 98 mol%, and most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, there is a concern that the effects (e.g., higher heat resistance, higher transparency) derived from the (meth) alkyl acrylate unit may not be fully exerted. If the above content ratio is more than 98 mol%, there is a concern that the resin becomes brittle and easily cracks, and a higher mechanical strength cannot be fully exerted, resulting in poor productivity. The acrylic resin may also contain units other than the pentamethyleneimide unit and the (meth) alkyl acrylate unit. In one embodiment, the acrylic resin may contain, for example, 0 to 10% by weight of unsaturated carboxylic acid units that do not participate in the intramolecular imidization reaction described below. The content of the unsaturated carboxylic acid units is preferably 0 to 5% by weight, more preferably 0 to 1% by weight. If the content is within this range, transparency, retention stability, and moisture resistance can be maintained. In one embodiment, the acrylic resin may contain copolymerizable vinyl monomer units other than those described above (other vinyl monomer units). Examples of the other vinyl monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexyl methacrylate, The monomers include aminoethyl ester, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methylallylamine, N-methylallylamine, 2-isopropenyloxazoline, 2-vinyloxazoline, 2-acryloyloxazoline, N-phenylbutylene diimide, methacrylate phenylaminoethyl ester, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-phenylvinyloxazoline, etc. These monomers can be used alone or in combination. Preferred monomers are styrene monomers such as styrene and α-methylstyrene. The content of other vinyl monomer units is preferably 0 to 1% by weight, and more preferably 0 to 0.1% by weight. If it is within this range, the expression of undesired phase difference and the reduction of transparency can be suppressed. The imidization rate in the above-mentioned acrylic resin is preferably 2.5%~20.0%. If the imidization rate is in this range, a resin with excellent heat resistance, transparency and molding processability can be obtained, which can prevent the occurrence of scorching or reduction of mechanical strength during film formation. In the above-mentioned acrylic resin, the imidization rate is expressed as the ratio of the pentamethyleneimine unit to the (meth) alkyl acrylate unit. The ratio can be obtained, for example, based on the NMR (nuclear magnetic resonance) spectrum, IR (infrared) spectrum, etc. of the acrylic resin. In this embodiment, the imidization rate can be obtained by using ¹ H-NMR measurement of the resin using ¹ HNMR BRUKER AvanceIII (400 MHz). More specifically, the peak area of O-CH ₃ protons derived from (meth) alkyl esters around 3.5 to 3.8 ppm is set as A, and the peak area of N-CH ₃ protons derived from pentylene diimide around 3.0 to 3.3 ppm is set as B, and the following formula is used to calculate. Imidization rate Im(%) = {B/(A+B)}×100 The acid value of the above-mentioned acrylic resin is preferably 0.10 mmol/g~0.50 mmol/g. If the acid value is in this range, a resin with excellent balance of heat resistance, mechanical properties and molding processability can be obtained. If the acid value is too small, there are problems such as increased cost due to the use of a modifier for adjusting to the required acid value, and the generation of a gel-like substance due to the residue of the modifier. If the acid value is too large, it tends to cause foaming during film forming (for example, during melt extrusion) and thus reduce the productivity of the molded product. Regarding the above-mentioned acrylic resin, the acid value is the content of carboxylic acid units and carboxylic anhydride units in the acrylic resin. In this embodiment, the acid value can be calculated by the titration method described in WO2005/054311 or Japanese Patent Publication No. 2005-23272. The weight average molecular weight of the above-mentioned acrylic resin is preferably 1000~2000000, more preferably 5000~1000000, further preferably 10000~500000, particularly preferably 50000~500000, and most preferably 60000~150000. The weight average molecular weight can be determined, for example, by converting to polystyrene using a gel permeation chromatograph (GPC system, manufactured by Tosoh). Furthermore, tetrahydrofuran can be used as a solvent. The Tg (glass transition temperature) of the above-mentioned acrylic resin is preferably above 110°C, more preferably above 115°C, further preferably above 120°C, particularly preferably above 125°C, and optimally above 130°C. If Tg is above 110°C, a polarizing plate containing a substrate film obtained from such a resin tends to have excellent durability. The upper limit of Tg is preferably below 300°C, more preferably below 290°C, further preferably below 285°C, particularly preferably below 200°C, and optimally below 160°C. If Tg is within this range, the formability will be excellent. B-2-2. Polymerization of acrylic resin The acrylic resin can be produced, for example, by the following method. The method comprises: (I) copolymerizing an alkyl (meth)acrylate monomer corresponding to the alkyl (meth)acrylate unit represented by general formula (2) with an unsaturated carboxylic acid monomer and/or its precursor monomer to obtain a copolymer (a); and (II) treating the copolymer (a) with an imidizing agent to carry out an intramolecular imidization reaction of the alkyl (meth)acrylate monomer unit and the unsaturated carboxylic acid monomer and/or its precursor monomer unit in the copolymer (a), thereby introducing the pentylene imide unit represented by general formula (1) into the copolymer. Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. As its precursor monomer, for example, acrylamide, methacrylamide, etc. can be listed. These can be used alone or in combination. The preferred unsaturated carboxylic acid monomer is acrylic acid or methacrylic acid, and the preferred precursor monomer is acrylamide. As a method for treating the copolymer (a) with an imide agent, any suitable method can be used. As a specific example, a method using an extruder and a method using a batch reactor (pressure vessel) can be listed. The method using an extruder includes heating and melting the copolymer (a) using an extruder and treating it with an imide agent. In this case, any suitable extruder can be used as the extruder. As specific examples, there can be cited: a single-screw extruder, a double-screw extruder, and a multi-screw extruder. In the method using a batch reactor (pressure vessel), any suitable batch reactor (pressure vessel) can be used. As the imidizing agent, any suitable compound can be used as long as it can generate the pentamethylenediamine unit represented by the above general formula (1). As specific examples of the imidizing agent, there can be cited: amines containing aliphatic hydrocarbon groups such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; amines containing aromatic hydrocarbon groups such as aniline, benzylamine, toluidine, and trichloroaniline; and amines containing alicyclic hydrocarbon groups such as cyclohexylamine. Furthermore, for example, urea compounds that generate such amines by heating can also be used. Examples of urea compounds include urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea. The imidizing agent is preferably methylamine, ammonia, or cyclohexylamine, and more preferably methylamine. In the imidization, in addition to the above-mentioned imidizing agent, a ring-closing promoter can also be added as needed. The amount of the imidizing agent used in the imidization is preferably 0.5 to 10 parts by weight, and more preferably 0.5 to 6 parts by weight, relative to 100 parts by weight of the copolymer (a). If the amount of the imidizing agent used is less than 0.5 parts by weight, the desired imidization rate is often not achieved. As a result, the heat resistance of the obtained resin may be extremely insufficient, and appearance defects such as scorching may occur after molding. If the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent may remain in the resin, and the imidizing agent may cause appearance defects such as scorching or foaming after molding. The production method of this embodiment may include treatment with an esterifying agent in addition to the above-mentioned imidization, if necessary. Examples of the esterifying agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethanesulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl tert-butylsilyl Chlorine, isopropyl acetate, dimethyl urea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl (trimethylsilyl) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, hexyl oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether. Among them, dimethyl carbonate is preferred from the viewpoints of cost and reactivity. The amount of the esterifying agent added can be set in such a way that the acid value of the acrylic resin becomes the desired value. B-2-3. Concurrent use of other resins In the embodiment of the present invention, the above-mentioned acrylic resin can be used in combination with other resins. That is, the monomer components constituting the acrylic resin can be copolymerized with the monomer components constituting other resins, and the copolymer can be used for film formation as described in the following item B-4; or a blend of the acrylic resin and other resins can be used for film formation. Examples of other resins include: styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene ether, polyacetal, polyimide, polyetherimide and other thermoplastic resins; phenol resins, melamine resins, polyester resins, silicone resins, epoxy resins and other thermosetting resins. The type and amount of the resin used in combination can be appropriately set according to the purpose and the expected properties of the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a phase difference control agent. When an acrylic resin is used in combination with other resins, the content of the acrylic resin in the blend of the acrylic resin and other resins is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, further preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. When the content is less than 50% by weight, there is a risk that the higher heat resistance and higher transparency of the acrylic resin itself cannot be fully reflected. B-3. Core-shell particles In the above-mentioned substrate film, the core-shell particles are preferably formulated at 5 to 50 parts by weight, and more preferably 5 to 40 parts by weight, relative to 100 parts by weight of the acrylic resin. Thereby, the dimensional change rate of the substrate film can be reduced. As a result, the shrinkage in the state where the surface treatment layer is formed can be suppressed, and an optical film with high adhesion between the substrate film and the surface treatment layer can be obtained. The core-shell particles typically have a core containing a rubber-like polymer, and a coating layer containing a glass-like polymer and coating the core. The core-shell particles have one or more layers containing a glass-like polymer as the innermost layer or the middle layer. The Tg of the rubbery polymer constituting the core is preferably below 20°C, more preferably -60°C to 20°C, and further preferably -60°C to 10°C. If the Tg of the rubbery polymer constituting the core exceeds 20°C, there is a possibility that the mechanical strength of the acrylic resin will not be sufficiently improved. The Tg of the glassy polymer (hard polymer) constituting the coating layer is preferably above 50°C, more preferably 50°C to 140°C, and further preferably 60°C to 130°C. If the Tg of the glassy polymer constituting the coating layer is lower than 50°C, there is a possibility that the heat resistance of the acrylic resin will be reduced. The content ratio of the core in the core-shell type particles is preferably 30% by weight to 95% by weight, and further preferably 50% by weight to 90% by weight. The ratio of the glassy polymer layer in the core is 0-60% by weight, preferably 0-45% by weight, and more preferably 10%-40% by weight, relative to the total amount of the core (100% by weight). The content ratio of the coating layer in the core-shell particles is preferably 5%-70% by weight, and more preferably 10%-50% by weight. In one embodiment, the core-shell particles dispersed in the acrylic resin may have a flat shape. The core-shell particles may be flattened by the extension described in item B-4 below. The length/thickness ratio of the flattened core-shell particles is 7.0 or less. The length/thickness ratio is preferably 6.5 or less, and more preferably 6.3 or less. On the other hand, the length/thickness ratio is preferably 4.0 or more, more preferably 4.5 or more, and further preferably 5.0 or more. In this specification, the so-called "ratio of length/thickness" means the ratio of the representative length of the top-view shape of the core-shell particle to the thickness. Here, the so-called "representative length" refers to the diameter when the top-view shape is circular, the major diameter when it is elliptical, and the length of the diagonal when it is rectangular or polygonal. The ratio can be calculated according to the following procedure. The obtained film cross section is photographed using a transmission electron microscope (for example, accelerating voltage 80 kV, _RuO4 staining ultrathin section method), and 30 of the longer core-shell particles (those with cross sections close to the representative length) in the obtained photograph are selected in sequence, and the (average value of length)/(average value of thickness) is calculated to obtain the ratio. The rubbery polymer constituting the core of the core-shell type particles, the glassy polymer (hard polymer) constituting the coating layer, the polymerization method thereof, and other detailed contents of the composition are described, for example, in Japanese Patent Publication No. 2016-33552. The description of the publication is cited in this specification as a reference. B-4. Formation of substrate film The substrate film of the embodiment of the present invention can be formed by a method of forming a film of a composition containing the above-mentioned acrylic resin (when other resins are used in combination, it is a blend with the other resins) and core-shell type particles. Furthermore, the method of forming the substrate film may include extending the above-mentioned film. The average particle size of the core-shell particles used for film formation is preferably 1 nm to 500 nm. The average particle size of the core is preferably 50 nm to 300 nm, more preferably 70 nm to 300 nm. Any suitable method can be used as a method for forming a film. As specific examples, there can be listed: flow casting coating method (for example, cast film method), extrusion molding method, injection molding method, compression molding method, transfer molding method, blow molding method, powder molding method, FRP (Fiber Reinforced Plastic) molding method, calendering molding method, hot pressing method. Extrusion molding method or flow casting coating method is preferred. The reason is that the smoothness of the obtained film can be improved and good optical uniformity can be obtained. Extrusion molding method is particularly preferred. The reason is that there is no need to consider the problem caused by residual solvent. Among them, the extrusion molding method using a T-die is better from the viewpoint of the productivity of the film and the ease of subsequent stretching treatment. The molding conditions can be appropriately set according to the composition or type of the resin used, the expected properties of the obtained film, etc. As a stretching method, any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching speed, stretching direction) can be adopted. As specific examples of stretching methods, free end stretching, fixed end stretching, free end shrinkage, and fixed end shrinkage can be listed. These can be used alone, at the same time, or in sequence. By stretching a film in which the amount of core-shell particles relative to the acrylic resin has been appropriately adjusted under appropriate stretching conditions, the dimensional change rate of the obtained substrate film can be reduced. As a result, shrinkage in a state where a surface treatment layer is formed can be suppressed, and an optical film with high adhesion between the base film and the surface treatment layer can be obtained. The stretching direction can be an appropriate direction depending on the purpose. Specifically, it can be listed as: length direction, width direction, thickness direction, oblique direction. The stretching direction can be one direction (uniaxial stretching), two directions (biaxial stretching), or three or more directions. In the embodiment of the present invention, representatively, uniaxial stretching in the length direction, simultaneous biaxial stretching in the length direction and the width direction, and sequential biaxial stretching in the length direction and the width direction can be adopted. Biaxial stretching (simultaneously or sequentially) is preferred. The reason is that it is easy to control the in-plane phase difference and easy to achieve optical isotropy. The stretching temperature may vary according to the optical properties, mechanical properties and thickness expected of the substrate film, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching ratio, the stretching speed, etc. Specifically, the stretching temperature is preferably Tg~Tg+50℃, more preferably Tg+15℃~Tg+50℃, and most preferably Tg+35℃~Tg+50℃. By stretching at such a temperature, a substrate film with suitable properties can be obtained. The specific stretching temperature is, for example, 110℃~200℃, preferably 120℃~190℃, and more preferably 150℃~190℃. If the stretching temperature is within this range, by appropriately adjusting the stretching ratio and the stretching speed, the film in which the amount of the shell-type particles is appropriately adjusted can be stretched under appropriate stretching conditions, thereby reducing the dimensional change rate of the obtained base film. As a result, the shrinkage in the state where the surface treatment layer is formed can be suppressed, and an optical film with high adhesion between the base film and the surface treatment layer can be obtained. In addition, the stretching ratio can also be changed according to the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching speed, etc., just like the stretching temperature. When biaxial stretching is used, the ratio of the stretching ratio in the width direction (TD) to the stretching ratio in the length direction (MD) (TD/MD) is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, and further preferably 1.0 to 1.3. In addition, the surface ratio (the product of the stretching ratio in the length direction and the stretching ratio in the width direction) when biaxial stretching is used is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, and further preferably 3.5 to 5.2. If the stretching ratio is within this range, the dimensional change rate of the obtained substrate film can be reduced by appropriately adjusting the stretching temperature and the stretching speed. As a result, shrinkage in a state where a surface treatment layer is formed can be suppressed, and an optical film with a high degree of adhesion between the substrate film and the surface treatment layer can be obtained. In addition, the stretching speed can also vary according to the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching ratio, etc., just like the stretching temperature. The stretching speed is preferably 3%/second to 20%/second, more preferably 3%/second to 15%/second, and further preferably 3%/second to 10%/second. When biaxial stretching is adopted, the stretching speed in one direction may be the same as or different from the stretching speed in the other direction. If the stretching speed is within this range, the dimensional change rate of the obtained substrate film can be reduced by appropriately adjusting the stretching temperature and the stretching ratio. As a result, shrinkage in a state where the surface treatment layer is formed can be suppressed, and an optical film with high adhesion between the substrate film and the surface treatment layer can be obtained. The substrate film can be formed in the above manner. C. Surface treatment layer The surface treatment layer is any suitable functional layer formed on one side of the substrate film according to the function required for the optical film. Specific examples of the surface treatment layer include a hard coating layer, an anti-glare layer, and an anti-reflection layer. The thickness of the surface treatment layer is preferably 3 μm to 20 μm, and more preferably 5 μm to 15 μm. The surface treatment layer is typically a hardened layer of a resin composition formed on the substrate film. The step of forming the surface treatment layer may include: coating a resin composition for forming the surface treatment layer on the substrate film to form the coating layer; and drying the coating layer to harden it to form the surface treatment layer. Drying the coating layer to harden it may include heating the coating layer. As a coating method of the resin composition, any suitable method may be adopted. For example, the following methods may be listed: rod coating method, roller coating method, gravure coating method, rod coating method, hole coating method, curtain coating method, spray coating method, and notch wheel coating method. From the viewpoint of facilitating coating, the resin composition preferably contains a solvent for dilution. The heating temperature of the coating layer can be set to any appropriate temperature corresponding to the composition of the resin composition, and is preferably set to a temperature below the glass transition temperature of the acrylic resin contained in the substrate film. If the heating is performed at a temperature below the glass transition temperature of the acrylic resin contained in the substrate film, an optical film in which deformation due to heating is suppressed can be obtained. The heating temperature of the coating layer is, for example, 50°C to 140°C, and preferably 60°C to 100°C. By heating at such a heating temperature, an optical film having excellent adhesion between the substrate film and the surface treatment layer can be obtained. C-1. Hard coating layer The hard coating layer is a layer that imparts abrasion resistance and chemical resistance to the surface of the base film. The hard coating layer preferably has a hardness of H or more, more preferably 3H or more in a pencil hardness test. The pencil hardness test can be measured in accordance with JIS K 5400. The resin composition used to form the hard coating layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.) or electron beams. The details of the hard coating layer and the resin composition used to form the hard coating layer are described, for example, in Japanese Patent Publication No. 2014-240955. All the contents of the publication are cited in this specification as a reference. C-2. Anti-glare layer The anti-glare layer is a layer used to prevent external light from being reflected by scattering and reflecting light. The resin composition used to form the anti-glare layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.) or electron beams. The anti-glare layer typically has a fine concave-convex shape on the surface. As a method for forming such a fine concave-convex shape, for example, a method of making the above-mentioned curable compound contain microparticles can be cited. The details of the anti-glare layer and the resin composition used to form the anti-glare layer are described in, for example, Japanese Patent Gazette No. 2017-32711. All the records in the gazette are cited in this specification as a reference. C-3. Anti-reflection layer The anti-reflection layer is a layer used to prevent the reflection of external light. The resin composition used to form the anti-reflection layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.) or electron beams, etc. The anti-reflection layer may be a single layer consisting of only one layer, or may be a plurality of layers including two or more layers. The details of the anti-reflection layer and the resin composition used to form the anti-reflection layer are described, for example, in Japanese Patent Gazette No. 2012-155050. All the records in the gazette are cited in this specification as a reference. D. Polarizing Plate The optical film described in Items A to C above can be applied to a polarizing plate. Therefore, the present invention also includes a polarizing plate using such an optical film. Typically, the polarizing plate has a polarizing element, and the optical film of the present invention disposed on one side of the polarizing element. For the optical film, the substrate film side thereof can be bonded to the polarizing element, and the film can function as a protective layer of the polarizing element. As the polarizing element, any suitable polarizing element can be used. For example, the resin film forming the polarizing element can be a single-layer resin film, or a laminate of two or more layers. Specific examples of polarizing elements including a single-layer resin film include: hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified films of ethylene-vinyl acetate copolymers, which are dyed and stretched using dichroic substances such as iodine or dichroic dyes; polyene-based alignment films such as dehydrated PVA films or dehydrochlorinated polyvinyl chloride films, etc. In terms of excellent optical properties, it is preferable to use a polarizing element obtained by dyeing a PVA film with iodine and uniaxially stretching it. The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, dyeing can also be performed after stretching. The PVA film is subjected to swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc. as needed. For example, by immersing the PVA film in water and washing it before dyeing, not only can the dirt or anti-adhesion agent on the surface of the PVA film be washed, but the PVA film can also be swelled to prevent uneven dyeing. As specific examples of polarizing elements obtained using a laminate, there can be cited a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by the following method: a PVA-based resin solution is coated on the resin substrate, and the PVA-based resin layer is formed on the resin substrate by drying, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing element. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution for stretching. Furthermore, stretching can further include stretching the laminate in the air at a high temperature (e.g., above 95° C.) before stretching in the boric acid aqueous solution, as needed. The obtained resin substrate/polarizing element laminate can be used directly (that is, the resin substrate can be set as a protective layer of the polarizing element), or the resin substrate can be peeled off from the resin substrate/polarizing element laminate and used on any suitable protective layer that meets the purpose on the peeled area layer. The details of the manufacturing method of such a polarizing element are described, for example, in Japanese Patent Publication No. 2012-73580. All the records in the publication are cited in this specification as a reference. The thickness of the polarizing element is, for example, 1 μm~80 μm. In one embodiment, the thickness of the polarizing element is preferably 1 μm~20 μm, and more preferably 3 μm~15 μm. E. Image display device The polarizing plate described in the above item D can be applied to an image display device. Therefore, the present invention also includes an image display device using such a polarizing plate. As representative examples of image display devices, there can be cited: a liquid crystal display device and an organic electroluminescent (EL) display device. The image display device adopts a structure well known in the industry, so a detailed description is omitted. Embodiments The present invention is specifically described below by using embodiments, but the present invention is not limited to these embodiments. The measurement method of each characteristic is described below. Furthermore, unless otherwise specifically stated, the "parts" and "%" in the embodiments are based on weight. (1) Dimensional change rate of substrate film The substrate film is cut into 10 cm×10 cm along its long side and short side directions to prepare a measurement sample. The above-mentioned test sample was bonded to a glass plate via an adhesive, placed in an environmental tester at 100°C for 120 hours, and the dimensional change rate of the substrate film was measured using QVA606-PRO-AE10 manufactured by Mitutoyo. The test sample and the glass plate were bonded using an adhesive containing 95 parts of butyl acrylate, 5 parts of acrylic acid, 0.1 parts of 2-hydroxyethyl acrylate, and 0.05 parts of 2-2-azobisisobutyronitrile. Furthermore, the dimensional change rate was measured for the test sample after being placed in the environmental tester, along a direction parallel to the cut surface (each side of the test sample) at a position 1 cm from the inner side of the end, and the dimensional change rate was calculated using the following formula. The dimensional change rate in the direction corresponding to the long side direction of the substrate film and the dimensional change rate in the direction corresponding to the short side direction were measured separately. Dimensional change rate (%) = (dimension after 120 hours at 100°C - initial dimension) / initial dimension × 100 (2) Evaluation of adhesion The adhesion of the surface treatment layer to the substrate film was evaluated according to the grid peeling test (grid number: 100) of JIS K-5400, and the following indexes were used to determine the adhesion. : Grid peeling number is 0 Δ: Grid peeling number is 1 or more and less than 10 ×: Grid peeling number is 10 or more <Production Example 1> The following compositions A to C were prepared as resin compositions for forming a surface treatment layer. (1) Composition A 16 parts by weight of 4-HBA (4-hydroxybutyl acrylate) (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 32 parts by weight of NK oligomer UA-53H-80BK (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), 48 parts by weight of Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 4 parts by weight of A-GLY-9E (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), and 2.4 parts by weight of IRGACURE 907 (manufactured by BASF) were mixed and diluted with a solvent of MIBK (methyl isobutyl ketone) and PGM (propylene glycol monomethylether) in a ratio of 50:50 to give a solid content concentration of 42.0% to obtain a UV curable resin. (2) Composition B 100 parts by weight of Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 2.4 parts by weight of IRGACURE 907 (manufactured by BASF) were mixed and diluted with a solvent of MIBK:PGM=50:50 to a solid content concentration of 42.0% to obtain a UV curable resin. (3) Composition C 20 parts by weight of 4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 40 parts by weight of NK oligomer UA-53H-80BK (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), 60 parts by weight of Viscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 5 parts by weight of IRGACURE 907 (manufactured by BASF), and 0.5 parts by weight of Techpolymer SSX-103DXE (manufactured by Sekisui Chemicals Co., Ltd.) were mixed and diluted with a solvent of toluene:MEK (methyl ethyl ketone) = 70:30 to give a solid content concentration of 40.0% to obtain a UV curable resin. <Example 1> 1. Preparation of substrate film An MS resin (MS-200; copolymer of methyl methacrylate/styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine (imidization rate: 5%). The imidized MS resin obtained has a pentylene imide unit represented by the general formula (1) (R ¹ and R ³ are methyl groups, R ² is a hydrogen atom), a (meth)acrylate unit represented by the general formula (2) (R ⁴ and R ⁵ are methyl groups), and a styrene unit. The imidization was carried out using a 15 mm diameter, unidirectional rotary double-spindle extruder. The set temperature of each temperature adjustment zone of the extruder is set to 230°C, the screw speed is set to 150 rpm, and the MS resin is supplied at 2.0 kg/hr. The supply amount of monomethylamine is set to 2 parts by weight relative to 100 parts by weight of MS resin. The MS resin is added from the hopper, and after the resin is melted and filled by the kneading section, monomethylamine is injected from the nozzle. A sealing ring is installed at the end of the reaction zone to fill the resin. The pressure of the exhaust port is reduced to -0.08 MPa to remove volatiles from the by-products and excess methylamine after the reaction. The resin discharged from the mold installed at the outlet of the extruder in the form of strands is cooled in a water tank and then granulated by a granulator. The imidization rate of the imidized MS resin obtained is 5.0%, and the acid value is 0.5 mmol/g. 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of the core-shell particles are put into a uniaxial extruder for melt mixing, and a film is formed through a T-die to obtain an extruded film. The extruded film obtained is biaxially stretched to 2 times in the length direction and the width direction at a stretching temperature of 160°C. The stretching speed is 10%/second in both the length direction and the width direction. Thus, a substrate film A is prepared. The thickness of the obtained substrate film A is 40 μm. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film A are measured. The results are shown in Table 1. 2. Preparation of optical film Composition A is applied on one side of the substrate film A to form a coating layer in such a manner that the thickness after curing becomes 6 μm. Subsequently, the coating layer is dried at 70°C and UV cured to obtain an optical film 1 having a hard coating layer formed on one side of the substrate film A. The optical film 1 is subjected to adhesion evaluation. The results are shown in Table 1. <Example 2> 1. Preparation of substrate film 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of core-shell particles are put into a uniaxial extruder for melt mixing, and a film is formed by passing through a T-die to obtain an extruded film. The extruded film obtained was biaxially stretched to 2 times in both the length direction and the width direction at a stretching temperature of 160°C. The stretching speed was 10%/sec in both the length direction and the width direction. Thus, a substrate film B was prepared. The thickness of the obtained substrate film B was 35 μm. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film B were measured. The results are shown in Table 1. 2. Preparation of optical film In addition to using the above-mentioned substrate film B, an optical film 2 having a hard coating layer formed on one side of the substrate film B was obtained in the same manner as in Example 1. The above-mentioned optical film 2 was provided for adhesion evaluation. The results are shown in Table 1. <Example 3> 1. Preparation of substrate film The imidized MS resin obtained above is put into a uniaxial extruder for melt mixing, and a film is formed through a T-die to obtain an extruded film. The extruded film obtained is biaxially stretched to 2 times in both the length direction and the width direction at a stretching temperature of 160°C. The stretching speed is 10%/sec in both the length direction and the width direction. In this way, a substrate film C is prepared. The thickness of the obtained substrate film C is 30 μm. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film C are measured. The results are shown in Table 1. 2. Preparation of optical film Except for using the above-mentioned substrate film C, an optical film 3 having a hard coating layer formed on one side of the substrate film C is obtained in the same manner as in Example 1. The above-mentioned optical film 3 is provided for adhesion evaluation. The results are shown in Table 1. <Example 4> 1. Preparation of substrate film Except for setting the formulation amount of core-shell type particles to 10 parts by weight, a substrate film D is prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film D are measured. The results are shown in Table 1. 2. Preparation of optical film Except for using the above-mentioned substrate film D, an optical film 4 having a hard coating layer formed on one side of the substrate film D is obtained in the same manner as in Example 1. The above-mentioned optical film 4 is provided for adhesion evaluation. The results are shown in Table 1. <Example 5> In the same manner as in Example 4, an optical film 5 having a hard coating layer formed on one side of the substrate film D was obtained except that the composition B was applied to one side of the substrate film D and dried to cure. The optical film 5 was subjected to an adhesiveness evaluation. The results are shown in Table 1. <Example 6> In the same manner as in Example 4, an optical film 6 having an anti-glare layer formed on one side of the substrate film D was obtained except that the composition C was applied to one side of the substrate film D and cured to form an anti-glare layer. The optical film 6 was subjected to an adhesiveness evaluation. The results are shown in Table 1. <Example 7> 1. Preparation of substrate film The amount of core-shell particles was set to 10 parts by weight, and the stretching temperature of the extruded film was set to 150°C. Substrate film E was prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of substrate film E were measured. The results are shown in Table 1. 2. Preparation of optical film In addition to using the above-mentioned substrate film E, an optical film 7 having a hard coating layer formed on one side of substrate film E was obtained in the same manner as in Example 1. The above-mentioned optical film 7 was subjected to adhesion evaluation. The results are shown in Table 1. <Example 8> 1. Preparation of substrate film A substrate film F is prepared in the same manner as Example 3, except that the amount of core-shell particles is set to 15 parts by weight and the stretching temperature of the extruded film is set to 152°C. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film F are measured. The results are shown in Table 1. 2. Preparation of optical film An optical film 8 having a hard coating layer formed on one side of the substrate film F is obtained in the same manner as Example 1, except that the above-mentioned substrate film F is used. The above-mentioned optical film 8 is provided for adhesion evaluation. The results are shown in Table 1. <Example 9> 1. Preparation of substrate film A substrate film G is prepared in the same manner as Example 3, except that the stretching temperature of the extruded film is set to 155°C. The dimensional change rate of the substrate film G in the long side direction and the dimensional change rate in the short side direction were measured. The results are shown in Table 1. 2. Preparation of optical film An optical film 9 having a hard coating layer formed on one side of the substrate film G was obtained in the same manner as in Example 1 except that the above-mentioned substrate film G was used. The above-mentioned optical film 9 was subjected to adhesion evaluation. The results are shown in Table 1. <Example 10> 1. Preparation of substrate film A substrate film H was prepared in the same manner as in Example 3 except that the amount of core-shell particles was set to 10 parts by weight and the stretching temperature of the extruded film was set to 140°C. The dimensional change rate of the substrate film H in the long side direction and the dimensional change rate in the short side direction were measured. The results are shown in Table 1. 2. Preparation of optical film In addition to using the above-mentioned substrate film H, an optical film 10 having a hard coating layer formed on one side of the substrate film H is obtained in the same manner as in Example 1. The above-mentioned optical film 10 is provided for adhesion evaluation. The results are shown in Table 1. <Example 11> 1. Preparation of substrate film In addition to setting the formulation amount of core-shell particles to 23 parts by weight and setting the stretching temperature of the extruded film to 152°C, a substrate film I is prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film I are measured. The results are shown in Table 1. 2. Preparation of optical film In addition to using the above-mentioned substrate film I, an optical film 11 having a hard coating layer formed on one side of the substrate film I is obtained in the same manner as in Example 1. The optical film 11 was subjected to an evaluation of adhesion. The results are shown in Table 1. <Example 12> 1. Preparation of substrate film The amount of core-shell particles was set to 5 parts by weight, and the stretching temperature of the extruded film was set to 140°C. A substrate film J was prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film J were measured. The results are shown in Table 1. 2. Preparation of optical film An optical film 12 having a hard coating layer formed on one side of the substrate film J was obtained in the same manner as in Example 1, except that the substrate film J was used. The optical film 12 was subjected to an evaluation of adhesion. The results are shown in Table 1. <Example 13> 1. Preparation of substrate film A substrate film K is prepared in the same manner as Example 3, except that the amount of core-shell particles is set to 23 parts by weight and the stretching temperature of the extruded film is set to 140°C. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film K are measured. The results are shown in Table 1. 2. Preparation of optical film An optical film 13 having a hard coating layer formed on one side of the substrate film K is obtained in the same manner as Example 1, except that the above-mentioned substrate film K is used. The above-mentioned optical film 13 is provided for adhesion evaluation. The results are shown in Table 1. <Example 14> 1. Preparation of substrate film A substrate film L is prepared in the same manner as Example 3, except that the stretching temperature of the extruded film is set to 150°C. The dimensional change rate of the substrate film L in the long side direction and the dimensional change rate in the short side direction were measured. The results are shown in Table 1. 2. Preparation of optical film An optical film 14 having a hard coating layer formed on one side of the substrate film L was obtained in the same manner as in Example 1 except that the above-mentioned substrate film L was used. The above-mentioned optical film 14 was provided for adhesion evaluation. The results are shown in Table 1. <Comparative Example 1> 1. Preparation of substrate film A substrate film M was prepared in the same manner as in Example 3 except that the stretching temperature of the extruded film was set to 130°C. The dimensional change rate of the substrate film M in the long side direction and the dimensional change rate in the short side direction were measured. The results are shown in Table 1. 2. Preparation of optical film Except for using the above-mentioned substrate film M, an optical film 15 having a hard coating layer formed on one side of the substrate film M is obtained in the same manner as in Example 1. The above-mentioned optical film 15 is provided for adhesion evaluation. The results are shown in Table 1. <Comparative Example 2> 1. Preparation of substrate film Except for setting the stretching temperature of the extruded film to 140°C, a substrate film N is prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film N are measured. The results are shown in Table 1. 2. Preparation of optical film Except for using the above-mentioned substrate film N, an optical film 16 having a hard coating layer formed on one side of the substrate film N is obtained in the same manner as in Example 1. The above-mentioned optical film 16 is provided for adhesion evaluation. The results are shown in Table 1. <Comparative Example 3> In addition to forming a hard coating layer by coating composition B on one side of the above-mentioned substrate film N and drying and hardening it, an optical film 17 having a hard coating layer formed on one side of the substrate film N was obtained in the same manner as in Comparative Example 2. The optical film 17 was subjected to an adhesion evaluation. The results are shown in Table 1. <Comparative Example 4> In addition to forming an anti-glare layer by coating composition C on one side of the above-mentioned substrate film N and drying and hardening it, an optical film 18 having an anti-glare layer formed on one side of the substrate film N was obtained in the same manner as in Comparative Example 2. The optical film 18 was subjected to an adhesion evaluation. The results are shown in Table 1. <Comparative Example 5> 1. Preparation of substrate film The amount of core-shell particles was set to 3 parts by weight, and the stretching temperature of the extruded film was set to 140°C. In addition, a substrate film O was prepared in the same manner as in Example 3. The dimensional change rate in the long side direction and the dimensional change rate in the short side direction of the substrate film O were measured. The results are shown in Table 1. 2. Preparation of optical film In addition to using the above-mentioned substrate film O, an optical film 19 having a hard coating layer formed on one side of the substrate film O was obtained in the same manner as in Example 1. The above-mentioned optical film 19 was provided for adhesion evaluation. The results are shown in Table 1. [Table 1] According to Table 1, the optical films of Examples 1 to 14 using substrate films with a dimensional change rate in the long side direction and a dimensional change rate in the short side direction of -2.0% to 0% have a higher adhesion of the surface treatment layer to the substrate film. [Industrial Applicability] The optical film of the present invention can be suitably used as a protective layer of a polarizing element. A polarizing plate having the optical film of the present invention as a protective layer can be suitably used in an image display device. The image display device as described above can be used for: portable devices such as portable information terminals (PDAs), smart phones, mobile phones, clocks, digital cameras, portable game consoles, etc.; OA devices such as computer monitors, laptops, and copiers; home electrical appliances such as video recorders, televisions, and microwave ovens; vehicle-mounted devices such as rear monitors, monitors for car navigation systems, and car stereos; display devices such as digital signs and information displays for commercial stores; security devices such as surveillance monitors; nursing and medical devices such as nursing monitors and medical monitors, etc.

10‧‧‧Substrate film 20‧‧‧Surface treatment layer 100‧‧‧Optical film

FIG. 1 is a schematic cross-sectional view of an optical film according to an embodiment of the present invention.

10‧‧‧Substrate film

20‧‧‧Surface treatment layer

100‧‧‧Optical film

Claims (7)

An optical film, which includes a base film as a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the base film, wherein the base film in the optical film is cut to 10 cm× 10cm and attached to the glass plate through an adhesive material, the dimensional change rate when left to stand at 100°C for 120 hours is -2.0%~0%, and the above-mentioned surface treatment layer is coated on the above-mentioned base film Hardened layer of resin composition. The optical film of claim 1, wherein the base film contains the acrylic resin and core-shell particles dispersed in the acrylic resin. The optical film of claim 2, wherein the base film contains 5 to 50 parts by weight of the core-shell particles based on 100 parts by weight of the acrylic resin. The optical film according to any one of claims 1 to 3, wherein the acrylic resin has a component selected from the group consisting of glutadiyl imine units, lactone ring units, maleic anhydride units, maleic imine units, and At least one of the group consisting of glutaric anhydride units. An optical film as claimed in any one of claims 1 to 3, wherein the surface treatment layer is at least one selected from the group consisting of a hard coating layer, an anti-glare layer and an anti-reflection layer. A polarizing plate, which includes a polarizing element and a protection arranged on one side of the polarizing element. layer, and the above-mentioned protective layer is an optical film according to any one of claims 1 to 5. An image display device provided with the polarizing plate of claim 6.