CN110537115B

CN110537115B - Optical film, polarizing plate and image display device

Info

Publication number: CN110537115B
Application number: CN201880024168.2A
Authority: CN
Inventors: 茂手木佑辅; 岸敦史; 上野友德; 平冈慎哉
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-04-10
Filing date: 2018-04-02
Publication date: 2023-02-17
Anticipated expiration: 2038-04-02
Also published as: CN110537115A; KR20190132410A; WO2018190172A1; TW201842364A; JPWO2018190172A1; TWI763824B; JP7083339B2

Abstract

The invention provides an optical film with high adhesion between a base material film and a surface treatment layer. The optical film of the present invention is an optical film comprising a base film which is a stretched film containing an acrylic resin and a surface treatment layer formed on one side of the base film, wherein the maximum elongation of the base film to the softening point in the optical film is 0.40% or more in TMA measurement in which the temperature is raised from 24 ℃ to 150 ℃ at 5 ℃/min while applying a tensile load of 98 mN/min.

Description

Optical film, polarizing plate and image display device

Technical Field

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

Background

In recent years, an optical film in which a functional layer (surface treatment layer) such as a hard coat layer, an antiglare layer, and an antireflection layer is formed on one side of a base film made of an acrylic resin has been known (patent document 1). The surface treatment layer may be formed by coating a resin composition on one side of the substrate film and drying or hardening. Such an optical film can be used, for example, as a protective film for a polarizer or a front panel of an image display device.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-218478

Disclosure of Invention

Problems to be solved by the invention

However, in the conventional optical film as described above, wrinkles may be generated in the base film by heat shrinkage in the step of drying the resin composition, which may result in poor appearance. When the resin composition is dried at a low temperature in order to prevent the above-described problems caused by thermal shrinkage, there is a problem that the adhesion between the base film and the surface-treated layer is insufficient.

The present invention has been made to solve the above conventional problems, and a main object thereof is to provide an optical film having high adhesion between a base film and a surface-treated layer, a polarizing plate provided with the optical film, and an image display device provided with the polarizing plate.

Means for solving the problems

The optical film of the present invention comprises a base film which is a stretched film containing an acrylic resin, and a surface treatment layer formed on one side of the base film, and the maximum elongation of the base film to the softening point in the optical film is 0.40% or more in TMA (thermal mechanical analysis) measurement in which the temperature is raised from 24 ℃ to 150 ℃ at 5 ℃/min while applying a tensile load of 98 mN/min.

In one embodiment, the base film includes the acrylic resin and core-shell particles dispersed in the acrylic resin.

In one embodiment, the base film contains 5 to 50 parts by weight of the core-shell particles per 100 parts by weight of the acrylic resin.

In one embodiment, the acrylic resin has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit.

In one embodiment, the surface treatment layer is a hardened layer of a resin composition applied to the substrate film.

In one embodiment, the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an antiglare layer, and an antireflection layer.

According to another aspect of the present invention, there is provided a polarizing plate. The polarizing plate includes a polarizer and a protective layer disposed on one side of the polarizer, and the protective layer is the optical film.

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

Effects of the invention

According to the present invention, by using the base film having the maximum elongation of 0.40% or more, an optical film having high adhesion between the base film and the surface treatment layer, a polarizing plate including the optical film, and an image display device including the polarizing plate can be provided.

Drawings

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

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Integral construction of optical films

Fig. 1 is a schematic cross-sectional view of an optical film according to an 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 base film 10 is a stretched film containing an acrylic resin. The maximum elongation of the base film 10 to the softening point in the TMA measurement in which the temperature is raised from 24 ℃ to 150 ℃ at 5 ℃/min while applying a tensile load of 98 mN/min in a predetermined direction is 0.40% or more. The maximum elongation of the base film can be measured by cutting the film to a size suitable for TMA measurement, if necessary, using a thermomechanical analyzer. When the base material film is in a long or rectangular shape, the predetermined direction is typically at least one of a longitudinal direction and a transverse direction (a direction orthogonal to the longitudinal direction) of the base material film. When the base film is square, the predetermined direction is typically a direction along at least any one side of the base film. In one embodiment, the base film 10 includes an acrylic resin and core-shell type particles dispersed in the acrylic resin. In this case, the base film 10 preferably contains 5 to 50 parts by weight of the core-shell particles per 100 parts by weight of the acrylic resin. 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 maleimide unit, and a glutaric anhydride unit. The surface treatment layer 20 is typically a hardened layer of a resin composition applied to the base film 10. The surface treatment layer 20 is preferably at least one selected from the group consisting of a hard coat layer, an antiglare layer, and an antireflection layer. According to the optical film, the penetration of the composition for forming the surface treatment layer 20 into the substrate film 10 can be promoted. As a result, the adhesion between the base material film 10 and the surface treatment layer 20 can be improved by the Anchoring effect (Anchoring effect). In particular, when the surface treatment layer 20 is formed by applying the resin composition onto the base film 10, drying the resin composition, and curing the resin composition, sufficient adhesion between the base 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 in the base film due to heat at the time of drying the resin composition can be suppressed.

B. Substrate film

B-1. Characteristics of the substrate film

The base film is a stretched film containing an acrylic resin as described above, and the maximum elongation to the softening point in TMA measurement in which the temperature is raised from 24 ℃ to 150 ℃ at 5 ℃/min while applying a tensile load of 98 mN/min in a predetermined direction is 0.40% or more. The maximum elongation is preferably 0.50% or more, and more preferably 0.60% or more. On the other hand, the upper limit of the maximum elongation is preferably 2.0%. If the maximum elongation is too high, the polarizer may be cracked due to a difference in shrinkage rate between the polarizer and the optical film when the optical film is bonded to the polarizer and used as a protective layer for the polarizer. In one embodiment, the base material film includes an acrylic resin and core-shell particles dispersed in the acrylic resin. The thickness of the base film is preferably 5 to 150. Mu.m, more preferably 10 to 100. Mu.m.

The substrate film preferably has substantial optical isotropy. In the present specification, the phrase "having substantially optical isotropy" means that the in-plane retardation Re (550) is from 0nm to 10nm and the retardation Rth (550) in the thickness direction is from-10 nm to +10nm. The in-plane retardation Re (550) is more preferably 0nm to 5nm, still more preferably 0nm to 3nm, particularly preferably 0nm to 2nm. The retardation Rth (550) in the thickness direction is more preferably from-5 nm to +5nm, still more preferably from-3 nm to +3nm, and particularly preferably from-2 nm to +2nm. When Re (550) and Rth (550) of the base film are in such ranges, adverse effects on display characteristics can be prevented when the optical film is applied to an image display device. Re (550) is an in-plane retardation of the film measured by light having a wavelength of 550nm at 23 ℃. Re (550) can be represented by the formula: re (550) = (nx-ny) × d. Rth (550) is a retardation in the thickness direction of the film measured by light having a wavelength of 550nm at 23 ℃. Rth (550) can be represented by the formula: rth (550) = (nx-nz) × d. Where nx is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., the slow axis direction), ny is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), nz is a refractive index in the thickness direction, and d is a thickness (nm) of the film.

The higher the light transmittance at 380nm when the thickness of the substrate film is 30 μm, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and further preferably 90% or more. When the light transmittance is in such a range, desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the substrate film, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good transparent feeling can be imparted to the film. Further, even when the optical film is used as a protective layer of a polarizing plate on the visual confirmation side of an image display device, the display contents can be visually confirmed well.

The YI (Yellowness Index) of the substrate film at a thickness of 30 μm is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20 or less. When YI exceeds 1.3, optical transparency may be insufficient. YI can be obtained from the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere type spectral transmittance measuring instrument (trade name DOT-3C: manufactured by Colorkun technical research in village), for example, by the following equation.

YI＝[(1.28X-1.06Z)/Y]×100

The b value (scale of hue according to the hanter (Hunter) color system) when the thickness of the base film is 30 μm is preferably less than 1.5, and more preferably 1.0 or less. When the b value is 1.5 or more, an undesirable color tone may appear. The b value can be obtained by, for example, cutting a substrate film sample to a 3cm square, measuring the hue using a high-speed integrating sphere type spectral transmittance measuring instrument (trade name DOT-3C, manufactured by murakamura color technology research), and evaluating the hue according to the hanter color system.

The substrate film preferably has a moisture permeability of 300g/m ² 24 hours or less, more preferably 250g/m ² 24 hours or less, more preferably 200g/m ² 24 hours or less, particularly preferably 150g/m ² 24 hours or less, most preferably 100g/m ² 24 hours or less. When the base film has a moisture permeability in such a range, a polarizing plate having excellent durability and moisture resistance can be obtained when the base film is used as a protective layer for a polarizer.

The tensile strength of the base film is preferably 10MPa or more and less than 100MPa, and more preferably 30MPa or more and less than 100MPa. When the pressure is less than 10MPa, sufficient mechanical strength may not be exhibited. If the pressure exceeds 100MPa, the workability may be insufficient. Tensile strength can be determined, for example, according to ASTM-D-882-61T.

The tensile elongation of the base 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. Tensile elongation can be measured, for example, according to ASTM-D-882-61T.

The tensile elastic modulus of the base film is preferably 0.5GPa or more, more preferably 1GPa or more, and still more preferably 2GPa or more. The upper limit of the tensile modulus of elasticity is, for example, 20GPa. When the tensile elastic modulus is less than 0.5GPa, sufficient mechanical strength may not be exhibited. Tensile modulus can be measured, for example, according to ASTM-D-882-61T.

The substrate film may contain any suitable additive according to the purpose. Specific examples of the additive include an ultraviolet absorber; antioxidants such as hindered phenol type, phosphorus type, and sulfur type; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; a near infrared ray absorber; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; an organic filler or an inorganic filler; a resin modifier; organic or inorganic fillers; a plasticizer; lubricants, and the like. The additives may be added during polymerization of the acrylic resin or during film formation. The kind, amount, combination, addition amount, and the like of the additive can be appropriately set according to the purpose.

B-2 acrylic resin

B-2-1. Constitution of acrylic resin

As the acrylic resin, any suitable acrylic resin can be used. Typically, an acrylic resin contains an alkyl (meth) acrylate as a monomer unit as a main component. In the present specification, "(meth) acrylic" means acrylic acid and/or methacrylic acid. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include alkyl (meth) acrylates in which the alkyl group having a straight chain or branched chain has 1 to 18 carbon atoms. They may be used alone or in combination. Further, any suitable comonomer may be introduced into the acrylic resin by copolymerization. The kind, amount, copolymerization ratio and the like of such comonomers can be appropriately set according to the purpose. The constituent components (monomer units) of the main skeleton of the acrylic resin are described below with reference to the 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 maleimide unit, and a glutaric anhydride unit. An acrylic resin having a lactone ring unit is described in, for example, japanese patent application laid-open No. 2008-181078, and the description of this publication is incorporated herein by reference. The glutarimide unit is preferably represented by the following general formula (1):

in the general formula (1), R ¹ And R ² Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ³ Represents 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), R is preferably ¹ And R ² Each independently is a hydrogen atom or a methyl group, and R ³ Is a hydrogen atom, a methyl group, a butyl group or a cyclohexyl group. More preferably R ¹ Is methyl, R ² Is a hydrogen atom, and R ³ Is methyl.

The above-mentioned alkyl (meth) acrylate is typically represented by the following general formula (2):

in the general formula (2), R ⁴ Represents a hydrogen atom or a methyl group, R ⁵ Represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. As substituents, e.g.Examples thereof include halogen and hydroxyl. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, 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, 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 Preferably a hydrogen atom or a methyl group. Thus, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single glutarimide unit, or may contain R in the general formula (1) ¹ 、R ² And R ³ Different glutarimide units.

The content ratio of the glutarimide unit in the acrylic resin is preferably 2 to 50 mol%, more preferably 2 to 45 mol%, even more preferably 2 to 40 mol%, particularly preferably 2 to 35 mol%, and most preferably 3 to 30 mol%. If the content is less than 2 mol%, the effects derived from the glutarimide unit (for example, high optical characteristics, high mechanical strength, excellent adhesiveness to a polarizer, and thinning) may not be sufficiently exhibited. If the content exceeds 50 mol%, for example, heat resistance and transparency may become insufficient.

The acrylic resin may contain only a single alkyl (meth) acrylate unit, or may contain R in the general formula (2) ⁴ And R ⁵ Different plurality of alkyl (meth) acrylate units.

The content ratio of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 to 98 mol%, more preferably 55 to 98 mol%, still more preferably 60 to 98 mol%, particularly preferably 65 to 98 mol%, and most preferably 70 to 97 mol%. If the content is less than 50 mol%, the effects (e.g., high heat resistance and high transparency) derived from the alkyl (meth) acrylate unit may not be sufficiently exhibited. If the content is more than 98 mol%, the resin may be brittle and easily cracked, and a high mechanical strength may not be sufficiently exhibited, resulting in poor productivity.

The acrylic resin may contain units other than the glutarimide units and the alkyl (meth) acrylate units.

In one embodiment, the acrylic resin may contain unsaturated carboxylic acid units, for example, 0 to 10% by weight, which do not participate in the intramolecular imidization reaction described below. The content ratio of the unsaturated carboxylic acid unit is preferably 0 to 5% by weight, more preferably 0 to 1% by weight. When the content is within such a range, transparency, retention stability and moisture resistance can be maintained.

In one embodiment, the acrylic resin may contain a copolymerizable vinyl monomer unit (other vinyl monomer unit) other than those described above. Examples of the other vinyl monomer 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, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methallylamine, 2-isopropenyloxazoline, 2-vinyloxazoline, 2-acryloyloxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α -methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryloxazoline and the like. They may be used alone or in combination. Styrene monomers such as styrene and α -methylstyrene are preferred. The content ratio of the other vinyl monomer unit is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. Within such a range, undesirable expression of retardation and deterioration of transparency can be suppressed.

The imidization ratio in the acrylic resin is preferably 2.5% to 20.0%. When the imidization ratio is in such a range, a resin excellent in heat resistance, transparency and molding processability can be obtained, and occurrence of scorching and reduction in mechanical strength at the time of film molding can be prevented. In the above-mentioned acrylic resin, the imidization ratio is represented by the ratio of glutarimide units to alkyl (meth) acrylate units. This ratio can be obtained, for example, from an NMR (Nuclear magnetic resonance) spectrum, an IR (Infrared) spectrum, or the like of the acrylic resin. In the present embodiment, the imidization ratio can be used ¹ HNMR BRUKER AvanceIII (400 MHz), by resin ¹ H-NMR was measured. More specifically, about 3.5 to 3.8ppm of O-CH derived from an alkyl (meth) acrylate ₃ A represents the area of proton peak, and N-CH derived from glutarimide in the vicinity of 3.0 to 3.3ppm ₃ The peak area of proton is represented by B and is determined by the following equation.

Imidization ratio Im (%) = { B/(A + B) } × 100

The acid value of the acrylic resin is preferably 0.10mmol/g to 0.50mmol/g. When the acid value is within such a range, a resin having an excellent balance among heat resistance, mechanical properties, and moldability can be obtained. If the acid value is too small, there may be problems such as an increase in cost due to the use of a modifier for adjusting the acid value to a desired value, and generation of a gel-like material due to the remaining modifier. If the acid value is too large, foaming tends to occur during film molding (for example, during melt extrusion), and the productivity of the molded article tends to be lowered. The acid value of the acrylic resin is the content of carboxylic acid units and carboxylic acid anhydride units in the acrylic resin. In the present embodiment, the acid value can be calculated by a titration method described in, for example, WO2005/054311 or Japanese patent application laid-open No. 2005-23272.

The weight average molecular weight of the acrylic resin is preferably 1000 to 2000000, more preferably 5000 to 1000000, still more preferably 10000 to 500000, particularly preferably 50000 to 500000, and most preferably 60000 to 150000. The weight average molecular weight can be determined by polystyrene conversion using a gel permeation chromatograph (GPC system, manufactured by Tosoh), for example. Tetrahydrofuran may be used as a solvent.

The Tg (glass transition temperature) of the acrylic resin is preferably 110 ℃ or higher, more preferably 115 ℃ or higher, still more preferably 120 ℃ or higher, particularly preferably 125 ℃ or higher, and most preferably 130 ℃ or higher. When the Tg is 110 ℃ or higher, a polarizing plate including a base film obtained from such a resin tends to have excellent durability. The upper limit of Tg is preferably 300 ℃ or lower, more preferably 290 ℃ or lower, still more preferably 285 ℃ or lower, particularly preferably 200 ℃ or lower, and most preferably 160 ℃ or lower. When Tg is in such a range, moldability is excellent.

B-2-2 polymerization of acrylic resin

The acrylic resin can be produced, for example, by the following method. The method comprises the following steps: (I) Copolymerizing an alkyl (meth) acrylate monomer corresponding to the alkyl (meth) acrylate unit represented by the general formula (2) with an unsaturated carboxylic acid monomer and/or a precursor monomer thereof to obtain a copolymer (a); and (II) treating the copolymer (a) with an imidizing agent to thereby effect intramolecular imidization of the alkyl (meth) acrylate monomer units in the copolymer (a) with the unsaturated carboxylic acid monomer and/or precursor monomer units thereof, thereby introducing the glutarimide units represented by the 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. Examples of the precursor monomer include acrylamide and methacrylamide. They may 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 imidizing agent, any appropriate method can be used. Specific examples thereof include a method using an extruder and a method using a batch-type reaction tank (pressure vessel). The method using an extruder includes melting the copolymer (a) by heating using an extruder and treating it with an imidizing agent. In this case, any suitable extruder can be used as the extruder. Specific examples thereof include a single screw extruder, a twin screw extruder, and a multi-screw extruder. In the method using a batch reaction tank (pressure vessel), any suitable batch reaction tank (pressure vessel) may be used.

As the imidizing agent, any suitable compound can be used as long as it can form a glutarimide unit represented by the above general formula (1). Specific examples of the imidizing agent include aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine and trichloroaniline; alicyclic hydrocarbon group-containing amines such as cyclohexylamine. Further, for example, a urea compound which generates such an amine by heating may be used. Examples of the urea compound include urea, 1, 3-dimethylurea, 1, 3-diethylurea, and 1, 3-dipropylurea. The imidizing agent is preferably methylamine, ammonia, cyclohexylamine, more preferably methylamine.

In the imidization, a ring-closing accelerator may be added as needed in addition to the above-mentioned imidizing agent.

The amount of the imidizing agent used in imidization is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 6 parts by weight, based on 100 parts by weight of the copolymer (a). If the amount of the imidizing agent used is less than 0.5 part by weight, the desired imidization rate may not be achieved in many cases. As a result, the heat resistance of the obtained resin may be extremely insufficient, and appearance defects such as scorch may be induced after molding. If the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent may remain in the resin and induce appearance defects such as scorch after molding or foaming.

The production method of the present embodiment may include, in addition to the above imidization, a treatment with an esterifying agent, if necessary.

Examples of the esterifying agent include dimethyl carbonate, 2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl tosylate, methyl triflate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl phosphite (trimethylsilane) ester, trimethyl phosphite, trimethyl phosphate, tritolyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among them, dimethyl carbonate is preferable from the viewpoint of cost, reactivity, and the like.

The amount of the esterification agent to be added may be set so that the acid value of the acrylic resin becomes a desired value.

B-2-3. Combinations of other resins

In an embodiment of the present invention, the acrylic resin may be used in combination with another resin. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be subjected to film formation as described in the following item B-4; blends of acrylic resins with other resins may also be used for film formation. Examples of the other resin include other thermoplastic resins such as styrene-based resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene ether, polyacetal, polyimide, and polyether imide; thermosetting resins such as phenol-based resins, melamine-based resins, polyester-based resins, silicone-based resins, and epoxy-based resins. The kind and blending amount of the resin to be used may be appropriately set according to the purpose, the desired properties of the obtained film, and the like. For example, a styrene resin (preferably, an acrylonitrile-styrene copolymer) can be used in combination as a retardation controller.

When the acrylic resin is used in combination with another resin, the content of the acrylic resin in the blend of the acrylic resin and another resin is preferably 50 to 100% by weight, more preferably 60 to 100% by weight, still more preferably 70 to 100% by weight, and particularly preferably 80 to 100% by weight. When the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected.

B-3. Core-shell particles

In the base film, the core-shell particles are preferably incorporated in an amount of 5 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the acrylic resin. Thus, when the surface-treated layer is formed on the base film, the penetration of the composition for forming the surface-treated layer into the base film can be further promoted, and an optical film having high adhesion between the base film and the surface-treated layer can be obtained.

The core-shell particles typically have a core made of a rubbery polymer and a covering layer made of a glassy polymer and covering the core. The core-shell particles have one or more layers composed of a glassy polymer as an innermost layer or an intermediate layer.

The Tg of the rubbery polymer constituting the core is preferably 20 ℃ or lower, more preferably-60 to 20 ℃, and still more preferably-60 to 10 ℃. If the Tg of the rubbery polymer constituting the core exceeds 20 ℃, there is a possibility that the mechanical strength of the acrylic resin is not sufficiently improved. The Tg of the glassy polymer (hard polymer) constituting the covering layer is preferably 50 ℃ or higher, more preferably 50 to 140 ℃, and further preferably 60 to 130 ℃. If the Tg of the glassy polymer constituting the cover layer is less than 50 ℃, the heat resistance of the acrylic resin may be lowered.

The content ratio of the core in the core-shell particles is preferably 30 to 95 wt%, and more preferably 50 to 90 wt%. The proportion of the glassy polymer layer in the core is 0 to 60 wt%, preferably 0 to 45 wt%, and more preferably 10 to 40 wt% with respect to 100 wt% of the total amount of the core. The content ratio of the coating layer in the core-shell particles is preferably 5 to 70 wt%, and more preferably 10 to 50 wt%.

In one embodiment of the present invention, the substrate is,the core-shell particles dispersed in the acrylic resin may have a flat shape. The core-shell particles can be flattened by stretching as described in item B-4 below. The ratio of length/thickness of the flattened core-shell particles is 7.0 or less. The length/thickness ratio is preferably 6.5 or less, 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 the present specification, the "length/thickness ratio" refers to a ratio of a representative length to a representative thickness of a planar shape of the core-shell particles. The term "representative length" refers to a diameter in the case of a circular shape in plan view, a major diameter in the case of an elliptical shape, and a length of a diagonal line in the case of a rectangular or polygonal shape. This ratio can be obtained, for example, by the following procedure. Using transmission electron microscope (e.g. accelerating voltage of 80kV, ruO) ₄ Dyed ultrathin section method), the ratio can be obtained by taking an image of the obtained film cross section, sequentially selecting 30 particles (particles having a cross section close to a representative length) from among the longer particles present in the obtained photograph, and calculating the (average value of the length)/(average value of the thickness).

The rubber-like polymer constituting the core of the core-shell particles, the glassy polymer (hard polymer) constituting the coating layer, the polymerization method thereof, and the details of the other constitution are described in, for example, japanese patent laid-open No. 2016-33552. The disclosure of this publication is incorporated herein by reference.

B-4 formation of base Material film

The base film according to an embodiment of the present invention can be formed typically by a method including forming a film from a composition containing the above-described acrylic resin (a blend with another resin in the case where the other resin is used in combination) and the core-shell particles. Further, the method of forming the substrate film may include stretching the above-described film.

The average particle diameter of the core-shell particles used for film formation is preferably 1nm to 500nm. The average particle diameter of the core is preferably 50nm to 300nm, more preferably 70nm to 300nm.

As a method of forming the film, any suitable method may be adopted. Specific examples thereof include a casting method (e.g., a casting method), an extrusion molding method, an injection molding method, a compression molding method, a transfer molding method, a blow molding method, a powder molding method, an FRP (Fiber Reinforced Plastic) molding method, a calendar molding method, and a hot press method. Extrusion or cast coating is preferred. The reason for this is that: the smoothness of the obtained film can be improved and good optical uniformity can be obtained. Extrusion molding is particularly preferred. The reason for this is that there is no need to consider the problem caused by the residual solvent. Among them, the extrusion molding method using a T die is preferable from the viewpoint of productivity of the film and easiness of subsequent stretching treatment. The molding conditions may be appropriately set according to the composition or kind of the resin used, the properties desired for the obtained film, and the like.

As the stretching method, any suitable stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching speed, and stretching direction) can be adopted. Specific examples of the stretching method include free end stretching, fixed end stretching, free end shrinking, and fixed end shrinking. They can be used alone, simultaneously or gradually. When a surface-treated layer is formed on the obtained base film by stretching a film in which the amount of the core-shell particles blended with the acrylic resin is appropriately adjusted under appropriate stretching conditions, the penetration of the composition for forming the surface-treated layer into the base film can be further promoted, and an optical film having high adhesion between the base film and the surface-treated layer can be obtained.

The stretching direction may be an appropriate direction according to the purpose. Specifically, the longitudinal direction, the width direction, the thickness direction, and the oblique direction can be mentioned. The stretching direction may be one direction (uniaxial stretching), two directions (biaxial stretching), or three or more directions. In the embodiment of the present invention, uniaxial stretching in the longitudinal direction, simultaneous biaxial stretching in the longitudinal direction and the width direction, and stepwise biaxial stretching in the longitudinal direction and the width direction can be representatively used. Biaxial stretching (simultaneous or stepwise) is preferred. The reason for this is that: the in-plane retardation is easily controlled, and optical isotropy is easily achieved.

The stretching temperature may vary depending on the optical properties, mechanical properties, and thickness desired for the base 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, and the like. Specifically, the stretching temperature is preferably from Tg to Tg +50 ℃, more preferably from Tg +15 to Tg +50 ℃, and most preferably from Tg +35 to Tg +50 ℃. By stretching at such a temperature, a substrate film having appropriate characteristics can be obtained. The stretching temperature is, for example, 110 to 200 ℃, preferably 120 to 190 ℃, and more preferably 150 to 190 ℃. When the stretching temperature is within such a range, the stretching ratio and the stretching speed are appropriately adjusted, and when the surface-treated layer is formed on the obtained base film, the penetration of the composition for forming the surface-treated layer into the base film can be further promoted, and an optical film having high adhesion between the base film and the surface-treated layer can be obtained.

The stretching ratio may also vary depending on 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, and the like, as well as the stretching temperature. When biaxial stretching is employed, the ratio (TD/MD) of the stretching ratio in the width direction (TD) to the stretching ratio in the longitudinal direction (MD) is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, and still more preferably 1.0 to 1.3. In addition, the area magnification (the product of the stretch magnification in the longitudinal direction and the stretch magnification in the width direction) in the case of biaxial stretching is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, and even more preferably 3.5 to 5.2. When the stretching ratio is within such a range, by appropriately adjusting the stretching temperature and the stretching speed, in the case where the surface-treated layer is formed on the obtained base film, the penetration of the composition for forming the surface-treated layer into the base film can be further promoted, and an optical film having high adhesion between the base film and the surface-treated layer can be obtained.

The stretching speed may also vary depending on 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 magnification, and the like, similarly to 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. In the case of biaxial stretching, the stretching speed in one direction may be the same as or different from that in the other direction. When the stretching speed is in such a range, by appropriately adjusting the stretching temperature and the stretching magnification, in the case where the surface-treated layer is formed on the obtained base film, the penetration of the composition for forming the surface-treated layer into the base film can be further promoted, and an optical film having high adhesion between the base film and the surface-treated 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 base film according to the function required for the optical film. Specific examples of the surface treatment layer include a hard coat layer, an antiglare layer, and an antireflection layer. The thickness of the surface treatment layer is preferably 3 to 20 μm, more preferably 5 to 15 μm.

The surface treatment layer is typically a hardened layer of a resin composition formed on the substrate film. The process of forming the surface treatment layer may include: coating a resin composition for forming a surface treatment layer on a base film to form a coating layer; and drying and hardening the coating layer to form a surface treatment layer. Drying and hardening the coating layer may include heating the coating layer.

As a method for applying the resin composition, any suitable method can be adopted. Examples of the coating method include a bar coating method, a roll coating method, a gravure coating method, a bar coating method, a slot coating method, a curtain coating method, a spray coating method, and a comma coating method. The resin composition preferably contains a solvent for dilution from the viewpoint of facilitating application.

The heating temperature of the coating layer may be set to any appropriate temperature according to the composition of the resin composition, and is preferably set to a temperature not higher than the glass transition temperature of the acrylic resin contained in the base film. When heating is performed at a temperature equal to or lower than the glass transition temperature of the acrylic resin contained in the base 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 to 140 ℃, preferably 60 to 100 ℃. By heating at such a heating temperature, an optical film having excellent adhesion between the base film and the surface-treated layer can be obtained.

C-1. Hard coating

The hard coat layer is a layer that imparts scratch resistance, chemical resistance, and the like to the surface of the base film. The hard coat layer has a hardness of preferably H or more, more preferably 3H or more in the pencil hardness test. The pencil hardness test can be measured according to JIS K5400. The resin composition for forming the hard coat layer may contain a curable compound which can be cured by heat, light (ultraviolet rays, etc.), electron beams, or the like. Details of the hard coat layer and the resin composition for forming the hard coat layer are described in, for example, jp 2014-240955 a. The entire disclosure of this publication is incorporated herein by reference.

C-2. Anti-dazzle layer

The antiglare layer is a layer for preventing reflection of external light by scattering and reflecting light. The resin composition for forming the antiglare layer may contain a curable compound which can be cured by heat, light (ultraviolet rays, etc.), an electron beam, or the like, for example. The antiglare layer typically has a fine uneven surface. As a method for forming such a fine uneven shape, for example, a method of including fine particles in the curable compound is exemplified. Details of an antiglare layer and a resin composition for forming an antiglare layer are described in, for example, japanese patent application laid-open No. 2017-32711. The entire disclosure of this publication is incorporated herein by reference.

C-3 anti-reflection layer

The anti-reflection layer is a layer for preventing reflection of external light. The resin composition for forming the antireflection layer may contain a curable compound that can be cured by heat, light (ultraviolet rays, etc.), electron beams, or the like, for example. The antireflection layer may be a single layer composed of only 1 layer, or may be a multilayer including 2 or more layers. Details of the anti-reflective layer and the resin composition for forming the anti-reflective layer are described in, for example, japanese patent laid-open No. 2012-155050. The entire disclosure of this publication is incorporated herein by reference.

D. Polarizing plate

The optical film according to 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 polarizer and the optical film of the present invention disposed on one side of the polarizer. The optical film may be bonded to a polarizer on the substrate film side thereof, and may function as a protective layer for the polarizer.

As the polarizer, any suitable polarizer can be used. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include polarizers obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye and a stretching treatment; and polyene-based alignment films such as dehydrated products of PVA and desalted products of polyvinyl chloride. From the viewpoint of excellent optical properties, it is preferable to use a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film.

The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. In addition, dyeing may be performed after stretching. The PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only dirt or an antiblocking agent on the surface of the PVA-based film can be washed off, but also the PVA-based film can be swollen to prevent uneven dyeing or the like.

Specific examples of the polarizer obtained using the laminate include polarizers obtained by using 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 formed on the resin substrate by coating. The polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced, for example, by the following method: coating a PVA-based resin solution on a resin base material, and drying the coating to form a PVA-based resin layer on the resin base material, thereby obtaining a laminate of the resin base material and the PVA-based resin layer; the laminate is stretched and dyed to form a polarizer from the PVA resin layer. In the present embodiment, the stretching representatively includes immersing the laminate in an aqueous boric acid solution to perform stretching. Further, the stretching may further include subjecting the laminate to in-air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution, if necessary. The obtained laminate of the resin base material and the polarizer may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), or the resin base material may be peeled from the laminate of the resin base material and the polarizer, and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of a method for producing such a polarizer are described in, for example, japanese patent laid-open No. 2012-73580. The entire disclosure of this publication is incorporated herein by reference.

The thickness of the polarizer is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizer is preferably 1 μm to 20 μm, and more preferably 3 μm to 15 μm.

E. Image display device

The polarizing plate described in item D above can be applied to an image display device. Therefore, the present invention also includes an image display device using such a polarizing plate. Typical examples of the image display device include a liquid crystal display device and an organic Electroluminescence (EL) display device. The image display device may have a configuration known in the art, and thus, a detailed description thereof will be omitted.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method of each property is as follows. Unless otherwise explicitly stated, "parts" and "%" in the examples are based on weight.

(1) Maximum elongation of base film (TMA measurement)

The substrate film was cut into a size of 4mm in width × 20mm in length to prepare a measurement sample having an initial length of 20 mm. A measurement sample a obtained by cutting the base film so that the longitudinal direction of the base film is the longitudinal direction and a measurement sample B obtained by cutting the base film so that the direction orthogonal to the longitudinal direction of the base film is the longitudinal direction were prepared.

For each of the measurement samples a and B, the maximum elongation up to the softening point at the time was measured by placing the measurement sample on a measurement jig and applying a tensile load of 98 mN/min in the longitudinal direction of the measurement sample while increasing the temperature from 24 ℃ to 150 ℃ at 5 ℃/min using a thermomechanical analyzer (model "TMA7100" manufactured by Hitachi High-Tech Science).

The maximum elongation is calculated using the following equation.

Maximum elongation (%) = (sample length at maximum elongation-initial sample length)/initial sample length × 100

The maximum elongation of the measurement sample a corresponds to the maximum elongation in the longitudinal direction of the base film, and the maximum elongation of the measurement sample B corresponds to the maximum elongation in the short-side direction (direction orthogonal to the longitudinal direction) of the base film.

(2) Evaluation of adhesion

The adhesion of the surface-treated layer to the base film was evaluated according to the cross-cut peel test (number of cross-cuts: 100) of JIS K-5400, and the evaluation was made according to the following criteria.

Good component: the number of the peeling of the checkerboard is 0

X: the number of the peeled checks is more than 1

< 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 ) (available from Osaka, organischen Co., ltd.), 32 parts by weight of NK OLIGO UA-53H-80BK (available from Newzhongcun chemical Co., ltd.), 48 parts by weight of Viscoat #300 (available from Osaka, organin chemical Co., ltd.), 4 parts by weight of A-GLY-9E (available from Newzhongcun chemical Co., ltd.) and 2.4 parts by weight of IRGACURE 907 (available from BASF) were mixed, and MIBK (methyl isobutyl ketone): PGM (propylene glycol monomethyl ether) =50:50 solvent so that the solid content concentration of the resin is 42.0% and the 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 the mixture was mixed by MIBK: PGM =50:50 solvent so as to make the solid content concentration of 42.0% dilution and UV curable resin.

(3) Composition C

20 parts by weight of 4-HBA (manufactured by Osaka Organische chemical Co., ltd.), 40 parts by weight of NK OLIGO UA-53H-80BK (manufactured by Ningmura chemical Co., ltd.), 60 parts by weight of Viscoat #300 (manufactured by Osaka Organische chemical Co., ltd.), 5 parts by weight of IRGACURE 907 (manufactured by BASF) and 0.5 part by weight of Techmer SSX-103DXE (manufactured by Water accumulation chemical industries Co., ltd.) were mixed, and passed through toluene: MEK (methyl ethyl ketone) =70:30 is diluted so that the solid content concentration becomes 40.0% to obtain a UV curable resin.

< example 1 >

1. Production of substrate film

An MS resin (MS-200; a copolymer of methyl methacrylate/styrene (molar ratio) =80/20, manufactured by Nissi chemical Co., ltd.) was imidized with monomethylamine (imidization rate: 5%). The obtained imidized MS resin has glutarimide units (R) represented by the general formula (1) ¹ And R ³ Is methyl, R ² A hydrogen atom, a (meth) acrylate unit (R) represented by the general formula (2) ⁴ And R ⁵ Methyl) and styrene units. To be explainedIn the imidization, an intermeshing type co-rotating twin-screw extruder having a bore diameter of 15mm was used. The MS resin was fed at 2.0 kg/hr with the set temperature of each temperature control zone of the extruder set at 230 ℃ and the screw rotation speed set at 150rpm, and the amount of the monomethylamine fed was set at 2 parts by weight with respect to 100 parts by weight of the MS resin. The MS resin was charged from a hopper, and after the resin was melted and filled through a kneading section, monomethylamine was injected from a nozzle. A packing ring was fitted to the end of the reaction zone to fill the resin. The pressure of the exhaust port was reduced to-0.08 MPa to remove the volatile matter from the by-product and the excess methylamine after the reaction. The resin discharged as a strand from a die provided at the outlet of the extruder was cooled in a water tank and pelletized by a pelletizer. The imidized MS resin obtained had an imidization ratio of 5.0% and an acid value of 0.5mmol/g.

An extruded film was obtained by feeding 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of the core-shell particles into a single-screw extruder, melt-mixing them, and forming a film through a T-die. The obtained extruded film was simultaneously biaxially stretched 2 times in the length direction and the width direction, respectively, at a stretching temperature of 160 ℃. The stretching speed was 10%/second in both the longitudinal direction and the width direction.

Thus, a base film a was produced. The thickness of the obtained substrate film A was 30 μm. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film a were measured. The results are shown in table 1.

2. Production of optical film

The coating layer was formed by applying the composition a to one side of the base film a so that the thickness after curing became 6 μm. Next, the coating layer was dried at 70 ℃, and UV-cured, thereby obtaining an optical film 1 having a hard coating layer formed on one side of the base film a. The optical film 1 was subjected to adhesion evaluation. The results are shown in table 1.

< example 2 >

An optical film 2 having a hard coat layer formed on one side of the base film a was obtained in the same manner as in example 1, except that the composition B was applied to one side of the base film a, and dried and cured to form a hard coat layer. The optical film 2 was subjected to adhesion evaluation. The results are shown in table 1.

< example 3 >

An optical film 3 having an antiglare layer formed on one side of a substrate film a was obtained in the same manner as in example 1, except that the composition C was applied to one side of the substrate film a and cured to form an antiglare layer. The optical film 3 was subjected to adhesion evaluation. The results are shown in table 1.

< example 4 >

1. Production of substrate film

A base material film B was produced in the same manner as in example 1, except that the blending amount of the core-shell particles was set to 15 parts by weight, and the stretching temperature of the extruded film was set to 152 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film B were measured. The results are shown in table 1.

2. Production of optical film

An optical film 4 having a hard coat layer formed on one side of the base film B was obtained in the same manner as in example 1, except that the base film B described above was used. The optical film 4 was subjected to adhesion evaluation. The results are shown in table 1.

< example 5 >

1. Production of substrate film

An extruded film was obtained by feeding 100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of the core-shell particles into a single-screw extruder, melt-mixing them, and forming a film through a T-die. The obtained extruded film was biaxially stretched at a stretching temperature of 160 ℃ simultaneously in the length direction and the width direction by 2 times, respectively. The stretching speed was 10%/second in both the longitudinal direction and the width direction.

Thereby producing a base film C. The thickness of the obtained substrate film C was 40 μm. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film C were measured. The results are shown in table 1.

2. Production of optical film

An optical film 5 having a hard coat layer formed on one side of the base film C was obtained in the same manner as in example 1, except that the base film C described above was used. The optical film 5 was subjected to adhesion evaluation. The results are shown in table 1.

< example 6 >

1. Production of substrate film

Thereby producing a substrate film D. The thickness of the obtained substrate film D was 35 μm. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film D were measured. The results are shown in table 1.

2. Production of optical film

An optical film 6 having a hard coat layer formed on one side of the base film D was obtained in the same manner as in example 1, except that the base film D described above was used. The optical film 6 was subjected to adhesion evaluation. The results are shown in table 1.

< example 7 >

1. Production of substrate film

A base film E was produced in the same manner as in example 1, except that the stretching temperature of the extruded film was set to 150 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film E were measured. The results are shown in table 1.

2. Production of optical film

An optical film 7 having a hard coat layer formed on one side of the base film E was obtained in the same manner as in example 1, except that the base film E described above was used. The optical film 7 was subjected to adhesion evaluation. The results are shown in table 1.

< example 8 >

1. Production of substrate film

A base film F was produced in the same manner as in example 1, except that the blending amount of the core-shell particles was set to 23 parts by weight and the stretching temperature of the extruded film was set to 152 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film F were measured. The results are shown in table 1.

2. Production of optical film

An optical film 8 having a hard coat layer formed on one side of the base film F was obtained in the same manner as in example 1, except that the base film F described above was used. The optical film 8 was subjected to adhesion evaluation. The results are shown in table 1.

< example 9 >

1. Production of substrate film

A base material film G was produced in the same manner as in example 1, except that the core-shell particles were not blended. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film G were measured. The results are shown in table 1.

2. Production of optical film

An optical film 9 having a hard coat layer formed on one side of the substrate film G was obtained in the same manner as in example 1, except that the above-described substrate film G was used. The optical film 9 was subjected to adhesion evaluation. The results are shown in table 1.

< example 10 >

1. Production of substrate film

A base material film H was produced in the same manner as in example 1, except that the stretching temperature of the extruded film was set to 140 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film H were measured. The results are shown in table 1.

2. Production of optical film

An optical film 10 having a hard coat layer formed on one side of the substrate film H was obtained in the same manner as in example 1, except that the substrate film H described above was used. The optical film 10 was subjected to adhesion evaluation. The results are shown in table 1.

< example 11 >

1. Production of substrate film

A base material film I was produced in the same manner as in example 1, except that the blending amount of the core-shell particles was set to 23 parts by weight and the stretching temperature of the extruded film was set to 137 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film I were measured. The results are shown in table 1.

2. Production of optical film

An optical film 11 having a hard coat layer formed on one side of the substrate film I was obtained in the same manner as in example 1, except that the above-described substrate film I was used. The optical film 11 was subjected to adhesion evaluation. The results are shown in table 1.

< example 12 >

1. Production of substrate film

A base material film J was produced in the same manner as in example 1, except that the core-shell particles were not blended and the stretching temperature of the extruded film was set to 155 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film J were measured. The results are shown in table 1.

2. Production of optical film

An optical film 12 having a hard coat 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 described above was used. The optical film 12 was subjected to adhesion evaluation. The results are shown in table 1.

< example 13 >

1. Production of substrate film

A base material film K was produced in the same manner as in example 1, except that the blending amount of the core-shell particles was set to 5 parts by weight and the stretching temperature of the extruded film was set to 140 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film K were measured. The results are shown in table 1.

2. Production of optical film

An optical film 13 having a hard coat layer formed on one side of the substrate film K was obtained in the same manner as in example 1, except that the above-described substrate film K was used. The optical film 13 was subjected to adhesion evaluation. The results are shown in table 1.

< example 14 >

1. Production of substrate film

A base material film L was produced in the same manner as in example 1, except that the core-shell particles were not blended and the stretching temperature of the extruded film was set to 150 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film L were measured. The results are shown in table 1.

2. Production of optical film

An optical film 14 having a hard coat layer formed on one side of the substrate film L was obtained in the same manner as in example 1, except that the substrate film L described above was used. The optical film 14 was subjected to adhesion evaluation. The results are shown in table 1.

< comparative example 1 >

1. Production of substrate film

A base material film M was produced in the same manner as in example 1, except that the blending amount of the core-shell particles was set to 3 parts by weight, and the stretching temperature of the extruded film was set to 140 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film M were measured. The results are shown in table 1.

2. Production of optical film

An optical film 15 having a hard coat layer formed on one side of the substrate film M was obtained in the same manner as in example 1, except that the above-described substrate film M was used. The optical film 15 was subjected to adhesion evaluation. The results are shown in table 1.

< comparative example 2 >

1. Production of substrate film

A base material film N was produced in the same manner as in example 1, except that the core-shell particles were not blended and the stretching temperature of the extruded film was set to 140 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film N were measured. The results are shown in table 1.

2. Production of optical film

An optical film 16 having a hard coat layer formed on one side of the substrate film N was obtained in the same manner as in example 1, except that the substrate film N described above was used. The optical film 16 was subjected to adhesion evaluation. The results are shown in table 1.

< comparative example 3 >

An optical film 17 having a hard coat layer formed on one side of the base film N was obtained in the same manner as in comparative example 2, except that the composition B was applied to one side of the base film N, and dried and cured to form a hard coat layer. The optical film 17 was subjected to adhesion evaluation. The results are shown in table 1.

< comparative example 4 >

An optical film 18 having an antiglare layer formed on one side of the base film N was obtained in the same manner as in comparative example 2, except that the composition C was applied to one side of the base film N, and dried and cured to form an antiglare layer. The optical film 18 was subjected to adhesion evaluation. The results are shown in table 1.

< comparative example 5 >

1. Production of substrate film

A base material film O was produced in the same manner as in example 1, except that the core-shell particles were not blended and the stretching temperature of the extruded film was set to 130 ℃. The maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction of the base film O were measured. The results are shown in table 1.

2. Production of optical film

An optical film 19 having a hard coat layer formed on one side of the substrate film O was obtained in the same manner as in example 1, except that the substrate film O described above was used. The optical film 19 was subjected to adhesion evaluation. The results are shown in table 1.

[ Table 1]

As is clear from table 1, the optical films of examples 1 to 14 using the base film in which at least one of the maximum elongation in the longitudinal direction and the maximum elongation in the short-side direction was 0.40% or more had high adhesion of the surface-treated layer to the base film.

Industrial applicability

The optical film of the present invention can be suitably used as a protective layer for a polarizer. The polarizing plate having the optical film of the present invention as a protective layer can be suitably used for an image display device. The image display apparatus as described above may be used to: portable devices such as portable information terminals (PDAs), smart phones, mobile phones, clocks, digital cameras, and portable game machines; OA equipment such as computer monitors, notebook computers, and copiers; home electric appliances such as a camcorder, a television, a microwave oven, and the like; vehicle-mounted devices such as a rear monitor, a monitor for a car navigation system, and a car audio; display devices such as digital signage and information monitors for commercial stores; police equipment such as monitors for monitoring; various uses such as nursing care and medical care such as a nursing monitor and a medical monitor, and medical equipment.

Description of the symbols

10. Substrate film

20. Surface treatment layer

100. Optical film

Claims

1. An optical film comprising a base film which is a stretched film containing an acrylic resin and a surface-treated layer formed on one side of the base film, wherein,

in TMA measurement in which the temperature is raised from 24 ℃ to 150 ℃ at 5 ℃/min while applying a tensile load of 98 mN/min, the maximum elongation of the base film in the optical film up to the softening point is 0.40% or more.

2. The optical film according to claim 1, wherein the base film contains the acrylic resin and core-shell particles dispersed in the acrylic resin.

3. The optical film according to claim 2, wherein the base film contains 5 to 50 parts by weight of the core-shell-type particles with respect to 100 parts by weight of the acrylic resin.

4. The optical film according to any one of claims 1 to 3, wherein the acrylic resin has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutaric anhydride unit.

5. The optical film according to any one of claims 1 to 3, wherein the surface treatment layer is a hardened layer of a resin composition applied to the substrate film.

6. The optical film according to any one of claims 1 to 3, wherein the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an antiglare layer, and an antireflection layer.

7. A polarizing plate comprising a polarizer and a protective layer disposed on one side of the polarizer, wherein the protective layer is the optical film according to any one of claims 1 to 6.

8. An image display device comprising the polarizing plate according to claim 7.