Optical film, polarizing plate and resin composition

Abstract

To provide an optical film having high blocking resistance and punching processability. [Solution] The optical film contains a non-crosslinked resin and crosslinked acrylic particles. The optical film is composed primarily of acrylic resin, contains aromatic vinyl units, has a glass transition temperature of 120°C or higher, and a weight-average molecular weight of 200,000 or lower. The crosslinked acrylic particles have an average particle diameter of 0.3 μm or higher and 2.5 μm or lower. In the optical film, the average modulus of elasticity of the region where the non-crosslinked resin exists is E1 [GPa], and the average modulus of elasticity of the region where the crosslinked acrylic particles exist is E2 [GPa], so that E2 / E1 is 0.5 or higher but less than 0.9.

Description

[Technical Field]

[0001] The present invention relates to an optical film, a polarizing plate, and a resin composition. [Background technology]

[0002] A liquid crystal display typically has polarizing plates disposed on both sides of a liquid crystal cell, and the polarizing plates typically have polarizer protective films bonded to both sides of the polarizer. For example, an acrylic resin film is used as the polarizer protective film, and an antiblocking agent is added to the acrylic resin film to enhance blocking resistance.

[0003] Patent Document 1 describes an optical film containing an acrylic resin with a weight-average molecular weight of 280,000 and crosslinked methyl methacrylate-styrene copolymer microparticles with an average primary particle size of 90 nm. In this case, when the average modulus of elasticity of the acrylic resin portion not containing the crosslinked methyl methacrylate-styrene copolymer microparticles is E1 and the average modulus of elasticity of the crosslinked methyl methacrylate-styrene copolymer microparticle portion is E2, the ratio E2 / E1 is 1.9.

[0004] Furthermore, Patent Document 2 describes the addition of silica fine particles to an optical film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-190687 [Patent Document 2] International Publication No. 2018 / 074513 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the optical film described in Patent Document 1 has poor blocking resistance due to a small average primary particle size of the crosslinked methyl methacrylate-styrene copolymer particles. Furthermore, the optical film described in Patent Document 1 is thought to have poor punching processability due to a large weight-average molecular weight of the acrylic resin. In particular, when an optical film is produced using a long roll, poor punching processability reduces the yield of the optical film.

[0007] On the other hand, when the silica fine particles described in Patent Document 2 are added to an acrylic resin film, the punching processability is reduced.

[0008] An object of the present invention is to provide an optical film that has high blocking resistance and punching processability. [Means for solving the problem]

[0009] (1) An optical film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin is composed primarily of an acrylic resin and contains an aromatic vinyl unit, has a glass transition temperature of 120°C or higher, and a weight-average molecular weight of 200,000 or lower, and the crosslinked acrylic particles have an average particle diameter of 0.3 μm or higher and 2.5 μm or lower, and wherein, when the average modulus of elasticity of a region where the non-crosslinked resin is present is E1 [GPa] and the average modulus of elasticity of a region where the crosslinked acrylic particles are present is E2 [GPa], E2 / E1 is 0.5 or higher and lower than 0.9.

[0010] (2) The optical film according to (1), which has an internal haze of 1.0% or less.

[0011] (3) The optical film according to (1) or (2), which has a static friction coefficient of 0.8 or less.

[0012] (4) The optical film according to any one of (1) to (3), wherein the acrylic resin contains one or more rings selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings in the main chain.

[0013] (5) The optical film according to any one of (1) to (4), wherein the content of the crosslinked acrylic particles is 0.05% by weight or more and 0.9% by weight or less.

[0014] (6) The optical film according to any one of (1) to (5), wherein the non-crosslinked resin further contains a copolymer containing an aromatic vinyl unit.

[0015] (7) The optical film according to (6), wherein the copolymer further contains a (meth)acrylonitrile unit or a (meth)acrylic acid ester unit.

[0016] (8) The optical film according to any one of (1) to (7), which is a biaxially stretched film.

[0017] (9) The optical film according to any one of (1) to (8), which is a polarizer protective film.

[0018] (10) A polarizing plate comprising the optical film according to any one of (1) to (9).

[0019] (11) A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin is composed mainly of an acrylic resin, contains aromatic vinyl units, has a glass transition temperature of 120°C or higher, and has a weight-average molecular weight of 200,000 or lower, the crosslinked acrylic particles have an average particle diameter of 0.3 μm or higher and 2.5 μm or lower, and a film formed from the resin composition has an E2 / E1 ratio of 0.5 or higher to less than 0.9, where E1 [GPa] is the average modulus of elasticity in the region where the non-crosslinked resin is present, and E2 [GPa] is the average modulus of elasticity in the region where the crosslinked acrylic particles are present. [Effects of the Invention]

[0020] According to the present invention, an optical film having high blocking resistance and punching processability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described.

[0022] (Optical film) The optical film of this embodiment comprises a non-crosslinked resin and crosslinked acrylic particles.

[0023] The non-crosslinked resin is primarily composed of an acrylic resin and has a glass transition temperature of 120°C or higher. Because the non-crosslinked resin has a glass transition temperature of 120°C or higher, the dimensional change rate of the optical film of this embodiment in a high-temperature environment is small. The glass transition temperature of the non-crosslinked resin is preferably higher than 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. The glass transition temperature of the non-crosslinked resin is, for example, 160°C or lower.

[0024] In this specification and claims, acrylic resin refers to a polymer of a monomer having an acryloyl group and / or a monomer having a methacryloyl group. In this case, the acrylic resin may be either a homopolymer or a copolymer. When the acrylic resin is a copolymer, it may also be a copolymer of a monomer not having an acryloyl group or a methacryloyl group.

[0025] The acrylic resin constituting the crosslinked acrylic particles is the same as above except that it is crosslinked.

[0026] Furthermore, "mainly composed of acrylic resin" means that the content of acrylic resin is 70% by weight or more and 100% by weight or less.

[0027] The weight-average molecular weight of the non-crosslinked resin is 200,000 or less, and preferably 150,000 or less. Since the weight-average molecular weight of the non-crosslinked resin is 200,000 or less, the blocking resistance of the optical film of this embodiment is improved. The weight-average molecular weight of the non-crosslinked resin may be, for example, 50,000 or more, or 70,000 or more.

[0028] The non-crosslinked resin contains an aromatic vinyl unit. The aromatic vinyl unit may be contained in the acrylic resin as the main component, or in a resin other than the acrylic resin as the main component (for example, a copolymer containing an aromatic vinyl unit). The content of the aromatic vinyl unit in the non-crosslinked resin is preferably more than 0 wt% and not more than 25 wt%, more preferably 0.5 wt% or more and not more than 20 wt%.

[0029] The average particle size of the crosslinked acrylic particles is 0.3 μm or more and 2.5 μm or less, preferably 0.4 μm or more and 2.3 μm or less, more preferably 0.5 μm or more and 2.2 μm or less, and even more preferably 0.5 μm or more and 2.0 μm or less. When the average particle size of the crosslinked acrylic particles is 0.3 μm or more, the blocking resistance of the optical film of this embodiment is improved, and when the average particle size is 2.5 μm or less, the manufacturing stability of the optical film of this embodiment is improved.

[0030] When the average modulus of elasticity of the region of the optical film of this embodiment where the non-crosslinked resin is present is E1 [GPa] and the average modulus of elasticity of the region where the crosslinked acrylic particles are present is E2 [GPa], E2 / E1 is 0.5 or more and less than 0.9, preferably 0.6 or more and 0.8 or less, and more preferably 0.7 or more and 0.8 or less. When E2 / E1 is 0.5 or more, the blocking resistance of the optical film of this embodiment is improved, and when it is less than 0.9, the punching processability of the optical film of this embodiment is improved.

[0031] The internal haze of the optical film of this embodiment is preferably 1.0% or less, more preferably 0.8% or less. When the internal haze of the optical film of this embodiment is 1.0% or less, the transparency of the optical film of this embodiment is maintained. The internal haze of the optical film of this embodiment is, for example, 0.2% or more.

[0032] The haze of the optical film of this embodiment is preferably 1.5% or less, and more preferably 1.0% or less. When the haze of the optical film of this embodiment is 1.5% or less, the transparency of the optical film of this embodiment is maintained. The haze of the optical film of this embodiment is, for example, 0.2% or more.

[0033] The static friction coefficient of the optical film of this embodiment is preferably 0.8 or less, more preferably 0.7 or less. When the static friction coefficient of the optical film of this embodiment is 0.8 or less, the blocking resistance of the optical film of this embodiment is high. The static friction coefficient of the optical film of this embodiment is, for example, 0.4 or more.

[0034] When the optical film of this embodiment is punched using a Thomson die, the distance between the crack along the cut surface and the cut surface is preferably 50 μm or less, more preferably 45 μm or less. When the optical film of this embodiment is punched using a Thomson die, the distance between the crack along the cut surface and the cut surface is 50 μm or less, which improves the punching processability of the optical film of this embodiment. When the optical film of this embodiment is punched using a Thomson die, the distance between the crack along the cut surface and the cut surface is, for example, 30 μm or more.

[0035] The optical film of the present embodiment may further contain additives within a range that does not impair the object of the present invention. The additives are not particularly limited, and examples thereof include antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, specific wavelength absorbers or specific wavelength absorbing dyes for cutting blue light, light resistance stabilizers such as radical scavengers, retardation adjusters, catalysts, plasticizers, lubricants, antistatic agents, colorants, shrinkage inhibitors, antibacterial and deodorizing agents, fluorescent brighteners, and compatibilizers, and two or more of these may be used in combination.

[0036] (Non-crosslinked resin) The acrylic resin contained in the non-crosslinked resin and having a glass transition temperature of 120° C. or higher is not particularly limited, but examples thereof include acrylic resins containing a ring structure in the main chain.

[0037] The acrylic resin containing a ring structure in the main chain preferably contains one or more rings selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings in the main chain. Hereinafter, an acrylic resin containing a glutarimide ring or a lactone ring in the main chain will be described as an example of an acrylic resin containing a ring structure in the main chain.

[0038] The acrylic resin containing a glutarimide ring in the main chain contains, for example, a constitutional unit represented by the following formula (1).

[0039] [ka] (In the formula, R 1 and R 2 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms.

[0040] The acrylic resin containing the structural unit represented by formula (1) can be produced by a known method. An example of the method for producing the acrylic resin containing the structural unit represented by formula (1) will be described below.

[0041] First, a twin-screw extruder equipped with a die at the outlet is used to melt the methyl methacrylate resin, which is then imidized, and a strand is extruded from the die. Next, the strand is cooled using a water bath and then pelletized using a pelletizer to obtain an imidized methyl methacrylate resin. Next, a twin-screw extruder equipped with a die at the outlet is used to melt the imidized methyl methacrylate resin, which is then esterified, and a strand is extruded from the die. Next, the strand is cooled using a water bath and then pelletized using a pelletizer to obtain an acrylic resin containing a structural unit represented by formula (1).

[0042] Examples of imidizing agents used when imidizing methyl methacrylate resin include ammonia and primary amines represented by the following formula (2): Among these, monomethylamine is preferred.

[0043] R 3 NH2(2) (In the formula, R 3 is the same as formula (1).

[0044] Examples of esterifying agents used in esterifying the imidized methyl methacrylate resin include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, and dimethylcarbodiimide. , dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among these, dimethyl carbonate is preferred.

[0045] The acrylic resin having a lactone ring in the main chain can be obtained, for example, by polymerizing a monomer represented by the following formula (3) and then heat treating it to form a lactone ring.

[0046] [ka] (In the formula, R 4 and R 5are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0047] Examples of the monomer represented by formula (3) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and t-butyl 2-(hydroxymethyl)acrylate, and two or more of them may be used in combination. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred.

[0048] As the acrylic resin containing a ring structure in the main chain other than the acrylic resin containing a glutarimide ring or lactone ring in the main chain, known acrylic resins used in optical films can be used.

[0049] The content of the structural unit containing a ring structure in the acrylic resin containing a ring structure in the main chain is not particularly limited, but is, for example, from 1% by weight to 80% by weight.

[0050] The acrylic resin containing a ring structure in the main chain may further contain a (meth)acrylic acid ester unit.

[0051] Examples of (meth)acrylic acid ester units include (meth)acrylic acid alkyl units such as (meth)acrylic acid methyl units, (meth)acrylic acid ethyl units, (meth)acrylic acid n-propyl units, (meth)acrylic acid n-butyl units, (meth)acrylic acid isobutyl units, etc.; (meth)acrylic acid aryl units such as (meth)acrylic acid phenyl units, etc.; (meth)acrylic acid aralkyl units such as (meth)acrylic acid benzyl units, etc.; (meth)acrylic acid cycloalkyl units such as (meth)acrylic acid cyclohexyl units, etc., and two or more of them may be used in combination. Among these, methacrylic acid alkyl units are preferred, and methacrylic acid methyl units are particularly preferred.

[0052] The acrylic resin containing a ring structure in the main chain may further contain other monomer units. Examples of the other monomer units include, but are not limited to, aromatic vinyl units and (meth)acrylonitrile units. Examples of the aromatic vinyl units include, but are not limited to, styrene units, α-methylstyrene units, methoxystyrene units, vinyltoluene units, and halostyrene units. Among these, styrene units are preferred.

[0053] In this specification and claims, the (meth)acrylonitrile unit means an acrylonitrile unit or a methacrylonitrile unit.

[0054] The non-crosslinked resin may further contain a copolymer containing an aromatic vinyl unit. The copolymer containing an aromatic vinyl unit is not particularly limited, but examples thereof include a copolymer containing a (meth)acrylonitrile unit and an aromatic vinyl unit, and a copolymer containing a (meth)acrylic acid ester unit and an aromatic vinyl unit. Here, the (meth)acrylonitrile unit and the aromatic vinyl unit are the same as the (meth)acrylonitrile unit and the aromatic vinyl unit described above, respectively.

[0055] The content of (meth)acrylonitrile units in the copolymer containing (meth)acrylonitrile units and aromatic vinyl units is preferably 22% by weight or more and 28% by weight or less, and more preferably 23% by weight or more and 27% by weight or less. When the content of (meth)acrylonitrile units in the copolymer containing (meth)acrylonitrile units and aromatic vinyl units is 22% by weight or more and 28% by weight or less, the transparency of the optical film of this embodiment is maintained.

[0056] The content of aromatic vinyl units in the copolymer containing (meth)acrylic acid ester units and aromatic vinyl units is preferably 10% by weight or more and 30% by weight or less, and more preferably 15% by weight or more and 28% by weight or less. When the content of aromatic vinyl units in the copolymer containing (meth)acrylic acid ester units and aromatic vinyl units is 10% by weight or more and 30% by weight or less, the transparency of the optical film of this embodiment is maintained.

[0057] The content of the copolymer containing an aromatic vinyl unit in the non-crosslinked resin is not particularly limited, but is, for example, from 0% by weight to 20% by weight.

[0058] (crosslinked acrylic particles) The acrylic resin constituting the crosslinked acrylic particles preferably contains methyl methacrylate units. The content of methyl methacrylate units in the acrylic resin constituting the crosslinked acrylic particles is preferably 80% by weight or more and 99% by weight or less, and more preferably 83% by weight or more and 96% by weight or less. When the content of methyl methacrylate units in the acrylic resin constituting the crosslinked acrylic particles is 80% by weight or more and 99% by weight or less, the transparency of the optical film of this embodiment is maintained.

[0059] The acrylic resin constituting the crosslinked acrylic particles preferably contains a polyfunctional monomer unit. The content of the polyfunctional monomer unit in the acrylic resin constituting the crosslinked acrylic particles is preferably 0.5% by weight or more and 30% by weight or less. When the content of the polyfunctional monomer unit in the acrylic resin constituting the crosslinked acrylic particles is 0.5% by weight or more, the heat resistance and dispersibility of the crosslinked acrylic particles are improved, and when it is 30% by weight or less, the production stability of the crosslinked acrylic particles is improved.

[0060] The refractive index of the crosslinked acrylic particles is preferably 1.47 to 1.55, more preferably 1.47 to 1.53, and even more preferably 1.48 to 1.52. When the refractive index of the crosslinked acrylic particles is 1.47 to 1.55, the transparency of the optical film of this embodiment is maintained.

[0061] The crosslinked acrylic particles may be multilayer structure particles (see, for example, JP 2017-177596 A).

[0062] The content of the crosslinked acrylic particles in the optical film of this embodiment is preferably 0.05% by weight or more and 0.9% by weight or less, more preferably 0.07% by weight or more and 0.6% by weight or less, and even more preferably 0.1% by weight or more and 0.2% by weight or less. When the content of the crosslinked acrylic particles in the optical film of this embodiment is 0.05% by weight or more, the blocking resistance of the optical film of this embodiment is improved, and when it is 0.9% by weight or less, the transparency of the optical film of this embodiment is maintained.

[0063] (Resin composition) The resin composition of this embodiment contains a non-crosslinked resin and crosslinked acrylic particles, and is used, for example, in the production of the optical film of this embodiment. The non-crosslinked resin is primarily composed of an acrylic resin, contains aromatic vinyl units, has a glass transition temperature of 120°C or higher, and a weight-average molecular weight of 200,000 or lower. The crosslinked acrylic particles have an average particle diameter of 0.3 μm or higher and 2.5 μm or lower. Furthermore, in a film formed from the resin composition of this embodiment, the average modulus of elasticity of the region where the non-crosslinked resin is present is E1 [GPa], and the average modulus of elasticity of the region where the crosslinked acrylic particles are present is E2 [GPa], where E2 / E1 is 0.5 or higher and less than 0.9.

[0064] (Method of manufacturing optical film) The optical film of this embodiment can be produced by a known method, and an example of the method for producing the optical film of this embodiment will be described below.

[0065] First, a non-crosslinked resin and crosslinked acrylic particles are kneaded using an extruder equipped with a die at the outlet, and then a strand is extruded from the die. Next, the strand is cooled using a water bath, and then the strand is pelletized using a pelletizer to obtain the resin composition of this embodiment. Next, the resin composition of this embodiment is melted using an extruder equipped with a T-die at the outlet, and then a sheet is extruded from the T-die. Next, the sheet is cooled using a cooling roll to obtain a raw film. Next, the raw film is biaxially stretched to obtain the optical film of this embodiment. In this case, the biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.

[0066] The temperature when biaxially stretching the raw film is preferably (Tg + 5)°C or higher (Tg + 20)°C or lower, more preferably (Tg + 6)°C or higher (Tg + 18)°C or lower, and even more preferably (Tg + 7)°C or higher (Tg + 15)°C or lower, where Tg is the glass transition temperature of the acrylic resin. The areal stretching ratio when biaxially stretching the raw film is not particularly limited, but is, for example, 2 times or higher and 10 times or lower. The stretching speed when biaxially stretching the raw film is not particularly limited, but is, for example, 1.1 times / min or higher and 100 times / min or lower. When sequentially biaxially stretching the raw film, the stretching speeds in the first stage and the second stage may be the same or different. In sequential biaxial stretching, the first stage stretching is usually stretching in the longitudinal direction (MD), and the second stage stretching is stretching in the transverse direction (TD).

[0067] (Application) The optical film of this embodiment can be used, for example, as a polarizer protective film.

[0068] (polarizing plate) The polarizing plate of this embodiment includes a polarizer protective film as the optical film of this embodiment. In the polarizing plate of this embodiment, for example, polarizer protective films are bonded to both sides of a polarizer. The polarizer is not particularly limited, and any known polarizer can be used. The polarizing plate of this embodiment can be applied to displays such as liquid crystal displays and organic EL displays.

[0069] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Example]

[0070] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0071] (glass transition temperature of acrylic resin or non-crosslinked resin) Using a high-sensitivity differential scanning calorimeter DSC7000X (Hitachi High-Tech Science), 10 mg of acrylic resin or non-crosslinked resin was heated at a heating rate of 10°C / min under a nitrogen atmosphere, and the glass transition temperature of the acrylic resin or non-crosslinked resin was measured by the midpoint method.

[0072] (Weight average molecular weight Mw of non-crosslinked resin) The weight average molecular weight of the non-crosslinked resin was calculated using gel permeation chromatography (GPC) in terms of standard polystyrene.

[0073] (Average particle size of cross-linked acrylic particles) Using a laser diffraction particle size analyzer, Mastersizer 3000 (Malvern Instruments), the volumetric particle size distribution of the crosslinked acrylic particles was measured by the laser diffraction / scattering method based on the Mie theory in accordance with ISO13320:2009 and JIS Z8825-1, and the average particle size of the crosslinked acrylic particles was calculated.

[0074] (Average elastic moduli E1 and E2 of optical films) The average elastic moduli E1 and E2 of the optical film were measured under the following conditions using an atomic force microscope, Dimension Icon (manufactured by Buruker). Specifically, from the elastic modulus mapping image of the cross section of the optical film, the average values ​​of the elastic modulus of the region where the non-crosslinked resin was present and the elastic modulus of the region where the antiblocking agent (crosslinked acrylic particles or silica particles) was present were calculated and designated as E1 and E2, respectively. Cantilever spring constant: 20N / m Measurement mode: PeakForce QNM mode Frequency: 2kHz Maximum load: 20nN Measurement range: 1-2 μm x 1-2 μm

[0075] (Static friction coefficient of optical film) The static friction coefficient of the optical film was measured using a digital force gauge ZTS-5N and a friction coefficient measuring jig COF-2N-V (both manufactured by Imada) in accordance with JIS K7125:1999. Specifically, one side of the film was fixed to a smooth stainless steel plate, and the other side of the film was attached to a 60 x 60 mm, 200 g sled with double-sided tape. The sled was moved at a speed of 100 mm / min via a pulley, and the load was read with a load cell to calculate the static friction coefficient between the films. The static friction coefficient of the optical film was measured five times, and the average value was calculated.

[0076] (Optical film haze, internal haze) The haze of the optical film was measured using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS 7136: 2000. The optical film was placed in a glass cell for measuring liquid, and the internal haze of the optical film was measured by bringing distilled water into contact with both sides of the optical film.

[0077] (Blocking resistance of optical film) Ten optical films, each measuring 100 mm x 100 mm, were stacked and left at 60°C for 2 hours with a 1 kg load. After cooling at 23°C for 1 hour, the condition of the optical films was visually inspected and the optical films were peeled off by hand to evaluate their blocking resistance. The criteria for judging blocking resistance were as follows: 1: When the films are stuck together and peeling marks appear when peeled off 2: The films are stuck together, but no marks are left when peeled off. 3: When the films are not stuck together

[0078] (Punching processability of optical film) The optical film was punched out to a size of 43 mm x 43 mm using a Thomson die, and then the distance between the crack along the cut surface and the cut surface was measured using a laser microscope to evaluate the punching processability of the optical film. Note that a smaller distance between the crack along the cut surface and the cut surface indicates better punching processability of the optical film.

[0079] (Production of acrylic resin 1) A 40mm diameter co-rotating intermeshing twin-screw extruder (L / D = 90) equipped with a die at the outlet was used. The temperature of each temperature-controlled zone was set to 250-280°C, and the screw rotation speed was set to 85 rpm. Methyl methacrylate resin was melted and filled using a kneading block. Next, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical Company) per 100 parts by weight of methyl methacrylate resin was injected through the nozzle to imidize the methyl methacrylate resin. The strand extruded from the die was then cooled in a water bath and pelletized using a pelletizer to obtain imidized resin 1.

[0080] The temperature of each temperature-controlled zone of a 40 mm diameter co-rotating intermeshing twin-screw extruder (L / D = 90) equipped with a die at the outlet was set to 240-260°C, and the screw rotation speed was set to 85 rpm. The imidized resin 1 was melted and filled using a kneading block. Next, 0.56 parts by weight of dimethyl carbonate was injected per 100 parts by weight of imidized resin 1 to esterify the carboxyl groups in imidized resin 1. The by-products and excess dimethyl carbonate were removed after the reaction. The strand extruded from the die was cooled in a water bath and then pelletized using a pelletizer to obtain acrylic resin 1. Acrylic resin 1 had a glass transition temperature of 123°C and a weight-average molecular weight of 97,800.

[0081] Example 1 Using a 15mm diameter co-rotating intermeshing twin-screw extruder (L / D = 45) equipped with a die at the outlet, 89.9 wt% acrylic resin 1, 0.1 wt% crosslinked acrylic particles MX80H3wT (manufactured by Soken Chemical & Engineering Co., Ltd.) with an average particle size of 0.8 μm and a refractive index of 1.49 (hereinafter referred to as crosslinked acrylic particles 1), and 10 wt% acrylonitrile-styrene copolymer AS-61NT (manufactured by Shin Chemical Shoji Co., Ltd.) with a content of 26 wt% acrylonitrile (AN) units and 74 wt% styrene (ST) units (hereinafter referred to as AS resin 1) were kneaded. The strands extruded from the die were then cooled in a water bath, pelletized using a pelletizer, and dried at 100°C for 5 hours to obtain a resin composition. The non-crosslinked resins (acrylic resin 1 and AS resin 1) had a glass transition temperature of 121°C and a weight-average molecular weight of 104,200.

[0082] The resin composition was melted using a 15 mm diameter intermeshing co-rotating twin-screw extruder (L / D=45) equipped with a T-die at the outlet, and then the sheet extruded from the T-die was cooled using a cooling roll to obtain a raw film having a width of 160 mm and a thickness of 160 μm.

[0083] Using a film biaxial stretching device IMC-1905 (manufactured by Imoto Manufacturing Co., Ltd.), the raw film was simultaneously biaxially stretched at 145°C so that the stretching ratio in the longitudinal and transverse directions became 2 times, to obtain an optical film. The optical film had an E2 / E1 ratio of 0.76.

[0084] Example 2 An optical film was obtained in the same manner as in Example 1, except that an acrylonitrile-styrene copolymer AS-61NT7200 (manufactured by Shin Chemical Shoji Co., Ltd.) (hereinafter referred to as AS Resin 2), which had an AN unit content of 26% by mass, an ST unit content of 74% by weight, and contained a colorant, was used instead of AS Resin 1. The non-crosslinked resins (Acrylic Resin 1 and AS Resin 2) had a glass transition temperature of 121°C and a weight-average molecular weight of 109,500. The optical film also had an E2 / E1 ratio of 0.70.

[0085] Example 3 An optical film was obtained in the same manner as in Example 2, except that the amount of crosslinked acrylic particles 1 was changed to 0.2 wt % and the amount of acrylic resin 1 was changed to 89.8 wt %. The non-crosslinked resins (acrylic resin 1 and AS resin 2) had a glass transition temperature of 121°C and a weight-average molecular weight of 109,500. The optical film also had an E2 / E1 ratio of 0.78.

[0086] Example 4 An optical film was obtained in the same manner as in Example 2, except that the amount of crosslinked acrylic particles 1 was changed to 0.07% by weight, and 0.03% by weight of crosslinked acrylic particles xx-6390Z (manufactured by Sekisui Chemical Co., Ltd.) having an average particle size of 0.15 μm and a refractive index of 1.49 (hereinafter referred to as crosslinked acrylic particles 2) was further added.

[0087] Example 5 An optical film was obtained in the same manner as in Example 1, except that a methyl methacrylate-styrene copolymer MS-750 (manufactured by Toyo Styrene) (hereinafter referred to as MS Resin 1), having a methyl methacrylate (MMA) unit content of 75 wt% and an ST unit content of 25 wt%, was used instead of AS Resin 1. The non-crosslinked resins (acrylic resin 1 and MS Resin 1) had a glass transition temperature of 122°C and a weight-average molecular weight of 95,400. The optical film also had an E2 / E1 ratio of 0.76.

[0088] Example 6 An optical film was obtained in the same manner as in Example 5, except that the amount of acrylic resin 1 added was changed to 79.9 wt % and the amount of MS resin 1 added was changed to 20 wt %. At this time, the non-crosslinked resins (acrylic resin 1 and MS resin 1) had a glass transition temperature of 121°C and a weight-average molecular weight of 96,200. The optical film also had an E2 / E1 ratio of 0.76.

[0089] Example 7 An optical film was obtained in the same manner as in Example 6, except that the amount of acrylic resin 1 added was changed to 79.8 wt % and the amount of crosslinked acrylic particles 1 added was changed to 0.2 wt %. In this case, the non-crosslinked resins (acrylic resin 1 and MS resin 1) had a glass transition temperature of 121°C and a weight average molecular weight of 96,200. The optical film also had an E2 / E1 ratio of 0.76.

[0090] Example 8 An optical film was obtained in the same manner as in Example 4, except that MS resin 1 was used instead of AS resin 2. At this time, the non-crosslinked resins (acrylic resin 1 and MS resin 1) had a glass transition temperature of 122°C and a weight average molecular weight of 95,400. The optical film also had an E2 / E1 ratio of 0.76.

[0091] (Production of Crosslinked Acrylic Particles 3) Crosslinked acrylic particles 5 (multilayer structure particles) having an average particle size of 0.29 μm were obtained in the same manner as in Production Example 3 of JP 2017-177596 A.

[0092] (Comparative Example 1) An optical film was obtained in the same manner as in Example 1, except that crosslinked acrylic particles 3 were used instead of crosslinked acrylic particles 1, AS resin 1 was not used, and the amount of acrylic resin 1 added was changed to 99.9 wt %. The optical film had an E2 / E1 ratio of 0.73.

[0093] (Comparative Example 2) An optical film was obtained in the same manner as in Comparative Example 1, except that the amount of acrylic resin 1 added was changed to 99.8% by weight and the amount of crosslinked acrylic particles 3 added was changed to 0.2% by weight. The optical film had an E2 / E1 ratio of 0.73.

[0094] (Comparative Example 3) An optical film was obtained in the same manner as in Comparative Example 1, except that the amount of acrylic resin 1 added was changed to 99.4% by weight and the amount of crosslinked acrylic particles 3 added was changed to 0.6% by weight. The optical film had an E2 / E1 ratio of 0.73.

[0095] (Production of Crosslinked Acrylic Particles 6) Crosslinked acrylic particles 6 (multilayer structure particles) having an average particle size of 0.21 μm were obtained in the same manner as in Production Example 3 of JP 2017-177596 A.

[0096] Comparative Example 4 An optical film was obtained in the same manner as in Comparative Example 1, except that crosslinked acrylic particles 4 were used instead of crosslinked acrylic particles 3. The optical film had an E2 / E1 ratio of 0.73.

[0097] (Comparative Example 5) An optical film was obtained in the same manner as in Comparative Example 2, except that crosslinked acrylic particles 4 were used instead of crosslinked acrylic particles 3. The optical film had an E2 / E1 ratio of 0.73.

[0098] (Comparative Example 6) An optical film was obtained in the same manner as in Comparative Example 1, except that silica particles contained in colloidal silica Quartron PL-3 (manufactured by Fuso Chemical Co., Ltd.) having a solid content of 20 wt % and an average primary particle diameter of 35 nm were used instead of the crosslinked acrylic particles 4. The optical film had an E2 / E1 ratio of 2.78.

[0099] (Comparative Example 7) An optical film was obtained in the same manner as in Example 2, except that crosslinked acrylic particles J-4PY (manufactured by Negami Chemical Industries, Ltd.) having an average particle size of 2.2 μm and a refractive index of 1.50 (hereinafter referred to as crosslinked acrylic particles 5) were used instead of crosslinked acrylic particles 1. The optical film had an E2 / E1 ratio of 0.96.

[0100] Table 1 shows the properties of the AS resin and the MS resin.

[0101] [Table 1]

[0102] Table 2 shows the properties of the crosslinked acrylic particles.

[0103] [Table 2]

[0104] Table 3 shows the properties and evaluation results of the optical film.

[0105] [Table 3]

[0106] Table 3 shows that the optical films of Examples 1 to 14 have high blocking resistance and punching processability. In contrast, the optical films of Comparative Examples 1 to 3 have low blocking resistance because they contain crosslinked acrylic particles 3 with an average particle size of 0.29 μm. The optical films of Comparative Examples 4 and 5 have low blocking resistance because they contain crosslinked acrylic particles 4 with an average particle size of 0.21 μm. The optical films of Comparative Examples 6 and 7 have low punching processability because their E1 / E2 ratios are 0.96 to 2.78.

Claims

1. Contains non-crosslinked resin and crosslinked acrylic particles, the non-crosslinked resin is composed mainly of an acrylic resin, contains an aromatic vinyl unit, has a glass transition temperature of 120°C or higher, and has a weight average molecular weight of 200,000 or lower; the crosslinked acrylic particles have an average particle size of 0.3 μm or more and 2.5 μm or less; an optical film in which E2 / E1 is 0.5 or more and less than 0.9, where E1 [GPa] is the average modulus of elasticity of the region where the non-crosslinked resin is present and E2 [GPa] is the average modulus of elasticity of the region where the crosslinked acrylic particles are present.

2. 10. The optical film of claim 1, wherein the internal haze is 1.0% or less.

3. The optical film according to claim 1 , having a static friction coefficient of 0.8 or less.

4. 2. The optical film according to claim 1, wherein the acrylic resin contains at least one ring selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a maleimide ring, and a glutaric anhydride ring in the main chain.

5. The optical film according to claim 1 , wherein the content of the crosslinked acrylic particles is 0.05% by weight or more and 0.9% by weight or less.

6. The optical film according to claim 1 , wherein the non-crosslinked resin further comprises a copolymer containing an aromatic vinyl unit.

7. The optical film according to claim 6 , wherein the copolymer further comprises a (meth)acrylonitrile unit or a (meth)acrylic acid ester unit.

8. The optical film of claim 1 , which is a biaxially stretched film.

9. The optical film according to claim 1 , which is a polarizer protective film.

10. A polarizing plate comprising the optical film according to claim 9 .

11. A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, the non-crosslinked resin is composed mainly of an acrylic resin, contains an aromatic vinyl unit, has a glass transition temperature of 120°C or higher, and has a weight average molecular weight of 200,000 or lower; the crosslinked acrylic particles have an average particle size of 0.3 μm or more and 2.5 μm or less; In a film formed from the resin composition, the average modulus of elasticity of the region where the non-crosslinked resin is present is E1 [GPa], and the average modulus of elasticity of the region where the crosslinked acrylic particles are present is E2 [GPa], where E2 / E1 is 0.5 or more and less than 0.9.

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