Resin composition, resin film, and polarizing plate

Abstract

Provided is a resin composition which contains a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin contains an acrylic resin that has a weight average molecular weight of 400,000 or more, the crosslinked acrylic particles have an average particle diameter of 0.3-2.5 μm (inclusive), and the glass transition temperature thereof is 120°C or higher.

Description

Resin composition, resin film and polarizing plate

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

[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 having a weight-average molecular weight of 280,000 and crosslinked methyl methacrylate-styrene copolymer fine particles having an average primary particle size of 90 nm.

[0004] Japanese Patent Application Laid-Open No. 2020-190687

[0005] However, the optical film described in Patent Document 1 has a low glass transition temperature, which results in a large dimensional change rate in a high-temperature environment.Furthermore, the optical film described in Patent Document 1 has a low blocking resistance due to a small average primary particle size of the crosslinked methyl methacrylate-styrene copolymer fine particles.

[0006] The present invention aims to provide a resin composition that can reduce the dimensional change rate of a resin film in a high-temperature environment and increase the blocking resistance and folding resistance of the resin film, and a resin film that has a small dimensional change rate in a high-temperature environment and high blocking resistance and folding resistance.

[0007] (1) A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight-average molecular weight of 400,000 or more, and the crosslinked acrylic particles have an average particle diameter of 0.3 μm or more and 2.5 μm or less and a glass transition temperature of 120° C. or more.

[0008] (2) The resin composition according to (1), wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

[0009] (3) A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, and the crosslinked acrylic particles have an average particle diameter of 0.3 μm or more and 2.5 μm or less.

[0010] (4) The resin composition according to any one of (1) to (3), wherein the acrylic resin does not substantially contain a ring structure in the main chain.

[0011] (5) The resin composition according to any one of (1) to (4), wherein the crosslinked acrylic particles have an average particle size of 0.5 μm or more.

[0012] (6) The resin composition according to any one of (1) to (5), which is substantially free of a solvent and has a content of the crosslinked acrylic particles of 0.05% by weight or more and 0.9% by weight or less.

[0013] (7) The resin composition according to any one of (1) to (6), further comprising a solvent.

[0014] (8) The resin composition according to any one of (1) to (7), which is used for producing a resin film.

[0015] (9) A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight-average molecular weight of 400,000 or more, a glass transition temperature of 120°C or more, and a sum of 10-point average roughnesses Rzjis of both surfaces of the resin film being 0.05 μm or more and 1.0 μm or less.

[0016] (10) The resin film according to (9), wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

[0017] (11) A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, and the sum of the 10-point average roughness Rzjis of both surfaces is 0.05 μm or more and 1.0 μm or less.

[0018] (12) A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more, a glass transition temperature of 120°C or more, and a sum of kurtosis Rku on both sides of the resin film being 20 or more and 50 or less.

[0019] (13) The resin film according to (12), wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

[0020] (14) A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, a glass transition temperature of 120°C or more, and a sum of kurtosis Rku on both sides of the resin film of 20 or more and 50 or less.

[0021] (15) The resin film according to any one of (9) to (14), having an internal haze of 1.0% or less.

[0022] (16) The resin film according to any one of (9) to (15), having a static friction coefficient of 0.8 or less.

[0023] (17) The resin film according to any one of (9) to (16), wherein the acrylic resin does not substantially contain a ring structure in the main chain.

[0024] (18) The resin film according to any one of (9) to (17), wherein the crosslinked acrylic particles have an average particle diameter of 0.3 μm or more and 2.5 μm or less.

[0025] (19) The resin film according to any one of (9) to (18), wherein the content of the crosslinked acrylic particles is 0.05% by weight or more and 0.9% by weight or less.

[0026] (20) The resin film according to any one of (9) to (19), which is a polarizer protective film.

[0027] According to the present invention, it is possible to provide a resin composition that can reduce the dimensional change rate of a resin film in a high-temperature environment and increase the blocking resistance and folding resistance of the resin film, and a resin film that has a small dimensional change rate in a high-temperature environment and high blocking resistance and folding resistance.

[0028] Hereinafter, an embodiment of the present invention will be described.

[0029] [First embodiment] (Resin composition) The resin composition of this embodiment contains a non-crosslinked resin and crosslinked acrylic particles. The resin composition of this embodiment may contain a solvent, or may be substantially free of a solvent. The content of the solvent in a resin composition that is substantially free of a solvent is preferably 1 wt% or less, and more preferably 0.5 wt% or less.

[0030] The non-crosslinked resin includes an acrylic resin having a weight-average molecular weight of 400,000 or more. Because the weight-average molecular weight of the acrylic resin is 400,000 or more, when the resin composition of this embodiment is applied to a resin film, the folding endurance is high. The weight-average molecular weight of the acrylic resin is preferably 600,000 or more, more preferably 700,000 or more, and even more preferably 800,000 or more. From the viewpoint of formability, the weight-average molecular weight of the acrylic resin is preferably 4,000,000 or less, more preferably 3,500,000 or less, even more preferably 2,500,000 or less, and particularly preferably 1,500,000 or less.

[0031] The average particle size of the crosslinked acrylic particles is 0.3 μm or more and 2.5 μm or less, preferably 0.5 μm or more and 2.2 μm or less, and more preferably 0.6 μm or more and 1.5 μm or less. When the resin composition of this embodiment is applied to a resin film, the blocking resistance is improved because the average particle size of the crosslinked acrylic particles is 0.3 μm or more, and when the average particle size is 2.5 μm or less, the production stability of the resin composition of this embodiment is improved.

[0032] 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 be a copolymer of a monomer not having an acryloyl group or a methacryloyl group.

[0033] The acrylic resin constituting the crosslinked acrylic particles is the same as above except that it is crosslinked.

[0034] The glass transition temperature of the resin composition of this embodiment is 120°C or higher, preferably greater than 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. Since the glass transition temperature of the resin composition of this embodiment is 120°C or higher, when the resin composition of this embodiment is applied to a resin film, the dimensional change rate of the resin film in a high-temperature environment is small. Note that, from the viewpoints of molding temperature and secondary processability of the molded article, the glass transition temperature of the resin composition of this embodiment is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 135°C or lower.

[0035] The resin composition of this embodiment may contain an acrylic resin having a syndiotacticity of 54% or more, expressed in triad form as described below, instead of having a glass transition temperature of 120° C. or more. Since the syndiotacticity of the acrylic resin is 54% or more, expressed in triad form, when the resin composition of this embodiment is applied to a resin film, the dimensional change rate of the resin film in a high-temperature environment is small.

[0036] The non-crosslinked resin may further contain a resin other than an acrylic resin. Examples of resins other than an acrylic resin include styrene resins such as acrylonitrile-styrene resin and styrene-maleic anhydride resin, fluororesins such as polycarbonate, polyvinyl acetal, cellulose acylate, polyvinylidene fluoride and polyfluorinated alkyl (meth)acrylate, silicone resin, polyolefin, polyethylene terephthalate, and polybutylene terephthalate. In this case, the glass transition temperature of the non-crosslinked resin is preferably 120°C or higher, more preferably greater than 120°C, even more preferably 121°C or higher, and particularly preferably 122°C or higher.

[0037] The resin composition 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, but examples thereof include antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, specific wavelength absorbers or specific wavelength absorbing dyes for the purpose of 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.

[0038] (Acrylic Resin) The glass transition temperature of the acrylic resin is preferably 120°C or higher, more preferably higher than 120°C, even more preferably 121°C or higher, and particularly preferably 122°C or higher.

[0039] The acrylic resin preferably does not substantially contain a ring structure in the main chain. The content of structural units containing ring structures in the acrylic resin that does not substantially contain a ring structure in the main chain is, for example, less than 1 wt %. Examples of ring structures include glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings.

[0040] The acrylic resin is not particularly limited as long as it can raise the glass transition temperature of the resin composition of this embodiment to 120°C or higher, but examples include acrylic resins having a syndiotacticity of 54% or higher in triad notation. The syndiotacticity of the acrylic resin in triad notation is preferably 55% or higher, more preferably 56% or higher, and even more preferably 57% or higher. Note that, from the viewpoints of molding temperature, toughness of the molded body, and secondary processability, the syndiotacticity of the acrylic resin in triad notation is preferably 70% or lower, more preferably 67% or lower.

[0041] The syndiotacticity of acrylic resins, expressed as a triad, is the proportion of three structural unit chains (triads) that are rr. In a chain of two structural units (diads), those with the same configuration are called meso (m) and those with the opposite configuration are called racemo (r).

[0042] The synthesis method of an acrylic resin having a syndiotacticity of 54% or more in terms of triads is not particularly limited, but examples thereof include anionic polymerization and radical polymerization. Among these, radical polymerization is preferred from an environmental perspective (see, for example, International Publication No. 2023 / 238886). Here, the glass transition temperature and syndiotacticity of the acrylic resin in terms of triads can be controlled by the polymerization temperature of the acrylic resin. For example, by lowering the polymerization temperature of the acrylic resin, the glass transition temperature and syndiotacticity of the acrylic resin can be increased. The glass transition temperature of the acrylic resin can also be controlled by the molecular weight of the acrylic resin.

[0043] The content of methyl methacrylate units in an acrylic resin having a triad syndiotacticity of 54% or more is preferably 98% by weight or more, more preferably 99% by weight or more, and even more preferably 100% by weight.

[0044] Monomers other than methyl methacrylate that can be used when synthesizing an acrylic resin having a syndiotacticity of 54% or more in triad notation are not particularly limited, and examples thereof include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cycloalkyl acrylates such as cyclohexyl acrylate and norbornenyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate and norbornenyl methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; and methacrylonitrile.

[0045] (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, transparency is maintained when the resin composition of this embodiment is applied to a resin film.

[0046] 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.

[0047] 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, transparency is maintained when the resin composition of this embodiment is applied to a resin film.

[0048] The crosslinked acrylic particles may be multilayer structure particles (see, for example, JP 2017-177596 A).

[0049] When the resin composition of this embodiment is substantially free of a solvent, the content of the crosslinked acrylic particles in the resin composition 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 resin composition of this embodiment is 0.05% by weight or more, when the resin composition of this embodiment is applied to a resin film, the blocking resistance is improved, and when the content is 0.9% by weight or less, when the resin composition of this embodiment is applied to a resin film, the transparency is maintained.

[0050] The form of the resin composition substantially free of a solvent is not particularly limited, but may be, for example, beads (powder or granules), while the form of the resin composition containing a solvent is not particularly limited, but may be, for example, a dope.

[0051] The (dope) solvent preferably includes a first solvent having a hydrogen bond parameter δH of 1 or more and 12 or less in Hansen solubility parameters, and a second solvent having a hydrogen bond parameter δH of 14 or more and 24 or less.

[0052] Examples of the first solvent include 1,4-dioxane (9.0), 2-phenylethanol (11.2), acetone (7.0), acetonitrile (6.1), chloroform (5.7), dibasic acid ester (8.4), diacetone alcohol (10.8), N,N-dimethylformamide (11.3), dimethyl sulfoxide (10.2), ethyl acetate (7.2), γ-butyrolactone (7.4), methyl ethyl ketone (5.1), methyl isobutyl ketone (4.1), methylene chloride (7.1), n-butyl acetate (6.3), N-methyl-2-pyrrolidone (7.2), propylene carbonate (4.1), 1,1,2,2-tetrachloroethane (5.3), tetrahydrofuran (8.0), and toluene (2.0). Two or more of these may be used in combination. The numerical value in parentheses indicates the value of the hydrogen bond parameter δH. Among these, from the viewpoint of the solubility and evaporation rate of the acrylic resin, methyl ethyl ketone, chloroform and methylene chloride are preferred, and methylene chloride is more preferred.

[0053] Examples of the second solvent include methanol (22.3), ethanol (19.4), isopropanol (16.4), butanol (15.8), and ethylene glycol monoethyl ether (14.3), and two or more of these may be used in combination. The values ​​in parentheses indicate the values ​​of the hydrogen bond parameter δH. Among these, methanol and ethanol are preferred, and ethanol is more preferred.

[0054] The solid content of the dope is not particularly limited, but is, for example, 5% by weight to 50% by weight, and the content of the first solvent in the solvent is not particularly limited, but is, for example, 55% by weight to 95% by weight.

[0055] The method for producing the dope is not particularly limited, but for example, a method in which a resin composition containing an acrylic resin and crosslinked acrylic particles is dissolved or dispersed in a solvent using a homogenizer can be mentioned.

[0056] (Resin Film) The sum of the kurtosis Rku on both sides of the resin film is preferably 20 or more and 50 or less, more preferably 25 or more and 45 or less, and even more preferably 30 or more and 40 or less. When the sum of the kurtosis Rku on both sides of the resin film is 20 or more, the blocking resistance of the resin film is increased, and when it is 50 or less, the clarity is increased when the resin film is applied to a display.

[0057] Here, kurtosis Rku represents the sharpness in the height direction in accordance with JIS B 0601. When Rku is 3, the height distribution is a normal distribution, when Rku exceeds 3, there are many sharp peaks and valleys on the surface, and when Rku is less than 3, the surface is flat.

[0058] The sum of the ten-point average roughnesses Rzjis on both sides of the resin film is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.06 μm or more and 0.6 μm or less. When the sum of the ten-point average roughnesses Rzjis on both sides of the resin film is 0.05 μm or more, the blocking resistance of the resin film is increased, and when it is 1.0 μm or less, the transparency of the resin film is increased.

[0059] The internal haze of the resin film is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. When the internal haze of the resin film is 1.0% or less, the transparency of the resin film is maintained. The internal haze of the resin film is, for example, 0.1% or more.

[0060] The haze of the resin film is preferably 2.0% or less, and more preferably 1.5% or less. The haze of the resin film of this embodiment is, for example, 0.1% or more.

[0061] The static friction coefficient of the resin film is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. When the static friction coefficient of the resin film is 0.8 or less, the blocking resistance of the resin film is high. The static friction coefficient of the resin film is, for example, 0.2 or more.

[0062] (Method for producing resin film) The resin film can be produced using a known method. An example of a method for producing a resin film will be described below. First, a dope is cast onto a substrate, and then the film is peeled off from the substrate. Next, the film is dried to obtain a raw film. Next, the raw film is stretched uniaxially or biaxially to obtain a resin film. This increases the mechanical strength and thickness accuracy of the resin film of this embodiment.

[0063] During the formation of the raw film, the raw film may be suitably stretched uniaxially or biaxially as the drying process progresses to produce a resin film. In this case, the resin film may be further stretched.

[0064] The stretching temperature of the raw film is preferably (Tg + 7)°C or higher and (Tg + 50)°C or lower, and more preferably (Tg + 10)°C or higher and (Tg + 40)°C or lower, where Tg is the glass transition temperature of the raw film. The stretching ratio of the raw film is, for example, 1.5 times or higher and 3.0 times or lower. The stretching speed of the raw film is, for example, 1.1 times / min or higher and 100 times / min or lower.

[0065] The resin film can be applied to optical films such as polarizer protective films, for example.

[0066] (Polarizing Plate) The polarizing plate includes a polarizer protective film. For example, the polarizer protective film is bonded to both sides of a polarizer. The polarizer is not particularly limited, and a known polarizer can be used. The polarizing plate can be applied to displays such as liquid crystal displays and organic EL displays.

[0067] Second Embodiment (Resin Film) The resin film of this embodiment contains a non-crosslinked resin and crosslinked acrylic particles.

[0068] The non-crosslinked resin includes an acrylic resin having a weight-average molecular weight of 400,000 or more. Because the weight-average molecular weight of the acrylic resin is 400,000 or more, the resin film of this embodiment has high folding endurance. The weight-average molecular weight of the acrylic resin is preferably 600,000 or more, more preferably 700,000 or more, and even more preferably 800,000 or more. From the viewpoint of formability, the weight-average molecular weight of the acrylic resin is preferably 4,000,000 or less, more preferably 3,500,000 or less, even more preferably 2,500,000 or less, and particularly preferably 1,500,000 or less.

[0069] The glass transition temperature of the resin film of this embodiment is 120°C or higher, preferably greater than 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. Since the glass transition temperature of the resin film of this embodiment is 120°C or higher, the dimensional change rate of the resin film of this embodiment in a high-temperature environment is small. Note that, from the viewpoints of the molding temperature and the secondary processability of the molded article, the glass transition temperature of the resin film of this embodiment is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 135°C or lower.

[0070] The resin film of this embodiment may contain an acrylic resin having a syndiotacticity of 54% or more, expressed in triad form as described below, instead of having a glass transition temperature of 120° C. or higher. Since the syndiotacticity of the acrylic resin is 54% or more, the dimensional change rate of the resin film of this embodiment in a high-temperature environment is small.

[0071] The non-crosslinked resin may further contain a resin other than an acrylic resin. Examples of resins other than an acrylic resin include styrene resins such as acrylonitrile-styrene resin and styrene-maleic anhydride resin, fluororesins such as polycarbonate, polyvinyl acetal, cellulose acylate, polyvinylidene fluoride and polyfluorinated alkyl (meth)acrylate, silicone resin, polyolefin, polyethylene terephthalate, and polybutylene terephthalate. In this case, the glass transition temperature of the non-crosslinked resin is preferably 120°C or higher, more preferably greater than 120°C, even more preferably 121°C or higher, and particularly preferably 122°C or higher.

[0072] In one aspect, the sum of the 10-point average roughnesses Rzjis of both surfaces of the resin film of this embodiment is 0.05 μm or more and 1.0 μm or less, and preferably 0.06 μm or more and 0.6 μm or less. Since the sum of the 10-point average roughnesses Rzjis of both surfaces of the resin film of this embodiment is 0.05 μm or more, the blocking resistance of the resin film of this embodiment is high, and since it is 1.0 μm or less, the transparency of the resin film of this embodiment is high.

[0073] In another aspect, the sum of the kurtosis Rku on both sides of the resin film of this embodiment is 20 or more and 50 or less, preferably 25 or more and 45 or less, and more preferably 30 or more and 40 or less. Since the sum of the kurtosis Rku on both sides of the resin film of this embodiment is 20 or more, the blocking resistance of the resin film of this embodiment is high, and since it is 50 or less, when the resin film of this embodiment is applied to a display, the clarity is high.

[0074] Here, kurtosis Rku represents the sharpness in the height direction in accordance with JIS B 0601. When Rku is 3, the height distribution is a normal distribution, when Rku exceeds 3, there are many sharp peaks and valleys on the surface, and when Rku is less than 3, the surface is flat.

[0075] The internal haze of the resin film of this embodiment is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. When the internal haze of the resin film of this embodiment is 1.0% or less, the transparency of the resin film of this embodiment is maintained. The internal haze of the resin film of this embodiment is, for example, 0.1% or more.

[0076] The haze of the resin film of this embodiment is preferably 2.0% or less, more preferably 1.5% or less, and is, for example, 0.1% or more.

[0077] The static friction coefficient of the resin film of this embodiment is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. When the static friction coefficient of the resin film of this embodiment is 0.8 or less, the blocking resistance of the resin film of this embodiment is high. The static friction coefficient of the resin film of this embodiment is, for example, 0.2 or more.

[0078] The resin 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.

[0079] (Acrylic Resin) The acrylic resin is the same as that in the first embodiment.

[0080] (Crosslinked Acrylic Particles) The average particle size of the crosslinked acrylic particles is preferably 0.3 μm or more and 2.5 μm or less, more preferably 0.5 μm or more and 2.2 μm or less, and particularly preferably 0.6 μm or more and 1.5 μm or less. When the average particle size of the crosslinked acrylic particles is 0.3 μm or more, the blocking resistance of the resin film of this embodiment is improved, and when it is 2.5 μm or less, the production stability of the resin film of this embodiment is improved.

[0081] 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 resin film of this embodiment is maintained.

[0082] 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.

[0083] 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 resin film of this embodiment is maintained.

[0084] The crosslinked acrylic particles may be multilayer structure particles (see, for example, JP 2017-177596 A).

[0085] The content of the crosslinked acrylic particles in the resin 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 resin film of this embodiment is 0.05% by weight or more, the blocking resistance of the resin film of this embodiment is improved, and when it is 0.9% by weight or less, the transparency of the resin film of this embodiment is maintained.

[0086] (Method for Producing Resin Film) The resin film of this embodiment can be produced by a known method. An example of the method for producing the resin film of this embodiment will be described below.

[0087] First, a resin composition containing an acrylic resin and crosslinked acrylic particles is dissolved or dispersed in a solvent using a homogenizer to obtain a dope. Next, the dope is cast onto a substrate, and a film is peeled off from the substrate. Next, the film is dried to obtain a raw film. Next, the raw film is stretched uniaxially or biaxially to obtain the resin film of this embodiment. This increases the mechanical strength and thickness accuracy of the resin film of this embodiment.

[0088] The resin film of the present embodiment may be produced by appropriately uniaxially or biaxially stretching the raw film as the drying process progresses during the formation of the raw film. In this case, the resin film of the present embodiment may be further stretched.

[0089] The solvent preferably includes a first solvent having a hydrogen bond parameter δH of 1 or more and 12 or less in the Hansen solubility parameters, and a second solvent having a hydrogen bond parameter δH of 14 or more and 24 or less.

[0090] Examples of the first solvent include 1,4-dioxane (9.0), 2-phenylethanol (11.2), acetone (7.0), acetonitrile (6.1), chloroform (5.7), dibasic acid ester (8.4), diacetone alcohol (10.8), N,N-dimethylformamide (11.3), dimethyl sulfoxide (10.2), ethyl acetate (7.2), γ-butyrolactone (7.4), methyl ethyl ketone (5.1), methyl isobutyl ketone (4.1), methylene chloride (7.1), n-butyl acetate (6.3), N-methyl-2-pyrrolidone (7.2), propylene carbonate (4.1), 1,1,2,2-tetrachloroethane (5.3), tetrahydrofuran (8.0), and toluene (2.0). Two or more of these may be used in combination. The numerical value in parentheses indicates the value of the hydrogen bond parameter δH. Among these, from the viewpoint of the solubility and evaporation rate of the acrylic resin, methyl ethyl ketone, chloroform and methylene chloride are preferred, and methylene chloride is more preferred.

[0091] Examples of the second solvent include methanol (22.3), ethanol (19.4), isopropanol (16.4), butanol (15.8), and ethylene glycol monoethyl ether (14.3), and two or more of these may be used in combination. The values ​​in parentheses indicate the values ​​of the hydrogen bond parameter δH. Among these, methanol and ethanol are preferred, and ethanol is more preferred.

[0092] The solid content of the dope is not particularly limited, but is, for example, 5% by weight to 50% by weight, and the content of the first solvent in the solvent is not particularly limited, but is, for example, 55% by weight to 95% by weight.

[0093] The stretching temperature of the raw film is preferably (Tg + 7)°C or higher and (Tg + 50)°C or lower, and more preferably (Tg + 10)°C or higher and (Tg + 40)°C or lower, where Tg is the glass transition temperature of the raw film. The stretching ratio of the raw film is, for example, 1.5 times or higher and 3.0 times or lower. The stretching speed of the raw film is, for example, 1.1 times / min or higher and 100 times / min or lower.

[0094] The resin film of this embodiment can be applied to optical films such as polarizer protective films, for example.

[0095] (Polarizing Plate) The polarizing plate of this embodiment includes the resin film of this embodiment as a polarizer protective film. In the polarizing plate of this embodiment, for example, the resin film of this embodiment is bonded to both sides of a polarizer. The polarizer is not particularly limited, and a 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.

[0096] 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.

[0097] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0098] (Polymerization Conversion Rate) The polymerization conversion rate [%] was calculated by the following formula: After drying the acrylic resin for 30 minutes using an oven heated to 150°C, the solid weight of the acrylic resin was measured: (Solid weight of acrylic resin) x 100 / (Weight of charged monomers)

[0099] (Syndiotacticity rr in triad notation) Using a 400 MHz nuclear magnetic resonance spectrometer AVANCE III (manufactured by Bruker), the syndiotacticity of an acrylic resin was measured in a deuterated chloroform solution at 22°C and with 16 cumulative cycles. １ The H-NMR spectrum of the acrylic resin was measured. １ The area (X) of the region from 0.60 to 0.95 ppm and the area (Y) of the region from 0.60 to 1.25 ppm in the H-NMR spectrum, where the peak of tetramethylsilane (TMS) is set to 0 ppm, were measured, and the syndiotacticity (rr) of the acrylic resin in triad expression was calculated using the following formula: (X / Y)×100

[0100] (Weight-average molecular weight Mw) The weight-average molecular weight Mw of the acrylic resin was calculated using gel permeation chromatography (GPC). Specifically, a sample solution prepared by dissolving 20 mg of acrylic resin in 10 mL of tetrahydrofuran was used to measure GPC under the following conditions. Measuring instrument: High-speed GPC apparatus HLC-8220GPC (manufactured by Tosoh Corporation) Detector: RI detector Solvent: Tetrahydrofuran Guard column: TSKgel guard column SuperHZ-H (manufactured by Tosoh Corporation) Analytical column: TSKgel SuperHZM-H x 2 (manufactured by Tosoh Corporation) Measurement temperature: 40°C Standard material: Standard polystyrene (manufactured by Tosoh Corporation)

[0101] (Glass transition temperature Tg) The glass transition temperature of the acrylic resin or raw film was measured using a high-sensitivity differential scanning calorimeter DSC7000X (manufactured by Hitachi High-Tech Science). Specifically, under the condition of a nitrogen flow rate of 40 mL / min, the temperature was first raised from 40 ° C. to 160 ° C. at a heating rate of 10 ° C. / min, cooled to 40 ° C., and then raised from 40 ° C. to 160 ° C. at a heating rate of 10 ° C. / min. Next, the midpoint glass transition temperature was read from the DSC curve measured during the second heating.

[0102] (Kurtosis Rku and 10-point average roughness Rzjis) The kurtosis Rku of the resin film was measured using a laser microscope VK-X3000 (manufactured by Keyence) equipped with a white light interferometer. Specifically, first, a confocal image of the resin film in an area of ​​208 μm × 277 μm was captured using an objective lens with a magnification of 50x and a numerical aperture of 0.80. Three evaluation lines were then drawn at equal intervals in each of the vertical and horizontal directions to extract a roughness curve. Next, using analysis software, the kurtosis Rku and 10-point average roughness Rzjis were calculated from the roughness curve. At this time, the measurement position was changed, and the kurtosis Rku and 10-point average roughness Rzjis were calculated three times, and the average values ​​were calculated. However, if partial abnormalities such as scratches were clearly observed in the image, the kurtosis Rku and 10-point average roughness Rzjis were not calculated, and the measurement position was changed.

[0103] (Static Friction Coefficient) In accordance with JIS K7125:1999, the static friction coefficient of the resin film was measured using a digital force gauge ZTS-5N and a friction coefficient measuring jig COF-2N-V (both manufactured by Imada). Specifically, side A of the resin film was fixed on a smooth stainless steel plate, and side B of the resin 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. At this time, the static friction coefficient of the resin film was measured four times, and the average value was calculated.

[0104] (Haze) The haze of the resin film was measured using a haze meter HZ-V3 (manufactured by Suga Test Instruments) in accordance with JIS K7136:2000. The haze of the resin film was measured twice, and the average value was calculated. After measuring the haze of the resin film, it was converted into a value equivalent to a film thickness of 40 μm.

[0105] (Internal Haze) According to JIS K7136:2000, the internal haze of the resin film was measured using a haze meter HZ-V3 (manufactured by Suga Test Instruments). At this time, both sides of the resin film were sandwiched between glycerin and glass in that order, and the internal haze of the resin film was measured twice, and the average value was calculated. In addition, after measuring the internal haze of the resin film, it was converted into a value equivalent to a film thickness of 40 μm.

[0106] (Folding endurance) The resin film was cut into a strip shape with a width of 15 mm with the stretching direction being the longitudinal direction, to obtain a test piece. Next, using a deadweight type MIT folding endurance tester (manufactured by Toyo Seiki Seisakusho), the number of times the test piece was bent until it broke was measured under the conditions of a load of 1.96 N, a bending speed of 175 times / min, a bending clamp curvature radius of 0.38 mm, and a bending angle of 135 °, to evaluate the folding endurance of the resin film. At this time, the number of times the test piece was bent until it broke was measured three times, and the average value was calculated.

[0107] (Dimensional change rate) After cutting out an 80 mm x 80 mm test piece from the resin film using a cutter, a cross was drawn with an oil-based pen at a point 10 mm away from the four sides of the test piece inward so that the intersections were 20 mm apart, and the distance between the intersections of the cross was measured using an image dimension measuring instrument IM-6225 / 6700 (manufactured by Keyence). Next, the resin film was left to stand for 120 hours in an electronic thermo-hygrostat THR050FB (manufactured by Advantec) set at 85 ° C. and 85% RH, and the distance between the intersections of the cross was measured again. Next, the dimensional change rate in the stretching direction and the direction perpendicular to the stretching direction (width direction) was calculated using the following formula from the distance between the intersections of the cross before and after standing. At this time, the dimensional change rate of the resin film was calculated twice, and the average value was calculated. [(Spacing between intersections of the crosses after standing) - (Spacing between intersections of the crosses before standing)] x 100 / (Spacing between intersections of the crosses before standing)

[0108] (Blocking Resistance) Using a cutter, a 30 mm x 30 mm test piece was cut out from the resin film, and five test pieces were stacked with the A side facing up. Next, a load of 1 kg was applied from above the stacked test pieces, and the pieces were left at 60°C for 2 hours, and then allowed to cool at 23°C for 1 hour. Next, the condition of the test pieces was visually confirmed, and the test pieces were peeled off by hand to evaluate the blocking resistance of the resin film. The criteria for judging blocking resistance are as follows: 1: When the test pieces are stuck together 2: When the test pieces are not stuck together

[0109] (Production of Acrylic Resin A) A 5-L glass reactor equipped with an agitator having an H-shaped agitator blade was charged with 150 parts by weight of deionized water, 0.40 parts by weight of tribasic calcium phosphate as a dispersant, 0.0075 parts by weight of sodium α-olefin sulfonate, and 0.30 parts by weight of sodium chloride. Next, under a nitrogen atmosphere, while stirring at 250 rpm, 100 parts by weight of methyl methacrylate, 0.02 parts by weight of n-octyl mercaptan as a chain transfer agent, and 0.012 parts by weight of 2,2'-azobis(isobutyrate)dimethyl V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were added to the reactor. Next, the liquid temperature in the reactor was raised to 75°C to initiate polymerization, and 2 hours after the start of polymerization, 0.10 parts by weight of tribasic calcium phosphate was added to the reactor. At this time, an exothermic peak associated with the gel effect was observed 4 hours and 35 minutes after the start of polymerization. Next, 5 hours and 30 minutes after the start of polymerization, heating was started and the liquid temperature in the reactor was raised to 95°C. The polymerization conversion rate 5 hours and 30 minutes after the start of polymerization was 94%. Next, 3 hours after the liquid temperature in the reactor reached 95°C, the liquid temperature was cooled to room temperature to terminate the polymerization, and an acrylic resin dispersion was obtained. The polymerization conversion rate at the time of termination of polymerization was 99%.

[0110] The acrylic resin dispersion was acid washed using 0.1 times by weight of 1N hydrochloric acid relative to the weight of the charged monomer, followed by rinsing with water to remove the dispersant, etc. The washed acrylic resin dispersion was then dehydrated and dried to obtain acrylic resin A. Acrylic resin A had a triad syndiotacticity of 58%, a weight-average molecular weight of 1,119,000, a methyl methacrylate unit content of 100% by weight, and a glass transition temperature of 123°C.

[0111] After placing 90% by weight of methylene chloride in a screw tube, 10% by weight of acrylic resin A was added while stirring with a magnetic stirrer and stirred until completely dissolved. The resulting solution was filtered through a filter with a filtration accuracy of 1 μm, and the filtrate was dried in an oven at 50° C. to purify acrylic resin A.

[0112] Example 1: A mixed solvent consisting of 93% by mass of methylene chloride and 7% by mass of ethanol was placed in a screw tube, and then 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 A) were added and dispersed for 5 minutes at 5000 rpm using a homogenizer, Ultra-Turrax T25 (manufactured by IKA). Next, acrylic resin A was added with stirring so that the solid content of the crosslinked acrylic particles A became 0.10% by mass, and the mixture was stirred until completely dissolved to obtain a dope with a solid concentration of 12% by mass.

[0113] The dope was cast onto a glass substrate so that the thickness of the dried resin film was approximately 80 μm, and then coated with an applicator to form a uniform film. The film was then peeled off from the glass substrate. The surface of the film facing the glass substrate was designated as side B, and the other side was designated as side A. The film was then fixed to a stainless steel frame and dried in an oven at 40°C for 1 hour, followed by drying in an oven at 140°C for 2 hours to obtain a raw film. The glass transition temperature of the raw film was 125°C. The raw film was then uniaxially stretched at a temperature (145°C) 20°C higher than the glass transition temperature of the raw film to obtain a resin film. The stretching ratio was 2x, and the stretching speed was 2.3x / min.

[0114] Example 2 A raw film and a resin film were obtained in the same manner as in Example 1, except that crosslinked acrylic particles J-3PY (manufactured by Negami Chemical Industries, Ltd.) having an average particle size of 1.2 μm and a refractive index of 1.49 (hereinafter referred to as crosslinked acrylic particles B) were used instead of crosslinked acrylic particles A, and the solid content of crosslinked acrylic particles B was set to 0.12 wt %. The glass transition temperature of the raw film was 125° C.

[0115] Example 3 A raw film and a resin film were 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 C) were used instead of crosslinked acrylic particles B. The raw film had a glass transition temperature of 125° C.

[0116] Comparative Example 1 A raw film and a resin film were obtained in the same manner as in Example 1, except that the crosslinked acrylic particles A were not added. The raw film had a glass transition temperature of 124°C.

[0117] Comparative Example 2 A raw film and a resin film were obtained in the same manner as in Example 1, except that crosslinked acrylic particles xx-6390Z (manufactured by Sekisui Plastics 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 D) were used instead of the crosslinked acrylic particles A. The glass transition temperature of the raw film was 126° C.

[0118] Comparative Example 3: A mixed solvent consisting of 93% by mass of methylene chloride and 7% by mass of ethanol was placed in a screw tube, and the crosslinked acrylic particles A were then added and dispersed for 5 minutes at 5,000 rpm using an Ultra-Turrax T25 homogenizer (manufactured by IKA). Next, a methacrylic resin Parapet HR-F (manufactured by Kuraray) (hereinafter referred to as acrylic resin B) having a syndiotacticity of 56% in triad expression and a weight-average molecular weight of 100,000 was added with stirring so that the solid content of the crosslinked acrylic particles A became 0.10% by mass, and the mixture was stirred until completely dissolved to obtain a dope with a solid concentration of 20% by mass.

[0119] Except for using the obtained dope, a raw film and a resin film were obtained in the same manner as in Example 1. The raw film had a glass transition temperature of 115°C.

[0120] Comparative Example 4: A mixed solvent consisting of 93% by mass of methylene chloride and 7% by mass of ethanol was placed in a screw tube, and the crosslinked acrylic particles A were then added and dispersed using an Ultra-Turrax T25 homogenizer (manufactured by IKA) at 5,000 rpm for 5 minutes. Next, a methacrylic resin Parapet EH (manufactured by Kuraray) (hereinafter referred to as acrylic resin C) having a triad syndiotacticity of 53% and a weight-average molecular weight of 159,800 was added with stirring so that the solid content of the crosslinked acrylic particles A became 0.10% by mass, and the mixture was stirred until completely dissolved to obtain a dope with a solid concentration of 20% by mass.

[0121] Except for using the obtained dope, a raw film and a resin film were obtained in the same manner as in Example 1. The raw film had a glass transition temperature of 109°C.

[0122] Table 1 shows the properties of the acrylic resin.

[0123]

[0124] Table 2 shows the properties of the crosslinked acrylic particles.

[0125]

[0126] Table 3 shows the properties and evaluation results of the raw film or resin film.

[0127]

[0128] Table 3 shows that the resin films of Examples 1 to 3 have high heat resistance, folding resistance, and blocking resistance. In contrast, the resin film of Comparative Example 1 has low blocking resistance because the resin composition does not contain crosslinked acrylic particles. The resin film of Comparative Example 2 has low blocking resistance because the resin composition contains crosslinked acrylic particles D, and the average particle diameter of the crosslinked acrylic particles D is 0.15 μm. The resin film of Comparative Example 3 has low folding resistance because the resin composition contains acrylic resin B, and the Mw of acrylic resin B is 100,000. The resin film of Comparative Example 4 has a large dimensional change rate because its Tg is 109°C or its resin composition contains acrylic resin C, and the rr of acrylic resin C is 53%. Furthermore, the resin films of Comparative Examples 1 and 2 have low blocking resistance because the sum of Rku on both sides is 10.3 to 10.7 or the sum of Rzjis on both sides is 0.033 to 0.040 μm. The resin film of Comparative Example 3 has low folding endurance because it contains acrylic resin B with an Mw of 100,000. The resin film of Comparative Example 4 has a large dimensional change rate because it contains acrylic resin C with a Tg of 109°C or an rr of 53%.

Claims

1. A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more, and the crosslinked acrylic particles have an average particle diameter of 0.3 μm or more and 2.5 μm or less, and a glass transition temperature of 120°C or more.

2. The resin composition according to claim 1, wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

3. A resin composition comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, and the crosslinked acrylic particles have an average particle diameter of 0.3 μm or more and 2.5 μm or less.

4. The resin composition according to any one of claims 1 to 3, wherein the acrylic resin is substantially free of ring structures in the main chain.

5. A resin composition according to any one of claims 1 to 3, wherein the crosslinked acrylic particles have an average particle size of 0.5 μm or more and 2.2 μm or less.

6. A resin composition according to any one of claims 1 to 3, which is substantially free of solvent and has a content of the crosslinked acrylic particles of 0.05% by weight or more and 0.9% by weight or less.

7. The resin composition according to any one of claims 1 to 3, further comprising a solvent.

8. The resin composition according to any one of claims 1 to 3, which is used for producing a resin film.

9. A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more, the glass transition temperature being 120°C or higher, and the sum of the 10-point average roughness Rzjis of both surfaces being 0.05 μm or more and 1.0 μm or less.

10. The resin film according to claim 9, wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

11. A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, and wherein the sum of the 10-point average roughness Rzjis on both surfaces is 0.05 μm or more and 1.0 μm or less.

12. A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more, the glass transition temperature being 120°C or more, and the sum of the kurtosis Rku on both sides being 20 or more and 50 or less.

13. The resin film according to claim 12, wherein the acrylic resin has a syndiotacticity of 54% or more in triad expression.

14. A resin film comprising a non-crosslinked resin and crosslinked acrylic particles, wherein the non-crosslinked resin comprises an acrylic resin having a weight average molecular weight of 400,000 or more and a triad syndiotacticity of 54% or more, wherein the glass transition temperature is 120°C or more, and the sum of the kurtosis Rku on both sides is 20 or more and 50 or less.

15. A resin film according to any one of claims 9 to 14, having an internal haze of 1.0% or less.

16. A resin film according to any one of claims 9 to 14, having a static friction coefficient of 0.8 or less.

17. A resin film according to any one of claims 9 to 14, wherein the acrylic resin is substantially free of ring structures in the main chain.

18. A resin film according to any one of claims 9 to 14, wherein the crosslinked acrylic particles have an average particle size of 0.3 μm or more and 2.5 μm or less.

19. A resin film according to any one of claims 9 to 14, wherein the content of the crosslinked acrylic particles is 0.05% by weight or more and 0.9% by weight or less.

20. The resin film according to any one of claims 9 to 14, which is a polarizer protective film.

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