Resin film, polarizing plate, liquid crystal display panel, and resin composition

Abstract

This invention provides a resin film that offers high heat resistance, UV protection, and slipperiness, and is less likely to contaminate cast rolls during manufacturing. [Solution] The resin film comprises an acrylic resin having a ring structure in its main chain, and an ultraviolet absorber having a 1% weight loss temperature of 610K or higher and a maximum absorption wavelength of 340nm or higher, a glass transition temperature of 120°C or higher, a sum of kurtosis Rku on both sides of 10 to 50, and a transmittance of light at a wavelength of 370nm at an optical path length of 40μm of less than 2%.

Description

Technical Field

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

Background Art

[0002] A resin composition containing an acrylic resin and an ultraviolet absorber has excellent transparency, color tone, appearance, heat resistance, processability, and ultraviolet shielding properties, and is therefore applied to, for example, a polarizer protection film. Here, the polarizer protection film is applied to a liquid crystal panel by being bonded to both sides of a polarizer to form a polarizing plate and then disposed on both sides of a liquid crystal cell.

[0003] Patent Document 1 describes a polarizer protection film made of a thermoplastic resin composition containing a thermoplastic acrylic resin having a ring structure in the main chain and an ultraviolet absorber having a hydroxyphenyltriazine skeleton.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, when manufacturing a polarizer protection film, suppression of contamination of a casting roll has been studied, but there is still room for improvement.

[0006] An object of the present invention is to provide a resin film having high heat resistance, ultraviolet shielding properties, and slipperiness, and being less likely to be contaminated by a casting roll during production.

Means for Solving the Problems

[0007] [1] A resin film comprising an acrylic resin having a ring structure in its main chain, and an ultraviolet absorber having a 1% weight loss temperature of 610K or higher and a maximum absorption wavelength of 340nm or higher, having a glass transition temperature of 120°C or higher, a sum of kurtosis Rku on both sides of 10 to 50, and a transmittance of light at a wavelength of 370nm at an optical path length of 40μm of less than 2%.

[0008] [2] Contains cross-linked acrylic particles with an average particle diameter of 0.1 μm or more and 2.0 μm or less, The resin film according to [1], wherein the content of the cross-linked acrylic particles is 0.05% by weight or more and 1.0% by weight or less.

[0009] [3] A resin film comprising an acrylic resin having a ring structure in its main chain, an ultraviolet absorber having a 1% weight loss temperature of 610K or higher and a maximum absorption wavelength of 340nm or higher, and crosslinked acrylic particles having an average particle size of 0.1μm or more and 2.0μm or less, wherein the content of the crosslinked acrylic particles is 0.05% by weight or more and 1.0% by weight or less, the glass transition temperature is 120℃ or higher, and the transmittance of light at a wavelength of 370nm at an optical path length of 40μm is less than 2%.

[0010] [4] The resin film according to any one of [1] to [3], comprising 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine as the ultraviolet absorber.

[0011] [5] The resin film according to any one of [1] to [4], wherein the acrylic resin comprises in its main chain one or more selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a maleimide ring, and a glutaric anhydride ring.

[0012] [6] The resin film according to any one of [1] to [5], wherein the content of the ultraviolet absorber is 0.20% by weight or more and less than 0.90% by weight.

[0013] [7] A resin film according to any one of [1] to [6], having a haze of 1.0% or less.

[0014] [8] A resin film according to any one of [1] to [7], having an internal haze of 0.5% or less.

[0015] [9] A resin film according to any one of [1] to [8], being a polarizer protection film.

[0016]

[10] A polarizing plate comprising the resin film described in [9].

[0017]

[11] A liquid crystal display panel comprising the polarizing plate described in

[10] .

[0018]

[12] A resin composition comprising an acrylic resin containing a ring structure in the main chain, an ultraviolet absorber having a weight loss temperature of 610 K or higher and a maximum absorption wavelength of 340 nm or longer, and crosslinked acrylic particles having an average particle diameter of 0.1 μm or more and 2.0 μm or less, wherein the acrylic resin has a glass transition temperature of 120° C or higher, the content of the crosslinked acrylic particles is 0.05% by weight or more and 1.0% by weight or less, and the content of the ultraviolet absorber is 0.20% by weight or more and less than 0.90% by weight.

[0019]

[13] The resin composition according to

[12] , wherein the ultraviolet absorber contains 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine. [The effects of the invention]

[0020] According to the present invention, it is possible to provide a resin film having high heat resistance, ultraviolet shielding property and slipperiness, and being difficult to contaminate a casting roll during production. [Embodiments for carrying out the invention]

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

[0022] (Resin film) The resin film of this embodiment contains an acrylic resin having a ring structure in the main chain and an ultraviolet absorber. Here, the 1% weight loss temperature of the ultraviolet absorber is 610 K or higher, preferably 620 K or higher, and more preferably 630 K or higher. Since the 1% weight loss temperature of the ultraviolet absorber is 610 K or higher, the ultraviolet absorber is less likely to volatilize during the production of the resin film of this embodiment, and as a result, the casting roll is less likely to be contaminated. Note that the 1% weight loss temperature of the ultraviolet absorber is, for example, 660 K or lower. Further, the maximum absorption wavelength of the ultraviolet absorber is 340 nm or longer, preferably 350 nm or longer, and more preferably 355 nm or longer. Since the maximum absorption wavelength of the ultraviolet absorber is 340 nm or longer, the ultraviolet shielding property of the resin composition of this embodiment is enhanced. Note that the maximum absorption wavelength of the ultraviolet absorber is, for example, 365 nm or shorter.

[0023] In this specification and the claims, the acrylic resin means a polymer of a monomer having an acryloyl group and / or a monomer having a methacryloyl group and a modified product of the polymer. At this time, the acrylic resin may be either a homopolymer or a copolymer. When the acrylic resin is a copolymer, the acrylic resin may be a copolymer with a monomer having no acryloyl group or methacryloyl group. Note that the acrylic resin may be a mixture of two or more polymers having different monomer compositions.

[0024] The glass transition temperature of the resin film of this embodiment is 120°C or higher, preferably higher 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, the heat resistance of the resin film of this embodiment is enhanced. Note that the glass transition temperature of the resin film of this embodiment is, for example, 160°C or lower.

[0025] The transmittance of light at a wavelength of 370 nm at an optical path length of 40 μm of the resin film of this embodiment is less than 2%, and preferably less than 1.5%. Because the transmittance of light at a wavelength of 370 nm at an optical path length of 40 μm of the resin film of this embodiment is less than 2%, the ultraviolet shielding performance of the resin film of this embodiment is high.

[0026] In one embodiment of the resin film of this embodiment, the sum of the kurtosis Rku on both sides is 10 or more and 50 or less, preferably 15 or more and 30 or less. Because the sum of the kurtosis Rku on both sides of the resin film of this embodiment is 10 or more and 50 or less, even if the ultraviolet absorber volatilizes during the manufacturing of the resin film of this embodiment, the volatilized ultraviolet absorber is less likely to adhere to the cast roll, and as a result the cast roll is less likely to be contaminated. In addition, the slipperiness of the resin film of this embodiment is improved.

[0027] In another embodiment of the resin film of this embodiment, the average particle size of the cross-linked acrylic particles is 0.1 μm or more and 2.0 μm or less, preferably 0.15 μm or more and 1.0 μm or less. Because the average particle size of the cross-linked acrylic particles is 0.1 μm or more and 2.0 μm or less, even if the ultraviolet absorber volatilizes during the manufacturing of the resin film of this embodiment, the volatilized ultraviolet absorber is less likely to adhere to the cast roll, and the slipperiness of the resin film of this embodiment is improved.

[0028] The reason why the volatile UV absorber becomes less likely to adhere to the cast roll is unclear, but It is presumed that this is due to the fact that when manufacturing a resin film having a predetermined sum of kurtosis Rku on both sides, the contact area with the cast roll is reduced, making it difficult for volatile UV absorbers to adhere to the cast roll, and that melted UV absorbers are captured on the surface of cross-linked acrylic particles, making them less likely to bleed out.

[0029] In this case, the content of cross-linked acrylic particles in the resin film of this embodiment is preferably 0.05% by weight or more and 1.0% by weight or less, and preferably 0.1% by weight or more and 0.5% by weight or less. Because the content of cross-linked acrylic particles in the resin film of this embodiment is 0.05% by weight or more and 1.0% by weight or less, even if the ultraviolet absorber volatilizes during the manufacture of the resin film of this embodiment, the volatilized ultraviolet absorber is less likely to adhere to the cast roll, and the slipperiness of the resin film of this embodiment is improved.

[0030] Furthermore, one embodiment of the resin film of this embodiment may also serve as another embodiment of the resin film of this embodiment.

[0031] (UV absorber) The UV absorber preferably contains 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine. This increases the UV shielding ability of the UV absorber, so that the UV shielding performance of the resin film of this embodiment is improved even when the amount of UV absorber added is reduced. In this case, reducing the amount of UV absorber added makes the cast roll less susceptible to contamination.

[0032] The UV absorber content in the resin film of this embodiment is preferably 0.20% by weight or more and less than 0.90% by weight, more preferably 0.30% by weight or more and less than 0.70% by weight, and even more preferably 0.50% by weight or more and less than 0.65% by weight. When the UV absorber content in the resin film of this embodiment is 0.20% by weight or more, the UV shielding performance of the resin film of this embodiment is increased, and when it is less than 0.90% by weight, the cast roll becomes less susceptible to contamination.

[0033] The content of 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine in the UV absorber is preferably 20% by weight or more. When the content of 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine in the UV absorber is 20% by weight or more, the UV shielding performance of the resin film of this embodiment is improved even when the amount of UV absorber added is reduced.

[0034] The ultraviolet absorber may further contain compounds other than 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine (hereinafter referred to as "other compounds").

[0035] Other compounds are not particularly limited, but examples include hydroxyphenyltriazine-based UV absorbers, benzotriazole-based UV absorbers, and benzophenone-based UV absorbers, and two or more may be used in combination. Examples of hydroxyphenyltriazine-based UV absorbers include 2,4,6-tris(4-hexyloxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine, 2,4-bis[4-(2-ethylhexyloxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazine, and 2,4-bis(2-hydroxy-4-butyloxyphenyl)-6-(2,4-bis(butyloxyphenyl))-1,3,5-triazine. Among these, 2,4,6-tris(4-hexyloxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine is preferred because it reduces the volatilization of the UV absorber during the production of the resin film of this embodiment.

[0036] (Cross-linked acrylic particles) The resin film of this embodiment preferably contains cross-linked acrylic particles. This makes it less likely for the UV absorber to adhere to the cast roll even if it volatilizes during the manufacturing of the resin film of this embodiment, and as a result the cast roll is less likely to be contaminated. In addition, the slipperiness of the resin film of this embodiment is improved.

[0037] The acrylic resin constituting the cross-linked acrylic particles preferably contains methyl methacrylate units. The content of methyl methacrylate units in the acrylic resin constituting the cross-linked acrylic particles is preferably 80% to 99% by weight, and more preferably 83% to 96% by weight. When the content of methyl methacrylate units in the acrylic resin constituting the cross-linked acrylic particles is 80% to 99% by weight, the transparency of the resin film of this embodiment is increased.

[0038] The acrylic resin constituting the crosslinked acrylic particles preferably contains polyfunctional monomer units. The content of polyfunctional monomer units 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 polyfunctional monomer units 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 manufacturing stability of the crosslinked acrylic particles is improved.

[0039] The refractive index of the crosslinked acrylic particles is preferably between 1.47 and 1.55, more preferably between 1.47 and 1.53, and even more preferably between 1.48 and 1.52. When the refractive index of the crosslinked acrylic particles is between 1.47 and 1.55, the transparency of the resin film of this embodiment is increased.

[0040] Furthermore, the cross-linked acrylic particles may also be multilayer particles (see, for example, Japanese Patent Publication No. 2017-177596).

[0041] (Acrylic resin containing a ring structure in the main chain) The glass transition temperature of the acrylic resin containing a ring structure in the main chain is 120°C or higher, preferably above 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. Because the glass transition temperature of the acrylic resin containing a ring structure in the main chain is 120°C or higher, the heat resistance of the resin film of this embodiment is high. For example, the glass transition temperature of the acrylic resin containing a ring structure in the main chain is 160°C or lower.

[0042] The weight-average molecular weight of the acrylic resin containing a ring structure in the main chain is preferably 50,000 to 200,000, more preferably 80,000 to 150,000, and even more preferably 90,000 to 150,000. When the weight-average molecular weight of the acrylic resin containing a ring structure in the main chain is 50,000 or more, the mechanical properties of the resin film of this embodiment are improved, and when it is 200,000 or less, the moldability of the resin film of this embodiment is improved.

[0043] Acrylic resins containing a ring structure in the main chain preferably contain one or more rings selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric acid anhydride rings. Below, as an example of an acrylic resin containing a ring structure in the main chain, an acrylic resin containing a glutarimide ring or a lactone ring in the main chain will be described.

[0044] Acrylic resins containing glutarimide rings in the main chain include, for example, constituent units represented by the following formula (1).

[0045] [ka] (In the formula, R 1 and R 2 Each is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 (This is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms.)

[0046] Acrylic resins containing the constituent units represented by formula (1) can be manufactured using known methods. An example of a method for manufacturing acrylic resins containing the constituent units represented by formula (1) is described below.

[0047] First, using a twin-screw extruder equipped with a die at the outlet, methyl methacrylate resin is melted, imidized, and then the strand is extruded from the die. Next, the strand is cooled in a water bath, and then the strand is pelletized using a pelletizer to obtain imidized methyl methacrylate resin. Next, using a twin-screw extruder equipped with a die at the outlet, the imidized methyl methacrylate resin is melted, esterified, and then the strand is extruded from the die. Next, the strand is cooled in a water bath, and then the strand is pelletized using a pelletizer to obtain an acrylic resin containing the constituent units represented by formula (1).

[0048] 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.

[0049] R 3 NH2(2) (In the formula, R 3 This is equivalent to equation (1).

[0050] Examples of esterifying agents used when esterifying imidized methyl methacrylate resins include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyltoluenesulfonate, methyltrifluoromethylsulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, and dimethylcarbodiimide. Examples include dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexylglycidyl ether, phenylglycidyl ether, and benzylglycidyl ether. Among these, dimethyl carbonate is preferred.

[0051] Acrylic resins having lactone rings in the main chain can be obtained, for example, by polymerizing monomers represented by the following formula (3) and then heat-treating them to form lactone rings.

[0052] [ka] (In the formula, R 4 and R 5 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0053] Examples of monomers 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 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.

[0054] In addition, as acrylic resins containing a ring structure in the main chain other than acrylic resins containing a glutarimide ring or lactone ring in the main chain, known acrylic resins used in resin films can be used.

[0055] The content of ring-structured constituent units in the acrylic resin containing a ring structure in the main chain is not particularly limited, but is, for example, 1% by weight or more and 80% by weight or less.

[0056] Acrylic resins containing a ring structure in the main chain may further contain (meth)acrylic acid ester units.

[0057] Examples of (meth)acrylic acid ester units include alkyl (meth)acrylate units such as methyl (meth)acrylate units, ethyl (meth)acrylate units, n-propyl (meth)acrylate units, n-butyl (meth)acrylate units, and isobutyl (meth)acrylate units; aryl (meth)acrylate units such as phenyl (meth)acrylate units; aralkyl (meth)acrylate units such as benzyl (meth)acrylate units; and cycloalkyl (meth)acrylate units such as cyclohexyl (meth)acrylate units. Two or more of these may be used in combination. Among these, alkyl methacrylate units are preferred, and methyl methacrylate units are particularly preferred.

[0058] Acrylic resins containing a ring structure in the main chain may further contain other monomer units. These other monomer units are not particularly limited, but examples include aromatic vinyl units and (meth)acrylonitrile units. Examples of aromatic vinyl units are not particularly limited, but examples include styrene units, α-methylstyrene units, methoxystyrene units, vinyltoluene units, and halostyrene units. Among these, styrene units are preferred.

[0059] In this specification and in the claims, (meth)acrylonitrile unit means acrylonitrile unit or methacrylonitrile unit.

[0060] (Other resins) The resin film of this embodiment may further contain resins other than acrylic resin. Examples of resins other than 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 polyalkyl (meth)acrylate, silicone resins, polyolefins, polyethylene terephthalate, polybutylene terephthalate, and polyimide.

[0061] (Antioxidant) The resin composition of this embodiment may further contain an antioxidant. This enhances the oxidative degradation resistance of the resin composition of this embodiment. Examples of antioxidants include phosphorus-based antioxidants, hindered phenol-based antioxidants, and thioether-based antioxidants. The antioxidant content in the resin film of this embodiment is, for example, 0.1% by weight or more and 2.0% by weight or less.

[0062] (Other additives) The resin composition of this embodiment may further contain additives such as light stabilizers, heat stabilizers, matting agents, light diffusing agents, colorants, dyes, pigments, antistatic agents, heat reflective materials, lubricants, plasticizers, stabilizers, flame retardants, mold release agents, polymer processing aids, toughness modifiers, and fillers.

[0063] (Resin composition) The resin composition of this embodiment comprises an acrylic resin having a ring structure in its main chain, an ultraviolet absorber having a 1% weight loss temperature of 610K or higher and a maximum absorption wavelength of 340nm or higher, and crosslinked acrylic particles having an average particle size of 0.1μm or more and 2.0μm or less, and is used in the manufacture of the resin film of this embodiment. Here, the acrylic resin has a glass transition temperature of 120°C or higher, the content of crosslinked acrylic particles in the resin composition of this embodiment is 0.05% by weight or more and 1.0% by weight or less, and the content of ultraviolet absorber in the resin composition of this embodiment is less than 0.90% by weight.

[0064] The form of the resin composition in this embodiment is not particularly limited, but examples include pellets.

[0065] (Method for manufacturing resin compositions) The resin composition of this embodiment can be manufactured using known methods. An example of a manufacturing method for the resin composition of this embodiment is described below.

[0066] First, using a twin-screw extruder equipped with a die at the outlet, an acrylic resin containing a ring structure in the main chain is mixed with an ultraviolet absorber and crosslinked acrylic particles. Next, the strand extruded from the die is cooled in a water bath and then pelletized in a pelletizer to obtain the resin composition of this embodiment.

[0067] (Resin film) The resin film of this embodiment is formed by molding the resin composition of this embodiment.

[0068] The fold resistance of the resin film in this embodiment is preferably 400 times or more, and more preferably 500 times or more. When the fold resistance of the resin film in this embodiment is 400 times or more, the bending resistance of the resin film in this embodiment is increased.

[0069] The haze of the resin film in this embodiment is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. When the haze of the resin film in this embodiment is 1.0% or less, the transparency of the resin film in this embodiment is maintained. For example, the haze of the resin film in this embodiment is 0.1% or more.

[0070] The internal haze of the resin film in this embodiment is preferably 0.5% or less, more preferably 0.4% or less, even more preferably 0.3% or less, even more preferably 0.2% or less, and particularly preferably 0.1% or less. When the internal haze of the resin film in this embodiment is 0.5% or less, the transparency of the resin film in this embodiment is increased. For example, the internal haze of the resin film in this embodiment is 0.05% or more.

[0071] The in-plane phase difference Re of the resin film of this embodiment at a wavelength of 590 nm is preferably 5.0 nm or less, more preferably 3.0 nm or less, even more preferably 2.0 nm or less, particularly preferably 1.0 nm or less, and most preferably 0.5 nm or less. The thickness-direction phase difference Rth of the resin film of this embodiment at a wavelength of 590 nm is preferably -10.0 nm or more and 10.0 nm or less, preferably -5.0 nm or more and 5.0 nm or less, even more preferably -2.0 nm or more and 2.0 nm or less, and particularly preferably -1.0 nm or more and 1.0 nm or less. When the resin film of this embodiment has the above-mentioned phase differences, it has excellent optical properties and can be suitably used as a polarizer protective film for liquid crystal display devices.

[0072] Here, the in-plane phase difference Re and the thickness-direction phase difference Rth of the resin film at a wavelength of 590 nm are given by the formula: Re=(nx-ny)×d Rth = [(nx + ny) / 2 - nz] × d It is calculated by the following formula. Here, nx, ny, and nz are the refractive indices in the X-axis direction, Y-axis direction, and Z-axis direction, respectively, with the MD direction being the X-axis, the TD direction being the Y-axis, and the film thickness direction being the Z-axis. Also, d is the thickness of the resin film.

[0073] The thickness of the resin film in this embodiment is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 300 μm or less, and even more preferably 30 μm or more and 100 μm or less. When the thickness of the resin film in this embodiment is 10 μm or more, the ultraviolet shielding performance of the resin film in this embodiment is improved, and when it is 500 μm or less, the bending resistance of the resin film in this embodiment is improved.

[0074] (Application) The resin film of this embodiment can be applied to, for example, transportation equipment, solar cell components, civil engineering and construction components, daily necessities, electrical and electronic equipment, optical components, and medical supplies, but it is preferably used as an optical film for displays, particularly as a polarizer protective film. In this case, the resin film of this embodiment is laminated with a polarizer to form a polarizing plate. The polarizing plate can be applied to, for example, liquid crystal display panels and organic EL display panels.

[0075] (Method of manufacturing resin film) The resin film of this embodiment can be manufactured using known methods. An example of a method for manufacturing the resin film of this embodiment will be described below.

[0076] First, the resin composition of this embodiment is melted using a twin-screw extruder equipped with a T-die at the outlet, and then the sheet extruded from the T-die is cooled with a cooling roll to obtain a raw film. Next, the raw film is biaxially stretched to obtain the resin film of this embodiment. At this time, the biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.

[0077] The temperature at which the raw film is biaxially stretched is preferably (Tg+5)°C to (Tg+30)°C, more preferably (Tg+6)°C to (Tg+25)°C, and even more preferably (Tg+7)°C to (Tg+20)°C, where Tg is the glass transition temperature of the acrylic resin. The surface ratio at which the raw film is biaxially stretched is not particularly limited, but for example, it is between 2 and 10 times. The stretching speed at which the raw film is biaxially stretched is not particularly limited, but for example, it is between 1.1 times / min and 100 times / min. When the raw film is sequentially biaxially stretched, the stretching speed of the first stage and the stretching speed of the second stage may be the same or different. In sequential biaxial stretching, the first stage stretching is usually in the longitudinal direction (MD direction), and the second stage stretching is in the width direction (TD direction).

[0078] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Examples]

[0079] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0080] (Weight average molecular weight) The weight-average molecular weight of the acrylic resin was calculated using gel permeation chromatography (GPC) and the standard polystyrene equivalent method.

[0081] (1% weight loss temperature Td1) Using a differential thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science), 10 mg of ultraviolet absorber was heated from 40°C at a heating rate of 5°C / min under a nitrogen atmosphere, and the temperature Td1 [K] at which the weight decreased by 1% was determined. When two or more ultraviolet absorbers were used, Td1 was defined as the temperature at which the ultraviolet absorbers mixed in a predetermined ratio lost 1% of their weight.

[0082] (Maximum absorption wavelength λmax) Using a V-560 UV-Vis spectrophotometer (manufactured by JASCO), the UV-Vis absorption spectrum of a solution prepared by dissolving an ultraviolet absorber at a concentration of 10 mg / L in chloroform was measured, and the maximum absorption wavelength λmax was determined.

[0083] (Glass transition temperature Tg) The glass transition temperature of acrylic resin or raw film was measured using a differential scanning calorimetry system (DSC7000X, manufactured by Hitachi High-Tech Science). Specifically, the temperature was first raised from 40°C to 190°C at a heating rate of 10°C / min under a nitrogen flow rate of 40 mL / min, then cooled to 40°C, and then raised again from 40°C to 190°C at a heating rate of 10°C / min. Next, the glass transition temperature Tg (midpoint glass transition temperature) was read from the DSC curve measured during the second heating cycle. Here, the midpoint glass transition temperature is the temperature at the point where a line equidistant in the vertical axis direction from both the line obtained by extrapolating the baseline before the inflection point of the DSC curve to the higher temperature side, and the line obtained by extrapolating the baseline after the inflection point of the DSC curve to the lower temperature side, intersects with the stepwise change portion of the glass transition in the DSC curve.

[0084] (Kurtosis Rku) In accordance with JIS B 0601, the surface roughness of a resin film was measured using a white light interferometer-equipped laser microscope VK-X3000 (manufactured by Keyence). A confocal image of a 257 μm × 257 μm area of ​​the resin film was captured using a 50x magnification objective lens. The captured image was processed using three image processing tools: reference plane setting, surface shape correction (undulation removal), and noise reduction (intensity, medium mode). Next, three evaluation lines were drawn at equal intervals in both the MD and TD directions using line roughness measurement mode, and the average value of the kurtosis Rku of the resin film was calculated using analysis software based on the obtained line roughness information. The measurement was performed five times with different measurement positions, and the average value was calculated. The measurement was performed on both sides of the resin film, and the total kurtosis Rku value from both sides was calculated. The kurtosis (Rku) represents the sharpness in the height direction. Rku=3 means the height distribution is normal, Rku>3 means there are many sharp peaks and valleys on the surface, and Rku<3 means the surface is flat.

[0085] (Static friction coefficient) In accordance with JIS K7125:1999, the static friction coefficient of a 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, one side of the resin 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 thread with double-sided tape. The load was read using a load cell while the thread was moved at a speed of 100 mm / min via a pulley, and the static friction coefficient between one side of the resin film and the other side was calculated. The static friction coefficient of the resin film was measured five times, and the average value was calculated.

[0086] (Transmittance of light with a wavelength of 370 nm) Using a V-560 UV-Vis spectrophotometer (manufactured by JASCO), the UV-Vis absorption spectrum of a 40 μm thick resin film was measured, and the transmittance of light at a wavelength of 370 nm was determined.

[0087] (Total light transmittance) The total light transmittance of the resin film was measured using a haze meter HZ-V3 (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K7361-1:1997.

[0088] (Haze and internal haze) Using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries), the haze and internal haze of the resin film were measured in accordance with JIS 7136:2000. For internal haze, to cancel the effect of surface scattering of the resin film, glycerin was first dropped onto both the front and back surfaces of the resin film, then sandwiched between glass plates, and the haze was measured with the interface between the resin film and the glass plates filled with glycerin. Subsequently, the internal haze of the resin film was determined by subtracting the previously measured haze of the glass plates.

[0089] (In-plane phase difference Re and thickness-direction phase difference Rth) A 40mm x 40mm test piece was cut from a resin film, and the in-plane phase difference Re at a wavelength of 590nm was measured using an automatic birefringent KOBRA-WR (manufactured by Oji Instruments Co., Ltd.) under conditions of a temperature of 23±2℃, humidity of 50±5%, and an incident angle of 0°.

[0090] The thickness d of the specimen was measured using a Digimatic indicator (Mitutoyo). The refractive index n of the specimen was measured using an Abbe refractometer 3T (Atago). Furthermore, using an automatic birefringent KOBRA-WR (Oji Instruments), the in-plane phase difference Re at a wavelength of 590 nm and the phase difference at an incident angle of 40° and a wavelength of 590 nm were measured in the same manner as above, and the three-dimensional refractive indices nx, ny, and nz were determined. Next, the equation... Rth = ((nx + ny) / 2 - nz) × d Based on this, the thickness direction phase Rth was determined.

[0091] (folding durability) Test specimens were prepared by cutting the resin film into strips 15 mm wide. The fold resistance of the resin film was measured using an MIT folding fatigue tester, model D (manufactured by Toyo Seiki), under the following conditions. The fold resistance of the resin film was measured in both the MD and TD directions and the arithmetic mean was calculated. Load: 1.96N Folding angle: 135° Folding speed: 175 times / minute Radius of curvature of the bending clamp: 0.38 mm

[0092] (Roll stain resistance) The roll contamination resistance of the resin film was evaluated as follows: A mixture of acrylic resin, UV absorber, and cross-linked acrylic particles, hand-blended, was fed into a 15mm diameter, L / D=45 meshing type co-rotating twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel) equipped with a T-die at the outlet. The resin film was formed at an extrusion temperature of 260°C to a thickness of 100 μm. At this time, the screw rotation speed was set to 300 rpm, the feeder rotation speed to 65 rpm, and the cast roll temperature to 110°C. Before film formation, a 15 cm square area in the center of the cast roll (where the molten film would come into contact) was wiped using a Bencot (cellulose nonwoven fabric wiper) soaked in 4 ml of chloroform, and then immersed in 30 ml of pre-prepared chloroform (hereinafter referred to as the BF sample). Subsequently, after continuing the film formation process for one hour, the same area in the center of the cast roll was wiped with a chloroform-soaked cloth, as before film formation, and immersed in 30 ml of pre-prepared chloroform to extract the UV absorber adhering to the surface of the cast roll into the chloroform (hereinafter referred to as the AF sample). Next, using a UV-Vis spectrophotometer V-560 (manufactured by JASCO), the absorbance Abs of the chloroform solution at wavelengths of 350 nm, 360 nm, and 370 nm was measured for both the BF sample and the AF sample, and the sum of Abs was calculated. The resistance to roll contamination was evaluated by calculating ΔAbs, which is the sum of Abs of the AF sample minus the sum of Abs of the BF sample. Here, since the UV absorber absorbs light with a wavelength of 350 to 370 nm, a larger ΔAbs indicates a greater amount of UV absorber adhering to the cast roll, and therefore the cast roll is more contaminated.

[0093] (Manufacturing of acrylic resin 1) A 40mm diameter, co-rotating twin-screw extruder (L / D=90) equipped with a die at the outlet was used. Each temperature control zone was set to 250-280°C, and the screw rotation speed was set to 85 rpm. Methyl methacrylate resin was melted and filled into the extruder using a kneading block. Next, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical) was injected through a nozzle for every 100 parts by weight of methyl methacrylate resin to imide the methyl methacrylate resin. Then, the strands extruded from the die were cooled in a water bath, and the strands were pelletized using a pelletizer to obtain imide resin 1.

[0094] A 40mm diameter, co-rotating twin-screw extruder (L / D=90) equipped with a die at the outlet was used. The temperature of each temperature control zone was set to 240-260°C, and the screw rotation speed was set to 85 rpm. Imidized resin 1 was melted and filled using a kneading block. Next, 0.56 parts by weight of dimethyl carbonate was injected into 100 parts by weight of imidized resin 1 to esterify the carboxyl groups in the imidized resin 1. At this time, by-products and excess dimethyl carbonate were removed after the reaction. Next, the strand extruded from the die was cooled using a water bath, and then the strand was 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.

[0095] (Example 1) (Manufacturing of resin compositions) A mixture was hand-blended with 100 parts by weight of acrylic resin A, containing 0.53 parts by weight of the ultraviolet absorber 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine (hereinafter referred to as UVA1), 0.077 parts by weight of cross-linked acrylic particles MX80H3wT (manufactured by Soken Chemical Co., Ltd.) (hereinafter referred to as cross-linked acrylic particles 1) with an average particle size of 0.8 μm and a refractive index of 1.49, and 0.033 parts by weight of cross-linked acrylic particles xx-6390Z (manufactured by Sekisui Chemical Co., Ltd.) (hereinafter referred to as cross-linked acrylic particles 2) with an average particle size of 0.15 μm and a refractive index of 1.49. This mixture was then extruded at an extrusion temperature of 255°C using a meshing type co-rotating twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel Co., Ltd.) equipped with a die at the outlet with a diameter of 15 mm and an L / D ratio of 45. Next, the strands extruded from the die were cooled in a water bath, pelletized in a pelletizer, and then dried at 90°C for 4 hours to obtain a pelletized resin composition.

[0096] (Manufacturing of resin films) A resin composition was extruded at an extrusion temperature of 240°C using a 15mm diameter, L / D=45 meshing type coaxial rotary twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel) equipped with a T-die at the outlet. Next, the sheet extruded from the T-die was cooled with a cooling roll to obtain a raw film with a width of 160mm and a thickness of 160μm. The raw film had a Tg of 122.7°C. Next, a 100mm × 100mm small piece was cut from the raw film so that two sides were parallel to the extrusion direction. Next, the small piece was set in a pantograph type biaxial stretching device and simultaneously biaxially stretched at a stretching temperature of 145°C and a stretching speed of 100mm / min so that the stretching ratio in the direction parallel and perpendicular to the extrusion direction was doubled. Next, the stretched small piece was removed to room temperature and cooled to obtain a resin film with a thickness of 40μm.

[0097] (Example 2) A resin film was obtained in the same manner as in Example 1, except that in the (production of the resin composition), a mixture of 0.22 parts by weight of UVA-1 and 0.41 parts by weight of 2,4,6-tris(4-hexyloxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine (hereinafter referred to as UVA2) was used instead of 0.53 parts by weight of UVA1. The raw film had a Tg of 122.6°C.

[0098] (Comparative Example 1) A resin film was obtained in the same manner as in Example 1, except that crosslinked acrylic particle 1 and crosslinked acrylic particle 2 were not added in the (production of the resin composition). The raw film had a Tg of 121.9°C.

[0099] (Comparative Example 2) A resin film was obtained in the same manner as in Example 2, except that crosslinked acrylic particle 1 and crosslinked acrylic particle 2 were not added in the (production of the resin composition). The raw film had a Tg of 122.3°C.

[0100] Table 1 shows the properties of cross-linked acrylic particles.

[0101] [Table 1]

[0102] Table 2 shows the evaluation results for the resin film.

[0103] [Table 2]

[0104] Table 2 shows that the resin films of Examples 1 and 2 have high heat resistance, UV shielding properties, and slipperiness, and the cast rolls are less likely to be contaminated during manufacturing. In contrast, the resin films of Comparative Examples 1 and 2 have a sum of kurtosis Rku on both sides of 6.3 and 7.5, respectively, resulting in low slipperiness and a large ΔAbs, which makes the cast rolls more susceptible to contamination during manufacturing.

Claims

1. Acrylic resin containing a ring structure in the main chain, It contains an ultraviolet absorber whose 1% weight loss temperature is 610 K or higher and whose maximum absorption wavelength is 340 nm or higher. The glass transition temperature is 120°C or higher. The sum of the kurtosis Rku on both sides is between 10 and 50, A resin film having a transmittance of less than 2% for light with a wavelength of 370 nm at an optical path length of 40 μm.

2. It contains cross-linked acrylic particles with an average particle diameter of 0.1 μm or more and 2.0 μm or less. The resin film according to claim 1, wherein the content of the cross-linked acrylic particles is 0.05% by weight or more and 1.0% by weight or less.

3. Acrylic resin containing a ring structure in the main chain, An ultraviolet absorber having a 1% weight loss temperature of 610 K or higher and a maximum absorption wavelength of 340 nm or higher, It contains cross-linked acrylic particles with an average particle diameter of 0.1 μm or more and 2.0 μm or less. The content of the cross-linked acrylic particles is 0.05% by weight or more and 1.0% by weight or less. The glass transition temperature is 120°C or higher. A resin film having a transmittance of less than 2% for light with a wavelength of 370 nm at an optical path length of 40 μm.

4. The resin film according to any one of claims 1 to 3, wherein the ultraviolet absorber comprises 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine.

5. The resin film according to any one of claims 1 to 3, wherein the acrylic resin comprises in its main chain one or more elements selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a maleimide ring, and a glutaric anhydride ring.

6. The resin film according to any one of claims 1 to 3, wherein the content of the ultraviolet absorber is 0.20% by weight or more and less than 0.90% by weight.

7. A resin film according to any one of claims 1 to 3, wherein the haze is 1.0% or less.

8. A resin film according to any one of claims 1 to 3, wherein the internal haze is 0.5% or less.

9. A resin film according to any one of claims 1 to 3, which is a polarizer protective film.

10. A polarizing plate comprising the resin film described in claim 9.

11. A liquid crystal display panel comprising a polarizing plate as described in claim 10.

12. Acrylic resin containing a ring structure in the main chain, An ultraviolet absorber having a 1% weight loss temperature of 610 K or higher and a maximum absorption wavelength of 340 nm or higher, It contains cross-linked acrylic particles with an average particle diameter of 0.1 μm or more and 2.0 μm or less. The aforementioned acrylic resin has a glass transition temperature of 120°C or higher. The content of the cross-linked acrylic particles is 0.05% by weight or more and 1.0% by weight or less. A resin composition in which the content of the ultraviolet absorber is 0.20% by weight or more and less than 0.90% by weight.

13. The resin composition according to claim 12, wherein the ultraviolet absorber comprises 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-butoxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine.

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