Acrylic resin film, polarizing plate, liquid crystal display panel, and acrylic resin composition

Abstract

Provided is an acrylic resin film that is excellent in heat resistance, transparency and ultraviolet shielding, and that can suppress blocking during film roll storage. [Solution] The acrylic resin film is composed primarily of an acrylic resin. The acrylic resin has a methyl methacrylate unit content of 98% by mass or more and a triad syndiotacticity of 56% to 65%. The acrylic resin film has a glass transition temperature of 120°C or more, an internal haze of 1.0% or less, and a transmittance of light with a wavelength of 380 nm of 10% or less. When one side of the acrylic resin film is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m 2 More than 5μC / m 2 The following is the result.

Description

[Technical Field]

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

[0002] In a liquid crystal display device, two polarizing plates are usually placed on both sides of a liquid crystal cell. A polarizing plate generally has a polarizer protective film attached to both sides of the polarizer with an adhesive to protect the polarizer. High transparency is required for the polarizer protective film, and optical films made of cellulose-based materials are often used.

[0003] It has been proposed to use optical films made of acrylic resins or norbornene resins as polarizer protective films for the purpose of improving heat resistance, etc. However, these optical films are prone to wrinkles and wrinkle marks due to contact between films when wound into a roll, and as a method for solving this problem, a method has been proposed in which fine particles such as silica particles are added to a norbornene resin film to ensure roll winding properties (slipperiness) (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 074513 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the method described in Patent Document 1 can solve the problem of wrinkles and wrinkle marks occurring during winding, the inventors' investigations have revealed that, as the quality standards of films improve due to the higher resolution and larger area of ​​liquid crystal display panels, defects occur due to tight winding of the film during storage in a film roll. The inventors also attempted to solve the above-mentioned problem by adding silica to an acrylic resin film using the method described in Patent Document 1, but found that the conventional method resulted in high haze and other problems that made it difficult to meet the requirements for an optical film. Meanwhile, there is a demand for improving the ultraviolet shielding properties of acrylic resin films.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an acrylic resin film that is excellent in transparency, heat resistance, and UV shielding properties and that can suppress blocking during film roll storage. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0008] That is, one aspect of the present invention relates to the following.

[0009] [1] An acrylic resin film containing an acrylic resin as a main component, wherein the acrylic resin has a methyl methacrylate unit content of 98% by mass or more, a triad syndiotacticity of 56% to 65%, a glass transition temperature of 120°C or more, an internal haze of 1.0% or less, and a transmittance of light with a wavelength of 380 nm of 10% or less, and wherein the amount of electrostatic charge generated per friction area when one side of the acrylic resin film is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH is 1 μC / m 2 More than 5μC / m 2 The following is an acrylic resin film.

[0010] [2] When one side of the acrylic resin film is rubbed against the other side at a friction speed of 500 mm / min under an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m 2 More than 3μC / m 2 The acrylic resin film according to [1] below.

[0011] [3] The acrylic resin film according to [1] or [2], wherein the acrylic resin has a weight average molecular weight of 80,000 or more and 200,000 or less and a polydispersity index of 1.6 or more and 2.5 or less.

[0012] [4] The acrylic resin film according to any one of [1] to [3], wherein the sum of the kurtosis Rku on both sides is 10 or more and 50 or less.

[0013] [5] The acrylic resin film according to any one of [1] to [4], wherein the coefficient of static friction between one surface and the other surface is 0.8 or less.

[0014] [6] The acrylic resin film according to any one of [1] to [5], which contains an antiblocking agent, and the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

[0015] [7] The acrylic resin film according to [6], wherein the ratio of the acrylic crosslinked particles to the acrylic resin is 0.05% by weight or more and 0.5% by weight or less.

[0016] [8] The acrylic resin film according to any one of [1] to [7], which contains one or more ultraviolet absorbers selected from the group consisting of triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers.

[0017] [9] The acrylic resin film according to any one of [1] to [8], which has a dimensional change rate of −2.0% or more and −0.1% or less when left standing in an atmosphere of 85° C. and 85% RH for 120 hours.

[0018]

[10] The acrylic resin film according to any one of [1] to [9], which is a polarizer protective film.

[0019]

[11] A polarizing plate comprising the acrylic resin film according to

[10] .

[0020]

[12] A liquid crystal display panel comprising the polarizing plate according to

[11] .

[0021]

[13] An acrylic resin composition containing an acrylic resin as a main component and containing an ultraviolet absorber and an antiblocking agent, wherein the acrylic resin has a methyl methacrylate unit content of 98% by mass or more, a triad syndiotacticity of 56% to 65%, and a glass transition temperature of 120°C or more. A 40 μm thick film formed from the acrylic resin composition has a transmittance of 10% or less for light with a wavelength of 380 nm, and the amount of electrostatic charge generated per friction area by rubbing one surface of the film against the other surface at a friction speed of 100 mm / min in an environment of 20°C and 20% RH is 1 μC / m 2 More than 5μC / m 2 An acrylic resin composition, which is:

[0022]

[14] The acrylic resin composition according to

[13] , wherein the ultraviolet absorber is at least one selected from the group consisting of triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers.

[0023]

[15] The acrylic resin composition according to

[13] or

[14] , wherein the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

[0024]

[16] The acrylic resin composition according to

[15] , wherein the ratio of the acrylic crosslinked particles to the acrylic resin is 0.05% by weight or more and 0.5% by weight or less. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide an acrylic resin film that is excellent in transparency, heat resistance and ultraviolet shielding properties and that can suppress blocking during storage of the film roll. DETAILED DESCRIPTION OF THE INVENTION

[0026] Although one embodiment of the present invention will be described below, the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. All academic literature and patent documents described in this specification are incorporated herein by reference. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A)" or "B or less (including B and less than B)."

[0027] (acrylic resin film) The acrylic resin film of this embodiment is an acrylic resin film containing an acrylic resin as a main component, and has a glass transition temperature of 120°C or higher, an internal haze of 1.0% or lower, and a transmittance of light with a wavelength of 380 nm of 10% or lower. When one surface of the acrylic resin film of this embodiment is rubbed against the other surface at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m 2 More than 5μC / m 2 The acrylic resin is characterized by the following: Here, the acrylic resin has a methyl methacrylate unit content of 98% by mass or more and a triad syndiotacticity of 56% to 65%. In this way, by using a predetermined acrylic resin as the main component, controlling the glass transition temperature, internal haze, and light transmittance to predetermined values, and further controlling the amount of electrostatic charge to predetermined values, an acrylic resin film can be obtained that is excellent in heat resistance, transparency, and UV shielding properties, and also has excellent anti-blocking properties during film roll storage.

[0028] The glass transition temperature of the acrylic resin film of this embodiment is 120°C or higher. It is preferably higher than 120°C, more preferably 121°C or higher, even more preferably 122°C or higher, and particularly preferably 123°C or higher. When the acrylic resin film has a glass transition temperature of 120°C or higher, the dimensional change rate of the stretched film when the film is placed in a high-temperature environment is reduced. In practical use, the acrylic resin film of this embodiment is often laminated with other films, and a small dimensional change rate can suppress the occurrence of distortion and warping caused by the difference in dimensional change rate between the film and the laminated film.

[0029] The glass transition temperature of the acrylic resin constituting the acrylic resin film is preferably 120°C or higher, more preferably over 120°C, even more preferably 121°C or higher, even more preferably 122°C or higher, and particularly preferably 123°C or higher.

[0030] Here, as the acrylic resin having a glass transition temperature of 120°C or higher, an acrylic resin having a methyl methacrylate unit content of 98% by mass or higher and a triad syndiotacticity of 56% or higher and 65% or lower can be used.

[0031] The acrylic resin film contains an acrylic resin as a main component, and the content of the acrylic resin in the acrylic resin film is preferably more than 50% by weight, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more.

[0032] The internal haze of the acrylic resin film of this embodiment is 1.0% or less. In particular, the internal haze is preferably 0.7% or less, more preferably 0.5% or less, and particularly preferably 0.3% or less. By having an internal haze of 1.0% or less, the quality when mounted on a liquid crystal panel is good.

[0033] In this specification, the internal haze is defined as the haze value measured using a haze meter (turbidity meter) on a glass cell for measuring liquid, with the obtained film placed in the cell and the surrounding area filled with pure water.

[0034] The haze of the acrylic resin film of the present embodiment is not particularly limited as long as the internal haze is within the above-mentioned range. However, from the viewpoint of transparency, the haze is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less.

[0035] The transmittance of the acrylic resin film of this embodiment to light with a wavelength of 380 nm is 10% or less, and preferably 9.5% or less.

[0036] When one side of the acrylic resin film of this embodiment is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m 2 More than 5μC / m 2 less than 1μC / m 2 More than 3μC / m 2 It is preferable that the amount of charge per friction area is 1 μC / m or less. 2 More than 5μC / m 2 Since the contact area between one side and the other side of the acrylic resin film of this embodiment is small, blocking during film roll storage can be effectively suppressed. In addition, the amount of electrostatic charge per friction area is 5 μC / m 2 If the thickness is equal to or less than this, adhesion of dust particles in the air to the acrylic resin film, which may occur due to charging of the acrylic resin film, is suppressed.

[0037] Here, "blocking" refers to a state in which films are stuck together, including a state in which they are partially melted at high temperatures and a state in which they are completely overlapped. When tight winding occurs, pressure is applied to the film, causing blocking (sticking) between the films. As a result, when the films are peeled apart, a strong force is required, causing damage to the film. Therefore, by setting the amount of charge per friction area within a predetermined range as in this embodiment, even if tight winding occurs, it is possible to prevent the films from sticking together in the film roll, and the films can be peeled apart with a weak force, thereby preventing damage to the film (film defects).

[0038] In the acrylic resin film of this embodiment, the sum of the kurtosis Rku values ​​on both sides is preferably 10 or more and 50 or less. By setting the sum of the kurtosis Rku values ​​on both sides of the acrylic resin film to 10 or more and 50 or less, blocking during film roll storage can be effectively suppressed. This can suppress defects that may occur in the film. Here, setting the sum of the kurtosis Rku values ​​on both sides of the acrylic resin film to 10 or more can suppress blocking due to tight winding during film roll storage, thereby suppressing film defects. This tendency is more pronounced when storing long film rolls (e.g., 8000 m). Therefore, acrylic resin films other than standard lengths (e.g., 4000 m) can also be wound, improving yield. Even in the case of standard-length acrylic resin films, the inner acrylic resin film is less likely to undergo plastic deformation during film roll storage, making the acrylic resin film easier to use. On the other hand, setting the sum of the kurtosis Rku values ​​on both sides of the acrylic resin film to 50 or less can suppress a decrease in the transparency of the acrylic resin film. The sum of the kurtosis Rku on both sides of the acrylic resin film is more preferably 15 or more and 30 or less. When the sum of the kurtosis on both sides is 10 or more, friction between the films is easily reduced. Furthermore, when the film is stacked in a roll, air trapped between the films is easily released, which is thought to suppress blocking associated with tight winding and reduce film defects. Furthermore, when the sum of the kurtosis on both sides is 50 or less, diffuse reflection of light on the film surface can be suppressed, preventing a decrease in the clarity of the panel display.

[0039] Here, kurtosis Rku can be calculated from a roughness curve in accordance with JIS B 0601. Kurtosis Rku represents the sharpness in the height direction, where Rku=3 means that the height distribution is normal, Rku>3 means that the surface has many sharp peaks and valleys, and Rku<3 means that the surface is flat.

[0040] The acrylic resin film of this embodiment preferably has a sum of the ten-point average roughness Rzjis of both surfaces of 0.05 μm or more and 1.0 μm or less. If the sum of the ten-point average roughness Rzjis of both surfaces of the film is 0.05 μm or more, friction between the films is easily reduced. Furthermore, when the films are stacked in a roll, air trapped between the films is easily released, suppressing blocking due to tight winding and presumably reducing film defects. Here, if the sum of the ten-point average roughness Rzjis of both surfaces of the acrylic resin film is 0.05 μm or more, blocking due to tight winding during film roll storage can be suppressed, thereby suppressing film defects. This tendency becomes more pronounced when long film rolls (e.g., 8000 m) are stored. As a result, only a fixed length (e.g., 4000 m) of acrylic resin film can be wound, resulting in a reduced yield. Furthermore, even with standard-length acrylic resin films, the inner acrylic resin film undergoes plastic deformation during film roll storage, rendering the plastically deformed acrylic resin film unusable. On the other hand, when the sum of the 10-point average roughness Rzjis of both surfaces of an acrylic resin film is 1.0 μm or less, the decrease in transparency of the acrylic resin film can be suppressed. Furthermore, when the sum of the 10-point average roughness Rzjis of both surfaces is 1.0 μm or less, diffuse reflection of light on the film surface can be suppressed, thereby suppressing a decrease in the clarity of the panel display. In particular, the sum of the 10-point average roughness Rzjis of both surfaces of an acrylic resin film is more preferably 0.05 μm or more and 0.6 μm or less, and even more preferably 0.05 μm or more and 0.5 μm or less.

[0041] The kurtosis Rku and ten-point average roughness Rzjis of a film can be measured using an optical surface roughness tester such as a laser microscope. The acrylic resin film of this embodiment has a surface roughness value that is smaller than the resolution of the laser microscope, so sufficient measurement accuracy cannot be achieved with a lens with a small numerical aperture. Therefore, in this specification, values ​​measured using a lens with a numerical aperture of 0.95 or more are used.

[0042] From the viewpoints of economy and environmental load, it is preferable to add an antiblocking agent to the acrylic resin to improve the surface roughness of the film. Among these, organic fine particles are preferred from the viewpoints of affinity with the acrylic resin and dispersibility, and crosslinked acrylic particles are most preferred because they allow for easy control of haze.

[0043] The static friction coefficient of the acrylic resin film, measured with one side of the film facing the other side, is preferably 0.8 or less, more preferably 0.7 or less, even more preferably 0.6 or less, and particularly preferably 0.5 or less. If the static friction coefficient is 0.8 or less, blocking between films during film roll storage can be effectively suppressed. There is no particular lower limit for the static friction coefficient, but from the viewpoint of winding slippage and meandering during production, a value of 0.2 or more is preferred.

[0044] The acrylic resin film preferably has a dimensional change rate (average value in the longitudinal direction (MD) and transverse direction (TD)) of -2.0% or more, more preferably -1.7% or more, and even more preferably -1.5% or more, when left standing for 120 hours in an atmosphere of 85°C and 85% RH. A dimensional change rate of -2.0% or more suppresses shrinkage over time during film roll storage, improving the stability of the wound appearance over time. In addition, warping and dimensional changes when the film is attached to a polarizer are alleviated, thereby suppressing a decrease in contrast and peripheral unevenness in a liquid crystal display device. The dimensional change rate may be, for example, -0.1% or less. A dimensional change rate of -0.1% or less allows the acrylic resin film to easily follow the shrinkage of the polarizer itself when attached to the polarizer. The dimensional change rate when left standing in an atmosphere of 85°C and 85% RH for 120 hours can be measured using a three-dimensional measuring device by leaving the acrylic resin film standing in an environmental tester set to 85°C and 85% RH for 120 hours and measuring the dimensional change before and after.

[0045] In this specification and claims, the dimensional change rate refers to the rate of change in the spacing between the intersections of a cross drawn with an oil-based pen at a distance of 10 mm inward from each of the four sides of an 80 mm x 80 mm film, with the intersections spaced 20 mm apart, before and after leaving the film to stand for 120 hours in an atmosphere of 85°C and 85% RH. Here, the rate of change in the spacing between the intersections of the cross means the rate of change in the spacing between the intersections of the cross after leaving the film to stand, based on the spacing between the intersections of the cross before leaving the film to stand, and is calculated using the formula [(Spacing between cross points after settling) - (Spacing between cross points before settling)] x 100 / (Spacing between cross points before settling) It is calculated as follows.

[0046] The linear expansion coefficient of the acrylic resin film at 40 to 60°C is preferably 80 ppm or less, and more preferably 72 ppm or less. If it is 80 ppm or less, shrinkage and expansion of the film due to temperature changes during storage and transportation of the film roll are suppressed, and tight winding is less likely to occur. On the other hand, the lower limit is preferably 40 ppm or more. If the linear expansion of the film is 40 ppm or more, when laminated with a polarizer, the difference in linear expansion from other components is small, and warping is less likely to occur.

[0047] (Anti-blocking agent) The acrylic resin film is preferably formed from an acrylic resin composition in which an antiblocking agent is added to an acrylic resin. The antiblocking agent is preferably an acrylic crosslinked particle from the viewpoints of compatibility with the acrylic resin, dispersibility, and transparency. Any particle shape can be selected, but spherical particles are preferred because they are more likely to exhibit antiblocking properties.

[0048] The refractive index of the antiblocking agent is preferably 98% to 102% and more preferably 99% to 101% when the refractive index of the acrylic resin is taken as 100%. The refractive index of the antiblocking agent is preferably 1.47 to 1.55, more preferably 1.47 to 1.53, and even more preferably 1.48 to 1.52. By using an antiblocking agent with a refractive index within this range, a highly transparent acrylic resin film can be obtained. Among these, acrylic crosslinked particles are preferred because they satisfy the above refractive index.

[0049] The polymerizable monomer forming the acrylic crosslinked particles can be selected from any (meth)acrylic acid ester and other monomers copolymerizable with (meth)acrylic acid ester, but preferably contains methyl methacrylate in terms of compatibility with the acrylic resin and refractive index. The content of structural units derived from methyl methacrylate in the acrylic crosslinked particles is preferably 80% by weight or more and 99% by weight or less, more preferably 83% by weight or more and 96% by weight or less. Note that when the content of methyl methacrylate units in the acrylic resin is high, the content of methyl methacrylate units in the acrylic crosslinked particles is preferably high.

[0050] The acrylic crosslinked particles further contain structural units derived from a polyfunctional monomer containing two or more polymerizable groups in the molecule as a polymerizable monomer. The content of the polyfunctional monomer in the polymerizable monomer can be set arbitrarily, but is preferably 0.5% by weight or more and 30% by weight or less. If the content is less than 0.5% by weight, the heat resistance and dispersibility of the acrylic crosslinked particles are poor. If the content is greater than 30% by weight, particle coalescence and the formation of irregularly shaped particles may occur during the production of the acrylic crosslinked particles.

[0051] The average particle size of the acrylic crosslinked particles is preferably 0.1 μm or more and 2.5 μm or less, and more preferably 0.1 μm or more and 2.0 μm or less. When the average particle size of the acrylic crosslinked particles is 0.1 μm or more, a large amount is not required to exhibit antiblocking properties, resulting in excellent mechanical properties and economic efficiency. On the other hand, when the average particle size of the acrylic crosslinked particles is 2.5 μm or less, the possibility of clogging the polymer filter is reduced. Furthermore, from the viewpoint of the long-term running properties of the polymer filter, it is preferable to use acrylic crosslinked particles with a narrow particle size distribution and a low content of coarse particles.

[0052] The ratio of acrylic crosslinked particles to the acrylic resin is preferably 0.05% by weight or more and 0.5% by weight or less, more preferably 0.07% by weight or more and 0.5% by weight or less, and even more preferably 0.1% by weight or more and 0.2% by weight or less. A ratio of acrylic crosslinked particles to the acrylic resin of 0.05% by weight or more enhances the blocking suppression effect, while a ratio of 0.5% by weight or less can suppress deterioration in economic efficiency and increase in haze. Furthermore, multiple types of acrylic crosslinked particles with different particle size distributions may be mixed to control slip properties and surface properties. In this case, the amount of acrylic crosslinked particles added is the sum of the amounts of the multiple types of acrylic crosslinked particles added.

[0053] (ultraviolet absorber) The acrylic resin film is preferably formed from an acrylic resin composition in which an ultraviolet absorber is added to an acrylic resin. The ultraviolet absorber is not particularly limited, but examples thereof include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, anilide oxalate-based ultraviolet absorbers, malonic acid ester-based ultraviolet absorbers, and formamidine-based ultraviolet absorbers, and two or more of these may be used in combination. Among these, triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers are preferred from the viewpoints of stability, ultraviolet absorption ability, heat resistance, and solubility. Examples of triazine-based ultraviolet absorbers include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine, 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine, 2,4,6-tris(4-hexyloxy-2-hydroxy-3-methylphenyl)-1,3,5-triazine, and 2,4-bis[4-(2-ethylhexyloxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazine. Examples of benzotriazole-based ultraviolet absorbers include 2,2'-mesitylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol].

[0054] The molecular weight of the ultraviolet absorber is preferably 500 or more, more preferably 550 or more, and even more preferably 600 or more. When the molecular weight of the ultraviolet absorber is 500 or more, bleeding out of the ultraviolet absorber is suppressed during film formation of the acrylic resin film of this embodiment. The molecular weight of the ultraviolet absorber is, for example, 1000 or less.

[0055] (Easy adhesion layer) The acrylic resin film of this embodiment may be used with an easy-adhesion layer provided on one or both sides thereof. For example, when used as a polarizer protective film, the provision of an easy-adhesion layer can reinforce the adhesive between the polarizer protective film and the polarizer when the film is attached to the polarizer via an adhesive. Furthermore, a stretched film having an easy-adhesion layer can be obtained by providing an easy-adhesion layer on an unstretched film and then stretching the film.

[0056] The easy-adhesion layer used in this embodiment can be formed using known techniques described in, for example, JP 2009-193061 A and JP 2010-55062 A. That is, for example, the easy-adhesion layer can be formed from an easy-adhesion composition containing a urethane resin having a carboxyl group and a crosslinking agent. By using a urethane resin, an easy-adhesion layer having excellent adhesion between the polarizer protective film and the polarizer can be obtained. The easy-adhesion composition is preferably aqueous from the viewpoints of workability and environmental protection.

[0057] (acrylic resin) As described above, the acrylic resin film has a glass transition temperature of 120° C. or higher, and an acrylic resin having a glass transition temperature of 120° C. or higher can be suitably used as the acrylic resin film. As described above, an acrylic resin having a methyl methacrylate unit content of 98% by mass or higher and a triad syndiotacticity of 56% or higher and 65% or lower can be used as the acrylic resin having a glass transition temperature of 120° C. or higher.

[0058] When the syndiotacticity of the acrylic resin expressed as a triad is 56% or more, the glass transition temperature of the acrylic resin increases, and the heat resistance of the acrylic resin tends to improve. The syndiotacticity of the acrylic resin expressed as a triad is preferably 57% or more. Furthermore, from the viewpoints of the molding temperature of the acrylic resin, the toughness of the molded body, and secondary processability, the syndiotacticity of the acrylic resin expressed as a triad is 65% or less, and preferably 63% or less.

[0059] The syndiotacticity of acrylic resins, expressed as a triad, is the proportion of three structural unit sequences (triads) that are rr. In addition, in two structural unit sequences (diads), those with the same configuration are called meso (m) and those with the opposite configuration are called racemo (r).

[0060] Methods for synthesizing acrylic resins having a syndiotacticity of 56% or more and 65% or less, expressed as triads, are not particularly limited, but include, for example, anionic polymerization and radical polymerization. Among these, radical polymerization is preferred (see, for example, International Publication Nos. 2023 / 238885 and 2023 / 238886). Radical polymerization does not use organometallic compounds as polymerization initiators or organic solvents as media, as used in anionic polymerization, making it less likely for impurities to remain, making it preferable from an environmental perspective. The glass transition temperature and syndiotacticity of the acrylic resin can be controlled by the polymerization temperature of the acrylic resin. For example, lowering the polymerization temperature of the acrylic resin increases the syndiotacticity of the acrylic resin, thereby increasing the glass transition temperature of the acrylic resin. The glass transition temperature of the acrylic resin can also be controlled by the molecular weight of the acrylic resin.

[0061] The content of methyl methacrylate units in the acrylic resin is 98% by weight or more, preferably 99% by weight or more, and more preferably 100% by weight.

[0062] The monomer other than methyl methacrylate that constitutes the acrylic resin is not particularly limited, but examples thereof include alkyl acrylate esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylate esters such as phenyl acrylate; cycloalkyl acrylate esters such as cyclohexyl acrylate and norbornenyl acrylate; alkyl methacrylate esters other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate; aryl methacrylate esters such as phenyl methacrylate; cycloalkyl methacrylate esters such as cyclohexyl methacrylate and norbornenyl methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; and methacrylonitrile.

[0063] (Other properties of acrylic resins) Other properties of the acrylic resin will be described below.

[0064] The weight-average molecular weight of the acrylic resin is preferably 80,000 or more and 200,000 or less, and more preferably 90,000 or more and 150,000 or less. When the weight-average molecular weight of the acrylic resin is 80,000 or more, the mechanical properties of the molded product of the acrylic resin tend to be improved, and when it is 200,000 or less, the moldability of the acrylic resin tends to be improved.

[0065] The weight-average molecular weight of the acrylic resin may be 400,000 or more. When the weight-average molecular weight of the acrylic resin is 400,000 or more, the mechanical properties of the acrylic resin molded article tend to be further improved, and for example, an acrylic resin film with excellent flex resistance can be obtained. In this case, 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. Furthermore, from the viewpoint of moldability when molding the acrylic resin by a solution casting method, the weight-average molecular weight of the acrylic resin is preferably 2.5 million or less, more preferably 2 million or less, even more preferably 1.5 million or less, and particularly preferably 1.2 million or less.

[0066] The polydispersity of the acrylic resin (ratio of weight average molecular weight to number average molecular weight) is preferably 1.6 to 2.5, more preferably 1.7 to 2.2. When the polydispersity of the acrylic resin is 1.6 or more, the flowability of the acrylic resin tends to improve and molding becomes easier, while when it is 2.5 or less, the mechanical properties such as impact resistance, toughness, and flex resistance of the molded acrylic resin tend to improve.

[0067] The number-average molecular weight and weight-average molecular weight of the acrylic resin are values ​​measured by gel permeation chromatography (GPC) in terms of standard polystyrene. The number-average molecular weight and weight-average molecular weight of the acrylic resin can be controlled by the type and amount of polymerization initiator and chain transfer agent used in synthesizing the acrylic resin.

[0068] (Acrylic resin composition) The acrylic resin composition of this embodiment is primarily composed of an acrylic resin and contains an ultraviolet absorber and an antiblocking agent, and is used to produce the acrylic resin film of this embodiment. The acrylic resin has a methyl methacrylate unit content of 98% by mass or more, a triad syndiotacticity of 56% to 65%, and a glass transition temperature of 120°C or higher. Furthermore, a 40 μm-thick film molded from the acrylic resin composition of this embodiment has a transmittance of 10% or less for light with a wavelength of 380 nm, and generates an electrostatic charge per friction area of ​​1 μC / m when one side of the film is rubbed against the other side at a friction speed of 100 mm / min in an environment of 20°C and 20% RH. 2 More than 5μC / m 2 The following is the result.

[0069] The acrylic resin composition of the present embodiment may 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 combined.

[0070] The antioxidant is not particularly limited, but examples thereof include phosphorus-based antioxidants, hindered phenol-based antioxidants, and thioether-based antioxidants, and two or more of these may be used in combination. Among these, hindered phenol-based antioxidants are preferred from the viewpoint of suppressing deterioration of optical properties due to coloration. Examples of hindered phenol-based antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0071] The hindered phenol-based antioxidant preferably has an acryloyl group and / or a methacryloyl group. During extrusion molding of the acrylic resin composition, the terminal of the acrylic resin bonds with the acryloyl group and / or methacryloyl group of the hindered phenol-based antioxidant, thereby suppressing bleeding out of the hindered phenol-based antioxidant during production of the acrylic resin film of this embodiment.

[0072] Examples of hindered phenol antioxidants having an acryloyl group and / or a methacryloyl group include 2-tert-butyl-6-(3'-tert-butyl-5'-methyl-hydroxybenzyl)-4-methylphenyl acrylate and 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate. Among these, 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate is preferred.

[0073] The molecular weight of the antioxidant is preferably 500 or more, more preferably 550 or more, and even more preferably 600 or more. When the molecular weight of the antioxidant is 500 or more, bleeding out of the antioxidant is suppressed during film formation of the acrylic resin film of this embodiment. The molecular weight of the antioxidant is, for example, 1500 or less.

[0074] When the retardation adjuster is to impart a negative retardation, it may be, for example, a compound having a styrene skeleton, such as an acrylonitrile-styrene copolymer.

[0075] The method for mixing the acrylic resin and the antiblocking agent is not particularly limited, and any conventionally known method can be used, such as feeding them into an extruder using a gravimetric feeder and melt-kneading them, or mixing them in the form of a solution in a solvent that has excellent compatibility with both the acrylic resin and the antiblocking agent.

[0076] When mixing is performed using an extruder, the extruder used is not particularly limited, and various extruders can be used. Specifically, a single-screw extruder, twin-screw extruder, or multi-screw extruder can be used. Among these, a twin-screw extruder is preferably used. A twin-screw extruder allows for greater flexibility in the conditions for uniformly mixing the acrylic resin and the antiblocking agent. Alternatively, the acrylic resin and the antiblocking agent may be introduced and mixed from the upstream side of the extruder using a raw material introduction hopper or the like, or the antiblocking agent alone may be introduced and mixed midway through the extruder using a side feeder, gravimetric feeder, or the like. Alternatively, the antiblocking agent may be prepared in advance as a masterbatch in a separate extruder and used.

[0077] A filter can be installed at the end of the extruder to reduce foreign matter in the acrylic resin. A gear pump is preferably installed before the filter to increase the pressure of the (A) acrylic resin / acrylic resin composition. The preferred type of filter is a stainless steel leaf disc filter capable of removing foreign matter from the molten polymer, and the preferred filter element is a fiber type, powder type, or a combination of these.

[0078] (Method of manufacturing acrylic resin film) Although one embodiment of the method for producing the acrylic resin film of the present embodiment will be described, the present invention is not limited thereto. In other words, any conventionally known method can be used as long as it can produce a film by molding the acrylic resin composition of the present embodiment.

[0079] Specifically, examples of the molding method include injection molding, melt extrusion molding, inflation molding, blow molding, and compression molding. The film according to the present embodiment can also be produced by a solution casting method or spin coating method in which the acrylic resin composition according to the present embodiment is dissolved in a solvent capable of dissolving the composition, and then molding the resulting composition.

[0080] Among these, it is preferable to use a melt extrusion method that does not use a solvent, which can reduce production costs and the burden on the global environment and working environment caused by solvents.

[0081] When the acrylic resin composition of this embodiment is formed into a film by melt extrusion, the acrylic resin composition of this embodiment is first pre-dried and then fed into an extruder, where the acrylic resin composition is heated and melted. The acrylic resin composition is then fed into a die such as a T-die through a gear pump or filter. The acrylic resin composition fed into the T-die is then extruded as a sheet-like molten resin and cooled and solidified using a cooling roll or the like to obtain an unstretched film (also referred to as a raw film). To improve the surface properties (smoothness) of the film, the film can be sandwiched between a metal roll and a flexible roll equipped with a metal elastic outer cylinder.

[0082] When the acrylic resin composition of this embodiment is formed into an unstretched film by solution casting, the acrylic resin composition of this embodiment is dissolved in an organic solvent, the solution is cast onto a support, and the resulting unstretched film is then dried by heating. Solvents that can be used in the solution casting method can be selected from known solvents. Halogenated hydrocarbon solvents such as methylene chloride and trichloroethane are preferred because they readily dissolve the acrylic resin composition of this embodiment and have low boiling points. Highly polar non-halogenated solvents such as dimethylformamide and dimethylacetamide can also be used. Aromatic solvents such as toluene, xylene, and anisole, cyclic ether solvents such as dioxane, dioxolane, tetrahydrofuran, and pyran, and ketone solvents such as methyl ethyl ketone can also be used. These solvents may be used alone or in combination. The amount of solvent used can be any amount as long as it dissolves the thermoplastic resin to an extent that sufficient casting can be performed. In this specification, "dissolved" means that the acrylic resin composition of this embodiment is present in a solvent in a homogeneous state to the extent that casting can be performed sufficiently. It is not necessarily required that the acrylic resin composition of this embodiment be completely dissolved in the solvent. The concentration of the acrylic resin composition of this embodiment in the solution is preferably 1 wt % to 90 wt %, more preferably 5 wt % to 70 wt %, and even more preferably 10 wt % to 50 wt %. A preferred support may be an endless belt made of stainless steel. Alternatively, a film such as a polyimide film or a polyethylene terephthalate film may also be used.

[0083] The acrylic resin film of the present embodiment is obtained by stretching an unstretched film (also referred to as a raw film). By stretching the unstretched film, it is possible to produce a stretched film of a desired thickness, and further, it is possible to improve the mechanical properties of the stretched film.

[0084] As the stretching method, a conventionally known method can be used. For example, an unstretched raw film formed by melt extrusion can be stretched uniaxially or biaxially to produce a film of a predetermined thickness. Biaxial stretching is preferred to impart excellent mechanical properties to the stretched film in both the longitudinal direction (MD) and the width direction (TD). The biaxial stretching method may be simultaneous biaxial stretching or sequential biaxial stretching.

[0085] The stretching ratio (in both the MD and TD directions of the film in the case of biaxial stretching) is preferably 1.5 to 3.0 times, and more preferably 1.8 to 2.8 times. A stretching ratio within this range can sufficiently improve the mechanical properties of the film during stretching. Furthermore, the degree of orientation does not increase too much, and dimensional change after standing for 120 hours in an atmosphere of 85°C and 85% RH can be reduced. Furthermore, there is little possibility of a decrease in peel strength when the film is attached to a polarizer. The stretching speed is preferably 1.1 times / min or more, and more preferably 5 times / min or more. It is also preferably 100 times / min or less, and more preferably 50 times / min or less. In the case of sequential biaxial stretching, the stretching speeds in the first stage and the second stage may be the same or different. In sequential biaxial stretching, the first stage stretching is usually in the longitudinal direction (MD), and the second stage stretching is in the width direction (TD).

[0086] The stretching temperature is not particularly limited, but is preferably Tg+7°C to Tg+50°C, and more preferably Tg+10°C to Tg+40°C. A stretching temperature of Tg+7°C or higher can reduce the risk of breakage during the stretching process. On the other hand, a stretching temperature of Tg+50°C or lower can achieve sufficient molecular orientation and prevent a decrease in the mechanical strength of the film. If the stretching temperature is higher within the above range, molecular orientation is relaxed, resulting in a decrease in mechanical strength, while dimensional change in an 85°C, 85% RH atmosphere is reduced. Furthermore, in the case of a film containing an antiblocking agent, stretching at a low temperature tends to cause particles to float to the surface, resulting in surface roughness, slipperiness, and external haze. Those skilled in the art can arbitrarily set the stretching conditions while taking the above balance into consideration.

[0087] The acrylic resin film of this embodiment is wound into a roll by a known method. The film of this embodiment is less likely to have defects due to inter-film blocking, even when the film width is wide or the wound length is long. Furthermore, it is more effective to combine it with knurling of the edges, which has traditionally been used to prevent blocking.

[0088] (Application) When the acrylic resin film of the present embodiment is used as a polarizer protective film, it is bonded to a polarizer to form a polarizing plate. The polarizer is not particularly limited, and any conventionally known polarizer can be used. For example, a polarizer obtained by incorporating iodine into stretched polyvinyl alcohol can be used.

[0089] This polarizing plate can be further laminated with various films and suitably used in the field of displays such as liquid crystal displays and organic EL displays, although its applications are not limited to these. [Example]

[0090] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0091] (conversion rate) The weight ratio of the solid content of the acrylic resin after drying for 30 minutes in an oven heated to 150°C to the weight of the charged monomers by the gravimetric method, that is, the formula (Solid weight of acrylic resin) x 100 / (weight of charged monomer) The conversion rate was calculated from the

[0092] (Syndiotacticity in triplicate display) Using a nuclear magnetic resonance spectrometer (Bruker, AVANCEIII 400MHz), the acrylic resin was measured in a deuterated chloroform solution at 22°C with 16 cycles of accumulation. 1 H-NMR spectrum was measured. Next, 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 when tetramethylsilane (TMS) was set to 0 ppm were measured, and then the area was calculated using the formula (X / Y)×100 The syndiotacticity (rr) of the triad was calculated by the following formula.

[0093] (weight average molecular weight, number average molecular weight and polydispersity index) The weight-average molecular weight (Mw), number-average molecular weight (Mn), and polydispersity (Mw / Mn) of the acrylic resin were calculated using gel permeation chromatography (GPC) under the following conditions: Measuring equipment: HLC-8420GPC (Tosoh) Detector: RI detector Eluent: tetrahydrofuran Guard column: TSKgel guard column SuperH-L (manufactured by Tosoh) Analytical columns: TSKgel SuperH5000, SuperH4000, SuperH3000, SuperH2000 (Tosoh) (in series) Eluent flow rate: 0.6 mL / min Measurement temperature: 40℃ Standard material: Standard polystyrene (manufactured by Tosoh)

[0094] (glass transition temperature) The glass transition temperature (Tg) of the acrylic resin or raw film (10 mg) was measured using a differential scanning calorimeter (Hitachi High-Tech Science, DSC7000X) under a nitrogen atmosphere at a heating rate of 20°C / min, and the Tg was determined by the midpoint method.

[0095] (dimensional change rate) Using a cutter, an 80 mm x 80 mm test piece was cut from the acrylic resin film. Crosses were drawn with an oil-based pen at points 10 mm inward from the four sides of the test piece, with the intersections spaced 20 mm apart. The spacing between the intersections of the crosses was measured using an image dimension measuring instrument IM-6225 / 6700 (Keyence Corporation). The acrylic resin film was then left to stand for 120 hours in an electronic thermo-hygrostat THR050FB (Advantec Corporation) set at 85°C and 85% RH, after which the spacing between the intersections of the crosses was measured again. The dimensional change rates in the stretching direction and the direction perpendicular to the stretching direction (width direction) were calculated using the following formula from the spacing between the intersections of the crosses before and after standing. The dimensional change rate of the acrylic resin film was calculated twice, and the average value was calculated. [(Spacing between cross points after settling) - (Spacing between cross points before settling)] x 100 / (Spacing between cross points before settling)

[0096] (Amount of charge per friction area) The charge per friction area of ​​an acrylic resin film was measured using the JIS L 1094 C triboelectric charge measurement method at 20°C and 20% RH. Specifically, both sides of two 12-14 cm square, 40 μm thick acrylic resin films (test pieces) were neutralized using an ionizer (STABLO EX, Shimadzu Corporation). Two neutralized test pieces were stacked, and a 7 cm x 7 cm x 2.4 cm (75 g) wooden block was placed in the center of the stack. The upper test piece was then pulled at a friction speed of 500 mm / min, causing friction between the test pieces. The pulled test piece was placed in a Faraday cage (Nihon Static), and the voltage was measured using a precision static electricity measuring device (SV-73A, Nihon Static). The voltage of the lower test piece was then measured in the same way. The amount of charge per friction area of ​​the test piece σ (μC / m 2 The same measurement was carried out five times, and the average value of the obtained measurements was taken as the amount of electrified charge per friction area of ​​the acrylic resin film. σ = CV / A (1) C: Capacitor capacitance = 275 (μF) V: voltage of the electrometer (V) A: Friction area of ​​the test piece (m 2 )

[0097] (Kurtosis Rku and 10-point average roughness Rzjis) The kurtosis Rku and 10-point average roughness Rzjis of acrylic resin films were measured using a VK-X3000 laser microscope equipped with a white light interferometer (Keyence Corporation). Specifically, a confocal image of a 208 μm × 277 μm area of ​​the film was captured using a 50x magnification, 0.80 numerical aperture objective lens. Three equally spaced evaluation lines were then drawn in each of the MD and TD directions to create a roughness curve. The kurtosis Rku and 10-point average roughness Rzjis were calculated from the resulting roughness curve using analysis software, and the average values ​​at each measurement point were calculated. Measurements were performed three times at different measurement points, and the average values ​​were used as the kurtosis Rku and 10-point average roughness Rzjis. However, if localized defects such as scratches were clearly visible in the image, they were not included in the measurement and the measurement was repeated, avoiding the abnormal area.

[0098] (static friction coefficient) The static friction coefficient of acrylic resin film was measured in accordance with JIS K7125:1999 using Imada's ZTS-5N digital force gauge and COF-2N-V friction coefficient measurement jig. Specifically, side A of the film was fixed to a smooth stainless steel plate, and side B of the film was attached with double-sided tape to a 60 x 60 mm, 200 g sled. The load applied when the sled was moved at a speed of 100 mm / min via a pulley was read with a load cell, and the static friction coefficient between sides A and B was calculated. The measurement was performed six times with different pieces of film, and the average value was calculated.

[0099] (internal haze) The internal haze of the acrylic resin film was measured using a haze meter HZ-V3 (manufactured by Suga Test Instruments) in accordance with JIS 7136:2000. The acrylic resin film was sandwiched between glycerin and glass, in that order, and the internal haze of the acrylic resin film was measured twice, and the average value was calculated. After measuring the internal haze of the acrylic resin film, it was converted to a value equivalent to a film thickness of 40 μm.

[0100] (Blocking test) Ten 100mm x 100mm test pieces (acrylic resin film) were stacked on top of each other, and then a pressure of 1kg was applied from above and left at 60°C for 2 hours. After that, the test pieces were left to cool at 23°C for 1 hour, and the condition of the acrylic resin film was visually inspected and the acrylic resin film was peeled off by hand and evaluated according to the following criteria. 1: The films are stuck together, leaving marks when peeled off. 2: The films are stuck together, but no marks are left when peeled off. 3: The films are not stuck together.

[0101] (Transmittance of light with a wavelength of 380 nm) The ultraviolet-visible absorption spectrum of the acrylic resin film was measured using an ultraviolet-visible spectrophotometer V-560 (manufactured by JASCO Corporation), and the transmittance of light with a wavelength of 380 nm was determined.

[0102] <Production of acrylic resin> (Production example of acrylic resin 1) A 4L glass reactor equipped with an H-shaped impeller was charged with 150 parts by weight of deionized water, 0.20 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, 100 parts by weight of methyl methacrylate (MMA), 0.289 parts by weight of n-octyl mercaptan (as a chain transfer agent), and 0.065 parts by weight of dimethyl 2,2'-azobis(isobutyrate) (Fujifilm Wako Pure Chemical Industries, V-601) (as a polymerization initiator) were added to the reactor while stirring at 250 rpm. The liquid temperature in the reactor was then raised to 70°C to initiate polymerization. Two hours after the start of polymerization, 0.10 parts by weight of tribasic calcium phosphate was added to the reactor. An exothermic peak associated with the gel effect was observed 4 hours and 20 minutes after the start of polymerization. Next, heating was started 7 hours after the start of polymerization, and the liquid temperature in the reactor was raised to 95°C. The conversion rate 7 hours after the start of polymerization was 93%. Next, 2 hours after the liquid temperature in the reactor reached 95°C, the liquid temperature in the reactor was cooled to room temperature to terminate the polymerization, and an acrylic resin dispersion was obtained. The conversion rate at the end of polymerization was 99%.

[0103] The acrylic resin dispersion was acid-washed using 0.1 times the weight of the charged monomer with 1N hydrochloric acid, followed by rinsing with water to remove the dispersant. The washed acrylic resin dispersion was then dehydrated and dried to obtain beads of acrylic resin 1. Acrylic resin 1 had a Tg of 120°C, an rr of 57%, an Mw of 83,000, an Mw / Mn of 1.63, and an MMA unit content of 100% by weight.

[0104] Example 1 A mixture containing 100 parts by weight of acrylic resin 1, 0.7 parts by weight of ultraviolet absorber LA-F70 (manufactured by ADEKA) (hereinafter referred to as UVA1), and 0.1 parts by weight of acrylic crosslinked particles with an average particle size of 0.8 μm (manufactured by Soken Chemical & Engineering Co., Ltd., MX80H3wT, refractive index 1.49) (hereinafter referred to as AB agent 1) as an antiblocking agent (AB agent) was kneaded in a 15 mm diameter, intermeshing co-rotating twin-screw extruder (L / D = 45). The resin extruded as strands from the die at the extruder outlet was cooled in a water bath and then pelletized in a pelletizer to obtain an acrylic resin composition. UVA-1 is 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0105] The resulting acrylic resin composition was dried at 90°C for 4 hours and then formed into a film using a 15mm diameter, co-rotating, intermeshing twin-screw extruder (L / D = 45) equipped with a T-die at the extruder outlet. The sheet-like molten resin extruded from the T-die at the extruder outlet was cooled with a cooling roll to obtain a raw film having a width of 150mm and a thickness of 160µm. The Tg of the raw film was 120°C. In this case, the surface in contact with the casting roll was defined as side B, and the other side was defined as side A.

[0106] The obtained raw film was simultaneously biaxially stretched at a stretch ratio of 2 (longitudinal and transverse directions) and a stretching temperature of 135°C using a biaxial stretching device (IMC-1905) manufactured by Imoto Manufacturing Co., Ltd., to produce a stretched film (acrylic resin film).

[0107] Example 2 An acrylic resin film was produced in the same manner as in Example 1, except that acrylic crosslinked particles having an average particle size of 1.2 μm (J-3PY manufactured by Negami Chemical Industries, Ltd., refractive index 1.49) (hereinafter referred to as AB agent 2) were used instead of AB agent 1. The raw film had a Tg of 120° C.

[0108] Example 3 An acrylic resin film was produced in the same manner as in Example 1, except that acrylic crosslinked particles having an average particle size of 2.2 μm (J-4PY manufactured by Negami Chemical Industries, Ltd., refractive index 1.50) (hereinafter referred to as AB agent 3) were used instead of AB agent 1. The raw film had a Tg of 120° C.

[0109] Example 4 An acrylic resin film was produced in the same manner as in Example 1, except that 0.6 parts by weight of the ultraviolet absorber 2,4-bis(4-butoxy-2-hydroxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (hereinafter referred to as UVA2) was used instead of 0.7 parts by weight of UVA1. The raw film had a Tg of 120°C.

[0110] Example 5 An acrylic resin film was produced in the same manner as in Example 1, except that a mixture containing 0.3 parts by weight of the antioxidant Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) (hereinafter referred to as AO1) and 0.2 parts by weight of the antioxidant AO-60 (manufactured by ADEKA Co., Ltd.) (hereinafter referred to as AO2) was further added. AO1 and AO-2 were 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], respectively. The raw film had a Tg of 120°C.

[0111] (Comparative Example 1) An acrylic resin film was obtained in the same manner as in Example 1, except that UVA1 and AB agent 1 were not added and the stretching temperature was changed to 145°C. The raw film had a Tg of 120°C.

[0112] (Comparative Example 2) Except for not adding UVA1, an acrylic resin film was obtained in the same manner as in Example 5. The raw film had a Tg of 120°C.

[0113] (Comparative Example 3) An acrylic resin film was produced in the same manner as in Example 1, except that Parapet HR-S (manufactured by Kuraray) (hereinafter referred to as acrylic resin 2) was used instead of acrylic resin 1. Acrylic resin 2 had a Tg of 116°C, an rr of 51%, an Mw of 91,000, an Mw / Mn of 1.68, and an MMA unit content of 98% by weight or more. The raw film also had a Tg of 116°C.

[0114] Table 1 shows the properties of acrylic resins 1 and 2.

[0115] [Table 1]

[0116] Table 2 shows the properties of AB agents 1 to 3.

[0117] [Table 2]

[0118] Table 3 shows the evaluation results of Tg, dimensional change rate, electrification voltage, Rku, static friction coefficient, haze, internal haze, transmittance of light with a wavelength of 380 nm, and blocking test.

[0119] [Table 3]

[0120] From Table 3, it can be seen that the acrylic resin films of Examples 1 to 5 are excellent in transparency, heat resistance, and UV shielding properties, and can suppress blocking during film roll storage. In contrast, the acrylic resin film of Comparative Example 1 has a transmittance of 91.49% at a wavelength of 380 nm, and a σ of 0.9 μC / m 2Therefore, it has poor UV-shielding properties and cannot suppress blocking during film roll storage. The acrylic resin film of Comparative Example 2 has a transmittance of 91.12% at a wavelength of 380 nm, so it also has poor UV-shielding properties. The acrylic resin film of Comparative Example 3 contains acrylic resin 2 with an rr of 51% and a Tg of 116.3°C, so it has a dimensional change rate of -2.29%, and therefore poor heat resistance.

Claims

1. An acrylic resin film containing an acrylic resin as a main component, The acrylic resin has a methyl methacrylate unit content of 98% by mass or more and a triad syndiotacticity of 56% or more and 65% or less, The glass transition temperature is 120°C or higher, The internal haze is 1.0% or less, The transmittance of light with a wavelength of 380 nm is 10% or less, When one side of the acrylic resin film is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m ２ 5 μC / m or more ２ The following is an acrylic resin film.

2. When one side of the acrylic resin film is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m ２ 3μC / m or more ２ The acrylic resin film according to claim 1, wherein:

3. The acrylic resin film according to claim 1 or 2, wherein the acrylic resin has a weight average molecular weight of 80,000 or more and 200,000 or less and a polydispersity of 1.6 or more and 2.5 or less.

4. The acrylic resin film according to claim 1 or 2, wherein the sum of the kurtosis Rku on both surfaces is 10 or more and 50 or less.

5. 3. The acrylic resin film according to claim 1, wherein the coefficient of static friction between one surface and the other surface is 0.8 or less.

6. Contains an anti-blocking agent, The acrylic resin film according to claim 1 or 2, wherein the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

7. The acrylic resin film according to claim 6 , wherein the ratio of the acrylic crosslinked particles to the acrylic resin is 0.05% by weight or more and 0.5% by weight or less.

8. 3. The acrylic resin film according to claim 1, further comprising one or more ultraviolet absorbers selected from the group consisting of triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers.

9. 3. The acrylic resin film according to claim 1, wherein the dimensional change rate when left standing in an atmosphere of 85° C. and 85% RH for 120 hours is −2.0% or more and −0.1% or less.

10. The acrylic resin film according to claim 1 or 2, which is a polarizer protective film.

11. A polarizing plate comprising the acrylic resin film according to claim 10.

12. A liquid crystal display panel comprising the polarizing plate according to claim 11.

13. An acrylic resin composition containing an acrylic resin as a main component, an ultraviolet absorber, and an antiblocking agent, The acrylic resin has a methyl methacrylate unit content of 98% by mass or more, a triad syndiotacticity of 56% or more and 65% or less, and a glass transition temperature of 120°C or more, A 40 μm thick film formed from the acrylic resin composition has a transmittance of 10% or less for light with a wavelength of 380 nm, and when one side of the film is rubbed against the other side at a friction speed of 500 mm / min in an environment of 20°C and 20% RH, the amount of electrostatic charge generated per friction area is 1 μC / m ２ 5 μC / m or more ２ An acrylic resin composition, which is:

14. 14. The acrylic resin composition according to claim 13, wherein the ultraviolet absorber is at least one selected from the group consisting of triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers.

15. The acrylic resin composition according to claim 13 or 14, wherein the antiblocking agent comprises acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

16. 16. The acrylic resin composition according to claim 15, wherein the ratio of the acrylic crosslinked particles to the acrylic resin is 0.05% by weight or more and 0.5% by weight or less.

Images