Optical film, polarizing plate, and liquid crystal display panel

Abstract

To provide an optical film which is excellent in transparency and heat resistance and which can suppress blocking when a film roll is stored.SOLUTION: An optical film includes: an acrylic resin film mainly made of an acrylic resin; and an easy adhesive layer formed on the acrylic resin film. The acrylic resin has syndiotacticity of 54% or more at triad display. The acrylic resin film has a glass transition temperature of 120°C or more. The sum of 10-point average roughness Rzjis on each of both sides of the optical film is 0.05 μm or more and 1.0 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical film, a polarizing plate, a liquid crystal display panel, an acrylic resin composition, and an acrylic resin film. [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, when these optical films are wound into a roll, the films come into contact with each other, which tends to cause wrinkles and wrinkle marks. To solve 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 (Patent Document 1). Another method has been proposed in which an easy-adhesion layer containing particles such as silica is formed on one side of the film to ensure roll winding properties (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 074513 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-127893 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-55062 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the methods described in Patent Documents 1 to 3 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, etc. Furthermore, the inventors attempted to solve the above-mentioned phenomenon 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.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an optical film that has excellent heat resistance and transparency and is capable of suppressing blocking during storage in a film roll. [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 optical film having an acrylic resin film containing an acrylic resin as a main component and an easy-adhesion layer formed on the acrylic resin film, wherein the acrylic resin has a syndiotacticity of 54% or more, expressed as a triplet, and the acrylic resin film has a glass transition temperature of 120°C or more. The sum of the 10-point average roughness Rzjis of both surfaces of the optical film is 0.05 μm or more and 1.0 μm or less.

[0010] [2] An optical film having an acrylic resin film containing an acrylic resin as a main component and an easy-adhesion layer formed on the acrylic resin film, wherein the acrylic resin has a syndiotacticity of 54% or more, expressed as a triplet, a content of structural units derived from methyl methacrylate of 98% by weight or more, and the sum of the 10-point average roughness Rzjis of both surfaces of the optical film is 0.05 μm or more and 1.0 μm or less.

[0011] [3] The optical film according to [1] or [2], wherein the coefficient of static friction between one surface and the other surface of the optical film is 0.8 or less.

[0012] [4] The optical film according to any one of [1] to [3], wherein the acrylic resin film contains an antiblocking agent, and the antiblocking agent contains acrylic crosslinked particles having an average particle diameter of 0.1 μm or more and 2.5 μm or less.

[0013] [5] The optical film according to [4], wherein the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.0 μm or less.

[0014] [6] The optical film according to [4] or [5], wherein the acrylic resin film contains 0.05% by weight or more and 0.9% by weight or less of the acrylic crosslinked particles.

[0015] [7] The optical film according to any one of [1] to [6], 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.

[0016] [8] The optical film according to any one of [1] to [7], wherein the acrylic resin has a syndiotacticity of 55% or more in triad expression.

[0017] [9] The optical film according to any one of [1] to [8], wherein the easy-adhesion layer has a lubricating particle content of 0.1 wt % or less.

[0018]

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

[0019]

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

[10] .

[0020]

[12] An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, wherein the acrylic resin has a syndiotacticity of 54% or more, expressed as a triad, 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, the acrylic resin composition contains 0.05% by weight or more and 0.9% by weight or less of the acrylic crosslinked particles, and the acrylic resin composition has a glass transition temperature of 120°C or more.

[0021]

[13] An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, wherein the acrylic resin has a syndiotacticity of 54% or more, expressed as a triad, and a content of structural units derived from methyl methacrylate of 98% by weight or more, 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, and the acrylic resin composition contains 0.05% by weight or more and 0.9% by weight or less of the acrylic crosslinked particles.

[0022]

[14] An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, wherein the acrylic resin is substantially free of a ring structure in its main chain, 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, the acrylic resin composition contains 0.05 wt % or more and 0.9 wt % or less of the acrylic crosslinked particles, and the acrylic resin composition has a glass transition temperature of 120°C or more.

[0023]

[15] The acrylic resin composition according to any one of

[12] to

[14] , which is in the form of pellets.

[0024]

[16] An acrylic resin film obtained by molding the acrylic resin composition according to any one of

[12] to

[15] . [Effects of the Invention]

[0025] According to the present invention, it is possible to provide an optical film that is excellent in transparency and heat resistance and that can suppress blocking during storage of a 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. In this specification, unless otherwise specified, "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] (Optical film) The optical film of this embodiment is an optical film comprising an acrylic resin film containing an acrylic resin as a main component and an easy-adhesion layer formed on the acrylic resin film, characterized in that the glass transition temperature of the acrylic resin film is 120°C or higher, and the sum of the 10-point average roughness Rzjis of each of the two surfaces of the optical film is 0.05 μm or higher and 1.0 μm or lower. In this way, by controlling the sum of the 10-point average roughness Rzjis of each of the two surfaces of the film to a predetermined value while using an acrylic resin as a main component, an optical film excellent in heat resistance and transparency and also excellent in anti-blocking properties during film roll storage can be obtained.

[0028] (acrylic resin film) 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 heat resistance of the film is increased, and the dimensional change rate of the film in a high-temperature environment is reduced. In practical use, the acrylic resin film of this embodiment is often used by being laminated with an easy-adhesion layer or other films, and a small dimensional change rate can suppress the occurrence of distortion or 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 that is the main component of 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, an acrylic resin having a triad syndiotacticity of 54% or more can be suitably used as the acrylic resin having a glass transition temperature of 120°C or higher. This makes it possible to impart heat resistance. If the content of structural units derived from methyl methacrylate in the acrylic resin having a triad syndiotacticity of 54% or more is 98% by weight or more, the heat resistance of the acrylic resin film will be enhanced.

[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 optical film of this embodiment is preferably 1.0% or less. In particular, the internal haze is more preferably 0.7% or less, even 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 display panel is improved.

[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 optical film of this embodiment is not particularly limited as long as the internal haze is within the above-mentioned range, but 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 sum of the ten-point average roughness Rzjis on both sides of the optical film is 0.05 μm or more and 1.0 μm or less. When the sum of the ten-point average roughness Rzjis on both sides 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 reducing film defects. Here, when the sum of the ten-point average roughness Rzjis on both sides of the optical film is 0.05 μm or more, blocking due to tight winding during film roll storage can be suppressed, thereby reducing film defects. This tendency is particularly pronounced when storing long film rolls (e.g., 8000 m). This allows optical film to be wound in lengths other than the standard length (e.g., 4000 m), improving yield. Even with standard-length optical film, the inner optical film is less susceptible to plastic deformation during film roll storage, making the optical film easier to use. On the other hand, when the sum of the 10-point average roughness Rzjis of both surfaces of an optical film is 1.0 μm or less, a decrease in the transparency of the optical 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, and a decrease in the clarity of the panel display can be suppressed. In particular, the sum of the 10-point average roughness Rzjis of both surfaces of an optical film is preferably 0.05 μm or more and 0.6 μm or less, more preferably 0.06 μm or more and less than 0.5 μm, even more preferably 0.06 μm or more and 0.4 μm or less, and even more preferably 0.07 μm or more and 0.3 μm or less.

[0036] 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 off, a strong force is required, causing damage to the film. Therefore, by setting the sum of the 10-point average roughness Rzjis on both sides of the film within a predetermined range as in the present embodiment, it is possible to prevent sticking between films in the film roll even when tight winding occurs, and the films can be peeled off with a weak force, thereby preventing damage to the film (film defects).

[0037] The optical film preferably has a 10-point average roughness Rzjis of more than 0.020 μm and 0.20 μm or less on one surface and / or the other surface.

[0038] The Rzjis (surface roughness) of a film can be measured using an optical surface roughness tester such as a laser microscope. Since the surface roughness of the optical film of this embodiment is smaller than the resolution of the laser microscope, sufficient measurement accuracy cannot be achieved with a lens having a small numerical aperture. Therefore, in this specification, values ​​measured using a lens with a numerical aperture of 0.95 or more are used.

[0039] 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.

[0040] The static friction coefficient of the optical film, measured when one side of the film is placed against 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 in the film roll can be effectively suppressed. There is no particular restriction on the lower limit of the static friction coefficient, but from the viewpoint of winding slippage and meandering during production, it is preferably 0.2 or more.

[0041] The optical film preferably has a dimensional change rate, when left standing for 120 hours in an atmosphere of 85°C and 85% RH, of -2.0% or more, more preferably -1.7% or more, and even more preferably -1.5% or more, as an average value in the longitudinal direction (MD) and transverse direction (TD) of the film. A dimensional change rate of -2.0% or more suppresses shrinkage over time during film roll storage, improving the stability of the rolled appearance over time. Furthermore, warping and dimensional change upon attachment to a polarizer are alleviated, thereby suppressing a decrease in contrast and peripheral unevenness in liquid crystal display devices. The dimensional change rate may be, for example, -0.1% or less. A dimensional change rate of -0.1% or less allows the optical film to easily follow the shrinkage of the polarizer itself when attached to the polarizer. Here, 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 optical film standing in an environmental tester set to 85°C and 85% RH for 120 hours and measuring the dimensional change before and after.

[0042] In this specification and claims, the dimensional change rate refers to the rate of change in the hole spacing before and after opening 1 mm diameter holes at positions 20 mm inward from the four corners of a 90 mm x 90 mm film and leaving the film standing for 120 hours in an atmosphere of 85°C and 85% RH. Here, the rate of change in the hole spacing refers to the rate of change in the hole spacing after leaving the film standing, based on the hole spacing before leaving the film standing, and is calculated by the formula [(Hole spacing after standing) - (Hole spacing before standing)] × 100 / (Hole spacing before standing) (A) It is calculated as follows.

[0043] The linear expansion coefficient of the optical 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.

[0044] The linear expansion coefficient can be measured using, for example, a Bruker AXS TMA-4000SA thermomechanical analyzer. Specifically, in a nitrogen atmosphere, a 4 mm x 20 mm piece of film is cut and heated at a rate of 2°C / min within a temperature range not exceeding the glass transition temperature under a tensile load of 3.1 g. A chart is then created with temperature plotted on the X axis and the change in film length plotted on the Y axis. The slope of the curve over the temperature range from 40°C to 60°C during the heating and cooling process is calculated using the least squares method to determine the linear expansion coefficient.

[0045] (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.

[0046] 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.

[0047] 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 structural units derived from methyl methacrylate in the acrylic resin is high, the content of structural units derived from methyl methacrylate in the acrylic crosslinked particles is preferably high.

[0048] 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 it is less than 0.5% by weight, the heat resistance and dispersibility of the acrylic crosslinked particles will be poor. If it is more than 30% by weight, particle coalescence and the formation of irregularly shaped particles may occur during the production of the acrylic crosslinked particles.

[0049] The average particle size of the acrylic crosslinked particles is preferably 0.1 μm to 2.5 μm, more preferably 0.1 μm to 2.0 μm, even more preferably 0.3 μm to 2.0 μm, even more preferably 0.5 μm to 1.8 μm, and particularly preferably 0.6 μm to 1.5 μm. 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 economical 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 long-term run performance 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.

[0050] The amount of acrylic crosslinked particles added in this embodiment is preferably 0.05% by weight or more and 0.9% by weight or less, more preferably 0.07% by weight or more and 0.5% by weight or less, and even more preferably 0.1% by weight or more and 0.2% by weight or less. When the amount of acrylic crosslinked particles added is 0.05% by weight or more, the blocking suppression effect is enhanced, and when the amount is 0.9% by weight or less, deterioration in economic efficiency can be suppressed and an increase in haze can be suppressed. 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 total amount of the multiple types of acrylic crosslinked particles added.

[0051] (Easy adhesion layer) The optical film of this embodiment has an easy-adhesion layer on an acrylic resin film. The easy-adhesion layer is formed on one or both sides of the acrylic resin film. For example, when used as a polarizer protective film, the provision of the 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. It is also possible to provide an easy-adhesion layer on an unstretched film and then stretch the film to obtain a stretched film having an easy-adhesion layer.

[0052] 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.

[0053] The adhesion layer may contain lubricating particles, but the content of the lubricating particles in the adhesion layer is preferably 0.1 wt% or less. Because the acrylic resin film contains an antiblocking agent, the optical film of this embodiment has antiblocking properties even if the content of the lubricating particles in the adhesion layer is 0.1 wt% or less. The lubricating particles are not particularly limited as long as they can impart antiblocking properties to the adhesion layer, and examples thereof include silica particles.

[0054] (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 syndiotacticity (triad) of 54% or higher can be used as the acrylic resin having a glass transition temperature of 120°C or higher. When the syndiotacticity (triad) of the acrylic resin is 54% or higher, the glass transition temperature of the acrylic resin increases, and the heat resistance of the acrylic resin tends to improve. The syndiotacticity (triad) of the acrylic resin is preferably 55% or higher, more preferably 56% or higher, and even more preferably 57% or higher. Furthermore, from the viewpoints of the molding temperature of the acrylic resin, the toughness of the molded body, and secondary processability, the syndiotacticity (triad) of the acrylic resin is preferably 70% or lower, more preferably 67% or lower, even more preferably 65% ​​or lower, and even more preferably 63% or lower.

[0055] 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).

[0056] Methods for synthesizing acrylic resins having a triad syndiotacticity of 54% or more include, but are not limited to, anionic polymerization and radical polymerization. Among these, radical polymerization is preferred (see, for example, International Publication Nos. WO 2023 / 238885 and WO 2023 / 238886). Radical polymerization does not use organometallic compounds as polymerization initiators or organic solvents as media, as used in anionic polymerization. This makes 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.

[0057] The content of structural units derived from methyl methacrylate in an acrylic resin having a triad syndiotacticity of 54% or more is preferably 98% by weight or more, more preferably 99% by weight or more, and even more preferably 100% by weight.

[0058] Monomers other than methyl methacrylate that constitute acrylic resins having a syndiotacticity of 54% or more, expressed as triads, are not particularly limited, and examples thereof include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cycloalkyl acrylates such as cyclohexyl acrylate and norbornenyl acrylate; alkyl methacrylates other than methyl methacrylate, such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate and norbornenyl methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; and methacrylonitrile.

[0059] The weight-average molecular weight of the acrylic resin is preferably from 50,000 to 200,000, and more preferably from 90,000 to 150,000. When the weight-average molecular weight of the acrylic resin is 50,000 or more, the mechanical properties of the molded body of the acrylic resin tend to be improved, and when it is 200,000 or less, the melt moldability of the acrylic resin tends to be improved.

[0060] 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 molded product of the acrylic resin 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 4,000,000 or less, more preferably 3,500,000 or less, even more preferably 3,000,000 or less, even more preferably 2,000,000 or less, and particularly preferably 1,500,000 or less.

[0061] The ratio of the weight-average molecular weight to the number-average molecular weight of the acrylic resin (polydispersity index) is preferably 1.6 to 2.5, more preferably 1.7 to 2.2. When the polydispersity index of the acrylic resin is 1.6 or more, the flowability of the acrylic resin tends to improve and it tends to be easier to mold, 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.

[0062] 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.

[0063] The acrylic resin may be a resin that does not substantially contain a ring structure in the main chain. The content of structural units containing ring structures in the acrylic resin is, for example, less than 1% by weight. Examples of ring structures include glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings.

[0064] For example, the content of the glutarimide ring-containing structural unit in an acrylic resin composed of a methyl methacrylate unit and a glutarimide ring-containing structural unit can be determined as follows: 1 The H-NMR spectrum is measured. Next, the molar ratio of the methyl methacrylate units to the structural units containing glutarimide rings is determined from the peak area A derived from the O-CH3 protons of the methyl methacrylate units around 3.5 to 3.8 ppm and the peak area B derived from the N-CH3 protons of the glutarimide rings around 3.0 to 3.3 ppm. Next, the molar ratio of the methyl methacrylate units to the structural units containing glutarimide rings is converted into weight to calculate the content of the structural units containing glutarimide rings.

[0065] (Acrylic resin composition) The acrylic resin composition of this embodiment is primarily composed of an acrylic resin and contains an antiblocking agent. It is used to produce the acrylic resin film that constitutes the optical film of this embodiment. Specifically, the acrylic resin is a resin having a triad syndiotacticity of 54% or more, or a resin substantially free of ring structures in its main chain. The antiblocking agent also contains acrylic crosslinked particles having an average particle size of 0.1 μm to 2.5 μm. Furthermore, the acrylic resin composition of this embodiment contains 0.05 wt% to 0.9 wt% of acrylic crosslinked particles and has a glass transition temperature of 120°C or higher. When the content of structural units derived from methyl methacrylate in the acrylic resin having a triad syndiotacticity of 54% or more is 98 wt% or higher, the glass transition temperature of the acrylic resin composition of this embodiment is 120°C or higher. The form of the acrylic resin composition is not particularly limited, but examples include pellets.

[0066] The acrylic resin film may be formed from an acrylic resin composition containing an additive added to the acrylic resin. In this case, an antiblocking agent and an additive are used in combination. Examples of additives include commonly used antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, specific wavelength absorbers or specific wavelength absorbing dyes for blue light blocking, and 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, either alone or in combination, as long as they do not impair the objectives of the present invention.

[0067] Examples of ultraviolet absorbers include triazine-based compounds, benzotriazole-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, benzoxazine-based compounds, and oxadiazole-based compounds. Among these, triazine-based compounds are preferred in terms of ultraviolet absorption performance relative to the amount added and volatility when melt extrusion is performed.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] (Method of manufacturing optical film) One embodiment of the method for producing an optical film of the present invention will be described below, but 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.

[0073] Specific examples of the method include injection molding, melt extrusion molding, inflation molding, blow molding, compression molding, etc. The film according to this embodiment can also be produced by a solution casting method or spin coating method in which the acrylic resin composition according to this embodiment is dissolved in a solvent capable of dissolving the composition, and then the resulting mixture is molded.

[0074] Among these, it is preferable to use the melt extrusion method, which does not use a solvent, because the melt extrusion method can reduce production costs and the burden on the global environment and working environment caused by solvents.

[0075] 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.

[0076] 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 can dissolve 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.

[0077] The optical film of this embodiment is obtained by stretching an unstretched film (also referred to as a raw film). Stretching an unstretched film makes it possible to produce a stretched film of a desired thickness, and furthermore, improves the mechanical properties of the stretched film. Conventionally known methods can be used as the stretching method. For example, a film of a desired thickness can be produced by uniaxially or biaxially stretching an unstretched raw film formed by melt extrusion. 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.

[0078] 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).

[0079] 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 atmosphere of 85°C and 85% RH 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.

[0080] The optical film of this embodiment is wound into a roll by a known method. With the film of this embodiment, defects due to blocking between films are unlikely to occur 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.

[0081] (Application) When the optical 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.

[0082] 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]

[0083] 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 may make various changes, modifications, and alterations without departing from the scope of the present invention.

[0084] (10-point average roughness) The surface roughness of optical films was measured using an Evident LEXT OLS5100 laser microscope in accordance with JIS B 0601:2013. Specifically, a 50x magnification, 0.95 numerical aperture objective lens was used to capture a confocal image of a 257 μm x 257 μm area of ​​the film. Three equally spaced evaluation lines were then drawn in both the MD and TD directions to extract a roughness curve. The resulting roughness curve was then used to calculate the 10-point average roughness (Rzjis) using analysis software, and the average value at each measurement point was calculated. Measurements were performed five times at different measurement points, and the average value was used as the 10-point average roughness. 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.

[0085] (static friction coefficient) The static friction coefficient of the optical 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 was calculated. The measurement was performed five times with different pieces of film, and the average value was calculated.

[0086] (haze, internal haze) The haze of the optical film was measured in accordance with JIS 7136: 2000 using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. The internal haze of the optical film was measured by placing the optical film in a glass cell for measuring liquid so that distilled water was in contact with both sides of the optical film.

[0087] (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 glass transition temperature was determined by the midpoint method.

[0088] (dimensional change rate) A 90mm x 90mm piece of optical film was cut using a cutter, and holes were punched with a 1mm diameter punch at positions 20mm inward from the four corners of the film diagonally. The hole spacing was measured using a Mitutoyo MF201 three-dimensional measuring instrument. The film after the hole spacing measurement was then left to stand for 120 hours in a Nagano Science LH-20 environmental tester set at 85°C and 85% RH, and the hole spacing was measured again. The dimensional change rate was calculated from the hole spacing before and after standing in an 85°C, 85% RH atmosphere using formula (A).

[0089] (Refractive Index of Acrylic Resin Composition and Acrylic Crosslinked Particles) First, the refractive index of the acrylic resin composition was determined in accordance with JIS K7142:2014 as follows. Specifically, the acrylic resin composition was melt-pressed at 240°C to form a film with a thickness of 100 μm, and the refractive index (wavelength 589 nm) of the obtained film was measured under conditions of 23°C using a refractometer (Atago, Digital Abbe Refractometer DR-M2). The obtained refractive index was defined as the refractive index of the acrylic resin composition.

[0090] Next, the refractive index of the acrylic crosslinked particles was determined by the following method using mixed solutions of a halogen-based high-refractive index liquid and a low-refractive index liquid such as methanol at different ratios. When the acrylic crosslinked particles were dispersed in the mixed solution, if the refractive indexes of the mixed solution and the acrylic crosslinked particles did not match, the dispersion became cloudy. However, if the refractive indexes of the mixed solution and the acrylic crosslinked particles matched, the dispersion became transparent. Therefore, the refractive index of the mixed solution when it became transparent was used as the refractive index of the acrylic crosslinked particles.

[0091] <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%.

[0092] 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 glass transition temperature (Tg) of 120°C, a triad syndiotacticity (rr) of 57%, a weight-average molecular weight (Mw) of 83,000, a polydispersity (Mw / Mn) of 1.63, and a content of structural units derived from methyl methacrylate (MMA units) of 100% by weight.

[0093] (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

[0094] (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.

[0095] (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-8220GPC (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: 0.60 mL / min Measurement temperature: 40℃ Standard material: Standard polystyrene (manufactured by Tosoh)

[0096] Example 1 A mixture containing the acrylic resin 1 produced in the above-mentioned Acrylic Resin Production Example and 0.1 wt % of acrylic crosslinked particles (MX80H3wT, manufactured by Soken Chemical & Engineering Co., Ltd., refractive index 1.49) having an average particle size of 0.8 μm as an antiblocking agent (AB agent) was kneaded in a 15 mm diameter, intermeshing, co-rotating twin-screw extruder (L / D = 45). The resin that emerged as strands from a die installed at the extruder outlet was cooled in a water bath and then pelletized in a pelletizer to obtain pellets of an acrylic resin composition (refractive index 1.49).

[0097] The resulting pellets of the acrylic resin composition were dried at 100°C for 5 hours, and then a film was produced by sandwiching the pellets between touch rolls using a 15mm diameter intermeshing co-rotating 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 with a width of 160mm and a thickness of 160µm. The glass transition temperature of the raw film was measured using the method described above and found to be 121°C. The surface in contact with the casting roll was defined as side B, and the other side as side A.

[0098] Next, the surface B of the raw film was coated with an easy-adhesion coating as described below to obtain an optical film.

[0099] (Formation of easy-adhesion layer) One side of the raw film is corona discharge treated (irradiation dose of corona discharge electrons: 100 W / m 2 / min). 0.6 g of a crosslinker (Nippon Shokubai, trade name: Epocross WS700, solids content: 25%) and 18.9 g of deionized water were added to 3 g of an aqueous urethane resin having a carboxyl group (Dai-ichi Kogyo Seiyaku, trade name: Superflex 210, solids content: 33%) and stirred for 3 minutes to obtain an easy-adhesion composition. The obtained easy-adhesion composition was applied to the corona-discharge-treated surface of a raw film that had been subjected to a corona discharge treatment using a bar coater (number 6 wire). The raw film to which the easy-adhesion composition had been applied was placed in a hot air dryer (80°C), and the urethane composition was dried for about 1 minute to obtain an easy-adhesion-treated film having an easy-adhesion layer formed thereon.

[0100] The obtained easy-adhesion treated film was subjected to simultaneous biaxial stretching at a stretch ratio of 2 (longitudinal and transverse directions) at 135°C using a biaxial stretching device (IMC-1905) manufactured by Imoto Manufacturing Co., Ltd. to produce a stretched film (optical film). The stretched film had a thickness of 40 μm, and the easy-adhesion layer had a thickness of 0.16 μm.

[0101] (Blocking test) Ten test pieces (optical films) measuring 100 mm x 100 mm were stacked on top of each other, and then a pressure of 1 kg was applied from above and left at 60°C for 2 hours. After that, the pieces were allowed to cool at 23°C for 1 hour, and the condition of the optical films was visually checked, and the optical films were 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.

[0102] Table 1 shows the evaluation results of the 10-point average roughness (Rzjis), static friction coefficient, haze, internal haze, glass transition temperature (Tg), dimensional change rate, and blocking test.

[0103] Example 2 Except for using 0.12 wt% of acrylic crosslinked particles (J-3PY manufactured by Negami Chemical Industries, Ltd., refractive index 1.50) having an average particle size of 1.2 μm instead of 0.1 wt% of acrylic crosslinked particles having an average particle size of 0.8 μm, pellets of an acrylic resin composition, a raw film, and an optical film were obtained in the same manner as in Example 1. The glass transition temperature (Tg) of the raw film was measured and found to be 120°C.

[0104] Example 3 Pellets of an acrylic resin composition, a raw film, and an optical film were obtained in the same manner as in Example 1, except that 0.12 wt% of acrylic crosslinked particles (J-4PY manufactured by Negami Chemical Industries, Ltd., refractive index 1.50) having an average particle size of 2.2 μm were used instead of 0.1 wt% of acrylic crosslinked particles having an average particle size of 0.8 μm. The glass transition temperature (Tg) of the raw film was measured and found to be 120°C.

[0105] (Comparative Example 1) Pellets of the acrylic resin composition, a raw film, and an optical film were obtained in the same manner as in Example 1, except that the AB agent was not added.

[0106] (Comparative Example 2) Pellets of an acrylic resin composition, a raw film, and an optical film were obtained in the same manner as in Comparative Example 1, except that acrylic resin 2 (Parapet HR-S manufactured by Kuraray) was used instead of acrylic resin 1. Acrylic resin 2 had a glass transition temperature (Tg) of 116°C, a triad syndiotacticity (rr) of 51%, a weight-average molecular weight (Mw) of 91,000, a polydispersity (Mw / Mn) of 1.68, and a content of structural units derived from methyl methacrylate (MMA units) of 98% by weight or more.

[0107] (Comparative Example 3) Pellets of the acrylic resin composition, a raw film, and an optical film were obtained in the same manner as in Example 1, except that acrylic resin 2 (Parapet HR-S manufactured by Kuraray) was used instead of acrylic resin 1. The glass transition temperature (Tg) of the raw film was measured and found to be 117°C.

[0108] [Table 1]

[0109] Table 1 shows that the optical films of Examples 1 to 3 are excellent in transparency and heat resistance, and can suppress blocking during film roll storage. Here, the optical films of Examples 1 to 3 have excellent heat resistance, so their dimensional change rate is small in a high-temperature environment. In contrast, the optical films of Comparative Examples 1 and 2 have a sum of the 10-point average roughness Rzjis of each of the two surfaces of 0.030 to 0.036, so they cannot suppress blocking during film roll storage. Furthermore, the optical films of Comparative Examples 2 and 3 contain an acrylic resin 2 with an rr of 51% or have a Tg of 116 to 117°C, so they have poor heat resistance and a large dimensional change rate under a high-temperature environment.

[0110] Table 2 shows the properties of acrylic resins 1 and 2.

[0111] [Table 2]

Claims

1. An optical film having an acrylic resin film containing an acrylic resin as a main component and an easy-adhesion layer formed on the acrylic resin film, The acrylic resin has a syndiotacticity of 54% or more in triad expression, The acrylic resin film has a glass transition temperature of 120°C or higher, The optical film, wherein the sum of ten-point average roughnesses Rzjis of both surfaces of the optical film is 0.05 μm or more and 1.0 μm or less.

2. An optical film having an acrylic resin film containing an acrylic resin as a main component and an easy-adhesion layer formed on the acrylic resin film, The acrylic resin has a triad syndiotacticity of 54% or more and a content of structural units derived from methyl methacrylate of 98% by weight or more, The optical film, wherein the sum of ten-point average roughnesses Rzjis of both surfaces of the optical film is 0.05 μm or more and 1.0 μm or less.

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

4. the acrylic resin film contains an antiblocking agent, The optical film according to claim 1 , 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.

5. The optical film according to claim 4 , wherein the antiblocking agent comprises acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.0 μm or less.

6. The optical film according to claim 4 , wherein the acrylic resin film contains the acrylic crosslinked particles in an amount of 0.05% by weight or more and 0.9% by weight or less.

7. 3. The optical 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.

8. 3. The optical film according to claim 1, wherein the acrylic resin has a syndiotacticity of 55% or more in triad expression.

9. The optical film according to claim 1 , wherein the adhesive layer has a lubricating particle content of 0.1% by weight or less.

10. A polarizing plate comprising the optical film according to claim 1 or 2.

11. A liquid crystal display panel comprising the polarizing plate according to claim 10.

12. An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, The acrylic resin has a syndiotacticity of 54% or more in triad expression, the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less, The acrylic crosslinked particles are contained in an amount of 0.05% by weight or more and 0.9% by weight or less, An acrylic resin composition having a glass transition temperature of 120°C or higher.

13. An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, The acrylic resin has a triad syndiotacticity of 54% or more and a content of structural units derived from methyl methacrylate of 98% by weight or more, the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less, The acrylic resin composition contains the acrylic crosslinked particles in an amount of 0.05% by weight or more and 0.9% by weight or less.

14. An acrylic resin composition containing an acrylic resin as a main component and an antiblocking agent, The acrylic resin is substantially free of a ring structure in the main chain, the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less, The acrylic crosslinked particles are contained in an amount of 0.05% by weight or more and 0.9% by weight or less, An acrylic resin composition having a glass transition temperature of 120°C or higher.

15. The acrylic resin composition according to any one of claims 12 to 14, which is in the form of pellets.

16. An acrylic resin film obtained by molding the acrylic resin composition according to any one of claims 12 to 14.

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