Optical film

Abstract

Provided is an optical film which comprises: a (meth) acrylic resin film that contains a (meth) acrylic resin as a main component, contains crosslinked particles, and has a glass transition temperature of 120 DEG C or higher; the average particle diameter of the crosslinked particles is 1.0 [mu] m or more and 2.5 [mu] m or less, the content of the lubricating particles in the highly adhesive layer is 0.1 wt% or less, and the total value of the ten-point average roughness (Rzjis) of the surface of the highly adhesive layer and the ten-point average roughness (Rzjis) of the surface of the (meth) acrylic resin film on the opposite side from the highly adhesive layer is 23 nm or more and 200 nm or less. Also provided is a composition for forming an easily adhesive layer, which is used for forming an easily adhesive layer on a (meth) acrylic resin film.

Description

Technical Field

[0001] This invention relates to optical thin films. Background Technology

[0002] Optical films, such as those used for polarizer protection, require optical transparency, optical uniformity, and smoothness. Previously, cellulose-based films were commonly used as polarizer protection films; however, in recent years, (meth)acrylic resin films have sometimes been used to improve durability. Furthermore, to improve adhesion to polarizers, an easy-adhesion layer is formed by coating the surface of the (meth)acrylic resin film with an easy-adhesion layer forming composition.

[0003] When these optical films are rolled into rolls, they sometimes come into contact with each other, resulting in damage, unevenness, and other defects. Therefore, in order to prevent such damage and unevenness, a solution has been proposed to improve the smoothness of the optical film by adding lubricating particles with anti-adhesion properties, such as silica particles with a specific particle size, to the easy-to-adhere layer (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-52944 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, lubricating particles such as silica particles tend to aggregate in compositions used to form easily bonded layers. Therefore, it is sometimes difficult to uniformly distribute the lubricating particles on the surface of (meth)acrylic resin films, thus failing to fully exert their anti-blocking properties. In addition, the aggregation of lubricating particles can sometimes also affect the transparency and other functions of optical films.

[0009] Therefore, the objective of this invention is to provide an optical film that does not impair its function as an optical film and has anti-adhesion properties.

[0010] Solution for solving the problem

[0011] The specific means used to solve the above problems include the following implementation methods.

[0012] <1> An optical film comprising a (meth)acrylic resin film and an easily bondable layer formed on the (meth)acrylic resin film, wherein the (meth)acrylic resin film is mainly composed of (meth)acrylic resin and contains cross-linked particles, and the optical film satisfies the following conditions:

[0013] (i) The glass transition temperature of the aforementioned (meth)acrylic resin film is above 120°C.

[0014] (ii) The average particle size of the aforementioned cross-linked particles is greater than 1.0 μm and less than 2.5 μm.

[0015] (iii) The content of lubricating particles in the aforementioned easily bondable layer is less than 0.1% by weight.

[0016] (iv) The sum of the ten-point average roughness Rzjis of the surface of the aforementioned easy-to-adhere layer and the ten-point average roughness Rzjis of the surface of the aforementioned (meth)acrylic resin film on the opposite side of the aforementioned easy-to-adhere layer is 23 nm or more and 200 nm or less.

[0017] <2> An optical film having a (meth)acrylic resin film and an easy-to-adhere layer formed on the (meth)acrylic resin film, wherein the (meth)acrylic resin film is mainly composed of (meth)acrylic resin and contains cross-linked particles, and the optical film satisfies the following conditions.

[0018] (i) The aforementioned (meth)acrylic resin film contains methyl methacrylate units in a proportion of 98% or more and has a syndiotactic regularity of 54% or more in the form of tripartite groups.

[0019] (ii) The average particle size of the aforementioned cross-linked particles is greater than 1.0 μm and less than 2.5 μm.

[0020] (iii) The content of lubricating particles in the aforementioned easily bondable layer is less than 0.1% by weight.

[0021] (iv) The sum of the ten-point average roughness Rzjis of the surface of the aforementioned easy-to-adhere layer and the ten-point average roughness Rzjis of the surface of the aforementioned (meth)acrylic resin film on the opposite side of the aforementioned easy-to-adhere layer is 23 nm or more and 200 nm or less.

[0022] <3> according to <1> or <2> The optical thin film, wherein the thickness of the aforementioned easy-to-adhere layer is 50 nm or more and 600 nm or less.

[0023] <4> according to <1> or <2> The optical film, wherein when two of the aforementioned optical films are overlapped in such a manner as to contact the aforementioned (meth)acrylic resin film with the aforementioned easy-to-adhere layer, has a static friction coefficient of 0.3 or more and 2.0 or less, as measured according to JIS K7125:1999.

[0024] <5> according to <1> The optical thin film, wherein the aforementioned (meth)acrylic resin film comprises a (meth)acrylic resin having a ring structure in the main chain.

[0025] <6> according to <5> The optical thin film, wherein the aforementioned ring structure is selected from at least one of the group consisting of glutarimide structure, lactone ring structure, maleic anhydride structure, N-substituted maleimide structure and glutaric anhydride structure.

[0026] <7> according to <5> The optical thin film, wherein the aforementioned (meth)acrylic resin having a ring structure in the main chain comprises the structural unit shown in the following general formula (1).

[0027]

[0028] (where R is in the formula) 1 and R 2 Each independently represents an alkyl group having 1 to 8 hydrogen atoms or carbon atoms; R 3 (This refers to a hydrogen atom, an alkyl group with 1 to 18 carbon atoms, a cycloalkyl group with 3 to 12 carbon atoms, or an aryl group with 6 to 10 carbon atoms.)

[0029] <8> according to <7> The optical thin film wherein the proportion of the structural unit of the aforementioned general formula (1) in the (meth)acrylic resin having a ring structure in the main chain is 2% by weight or more and 30% by weight or less.

[0030] <9> according to <1> The optical film, wherein the aforementioned (meth)acrylic resin film contains methyl methacrylate units in a proportion of 98% or more and the syndiotactic regularity of the tri-unit group is 54% or more.

[0031] <10> according to <1> ~ <9> The optical film according to any one of the above-mentioned (meth)acrylic resin films comprises aromatic vinyl units.

[0032] <11> according to <5> or <9> The optical film, wherein the aforementioned (meth)acrylic resin film further contains a copolymer comprising aromatic vinyl units.

[0033] <12> according to <11> The optical film, wherein the aforementioned copolymer further comprises (meth)acrylate units or (meth)acrylonitrile units.

[0034] <13> A composition for forming an easy-adhesive layer, used to form an easy-adhesive layer on a (meth)acrylic resin film.

[0035] The aforementioned (meth)acrylic resin film uses (meth)acrylic resin as the main component, contains cross-linked particles with an average particle size of 1.0 μm or more and 2.5 μm or less, and has a glass transition temperature of 120°C or more.

[0036] The content of lubricating particles in the aforementioned composition for forming an easy-to-adhesive layer is 0.1% by weight or less.

[0037] <14> A composition for forming an easy-adhesive layer, used to form an easy-adhesive layer on a (meth)acrylic resin film.

[0038] The aforementioned (meth)acrylic resin film uses (meth)acrylic resin as the main component and contains cross-linked particles with an average particle size of 1.0 μm or more and 2.5 μm or less.

[0039] The aforementioned (meth)acrylic resin film contains methyl methacrylate units in a proportion of 98% or more and has a syndiotactic regularity of 54% or more in the form of tripartite groups.

[0040] The content of lubricating particles in the aforementioned composition for forming an easy-to-adhesive layer is 0.1% by weight or less.

[0041] The effects of the invention

[0042] According to the present invention, an optical film with anti-adhesion properties can be provided without impairing its function as an optical film. Attached Figure Description

[0043] Figure 1 This is a schematic cross-sectional view of the optical thin film described in this embodiment.

[0044] Explanation of reference numerals in the attached figures

[0045] 1. Optical thin films

[0046] 2 Easy-to-adhere layer

[0047] 3-(meth)acrylic resin film

[0048] 4-crosslinked particles Detailed Implementation

[0049] The following description pertains to one embodiment of the present invention, but the invention is not limited to this embodiment. In this specification, the term "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid". The same applies to terms such as "(meth)acryloyl", "(meth)acrylic acid", and "(meth)acrylonitrile".

[0050] <Optical Thin Films>

[0051] The optical film described in this embodiment has a (meth)acrylic resin film and an easy-to-adhere layer formed on the (meth)acrylic resin film, wherein the (meth)acrylic resin film has (meth)acrylic resin as the main component and contains cross-linked particles.

[0052] Here, (meth)acrylic resin refers to a resin in which the proportion of structural units derived from polymerizable monomers having (meth)acryloyl groups is 50% or more. Furthermore, (meth)acrylic resin as the main component means that the content of (meth)acrylic resin in the (meth)acrylic resin film is 50% or more.

[0053] A schematic cross-sectional view of the optical thin film described in this embodiment is shown in Figure 1 . Figure 1 The optical film 1 shown has a (meth)acrylic resin film 3 containing cross-linked particles 4 and an easy-adhesive layer 2 formed on the (meth)acrylic resin film 3. By including the cross-linked particles 4 in the (meth)acrylic resin film 3, an uneven surface is formed on the surface of the (meth)acrylic resin film 3. The easy-adhesive layer 2 is formed on the surface of the (meth)acrylic resin film 3 with the uneven surface, therefore, an uneven surface also appears on the surface of the easy-adhesive layer 2. As a result, the optical film 1 has anti-adhesion properties.

[0054] Regarding the optical film described in this embodiment, when two optical films are overlapped in a manner where a (meth)acrylic resin film and an easy-to-adhere layer are in contact, the static friction coefficient measured according to JIS K 7125:1999 is preferably 0.3 or more and 2.0 or less, more preferably 0.4 or more and 1.8 or less. If the static friction coefficient between the (meth)acrylic resin film and the easy-to-adhere layer is within the above range, there is a tendency to exhibit good anti-adhesion properties.

[0055] [(Meth)acrylic resin film]

[0056] The substrate for the optical film is a (meth)acrylic resin film, which contains (meth)acrylic resin as the main component. The content of (meth)acrylic resin in the (meth)acrylic resin film is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 70% by weight or more, and particularly preferably 75% by weight or more.

[0057] As the (meth)acrylic resin, any suitable (meth)acrylic resin can be used. Specific examples include poly(meth)acrylates (e.g., polymethyl methacrylate, etc.), methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylate copolymers, methyl methacrylate-acrylate-(meth)acrylic acid copolymers, methyl methacrylate-styrene copolymers, and polymers having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norborneol methacrylate copolymers, etc.). Among these, poly(meth)acrylate C1-C6 alkyl esters (poly(meth)acrylate resins having alkyl groups having 1 to 6 carbon atoms) such as poly(meth)acrylate are preferred, and polymethyl methacrylate resins with methyl methacrylate as the main component (50% by weight or more, preferably 70% by weight or more) are more preferred.

[0058] (Meth)acrylic resin films may contain aromatic vinyl units. These aromatic vinyl units may constitute a (meth)acrylic resin as a main component, or they may constitute a resin different from the (meth)acrylic resin as a main component. The content of aromatic vinyl units in the (meth)acrylic resin film is preferably 0% by weight or more and 25% by weight or less, more preferably 0.5% by weight or more and 20% by weight or less.

[0059] The glass transition temperature of the (meth)acrylic resin film is preferably 120°C or higher, more preferably above 120°C, further preferably 121°C or higher, and particularly preferably 122°C or higher. If the glass transition temperature of the (meth)acrylic resin film is 120°C or higher, there is a tendency for the film's dimensional change rate to decrease under high-temperature conditions. In practical applications, (meth)acrylic resin films are mostly used in laminates with other films. In this case, a small dimensional change rate can suppress deformation and warping caused by the difference in dimensional change rates between the film and the other laminated films.

[0060] The glass transition temperature can be measured using a differential scanning calorimeter (Hitachi Advanced Scientific Corporation, DSC7000X) under a nitrogen atmosphere at a heating rate of 20 °C / min, and determined using the midpoint method.

[0061] (In (meth)acrylic resins with a ring structure in the main chain)

[0062] In (meth)acrylic resin films, the (meth)acrylic resin with a glass transition temperature of 120°C or higher is preferably included as a (meth)acrylic resin having a ring structure in the main chain (hereinafter also referred to as "first (meth)acrylic resin"). Examples of ring structures include at least one selected from glutarimide, lactone ring, maleic anhydride, N-substituted maleimide, and glutaric anhydride structures. Among these, (meth)acrylic resins having a glutarimide or lactone ring structure in the main chain are preferred, and (meth)acrylic resins having a glutarimide structure in the main chain are more preferred from the viewpoints of ease of production, cost, and quality stability against moisture.

[0063] The proportion of ring structures in the first (meth)acrylic resin is not particularly limited, but is, for example, 1% by weight or more and 80% by weight or less, preferably 2% by weight or more and 30% by weight or less. If the proportion of ring structures is high within this range, it is preferable from the viewpoint of increasing the glass transition temperature; if the proportion of ring structures is low within this range, it is preferable from the viewpoint of decreasing the phase difference.

[0064] The following is a description of the structure of each ring.

[0065] (Meth)acrylic resins having a glutarimide structure in the main chain are, for example, resins having glutarimide units and methyl methacrylate units as shown in the following general formula (1), which can be manufactured by heating and melting polymethyl methacrylate resin and then treating it with an imidizing agent.

[0066]

[0067] (where R is in the formula) 1 and R 2 Each independently represents an alkyl group having 1 to 8 hydrogen atoms or carbon atoms; R 3 (This refers to a hydrogen atom, an alkyl group with 1 to 18 carbon atoms, a cycloalkyl group with 3 to 12 carbon atoms, or an aryl group with 6 to 10 carbon atoms.)

[0068] In (meth)acrylic resins with a glutarimide structure in the main chain, the proportion of glutarimide units is preferably 2% by weight or more and 30% by weight or less. If the proportion of glutarimide units is 2% by weight or more, there is a tendency to readily impart the desired heat resistance. Furthermore, if the proportion of glutarimide units is 30% by weight or less, there is a tendency to suppress the amount of imidizing agent added and to suppress odors caused by residual volatile components, thereby reducing the phase difference Rth in the thickness direction.

[0069] In the above general formula (1), R 3When the methyl group is used, the proportion of glutarimide units can be determined using, for example, the following method. First, using... 1 H-NMR BRUKER AvanceIII (400MHz) was used to analyze the resin. 1 H-NMR determination was performed. The molar ratio was calculated based on the peak area A (near 3.5 ppm to 3.8 ppm) originating from the O-CH3 protons constituting methyl methacrylate and the peak area B (near 3.0 ppm to 3.3 ppm) originating from the N-CH3 protons constituting the glutarimide ring. By performing a weight conversion on this molar ratio, the proportion of glutarimide units could be calculated.

[0070] In manufacturing polymethyl methacrylate (PMMA) resin, in addition to methyl methacrylate, other monomers such as methyl acrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, benzyl methacrylate, and cyclohexyl methacrylate can be used in combination. Furthermore, besides the above, nitrile monomers such as acrylonitrile and methacrylonitrile; maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide; and aromatic vinyl monomers such as styrene and α-methylstyrene can also be used in combination. Preferably, the proportion of acrylate units in the PMMA resin is less than 1% by weight. In particular, the proportion of methyl acrylate units is preferably less than 0.5% by weight, more preferably less than 0.3% by weight.

[0071] The structure of polymethyl methacrylate resin is not particularly limited and can be any of linear (linear) polymers, block polymers, core-shell polymers, branched polymers, ladder polymers, crosslinked polymers, etc.

[0072] There are no particular limitations on the manufacturing method of polymethyl methacrylate resin, and well-known methods such as emulsion polymerization, emulsion-suspension polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used. In the case of application in the optical field, from the viewpoint of minimizing impurities, bulk polymerization and solution polymerization are preferred. Polymethyl methacrylate resin can be manufactured according to methods described in, for example, Japanese Patent Application Publication No. 56-8404, Japanese Patent Publication No. 6-86492, Japanese Patent Publication No. 7-37482, and Japanese Patent Publication No. 52-32665.

[0073] The manufacturing method of (meth)acrylic resin having a glutarimide structure in the main chain includes a step of heating and melting the above-mentioned polymethyl methacrylate resin and then treating it with an imidizing agent (imidization step).

[0074] The imidizing agent is not particularly limited as long as it can generate the glutarimide unit shown in the above general formula (1), and substances described in International Publication No. 2005 / 054311 may be used. Specifically, examples of imidizing agents include amines containing aliphatic hydrocarbon groups such as ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; amines containing aromatic hydrocarbon groups such as aniline, benzylamine, toluene, and trichloroaniline; and amines containing alicyclic hydrocarbon groups such as cyclohexylamine. Among these, methylamine, ammonia, and cyclohexylamine are preferred from the viewpoint of cost and physical properties, and methylamine is more preferred. It should be noted that methylamine and the like, which are gaseous at room temperature, can be used in a state of dissolution in alcohols such as methanol.

[0075] In the imidization process, the ratio of glutarimide units to (meth)acrylate units in the resulting (meth)acrylate resin can be adjusted by changing the amount of imidizing agent added. Furthermore, by adjusting the degree of imidization, the physical properties of the resulting (meth)acrylate resin and the optical properties of the (meth)acrylate resin film formed from the (meth)acrylate resin can be modified.

[0076] The amount of imidizing agent added is preferably 0.5 parts by weight or more and 20 parts by weight or less relative to 100 parts by weight of polymethyl methacrylate resin. If the amount of imidizing agent added is 0.5 parts by weight or more, the proportion of glutarimide units increases, resulting in improved heat resistance of the (meth)acrylic resin and a tendency to prevent appearance defects after molding. Furthermore, if the amount of imidizing agent added is 20 parts by weight or less, there is a tendency for imidizing agent to remain in the (meth)acrylic resin less, preventing appearance defects and foaming after molding.

[0077] It should be noted that in the imidization process, a ring-closing promoter (catalyst) can be added in addition to the imidizing agent.

[0078] There are no particular limitations on the method of heating and melting polymethyl methacrylate resin and treating it with an imidizing agent; all currently known methods can be used. For example, polymethyl methacrylate resin can be imidized by using an extruder, a batch reaction tank (pressure vessel), etc.

[0079] When polymethyl methacrylate (PMMA) resin is heated and melted using an extruder and then treated with an imidizing agent, various extruders can be used, such as single-screw extruders, twin-screw extruders, and multi-screw extruders. Among these, a twin-screw extruder is preferred. Using a twin-screw extruder facilitates the mixing of the imidizing agent (or, when using a ring-closing accelerator, both the imidizing agent and the ring-closing accelerator) with the PMMA resin.

[0080] Examples of twin-screw extruders include non-meshing co-rotating, meshing co-rotating, non-meshing counter-rotating, and meshing counter-rotating types, with the meshing co-rotating type being preferred. Meshing co-rotating twin-screw extruders can rotate at high speeds, thus further promoting the mixing of the imidizing agent (or, when using a ring-closing accelerator, both the imidizing agent and the ring-closing accelerator) with the polymethyl methacrylate resin.

[0081] The extruders illustrated above can be used individually or in series. For example, a series-type reactive extruder as described in Japanese Patent Application Publication No. 2008-273140 can be used.

[0082] When performing an imidization reaction in an extruder, for example, polymethyl methacrylate resin is fed into the feed section of the extruder, allowing the resin to melt and fill the barrel, and then an imidizing agent is injected into the extruder using a feed pump.

[0083] In this case, it is preferable to set the temperature (resin temperature) of the reaction zone in the extruder to 180°C or higher and 270°C or lower, more preferably 200°C or higher and 250°C or lower. If the temperature (resin temperature) of the reaction zone is 180°C or higher, there is a tendency for the imidization reaction to proceed sufficiently and for heat resistance to improve. Furthermore, if the temperature of the reaction zone is 270°C or lower, resin decomposition can be suppressed, resulting in a tendency for the reduction in flexural strength of the film formed from the resulting (meth)acrylic resin to be suppressed. Here, the reaction zone in the extruder refers to the area in the barrel of the extruder from the injection point of the imidizing agent to the resin ejection point (die section).

[0084] By extending the reaction time within the reaction zone of the extruder, further imidization can be achieved. The reaction time within the reaction zone of the extruder is preferably more than 10 seconds, more preferably more than 30 seconds. Within a reaction time of less than 10 seconds, there is a possibility that imidization may hardly occur.

[0085] The resin pressure inside the extruder is preferably set to above atmospheric pressure and below 50 MPa, more preferably above 1 MPa and below 30 MPa. If the resin pressure is above 1 MPa, the solubility of the imidizing agent increases, and there is a tendency for further reaction. In addition, if the resin pressure is below 50 MPa, no special equipment is required, which is preferable in terms of cost.

[0086] When using an extruder, in order to remove unreacted imidizing agents, byproducts such as methanol, monomers, etc., it is preferable to install ventilation holes that can reduce pressure to below atmospheric pressure.

[0087] It should be noted that horizontal twin-shaft reactors such as the BIVOLAK manufactured by Sumitomo Heavy Industries, Ltd., and vertical twin-shaft mixing tanks such as SUPERBLEND, which are suitable for handling high viscosity, can also be used instead of extruders.

[0088] When using a batch reaction vessel (pressure vessel) to heat and melt polymethyl methacrylate resin and treat it with an imidizing agent, the structure of the batch reaction vessel is not particularly limited. As long as the batch reaction vessel has a structure capable of melting and stirring the polymethyl methacrylate resin by heating, and capable of adding an imidizing agent (or both an imidizing agent and a ring-closing accelerator when using a ring-closing accelerator), a structure with good stirring efficiency is preferred. Using such a batch reaction vessel prevents the polymer viscosity from increasing due to the reaction and preventing insufficient stirring. Examples of batch reaction vessels with this structure include, for instance, the MAXBLEND stirred tank manufactured by Sumitomo Heavy Industries, Ltd.

[0089] Specific examples of imidization methods include known methods described in Japanese Patent Application Publication Nos. 2008-273140 and 2008-274187.

[0090] In a method for manufacturing (meth)acrylic resins with a glutarimide structure in the main chain, an esterification step may be included in addition to the imidization step. This esterification step allows the acid value of the imidized resin obtained in the imidization step to be adjusted to a desired range.

[0091] Examples of esterifying agents include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl formate, trimethyl o-acetate, trimethyl o-formate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl-tert-butylsilyl chloride, isopropyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-N-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexane oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, etc. Among these, dimethyl carbonate and trimethyl o-acetate are preferred from the perspectives of cost and reactivity, and dimethyl carbonate is more preferred from the perspective of cost.

[0092] The amount of esterifying agent added relative to 100 parts by weight of polymethyl methacrylate resin is preferably 0 parts by weight or more and 12 parts by weight or less, more preferably 0 parts by weight or more and 8 parts by weight or less. If the esterifying agent is within the above range, there is a tendency to adjust the acid value to an appropriate range and unreacted esterifying agent is less likely to remain in the resin.

[0093] In the esterification process, a catalyst can be used in combination with the esterifying agent. Examples of catalysts include aliphatic tertiary amines such as trimethylamine, triethylamine, and tributylamine. Among these, triethylamine is preferred from the viewpoints of cost and reactivity.

[0094] It should be noted that in the esterification process, heat treatment alone is also possible without the use of an esterifying agent. When only heat treatment is performed (mixing and dispersing the molten resin in the extruder), at least some of the carboxyl groups can be converted into anhydride groups through the dehydration reaction between the carboxyl groups generated in the imidization process and the dealcoholization reaction between the carboxyl groups and alkyl ester groups. In this case, a ring-closing accelerator (catalyst) can also be used. Even when using an esterifying agent, anhydride formation can still be achieved through heat treatment.

[0095] There are no particular limitations on (meth)acrylic resins with a lactone ring structure in the main chain, as long as they are thermoplastic polymers with an intramolecular lactone ring structure (thermoplastic polymers with a lactone ring structure introduced into the molecular chain). There are also no limitations on their manufacturing methods. Preferably, they are obtained by: obtaining a polymer with hydroxyl and ester groups in the molecular chain through polymerization (polymerization step), and then subjecting the resulting polymer to heat treatment, thereby introducing a lactone ring structure into the polymer (lactone cyclization condensation step).

[0096] In the polymerization process, a polymer having hydroxyl and ester groups in the molecular chain is obtained by carrying out a polymerization reaction of a monomer component containing an unsaturated monomer as shown in the following general formula (2).

[0097]

[0098] (where R is in the formula) 4 and R 5 Each can independently represent an alkyl group having 1 to 20 hydrogen atoms or carbon atoms.

[0099] Examples of unsaturated monomers represented by the general formula (2) above include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and tert-butyl 2-(hydroxymethyl)acrylate. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is more preferred from the viewpoint of improving heat resistance. One of these unsaturated monomers may be used alone, or two or more may be used in combination.

[0100] The content of the unsaturated monomer shown in the above general formula (2) in the monomer component is preferably 5% by weight or more and 50% by weight or less, more preferably 10% by weight or more and 40% by weight or less, and even more preferably 10% by weight or more and 30% by weight or less. If the content of the unsaturated monomer shown in the above general formula (2) is 5% by weight or more, there is a tendency to improve the heat resistance, solvent resistance, and surface hardness of the obtained resin. In addition, if the content of the unsaturated monomer shown in the above general formula (2) is 50% by weight or less, there is a tendency to suppress the cross-linking reaction that occurs during the formation of the lactone ring structure and to suppress the decrease in fluidity. In addition, there is a tendency to suppress the further condensation reaction during molding due to unreacted hydroxyl residues, the generation of volatile substances, the generation of silver streaks, and the increase of the phase difference Rth in the thickness direction.

[0101] In addition to the unsaturated monomer shown in general formula (2) above, the monomer component may also contain other monomers. Examples of other monomers include (meth)acrylates, hydroxyl-containing monomers, unsaturated carboxylic acids, and unsaturated monomers shown in general formula (3) below. Other monomers may be used alone or in combination of two or more.

[0102]

[0103] (where R is in the formula) 6 X represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group with 1 to 20 carbon atoms, an aryl group, an -OAc group, a -CN group, or a -CO-R group. 7 The group, Ac, represents acetyl, and R... 7 (This refers to an alkyl group having 1 to 20 hydrogen atoms or carbon atoms.)

[0104] As for the aforementioned (meth)acrylates, there are no particular limitations on any (meth)acrylate other than the unsaturated monomers shown in the general formula (2) above. Examples include acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate; and methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. Among these, methyl methacrylate is preferred from the viewpoint of heat resistance and transparency.

[0105] When using (meth)acrylates, the content of (meth)acrylates in the monomer component is preferably 10% by weight or more and 95% by weight or less, more preferably 10% by weight or more and 90% by weight or less, even more preferably 40% by weight or more and 90% by weight or less, and particularly preferably 50% by weight or more and 90% by weight or less.

[0106] (Meth)acrylic resins with a methyl methacrylate unit content of 98% or more and a syndiotactic regularity (rr) of 54% or more in terms of the three-unit group)

[0107] (Meth)acrylic resin films are also preferably (meth)acrylic resins that contain methyl methacrylate units in a proportion of 98% or more and have a syndiotactic regularity of 54% or more in the form of tri-unit groups (hereinafter also referred to as "second (meth)acrylic resins").

[0108] The second (meth)acrylic resin preferably has a methyl methacrylate unit content of 99% or more and a content of other polymerizable monomer units other than methyl methacrylate units of 1% or less. More preferably, it has a methyl methacrylate unit content of 99.5% or more and a content of other polymerizable monomer units other than methyl methacrylate units of 0.5% or less. It is even more preferably a homopolymer of methyl methacrylate.

[0109] Other polymerizable monomers besides methyl methacrylate include, for example, alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cyclohexyl acrylates such as cyclohexyl acrylate and norbornyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, and n-butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cyclohexyl methacrylates such as cyclohexyl methacrylate and norbornyl methacrylate; aromatic vinyl monomers such as styrene and α-methylstyrene; cyanide monomers such as acrylonitrile and methacrylonitrile; acrylamide; and methacrylamide.

[0110] The syndiotactic regularity (rr) of the second (meth)acrylic resin, expressed as a ternary unit group, is 54% or more, preferably 55% or more, more preferably 56% or more, and even more preferably 57% or more. If the syndiotactic regularity (rr) expressed as a ternary unit group is 54% or more, there is a tendency for the (meth)acrylic resin to have a higher glass transition temperature and improved heat resistance. There is no particular upper limit to the syndiotactic regularity (rr), but from the viewpoint of molding processing temperature, as well as the toughness and secondary processability of the molded article, it is preferably 70% or less, more preferably 67% or less, even more preferably 65% ​​or less, and particularly preferably 63% or less.

[0111] Synthetic regularity (rr) is the proportion of three consecutive structural units (triads) in which two of their chains (diads) are racemic (rr). It should be noted that the case where the three-dimensional arrangement of the structural units (diads) in a polymer molecule is the same is called meso, and the opposite case is called racemo, denoted as m and r respectively.

[0112] The isotactic regularity (rr) can be calculated as follows: In deuterated chloroform, it is measured at 22°C for a cumulative total of 16 times. 1 The H-NMR spectrum was used to measure the area (X) of the region from 0.60 ppm to 0.95 ppm and the area (Y) of the region from 0.60 ppm to 1.25 ppm when tetramethylsilane (TMS) was set to 0 ppm, and the results were calculated using the formula: (X / Y)×100.

[0113] As a method for manufacturing the second (meth)acrylate resin, existing known polymerization methods can be employed, such as continuous bulk polymerization, solution polymerization, emulsion polymerization, emulsion polymerization without emulsifiers (soap-free) emulsion polymerization, suspension polymerization, and other free radical polymerization methods. Among these, from the viewpoints of structural design freedom, polymerization simplicity, and productivity of (meth)acrylate resins, aqueous polymerization is preferred, suspension polymerization and emulsion polymerization are more preferred, and suspension polymerization is even more preferred. The second (meth)acrylate resin can be manufactured according to methods described, for example, in International Publication No. 2023 / 238885.

[0114] (Copolymer containing aromatic vinyl units)

[0115] In addition to containing a first (meth)acrylic resin or a second (meth)acrylic resin, the (meth)acrylic resin film may also contain a copolymer containing aromatic vinyl units. Examples of copolymers containing aromatic vinyl units include (meth)acrylic ester-aromatic vinyl copolymers such as methyl methacrylate-styrene copolymers and (meth)acrylonitrile-aromatic vinyl copolymers such as acrylonitrile-styrene copolymers.

[0116] Examples of aromatic vinyl groups include styrene, α-methylstyrene, methoxystyrene, vinyltoluene, and halostyrene. Among these, styrene is preferred.

[0117] Examples of (meth)acrylates include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, etc.; and methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc. Among these, methyl methacrylate is preferred.

[0118] The proportion of aromatic vinyl units in the (meth)acrylate-aromatic vinyl copolymer is preferably 10% by weight or more and 30% by weight or less, more preferably 15% by weight or more and 28% by weight or less. If the proportion of aromatic vinyl units is within the above range, there is a tendency to maintain the transparency of the (meth)acrylate resin film.

[0119] The proportion of (meth)acrylonitrile units in the (meth)acrylonitrile-aromatic vinyl copolymer is preferably 22% by weight or more and 28% by weight or less, more preferably 23% by weight or more and 27% by weight or less. If the proportion of (meth)acrylonitrile units is within the above range, there is a tendency to maintain the transparency of the (meth)acrylic resin film.

[0120] The content of copolymers containing aromatic vinyl units in (meth)acrylic resin films is preferably 0% by weight or more and 30% by weight or less, more preferably 3% by weight or more and 25% by weight or less.

[0121] (Other thermoplastic resins)

[0122] (Meth)acrylic resin films may contain other thermoplastic resins besides those mentioned above. Examples of other thermoplastic resins include olefin polymers, halogenated vinyl polymers, styrene polymers, ester polymers, and amide polymers.

[0123] The content of other thermoplastic resins in the (meth)acrylic resin film is preferably 0% by weight or more and 50% by weight or less, more preferably 0% by weight or more and 30% by weight or less.

[0124] The lower the orientation birefringence of the (meth)acrylic resin film, the better; the preferred orientation birefringence is -1.7 × 10⁻⁶. -4 Above and 1.7×10 -4 Below. If the oriented birefringence is within the above range, there is a tendency for the phase difference value of the (meth)acrylic resin film to decrease.

[0125] In addition, the lower the photoelasticity of the (meth)acrylic resin film, the better; the preferred photoelasticity is -10 × 10⁻⁶. -12 Pa -1 Above and 10×10 -12 Pa -1 The following is more preferably -4×10 -12 Pa -1 Above and 4×10 -12 Pa -1 the following.

[0126] (Cross-linked particles)

[0127] By including cross-linked particles in the (meth)acrylic resin film, an uneven surface is formed on the surface of the (meth)acrylic resin film. An easy-adhesive layer is formed on the surface of the (meth)acrylic resin film with the uneven surface; therefore, an uneven surface also appears on the easy-adhesive layer, thereby achieving anti-blocking properties.

[0128] Examples of cross-linked particles include cross-linked acrylic resin particles, cross-linked polystyrene resin particles, melamine resin particles, and cross-linked silicone resin particles. Among these, cross-linked acrylic resin particles are preferred from the viewpoints of compatibility, dispersibility, and transparency with (meth)acrylic resins.

[0129] As the monomer for forming crosslinked acrylic resin particles, any (meth)acrylate and other monomers capable of copolymerizing with (meth)acrylate can be selected. Among these, methyl methacrylate is preferred from the viewpoint of compatibility with (meth)acrylate resins and refractive index. In this case, the proportion of methyl methacrylate units in the crosslinked acrylic resin particles is preferably 80% by weight or more and 99% by weight or less.

[0130] The cross-linked acrylic resin particles also contain structural units derived from polyfunctional monomers having two or more polymerizable groups within the molecule. The proportion of polyfunctional monomer units in the cross-linked acrylic resin particles is preferably 0.5% by weight or more and 30% by weight or less.

[0131] When the refractive index of the (meth)acrylic resin is set to 100%, the refractive index of the crosslinked particles is preferably 98% or higher and 102% or lower, more preferably 99% or higher and 101% or lower. The refractive index of the crosslinked particles is preferably 1.47 or higher and 1.55 or lower, more preferably 1.47 or higher and 1.53 or lower, and even more preferably 1.48 or higher and 1.52 or lower. By using crosslinked particles with refractive indices within this range, it is likely to obtain (meth)acrylic resin films with high transparency. Crosslinked acrylic resin particles satisfying the above-mentioned refractive index are therefore preferred.

[0132] From the viewpoint of imparting anti-adhesion properties, the average particle size of the crosslinked particles is 1.0 μm or more and 2.5 μm or less, preferably 1.2 μm or more and 2.3 μm or less, and more preferably 1.5 μm or more and 2.3 μm or less. If the average particle size of the crosslinked particles is 1.0 μm or more, there is a tendency to form unevenness on the surface of the (meth)acrylic resin film, thus imparting anti-adhesion properties to the easily adhesive layer formed on the surface of the (meth)acrylic resin film. Furthermore, if the average particle size of the crosslinked particles is 2.5 μm or less, there is a tendency to not impair the surface smoothness of the optical film, thus maintaining the optical properties required for an optical film.

[0133] The content of crosslinked particles in the (meth)acrylic resin film, based on the weight of the (meth)acrylic resin film, is preferably 0.01% by weight or more and 1.0% by weight or less, more preferably 0.03% by weight or more and 0.7% by weight or less, even more preferably 0.05% by weight or more and 0.5% by weight or less, and particularly preferably 0.08% by weight or more and 0.4% by weight or less. If the content of crosslinked particles is 0.01% by weight or more, there is a tendency to obtain sufficient rollability. Furthermore, if the content of crosslinked particles is 1.0% by weight or less, there is a tendency to maintain the transparency of the (meth)acrylic resin film.

[0134] The ten-point average roughness Rzjis of the (meth)acrylic resin film surface is preferably 5 nm or more and 100 nm or less, more preferably 10 nm or more and 90 nm or less. If the ten-point average roughness Rzjis of the (meth)acrylic resin film surface is 5 nm or more, there is a tendency that when the optical film on which the easy-to-adhere layer is formed is rolled into a roll, even if the surface on the easy-to-adhere layer side overlaps with the surface on the opposite side of the easy-to-adhere layer, anti-adhesion properties can still be maintained. In addition, if the ten-point average roughness Rzjis of the (meth)acrylic resin film surface is 100 nm or less, there is a tendency that the unevenness formed on the surface will not become too large, which can prevent the influence on the transparency and other functions of the optical film, and when the optical film is rolled into a roll, damage and unevenness defects on the surface of the film can be prevented.

[0135] The ten-point average roughness Rzjis of the surface of (meth)acrylic resin film can be measured according to JIS B0601:2013 using an Evident LEXT OLS5100 laser microscope.

[0136] (additive)

[0137] (Meth)acrylic resin films may contain optional additives as needed. Examples of additives include, for instance, antioxidants; light stabilizers, weather stabilizers, heat stabilizers, and other stabilizers; UV absorbers, flame retardants, antistatic agents, fillers, plasticizers, lubricants, etc.

[0138] (Methods for manufacturing thin films)

[0139] There are no particular limitations on the manufacturing method of (meth)acrylic resin films; injection molding, melt extrusion molding, blow molding, blow molding, compression molding, and other methods can be used. Alternatively, solution casting and spin coating methods can be employed, where the (meth)acrylic resin is dissolved in a solvent before molding. Among these, solvent-free melt extrusion is preferred. Melt extrusion reduces manufacturing costs and minimizes the environmental and work environment impacts of solvents.

[0140] The following describes an example of manufacturing (meth)acrylic resin films using melt extrusion. It should be noted that, in the following description, films obtained by melt extrusion will be referred to as "melt extruded films" to distinguish them from films obtained by other methods such as solution casting.

[0141] When manufacturing (meth)acrylic resin films by melt extrusion, the (meth)acrylic resin is first fed into an extruder and heated to melt.

[0142] (Meth)acrylic resins are preferably pre-dried before being fed to the extruder. This pre-drying prevents foaming of the resin extruded from the extruder. The pre-drying method is not particularly limited; for example, the raw material ((meth)acrylic resin, etc.) can be prepared into granules or similar forms and dried using a hot air dryer, vacuum dryer, or the like.

[0143] Next, the (meth)acrylic resin, which has been heated and melted in the extruder, is fed into the T-die via a gear pump, a filter, etc. If a gear pump is used, the extrusion rate of the (meth)acrylic resin tends to become more uniform, reducing film thickness unevenness along its length. On the other hand, if a filter is used, foreign matter in the (meth)acrylic resin can be removed, resulting in a defect-free (meth)acrylic resin film with excellent appearance.

[0144] Next, the (meth)acrylic resin supplied to mold T is extruded from mold T as molten resin in sheet form. Then, the molten resin sheet is clamped and cooled using two cooling rollers to form a film.

[0145] Preferably, the two cooling rollers used to hold the sheet-like molten resin are: one a rigid metal roller with a smooth surface, and the other a flexible roller with a smooth surface and an elastically deformable metal outer cylinder. By using the rigid metal roller and the flexible roller with the elastic metal outer cylinder to hold the sheet-like molten resin and cool it to form a film, minor surface irregularities, die lines, etc., can be corrected, and a film with a smooth surface and a thickness of less than 5 μm with non-uniformity can be obtained. It should be noted that in this specification, the term "cooling roller" is used in a sense that includes "contact roller".

[0146] Even when using rigid metal rollers and flexible rollers, since the surface of any cooling roller is metal, if the produced film is thin, there is a risk of damage to the outer surface of the cooling rollers due to contact between their surfaces, or even breakage of the cooling rollers themselves. Therefore, when using two cooling rollers to hold a sheet of molten resin and form a film, it is preferable to first use two cooling rollers to hold and cool the sheet of molten resin, temporarily obtaining a preform film with a relatively thick thickness, and then perform uniaxial or biaxial stretching on the preform film to produce a film of a specified thickness. For example, when producing a film with a thickness of 40 μm, it is preferable to first use two cooling rollers to hold and cool the sheet of molten resin, temporarily obtaining a preform film with a thickness of 150 μm, and then stretch the preform film by longitudinal and transverse biaxial stretching to produce a film with a thickness of 40 μm.

[0147] In this way, when the (meth)acrylic resin film is a stretched film, it is possible to manufacture a stretched film by molding the (meth)acrylic resin into a preform film in an unstretched state and then performing uniaxial or biaxial stretching.

[0148] To improve the bending resistance of (meth)acrylic resin films in both the length direction (MD direction) and width direction (TD direction), biaxial stretching is preferred.

[0149] In this specification, for ease of explanation, the film formed from (meth)acrylic resin before stretching, i.e., the unstretched film, is referred to as the "preform film".

[0150] When stretching a preform film, the stretching can be performed continuously immediately after the preform film is formed, or the preform film can be temporarily stored or moved after it is formed and then stretched.

[0151] It should be noted that when stretching the preform film immediately after it has been formed, even for a very short time during the film manufacturing process, it is sufficient for the preform film to maintain a sufficiently thin film shape for stretching; it does not need to be in a fully formed film state. Furthermore, the preform film may not possess the properties of a finished film.

[0152] (Thin film stretching methods)

[0153] There are no particular limitations on the method for stretching the preform film; any known stretching method can be used. For example, transverse stretching based on a tenter frame, longitudinal stretching based on rollers, and sequential biaxial stretching obtained by combining them one by one can be used. Alternatively, a method of simultaneous biaxial stretching in both longitudinal and transverse directions can be used, or a method of longitudinal stretching using rollers followed by transverse stretching using a tenter frame can be used.

[0154] When stretching the preform film, it is preferable to temporarily preheat the preform film to a temperature 0.5°C to 5°C, preferably 1°C to 3°C, higher than the stretching temperature, then cool it to the stretching temperature and stretch it. By preheating within the above range, there is a tendency to maintain the thickness of the preform film in the width direction with good accuracy, and to suppress the reduction of thickness accuracy or unevenness of the stretched film. Furthermore, there is a tendency to prevent the preform film from sticking to the roller or loosening due to its own weight.

[0155] There is no particular limitation on the stretching temperature when stretching the preform film; it can be appropriately determined based on the required mechanical strength, surface properties, and thickness accuracy of the stretched film. Generally, when the glass transition temperature ((meth)acrylic resin composition) of the preform film (determined by DSC) is set as Tg, it is preferably set to a temperature range of (Tg-30℃) to (Tg+30℃), more preferably to a temperature range of (Tg-20℃) to (Tg+30℃), even more preferably to a temperature range of (Tg) to (Tg+30℃), and particularly preferably to a temperature range of (Tg+10℃) to (Tg+30℃). If the stretching temperature is within the above temperature range, there is a tendency to reduce the thickness unevenness of the resulting stretched film, thereby resulting in good mechanical properties such as elongation, tear propagation strength, and MIT bending resistance. In addition, there is a tendency to prevent defects such as film adhesion to rollers.

[0156] There is no particular limitation on the stretching ratio when stretching the preform film; it can be appropriately determined based on the mechanical strength, surface properties, and thickness accuracy of the stretched film. It also depends on the stretching temperature. The stretching ratio is generally preferably selected in the range of 1.1 to 3 times, more preferably in the range of 1.3 to 2.5 times, and even more preferably in the range of 1.5 to 2.3 times. If the stretching ratio is within the above range, there is a tendency to significantly improve the film's elongation, tear propagation strength, and resistance to tumbling fatigue. Therefore, it is possible to manufacture stretched films with a thickness not uniformly below 5 μm and an internal haze of less than 1.0%.

[0157] When (meth)acrylic resin films contain crosslinked elastomers, unstretched films, uniaxially stretched films, and biaxially stretched films can all be used appropriately from the perspective of excellent mechanical strength.

[0158] The smaller the phase difference value of the (meth)acrylic resin film, the better. Preferably, the in-plane phase difference Δnd is less than 5.0 nm and the thickness direction phase difference Rth is less than 20.0 nm. More preferably, Δnd is less than 2.0 nm and Rth is less than 5.0 nm. Even more preferably, Δnd is less than 1.0 nm and Rth is less than 3.0 nm.

[0159] The thickness of the (meth)acrylic resin film is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less. If the thickness of the (meth)acrylic resin film is 5 μm or more, there is a tendency to obtain sufficient strength. In addition, if the thickness of the (meth)acrylic resin film is 200 μm or less, there is a tendency to suppress the reduction of transparency and the reduction of the drying properties of the adhesive solvent (water, etc.), and it is also possible to thin the optical film.

[0160] The wetting tension of the (meth)acrylic resin film is preferably 40 mN / m or more, more preferably 50 mN / m or more. To improve the surface wetting tension, corona discharge treatment, plasma treatment, ozone treatment, ultraviolet irradiation, flame treatment, chemical treatment, etc., can be performed. Among these, corona discharge treatment and plasma treatment are preferred.

[0161] [Easy-to-adhere layer]

[0162] By forming an easy-adhesive layer on the surface of a (meth)acrylic resin film, the adhesion to the polarizing element is significantly improved. The easy-adhesive layer is formed by coating an easy-adhesive layer forming composition onto the surface of a (meth)acrylic resin film with an uneven surface created by mixing cross-linked particles and then drying it. As a result, the surface of the easy-adhesive layer formed on the surface of the (meth)acrylic resin film also exhibits an uneven surface, achieving anti-adhesion properties (see reference). Figure 1 ).

[0163] The content of lubricating particles in the easy-to-adhesive layer is 0.1% by weight or less. Lubricating particles, such as silica particles, tend to aggregate in the composition for forming the easy-to-adhesive layer. Therefore, it is sometimes difficult to uniformly distribute the lubricating particles on the surface of the (meth)acrylic resin film, thus failing to fully exert the anti-blocking properties. Furthermore, the aggregation of lubricating particles can sometimes affect the transparency and other functions of the optical film. Therefore, the content of lubricating particles, such as silica particles, in the composition for forming the easy-to-adhesive layer is set to 0.1% by weight or less, and more preferably, it is absent. It should be noted that lubricating particles refer to particles that impart anti-blocking properties.

[0164] The content of lubricating particles in the easy-to-adhere layer can be determined by, for example, by observing with a transmission electron microscope (TEM) to determine the number concentration, preparing several easy-to-adhere layers with a number concentration close to that, plotting a standard curve and performing calculations to obtain the content.

[0165] Compositions for forming an easy-to-adhesive layer for coating the surface of (meth)acrylic resin films include aqueous and organic compositions. From an environmental and workability perspective, aqueous compositions are preferred. From the viewpoints of dispersibility and solubility, a small amount of organic solvent may be included. As the organic solvent, alcohol-based, ketone-based, ester-based, and ether-based solvents are preferred, considering compatibility with water and ease of handling.

[0166] The easy-adhesive layer can be formed using known techniques described in Japanese Patent Application Publication Nos. 2009-193061 and 2010-55062. For example, it can be formed using a composition for forming an easy-adhesive layer comprising a urethane resin having carboxyl groups and a crosslinking agent. By using a urethane resin, an easy-adhesive layer with excellent adhesion to polarizing elements can be obtained.

[0167] Before applying the composition for forming an easy-to-adhere layer, it is preferable to pre-treat the surface of the (meth)acrylic resin film with corona discharge treatment, plasma treatment, or the like.

[0168] The coating method for the composition used to form the easy-to-adhere layer can be any suitable method. For example, rod coating, roller coating, gravure coating, bar coating, slotted mesh coating, curtain coating, jet coating, etc.

[0169] The drying temperature of the composition for forming the easy-to-adhesive layer is preferably 50°C or higher, more preferably 80°C or higher.

[0170] The Young's modulus of the easy-to-adhesive layer is not particularly limited, but is, for example, set to 0.005 GPa or more and 2.5 GPa or less. Preferably, the Young's modulus of the easy-to-adhesive layer is 1.0 GPa or more and 2.5 GPa or less. Generally, if the Young's modulus of the easy-to-adhesive layer is less than 1.0 GPa, there is a tendency for the static friction coefficient between the (meth)acrylic resin film and the easy-to-adhesive layer to increase, resulting in poor anti-adhesion properties. Regarding this, in the optical film described in this embodiment, since the (meth)acrylic resin film contains cross-linked particles with an average particle size of 1.0 μm or more and 2.5 μm or less, good anti-adhesion properties can be achieved even when an easy-to-adhesive layer with a low Young's modulus is formed.

[0171] The Young's modulus of the easy-to-adhesive layer can be determined as follows: a film of the composition for forming only the easy-to-adhesive layer is prepared such that the dried thickness of the film is 100 μm, and the film is measured by tensile testing in accordance with JIS K 7161-2:2014.

[0172] The ten-point average roughness Rzjis of the surface of the easy-to-adhesive layer is preferably 18 nm or more and 100 nm or less, more preferably 30 nm or more and 90 nm or less. If the ten-point average roughness Rzjis of the surface of the easy-to-adhesive layer is 18 nm or more, there is a tendency for the surface of the easy-to-adhesive layer to become sufficiently uneven, thus exhibiting anti-adhesion properties. In addition, if the ten-point average roughness Rzjis of the surface of the easy-to-adhesive layer is 100 nm or less, there is a tendency for the unevenness formed on the surface to not be too large, thus preventing any impact on the transparency and other functions of the optical film, and preventing damage or unevenness defects on the surface of the film when the optical film is rolled into a roll.

[0173] The ten-point average roughness Rzjis of the surface of the easily bonded layer can be measured according to JIS B 0601:2013 using an Evident LEXT OLS5100 laser microscope.

[0174] The sum of the ten-point average roughness Rzjis of the surface of the easy-to-adhere layer and the ten-point average roughness Rzjis of the surface of the (meth)acrylic resin film on the opposite side of the easy-to-adhere layer is 23 nm or more and 200 nm or less, preferably 30 nm or more and 90 nm or less. If the sum of Rzjis is 23 nm or more, there is a tendency to ensure slipability. In addition, if the sum of Rzjis is 200 nm or less, there is a tendency to prevent external haze caused by surface unevenness, thus preventing the deterioration of transparency.

[0175] The thickness of the easy-to-adhesive layer is preferably 50 nm or more and 600 nm or less. If the thickness of the easy-to-adhesive layer is 50 nm or more, there is a tendency for the strength of the easy-to-adhesive layer to be increased and for the adhesion to be improved. On the other hand, if the thickness of the easy-to-adhesive layer is 600 nm or less, there is a tendency for the easy-to-adhesive layer to smooth out the unevenness caused by cross-linking particles contained in the (meth)acrylic resin film, thereby ensuring anti-blocking properties.

[0176] [use]

[0177] The optical thin film described in this embodiment is preferably a functional thin film used in various display devices and touch panels, such as liquid crystal displays, plasma displays, and organic EL displays. Specifically, the optical thin film described in this embodiment can be a polarizer protection film, phase retardation film, anti-reflection film, brightness enhancement film, hard coating film, anti-glare film, antistatic film, optical compensation film for widening the field of view, etc., used in liquid crystal display devices.

[0178] Example

[0179] The present invention will now be described in more detail with reference to embodiments, but the present invention is not limited to the following embodiments.

[0180] The methods for measuring various physical properties, etc., described in the examples are as follows.

[0181] (Calculation of the proportion of glutarimide units)

[0182] The proportion of glutarimide units in the (meth)acrylic resin (resin 1) was calculated as follows. First, the (meth)acrylic resin was analyzed using a nuclear magnetic resonance (NMR) apparatus (Bruker, AVANCEIII 400MHz). 1¹H-NMR determination was performed. The molar ratio was calculated based on the peak area A (near 3.5 ppm to 3.8 ppm) originating from the O-CH₃ protons constituting methyl methacrylate and the peak area B (near 3.0 ppm to 3.3 ppm) originating from the N-CH₃ protons constituting the glutarimide ring. The proportion of glutarimide units was then calculated by weight conversion of this molar ratio.

[0183] (Conversion rate)

[0184] The conversion rate is calculated based on the ratio of the solid component weight of the (meth)acrylic resin to the weight of the fed monomer after drying in an oven at 150°C for 30 minutes, i.e., the formula: ((meth)acrylic resin solid component weight) × 100 / (feed monomer weight).

[0185] (The regularity of isotopic representation of ternary units)

[0186] The synthetic isotactic regularity (rr) of the ternary unit group of (meth)acrylic resin (resin 2) was calculated as follows. First, the (meth)acrylic resin was subjected to nuclear magnetic resonance (NMR) testing in a deuterated chloroform solution at 22°C for a cumulative total of 16 times using a Bruker AVANCEIII 400MHz instrument. 1 ¹H-NMR determination. Based on the spectrum, the area (X) of the region from 0.60 ppm to 0.95 ppm and the area (Y) of the region from 0.60 ppm to 1.25 ppm when tetramethylsilane (TMS) is set to 0 ppm were measured. Then, the syndiotactic regularity (rr) represented by the ternary unit was calculated using the formula: (X / Y)×100.

[0187] (weight-average molecular weight, number-average molecular weight, and dispersity)

[0188] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersity (Mw / Mn) of the (meth)acrylic resin (resin 2) were calculated using the standard polystyrene conversion method via gel permeation chromatography (GPC). Specifically, the analysis was performed using a sample solution prepared by dissolving 20 mg of the (meth)acrylic resin in 10 mL of tetrahydrofuran, under the following apparatus and conditions.

[0189] Measurement equipment: HLC-8220GPC (manufactured by Tosoh Corporation)

[0190] Detector: RI detector

[0191] Eluent: Tetrahydrofuran

[0192] Protective column: TSKgel guardcolumn SuperHL (manufactured by Tosoh Corporation)

[0193] Analytical column: A column consisting of TSKgel SuperH5000, SuperH4000, SuperH3000 and SuperH2000 (all manufactured by Tosoh Corporation) connected in series.

[0194] Eluent flow rate: 0.60 mL / min

[0195] Measurement temperature: 40℃

[0196] Standard reference material: Standard polystyrene (manufactured by Tosoh Corporation)

[0197] (Glass transition temperature)

[0198] The glass transition temperature was determined using a differential scanning calorimeter (DSC7000X, Hitachi Advanced Scientific Corporation) at a heating rate of 20 °C / min under a nitrogen atmosphere, and the midpoint method was employed.

[0199] (Young's modulus)

[0200] Young's modulus was determined by preparing a film of the composition for forming the easy-to-adhesive layer using a tensile test according to JIS K7161-2:2014. The film preparation of the composition for forming the easy-to-adhesive layer was carried out by: pouring an aqueous dispersion of polyurethane into a glass container to a dried film thickness of 100 μm, allowing it to stand at room temperature for 24 hours, then drying it at 50°C for 3 hours and at 120°C for 20 minutes.

[0201] (Surface roughness)

[0202] Surface roughness was measured according to JIS B 0601:2013 using an Evident LEXTOLS 5100 laser microscope. A confocal image of the thin film measuring 257 μm × 257 μm was acquired using a 50x objective lens with 0.95 apertures. Next, three evaluation lines were drawn at equal intervals along both the MD and TD directions to extract roughness curves. Based on the obtained roughness curves, the ten-point average roughness Rzjis was calculated using analysis software, and the average value at each measurement location was calculated. The measurement was performed five times at different locations, and the average value was used as the surface roughness. Local anomalies such as damage clearly identified in the images were not used as measurement values; the abnormal areas were avoided, and the measurement was repeated.

[0203] (Coefficient of static friction)

[0204] The static friction coefficient was determined according to JIS K 7125:1999. A diaphragm sheet was fixed to a smooth stainless steel plate, and another diaphragm sheet was attached to a 60mm × 60mm slider weighing 200g using double-sided tape. Then, a force sensor was used to read the load when the slider moved at a speed of 20mm / min with the aid of a pulley, and the static friction coefficient was calculated. The measurement was performed five times by changing the diaphragm sheet, and the average value was calculated.

[0205] (Adhesion test)

[0206] Ten 100mm x 100mm film sheets were arranged with the substrate ((meth)acrylic resin film) side surface in contact with the easy-to-adhere layer side surface, and 1kg of pressure was applied from above. The sheets were then placed at 60°C for 2 hours. Afterward, they were allowed to cool naturally at 23°C for 1 hour. The film condition was visually checked, and the films were peeled off by hand. The following criteria were used for evaluation.

[0207] -Evaluation Criteria-

[0208] A: No adhesion between the thin films can be observed.

[0209] B: The films are fixed to each other.

[0210] C: The films are firmly attached to each other, resulting in peeling marks.

[0211] <Manufacturing Example 1: Manufacturing of (meth)acrylic resins>

[0212] As the extruder, a 40mm diameter, co-rotating twin-screw extruder (L / D = 90) was used. The temperature settings of each temperature control zone of the extruder were set to 250°C–280°C, and the screw speed was set to 85 rpm. After the polymethyl methacrylate resin was melted and filled using a kneading block, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical Co., Ltd.) relative to 100 parts by weight of the polymethyl methacrylate resin was injected. The resin extruded from the die located at the extruder outlet in the form of strands was cooled in a water bath and then granulated using a granulator to obtain resin (I). Next, the temperature settings of each temperature control zone of the 40mm diameter, co-rotating twin-screw extruder were set to 240°C–260°C, and resin (I) was supplied from the hopper. 0.56 parts by weight of dimethyl carbonate relative to 100 parts by weight of the polymethyl methacrylate resin was injected from the nozzle to reduce the carboxyl groups in resin (I). Furthermore, the byproducts and excess dimethyl carbonate after the reaction are removed. The resin extruded from the die located at the extruder outlet in the form of a strand is cooled in a water bath and then granulated using a granulator to obtain a (meth)acrylic resin having a glutarimide structure in the main chain. The glass transition temperature of the obtained (meth)acrylic resin is 123°C, and the proportion of glutarimide units in the (meth)acrylic resin is 6% by weight. Hereinafter, the (meth)acrylic resin obtained in Manufacturing Example 1 will be referred to as "Resin 1".

[0213] <Manufacturing Example 2: Manufacturing of (meth)acrylic resins>

[0214] 150 parts by weight of deionized water, 0.20 parts by weight of tricalcium phosphate as a dispersant, 0.0075 parts by weight of sodium α-olefin sulfonate, and 0.30 parts by weight of sodium chloride were added to a 4L glass reactor equipped with an H-type stirring blade. Then, under a nitrogen atmosphere, while stirring at 250 rpm, 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) (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., V-601) as a polymerization initiator were added to the reactor. The liquid temperature in the reactor was then raised to 70°C and polymerization was initiated. Two hours after the start of polymerization, 0.10 parts by weight of tricalcium phosphate were added to the reactor. At this point, an exothermic peak associated with the gelation effect was observed 4 hours and 20 minutes after the start of polymerization. Next, heating was initiated 7 hours after the start of polymerization, raising the liquid temperature in the reactor to 95°C. It should be noted that the conversion rate after 7 hours was 93%. Then, 2 hours after the liquid temperature in the reactor reached 95°C, the liquid temperature was cooled to room temperature, ending the polymerization and yielding a (meth)acrylic acid resin dispersion. It should be noted that the conversion rate at the end of polymerization was 99%.

[0215] The (meth)acrylic resin dispersion was acid-washed using 1 equivalent of hydrochloric acid (0.1 times the weight of the fed monomers) followed by water washing to remove the dispersant. The washed (meth)acrylic resin dispersion was then dehydrated and dried to obtain bead-like (meth)acrylic resin. The obtained (meth)acrylic resin had a glass transition temperature of 120°C, a syndiotactic regularity of 57% (represented by ternary units), a weight-average molecular weight (Mw) of 83,000, a dispersion ratio (Mw / Mn) of 1.63, and a methyl methacrylate unit proportion of 100% by weight. Hereinafter, the (meth)acrylic resin obtained in Manufacturing Example 2 will be referred to as "Resin 2".

[0216] <Example 1>

[0217] Using a 15mm diameter, co-rotating twin-screw extruder (L / D = 45), a mixture containing 79.9 parts by weight of resin 1 manufactured in Example 1, 20 parts by weight of methyl methacrylate-styrene copolymer (manufactured by Toyo Styrene Co., MS-750; hereinafter referred to as "resin 3") with a styrene unit ratio of 25% by weight, and 0.1 parts by weight of cross-linked acrylic resin particles (manufactured by Negami Kogyo Co., J-4PY, refractive index: 1.50; hereinafter referred to as "particle 1") with an average particle size of 2.2 μm, was kneaded. After the resin extruded from the die located at the extruder outlet in the form of strands was cooled in a water bath, it was granulated using a granulator to obtain a (meth)acrylic resin composition (refractive index: 1.49).

[0218] After drying the obtained (meth)acrylic resin composition at 100°C for 5 hours, film was formed using a co-rotating twin-screw extruder (L / D = 45) with a 15mm diameter T-die at the extruder outlet. The sheet-like molten resin extruded from the T-die at the extruder outlet was cooled with cooling rollers to obtain a preform film with a width of 160mm and a thickness of 160μm. The surface in contact with the casting rollers is defined as surface B, and the other surface as surface A. The glass transition temperature of the preform film is 123°C.

[0219] Corona discharge treatment was applied to the B side of the preform film (corona discharge electron irradiation dose: 100W / m). 2 / min). 5g of a carboxyl-based aqueous urethane resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., SUPERFLEX 210, solids content: 35%) and 1g of a crosslinking agent (manufactured by Nippon Shokubai Co., Ltd., epocros WS700, solids content: 25%) were added to 26g of pure water and stirred for 3 minutes to prepare an easy-to-adhere layer forming composition. Using a rod coater (wire number #10), the obtained easy-to-adhere layer forming composition was coated onto the corona-treated surface of a preform film that had undergone corona discharge treatment. Subsequently, the preform film was placed in a hot air dryer (100°C) and dried for 3 minutes to obtain an easy-to-adhere treated film.

[0220] For the obtained easily bondable film, an optical film was fabricated by simultaneously biaxially stretching the film at a stretch ratio of 2 (longitudinal and transverse) and a temperature of 145°C using a biaxial stretching apparatus (IMC-1905 manufactured by Imoto Co., Ltd.).

[0221] <Example 2>

[0222] The type of aqueous urethane resin used to form the easily bondable layer was changed, but otherwise the optical film was prepared in the same manner as in Example 1.

[0223] <Example 3>

[0224] The type of aqueous urethane resin used to form the easily bondable layer was changed, but otherwise the optical film was prepared in the same manner as in Example 1.

[0225] <Example 4>

[0226] A preform film was prepared using a (meth)acrylic resin composition containing 1:99.9 parts by weight of resin and 1:0.1 parts by weight of particles. Otherwise, an optical film was prepared in the same manner as in Example 3.

[0227] <Example 5>

[0228] Resin 3 was replaced with an acrylonitrile-styrene copolymer (manufactured by Shin-Kakusho Co., AS-61NT7200; hereinafter referred to as "resin 4") with a styrene unit ratio of 74% by weight and a colorant added. Otherwise, the optical film was prepared in the same manner as in Example 3.

[0229] <Example 6>

[0230] The optical film was fabricated by replacing resin 1 with resin 2, but otherwise proceeding in the same manner as in Example 3.

[0231] <Example 7>

[0232] Particle 1 was replaced with cross-linked acrylic resin particles (manufactured by Negami Kogyo Co., Ltd., J-3PY, refractive index: 1.50; hereinafter referred to as "particle 2") with an average particle size of 1.2 μm. Otherwise, the optical film was prepared in the same manner as in Example 3.

[0233] <Example 8>

[0234] The optical thin film was fabricated by changing particle 1 to particle 2, otherwise proceeding in the same manner as in Example 4.

[0235] <Example 9>

[0236] The optical thin film was fabricated by changing particle 1 to particle 2, otherwise proceeding in the same manner as in Example 5.

[0237] <Example 10>

[0238] The optical thin film was fabricated by changing particle 1 to particle 2, otherwise proceeding in the same manner as in Example 6.

[0239] <Comparative Example 1>

[0240] Particle 1 was replaced with cross-linked acrylic resin particles (manufactured by Soken Chemical Co., Ltd., MX80H3wT, refractive index: 1.49; hereinafter referred to as "particle 3") with an average particle size of 0.8 μm. Otherwise, the same procedure as in Example 3 was followed to prepare an optical thin film.

[0241] <Comparative Example 2>

[0242] Particle 1 was replaced with cross-linked acrylic resin particles (manufactured by Sekisui Chemicals Co., Ltd., xx-6390Z, refractive index: 1.49; hereinafter referred to as "particle 4") with an average particle size of 0.15 μm. Otherwise, the optical film was prepared in the same manner as in Example 3.

[0243] <Comparative Example 3>

[0244] The optical thin film was fabricated by changing particle 1 to particle 4, otherwise proceeding in the same manner as in Example 4.

[0245] <Comparative Example 4>

[0246] The optical thin film was fabricated by changing particle 1 to particle 4, otherwise proceeding in the same manner as in Example 5.

[0247] <Comparative Example 5>

[0248] The optical thin film was fabricated by changing particle 1 to particle 4, otherwise proceeding in the same manner as in Example 1.

[0249] <Comparative Example 6>

[0250] The type of aqueous urethane resin used to form the easily bondable layer was changed, but otherwise the optical film was prepared in the same manner as in Comparative Example 3.

[0251] <Comparative Example 7>

[0252] The type of aqueous urethane resin used to form the easily bondable layer was changed, but otherwise the optical film was prepared in the same manner as in Comparative Example 4.

[0253] The values ​​of glass transition temperature, Young's modulus, surface roughness, and static friction coefficient obtained by the above method are shown together with the evaluation results based on the adhesion test in Tables 1 and 2.

[0254] The resins that form the easy-to-adhere layer are shown in Tables 1 and 2.

[0255] Resin A: urethane resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., SUPERFLEX 210) and crosslinking agent (manufactured by Nippon Shokubai Co., Ltd., EPOCROS WS700)

[0256] Resin B: Carbamate resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., SUPERFLEX 870)

[0257] Resin C: Carbamate resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., SUPERFLEX 460S) [Table 1]

[0258]

[0259] [Table 2]

[0260]

[0261] As shown in Tables 1 and 2, in Examples 1 to 10, a suitable unevenness is formed on the surface of the easy-to-adhere layer, which provides an appropriate surface roughness. Therefore, when the optical film is rolled into a roll, the coefficient of friction between the substrate surface and the easy-to-adhere layer surface can be reduced. Thus, based on the evaluation results in Tables 1 and 2, it can be confirmed that it possesses anti-adhesion properties.

Claims

1. An optical film comprising a (meth)acrylic resin film and an easy-to-adhere layer formed on the (meth)acrylic resin film, wherein the (meth)acrylic resin film is composed primarily of (meth)acrylic resin and contains cross-linked particles, and the optical film satisfies the following conditions: (i) The glass transition temperature of the (meth)acrylic resin film is above 120°C. (ii) The average particle size of the cross-linked particles is greater than 1.0 μm and less than 2.5 μm. (iii) The content of lubricating particles in the easily bondable layer is less than 0.1% by weight. (iv) The sum of the ten-point average roughness Rzjis of the surface of the easy-to-adhere layer and the ten-point average roughness Rzjis of the surface of the (meth)acrylic resin film on the opposite side of the easy-to-adhere layer is 23 nm or more and 200 nm or less.

2. An optical film comprising a (meth)acrylic resin film and an easy-to-adhere layer formed on the (meth)acrylic resin film, wherein the (meth)acrylic resin film is composed primarily of (meth)acrylic resin and contains cross-linked particles, and the optical film satisfies the following conditions: (i) The (meth)acrylic resin film comprises methyl methacrylate units in a proportion of 98% or more and has a syndiotactic regularity of 54% or more in the form of tripartite groups. (ii) The average particle size of the cross-linked particles is greater than 1.0 μm and less than 2.5 μm. (iii) The content of lubricating particles in the easily bondable layer is less than 0.1% by weight. (iv) The sum of the ten-point average roughness Rzjis of the surface of the easy-to-adhere layer and the ten-point average roughness Rzjis of the surface of the (meth)acrylic resin film on the opposite side of the easy-to-adhere layer is 23 nm or more and 200 nm or less.

3. The optical thin film according to claim 1 or 2, wherein, The thickness of the easy-to-adhere layer is above 50 nm and below 600 nm.

4. The optical thin film according to claim 1 or 2, wherein, When two optical films are overlapped in such a manner that the (meth)acrylic resin film is in contact with the easy-to-adhere layer, the static friction coefficient, as measured according to JIS K 7125:1999, is 0.3 or more and 2.0 or less.

5. The optical thin film according to claim 1, wherein, The (meth)acrylic resin film comprises a (meth)acrylic resin with a ring structure in the main chain.

6. The optical thin film according to claim 5, wherein, The ring structure is selected from at least one of the following groups: glutarimide structure, lactone ring structure, maleic anhydride structure, N-substituted maleimide structure, and glutaric anhydride structure.

7. The optical thin film according to claim 5, wherein, The (meth)acrylic resin having a ring structure in the main chain comprises the structural unit shown in the following general formula (1). In equation (1), R 1 and R 2 Each independently represents an alkyl group having 1 to 8 hydrogen atoms or carbon atoms; R 3 It represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

8. The optical thin film according to claim 7, wherein, The proportion of the structural unit of general formula (1) in the (meth)acrylic resin having a ring structure in the main chain is more than 2% by weight and less than 30% by weight.

9. The optical thin film according to claim 1, wherein, The (meth)acrylic resin film contains 98% by weight or more of methyl methacrylate units and has a syndiotactic regularity of 54% or more in the form of terunit groups.

10. The optical thin film according to claim 1 or 2, wherein, The (meth)acrylic resin film contains aromatic vinyl units.

11. The optical thin film according to claim 5 or 9, wherein, The (meth)acrylic resin film also contains copolymers comprising aromatic vinyl units.

12. The optical thin film according to claim 11, wherein, The copolymer also contains (meth)acrylate units or (meth)acrylonitrile units.

13. The optical thin film according to claim 1 or 2, wherein, The copolymer containing aromatic vinyl units in the (meth)acrylic resin film contains more than 0% by weight and less than 30% by weight.

14. A composition for forming an easy-adhesive layer, used to form an easy-adhesive layer on a (meth)acrylic resin film. The (meth)acrylic resin film uses (meth)acrylic resin as the main component, contains cross-linked particles with an average particle size of 1.0 μm or more and 2.5 μm or less, and has a glass transition temperature of 120°C or more. The content of lubricating particles in the composition for forming the easy-to-adhesive layer is less than 0.1% by weight.

15. A composition for forming an easy-adhesive layer, used to form an easy-adhesive layer on a (meth)acrylic resin film. The (meth)acrylic resin film uses (meth)acrylic resin as the main component and contains cross-linked particles with an average particle size of 1.0 μm or more and 2.5 μm or less. The (meth)acrylic resin film comprises (meth)acrylic resin with a methyl methacrylate unit content of 98% or more and a syndiotactic regularity of 54% or more in the form of tripartite groups. The content of lubricating particles in the composition for forming the easy-to-adhesive layer is less than 0.1% by weight.

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