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

Abstract

Provided is an acrylic resin film having an acrylic resin as the main component, the acrylic resin film having a glass transition temperature of 120 DEG C or higher, the sum of 10-point average roughness Rzjis on each of both surfaces of the acrylic resin film being 0.05-1.0 [mu] m, the static friction coefficient between one surface and the other surface being 0.8 or less, and the thickness of the acrylic resin film being 0.5-5 [mu] m. And an internal haze of 1.0% or less.

Description

Technical Field

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

[0002] Liquid crystal display devices typically use two polarizing plates on either side of the liquid crystal cell. These plates typically have a polarizer protective film attached to both sides of the polarizer with an adhesive to protect the polarizer. High transparency is required for polarizer protective films, and optical films made of cellulose materials are often used.

[0003] To improve durability, optical films made of acrylic resins and norbornene resins have been proposed as polarizer protective films. However, when these optical films are wound into rolls, they come into contact with each other, which can easily cause wrinkles and wrinkle marks. To address this issue, methods have been proposed that improve the windability (sliding properties) of the roll by adding microparticles such as silica particles to norbornene resin films (Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 074513 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] While the method described in Patent Document 1 can be used to address wrinkles and wrinkle marks during winding, the present inventors' research has revealed that, as film quality improves with the increasing resolution and size of liquid crystal display panels, defects can arise due to, for example, tightness during film roll storage. Furthermore, the present inventors have attempted to address this issue by adding silica to acrylic resin films using the method described in Patent Document 1. However, this conventional method, however, resulted in increased haze and difficulty meeting the requirements for acrylic resin films.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to suppress blocking during storage of an acrylic resin film roll while maintaining the heat resistance and transparency of the film.

[0010] Solutions for solving problems

[0011] The present inventors have conducted intensive studies to solve the above-mentioned problems and have consequently completed the present invention.

[0012] That is, one embodiment of the present invention relates to the following.

[0013] [1] An acrylic resin film comprising acrylic resin as a main component,

[0014] The glass transition temperature of the acrylic resin film is 120° C. or higher.

[0015] The acrylic resin film has a sum of 10-point average roughness Rzjis of 0.05 μm to 1.0 μm on both sides, a static friction coefficient of 0.8 or less between one side and the other side, and an internal haze of 1.0% or less.

[0016] [2] The acrylic resin film according to [1], wherein the 10-point average roughness Rzjis of one surface and / or the other surface of the acrylic resin film exceeds 0.080 μm and is 0.25 μm or less.

[0017] [3] The acrylic resin film according to [1] or [2], wherein the acrylic resin contains at least one ring structure selected from the group consisting of a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure.

[0018] [4] The acrylic resin film according to [1] or [2], wherein the syndiotacticity expressed by triads of the acrylic resin is 54% or more.

[0019] [5] The acrylic resin film according to any one of [1] to [4], wherein the acrylic resin film contains an anti-blocking agent, and the anti-blocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm to 2.5 μm.

[0020] [6] The acrylic resin film according to [5], wherein the anti-blocking agent comprises acrylic cross-linked particles having an average particle size of 0.1 μm to 2.0 μm.

[0021] [7] The acrylic resin film according to [5] or [6], wherein the acrylic resin film contains 0.05 wt % or more and 0.9 wt % or less of acrylic crosslinked particles.

[0022] [8] The acrylic resin film according to any one of [1] to [7], wherein the dimensional change rate thereof when left to stand in an atmosphere of 85° C. and 85% RH for 120 hours is from −2.0% to −0.1%.

[0023] [9] A polarizing plate comprising the acrylic resin film according to any one of [1] to [8].

[0024]

[10] A liquid crystal display panel comprising the polarizing plate described in [9].

[0025] Effects of the Invention

[0026] According to the present invention, it is possible to provide an acrylic resin film which is excellent in transparency and heat resistance and can prevent blocking during storage of a film roll. DETAILED DESCRIPTION

[0027] An embodiment of the present invention is described, but the present invention is not limited thereto. The present invention is not limited to the various structures described below, and various changes can be made within the scope indicated in the claims. The 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. In addition, all academic documents and patent documents described in this specification are cited as references in this specification. It should be noted that in this specification, unless otherwise specified, "A to B" indicating a numerical range refers to "above A (including A and greater than A) and below B (including B and less than B)".

[0028] (Acrylic resin film)

[0029] The acrylic resin film of this embodiment is characterized by comprising an acrylic resin as a primary component, having a glass transition temperature of 120°C or higher, a sum of 10-point average roughness Rzjis of 0.14 μm to 1.0 μm on both sides of the acrylic resin film, a static friction coefficient of 0.8 or less between one side and the other side, and an internal haze of 1.0% or less. Thus, by comprising an acrylic resin as a primary component, controlling the sum of Rzjis and the static friction coefficient on both sides of the film to predetermined values, and further controlling the internal haze to predetermined values, an acrylic resin film having excellent heat resistance and transparency, as well as excellent blocking resistance during film roll storage, can be obtained.

[0030] 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. A glass transition temperature of 120°C or higher for the acrylic resin film minimizes the dimensional change of the film when stretched in a high-temperature environment. In practical applications, the acrylic resin film of this embodiment is often layered with other films. A low dimensional change can suppress strain and warping caused by differences in dimensional change between the films layered with the film.

[0031] The glass transition temperature of the acrylic resin constituting the acrylic resin film is preferably 120°C or higher, more preferably higher than 120°C, further preferably 121°C or higher, further more preferably 122°C or higher, particularly preferably 123°C or higher.

[0032] Here, acrylic resins having a main chain ring structure are preferably used as acrylic resins with a glass transition temperature of 120°C or higher. Examples of such ring structures include at least one ring structure selected from the group consisting of a glutarimide ring, a lactone ring, maleic anhydride, maleimide, and glutaric anhydride. This imparts heat resistance. Of these, a glutarimide ring structure is particularly preferred from the perspectives of ease of production, cost, and quality stability against moisture.

[0033] The content of the ring structure in the acrylic resin having a glass transition temperature of 120°C or higher is preferably in the range of 2% to 80% by weight, more preferably in the range of 3% to 60% by weight. If the content of the ring structure is within this range, both the glass transition temperature and the thickness direction retardation Rth become good, which is preferred. The content of the ring structure in the acrylic resin can be used 1 H-NMR is used to measure the molar ratio of the target ring structure to the remaining moieties, and the ratio is calculated by weight conversion. Furthermore, an acrylic resin having a glass transition temperature of 120°C or higher is the main component of the acrylic resin film, and contains more than 50% by weight of the acrylic resin film (100% by weight). Of these, the acrylic resin content is preferably 70% or higher, more preferably 80% or higher, even more preferably 85% or higher, and particularly preferably 90% or higher.

[0034] In addition, as the acrylic resin having a glass transition temperature of 120° C. or higher, an acrylic resin having no ring structure in the main chain may be used.

[0035] The acrylic resin film of this embodiment has an internal haze of 1.0% or less. The internal haze is preferably 0.7% or less, more preferably 0.5% or less, and particularly preferably 0.3% or less. By setting the internal haze to 1.0% or less, the quality of the film when mounted on a liquid crystal panel is improved.

[0036] In this specification, internal haze is defined as a haze value measured using a haze meter (turbidimeter) in a glass sample cell for liquid measurement in which the obtained thin film is placed and the periphery of the glass sample cell is filled with pure water.

[0037] The haze of the acrylic resin film of the present embodiment is not particularly limited as long as the internal haze is within the above-mentioned range, but is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less from the viewpoint of transparency.

[0038] The sum of the 10-point average roughness Rzjis of each of the two sides of the acrylic resin film is more than 0.05 μm and less than 1.0 μm. If the sum of the 10-point average roughness Rzjis of each of the two sides is more than 0.05 μm, it is easy to reduce the friction between the films. In addition, it is speculated that when the films are overlapped into a roll, the air trapped between the films is easily discharged, which can suppress adhesion accompanied by tight winding and film defects. Here, if the sum of the 10-point average roughness Rzjis of each of the two sides of the acrylic resin film is less than 0.05 μm, adhesion accompanied by tight winding occurs during the storage of the film roll, resulting in film defects. This tendency becomes significant when a long film roll (e.g., 8000 m) is stored. Therefore, only acrylic resin films of a specified size (e.g., 4000 m) can be wound, and the yield is reduced. In addition, even if the acrylic resin film is of a specified size, the inner acrylic resin film undergoes plastic deformation during storage of the film roll, so an acrylic resin film that has undergone plastic deformation cannot be used. On the other hand, if the sum of the 10-point average roughness Rzjis of each side of the acrylic resin film exceeds 1.0 μm, the transparency of the acrylic resin film is reduced. In addition, if the sum of the 10-point average roughness Rzjis of each side is 1.0 μm or less, it is possible to suppress diffuse reflection of light on the surface, which can suppress the situation where the clarity of the panel display is damaged. Among them, the sum of the 10-point average roughness Rzjis of each side of the acrylic resin film is more preferably 0.05 μm or more and 0.6 μm or less, and further preferably 0.05 μm or more and 0.5 μm or less.

[0039] When the acrylic resin has a ring structure in the main chain, the sum of the 10-point average roughness Rzjis on both sides of the acrylic resin film is preferably 0.15 μm to 1.0 μm, more preferably 0.16 μm to less than 1.0 μm, even more preferably 0.17 μm to 0.6 μm, and even more preferably 0.2 μm to 0.5 μm. Furthermore, the 10-point average roughness Rzjis on one side and / or the other side of the acrylic resin film is preferably greater than 0.080 μm and less than 0.25 μm.

[0040] On the other hand, when the acrylic resin does not have a ring structure in the main chain, and particularly when the syndiotacticity expressed by triads described below is 54% or higher, the sum of the 10-point average roughness Rzjis on both sides of the acrylic resin film is preferably 0.05 μm or higher and 1.0 μm or lower, more preferably 0.06 μm or higher and less than 0.60 μm, even more preferably 0.06 μm or higher and less than 0.50 μm, even more preferably 0.06 μm or higher and 0.40 μm or lower, and even more preferably 0.07 μm or higher and 0.30 μm or lower. Furthermore, the 10-point average roughness Rzjis on one side and / or the other side of the acrylic resin film is preferably greater than 0.020 μm and less than 0.20 μm.

[0041] Here, "blocking" refers to the state in which films adhere to each other, including a state in which they partially melt at high temperatures or a state in which they overlap tightly. If the film is rolled tightly, pressure is applied to the films, causing them to adhere (stick). As a result, the films must be peeled off with a strong force, causing damage to the films. Therefore, by setting the kurtosis of both surfaces of the film within a specified range, as in this embodiment, even if the film is rolled tightly, the adhesion of the films within the roll can be suppressed, allowing the films to be peeled off with relatively weak force, thereby preventing damage to the film (film defects).

[0042] The film's Rzjis (surface roughness) can be measured using an optical surface roughness meter, such as a laser microscope. The surface roughness value of the acrylic resin film of this embodiment is smaller than the resolution of a laser microscope, so sufficient measurement accuracy cannot be achieved using a lens with a small numerical aperture. Therefore, in this specification, values ​​measured using a lens with a numerical aperture of 0.95 or greater are used.

[0043] Regarding the surface roughness of the film, it is preferred to add an anti-blocking agent, described below, to the acrylic resin from the viewpoints of economic efficiency and environmental impact. Among these, organic fine particles are preferred from the viewpoints of affinity and dispersibility with the acrylic resin, and acrylic cross-linked particles are most preferred from the viewpoint of ease of haze control.

[0044] The static friction coefficient of an acrylic resin film, measured with one side of the film attached to the other, is 0.8 or less. Preferably, it is 0.7 or less, more preferably 0.6 or less, and particularly preferably 0.5 or less. A static friction coefficient of 0.8 or less effectively prevents adhesion of the films within a film roll. While the lower limit of the static friction coefficient is not particularly limited, it is preferably 0.2 or greater to prevent winding deviation and snaking during production.

[0045] The dimensional change rate of the acrylic resin film when left to stand for 120 hours in an atmosphere of 85°C and 85% RH is preferably an average value of -2.0% or more in the longitudinal direction (MD direction) and the width direction (TD direction) of the film, more preferably -1.7% or more, and further preferably -1.5% or more. If the above-mentioned dimensional change rate is -2.0% or more, the shrinkage over time can be suppressed during the storage of the film roll, and the stability of the winding appearance over time is improved. In addition, the warping and dimensional changes when attached to the polarizer are alleviated, which can suppress the contrast reduction and peripheral unevenness of the liquid crystal display device. The above-mentioned dimensional change rate can be, for example, -0.1% or less. If the above-mentioned dimensional change rate is -0.1% or less, when attached to the polarizer, even if the polarizer itself shrinks, the acrylic resin film will easily follow the shrinkage. The dimensional change rate after standing for 120 hours in an atmosphere of 85°C and 85% RH can be measured by using a three-dimensional measuring instrument to measure the dimensional change of an acrylic resin film before and after standing for 120 hours in an environmental testing machine set at 85°C and 85% RH.

[0046] In this specification and claims, the dimensional change rate refers to the rate of change in the spacing between 1 mm diameter holes drilled in a 90 mm x 90 mm film at positions 20 mm inward from the four corners of the film on a diagonal line before and after the film is left standing for 120 hours in an atmosphere of 85°C and 85% RH. The dimensional change rate is the rate of change in the spacing after standing, based on the spacing before standing, and is calculated using the following formula.

[0047] [(hole spacing after standing) - (hole spacing before standing)] × 100 / (hole spacing before standing) ... (A)

[0048] The coefficient of linear expansion of the acrylic resin film at 40°C to 60°C is preferably 80 ppm or less, more preferably 72 ppm or less. If it is 80 ppm or less, the shrinkage and expansion of the film due to temperature changes during storage and transportation of the roll can be suppressed, making it less likely to cause tightness. On the other hand, as a lower limit, it is preferably 40 ppm or more. If the linear expansion of the film is 40 ppm or more, the linear expansion difference with other components is small when stacked with a polarizer, making it less likely to cause warping.

[0049] The linear expansion coefficient can be measured using, for example, a thermomechanical analyzer TMA-4000SA manufactured by Bruker AXS. Specifically, under a nitrogen atmosphere, a film cut into 4 mm x 20 mm pieces is subjected to a tensile load of 3.1 g. The film is heated at a rate of 2°C / min within a temperature range not exceeding the glass transition temperature. The temperature is plotted on the X-axis and the change in film length is plotted on the Y-axis to create a graph. During the heating and cooling processes, the slope within the temperature range of 40°C to 60°C is calculated using the least squares method to determine the linear expansion coefficient.

[0050] (Anti-blocking agent)

[0051] The acrylic resin film is preferably formed from an acrylic resin composition comprising an acrylic resin and an anti-blocking agent. The anti-blocking agent is preferably acrylic crosslinked particles from the viewpoints of compatibility with the acrylic resin, dispersibility, and transparency. The particles may be in any shape, but are preferably spherical from the viewpoint of exhibiting anti-blocking properties.

[0052] When the refractive index of the acrylic resin is set to 100%, the refractive index of the anti-blocking agent is preferably 98% to 102%, more preferably 99% to 101%. The refractive index of the anti-blocking agent is preferably 1.47 to 1.55, more preferably 1.47 to 1.53, and even more preferably 1.48 to 1.52. Using an anti-blocking agent with a refractive index within this range can produce a highly transparent acrylic resin film. Acrylic crosslinked particles are preferred because they meet the above refractive index requirements.

[0053] The polymerizable monomer forming the above-mentioned acrylic crosslinked particles can be selected from any (meth)acrylate and other copolymerizable monomers. From the perspective of compatibility with the acrylic resin and refractive index, it preferably contains methyl methacrylate. The content of structural units derived from methyl methacrylate in the acrylic crosslinked particles is preferably from 80% to 99% by weight, and more preferably from 83% to 96% by weight. It should be noted 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.

[0054] The acrylic crosslinked particles further contain structural units derived from a polyfunctional monomer containing two or more polymerizable groups within the molecule as a polymerizable monomer. The content of the polyfunctional monomer in the polymerizable monomer can be arbitrarily set, but is preferably from 0.5% to 30% by weight. If the content is less than 0.5% by weight, the acrylic crosslinked particles may have poor heat resistance and dispersibility. If the content is greater than 30% by weight, particles may aggregate and form irregular particles during production.

[0055] The average particle size of the acrylic acid-based crosslinked particles is preferably between 0.1 μm and 2.5 μm, more preferably between 0.1 μm and 2.0 μm. A particle size less than 0.1 μm requires a larger amount to enhance anti-blocking properties, resulting in poor mechanical properties and economic efficiency. An upper limit of greater than 2.5 μm may lead to clogging of the polymer filter. Furthermore, from the perspective of long-term operation of the polymer filter, acrylic acid-based crosslinked particles with a narrow particle size distribution and a low content of coarse particles are preferred.

[0056] The amount of acrylic acid crosslinked particles added in this embodiment is preferably from 0.05% to 0.9% by weight, more preferably from 0.07% to 0.5% by weight, and even more preferably from 0.1% to 0.2% by weight. An amount less than 0.05% by weight will not provide a sufficient anti-blocking effect. However, by adjusting the amount to 0.9% or less by weight, it is possible to prevent deterioration in economic efficiency and increase in haze. Furthermore, to control slippage and surface properties, multiple particles having different particle size distributions may be mixed. In this case, the amount of acrylic acid crosslinked particles added is the sum of the amounts of the multiple particles added.

[0057] (easy bonding layer)

[0058] The acrylic resin film of this embodiment may be provided with an adhesive layer on one or both sides. The provision of an adhesive layer, for example, when used as a polarizer protective film, can enhance the adhesion between the polarizer protective film and the polarizer when attached to the polarizer with the aid of an adhesive. Furthermore, a stretched film having an adhesive layer can be obtained by providing an adhesive layer on an unstretched film and then stretching the film.

[0059] The easy bonding layer used in the present embodiment can be formed using the known techniques described in Japanese Patent Application Publication No. 2009-193061 and Japanese Patent Application Publication No. 2010-55062. That is, for example, it can be formed from an easy bonding agent composition comprising a polyurethane resin having a carboxyl group and a cross-linking agent. By using a polyurethane resin, an easy bonding layer having excellent adhesion between the polarizer protective film and the polarizer can be obtained. From the perspective of its operability and environmental protection, the easy bonding agent composition is preferably an aqueous system.

[0060] (Acrylic resin)

[0061] As mentioned above, the glass transition temperature of acrylic resin films is 120°C or higher. As acrylic resins used for acrylic resin films, those having a glass transition temperature of 120°C or higher can be suitably used. As mentioned above, acrylic resins having a glass transition temperature of 120°C or higher can include those having a ring structure in the main chain and those not having a ring structure in the main chain. Each ring structure is described below.

[0062] (Acrylic resin having a glutarimide ring in the main chain)

[0063] An acrylic resin having a glutarimide ring as a ring structure in its main chain is a resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, and is obtained by heating and melting an acrylic resin having an acrylate unit content of less than 1% by weight and then treating it with an imidizing agent.

[0064]

[0065] (Here, R 1 and R 2 Each independently represents hydrogen or an alkyl group having 1 to 8 carbon atoms, R 3 represents 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.

[0066] The glutarimide ring content in this embodiment is a value that can be measured by the following method, for example. 1 H-NMR was performed. Based on the area of ​​the peak of O-CH3 proton derived from methyl methacrylate near 3.5ppm to 3.8ppm and the NR derived from glutarimide group near 3.0ppm to 3.3ppm, the 3 The proton peak area was converted to weight using the calculated molar ratio.

[0067] In the step of treating with an imidizing agent, in addition to methyl methacrylate, for example, methyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. may be used in combination. When these are used in combination, the content of acrylate units is preferably less than 1% by weight. Furthermore, the content of acrylate units is more preferably less than 0.5% by weight, and even more preferably less than 0.3% by weight.

[0068] In addition to the above monomers, nitrile monomers such as polyacrylonitrile and methacrylonitrile, maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide, and aromatic vinyl monomers such as styrene may be copolymerized.

[0069] The structure of the methyl methacrylate resin is not particularly limited, and may be any of a linear (chain) polymer, a block polymer, a core-shell polymer, a branched polymer, a ladder polymer, and a cross-linked polymer.

[0070] In the case of a block polymer, any of AB type, ABC type, ABA type, and other types of block polymers may be used. In the case of a core-shell polymer, it may be composed of only one core layer and one shell layer, or may be composed of multiple layers.

[0071] The manufacture method of polymethyl methacrylate is not particularly limited. Known emulsion polymerization, emulsion-suspension polymerization, suspension polymerization, bulk polymerization, solution polymerization, etc. can be used. When used in the optical field, bulk polymerization and solution polymerization are particularly preferred from the viewpoint of few impurities. For example, the method of recording in writing according to Japanese Patent Application Laid-Open No. 56-8404, Japanese Patent Publication No. 6-86492, Japanese Patent Publication No. 7-37482 or Japanese Patent Publication No. 52-32665, etc. can be manufactured.

[0072] The method for producing an acrylic resin according to this embodiment includes heating and melting a methyl methacrylate resin or an acrylic resin copolymerized with a monomer other than the methyl methacrylate monomer, and treating the resin with an imidizing agent (imidization step).

[0073] The imidizing agent is not particularly limited as long as it can generate a glutarimide ring represented by the general formula (1), and examples thereof include the imidizing agents described in WO2005 / 054311. Specifically, examples thereof include: amines containing aliphatic hydrocarbon groups, such as ammonia, methylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; amines containing aromatic hydrocarbon groups, such as aniline, benzylamine, toluidine, and trichloroaniline; and amines containing alicyclic hydrocarbons, such as cyclohexylamine. In addition, urea-based compounds such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, which generate the amines listed above upon heating, can also be used. Among these imidizing agents, methylamine, ammonia, and cyclohexylamine are preferably used from the perspectives of both cost and physical properties, and methylamine is particularly preferred. Methylamine, which is gaseous at room temperature, can be used dissolved in an alcohol such as methanol.

[0074] In the imidization step, the ratio of the glutarimide unit and the (meth)acrylate unit in the obtained acrylic resin can be adjusted by adjusting the addition ratio of the imidization agent.

[0075] Furthermore, by adjusting the degree of imidization, it is possible to adjust the physical properties of the resulting acrylic resin, the transparency of a stretched film formed by molding the acrylic resin of the present embodiment, and the like.

[0076] The amount of the imidizing agent is preferably 0.5 to 20 parts by weight per 100 parts by weight of the acrylic resin containing methyl methacrylate units. When the amount of the imidizing agent added is within this range, the imidizing agent is less likely to remain in the resin, and the likelihood of causing appearance defects and foaming after molding is extremely low. Furthermore, the final resin composition also has an appropriate glutarimide ring content, which is preferable because it minimizes degradation in heat resistance and minimizes the occurrence of appearance defects after molding.

[0077] In this imidization step, a ring closure accelerator (catalyst) may be added as needed in addition to the imidization agent.

[0078] The method of heating, melting, and treating with an imidizing agent is not particularly limited, and all conventionally known methods can be used. For example, the acrylic resin containing methyl methacrylate units can be imidized by using an extruder, a batch reaction tank (pressure vessel), or the like.

[0079] The extruder is not particularly limited. For example, a single screw extruder, a twin screw extruder or a multi-screw extruder etc. can be used. The extruder can be used alone or a plurality of them can be connected in series and used. When a twin screw extruder is used, non-meshing co-rotating type, meshing co-rotating type, non-meshing counter-rotating type and meshing counter-rotating type etc. can be cited. Among them, the meshing co-rotating twin screw extruder can rotate at high speed, and therefore can further promote the mixing of the imidizing agent (imidizing agent and ring closure accelerator in the case of using a ring closure accelerator) relative to the base polymer, and is therefore preferred.

[0080] When imidization is carried out in an extruder, for example, methyl methacrylate resin is introduced from the raw material introduction portion of the extruder, the resin is melted, and after filling the cylinder, the imidization agent is injected into the extruder using an addition pump, thereby allowing the imidization reaction to proceed in the extruder.

[0081] In this case, the temperature (resin temperature), time (reaction time), and resin pressure during treatment in the extruder are not particularly limited as long as glutarimidation can proceed.

[0082] When using an extruder, it is preferable to install a vent that can reduce the pressure to below atmospheric pressure in order to remove unreacted imidizing agent and by-products. With such a configuration, unreacted imidizing agent, by-products such as methanol, and monomers can be removed.

[0083] When an acrylic resin containing a glutarimide ring in its main chain is produced using a batch reactor (pressure vessel), the structure of the batch reactor (pressure vessel) is not particularly limited. Any structure is sufficient as long as it allows the acrylic resin containing methyl methacrylate units to be melted and stirred by heating, and allows the addition of an imidizing agent (both the imidizing agent and the ring-closing accelerator when a ring-closing accelerator is used). A structure with good stirring efficiency is preferred.

[0084] Specific examples of the imidization method include known methods such as the methods described in JP-A-2008-273140 and JP-A-2008-274187.

[0085] The method for producing an acrylic resin according to the present embodiment may further include a step of treating the resin with an esterifying agent in addition to the above-mentioned imidization step. The acid value of the imidized resin obtained in the imidization step can be adjusted to a desired range through the esterification step.

[0086] The esterifying agent is not particularly limited as long as it can esterify the remaining carboxyl groups in the molecular chain. Examples include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethylsulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, and dimethylcarbodiimide. Among these, dimethyl carbonate and trimethyl orthoacetate are preferred from the perspectives of cost and reactivity, and dimethyl carbonate is preferred from the perspective of cost.

[0087] In this imidization step, the amount of the esterifying agent is preferably 0 to 30 parts by weight, more preferably 0 to 15 parts by weight, per 100 parts by weight of the acrylic resin containing methyl methacrylate units. When the esterifying agent is within these ranges, the acid value can be adjusted to an appropriate range. On the other hand, when the amount exceeds these ranges, unreacted esterifying agent may remain in the resin, which may cause foaming and odor generation when the resulting resin is molded.

[0088] In addition to the esterifying agent, a catalyst may be used in combination. The catalyst is not particularly limited as long as it can promote esterification. Examples include aliphatic tertiary amines such as trimethylamine, triethylamine, and tributylamine. Among them, triethylamine is preferred from the perspectives of cost and reactivity.

[0089] In this esterification step, it is also possible to perform only a heat treatment, etc., without using an esterifying agent. When only a heat treatment (such as kneading and dispersion of the molten resin in the extruder) is performed, a portion or all of the carboxyl groups in the acrylic resin having glutarimide rings produced as a by-product in the imidization step can be converted to anhydride groups through dehydration reactions between the carboxyl groups, dealcoholization reactions between the carboxyl groups and alkoxycarbonyl groups, etc. In this case, a ring closure accelerator (catalyst) can also be used. Even when using an esterifying agent, anhydride conversion can be achieved by heat treatment.

[0090] Since the imide resin after the imidization and esterification steps contains unreacted imidization agent, unreacted esterification agent, volatile components produced as reaction by-products, and resin decomposition products, a vent hole capable of reducing the pressure to below atmospheric pressure may be provided.

[0091] (Acrylic resin having a lactone ring in the main chain)

[0092] The acrylic resin having a lactone ring as a ring structure in the main chain is not limited as long as it is a thermoplastic polymer having a lactone ring structure in the molecule (a thermoplastic polymer having a lactone ring structure introduced into the molecular chain). The production method is also not limited. However, it is preferably obtained by obtaining a polymer (a) having a hydroxyl group and an ester group in the molecular chain by polymerization (polymerization step), and then introducing the lactone ring structure into the polymer by heat treatment of the obtained polymer (lactone cyclocondensation step).

[0093] In the polymerization step, a polymerization reaction of monomer components including an unsaturated monomer represented by the following general formula (2) is carried out to obtain a polymer having a hydroxyl group and an ester group in the molecular chain.

[0094]

[0095] (Among them, R 4 and R 5 Each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. ).

[0096] Examples of the unsaturated monomer represented by general formula (2) 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 particularly preferred due to its high heat resistance-enhancing effect. These unsaturated monomers may be used alone or in combination of two or more.

[0097] The content of the unsaturated monomer represented by general formula (2) in the monomer component is preferably 5% to 50% by weight, more preferably 10% to 40% by weight, and even more preferably 10% to 30% by weight. If the content is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness of the obtained lactone ring-containing polymer may be reduced. If the content is more than 50% by weight, a cross-linking reaction may occur during the formation of the lactone ring structure, resulting in gelation, reduced fluidity, and difficulty in melt molding. Alternatively, unreacted hydroxyl groups may remain, causing further condensation reactions during molding to generate volatile substances, which may easily cause silver streaks or increase the thickness direction retardation Rth.

[0098] The monomer component preferably includes other monomers other than the unsaturated monomer represented by general formula (2). As such other monomers, there is no limitation as long as they are selected within the range that does not impair the effects of the present invention. For example, preferably, (meth)acrylates, hydroxyl-containing monomers, unsaturated carboxylic acids, and unsaturated monomers represented by the following general formula (3) can be mentioned. The above other monomers may be used alone or in combination of two or more.

[0099]

[0100] (Among them, R 6 represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an -OAc group, a -CN group, or a -CO-R 7 Ac represents acetyl, R 7 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.)

[0101] The (meth)acrylate is not limited as long as it is a (meth)acrylate other than the unsaturated monomer represented by general formula (2). Examples thereof include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferred from the viewpoints of heat resistance and transparency.

[0102] When the above-mentioned (meth)acrylate is used, in order to fully exert the effect of the present invention, the content ratio thereof in the monomer component is preferably 10% by weight to 95% by weight, more preferably 10% by weight to 90% by weight, further preferably 40% by weight to 90% by weight, and particularly preferably 50% by weight to 90% by weight.

[0103] (Acrylic resin having maleic anhydride, maleimide and glutaric anhydride structures in the main chain)

[0104] In this embodiment, an acrylic resin having a maleimide or glutaric anhydride structure as a ring structure in the main chain is also preferably used. Examples of maleic anhydride structures include styrene-N-phenylmaleimide-maleic anhydride copolymers. Examples of maleimide structures include olefin-maleimide copolymers described in Japanese Patent Application Laid-Open No. 2004-45893. Examples of glutaric anhydride structures include copolymers having glutaric anhydride units described in Japanese Patent Application Laid-Open No. 2003-137937.

[0105] (Acrylic resin having no ring structure in the main chain)

[0106] Acrylic resins with a glass transition temperature of 120°C or higher can be obtained, for example, by introducing carboxyl groups such as methacrylic acid. Exceeding a certain level of carboxyl groups increases the risk of crosslinking and foaming during film formation, so it is preferable to suppress the amount to a certain level or less. Specifically, the amount of carboxyl groups in the acrylic resin is preferably 0.6 mmol / g or less, and more preferably 0.4 mmol / g or less.

[0107] As acrylic resins having a glass transition temperature of 120°C or higher, those having a syndiotacticity expressed by triads of 54% or higher can be suitably used. When the syndiotacticity expressed by triads of an acrylic resin is 54% or higher, the glass transition temperature of the acrylic resin tends to be higher, and the heat resistance of the acrylic resin tends to be improved. The syndiotacticity expressed by triads of an acrylic resin is preferably 55% or higher, more preferably 56% or higher, and even more preferably 57% or higher. Furthermore, from the perspectives of the molding temperature of the acrylic resin, the toughness of the molded article, and the secondary processability, the syndiotacticity expressed by triads of the acrylic resin is preferably 67% or lower, more preferably 65% ​​or lower, and even more preferably 63% or lower.

[0108] The syndiotacticity of an acrylic resin, expressed as a triad, is the ratio of a chain of three structural units (triad) to rr. Furthermore, chains of two structural units (diads) with the same stereo configuration are called meso (m), while those with opposite stereo configurations are called racemic (r).

[0109] The method for synthesizing an acrylic resin having a syndiotacticity of 55% or more as a triad is not particularly limited, and examples thereof include anionic polymerization and free radical polymerization. Among them, free radical polymerization is preferred (for example, with reference to International Publication No. 2023 / 238885 and International Publication No. 2023 / 238886). In the free radical polymerization method, since the organic metal compound as a polymerization initiator and the organic solvent as a medium used in the anionic polymerization method are not used, impurities are not easily retained, which is preferred from an environmental point of view. Here, the glass transition temperature of the acrylic resin and the syndiotacticity represented by the triad can be controlled by the polymerization temperature of the acrylic resin. For example, by lowering the polymerization temperature of the acrylic resin, the glass transition temperature of the acrylic resin becomes higher, and the syndiotacticity of the acrylic resin becomes larger. In addition, the glass transition temperature of the acrylic resin can also be controlled by the molecular weight of the acrylic resin.

[0110] The content of the structural unit derived from methyl methacrylate in the acrylic resin having a syndiotacticity represented by triads 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.

[0111] The monomers other than methyl methacrylate that constitute the acrylic resin having a syndiotacticity of 54% or more expressed as a triad 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 norbornene 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 norbornene methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; and methacrylonitrile.

[0112] (Other properties of acrylic resin)

[0113] The following describes other properties of acrylic resins having a ring structure in their main chains and acrylic resins not having a ring structure in their main chains. Hereinafter, the term "acrylic resin" refers to at least one of an acrylic resin having a ring structure in its main chain and an acrylic resin not having a ring structure in its main chain.

[0114] The weight average molecular weight of the acrylic resin is preferably 50,000 to 200,000, more preferably 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 acrylic resin molded article tend to be improved, while when it is 200,000 or less, the moldability of the acrylic resin tends to be improved.

[0115] The weight-average molecular weight of the acrylic resin may be 400,000 or greater. When the weight-average molecular weight of the acrylic resin is 400,000 or greater, the mechanical properties of the acrylic resin molded article tend to be further improved, and for example, a 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 greater, more preferably 700,000 or greater, and even more preferably 800,000 or greater. Furthermore, from the perspective of the moldability of the acrylic resin, the weight-average molecular weight of the acrylic resin is preferably 2.5 million or less, more preferably 2 million or less, even more preferably 1.5 million or less, and particularly preferably 1.2 million or less.

[0116] The ratio of the weight average molecular weight to the number average molecular weight (dispersity) of the acrylic resin is preferably 1.6 or more and 2.5 or less, and more preferably 1.7 or more and 2.2 or less. When the dispersity of the acrylic resin is 1.6 or more, the flowability of the acrylic resin tends to be improved, thereby facilitating molding. When the dispersity is 2.5 or less, the mechanical properties of the acrylic resin molded article, such as impact resistance, toughness, and flex resistance, tend to be improved.

[0117] It should be noted that 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. Furthermore, the number average molecular weight and weight average molecular weight of the acrylic resin can be controlled by the type and amount of the polymerization initiator and chain transfer agent used in synthesizing the acrylic resin.

[0118] (Acrylic resin composition)

[0119] As the acrylic resin film, an acrylic resin composition containing an additive added to an acrylic resin may be used, or an anti-blocking agent and an additive may be used in combination. As the additive, commonly used antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, specific wavelength absorbers or specific wavelength absorbing pigments for the purpose of blue light protection, free radical scavengers and other light resistance stabilizers, phase difference adjusters, catalysts, plasticizers, lubricants, antistatic agents, colorants, shrinkage inhibitors, antibacterial / deodorizing agents, fluorescent whitening agents, compatibilizers, etc. may be added alone or in combination of two or more, within a range that does not impair the purpose of the present invention.

[0120] Examples of ultraviolet absorbers include triazine compounds, benzotriazole compounds, benzophenone compounds, cyanoacrylate compounds, benzoxazine compounds, and oxadiazole compounds. Among them, triazine compounds are preferred from the perspective of ultraviolet absorption performance relative to the amount added and volatility during melt extrusion.

[0121] Regarding the retardation adjusting agent, when imparting a negative retardation, for example, any compound having a styrene skeleton may be used, and an acrylonitrile-styrene copolymer can be exemplified.

[0122] The method for mixing the acrylic resin and the anti-blocking agent is not particularly limited, and any conventionally known method can be used. Examples include a method of feeding the acrylic resin and the anti-blocking agent to an extruder using a gravimetric feeder for melt kneading, and mixing the acrylic resin and the anti-blocking agent in a solution using a solvent with excellent compatibility.

[0123] When using an extruder to mix, the extruder used is not particularly limited, and various extruders can be used. Specifically, single screw extruder, twin screw extruder or multi-screw extruder etc. can be used. Wherein, preferably use a twin screw extruder. When utilizing a twin screw extruder, the degree of freedom of the condition in which acrylic resin and antiblocking agent are uniformly mixed is wide. In addition, raw material input hopper etc. can be used to drop into acrylic resin and antiblocking agent and mix from the upstream side of the extruder, or side feeder, weight feeder etc. can be used to only drop into antiblocking agent and mix from the midway of the extruder. Alternatively, also can use the material that antiblocking agent is made into masterbatch with other extruders in advance.

[0124] To reduce foreign matter in the resin, a filter may be installed at the end of the extruder. A gear pump is preferably installed before the filter to increase the pressure of the (A) acrylic resin / acrylic resin composition. A stainless steel leaf disc filter capable of removing foreign matter from the molten polymer is preferably used as the filter type. Fiber-type, powder-type, or a combination thereof filter elements are preferably used.

[0125] (Method for producing acrylic resin film)

[0126] One embodiment of the method for producing a stretched film of the present invention will be described, but the present invention is not limited thereto. That is, any conventionally known method can be used as long as it is a method for molding the acrylic resin composition of this embodiment to produce a film.

[0127] Specifically, examples include injection molding, melt extrusion molding, inflation molding, blow molding, compression molding, etc. Furthermore, the film of this embodiment can be produced by solution casting or spin coating, in which the acrylic resin composition of this embodiment is dissolved in a soluble solvent and then molded.

[0128] Among them, melt extrusion, which does not use a solvent, is preferably used. The melt extrusion method can reduce production costs and reduce the load of solvents on the global environment and the working environment.

[0129] When the acrylic resin composition of the present embodiment is formed into a film by melt extrusion, first, the acrylic resin composition of the present embodiment is pre-dried and then supplied to an extruder to heat and melt the acrylic resin composition. Then, it is supplied to a mold such as a T-die through a gear pump and a filter. Next, the acrylic resin composition supplied to the T-die is extruded into a sheet-like molten resin, which is cooled and solidified using a cooling roller to obtain an unstretched film (also referred to as a raw material film). At this time, in order to make the surface property (smoothness) of the film good, it can also be sandwiched between a metal roller and a flexible roller having a metal elastic outer cylinder.

[0130] The situation that the acrylic resin composition of the present embodiment is shaped into an unstretched film by the solution casting method is that after the acrylic resin composition of the present embodiment is made into a solution together with an organic solvent, the solution is cast on a support, and the method of heating and drying to manufacture an unstretched film. The solvent that can be used for the solution casting method can be selected from known solvents. Halogenated hydrocarbon solvents such as dichloromethane and trichloroethane are easy to dissolve the acrylic resin of the present embodiment, and have low boiling points, so they are preferred solvents. In addition, non-halogen solvents with high polarity such as dimethylformamide and dimethylacetamide can also be used. And then, 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 can be used alone. In addition, multiple solvents can also be used in combination. The amount of solvent used can be set to any amount as long as it can dissolve the thermoplastic resin to the extent that it can fully carry out casting (casting). It should be noted that, in this specification, "dissolved" means that the resin is present in the solvent in a uniform state sufficient for casting. The solute does not necessarily need to be completely dissolved in the solvent. The resin concentration in the solution is preferably 1% to 90% by weight, more preferably 5% to 70% by weight, and even more preferably 10% to 50% by weight. As a preferred support, a stainless steel endless belt can be used. Alternatively, a film such as a polyimide film or a polyethylene terephthalate film can be used.

[0131] The acrylic resin film of this embodiment is obtained by stretching an unstretched film (also referred to as a raw film). By stretching the unstretched film, a stretched film of a desired thickness can be produced, and the mechanical properties of the stretched film can be improved.

[0132] As a stretching method, conventionally known methods can be used. For example, an unstretched raw film formed by melt extrusion can be subjected to uniaxial stretching or biaxial stretching to produce a film of a specified thickness. In order to ensure that the stretched film has excellent mechanical properties in both the longitudinal direction (MD direction) and the width direction (TD direction), biaxial stretching is preferably performed. The biaxial stretching method can be simultaneous biaxial stretching or sequential biaxial stretching.

[0133] Regarding the stretching ratio (in the case of biaxial stretching, both the MD direction and the TD direction of the film), it is preferably 1.5 times to 3.0 times, and more preferably 1.8 times to 2.8 times. If the stretching ratio is within this range, the mechanical properties of the film accompanying the stretching can be fully improved. In addition, the degree of orientation will not increase excessively, and the dimensional change when standing for 120 hours in an atmosphere of 85°C and 85% RH can be reduced, and the possibility of a decrease in the peel strength when attached to a polarizer is also small. Regarding the stretching speed, it is preferably carried out at 1.1 times / minute or more, and more preferably at 5 times / minute or more. In addition, it is preferably 100 times / minute or less, and more preferably 50 times / minute or less. In the case of successive biaxial stretching, the stretching speed of the first stage and the stretching speed of the second stage may be the same or different. In successive biaxial stretching, usually, the stretching in the first stage is the stretching in the longitudinal direction (MD direction), and the stretching in the second stage is the stretching in the width direction (TD direction).

[0134] The stretching temperature is not particularly limited, but is preferably carried out at Tg+7°C to Tg+50°C, more preferably at Tg+10°C to Tg+40°C. When the stretching temperature is Tg+7°C or higher, the risk of breakage can be suppressed during the stretching process. On the other hand, when the stretching temperature is Tg+50°C or lower, sufficient molecular orientation can be obtained, which can suppress the reduction in the mechanical strength of the film. When the stretching temperature is high within the above range, the molecular orientation is relaxed, so the mechanical strength is reduced. On the other hand, the dimensional change in an atmosphere of 85°C and 85% RH becomes smaller. In addition, in the case of a film containing an anti-blocking agent, if stretched at low temperatures, particles tend to float on the surface, and surface roughness, slippage, and external haze tend to appear. Those skilled in the art can arbitrarily set the stretching conditions in consideration of the above balance.

[0135] The acrylic resin film of this embodiment is wound into a roll using a known method. Even when the film width is increased or the wound length is increased, defects caused by inter-film adhesion are less likely to occur. Furthermore, combining this film with knurling, a conventional method for combating adhesion, can be even more effective.

[0136] (use)

[0137] When the acrylic resin film of this embodiment is used as a polarizer protective film, it is laminated 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 adding iodine to stretched polyvinyl alcohol can be used.

[0138] This polarizing plate can be further bonded to various films and is suitable for use in display fields such as liquid crystal displays and organic EL displays. However, its use is not limited to these.

[0139] Example

[0140] The present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited thereto. A person skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0141] (Surface roughness)

[0142] The surface roughness of acrylic resin films was measured using a laser microscope LEXT OLS5100 manufactured by Evident in accordance with JIS B0601:2013. Specifically, a confocal image of the film in an area of ​​257 μm × 257 μm was first obtained using an objective lens with a magnification of 50 times and a numerical aperture of 0.95. Next, three evaluation lines were drawn at equal intervals in the MD direction and the TD direction, and a roughness curve was extracted. Based on the obtained roughness curve, the 10-point average roughness Rzjis was calculated using analysis software, and the average value at the measurement position was calculated. The measurement position was changed and the measurement was performed 5 times, and the average value was used as the surface roughness. In the case where local abnormalities such as damage were clearly confirmed from the image, they were not included in the measured value, and the abnormal part was avoided and re-measured.

[0143] (Static friction coefficient)

[0144] The static friction coefficient of acrylic resin film was measured in accordance with JIS K7125:1999 using a digital dynamometer ZTS-5N and a friction coefficient measuring jig COF-2N-V manufactured by IMADA. Specifically, surface A of the film was fixed to a smooth stainless steel plate, and surface B of the film was adhered to a 60×60 mm, 200 g slider using double-sided tape. The static friction coefficient was calculated by measuring the load applied by the slider at a speed of 100 mm / min via a pulley using a load cell. Five measurements were performed, with each film sheet replaced, and the average value was calculated.

[0145] (Haze, internal haze)

[0146] The haze of the acrylic resin film was measured using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS 7136:2000. Alternatively, the internal haze of the acrylic resin film was measured by placing the acrylic resin film in a glass sample cell for liquid measurement and allowing distilled water to contact both surfaces of the acrylic resin film.

[0147] (Glass transition temperature)

[0148] The glass transition temperature of the acrylic resin or acrylic resin film was measured using 10 mg of the acrylic resin or acrylic resin composition. Specifically, the glass transition temperature was determined by the midpoint method using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) at a heating rate of 20°C / min under a nitrogen atmosphere.

[0149] (Dimensional change rate)

[0150] Using a 1 mm diameter punch, holes were punched 20 mm inward from the four corners of a 90 mm x 90 mm acrylic resin film cut with a cutter. The hole spacing was measured using a Mitutoyo MF201 three-dimensional measuring instrument. The stretched film, after measuring the hole spacing, was then allowed to stand for 120 hours in a NaganoScience LH-20 environmental testing machine set at 85°C and 85% RH. The hole spacing was then measured again. The dimensional change rate was calculated using formula (A) based on the hole spacing before and after standing at 85°C and 85% RH.

[0151] (Refractive Index of Acrylic Resin Composition and Acrylic Crosslinked Particles)

[0152] First, the refractive index of the acrylic resin composition was determined as follows according to JIS K7142:2014. Specifically, the acrylic resin composition was melt-pressed at 240°C to form a 100 μm thick film. The refractive index of the resulting film was measured at 23°C (wavelength: 589 nm) using a refractometer (Atago Digital Abbe Refractometer DR-M2). The resulting refractive index was used as the refractive index of the acrylic resin composition.

[0153] Next, the refractive index of the acrylic crosslinked particles was determined using the following method using a mixture of a halogen-based high-refractive-index liquid and a low-refractive-index liquid such as methanol at varying ratios. Here, the acrylic crosslinked particles were dispersed in the mixture. When the refractive index of the mixture and the acrylic crosslinked particles did not match, the dispersion became turbid. When the refractive index of the mixture matched that of the acrylic crosslinked particles, the dispersion became transparent. Therefore, the refractive index of the mixture when it became a transparent liquid was used as the refractive index of the acrylic crosslinked particles.

[0154] <Manufacturing of Acrylic Resin>

[0155] (Production Example of Acrylic Resin 1)

[0156] The extruder used is a meshing co-rotating twin-screw extruder with a diameter of 40 mm (L / D=90). The set temperature of each temperature control zone of the extruder is set to 250-280°C, and the screw speed is set to 85 rpm. After the methyl methacrylate resin is melted and filled with a kneading block, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical Co., Ltd.) is injected from the nozzle relative to 100 parts by weight of the above-mentioned methyl methacrylate resin. The resin that comes out in the form of strands from the die set at the outlet of the extruder is cooled in a water tank and granulated with a granulator to obtain resin (I). Next, a meshing co-rotating twin-screw extruder with a diameter of 40 mm is used, and the set temperature of each temperature control zone of the extruder is set to 240-260°C. 0.56 parts by weight of dimethyl carbonate is injected from the nozzle relative to 100 parts by weight of the above-mentioned methyl methacrylate resin to reduce the carboxyl groups in the resin. The by-products and excess dimethyl carbonate after the reaction are removed. The resin, which emerged as strands from the die at the extruder outlet, was cooled in a water tank and then pelletized using a pelletizer to obtain acrylic resin 1 having glutarimide rings. Acrylic resin 1 had a glass transition temperature of 123°C, an Mw of 81,000, and an Mw / Mn ratio of 1.59.

[0157] (Calculation of Ring Structure Content)

[0158] use 1 The obtained acrylic resin was measured using an H-NMR BRUKER Avance III (400 MHz). The molar ratio of the ring structure to the remaining moieties was used to convert the molar ratio by weight. Specifically, in the case of glutarimide, the molar ratio was calculated by converting the molar ratio by weight using the peak area A of the O-CH3 protons derived from methyl methacrylate at around 3.5 to 3.8 ppm and the peak area B of the N-CH3 protons derived from glutarimide at around 3.0 to 3.3 ppm. The ring structure content was 6% by weight.

[0159] (Example 1)

[0160] A mixture containing acrylic resin 1 produced in the acrylic resin production example described above and 0.08% by weight of acrylic crosslinked particles (J-3PY manufactured by Negami Kogyo Co., Ltd., refractive index 1.49) having an average particle size of 1.2 μm as an anti-blocking agent (AB agent) was kneaded in a 15 mm diameter intermeshing co-rotating twin-screw extruder (L / D = 45). The resin, which emerged as strands from a die at the extruder outlet, was cooled in a water tank and then pelletized in a pelletizer to obtain an acrylic resin composition (refractive index 1.49).

[0161] The resulting acrylic resin composition was dried at 100°C for 5 hours and then formed into a film using an intermeshing, co-rotating twin-screw extruder (L / D = 45) equipped with a 15 mm diameter T-die at the extruder outlet. The sheet of molten resin extruded from the T-die at the extruder outlet was cooled with a chill roll to produce a raw film with a width of 160 mm and a thickness of 160 μm. The surface in contact with the casting roll was designated as surface B, and the other surface was designated as surface A.

[0162] The glass transition temperature of the original film was measured according to the above method and was found to be 123°C.

[0163] The obtained raw film was simultaneously biaxially stretched at 145° C. using a biaxial stretching apparatus (IMC-1905) manufactured by Imoto Seisakusho Co., Ltd. at a stretching ratio of 2 (vertical and transverse) to produce a stretched film (acrylic resin film).

[0164] (Adhesion test)

[0165] Ten 100 mm x 100 mm test pieces (acrylic resin films) were stacked, a 1 kg pressure was applied from above, and the test pieces were left at 60°C for 2 hours. The test pieces were then naturally cooled at 23°C for 1 hour. The condition of the acrylic resin films was visually inspected and manually peeled off, and evaluation was performed according to the following criteria.

[0166] 1: The films were firmly adhered to each other, and peeling marks were produced on the films when they were peeled off.

[0167] 2: The films are fixed to each other, and no peeling marks are produced on the films when they are peeled off.

[0168] 3: No adhesion between the films was observed.

[0169] Table 1 shows Rzjis, static friction coefficient, haze, internal haze, glass transition temperature, dimensional change rate, and blocking test evaluation results.

[0170] (Example 2)

[0171] An acrylic resin composition (refractive index: 1.49) was obtained in the same manner as in Example 1 except that the added amount of the AB agent was changed to 0.12% by weight, and an acrylic resin film was obtained using the acrylic resin composition.

[0172] (Comparative Example 1)

[0173] An acrylic resin film was obtained in the same manner as in Example 1 except that the AB agent was not added.

[0174] (Comparative Example 2)

[0175] An acrylic resin film was obtained in the same manner as in Example 1 except that acrylic crosslinked particles with an average particle size of 0.8 μm (MX80H3wT manufactured by Soken Chemical Co., Ltd., refractive index 1.49) were used in place of acrylic crosslinked particles with an average particle size of 1.2 μm and the addition amount was changed to 0.03 wt %.

[0176] (Comparative Example 3)

[0177] An acrylic resin film was obtained in the same manner as in Comparative Example 2 except that the added amount of the AB agent was changed to 1.0% by weight.

[0178] (Comparative Example 4)

[0179] An acrylic resin film was obtained in the same manner as in Comparative Example 2, except that PARAPET HM (manufactured by Kuraray Co., Ltd., refractive index 1.49, Tg 118°C, Mw = 78,000, Mw / Mn = 1.72), which is a PMMA resin without a ring structure, was used as acrylic resin 2, instead of acrylic resin 1, and the amount of acrylic cross-linked particles having an average particle size of 0.8 μm was set to 0.1% by weight.

[0180] [Table 1]

[0181]

[0182] As can be seen from Table 1, the acrylic resin films of Examples 1 and 2 have excellent transparency and heat resistance, and can prevent blocking during film roll storage. In contrast, the acrylic resin film of Comparative Example 1 has a 10-point average roughness Rzjis sum of 0.104 on both sides and a static friction coefficient of 2.50, so it cannot prevent blocking during film roll storage. The acrylic resin film of Comparative Example 2 has a 10-point average roughness Rzjis sum of 0.113 on both sides and a static friction coefficient of 1.80, so it cannot prevent blocking during film roll storage. The acrylic resin film of Comparative Example 3 has a 10-point average roughness Rzjis sum of 1.130 on both sides, so its transparency is reduced. The acrylic resin film of Comparative Example 4 has a glass transition temperature of 118°C, so its heat resistance is reduced.

[0183] <Manufacturing of Acrylic Resin>

[0184] (Production Example of Acrylic Resin 3)

[0185] A 4L glass reactor equipped with an H-shaped stirring blade was charged with 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. Subsequently, 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 2,2'-azobis(isobutyric acid)dimethyl ester (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the reactor. Polymerization was initiated by raising the temperature of the reactor to 70°C. Two hours after the start of polymerization, 0.10 parts by weight of tricalcium phosphate was added to the reactor. An exothermic peak associated with a gelling effect was observed 4 hours and 20 minutes after the start of polymerization. Next, 7 hours after the start of polymerization, heating was initiated, raising the liquid temperature in the reactor 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, and polymerization was terminated to obtain an acrylic resin dispersion. The conversion rate at the end of polymerization was 99%.

[0186] The acrylic resin dispersion was acid-washed with 1N hydrochloric acid in an amount 0.1 times the weight of the monomers charged, followed by water washing to remove the dispersant. The washed acrylic resin dispersion was then dehydrated and dried to obtain beads of acrylic resin 3. Acrylic resin 3 had a glass transition temperature of 120°C, a syndiotacticity expressed as a triad of 57%, an Mw of 83,000, an Mw / Mn ratio of 1.63, and a content of structural units derived from methyl methacrylate of 100% by weight.

[0187] (Conversion Rate)

[0188] The conversion rate was determined by a gravimetric method from the ratio of the solid content weight of the acrylic resin to the weight of the charged monomers after drying in an oven heated to 150° C. for 30 minutes, namely, from the following formula.

[0189] (Weight of solid content of acrylic resin) × 100 / (Weight of monomer added)

[0190] (Syndiotacticity expressed as triad)

[0191] The acrylic resin was measured using a nuclear magnetic resonance apparatus (AVANCE III 400 MHz, manufactured by Bruker) in a deuterated chloroform solution at 22°C and a cumulative frequency of 16. 1H-NMR spectrum. Next, the area (X) of the region between 0.60 and 0.95 ppm and the area (Y) of the region between 0.60 and 1.25 ppm were measured when tetramethylsilane (TMS) was set to 0 ppm, and the area was calculated by the formula (X / Y) × 100.

[0192] To calculate the syndiotacticity represented by the triad.

[0193] (Weight average molecular weight, number average molecular weight and dispersity)

[0194] The weight average molecular weight (Mw), number average molecular weight (Mn), and dispersion (Mw / Mn) of the acrylic resin were calculated using gel permeation chromatography (GPC). Analysis was performed under the following conditions using a sample solution prepared by dissolving 20 mg of the acrylic resin in 10 mL of tetrahydrofuran.

[0195] Measuring machine: HLC-8420GPC (manufactured by Tosoh Corporation)

[0196] Detector: RI detector

[0197] Eluent: tetrahydrofuran

[0198] Guard column: TSKgel guardcolumn SuperH-L (manufactured by Tosoh Corporation)

[0199] Analytical columns: TSKgel SuperH5000, SuperH4000, SuperH3000, SuperH2000 (manufactured by Tosoh Corporation) (connected in series)

[0200] Eluent flow rate: 0.6mL / min

[0201] Measurement temperature: 40°C

[0202] Standard material: Standard polystyrene (manufactured by Tosoh Corporation)

[0203] (Example 3)

[0204] An acrylic resin film was obtained in the same manner as in Example 1 except that acrylic resin 3 was used instead of acrylic resin 1, and 0.12 wt % of acrylic crosslinked particles (J-4PY manufactured by Negami Industry Co., Ltd., refractive index 1.50) having an average particle size of 2.2 μm was used instead of 0.1 wt % of acrylic crosslinked particles having an average particle size of 0.8 μm.

[0205] (Comparative Example 5)

[0206] An acrylic resin film was obtained in the same manner as in Example 3 except that the AB agent was not added.

[0207] [Table 2]

[0208]

[0209] As shown in Table 2, the acrylic resin film of Example 3 exhibits excellent transparency and heat resistance, preventing blocking during film roll storage. In contrast, the acrylic resin film of Comparative Example 5 has a 10-point average roughness Rzjis sum of 0.030 on both sides and a static friction coefficient of 1.94, failing to prevent blocking during film roll storage.

Claims

1. An acrylic resin film, which has acrylic resin as its main component, The glass transition temperature of the acrylic resin film is 120° C. or higher. The acrylic resin film has a sum of 10-point average roughness Rzjis of 0.05 μm to 1.0 μm on both sides, a static friction coefficient of 0.8 or less between one side and the other side, and an internal haze of 1.0% or less.

2. The acrylic resin film according to claim 1, wherein The 10-point average roughness Rzjis of one surface and / or the other surface of the acrylic resin film exceeds 0.080 μm and is 0.25 μm or less.

3. The acrylic resin film according to claim 1, wherein The acrylic resin contains at least one ring structure selected from the group consisting of a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure.

4. The acrylic resin film according to claim 1, wherein The syndiotacticity expressed by triads of the acrylic resin is 54% or more.

5. The acrylic resin film according to claim 1, wherein The acrylic resin film contains an anti-blocking agent, The anti-blocking agent includes acrylic cross-linked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

6. The acrylic resin film according to claim 5, wherein The anti-blocking agent includes acrylic cross-linked particles having an average particle size of 0.1 μm or more and 2.0 μm or less.

7. The acrylic resin film according to claim 5, wherein The acrylic resin film contains 0.05 wt % or more and 0.9 wt % or less of acrylic cross-linked particles. The acrylic resin film according to any one of claims 1 to 5, wherein the dimensional change rate thereof when left to stand in an atmosphere of 85°C and 85% RH for 120 hours is -2.0% or more and -0.1% or less. 9 . A polarizing plate comprising the acrylic resin film according to claim 1 . 10 . A liquid crystal display panel comprising the polarizing plate according to claim 9 .

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