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

Abstract

To suppress blocking during storage of a film roll, while maintaining heat resistance and transparency of an acrylic resin film.SOLUTION: An acrylic resin film contains an acrylic resin as a main component, wherein the acrylic resin film has a glass transition temperature of 120°C or higher, and the sum of ten point average roughness Rzjis of each of both surfaces of the acrylic resin film is 0.05 μm or more and 1.0 μm or less, a coefficient of static friction of one surface and the other surface thereof is 0.8 or less, and an internal haze is 1.0% or less.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In a liquid crystal display device, two polarizing plates are usually arranged on both sides of a liquid crystal cell. A polarizing plate is generally used in which a polarizer protective film for protecting a polarizer is attached to both sides of the polarizer with an adhesive. The polarizer protective film is required to have high transparency, and an optical film made of a cellulose-based material is often used.

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

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

[0005] Although the method such as Patent Document 1 can solve the occurrence of wrinkles and creases during winding, according to the study by the present inventors, with the improvement of the film quality level due to the high definition and large area of the liquid crystal display panel, defects caused by winding tightness of the film during storage as a film roll have become clear. In addition, although the present inventors tried to solve the above phenomenon by adding silica to the acrylic resin film by the method described in Patent Document 1, it has been found that it is difficult to meet the requirements as an acrylic resin film, such as an increase in haze, by the conventional method.

[0006] The present invention has been made to solve the above problems. An object of the present invention is to suppress blocking during film roll storage while maintaining the heat resistance and transparency of the acrylic resin film.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

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

[0009] [1] An acrylic resin film mainly composed of an acrylic resin, wherein the glass transition temperature of the acrylic resin film is 120° C. or higher, the sum of the 10-point average roughness Rzjis of each of both surfaces of the acrylic resin film is 0.05 μm or more and 1.0 μm or less, the static friction coefficient of one surface and the other surface is 0.8 or less, and the internal haze is 1.0% or less.

[0010] [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 is more than 0.080 μm and 0.25 μm or less.

[0011] [3] The acrylic resin film according to [1] or [2] contains at least one or more ring structures selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure.

[0012] [4] The acrylic resin film according to [1] or [2], wherein the syndiotacticity of the triple display is 54% or more.

[0013] [5] The acrylic resin film according to any one of [1] to [4] contains an antiblocking agent, and the antiblocking agent contains acrylic crosslinked particles having an average particle diameter of 0.1 μm or more and 2.5 μm or less.

[0014] [6] The acrylic resin film according to [5], wherein the antiblocking agent contains acrylic crosslinked particles having an average particle diameter of 0.1 μm or more and 2.0 μm or less.

[0015] [7] The acrylic resin film according to [5] or [6] contains 0.05% by weight or more and 0.9% by weight or less of acrylic crosslinked particles.

[0016] [8] The acrylic resin film according to any one of [1] to [7], wherein the dimensional change rate when left standing in an atmosphere of 85 °C and 85% RH for 120 hours is -2.0% or more and -0.1% or less.

[0017] [9] A polarizing plate including the acrylic resin film according to any one of [1] to [8].

[0018]

[10] A liquid crystal display panel including the polarizing plate according to [9].

Advantages of the Invention

[0019] According to the present invention, it is possible to provide an acrylic resin film that is excellent in transparency and heat resistance and can prevent blocking during storage of a film roll.

Best Mode for Carrying Out the Invention

[0020] An embodiment of the present invention will be described, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims. Embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. All academic documents and patent documents described in this specification are incorporated herein by reference. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)", respectively.

[0021] (Acrylic resin film) The acrylic resin film of the present embodiment is an acrylic resin film mainly composed of an acrylic resin, wherein the glass transition temperature of the acrylic resin film is 120°C or higher, the sum of the 10-point average roughness Rzjis of each of both sides of the acrylic resin film is 0.14 μm or more and 1.0 μm or less, the static friction coefficient of one side and the other side is 0.8 or less, and the internal haze is 1.0% or less. Thus, while mainly composed of an acrylic resin, by controlling the sum of Rzjis of both sides of the film and the static friction coefficient to predetermined values, and further controlling the internal haze to a predetermined value, an acrylic resin film excellent in heat resistance and transparency and further excellent in antiblocking properties during film roll storage can be obtained.

[0022] The glass transition temperature of the acrylic resin film of this embodiment is 120°C or higher. Preferably, it is above 120°C, more preferably 121°C or higher, still more preferably 122°C or higher, and particularly preferably 123°C or higher. When the glass transition temperature of the acrylic resin film is 120°C or higher, the dimensional change rate of the stretched film under high-temperature environments of the film becomes small. In actual use, the acrylic resin film of this embodiment is often laminated and used with other films. When the dimensional change rate is small, it is possible to suppress the occurrence of distortion and warping caused by the difference in dimensional change rate that occurs between the laminated other films.

[0023] Preferably, the glass transition temperature of the acrylic resin constituting the acrylic resin film is 120°C or higher, more preferably above 120°C, still more preferably 121°C or higher, even more preferably 122°C or higher, and particularly preferably 123°C or higher.

[0024] Here, as the acrylic resin having a glass transition temperature of 120°C or higher, an acrylic resin having a ring structure in the main chain can be preferably used. For example, as the ring structure, at least one ring structure selected from the group consisting of a glutarimide ring, a lactone ring, maleic anhydride, maleimide, and glutaric anhydride can be mentioned. According to these, it becomes possible to impart heat resistance. Among them, in particular, it is preferable that the ring structure is glutarimide from the viewpoints of production simplicity, cost, and quality stability against moisture.

[0025] 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% by weight to 80% by weight, and more preferably in the range of 3% by weight to 60% by weight. In the case of the content of the ring structure within this range, both the glass transition temperature and the retardation Rth in the thickness direction are favorable, so it is preferable. The content of the ring structure in the acrylic resin is 1Using \(^1H-NMR\), the molar ratio between the target ring structure part and the other parts can be measured and calculated by weight conversion. An acrylic resin with a glass transition temperature of 120 °C or higher is the main component of the acrylic resin film and is contained in the acrylic resin film at more than 50% by weight based on 100% by weight of the acrylic resin film. Among them, it is preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, and particularly preferably 90% by weight or more based on 100% by weight of the acrylic resin film.

[0026] Note that as the acrylic resin with a glass transition temperature of 120 °C or higher, an acrylic resin having no ring structure in the main chain may be used.

[0027] The haze inside the acrylic resin film of this embodiment is 1.0% or less. Among them, the internal haze is preferably 0.7% or less, more preferably 0.5% or less, and particularly preferably 0.3% or less. When the internal haze is 1.0% or less, the quality when mounted on a liquid crystal panel becomes good.

[0028] In this specification, the internal haze is defined as the haze value measured using a haze meter (turbidimeter) for a glass cell filled with pure water around a film placed in a glass cell for liquid measurement.

[0029] Regarding the haze of the acrylic resin film of this embodiment, it is not particularly limited as long as the internal haze is within the above range. However, from the viewpoint of transparency, it is preferably 3.0% or less, more preferably 2.0% or less, and further preferably 1.0% or less.

[0030] The acrylic resin film has a sum of the ten-point average roughness Rzjis of each of the two sides in the range of 0.05 μm or more and 1.0 μm or less. If the sum of the ten-point average roughness Rzjis of each of the two sides is 0.05 μm or more, it becomes easier to reduce the friction between the films. Also, when the films are stacked in a roll shape, the air trapped between the films can easily escape, it is presumed that blocking due to winding tightness can be suppressed and film defects can be suppressed. Here, if the sum of the ten-point average roughness Rzjis of each of the two sides in the acrylic resin film is less than 0.05 μm, blocking due to winding tightness occurs during storage of the film roll, and as a result, film defects occur. This tendency becomes prominent during storage of a long film roll (for example, 8000 m). For this reason, only a fixed-length (for example, 4000 m) acrylic resin film can be wound, and the yield decreases. Also, even for a fixed-length acrylic resin film, the inner acrylic resin film plastically deforms during storage of the film roll, so the plastically deformed acrylic resin film cannot be used. On the other hand, if the sum of the ten-point average roughness Rzjis of each of the two sides in the acrylic resin film exceeds 1.0 μm, the transparency of the acrylic resin film decreases. Also, if the sum of the ten-point average roughness Rzjis of each of the two sides is 1.0 μm or less, it is possible to suppress diffuse reflection of light on the surface and suppress impairment of the sharpness of the panel display. Among them, it is more preferable that the sum of the ten-point average roughness Rzjis of each of the two sides of the acrylic resin film is 0.05 μm or more and 0.6 μm or less, and even more preferable that it is 0.05 μm or more and 0.5 μm or less.

[0031] When the acrylic resin has a ring structure in the main chain, the sum of the ten-point average roughness Rzjis of each of the two sides of the acrylic resin film is preferably 0.15 μm or more and 1.0 μm or less, more preferably 0.16 μm or more and less than 1.0 μm, even more preferably 0.17 μm or more and 0.6 μm or less, and still more preferably 0.2 μm or more and 0.5 μm or less. Also, it is preferable that the ten-point average roughness Rzjis of one side and / or the other side of the acrylic resin film is more than 0.080 μm and 0.25 μm or less.

[0032] On the other hand, when the acrylic resin does not have a ring structure in the main chain, particularly when the syndiotacticity of the triad display described later is 54% or more, the sum of the 10-point average roughness Rzjis on each of the two sides of the acrylic resin film is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.06 μm or more and less than 0.60 μm, still more preferably 0.06 μm or more and less than 0.50 μm, even more preferably 0.06 μm or more and 0.40 μm or less, and still more preferably 0.07 μm or more and 0.30 μm or less. Further, the 10-point average roughness Rzjis of one side and / or the other side of the acrylic resin film is preferably more than 0.020 μm and 0.20 μm or less.

[0033] Here, "blocking" means a state in which the films are adhered to each other, including a state in which they are partially melted at a high temperature or a state in which they are perfectly overlapped. When winding occurs, pressure is applied to the film, and blocking (adhesion) between the films occurs. As a result, when peeling the films from each other, a strong force is required to peel them, causing damage to the film. Therefore, by setting the kurtosis on both sides of the film within a predetermined range as in this embodiment, even if winding occurs, adhesion between the films in the film roll can be suppressed, and the films can be peeled with a weak force, so that damage (film defects) to the film can be suppressed.

[0034] The Rzjis (surface roughness) of the film can be measured using an optical surface roughness such as a laser microscope. Since the value of the surface roughness of the acrylic resin film in this embodiment is small compared to the resolution of the laser microscope, sufficient measurement accuracy cannot be obtained with a lens having a small numerical aperture. Therefore, in this specification, the value measured using a lens having a numerical aperture of 0.95 or more is used.

[0035] From the viewpoints of economy and environmental impact, it is preferable to add the following anti-blocking agent to the acrylic resin for the surface roughness of the film. Among them, organic fine particles are preferable from the viewpoints of affinity and dispersibility with the acrylic resin, and acrylic cross-linked particles are most preferable in terms of easy control of haze.

[0036] The static friction coefficient of the acrylic resin film is 0.8 or less as measured in a state where one surface and the other surface of the film are combined. Among them, it is preferably 0.7 or less, more preferably 0.6 or less, and particularly preferably 0.5 or less. If the static friction coefficient is 0.8 or less, blocking between the films in the film roll can be effectively suppressed. The lower limit of the static friction coefficient is not particularly limited, but is preferably 0.2 or more from the viewpoints of winding deviation and meandering during manufacturing.

[0037] In the acrylic resin film, the dimensional change rate when left standing for 120 hours in an atmosphere of 85°C and 85% RH is preferably such that the average value in the longitudinal direction (MD direction) and the width direction (TD direction) of the film is -2.0% or more, more preferably -1.7% or more, and even more preferably -1.5% or more. When the above dimensional change rate is -2.0% or more, shrinkage over time during storage of the film roll can be suppressed, the temporal stability of the winding appearance is improved, warping and dimensional changes when laminated to a polarizer are alleviated, and a decrease in contrast and peripheral unevenness of the liquid crystal display device can be suppressed. The above dimensional change rate may be, for example, -0.1% or less. When the above dimensional change rate is -0.1% or less, when laminated to a polarizer, even if the polarizer itself shrinks, the acrylic resin film easily follows the shrinkage. Here, the dimensional change rate when left standing for 120 hours in an atmosphere of 85°C and 85% RH can be measured using a three-dimensional measuring instrument for the dimensional changes before and after leaving the acrylic resin film standing for 120 hours in an environmental test chamber set at 85°C and 85% RH.

[0038] In this specification and the claims, the dimensional change rate means the change rate of the hole interval before and after standing for 120 hours in an atmosphere of 85°C and 85% RH after making a hole with a diameter of 1 mm at a position where the distance from the four corners of a 90 mm × 90 mm film is 20 mm in the inner direction of the diagonal. Here, the change rate of the hole interval means the change rate of the hole interval after standing based on the hole interval before standing, and is expressed by the formula [(hole interval after standing) - (hole interval before standing)] × 100 / (hole interval before standing) ··· (A) and is calculated by

[0039] The linear expansion coefficient of the acrylic resin film at 40 to 60°C is preferably 80 ppm or less, more preferably 72 ppm or less. If it is 80 ppm or less, shrinkage and expansion of the film due to temperature changes during storage and transportation of the roll can be suppressed, and winding tightness is less likely to occur. On the other hand, the lower limit is preferably 40 ppm or more. If the linear expansion of the film is 40 ppm or more, when laminated with a polarizer, the difference in linear expansion with other members is small, so warping and the like are less likely to occur.

[0040] The linear expansion coefficient can be measured, for example, using a thermomechanical analyzer TMA - 4000SA manufactured by Bruker AXS. Specifically, in a nitrogen atmosphere, while applying a tensile load of 3.1 g to a film cut into 4 mm × 20 mm, the film is heated at a rate of 2°C / min in a temperature range not exceeding the glass transition temperature, a chart is created with the temperature plotted on the X-axis and the change in the length of the film plotted on the Y-axis, and the slope in the temperature range from 40°C to 60°C during the heating and cooling process is calculated by the least squares method and can be obtained as the linear expansion coefficient.

[0041] (Antiblocking agent) The acrylic resin film is preferably formed from an acrylic resin composition in which an anti-blocking agent is added to the acrylic resin. As the anti-blocking agent, acrylic crosslinked particles are preferable from the viewpoints of compatibility, dispersibility, and transparency with the acrylic resin. The shape of the particles can be arbitrarily selected, but spherical particles are preferable because anti-blocking property is likely to be exhibited.

[0042] The refractive index of the anti-blocking agent is preferably 98% or more and 102% or less, more preferably 99% or more and 101% or less, when the refractive index of the acrylic resin is taken as 100%. As the refractive index of the anti-blocking agent, 1.47 or more and 1.55 or less is preferable, 1.47 or more and 1.53 or less is more preferable, and 1.48 or more and 1.52 or less is more preferable. By using an anti-blocking agent having a refractive index within the above range, an acrylic resin film with high transparency can be obtained. Among them, acrylic crosslinked particles are preferable because they satisfy the above refractive index.

[0043] The polymerizable monomer forming the acrylic crosslinked particles can be selected from any (meth)acrylic acid ester and other copolymerizable monomers, but it preferably contains methyl methacrylate from the viewpoints of compatibility with the acrylic resin and refractive index. The content of the structural unit derived from methyl methacrylate in the acrylic crosslinked particles is preferably 80% by weight or more and 99% by weight or less, more preferably 83% by weight or more and 96% by weight or less. When the content of the structural unit derived from methyl methacrylate in the acrylic resin is high, it is preferable that the content of the structural unit derived from methyl methacrylate in the acrylic crosslinked particles is high.

[0044] The above acrylic crosslinked particles further contain a structural unit derived from a polyfunctional monomer containing two or more polymerizable groups in the molecule as a polymerizable monomer. The content of the polyfunctional monomer in the polymerizable monomer can be arbitrarily set, but is preferably 0.5% by weight or more and 30% by weight or less. When it is less than 0.5% by weight, the heat resistance and dispersibility of the acrylic crosslinked particles are poor. When it exceeds 30% by weight, coalescence of particles and formation of deformed particles may occur during the production of the acrylic crosslinked particles.

[0045] The average particle diameter of the above acrylic crosslinked particles is preferably 0.1 μm or more and 2.5 μm or less, more preferably 0.1 μm or more and 2.0 μm or less. When it is less than 0.1 μm, the amount of additive required to exhibit antiblocking properties needs to be increased, which may result in inferior mechanical properties and economy. When the upper limit exceeds 2.5 μm, it may induce clogging of the polymer filter. Also, from the perspective of the long-term performance of the polymer filter, it is preferable to use those with a narrow particle size distribution and a small content of coarse particles.

[0046] Regarding the addition amount of the acrylic crosslinked particles of this embodiment, it is preferably 0.05% by weight or more and 0.9% by weight or less, more preferably 0.07% by weight or more and 0.5% by weight or less, and even more preferably 0.1% by weight or more and 0.2% by weight or less. When the addition amount is less than 0.05% by weight, a sufficient antiblocking effect cannot be obtained. By setting the addition amount to 0.9% by weight or less, deterioration of economy can be prevented, and an increase in haze can also be prevented. Also, for the purpose of controlling slipperiness and surface properties, a plurality of types of particles having different particle size distributions may be mixed. In this case, the addition amount of the acrylic crosslinked particles is the total of the addition amounts of the plurality of types of particles.

[0047] (Easy adhesion layer) The acrylic resin film of this embodiment may be provided with an easy-adhesion layer on one or both of its surfaces. By providing the easy-adhesion layer, for example, when used as a polarizer protection film, the adhesion between the polarizer protection film and the polarizer by the adhesive can be reinforced when laminating to the polarizer via the adhesive. Also, it is possible to obtain a stretched film having an easy-adhesion layer by providing an easy-adhesion layer on an unstretched film and then stretching it.

[0048] As the easy-adhesion layer used in this embodiment, it can be formed using known techniques described in, for example, JP-A-2009-193061 and JP-A-2010-55062. That is, for example, it can be formed with an easy-adhesive composition containing a urethane resin having a carboxyl group and a crosslinking agent. By using a urethane resin, an easy-adhesion layer excellent in adhesion between the polarizer protection film and the polarizer can be obtained. The easy-adhesive composition is preferably aqueous from the viewpoints of workability and environmental protection.

[0049] (Acrylic resin) As described above, the acrylic resin film has a glass transition temperature of 120°C or higher, and as the acrylic resin used as the acrylic resin film, those having a glass transition temperature of 120°C or higher can be preferably used. As the acrylic resin having a glass transition temperature of 120°C or higher, as described above, an acrylic resin having a ring structure in the main chain and an acrylic resin having no ring structure in the main chain can be used. Hereinafter, each ring structure will be described.

[0050] (Acrylic resin having a glutarimide ring in the main chain) The acrylic resin having a glutarimide ring as a ring structure in the 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 a content of an acrylate unit of less than 1% by weight and treating it with an imidizing agent.

[0051] [Chemical formula]

[0052] (Here, R 1 and R 2 each independently represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and 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.)

[0053] The content rate of the glutarimide ring according to this embodiment is a value that can be measured, for example, by the following method. 1 It is performed using H-NMR. The area of the peak derived from the O-CH proton of methyl methacrylate around 3.5 ppm to 3.8 ppm and the N-R of the glutarimide group around 3.0 ppm to 3.3 ppm 3 Perform weight conversion using the molar ratio obtained from the peak area of the proton. 3

[0054] 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, t-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. may be used in combination, but when these are used in combination, the acrylate unit is preferably less than 1% by weight. More preferably, the acrylate unit is less than 0.5% by weight, and even more preferably less than 0.3% by weight.

[0055] In addition to the above monomer, it is also possible to copolymerize 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.

[0056] ​The structure of the above methyl methacrylate resin is not particularly limited, and it may be any of a linear (chain) polymer, block polymer, core-shell polymer, branched polymer, ladder polymer, crosslinked polymer, etc.

[0057] In the case of a block polymer, it may be any of A-B type, A-B-C type, A-B-A type, and other types of block polymers. In the case of a core-shell polymer, it may consist of only one layer of core and one layer of shell, or each may consist of multiple layers.

[0058] The method for producing polymethyl methacrylate is not particularly limited, and known emulsion polymerization methods, emulsion-suspension polymerization methods, suspension polymerization methods, bulk polymerization methods, solution polymerization methods, etc. are applicable. However, when used in the optical field, from the perspective of having fewer impurities, bulk polymerization methods and solution polymerization methods are particularly preferred. For example, it can be produced according to the methods described in JP-A-56-8404, JP-B-6-86492, JP-B-7-37482, or JP-B-52-32665.

[0059] The method for producing the acrylic resin of this embodiment includes a step (imidation step) of heating and melting a methyl methacrylate resin or an acrylic resin copolymerized with a monomer other than the above methyl methacrylate monomer and treating it with an imidizing agent. Thereby, an acrylic resin having glutarimide can be produced.

[0060] The imidizing agent is not particularly limited as long as it can form a glutarimide ring represented by the general formula (1), and examples include those described in WO2005 / 054311. Specifically, for example, aliphatic hydrocarbon group-containing amines such as ammonia, methylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, n-hexylamine; aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine, trichloroaniline; and alicyclic hydrocarbon-containing amines such as cyclohexylamine can be mentioned. Also, urea-based compounds that generate the exemplified amines upon heating, such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, can be used. Among these imidizing agents, it is preferable to use methylamine, ammonia, or cyclohexylamine from the viewpoints of cost and physical properties, and it is particularly preferable to use methylamine. Gaseous methylamine etc. at room temperature may be used in a state dissolved in alcohols such as methanol.

[0061] In this imidization step, by adjusting the addition ratio of the above imidizing agent, the ratios of the glutarimide units and (meth)acrylate units in the resulting acrylic resin can be adjusted.

[0062] Also, by adjusting the degree of imidization, the physical properties of the resulting acrylic resin and the transparency etc. of the stretched film formed by molding the acrylic resin according to this embodiment can be adjusted.

[0063] The imidizing agent is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the acrylic resin containing methyl methacrylate units. When the addition amount of the imidizing agent is within this range, it is difficult for the imidizing agent to remain in the resin, and the possibility of inducing appearance defects or foaming after molding is extremely low. Also, since the content of the glutarimide ring in the finally obtained resin composition becomes appropriate, its heat resistance is less likely to decrease, and it is less likely to induce appearance defects after molding, which is preferable.

[0064] In this imidization step, in addition to the imidizing agent, a ring-closing accelerator (catalyst) may be added as necessary.

[0065] The method of heating and melting and treating with the imidizing agent is not particularly limited, and any conventionally known method can be used. For example, the acrylic resin containing the methyl methacrylate unit can be imidized by a method using an extruder, a batch reactor (pressure vessel), or the like.

[0066] The extruder is not particularly limited. For example, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder can be used. The extruder may be used alone or a plurality of extruders may be connected in series. When using a twin-screw extruder, examples include a non-intermeshing co-rotating type, an intermeshing co-rotating type, a non-intermeshing counter-rotating type, and an intermeshing counter-rotating type. Among them, the intermeshing co-rotating twin-screw extruder is preferable because it can rotate at high speed and can further promote the mixing of the imidizing agent (when using a ring-closing accelerator, the imidizing agent and the ring-closing accelerator) with respect to the raw material polymer.

[0067] When performing imidization in an extruder, for example, a methyl methacrylate resin is introduced from the raw material input section of the extruder, the resin is melted and filled in the cylinder, and then the imidizing agent is injected into the extruder using a dosing pump, whereby the imidization reaction can proceed in the extruder.

[0068] 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 glutarimide formation is possible.

[0069] When using an extruder, it is also preferable to install a vent hole capable of reducing the pressure below atmospheric pressure in order to remove unreacted imidizing agent and by-products. According to such a configuration, unreacted imidizing agent, by-products such as methanol, or monomers can be removed.

[0070] When producing an acrylic resin containing a glutarimide ring in the main chain using a batch reactor (pressure vessel), the structure of the batch reactor (pressure vessel) is not particularly limited. It suffices to have a structure that can melt and stir an acrylic resin containing methyl methacrylate units by heating, and can add an imidizing agent (when using a ring-closing accelerator, the imidizing agent and the ring-closing accelerator), but preferably has a structure with good stirring efficiency.

[0071] Specific examples of the imidization method include, for example, known methods such as those described in JP-A-2008-273140 and JP-A-2008-274187.

[0072] In the method for producing an acrylic resin of this embodiment, in addition to the above imidization step, it can include a step of treating with an esterifying agent. By this esterification step, the acid value of the imidized resin obtained in the imidization step can be adjusted within a desired range.

[0073] The esterifying agent is not particularly limited as long as it can esterify the carboxyl groups remaining in the molecular chain. For example, 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, dimethylcarbodiimide, etc. can be mentioned. Among these, from the viewpoints of cost, reactivity, etc., dimethyl carbonate and trimethyl orthoacetate are preferred, and dimethyl carbonate is preferred from the viewpoint of cost.

[0074] In this imidization step, it is preferable that the esterifying agent is in an amount of 0 to 30 parts by weight, more preferably 0 to 15 parts by weight, based on 100 parts by weight of the acrylic resin containing methyl methacrylate units. If the esterifying agent is within these ranges, the acid value can be adjusted to an appropriate range. On the other hand, if it is more than this range, unreacted esterifying agent may remain in the resin, which may cause foaming or odor generation when molding is performed using the obtained resin.

[0075] In addition to the esterifying agent, a catalyst can also be used in combination. The catalyst is not particularly limited as long as it can promote esterification. For example, aliphatic tertiary amines such as trimethylamine, triethylamine, and tributylamine can be mentioned. Among these, triethylamine is preferable from the viewpoints of cost, reactivity, etc.

[0076] In this esterification step, only heat treatment or the like can be performed without treatment with an esterifying agent. When only heat treatment (such as kneading and dispersing of molten resin in an extruder) is performed, a part or all of the carboxyl groups in the acrylic resin having a glutarimide ring by-produced in the imidization step can be converted into acid anhydride groups by dehydration reaction between carboxyl groups, dealcoholization reaction between carboxyl group and alkyloxycarbonyl group, etc. At this time, it is also possible to use a ring-closing accelerator (catalyst). Even when treated with an esterifying agent, it is also possible to promote acid anhydride group formation by heat treatment.

[0077] Since the imide resin obtained through the imidization step and the esterification step contains unreacted imidizing agent, unreacted esterifying agent, volatile components by-produced by the reaction, resin decomposition products, etc., it is possible to attach a vent hole capable of reducing the pressure below atmospheric pressure.

[0078] (Acrylic resin having a lactone ring in the main chain) 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 in which a lactone ring structure is introduced into the molecular chain), and the production method thereof is also not limited. Preferably, after obtaining a polymer (a) having a hydroxyl group and an ester group in the molecular chain by polymerization (polymerization step), the obtained polymer (a) is heat-treated to introduce a lactone ring structure into the polymer (lactonization condensation step).

[0079] In the polymerization step, a polymer having a hydroxyl group and an ester group in the molecular chain is obtained by performing a polymerization reaction of a monomer component containing an unsaturated monomer represented by the following general formula (2).

[0080] [Chemical formula]

[0081] (However, R 4 and R 5 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.).

[0082] Examples of the unsaturated monomer represented by the general formula (2) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, normal butyl 2-(hydroxymethyl)acrylate, and tertiary butyl 2-(hydroxymethyl)acrylate. Among them, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred in terms of its high effect of improving heat resistance. These unsaturated monomers may be used alone or in combination of two or more.

[0083] The content ratio of the unsaturated monomer represented by the general formula (2) in the monomer component is preferably 5% by weight to 50% by weight, more preferably 10% by weight to 40% by weight, and still more preferably 10% by weight to 30% by weight. If the above content ratio is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness of the resulting lactone ring-containing polymer may decrease. If it is more than 50% by weight, a crosslinking reaction may occur during the formation of the lactone ring structure, making it easy to gel, the fluidity may decrease, making it difficult to perform melt molding, or unreacted hydroxyl groups may remain easily, so that a condensation reaction may further proceed during molding, generating volatile substances and making it easy to enter silver streaks, or there may be a risk of increasing the retardation in the thickness direction Rth.

[0084] The monomer component preferably contains other monomers in addition to the unsaturated monomer represented by the general formula (2). The other monomers are not limited as long as they are selected within a range that does not impair the effects of the present invention. For example, (meth)acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and unsaturated monomers represented by the following general formula (3) are preferably mentioned. The above other monomers may be used alone or in combination of two or more.

[0085]

Chemical formula

[0086] (However, R 6 represents a hydrogen atom or a methyl group, 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 group, the Ac group represents an acetyl group, and R 7 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.)

[0087] The above (meth)acrylic acid ester is not limited as long as it is a (meth)acrylic acid ester other than the unsaturated monomer represented by the general formula (2). For example, acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate can be mentioned. These may be used alone or in combination of two or more. Among them, methyl methacrylate is particularly preferable from the viewpoints of heat resistance and transparency.

[0088] When using the above (meth)acrylic acid ester, its content ratio in the monomer component is preferably 10% by weight to 95% by weight, more preferably 10% by weight to 90% by weight, still more preferably 40% by weight to 90% by weight, and particularly preferably 50% by weight to 90% by weight in order to sufficiently exhibit the effects of the present invention.

[0089] (Acrylic resin having maleic anhydride, maleimide and glutaric anhydride structures in the main chain) In the present embodiment, it is also preferable to use an acrylic resin having a maleimide or glutaric anhydride structure as a ring structure in the main chain. Examples of the maleic anhydride structure include styrene-N-phenylmaleimide-maleic anhydride copolymer. Examples of the maleimide structure include olefin-maleimide copolymers as described in JP-A-2004-45893. Examples of the glutaric anhydride structure include copolymers having a glutaric anhydride unit as described in JP-A-2003-137937.

[0090] (Acrylic resin having no ring structure in the main chain) Examples of acrylic resins having a glass transition temperature of 120°C or higher include a method of introducing a carboxyl group such as methacrylic acid. When the amount of the carboxyl group exceeds a certain level, there is a risk of forming a crosslinked body or an increased risk of foaming during film formation. Therefore, it is preferably suppressed to a certain amount or less. Specifically, the amount of the carboxyl group in the acrylic resin is preferably 0.6 mmol / g or less, more preferably 0.4 mmol / g or less.

[0091] As the acrylic resin having a glass transition temperature of 120°C or higher, an acrylic resin having a syndiotacticity of 54% or more in the triad display can be preferably used. When the syndiotacticity of the triad display of the acrylic resin is 54% or more, the glass transition temperature of the acrylic resin tends to increase and the heat resistance of the acrylic resin tends to improve. The syndiotacticity of the triad display of the acrylic resin is preferably 55% or more, more preferably 56% or more, and even more preferably 57% or more. Also, the syndiotacticity of the triad display of the acrylic resin is preferably 67% or less, more preferably 65% or less, and even more preferably 63% or less from the viewpoints of the molding processing temperature, toughness of the molded body, and secondary processability of the acrylic resin.

[0092] The syndiotacticity of the triad display of the acrylic resin is the ratio of the chains (triads) of the three structural units being rr. In the chains (dyads) of two structural units, those having the same configuration are called meso (m), and those having the opposite configuration are called racemo (r).

[0093] The method for synthesizing an acrylic resin having a syndiotacticity of 55% or more in the triad representation is not particularly limited, and examples thereof include an anionic polymerization method and a radical polymerization method. Among these, the radical polymerization method is preferred (see, for example, International Publication No. 2023 / 238885 and International Publication No. 2023 / 238886). In the radical polymerization method, since an organometallic compound as a polymerization initiator and an organic solvent as a medium used in the anionic polymerization method are not used, it is difficult for impurities to remain, which is preferable from the environmental viewpoint. Here, the glass transition temperature and the syndiotacticity in the triad representation of the acrylic resin 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 increases, and the syndiotacticity of the acrylic resin also increases. Further, the glass transition temperature of the acrylic resin can also be controlled by the molecular weight of the acrylic resin.

[0094] The content of the structural unit derived from methyl methacrylate in the acrylic resin having a syndiotacticity of 54% or more in the triad representation is preferably 98% by weight or more, more preferably 99% by weight or more, and still more preferably 100% by weight.

[0095] The monomers other than methyl methacrylate that constitute the acrylic resin with a syndiotacticity of the triad representation of 54% or more are not particularly limited. For example, alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cycloalkyl acrylates such as cyclohexyl acrylate, norbornenyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate, norbornenyl methacrylate; aromatic vinyl compounds such as styrene, α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; methacrylonitrile can be mentioned.

[0096] (Other properties of the acrylic resin) Hereinafter, other properties of the acrylic resin having a ring structure in the main chain and the acrylic resin not having a ring structure in the main chain will be described. Hereinafter, the description of "acrylic resin" shall mean at least either the acrylic resin having a ring structure in the main chain or the acrylic resin not having a ring structure in the main chain.

[0097] The weight average molecular weight of the acrylic resin is preferably 50,000 or more and 200,000 or less, and more preferably 90,000 or more and 150,000 or less. When the weight average molecular weight of the acrylic resin is 50,000 or more, the mechanical properties of the molded body of the acrylic resin tend to improve, and when it is 200,000 or less, the moldability of the acrylic resin tends to improve.

[0098] The weight average molecular weight of the acrylic resin may be 400,000 or more. When the weight average molecular weight of the acrylic resin is 400,000 or more, the mechanical properties of the molded article of the acrylic resin tend to be further improved. For example, a resin film excellent in bending resistance can be obtained. In this case, the weight average molecular weight of the acrylic resin is preferably 600,000 or more, more preferably 700,000 or more, and even more preferably 800,000 or more. Further, from the viewpoint 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.

[0099] The ratio (dispersion degree) of the weight average molecular weight to the number average molecular weight 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 dispersion degree of the acrylic resin is 1.6 or more, the fluidity of the acrylic resin tends to be improved and it becomes easier to mold. When it is 2.5 or less, the mechanical properties such as impact resistance, toughness, and bending resistance of the molded article of the acrylic resin tend to be improved.

[0100] The number average molecular weight and the weight average molecular weight of the acrylic resin are values in terms of standard polystyrene measured by gel permeation chromatography (GPC). Further, the number average molecular weight and the weight average molecular weight of the acrylic resin can be controlled by the types and amounts of the polymerization initiator and the chain transfer agent used when synthesizing the acrylic resin.

[0101] (Acrylic resin composition) As the acrylic resin film, an acrylic resin composition obtained by adding an additive to an acrylic resin may be used, and an antiblocking agent and an additive may be used in combination. As the additive, generally used antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, specific wavelength absorbers or specific wavelength absorbing dyes for the purpose of blocking blue light, radical scavengers and other light resistance stabilizers, retardation adjusters, catalysts, plasticizers, lubricants, antistatic agents, colorants, shrinkage preventers, antibacterial and deodorizing agents, fluorescent brighteners, compatibilizers, etc. may be added alone or in combination of two or more kinds as long as the object of the present invention is not impaired.

[0102] Examples of the ultraviolet absorber include triazine compounds, benzotriazole compounds, benzophenone compounds, cyanoacrylate compounds, benzoxazine compounds, oxadiazole compounds, etc. Among these, triazine compounds are preferable from the viewpoints of ultraviolet absorption performance with respect to the addition amount and volatility when melt-extruded.

[0103] Regarding the retardation adjuster, when imparting negative retardation, for example, a compound having a styrene skeleton may be used, and acrylonitrile-styrene copolymer is exemplified.

[0104] The mixing method of the acrylic resin and the antiblocking agent is not particularly limited, and any conventionally known method can be used. For example, a method of supplying to an extruder using a gravimetric feeder and melt-kneading, or a method of mixing in a solution state with a solvent having excellent compatibility with both the acrylic resin and the antiblocking agent can be mentioned.

[0105] When mixing using an extruder, the extruder to be used is not particularly limited, and various extruders can be used. Specifically, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, etc. can be used. Among them, it is preferable to use a twin-screw extruder. According to the twin-screw extruder, the degree of freedom of the conditions for uniformly mixing the acrylic resin and the anti-blocking agent is wide. Also, the acrylic resin and the anti-blocking agent may be introduced and mixed using a raw material input hopper or the like from the upstream side of the extruder, or only the anti-blocking agent may be introduced and mixed using a side feeder, a gravimetric feeder, etc. from the middle of the extruder. Alternatively, a masterbatch of the anti-blocking agent prepared by another extruder in advance may be used.

[0106] For the purpose of reducing foreign matter in the resin, it is also possible to install a filter at the end of the extruder. It is preferable to install a gear pump (A) in front of the filter to boost the pressure of the acrylic resin / acrylic resin composition. As the type of filter, it is preferable to use a stainless steel leaf disk filter capable of removing foreign matter from the molten polymer, and as the filter element, it is preferable to use a fiber type, a powder type, or a composite type thereof.

[0107] (Method for producing an acrylic resin film) An embodiment of the method for producing the 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 capable of forming the acrylic resin composition of the present embodiment to produce a film.

[0108] Specifically, for example, injection molding, melt extrusion molding, inflation molding, blow molding, compression molding, etc. can be mentioned. Also, after dissolving the acrylic resin composition according to the present embodiment in a solvent capable of dissolving it, the film according to the present embodiment can be produced by a solution casting method or a spin coating method for molding.

[0109] Among these, it is preferable to use a melt extrusion method without using a solvent. According to the melt extrusion method, the manufacturing cost and the load on the global environment and the working environment caused by the solvent can be reduced.

[0110] When the acrylic resin composition of this embodiment is formed into a film by the melt extrusion method, first, the acrylic resin composition of this embodiment is pre-dried and then supplied to an extruder to heat and melt the acrylic resin composition. Further, it is supplied to a die such as a T-die through a gear pump or a filter. Next, the acrylic resin composition supplied to the T-die is extruded as a sheet-like molten resin and cooled and solidified using a cooling roll or the like to obtain an unstretched film (also referred to as a mother roll film). At this time, in order to improve the surface property (smoothness) of the film, it is also possible to sandwich it between a metal roll and a flexible roll provided with a metal elastic outer cylinder.

[0111] When the acrylic resin composition of the present embodiment is formed into an unstretched film by the solution casting method, the acrylic resin composition of the present embodiment is made into a solution together with an organic solvent, and then the solution is cast onto a support and dried by heating to produce an unstretched film. The solvent that can be used in the solution casting method can be selected from known solvents. Halogenated hydrocarbon solvents such as methylene chloride and trichloroethane are preferred solvents because they easily dissolve the acrylic resin of the present embodiment and have a low boiling point. In addition, highly polar non-halogenated solvents such as dimethylformamide and dimethylacetamide can also be used. Furthermore, aromatic solvents such as toluene, xylene, and anisole, cyclic ether solvents such as dioxane, dioxolane, tetrahydrofuran, and pyran, and ketone solvents such as methyl ethyl ketone can also be used. These solvents may be used alone or in combination of multiple types. The amount of the solvent used can be any amount as long as the thermoplastic resin can be dissolved to an extent that enables sufficient casting. In this specification, "dissolution" means that the resin is present in the solvent in a uniform state to an extent that enables sufficient casting. It is not necessarily required that the solute is completely dissolved in the solvent. The resin concentration in the solution is preferably 1% by weight to 90% by weight, more preferably 5% by weight to 70% by weight, and still more preferably 10% by weight to 50% by weight. As a preferred support, an endless belt made of stainless steel may be used. Alternatively, a film such as a polyimide film or a polyethylene terephthalate film can also be used.

[0112] The acrylic resin film of the present embodiment is obtained by stretching an unstretched film (also referred to as a raw film). By stretching the unstretched film, it is possible to produce a stretched film having a desired thickness, and furthermore, the mechanical properties of the stretched film can be improved. As the stretching method, a conventionally known method can be used. For example, an unstretched raw film formed by melt extrusion can be uniaxially or biaxially stretched to produce a film with a predetermined thickness. In order to endow the stretched film with excellent mechanical properties in both the longitudinal direction (MD direction) and the width direction (TD direction), biaxial stretching is preferably performed. As the biaxial stretching method, either simultaneous biaxial stretching or sequential biaxial stretching may be used.

[0113] Regarding the stretching ratio (in the case of biaxial stretching, both in the MD direction and TD direction of the film), it is preferably 1.5 to 3.0 times, and more preferably 1.8 to 2.8 times. If the stretching ratio is within this range, the mechanical properties of the film associated with stretching can be sufficiently improved. Also, the degree of orientation does not increase too much, the dimensional change when left standing for 120 hours in an atmosphere of 85°C and 85% RH can be reduced, and furthermore, the possibility of a decrease in the peel strength when laminated to a polarizer is small. Regarding the stretching speed, it is preferably performed at 1.1 times / minute or more, and more preferably 5 times / minute or more. Also, it is preferably 100 times / minute or less, and more preferably 50 times / minute or less. In the case of sequential biaxial stretching, the stretching speed in the first stage and the stretching speed in the second stage may be the same or different. In sequential biaxial stretching, usually, the first stage of stretching is in the longitudinal direction (MD direction), and the second stage of stretching is in the width direction (TD direction).

[0114] The stretching temperature is not particularly limited, but it is preferably carried out at Tg + 7°C to Tg + 50°C, and more preferably at Tg + 10°C to Tg + 40°C. When the stretching temperature is Tg + 7°C or higher, the risk of breakage in the stretching process can be suppressed. On the other hand, when the stretching temperature is Tg + 50°C or lower, sufficient molecular orientation can be obtained, and a decrease in the mechanical strength of the film can be suppressed. When the stretching temperature is high within the above range, the molecular orientation is relaxed, so the mechanical strength decreases, while the dimensional change in an atmosphere of 85°C and 85% RH becomes small. Also, in the case of a film containing an anti-blocking agent, when stretching at a low temperature, particles are likely to float to the surface, and surface roughness, slipperiness, and external haze are likely to occur. Those skilled in the art can arbitrarily set the stretching conditions in consideration of the above balance.

[0115] The acrylic resin film of this embodiment is wound into a roll by a known method. According to the film according to this embodiment, even when the film width becomes wider or the winding length becomes longer, defects caused by blocking between the films are less likely to occur. Further, in combination with the end nailing process or the like that has been conventionally used for blocking countermeasures, it is more effective.

[0116] (Usage) When the acrylic resin film of this embodiment is used as a polarizer protection film, it is bonded to a polarizer to form a polarizing plate. The polarizer is not particularly limited, and any conventionally known polarizer can be used. For example, a polarizer obtained by containing iodine in stretched polyvinyl alcohol can be mentioned.

[0117] This polarizing plate is further bonded to various films and can be suitably used in display fields such as liquid crystal displays and organic EL displays. However, the applications are not limited to these.

Examples

[0118] The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0119] (Surface roughness) The surface roughness of the acrylic resin film was measured using the evident laser microscope LEXT OLS5100 in accordance with JIS B 0601:2013. Specifically, first, an objective lens with a magnification of 50 times and an aperture number of 0.95 was used to capture a confocal image of a 257 μm × 257 μm range of the film. Next, evaluation lines were drawn at equal intervals three times each in the MD direction and the TD direction, and roughness curves were extracted. From the obtained roughness curves, the 10-point average roughness Rzjis was calculated using analysis software, and the average value at the measurement position was calculated. The measurement was performed five times by changing the measurement position, and their average value was adopted as the surface roughness. However, if partial abnormalities such as scratches were clearly recognized in the image, they were not included in the measured values, and the measurement was repeated after avoiding the abnormal parts.

[0120] (Coefficient of static friction) In accordance with JIS K7125:1999, the coefficient of static friction of the acrylic resin film was measured using the digital force gauge ZTS-5N manufactured by IMADA and the friction coefficient measuring jig COF-2N-V. Specifically, the A side of the film was fixed on a smooth stainless steel plate, the B side of the film was adhered to a 60 × 60 mm thread weighing 200 g with double-sided tape, and the load when the thread was moved at a speed of 100 mm / min via a pulley was read by a load cell to calculate the coefficient of static friction. The measurement was carried out five times by replacing the film piece, and the average value was calculated.

[0121] (Haze, internal haze) In accordance with JIS 7136:2000, the haze of the acrylic resin film was measured using the haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. Also, the acrylic resin film was placed in a glass cell for liquid measurement so that distilled water contacted both sides of the acrylic resin film, and the internal haze of the acrylic resin film was measured.

[0122] (Glass transition temperature) Using 10 mg of an acrylic resin or an acrylic resin composition, the glass transition temperature of the acrylic resin or acrylic resin film was measured. Specifically, using a differential scanning calorimeter (manufactured by Hitachi High-Technologies Corporation, DSC7000X), the temperature was raised at a rate of 20 °C / min under a nitrogen atmosphere, and the glass transition temperature was determined by the midpoint method.

[0123] (Dimensional change rate) From the four corners of a film cut out from an acrylic resin film to a size of 90 mm × 90 mm using a cutter, holes were drilled at a location 20 mm in the inner direction of the diagonal with a 1 mm diameter punch, and the hole spacing was measured using a Mitutoyo MF201 type three-dimensional measuring instrument. Subsequently, the hole spacing of the stretched film whose hole spacing was measured was measured again after standing still for 120 hours in an LH-20 type environmental test machine manufactured by Nagano Science set at 85 °C and 85% RH. The dimensional change rate was calculated by formula (A) from the hole spacing before and after standing still in an atmosphere of 85 °C and 85% RH.

[0124] (Refractive index of acrylic resin composition and acrylic crosslinked particles) First, in accordance with JIS K7142:2014, the refractive index of the acrylic resin composition was determined as follows. Specifically, the acrylic resin composition was melt-pressed at 240 °C to form a film with a thickness of 100 μm, and the refractive index (wavelength 589 nm) of the obtained film was measured under the condition of 23 °C using a refractometer (manufactured by Atago Co., Ltd., digital Abbe refractometer DR-M2). The obtained refractive index was taken as the refractive index of the acrylic resin composition.

[0125] Next, using a halogen-based high refractive index liquid and a low refractive index liquid such as methanol, a refractive index of acrylic crosslinked particles was determined by the following method using a mixed liquid with a changed ratio. Here, when acrylic crosslinked particles are dispersed in the mixed liquid, a turbid dispersion liquid is formed when the refractive indices of the mixed liquid and the acrylic crosslinked particles do not match, and a transparent liquid is formed when the refractive indices of the mixed liquid and the acrylic crosslinked particles match. Therefore, the refractive index of the mixed liquid when it became a transparent liquid was taken as the refractive index of the acrylic crosslinked particles.

[0126] <Production of Acrylic Resin> (Production Example of Acrylic Resin 1) The extruder used was an intermeshing 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 was 250 to 280 °C, and the screw rotation speed was 85 rpm. After melting and filling the methyl methacrylate resin with a kneading block, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was injected from the nozzle with respect to 100 parts by weight of the above methyl methacrylate resin. The resin that came out as a strand from the die provided at the extruder outlet was cooled in a water tank and then pelletized with a pelletizer to obtain Resin (I). Next, in an intermeshing co-rotating twin-screw extruder with a diameter of 40 mm, the set temperature of each temperature control zone of the extruder was set to 240 to 260 °C. 0.56 part by weight of dimethyl carbonate was injected from the nozzle with respect to 100 parts by weight of the above methyl methacrylate resin to reduce the carboxyl groups in the resin. The by-products after the reaction and the excess dimethyl carbonate were removed. The resin that came out as a strand from the die provided at the extruder outlet was cooled in a water tank and then pelletized with a pelletizer to obtain Acrylic Resin 1 having a glutarimide ring. The glass transition temperature of the Acrylic Resin 1 was 123 °C, Mw was 81,000, and Mw / Mn was 1.59.

[0127] (Calculation of the Content of Ring Structure) The obtained acrylic resin was 1 measured using H-NMR BRUKER AvanceIII (400 MHz). It was calculated by performing weight conversion from the molar ratio of the target ring structure part and the other parts. Specifically, in the case of glutarimide, the area A of the peak derived from the proton of O-CH of methyl methacrylate around 3.5 to 3.8 ppm and the area B of the peak derived from the proton of N-CH of glutarimide around 3.0 to 3.3 ppm were used. When the weight conversion was performed using the obtained molar ratio, the ring structure content was 6% by weight. 3 3

[0128] (Example 1) A mixture containing 1 part of the acrylic resin 1 produced in the above acrylic resin production example and 0.08% by weight of acrylic crosslinked particles (J-3PY manufactured by Negami Kogyo, refractive index 1.49) with an average particle diameter of 1.2 μm as an antiblocking agent (AB agent) was kneaded using a meshing type co-rotating twin-screw extruder with a diameter of 15 mm (L / D = 45). The resin that came out as a strand from the die provided at the extruder outlet was cooled in a water tank and then pelletized with a pelletizer to obtain an acrylic resin composition (refractive index 1.49).

[0129] The obtained acrylic resin composition was dried at 100 °C for 5 hours and then formed into a film using a meshing type co-rotating twin-screw extruder with a diameter of 15 mm (L / D = 45) equipped with a T-die at the extruder outlet. The sheet-like molten resin extruded from the T-die provided at the extruder outlet was cooled with a cooling roll to obtain a raw film with a width of 160 mm and a thickness of 160 μm. At this time, the surface in contact with the casting roll was defined as the B surface, and the other surface was defined as the A surface.

[0130] Regarding the raw film, as a result of measuring the glass transition temperature according to the above method, it was 123 °C.

[0131] The obtained raw film was simultaneously biaxially stretched at a stretching ratio of 2 times (longitudinal and transverse) and 145 °C using a biaxial stretching device (IMC-1905) manufactured by Imoto Seisakusho to produce a stretched film (acrylic resin film).

[0132] (Blocking test) After stacking 10 test pieces (acrylic resin films) of 100 mm × 100 mm, a pressure of 1 kg was applied from above and left at 60 °C for 2 hours. Then, it was allowed to cool at 23 °C for 1 hour, and the state of the acrylic resin film was visually confirmed, and the acrylic resin film was peeled off by hand and judged according to the following criteria. 1: The films are strongly adhered to each other, and peeling marks are formed on the film when peeled. 2: The films are adhered to each other, and no peeling marks are formed on the film when peeled. 3: No adhesion between the films is observed.

[0133] Table 1 shows the evaluation results of Rzjis, coefficient of static friction, haze, internal haze, glass transition temperature, dimensional change rate, and blocking test.

[0134] (Example 2) An acrylic resin composition (refractive index 1.49) was obtained in the same manner as in Example 1 except that the addition amount of the AB agent was 0.12% by weight, and an acrylic resin film was obtained using the acrylic resin composition.

[0135] (Comparative Example 1) An acrylic resin film was obtained in the same manner as in Example 1 except that the AB agent was not added.

[0136] (Comparative Example 2) An acrylic resin film was obtained in the same manner as in Example 1 except that acrylic crosslinked particles with an average particle diameter of 0.8 μm (MX80H3wT manufactured by Soken Chemical & Engineering Co., Ltd., refractive index 1.49) were used instead of acrylic crosslinked particles with an average particle diameter of 1.2 μm, and the addition amount was 0.03% by weight.

[0137] (Comparative Example 3) An acrylic resin film was obtained in the same manner as in Comparative Example 2 except that the addition amount of the AB agent was 1.0% by weight.

[0138] (Comparative Example 4) Parapet HM (manufactured by Kuraray Co., Ltd., refractive index 1.49, Tg 118°C, Mw = 78,000, Mw / Mn = 1.72), a PMMA resin without a ring structure, was used as acrylic resin 2 instead of acrylic resin 1, and an acrylic resin film was obtained in the same manner as in Comparative Example 2 except that the addition amount of acrylic crosslinked particles with an average particle diameter of 0.8 μm was 0.1% by weight.

[0139]

Table 1

[0140] From Table 1, it can be seen that the acrylic resin films of Examples 1 and 2 are excellent in transparency and heat resistance and can prevent blocking during film roll storage. In contrast, for the acrylic resin film of Comparative Example 1, the sum of the 10-point average roughness Rzjis of each side is 0.104 and the static friction coefficient is 2.50, so blocking during film roll storage cannot be prevented. For the acrylic resin film of Comparative Example 2, the sum of the 10-point average roughness Rzjis of each side is 0.113 and the static friction coefficient is 1.80, so blocking during film roll storage cannot be prevented. For the acrylic resin film of Comparative Example 3, since the sum of the 10-point average roughness Rzjis of each side is 1.130, the transparency decreases. For the acrylic resin film of Comparative Example 4, since the glass transition temperature is 118 °C, the heat resistance decreases.

[0141] <Production of Acrylic Resin> (Production Example of Acrylic Resin 3) Into a 4 L glass reactor equipped with a stirrer having an H-type stirring blade, 150 parts by weight of deionized water, 0.20 part by weight of tricalcium phosphate as a dispersant, 0.0075 part by weight of sodium α-olefin sulfonate and 0.30 part by weight of sodium chloride were charged. Next, under a nitrogen atmosphere, while stirring at 250 rpm, 100 parts by weight of methyl methacrylate (MMA), 0.289 part by weight of n-octyl mercaptan as a chain transfer agent and 0.065 part by weight of 2,2'-azobis(isobutyric acid)dimethyl (manufactured by Fuji Film Wako Pure Chemical Industries, V-601) as a polymerization initiator were added to the reactor. Next, the liquid temperature in the reactor was raised to 70 °C to initiate polymerization, and 0.10 part by weight of tricalcium phosphate was added to the reactor 2 hours after the start of polymerization. At this time, a heat generation peak associated with the gel effect was observed 4 hours and 20 minutes after the start of polymerization. Next, heating was started 7 hours after the start of polymerization, and the liquid temperature in the reactor was raised to 95 °C. The conversion rate 7 hours after the start of polymerization was 93%. Next, 2 hours after the liquid temperature in the reactor reached 95 °C, the liquid temperature in the reactor was cooled to room temperature to terminate the polymerization, and an acrylic resin dispersion was obtained. The conversion rate at the end of polymerization was 99%.

[0142] Using hydrochloric acid of 1N in an amount 0.1 times the weight of the charged monomer by weight, the acrylic resin dispersion was washed with acid and then washed with water to remove the dispersant. Next, the washed acrylic resin dispersion was dehydrated and then dried to obtain bead-shaped acrylic resin 3. The acrylic resin 3 had a glass transition temperature of 120°C, a syndiotacticity of 57% in the triad display, an Mw of 83,000, an Mw / Mn of 1.63, and a content of structural units derived from methyl methacrylate of 100% by weight.

[0143] (Conversion rate) By the gravimetric method, the ratio of the solid content weight of the acrylic resin after drying for 30 min in an oven heated to 150°C to the weight of the charged monomer, that is, the formula (Solid content weight of acrylic resin)×100 / (Weight of charged monomer) was used to determine the conversion rate.

[0144] (Syndiotacticity of triad display) Using a nuclear magnetic resonance apparatus (Bruker, AVANCEIII 400 MHz), the 1H-NMR spectrum of the acrylic resin was measured in a deuterated chloroform solution at 22°C under the condition of 16 integration times. Next, after measuring the area (X) of the region from 0.60 to 0.95 ppm and the area (Y) of the region from 0.60 to 1.25 ppm when tetramethylsilane (TMS) was set to 0 ppm, the formula 1 (X / Y)×100 was used to calculate the syndiotacticity of the triad display.

[0145] (Weight-average molecular weight, number-average molecular weight, and dispersity)(Weight-average molecular weight, number-average molecular weight, and dispersity) Using gel permeation chromatography (GPC), the weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersity (Mw / Mn) of the acrylic resin were calculated. At this time, using a sample solution prepared by dissolving 20 mg of the acrylic resin in 10 mL of tetrahydrofuran, analysis was performed under the following conditions. Measuring instrument: HLC-8420GPC (manufactured by Tosoh Corporation) Detector: RI detector Eluent: Tetrahydrofuran Guard column: TSKgel guardcolumn SuperH-L (manufactured by Tosoh Corporation) Analysis column: TSKgel SuperH5000, SuperH4000, SuperH3000, SuperH2000 (manufactured by Tosoh Corporation) (in series) Eluent flow rate: 0.6 mL / min Measurement temperature: 40 °C Standard substance: Standard polystyrene (manufactured by Tosoh Corporation)

[0146] (Example 3) 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% by weight of acrylic crosslinked particles with an average particle diameter of 2.2 μm (J-4PY manufactured by Negami Kogyo Co., refractive index 1.50) was used instead of 0.1% by weight of acrylic crosslinked particles with an average particle diameter of 0.8 μm.

[0147] (Comparative Example 5) An acrylic resin film was obtained in the same manner as in Example 3, except that the AB agent was not added.

[0148]

Table 2

[0149] From Table 2, it can be seen that the acrylic resin film of Example 3 is excellent in transparency and heat resistance and can prevent blocking during film roll storage. On the other hand, for the acrylic resin film of Comparative Example 5, the sum of the 10-point average roughness Rzjis of each side is 0.030 and the static friction coefficient is 1.94, so blocking during film roll storage cannot be prevented.

Claims

1. An acrylic resin film mainly composed of an acrylic resin, The acrylic resin film has a glass transition temperature of 120° C. or higher, The acrylic resin film has a sum of 10-point average roughness Rzjis of 0.05 μm or more and 1.0 μm or less on both sides, a static friction coefficient of one side and the other side of 0.8 or less, 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 is more than 0.080 μm and 0.25 μm or less.

3. 2. The acrylic resin film according to claim 1, wherein the acrylic resin contains at least one type of ring structure selected from 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 acrylic resin has a syndiotacticity of 54% or more in terms of triad expression.

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

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

7. The acrylic resin film according to claim 5 , wherein the acrylic resin film contains 0.05% by weight or more and 0.9% by weight or less of acrylic crosslinked particles.

8. The acrylic resin film according to any one of claims 1 to 5, which has a dimensional change rate of -2.0% or more and -0.1% or less when left standing in an atmosphere of 85°C and 85% RH for 120 hours.

9. A polarizing plate comprising the acrylic resin film according to any one of claims 1 to 5.

10. A liquid crystal display panel comprising the polarizing plate according to claim 9 .

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