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 kurtosis Rku of both surfaces of the acrylic resin film is 10 or more and 50 or less, and an internal haze thereof 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 Art

[0002] In a liquid crystal display device, usually, two polarizing plates are arranged on both sides of a liquid crystal cell. As the polarizing plate, a polarizer protection film for protecting the polarizer on both sides of the polarizer is generally used, which is bonded with an adhesive. As the polarizer protection film, high transparency is required, and an optical film made of a cellulose-based material is frequently used.

[0003] For the purpose of improving durability and the like, it has been proposed to use an optical film made of an acrylic resin or a norbornene resin as the polarizer protection film. However, when these optical films are wound as a roll, the films come into contact with each other, and wrinkles and creases are likely to occur. As a method for solving this problem, a method of adding fine particles such as silica particles to a norbornene resin film to ensure roll winding property (slip property) has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the method such as in Patent Document 1 can solve the generation of wrinkles and creases during winding, according to the study by the present inventors, along with the improvement of the film quality level due to the high definition and large area of the liquid crystal display panel, it has become clear that defects caused by winding tightness of the film during storage in the form of a film roll occur. Further, 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 is known that it is difficult to meet the requirements as an optical 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 research 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 kurtosis Rku on both sides of the acrylic resin film is 10 or more and 50 or less, and the internal haze is 1.0% or less. Acrylic resin film.

[0010] [2] The acrylic resin film according to [1], wherein the coefficient of static friction between one surface and the other surface of the acrylic resin film is 0.8 or less.

[0011] [3] The acrylic resin film according to [1] or [2], wherein the acrylic resin 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 is the acrylic resin film according to [1] or [2], having a syndiotacticity of 54% or more in a triple display.

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

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

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

[0016] [8] The acrylic resin film according to any one of [1] to [7], having 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.

[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 excellent in transparency and heat resistance and capable of preventing blocking during storage of a film roll. [Embodiments 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~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 this 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 kurtosis Rku on both sides of the acrylic resin film is 10 or more and 50 or less, and the internal haze is 1.0% or less. Thus, while mainly composed of an acrylic resin, by controlling the sum of the kurtosis on both sides of the film to a predetermined value 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 property 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 a high-temperature environment of the film becomes small. In actual use, the acrylic resin film of this embodiment is often used by being laminated with other films. When the dimensional change rate is small, the occurrence of distortion and warpage caused by the difference in the dimensional change rate generated between the laminated other films can be suppressed.

[0023] 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, even 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, heat resistance can be imparted. 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 good, so it is preferable. The content of the ring structure in the acrylic resin can be 1 measured by using H-NMR to measure the molar ratio of the target ring structure part to the other parts and performing weight conversion. Further, the acrylic resin having a glass transition temperature of 120°C or higher is the main component of the acrylic resin film and is contained in an amount of more than 50% by weight in 100% by weight of the acrylic resin film. Among them, in 100% by weight of the acrylic resin film, 70% by weight or more is preferable, 80% by weight or more is more preferable, 85% by weight or more is even more preferable, and 90% by weight or more is particularly preferable.

[0026] 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.

[0027] The haze inside the acrylic resin film of this embodiment is 1.0% or less. Among these, 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, the haze is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less.

[0030] In an acrylic resin film, by setting the sum of the kurtosis Rku on both sides to be 10 or more and 50 or less, blocking during storage of the film roll can be effectively prevented. Thereby, defects that can occur in the film can be prevented. Here, if the sum of the kurtosis Rku on both sides of the acrylic resin film is less than 10, blocking due to winding 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 an acrylic resin film of a fixed length (for example, 4000 m) can be wound, and the yield decreases. Also, even for an acrylic resin film of a fixed length, 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 kurtosis Rku on both sides of the acrylic resin film exceeds 50, the transparency of the acrylic resin film decreases. More preferably, the sum of the kurtosis Rku on both sides of the acrylic resin film is 15 or more and 30 or less. When the sum of the kurtosis is 10 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 easily escapes, and it is presumed that blocking due to winding can be suppressed and film defects can be suppressed. Also, when the sum of the kurtosis is 50 or less, it is possible to suppress the diffuse reflection of light on the surface and suppress the impairment of the sharpness of the panel display.

[0031] Here, "blocking" means a state where the films are stuck together, including a state where they are partially melted at a high temperature or a state where they are perfectly overlapped. When winding occurs, pressure is applied to the film, and blocking (sticking) between the films occurs. As a result, when separating the films from each other, a strong force is required to separate 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, sticking between the films in the film roll can be suppressed even when winding occurs, and the films can be separated with a weak force, so damage (film defects) to the film can be suppressed.

[0032] Here, kurtosis Rku conforms to JIS B 0601 and can be calculated from the roughness curve. Kurtosis Rku represents the sharpness in the height direction, where Rku = 3 means the height distribution is a normal distribution, Rku > 3 means there are many sharp peaks and valleys on the surface, and Rku < 3 means the surface is flat.

[0033] The kurtosis Rku (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 with a numerical aperture of 0.95 or more is used.

[0034] From the viewpoints of economy and environmental load, it is preferable to add an anti-blocking agent described below 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 being easy to control haze.

[0035] The static friction coefficient of the acrylic resin film is preferably 0.8 or less, more preferably 0.7 or less, even more preferably 0.6 or less, and particularly preferably 0.5 or less when measured with one surface of the film and the other surface in contact. If the static friction coefficient is 0.8 or less, blocking between the films during film roll storage 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.

[0036] 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 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, and 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 dimensional change rate may be, for example, -0.1% or less. When the 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. The dimensional change rate when left standing for 120 hours in an atmosphere of 85°C and 85% RH here can be measured using a three-dimensional measuring instrument for the dimensional change before and after leaving the acrylic resin film standing for 120 hours in an environmental test chamber set at 85°C and 85% RH.

[0037] In this specification and the claims, the dimensional change rate means the change rate of the hole interval before and 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 and leaving it standing for 120 hours in an atmosphere of 85°C and 85% RH. Here, the change rate of the hole interval means the change rate of the hole interval after standing with respect to 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

[0038] The linear expansion coefficient of the acrylic resin film at 40 to 60°C is preferably 80 ppm or less, and more preferably 72 ppm or less. If it is 80 ppm or less, shrinkage and expansion of the film due to temperature changes during storage and transportation of the roll can be suppressed, and winding is less likely to occur. On the other hand, the lower limit is preferably 40 ppm or more. If the linear expansion of the film is 40 ppm or more, when laminated with a polarizer, the difference in linear expansion from other members is small, so warping and the like are less likely to occur.

[0039] 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 by plotting the temperature on the X-axis and the change in the length of the film on the Y-axis. The slope in the temperature range from 40 °C to 60 °C during the heating and cooling process can be calculated by the least squares method and used as the linear expansion coefficient.

[0040] (Antiblocking agent) The acrylic resin film is preferably formed from an acrylic resin composition in which an antiblocking agent is added to the acrylic resin. As the antiblocking 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 antiblocking properties are likely to be exhibited.

[0041] The refractive index of the antiblocking 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 antiblocking 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 antiblocking agent having a refractive index within this 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.

[0042] The polymerizable monomer forming the above acrylic crosslinked particles can be selected from any (meth)acrylic acid ester and other copolymerizable monomers, but it is preferably contained 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.

[0043] 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 the 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. If it is less than 0.5% by weight, the heat resistance and dispersibility of the acrylic crosslinked particles are inferior. If it exceeds 30% by weight, coalescence of the particles and formation of deformed particles may occur when producing the acrylic crosslinked particles.

[0044] 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 added for expressing antiblocking properties needs to be increased, so the mechanical properties and economy may be inferior. When the upper limit exceeds 2.5 μm, it may induce clogging of the polymer filter. Also, from the viewpoint 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.

[0045] Regarding the addition amount of the acrylic crosslinked particles of the present 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 blocking prevention 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. Further, 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.

[0046] (Easy-adhesion layer) The acrylic resin film of the present 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 bonding to the polarizer via the adhesive. It is also possible to provide an easy-adhesion layer on the unstretched film and then stretch it to obtain a stretched film having an easy-adhesion layer.

[0047] As the easy-adhesion layer used in the present 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 the 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.

[0048] (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, an acrylic resin 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.

[0049] (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.

[0050] [Chemical formula]

[0051] (Here, R 1 and R 2 each independently represent 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.)

[0052] The content of the glutarimide ring according to this embodiment is a value that can be measured by the following method, for example. 1 Performed using H-NMR. From the area of the peak derived from the O-CH 3 proton of methyl methacrylate in the vicinity of 3.5 ppm to 3.8 ppm and the peak area of the proton derived from the N-R 3 of the glutarimide group in the vicinity of 3.0 ppm to 3.3 ppm, weight conversion is performed using the obtained molar ratio.

[0053] 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. However, when these are used in combination, it is preferable that the acrylate unit is less than 1% by weight. More preferably, the acrylate unit is less than 0.5% by weight, and even more preferably, it is less than 0.3% by weight.

[0054] In addition to the above monomers, it is also possible to copolymerize nitrile monomers such as acrylonitrile and methacrylonitrile, maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide, and aromatic vinyl monomers such as styrene.

[0055] 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, and crosslinked polymer, etc.

[0056] 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.

[0057] 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 viewpoint of having few impurities, bulk polymerization methods and solution polymerization methods are particularly preferable. 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, etc.

[0058] The method for producing an acrylic resin according to 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 methyl methacrylate monomer and treating it with an imidizing agent. Thereby, an acrylic resin having glutarimide can be produced.

[0059] The imidizing agent is not particularly limited as long as it can generate 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. Further, urea-based compounds that generate the exemplified amines by heating, such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, can also be used. Among these imidizing agents, it is preferable to use methylamine, ammonia, or cyclohexylamine from the viewpoints of both cost and physical properties, and it is particularly preferable to use methylamine.

[0060] Gaseous methylamine or the like at room temperature may be used in a state dissolved in alcohols such as methanol.

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

[0062] Further, by adjusting the degree of imidation, the physical properties of the obtained acrylic resin and the transparency 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. In addition, since the content of the glutarimide ring in the finally obtained resin composition is also 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 a twin-screw extruder is used, 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 a high speed, and thus can further promote the mixing of the imidizing agent (when a ring-closing accelerator is used, the imidizing agent and the ring-closing accelerator) with respect to the raw material polymer.

[0067] When performing imidization in an extruder, for example, the methyl methacrylate resin is charged from the raw material charging section of the extruder, the resin is melted and filled in the cylinder, and then the imidizing agent is injected into the extruder using an addition 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 processing 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 that can be depressurized to below atmospheric pressure in order to remove unreacted imidizing agents and by-products. According to such a configuration, unreacted imidizing agents, 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 may 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 it is preferably a structure with good stirring efficiency.

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

[0072] In the method for producing the acrylic resin of this embodiment, in addition to the imidization step, a step of treating with an esterifying agent can be included. 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, the esterifying agent is preferably 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 preferred from the viewpoints of cost, reactivity, etc.

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

[0077] Even when treating with an esterifying agent, it is also possible to promote the formation of acid anhydride groups by heat treatment.

[0078] 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.

[0079] (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).

[0080] 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).

[0081]

Chemical formula

[0082] (However, R 4 and R 5 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.).

[0083] 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 preferable, and methyl 2-(hydroxymethyl)acrylate is particularly preferable in terms of its high effect of improving heat resistance. These unsaturated monomers may be used alone or in combination of two or more.

[0084] 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 cross-linking reaction may occur during the formation of the lactone ring structure, making it easy to gel, and the fluidity may decrease, making melt molding difficult. In addition, unreacted hydroxyl groups may remain, and further condensation reactions may proceed during molding, generating volatile substances and making silver streaks likely to occur, or the retardation in the thickness direction Rth may increase.

[0085] 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)acrylate esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and unsaturated monomers represented by the following general formula (3) are preferably mentioned. These other monomers may be used alone or in combination of two or more.

[0086] [Chem.]

[0087] (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.)

[0088] 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.

[0089] When using the above (meth)acrylic acid ester, 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, 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.

[0090] (Acrylic resin having maleic anhydride, maleimide and glutaric anhydride structures in the main chain) In this 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 a styrene-N-phenylmaleimide-maleic anhydride copolymer. Examples of the maleimide structure include an olefin-maleimide copolymer as described in JP-A-2004-45893. Examples of the glutaric anhydride structure include a copolymer having a glutaric anhydride unit as described in JP-A-2003-137937.

[0091] (Acrylic resin having no ring structure in the main chain) As an acrylic resin having a glass transition temperature of 120°C or higher, for example, a method of introducing a carboxyl group such as methacrylic acid can be mentioned. 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 when forming a film, so 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.

[0092] As an 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 be high and the heat resistance of the acrylic resin tends to be improved. 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 of the acrylic resin, the toughness of the molded body, and the secondary processability.

[0093] The syndiotacticity of the triad display of an acrylic resin is the ratio of the chains of three structural units (triads) that are rr. In the chains of two structural units (dyads), those with the same configuration are called meso (m), and those with the opposite configuration are called racemo (r).

[0094] The method for synthesizing an acrylic resin with a syndiotacticity of the triad display of 55% or more is not particularly limited, and examples include anionic polymerization and radical polymerization. Among these, radical polymerization is preferred (see, for example, International Publication No. 2023 / 238885 and International Publication No. 2023 / 238886). In radical polymerization, since an organometallic compound as a polymerization initiator and an organic solvent as a medium used in anionic polymerization are not used, it is difficult for impurities to remain, which is preferable from an environmental perspective. Here, the glass transition temperature of the acrylic resin and the syndiotacticity of the triad display 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. In addition, the glass transition temperature of the acrylic resin can also be controlled by the molecular weight of the acrylic resin.

[0095] The content of the structural unit derived from methyl methacrylate in the acrylic resin with a syndiotacticity of the triad display 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.

[0096] The monomers other than methyl methacrylate that constitute the acrylic resin having a syndiotacticity of 54% or more in the triad representation 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.

[0097] (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 having no 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 having no ring structure in the main chain.

[0098] 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.

[0099] 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 flexural 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. Also, 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.

[0100] 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 flexural resistance of the molded article of the acrylic resin tend to be improved.

[0101] Note that 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). Also, 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.

[0102] (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 blue light cut, light resistance stabilizers such as radical scavengers, 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 within a range not impairing the object of the present invention.

[0103] Examples of the ultraviolet absorber include triazine-based compounds, benzotriazole-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, benzoxazine-based compounds, and oxadiazole-based compounds. Among these, from the viewpoints of ultraviolet absorption performance with respect to the addition amount and volatility when melt-extruding, triazine-based compounds are preferable.

[0104] Regarding the retardation adjuster, when imparting a negative retardation, for example, a compound having a styrene skeleton may be used, and acrylonitrile-styrene copolymer is exemplified.

[0105] 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.

[0106] 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.

[0107] 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 in front of the filter to (A) 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.

[0108] (Method for manufacturing an acrylic resin film) An embodiment of the method for manufacturing 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 molding the acrylic resin composition of the present embodiment to produce a film.

[0109] 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 manufactured by a solution casting method or a spin coating method for molding.

[0110] Among them, 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.

[0111] When the acrylic resin composition of this embodiment is formed into a film by a 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 raw 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.

[0112] When the acrylic resin composition of the present embodiment is formed into an unstretched film by the solution casting method, after the acrylic resin composition of the present embodiment is made into a solution together with an organic solvent, 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. Also, highly polar non-halogenated solvents such as dimethylformamide and dimethylacetamide can 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 allows sufficient casting. In this specification, "dissolution" means that the resin is present in the solvent in a uniform state to an extent that allows 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 wt% to 90 wt%, more preferably 5 wt% to 70 wt%, and even more preferably 10 wt% to 50 wt%. 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.

[0113] 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.

[0114] As the stretching method, a conventionally known method can be used. For example, an unstretched original 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.

[0115] 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 due to 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 / min or more, and more preferably 5 times / min or more. Also, it is preferably 100 times / min or less, and more preferably 50 times / min 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 stretching in the longitudinal direction (MD direction), and the second stage of stretching is stretching in the width direction (TD direction).

[0116] 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 antiblocking agent, when stretching at a low temperature, the 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.

[0117] 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. In addition, it is more effective to combine with, for example, the nailing process at the end used for blocking countermeasures in the past.

[0118] (Use) 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.

[0119] This polarizing plate is further bonded to various films and can be suitably used, for example, in display fields such as liquid crystal displays and organic EL displays. However, the applications are not limited to these.

Examples

[0120] 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.

[0121] (Surface roughness) Using a laser microscope LEXT OLS5100 manufactured by Olympus, the surface roughness of the acrylic resin film was measured in accordance with JIS B0601:2013. Specifically, first, an objective lens with a magnification of 50 times and a numerical aperture of 0.95 was used to capture a confocal image of a 257 μm × 257 μm area of the film. Next, three evaluation lines were drawn at equal intervals in each of the MD direction and the TD direction, and the roughness curve was extracted. From the obtained roughness curve, the kurtosis Rku was calculated by analysis software, and the average value at the measurement position was calculated. The measurement was performed 5 times by changing the measurement position, and the average value was adopted as the surface roughness. However, if partial abnormalities such as scratches were clearly observed in the image, they were not included in the measured values, and the measurement was repeated after avoiding the abnormal parts.

[0122] (Coefficient of static friction) In accordance with JIS K7125:1999, the coefficient of static friction of the acrylic resin film was measured using a digital force gauge ZTS-5N manufactured by IMADA and a 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, 200 g weight thread 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 5 times by replacing the film piece, and the average value was calculated.

[0123] (Haze, internal haze) In accordance with JIS 7136:2000, the haze of the acrylic resin film was measured using a 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.

[0124] (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.

[0125] (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 after measuring the hole spacing was measured again after standing 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 in an atmosphere of 85 °C and 85% RH.

[0126] (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 100 μm thick film, 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, digital Abbe refractometer DR-M2). The obtained refractive index was taken as the refractive index of the acrylic resin composition.

[0127] 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, the dispersion liquid becomes cloudy when the refractive index of the mixed liquid and the acrylic crosslinked particles do not match, and the liquid becomes transparent when the refractive index 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.

[0128] <Production of acrylic resin> (Production Example of Acrylic Resin 1) The extruder used was a 40 mm diameter co-rotating intermeshing twin screw extruder (L / D=90). The set temperature of each temperature control zone of the extruder was 250-280°C, and the screw speed was 85 rpm. After the methyl methacrylate resin was melted and filled by the kneading block, 1.8 parts by weight of monomethylamine (manufactured by Mitsubishi Gas Chemical) was injected from the nozzle per 100 parts by weight of the 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 pelletized with a pelletizer to obtain resin (I). Next, the set temperature of each temperature control zone of the extruder was set to 240-260°C using a 40 mm diameter co-rotating intermeshing twin screw extruder. 0.56 parts by weight of dimethyl carbonate was injected from the nozzle per 100 parts by weight of the methyl methacrylate resin to reduce the carboxyl group in the resin. By-products and excess dimethyl carbonate after the reaction were removed. The resin that came out as strands from the die provided at the outlet of the extruder was cooled in a water tank and then pelletized in a pelletizer to obtain acrylic resin 1 having glutarimide rings. The glass transition temperature of the acrylic resin 1 was 123°C, Mw was 81,000, and Mw / Mn was 1.59.

[0129] (Calculation of ring structure content) The obtained acrylic resin 1 H-NMR Measurements were performed using a BRUKER AvanceIII (400MHz). The weights were calculated from the molar ratio of the target ring structure and the other parts. Specifically, in the case of glutarimide, the O-CH 3 The area A of the peak derived from protons and the N-CH 3 The content of the ring structure was calculated by converting the weight from the area B of the peak derived from the proton using the determined molar ratio, and was found to be 6% by weight.

[0130] Example 1 A mixture containing 1 part of the acrylic resin produced in the above acrylic resin production example and 0.1% by weight of acrylic crosslinked particles (MX80H3wT manufactured by Soken Chemical & Engineering Co., Ltd., refractive index 1.49) with an average particle diameter of 0.8 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. The refractive index of the acrylic resin composition was 1.49.

[0131] 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.

[0132] Regarding the raw film, as a result of measuring the glass transition temperature according to the above method, it was 123 °C.

[0133] 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).

[0134] (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.

[0135] Table 1 shows the evaluation results of Rku, coefficient of static friction, haze, internal haze, glass transition temperature, dimensional change rate, and blocking test.

[0136] (Example 2) An acrylic resin composition (refractive index 1.49) was obtained in the same manner as in Example 1, except that in addition to 0.1% by weight of acrylic crosslinked particles having an average particle diameter of 0.8 μm, 0.04% by weight of acrylic crosslinked particles having an average particle diameter of 0.15 μm (manufactured by Sekisui Chemical Co., Ltd., xx-6390Z, refractive index 1.49) was added, and an acrylic resin film was obtained using the acrylic resin composition.

[0137] (Comparative Example 1) An acrylic resin film was obtained in the same manner as in Example 1, except that no AB agent was added.

[0138] (Comparative Example 2) An acrylic resin film was obtained in the same manner as in Example 1, except that the addition amount of the AB agent was 0.03% by weight.

[0139] (Comparative Example 3) An acrylic resin film was obtained in the same manner as in Example 1, except that the addition amount of the AB agent was 1.0% by weight.

[0140] (Comparative Example 4) An acrylic resin film was obtained in the same manner as in Example 1, except that parapet HM (manufactured by Kuraray Co., Ltd., refractive index 1.49, Tg 118°C, Mw = 78,000, Mw / Mn = 1.72), a PMMA resin containing no ring structure, was used as acrylic resin 2 instead of acrylic resin 1.

[0141]

Table 1

[0142] 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 storage of film rolls. In contrast, for the acrylic resin films of Comparative Examples 1 and 2, since the sum of the kurtosis Rku on both sides is 7.8 and 9.6 respectively, blocking during storage of film rolls cannot be prevented. For the acrylic resin film of Comparative Example 3, since the sum of the kurtosis Rku on both sides is 74.0, the transparency decreases. For the acrylic resin film of Comparative Example 4, since the glass transition temperature is 118 °C, the heat resistance decreases.

[0143] <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 start 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%.

[0144] The acrylic resin dispersion was washed with hydrochloric acid of 1 N in an amount 0.1 times the weight of the charged monomer by weight, 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. Acrylic resin 3 had a glass transition temperature of 120 °C, a syndiotacticity of 57% in the triad representation, an Mw of 83,000, an Mw / Mn of 1.63, and a content rate of structural units derived from methyl methacrylate of 100% by weight.

[0145] (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.

[0146] (Syndiotacticity in the triad representation) Using a nuclear magnetic resonance apparatus (Bruker, AVANCEIII 400 MHz), in a deuterated chloroform solution, at 22 °C, with the number of integrations being 16 times, the 1 1H-NMR spectrum of the acrylic resin was measured. 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 (X / Y) × 100 was used to calculate the syndiotacticity in the triad representation.

[0147] (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 carried out 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)

[0148] (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.

[0149] Table 2 shows the evaluation results of Rku, coefficient of static friction, haze, internal haze, glass transition temperature, dimensional change rate, and blocking test.

[0150] (Example 4) An acrylic resin film was obtained in the same manner as in Example 3, except that 0.12% by weight of acrylic crosslinked particles with an average particle diameter of 1.2 μm (J-3PY manufactured by Negami Kogyo Co., refractive index 1.49) was used instead of 0.1% by weight of acrylic crosslinked particles with an average particle diameter of 0.8 μm.

[0151] (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.

[0152]

Table 2

[0153] From Table 2, it can be seen that the acrylic resin films of Examples 3 and 4 are excellent in transparency and heat resistance and can prevent blocking during film roll storage. On the other hand, since the sum of the kurtosis Rku on both sides of the acrylic resin film of Comparative Example 5 is 7.1, 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 kurtosis Rku on both sides of the acrylic resin film of 10 or more and 50 or less, and an internal haze of 1.0% or less.

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

3. 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 or 2, 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 or 2, wherein the antiblocking agent contains acrylic crosslinked particles having an average particle size of 0.1 μm or more and 2.5 μm or less.

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 , comprising 0.05% by weight or more and 0.9% by weight or less of acrylic crosslinked particles.

8. 3. The acrylic resin film according to claim 1, 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 claim 1 .

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

Images