Acrylic film, optical laminate, polarizing plate, surface plate and image display device including the acrylic film, and method for manufacturing the acrylic film.

Abstract

To provide an acryl film that exhibits stable quality even in a high temperature region of 100°C or higher.SOLUTION: An acryl film includes an absolute value of thermal expansion variation of 3% or less at 130°C, and a tensile elasticity of 300 MPa or more and 1300 MPa or less at 100°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to an acrylic film, as well as an optical laminate, polarizing plate, surface plate and image display device including the acrylic film, and a method for manufacturing the acrylic film. [Background technology]

[0002] High-molecular-weight resin films such as acrylic films, polyester films, and cyclic olefin films are used as substrates for functional films for image display devices, and for functional films used to protect or decorate items such as vehicles, furniture, and electrical appliances, due to their excellent transparency.

[0003] Among polymer resin films, acrylic films, primarily composed of acrylic polymers such as PMMA, are characterized by their excellent optical properties and weather resistance. For this reason, acrylic films are used in a variety of applications. In particular, acrylic films are expected to be used as a substrate for functional films in image display devices. Examples of acrylic films are proposed in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-292961 [Patent Document 2] Japanese Patent Publication No. 2018-44171 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The acrylic film described in Patent Document 1 addresses the issue of improving thermal shrinkage characteristics during processing. The acrylic film described in Patent Document 2 addresses the issue of reducing the coefficient of thermal expansion in the MD and TD directions. The acrylic films described in Patent Documents 1 and 2 can improve thermal behavior to a predetermined level. However, the image display devices containing functional films based on acrylic films as described in Patent Documents 1 and 2 frequently experienced problems such as quality degradation during use or quality degradation over time. An example of quality degradation is light leakage. Furthermore, in recent years, there has been a demand for higher quality functional films. However, when using the acrylic films described in Patent Documents 1 and 2 as the base material for high-quality functional films, there have been frequent cases where the expected quality could not be obtained. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have determined that the cause of the aforementioned quality problems is high temperatures exceeding 100°C. For example, recent image display devices, such as smartphones, can reach internal temperatures exceeding 100°C during use. Also, functional films used near the dashboard of automobiles can reach high temperatures during the summer. Furthermore, in order to improve the quality of functional films, high-temperature processing exceeding 100°C may be required during the manufacturing process. The inventors have now succeeded in developing an acrylic film that can maintain stable quality even in high-temperature ranges of 100°C or higher.

[0007] This disclosure provides the following [1] to [6]. [1] Acrylic film, The acrylic film is an acrylic film in which the absolute value of the rate of change in thermal expansion at 130°C is 3.0% or less, and the tensile modulus of elasticity at 100°C is 300 MPa or more and 1300 MPa or less. An optical laminate having one or more functional layers on the acrylic film described in [2][1]. [3] A polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, The polarizing plate, wherein at least one of the first transparent protective plate and the second transparent protective plate includes the acrylic film according to [1]. [4] A front plate for an image display device in which a protective film is laminated on a resin plate or a glass plate, and the protective film includes the acrylic film according to [1]. [5] An image display device having the acrylic film according to [1] on a display element. [6] A method for manufacturing the acrylic film according to [1], comprising the following steps 1 to 3. Step 1: A step of obtaining a coating film from a composition for an acrylic film including an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups. Step 2: A step of irradiating the coating film with ultraviolet rays. Step 3: A step of further heating the coating film at a temperature not lower than the glass transition temperature of the acrylic polymer.

Advantages of the Invention

[0008] The acrylic film, optical laminate, polarizing plate, front plate, and image display device of the present disclosure can maintain stable quality even in a high-temperature region of 100 °C or higher. The method for manufacturing the acrylic film of the present disclosure can easily manufacture an acrylic film that can maintain stable quality even in a high-temperature region of 100 °C or higher.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic cross-sectional view for explaining a method for evaluating rigidity.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the acrylic film, optical laminate, polarizing plate, front plate, and image display device of the present disclosure will be described.

[0011] In this specification, unless otherwise specified, “acrylic film” refers to acrylic films and methacrylic films. In this specification, unless otherwise specified, “acrylic polymer” refers to acrylic polymers and methacrylic polymers. In this specification, unless otherwise specified, “acrylic monomer” refers to acrylic monomers and methacrylic monomers. In this specification, unless otherwise specified, “(meth)acrylate” refers to acrylate and methacrylate, and “(meth)acrylic” refers to acrylic and methacrylic.

[0012] [Acrylic film] The acrylic film of this disclosure has an absolute value of 3.0% or less in the rate of change of thermal expansion at 130°C, and a tensile modulus of elasticity of 300 MPa or more and 1300 MPa or less at 100°C.

[0013] <Coefficient of change in thermal expansion> The acrylic film of this disclosure must have an absolute value of 3.0% or less in the rate of change of thermal expansion at 130°C. In this specification, the "absolute value of the rate of change of thermal expansion at 130°C" may be referred to as the "absolute value of the rate of change of thermal expansion."

[0014] If the absolute value of the thermal expansion rate exceeds 3.0%, wrinkles will form in the acrylic film at a temperature of 130°C. Therefore, when the absolute value of the thermal expansion rate exceeds 3.0%, functional films using acrylic film as a base material are more likely to experience quality degradation during use. Furthermore, when the absolute value of the thermal expansion rate exceeds 3%, high-temperature processing at 130°C during the manufacturing process of functional films is more likely to result in failure to achieve the expected quality. On the other hand, acrylic films with an absolute value of 3.0% or less in thermal expansion change rate can suppress the above problems and stabilize the quality of functional films. In recent years, due to the increased performance of image display devices and the improvement of the quality of functional films, acrylic films are more likely to be subjected to high temperatures during use and during the manufacturing process of functional films. For this reason, there is technical significance in making the absolute value of the thermal expansion change rate of acrylic films at 130°C 3% or less. Conventional acrylic films cannot achieve an absolute value of 3.0% or less in thermal expansion change rate at 130°C because the acrylic polymer softens at 130°C. The acrylic film of this disclosure makes it easier to achieve an absolute value of 3.0% or less in thermal expansion change rate by forming an acrylic film using an acrylic film composition containing an acrylic polymer and a polymerizable acrylic monomer through a predetermined process.

[0015] The absolute value of the thermal expansion rate of the acrylic film is preferably 2.0% or less, and more preferably 1.0% or less. There is no particular lower limit to the absolute value of the thermal expansion rate of the acrylic film, but it is usually 0.1% or more.

[0016] In this specification, the rate of change in thermal expansion at 130°C is calculated using the following formula. In the following formula, L 130 ∫ represents the sample length at 130°C, and L represents the original sample length. In this specification, the original sample length is defined as the sample length at 20°C. The rate of change in thermal expansion at 130°C can be measured, for example, by the method described in the Examples. Thermal expansion rate = {(L 130 -L) / L}×100

[0017] The acrylic film may have a negative coefficient of thermal expansion at 130°C, but it is preferable that it has a positive coefficient.

[0018] <Tensile modulus> The acrylic film of this disclosure must have a tensile modulus of 300 MPa or more and 1300 MPa or less at 100°C. In this specification, "tensile modulus at 100°C" may be referred to simply as "tensile modulus."

[0019] When the tensile modulus is less than 300 MPa, wrinkles are more likely to form along the tensile direction of the acrylic film when it is stretched in an environment of 100°C. Specifically, when the tensile modulus is less than 300 MPa, wrinkles tend to form in the acrylic film along the transport direction when the acrylic film is transported while the functional layer ink applied to the acrylic film is heated and dried. Furthermore, when a protective film is laminated onto a polarizer, it is often subjected to heat of around 100°C. Because polarizers do not have high heat resistance, it is difficult to apply heat of 130°C to them, and they are usually subjected to heat of around 100°C. For this reason, if the tensile modulus is less than 300 MPa, when the acrylic film used as a protective film is laminated onto the polarizer, wrinkles are likely to form in the acrylic film. Based on the above, when the tensile modulus of elasticity is less than 300 MPa, functional films using acrylic film as a base material are prone to problems such as failing to achieve the expected quality or experiencing a decrease in quality when laminated with other materials.

[0020] On the other hand, if the tensile modulus exceeds 1300 MPa, the acrylic film becomes more prone to tearing when stretched in a 100°C environment. Specifically, when the tensile modulus exceeds 1300 MPa, the acrylic film becomes more prone to breakage when transporting it while heating and drying the functional layer ink applied to the acrylic film. Furthermore, if the tensile modulus exceeds 1300 MPa, the acrylic film becomes more prone to tearing when it is laminated to the polarizer as a protective film. Based on the above, when the tensile modulus exceeds 1300 MPa, functional films based on acrylic film become extremely difficult to handle.

[0021] The tensile modulus of the acrylic film is preferably 320 MPa or higher at the lower limit, more preferably 340 MPa or higher, and preferably 1200 MPa or lower at the upper limit, more preferably 1150 MPa or lower.

[0022] As mentioned above, in the process of applying tension to the acrylic film, it is possible to apply heat at 100°C, but not at 130°C. For this reason, there is technical significance in specifying the rate of change in thermal expansion at 130°C while specifying the tensile modulus at 100°C in the acrylic film of this disclosure.

[0023] In this specification, the tensile modulus at 100°C is measured by a tensile test in accordance with JIS K7127:1999. More specifically, the tensile modulus at 100°C can be measured by the method described in the examples, for example.

[0024] In the constituent elements shown herein, if multiple options are provided for both the upper and lower limits of a numerical value, one selected from the upper limit options and one selected from the lower limit options can be combined to form an embodiment of the numerical range. For example, in the case of tensile modulus, embodiments of the numerical range include 300 MPa to 1300 MPa, 300 MPa to 1200 MPa, 300 MPa to 1150 MPa, 320 MPa to 1300 MPa, 320 MPa to 1200 MPa, 320 MPa to 1150 MPa, 340 MPa to 1300 MPa, 340 MPa to 1200 MPa, and 340 MPa to 1150 MPa.

[0025] <Coefficient of thermal expansion> The acrylic film of this disclosure preferably has an absolute value of 250 ppm / °C or less for its coefficient of thermal expansion at temperatures between 40°C and 130°C. In this specification, the "coefficient of thermal expansion at 40°C to 130°C" may be referred to simply as the "coefficient of thermal expansion."

[0026] By setting the coefficient of thermal expansion to 250 ppm / °C or less, it is easier to suppress the formation of wrinkles in the acrylic film due to high heat. The coefficient of thermal expansion is more preferably 200 ppm / °C or less, even more preferably 150 ppm / °C or less, and even more preferably 110 ppm / °C or less. The lower limit of the coefficient of thermal expansion is not particularly limited, but is usually 10 ppm / °C or more.

[0027] In this specification, the coefficient of thermal expansion from 40°C to 130°C is calculated using the following formula. In the following formula, L 130 The sample length is L at 130°C. 40 θ represents the sample length at 40°C, and L represents the original sample length. In this specification, the original sample length is defined as the sample length at 20°C. In the following formula, the coefficient of thermal expansion can be measured, for example, by the method described in the examples. Thermal expansion coefficient = {(L 130 -L 40 ) / L} / 90[℃]

[0028] <Coupling ratio> The acrylic film of this disclosure preferably comprises an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups, and the ratio of C=C bonds to C=O bonds in the acrylic film is 0.55 or less.

[0029] The presence of acrylic monomers having two or more (meth)acryloyl groups in an acrylic film means that "the acrylic film contains polymerizable acrylic monomers as raw materials, and unreacted polymerizable monomers remain in the acrylic film." Furthermore, C=0 bonds in acrylic film are found in the acrylic polymer, the reactants of polymerizable acrylic monomers, and the unreacted polymerizable acrylic monomers. In addition, C=C bonds in acrylic film are mainly found in the unreacted polymerizable monomers. Therefore, the ratio of C=C bonds to C=O bonds in an acrylic film can be considered an indicator of the proportion of unreacted polymerizable monomers in the acrylic film.

[0030] A ratio of C=C bonds to C=O bonds in an acrylic film of 0.55 or less indicates that the reaction of polymerizable monomers has progressed within the acrylic film, and that the polymerizable acrylic monomers have formed a network of bonds. Therefore, by setting the bond ratio to 0.55 or less, it is easier to keep the absolute value of the thermal expansion change rate of the acrylic film to 3.0% or less. Furthermore, by setting the bond ratio to 0.55 or less, it is easier to keep the tensile modulus of the acrylic film to 300 MPa or more. Furthermore, unreacted polymerizable acrylic monomers remaining in the acrylic film may act like plasticizers, lowering the glass transition temperature of the acrylic film and reducing its tensile modulus. Therefore, reducing the proportion of unreacted polymerizable acrylic monomers to achieve a bond ratio of 0.55 or less has technical significance. Furthermore, when forming a functional layer such as a phase difference layer on an acrylic film, the functional layer may be formed by coating. The coating solution used for the functional layer may contain a solvent. Depending on the type of solvent, the general-purpose acrylic film may dissolve or swell, impairing the quality of the functional layer. For example, if the acrylic film dissolves or swells, the liquid crystals become difficult to orient, and the quality of the phase difference layer deteriorates. On the other hand, if the bonding ratio is 0.55 or less, the polymerizable acrylic monomers form a network bond, which improves the solvent resistance of the acrylic film. In other words, by setting the bonding ratio to 0.55 or less, the solvent resistance of the acrylic film can be improved, making it easier to suppress the deterioration of the quality of the functional layer.

[0031] The aforementioned bonding ratio is more preferably 0.50 or less, and even more preferably 0.45 or less. If the bonding ratio is too small, the reaction of the polymerizable acrylic monomer in the acrylic film may proceed too far, and the tensile modulus of the acrylic film may become too large. Therefore, the ratio is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more. The bonding ratio can be adjusted, for example, by step 3 of the method for producing the acrylic film of the present disclosure described later.

[0032] In this specification, the ratio can be measured, for example, by the following methods (1) to (4). (1) Prepare a sample for measurement by vertically cutting the acrylic film. (2) Measure the scattering intensities of the C=O bond and the C=C bond from the cross-sectional direction of the sample by Raman spectroscopy. The scattering intensity of the C=C bond is the scattering intensity at 1620 cm -1 or more and 1680 cm -1 The scattering intensity of the C=O bond is the scattering intensity at positions of 1710 cm -1 or more and 1780 cm -1 or more. (3) The measurement is performed every 2 μm in the thickness direction of the cross-section of the sample. Specifically, a position 2 μm deep from the upper surface of the cross-section of the sample is taken as the first measurement position. Further, the measurement is performed for each position advanced 2 μm in the depth direction. (4) Calculate the ratio of the C=C bond to the C=O bond for each measurement position. Then, the average of the ratios at all measurement positions is taken as the ratio of the C=C bond to the C=O bond of the sample.

[0033] <Acrylic polymer> The acrylic polymer is preferably a polymer obtained by polymerizing (meth)acrylic acid and / or a derivative of (meth)acrylic acid as main raw material monomers. As the polymer for the acrylic film, a commonly used polymer can be used.

[0034] Examples of derivatives of (meth)acrylic acid include methacrylic acid esters and acrylic acid esters. Examples of methacrylic acid esters include cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, and methyl methacrylate. Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, and 2-ethylhexyl acrylate.

[0035] The acrylic polymer may contain other monomers as raw material monomers, other than (meth)acrylic acid or derivatives of (meth)acrylic acid. Other monomers include styrene and aromatic vinyl compounds such as styrene and nuclear alkyl-substituted styrenes such as o-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, p-ethylstyrene, and p-tert-butylstyrene, and α-alkyl-substituted styrenes such as α-methylstyrene and α-methyl-p-methylstyrene, vinyl cyanides such as acrylonitrile and methacrylicnitrile, maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide, lactone ring units, glutaric acid anhydride units, unsaturated carboxylic acid anhydrides such as maleic anhydride, unsaturated acids such as maleic acid, and glutarimide units.

[0036] The acrylic polymer preferably contains methyl methacrylate as a raw material monomer. The proportion of methyl methacrylate to the total monomer of the raw material monomer is preferably 30 mol% or more, and more preferably 50 mol% to 95 mol%.

[0037] The glass transition temperature of the acrylic polymer contained in the acrylic film of this disclosure may be equivalent to that of the acrylic polymer constituting a general-purpose acrylic film. Specifically, the acrylic polymer contained in the acrylic film of this disclosure preferably has a glass transition temperature of 95°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher. By setting the glass transition temperature of the acrylic polymer to 95°C or higher, it is easier to improve the handling properties of the acrylic film. Furthermore, by forming an acrylic film using an acrylic film composition containing an acrylic polymer with a glass transition temperature of 95°C or higher and a polymerizable acrylic monomer, through a predetermined process, it is easier to bring the absolute value of the rate of change in thermal expansion and the tensile modulus into the above-mentioned range. There is no particular upper limit to the glass transition temperature of acrylic polymers, but it is usually below 120°C. The glass transition temperature of acrylic polymers can be adjusted by changing the composition of the raw material monomers used in the acrylic polymer.

[0038] The acrylic polymer preferably has a weight-average molecular weight of 50,000 to 1,000,000, more preferably 80,000 to 500,000, and even more preferably 100,000 to 300,000. By setting the weight-average molecular weight of the acrylic polymer to 50,000 or higher, it is easier to improve the mechanical strength of the acrylic film. By setting the weight-average molecular weight of the acrylic polymer to 1,000,000 or lower, it is easier to manufacture the acrylic film. In this specification, weight-average molecular weight is the average molecular weight measured by GPC analysis and converted to standard polystyrene.

[0039] <Acrylic monomers having two or more (meth)acryloyl groups> Examples of acrylic monomers having two (meth)acryloyl groups include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiaacrylate, bisphenol A tetrapropoxydiaacrylate, and 1,6-hexanediol diacrylate. Examples of acrylic monomers having three or more (meth)acryloyl groups include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. In this specification, "acrylic monomers having two or more (meth)acryloyl groups" may be referred to as polyfunctional acrylic monomers. One or more polyfunctional acrylic monomers may be used.

[0040] The polyfunctional acrylic monomer preferably has three or more (meth)acryloyl groups in order to reduce the absolute value of the rate of change in thermal expansion of the acrylic film and to facilitate the increase in tensile modulus. The number of (meth)acryloyl groups in the polyfunctional acrylic monomer is preferably six or less, and more preferably five or less, in order to avoid making the tensile modulus of the acrylic film too high. To adjust the absolute value of the rate of change in thermal expansion and the tensile modulus, an acrylic monomer having three or more (meth)acryloyl groups and an acrylic monomer having two (meth)acryloyl groups may be used in combination.

[0041] The polyfunctional acrylic monomer preferably contains alkylene oxide in its molecular backbone. By including alkylene oxide in the molecular backbone, it is possible to maintain the flexibility of the acrylic film while making it easier to keep the absolute value of the rate of change in thermal expansion and the tensile modulus within the above range. To adjust the absolute value of the rate of change in thermal expansion and the tensile modulus, a polyfunctional acrylic monomer containing alkylene oxide in its molecular skeleton and a polyfunctional acrylic monomer not containing alkylene oxide in its molecular skeleton may be used in combination.

[0042] In an acrylic film composition comprising an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups, the content of the acrylic monomer is preferably 10 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the acrylic polymer. By including 10 parts by mass or more of acrylic monomer, the absolute value of the thermal expansion rate of the acrylic film can be reduced, and the tensile modulus can be increased more easily. Furthermore, including 10 parts by mass or more of acrylic monomer can improve the solvent resistance of the acrylic film. By including 90 parts by mass or less of acrylic monomer, it is possible to suppress the tensile modulus of the acrylic film from becoming excessively high, and to suppress the decrease in the bending resistance of the acrylic film. The acrylic monomer content is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and more preferably 70 parts by mass or less, and more preferably 60 parts by mass or less, per 100 parts by mass of acrylic polymer.

[0043] The acrylic film preferably contains a cured product of an ultraviolet-curable resin composition. In other words, the acrylic film preferably contains a cured product of an acrylic monomer having two or more (meth)acryloyl groups. By including a predetermined amount of a cured product of an ultraviolet-curable resin composition in the acrylic film, the absolute value of the rate of change in thermal expansion and the tensile modulus can be easily brought within the above range. Furthermore, by including a predetermined amount of a cured product of an ultraviolet-curable resin composition in the acrylic film, the solvent resistance of the acrylic film can be easily improved.

[0044] The ratio of the cured product of the UV-curable resin composition to the total solid content of the acrylic film is preferably 10% by mass or more at the lower limit, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0045] The proportion of cured product of the UV-curable resin composition in the acrylic film can be calculated, for example, by immersing the acrylic film in a solvent that dissolves acrylic polymer and determining the proportion of components that remain undissolved.

[0046] <Additives> The acrylic film may contain additives such as plasticizers, ultraviolet absorbers, light stabilizers, blocking inhibitors, and antioxidants, to the extent that they do not impair the effects of the acrylic film of this disclosure.

[0047] <thickness> The thickness of the acrylic film is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, in order to obtain good mechanical strength. The thickness of the acrylic film is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less, in order to ensure good processability. In this specification, the thickness of an acrylic film refers to the average thickness of any 10 points on the acrylic film. The thickness of any 10 points on the acrylic film can be measured using a general-purpose film thickness gauge.

[0048] <Physical properties> 《Surface orientation ratio》 The acrylic film preferably has a surface orientation ratio of 1.00. A surface orientation ratio of 1.00 means that the acrylic film is substantially unoriented. Furthermore, if the acrylic film is oriented, it is difficult to keep the absolute value of the thermal expansion change within the above range. In other words, by setting the surface orientation ratio to 1.00, it becomes easier to keep the absolute value of the thermal expansion change within the above range.

[0049] The surface orientation ratio of the acrylic film can be measured by the following methods (1) to (3). (1) The starting point (0 degrees) is the slow axis direction, which is the direction with the greatest refractive index within the plane of the acrylic film measurement area. (2) A light source that produces polarized light vibrating in the 0-degree direction, in the range of 0 to 170 degrees, on an acrylic film at 1388 cm². -1 Absorption intensity in (I 1388 ), and 1730cm -1 Absorption intensity in (I 1730 ) is measured every 10 degrees. For example, the above measurement can be performed by fixing the light source and rotating the acrylic film 10 degrees in the planar direction. 1388 / I 1730 Let Y be the orientation parameter for each angle. (3) The maximum value among the 18 orientation parameters Y measured is Y max , the minimum value is Y min Y max / Y min This is defined as the surface orientation ratio of the acrylic film.

[0050] The surface orientation ratio can be measured, for example, by analyzing the infrared absorption spectrum of a single reflection using the FTIR-S polarized ATR method, with a Thermo Fisher Scientific FT-IR detector (product name: NICOLET6700, measurement spot: 2 mm diameter) equipped with a Haric ATR device (product name: Seagull) and a polarizer (product name: KRS-5, wire grid). Note that the measurement range is 1388 cm⁻¹. -1 The absorption band is a C-αCH3 symmetric bending vibration, quantitatively indicating a highly oriented state where the polymethyl methacrylate molecule is stretched. On the other hand, at 1730 cm⁻¹ -1 The absorption band is used as a reference band to standardize absorption intensity because, in C=O stretching vibrations, the absorption intensity is constant during in-plane rotation.

[0051] In this specification, the surface orientation ratio, in-plane phase difference, and phase difference in the thickness direction are values ​​at a wavelength of 590 nm. In this specification, the atmosphere used for measuring the bond ratio, surface orientation ratio, in-plane phase difference, thickness-direction phase difference, total light transmittance, and haze shall be a temperature of 23°C ± 5°C and a relative humidity of 40% to 65%. Furthermore, before each measurement, the sample shall be exposed to the aforementioned atmosphere for 30 to 60 minutes.

[0052] 《Phase difference》 The acrylic film preferably has an absolute value of 3 nm or less in in-plane phase difference, more preferably 2 nm or less, and even more preferably 1 nm or less. The acrylic film preferably has an absolute value of 5 nm or less in the thickness direction of the phase difference, more preferably 3 nm or less, and even more preferably 2 nm or less.

[0053] The in-plane phase difference and the phase difference in the thickness direction can be measured using a phase difference measuring device. An example of a phase difference measuring device is the "KOBRA-WR" product name from Oji Instruments Co., Ltd. The in-plane phase difference is the measurement value obtained using the aforementioned measuring device when the angle of incidence is the direction normal to the plane of the acrylic film. The phase difference in the thickness direction is a value automatically calculated using the aforementioned measuring device from the value obtained when the angle of incidence is 40 degrees from the normal direction, the value of the in-plane phase difference, and the input value of the average refractive index of the acrylic film. The average refractive index of the acrylic film is approximately 1.49.

[0054] Haze, total light transmittance The acrylic film preferably has a haze of 2.0% or less, more preferably 1.0% or less, more preferably 0.5% or less, and more preferably 0.3% or less, according to JIS K7136:2000. The acrylic film preferably has a total light transmittance of 85% or more, more preferably 87% or more, and even more preferably 90% or more, according to JIS K7361-1:1997.

[0055] <Size, shape, etc.> The acrylic film may be in the form of a single sheet cut to a predetermined size, or in the form of a roll formed by winding a long sheet into a roll. The size of the sheet is not particularly limited, but the maximum diameter should be between 2 inches and 500 inches. "Maximum diameter" refers to the maximum length when connecting any two points on the acrylic film. For example, if the acrylic film is rectangular, the diagonal of the rectangle will be the maximum diameter. If the acrylic film is circular, the diameter of the circle will be the maximum diameter. The width and length of the roll are not particularly limited, but generally, the width is between 500 mm and 8000 mm, and the length is between 100 m and 10000 m. The acrylic film in roll form can be cut into sheets to match the size of image display devices, etc. When cutting, it is preferable to remove the roll ends, which have unstable physical properties. The shape of the leaflets is not particularly limited; for example, they may be polygons such as triangles, squares, or pentagons, or they may be circular or randomly irregular in shape.

[0056] [Method of manufacturing acrylic film] The method for manufacturing the acrylic film described herein comprises the following steps 1 to 3. Step 1: A step to obtain a coating film from an acrylic film composition comprising an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups. Step 2: A step of irradiating the coating film with ultraviolet light. Step 3: A further step of heating the coating film at a temperature above the glass transition temperature of the acrylic polymer.

[0057] <Process 1> Step 1 is a step of obtaining a coating film from an acrylic film composition comprising an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups.

[0058] In step 1, the acrylic film composition may contain a solvent. In step 1, it is preferable to form the coating film by a casting method. For example, it is preferable to apply an acrylic film composition onto a substrate such as a plastic film and then dry the solvent contained in the composition to form the coating film.

[0059] The composition for acrylic film preferably contains a photopolymerization initiator and / or a photopolymerization accelerator. A higher content of the photopolymerization initiator and / or photopolymerization accelerator makes it easier to reduce the absolute value of the rate of change in thermal expansion and to increase the tensile modulus. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzyldimethyl ketal, benzoyl benzoate, α-acyloxime ester, anthraquinone, halogenoketone, thioxanthone, etc.

[0060] Photopolymerization accelerators reduce polymerization inhibition by air and can accelerate the curing rate. Examples of photopolymerization accelerators include one or more selected from p-dimethylaminobenzoate isoamyl ester, p-dimethylaminobenzoate ethyl ester, etc.

[0061] <Process 2> Step 2 is the step of irradiating the coating film with ultraviolet light.

[0062] Step 2 generates radicals within the coating film, providing an opportunity for polymerization of acrylic monomers having two or more (meth)acryloyl groups. The amount of ultraviolet radiation is not particularly limited, but 150 mJ / cm² is a good starting point. 2 More than 500mJ / cm 2 The following is preferable:

[0063] <Process 3> Step 3 is a step of further heating the coating film to a temperature above the glass transition temperature of the acrylic polymer.

[0064] Step 2 alone is insufficient to adequately react the acrylic monomers having two or more (meth)acryloyl groups in the acrylic film. This is because the acrylic film contains a large proportion of non-fluid acrylic polymer, preventing the acrylic monomers from moving freely within the film. Step 3 increases the fluidity of the acrylic polymer, making it easier for the acrylic monomer to move within the acrylic film. Therefore, performing Step 3 facilitates the reaction of the polymerizable acrylic monomer.

[0065] The temperature in step 3 should be above the glass transition temperature of the acrylic polymer, but it is preferably between 90°C and 130°C. Furthermore, the heating time in step 3 is preferably between 30 seconds and 300 seconds.

[0066] Step 3 is preferably carried out within a predetermined time after the completion of Step 2. This is because if too much time passes after Step 2, the radicals generated in the coating film will become inactive. The shorter the interval between Step 2 and Step 3, the easier it is to increase the reactivity of the acrylic monomer having two or more (meth)acryloyl groups. Furthermore, shortening the interval between step 2 and step 3 reduces the proportion of unreacted acrylic monomer, thereby suppressing the decrease in the tensile modulus of the acrylic film caused by the unreacted acrylic monomer acting as a plasticizer. Step 3 is preferably carried out within 4 hours, more preferably within 2 hours, more preferably within 30 minutes, and more preferably within 10 minutes after the completion of Step 2.

[0067] If step 1 is performed using the casting method, an acrylic film can be obtained after step 3 by peeling off the substrate.

[0068] [Optical laminate] The optical laminate of this disclosure has one or more functional layers on the acrylic film of this disclosure described above.

[0069] <Functional Layer> The functional layer may be a single layer or a multilayer structure. The functional layer may be formed on only one side of the acrylic film or on both sides.

[0070] Examples of layers constituting the functional layer include an easy-adhesion layer, a phase difference layer, a hard coat layer, an anti-glare layer, an anti-reflective layer, an anti-fouling layer, an anti-static layer, and an adhesive layer. A single functional layer may have multiple functions. Among the functional layers, anti-reflective layers can be single-layer or multi-layer. A single-layer anti-reflective layer can be a single layer of low refractive index. A multi-layer anti-reflective layer can consist of two layers, a high refractive index layer and a low refractive index layer, and can also consist of three or more layers. The configuration of functional layers such as the easy-adhesion layer, phase difference layer, hard coat layer, anti-glare layer, anti-reflective layer, anti-fouling layer, anti-static layer, and adhesive layer can be a general-purpose configuration.

[0071] Examples of the lamination configuration of the optical laminate include the embodiments B1 to B15 below. In B1 to B15 below, " / " represents the interface between layers. Furthermore, embodiments of the lamination configurations B1 to B15 below may include having an easy-adhesion layer between one or more layers.

[0072] B1: Acrylic film / hard coat layer B2: Acrylic film / Anti-glare layer B3: Acrylic film / Hard coat layer / Anti-reflective layer B4: Acrylic film / Anti-glare layer / Anti-reflective layer B5: Acrylic film / Hard coat layer / Anti-fouling layer B6: Acrylic film / Anti-glare layer / Anti-fouling layer B7: Acrylic film / phase difference layer B8: Adhesive layer / acrylic film B9: Adhesive layer / Acrylic film / Hard coat layer B10: Adhesive layer / Acrylic film / Anti-glare layer B11: Adhesive layer / Acrylic film / Hard coat layer / Anti-reflective layer B12: Adhesive layer / Acrylic film / Anti-glare layer / Anti-reflective layer B13: Adhesive layer / Acrylic film / Hard coat layer / Anti-fouling layer B14: Adhesive layer / Acrylic film / Anti-glare layer / Anti-fouling layer B15: Adhesive layer / Acrylic film / Phase difference layer

[0073] Optical laminates may be subjected to heat during the formation of their functional layers. Furthermore, optical laminates may be exposed to heat during use (e.g., the internal temperature of an image display device, the temperature of a car's dashboard). Additionally, optical laminates may be subjected to heat during bonding with other components such as polarizers. Since the optical laminate of this disclosure uses the acrylic film described above, it is possible to suppress the deterioration of the quality of the optical laminate due to the heat described above.

[0074] [Polarizing plate] The polarizing plate of the present disclosure is a polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate includes the acrylic film of the present disclosure described above.

[0075] <Polarizer> Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, and ethylene-vinyl acetate copolymer saponified film dyed with iodine or the like and stretched; wire grid-type polarizers consisting of numerous parallel metal wires; coated polarizers coated with lyotropic liquid crystal or dichroic guest-host materials; and multilayer thin-film polarizers. These polarizers may also be reflective polarizers that have the function of reflecting polarization components that do not transmit through them.

[0076] <Transparent protection plate> A first transparent protective plate is positioned on one side of the polarizer, and a second transparent protective plate is positioned on the other side. At least one of the first and second transparent protective plates includes the acrylic film of the present disclosure described above.

[0077] Preferably, both the first transparent protective plate and the second transparent protective plate include the acrylic film of the present disclosure as described above.

[0078] The acrylic film included in the first transparent protective plate and / or the second transparent protective plate may have a functional layer formed on the acrylic film. That is, the first transparent protective plate and / or the second transparent protective plate may be the optical laminate of the present disclosure described above.

[0079] Of the first and second transparent protective plates, the transparent protective plate that does not contain the acrylic film of this disclosure can be a general-purpose plastic film, glass, or the like.

[0080] It is preferable to bond the polarizer and the transparent protective plate together using an adhesive. A general-purpose adhesive can be used, and a PVA-based adhesive is preferred.

[0081] The polarizing plate of this disclosure can easily suppress quality degradation such as light leakage.

[0082] [Surface plate for image display device] The surface plate for an image display device disclosed herein is a surface plate for an image display device comprising a protective film laminated onto a resin plate or a glass plate, wherein the protective film includes the acrylic film described above.

[0083] The protective film may be an acrylic film on which a functional layer is formed. In other words, the protective film may be the optical laminate described above.

[0084] As the resin plate or glass plate, a resin plate or glass plate commonly used as a surface plate for image display devices can be used.

[0085] The thickness of the resin or glass plate is preferably 10 μm or more to ensure good strength. The upper limit of the thickness of the resin or glass plate is usually 5000 μm or less. For thinning, the upper limit of the thickness of the resin or glass plate is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less.

[0086] [Image display device] The image display device of this disclosure has the acrylic film of this disclosure described above on a display element.

[0087] The acrylic film may have a functional layer formed on it. That is, the image display device of this disclosure may have the optical laminate of this disclosure described above on a display element.

[0088] Examples of display elements include liquid crystal display elements, organic EL display elements, inorganic EL display elements, and other EL display elements, as well as plasma display elements. Furthermore, LED display elements such as mini-LED display elements and micro-LED display elements are also included. These display elements may have a touch panel function inside the display element. Examples of liquid crystal display methods for liquid crystal display elements include IPS, VA, multi-domain, OCB, STN, and TSTN methods. When the display element is a liquid crystal display element, a backlight is required. Examples of backlights include quantum dot backlights and white light-emitting diode backlights. The image display device may be a foldable image display device or a rollable image display device. Furthermore, the image display device may be an image display device with a touch panel. [Examples]

[0089] The acrylic films of this disclosure will be described in detail below with reference to examples and comparative examples. The acrylic films of this disclosure are not limited to the forms described in the examples.

[0090] 1. Evaluation and Measurement The acrylic films obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1 or 2.

[0091] 1-1. Rate of change of thermal expansion, coefficient of thermal expansion For the acrylic films of the examples and comparative examples, the "rate of change in thermal expansion at 130°C" and the "coefficient of thermal expansion from 40°C to 130°C" were measured. The measuring device used was Hitachi High-Tech Corporation's product name "TMASS7100". The size of the sample incorporated into the measuring device was approximately 10 mm x approximately 10 mm. The measurement conditions and temperature program were as follows. The acrylic film of Comparative Example 3 was too hard and cracked when preparing the sample, when attaching the sample, or during measurement. For this reason, the rate of change in thermal expansion and the coefficient of thermal expansion were not measured for Comparative Example 3. <Measurement conditions> • Under a nitrogen atmosphere • Load 9.8mN • Sample length: 10 mm • Pulling mode ·Starting temperature 20℃ <Temperature Program> The temperature was changed in the following order under liquid nitrogen control. The sample length at room temperature was defined as the sample length at the temperature in Step 1. The sample lengths at 40°C and 130°C were defined as the sample lengths at the temperature in Step 2. Step 1: Heating rate -10°C / min, target 20°C, holding time 10 minutes Step 2: Heating rate 10°C / min, target 210°C, holding time 5 minutes Step 3: Heating rate -10°C / min, target 20°C, holding time 0 minutes

[0092] 1-2. Tensile modulus The tensile modulus at 100°C of the acrylic films in the examples and comparative examples was measured by tensile testing in accordance with JIS K7127:1999. The measuring device used was Instron's universal material testing machine "Model No. 5565". The measurement conditions were as follows. The acrylic film of Comparative Example 2 was below the measurement limit, and therefore the value of the tensile modulus could not be measured, so it is indicated as "below the lower limit". <Measurement conditions> • Sample size: 10mm wide, 150mm long After placing the sample in the measuring device, measurement should begin 6 minutes after the furnace temperature reaches 100°C. • Test speed: 10 mm / min • Load cell: 1kN • Chuck spacing: 100mm

[0093] 1-3.Coupling ratio Following the methods described in (1) to (4) of the specification, the ratio of C=C bonds to C=O bonds in the acrylic films of the examples and comparative examples was calculated. A Thermo Fisher Raman spectrometer (model number: DXR3) was used to measure the C=O and C=C bonds. The objective lens magnification was set to 100x. The acrylic films of Comparative Examples 4 to 7 did not contain acrylic monomers having two or more (meth)acryloyl groups in the acrylic film composition, so the bond ratio was not measured.

[0094] 1-4. Total light transmittance, haze The total light transmittance and haze of the acrylic films in the examples and comparative examples were measured using a haze meter (product number: HM-150, Murakami Color Technology Research Institute Co., Ltd.).

[0095] 1-5.Phase difference The in-plane phase difference and the phase difference in the thickness direction of the acrylic films of the examples and comparative examples were measured using a phase difference measuring device (Oji Instruments Co., Ltd., product name: KOBRA-WR). The measurement method was as described in the main text of the specification.

[0096] 1-6. Mandrel Test The acrylic films of the examples and comparative examples were subjected to a flexural resistance test using the cylindrical mandrel method specified in JIS K5600-5-1:1999. The diameter of the mandrel was gradually reduced to a minimum of 2 mm, and the diameter of the mandrel at which the acrylic film first cracked was recorded as the value for each acrylic film. Acrylic films that did not crack even at a diameter of 2 mm were recorded as having a value of 2 mm. A smaller value indicates better flexural resistance.

[0097] Drying suitability from 1-7 to 130°C, peelability, and rigidity at 100°C. (1) Suitable for drying at 130°C In the examples and comparative examples, before peeling the acrylic film from the polyethylene terephthalate film, the hard coat layer ink was applied to the acrylic film as described below and dried at 130°C for 1 minute to obtain a laminate having the polyethylene terephthalate film, acrylic film, and hard coat layer in that order. The presence or absence of wrinkles in the laminate was evaluated visually. Laminates without wrinkles were designated as "A," and those with wrinkles were designated as "C."

[0098] <Ink for hard coat layer> • Polyfunctional acrylic monomer 5.0 parts by mass (Product name: KAYARAD PET-30, Nippon Kayaku Co., Ltd., Number of functional groups: 3) • Photopolymerization initiator 0.15 parts by mass (Product name: Omnirad 184, BASF) • Methyl ethyl ketone 10.0 parts by mass

[0099] (2) Peelability In (1) above, the peelability was evaluated for laminates in which no wrinkles occurred. Specifically, when peeling the acrylic film and hard coat layer from the laminate obtained in (1) above, those in which the acrylic film did not break were designated as "A", and those in which the acrylic film broke were designated as "C".

[0100] (3) Rigidity at 100℃ In (2) above, the rigidity at 100°C was evaluated for those laminates from which the acrylic film and hard coat layer could be peeled off. Hereinafter, the optical laminates with a hard coat layer on an acrylic film, peeled off in (2), will be referred to as the sample. The rigidity at 100°C was evaluated using the sample by the following method. <Evaluation Method> A sample was placed in a B4-sized stainless steel frame with a hollowed-out interior (the stainless steel portion was 2 cm around the edge), and secured with tape to prevent sagging. The stainless steel frame with the sample was heated in a 100°C oven for 1 minute. The stainless steel frame with the sample was removed from the oven, and the rigidity of the sample was visually evaluated. Samples that did not sag, as shown in Figure 1(A), were designated as "A," and samples that sagged, as shown in Figure 1(B), were designated as "C."

[0101] 2. Making the acrylic film [Example 1] The following acrylic film composition 1 was coated onto a polyethylene terephthalate film by casting using an applicator to obtain a laminate having an acrylic coating on the polyethylene terephthalate film. Next, the laminate was placed in a 130°C oven for 3 minutes to dry the solvent. Then, ultraviolet light (240 mJ / cm²) was irradiated from the acrylic coating side of the laminate. 2 Next, 5 minutes after irradiation with ultraviolet light, the laminate was placed in a 130°C oven for 1 minute and then removed. The acrylic film was then peeled off the laminate to obtain the acrylic film of Example 1 with a thickness of 30 μm.

[0102] <Composition for acrylic film 1> • Acrylic polymer 6.5 parts by mass (Product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.) • Polyfunctional acrylic monomer 3.5 parts by mass (Product name: NK Ester ATM-4E, Shin Nakamura Chemical Industry Co., Ltd., Number of functional groups: 4, Contains alkylene oxide in the molecular skeleton) • Photopolymerization initiator 0.07 parts by mass (Product name: Omnirad907, BASF) Methyl ethyl ketone 21.2 parts by mass

[0103] [Example 2] The acrylic film of Example 2 was obtained in the same manner as in Example 1, except that the time from irradiation with ultraviolet light to placing the laminate in a 130°C oven was changed to 1 hour.

[0104] [Example 3] The acrylic film of Example 3 was obtained in the same manner as in Example 1, except that the time from irradiation with ultraviolet light to placing the laminate in a 130°C oven was changed to 3 hours.

[0105] [Example 4] An acrylic film of Example 4 was obtained in the same manner as in Example 1, except that composition 1 for acrylic film was replaced with composition 2 for acrylic film described below.

[0106] <Composition for acrylic film 2> • Acrylic polymer 6.5 parts by mass (Product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.) • Polyfunctional acrylic monomer 2.5 parts by mass (Product name: NK Ester ATM-4E, Shin Nakamura Chemical Industry Co., Ltd., Number of functional groups: 4, Contains alkylene oxide in the molecular skeleton) • Polyfunctional acrylic monomer 1.0 parts by mass (Product name: NK Ester ATM-35E, Shin Nakamura Chemical Industry Co., Ltd., Number of functional groups: 4, Contains alkylene oxide in the molecular skeleton) • Photopolymerization initiator 0.07 parts by mass (Product name: Omnirad907, BASF) Methyl ethyl ketone 21.2 parts by mass

[0107] [Example 5] An acrylic film of Example 4 was obtained in the same manner as in Example 1, except that composition 1 for acrylic film was replaced with composition 3 for acrylic film described below.

[0108] <Composition for acrylic film 3> • Acrylic polymer 6.5 parts by mass (Product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.) • Polyfunctional acrylic monomer 1.5 parts by mass (Product name: Light Acrylate 9EG-A, Kyoeisha Chemical Co., Ltd., Number of functional groups: 2, Contains alkylene oxide in the molecular skeleton) • Polyfunctional acrylic monomer 1.0 parts by mass (Product name: KAYARAD PET-30, Nippon Kayaku Co., Ltd., Number of functional groups: 3-4, Molecular backbone does not contain alkylene oxides) • Photopolymerization initiator 0.05 parts by mass (Product name: Omnirad907, BASF) Methyl ethyl ketone 21.2 parts by mass

[0109] [Example 6] An acrylic film of Example 6 was obtained in the same manner as in Example 1, except that the acrylic polymer in acrylic film composition 1 was replaced with an acrylic polymer from Mitsubishi Chemical Corporation (product name: BR-80).

[0110] [Comparative Example 1] The acrylic film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the time from irradiation with ultraviolet light to placing the laminate in a 130°C oven was changed to 5 hours.

[0111] [Comparative Example 2] The acrylic film of Comparative Example 2 was obtained in the same manner as in Example 1, except that after irradiation with ultraviolet light, the laminate was not placed in a 130°C oven but left at room temperature.

[0112] [Comparative Example 3] An acrylic film of Comparative Example 3 was obtained in the same manner as in Example 1, except that acrylic film composition 1 was replaced with acrylic film composition 4 described below.

[0113] <Composition for acrylic film 4> • Acrylic polymer 6.0 parts by mass (Product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.) • Polyfunctional acrylic monomer 4.0 parts by mass (Product name: NK Ester ATM-4E, Shin Nakamura Chemical Industry Co., Ltd., Number of functional groups: 4, Contains alkylene oxide in the molecular skeleton) • Photopolymerization initiator 0.08 parts by mass (Product name: Omnirad907, BASF) Methyl ethyl ketone 21.2 parts by mass

[0114] [Comparative Example 4] An acrylic film of Comparative Example 4 was obtained in the same manner as in Example 1, except that acrylic film composition 1 was replaced with acrylic film composition 5 described below.

[0115] <Composition for acrylic film 5> • Acrylic polymer 10 parts by mass (Product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.) • Methyl ethyl ketone 56 parts by mass

[0116] [Comparative Example 5] An acrylic film of Comparative Example 5 was obtained in the same manner as in Example 1, except that acrylic film composition 1 was replaced with acrylic film composition 6 described below.

[0117] <Composition for acrylic film 6> • Acrylic polymer 10 parts by mass (Product name: BR-80, Mitsubishi Chemical Corporation) • Methyl ethyl ketone 56 parts by mass

[0118] [Comparative Example 6] For Comparative Example 6, a commercially available acrylic film (product name: HX40-UF, Toyo Kohan Co., Ltd., thickness 39 μm, stretched film) was used as the acrylic film.

[0119] [Comparative Example 7] For Comparative Example 7, a commercially available acrylic film (product name: W001KU60, Sumitomo Chemical Co., Ltd., thickness 59 μm, stretched film) was used as is.

[0120] [Table 1]

[0121] [Table 2]

[0122] The results in Tables 1 and 2 confirm that the acrylic film of the example can maintain stable quality even in high-temperature ranges above 100°C. [Explanation of Symbols]

[0123] 10: Stainless steel frame 20: Fixing tape 30: Sample

Claims

1. It is an acrylic film, The acrylic film has an absolute value of 3.0% or less in the rate of change of thermal expansion at 130°C, and a tensile modulus of elasticity of 300 MPa or more and 1300 MPa or less at 100°C. The acrylic film comprises an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups, wherein the ratio of C=C bonds to C=O bonds in the acrylic film is 0.10 or more and 0.55 or less.

2. The acrylic film according to claim 1, wherein the absolute value of the coefficient of thermal expansion at 40°C to 130°C is 250 ppm / °C or less.

3. The acrylic film according to claim 1 or 2, wherein the absolute value of the rate of change in thermal expansion is 0.1% or more and 1.0% or less.

4. The acrylic film is the acrylic film according to any one of claims 1 to 3, wherein the surface orientation ratio is 1.

00.

5. The acrylic film according to any one of claims 1 to 4, wherein the acrylic film includes a cured product of an ultraviolet-curable resin composition.

6. The acrylic film is the acrylic film according to any one of claims 1 to 5, wherein the total light transmittance is 85% or more.

7. The acrylic film is the acrylic film according to any one of claims 1 to 6, wherein the haze is 2.0% or less.

8. An optical laminate having one or more functional layers on an acrylic film according to any one of claims 1 to 7.

9. A polarizing plate comprising a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, A polarizing plate in which at least one of the first transparent protective plate and the second transparent protective plate includes the acrylic film described in any one of claims 1 to 7.

10. A surface plate for an image display device, comprising a resin plate or a glass plate with a protective film laminated on it, wherein the protective film includes the acrylic film described in any one of claims 1 to 7.

11. An image display device having an acrylic film according to any one of claims 1 to 7 on a display element.

12. A method for manufacturing an acrylic film according to any one of claims 1 to 7, comprising the following steps 1 to 3. Step 1: A step to obtain a coating film from an acrylic film composition comprising an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups. Step 2: A step of irradiating the coating film with ultraviolet light. Step 3: A further step of heating the coating film at a temperature above the glass transition temperature of the acrylic polymer.

Images