JP2023146811A - Acryl film, optical laminate, polarizing plate, surface plate and image display device each including acryl film, and method for producing acryl film - Google Patents

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

The present disclosure relates to an acrylic film, an optical laminate, a polarizing plate, a surface plate, and an image display device including the acrylic film, and a method for producing an acrylic film.

Polymer resin films such as acrylic films, polyester films, and cyclic olefin films have excellent transparency, so they can be used as base materials for functional films for image display devices, and to protect or decorate objects such as vehicles, furniture, and electrical appliances. It is used as a base material for functional films.

Among polymeric resin films, acrylic films whose main component is acrylic polymer represented by PMMA are characterized by excellent optical properties and weather resistance. For this reason, acrylic films are used for various purposes. Among these, acrylic films are expected to be used as base materials for functional films of image display devices.
For example, Patent Documents 1 and 2 have been proposed as acrylic films.

JP2009-292961A Japanese Patent Application Publication No. 2018-44171

The acrylic film of Patent Document 1 aims to improve heat shrinkage characteristics in the processing stage. The acrylic film of Patent Document 2 aims to reduce the coefficient of thermal expansion in the MD direction and the TD direction. The acrylic films of Patent Documents 1 and 2 can improve thermal behavior to a predetermined level.
However, image display devices including functional films based on acrylic films disclosed in Patent Documents 1 and 2 frequently suffer from a problem in which quality deteriorates during use or quality deteriorates over time. An example of quality deterioration is light leakage.
Furthermore, in recent years, there has been a demand for higher quality functional films. As described above, when the acrylic films of Patent Documents 1 and 2 were used as base materials for high-quality functional films, there were frequent cases in which the expected quality could not be obtained.

As a result of intensive research, the present inventors found that the cause of the above-mentioned quality problems was a high temperature of 100° C. or higher. For example, the interior of recent image display devices, such as smartphones, may reach a high temperature of 100° C. or higher during use. Furthermore, functional films used near the dashboard of automobiles may reach high temperatures during the summer. Moreover, when improving the quality of a functional film, high temperature treatment of 100° C. or higher may be required in the process of manufacturing the functional film.
The present inventors have now completed an acrylic film whose quality can be stabilized even in a high temperature range of 100° C. or higher.

The present disclosure provides the following [1] to [6].
[1] An acrylic film,
The acrylic film has an absolute value of thermal expansion change rate at 130°C of 3.0% or less, and a tensile modulus of elasticity at 100°C of 300 MPa or more and 1300 MPa or less.
[2] An optical laminate having one or more functional layers on the acrylic film according to [1].
[3] 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. hand,
A polarizing plate, wherein at least one of the first transparent protection plate and the second transparent protection plate includes the acrylic film according to [1].
[4] A surface plate for an image display device in which a protective film is laminated onto a resin plate or a glass plate, wherein the protective film includes the acrylic film according to [1].
[5] An image display device comprising the acrylic film according to [1] on a display element.
[6] The method for producing an acrylic film according to [1], which includes the following steps 1 to 3.
Step 1: A step of obtaining a coating film from an acrylic film composition containing an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups.
Step 2: Step of irradiating the coating film with ultraviolet rays.
Step 3: Further, a step of heating the coating film at a temperature equal to or higher than the glass transition temperature of the acrylic polymer.

The acrylic film, optical laminate, polarizing plate, surface plate, and image display device of the present disclosure can stabilize quality even in a high temperature range of 100° C. or higher. The method for producing an acrylic film of the present disclosure can easily produce an acrylic film whose quality can be stabilized even in a high temperature range of 100° C. or higher.

FIG. 3 is a schematic cross-sectional view for explaining a stiffness evaluation method.

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

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 stated, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acrylic" refers to acrylic and methacrylic.

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

<Thermal expansion change rate>
The acrylic film of the present disclosure requires that the absolute value of the rate of change in thermal expansion at 130°C is 3.0% or less.
In this specification, the "absolute value of the rate of change in thermal expansion at 130°C" may be referred to as the "absolute value of the rate of change in thermal expansion."

If the absolute value of the rate of change in thermal expansion exceeds 3.0%, wrinkles will occur in the acrylic film in an environment of 130°C. For this reason, when the absolute value of the rate of change in thermal expansion exceeds 3.0%, a functional film based on an acrylic film is likely to suffer from deterioration in quality during use. Furthermore, if the absolute value of the thermal expansion change rate exceeds 3%, the problem that the expected quality may not be obtained is likely to occur when a high temperature treatment at 130° C. is performed in the process of manufacturing a functional film.
On the other hand, an acrylic film having an absolute value of thermal expansion change rate of 3.0% or less can suppress the above problems and stabilize the quality of the functional film. In recent years, due to improvements in the performance of image display devices and in the quality of functional films, acrylic films are more likely to be exposed to high heat during the use of the functional film and in the process of manufacturing the functional film. Therefore, it is technically significant to set the absolute value of the thermal expansion rate of the acrylic film at 130° C. to 3% or less.
In a normal acrylic film, since the acrylic polymer softens at 130°C, the absolute value of the rate of change in thermal expansion at 130°C cannot be reduced to 3.0% or less. The acrylic film of the present disclosure is produced by forming an acrylic film through predetermined steps using an acrylic film composition containing an acrylic polymer and a polymerizable acrylic monomer. It can be easily reduced to .0% or less.

The absolute value of the thermal expansion rate of the acrylic film is preferably 2.0% or less, more preferably 1.0% or less. The lower limit of the absolute value of the rate of change in thermal expansion of the acrylic film is not particularly limited, but is usually 0.1% or more.

In this specification, the rate of change in thermal expansion at 130°C is calculated using the following formula. In the formula below, L ₁₃₀ means the sample length at 130°C, and L means the original sample length. The original sample length is referred to herein 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 Examples.
Thermal expansion rate of change = {(L ₁₃₀ −L)/L}×100

Although the acrylic film may have a negative thermal expansion change rate at 130°C, it is preferably a positive value.

<Tensile modulus>
The acrylic film of the present disclosure needs to have a tensile modulus of elasticity 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 as "tensile modulus".

When the tensile modulus is less than 300 MPa, wrinkles are likely to occur along the tensile direction of the acrylic film when the acrylic film is stretched in an environment of 100°C.
Specifically, when the tensile modulus is less than 300 MPa, wrinkles are likely to occur in the acrylic film along the transport direction when the acrylic film is transported while heating and drying the ink for the functional layer coated on the acrylic film. .
Furthermore, when attaching a protective film to a polarizer, heat of about 100° C. is often applied. Polarizers do not have high heat resistance, so it is difficult to heat them to 130°C, and they are usually heated to about 100°C. For this reason, when the tensile modulus is less than 300 MPa, wrinkles are likely to occur in the acrylic film when bonding the acrylic film as a protective film to the polarizer.
From the above, when the tensile modulus is less than 300 MPa, functional films based on acrylic film may not have the expected quality, or the quality may deteriorate when bonded to other materials. becomes more likely to occur.

On the other hand, when the tensile modulus exceeds 1300 MPa, the acrylic film is likely to break when stretched in an environment of 100°C.
Specifically, when the tensile modulus exceeds 1300 MPa, the acrylic film is likely to break when the acrylic film is transported while heating and drying the functional layer ink coated on the acrylic film.
Moreover, when the tensile modulus exceeds 1300 MPa, the acrylic film is likely to break when bonding the acrylic film as a protective film to the polarizer.
From the above, when the tensile modulus exceeds 1300 MPa, the functional film based on an acrylic film has extremely poor handling properties.

The lower limit of the tensile modulus of the acrylic film is preferably 320 MPa or more, more preferably 340 MPa or more, and the upper limit is preferably 1200 MPa or less, more preferably 1150 MPa or less.

As mentioned above, in the process of applying tension to the acrylic film, although heat of 100° C. is applied, there are cases where heat of 130° C. is not applied. Therefore, in the acrylic film of the present disclosure, there is technical significance in specifying the thermal expansion change rate at 130°C and the tensile modulus at 100°C.

In this specification, the tensile modulus at 100°C is measured by a tensile test based on JIS K7127:1999. More specifically, the tensile modulus at 100° C. can be measured, for example, by the method described in Examples.

In the configuration requirements shown in this specification, if multiple numerical upper limit options and multiple lower limit options are shown, one selected from the upper limit options and one selected from the lower limit options are combined, A range of embodiments may be used.
For example, in the case of tensile modulus, embodiments of numerical ranges 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 1 300MPa or less , 340 MPa or more and 1200 MPa or less, and 340 MPa or more and 1150 MPa or less.

<Thermal expansion coefficient>
The acrylic film of the present disclosure preferably has an absolute value of thermal expansion coefficient of 250 ppm/°C or less between 40°C and 130°C.
In this specification, the "coefficient of thermal expansion from 40°C to 130°C" may be referred to as the "coefficient of thermal expansion."

By setting the thermal expansion coefficient to 250 ppm/°C or less, it is possible to more easily suppress wrinkles from forming 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, even more preferably 110 ppm/°C or less. The lower limit of the thermal expansion coefficient is not particularly limited, but is usually 10 ppm/°C or more.

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

<Coupling ratio>
The acrylic film of the present disclosure includes 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. is preferred.

Containing an acrylic monomer having two or more (meth)acryloyl groups in an acrylic film means that ``a polymerizable acrylic monomer is contained as a raw material for the acrylic film, and unreacted substances of the polymerizable monomer are contained in the acrylic film. It can be said to mean that "is still present."
The C=0 bond in the acrylic film is contained in the acrylic polymer, the reacted product of the polymerizable acrylic monomer, and the unreacted product of the polymerizable acrylic monomer. Further, the C=C bonds in the acrylic film are mainly contained in unreacted polymerizable monomers.
Therefore, the ratio of C=C bonds to C=O bonds in the acrylic film can be said to be an indicator of the proportion of unreacted polymerizable monomers in the acrylic film.

The fact that the ratio of C=C bonds to C=O bonds in the acrylic film is 0.55 or less means that the reaction of the polymerizable monomers progresses in the acrylic film, and the polymerizable acrylic monomers form a network bond. It means that. Therefore, by setting the bonding ratio to 0.55 or less, the absolute value of the thermal expansion rate of the acrylic film can be easily set to 3.0% or less. Furthermore, by setting the bonding ratio to 0.55 or less, the tensile modulus of the acrylic film can be easily increased to 300 MPa or more.
In addition, the unreacted polymerizable acrylic monomer remaining in the acrylic film may act like a plasticizer, lowering the glass transition temperature of the acrylic film and lowering the tensile modulus of the acrylic film. . Therefore, it is technically significant to reduce the bonding ratio to 0.55 or less by reducing the proportion of unreacted polymerizable acrylic monomer.
Furthermore, when forming a functional layer such as a retardation layer on an acrylic film, the functional layer may be formed by coating. The functional layer coating liquid used for coating may contain a solvent. Depending on the type of solvent, a general-purpose acrylic film may dissolve or swell, which may impair the quality of the functional layer. For example, if the acrylic film dissolves or swells, it becomes difficult to align the liquid crystal, and the quality of the retardation layer deteriorates. On the other hand, if the bonding ratio is 0.55 or less, the polymerizable acrylic monomer forms a network bond, so that the acrylic film can have good resistance to solvents. That is, by setting the bonding ratio to 0.55 or less, the solvent resistance of the acrylic film can be improved, and deterioration in the quality of the functional layer can be easily suppressed.

The 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 much, 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, in step 3 of the method for producing an acrylic film of the present disclosure, which will be described later.

In this specification, the ratio can be measured, for example, by the following methods (1) to (4).
(1) A sample for measurement is prepared by cutting an acrylic film vertically.
(2) Measure the scattering intensities of C=O bonds and C=C bonds from the cross-sectional direction of the sample by Raman spectroscopy. The scattering intensity of the C=C bond is defined as the scattering intensity at 1620 cm ^-1 or more and 1680 cm ^-1 . The scattering intensity of the C═O bond is defined as the scattering intensity at 1710 cm ⁻¹ or more and 1780 cm ⁻¹ .
(3) The measurement is performed every 2 μm in the thickness direction of the cross section of the sample. Specifically, a location 2 μm in the depth direction from the top surface of the cross section of the sample is defined as the first measurement location. Furthermore, measurements are performed at every location 2 μm further in the depth direction.
(4) Calculate the ratio of C=C bonds to C=O bonds for each measurement location. Then, the average of the ratios for all measurement locations is taken as the ratio of C=C bonds to C=O bonds of the sample.

<Acrylic polymer>
The acrylic polymer is preferably a polymer obtained by polymerizing (meth)acrylic acid and/or (meth)acrylic acid derivatives as the main components and these monomers. As the acrylic polymer, a polymer commonly used as a polymer for acrylic films can be used.

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

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

The raw material monomer for the acrylic polymer preferably contains methyl methacrylate. The ratio of methyl methacrylate to all monomers in the raw material monomers is preferably 30 mol% or more, more preferably 50 mol% or more and 95 mol% or less.

The glass transition temperature of the acrylic polymer included in the acrylic film of the present disclosure may be equivalent to the glass transition temperature of the acrylic polymer constituting a general-purpose acrylic film.
Specifically, the acrylic polymer contained in the acrylic film of the present 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, the acrylic film can be easily handled. In addition, by forming an acrylic film through a predetermined process using an acrylic film composition containing an acrylic polymer with a glass transition temperature of 95°C or higher and a polymerizable acrylic monomer, the absolute value of the thermal expansion rate And the tensile modulus can be easily controlled within the above-mentioned range.
The upper limit of the glass transition temperature of the acrylic polymer is not particularly limited, but is usually 120°C or lower.
The glass transition temperature of the acrylic polymer can be adjusted by blending the raw material monomers of the acrylic polymer.

The weight average molecular weight of the acrylic polymer is preferably 50,000 or more and 1,000,000 or less, more preferably 80,000 or more and 500,000 or less, and 100,000 or more and 300,000 or less. is even more preferable.
By setting the weight average molecular weight of the acrylic polymer to 50,000 or more, the mechanical strength of the acrylic film can be easily improved. By setting the weight average molecular weight of the acrylic polymer to 1,000,000 or less, it is possible to easily form an acrylic film.
In this specification, the weight average molecular weight is an average molecular weight measured by GPC analysis and converted to standard polystyrene.

<Acrylic monomer having two or more (meth)acryloyl groups>
Examples of the acrylic monomer having two (meth)acryloyl groups include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxy diacrylate, bisphenol A tetrapropoxy diacrylate, 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, and dipentaerythritol hexa(meth)acrylate. Examples include pentaerythritol tetra(meth)acrylate, isocyanuric acid-modified tri(meth)acrylate, and the like.
In this specification, "acrylic monomer having two or more (meth)acryloyl groups" may be referred to as a polyfunctional acrylic monomer.
One type or two or more types of polyfunctional acrylic monomers can be used.

The polyfunctional acrylic monomer preferably has three or more (meth)acryloyl groups in order to easily reduce the absolute value of the rate of change in thermal expansion of the acrylic film and increase the tensile modulus. The number of (meth)acryloyl groups in the polyfunctional acrylic monomer is preferably 6 or less, more preferably 5 or less, in order to prevent the tensile modulus of the acrylic film from becoming too large.
In order to adjust the absolute value of the thermal expansion rate 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 together.

The polyfunctional acrylic monomer preferably contains alkylene oxide in its molecular skeleton. By including alkylene oxide in the molecular skeleton, the absolute value of the rate of change in thermal expansion and the tensile modulus can be easily controlled within the above ranges while maintaining the flexibility of the acrylic film.
In order 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.

In an acrylic film composition containing an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups, the content of the acrylic monomer is 10 parts by mass or more and 90 parts by mass based on 100 parts by mass of the acrylic polymer. It is preferable that the amount is less than 100%.
By setting the content of the acrylic monomer to 10 parts by mass or more, the absolute value of the rate of change in thermal expansion of the acrylic film can be reduced and the tensile modulus can be easily increased. Further, by setting the content of the acrylic monomer to 10 parts by mass or more, the solvent resistance of the acrylic film can be easily improved. By setting the content of the acrylic monomer to 90 parts by mass or less, it is possible to easily prevent the tensile modulus of the acrylic film from becoming too large, and it is also possible to easily prevent the bending resistance of the acrylic film from decreasing.
The lower limit of the content of the acrylic monomer is preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and the upper limit is 70 parts by mass or less, based on 100 parts by mass of the acrylic polymer. The amount is more preferably 60 parts by mass or less.

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. When the acrylic film contains a predetermined amount of the cured product of the ultraviolet curable resin composition, the absolute value of the rate of change in thermal expansion and the tensile modulus can be easily controlled within the above ranges. Further, since the acrylic film contains a predetermined amount of the cured product of the ultraviolet curable resin composition, the solvent resistance of the acrylic film can be easily improved.

The lower limit of the ratio of the cured product of the ultraviolet curable resin composition to the total solid content of the acrylic film is preferably 10% by mass or more, more preferably 15% by mass or more, and 20% by mass or more. is more preferable, and 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.

The proportion of the cured product of the ultraviolet curable resin composition in the acrylic film can be calculated, for example, by immersing the acrylic film in a solvent that dissolves the acrylic polymer, and calculating from the proportion of the components that remain undissolved.

<Additives>
The acrylic film may contain additives such as plasticizers, ultraviolet absorbers, light stabilizers, antiblocking agents, and antioxidants, as long as the effects of the acrylic film of the present disclosure are not impaired.

<Thickness>
In order to improve mechanical strength, 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 improve processability, 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 this specification, the thickness of the acrylic film means the average value of the thicknesses of ten arbitrary locations on the acrylic film. The thickness of any 10 points on the acrylic film can be measured using a general-purpose film thickness meter.

<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, when the acrylic film is oriented, it is difficult to keep the absolute value of the thermal expansion rate within the above range. That is, by setting the surface orientation ratio to 1.00, the absolute value of the rate of change in thermal expansion can be easily set within the above range.

The surface orientation ratio of an acrylic film can be measured by the following methods (1) to (3).
(1) The slow axis direction, which is the direction with the largest refractive index in the plane of the measurement area of the acrylic film, is the starting point (0 degrees).
(2) A light source that generates polarized light vibrating in the 0 degree direction, in the range of 0 degrees to 170 degrees, the absorption intensity of the acrylic film at 1388 cm ^-1 (I ₁₃₈₈ ) and the absorption intensity at 1730 cm ^-1 (I ₁₇₃₀ ) is measured every 10 degrees. For example, the above-mentioned measurement can be carried out by fixing the light source and rotating the acrylic film in 10 degree increments in the plane direction. Let I ₁₃₈₈ /I ₁₇₃₀ be the orientation parameter Y of each angle.
(3) Let Y _max be the maximum value and Y _min be the minimum value among the 18 measured orientation parameters Y, and let Y _max /Y _min be the surface orientation degree ratio of the acrylic film.

The surface orientation ratio can be measured using, for example, an FT-IR measuring device (trade name: NICOLET6700, measurement spot: diameter 2 mm) manufactured by Thermo Fisher Scientific, an ATR device (trade name: Seagull) manufactured by Harrick, and a polarizer ( It can be measured by installing an FTIR-S polarized light ATR method (infrared absorption spectrum analysis in one reflection) by installing a wire grid (trade name: KRS-5, wire grid). The absorption band at 1388 cm ^-1 is C-αCH ₃ symmetric bending vibration, which quantitatively indicates a strongly oriented state in which polymethyl methacrylate molecules are stretched. On the other hand, the absorption band at 1730 cm ^-1 is a C=O stretching vibration and the absorption intensity during in-plane rotation is constant, so it is used as a reference band to normalize the absorption intensity.

In this specification, the surface orientation ratio, in-plane retardation, and thickness direction retardation are values at a wavelength of 590 nm.
In this specification, the atmosphere in which the bonding ratio, surface orientation ratio, in-plane retardation, thickness direction retardation, total light transmittance, and haze are measured is a temperature of 23°C ± 5°C and a relative humidity of 40% or more and 65%. The following shall apply. Furthermore, before each measurement, the sample shall be exposed to the atmosphere for 30 minutes or more and 60 minutes or less.

《Phase difference》
The absolute value of the in-plane retardation of the acrylic film is preferably 3 nm or less, more preferably 2 nm or less, and even more preferably 1 nm or less.
The absolute value of the retardation in the thickness direction of the acrylic film is preferably 5 nm or less, more preferably 3 nm or less, and even more preferably 2 nm or less.

The in-plane phase difference and the thickness direction phase difference can be measured with a phase difference measuring device. As a phase difference measuring device, there is a product name "KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd. The in-plane retardation is a value measured using the measuring device when the incident angle is the normal direction to the plane of the acrylic film. The retardation in the thickness direction is calculated by using the measuring device and calculating the input value of the input value of the in-plane retardation value, the value of the in-plane retardation value, and the average refractive index of the acrylic film. This value is automatically calculated from . The average refractive index of the acrylic film is approximately 1.49.

《Haze, total light transmittance》
The haze of the acrylic film according to JIS K7136:2000 is preferably 2.0% or less, more preferably 1.0% or less, more preferably 0.5% or less, and 0.3%. It is more preferable that it is below.
The total light transmittance of the acrylic film according to JIS K7361-1:1997 is preferably 85% or more, more preferably 87% or more, and still more preferably 90% or more.

<Size, shape, etc.>
The acrylic film may be in the form of a sheet cut into a predetermined size, or may be in the form of a roll formed by winding a long sheet into a roll. The size of the leaves is not particularly limited, but the maximum diameter is about 2 inches or more and 500 inches or less. The term "maximum diameter" refers to the maximum length when any two points of the acrylic film are connected. For example, if the acrylic film is rectangular, the diagonal of the rectangle has the maximum diameter. When the acrylic film is circular, the diameter of the circle is the maximum diameter.
The width and length of the roll are not particularly limited, but generally the width is about 500 mm or more and 8000 mm or less, and the length is about 100 m or more and 10000 m or less. The acrylic film in the form of a roll can be cut into sheets according to the size of the image display device or the like. When cutting, it is preferable to exclude the ends of the roll whose physical properties are unstable.
The shape of the leaf is not particularly limited, and may be, for example, a polygon such as a triangle, a quadrangle, or a pentagon, a circle, or a random amorphous shape.

[Method for manufacturing acrylic film]
The method for producing an acrylic film of the present disclosure includes the following steps 1 to 3.
Step 1: A step of obtaining a coating film from an acrylic film composition containing an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups.
Step 2: Step of irradiating the coating film with ultraviolet rays.
Step 3: Further, a step of heating the coating film at a temperature equal to or higher than the glass transition temperature of the acrylic polymer.

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

In Step 1, the composition for acrylic film may contain a solvent.
In step 1, it is preferable to form a coating film by a casting method. For example, it is preferable to form a coating film by applying an acrylic film composition onto a base material such as a plastic film and drying the solvent contained in the composition.

It is preferable that the composition for acrylic film contains a photopolymerization initiator and/or a photopolymerization accelerator. When the content of the photopolymerization initiator and/or photopolymerization accelerator is large, the absolute value of the rate of change in thermal expansion can be easily reduced, and the tensile modulus can be easily increased.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl dimethyl ketal, benzoyl benzoate, α-acyl oxime ester, anthraquinone, halogenoketone, thioxanthone, etc. It will be done.

The photopolymerization accelerator is capable of reducing polymerization inhibition caused by air and increasing the curing speed. Examples of the photopolymerization accelerator include one or more selected from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like.

<Step 2>
Step 2 is a step of irradiating the coating film with ultraviolet rays.

In Step 2, radicals are generated within the coating film, which can provide an opportunity for the acrylic monomer having two or more (meth)acryloyl groups to polymerize.
Although the amount of ultraviolet ray irradiation is not particularly limited, it is preferably 150 mJ/cm ² or more and 500 mJ/cm ² or less.

<Step 3>
Step 3 is a step of further heating the coating film at a temperature equal to or higher than the glass transition temperature of the acrylic polymer.

Step 2 alone cannot sufficiently react the acrylic monomer having two or more (meth)acryloyl groups in the acrylic film. This is because the acrylic film has a large proportion of non-flowable acrylic polymer, and the acrylic monomer cannot move freely within the acrylic film.
Step 3 increases the fluidity of the acrylic polymer, making it easier for the acrylic monomer to move within the acrylic film. Therefore, by performing Step 3, the reaction of the polymerizable acrylic monomer can be made easier to proceed.

The temperature in step 3 may be at least the glass transition temperature of the acrylic polymer, but is preferably 90°C or higher and 130°C or lower. Further, the heating time in step 3 is preferably 30 seconds or more and 300 seconds or less.

It is preferable that step 3 is performed within a predetermined time after step 2 is completed. This is because if too much time passes after step 2, the radicals generated within the coating will be deactivated. 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.
In addition, the shorter the interval between step 2 and step 3, the lower the proportion of unreacted acrylic monomer, so the unreacted acrylic monomer acts like a plasticizer, improving the tensile elasticity of the acrylic film. It is possible to suppress the rate from decreasing.
Step 3 is preferably carried out within 4 hours, more preferably within 2 hours, more preferably carried out within 30 minutes, and preferably carried out within 10 minutes after the completion of Step 2. More preferred.

When step 1 is performed by a casting method, an acrylic film can be obtained by peeling off the base material after step 3.

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

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

Examples of the layers constituting the functional layer include an easy-adhesion layer, a retardation layer, a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, and an adhesive layer. A single functional layer may have multiple functions.
Among the functional layers, the antireflection layer has a single layer structure and a multilayer structure. Examples of the single-layer antireflection layer include a single-layer low refractive index layer. Examples of the multilayer antireflection layer include two layers, a high refractive index layer and a low refractive index layer, and also a structure with three or more layers.
The functional layers such as an easy-adhesion layer, a retardation layer, a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, and an adhesive layer can have a general-purpose configuration.

Examples of the laminated structure of the optical laminate include embodiments B1 to B15 below. In B1 to B15 below, "/" means the interface between layers. Furthermore, in the laminated structures of B1 to B15 below, an embodiment in which an easily bonding layer is provided between one or more layers is also included.

B1: Acrylic film/hard coat layer B2: Acrylic film/anti-glare layer B3: Acrylic film/hard coat layer/anti-reflection layer B4: Acrylic film/anti-glare layer/anti-reflection layer B5: Acrylic film/hard coat layer/anti-reflection layer Fouling layer B6: Acrylic film/antiglare layer/antifouling layer B7: Acrylic film/retardation 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-reflection layer B12: Adhesive layer / Acrylic film / Anti-glare layer / Anti-reflection layer B13: Adhesive layer / Acrylic film / Hard coat layer / Anti-reflection layer Stain layer B14: Adhesive layer/acrylic film/antiglare layer/antifouling layer B15: Adhesive layer/acrylic film/retardation layer

Heat may be applied to the optical laminate when forming the functional layer. Additionally, optical laminates may be exposed to heat during use (eg, the internal temperature of an image display device, the temperature of an automobile dashboard). Furthermore, heat may be applied to the optical laminate when bonding it to other members such as a polarizer.
Since the optical laminate of the present disclosure uses the above-described acrylic film of the present disclosure, it is possible to suppress the quality of the optical laminate from deteriorating due to the heat described above.

[Polarizer]
The polarizing plate of the present disclosure includes a polarizer, a first transparent protective plate placed on one side of the polarizer, and a second transparent protective plate placed on the other side of the polarizer. The polarizing plate is one in which at least one of the first transparent protective plate and the second transparent protective plate includes the above-described acrylic film of the present disclosure.

<Polarizer>
Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol films dyed with iodine and stretched, polyvinyl formal films, polyvinyl acetal films, saponified ethylene-vinyl acetate copolymer films, and many sheets arranged in parallel. Examples include wire grid type polarizers made of metal wires, coated type polarizers coated with lyotropic liquid crystals or dichroic guest-host materials, and multilayer thin film type polarizers. These polarizers may be reflective polarizers having a function of reflecting polarized light components that are not transmitted.

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

It is preferable that both the first transparent protection plate and the second transparent protection plate include the acrylic film of the present disclosure described above.

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

Among the first transparent protective plate and the second transparent protective plate, a general-purpose plastic film, glass, or the like can be used as the transparent protective plate that does not include the acrylic film of the present disclosure.

It is preferable that the polarizer and the transparent protective plate are bonded together via an adhesive. A general-purpose adhesive can be used as the adhesive, and a PVA-based adhesive is preferable.

The polarizing plate of the present disclosure can easily suppress deterioration in quality such as light leakage.

[Surface plate for image display device]
The surface plate for an image display device of the present disclosure is a surface plate for an image display device in which a protective film is laminated onto a resin plate or a glass plate, and the protective film includes the acrylic film of the present disclosure described above. .

The protective film may be one in which a functional layer is formed on an acrylic film. That is, the protective film may be the optical laminate of the present disclosure described above.

As the resin plate or glass plate, a resin plate or a glass plate that is commonly used as a surface plate of an image display device can be used.

The thickness of the resin plate or glass plate is preferably 10 μm or more in order to improve the strength. The upper limit of the thickness of the resin plate or glass plate is usually 5000 μm or less. In order to reduce the thickness, the upper limit of the thickness of the resin plate or glass plate is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less.

[Image display device]
The image display device of the present disclosure includes the above-described acrylic film of the present disclosure on a display element.

The acrylic film may have a functional layer formed thereon. That is, the image display device of the present disclosure may include the above-described optical laminate of the present disclosure on a display element.

Examples of display elements include liquid crystal display elements, EL display elements such as organic EL display elements and inorganic EL display elements, plasma display elements, etc., and furthermore, LED display elements such as mini LED display elements and micro LED display elements. Can be mentioned. These display elements may have a touch panel function inside the display element.
Examples of the liquid crystal display method of the liquid crystal display element include an IPS method, a VA method, a multi-domain method, an OCB method, an STN method, and a TSTN method. If the display element is a liquid crystal display element, a backlight is required. Examples of the backlight include a backlight using quantum dots and a backlight using white light emitting diodes.
The image display device may be a foldable type image display device or a rollable type image display device. Further, the image display device may be an image display device with a touch panel.

Hereinafter, the acrylic film of the present disclosure will be specifically described with reference to Examples and Comparative Examples. The acrylic film of the present disclosure is not limited to the forms described in the Examples.

1. Evaluation and Measurement The following measurements and evaluations were performed on the acrylic films obtained in the Examples and Comparative Examples. The results are shown in Table 1 or 2.

1-1. Thermal Expansion Change Rate, Thermal Expansion Coefficient For the acrylic films of Examples and Comparative Examples, "thermal expansion change rate at 130°C" and "thermal expansion coefficient from 40°C to 130°C" were measured. As the measuring device, a product name "TMASS7100" manufactured by Hitachi High-Tech Corporation was used. The size of the sample to be incorporated into the measuring device was about 10 mm x about 10 mm. The measurement conditions and temperature program were as follows. Since the acrylic film of Comparative Example 3 is too hard, it breaks when preparing the sample, when attaching the sample, or during measurement. Therefore, in Comparative Example 3, the rate of change in thermal expansion and the coefficient of thermal expansion were not measured.
<Measurement conditions>
・Under nitrogen atmosphere ・Load 9.8mN
・Sample length 10mm
・Tension mode ・Start temperature 20℃
<Temperature program>
The temperature was changed in the following order using liquid nitrogen control. The sample length at room temperature was the sample length at the temperature in Step 1. The sample length at 40°C and the sample length at 130°C were the sample lengths at the temperature in Step 2.
Step 1: Temperature increase rate -10℃/min, target 20℃, holding time 10 minutes Step 2: Temperature increase rate 10℃/min, target 210℃, holding time 5 minutes Step 3: Temperature increase rate -10℃/min, target 20 °C, holding time 0 minutes

1-2. Tensile Modulus The tensile modulus of the acrylic films of Examples and Comparative Examples at 100° C. was measured by a tensile test in accordance with JIS K7127:1999. As the measuring device, Instron's universal material testing machine "Product number: 5565" was used. The measurement conditions were as follows. The acrylic film of Comparative Example 2 was written as "below the lower limit" because it was below the measurement limit and the tensile modulus value could not be measured.
<Measurement conditions>
・Sample size: width 10mm, length 150mm
・After placing the sample in the measuring device, start measurement 6 minutes after the temperature inside the furnace reaches 100°C.
・Test speed: 10mm/min
・Load cell: 1kN
・Distance between chucks: 100mm

1-3. Bond Ratio According to the methods (1) to (4) in the main text of the specification, the ratio of C=C bonds to C=O bonds in the acrylic films of Examples and Comparative Examples was calculated. A Raman spectrometer (product number: DXR3) manufactured by Thermo Fisher was used as a device for measuring C═O bonds and C═C bonds. The magnification of the objective lens was 100x. The acrylic films of Comparative Examples 4 to 7 did not contain an acrylic monomer having two or more (meth)acryloyl groups in the acrylic film composition, so the bond ratio was not measured.

1-4. Total light transmittance and haze The total light transmittance and haze of the acrylic films of Examples and Comparative Examples were measured using a haze meter (product number: HM-150, Murakami Color Research Institute).

1-5. Phase Difference Using a phase difference measurement device (Oji Scientific Instruments Co., Ltd., trade name: KOBRA-WR), the in-plane retardation and thickness direction retardation of the acrylic films of Examples and Comparative Examples were measured. The measurement method was as described in the main text of the specification.

1-6. Mandrel Test The acrylic films of Examples and Comparative Examples were subjected to a bending 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 where the acrylic film first cracked was taken as the value for each acrylic film. For acrylic films that did not crack even with a diameter of 2 mm, the value was set to 2 mm. It can be said that the smaller the value, the better the bending resistance.

1-7. Drying suitability at 130°C, peeling suitability, rigidity at 100°C (1) Drying suitability at 130°C In the Examples and Comparative Examples, before peeling the acrylic film from the polyethylene terephthalate film, the following acrylic film was An ink for a hard coat layer was applied to the film and dried at 130°C for 1 minute to obtain a laminate having a polyethylene terephthalate film, an acrylic film, and a hard coat layer in this order. Whether or not wrinkles were generated in the laminate was visually evaluated. The sample with no wrinkles was graded "A," and the sample with wrinkles was graded "C."

<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: Omnirad184, BASF)
・Methyl ethyl ketone 10.0 parts by mass

(2) Peelability In the above (1), the peelability of the laminate in which wrinkles did not occur was evaluated. Specifically, when the acrylic film and hard coat layer were peeled from the laminate obtained in (1) above, the acrylic film did not break, and the acrylic film did not break, and the acrylic film did. ”.

(3) Rigidity at 100°C In (2) above, the rigidity at 100°C was evaluated for the laminate from which the acrylic film and hard coat layer could be peeled off. Hereinafter, the optical laminate having a hard coat layer on an acrylic film that was peeled off in (2) will be referred to as a sample. Using the sample, the rigidity at 100°C was evaluated by the following method.
<Evaluation method>
The sample was placed in a B4 size stainless steel frame with a hollowed out interior (the stainless steel part was 2 cm from the edge) and fixed with tape to prevent sagging. The stainless steel frame on which the sample was fixed was heated in an oven at 100° C. for 1 minute. The stainless steel frame to which the sample was fixed was removed from the oven, and the rigidity of the sample was visually evaluated. As shown in FIG. 1(A), a sample with no hanging down was designated as "A", and as in FIG. 1(B), with a sample hanging down, "C" was designated.

2. Production of acrylic film [Example 1]
Composition 1 for acrylic film described below was applied onto a polyethylene terephthalate film by a casting method using an applicator to obtain a laminate having an acrylic coating on the polyethylene terephthalate film. Next, the laminate was placed in an oven at 130° C. for 3 minutes to dry the solvent. Next, ultraviolet rays were irradiated from the acrylic coating side of the laminate (240 mJ/cm ² ). Then, 5 minutes after irradiation with ultraviolet rays, the laminate was placed in an oven at 130° C. for 1 minute and taken out. Next, the acrylic film was peeled from the laminate to obtain the acrylic film of Example 1 having a thickness of 30 μm.

<Composition 1 for acrylic film>
・Acrylic polymer 6.5 parts by mass (product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.)
・3.5 parts by mass of polyfunctional acrylic monomer (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

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

[Example 3]
An acrylic film of Example 3 was obtained in the same manner as Example 1, except that the time from irradiation with ultraviolet rays to putting the laminate in an oven at 130° C. was changed to 3 hours.

[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 changed to Composition 2 for acrylic film below.

<Composition 2 for acrylic film>
・Acrylic polymer 6.5 parts by mass (product name: SUMIPEX MM, Sumitomo Chemical Co., Ltd.)
・2.5 parts by mass of polyfunctional acrylic monomer (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

[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 changed to Composition 3 for acrylic film below.

<Composition 3 for acrylic film>
・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 to 4, does not contain alkylene oxide in the molecular skeleton)
・Photopolymerization initiator 0.05 parts by mass (product name: Omnirad907, BASF)
・Methyl ethyl ketone 21.2 parts by mass

[Example 6]
An acrylic film of Example 6 was obtained in the same manner as in Example 1, except that the acrylic polymer of Composition 1 for Acrylic Film was changed to an acrylic polymer (trade name: BR-80) manufactured by Mitsubishi Chemical Corporation.

[Comparative example 1]
An acrylic film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the time from irradiation with ultraviolet rays to placing the laminate in an oven at 130° C. was changed to 5 hours.

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

[Comparative example 3]
An acrylic film of Comparative Example 3 was obtained in the same manner as in Example 1 except that Composition 1 for acrylic film was changed to Composition 4 for acrylic film below.

<Composition 4 for acrylic film>
・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

[Comparative example 4]
An acrylic film of Comparative Example 4 was obtained in the same manner as in Example 1 except that Composition 1 for acrylic film was changed to Composition 5 for acrylic film below.

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

[Comparative example 5]
An acrylic film of Comparative Example 5 was obtained in the same manner as in Example 1 except that Composition 1 for acrylic film was changed to Composition 6 for acrylic film below.

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

[Comparative example 6]
As the acrylic film in Comparative Example 6, a commercially available acrylic film (trade name: HX40-UF, Toyo Kohansha, thickness 39 μm, stretched film) was used as it was.

[Comparative Example 7]
As the acrylic film of Comparative Example 7, a commercially available acrylic film (trade name: W001KU60, Sumitomo Chemical Co., Ltd., thickness 59 μm, stretched film) was used as it was.

From the results in Tables 1 and 2, it can be confirmed that the acrylic films of Examples can maintain stable quality even in a high temperature range of 100° C. or higher.

10: Stainless steel frame 20: Fixed tape 30: Sample

Claims (12)

It is an acrylic film,
The acrylic film has an absolute value of thermal expansion change rate at 130°C of 3.0% or less, and a tensile modulus of elasticity at 100°C of 300 MPa or more and 1300 MPa or less. The acrylic film according to claim 1, wherein the acrylic film has an absolute value of a coefficient of thermal expansion from 40°C to 130°C of 250 ppm/°C or less. The acrylic film includes 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. Item 2. The acrylic film according to item 1 or 2. The acrylic film according to any one of claims 1 to 3, wherein the acrylic film has a surface orientation ratio of 1.00. The acrylic film according to any one of claims 1 to 4, wherein the acrylic film contains a cured product of an ultraviolet curable resin composition. The acrylic film according to any one of claims 1 to 5, wherein the acrylic film has a total light transmittance of 85% or more. The acrylic film according to claim 1, wherein the acrylic film has a haze of 2.0% or less. An optical laminate comprising one or more functional layers on the acrylic film according to any one of claims 1 to 7. 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, wherein at least one of the first transparent protection plate and the second transparent protection plate includes the acrylic film according to any one of claims 1 to 7. A surface plate for an image display device comprising a protective film laminated onto a resin plate or a glass plate, the protective film comprising the acrylic film according to any one of claims 1 to 7. Face plate. An image display device comprising the acrylic film according to any one of claims 1 to 7 on a display element. The method for producing an acrylic film according to any one of claims 1 to 7, comprising the following steps 1 to 3.
Step 1: A step of obtaining a coating film from an acrylic film composition containing an acrylic polymer and an acrylic monomer having two or more (meth)acryloyl groups.
Step 2: Step of irradiating the coating film with ultraviolet rays.
Step 3: Further, a step of heating the coating film at a temperature equal to or higher than the glass transition temperature of the acrylic polymer.