KR102604388B1 - Optical laminates, polarizers, and image display devices - Google Patents

Abstract

An optical laminate capable of excellent appearance is provided. The optical laminate of the present invention includes a base film containing an acrylic resin and a surface treatment layer formed on one side of the base film, and among the components constituting a position at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer The proportion of acrylic resin component eluted into the surface treatment layer is more than 18%.

Description

Optical laminates, polarizers, and image display devices

The present invention relates to optical laminates, polarizers, and image display devices.

Recently, an optical laminate is known in which a functional layer (surface treatment layer) such as a hard coat layer, an anti-glare layer, and an anti-reflection layer is formed on one side of a base film made of acrylic resin (Patent Document 1). This optical laminate can be used, for example, as a protective film for a polarizer or a front plate of an image display device.

Japanese Patent Publication No. 2016-218478

However, the conventional optical laminate as described above has a problem in that when a scratch occurs in the acrylic resin film, the scratch becomes visible by forming a surface treatment layer. This phenomenon can occur even if the scratches on the acrylic resin film are so small that they cannot be seen, and the scratches that cannot be seen can cause visible appearance defects in the obtained optical laminate.

The present invention is intended to solve the above-described conventional problems, and its main purpose is to provide an optical laminate capable of excellent appearance, a polarizing plate equipped with such an optical laminate, and an image display device equipped with such a polarizing plate. .

The optical laminate of the present invention includes a base film containing an acrylic resin and a surface treatment layer formed on one side of the base film, and is positioned at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer. Among the components, the proportion of the acrylic resin component eluted into the surface treatment layer is 18% or more.

In one embodiment, the refractive index of the base film is R1, the refractive index of the surface treatment layer is R2, and the refractive index at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer is When R3 is defined, R3≤ 0.18R1+0.82R2 (however, R1<R2) is satisfied.

In one embodiment, the thickness of the surface treatment layer is 3 μm to 20 μm.

In one embodiment, the base film includes the acrylic resin and core-shell particles dispersed in the acrylic resin.

In one embodiment, the base film contains 3 to 50 parts by weight of the core-shell particles relative to 100 parts by weight of the acrylic resin.

In one embodiment, the acrylic resin has at least one selected from the group consisting of glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units.

In one embodiment, the surface treatment layer is a cured layer of a resin applied on the base film.

In one embodiment, the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an anti-glare layer, and an anti-reflection layer.

According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate includes a polarizer and a protective layer disposed on one side of the polarizer, and the protective layer is the optical laminate.

According to another aspect of the present invention, an image display device is provided. This image display device is provided with the above polarizing plate.

According to the present invention, the acrylic resin component eluted into the surface treatment layer is 18% or more among the components constituting the position at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer, so that the optical lamination can have an excellent appearance. It is possible to provide a sieve, a polarizing plate provided with such an optical laminate, and an image display device provided with such a polarizing plate.

1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Overall composition of optical laminate

1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 includes a base film 10 and a surface treatment layer 20 formed on one side of the base film 10. In the optical laminate 100, the proportion of the acrylic resin component eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 μm in the direction from the base film 10 side to the surface treatment layer 20 is 18% or more. . The position at a depth of 3.0 μm in the direction of the surface treatment layer from the base film side is typically a position 3.0 μm away from the interface with the surface treatment layer of the base film in the direction of the surface treatment layer. The ratio of the acrylic resin component at the above “position at a depth of 3 μm” is typically derived by the following method.

Calculation position of acrylic resin component (position on the surface treatment side) = Surface treatment layer thickness (PET base hard coat thickness) - (3㎛)

For example, when (PET base hard coat thickness) is 15 ㎛, the ratio of the acrylic resin component at a position of 12 ㎛ from the surface treatment side is measured. The surface treatment layer thickness (hard coat thickness) is typically derived in the following order. First, a PET substrate (manufactured by Toray Industries, Inc., brand name: U48-3, refractive index: 1.60) is used as a base film, and the application layer is heated to a temperature of 70°C, dried and UV cured to form a hard coat. A layered optical laminate is obtained. A black acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., 2 mm thick) was adhered to the base layer side of the obtained optical laminate through an acrylic adhesive with a thickness of 20 μm. Next, the reflection spectrum of the hard coat layer is measured using an instantaneous multi-photometry system (manufactured by Otsuka Electronics Co., Ltd., brand name: MCPD3700) under the following conditions. Since the composition for forming the hard coat layer does not penetrate into the PET substrate used in these laminates, the thickness of only the hard coat layer is measured from the peak position of the FFT spectrum obtained from the laminate.

·Reflection spectrum measurement conditions

Reference: Mirror

Algorithm: FFT method

Calculated wavelength: 450nm∼850nm

·Detection conditions

Exposure time: 20ms

Ramp Gain: Normal

Accumulated number of times: 10 times

·FFT method

Range of film thickness value: 2∼15㎛

Film thickness resolution: 24nm

The above ratio is preferably 18% to 30%, and more preferably 18.5% to 25%. The proportion of the acrylic resin component eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 μm in the direction of the surface treatment layer 20 from the base film 10 side can be measured, for example, by the prism coupler method. You can. Specifically, let the refractive index of the base film be R1, the refractive index of the surface treatment layer be R2, and the refractive index at a depth of 3.0 ㎛ from the base film side in the direction of the surface treatment layer measured by the prism coupler method. Assuming that is R3, the ratio

X(%)=(R3-R2)×100/(R1-R2)

Therefore, the optical laminate 100 preferably has the following values for the refractive index R1 of the base film, the refractive index R2 of the surface treatment layer, and the refractive index R3 at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer. Satisfies the inequality of

R3≤0.18R1+0.82R2 (R1<R2)

The thickness of the surface treatment layer is preferably 3 ㎛ to 20 ㎛, more preferably 5 ㎛ to 15 ㎛. In one embodiment, the base film 10 includes an acrylic resin and core-shell particles dispersed in the acrylic resin. In this case, the base film 10 preferably contains 3 to 50 parts by weight of core-shell particles based on 100 parts by weight of the acrylic resin. The acrylic resin preferably has at least one selected from the group consisting of glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. The surface treatment layer 20 is typically a cured layer of a resin composition applied on the base film 10. The surface treatment layer 20 is preferably at least one selected from the group consisting of a hard coat layer, an anti-glare layer, and an anti-reflection layer. In conventional optical laminates, when a long base film is wound on a roll, scratches along the long direction are sometimes made visible by forming a surface treatment layer on the base film. In contrast, according to the optical laminate 100 of the present invention, the amount of acrylic resin contained in the base film 10 eluted into the surface treatment layer 20 is sufficiently large. As a result, it is possible to suppress the appearance of scratches on the base film 10 caused by forming the surface treatment layer 20 on the base film 10. Additionally, the adhesion between the base film 10 and the surface treatment layer 20 can be improved.

B. Base film

B-1. Characteristics of the base film

The base film contains an acrylic resin as described above. In one embodiment, the base film includes an acrylic resin and core-shell particles dispersed in the acrylic resin. The thickness of the base film is preferably 5 μm to 150 μm, and more preferably 10 μm to 100 μm. When the base film forms a surface treatment layer, which will be described later, the acrylic resin is eluted into the surface treatment layer. As the acrylic resin is eluted into the surface treatment layer, the proportion of the acrylic resin component among the components constituting the position at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer becomes 18% or more.

The base film is preferably substantially optically isotropic. In this specification, “substantially optically isotropic” means that the in-plane phase difference Re (550) is 0 nm to 10 nm and the thickness direction phase difference Rth (550) is -10 nm to +10 nm. The in-plane retardation Re(550) is more preferably 0 nm to 5 nm, further preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The phase difference Rth (550) in the thickness direction is more preferably -5 nm to +5 nm, further preferably -3 nm to +3 nm, and particularly preferably -2 nm to +2 nm. If the Re(550) and Rth(550) of the base film are within this range, adverse effects on display characteristics can be prevented when the optical laminate is applied to an image display device. In addition, Re(550) is the in-plane phase difference of the film measured with light with a wavelength of 550 nm at 23°C. Re(550) is obtained by the equation: Re(550)=(nx-ny)×d. Rth (550) is the phase difference in the thickness direction of the film measured with light with a wavelength of 550 nm at 23°C. Rth(550) is obtained by the equation: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), ny is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., fast axis direction), and nz is the refractive index in the thickness direction. is the refractive index, and d is the thickness of the film (nm).

The higher the light transmittance at 380 nm at a thickness of 40 μm of the base film, the more preferable it is. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. If the light transmittance is within this range, desired transparency can be secured. Light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the base film, the more preferable it is. Specifically, the haze is preferably 5% or less, more preferably 3% or less, further preferably 1.5% or less, and particularly preferably 1% or less. If the haze is 5% or less, good clearance can be provided to the film. Additionally, even when the optical laminate is used as a protective layer for the polarizing plate on the viewing side of an image display device, display content can be viewed satisfactorily.

YI at a thickness of 40 μm of the base film is preferably 1.27 or less, more preferably 1.25 or less, further preferably 1.23 or less, and particularly preferably 1.20 or less. When YI exceeds 1.3, optical transparency may become insufficient. In addition, YI can be obtained from the color tristimulus values (X, Y, Z) obtained from measurement using, for example, a high-speed integrating sphere type spectral transmittance meter (product name DOT-3C: manufactured by Murakami Color Research Laboratory) using the following equation. .

YI=[(1.28X-1.06Z)/Y]×100

The b value (a scale of color based on Hunter's colorimetric system) at a thickness of 40 μm of the base film is preferably less than 1.5, more preferably 1.0 or less. When the b value is 1.5 or more, undesirable coloring may appear. In addition, the b value is determined by, for example, cutting a base film sample into 3cm It is obtained by evaluating according to the colorimetric system of .

The moisture permeability of the base film is preferably 300g/m2·24hr or less, more preferably 250g/m2·24hr or less, further preferably 200g/m2·24hr or less, particularly preferably 150g/m2·24hr or less, most preferably It is less than 100g/㎡·24hr. If the moisture permeability of the base film is within this range, when used as a protective layer of a polarizer, a polarizing plate excellent in durability and moisture resistance can be obtained.

The tensile strength of the base film is preferably 10 MPa or more and less than 100 MPa, and more preferably 30 MPa or more and less than 100 MPa. In the case of less than 10 MPa, sufficient mechanical strength may not be achieved. If it exceeds 100 MPa, there is a risk that processability may become insufficient. Tensile strength can be measured, for example, according to ASTM-D-882-61T.

The tensile elongation of the base film is preferably 1.0% or more, more preferably 3.0% or more, and even more preferably 5.0% or more. The upper limit of tensile elongation is, for example, 100%. When the tensile elongation is less than 1%, toughness may become insufficient. Tensile elongation can be measured, for example, according to ASTM-D-882-61T.

The tensile modulus of elasticity of the base film is preferably 0.5 GPa or more, more preferably 1 GPa or more, and even more preferably 2 GPa or more. The upper limit of the tensile modulus is, for example, 20 GPa. If the tensile modulus is less than 0.5 GPa, sufficient mechanical strength may not be achieved. Tensile modulus can be measured, for example, according to ASTM-D-882-61T.

The base film may contain any appropriate additives depending on the purpose. Specific examples of additives include ultraviolet absorbers; Antioxidants such as hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; Stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; Reinforcing materials such as glass fiber and carbon fiber; Near-infrared absorber; Flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; Antistatic agents such as anionic, cationic, and nonionic surfactants; Colorants such as inorganic pigments, organic pigments, and dyes; Organic or inorganic filler; Resin modifier; Organic or inorganic fillers; plasticizer; slush; etc. can be mentioned. The additive may be added during polymerization of the acrylic resin, or may be added during film formation. The type, number, combination, addition amount, etc. of additives can be appropriately set depending on the purpose.

B-2. Acrylic resin

B-2-1. Composition of acrylic resin

As the acrylic resin, any suitable acrylic resin may be employed. Acrylic resins typically contain alkyl (meth)acrylate as a main component as a monomer unit. In this specification, “(meth)acrylic” means acrylic and/or methacryl. Examples of the alkyl (meth)acrylate constituting the main skeleton of the acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Additionally, any appropriate copolymerization monomer may be introduced into the acrylic resin by copolymerization. The type, number, copolymerization ratio, etc. of these copolymerized monomers can be appropriately set depending on the purpose. The components (monomer units) of the main skeleton of the acrylic resin will be described later with reference to General Formula (2).

The acrylic resin preferably has at least one selected from glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. Acrylic resins having lactone ring units are described, for example, in Japanese Patent Application Laid-Open No. 2008-181078, the description of which is incorporated herein by reference. The glutarimide unit is preferably represented by the general formula (1):

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group with 1 to 8 carbon atoms, and R ³ is a hydrogen atom, an alkyl group with 1 to 18 carbon atoms, a cycloalkyl group with 3 to 12 carbon atoms, Or it represents an aryl group having 6 to 10 carbon atoms. In general formula (1), preferably R ¹ and R ² are each independently a hydrogen atom or a methyl group, and R ³ is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is a hydrogen atom, and R ³ is a methyl group.

The alkyl (meth)acrylate is typically represented by the following general formula (2):

In general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Examples of the substituent include halogen and hydroxyl group. Specific examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, and n-(meth)acrylate. -hexyl, cyclohexyl (meth)acrylic acid, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylic acid, 2-hydroxyethyl (meth)acrylic acid, 3-hydroxypropyl (meth)acrylic acid, (meth)acrylic acid Examples include 2,3,4,5,6-pentahydroxyhexyl and 2,3,4,5-tetrahydroxypentyl (meth)acrylic acid. In general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Accordingly, particularly preferred alkyl (meth)acrylates are methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units with different R ¹ , R ² and R ³ in the general formula (1).

The content ratio of the glutarimide unit in the acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, further preferably 2 mol% to 40 mol%, especially Preferably it is 2 mol% to 35 mol%, most preferably 3 mol% to 30 mol%. If the content ratio is less than 2 mol%, there is a risk that the effects derived from the glutarimide unit (e.g., high optical properties, high mechanical strength, excellent adhesion to the polarizer, thinning) may not be sufficiently exhibited. If the content ratio exceeds 50 mol%, there is a risk that heat resistance and transparency may become insufficient, for example.

The acrylic resin may contain only a single alkyl (meth)acrylate unit, or may contain a plurality of alkyl (meth)acrylate units in which R ⁴ and R ⁵ in the general formula (2) are different.

The content ratio of the alkyl (meth)acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, and even more preferably 60 mol% to 98 mol%. %, particularly preferably 65 mol% to 98 mol%, and most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, there is a risk that the effects derived from the alkyl (meth)acrylate unit (e.g., high heat resistance, high transparency) may not be sufficiently exhibited. If the content is more than 98 mol%, the resin becomes soft and prone to breakage, so high mechanical strength cannot be sufficiently exhibited, and there is a risk that productivity may deteriorate.

The acrylic resin may contain units other than glutarimide units and alkyl (meth)acrylate units.

In one embodiment, the acrylic resin may contain, for example, 0 to 10% by weight of unsaturated carboxylic acid units that do not participate in the intramolecular imidation reaction described later. The content ratio of the unsaturated carboxylic acid unit is preferably 0 to 5% by weight, and more preferably 0 to 1% by weight. If the content is within this range, transparency, retention stability, and moisture resistance can be maintained.

In one embodiment, the acrylic resin may contain copolymerizable vinyl monomer units (other vinyl monomer units) other than the above. Other vinyl monomers include, for example, acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N -Cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, Allylamine, methallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate , styrene, α-methylstyrene, p-glycidyl styrene, p-aminostyrene, 2-styryl-oxazoline, etc. These may be used alone or in combination. Preferably, it is a styrene-based monomer such as styrene and α-methylstyrene. The content ratio of other vinyl monomer units is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. Within this range, it is possible to suppress the occurrence of undesired phase difference and the decrease in transparency.

The imidization rate of the acrylic resin is preferably 2.5% to 20.0%. If the imidization rate is within this range, a resin excellent in heat resistance, transparency, and molding processability can be obtained, and occurrence of burning during film molding and a decrease in mechanical strength can be prevented. In the above acrylic resin, the imidization rate is expressed as the ratio of glutarimide units and alkyl (meth)acrylate units. This ratio can be obtained, for example, from the NMR spectrum, IR spectrum, etc. of the acrylic resin. In this embodiment, the imidization rate can be determined by ¹ H-NMR measurement of the resin using ¹ H-NMR BRUKER Avance III (400 MHz). More specifically, let the peak area derived from the O-CH ₃ proton of alkyl (meth)acrylate around 3.5 to 3.8 ppm be A, and the peak area derived from the N-CH ₃ proton of glutarimide around 3.0 to 3.3 ppm. Let the area be B, and it is obtained by the following equation.

Imidation rate Im(%)={B/(A+B)}×100

The acid value of the acrylic resin is preferably 0.10 mmol/g to 0.50 mmol/g. If the acid value is within this range, a resin with an excellent balance of heat resistance, mechanical properties, and molding processability can be obtained. If the acid value is too small, problems such as increased costs due to the use of a denaturant to adjust the acid value to the desired level and generation of a gelled product due to the remaining denaturant may occur. If the acid value is too large, foaming occurs easily during film molding (for example, during melt extrusion), and the productivity of the molded product tends to decrease. In the acrylic resin, the acid value is the content of carboxylic acid units and carboxylic acid anhydride units in the acrylic resin. In this embodiment, the acid value can be calculated by the titrimetric method described in, for example, WO2005/054311 or Japanese Patent Application Laid-Open No. 2005-23272.

The weight average molecular weight of the acrylic resin is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, further preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 to 150,000. The weight average molecular weight can be determined by polystyrene conversion, for example, using a gel permeation chromatograph (GPC system, Tosoh Corporation). Additionally, tetrahydrofuran can be used as a solvent.

The acrylic resin has a Tg (glass transition temperature) of preferably 110°C or higher, more preferably 115°C or higher, further preferably 120°C or higher, particularly preferably 125°C or higher, and most preferably 130°C or higher. . When Tg is 110°C or higher, a polarizing plate containing a base film obtained from such a resin is likely to have excellent durability. The upper limit of Tg is preferably 300°C or lower, more preferably 290°C or lower, further preferably 285°C or lower, particularly preferably 200°C or lower, and most preferably 160°C or lower. If Tg is in this range, moldability can be excellent.

B-2-2. Polymerization of acrylic resin

The acrylic resin can be produced, for example, by the following method. This method (I) copolymerizes an alkyl (meth)acrylate monomer corresponding to the alkyl (meth)acrylate unit represented by general formula (2) and an unsaturated carboxylic acid monomer and/or its precursor monomer to form a copolymer. Obtaining (a); and (II) intramolecular imidization of the alkyl (meth)acrylate monomer unit and the unsaturated carboxylic acid monomer and/or its precursor monomer unit in the copolymer (a) by treating the copolymer (a) with an imidizing agent. This includes performing a dehydration reaction to introduce a glutarimide unit represented by general formula (1) into the copolymer.

Examples of unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. Examples of the precursor monomer include acrylamide, methacrylamide, and the like. These may be used alone or in combination. The preferred unsaturated carboxylic acid monomer is acrylic acid or methacrylic acid, and the preferred precursor monomer is acrylamide.

As a method for treating copolymer (a) with an imidizing agent, any suitable method can be used. Specific examples include a method using an extruder and a method using a batch reaction tank (pressure vessel). The method of using an extruder includes heating and melting the copolymer (a) using an extruder and treating it with an imidizing agent. In this case, any suitable extruder can be used as the extruder. Specific examples include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder. In the method of using a batch reaction tank (pressure vessel), any suitable batch reaction tank (pressure vessel) can be used.

As the imidizing agent, any suitable compound can be used as long as it can produce the glutarimide unit represented by the above general formula (1). Specific examples of imidizing agents include amines containing aliphatic hydrocarbon groups such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine, and aniline. , amines containing aromatic hydrocarbon groups such as benzylamine, toluidine, and trichloroaniline, and amines containing alicyclic hydrocarbon groups such as cyclohexylamine. Additionally, for example, a urea-based compound that generates such an amine by heating can also be used. Examples of urea compounds include urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea. The imidizing agent is preferably methylamine, ammonia, and cyclohexylamine, and more preferably methylamine.

In imidization, in addition to the imidization agent, a ring-closure accelerator may be added as needed.

The amount of the imidizing agent used in imidization is preferably 0.5 parts by weight to 10 parts by weight, more preferably 0.5 parts by weight to 6 parts by weight, based on 100 parts by weight of copolymer (a). If the amount of imidizing agent used is less than 0.5 parts by weight, the desired imidization rate is often not achieved. As a result, the heat resistance of the resulting resin becomes very insufficient, and appearance defects such as burning after molding may occur. If the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent remains in the resin, and the imidizing agent may cause appearance defects such as burning after molding or foaming.

The production method of the present embodiment may, if necessary, include treatment with an esterification agent in addition to the above imidization.

Examples of the esterifying agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, Methyl trifluoromethane sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethyl carbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethyl ammonium hydroxide , dimethyl diethoxysilane, tetra-N-butoxysilane, dimethyl (trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2- Examples include ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among these, dimethyl carbonate is preferable from viewpoints of cost, reactivity, etc.

The amount of the esterifying agent added can be set so that the acid value of the acrylic resin becomes a desired value.

B-2-3. Combination use of other resins

In embodiments of the present invention, the acrylic resin and other resins may be used together. That is, the monomer component constituting the acrylic resin may be copolymerized with the monomer component constituting another resin, and the copolymer may be used for film formation described later in paragraph B-4; A blend of acrylic resin and other resins may be used for film formation. Other resins include, for example, styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, etc. Thermosetting resins such as other thermoplastic resins, phenol-based resins, melamine-based resins, polyester-based resins, silicone-based resins, and epoxy-based resins can be mentioned. The type and mixing amount of the resin used together can be appropriately set depending on the purpose, properties desired for the obtained film, etc. For example, a styrene-based resin (preferably an acrylonitrile-styrene copolymer) can be used together as a phase difference control agent.

When using an acrylic resin and another resin together, the content of the acrylic resin in the blend of the acrylic resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, even more preferably. Typically, it is 70% by weight to 100% by weight, particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, there is a risk that the high heat resistance and high transparency inherent in acrylic resin may not be sufficiently reflected.

B-3. core-shell particles

In the above base film, the core-shell type particles are preferably 3 parts by weight to 50 parts by weight, more preferably 5 parts by weight to 25 parts by weight, and even more preferably 7 parts by weight to 15 parts by weight, based on 100 parts by weight of the acrylic resin. It is combined. As a result, the elution of the acrylic resin forming the base film into the surface treatment layer is promoted, and as a result, a highly uniform compatible layer of the acrylic resin and the composition forming the surface treatment layer can be formed on the base film. As a result, it is possible to suppress the appearance of scratches on the base film due to forming a surface treatment layer on the base film. Additionally, the adhesion between the base film and the surface treatment layer can be improved.

Core-shell particles typically have a core made of a rubber-like polymer and a coating layer made of a glass-like polymer that covers the core. The core-shell type particles may have one or more layers composed of a glassy polymer as the innermost layer or middle layer.

The Tg of the rubbery polymer constituting the core is preferably 20°C or lower, more preferably -60°C to 20°C, and still more preferably -60°C to 10°C. If the Tg of the rubbery polymer constituting the core exceeds 20°C, there is a risk that the mechanical strength of the acrylic resin may not be sufficiently improved. The Tg of the glassy polymer (hard polymer) constituting the coating layer is preferably 50°C or higher, more preferably 50°C to 140°C, and even more preferably 60°C to 130°C. If the Tg of the glassy polymer constituting the coating layer is lower than 50°C, there is a risk that the heat resistance of the acrylic resin may decrease.

The content ratio of the core in the core-shell type particles is preferably 30% by weight to 95% by weight, more preferably 50% by weight to 90% by weight. The proportion of the glassy polymer layer in the core is 0 to 60% by weight, preferably 0 to 45% by weight, more preferably 10 to 40% by weight, based on 100% by weight of the total weight of the core. The content ratio of the coating layer in the core-shell type particles is preferably 5% by weight to 70% by weight, more preferably 10% by weight to 50% by weight.

In one embodiment, the core-shell particles dispersed in the acrylic resin may have a flat shape. Core-shell particles can be flattened by stretching as described later in Section B-4. The length/thickness ratio of the flattened core-shell particles is 7.0 or less. The length/thickness ratio is preferably 6.5 or less, and more preferably 6.3 or less. On the other hand, the length/thickness ratio is preferably 4.0 or more, more preferably 4.5 or more, and still more preferably 5.0 or more. In this specification, “length/thickness ratio” means the ratio of the representative length and thickness of the shape of a core-shell particle when viewed from a plane. Here, the “representative length” refers to the diameter when the shape when viewed in plan is circular, the major axis when it is oval, and the diagonal length when it is rectangular or polygonal. The above ratio can be obtained, for example, using the following procedure. The cross-section of the obtained film was photographed with a transmission electron microscope (e.g., acceleration voltage 80 kV, RuO ₄ staining ultra-thin sectioning), and among the core-shell particles present in the obtained photograph, the longest ones (those from which a cross-section close to the representative length was obtained) were selected. The above ratio can be obtained by sequentially extracting 30 pieces and calculating (average value of length)/(average value of thickness).

Details of the rubber-like polymer constituting the core of the core-shell particle, the glass-like polymer (hard polymer) constituting the coating layer, their polymerization method, and other structural details are described, for example, in Japanese Patent Application Laid-Open No. 2016-33552. . The description of this publication is incorporated herein by reference.

B-4. Formation of Base Film

The base film according to an embodiment of the present invention is typically formed by a method comprising forming a film of a composition containing the acrylic resin (or blend with the other resin when using other resins) and core-shell particles. It can be. Additionally, the method of forming the base film may include stretching the film.

The average particle diameter of the core-shell type particles used for film formation is preferably 1 nm to 500 nm. The average particle diameter of the core is preferably 50 nm to 300 nm, and more preferably 70 nm to 300 nm.

As a method for forming the film, any suitable method can be adopted. Specific examples include cast coating method (e.g., casting method), extrusion molding method, injection molding method, compression molding method, transfer molding method, blow molding method, powder molding method, FRP molding method, calendar molding method, and heat pressing method. Preferably, extrusion molding or cast coating method. This is because the smoothness of the resulting film can be increased and good optical uniformity can be obtained. Particularly preferred is extrusion molding. This is because there is no need to consider problems caused by residual solvent. Among them, the extrusion molding method using a T die is preferable from the viewpoint of film productivity and ease of subsequent stretching treatment. Molding conditions can be appropriately set depending on the composition and type of the resin used, the properties desired for the obtained film, etc.

As the stretching method, any suitable stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, stretching speed, stretching direction) can be employed. Specific examples of stretching methods include free end stretching, fixed end stretching, free end shrinkage, and fixed end shrinkage. These may be used individually, simultaneously, or sequentially. By stretching a film in which the blending amount of core-shell particles relative to acrylic resin is appropriately adjusted under appropriate stretching conditions, dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, acrylic resin and a surface treatment layer are formed on the base film. A highly uniform commercial layer of the composition can be formed.

An appropriate stretching direction may be adopted depending on the purpose. Specifically, the longitudinal direction, width direction, thickness direction, and oblique direction can be mentioned. The stretching direction may be one direction (uniaxial stretching), two directions (biaxial stretching), or three or more directions. In embodiments of the present invention, uniaxial stretching in the longitudinal direction, simultaneous biaxial stretching in the longitudinal and transverse directions, and sequential biaxial stretching in the longitudinal and transverse directions can be typically employed. Preferably, it is biaxial stretching (simultaneous or sequentially). This is because the in-plane phase difference is easy to control and optical isotropy is easy to realize.

Stretching temperature can vary depending on the optical properties, mechanical properties and thickness desired for the base film, type of resin used, thickness of the film used, stretching method (uniaxial stretching or biaxial stretching), stretching ratio, stretching speed, etc. there is. Specifically, the stretching temperature is preferably Tg to Tg+50°C, more preferably Tg+15°C to Tg+50°C, and most preferably Tg+35°C to Tg+50°C. By stretching at this temperature, a base film with appropriate properties can be obtained. The specific stretching temperature is, for example, 110°C to 200°C, and is preferably 120°C to 190°C. If the stretching temperature is within this range, by appropriately adjusting the stretching ratio and stretching speed, the dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, the uniformity of the composition constituting the acrylic resin and the surface treatment layer on the base film is increased. A high commercial layer can be formed.

Like the stretching temperature, the stretching ratio can also vary depending on optical properties, mechanical properties and thickness, type of resin used, thickness of the film used, stretching method (uniaxial stretching or biaxial stretching), stretching temperature, stretching speed, etc. You can. When biaxial stretching is adopted, the ratio (TD/MD) of the stretch ratio in the transverse direction (TD) and the stretch ratio in the longitudinal direction (MD) is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, More preferably, it is 1.0 to 1.3. In addition, when biaxial stretching is adopted, the surface magnification (the product of the longitudinal stretch magnification and the transverse direction stretch ratio) is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, and still more preferably 3.5. It is ~5.2. If the stretching ratio is within this range, by appropriately adjusting the stretching temperature and stretching speed, the dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, the uniformity of the composition constituting the acrylic resin and the surface treatment layer on the base film is increased. A high commercial layer can be formed.

Stretching speed, like stretching temperature, can also vary depending on optical properties, mechanical properties and thickness, type of resin used, thickness of film used, stretching method (uniaxial stretching or biaxial stretching), stretching temperature, stretching ratio, etc. You can. The stretching speed is preferably 3%/sec to 20%/sec, more preferably 3%/sec to 15%/sec, and even more preferably 3%/sec to 10%/sec. When biaxial stretching is adopted, the stretching speed in one direction and the stretching speed in the other direction may be the same or different. If the stretching speed is within this range, by appropriately adjusting the stretching temperature and stretching ratio, the dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, the uniformity of the composition constituting the acrylic resin and the surface treatment layer on the base film is increased. A high commercial layer can be formed.

A base film can be formed as described above.

C. Surface treatment layer

The surface treatment layer is any appropriate functional layer formed on one side of the base film depending on the function required for the optical laminate. Specific examples of the surface treatment layer include a hard coat layer, an anti-glare layer, and an anti-reflection layer. The thickness of the surface treatment layer is preferably 3 ㎛ to 20 ㎛, more preferably 5 ㎛ to 15 ㎛.

The surface treatment layer is typically a cured layer of a resin composition formed on a base film. The process of forming a surface treatment layer may include forming an application layer by applying a resin composition for forming a surface treatment layer on a base film, and drying and curing the application layer to form a surface treatment layer. Drying and curing the application layer may include heating the application layer.

As a method of applying the resin composition, any suitable method can be adopted. Examples include bar coating method, roll coating method, gravure coating method, rod coating method, slot orifice coating method, curtain coating method, fountain coating method, and comma coating method. From the viewpoint of facilitating application, it is preferable that the resin composition contains a solvent for dilution.

The heating temperature of the application layer can be set to any appropriate temperature depending on the composition of the resin composition, and is preferably set to the glass transition temperature or lower of the acrylic resin included in the base film. When heated at a temperature below the glass transition temperature of the acrylic resin included in the base film, an optical laminate with suppressed deformation due to heating can be obtained. The heating temperature of the application layer is, for example, 50°C to 140°C, and is preferably 60°C to 100°C. By heating at this heating temperature, an optical laminate with excellent adhesion between the base film and the surface treatment layer can be obtained.

C-1. hard coat layer

The hard coat layer is a layer that provides scratch resistance and chemical resistance to the surface of the base film. The hard coat layer preferably has a hardness of H or higher, more preferably 3H or higher, in a pencil hardness test. Pencil hardness test can be measured according to JIS K 5400. The resin composition for forming a hard coat layer may contain a curable compound that can be cured by, for example, heat, light (ultraviolet rays, etc.), or electron beam. Details of the hard coat layer and the resin composition for forming the hard coat layer are described in, for example, Japanese Patent Application Laid-Open No. 2014-240955. The entire disclosure of the above publication is incorporated herein by reference.

C-2. anti-glare layer

The anti-glare layer is a layer to prevent glare from external light by scattering and reflecting light. The resin composition for forming an anti-glare layer may contain a curable compound that can be cured by, for example, heat, light (ultraviolet rays, etc.), or electron beam. The anti-glare layer typically has a fine uneven shape on its surface. As a method of forming such a fine concavo-convex shape, for example, a method of making the curable compound contain fine particles is included. Details of the anti-glare layer and the resin composition for forming the anti-glare layer are described, for example, in Japanese Patent Application Laid-Open No. 2017-32711. The entire disclosure of the above publication is incorporated herein by reference.

C-3. Anti-reflection layer

The anti-reflection layer is a layer to prevent reflection of external light. The resin composition for forming an antireflection layer may include a curable compound that can be cured by, for example, heat, light (ultraviolet rays, etc.), or electron beams. The anti-reflection layer may be a single layer consisting of only one layer, or may be a multiple layer consisting of two or more layers. Details of the anti-reflection layer and the resin composition for forming the anti-reflection layer are described, for example, in Japanese Patent Application Laid-Open No. 2012-155050. The entire disclosure of the above publication is incorporated herein by reference.

D. Polarizer

The optical laminate described in paragraphs A to C above can be applied to a polarizing plate. Accordingly, the present invention also includes a polarizing plate using such an optical laminate. Typically, a polarizing plate has a polarizer and the optical laminated body of the present invention disposed on one side of the polarizer. The optical laminate can function as a protective layer for the polarizer by bonding the base film side to the polarizer.

As the polarizer, any suitable polarizer may be employed. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films, and dichromats such as iodine or dichroic dyes. Examples include polyene-based oriented films, such as those that have been dyed and stretched with chemical substances, and those that have been treated with dehydrated PVA or dechlorinated acid-treated polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because it has excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Additionally, it may be dyed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can contamination and anti-blocking agents on the surface of the PVA-based film be removed, but also the PVA-based film can be swelled to prevent dyeing stains.

Specific examples of the polarizer obtained using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer applied to the resin substrate. A polarizer obtained using . A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by applying to the resin substrate is, for example, applying a PVA-based resin solution to a resin substrate and drying it to form a PVA-based resin layer on the resin substrate. , obtaining a laminate of a resin substrate and a PVA-based resin layer; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as a polarizer. In this embodiment, stretching typically includes stretching the laminate by immersing it in an aqueous boric acid solution. Additionally, stretching may, if necessary, further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in an aqueous boric acid solution. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), and the resin substrate may be peeled from the resin substrate/polarizer laminate, and the peeled surface may be optionally used according to the purpose. You may use it by laminating an appropriate protective layer. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire disclosure of the above publication is incorporated herein by reference.

The thickness of the polarizer is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizer is preferably 2 μm to 30 μm, and more preferably 3 μm to 25 μm.

E．Image display device

The polarizing plate described in paragraph D above can be applied to an image display device. Accordingly, the present invention also includes an image display device using such a polarizing plate. Representative examples of image display devices include liquid crystal display devices and organic electroluminescence (EL) display devices. Since the image display device adopts a configuration well known in the industry, detailed description is omitted.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement method for each characteristic is as follows. In addition, unless otherwise specified, “part” and “%” in the examples are based on weight.

(1) Proportion of acrylic resin component eluted into the surface treatment layer

The ratio of the acrylic resin component eluted into the surface treatment layer was measured by using a three-dimensional optical refractive index/film thickness measuring device prism coupler (Metricon 2010/M, manufactured by Metricon Corporation). The measurement of refractive index using a prism coupler was performed under the following conditions.

·Measuring conditions

Light source: 594nm

Mode: TE

Scan: 300∼-300

(1-1) Refractive index R1 of the base film

Measurement type: Bulk/Substrate

The mode (referred to as Knee) was detected by measurement of the base film. The refractive index obtained by measurement was referred to as R1.

(1-2) Refractive index R2 of surface treatment layer

Measurement type: Single Film(Prism Couple)

A PET substrate (manufactured by Toray Industries, Inc., brand name: U48-3, refractive index: 1.60) was used as the base film, and the heating temperature of the coating layer was set to 60°C, in the same manner as in each example. A laminate of the same thickness was obtained. By measuring this laminate in Single Film mode, multiple modes were detected. The refractive index obtained by measurement was referred to as R2.

(1-3) Refractive index R3 at a depth of 3.0 μm in the direction of the surface treatment layer from the base film side

Measurement type: Single Film(Prism Couple)

Interpretation method: Index gradient

In the case where the refractive index changes in the depth direction in the optical laminate, the change in refractive index in the depth direction can be quantitatively determined by the method using the above prism coupler.

Multiple modes were detected by measuring the optical laminate, and the change in refractive index in the depth direction was calculated through index gradient analysis. The “position at a depth of 3.0 μm” from the base film side toward the surface treatment layer was determined based on the following equation, and the obtained refractive index was set to R3.

“Position at a depth of 3.0 ㎛” (position from the surface treatment side) = Surface treatment layer thickness (PET base hard coat thickness) - (3 ㎛)

(1-4) Ratio of the acrylic resin component eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 ㎛ in the direction of the surface treatment layer from the base film side

From the following equation, the ratio

X(%)=(R3-R2)×100/(R1-R2)

(2) Appearance evaluation

With respect to the optical laminates obtained in the examples and comparative examples, the presence or absence of appearance defects (appearance defects resulting from scratches formed on the base film) was confirmed visually, and judgment was made using the following indicators.

○: Marks of wounds are visible

×: No marks of wound are visible

(3) Adhesion evaluation

The adhesion of the surface treatment layer to the base film was evaluated according to the checkerboard peeling test of JIS K-5400 (number of checkerboard marks: 100), and judged by the following indices.

○: The number of checkerboard peelings is 0.

×: Number of checkerboard scale peels is 1 or more

<Example 1>

1. Production of base film

MS resin (MS-200; copolymer of methyl methacrylate/styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine (imidation rate: 5%). . The obtained imidized MS resin is a glutarimide unit represented by the general formula (1) (R ¹ and R ³ are methyl groups and R ² is a hydrogen atom), a (meth)acrylic acid ester unit represented by the general formula (2) ( R ⁴ and R ⁵ are methyl groups), and a styrene unit. In addition, for the imidization, an intermeshing type co-rotating twin-screw extruder with a diameter of 15 mm was used. The set temperature of each temperature control zone of the extruder was 230°C and the screw rotation speed was 150 rpm, MS resin was supplied at 2.0 kg/hr, and the supply amount of monomethylamine was 2 parts by weight for 100 parts by weight of MS resin. MS resin was injected from the hopper, the resin was melted and filled with a kneading block, and then monomethylamine was injected from the nozzle. A sealing ring was placed at the end of the reaction zone to fill it with resin. The by-products and excess methylamine after the reaction were devolatilized by reducing the pressure of the vent port to -0.08 MPa. The resin that came out as a strand from the die installed at the extruder outlet was cooled in a water bath and then pelletized with a pelletizer. The imidization rate of the obtained imidized MS resin was 5.0% and the acid value was 0.5 mmol/g.

100 parts by weight of the imidized MS resin and 5 parts by weight of the core-shell type particles obtained above were put into a single screw extruder, melted and mixed, and formed into a film through a T die to obtain an extruded film. The obtained extruded film was simultaneously biaxially stretched twice in the longitudinal direction and the width direction at a stretching temperature of 140°C. The stretching speed was 10%/sec in both the longitudinal and width directions.

In this way, base film A with a thickness of 30 μm was produced.

2. Fabrication of optical laminate

On one side of the base film A, 16 parts by weight of UV curable resin (4-HBA (manufactured by Osaka Organic Chemical Industry Ltd.), NK Oligo UA-53H-80BK (Shin-Nakamura Chemical Co., Ltd.) was added so that the thickness after curing was 6 μm. , Ltd.) 32 parts by weight, Viscoat #300 (manufactured by Osaka Organic Chemical Industry Ltd.) 48 parts by weight, A-GLY-9E (manufactured by Shin-Nakamura Chemical Co., Ltd.) 4 parts by weight, IRGACURE 907 (BASF) 2.4 parts by weight were mixed and each diluted to a solid content concentration of 42.0% in a solvent of MIBK:PGM=50:50 was applied to form an application layer. Next, the application layer was dried at 70°C and UV cured to obtain an optical laminate 1 in which a hard coat layer was formed on one side of the base film A. The optical laminate 1 was used for each evaluation. The results are shown in Table 1.

<Example 2>

1. Production of base film

Base film B was produced in the same manner as in Example 1, except that the blending amount of core-shell particles was 10 parts by weight and the stretching temperature of the extruded film was 150°C.

2. Fabrication of optical laminate

An optical laminate 2 in which a hard coat layer was formed on one side of the base film B was obtained in the same manner as in Example 1 except that the base film B was used. The optical laminate 2 was used for each evaluation. The results are shown in Table 1.

<Example 3>

1. Production of base film

Base film C was produced in the same manner as in Example 1, except that the blending amount of the core-shell type particles was 10 parts by weight and the stretching temperature of the extruded film was 160°C.

2. Fabrication of optical laminate

An optical laminate 3 in which a hard coat layer was formed on one side of the base film C was obtained in the same manner as in Example 1 except that the base film C was used. The optical laminate 3 was used for each evaluation. The results are shown in Table 1.

<Example 4>

1. Production of base film

Base film D was produced in the same manner as in Example 1, except that the blending amount of core-shell particles was 13 parts by weight and the stretching temperature of the extruded film was 152°C.

2. Fabrication of optical laminate

An optical laminate 4 in which a hard coat layer was formed on one side of the base film D was obtained in the same manner as in Example 1 except that the base film D was used. The optical laminate 4 was used for each evaluation. The results are shown in Table 1.

<Example 5>

1. Production of base film

100 parts by weight of the imidized MS resin and 15 parts by weight of the core-shell type particles obtained above were put into a single screw extruder, melted and mixed, and formed into a film through a T die to obtain an extruded film. The obtained extruded film was simultaneously biaxially stretched twice in the longitudinal and width directions at a stretching temperature of 152°C. The stretching speed was 10%/sec in both the longitudinal and width directions.

In this way, base film E with a thickness of 40 μm was produced.

2. Fabrication of optical laminate

Optical laminate 5, in which a hard coat layer was formed on one side of the base film E, was obtained in the same manner as in Example 1 except that the base film E was used. The optical laminate 5 was used for each evaluation. The results are shown in Table 1.

<Example 6>

1. Production of base film

Base film F was produced in the same manner as in Example 1, except that the blending amount of core-shell particles was 23 parts by weight and the stretching temperature of the extruded film was 137°C.

2. Fabrication of optical laminate

An optical laminate 6 in which a hard coat layer was formed on one side of the base film F was obtained in the same manner as in Example 1 except that the base film F was used. The optical laminate 6 was used for each evaluation. The results are shown in Table 1.

<Example 7>

1. Production of base film

An extruded film was obtained by melting and mixing 100 parts by weight of the imidized MS resin and 23 parts by weight of the core-shell type particles obtained above into a single screw extruder and forming a film through a T die. The obtained extruded film was simultaneously biaxially stretched twice in the longitudinal and width directions at a stretching temperature of 152°C. The stretching speed was 10%/sec in both the longitudinal and width directions.

In this way, base film G with a thickness of 20 μm was produced.

2. Fabrication of optical laminate

An optical laminate 7 in which a hard coat layer was formed on one side of the base film G was obtained in the same manner as in Example 1 except that the base film G was used. The optical laminate 7 was used for each evaluation. The results are shown in Table 1.

<Example 8>

1. Production of base film

Base film H was produced in the same manner as in Example 1, except that the mixing amount of core-shell particles was 10 parts by weight and the stretching temperature of the extruded film was 160°C.

2. Fabrication of optical laminate

An optical laminate 8 was obtained in which the hard coat layer was formed on one side of the base film H in the same manner as in Example 1 except that the base film H was used and the film thickness after drying was 15 μm. The optical laminate 8 was used for each evaluation. The results are shown in Table 1.

<Comparative Example 1>

1. Production of base film

An extruded film was obtained by putting the imidized MS resin obtained above into a single-screw extruder, melting and mixing, and forming a film through a T-die. The obtained extruded film was simultaneously biaxially stretched twice in the longitudinal direction and in the width direction at a stretching temperature of 130°C. The stretching speed was 10%/sec in both the longitudinal and width directions.

In this way, base film I with a thickness of 40 μm was produced.

2. Fabrication of optical laminate

An optical laminate 9 in which a hard coat layer was formed on one side of the base film I was obtained in the same manner as in Example 1 except that the base film I was used. The optical laminate 9 was used for each evaluation. The results are shown in Table 1.

<Comparative Example 2>

1. Production of base film

Base film J was produced in the same manner as Example 1, except that core-shell particles were not mixed.

2. Fabrication of optical laminate

An optical laminate 10 in which a hard coat layer was formed on one side of the base film J was obtained in the same manner as in Example 1 except that the base film J was used. The optical laminate 10 was used for each evaluation. The results are shown in Table 1.

<Comparative Example 3>

1. Production of base film

Base film K was produced in the same manner as in Example 1, except that core-shell particles were not mixed and the stretching temperature of the extruded film was set to 160°C.

2. Fabrication of optical laminate

An optical laminate 11 in which a hard coat layer was formed on one side of the base film K was obtained in the same manner as in Example 1 except that the base film K was used. The optical laminate 11 was used for each evaluation. The results are shown in Table 1.

As is clear from Table 1, Example 1 using a base film in which the proportion of the acrylic resin component eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer is 18% or more. The optical laminate of ~8 had excellent appearance and adhesion.

The optical laminate of the present invention is suitably used as a protective layer for a polarizer. A polarizing plate having the optical laminate of the present invention as a protective layer is suitably used in an image display device. The above image display devices include portable devices such as portable digital assistants (PDAs), smartphones, mobile phones, watches, digital cameras, and portable game consoles; OA devices such as PC monitors, laptops, and copiers; Household electrical appliances such as video cameras, televisions, and microwave ovens; Vehicle-mounted devices such as back monitors, car navigation system monitors, and car audio; Exhibition equipment such as digital signage and information monitors for commercial stores; Security devices such as surveillance monitors; Nursing care and medical equipment such as nursing care monitors and medical monitors; It can be used for various purposes such as:

10: Base film
20: Surface treatment layer
100: Optical laminate

Claims (10)

It includes a base film containing an acrylic resin and a surface treatment layer formed on one side of the base film,
An optical laminate in which the ratio of the acrylic resin component eluted into the surface treatment layer among the components constituting a position at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer is 18% or more. According to claim 1,
Let the refractive index of the base film be R1, the refractive index of the surface treatment layer be R2, and the refractive index at a depth of 3.0 μm in the direction from the base film side to the surface treatment layer be R3,
An optical laminate that satisfies R3≤0.18R1+0.82R2 (however, R1<R2). According to claim 1,
An optical laminate wherein the surface treatment layer has a thickness of 3㎛ to 20㎛. The method according to any one of claims 1 to 3,
An optical laminate wherein the base film includes the acrylic resin and core-shell particles dispersed in the acrylic resin. According to claim 4,
An optical laminate in which the base film contains 3 to 50 parts by weight of the core-shell particles based on 100 parts by weight of the acrylic resin. The method according to any one of claims 1 to 3,
An optical laminate wherein the acrylic resin has at least one selected from the group consisting of glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. The method according to any one of claims 1 to 3,
An optical laminate wherein the surface treatment layer is a cured layer of a resin applied on the base film. The method according to any one of claims 1 to 3,
An optical laminate wherein the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an anti-glare layer, and an anti-reflection layer. It includes a polarizer and a protective layer disposed on one side of the polarizer,
A polarizing plate wherein the protective layer is the optical laminate according to any one of claims 1 to 3. An image display device comprising the polarizing plate according to claim 9.