JP7083814B2 - Optical laminates, polarizing plates, and image display devices - Google Patents

Description

The present invention relates to an optical laminate, a polarizing plate, and an image display device.

In recent years, an optical laminate in which a functional layer (surface treatment layer) such as a hard coat layer, an antiglare layer, and an antireflection layer is formed on one side of a base film made of an acrylic resin is known (Patent Document 1). ). Such an optical laminate can be used, for example, as a protective film for a polarizing element or as a front plate of an image display device.

Japanese Unexamined Patent Publication No. 2016-218478

However, the conventional optical laminate as described above may not be sufficiently provided with the function of the surface treatment layer.

The present invention has been made to solve the above-mentioned conventional problems, and the main object thereof is an optical laminate to which the function of a surface treatment layer is sufficiently imparted, a polarizing plate provided with such an optical laminate, and the like. Further, it is an object of the present invention to provide an image display device provided with such a polarizing plate.

The optical laminate of the present invention includes a base film and a surface treatment layer formed on one side of the base film, and the base film is dispersed in an acrylic resin and an acrylic resin. Among the components containing core-shell type particles, the base film has an elastic coefficient of 4.0 GPa or more, and constitutes a position at a depth of 3.0 μm from the base film side toward the surface treatment layer. The ratio of the components of the acrylic resin eluted in the surface treatment layer is less than 20%.
In one embodiment, when the refractive index of the base film is R1 and the refractive index at a depth of 3.0 μm from the base film side toward the surface treatment layer is R3, then R3>. Satisfy 0.2R1 + 0.8R2 (however, R1 <R2).
In one embodiment, the surface treatment layer has a thickness of 3 μm to 20 μm.
In one embodiment, the base film contains 5 parts by weight to 20 parts by weight of the core-shell type particles with respect 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 resin coated on the base film.
In one embodiment, the surface treatment layer is at least one selected from the group consisting of a hardcoat layer, an antiglare layer and an antireflection layer.
According to another aspect of the invention, a polarizing plate is provided. This polarizing plate includes a polarizing element and a protective layer arranged on one side of the polarizing element, 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 includes the above-mentioned polarizing plate.

According to the present invention, among the components constituting the base film having an elastic coefficient of 4.0 GPa or more and a depth of 3.0 μm in the direction of the surface treatment layer from the base film side, the surface treatment layer is used. An optical laminate in which the function of the surface treatment layer is sufficiently imparted by the content of the eluted acrylic resin being less than 20%, a polarizing plate having such an optical laminate, and such a polarizing plate An image display device can be provided.

It is a schematic sectional drawing of the optical laminated body by one Embodiment of this invention.

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

A. Overall Configuration of Optical Laminate Figure 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. The base film 10 contains an acrylic resin and core-shell type particles dispersed in the acrylic resin. The elastic modulus of the base film 10 is 4.0 GPa or more. The proportion of the acrylic resin component eluted in the surface treatment layer is less than 20% among the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer. The position at a depth of 3.0 μm from the base film side toward the surface treatment layer is typically 3.0 μm away from the interface of the base film with the surface treatment layer toward the surface treatment layer. Position. The ratio of the components of the acrylic resin at the "position at a depth of 3 μm" is typically derived by the following method.
Calculation position of acrylic resin component (position from the surface treatment side) = Surface treatment layer thickness (PET base material hard coat thickness)-(3 μm)
For example, when the (PET base material hard coat thickness) is 15 μm, the ratio of the acrylic resin component at the position 12 μm from the surface treatment side is measured. The surface treatment layer thickness (hard coat thickness) is typically derived by the following procedure. First, a PET base material (manufactured by Toray Industries, Inc., trade name: U48-3, refractive index: 1.60) is used as a base film, and the coating layer is dried at 70 ° C. and UV-cured. , Obtain an optical laminate on which a hardcoat layer is formed. A black acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., thickness 2 mm) was attached to the base material layer side of the obtained optical laminate via an acrylic pressure-sensitive adhesive having a thickness of 20 μm. Next, the reflection spectrum of the hard coat layer is measured under the following conditions using an instantaneous multiphotometric system (manufactured by Otsuka Electronics Co., Ltd., trade name: MCPD3700). Since the composition for forming a hard coat layer does not penetrate into the PET substrate used for 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 Calculation wavelength: 450 nm to 850 nm
-Detection conditions Exposure time: 20 ms
Lamp gain: Normal Number of integrations: 10 times ・ FFT method Film thickness value range: 2 to 15 μm
Film thickness resolution: 24 nm

When the above ratio is 20% or more, the function of the surface treatment layer (typically scratch resistance when the surface treatment layer is a hard coat layer) may not be sufficiently imparted, and the base film and the surface may not be sufficiently imparted. Adhesion with the treated layer may decrease. The proportion of the acrylic resin component eluted in the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the base film 10 side toward the surface treatment layer 20 is measured, for example, by the prism coupler method. be able to. Specifically, the refractive index of the base film is R1, the refractive index of the surface-treated layer is R2, and the depth is 3.0 μm from the base film side measured by the prism coupler method toward the surface-treated layer. When the refractive index at the position is R3, the ratio X of the acrylic resin component eluted in the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer ( %) Is expressed by the following equation.
X (%) = (R3-R2) x 100 / (R1-R2)
Therefore, the optical laminate 100 has a refractive index R1 of the base film, a refractive index R2 of the surface-treated layer, and a refractive index R3 at a depth of 3.0 μm from the base film side toward the surface-treated layer. Preferably, the following inequality is satisfied.
R3> 0.2R1 + 0.8R2 (R1 <R2)
The thickness of the surface treatment layer is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm. The base film 10 preferably contains 5 parts by weight to 20 parts by weight of core-shell type particles with respect to 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 the resin composition coated 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 antiglare layer and an antireflection layer. According to the optical laminate 100, the amount of the acrylic resin contained in the base film 10 eluted into the surface treatment layer 20 is sufficiently small. As a result, it is possible to suppress the deterioration of the functionality of the surface-treated layer due to the acrylic resin being eluted into the surface-treated layer 20. Specifically, when the surface treatment layer is a hard coat layer, deterioration of the scratch resistance of the hard coat layer can be suppressed, and when the surface treatment layer is an antiglare layer, the antiglare layer is prevented. The decrease in glare can be suppressed, and when the surface treatment layer is an antireflection layer, the decrease in antireflection property of the antireflection layer can be suppressed. Further, 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 As described above, the base film contains an acrylic resin and core-shell type particles dispersed in the acrylic resin. The thickness of the base film is preferably 5 μm to 150 μm, more preferably 10 μm to 100 μm. The elastic modulus of the base film is 4.0 GPa or more as described above. In the base film, when the surface treatment layer described later is formed, the acrylic resin may be 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 from the base film side toward the surface treatment layer is less than 20%.

The substrate film is preferably substantially optically isotropic. As used herein, "substantially optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. Say something. 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. When the Re (550) and Rth (550) of the base film are in such a range, it is possible to prevent an adverse effect on the display characteristics when the optical laminate is applied to an image display device. Re (550) is an in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (550) is obtained by the formula: Re (550) = (nx-ny) × d. Rth (550) is a phase difference in the thickness direction of the film measured with light having a wavelength of 550 nm at 23 ° C. Rth (550) is obtained by the formula: Rth (550) = (nx-nz) × d. Here, nx is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the slow phase axis direction), and ny is the direction orthogonal to the slow phase axis in the plane (that is, the phase advance axis direction). It is the refractive index, nz is the refractive index in the thickness direction, and d is the thickness (nm) of the film.

The higher the light transmittance at 380 nm at a thickness of 40 μm of the base film, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. If the light transmittance is in such a range, the desired transparency can be ensured. The 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. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good clear feeling can be given to the film. Further, even when the optical laminate is used as a protective layer of the polarizing plate on the visual recognition side of the image display device, the displayed contents can be visually recognized satisfactorily.

The YI at a thickness of 40 μm of the base film is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the optical transparency may be insufficient. The YI is obtained from, for example, the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere type spectral transmittance measuring device (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory). , Can be calculated by the following equation.
YI = [(1.28X-1.06Z) / Y] × 100

The b value (a measure of hue according to the Munsell color system of the hunter) 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, an undesired color may appear. For the b value, for example, a base film sample is cut into 3 cm squares, and the hue is measured using a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory). It can be obtained by evaluating the hue according to the color system of the hunter.

The moisture permeability of the base film is preferably 300 g / m 2.24 hr or less, more preferably ²⁵⁰ g / ^m 2.24 hr or less, still more preferably ²⁰⁰ g / m 2.24 hr or less, and particularly preferably 150 g / ^m 2.24 hr or less. Most preferably, it is 100 g / ^m 2.24 hr or less. When the moisture permeability of the base film is within such a range, a polarizing plate having excellent durability and moisture resistance can be obtained when used as a protective layer for a polarizing element.

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. If it is less than 10 MPa, sufficient mechanical strength may not be exhibited. If it exceeds 100 MPa, the workability may be insufficient. The tensile strength can be measured according to, for example, ASTM-D-882-61T.

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

The tensile elastic modulus of the base film is 4 GPa or more, preferably 4.5 GPa or more. The upper limit of the tensile elastic modulus is, for example, 20 GPa. The tensile modulus can be measured, for example, according to ASTM-D-882-61T.

The base film may contain any suitable additive depending on the intended purpose. Specific examples of additives include ultraviolet absorbers; antioxidants such as hindered phenols, phosphorus and sulfur; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers and heat-stabilizing agents; glass fibers, carbon fibers and the like. Reinforcing materials; Near-infrared absorbers; Flame-retardant agents such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic, nonionic surfactants; Inorganic pigments, organic pigments , Colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; and the like. The additive may be added at the time of polymerization of the acrylic resin, or may be added at the time of film formation. The type, number, combination, amount of additive, etc. of the additive can be appropriately set according to the purpose.

B-2. Acrylic resin B-2-1. Composition of Acrylic Resin As the acrylic resin, any suitable acrylic resin can be adopted. Acrylic resins typically contain an alkyl (meth) acrylate as a main component as a monomer unit. As used herein, the term "(meth) acrylic" means acrylic and / or methacrylic. 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. Further, any suitable copolymerization monomer may be introduced into the acrylic resin by copolymerization. The type, number, copolymerization ratio, etc. of such copolymerization monomers can be appropriately set according to the purpose. The constituent components (monomer unit) of the main skeleton of the acrylic resin will be described later with reference to the 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 a lactone ring unit are described in, for example, Japanese Patent Application Laid-Open No. 2008-181078, and the description in this publication is incorporated herein by reference. The glutarimide unit is preferably represented by the following general formula (1):

In the general formula (1), R ¹ and R ² independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ³ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and carbon. It indicates a cycloalkyl group having a number of 3 to 12 or an aryl group having 6 to 10 carbon atoms. In the general formula (1), preferably, R ¹ and R ² are independently hydrogen atoms or methyl groups, and R ³ is a hydrogen atom, a methyl group, a butyl group or a cyclohexyl group, respectively. 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 the general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ is a hydrogen atom or an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms which may be substituted. show. Examples of the substituent include halogens and hydroxyl groups. Specific examples of alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth) acrylate. Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylate Examples include 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl and (meth) acrylic acid 2,3,4,5-tetrahydroxypentyl. In the general formula ( ² ), R5 is preferably a hydrogen atom or a methyl group. Therefore, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units having different ^{R1 , R2} and R3 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%, and particularly preferably 2 mol. % To 35 mol%, most preferably 3 mol% to 30 mol%. When the content ratio is less than 2 mol%, the effects exhibited from the glutarimide unit (for example, high optical properties, high mechanical strength, excellent adhesion to the modulator, thinning) are sufficiently exhibited. It may not be done. If the content ratio exceeds 50 mol%, for example, heat resistance and transparency may be insufficient.

The acrylic resin may contain only a single alkyl (meth) acrylate unit, or may contain a plurality of alkyl (meth) acrylate units having different ^R4 and R5 in the general formula ( ² ). May be good.

The content of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, still more preferably 60 mol% to 98 mol%, and particularly preferably. Is 65 mol% to 98 mol%, most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, the effects expressed from the alkyl (meth) acrylate unit (for example, high heat resistance and high transparency) may not be sufficiently exhibited. If the content ratio is more than 98 mol%, the resin is brittle and easily cracked, high mechanical strength cannot be sufficiently exhibited, and productivity may be inferior.

The acrylic resin may contain a unit other than the glutarimide unit and the alkyl (meth) acrylate unit.

In one embodiment, the acrylic resin can contain, for example, 0 to 10% by weight of unsaturated carboxylic acid units that are not involved in the intramolecular imidization reaction described below. The content ratio of the unsaturated carboxylic acid unit is preferably 0 to 5% by weight, more preferably 0 to 1% by weight. When the content is in such a range, transparency, retention stability and moisture resistance can be maintained.

In one embodiment, the acrylic resin can contain a copolymerizable vinyl-based monomer unit (another vinyl-based monomer unit) other than the above. Examples of other vinyl-based monomers include acrylonitrile, methacrylic acid, etacrylonitrile, allylglycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, and acrylic acid. Aminoethyl acid, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, 2 -Isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryl- Examples include oxazoline. These may be used alone or in combination. Styrene-based monomers such as styrene and α-methylstyrene are preferable. The content ratio of the other vinyl-based monomer unit is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. Within such a range, the development of undesired phase difference and the decrease in transparency can be suppressed.

The imidization rate of the acrylic resin is preferably 2.5% to 20.0%. When the imidization ratio is within such a range, a resin having excellent heat resistance, transparency and moldability can be obtained, and the generation of kogation and the decrease in mechanical strength during film molding can be prevented. In the acrylic resin, the imidization ratio is represented by the ratio of the glutarimide unit and the alkyl (meth) acrylate unit. This ratio can be obtained from, for example, an NMR spectrum, an IR spectrum, or the like of an acrylic resin. In this embodiment, the imidization ratio can be determined by ^{1 1} H-NMR measurement of the resin using ^{1 1} HNMR BRUKER Avance III (400 MHz). More specifically, the peak area derived from the O-CH ₃ proton of the alkyl (meth) acrylate around 3.5 to 3.8 ppm is defined as A, and the peak area of glutarimide near 3.0 to 3.3 ppm is N-CH ₃ . It is calculated by the following equation, where B is the area of the peak derived from the proton.
Imidization rate Im (%) = {B / (A + B)} × 100

The acid value of the acrylic resin is preferably 0.10 mmol / g to 0.50 mmol / g. When the acid value is in such a range, a resin having an excellent balance between heat resistance, mechanical properties and molding processability can be obtained. If the acid value is too small, problems such as cost increase due to the use of a denaturant for adjusting to a desired acid value and generation of a gel-like substance due to residual denaturant may occur. If the acid value is too high, foaming tends to occur 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 the carboxylic acid unit and the carboxylic acid anhydride unit in the acrylic resin. In the present embodiment, the acid value can be calculated by, for example, WO2005 / 054311 or the titration method described in JP-A-2005-23272.

The weight average molecular weight of the acrylic resin is preferably 1,000,000 to 2000000, more preferably 5000 to 1,000,000, still more 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 using, for example, a gel permeation chromatograph (GPC system, manufactured by Tosoh). Tetrahydrofuran can be used as the solvent.

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

B-2-2. Polymerization of Acrylic Resin The acrylic resin can be produced, for example, by the following method. In this method, (I) an alkyl (meth) acrylate monomer corresponding to an alkyl (meth) acrylate unit represented by the general formula (2) and an unsaturated carboxylic acid monomer and / or a precursor thereof are used alone. The body and the copolymer are copolymerized to obtain the copolymer (a); and (II) the copolymer (a) is treated with an imidizing agent to obtain the copolymer (a) in the copolymer (a). An intramolecular imidization reaction was carried out between the alkyl (meth) acrylate monomer unit and the unsaturated carboxylic acid monomer and / or its precursor monomer unit, and the glutarimide unit represented by the general formula (1) was used together. Introducing into the polymer;

Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. Examples of the precursor monomer include acrylamide and methacrylamide. 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.

Any suitable method can be used as the method for treating the copolymer (a) with the imidizing agent. Specific examples include a method using an extruder and a method using a batch type reaction vessel (pressure vessel). The method using an extruder includes heating and melting the copolymer (a) using an extruder and treating the copolymer (a) 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 using a batch type reaction vessel (pressure vessel), any suitable batch type reaction vessel (pressure vessel) can be used.

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

In imidization, a ring closure promoter may be added, if necessary, in addition to the imidizing agent.

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 the copolymer (a). Is. If the amount of the 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 obtained resin becomes extremely insufficient, which may induce appearance defects such as kogation after molding. If the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent may remain in the resin, and the imidizing agent may induce appearance defects such as kogation after molding and foaming.

If necessary, the production method of the present embodiment can include treatment with an esterifying agent in addition to the above-mentioned imidization.

Examples of the esterifying agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyltoluenesulfonate, and methyltrifluoromethanesulfonate. Methylacetate, methanol, ethanol, methylisocyanate, p-chlorophenylisocyanate, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenylacetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-N-butoxysilane , Dimethyl (trimethylsilane) phosphite, trimethylphosphite, trimethylphosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether. .. Among these, dimethyl carbonate is preferable from the viewpoint of cost and reactivity.

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. Concomitant use of other resins In the embodiment of the present invention, the above acrylic resin and other resins may be used in combination. That is, the monomer component constituting the acrylic resin and the monomer component constituting another resin may be copolymerized, and the copolymer may be used for forming a film described later in Section B-4; the acrylic resin and others. The blend with the resin of the above may be used for film formation. Examples of other resins include styrene resins, polyethylene, polypropylene, polyamides, polyphenylene sulfides, polyether ether ketones, polyesters, polysulfones, polyphenylene oxides, polyacetals, polyimides, polyetherimides and the like, and other thermoplastic resins and phenolic resins. Examples thereof include thermoplastic resins such as resins, melamine-based resins, polyester-based resins, silicone-based resins, and epoxy-based resins. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the properties desired for the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

When the acrylic resin is used in combination with another resin, 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. By weight%, more preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected.

B-3. Core-shell type particles In the base film, the core-shell type particles are preferably blended in an amount of 5 parts by weight to 20 parts by weight, more preferably 5 parts by weight to 13 parts by weight, based on 100 parts by weight of the acrylic resin. As a result, it is possible to obtain a base film having a desired elastic modulus and suppressing elution of the acrylic resin into the surface treatment layer. As a result, it is possible to suppress the deterioration of the functionality of the surface treatment layer when the surface treatment layer is formed on the base film, and further improve the adhesion between the base film and the surface treatment layer.

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

The Tg of the rubber-like polymer constituting the core is preferably 20 ° C. or lower, more preferably −60 ° C. to 20 ° C., and further preferably −60 ° C. to 10 ° C. If the Tg of the rubber-like polymer constituting the core exceeds 20 ° C., the improvement in the mechanical strength of the acrylic resin may not be sufficient. 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 further preferably 60 ° C. to 130 ° C. If the Tg of the glassy polymer constituting the coating layer is lower than 50 ° C., 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, and more preferably 10% by weight to 40% by weight with respect to 100% by weight of the total amount 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 type particles dispersed in the acrylic resin may have a flat shape. The core-shell type particles can be flattened by the stretching 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, 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 further preferably 5.0 or more. As used herein, the "length / thickness ratio" means the ratio between the representative length and the thickness of the plan-view shape of the core-shell type particles. Here, the "representative length" means a diameter when the shape in a plan view is circular, a major axis when the shape is elliptical, and a diagonal length when the shape is rectangular or polygonal. The ratio can be determined, for example, by the following procedure. The cross section of the obtained film was photographed with a transmission electron microscope (for example, acceleration voltage 80 kV, _RuO4 stained ultrathin section method), and the long core-shell type particles present in the obtained photograph (cross section close to the representative length). The ratio can be obtained by extracting 30 particles in order from the one in which is obtained) and calculating (average value of length) / (average value of thickness).

For details of the rubber-like polymer constituting the core of the core-shell type particles, the glass-like polymer (hard polymer) constituting the coating layer, the polymerization method thereof, and other configurations, for example, Japanese Patent Application Laid-Open No. 2016-33552. It is described in. The description of this publication is incorporated herein by reference.

B-4. Formation of Base Film The base film according to the embodiment of the present invention typically contains the above acrylic resin (in the case of using other resins in combination, a blend with the other resins) and core-shell type particles. The composition can be formed by a method comprising forming a film. Further, the method of forming the base film may include stretching the film.

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

Any suitable method can be adopted as the method for forming the film. Specific examples include a cast coating method (for example, casting method), an extrusion molding method, an injection molding method, a compression molding method, a transfer molding method, a blow molding method, a powder molding method, an FRP molding method, a calendar molding method, and a hot press. The law is mentioned. An extrusion molding method or a cast coating method is preferable. This is because the smoothness of the obtained film can be enhanced and good optical uniformity can be obtained. A particularly preferable method is an extrusion molding method. This is because it is not necessary to consider the problem caused by the residual solvent. Above all, the extrusion molding method using a T-die is preferable from the viewpoint of film productivity and ease of subsequent stretching treatment. The molding conditions can be appropriately set according to the composition and type of the resin used, the properties desired for the obtained film, and the like.

As the stretching method, any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching speed, stretching direction) can be adopted. Specific examples of the stretching method include free-end stretching, fixed-end stretching, free-end shrinkage, and fixed-end shrinkage. These may be used alone, simultaneously, or sequentially. By stretching the film in which the blending amount of the core-shell type particles with respect to the acrylic resin was appropriately adjusted under appropriate stretching conditions, the film had a desired elastic modulus and the elution of the acrylic resin into the surface treatment layer was suppressed. A base film can be obtained. As a result, it is possible to suppress the deterioration of the functionality of the surface treatment layer when the surface treatment layer is formed on the base film, and further improve the adhesion between the base film and the surface treatment layer.

As the stretching direction, an appropriate direction may be adopted depending on the purpose. Specific examples thereof include a length direction, a width direction, a thickness direction, and an oblique direction. The stretching direction may be one direction (uniaxial stretching), bidirectional stretching (biaxial stretching), or three or more directions. In the embodiment of the present invention, typically, uniaxial stretching in the length direction, simultaneous biaxial stretching in the length direction and width direction, and sequential biaxial stretching in the length direction and width direction can be adopted. Biaxial stretching (simultaneous or sequential) is preferred. This is because it is easy to control the in-plane phase difference and it is easy to realize optical anisotropy.

The stretching temperature is the desired optical properties, mechanical properties and thickness of the base film, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching ratio, and the stretching. It may change depending on the speed and the like. 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 such a temperature, a base film having appropriate properties can be obtained. The specific stretching temperature is, for example, 110 ° C to 200 ° C, preferably 120 ° C to 190 ° C. When the stretching temperature is within such a range, the base film having a desired elastic modulus and suppressing elution of the acrylic resin into the surface treatment layer by appropriately adjusting the stretching ratio and the stretching speed can be obtained. Can be obtained. As a result, it is possible to suppress the deterioration of the functionality of the surface treatment layer when the surface treatment layer is formed on the base film, and further improve the adhesion between the base film and the surface treatment layer.

The draw ratio is also the same as the draw temperature, optical properties, mechanical properties and thickness, type of resin used, thickness of film used, stretching method (uniaxial stretching or biaxial stretching), stretching temperature, stretching. It may change depending on the speed and the like. When biaxial stretching is adopted, the ratio (TD / MD) of the stretching ratio in the width direction (TD) and the stretching ratio in the length direction (MD) is preferably 1.0 to 1.5, which is more preferable. Is 1.0 to 1.4, more preferably 1.0 to 1.3. Further, when biaxial stretching is adopted, the surface magnification (the product of the stretching magnification in the length direction and the stretching magnification in the width direction) is preferably 2.0 to 6.0, and more preferably 3.0 to 6.0. It is 5.5, more preferably 3.5 to 5.2. When the stretching ratio is within such a range, the base film having a desired elastic modulus and suppressing elution of the acrylic resin into the surface treatment layer by appropriately adjusting the stretching temperature and stretching speed can be obtained. Can be obtained. As a result, it is possible to suppress the deterioration of the functionality of the surface treatment layer when the surface treatment layer is formed on the base film, and further improve the adhesion between the base film and the surface treatment layer.

The stretching speed, as well as the stretching temperature, is also the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), stretching temperature, stretching. It may change depending on the magnification and the like. 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. When the stretching speed is within such a range, the base film having a desired elastic modulus and suppressing elution of the acrylic resin into the surface treatment layer by appropriately adjusting the stretching temperature and the stretching ratio can be obtained. Can be obtained. As a result, it is possible to suppress the deterioration of the functionality of the surface treatment layer when the surface treatment layer is formed on the base film, and further improve the adhesion between the base film and the surface treatment layer.

As described above, the base film can be formed.

C. Surface-treated layer The surface-treated layer is any suitable functional layer formed on one side of the base film according to the function required for the optical laminate. Specific examples of the surface treatment layer include a hard coat layer, an antiglare layer, an antireflection layer and the like. The thickness of the surface treatment layer is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm.

The surface treatment layer is typically a cured layer of the resin composition formed on the base film. The steps of forming the surface treatment layer are to apply the resin composition for forming the surface treatment layer on the base film to form the coating layer, and to dry and cure the coating layer to obtain the surface treatment layer. May include. Drying and curing the coating layer may include heating the coating layer.

Any suitable method can be adopted as the method for applying the resin composition. For example, a bar coat method, a roll coat method, a gravure coat method, a rod coat method, a slot orifice coat method, a curtain coat method, a fountain coat method, and a comma coat method can be mentioned. From the viewpoint of facilitating application, the resin composition preferably contains a solvent for dilution.

The heating temperature of the coating layer can be set to an arbitrary appropriate temperature depending on the composition of the resin composition, and is preferably set to be equal to or lower than the glass transition temperature of the acrylic resin contained in the base film. By heating at a temperature equal to or lower than the glass transition temperature of the acrylic resin contained in the base film, an optical laminate in which deformation due to heating is suppressed can be obtained. The heating temperature of the coating layer is, for example, 50 ° C to 140 ° C, preferably 60 ° C to 100 ° C. By heating at such a heating temperature, an optical laminate having excellent adhesion between the base film and the surface treatment layer can be obtained.

C-1. Hardcoat layer The hardcoat layer is a layer that imparts scratch resistance, chemical resistance, and the like to the surface of the base film. The hard coat layer has a hardness of preferably H or higher, more preferably 3H or higher in the pencil hardness test. The pencil hardness test can be measured according to JIS K 5400. The resin composition for forming a hard coat layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), an electron beam, or the like. 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 description of the publication is incorporated herein by reference.

C-2. Anti-glare layer The anti-glare layer is a layer for preventing reflection of external light by scattering and reflecting light. The resin composition for forming the antiglare layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), an electron beam, or the like. The antiglare layer typically has a fine uneven shape on the surface. Examples of the method for forming such a fine uneven shape include a method in which fine particles are contained in the curable compound. Details of the antiglare layer and the resin composition for forming the antiglare layer are described in, for example, Japanese Patent Application Laid-Open No. 2017-32711. The entire description of the publication is incorporated herein by reference.

C-3. Antireflection layer The antireflection layer is a layer for preventing the reflection of external light. The resin composition for forming the antireflection layer may contain, for example, a curable compound that can be cured by heat, light (ultraviolet rays, etc.), an electron beam, or the like. The antireflection layer may be a single layer composed of only one layer, or may be a plurality of layers composed of two or more layers. Details of the antireflection layer and the resin composition for forming the antireflection layer are described in, for example, Japanese Patent Application Laid-Open No. 2012-155050. The entire description of the publication is incorporated herein by reference.

D. Polarizers The optical laminates described in Items A to C above can be applied to polarizing plates. Therefore, the present invention also includes a polarizing plate using such an optical laminate. Typically, the polarizing plate has a polarizing element and an optical laminate of the present invention arranged on one side of the polarizing element. The base film side of the optical laminate is bonded to the polarizing element, and can function as a protective layer for the polarizing element.

As the polarizing element, any suitable polarizing element may be adopted. For example, the resin film forming the polarizing element may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizing element composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine and a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical properties, a polarizing element obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Further, it may be dyed after being stretched. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a cleaning treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt and blocking inhibitor on the surface of the PVA-based film, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizing element obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizing element obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The ligand obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on top of the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further comprise, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin base material / polarizing element laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizing element), and the resin base material is peeled off from the resin base material / polarizing element laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. Details of the method for producing such a polarizing element are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

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

E. Image display device The polarizing plate according to the above item D can be applied to an image display device. Therefore, the present invention also includes an image display device using such a polarizing plate. Typical examples of the image display device include a liquid crystal display device and an organic electroluminescence (EL) display device. Since the image display device adopts a configuration well known in the industry, detailed description thereof will be omitted.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.
(1) Percentage of acrylic resin components eluted in the surface treatment layer Acrylic resin eluted in the surface treatment layer by a method using a three-dimensional photorefractive index / film thickness measuring device prism coupler (Metericon 2010 / M, manufactured by Metallikon). The proportion of the resin component was measured. The refractive index was measured using the prism coupler under the following conditions.
-Measurement condition Light source: 594 nm
Mode: TE
Scan: 300-300
(1-1) Refractive index R1 of the base film
Measurement type: Bulk / Substrate
The mode (called Knee) was detected by measuring the base film. The refractive index obtained by the measurement was defined as R1.
(1-2) Refractive index R2 of the surface treatment layer
Measurement type: Single Film (Prime Couple)
A PET base material (manufactured by Toray Industries, Inc., trade 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 laminated body having the same thickness as that of each example was obtained. By measuring this laminated body in the Single Film mode, a plurality of modes were detected. The refractive index obtained by the measurement was defined as R2.
(1-3) Refractive index R3 at a depth of 3.0 μm from the base film side toward the surface treatment layer.
Measurement type: Single Film (Prime Couple)
Analysis method: Index gradient
When the refractive index changes in the depth direction in the optical laminate, the change in the refractive index in the depth direction can be quantitatively obtained by the method using the prism coupler.
Multiple modes were detected by measuring the optical laminate, and the change in refractive index in the depth direction was calculated by 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 formula, and the obtained refractive index was defined as R3.
"Position with a depth of 3.0 μm" (position from the surface treatment side) = Surface treatment layer thickness (PET substrate hard coat thickness)-(3 μm)
(1-4) Percentage of the acrylic resin component eluted in the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer X
From the following formula, the ratio X (%) of the acrylic resin component eluted in the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer was calculated. ..
X (%) = (R3-R2) x 100 / (R1-R2)
(2) Elastic modulus of the base film A TI900 TriboIndenter (manufactured by Hysiron) was used to measure the elastic modulus of the base film. The base film was cut into a size of 10 mm × 10 mm, fixed to a support equipped with a TriboIndenter, and the compressive elastic modulus was measured by the nanoindentation method. At that time, the position was adjusted so that the indenter used pushed in the vicinity of the center of the transparent layer. The measurement conditions are shown below.
Indenter used: Berkovich (triangular pyramid type)
Measurement method: Single push measurement Measurement temperature: 25 ° C
Pushing depth: 500 nm
Pushing speed: 100 nm / s
(3) Evaluation of Functionality of Surface Treatment Layer The optical laminates obtained in Examples and Comparative Examples were cut into a size of 11 mm in width and 100 mm in length, and placed on a glass plate with the base film facing down. Next, on the surface treatment layer (hard coat layer) side surface of the optical laminate, steel wool # 0000 attached to the cross section of a cylinder having a diameter of 11 mm was reciprocated 10 times at a load of 800 g or 600 g at 100 mm / sec. After that, the surface on the hardcourt layer side was visually observed and evaluated according to the following criteria.
〇: No scratches △: Slightly scratched ×: Slightly scratched (4) Adhesion evaluation The adhesion of the surface treatment layer to the base film was checked by the JIS K-5400 grid peeling test (number of grids). : 100 pieces) was evaluated and judged by the following indexes.
〇: The number of grid peels is 0 ×: The number of grid peels is 1 or more

<Example 1>
1. 1. Preparation of base film MS resin (MS-200; copolymer of methyl methacrylate / styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) is imidized with monomethylamine (imidization ratio: 5). %)did. The obtained imidized MS resin is represented by a glutarimide unit represented by the general formula (1) (R ¹ and R ³ are methyl groups and R ² is a hydrogen atom) and is represented by the general formula (2). It had a meta) acrylic acid ester unit (R ⁴ and R ⁵ are methyl groups), and a styrene unit. For the imidization, a meshing type co-rotating twin-screw extruder having a diameter of 15 mm was used. The set temperature of each temperature control zone of the extruder is set to 230 ° C., the screw rotation speed is 150 rpm, the MS resin is supplied at 2.0 kg / hr, and the supply amount of monomethylamine is 2 parts by weight with respect to 100 parts by weight of the MS resin. did. The MS resin was charged from the hopper, the resin was melted and filled with the kneading block, and then monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. The by-products and excess methylamine after the reaction were devolatile by reducing the pressure at the vent port to −0.08 MPa. The resin that came out as a strand from the die provided at the outlet of the extruder was cooled in a water tank and then pelletized with a pelletizer. The imidized MS resin obtained had an imidization rate of 5.0% and an acid value of 0.5 mmol / g.
An extruded film was obtained by charging 100 parts by weight of the imidized MS resin obtained above and 5 parts by weight of core-shell type particles into a single-screw extruder, melting and mixing them, and forming a film through a T-die. The obtained extruded film was simultaneously biaxially stretched twice in the length direction and the width direction at a stretching temperature of 140 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
In this way, a base film A having a thickness of 30 μm was produced.
2. 2. Preparation of optical laminate 16 parts by weight of UV curable resin (4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.), NK Oligo UA-53H) on one side of the base film A so that the thickness after curing is 6 μm. -80BK (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 32 parts by weight, Viscort # 300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 48 parts by weight, A-GLY-9E (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 4 parts by weight, IRGACURE907 2.4 parts by weight (manufactured by BASF) was mixed and diluted with a solvent of MIBK: PGM = 50: 50 so as to have a solid content concentration of 42.0%) to form a coating layer. Next, the coating layer was dried at 70 ° C. and UV-cured to obtain an optical laminate 1 having a hard coat layer formed on one side of the base film A. The above optical laminate 1 was subjected to each evaluation. The results are shown in Table 1.

<Example 2>
1. 1. Preparation of Base Film A base film B was prepared 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 150 ° C.
2. 2. Preparation of Optical Laminate A optical laminate 2 having a hard coat layer formed on one side of the substrate 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 subjected to each evaluation. The results are shown in Table 1.

<Example 3>
1. 1. Preparation of Base Film A base film C was prepared 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. 2. Preparation of Optical Laminated Body In the same manner as in Example 1 except that the base film C was used, an optical laminate 3 having a hard coat layer formed on one side of the base film C was obtained. The optical laminate 3 was subjected to each evaluation. The results are shown in Table 1.

<Example 4>
1. 1. Preparation of Base Film A base film D was prepared in the same manner as in Example 1 except that the blending amount of the core-shell type particles was 13 parts by weight and the stretching temperature of the extruded film was 152 ° C.
2. 2. Preparation of Optical Laminate A optical laminate 4 having a hard coat layer formed on one side of the substrate 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 subjected to each evaluation. The results are shown in Table 1.

<Comparative Example 1>
1. 1. Preparation of Base Film An extruded film is obtained by putting 100 parts by weight of the imidized MS resin obtained above and 15 parts by weight of core-shell type particles into a single-screw extruder, melt-mixing them, and forming a film through a T-die. rice field. The obtained extruded film was simultaneously biaxially stretched twice in the length direction and the width direction at a stretching temperature of 152 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
In this way, a base film E having a thickness of 40 μm was produced.
2. 2. Preparation of Optical Laminate A optical laminate 5 having a hard coat layer formed on one side of the substrate 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 subjected to each evaluation. The results are shown in Table 1.

<Comparative Example 2>
1. 1. Preparation of base film 100 parts by weight of the imidized MS resin obtained above and 23 parts by weight of core-shell type particles are put into a single-screw extruder, melt-mixed, and formed into a film through a T-die to obtain an extruded film. rice field. The obtained extruded film was simultaneously biaxially stretched twice in the length direction and the width direction at a stretching temperature of 137 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
In this way, a base film F having a thickness of 40 μm was produced.
2. 2. Preparation of Optical Laminate A optical laminate 6 having a hard coat layer 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 subjected to each evaluation. The results are shown in Table 1.

<Comparative Example 3>
1. 1. Preparation of Base Film A base film G was prepared in the same manner as in Example 1 except that the core-shell type particles were not blended and the stretching temperature of the extruded film was set to 130 ° C.
2. 2. Preparation of Optical Laminate A optical laminate 7 having a hard coat layer 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 subjected to each evaluation. The results are shown in Table 1.

As is clear from Table 1, the acrylic system eluted in the surface-treated layer among the components having an elastic modulus of 4 GPa or more and constituting a position at a depth of 3.0 μm from the base film side toward the surface-treated layer. The optical laminates of Examples 1 to 4 using the base film having a resin component ratio of less than 20% were excellent in scratch resistance and adhesion.

The optical laminate of the present invention is suitably used as a protective layer for a polarizing element. The polarizing plate having the optical laminate of the present invention as a protective layer is suitably used for an image display device. Image display devices such as those described above are portable devices such as mobile information terminals (PDAs), smartphones, mobile phones, watches, digital cameras, and portable game machines; OA devices such as personal computer monitors, laptop computers, and copy machines; video cameras, Household electrical equipment such as TVs and microwaves; in-vehicle equipment such as back monitors, car navigation system monitors, and car audio; exhibition equipment such as digital signage and commercial store information monitors; security equipment such as monitoring monitors; It can be used for various purposes such as nursing care / medical equipment such as nursing care monitors and medical monitors.

10 Base film 20 Surface treatment layer 100 Optical laminate

Claims (9)

A base film and a surface treatment layer formed on one side of the base film are included.
The base film contains an acrylic resin and core-shell type particles dispersed in the acrylic resin.
The elastic modulus of the base film is 4.0 GPa or more, and the elastic modulus is 4.0 GPa or more.
The ratio of the component of the acrylic resin eluted in the surface treatment layer to the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer is less than 20%. Laminated body. The refractive index of the base film was R1, the refractive index of the surface-treated layer was R2, and the refractive index at a depth of 3.0 μm from the base film side toward the surface-treated layer was R3. When
R3> 0.2R1 + 0.8R2 (However, R1 <R2)
The optical laminate according to claim 1. The optical laminate according to claim 1 or 2, wherein the surface treatment layer has a thickness of 3 μm to 20 μm. The optical laminate according to any one of claims 1 to 3, wherein the base film contains 5 parts by weight to 20 parts by weight of the core-shell type particles with respect to 100 parts by weight of the acrylic resin. The invention according to any one of claims 1 to 4, wherein the acrylic resin has at least one selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit and a glutaric anhydride unit. Optical laminate. The optical laminate according to any one of claims 1 to 5, wherein the surface-treated layer is a cured layer of a resin coated on the base film. The optical laminate according to any one of claims 1 to 6, wherein the surface treatment layer is at least one selected from the group consisting of a hard coat layer, an antiglare layer and an antireflection layer. Includes a polarizing element and a protective layer disposed on one side of the polarizing element.
A polarizing plate in which the protective layer is the optical laminate according to any one of claims 1 to 7. An image display device comprising the polarizing plate according to claim 8.

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