JPWO2018190174A1 - Optical laminate, polarizing plate, and image display device - Google Patents

Abstract

Provided is an optical laminate that can have excellent appearance. 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 3.0 μm in a direction from the base film side to the surface treatment layer. The ratio of the acrylic resin component eluted into the surface treatment layer among the components constituting the depth position is 18% or more.

Description

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

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

JP-A-2006-178478

  However, the conventional optical laminate as described above has a problem that, when a scratch is generated in the acrylic resin film, the scratch becomes apparent by forming a surface treatment layer. Such a phenomenon may occur even if the scratches generated on the acrylic resin film are so small that they cannot be visually recognized, and the scratches that cannot be visually recognized may cause a visually impaired appearance of the obtained optical laminate.

  The present invention has been made to solve the above-mentioned conventional problems, and its main objects are an optical laminate capable of providing an excellent appearance, a polarizing plate having such an optical laminate, and such a polarizing plate. An image display device provided with the above.

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 in the direction of the surface treatment layer from the base film side. The proportion of the component of the acrylic resin eluted into the surface treatment layer among the components constituting the position at the depth of 3.0 μm 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 a position at a depth of 3.0 μm from the base film side toward the surface treatment layer. Satisfies R3 ≦ 0.18R1 + 0.82R2 (where R1 <R2).
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 based on 100 parts by weight of the acrylic resin.
In one embodiment, 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.
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 antiglare layer, and an antireflection layer.
According to another aspect of the present invention, a polarizing plate is provided. The 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 includes the polarizing plate.

  According to the present invention, among components constituting a position at a depth of 3.0 μm from the base film side toward the surface treatment layer, the component of the acrylic resin eluted into the surface treatment layer is 18% or more. Accordingly, it is possible to provide an optical laminate having an excellent appearance, a polarizing plate including such an optical laminate, and an image display device including 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. FIG. 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 from the base film 10 toward the surface treatment layer 20 is 18% or more. It is. The position having a depth of 3.0 μm in the direction of the surface treatment layer from the substrate film side is typically away from the interface of the substrate film with the surface treatment layer by 3.0 μm in the direction of the surface treatment layer. Position. The proportion of the acrylic resin component at the “3 μm depth position” is typically derived by the following method.
Calculation position of acrylic resin component (position from surface treatment side) = thickness of surface treatment layer (thickness of PET substrate hard coat)-(3 µm)
For example, when (PET base material hard coat thickness) is 15 μm, the ratio of the acrylic resin component at a position of 12 μm from the surface treatment side is measured. The thickness of the surface treatment layer (hard coat thickness) is typically derived by the following procedure. First, by using a PET substrate (manufactured by Toray Industries, trade name: U48-3, refractive index: 1.60) as a substrate film, the coating layer is dried at a heating temperature of 70 ° C. and UV-cured. Then, an optical laminate on which the hard coat layer is formed is obtained. A black acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., thickness: 2 mm) was adhered to the base 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 multi-photometry system (manufactured by Otsuka Electronics Co., Ltd., trade name: MCPD3700). Since the composition for forming a hard coat layer does not penetrate the PET base material 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: Miller Algorithm: FFT method Calculation wavelength: 450 nm to 850 nm
・ Detection conditions Exposure time: 20 ms
Lamp gain: Normal Number of times of accumulation: 10 times, FFT method Range of film thickness value: 2 to 15 μm
Film thickness resolution: 24 nm

The ratio is preferably from 18% to 30%, more preferably from 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 from the base film 10 toward the surface treatment layer 20 is measured by, for example, a prism coupler method. be able to. Specifically, the refractive index of the base film is R1, the refractive index of the surface treatment layer is R2, and a depth of 3.0 μm from the base film side toward the surface treatment layer measured by a prism coupler method. Assuming that the refractive index at the position is R3, the ratio X of the component of the acrylic resin eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the substrate film side toward the surface treatment layer X ( %) Is represented by the following equation.
X (%) = (R3-R2) × 100 / (R1-R2)
Accordingly, the optical laminate 100 has a refractive index R1 of the base film, a refractive index R2 of the surface treatment layer, and a refractive index R3 at a depth of 3.0 μm from the base film side toward the surface treatment layer. Preferably, the following inequality is satisfied.
R3 ≦ 0.18R1 + 0.82R2 (R1 <R2)
The thickness of the surface treatment layer is preferably 3 μm to 20 μm, and more preferably 5 μm to 15 μm. 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 type 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 the 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 antiglare layer, and an antireflection layer. In conventional optical laminates, scratches generated along the longitudinal direction by winding a long base film into a roll may become apparent by forming a surface treatment layer on the base film. Was. On the other hand, according to the optical laminate 100 of the present invention, the amount of the acrylic resin contained in the base film 10 eluted into the surface treatment layer 20 is sufficiently large. Thereby, it is possible to suppress the appearance of scratches on the base film 10 due to the formation of the surface treatment layer 20 on the base film 10. Further, the adhesion between the base film 10 and the surface treatment layer 20 can be improved.

B. Base film B-1. Characteristics of Base Film As described above, the base film contains an acrylic resin. In one embodiment, the substrate film includes an acrylic resin and core-shell particles dispersed in the acrylic resin. The thickness of the base film is preferably from 5 μm to 150 μm, more preferably from 10 μm to 100 μm. When a surface treatment layer described later is formed on the substrate film, the acrylic resin elutes into the surface treatment layer. When the acrylic resin is eluted into the surface treatment layer, the proportion of the component of the acrylic resin in the component constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer is 18% or more. Becomes

  The substrate film preferably has substantially optical isotropic properties. In the present specification, “having substantially optical isotropy” 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. It means 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 thickness direction retardation Rth (550) is more preferably -5 nm to +5 nm, further preferably -3 nm to +3 nm, and particularly preferably -2 nm to +2 nm. When Re (550) and Rth (550) of the base film are in such a range, when the optical laminate is applied to an image display device, adverse effects on display characteristics can be prevented. Re (550) is an in-plane retardation of the film measured at 23 ° C. with light having a wavelength of 550 nm. Re (550) is obtained by the formula: Re (550) = (nx−ny) × d. Rth (550) is a retardation in the thickness direction of the film measured at 23 ° C. with light having a wavelength of 550 nm. Rth (550) is obtained by the formula: Rth (550) = (nx−nz) × d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction), and ny is the direction perpendicular to the slow axis in the plane (ie, the fast axis direction). It is a 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 the substrate film of 40 μm, the better. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and further preferably 90% or more. If the light transmittance is in such a range, desired transparency can be secured. 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 better. Specifically, the haze is preferably at most 5%, more preferably at most 3%, further preferably at most 1.5%, particularly preferably at most 1%. 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 a polarizing plate on the viewing side of an image display device, the display content can be visually recognized well.

YI at a substrate film thickness of 40 μm 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 be insufficient. In addition, YI is calculated from tristimulus values (X, Y, Z) of colors obtained by measurement using, for example, a high-speed integrating sphere-type spectral transmittance measuring device (trade name: DOT-3C: manufactured by Murakami Color Research Laboratory). Can be obtained by the following equation.
YI = [(1.28X-1.06Z) / Y] × 100

  The b value (a measure of hue according to the Hunter's color system) at a thickness of the base film of 40 μm 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. The b value is determined, for example, by cutting a base film sample into a 3 cm square and measuring the hue using a high-speed integrating sphere-type spectral transmittance measurement device (trade name: DOT-3C: manufactured by Murakami Color Research Laboratory). It can be obtained by evaluating the hue according to the color system of Hunter.

Moisture permeability of the base film is preferably from 300g ^/ m 2 · 24hr or less, more preferably 250g ^/ m 2 · 24hr or less, more preferably 200g ^/ m 2 · 24hr or less, particularly preferably 150g ^/ m 2 · 24hr or less , Most preferably 100 g / m ² · 24 hr or less. When the moisture permeability of the base film is in such a range, a polarizing plate having excellent durability and moisture resistance can be obtained when used as a protective layer of a polarizer.

  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, 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, and still more preferably 5.0% or more. The upper limit of the 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, for example, according to ASTM-D-882-61T.

  The tensile modulus of the base film is preferably 0.5 GPa or more, more preferably 1 GPa or more, and further 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 exhibited. The tensile modulus can be measured, for example, according to ASTM-D-882-61T.

  The base film may contain any appropriate additive depending on the purpose. Specific examples of the additives include an ultraviolet absorber; an antioxidant such as a hindered phenol-based compound, a phosphorus-based compound, and a sulfur-based compound; a stabilizer such as a light stabilizer, a weather stabilizer, and a heat stabilizer; glass fiber, carbon fiber, and the like. Near-infrared absorber; Flame retardant such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic and nonionic surfactants; Inorganic pigments, organic pigments Organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; 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, addition amount and the like of the additives can be appropriately set according to the purpose.

B-2. Acrylic resin B-2-1. Configuration of Acrylic Resin As the acrylic resin, any appropriate acrylic resin can be adopted. The acrylic resin typically contains an alkyl (meth) acrylate as a main component as a monomer unit. In the present specification, “(meth) acryl” means acryl and / or methacryl. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include those having a linear or branched alkyl group having 1 to 18 carbon atoms. These can be used alone or in combination. Further, any appropriate copolymerizable monomer may be introduced into the acrylic resin by copolymerization. The type, number, copolymerization ratio and the like of such a copolymerized monomer can be appropriately set according to the purpose. The constituent components (monomer units) 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 a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit and a glutaric anhydride unit. The acrylic resin having a lactone ring unit is described in, for example, JP-A-2008-181078, and the description of the 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 each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ³ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, A cycloalkyl group having 3 to 12 carbon atoms or an aryl group having 6 to 10 carbon atoms. In the 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 the 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. Show. Examples of the substituent include a halogen and a hydroxyl group. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t- (meth) acrylate. Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid 3-hydroxypropyl, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate. In the general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Thus, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

The acrylic resin may include only a single glutarimide unit, or may include a plurality of glutarimide units having 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%, and particularly preferably 2 mol%. % To 35 mol%, most preferably 3 mol% to 30 mol%. If the content is less than 2 mol%, the effects (for example, high optical properties, high mechanical strength, excellent adhesiveness with a polarizer, and thinness) exhibited from the glutarimide unit are sufficiently exhibited. It may not be done. If the content exceeds 50 mol%, for example, heat resistance and transparency may be insufficient.

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

  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%, further preferably 60 mol% to 98 mol%, and particularly preferably. Is from 65 mol% to 98 mol%, most preferably from 70 mol% to 97 mol%. If the content is less than 50 mol%, the effects (for example, high heat resistance and high transparency) expressed from the alkyl (meth) acrylate unit may not be sufficiently exhibited. If the content is more than 98 mol%, the resin becomes brittle and easily cracked, so that high mechanical strength cannot be sufficiently exhibited and productivity may be poor.

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

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

  In one embodiment, the acrylic resin can contain a copolymerizable vinyl monomer unit (other vinyl monomer unit) 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, acrylic Aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, -Isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-meth Rusuchiren, p- glycidyl styrene, p- aminostyrene, 2-styryl - and oxazoline and the like. These may be used alone or in combination. Preferred are styrene monomers such as styrene and α-methylstyrene. The content ratio of the other vinyl monomer unit is preferably from 0 to 1% by weight, more preferably from 0 to 0.1% by weight. Within such a range, occurrence of an undesired retardation and reduction in transparency can be suppressed.

The imidation ratio in the acrylic resin is preferably 2.5% to 20.0%. When the imidation ratio is in such a range, a resin excellent in heat resistance, transparency, and moldability can be obtained, and generation of kogation and reduction in mechanical strength during film formation can be prevented. In the acrylic resin, the imidization ratio is represented by the ratio of glutarimide units to alkyl (meth) acrylate units. This ratio can be obtained, for example, from the NMR spectrum, IR spectrum, etc. of the acrylic resin. In the present embodiment, the imidation ratio can be determined by ¹ H-NMR measurement of the resin using ¹ H NMR 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 glutarimide N-CH ₃ around 3.0 to 3.3 ppm is defined as A. Assuming that the area of the peak derived from the proton is B, the peak area can be obtained by the following equation.
Imidation ratio Im (%) = {B / (A + B)} × 100

  The acrylic resin preferably has an acid value of 0.10 mmol / g to 0.50 mmol / g. When the acid value is within such a range, a resin having an excellent balance between heat resistance, mechanical properties, and moldability can be obtained. If the acid value is too small, there may be problems such as an increase in cost due to the use of a denaturing agent for adjusting the acid value to a desired value and generation of a gel-like substance due to the remaining denaturant. If the acid value is too large, foaming tends to occur during film formation (for example, during melt extrusion), and the productivity of molded products tends to decrease. In the acrylic resin, the acid value is the content of a carboxylic acid unit and a carboxylic anhydride unit in the acrylic resin. In the present embodiment, the acid value can be calculated, for example, by the titration method described in WO2005 / 054311 or JP-A-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, for example, gel permeation chromatography (GPC system, manufactured by Tosoh Corporation) in terms of polystyrene. In addition, 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 the Tg is 110 ° C. or higher, the polarizing plate including 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, further preferably 285 ° C. or lower, particularly preferably 200 ° C. or lower, and most preferably 160 ° C. or lower. If Tg is in such a range, the moldability may be excellent.

B-2-2. Polymerization of Acrylic Resin The acrylic resin can be produced, for example, by the following method. This method comprises: (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. And (II) treating the copolymer (a) with an imidizing agent to obtain a copolymer (a). An alkyl (meth) acrylate monomer unit and an unsaturated carboxylic acid monomer and / or a precursor monomer unit thereof are subjected to an intramolecular imidization reaction, and a glutarimide unit represented by the general formula (1) is used. Introducing into a 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. A preferred unsaturated carboxylic acid monomer is acrylic acid or methacrylic acid, and a preferred precursor monomer is acrylamide.

  As a method of treating the copolymer (a) with an imidizing agent, any appropriate method can be used. 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 this with an imidizing agent. In this case, any appropriate 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 appropriate batch-type reaction vessel (pressure vessel) can be used.

  As the imidizing agent, any appropriate compound can be used as long as the glutarimide unit represented by the general formula (1) can be generated. 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. Furthermore, a urea-based compound that generates such an amine by heating, for example, 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 the imidization, a ring-closure accelerator may be added, if necessary, in addition to the above imidizing agent.

  The amount of the imidizing agent used in the 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). It is. If the amount of the imidizing agent is less than 0.5 part by weight, the desired imidization ratio is often not achieved. As a result, the heat resistance of the obtained resin becomes extremely insufficient, and appearance defects such as kogation after molding may be induced. If the amount of the imidizing agent exceeds 10 parts by weight, the imidizing agent may remain in the resin, and may cause appearance defects such as kogation and foaming after molding by the imidizing agent.

  The production method of the present embodiment can include, if necessary, a treatment with an esterifying 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, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-N-butoxysilane , Dimethyl (trimethylsilane) phosphite, trimethyl phosphite Trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether. Among these, dimethyl carbonate is preferred from the viewpoint of cost and reactivity.

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

B-2-3. Combination of Other Resins In the embodiment of the present invention, the acrylic resin and other resins may be used in combination. That is, a monomer component constituting the acrylic resin and a monomer component constituting the other resin may be copolymerized, and the copolymer may be subjected to a film formation described later in Section B-4; May be used for film formation. Other resins, for example, styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, other thermoplastic resins such as polyetherimide, phenolic Thermosetting resins such as resins, melamine resins, polyester resins, silicone resins, and epoxy resins are exemplified. The type and amount of the resin used in combination can be appropriately set according to the purpose and the properties desired for the obtained film. For example, a styrene-based resin (preferably, an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

  When the acrylic resin and another resin are used in combination, 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. %, More preferably 70% to 100% by weight, particularly preferably 80% 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 3 to 50 parts by weight, more preferably 5 to 25 parts by weight, and still more preferably 7 parts by weight, based on 100 parts by weight of the acrylic resin. Parts to 15 parts by weight. Thereby, the elution of the acrylic resin forming the base film into the surface treatment layer is promoted, and as a result, on the base film, the uniformity of the acrylic resin and the composition constituting the surface treatment layer is high. A compatible layer may be formed. Thereby, the appearance of scratches on the base film due to the formation of the surface treatment layer on the base film can be suppressed. Further, the adhesion between the substrate film and the surface treatment layer can be improved.

  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 composed of a glassy polymer as an innermost layer or an intermediate layer.

  The Tg of the rubbery polymer constituting the core is preferably 20C or lower, more preferably -60C to 20C, and further preferably -60C to 10C. If the Tg of the rubbery polymer constituting the core exceeds 20 ° C., 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 further preferably 60 ° C. to 130 ° C. When the Tg of the glassy polymer constituting the coating layer is lower than 50 ° C., the heat resistance of the acrylic resin may be reduced.

  The content ratio of the core in the core-shell particles is preferably 30% by weight to 95% by weight, and more preferably 50% by weight to 90% by weight. The ratio 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 amount of the core. The content ratio of the coating layer in the core-shell 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 particles can be flattened by 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 even more preferably 5.0 or more. In the present specification, the “length / thickness ratio” means the ratio between the representative length of the core-shell type particle in plan view shape and the thickness. Here, the “representative length” refers to a diameter when the shape in plan view is circular, a long diameter 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 of 80 kV, RuO ₄ stained ultrathin section method), and long core-shell particles (cross section close to the representative length) among the core-shell type particles present in the obtained photograph were obtained. Is obtained in this order, and the ratio can be obtained by calculating (average length) / (average 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 constitutions, see, for example, JP-A-2016-33552. It is described in. The description in 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-mentioned acrylic resin (when using another resin, a blend with the other resin) and core-shell type particles. The composition can be formed by a method comprising film forming. Further, a method of forming a base film may include stretching the film.

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

  Any appropriate method can be adopted as a method of forming a film. Specific examples include cast coating (eg, casting), extrusion, injection molding, compression molding, transfer molding, blow molding, powder molding, FRP molding, calender molding, and hot pressing. Law. Preferably, it is an extrusion molding method or a cast coating method. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained. Particularly preferred is an extrusion molding method. This is because there is no need to consider the problem due to the residual solvent. Among them, the extrusion molding method using a T-die is preferable from the viewpoint of the productivity of the film and the easiness of the subsequent stretching treatment. The molding conditions can be appropriately set according to the composition and type of the resin used, the characteristics 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 is appropriately adjusted under appropriate stretching conditions, the elution of the acrylic resin to the surface treatment layer is promoted, and as a result, on the substrate film Thus, a highly uniform compatible layer of the acrylic resin and the composition constituting the surface treatment layer can be formed.

  As the stretching direction, an appropriate direction can be adopted depending on the purpose. Specifically, there are a length direction, a width direction, a thickness direction, and an oblique direction. The stretching direction may be unidirectional (uniaxial stretching), bidirectional (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 the width direction, and sequential biaxial stretching in the length direction and the width direction can be employed. Preferably, it is biaxial stretching (simultaneous or sequential). This is because it is easy to control the in-plane phase difference, and it is easy to realize optical isotropy.

  The stretching temperature is determined by the optical properties, mechanical properties and thickness desired for 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 can change according to 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. A specific stretching temperature is, for example, 110 ° C to 200 ° C, and preferably 120 ° C to 190 ° C. When the stretching temperature is within such a range, the dissolution of the acrylic resin into the surface treatment layer is promoted by appropriately adjusting the stretching ratio and the stretching speed, and as a result, the acrylic resin And a composition having high uniformity with the composition constituting the surface treatment layer.

  The stretching ratio is also the same as the stretching temperature, 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. It can change according to the speed and the like. When employing biaxial stretching, the ratio (TD / MD) of the stretching ratio in the width direction (TD) to the stretching ratio in the length direction (MD) is preferably 1.0 to 1.5, and more preferably. Is 1.0 to 1.4, more preferably 1.0 to 1.3. Further, the area magnification (the product of the stretching ratio in the length direction and the stretching ratio in the width direction) when employing biaxial stretching is preferably 2.0 to 6.0, and more preferably 3.0 to 6.0. It is 5.5, More preferably, it is 3.5-5.2. When the stretching ratio is in such a range, by appropriately adjusting the stretching temperature and the stretching speed, the dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, the acrylic resin And a composition having high uniformity with the composition constituting the surface treatment layer.

  The stretching speed is also the same as the stretching temperature, such as 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. It may change according to the magnification or the like. The stretching speed is preferably 3% / sec to 20% / sec, more preferably 3% / sec to 15% / sec, and still more preferably 3% / sec to 10% / sec. When employing biaxial stretching, the stretching speed in one direction and the stretching speed in another direction may be the same or different. If the stretching speed is in such a range, by appropriately adjusting the stretching temperature and the stretching ratio, the dissolution of the acrylic resin into the surface treatment layer is promoted, and as a result, the acrylic resin And a composition having high uniformity with the composition constituting the surface treatment layer.

  As described above, a base film can be formed.

C. Surface treatment layer The surface treatment layer is any appropriate 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, and an antireflection layer. The thickness of the surface treatment layer is preferably 3 μm to 20 μm, and more preferably 5 μm to 15 μm.

  The surface treatment layer is typically a cured layer of a resin composition formed on a base film. The step of forming a surface treatment layer includes applying a resin composition for forming a surface treatment layer on a base film to form a coating layer, and drying and curing the coating layer to form a surface treatment layer. May be included. Drying and curing the coating layer can include heating the coating layer.

  Any appropriate method can be adopted as a method for applying the resin composition. Examples include a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method, and a comma coating method. From the viewpoint of facilitating coating, the resin composition preferably contains a solvent for dilution.

  The heating temperature of the coating layer can be set to any appropriate temperature according to 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, 50C to 140C, and preferably 60C to 100C. By heating at such a heating temperature, an optical laminate having excellent adhesion between the substrate film and the surface treatment layer can be obtained.

C-1. Hard coat layer The hard coat layer is a layer that imparts abrasion resistance, chemical resistance, and the like to the surface of the base film. The hard coat layer has a hardness of preferably H or more, more preferably 3H or more in a pencil hardness test. The pencil hardness test can be measured according to JIS K5400. The resin composition for forming the hard coat layer may include, for example, a curable compound that can be cured by heat, light (such as ultraviolet rays), or an electron beam. Details of the hard coat layer and the resin composition for forming the hard coat layer are described in, for example, JP-A-2014-240955. This publication is incorporated herein by reference in its entirety.

C-2. Anti-glare layer The anti-glare layer is a layer for scattering and reflecting light to prevent reflection of external light. The resin composition for forming the anti-glare layer may include, for example, a curable compound that can be cured by heat, light (such as ultraviolet light), or an electron beam. The antiglare layer typically has fine irregularities on the surface. As a method of forming such fine irregularities, for example, a method of including fine particles in the curable compound can be mentioned. Details of the antiglare layer and the resin composition for forming the antiglare layer are described in, for example, JP-A-2017-32711. This publication is incorporated herein by reference in its entirety.

C-3. Anti-reflection layer The anti-reflection layer is a layer for preventing reflection of external light. The resin composition for forming the anti-reflection layer may include, for example, a curable compound that can be cured by heat, light (such as ultraviolet light), or electron beam. The anti-reflection layer may be a single layer composed of only one layer, or 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, JP-A-2012-155050. This publication is incorporated herein by reference in its entirety.

D. Polarizing plate The optical laminate described in the above items A to C can be applied to a polarizing plate. Therefore, the present invention also includes a polarizing plate using such an optical laminate. Typically, the polarizing plate has a polarizer and the optical laminate of the present invention disposed on one side of the polarizer. The optical laminate is bonded to the polarizer on the base film side, and can function as a protective layer of the polarizer.

  Any appropriate polarizer can be adopted as the polarizer. 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 the polarizer composed of a single-layer resin film include hydrophilic polymer films such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. And polyene-based oriented films such as those subjected to a dyeing treatment and a stretching treatment with a dichroic substance such as iodine or a dichroic dye, and a dehydration treatment of PVA and a dehydrochlorination treatment of polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because of its excellent optical properties.

  The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye after extending | stretching. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only can the dirt and the antiblocking agent on the surface of the PVA-based film be washed, but also the swelling of the PVA-based film causes uneven dyeing and the like. Can be prevented.

  Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base and a PVA-based resin layer (PVA-based resin film) laminated on the resin base, or a resin base and the resin A polarizer obtained by using a laminate with a PVA-based resin layer applied and formed on a substrate is exemplified. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer applied and formed on the resin base material is, for example, a PVA-based resin solution applied to a resin base material and dried to form a resin base material. Forming a PVA-based resin layer thereon to obtain a laminate of a resin base material and a PVA-based resin layer; stretching and dyeing the laminate to form a PVA-based resin layer as a polarizer; obtain. In the present embodiment, the stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, the stretching may optionally further include stretching the laminate in air at a high temperature (for example, 95 ° C. or higher) before stretching in a boric acid aqueous solution. The obtained resin substrate / polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer of the polarizer), and the resin substrate is separated from the resin substrate / polarizer laminate. Then, any appropriate protective layer depending on the purpose may be laminated on the release surface. Details of such a method for producing a polarizer are described in, for example, JP-A-2012-73580. This publication is incorporated herein by reference in its entirety.

  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, more preferably 3 μm to 25 μm.

E. FIG. Image display device The polarizing plate described in the above section 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 employs a configuration well known in the industry, a detailed description is omitted.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. The measuring method of each characteristic is as follows. Unless otherwise specified, “parts” and “%” in Examples are on a weight basis.
(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 optical refractive index / thickness measuring device prism coupler (Metricon 2010 / M). The proportions of the resin components were measured. The measurement of the refractive index using the prism coupler was performed under the following conditions.
・ Measurement conditions Light source: 594 nm
Mode: TE
Scan: 300 to -300
(1-1) Refractive index R1 of 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 surface treatment layer
Measurement type: Single Film (Prism Couple)
Except that a PET substrate (manufactured by Toray Industries, trade name: U48-3, refractive index: 1.60) was used as the substrate film, and the heating temperature of the coating layer was 60 ° C., the same as in each example, A laminate having the same thickness as in each example was obtained. A plurality of modes were detected by measuring the laminate in the Single Film mode. 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 (Prism 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 determined by the method using the prism coupler.
A plurality of modes were detected by measuring the optical laminate, and a change in the refractive index in the depth direction was calculated by Index gradient analysis. The “position at a depth of 3.0 μm” in the direction of the surface treatment layer from the base film side was determined based on the following equation, and the obtained refractive index was defined as R3.
“Position at 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) The ratio X of the component of the acrylic resin eluted into 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
From the following formula, the ratio X (%) of the component of the acrylic resin eluted into the surface treatment layer among the components constituting the position at a depth of 3.0 μm from the base film side to the surface treatment layer was calculated. .
X (%) = (R3-R2) × 100 / (R1-R2)
(2) Appearance evaluation The optical laminates obtained in the examples and comparative examples were visually inspected for the presence or absence of appearance defects (appearance defects due to scratches formed on the base film), and evaluated by the following indices.
：: Scar marks are visually observed ×: Scar marks are not visually observed (3) Adhesion evaluation The adhesion of the surface treatment layer to the substrate film was measured by a JIS K-5400 cross-cut peel test (number of crosses: 100). And evaluated according to the following indices.
〇: Number of cross-cut strips is 0 ×: Number of cross-cut strips is 1 or more

<Example 1>
1. Preparation of Base Film MS resin (MS-200; a copolymer of methyl methacrylate / styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine (imidation 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, R ² is a hydrogen atom), and a general formula (2) ( It had a (meth) acrylate unit (R ⁴ and R ⁵ are methyl groups) and a styrene unit. The imidization was carried out using a mesh-type co-rotating twin-screw extruder having a diameter of 15 mm. The set temperature of each temperature control zone of the extruder was 230 ° C., the screw rotation speed was 150 rpm, the MS resin was supplied at 2.0 kg / hr, and the supply amount of monomethylamine was 2 parts by weight with respect to 100 parts by weight of the MS resin. did. After charging the MS resin from the hopper and melting and filling the resin with the kneading block, monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. The by-product after the reaction and excess methylamine were devolatilized by reducing the pressure at the vent port to -0.08 MPa. The resin that came out as a strand from a die provided at the extruder outlet was cooled in a water tank and then pelletized by a pelletizer. The imidation 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 obtained above and 5 parts by weight of core-shell type particles were charged into a single screw extruder, melt-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 length and width directions at a stretching temperature of 140 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
Thus, a base film A having a thickness of 30 μm was produced.
2. Preparation of Optical Laminate On one side of the base film A, 16 parts by weight of a UV curable resin (4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd.), NK Oligo UA-53H) so that the thickness after curing becomes 6 μm. -80BK (Shin-Nakamura Chemical Co., Ltd.) 32 parts by weight, VISCOAT # 300 (Osaka Organic Chemicals Co., Ltd.) 48 parts by weight, A-GLY-9E (Shin-Nakamura Chemical Co., Ltd.) 4 parts by weight, IRGACURE907 2.4 parts by weight (manufactured by BASF) were 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 cured by UV 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 subjected to each evaluation. Table 1 shows the results.

<Example 2>
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 particles was 10 parts by weight and the stretching temperature of the extruded film was 150 ° C.
2. Production of Optical Laminate An optical laminate 2 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Example 3>
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 particles was 10 parts by weight and the stretching temperature of the extruded film was 160 ° C.
2. Production of Optical Laminate An optical laminate 3 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Example 4>
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 particles was 13 parts by weight and the stretching temperature of the extruded film was 152 ° C.
2. Production of Optical Laminate An optical laminate 4 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Example 5>
1. Preparation of base film 100 parts by weight of the imidized MS resin obtained above and 15 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. Was. The obtained extruded film was simultaneously biaxially stretched twice in the length and width directions at a stretching temperature of 152 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
Thus, a base film E having a thickness of 40 μm was produced.
2. Production of Optical Laminate An optical laminate 5 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Example 6>
1. Preparation of Base Film A base film F was prepared in the same manner as in Example 1 except that the blending amount of the core-shell particles was 23 parts by weight and the stretching temperature of the extruded film was 137 ° C.
2. Production of Optical Laminate An 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. Table 1 shows the results.

<Example 7>
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. Was. The obtained extruded film was simultaneously biaxially stretched twice in the length and width directions at a stretching temperature of 152 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
Thus, a base film G having a thickness of 20 μm was produced.
2. Production of Optical Laminate An 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. Table 1 shows the results.

<Example 8>
1. Preparation of Base Film A base film H was prepared in the same manner as in Example 1 except that the blending amount of the core-shell particles was 10 parts by weight and the stretching temperature of the extruded film was 160 ° C.
2. Preparation of Optical Laminate An optical laminate in which a hard coat layer was formed on one side of the base film H in the same manner as in Example 1 except that the thickness of the base film H after drying was 15 μm. 8 was obtained. The optical laminate 8 was subjected to each evaluation. Table 1 shows the results.

<Comparative Example 1>
1. Production of Base Film The imidized MS resin obtained above was charged into a single screw extruder, melt-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 length direction and the width direction at a stretching temperature of 130 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
Thus, a base film I having a thickness of 40 μm was produced.
2. Production of Optical Laminate An optical laminate 9 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Comparative Example 2>
1. Preparation of Base Film A base film J was prepared in the same manner as in Example 1 except that the core-shell type particles were not blended.
2. Production of Optical Laminate An optical laminate 10 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

<Comparative Example 3>
1. Preparation of Base Film A base film K 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 160 ° C.
2. Production of Optical Laminate An optical laminate 11 having a hard coat layer 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 subjected to each evaluation. Table 1 shows the results.

  As is clear from Table 1, the proportion of the acrylic resin component eluted in the surface treatment layer out of the components constituting the position at a depth of 3.0 μm from the base film side toward the surface treatment layer was 18%. The optical laminates of Examples 1 to 8 using the above base films were excellent in appearance and adhesion.

  The optical laminate of the present invention is suitably used as a protective layer of a polarizer. The polarizing plate having the optical laminate of the present invention as a protective layer is suitably used for an image display device. The image display devices as described above include mobile devices such as personal digital assistants (PDAs), smartphones, mobile phones, watches, digital cameras, and portable game machines; OA devices such as personal computer monitors, notebook computers, and copiers; Home electric appliances such as televisions and microwave ovens; on-board equipment such as back monitors, car navigation system monitors, car audios; display equipment such as digital signage and commercial store information monitors; security equipment such as monitoring monitors; It can be used for various applications such as care / medical equipment such as care monitors and medical monitors.

Reference Signs List 10 base film 20 surface treatment layer 100 optical laminate

Claims (10)

A base film containing an acrylic resin, and a surface treatment layer formed on one side of the base film,
The ratio of the component of the acrylic resin eluted into the surface treatment layer among components constituting a position at a depth of 3.0 μm in the direction of the surface treatment layer from the base film side is 18% or more. Laminate. The refractive index of the base film was R1, the refractive index of the surface treatment layer was R2, and the refractive index at a depth of 3.0 μm from the base film side in the direction of the surface treatment layer was R3. When
R3 ≦ 0.18R1 + 0.82R2 (however, R1 <R2)
The optical laminate according to claim 1, which satisfies the following.   The optical laminate according to claim 1, wherein the thickness of the surface treatment layer is 3 μm to 20 μm.   The optical laminate according to any one of claims 1 to 3, wherein the base film includes the acrylic resin and core-shell particles dispersed in the acrylic resin.   The optical laminate according to claim 4, wherein the base film contains 3 to 50 parts by weight of the core-shell type particles based on 100 parts by weight of the acrylic resin.   The acrylic resin according to any one of claims 1 to 5, 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 6, wherein the surface treatment layer is a cured layer of a resin applied on the base film.   The optical laminate according to any one of claims 1 to 7, 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. Including 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 8. An image display device comprising the polarizing plate according to claim 9.

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