JP2022009348A - Method for manufacturing polarizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizer with less scratches on the surface by a simple structure.

SOLUTION: The method for manufacturing a polarizer according to an embodiment of the present invention includes the steps of: forming a composition including an acrylic resin and core shell-type particles into a film; and forming a protective film by biaxially elongating the film at an elongation temperature of at least 140°C. In the step of the biaxial elongation of the film, a part of the core shell-type particles is exposed to the surface of the protective film and/or a part of the core shell-type particles is located in the surface of the protective film while being covered with the acrylic resin so that protrusions and recesses are formed in the surface of the protective film.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a method for manufacturing a polarizing plate.

In an image display device (for example, a liquid crystal display device or an organic EL display device), a polarizing plate is often arranged on at least one side of a display cell due to the image forming method. A typical polarizing plate includes a polarizing element and a protective film arranged on one side or both sides of the polarizing element. In recent years, for the purpose of improving durability, it has been proposed to use a protective film made of a (meth) acrylic resin film containing a crosslinked elastic body (Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-218478

In recent years, with the demand for thinner image display devices, it has become necessary to arrange each optical member constituting the image display device in close proximity to each other. As a result, the polarizing plate may come into contact with an optical member such as a diffusion sheet arranged adjacent to the polarizing plate, so that the protective film of the polarizing plate may be scratched. To solve such a problem, it has been conventionally proposed to suppress scratches on the protective film by forming a hard coat layer or a diffusion layer on the surface of the polarizing plate. However, these methods may have a problem that productivity may be lowered and cost is high due to an increase in manufacturing processes.

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a polarizing plate in which surface scratches are suppressed by a simple configuration and an image display device including the above-mentioned polarizing plate. be.

The method for producing a polarizing plate of the present invention is a method for producing a polarizing plate having a polarizing element and a protective film arranged on at least one side of the polarizing element, wherein an acrylic resin and a core-shell type particle are used. It comprises a step of forming a film of the composition containing; and a step of biaxially stretching the film at a stretching temperature of 140 ° C. or higher to form a protective film. In the step of biaxially stretching the film, a part of the core-shell type particles is exposed on the surface of the protective film and / or a part of the core-shell type particles is covered with an acrylic resin on the surface of the protective film. Position and form irregularities on the surface of the protective film.
In one embodiment, the arithmetic average roughness Ra of the protective film is 6.0 nm or more.
In one embodiment, the stretching temperature is 160 ° C. or higher.
In one embodiment, the arithmetic average roughness Ra of the protective film is 12.37 nm or more.
In one embodiment, in the step of biaxially stretching the film, the ratio (TD / MD) of the stretch ratio in the width direction (TD) of the film and the stretch ratio in the length direction (MD) of the film. However, it is 1.0 to 1.5.
In one embodiment, in the step of biaxially stretching the film, the product of the stretch ratio in the length direction of the film and the stretch ratio in the width direction of the film is 2.0 to 6.0. ..
In one embodiment, in the step of biaxially stretching the film, the stretching speed in one stretching direction is 3% / sec to 20% / sec.

According to the present invention, it is possible to provide an image display device including a polarizing plate in which surface scratches are suppressed by a simple configuration and the above-mentioned polarizing plate.

It is sectional drawing of the polarizing plate by one Embodiment of this invention. It is sectional drawing of the polarizing plate by another 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 Polarizing Plate FIG. 1 is a cross-sectional view of the polarizing plate according to one embodiment of the present invention. The polarizing plate 10 has a polarizing element 1 and a protective film 2 arranged on one side of the polarizing element 1. The protective film 2 contains an acrylic resin and core-shell type particles dispersed in the acrylic resin. The arithmetic average roughness Ra of the surface of the protective film 2 is 6.0 nm or more. Preferably, unevenness due to the core-shell type particles is formed on the surface of the protective film 2 on the opposite side of the polarizing element 1. The protective film 2 preferably contains 3 parts by weight to 50 parts by weight of core-shell type particles with respect to 100 parts by weight of the acrylic resin. 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 protective film 2 is preferably a biaxially stretched film. In one embodiment, the polarizing plate 10 does not have a diffusion layer on the surface of the protective film 2. Even when the polarizing plate of the present invention is incorporated in an image display device and comes into contact with another optical member such as a diffusion sheet, it is possible to suppress the occurrence of scratches due to friction with the other optical member.

FIG. 2 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. The polarizing plate 11 includes a polarizing element 1, a protective film 2 (first protective film) arranged on one side of the polarizing element 1, and a second protective film 3 arranged on the other side of the polarizing element 1. And have. The second protective film 3 may be a film formed of the same material as the first protective film 2, or may be a film formed of another material. The polarizing plate 11 may have any suitable optical functional film according to the purpose and application instead of the second protective film 3.

The polarizing plate 10 and the polarizing plate 11 may have a single-wafer shape or a long shape. Further, the polarizing plate 10 may have an adhesive layer (not shown) on the surface of the polarizing element 1, and the polarizing plate 11 may have an adhesive layer (not shown) on the surface of the second protective film 3. (Not shown) may be possessed.

B. Polarizer As the splitter, any suitable splitter can 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 polarizing element 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 it. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer a stator. 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 1 μm to 15 μm, more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

C. Protective film C-1. Characteristics of Protective Film As described above, the protective film contains an acrylic resin and core-shell type particles dispersed in the acrylic resin, and the arithmetic mean roughness Ra of the surface of the protective film is 6.0 nm or more. The arithmetic average roughness Ra is preferably 6 nm to 50 nm, more preferably 6 nm to 40 nm. By setting the arithmetic average roughness Ra to a value within the above range, it is possible to prevent the surface of the protective film from becoming too slippery, and as a result, winding when the protective film (and the polarizing plate) is lengthened. The deviation can be suppressed. The arithmetic average roughness Ra can be adjusted within a desired range depending on the content of core-shell type particles in the protective film, stretching conditions in the method for producing the protective film described later, and the like. The thickness of the protective film is preferably 5 μm to 150 μm, more preferably 10 μm to 100 μm.

The protective 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 protective film are in such a range, it is possible to prevent an adverse effect on the display characteristics when the polarizing plate 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 in-plane refractive index is maximized (that is, the slow-phase axis direction), and ny is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advancing 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 in the protective film having a thickness of 80 μm, 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 protective 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 polarizing plate on the visual recognition side of the image display device is used, the displayed contents can be visually recognized satisfactorily.

The YI at a thickness of 80 μm of the protective 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 machine (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 80 μm of the protective 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 protective 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 protective 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 protective film is within such a range, a polarizing plate having excellent durability and moisture resistance can be obtained.

The tensile strength of the protective 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 protective 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 protective 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 elastic 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 protective film may contain any suitable additive depending on the purpose. Specific examples of the additive include ultraviolet absorbers; antioxidants such as hindered phenol-based, phosphorus-based and sulfur-based; 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) phosphates, triallyl phosphates, antimony oxides; Antistatic agents such as anionic, cationic and nonionic surfactants; Inorganic pigments and 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, addition amount, etc. of the additive can be appropriately set according to the purpose.

In one embodiment, the second protective film can be made of the same material as the first protective film. In another embodiment, the second protective film may be made of a different material than the first protective film. When the second protective film is formed of a material different from that of the first protective film, the material for forming the second protective film may be, for example, an acrylic resin containing no core-shell type particles, diacetyl cellulose, or triacetyl cellulose. Examples thereof include cellulose-based resins such as, cycloolefin-based resins, olefin-based resins such as polypropylene, ester-based resins such as polyethylene terephthalate-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. The thickness of the second protective film is preferably 10 μm to 100 μm.

C-2. Acrylic resin C-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) acrylates 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 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%, 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, methacrylonitrile, etacrylonitrile, allylglycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, and acrylic. Aminoethyl acid 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, it is possible to suppress the appearance of an undesired phase difference and the decrease in transparency.

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 of 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 protective 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, moldability can be excellent.

C-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 monomer 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, methyl toluene sulfonate, and methyl trifluoromethane sulfonate. 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.

C-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 the other resin may be copolymerized, and the copolymer may be subjected to the film formation described later in Section D; the acrylic resin and the other resin. The blend with 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 desired characteristics of 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.

C-3. Core-shell type particles In the protective film, the core-shell type particles are preferably blended in an amount of 3 parts by weight to 50 parts by weight, more preferably 3 parts by weight to 40 parts by weight, based on 100 parts by weight of the acrylic resin. Thereby, the arithmetic average roughness Ra of the surface of the protective film can be adjusted within a desired range. The core-shell type particles may form irregularities on the surface of the protective film by partially exposing the surface of the protective film, or the core-shell type particles may be formed without being exposed on the surface of the protective film (in a state of being covered with an acrylic resin). ) The surface of the protective film may be uneven.

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 C-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 an ellipse, 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 among the core-shell type particles present in the obtained photograph, the long one (cross section close to the representative length). The ratio can be obtained by extracting 30 particles in order from those obtained) and 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 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.

C-4. Formation of Protective Film The protective film according to the embodiment of the present invention is typically a composition containing the above acrylic resin (in the case of using other resins in combination, a blend with the other resins) and core-shell type particles. Can be formed by a method comprising forming a film. Further, the method of forming the protective 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. With such an average particle size, the arithmetic average roughness Ra of the surface of the obtained protective film can be adjusted within a desired range. 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 a 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 core-shell type particles move (bleed) to the surface of the film, and as a result, the surface of the film becomes uneven. Is formed, and the arithmetic mean roughness Ra of the surface of the obtained protective film can be adjusted within the above desired range.

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 optical properties, mechanical properties and thickness desired for the protective 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 speed. And so on. 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 protective 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 in such a range, the core-shell type particles bleed on the surface of the film by appropriately adjusting the stretching ratio and the stretching speed, and the arithmetic average roughness Ra of the surface of the obtained protective film is obtained as desired. Can be adjusted within the range of.

The draw ratio, as well as the draw temperature, is the arithmetic mean roughness Ra of the surface desired for the protective film, the optical properties, the mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretch. It may vary depending on the method (uniaxial stretching or biaxial stretching), stretching temperature, stretching 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, the surface magnification (product of the stretching ratio in the length direction and the stretching ratio in the width direction) in the case of adopting biaxial stretching 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 in such a range, the core-shell type particles bleed on the surface of the film by appropriately adjusting the stretching temperature and the stretching speed, and the arithmetic average roughness Ra of the surface of the obtained protective film is desired. Can be adjusted within the range of.

The stretching speed, as well as the stretching temperature, is the arithmetic mean roughness Ra of the surface desired for the protective film, optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, stretching. It may vary depending on the method (uniaxial stretching or biaxial stretching), stretching temperature, stretching ratio, 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 in such a range, the core-shell type particles bleed on the surface of the film by appropriately adjusting the stretching temperature and the stretching ratio, and the arithmetic average roughness Ra of the surface of the obtained protective film can be obtained. Can be adjusted within the range of.

As described above, the protective film can be formed.

D. Image display device The polarizing plate according to the above items A to C 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. The image display device typically includes a display cell, a polarizing plate, a diffusion sheet, and a light source (backlight) in this order, and a protective film for the polarizing plate is arranged facing the diffusion sheet.

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) Thickness Measured using a digital micrometer (manufactured by Anritsu, product name "KC-351C").
(2) Arithmetic mean roughness Ra on the surface of the protective film
The arithmetic mean roughness Ra was measured using an optical profile meter (manufactured by Veeco Instruments, trade name "Optical Profiler NT3300").
(3) Scratch evaluation Glass plate (MICRO SLIDE GLASS Pre-cleared water green polish t1.3 (manufactured by MATSUNAMI), product model number "S200243", size: 65 mm x 165 mm, Tickness 1.2 to 1.5 mm), 50 mm x The above-mentioned polarizing plate cut to a size of 1500 mm was bonded to each other via an adhesive layer to prepare a laminated body of a glass plate and a polarizing plate. The laminated body simulates the configuration of the liquid crystal panel.
A diffusion sheet (manufactured by Sumitomo 3M Ltd., product name "DBEF-D2-400") is placed in the tray, and the laminate is placed on the diffusion sheet with the polarizing plate side side down. did. Next, the tray was shaken under the condition of 200 times / min × 10 min. Then, the laminate was taken out, and the presence or absence of wear scratches (lumps of scratches) on the first protective film of the polarizing plate was visually confirmed.

<Example 1>
(Manufacturing of polarizing plate)
1. 1. Preparation of protective 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.
100 parts by weight of the imidized MS resin obtained above and 10 parts by weight of core-shell type particles were put into a single-screw extruder, melt-mixed, and formed into a film through a T-die to obtain an extruded film having a thickness of 40 μm. .. The obtained extruded film was simultaneously biaxially stretched twice in the length direction and the width direction at a stretching temperature of 160 ° C. The stretching speed was 10% / sec in both the length direction and the width direction.
In this way, a protective film was produced. The thickness of the obtained protective film was 10 μm, the arithmetic surface roughness Ra was 22.18 nm, the in-plane retardation Re (550) was 2 nm, and the thickness direction retardation Rth (550) was 2 nm.
2. 2. Fabrication of Polarizer A long roll of polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000") with a thickness of 30 μm is uniaxially oriented in the longitudinal direction so as to be 5.9 times in the longitudinal direction by a roll stretching machine. While stretching, swelling, dyeing, cross-linking, and washing treatment were performed at the same time, and finally drying treatment was performed to prepare a polarizing element having a thickness of 12 μm.
Specifically, the swelling treatment was carried out by stretching 2.2 times while treating with pure water at 20 ° C. Next, the dyeing treatment was carried out in an aqueous solution at 30 ° C. in which the weight ratio of iodine and potassium iodide was adjusted so that the simple substance transmittance of the obtained polarizing element was 45.0% and the weight ratio was 1: 7. However, it was stretched 1.4 times. Further, the cross-linking treatment adopted a two-step cross-linking treatment, and the first-step cross-linking treatment was carried out 1.2 times while being treated with an aqueous solution in which boric acid and potassium iodide were dissolved at 40 ° C. The boric acid content of the aqueous solution of the first-step crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The second-step cross-linking treatment was carried out by stretching 1.6 times while treating with an aqueous solution in which boric acid and potassium iodide were dissolved at 65 ° C. The boric acid content of the aqueous solution of the second-step crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. The washing treatment was carried out with an aqueous potassium iodide solution at 20 ° C. The potassium iodide content of the aqueous solution of the washing treatment was set to 2.6% by weight. Finally, the drying treatment was carried out at 70 ° C. for 5 minutes to obtain a stator.
3. 3. Fabrication of polarizing plate (second protective film)
The protective film obtained above as the first protective film is attached to one surface of the polarizing element via a polyvinyl alcohol-based adhesive, and the polyvinyl alcohol-based adhesive is applied to the other surface of the polarizing element. A TAC film (manufactured by Dainippon Printing Co., Ltd., trade name "DSG-03", thickness 70 μm) was bonded as a second protective film.
(Adhesive layer)
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 94.9 parts of butyl acrylate, 5 parts of acrylate, 0.1 part of 2-hydroxyethyl acrylate, and dibenzoyl peroxide were added. To 100 parts of the total monomer (solid content), 0.3 part was added together with ethyl acetate, and the mixture was reacted at 60 ° C. for 7 hours under a nitrogen gas stream, and then ethyl acetate was added to the reaction solution, and the weight average molecular weight was increased. A solution containing an acrylic polymer (B) having a dispersion ratio of 2.2 million and a dispersion ratio of 3.9 was obtained (solid content concentration: 30%). 0.6 parts of trimethylolpropane tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd .: Coronate L) and 0.075 parts of γ- per 100 parts of the solid content of the solution containing the acrylic polymer (B). A solution of the pressure-sensitive adhesive was obtained by blending glycidoxypropylmethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-403). The above solution was diluted with ethyl acetate so that the solid content concentration became 15% to prepare a pressure-sensitive adhesive coating solution. The pressure-sensitive adhesive coating solution prepared above is applied to one side of a 38 μm polyethylene terephthalate (PET) film (MRF38, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) that has been treated with silicone to achieve a coating thickness of 134.0 μm. As described above, the coating was applied using a fountain die coater. Then, it was dried at 155 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 20 μm. The pressure-sensitive adhesive layer was transferred to the surface of the TAC film to prepare a polarizing plate (with a pressure-sensitive adhesive layer). The obtained polarizing plate was subjected to the above evaluation. The results are shown in Table 1.

<Example 2>
An extruded film having a thickness of 80 μm was formed, and a protective film was prepared in the same manner as in Example 1 except that the extruded film was used. The thickness of the obtained protective film was 20 μm, and the arithmetic mean roughness Ra was 12.37 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 3>
An extruded film having a thickness of 160 μm was formed, and a protective film was prepared in the same manner as in Example 1 except that the extruded film was used. The thickness of the obtained protective film was 40 μm, and the arithmetic mean roughness Ra was 6.48 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 4>
An extruded film having a thickness of 120 μm was formed, and a protective film was prepared in the same manner as in Example 1 except that the extruded film was used. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 8.17 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 5>
An extruded film was formed by charging 100 parts by weight of the imidized MS resin and 3 parts by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 4 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 6.11 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 6>
An extruded film was formed by putting 100 parts by weight of the imidized MS resin and 5 parts by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 4 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 30 μm, and the arithmetic mean roughness Ra was 6.79 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 7>
An extruded film was formed by charging 100 parts by weight of the imidized MS resin and 20 parts by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 4 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 23.45 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 8>
An extruded film was formed by charging 100 parts by weight of the imidized MS resin and 30 parts by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 4 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 31.37 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 9>
An extruded film was formed by charging 100 parts by weight of the imidized MS resin and 40 parts by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 4 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 32.79 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 10>
A protective film was prepared in the same manner as in Example 4 except that the obtained extruded film was stretched at a stretching temperature of 140 ° C. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 8.06 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 11>
A protective film was prepared in the same manner as in Example 4 except that the obtained extruded film was stretched at a stretching temperature of 130 ° C. The thickness of the obtained protective film was 30 μm, and the arithmetic mean roughness Ra was 6.72 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 12>
A protective film was prepared in the same manner as in Example 4 except that the obtained extruded film was stretched at a stretching temperature of 170 ° C. The thickness of the obtained protective film was 30 μm, and the arithmetic mean roughness Ra was 15.76 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Example 13>
A protective film was prepared in the same manner as in Example 4 except that the obtained extruded film was stretched at a stretching temperature of 180 ° C. The thickness of the obtained protective film was 30 μm, and the arithmetic average roughness Ra was 17.29 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
An extruded film was formed by charging only the imidized MS resin into a single-screw extruder and melt-mixing the extruded film, and the obtained extruded film was stretched at a stretching temperature of 145 ° C. It was created. The thickness of the obtained protective film was 40 μm, and the arithmetic average roughness Ra was 4.2 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 2>
An extruded film was formed by charging 100 parts by weight of the imidized MS resin and 1 part by weight of the core-shell type particles into a single-screw extruder and melt-mixing them, and the same as in Example 3 except that this extruded film was used. I made a protective film. The thickness of the obtained protective film was 40 μm, and the arithmetic average roughness Ra was 4.93 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 3>
Extruded film was formed by putting 100 parts by weight of imidized MS resin and 5 parts by weight of core-shell type particles into a single-screw extruder and melt-mixing them, and the obtained extruded film was stretched at a stretching temperature of 100 ° C. Made a protective film in the same manner as in Example 3. The thickness of the obtained protective film was 40 μm, and the arithmetic mean roughness Ra was 5.14 nm. A polarizing plate was produced in the same manner as in Example 1 except that the protective film was used. The above polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

As is clear from Table 1, the polarizing plates of Comparative Examples 1 to 3 were damaged by being shaken in contact with the diffusion sheet, but the polarizing plates of Examples 1 to 13 were the diffusion sheets. No wear scratches occurred even when shaken in contact with.

The polarizing plate of the present invention is suitably used for an image display device. The image display device of the present invention is a portable device such as a portable information terminal (PDA), a smartphone, a mobile phone, a clock, a digital camera, a portable game machine; an OA device such as a personal computer monitor, a laptop computer, a copy machine; a video camera, a television. , Home electrical equipment such as microwave ovens; In-vehicle equipment such as back monitors, car navigation system monitors, car audio; Exhibition equipment such as digital signage and information monitors for commercial stores; Security equipment such as monitoring monitors; Nursing care It can be used for various purposes such as nursing / medical equipment such as monitors and medical monitors.

1 Polarizer 2 Protective film 3 Second protective film 10 Polarizing plate 11 Polarizing plate

Claims (7)

A method for manufacturing a polarizing plate having a polarizing element and a protective film arranged on at least one side of the polarizing element.
A process of forming a film of a composition containing an acrylic resin and core-shell type particles,
A step of biaxially stretching the film at a stretching temperature of 140 ° C. or higher to form the protective film, and the like.
In the step of biaxially stretching the film, a part of the core-shell type particles is exposed on the surface of the protective film, and / or the part of the core-shell type particles is covered with the acrylic resin. A method for manufacturing a polarizing plate, which is located on the surface of a protective film and forms irregularities on the surface of the protective film. The method for manufacturing a polarizing plate according to claim 1, wherein the arithmetic average roughness Ra of the protective film is 6.0 nm or more. The method for producing a polarizing plate according to claim 1 or 2, wherein the stretching temperature is 160 ° C. or higher. The method for manufacturing a polarizing plate according to claim 3, wherein the arithmetic average roughness Ra of the protective film is 12.37 nm or more. In the step of biaxially stretching the film, the ratio (TD / MD) of the stretching ratio in the width direction (TD) of the film and the stretching ratio in the length direction (MD) of the film is 1.0 to 1. The method for manufacturing a polarizing plate according to any one of claims 1 to 4, which is 5. 13. The method for manufacturing a polarizing plate according to any one. The method for producing a polarizing plate according to any one of claims 1 to 6, wherein in the step of biaxially stretching the film, the stretching speed in one stretching direction is 3% / sec to 20% / sec.

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