JP7182854B2 - Polarizing plate and image display device - Google Patents

Description

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

Due to the image forming method of an image display device (for example, a liquid crystal display device or an organic EL display device), in many cases, a polarizing plate is arranged on at least one side of the display cell. A typical polarizing plate includes a polarizer and protective films disposed on one side or both sides of the polarizer. 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).

JP 2016-218478 A

2. Description of the Related Art In recent years, along with the demand for thinner image display devices, it has become necessary to arrange each optical member forming the image display device close to each other. As a result, the protective film of the polarizing plate may be damaged when the polarizing plate comes into contact with an optical member such as a diffusion sheet placed adjacent to the polarizing plate. In order to address such problems, 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, with these methods, the increase in the number of manufacturing steps may reduce productivity and increase costs.

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate in which scratches on the surface are suppressed by a simple structure, and an image display device equipped with the polarizing plate. be.

The polarizing plate of the present invention has a polarizer and a protective film disposed on at least one side of the polarizer, wherein the protective film is an acrylic resin and a core-shell type polarizer dispersed in the acrylic resin. The surface of the protective film has an arithmetic mean roughness Ra of 6.0 nm or more.
In one embodiment, the acrylic resin has at least one selected from the group consisting of glutarimide units, lactone ring units, maleic anhydride units, maleimide units and glutaric anhydride units.
In one embodiment, unevenness is formed by the core-shell particles on the surface of the protective film opposite to the polarizer.
In one embodiment, the protective film contains 3 to 50 parts by weight of the core-shell type particles with respect to 100 parts by weight of the acrylic resin.
In one embodiment, the core-shell particles have a core made of a rubber-like polymer and a coating layer made of a glass-like polymer and covering the core.
In one embodiment, the protective film is a biaxially stretched film.
In one embodiment, the surface of the protective film does not have a diffusion layer.
According to another aspect of the present invention, an image display device is provided. This image display device includes a display cell, the polarizing plate, a diffusion sheet, and a light source in this order, and the protective film of the polarizing plate is arranged to face the diffusion sheet.

ADVANTAGE OF THE INVENTION According to this invention, the image display apparatus provided with the polarizing plate and the said polarizing plate which the damage|wound of the surface was suppressed by simple structure can be provided.

1 is a cross-sectional view of a polarizer according to one embodiment of the invention; FIG. FIG. 4 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention;

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

A. Overall Configuration of Polarizing Plate FIG. 1 is a cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 10 has a polarizer 1 and a protective film 2 arranged on one side of the polarizer 1 . The protective film 2 contains an acrylic resin and core-shell particles dispersed in the acrylic resin. The arithmetic mean roughness Ra of the surface of the protective film 2 is 6.0 nm or more. Preferably, the surface of the protective film 2 on the side opposite to the polarizer 1 is formed with irregularities due to core-shell type particles. The protective film 2 preferably contains 3 to 50 parts by weight of the core-shell type particles with respect to 100 parts by weight of the acrylic resin. Core-shell type particles typically have a core made of a rubbery polymer and a coating layer made of a glassy polymer covering the core. Protective film 2 is preferably a biaxially stretched film. In one embodiment, polarizing plate 10 does not have a diffusion layer on the surface of 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, the occurrence of scratches due to friction with the other optical member can be suppressed.

FIG. 2 is a cross-sectional view of a polarizer according to another embodiment of the invention. The polarizing plate 11 includes a polarizer 1, a protective film 2 (first protective film) arranged on one side of the polarizer 1, and a second protective film 3 arranged on the other side of the polarizer 1. and The second protective film 3 may be a film made of the same material as the first protective film 2, or may be made of a different material. The polarizing plate 11 may have any appropriate optical functional film in place of the second protective film 3 depending on the purpose and application.

The polarizing plate 10 and the polarizing plate 11 may be sheet-shaped or elongated. The polarizing plate 10 may have an adhesive layer (not shown) on the surface of the polarizer 1 , and the polarizing plate 11 may have an adhesive layer (not shown) on the surface of the second protective film 3 . not shown).

B. Polarizer Any appropriate polarizer can be employed 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 polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. In addition, oriented polyene films such as those dyed with dichroic substances such as iodine and dichroic dyes and stretched, and dehydrated PVA and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used because of its excellent optical properties.

The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing 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 swelling treatment, cross-linking treatment, washing treatment, 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 dirt and anti-blocking agents on the surface of the PVA-based film be washed away, but also the PVA-based film can be swollen to remove uneven dyeing. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material is obtained, for example, by applying a PVA-based resin solution to the resin base material and drying the resin base material. forming a PVA-based resin layer thereon to obtain a laminate of a resin substrate and a PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, stretching may further include stretching the laminate in air at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained resin substrate/polarizer laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate. Then, any appropriate protective layer may be laminated on the release surface according to the purpose. Details of a method for manufacturing such a polarizer are described, for example, in Japanese Patent Application Laid-Open No. 2012-73580. The 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 1 μm to 15 μm, more preferably 3 μm to 10 μm, particularly preferably 3 μm to 8 μm.

C. Protective film C-1. Properties of Protective Film As described above, the protective film contains an acrylic resin and core-shell particles dispersed in the acrylic resin, and the surface arithmetic mean roughness Ra of the protective film is 6.0 nm or more. The arithmetic mean roughness Ra is preferably 6 nm to 50 nm , more preferably 6 nm to 40 nm . By setting the arithmetic mean roughness Ra to a value within the above range, it is possible to suppress the slipperiness of the surface of the protective film from becoming too high, and as a result, the protective film (and the polarizing plate) can be wound when it is elongated. Displacement can be suppressed. The arithmetic mean roughness Ra can be adjusted within a desired range depending on the content of the core-shell type particles in the protective film, the 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, the term “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, still more 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, still more preferably −3 nm to +3 nm, and particularly preferably −2 nm to +2 nm. If the Re(550) and Rth(550) of the protective film are within such ranges, adverse effects on display characteristics can be prevented when the polarizing plate is applied to an image display device. Note that Re(550) is the 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 the thickness direction retardation 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 (that is, the slow axis direction), and ny is the in-plane refractive index in the direction perpendicular to the slow axis (that is, the fast axis direction). is the refractive index, nz is the refractive index in the thickness direction, and d is the film thickness (nm).

The higher the light transmittance at 380 nm when the thickness of the protective film is 80 μm, the better. Specifically, the light transmittance is preferably 85% or higher, more preferably 88% or higher, and even more preferably 90% or higher. If the light transmittance is in such a range, desired transparency can be ensured. Light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The haze of the protective film is preferably as low as possible. Specifically, the haze is preferably 5% or less, more preferably 3% or less, even more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, the film can have a good clear feeling. Furthermore, even when it is used as a polarizing plate on the viewing side of an image display device, display contents can be visually recognized well.

YI at a protective film thickness of 80 μm is preferably 1.27 or less, more preferably 1.25 or less, even more preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the optical transparency may become insufficient. YI is obtained from the tristimulus values (X, Y, Z) of the color obtained by measurement using, for example, a high-speed integrating sphere type spectral transmittance meter (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 (scale of hue according to Hunter's color system) 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 tint 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 meter (trade name DOT-3C: manufactured by Murakami Color Research Laboratory). It can be obtained by evaluating the hue according to the Hunter color system.

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, particularly preferably 150 g/m ² ·24 hr or less. Most preferably, it is 100 g/m ² ·24 hr or less. If the moisture permeability of the protective film is within this range, a polarizing plate with 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, 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 become insufficient. Tensile strength can be measured, for example, according to ASTM-D-882-61T.

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

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

The protective film may contain any appropriate additive depending on the purpose. Specific examples of additives include UV absorbers; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; glass fibers, carbon fibers, etc. Reinforcing material; Near-infrared absorber; Flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic, and nonionic surfactants; Inorganic pigments, organic pigments , coloring agents such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; The additive may be added during polymerization of the acrylic resin, or may be added during film formation. The type, number, combination, addition amount, etc. of additives can be appropriately set 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 can 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, examples of the material for forming the second protective film include acrylic resins that do not contain core-shell type particles, diacetyl cellulose, and triacetyl cellulose. and the like, cycloolefin resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate 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 Any appropriate acrylic resin may be employed as the acrylic resin. Acrylic resins typically contain alkyl (meth)acrylate as a main component as a monomer unit. As used herein, "(meth)acryl" means acryl and/or methacryl. Examples of the alkyl (meth)acrylate constituting the main skeleton of the acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Furthermore, any appropriate copolymerization monomer may be introduced into the acrylic resin by copolymerization. The type, number, copolymerization ratio, etc. of such copolymerizable monomers can be appropriately set according to the purpose. Constituent components (monomer units) of the main skeleton of the acrylic resin will be described later with reference to general formula (2).

The acrylic resin preferably has at least one selected from glutarimide units, lactone ring units, maleic anhydride units, maleimide units and glutaric anhydride units. An acrylic resin having a lactone ring unit is described, for example, in 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 general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ³ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a carbon It represents a cycloalkyl group having 3 to 12 carbon atoms or an aryl group having 6 to 10 carbon atoms. In general formula (1), preferably R ¹ and R ² are each independently a hydrogen atom or a methyl group, and R ³ is a hydrogen atom, a methyl group, a butyl group or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is a hydrogen atom and R ³ is a methyl group.

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

In general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. show. Examples of substituents 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, 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 general formula (2), ^R5 is preferably a hydrogen atom or a methyl group. A particularly preferred alkyl (meth)acrylate is therefore methyl acrylate or methyl methacrylate.

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

The content of the glutarimide unit in the acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, still more preferably 2 mol% to 40 mol%, particularly preferably 2 mol. % to 35 mol %, most preferably 3 mol % to 30 mol %. When the content is less than 2 mol%, the effects derived from the glutarimide unit (e.g., high optical properties, high mechanical strength, excellent adhesion to polarizers, thinness) are fully 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 contain only a single alkyl (meth)acrylate unit, or may contain a plurality of alkyl (meth)acrylate units in which R ⁴ and R ⁵ in the general formula (2) are different. good too.

The content of alkyl (meth)acrylate units 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 is less than 50 mol %, the effects derived from the alkyl (meth)acrylate units (eg, high heat resistance and high transparency) may not be exhibited sufficiently. If the content is more than 98 mol %, the resin becomes brittle and easily cracked, and high mechanical strength cannot be sufficiently exhibited, which may lead to poor productivity.

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

In one embodiment, the acrylic resin may contain copolymerizable vinyl-based monomer units (other vinyl-based monomer units) other than those described 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 methacrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, 2 -isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryl- and oxazoline. These may be used alone or in combination. Styrenic monomers such as styrene and α-methylstyrene are preferred. The content of other vinyl-based monomer units 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 occurrence of undesired retardation and the decrease in transparency.

The imidization rate in the acrylic resin is preferably 2.5% to 20.0%. If the imidization rate is within such a range, a resin having excellent heat resistance, transparency and moldability can be obtained, and occurrence of burnt deposits and reduction in mechanical strength during film molding can be prevented. In the above acrylic resin, the imidization rate 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 this embodiment, the imidization rate can be determined by ¹ H-NMR measurement of the resin using ¹ H NMR BRUKER Avance III (400 MHz). More specifically, the peak area derived from O—CH ₃ protons of alkyl (meth)acrylate near 3.5 to 3.8 ppm is A, and N—CH ₃ of glutarimide near 3.0 to 3.3 ppm It is obtained by the following formula, where B is the area of the peak derived from protons.
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. If the acid value is within such a range, a resin having an excellent balance of heat resistance, mechanical properties and moldability can be obtained. If the acid value is too low, the use of a modifying agent for adjusting the acid value to a desired value may cause problems such as an increase in cost and the generation of a gel-like substance due to residual modifying agent. If the acid value is too high, foaming tends to occur during film molding (for example, during melt extrusion), and the productivity of molded articles tends to decrease. In the acrylic resin, the acid value is the content of carboxylic acid units and carboxylic anhydride units in the acrylic resin. In this 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, 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, for example, by polystyrene conversion using 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, even more preferably 120° C. or higher, particularly preferably 125° C. or higher, and most preferably 130° C. or higher. When Tg is 110° C. or higher, a polarizing plate including a 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. If Tg is such a range, it can be excellent in moldability.

C-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 the alkyl (meth)acrylate unit represented by the general formula (2), an unsaturated carboxylic acid monomer and/or a precursor monomer thereof and (II) by treating the copolymer (a) with an imidizing agent, An alkyl (meth)acrylate monomer unit and an unsaturated carboxylic acid monomer and/or its precursor monomer unit are subjected to an intramolecular imidization reaction, and a glutarimide unit represented by the general formula (1) is covalently formed. introducing into a polymer;

Examples of unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. Examples of precursor monomers thereof 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.

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

Any appropriate compound can be used as the imidizing agent as long as it can form the glutarimide unit represented by the general formula (1). Specific examples of imidizing agents include aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine and n-hexylamine; Examples include aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine and trichloroaniline, and alicyclic hydrocarbon group-containing amines such as cyclohexylamine. Furthermore, urea-based compounds that generate such amines by heating, for example, can also be used. Urea compounds include, for example, urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea. The imidizing agent is preferably methylamine, ammonia or cyclohexylamine, more preferably methylamine.

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

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, relative to 100 parts by weight of the copolymer (a). is. If the amount of the imidization agent used is less than 0.5 parts by weight, the desired imidization rate is often not achieved. As a result, the heat resistance of the resulting resin becomes extremely insufficient, which may induce appearance defects such as burnt deposits after molding. When the amount of the imidizing agent used exceeds 10 parts by weight, the imidizing agent remains in the resin, and the imidizing agent may induce appearance defects such as burnt deposits and foaming after molding.

The production method of the present embodiment can optionally include treatment with an esterification agent in addition to the imidization.

Esterifying agents include, for example, dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyltoluenesulfonate, methyltrifluoromethanesulfonate, Methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, 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 preferable from the viewpoint of cost and reactivity.

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

C-2-3. Combined use of other resins In the embodiment of the present invention, the above acrylic resin and other resins may be used together. 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. may be subjected to film formation. Other resins include, for example, styrene resins, other thermoplastic resins such as polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide, and phenolic resins. thermosetting 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 desired properties of the resulting film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used together as a retardation control agent.

When an 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% to 100% by weight, more preferably 60% to 100% by weight. % 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 fully reflected.

C-3. Core-Shell Particles In the above protective film, the core-shell particles are blended in an amount of preferably 3 to 50 parts by weight, more preferably 3 to 40 parts by weight, per 100 parts by weight of the acrylic resin. Thereby, the arithmetic mean roughness Ra of the surface of the protective film can be adjusted within a desired range. The core-shell type particles may form unevenness on the surface of the protective film by partially exposing on the surface of the protective film, or may be formed without being exposed on the surface of the protective film (while being covered with acrylic resin ) Concavities and convexities may be formed on the surface of the protective film.

Core-shell particles typically have a core made of a rubbery polymer and a coating layer made of a glassy polymer covering the core. The core-shell particles may have one or more layers composed of a glassy polymer as the innermost layer or intermediate layer.

The Tg of the rubber-like polymer constituting the core is preferably 20°C or less, more preferably -60°C to 20°C, still more preferably -60°C to 10°C. If the Tg of the rubber-like 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, still more 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 deteriorate.

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

In one embodiment, the core-shell particles dispersed in the acrylic resin may have a flattened shape. The core-shell particles can be flattened by stretching as described later in Section C-4. The flattened core-shell particles have a length/thickness ratio of 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 greater, more preferably 4.5 or greater, and even more preferably 5.0 or greater. As used herein, the term "length/thickness ratio" means the ratio of the representative length and thickness of the core-shell type particle in plan view. Here, the "representative length" refers to the diameter when the shape in plan view is circular, the length of the major axis when the shape is elliptical, and the length of the diagonal when the shape is rectangular or polygonal. The said ratio can be calculated|required by the following procedures, for example. The obtained film cross section was photographed with a transmission electron microscope (e.g., accelerating voltage 80 kV, RuO ₄ stained ultrathin section method), and among the core-shell particles present in the obtained photograph, the longer ones (cross section close to representative length The ratio can be obtained by extracting 30 pieces in order from those obtained) and calculating (average value of length)/(average value of thickness).

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, their polymerization methods, and other configurations are disclosed, for example, in JP-A-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 acrylic resin (when used in combination with other resins, a blend with the other resins) and core-shell particles. can be formed by a method comprising film forming a Additionally, a method of forming a protective film can 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 surface arithmetic mean roughness Ra of the resulting 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 appropriate method can be adopted as a method for forming the film. Specific examples include cast coating method (e.g., casting method), extrusion molding method, injection molding method, compression molding method, transfer molding method, blow molding method, powder molding method, FRP molding method, calendar molding method, heat press. law. Extrusion molding or cast coating is preferred. This is because the smoothness of the resulting film can be enhanced and good optical uniformity can be obtained. Extrusion molding is particularly preferred. This is because there is no need to consider problems due to 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 process. Molding conditions can be appropriately set according to the composition and type of the resin used, the properties desired for the resulting film, and the like.

As the stretching method, any suitable stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching speed, stretching direction) can be adopted. Specific examples of stretching methods include free-end stretching, fixed-end stretching, free-end shrinkage, and fixed-end shrinkage. These may be used singly, simultaneously, or sequentially. By stretching a film in which the blending amount of core-shell type particles to the acrylic resin is appropriately adjusted under appropriate stretching conditions, the core-shell type particles migrate (bleed) to the surface of the film, resulting in irregularities on the surface of the film. is formed, and the surface arithmetic mean roughness Ra of the resulting protective film can be adjusted within the above desired range.

A suitable stretching direction can be adopted depending on the purpose. Specifically, the length direction, width direction, thickness direction, and oblique direction are mentioned. The stretching direction may be one direction (uniaxial stretching), two directions (biaxial stretching), or three or more directions. In an 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. Biaxial stretching (simultaneous or sequential) is preferred. This is because it is easy to control the in-plane retardation and easily achieve optical isotropy.

The stretching temperature is the desired optical properties, mechanical properties and thickness of 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, the stretching speed. etc. Specifically, the stretching temperature is preferably Tg to Tg+50°C, more preferably Tg+15°C to Tg+50°C, most preferably Tg+35°C to Tg+50°C. By stretching at such temperatures, a protective film with suitable properties can be obtained. A specific stretching temperature is, for example, 110°C to 200°C, preferably 120°C to 190°C. If the stretching temperature is within such a range, the core-shell type particles will bleed onto the surface of the film by appropriately adjusting the stretching ratio and the stretching speed, and the surface arithmetic mean roughness Ra of the resulting protective film will be adjusted to the desired value. can be adjusted within the range of

The stretching ratio is also the same as the stretching temperature, the surface arithmetic mean roughness Ra, optical properties, mechanical properties and thickness desired for the protective film, the type of resin used, the thickness of the film used, stretching It can vary depending on the method (uniaxial stretching or biaxial stretching), stretching temperature, stretching speed, and the like. When biaxial stretching is employed, the ratio (TD/MD) of the draw ratio in the width direction (TD) and the draw ratio in the length direction (MD) is preferably 1.0 to 1.5, more preferably. is 1.0 to 1.4, more preferably 1.0 to 1.3. Further, when biaxial stretching is employed, the area ratio (the product of the draw ratio in the length direction and the draw ratio in the width direction) is preferably 2.0 to 6.0, more preferably 3.0 to 3.0. 5.5, more preferably 3.5 to 5.2. If the draw ratio is within such a range, the core-shell type particles will bleed onto the surface of the film by appropriately adjusting the drawing temperature and drawing speed, and the surface arithmetic mean roughness Ra of the resulting protective film will be reduced to the desired value. can be adjusted within the range of

The stretching speed, like the stretching temperature, also depends on the surface arithmetic mean roughness Ra, optical properties, mechanical properties and thickness desired for the protective film, the type of resin used, the thickness of the film used, stretching It can vary depending on the method (uniaxial stretching or biaxial stretching), stretching temperature, stretching ratio and the like. The drawing 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 biaxial stretching is employed, the stretching speed in one direction and the stretching speed in the other direction may be the same or different. If the stretching speed is within such a range, the core-shell type particles will bleed onto the surface of the film by appropriately adjusting the stretching temperature and the stretching ratio, and the surface arithmetic mean roughness Ra of the resulting protective film will be adjusted to the desired value. can be adjusted within the range of

A protective film can be formed as described above.

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 image display devices include liquid crystal display devices and organic electroluminescence (EL) display devices. An 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 to face the diffusion sheet.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. "Parts" and "%" in the examples are by weight unless otherwise specified.
(1) Thickness Measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
(2) Arithmetic mean roughness Ra of the surface of the protective film
The arithmetic mean roughness Ra was measured using an optical profilometer (manufactured by Veeco Instruments, trade name "Optical Profilometer NT3300").
(3) Scratch evaluation Glass plate (MICRO SLIDE GLASS Pre-cleaned water green polish t1.3 (manufactured by MATSUNAMI), product model number “S200423”, size: 65 mm × 165 mm, Thickness 1.2 to 1.5 mm), 50 mm × A laminate of a glass plate and a polarizing plate was produced by pasting together the polarizing plate cut into a size of 1500 mm with an adhesive layer interposed therebetween. The laminated body simulates the structure of a liquid crystal panel.
A diffusion sheet (manufactured by Sumitomo 3M Limited, product name "DBEF-D2-400") is placed in the tray, and the laminate is placed on the diffusion sheet with the polarizing plate side facing down. did. Then, the tray was shaken under conditions of 200 times/min×10 min. After that, the laminate was taken out, and the presence or absence of abrasion scratches (mass of scratches) on the first protective film of the polarizing plate was visually confirmed.

<Example 1>
(Preparation of polarizing plate)
1. Preparation of protective film MS resin (MS-200; methyl methacrylate / styrene (molar ratio) = 80/20 copolymer, manufactured by Nippon Steel Chemical Co., Ltd.) is imidized with monomethylamine (imidization rate: 5 %)did. The resulting imidized MS resin has a glutarimide unit represented by general formula (1) (R ¹ and R ³ are methyl groups and R ² is a hydrogen atom) and general formula (2) ( It had meth)acrylate units ( ^R4 and ^R5 are methyl groups) and styrene units. For the imidization, an intermeshing co-rotating twin-screw extruder with a diameter of 15 mm was used. The set temperature of each temperature control zone of the extruder was 230° C., the screw rotation speed was 150 rpm, the MS resin was supplied at 2.0 kg/hr, and the amount of monomethylamine supplied was 2 parts by weight per 100 parts by weight of the MS resin. did. MS resin was charged from a hopper, melted and filled with a kneading block, and then monomethylamine was injected from a nozzle. A seal ring was placed at the end of the reaction zone and filled with resin. By-products and excess methylamine after the reaction were devolatilized by reducing the pressure at the vent port to -0.08 MPa. The resin coming out as a strand from a die provided at the outlet of the extruder was cooled in a water tank and then pelletized by a pelletizer. The obtained imidized MS resin 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 the 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 having a thickness of 40 μm. . The resulting extruded film was simultaneously biaxially stretched at a stretching temperature of 160° C. to double in both the length direction and the width direction. The stretching speed was 10%/sec in both the length direction and the width direction.
Thus, a protective film was produced. The resulting protective film had a thickness of 10 μm, an arithmetic surface roughness Ra of 22.18 nm , an in-plane retardation Re(550) of 2 nm, and a thickness direction retardation Rth(550) of 2 nm.
2. Preparation of polarizer A long roll of polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name “PE3000”) with a thickness of 30 μm was uniaxially stretched in the longitudinal direction by a roll stretching machine so that it was 5.9 times longer in the longitudinal direction. A polarizer having a thickness of 12 μm was produced by simultaneously performing swelling, dyeing, cross-linking, and washing treatments while stretching, and finally performing a drying treatment.
Specifically, in the swelling treatment, the film was stretched 2.2 times while being treated with pure water at 20°C. Next, the dyeing treatment is performed in an aqueous solution at 30° C. in which the weight ratio of iodine and potassium iodide is 1:7 and the iodine concentration is adjusted so that the single transmittance of the resulting polarizer is 45.0%. while stretching to 1.4 times. Further, the cross-linking treatment employed a two-step cross-linking treatment, and the first-step cross-linking treatment was performed by stretching the film 1.2 times while treating it in an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content of the aqueous solution for the first-stage cross-linking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second-stage cross-linking treatment, the film was stretched 1.6 times while being treated in an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution for the second-stage cross-linking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Further, the cleaning treatment was performed with an aqueous solution of potassium iodide at 20°C. The potassium iodide content of the aqueous solution for the cleaning treatment was 2.6% by weight. Finally, the drying treatment was performed at 70° C. for 5 minutes to obtain a polarizer.
3. Preparation of polarizing plate (second protective film)
The protective film obtained above as a first protective film is attached to one surface of the polarizer via a polyvinyl alcohol adhesive, and the polyvinyl alcohol adhesive is applied to the other surface of the polarizer. A TAC film (manufactured by Dai Nippon Printing Co., Ltd., trade name “DSG-03”, thickness 70 μm) was laminated as a second protective film through the intervening layer.
(Adhesive layer)
94.9 parts of butyl acrylate, 5 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, and dibenzoyl peroxide were added to a reaction vessel equipped with a condenser, nitrogen inlet, thermometer and stirring device. Add 0.3 parts with ethyl acetate to 100 parts of the total monomer (solid content) and react at 60 ° C. for 7 hours under a nitrogen gas stream, then add ethyl acetate to the reaction solution to adjust the weight average molecular weight 2,200,000 and a solution containing the acrylic polymer (B) with a dispersion ratio of 3.9 was obtained (solid concentration: 30%). Per 100 parts of the solid content of the solution containing the acrylic polymer (B), 0.6 parts of trimethylolpropane tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd.: Coronate L) and 0.075 parts of γ- Glycidoxypropylmethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-403) was blended to obtain an adhesive solution. The above solution was diluted with ethyl acetate to give a solid content concentration of 15% to prepare an adhesive coating solution. On one side of a 38 μm polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) that has been subjected to silicone treatment, the adhesive coating solution prepared above is applied to a thickness of 134.0 μm. It was coated using a fountain die coater as follows. Then, drying was performed at 155° C. for 1 minute to form a pressure-sensitive adhesive layer with 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 pressure-sensitive adhesive layer). The obtained polarizing plate was subjected to the above evaluation. Table 1 shows the results.

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

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

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

<Example 5>
100 parts by weight of the imidized MS resin and 3 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film. to create a protective film. The resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 6.11 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Example 6>
100 parts by weight of the imidized MS resin and 5 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film. to create a protective film. The resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 6.79 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Example 7>
100 parts by weight of the imidized MS resin and 20 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film. to create a protective film. The resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 23.45 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Example 8>
100 parts by weight of the imidized MS resin and 30 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film. to create a protective film. The resulting protective film had a thickness of 30 μm and an arithmetic mean roughness Ra of 31.37 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Example 9>
100 parts by weight of the imidized MS resin and 40 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film. to create a protective film. The obtained protective film had a thickness of 30 μm and an arithmetic mean roughness Ra of 32.79 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<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 resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 8.06 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<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 resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 6.72 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<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 resulting protective film had a thickness of 30 µm and an arithmetic mean roughness Ra of 15.76 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<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 obtained protective film had a thickness of 30 μm and an arithmetic mean roughness Ra of 17.29 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Comparative Example 1>
A protective film was prepared in the same manner as in Example 3, except that only the imidized MS resin was put into a single-screw extruder and melt-mixed to form an extruded film, and the resulting extruded film was stretched at a stretching temperature of 145°C. It was created. The obtained protective film had a thickness of 40 μm and an arithmetic mean roughness Ra of 4.2 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<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. to create a protective film. The resulting protective film had a thickness of 40 µm and an arithmetic mean roughness Ra of 4.93 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

<Comparative Example 3>
100 parts by weight of the imidized MS resin and 5 parts by weight of the core-shell type particles were put into a single-screw extruder and melt-mixed to form an extruded film, and the resulting extruded film was stretched at a stretching temperature of 100°C. prepared a protective film in the same manner as in Example 3. The resulting protective film had a thickness of 40 µm and an arithmetic mean roughness Ra of 5.14 nm . A polarizing plate was produced in the same manner as in Example 1, except that the above protective film was used. The polarizing plate was subjected to the same evaluation as in Example 1. Table 1 shows the results.

As is clear from Table 1, the polarizing plates of Comparative Examples 1 to 3 suffered from abrasion when shaken while in contact with the diffusion sheet. Even if it was shaken in a state of being in contact with , no wear scar occurred.

The polarizing plate of the present invention is suitable for use in image display devices. The image display device of the present invention includes mobile devices such as personal digital assistants (PDA), smart phones, mobile phones, clocks, digital cameras, and portable game machines; OA devices such as personal computer monitors, notebook computers, and copiers; video cameras, and televisions. , microwave ovens and other household electrical appliances; back monitors, car navigation system monitors, car audio and other automotive equipment; display equipment such as digital signage and information monitors for commercial stores; security equipment such as surveillance monitors; care and medical equipment such as monitors for personal use and medical monitors;

REFERENCE SIGNS LIST 1 polarizer 2 protective film 3 second protective film 10 polarizing plate 11 polarizing plate

Claims (7)

a polarizer and a protective film disposed on at least one side of the polarizer;
The protective film includes an acrylic resin and core-shell particles dispersed in the acrylic resin,
The acrylic resin has a glutarimide unit,
The polarizing plate, wherein the surface of the protective film has an arithmetic mean roughness Ra of 12.37 nm or more and 50 nm or less . 2. The polarizing plate according to claim 1, wherein the surface of the protective film opposite to the polarizer is formed with unevenness due to the core-shell particles. 3. The polarizing plate according to claim 1, wherein the protective film contains 3 to 50 parts by weight of the core-shell particles with respect to 100 parts by weight of the acrylic resin. 4. The polarizing plate according to any one of claims 1 to 3, wherein the core-shell type particles have a core made of a rubbery polymer and a coating layer made of a glassy polymer and covering the core. The polarizing plate according to any one of claims 1 to 4, wherein the protective film is a biaxially stretched film. 6. The polarizing plate according to any one of claims 1 to 5, wherein the surface of said protective film does not have a diffusion layer. A display cell, a polarizing plate according to any one of claims 1 to 6, a diffusion sheet, and a light source are provided in this order,
The image display device, wherein the protective film of the polarizing plate is arranged to face the diffusion sheet.

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