TW201408482A - Method for manufacturing polarizing plate - Google Patents

Abstract

The present invention provides a method for manufacturing a polarizing plate 15 by bonding an acrylic resin film on a polarizing film containing a polyvinyl alcohol resin having a dichroic pigment being adsorbed and oriented, wherein the method includes the following processes: a heating treatment process for processing the heating treatment, in which the acrylic resin film 20 pass through a heating furnace 40 being kept at a temperature in the range of (Tg-30 DEG C ) or more and (Tg+5 DEG C ) or less, wherein the Tg is a glass transition temperature of the acrylic resin film; and a bonding process for bonding the heat-treated acrylic resin film 21 on the polarizing film 10 by a bonding roll 50, 51.

Description

Polarizing plate manufacturing method

The present invention relates to a method of producing a polarizing plate by bonding an acrylic resin film which is a protective film to a polyvinyl alcohol-based polarizing film.

The polarizing plate is widely used mainly as a constituent member of a liquid crystal display device. The polarizing plate is generally distributed in a state in which at least one area of the polarizing film containing the polyvinyl alcohol-based resin is provided with a protective film, and is incorporated in a liquid crystal display device or the like. A protective film of a polyvinyl alcohol-based polarizing film constituting the polarizing plate has conventionally used a triacetyl cellulose film. However, the heat and humidity resistance of the triacetyl cellulose is insufficient, and the polarizing plate using the triethylene glycol film as the protective film may have a degree of polarization or a decrease in color performance under high temperature conditions and under moist heat conditions.

Then, an acrylic resin film excellent in transparency and heat and humidity resistance was used as a protective film instead of triacetyl cellulose. For example, Japanese Laid-Open Patent Publication No. 2007-25008 (Patent Document 1) discloses that a thermoplastic resin layer is formed on both surfaces of an acrylic resin film having a thickness of 40 μm or less, and the thermoplastic resin layer on both sides is peeled off before use to form a polarizing plate. Protective film. JP-A-2007-41563 (Patent Document 2) discloses a protective film comprising a three-layer structure including an acrylic resin film/polyethyleneimine layer/polyvinyl alcohol resin layer, and the polyvinyl alcohol. The resin layer side is bonded to a polyvinyl alcohol-based polarizing film, and Become a polarizing plate. JP-A-2007-52404 (Patent Document 3) discloses that an adhesive layer/metal salt layer/protective film is provided on one surface of a polyvinyl alcohol-based polarizing film in order to form a polarizing plate, and the acrylic resin is used. Protective film. Japanese Laid-Open Patent Publication No. 2009-25762 (Patent Document 4) discloses that a protective film of a polarizing plate is prepared by blending 0.1 to 1.5 parts by weight of a lubricant containing a metal salt with respect to 100 parts by weight of the resin component of the acrylic resin main body. . Japanese Laid-Open Patent Publication No. 2009-163216 (Patent Document 5) discloses an anti-glare film comprising an acrylic resin film having a hard coat layer on one of the polyvinyl alcohol-based polarizing films. In the polarizing plate on the viewing side of the liquid crystal display device, the acrylic resin constituting the anti-glare film preferably contains acrylic rubber particles from the viewpoint of the impact resistance of the film or the film forming property.

The resin film is not limited to the acrylic resin film, and the resin film is generally wound up in a cylindrical core after production and stored in a roll shape. Then, after a predetermined period of storage, for example, it is tightened in a curled state, and a phenomenon in which a depression or the like is observed on the outermost surface of the roll film is called curling and contracting. If such a crimping is produced, the depression or the like causes a defect, which in fact makes it unusable for optical use. In particular, in the acrylic resin film, such curling and shrinking is remarkably easy.

Accordingly, an object of the present invention is to provide a method for producing a polarizing plate which can be repaired even when an acrylic resin film which is defective due to crimping is used, and which can be produced by being bonded to a polarizing film. A polarizing plate with few defects.

According to the present invention, a method of manufacturing a polarizing plate can be provided A polarizing film comprising a polyvinyl alcohol-based resin adsorbed to a dichroic dye is bonded to an acrylic resin film to produce a polarizing plate. The method has the following steps: a heat treatment step of using a glass transition temperature of the acrylic resin film as a Tg When the acrylic resin film is subjected to heat treatment at a temperature of (Tg-30 ° C) or more and (Tg + 5 ° C) or less, and a bonding step, the acrylic resin film which has been subjected to heat treatment is attached. In combination with the aforementioned polarizing film.

The acrylic resin film used in the method is preferably formed of an acrylic resin composition in which rubber elastomer particles are blended in an acrylic matrix resin, and the rubber elastomer particles preferably have a number average particle diameter of 10 to The range of 300 nm, in addition, is preferably blended in a ratio of 25 to 45 wt% with respect to the above acrylic matrix resin.

In these methods, the heat treatment step is preferably carried out in a heating furnace heated to the above temperature. Further, the progress time of the heat treatment step is preferably in the range of 5 seconds or more and 60 seconds or less. Preferably, the acrylic resin film is subjected to the heat treatment step while being wound up in a state of being wound into a roll, and then subjected to a bonding step. In this case, the heat treatment step is preferably performed such that the dimensional change ratio in the width direction perpendicular to the traveling direction of the acrylic resin film before and after the heat treatment is 0.3% or less.

According to the method of the present invention, even if the acrylic resin before bonding with the polarizing film is defective due to crimping, it can be bonded to the polarizing film after heat treatment to produce a polarizing plate having few defects. Therefore, even a roll which produces a crimped acrylic resin film can be used, and the productivity of the polarizing plate using the acrylic resin film as a protective film can be greatly improved.

10‧‧‧Polarized film

15‧‧‧Polar plate

20‧‧‧Acrylic resin film (raw film before heat treatment)

21‧‧‧Acrylic resin film subjected to heat treatment

25‧‧‧First delivery reel

30‧‧‧Second resin film

35‧‧‧Second delivery reel

40‧‧‧heating furnace

45‧‧‧Conveying roller

50, 51‧‧‧ affixing rolls

60‧‧‧ product reel

Fig. 1 is a side view schematically showing an arrangement example of a device used for manufacturing a polarizing plate.

The invention will be described with reference to Fig. 1. In the present invention, the acrylic resin film 20 (21) is bonded to the polarizing film 10 containing a polyvinyl alcohol-based resin which adsorbs the dichroic dye, and the polarizing plate 15 is produced. Then, the acrylic resin film (raw material film) 20 is subjected to heat treatment before being bonded to the polarizing film 10, and the acrylic resin film 21 thus subjected to heat treatment is bonded to the polarizing film 10.

In the example shown in Fig. 1, the acrylic resin film 20 sent from the first delivery reel 25 passes through the heating furnace 40 and is subjected to heat treatment. The acrylic resin film 21 subjected to the heat treatment is supplied to one surface of the polarizing film 10, and the second resin film 30 sent from the second delivery roll 35 is supplied to the other surface of the polarizing film 10, and is heated according to the heating. The order of the acrylic resin film 21/polarized film 10/second resin film 30 to be processed is bonded by the bonding rolls 50 and 51. The polarizing plate 15 thus obtained is wound up on the product roll 60. In the heating furnace 40, the acrylic resin film 20 is conveyed by a plurality of conveying rollers 45 and 45. In general, the polarizing film 10 is directly sent out by a person who manufactures the polarizing film which will be described later. In Fig. 1, a straight arrow symbol indicates the direction in which the film is made, and a curved line arrow symbol indicates the direction in which the roller rotates. In the example shown in Fig. 1, the stage of passing the heating furnace 40 corresponds to the heat treatment step, and the stage in which the bonding rolls 50 and 51 are bonded together corresponds to the bonding step.

In the example shown in Fig. 1, when the polarizing plate 15 is produced by laminating a resin film on both surfaces of the polarizing film 10, at least one of the trees is made of an acrylic resin. The lipid film can be used. When the acrylic resin film is bonded to both surfaces of the polarizing film 10 to form the polarizing plate 15, it is preferred that the acrylic resin film is subjected to the heat treatment of the present invention and then supplied to the bonding step. On the other hand, the resin film may be bonded to only one surface of the polarizing film 10 to form a polarizing plate. In this case, the resin film may be formed of an acrylic resin.

Hereinafter, the polarizing film 10 and the acrylic resin film 20 used in the present invention and the second resin film 30 which is used arbitrarily will be described in order, and a method of manufacturing the polarizing plate will be described later.

[Polarized film]

The polarizing film 10 is obtained by adsorbing a dichroic dye to a polyvinyl alcohol-based resin film to obtain a predetermined polarizing property. Typically, dichroic dyes use iodine or a dichroic organic dye. In other words, the polarizing film is classified into an iodine-based polarizing film in which a iodine-based iodine-based polarizing film is adsorbed on a polyvinyl alcohol-based resin film, and a dye-based polarizing film in which a dichroic organic dye is adsorbed on a polyvinyl alcohol-based resin film.

The polyvinyl alcohol-based resin constituting the polarizing film 10 is obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. Further, the polyvinyl alcohol-based resin may be modified, and for example, poly(vinyl formal), poly(vinyl acetal), or polyethylene modified with an aldehyde may be used. Poly (vinyl butyral) and the like.

The polarizing film 10 is usually produced by the following steps: a humidity conditioning step of adjusting the moisture of the polyvinyl alcohol resin film, and a polyvinyl alcohol resin film. a step of uniaxially stretching, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and a step of treating the polyvinyl alcohol resin film adsorbed to the dichroic dye with an aqueous solution of boric acid A step of washing the free boric acid adhered to the surface after boric acid treatment, and a step of drying after washing with water.

Uniaxial stretching can be carried out before dyeing, in dyeing, or in boric acid treatment after dyeing. Uniaxial stretching can also be performed in these plurality of stages. The uniaxial extension can be carried out between rolls of different speeds or by means of a hot roll. Further, it may be a dry stretching which is extended in the atmosphere, or a wet stretching which is extended in a state of being swollen by a solvent. The stretching ratio is usually about 4 to 8 times. The polyvinyl alcohol-based polarizing film obtained by performing uniaxial stretching and dyeing and further performing boric acid treatment, water washing, and drying may have a thickness of, for example, about 1 to 50 μm, preferably 10 to 35 μm.

[Acrylic resin film]

Next, the acrylic resin film 20 bonded to the polarizing film 10 will be described. The acrylic resin is usually a polymer mainly composed of an alkyl methacrylate. Specifically, it may be a homopolymer of an alkyl methacrylate or a copolymer of two or more kinds of alkyl methacrylates, or may be a monomer other than 50% by weight or more of an alkyl methacrylate and an alkyl methacrylate. The copolymer is 50% by weight or less. The alkyl methacrylate is usually used in an alkyl group having a carbon number of from 1 to 4, and among them, methyl methacrylate is preferably used.

Further, the monomer other than the alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or may have two or more polymerizable carbon-carbon double bonds in the molecule. Polyfunctional monomer, but especially preferably monofunctional monomer. Examples thereof include alkyl acrylates such as methyl acrylate or ethyl acrylate, styrene monomers such as styrene or alkyl styrene, and unsaturated nitriles such as acrylonitrile or methacrylonitrile. When an alkyl acrylate is used as the copolymerization component, the alkyl group is usually from about 1 to about 8 carbon atoms. The monomer composition of the acrylic resin is preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, based on the total amount of the monomers, more preferably 99% by weight or less.

The acrylic resin preferably does not have a glutarylene imide derivative, a glutaric anhydride derivative, a lactone ring structure or the like. An acrylic resin having a cyclic structure such as a glutarylenediamine derivative, a glutaric anhydride derivative, or a lactone ring structure tends to have insufficient mechanical strength and moist heat resistance as an optical film. In other words, the acrylic resin is preferably one in which the monomer is substantially composed only of an alkyl methacrylate, or the alkyl methacrylate is, for example, 70% by weight or more, preferably 90% by weight or more based on the monomer composition. And substantially only a copolymer composed of a monomer selected from the group consisting of an alkyl acrylate, a styrene monomer, and an unsaturated nitrile.

The acrylic resin may be an acrylic resin composition in which rubber elastomer particles are blended in the acrylic matrix resin from the viewpoints of film forming properties of the film or impact resistance at the time of film formation. The rubber elastic particles are particles having a layer exhibiting rubber elasticity, and may be particles composed only of a layer exhibiting rubber elasticity, or particles having a multilayer structure of a layer exhibiting rubber elasticity and other layers. Examples of the rubber elastic system include an olefin-based elastic polymer, a diene-based elastic polymer, a styrene-diene-based elastic copolymer, and an acrylic elastomer. Among them, from the viewpoint of surface hardness, light resistance, and transparency when used as a protective film for a polarizing plate, an acrylic elastic polymer is preferably used.

Acrylic elastomeric polymer can be polymerized by alkyl acrylate Composition. It may be a homopolymer of an alkyl acrylate, or may be a copolymer of 50% by weight or more of an alkyl acrylate and 50% by weight or less of other monomers. The alkyl acrylate is usually used in an alkyl group having 4 to 8 carbon atoms. When a monomer other than the alkyl acrylate is copolymerized, examples thereof include alkyl methacrylate such as methyl methacrylate or ethyl methacrylate, and styrene monomers such as styrene or alkyl styrene. A monofunctional monomer such as an unsaturated nitrile such as acrylonitrile or methacrylonitrile, and examples thereof include an ester of an unsaturated carboxylic acid such as allyl (meth)acrylate or methyl allyl (meth)acrylate. A polyfunctional monomer such as a dibasic acid such as a dibasic acid such as diallyl maleate or an unsaturated carboxylic acid diester of a glycol such as an alkanediol di(meth)acrylate.

The rubber elastomer particles are preferably multilayer structured particles having an acrylic elastomeric polymer layer. Specifically, a two-layer structure having a hard polymer layer mainly composed of an alkyl methacrylate on the outer side of the acrylic elastomer, or an alkyl methacrylate further inside the acrylic elastomer may be mentioned. A three-layer structure of the hard polymer layer of the main body. When a hard polymer layer is formed on the outer side or the inner side of the acrylic elastomer, the hard polymer layer is composed of a polymer mainly composed of an alkyl methacrylate, and the monomer composition in the polymer is the same as As an example of the monomer composition of the polymer mainly composed of an alkyl methacrylate, which is exemplified by the above-mentioned acrylic resin, it is particularly preferable to use a monomer composition mainly composed of methyl methacrylate. The acrylic rubber elastomer particles having such a multilayer structure can be produced by a method described in, for example, Japanese Patent Publication No. 55-27576.

In the acrylic rubber elastomer particles having a multilayer structure, the number average particle diameter of the rubber elastomer layer is preferably in the range of 10 to 300 nm. By blending such rubber elastomer particles, a protective film which is not easily peeled off from the adhesive layer can be obtained by bonding an adhesive to a polarizing film. The average particle diameter of the rubber elastomer layer is preferably 50 nm or more, and more preferably 250 nm or less.

The average particle diameter of the rubber elastomer layer was measured in the following manner. That is, when such a rubber elastomer particle is mixed with an acrylic matrix resin and thinned, and the cross section is dyed with an aqueous cerium oxide solution, only the rubber elastic layer is colored and observed to be slightly circular, and the mother layer is The acrylic resin was not dyed. Here, the cross section of the film dyed in this manner is adjusted using a sheet slicer or the like, and observed under an electron microscope. Then, 100 dyed rubber elastic particles were randomly selected, and the respective particle diameters were calculated, and the average value was used as the average particle diameter. Since it is measured by such a method, the average particle diameter of the rubber elastic layer prescribed by the present invention is a number average particle diameter.

When a rubber elastomer particle in which the outermost layer is a hard polymer mainly composed of methyl methacrylate and an acrylic elastomer polymer is contained therein, if it is mixed with an acrylic matrix resin, the rubber elastomer particles are used. The outermost layer is mixed with the acrylic matrix resin. Therefore, when the cross section is dyed with cerium oxide and observed by an electron microscope, the rubber elastomer particles observed are particles in a state in which the outermost layer is removed. Specifically, when a rubber elastomer particle having a two-layer structure in which an inner layer is an acrylic elastic polymer and an outer layer is a hard polymer mainly composed of methyl methacrylate is used, the acrylic elastic polymer portion of the inner layer is used. Particles of a single-layer structure are observed by dyeing, and when the innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is methacrylic acid. When the rubber elastomer particles of the three-layer structure in which the ester is the main hard polymer, the central portion of the innermost layer of the particles is not dyed, and the two-layer structure in which only the acrylic elastic polymer portion of the intermediate layer is dyed is observed. particle of. When acrylic rubber elastomer particles are used, in the present invention, the rubber elastomer layer thus measured is The particle size is regarded as the particle diameter of the rubber elastomer particles.

When the rubber elastomer particles and the transparent acrylic base resin are combined, the rubber elastomer particles are preferably blended in a ratio of 25 to 45% by weight. When the rubber elastomer particles are blended in this ratio, the film forming property of the film is improved and the impact resistance of the resulting film is improved.

The acrylic resin used in the present invention (including the case where an acrylic resin composition of a rubber elastomer is blended in an acrylic matrix resin, and the same applies hereinafter) may contain an ultraviolet absorber, an infrared absorbing agent, a lubricating material, or a fluorescent light as needed. Various additives such as brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, and antioxidants.

The ultraviolet absorber is a compound that absorbs ultraviolet rays having a wavelength of 400 nm or less. When an ultraviolet absorber is contained in the acrylic resin film used as the protective film of the polyvinyl alcohol-based polarizing film, the effect of improving the durability of the polarizing plate in which the protective film is bonded to the polarizing film can be obtained. As the ultraviolet absorber, a known ones such as a diphenylketone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, and an acrylonitrile-based ultraviolet absorber can be used. Specific examples of the ultraviolet absorber include 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl) Phenol], 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2,4-di(t-butyl)-6 -(5-chlorobenzotriazol-2-yl)phenol, 2,2'-dihydroxy-4,4'-dimethoxydiphenyl ketone, 2,2',4,4'-tetrahydroxyl Diphenyl ketone and the like. Among these, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol] is One of the preferred ultraviolet absorbers. The blending amount of the ultraviolet absorber may be selected such that the transmittance of the obtained resin film at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, still more preferably 2% or less. Method containing ultraviolet absorber In the method of blending an ultraviolet absorber with an acrylic resin and pelletizing it, and forming it into a film by melt-extruding or the like, or directly adding a UV absorber during melt extrusion molding, etc. ; Any method can be used.

The infrared absorbing agent is a compound that absorbs infrared rays having a wavelength of 800 nm or more. Examples thereof include a nitroso compound, a metal salt thereof, a cyanine compound, a squarylium compound, a thiol nickel salt compound, a phthalocyanine compound, and naphthoquinone. Naphthalocyanine compound, triarylmethane compound, immonium compound, diimine ion compound, naphthoquinone compound, onion compound, amine compound, aminium salt A compound, carbon black, indium tin oxide, antimony tin oxide, an oxide, a carbide or a boride of a metal belonging to Group 4A or Group 5A or Group 6A of the periodic table. The infrared ray absorbing agent is preferably selected to absorb infrared rays (light having a wavelength in the range of about 800 nm to 1100 nm), or two or more types may be used in combination. The blending amount of the infrared ray absorbing agent can be appropriately adjusted, for example, so that the light transmittance of the obtained resin film at a wavelength of 800 nm or more becomes 10% or less.

The acrylic resin used to form the acrylic resin film preferably has a glass transition temperature Tg of 80 to 110 °C. When the glass transition temperature Tg is less than 80 ° C, the film obtained from the film is bonded to the polarizing film obtained by the polarizing film, and the amount of shrinkage in the heat resistance test becomes large, and sufficient heat resistance cannot be obtained. On the other hand, when the glass transition temperature is higher than 110 ° C, even if heat treatment described later is performed, defects due to crimping and shrinkage cannot be sufficiently repaired.

Further, the film made of the resin is preferably high in surface hardness, and specifically, it is preferably in accordance with JIS K 5600-5-4:1999 "General Test Method for Coatings". - Part 5: Mechanical properties of the coating film - Section 4: Scratch hardness (pencil method)", the pencil hardness measured by a load of 500 g is H or harder.

In addition, from the viewpoint of flexibility, the film is preferably one having a flexural modulus of 1,500 MPa or less as measured according to JIS K 7171:2008 "Method for determining plastic-bending properties". The flexural modulus is more preferably 1,300 MPa or less, and still more preferably 1,200 MPa or less. The flexural modulus varies depending on the type of the acrylic resin, the presence or absence of the rubber elastomer particles, and the type or amount of the rubber elastomer particles. For example, in the case of an acrylic resin, When a homopolymer of an alkyl acrylate is used, when a copolymer of an alkyl methacrylate and an alkyl acrylate or the like is used, the bending elastic modulus is generally small. Further, as the content of the rubber elastomer particles is larger, the bending elastic modulus is generally small. On the other hand, in the rubber elastomer particles, when the acrylic elastic polymer particles having the two-layer structure are used, the bending elastic modulus is generally small as compared with the case of using the acrylic elastic polymer particles having the three-layer structure. When the acrylic elastic polymer particles having a single layer structure are used, the bending elastic modulus is smaller. Further, the smaller the average particle diameter of the elastomer layer in the rubber elastomer particles or the larger the amount of the elastomer, the smaller the bending elastic modulus generally. Then, the type of the acrylic resin and the type and/or amount of the rubber elastic particles are adjusted within the predetermined range, and the bending elastic modulus may be 1,500 MPa or less.

The acrylic resin film may have a multilayer structure in which a layer formed of an acrylic resin is formed into one layer. When the resin film is formed into a multilayer structure, the layer which may be present other than the acrylic resin layer is not particularly limited in composition. Further, it may be composed of two or more kinds of acrylic resin films, and in this case, the content of the rubber elastic particles or the additives in the respective layers may be different from each other. For example, it may be formed by sandwiching a layer containing an ultraviolet absorber and/or an infrared absorber. The layer does not contain a layer of a UV absorber and an infrared absorber.

The acrylic resin film used in the present invention can be produced by forming the acrylic resin described above into a film. Since the acrylic resin film is used as a protective film of a polyvinyl alcohol-based polarizing film, the thickness thereof can be arbitrarily selected in the range of about 5 to 200 μm. The thickness thereof is preferably 10 μm or more, more preferably 150 μm or less, and still more preferably 100 μm or less.

The film formation is preferably carried out by melt-extruding the acrylic resin described so far and sandwiching it in a state of two metal rolls. In this case, the metal roll is preferably a mirror roll, whereby a resin film excellent in surface smoothness can be obtained. When the acrylic resin film is produced in a multilayer structure, the acrylic resin layer may be subjected to multilayer coextrusion so as to form one film or two or more layers.

[The function of arbitrarily added to the acrylic resin film]

From the viewpoint of preventing surface scratches in the assembly process of the liquid crystal module, the acrylic resin film can be subjected to a hard coat treatment. In addition, surface treatment such as antistatic treatment can also be performed. In addition, the antistatic function in the polarizing plate can be imparted by subjecting the acrylic resin film to surface treatment, and can be applied to other portions of the polarizing plate to which the acrylic resin film is bonded, such as an adhesive layer. The surface treatment of the acrylic resin film may be an antireflection treatment or an antifouling treatment. Further, an anti-glare treatment can be performed from the viewpoints of improving visibility, preventing external light from being reflected, and reducing moiré waves caused by drying of the enamel sheet and the color filter.

[Second resin film arbitrarily bonded]

In the first drawing, the above description is applied to one surface of the polarizing film 10. The acrylic resin film 20 (21) is formed as a polarizing plate, but the second resin film 30 can be bonded to the other surface of the polarizing film 10. The second resin film 30 may be made of an acrylic resin or may be made of another resin. Examples of the resin other than the acrylic resin which can be the second resin film 30 include a cellulose ester resin represented by triacetyl cellulose, and a norbornene resin or a polypropylene resin. Representative examples of polyolefin resins and the like.

A phase difference can be imparted to the second resin film 30. The phase difference can be imparted by performing uniaxial or biaxial stretching on the resin film. When the obtained polarizing plate 15 is bonded to a liquid crystal cell and is formed into a liquid crystal panel or a liquid crystal display device, in particular, when the second resin film 30 side is bonded to the liquid crystal cell, a phase difference is imparted to the second resin film 30. It is effective to make the optical compensation function of the liquid crystal cell.

[Method of Manufacturing Polarizing Plate]

The acrylic resin film 20 (21) is bonded to one surface of the polarizing film 10, and the second resin film 30 is bonded to the other surface of the polarizing film 10 as needed to produce the polarizing plate 15. However, in the present invention, the acrylic resin is used. The resin film 20 is subjected to heat treatment, and the heat-treated acrylic resin film 21 is bonded to the polarizing film 10. When the second resin film 30 is also made of an acrylic resin, it is preferably subjected to heat treatment and then bonded to the polarizing film 10.

When the glass transition temperature of the acrylic resin film 20 is Tg, the heat treatment is carried out at a temperature of (Tg-30 ° C) or more and (Tg + 5 ° C) or less. By performing the heat treatment at a temperature in this range, even if the acrylic resin film 20 is defective in curling due to the above-described crimping, the polarizing plate 15 can be prevented from being easily displayed. If the heat treatment temperature is lower than (Tg - 30 ° C), the curling due to the crimping of the acrylic resin film 20 cannot be sufficiently repaired. The defect is that the polarizing plate 15 obtained by bonding it to the polarizing film 10 is also likely to exhibit defects. On the other hand, when the temperature is higher than (Tg + 5 ° C), the acrylic resin film 20 is easily deformed, and the mechanical and optical uniformity of the heat-treated acrylic resin film 21 may be impaired. The heat treatment temperature is preferably not more than Tg from the viewpoint of minimizing the possibility of such deformation.

This heat treatment is preferably performed by passing the acrylic resin film 20 through the heating furnace 40 heated to the above temperature. Further, the heat treatment time is preferably in the range of 5 seconds or more and 60 seconds or less. If the heat treatment time is less than 5 seconds, the defects due to the crimping of the acrylic resin film 20 may not be sufficiently repaired. On the other hand, when the time exceeds 60 seconds, the acrylic resin film 20 is stretched to make the film width narrow.

This heat treatment is preferably performed immediately before bonding to the polarizing film 10 in order to repair defects caused by crimping and shrinkage in the acrylic resin film 20. In addition, it is preferable that the acrylic resin film 20 is wound from a long state and is wound into a roll, and is specifically sent out from the state of being wound on the first delivery roll 25 as shown in the figure. The above heat treatment is carried out, followed by bonding to the polarizing film 10. In the case of such a long resin film, the dimensional change ratio in the film width direction of the acrylic resin film 20 before the heat treatment and the acrylic resin film 21 after the heat treatment is preferably 0.3% or less. The change in the dimensional change ratio (shrinkage ratio) in the direction perpendicular to the traveling direction of the film (that is, the width direction of the film) is related to the extension of the film, and it is possible to change the optical characteristics of the protective film as a polarizing plate, and may cause There are obstacles in the production side.

"The subsequent application of the heat-treated acrylic resin film 21 to the polarizing film 10" means that the acrylic resin film 21 is not usually a roll. It is stored in a roll and attached to the polarizing film 10.

The acrylic resin film 21 subjected to heat treatment in this manner is bonded to the polarizing film 10. When the anti-glare treatment is performed on the acrylic resin film 21, the surface opposite to the anti-glare treatment layer is bonded to the polarizing film 10. When the second resin film 30 is bonded to the other surface of the polarizing film 10, as shown in the figure, the acrylic resin film 21 and the second resin film 30 which are subjected to heat treatment by the bonding rolls 50 and 51 are preferably simultaneously performed. Fit. It is preferable that the bonding surface of the polarizing film 10 of each of the acrylic resin film 21 and the second resin film 30 is subjected to physical or physicochemical properties such as corona discharge treatment. The adhesion between the polarizing film and the films 21 and 30 bonded to the both faces can be improved by performing an easy-to-continue process. The corona discharge treatment is a treatment in which a high voltage is applied between electrodes to discharge and a resin film disposed between the electrodes is activated. The effect of the corona discharge treatment varies depending on the type of the electrode, the electrode interval, the voltage, the humidity, the type of the resin film to be used, and the like, but is preferably set to, for example, an electrode interval of 1 to 5 mm and a moving speed of about 3 to 20 m/min.

The bonding of the polarizing film 10 to the acrylic resin film 21 or the bonding of the polarizing film 10 and the second resin film 30 generally uses an adhesive. When the above-described easy-to-attach treatment has been carried out, the polarizing film is bonded to the treated surface via an adhesive.

As the subsequent agent, an adhesive component such as an epoxy resin, an urethane resin, a cyanoacrylate resin, or an acrylamide resin can be used. One of the adhesives suitable for use is a solventless adhesive. A solventless type of adhesive does not contain a significant amount of solvent, but contains a hardened reaction hardened by heating or active energy rays (eg, ultraviolet light, visible light, electron beam, X-ray, etc.). a chemical component (monomer or oligomer) which forms an adhesive layer by hardening of the curable component, and typically contains a hardening component which is reactively hardened by heating or active energy ray irradiation. And a polymerization initiator. From the viewpoint of reactivity, the solventless adhesive is preferably a one which is cured by cationic polymerization, in particular, an epoxy-based compound as a curable component, and a solvent-free epoxy-based adhesive, which is a polarizing film. Since 10 is excellent in adhesion to other resin films which are the acrylic resin film 21 and the second resin film 30, it is preferably used.

The epoxy compound which is a curable component contained in the solventless epoxy-based adhesive is preferably cured by cationic polymerization, and is particularly preferably a molecule from the viewpoints of weather resistance, refractive index, and the like. An epoxy compound containing no aromatic ring. Such an epoxy compound which does not contain an aromatic ring in the molecule can be exemplified by a hydride of an aromatic epoxy compound, an alicyclic epoxy compound, an aliphatic epoxy compound or the like. Further, the epoxy compound which is a curable component usually contains two or more epoxy groups in the molecule.

First, a hydride of an aromatic epoxy compound will be described. A hydrogenated product of an aromatic epoxy compound, wherein an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound is selectively hydrogenated in the presence of a catalyst and under pressure to obtain a nuclear hydrogenated polyhydroxy compound. And it is added to the method of glycidyl ether. Examples of the aromatic epoxy compound include bisphenol epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diepoxypropyl ether of bisphenol S. ; phenol novolac epoxy resin, cresol novolac epoxy resin, and hydroxybenzaldehyde phenol phenol lacquer aldehyde epoxy resin and other novolac type epoxy resin; tetrahydroxydiphenylmethane a polyfunctional ring such as a epoxidized propyl ether, a hydroxypropyl ether of tetrahydroxydiphenyl ketone, or an epoxylated polyvinyl phenol Oxygen resin, etc. Among these raw materials, an aromatic polyhydroxy compound represented by a bisphenol which is a raw material of these is subjected to nuclear hydrogenation as described above, and a hydroxyl group thereof is reacted with epichlorohydrin to obtain an aromatic group. A hydride of an epoxy compound. Among them, the hydride of the aromatic epoxy compound is preferably a diglycidyl ether of hydrogenated bisphenol A.

Next, an alicyclic epoxy compound will be described. The alicyclic epoxy compound is an epoxy compound having one or more epoxy groups bonded to an alicyclic ring, and "having one or more epoxy groups bonded to an alicyclic ring" means having the following formula The configuration shown. Where m is an integer from 2 to 5.

Therefore, the alicyclic epoxy compound means a compound having one or more structures represented by the above formula and including two or more epoxy groups in total in the molecule. More specifically, an alicyclic epoxy compound can be obtained by removing a compound in which one or a plurality of hydrogen atoms in the above formula (CH ₂ ) _m is bonded to another chemical structure. One or a plurality of hydrogen atoms of (CH ₂ ) _m may be suitably substituted with a linear alkyl group such as a methyl group or an ethyl group. Among such alicyclic epoxy compounds, an epoxy having an epoxycyclopentane ring (m=3 in the above formula) or an epoxycyclohexane ring (m=4 in the above formula) Since the compound can obtain an adhesive having excellent adhesion strength, it is more suitable for use. Specific examples of suitable alicyclic epoxy compounds are disclosed below. Here, first, the compound name is given, and then the corresponding chemical formula is shown, and the same reference numerals are attached to the compound name and the chemical formula corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid, 3:4-ring of 3,4-epoxy-6-methylcyclohexanecarboxylic acid Oxy-6-methylcyclohexylmethyl ester, C: exoethyl bis(3,4-epoxycyclohexanecarboxylate), D: adipic acid bis(3,4-epoxycyclohexyl) Methyl)ester, E: bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, F: diethylene glycol bis(3,4-epoxycyclohexylmethyl) Ether), G: ethylene glycol bis(3,4-epoxycyclohexylmethyl ether), H:2,3,14,15-diepoxy-7,11,18,21-tetraoxa Snail-[5.2.2.5.2.2] hexadecane (this compound can be named 3,4-epoxycyclohexane spiro-2',6'-di Alkane-3", 5"-two Alkyl-3''', 4'''-epoxycyclohexane), I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-di Oxaspiro[5.5]undecane, J:4-vinylcyclohexene dioxide, K:bis-2,3-epoxycyclopentyl ether, L: dicyclopentadiene dioxide, etc. .

Further, the aliphatic epoxy compound may be an aliphatic polyhydric alcohol or a polyepoxypropyl ether of an alkylene oxide addition product thereof. More specifically, it may be diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, and triglycidyl glycerol. Ethyl ether, trimethylol propyl ether of trimethylolpropane, diepoxypropyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, by means of ethylene glycol or propylene glycol and glycerol A polyepoxy propyl ether of a polyether polyol obtained by adding one or more kinds of alkylene oxides (extended ethyl oxide or propyl oxide) to an aliphatic polyol.

The epoxy compounds described above may be used alone or in combination of two or more.

The epoxy group equivalent of the epoxy compound contained in the solventless epoxy-based adhesive is usually from 30 to 3,000 g/equivalent, preferably from 50 to 1,500 g/equivalent. When the epoxy group equivalent is less than 30 g/eq, the flexibility of the polarizing plate after the adhesive layer is cured may be lowered or the bonding strength may be lowered. On the other hand, when the epoxy group equivalent exceeds 3,000 g/eq, the compatibility with other components contained in the epoxy-based adhesive may be lowered.

In order to cationically polymerize the above epoxy compound, the solventless epoxy-based adhesive usually contains a cationic polymerization initiator. The cationic polymerization initiator is a polymer which generates a cationic species or a Lewis acid by irradiation or heating of an active energy ray such as visible light, ultraviolet rays, X-rays, or electron beams and starts the polymerization of an epoxy group. Any of these types of cationic polymerization initiators can be used, but it is preferred to impart potential from the viewpoint of workability. In addition, a cationic polymerization initiator which generates a cationic species or a Lewis acid and initiates polymerization of an epoxy group by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams is also referred to as light. Cationic polymerization initiator.

When a photocationic polymerization initiator is used, the adhesive component can be hardened at normal temperature, so that the fear of the heat resistance or swelling caused by the polarizing film can be reduced, and the resin film adhered thereto can be used. Formed in a good manner On the polarizing film. Further, when a photocationic polymerization initiator is used, since it is catalyzed by light, it is excellent in storage stability and workability even when it is mixed in an epoxy-based adhesive.

As the photocationic polymerization initiator, for example, an aromatic diazonium salt; an onium salt such as an aromatic onium salt or an aromatic onium salt; a ruthenium-arene complex or the like can be used. These photocationic polymerization initiators may be used singly or in combination of two or more kinds. Among these, the aromatic sulfonium salt is particularly suitable for use because it has ultraviolet absorbing properties even in the wavelength range of 300 nm or more, and therefore has excellent curability and can provide a cured product having good mechanical strength and adhesion strength.

These photocationic polymerization initiators can be easily obtained from commercially available products, and for example, the following are commercially available: "KAYARAD PCI-220" and "KAYARAD PCI-620" sold by Nippon Kayaku Co., Ltd. "UVI-6990" sold by Union Carbide; "ADEKAOPTOMER SP-150" and "ADEKAOPTOMER SP-170" sold by ADEKA Co., Ltd.; "CI-5102" sold by Japan Soda Co., Ltd. "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" and "CIP-2064S"; "DPI-101" and "DPI-102" sold by Midori Chemical Co., Ltd. ", "DPI-103", "DPI-105", "MPI-103", "MPI-105", "BBI-101", "BBI-102", "BBI-103", "BBI-105", "TPS-101", "TPS-102", "TPS-103", "TPS-105", "MDS-103", "MDS-105", "DTS-102" and "DTS-103"; Rhodia "PI-2074" sold, etc.

The blending amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and more preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound of the curable component.

The solventless epoxy-based adhesive contains a photosensitizer as needed in addition to the photocationic polymerization initiator. The reactivity is improved by using a photosensitizer, and the mechanical strength and the strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a reduction compound, an azo, a diazo compound, a halogen compound, and a photoreactive dye. When the photo-sensitizer is blended, the amount is from about 0.1 to 20 parts by weight based on 100 parts by weight of the epoxy compound.

Further, examples of the thermal cationic polymerization initiator which generates a cationic species or a Lewis acid by heating and initiates polymerization of an epoxy group include, for example, a benzyl phosphonium salt, a thiophenium salt, and tetrahydrothiophene ( Thiolanium) salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylate, sulfonate, aminimide, and the like. These thermal cationic polymerization initiators can also be easily obtained from commercially available products, and for example, the following are commercially available: "ADEKAOPTON CP77" and "ADEKAOPTON CP66" sold by ADEKA Co., Ltd.; "CI-2639" and "CI-2624" sold by the company; "SUNAID SI-60L", "SUNAID SI-80L" and "SUNAID SI-100L" sold by Sanshin Chemical Industry Co., Ltd. These thermal cationic polymerization initiators may be used alone or in combination of two or more. Further, a photocationic polymerization initiator and a thermal cationic polymerization initiator may also be used in combination.

The solventless epoxy-based adhesive may further contain a compound which promotes cationic polymerization such as an oxetane or a polyhydric alcohol.

When a solventless epoxy-based adhesive is used, the polarizing film 10 and the resin film 21 or 30 may be applied by applying the adhesive to the adhesive film and/or the surface of the polarizing film and bonding the two. And proceed. The method of applying the solventless epoxy-based adhesive to the resin film and/or the polarizing film is not particularly limited, and for example, it can be used. Various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater are used. In addition, each coating method has a suitable viscosity range, so a small amount of solvent can be used for viscosity adjustment. The solvent to be used for this purpose may be any one which does not lower the optical properties of the polarizing film and dissolves the epoxy-based adhesive well. For example, a hydrocarbon represented by toluene or an ester represented by ethyl acetate may be used. And other organic solvents.

After bonding the resin films 21 and 30 to the polarizing film 10 through an adhesive layer composed of an uncured epoxy-based adhesive, the adhesive film is cured by irradiation of an active energy ray or heating to form a resin film. Fixed on the polarizing film. When it is hardened by irradiation of an active energy ray, it is preferred to use ultraviolet rays. Specifically, examples of the ultraviolet light source include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a black light, a metal halide lamp, and the like. The active energy ray, for example, the irradiation intensity or the irradiation amount of the ultraviolet ray is appropriately selected so as to sufficiently activate the cationic polymerization initiator and not adversely affect the adhesive layer, the polarizing film, and the optical film after curing. In addition, when it is hardened by heating, it can be heated according to a generally known method, and the temperature and time at this time also fully activate the cationic polymerization initiator and do not cause an adhesive layer and a polarizing film or an optical film after hardening. Choose the appropriate way of adverse effects.

The adhesive layer composed of the cured product of the epoxy-based adhesive obtained in the above manner may have a thickness of usually about 0.1 to 50 μm, preferably 1 μm or more. Further, it is more preferably in the range of 1 to 20 μm, or even 2 to 10 μm.

Further, other preferred adhesives which can be used for bonding the polarizing film 10 to the acrylic resin film 21 and/or the second resin film 30 are exemplified by water connection. The agent may also be one in which the adhesive component is dissolved in water or dispersed in water. If a water based adhesive is used, the thickness of the adhesive layer can be made smaller. Examples of the aqueous binder include those in which the binder component is a water-soluble crosslinkable epoxy resin or a hydrophilic urethane-based resin.

The water-soluble crosslinkable epoxy resin may, for example, be a polyalkylamine polyamine obtained by reacting a polyalkyleneamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid, and Its polyamine epoxy resin obtained by reacting with epichlorohydrin. As a commercial product of such a polyamide resin, "Sumirez Resin 650" and "Sumirez Resin 675", which are sold under the trade name of Sumika Chemtex Co., Ltd., are available.

When the water-soluble crosslinkable epoxy resin is used as the adhesive component, it is preferable to mix another water-soluble resin such as a polyvinyl alcohol-based resin in order to further improve coatability and adhesion. The polyvinyl alcohol-based resin may be a partially modified saponified polyvinyl alcohol or a fully saponified polyvinyl alcohol, or may be a carboxy-modified polyvinyl alcohol, an ethylene-ethyl phthalate-modified polyvinyl alcohol or a hydroxymethyl-modified polyvinyl alcohol. And a modified polyvinyl alcohol-based resin such as an amine-modified polyvinyl alcohol. Among them, a saponified product of a copolymer of vinyl acetate and an unsaturated carboxylic acid or a salt, that is, a carboxy-modified polyvinyl alcohol is preferably used. Further, the "carboxy group" described herein includes the concept of -COOH and the salt.

Examples of suitable commercially available carboxy-modified polyvinyl alcohols include those of the following brands: "Kuraray Poval KL-506", "Kuraray Poval KL-318", and "Kuraray Poval KL-118" sold by Kuraray Co., Ltd. "Gohsenol T-330" and "Gohsenol T-350" sold by Japan Synthetic Chemical Industry Co., Ltd.; "DR-0415" sold by Electric Chemical Industry Co., Ltd., JAPAN VAM & POVAL Co., Ltd. "AF-17", "AT-17" and "AP-17" sold.

An adhesive containing a water-soluble crosslinkable epoxy resin can be prepared as an aqueous solution of an adhesive by dissolving the water-soluble resin such as the epoxy resin and the polyvinyl alcohol-based resin to be added as needed in water. In this case, the water-soluble crosslinkable epoxy resin preferably has a concentration in the range of about 0.2 to 2 parts by weight based on 100 parts by weight of water. Further, when the polyvinyl alcohol-based resin is blended, the amount is about 1 to 10 parts by weight, preferably about 1 to 5 parts by weight, per 100 parts by weight of water.

On the other hand, when a water-based adhesive containing an urethane-based resin is used, an example of a suitable urethane resin is an ionic polymer type urethane resin, particularly a polyester-based ionic polymer type amine. Ethyl formate resin. Here, the ionic polymer type refers to a small amount of an ionic component (that is, a hydrophilic component) introduced into the urethane resin constituting the skeleton. Further, the polyester-based ionic polymer type urethane resin refers to a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. Since the ionic polymer type urethane resin is directly emulsified in water to form an emulsion without using an emulsifier, it is suitable as a water-based adhesive. Commercially available products of the polyester-based ionic polymer type urethane resin are, for example, "Hydran AP-20" and "Hydran APX-101H" which are sold under the trade name of DIC Corporation. Obtained from the emulsion form.

When an ionic polymer type urethane resin is used as the adhesive component, a crosslinking agent such as an isocyanate is preferably blended. The isocyanate crosslinking agent is a compound having at least two isocyanato groups (-NCO) in the molecule, and examples thereof are 2,4-tolyl diisocyanate, phenyl diisocyanate, 4,4'-diphenyl group. a polyisocyanate monomer such as methane diisocyanate, 1,6-hexamethylene diisocyanate or isophorone diisocyanate, in addition to the addition of a polyhydric alcohol such as trimethylolpropane to the plurality of molecules The product, three molecules of diisocyanate each with its single terminal isocyanate moiety The polyisocyanate such as a biuret formed by hydrating/decarboxylation of a trifunctional isocyanate forming a trimeric isocyanate ring and 3 molecules of a diisocyanate 3 molecule each having a mono-terminal isocyanate moiety Quality and so on. A commercially available isocyanate-based crosslinking agent which is suitable for use is, for example, a product name "HydranAssist C-1" sold by DIC Corporation.

When a water-based adhesive containing an ionic polymer type urethane resin is used, it is preferably dissolved in such a manner that the urethane resin concentration is about 10 to 70% by weight from the viewpoint of viscosity and adhesion. The dispersion in water is more preferably 20% by weight or more and 50% by weight or less. When the isocyanate-based crosslinking agent is blended, the blending amount is appropriately selected from about 100 parts by weight to the urethane-based resin, and the isocyanate-based crosslinking agent is used in an amount of from 5 to 100 parts by weight.

When such a water-based adhesive is used, the polarizing film 10 and the heat-treated acrylic resin film 21 and/or the second resin film 30 may be applied to the polarizing film 10 and/or paste by the adhesive. The bonding surfaces of the films 21 and 30 which are bonded thereto are bonded together and bonded together. More specifically, a method in which a water-based adhesive is uniformly applied to a polarizing film by a coating method such as a doctor blade, a wire bar, a die coater, a notch coater, or a gravure coater is exemplified. After 10 and/or the films 21 and 30 bonded thereto, the other film is superposed on the coated surface, and the film is attached and dried by a roll or the like. Drying can be carried out, for example, at a temperature of from about 60 to 100 °C. In order to improve the adhesion, it is preferred to maintain the temperature at a temperature slightly above room temperature, for example, at a temperature of about 30 to 50 ° C for about 1 to 10 days after drying.

The acrylic resin film 21 is bonded to one surface of the polarizing film 10, and the second resin film bonded to the other surface of the polarizing film 10 is made of an acrylic resin film or a resin film other than the acrylic resin. Time, The same adhesive may be used for the film to be bonded to both sides of the polarizing film 10, and a different adhesive may be used. However, in order to simplify the manufacturing steps and to reduce the constituent members of the polarizing plate, it is preferable to use the same adhesive under an appropriate adhesion.

Example

The present invention will be more specifically described below by showing examples and comparative examples, but the present invention is not limited to the examples. In the example, the "parts" of the usage amount are based on the weight basis unless otherwise specified.

[Example 1] (acrylic resin and acrylic rubber elastomer particles)

A copolymer of methyl methacrylate/methyl acrylate in a weight ratio of 96/4 was used as the acrylic matrix resin. Further, the three-layer structure rubber elastomer particles are composed of acrylic rubber elastomer particles, and the three-layer structure rubber elastomer particles are composed of the following innermost layer, intermediate layer, and outermost layer, and the innermost layer is in methacrylic acid. The methyl ester is a hard polymer obtained by polymerizing a small amount of allyl methacrylate. The middle layer is a soft elastomer mainly composed of butyl acrylate and styrene and a small amount of allyl methacrylate. The outer layer was a hard polymer obtained by polymerizing a small amount of ethyl acrylate in methyl methacrylate, and the average particle diameter to the elastomer belonging to the intermediate layer was 240 nm.

(Production of acrylic resin film)

The weight ratio of the acrylic resin and the acrylic rubber elastomer particles of the former/the latter = 70/30 is blended into a pellet, and the ingot is melt-kneaded in a twin-screw extruder while being 100 parts by weight. 0.05 parts of stearic acid which is a lubricant was added and mixed to prepare an acrylic resin composition ingot. The acrylic resin group was measured by a differential scanning calorimeter (DSC) manufactured by Seiko Instruments Co., Ltd. The glass transition temperature Tg of the resultant was 106 °C. The ingot was placed in a 65 mm φ single-axis extruder and extruded through a T-die at a set temperature of 275 ° C. The two sides of the extruded film-like molten resin were mirror-mounted with two polishing rolls at a set temperature of 45 ° C. The (polishing roll) was cooled by sandwiching to prepare an acrylic resin film. The resulting film was taken up in a core of 6 直径 (15.2 cm) in diameter.

(heat treatment of acrylic resin film and polarizing plate)

The acrylic resin film obtained above was taken up from a roll, and while being subjected to a tensile force of 500 N in the longitudinal direction, the film was passed through a heating furnace maintained at 85 ° C (Tg - 21 ° C) for 17 seconds to carry out heat treatment. After the film leaves the furnace, the dimensional shrinkage in the width direction is 0.2%. The film which leaves the furnace is then subjected to a corona discharge treatment, and its state is maintained without being taken up, and is directly supplied to the subsequent bonding of the polarizing film. One side of a polarizing film having a thickness of about 30 μm in which polyvinyl alcohol is adsorbed to iodine is adhered to the corona discharge treated surface of the acrylic resin film subjected to heat treatment and corona discharge treatment through an adhesive, and is polarized. The other surface of the film was bonded to the corona discharge treated surface of the decene-based resin film subjected to corona discharge treatment through an adhesive, and the adhesive was cured to prepare a polarizing plate.

(Cutting and inspection of polarizing plates)

Using a presser, 100 sheets of a wide 46 type television (about 103 cm x about 59 cm) were cut from the polarizing plate obtained above. With respect to the 100 polarizing plates thus cut, the number of polarizing plates which exhibited unevenness defects due to the acrylic resin film was calculated. As a result, defects due to the acrylic resin film were observed on 9 polarizing plates.

[Embodiment 2]

A polarizing plate was produced in the same manner as in Example 1 except that the tension at the time of heat treatment was changed from 500 N to 300 N, and the film was cut and inspected. this At this time, the dimensional shrinkage ratio of the acrylic resin film in the width direction after leaving the heating furnace was 0.2%. As a result of the inspection, defects due to the acrylic resin film were observed on 9 polarizing plates.

[Example 3]

A polarizing plate was produced in the same manner as in Example 1 except that the temperature of the heating furnace subjected to the heat treatment was changed from 85 ° C to 95 ° C (Tg - 11 ° C), and the tension applied to the film at this time was changed from 500 N to 300 N. , cut and check. At this time, the dimensional shrinkage ratio of the acrylic resin film in the width direction after leaving the heating furnace was 0.2%. As a result of the inspection, defects due to the acrylic resin film were observed on one polarizing plate.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 1 except that the temperature of the heating furnace subjected to the heat treatment was changed from 85 ° C to 23 ° C (Tg - 83 ° C), and the film was cut and inspected. At this time, the dimensional shrinkage ratio of the acrylic resin film in the width direction after leaving the heating furnace was 0.1%. As a result of the inspection, defects due to the acrylic resin film were observed on 90 polarizing plates.

[Comparative Example 2]

A polarizing plate was produced in the same manner as in Example 1 except that the temperature of the heating furnace subjected to the heat treatment was changed from 85 ° C to 75 ° C (Tg - 31 ° C), and the film was cut and inspected. At this time, the dimensional shrinkage ratio of the acrylic resin film in the width direction after leaving the heating furnace was 0.1%. As a result of the inspection, defects due to the acrylic resin film were observed on 27 polarizing plates.

[Comparative Example 3]

In addition to changing the temperature of the furnace that performs the heat treatment from 85 ° C to A polarizing plate was produced in the same manner as in Example 1 except that the tension applied to the film at this time was changed from 500 N to 300 N at 75 ° C (Tg - 31 ° C), and the film was cut and inspected. At this time, the dimensional shrinkage ratio of the acrylic resin film in the width direction after leaving the heating furnace was 0.1%. As a result of the inspection, defects due to the acrylic resin film were observed on 26 polarizing plates.

The main fluctuation conditions and results in the above examples and comparative examples are summarized in Table 1. In the "judgment" column of the "polarization plate inspection result", if the number of defects determined in the 100 polarizing plates examined is 20 or less (the defect rate is 20% or less), it is represented as a representative. In the case of "○" which is a good one, if it is judged that the number of defects is more than 20 pieces (the defect rate exceeds 20%), it means "x" which is a defective.

As shown in Table 1, Comparative Example 1 in which the furnace temperature was 23 ° C (room temperature) corresponds to an example in which heat treatment was not actually performed, but at this time, most of the polarizing plates were observed to have defects, which was represented by acrylic acid. The defects caused by the crimping of the resin film are directly transferred to the polarizing plate. In Comparative Examples 2 and 3 in which the temperature of the heating furnace was raised to 75 ° C, the number of polarizing plates in which defects were observed was decreased as compared with Comparative Example 1, but the curling contraction caused by the acrylic resin film was observed. Defect It is repaired to some extent by heat treatment, but it is still insufficient.

On the other hand, in Examples 1 to 3 in which the temperature of the heating furnace was (Tg - 30 ° C) or more, it was found that the defects caused by the crimping of the acrylic resin film were largely repaired, and the defect rate of the polarizing plate was 20% or less. (10% or less). When the tension applied to the film during the heat treatment is appropriately adjusted according to the treatment temperature, the dimensional change ratio (shrinkage ratio) in the film width direction by the heat treatment can be suppressed to a small value.

(industrial availability)

According to the method of the present invention, even if the acrylic resin before bonding with the polarizing film is defective due to crimping, the polarizing film having less defects can be produced by bonding the polarizing film after the heat treatment. . Therefore, even if it is a roll which melts and shrinks the acrylic resin film, the productivity of the polarizing plate which uses an acryl resin film as a protective film can be improved highly.

10‧‧‧Polarized film

15‧‧‧Polar plate

20‧‧‧Acrylic resin film (raw film before heat treatment)

21‧‧‧A heat-treated acrylic resin film

25‧‧‧First delivery reel

30‧‧‧Second resin film

35‧‧‧Second delivery reel

40‧‧‧heating furnace

45‧‧‧Conveying roller

50, 51‧‧‧ affixing rolls

60‧‧‧ product reel

Claims (6)

A method for producing a polarizing plate, wherein a polarizing film is bonded to a polarizing film containing a polyvinyl alcohol-based resin that adsorbs a dichroic dye to produce a polarizing plate, wherein the manufacturing method has the following steps: a heat treatment step, When the glass transition temperature of the acrylic resin film is Tg, the acrylic resin film is subjected to heat treatment at a temperature within a range of (Tg-30 ° C) or more and (Tg + 5 ° C) or less; and a bonding step Then, the acrylic resin film subjected to the heat treatment is bonded to the polarizing film. The method for producing a polarizing plate according to the first aspect of the invention, wherein the acrylic resin film is formed of an acrylic resin composition, and the acrylic resin composition is 25 to 45 in an acrylic matrix resin. The ratio of % by weight is blended with rubber elastomer particles having a number average particle diameter of 10 to 300 nm. The method for producing a polarizing plate according to claim 1 or 2, wherein the heat treatment step is performed in a heating furnace heated to the above temperature. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the heating treatment step is performed in a range of 5 seconds or longer and 60 seconds or shorter. The method for producing a polarizing plate according to any one of the first to fourth aspect, wherein the acrylic resin film is subjected to the heating while being wound up in a state of being wound into a roll. The processing steps are followed by the aforementioned bonding step. The method for producing a polarizing plate according to claim 5, wherein the heat treatment step is performed in the following manner: before the heat treatment and after the heat treatment The dimensional change ratio of the acrylic resin film in the width direction perpendicular to the traveling direction is 0.3% or less.