JP2017120440A - Method for manufacturing polarizing plate - Google Patents

Abstract

The present invention provides a method capable of manufacturing a polarizing plate with few defects in a state where the defect is repaired and bonded to a polarizing film even when an acrylic resin film in which a defect occurs due to winding tightening is used. A method for producing a polarizing plate by laminating an acrylic resin film to a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented, the glass transition temperature of the acrylic resin. Is a heat treatment step of performing heat treatment by passing the acrylic resin film 20 through a heating furnace 40 maintained at a temperature in the range of (Tg−30 ° C.) to (Tg + 5 ° C.) The manufacturing method of the polarizing plate 15 provided with the bonding process which bonds the acrylic resin film 21 with which it was applied to the polarizing film 10 with the bonding rolls 50 and 51 continuously is provided. [Selection] Figure 1

Description

  The present invention relates to a method for producing a polarizing plate by bonding an acrylic resin film as a protective film to a polyvinyl alcohol polarizing film.

  A polarizing plate is widely used mainly for components of liquid crystal display devices. A polarizing plate usually circulates in a state where a protective film is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol-based resin, and is incorporated into a liquid crystal display device or the like. Traditionally, a triacetyl cellulose film has been used as a protective film for a polyvinyl alcohol polarizing film constituting such a polarizing plate. However, triacetyl cellulose does not have sufficient heat-and-moisture resistance, and a polarizing plate using a triacetyl cellulose film as a protective film sometimes has reduced performance such as degree of polarization and hue under high-temperature and wet-heat conditions. .

  Then, use of the acrylic resin film excellent in transparency and heat-and-moisture resistance is examined as a protective film which replaces triacetylcellulose. For example, in JP 2007-25008 A (Patent Document 1), a thermoplastic resin layer that can be peeled off on both sides of an acrylic resin film having a thickness of 40 μm or less is formed, and the thermoplastic resin layers on both sides are not used before use. And a protective film for a polarizing plate is disclosed. JP 2007-41563 A (Patent Document 2) discloses a protective film having a three-layer structure of an acrylic resin film / polyethyleneimine layer / polyvinyl alcohol resin layer, and a polyvinyl alcohol resin on the polyvinyl alcohol resin layer side. It is disclosed that it is bonded to a polarizing film to form a polarizing plate. JP 2007-52404 A (Patent Document 3) discloses that a polarizing plate is provided on one surface of a polyvinyl alcohol polarizing film in the order of an adhesive layer / metal salt layer / protective film, and the protective film. Is made of an acrylic resin. In JP 2009-25762 (Patent Document 4), 0.1 to 1.5 parts by weight of a lubricant composed of a metal salt is blended with 100 parts by weight of a resin component mainly composed of an acrylic resin. A protective film is disclosed. JP 2009-163216 (Patent Document 5) discloses a liquid crystal display in which an antiglare film made of an acrylic resin film having a hard coat layer is laminated on one surface of a polyvinyl alcohol polarizing film. It is disclosed that the polarizing plate is disposed on the viewing side of the apparatus, and the acrylic resin constituting the antiglare film contains acrylic rubber particles from the viewpoint of impact resistance and film forming property of the film. There is also a statement that it is preferable.

  Not only the acrylic resin film but also the resin film is generally wound up around a cylindrical core after production and stored in a roll shape. Then, after storage for a predetermined period, for example, it may be tightened in a wound state, and a phenomenon called tightening in which a dent or the like is observed on the outermost surface of the roll film may occur. When such tightening occurs, the indentation or the like becomes a defect, making it practically impossible to apply to optical applications. In particular, it has been clarified that such tightening is likely to occur in an acrylic resin film.

JP 2007-25008 A JP 2007-41563 A JP 2007-52404 A JP 2009-25762 A JP 2009-163216 A

  Therefore, the object of the present invention is to produce a polarizing plate with few defects even when an acrylic resin film in which defects are generated by winding tightening is used and the defects are repaired and bonded to a polarizing film. Is to provide.

  The present inventors have found that a polarizing plate with few defects can be produced by applying a heat treatment to an acrylic resin film in which defects have occurred due to tightening and then bonding the film to a polarizing film. The present invention has been completed.

  That is, according to the present invention, there is provided a method for producing a polarizing plate by laminating an acrylic resin film to a polarizing film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. A heat treatment step for heat-treating the film at a temperature within the range of (Tg−30 ° C.) to (Tg + 5 ° C.), where the glass transition temperature is Tg, and an acrylic resin film subjected to the heat treatment A manufacturing method of a polarizing plate provided with the pasting process of pasting on a polarizing film continuously is provided.

  The acrylic resin film used in this method is preferably formed from an acrylic resin composition in which rubber elastic particles are blended with an acrylic base resin, and the rubber elastic particles have a number average particle diameter. It is preferable that it exists in the range of 10-300 nm, and is mix | blended in the ratio of 25 to 45 weight% with respect to said acrylic base resin.

  In these methods, the heat treatment step is preferably performed in a heating furnace heated to the above temperature. Moreover, it is preferable that a heat processing process is performed for the time within the range of 5 second or more and 60 second or less. The acrylic resin film is preferably subjected to the heat treatment step and then the bonding step while unwinding from a long and rolled state. In this case, the heat treatment step is preferably performed so that the dimensional change rate in the width direction orthogonal to the flow 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, a polarizing plate with few defects can be produced by bonding to a polarizing film after heat treatment even for an acrylic resin film in which defects due to tightening have occurred. . Therefore, even a roll of an acrylic resin film in which winding tightening has occurred can be used, and the productivity of a polarizing plate using the acrylic resin film as a protective film can be significantly increased.

It is a side view which shows typically the example of arrangement | positioning of the apparatus used for manufacture of a polarizing plate.

  With reference to FIG. 1, in this invention, the acrylic resin film 20 (21) is bonded to the polarizing film 10 which consists of polyvinyl alcohol-type resin in which the dichroic pigment | dye has adsorbed and oriented, and the polarizing plate 15 is manufactured. To do. Then, the acrylic resin film (raw film) 20 is subjected to a heat treatment before being bonded to the polarizing film 10, and the acrylic resin film 21 thus subjected to the heat treatment is bonded to the polarizing film 10. The

  In the example shown in FIG. 1, the raw film 20 made of an acrylic resin fed from the first feeding roll 25 passes through a heating furnace 40, where heat treatment is performed, and thus the heat-treated acrylic resin. The film 21 is supplied to one surface of the polarizing film 10, and a second resin film 30 fed separately from the second feeding roll 35 is supplied to the other surface of the polarizing film 10 and subjected to heat treatment. The polarizing plate 15 obtained by being bonded by the bonding rolls 50 and 51 so as to be in the order of the acrylic resin film 21 / polarizing film 10 / second resin film 30 is wound around the product roll 60. Yes. In the heating furnace 40, the acrylic resin film 20 is transported by a plurality of transport rolls 45, 45. As for the polarizing film 10, what was manufactured in the polarizing film manufacturing process mentioned later is generally sent as it is. In FIG. 1, the straight arrow means the film traveling direction, and the curved arrow means the roll rotation direction. In the example shown in FIG. 1, the step of passing through the heating furnace 40 corresponds to the heat treatment step, and the step of bonding by the bonding rolls 50 and 51 corresponds to the bonding step.

As in the example shown in FIG. 1, when the polarizing plate 15 is manufactured by bonding resin films on both surfaces of the polarizing film 10, at least one resin film may be made of an acrylic resin.
When an acrylic resin film is bonded to both surfaces of the polarizing film 10 to form the polarizing plate 15, it is preferable that each of the acrylic resin films is subjected to a heat treatment according to the present invention and then subjected to a bonding process. . On the other hand, a resin film can be bonded to only one surface of the polarizing film 10 to form a polarizing plate. In that case, the resin film may be made of an acrylic resin.

  Hereinafter, the polarizing film 10 and the acrylic resin film 20 that are used in the present invention, and the second resin film 30 that is optionally used will be described step by step, and then the manufacturing method of the polarizing plate will be described. To do.

[Polarized film]
The polarizing film 10 is obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film so as to obtain predetermined polarization characteristics. Typically, iodine or a dichroic organic dye is used as the dichroic dye. That is, the polarizing film includes an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol resin film, and a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin film.

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

  The polarizing film 10 is usually a humidity adjusting step for adjusting the moisture of the polyvinyl alcohol-based resin film, a step of uniaxially stretching the polyvinyl alcohol-based resin film, and a dichroic dye that is obtained by dyeing a polyvinyl alcohol-based resin film with a dichroic pigment , A step of treating a polyvinyl alcohol resin film having a dichroic dye adsorbed and oriented with an aqueous boric acid solution, a water washing step of washing away boric acid adhering to the surface after boric acid treatment, and water washing It is manufactured through a step of drying later.

  Uniaxial stretching may be performed before dyeing, may be performed during dyeing, or may be performed during boric acid treatment after dyeing. You may uniaxially stretch in these several steps. Uniaxial stretching may be performed between rolls having different peripheral speeds, or may be performed using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times. The polyvinyl alcohol polarizing film obtained by uniaxial stretching and dyeing and further boric acid treatment, washing with water and drying can have a thickness of, for example, about 1 to 50 μm, preferably 10 ~ 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 alkyl methacrylate. Specifically, a homopolymer of alkyl methacrylate or a copolymer using two or more kinds of alkyl methacrylate may be used, or 50 wt% or more of alkyl methacrylate and 50 wt% of monomers other than alkyl methacrylate. % Or less copolymer. As the alkyl methacrylate, those having 1 to 4 carbon atoms of the alkyl group are usually used, and methyl methacrylate is preferably used among them.

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

  This acrylic resin preferably does not have a glutarimide derivative, a glutaric anhydride derivative, a lactone ring structure, or the like. An acrylic resin having a cyclic structure such as a glutarimide derivative, a glutaric anhydride derivative, or a lactone ring structure tends to make it difficult to obtain sufficient mechanical strength and wet heat resistance as an optical film. In other words, in this acrylic resin, the monomer consists essentially of alkyl methacrylate, or the alkyl methacrylate accounts for 70% by weight or more, preferably 90% by weight or more of the monomer composition, It is preferably a copolymer of only a monomer selected from alkyl acrylate, a styrene monomer and an unsaturated nitrile.

  The acrylic resin is an acrylic resin composition in which rubber elastic particles are blended with the above-mentioned acrylic base resin from the viewpoint of film-formability to a film and impact resistance when made into a film. You can also. This rubber elastic body particle is a particle having a layer exhibiting rubber elasticity, and may be a particle composed only of a layer exhibiting rubber elasticity, or a particle having a multilayer structure having another layer together with a layer exhibiting rubber elasticity. There may be. Examples of the rubber elastic body include an olefin elastic polymer, a diene elastic polymer, a styrene-diene elastic copolymer, an acrylic elastic polymer, and the like. Among these, an acrylic elastic polymer is preferably used from the viewpoints of surface hardness, light resistance, and transparency when used as a protective film for a polarizing plate.

  The acrylic elastic polymer can be composed of a polymer mainly composed of alkyl acrylate. This may be a homopolymer of alkyl acrylate or a copolymer of 50% by weight or more of alkyl acrylate and 50% by weight or less of other monomers. As the alkyl acrylate, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of copolymerization of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkylstyrene, acrylonitrile and methacrylo Monofunctional monomers such as unsaturated nitriles such as nitriles, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate, and dibasic acids such as diallyl maleate And polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

  The rubber elastic particles containing the acrylic elastic polymer are preferably multi-layered particles having an acrylic elastic polymer layer. Specifically, a two-layer structure having a hard polymer layer mainly composed of alkyl methacrylate on the outside of the acrylic elastic body, or a hard body mainly composed of alkyl methacrylate inside the acrylic elastic body. The thing of the 3 layer structure which has a polymer layer is mentioned. An example of the monomer composition in the polymer mainly composed of alkyl methacrylate constituting the hard polymer layer formed on the outside or inside of the acrylic elastic body is the methacrylic acid mentioned above as an example of the acrylic resin. This is the same as the monomer composition example of the polymer mainly composed of alkyl, and a monomer composition mainly composed of methyl methacrylate is preferably used. Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

  The rubber elastic particles blended in the acrylic base resin preferably have a number average particle size of the rubber elastic layer contained therein in the range of 10 to 300 nm. By blending such rubber elastic particles, a protective film that hardly peels off from the adhesive layer can be obtained when it is bonded to a polarizing film using an adhesive. The average particle diameter of the rubber elastic particles is preferably 50 nm or more, and preferably 250 nm or less.

  The average particle diameter of the rubber elastic particles containing the acrylic elastic polymer is measured as follows. That is, such rubber elastic particles are mixed with an acrylic base resin to form a film, and when the cross section is dyed with an aqueous solution of ruthenium oxide, only the rubber elastic layer is colored and observed in a substantially circular shape, The acrylic resin of the mother layer is not dyed. Therefore, from the cross section of the film dyed in this way, a thin piece is prepared using a microtome or the like, and this is observed with an electron microscope. And after extracting 100 dye | stained rubber elastic body particles at random and calculating each particle diameter, let the number average value be an average particle diameter. In order to measure by such a method, the average particle diameter of the rubber elastic body prescribed | regulated by this invention turns into a number average particle diameter.

  When the outermost layer is a hard polymer mainly composed of methyl methacrylate and rubber elastic particles in which an acrylic elastic polymer is encapsulated are used, when mixed with an acrylic base resin, The outermost layer of the rubber elastic particles is mixed with the acrylic base resin. Therefore, when the cross section is dyed with ruthenium oxide and observed with an electron microscope, the rubber elastic particles are observed as particles excluding the outermost layer. Specifically, when rubber elastic particles having a two-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a hard polymer mainly composed of methyl methacrylate, the acrylic elastic of the inner layer is used. The polymer part is dyed and observed as particles of a single layer structure, 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. When rubber elastic particles with a three-layer structure, which is a hard polymer mainly composed of methyl acid, are used, the innermost particle center portion is not dyed, and only the acrylic elastic polymer portion of the intermediate layer is dyed. It will be observed as particles having a two-layer structure.

  Such rubber elastic particles are preferably blended in a proportion of 25 to 45% by weight based on the total amount with the transparent acrylic base resin described above. By blending the rubber elastic particles at this ratio, the effect of improving the film-forming property to the film and improving the impact resistance of the obtained film is exhibited.

  The acrylic resin used in the present invention (including the case of an acrylic resin composition in which a rubber elastic body is blended with an acrylic base resin, the same shall apply hereinafter), an ultraviolet absorber, an infrared absorber, Various additives such as a lubricant, a fluorescent brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, and an antioxidant may be contained.

  The ultraviolet absorber is a compound that absorbs ultraviolet rays having a wavelength of 400 nm or less. The effect which improves the durability of the polarizing plate by which this protective film was bonded to the polarizing film is acquired because the acrylic resin film used as a protective film of a polyvinyl-alcohol-type polarizing film contains a ultraviolet absorber. As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile 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-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, and the like. Among these, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol] is one of preferable ultraviolet absorbers. One. The blending amount of the ultraviolet absorber can be selected in such a range 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, and further preferably 2% or less. As a method of containing the ultraviolet absorber, the ultraviolet absorber is premixed in an acrylic resin and pelletized, and this is formed into a film by melt extrusion or the like. Any method can be used.

  An infrared absorber is a compound that absorbs infrared rays having a wavelength of 800 nm or more. For example, nitroso compounds, metal complex salts thereof, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, naphthalocyanine compounds, triarylmethane compounds, imonium compounds, diimonium compounds, naphthoquinone compounds, List anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides, carbides or borides of metals belonging to groups 4A, 5A or 6A of the periodic table Can do. These infrared absorbers are preferably selected so that they can absorb the entire infrared rays (light having a wavelength in the range of about 800 nm to 1100 nm), and two or more types may be used in combination. The compounding quantity of an infrared absorber can be suitably adjusted, for example so that the light transmittance in wavelength 800nm or more of the resin film obtained may be 10% or less.

  The acrylic resin for forming an acrylic resin film preferably has a glass transition temperature Tg in the range of 80 to 110 ° C. When the glass transition temperature Tg is lower than 80 ° C., the polarizing plate obtained by laminating the film formed from the polarizing film has a large shrinkage in the heat resistance test, and sufficient heat resistance cannot be obtained. There is. On the other hand, when the glass transition temperature is higher than 110 ° C., a defect generated by tightening may not be sufficiently repaired even if a heat treatment described later is performed.

  The film formed from this resin has a high surface hardness. Specifically, JIS K 5600-5-4: 1999 “Paint General Test Method—Part 5: Mechanical Properties of Coating Film— It is preferable that the pencil hardness measured with a load of 500 g according to “Section 4: Scratch hardness (pencil method)” is H or higher.

Further, from the viewpoint of flexibility, this film preferably has a flexural modulus of 1,500 MPa or less measured according to JIS K 7171: 2008 "Plastics-Determination of 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 acrylic resin, the presence / absence of rubber elastic particles, and the type and amount of rubber elastic particles when blended. In general, the flexural modulus is smaller when a copolymer of alkyl methacrylate and alkyl acrylate is used than when an alkyl homopolymer is used. In general, the flexural modulus decreases as the content of the rubber elastic particles increases.
On the other hand, the elastic modulus particles generally have a smaller bending elastic modulus than the acrylic elastic polymer particles having the three-layer structure described above rather than the acrylic elastic polymer particles having the two-layer structure described above. The bending elastic modulus becomes even smaller when the acrylic elastic polymer particles having a layer structure are used. Furthermore, as the average particle size of the elastic body in the rubber elastic body particles is smaller or the amount of the elastic body is larger, the bending elastic modulus is generally smaller. Therefore, the kind of acrylic resin, and further, the kind and / or amount of the elastic rubber particles may be adjusted within the predetermined range so that the flexural modulus is 1,500 MPa or less.

  The acrylic resin film may have a multilayer structure in which a layer formed from an acrylic resin is a single layer. When the resin film has a multilayer structure, the composition of the layer that can exist other than the acrylic resin layer is not particularly limited. Moreover, it can also be set as the structure on which 2 or more types of acrylic resin films were laminated | stacked, In that case, you may mutually differ content in each layer of rubber elastic-body particle | grains or an above-described additive. For example, a configuration in which layers containing no ultraviolet absorber and no infrared absorber are stacked with a layer containing an ultraviolet absorber and / or an infrared absorber interposed therebetween may be employed.

  By forming the acrylic resin described above into a film, the acrylic resin film used in the present invention can be manufactured. Since this acrylic resin film is used as a protective film for a polyvinyl alcohol polarizing film, the thickness can be arbitrarily selected from the range of about 5 to 200 μm. The thickness is preferably 10 μm or more, preferably 150 μm or less, more preferably 100 μm or less.

  For film formation, a method in which the acrylic resin described so far is melt-extruded and sandwiched between two metal rolls is preferably employed. In this case, the metal roll is preferably a mirror roll, whereby a resin film having excellent surface smoothness can be obtained. When the acrylic resin film is produced in a multilayer structure, the multilayer film may be formed by co-extrusion so that the acrylic resin layer has one layer or two or more layers.

[Functions that can be arbitrarily added to the acrylic resin film]
The acrylic resin film can be subjected to a hard coat treatment from the viewpoint of preventing surface scratches in the assembly process of the liquid crystal module. In addition, surface treatment such as antistatic treatment can be performed. In addition, the antistatic function in the polarizing plate can be imparted by applying a surface treatment to the acrylic resin film, and other parts of the polarizing plate to which the acrylic resin film is bonded, such as an adhesive layer. It can also be granted. Other examples of surface treatment for the acrylic resin film include antireflection treatment and antifouling treatment.
Furthermore, an antiglare treatment can be performed from the viewpoints of improving visibility, preventing reflection of external light, and reducing moire due to interference between the prism sheet and the color filter.

[Second resin film to be arbitrarily bonded]
With reference to FIG. 1, in this invention, the acrylic resin film 20 (21) demonstrated above is bonded to one surface of the polarizing film 10, and it is set as a polarizing plate. The second resin film 30 can be bonded to the surface. The second resin film 30 may be composed of an acrylic resin or may be composed of other resins. Examples of resins other than acrylic resins that can be the second resin film 30 include cellulose ester resins typically represented by triacetyl cellulose, polyolefin resins typically represented by norbornene resins and polypropylene resins. is there.

  The second resin film 30 may be provided with a phase difference. The phase difference can be imparted by uniaxially or biaxially stretching the resin film. When the obtained polarizing plate 15 is bonded to a liquid crystal cell to form a liquid crystal panel or a liquid crystal display device, particularly when the second resin film 30 side is bonded to the liquid crystal cell, it is positioned on the second resin film 30. It is effective to provide a phase difference to serve as an optical compensation function for the liquid crystal cell.

[Production method of polarizing plate]
An acrylic resin film 20 (21) is bonded to one surface of the polarizing film 10, and a second resin film 30 is bonded to the other surface of the polarizing film 10 as necessary. In the present invention, the acrylic resin film 20 is subjected to heat treatment, and the acrylic resin film 21 subjected to the heat treatment is bonded to the polarizing film 10.
When the second resin film 30 is also made of an acrylic resin, it is preferable that the second resin film 30 is also bonded to the polarizing film 10 after being subjected to heat treatment.

  This heat treatment is performed at a temperature in the range of (Tg−30 ° C.) to (Tg + 5 ° C.), where Tg is the glass transition temperature of the acrylic resin film 20. By performing the heat treatment at a temperature within this range, even if the acrylic resin film 20 has the defect due to the above-described winding tightening, the defect is repaired and the defect is less likely to appear on the polarizing plate 15. it can. When the temperature of the heat treatment is lower than (Tg-30 ° C.), the repair of defects due to tightening occurring in the acrylic resin film 20 becomes insufficient, and the polarizing plate obtained by bonding it to the polarizing film 10 15 also tends to show defects. On the other hand, when the temperature exceeds (Tg + 5 ° C.), the acrylic resin film 20 is likely to be deformed, and the mechanical and optical uniformity of the heat-treated acrylic resin film 21 may be impaired. From the viewpoint of reducing the possibility of such deformation as much as possible, the temperature of the heat treatment is preferably Tg or less.

  As shown in the figure, this heat treatment is preferably performed by passing the acrylic resin film 20 through a heating furnace 40 heated to the above temperature. The heat treatment time is preferably in the range of 5 seconds to 60 seconds. If the heat treatment time is less than 5 seconds, there is a possibility that defects due to tightening occurring in the acrylic resin film 20 cannot be sufficiently repaired. On the other hand, when the time exceeds 60 seconds, the acrylic resin film 20 is stretched, and the width of the film may be narrowed.

  Since this heat treatment is for repairing defects caused by tightening occurring in the acrylic resin film 20, it is preferably performed immediately before being bonded to the polarizing film 10. Further, from the same viewpoint, the acrylic resin film 20 is long and wound in a roll shape, specifically, while being unwound from the state wound on the first feeding roll 25 as shown above, It is preferable that the heat treatment is performed, and subsequently subjected to bonding to the polarizing film 10. When a long resin film is thus targeted, the dimensional change rate in the width direction orthogonal to the flow direction between 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. An increase in the dimensional change rate (shrinkage rate) in the film width direction leads to stretching of the film, which may cause a change in the optical specification as a polarizing plate protective film, and also hinders production. I must come.

  The acrylic resin film 21 thus heat-treated is bonded to the polarizing film 10. In the case where the above-described antiglare treatment is applied to the acrylic resin film 21, the acrylic resin film 21 is bonded to the polarizing film 10 on the surface opposite to the antiglare treatment layer. When the second resin film 30 is bonded to the other surface of the polarizing film 10, the bonding of the acrylic resin film 21 and the second resin film 30 that have been heat-treated is bonded as illustrated. It is preferable to carry out simultaneously by the combined rolls 50 and 51. Prior to bonding, the bonding surfaces of the acrylic resin film 21 and the second resin film 30 to the polarizing film 10 are subjected to physical or physicochemical easy adhesion treatment such as corona discharge treatment. It is preferable to keep it. By performing the easy adhesion treatment, the adhesive force between the polarizing film and the films 21 and 30 bonded to both surfaces thereof can be increased. The corona discharge treatment is a treatment for activating the resin film disposed between the electrodes by discharging by applying a high voltage between the electrodes. The effect of corona discharge treatment varies depending on the type of electrode, electrode interval, voltage, humidity, type of resin film used, etc., but for example, the electrode interval is set to 1 to 5 mm and the moving speed is set to about 3 to 20 m / min. It is preferable to do this.

  In general, an adhesive is used for bonding the polarizing film 10 and the acrylic resin film 21 and bonding the polarizing film 10 and the second resin film 30. When the above-mentioned easy adhesion treatment is performed, a polarizing film is bonded to the treated surface via an adhesive.

  As the adhesive, an adhesive having epoxy resin, urethane resin, cyanoacrylate resin, acrylamide resin, or the like as an adhesive component can be used. One of the adhesives preferably used is a solventless adhesive. Solventless adhesives do not contain a significant amount of solvent, and are curable components (monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.). The adhesive layer is formed by curing of the curable component, and typically comprises a curable component that is reactively cured by heating or irradiation with active energy rays, and a polymerization initiator. The Among the solventless adhesives, those that are cured by cationic polymerization are preferable from the viewpoint of reactivity. Particularly, the solventless epoxy adhesive having an epoxy compound as a curable component includes the polarizing film 10, an acrylic type, and the like. Since it is excellent in adhesiveness with the other resin film used as the resin film 21 and the 2nd resin film 30, it is used preferably.

  The epoxy compound, which is a curable component contained in the solventless epoxy adhesive, is preferably cured by cationic polymerization, and particularly contains no aromatic ring in the molecule from the viewpoint of weather resistance, refractive index, and the like. It is more preferable to use an epoxy compound. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. In addition, the epoxy compound that is a curable component usually has two or more epoxy groups in the molecule.

  First, the hydride of an aromatic epoxy compound will be described. The hydride of an aromatic epoxy compound is a nuclear water obtained by selectively subjecting an aromatic polyhydroxy compound, which is a raw material of an aromatic epoxy compound, to an aromatic ring in the presence of a catalyst and under pressure. The additive polyhydroxy compound can be obtained by a method of glycidyl etherification. Examples of the aromatic epoxy compound include bisphenol type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, and Examples include novolak-type epoxy resins such as hydroxybenzaldehyde phenol novolak epoxy resins; glycidyl ethers of tetrahydroxydiphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol. If these raw materials are nucleated with an aromatic polyhydroxy compound typified by bisphenol as described above and epichlorohydrin is reacted with the hydroxyl group, a hydride of the aromatic epoxy compound is obtained. can get. Of these, hydrogenated diglycidyl ether of bisphenol A is preferable as the hydride of the aromatic epoxy compound.

  Next, the alicyclic epoxy compound will be described. An alicyclic epoxy compound means 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” is expressed by the following formula: Means having the structure shown. M in a formula is an integer of 2-5.

Therefore, the alicyclic epoxy compound is a compound having at least one structure represented by the above formula and having a total of two or more epoxy groups in the molecule including the structure. More specifically, a compound in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the above formula are removed and bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among such alicyclic epoxy compounds, an epoxy compound having an epoxycyclopentane ring (m = 3 in the above formula) or an epoxycyclohexane ring (m = 4 in the above formula) has high adhesion strength. Since an excellent adhesive is obtained, it is more preferably used. Specific examples of suitable alicyclic epoxy compounds are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: diethylene glycol bis (3,4-epoxycyclohexyl methyl ether), G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro- [5.2.2.5.2.2] henicosane (this compound is also a 3,4-epoxy Cyclohexanespiro-2 ′, 6′-dioxanespiro-3 ″, 5 ″ -dioxanespiro-3 ′ ″, 4 ′ ″-epoxycyclohexane),
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide,
K: bis-2,3-epoxycyclopentyl ether,
L: Dicyclopentadiene dioxide and the like.

  The aliphatic epoxy compound may be an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof. More specifically, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene Polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to diglycidyl ether of glycol, aliphatic polyhydric alcohol such as ethylene glycol or propylene glycol, and glycerin And polyglycidyl ether.

  The epoxy compound demonstrated above may be used individually by 1 type, and may be used in combination of 2 or more type.

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

  The solventless epoxy adhesive usually contains a cationic polymerization initiator in order to cause the epoxy compound to undergo cationic polymerization. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, or heating, and initiates an epoxy group polymerization reaction. Any of these types of cationic polymerization initiators may be used, but it is preferable from the viewpoint of workability that the potential is imparted. In the following, a cationic polymerization initiator that generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams and initiates a polymerization reaction of an epoxy group is a photocationic polymerization initiator. Also called.

  When the photocationic polymerization initiator is used, it becomes possible to cure the adhesive component at room temperature, so the need to consider the heat resistance of the polarizing film or the distortion due to expansion is reduced. It can be formed on a polarizing film with good adhesion. In addition, when a cationic photopolymerization initiator is used, it acts catalytically by light, so that it is excellent in storage stability and workability even when mixed with an epoxy adhesive.

  Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes. These cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferable since they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength. Used.

  These photocationic polymerization initiators can be easily obtained as commercial products, for example, “Kayarad PCI-220” sold by Nippon Kayaku Co., Ltd., and “ “Kayarad PCI-620”, “UVI-6990” sold by Union Carbide, “Adekaoptomer SP-150” and “Adekaoptomer SP-170” sold by ADEKA Corporation, Nippon Soda ( "CI-5102", "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" and "CIP-2064S", sold by Midori Chemical Co., Ltd. "DPI-101", "DPI-102", "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 by the company.

  The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds which are sclerosing | hardenable components, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less. is there.

  The solventless epoxy adhesive can contain a photosensitizer as necessary in addition to the photocationic polymerization initiator. By using a photosensitizer, the reactivity is improved and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. When mix | blending a photosensitizer, the quantity is about 0.1-20 weight part with respect to 100 weight part of epoxy compounds.

  In addition, as a thermal cationic polymerization initiator that generates a cationic species or a Lewis acid by heating and initiates a polymerization reaction of an epoxy group, for example, benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt Carboxylic acid ester, sulfonic acid ester, amine imide and the like. These thermal cationic polymerization initiators can also be easily obtained as commercial products, for example, “Adeka Opton CP77” and “Adeka Opton CP66” sold by ADEKA Co., Ltd. "CI-2639" and "CI-2624" sold by Sanshin Chemical Industry Co., Ltd. "Sun-Aid SI-60L", "Sun-Aid SI-80L" and "Sun-Aid 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. Moreover, a photocationic polymerization initiator and a thermal cationic polymerization initiator can be used in combination.

  The solventless epoxy adhesive may further contain a compound that promotes cationic polymerization, such as oxetanes and polyols.

  When a solventless epoxy adhesive is used, the adhesive between the polarizing film 10 and the resin film 21 or 30 is performed by applying the adhesive to the adhesive surface of the resin film and / or the polarizing film and bonding them together. It can be carried out. There is no particular limitation on the method of applying the solventless epoxy adhesive to the resin film and / or the polarizing film. For example, various coatings such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater. A scheme is available. Moreover, since each coating method has an optimum viscosity range, the viscosity may be adjusted using a small amount of solvent. The solvent used for this purpose is not particularly limited as long as it can dissolve the epoxy adhesive well without degrading the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, and the like. Organic solvents such as esters can be used.

  After bonding the resin films 21 and 30 to the polarizing film 10 through an adhesive layer made of an uncured epoxy adhesive, the adhesive layer is applied by irradiating active energy rays or heating. Curing is performed to fix the resin film on the polarizing film. In the case of curing by irradiation with active energy rays, ultraviolet rays are preferably used. Specific 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 lamp, and a metal halide lamp. The irradiation intensity and irradiation amount of active energy rays such as ultraviolet rays are appropriately selected so as to sufficiently activate the cationic polymerization initiator and not adversely affect the cured adhesive layer, polarizing film, and optical film. In addition, when cured by heating, it can be heated by a generally known method, and the temperature and time at that time can sufficiently activate the cationic polymerization initiator, and the cured adhesive layer or It is appropriately selected so as not to adversely affect the polarizing film and the optical film.

  The adhesive layer made of a cured product of the epoxy adhesive obtained as described above can have a thickness in the range of usually about 0.1 to 50 μm, preferably 1 μm or more. Moreover, it is more preferable that it is in the range of 1 to 20 μm, more preferably 2 to 10 μm.

  Moreover, as another preferable adhesive agent which can be used for bonding with the polarizing film 10 and the acrylic resin film 21 and / or the second resin film 30, a water-based adhesive, that is, an adhesive component in water. What melt | dissolved or what disperse | distributed this to water can be mentioned. When a water-based adhesive is used, the thickness of the adhesive layer can be further reduced. Examples of water-based adhesives include those containing water-soluble crosslinkable epoxy resins or hydrophilic urethane resins as adhesive components.

  As a water-soluble crosslinkable epoxy resin, for example, a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a polyamide polyamine obtained by a reaction of a dicarboxylic acid such as adipic acid are reacted with epichlorohydrin. Mention may be made of the polyamide epoxy resin obtained. Commercially available products of such polyamide epoxy resins include “Smiles Resin 650” and “Smiles Resin 675” sold by Sumika Chemtex Co., Ltd. under the trade name.

  When a water-soluble crosslinkable epoxy resin is used as the adhesive component, it is preferable to mix other water-soluble resins such as a polyvinyl alcohol-based resin in order to further improve coatability and adhesiveness. Polyvinyl alcohol-based resins include partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, as well as carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. It may be a polyvinyl alcohol resin. Among these, a saponified product of a copolymer of vinyl acetate and unsaturated carboxylic acid or a salt thereof, that is, carboxyl group-modified polyvinyl alcohol is preferably used. Here, the “carboxyl group” is a concept including —COOH and a salt thereof.

  Examples of suitable commercially available carboxyl group-modified polyvinyl alcohols are “Kuraraypoval KL-506”, “Kuraraypoval KL-318” and “Kuraray” sold by Kuraray Co., Ltd. POVAL KL-118 ”,“ GOHSENAL T-330 ”and“ GOHSENAL T-350 ”sold by Nippon Synthetic Chemical Industry Co., Ltd.“ DR-0415 ”sold by Denki Kagaku Kogyo Co., Ltd., Japan There are "AF-17", "AT-17" and "AP-17", etc., which are sold by Vintner Poval.

  The adhesive containing a water-soluble crosslinkable epoxy resin can be prepared as an aqueous adhesive solution by dissolving the above epoxy resin and other water-soluble resin such as a polyvinyl alcohol resin added as necessary in water. In this case, it is preferable that the water-soluble crosslinkable epoxy resin has a concentration in the range of about 0.2 to 2 parts by weight with respect to 100 parts by weight of water. Moreover, when mix | blending polyvinyl alcohol-type resin, the quantity is about 1-10 weight part with respect to 100 weight part of water, Furthermore, it is preferable to set it as about 1-5 weight part.

  On the other hand, when a water-based adhesive containing a urethane resin is used, examples of suitable urethane resins include ionomer-type urethane resins, particularly polyester-based ionomer-type urethane resins. Here, the ionomer type is obtained by introducing a small amount of an ionic component (that is, a hydrophilic component) into a urethane resin constituting the skeleton. The polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion. Examples of commercially available polyester ionomer-type urethane resins include “Hydran AP-20” and “Hydran APX-101H” sold by DIC Corporation, both of which are in the form of emulsions. Available.

  When an ionomer-type urethane resin is used as an adhesive component, it is preferable to further blend an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent is a compound having at least two isocyanato groups (—NCO) in the molecule. Examples thereof include 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1, In addition to polyisocyanate monomers such as 6-hexamethylene diisocyanate and isophorone diisocyanate, adducts in which a plurality of these molecules are added to a polyhydric alcohol such as trimethylolpropane, and three molecules of diisocyanate are each one-terminal isocyanato group Modified with polyisocyanate such as trifunctional isocyanurate with an isocyanurate ring formed at the part and burette formed by hydration and decarboxylation of three diisocyanate molecules at each isocyanato group. And the like. Examples of commercially available isocyanate-based cross-linking agents that can be suitably used include those sold by DIC Corporation under the trade name “Hydran Assister C-1”.

  When an aqueous adhesive containing an ionomer type urethane resin is used, the concentration of the urethane resin is about 10 to 70% by weight, further 20% by weight or more, and 50% by weight or less from the viewpoint of viscosity and adhesiveness. Thus, those dissolved or dispersed in water are preferred. When the isocyanate crosslinking agent is blended, the blending amount is appropriately selected so that the isocyanate crosslinking agent is about 5 to 100 parts by weight with respect to 100 parts by weight of the urethane resin.

  When such a water-based adhesive is used, the polarizing film 10 and the acrylic resin film 21 and / or the second resin film 30 subjected to the heat treatment are bonded to the polarizing film 10 and the adhesive film. It can apply by apply | coating to the adhesive surface of the films 21 and 30 bonded there / or, and bonding both together. More specifically, a water-based adhesive is applied to the polarizing film 10 and / or the films 21 and 30 bonded thereto, for example, a coating method such as a doctor blade, a wire bar, a die coater, a comma coater, or a gravure coater. And the like, and the other film is laminated on the coated surface, bonded with a roll or the like, and dried. Drying can be performed at a temperature of about 60 to 100 ° C., for example. In order to further improve the adhesiveness, it is preferable to cure for about 1 to 10 days after drying at a temperature slightly higher than room temperature, for example, a temperature of about 30 to 50 ° C.

  When 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 composed of an acrylic resin film, and other than the acrylic resin In either case of constituting the resin film, the same adhesive may be used for adhesion of the film bonded to both surfaces of the polarizing film 10, or different adhesives may be used. However, in order to simplify the manufacturing process and reduce the number of constituent members of the polarizing plate, it is preferable to use the same adhesive as long as an appropriate adhesive force is obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, the part representing the amount used is based on weight unless otherwise specified.

[Example 1]
(Acrylic resin and acrylic rubber elastic particles)
A copolymer having a weight ratio of methyl methacrylate / methyl acrylate of 96/4 was used as an acrylic base resin. The innermost layer is a hard polymer polymerized with methyl methacrylate using a small amount of allyl methacrylate, and the intermediate layer is polymerized with butyl acrylate as the main component, and further using styrene and a small amount of allyl methacrylate. Soft elastic body, the outermost layer is a rubber elastic body particle having a three-layer structure made of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, and is an intermediate body elastic body A particle having an average particle diameter of 240 nm was used as an acrylic rubber elastic particle.

(Preparation of acrylic resin film)
While pellets in which the above acrylic resin and the above acrylic rubber elastic particles are blended in a weight ratio of the former / the latter = 70/30 are melt-kneaded with a twin screw extruder, 0.05 part of a certain stearic acid was added and mixed to obtain an acrylic resin composition pellet. It was 106 degreeC when the glass transition temperature Tg of this acrylic resin composition was measured with the differential scanning calorimeter (DSC) by Seiko Instruments Inc. This pellet is put into a 65 mmφ single-screw extruder, extruded through a T die having a set temperature of 275 ° C., and two polishings having mirror surfaces whose temperatures are set to 45 ° C. on both sides of the extruded film-like molten resin. Acrylic resin film was prepared by sandwiching between rolls and cooling. The resulting film was wound onto a 6 inch (15.2 cm) diameter core.

(Acrylic resin film heat treatment and polarizing plate)
The acrylic resin film obtained above was unwound from a roll and passed through a heating furnace maintained at 85 ° C. (Tg-21 ° C.) over 17 seconds while applying a tension of 500 N in the longitudinal direction. gave. The dimensional shrinkage in the width direction perpendicular to the flow direction after the film exited the heating furnace was 0.2%. The film after exiting the heating furnace was subsequently subjected to corona discharge treatment and used for pasting to the next polarizing film without being wound up as it was. On one side of a polarizing film having a thickness of about 30 μm in which iodine is adsorbed and oriented on polyvinyl alcohol, the corona discharge treatment side of the acrylic resin film subjected to the above heat treatment and corona discharge treatment is provided on the other side of the polarizing film. Respectively bonded the corona discharge treated surfaces of the norbornene-based resin film subjected to the corona discharge treatment via an adhesive, and cured the adhesive to produce a polarizing plate.

(Cutting and inspection of polarizing plate)
From the polarizing plate obtained above, 100 sheets were cut into a size of a wide 46 type television (about 103 cm × about 59 cm) using a push cutter. With respect to the 100 polarizing plates thus cut, the polarizing plates on which irregularities due to the acrylic resin film appeared were counted. As a result, defects due to the acrylic resin film were observed on nine polarizing plates.

[Example 2]
A polarizing plate was produced, cut and inspected 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. At this time, the dimensional shrinkage in the width direction perpendicular to the flow direction after the acrylic resin film exited the heating furnace was 0.2%. As a result of the inspection, defects due to the acrylic resin film were observed on nine polarizing plates.

[Example 3]
In the same manner as in Example 1, except that the temperature of the heating furnace for performing the heat treatment was changed from 85 ° C. to 95 ° C. (Tg-11 ° C.) and the tension applied to the film at that time was changed from 500 N to 300 N. Plates were made, cut and inspected. Also at this time, the dimensional shrinkage ratio in the width direction orthogonal to the flow direction after the acrylic resin film exited 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, cut and inspected in the same manner as in Example 1 except that the temperature of the heating furnace for performing the heat treatment was changed from 85 ° C. to 23 ° C. (Tg−83 ° C.). At this time, the dimensional shrinkage in the width direction perpendicular to the flow direction after the acrylic resin film exited 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, cut and inspected in the same manner as in Example 1 except that the temperature of the heating furnace for performing the heat treatment was changed from 85 ° C. to 75 ° C. (Tg−31 ° C.). At this time, the dimensional shrinkage in the width direction perpendicular to the flow direction after the acrylic resin film exited the heating furnace was 0.1%. As a result of the inspection, defects due to the acrylic resin film were observed on the 27 polarizing plates.

[Comparative Example 3]
In the same manner as in Example 1, except that the temperature of the heating furnace for performing the heat treatment was changed from 85 ° C. to 75 ° C. (Tg−31 ° C.) and the tension applied to the film at that time was changed from 500 N to 300 N. Plates were made, cut and inspected. At this time, the dimensional shrinkage in the width direction perpendicular to the flow direction after the acrylic resin film exited the heating furnace was 0.1%. As a result of the inspection, defects due to the acrylic resin film were observed on the 26 polarizing plates.

  Table 1 summarizes main fluctuation conditions and results in the above Examples and Comparative Examples. In Table 1, the “determination” column of “polarization plate inspection result” is generally good if the number of defects detected is 20 or less (the defect rate is 20% or less) among 100 inspected polarizing plates. If the number of defects recognized is more than 20 (defect rate is more than 20%), it is displayed as “x” meaning failure.

  As shown in Table 1, Comparative Example 1 in which the temperature of the heating furnace was 23 ° C. (room temperature) corresponds to an example in which heat treatment is not practically performed, but in this case, most of the polarizing plates have defects, Means that the defect due to the tightening that occurred in the acrylic resin film was transferred to the polarizing plate as it was. 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 found was reduced as compared with Comparative Example 1, and due to the tightening that had occurred in the acrylic resin film. Although it is recognized that the defect has been repaired to some extent by heat treatment, it is still not sufficient.

  On the other hand, in Examples 1 to 3 in which the temperature of the heating furnace was set to (Tg-30 ° C.) or higher, defects due to tightening of the acrylic resin film were greatly repaired, and the defect rate of the polarizing plate was 20% or less ( 10% or less). If the tension applied to the film during the heat treatment is appropriately adjusted according to the treatment temperature, the dimensional change rate (shrinkage rate) in the film width direction due to the heat treatment can also be kept small.

10: Polarizing film,
15 …… Polarizing plate,
20: Acrylic resin film (raw film before heat treatment),
21 ... Acrylic resin film that has been heat-treated,
25 …… First feeding roll,
30 …… Second resin film,
35 …… Second feeding roll,
40 ... heating furnace,
45 …… Conveying roll,
50, 51 ... Pasting roll,
60: Product roll.

[Example 1] (Reference)
(Acrylic resin and acrylic rubber elastic particles)
A copolymer having a weight ratio of methyl methacrylate / methyl acrylate of 96/4 was used as an acrylic base resin. In addition, the innermost layer is a hard polymer polymerized with methyl methacrylate using a small amount of allyl methacrylate, and the intermediate layer is polymerized using butyl acrylate as the main component, and further using styrene and a small amount of allyl methacrylate. Soft elastic body, the outermost layer is a rubber elastic body particle having a three-layer structure made of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, and is an intermediate body elastic body A particle having an average particle diameter of 240 nm was used as an acrylic rubber elastic particle.

[Example 2] (Reference)
A polarizing plate was produced, cut and inspected 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. At this time, the dimensional shrinkage in the width direction perpendicular to the flow direction after the acrylic resin film exited the heating furnace was 0.2%. As a result of the inspection, defects due to the acrylic resin film were observed on nine polarizing plates.

Claims (6)

A method for producing a polarizing plate by laminating an acrylic resin film to a polarizing film comprising a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented,
A heat treatment step of heat-treating the acrylic resin film at a temperature within a range of (Tg-30 ° C.) or more and (Tg + 5 ° C.), where Tg is the glass transition temperature thereof, and the acrylic subjected to the heat treatment. The manufacturing method of the polarizing plate characterized by including the bonding process which bonds a system resin film to the said polarizing film continuously. The acrylic resin film is formed from an acrylic resin composition in which rubber elastic particles having a number average particle diameter in the range of 10 to 300 nm are blended in an acrylic base resin at a ratio of 25 to 45% by weight. The manufacturing method of the polarizing plate of Claim 1 currently performed. The said heat processing process is a manufacturing method of the polarizing plate of Claim 1 or 2 performed in the heating furnace heated to the said temperature. The said heat processing process is a manufacturing method of the polarizing plate in any one of Claims 1-3 performed by the time within the range of 5 second or more and 60 second or less. The polarizing plate according to claim 1, wherein the acrylic resin film is attached to the heat treatment step and then the bonding step while being unwound from a long and rolled state. Manufacturing method. The heat treatment step is performed such that the dimensional change rate in the width direction orthogonal to the flow direction of the acrylic resin film before and after the heat treatment is 0.3% or less. The manufacturing method of the polarizing plate of description.

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