TWI617442B - Method for manufacturing polarizing plate - Google Patents

Abstract

A method for manufacturing polarizing plate 15 is to attach an acrylic resin film to a polarizing film containing a polyvinyl alcohol-based resin that adsorbs an alignment dichroic dye to manufacture a polarizing plate, wherein the method has the following steps: a heat treatment step, When the glass transition temperature of the acrylic resin film is used as Tg, the acrylic resin film 20 is passed through a heating furnace 40 maintained at a temperature in the range of (Tg-30 ° C) or more and (Tg + 5 ° C) or less. The heat treatment; and the bonding step, the acrylic resin film 21 that has been subjected to the heat treatment is then bonded to the polarizing film 10 with bonding rollers 50, 51.

Description

Method for manufacturing polarizing plate

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

The polarizing plate is widely used centering on the constituent members of the liquid crystal display device. The polarizing plate is usually circulated in a state where a protective film is layered on at least one area of the polarizing film containing a polyvinyl alcohol-based resin, and is assembled into a liquid crystal display device or the like. The protective film of the polyvinyl alcohol polarizing film constituting the polarizing plate has conventionally used triethyl cellulose film. However, the hygrothermal resistance of triethyl cellulose is insufficient, and the polarizing plate using triacetyl cellulose film as a protective film may have a decrease in polarizing degree or color equivalent performance under high temperature and humid conditions.

Therefore, it was reviewed to use an acrylic resin film excellent in transparency and moisture resistance as a protective film instead of triacetyl cellulose. For example, Japanese Unexamined Patent Publication No. 2007-25008 (Patent Document 1) discloses that a thermoplastic resin layer is formed on both sides of an acrylic resin film with a thickness of 40 μm or less, and the thermoplastic resin layer on both sides is peeled off before use to make a polarizing plate Protective film. Japanese Patent Laid-Open No. 2007-41563 (Patent Document 2) discloses that a three-layer protective film including an acrylic resin film / polyethyleneimine layer / polyvinyl alcohol-based resin layer is formed by using the polyvinyl alcohol The resin layer side is bonded to the polyvinyl alcohol polarizing film Into a polarizer. Japanese Patent Laid-Open No. 2007-52404 (Patent Document 3) discloses that a polarizer is formed by sequentially providing an adhesive layer / metal salt layer / protective film on one side of a polyvinyl alcohol-based polarizing film, and the acrylic resin is used to form the polarizing plate Protective film. Japanese Unexamined Patent Publication No. 2009-25762 (Patent Document 4) discloses that a lubricant film containing a metal salt is mixed with 0.1 to 1.5 parts by weight of a resin component containing 100 parts by weight of an acrylic resin body to form a protective film for a polarizing plate . In addition, Japanese Patent Laid-Open No. 2009-163216 (Patent Document 5) discloses that an anti-glare film composed of an acrylic resin film having a hard coat layer on one area layer of a polyvinyl alcohol-based polarizing film is made and arranged In the polarizing plate on the viewing side of the liquid crystal display device, the acrylic resin constituting the antiglare film preferably contains acrylic rubber particles from the viewpoint of impact resistance or film formability of the film.

It is not limited to the acrylic resin film, and the resin film is generally taken up in a cylindrical core after being manufactured and stored in a roll shape. Then, after a predetermined period of storage, for example, it shrinks in a curled state, and a phenomenon called squeeze is observed when a dent is observed on the outermost surface of the roll film. If such crimp shrinkage occurs, its dents and the like will cause defects, and in fact, it cannot be used for optical purposes. Especially in the acrylic resin film, it is obviously easy to produce such curling and shrinking.

Therefore, the object of the present invention is to provide a method of manufacturing a polarizing plate, which can repair the defect even when using an acrylic resin film that has a defect due to curling, and can be produced in a state of being attached to the polarizing film Polarizer with few defects.

According to the present invention, a method for manufacturing a polarizing plate can be provided A polarizing film containing a polyvinyl alcohol resin adsorbing and aligning a dichroic dye is laminated with an acrylic resin film to produce a polarizing plate. The method has the following steps: a heat treatment step, and the glass transition temperature of the acrylic resin film is taken as Tg At the time, the acrylic resin film is heat-treated at a temperature in the range of (Tg-30 ° C) or higher and (Tg + 5 ° C) or lower; and the bonding step is to stick the heat-treated acrylic resin film Combined with the aforementioned polarizing film.

The acrylic resin film used in this method is preferably formed of an acrylic resin composition in which rubber elastomer particles are blended into an acrylic matrix resin. The rubber elastomer particles preferably have a number average particle diameter of 10 to In the range of 300 nm, it is preferably blended at a ratio of 25 to 45% by weight relative to the acrylic matrix resin.

In these methods, the heat treatment step is preferably performed in a heating furnace heated to the above temperature. In addition, the time for the heat treatment step is preferably in the range of 5 seconds or more and 60 seconds or less. Preferably, while the acrylic resin film is rolled out from a long state and wound into a roll, the aforementioned heat treatment step is performed and then the bonding step is performed. At this time, the heat treatment step is preferably performed in such a manner that the dimensional change rate of the acrylic resin film before and after the heat treatment in the width direction perpendicular to the traveling direction is 0.3% or less.

According to the method of the present invention, even if the acrylic resin before being bonded to the polarizing film has a defect caused by curling, it is possible to manufacture a polarizing plate with fewer defects by bonding to the polarizing film after the heat treatment. Therefore, even rolls of acrylic resin films that produce curling and shrinkage can be used, which can greatly improve the productivity of polarizing plates using acrylic resin films as protective films.

10‧‧‧ Polarized film

15‧‧‧ Polarizer

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

21‧‧‧ Heat-treated acrylic resin film

25‧‧‧First delivery roll

30‧‧‧Second resin film

35‧‧‧Second delivery roll

40‧‧‧Heating furnace

45‧‧‧Conveying roller

50、51‧‧‧ Laminating roller

60‧‧‧Product reel

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

The present invention will be described with reference to FIG. In the present invention, the acrylic resin film 20 (21) is bonded to the polarizing film 10 containing a polyvinyl alcohol resin that absorbs the alignment dichroic dye, and the polarizing plate 15 is manufactured. Then, before bonding to the polarizing film 10, the acrylic resin film (raw film) 20 is subjected to a heat treatment, and the acrylic resin film 21 thus subjected to the heat treatment is bonded to the polarizing film 10.

In the example shown in FIG. 1, the acrylic resin film 20 sent out from the first delivery roll 25 passes through the heating furnace 40, and heat treatment is performed here. The acrylic resin film 21 subjected to the heat treatment in this way 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 according to the heating The treated acrylic resin film 21 / polarizing film 10 / second resin film 30 are bonded by bonding rollers 50 and 51 in this order. The polarizing plate 15 thus obtained is wound up on the product reel 60. In the heating furnace 40, the acrylic resin film 20 is conveyed by a plurality of conveying rollers 45, 45. In general, the polarizing film 10 is directly sent out by the manufacturer who will be described in the polarizing film manufacturing step described later. In the first figure, the straight arrow symbol indicates the direction of film progress, and the curved arrow symbol indicates the direction of rotation of the roller. 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 with the bonding rollers 50 and 51 corresponds to the bonding step.

As shown in the example of FIG. 1, when the polarizing film 10 is bonded to both sides of the polarizing film 10 to manufacture the polarizing plate 15, as long as at least one tree is composed of acrylic resin Grease film is sufficient. When an acrylic resin film is bonded to both sides of the polarizing film 10 to form the polarizing plate 15, it is preferable to apply the heat treatment of the present invention to these acrylic resin films separately before supplying to the bonding step. On the other hand, a polarizing plate may be formed by bonding a resin film on only one side of the polarizing film 10, and in this case, the resin film may be formed of acrylic resin.

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

[Polarizing film]

The polarizing film 10 is one in which a polyvinyl alcohol resin film adsorbs an alignment dichroic dye to obtain predetermined polarizing characteristics. Typically, dichroic pigments use iodine or dichroic organic dyes. That is, the polarizing film is divided into: an iodine-based polarizing film that adsorbs iodine to the polyvinyl alcohol-based resin film, and a dye-based polarizing film that adsorbs to the dichroic organic dye on the polyvinyl alcohol-based resin film.

The polyvinyl alcohol-based resin constituting the polarizing film 10 is obtained by saponifying the polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. In addition, the polyvinyl alcohol-based resin system can be modified, for example, polyvinyl (formal formal) modified by aldehydes, poly (vinyl acetal), polyethylene Poly (vinyl butyral), etc.

The polarizing film 10 is usually manufactured through the following steps: a humidity control step to adjust the moisture of the polyvinyl alcohol-based resin film, and the polyvinyl alcohol-based resin film to Steps of uniaxial stretching, steps of dyeing the polyvinyl alcohol-based resin film with dichroic pigments and adsorbing the dichroic pigments, steps of treating the polyvinyl alcohol-based resin film adsorbed to the dichroic pigments with boric acid After washing with boric acid, the steps of washing the free boric acid attached to the surface to wash, and drying after washing with water.

Uniaxial stretching can be carried out before dyeing, can also be carried out in dyeing, can also be carried out in boric acid treatment after dyeing. Uniaxial extension can also be performed in these plural stages. Uniaxial stretching can be performed between rollers with different rotation speeds, or it can be performed using hot rollers. In addition, it may be dry-stretching that is stretched in the atmosphere, or wet-stretching that is stretched in a state swollen with a solvent. The stretch magnification is usually about 4 to 8 times. The thickness of the polyvinyl alcohol-based polarizing film obtained by performing uniaxial stretching and dyeing, followed by boric acid treatment, water washing, and drying may be, 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 alkyl methacrylate. Specifically, it may be a homopolymer of alkyl methacrylate or a copolymer using two or more alkyl methacrylates, or may be a monomer other than 50% by weight of alkyl methacrylate and alkyl methacrylate. 50% by weight or less of the copolymer. Alkyl methacrylate usually uses an alkyl carbon number of 1 to 4, and methyl methacrylate is preferably used.

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

This acrylic resin preferably does not have glutarimide derivatives, glutaric anhydride derivatives, lactone ring structures, or the like. Acrylic resins having a cyclic structure such as glutarimide derivatives, glutaric anhydride derivatives, or lactone ring structures tend to be difficult to obtain sufficient mechanical strength and moisture resistance when used as optical films. In other words, the acrylic resin is preferably: the monomer consists essentially of alkyl methacrylate, or the alkyl methacrylate accounts for 70% by weight or more of the monomer, preferably 90% by weight or more And essentially only copolymers with monomers selected from alkyl acrylates, styrene monomers and unsaturated nitriles.

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

Acrylic elastic polymers can be polymerized mainly with alkyl acrylate Composition. It can 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. Alkyl acrylate is generally used with an alkyl carbon number of 4 to 8. When copolymerizing monomers other than alkyl acrylate, examples thereof include alkyl methacrylate such as methyl methacrylate or ethyl methacrylate, styrene monomers such as styrene or alkyl styrene, Monofunctional monomers such as unsaturated nitriles such as acrylonitrile and methacrylonitrile, in addition, allyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate or methallyl (meth) acrylate , Difunctional esters of dibasic acids such as diallyl maleate and polyfunctional monomers such as unsaturated carboxylic acid diesters of diols such as alkanediol di (meth) acrylates.

The rubber elastomer particles are preferably multilayer structure 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 elastomer, or more preferably an alkyl methacrylate on the inside of the acrylic elastomer It is a three-layer constructor of the main hard polymer layer. When a hard polymer layer is formed on the outside or inside of the acrylic elastomer, the hard polymer layer is composed of a polymer mainly composed of alkyl methacrylate, and the monomer composition examples in the polymer are the same as The examples of the acrylic resin mentioned above are examples of monomer compositions of polymers mainly composed of alkyl methacrylate, and it is particularly preferable to use monomer compositions composed mainly of methyl methacrylate. The acrylic rubber elastomer particles having such a multi-layer structure can be produced by, for example, the method described in 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, it is possible to obtain a protective film that is not easily peeled off from the adhesive layer when the adhesive is applied to the polarizing film. The average particle size of this rubber elastomer layer is preferably 50 nm or more, and preferably 250 nm or less.

The average particle diameter of the rubber elastomer layer is measured in the following manner. That is, if such rubber elastomer particles are mixed with an acrylic matrix resin and made into a thin film, and its cross-section is dyed with an aqueous solution of ruthenium oxide, it is colored only in the rubber elastomer layer and is observed to be slightly round. The acrylic resin is not dyed. Here, the film cross-section dyed in this way is prepared using a slicer or the like, and observed with an electron microscope. Then, 100 dyed rubber elastomer particles were randomly selected and their respective particle diameters were calculated, and the average value of these numbers was used as the average particle diameter. Since it is measured in this way, the average particle diameter of the rubber elastomer layer specified in the present invention is a number average particle diameter.

When the outermost layer is a hard polymer mainly composed of methyl methacrylate, and a rubber elastomer particle in which an acrylic elastic polymer is encapsulated therein, if it is mixed with an acrylic matrix resin, the rubber elastomer particle The outermost layer will be mixed with acrylic matrix resin. Therefore, if the cross-section is stained with ruthenium oxide and observed with an electron microscope, the rubber elastomer particles observed are particles with the outermost layer removed. Specifically, when using a rubber elastomer particle 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 polymer portion of the inner layer It will be dyed to observe particles with a single-layer structure. In addition, when the innermost layer is a hard polymer mainly composed of methyl methacrylate, the middle layer is an acrylic elastic polymer, and the outermost layer is methacrylic acid. In the case of rubber elastomer particles with a three-layer structure composed mainly of an ester of a hard polymer, the center part of the innermost particle will not be stained, but a two-layer structure in which only the acrylic elastic polymer part of the middle 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 size of the rubber elastomer particles.

When the total amount of the rubber elastomer particles and the transparent acrylic matrix resin is used as a reference, the rubber elastomer particles are preferably blended in a proportion of 25 to 45% by weight. When the rubber elastomer particles are blended in this ratio, the effect of improving the film-forming properties of the film and improving the shock resistance of the resulting film is exhibited.

The acrylic resin used in the present invention (including the acrylic resin composition in which a rubber elastomer is blended with the acrylic matrix resin. The same applies hereinafter) may contain an ultraviolet absorber, an infrared absorber, a lubricating material, and fluorescent light as needed Brightener, dispersant, heat stabilizer, light stabilizer, antistatic agent, antioxidant and other additives.

The ultraviolet absorber is a compound that absorbs ultraviolet rays with a wavelength of 400 nm or less. When the acrylic resin film used as the protective film of the polyvinyl alcohol-based polarizing film contains an ultraviolet absorber, the effect of improving the durability of the polarizing plate to which the protective film is bonded to the polarizing film can be obtained. As the ultraviolet absorber, known ones such as a diphenyl ketone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Specific examples of ultraviolet absorbers 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'-dimethoxydiphenyl ketone, 2,2 ', 4,4'-tetrahydroxy Diphenyl ketone, etc. 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 can be selected so that the resulting resin film has a transmittance at a wavelength of 370 nm or less of preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less. Method containing ultraviolet absorber Examples include a method of blending an ultraviolet absorber into an acrylic resin in advance and pelletizing it and forming it into a film by melt extrusion, etc., a method of directly adding an ultraviolet absorber during melt extrusion, etc. ; Either method can be used.

Infrared absorbers are compounds that absorb infrared rays with wavelengths above 800 nm. Examples include nitroso compounds, their metal complex salts, cyanine-based compounds, squarylium-based compounds, thiol nickel complex-based compounds, phthalocyanine-based compounds, naphthalene Naphthalocyanine compounds, triarylmethane compounds, immonium compounds, diimine ion compounds, naphthoquinone compounds, allium quinone compounds, amino compounds, ammonium salts Compounds, carbon black, indium tin oxide, antimony tin oxide, oxides, carbides or borides of metals belonging to Group 4A, Group 5A or Group 6A of the periodic table. These infrared absorbers are preferably selected to absorb all infrared rays (light having a wavelength of about 800 nm to 1100 nm), or two or more kinds may be used in combination. The blending amount of the infrared absorber can be appropriately adjusted, for example, so that the light transmittance of the resulting resin film at a wavelength of 800 nm or more becomes 10% or less.

The acrylic resin used to make the acrylic resin film preferably has a glass transition temperature Tg of 80 to 110 ° C. When the glass transition temperature Tg is lower than 80 ° C, the polarizing plate obtained by bonding the film made of the same to the polarizing film has a large shrinkage amount in the heat resistance test, and sufficient heat resistance cannot be obtained. On the other hand, when the glass transition temperature is higher than 110 ° C, even if the heat treatment to be described later is performed, it is not possible to sufficiently repair defects caused by curling.

In addition, the film made of this resin is preferably high in surface hardness, specifically, it is preferably based on JIS K 5600-5-4: 1999 -Part 5: Mechanical properties of the coating film-Section 4: Scratch hardness (pencil method) ", the pencil hardness measured with a load of 500g is H or harder.

In addition, from the viewpoint of flexibility, the film is preferably one having a bending elasticity rate of 1,500 MPa or less, as measured in accordance with JIS K 7171: 2008 "Method for Calculation of Plastic-Bending Properties". This bending elastic modulus is more preferably 1,300 MPa or less, and still more preferably 1,200 MPa or less. The bending elastic modulus will vary depending on the type of acrylic resin, the presence or absence of rubber elastomer particles, the type or amount of rubber elastomer particles blended, etc. For example, for acrylic resins, the Compared with the homopolymer of alkyl acrylate, when using a copolymer of alkyl methacrylate and alkyl acrylate, the bending elastic modulus is generally smaller. In addition, the greater the content of rubber elastomer particles, the lower the bending elasticity. On the other hand, as for the rubber elastomer particles, the acrylic elastic polymer particles having a two-layer structure generally have a lower bending elastic modulus than the acrylic elastic polymer particles having a two-layer structure. When the acrylic elastic polymer particles having a single-layer structure are used, the bending elastic modulus is smaller. Furthermore, the smaller the average particle diameter of the elastomer layer in the rubber elastomer particles or the larger the amount of the elastomer, the lower the bending elastic modulus in general. Therefore, it is sufficient to adjust the type of acrylic resin and the type and / or amount of rubber elastomer particles within the aforementioned predetermined range so that the bending elastic modulus becomes 1,500 MPa or less.

The acrylic resin film can also be made into a multilayer structure in which a layer formed of acrylic resin is made into one layer. When the resin film is formed into a multilayer structure, the layer system that can exist other than the acrylic resin layer is not particularly limited in its composition. In addition, it may be constituted by laminating two or more types of acrylic resin films. In this case, the content of the rubber elastomer particles or the aforementioned additives in each layer may be different from each other. For example, a layer containing an ultraviolet absorber and / or an infrared absorber can also be used The layer does not contain an ultraviolet absorber and an infrared absorber.

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

The film formation is preferably a method in which the acrylic resin described above is melt-extruded and sandwiched between two metal rolls. In this case, the metal roller is preferably a mirror roller, whereby a resin film excellent in surface smoothness can be obtained. When producing an acrylic resin film with a multilayer structure, it is sufficient to perform multilayer coextrusion and form a film so that the acrylic resin layer becomes one layer or two or more layers.

[Function that can be arbitrarily added to acrylic resin film]

From the viewpoint of preventing surface scratches during the assembly process of the liquid crystal module, the acrylic resin film can be hard-coated. In addition, surface treatments such as antistatic treatment can also be performed. In addition, the antistatic function in the polarizing plate can be imparted by performing surface treatment on the acrylic resin film, and can also be imparted to other parts of the polarizing plate to which the acrylic resin film is attached, such as an adhesive layer. Regarding the surface treatment of the acrylic resin film, antireflection treatment or antifouling treatment can also be mentioned. In addition, anti-glare treatment can be implemented from the viewpoints of improving visibility, preventing reflection of external light, and reducing moire caused by the interference of thin sheets and color filters.

[Second resin film attached arbitrarily]

In the first figure, the above description is attached to one surface of the polarizing film 10 The acrylic resin film 20 (21) is also used as a polarizing plate, but the second resin film 30 may be attached to the other surface of the polarizing film 10. The second resin film 30 may be composed of acrylic resin, or may be composed of other resin. Examples of resins other than acrylic resins that can be used for the second resin film 30 include cellulose ester resins exemplified by triacetyl cellulose, norbornene resins or polypropylene resins. Typical examples are polyolefin resins.

The second resin film 30 can be given a phase difference. The phase difference can be imparted by uniaxial or biaxial stretching of 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, especially when the second resin film 30 side is bonded to the liquid crystal cell, the second resin film 30 is given a phase difference. It is effective to have the function of optical compensation of the liquid crystal cell.

[Manufacturing 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 to manufacture the polarizing plate 15, but in the present invention, the acrylic 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 acrylic resin, it is preferable to perform heat treatment on the second resin film 30 before bonding to the polarizing film 10.

When the glass transition temperature of the acrylic resin film 20 is taken as Tg, the heat treatment is performed at a temperature in the range of (Tg-30 ° C) or more and (Tg + 5 ° C) or less. By performing heat treatment at a temperature in this range, even if the aforementioned defect due to curling and shrinkage occurs in the acrylic resin film 20, it can be repaired, making it difficult for the polarizing plate 15 to display the defect. If the heat treatment temperature is lower than (Tg-30 ° C), the acrylic resin film 20 cannot be sufficiently repaired due to curling and contraction Defects, the polarizing plate 15 obtained by attaching it to the polarizing film 10 will also easily show defects. On the other hand, if the temperature is higher than (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 damaged. From the viewpoint of reducing the possibility of such deformation as much as possible, the heat treatment temperature 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. In addition, 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, it may not be possible to sufficiently repair the defects due to curling and shrinkage generated in the acrylic resin film 20. On the other hand, if the time exceeds 60 seconds, the acrylic resin film 20 may be stretched to narrow the film width.

This heat treatment is for repairing the defects caused by the curling and shrinking of the acrylic resin film 20, so it is preferable to perform it just before bonding to the polarizing film 10. In addition, from the same viewpoint, the acrylic resin film 20 is preferably in a state of being long and wound into a roll, specifically, as shown in the figure, while being fed from the state of being wound on the first delivery roll 25, After performing the above heat treatment, it is bonded to the polarizing film 10. When such a long resin film is targeted, it is preferable that the dimensional change rate of the acrylic resin film 20 before the heat treatment and the acrylic resin film 21 after the heat treatment in the film width direction be 0.3% or less. The increase in the size change rate (shrinkage rate) in the direction perpendicular to the film travel direction (that is, the width direction of the film) is related to the extension of the film, which may change the optical characteristics of the polarizing plate protective film and may Obstacles in production.

"Then the heat-treated acrylic resin film 21 is attached to the polarizing film 10" means that usually the acrylic resin film 21 is not a roll It is taken from the roller and stored, but is attached to the polarizing film 10.

The acrylic resin film 21 subjected to heat treatment in this way is bonded to the polarizing film 10. When the acrylic resin film 21 is subjected to the anti-glare treatment, the polarizing film 10 is bonded to the surface opposite to the anti-glare treatment layer. When the second resin film 30 is bonded to the other surface of the polarizing film 10, as shown in the figure, it is preferable that the acrylic resin film 21 and the second resin film 30 which are simultaneously subjected to heat treatment with the bonding rollers 50 and 51 Fit. Before bonding, it is preferable to perform physical or physicochemical easy adhesion treatment such as corona discharge treatment on the bonding surfaces of the polarizing film 10 of each of the acrylic resin film 21 and the second resin film 30. The adhesion between the polarizing film and the films 21 and 30 attached to the two surfaces can be improved by performing easy adhesion processing. Corona discharge treatment refers to a treatment in which a high voltage is applied between the electrodes and discharged to activate the resin film arranged 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 it 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 and the acrylic resin film 21 or the bonding of the polarizing film 10 and the second resin film 30 is generally an adhesive. When the above-mentioned easy-adhesion treatment has been carried out, the polarizing film is bonded to the treatment surface via an adhesive.

Adhesive agents such as epoxy-based resins, urethane-based resins, cyanoacrylate-based resins, and acrylamide-based resins can be used as the adhesive. One of the suitable adhesives is a solventless adhesive. Solvent-free adhesives do not contain a significant quantity of solvent, but contain a hardening that can be hardened by heat or reactive energy rays (such as ultraviolet, visible, electron, X-ray, etc.) Chemical components (monomers or oligomers), and the adhesive layer is formed by the hardening of the hardening component, typically contains a hardening component that reacts and hardens by heating or active energy ray irradiation , And polymerization initiator. From the viewpoint of reactivity, the solvent-free adhesive is preferably cured by cationic polymerization, especially the solvent-free epoxy-based adhesive that uses an epoxy compound as a hardening component due to the polarizing film 10 is excellent in adhesiveness with other resin films that become the acrylic resin film 21 and the second resin film 30, so it is more suitable for use.

The epoxy compound which is a curable component contained in the solvent-free epoxy-based adhesive is preferably cured by cationic polymerization, and particularly from the viewpoint of weather resistance or refractive index, it is more preferable to use a molecule Epoxy compound without aromatic ring. Examples of the epoxy compound containing no aromatic ring in the molecule include hydrides of aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. In addition, epoxy compounds that are hardening components usually contain two or more epoxy groups in the molecule.

First, the hydride of the aromatic epoxy compound will be described. Aromatic epoxy compound hydride is an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound and selectively hydrogenates an aromatic ring in the presence of a catalyst and under pressure to obtain a nuclear hydrogenated polyhydroxy compound And, it will be glycidyl ether (glycidyl ether) method. Examples of the aromatic epoxy compound include bisphenol 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 hydroxybenzaldehyde novolac epoxy resin and other novolac (novolac) type epoxy resin; tetrahydroxydiphenyl methane Epoxypropyl ether, epoxypropyl ether of tetrahydroxydiphenyl ketone, and polyfunctional rings such as epoxy-based polyvinyl phenol Oxygen resin, etc. Among these raw materials, aromatic polyhydroxy compounds represented by bisphenols belonging to these raw materials are subjected to nuclear hydrogenation as described above, and their hydroxyl groups are reacted with epichlorohydrin to obtain aromatic Hydrides of epoxy compounds. Among them, the hydride of the aromatic epoxy compound is preferably a diglycidyl ether of hydrogenated bisphenol A.

Next, the alicyclic epoxy compound will be described. An alicyclic epoxy compound refers to an epoxy compound having one or more epoxy groups bonded to an alicyclic ring, and "an epoxy group having more than one bond to an alicyclic ring" means having the following formula The structure shown. In the formula, m is an integer of 2 to 5.

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

A: 3,4-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexyl methyl ester, B: 3,4-epoxy-6-methylcyclohexanecarboxylic acid 3,4-cyclo Oxy-6-methylcyclohexyl methyl ester, C: ethylidene bis (3,4-epoxycyclohexane carboxylate), D: bis (3,4-epoxycyclohexyl adipic acid) Methyl) ester, E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, F: diethylene glycol bis (3,4-epoxycyclohexylmethyl) Ether), G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether), H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxa Trispiro- [5.2.2.5.2.2] cosane (this compound can also be named 3,4-epoxycyclohexanespiro-2 ', 6'-di Hexane-3 ", 5" -two Alkyl spiro-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. .

In addition, the aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, there may be mentioned diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, and triglycidyl glycerol. Base ether, triglycidyl ether of trimethylolpropane, diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, and the like for ethylene glycol or propylene glycol and glycerin Polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides (ethyl oxide or propyl oxide) to aliphatic polyols.

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

The epoxy equivalent of the epoxy compound contained in the solventless epoxy-based 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 hardened may decrease, or the adhesive strength may decrease. On the other hand, if the epoxy equivalent exceeds 3,000 g / equivalent, the compatibility with other components contained in the epoxy-based adhesive may be reduced.

In order to cationic polymerize the above epoxy compound, the solventless epoxy-based adhesive usually contains a cationic polymerization initiator. Cationic polymerization initiators are those that generate active species such as cationic species or Lewis acid by irradiation or heating of active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, etc. and start the polymerization of epoxy groups. Any one of these types of cationic polymerization initiators can be used, but from the viewpoint of workability, it is preferable to impart potential. In addition, in the following, the cationic polymerization initiator that generates cationic species or Lewis acid and starts the polymerization reaction of epoxy groups by the irradiation of active energy rays such as visible rays, ultraviolet rays, X rays, electron rays, etc. is called light Cationic polymerization initiator.

If a photo-cationic polymerization initiator is used, the adhesive component can be hardened at normal temperature, so the concern about the distortion caused by the heat resistance or expansion of the polarizing film is reduced, and the resin film attached to it can be Formed in a way with good adhesion On polarizing film. In addition, if a photo-cationic polymerization initiator is used, since it is catalyzed by light, even if it is mixed with an epoxy-based adhesive, its storage stability and workability are also excellent.

As the photocationic polymerization initiator, for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic osmium salt; an iron-aromatic hydrocarbon complex and the like can be used. These photo-cationic polymerization initiators may be used alone or in combination of two or more. Among these, especially the aromatic cerium salt system has ultraviolet absorption characteristics even in the wavelength range of 300 nm or more, so it has excellent curability, and can give a cured product having good mechanical strength and adhesive strength, so it is more suitable for use.

Such photo-cationic polymerization initiators can be easily obtained from commercially available products, for example, the following are all brand names: "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 Corporation; "CI-5102" sold by Japan Soda Corporation , "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" and "CIP-2064S"; "DPI-101", "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" etc. sold.

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 with respect to 100 parts by weight of the epoxy compound of the curable component.

The solvent-free epoxy-based adhesive contains a photosensitizer in addition to the photocationic polymerization initiator as needed. By using a light sensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the hardened product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, reduction compounds, azo and diazo compounds, halogen compounds, and light-reducing dyes. When the light sensitizer is blended, the amount is about 0.1 to 20 parts by weight relative to 100 parts by weight of the epoxy compound.

In addition, the thermal cationic polymerization initiator that generates a cationic species or Lewis acid by heating and starts the polymerization reaction of an epoxy group includes, for example, a benzyl alkoxide salt, a thiophenium salt, and a tetrahydrothiophenium salt ( thiolanium) salt, benzyl ammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, aminimide, etc. These thermal cationic polymerization initiators can also be easily obtained from commercially available products, for example, the following are all brand names: "ADEKAOPTON CP77" and "ADEKAOPTON CP66" sold by ADEKA Corporation; Japan Soda Co., Ltd. "CI-2639" and "CI-2624" sold by the company; "SUNAID SI-60L", "SUNAID SI-80L" and "SUNAID SI-100L" sold by Sanxin Chemical Industry Co., Ltd. These thermal cationic polymerization initiators may be used alone or in combination of two or more. In addition, a photo cationic polymerization initiator and a thermal cationic polymerization initiator may be used in combination.

The solvent-free epoxy-based adhesive may further contain a compound that promotes cationic polymerization such as oxetanes or polyols.

When a solvent-free epoxy-based adhesive is used, the polarizing film 10 and the resin film 21 or 30 can be adhered by applying the adhesive to the adhesive surface of the resin film and / or polarizing film and bonding the two And proceed. The method of applying the solventless epoxy-based adhesive to the resin film and / or polarizing film is not particularly limited, for example, 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 its own suitable viscosity range, so a small amount of solvent can be used to adjust the viscosity. The solvent used for this purpose may be any one that does not reduce the optical properties of the polarizing film and dissolves the epoxy-based adhesive well, for example, hydrocarbons represented by toluene and esters represented by ethyl acetate can 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 irradiating active energy rays or heating to make the resin film It is fixed on the polarizing film. When curing by irradiating active energy rays, it is preferable to use ultraviolet rays. Specifically, the ultraviolet light source may be a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a black light, a metal halogen lamp, or the like. The active energy rays, such as the irradiation intensity or the irradiation amount of ultraviolet rays, are appropriately selected in such a manner that the cationic polymerization initiator is sufficiently activated and does not cause adverse effects on the cured adhesive layer, polarizing film, and optical film. In addition, when it is cured by heating, it can be heated according to a generally known method. At this time, the temperature and time are also sufficient to activate the cationic polymerization initiator and will not cause damage to the cured adhesive layer, polarizing film, and optical film. The method of adverse effects is appropriately selected.

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

In addition, other preferred adhesives that can be used for bonding the polarizing film 10 to the acrylic resin film 21 and / or the second resin film 30 include water-based bonding The agent can be exemplified by those who dissolve the adhesive component in water or disperse it in water. If an aqueous adhesive is used, the thickness of the adhesive layer can be made smaller. Examples of the water-based adhesive include those in which the adhesive component contained is a water-soluble crosslinkable epoxy resin or a hydrophilic urethane-based resin.

Examples of the water-soluble cross-linkable epoxy resin include polyalkylene polyamines such as diethylenetriamine or triethylenetetramine and dicarboxylic acids such as adipic acid to obtain polyamidopolyamines, and Polyamide epoxy resin obtained by reaction with epichlorohydrin. Such commercially available products of polyamide epoxy resin include "SumirezResin 650" and "SumirezResin 675" sold by Sumika Chemtex Co., Ltd. under the trade names of the following.

When the adhesive component is a water-soluble cross-linkable epoxy resin, in order to further improve coating properties and adhesiveness, it is preferable to mix other water-soluble resins such as a polyvinyl alcohol-based resin. In addition to partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, the polyvinyl alcohol-based resin can also be carboxy-modified polyvinyl alcohol, acetyl-acetyl-modified polyvinyl alcohol, and hydroxymethyl-modified polyvinyl alcohol. , And modified phenolic resins such as amine-modified polyvinyl alcohol. Among them, it is preferable to use saponified products of copolymers of vinyl acetate and unsaturated carboxylic acid or the salt, that is, carboxyl-modified polyvinyl alcohol. In addition, the "carboxyl group" mentioned here includes the concept of -COOH and the salt.

Examples of suitable commercially-available carboxy-modified polyvinyl alcohol include the following brand names: "KurarayPoval KL-506", "KurarayPoval KL-318" and "KurarayPoval 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. The "AF-17", "AT-17", and "AP-17" sold are sold.

The adhesive agent containing a water-soluble crosslinkable epoxy resin can be prepared as an aqueous solution of an adhesive agent by dissolving the above-mentioned epoxy resin and other water-soluble resins such as a polyvinyl alcohol-based resin 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 with respect to 100 parts by weight of water. In addition, 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 with respect to 100 parts by weight of water.

On the other hand, when an aqueous adhesive containing urethane resin is used, examples of suitable urethane resins include ionic polymer urethane resins, especially polyester ionic polymer amines. Ethyl formate resin. Here, the ionic polymer type refers to one in which a small amount of ionic component (that is, hydrophilic component) is introduced into the urethane resin constituting the skeleton. The polyester-based ionic polymer urethane resin refers to a urethane resin having a polyester skeleton, and a small amount of ionic component (hydrophilic component) is introduced into it. Since this ionic polymer urethane resin system is emulsified directly in water without using an emulsifier to become an emulsion, it is suitable as an aqueous adhesive. The commercially available products of polyester ionomer urethane resins include, for example, "Hydran AP-20" and "Hydran APX-101H" sold by DIC Co., Ltd. under the trade names of the following. Obtained in emulsion form.

When an ionic polymer urethane resin is used as an adhesive component, it is preferable to additionally mix a crosslinking agent such as isocyanate series. The isocyanate-based cross-linking agent is a compound having at least 2 isocyanate groups (-NCO) in the molecule, examples of which are 2,4-tolyl diisocyanate, phenyl diisocyanate, 4,4'-diphenyl In addition to polyisocyanate monomers such as methane diisocyanate, 1,6-hexamethylene diisocyanate and isophorone diisocyanate, there are additions of polyhydric alcohols such as trimethylolpropane to these plural molecules The product, three molecules of diisocyanate, each come from its single terminal isocyanate group Polyfunctional isocyanates such as biuret formed by hydration / decarboxylation of 3-functional triisocyanate which forms triisocyanate ring and 3 molecules of 3 molecules of diisocyanate each with a single terminal isocyanate group Substances, etc. Commercially available isocyanate-based crosslinking agents that can be suitably used include, for example, the brand name "HydranAssist C-1" sold by DIC Corporation.

When an aqueous adhesive containing an ionic polymer urethane resin is used, from the viewpoint of viscosity and adhesion, it is preferable to dissolve the urethane resin at a concentration of about 10 to 70% by weight or Those dispersed in water are 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 so that the isocyanate-based crosslinking agent is about 5 to 100 parts by weight based on 100 parts by weight of the urethane-based resin.

When such an aqueous adhesive is used, the polarizing film 10 and the heat-treated acrylic resin film 21 and / or the second resin film 30 can be adhered to the polarizing film 10 and / or the adhesive by applying the adhesive The bonding surfaces of the films 21 and 30 bonded thereto are bonded together. More specifically, the following methods may be mentioned: the water-based adhesive is uniformly coated on the polarizing film by a coating method such as a doctor blade, a wire bar, a die coater, a corner wheel coater, and a gravure coater After 10 and / or the films 21 and 30 laminated thereon, the other film is overlapped on the coated surface, and the method of bonding and drying is performed by a roller or the like. Drying can be carried out, for example, at a temperature of about 60 to 100 ° C. In order to improve the adhesiveness, it is preferable to keep it at a temperature slightly higher than room temperature after drying, for example, at a temperature of about 30 to 50 ° C for about 1 to 10 days.

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 or a resin film other than acrylic resin Time, The same adhesive or different adhesives can be used for the bonding of the films bonded on both sides of the polarizing film 10. However, in order to simplify the manufacturing process and reduce the constituent members of the polarizing plate, it is preferable to use the same adhesive agent when moderate adhesion is available.

Examples

The following shows examples and comparative examples to explain the present invention more specifically, but the present invention is not limited to these examples. In the example, the "parts" indicating the amount of use are based on weight 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. In addition, three-layer rubber elastomer particles are used as acrylic rubber elastomer particles. The three-layer rubber elastomer particles are composed of the innermost layer, the intermediate layer, and the outermost layer described below. The innermost layer is methacrylic acid. The methyl ester is a hard polymer polymerized with a small amount of allyl methacrylate. The middle layer is a soft elastomer composed of butyl acrylate as the main component and styrene and a small amount of allyl methacrylate. The outer layer is a hard polymer polymerized with a small amount of ethyl acrylate in methyl methacrylate, and the average particle diameter up to the elastomer belonging to the middle layer is 240 nm.

(Production of acrylic resin film)

The acrylic resin and the acrylic rubber elastomer particles are blended into a pellet with a weight ratio of the former / the latter = 70/30, and the pellet is melt-kneaded with a twin-screw extruder, and 100 parts are added to it at the same time. Add 0.05 parts of stearic acid, which is a lubricant, and mix to make an acrylic resin composition ingot. The acrylic resin group was measured with a differential scanning calorimeter (DSC) manufactured by Seiko Instruments Co., Ltd. The glass transition temperature Tg of the product was 106 ° C. Put this ingot into a single-shaft extruder of 65mm φ and extrude it through a T-die with a set temperature of 275 ° C. Two sides of the extruded film-shaped molten resin with a mirror surface of 2 polished rollers with a set temperature of 45 ° C (polishing roll) sandwiched and cooled to produce an acrylic resin film. The resulting film was wound around a 6-inch (15.2 cm) diameter core.

(Heating treatment and polarizing plate of acrylic resin film)

The acrylic resin film obtained above was rolled out from the roll, and while applying a tension of 500 N in the longitudinal direction, it was passed through a heating furnace maintained at 85 ° C (Tg-21 ° C) for 17 seconds to perform heat treatment. After the film leaves the furnace, the shrinkage in the width direction is 0.2%. The film after leaving the heating furnace is then subjected to corona discharge treatment to maintain its state without being wound up, and is directly used for the subsequent bonding of the polarizing film. On one side of a polarizing film with a thickness of about 30 μm formed by polyvinyl alcohol adsorbing and aligning iodine, the corona discharge treatment surface of the acrylic resin film subjected to the heat treatment and corona discharge treatment described above is adhered through an adhesive agent The other side of the film was bonded to the corona discharge treatment surface of the norbornene-based resin film subjected to corona discharge treatment through an adhesive, and the adhesive was hardened to produce a polarizing plate.

(Cutting and inspection of polarizer)

Using a press cutter, 100 pieces of the size 46 TV (approximately 103 cm x approximately 59 cm) wide were cut from the polarizing plate obtained above. For the 100 polarizing plates cut in this way, the number of polarizing plates showing irregularities caused by the acrylic resin film was calculated. As a result, defects caused by acrylic resin films were observed in 9 polarizing plates.

[Example 2]

A polarizing plate was produced in the same manner as in Example 1, except that the tension during heating treatment was changed from 500N to 300N, cut and inspected. this At that time, the 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 caused by the acrylic resin film were observed in 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 500N to 300N. , Cut and check. At this time, the dimensional shrinkage of the acrylic resin film in the width direction after leaving the heating furnace was 0.2%. As a result of the inspection, a defect caused by the acrylic resin film was 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), cut and inspected. At this time, the dimensional shrinkage of the acrylic resin film in the width direction after leaving the heating furnace was 0.1%. As a result of the inspection, defects caused by the acrylic resin film were observed in 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), cut and inspected. At this time, the dimensional shrinkage of the acrylic resin film in the width direction after leaving the heating furnace was 0.1%. As a result of the inspection, defects caused by the acrylic resin film were observed in the 27 polarizing plates.

[Comparative Example 3]

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

The main change conditions and results in the above examples and comparative examples are summarized in Table 1. In Table 1, in the "Judgment" column of "Polarizing Plate Inspection Results", if the number of the 100 polarizing plates inspected is determined to be defective or less than 20 (the defect rate is less than or equal to 20%), it means that the representative is roughly In terms of good "○", if the number of defects judged to be more than 20 (the defect rate exceeds 20%), it is represented as "X" representing bad.

As shown in Table 1, Comparative Example 1 with a heating furnace temperature of 23 ° C (room temperature) is equivalent to an example in which no heating treatment is actually performed, but at this time most of the polarizing plates will have defects observed. The defects caused by the shrinkage of the resin film are directly transferred to the polarizer. In Comparative Examples 2 and 3 where the temperature of the heating furnace was raised to 75 ° C, the number of polarizing plates where defects were observed was reduced compared to Comparative Example 1. However, although curling caused by the acrylic resin film was observed Defect It was repaired to some extent by heat treatment, but it was still insufficient.

In contrast, in Examples 1 to 3 where the heating furnace temperature is (Tg-30 ° C) or higher, it can be seen that the defects caused by the curling of the acrylic resin film are largely repaired, and the defect rate of the polarizing plate becomes 20% or less (Less than 10%). If the tension applied to the film during the heat treatment is appropriately adjusted according to the treatment temperature, the rate of dimensional change (shrinkage rate) of the film in the width direction due to the heat treatment can also be suppressed to a small value.

(Industry availability)

According to the method of the present invention, even if the acrylic resin before being bonded to the polarizing film may cause defects due to curling and shrinking, by performing heat treatment and then bonding to the polarizing film, a polarizing plate with few defects can be manufactured . Therefore, even a roll of an acrylic resin film that is curled and contracted can be used, and the productivity of a polarizing plate that uses an acrylic resin film as a protective film can be greatly improved.

10‧‧‧ Polarized film

15‧‧‧ Polarizer

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

21‧‧‧ Heat-treated acrylic resin film

25‧‧‧First delivery roll

30‧‧‧Second resin film

35‧‧‧Second delivery roll

40‧‧‧Heating furnace

45‧‧‧Conveying roller

50、51‧‧‧ Laminating roller

60‧‧‧Product reel

Claims (4)

A method for manufacturing a polarizing plate is to attach an acrylic resin film to a polarizing film containing a polyvinyl alcohol-based resin that adsorbs an alignment dichroic dye to manufacture 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 used as Tg, the acrylic resin film is subjected to heat treatment at a temperature within the range of (Tg-30 ° C) or more and (Tg + 5 ° C) or less; and the bonding step , The acrylic resin film that has been subjected to the heat treatment is then attached to the polarizing film, wherein the acrylic resin film is subjected to the heat treatment while being rolled out from a long and rolled state The step is followed by the aforementioned bonding step, the aforementioned heat treatment step is performed in such a manner that the dimension change rate of the acrylic resin film before and after the heat treatment in the width direction perpendicular to the direction of travel becomes 0.3% or less . The method for manufacturing a polarizing plate as described in item 1 of the patent application, wherein the acrylic resin film is formed of an acrylic resin composition, and the acrylic resin composition is contained in an acrylic matrix resin in a range of 25 to 45 The ratio of the weight% is blended with rubber elastomer particles having a number average particle diameter in the range of 10 to 300 nm. The method for manufacturing a polarizing plate as described in item 1 or 2 of the patent application, wherein the heat treatment step is performed in a heating furnace heated to the aforementioned temperature. The method for manufacturing a polarizing plate as described in item 1 or 2 of the patent application, wherein the heat treatment step is performed within a range of 5 seconds to 60 seconds.