TWI592305B - Polarizing film and polarizing plate manufacturing method - Google Patents

Description

Polarizing laminated film and method for producing polarizing plate

The present invention relates to a polarizing laminated film and a method of producing the polarizing plate.

The polarizing plate is widely used as a supply element for polarized light in a display device such as a liquid crystal display device. Conventionally, a polarizing element layer including a polyvinyl alcohol-based resin and a protective film such as cellulose triacetate are used as the polarizing plate. In the polarizing element layer (polarizing film), high optical performance is required, and in recent years, thin-wall lightweighting is required as the development of mobile devices such as a notebook type personal computer or a mobile phone of a liquid crystal display device.

As an example of the method for producing a polarizing plate, it is known that a film containing a polyvinyl alcohol-based resin is separately stretched or stretched while being subjected to a dyeing treatment or a crosslinking treatment to form a polarizing film, and laminated on a protective film. A method of manufacturing a polarizing plate by this (for example, refer to JPH11-49878-A).

As another example of the method for producing a polarizing plate, a method of applying a solution containing a polyvinyl alcohol-based resin to a surface of a base film to form a resin layer, and then extending the laminated film including the base film and the resin layer is proposed. Then, the polarizing element layer is formed of a resin layer to obtain a polarizing layer film having a polarizing element layer (for example, refer to JP 2000-338329-A). A method in which a polarizing plate is directly used as a polarizing plate or a protective film is bonded to the film, and a substrate film is peeled off is used as a polarizing plate.

As another example of the method for producing a polarizing plate, it is proposed to form a laminated film by co-extruding a resin for a protective film and a polyvinyl alcohol-based resin, and extending the laminated film, followed by dyeing, thereby obtaining a polarizing element layer and a method of protecting a polarizing plate of a film (for example, Photo JP2009-25821-A).

However, in the method of producing a polarizing film by separately stretching, dyeing, and cross-linking a film containing a polyvinyl alcohol-based resin, cracking or wrinkles are likely to occur, so that it is difficult to handle a thin film of 50 μm or less, and thus it is difficult to achieve polarized light. The film is thinned.

In the method of applying a solution containing a polyvinyl alcohol-based resin to a surface of a base film and providing a resin layer, the resin layer is likely to wrinkle due to drying shrinkage of the solution containing the polyvinyl alcohol-based resin, and as a result, a base may be formed. When the both ends of the material film are warped toward the resin layer side, if the base film having the resin layer is continuously passed through in this state, the end of the base film in the drying furnace or the outlet of the drying furnace may be caused. Defects such as folding.

In the method of producing a laminated film by co-extruding a resin for a protective film and a polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin is usually melted and extruded together with a solvent, so that it is caused by drying shrinkage as described above. The case where the end portion of the base film is folded or the like is defective.

Therefore, an object of the present invention is to provide a polarizing laminate film and a polarizing plate which have a thin polarizing element layer without causing defects such as folding of the end portion of the base film.

The present invention encompasses the following.

[1] A method for producing a polarizing laminated film, comprising: a method of producing a polarizing laminated film comprising a base film and a polarizing element layer formed on one surface of the base film, and sequentially comprising the steps of: a resin film bonding step in which a resin film containing a polyvinyl alcohol resin having a thickness of 50 μm or less is bonded to one surface of a base film to obtain a laminated film; an extending step of uniaxially stretching the laminated film; and a dichroic dye A dyeing step of dyeing the resin film of the uniaxially stretched laminated film to form a polarizing element layer.

[2] The method for producing a polarizing laminated film according to [1], wherein the resin film is bonded to the substrate via an adhesive layer or an adhesive layer in the resin film bonding step. On one side of the membrane.

[3] The method for producing a polarizing laminated film according to [1], wherein the resin film is bonded to the resin film in a thickness of 15 μm or more.

[4] The method for producing a polarizing laminated film according to any one of [1] to [3] wherein the resin film used in the resin film bonding step is a manufacturing method comprising the following steps in sequence A resin film to be produced: a resin layer forming step of forming a resin layer containing a polyvinyl alcohol resin on a support; a first drying step of drying the resin layer; and peeling the resin layer from the support to obtain the resin layer a resin layer separation step; and a second drying step of drying the resin layer at a drying temperature higher than a temperature in the first drying step.

[5] A method of producing a polarizing plate, which is a method of producing a polarizing plate including a polarizing element layer and a protective film formed on one surface of the polarizing element layer, and manufacturing polarized light by the method described in [1] After the film is laminated, the protective film bonding step of bonding the protective film to the surface of the polarizing layer in the polarizing layer on the side opposite to the surface of the substrate film side; and The polarizing laminate film is a substrate film peeling step in which the base film is peeled off.

According to the invention, it is possible to produce a polarizing laminated film having a thin polarizing element layer and a polarizing plate without causing the end portion of the base film to be folded in the production step.

S10‧‧‧ resin film bonding step

S20‧‧‧Extension step

S30‧‧‧Staining step

S40‧‧‧Protective film bonding step

S50‧‧‧Substrate film peeling step

S110‧‧‧ resin layer forming step

S120‧‧‧1st drying step

S130‧‧‧Resin layer separation step

S140‧‧‧2nd drying step

Fig. 1 is a flow chart showing an embodiment of a method for producing a polarizing laminated film of the present invention.

Fig. 2 is a flow chart showing an embodiment of a method for producing a polarizing plate of the present invention.

Fig. 3 is a flow chart showing an embodiment of a method for producing a polyvinyl alcohol resin film.

Hereinafter, preferred embodiments of the method for producing a polarizing laminated film of the present invention and a method for producing a polarizing plate will be described in detail with reference to the drawings.

[Method of Manufacturing Polarized Laminated Film]

Fig. 1 is a flow chart showing an embodiment of a method for producing a polarizing laminated film of the present invention. The polarizing laminate film produced in the present embodiment includes a base film and a polarizing element layer formed on one surface of the base film. The method for producing a polarizing laminated film of the present embodiment is generally carried out in the following steps: a resin film bonding step of obtaining a laminated film by bonding a resin film containing a polyvinyl alcohol resin to one surface of a base film (S10); The step of extending the laminated film uniaxially (S20); and dyeing the resin film of the laminated film with a dichroic dye to form a polarizing element layer (S30).

In the present specification, a laminated body in which a resin film containing a polyvinyl alcohol-based resin (hereinafter also referred to as a "polyvinyl alcohol-based resin film") is bonded to one surface of a base film is referred to as a "laminated film". A polyvinyl alcohol-based resin film having a function as a polarizing element is referred to as a "polarizing element layer", and a laminated body having a polarizing element layer on one surface of a base film is referred to as a "polarizing laminated film". Further, a laminate having a protective film on one surface of the polarizing element layer is referred to as a "polarizing plate".

According to the above production method, a polarizing laminated film having a polarizing element layer having a thickness of 25 μm or less having sufficient polarizing performance can be obtained on the base film. The thickness of the polarizing element layer of the polarizing laminated film obtained by the above production method is preferably 25 μm or less, more preferably 20 μm or less. The polarizing laminated film can be used as an intermediate product for transferring a polarizing element layer onto a protective film as described below, and when the base film has a function as a protective film, the polarizing laminated film can also be used. Used directly as a polarizing plate.

[Method of Manufacturing Polarizing Plate]

Fig. 2 is a flow chart showing an embodiment of a method for producing a polarizing plate of the present invention. The polarizing plate manufactured in the present embodiment includes a polarizing element layer and a protective film formed on one surface of the polarizing element layer. In the method for producing a polarizing plate of the present embodiment, a step of bonding a polyvinyl alcohol resin film to one surface of a base film to obtain a laminated film of a resin film is carried out (S10); a step of extending the axial extension (S20); and a dyeing step of dyeing the polyvinyl alcohol-based resin film of the laminated film with a dichroic dye to form a polarizing element layer (S30); and after obtaining the polarizing laminated film, usually The step of attaching a protective film to the surface of the polarizing element layer on the side opposite to the surface of the substrate film side in the polarizing laminated film (S40); and the substrate from the polarizing laminated film A peeling step of the film peeling (S50).

According to the above production method, a polarizing plate having a polarizing element layer having a thickness of 25 μm or less having sufficient polarizing performance can be obtained on the protective film. The thickness of the polarizing element layer of the polarizing plate obtained by the above production method is preferably 25 μm or less, more preferably 20 μm or less. The polarizing plate can be used, for example, by bonding it to another optical film, a liquid crystal cell, or the like via a pressure-sensitive adhesive.

Hereinafter, each step of S10 to S50 in FIGS. 1 and 2 will be described in detail. Furthermore, the steps of S10 to S30 of FIGS. 1 and 2 are the same steps.

<Resin film bonding step (S10)>

A polyvinyl alcohol-based resin film is bonded to one surface of the base film. The bonding method of the base film and the polyvinyl alcohol resin film is not particularly limited as long as it does not peel off even after the subsequent stretching step (S20) and the dyeing step (S30). For example, an adhesive layer or an adhesive layer is formed on the bonding surface of the polyvinyl alcohol-based resin film and/or the base film, and the two are bonded together via an adhesive layer or an adhesive layer.

(polyvinyl alcohol resin film)

The thickness of the polyvinyl alcohol-based resin film used in the resin film bonding step is 50 μm or less. The polyvinyl alcohol-based resin film is formed into a polarizing element layer through a subsequent stretching step and a dyeing step, and the polyvinyl alcohol-based resin film in the resin film bonding step (S10) is extended. When the thickness of the polyvinyl alcohol-based resin film exceeds 50 μm, the stretching step and the dyeing step can be carried out without being bonded to the base film as described in the present invention. Therefore, the advantages of the present invention are small. In the case where the thickness of the polyvinyl alcohol-based resin film exceeds 50 μm, there is a case where it is difficult to form the film of the polarizing element layer to a film of 25 μm or less. Further, the thickness of the polyvinyl alcohol-based resin film (before stretching) is preferably 10 μm or more, and more preferably 15 μm or more. When the thickness of the polyvinyl alcohol-based resin film is less than 10 μm, it is difficult to obtain a polyvinyl alcohol-based resin film alone. The thickness of the polyvinyl alcohol-based resin film is preferably 15 to 45 μm.

A polyvinyl alcohol-based resin which forms a polyvinyl alcohol-based resin film can be used by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin is exemplified by a copolymer of vinyl acetate and another monomer copolymerizable, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The polyvinyl alcohol-based resin is preferably a completely saponified product. The degree of saponification is preferably in the range of from 80 mol% to 100 mol%, more preferably from 90 mol% to 100 mol%, and most preferably in the range of from 94 mol% to 100 mol%. If the degree of saponification is less than 80 mol%, there is a problem that the water resistance and the moist heat resistance after the formation of the polarizing element layer are remarkably poor.

The degree of saponification referred to herein means the ratio of the acetic acid group contained in the polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification step in terms of the unit ratio (% by mole). Those are the values defined by the following formula. It can be obtained by the method specified in JIS K 6726 (1994).

Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

The higher the degree of saponification, the higher the proportion of the hydroxyl group, that is, the lower the proportion of the acetate group which inhibits crystallization.

Further, the polyvinyl alcohol-based resin may be a part of the modified modified polyvinyl alcohol. For example, the polyvinyl alcohol-based resin may be subjected to an olefin such as ethylene or propylene, acrylic acid or methacryl. An unsaturated carboxylic acid such as an acid or a crotonic acid, an alkyl ester of an unsaturated carboxylic acid, or a modified acrylamide or the like. The proportion of the modification is preferably less than 30% by mole, more preferably less than 10% by mole. When the modification is performed in excess of 30 mol%, it becomes difficult to adsorb the dichroic dye, resulting in defects such as low polarizing performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, and still more preferably from 2,000 to 5,000. The average degree of polymerization referred to herein is also a value obtained by a method specified in JIS K 6726 (1994).

Examples of the polyvinyl alcohol-based resin having such a property include PVA124 (saponification degree: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd., PVA117 (saponification degree: 98.0 to 99.0 mol %), and PVA624 ( Saponification degree: 95.0 to 96.0 mol%) and PVA617 (saponification degree: 94.5 to 95.5 mol%); for example, AH-26 manufactured by Japan Synthetic Chemical Industry Co., Ltd. (saponification degree: 97.0 to 98.8 mol%) ), AH-22 (saponification degree: 97.5 to 98.5 mol%), NH-18 (saponification degree: 98.0 to 99.0 mol%), and N-300 (saponification degree: 98.0 to 99.0 mol%); for example, List: JC-33 (saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5~95.5 mol%), JM-26 (saponification degree: 95.5~97.5 Mo) of JAPAN VAM & POVAL (share) Ear %), JP-45 (saponification degree: 86.5-89.5 mol%), JF-17 (saponification degree: 98.0-99.0 mol%), JF-17L (saponification degree: 98.0-99.0 mol%), and JF-20 (degree of saponification: 98.0 to 99.0 mol%), etc., can be preferably used for the formation of the polyvinyl alcohol-based resin film of the present invention.

The polyvinyl alcohol-based resin as described above is formed into a film to form a polyvinyl alcohol-based resin film. The method of forming a film of the polyvinyl alcohol-based resin film is not particularly limited. For example, a solvent casting method in which a polyvinyl alcohol-based resin solution is applied onto a support and dried, or a polyvinyl alcohol-based resin containing water is melt-kneaded and extruded on a support by an extruder. In the melt extrusion method, a polyvinyl alcohol-based resin aqueous solution is sprayed into a poor solvent (low-solubility solvent), and the like. Among these, you can get more transparent In terms of the film, a casting method or a melt extrusion method is preferred.

Hereinafter, preferred embodiments of the method for producing a polyvinyl alcohol resin film will be described. Fig. 3 is a flow chart showing a method for producing a polyvinyl alcohol-based resin film of the present embodiment. In this embodiment, the steps of forming a resin layer comprising a resin layer comprising a polyvinyl alcohol resin on a support (S110), and drying the first drying step of the resin layer (S120); The resin layer is separated from the support to obtain a resin layer separation step of the resin layer (S130), and the second drying step of the resin layer is dried at a temperature higher than the temperature in the first drying step (S140).

Examples of the support mentioned here include a release film, a stainless steel belt, and a cooling roll. As a method of forming the resin layer on the support in the resin layer forming step (S110), the solvent casting method and the melt extrusion method described above are exemplified. For example, it is preferred to dissolve the powder of the polyvinyl alcohol-based resin in a good solvent (highly soluble solvent) and apply the obtained polyvinyl alcohol-based resin solution to one surface of the support, and to make the solvent A solvent casting method which is formed by evaporation and drying. By forming the polyvinyl alcohol resin layer in this manner, a polyvinyl alcohol resin layer having a thickness of 10 to 50 μm can be formed.

As a method of applying the polyvinyl alcohol-based resin solution to the support, a roll coating method such as a bar coating method, a reverse coating method, or a gravure coating method, a die coating method, or a Kama can be appropriately selected. (comma) a known method such as a coating method, a lip coating method, a spin coating method, a screen coating method, a spray coating method, a dipping method, and a spray method.

The polyvinyl alcohol-based resin solution used in these methods can be obtained, for example, by dissolving a polyvinyl alcohol-based resin in water heated to 80 to 90 °C.

The solid content concentration of the polyvinyl alcohol-based resin is preferably in the range of 6 wt% to 50 wt%. When the concentration of the solid content component is less than 6% by weight, the viscosity becomes too low, and the fluidity at the time of formation of the resin layer becomes too high, and it becomes difficult to obtain a uniform film. On the other hand, when the solid content exceeds 50% by weight, the viscosity becomes too high and the fluidity at the time of formation of the resin layer becomes low, so that it becomes difficult to form a film.

A plasticizer can be added to the polyvinyl alcohol-based resin solution. Among them, a polyhydric alcohol is preferably used, and examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. Multiples can also be combined. Ethylene glycol or glycerol is particularly preferably used. Further, an anti-caking agent such as a surfactant may be used in combination as needed.

After the resin layer forming step (S110), in the first drying step (S120), the resin layer formed on the support is dried at a low temperature, usually at a drying temperature of 60 ° C or lower, to such an extent that it can be peeled off from the support. The degree of peeling from the support means that the coating liquid is in a solid state to some extent and can be peeled off as a film. Usually, as long as it is dried until the water content reaches 30% by weight or less, the entire film can be stably peeled off. If it is dried to 20 wt% or less, it can be peeled off more easily, and therefore it is preferable. The water content referred to herein means the amount of water determined by the dry weight method, and can be obtained by the following method.

The film weight was measured after leaving the peeled PVA film at room temperature (about 25 ° C, 55% RH) for 30 minutes or more.

After that, it was dried at 105 ° C for 60 minutes and taken out, and then left for several minutes until the film temperature returned to normal temperature.

● After standing for a few minutes, the weight of the film was measured again.

● Substituting the obtained value into the following formula.

Moisture content = (weight before drying - weight after drying) / weight before drying × 100 (wt / wt%)

As a specific method of drying the resin layer formed on the support until the extent of peeling from the support, for example, in actual production, it is preferred to confirm the drying condition in the peelable state in advance by preliminary experiments, and This condition is carried out. For example, it is preferably dried at a temperature ranging from 40 ° C to 60 ° C for 1 to 30 minutes, more preferably at a temperature of 50 ° C for about 3 to 20 minutes.

In the first drying step (S120), by drying at a low temperature, or drying the resin layer It is possible to prevent the occurrence of curling of the end portions in the support by peeling off from the support rather than completely drying, and drying shrinkage in the resin layer is less likely to occur.

Then, in the resin layer separation step (S130), the dried resin layer is peeled off from the support in the first drying step to obtain a resin layer. Then, in the second drying step (S140), the resin layer peeled off from the support is dried. In the second drying step (S140), the resin layer is sufficiently dried. Therefore, drying is performed at a drying temperature which is higher than the first drying step. The high temperature referred to herein is usually 150 ° C or lower, preferably 120 ° C or lower, more preferably 100 ° C or lower, and is preferably 60 ° C or higher, more preferably 70 ° C or higher. The drying method includes a method of blowing hot air, a method of contacting with a heat roller, and a method of heating by an infrared heater (infrared heater), and any of them may be preferably used. Further, the drying temperature mentioned in the first drying step and the second drying step refers to a method of blowing hot air or an ambient temperature in a drying furnace in the case of a drying apparatus such as an IR heater provided with a drying furnace, In the case of a contact type drying apparatus such as a heat roller, it means the surface temperature of the heat roller. Through the above steps, a polyvinyl alcohol-based resin film was produced.

The polyvinyl alcohol-based resin film produced by the method of the present embodiment is excellent in curl suppression.

(substrate film)

As the resin used for the substrate film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, elongation, and the like can be used, depending on the glass transition temperature or the melting point Tm (melting temperature). ) and choose the right resin. The base film is preferably stretched in a temperature range capable of extending over the polyvinyl alcohol-based resin film which is laminated thereon.

Specific examples of the thermoplastic resin include a polyolefin resin, a polyester resin, and a cyclic polyolefin resin. Ethylene resin, (meth)acrylic resin, cellulose ester resin, polycarbonate resin, polyvinyl alcohol resin, vinyl acetate resin, polyarylate resin, polystyrene resin, poly An ether oxime resin, a polyfluorene-based resin, a polyamine-based resin, a polyimide-based resin, and a mixture or a copolymer thereof.

The base film may be a film containing only one of the above resins, or may be a film obtained by blending two or more kinds of resins. The substrate film may be a single layer film or a multilayer film.

The polyolefin-based resin may, for example, be polyethylene or polypropylene, and is preferably easily and stably extended at a high rate. Further, a propylene-ethylene copolymer obtained by copolymerizing ethylene and propylene or the like can also be used. The copolymerization may be another type of monomer, and examples of other types of monomers copolymerizable with propylene include ethylene and an α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and an α-olefin having 4 to 10 carbon atoms is more preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene. a branched monoolefin such as 3-methyl-1-butene, 3-methyl-1-pentene or 4-methyl-1-pentene; ethylene cyclohexane or the like. The copolymer of propylene and a monomer copolymerizable therewith may be a random copolymer or may be a block copolymer. The content of the constituent unit derived from the other monomer in the copolymer can be determined by infrared (IR) spectroscopy according to the method described in the "Handbook of Polymer Analysis" (published by Kiyoshiya Shoten, 1995) on page 616. Out.

In the above, as the propylene-based resin constituting the propylene-based resin film, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and propylene-ethylene-1- are preferably used. Random copolymer.

Moreover, the stereoregularity of the propylene-based resin constituting the propylene-based resin film is preferably substantially isotactic or syndiotactic. The propylene-based resin film containing a propylene-based resin having substantially uniform or regular stereoregularity is relatively excellent in handleability and excellent in mechanical strength in a high-temperature environment.

The polyester resin is a polymer having an ester bond, and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acid, a divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalate. Again The polyol to be used mainly uses a divalent diol, and examples thereof include propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polytrimethylene terephthalate. , polytrimethylene naphthalate (polytrimethylene naphthalate), polybutylene terephthalate dimethyl ester, polynaphthalene dicarboxylate dimethyl dimethyl ester and the like. It is also preferred to use such blended resins or copolymers.

As the cyclic polyolefin resin, it is preferred to use a drop An olefinic resin. The cyclic polyolefin resin is a general term for a resin which is polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include resins described in JPH01-240517-A, JPH03-14882-A, and JPH03-122137-A. Specific examples thereof include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (representatively random) a copolymer), a graft polymer obtained by modifying the unsaturated carboxylic acid or a derivative thereof, and the like, and the like. Specific examples of the cyclic olefin include a descending An olefinic monomer.

Various products are sold as the cyclic polyolefin resin. Specific examples include Topas (registered trademark) (manufactured by Ticona Co., Ltd.), Artone (registered trademark) (manufactured by JSR Co., Ltd.), Zeonor (ZEONOR) (registered trademark) (manufactured by Japan ZEON Co., Ltd.), and Zeonex ( ZEONEX) (registered trademark) (manufactured by Japan ZEON Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals Co., Ltd.), etc.

Any suitable (meth)acrylic resin can be used as the (meth)acrylic resin. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methyl group Methyl acrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate- Cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid Ester copolymers, etc.).

Preferably, a poly(meth)acrylic acid C1-6 alkyl ester such as poly(methyl) acrylate is used. As the (meth)acrylic resin, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is more preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate.

Further, those obtained by modifying the copolymer or a part of the hydroxyl group with another type of substituent or the like may be mentioned. Among these, cellulose triacetate is preferred. The sale of cellulose triacetate with a variety of products is also advantageous in terms of availability or cost. Examples of the sales of the cellulose triacetate include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark). TD80UZ (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (manufactured by Fuji Film Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC4UY (manufactured by Konica Minolta Opto Co., Ltd.), and the like.

The polycarbonate resin is an engineering plastic containing a polymer in which a monomer unit is bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, and flame retardancy. Moreover, it is preferably used for optical applications because of its high transparency. A resin called modified polycarbonate which is a modification of the polymer skeleton for reducing the photoelastic coefficient in optical use, or a copolymerized polycarbonate which has improved wavelength dependence, can be preferably used. Such a carbonate resin is widely sold, and examples thereof include Panlite (registered trademark) (Teijin Chemical Co., Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering-Plastic), and SD Polyca (registered trademark) (Sumitomo Dow ( Share)), Calibre (registered trademark) (Dow Chemical) and so on.

Any suitable additive may be added to the base film in addition to the above thermoplastic resin. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a color preventive agent, a flame retardant, a nucleating agent, an antistatic agent, and the like. Pigments, colorants, etc. The content of the thermoplastic resin exemplified above in the base film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight. The reason for this is that when the content of the thermoplastic resin in the base film is less than 50% by weight, the thermoplastic resin inherently has high transparency and the like.

The thickness of the base film before stretching can be appropriately determined. Generally, it is preferably from 1 to 500 μm, more preferably from 1 to 300 μm, even more preferably from 5 to 200 μm, in terms of workability such as strength and handleability. Good for 5~150μm.

In order to improve the adhesion between the base film and the polyvinyl alcohol resin film, at least the surface on the side to which the polyvinyl alcohol resin film is bonded may be subjected to corona treatment, plasma treatment, flame treatment, or the like. Further, in order to improve the adhesion, a thin layer such as an undercoat layer may be formed on the surface of the base film on the side where the polyvinyl alcohol-based resin film is formed.

(primer coating)

An undercoat layer may be formed on the surface of the base film to which the side of the polyvinyl alcohol-based resin film is bonded. The undercoat layer is not particularly limited as long as it exhibits a certain degree of adhesion to both the base film and the polyvinyl alcohol resin film. For example, a thermoplastic resin excellent in transparency, heat stability, and elongation can be used. Specifically, an acrylic resin or a polyvinyl alcohol resin is mentioned, but it is not limited to these. Among them, a polyvinyl alcohol-based resin having good adhesion is preferably used.

Examples of the polyvinyl alcohol-based resin used as the undercoat layer include a polyvinyl alcohol resin and a derivative thereof. Examples of the polyvinyl alcohol resin derivative include, in addition to polyethylene formaldehyde and polyvinyl acetal, an olefin such as ethylene or propylene, or an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid. The alkyl ester of an unsaturated carboxylic acid, acrylamide or the like is modified. Among the above polyvinyl alcohol-based resin materials, a polyvinyl alcohol resin is preferably used.

A crosslinking agent may also be added to the above thermoplastic resin in order to increase the strength of the undercoat layer. add A known agent such as an organic system or an inorganic system can be used as the crosslinking agent to be added to the thermoplastic resin. Just choose a thermoplastic resin that is more suitable for the thermoplastic resin used. For example, a methylolated melamine resin or a polyether may be used in addition to a low molecular crosslinking agent such as an epoxy crosslinking agent, an isocyanate crosslinking agent, a dialdehyde crosslinking agent, or a metal chelate crosslinking agent. A polymer crosslinking agent such as a guanamine epoxy resin. When a polyvinyl alcohol-based resin is used as the thermoplastic resin, it is particularly preferable to use a polyamine epoxy resin, a methylolated melamine, a dialdehyde, a metal chelate crosslinking agent or the like as a crosslinking agent.

The thickness of the undercoat layer is preferably from 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the adhesion between the base film and the polyvinyl alcohol film is lowered, and when it is thicker than 1 μm, the polarizing plate becomes thick, which is not preferable.

(adhesive layer)

The adhesive constituting the adhesive layer is also called a pressure-sensitive adhesive. Usually, an acrylic resin, a styrene resin, a lanthanum resin, or the like is used as a base polymer, and an isocyanate compound, an epoxy compound, and aziridine are added thereto. A composition obtained by crosslinking a compound or the like. Further, fine particles may be blended in the adhesive to form an adhesive layer exhibiting light scattering properties.

The thickness of the adhesive layer is preferably from 1 to 40 μm, and further preferably is thinly applied within a range of characteristics of non-destructive workability and durability, and more preferably from 3 to 25 μm. If it is 3 to 25 μm, it has good workability and is also preferable in terms of controlling the dimensional change of the polarizing film. When the adhesive layer is less than 1 μm, the adhesiveness is lowered, and if it exceeds 40 μm, defects such as an overflow of the adhesive tend to occur.

The method of forming the adhesive layer on the base film or the polyvinyl alcohol resin film is not particularly limited, and the base film surface or the polyvinyl alcohol resin film surface may be coated with each of the base polymer. After the solution of the component is dried to form an adhesive layer, it is bonded to a separator or other type of film, or after forming an adhesive layer on the separator, on the substrate film surface or polyvinyl alcohol resin Attachment and lamination on the film surface. Also, in the substrate film When the adhesive layer is formed on the surface of the polyvinyl alcohol-based resin film, it may be subjected to a close-treatment such as electricity on the substrate film surface or the polyvinyl alcohol resin film surface or the adhesive layer as needed. Halo treatment, etc.

(adhesive layer)

Examples of the adhesive agent constituting the adhesive layer include a polyvinyl alcohol-based resin aqueous solution and a water-based adhesive using an aqueous two-liquid polyurethane latex adhesive. Among them, a polyvinyl alcohol-based resin aqueous solution is preferably used. In the polyvinyl alcohol-based resin used as an adhesive, in addition to the vinyl alcohol homopolymer obtained by subjecting polyvinyl acetate as a homopolymer of vinyl acetate to a saponification treatment, there is a copolymerization of vinyl acetate with it. The copolymer of the other monomer is subjected to a saponification treatment to obtain a vinyl alcohol-based copolymer, and a modified polyvinyl alcohol-based polymer in which the hydroxyl groups are partially modified. A polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, a zinc compound or the like may be added to the aqueous binder as an additive. In the case of using such a water-based adhesive, the adhesive layer obtained thereafter is usually much thinner than 1 μm, and the adhesive layer is not actually observed even when the cross section is observed by a usual optical microscope.

The bonding method of the film using the water-based adhesive is not particularly limited, and examples thereof include uniformly coating or flowing an adhesive on the surface of the base film or the polyvinyl alcohol-based resin film, and superposing another film on the coating. The surface is bonded by a roll or the like, and dried. Usually, the adhesive is applied at a temperature of 15 to 40 ° C after the preparation thereof, and the bonding temperature is usually in the range of 15 to 30 ° C.

When a water-based adhesive is used, after the film is bonded, the water contained in the water-based adhesive is removed to be dried. The temperature of the drying furnace is preferably from 30 ° C to 90 ° C. If it is less than 30 ° C, the adhesive surface tends to be easily peeled off. When it is 90 ° C or more, the optical performance of the polarizing element or the like is deteriorated due to heat. The drying time can be set to 10 to 1000 seconds.

After drying, it can also be at room temperature or a slightly higher temperature, for example, at 20 to 45 ° C left. It is aged for about 12 to 600 hours at the right temperature. The temperature at the time of ripening is usually set lower than the temperature used at the time of drying.

Further, a photocurable adhesive can also be used as the non-aqueous adhesive. The photocurable adhesive agent may, for example, be a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

As a method of film bonding by a photocurable adhesive, a conventionally known method can be used, and examples thereof include a cast molding method, a Meyer bar coating method, a gravure coating method, and a comma coating. The cloth method, the doctor blade method, the die coating method, the dip coating method, and the spray method are equal to the method of applying the adhesive to the adhesive layer of the film to make the two films overlap. The casting method is a method in which two sheets of the object to be coated are moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction therebetween, and the adhesive is spread on the surface thereof to spread the coating.

After the adhesive is applied to the surface of the film, the film is bonded and held by a nip roll or the like. Further, a method of pressurizing the laminated body by a roll or the like to uniformly spread the laminate may be preferably used. In this case, metal or rubber or the like may be used as the material of the roll. Further, it is also preferred to use a method in which the laminate is passed between a roll and a roll to be pressurized and spread. In this case, the rolls may be of the same material or different materials. The thickness before drying or hardening of the adhesive layer after bonding using the above nip rolls or the like is preferably 5 μm or less and 0.01 μm or more.

In order to improve the adhesion, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment may be appropriately performed on the subsequent surface of the film.

The saponification treatment may be immersed in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

When a photocurable resin is used as the adhesive, the photocurable adhesive is cured by irradiating the active energy ray after the laminated film. The light source of the active energy ray is not particularly limited, and is preferably an active energy ray having a luminescent distribution at a wavelength of 400 nm or less. The wire is specifically preferably used: a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, and the like.

The light irradiation intensity of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited. It is preferably an irradiation intensity in a wavelength region effective for activation of the polymerization initiator of 0.1 to 6000 mW/cm. ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and in the case of 6000 mW/cm ² or less, the heat of the light source and the heat of the photocurable adhesive harden. The yellowing which causes the yellowing of the epoxy resin or the deterioration of the polarizing film is small. The light irradiation time of the photocurable adhesive is not particularly limited as long as it is a photocurable adhesive which is cured, and it is preferable that the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ. Set in /cm ² mode. When the integrated light amount of the photocurable adhesive is 10 mJ/cm ² or more, a sufficient amount of the active material derived from the polymerization initiator can be generated to more accurately perform the hardening reaction at 10,000 mJ/cm ² or less. In the case, the irradiation time does not become too long, and good productivity can be maintained. Further, the thickness of the adhesive layer after the active energy ray irradiation is usually about 0.001 to 5 μm, preferably 0.01 μm or more and 2 μm or less, and more preferably 0.01 μm or more and 1 μm or less.

In the case where the base film or the photocurable adhesive on the polyvinyl alcohol resin film is cured by irradiation with an active energy ray, the transmittance, hue, transparency, and the like of the films are preferably used. Hardening is performed under the condition that the functions of the polarizing plate after all the steps are not lowered.

<Extension step (S20)>

Here, the laminated film including the base film and the polyvinyl alcohol resin film is uniaxially stretched. Preferably, the uniaxial stretching is performed at a stretching ratio of more than 5 times and 17 times or less. Further preferably, the uniaxial stretching is performed at a stretching ratio of more than 5 times and 8 times or less. When the stretching ratio is 5 or less, the polyvinyl alcohol-based resin film is not sufficiently aligned, and as a result, the degree of polarization of the polarizing element layer may not be sufficiently high. On the other hand, the extension ratio exceeds 17 In the case of the case, the fracture of the laminated film at the time of stretching is liable to occur, and the workability and workability in the subsequent steps are deteriorated. The extension process in the extension step (S20) can be carried out in multiple stages without being limited to the extension in one stage. In the case of performing in multiple stages, it is preferred to carry out the stretching treatment at a stretching ratio of more than 5 times in all stages of the elongation processing.

In the extending step (S20) of the present invention, a longitudinal stretching process in the longitudinal direction of the laminated film or a lateral stretching process in which the width direction is extended may be performed. Examples of the longitudinal stretching method include a roll stretching method, a compression stretching method, and the like. Examples of the horizontal stretching method include a tenter method.

<Staining step (S30)>

Here, the resin layer of the laminated film is dyed with a dichroic dye. Examples of the dichroic dye include iodine or an organic dye. As the organic dye, for example, red BR, red LR, red R, pink LB, jade red BL, purple red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue RY, green LG, purple LB, Purple B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Bright Purple BK, Super Blue G, Super Blue GL, Super Orange GL Direct blue sky, direct dry orange S, quick dry black, etc. These dichroic substances may be used alone or in combination of two or more.

The dyeing step is carried out, for example, by immersing the entire stretched film in an aqueous solution (dyeing solution) containing a dichroic dye. A solution obtained by dissolving the above dichroic dye in a solvent can be used as the dyeing solution. As the solvent of the dyeing solution, water is generally used, and an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably from 0.01 to 10% by weight, more preferably from 0.02 to 7% by weight, particularly preferably from 0.025 to 5% by weight.

When iodine is used as the dichroic dye, it is preferable to further add iodide in terms of further improving the dyeing efficiency. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. Wait. The proportion of the iodide added is preferably solubilized The liquid is 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, particularly preferably In the range of 1:7~1:70.

The immersion time of the stretched film in the dyeing solution is not particularly limited, but is usually preferably in the range of 15 seconds to 15 minutes, more preferably 1 minute to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

<Crosslinking step>

The crosslinking treatment can be carried out after the dyeing step. The crosslinking treatment is carried out, for example, by immersing the stretched film in a solution (crosslinking solution) containing a crosslinking agent. A previously known substance can be used as a crosslinking agent. For example, a boron compound such as boric acid or borax, or glyoxal or glutaraldehyde can be mentioned. These may be used alone or in combination of two or more.

A solution obtained by dissolving a crosslinking agent in a solvent can be used as the crosslinking solution. As the solvent, for example, water may be used, and further, an organic solvent compatible with water may be contained. The concentration of the crosslinking agent in the crosslinking solution is not particularly limited, but is preferably in the range of 1 to 20% by weight, more preferably 6 to 15% by weight.

Iodide may also be added to the crosslinking solution. By the addition of iodide, the polarization characteristics in the surface of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The content of the iodide is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The immersion time of the laminated film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes. Further, the temperature of the crosslinking solution is preferably in the range of 10 to 80 °C.

<washing step>

After the crosslinking step, it is preferred to carry out the washing step. As a washing step, it can be practical Wash and wash. The water washing treatment can be usually carried out by immersing the laminated film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 to 50 ° C, preferably from 4 ° C to 20 ° C. The immersion time is usually from 2 to 300 seconds, preferably from 3 seconds to 240 seconds.

The washing step may be a combination of a washing treatment using an iodide solution and a water washing treatment, or a solution prepared by appropriately mixing a liquid alcohol such as methanol, ethanol, isopropanol, butanol or propanol.

<drying step>

The drying step can also be carried out after the washing step. As the drying step, any appropriate method (for example, natural drying, air drying, and heat drying) may be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C, and the drying time is usually about 1 to 15 minutes.

Through the above steps, the polyvinyl alcohol-based resin film has a function as a polarizing element layer, and a polarizing laminated film having a polarizing element layer on one surface of the base film is produced.

(polarized element layer)

Specifically, the polarizing element layer is obtained by adsorbing a dichroic dye to a uniaxially stretched polyvinyl alcohol resin film. The stretching ratio is preferably more than 5 times, more preferably more than 5 times and 17 times or less.

The thickness of the polarizing element layer (the thickness of the polyvinyl alcohol-based resin film after stretching) is preferably 25 μm or less, more preferably 20 μm or less, and is preferably 2 μm or more. By setting the thickness of the polarizing element layer to 25 μm or less, a thin polarizing laminated film can be formed.

<Protective film bonding step (S40)>

A protective film is bonded to the surface of the polarizing element layer of the polarizing laminated film opposite to the surface on the substrate film side. The bonding method of the polarizing element layer and the protective film is not particularly limited. For example, an adhesive layer or an adhesive layer is formed on the bonding surface of the polarizing element layer and/or the protective film, and the two are bonded via an adhesive layer or an adhesive layer. A material suitable as an adhesive layer or an adhesive layer and an adhesive layer or a joint described in the column of the above-mentioned resin film bonding step (S10) The primer layer is the same.

(protective film)

The protective film may be a single protective film having no optical function, or may be a protective film having an optical function of a so-called retardation film or a brightness enhancement film.

The material of the protective film is not particularly limited, and examples thereof include a cyclic polyolefin resin film, and a cellulose acetate resin film containing a resin such as cellulose triacetate or cellulose diacetate, and polyphenylene terephthalate. A polyester resin film of a resin such as ethylene formate, polyethylene naphthalate or polybutylene terephthalate, a polycarbonate resin film, an acrylic resin film, a polypropylene resin film, etc. , a membrane widely used in the field since the prior art.

As the cyclic polyolefin-based resin, a suitable product can be preferably used, for example, Topas (registered trademark) (manufactured by Ticona Co., Ltd.), Artone (registered trademark) (manufactured by JSR Co., Ltd.), and Zeonor (ZEONOR) (registered trademark) (made by Japan Zeon), Zeonex (registered trademark) (ZEONEX) (made by Zeon, Japan), Apel (registered trademark) (made by Mitsui Chemicals Co., Ltd.), etc. When a film is formed by forming a film of the cyclic polyolefin-based resin, a known method such as a solvent casting method or a melt extrusion method is suitably used. In addition, it can be pre-formed using S-SINA (registered trademark) (made by Sekisui Chemical Industry Co., Ltd.), SCA40 (made by Sekisui Chemical Industry Co., Ltd.), Zeonor (registered trademark) Film (made by Optronics). A product of a film made of a cyclic polyolefin resin of a film.

The cyclic polyolefin resin film may also be a uniaxially stretched or biaxially stretched one. By extending, an arbitrary phase difference value can be given to the cyclic polyolefin resin film. The stretching is usually performed by winding the film roll one by one, continuously extending in the heating furnace toward the roll, in a direction perpendicular to the advancing direction, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 °C. The magnification of the extension is usually 1.1 to 6 times, preferably 1.1 to 3.5 times, in each direction.

The cyclic polyolefin resin film generally has a poor surface activity, so it is preferably a pair of polarizing elements. The surface of the layer is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment or the like. Among them, plasma treatment and corona treatment which can be carried out relatively easily are preferred.

As the cellulose acetate-based resin film, a suitable product can be preferably used, for example, Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UZ (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (manufactured by Fuji Film Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) Wait.

A liquid crystal layer or the like may be formed on the surface of the cellulose acetate resin film in order to improve the viewing angle characteristics. Further, the cellulose acetate resin film may be stretched in order to impart a phase difference. In order to improve the adhesion to the polarizing film, the cellulose acetate resin film is usually subjected to a saponification treatment. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface of the protective film as described above. The method of forming the optical layers on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the protective film is preferably as thin as possible, and is preferably 90 μm or less, more preferably 50 μm or less. On the other hand, if it is too thin, the strength is lowered and the workability is deteriorated, so it is preferably 5 μm or more.

<Substrate film peeling step (S50)>

In the method of manufacturing a polarizing plate of the present embodiment, as shown in FIG. 2, after the protective film bonding step (S40) of bonding the protective film to the polarizing element layer, the substrate film peeling step (S50) is performed. In the base film peeling step (S50), the base film is peeled off from the polarizing laminated film. The method of peeling off the base film is not particularly limited, and the same method as the peeling step of the release film performed in a usual polarizing plate with an adhesive can be employed. Protective film bonding step After (S40), it may be peeled off immediately, or may be peeled off by separately providing a peeling process after winding up once in a roll shape. Through the above steps, a polarizing plate having a protective film on one side of the polarizing element layer is manufactured.

(other optical layers)

When the polarizing plate is used in practice, it can be used as a polarizing plate in which other optical layers are laminated.

Further, the protective film may have the function of the optical layers.

Examples of the other optical layer include a reflective polarizing film that transmits a certain polarized light and reflects polarized light having a property opposite thereto, and an anti-glare film having a concave-convex shape on the surface, and a surface. A film having an anti-reflection function, a reflective film having a reflective function on the surface, a semi-transmissive reflective film having both a reflecting function and a penetrating function, and a viewing angle compensation film.

As a sales item of a reflective polarizing film that is equivalent to a polarized light that reflects a certain polarized light and reflects the opposite property, for example, DBEF (manufactured by 3M Company, available from Sumitomo 3M), APF (Made by 3M Company, available from Sumitomo 3M (share)), etc. Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystal compound is applied to a surface of a substrate, a retardation film containing a polycarbonate resin, and a retardation film containing a cyclic polyolefin resin. The sales item of the optical compensation film which is applied to the surface of the substrate and which is coated with the liquid crystal compound is exemplified by WV Film (manufactured by Fuji Film Co., Ltd.), NH Film (manufactured by Nippon Oil Co., Ltd.), and NR. Film (manufactured by Nippon Oil Co., Ltd.) and the like. In addition, as a sales item of a retardation film containing a cyclic polyolefin-based resin, Artone (registered trademark) Film (JSR (manufactured)), S-SINA (registered trademark) (Sui Shui Chemical Industry Co., Ltd.) ) Manufacturing), Zeonor (registered trademark) Film (manufactured by Optronics), and the like.

[Examples] [Example 1]

<Production of polyvinyl alcohol resin film>

The powder of the fully saponified polyvinyl alcohol resin (trade name: PVA124) sold by Kuraray Co., Ltd. was dissolved in warm water of 90 ° C to prepare a polyvinyl alcohol resin aqueous solution having a solid content concentration of 10% by weight. The obtained polyvinyl alcohol resin aqueous solution was applied to a PET substrate subjected to release treatment by a lip coating method to a thickness of about 400 μm. After drying at 50 ° C for 10 minutes, the polyvinyl alcohol-based resin film was peeled off from the PET substrate, and further dried at 80 ° C for 5 minutes to obtain a curl-free polyvinyl alcohol-based resin film. The thickness after drying was 41 μm.

<Resin film bonding step>

The polyvinyl alcohol powder and the crosslinking agent were dissolved in hot water to prepare an aqueous solution of an adhesive having the following composition. In addition, a corona discharge treatment was performed on a 110 μm-thick base film containing a polypropylene resin (trade name: FLX80E4, manufactured by Sumitomo Chemical Co., Ltd.), and the thickness after drying was about 0.2 μm using a gravure coater. In this manner, the above aqueous solution of the adhesive is applied. Thereafter, the polyvinyl alcohol-based resin film was bonded to the film, and then dried at 50 ° C for 3 minutes to obtain a laminated film. The obtained laminated film is smooth and easy to handle.

(adhesive aqueous solution)

Water: 100 parts by weight, polyvinyl alcohol resin powder (manufactured by Kuraray, average polymerization degree 18000, trade name: KL-318): 3 parts by weight, polyamide resin (crosslinking agent, Sumika Chemtex) ) Manufactured, trade name: SR650 (30)): 1.5 parts by weight.

<Extension step>

The laminate film was subjected to a 5.8-fold free end uniaxial extension at 160 ° C using a tenter apparatus. The thickness of the stretched polyvinyl alcohol resin film was 18 μm.

<staining step>

Thereafter, the laminated film was immersed in a dyeing solution of 30 ° C in a mixed aqueous solution of iodine and potassium iodide for about 180 seconds, and the polyvinyl alcohol-based resin film was dyed, and then the remaining iodine solution was washed with pure water at 10 ° C. Then, it was immersed in a crosslinking solution of a mixed aqueous solution of boric acid and potassium iodide at 76 ° C for 300 seconds. After that, it is washed with pure water at 10 ° C for 4 seconds, and finally with a nip roller. The remaining moisture on the surface is removed. The mixing ratio of the liquid chemicals of each layer is as follows. The laminated film after dyeing was dried at 80 ° C for 5 minutes to obtain a polarizing laminated film.

(dyeing solution)

Water: 100 parts by weight, iodine: 0.6 parts by weight, potassium iodide: 10 parts by weight.

(cross-linking solution)

Water: 100 parts by weight, boric acid: 9.5 parts by weight, potassium iodide: 5 parts by weight.

<Protective film bonding step>

An aqueous solution of an adhesive similar to the resin film bonding step was prepared. After applying the aqueous solution of the above-mentioned adhesive to the surface of the polarizing element layer of the polarizing laminated film on the side opposite to the surface on the side of the substrate film, a protective film (TAC: KC4UY manufactured by Konica Minolta Opto Co., Ltd.) was bonded thereto. A polarizing plate comprising five layers of a base film, an adhesive layer, a polarizing element layer, an adhesive layer, and a protective film.

<Substrate film peeling step>

The polarizing plate was dried at 80 ° C for 5 minutes to obtain a polarizing plate. The base film was peeled off from the obtained polarizing plate. The base film is easily peeled off, and a polarizing plate including four layers of an adhesive layer, a polarizing element layer, an adhesive layer, and a protective film is obtained. The thickness of the polarizing plate was 18 μm. The polarizing performance of the obtained polarizing plate was measured by a spectrophotometer (V7100) manufactured by JASCO Corporation. The incident direction of light is taken from the side of the polarizing element layer. The visibility correction monomer transmittance is 41.8%, the visibility correction polarization degree is 99.997%, and the polarization performance is excellent, which is sufficient for the performance of the polarizing plate.

[Comparative Example 1]

After the corona discharge treatment was performed on the same base film as in Example 1, the polyvinyl alcohol resin aqueous solution for producing a polyvinyl alcohol-based resin film in Example 1 was directly applied by a gap coating method. Thereafter, the film was continuously dried at 50 ° C for 10 minutes and at 80 ° C for 5 minutes to cause significant curling due to drying shrinkage of the polyvinyl alcohol resin layer, and the end portion of the drying furnace was folded. Thickness of the obtained polyvinyl alcohol resin layer after drying The degree is about 39 μm.

S10‧‧‧ resin film bonding step

S20‧‧‧Extension step

S30‧‧‧Staining step

S40‧‧‧Protective film bonding step

S50‧‧‧Substrate film peeling step

Claims (6)

A method for producing a polarizing laminated film, which is a method for producing a polarizing laminated film comprising a base film and a polarizing element layer formed on one surface of the base film, and sequentially comprising the following steps: resin film bonding a method in which a resin film containing a polyvinyl alcohol-based resin having a thickness of 50 μm or less is bonded to one surface of a base film to continuously produce a laminated film; an extending step of uniaxially stretching the laminated film; and a dyeing step of the above-mentioned single The resin film of the axially extending laminated film is immersed in a dyeing solution containing iodine or an organic dye to perform dyeing to form a polarizing element layer. The method for producing a polarizing laminated film according to claim 1, wherein the resin film is bonded to one surface of the base film via an adhesive layer or an adhesive layer in the resin film bonding step. The method for producing a polarizing laminated film according to claim 1 or 2, wherein in the resin film bonding step, the thickness of the resin film is 15 μm or more. The method for producing a polarizing laminated film according to claim 1 or 2, wherein the resin film used in the resin film bonding step is a resin film produced by a method comprising the following steps: a resin layer forming step, a resin layer containing a polyvinyl alcohol-based resin is formed on the support; a first drying step of drying the resin layer formed on the support; and a resin layer separation step of peeling the dried resin layer from the support to obtain the resin layer And a second drying step of drying the peeled resin layer at a drying temperature higher than the temperature in the first drying step. The method for producing a polarizing laminated film according to claim 3, wherein The resin film used in the resin film bonding step is a resin film produced by a method comprising the following steps: a resin layer forming step of forming a resin layer containing a polyvinyl alcohol-based resin on a support; a drying step of drying the resin layer formed on the support; a resin layer separating step of peeling the dried resin layer from the support to obtain the resin layer; and a second drying step higher than the first drying step The peeled resin layer is dried at a drying temperature of the temperature. A method for producing a polarizing plate, which is a method of producing a polarizing plate comprising a polarizing element layer and a protective film formed on one surface of the polarizing element layer, after manufacturing a polarizing laminated film by the manufacturing method of claim 1 And a step of: a protective film bonding step of bonding a protective film on a surface of the polarizing layer film opposite to a surface of the polarizing element layer on a side opposite to the substrate film side; and a substrate film peeling step The base film is peeled off from the polarizing laminate film.