TW201606360A - Method of manufacture of polarizing plate having protective films on two sides - Google Patents

Abstract

This invention provides a method for manufacture of polarizing plate having protective films on two sides, the method including the steps of: removing by peeling a substrate film from a laminate of multi-layer films which contains a substrate film, a iodine group polarizing element and a first protective layer in this order, bonding a second protective order on the outer surface of the iodine group polarizing element, wherein the first and second protective films are thermoplastic resin films having a moisture permeability of 150/m2/24hr or less, and the iodine group polarizing element has a moisture content rate of less than 8 %wt when the second protective film in bonded. The invention also provides a polarizing plate having protective films on two sides, the polarizing film having thermoplastic resin films laminated on two sides of the iodine group polarizing element having a moisture content rate of less than 8 %wt and the thermoplastic resin films having a moisture permeability of 150g/m2/24hr or less.

Description

Method for manufacturing polarizing plate with double-sided protective film

The present invention relates to a method for producing a polarizing plate having a protective film adhered to both sides of a double-sided iodine-based polarizer, and in detail, a protective film having a low moisture permeability is successively attached to iodine. A method of manufacturing a polarizing plate with a protective film on both sides of the polarizing plate.

The polarizing plate is widely used in display devices such as liquid crystal display devices, and is particularly widely used in various portable computers such as smart phones in recent years. The polarizing plate is generally formed by bonding a protective film to one side or both sides of a polarizing plate using an adhesive.

The polarizer itself is low in heat and humidity resistance, and the polarizing property is easily deteriorated in a hot and humid environment. In the past, a triethylenesulfonated cellulose film can be used as the protective film for protecting the polarizer. However, since the triacetyl cellulose film has a high moisture permeability, the polarizing plate is used as a protective film, especially when an iodine-based polarizer is used. When the polarizer is used, there is a problem that the heat and humidity resistance becomes insufficient.

Therefore, in order to improve the heat-and-moisture resistance of the polarizing plate, a protective film having a low moisture permeability such as a decene-based resin film has been proposed, and it is bonded to an iodine-based polarizer instead of the triacetyl cellulose film [for example, open Paragraph [0005] of Japanese Patent Publication No. 2004-245925 (Patent Document 1).

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-245925

When the protective film having a low moisture permeability is bonded to both surfaces of the iodine-based polarizer, the intrusion of moisture from the outside can be reduced, so that the heat-and-moisture resistance of the polarizing plate can be improved. On the other hand, however, it has been found by the inventors of the present invention that a protective film having a low moisture permeability can be used in a conventional double-sided polarizing plate with a protective film on both sides, and a more general heat and humidity resistance test is carried out. When the heat resistance test is performed in a high temperature environment, light leakage under orthogonal polarized light is generated (fading is caused, and the light in the red region leaks from the polarizing plate to cause the polarizing plate to turn red), which is also called red light. Or to reduce the polarization characteristics. The problem of poor heat resistance is that the thickness of the iodine-based polarizer is as small as possible.

Therefore, an object of the present invention is to provide a double-sided polarizing plate for bonding a protective film having a low moisture permeability to an iodine-based polarizing film, and a double-sided protective film having both moist heat resistance and heat resistance. A method of polarizing a plate, and a polarizing plate with a protective film on both sides which have both heat and humidity resistance and heat resistance.

The present invention provides a method for producing a polarizing plate with a protective film on both sides as shown below, and a polarizing plate having a protective film on both sides.

[1] A method for producing a polarizing plate having a double-sided protective film, comprising: a multilayer film comprising a base film, an iodine-based polarizer, and a first protective film in this order, wherein the base film is peeled off and removed a step of attaching a polarizing plate with a protective film on one side, and attaching a second protective film to the outside of the iodine-based polarizing plate of the polarizing plate with a protective film on one side thereof to obtain a polarizing plate with a protective film on both sides The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m ² /24 hr or less; and the moisture content of the iodine-based polarizing film when the second protective film is bonded is less than 8 weight %.

[2] The production method according to [1], wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive.

[3] The production method according to [1], wherein the iodine-based polarizer has a thickness of 10 μm or less.

[4] A method for producing a polarizing plate having a double-sided protective film, comprising: bonding a second protective film to a first protective film comprising an iodine-based polarizer and a single layer laminated on the iodine-based polarizer; The outer surface of the iodine-based polarizer in the polarizing plate of the protective film is provided on one side, and the polarizing plate having the protective film on both sides is obtained. The first protective film and the second protective film are moisture-permeable to 150 g/m. A thermoplastic resin film of ² / 24 hr or less; the moisture content of the iodine-based polarizer when the second protective film is bonded is less than 8% by weight.

[5] The production method according to [4], wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive.

[6] The production method according to [4], wherein the iodine-based polarizer has a thickness of 10 μm or less.

[7] A polarizing plate having a double-sided protective film, comprising: an iodine-based polarizer and a protective film laminated on the double-sided film; and a protective film laminated on both sides of the protective film having a moisture permeability of 150 g/m ² /24 hr or less The thermoplastic resin film; the moisture content of the iodine-based polarizer is less than 8% by weight.

[8] The polarizing plate with a protective film on both sides as described in [7], wherein the iodine-based polarizer has a thickness of 10 μm or less.

According to the present invention, it is possible to provide a double-sided polarizing plate for bonding a protective film having a low moisture permeability to an iodine-based polarizing film, and a polarizing film with a protective film which has both heat and heat resistance and heat resistance The method of the present invention, and a polarizing plate having a double-sided polarizing plate in which a protective film having a low moisture permeability is bonded to an iodine-based polarizing film and having both a heat-resistant and heat-resistant double-sided protective film.

5‧‧‧Iodine polarizer

6‧‧‧Polyvinyl alcohol resin layer

6'‧‧‧ Stretched polyvinyl alcohol resin layer

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

30‧‧‧Base film

30'‧‧‧Stretched base film

100‧‧‧Polarized polarizing plate with protective film

200‧‧‧ laminated film

300‧‧‧ Stretch film

400‧‧‧Polarized laminated film

500‧‧‧Multilayer film

600‧‧ ‧ double-sided polarizing plate with protective film

Fig. 1 is a flow chart showing a preferred example of a method for producing a polarizing plate having a protective film on both sides of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate having a protective film on one side.

Fig. 3 is a flow chart showing a preferred example of the preparation steps of the polarizing plate having the protective film on one side.

Fig. 4 is a schematic cross-sectional view showing an example of a layer structure of a laminated film obtained in the resin layer forming step.

Fig. 5 is a schematic cross-sectional view showing an example of a layer structure of a stretched film obtained in the stretching step.

Fig. 6 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing laminate film obtained in the dyeing step.

Fig. 7 is a schematic cross-sectional view showing an example of a layer structure of a multilayer film obtained in the bonding step.

Fig. 8 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate having a protective film on both sides of the present invention.

<Manufacturing method of polarizing plate with double-sided protective film>

The method for producing a polarizing plate having a protective film on both sides of the present invention, as shown in Fig. 1, may include the following steps.

(1) Preparation of an iodine-based polarizer and a step S10 of a polarizing plate having a protective film laminated on one side of the first protective film on one side of the iodine-based polarizer (hereinafter also referred to as "single-sided protection" Step S10") of preparing a polarizing plate for a film, and (2) bonding a second protective film to the outside of an iodine-based polarizing plate of a polarizing plate having a protective film on one side thereof to obtain a polarizing film with a protective film on both sides thereof Step S20 of the board (hereinafter also referred to as "the manufacturing step S20 of the polarizing plate with the protective film on both sides").

As described above, in the present invention, the first protective film and the second protective film are successively bonded to the iodine-based polarizer. In this case, in order to enhance the moist heat resistance of the obtained polarizing plate with a protective film on both sides, the first protective film bonded to one of the surfaces of the iodine-based polarizing film and the second protective film bonded to the other surface are provided. A low-humidity thermoplastic resin film having a moisture permeability of 150 g/m ² /24 hr or less is used.

In addition, in order to improve the heat resistance of the obtained polarizing plate with a protective film on both sides, the moisture content of the iodine-based polarizer when the second protective film is bonded to the iodine-based polarizer is less than 8% by weight. In the present invention, in order to improve the heat and humidity resistance, a protective film having a low moisture permeability is bonded to both surfaces of the iodine-based polarizer, and the polarizing plate is used. However, the following conditions are obtained: a) if the moisture permeability is low The protective film is applied to both sides, the moisture in the iodine-based polarizer is not easily released to the outside, the moisture accumulates in the iodine-based polarizer, and b) the redness or the polarization characteristic in the heat resistance test is reduced by In the above-described iodine-based polarizer, it is effective to control the water content of the iodine-based polarizer when the second protective film is bonded. The moisture content of the iodine-based polarizer was measured in accordance with the method described in the item of the examples.

The moisture content of the iodine-based polarizer can be achieved by providing the following step S30, that is, in the step of producing a polarizing plate having a protective film on both sides, before bonding the second protective film to the iodine-based polarizer In any of the stages, (3) a step S30 of applying a moisture rate reduction treatment to the film containing the iodine-based polarizer (hereinafter also referred to as "water content reduction step S30") (refer to the first item) Figure).

Each step will be described below with reference to Figs. 2 to 8.

(1) Preparation step S10 of a polarizing plate with a protective film on one side

This step is a step of preparing (preparing) a polarizing plate 100 having a protective film on one side as shown in FIG. 2, and the polarizing plate 100 having a protective film on one side thereof contains an iodine-based polarizing film 5 and is laminated on the iodine system. The first protective film 10 of the polarizer 5. As shown in FIG. 2, the first protective film 10 is usually bonded (and subsequently fixed) to the single surface of the iodine-based polarizer 5 in the first adhesive layer 15.

[Iodine Polarizer]

The iodine-based polarizer 5 is a polarizer in which iodine is adsorbed and aligned as a dichroic dye, and specifically, a iodine-adsorbed uniaxially stretched polyvinyl alcohol-based resin layer (or film). The thickness of the iodine-based polarizer 5 is, for example, 30 μm or less, and more preferably 20 μm or less. In particular, in portable device applications, from the viewpoint of reducing the thickness of the polarizing plate having the protective film on both sides, it is preferably 10 μm or less. It is preferably 8 μm or less. The thickness of the iodine-based polarizer 5 is usually 2 μm or more.

When the thickness of the iodine-based polarizer 5 is small, the concentration of iodine is further increased, and the concentration of the iodine complex existing in the vicinity of the interface of the protective film laminated on both sides is also increased, so that it is easily exposed to moisture from the outside. influences. Therefore, the smaller the thickness of the iodine-based polarizer 5, the more easily the moist heat resistance is lowered. In addition, when the thickness of the iodine-based polarizer 5 is small and the concentration of iodine is further increased, it is likely to be affected by moisture remaining in the iodine-based polarizer, and heat resistance is also likely to be lowered. Thus, the smaller the thickness of the iodine-based polarizer 5, the moist heat resistance and the resistance The heat resistance is more likely to decrease. Thus, the present invention is particularly advantageous when the thickness of the iodine-based polarizer 5 is small.

The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer can be used by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and another monomer copolymerizable with the vinyl acetate, in addition to the polyvinyl acetate of 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.

In the present specification, "(meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. The same applies to the case of "(meth)acrylonitrile" or the like.

The iodine-based polarizer 5 is formed by forming a film of the above polyvinyl alcohol-based resin. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a generally known method, and the iodine-based polarizer 5 having a small thickness and the iodine-based polarizer 5 of the film in the step are easily obtained. Since the handleability is also excellent, a method of forming a film by applying a solution of a polyvinyl alcohol-based resin to a base film as described later is preferred.

The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, and particularly preferably in the range of 94.0 to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and the moist heat resistance of the obtained polarizing plate with a protective film on both sides are lowered. When the degree of saponification exceeds 99.5 mol%, when a polyvinyl alcohol-based resin is used, the dyeing speed of iodine is slowed down, productivity is lowered, and sometimes it is impossible to obtain An iodine-based polarizer 5 having sufficient polarizing properties.

The saponification degree means the acetoxy group contained in the polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin by the saponification step in the unit ratio (% by mole) (acetoxy group: -OCOCH _{3 )} The ratio of conversion to hydroxyl groups, and is defined by the following formula.

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

The degree of saponification can be determined in accordance with JIS K 6726-1994. The higher the degree of saponification, the higher the ratio of the hydroxyl group, and thus the lower the ratio of the acetate group which hinders crystallization.

The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol-based resin. For example, an olefin such as ethylene or propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; an alkyl ester of an unsaturated carboxylic acid or a (meth)acrylamide; The alcohol resin is modified. The ratio of upgrading is preferably less than 30% by mole, and particularly preferably less than 10% by mole. When the modification is more than 30 mol%, it is difficult to adsorb iodine, and it is difficult to obtain the iodine-based polarizer 5 having sufficient polarizing performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, particularly preferably from 1,500 to 8,000, more preferably from 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726-1994.

[First protective film]

The first protective film 10 is a film made of a thermoplastic resin having light transmissivity (preferably optical transparency) and having a moisture permeability of 150 g/m ² /24 hr or less. The moisture permeability is a moisture permeability of the second protective film to be described later, and is a temperature of 40° C. and a relative humidity of 90% measured in accordance with JIS Z 0208-1976 “Test method for moisture permeability of moisture-proof packaging materials (cup method)”. humidity. The moisture permeability is preferably 100 g/m ² /24 hr or less.

The means for setting the moisture permeability of the first protective film 10 to 150 g/m ² /24 hr or less may be a method of using a thermoplastic resin having a low moisture permeability as a constituent film, or increasing the thickness of the film or on the film. A means for providing a barrier layer having a low moisture permeability.

The thermoplastic resin constituting the first protective film 10 is not particularly limited as long as the moisture permeability can be achieved, and since the moisture permeability is low and the thickness of the first protective film 10 can be reduced, chain aggregation can be preferably used. a polyolefin-based resin such as an olefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin); a polyester resin such as a polyethylene terephthalate resin; A carbonate resin; a (meth)acrylic resin; a polystyrene resin; or a mixture or a copolymer thereof.

The first protective film 10 may be a protective film having an optical function like a retardation film or a brightness enhancement film. For example, the film made of the thermoplastic resin may be stretched (uniaxially stretched or biaxially stretched), or a liquid crystal layer or the like may be formed on the film to form an arbitrary phase difference value. Phase difference film.

In addition to a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, the chain polyolefin resin may be exemplified by two kinds. A copolymer composed of the above chain olefins.

The cyclic polyolefin resin is a general term for a resin polymerized by a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene ( Representative examples are random copolymers, and graft polymers which have been modified with unsaturated carboxylic acids or such derivatives, and such hydrides. Among them, a norbornene-based resin having a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin can be preferably used.

The polyester resin is a resin having an ester bond, and is generally composed of a polyvalent carboxylic acid or a polycondensate of the derivative and a polyhydric alcohol. As the polyvalent carboxylic acid or the derivative, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. A diol may be used for the polyhydric alcohol, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polybutylene terephthalate. Ester, propylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

The polycarbonate resin is composed of a polymer in which a monomer unit is bonded to a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate which is modified by a polymer skeleton, or a copolymerized polycarbonate or the like.

The (meth)acrylic resin is a resin having a compound having a (meth)acrylonitrile group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, polymethyl methacrylate-like poly(meth)acrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl methacrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and fat A copolymer of a compound of a cycloalkyl group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl decyl methacrylate copolymer, etc.). Preferably, a polymer having a poly(methyl) acrylate-like poly(meth)acrylic acid C _1-6 alkyl ester as a main component is used, and it is particularly preferred to use methyl methacrylate as a main component (50~). 100% by weight, preferably 70 to 100% by weight, of a methyl methacrylate-based resin.

On the surface of the first protective film 10 opposite to the iodine-based polarizer 5, a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer may be formed. . The method of forming the surface treatment layer is not particularly limited, and a generally known method can be used.

The first protective film 10 may contain one or more kinds of lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidant-like additives.

The thickness of the first protective film 10 is preferably 90 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less from the viewpoint of thinning of the polarizing plate having the protective film on both sides. The thickness of the first protective film 10 is usually 5 μm or more from the viewpoint of strength and handleability.

[1st adhesive layer]

The first adhesive layer 15 is a layer for subsequently fixing the first protective film 10 to one of the surfaces of the iodine-based polarizer 5 . The adhesive forming the first adhesive layer 15 may be an active energy ray-curable adhesive containing a curable compound which is cured by irradiation of an ultraviolet ray, visible light, an electron beam, or an X-ray active energy ray. An ultraviolet curable adhesive is preferred, or a water-based adhesive in which a binder component such as a polyvinyl alcohol-based resin is dissolved or dispersed in water.

The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or two or more epoxy groups in the molecule) or an oxetane compound (one in the molecule). Or a compound of two or more oxonium rings), or a combination thereof. Examples of the radically polymerizable curable compound include a (meth)acrylic compound (a compound having one or two or more (meth)acryloxy groups in the molecule) or a radical polymerizable property. Other vinyl compounds of double bonds, or combinations of these. A cationically polymerizable curable compound and a radically polymerizable curable compound may also be used in combination. The active energy ray-curable adhesive generally further includes a cationic polymerization initiator and/or a radical polymerization initiator for allowing the curing reaction of the curable compound to proceed.

The polarizing plate 100 with a protective film on one side may be prepared in advance or manufactured by any method. The manufacturing method is as follows.

(i) a method of bonding the first protective film 10 to one side of the iodine-based polarizer 5 composed of a monomer (separate) film produced by a generally known method, and (ii) including the third The manufacturing method of the following steps shown in the figure.

After coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film, a polyvinyl alcohol-based resin layer is formed by drying to obtain a resin layer forming step S10-1 of the laminated film; and the laminated film is stretched. The stretching step S10-2 of the stretched film is obtained; the polyvinyl alcohol-based resin layer of the stretched film is dyed with iodine to form an iodine-based polarizer, and a dyeing step S10-3 of the polarizing laminated film is obtained; The film 10 is bonded to the iodine-based polarizer of the polarizing laminate film to obtain a multilayer film bonding step S10-4, and the base film is peeled off from the multilayer film to obtain a peeling of the polarizing plate 100 having the protective film on one side. Step S10-5.

[Resin layer forming step S10-1]

Referring to Fig. 4, this step is a step of forming a laminated film 200 by forming a polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30. The polyvinyl alcohol-based resin layer 6 is a layer which becomes the iodine-based polarizer 5 by the stretching step S10-2 and the dyeing step S10-3. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one side or both sides of the base film 30 and drying it. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that the iodine-based polarizer 5 of the film is easily obtained.

The base film 30 may be composed of a thermoplastic resin, and among them, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and stretchability is preferably used. Specific examples of such a thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (such as a decene-based resin); a polyester resin; and a (meth)acrylic resin. Resin; cellulose triacetate, cellulose diacetate cellulose ester resin; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; polyarylate resin; Styrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures and copolymers thereof.

The base film 30 may be a single layer structure formed of one or more resin layers composed of one or two or more kinds of thermoplastic resins, or a resin composed of one or more thermoplastic resins in a plurality of layers. Multilayer construction of layers. When the polyvinyl alcohol-based resin layer 6 is stretched in the stretching step S10-2 to be described later, the base film 30 is preferably made of a resin which can be stretched at a suitable stretching temperature.

The substrate film 30 may contain an additive. Specific examples of the additive include a UV absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a color former.

The thickness of the base film 30 is generally from 1 to 500 μm, preferably from 1 to 300 μm, particularly preferably from 5 to 200 μm, more preferably from 5 to 150 μm, from the viewpoints of strength and handleability.

The coating liquid applied to the substrate film 30 is preferably made of polyethylene The powder of the enol-based resin is dissolved in a polyvinyl alcohol-based resin solution obtained by a good solvent (for example, water). The details of the polyvinyl alcohol-based resin are as described above. The coating liquid may contain an additive such as a plasticizer, a surfactant, or the like as necessary.

The method of applying the coating liquid to the base film 30 can be suitably selected from a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die casting coating method; a comma wheel coating method; and a lip coating method; Spin coating method; screen coating method; fountain coating method; dipping method; spray method, and the like.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) can be set depending on the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher.

The polyvinyl alcohol-based resin layer 6 can be formed only on one side of the base film 30 or on both sides. When it is formed on both sides, curling of the film which may occur during the production of the polarizing laminated film 400 (refer to FIG. 6) can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 400, and the polarizing plate can be obtained. It is also advantageous in terms of production efficiency. 11

The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 200 is preferably from 3 to 30 μm, particularly preferably from 5 to 20 μm. When the polyvinyl alcohol-based resin layer 6 having the thickness within the above range is subjected to the stretching step S10-2 and the dyeing step S10-3 described later, the dyeing property of iodine is excellent, the polarizing performance is excellent, and the thickness is extremely thin ( For example, the iodine-based polarizer 5 having a thickness of 10 μm or less.

Before the coating liquid is applied, in order to lift the substrate film 30 The adhesion to the polyvinyl alcohol-based resin layer 6 can be applied to at least the surface of the base film 30 on the side on which the polyvinyl alcohol-based resin layer 6 is formed by corona treatment, plasma treatment, flame treatment, or the like. . Further, for the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 30 in the primer layer or the like.

The primer layer can be formed by applying a coating liquid for forming a primer layer on the surface of the base film 30 and then drying it. The coating liquid contains a component which exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually contains a resin component and a solvent which can impart the adhesion. The resin component is preferably a thermoplastic resin which is excellent in transparency, heat stability, and stretchability, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol resin. Among them, a polyvinyl alcohol-based resin which imparts a good adhesion is preferably used. It is especially preferred to use a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent which can dissolve the above resin component is usually used, and a primer layer is preferably formed from a coating liquid containing water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating liquid for forming a primer layer. Specific examples of the crosslinking agent include an epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, a metal salt, a metal oxide, a metal hydroxide, or an organometallic compound), and a polymer-based crosslinking agent. When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, it is preferred to use a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, and a metal chelate compound to crosslink. Agents, etc.

The thickness of the primer layer is preferably from 0.05 to 1 μm, particularly preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the effect of improving the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6 is small, and when it is thicker than 1 μm, it is disadvantageous. The polarizing plate with a protective film on both sides is thinned.

The method of applying the coating liquid for forming a primer layer to the base film 30 can be the same as in the case of the coating liquid for forming a polyvinyl alcohol-based resin layer. The drying temperature of the coating layer composed of the coating liquid for forming a primer layer is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher.

[Stretching step S10-2]

Referring to Fig. 5, this step is a step of stretching the laminated film 200 to obtain a stretched film 300 composed of a stretched base film 30' and a polyvinyl alcohol-based resin layer 6'. The stretching process is usually uniaxial stretching.

The stretching ratio of the laminated film 200 can be appropriately selected depending on the desired polarizing characteristics, and is preferably more than 5 times and 17 times or less, and more preferably more than 5 times and 8 times the original length of the laminated film 200. the following. When the draw ratio is 5 or less, the polyvinyl alcohol-based resin layer 6' is not sufficiently aligned, and thus the degree of polarization of the iodine-based polarizer 5 may not be sufficiently improved. On the other hand, when the draw ratio exceeds 17 times, breakage of the film is liable to occur at the time of stretching, and the thickness of the stretched film 300 is thinned to a desired degree or more, and workability and handleability in a subsequent step are obtained. Reduce the embarrassment.

The stretching treatment is not limited to stretching in a single stage, and may be carried out in multiple stages. At this time, all of the multi-stage stretching treatment may be continuously performed before the dyeing step S10-3, or may be performed simultaneously with the dyeing treatment and/or the cross-linking treatment in the dyeing step S10-3. Stretch processing. When the stretching treatment is carried out in such a plurality of stages, it is preferably stretched. The entire section is subjected to a stretching treatment in such a manner that the stretching ratio is more than 5 times.

The stretching treatment may be a longitudinal stretching in which the film is stretched in the film length direction (film transport direction), or a transverse stretching or oblique stretching in which the stretching is performed in the film width direction. Examples of the longitudinal stretching method include stretching between rolls by stretching with a roll, compression stretching, stretching using a suction pad (clamp), and the like. The transverse stretching method may be a tenter method or the like. The stretching treatment is a wet stretching method and a dry stretching method.

The stretching temperature is set to a temperature higher than the fluidity at which the entire polyvinyl alcohol-based resin layer 6 and the base film 30 exhibit a stretchable degree, and preferably the phase transition temperature (melting point or glass transition temperature of the base film 30). The range of -30 ° C to +30 ° C is particularly preferably in the range of -30 ° C to +5 ° C, more preferably in the range of -25 ° C to +0 ° C. When the base film 30 is composed of a plurality of resin layers, the above phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

When the stretching temperature is lower than -30 ° C of the phase transition temperature, it is difficult to achieve a high-magnification stretching of more than 5 times, or the fluidity of the base film 30 is too low, and the stretching treatment tends to be difficult. When the stretching temperature exceeds +30 ° C of the phase transition temperature, the fluidity of the base film 30 is excessively large and tends to be difficult to stretch. In order to more easily achieve a high-magnification stretching of more than 5 times, the stretching temperature is preferably in the above range, more preferably 120 ° C or more.

The heating method of the laminated film 200 in the stretching treatment is a hot zone heating method (for example, a method of heating in a stretching hot zone such as a furnace adjusted to a predetermined temperature by blowing hot air); Method of heating the roller itself when stretching; heater heating method (infrared heater, A halogen heater, a plate heater, or the like is provided above and below the laminated film 200 and heated by radiant heat). In the inter-roll stretching method, from the viewpoint of the uniformity of the stretching temperature, a hot zone heating method is preferred.

A preheating step of preheating the laminated film 200 may be provided before the stretching step S10-2. The preheating method can use the same method as the heating method in the stretching treatment. The preheating temperature is preferably in the range of -50 ° C to ± 0 ° C of the stretching temperature, and more preferably in the range of -40 ° C to the stretching temperature to - 10 ° C in the stretching temperature.

Further, after the stretching treatment of the stretching step S10-2, a thermosetting treatment step may be provided. The thermosetting treatment is a treatment in which the heat treatment is performed at a temperature higher than the crystallization while maintaining the tension state while holding the end portion of the stretched film 300 with a tong. By this thermosetting treatment, crystallization of the polyvinyl alcohol-based resin layer 6' can be promoted. The temperature of the thermosetting treatment is preferably in the range of -0 ° C to -80 ° C of the stretching temperature, and particularly preferably in the range of -0 ° C to -50 ° C in the stretching temperature.

[Staining step S10-3]

Referring to Fig. 6, this step is a step of dyeing and aligning the polyvinyl alcohol-based resin layer 6' of the stretched film 300 with iodine to form an iodine-based polarizer 5. Through this step, the polarizing laminated film 400 having the iodine-based polarizer 5 on one or both sides of the base film 30' can be obtained.

The dyeing step can be carried out by immersing the stretched film 300 in a solution containing iodine (dyeing solution). As the dyeing solution, a solution in which iodine is dissolved in a solvent can be used. Solvents are generally water, and can be further added Water is a compatible organic solvent. The concentration of iodine in the dyeing solution is preferably 0.01 to 10% by weight, particularly preferably 0.02 to 7% by weight.

Since the dyeing efficiency can be improved, it is preferred to add iodide to the dyeing solution. 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 concentration of the iodide in the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably from 1:5 to 1:100 by weight ratio, particularly preferably from 1:6 to 1:80. The temperature of the dyeing solution is preferably from 10 to 60 ° C, particularly preferably from 20 to 40 ° C.

The dyeing step S10-3 may be carried out before the stretching step S10-2, or may be carried out simultaneously, but it is preferred that the iodine adsorbed on the polyvinyl alcohol-based resin layer can be well aligned to laminate The film 200 is subjected to a dyeing step S10-3 at least after a certain degree of stretching treatment.

The dyeing step S10-3 may include a crosslinking treatment step performed after the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) in which a crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include boric acid, borax-like boride, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more. The solvent of the crosslinking solution may be water or may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably from 1 to 20% by weight, particularly preferably from 6 to 15% by weight.

The crosslinking solution may further comprise an iodide. By the addition of iodide, the polarizing performance in the plane of the iodine-based polarizer 5 can be made uniform. Chemical. Specific examples of the iodide are the same as described above. The concentration of the iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, particularly preferably from 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably from 10 to 90 °C.

The crosslinking treatment can also be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the dyeing solution. Further, two or more kinds of crosslinking solutions having different compositions may be used, and two or more times of immersion in the crosslinking solution may be used.

After the dyeing step S10-3, it is preferred to perform a washing step and a drying step before the step S10-4 described later. The washing step typically includes a water washing step. The water washing step can be carried out by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 to 50 ° C, preferably 4 to 20 ° C. The washing step may also be a combination of a water washing step and a washing step according to the iodide solution. The drying step performed after the washing step may be any appropriate method such as natural drying, air drying, and heat drying. For example, when heating and drying, the drying temperature is usually 20 to 95 °C.

[Fitting step S10-4]

With reference to Fig. 7, in this step, the first protective film 10 is bonded to the iodine-based polarizing film 5 of the polarizing laminated film 400 via the first adhesive layer 15, that is, the substrate film of the iodine-based polarizing film 5 The 30' side is the face on the opposite side, and the step of obtaining the multilayer film 500 is obtained. The adhesive for forming the first adhesive layer 15 is as described above.

When the polarizing laminate film 400 is on both sides of the substrate film 30' When the iodine-based polarizer 5 is provided, the first protective film 10 is bonded to the iodine-based polarizer 5 on both sides. In this case, the first protective film may be the same type of protective film or a different type of protective film.

When the first protective film 10 is bonded by an active energy ray-curable adhesive, the first protective film 10 is laminated on the iodine-based polarizer 5 after passing through the active energy ray-curable adhesive which is the first adhesive layer 15 The ultraviolet ray, visible light, electron beam, and X-ray activation energy ray are used to harden the adhesive layer. Among them, ultraviolet light is preferred, and 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, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used as the light source. When a water-based adhesive is used, the first protective film 10 may be laminated on the iodine-based polarizer 5 by a water-based adhesive, and then dried by heating.

When the first protective film 10 is bonded to the iodine-based polarizing film 5, the bonding surface of the first protective film 10 and/or the iodine-based polarizing film 5 can be electrically connected in order to improve the adhesion to the iodine-based polarizing film 5. Surface treatment (easily followed by treatment) such as slurry treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc., among which plasma treatment, corona treatment or saponification treatment is preferred.

[Peeling step S10-5]

This step is a step of peeling off the base film 30' from the multilayer film 500. Through this step, the polarizing plate 100 having the protective film on one side as in the second drawing can be obtained. The polarizing laminated film 400 has the iodine-based polarizer 5 on both surfaces of the base film 30 ′, and the first protective film 10 is bonded thereto. In the case of the iodine-based polarizer 5, by the peeling step S10-5, two polarizing plates 100 having a protective film on one side thereof can be obtained from one polarizing laminated film 400.

The method of peeling off the base film 30' is not particularly limited, and it can usually be peeled off by the same method as the peeling step of the separator (release film) by the polarizing plate with the adhesive. The base film 30' may be directly peeled off after the bonding step S10-4, or may be wound into a roll shape after the bonding step S10-4, and peeled off while being rolled out in the subsequent step.

(2) Step S20 of manufacturing a polarizing plate with a protective film on both sides

In this step, the second protective film 20 is bonded to the outer surface of the iodine-based polarizing film 5 of the polarizing plate 100 having the protective film on one side thereof, whereby a polarizing plate having a protective film on both sides thereof is obtained. An example of a layer structure of a polarizing plate with a protective film on both sides is shown in Fig. 8. As in the case of the polarizing plate 600 having the protective film on both sides as shown in FIG. 8, the second protective film 20 is usually bonded (and subsequently fixed) to the iodine-based polarizer 5 through the second adhesive layer 25. The outer surface of the iodine-based polarizer 5 means a surface opposite to the first protective film 10 of the iodine-based polarizer 5, and a step of peeling off the base film 30' is performed to produce a protective film on one side. In the case of the polarizing plate 100, it means that the surface of the exposed iodine-based polarizer 5 is removed by peeling of the base film 30'.

In addition, the second protective film 20 is formed of a thermoplastic resin having light transmissivity (preferably optically transparent) and having a moisture permeability of 150 g/m ² /24 hr or less, similarly to the first protective film 10 . It can also be a protective film that has an optical function like a retardation film or a brightness enhancement film. The thickness, material, and the like of the surface treatment layer and the film which the second protective film 20 can have can be referred to as described above in the first protective film 10. The first protective film 10 and the second protective film 20 may be a protective film made of the same type of resin or a protective film made of a different type of resin.

The adhesive for forming the second adhesive layer 25 may be an active energy ray-curable adhesive or a water-based adhesive similar to the first adhesive layer 15, but is preferably an ultraviolet curable adhesive-like active energy ray hardenability. Follow-up agent. When the water-based adhesive is used, the moisture is supplied to the iodine-based polarizer 5, so that the moisture content of the iodine-based polarizer 5 when the second protective film 20 is bonded may not be as low as 8% by weight. The adhesive forming the second adhesive layer 25 may have the same composition as the adhesive forming the first adhesive layer 15, and may have a different composition.

(3) Water rate reduction step S30

In the method for producing a polarizing plate having a protective film on both sides of the present invention, in order to prevent the moisture content of the iodine-based polarizing film 5 when the second protective film 20 is bonded to less than 8% by weight, the double-sided attachment described above is manufactured. The step of protecting the polarizing plate of the protective film includes a moisture content lowering step S30 performed in any one or more stages before the production step S20 of the polarizing plate having the protective film on both sides. The water content reduction step S30 is a step of applying a treatment for lowering the moisture content of the iodine-based polarizer 5 to the film containing the iodine-based polarizer 5.

An example of the timing of implementing the moisture rate lowering step S30 is as follows.

1) The first protective film 10 is bonded to one surface of the iodine-based polarizer 5 composed of a single (separate) film, and a polarizing plate 100 having a protective film on one side is obtained. After that, in the method of bonding the second protective film 20, before and after the bonding of the first protective film 10 (before the production step S20 of the polarizing plate having the protective film on both sides is performed) or the like Both. However, when the moisture content is lowered in the state of the monomer (separate) film, the iodine-based polarizer 5 is likely to be cracked or broken, so that it is preferably after the bonding of the first protective film 10.

2) After obtaining the polarizing plate 100 having the protective film on one side thereof according to the method shown in FIG. 3, the method of bonding the second protective film 20 is performed after the dyeing step S10-3 and after the bonding step S10-4 After the step S10-5 is removed (including immediately before the step S20 of the production of the polarizing plate having the protective film on both sides) or two or more stages. The moisture content lowering step S30 is preferably at a stage in which the surface of the iodine-based polarizer 5 is exposed, for example, before the bonding step S10-4 or after the stripping step S10-5.

For example, in the above 2), in the case where the moisture content reduction step S30 is performed before the bonding step S10-4, the step of producing the polarizing plate with the protective film on both sides of the water content reduction step S30 regardless of the above 1) or 2) When there is a relatively long interval between the S20s, the moisture absorption suppressing means is provided so as not to cause the moisture content to be 8 wt% or more at the time of bonding the second protective film 20 due to moisture absorption in the section, or The moisture rate lowering step S30 is performed again in this section.

The moisture absorption suppressing means is a method of temporarily attaching the peelable moisture-proof film to the exposed surface of the iodine-based polarizer 5, and a step of forming a film containing the iodine-based polarizer 5 having an exposed surface. After the completion, the film is wound into a roll as quickly as possible to suppress the intrusion of moisture from the outside; and the method of bundling the roll-shaped film with a moisture-proof film like an aluminum laminated film Wait. The method of winding into a roll shape is particularly advantageous when the film to be wound has a base film and the base film is low in moisture permeability. Alternatively, the moisture absorption rate of the iodine-based polarizer 5 is not particularly required, and the moisture absorption rate of the iodine-based polarizer 5 is considered to be double-sidedly attached before the water content is 8 wt% or more due to moisture absorption. The design step is performed in the manner of the step S20 of manufacturing the polarizing plate of the protective film.

Further, for example, when there is a relatively long section between the moisture content reduction step S30 and the production step S20 of the polarizing plate having the protective film on both sides, the moisture absorption rate of the iodine-based polarizer 5 is considered, and the moisture rate reduction step S30 In the middle, the moisture content is lowered to be sufficiently lower than 8% by weight. By this method, it is not necessary to provide a special means between the moisture content lowering step S30 and the manufacturing step S20 of the polarizing plate having the protective film on both sides, so that the moisture content when the second protective film 20 is bonded can be set to be less than 8 wt%.

As described above, a water-based adhesive can be used for bonding the iodine-based polarizer 5 and the first protective film 10. However, when a water-based adhesive is used, water is supplied to the iodine-based polarizer 5, so it is preferable to apply it. The moisture content reduction step S30 is performed between the first protective film 10 and the second protective film 20 after bonding. This moisture rate lowering step S30 does not need to be the initial moisture rate lowering step S30.

The moisture content of the iodine-based polarizer 5 when the second protective film 20 is bonded is preferably less than 6% by weight, and particularly preferably 5% by weight or less, from the viewpoint of heat resistance. The specific method for lowering the water content is not particularly limited, and examples thereof include a method of blowing dry air, a method of adjusting a humidity-conditioning zone by low humidity, a method of drying a furnace by hot air, and using infrared rays. A method of heating a heater like a heating device, and combinations thereof.

<Polarized plate with double-sided protective film>

As shown in Fig. 8, the polarizing plate with a protective film on both sides of the present invention includes an iodine-based polarizing film 5, a first protective film 10 laminated on the one surface, and a surface laminated on the other surface. The second protective film 20. Usually, the first protective film 10 and the second protective film 20 are bonded to each other (and then fixed) to the iodine-based polarizer 5 via the first adhesive layer 15 and the second adhesive layer 25, respectively.

In the polarizing plate with a protective film on both sides of the present invention, the moisture content of the iodine-based polarizing film 5 is less than 8% by weight, preferably less than 6% by weight, and particularly preferably 5% by weight or less. Further, each of the first protective film 10 and the second protective film 20 is a thermoplastic resin film having a moisture permeability of 150 g/m ² /24 hr or less, preferably 100 g/m ² /24 hr or less. The specific configuration of the iodine-based polarizer 5, the first protective film 10, and the second protective film 20 is referred to the above description.

The polarizing plate with a protective film on both sides of the present invention can be suitably produced by the method described above. In the polarizing plate with a protective film on both sides of the present invention, since the moisture content of the iodine-based polarizer 5 is less than 8% by weight and the protective film having a low moisture permeability is laminated on both sides, even the iodine-based polarizing film 5 The thickness is small (for example, the thickness is 10 μm or less), and it is also resistant to moist heat and heat resistance. The polarizing plate with a protective film on both sides can be suitably applied to a liquid crystal display device or an organic electroluminescence device. When applied to a liquid crystal display device, the polarizing plate with a protective film on both sides of the present invention may be a polarizing plate disposed on the front (viewing) side of the liquid crystal cell or disposed on the back side. The polarizing plate on the side (backlight) side.

The polarizing plate with a protective film on both sides may be provided with adhesion to other members laminated on the first protective film 10 or the second protective film 20 (for example, a liquid crystal cell when applied to a liquid crystal display device) Agent layer. The adhesive for forming the adhesive layer is usually a (meth)acrylic resin, a styrene resin, a polyoxymethylene resin or the like as a matrix polymer, and is an isocyanate compound, an epoxy compound or an aziridine compound. The cross-linking agent is added to the adhesive composition. Further, it may be configured as an adhesive layer which further contains fine particles and exhibits light scattering properties. The thickness of the adhesive layer is usually from 1 to 40 μm, preferably from 3 to 25 μm.

Further, the polarizing plate having the protective film on both sides thereof may further include another optical layer laminated on the first protective film 10 or the second protective film 20. The other optical layer may be a reflective polarizing film that can transmit light of a certain polarized light and reflect light having a polarized light having opposite properties; and a film having an anti-glare function having a concave-convex shape on the surface; A film with an anti-reflective function on the surface; a reflective film having a reflective function on the surface; a transflective film having both a reflective function and a penetrating function; a viewing angle compensation film.

[Examples]

Hereinafter, the present invention will be more specifically described by showing examples and comparative examples, but the present invention is not limited to these examples.

<Example 1>

(1) Primer layer forming step

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. A crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution at a ratio of 5 parts by weight based on 6 parts by weight of the polyvinyl alcohol powder to obtain a primer layer. Coating solution.

Next, a single surface of a substrate film (melting point: 163 ° C, moisture permeability: 15 g/m ² /24 hr) having a thickness of 90 μm made of polypropylene was subjected to corona treatment, and then the above was carried out using a small-diameter micro gravure coater. The coating liquid for forming a primer layer was applied onto the corona-treated surface, and dried at 80 ° C for 10 minutes, thereby obtaining a primer layer having a thickness of 0.2 μm.

(2) Production of laminated film (resin layer forming step)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%. This is used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The coating liquid for forming a polyvinyl alcohol-based resin layer was applied onto the surface of the primer layer of the base film having the primer layer produced in the above (1), and then dried at 80 ° C for 20 minutes, using a die-casting machine. Thus, a polyvinyl alcohol-based resin layer was formed on the primer layer to obtain a laminated film composed of a base film/primer layer/polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching step)

The laminated film produced in the above (2) was subjected to free end uniaxial stretching to 5.3 times at 160 ° C using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the polyvinyl alcohol-based resin layer after stretching was 5.1 μm.

(4) Production of polarizing laminated film (dyeing step)

The stretched film prepared in the above (3) was immersed in a dyeing aqueous solution (water containing 0.6 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water containing 30% by weight of iodine and potassium iodide) for about 180 seconds. After the dyeing treatment of the polyvinyl alcohol-based resin layer, the excess dyeing aqueous solution was washed away with pure water at 10 °C.

Next, it was immersed in a first crosslinked aqueous solution containing 78% by weight of boric acid (water containing 10.4 parts by weight of boric acid per 100 parts by weight) for 120 seconds, and then immersed in a second crosslinked aqueous solution (water at 70 ° C containing boric acid and potassium iodide). Each of 100 parts by weight contained 5.7 parts by weight of boric acid and 12 parts by weight of potassium iodide for 60 seconds to carry out a crosslinking treatment. Then, it was washed with pure water of 80 ° C for 10 seconds. Finally, the film was dried at 50 ° C for 60 seconds and dried at 80 ° C for 60 seconds (water content reduction step), whereby a polarizing laminated film composed of a base film/iodine-based polarizer was obtained. The moisture content of the iodine-based polarizer included in the polarizing laminated film at the end of drying was 0.4% by weight. Further, the thickness of the iodine-based polarizer was 5.6 μm.

By absorbing moisture in the air and suppressing an increase in the moisture content of the iodine-based polarizer, the surface of the iodine-based polarizer opposite to the base film is bonded to the surface immediately after drying to have re-peelability. A moisture-proof film having a low humidity (a polyolefin resin film having a moisture permeability of 30 g/m ² /24 hr). Thereby, since the iodine-based polarizer is sandwiched between the base film having low moisture permeability and the moisture-proof film, the low moisture content can be maintained.

(5) Production of multilayer film (bonding step)

The moisture-proof film which adhered to the moisture-proof film produced in the above (4) was peeled off, and the first protective film was bonded to the peeling surface immediately (within 1 minute). In the first protective film, a thermoplastic resin film ("ZF14" manufactured by Zeon Japan Co., Ltd.) having a thickness of 23 μm and having a moisture permeability of 16 g/m ² /24 hr and a cyclic polyolefin resin was used. The first protective film is applied to the first protective film by applying a UV curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.) to the first protective film so as to have a thickness of 1.0 μm after hardening. After the single-sided surface, the adhesive layer was bonded to the peeling surface by a bonding roll, and then the high-pressure mercury lamp was used to irradiate the substrate film side with ultraviolet light at a total amount of 200 mJ/cm ² to cure the adhesive layer.

(6) Production of a polarizing plate with a protective film on both sides (stripping step and manufacturing steps of a polarizing plate with a protective film on both sides)

The base film is peeled off from the multilayer film produced in the above (5), and the second protective film is immediately bonded to the release surface to obtain a first protective film/adhesive layer/iodine-based polarizer/adhesive layer. / A polarizing plate having a protective film on both sides of the second protective film. In the second protective film, a thermoplastic resin film ("ZF14" manufactured by Zeon Japan Co., Ltd.) having a thickness of 23 μm and having a moisture permeability of 16 g/m ² /24 hr and a cyclic polyolefin resin was used. The bonding of the second protective film is carried out by applying a UV curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.) to the single sheet by using a small-diameter gravure coater so that the thickness after curing is 1.0 μm. After the surface, the bonding surface was bonded to the peeling surface, and then the high-pressure mercury lamp was used to irradiate the second protective film side with ultraviolet light at 200 mJ/cm ² to cure the adhesive layer. The moisture content of the iodine-based polarizer when the second protective film was bonded was 0.5% by weight.

<Example 2>

The conditions of the drying treatment (water content reduction step) at the end of the dyeing step were carried out at 50 ° C for 60 seconds and then at 65 ° C for 60 seconds, except that the same procedure as in Example 1 was carried out to prepare a double-sided attachment. A polarizing plate with a protective film. The moisture content of the iodine-based polarizer when the second protective film was bonded was 4.6% by weight.

<Example 3>

In the same manner as in Example 2, a polarizing plate having a protective film on both sides was produced. The moisture content of the iodine-based polarizer when the second protective film was bonded was 4.4% by weight, and the opacity correction Py of the polarizing plate having the protective film on both sides was 99.995%, and the opacity-corrected monomer transmittance Ty was 40.9%.

<Example 4>

For the first protective film and the second protective film, a thermoplastic resin film having a thickness of 80 μm and having a moisture permeability of 63 g/m ² /24 hr and an acrylic resin was used, and an ultraviolet curable adhesive (ADKA Co., Ltd.) was used. In the same manner as in Example 2 except for "KR-15P"), a polarizing plate with a protective film on both sides was produced. The moisture content of the iodine-based polarizer when the second protective film was bonded was 4.2% by weight, and the luminosity-corrected polarization Py of the polarizing plate having the protective film on both sides was 99.994%, and the opacity-corrected monomer transmittance Ty was 41.4%.

<Example 5>

The first protective film is a thermoplastic resin film having a thickness of 80 μm and having a moisture permeability of 63 g/m ² /24 hr, and a second protective film having a moisture permeability of 16 g/m ² /24 hr and having a cyclic polycondensation. A thermoplastic resin film ("ZF14" manufactured by Zeon Japan Co., Ltd.) having a thickness of 23 μm composed of an olefin resin. The first protective film is an ultraviolet curable adhesive ("KR-15P" manufactured by ADEKA Co., Ltd.), and the second protective film is an ultraviolet curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.). Except for this, in the same manner as in Example 2, a polarizing plate with a protective film on both sides was produced. The moisture content of the iodine-based polarizer when the second protective film was bonded was 4.8% by weight, and the opacity correction Py of the polarizing plate having the protective film on both sides was 99.994%, and the opacity-corrected monomer transmittance Ty was 41.4%.

<Comparative Example 1>

The conditions of the drying treatment (water content reduction step) at the end of the dyeing step were the same as in Example 1 except that the conditions were 40 ° C for 60 seconds and then 50 ° C for 60 seconds. A polarizing plate with a protective film. The moisture content of the iodine-based polarizer when the second protective film is attached is 10.7. weight%.

<Comparative Example 2>

In the same manner as in Example 1, except that the conditions of the drying treatment (water content reduction step) at the end of the dyeing step were carried out at 40 ° C for 120 seconds, a polarizing plate having a protective film on both sides was produced. The moisture content of the iodine-based polarizer when the second protective film was bonded was 12.5% by weight.

<Comparative Example 3>

After the drying treatment (water content reduction step) at the end of the dyeing step, the moisture-proof film is not bonded, and it is stored in an environment of 25° C. and 55% RH for about 2 days to increase the moisture content of the iodine-based polarizer to equilibrium. A polarizing plate having a protective film on both sides was produced in the same manner as in Example 2 except that the first and second protective films were bonded to each other in the vicinity of the water content. The moisture content of the iodine-based polarizer when the second protective film was bonded was 15.3% by weight.

The moisture permeability of the film of each of the examples and the comparative examples and the moisture content of the iodine-based polarizer were measured by the following methods.

(1) moisture permeability

According to JIS Z 0208-1976 "Test method for moisture permeability of moisture-proof packaging materials (cup method)", the moisture permeability at a temperature of 40 ° C and a relative humidity of 90% was measured.

(2) Moisture rate of iodine-based polarizer

For a plurality of iodine-based polarizer samples with different water rates, The moisture content measured by the near-infrared moisture meter ("IRMA1100S" manufactured by Chino Co., Ltd.) and the moisture rate measured by the dry weight method, and obtained from the obtained two moisture ratios in advance. A calibration curve indicating the relationship between the two moisture rates, using the above-described calibration curve, converting the moisture content measured by the near-infrared moisture meter into a moisture content according to the dry weight method, and setting this as an iodine-based polarizer Moisture rate. According to the moisture content of the dry weight method, the weight of the sample before drying is set to W0, and when the weight of the same sample after drying at 105 ° C for 1 hour is W1, it is defined by the following formula.

Moisture rate (% by weight) = 100 × (W0 - W1) / W0

[Evaluation of the heat and humidity resistance and heat resistance of a polarizing plate with a protective film on both sides]

(1) Evaluation of heat and humidity resistance

In the polarizing plates having the protective film on both sides prepared in the first and second examples and the comparative examples 1 to 3, an absorbance photometer ("V7100" manufactured by JASCO Corporation) was used, and the measurement was carried out at 65 ° C and 90%. In the RH environment, the visual sensitivity after the 500-hour heat and humidity resistance test was corrected for the Py and the Py before the test, and the difference between the two was ΔPy (Py after the test, Py before the test). . The smaller the absolute value of ΔPy, the higher the heat and humidity resistance. The results are shown in Table 1. In the measurement of Py, a polarizing plate having a protective film on both sides thereof is provided so that incident light is irradiated onto the second protective film side. The opacity correction degree Py after the moisture heat resistance test was measured after standing for 12 hours in an environment of 23 ° C and 55% RH after the heat and humidity resistance test.

Before the heat and humidity resistance test (and the heat resistance test described below) Py, each of the examples and comparative examples was 99.995%. Further, the transmittance of the monomer was corrected by the same absorbance photometer, and the examples and comparative examples were 41.6%.

(2) Evaluation of heat resistance

The polarizing plates having the protective film on both sides prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a heat resistance test at 85 ° C for 500 hours in a dry environment, thereby The evaluation of the moist heat was the same, and the heat resistance was evaluated from ΔPy (Py after the test before the test). The smaller the absolute value of ΔPy, the higher the heat resistance. The results are shown in Table 1.

(3) Evaluation of heat and humidity resistance under accelerated conditions

The polarizing plate having the protective film on both sides prepared in Examples 3 to 5 was allowed to stand in an environment of 80 ° C and 90% RH by the same method as the evaluation of the heat and humidity resistance of the above (1). Hour heat and humidity test. The results are shown in Table 2.

(4) Evaluation of heat resistance under accelerated conditions

The polarizing plate having the protective film on both sides prepared in Examples 3 to 5 was heat-treated at 105 ° C in a dry environment for 48 hours by the same method as the evaluation of the heat resistance of the above (2). Sex test. The results are shown in Table 2.

In addition, the degree of light leakage (red light) was visually confirmed for the polarizing plate with a protective film on both sides after the heat resistance test. in particular, Two 10 cm × 20 cm sample pieces were cut out from the polarizing plate with the protective film on both sides after the heat resistance test, and the samples were attached to both sides of the glass plate using an adhesive. In this case, the second protective film side is placed on the glass plate side, and the sample sheets placed on both sides are in a positional relationship of orthogonal polarization. Then, in a dark room, the backlight was irradiated from one side of the polarizing plate, and visual evaluation of reding was performed in accordance with the following evaluation criteria. The results are shown in Tables 1 and 2.

A: Keep it in a black state, and you cannot recognize the red change by visual inspection.

B: Obvious red change was observed.

5‧‧‧Iodine polarizer

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

600‧‧ ‧ double-sided polarizing plate with protective film

Claims (8)

A method for producing a polarizing plate with a protective film on both sides thereof, comprising: a multilayer film comprising a base film, an iodine-based polarizer, and a first protective film in sequence, and peeling off the base film to obtain a single-sided attachment a step of protecting the polarizing plate of the protective film, and a step of bonding the second protective film to the outside of the iodine-based polarizing plate of the polarizing plate having the protective film on one side thereof to obtain a polarizing plate having a protective film on both sides; The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m ² /24 hr or less; and the moisture content of the iodine-based polarizing film when the second protective film is bonded is less than 8% by weight . The production method according to the first aspect of the invention, wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive. The production method according to claim 1 or 2, wherein the iodine-based polarizer has a thickness of 10 μm or less. A method for producing a polarizing plate having a double-sided protective film, comprising: bonding a second protective film to one side of a first protective film comprising an iodine-based polarizer and a single layer laminated on one side of the iodine-based polarizer; a step of obtaining a polarizing plate having a protective film on both sides of the iodine-based polarizer in the polarizing plate of the protective film; and the first protective film and the second protective film are at a moisture permeability of 150 g/m ² / The thermoplastic resin film of 24 hr or less; the moisture content of the iodine-based polarizer when the second protective film is bonded is less than 8% by weight. The production method according to the fourth aspect of the invention, wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive. The production method according to Item 4 or 5, wherein the iodine-based polarizer has a thickness of 10 μm or less. A polarizing plate with a protective film on both sides, comprising: an iodine-based polarizer and a protective film laminated on the double-sided; the protective film laminated on both sides is a thermoplastic resin having a moisture permeability of 150 g/m ² /24 hr or less The film; the moisture content of the iodine-based polarizer is less than 8% by weight. A polarizing plate having a protective film on both sides as described in the seventh aspect of the invention, wherein the iodine-based polarizer has a thickness of 10 μm or less.