TWI696853B - Method of producing polarizing plate - Google Patents

Abstract

The present invention provides a method of producing a polarizing plate, comprising in sequence the following steps of: heating a first thermoplastic resin film; humidifying a first thermoplastic resin film; and laminating a first thermoplastic resin film on a surface of a polarizing film while laminating a second thermoplastic resin film having an lower equilibrium moisture content as compared with the first thermoplastic resin film at 23 ℃ and a relative humidity of 55 % on the other surface of a polarizing film.

Description

Method for manufacturing polarizing plate

The present invention relates to a method of manufacturing a polarizing plate containing a polarizing film and a thermoplastic resin film laminated thereon.

In recent years, mobile terminals such as smart phones are rapidly progressing in terms of design and portability in terms of large screen size and thinness. In order to achieve long-term driving at a limited thickness, the polarizing plates used are also expected to be brighter, thinner and lighter.

As a polarizing plate, from the past, it is generally used on a polarizing film made of a polyvinyl alcohol-based resin, and a protective film made of cellulose triacetate (TAC) is bonded by an adhesive. However, in recent years, from the viewpoint of thinning, durability, cost, productivity, etc., a method of using a protective film made of a resin other than TAC (for example, Japanese Patent Laid-Open No. 2004-245925) has been adopted.

The polarizing plate is very sensitive to the environment in which it is placed, and subject to environmental conditions, it is prone to warp deformation. In this specification, this deformation is also called "curl". The polarizing plate tends to curl like a film. There are two types of curling: "forward curling" and "reverse curling". On the polarizing plate, there is a first main surface bonded to the side of an image display element such as a liquid crystal element, and a second main surface opposite to this side. "Positive curl" means that the first main surface side is convex Curl, "reverse curl" refers to a curl that makes the second main surface side convex. When the polarizing plate is reversely curled, when it is attached to the image display element through the adhesive layer, it may easily cause adhesion errors, or poor mixing of bubbles at the interface between the adhesive layer and the image display element . In order to suppress these unfavorable situations, in order to carry out the bonding of the polarizing plate and the image display element with good productivity, although the polarizing plate is preferably a flat plate, the curl generated is a part of positive curl. In terms of productivity, there is no problem in particular.

In addition, Japanese Unexamined Patent Publication No. 2006-030480 discloses that in order to suppress the streak-like unevenness of the polarizing plate, before the polarizing film and the protective film are laminated, the moisture content of the protective film is adjusted to a predetermined range.

An object of the present invention is to provide a method for manufacturing a polarizing plate that does not have reverse curl or suppresses reverse curl.

The present invention provides the following method for manufacturing a polarizing plate.

[1] A method of manufacturing a polarizing plate, which sequentially includes the following steps: a step of heating a first thermoplastic resin film; a step of humidifying the first thermoplastic resin film; and, on one side of the polarizing film The step of laminating the first thermoplastic resin film and laminating a second thermoplastic resin film having a balanced moisture content at a temperature of 23° C. and a relative humidity of 55% at a temperature of 23° C. and a relative humidity of 55%.

[2] The production method according to [1], wherein the second thermoplastic resin film is not subjected to the humidification treatment.

[3] The production method according to [1] or [2], wherein the first thermoplastic resin film contains a cellulose-based resin film.

[4] The production method according to any one of [1] to [3], wherein the second thermoplastic resin film contains a cyclic polyolefin-based resin film.

[5] The production method according to any one of [1] to [4], wherein the temperature during the heat treatment is equal to or higher than the temperature during the humidification treatment.

[6] The production method according to [5], wherein the temperature during the heat treatment is higher than the temperature during the humidification treatment by 30° C. or more.

[7] The manufacturing method according to any one of [1] to [6], wherein in the step of the heat treatment, the first thermoplastic resin film is in an environment with a temperature of 50° C. or higher and a relative humidity of 50% or less Perform heat treatment.

[8] The production method according to any one of [1] to [7], wherein in the step of the humidification treatment, the first thermoplastic resin film is at a temperature of 40° C. or higher and a relative humidity of 60% or more The environment is humidified.

[9] The production method according to any one of [1] to [8], wherein, At least one of the first thermoplastic resin film and the second thermoplastic resin film is laminated on the polarizing film via an adhesive layer.

[10] The production method according to any one of [1] to [9], wherein the thickness of the first thermoplastic resin film is 40 μm or less, and the thickness of the second thermoplastic resin film is 40 μm or less.

[11] The manufacturing method according to any one of [1] to [10], wherein the thickness of the polarizing film is 15 μm or less.

[12] The manufacturing method according to any one of [1] to [11], wherein, in the step of the humidification process, the first thermoplastic resin film has a moisture content that is higher than that of the first thermoplastic resin film Humidification treatment is carried out at a temperature of 23°C and a relative humidity of 55% with a higher equilibrium moisture content.

According to the present invention, a polarizing plate that does not have reverse curl or can suppress reverse curl can be manufactured.

1‧‧‧Polarized polarizer on both sides

2‧‧‧Single-sided protective polarizer

3‧‧‧Single-sided protective polarizer with temporary protective film

4‧‧‧Single-sided protective polarizer with adhesive layer

5‧‧‧ Polarizing film

10‧‧‧The first thermoplastic resin film

15‧‧‧The first adhesive layer

20‧‧‧The second thermoplastic resin film

25‧‧‧ 2nd adhesive layer

30‧‧‧Adhesive layer

40‧‧‧ Laminated roller

50‧‧‧The first adhesive

55‧‧‧ Second Adhesive

60‧‧‧Guide roller

70‧‧‧Heating furnace

80‧‧‧Humidifier

90‧‧‧The first injection device

91‧‧‧The second injection device

S100, S200, S300 ‧‧‧ steps

Fig. 1 is a flowchart showing an example of a method of manufacturing a polarizing plate according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate that can be obtained by the manufacturing method according to the present invention.

FIG. 3 is a side view schematically showing an example of a manufacturing method of a polarizing plate and a manufacturing apparatus used herein according to the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of the layer structure of a single-sided protective polarizing plate.

Figure 5 shows the layer of a single-sided protective polarizer with a temporary protective film A schematic cross-sectional view of an example of a structure.

FIG. 6 is a schematic cross-sectional view showing an example of the layer structure of a single-sided protective polarizing plate with an adhesive layer.

[The best form for carrying out the invention]

Referring to FIG. 1, the manufacturing method of the polarizing plate according to the present invention includes the following steps in sequence: (1) a heat treatment step S100 of heat-treating the first thermoplastic resin film; (2) a humidification treatment of the first thermoplastic resin Step S200 of humidifying the film; and (3) Step S300 of depositing a first thermoplastic resin film on one side of the polarizing film and a second thermoplastic resin film on the other side of the polarizing film. For the second thermoplastic resin film, a lower equilibrium moisture rate than the first thermoplastic resin film is used. Here, the equilibrium moisture content refers to the measurement of the equilibrium moisture content of the film stored for 24 hours by the dry weight method in an environment of a temperature of 23° C. and a relative humidity of 55%.

According to the manufacturing method of the present invention, the first thermoplastic resin film after heat treatment followed by humidification is laminated on one side of the polarizing film, and the second thermoplastic resin film is laminated on the other side to reduce or prevent the resulting polarizing plate The reverse curl. Reverse curling, as described above, refers to a deformation in which the second main surface on the side opposite to the side to which the image display element such as a liquid crystal cell is bonded is convex and the polarizing plate is bow-shaped and warped. Usually, this deformation system Produced in the blade body of the polarizer. In the case of manufacturing a long polarizing plate using a long raw material film (first and second thermoplastic resin films, and polarizing film), the reverse curl is called The reverse curl generated by the polarizer blade body typically obtained by cutting a long polarizer.

FIG. 2 shows an example of the layer structure of the polarizing plate obtained by the manufacturing method according to the present invention. The polarizing plate shown in FIG. 2 includes the following two sides protecting the polarizing plate 1: a polarizing film 5; a first thermoplastic resin film 10 laminated on one side via a first adhesive layer 15; and, in On the other hand, the second thermoplastic resin film 20 is bonded on the surface via the second adhesive layer 25. The first and second thermoplastic resin films 10 and 20 in the two-sided protection polarizing plate 1 are optical films that protect the polarizing film 5, that is, the protective film, which is then adhered to the surface of the polarizing film 5 using an adhesive. The other layer structure of the polarizing plate obtained by the manufacturing method related to the present invention will be described later.

Hereinafter, each step will be described with reference to FIG. 3. FIG. 3 is a side view schematically showing an example of the manufacturing method of the polarizing plate of the present invention and the manufacturing apparatus using the same. The arrow in Fig. 3 indicates the transport direction of the film. In general, as shown in FIG. 3, the polarizing plate is continuously rolled out and conveyed while carrying out the processing in each step, and the elongated product can be continuously manufactured. However, the manufacturing method of the present invention is not limited to a continuous producer using such a long raw material film, and a method of using a leaf film can also be used.

(1) Heating process step S100

This step is a step of heat-treating the first thermoplastic resin film 10. One feature of the present invention is to perform humidification treatment on the first thermoplastic resin film 10 Prior to the heat treatment, it is possible to effectively suppress or prevent the reverse curl of the polarizing plate (typically, the main surface of the first thermoplastic resin film 10 side is used as a convex curl), and, only with the humidification treatment Compared with the case, the reverse curl of the polarizing plate can be suppressed or prevented more efficiently.

The first thermoplastic resin film 10 is a thermoplastic resin having translucency, and is preferably a film composed of an optically transparent thermoplastic resin. The thermoplastic resin constituting the first thermoplastic resin film 10 may be, for example, a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.) or a cyclic polyolefin resin (norbornene resin, etc.); Cellulose resins such as triethyl acetyl cellulose and diethyl acetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; Such as (meth)acrylic resin of methyl methacrylate resin; polystyrene resin; polyvinyl chloride resin; acrylonitrile/butadiene/styrene resin; acrylonitrile/styrene resin; poly Vinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polyphenol resin; Polyether resin; Polyarylate Resin; Polyamide imide resin; Polyimide resin, etc.

In this specification, "(meth)acrylic resin" means at least one selected from the group consisting of acrylic resin and methacrylic resin. The same applies to other terms with "(methyl)".

Examples of the chain polyolefin resin include, in addition to chain olefin homopolymers of polyethylene resin and polypropylene resin, copolymers composed of two or more chain olefins. A more specific example is the Department Contains: polypropylene resin (polypropylene resin with homopolymer of propylene, or copolymer with propylene as the main component), polyethylene resin (polyethylene resin with homopolymer of ethylene, or copolymer with the main component of ethylene) .

The cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerization units. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (Representatives are random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and their hydrides. Among them, it is preferred to use norbornene-based monomers such as norbornene or polycyclic norbornene-based monomers as cyclic olefins.

Cellulose-based resins are so-called cellulose fibers obtained from raw cellulose such as cotton staple fiber or wood pulp (broad-leaved wood pulp, coniferous wood pulp). Part or all of the hydrogen atoms of the cellulose are acetyl and propyl. Cellulose organic acid ester or cellulose mixed organic acid ester substituted with a base and/or butyl group. For example, those made from cellulose acetate, propionate, butyrate, and mixed esters thereof can be cited. Among them, triethyl acetyl cellulose, diethyl acetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

The polyester-based resin is generally a resin other than the cellulose-based resin having an ester bond, and is composed of a polycondensate of a polycarboxylic acid or its derivative and a polyhydric alcohol. As the polycarboxylic acid or its derivative system, a dibasic dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and naphthalene dicarboxylic acid. Dimethyl acid, etc. As the polyol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexane dimethanol. Examples of suitable polyester resins include polyethylene terephthalate.

Polycarbonate resin is an engineering plastic composed of a polymer in which monomer units are bonded via a carbonate group. It is a resin with high impact resistance, heat resistance, flame retardancy and transparency. The polycarbonate-based resin may also be a resin called modified polycarbonate used to reduce the photoelastic coefficient, such as modifying the polymer skeleton, or a copolymerized polycarbonate with improved wavelength dependence.

The (meth)acrylic resin-based polymer contains a structural unit derived from a (meth)acrylic monomer. The polymer is typically a polymer containing methacrylate. The ratio of structural units derived from methacrylate is preferably 50% by weight or more of the polymer relative to the total structural units. The (meth)acrylic resin may be a homopolymer of methacrylate, or a copolymer containing structural units derived from other polymerizable monomers. In this case, the ratio of structural units derived from other polymerizable monomers is preferably 50% by weight or less based on the total structural units.

As the methacrylate that can constitute the (meth)acrylic resin, alkyl methacrylate is preferred. Examples of alkyl methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate. , The third butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate alkyl methacrylate alkyl having 1 to 8 carbon atoms ester. In methacrylic acid The carbon number of the alkyl group contained in the alkyl ester is preferably 1 to 4. In the (meth)acrylic resin, only one kind of methacrylate may be used alone, or two or more kinds may be used in combination.

Examples of the above-mentioned other polymerizable monomers that can constitute a (meth)acrylic resin include acrylates and compounds having a polymerizable carbon-carbon double bond in other molecules. As for other polymerizable monomers, only one kind may be used alone, or two or more kinds may be used in combination. As the acrylic ester, alkyl acrylate is preferred. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, third butyl acrylate, and 2-ethylhexyl acrylate. , Cyclohexyl acrylate, alkyl acrylate of 2-hydroxyethyl acrylate alkyl having 1 to 8 carbon atoms, etc. The carbon number of the alkyl group contained in the alkyl acrylate is preferably 1 to 4. Among (meth)acrylic resins, only one kind of acrylate may be used alone, or two or more kinds may be used in combination.

Examples of the compound having a polymerizable carbon-carbon double bond in other molecules include vinyl compounds such as ethylene, propylene, and styrene, and vinyl cyanide compounds such as acrylonitrile. Compounds having polymerizable carbon-carbon double bonds in other molecules may be used alone or in combination of two or more.

The first thermoplastic resin film 10 is a protective film laminated on one side of the polarizing film 5 to protect the polarizing film 5 or a temporary protective film for temporarily protecting the surface of the polarizing film 5. The first thermoplastic resin film 10 that temporarily protects the film is peeled off and removed within a desired period of time after the polarizing plate is constructed. In addition, the first thermoplastic resin film 10 may be combined with Protective film for optical function of retardation film and brightness enhancement film. For example, by stretching a thermoplastic resin film composed of the above-mentioned materials (uniaxial stretching or biaxial stretching, etc.), or forming a liquid crystal layer on the film, a retardation film can be formed to give an arbitrary retardation value. The first thermoplastic resin film 10 may also have a surface treatment layer (coating layer) such as a hard coat layer, an anti-glare layer, an anti-reflection layer, an anti-fouling layer, and an anti-fouling layer stacked on its surface.

The thickness of the first thermoplastic resin film 10 is usually 1 to 100 μm, but from the viewpoint of strength and handleability, it is preferably 5 to 60 μm, more preferably 5 to 50 μm. If the thickness is within this range, the polarizing film 5 can be mechanically protected, and the shrinkage of the polarizing film 5 when the polarizing plate is exposed to a hot and humid environment can be suppressed. The smaller the thickness of the first thermoplastic resin film 10 is, the more easily the polarizing plate is curled. However, according to the present invention, the thickness of the first thermoplastic resin film 10 can be effectively reduced to, for example, 40 μm or less and 30 μm or less. Suppress or prevent reverse curling of the obtained polarizing plate.

The first thermoplastic resin film 10 is a film having a higher equilibrium moisture rate than the second thermoplastic resin film 20 used in the lamination step S300 described later. In this specification, the equilibrium moisture content is determined by the dry gravimetric method when the moisture content of the film stored for 24 hours in an environment with a temperature of 23° C. and a relative humidity of 55% is specifically based on the following formula: The equilibrium moisture content (wt%) = {(film weight after storage-film weight after drying)/film weight after storage}×100 was obtained. Drying refers to the process of drying the film at 105°C for 2 hours. At least heat-treat the first thermoplastic resin film 10 having a high equilibrium moisture content As well as the subsequent humidification treatment, the method of the present invention for manufacturing a polarizing plate by using such a first thermoplastic resin film 10 can suppress or prevent reverse curling of the obtained polarizing plate.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 preferably have a difference in equilibrium moisture rate measured by the method described above of 0.5% by weight or more, that is, the equilibrium moisture rate of the first thermoplastic resin film 10 is higher than that of the second The thermoplastic resin film 20 is greater than 0.5% by weight. As a result, in the humidification step S200 to be described later, the moisture content of the first thermoplastic resin film 10 can be more effectively increased, which is advantageous in suppressing or preventing reverse curling. The difference in equilibrium moisture content is preferably 1% by weight or more, and more preferably 1.5% by weight or more.

The first thermoplastic resin film 10 preferably has an equilibrium moisture content of 1.5% by weight or more, and more preferably 2% by weight or more. As a result, in the humidification step S200 to be described later, the moisture content of the first thermoplastic resin film 10 can be more efficiently increased, which is advantageous in suppressing or preventing reverse curling. The equilibrium moisture content of the first thermoplastic resin film 10 is usually 5% by weight or less.

As a combination of thermoplastic resin films having a difference in equilibrium moisture content of 0.5% by weight or more, for example, a combination of a cellulose resin film (such as a TAC film) and a cyclic polyolefin resin film, a cellulose resin film ( TAC film, etc.) in combination with (meth)acrylic resin film, cellulose resin film (TAC film, etc.) and polyester resin film, cellulose resin film (TAC film, etc.), and chain polyolefin Combination of resin film, combination of (meth)acrylic resin film and cyclic polyolefin resin, combination of (meth)acrylic resin film and polyester resin film, etc. The difference between the equilibrium moisture content of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5% by weight or less.

The equilibrium moisture content of the thermoplastic resin film is adjusted according to the thickness of the film, the presence or absence of a surface treatment layer (coating layer) that can be attached to the surface of the film, the material, etc., in addition to its material (the type of thermoplastic resin constituting the film) .

The first thermoplastic resin film 10 is preferably a film having a higher moisture permeability than the second thermoplastic resin film 20. In this specification, the moisture permeability is the moisture permeability at a temperature of 40°C and a relative humidity of 90% measured by the cup method specified in JIS Z 0208. At least the first thermoplastic resin film 10 having a relatively high moisture permeability is subjected to heat treatment and subsequent humidification treatment. According to the method of the present invention for manufacturing a polarizing plate using such a first thermoplastic resin film 10, it is advantageous to suppress or prevent all Reverse curling of the obtained polarizing plate.

The difference between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 measured by the cup method according to JIS Z 0208 at a temperature of 40°C and a relative humidity of 90% is 30 g/(m ² ‧24hr) or more That is, the moisture permeability of the first thermoplastic resin film 10 is preferably greater than the second thermoplastic resin film 20 by 30 g/(m ² ‧24hr) or more. As a result, in the humidification step S200 to be described later, the moisture content of the first thermoplastic resin film 10 can be more effectively raised, which is advantageous for suppressing or preventing reverse curling. The difference in moisture permeability is preferably 50 g/(m ² ‧24hr) or more, and more preferably 100g/(m ² ‧24hr) or more.

The moisture permeability of the first thermoplastic resin film 10 is preferably 300 g/(m ² ‧24hr) or more, and more preferably 400g/(m ² ‧24hr) or more. As a result, in the humidification step S200 described later, the moisture content of the first thermoplastic resin film 10 can be more efficiently increased, which is advantageous for suppressing or preventing reverse curling. In addition, when the moisture permeability is 300 g/(m ² ‧24hr) or more, when the first thermoplastic resin film 10 and the polarizing film 5 are bonded using an aqueous adhesive, the layer composed of the aqueous adhesive can be efficiently Drying is advantageous in that it can improve productivity. The moisture permeability of the first thermoplastic resin film 10 is usually 5000 g/(m ² ‧24hr) or less.

Examples of the combination of thermoplastic resin films having a difference in moisture permeability of 30 g/(m ² ‧24 hr) or more include, for example, a combination of a cellulose-based resin film (such as a TAC film) and a cyclic polyolefin-based resin film, cellulose Combination of resin film (TAC film, etc.) and (meth)acrylic resin film, combination of cellulose resin film (TAC film, etc.) and polyester resin film, cellulose resin film (TAC film, etc.) and Combination of chain polyolefin resin film, combination of (meth)acrylic resin film and cyclic polyolefin resin, combination of (meth)acrylic resin film and polyester resin film, etc. The difference in moisture permeability between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5000 g/(m ² ‧24 hr) or less.

The moisture permeability of the thermoplastic resin film, in addition to its material (the type of thermoplastic resin constituting the film), can also be adjusted according to the thickness of the film, the presence or the material of the surface treatment layer (coating layer) that can be attached to the film surface, etc. .

The heat treatment of the first thermoplastic resin film 10 in this step is as long as the first thermoplastic resin film 10 is heated to a desired temperature, and this means is not particularly limited. As shown in FIG. 3, the heat treatment can be performed by introducing the first thermoplastic resin film 10 into the heating furnace 70, for example. The heating furnace 70 is preferably capable of controlling the temperature in the furnace. The heating furnace 70 can be a hot air oven that raises the temperature in the furnace by the supply of hot air, for example.

In addition, the heat treatment of the first thermoplastic resin film 10 may be a place where one or two or more heating bodies having convex curved surfaces adhere the film Treatment, or use a heater to heat the film. Examples of the heating body include a heat source (for example, a heat medium such as warm water or an infrared heater) and a roller that can increase the surface temperature (for example, a heat roller such as a guide roller made of metal on the surface). Examples of the heater include infrared heaters, halogen heaters, and plate heaters. FIG. 3 shows an example in which the first thermoplastic resin film 10 is introduced into the heating furnace 70 and the film is heated while being conveyed along the guide roller 60 in the furnace.

Among them, the first thermoplastic resin film 10 is introduced into a heating furnace 70 whose temperature in the furnace is adjusted to a desired temperature, and the film is conveyed along one or more guide rollers 60 located in the furnace The method of heating; or the method of heating the film while adhering it to one or more heating bodies having convex curved surfaces, so that the surface of the first thermoplastic resin film 10 can be deposited in the step S300 described later From the point of smoothing before, it is better. That is, the raw material film such as the first thermoplastic resin film 10 may have minute surface irregularities during production, or when minute irregularities appear on the surface during the storage step after the production, the above method is used in this step. Since the surface of the first thermoplastic resin film 10 is smooth, the appearance quality of the polarizing plate can be improved, and the adhesion to the polarizing film 5 can be improved.

The temperature T _1-1 during the heat treatment (for example, the temperature in the furnace 70 of the heating furnace, the surface temperature of the heat roller, etc.), and the temperature T _1-2 of the first thermoplastic resin film 10 reached by the heat treatment are The temperature T _2-1 (for example, the temperature in the furnace of the humidification furnace 80) during the humidification process in the humidification process step S200 described later is preferably higher than the temperature T _2-1 during the humidification process. good. In addition, the temperatures T _1-1 and T _1-2 are preferably the temperature T _2-2 or higher of the first thermoplastic resin film 10 reached by the humidification treatment, and more preferably higher than the temperature T _2-2 . This can effectively suppress or prevent reverse curling of the obtained polarizing plate. That is, by fully satisfying the above temperature relationship, condensation can be prevented from forming on the surface of the first thermoplastic resin film 10 when the humidification step S200 is introduced, so that the entire film can be reliably covered under the desired temperature and humidity conditions. Implement humidification treatment. This improves the effect of suppressing/preventing reverse curling. T _1-1 and T _1-2 are preferably higher than T _2-1 and T _{2-2 by} 10°C or higher, preferably higher by 20°C or higher, and higher by 30°C or higher. The difference between T _1-1 and T _2-1 or T _{2-2 and} the difference between T _1-2 and T _2-1 or T _2-2 are usually 70° C. or lower.

In addition, the temperature T _1-1 during the heat treatment is preferably the same as or almost the same as the temperature T _1-2 of the first thermoplastic resin film 10 reached by the heat treatment. In addition, the temperature T _2-1 during the humidification process is preferably the same as or nearly the same as the temperature T _2-2 of the first thermoplastic resin film 10 reached by the humidification process.

In the humidification step S200, when condensation occurs on the surface of the first thermoplastic resin film 10, the latent heat of evaporation of the water does not cause the temperature of the film to rise to the desired value in the condensation part. The humidification treatment is performed under the desired temperature and humidity conditions, so the suppression/preventing effect of reverse curling may be reduced, or the reverse curling cannot be suppressed. In addition, the heat treatment step S100 is not performed. For example, when the first thermoplastic resin film 10 at normal temperature (23° C.) is introduced into the humidification treatment step S200 and the humidification treatment is performed under the temperature and humidity conditions where condensation does not occur, humidification is performed. The treatment becomes insufficient, and the reverse curl of the polarizing plate cannot be suppressed.

Also, condensation occurs on the surface of the first thermoplastic resin film 10 At this time, dew condensation traces on the surface of the polarizing plate (condensation occurs, and drying traces left after drying) will reduce the appearance quality of the polarizing plate. If the method of the present invention for manufacturing a polarizing plate using the first thermoplastic resin film subjected to the heat treatment followed by the humidification treatment, the occurrence of such condensation marks can also be reduced.

The temperature T _1-1 during the heat treatment and the temperature T _1-2 of the first thermoplastic resin film 10 by the heat treatment are usually 50 to 150°C, preferably 60 to 130°C, and more preferably 70 to 120℃. When the temperatures T _1-1 and T _{1-2 do} not reach 50°C, it is difficult to fully satisfy the above temperature relationship (T _1-1 , T _1-2 ≧T _2-1 , T _2-2 ), or even if they are sufficient Satisfying this relationship, the humidification process cannot be performed under the appropriate temperature and humidity conditions in the humidification process step S200. As a result, the suppression/prevention effect of reverse curl tends to decrease. In addition, when the temperatures T _1-1 and T _{1-2 do} not reach 50° C., the smoothness of the surface of the first thermoplastic resin film 10 tends to be insufficient. On the other hand, when the temperatures T _1-1 and T _1-2 exceed 150°C, thermal degradation may occur in the first thermoplastic resin film 10, and at the same time, in the humidification step S200, the first humidifier may not be effectively humidified. Thermoplastic resin film 10. In the humidification step S200, from the viewpoint of effectively humidifying the first thermoplastic resin film 10, the temperatures T _1-1 and T _{1-2 are more} preferably 110°C or less, and particularly preferably 100°C or less .

The heat treatment in this step is carried out in an environment with a relative humidity of 50% or less, preferably 45% or less. In other words, heat treatment in an environment with a relative humidity of less than 50% is called "heating treatment" in this specification. At this point, relative humidity is higher than this (for example, relative humidity of 60% or more). It is different from the "humidification process" of the humidification process step S200 of heating and humidifying while heating. The relative heat treatment environment The humidity is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less (for example, 5% or less).

The heat treatment time in this step is, for example, about 2 to 300 seconds, preferably about 5 to 120 seconds. When the heat treatment time is too short, it is difficult for the temperature T _{1-2 of the} first thermoplastic resin film 10 to reach the above-mentioned temperature. Too long a heat treatment time may cause thermal deterioration in the first thermoplastic resin film 10, and because a long film conveyance path is required, the polarizer manufacturing equipment may be excessively enlarged. The time of the heat treatment refers to the residence time of the film in the heating furnace 70, the time between adhesion to the heating body, or the time to heat the film using a heater.

(2) Humidification process step S200

This step is a step of performing a humidification treatment on the first thermoplastic resin film 10 after the heat treatment. The humidification treatment refers to a treatment to increase the moisture content of the first thermoplastic resin. As described above, the heat treatment followed by the humidification treatment can effectively suppress or prevent the reverse curl of the polarizing plate, and, compared with the case where only the humidification treatment is performed, the polarized light can be suppressed or prevented more efficiently The reverse curl of the board.

The humidification treatment of the first thermoplastic resin film 10 is as shown in FIG. 3, which can be performed by introducing the first thermoplastic resin film 10 into the humidification furnace 80 to humidify the treatment, etc. In the environment of the environment. The humidification furnace 80 is preferably one capable of controlling the relative humidity in the furnace, and more preferably one capable of further controlling the temperature in the furnace. The humidifying furnace 80 can raise the temperature in the furnace by the supply of hot air, etc., and can be adjusted by adjusting the moisture in the furnace. An oven that controls the relative humidity in the furnace.

Between the heat treatment and the humidification treatment, the temperature of the heat-treated first thermoplastic resin film 10 can be maintained even when the humidification treatment step is introduced, or it can be greatly reduced as short as possible . FIG. 3 shows an example in which the first thermoplastic resin film 10 from the heating furnace 70 is immediately introduced into the humidification furnace 80, and the film is humidified while being conveyed along the guide roller 60 in the furnace. In order to adjust the temperature during the humidification process using the humidification furnace 80, the above-mentioned heater may be used instead of the hot air, or the above-mentioned heating body (for example, a heat roller) may be used.

The environment in which the relative humidity is adjusted, for example, in the humidifier 80, is adjusted to a relative humidity of at least more than 50%, preferably adjusted to more than 60%, and more preferably to a relative humidity of more than 70%. Thereby, the humidification treatment of the first thermoplastic resin film 10 can be efficiently performed. The above-mentioned relative humidity is the relative humidity of the adjusted environment, usually 99% or less, preferably 95% or less. When the relative humidity is too high, condensation may occur due to the temperature of the first thermoplastic resin film 10.

The temperature T _2-1 during the humidification process (the above relative humidity is the temperature of the adjusted environment), and the temperature T _2-2 of the first thermoplastic resin film 10 achieved by the humidification process, usually 35° C. or higher It is preferably at least 40°C, more preferably at least 45°C. When the temperatures T _2-1 and T _2-2 are 35° C. or higher, the humidification treatment can be efficiently performed. On the other hand, when the temperatures T _2-1 and T _{2-2 are} too high, it is difficult to sufficiently satisfy the above temperature relationship (T _1-1 , T _1-2 ≧T _2-1 , T _2-2 ), so the temperature T _2-1 and T _{2-2 are} preferably within a range of 90° C. or less and sufficiently satisfying the above temperature relationship, and more preferably within a range of 80° C. or less and sufficiently satisfying the above temperature relationship.

The humidification treatment time in this step is, for example, about 5 to 500 seconds, preferably about 20 to 300 seconds. When the time of the humidification treatment is too short, the humidification (increasing the moisture content) of the first thermoplastic resin film 10 becomes insufficient. In addition, the excessively long humidification treatment time requires a long film conveying path, so it may cause excessive enlargement of polarizing plate manufacturing equipment. The time of the humidification treatment refers to the residence time of the film in the humidification furnace 80 and the like.

The preferred moisture content of the first thermoplastic resin film 10 after the humidification step S200 depends on the equilibrium moisture content of the film (more typically, the material of the film). The first thermoplastic resin film 10 by humidification is preferably adjusted to have a higher equilibrium moisture rate than the normal environment (temperature 23°C, relative humidity 55%) after storage under normal conditions of storage Moisture rate. For example, when the first thermoplastic resin film 10 is a triacyl cellulose film, the moisture content after the humidification treatment is preferably 1 to 5% by weight, more preferably 2 to 4.5% by weight (for example, 2 to 4% by weight). The moisture content is measured by the dry weight method in the same way as the equilibrium moisture content. Specifically, it is based on the following formula: Moisture content (weight %) = {(film weight before drying-film weight after drying) / film weight before drying} × 100 to obtain. Drying means drying the film at 105°C for 2 hours.

In the humidification process step S200, the first thermoplastic resin film 10 is humidified in such a way that its moisture content is higher than the equilibrium moisture content at a temperature of 23° C. and a relative humidity of 55%, thereby effectively suppressing or Prevent reverse curling of polarizer. The moisture content of the first thermoplastic resin film 10 after the humidification step S200 is the same as the first thermoplastic resin at a temperature of 23°C and a relative humidity of 55% When the equilibrium moisture content of the film 10 is the same or lower than this, reverse curling cannot be sufficiently suppressed.

The difference between the moisture content of the first thermoplastic resin film 10 after the humidification step S200 and the equilibrium moisture content of the first thermoplastic resin film 10 at a temperature of 23° C. and a relative humidity of 55% is preferably 0.1% by weight or more. From the viewpoint of suppressing excessive positive curl, the difference is preferably 3% by weight or less (for example, 2% by weight or less).

Even if the first thermoplastic resin film 10 is in the lamination step S300 after the humidification treatment step S200, it is desirable to maintain or roughly maintain the moisture content after the humidification treatment.

(3) Lamination step S300

Referring to this step of FIG. 3, the first thermoplastic resin film 10 is deposited on one side of the polarizing film 5, and the second thermoplastic resin film 20 is deposited on the other side of the polarizing film 5.

(3-1) Polarizing film

The polarizing film 5 may be one that adsorbs and aligns the dichroic dye on the polyvinyl alcohol-based resin film that extends uniaxially. As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film, a saponified polyvinyl acetate resin can be used. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith can be exemplified. Other monomers copolymerizable in vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated And sulfonic acids, (meth)acrylamide with amino groups, etc.

The saponification degree of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, but it is preferably in the range of 90.0 to 100.0 mol%, and more preferably in the range of 98.0 to 100.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and humidity and heat resistance of the obtained polarizing plate will decrease.

The degree of saponification refers to the ratio of the acetate group (ethoxyl group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is the raw material of the polyvinyl alcohol-based resin, to the hydroxyl group by the saponification step. Ear %) is expressed by the following formula: Saponification degree (mol %) = 100 × (number of hydroxyl groups)/(number of hydroxyl groups + number of acetate groups). The degree of saponification can be obtained in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of hydroxyl groups, and therefore, the lower the ratio of acetate groups that hinder crystallization.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, preferably 1500 to 8000, and more preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be obtained in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain better polarizing performance. When it exceeds 10,000, the solubility to the solvent deteriorates, and the formation of the polyvinyl alcohol-based resin film becomes difficult.

The dichroic dye contained in the polarizing film 5 (adsorption alignment) may be iodine or a dichroic organic dye. Specific examples of dichroic organic dyes include: red BR, red LR, red R, pink LB, ruby BL, date 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 Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL , Direct sky blue, direct light fast orange S, solid black. Only one kind of dichroic pigment may be used alone, or two or more kinds may be used in combination. The dichroic pigment is preferably iodine.

The polarizing film 5 series can be manufactured through the following steps: a step of uniaxially extending the polyvinyl alcohol-based resin film; a step of dyeing the polyvinyl alcohol-based resin film with a dichroic pigment and adsorbing the dichroic pigment; The step of cross-linking the polyvinyl alcohol resin film of the pigment; and the step of washing with water after the cross-linking.

The polyvinyl alcohol-based resin film is a film-former that produces the above-mentioned polyvinyl alcohol-based resin. The method of film formation is not particularly limited, and conventional methods such as a melt extrusion method and a solvent casting method can be used. The thickness of the polyvinyl alcohol-based resin film is, for example, about 10 to 150 μm, preferably 50 μm or less, and more preferably 35 μm or less.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before the dyeing of the dichroic pigment, simultaneously with the dyeing, or after the dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may also be performed before or during the cross-linking treatment. In addition, uniaxial stretching may be performed in these plural stages.

When uniaxially extended, uniaxial extension can also be performed between rollers with different peripheral speeds, or uniaxial extension can also be performed using hot rollers. In addition, the uniaxial stretching may be dry stretching in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is stretched in the solution. Extension magnification is usually About 3 to 8 times.

As a method of dyeing the polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing a dichroic dye can be used. The polyvinyl alcohol-based resin film is preferably subjected to water immersion treatment (swelling treatment) before the dyeing treatment.

When iodine is used as a dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is generally used. The content of iodine in the dyeing aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing aqueous solution is usually about 20 to 40°C.

On the other hand, when a dichroic organic dye is used as a dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in a dyeing aqueous solution containing a water-soluble dichroic organic dye is generally used. The content of the dichroic organic dye in the dyeing aqueous solution per 100 parts by weight of water is usually 1×10 ^-4 to 10 parts by weight, preferably 1×10 ^-3 to 1 part by weight. This dyeing aqueous solution may also contain inorganic salts such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80°C.

The cross-linking treatment after dyeing by the dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing a cross-linking agent. Although a suitable example of the cross-linking agent is boric acid, other cross-linking agents such as boron compounds of borax, glyoxal, glutaraldehyde and the like can also be used. Only one type of crosslinking agent may be used, or two or more types may be used in combination.

The amount of the cross-linking agent in the aqueous solution containing the cross-linking agent is usually 2 to 15 parts by weight per 100 parts by weight of water, preferably 5 to 12 parts by weight. When iodine is used as the dichroic dye, the aqueous solution containing the crosslinking agent preferably contains potassium iodide. In the aqueous solution containing the crosslinking agent, the amount of potassium iodide is usually 0.1 to 15 parts by weight per 100 parts by weight of water, preferably 5 to 12 parts by weight. The temperature of the aqueous solution containing the cross-linking agent is usually above 50°C, preferably 50 to 85°C.

The polyvinyl alcohol resin film after the cross-linking treatment is usually washed with water. The water washing treatment system can be performed, for example, by immersing the cross-linked polyvinyl alcohol resin film in water. The temperature of the water in the washing process is usually about 1 to 40°C.

After washing with water and performing a drying process, the polarizing film 5 can be obtained. The drying process can be performed by a hot air dryer, by contact with a hot roller, by a far-infrared heater, etc. The drying temperature is usually about 30 to 100°C, preferably 50 to 90°C.

The thickness of the polarizing film 5 is usually about 2 to 40 μm. From the viewpoint of thinning the polarizing plate, the thickness of the polarizing film 5 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The smaller the thickness of the polarizing film 5 is, the more easily the polarizing plate is curled. However, according to the present invention, the thickness of the polarizing film 5 is, for example, 15 μm or less, and even if it is as thin as 10 μm or less, it can effectively suppress or prevent Reverse curl.

By the drying process, the moisture content of the polarizing film 5 is reduced to a practical level. This moisture content is usually 5 to 20% by weight, and 8 to 15% by weight Better. When the moisture content drops to 5 wt%, the flexibility of the polarizing film 5 is lost, and the polarizing film 5 may be damaged or cracked after being dried. In addition, when the moisture content rises to 20% by weight, the thermal stability of the polarizing film 5 may deteriorate. Here, the so-called moisture content is measured by the dry weight method, and the measurement method is as described above.

(3-2) Second thermoplastic resin film

The second thermoplastic resin film 20 is the same as the first thermoplastic resin film 10 and has a light-transmitting thermoplastic resin, and is preferably composed of an optically transparent thermoplastic resin. For a specific example of the thermoplastic resin that can constitute the second thermoplastic resin film 20, the description about the first thermoplastic resin film 10 is cited. However, the thermoplastic resin constituting the second thermoplastic resin film 20 is selected in such a manner that the equilibrium moisture rate of the film at a temperature of 23° C. and a relative humidity of 55% is lower than that of the first thermoplastic resin film 10.

Like the first thermoplastic resin film 10, the second thermoplastic resin film 20 may be a protective film incorporating an optical function such as a protective film, a temporary protective film, or a retardation film or a brightness enhancement film. The second thermoplastic resin film 20 may have a surface treatment layer (coating layer) such as a hard coat layer, an anti-glare layer, an anti-reflection layer, an electrical anti-fouling layer, and an antifouling layer deposited on its surface. The thickness of the second thermoplastic resin film 20 is usually 1 to 100 μm, but from the viewpoint of strength and handleability, it is preferably 5 to 60 μm, and more preferably 5 to 50 μm. The smaller the thickness of the second thermoplastic resin film 20 is, the more easily the polarizing plate is curled. However, according to the present invention, the thickness of the second thermoplastic resin film 20 is as thin as 40 μm or less and further 30 μm or less, which can be effectively suppressed. Or to prevent reverse curling of the polarizing plate obtained.

As mentioned above, the equilibrium moisture rate (and moisture permeability) of the thermoplastic resin film can be determined by its material (the type of thermoplastic resin constituting the film), the thickness of the film, and the surface treatment layer (coating layer) that can be attached to the surface of the film Adjust with or without material. Therefore, although the first thermoplastic resin film 10 and the second thermoplastic resin film 20 have different equilibrium moisture ratios from each other, they may be composed of the same thermoplastic resin.

The equilibrium moisture content of the second thermoplastic resin film 20 is usually 0.05 to 1.5% by weight, preferably 0.05 to 1% by weight. The moisture permeability of the second thermoplastic resin film 20 is usually 1 to 350 g/(m ² ‧24hr), preferably 5 to 200 g/(m ² ‧24hr). Examples of the thermoplastic resin constituting the second thermoplastic resin film 20 that can achieve such a balanced moisture content and moisture permeability are cyclic polyolefin resin, (meth)acrylic resin, polyester resin, chain polyolefin resin Resin etc.

The second thermoplastic resin film 20 may be subjected to the same humidification treatment as the first thermoplastic resin film 10 or a combination of heat treatment and humidification treatment before the stacking step S300, but this suppresses or prevents the reverse of the polarizing plate From the viewpoint of curling, the second thermoplastic resin film 20 is preferably not subjected to humidification treatment, or a combination of heat treatment and humidification treatment. However, for the second thermoplastic resin film 20, by performing the same heat treatment as the first thermoplastic resin film 10, the surface of the second thermoplastic resin film 20 can be smoothed.

(3-3) Lamination step

Referring to FIG. 3, in this step, the first and second heats of the polarizing film 5 are The lamination of the plastic resin films 10 and 20 is, for example, a long article using each raw material film, and this can be carried out continuously while being continuously conveyed. Each raw material film is conveyed in such a manner that the longitudinal direction becomes the conveying direction. The conveying path of the film is suitably provided as a guide roller (free roller) 60 that supports the film that enters, or a driving roller in response to the necessary bite roller or the like. In general, the transport direction (film length direction) of the polarizing film 5 is parallel to the transport direction (film length direction) of the first and second thermoplastic resin films 10 and 20.

When both the first and second thermoplastic resin films 10 and 20 are combined to hold a protective film or a protective film for optical functions, the first and second thermoplastic resin films 10 and 20 are usually separated by the first and second adhesives, respectively. The layers 15 and 25 are laminated and laminated on the polarizing film 5. Specifically, as shown in FIG. 3, the first thermoplastic resin film 10, the polarizing film 5 and the second thermoplastic resin film 20 are superposed in such a way that their longitudinal directions (transport directions) become parallel, and by passing a pair Between the laminating rollers 40, 40, the laminated film can be laminated by pressing the laminated film up and down, but in this case, the first injection device 90 is used before passing between the laminating rollers 40, 40. The second injection device 91 injects the first adhesive 50 and the second adhesive 55 between the polarizing film 5 and the first thermoplastic resin film 10, and between the polarizing film 5 and the second thermoplastic resin film 20, respectively Intervene in the adhesive layer.

After lamination, by drying and/or hardening the adhesive layer, the double-sided protective polarizing plate 1 shown in FIG. 2 can be obtained. The first adhesive layer 15 is formed of the first adhesive 50 and the second adhesive layer 25 is formed of the second adhesive 55.

Also, a method to intervene in the layer composed of the adhesive, It is not limited to the injection using the injection devices 90 and 91. For example, in accordance with the viscosity of the adhesive, etc., a doctor blade method, a wire bar coating method, a die coating method, a corner wheel coating method, a gravure coating method, In the coating method of the dip coating method or the casting method, the adhesive may be applied to the bonding surface of at least one of the overlapping films.

Before the polarizing film 5 is laminated and bonded to the first and second thermoplastic resin films 10 and 20, such as plasma may also be performed on the bonding surface of the polarizing film 5 and/or the first and second thermoplastic resin films 10 and 20. Surface activation treatment of treatment, corona treatment, ultraviolet irradiation treatment, flame (fire) treatment, saponification treatment. By the surface activation treatment, the adhesion between the polarizing film 5 and the first and second thermoplastic resin films 10 and 20 can be improved.

As the first adhesive 50 and the second adhesive 55, water-based adhesives, active energy ray-curable adhesives or thermosetting adhesives can be used, preferably water-based adhesives and active energy ray-curable adhesives. The first adhesive 50 and the second adhesive 55 may be the same kind of adhesive, or may be different kinds of adhesive. When different kinds of adhesives are used, the curling of the polarizing plate is easy to occur, but according to the present invention, the reverse curling of the polarizing plate can be effectively suppressed or prevented under such circumstances.

Aqueous adhesives are those in which the components of the adhesive are dissolved or dispersed in water. The water-based adhesive that is preferably used, for example, uses an adhesive composition of a polyvinyl alcohol resin or an urethane resin as a main component.

When using a polyvinyl alcohol-based resin as the main component of the adhesive, the polyvinyl alcohol-based resin may be, in addition to polyvinyl alcohol resins such as partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, or modified such as carboxyl group. Modified polyvinyl alcohol-based resins of high-quality polyvinyl alcohol, acetyl-acetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, and amine-modified polyvinyl alcohol. Polyvinyl alcohol-based resins are not only vinyl alcohol homopolymers obtained by saponification of polyvinyl acetate homopolymer polyvinyl acetate, but also other monomers that may be copolymerized with vinyl acetate Polyvinyl alcohol-based copolymer obtained by saponification treatment of the copolymer.

The water-based adhesive containing the polyvinyl alcohol-based resin as the adhesive component is usually an aqueous solution of the polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol resin in the adhesive is generally 1 to 10 parts by weight, preferably 1 to 5 parts by weight, relative to 100 parts by weight of water.

The adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin preferably contains, for example, polyaldehyde, melamine-based compound, zirconia compound, zinc compound, glyoxal, glyoxal derivative, water-soluble The hardening component or crosslinking agent of epoxy resin. As the water-soluble epoxy resin, for example, polyamidoamines obtained by the reaction of polyalkylene polyamines such as diethylenetriamine and triethylenetetramine, and dicarboxylic acids such as adipic acid can be suitably used. Polyamide epoxy resin obtained by reaction of epichlorohydrin. Examples of commercially available products of such polyamine polyamine epoxy resins include: "SUMIREZ RESIN 650" (manufactured by Taoka Chemical Industry Co., Ltd.), "SUMIREZ RESIN675" (manufactured by Taoka Chemical Industry Co., Ltd.), "WS -525" (Japan PMC (stock) system) etc. The addition amount of these hardening components or crosslinking agent (the total amount when added together as the hardening component and the crosslinking agent) is usually 1 to 100 parts by weight relative to 100 parts by weight of the polyvinyl alcohol resin. It is preferably 1 to 50 parts by weight. The addition amount of the above hardening component or crosslinking agent, relative to polyethylene When 100 parts by weight of the enol-based resin is less than 1 part by weight, the effect of improving the adhesion tends to be small. In addition, when the added amount exceeds 100 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the adhesive The layer has a tendency to become brittle.

In addition, suitable examples when using an urethane resin as the main component of the adhesive include a mixture of a polyester-based ionic polymer urethane resin and a compound having a glycidyloxy group. The polyester ionic polymer urethane resin refers to an urethane resin having a polyester skeleton into which a small amount of ionic components (hydrophilic components) are introduced. Such an ionic polymer urethane resin is suitable as a water-based adhesive without emulsifier for emulsification in water to form latex.

The active energy ray-curable adhesive is an adhesive that is hardened by irradiation of active energy rays such as ultraviolet rays, visible light, electron rays, and X-rays. When an active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate is a hardened layer of the adhesive.

The active energy ray-curable adhesive may be an adhesive containing an epoxy-based compound hardened by cationic polymerization as a curable component, and preferably an ultraviolet-curable adhesive containing such an epoxy-based compound as a curable component . The epoxy compound here means a compound having an average of one or more epoxy groups in the molecule, preferably two or more epoxy groups. Only one type of epoxy compound system may be used, or two or more types may be used in combination.

Specific examples of epoxy compounds that can be suitably used include hydrogenated epoxy compounds obtained by reacting epichlorohydrin with an alicyclic polyol obtained by hydrogenating an aromatic ring in an aromatic polyol Compound (glycidyl ether of polyol with alicyclic ring); aliphatic polyhydric An aliphatic epoxy compound such as alcohol or an alkylene oxide adduct such as polyglycidyl ether; an alicyclic epoxy compound having more than one epoxy group bonded to an alicyclic ring in the molecule Formula epoxy compound.

The active energy ray-curable adhesive may replace the above-mentioned epoxy-based compound as a curable component, or may contain a radically polymerizable (meth)acrylic compound. Examples of (meth)acrylic compounds include: (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule; obtained by reacting two or more functional group-containing compounds A compound containing (meth)acryloyloxy groups such as (meth)acrylate oligomers having at least two (meth)acryloyloxy groups in the molecule.

When the active energy ray-curable adhesive agent contains an epoxy-based compound hardened by cationic polymerization as a curable component, it is preferable to contain a photo-cationic polymerization initiator. Examples of the photocationic polymerization initiator include: aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-propadiene complexes. In addition, when the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth)acrylic compound, it is preferable to contain a photoradical polymerization initiator. Examples of photo radical polymerization initiators include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, and xanthenes. Ketone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, etc.

One of the first and second thermoplastic resin films 10 and 20 may be a temporary protective film for temporarily protecting the surface of the polarizing film 5. In this case, in the stacking step S300, the polarizing film 5 and the temporary protective film are not Intervening adhesives, but intervening in volatile liquids, or layering a temporary protective film without any intervention. The temporary protective film is a film that can be peeled off from the polarizing film 5, and after the polarizing plate is manufactured, it is peeled off and removed within a desired time (for example, when the polarizing plate is attached to the liquid crystal element). "Removable" means that the polarizing film 5 and the temporary protective film can be separated without breaking or scratching the polarizing film 5 and the temporary protective film.

As an example, using the second thermoplastic resin film 20 as a temporary protective film, after performing the lamination step S300, the layer configuration of the single-sided protective polarizing plate 2 obtained by peeling and removing the temporary protective film is shown in FIG. 4.

When a temporary protective film is used, it is preferable to interpose a volatile liquid between the polarizing film 5 and the temporary protective film in the stacking step S300. By this, the polarizing film 5 is cracked and cracked during the manufacturing process of the polarizing plate compared to the case where there is no such thing, and the unsuitable phenomenon of wrinkles can be suppressed in the film laminate containing the polarizing film 5.

The peeling force between the polarizing film 5 and the temporary protective film is, for example, 0.01 to 0.5 N/25 mm, preferably 0.01 to 0.2 N/25 mm, and more preferably 0.01 to 0.15 N/25 mm. When the peeling force is less than 0.01N/25mm, the adhesion between the polarizing film 5 and the temporary protective film is small, so the part of the temporary protective film is peeled off, and the single-sided protective polarizing plate with the temporary protective film is made into a roller state. During storage, the polarizing film 5 may crack along the extending direction. In addition, when the peeling force exceeds 0.5 N/25 mm, it is difficult to peel off the temporary protective film from the polarizing film 5, so when the temporary protective film is peeled off, the polarizing film 5 is likely to crack along the extending direction.

The above peeling force is to cut a single-sided protective polarizing plate with a temporary protective film into a 25mm wide sample to obtain the measurement, using Shimadzu The precision universal testing machine "AUTOGRAPH AG-50NX" made by the company (stock) grabs the temporary protective film and single-sided protective polarizing plate of the measured sample, and is obtained by measuring the force when peeling in the direction of 180°. The measurement of the peeling force is carried out in an environment with a peeling speed of 300 mm/min, a temperature of 23±2°C, and a relative humidity of 50±5%.

The intervening volatile liquid system is volatilized and removed after the stacking step S300. Thereby, a single-sided protective polarizing plate attached to the temporary protective film can be obtained. FIG. 5 shows an example of the layer structure of the single-sided protective polarizing plate 3 with a temporary protective film. In the example of FIG. 5, the second thermoplastic resin film 20 is a temporary protective film. The volatile liquid system can be volatilized and removed by heating. By this heat treatment, the temporary protective film is directly laminated on the surface of the polarizing film 5 with moderate adhesion. The heating temperature is, for example, 30 to 90°C.

The volatile liquid system is a liquid that can be volatilized by the above heat treatment, and is preferably a liquid that does not adversely affect the polarizing film 5. If it does not cause adverse effects, it can also be added to prevent electricity. If exemplified as a volatile liquid, for example, water or a mixture of water and a hydrophilic liquid. The hydrophilic liquid system is preferably one that does not remain after heat treatment, for example, methanol, ethanol, 1-propanol, tetrahydrofuran, acetone, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide , Formic acid, acetic acid, etc.

(4) Other steps

When the water-based adhesive is used for laminating the polarizing film 5 and the first and/or second thermoplastic resin films 10 and 20, the laminating step S300 is implemented The drying step for removing water contained in the water-based adhesive is preferred. The drying temperature is, for example, 30 to 90°C. When a temporary protective film is laminated on the polarizing film 5 via a volatile liquid, this drying step may also be combined with the above-mentioned heat treatment for volatile liquid removal. After the drying step, for example, at 20 to 50°C, preferably at a temperature of 30 to 45°C, a aging step is performed.

When the active energy ray-curable adhesive is used for laminating the polarizing film 5 and the first and/or second thermoplastic resin films 10 and 20, after the laminating step S300, a drying step is performed as necessary, and then, The curing step of curing the active energy ray-curable adhesive is performed by irradiating the active energy ray. The light source of the active energy ray is not particularly limited, but ultraviolet rays with a luminous distribution below 400 nm are preferred. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, and microwave excitation can be used Mercury lamps, metal halide lamps, etc.

The irradiation intensity of the active energy ray to the adhesive layer composed of the active energy ray hardening adhesive can be appropriately determined by the composition of the adhesive, but it is irradiated in the wavelength region effective for activation of the polymerization initiator It is preferable to set the intensity to 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1mW/cm ² or more, the reaction time is not too long. When it is 6000mW/cm ² or less, the yellowing of the adhesive layer due to the heat radiated by the light source and the heat generated when the adhesive is hardened or The polarizing film 5 is less likely to deteriorate.

The irradiation time of the active energy ray can be appropriately determined according to the composition of the adhesive, but the cumulative light amount indicated by the product of the irradiation intensity and the irradiation time is preferably set in a manner of 10 to 10000 mJ/cm ² . When the accumulated light amount is 10mJ/cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to more reliably perform the hardening reaction. When it is 10000mJ/cm ² or less, the irradiation time is not too long and can be maintained well Productivity.

When one of the first and second thermoplastic resin films 10, 20 uses the temporary protective film to perform the stacking step S300, as described above, for example, the single-sided protective polarized light with the temporary protective film shown in FIG. 5 can be obtained The plate 3 is peeled off and the temporary protective film is removed therefrom, whereby, for example, the single-sided protective polarizing plate 2 shown in FIG. 4 can be obtained. As also described above, in FIGS. 4 and 5, although the second thermoplastic resin film 20 is used as a temporary protective film, the first thermoplastic resin film 10 may be a temporary protective film. It is also possible to provide a step of laminating the adhesive layer 30 on the polarizing film surface laminated with the temporary protective film in the single-sided protective polarizing plate 2 to obtain single-sided protection with the adhesive layer shown in FIG. 6, for example Polarizing plate 4. The adhesive layer 30 can be used to attach the single-sided protective polarizing plate to the liquid crystal cell.

Even in the double-sided protective polarizing plate 1 shown in FIG. 2, the adhesive layer 30 may be layered on the area other than the first thermoplastic resin film 10 or the second thermoplastic resin film 20. The adhesive layer 30 can be used for bonding the protective polarizer 1 on both sides to the liquid crystal element. The adhesive layer 30 in the polarizing plate 1 for protecting both sides is preferably laminated on the outer surface of the second thermoplastic resin film 20.

The adhesive layer 30 can be composed of an adhesive composition such as (meth)acrylic, rubber, urethane, ester, polysiloxane, and polyvinyl ether resin as the main component (matrix polymer). . Among them, an adhesive composition using a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, and the like as a matrix polymer is suitable. Adhesive composition can also be Energy linear hardening type, heat hardening type.

As the (meth)acrylic resin used in the adhesive composition, for example, butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, ( A polymer or copolymer of one or more (meth)acrylates of 2-ethylhexyl methacrylate as monomers. Among (meth)acrylic resins, it is preferable to copolymerize polar monomers. Examples of polar monomers include, for example, (meth)acrylic acid, (meth)acrylic acid 2-hydroxypropyl ester, (meth)acrylic acid hydroxyethyl ester, (meth)acrylic acid amide, N,N -Monomers of carboxyl group, hydroxyl group, amide group, amine group, epoxy group, etc. of dimethylaminoethyl (meth) acrylate, glycidyl (meth) acrylate.

Although the adhesive composition may contain only the above matrix polymer, it usually further contains a crosslinking agent. As a cross-linking agent, there can be listed: metal ions with a valence of 2 or more form a metal salt of a carboxylic acid with a carboxyl group; a polyamine compound forms an amide bond with a carboxyl group; a polyepoxy compound or a polyol Those that form ester bonds between carboxyl groups; those that form amide bonds between carboxyl groups and polyisocyanate compounds. Among them, polyisocyanate compounds are preferred.

The so-called active energy ray-curable adhesive composition has the property of being hardened by being irradiated with active energy rays such as ultraviolet rays or electron rays, and it has adhesiveness even before the active energy ray is irradiated and adheres to an object such as a film , Adhesive composition that is hardened by the irradiation of active energy rays and has the property of adjustable adhesion. The active energy ray-curable adhesive composition is preferably ultraviolet-curable. In addition to the matrix polymer and crosslinking agent, the active energy ray-curable adhesive composition contains active energy ray polymer Compound compounds. According to necessity, it also contains photopolymerization initiator or photo-sensitizer.

The adhesive composition may contain fine particles, beads (resin beads, glass beads, etc.), resins other than glass fibers, matrix polymers, tackifiers, fillers (metal powder or other Inorganic powders, etc.), oxidation inhibitors, ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, photopolymerization initiators and other additives.

The adhesive layer 30 can apply the organic solvent dilution of the above adhesive composition on the adhesive layer forming surface of the polarizing plate (that is, the polarizing film 5, the first or second thermoplastic resin film 10, 20) by Let it dry to form. Alternatively, after applying the organic solvent dilution of the above adhesive composition on the separation film (thermoplastic resin film subjected to release treatment) and drying it to form an adhesive layer, this can also be transferred to the polarizer Adhesive layer forming surface. Even in either method, it is better to stick the adhesive separation film on the outer surface of the adhesive layer 30 until the adhesive layer 30 is protected during use. When an active energy ray hardening type adhesive composition is used, an active energy ray can be irradiated on the formed adhesive layer to form a hardened product having a desired degree of hardening. The thickness of the adhesive layer 30 is usually 1 to 40 μm, but from the viewpoint of thinning of the polarizing plate, it is preferably 3 to 25 μm.

A step of protecting the polarizing plate 1 on both sides and protecting the polarizing plate 1 on one side from the first and/or second thermoplastic resin films 10 and 20 may be further provided. The protective film is composed of a base film and an adhesive layer stacked thereon. The protective film is a film for protecting the surface of the polarizing plate. Usually, for example, after a polarizing plate with a protective film is attached to a liquid crystal cell, etc., the protective film is peeled off. Remove the entire adhesive layer it has. The base film can be a thermoplastic resin, such as polyolefin resin of polyethylene resin and polypropylene resin; cyclic polyolefin resin; such as polyethylene terephthalate or polyethylene naphthalate. Ester resin; polycarbonate resin; (meth)acrylic resin, etc.

In addition, a step of protecting the polarizing plate 1 on both sides and protecting the polarizing plate 1 on one side and the first and/or second thermoplastic resin films 10 and 20 may be provided with an optical film other than the polarizing film. Examples of other optical films are retardation films or brightness enhancement films. Other optical films can be laminated and laminated through an adhesive layer or an adhesive layer.

According to the manufacturing method of the present invention, it is possible to obtain a blade body of a polarizing plate (a double-sided protective polarizing plate or a single-sided protective polarizing plate) that suppresses or prevents reverse curling. As described above, reverse curling refers to making the second main surface opposite to the side bonded to an image display element such as a liquid crystal cell into a convex curl, protecting the polarizing plate 1 on both sides or protecting the polarizing plate 2 on one side Typically, the first thermoplastic resin film 10 side is convexly curled. In the blade body of the polarizing plate obtained according to the present invention, the reverse curl that makes such a first thermoplastic resin film 10 side convex can be well suppressed or prevented, and typically a flat plate shape that does not have curl, or a few , It has a positive curl shape, or even if it has a reverse curl, the amount becomes a certain amount of shape. It is preferably a flat plate shape without curling, or a shape with several curls.

[Example]

Although the examples are shown below and the present invention will be described more specifically, the present invention is not limited to these examples. Also, in the following In the examples, the equilibrium moisture rate, moisture rate, moisture permeability, and thickness of the film, and the curling amount of the polarizing plate were measured according to the following methods.

(1) Balanced moisture rate of membrane W _H

Cut out the test piece with MD length 150mm×TD length 100mm. The weight of the film after storage for 24 hours in an environment with a temperature of 23°C and a relative humidity of 55% was measured. Thereafter, a drying process was performed at 105°C for 2 hours, and the weight of the film after the drying process was measured. From the weight of the film before and after drying, according to the following formula: Balanced moisture rate (wt%) = {(weight of film before drying-weight of film after drying)/weight of film before drying}×100 Rate W _H.

(2) Moisture rate of membrane W

A test piece with an MD length of 150 mm and a TD length of 100 mm was cut out, and the weight was immediately measured. Next, a drying process was performed at 105°C for 2 hours, and the weight of the film after the drying process was measured. From the weight of the film before and after drying, according to the following formula: Moisture content (weight %) = {(film weight before drying treatment-film weight after drying treatment)/film weight before drying treatment}×100 The moisture content W was obtained.

(3) Permeability of membrane

According to the cup method stipulated in JIS Z 0208, the moisture permeability [g/(m ² ‧24hr)] at a temperature of 40°C and a relative humidity of 90% is measured.

(4) Film thickness

It was measured using a digital micro-instrument "MH-15M" made by Nikon Corporation.

(5) The curling amount of polarizing plate

From the obtained two-sided protective polarizing plate, the absorption axis direction (MD) of each side was cut to a test piece of 300 mm×200 mm so as to become 45°, and the test piece was placed in an environment with a temperature of 25° C. and a relative humidity of 55% for 24 hours. . Place the test piece with the concave surface facing upwards, that is, the four edges become swollen, and place it on the reference surface (horizontal stage). In this state, the height from the reference plane was measured for each of the four corners of the test piece, and the average height of the four corners was determined as the curl amount [mm]. A positive curl value means that the first thermoplastic resin film side becomes concave (positive curl), and a negative value means that the second thermoplastic resin film side becomes concave (reverse curl). In addition, the polarizing plates on both sides of Examples 2 and 3 were protected so that neither the first thermoplastic resin film side nor the second thermoplastic resin film side faced upward, and curling did not occur.

<Example 1>

(A) Production of polarizing film

The long polyvinyl alcohol film (average degree of polymerization: about 2400, saponification degree: 99.9 mol% or more, thickness: 30 μm) was continuously conveyed while being stretched by dry-type uniaxially about 4 times, and further kept in a tight state, After being directly immersed in pure water at 40°C for 1 minute, it was immersed in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.1/5/100 at 28°C for 60 seconds. After that, it is immersed in an aqueous solution with a weight ratio of potassium iodide/boric acid/water of 10.5/7.5/100 at 68°C Stain for 300 seconds. Then, after washing with pure water at 5°C for 5 seconds, it was dried at 70°C for 180 seconds to obtain a long polarizing film with iodine adsorbed and aligned on the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film is 11 μm.

(B) Fabrication of polarizer on both sides

Using the same apparatus as the polarizing plate manufacturing apparatus shown in FIG. 3, a double-sided protective polarizing plate was produced in the following order. The long first thermoplastic resin film [TAC film "KC2UAW" manufactured by Konica Minolta Opto Co., Ltd., thickness: 25 μm, equilibrium moisture rate WH: 3.0% by weight, moisture permeability: 1207 g/(m ² ‧24hr)] is continuous Transported to the ground while being introduced into a heating furnace set at a furnace temperature of 95°C and a relative humidity of 3% in the furnace, and then introduced into a humidifying furnace set at a furnace temperature of 50°C and a relative humidity of 70% in the furnace The humidification process. The residence time of the film in the drying furnace and the humidifying furnace was set to 8 seconds and 12 seconds, respectively. The humidification furnace is installed directly after the heating furnace, and the temperature of the film before being introduced into the humidification furnace is almost the same as the temperature inside the heating furnace. Both the heating furnace and the humidifying furnace raise the temperature in the furnace by the supply of hot air. The moisture content W of the first thermoplastic resin film after the humidification treatment was 3.1% by weight.

While the polarizing film obtained in the above (A) is continuously transported, the first thermoplastic resin film after the humidification treatment and the elongated second thermoplastic resin film [cyclic polyolefin system made by JSR (shares)] The trade name of the resin film "FEK B015D3", thickness: 15 μm, equilibrium moisture rate W _H : 0.8% by weight, moisture permeability: 115 g/(m ² ‧24hr), use the purchased product without heating/humidification] continuously Transporting, between the polarizing film and the first thermoplastic resin film, and between the polarizing film and the second thermoplastic resin film, the first thermoplastic resin film/water-based adhesive is made by passing between the bonding rollers while injecting the water-based adhesive Layered film consisting of layer/polarizing film/water-based adhesive layer/second thermoplastic resin film (first step). This lamination step is performed within 10 seconds after the humidification treatment of the first thermoplastic resin film.

For the above-mentioned water-based adhesives, polyvinyl alcohol powder [trade name "GOHSEFIMER" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100] was dissolved in hot water at 95°C at a concentration of 3 weight An aqueous solution obtained by mixing a cross-linking agent [sodium glyoxylate manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] in a ratio of 1 part by weight to 10 parts by weight of polyvinyl alcohol powder in a polyvinyl alcohol aqueous solution.

Then, the obtained laminated film was transported, and the water-based adhesive layer was dried by performing a heat treatment at 80° C. for 300 seconds in a hot air dryer to obtain a double-sided protective polarizing plate.

<Examples 2 to 3, Comparative Examples 1 to 3>

Except that the furnace environment of the heating furnace and the humidification furnace and the residence time of the film are shown in Table 1, the same operation as in Example 1 was carried out to produce a double-sided protective polarizing plate. In Comparative Examples 2 and 3, the first thermoplastic resin film was not heated.

Table 1 shows the curling amount of the double-sided protective polarizing plates obtained in Examples 1 to 3 and Comparative Examples 1 to 3. In Table 1, the furnace environment of the heating furnace and the humidification furnace and the residence time of the film are collectively described. Table 1 and the combined moisture content W represents the first thermoplastic resin film after the humidity treatment, the equilibrium water content of the first thermoplastic resin film W _H, and the moisture content W and humidity treatment after the equilibrium water content of W _H difference. In Comparative Example 1, the first thermoplastic resin film was passed through a humidification furnace, but the humidification treatment was not performed. In Comparative Example 1 of Table 1, the numerical value described in the column of “moisture content after humidification treatment” refers to the moisture content of the first thermoplastic resin film after passing through the humidification furnace.

Even in any of Examples 1 to 3, Comparative Example 1, and Comparative Example 3, the surface of the first thermoplastic resin film could not be confirmed with dew condensation marks. In Comparative Example 2, condensation marks were observed on the surface of the first thermoplastic resin film.

<Examples 4 and 5>

Except for using a hard coating film [a TAC film "KC2U AW" made by Konica Minolta Opto Co., Ltd.) to form a hard coating layer, thickness: 32.4 μm, equilibrium moisture rate W _H : 1.9% by weight, moisture permeability: 455 g/ (m ² ‧24hr)] As the first thermoplastic resin film, a cyclic polyolefin resin film [trade name "ZF 14-023" manufactured by Japan Zeon Co., Ltd., thickness: 22.9 μm, equilibrium moisture rate W _H : 0.1% by weight, moisture permeability: 17g/(m ² ‧24hr)] as the second thermoplastic resin film, and the furnace environment of the heating furnace and humidification furnace, and the residence time of the film are as shown in Table 2 The rest is the same as in Example 1, and a double-sided protective polarizing plate is manufactured. Table 2 shows the curling amount of the double-sided protective polarizing plates obtained in Examples 4 and 5. In Table 2, the furnace environment of the heating furnace and the humidification furnace and the residence time of the film are collectively described. In Table 2 and the combined moisture content W represents a first thermoplastic resin film after the humidification process, the balance of the first thermoplastic resin film of the moisture content of the water W _H and humidity treatment after the equilibrium moisture content ratio of the W and the W _H difference.

S100, S200, S300 ‧‧‧ steps

Claims (11)

A method of manufacturing a polarizing plate includes the following steps in sequence: a step of heat-treating a first thermoplastic resin film; a step of humidifying the first thermoplastic resin film; and stacking the aforementioned first on one surface of the polarizing film A step of stacking a thermoplastic resin film on the other surface of the polarizing film with a second thermoplastic resin film at a temperature of 23° C. and a relative humidity of 55% that is lower than the first thermoplastic resin film; the step of the humidification process In the above, the first thermoplastic resin film is humidified so that its moisture content is higher than the equilibrium moisture content of the first thermoplastic resin film at a temperature of 23° C. and a relative humidity of 55%. The manufacturing method as described in item 1 of the patent application range, wherein the second thermoplastic resin film is one that has not been subjected to the humidification treatment. The manufacturing method as described in item 1 of the patent application range, wherein the first thermoplastic resin film contains a cellulose-based resin film. The manufacturing method as described in item 1 of the patent application range, wherein the second thermoplastic resin film contains a cyclic polyolefin-based resin film. The manufacturing method as described in item 1 of the patent application range, wherein the temperature during the heat treatment is equal to or higher than the temperature during the humidification treatment. The manufacturing method as described in item 5 of the patent application range, wherein the temperature during the heat treatment is higher than the temperature during the humidification treatment by 30°C or more. The manufacturing method according to item 1 of the patent application scope, wherein in the step of the heat treatment, the first thermoplastic resin film is at a temperature Heat treatment in an environment above 50°C and relative humidity below 50%. The manufacturing method as described in item 1 of the patent application range, wherein in the step of the humidification process, the first thermoplastic resin film is subjected to a humidification process in an environment with a temperature of 40° C. or more and a relative humidity of 60% or more. The manufacturing method according to item 1 of the patent application range, wherein at least one of the first thermoplastic resin film and the second thermoplastic resin film is laminated on the polarizing film via an adhesive layer. The manufacturing method as described in item 1 of the patent application range, wherein the thickness of the first thermoplastic resin film is 40 μm or less, and the thickness of the second thermoplastic resin film is 40 μm or less. The manufacturing method as described in item 1 of the patent application range, wherein the thickness of the polarizing film is 15 μm or less.

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