KR102473609B1 - Method for manufacturing laminated polarizing plate and method for manufacturing polarizing plate - Google Patents

Abstract

On the polarizer layer of the light-polarizing laminated film provided with a polarizer layer on at least one side of the base film, a protective film with a moisture-proof film provided with a moisture-proof film on one side of the protective film through an adhesive layer, A method for producing a laminated polarizing plate is provided, including a step of bonding on the protective film side, and wherein the moisture barrier film has a moisture permeability of 500 g/m ² /24 hr or less at a temperature of 40° C. and a relative humidity of 90%.

Description

Manufacturing method of laminated polarizing plate and manufacturing method of polarizing plate

The present invention relates to a method for manufacturing a laminated polarizing plate and a method for manufacturing a polarizing plate.

BACKGROUND OF THE INVENTION [0002] Polarizing plates are widely used in display devices such as liquid crystal display devices, especially in recent years flat screen televisions and various mobile devices. As a polarizing plate, the thing of the structure which bonded the protective film to one side or both surfaces of a polarizer using an adhesive is common.

The polarizing plate can be manufactured by a method of bonding a protective film to a polarizer (polarizing film) made of a single film (single film) through an adhesive layer (hereinafter also referred to as "single film method"), and can be applied to coating (application) a step of forming a resin layer on a base film by; Process of obtaining a light-polarizing laminated film by making this resin layer into a polarizer layer through extending|stretching and dyeing; bonding a protective film on the polarizer layer of the polarizing laminated film through an adhesive layer; It can manufacture also by the method (henceforth a "coating method") including the process of peeling and removing a base film after bonding a protective film. The latter method is advantageous in terms of excellent handling properties of the film during the process and easy obtaining of a thin film polarizer layer.

Japanese Unexamined Patent Publication No. 2009-098653 and Japanese Unexamined Patent Publication No. 2009-093074 describe manufacturing a polarizing plate by a method similar to the coating method.

[0003] With the popularization of flat-screen televisions and mobile devices, the demand for thinning polarizers has recently increased. However, when the polarizing plate is thin, there is a problem that curling is likely to occur. If unsuitable Curl|Karl has arisen in a polarizing plate, when bonding a polarizing plate to display cells, such as a liquid crystal cell, and setting it as a display device with an adhesive layer, it is easy to mix air bubbles. If such air bubbles are present in a display device such as a liquid crystal display device, light scattering occurs due to the air bubbles when turned on, and light leakage in a black display state (bubbles become bright spots) may cause display problems.

Japanese Unexamined Patent Publication No. 2009-098653 and Japanese Unexamined Patent Publication No. 2009-093074 describe that curling of a polarizing plate can be suppressed according to a method similar to the coating method described above. However, the polarizing plate with suppressed curl as described in these documents is a polarizing plate used as a protective film for the polarizer layer as it is without peeling and removing the base film in the coating method described above, and obtained by peeling and removing the base film and protecting the polarizer layer. No mention is made of the curling of the polarizing plate made of the film.

An object of the present invention is a method for manufacturing a laminated polarizing plate by bonding a protective film on a polarizer layer of a polarizing laminated film, and manufacturing a laminated polarizing plate capable of suppressing curling of a polarizing plate obtained by peeling and removing a base film from the laminated polarizing plate. To provide a method, and to provide a manufacturing method of a polarizing plate with curl suppressed.

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

[1] A protective film with moisture-proof film provided with a moisture-proof film on one side of a protective film via an adhesive layer on the polarizer layer of a light-polarizing laminated film provided with a polarizer layer on at least one side of a base film. is provided with a step of bonding on the protective film side,

The moisture-proof film has a water vapor transmission rate of 500 g / m ² / 24 h or less at a temperature of 40 ° C. and a relative humidity of 90%.

[2] The method for producing a laminated polarizing plate according to [1], wherein the adhesive layer is made of a water-based adhesive.

[3] The polarizing laminated film,

A step of forming a polyvinyl alcohol-based resin layer by coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film and then drying it to obtain a laminated film;

A step of stretching the laminated film to obtain a stretched film;

Step of obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form the polarizer layer

The method for producing a laminated polarizing plate according to [1] or [2], which is manufactured by a method including.

[4] The method for producing a laminated polarizing plate according to any one of [1] to [3], wherein the protective film is made of a cellulose ester-based resin or a (meth)acrylic-based resin.

[5] The ratio of the moisture permeability of the base film at a temperature of 40 ° C. and a relative humidity of 90% to the moisture permeability of the moisture-proof film at a temperature of 40 ° C. and a relative humidity of 90% is 0.01 to 150, the laminated polarizing plate according to [4] manufacturing method.

[6] The method for producing a laminated polarizing plate according to any one of [1] to [5], wherein the polarizer layer has a thickness of 10 µm or less.

In addition, the present invention provides a method for manufacturing the following polarizing plate.

[7] a step of obtaining a laminated polarizing plate by the method for manufacturing a laminated polarizing plate according to any one of [1] to [6];

Step of peeling and removing the base film and the moisture-proof film from the laminated polarizing plate

A method of manufacturing a polarizing plate comprising a.

According to the present invention, as a method for manufacturing a laminated polarizing plate by bonding a protective film on a polarizer layer of a polarizing laminated film, a method for manufacturing a laminated polarizing plate capable of suppressing curling of a polarizing plate obtained by peeling and removing a base film from the laminated polarizing plate. It is possible to provide, and a method for manufacturing a polarizing plate in which curl is suppressed.

1 is a flowchart showing a preferable example of a method for producing a light-polarizing laminated film.
2 is a flow chart showing a preferred example of a method for producing a polarizing plate according to the present invention.
Fig. 3 is a flow chart showing another preferred example of a method for producing a polarizing plate according to the present invention.
Fig. 4 is a schematic cross-sectional view showing an example of the layer structure of the laminated film obtained in the resin layer forming step.
Fig. 5 is a schematic cross-sectional view showing an example of the layer configuration of a stretched film obtained in the stretching step.
Fig. 6 is a schematic cross-sectional view showing an example of the layer structure of the light-polarizing laminated film obtained in the dyeing step.
Fig. 7 is a schematic sectional view showing an example of the layer configuration of a protective film with a moisture barrier film.
8 is a schematic cross-sectional view showing an example of the layer structure of the laminated polarizing plate obtained in the first protective film bonding step.
9 : is a figure explaining suppression of curl of the polarizing plate concerning this invention.
Fig. 10 is a schematic cross-sectional view showing the layer structure of a polarizing plate with a single-sided protective film obtained in a peeling step.
Fig. 11 is a schematic cross-sectional view showing the layer configuration of a polarizing plate with double-sided protective films obtained in the second protective film bonding step.

[1] Manufacturing method of laminated polarizing plate

A method for manufacturing a laminated polarizing plate is a moisture barrier comprising a moisture-proof film on one side of a protective film via an adhesive layer on a polarizer layer of a light-polarizing laminated film having a polarizer layer on at least one side of a base film. A process of bonding the protective film with a film on the protective film side (hereinafter also referred to as "first protective film bonding process (S10)") is provided.

Also, as shown in Fig. 1, the polarizing laminated film is preferably processed in the following steps, like the coating method described above:

[a] Resin layer formation step of obtaining a laminated film by coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film and then drying it to form a polyvinyl alcohol-based resin layer (S1-1 ),

[b] a stretching step (S1-2) of stretching the laminated film to obtain a stretched film;

[c] Dyeing step of obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer (S1-3)

It is prepared by a method including.

By the above manufacturing method, the laminated polarizing plate provided with the base film, the polarizer layer, the protective film, and the moisture proof film in the above-mentioned order is obtained.

The "light-polarizing laminated film" in the present invention includes a base film and a polarizer layer laminated on at least one surface thereof, and is not bonded with a protective film. A film formed by bonding a protective film with a moisture proof film to a polarizer layer in the first protective film bonding step (S10) (having a base film) is referred to as a "laminated polarizing plate" in this specification. In addition, in this specification, a "polarizing plate" is composed of a polarizer layer and a protective film laminated on at least one surface thereof via an adhesive layer (ie, a polarizing plate with a single-sided protective film or a polarizing plate with a double-sided protective film), and , It does not have the base film contained in the light-polarizing laminated film which is the precursor.

Hereinafter, each process is explained in detail. Further, in the resin layer forming step (S1-1), the polyvinyl alcohol-based resin layer may be formed on both sides of the base film, but the case where it is mainly formed on one side will be described below.

<First protective film bonding step (S10)>

As described above, the polarizing laminated film preferably includes [a] a resin layer forming step (S1-1), [b] a stretching step (S1-2), and [c] a dyeing step (S1-3). It is prepared by the method of

[a] Resin layer formation step (S1-1)

Referring to FIG. 4 , this step is a step of obtaining the laminated film 100 by forming the polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 . This polyvinyl alcohol-based resin layer 6 is a layer used as the polarizer layer 5 through the stretching step (S1-2) and the dyeing step (S1-3). The polyvinyl alcohol-based resin layer 6 can be formed by coating a coating solution containing the polyvinyl alcohol-based resin on one or both surfaces of the base film 30 and drying the coated layer.

(substrate film)

The base film 30 can be composed of a thermoplastic resin, and among these, it is preferable to be composed of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include, for example, polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (norbornene-based resins and the like); polyester-based resin; (meth)acrylic resin; cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polycarbonate-based resin; polyvinyl alcohol-based resin; polyvinyl acetate-based resin; polyarylate-based resins; polystyrene-based resin; polyethersulfone-based resins; polysulfone-based resins; polyamide-based resin; polyimide-based resin; and mixtures and copolymers thereof. In this specification, "(meth)acryl" means at least one selected from acryl and methacryl. The same applies when referring to "(meth)acryloyl" or the like.

The base film 30 may have a single layer structure composed of one resin layer composed of one or two or more types of thermoplastic resins, or may have a multilayer structure in which a plurality of resin layers composed of one or two or more types of thermoplastic resins are laminated. The base film 30 can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 when the laminated film 100 is stretched in the stretching step (S1-2) described later. It is preferable to be composed of the same resin.

The base film 30 may contain additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the base film 30 is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight. to be.

The thickness of the base film 30 is usually 1 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, still more preferably 5 to 150 μm, from the viewpoint of workability such as strength and handleability. μm.

(coating liquid)

The coating liquid applied to the base film 30 is preferably a polyvinyl alcohol-based resin solution obtained by dissolving powder of the polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. Examples of derivatives of polyvinyl alcohol resins include polyvinyl formal and polyvinyl acetal, and other polyvinyl alcohol resins modified with olefins such as ethylene and propylene; those modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; What modified|denatured with the alkyl ester of unsaturated carboxylic acid; What modified|denatured with (meth)acrylamide, etc. are mentioned. The ratio of modification is preferably less than 30 mol%, and more preferably less than 10 mol%. When modification is performed in excess of 30 mol%, it becomes difficult to adsorb the dichroic dye, which may cause a problem in that polarization performance is lowered. Among the polyvinyl alcohol-based resins described above, it is preferable to use a polyvinyl alcohol resin.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10000, more preferably in the range of 1000 to 10000, still more preferably in the range of 1500 to 8000, and more preferably in the range of 2000 to 5000. It is most preferable to be in The average degree of polymerization can be obtained by the method specified in JIS K 6726-1994 "Polyvinyl Alcohol Test Method". If the average degree of polymerization is less than 100, it is difficult to obtain desirable polarization performance, and if it exceeds 10,000, solubility in solvents deteriorates, making it difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of polyvinyl acetate-based resin. The range of saponification degree is 80 mol% or more, Furthermore, it is 90 mol% or more, It is preferable that it is especially 94 mol% or more. When the degree of saponification is too low, there is a possibility that water resistance or heat and moisture resistance when used as a polarizing laminated film, a laminated polarizing plate, or a polarizing plate may not be sufficient. Further, it may be a completely saponified product (with a degree of saponification of 100 mol%), but if the degree of saponification is too high, the dyeing speed becomes slow, and the manufacturing time becomes long to impart sufficient polarization performance. There is a case where a polarizer layer having is not obtained. Therefore, the saponification degree is preferably 99.5 mol% or less, and further 99.0 mol% or less.

The degree of saponification refers to the rate at which the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, is changed to a hydroxyl group by saponification treatment in unit ratio (mol%), Eq.

Saponification degree (mol%) = [(number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetic acid groups)] × 100

is defined as 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 thus the lower the ratio of acetic acid groups that inhibit crystallization.

Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

Coating liquid may contain additives, such as a plasticizer and surfactant, as needed. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerol, ethylene glycol, propylene glycol, and polyethylene glycol. It is preferable that the blending amount of the additive is 20% by weight or less of the polyvinyl alcohol-based resin.

A method of coating the coating solution on the base film 30 may include a wire bar coating method; roll coating methods such as reverse coating and gravure coating; die coat method; comma coat method; lip coat method; spin coating method; screen coating method; fountain coating method; dipping method; It can select suitably from methods, such as a spray method.

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

(Polyvinyl alcohol-based resin layer)

The polyvinyl alcohol-based resin layer 6 may be formed on only one surface of the base film 30 or may be formed on both surfaces. If formed on both sides, since two polarizing plates can be obtained from one polarizing laminated film 300, it is advantageous also in terms of production efficiency of polarizing plates.

It is preferable that it is 3-30 micrometers, and, as for the thickness of the polyvinyl alcohol-type resin layer 6 in the laminated|multilayer film 100, it is more preferable that it is 5-20 micrometers. If the polyvinyl alcohol-based resin layer 6 having a thickness within this range, through a stretching step (S1-2) and a dyeing step (S1-3) described later, the dyeability of the dichroic dye is good and the polarization performance is excellent, , and a polarizer layer 5 that is also sufficiently thin (e.g., less than 10 μm in thickness) can be obtained. If the thickness of the polyvinyl alcohol-based resin layer 6 is less than 3 μm, it tends to become too thin after stretching and the dyeability deteriorates.

Prior to coating of the coating solution, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, at least the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed. Corona treatment, plasma treatment, flame treatment, etc. may be performed on the surface.

(primer layer)

In addition, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6 prior to coating of the coating solution, the polyvinyl alcohol-based resin layer is interposed on the base film 30 through a primer layer or the like. (6) may be formed.

A primer layer can be formed by coating the coating liquid for primer layer formation on the surface of the base film 30, and then drying it. The coating liquid for forming a primer layer contains a component that exhibits strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6 to some extent. The coating liquid for forming a primer layer usually contains a resin component and a solvent for imparting such adhesion. As the resin component, a thermoplastic resin having excellent transparency, thermal stability, stretchability and the like is preferably used, and examples thereof include (meth)acrylic resins and polyvinyl alcohol resins. Among them, a polyvinyl alcohol-based resin that imparts good adhesion is preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution using water as the solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming the primer layer. An appropriate crosslinking agent is appropriately selected from known ones such as organic type and inorganic type according to the type of thermoplastic resin to be used. Examples of the crosslinking agent include, for example, epoxy-based, isocyanate-based, dialdehyde-based, metal-based (eg, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking agents. In the case of using a polyvinyl alcohol-based resin as the resin component forming the primer layer, a polyamide epoxy resin, a methylolized melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, and the like are suitably used.

The thickness of the primer layer is preferably about 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. If it is thinner than 0.05 μm, the effect of improving the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6 is small, and if it is thicker than 1 μm, it is disadvantageous to thinning the polarizing plate.

A method of applying the coating solution for forming the primer layer to the base film 30 may be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The primer layer is coated on the surface on which the coating solution for forming the polyvinyl alcohol-based resin layer is coated. The drying temperature of the coating layer composed of the coating solution for forming the primer layer is, for example, 50 to 200°C, preferably 60 to 150°C. When the solvent contains water, the drying temperature is preferably 80°C or higher.

[b] Stretching process (S1-2)

Referring to FIG. 5, in this step, the laminated film 100 composed of the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched, and the stretched base film 30' and the polyvinyl alcohol-based resin layer are stretched. It is a process of obtaining the stretched film 200 which consists of (6'). The stretching treatment is usually uniaxial stretching.

The draw ratio of the laminated film 100 can be appropriately selected depending on the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times and 8 times the original length of the laminated film 100. less than twice If the draw ratio is 5 times or less, the polarization degree of the polarizer layer 5 may not be sufficiently high because the polyvinyl alcohol-based resin layer 6' is not sufficiently oriented. On the other hand, when the draw ratio exceeds 17 times, breakage of the film tends to occur during stretching, and at the same time, the thickness of the stretched film 200 becomes thinner than necessary, and there is a concern that workability and handling properties in the subsequent process may deteriorate. have.

The stretching treatment is not limited to stretching in one stage, and may be performed in multiple stages. In this case, all of the multi-step stretching treatment may be performed continuously before the dyeing step (S1-3), and the stretching treatment after the second step is combined with the dyeing treatment and/or the crosslinking treatment in the dyeing step (S1-3). may be done at the same time. When performing the stretching treatment in multiple stages in this way, it is preferable to perform the stretching treatment so as to achieve a draw ratio of more than 5 times in total of the previous stages of the stretching treatment.

The stretching treatment may be longitudinal stretching in which the film is stretched in the film longitudinal direction (film transport direction), or transverse stretching or oblique stretching in which the film is stretched in the width direction. Examples of the longitudinal stretching method include inter-roll stretching using rolls, compression stretching, and stretching using a chuck (clip), and examples of the transverse stretching method include a tenter method. For the stretching treatment, either a wet stretching method or a dry stretching method can be employed, but a dry stretching method is preferred because the stretching temperature can be selected from a wide range.

The stretching temperature is set to a temperature equal to or higher than a temperature exhibiting fluidity to the extent that the entire polyvinyl alcohol-based resin layer 6 and the base film 30 can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base film 30. ) in the range of -30°C to +30°C, more preferably in the range of -30°C to +5°C, and still more preferably in the range of -25°C to +0°C. When the base film 30 is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

If the stretching temperature is lower than -30°C of the phase transition temperature, it is difficult to achieve a high-magnification stretching of more than 5 times, or the flowability of the base film 30 tends to be too low, making the stretching process difficult. When the stretching temperature exceeds +30°C of the phase transition temperature, the fluidity of the base film 30 is too large, and stretching tends to be difficult. From the viewpoint of more easily achieving a high draw ratio of more than 5 times, the stretching temperature is within the above range, and is more preferably 120°C or higher.

Methods for heating the laminated film 100 in the stretching treatment include a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature by blowing hot air); In the case of stretching using a roll, a method of heating the roll itself; There is a heater heating method (a method of installing an infrared heater, a halogen heater, a panel heater, or the like above and below the laminated film 100 to heat with radiant heat) and the like. In the roll-to-roll stretching method, the zone heating method is preferred from the viewpoint of uniformity of the stretching temperature.

Prior to the stretching step (S1-2), a preheating treatment step of preheating the laminated film 100 may be provided. As the preheating method, the same method as the heating method in the stretching treatment can be used. The preheating temperature is preferably in the range of -50°C to ±0°C of the stretching temperature, and more preferably in the range of -40°C to -10°C of the stretching temperature.

Further, after the stretching treatment in the stretching step (S1-2), a heat setting treatment step may be provided. The heat setting treatment is a treatment in which heat treatment is performed at a crystallization temperature or higher while maintaining a tensioned state in a state where the end portion of the stretched film 200 is held by a clip. Crystallization of the polyvinyl alcohol-based resin layer 6' is promoted by this heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0°C to -80°C of the stretching temperature, and more preferably in the range of -0°C to -50°C of the stretching temperature.

[c] Dyeing process (S1-3)

Referring to FIG. 6 , this process is a process of dyeing the polyvinyl alcohol-based resin layer 6' of the stretched film 200 with a dichroic dye, adsorbing and orienting this, and forming the polarizer layer 5. Through this process, the polarizing laminated film 300 in which the polarizer layer 5 is laminated on one or both surfaces of the base film 30' is obtained. As the dichroic dye, iodine or a dichroic organic dye can be used specifically.

The dyeing step can be performed by immersing the entire stretched film 200 in a solution containing a dichroic dye (dyeing solution). As the dyeing solution, a solution obtained by dissolving the dichroic dye in a solvent can be used. Although water is generally used as a solvent for the dyeing solution, an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, still more preferably 0.025 to 5% by weight.

When using iodine as a dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine from the viewpoint of further improving the dyeing efficiency. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, in terms of weight ratio, 1: It is more preferable that it exists in the range of 7-1:70. The temperature of the dyeing solution is preferably in the range of 10 to 60°C, and more preferably in the range of 20 to 40°C.

It is also possible to carry out the dyeing step (S1-3) before the stretching step (S1-2) or to perform these steps simultaneously, but it is possible to properly orient the dichroic dye adsorbed to the polyvinyl alcohol-based resin layer. It is preferable to carry out the dyeing process (S1-3) after performing at least a certain degree of stretching treatment with respect to the laminated film 100 so that it can be made. That is, the stretched film 200 obtained by performing the stretching treatment until reaching the target magnification in the stretching step (S1-2) can be used in the dyeing step (S1-3), and the stretching step (S1-2) After performing the stretching treatment at a magnification lower than the target in ), the stretching treatment may be performed until the total draw ratio reaches the target magnification during the dyeing step (S1-3). As the latter embodiment, 1) After performing the stretching treatment at a magnification lower than the target in the stretching step (S1-2), the total draw ratio is the target magnification during the dyeing treatment in the dyeing step (S1-3). As will be described in the aspect of performing the stretching treatment, or in the case of performing the crosslinking treatment after the dyeing treatment as described later, 2) after performing the stretching treatment at a magnification lower than the target in the stretching step (S1-2), the dyeing step (S1-3 During the dyeing treatment in), the stretching treatment is performed to the extent that the total draw ratio does not reach the target magnification, and then the stretching treatment is performed during the crosslinking treatment so that the final total draw ratio becomes the target magnification. can

The dyeing step (S1-3) may include a crosslinking treatment step performed following the dyeing treatment. The crosslinking treatment can be performed by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, conventionally known substances can be used, and examples thereof include boric acid, boron compounds such as borax, glyoxal, glutaraldehyde, and the like. A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

The crosslinking solution may specifically be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, and more preferably in the range of 6 to 15% by weight.

The crosslinking solution may contain iodide. By adding iodide, polarization performance within the surface of the polarizer layer 5 can be more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably in the range of 10 to 90°C.

The crosslinking treatment may be performed simultaneously with the dyeing treatment by blending a crosslinking agent into the dyeing solution. Further, stretching treatment may be performed during the crosslinking treatment. The specific aspect of performing the stretching treatment during the crosslinking treatment is as described above. Moreover, you may perform the process of immersing in crosslinking solution twice or more using two or more types of crosslinking solutions with different compositions.

After the dyeing step (S1-3), it is preferable to perform a washing step and a drying step before bonding the first protective film. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after dyeing treatment or crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50°C, preferably 4 to 20°C. The washing process may be a combination of a water washing process and a washing process using an iodide solution.

As the drying step performed after the washing step, any suitable method such as natural drying, blow drying, heat drying, or the like can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95°C.

The thickness of the polarizer layer 5 of the polarizing laminated film 300 may be, for example, 30 μm or less, or even 20 μm or less, but from the viewpoint of thinning the polarizing plate, it is preferably 10 μm or less, and more preferably 8 μm or less. . The thickness of the polarizer layer 5 is 2 micrometers or more normally.

In this step, with reference to FIGS. 7 and 8 , a moisture proof film 35 is provided on one side of the first protective film 10 on the polarizer layer 5 of the polarizing laminated film 300. A protective film 400 with a moisture-proof film to be described is bonded from the protective film side to obtain a laminated polarizing plate 500. The moisture barrier film 35 has a moisture permeability of 500 g/m ² /24 h or less at a temperature of 40° C. and a relative humidity of 90%. Water vapor permeability is a value measured by the cup method specified in JIS Z 0208.

The laminated polarizing plate obtained by bonding the first protective film 10 provided with the moisture-proof film 35 having a predetermined moisture permeability as described above to the polarizer layer 5 of the polarizing laminated film 300 is The moisture content of the protective film can be maintained, and curling of the polarizing plate manufactured by peeling and removing the base film 30 ′ and the moisture barrier film 35 from the laminated polarizing plate can be effectively suppressed.

Here, a description is added regarding the curl of the polarizing plate and the curl suppressing effect of the present invention. Curl is a phenomenon in which a film (including a laminated film) such as a polarizing plate is curved in an arc shape (or in a remarkable case, in a cylindrical shape). When it comes to a polarizing plate with a single-sided protective film obtained by bonding the first protective film 10 to one side of the polarizer layer 5 via the adhesive layer 15, curling the first protective film 10 side inside The state in which this has arisen is called regular curl, and the state in which curl has arisen with the polarizer layer 5 side turned inside is called reverse curl.

Curl becomes a problem in a polarizing plate when it bonds a polarizing plate to display cells, such as a liquid crystal cell, through an adhesive layer, and curling occurs in the polarizing plate. That is, since the polarizing plate is usually made into a composite polarizing plate by bonding other peripheral members such as various films and layers at the time of bonding to a display cell such as a liquid crystal cell, it is important to suppress curl in this composite polarizing plate. As the peripheral member, a protection film for preventing scratches bonded on a protective film; an adhesive layer for bonding a polarizing plate to a display cell or other optical member, laminated on a protective film (eg, in the case of a polarizing plate with a double-sided protective film) or on a polarizer layer (eg, in the case of a polarizing plate with a single-sided protective film); A separate film laminated on the outer surface of the pressure-sensitive adhesive layer; An optical compensation film such as a retardation film laminated on a protective film (eg, in the case of a polarizing plate with a double-sided protective film) or on a polarizer layer (eg, in the case of a polarizing plate with a single-sided protective film), and other optical functional films; and a surface treatment layer laminated on a protective film.

The composite polarizing plate is best when it is flat without curl or slightly curled with the pressure-sensitive adhesive layer side of the composite polarizing plate facing outward (convex). Accordingly, when the composite polarizing plate is bonded to the display cell, it is possible to suppress air bubbles from being mixed between the pressure-sensitive adhesive layer and the display cell, causing display problems in the display device or defects at the end of the bonding surface. can cause or suppress it. Conversely, when the composite polarizing plate is curled with the pressure-sensitive adhesive layer side inside (concave), air bubbles are likely to be mixed during bonding, and the above problem is likely to occur.

When bonding the peripheral member, it is possible to intentionally suppress the curling amount of the composite polarizing plate or correct the curling direction to some extent. It is difficult to control the curl of the composite polarizer unless the curl is small. Therefore, it is important to suppress curl of the polarizing plate itself formed by bonding a protective film to at least one side of the polarizer layer.

That is, the curl of a polarizing plate formed by bonding a protective film to at least one surface of the polarizer layer is preferably small to the extent that can be corrected by bonding of peripheral members regardless of whether it is regular curl or reverse curl, and it is preferably as flat as possible. more preferable According to the present invention, this can be realized. In particular, in the conventional coating method, when the base film is peeled off after bonding the protective film to the polarizer layer, the obtained polarizing plate tends to greatly curl in the reverse curl direction, but according to the present invention, this reverse curl is particularly effectively suppressed. can do.

It is thought that the reason why reverse curling easily occurs in the conventional coating method is because the restraining force by the base film acts. In the light-polarizing laminated film formed by the coating method, the polarizer layer is in a state in which it is not shrunk due to the rigidity of the base film, and it is considered that shrinkage occurs in the polarizer layer when the base film is peeled off after bonding the protective film. . On the other hand, in the case of a single film method in which a protective film is bonded to a polarizer (polarizing film) made of a single (single) film through an adhesive layer, the polarizer is sufficiently bonded by moisture evaporation, drying, tension control, etc. before bonding the protective film. Since it is shrunk, a dimensional change does not occur so much in a polarizer even after bonding a protective film, and the problem of curling is hard to occur in the first place.

The laminated polarizing plate obtained by bonding a protective film in which a moisture-proof film having a moisture permeability of 500 g/m ² /24 hr or less is laminated to the polarizer layer through an adhesive on the opposite side of the protective film to the surface bonded to the polarizer layer is the laminated polarizing plate It is estimated that the reverse curl of the polarizing plate manufactured by peeling and removing the base film and the moisture-proof film can be effectively suppressed for the following reason.

Even when the first protective film 10 on which the moisture-proof film 35 is laminated is bonded and dried through the polarizer layer 5 and the adhesive layer 15, moisture does not escape easily from the first protective film 10. Therefore, the first protective film 10 can retain moisture, and shrinkage is suppressed. On the other hand, since the polarizer layer 5 is also constrained by the base film 30', shrinkage is suppressed.

As shown in FIG. 9 , when the base film 30' is removed from the stacked polarizing plate 500, the polarizer layer 5 is freed from restraint by the base film 30', and the polarizer layer 5 is, for example, , shrinks in the direction of arrow b, resulting in reverse curl. On the other hand, when the moisture barrier film 35 is removed from the stacked polarizing plate 500, the first protective film 10 is released from the restraint by the moisture barrier film 35, and the first protective film 10 is, for example, indicated by arrow a. By contracting in the direction, the force of the junk is generated. In this way, in the polarizing plate 1 manufactured by removing the base film 30' and the moisture barrier film 35 from the laminated polarizing plate 500, since the force of the reverse curl suppressing the reverse curl acts, the entire polarizing plate 1 As , it is guessed that curl is suppressed.

From the viewpoint of maintaining the balance of the curling force acting on the polarizing plate, the moisture permeability of the base film 30' at a temperature of 40°C and a relative humidity of 90% relative to the moisture permeability of the moisture-proof film 35 at a temperature of 40°C and a relative humidity of 90%. The ratio of is preferably 0.01 to 150, and more preferably 0.03 to 150, for example, when the protective film 10 is made of a cellulose ester-based resin or a (meth)acrylic-based resin. By selecting such a moisture-proof film 35, base film 30', and protective film 10, curl is controlled more remarkably. Since it is easy to make the ratio of moisture permeability within the above range, the moisture permeability of the base film 30 ′ (and the base film 30) at a temperature of 40° C. and a relative humidity of 90% is 0 to 100 g/m ² /24 It is preferably hr, and more preferably 0 to 50 g/m ² /24 hr.

(moisture-proof film)

The moisture proof film 35 is a peelable film and is a member for maintaining the moisture content of the protective film 10 or protecting the surface from damage, abrasion, or the like. The moisture-proof film 35 is constituted by, for example, a base film made of transparent resin and a pressure-sensitive adhesive layer having weak adhesiveness laminated on the surface of the base film. The moisture proof film 35 is bonded to the protective film 10 until the time of use of the polarizing plate, and at the time of use, the adhesive layer is peeled off from the protective film 10.

As the moisture-proof film 35, for example, a protective film for temporarily attaching and protecting the surface of the protective film of the polarizing plate can be used. The protection film can be easily obtained as a commercial item. Examples of commercially available products include "Mastag" sold by Fujimori Kogyo Co., Ltd., "Sanitec" sold by Sun-A Kaken Co., Ltd., "E-Mask" sold by Nitto Denko Co., Ltd., Toray There is "Doretech" sold by Film Processing Co., Ltd. and the like.

When the water vapor transmission rate of the moisture proof film 35 is too low, the Curl|Karl in the regular curl direction will become strong, and it will become easy to raise the problem of air bubble mixing. In addition, when placed under a harsh environment, there is a possibility that the end of the polarizing plate may be peeled off from the display cell due to further promotion of junk curl. For this reason, the water vapor transmission rate of the moisture proof film 35 at a temperature of 40°C and a relative humidity of 90% is preferably 5 g/m ² /24 h or more, and more preferably 10 g/m ² /24 h or more.

As for the thickness of the moisture proof film 35, 1 micrometer or more and 100 micrometers or less are preferable. From the viewpoint of thinning, 1 μm or more and 80 μm or less are more preferable. When the thickness of the moisture proof film 35 exceeds 100 μm, it is disadvantageous in terms of cost, roll transportability, and reworkability of the moisture proof film 35 .

The base film constituting the moisture-proof film 35 is made of, for example, a thermoplastic resin excellent in mechanical strength, thermal stability, and the like. Suitable resin can be selected for the thermoplastic resin used for the moisture proof film 35 according to moisture permeability. Specific examples include polyolefin-based resins, polyester-based resins, cyclic polyolefin-based resins (norbornene-based resins), (meth)acrylic-based resins, cellulose ester-based resins, polycarbonate-based resins, polyvinyl alcohol-based resins, and vinyl acetate. based resins, polyarylate-based resins, polystyrene-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, and mixtures and copolymers thereof. Among them, polyester-based resins are preferably used from the strength of elasticity.

Polyester-based resin is a polymer having an ester bond, and is mainly a polycondensate of a polyhydric carboxylic acid and a polyhydric alcohol. As the polyhydric carboxylic acid used, divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylic acid. In addition, as for the polyhydric alcohol used, dihydric diol is mainly used, and propanediol, butanediol, neopentylglycol, cyclohexane dimethanol, etc. are mentioned. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, and the like. can be heard Mixtures and copolymers thereof can also be suitably used.

The base film may have a single layer structure or a multilayer structure. For example, even when using a resin film having a relatively high moisture permeability, the moisture vapor transmission rate of the moisture proof film 35 can be adjusted within the above range by laminating a film or layer having low moisture permeability thereon. The base film is preferably a single-layer structure from the viewpoints of ease of manufacture and manufacturing cost.

Moreover, you may adjust the water vapor transmission rate of the moisture proof film 35 within the said range by enlarging the thickness of a base film. The thickness of the base film may be 1 μm or more and 90 μm or less, and the moisture barrier film 35 may have a thickness of 1 μm or more and 100 μm or less.

The pressure-sensitive adhesive layer constituting the moisture-proof film 35 is a pressure-sensitive adhesive obtained by adding a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound to which a base polymer is a (meth)acrylic resin, a styrene resin, or a silicone resin. composition can be used. Further, the moisture permeability of the moisture-proof film 35 can be adjusted within the above range by increasing the thickness of the pressure-sensitive adhesive layer or by making the pressure-sensitive adhesive layer contain hygroscopic substances (such as hygroscopic particles). You may adjust the water vapor transmission rate of the moisture proof film 35 within the said range by combining multiple methods mentioned above.

The moisture proof film 35 may be uniaxially stretched or biaxially stretched. Desired strength can be imparted by stretching. Stretching is usually performed continuously while unwinding the film roll, and the film is stretched in a heating furnace in the traveling direction of the roll, in the direction perpendicular to the traveling direction, or both.

(First protective film)

The material constituting the first protective film 10 is preferably a light-transmitting (preferably optically transparent) thermoplastic resin, and examples of such a resin include chain polyolefin-based resins (such as polypropylene-based resins), polyolefin-based resins such as cyclic polyolefin-based resins (norbornene-based resins and the like); cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polyester-based resin; polycarbonate-based resin; (meth)acrylic resin; polystyrene-based resin; or mixtures and copolymers thereof.

Since the method of this invention aims at suppression of curl by using the protective film 400 with a moisture barrier film provided with the moisture barrier film 35 which has a predetermined|prescribed moisture permeability, irrespective of the kind of protective film, the polarizing plate obtained is obtained. There is an advantage that the curl of the can be suppressed. Among them, a protective film with high moisture permeability such as a cellulose ester-based resin (eg, cellulose triacetate) or a (meth)acrylic-based resin (eg, polymethyl methacrylate resin) (eg, at a temperature of 40 ° C. and a relative humidity of 90%) When a protective film having a water vapor transmission rate of 30 g/m ² /24 hr or more, and furthermore 50 g/m ² /24 hr or more) is used, the effect of suppressing reverse curl is remarkable because the dimensional difference due to the change in moisture content is large.

The first protective film 10 may also be a protective film having an optical function such as a retardation film or a brightness enhancing film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching the film made of the thermoplastic resin (eg, uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, as well as copolymers composed of two or more types of chain olefins.

Cyclic polyolefin resin is a generic term for resins polymerized using cyclic olefins as polymerization units. Specific examples of cyclic polyolefin-based 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 (typically random copolymers). ), graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

Cellulose ester-type resin is an ester of a cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Copolymers of these or those in which a part of hydroxyl groups are modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

The polyester-based resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyhydric carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyhydric carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof may be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylic acid. As the polyhydric alcohol, dihydric diols can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane. Contains dimethylnaphthalate.

A polycarbonate-type resin consists of a polymer to which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate obtained by modifying a polymer skeleton, a copolymerized polycarbonate, or the like.

A (meth)acrylic resin is a resin that uses a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid esters such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth)acrylic acid ester copolymer; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymers (such as MS resin); and copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, a polymer containing poly(meth)acrylic acid C _1-6 alkyl ester as a main component such as poly(meth)acrylate is used, more preferably, methyl methacrylate as a main component (50 to 100% by weight, Preferably 70 to 100% by weight) of methyl methacrylate-based resin is used.

In addition, the description about each thermoplastic resin shown above is applicable also about the thermoplastic resin which comprises the base film 30.

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

The thickness of the first protective film 10 is preferably thin from the viewpoint of reducing the thickness of the polarizing plate, but when it is too thin, the strength is reduced and workability is poor. Therefore, the thickness of the first protective film 10 is preferably 5 to 90 μm or less, more preferably 5 to 60 μm, still more preferably 5 to 50 μm.

The first protective film 10 is placed on the polarizer layer 5 of the polarizing laminated film 300 through the adhesive layer 15 (the surface of the polarizer layer 5 on the opposite side to the base film 30'). are stacked on When the polarizing laminated film 300 has the polarizer layers 5 on both sides of the base film 30', protective films are usually bonded on the polarizer layers 5 on both sides. In this case, these protective films may be the same type of protective film or a different type of protective film.

In bonding the first protective film 10 on the polarizer layer 5, the bonding surface of the first protective film 10 is subjected to plasma treatment or corona treatment in order to improve adhesiveness with the polarizer layer 5. , surface treatment (adhesion-facilitating treatment) such as ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment can be performed, and among these, plasma treatment, corona treatment, or saponification treatment is preferably performed. For example, when the first protective film 10 is made of cyclic polyolefin-based resin, plasma treatment or corona treatment is usually performed. In addition, when it consists of cellulose ester-type resin, a saponification process is performed normally. As the saponification treatment, a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide is exemplified.

(glue)

As the adhesive used for bonding, a water-based adhesive or a photocurable adhesive can be used. Among them, water-based adhesives are preferably used from the viewpoint of thinning the adhesive layer. Examples of the water-based adhesive include adhesives made of a polyvinyl alcohol-based resin aqueous solution, water-based two-component urethane emulsion adhesives, and the like. In particular, when a cellulose ester-based resin film subjected to surface treatment (hydrophilization treatment) by saponification treatment or the like is used as the first protective film 10, it is preferable to use a water-based adhesive made of a polyvinyl alcohol-based resin aqueous solution.

Examples of the polyvinyl alcohol-based resin include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and (meth)acrylamides having an ammonium group. The polyvinyl alcohol-based resin used in the adhesive preferably has an appropriate degree of polymerization, and for example, when used as an aqueous solution at a concentration of 4% by weight, the viscosity is within the range of 4 to 50 mPa sec, and further 6 to 30 mPa. It is more preferable to be within the range of sec.

Further, a modified polyvinyl alcohol-based resin can also be preferably used. Suitable modified polyvinyl alcohol-based resins include acetoacetyl group-modified polyvinyl alcohol-based resins, anion-modified polyvinyl alcohol-based resins, and cation-modified polyvinyl alcohol-based resins. When such a modified polyvinyl alcohol-based resin is used, the effect of improving the water resistance of the adhesive layer is easily obtained.

The water-based adhesive used in the present invention may, of course, contain two or more of the above-mentioned modified polyvinyl alcohol-based resins, and may also contain an unmodified polyvinyl alcohol-based resin (specifically, completely or partially of polyvinyl acetate). saponified product) and the modified polyvinyl alcohol-based resin described above may be included.

The polyvinyl alcohol-based resin constituting the water-based adhesive can be appropriately selected from commercial products and used. Specifically, for example, "PVA-117H", "KL-318", "KM-118" and "CM-318" sold from Kuraray Co., Ltd., sold from Nippon Kose Chemical Industry Co., Ltd. "Gosenol NH-20", "Gosepima Z" series, "Gosepima K-210", and "Gosene T-330" (above, all trade names), etc. are mentioned.

A cross-linking agent may be incorporated into the water-based adhesive containing polyvinyl alcohol-based resin as a main component. Examples of compounds capable of serving as a crosslinking agent for each functional group include isocyanate compounds having at least two isocyanato groups (-NCO) in the molecule; Epoxy compounds having at least two epoxy groups (cross-linked -O-) in the molecule; mono- or di-aldehyde; organotitanium compounds; inorganic salts of divalent or trivalent metals such as magnesium, calcium, iron, nickel, zinc and aluminum; metal salts of glyoxylic acid; and methylol melamine.

Among these crosslinking agents, epoxy compounds such as the aforementioned water-soluble polyamide epoxy resins, aldehydes, methylol melamine, alkali metal or alkaline earth metal salts of glyoxylic acid, and the like are suitably used.

The crosslinking agent is preferably dissolved in water together with the polyvinyl alcohol-based resin to form an adhesive. However, since the amount of the crosslinking agent in the aqueous solution may be small as described below, any crosslinking agent having solubility in water of, for example, at least about 0.1% by weight can be used as the crosslinking agent. Of course, a compound having solubility in water to a level generally called water-soluble is more suitable as a crosslinking agent used in the present invention.

The blending amount of the crosslinking agent is appropriately designed according to the type of polyvinyl alcohol-based resin, but is usually about 5 to 60 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol-based resin. When a crosslinking agent is blended within this range, good adhesiveness is obtained. If the compounding amount of the crosslinking agent is too large, the reaction of the crosslinking agent proceeds in a short time, and the adhesive tends to gel at an early stage. As a result, the pot life is extremely short, making industrial use difficult.

The water-based adhesive may contain conventionally known appropriate additives such as, for example, a silane coupling agent, a plasticizer, an antistatic agent, and fine particles within a range that does not impair the effects of the present invention.

In the case of using a urethane resin as the main component of the water-based adhesive, examples of suitable adhesives include a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester ionomer type urethane resin referred to herein is a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced. Since such an ionomer type urethane resin emulsifies directly in water without using an emulsifier to form an emulsion, it is suitably used for water-based adhesives. The use of a polyester-based ionomer type urethane resin in the adhesive layer between the polarizer and the protective film is described, for example, in Japanese Patent Laid-Open No. 2005-070140, Japanese Patent No. 4432487, and Japanese Unexamined Patent Publication No. 2005-208456 has been

A water-based adhesive is applied to the bonding surfaces of the polarizer layer 5 of the polarizing laminated film 300 and/or the first protective film 10 of the protective film 400 with a moisture-proof film, and these films are bonded through the adhesive layer. And, preferably, the bonding step is performed by pressing and adhering using a bonding roll or the like. The coating method of the water-based adhesive (the same applies to the photocurable adhesive described later) is not particularly limited, and may include a casting method, a Mayer bar coating method, a gravure coating method, a comma coating method, a doctor blade method, a die coating method, a dip coating method, A conventionally known method such as a spray method can be used.

In the case of using a water-based adhesive, it is preferable to perform a drying step of drying the film in order to remove water contained in the water-based adhesive after performing the bonding described above. Drying can be performed, for example, by introducing a film into a drying furnace. Although the method of drying is arbitrary, for example, drying using a so-called hot air drying furnace in which hot air is blown, drying by an infrared heater, and the like are exemplified. It is also preferable to adjust the humidity in the drying oven in order to suppress a rapid decrease in moisture content and to perform drying in a mild manner. The drying temperature is, for example, 50 to 200°C, preferably 60 to 150°C. When the solvent contains water, the highest temperature during drying is preferably 80°C or higher.

After the drying step, a curing step of curing at room temperature or a temperature slightly higher than that, for example, at a temperature of about 20 to 45°C may be provided. Curing temperature is generally set lower than drying temperature.

A photocurable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, and includes, for example, one containing a polymerizable compound and a photopolymerization initiator, one containing a photoreactive resin, one containing a binder resin and a photoreactive crosslinking agent. things, etc. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth)acrylic monomers, and photocurable urethane monomers, and oligomers derived from photopolymerizable monomers. Examples of the photopolymerization initiator include substances that generate active species such as neutral radicals, anion radicals, and cation radicals when irradiated with active energy rays such as ultraviolet rays. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, one containing a photocurable epoxy-based monomer and a photocationic polymerization initiator can be preferably used.

In the case of using a photocurable adhesive, a curing step of curing the photocurable adhesive by performing the bonding described above, followed by a drying step if necessary (when the photocurable adhesive contains a solvent, etc.) and subsequently irradiating active energy rays. do The light source of the active energy ray is not particularly limited, but an active energy ray having a luminous distribution at a wavelength of 400 nm or less is preferable. Specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave Here, a mercury vapor lamp, a metal halide lamp, or the like is preferably used.

[2] Manufacturing method of polarizer

2 is a flowchart showing a preferred example of a method for manufacturing a polarizing plate according to an embodiment of the present invention. As shown in FIG. 2, the manufacturing method of a polarizing plate is the following process:

(1) a first protective film bonding step (S10) of obtaining a laminated polarizing plate by the above manufacturing method of the laminated polarizing plate;

(2) Peeling step (S20) of peeling and removing the base film and the moisture proof film from the laminated polarizing plate

to provide

By the above manufacturing method, the polarizing plate with a single-sided protective film in which the 1st protective film was bonded to one surface of the polarizer layer is obtained. As shown in Fig. 3, after the peeling step (S20), a second protective film bonding step (S30) of bonding the second protective film to the polarizer layer side surface of the polarizing plate with a single-sided protective film via an adhesive layer is formed, A polarizing plate with a protective film may be obtained.

In addition, as described above, the polarizing plate (polarizing plate obtained by the production method of the present invention) in the present invention is composed of a polarizer layer and a protective film laminated on at least one side thereof via an adhesive layer (ie, one side A polarizing plate with a protective film or a polarizing plate with a double-sided protective film), and it does not have the base film contained in the light-polarizing laminated film which is the precursor. However, the polarizing plate obtained by the production method of the present invention may be a composite polarizing plate obtained by laminating another optical member (peripheral member) such as another film or layer, or used as such a composite polarizing plate. The polarizer layer may be one in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin layer (or film) uniaxially stretched.

The first protective film bonding step (S10) in one embodiment of the present invention is the same as the protective film bonding step (S10) in the above-described method for manufacturing a laminated polarizing plate. Therefore, the peeling step (S20) and the second protective film bonding step (S30) will be described below.

<Separation step (S20)>

Referring to FIG. 10, this process is a process of peeling and removing the base film 30' after the 1st protective film bonding process (S10). In this process, the polarizing plate 1 with a single-sided protective film is obtained. When the polarizing laminated film 300 has the polarizer layer 5 on both sides of the base film 30' and the protective film is bonded to both polarizer layers 5, by this peeling step (S20) , From one sheet of polarizing laminated film 300, two polarizing plates 1 with single-sided protective films are obtained.

The method of peeling and removing the base film 30' is not particularly limited, and can be peeled by the same method as the separator (peeling film) peeling step performed with a normal polarizing plate with an adhesive. The base film 30' may be peeled immediately after the first protective film bonding step (S10), or may be wound up once in a roll shape after the first protective film bonding step (S10) and peeled while unwinding in a subsequent step. good night.

<Second Protective Film Bonding Step (S30)>

3 and 11, if this step of bonding the second protective film 20 to the surface of the polarizer layer 5 side of the polarizing plate 1 with a single-sided protective film via the adhesive layer 25 is performed, , the polarizing plate 2 with double-sided protective films can be obtained. Regarding the 2nd protective film 20 and the adhesive layer 25 which joins this, the technique described about the 1st protective film 10 and the adhesive layer 15 is cited. The first protective film 10 and the second protective film 20 may be protective films of the same type or different types of protective films. The adhesive layer 15 and the adhesive layer 25 may be formed of the same type of adhesive or of a different type of adhesive.

When the 2nd protective film 20 is a protective film with a moisture-proof film provided with a moisture-proof film on one side of the second protective film and bonded to the polarizer layer 5 via the adhesive layer 25, both sides protection There is a case where curling in the polarizing plate 2 with a film can be further improved.

As described above, the obtained polarizing plate 1 with a single-sided protective film and polarizing plate 2 with a double-sided protective film can be made into a composite polarizing plate by bonding peripheral members as illustrated above, or can be used as such a composite polarizing plate.

The pressure-sensitive adhesive layer, which is an example of the peripheral member, can be laminated on the outer surface of any protective film in the polarizing plate 2 with a double-sided protective film, and in the polarizing plate 1 with a single-sided protective film, for example, on the side opposite to the protective film of the polarizer layer. can be laminated on the surface of The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually made of a pressure-sensitive adhesive composition in which a (meth)acrylic resin, a styrene resin, a silicone resin, or the like is used as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. . Moreover, it can also be set as the adhesive layer which contains microparticles|fine-particles and shows light-scattering property. The thickness of the pressure-sensitive adhesive layer is usually 1 to 40 μm, preferably 3 to 25 μm.

In addition, as another example of the optical functional film of the peripheral member, a reflective polarizing film that transmits a certain type of polarized light and reflects polarized light exhibiting the opposite property; An anti-glare function imparting film having a concavo-convex shape on the surface; a surface anti-reflection function imparted film; a reflective film having a reflective function on its surface; a semi-transmissive reflective film having both a reflective function and a transmissive function; A viewing angle compensation film etc. are mentioned.

Example

Hereinafter, Examples and Comparative Examples are disclosed to explain the present invention more specifically, but the present invention is not limited by these examples.

[Example 1]

(1) Primer layer formation process

Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Kosei Chemical Industry Co., Ltd., average degree of polymerization 1100, degree of saponification 99.5 mol%) was dissolved in hot water at 95° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight did. A cross-linking agent ("Sumirase (registered trademark) Resin 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with the obtained aqueous solution in a ratio of 5 parts by weight to 6 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, as a base film, an unstretched polypropylene (PP) film having a thickness of 90 μm (melting point: 163 ° C., temperature 40 ° C., water vapor transmission rate at 90% relative humidity: 15 g / m ² /24 hr. The thickness after stretching is 50 μm, and the moisture permeability at a temperature of 40 ° C. and a relative humidity of 90% was 3 g / m ² /24 hr), corona treatment was performed on one side, and then a small diameter gravure coater was used on the corona treatment side A primer layer having a thickness of 0.2 μm was formed by coating the coating solution for forming the primer layer and drying it at 80° C. for 10 minutes. The water vapor transmission rate of the base film was measured by the cup method specified in JIS Z 0208 under conditions of 40°C and 90% relative humidity.

(2) Preparation of laminated film (resin layer formation process)

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

After coating the coating solution for forming the polyvinyl alcohol-based resin layer using a lip coater on the surface of the primer layer of the base film having the primer layer prepared in (1) above, by drying at 80 ° C. for 20 minutes, on the primer layer A polyvinyl alcohol-based resin layer was formed thereon to obtain a laminated film composed of a base film/primer layer/polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)

With respect to the laminated|multilayer film produced in said (2), 5.2-times free end uniaxial stretching was performed at 160 degreeC using the floating longitudinal uniaxial stretching apparatus, and the stretched film was obtained. The thickness of the polyvinyl alcohol-based resin layer after stretching was 5.0 µm.

(4) Preparation of polarizing laminated film (dyeing process)

The stretched film produced in (3) above was immersed in a 26°C dyeing solution containing iodine and potassium iodide (containing 0.35 parts by weight of iodine and 10.0 parts by weight of potassium iodide per 100 parts by weight of water) for about 90 seconds. Subsequently, it was immersed for 300 seconds in a 78°C crosslinking aqueous solution containing boric acid and potassium iodide (9.5 parts by weight of boric acid and 5.0 parts by weight of potassium iodide per 100 parts by weight of water). Thereafter, it was washed with pure water at 8°C for 10 seconds and finally dried at 65°C for 300 seconds. By the above process, the polarizer layer was formed from the polyvinyl alcohol-type resin layer, and the light-polarizing laminated film was obtained.

(5) Production of protective film with moisture-proof film

Protective film [transparent protective film made of triacetyl cellulose (TAC) (“KC-2UAW” manufactured by Konica Minolta Opto Co., Ltd.)], moisture permeability at a temperature of 40° C. and a relative humidity of 90% of 1207 g/m ² /24 hr A moisture barrier film (temperature: 40°C, relative humidity: 90%, moisture permeability: 29 g/m ² /24h, thickness: 30 µm) was bonded to one side of [0085] to obtain a protective film with a moisture barrier film. The moisture permeability of the protective film and the moisture barrier film was measured by the cup method specified in JIS Z 0208 under conditions of a temperature of 40°C and a relative humidity of 90%. The same applies to the following Examples and Comparative Examples.

(6) Production of polarizing plate with single-sided protective film (first protective film bonding step, peeling step)

A polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization: 1800) was dissolved in hot water at 95°C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. A cross-linking agent ("Sumirase (registered trademark) Resin 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with the obtained aqueous solution in a ratio of 1 part by weight to 2 parts by weight of polyvinyl alcohol powder to obtain an adhesive solution.

After applying the adhesive solution on the polarizer layer of the light-polarizing laminated film produced in the above (4), the protective film side of the protective film with a moisture-proof film is bonded, and the adhesive is dried at 80 ° C. for 5 minutes. /Protective film/Adhesive layer/Polarizer layer/Base film were obtained to obtain a laminated polarizing plate (first protective film bonding step). Then, the base film and the moisture proof film were removed from the obtained laminated polarizing plate to obtain a polarizing plate with a single-sided protective film (peeling step).

[Example 2]

A polarizing plate was obtained in the same manner as in Example 1, except that a moisture barrier film having a moisture vapor transmission rate of 87 g/m ² /24h and a thickness of 53 μm was used as the moisture barrier film.

[Example 3]

A polarizing plate was obtained in the same manner as in Example 1, except that a moisture barrier film having a moisture vapor transmission rate of 455 g/m ² /24h and a thickness of 25 μm was used as the moisture barrier film.

[Comparative Example 1]

A polarizing plate was obtained in the same manner as in Example 1, except that a moisture barrier film having a moisture vapor transmission rate of 827 g/m ² /24h and a thickness of 40 μm was used as the moisture barrier film.

[Comparative Example 2]

A polarizing plate was obtained in the same manner as in Example 1, except that the moisture proof film was not bonded to the protective film.

[Measurement of Curl Amount]

The polarizing plate was cut into 80 mm in the TD direction and 80 mm in the MD direction, and left still for 24 hours in an environment of a temperature of 25°C and a relative humidity of 55%. When this polarizing plate is placed with the concave surface facing up on a reference plane (horizontal table), the four end portions are lifted up. The amount of curl was determined as an average of the heights of these four corners, and the degree of suppression of curl was evaluated according to the following evaluation criteria. The larger the positive curl, the stronger the reverse curl, the larger the negative curl. The results are shown in Table 1.

[Evaluation of polarizer]

In Examples 1 to 3, the amount of curl was 0 mm or more. In the polarizing plates of Examples 1 to 3, a protection film for preventing scratches (a pressure-sensitive adhesive is applied on a PET film) is bonded onto a protective film (TAC film), and a substantially flat or slightly juncal protection film is attached. A polarizing plate was obtained. Moreover, although the pressure-sensitive adhesive for bonding with a display cell was bonded to the surface of this polarizing plate on the polarizer side, the polarizing plate maintained a substantially flat or slightly juncal state.

In Comparative Example 1 and Comparative Example 2, the amount of curl was less than 0 mm. Even if the polarizing plate of Comparative Example 1 and Comparative Example 2 bonded the said protection film on a protective film, the obtained polarizing plate was slightly reverse curled. Moreover, although the pressure-sensitive adhesive for bonding with a display cell was bonded to the surface of this polarizing plate on the polarizer side, the polarizing plate remained reverse-curled. In addition, when it was observed again after leaving it for several days in an environment of a temperature of 25 ° C. and a relative humidity of 55%, the problem of further increasing reverse curl was caused.

In view of the above, the following criteria evaluated the amount of curl and suppression of curl. The results are shown in Table 1.

A: The amount of curl is 0 mm or more, and the reverse curl of the polarizing plate is sufficiently suppressed.

B: The amount of curl is less than 0 mm, and the reverse curl of the polarizing plate is remarkable.

moisture proof film curl of polarizer Permeability of base film/
Moisture permeability of moisture-proof film moisture permeability
(g/m ² /24 hr) thickness
(μm) amount of curl
(mm) evaluation Example 1 29 30 9.0 A 0.103 Example 2 87 53 7.2 A 0.034 Example 3 455 25 1.4 A 0.007 Comparative Example 1 827 40 -8.0 B 0.004 Comparative Example 2 - - -7.9 B -

Claims (8)

On the polarizer layer of the light-polarizing laminated film provided with a polarizer layer on at least one side of the base film, a protective film with a moisture-proof film provided with a moisture-proof film on one side of the protective film through an adhesive layer, Equipped with a step of bonding on the protective film side,
The moisture-proof film has a moisture permeability of 500 g/m ² /24 h or less at a temperature of 40° C. and a relative humidity of 90%,
The polarizing laminated film,
A step of forming a polyvinyl alcohol-based resin layer by coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film and then drying it to obtain a laminated film;
A step of stretching the laminated film to obtain a stretched film;
Step of obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form the polarizer layer
To be manufactured by a method comprising a, a method of manufacturing a laminated polarizing plate. The method of claim 1, wherein the moisture-proof film is a film that can be peeled from the protective film, and when the moisture-proof film is composed of a base film and a pressure-sensitive adhesive layer, peeling from the protective film together with the pressure-sensitive adhesive layer is possible. Possible, method of manufacturing a laminated polarizing plate. The method of claim 1 , wherein the adhesive layer is made of a water-based adhesive. delete The method of claim 1, wherein the protective film is made of a cellulose ester-based resin or a (meth)acrylic-based resin. The method of claim 5, wherein the ratio of the moisture permeability of the base film to the moisture permeability of the moisture-proof film at a temperature of 40 °C and a relative humidity of 90% is 0.01 to 150 at a relative humidity of 90%. . The method of claim 1 , wherein the polarizer layer has a thickness of 10 μm or less. A step of obtaining a laminated polarizing plate by the method for manufacturing a laminated polarizing plate according to any one of claims 1 to 3 and 5 to 7;
Step of peeling and removing the base film and the moisture-proof film from the laminated polarizing plate
A method of manufacturing a polarizing plate comprising a.

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