JP6730009B2 - Method for manufacturing polarizing plate with protect film - Google Patents

Description

The present invention relates to a method for producing a polarizing plate with a protect film, which is formed by laminating a protect film on the surface of a polarizing plate.

2. Description of the Related Art In recent years, mobile terminals such as smartphones are rapidly becoming larger and slimmer in terms of design and portability. In order to realize driving for a long time with a limited thickness, polarizing plates used are also required to have high brightness and be thin and lightweight.

As a polarizing plate, conventionally, a polarizing film made of a polyvinyl alcohol-based resin and a protective film made of triacetyl cellulose (TAC) bonded to the polarizing film is generally used. However, in recent years, a protective film made of a resin other than TAC has also been used from the viewpoints of thinning, durability, cost, productivity, etc. (for example, Patent Document 1).

JP, 2004-245925, A

The polarizing plate is sensitive to the environment in which it is placed and, depending on the environmental conditions, is prone to bow and warp deformation. In the present specification, this deformation is also referred to as “curl”. There are two types of curl, "normal curl" and "reverse curl". The polarizing plate has a first main surface on the side to be bonded to an image display device such as a liquid crystal cell, and a second main surface on the opposite side. The curl having a convex surface side, and the "reverse curl" is a curl having a convex surface on the second main surface side. If the polarizing plate has a reverse curl, when it is attached to the image display element via the pressure-sensitive adhesive layer, a bonding error may occur, or air bubbles may enter the interface between the pressure-sensitive adhesive layer and the image display element. It is easy to cause a malfunction.

Therefore, the present invention is to provide a method capable of producing an optical member including a polarizing plate structure, in which reverse curl is sufficiently suppressed.

The present inventors have found that 1) a polarizing plate is usually marketed as a protective film-attached polarizing plate to which a peelable protect film (also referred to as a surface protective film) for protecting the surface of the polarizing plate is attached to an image display device. In the pasting, in many cases, it is pasted in the form of a polarizing plate with a protect film, and 2) Therefore, in order to solve the above-mentioned problems, reverse curl is sufficiently suppressed as a polarizing plate with a protect film. The present invention has been achieved through further diligent studies based on the idea that it should be done. That is, the present invention provides the following method for producing a polarizing plate with a protective film.

[1] A method for producing a polarizing plate with a protective film, which comprises a step of stacking a protective film on one surface of a polarizing plate and pressing it by passing it between a pair of bonding rolls,
In the pair of laminating rolls, the surface hardness H ₁ of the laminating roll that comes into contact with the protect film and the surface hardness H ₁ of the laminating roll that comes into contact with the protect film, measured by a type A durometer hardness tester specified in JIS K 6253. The surface hardness H ₂ of the laminating roll is represented by the following formula (I):
H ₁ >H ₂ (I)
Manufacturing method that satisfies the relationship of.

[2] The manufacturing method according to [1], wherein the polarizing plate, when formed into a sheet, causes curl having a convex side on which the protective film is stacked.

[3] The polarizing plate includes a polarizing film, a first thermoplastic resin film laminated on one surface of the polarizing film, and a second thermoplastic resin film laminated on the other surface, [1] or [1] 2] The production method described in [2].

[4] The production method according to [3], wherein the first thermoplastic resin film has a higher equilibrium moisture content at a temperature of 23° C. and a relative humidity of 55% than that of the second thermoplastic resin film.

[5] The manufacturing method according to [4], wherein the first thermoplastic resin film and the second thermoplastic resin film have a difference in equilibrium moisture content of 0.5% by weight or more.

The said protective film is a manufacturing method in any one of [3]-[5] arrange|positioned at the said 1st thermoplastic resin film side.

The said 1st thermoplastic resin film is a manufacturing method in any one of [3]-[6] whose said equilibrium moisture content is 1.5 weight% or more.

The manufacturing method according to any one of [1] to [7], wherein the polarizing plate has a thickness of 100 μm or less.

According to the present invention, it is possible to manufacture a polarizing plate with a protect film in which reverse curl is sufficiently suppressed. According to this polarizing plate with a protective film, it is possible to suppress the above-mentioned problems and perform the bonding to the image display element with high productivity.

It is a side view which shows typically an example of the manufacturing method of the polarizing plate with a protect film which concerns on this invention. It is the schematic explaining MD curl, (a) is a side view, (b) is a top view. It is a schematic sectional drawing which shows an example of the layer structure of a polarizing plate. It is a schematic sectional drawing which shows another example of the layer structure of a polarizing plate. It is a schematic sectional drawing which shows another example of the layer structure of a polarizing plate.

(1) Step of pressing With reference to FIG. 1, the method of manufacturing a polarizing plate with a protect film according to the present invention is such that the protect film 1 is superposed on one surface of a polarizing plate 2 and a pair of bonding rolls 5 and 5' The step of pressing the laminated body of the protect film 1 and the polarizing plate 2 from above and below is carried out through the above, and the polarizing plate with a protect film 3 is manufactured by the step. Usually, the protect film 1 and the polarizing plate 2 that are subjected to the pressing step are continuously fed out from a feeding roll (not shown) and are continuously conveyed, and thus, between the pair of bonding rolls 5 and 5′. be introduced. The transport direction of the protect film 1 and the polarizing plate 2 is the longitudinal direction of the film, and the transport directions of both are usually parallel. In this specification, MD means the machine direction of the film, that is, the longitudinal direction of the film. The direction orthogonal to the MD, that is, the film width direction is also referred to as TD in this specification.

In the pair of bonding rolls, the surface hardness H ₁ of the bonding roll 5 in contact with the protect film 1 measured by a type A durometer hardness tester specified in JIS K 6253, and the polarizing plate 2 The surface hardness H ₂ of the bonding roll 5′ that comes into contact with the following formula (I):
H ₁ >H ₂ (I)
Meet the relationship.

When the surface hardness of the pair of bonding rolls 5 and 5′ satisfies the above formula (I), the bonding roll 5 having a large surface hardness in the nip portion protects the bonding roll 5′ having a small hardness while protecting. In order to press the film 1 and the polarizing plate 2, the protect film 1 and the polarizing plate 2 are bonded together in a shape in which the main surface on which the protect film 1 is overlapped is concave. Therefore, in the protective film-attached polarizing plate 3 that has passed through the nip portion, the shape of the polarizing plate 2 is corrected (curl correction) in the direction in which the main surface on which the protect film 1 is superposed is concave (that is, the positive curl direction). be able to. Therefore, for example, when the polarizing plate 2 used in the pressing step has a reverse curl (curl having a convex main surface side on which the protect film 1 is stacked) when formed into a sheet, the present invention According to the method, the reverse curl can be corrected in the positive curl direction, and as a result, the reverse curl is sufficiently suppressed when the sheet is made into a sheet, is flat without curl, or is normal. The polarizing plate 3 with a curl film having a curl can be obtained. The obtained polarizing plate with a protect film 3 is preferably flat without curling or has a regular curl when formed into a sheet.

The surface hardness H ₁ of the bonding roll 5 is, for example, 90° to 100°, and may be 95° to 100°. The surface hardness H ₂ of the bonding roll 5′ is, for example, 60° to 90°, and may be 70° to 80°. The hardness of the laminating rolls 5 and 5'can be measured with a type A durometer hardness tester specified in JIS K6253. As a commercially available hardness tester, for example, a rubber hardness tester "Type-A" manufactured by Asuka Co., Ltd. is used. Specifically, the resistance of the surface of the bonding roll when the surface is pressed with a stick is measured with a hardness meter.

The relation of the above formula (I) can be realized by appropriately selecting the surface material of each of the bonding roll 5 and the bonding roll 5'. Here, the surface of the bonding roll means that the surface of the bonding roll is in contact with the protective film or the polarizing plate and has a depth of at least 5 mm toward the central axis of rotation of the bonding roll. Each of the bonding rolls 5 and 5′ may be made of the same material, or the surface material of the bonding roll and the material inside the bonding roll covered with the surface material are different. May be.

Examples of the combination of the materials of the laminating roll 5 and the laminating roll 5′ (hereinafter, A/B indicates the material of the surface of the laminating roll 5/the material of the surface of the laminating roll 5′) include metal. /Rubber, alloy/rubber, elastic metal/rubber, rubber/rubber and the like.

As the metal, iron, aluminum or the like can be used. As the alloy, stainless steel can be used, and preferably SUS304 (stainless steel containing 18% Cr and 8% Ni) can be used. When the material of the laminating roll is metal and/or alloy, it is preferable to perform surface treatment such as chromium plating, nickel plating, DLC (diamond-like carbon) for the purpose of improving corrosion resistance and scratch resistance. Further, the surface treatment may be a single layer or a plurality of layers.

The elastic metal has a structure in which the surface of an elastic body such as rubber or oil is covered with a metal layer having a thickness of 0.2 to 2 mm. As the outermost metal layer of the elastic metal, nickel, stainless steel or the like can be used. The outermost metal layer of the elastic metal is also preferably subjected to a surface treatment such as chromium plating, nickel plating, DLC (diamond-like carbon) for the purpose of improving corrosion resistance and scratch resistance.

As the rubber, NBR (nitrile rubber), titan, urethane, silicon, EPDM (ethylene-propylene-diene rubber), or the like can be used, and preferably NBR, titan, or urethane can be used. When using both rubber as the surface material of the bonding roll 5 and the bonding roll 5′, the surface hardness H ₁ of the bonding roll 5 is set to 90° to 100°, and the surface hardness H of the bonding roll 5′ is set. ₂ is preferably 60° to 90°.

The diameter of the laminating roll 5 and the laminating roll 5'is preferably 50 mm to 300 mm, more preferably 100 mm to 200 mm. If the diameter is less than 50 mm, the effect of correcting the reverse curl becomes strong, and the normal curl may become larger than necessary. When the diameter exceeds 300 mm, the curvature of the nip portion becomes small, and there is a possibility that a sufficient reverse curl correction effect cannot be obtained.

The curl will be described here. The curl refers to a deformation in which an optical member (optical film) such as the polarizing plate 2 and the polarizing plate 3 with a protective film warps in a bow shape, and this deformation usually occurs in a sheet of the optical member. Curl tends to occur as the optical member becomes thinner.

The curl can be classified into two types, “normal curl” and “reverse curl”, depending on which of the two main surfaces of the optical member that oppose each other is convex. When the main surface on the side to be bonded to an image display device such as a liquid crystal cell is the first main surface and the main surface on the opposite side is the second main surface, the "normal curl" means the first main surface. The curl has a convex side, and the "reverse curl" is a curl having a convex second side. The polarizing plate 2 used in the manufacturing method according to the present invention typically causes a reverse curl (a curl having a convex main surface on which the protect film 1 is stacked) when formed into a sheet. is there.

The curl can be classified into two types, “MD curl” and “TD curl”, depending on which end (side) of the optical member that is a sheet. With reference to FIG. 2, when a sheet of curled optical members is placed on a flat table with the surface on the convex side facing down, “MD curl” means the end portion in MD (typically both ends). Part) is a curl that lifts up, and the "TD curl" is a curl that lifts up the end parts (typically both ends) of the TD. According to the manufacturing method of the present invention, both MD curl and TD curl can be effectively corrected.

The evaluation of the curl that optical members such as the polarizing plate 2 and the polarizing plate 3 with a protective film can have (identification of the type of normal curl, reverse curl, MD curl, TD curl and the amount of curl) is the optical member obtained. This is done for the sheet cut from. This sheet is a rectangular sheet having a pair of opposite sides parallel to MD and the other pair of opposite sides parallel to TD, and has an MD length of 300 mm and a TD length of 200 mm. And

According to the present invention, it is possible to obtain a protective film-attached polarizing plate 3 in which reverse curl is sufficiently suppressed when formed into a sheet, preferably flat without curl or having positive curl. it can. According to this protective film-attached polarizing plate 3, a bonding error may occur when bonding to the image display element via the pressure-sensitive adhesive layer, or bubbles may be mixed in the interface between the pressure-sensitive adhesive layer and the image display element. Problems can be effectively suppressed, and the protection film-attached polarizing plate 3 and the image display element can be bonded with high productivity. Since the curl generated in the polarizing plate with a protect film 3 is a positive curl, even if the curl amount is relatively large, there is no particular problem in terms of the above problems and productivity. The polarizing plate with a protect film 3 obtained by the present invention may have a reverse curl to the extent that the above-mentioned problems can be suppressed (preferably the above-mentioned problems do not occur).

The correction amount in the positive curl direction according to the present invention depends on the difference between the left side and the right side of the above formula (I), and the larger this difference is, the larger the correction amount tends to be. Although it depends on how much the polarizing plate 2 used in the pressing step curls when formed into a sheet, the resulting polarizing plate with a protect film 3 does not have reverse curl, In order to obtain a flat or positive curl, the pressing step is performed by the following formula (II):
H ₁ −H ₂ ≧10 (II)
It is preferable to carry out under conditions satisfying the conditions. In the case where the polarizing plate 2 used in the pressing step has a large reverse curl, in order to make the resulting polarizing plate with a protect film 3 flat or have a positive curl, the above formula (II) is used. It may be necessary to make the left-hand side of the line larger than 20 (for example, 30 or more or 35 or more). The left side of the above formula (II) may be 40 or less, for example.

When the long protective film 1 is placed on one side of the polarizing plate 2 and passed through the pair of bonding rolls 5 and 5′, the adhesive layer of the protective film 1 should be in contact with the one side of the polarizing plate 2. Can be stacked. Prior to the lamination of the protect film 1 and the polarizing plate 2, at least one of the adhesive layer of the protect film 1 and the polarizing plate 2 is subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, Surface activation treatment such as saponification treatment may be performed.

In the step of pressing with the pair of bonding rolls 5 and 5′, the pressure (nip pressure) applied to the laminate of the protect film 1 and the polarizing plate 2 is, for example, 0.01 to 1 MPa, and 0.05 to 0. It may be 0.5 MPa. In the step of pressing with the pair of bonding rolls 5 and 5′, the contacting width (nip width) between the bonding roll 5 and the bonding roll 5′ is, for example, 1 to 20 mm, and 5 to 15 mm. Good. If the nip pressure and the nip width are below the exemplified range, the curl correction effect may be weakened.

(2) Protect Film The protect film 1 is usually composed of a base film and an adhesive layer laminated on the base film. The protect film 1 is a film for protecting the surface of the polarizing plate 2. Usually, the protective film-attached polarizing plate 3 is attached to an image display device or the like, and then, the adhesive layer of the protect film 1 is peeled off. .. The base film is a thermoplastic resin, for example, a polyolefin resin such as a polyethylene resin, a polypropylene resin, or a cyclic polyolefin resin; a polyester resin such as polyethylene terephthalate or polyethylene naphthalate; a polycarbonate resin; a (meth)acrylic resin. It can be made of resin or the like. The pressure-sensitive adhesive layer can be composed of an acrylic pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or the like. Further, it may be composed of a resin layer having self-adhesiveness such as polypropylene resin and polyethylene resin.

In addition, in this specification, "(meth)acrylic resin" represents at least 1 sort(s) selected from the group which consists of acrylic resin and methacrylic resin. The same applies to other terms with "(meta)".

The thickness T ₁ of the protect film 1 can be, for example, 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 120 μm, and further preferably 25 to 100 μm (for example, 90 μm or less). If the thickness T ₁ is less than 5 μm, the polarizing plate 2 may be insufficiently protected and is disadvantageous in terms of handleability. Further, the strength becomes insufficient, and the curl correction effect may be reduced. The thickness T ₁ exceeding 200 μm is disadvantageous in terms of cost and reworkability of the protect film 1. From the viewpoint of thinning, it is difficult to adjust the thickness of the polarizing film and the protective film constituting the polarizing plate in order to make the curl when the polarizing plate 2 is a sheet into a flat or positive curl, but it is difficult to protect. Since the film is usually peeled and removed after the polarizing plate 3 with a protective film is attached to an image display element or the like, the thickness can be adjusted for the purpose of curl correction.

(3) Polarizing Plate The polarizing plate 2 is a polarizing element including at least a polarizing film, and usually further includes a thermoplastic resin film such as a protective film laminated on at least one surface of the polarizing film. The protective film is an optical film that protects the polarizing film.

(3-1) Configuration Example of Polarizing Plate The polarizing plate 2 may include a layer or film other than the polarizing film and the protective film, for example, an optical layer or an optical film having an optical function other than the polarizing film. Examples of the optical layer or optical film having the other optical function are a retardation film (or a retardation layer), a brightness enhancement film, and the like. Various optical films including a protective film can be laminated and laminated on a polarizing film via an adhesive layer or a pressure-sensitive adhesive layer. Further, the polarizing plate 2 may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer.

The thickness T _{2 of the} polarizing plate 2 is usually 200 μm or less, preferably 125 μm or less, more preferably 100 μm or less, and further preferably 75 μm or less from the viewpoint of thinning. The smaller the thickness T ₂ is, the more easily the polarizing plate 2 is curled in the sheet, but according to the present invention, the thickness T ₂ of the polarizing plate 2 is thin, and when the polarizing plate 2 is made into a sheet, it is reversed. Even if a curl occurs, this reverse curl can be effectively corrected in the normal curl direction.

Examples of the layer structure of the polarizing plate 2 will be described with reference to FIGS. 3 to 5, but the layer structure is not limited to these examples. The polarizing plate 2a shown in FIG. 3 includes a polarizing film 10; a first thermoplastic resin film 20 bonded to one surface of the polarizing film 10; a second thermoplastic resin film bonded to the other surface of the polarizing film 10. The resin film 30 includes an adhesive layer 40 laminated on the outer surface of the second thermoplastic resin film 30, and a separate film 50 laminated on the outer surface of the adhesive layer 40. The separate film 50 is a peelable film for protecting the surface (outer surface) of the adhesive layer 40. The first and second thermoplastic resin films 20 and 30 are, for example, protective films.

Like the polarizing plate 2b shown in FIG. 4, one of the first and second thermoplastic resin films 20 and 30 may be omitted. In the polarizing plate 2b, the second thermoplastic resin film 30 is omitted, and the pressure-sensitive adhesive layer 40 is directly attached to the outer surface of the polarizing film 10 (the surface opposite to the surface on which the first thermoplastic resin film 20 is laminated). Is pasted. Such a polarizing plate having a thermoplastic resin film on only one surface of the polarizing film 10 is advantageous for thinning the polarizing plate. When the thermoplastic resin film is laminated on only one surface of the polarizing film 10, the polarizing plate 2 is likely to curl in its sheet, but according to the present invention, only one surface of the polarizing film 10 is formed. Even if the polarizing plate 2 has a reverse curl when the thermoplastic resin film is laminated and laminated on the polarizing plate 2 as a sheet, the reverse curl can be effectively corrected in the forward curl direction. ..

Further, as in the polarizing plate 2c shown in FIG. 5, the adhesive layer 40 and the separate film 50 may be omitted. The polarizing plate 2 may have a protect film different from the protect film 1 used in the pressing step on one surface in advance. In this case, the obtained polarizing plate with a protect film 3 is a polarizing plate having protect films on both sides.

Although illustration is omitted in FIGS. 3 to 5, the bonding of the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be preferably performed using an adhesive.

(3-2) Polarizing Film The polarizing film 10 may be a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented. As the polyvinyl alcohol resin forming the polyvinyl alcohol resin film, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. 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.

The degree of saponification of the polyvinyl alcohol resin can be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 100.0 mol%, and more preferably 94.0. It is in the range of 100.0 mol%. When the saponification degree is less than 80.0 mol%, the water resistance and the wet heat resistance of the obtained polarizing plate 2 may be reduced.

The degree of saponification is the unit ratio (mol %) of the ratio of the acetic acid group (acetoxy group: —OCOCH ₃ ) contained in the polyvinyl acetate resin, which is a raw material of the polyvinyl alcohol resin, converted to a hydroxyl group by the saponification step. The following formula:
Degree of saponification (mol %)=100×(number of hydroxyl groups)/(number of hydroxyl groups+number of acetic acid groups)
Is defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined according to JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain preferable polarization performance, and if it exceeds 10,000, the solubility in a solvent is deteriorated, and it may be difficult to form a polyvinyl alcohol-based resin film.

The dichroic dye contained (adsorption orientation) in the polarizing film 10 can be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Includes Sky Blue, Direct First Orange S and First Black. The dichroic dyes may be used alone or in combination of two or more. The dichroic dye is preferably iodine.

The polarizing film 10 includes a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye; It can be manufactured through a step of crosslinking the alcohol-based resin film; and a step of washing with water after the crosslinking treatment.

The polyvinyl alcohol-based resin film is a film formed from the polyvinyl alcohol-based resin described above. The film forming method is not particularly limited, and a known method such as a melt extrusion method or a solvent casting method can be adopted. 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 can be performed before the dyeing of the dichroic dye, at the same time as the dyeing, or after the dyeing. When the uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during the crosslinking treatment. In addition, uniaxial stretching may be performed in these plural stages.

In the uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which a polyvinyl alcohol-based resin film is stretched in a solution. The draw ratio is usually about 3 to 8 times.

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

When iodine is used as the dichroic dye, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing is usually employed. The content of iodine in this 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 the dichroic dye, a method of immersing a polyvinyl alcohol resin film in a dyeing aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually employed. The content of the dichroic organic dye in the dyeing aqueous solution is usually 1×10 ⁻⁴ to 10 parts by weight, preferably 1×10 ⁻³ to 1 part by weight per 100 parts by weight of water. This dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80°C.

The crosslinking treatment after dyeing with the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing a crosslinking agent. A preferred example of the cross-linking agent is boric acid, but other cross-linking agents such as boron compounds such as borax, glyoxal, and glutaraldehyde can also be used. As the crosslinking agent, only one kind may be used, or two or more kinds may be used in combination.

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

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

The polarizing film 10 is obtained by performing a drying process after washing with water. The drying treatment can be drying with a hot air dryer, drying by contact with a hot roll, drying with a far infrared heater, and the like. The temperature of the drying treatment is usually about 30 to 100°C, preferably 50 to 90°C.

The thickness of the polarizing film 10 is usually about 2 to 40 μm. From the viewpoint of thinning the polarizing plate 2, the thickness of the polarizing film 10 is preferably 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less. The smaller the thickness of the polarizing film 10 is, the more easily the polarizing plate 2 curls in the sheet, but according to the present invention, the polarizing film 10 has a small thickness, and when the polarizing plate 2 is made into a sheet, it is reversed. Even if a curl occurs, this reverse curl can be effectively corrected in the normal curl direction.

(3-3) First and Second Thermoplastic Resin Films The first and second thermoplastic resin films 20 and 30 are each independently a translucent thermoplastic resin, preferably an optically transparent heat. It is a film made of a plastic resin. The thermoplastic resin forming the first and second thermoplastic resin films 20 and 30 is, for example, a polyolefin resin such as a chain polyolefin resin (polypropylene resin) or a cyclic polyolefin resin (norbornene resin). Cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; (meth)acrylic resins such as methyl methacrylate resins; polystyrene resins; Polyvinyl chloride resin; Acrylonitrile-butadiene-styrene resin; Acrylonitrile-styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polysulfone resin; It may be a polyether sulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin or the like.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more chain olefins. More specific examples include polypropylene resin (polypropylene resin that is a homopolymer of propylene or a copolymer that mainly contains propylene), polyethylene resin (a polyethylene resin that is a homopolymer of ethylene, or mainly ethylene. And a copolymer).

Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefins as polymerized units. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids or their derivatives, and hydrides thereof. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as the cyclic olefin are preferably used.

Cellulosic resin means that some or all of hydrogen atoms in hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, softwood pulp) are substituted with acetyl group, propionyl group and/or butyryl group. Also, it means a cellulose organic acid ester or a cellulose mixed organic acid ester. Examples thereof include those made of cellulose acetate, propionate, butyrate and mixed esters thereof. Among them, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferable.

The polyester resin is a resin having an ester bond other than the above cellulose resin, and is generally made of a polycondensate of a polyvalent carboxylic acid or its derivative and a polyhydric alcohol. As the polyvalent carboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. A divalent diol can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

A polycarbonate resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and has high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called modified polycarbonate in which the polymer skeleton is modified to lower the photoelastic coefficient, a copolymerized polycarbonate having improved wavelength dependence, or the like.

The (meth)acrylic resin is a polymer containing a structural unit derived from a (meth)acrylic monomer. The polymer is typically a polymer containing methacrylic acid ester. It is preferably a polymer in which the proportion of structural units derived from methacrylic acid ester is 50% by weight or more based on the total structural units. The (meth)acrylic resin may be a homopolymer of methacrylic acid ester or a copolymer containing a constitutional unit derived from another polymerizable monomer. In this case, the ratio of the constitutional unit derived from another polymerizable monomer is preferably 50% by weight or less based on all structural units.

As the methacrylic acid ester that can form the (meth)acrylic resin, a methacrylic acid alkyl ester is preferable. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate. , 2-hydroxyethyl methacrylate, and alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms. The alkyl group contained in the methacrylic acid alkyl ester preferably has 1 to 4 carbon atoms. In the (meth)acrylic resin, the methacrylic acid ester may be used alone or in combination of two or more.

Examples of the other polymerizable monomer that can form the (meth)acrylic resin include acrylic acid esters and other compounds having a polymerizable carbon-carbon double bond in the molecule. The other polymerizable monomers may be used alone or in combination of two or more. As the acrylic acid ester, an acrylic acid alkyl ester is preferable. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate. , 2-hydroxyethyl acrylate, and alkyl acrylates having an alkyl group having 1 to 8 carbon atoms. The alkyl group contained in the acrylic acid alkyl ester preferably has 1 to 4 carbon atoms. In the (meth)acrylic resin, the acrylic ester may be used alone or in combination of two or more.

Other compounds having a polymerizable carbon-carbon double bond in the molecule include vinyl compounds such as ethylene, propylene and styrene, and vinyl cyan compounds such as acrylonitrile. Other compounds having a polymerizable carbon-carbon double bond in the molecule may be used alone or in combination of two or more.

The first and second thermoplastic resin films 20 and 30 may be protective films that are laminated and attached to one surface of the polarizing film 10 to protect the polarizing film 10. The first or second thermoplastic resin film 20 or 30 may be a protective film having an optical function as well, such as a retardation film or a brightness enhancement film. For example, by stretching (uniaxially stretching or biaxially stretching) a thermoplastic resin film made of the above material, or by forming a liquid crystal layer or the like on the film, a retardation having an arbitrary retardation value is given. It can be a film. The first and/or second thermoplastic resin films 20 and 30 are surface-treated layers (coatings) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer, which are laminated on the surface thereof. Layer).

The thickness of the first and second thermoplastic resin films 20 and 30 is usually 1 to 100 μm, but preferably 5 to 60 μm, and more preferably 5 to 50 μm from the viewpoint of strength and handleability. When the thickness is within this range, the polarizing film 10 can be mechanically protected and the shrinkage of the polarizing film 10 when the polarizing plate 2 is exposed to a humid heat environment can be suppressed. As the thickness of the first thermoplastic resin film 20 or the second thermoplastic resin film 30 is smaller, the polarizing plate 2 is more likely to curl in its sheet, but according to the present invention, the first thermoplastic resin film 20 or Even if the second thermoplastic resin film 30 has a thin thickness of, for example, 40 μm or less, further 30 μm or less, and causes a reverse curl when the polarizing plate 2 is a sheet, this reverse curl is directed in the normal curl direction. Can be effectively corrected.

When the first thermoplastic resin film 20 is provided on one surface of the polarizing film 10 and the second thermoplastic resin film 30 is provided on the other surface like the polarizing plates 2a and 2c shown in FIGS. 3 and 5. The first thermoplastic resin film 20 and the second thermoplastic resin film 30 may be made of the same kind of thermoplastic resin, or may be made of different kinds of thermoplastic resins. When the thermoplastic resin films attached to both surfaces have different equilibrium moisture contents or moisture permeabilities, such as when composed of a plastic resin, curling is particularly likely to occur in the sheet of the polarizing plate 2, In such a case, the present invention is particularly advantageous.

For example, as the first thermoplastic resin film 20, a film having a higher equilibrium moisture content than the second thermoplastic resin film 30 can be used. Although the greater the difference in the equilibrium moisture content between the first thermoplastic resin film 20 and the second thermoplastic resin film 30 attached to both surfaces of the polarizing film 10, the polarizing plate 2 is more likely to curl in its sheet. According to the present invention, the difference in the equilibrium moisture content is 0.5% by weight or more, further 1% by weight or more, and even 1.5% by weight or more, and when the polarizing plate 2 is a sheet, Even if the reverse curl occurs, the reverse curl can be effectively corrected in the normal curl direction.

In the present specification, the equilibrium moisture content of a film is measured by a dry weight method, and specifically, the following formula:
Equilibrium moisture content (wt %)={(film weight before drying treatment−film weight after drying treatment)/film weight before drying treatment}×100
Sought according to. Here, the weight of the film before the drying treatment is the weight after the film is stored for 24 hours under the environment of the temperature of 23° C. and the relative humidity of 55%, and the drying means the treatment of drying the film at 105° C. for 2 hours. Examples of the combination of thermoplastic resin films having a difference in equilibrium moisture content of 0.5% by weight or more include, for example, a combination of a cellulose resin film (TAC film or the like) and a cyclic polyolefin resin film, a cellulose resin film (TAC Film) and a (meth)acrylic resin film, a cellulose resin film (TAC film etc.) and a polyester resin film, a cellulose resin film (TAC film etc.) and a chain polyolefin resin film , A combination of a (meth)acrylic resin film and a cyclic polyolefin resin, a combination of a (meth)acrylic resin film and a polyester resin film, and the like. The difference in equilibrium moisture content between 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 first thermoplastic resin film 20 is, for example, 1.5% by weight or more, and may be 2% by weight or more. The equilibrium moisture content of the first thermoplastic resin film 20 is usually 5% by weight or less.

When a film having a higher equilibrium moisture content than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, the equilibrium moisture content of the second thermoplastic resin film 20 is usually 0.1 to 1.5. %, and preferably 0.1 to 1% by weight. Examples of the thermoplastic resin that constitutes the second thermoplastic resin film 20 that can achieve such an equilibrium moisture content are cyclic polyolefin resin, (meth)acrylic resin, polyester resin, chain polyolefin resin, and the like.

The equilibrium moisture content of a thermoplastic resin film is not only the material (type of thermoplastic resin that constitutes the film), but also the thickness of the film, the presence or absence of a surface treatment layer (coating layer) that can be attached to the film surface, and the material. Can also be adjusted by.

When a film having an equilibrium moisture content higher than that of the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, from the viewpoint of correcting the reverse curl that tends to occur in the polarizing plate 2 in the normal curl direction, In the pressing step, the protect film 1 is arranged on the polarizing plate 2 on the side of the first thermoplastic resin film 20.

Further, for example, as the first thermoplastic resin film 20, a film having a higher moisture permeability than the second thermoplastic resin film 30 can be used. The larger the difference in moisture permeability between the first thermoplastic resin film 20 and the second thermoplastic resin film 30 attached to both surfaces of the polarizing film 10, the more likely the polarizing plate 2 to curl in its sheet, According to the present invention, this difference in water vapor transmission rate is 30 g/(m ² ·24 hr) or more, further 50 g/(m ² ·24 hr) or more, and even further 100 g/(m ² ·24 hr) or more. Even if the plate 2 has a sheet-like body and causes a reverse curl, the reverse curl can be effectively corrected in the forward curl direction.

In the present specification, the water vapor transmission rate of a film is the water vapor transmission rate at a temperature of 40° C. and a relative humidity of 90% measured by a cup method specified in JIS Z 0208. 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 resin film (TAC film or the like) and a cyclic polyolefin resin film, a cellulose resin film. (TAC film etc.) and (meth)acrylic resin film combination, cellulose resin film (TAC film etc.) and polyester resin film combination, cellulose resin film (TAC film etc.) and chain polyolefin resin Examples include a combination with a film, a combination with a (meth)acrylic resin film and a cyclic polyolefin resin, and a combination with a (meth)acrylic resin film and a polyester resin film. The difference in water vapor 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 first thermoplastic resin film 20 is, for example, 300 g/(m ² ·24 hr) or more, and may be 400 g/(m ² ·24 hr) or more. A water vapor permeability of 300 g/(m ² ·24 hr) or more means that when the first thermoplastic resin film 20 and the polarizing film 10 are bonded together using a water-based adhesive, a layer made of a water-based adhesive is efficiently used. It is also advantageous in that it can be well dried and productivity can be improved. The water vapor permeability of the first thermoplastic resin film 20 is usually 5000 g/(m ² ·24 hr) or less.

When a film having a higher moisture permeability than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, the moisture permeability of the second thermoplastic resin film 20 is usually 1 to 350 g/(m ² ·24 hr). ), and preferably 5 to 200 g/(m ² ·24 hr). Examples of the thermoplastic resin forming the second thermoplastic resin film 20 that can achieve such moisture permeability are cyclic polyolefin resin, (meth)acrylic resin, polyester resin, chain polyolefin resin, and the like.

The moisture permeability of a thermoplastic resin film depends on the material (type of thermoplastic resin that constitutes the film), the thickness of the film, the presence or absence of a surface treatment layer (coating layer) that can be attached to the film surface, and the material. Can also be adjusted.

When a film having a higher water vapor transmission rate than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, from the viewpoint of correcting the reverse curl, which is likely to occur in the polarizing plate 2, in the normal curl direction, the above-mentioned case is usually used. In the pressing step, the protect film 1 is disposed on the polarizing plate 2 on the side of the first thermoplastic resin film 20.

As described above, the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be attached using an adhesive. Prior to laminating and laminating the first and second thermoplastic resin films 20 and 30 on the polarizing film 10, plasma is formed on the laminating surfaces of the polarizing film 10 and/or the first and second thermoplastic resin films 20 and 30. Surface activation treatment such as treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment and saponification treatment may be performed. By this surface activation treatment, the adhesiveness between the polarizing film 10 and the first and second thermoplastic resin films 20, 30 can be enhanced.

As the adhesive, a water-based adhesive, an active energy ray-curable adhesive or a thermosetting adhesive can be used, and preferably a water-based adhesive or an active energy ray-curable adhesive. When laminating the thermoplastic resin films on both surfaces of the polarizing film 10, the adhesive on both surfaces may be the same kind of adhesive or different kinds of adhesive. When different kinds of adhesives are used, the polarizing plate 2 is apt to curl in the sheet, but according to the present invention, when the different kinds of adhesives are used, when the polarizing plate 2 is made into a sheet. Even if a reverse curl occurs, the reverse curl can be effectively corrected in the normal curl direction.

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

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be a polyvinyl alcohol resin such as partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, or a carboxyl group-modified polyvinyl alcohol. It may be a modified polyvinyl alcohol-based resin such as acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, or amino group-modified polyvinyl alcohol. Polyvinyl alcohol-based resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymerization of vinyl acetate and other monomers copolymerizable with it. It may be a polyvinyl alcohol-based copolymer obtained by saponifying the combined product.

An aqueous adhesive containing a polyvinyl alcohol resin as an adhesive component is usually an aqueous solution of polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

An adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is a polyhydric aldehyde, a melamine-based compound, a zirconia compound, a zinc compound, a glyoxal, a glyoxal derivative, or a curable component such as a water-soluble epoxy resin in order to improve adhesiveness. It is preferable to contain a crosslinking agent. As the water-soluble epoxy resin, for example, a polyamidoamine obtained by reacting a polyalkylenepolyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid, a polyamide polyamine epoxy resin obtained by reacting epichlorohydrin Can be preferably used. Commercially available products of such polyamide polyamine epoxy resin include "SUMIREZ RESIN 650" (manufactured by Taoka Chemical Industry Co., Ltd.), "SUMIREZ RESIN 675" (manufactured by Taoka Chemical Industry Co., Ltd.), "WS-525" (Japan PMC Co., Ltd. etc. are mentioned. The addition amount of these curable components and crosslinking agents (the total amount when both are added as curable components and crosslinking agents) is usually 1 to 100 parts by weight, preferably 100 parts by weight of the polyvinyl alcohol resin. It is 1 to 50 parts by weight. When the addition amount of the curable component or the cross-linking agent is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol resin, the effect of improving the adhesiveness tends to be small, and the addition amount of polyvinyl When the amount exceeds 100 parts by weight with respect to 100 parts by weight of the alcohol resin, the adhesive layer tends to become brittle.

Further, as a preferred example of using a urethane resin as the main component of the adhesive, a mixture of a polyester-based ionomer urethane resin and a compound having a glycidyloxy group can be mentioned. The polyester-based ionomer type urethane resin is a urethane resin having a polyester skeleton and a small amount of an ionic component (hydrophilic component) introduced therein. Such an ionomer type urethane resin is suitable as a water-based adhesive because it directly emulsifies in water to form an emulsion without using an emulsifier.

When a water-based adhesive is used, after the polarizing film 10 and the first and/or second thermoplastic resin films 20 and 30 are bonded together, a drying step for removing water contained in the water-based adhesive is performed. It is preferably carried out. After the drying step, a curing step of curing at a temperature of 20 to 45° C., for example, may be provided.

The active energy ray curable adhesive is an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. When the active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate 2 is a cured product layer of the adhesive.

The active energy ray-curable adhesive can be an adhesive containing an epoxy compound that cures by cationic polymerization as a curable component, and preferably an ultraviolet curable adhesive containing such an epoxy compound as a curable component. It is an agent. The epoxy compound as used herein means a compound having an average of 1 or more, and preferably 2 or more epoxy groups in the molecule. The epoxy compounds may be used alone or in combination of two or more.

A specific example of an epoxy compound that can be preferably used is a hydrogenated epoxy compound obtained by reacting epichlorohydrin with an alicyclic polyol obtained by performing a hydrogenation reaction on an aromatic ring of an aromatic polyol ( Glycidyl ether of polyol having alicyclic ring); Aliphatic epoxy compound such as polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct; Epoxy group bonded to alicyclic ring in molecule 1 It includes an alicyclic epoxy compound which is an epoxy compound having one or more epoxy compounds.

The active energy ray-curable adhesive may contain a radical-polymerizable (meth)acrylic compound as a curable component, instead of or together with the epoxy compound. The (meth)acrylic compound is a (meth)acrylate monomer having at least one (meth)acryloyloxy group in the molecule; obtained by reacting two or more functional group-containing compounds, and at least two in the molecule. (Meth)acryloyloxy group-containing compounds such as (meth)acrylate oligomers having a (meth)acryloyloxy group.

When the active energy ray-curable adhesive contains an epoxy compound that is cured by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the cationic photopolymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes and the like. When the active energy ray-curable adhesive contains a radical-polymerizable curable component such as a (meth)acrylic compound, it preferably contains a photo-radical polymerization initiator. Examples of the photoradical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthones, fluorenones, camphorquinones, benzaldehydes, and anthraquinones.

When an active energy ray-curable adhesive is used for laminating and laminating the polarizing film 10 and the first and/or second thermoplastic resin films 20 and 30, after laminating and laminating, a drying step is performed if necessary. Then, a curing step of curing the active energy ray-curable adhesive by irradiating the active energy ray is performed. The light source of the active energy rays is not particularly limited, but ultraviolet rays having a light emission distribution at a wavelength of 400 nm or less are preferable, and specifically, low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, chemical lamp, black light lamp, micro A wave excitation mercury lamp, a metal halide lamp, etc. can be used.

The irradiation intensity of the active energy ray to the adhesive layer made of the active energy ray-curable adhesive is appropriately determined according to the composition of the adhesive, but the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1. It is preferably set to be about 6000 mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and when the irradiation intensity is 6000 mW/cm ² or less, the heat radiated from the light source and the heat generated during curing of the adhesive cause the adhesive layer There is little risk of yellowing or deterioration of the polarizing film 10.

The irradiation time of the active energy ray is also appropriately determined depending on the composition of the adhesive, but it should be set so that the integrated light amount represented by the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ/cm ^2. Is preferred. When the integrated light amount is 10 mJ/cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated so that the curing reaction can proceed more reliably, and when it is 10000 mJ/cm ² or less, the irradiation time is long. It is possible to maintain good productivity of the polarizing plate 2 without becoming too much.

(3-4) Adhesive Layer and Separate Film As shown in FIGS. 3 and 4, the polarizing plate 2 may include an adhesive layer 40. The pressure-sensitive adhesive layer 40 can be directly laminated on the surface of the first or second thermoplastic resin film 20, 30 or the polarizing film 10, and the protective film-attached polarizing plate 3 is attached to an image display element (for example, a liquid crystal cell). Can be used for matching.

The pressure-sensitive adhesive layer 40 for sticking the protective film-attached polarizing plate 3 to an image display element (for example, a liquid crystal cell) is a main surface (first main surface) of the polarizing plate to be stuck to an image display element such as a liquid crystal cell. It is placed on the (face) side. For example, the polarizing plate 2 includes first and second thermoplastic resin films 20 and 30, and as the first thermoplastic resin film 20, a film having a higher equilibrium moisture content and/or moisture permeability than the second thermoplastic resin film 30 is used. When used, the pressure-sensitive adhesive layer 40 can be arranged on the second thermoplastic resin film 30 side.

The pressure-sensitive adhesive layer 40 can be composed of a pressure-sensitive adhesive composition containing a resin such as a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin as a main component (base polymer). .. Among them, a pressure-sensitive adhesive composition containing a (meth)acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, etc., is preferable. The pressure-sensitive adhesive composition may be an active energy ray curable type or a thermosetting type.

Examples of the (meth)acrylic resin used in the pressure-sensitive adhesive composition include butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Polymers or copolymers having one or more types of (meth)acrylic acid ester as a monomer are preferably used. The (meth)acrylic resin is preferably copolymerized with a polar monomer. Examples of polar monomers include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, glycidyl ( Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like such as (meth)acrylate.

The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a crosslinking agent. As the cross-linking agent, a metal ion having a valence of 2 or more and forming a carboxylic acid metal salt with a carboxyl group; a polyamine compound forming an amide bond with a carboxyl group; Examples thereof include epoxy compounds and polyols that form an ester bond with a carboxyl group; and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are preferable.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by being irradiated with an active energy ray such as an ultraviolet ray or an electron beam, and has adhesiveness even before irradiation with the active energy ray. It is a pressure-sensitive adhesive composition having a property that it can be brought into close contact with an adherend such as the above, and can be cured by irradiation with an active energy ray to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably UV-curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, if necessary, a photopolymerization initiator, a photosensitizer and the like may be contained.

The pressure-sensitive adhesive composition includes fine particles for imparting light-scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powder and other inorganic powders). Etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, photopolymerization initiators, and other additives.

The pressure-sensitive adhesive layer 40 is obtained by applying the organic solvent dilution liquid of the pressure-sensitive adhesive composition on the pressure-sensitive adhesive layer forming surface of the polarizing plate 2 (that is, the polarizing film 10 or the first or second thermoplastic resin film 20, 30). Then, it can be formed by drying. Alternatively, an organic solvent diluted solution of the pressure-sensitive adhesive composition is applied on a separate film (for example, the separate film 50) and dried to form a pressure-sensitive adhesive layer, which is then transferred to the pressure-sensitive adhesive layer-forming surface of the polarizing plate 2. You may. In either method, it is preferable that a separate film be attached to the outer surface of the pressure-sensitive adhesive layer 40 to protect the pressure-sensitive adhesive layer 40 until use. When the active energy ray-curable pressure-sensitive adhesive composition is used, the formed pressure-sensitive adhesive layer can be irradiated with an active energy ray to obtain a cured product having a desired degree of curing. The thickness of the pressure-sensitive adhesive layer 40 is usually 1 to 40 μm, but from the viewpoint of thinning the polarizing plate 2, it is preferably 3 to 25 μm.

The separate film 50 is a film attached to protect the surface of the adhesive layer 40 until it is attached to an image display element (for example, a liquid crystal cell). The separate film 50 is usually composed of a thermoplastic resin film having one surface subjected to a release treatment, and the release-treated surface is bonded to the pressure-sensitive adhesive layer 40. The thermoplastic resin forming the separate film 50 can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or the like. The thickness of the separate film 50 is, for example, 10 to 100 μm.

(3-5) Other constituent elements of the polarizing plate The polarizing plate 2 may include constituent elements other than the above. Other constituent elements may include an optical layer or an optical film having an optical function other than the polarizing film 10, and specific examples thereof are optical films such as a retardation film and a brightness enhancement film. Other optical films can be laminated and laminated via a pressure-sensitive adhesive layer or an adhesive layer.

Further, the polarizing plate 2 can include a protect film different from the protect film 1 used in the pressing step. This protect film is arranged on one surface of the polarizing plate 2. Regarding the structure of the protect film, the description of the protect film 1 described above is cited.

(3-6) Curling of Polarizing Plate As described above, according to the present invention, it is possible to correct the polarizing plate 2 in the positive curl direction, whereby the reverse curl is sufficiently suppressed when the sheet is made into a sheet. It is possible to obtain the protective film-attached polarizing plate 3 having a curl, which is flat without curl or has a positive curl. In the manufacturing method according to the present invention, when the polarizing plate 2 is a sheet, a reverse curl (a curl whose main surface side on which the protect film 1 is stacked is convex) is generated (further, the reverse curl is used). And which causes MD curl).

In the above, as one of the forms of the polarizing plate 2 in which the reverse curl is likely to occur when formed into a sheet, the first thermoplastic resin film 20 and the second thermoplastic resin film 30 have different equilibrium moisture contents and/or Although the case of having moisture permeability is mentioned, the present invention is not limited to this, and reverse curl is likely to occur when the polarizing plate 2 has an asymmetric layer structure with respect to the polarizing film 10.

An example of the configuration of the polarizing plate 2 that easily causes reverse curl is as follows.
(A) A structure in which a thermoplastic resin film (protective film or the like) is attached only to one surface of the polarizing film 10,
(B) A configuration in which a protective film is attached to one surface of the polarizing film 10 and an optical film (such as a brightness enhancement film) other than the protective film is attached to the other surface,
(C) A configuration in which thermoplastic resin films (protective film or the like) attached to both sides of the polarizing film 10 have different configurations (resin type, thickness, equilibrium moisture content, moisture permeability, presence or absence of surface treatment layer, etc.),
(D) A configuration in which adhesive layers for laminating thermoplastic resin films (protective films and the like) on both surfaces of the polarizing film 10 are formed of different kinds of adhesives,
(E) A structure in which a thermoplastic resin film (protective film or the like) is attached to both surfaces of the polarizing film 10, and another optical film is attached to one thermoplastic resin film,
(F) In addition, the total number of films and layers on one side and the total number of films and layers on the other side are different from each other with reference to the polarizing film 10.

(4) Other Steps The production method according to the present invention further includes a step of cutting the protective film-attached polarizing plate 3 obtained by the pressing step to obtain a sheet of the protect film-attached polarizing plate 3. it can. A commonly used cutting device such as a shear cutter can be used for the cutting.

Although the shape of the sheet is not particularly limited, it is usually a rectangular shape, preferably a rectangular shape having a long side and a short side, and more preferably a rectangular shape. This sheet is usually cut so that a pair of opposing sides are parallel to MD and the other pair of opposing sides are parallel to TD, but each side is a direction inclined from MD or TD. May be cut so that The length of the long side and the short side of the sheet is not particularly limited, but usually the long side is 50 mm or more and the short side is 30 mm or more. Curl is more likely to occur as the size of the sheet is increased. If the size (long side and/or short side) is too small, the curl problem itself is less likely to occur.

Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following examples, the equilibrium moisture content, the moisture permeability, the thickness, the hardness of the laminating roll and the curl amount were measured according to the following methods.

(1) Equilibrium Moisture Content of Film A test piece having an MD length of 150 mm and a TD length of 100 mm was cut out. The film weight was measured after the film was stored for 24 hours in an environment of a temperature of 23° C. and a relative humidity of 55%. Then, 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 film weight before and after drying, the following formula:
Equilibrium moisture content (wt %)={(film weight before drying treatment−film weight after drying treatment)/film weight before drying treatment}×100
The equilibrium moisture content was calculated based on

(2) Moisture Permeability of Film The moisture permeability [g/(m ² ·24 hr)] at a temperature of 40° C. and a relative humidity of 90% was measured by the cup method specified in JIS Z 0208.

(3) Thickness of Polarizing Plate and Film The thickness was measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(4) Hardness of Laminating Roll Using a type A durometer hardness tester (rubber hardness meter "Type-A" manufactured by Asuka Co., Ltd.) specified in JIS K 6253, the temperature was 23°C and the relative humidity was 50%. Hardness [°] was measured.

(5) Polarizing Plate with Protect Film and Curling Amount of Polarizing Plate A rectangular test piece having an MD length of 300 mm and a TD length of 200 mm was cut out from the obtained polarizing plate with a protect film, and the temperature was 25° C. and the relative humidity was 55%. It was left in the environment for 24 hours. This test piece was placed on the reference surface (horizontal table) with its concave surface facing upward, that is, with four edges raised. In this state, the height from the reference surface was measured for each of the four corners of the test piece, and the curl amount [mm] was determined as the average of the heights of these four corners. When the curl amount is a positive value, it means that the first thermoplastic resin film side is concave (positive curl), and when the curl amount is a negative value, the second thermoplastic resin film side is concave. It means that (reverse curl).

<Example 1>
(A) Production of Polarizing Film While continuously transporting a long polyvinyl alcohol film (average degree of polymerization: about 2400, degree of saponification: 99.9 mol% or more, thickness: 30 μm), it is about 4 times as dry. After uniaxially stretching and immersing in pure water at 40°C for 1 minute while maintaining the tension, it was immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.1/5/100 at 28°C for 60 seconds. Soaked. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 10.5/7.5/100 at 68° C. for 300 seconds. Subsequently, it was washed with pure water at 5° C. for 5 seconds and then dried at 70° C. for 180 seconds to obtain a long polarizing film in which iodine was adsorbed and oriented on the uniaxially stretched polyvinyl alcohol film. The polarizing film had a thickness of 11.1 μm.

(B) Production of Polarizing Plate While continuously transporting the polarizing film obtained in (A) above, a long first thermoplastic resin film [TAC film “KC2UAW” manufactured by Konica Minolta Opto Co., Ltd. Film having a coat layer formed thereon, thickness: 32.4 μm, equilibrium moisture content: 1.9% by weight, moisture vapor transmission rate: 455 g/(m ² ·24 hr)] and long second thermoplastic resin film [JSR (stock) ) Made of cyclic polyolefin resin film, "FEKB015D3", thickness: 15.1 μm, equilibrium moisture content: 0.8 wt%, moisture vapor transmission rate: 115 g/(m ² ·24 hr)] , A first thermoplastic resin film that is passed through a bonding roll while injecting an aqueous adhesive between the polarizing film and the first thermoplastic resin film and between the polarizing film and the second thermoplastic resin film. A laminated film composed of water-based adhesive layer/polarizing film/water-based adhesive layer/second thermoplastic resin film was obtained. Subsequently, the obtained laminated film was transported and passed through a hot air dryer to be heated at 80° C. for 300 seconds to dry the water-based adhesive layer to obtain a polarizing plate. For the above water-based adhesive, polyvinyl alcohol powder [trade name “Gosephimmer” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization 1100] was dissolved in hot water at 95° C. to obtain a concentration of 3% by weight. % Polyvinyl alcohol aqueous solution was mixed with a crosslinking agent [sodium glyoxylate manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] at a ratio of 1 part by weight with respect to 10 parts by weight of polyvinyl alcohol powder.

The polarizing plate had a thickness T ₂ of 58.6 μm. When the curl amount of the polarizing plate was measured according to the above method, it was -10 mm (reverse curl).

(C) Preparation of Polarizing Plate with Protective Film The polarizing film obtained in (B) above is continuously conveyed, and a long protective film [the base film is made of polyethylene terephthalate and (meth)acrylic A protective film having a pressure-sensitive adhesive layer, total thickness T ₁ : 57.3 μm] is continuously conveyed, and these are stacked and passed between bonding rolls to press the laminate of the protective film and the polarizing plate from above and below. Then, a polarizing plate with a protective film was produced. The protect film is attached to the first thermoplastic resin film (TAC film) surface of the polarizing plate via the adhesive layer. The sticking roll that comes into contact with the protect film 1 is made of SUS with chrome plating [hardness 100°], and the sticking roll that comes into contact with the polarizing plate 2 is made of NBR (nitrile rubber) [hardness 70°]. I was there. The pressure (nip pressure) applied to the laminate of the protect film and the polarizing plate by the laminating roll is 0.1 MPa, and this numerical value is approximately the same in the following examples and comparative examples.

Table 1 shows the curl amount of the polarizing plate with the protect film.
<Comparative Example 1>
In the step (C), the bonding roll that comes into contact with the protect film 1 is made of NBR (nitrile rubber) [hardness 70°], and the bonding roll that comes into contact with the polarizing plate 2 has SUS plated with chrome. A polarizing plate with a protect film was prepared in the same manner as in Example 1 except that the hardness was 100°. Table 1 shows the curl amount of the polarizing plate with the protect film.

DESCRIPTION OF SYMBOLS 1 protect film, 2, 2a, 2b, 2c polarizing plate, 3 protective film-attached polarizing plate, 5, 5'bonding roll, 10 polarizing film, 20 first thermoplastic resin film, 30 second thermoplastic resin film, 40 Adhesive layer, 50 separate film.

Claims (7)

A method for producing a polarizing plate with a protective film, which comprises a step of stacking a protective film on one surface of a polarizing plate and pressing it by passing it between a pair of bonding rolls,
In the pair of laminating rolls, the surface hardness H ₁ of the laminating roll that comes into contact with the protect film and the surface hardness H ₁ of the laminating roll that comes into contact with the protect film, measured by a type A durometer hardness tester specified in JIS K 6253. The surface hardness H ₂ of the laminating roll is represented by the following formulas (I) and (II):
H ₁ >H ₂ (I)
H ₁ −H ₂ ≧30 ° (II)
Meet the relationship of
The said polarizing plate is a manufacturing method containing a polarizing film, the 1st thermoplastic resin film laminated|stacked on the one surface, and the 2nd thermoplastic resin film laminated|stacked on the other surface. The manufacturing method according to claim 1, wherein, when the polarizing plate is formed into a sheet, curls having a convex side on which the protective film is stacked are formed. The manufacturing method according to claim 1, wherein the first thermoplastic resin film has a higher equilibrium moisture content at a temperature of 23° C. and a relative humidity of 55% than that of the second thermoplastic resin film. The manufacturing method according to claim 3, wherein the difference in the equilibrium moisture content between the first thermoplastic resin film and the second thermoplastic resin film is 0.5% by weight or more. The said protective film is a manufacturing method as described in any one of Claims 1-4 arrange|positioned at the said 1st thermoplastic resin film side. The manufacturing method according to claim 3, wherein the equilibrium moisture content of the first thermoplastic resin film is 1.5% by weight or more. The manufacturing method according to claim 1, wherein the polarizing plate has a thickness of 100 μm or less.