TW201433833A - Method for manufacturing polarizer plate - Google Patents

Abstract

The present invention provides a method for manufacturing a polarizer plate, which is to laminate transparent protective films on two surfaces of a polarization element between a pair of rolls and capable of suppressing warpage. The method of manufacturing a polarizer plate is to have a first transparent protective film and a second transparent protective film that have different elasticity defined as elastic module (MPa) x thickness (μm), with bonding layers arranged therebetween, while passing between a pair of rolls having a difference in roll hardness to laminate to two surfaces of a polarization element. In such a pair of rolls, the high elasticity film is conveyed from the low hardness roll side, and the low elasticity film is conveyed from the high hardness roll side.

Description

Method for manufacturing polarizing plate

The present invention relates to a method for producing a polarizing plate in which a first and a second transparent protective film are bonded to both surfaces of a polarizing element via an adhesive layer.

Conventionally, when a transparent protective film is bonded to both surfaces of a polarizing element having a specific moisture content to produce a polarizing plate, a water-based adhesive or an adhesive is usually used. As a method of bonding the transparent protective film to both surfaces of the polarizing element, for example, a method of laminating a polarizing element between a pair of rolls and transporting a transparent protective film to simultaneously bond the transparent protective film to both surfaces thereof is employed; A stepwise lamination method in which a polarizing element is transferred between a pair of rolls, and a transparent protective film is transferred and bonded to one surface thereof, and then the transparent protective film is bonded to the other surface of the polarizing element.

However, when the polarizing element and the transparent protective film are bonded together by the above-described lamination method, there is a problem that curling occurs in the obtained polarizing plate. When the curl is large, air bubbles are mixed when the obtained polarizing plate (for example, a polarizing plate) is bonded to another member (for example, a liquid crystal cell), which causes a step failure. Further, since the transportability of the polarizing plate which is curled is also deteriorated, there is a problem that stable production cannot be achieved.

In the above-mentioned problem, Patent Document 1 proposes a method of suppressing the occurrence of curl of the polarizing plate by bonding the transparent protective film to both surfaces of the polarizing element so that the directions of the curls are opposite directions. Further, Patent Document 2 proposes a technique of strictly controlling the polarizing plates before and after lamination of the adhesive layer and the spacer for the polarizing plate with the adhesive layer and the spacer attached with the adhesive. Moisture content The curl of the polarizing plate is produced. Further, Patent Document 3 proposes a method of suppressing curl by controlling the thickness and water content of the transparent protective film attached to both surfaces of the polarizing element.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-184809

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-326531

[Patent Document 3] Japanese Patent No. 4335901

However, in the methods described in Patent Documents 1 to 3, a transparent protective film having a curl is used, or it is necessary to strictly control the water content of each member, which is cumbersome to manufacture.

An object of the present invention is to provide a method for producing a polarizing plate in which a transparent protective film is bonded to both sides of a polarizing element between a pair of rolls, and curling can be suppressed with high efficiency.

In order to solve the above problems, the inventors of the present invention have made an effort to achieve the above object by the method for producing a polarizing plate described below, and have completed the present invention.

In other words, the present invention relates to a method for producing a polarizing plate, wherein the first transparent protective film and the second transparent protective film are bonded to each other via a pair of rolls while passing through the adhesive layer. Bonding to both sides of the polarizing element is characterized in that the first transparent protective film and the second transparent protective film have different elasticity defined by values of elastic modulus (MPa) × thickness (μm) The elastic material is defined as a high elastic film, and the one having low elasticity is defined as a low elastic film, and the hardness of the rolls of the above pair of rolls is different, and those having high hardness are defined as high hardness rolls, and those having low hardness are defined as low hardness. In the case of a roller, The high elastic film is conveyed from the low hardness roll side, and the low elastic film is conveyed from the high hardness roll side.

In the above method for producing a polarizing plate, it is preferable that at least the low-hardness roller is an elastic roller coated with a metal core portion via a rubber layer or a resin layer.

In the above method for producing a polarizing plate, a metal roll can be used as the high hardness roll. Further, when an elastic roller is used as both the high-hardness roller and the low-hardness roller, it is preferable to use an elastic roller in which the difference in hardness between the high-hardness roller and the low-hardness roller is 10 or more.

In the above method for producing a polarizing plate, the roller hardness of the elastic roller is preferably 40 to 100°.

In the method for producing a polarizing plate for producing a first transparent protective film/polarizing element/second transparent protective film by a simultaneous lamination method, when the first and second transparent protective films have different elasticity, The strain is generated at the time of lamination due to the difference in elasticity, and the obtained polarizing plate is curled.

In the method for producing a polarizing plate of the present invention, the first and second transparent protective films having different elasticity are bonded to both surfaces of the polarizing element between the pair of rolls, and one of the rolls having a difference in the hardness of the rolls is used. The high elastic film is conveyed on the side of the hardness roller, and the low elastic film is conveyed from the side of the high hardness roller. When one of the rolls having different hardnesses as described above is used, the strain of the film to be conveyed becomes large on the low-hardness roll side, and a speed difference is generated, so that a high-elastic film which is less likely to be strained on the low-hardness roll side is conveyed. . By the combination of the elasticity of the film (high elastic film and low elastic film) conveyed and bonded in this manner and the hardness of the roll (high hardness roll and low hardness roll), the curl of the obtained polarizing plate can be suppressed.

According to the above production method, a polarizing plate in which curl generation is suppressed can be obtained. Therefore, it is expected to reduce the number of steps in the process of manufacturing the liquid crystal panel by bonding the polarizing plate to the liquid crystal cell. Further, in the above-described production method, by selecting the hardness of the roll, it is possible to obtain a polarizing plate having a good appearance without suppressing generation of bubbles between the films without unevenness of wrinkles or irregularities in the stripe shape. The in-plane uniformity of the polarizing plate is excellent, so that high resolution and high contrast can be achieved. An image display device such as a liquid crystal display (LCD) or an electroluminescence display device (ELD).

A‧‧‧ polarizing element

B1‧‧‧1st transparent protective film (low elastic film)

B2‧‧‧2nd transparent protective film (high elastic film)

L‧‧‧ polarizing plate

p‧‧‧Clamping contact points

R1‧‧‧1st roll (low hardness roll)

R2‧‧‧2nd roller (high hardness roller)

Fig. 1 is a view showing an example of a schematic view of a method of producing a polarizing plate of the present invention.

Hereinafter, a method of manufacturing the polarizing plate of the present invention will be described with reference to the drawings. 1 is a view showing an example of a method for producing a polarizing plate of the present invention, in which a first transparent protective film B1 and a second transparent protective film B2 are pressed between a pair of rolls of a first roll R1 and a second roll R2. The polarizing plate L is formed by being connected to both sides of the polarizing element A. The first transparent protective film B1 and the second transparent protective film B2 have different elastic modulus. In FIG. 1, the elastic modulus of the second transparent protective film B2 is higher than the elastic modulus of the first transparent protective film B1, the second transparent protective film B2 is a high elastic film, and the first transparent protective film B1 is a low elastic film.

Moreover, the roll hardness of each of the first roll R1 and the second roll R2 is different. In FIG. 1, the roll hardness of the second roll R2 is higher than the roll hardness of the first roll R1, the second roll R2 is a high hardness roll, and the first roll R1 is a low hardness roll.

In the present invention, the three films (the polarizing element A, the first transparent protective film B1, and the second transparent protective film B2) are simultaneously passed through a pair of the first roller R1 and the second roller R2 to be crimped. As shown in Fig. 1, the high elastic film (second transparent protective film B2) is transferred from the low hardness roller (first roller R1) side, and the low elastic film is transferred from the high hardness roller (second roller R2) side. 1 transparent protective film B1).

As shown in Fig. 1, when the hardness of each of the first roller R1 and the second roller R2 is different, the roller surface of the low hardness roller (first roller R1) (for example, the rubber layer or the resin layer of the elastic roller) Stretched and stretched. In this case, the second transparent protective film B2 (high elastic film) conveyed from the low hardness roller side is increased in the vicinity of the pinch contact point p between the first roller R1 and the second roller R2. Immediately after contact with the polarizing element A, the polarizing element A is attached to the state in which tension is applied. Generally, the film tends to curl toward the person who applies the tension. The curl of the obtained polarizing plate L can be suppressed by utilizing the elastic modulus of the film and the characteristics of the roll.

That is, when the same tension is applied to the film to be bonded, the film having higher elasticity has a property of being less likely to be elongated, and the film having lower elasticity is easily stretched. In Fig. 1, the second transparent protective film B2 (high elastic film) conveyed from the low hardness roller (first roll R1) side is bonded while being applied with a larger tension, but is elongated due to a high elastic film. Get suppressed. On the other hand, in the high hardness roller (second roller R2), since the elongation of the roller surface is small, the tension in the vicinity of the grip contact point p is weak. Therefore, by transferring the low elastic film from the high hardness roller side, the two can be bonded in a well-balanced manner, and the curl of the obtained polarizing plate L can be suppressed.

Further, between the first roller R1 and the second roller R2, the first transparent protective film B1 and the second transparent protective film B2 are bonded to each other on both surfaces of the polarizing element A via an adhesive layer (not shown). The adhesive layer may be provided on the first transparent protective film B1 and the second transparent protective film B2, or may be provided on the polarizing element A or may be provided on both sides. Further, the polarizing element A, the first transparent protective film B1, and the second transparent protective film B2 can be passed together with an adhesive (solution) or an adhesive (solution) adjusted in concentration or viscosity immediately before bonding. The first roll R1 and the second roll R2 are pressure-bonded between the pair of rolls.

The rolls of the first roll and the second roll have different hardnesses. A person having high hardness is defined as a high hardness roller, and a person having low hardness is defined as a low hardness roller. As the high-hardness roller and the low-hardness roller, either one of an elastic roller and a metal roller can be used. However, in the first roller and the second roller, the high-hardness roller and the low-hardness roller are in contact with each other due to the difference in hardness. In the case where the surface of the low-hardness roller side is easily deformed (elongated due to extrusion), it is preferable that at least the low-hardness roller uses an elastic roller coated with a metal core or a rubber layer or a resin layer.

As the elastic roller, an elastic roller coated with a metal core through a rubber layer or a resin layer can be preferably used. As the hardness of the rubber layer or the resin layer, a range of 40 to 100 ° can be preferably used. The hardness is preferably from 60 to 90°. It is preferable to set the hardness to 40° or more in terms of preventing the deformation of the surface on the low-hardness roll side from being excessively large and causing bubbles to be formed when the polarizing plate is bonded to deteriorate the appearance. Moreover, in terms of preventing damage to the surface of the film, it is preferred To set the hardness to 100° or less. The hardness at this time can be measured, for example, by a method disclosed in JIS K6253 (1997) using a commercially available hardness meter (type A). Specifically, the measurement of the roll hardness was carried out using Type A of GS-719N manufactured by Teclock Co., Ltd. (JIS K 6253). Further, in terms of the uniformity of the surface pressure distribution, the thickness of the rubber layer or the resin layer is preferably about 1 to 15 mm, more preferably about 3 to 10 mm.

On the other hand, as the high hardness roller, a metal roller can be used. For example, in the case where the above elastic roller is used as the low hardness roller, a metal roller can be used as the high hardness roller. Examples of the material of the metal roll include iron, stainless steel, titanium, aluminum, and the like. As the metal roll, an iron roll or a stainless steel roll is preferable in terms of cost effectiveness and corrosion resistance. The roll hardness of the metal roll is higher than that of the elastic roll.

When the combination of the high hardness roller and the low hardness roller is a metal roller and an elastic roller, the roller hardness (hardness of the rubber layer or the resin layer) of the elastic roller as the low hardness roller is preferably 40 to 90°, and further preferably It is 60~80°.

Further, for either of the high hardness roller and the low hardness roller, an elastic roller can be used. In this case, the difference in hardness between the high hardness roller and the low hardness roller is preferably 10 or more. On the other hand, when the hardness difference is too large, the lamination pressure is lowered by the decrease in hardness, and bubbles are easily generated between the films. In order to obtain a polarizing plate having a good appearance, the hardness difference is preferably 40 or less, more preferably 30 or less, still more preferably 20 or less.

Further, the roll diameter of each roll, the conveyance speed at the time of bonding, and the like can be appropriately adjusted, and the thickness of the subsequent layer can be appropriately adjusted.

Further, as the diameter of the roller is smaller, the area where the polarizing element A contacts the first transparent protective film B1 and the second transparent protective film B2 is smaller, so that the pressure applied to the film surface is relatively higher. Therefore, as the diameter of the roll, it is preferable to use 250 mm or less, and more preferably 200 mm or less. However, if the diameter is too small, the durability of the roll becomes weak, so that a sufficient force cannot be applied. Therefore, it is preferable to use 50 mm or more. The roller is more preferably a roller of 100 mm or more.

Moreover, the conveyance speed at the time of bonding is not particularly limited, and it is usually preferably adjusted from about 2 m/min to 50 m/min.

Moreover, the lamination pressure between the rolls at the time of bonding is not particularly limited, and can be appropriately set. The lamination pressure is preferably 2 MPa or more and 5 MPa or less, and more preferably 3 MPa or more and 4 MPa or less in terms of ease of adjustment or productivity of the polarizing plate. If the lamination pressure is less than 2 MPa, sufficient extrusion cannot be performed, so that bubbles are generated between the membranes. Moreover, if the lamination pressure is more than 5 MPa, an excessive load is applied to the roll or the device, which is a cause of breakage. The lamination pressure was measured by using the pressure sensitive paper "PRESCALE" manufactured by Fuji Film Co., Ltd., and the color change of the pressure sensitive paper was binarized by computer image processing, and the pressure standard was produced according to the color development area and concentration thereof. The approximate formula of the line is obtained.

The polarizing element is not particularly limited, and various types can be used. Examples of the polarizing element include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, which adsorbs iodine or a dichroic dye. The dichroic material is a material which is uniaxially stretched, a dehydration treatment of polyvinyl alcohol, a polyalkylene alignment film such as a dechlorination treatment of polyvinyl chloride, or the like. Among these, a polarizing element including a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of the polarizing elements is not particularly limited, but is usually about 5 to 80 μm. The thickness of the polarizing element is preferably 15 to 35 μm. When the thickness of the polarizing element is too thin, it is likely to be damaged when it is bonded to the transparent protective film. On the other hand, when the thickness of the polarizing element is too thick, the drying efficiency tends to be deteriorated, which is not preferable in terms of productivity.

A polarizing element in which a polyvinyl alcohol-based film is dyed with iodine and uniaxially stretched can be produced, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine for dyeing and extending to a length of 3 to 7 Times. It may also be immersed in an aqueous solution of boric acid or potassium iodide as needed. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. The surface of the polyvinyl alcohol film can be stained or anti-adhesive by washing the polyvinyl alcohol film with water. The cleaning agent is also washed, and the polyvinyl alcohol-based film is swollen to have an effect of preventing unevenness in dyeing unevenness. The stretching may be carried out after dyeing with iodine, or may be carried out while dyeing, or may be dyed with iodine after stretching. It can also be extended in an aqueous solution of boric acid or potassium iodide or in a water bath.

Further, the water content of the polarizing element is not particularly limited, but it is usually preferably from 8 to 30% by weight, more preferably from 10 to 20% by weight. The water content of the polarizing element is preferably lower in terms of improving the drying efficiency in the drying step and improving the productivity of the production speed. Further, the water content of the polarizing element is preferably lower in terms of obtaining a polarizing plate having excellent optical characteristics. On the other hand, when the water content of the polarizing element is too low, the rigidity of the film as the polarizing element is improved, and it is easily damaged, and appearance defects are likely to occur. The moisture content of such a polarizing element can usually be adjusted by the conditions of the drying treatment in the manufacturing steps of the polarizing element, but it is also possible to additionally provide a humidity conditioning treatment step, a dipping in a water bath or a spray of water droplets, or again. Heat dry or dry under reduced pressure.

Further, the method for producing the polarizing element is not limited to the above-described production method, and if the water content is 8 to 30% by weight (preferably, the water content is 10 to 20% by weight), the polarizing element can be produced by another manufacturing method. For example, it may be a dry stretching method, or may be a method in which a dichroic substance is kneaded into a polymer film such as polyethylene terephthalate (PET), and a film is formed and extended. A directional alignment liquid crystal is used as a host, and a dichroic dye is used as a guest of the O type (U.S. Patent No. 5,523,863, Japanese Patent Application Laid-Open No. Hei No. Hei. Type E of a liquid crystal type or the like (U.S. Patent No. 6,049,428).

The elastic modulus of the first and second transparent protective films is not particularly limited, but it is preferably in the range of from 1,000 to 10,000 MPa. The above elastic modulus is preferably 1200 to 5,000 MPa, and more preferably 1300 to 4,000 MPa. Further, the first and second transparent protective films have elastic modes of the first and second transparent protective films as long as they have differences in elasticity. The numbers can be the same or different.

The elastic modulus of the above transparent protective film is a value (N/mm ² = MPa) measured in accordance with the tensile test method of JIS K 7127. Specifically, the elastic modulus was measured in accordance with the following criteria.

The horizontal axis when the elastic modulus (the slope of the graph) is obtained: strain (%)

The longitudinal axis when the elastic modulus (the slope of the graph) is obtained: tensile stress σ (MPa = N / mm ² ) = F / initial sectional area of the test piece A (mm ² )

The range in which the elastic modulus (the slope of the graph) is obtained: linear regression between strains of 0.05 to 0.25%

Test piece shape: strip shape (rectangular)

Distance between chucks: 100mm

Although the thickness of the first and second transparent protective films can be appropriately determined, it is preferably from about 20 to 200 μm, more preferably from 30 to 100 μm, in terms of handleability such as strength and handleability, and thin layer properties. When the thickness of the first and second transparent protective films is within the above range, the drying efficiency is good, and the roll of the original sheet can be elongated, which is preferable in terms of productivity. On the other hand, when the thickness of the first and second transparent protective films is increased, the drying efficiency is inferior and the productivity is not good.

Further, the first and second transparent protective films are selected such that the respective elastic modulus and thickness are different so that the elasticity defined by the product of the elastic modulus (MPa) × thickness (μm) is different. Regarding the first transparent protective film and the second transparent protective film, a person having a high elastic modulus is defined as a high elastic film, and a person having a low elastic modulus is defined as a low elastic film.

Further, the difference between the elasticity of the high elastic film and the elasticity of the low elastic film is preferably from 0 to 170,000 in terms of wrinkles, and the case is more than 30,000 or less. good. In particular, when the difference is 1000 or more and further 3,000 or more, and further, when it is 10,000 or more, strain is likely to occur due to the difference in elasticity, and thus the present invention can be preferably applied.

Various types of the first and second transparent protective films can be used. 1st and 2nd above The transparent protective film is selected such that one of them is a highly elastic film and the other is a low elastic film. Further, the control of the elasticity of the high elastic film and the low elastic film can be controlled by the material (modulus of elasticity) and thickness of the first and second transparent protective films.

The material for forming the transparent protective film is preferably a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. For example, a polyester-based polymer such as polyethylene terephthalate or polyethylene naphthalate, a cellulose-based polymer such as diethyl phthalocyanine or triethylene fluorene cellulose, or polymethyl methacrylate may be mentioned. An acrylic polymer such as an ester, a styrene polymer such as polystyrene or an acrylonitrile-styrene copolymer (AS resin), or a polycarbonate polymer. Further, examples of the polymer forming the transparent protective film include polyethylene, polypropylene, ring system or have a lowering A polyolefin polymer such as an olefin structure, a polyolefin polymer such as an ethylene-propylene copolymer, a vinyl chloride polymer, a guanamine polymer such as nylon or an aromatic polyamine, a ruthenium-based polymer, or an oxime polymerization. , polyether oxime polymer, polyetheretherketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, ethylene butyral polymer, arylate polymerization , a polyoxymethylene polymer, an epoxy polymer, or a mixture of the above polymers. Further, a transparent protective film is usually laminated on the polarizing element by an adhesive layer, and as the transparent protective film, (meth)acrylic, urethane-based, or acryl-yl urethane can be used. A thermosetting resin such as an epoxy resin or an anthrone or an ultraviolet curable resin. The transparent protective film may contain one or more optional additives. Examples of the additive include a UV absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a colorant, and the like. The content of the above thermoplastic resin in the transparent protective film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, still more preferably from 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the high transparency and the like which the thermoplastic resin originally has cannot be sufficiently exhibited.

As the transparent protective film of the present invention, it is preferred to use a cellulose resin (polymer), a polycarbonate resin (polymer), a cyclic polyolefin resin (ring system or have a drop). At least one of a polyolefin structure of an olefin structure and a (meth)acrylic resin.

Further, in terms of polarization characteristics, durability, and improvement in adhesion characteristics, the surface of the transparent protective film may be subjected to corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, and saponification treatment. Surface modification treatment. In the case of using the cellulose resin (polymer) as the transparent protective film in the surface modification treatment, it is preferred to carry out the saponification treatment using an alkali or the like.

The surface of the transparent protective film that is not attached to the polarizing element may be subjected to a hard coat layer or an anti-reflection treatment, and is intended to be resistant to adhesion, diffusion, or anti-glare.

Further, the antireflection layer, the anti-blocking layer, the diffusion layer, the antiglare layer, and the like may be provided as the transparent protective film itself, or may be provided in the form of an optical layer as another layer different from the transparent protective film.

The above-mentioned adhesive layer is not particularly limited, and various forms of a water system, a solvent system, a hot melt system, and a radical curing type can be used. The adhesive layer used in the bonding of the polarizing element and the transparent protective film is not particularly limited as long as it is optically transparent. In the formation of the adhesive layer used for bonding the polarizing element and the transparent protective film, a water-based adhesive or a radical-curable adhesive is preferred.

The water-based adhesive for forming the adhesive layer is not particularly limited, and examples thereof include a vinyl polymer system, a gelatin system, a vinyl latex system, a polyurethane resin, an isocyanate system, a polyester system, and a ring. Oxygen and the like. The adhesive layer containing such a water-based adhesive may be formed in the form of a coating dry layer of an aqueous solution or the like, and when preparing the aqueous solution, a crosslinking agent or other additives, an acid or the like may be blended as needed. As the water-based adhesive, an adhesive containing a vinyl polymer or the like is preferably used, and as the vinyl polymer, a polyvinyl alcohol-based resin is preferable. Further, the polyvinyl alcohol-based resin may contain a water-soluble crosslinking agent such as boric acid or borax, glutaraldehyde or melamine or oxalic acid. In particular, when a polyvinyl alcohol-based polymer film is used as the polarizing element, it is preferably used in terms of adhesion. An adhesive for polyvinyl alcohol-based resins. Further, in terms of improving durability, an adhesive containing a polyvinyl alcohol-based resin having an ethyl acetate group is more preferable.

The polyvinyl alcohol-based resin is not particularly limited, but in terms of adhesion, the average degree of polymerization is preferably about 100 to 3,000, and the average degree of saponification is about 85 to 100 mol%. In addition, the concentration of the aqueous solution of the adhesive agent is not particularly limited as long as it is appropriately determined depending on the thickness of the target adhesive layer, and is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight. When the concentration of the solution is too high, the viscosity is excessively increased, so that streaky unevenness is likely to occur, and if the concentration of the solution is too low, the coatability is deteriorated and the unevenness is likely to occur.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; and a saponified product of a copolymer of vinyl acetate and a copolymerizable monomer; and acetalization of polyvinyl alcohol Modified polyvinyl alcohol obtained by urethanization, etherification, grafting, phosphorylation, and the like. Examples of the monomer include unsaturated carboxylic acids such as maleic acid (anhydride), fumaric acid, crotonic acid, methylene succinic acid, and (meth)acrylic acid, and esters thereof, and ethylene. , α-olefin such as propylene, (meth)allylsulfonic acid (sodium), sodium sulfonate (single alkyl maleate), sodium disulfonate maleate, N- Methylol methacrylate, acrylamide alkyl sulfonate alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivative, and the like. These polyvinyl alcohol-based resins may be used alone or in combination of two or more.

The polyvinyl alcohol-based resin containing an ethyl acetonitrile group can be obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method in which a polyvinyl alcohol-based resin is previously dispersed in a solvent such as acetic acid, and a diketene is added thereto, and a polyvinyl alcohol-based resin is previously dissolved in dimethylformamide or two. A method of adding a diketene to a solvent such as an alkane or the like. Further, a method of directly contacting the diketene gas or the liquid diketene with polyvinyl alcohol can be mentioned.

The degree of modification of the ethylenic acid group of the polyvinyl alcohol-based resin containing an ethyl acetate group is not particularly limited as long as it is 0.1 mol% or more. If less than 0.1 mol%, the resistance of the adhesive layer Water is not sufficient and is therefore not suitable. The degree of modification of the acetamidine group is preferably from about 0.1 to 40 mol%, more preferably from 1 to 20 mol%, and particularly preferably from 2 to 7 mol%. When the degree of modification of the ethyl hydrazide group exceeds 40 mol%, the reaction point with the crosslinking agent decreases, and the effect of improving the water resistance is small. The degree of modification of such an oxime group can be measured using a nuclear magnetic resonance apparatus (NMR: Nuclear Magnetic Resonance).

As the crosslinking agent, a crosslinking agent generally used for an adhesive agent can be used without particular limitation. For example, in the case of using an adhesive of a polyvinyl alcohol-based resin as described above, it is preferable to use at least two A polyvinyl alcohol-based resin has a reactive functional group. For example, an alkyl diamine having an alkylene group and two amine groups such as ethylenediamine, triethylamine, hexamethylenediamine, etc.; toluene diisocyanate, hydrogenated toluene diisocyanate, trimethylolpropane Isocyanate, toluene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis(4-phenylmethane triisocyanate), isophorone diisocyanate, and the like, such as ketone oxime endblocks or phenol cappings Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether or glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane tricondensate Ethylenes such as glyceryl ether, diglycidyl aniline, diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, Dialdehydes such as maleic acid and phthalaldehyde; methylol urea, methylol melamine, alkylated methylol urea, alkylated methylol melamine, acetamidine An amine-formaldehyde resin such as a condensate of benzoguanamine and formaldehyde; further a divalent metal such as sodium, potassium, magnesium, calcium, aluminum, iron or nickel, or a salt of a trivalent metal and an oxide thereof. Among these, an amine-formaldehyde resin is preferred, and a hydroxymethyl compound having a methylol group is particularly preferred.

The amount of the crosslinking agent is usually from 0.1 to 35 parts by weight based on 100 parts by weight of the resin, and preferably from 10 to 25 parts by weight, but in the case of paying attention to the durability of the adhesive, in order to become self-sufficient The time from the preparation of the agent to the formation of the adhesive layer is shortened, and it is also effective to prepare a crosslinking agent in an amount of 30 parts by weight or more and 46 parts by weight or less, more preferably 32 parts by weight or more and 40 parts by weight or less.

The radical curing type adhesive agent may, for example, be an active energy ray-curing type or a thermosetting type such as an electron beam curing type or an ultraviolet curing type, and is preferably an active energy ray curing type which can be cured in a short time. It is especially suitable for UV curing.

Examples of the curable component include a compound having a (meth)acryl fluorenyl group and a compound having a vinyl group. As the curable component, any of a monofunctional or difunctional or higher curative component can be used. In addition, these curable components may be used alone or in combination of two or more. As such a curable component, for example, a compound having a (meth)acryl fluorenyl group is preferable, and examples thereof include various epoxy (meth) acrylate, (meth) acrylate urethane, and polyester (A). Acrylate, or various (meth) acrylate monomers, and the like.

The hardening type adhesive contains a curable component, and in addition to the above components, a radical initiator is added depending on the type of hardening. In the case where the above-mentioned adhesive is used in the electron beam curing type, it is not particularly necessary to include a radical initiator in the above-mentioned adhesive, but in the case of using an ultraviolet curing type or a thermosetting type, a radical initiator is used. . The amount of the radical initiator to be used is usually from 0.1 to 10 parts by weight, preferably from 0.5 to 3 parts by weight, per 100 parts by weight of the curable component.

Further, a metal compound filler may be contained in the above-mentioned adhesive. The film thickness can be stabilized by controlling the fluidity of the adhesive layer by the metal compound filler, whereby a polarizing plate having a good appearance, uniform in-plane, and unevenness in adhesion can be obtained.

Further, in the formation of the adhesive layer, a dry lamination method which can be bonded in a solventless or low solvent state can be preferably used. As the dry lamination method, a conventionally known dry laminating adhesive and a bonding method can be used, and the method can be used in addition to the present invention. Thereby, there is an effect of further reducing the unevenness of the streaks.

Examples of the above-mentioned adhesive for dry lamination include a two-liquid curing type adhesive, a two-liquid solvent type adhesive, and a one-liquid solventless type adhesive. As the two-liquid curing type adhesive, an acrylic type can be used, and as a two-liquid solvent type adhesive, a polyester type, an aromatic polyester type, an aliphatic polyester type, a polyester/polyurethane type, or the like can be used. Polyether/polyurethane As a one-liquid solvent-free type adhesive (type of moisture-curing type), a resin such as a polyether/polyurethane type or the like can be used.

The above-mentioned adhesive layer may be one which appropriately contains an additive as needed. Examples of the additive include a sensitizer represented by a carbonyl compound or the like, a sensitizer which increases the curing rate or sensitivity by an electron beam, a coupling agent such as a decane coupling agent or a titanium coupling agent, and a subsequent accelerator represented by ethylene oxide. An additive for improving the wettability of a transparent protective film, an additive for improving mechanical strength or processability, such as a propylene oxime compound or a hydrocarbon (natural, synthetic resin), ultraviolet absorber, anti-aging agent, dye , processing aids, ion trapping agents, antioxidants, adhesion-imparting agents, fillers (other than metal compound fillers), plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat-resistant stabilizers, hydrolysis-resistant stabilizers Stabilizers, etc.

A polarizing plate can be obtained by laminating a transparent protective film on both surfaces of the polarizing element via an adhesive layer, but an undercoat layer or an easy-to-process layer may be provided between the adhesive layer and the transparent protective film or the polarizing element. Wait.

When the adhesive layer formed by the above production method is formed of a water-based adhesive or the like, the thickness of the adhesive layer is preferably 30 to 300 nm. The thickness of the above adhesive layer is further preferably from 60 to 250 nm. On the other hand, in the case where the adhesive layer is formed of a hardening type adhesive, the thickness of the above-mentioned adhesive layer is preferably from 0.1 to 200 μm. More preferably, it is 0.5 to 50 μm, and further preferably 0.5 to 10 μm.

In the method for producing a polarizing plate described above, after the polarizing element and the transparent protective film are bonded together, the curing step is performed in accordance with the type of the adhesive. In the case of using a water-based adhesive, a drying step can be carried out. The drying conditions in the drying step are usually a drying temperature of about 40 to 100 ° C and a drying time of about 1 to 10 minutes. In the case of a radical hardening type adhesive, for example, an electron beam, an ultraviolet ray or the like can be irradiated.

The polarizing plate obtained by the production method of the present invention can be used in the form of an optical film laminated with other optical layers in actual use. There is no special about this optical layer For example, one or two or more reflective or semi-transmissive plates, phase difference plates (including 1/2 or 1/4 wavelength plates), viewing angle compensation films, and the like may be used, and may be used for liquid crystal display devices and the like. The optical layer formed. More preferably, it is a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is laminated on the polarizing plate of the present invention, and an elliptically polarizing plate or a circle formed by laminating a phase difference plate on a polarizing plate. A polarizing plate, a wide viewing angle polarizing plate formed by laminating a viewing angle compensation film on a polarizing plate, or a polarizing plate formed by laminating a brightness enhancement film on a polarizing plate.

The polarizing plate or the optical film of the present invention can be preferably used for formation of various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to the previous method. In other words, the liquid crystal display device is usually formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate, an optical film, and an unnecessary illumination system, and assembling them into a drive circuit or the like. However, in the present invention, the present invention is used. The aspect of the polarizing plate or the optical film is not particularly limited and may be based on the prior method. As the liquid crystal cell, for example, any type of liquid crystal cell such as TN (Twisted Nematic) or STN (Super Twisted Nematic) type or π type can be used.

A liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a liquid crystal display device such as a backlight or a reflector used in an illumination system can be formed. In this case, the polarizing plate or the optical film of the present invention may be disposed on one side or both sides of the liquid crystal cell. In the case where a polarizing plate or an optical film is provided on both sides, the same may be the same or different. Further, when the liquid crystal display device is formed, for example, one or two or more diffusion plates, an antiglare layer, an antireflection film, a protective plate, a tantalum array, a lens array sheet, a light diffusing plate, and the like may be disposed at appropriate positions. Suitable parts such as backlight.

Further, the production method of the present invention can be applied to a polarizing plate as a first film, a separator provided with an adhesive layer as a second film, and an adhesive layer-attached polarizing layer provided on the polarizing plate. The manufacturing method of the board. Further, the production method of the present invention can be applied to a polarizing plate or a polarizing plate with an adhesive layer as a first film, and a surface protective film is used. A method of producing a polarizing plate with a surface protective film attached to a second film or a polarizing plate with an adhesive layer.

In the case where an optical functional layer is laminated on the above polarizing plate, a method of laminating via an adhesive layer or an adhesive layer can be preferably used. As the adhesive layer or the adhesive layer at this time, an adhesive layer containing an adhesive can be preferably used.

The adhesive layer containing an adhesive can be formed, for example, by an appropriate adhesive such as an acrylic, an anthrone, a polyester, a polyurethane, a polyether or a rubber according to the prior art. As the adhesive, an image display device that prevents foaming or peeling due to moisture absorption, prevents deterioration of optical characteristics due to poor thermal expansion, or warps liquid crystal cells, and is high in quality and excellent in durability In terms of formability and the like, an adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable, and in order to prevent a change in optical characteristics of a polarizing plate or the like, it is preferred that high temperature is not required for hardening or drying. The process does not require long-term hardening or drying time. From this point of view, an acrylic adhesive can be preferably used for the polarizing plate or the optical film. Further, fine particles may be added to the above-mentioned adhesive to form an adhesive layer or the like which exhibits light diffusibility.

Such an adhesive layer or an adhesive layer may be disposed on the necessary surface as needed, for example, for the polarizing plate obtained by the polarizing element and the transparent protective film of the present invention, as long as it is required to be in the polarizing plate. The surface may be provided with an adhesive layer on the surface opposite to the surface to which the polarizing element is attached, in the case of a transparent protective film. The thickness of the adhesive layer containing the adhesive when used for laminating the optical functional layer is not particularly limited, but is usually about 1 to 500 μm, preferably 5 to 200 μm, more preferably 10 ~100μm. By setting the thickness of the adhesive layer or the adhesive layer to this range, the stress accompanying the dimensional behavior of the polarizing plate or the optical functional layer can be alleviated.

When the adhesive layer containing the above-mentioned adhesive is exposed on the surface, it is preferable to temporarily cover the adhesive layer for the purpose of preventing contamination during the period before the application of the adhesive layer. Preferably, the separator is used in accordance with the above-mentioned protective film or the like. A release coating using an appropriate release agent such as an anthrone or a long-chain alkyl group, a fluorine-based or a molybdenum sulfide is optionally provided on the film.

Further, as the surface protective film, those formed by providing an adhesive layer on the base film and peeling off the base film together with the adhesive layer can be used.

A polarizing plate can be obtained by laminating a transparent protective film on both surfaces of the polarizing element via an adhesive layer. However, an undercoat layer or an easy-to-process layer may be provided between the adhesive layer and the transparent protective film or the polarizing element.

[Examples]

Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited by the examples and comparative examples.

(Method for measuring moisture content of polarizing element)

A sample of 180 mm × 500 mm was cut out from the obtained polarizing element, and the initial weight (W (g)) was measured. After the sample was allowed to stand in a dryer at 120 ° C for 2 hours, the weight after drying (D (g)) was measured. Based on these measured values, the water content was determined by the following formula.

Moisture content (%) = {(W-D) / W} × 100

(production of polarizing element)

A polyvinyl alcohol film having an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% and a thickness of 75 μm was immersed in warm water of 30 ° C for 60 seconds to swell. Then, the film was dyed while being immersed in an aqueous solution of 0.3% by weight of iodine/potassium iodide (weight ratio = 0.5/8) while extending to 3.5 times. Thereafter, the solution was extended in a boric acid aqueous solution at 65 ° C so that the total stretching ratio was 6 times. After stretching, it was dried in an oven at 40 ° C for 3 minutes to obtain a PVA (polyvinyl alcohol)-based polarizing element (thickness: 23 μm). The polarizing element had a thickness of 23 μm and a water content of 18% by weight.

<Transparent protective film>

TAC: a triacetonitrile cellulose film having a thickness of 60 μm (manufactured by Fuji Film Co., Ltd.: TD60UL, elastic modulus: 4000 MPa); COP: a cyclic polyolefin film having a thickness of 50 μm (manufactured by Zeon Corporation, Japan: ZEONOR, elastic modulus: 1800 MPa); ACRYL: an acrylic film (elastic modulus: 2000 MPa) having a thickness of 40 μm.

<Active energy ray>

As the active energy ray, an ultraviolet ray (metal halide lamp sealed with gallium) irradiation device: Light HAMMER 10 manufactured by Fusion UV Systems, Inc., vacuum tube: V vacuum tube, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount 1000/mJ/ Cm ² (wavelength 380~440nm). Further, the illuminance of ultraviolet rays was measured using a Sola-Check system manufactured by Solatell.

<Preparation of active energy ray hardening type adhesive>

38.3 parts of N-hydroxyethyl acrylamide (manufactured by Xingren Co., Ltd.) as a radical polymerizable compound (A), and tripropylene glycol diacrylate as a radical polymerizable compound (B) (trade name: Aronix M- 220, manufactured by Toagosei Co., Ltd., 19.1 parts, 38.3 parts of propylene decylmorpholine (manufactured by Xingren Co., Ltd.) as a radical polymerizable compound (C), and a photopolymerization initiator (trade name: KAYACURE DETX-S, II) Ethyl-9-oxosulfur The mixture was mixed with 1.4 parts and made to stir at 50 ° C for 1 hour to obtain an active energy ray hardening type adhesive.

Example 1

<Production of polarizing plate>

A polarizing plate was produced by the method shown in FIG. The polarizing element A uses the above-described polarizing element. As the first transparent protective film B1, a cyclic polyolefin film having a thickness of 50 μm was used. After forming a urethane-based easy-adhesion layer having a thickness of 0.5 μm on the cyclic polyolefin film, an MCD coater (manufactured by Fuji Machinery Co., Ltd.) was used (unit shape: honeycomb shape, number of gravure rolls: 1000 pieces/ Inch, speed 140% / relative to the line speed), the above active energy ray hardening type The coating agent was applied onto the easy-adhesion layer so that the thickness of the adhesive layer became 0.5 μm. A TAC film with an adhesive layer was produced in the same manner as above except that a TAC film was used instead of the above-mentioned cyclic polyolefin film for the second transparent protective film B2. Then, the first transparent protective film B1 and the second transparent protective film B2 are bonded to both surfaces of the polarizing element A (polarizing element) by a roll press through the above-mentioned adhesive layer. In the roll press, an iron roll having a diameter of 200 mm was used as the first roll R1, and an elastic roll having a hardness of 60° of 200 mm in diameter was used as the second roll R2. As shown in FIG. 1 , the first transparent protective film B1 is transported from the second roller R2 side, and the second transparent protective film B2 is transported from the first roller R1 side. Thereafter, the two sides of the first and second transparent protective films that have been bonded are heated to 50° C. using an IR (infrared radiation) heater, and the ultraviolet rays are applied to both surfaces to form an active energy ray-curable adhesive. hardening. Further, hot air drying was performed at 70 ° C for 3 minutes to obtain a polarizing plate having a transparent protective film on both sides of the polarizing element. The line speed of the bonding was performed at 25 m/min.

Examples 2 to 4 and Comparative Examples 1 to 4

In the first embodiment, the types of the first transparent protective film, the second transparent protective film, and the types of the first roll and the second roll were changed as shown in Table 1, and the same procedure as in Example 1 was obtained. Polarizer.

The polarizing plates produced in the examples and the comparative examples were subjected to the following evaluations. The results are shown in Table 1.

(curly)

The obtained polarizing plate was statically placed on a horizontal plate, and the length of the portion where the distance between the side portion of the polarizing plate and the horizontal plate was the largest was defined as the amount of curl (mm).

(Appearance: confirmation of bubbles)

A sample of 1000 mm × 1000 mm was cut out from the obtained polarizing plate, and the number of bubbles between the polarizing element and the transparent protective film was confirmed.

As is apparent from the results of the above Table 1, according to the embodiment of the present invention, in the embodiment, the amount of crimping is 10 mm or less, and the curl can be suppressed to be small. The amount of curling can satisfy the curl requirement value when the polarizing plate is applied to a size of 32 inches.

A‧‧‧ polarizing element

B1‧‧‧1st transparent protective film (low elastic film)

B2‧‧‧2nd transparent protective film (high elastic film)

L‧‧‧ polarizing plate

p‧‧‧Clamping contact points

R1‧‧‧1st roll (low hardness roll)

R2‧‧‧2nd roller (high hardness roller)

Claims (5)

A method for producing a polarizing plate, wherein the first transparent protective film and the second transparent protective film are bonded to each other on both sides of the polarizing element by passing the adhesive layer between the pair of rolls through the adhesive layer, and are characterized in that The first transparent protective film and the second transparent protective film are different in elasticity defined by values of elastic modulus (MPa) × thickness (μm), and those having high elasticity are defined as high elastic films, which have low elasticity. It is defined as a low-elastic film, and the roll hardness of each of the pair of rolls is different, and a person having high hardness is defined as a high-hardness roll, and when a person having low hardness is defined as a low-hardness roll, from the above-mentioned low-hardness roll side The high elastic film is conveyed, and the low elastic film is conveyed from the high hardness roller side. A method of producing a polarizing plate according to claim 1, wherein at least the core of the low-hardness roller-based metal is coated with an elastic roller coated with a rubber layer or a resin layer. A method of producing a polarizing plate according to claim 1 or 2, wherein the high hardness roller is a metal roller. The manufacturing method of the polarizing plate of claim 1 or 2, wherein the high-hardness roller and the low-hardness roller are elastic rollers coated with a rubber core or a resin layer, and a hardness difference between the high-hardness roller and the low-hardness roller It is 10 or more. The method for producing a polarizing plate according to any one of claims 2 to 4, wherein the elastic roller has a roller hardness of 40 to 100°.