KR20140077102A - Method for producing polarizing plate - Google Patents

Abstract

The present invention relates to a method of producing a polarizing plate for attaching a transparent protective film to both surfaces of a polarizer between a pair of rolls and is to provide the method of producing the polarizing plate capable of suppressing a curl. The method of producing the polarizing plate comprises the steps of interposing a first transparent protective film, a second transparent protective film, and an adhesive layer which have different elasticity defined as a value of a modulus (Mpa)× thickness (μm) on both sides of the polarizer; passing between the rolls having a pair of different roll slopes simultaneously and being combined; returning a high elasticity film from a low sloe roll side between the pair of the rolls; and returning a low elasticity film from a high slope roll side.

Description

METHOD FOR PRODUCING POLARIZING PLATE [0002]

The present invention relates to a method of manufacturing a polarizing plate in which first and second transparent protective films are bonded to both surfaces of a polarizer with an adhesive layer interposed therebetween.

Conventionally, in order to produce a polarizing plate by bonding a transparent protective film to both surfaces of a polarizer having a predetermined moisture content, an aqueous adhesive or a pressure-sensitive adhesive is usually used. Examples of the method of bonding the transparent protective film to both surfaces of the polarizer include a simultaneous lamination method in which the polarizer is transported between a pair of rolls and the transparent protective film is transported to both sides thereof to simultaneously adhere the transparent protective film, A sequential lamination method is employed in which a polarizer is transported between rolls of a pair and a transparent protective film is transported to one side of the roll, and then a transparent protective film is stuck to the other side of the polarizer.

However, when the polarizer and the transparent protective film are laminated by the above-mentioned lamination method, the occurrence of curl in the obtained polarizing plate can be mentioned. When the curl is large, bubbles are mixed when a polarizing plate (for example, a polarizing plate) obtained is bonded to another member (for example, a liquid crystal cell or the like), which causes a process failure. Further, the polarizing plate on which the curl is formed deteriorates the conveying property, which results in a problem that stable production can not be performed.

With respect to the above-mentioned problems, a method of suppressing the generation of curl in the polarizing plate by applying a transparent protective film to both sides of the polarizer so that the curl directions are opposite to each other is proposed. Patent Document 2 discloses a technique for suppressing the generation of curl in a polarizing plate by precisely controlling the moisture content of the polarizing plate before and after lamination of the pressure-sensitive adhesive layer and the separator in the polarizing plate with the pressure-sensitive adhesive layer on which the pressure- Has been proposed. Patent Document 3 proposes a method of suppressing curl by controlling the thickness and water content of the transparent protective film on both sides that are adhered to the polarizer.

Japanese Patent Application Laid-Open No. 2004-184809 Japanese Patent Application Laid-Open No. 2005-326531 Japanese Patent No. 4335901 Specification

However, in the methods described in Patent Documents 1 to 3, transparent protective films having curls are used, or rigid control of water content is required for each member, and there is a problem in manufacturing.

An object of the present invention is to provide a method for producing a polarizing plate in which a transparent protective film is adhered to both surfaces of a polarizer between a pair of rolls, and a method of manufacturing a polarizing plate capable of effectively suppressing curling.

Means for Solving the Problems The present inventors have intensively studied in order to solve the above problems, and as a result, they have found that the above object can be achieved by the following polarizing plate production method, and have completed the present invention.

That is, the present invention provides a polarizing plate in which a first transparent protective film and a second transparent protective film are bonded to both surfaces of a polarizer through an adhesive layer, and the three films are pressed and bonded by passing through a pair of rolls at the same time In the production method,

The first transparent protective film and the second transparent protective film have different elasticity defined by the values of the modulus of elasticity (MPa) x thickness (占 퐉), the one having a high elasticity is called a high elasticity film, Film,

In the case where the pair of rolls is defined as a high hardness roll having a different hardness, a hardness roll having a high hardness, and a low hardness roll having a low hardness,

The high-elasticity film is transported from the low-hardness roll side,

And the low-elasticity film is transported from the high-hardness roll side.

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

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

In the method for producing a polarizing plate, the roll hardness of the elastic roll is preferably 40 to 100 DEG.

Conventionally, in a method for producing a polarizing plate in which a first transparent protective film / polarizer / second transparent protective film is produced by a simultaneous lamination method, when the first and second transparent protective films have different elasticity, At the time of simultaneous lamination, curling occurred in the resulting polarizing plate.

In the method of producing a polarizing plate of the present invention, a pair of rolls having a roll hardness difference is used for bonding first and second transparent protective films having different elasticity to both sides of a polarizer between a pair of rolls, A high-elasticity film is conveyed from the low-hardness roll side, and a low-elasticity film is conveyed from the high-hardness roll side. In the case of using a pair of rolls different in roll hardness as described above, a high-elasticity film is conveyed which causes deformation of the film to be conveyed on the low-hardness roll side to cause a speed difference but does not deform well on the low-hardness roll side. The curl of the obtained polarizing plate can be suppressed by the combination of the elasticity of the film (high-elasticity film and low-elasticity film) conveyed in this way and the hardness of the rolls (high-hardness roll and low-hardness roll).

According to the above production method, a polarizing plate in which curling is suppressed can be obtained. Therefore, it is expected that the process defects when the liquid crystal panel is produced by bonding the polarizing plate to the liquid crystal cell can be reduced. In addition, in the above production method, by selecting the roll hardness, it is possible to obtain a polarizing plate excellent in appearance without occurrence of wrinkles and irregularities on the stripe pattern and suppressing the generation of air bubbles between the films. Such a polarizing plate can realize an image display device such as a liquid crystal display device (LCD) and an electroluminescence display device (ELD) which have excellent in-plane uniformity, high resolution and high contrast.

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

Hereinafter, a method for producing a polarizing plate of the present invention will be described with reference to the drawings. 1 shows an example of a production method of a polarizing plate of the present invention. The first transparent protective film (B1) and the second transparent protective film (B2) are laminated on both surfaces of a polarizer (A) And passes between a pair of rolls of the second roll (R2), thereby forming a polarizing plate (L). The first transparent protective film (B1) and the second transparent protective film (B2) have different elastic moduli. 1, the elastic modulus of the second transparent protective film B2 is higher than that of the first transparent protective film B1, the second transparent protective film B2 is a high elastic film, the first transparent protective film B1 ) Is a low elastic film.

In addition, the first roll (R1) and the second roll (R2) have different roll hardnesses. 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, the first roll R1 is a low hardness roll, to be.

In the present invention, the three films (polarizer (A), first transparent protective film (B1) and second transparent protective film (B2)) are sandwiched between a pair of first and second rolls 1, a high-elasticity film (second transparent protective film B2) is laminated on the low-hardness roll (first roll Rl) side and a high-elasticity film (second transparent protective film B2) (The first transparent protective film (B1)) from the side of the first transparent protective film (B1).

As shown in Fig. 1, when the roll hardnesses of the pair of first and second rolls R1 and R2 are different, the roll surface of the low-hardness roll (first roll R1) (for example, Of the rubber layer or the resin layer) is pressed and stretched. At this time, since the rotation speed of the low-hardness roll side is increased in the vicinity of the nip point p of the first and second rolls R1 and R2, the second transparent protective film B2 (high- Is applied to the polarizer A in a state in which tension is applied immediately after the polarizer A is contacted. Generally, the film tends to curl toward the side of tension. Curling of the obtained polarizing plate (L) can be suppressed by using the film elastic modulus and the properties of the roll.

That is, when the same tension is applied to the film to be bonded, the film having a high elasticity does not elongate well, and the film having a low elasticity has a property of being elongated. In Fig. 1, the second transparent protective film B2 (high-elasticity film) conveyed from the low-hardness roll (first roll Rl) side is adhered in a more tensioned state, but stretching is suppressed because it is a high- . On the other hand, in the high-hardness roll (second roll R2), since the elongation of the roll surface is small, the tension in the vicinity of the nip point p becomes weak. Therefore, by conveying the low-elasticity film from the high-hardness roll side, the two films can be balanced to each other and the curl of the obtained polarizing plate (L) can be suppressed.

The first transparent protective film (B1) and the second transparent protective film (B2) are bonded on both sides of the polarizer (A) between the pair of rolls of the first roll (R1) and the second roll (Not shown). The adhesive layer may be formed on the first transparent protective film (B1) or the second transparent protective film (B2), or on the polarizer (A) or on both sides thereof. Immediately before the polarizer (A) is bonded to the first transparent protective film (B1) and the second transparent protective film (B2), an adhesive (solution) or a pressure sensitive adhesive And passing between a pair of rolls of the first roll (R1) and the second roll (R2).

The first roll and the second roll have different roll hardnesses. A side having a high hardness is defined as a high hardness roll, and a side having a low hardness is defined as a low hardness roll. The hardness rolls and the low-hardness rolls can be any of elastic rolls and metal rolls. However, among the first and second rolls, due to the difference in hardness between the nip points of the high- and low- It is preferable to use an elastic roll in which the metal core portion is coated with a rubber layer or a resin layer, at least in the case of a low-hardness roll, in view of easy occurrence of deformation (elongation by pressing) on the surface of the roll.

As the elastic roll, an elastic roll coated with a rubber layer or a resin layer on a metal core part can be preferably used. The hardness of the rubber layer or the resin layer is preferably in the range of 40 to 100 DEG. The hardness is preferably 60 to 90 DEG. The reason for setting the hardness to 40 DEG or more is that deformation at the surface of the low-hardness roll is excessively large, and bubbles are generated when the polarizing plate is kneaded to prevent deterioration of the appearance. In addition, it is preferable to set the hardness to 100 ° or less from the viewpoint of preventing scratches on the surface of the film. The hardness at this time can be measured using a durometer (Type A) commercially available, for example, by the method disclosed in JIS K 6253 (1997). Specifically, the measurement of the roll hardness was carried out using GS-719N Type A manufactured by Tekkock Co., Ltd. (JIS K 6253). The thickness of the rubber layer or the resin layer is preferably about 1 to 15 mm, more preferably about 3 to 10 mm in terms of the uniformity of the surface pressure distribution.

On the other hand, a metal roll can be used for the high hardness roll. For example, when the elastic roll is used as the low-hardness roll, a metal roll can be used as the high-hardness roll. 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 metal roll has a higher roll hardness than the elastic roll.

When the combination of the high-hardness roll and the low-hardness roll is a metal roll and an elastic roll, the roll hardness (rubber layer or hardness of the resin layer) of the elastic roll as the low-hardness roll is preferably 40 to 90 degrees, more preferably 60 to 80 Deg.].

In addition, elastic rolls can be used for both high-hardness rolls and low-hardness rolls. In this case, the hardness difference between the high-hardness roll and the low-hardness roll is preferably 10 ° or more. On the other hand, if the hardness difference is excessively large, the ram pressure is lowered due to the decrease in hardness, and bubbles are likely to be generated between the films. In order to obtain a polarizing plate having a good appearance, the difference in hardness is preferably 40 DEG or less, more preferably 30 DEG or less, further preferably 20 DEG or less.

Further, the roll diameter of each roll, the conveying speed at the time of coalescence, and the like are appropriately adjusted, and the thickness of the adhesive layer can also be appropriately adjusted.

In addition, as the diameter of the roll becomes smaller, the contact area between the polarizer A and the first and second transparent protective films B1 and B2 becomes smaller as the diameter becomes smaller, so that the pressure applied to the film surface relatively increases . Therefore, it is preferable to use a roll having a diameter of 250 mm or less, and more preferably 200 mm or less. However, if the diameter becomes too small, the durability of the roll becomes weak, so that sufficient force is not applied. Therefore, it is preferable to use rolls of 50 mm or more, more preferably 100 mm or more.

The conveying speed at the time of coalescence is not particularly limited, and is usually adjusted to about 2 m / min to 50 m / min.

In addition, the lamination pressure between the rolls at the time of kneading is suitably set without particular limitation. The laminate pressure is preferably about 2 MPa or more and 5 MPa or less, 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 laminate pressure is less than 2 MPa, sufficient pressurization is impossible and bubbles are generated between the films. If the laminate pressure is larger than 5 MPa, the load on the roll or the apparatus is excessively increased, which may cause breakage. The laminate pressure was measured by using a pressure-sensitive paper "Freescale" manufactured by Fuji Film, binarizing the color change of the pressure-sensitive paper by computer image processing, and calculating an approximation of the prepared pressure standard line .

The polarizer is not particularly limited, and various polarizers can be used. Examples of the polarizer include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially porous polyvinyl alcohol film, and an ethylene / vinyl acetate copolymerization system partially saponified film, and a dichromatic material such as iodine or a dichroic dye is adsorbed And polyene-based oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochloric acid treated products. Among them, a polarizer comprising a polyvinyl alcohol film and a dichromatic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 占 퐉. The thickness of the polarizer is preferably 15 to 35 mu m. When the thickness of the polarizer is excessively thin, it is likely to be damaged when it is laminated with the transparent protective film. On the other hand, if the thickness of the polarizer is excessively large, the drying efficiency tends to deteriorate, which is not preferable from the viewpoint of productivity.

The polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching can be produced by, for example, dying polyvinyl alcohol in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. If necessary, it may be immersed in an aqueous solution of boric acid, potassium iodide or the like. Further, if necessary, the polyvinyl alcohol film may be dipped in water and washed with water before dyeing. The polyvinyl alcohol film is washed with water to clean the surface of the polyvinyl alcohol film and to prevent unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. The stretching may be carried out after dyeing with iodine, followed by stretching while dyeing, or after stretching, followed by dyeing with iodine. It can be stretched either in an aqueous solution such as boric acid or potassium iodide or in an ice bath.

The water content of the polarizer is not particularly limited, and it is usually preferably 8 to 30% by weight, more preferably 10 to 20% by weight. The lower the moisture content of the polarizer is, the better the drying efficiency in the drying step is, and the productivity is improved in order to increase the production speed. It is preferable that the polarizer has a low water content because a polarizing plate having good optical characteristics can be obtained. On the other hand, if the water content of the polarizer is too low, the rigidity of the polarizer becomes high, and the film becomes liable to be damaged, and appearance defects are likely to occur. The moisture content of the polarizer can be generally adjusted by the conditions of the drying treatment in the production process of the polarizer. However, if necessary, a humidity conditioning treatment step may be separately provided, and the moisture content of the polarizer may be adjusted by spraying, Drying may be performed.

The method for producing the polarizer is not limited to the above-mentioned production method, and a polarizer may be produced by using another production method if the moisture content is 8 to 30% by weight (preferably, the moisture content is 10 to 20% by weight). For example, a dry stretching method or a polymer film such as polyethylene terephthalate (PET) may be formed by kneading and stretching a dichroic material, or a liquid crystal aligned in a uniaxial direction may be used as a host, (U.S. Patent No. 5,523,863, JP-A-3-503322) using dyes as guest, and E type using diatomic lyotropic liquid crystal (U.S. Patent No. 6,049,428).

The modulus of elasticity of the first and second transparent protective films is not particularly limited, but is preferably in the range of 1000 to 10000 MPa. The modulus of elasticity is preferably 1200 to 5000 MPa, more preferably 1300 to 4000 MPa. In addition, if the first and second transparent protective films have a difference in elasticity, the first and second transparent protective films may have the same or different elastic moduli.

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

The horizontal axis when calculating the elastic modulus (slope of the graph): Deformation (%)

Tensile stress σ (MPa = N / mm 2) = F / initial cross-sectional area A (mm 2) of the test piece

Range when determining the modulus of elasticity (slope of the graph): linear regression between 0.05 and 0.25% strain

Specimen shape: Strip (rectangular)

Chuck distance: 100 mm

The thickness of the first and second transparent protective films may be suitably determined, but is generally preferably from 20 to 200 탆, more preferably from 30 to 100 탆, from the viewpoints of workability such as strength and handling properties, More preferable. The thickness of the first and second transparent protective films is preferably in the above range in terms of productivity because the drying efficiency is good and the winding of the original can be made long. On the other hand, if the thicknesses of the first and second transparent protective films are increased, the drying efficiency is deteriorated, which is not preferable from the viewpoint of productivity.

The elastic modulus and thickness of the first and second transparent protective films are selected so that the elasticity defined by the product of the modulus of elasticity (MPa) x thickness (占 퐉) is different. The first transparent protective film and the second transparent protective film are defined as a high elastic film having a high elastic modulus and a low elastic film having a low elastic modulus.

The difference between the elasticity of the high-elasticity film and the elasticity of the low-elasticity film is preferably from 0 to 170,000, and more preferably from 30,000 to less than 30,000 from the viewpoint of wrinkles. Particularly, when the difference is 1000 or more, more preferably 3000 or more, and more than 10000, deformation may easily occur due to the difference in elasticity, so that the present invention can be preferably applied.

As the first and second transparent protective films, various materials can be used. Each of the first and second transparent protective films is selected so that one of them is a high elastic film and the other is a low elastic film. In addition, the control of the elasticity in the high-elasticity film and the low-elasticity film can be controlled by the material (elastic modulus) and the thickness of the first and second transparent protective films.

The material for forming the transparent protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like. For example, a polyester polymer such as polyethylene terephthalate or polyethylene naphthalate, a cellulose polymer such as diacetylcellulose or triacetylcellulose, an acryl polymer such as polymethyl methacrylate, a polystyrene or an acrylonitrile / styrene copolymer (AS resin), and polycarbonate-based polymers. Examples of the polymer include polyolefin polymers such as polyethylene, polypropylene, cycloolefin or norbornene structure, polyolefin polymers such as ethylene / propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, Based polymers, polyether sulfone-based polymers, polyetheretherketone-based polymers, polyphenylene sulfide-based polymers, vinyl alcohol-based polymers, vinylidene chloride-based polymers, vinyl butyral-based polymers, arylate- An epoxy-based polymer, or a blend of the above polymer may be mentioned as an example of the polymer forming the transparent protective film. A transparent protective film is usually adhered to the polarizer by an adhesive layer. As the transparent protective film, a thermosetting resin such as a (meth) acrylic, urethane, acrylic urethane, epoxy or silicone resin or an ultraviolet curable resin can be used. The transparent protective film may contain one or more optional additives. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight . When the content of the thermoplastic resin in the transparent protective film is 50 wt% or less, there is a fear that the transparency inherently possessed by the thermoplastic resin can not be sufficiently expressed.

As the transparent protective film of the present invention, at least one (1) selected from a cellulose resin (polymer), a polycarbonate resin (polymer), a cyclic polyolefin resin (polyolefin having a cyclic system or a norbornene structure) It is preferable to use a dog.

In addition, the surface of the transparent protective film may be subjected to surface modification treatment by corona treatment, plasma treatment, frame treatment, ozone treatment, primer treatment, glow treatment or saponification treatment, in view of polarization characteristics, durability and adhesion properties. Among these surface modification treatments, when a cellulose resin (polymer) is used as the transparent protective film, saponification treatment with alkali or the like is preferable.

The surface of the transparent protective film on which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, anti-sticking, diffusion or anti-glare treatment.

The antireflection layer, anti-sticking layer, diffusion layer, antiglare layer, and the like can be formed on the transparent protective film itself or may be formed as a separate optical layer as a separate material from the transparent protective film.

The adhesive layer is not particularly limited, and various types of water-based, solvent-based, hot-melt-based, and radical-curing types are used. The adhesive layer used for bonding the polarizer to the transparent protective film is not particularly limited as long as it is optically transparent. The formation of the adhesive layer used for bonding the polarizer and the transparent protective film is preferably an aqueous adhesive or a radical curable adhesive.

The water-based adhesive for forming the adhesive layer is not particularly limited, and examples thereof include a vinyl polymer type, a gelatin type, a vinyl type latex type, a polyurethane type, an isocyanate type, a polyester type and an epoxy type. The adhesive layer made of such an aqueous adhesive can be formed as a coating and drying layer of an aqueous solution. When preparing the aqueous solution, a catalyst such as a crosslinking agent, other additives, or an acid can be added as needed. As the water-based adhesive, it is preferable to use an adhesive containing a vinyl polymer, and as the vinyl polymer, a polyvinyl alcohol-based resin is preferable. The polyvinyl alcohol-based resin may contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, oxalic acid and the like. Particularly when a polyvinyl alcohol polymer film is used as a polarizer, it is preferable to use an adhesive containing a polyvinyl alcohol-based resin from the viewpoint of adhesiveness. Further, an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable in terms of improving durability.

The polyvinyl alcohol-based resin is not particularly limited, but an average degree of polymerization of about 100 to 3,000 and an average degree of saponification of about 85 to 100 mol% are preferable from the standpoint of adhesiveness. The concentration of the adhesive aqueous solution is not particularly limited, because it can be appropriately determined according to the thickness of the intended adhesive layer, but is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight. If the concentration of the solution is excessively high, the viscosity becomes excessively high, so that irregularities of irregularities on the striped surface tend to occur. When the concentration of the solution is too low, the coating property becomes poor and it becomes easy to become uneven.

The polyvinyl alcohol-based resin includes polyvinyl alcohol obtained by saponifying polyvinyl acetate; Derivatives thereof; A saponification of a copolymer of a monomer having a copolymer with vinyl acetate; Modified polyvinyl alcohols obtained by subjecting polyvinyl alcohol to acetalization, urethanization, etherification, grafting, phosphoric esterification and the like. Examples of the monomer include unsaturated carboxylic acids and esters thereof such as maleic acid (anhydride), fumaric acid, crotonic acid, itaconic acid, and (meth) acrylic acid; (Meth) allyl sulfonic acid (soda), soda sulfonate (monoalkyl maleate), disulfonic acid soda alkyl malate, N-methylol acrylamide, acrylamide alkylsulfonic acid alkali salt, N- Vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. These polyvinyl alcohol resins may be used singly or in combination of two or more.

The polyvinyl alcohol-based resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method of dispersing a polyvinyl alcohol-based resin in a solvent such as acetic acid and adding diketene thereto, a method of previously dissolving a polyvinyl alcohol-based resin in a solvent such as dimethylformamide or dioxane, And a method of adding edecetene. In addition, a method in which diketene gas or liquid diketene is directly contacted with polyvinyl alcohol can be mentioned.

The degree of modification of the acetoacetyl group of the polyvinyl alcohol-based resin containing an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. When the amount is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient, which is inappropriate. The acetoacetyl group modification degree is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. When the degree of modification of the acetoacetyl group is more than 40 mol%, the point of reaction with the crosslinking agent decreases and the effect of improving the water resistance is small. Such acetoacetyl group denaturation can be measured using nuclear magnetic resonance (NMR).

The crosslinking agent is not particularly limited as long as it is generally used as an adhesive. For example, in the case of an adhesive using a polyvinyl alcohol-based resin as described above, at least two functional groups having reactivity with a polyvinyl alcohol- Can be preferably used. Examples thereof include alkyl diamines having two alkylene groups and amino groups such as ethylenediamine, triethylenediamine, hexamethylenediamine and the like; Tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate and keto oxime block or phenol block water thereof) Isocyanates such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylol propane triglycidyl ether, diglycidyl Epoxies such as formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde and the like, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleic dialdehyde, maleic anhydride, , Dialdehydes such as phthalaldehyde, methylolurea, An amino-formaldehyde resin such as methylol melamine, alkylated methylol urea, alkylated methylol melamine, acetoguanamine, a condensate of benzoguanamine and formaldehyde, and an amino-formaldehyde resin such as sodium, potassium, magnesium, calcium, aluminum, Of these, an amino-formaldehyde resin, particularly a methylol compound having a methylol group, is preferred.

The blending amount of the crosslinking agent is generally about 0.1 to 35 parts by weight and preferably 10 to 25 parts by weight based on 100 parts by weight of the resin. When the durability of the adhesive is important, It is effective to blend 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, instead of shortening the time (usable time)

As the radical-curing adhesive, various types such as an actinic radiation ray-curable type such as an electron beam curable type and an ultraviolet ray curable type, a thermosetting type and the like can be mentioned, but an active energy ray curable type which can be cured in a short time is preferable. In particular, ultraviolet curing type is preferable.

Examples of the curable component include a compound having a (meth) acryloyl group and a compound having a vinyl group. These curable components may be either monofunctional or bifunctional or more. These curable components may be used singly or in combination of two or more. As the curable component, for example, a compound having a (meth) acryloyl group is preferable, and examples thereof include various epoxy (meth) acrylates, urethane (meth) acrylates, polyester Methacrylate-based monomers.

The curable adhesive contains a curable component, in addition to which the radical initiator is added, depending on the type of cure. When the adhesive is used in an electron beam hardening type, it is not particularly required to include a radical initiator in the adhesive, but when it is used in an ultraviolet curing type or thermosetting type, a radical initiator is used. The amount of the radical initiator used is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, per 100 parts by weight of the curing component.

The adhesive may contain a metal compound filler. The metallic compound filler can control the fluidity of the adhesive layer, stabilize the film thickness, obtain a polarizing plate having a good appearance, uniformity of surface, and no deviation in adhesion.

In order to form the adhesive layer, a dry lamination method which can be applied in a solventless or low-solvent state can be preferably used. As the dry lamination method, conventionally known adhesives for dry lamination and a bonding method may be used. In addition to the present invention, this method can be used. This has the effect of reducing uneven irregularity on the stripe pattern, which is even better.

Examples of the adhesive for dry lamination include a two-liquid curing type adhesive, a two-liquid solvent type adhesive, and a one-part solvent type adhesive. Examples of the two-component curing adhesives include acrylic adhesives, two-component solvent adhesives, polyester adhesives, aromatic polyester adhesives, aliphatic polyester adhesives, polyester / polyurethane adhesives, polyether / polyurethane adhesives, ) May be a polyether / polyurethane-based resin.

The adhesive layer may suitably contain an additive if necessary. Examples of the additives include coupling agents such as a sensitizer, a silane coupling agent, and a titanium coupling agent, which increase the curing rate and sensitivity by electron beams typified by carbonyl compounds, adhesion promoters such as ethylene oxide, wettability with a transparent protective film Additives for improving mechanical strength and processability, ultraviolet absorbers, antioxidants, dyes, processing aids, ion trapping agents, antioxidants, antioxidants and the like which are represented by acryloxy group compounds and hydrocarbon series (natural and synthetic resins) , A tackifier, a filler (other than a metal compound filler), a plasticizer, a leveling agent, a foam inhibitor, an antistatic agent, a heat stabilizer, and a stabilizer such as a moisture stabilizer.

A polarizing plate is obtained by bonding a transparent protective film to both sides of the polarizer via an adhesive layer. A lower layer (undercoat layer) or an easy-to-adhere treatment layer may be formed between the adhesive layer and the transparent protective film or polarizer.

When the adhesive layer formed by the above production method is formed of an aqueous adhesive or the like, the thickness of the adhesive layer is preferably 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 250 nm. On the other hand, when the adhesive layer is formed by a curing adhesive, the thickness of the adhesive layer is preferably 0.1 to 200 mu m. More preferably 0.5 to 50 占 퐉, and still more preferably 0.5 to 10 占 퐉.

In the method for producing a polarizing plate, after the polarizer and the transparent protective film are laminated, a curing process is performed depending on the kind of the adhesive. When an aqueous adhesive is used, a drying step is carried out. Drying conditions of the drying step are usually about 40 to 100 DEG C at a drying temperature and about 1 to 10 minutes for a drying time. In the case of the radical-curable adhesive, for example, an electron beam, an ultraviolet ray, or the like is irradiated.

The polarizing plate obtained by the production method of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, a liquid crystal display device such as a reflection plate, a semitransmissive plate, a retardation plate (including a wave plate of 1/2 or 1/4) One or more optical layers that may be used may be used. Particularly, a reflection type polarizing plate or a transflective polarizing plate in which a reflection plate or a transflective reflection plate is further laminated on the polarizing plate of the present invention, an elliptically polarizing plate or a circular polarizing plate in which a retardation plate is laminated in addition to the polarizing plate, Or a polarizing plate in which a brightness enhancement film is laminated on a polarizing plate.

The polarizing plate or optical film of the present invention can be suitably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be carried out conventionally. That is, the liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as needed, and inserting a drive circuit. In the present invention, There is no particular limitation except that a polarizing plate or an optical film is used. For the liquid crystal cell, any type of TN type, STN type, or π type, for example, can be used.

A suitable liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of the liquid crystal cell and a backlight or a reflector is used in the illumination system can be formed. In this case, the polarizing plate or optical film according to the present invention can be provided on one side or both sides of the liquid crystal cell. When a polarizing plate or an optical film is formed on both sides, they may be the same or different. In forming a liquid crystal display device, a suitable part such as a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, Or more.

The production method of the present invention is also applicable to a polarizing plate production method in which a polarizer is used as a first film and a pressure sensitive adhesive layer in which a pressure sensitive adhesive layer is formed on a polarizing plate using a separator having a pressure sensitive adhesive layer formed thereon can do. The production method of the present invention is a production method of a polarizing plate in which a polarizing plate or a polarizing plate having a pressure-sensitive adhesive layer formed thereon is used as the first film and a polarizing plate or a pressure- .

When an optical functional layer is laminated on the polarizing plate, a method of laminating with an adhesive layer or a pressure-sensitive adhesive layer is preferably used. As the adhesive layer or pressure-sensitive adhesive layer in this case, a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive is preferably used.

As the pressure-sensitive adhesive layer made of a pressure-sensitive adhesive, for example, it can be formed of a pressure-sensitive adhesive suitable for a conventional method such as an acrylic type, a silicone type, a polyester type, a polyurethane type, a polyether type or a rubber type. As the pressure-sensitive adhesive, there are problems in that the pressure-sensitive adhesive is prevented from foaming or peeling due to moisture absorption, the optical characteristics are lowered due to the thermal expansion difference and the like, but the curvature of the liquid crystal cell is prevented, and furthermore, the quality of the image display device with excellent durability A pressure-sensitive adhesive layer having a low moisture absorptivity and excellent heat resistance, and further, a high-temperature process is not required at the time of curing or drying in order to prevent a change in optical properties of a polarizing plate or the like. It is preferable that the drying time is not required. From such a viewpoint, an acrylic pressure sensitive adhesive is preferably used for the polarizing plate and the optical film. In addition, a pressure-sensitive adhesive layer or the like which exhibits light diffusibility by adding fine particles to the pressure-sensitive adhesive may also be used.

If necessary, the adhesive layer or the pressure-sensitive adhesive layer may be formed on a necessary surface. For example, the polarizing plate obtained from the polarizer and the transparent protective film according to the present invention will be described. If necessary, one side or both sides of the polarizing plate, In the film, a pressure-sensitive adhesive layer may be formed on the opposite surface to which the polarizer is adhered. The thickness after drying of the pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive in the case where it is used to laminate the optical functional layer is not particularly limited, but is generally about 1 to 500 μm, preferably 5 to 200 μm, Mu m. By setting the thickness of the adhesive layer or the pressure-sensitive adhesive layer within this range, the stress accompanying the dimensional behavior of the polarizing plate or the optical functional layer can be relaxed.

When the pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive is exposed on the surface, it is preferable that the pressure-sensitive adhesive layer is temporarily adhered and covered with a separator for the purpose of preventing contamination during practical use. As the separator, it is preferable to use a film obtained by forming a release coat with a suitable release agent such as silicon-based, long-chain alkyl, fluorine-based or molybdenum disulfide, if necessary, on a film suitable for the protective film or the like.

As the surface protective film, a pressure sensitive adhesive layer may be formed on a base film and the pressure sensitive adhesive layer may be peeled off together with the pressure sensitive adhesive layer.

A polarizing plate is obtained by bonding a transparent protective film to both surfaces of the polarizer with an adhesive layer interposed therebetween. A primer layer, an easy-to-adhere treatment layer and the like may be formed between the adhesive layer and the transparent protective film or polarizer.

Example

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

(Method of measuring moisture content of polarizer)

A sample of 180 mm x 500 mm was cut out from the obtained polarizer, and its initial weight (W (g)) was measured. The sample was allowed to stand in a dryer at 120 캜 for 2 hours, and then the weight (D (g)) after drying was measured. From these measured values, the water content was determined by the following formula.

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

<Production of Polarizer>

A polyvinyl alcohol film having an average degree of polymerization of 2400 and a degree of saponification of 99.9 mol% and a thickness of 75 mu m was immersed in hot water at 30 DEG C for 60 seconds to swell. Subsequently, the film was dipped in an aqueous solution having a concentration of 0.3% of iodine / potassium iodide (weight ratio = 0.5 / 8) and stretched to 3.5 times. Thereafter, stretching was carried out in an aqueous solution of boric ester at 65 DEG C such that the total draw ratio was 6 times. After stretching, the film was dried in an oven at 40 占 폚 for 3 minutes to obtain a PVA-based polarizer (thickness: 23 占 퐉). The thickness of this polarizer was 23 占 퐉 and the water content was 18% by weight.

<Transparent protective film>

TAC: triacetyl cellulose film having a thickness of 60 占 퐉 (TD60UL, manufactured by Fuji Film Co., Ltd., elastic modulus: 4000 MPa);

COP: a ring-shaped polyolefin film having a thickness of 50 mu m (ZEONOR, manufactured by Nippon Zeon Co., Ltd., elastic modulus: 1800 MPa);

Acrylic: an acrylic film having a thickness of 40 占 퐉 (elastic modulus 2000 MPa); .

<Active energy ray>

UV light (gallium-encapsulated metal halide lamp) as active energy ray, irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., valve: V valve, peak illuminance: 1600 mW / cm2, cumulative irradiation amount 1000 / mJ / 440 nm) was used. The illuminance of the ultraviolet ray was measured using a Sola-Check system manufactured by Solatell.

<Preparation of active energy ray-curable adhesive>

38.3 parts of N-hydroxyethyl acrylamide (manufactured by Kyokushin K.K.) as the radical polymerizable compound (A)

, 19.1 parts of tripropylene glycol diacrylate (trade name: Aronix M-220, manufactured by TOAGOSEI CO., LTD.) As the radical polymerizable compound (B)

As the radical polymerizable compound (C), 38.3 parts of acryloylmorpholine (manufactured by Kyokushin Co., Ltd.)

And 1.4 parts of a photopolymerization initiator (trade name: KAYACURE DETX-S, diethyl thioxanthone, manufactured by Nippon Kayaku Co., Ltd.) were mixed and stirred at 50 ° C for 1 hour to obtain an active energy ray curable adhesive.

Example 1

<Production of Polarizer>

A polarizing plate was produced by the method shown in Fig. The polarizer (A) used was the polarizer. For the first transparent protective film (B1), a cyclic polyolefin film having a thickness of 50 mu m was used. After the urethane-based easy-adhesion layer having a thickness of 0.5 탆 was formed on the cyclic polyolefin film, the active energy ray-curable adhesive was applied to the easy-to-stick layer using an MCD coater (manufactured by Fuji Machinery Co., Number of rolls, number of rolls / inch, speed of rotation of 140% / line) was applied so that the thickness of the adhesive layer became 0.5 탆. A TAC film having an adhesive layer formed thereon was prepared in the same manner as described above, except that the TAC film was used in place of the cyclic polyolefin film in the second transparent protective film (B2). Subsequently, the first transparent protective film (B1) and the second transparent protective film (B2) were bonded to both sides of the polarizer (A) (polarizer) with a roll roll through the adhesive layer. An iron roll having a diameter of 200 mm was used as the first roll R 1 and an elastic roll having a diameter of 200 mm and a hardness of 60 ° was used as the second roll R 2. As shown in Fig. 1, the first transparent protective film (B1) was transported from the second roll (R2) side and the second transparent protective film (B2) was transported from the first roll (R1) side. Thereafter, from both sides of the combined first and second transparent protective films, the film was heated to 50 DEG C by using an IR heater, and the ultraviolet rays were irradiated to both sides to cure the active energy ray curable adhesive. Further, hot air drying was conducted at 70 캜 for 3 minutes to obtain a polarizing plate having a transparent protective film on both sides of the polarizer. The line speed of the coupling was 25 m / min.

Examples 2 to 4 and Comparative Examples 1 to 4

A polarizing plate was obtained in the same manner as in Example 1 except that the first transparent protective film, the kind of the second transparent protective film, the kind of the first roll and the kind of the second roll were changed as shown in Table 1 .

The following evaluations were performed on the polarizing plates produced in Examples and Comparative Examples. The results are shown in Table 1.

(curl)

The obtained polarizing plate was allowed to stand on a horizontal plate, and the length of a point at which the distance between the edge of the polarizing plate and the horizontal plate became maximum was defined as a curl amount (mm).

(Appearance: Confirmation of air bubbles)

Samples of 1000 mm x 1000 mm were cut out from the obtained polarizing plate to confirm the number of bubbles between the polarizer and the transparent protective film.

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

A: Polarizer
B1: first transparent protective film (low elastic film)
B2: second transparent protective film (high elasticity film)
R1: first roll (low-hardness roll)
R2: second roll (high hardness roll)

Claims (5)

A method for producing a polarizing plate in which a first transparent protective film and a second transparent protective film are bonded to both surfaces of a polarizer by passing through a pair of rolls simultaneously through an adhesive layer,
The first transparent protective film and the second transparent protective film have different elasticity defined by the values of the modulus of elasticity (MPa) x thickness (占 퐉), the one having a high elasticity is called a high elasticity film, Film,
In the case where the pair of rolls is defined as a high hardness roll having a different hardness and a hardness roll having a different hardness and a low hardness roll having a low hardness,
The high-elasticity film is transported from the low-hardness roll side,
And the low-elasticity film is transported from the high-hardness roll side. The method according to claim 1,
Wherein at least the low-hardness roll is an elastic roll wherein the metallic core is coated with a rubber layer or a resin layer. 3. The method according to claim 1 or 2,
Wherein the high-hardness roll is a metal roll. 3. The method according to claim 1 or 2,
Wherein the hardness roll and the low-hardness roll are all elastic rolls coated with a rubber layer or a resin layer, and the difference in hardness between the high-hardness roll and the low-hardness roll is 10 or more. 5. The method according to any one of claims 2 to 4,
And the roll hardness of the elastic roll is 40 to 100 DEG.

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