KR101967931B1 - Method of manufacturing polarizing plate - Google Patents

Abstract

assignment
Provided is a method for producing a polarizing plate capable of obtaining a polarizing plate having good adhesiveness between a polarizer and a transparent protective film even when a polarizer having a low moisture content is used.
Solution
A method for producing a polarizing plate having a transparent protective film formed on at least one surface of a polarizer with an adhesive layer interposed therebetween, said transparent protective film being coated with an aqueous adhesive for a polarizing plate and dried, (1) of forming an adhesive layer in a coating film state in which a change in contact angle with respect to the substrate occurs within 30 seconds, a step (2) of bonding a polarizer having a water content of 12 to 25% by weight with the transparent protective film by the adhesive layer, And a step (3) of drying the adhesive layer.

Description

METHOD OF MANUFACTURING POLARIZING PLATE [0002]

The present invention relates to a method for producing a polarizing plate. The present invention also relates to a polarizing plate, an optical film using the polarizer, and further to an image display device such as a liquid crystal display device, an organic EL display device, and a PDP using the polarizer, the polarizing plate, and the optical film.

In the liquid crystal display device, it is indispensable to arrange the polarizers on both sides of the glass substrate forming the liquid crystal panel surface from the image forming system. Polarizers are generally obtained by dyeing a polyvinyl alcohol film with a dichroic material such as iodine, crosslinking using a crosslinking agent, and uniaxial stretching. Since the polarizer is produced by stretching, it is likely to shrink. Further, since a polyvinyl alcohol-based film uses a hydrophilic polymer, it is particularly susceptible to deformation under humidification conditions. Further, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. Therefore, a polarizing plate in which a transparent protective film such as triacetylcellulose is stuck to both sides or one side of the polarizer and the strength is supplemented is used. The polarizing plate is manufactured by bonding a polarizer and a transparent protective film with an adhesive.

For example, in producing a polarizing plate by blending a polarizer and a transparent protective film, there has been used a water-based adhesive relating to an aqueous solution containing a polyvinyl alcohol-based resin containing an acetoacetyl group and a crosslinking agent (Patent Document 1) . It is described that the water-based adhesive has good resistance to moisture and humidity, and water resistance. It has also been proposed that a water-based adhesive having a viscosity of 3 to 20 mPa ㆍ (25 캜) is used as the water-based adhesive to obtain a polarizing plate having excellent appearance (Patent Document 2). In Patent Documents 1 and 2, the polarizer and the transparent protective film are laminated without applying drying to the polarizer or the transparent protective film.

Further, there has been proposed a method of producing a polarizing plate by bonding a polarizer and a transparent protective film by forming an adhesive layer by drying an adhesive solution coated on a polarizer or a transparent protective film, and then introducing an aqueous liquid into these adhered surfaces Patent Document 3). Patent Document 3 discloses that a polarizing plate having less appearance defects can be produced compared to Patent Documents 1 and 2 by previously forming an adhesive layer. It has also been proposed that an adhesive containing a metal compound colloid blended with a polyvinyl alcohol-based resin containing an acetoacetyl group can improve the cracking defects of the resulting polarizing plate (Patent Document 4).

Japanese Laid-Open Patent Publication No. 2005-189615 Japanese Patent Application Laid-Open No. 2002-365432 Japanese Patent Application Laid-Open No. 2005-128490 Japanese Laid-Open Patent Publication No. 2009-122664

On the other hand, in the production of the polarizing plate, the polarizers have a low water content, and the orientation properties of the polyvinyl alcohol-based resin are improved, so that the optical properties (degree of polarization, etc.) are good. However, in Patent Document 3, since the degree of drying of the previously formed adhesive layer is high, the adhesive layer is hardly soluble in water. Therefore, in the case where the water content of the polarizer is low, there are cases where the aqueous solution to which the adhesive layer is added does not sufficiently dissolve sufficiently, and in some cases, the resulting polarizer may have poor adhesion between the polarizer and the transparent protective film. In addition, also in the case of an adhesive in which a colloid of a metal compound is blended with a polyvinyl alcohol-based resin containing an acetoacetyl group, there is a problem of adhesion failure as described above.

An object of the present invention is to provide a polarizing plate production method capable of obtaining a polarizing plate having good adhesiveness between a polarizer and a transparent protective film, even when a polarizer having a low moisture content is used.

As a result of intensive investigations to solve the above problems, the present inventors have found out that the above-mentioned object can be achieved by a polarizing plate production method or the like shown below, and have completed the present invention.

That is, the present invention provides a method for producing a polarizing plate in which a transparent protective film is formed on at least one surface of a polarizer with an adhesive layer interposed therebetween,

A step (1) of coating an aqueous adhesive for a polarizing plate on the transparent protective film, drying the coated transparent protective film, and forming an adhesive layer in a coating film state on the transparent protective film,

A step (2) of bonding the polarizer and the transparent protective film having a water content of 12 to 25% by weight with the adhesive layer, and a step (3) of drying the adhesive layer. .

In the method for producing a polarizing plate, it is preferable that the water-based adhesive is a polyvinyl alcohol-based adhesive containing a polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin preferably has a long-chain functional group having hydrophilicity in the side chain.

In the method for producing a polarizing plate of the present invention, an adhesive layer is formed on a transparent protective film in the same manner as in Patent Document 3 in the step (1), but the adhesive layer is not in a state of high degree of drying , And the film state. The state of the coating film can be controlled so that the time period until the contact angle change with water (time to start melting by water) occurs within a predetermined time, for example, in the adhesive layer in the semi-dry film state. By controlling the coating film state of the adhesive layer in this manner, it is possible to secure some moisture in the adhesive layer formed of the water-based adhesive, and even when the water content of the polarizer is low, the polarizer and the transparent protective film can be favorably adhered.

In the polarizing plate manufacturing method of the present invention, the adhesive layer in the coated state formed on the transparent protective film may be melted by moisture in the polarizer since the adhesive is formed by an aqueous adhesive. Therefore, in the method for producing a polarizing plate of the present invention, addition of an aqueous liquid is not particularly required as in Patent Document 3. In forming the adhesive layer in the coating film state of the step (1), moisture in the adhesive layer is removed in advance. Therefore, the polarizer and the transparent protective film can be carried out at a high speed, the drying step (3) can be carried out efficiently, and it is also advantageous from the viewpoint of productivity.

In the conventional adhesive layer having a high degree of drying, it is usually necessary that the water content of the polarizer is more than 25% by weight. In the method for producing a polarizing plate of the present invention, a polarizer having a water content of 25% . As described above, in the method for producing a polarizing plate of the present invention, a polarizer having a water content of 25% by weight or less can be used, so that the optical characteristics (polarization degree, etc.) of the polarizing plate obtained can be improved. 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.

According to the present invention, there is provided a method of manufacturing a polarizing plate in which a transparent protective film is formed on at least one surface of a polarizer with an adhesive layer interposed therebetween.

The polarizer is not particularly limited and various kinds of polarizers can be used. As the polarizer, a dichroic material such as iodine or a dichroic dye may be added to a hydrophilic polymer film such as a polyvinyl alcohol film, a partially porous polyvinyl alcohol film, or an ethylene / vinyl acetate copolymerization system partially saponified film A polyvinyl alcohol-based dehydrated product, a polyvinyl chloride dehydrochloric acid-treated product, and the like. Among them, a polyvinyl alcohol film and a polarizer made of a dichroic material such as iodine are preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 mu m. 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.

A polarizer obtained by dying 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. 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 in an aqueous solution such as boric acid or potassium iodide or in a water bath.

As the polarizer, a polarizer having a water content of 12 to 25% by weight is used. In the present invention, the water content of the polarizer can also be used at a low water content of 25% by weight or less. Also, the water content of the polarizer can be used at 23 wt% or less. The polarizer is preferable because the polarizer has a low water content and a good optical property can be obtained. In addition, the drying efficiency in the drying step (3) is improved, which is preferable from the viewpoint of productivity in which the production speed can be increased. 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 tend to occur. In this respect, the moisture content of the polarizer is preferably at least 12% by weight, and more preferably at least% by weight. The moisture content of the polarizer can be generally adjusted by the conditions of the drying treatment in the production process of the polarizer, but it is also possible to prepare a humidity treatment process separately if necessary, and spray the water or water in a water bath, Drying may be performed.

As a material for forming the transparent protective film formed on one side or both sides of the polarizer, it is preferable that the material is excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like. For example, a polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, a cellulose polymer such as diacetylcellulose or triacetylcellulose, an acrylic polymer such as polymethylmethacrylate, 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. As the transparent protective film, a thermosetting resin such as (meth) acrylic, urethane, acrylic urethane, epoxy, or silicone, or an ultraviolet ray-curable resin can be used as the polarizer. . The transparent protective film may contain one or more optional additives. Examples of the additive include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants and the like. 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 possibility that the transparency and the like inherently possessed by the thermoplastic resin may not be sufficiently manifested.

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 particular, the effect of the present invention is remarkable when a protective film made of triacetylcellulose is used.

The thickness of the transparent protective film can be appropriately determined, but generally it is about 1 to 500 占 퐉 in terms of workability such as strength and handling property, thin layer property, and the like. Particularly preferably from 1 to 300 mu m, and more preferably from 5 to 200 mu m.

When a transparent protective film is formed on both sides of the polarizer, a protective film made of the same polymer material may be used for the front and back sides, or a transparent protective film made of a different polymer material or the like may be used.

The surface of the transparent protective film to be adhered to the polarizer can be subjected to easy adhesion treatment. Examples of the adhesion treatment include a chemical treatment such as a dry treatment such as a plasma treatment and a corona treatment, an alkali treatment (saponification treatment), a coating treatment for forming the adhesive layer, and the like. Among these, a coating treatment or an alkali treatment for forming the adhesive layer is preferable. Various adhesive materials such as a polyol resin, a polycarboxylic acid resin, and a polyester resin can be used for forming the adhesive layer. The thickness of the adhesive layer is usually about 0.001 to 10 mu m, more preferably about 0.001 to 5 mu m, particularly preferably about 0.001 to 1 mu m.

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 separately from the transparent protective film as an optical layer.

As the adhesive used for forming the adhesive layer for bonding the polarizer and the transparent protective film, an aqueous adhesive is used.

The water-based adhesive is not particularly limited, and examples thereof include vinyl polymer, gelatin, vinyl latex, polyurethane, isocyanate, polyester, epoxy and the like. 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. Particularly when a polyvinyl alcohol-based polymer film is used as a polarizer, it is preferable to use an adhesive containing a polyvinyl alcohol-based resin in view of adhesion.

The polyvinyl alcohol-based resin may be a polyvinyl alcohol obtained by saponifying polyvinyl acetate, a derivative thereof, a saponification product of a copolymer of a monomer further copolymerized with vinyl acetate, a polyvinyl alcohol obtained by acetalization, urethanation, 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, α-olefins such as ethylene and propylene, (meth) ), Sodium sulphonate (monoalkyl maleate), sodium disulfonate alkylmaleate, N-methylol acrylamide, acrylamide alkylsulfonic acid alkali salt, N-vinylpyrrolidone and N-vinylpyrrolidone derivatives have. These polyvinyl alcohol resins may be used singly or in combination of two or more.

The polyvinyl alcohol-based resin is not particularly limited, but has an average degree of polymerization of about 100 to 5,000, preferably 1,000 to 4,000, and an average degree of saponification of 85 to 100% by mole, preferably 90 to 100% by mole in terms of adhesive surface.

The polyvinyl alcohol-based resin preferably has a long-chain functional group having hydrophilicity in the side chain. Examples of the hydrophilic long chain functional group in the side chain include an acetoacetyl group and a carbonyl group. An adhesive containing a polyvinyl alcohol-based resin having a long-chain-chain functional group (for example, acetoacetyl group) having hydrophilic side chains is more preferable in terms of improving durability. The polyvinyl alcohol resin having a hydrophilic long chain functional group in the side chain is excellent in swelling property, water absorbability, and swelling easily due to the presence of water (because it is easily soluble) Even when the water content of the resin is low, it is preferable to obtain good adhesiveness.

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 acetoacetyl group modification degree exceeds 40 mol%, the effect of improving the water resistance is small. The degree of acetoacetyl group modification is a value measured by NMR.

When the aqueous solution is prepared, the adhesive layer formed of the water-based adhesive may be blended with a catalyst such as a crosslinking agent, other additives, or an acid, if necessary.

As the crosslinking agent, those used in a polyvinyl alcohol-based adhesive can be used without particular limitation. A compound having at least two functional groups having reactivity with the polyvinyl alcohol-based resin can be used. Examples thereof include alkylenediamines having two alkylene groups and amino groups such as ethylenediamine, triethylenediamine, and hexamethylenediamine; alkylenediamines such as tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane Isocyanates such as triisocyanate, methylene bis (4-phenylmethanetriisocyanate), isophorone diisocyanate, and ketoxime block water phenol blockers thereof; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin Epoxies such as di- or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylol propane triglycidyl ether, diglycidyl aniline, and diglycidyl amine; formaldehyde, acetaldehyde, propion Monoaldehydes such as aldehyde and butylaldehyde, glyoxal, malondialdehyde Dialdehydes such as maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, maleic anhydride, Amino-formaldehyde resins such as condensates of formaldehyde, zirconium compounds such as zirconium acetate, zirconium nitrate, zirconium carbonate, zirconium hydroxide and zirconium oxychloride; metal glyoxylic acid salts such as lithium, Zinc, aluminum and the like), a glyoxylic acid amine salt (e.g., an alkali metal such as sodium and potassium, an alkaline earth metal such as magnesium and calcium, a transition metal such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, Examples of the amine include ammonia, monomethylamine, dimethylamine, trimethylamine, and the like), and the like; An acetal compound such as dimethoxyethane, diethoxyethane or dialkoxyvalerate, or a divalent metal such as sodium, potassium, magnesium, calcium, aluminum, iron or nickel; , Or salts of trivalent metals and oxides thereof. These may be used alone or in combination of two or more. Among them, it is preferable to use an amino acid or a sulfo amino acid having at least one basic group and at least one acidic group. The basic group is preferably an amino group, and the acidic group is preferably a carboxyl group or a sulfo group. Examples of the amino acid include glycine, alanine, phenylalanine, valine, leucine, isoleucine, lysine, proline, serine, threonine, tryptophan, histidine, tyrosine, arginine, asparagine, aspartic acid, aspartame, glutamine, A copolymer of an amino acid and (meth) acrylic acid, and the like. Examples of the sulfurous amino acid include methionine, cysteine, cystine, and taurine. Of these, it is particularly preferable to use a sulfur amino acid having a sulfo group such as taurine. As the crosslinking agent, a coupling agent such as a silane coupling agent or a titanium coupling agent can be used.

The blending amount of the crosslinking agent can be suitably designed according to the type of the polyvinyl alcohol-based resin, but is usually about 0.1 to 50 parts by weight, preferably 0.2 to 30 parts by weight, per 100 parts by weight of the polyvinyl alcohol- More preferably 0.5 to 20 parts by weight. Within this range, good adhesion can be obtained.

The method for producing a polarizing plate according to the present invention comprises the steps of (1) coating an adhesive on a transparent protective film and forming an adhesive layer on the transparent protective film, (2) a step of bonding the polarizer and the transparent protective film by the adhesive layer, , And a step (3) of drying the adhesive layer. With this manufacturing method, a polarizing plate having a transparent protective film formed on at least one surface of a polarizer with an adhesive layer interposed therebetween is obtained.

In the above step (1), the transparent protective film is coated with an adhesive and then dried to form an adhesive layer in the form of a film on the transparent protective film.

The coating of the adhesive on the transparent protective film is preferably performed so that the thickness of the adhesive layer after the drying step (3) is about 10 to 300 nm. The thickness of the adhesive layer is more preferably 10 to 200 nm, particularly preferably 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and obtaining a sufficient adhesive force. When the thickness of the adhesive layer is less than 10 nm, the adhesive force is not sufficient. When the thickness exceeds 300 nm, the optical reliability and the moisture-resistant adhesive force tend to decrease.

The method of adjusting the thickness of the adhesive layer is not particularly limited, and examples thereof include a method of adjusting the solid content concentration of the adhesive solution and the coating apparatus of the adhesive. The method for measuring the thickness of the adhesive layer is not particularly limited, but measurement of cross-sectional observation by SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) is preferably used.

The operation of applying the adhesive is not particularly limited, and various means such as a gravure coating method, a die coating method, a roll coating method, a spray coating method, and an immersion coating method can be employed. However, Gravure coating method and die coating method are preferable.

In the above step (1), the pressure sensitive adhesive layer formed on the transparent protective film is controlled so as to become a semi-dry film state. Specifically, a pressure-sensitive adhesive layer in a coating film state in which a change in contact angle with water occurs within 30 seconds is formed. The coating film state of the adhesive layer is determined based on a change time of the contact angle of the adhesive layer with respect to water. That is, the coated film state of the adhesive layer is an index indicating the swelling time of the adhesive layer against water (time for the adhesive layer to start melting). The change time of the contact angle of the adhesive layer with respect to water is specifically a time until the contact angle of the water in the adhesive layer (initial adhesion angle) changes by 10 degrees after the water comes into contact with the adhesive layer. The change time of the contact angle is preferably 30 seconds or less and 15 seconds or less. If the change time of the contact angle is 30 seconds or less, even if the moisture content of the polarizer is low, the adhesive layer can be swelled by moisture in the polarizer to improve the adhesiveness. The shorter the change time of the contact angle, the faster the adhesive layer is melted by water, and is preferable from the viewpoint of high-speed productivity. On the other hand, when the change time of the contact angle is more than 30 seconds, it is difficult to swell the adhesive layer by the water of the polarizer when the water content of the polarizer is low, resulting in adhesion failure.

The formation of the adhesive layer in the coating film state is carried out, for example, by drying the adhesive coated on the transparent protective film. The drying conditions are determined depending on the kind of the adhesive and the like, but the drying temperature is preferably 30 to 100 占 폚, more preferably 40 to 90 占 폚. The drying time is preferably 1 to 100 seconds, more preferably 20 to 80 seconds.

After the adhesive layer in the coated state is formed on the transparent protective film by the above step (1), a step (2) of bonding the polarizer and the transparent protective film with the adhesive layer is carried out. Although the method of the step (2) is not particularly limited, for example, a laminating method using a roll laminator or the like can be adopted. When a transparent protective film is formed on both surfaces of the polarizer, either a simultaneous or sequential lamination method can be employed.

Then, the drying step (3) is carried out after the bonding step (2). An adhesive layer is formed from the adhesive layer in the semi-dry film state by the drying step (3), and a polarizing plate having a transparent protective film formed on at least one surface of the polarizer with the adhesive layer interposed therebetween is obtained.

The drying condition of the drying step (3) is a drying temperature of 40 to 100 ° C and a drying time of 1 to 10 minutes. The drying temperature is preferably 50 to 90 占 폚, more preferably 60 to 80 占 폚. The drying time is preferably 2 to 9 minutes, more preferably 3 to 8 minutes.

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 mounting a drive circuit. In the present invention, Except that a polarizing plate or an optical film according to the present invention is used. As 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.

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)

From the obtained polarizing film, a sample of 180 mm x 500 mm was cut out 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} × 100

(Production of Polarizer)

Using a polyvinyl alcohol film having a thickness of 75 占 퐉 (VF-PS7500, manufactured by Kuraray Co., Ltd., width 1000 mm), the film was immersed in pure water at 30 占 폚 for 60 seconds to stretch the film to 2.5 times the stretching magnification, Was dyed in an aqueous solution (weight ratio: pure water / iodine (I) / potassium iodide (KI) = 100 / 0.01 / 1) for 45 seconds and stretched in an aqueous 4 wt.% Boric acid solution to give a draw ratio of 5.8, Thereafter, the film was dried at 60 DEG C for 3 minutes while maintaining the tension of the film to obtain a polarizer. The polarizer had a thickness of 25 mu m and a water content of 12 wt%. This is referred to as a polarizer 1.

Polarizers (2) to (5) having different moisture ratios were prepared in the same manner as in the case of the polarizer (1) except that the drying conditions were changed in the production of the polarizer (1). The drying conditions and the moisture content are shown below.

Polarizer (2): Drying condition (30 seconds at 40 캜), water content 20% by weight.

Polarizer (3): Drying condition (20 seconds at 40 캜), water content 25% by weight.

Polarizer (4): Drying condition (60 sec at 40 캜), water content 10 wt%.

(Preparation of Adhesive A)

100 parts by weight of a PVA resin (Ecomatty, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 35 parts by weight of a crosslinking agent (Watersol, manufactured by Dainippon Ink and Chemicals, Incorporated) were dissolved in 3760 parts by weight of pure water to prepare an adhesive A.

(Preparation of adhesive B)

100 parts by weight of a PVA resin (containing Gose Pimer Z: acetoacetyl group, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 35 parts by weight of a crosslinking agent (Watersol, manufactured by Dainippon Ink and Chemicals, Incorporated) were dissolved in 3760 parts by weight of pure water To prepare an adhesive B.

(Preparation of adhesive C)

18 parts by weight of an alumina colloid aqueous solution (average particle diameter 15 nm, solid concentration 10% by weight, positive charge) was added to 100 parts by weight of the adhesive B (aqueous solution) to prepare an adhesive C.

Example 1

(Production of polarizing plate)

The above adhesive A was coated with a slot die on one side of a triacetylcellulose (TAC) film (UZ-80T manufactured by Fuji Photo Film Co., Ltd., water content: 1.4 wt%) having a thickness of 80 탆 and dried at 65 캜 for 1 minute, A TAC film with an adhesive layer having an adhesive layer in the form of a film having a thickness of 0.1 mu m was obtained. Subsequently, a TAC film with an adhesive layer was bonded to both surfaces of the polarizer by a roll machine. Thereafter, a drying step at 80 캜 for 5 minutes was carried out to prepare a polarizing plate.

Examples 2 to 4 and Comparative Examples 1 to 5

A polarizing plate was produced in the same manner as in Example 1 except that the kind of adhesive and the kind of polarizer (water content) were changed as shown in Table 1.

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

<Change time of contact angle of water>

The pressure sensitive adhesive layer in the form of a semi-dry film formed on the transparent protective film was brought into contact with water and the contact angle of water was observed with the lapse of time. From the contact angle (initial angle) at the time when the adhesive layer was contacted with water, the time until the contact angle changed by 10 was measured. The measurement of the contact angle and the confirmation of the change in the contact angle (measurement of time) were carried out by a dynamic contact angle method (contact angle meter manufactured by Kyowa Scientific Co., Ltd.) by a droplet method.

<Adhesiveness>

The interface between the polarizer and the transparent protective film was peeled off from the end of the obtained polarizing plate, and the film was peeled off and the peeled film was peeled off.

&Lt; Measurement of polarization degree &

The degree of polarization of the polarizing plate was measured by using a spectrophotometer (V7100, manufactured by Nippon Denshoku Kogyo Co., Ltd.) equipped with an integrating sphere, and the spectral transmittance at a wavelength of 380 to 780 nm.

The degree of polarization was measured by measuring the transmittance (parallel transmittance: Tp) when two identical polarizing plates were superposed so that the transmission axes of the two polarizing plates were parallel to each other and the transmittance (orthogonal transmittance: Tc) Is obtained by applying the following equation.

Polarization degree (%) = {(Tp - Tc) / (Tp + Tc)} ^1/2 100

Each transmittance is a Y value measured by a 2-degree field of view (C light source) of JIS Z 8701 and subjected to visibility correction. The table shows the degree of polarization when the single transmittance is 42.8%.

Claims (3)

A method for producing a polarizing plate in which a transparent protective film is formed on at least one surface of a polarizer through an adhesive layer,
The transparent protective film is coated with an aqueous adhesive for a polarizing plate and then dried under conditions of 30 ° C or more and 65 ° C or less to form an adhesive layer in the form of a coated film on which a change in contact angle with water occurs within 30 seconds Processes (1),
A step (2) of bonding a polarizer with a water content of 12 to 25% by weight to the transparent protective film by the adhesive layer, and a step (3) of drying the adhesive layer. The method according to claim 1,
Wherein the water-based adhesive is a polyvinyl alcohol-based adhesive containing a polyvinyl alcohol-based resin. 3. The method of claim 2,
Wherein the polyvinyl alcohol-based resin has a long-chain functional group having hydrophilicity on the side chain.