JP5975625B2 - Manufacturing method of polarizing plate - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate. The present invention also relates to a polarizing plate and 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 a liquid crystal display device, it is indispensable to dispose polarizers on both sides of a glass substrate on which a liquid crystal panel surface is formed because of its image forming method. In general, a polarizer is obtained by dyeing a polyvinyl alcohol film with a dichroic material such as iodine, cross-linking with a cross-linking agent, and forming a film by uniaxial stretching. Since the polarizer is made by stretching, it easily contracts. In addition, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed particularly under humidified conditions. Moreover, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. Therefore, a polarizing plate is used in which a transparent protective film such as triacetyl cellulose is bonded to both sides or one side of the polarizer to supplement the strength. The polarizing plate is manufactured by bonding a polarizer and a transparent protective film with an adhesive.

  For example, in manufacturing a polarizing plate by laminating a polarizer and a transparent protective film, it is used to use a polyvinyl alcohol resin containing an acetoacetyl group and an aqueous adhesive relating to an aqueous solution containing a crosslinking agent. (Patent Document 1). It is described that the water-based adhesive has good heat and moisture resistance and water resistance. Moreover, it has been proposed that a polarizing plate having a good appearance can be obtained by using an aqueous adhesive having a viscosity of 3 to 20 mPa · s (25 ° C.) (Patent Document 2). . In Patent Documents 1 and 2, the polarizer and the transparent protective film are bonded together in the applied state without drying the adhesive solution applied to the polarizer or the transparent protective film.

  Moreover, after drying the adhesive agent solution applied to the polarizer or the transparent protective film to form an adhesive layer, the polarizer and the transparent protective film are obtained by allowing an aqueous liquid to be present on these bonding surfaces. A method of manufacturing a polarizing plate by bonding is proposed (Patent Document 3). Patent Document 3 describes that a polarizing plate having fewer appearance defects than that of Patent Documents 1 and 2 can be manufactured by forming an adhesive layer in advance. In addition, it has been proposed that an adhesive in which a metal compound colloid is blended with a polyvinyl alcohol-based resin containing an acetoacetyl group can improve nick defects in the obtained polarizing plate (Patent Document 4).

JP 2005-189615 A JP 2002-365432 A JP 2005-128490 A JP 2009-122664 A

  On the other hand, in the production of a polarizing plate, the lower the moisture content of the polarizer, the better the optical properties (polarization degree, etc.) because the orientation of the polyvinyl alcohol resin is improved. However, in Patent Document 3, the degree of drying of the adhesive layer formed in advance is high, and the adhesive layer is difficult to dissolve in water. Therefore, when the moisture content of the polarizer is low, it may not be sufficiently dissolved by the aqueous liquid to which the adhesive layer is added, which may cause poor adhesion between the polarizer and the transparent protective film in the resulting polarizing plate. there were. Moreover, the adhesive which mix | blended the metal compound colloid with the polyvinyl alcohol-type resin containing an acetoacetyl group also had the problem of the adhesion failure similar to the above.

  An object of the present invention is to provide a method for producing a polarizing plate, which can obtain a polarizing plate having good adhesion between the polarizer and the transparent protective film even when a polarizer having a low moisture content is used. And

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by a method for producing a polarizing plate shown below, and have completed the present invention.

That is, the present invention is a method for producing a polarizing plate in which a transparent protective film is provided on at least one surface of a polarizer via an adhesive layer,
A process of forming an adhesive layer in a coating state in which a contact angle change with respect to water occurs within 30 seconds on the transparent protective film by drying after applying a water-based adhesive for polarizing plate to the transparent protective film ( 1),
Polarized light comprising the step (2) of bonding a polarizer having a moisture content of 12 to 25% by weight and a transparent protective film, and the step (3) of drying the adhesive layer by the adhesive layer. The present invention relates to a method for manufacturing a plate.

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

  In the method for producing a polarizing plate of the present invention, in the step (1), an adhesive layer is formed on the transparent protective film as in Patent Document 3, and the adhesive layer is dried as in Patent Document 3. It is not a high state but a coating state. The adhesive layer in the semi-dry coating state can control the coating state so that, for example, the time until the contact angle change with water (the time when it starts to dissolve with water) occurs within a predetermined time is satisfied. it can. By controlling the coating state of the adhesive layer in this way, water can be secured to some extent in the adhesive layer formed from the water-based adhesive, and even when the polarizer has a low moisture content, the polarizer And a transparent protective film can be favorably bonded.

  Moreover, in the manufacturing method of the polarizing plate of this invention, the adhesive agent layer of the said coating-film state formed on a transparent protective film has the adhesive agent formed with the water-system adhesive agent, and it can dissolve with the water | moisture content in a polarizer. it can. Therefore, in the method for producing a polarizing plate of the present invention, it is not particularly necessary to add an aqueous liquid as in Patent Document 3. Moreover, in forming the adhesive layer in the coating film state in the step (1), moisture in the adhesive layer is removed in advance. Therefore, a polarizer and a transparent protective film can be performed at high speed, the drying step (3) can be performed efficiently, and this is advantageous in terms of productivity.

  Further, in the conventional adhesive layer in a high dry state, the polarizer usually needs to have a moisture content of more than 25% by weight. However, in the method for producing a polarizing plate of the present invention, the moisture content is 25. A weight% or less polarizer can be used. Thus, in the method for producing a polarizing plate of the present invention, a polarizer having a moisture content of 25% by weight or less can be used, so that the optical properties (polarization degree, etc.) of the obtained polarizing plate can be improved. Such a polarizing plate is excellent in in-plane uniformity, has a high resolution, and can realize an image display device such as a liquid crystal display device (LCD) or an electroluminescence display device (ELD) with high contrast.

  In this invention, the manufacturing method of the polarizing plate by which the transparent protective film is provided in the at least one surface of the polarizer through the adhesive bond layer is manufactured.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples include polyene-based oriented films such as those obtained by adsorbing a functional material and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm. The thickness of the polarizer is preferably 15 to 35 μm. If the thickness of the polarizer is too thin, it will be easily damaged when bonded to the transparent protective film. On the other hand, if the thickness of the polarizer is too thick, the drying efficiency tends to deteriorate, which is not preferable in terms of productivity.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be prepared, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  A polarizer having a moisture content of 12 to 25% by weight is used. In the present invention, the polarizer can be used even at a low moisture content of 25% by weight or less. Furthermore, the moisture content of the polarizer can be used even at 23% by weight or less. A lower moisture content of the polarizer is preferable in that a polarizing plate having good optical properties can be obtained. In addition, the drying efficiency in the drying step (3) is improved, which is preferable in terms of productivity that can increase the production rate. On the other hand, if the moisture content of the polarizer is too low, the rigidity of the polarizer as a film increases, and it is easy to be damaged and appearance defects are likely to occur. In view of this, the moisture content of the polarizer is preferably 12% by weight or more, and more preferably by weight% or more. The moisture content of such a polarizer can generally be adjusted by the conditions of the drying process during the manufacturing process of the polarizer, but if necessary, a separate humidity conditioning process is provided, soaking in a water bath or spraying water droplets, or You may heat-dry again or dry under reduced pressure.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) And polymers based on polycarbonate and polycarbonate. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Examples of the polymer that forms the transparent protective film include polymer blends. In addition, a transparent protective film is usually bonded to the polarizer by an adhesive layer. As the transparent protective film, thermosetting such as (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone-based, etc. Resin or ultraviolet curable resin can be used. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. 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, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  As the transparent protective film of the present invention, at least one selected from cellulose resin (polymer), polycarbonate resin (polymer), cyclic polyolefin resin (cycloolefin or polyolefin having norbornene structure) and (meth) acrylic resin is used. Is preferred. The effect of the present invention is particularly remarkable when a protective film made of triacetyl cellulose is used.

  Although the thickness of a transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  In addition, when providing a transparent protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the transparent protective film which consists of a different polymer material etc. may be used.

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

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  An aqueous adhesive is used as the adhesive used to form the adhesive layer that bonds the polarizer and the transparent protective film.

  Although it does not specifically limit as an aqueous adhesive, For example, a vinyl polymer type | system | group, a gelatin type, a vinyl type latex type, a polyurethane type, an isocyanate type, a polyester type, an epoxy type etc. can be illustrated. As the water-based adhesive, an adhesive containing a vinyl polymer is preferably used, and the vinyl polymer is preferably a polyvinyl alcohol resin. In particular, when a polyvinyl alcohol polymer film is used as the polarizer, it is preferable from the viewpoint of adhesiveness to use an adhesive containing a polyvinyl alcohol resin.

  Polyvinyl alcohol resin is polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Examples thereof include modified polyvinyl alcohols that have been converted into ethers, ethers, grafts, or phosphoric esters. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins can be used alone or in combination of two or more.

  The polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of adhesiveness, the average degree of polymerization is about 100 to 5000, preferably 1000 to 4000, the average saponification degree is about 85 to 100 mol%, preferably 90 to 100 mol%. It is.

  The polyvinyl alcohol-based resin preferably has a hydrophilic long-chain functional group 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 hydrophilic long-chain functional group (for example, acetoacetyl group) in the side chain is more preferable from the viewpoint of improving durability. Moreover, since the polyvinyl alcohol-type resin which has a hydrophilic long-chain functional group in a side chain has hydrophilicity, since it is excellent in swelling property, it has good water absorbability, and it is easy to swell by presence of water ( This is preferable for obtaining good adhesion even when the moisture content of the polarizer is low.

  A 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 in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto. A polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. And the like. Moreover, the method of making diketene gas or liquid diketene contact directly to polyvinyl alcohol is mentioned.

  The degree of acetoacetyl group modification of the polyvinyl alcohol-based resin containing an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. If it is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient and unsuitable. The degree of acetoacetyl group modification 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 water resistance is small. The degree of acetoacetyl modification is a value measured by NMR.

  In addition, the adhesive layer formed from the water-based adhesive can be blended with a catalyst such as a crosslinking agent, other additives, and an acid, if necessary, in preparing the aqueous solution.

  As a crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. A compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, ethylenediamine, triethylenediamine, hexamethylenediamine and other alkylene diamines having two amino groups and amino groups; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate), isophorone diisocyanate and isocyanates such as ketoxime block product or phenol block product thereof; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6- Hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycy Epoxys such as ruaniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde; dialdehydes such as glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde and phthaldialdehyde Amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylol melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; zirconium acetate, zirconium nitrate, zirconium carbonate, zirconium hydroxide, acid Zirconium compounds such as zirconium chloride; metal glyoxylate (metals include, for example, lithium, sodium, potassium Alkaline earth metals such as magnesium, calcium, transition metals such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, etc.), glyoxylic acid amine salts (amines) Examples thereof include glyoxylates such as ammonia, monomethylamine, dimethylamine, trimethylamine, etc .; amino acids or sulfur-containing amino acids having one or more basic groups and one or more acidic groups; dimethoxy Acetal compounds such as ethanal, diethoxyethanal, dialkoxyethanal; and divalent metals such as sodium, potassium, magnesium, calcium, aluminum, iron, nickel, and salts of trivalent metals and oxides thereof . These can be used alone or in combination of two or more. Among these, it is preferable to use an amino acid or a sulfur-containing amino acid having one or more basic groups and one or more acidic groups. 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 acids include glycine, alanine, phenylalanine, valine, leucine, isoleucine, lysine, proline, serine, threonine, tryptophan, histidine, tyrosine, arginine, asparagine, aspartic acid, aspartame, glutamine, glutamic acid, and these amino acids. Examples include copolymers with (meth) acrylic acid. Examples of the sulfur-containing amino acid include methionine, cysteine, cystine, and taurine. Among these, it is particularly preferable to use a sulfur-containing amino acid having a sulfo group such as taurine. Moreover, as a crosslinking agent, coupling agents, such as a silane coupling agent and a titanium coupling agent, can be used.

  The amount of the crosslinking agent can be appropriately designed according to the type of polyvinyl alcohol resin, etc., but is usually about 0.1 to 50 parts by weight, preferably 0.2 to 100 parts by weight of the polyvinyl alcohol resin. About 30 parts by weight, more preferably 0.5 to 20 parts by weight. In such a range, good adhesiveness can be obtained.

  The manufacturing method of the polarizing plate of this invention is a process (1) which coats an adhesive agent on a transparent protective film, and forms an adhesive bond layer on a transparent protective film, A polarizer and a transparent protective film are formed with the said adhesive bond layer. A step (2) of bonding, and a step (3) of drying the adhesive layer. By this manufacturing method, a polarizing plate in which a transparent protective film is provided on at least one surface of the polarizer via an adhesive layer is obtained.

  In the step (1), an adhesive is applied to the transparent protective film and then dried to form an adhesive layer in a coating state on the transparent protective film.

  The adhesive is preferably applied to the transparent protective film 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 from 10 to 200 nm, particularly preferably from 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and obtaining sufficient adhesive strength. When the thickness of the adhesive layer is less than 10 nm, the adhesive force is not sufficient, and when it 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 adhesive coating apparatus. The method for measuring the thickness of the adhesive layer is not particularly limited, but cross-sectional observation measurement using SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) is preferably used.

  The adhesive coating operation 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 a dip coating method can be adopted, but the adhesive can be applied uniformly. A gravure coating method and a die coating method are preferred.

  Moreover, in the said process (1), control is made so that the adhesive layer formed on a transparent protective film may be in a semi-dry coating state. Specifically, a pressure-sensitive adhesive layer in a coating state in which a change in contact angle with water occurs within 30 seconds is formed. The coating state of the adhesive layer is determined based on the change time of the contact angle of the adhesive layer with respect to water. That is, the coating state of the adhesive layer can be said to be an index representing the swelling time of the adhesive layer with respect to water (the time when the adhesive layer starts to dissolve). The change time of the contact angle of the adhesive layer with respect to water, specifically, the contact angle of water of the adhesive layer (initial adhesive angle) changes by 10 ° after water contacts the adhesive layer. It is time until. The change time of the contact angle is 30 seconds or less, and preferably 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 swollen by the moisture in the polarizer to improve the adhesiveness. The shorter the contact angle change time, the faster the adhesive layer dissolves with water, which is preferable from the viewpoint of high-speed productivity. On the other hand, if the change time of the contact angle exceeds 30 seconds, if the moisture content of the polarizer is low, it is difficult to swell the adhesive layer with the moisture of the polarizer, which causes poor adhesion. .

  The formation of the adhesive layer in the coating state is performed by, for example, drying the adhesive applied to the transparent protective film. The drying conditions are determined by the type of adhesive and the like, but the drying temperature is preferably 30 to 100 ° C, more preferably 40 to 90 ° C. The drying time is preferably 1 to 100 seconds, and more preferably 20 to 80 seconds.

  After the adhesive layer in the state of the coating film is formed on the transparent protective film by the step (1), a step (2) for bonding the polarizer and the transparent protective film with the adhesive layer is performed. Although the bonding method in a process (2) is not specifically limited, For example, the bonding method by a roll laminator etc. is employable. In addition, when providing with a transparent protective film on both surfaces of a polarizer, either the simultaneous or sequential bonding method can be employ | adopted.

  Next, after the bonding step (2), a drying step (3) is performed. By the drying step (3), an adhesive layer is formed from the semi-dry adhesive layer, and a transparent protective film is provided on at least one surface of the polarizer via the adhesive layer. A polarizing plate is obtained.

  The drying conditions in the drying step (3) are 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 ° C, more preferably 60 to 80 ° C. The drying time is preferably 2 to 9 minutes, and 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, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a 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 necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, According to the past. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate 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 a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to these examples and comparative examples.

(Measurement method of moisture content of polarizer)
A sample of 180 mm × 500 mm was cut out from the obtained polarizing film, and its initial weight (W (g)) was measured. The sample was left in a drier at 120 ° C. for 2 hours, and then the weight after drying (D (g)) was measured. From these measured values, the moisture content was determined by the following formula.
Moisture content (%) = {(WD) / W} × 100

(Production of polarizer)
Using a polyvinyl alcohol film having a thickness of 75 μm (manufactured by Kuraray Co., Ltd .: VF-PS7500, width 1000 mm), the film was stretched to 2.5 times the draw ratio while being immersed in 30 ° C. pure water for 60 seconds. Dyeing is performed in an aqueous iodine solution (weight ratio: pure water / iodine (I) / potassium iodide (KI) = 100 / 0.01 / 1) for 45 seconds, and the draw ratio is 5.8 in a 4% by weight boric acid aqueous solution. The film was stretched so as to be doubled, immersed in pure water for 10 seconds, and then dried at 60 ° C. for 3 minutes while maintaining the tension of the film to obtain a polarizer. This polarizer had a thickness of 25 μm and a moisture content of 12% by weight. This is designated as a polarizer (1).

In the production of the polarizer (1), polarizers (2) to (5) having different moisture contents were produced in the same manner as the polarizer (1) except that the drying conditions were changed. Drying conditions and moisture content are shown below.
Polarizer (2): Drying conditions (40 ° C. for 30 seconds), moisture content 20% by weight.
Polarizer (3): Drying conditions (20 seconds at 40 ° C.), moisture content of 25% by weight.
Polarizer (4): Drying conditions (40 ° C. for 60 seconds), moisture content of 10% by weight.

(Preparation of adhesive A)
100 parts by weight of PVA resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: Ecomati) and 35 parts by weight of a cross-linking agent (manufactured by Dainippon Ink Chemical Co., Ltd .: Watersol) are dissolved in 3760 parts by weight of pure water to form an adhesive. A was prepared.

(Preparation of adhesive B)
100 parts by weight of PVA resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: Goosephimer Z: containing acetoacetyl group) and 35 parts by weight of a crosslinking agent (manufactured by Dainippon Ink and Chemicals Co., Ltd .: Watersol) 3760 parts by weight of pure water The adhesive B was prepared by dissolving in the part.

(Preparation of adhesive C)
Adhesive C was prepared by adding 18 parts by weight of an alumina colloidal aqueous solution (average particle size 15 nm, solid content concentration 10% by weight, positive charge) to 100 parts by weight of the adhesive B (aqueous solution).

Example 1
(Preparation of polarizing plate)
The adhesive A was applied to one side of a 80 μm thick triacetylcellulose (TAC) film (Fuji Photo Film Co., Ltd .: UZ-80T, moisture content 1.4 wt%) with a slot die, and then 65 ° C. And dried for 1 minute to obtain a TAC film with an adhesive layer having a 0.1 μm thick adhesive layer in a coated state. Next, TAC films with an adhesive layer were bonded to both surfaces of the polarizer by a roll machine. Then, the polarizing plate was created by giving the drying process for 5 minutes at 80 degreeC.

Examples 2-4 and Comparative Examples 1-5
A polarizing plate was produced in the same manner as in Example 1 except that the type of adhesive and the type of polarizer (water content) were changed as shown in Table 1.

  The following evaluation was performed about the polarizing plate obtained by the said Example and comparative example. The evaluation results are shown in Table 1.

<Water contact angle change time>
About the adhesive layer of the semi-dry coating state formed in the transparent protective film, water was made to contact and the contact angle of water was observed over time. From the contact angle (initial angle) when water contacted the adhesive layer, the time until the contact angle changed by 10 ° was measured. Measurement of the contact angle and confirmation of the change of the contact angle (measurement of time) were performed by a dynamic contact angle method using a droplet method (manufactured by Kyowa Kagaku, contact angle meter).

<Adhesiveness>
From the end of the obtained polarizing plate, the interface between the polarizer and the transparent protective film was peeled off, and “×” indicates that it was peeled off, and “◯” indicates that it was not peeled off.

<Measurement of degree of polarization>
The polarization degree of the polarizing plate was measured by using a spectrophotometer with an integrating sphere (V7100 manufactured by JASCO Corporation) for spectral transmittance at a wavelength of 380 to 780 nm.
Note that the degree of polarization is such that two identical polarizing plates are superposed such that both transmission axes are parallel to each other so that both transmission axes are parallel (parallel transmittance: Tp), and the two transmission axes are orthogonal to each other. In this case, the transmittance (orthogonal transmittance: Tc) is determined by applying the transmittance to the following equation.
Polarization degree (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
Each transmittance is a Y value obtained by measuring the transmittance with a two-degree field of view (C light source) of JIS Z8701 and correcting the visibility. 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 provided on at least one surface of a polarizer via an adhesive layer,
A coating film in which a water-based adhesive for a polarizing plate is applied to the transparent protective film and then dried under conditions of 30 ° C. or higher and 65 ° C. or lower, and a change in contact angle with water occurs on the transparent protective film within 30 seconds. Forming an adhesive layer in a state (1),
Polarized light comprising the step (2) of bonding a polarizer having a moisture content of 12 to 25% by weight and a transparent protective film, and the step (3) of drying the adhesive layer by the adhesive layer. A manufacturing method of a board.   The method for producing a polarizing plate according to claim 1, wherein the water-based adhesive is a polyvinyl alcohol-based adhesive containing a polyvinyl alcohol-based resin. The method for producing a polarizing plate according to claim 2, wherein the polyvinyl alcohol-based resin has a hydrophilic long-chain functional group in a side chain.