JP2005128490A - Method for manufacturing polarizing plate , polarizing plate, optical film, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate that has uniform polarization characteristics and is excellent in durability. <P>SOLUTION: The method for manufacturing the polarizing plate having a transparent protective film provided at least on one side of a polarizer via an adhesive layer is characterized that the adhesive layer is formed on a surface of the transparent protective film for forming the adhesive layer or/and a surface of the polarizer for forming the adhesive layer by applying adhesive, and after that, when the transparent protective films and the polarizer are pasted continuously via the thus-formed adhesive layer, aqueous liquid is presented on the pasting surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a polarizing plate. Moreover, this invention relates to the polarizing plate obtained by the said manufacturing method. The polarizing plate is an optical film obtained by laminating the polarizing plate alone, or a flat panel display such as a liquid crystal display device (hereinafter abbreviated as LCD) or an electroluminescence display device (hereinafter abbreviated as ELD), or an image such as a PDP. A display device can be formed.

  In general, a polarizing plate for flat panel display, particularly a polarizing plate used for LCD, is mainly made of a polyvinyl alcohol film having a thickness of 70 μm or more. In addition, in order to obtain sufficient optical characteristics as an LCD, a polarizing plate is preferably used by stretching a PVA-based film containing a dichroic material such as iodine and bonding a transparent protective film thereto. Yes. The polyvinyl alcohol polarizer is easily contracted because it is produced by stretching. In addition, since the PVA 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. For this reason, a polarizing plate is used in which a transparent protective film such as saponified 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. As an adhesive for polarizing plates used for adhesion | attachment of the said polarizer and a transparent protective film, a water-system adhesive agent is preferable, for example, the polyvinyl alcohol-type adhesive agent which mixed the crosslinking agent in the polyvinyl alcohol aqueous solution is used.

  As LCDs have higher definition and higher functionality, improvements in screen uniformity and quality are required. Moreover, high heat resistance, moist heat resistance, water resistance and the like are also required due to diversification of use environments. Furthermore, recent LCDs are required to be thin and light in weight because of their portable functions. Due to the required characteristics of LCDs, LCD polarizing plates are required to have high performance and high functionality such as uniformity as polarizers, high heat resistance, moisture and heat resistance, water resistance, and thinning. .

  As a method of manufacturing a polarizing plate by bonding a polarizer and a transparent protective film, there are the following methods. For example, as one method, first, an adhesive solution is applied to one side of a polarizer, and then a transparent protective film is attached to the transparent polarizer so that the transparent protective film is attached to one side of the polarizer. Then, after apply | coating an adhesive solution to the other surface of a polarizer, a transparent protective film is stuck on the other surface of a polarizer by bonding a transparent protective film. Thereby, the polarizing plate by which the transparent protective film was each affixed on both surfaces of the polarizing plate through the adhesive bond layer is produced. The adhesive solution may be applied directly to the transparent protective film or may be applied to both the polarizer and the transparent protective film. As another method, transparent protective films are disposed on both sides of the polarizer, and an adhesive solution is supplied between the polarizer and the transparent protective film (see Patent Document 1), or the transparent protective film is bonded. In a state where the adhesive layer is formed by applying an adhesive to the surface forming the agent layer and / or the surface forming the adhesive layer of the polarizer, the adhesive layer is continuously passed between the rolls of the pair, A method of manufacturing a polarizing plate by sticking a transparent protective film and a polarizer by roll pressure has also been proposed.

  However, the above-described conventional manufacturing method has a problem that a streak-like appearance defect occurs during the bonding of the polarizer and the transparent protective film. Such streaky appearance defects particularly affect the optical uniformity among the highly required properties of the polarizing plate. For this reason, it has not been possible to cope with improvements in screen uniformity and quality as LCDs have higher definition and higher functionality. A streak-like appearance defect means that stripe-like streaks are seen in a reflection state parallel to the absorption axis direction of a polarizing plate obtained by laminating a transparent protective film. As a feature of streaks, it has a shape like a groove carved in a record board at a pitch of 1 to 2 mm.

  As described above, the polarizer is used as a polarizing plate whose strength is reinforced by a transparent protective film. Conventionally, however, the polyvinyl alcohol-based adhesive may peel off at the interface between the polarizer and the transparent protective film under humidified conditions. This may be because the polyvinyl alcohol resin, which is the main component of the adhesive, is a water-soluble polymer, and the adhesive may be dissolved under the dew condensation condition.

  In order to solve such problems, it has been proposed to improve the heat and moisture resistance and water resistance by using a resin solution containing a polyvinyl alcohol resin containing an acetoacetyl group and a crosslinking agent as a PVA adhesive. (See Patent Document 2). However, the adhesive for polarizing plates described in Patent Document 2 has insufficient water resistance. Further, it was not sufficient in that it had a streaky appearance defect.

In addition, an adhesive layer is provided on the polarizer or on the transparent protective film, and after the contact angle of the adhesive layer is controlled to be equal to or less than a predetermined angle by humidification, the polarizer and the transparent protective film are bonded together to form a polarizing plate. Has been proposed (see Patent Document 3 and Patent Document 4). However, the methods of Patent Document 3 and Patent Document 4 are difficult to control, and the manufacturing process is complicated, which is not a realistic manufacturing method.
JP-A-11-179871 JP-A-7-198945 JP-A-7-306315 JP-A-7-306316

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for efficiently producing a polarizing plate having uniform polarization characteristics and excellent durability.

  Another object of the present invention is to provide a polarizing plate obtained by the production method. It is another object of the present invention to provide an optical film in which the polarizing plate is laminated with a polarizing plate, and an image display device such as an LCD or an ELD using the polarizing plate or the optical film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the object can be achieved by the following method for producing a polarizing plate, and have completed the present invention. That is, the present invention is as follows.

1. A method for producing a polarizing plate, wherein a transparent protective film is provided on at least one surface of a polarizer via an adhesive layer,
After forming the adhesive layer by applying an adhesive to the surface of the transparent protective film forming the adhesive layer and / or the surface of the polarizer forming the adhesive layer,
A method for producing a polarizing plate, comprising: causing an aqueous liquid to be present on a bonding surface when a transparent protective film and a polarizer are continuously bonded through the adhesive layer.

  2. 2. The method for producing a polarizing plate according to 1 above, wherein the polarizer is a polyvinyl alcohol-based polarizer and the transparent protective film is a cellulose-based transparent protective film.

  3. 3. The method for producing a polarizing plate according to 1 or 2 above, wherein the polarizer has a thickness of 35 μm or less.

  4). 4. The method for producing a polarizing plate according to any one of 1 to 3, wherein the adhesive is a polyvinyl alcohol-based adhesive.

  5). 5. The method for producing a polarizing plate according to 4 above, wherein the polyvinyl alcohol-based adhesive is a polyvinyl alcohol-based adhesive having an acetoacetyl group.

  6). 6. The method for producing a polarizing plate according to any one of 1 to 5, wherein the adhesive contains a crosslinking agent.

  7). 7. The method for producing a polarizing plate according to 6 above, wherein the crosslinking agent is a methylol compound.

  8). 8. The method for producing a polarizing plate according to any one of 1 to 7, wherein the adhesive layer has a thickness of 30 to 300 nm.

  9. The method for producing a polarizing plate according to any one of 1 to 8 above, wherein the viscosity of the aqueous liquid is 0.1 to 10 cP.

  10. 10. The method for producing a polarizing plate according to any one of 6 to 9, wherein the aqueous liquid is water.

  11. 10. The method for producing a polarizing plate according to any one of 1 to 9 above, wherein the aqueous liquid is an aqueous solution in which a crosslinking agent is dissolved.

  12 12. The method for producing a polarizing plate as described in 11 above, wherein the crosslinking agent is a methylol compound.

  13. 13. The method for producing a polarizing plate according to any one of 1 to 12 above, wherein an aqueous liquid is supplied to the bonding surface of the transparent protective film and the polarizer.

  14 The adhesive liquid is applied only to the transparent protective film side, and the aqueous liquid is supplied onto the adhesive layer formed by this application, so that the aqueous liquid is present on the bonded surface. The manufacturing method of the polarizing plate in any one.

  15. 13. The adhesive according to any one of 1 to 12 above, wherein the adhesive is applied only to the transparent protective film side, and the aqueous liquid is present on the bonding surface by supplying the aqueous liquid to the polarizer side. Manufacturing method of polarizing plate.

  16. The adhesive according to any one of the above 1 to 12, wherein the adhesive is applied only to the polarizer side, and the aqueous liquid is present on the bonding surface by supplying the aqueous liquid to the transparent protective film side. Manufacturing method of polarizing plate.

  17. Any one of the above 1 to 16, wherein when the transparent protective film and the polarizer are continuously bonded via the adhesive layer, an aqueous liquid is supplied to the bonding surface immediately before bonding. The manufacturing method of the polarizing plate of description.

  18. The polarizing plate obtained by the manufacturing method in any one of said 1-17.

  19. 19. An optical film, wherein at least one polarizing plate according to the above 18 is laminated.

  20. 18. An image display device comprising the polarizing plate according to 18 or the optical film according to 19 above.

  In the manufacturing method of the polarizing plate of the present invention, before the polarizer and the transparent protective film are bonded together with an adhesive, an adhesive is applied to at least one surface of the transparent protective film or the polarizer to form an adhesive layer. The formed transparent protective film or polarizer is produced. Furthermore, when bonding a transparent protective film and a polarizer, aqueous liquid is made to exist in the bonding surface of a transparent protective film and a polarizer, ie, the said adhesive bond layer. As a result, a polarizing plate with reduced appearance defects, particularly streak-like unevenness, can be obtained. Such a polarizing plate has uniform polarization characteristics since the streak-like appearance defects are suppressed, and can provide a high-performance image display device such as an LCD or ELD. The production method of the present invention is suitable for continuous production and can produce a polarizing plate efficiently. Moreover, the polarizing plate excellent in durability is obtained by adding an aqueous liquid to an adhesive bond layer. In particular, when the adhesive is a polyvinyl alcohol-based adhesive having an acetoacetyl group and methylol melamine is included as a crosslinking agent, the durability is further improved.

  The detailed mechanism of why the production method of the present invention is effective in suppressing the streaky appearance defect that occurs in the polarizing plate is not clear. In the conventional manufacturing method as described above, the adhesive solution having a high viscosity is brought into contact with the surface of the polarizer or the transparent protective film when the polarizer and the transparent protective film are bonded together, and some physical force is applied. However, in the present invention, it is considered that the physical factor is removed due to the presence of the aqueous liquid.

  Surprisingly, it was also found that in the production method of the present invention, a highly reactive adhesive is more effective than a less reactive adhesive in suppressing such streaky appearance defects. . The mechanism is not always clear. Since an adhesive having low reactivity is generally highly soluble in water, the adhesive layer once formed on the surface of the transparent protective film or the polarizer is redissolved in the added aqueous liquid. And it is thought that it is for increasing the viscosity of an addition aqueous solution system in the vicinity of the polarizer or transparent protective film surface which is a partner bonded together. Therefore, the production method of the present invention is particularly effective for a highly reactive adhesive.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films 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. And 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 made of a dichroic substance such as a polyvinyl alcohol film and iodine or a dichroic dye is preferable.

  As the polyvinyl alcohol-based film, a film formed by any method such as a casting method, a casting method, an extrusion method, etc., in which a polyvinyl alcohol-based resin is cast in a stock solution in which water or an organic solvent is dissolved, is appropriately used. Can be used. The degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5000, and more preferably 1400 to 4000.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine or the like and uniaxially stretching can be produced, for example, by the following method.

  In the dyeing process, the polyvinyl alcohol film is immersed in a dyeing bath at about 20 to 70 ° C. to which iodine is added for about 1 to 20 minutes to adsorb iodine. The iodine concentration in the dyeing bath is usually about 0.1 to 1 part by weight per 100 parts by weight of water. In the dyeing bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of about 0.02 to 20 parts by weight, preferably 2 to 10 parts by weight. These additives are particularly preferable for increasing the dyeing efficiency. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The polyvinyl alcohol film may be subjected to a swelling treatment at about 20 to 60 ° C. for about 0.1 to 10 minutes in a water bath or the like before being dyed in an aqueous solution containing iodine or a dichroic dye. 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.

  The dyed polyvinyl alcohol film can be cross-linked as necessary. The composition of the aqueous crosslinking solution used for the crosslinking treatment is usually about 1 to 10 parts by weight per 100 parts by weight of water, alone or mixed with a crosslinking agent such as boric acid, borax, glyoxal, and glutaraldehyde. The concentration of the crosslinking agent is determined in consideration of the balance between the optical properties and the contraction of the polarizing plate caused by the stretching force generated in the polyvinyl alcohol film.

  In the crosslinking bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of 0.05 to 15% by weight, preferably 0.5 to 8% by weight. These additives are particularly preferable from the viewpoint of obtaining in-plane uniform characteristics of the polarizer. The temperature of the aqueous solution is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time is not particularly limited, but is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The total draw ratio of the polyvinyl alcohol film is about 3 to 7 times, preferably 5 to 7 times the original length. When the total draw ratio exceeds 7 times, the film is easily broken. Stretching may be performed after dyeing with iodine, may be performed while dyeing or crosslinking, or may be dyed with iodine after stretching. The stretching method and the number of stretching are not particularly limited, and may be performed only in any one step. Moreover, you may perform several times in the same process.

  In addition, the polyvinyl alcohol film subjected to iodine adsorption alignment treatment is further added to an aqueous iodide solution such as potassium iodide having a water temperature of about 10 to 60 ° C., preferably about 30 to 40 ° C. and a concentration of 0.1 to 10% by mass. A step of dipping for 1 minute to 1 minute can be provided. In the iodide aqueous solution, auxiliary agents such as zinc sulfate and zinc chloride may be added. The polyvinyl alcohol film subjected to the iodine adsorption alignment treatment can be provided with a water washing step and a drying step of about 20 to 80 ° C. for about 1 minute to 10 minutes.

  The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm. When the thickness of the polarizer is reduced, the moisture in the polarizer is likely to be volatilized in the drying process for bonding with the transparent protective film during the manufacturing process of the polarizing plate. Therefore, the elongation of the polarizer is reduced, and a noticeable streak-like appearance defect is likely to occur. Such a phenomenon becomes more prominent as the thickness of the polarizer is reduced. However, according to the method for manufacturing a polarizing plate of the present invention, even when the thickness of the polarizer is 35 μm or less, and even when the thickness is 20 μm or less, streaks occur. The occurrence of defects in the appearance can be suppressed.

  As the transparent polymer or film material for forming the transparent protective film, an appropriate transparent material can be used, but a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile, Examples thereof include styrene polymers such as styrene copolymers (AS resins), polycarbonate polymers, and the like. 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 Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  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. The thickness of the transparent protective film is preferably 50 μm or less.

  Moreover, it is preferable that a transparent protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A transparent protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the transparent protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the transparent protective film, a cellulose-based transparent protective film made of a cellulose-based polymer such as triacetylcellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a transparent protective film on both sides of a polarizer, the transparent 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, and coating treatment for forming an easy adhesive layer. Among these, the coating process which forms an easily adhesive layer is suitable. 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 0.01 to 10 μm, more preferably about 0.05 to 5 μm, and particularly preferably about 0.1 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 hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles made of a crosslinked or uncrosslinked polymer, etc. are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  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 transparent protective film as an optical layer.

  The adhesive used for bonding the polarizer and the transparent protective film is not particularly limited, but a polyvinyl alcohol-based adhesive is preferably used. As the polyvinyl alcohol-based adhesive, one containing a polyvinyl alcohol-based resin and a crosslinking agent is usually used. However, when an aqueous solution containing a crosslinking agent is used as the aqueous liquid, the adhesive may or may not contain a crosslinking agent.

  Examples of the polyvinyl alcohol resin include polyvinyl alcohol resins and polyvinyl alcohol resins having an acetoacetyl group. The polyvinyl alcohol resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable because the durability of the polarizing plate is improved.

  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 singly or in combination of two or more.

  The polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of adhesion, the average degree of polymerization is about 100 to 3000, preferably 500 to 3000, the average saponification degree is about 85 to 100 mol%, preferably 90 to 100 mol%. It is.

  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. Another example is a method in which diketene gas or liquid diketene is brought into direct contact with polyvinyl alcohol.

  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 degree of acetoacetyl modification exceeds 40 mol%, the number of reaction points with the cross-linking agent decreases, and the effect of improving water resistance is small. The degree of acetoacetyl modification is a value measured by NMR.

  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, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene diamine, hexamethylene diamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (Isocyanates such as 4-phenylmethane triisocyanate, isophorone diisocyanate and their ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexane Diol diglycidyl ether, trimethylolpropane triglycidyl ether, di Epoxies such as ricidylaniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succinaldehyde, glutardialdehyde, maleidialdehyde, phthaldialdehyde, etc. Dialdehydes; amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; further sodium, potassium, magnesium, calcium, aluminum, Examples thereof include divalent metals such as iron and nickel, and salts and oxides of trivalent metals, among which amino-formaldehyde resins, , Methylol compounds having a methylol group is preferable.

  The amount of the crosslinking agent is usually about 0.1 to 35 parts by weight, preferably 10 to 25 parts by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin. In such a range, a polarizing plate having uniform polarization characteristics and excellent durability can be obtained.

  On the other hand, in order to further improve the durability, the crosslinking agent can be blended in the range of more than 30 parts by weight and 46 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin. In particular, when a polyvinyl alcohol-based resin containing an acetoacetyl group is used, it is preferable to use the crosslinking agent in an amount exceeding 30 parts by weight. By blending the crosslinking agent in the range of more than 30 parts by weight and 46 parts by weight or less, the water resistance can be drastically improved. The blending amount of the crosslinking agent is preferably as large as possible within the above range, and is preferably 31 parts by weight or more, more preferably 32 parts by weight or more, and particularly preferably 35 parts by weight or more. On the other hand, if the amount of the crosslinking agent is too large, the reaction of the crosslinking agent proceeds in a short time and the adhesive tends to gel. As a result, the pot life as an adhesive is extremely shortened, making industrial use difficult. From such a viewpoint, the blending amount of the crosslinking agent is preferably 46 parts by weight or less, more preferably 45 parts by weight or less, and particularly preferably 40 parts by weight or less.

  The adhesive (including the case of containing a polyvinyl alcohol-based adhesive and a crosslinking agent) is usually used as an aqueous solution. The concentration of the aqueous solution is not particularly limited, but considering application properties, storage stability, etc., 0.1 to 15% by weight, preferably 0.5 to 10% by weight, more preferably about 0.5 to 2% by weight. It is. As the solution concentration increases, streaky unevenness easily occurs due to an increase in viscosity. When the solution concentration becomes too low, the viscosity becomes low and the applicability becomes poor.

  The adhesive further includes a silane coupling agent, a coupling agent such as a titanium coupling agent, various tackifiers, an ultraviolet absorber, an antioxidant, a heat stabilizer, a hydrolysis stabilizer, and the like. Etc. can also be blended.

  In addition, in the manufacturing method of a polarizing plate, what contains more than 30 weight part and 46 weight part or less of a crosslinking agent as said adhesive agent with respect to 100 weight part of polyvinyl alcohol-type resin containing an acetoacetyl group. When is used, it is preferable to prepare the adhesive within 4 hours before applying the adhesive. If an adhesive prepared by blending a polyvinyl alcohol resin containing an acetoacetyl group with a crosslinking agent is left for a long time, it tends to gel. Therefore, it is preferable to prepare the adhesive within as short a time as possible before applying the adhesive. The adhesive is preferably prepared within 4 hours before the adhesive is applied. Furthermore, it is preferably within 3 hours, particularly preferably within 30 minutes.

  In the method for producing a polarizing plate of the present invention, first, an adhesive is applied to the surface on which the adhesive layer of the transparent protective film is formed and / or the surface of the polarizer on which the adhesive layer is formed to form an adhesive layer. . The thickness of the adhesive layer affects the water resistance and heat-and-moisture resistance, and the durability increases as the total thickness of the adhesive increases. However, when the adhesive layer is thickened, a solution having a high viscosity is required in the production process, and therefore, some physical stress is applied to the PVA polarizer, resulting in the uniformity as the polarizer, particularly the appearance of streaky appearance defects. Along with. From such a viewpoint, 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. If it is less than 30 nm, coating may be difficult, and appearance defects may easily occur. On the other hand, when it exceeds 300 nm, appearance defects are likely to occur, and it is not preferable in terms of heat resistance.

  Application | coating of the said adhesive agent may be performed to any of a transparent protective film and a polarizer, and may be performed to both. The adhesive is preferably applied such that the thickness after drying is about 30 to 300 nm.

  The application operation is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed. After apply | coating an adhesive agent, a drying process is given and the adhesive bond layer which consists of an application | coating dry layer is formed. A drying temperature is about 5-150 degreeC, Preferably it is about 30-120 degreeC, is 120 second or more, Furthermore, it is 300 second or more.

  It is preferable to manage the temperature from the time of preparation to application of the adhesive. Water resistance can be further improved by controlling the temperature of the adhesive. The management temperature of the adhesive is preferably in the range of 30 to 50 ° C. More preferably, it is 30-45 degreeC, More preferably, it is 30-40 degreeC. 30 degreeC or more is preferable at the point of water resistance. On the other hand, if it exceeds 50 ° C., gelation is likely to occur immediately after mixing the cross-linking agent, making it difficult to use as an adhesive. In particular, the temperature control of the adhesive is effective when a material containing a crosslinking agent in a range of more than 30 parts by weight and not more than 46 parts by weight is used with respect to 100 parts by weight of a polyvinyl alcohol resin containing an acetoacetyl group. It is.

  As described above, when the adhesive contains a crosslinking agent in a range of more than 30 parts by weight and less than 46 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin containing an acetoacetyl group. The adhesive is preferably prepared within 4 hours before the adhesive is applied. In order to perform the process from the preparation of the adhesive to the application in a short time within 4 hours, the adhesive preparation process is incorporated into a part of a series of steps of the polarizing plate manufacturing process, or an appropriate preparation device is arranged. This can be done.

  Subsequently, in the manufacturing method of this invention, a transparent protective film and a polarizer are bonded together continuously by an adhesive bond layer. An adhesive layer is formed in advance on at least one surface of the transparent protective film or the polarizer.

  The bonding method is not particularly limited. For example, there is a method in which a transparent protective film and a polarizer are continuously passed between a pair of rolls through an adhesive layer. Such a method is shown in FIGS. 1 and 2, for example. In FIG. 1, a transparent protective film 2 provided with an adhesive layer 3 is bonded to one side of a polarizer 1 by passing them between rolls R, and thereafter the same is applied to the other side of the polarizer 1. In this case, the transparent protective film 2 provided with the adhesive layer 3 is bonded. On the other hand, FIG. 2 shows a case where the transparent protective film 2 provided with the adhesive layer 3 is bonded to both surfaces of the polarizer 1 by passing them between the rolls R.

  The roll R is not particularly limited as long as it can be bonded by roll pressure when the polarizer 1 and the transparent protective film 2 provided with the adhesive layer 3 pass through a pair of rolls. For example, a laminate nip roll is used. The material of the roll is not particularly limited, and may be made of rubber or metal.

  The transport speed of the transparent protective film and the polarizer (adhesive layer is formed on at least one of them) is not particularly limited, but is usually about 0.03 to 0.6 m / s, preferably 0.08 to It is about 0.5 m / s, more preferably about 0.11 to 0.34 m / s.

  In the manufacturing method of this invention, when bonding the said transparent protective film and polarizer through an adhesive bond layer, an aqueous liquid is made to exist in a bonding surface.

  As the aqueous liquid, for example, water is used. This water is preferably pure water. An aqueous solution that dissolves the crosslinking agent is used as the aqueous solution. As the cross-linking agent, a cross-linking agent corresponding to the type of adhesive is used. When a polyvinyl alcohol-based adhesive is used, a methylol compound is suitable as the crosslinking agent. The content of the crosslinking agent is not particularly limited, but is usually 40% by weight or less, preferably 5 to 40% by weight, and more preferably 10 to 35% by weight. In addition, when using the aqueous solution containing a crosslinking agent as an aqueous liquid, since it has an effect even if the quantity of a crosslinking agent is less than the case where it contains in an adhesive agent, it should just be 2 to 40 weight%. It is preferably ~ 35% by weight. Moreover, when using the aqueous solution containing a crosslinking agent as an aqueous liquid, it becomes unnecessary to add to a crosslinking agent in an adhesive agent solution, and the pot life of an adhesive agent can be improved significantly. This is effective when a polyvinyl alcohol resin containing an acetoacetyl group having a highly reactive functional group is used as the adhesive.

  The viscosity of the aqueous liquid is usually 0.1 to 10 cP, preferably 0.5 to 5 cP. The viscosity of the aqueous liquid is a value measured by the method described in the examples. If it is less than 0.1 cP, the coating may be difficult. On the other hand, if it exceeds 10 cP, appearance defects are likely to occur.

  The supply amount of the aqueous liquid is appropriately adjusted depending on the conveyance speed and the like, but is usually about 0.5 to 3.4 ml / s, preferably 0.5 to 1.7 ml / s. The supply amount of the aqueous liquid can be appropriately adjusted depending on the width of the raw film.

  If the said aqueous liquid exists in the bonding surface when bonding a transparent protective film and a polarizer through an adhesive bond layer, the supply method in particular will not be restrict | limited. For example, an aqueous liquid can be supplied to the bonding surface of the transparent protective film and the polarizer. If the aqueous liquid is supplied to the bonding surface immediately before bonding, the adhesive layer does not come into contact with the aqueous liquid until just before bonding, which is preferable in terms of durability of the adhesive and difficulty in causing streak-like unevenness. .

  Moreover, an aqueous liquid can be guide | induced to a bonding surface with conveyance by supplying to the transparent protective film or polarizer (adhesive layer is formed in any at least one) conveyed.

  In this invention, it is preferable to make an aqueous liquid exist in a bonding surface by apply | coating an adhesive only to the transparent protective film side, and supplying an aqueous liquid on the adhesive bond layer formed by this application | coating. In particular, it is suitable when a transparent protective film is bonded to both sides of the polarizer in the state as shown in FIG. In the example of FIG. 2, providing the adhesive layer on the polarizer side is because the adhesive may be dripped. For the same reason, the aqueous liquid is preferably supplied onto the adhesive layer formed on the transparent protective film.

  Moreover, when an adhesive is applied only to the transparent protective film side to form an adhesive layer, an aqueous liquid can be supplied to the polarizer side. According to this method, the adhesive layer does not come into contact with the aqueous liquid until just before the bonding as described above. Further, when the moisture content inside or on the surface of the polarizer is reduced, it greatly contributes to the generation of streaky appearance defects. On the other hand, when the moisture content of the polarizer is increased, streaky appearance defects are less likely to occur. If the aqueous liquid is supplied to the polarizer side, the moisture content of the polarizer increases before being guided to the laminating roll, and the occurrence of streaky appearance defects can be suppressed more effectively.

  Moreover, when an adhesive is applied only on the polarizer side to form an adhesive layer, the aqueous liquid is preferably supplied to the transparent protective film side. According to this method, the adhesive layer does not come into contact with the aqueous liquid until just before the bonding as described above. In addition, the supply of the aqueous liquid to the transparent protective film allows simultaneous and continuous bonding of the transparent protective film to both surfaces of the polarizer, which can be performed without dripping of the adhesive and the like, which is advantageous in terms of the manufacturing apparatus.

  When the transparent protective film and the polarizer are continuously bonded through the adhesive layer, it is preferable to supply an aqueous liquid immediately before bonding to the bonding surface. The term “immediately before bonding” means that bonding is performed within a short time of about 30 seconds after the aqueous liquid is supplied. This time is preferably as short as possible, and it is preferable to perform the bonding within 5 seconds, further within 2 seconds, further within 1 second, and further within 0.5 seconds after supplying the aqueous liquid. If the time until the pasting is too long, when the aqueous liquid is supplied onto the adhesive layer, the adhesive dissolves more than necessary, which easily causes unevenness. In addition, when the aqueous liquid is supplied onto the transparent protective film or the polarizer, the moisture content becomes too large, so that unevenness is likely to occur after drying. In addition, when supplying an aqueous liquid immediately before bonding, the supply location is not limited depending on which side the adhesive layer is provided, and the transparent protective film side, one side or both sides of the polarizer side Either is acceptable. Furthermore, a method may be used in which a puddle is provided at the bonding portion and the solution is passed immediately before bonding.

  1 and 2, the aqueous liquid 4 is supplied to the bonding surface of the adhesive layer 3 and the polarizer 1 provided on the transparent protective film 2. In FIG. 1 and FIG. 2, it is only necessary that the aqueous liquid exists between the pair of rolls R, and the setting location of the aqueous liquid 4 can be changed as appropriate. In FIG. 1 and FIG. 2, the supply location of the aqueous liquid 4 is one for a set of transport films (a combination of a polarizer and a transparent protective film), but a plurality of supply locations of the aqueous liquid 4 are provided. Can do. Moreover, the supply location of the aqueous liquid 4 can also be provided with respect to each conveyance film. Examples of the method for supplying the aqueous liquid include a dropping method, a coating method, and a spraying method. For these supply methods, nozzles, sprays, coaters and the like are appropriately selected and used.

  In addition, on the bonding surface of the transparent protective film and the polarizer, when the aqueous liquid is excessively present and leaks from the end of the bonding surface, the excess amount can be removed by a suction nozzle or the like, or the air nozzle or the like By bringing it closer to the center of the bonding surface, contamination due to leakage of the aqueous liquid can be prevented.

  As described above, after the polarizer and the transparent protective film are bonded to a roll laminator or the like through the adhesive layer in the presence of an aqueous liquid, a drying step is performed. A drying temperature is about 5-150 degreeC, Preferably it is 30-120 degreeC, is 120 second or more, Furthermore, it is 300 second or more.

  The polarizing plate 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 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.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things such as a thing can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of the liquid crystal display device and the like can be improved. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attaching the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator in accordance with the above, and this is applied to a polarizing plate or an optical film The method of transferring to is included.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  In the present invention, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, and a cyanoacrylate. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.

  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, and it can apply according to the former. 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.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In each example, parts and% are based on weight unless otherwise specified.

(Method for measuring viscosity of aqueous liquid)
Under the condition of 23 ° C., the viscosity at a shear rate of 82000 (1 / s) was measured using a viscosity measuring device (Thermo Haake, Rheometer Rheoless 1).

(Adhesive layer thickness measurement method)
It was measured by cross-sectional observation with SEM.

(Preparation of polarizer A)
A polyvinyl alcohol (PVA) film with an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 80 μm is immersed in pure water at 25 ° C. for 60 seconds to swell, and uniaxial up to a draw ratio of 2 times in the flow direction Stretched. Next, the film was immersed in an aqueous solution of iodine / potassium iodide (weight ratio = 1/10) at a concentration of 5% and stretched so that the total draw ratio was 2.5, and then boric acid concentration at 40 ° C. was 4% by weight. The film was stretched in an aqueous solution having a potassium iodide concentration of 3% by weight until the total stretching ratio became 3 times. Thereafter, the film was stretched in an aqueous solution having a potassium iodide concentration of 5% by weight at 25 ° C. so that the total stretching ratio was 5.5 times, and washed in pure water. Subsequently, drying was performed for 3 minutes in an oven at 40 ° C., and a polarizer A having a thickness of 30 μm was obtained.

(Preparation of polarizer B)
A polarizer having a thickness of 19 μm in the same manner as above except that a PVA film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 50 μm was used as the PVA film. B was obtained.

(Transparent protective film)
A 40 μm thick triacetyl cellulose (TAC) film was used.

Example 1
(Preparation of adhesive)
PVA resin containing acetoacetyl (AA) group (average polymerization degree: 1200, saponification degree: 98.5 mol%, AA group modification degree: 5 mol%, (in Table 1, indicated as AA-modified PVA)) ) To 100 parts, 20 parts of methylolmelamine was dissolved in pure water under a temperature condition of 30 ° C. to prepare an aqueous solution adjusted to a solid content concentration of 0.5%. This was used as an adhesive under a temperature condition of 30 ° C.

(Preparation of polarizing plate a)
The adhesive was applied to one side of the transparent protective film with a die coater. The adhesive was applied 30 minutes after its preparation. Subsequently, it dried at 50 degreeC for 3 minute (s), and the thickness after drying formed the adhesive bond layer of 31 nm.

  Next, as shown in FIG. 2, the TAC film with the adhesive layer was bonded to both surfaces of a polarizer A having a thickness of 30 μm with a roll machine while supplying pure water having a viscosity of 1 cP (23 ° C.). . The film conveyance speed was 0.25 m / s, and the supply amount of pure water was 0.80 ml / s. The pure water was supplied at a location on the transparent protective film (position where the time until bonding was 0.5 seconds). Thereafter, drying was performed at 55 ° C. for 6 minutes to produce a polarizing plate.

Examples 2-4
In Example 1 (Preparation of adhesive), a polarizing plate was obtained in the same manner as Example 1 except that the adhesive concentration was changed as shown in Table 1. The thickness of the adhesive layer is as shown in Table 1.

Examples 5-12
A polarizing plate in the same manner as in Example 1 except that in Example 1 (preparation of adhesive), the type of crosslinking agent used in the adhesive and the concentration of the adhesive were changed as shown in Table 1. Got. The thickness of the adhesive layer is as shown in Table 1.

Examples 13-16
In Example 1 (Preparation of adhesive), the resin used for the adhesive was replaced with a polyvinyl alcohol resin (average polymerization degree: 1200, saponification degree: 98.5 mol%), and the concentration of the adhesive is shown in Table 1. A polarizing plate was obtained in the same manner as in Example 1 except that a material changed as shown was used. The thickness of the adhesive layer is as shown in Table 1.

Example 17
In Example 1 (preparation of polarizing plate), a polarizing plate was prepared in the same manner as in Example 1 except that an aqueous solution containing 5% by weight of methylol melamine having a viscosity of 3 cP (23 ° C.) was used instead of pure water. Obtained. The thickness of the adhesive layer is as shown in Table 1.

Examples 18-20
In Example 1 (Preparation of adhesive), no cross-linking agent was used in the adhesive, and in Example 1 (Preparation of polarizing plate), instead of pure water, the aqueous solutions shown in Table 1 were used. Obtained a polarizing plate in the same manner as in Example 1. The thickness of the adhesive layer is as shown in Table 1.

Example 21
In Example 3, a polarizing plate was obtained in the same manner as in Example 3 except that no crosslinking agent was used for the adhesive. The thickness of the adhesive layer is as shown in Table 1.

Examples 22-24
In Example 3, a polarizing plate was obtained in the same manner as in Example 3 except that the crosslinking agent was not used for the adhesive and that the aqueous solution shown in Table 1 was used instead of pure water. The thickness of the adhesive layer is as shown in Table 1.

Example 25
In Example 3, a polarizing plate was obtained in the same manner as in Example 3 except that no crosslinking agent was used for the adhesive. The thickness of the adhesive layer is as shown in Table 1.

Examples 26-28
In Example 3, a polarizing plate was obtained in the same manner as in Example 3 except that the crosslinking agent was not used for the adhesive and that the aqueous solution shown in Table 1 was used instead of pure water. The thickness of the adhesive layer is as shown in Table 1.

Example 29
In Example 3, instead of dropping pure water just before bonding the triacetylcellulose film with the adhesive layer and the polarizer (position where the time until bonding is 0.5 seconds), the bonding position is 1 m. A polarizing plate in the same manner as in Example 3 except that pure water was dropped on the front film, the film conveyance speed was 0.25 m / s, and the time until bonding was 4 seconds. Got. The thickness of the adhesive layer is as shown in Table 1.

Example 30
In Example 3, instead of dropping pure water just before bonding the triacetylcellulose film with the adhesive layer and the polarizer (position where the time until bonding is 0.5 seconds), the bonding position is 1 m. A polarizing plate in the same manner as in Example 3 except that pure water was dropped on the front film, the film conveyance speed was 0.1 m / s, and the time until bonding was 10 seconds. Got. The thickness of the adhesive layer is as shown in Table 1.

Example 31
In Example 3, instead of dropping pure water just before bonding the triacetylcellulose film with the adhesive layer and the polarizer (position where the time until bonding is 0.5 seconds), the bonding position is 1 m. A polarizing plate in the same manner as in Example 3 except that pure water was dropped on the front film, the film conveyance speed was 0.04 m / s, and the time until bonding was 25 seconds. Got. The thickness of the adhesive layer is as shown in Table 1.

Example 32
In Example 3, a polarizing plate was obtained in the same manner as Example 3 except that the polarizer B was used instead of the polarizer A. The thickness of the adhesive layer is as shown in Table 1.

Comparative Example 1
A polarizing plate was produced in the same manner as in Example 1 except that (Preparation a of polarizing plate a) of Example 1 was changed to the following (Preparation b of polarizing plate b).

(Preparation of polarizing plate b)
As shown in FIG. 4, after supplying the said adhesive agent on both surfaces of the polarizer A with a roll machine, it dried at 55 degreeC for 6 minute (s), and the polarizing plate was produced. The film conveyance speed was 0.35 m / s, and the amount of adhesive supplied was 0.60 ml / s. The supply place was an adhesive layer having a thickness of 16 nm after drying performed on the transparent protective film (position where the time until bonding is 0.5 seconds).

Comparative Examples 2-20
In Comparative Example 1, a polarizing plate was prepared in the same manner as in Comparative Example 1, except that the type of polyvinyl alcohol resin used for the adhesive, the type of crosslinking agent, and the concentration of the adhesive were changed as shown in Table 1. Got. The thickness of the adhesive layer is as shown in Table 1. In Comparative Examples 17 to 20, a polyvinyl alcohol resin (average polymerization degree: 1200, saponification degree: 98.5 mol%) was used.

Comparative Example 21
In Comparative Example 3, a polarizing plate was obtained in the same manner as Comparative Example 3 except that Polarizer B was used instead of Polarizer A. The thickness of the adhesive layer is as shown in Table 1.

(Evaluation)
The polarizing plates obtained in Examples and Comparative Examples were cut out to be 50 mm in the absorption axis direction of the polarizer and 25 mm in the direction perpendicular to the absorption axis to obtain polarizing plate samples. The following evaluation was performed on this sample. The results are shown in Table 1.

(Appearance defect evaluation)
The obtained polarizing plate sample was reflected by fluorescent lamp irradiation light, and visually evaluated according to the following criteria.
○: No streaks, no point defects and no unevenness.
(Triangle | delta): There exists a stripe form, a point-like defect, and a nonuniformity in part.
X: There are stripes, dot-like defects and unevenness on the entire surface.

(Light loss evaluation)
Two obtained polarizing plate samples were overlapped with crossed Nicols so that the absorption axes thereof were orthogonal to each other, and the fluorescent light irradiation light was allowed to pass through and the light leakage was visually evaluated according to the following criteria.
○: No light loss.
X: There is light loss.

(durability)
After the obtained polarizing plate sample was immersed in warm water of 60 ° C. for 3 hours, the amount of peeling (mm) at the end of the sample was measured and evaluated according to the following criteria. The amount of peeling (mm) was measured using a caliper and a metal ruler.
A: No peeling.
○: Peeling less than 3 mm.
(Triangle | delta): Peeling 3-30mm.
X: 31 mm or more.

表１中、ＰＶＡ：ポリビニルアルコール、ＡＡ変性ＰＶＡ：アセトアセチル基を含有するポリビニルアルコール系樹脂である。

In Table 1, PVA: polyvinyl alcohol, AA-modified PVA: a polyvinyl alcohol resin containing an acetoacetyl group.

It is an example of the schematic of the manufacturing method of the polarizing plate of this invention. It is an example of the schematic of the manufacturing method of the polarizing plate of this invention. It is an example of the schematic of the manufacturing method of the conventional polarizing plate. It is an example of the schematic of the manufacturing method of the conventional polarizing plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Transparent protective film 3 Adhesive layer 3 'Adhesive 4 Aqueous liquid R roller

Claims (20)

A method for producing a polarizing plate, wherein a transparent protective film is provided on at least one surface of a polarizer via an adhesive layer,
After forming the adhesive layer by applying an adhesive to the surface of the transparent protective film forming the adhesive layer and / or the surface of the polarizer forming the adhesive layer,
A method for producing a polarizing plate, comprising: causing an aqueous liquid to be present on a bonding surface when a transparent protective film and a polarizer are continuously bonded through the adhesive layer.   The method for producing a polarizing plate according to claim 1, wherein the polarizer is a polyvinyl alcohol-based polarizer, and the transparent protective film is a cellulose-based transparent protective film.   The method for producing a polarizing plate according to claim 1, wherein the polarizer has a thickness of 35 μm or less.   The method for producing a polarizing plate according to claim 1, wherein the adhesive is a polyvinyl alcohol-based adhesive.   The method for producing a polarizing plate according to claim 4, wherein the polyvinyl alcohol-based adhesive is a polyvinyl alcohol-based adhesive having an acetoacetyl group.   The method for producing a polarizing plate according to claim 1, wherein the adhesive contains a crosslinking agent.   The method for producing a polarizing plate according to claim 6, wherein the crosslinking agent is a methylol compound.   The thickness of an adhesive bond layer is 30-300 nm, The manufacturing method of the polarizing plate in any one of Claims 1-7 characterized by the above-mentioned.   The method for producing a polarizing plate according to claim 1, wherein the viscosity of the aqueous liquid is 0.1 to 10 cP.   The method for producing a polarizing plate according to claim 6, wherein the aqueous liquid is water.   The method for producing a polarizing plate according to claim 1, wherein the aqueous liquid is an aqueous solution in which a crosslinking agent is dissolved.   The method for producing a polarizing plate according to claim 11, wherein the crosslinking agent is a methylol compound.   An aqueous liquid is supplied to the bonding surface of a transparent protective film and a polarizer, The manufacturing method of the polarizing plate in any one of Claims 1-12 characterized by the above-mentioned.   The adhesive is applied only on the transparent protective film side, and the aqueous liquid is supplied onto the adhesive layer formed by the application, so that the aqueous liquid is present on the bonding surface. The manufacturing method of the polarizing plate in any one of.   The adhesive is applied only to the transparent protective film side, and on the other hand, the aqueous liquid is made to exist on the bonding surface by supplying the aqueous liquid to the polarizer side. Manufacturing method of this polarizing plate.   The adhesive is applied only to the polarizer side, and on the other hand, the aqueous liquid is supplied to the transparent protective film side so that the aqueous liquid is present on the bonded surface. Manufacturing method of this polarizing plate.   The aqueous liquid is supplied to the bonding surface immediately before bonding, when the transparent protective film and the polarizer are continuously bonded through the adhesive layer. The manufacturing method of a polarizing plate of crab.   The polarizing plate obtained by the manufacturing method in any one of Claims 1-17.   19. An optical film, wherein at least one polarizing plate according to claim 18 is laminated.   An image display device comprising the polarizing plate according to claim 18 or the optical film according to claim 19.

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