JP2006220731A - Polarizer protective film and manufacturing method thereof, polarizing plate and manufacturing method thereof, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polarizer protective film which has a satisfactory conveyance property and is excellent in productivity, to provide a polarizer protective film having a high optical transparency, to provide a method for manufacturing a polarizing plate having little appearance defect with good productivity and the polarizing plate obtained by the method for manufacturing the same, and to provide a high-quality image display device using the polarizing plate. <P>SOLUTION: There is provided the manufacturing method of polarizer protective film having a (meth)acrylic resin layer and a thermoplastic resin layer by co-extruding a (meth)acrylic resin and a thermoplastic resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizer protective film and a manufacturing method thereof, a polarizing plate and a manufacturing method thereof, and an image display device such as a liquid crystal display device, an organic EL display device, and a PDP including at least one polarizing plate.

  In the liquid crystal display device, it is indispensable to dispose polarizing plates on both sides of the glass substrate on which the liquid crystal panel surface is formed because of the image forming method. In general, a polarizing plate is obtained by attaching a polarizer protective film using triacetyl cellulose or the like to both surfaces of a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine with a polyvinyl alcohol adhesive. Things are used.

  However, triacetyl cellulose does not have sufficient heat and heat resistance, and when a polarizing plate using a triacetyl cellulose film as a polarizer protective film is used at high temperature or high humidity, the performance of the polarizing plate such as the degree of polarization and the hue deteriorates. There is a drawback. In addition, the triacetyl cellulose film produces a phase difference with respect to incident light in an oblique direction. Such a phase difference significantly affects viewing angle characteristics as the size of liquid crystal displays increases in recent years.

  In order to solve the above problems, a cyclic olefin resin has been proposed as a material for the polarizer protective film instead of triacetyl cellulose. Cyclic olefin resin has low moisture permeability and has almost no phase difference in an oblique direction. However, the polyvinyl alcohol-based adhesive is excellent in adhesion between the triacetyl cellulose film and the polyvinyl alcohol-based polarizer, but has poor adhesion between the cyclic olefin resin film and the polyvinyl alcohol-based polarizer.

  Therefore, as a method of bonding the cyclic olefin resin film and the polyvinyl alcohol polarizer, a method of bonding via an acrylic pressure-sensitive adhesive layer has been proposed (see Patent Document 1). However, since this method requires thermocompression bonding and the heating time is long, there is a problem that the polyvinyl alcohol polarizer is discolored and the degree of polarization of the polarizing plate is significantly reduced. Further, since heating for a long time is required, there is a problem that the production efficiency is low and the film is deformed.

Moreover, as a polarizer protective film, a film having a layer formed of a polymer of styrenes, vinyl esters, maleic anhydrides, acrylic esters or methacrylic esters has been proposed (see Patent Documents 2 and 3). ). In terms of optical transparency, a (meth) acrylic resin which is a polymer such as acrylic acid esters and methacrylic acid esters is preferred. However, since these are very hard and brittle in the film state, there are problems in transportability such as breakage during film transport, and productivity is poor.
Japanese Patent Laid-Open No. 5-212828 JP-A-9-197128 JP-A-9-281333

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to provide (1) a method for producing a polarizer protective film having good film transportability and excellent productivity. (2) to provide a polarizer protective film with high optical transparency obtained from the production method, (3) to provide a method for producing a polarizing plate with few appearance defects with high productivity, (4 ) To provide a polarizing plate obtained from the production method, and (5) To provide a high-quality image display device using such a polarizing plate.

  A method for producing a polarizer protective film, wherein a film having a (meth) acrylic resin layer and a thermoplastic resin layer is formed by coextrusion molding of a (meth) acrylic resin and a thermoplastic resin.

  In a preferred embodiment, the thermoplastic resin is any one of a polyester resin, a nylon resin, a polycarbonate resin, a copolymer containing a styrene monomer and an olefin monomer as monomer units.

  According to another aspect of the present invention, a polarizer protective film is provided. This polarizer protective film is obtained by the method for producing a polarizer protective film of the present invention.

  According to another situation of this invention, the manufacturing method of a polarizing plate is provided. In this method for producing a polarizing plate, a thermoplastic resin layer is peeled after a polarizer formed from a polyvinyl alcohol-based resin is bonded to the (meth) acrylic resin layer side of the polarizer protective film of the present invention.

  In a preferred embodiment, the adhesion is performed with a polyvinyl alcohol-based adhesive.

  According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the manufacturing method of the polarizing plate of this invention.

  In preferable embodiment, it has an adhesive layer as at least one of outermost layers.

  According to another aspect of the present invention, an image display device is provided. This image display device includes at least one polarizing plate of the present invention.

  According to the present invention, a method for producing a polarizer protective film with good film transportability and excellent productivity, a polarizer protective film with high optical transparency, a method for producing a polarizing plate with few appearance defects with high productivity, and A polarizing plate obtained from the production method and a high-quality image display device using the polarizing plate can be provided. In particular, a polarizer protective film in which a thermoplastic resin layer is laminated on a (meth) acrylic resin layer having the disadvantages of excellent optical transparency and low retardation value but poor strength is produced. After adhering the polarizer to the acrylic resin layer side, the thermoplastic resin layer is peeled off, so that the (meth) acrylic resin layer with poor strength can be stably adhered to the polarizer. Can provide a polarizing plate and a high-quality image display device.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

[Production method of polarizer protective film]
The manufacturing method of the polarizer protective film concerning this invention makes it a film which has a (meth) acrylic-type resin layer and a thermoplastic resin layer by co-extrusion molding of a (meth) acrylic-type resin and a thermoplastic resin. .

Although it does not specifically limit as (meth) acrylic resin which comprises the said (meth) acrylic-type resin layer, For example, poly (meth) acrylic acid ester, such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid Copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc. ), Polymers having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer), and the like. Preferably, poly (meth) acrylate C _1-6 alkyl such as poly (meth) acrylate methyl, particularly preferably methyl methacrylate as the main component (50-100 wt%, preferably 70-100 wt%). And methyl methacrylate resin.

  The (meth) acrylic resin layer preferably has high light transmittance, low in-plane retardation Δnd, and low thickness direction retardation Rth.

  The (meth) acrylic resin preferably has a glass transition temperature of 120 ° C. or higher.

  The thickness of the (meth) acrylic resin layer is preferably 5 to 500 μm, and more preferably 5 to 200 μm. If it is thinner than 5 μm, it tends to break, causing a problem in strength when applied to a polarizing plate. If it is thicker than 500 μm, it is not suitable for a thin optical film.

  Any appropriate thermoplastic resin can be adopted as the thermoplastic resin as long as the effects of the present invention can be obtained. However, in order to fully exhibit the effects of the present invention, a thermoplastic resin having good toughness and slipperiness. Specifically, it is a polyester resin, a nylon resin, a polycarbonate resin, a copolymer containing a styrene monomer and an olefin monomer as monomer units.

  The polyester resin is not particularly limited. For example, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5 -Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexa Hydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid , Pime Dicarboxylic acids such as acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecadicarboxylic acid, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4- Cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis A diol such as (4-hydroxyphenyl) sulfone, a homopolymer obtained by polycondensation of one kind each, a copolymer obtained by polycondensation of one or more dicarboxylic acids and two or more diols, or two dicarboxylic acids It is a polycondensation of one or more of the above and a diol Polymers, and can include any of the polyester resin of these homopolymers and copolymers of two or more blend formed by blending resin. Of these, polyethylene terephthalate resin is preferably used.

  Although it does not specifically limit as said nylon-type resin, For example, nylon 66, nylon 6, nylon 612, nylon 12, nylon 11, these copolymers (for example, nylon 12 copolymer etc.), nylon-type elastomer (for example, nylon) And a copolymer of 12 components and polyol).

  Although it does not specifically limit as said polycarbonate-type resin, For example, aromatic polycarbonates, such as polycarbonate (PC) using bisphenol (bisphenol A etc.), aliphatic polycarbonates, such as diethylene glycol bisallyl carbonate (CR-39) Etc. A typical example of the bisphenol used is bisphenol A.

  Examples of the polycarbonate resin include Panlite L-1225, L-1250, K-1300 from Teijin Chemicals Ltd., Iupilon E-2, E-2U (polycarbonate containing UV absorber) from Mitsubishi Gas Chemical Company, Inc. Etc.

  Examples of the polycarbonate resin include triphenyl phosphite, tris (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, diphenyl hydrogen phosphite, irganox 1076 (stearyl-β- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate) and the like, for example 2- (2'-hydroxy-5'-methylphenyl) benzotriazole 2- (2'-hydroxy-3 ' , 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-4'-octoxyphenyl) benzotriazole, 2-hydroxy-4-octoxybenzophenone, etc. Additives, antistatic agents, mold release agents, lubricants, etc. May be added as long as the transparency of the film is not impaired.

  The copolymer containing the styrene monomer and the olefin monomer as monomer units is not particularly limited. For example, a block copolymer having an aromatic vinyl compound polymer block and a conjugated diene compound polymer block and / or Or it is formed with the hydrogenated product. The block copolymer preferably has a styrene polymer, a conjugated diene polymer block such as isoprene or butadiene, or a hydrogenated product thereof.

  Examples of the block copolymer include styrene-diene AB type block copolymers (diblock copolymers) such as styrene / butadiene (SB) and styrene / isoprene (SI); styrene / butadiene / styrene (SBS). ), Styrene-based ABA block copolymers (triblock copolymers) such as styrene / isoprene / styrene (SIS); styrene / butadiene / styrene / butadiene (SBSB), styrene / isoprene / styrene / isoprene (SISI), etc. Styrenic ABAB block copolymer (tetrablock copolymer); Styrene ABAB type block copolymer such as styrene / butadiene / styrene / butadiene / styrene (SBSBS), styrene / isoprene / styrene / isoprene / styrene (SISIS) Polymer ( Pointer block copolymer); more styrene having the same or more AB repeat units - diene multiblock copolymers; and the like. Examples of commercially available products include the clear resin series (manufactured by Denki Kagaku Kogyo Co., Ltd.).

  As the block copolymer, it is preferable to use a hydrogenated product obtained by hydrogenating an ethylenic double bond. For example, styrene / ethylene / butylene copolymer (SEB), styrene / ethylene / propylene copolymer (SEBS), styrene / ethylene / propylene copolymer / styrene (SEPS), styrene / ethylene / butylene copolymer / styrene -Ethylene-butylene copolymer (SEBSEB) etc. are mentioned. Commercially available block copolymer hydrogenated products include, for example, Tuftec H series, manufactured by Asahi Kasei Co., Ltd., Kraton G series (manufactured by Shell Japan Co., Ltd.), and Septon series (manufactured by Kuraray Co., Ltd.). Etc.

  Moreover, what has a functional group (a) can be used for the said block copolymer and / or its hydrogenated product. Examples of the functional group (a) include a carboxyl group or a derivative thereof. Carboxyl and the like can be introduced, for example, by adding maleic acid or the like. As a commercial item of the hydrogenated product of the block copolymer which has a carboxyl group or its derivative (s), Tuftec M series (made by Asahi Kasei Co., Ltd.), Clayton FG1901X (made by Shell Japan Co., Ltd.) etc. are mentioned, for example. Moreover, an epoxy group is mentioned as a functional group (a). The epoxy group can be introduced by graft polymerization of glycidyl (meth) acrylate.

  The thickness of the thermoplastic resin layer is preferably 5 to 500 μm, and more preferably 5 to 200 μm. If it is thinner than 5 μm, it tends to break during peeling. If it is thicker than 500 μm, the transportability of the film does not change, but the cost increases.

  In the method for producing a polarizer protective film according to the present invention, a (meth) acrylic resin and a thermoplastic resin are coextruded.

  Co-extrusion molding does not require drying and scattering of the solvent in the adhesive used during processing, such as the organic solvent in the adhesive for dry lamination, as in the case of the dry lamination method. Excellent in productivity. Specifically, (meth) acrylic resin is supplied to one of the two extruders connected to the T-die, and thermoplastic resin is supplied to the other one. After melt-kneading, extrusion and water cooling are performed. And a method for forming a laminated film. The screw type of the extruder used for melting each resin layer may be uniaxial or biaxial, and an additive such as a plasticizer or an antioxidant optimal for each resin may be added.

  The molding temperature can be appropriately set, but when the glass transition temperature of the resin is Tg (° C.), (Tg + 80) ° C. to (Tg + 150) ° C. is preferable, and (Tg + 100) ° C. to (Tg + 130) ° C. is more preferable. If the molding temperature is too low, the resin does not have fluidity and may not be molded. If the molding temperature is too high, the resin viscosity will be low, and there may be a problem in production stability such as uneven thickness of the molded product. In the case of a multilayer molded product, it is preferable to set a resin having a higher glass transition temperature.

  According to the co-extrusion molding, since the adhesive layer is not interposed, the process of drying and scattering the solvent in the adhesive is unnecessary, and the productivity is excellent. Further, when the two kinds of resins are in direct contact with each other, it is possible to suppress a decrease in durability caused by the adhesive layer such as a decrease in adhesive force and a decrease in optical characteristics due to deterioration of the adhesive layer.

[Polarizer protective film]
By the above method, a film (polarizer protective film) having a (meth) acrylic resin layer and a thermoplastic resin layer is obtained. In the obtained laminated film, the peel strength between the (meth) acrylic resin layer and the thermoplastic resin layer is preferably 5N or less, more preferably 3N or less, and further preferably 0.1 to 1N.

  On the (meth) acrylic resin layer, a coupling agent such as a silane coupling agent or a titanium coupling agent and a titanium-based or tin-based catalyst for efficiently reacting the coupling agent are laminated. Can do. Thereby, the adhesive force of a polarizer and a polarizer protective film can be strengthened more. Moreover, you may add another additive to the said thermoplastic resin layer. Specific examples include tackifiers such as terpene resins, phenol resins, terpene-phenol resins, rosin resins, and xylene resins, stabilizers such as ultraviolet absorbers, antioxidants, and heat stabilizers.

  The thickness of the polarizer protective film of the present invention is preferably 5 to 500 μm, more preferably 5 to 200 μm, in two layers of a (meth) acrylic resin layer and a thermoplastic resin layer.

[Production method of polarizing plate]
In the method for producing a polarizing plate according to the present invention, a polarizer formed from a polyvinyl alcohol resin is used as the polarizer protective film of the present invention (that is, a film having a (meth) acrylic resin layer and a thermoplastic resin layer). After bonding to the (meth) acrylic resin layer side, the thermoplastic resin layer is peeled off. The peeling method of a thermoplastic resin layer is not specifically limited, You may apply arbitrary peeling methods. The thermoplastic resin layer is peeled off at any time as long as the polarizer formed from the polyvinyl alcohol-based resin is adhered to the (meth) acrylic resin layer side of the polarizer protective film of the present invention. May be.

  As the polarizer formed from the polyvinyl alcohol-based resin, one obtained by dyeing a polyvinyl alcohol-based resin film with a dichroic substance (typically iodine, a dichroic dye) and uniaxially stretching is used. The polymerization degree of the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is preferably 100 to 5000, and more preferably 1400 to 4000. The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any suitable method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). . The thickness of the polarizer can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is typically 5 to 80 μm.

  As a method for producing a polarizer, any appropriate method can be adopted depending on the purpose, materials used, conditions, and the like. Typically, a method is employed in which the polyvinyl alcohol-based resin film is subjected to a series of production steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol-based resin film in a bath containing a solution used in each step. The order, frequency, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing with water, and drying can be appropriately set according to the purpose, materials used, conditions, and the like. For example, several processes may be performed simultaneously in one process, and a specific process may be omitted. More specifically, for example, the stretching process may be performed after the dyeing process, may be performed before the dyeing process, or may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. Further, for example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath (swelling bath) filled with water. By this treatment, dirt on the surface of the polyvinyl alcohol-based resin film and an anti-blocking agent can be washed, and unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based resin film. Glycerin, potassium iodide, or the like can be appropriately added to the swelling bath. The temperature of the swelling bath is typically about 20 to 60 ° C., and the immersion time in the swelling bath is typically about 0.1 to 10 minutes.

  The dyeing step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath (dye bath) containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. The dichroic substance is typically used at a ratio of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the solvent. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.02 to 20 parts by weight, more preferably 2 to 10 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium is mentioned. The temperature of the dyeing bath is typically about 20 to 70 ° C., and the immersion time in the dyeing bath is typically about 1 to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polyvinyl alcohol resin film in a treatment bath (crosslinking bath) containing a crosslinking agent. Arbitrary appropriate crosslinking agents can be employ | adopted as a crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These can be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. The crosslinking agent is typically used at a ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the solvent. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot often be obtained. When the concentration of the crosslinking agent exceeds 10 parts by weight, the stretching force generated in the film during stretching increases, and the resulting polarizing plate may shrink. The solution of the crosslinking bath preferably further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as in the dyeing step. The temperature of the crosslinking bath is typically about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is typically about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polyvinyl alcohol-based resin film needs to be 5 times or more, preferably 5 to 7 times, and more preferably 5 to 6.5 times. When the cumulative draw ratio is less than 5 times, it may be difficult to obtain a polarizing plate with a high degree of polarization. When the cumulative draw ratio exceeds 7 times, the polyvinyl alcohol-based resin film (polarizer) may be easily broken. Arbitrary appropriate methods may be employ | adopted as a specific method of extending | stretching. For example, when the wet stretching method is adopted, the polyvinyl alcohol-based resin film is stretched at a predetermined magnification in a treatment bath (stretching bath). As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polyvinyl alcohol-based resin film subjected to the above-described various treatments in a treatment bath (water washing bath). An unnecessary residue of the polyvinyl alcohol-based resin film can be washed away by the water washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide or sodium iodide). The concentration of the iodide aqueous solution is preferably 0.1 to 10% by mass. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is typically 1 second to 1 minute. The water washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process can be adjusted suitably. For example, the water washing step includes a step of immersing the polymer film in an aqueous potassium iodide solution (0.1 to 10% by mass, 10 to 60 ° C.) for 1 second to 1 minute, and a step of rinsing with pure water.

  Any appropriate drying method (for example, natural drying, air drying, heat drying) may be employed as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., and the drying time is typically 1 to 10 minutes. A polarizer is obtained as described above.

  Examples of the method for bonding the polarizer protective film and the polarizer include a method using an adhesive, a method using a pressure-sensitive adhesive, and a method of thermocompression bonding, but there is no particular limitation. A method using an adhesive is preferably used. This adhesive is preferably a polyvinyl alcohol-based adhesive. The polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin and a crosslinking agent.

  The polyvinyl alcohol-based resin is not particularly limited. For example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; and a saponified product of a copolymer with a monomer having copolymerizability with vinyl acetate. Modified polyvinyl alcohol obtained by acetalization, urethanization, etherification, grafting, phosphoric esterification, etc. of polyvinyl alcohol. 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 may be used alone or in combination of two or more.

  From the viewpoint of adhesiveness, the polyvinyl alcohol-based resin preferably has an average degree of polymerization of 100 to 3000, more preferably 500 to 3000, and an average degree of saponification of preferably 85 to 100 mol%, more preferably 90. ˜100 mol%.

  As the polyvinyl alcohol resin, a polyvinyl alcohol resin having an acetoacetyl group can be used. A polyvinyl alcohol-based resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable in terms of improving the durability of the polarizing plate.

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

  The degree of acetoacetyl group modification of the polyvinyl alcohol resin having 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, which is inappropriate. The degree of acetoacetyl modification is preferably 0.1 to 40 mol%, more preferably 1 to 20 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 said crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting.
As the crosslinking agent, 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 amine, hexamethylene diamine (hexamethylene diamine is preferred); tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylene propane tolylene Isocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate and isocyanates such as ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di Or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylo Epoxys such as rupropane triglycidyl ether, diglycidyl aniline, diglycidyl amine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleindialdehyde And dialdehydes such as phthaldialdehyde; amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde; sodium, potassium, magnesium Divalent metals such as calcium, aluminum, iron and nickel, or salts of trivalent metals and oxides thereof. Is to, melamine-based crosslinking agent is preferably, suitable in particular melamine.

  The amount of the crosslinking agent is preferably 0.1 to 35 parts by weight, more preferably 10 to 25 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. On the other hand, in order to further improve the durability, the crosslinking agent can be blended in a 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. Water resistance improves by mix | blending a crosslinking agent in the range of more than 30 weight part and 46 weight part or less.

  The polyvinyl alcohol-based adhesive further includes coupling agents such as silane coupling agents and titanium coupling agents, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and the like. A stabilizer or the like can also be blended.

  The polarizer protective film of the present invention can be subjected to an easy adhesion treatment for improving adhesion to the surface in contact with the polarizer. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment, and a method of forming an anchor layer, and these can be used in combination. Among these, a corona treatment, a method of forming an anchor layer, and a method of using these in combination are preferable.

  Examples of the anchor layer include a silicone layer having a reactive functional group. The material of the silicone layer having a reactive functional group is not particularly limited. For example, an isocyanate group-containing alkoxysilanol, an amino group-containing alkoxysilanol, a mercapto group-containing alkoxysilanol, a carboxy-containing alkoxysilanol, an epoxy group-containing Examples thereof include alkoxysilanols, vinyl-type unsaturated group-containing alkoxysilanols, halogen group-containing alkoxylanols, and isocyanate group-containing alkoxysilanols, and amino silanols are preferred. Furthermore, the adhesive force can be strengthened by adding a titanium-based catalyst or a tin-based catalyst for efficiently reacting the silanol. Moreover, you may add another additive to the silicone which has the said reactive functional group. Specifically, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins and other tackifiers, UV absorbers, antioxidants, heat stabilizers and other stabilizers may be used.

  The silicone layer having the reactive functional group is formed by coating and drying by a known technique. The thickness of the silicone layer is preferably 1 to 100 nm, more preferably 10 to 50 nm after drying. During coating, silicone having a reactive functional group may be diluted with a solvent. The dilution solvent is not particularly limited, and examples thereof include alcohols. The dilution concentration is not particularly limited, but is preferably 1 to 5% by weight, more preferably 1 to 3% by weight.

  An adhesive layer is formed by applying the adhesive to the (meth) acrylic resin film side of the polarizer protective film, either side or both sides of the polarizer. After the (meth) acrylic resin film side of the polarizer protective film and the polarizer are bonded together, a drying process is performed to form an adhesive layer composed of a coating dry layer. This can also be bonded after forming the adhesive layer. Bonding of a polarizer and a polarizer protective film can be performed with a roll laminator or the like. The heating and drying temperature and drying time are appropriately determined according to the type of adhesive.

  The thickness of the adhesive layer is preferably 0.01 to 10 μm, and more preferably 0.03 to 5 μm, because it is not preferable in terms of adhesiveness of the polarizer protective film if the thickness after drying becomes too thick. .

  The polarizer protective film can be bonded to the polarizer on both sides of the polarizer on the (meth) acrylic resin film side of the polarizer protective film.

  In addition, the polarizer protective film of the polarizer can be bonded by adhering to one side of the polarizer on the (meth) acrylic resin film side of the polarizer protective film and bonding the cellulosic resin to the other side. it can.

  The cellulose resin is not particularly limited, but triacetyl cellulose is preferable in terms of transparency and adhesiveness. The thickness of the cellulosic resin is preferably 30 to 100 μm, more preferably 40 to 80 μm. If the thickness is less than 30 μm, the film strength is lowered and workability is inferior.

〔Polarizer〕
As described above, after the polarizer is bonded to the (meth) acrylic resin layer side of the polarizer protective film, the thermoplastic resin layer is peeled off to obtain the polarizing plate of the present invention.

  The polarizing plate according to the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to other members such as other optical films and liquid crystal cells can be provided on the (meth) acrylic resin layer of the polarizer protective film.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is used as a base polymer. It can select suitably and 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 and heat resistance can be preferably used. In particular, an acrylic pressure-sensitive adhesive made of an acrylic polymer having 4 to 12 carbon atoms is preferable.

  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 pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler or pigment made of glass fiber, glass beads, metal powder, other inorganic powders, a colorant, an antioxidant. An additive to be added to the pressure-sensitive adhesive layer such as an agent may be contained.

  Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  The attachment of the pressure-sensitive adhesive layer 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 a pressure-sensitive adhesive layer is formed on a separator according to the above, and the surface is applied to a polarizer protective film. The method of transferring to is included.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of the polarizing plate as a superposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers with a different composition, a kind, thickness, etc. in the front and back of a polarizing plate.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is preferably 1 to 40 μm, more preferably 5 to 30 μm, and particularly preferably 10 to 25 μm. When the thickness is less than 1 μm, the durability is deteriorated. When the thickness is more than 40 μm, floating or peeling due to foaming or the like is liable to occur, resulting in poor appearance.

  In order to improve the adhesion between the polarizer protective film and the pressure-sensitive adhesive layer, an anchor layer may be provided between the layers.

  As the anchor layer, an anchor layer selected from polyurethane, polyester and polymers containing an amino group in the molecule is preferably used, and polymers containing an amino group in the molecule are particularly preferably used. Polymers containing amino groups in the molecule are good because the amino groups in the molecule exhibit interactions such as reaction or ionic interaction with carboxyl groups in the adhesive and polar groups in the conductive polymer. Adhesion is ensured.

  Examples of the polymer containing an amino group in the molecule include, for example, polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, and amino-containing groups such as dimethylaminoethyl acrylate shown as a copolymer monomer of the acrylic pressure-sensitive adhesive. Examples thereof include polymers of contained monomers.

  In order to impart antistatic properties to the anchor layer, an antistatic agent may be added. Antistatic agents for imparting antistatic properties include ionic surfactant systems, conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline, and metal oxide systems such as tin oxide, antimony oxide, and indium oxide. In particular, a conductive polymer system is preferably used from the viewpoint of optical characteristics, appearance, antistatic effect, and stability of the antistatic effect when heated and humidified. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used. This is because, when a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, it is possible to suppress deterioration of the optical film substrate due to an organic solvent during the coating process.

  In the present invention, the polarizer, polarizer protective film, and the like that form the polarizing plate described above, and the pressure-sensitive adhesive layer, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylate compounds. A compound or a compound having ultraviolet absorbing ability by a method such as a method of treating with a UV absorber such as a nickel complex salt compound may be used.

  The polarizing plate of the present invention may be provided on either the viewing side or the backlight side of the liquid crystal cell or on both sides, and is not limited.

[Image display device]
Next, the image display apparatus of the present invention will be described. The image display device of the present invention includes at least one polarizing plate of the present invention. Here, a liquid crystal display device will be described as an example, but it goes without saying that the present invention can be applied to any display device that requires a polarizing plate. Specific examples of image display devices to which the polarizing plate of the present invention can be applied include self-luminous display devices such as electroluminescence (EL) displays, plasma displays (PD), and field emission displays (FEDs). Can be mentioned. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. In the illustrated example, a transmissive liquid crystal display device will be described, but it goes without saying that the present invention is also applied to a reflective liquid crystal display device and the like.

  The liquid crystal display device 100 includes a liquid crystal cell 10, retardation films 20 and 20 ′ disposed across the liquid crystal cell 10, and polarizing plates 30 and 30 ′ disposed outside the retardation films 20 and 20 ′. A light guide plate 40, a light source 50, and a reflector 60 are provided. The polarizing plates 30 and 30 'are arranged so that their polarization axes are orthogonal to each other. The liquid crystal cell 10 includes a pair of glass substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium disposed between the substrates. One substrate 11 is provided with a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal ( Neither is shown). The other glass substrate 11 ′ is provided with a color layer constituting a color filter and a light shielding layer (black matrix layer) (both not shown). The distance (cell gap) between the substrates 11 and 11 ′ is controlled by the spacer 13. In the liquid crystal display device of the present invention, the polarizing plate of the present invention described above is employed as at least one of the polarizing plates 30 and 30 '.

  For example, in the case of the TN mode, in such a liquid crystal display device 100, when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 12 are arranged in a state where the polarization axis is shifted by 90 degrees. In such a state, incident light that is transmitted through only light in one direction by the polarizing plate is twisted 90 degrees by liquid crystal molecules. As described above, since the polarizing plates are arranged so that the polarization axes thereof are orthogonal to each other, the light (polarized light) reaching the other polarizing plate is transmitted through the polarizing plate. Therefore, when no voltage is applied, the liquid crystal display device 100 performs white display (normally white method). On the other hand, when a voltage is applied to such a liquid crystal display device 100, the arrangement of liquid crystal molecules in the liquid crystal layer 12 changes. As a result, the light (polarized light) that has reached the other polarizing plate cannot be transmitted through the polarizing plate, resulting in black display. An image is formed by switching such display for each pixel using an active element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight. Evaluation was performed as follows.

<Adhesiveness between polarizer protective film and polarizer>
The state when the polarizing plate (100 mm × 100 mm) was twisted by hand and threaded was evaluated according to the following criteria.
A: The polarizer and the polarizer protective film are integrated with each other so that peeling does not occur.
(Triangle | delta): Peeling is recognized by a polarizer, a polarizer protective film, and an edge part.
X: Peeling is recognized between the polarizer and the polarizer protective film.

<Appearance of polarizing plate>
The appearance of the obtained polarizing plate was evaluated. Evaluation was performed visually with respect to a polarizing plate of 50 mm × 50 mm according to the following criteria.
○: There are no floats or streaks.
X: A float and a stripe are not seen.
The term “floating” means that the polarizer and the polarizer protective film are not in close contact with each other, and the term “streak” means that the polarizer protective film or the polarizer has a very small area but is adhered by itself.

<Peelability>
After the polarizing plate with the thermoplastic resin layer was cut into a size of 25 mm × 100 mm, a cut was made between the (meth) acrylic resin layer and the thermoplastic resin layer. Using a tensile tester, the sample is sandwiched between the (meth) acrylic resin layer side and the thermoplastic resin layer side from the sample cut with a chuck, peeled 180 °, and at a pulling speed of 300 mm / min at room temperature ( The peel force was measured at 25 ° C.
○: 5N / 25mm or less ×: Greater than 5N / 25mm

<Film transportability of polarizer protective film>
The film transportability of the polarizer protective film when producing a polarizing plate was evaluated.
○: Breakage did not occur during transportation, and transportation was good.
X: Breakage occurred during conveyance.

[Example 1]
(Polarizer)
A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, after being immersed in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide and further stretched to 5.5 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. It was immersed in a 5% by weight aqueous potassium iodide solution. Then, it dried for 3 minutes in 40 degreeC oven, and obtained the 30-micrometer-thick polarizer.

(Preparation of polarizer protective film)
Polyethyl methacrylate (Tg = 130 ° C) and polyethylene terephthalate (Tg = 70 ° C) are respectively supplied to two extruders connected to a T-die. After melt-kneading, two layers are formed at a molding temperature of 250 ° C. The film was extruded from a T-die so as to be cooled with water using a cooling roll, and a film having a thickness of 40 μm (the thickness of each layer was polyethyl methacrylate: polyethylene terephthalate = 1: 1) was obtained. Thereafter, the acrylic resin surface was subjected to corona treatment at a discharge amount of 133 w · min / m ² .

(Easily adhesive layer)
A solution prepared by adding 66.7 parts of isopropyl alcohol to 100 parts of a silane coupling agent (APZ-6601) manufactured by Toray Dow Corning Silicone Co., Ltd. was applied to the corona-treated surface of the film obtained above. The coating was applied with bar # 5 to evaporate volatile components. The thickness of the anchor layer after evaporation was 50 nm.

(adhesive)
A polyvinyl alcohol adhesive aqueous solution prepared by adjusting an aqueous solution containing 20 parts by weight of methylolmelamine to 100 parts by weight of an acetoacetyl-modified polyvinyl alcohol resin (degree of acetylation 13%) to a concentration of 0.5% by weight It was adjusted.

(Preparation of polarizing plate)
The said polarizer protective film was bonded together using the polyvinyl alcohol-type adhesive so that the acrylic resin surface of the said polarizer protective film might contact | connect both surfaces of a polarizer. Each of the polyvinyl alcohol-based adhesives was applied to the acrylic resin surface side and dried at 70 ° C. for 10 minutes to obtain a polarizing plate with a thermoplastic resin layer. Finally, the thermoplastic resin layer was peeled off to obtain the polarizing plate of the present invention.

(Evaluation)
(1) Adhesiveness between the polarizer protective film and the polarizer, (2) appearance, (3) peelability, and (4) film transportability of the polarizer protective film in the obtained polarizing plate were evaluated. The results are shown in Table 1.

[Example 2]
(Preparation of polarizing plate)
In Example 1, a polarizing plate was obtained in the same manner as in Example 1 except that nylon 12 (Tg = 50 ° C.) was used instead of polyethylene terephthalate.

(Evaluation)
(1) Adhesiveness between the polarizer protective film and the polarizer, (2) appearance, (3) peelability, and (4) film transportability of the polarizer protective film in the obtained polarizing plate were evaluated. The results are shown in Table 1.

Example 3
(Preparation of polarizing plate)
In Example 1, a polarizing plate was obtained in the same manner as in Example 1 except that bisphenol A type polycarbonate (Tg = 150 ° C.) was used instead of polyethylene terephthalate and the molding temperature was 270 ° C.

(Evaluation)
(1) Adhesiveness between the polarizer protective film and the polarizer, (2) appearance, (3) peelability, and (4) film transportability of the polarizer protective film in the obtained polarizing plate were evaluated. The results are shown in Table 1.

Example 4
(Preparation of polarizing plate)
In Example 1, a polarizing plate was obtained in the same manner as in Example 1 except that styrene-butadiene copolymer (Tg = −44 ° C.) was used instead of polyethylene terephthalate.

(Evaluation)
(1) Adhesiveness between the polarizer protective film and the polarizer, (2) appearance, (3) peelability, and (4) film transportability of the polarizer protective film in the obtained polarizing plate were evaluated. The results are shown in Table 1.

[Comparative Example 1]
(Preparation of polarizing plate)
In Example 1, a polarizing plate was obtained in the same manner as in Example 1 except that a polarizer protective film was prepared using only polyethyl methacrylate.

(Evaluation)
(1) Adhesiveness between the polarizer protective film and the polarizer, (2) appearance, (3) peelability, and (4) film transportability of the polarizer protective film in the obtained polarizing plate were evaluated. The results are shown in Table 1.

It is sectional drawing which shows an example of the polarizer protective film of this invention. It is sectional drawing which shows an example of the polarizing plate with a thermoplastic resin layer using the polarizer protective film of this invention. It is sectional drawing which shows an example of the polarizing plate obtained with the manufacturing method of this invention. It is sectional drawing which shows an example of the polarizing plate with a thermoplastic resin layer using the polarizer protective film of this invention. It is sectional drawing which shows an example of the polarizing plate obtained with the manufacturing method of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Adhesive layer 3, 3 'Polarizer protective film a (meth) acrylic-type resin layer b Thermoplastic resin layer 10 Liquid crystal cell 11, 11' Glass substrate 12 Liquid crystal layer 13 Spacer 20, 20 'Retardation film 30 , 30 'polarizing plate 31 polarizing film 32 adhesive layer 33 transparent protective film 34 adhesive layer 35 second transparent protective film 40 light guide plate 50 light source 60 reflector 100 liquid crystal display device

Claims (8)

  A method for producing a polarizer protective film, wherein a film having a (meth) acrylic resin layer and a thermoplastic resin layer is formed by coextrusion molding of a (meth) acrylic resin and a thermoplastic resin.   The polarizer protective film according to claim 1, wherein the thermoplastic resin is any one of a copolymer containing a polyester resin, a nylon resin, a polycarbonate resin, a styrene monomer, and an olefin monomer as a monomer unit. Manufacturing method.   A polarizer protective film obtained by the production method according to claim 1.   The manufacturing method of a polarizing plate which peels a thermoplastic resin layer, after adhere | attaching the polarizer formed from a polyvinyl alcohol-type resin to the (meth) acrylic-type resin layer side of the polarizer protective film of Claim 3.   The manufacturing method of the polarizing plate of Claim 4 with which the said adhesion | attachment is performed with a polyvinyl alcohol-type adhesive agent.   A polarizing plate obtained by the production method according to claim 4.   The polarizing plate of Claim 6 which has an adhesive layer as at least one of outermost layers. An image display device comprising at least one polarizing plate according to claim 6.

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