JP2015121720A - Polarizing plate and method for manufacturing polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate with excellent appearance.SOLUTION: A method for manufacturing a polarizing plate includes the steps of: preparing a laminate 10 in which a polyvinyl alcohol resin layer 12 is formed on a resin base material 11 by applying a coating liquid containing a polyvinyl alcohol resin and a surface active agent onto the resin base material 11; preparing a polarizing film 12' by stretching and dyeing the polyvinyl alcohol resin layer formed on the resin base material; preparing an optical functional film laminate 100 by laminating an optical functional film 20 on the polarizing film side of the laminate; and peeling the resin base material from the optical functional film laminate. The content of the surface active agent in the coating liquid is not more than 0.5 pt.wt. with respect to 100 pts.wt. of the polyvinyl alcohol resin.

Description

  The present invention relates to a polarizing plate and a method for producing a polarizing plate.

  In a liquid crystal display device which is a typical image display device, polarizing films are arranged on both sides of a liquid crystal cell due to the image forming method. As a method for producing a polarizing film, for example, there is a method in which a laminate having a resin base material and a polyvinyl alcohol (PVA) resin layer is stretched and then subjected to a dyeing treatment to obtain a polarizing film on the resin base material. It has been proposed (for example, Patent Document 1). According to such a method, a polarizing film having a small thickness can be obtained, and thus has been attracting attention as being able to contribute to the recent thinning of image display devices.

  By the way, the polarizing film is usually used as a polarizing plate by being laminated with another optical functional film (for example, a protective film). However, a polarizing plate using a polarizing film produced using a resin base material has a problem that wrinkles, foreign matters, etc. are likely to occur and the appearance is inferior.

JP 2000-338329 A

  The present invention has been made to solve the above-described problems, and a main object thereof is to provide a method for producing a polarizing plate having an excellent appearance.

The method for producing a polarizing plate of the present invention is a laminate in which a coating liquid containing a polyvinyl alcohol resin and a surfactant is applied on a resin substrate, and a polyvinyl alcohol resin layer is formed on the resin substrate. Forming a polarizing film by stretching and dyeing the polyvinyl alcohol-based resin layer formed on the resin substrate, and laminating an optical functional film on the polarizing film side of the laminate A step of producing an optical functional film laminate, and a step of peeling the resin substrate from the optical functional film laminate, wherein the content of the surfactant in the coating liquid is the polyvinyl alcohol resin. It is 0.5 parts by weight or less with respect to 100 parts by weight.
In one embodiment, the stretching includes underwater stretching.
In one embodiment, the surfactant is a nonionic surfactant.
In one embodiment, the polarizing film has a thickness of 10 μm or less.
In one embodiment, the coating liquid further contains acetoacetyl-modified polyvinyl alcohol.
In one embodiment, the surface where the said coating liquid of the said resin base material is apply | coated is corona-treated.
According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the said manufacturing method.
According to still another aspect of the present invention, a laminate is provided. The laminate is a laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and the polyvinyl alcohol-based resin layer is formed on the resin substrate. It is formed by applying a coating liquid containing a resin and 0.5 parts by weight or less of a surfactant with respect to 100 parts by weight of the polyvinyl alcohol resin.

  According to the production method of the present invention, since the polyvinyl alcohol-based resin layer contains a surfactant, the polarizing film and the resin base material are satisfactorily suppressed while suppressing generation of wrinkles and foreign matters (for example, base material residue). Can be peeled off. Moreover, the surface smoothness of a polarizing film can be improved by making content of this surfactant into a predetermined amount or less in that case. As a result, a polarizing plate having an extremely excellent appearance can be obtained.

It is the schematic explaining the manufacturing method by preferable embodiment of this invention.

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

  FIG. 1 is a schematic diagram illustrating a manufacturing method according to a preferred embodiment of the present invention. In the method for producing a polarizing plate of the present invention, a coating liquid containing a polyvinyl alcohol resin and a surfactant is applied to the resin base material 11, and the polyvinyl alcohol resin layer 12 is formed on the resin base material 11. A step of producing the laminate 10 (FIG. 1A: a step of producing the laminate) and the polyvinyl alcohol-based resin layer 12 formed on the resin substrate 11 are stretched and dyed to obtain a polarizing film 12 ′. 1 (b): a polarizing film manufacturing step), and a step of stacking the optical functional film 20 on the polarizing film 12 ′ side of the laminate 10 to manufacture the optical functional film laminate 100 (FIG. 1). 1 (c): a production step of the optical functional film laminate) and a step of peeling the resin substrate 11 from the optical functional film laminate 100 (FIG. 1 (d): peeling step). Hereinafter, each process will be described.

[A. Laminate manufacturing process]
In the production process of the laminate, a coating solution containing a polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) and a surfactant is applied to a long resin substrate, and the resin substrate is coated on the resin substrate. A laminate in which a PVA resin layer is formed is produced. Preferably, a PVA-based resin layer is formed by applying a coating liquid containing a PVA-based resin and a surfactant to one side of the resin base material and drying. As shown in FIG. 1A, the laminate 10 includes a resin base material 11 and a PVA resin layer 12 formed on one side of the resin base material 11.

  Any appropriate thermoplastic resin can be adopted as the material for forming the resin base material. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, preferred are norbornene resins and amorphous polyethylene terephthalate resins.

  In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among these, amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol as a glycol.

  When an underwater stretching method is adopted in the stretching described later, the resin base material absorbs water, and the water can be plasticized by acting as a plasticizer. As a result, the stretching stress can be greatly reduced, the film can be stretched at a high magnification, and the stretchability can be superior to that during air stretching. As a result, a polarizing film having excellent optical characteristics can be produced. In one embodiment, the resin base material preferably has a water absorption rate of 0.2% or more, and more preferably 0.3% or more. On the other hand, the water absorption rate of the resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, it is possible to prevent problems such as a significant decrease in dimensional stability during production and deterioration of the appearance of the resulting polarizing film. Moreover, it can prevent that a base material fractures | ruptures at the time of extending | stretching in water, or a PVA-type resin layer peels from a resin base material. The water absorption rate of the resin base material can be adjusted, for example, by introducing a modifying group into the forming material. The water absorption is a value determined according to JIS K 7209.

  The glass transition temperature (Tg) of the resin base material is preferably 170 ° C. or lower. By using such a resin base material, the stretchability of the laminate can be sufficiently ensured while suppressing crystallization of the PVA-based resin layer. Furthermore, considering the plasticization of the resin base material with water and the good stretching in water, the temperature is more preferably 120 ° C. or lower. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 ° C. or higher. By using such a resin base material, the resin base material is deformed (for example, generation of unevenness, talmi, wrinkles, etc.) when the coating liquid containing the PVA-based resin and the surfactant is applied and dried. Such a problem as described above can be prevented and a laminate can be produced satisfactorily. In addition, the PVA-based resin layer can be satisfactorily stretched at a suitable temperature (for example, about 60 ° C.). In another embodiment, a glass transition temperature lower than 60 ° C. may be used as long as the resin base material is not deformed when applying and drying a coating solution containing a PVA resin and a surfactant. The glass transition temperature of the resin substrate can be adjusted by, for example, heating using a crystallization material that introduces a modifying group into the forming material. The glass transition temperature (Tg) is a value obtained according to JIS K7121.

  The thickness of the resin base material before stretching is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it exceeds 300 μm, for example, in stretching in water, it takes a long time for the resin base material to absorb water, and an excessive load may be required for stretching.

  Arbitrary appropriate resin may be employ | adopted as PVA-type resin which forms the said PVA-type resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

  The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. Average polymerization degree is 1000-10000 normally, Preferably it is 1200-5000, More preferably, it is 1500-4500. The average degree of polymerization can be determined according to JIS K 6726-1994.

  The coating solution is typically a solution obtained by dissolving the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferable. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the resin substrate can be formed.

  As described above, the coating solution contains a surfactant in addition to the PVA resin. The surfactant may be any type of nonionic, anionic, nonionic, and amphoteric. Of these, nonionic surfactants are preferably used. According to the nonionic surfactant, there are advantages that even if it elutes in the stretching bath, there are many effects that it is difficult to affect the ion balance in the bath and there are many options that can be used industrially.

  Any appropriate nonionic surfactant can be used as the nonionic surfactant. Specific examples of the nonionic surfactant include glycerin fatty acid ester, propylene glycol fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene alkyl ether, alkyl glyceryl ether, polyoxyethylene alkylphenyl. Ether, polyoxyethylene polyoxypropylene ether, polyoxyalkylene alkyl ether, acetylene glycol, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, alkyl glyceryl ether, fatty acid alkylene oxide adduct, polyoxyethylene cured castor Oil, fatty acid alkanolamide, fatty acid amide alkylene oxide adduct, amine EO adduct , Amine PO adducts, diamine alkylene oxide adducts and the like. Among them, a surfactant having a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group and an acetylene glycol-based surfactant having an acetylene group in the center and a symmetrical structure are used with a PVA resin. It can be preferably used in terms of excellent compatibility.

  Any appropriate anionic surfactant can be used as the anionic surfactant. Specific examples of anionic surfactants include alkali metal alkyl sulfates such as sodium dodecyl sulfate and potassium dodecyl sulfate; ammonium alkyl sulfates such as ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate, sodium sulfosinoate, sulfonation Alkali metal salts of paraffin; alkyl sulfonates such as ammonium salt of sulfonated paraffin; fatty acid salts such as sodium laurate, triethanolamine oleate, triethanolamine abiate; sodium dodecylbenzenesulfonate, alkali metal of alkali phenol hydroxyethylene Alkyl aryl sulfonates such as sulfate; higher alkyl naphthalene sulfo Salts, naphthalenesulfonic acid-formalin condensate, dialkyl sulfosuccinate, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkylaryl sulfate salts.

  Any appropriate cationic surfactant can be used as the cationic surfactant. Specific examples of the cationic surfactant include alkyl pyridinyl chloride, alkyl ammonium chloride and the like.

  Any appropriate amphoteric surfactant can be used as the amphoteric surfactant. Specific examples of the amphoteric surfactant include lauryl petaine, stearyl petaine, lauryl dimethylamine oxide and the like.

  The content of the surfactant in the coating solution is 0.5 parts by weight or less, preferably 0 with respect to 100 parts by weight of the PVA resin (including the modified PVA when the modified PVA described later is blended). .4 parts by weight or less. The content of the surfactant in the coating solution is, for example, 0.02 parts by weight or more, preferably 100 parts by weight or more, preferably 100 parts by weight of PVA resin (including the modified PVA described later when blended). 0.03 part by weight or more. If the content of the surfactant is within the above range, a PVA resin layer having high surface smoothness (as a result, a polarizing film having high surface smoothness, excellent transmittance and uniform optical properties) is formed. be able to. Furthermore, the releasability between the polarizing film and the resin base material can be improved while maintaining the adhesion between the resin base material and the PVA-based resin layer at the time of stretching described below, particularly underwater stretching. Moreover, the uniformity, dyeability, and stretchability of the obtained PVA resin layer can be improved.

  You may mix | blend an additive with a coating liquid further. Examples of the additive include a plasticizer. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. The plasticizer can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting PVA resin layer. Moreover, as another additive, an easily bonding component is mentioned, for example. By using the easy-adhesion component, the adhesion between the resin base material and the PVA-based resin layer can be improved. As a result, for example, problems such as peeling of the PVA-based resin layer from the substrate can be suppressed, and dyeing and underwater stretching described later can be performed satisfactorily.

  As the easily adhesive component, for example, modified PVA such as acetoacetyl-modified PVA is used. As the acetoacetyl-modified PVA, a polymer having at least a repeating unit represented by the following general formula (I) is preferably used.

  In the above formula (I), the ratio of n to l + m + n (degree of modification) is preferably 1% to 10%.

  The saponification degree of acetoacetyl-modified PVA is preferably 97 mol% or more. The pH of the 4% by weight aqueous solution of acetoacetyl-modified PVA is preferably 3.5 to 5.5.

  The modified PVA is preferably added so as to be 3% by weight or more, more preferably 5% by weight or more of the total weight of the PVA resin contained in the coating solution. On the other hand, the amount of the modified PVA added is preferably 30% by weight or less.

  Any appropriate method can be adopted as a coating method of the coating solution. Examples thereof include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method and the like).

  The coating / drying temperature of the coating solution is preferably 50 ° C. or higher. The drying time is preferably 1 second to 10 minutes.

  Before forming the PVA-based resin layer, the resin substrate may be subjected to surface treatment (for example, corona treatment), or an easy-adhesion layer may be formed on the resin substrate. Among these, it is preferable to form an easy-adhesion layer (coating treatment). As a material for forming the easy adhesion layer, for example, an acrylic resin, a polyvinyl alcohol resin, or the like is used, and a polyvinyl alcohol resin is particularly preferable. Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a modified product thereof. Examples of the modified product of the polyvinyl alcohol resin include the acetoacetyl-modified PVA. In addition, it is preferable that the thickness of an easily bonding layer shall be about 0.05-1 micrometer. By performing such a treatment, the adhesion between the resin substrate and the PVA resin layer can be improved. As a result, for example, problems such as peeling of the PVA-based resin layer from the substrate can be suppressed, and dyeing and underwater stretching described later can be performed satisfactorily.

  The PVA resin layer formed as described above is typically 0.5 parts by weight or less, preferably 0.02 parts by weight to 0.00 parts by weight with respect to 100 parts by weight of the PVA resin and the PVA resin. 4 parts by weight of a surfactant. The thickness (thickness before stretching described later) of the PVA-based resin layer is preferably 3 μm to 40 μm, more preferably 5 μm to 20 μm.

[B. Production process of polarizing film]
In the polarizing film manufacturing step, the PVA resin layer 12 formed on the resin substrate 11 is stretched and dyed to prepare the polarizing film 12 ′.

B-1. Stretching The stretching of the PVA-based resin layer is typically performed by stretching the laminate obtained in the laminate production process. Any appropriate method can be adopted as a method of stretching the laminate. Specifically, it may be fixed end stretching or free end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Preferably, it is free end stretching.

  The extending direction of the laminate can be appropriately set. In one embodiment, it extends | stretches in the longitudinal direction of an elongate laminated body. In this case, typically, a method of stretching the laminate between rolls having different peripheral speeds is employed. In another embodiment, it extends | stretches in the width direction of an elongate laminated body. In this case, typically, a method of stretching using a tenter stretching machine is employed.

  The stretching method is not particularly limited, and may be an air stretching method or an underwater stretching method. The underwater stretching method is preferable. According to the underwater stretching method, the resin base material and the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 ° C.), and the crystallization of the PVA resin layer is suppressed. However, it can be stretched at a high magnification. As a result, a polarizing film having excellent optical characteristics can be produced.

  The stretching of the laminate may be performed in one stage or in multiple stages. When performing in multiple stages, for example, the free end stretching and the fixed end stretching may be combined, or the underwater stretching method and the air stretching method may be combined. Moreover, when performing by multistep, the draw ratio (maximum draw ratio) of the laminated body mentioned later is a product of the draw ratio of each step.

  The stretching temperature of the laminate can be set to any appropriate value depending on the resin base material, the stretching method, and the like. When adopting the air stretching method, the stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10 ° C., and particularly preferably Tg + 15 ° C. That's it. On the other hand, the stretching temperature of the laminate is preferably 170 ° C. or lower. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin, and to suppress problems due to the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). it can.

  When employing the underwater stretching method, the temperature of the stretching bath is preferably 40 ° C to 85 ° C, more preferably 50 ° C to 85 ° C. If it is such temperature, it can extend | stretch at high magnification, suppressing melt | dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, when the stretching temperature is lower than 40 ° C., there is a possibility that the stretching cannot be satisfactorily performed even in consideration of plasticization of the resin base material with water. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical properties cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

  When employing an underwater stretching method, it is preferable to stretch the laminate by immersing it in an aqueous boric acid solution (stretching in boric acid in water). By using an aqueous boric acid solution as the stretching bath, the PVA resin layer can be provided with rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink with a PVA resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, the film can be stretched satisfactorily, and a polarizing film having excellent optical properties can be produced.

  The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight with respect to 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.

  When a dichroic substance (typically iodine) is previously adsorbed to the PVA-based resin layer by dyeing described later, preferably, an iodide is blended in the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. Among these, potassium iodide is preferable. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight with respect to 100 parts by weight of water.

  The draw ratio (maximum draw ratio) of the laminate is preferably 5.0 times or more with respect to the original length of the laminate. Such a high draw ratio can be achieved, for example, by employing an underwater drawing method (boric acid underwater drawing). In the present specification, the “maximum stretch ratio” refers to a stretch ratio immediately before the laminate is ruptured. Separately, a stretch ratio at which the laminate is ruptured is confirmed, and a value that is 0.2 lower than that value. .

  In a preferred embodiment, the laminate is stretched in the air at a high temperature (for example, 95 ° C. or higher), and then the boric acid solution is stretched and dyed as described below. Such air stretching can be positioned as preliminary or auxiliary stretching for boric acid water stretching, and is hereinafter referred to as “air-assisted stretching”.

  In some cases, the laminate can be stretched at a higher magnification by combining air-assisted stretching. As a result, a polarizing film having more excellent optical characteristics (for example, the degree of polarization) can be produced. For example, when a polyethylene terephthalate-based resin is used as the resin base material, the orientation of the resin base material is suppressed by combining the air auxiliary stretching and the boric acid water stretching rather than stretching by boric acid water stretching alone. While stretching. As the orientation of the resin base material is improved, the stretching tension increases, and stable stretching becomes difficult or breaks. Therefore, the laminate can be stretched at a higher magnification by stretching while suppressing the orientation of the resin substrate.

  Moreover, the orientation of the PVA resin can be improved by combining the air-assisted stretching, whereby the orientation of the PVA resin can be improved even after the boric acid solution is stretched. Specifically, by previously improving the orientation of the PVA resin by air-assisted stretching, the PVA resin is easily cross-linked with boric acid during boric acid water stretching, and boric acid is a nodal point. It is presumed that the orientation of the PVA-based resin is increased even after stretching in boric acid solution by being stretched in such a state. As a result, a polarizing film having excellent optical characteristics (for example, the degree of polarization) can be produced.

  The draw ratio in the air auxiliary drawing is preferably 3.5 times or less. The stretching temperature of the air auxiliary stretching is preferably equal to or higher than the glass transition temperature of the PVA resin. The stretching temperature is preferably 95 ° C to 150 ° C. In addition, the maximum draw ratio in the case of combining the air auxiliary stretching and the boric acid solution stretching is preferably 5.0 times or more, more preferably 5.5 times or more, and further preferably, the original length of the laminate. Is 6.0 times or more.

B-2. Dyeing The dyeing of the PVA resin layer is typically performed by adsorbing a dichroic substance (preferably iodine) to the PVA resin layer. As the adsorption method, for example, a method of immersing a PVA resin layer (laminate) in a staining solution containing iodine, a method of applying the staining solution to the PVA resin layer, and applying the staining solution to the PVA resin layer The method of spraying etc. are mentioned. Preferably, it is a method of immersing the laminate in the staining solution. This is because iodine can be adsorbed well.

  The staining solution is preferably an iodine aqueous solution. The compounding amount of iodine is preferably 0.1 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the aqueous iodine solution. Specific examples of the iodide are as described above. The blending amount of iodide is preferably 0.02 to 20 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of water. The liquid temperature during dyeing of the dyeing liquid is preferably 20 ° C. to 50 ° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the staining solution, the immersion time is preferably 5 seconds to 5 minutes in order to ensure the transmittance of the PVA resin layer. The staining conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the finally obtained polarizing film is within a predetermined range. In one embodiment, immersion time is set so that the polarization degree of the polarizing film obtained may be 99.98% or more. In another embodiment, the immersion time is set so that the single transmittance of the obtained polarizing film is 40% to 44%.

  The staining process can be performed at any appropriate timing. When performing the said underwater extending | stretching, Preferably, it performs before an underwater extending | stretching.

B-3. Other treatments In addition to stretching and dyeing, the laminate may be appropriately subjected to treatment for using the PVA resin layer as a polarizing film. Examples of the treatment for forming the polarizing film include insolubilization treatment, crosslinking treatment, washing treatment, and drying treatment. In addition, the frequency | count, order, etc. of these processes are not specifically limited.

  The insolubilization treatment is typically performed by immersing the PVA resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilizing bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization treatment is performed before the above-described underwater stretching or the above-described dyeing treatment.

  The crosslinking treatment is typically performed by immersing the PVA resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water. Moreover, when performing a crosslinking process after the said dyeing | staining process, it is preferable to mix | blend an iodide further. By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 60 ° C. Preferably, the crosslinking treatment is performed before the underwater stretching. In a preferred embodiment, the dyeing process, the crosslinking process and the underwater stretching are performed in this order.

  The cleaning treatment is typically performed by immersing the PVA resin layer in an aqueous potassium iodide solution. The drying temperature in the drying treatment is preferably 30 ° C to 100 ° C.

B-4. Polarizing Film The polarizing film is substantially a PVA resin film in which a dichroic substance is adsorbed and oriented. The thickness of the polarizing film is typically 25 μm or less, preferably 15 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and particularly preferably 5 μm or less. On the other hand, the thickness of the polarizing film is preferably 0.5 μm or more, more preferably 1.5 μm or more. The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more, further preferably 42.0% or more, and particularly preferably 43.0% or more. The polarization degree of the polarizing film is preferably 99.8% or more, more preferably 99.9% or more, and further preferably 99.95% or more.

[C. Production process of optical functional film laminate]
In the production process of the optical functional film laminate, the optical functional film laminate 100 is obtained by laminating the optical functional film 20 on the polarizing film 12 ′ side of the laminate 10. Typically, a long optical functional film is laminated on a long laminate so that the longitudinal directions thereof are aligned.

  The optical functional film can function as, for example, a protective film for a polarizing film, a retardation film, and the like.

  Any appropriate resin film can be adopted as the optical functional film. Examples of the material for forming the optical functional film include cellulose resins such as triacetyl cellulose (TAC), cycloolefin resins such as norbornene resins, olefin resins such as polyethylene and polypropylene, polyester resins, and (meth) acrylic. Based resins and the like. The “(meth) acrylic resin” refers to an acrylic resin and / or a methacrylic resin.

  The thickness of the optical function film is typically 10 μm to 100 μm, preferably 20 μm to 60 μm. The optical function film may be subjected to various surface treatments.

  The elastic modulus of the optical functional film is preferably 2 GPa or more, more preferably 2 GPa to 6 GPa. By using such an optical functional film, the below-mentioned peeling process can be performed more favorably.

  Arbitrary appropriate adhesives or adhesives are used for lamination | stacking of an optical function film. In a preferred embodiment, an adhesive is applied to the surface of the polarizing film, and the optical functional film is bonded. The adhesive may be a water-based adhesive or a solvent-based adhesive. Preferably, a water-based adhesive is used.

  Any appropriate aqueous adhesive may be employed as the aqueous adhesive. Preferably, an aqueous adhesive containing a PVA resin is used. The average degree of polymerization of the PVA resin contained in the aqueous adhesive is preferably about 100 to 5000, more preferably 1000 to 4000, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, from the viewpoint of adhesiveness.

  The PVA resin contained in the aqueous adhesive preferably contains an acetoacetyl group. This is because the adhesiveness between the PVA-based resin layer and the optical functional film is excellent and the durability can be excellent. The acetoacetyl group-containing PVA resin can be obtained, for example, by reacting a PVA resin and diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol. %, Particularly preferably 2 mol% to 7 mol%. The degree of acetoacetyl group modification is a value measured by NMR.

  The resin concentration of the water-based adhesive is preferably 0.1% by weight to 15% by weight, more preferably 0.5% by weight to 10% by weight.

  The thickness at the time of application | coating of an adhesive agent can be set to arbitrary appropriate values. For example, it is set so that an adhesive layer having a desired thickness is obtained after heating (drying). The thickness of the adhesive layer is preferably 10 nm to 300 nm, more preferably 10 nm to 200 nm, and particularly preferably 20 nm to 150 nm.

  It is preferable to heat after laminating the optical functional film. The heating temperature is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, further preferably 60 ° C. or higher, and particularly preferably 80 ° C. or higher. In addition, the heating performed after laminating the optical function film may be combined with the drying treatment for the laminate. Moreover, although you may perform after the below-mentioned peeling process, Preferably, it carries out before a peeling process.

[D. Peeling process]
In the peeling step, the resin base material 11 is peeled from the optical functional film laminate 100. According to the conventional optical functional film laminate, the peelability between the polarizing film and the resin base material is inferior, and therefore the peel direction, peel angle and the like when peeling these are limited. By mix | blending a predetermined amount of surfactant with a system resin layer, the peelability of the polarizing film obtained and a resin base material can be improved. As a result, these can be peeled without limiting the peeling direction, the peeling angle, and the like. Preferably, the polarizing film 12 ′ and the optical functional film 20 are directed upward at a desired angle while holding the optical functional film laminate 100 horizontally or transporting it horizontally so that the resin base material 11 is on the lower side. The resin base material 11 is peeled from the optical functional film laminate 100 by pulling. Alternatively, the polarizing film 12 ′ and the optical functional film 20 are pulled downward at a desired angle while holding the optical functional film laminate 100 horizontally or transporting it horizontally so that the resin base material 11 is on the upper side. The resin base material 11 is peeled from the optical functional film laminate 100.

  The tension necessary for the peeling (peeling tension) is preferably 0.5 N / mm or less, more preferably 0.3 N / mm or less, and particularly preferably 0.1 N / mm or less.

  In the peeling step, a peeling assisting means may be arranged on the optical functional film side of the optical functional film laminate in order to perform peeling more easily, better and more stably. Examples of the peeling assisting means include a peeling roll and a peeling bar. The peeling roll is brought into contact with the optical functional film side of the optical functional film laminate, and assists peeling while the roll itself rotates. When a peeling bar is used, the peeling bar typically has a semicircular tip, and the tip is brought into contact with the optical functional film side of the optical functional film laminate, and peels without rotating. Assist. At this time, in order to prevent generation | occurrence | production of the damage | wound by a peeling roll or a peeling bar, you may laminate | stack the surface protection film on the surface by the side of the optical function film of an optical function film laminated body. The surface protective film is not particularly limited, but typically, a polyethylene film having a pressure-sensitive adhesive layer provided on the surface thereof can be used, and the surface protective film can be bonded to the surface of the optical functional film by the pressure-sensitive adhesive layer.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of each characteristic is as follows.
1. Thickness Measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
2. Glass transition temperature (Tg)
It measured according to JIS K7121.

[Example 1]
A long amorphous polyethylene terephthalate film (manufactured by Mitsubishi Plastics, trade name “Novaclear SH046”, Tg: 70 ° C., thickness: 200 μm) is stretched twice in the width direction using a tenter in an oven at 90 ° C. Thus, a resin base material was obtained.

One side of the resin base material is subjected to corona treatment (treatment condition: 55 W · min / m ² ). Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) 90 parts by weight, aceto 10 parts by weight of acetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer Z200”) and nonionic A PVA-based resin layer-forming aqueous solution (PVA concentration: 7%) containing 0.07 part by weight of a polyoxyalkylene alkyl ether (trade name “Emulgen MS110”, manufactured by Kao Corporation) as a surfactant is applied, and a temperature of 60 ° C. to 70 ° C. The laminate was dried at 5 ° C. for 5 minutes to form a PVA resin layer having a thickness of 10 μm, thereby obtaining a laminate.

The obtained laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) twice in a longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 100 ° C. (air-assisted stretching).
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, it is immersed for 60 seconds in a dyeing bath having a liquid temperature of 30 ° C. (an iodine aqueous solution obtained by blending 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide with respect to 100 parts by weight of water). (Staining treatment).
Subsequently, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (Crosslinking treatment).
Thereafter, the laminate was immersed in a boric acid aqueous solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ° C. However, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds (underwater stretching). Here, it extended | stretched until just before a laminated body fracture | ruptures (a maximum draw ratio is 6.0 times).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. (cleaning treatment).

  Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the surface of the PVA-based resin layer of the laminate. , An optical fiber having a polarizing film having a thickness of 5 μm, bonded with a triacetylcellulose film having an elastic modulus of 4.0 GPa (trade name “KC4UY”, manufactured by Konica Minolta, Inc., thickness 40 μm) and heated in an oven maintained at 60 ° C. for 5 minutes. A functional film laminate was produced.

  The obtained optical functional film laminate is placed on a flat table so that the resin substrate is on the lower side, and the angle is held while gripping the end portions of the PVA resin layer (polarizing film) and the triacetyl cellulose film. And it peeled, changing a direction and obtained the polarizing plate.

[Example 2]
Except that an aqueous solution for forming a PVA resin layer was prepared using an acetylene glycol surfactant (trade name “Orphine EXP4123” manufactured by Nissin Chemical Industry Co., Ltd.) as a nonionic surfactant. Thus, a polarizing plate was obtained.

[Example 3]
Using an acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name “Orphine EXP4123”) as a nonionic surfactant, an aqueous solution for forming a PVA resin layer is prepared with a blending amount of 0.5 part by weight. A polarizing plate was obtained in the same manner as in Example 1 except that.

[Comparative Example 1]
A polarizing plate was obtained in the same manner as in Example 1 except that an aqueous solution for forming a PVA-based resin layer was prepared without using a nonionic surfactant.

[Comparative Example 2]
An aqueous solution for forming a PVA-based resin layer is prepared using an acetylene glycol-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name “Orphine EXP4123”) as a nonionic surfactant, with a blending amount of 0.7 parts by weight. A polarizing plate was obtained in the same manner as in Example 1 except that.

[Comparative Example 3]
A polarizing plate was obtained in the same manner as in Example 1 except that an aqueous solution for forming a PVA-based resin layer was prepared by adding 1.0 part by weight of the nonionic surfactant. In Comparative Example 3, peeling occurred between the resin base material and the PVA resin layer during stretching in water.

In each Example and Comparative Example, the obtained polarizing film was visually observed, and the surface smoothness was evaluated based on the following evaluation criteria. Furthermore, the peelability in the peeling process of each Example and Comparative Example was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1.
(Evaluation criteria for surface smoothness)
Good: When the fluorescent lamp is reflected, the edge of the reflected image looks linear. Poor: When the fluorescent lamp is reflected, the edge of the reflected image appears distorted (evaluation criteria for peelability)
Good: There was no restriction on the peeling angle and the peeling direction, and it was possible to peel continuously at the interface between the polarizing film and the resin substrate. It was difficult to peel continuously due to cohesive failure of the material

  As apparent from Table 1, according to the method for producing a polarizing plate of the present invention, the surface smoothness of the polarizing film can be obtained by blending a surfactant in the PVA resin layer and specifying the blending amount. Moreover, releasability between the polarizing film and the resin base material can be compatible. Therefore, according to the manufacturing method of the present invention, it is possible to prevent the generation of wrinkles and foreign matters on the polarizing film in the peeling step while maintaining the surface smoothness, so that a polarizing plate having an excellent appearance has an excellent production efficiency. Can be obtained.

  The polarizing plate of the present invention is a liquid crystal television, a liquid crystal display, a mobile phone, a digital camera, a video camera, a portable game machine, a car navigation system, a copier, a printer, a fax machine, a clock, a microwave oven, etc., and a reflection of an organic EL device. It is suitably used as a prevention film.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 Resin base material 12 PVA-type resin layer 12 'Polarizing film 20 Optical functional film 100 Optical functional film laminated body

Claims (8)

Applying a coating liquid containing a polyvinyl alcohol-based resin and a surfactant on a resin base material to produce a laminate in which a polyvinyl alcohol-based resin layer is formed on the resin base;
Stretching and dyeing the polyvinyl alcohol-based resin layer formed on the resin substrate to produce a polarizing film;
Laminating an optical functional film on the polarizing film side of the laminate to produce an optical functional film laminate;
Peeling the resin substrate from the optical functional film laminate,
The content of the surfactant in the coating solution is 0.5 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.
Manufacturing method of polarizing plate.   The manufacturing method according to claim 1, wherein the stretching includes underwater stretching.   The manufacturing method of Claim 1 or 2 whose said surfactant is a nonionic surfactant.   The manufacturing method in any one of Claim 1 to 3 whose thickness of the said polarizing film is 10 micrometers or less.   The manufacturing method in any one of Claim 1 to 4 with which the said coating liquid further contains acetoacetyl modified polyvinyl alcohol.   The manufacturing method according to claim 1, wherein a surface of the resin base material on which the coating liquid is applied is subjected to corona treatment.   A polarizing plate obtained by the production method according to claim 1. A laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate,
By applying a coating solution containing the polyvinyl alcohol resin and a surfactant of 0.5 parts by weight or less to 100 parts by weight of the polyvinyl alcohol resin on the resin substrate. A laminated body formed.