JP2015225122A - Method for manufacturing optical film laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical film laminate in which undesirable curling, wrinkles and axial misalignment are suppressed.SOLUTION: The method for manufacturing an optical film laminate comprises laminating a long optical functional film having a thickness of 30 μm or less along a conveyance direction on a long polarizing film laminate including a polarizing film and having a thickness of 80 μm or less. Prior to laminating the optical functional film, the polarizing film laminate is curled along a conveyance direction thereof to be convex in a direction toward a lamination surface of the optical functional film.

Description

  The present invention relates to a method for producing an optical film laminate.

  In a liquid crystal display device which is a typical image display device, polarizing plates are arranged on both sides of a liquid crystal cell due to the image forming method. As a method of manufacturing a polarizing plate, a protective film is disposed on each side of a polarizer, and an adhesive is supplied between the polarizer and the protective film while passing between a pair of rolls. A method is known in which a protective film is bonded to both sides of the film (for example, Patent Document 1).

  By the way, with the recent demand for thinning of an image display device, there is a demand for a technology capable of industrially manufacturing an optical film laminate having a thin polarizing film that is much thinner than the above polarizer. . In relation to such a method for producing an optical film laminate, for example, 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 element layer. After that, a method is proposed in which a protective film is bonded to the polarizing element layer side of the laminate, the resin substrate is peeled off, and another protective film is bonded to the surface from which the resin substrate is peeled to obtain a polarizing film laminate. (For example, Patent Document 2). An optical film laminate is obtained by laminating an optical functional film on such a polarizing film laminate. With the demand for thinning the image display device, there is a strong demand for thinning the optical functional film. Yes. However, when a thin polarizing film laminate and a thin optical functional film are laminated, undesired curls, wrinkles and / or axial misalignments may occur in the obtained optical film laminate.

Japanese Patent Laid-Open No. 11-179871 JP 2000-338329 A

  The present invention has been made to solve the above-described conventional problems, and a main object of the present invention is to provide a method for producing an optical film laminate in which undesired curling, wrinkling and axial displacement are suppressed.

The manufacturing method of the optical film laminated body by one Embodiment of this invention is a 80-micrometer-thick elongate polarizing film laminated body containing a polarizing film, and a 30-micrometer-thick elongate optical functional film in a conveyance direction. Laminating along. In this manufacturing method, before laminating the optical functional film, the polarizing film laminated body is curled so as to be convex in the direction of the laminated surface of the optical functional film along the transport direction.
In one embodiment, the polarizing film laminate includes a first protective film, the polarizing film, and a second protective film in this order, and the optical functional film is laminated on the first protective film side. The
In one embodiment, the curl of the polarizing film laminate is convex toward the first protective film.
In one embodiment, lamination | stacking of the said optical functional film is performed in the state which provided the tension | tensile_strength along a conveyance direction to each of the said polarizing film laminated body and this optical functional film, and the conveyance direction of this polarizing film laminated body The tension T _{1 applied} along the tension and the tension T _{2 applied} along the transport direction of the optical functional film satisfy the following formula: 100N ≦ T ₁ −T ₂ ≦ 170N.
In one embodiment, the polarizing film laminate is obtained by stretching and dyeing a laminate having a resin base material and a polyvinyl alcohol-based resin layer formed on one side of the resin base material. A step of producing a polarizing film; a step of laminating a first protective film on the opposite side of the polarizing film to the resin base; and peeling off the resin base to form the resin base of the polarizing film. And laminating a second protective film on the peeled side.
According to another aspect of the present invention, an optical film laminate is provided. This optical film laminate is obtained by the above production method.

  According to the present invention, in the method for producing an optical film laminate including laminating a thin and long optical functional film along a transport direction on a thin and long polarizing film laminate, Optical film lamination in which undesired curling, wrinkles, and axial misalignment are suppressed by curling the polarizing film laminate so as to be convex in the direction of the laminated surface of the optical functional film along the conveying direction before lamination. The body can be manufactured.

Fig.1 (a)-FIG.1 (e) are schematic which shows an example of the manufacturing method of the optical film laminated body by one Embodiment of this invention. It is the photograph which compares and shows the state of curl of the optical film laminated body obtained in Example 1 and Comparative Example 1, respectively.

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

  In the present specification, the expression “curl” is used in a context in which such a phenomenon of curling is preferred or a context that generally describes the phenomenon of curling. The phenomenon of curling is preferable means that the degree of curling is appropriate and the handleability of the polarizing film laminate and / or the optical film laminate is excellent. On the other hand, expressions such as “unwanted curl” or “severe curl” are used in the context that such a curl phenomenon is undesirable. More specifically, it means a case where the curl is so severe that operations such as bonding of the polarizing film laminate and / or the optical film laminate are difficult or impossible. It will be clear in which context the word “curl” will be used if the person skilled in the art reads the relevant description.

  In the method for producing an optical film laminate according to an embodiment of the present invention, a long optical film having a thickness of 30 μm or less is applied to a long polarizing film laminate having a thickness of 80 μm or less including a polarizing film along the conveying direction. Including laminating. Hereinafter, the production of the polarizing film, the production of the polarizing film laminate, and the production of the optical film laminate will be described in this order.

A. Production of polarizing film A-1. Laminated body Fig.1 (a)-FIG.1 (e) are schematic which shows an example of the manufacturing method of the optical film laminated body by one Embodiment of this invention. As shown in FIG. 1A, the laminate 10 includes a resin base material 11 and a PVA resin layer 12. The laminate 10 is typically manufactured by forming a PVA resin layer 12 on a long resin base material 11. Any appropriate method can be adopted as a method of forming the PVA-based resin layer 12. Preferably, the PVA-type resin layer 12 is formed by apply | coating the coating liquid containing PVA-type resin on the resin base material 11, and drying.

  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, it is possible to prevent problems such as deformation of the resin base material (for example, generation of unevenness, tarmi, wrinkles, etc.) when applying and drying the coating solution containing the PVA resin. Thus, a laminate can be manufactured 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 does not deform when applying and drying a coating solution containing a PVA-based resin. 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.

  You may mix | blend an additive with a coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer. Moreover, as an 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.

  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 thickness of the PVA resin layer before stretching is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

  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. By performing such a treatment, the adhesion between the resin substrate and the PVA resin layer can be improved.

A-2. Stretching of laminated body Any appropriate method may be adopted as a stretching method of the laminated body. 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 dissolved and infiltrated into the PVA-based resin layer by dyeing described later, preferably an iodide is blended in the stretching bath (boric acid aqueous solution). . By compounding iodide, elution of iodine dissolved and permeated into 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.

A-3. Dyeing The dyeing is typically performed by dissolving and penetrating a dichroic substance (preferably iodine) into the PVA resin layer. Examples of the dissolution and permeation method include a method of immersing a PVA resin layer (laminated body) in a staining solution containing iodine, a method of applying the staining solution to a PVA resin layer, and a method of applying the staining solution to a PVA resin. The method of spraying on a layer etc. is mentioned. Preferably, it is a method of immersing the laminate in the staining solution. This is because iodine can be dissolved and permeated 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.

A-4. 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 compounding iodide, elution of iodine dissolved and permeated into 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.

A-5. Polarizing Film The polarizing film is substantially a PVA resin film in which a dichroic substance dissolved and penetrated in a PVA resin is 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.

B. Lamination of the first protective film B-1. Outline of Lamination After the above treatments are applied to the laminate (PVA resin layer), as shown in FIG. 1B, a first protective film is formed on the polarizing film (PVA resin layer) 12 side of the laminate. 21 are stacked. Typically, the long first protective film is laminated on the long laminated body so that the longitudinal directions thereof are aligned (that is, along the conveying direction). In one embodiment, an adhesive is applied to the surface of the first protective film, and the first protective film is bonded to the surface of the polarizing film.

  In one embodiment, lamination | stacking (bonding) of a 1st protective film is performed under a heating. The heating temperature is a temperature at which the adhesive is dried when the adhesive described later is a water-based adhesive or a solvent-based adhesive, and the adhesive is cured when the adhesive is an active energy ray-curable adhesive. Temperature. The heating temperature is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and further preferably 60 ° C. or higher. On the other hand, the heating temperature is preferably 80 ° C. or lower. The heating performed when the first protective film is laminated may also serve as the drying treatment of the laminate.

B-2. The first protective film The first protective film may be a protective film that may be disposed on the optical cell side when the optical film laminate is bonded to the optical cell, and may be disposed on the opposite side of the optical cell. It may be a film. The first protective film may be a normal protective film and may have an optical compensation function (may be a retardation film). When the first protective film can be disposed on the optical cell side, the first protective film is substantially optically isotropic or has an appropriate optical compensation characteristic depending on the purpose (for example, a refractive index ellipsoid). , In-plane retardation, thickness direction retardation). When the first protective film can be disposed on the side opposite to the optical cell, the first protective film may be subjected to any appropriate surface treatment depending on the purpose. Specific examples of the surface treatment include hard coat treatment, antireflection treatment, antisticking treatment, diffusion treatment, and antiglare treatment.

  Any appropriate resin film may be employed as the first protective film depending on the purpose. Examples of the protective film forming material 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 resins. Examples thereof include resins. The “(meth) acrylic resin” refers to an acrylic resin and / or a methacrylic resin.

  The thickness of the first protective film is typically 10 μm to 45 μm, preferably 15 μm to 30 μm.

B-3. Adhesive used for laminating Any appropriate adhesive can be adopted as the adhesive used for laminating the first protective film. Specifically, the adhesive may be a water-based adhesive, a solvent-based adhesive, or an active energy ray-curable adhesive.

  As the active energy ray-curable adhesive, any appropriate adhesive can be used as long as it is an adhesive that can be cured by irradiation with active energy rays. Examples of the active energy ray curable adhesive include an ultraviolet curable adhesive and an electron beam curable adhesive. Specific examples of the curing type of the active energy ray-curable adhesive include a radical curing type, a cationic curing type, an anion curing type, and a combination thereof (for example, a radical curing type and a cationic curing type hybrid).

  Examples of the active energy ray-curable adhesive include an adhesive containing a compound (for example, a monomer and / or an oligomer) having a radical polymerizable group such as a (meth) acrylate group or a (meth) acrylamide group as a curing component. Can be mentioned.

  Specific examples of the active energy ray-curable adhesive and the curing method thereof are described in, for example, Japanese Patent Application Laid-Open No. 2012-144690. The description is incorporated herein by reference.

  Any appropriate aqueous adhesive can be adopted 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 5500, more preferably 1000 to 4500, 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 resin layer and the protective 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 1 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 curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm to 7 μm, more preferably 0.01 μm to 5 μm, still more preferably 0.01 μm to 2 μm, and most preferably 0.01 μm to 1 μm. If the thickness of the adhesive layer is too thin, the cohesive force of the adhesive itself cannot be obtained, and the adhesive strength may not be obtained. If the thickness of the adhesive layer is too hot, the polarizing film laminate and / or the optical film laminate may not be able to satisfy the durability.

C. Next, as shown in FIG. 1C, the resin base material 11 is peeled from the laminate of the resin base material 11, the polarizing film 12, and the first protective film 21. Any appropriate method can be adopted as the peeling method. For example, as shown in FIG. 1C, the resin base material 11 may be pulled down and peeled off, and the laminate of the polarizing film 12 and the first protective film 21 is pulled up to pull the resin base material 11. May be peeled off.

D. Production of polarizing film laminate (lamination of second protective film)
After peeling the resin base material, as shown in FIG. 1D, the second protective film 22 is laminated on the side of the laminate from which the resin base material has been peeled. In this way, the polarizing film laminate 100 is obtained. Typically, the long second protective film is laminated on the long laminated body so that the longitudinal directions thereof are aligned (that is, along the conveying direction). In one embodiment, an adhesive is applied to the second protective film, and the second protective film is bonded to the peeled side (substantially the polarizing film surface) of the laminate. The thickness of the second protective film is typically 20 μm to 100 μm, preferably 10 μm to 60 μm. The specific configuration and characteristics of the second protective film, the lamination conditions (for example, heating temperature) of the second protective film, and the adhesive used for laminating the second protective film are the lamination of the first protective film. Is as described above.

  The polarizing film laminate 100 obtained as described above has a thickness of 80 μm or less, preferably 35 μm to 75 μm. In the present invention, even if a thin optical functional film is laminated on such a thin polarizing film laminate, undesired curling, wrinkles and axial misalignment in the obtained optical film laminate can be satisfactorily prevented.

  In the present invention, the polarizing film laminate 100 is treated so as to be curled so as to be convex toward the surface on which the optical functional film is laminated before the optical functional film is laminated, which will be described in Section E below. . That is, when the optical functional film is laminated on the first protective film side, the polarizing film laminate 100 is processed so as to be curled on the first protective film side (the first protective film side is convex). When the optical functional film is laminated on the second protective film side, the polarizing film laminate 100 is treated so as to curl to the second protective film side (the second protective film side becomes convex). . By generating desired curl in the polarizing film laminate, it is possible to satisfactorily prevent undesired curling, wrinkles and axial misalignment in the obtained optical film laminate. As a process for generating a desired curl in the polarizing film laminate, typically, when the first protective film is bonded, the tension applied to the first protective film and the second protective film are bonded. And a method of adjusting the tension applied to the second protective film. The advantages of curling the polarizing film laminate as described above are as follows: The optical functional film used in the present invention is very thin and needs to be transported while maintaining a certain amount of tension along the transport direction. . That is, if the tension at the time of conveyance is insufficient, axis misalignment is likely to occur during lamination (bonding), and wrinkles are likely to occur in the optical functional film itself, resulting in poor appearance of the resulting optical film laminate. Is likely to occur. By curling the polarizing film laminate as described above, it is possible to bond the polarizing film laminate to the optical functional film while conveying the optical functional film while applying a tension of a predetermined value or more. As a result, it is possible to satisfactorily prevent axial misalignment, wrinkles and poor appearance in the obtained optical film laminate. In addition, when it bonds in this way, typically, the obtained optical film laminated body will be in the state curled so that it might become convex on the optical function film side. Since the optical functional film is usually disposed on the optical cell side, such curling makes it very easy to bond the optical film laminate to the optical cell. Therefore, such curl in the optical film laminate is a desired curl and is also referred to as a plus curl.

  The curl amount in the conveyance direction of the polarizing film laminate is preferably 40 mm to 80 mm, more preferably 50 mm to 60 mm. If the amount of curl in the transport direction is in such a range, undesired curling, wrinkling and axial misalignment in the obtained optical film laminate can be more satisfactorily prevented. In this specification, the “curl amount in the transport direction” means the curl amount at the end in the transport direction of the polarizing film laminate.

E. Production of optical film laminate (lamination of optical functional film)
Finally, as shown in FIG.1 (e), the optical function film 30 is laminated | stacked on the polarizing film laminated body 100, and the optical film laminated body 200 is obtained. Typically, the long optical functional film 30 is laminated on the long polarizing film laminate 100 along the transport direction. When laminating the optical functional film, the polarizing film laminate 100 is curled so as to be convex toward the surface on which the optical functional film is laminated as described above (in the illustrated example, it is convex toward the first protective film 21). (The curled state is not shown). The optical function film 30 may be laminated via an adhesive as described in the above section B-3, or may be laminated via any appropriate pressure-sensitive adhesive.

  The thickness of the optical functional film is 30 μm or less, preferably 10 μm to 25 μm. In the present invention, even when such a thin optical functional film is laminated on a thin polarizing film laminate, undesired curling, wrinkles and axial misalignment in the obtained optical film laminate can be satisfactorily prevented.

In one embodiment, lamination | stacking of the optical function film 30 is performed in the state which provided the tension | tensile_strength along a conveyance direction to each of the polarizing film laminated body 100 and the optical function film 30. FIG. In this case, the tension T _{1 applied} along the transport direction of the polarizing film laminate 100 and the tension T _{2 applied} along the transport direction of the optical function film 30 are preferably 100N ≦ T ₁ −T ₂ ≦ 170N. More preferably, 120N ≦ T ₁ −T ₂ ≦ 150N. By laminating under such conditions, undesired curls, wrinkles and axial misalignment in the resulting optical film laminate can be more satisfactorily prevented. Tension _{T 1} is preferably 300N～350N. Tension _{T 2} are, preferably 150N～250N.

  As the optical functional film 30, any appropriate optical film can be adopted depending on the purpose as long as it has the above thickness. Specific examples of the optical functional film include an optical compensation film (retardation film) and a wide viewing angle film. As the retardation film, a retardation film having any appropriate refractive index characteristic can be employed depending on the purpose and the driving mode of the liquid refueling device in which the optical film laminate is used. Preferably, the retardation film may be a retardation film capable of realizing desired optical compensation when the obtained optical film laminate is disposed in an IPS mode or VA mode liquid crystal display device.

F. Use of optical film laminate The optical film laminate can typically be used in an image display device. Typical examples of the image display device include a liquid crystal display device and an organic EL display device.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

[Example 1]
<Preparation of polarizing film laminate>
As the resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) was used. The resin substrate surface was subjected to corona treatment (58 W / m ² / min).
On the other hand, 10 wt% of acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer Z200”, polymerization degree 1200, saponification degree 99.0% or more, acetoacetyl modification degree 4.6%) The added PVA (polymerization degree 4200, saponification degree 99.2%) was prepared and applied to the corona-treated surface of the resin substrate so that the film thickness after drying was 12 μm. It dried for 10 minutes by drying and produced the laminated body which provided the PVA-type resin layer on the base material.

The obtained laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) 2.0 times between rolls having different peripheral speeds in an oven at 130 ° C. (air-assisted stretching).
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, the laminate was dyed at a liquid temperature of 30 ° C. (with water as a solvent, iodine concentration of 0.08 wt% to 0.25 wt%, potassium iodide concentration of 0.56 wt% to 1.75 wt%) Then, the concentration ratio of iodine and potassium iodide was immersed in 1: 7), and iodine was dissolved and infiltrated into the PVA resin layer (dyeing treatment). The immersion time and the iodine concentration in the dyeing bath were adjusted so that the obtained polarizing film (substantially the PVA resin layer) had a single transmittance of 42.0%.
Next, the laminate was added to 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 4 parts by weight of boric acid with respect to 100 parts by weight of water). It was immersed for 2 seconds (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). The underwater draw ratio was 2.0 times, and therefore the final draw ratio was 5.4 times. In this way, a polarizing film was produced on the resin substrate.
Thereafter, the laminate was immersed in a washing bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 3.5 parts by weight of potassium iodide with respect to 100 parts by weight of water) (cleaning treatment). Furthermore, the laminate was dried with hot air at 60 ° C. (drying process).

Subsequently, a first protective film (cycloolefin film, thickness 25 μm) is bonded to the polarizing film surface of the laminate of the polarizing film and the resin base material with a roll-to-roll method via a PVA adhesive. A laminate of resin base material / polarizing film / first protective film was prepared. Furthermore, after peeling the resin base material from this laminate, a second protective film (acrylic film, thickness 40 μm) was bonded to the peeled surface via a UV curable adhesive.
Thus, the elongate polarizing film laminated body which has a polarizing film with a thickness of 5 micrometers was produced. The thickness of the polarizing film laminate was 70 μm. The polarizing film laminate was curled so as to be convex toward the first protective film, and the curl amount in the transport direction was 60 mm.

<Preparation of optical film laminate>
An optical functional film (aliphatic ester-based retardation film, thickness 20 μm) is bonded to the first protective film side of the polarizing film laminate obtained above via an adhesive having a thickness of 20 μm. Was made. In addition, the tension T _{1 applied} in the transport direction of the polarizing film laminate at the time of bonding was 350 N, the tension T _{2 applied} in the transport direction of the optical function film was 230 N, and T ₁ -T ₂ was 120 N.

  The obtained optical film laminate was cut into sheets of a predetermined size, and the curled state and appearance were visually observed. The curl state is shown in FIG. 2 together with Comparative Example 1 described later. The curl amount was 1 mm to 5 mm, and was well suppressed. Furthermore, the obtained optical film laminate did not have defects in appearance such as bubbles and wrinkles.

[Measurement of curl amount of laminate]
Specific procedures and evaluation criteria for measuring the curl amount of the laminate are as follows (some are described above). The obtained polarizing film laminate or optical film laminate was cut into sheets of a predetermined size, and the curl amount was measured with the convex surface of the polarizing film laminate or optical film laminate facing downward. When the optical function film side is convex, it is defined as plus (+) curl, and when it is concave, it is defined as minus (−) curl.

[Comparative Example 1]
In the manufacturing process of the polarizing film laminate, the bonding conditions for bonding the first protective film were adjusted, except that the resulting polarizing film laminate was flat (the curl amount was 0 mm). In the same manner as in Example 1, an optical film laminate was produced. About the obtained optical film laminated body, the state and external appearance of the curl were observed visually. A curled state is shown in FIG. This optical film laminate had a cylindrical shape with severe concave curls on the optical functional film side.

  The optical film laminate of the present invention includes 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 copy machine, a printer, a fax machine, a clock, a microwave oven, etc., an organic EL panel It is suitably used for an antireflection film.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 Resin base material 12 Polyvinyl alcohol-type resin layer (polarizing film)
21 1st protective film 22 2nd protective film 30 Optical function film 100 Polarizing film laminated body 200 Optical film laminated body

Claims (6)

Including laminating a long optical functional film having a thickness of 30 μm or less along a transport direction on a long polarizing film laminate having a thickness of 80 μm or less including a polarizing film;
Before laminating the optical functional film, curling the polarizing film laminate so as to be convex in the direction of the laminated surface of the optical functional film along the transport direction,
Manufacturing method of optical film laminated body.   The said polarizing film laminated body contains a 1st protective film, the said polarizing film, and a 2nd protective film in this order, The said optical function film is laminated | stacked on this 1st protective film side. Production method.   The manufacturing method of Claim 2 with which the curl of the said polarizing film laminated body is convex on the said 1st protective film side. Lamination of the optical functional film is performed in a state in which tension is applied to each of the polarizing film laminate and the optical functional film along the transport direction, and tension applied along the transport direction of the polarizing film laminate. The manufacturing method according to any one of claims 1 to 3, wherein T ₁ and tension T _{2 applied} along the transport direction of the optical functional film satisfy the following formula:
100N ≦ T ₁ −T ₂ ≦ 170N The polarizing film laminate is
Stretching and dyeing a laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and producing a polarizing film on the resin substrate;
Laminating a first protective film on the opposite side of the polarizing film from the resin substrate;
5. The method according to claim 1, wherein the resin base material is peeled off and a second protective film is laminated on the side of the polarizing film from which the resin base material is peeled. Production method. The optical film laminated body obtained by the manufacturing method in any one of Claim 1 to 5.