JP2013061377A - Method of manufacturing polarizer plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a polarizer plate in which occurrence of wave curling is suppressed while employing a method in which transparent resin films are superposed on a polarizer film via an ultra violet curing adhesive, and the polarizer film is irradiated with ultra violet while brought into close contact with a roller.SOLUTION: The method for manufacturing the polarizer plate includes: forming a laminate 4 by transporting the polarizer film 1 in a constant direction, and laminating the transparent resin films 2 and 3 via an ultraviolet curing adhesive; bringing the laminate 4 into close contact with a roller 23 which is arranged so that its convex curved surface is placed in the transporting direction of the laminate 4; and radiating ultra violet by an ultraviolet radiating device 16 from a side opposite to the surface where the laminate 4 closely contacts with the roller 23 to cure the adhesive. The convex curved surface of the roller 23 has a surface roughness of 0.4 to 1.2 μm at maximum height Rz of its contour curve. The static friction coefficient of the convex curved surface with the surface of the closely contacted laminate 4 is within a range of 0.2 to 1.0.

Description

  The present invention relates to a method for producing a polarizing plate useful as one of optical components constituting a liquid crystal display device.

  In recent years, liquid crystal display devices that consume less power, operate at a low voltage, and are light and thin have rapidly spread as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. .

  A polarizing plate used as one of the optical components constituting a liquid crystal display device is a transparent resin film bonded on at least one side, usually both sides, of a polarizing film made of a polyvinyl alcohol resin to which a dichroic dye is adsorbed and oriented. The liquid crystal panel is adhered to a liquid crystal cell through an adhesive layer and used as a liquid crystal panel. The transparent resin film bonded to one surface of the polarizing film has a function as a so-called protective film for protecting the polarizing film made of a polyvinyl alcohol-based resin, but the transparent resin film is provided on both surfaces of the polarizing film. When pasting, the other transparent resin film has not only a function as a protective film but also a function as a so-called optical compensation film for the purpose of optical compensation of liquid crystal cells and improvement of the viewing angle of liquid crystal display devices. It is often.

  Conventionally, an aqueous solution mainly composed of a polyvinyl alcohol resin has been used as an adhesive for laminating a polarizing film and a transparent resin film, but such aqueous adhesives are limited to applicable resin films. Also, it takes a certain amount of time for drying and curing. In recent years, various transparent resin films have been required to be bonded to polarizing films as protective films and as optical compensation films. Then, since it has the advantage that it can be applied to various transparent resin films, has a short curing time, and does not dissipate harmful substances into the atmosphere, a proposal using an ultraviolet curable adhesive has been made. For example, in Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 1), a transparent resin film (referred to as “protection” in the same document) is applied to a polarizing film using an adhesive composed of an epoxy compound that does not contain an aromatic ring as a main component. A technique for making a polarizing plate is disclosed in which an adhesive is cured by irradiating an active energy ray typified by ultraviolet rays.

  However, a polarizing plate manufactured using such an ultraviolet curable adhesive is curled so that the side to be attached to the liquid crystal cell is concave, so-called reverse curling, or a state in which the polarizing plate is manufactured in a long length In other words, there is a problem that a so-called wave curl is generated in the width direction. Such reverse curl or wave curl tends to leave bubbles on the sticking surface when sticking to the liquid crystal cell, and causes a defect in the liquid crystal panel. Therefore, it is conventionally desired that the polarizing plate has no reverse curl or wave curl, does not curl, or has a so-called normal curl in which the side to be attached to the liquid crystal cell becomes convex even when curled.

  Therefore, JP 2009-134190 A (Patent Document 2) polymerizes an adhesive in a state in which a laminate in which a transparent resin film is superimposed on a polarizing film via an adhesive is bent so as to have a positive curl. A technique for suppressing the occurrence of reverse curling and wave curling by curing is disclosed. In the examples of this document, a triacetyl cellulose film is laminated on one side of a polarizing film, and an amorphous polyolefin resin film is laminated on the other side via an ultraviolet curable adhesive. While adhering the triacetyl cellulose film side to the outer peripheral surface of the cooling roll along its longitudinal direction (conveying direction), the above-mentioned adhesive is polymerized and cured by irradiating ultraviolet rays from the amorphous polyolefin resin film side. . In addition, there is a statement that the outer peripheral surface of the cooling roll that adheres the laminated body is mirror-finished. However, when the laminated body is adhered to the mirror-finished cooling roll and irradiated with ultraviolet rays, the cooling roll is cooled. Depending on the combination with the film in close contact with the roll and the operating conditions, wave curling may still occur.

JP 2004-245925 A JP 2009-134190 A

  Therefore, an object of the present invention is to superimpose a transparent resin film on a polarizing film via an ultraviolet curable adhesive, and to irradiate ultraviolet rays while adhering to a contact body having a convex curved surface formed along the longitudinal direction. An object of the present invention is to provide a method capable of producing a polarizing plate in which generation of wave curl is suppressed while being adopted.

  As a result of intensive research to solve such problems, a laminate in which a transparent resin film is superimposed on a polarizing film via an ultraviolet curable adhesive is used to obtain a convex surface that has been roughened to some extent so that it has a predetermined surface roughness. It has been found that the use of a contact body having a curved surface and having a static friction coefficient with the laminate surface in close contact with the surface of the laminate within a predetermined range suppresses the occurrence of wave curling, thereby completing the present invention.

  That is, according to the present invention, while a polarizing film made of a polyvinyl alcohol resin is conveyed in a certain direction, a transparent resin film is laminated thereon via an ultraviolet curable adhesive to form a laminated body. Adhering to a contact body having a convex curved surface formed in an arc shape along the conveying direction, and curing the adhesive by irradiating ultraviolet rays from the opposite side of the surface of the laminate to the contact body. A method of manufacturing a polarizing plate, wherein the convex surface of the contact body has a surface roughness in the range of 0.4 to 1.2 μm expressed by the maximum height Rz of the contour curve, and is in close contact therewith. There is provided a method for producing a polarizing plate, wherein the coefficient of static friction with the surface of the laminated body is in the range of 0.2 to 1.0.

  In this method, a transparent resin film is laminated on both surfaces of a polarizing film via an ultraviolet curable adhesive to form a laminate, and one transparent resin film of the laminate is adhered to the contact body, and the other transparent This is particularly effective when the adhesive is cured by irradiating ultraviolet rays from the resin film side. In these methods, the contact body having the convex curved surface is typically composed of a metal roll, but further has a surface temperature adjusting function, and the laminate is cooled and irradiated with ultraviolet rays. It is preferable to do so. The polarizing plate produced by these methods is typically bonded to a liquid crystal cell to form a liquid crystal panel, and the surface opposite to the surface bonded to the liquid crystal cell is the contact body described above. It is preferable that it adheres closely.

  According to the method of the present invention, a polarizing plate in which the occurrence of wave curl is suppressed can be produced.

It is a schematic side view which shows an example of the manufacturing apparatus of the polarizing plate suitable for enforcing the method of this invention. In the Example mentioned later, it is a figure which shows the evaluation method of the wave curl which arises in a polarizing plate, Comprising: (A) is a perspective view for demonstrating a wave number and the wavelength L, and a figure which shows the measurement location of an amplitude, (B ) Is an enlarged side view for explaining the wavelength L and the amplitude A. FIG.

  With reference to FIG. 1, in this invention, while conveying the polarizing film 1 in a fixed direction, the transparent resin films 2 and 3 are piled up there via a ultraviolet curable adhesive agent, and it is set as the laminated body 4, and obtained lamination | stacking The body 4 is brought into close contact with a contact body 23 having a convex curved surface formed in an arc shape along the conveying direction, and the ultraviolet irradiation device 16 is disposed on the opposite side of the surface of the laminate 4 that is in close contact with the contact body 23. Then, the above-mentioned adhesive is cured by irradiating with ultraviolet rays to manufacture the polarizing plate 5.

  The nip rolls 21 and 22 for bonding are used for superimposing the polarizing film 1 and the transparent resin films 2 and 3. The transparent resin films 2 and 3 may be bonded to one surface of the polarizing film 1 or may be bonded to both surfaces of the polarizing film 1, but preferably are bonded to both surfaces of the polarizing film 1 as illustrated. Is done. In either case, when the obtained polarizing plate 5 is attached to a liquid crystal cell to form a liquid crystal panel, the surface opposite to the surface attached to the liquid crystal cell is in close contact with the contact body 23, It is preferable that the polarizing plate 5 to be obtained has a positive curl so that the surface to be attached is irradiated with ultraviolet rays from the ultraviolet irradiation device 16. The contact body 23 is preferably composed of a roll as shown in the figure. The manufactured polarizing plate 5 is wound around the product roll 30 through the conveyance guide roll 24 and the pre-winding nip rolls 25 and 26. On one surface of the polarizing film 1 and the surfaces of the first transparent resin film 2 and the second transparent resin film 3 on which the adhesive is not applied, conveyance guide rolls 28 and 28 are appropriately provided. The straight arrows in the figure indicate the film flow direction, and the curved arrows indicate the roll rotation direction.

  Hereinafter, the polarizing film 1, the transparent resin films 2 and 3, and the adhesive constituting the polarizing plate 5 will be described first, and then the description of the method for manufacturing the polarizing plate will proceed.

[Polarized film]
The polarizing film 1 is made of a polyvinyl alcohol resin, and the polyvinyl alcohol resin is obtained by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin may be not only polyvinyl acetate, which is a homopolymer of vinyl acetate, but also a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group. The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably in the range of 1,500 to 5,000.

  What formed the polyvinyl alcohol-type resin into a film form is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The raw film made of a polyvinyl alcohol resin can have a thickness of about 10 to 150 μm, for example.

  A polarizing film is usually a step of stretching a polyvinyl alcohol-based resin film, a step of dyeing a polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, a polyvinyl alcohol-based adsorbed dichroic dye The resin film is manufactured through a step of treating with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing, or may be performed after dyeing. When stretching is performed after dyeing, this stretching may be performed before boric acid treatment or during boric acid treatment. Of course, it is also possible to perform stretching in these plural stages. In extending | stretching, you may extend | stretch between nip rolls from which peripheral speeds differ, and you may extend | stretch using a hot roll. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 3 to 8 times.

  In order to dye the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. In addition, before the dyeing | staining process by a dichroic dye, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water, and is fully swollen.

  When iodine is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine and potassium iodide content in this aqueous solution is usually 0.01 to 1 part by weight of iodine and 0.5 to 20 parts by weight of potassium iodide per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the dye aqueous solution used for dyeing is usually 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 10 to 1,800 seconds.

  The boric acid treatment after dyeing with the dichroic dye is performed by a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably further contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of immersing a boric acid-treated polyvinyl alcohol resin film in water. The water temperature in the water washing treatment is usually 2 to 40 ° C., and the immersion time is usually 2 to 120 seconds. After washing with water, a drying process is performed to obtain a polarizing film. The drying treatment can be performed using a hot air dryer or a far infrared heater. This drying process is performed in a drying furnace kept at 40 to 100 ° C., preferably 50 to 100 ° C., over about 30 to 600 seconds. There may be a plurality of drying furnaces, and when a plurality of drying furnaces are provided, each temperature may be the same or different. In particular, when performing drying by providing a plurality of drying furnaces, it is preferable to provide a temperature gradient so that the temperature increases from the front stage of the drying furnace to the rear stage of the drying furnace.

  The thickness of the polarizing film thus obtained can be, for example, about 5 to 40 μm, and preferably 10 to 35 μm.

[Transparent resin film]
In the present invention, the polarizing film 5 is obtained by laminating the transparent resin films 2 and 3 on one side or both sides of the polarizing film 1 made of the polyvinyl alcohol resin produced as described above via an ultraviolet curable adhesive. To manufacture.

  The transparent resin films 2 and 3 may be films made of a thermoplastic resin having transparency, and various types used in the field of polarizing plates can be used in the present invention as well. Examples of resins that can be used as transparent resin films 2 and 3 include cellulose acetate-based resins typically represented by triacetyl cellulose and diacetyl cellulose, amorphous polyolefin resins typically represented by cycloolefin-based resins, and polypropylene-based resins. There are a crystalline polyolefin resin as a representative example, an acrylic resin with a methyl methacrylate resin as a representative example, a polyester resin with a polyethylene terephthalate resin as a representative example, and a polycarbonate resin.

  The cellulose acetate-based resin is a cellulose partial or completely esterified product, and examples thereof include cellulose acetate ester, propionate ester, butyrate ester, and mixed ester thereof. More specifically, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like can be mentioned. An appropriate commercial item can be used for the film which consists of cellulose acetate type-resins. Examples of commercially available cellulose acetate-based resin films suitable for use in the present invention are “Fujitac TD80”, “Fujitac TD80UF” and “Fujitac TD80UF” sold by FUJIFILM Corporation. There are Fujitac TD80UZ, KC8UX2M, KC8UY and KC4UY sold by Konica Minolta Opto.

  The cellulose acetate-based resin film may be disposed on the liquid crystal cell side when the polarizing plate is attached to the liquid crystal cell. In that case, it is preferable to impart an optical compensation function to the cellulose acetate-based resin film. For example, a film in which a compound having a retardation adjustment function is contained in a cellulose acetate-based resin, a film in which a compound having a retardation adjustment function is applied to the surface of a cellulose acetate-based resin film, a cellulose acetate-based resin film uniaxially or biaxially And a stretched film. Examples of commercially available cellulose acetate-based optical compensation films include “WV (Wide View) film WV BZ 438” and “WV (WIDE VIEW) film WV EA”, Konica Minolta, sold by FUJIFILM Corporation. There are “KC4FR-1”, “KC4HR-1” and “KC4UEW” sold by Opt.

  Amorphous polyolefin resin is a resin having a structural unit derived from a cyclic olefin such as norbornene or a polycyclic norbornene-based monomer, and is a copolymer of a cyclic olefin and another compound having a polymerizable carbon-carbon double bond. It may be a coalescence. Specifically, ring-opening metathesis polymerization of norbornene or a derivative thereof, and what is called a thermoplastic saturated norbornene-based resin in which unsaturated bonds are eliminated by hydrogenation of the resulting polymer, norbornene or a derivative thereof with a chain olefin and And / or an aromatic vinyl compound obtained by addition polymerization. As the film made of the amorphous polyolefin resin, an appropriate commercial product can be used. Examples of commercially available amorphous polyolefin resin films suitable for use in the present invention are all trade names, “Arton Film” sold by JSR Corporation, and sold by Nippon Zeon Corporation. "Zeonor film" and "Essina retardation film" sold by Sekisui Chemical Co., Ltd.

  The crystalline polyolefin resin is a crystalline resin having a main structural unit of a chain olefin such as ethylene or propylene, and is typically a polypropylene resin. The polypropylene resin includes a propylene homopolymer, a random copolymer of propylene and other monomers copolymerizable therewith, such as a random copolymer of ethylene or α-olefin, a block copolymer, and the like. An appropriate commercial product can also be used for the film made of polypropylene resin. Examples of suitable commercially available polypropylene resin films are all trade names, “Tosero” sold by Mitsui Chemicals Tosero Co., Ltd., “Pyrene Films” sold by Toyobo Co., Ltd., There are "Trefan" sold by Toray Industries, Inc., "Santox" sold by Sun Tox Corporation, and "FILMAX CPP film" sold by FILMAX.

  The acrylic resin is a resin having alkyl methacrylate as a main structural unit, and among them, a methyl methacrylate resin having methyl methacrylate as a main structural unit is representative. As the film made of an acrylic resin, an appropriate commercially available product can be used. Examples of suitable commercially available acrylic resin films are trade names such as “Technoloy” sold by Sumitomo Chemical Co., Ltd. and “Acryprene” sold by Mitsubishi Rayon Co., Ltd. .

  The polyester resin is a resin having an ester bond —COO— in the main chain, and includes a polyethylene terephthalate resin, a polybutylene terephthalate resin, a polyethylene naphthalate resin, etc. Among them, a polyethylene terephthalate resin is typical. . The polyethylene terephthalate resin is usually a resin in which 80 mol% or more of the repeating units are composed of ethylene terephthalate, and may contain a structural unit derived from another copolymer component. As the film made of polyethylene terephthalate resin, an appropriate commercially available product can be used. Examples of suitable commercially available polyethylene terephthalate resin films include “Diafoil” sold by Mitsubishi Plastics, Inc. and “Teijin Tetron” sold by Teijin DuPont Films, Inc. Film "," Toyobo Ester Film "and" Cosmo Shine "sold by Toyobo Co., Ltd.," Lumirror "sold by Toray Industries, Inc. and" Emblet "sold by Unitika Co., Ltd. .

  The polycarbonate resin is a resin having a carbonate bond —O—CO—O— in the main chain. For example, a resin using bisphenol A as a raw material is typical. As the film made of polycarbonate resin, an appropriate commercial product can be used. Examples of suitable commercially available polycarbonate resins are "Iupilon sheet" sold by Mitsubishi Engineering Plastics Co., Ltd. and "Panlite sheet" sold by Teijin Chemicals Ltd. and so on.

  Prior to bonding to the polarizing film 1, the transparent resin films 2 and 3 may be subjected to easy adhesion treatment such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment on the bonding surface. Moreover, the surface on the opposite side to the bonding surface to the polarizing film 1 of the transparent resin films 2 and 3 may have various processing layers, such as a hard-coat layer, an antireflection layer, and an anti-glare layer. The thickness of the transparent resin films 2 and 3 is usually in the range of about 5 to 200 μm, preferably 10 to 120 μm, more preferably 10 to 85 μm.

[adhesive]
As an adhesive for bonding the polarizing film 1 and the transparent resin films 2 and 3, an ultraviolet curable adhesive is used from the viewpoints of weather resistance, refractive index, cationic polymerization, and the like. There are two types of ultraviolet curable adhesives, one that is cured by radical polymerization and the other that is cured by cationic polymerization. In particular, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-245925), A cationically polymerizable adhesive mainly comprising an epoxy compound containing no aromatic ring is preferably used. Examples of such epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. A cationically polymerizable compound, typically an epoxy compound, is mixed with a photocationic polymerization initiator that generates cationic species or Lewis acid upon irradiation with ultraviolet rays and initiates cationic polymerization of the cationically polymerizable compound. An adhesive is prepared. In addition to UV curable adhesives, various additives such as thermal cationic polymerization initiators and photosensitizers that generate cationic species or Lewis acids by heating to initiate cationic polymerization of cationically polymerizable compounds You can also.

[Production method of polarizing plate]
Next, the manufacturing method of the polarizing plate which concerns on this invention is demonstrated, referring FIG. 1 will be described again. In this example, the first transparent resin film 2 is supplied to one surface of the polarizing film 1 conveyed in a certain direction, and the other surface of the polarizing film 1 has a first surface. The second transparent resin film 3 is supplied, and these three films are superposed by the nip rolls 21 and 22 for bonding to form a laminate 4, and after receiving the ultraviolet irradiation from the ultraviolet irradiation device 16, the conveyance guide roll 24. And the apparatus is comprised so that the polarizing plate 5 obtained may be wound up by the product roll 30 through the nip rolls 25 and 26 before winding.

  In the polarizing film manufacturing process (not shown), the polarizing film 1 is left as it is in a state where it is manufactured by uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment after dyeing on the polyvinyl alcohol resin film by the method described above. Of course, the material manufactured in the polarizing film manufacturing process may be wound around a roll and then fed out by a feeding machine. On the other hand, the first transparent resin film 2 and the second transparent resin film 3 are each fed out from a roll (not shown) by a feeding machine. Each film is transported at the same transport speed so that the flow directions are the same.

  In the first transparent resin film 2, after the adhesive is applied in advance from the first coating machine 11 to the surface to be bonded to the polarizing film 1, the adhesive-coated surface is superimposed on one surface of the polarizing film 1. Is done. On the other hand, the second transparent resin film 3 is coated with an adhesive from the second coating machine 13 on the surface to be bonded to the polarizing film 1, and then the adhesive coating surface is the other of the polarizing film 1. Superimposed on the surface.

  In the 1st coating machine 11 and the 2nd coating machine 13, it seems to apply | coat an adhesive agent to the 1st transparent resin film 2 and the 2nd transparent resin film 3, respectively from the gravure rolls 12 and 14 with which each is equipped. It has become. Here, the gravure roll is a roll having a concave groove, and the concave groove is previously filled with an adhesive, and the transparent resin films 2 and 3 are rotated on the transparent resin films 2 and 3 in this state. It is designed to transfer the adhesive. In the example shown here, the gravure rolls 12 and 14 are configured to rotate in opposite directions at the respective contact portions with respect to the transport directions of the first transparent resin film 2 and the second transparent resin film 3. . In addition, other coating methods such as doctor blades, wire bars, die coaters, comma coaters, etc. can be applied to the coating machines 11 and 13, but thin film coating, freedom of pass lines, and widening of the width are possible. Considering the correspondence and the like, a gravure coater having gravure rolls 12 and 14 as shown in the drawing is preferable.

  When the adhesive is applied using the gravure coater having the gravure rolls 12 and 14 as the first coating machine 11 and the second coating machine 13, a line corresponding to the traveling speed of the transparent resin films 2 and 3. By adjusting the ratio of the speed and the rotational peripheral speed of the gravure rolls 12, 14, the thickness of the adhesive layer can be adjusted as appropriate. The coating thickness of the adhesive layer is preferably about 1 to 10 μm, for example.

  The first transparent resin film 2 and the second transparent resin film 3 to which the adhesive has been applied are overlapped with the polarizing film 1 on the adhesive application surface, respectively, and are sandwiched between the bonding nip rolls 21 and 22 and added in the thickness direction. The three layers 4 are conveyed to the contact body 23 by being pressed. The contact body 23 has a convex curved surface formed in an arc shape along the transport direction (longitudinal direction) of the laminate 4. Then, the laminate 4 is conveyed while being in close contact with the convex curved surface. In the process, the laminate 4 is irradiated with ultraviolet rays from the ultraviolet irradiation device 16 and the adhesive is polymerized and cured. In the illustrated example, the contact body 23 is configured by a roll. In addition to this, the contact body 23 can also be constituted by, for example, an endless belt. However, it is general that the contact body 23 is constituted by a roll as shown in FIG.

  In particular, when the adhesive is polymerized and cured by irradiating the laminate 4 with ultraviolet rays, heat may be generated. In such a case, the contact body 23 is constituted by a metal roll, and the temperature adjusting function is provided there. It is effective to make it act as a cooling roll. The temperature adjusting function can be provided by a method in which a fluid passage is provided inside the metal roll and a cooling fluid, for example, water is allowed to flow therethrough. In that case, it is preferable that the surface temperature of a cooling roll shall be about 20-25 degreeC. When the contact body 23 is composed of a metal roll, it is also effective to increase the surface hardness by subjecting the surface thereof to a hard chrome plating process or a ceramic spraying process.

  From the viewpoint of the stability of the polarizing plate 5 to be obtained, the contact body 23 preferably made of a roll makes the contact body 23 itself rotatable as shown in the figure, and rotates according to the conveyance of the laminated body 4 or the rotation thereof. Accordingly, it is preferable that the laminate 4 is conveyed. However, as defined in the present invention, if the surface is roughened to some extent and the coefficient of static friction with the surface of the laminate 4 adhered thereto is kept within a predetermined range, the line speed of the laminate 4 and the contact body Even when the outer peripheral movement speeds of 23 are not completely coincident with each other and some slip occurs between them, a polarizing plate having no surface defect and no wave curl can be produced.

  The second transparent resin film 3 side of the laminate 4 is brought into close contact with the contact body 23, and ultraviolet rays are irradiated from the ultraviolet irradiation device 16 on the opposite side of the laminate 4, that is, the first transparent resin film 2 side. By this ultraviolet irradiation, the adhesive between the first transparent resin film 2 and the polarizing film 1 and the adhesive between the polarizing film 1 and the second transparent resin film 3 are cured, respectively. One transparent resin film 2 and the polarizing film 1, and the second transparent resin film 3 and the polarizing film 1 are bonded together.

The light source used for the ultraviolet irradiation device 16 is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, A metal halide lamp or the like can be used. The light irradiation intensity to the ultraviolet curable adhesive may be determined according to the composition of the adhesive to be used and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the initiator is 0.1 to 0.1. It is preferable to be 1,000 mW / cm ² .

The irradiation time of the ultraviolet rays to the laminate 4 is determined according to the composition of the ultraviolet curable adhesive to be used and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 2. It is preferably set to be 000 mJ / cm ² . From the viewpoint of sufficiently polymerizing and curing the adhesive in a state where the laminate 4 is in close contact with the contact body 23, this accumulated light amount of 10 to 2,000 mJ / cm ² is achieved while the laminate 4 passes through the contact body 23. It is particularly preferable to do so. If the integrated light quantity at this time is too small, the generation of active species derived from the initiator is not sufficient, and the adhesive may be insufficiently cured. On the other hand, when the integrated light quantity is too large, the transparent resin film, the polarizing film and / or the adhesive may be deteriorated by the irradiated ultraviolet rays.

The line speed of the laminate 4 is not particularly limited, but at least irradiation intensity is 0.1 mW / cm ² or more and irradiation time is 0.3 seconds or more while applying a tension of 100 to 800 N in the conveying direction (longitudinal direction). It is preferable to carry it under conditions. Since the transparent resin film 2 located on the ultraviolet irradiation device 16 side effectively cures the adhesive by the irradiated ultraviolet rays, the transparent resin film 2 is in a part or all of the wavelength region effective for activating the initiator constituting the adhesive. The transmittance is preferably 60% or more.

  The laminated body 4 after receiving the irradiation of ultraviolet rays and curing the adhesive becomes the polarizing plate 5, and is wound around the product roll 30 through the conveyance guide roll 24 and the pre-winding nip rolls 25 and 26.

[Relationship between the contact body (roll) 23 and the surface of the laminate 4 in close contact therewith]
In the present invention, from the viewpoint of suppressing wave curling of the polarizing plate 5 to be obtained, the contact body 23 preferably composed of a roll and the surface of the laminated body 4 in close contact therewith, that is, in the example of FIG. The coefficient of static friction between the second transparent resin film 3 is set in the range of 0.2 to 1.0.

  When two objects try to move relative to each other while they are in contact, the force acting in the tangential direction of the contact surface in an attempt to stop the movement is called the static friction force, and the two objects just start to slide. When this occurs, the static friction force becomes maximum, and this value is called the maximum static friction force. At this time, a load is also applied in the vertical direction of the contact surface. The ratio F / P between the maximum static friction force F and the vertical load P acting on the two adjacent objects is called the static friction coefficient. This static friction coefficient is not only the combination of the materials constituting the two objects, but also the surface cleanliness. It is a value governed by degree, smoothness and quality. Therefore, the coefficient of static friction between the contact body (roll) 23 and the laminate 4 mainly depends on the material of the second transparent resin film 3 constituting the laminate 4 and the surface state of the contact body (roll) 23. Will be ruled.

  The friction coefficient test when both objects are in the form of a film or a sheet is specified in JIS K 7125: 1999 “Plastic-Film and Sheet-Friction Coefficient Test Method”. There is also a commercially available measuring machine configured to display the coefficient of static friction between both objects by simply placing the object (which must be in the form of a film or sheet) on the other object. Yes. One such measuring machine is the “Tribogear Portable Friction Meter Muse TYPE: 94i2” sold by Shinto Kagaku Co., Ltd. Details of this tribometer can be found at <URL: http: //www.heidon.co.jp/support/catalog/tst/pdf/TYPE94i.pdf> (searched on March 24, 2011) on the company's website. It has been published. When this portable tribometer is used, the coefficient of static friction can be easily measured.

  The transparent resin film 3 that is in close contact with the contact body (roll) 23 is cut into an appropriate size and attached to the detection unit of the portable tribometer, and is left on the stationary contact body (roll) 23 to start the start button. If you press, the coefficient of static friction between them is displayed. If necessary, this measurement can be performed a plurality of times, and the average value can be used as the coefficient of static friction between the two. In order to obtain a static friction coefficient close to the true value, it is preferable to employ an average value obtained by performing a plurality of measurements in this way.

  When the coefficient of static friction between the contact body (roll) 23 and the second transparent resin film 3 is less than 0.2, the polarizing plate 5 is shrunk with the curing shrinkage of the adhesive, and wave curling is likely to occur. On the other hand, when the coefficient of static friction exceeds 1.0, the contact force between the contact body (roll) 23 and the laminate 4 becomes too strong, and the contact body (roll) 23 and the nip rolls 25 and 26 before winding are between them. Abnormal tension occurs, and the laminate 4 is transformed into a polarizing plate while being deformed.

  In order to achieve the static friction coefficient as described above, the surface roughness of the contact body (roll) 23 is represented by the maximum height Rz of the contour curve so as to be within the range of 0.4 to 1.2 μm. This Rz is more preferably in the range of 0.4 to 0.8 μm. From this range, an optimal value may be selected as appropriate in consideration of the material of the transparent resin film 3 that is in close contact with the contact body (roll) 23. When the surface roughness Rz is less than 0.4 μm, the contact force between the contact body (roll) 23 and the second transparent resin film 3 that is in close contact therewith increases, and the possibility that the coefficient of static friction exceeds 1.0 increases. . On the other hand, if the Rz exceeds 1.2 μm, the possibility of generating minute scratches on the second transparent resin film 3 adhered thereto increases.

  The maximum height Rz of the contour curve is a value specified in JIS B 0601: 2001 “Product Geometric Characteristics Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definition, and Surface Property Parameters”. The contact body (roll) 23 employed in the present invention corresponds to the maximum height of the surface irregularities. The maximum height Rz of the contour curve can be measured using a commercially available surface roughness meter. “Handy Surf E-35A” used in the examples described later and sold by Tokyo Seimitsu Co., Ltd. is one of the commercially available surface roughness meters.

  When the contact body 23 is formed of a metal roll, for example, the surface thereof is subjected to a hard chrome plating process, and then the hard chrome plating surface is polished with a grindstone or a buff. By selecting the particle size, and in the case of buffing, it is possible to obtain an arbitrary surface roughness by selecting the type and particle size of the abrasive.

[Other description]
As described above, the polarizing plate produced by the method of the present invention is attached to a liquid crystal cell and is suitably used for constituting a liquid crystal panel. And the polarizing plate which gives a positive curl when sticking to a liquid crystal cell can be manufactured. The final curl state depends on the heat history after manufacturing the polarizing plate and the method of forming the pressure-sensitive adhesive layer. When the laminate 4 is brought into close contact with the outer peripheral surface of the contact body (roll) 23, the liquid crystal The surface to be attached to the cell is the outer side (convex), that is, the ultraviolet irradiation device 16 side, and the opposite surface is the inner side, that is, the contact body (roll) 23 side. If the convex state is maintained, the positive curl is easily obtained. In this form, when the transparent resin films 2 and 3 are bonded to both surfaces of the polarizing film 1 as in the example shown in FIG. 1, the surface bonded to the liquid crystal cell becomes the first transparent resin film 2. What should I do? It is customary to provide an adhesive layer on the surface to be adhered to the liquid crystal cell for the purpose of adhesion.

  On the other hand, when a transparent resin film is bonded to only one surface of the polarizing film 1 to form a polarizing plate, the polarizing film surface to which the transparent resin film is not bonded is usually bonded to a liquid crystal cell in many cases. Therefore, in that case, the polarizing film surface of the laminate laminated in the layer configuration of polarizing film / transparent resin film is the outer side (convex), that is, the ultraviolet irradiation device 16 side, and the transparent resin film surface is the inner side, that is, the contact body ( If the roll is on the side of the roll (23) and the convex state is maintained when the roll is in close contact with the contact body (roll) 23, then a positive curl is easily obtained. Also in this case, it is usual to provide a pressure-sensitive adhesive layer on the surface of the polarizing film to be adhered to the liquid crystal cell for the purpose of adhesion. Therefore, when a transparent resin film is bonded only to one surface of the polarizing film 1, the convex state when the wound state after curing the adhesive is brought into close contact with the contact body (roll) 23 is maintained. Assuming that the first transparent resin film in FIG. 1 is omitted, it is preferable that only the second transparent resin film 3 is overlaid on the polarizing film 1.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Example 1]
Using a device generally arranged as shown in FIG. 1, a polarizing film 1 having a thickness of about 30 μm in which iodine is adsorbed and oriented on a polyvinyl alcohol film is continuously conveyed, and on one side thereof, from Nippon Zeon Co., Ltd. “Zeonor film”, which is an amorphous polyolefin resin film having a thickness of 60 μm and a width of 1,330 mm, is used as the first transparent resin film 2, and the thickness obtained from FUJIFILM Corporation on the other side. “Fujitac TD80”, which is a triacetyl cellulose film having a width of 80 μm and a width of 1,330 mm, was supplied as the second transparent resin film 3, respectively. And on the bonding surface to the polarizing film 1 of the 1st transparent resin film 2, from the 1st coating machine 11 ("Micro chamber doctor" by Fuji Machine Co., Ltd.) provided with the gravure roll 12, it is 1st. Epoxy compounds from a second coating machine 13 (also a “micro chamber doctor” manufactured by Fuji Machine Co., Ltd.) also provided with a gravure roll 14 on the bonding surface of the second transparent resin film 3 to the polarizing film 1. And an ultraviolet curable adhesive in which a cationic photopolymerization initiator was blended, so that the thickness was about 2 μm.

  Next, the adhesive application surfaces of the first transparent resin film 2 and the second transparent resin film 3 are overlapped on both surfaces of the polarizing film 1, and are sandwiched and bonded by the nip rolls 21 and 22 for bonding. It was. While the laminated body 4 is continuously wound around the outer surface of the cooling roll 23 whose surface temperature is set to 23 ° C., the triacetyl cellulose film side which is the second transparent resin film 3 is wound, In minutes, it was conveyed with a tension of 600 N in the longitudinal direction. The cooling roll 23 has a surface roughness of 0.4 μm expressed by the maximum height Rz of the contour curve by polishing the surface of the steel roll with a hard chrome plating and polishing with a # 3000 grindstone. Was used. The surface roughness is a value measured with a surface roughness meter “Handy Surf E-35A” manufactured by Tokyo Seimitsu Co., Ltd. (hereinafter the same). The coefficient of static friction between the cooling roll and the triacetylcellulose film adhered to the cooling roll was measured by “Tribogear Portable Friction Meter Muse TYPE: 94i-2” manufactured by Shinto Kagaku Co., Ltd. Was 0.9. The static friction coefficient is obtained as an average value of three measurement values by placing a triacetyl cellulose film as one friction body on the detection unit of the portable tribometer and placing the film surface on the cooling roll 23 in a stationary state. Value.

The opposite side (the amorphous polyolefin resin film side which is the 1st transparent resin film 2) of the laminated body 4 conveyed in close contact with the cooling roll 23 is irradiated with ultraviolet rays from the ultraviolet irradiation device 16. The adhesive was cured. The ultraviolet irradiation device is manufactured by GS Yuasa Co., Ltd., and ultraviolet rays were irradiated from two “EHAN1700NAL high-pressure mercury lamps” which are ultraviolet lamps provided therein. The integrated light quantity of ultraviolet rays was 400 mJ / cm ² as a value measured based on irradiation in the UVB region having a wavelength of 280 to 320 nm. Subsequently, after passing the conveyance guide roll 24 and the pre-winding nip rolls 25 and 26 in this order, the amorphous polyolefin resin film 2 is provided on one side of the polarizing film 1, and the triacetyl cellulose film 3 is provided on the other side. A polarizing plate 5 having a thickness of about 174 μm was obtained and wound around a product roll 30.

[Example 2]
The transparent resin films 2 and 3 to be bonded to both surfaces of the polarizing film 1 are both “Zeonor films”, which are amorphous polyolefin resin films having a thickness of 60 μm and a width of 1,330 mm, and one after bonding A polarizing plate was produced in the same manner as in Example 1 except that the same Rz as used in Example 1 was brought into close contact with the outer peripheral surface of the cooling roll 23 having a surface temperature of 23 ° C. set to 0.4 μm. And wound on a product roll 30. When the static friction coefficient between the cooling roll 23 used in this example and the amorphous polyolefin resin film adhered thereto was measured by the same method as in Example 1, the static friction coefficient was still 0.9. It was.

[Comparative Example 1]
After the surface of the steel roll is subjected to a hard chrome plating treatment as a cooling roll 23 to which the second transparent resin film 3 (triacetyl cellulose film) is adhered, the surface is polished by a No. 6000 grindstone and mirror finished. A polarizing plate was produced in the same manner as in Example 1 except that the roughness was expressed by the maximum height Rz of the contour curve and became 0.1 μm, and was wound around a product roll 30. When the static friction coefficient between the cooling roll 23 used in this example and the triacetyl cellulose film 3 adhered thereto was measured by the same method as in Example 1, the static friction coefficient was 1.0.

[Comparative Example 2]
A polarizing plate was produced in the same manner as in Example 2 except that the cooling roll 23 having the same Rz of 0.1 μm as in Comparative Example 1 was used, and the product was wound around the product roll 30. When the static friction coefficient between the cooling roll 23 used in this example and the amorphous polyolefin resin film adhered thereto was measured by the same method as in Example 1, the static friction coefficient was 1.2. .

[Evaluation of wave curl of polarizing plate]
The polarizing plates having a width of 1,330 mm obtained in the above examples and comparative examples were each cut to a length of 600 mm in the longitudinal direction. For the 1,330 mm × 600 mm polarizing plate samples thus cut, the degree of wave curl was evaluated by the following method. That is, as shown to FIG. 2 (A), the 2nd transparent resin film 3 closely_contact | adhered to the outer peripheral surface of the cooling roll 23 (In Example 1 and Comparative Example 1, it is a triacetyl cellulose film, Example 2 and Comparative Example 2). Then, put the polarizing plate 5 on a flat surface (here, on a desk) with the surface on which one of the amorphous polyolefin resin films is bonded down, and obtain the wave number, wavelength and amplitude generated there, respectively. It was. In FIG. 1A, it is added that the thickness direction of the film is exaggerated and displayed so that the state of the wave can be easily understood.

  The wave number is the number of wave peaks appearing in the 1,330 mm width direction of the polarizing plate 5. FIG. 2 (A) shows an example in which there are 10 peaks numbered 1 to 10 with circled numbers and the wave number is 10. As shown in FIG. 2A, the wavelength L is a horizontal distance from the top of one mountain constituting the wave to the top of the adjacent mountain. When the wave curl is generated, there are a portion where the wave is dense and a portion where the wave is coarse. Therefore, here, the wavelength interval L is a representative interval between the dense portions. As shown in FIG. 2A, the amplitude A is a position a of 100 mm, a position b of 400 mm, a position c of 700 mm, a position d of 1,000 mm, and a position of 1,230 mm from one end in the width direction of the polarizing plate 5. Measurement was performed on 5 points e (position of 100 mm from the other end in the width direction of the polarizing plate 5). FIG. 2B shows the meaning of the amplitude A by extracting the position a in FIG. That is, the vertical distance between the apex of the peak closest to the measurement position a and the apex (low point) of the closest valley is obtained, and half the value is defined as the amplitude A. In FIG. 2B, the meaning of the wavelength L is also shown. These measurement results are summarized in Table 1. Table 1 shows the type of the second transparent resin film 3 on the side in close contact with the cooling roll, the measurement result of the surface roughness of the cooling roll 23, and the second transparent resin film 3 in close contact with the cooling roll 23. The results of measurement of the coefficient of static friction between the two are also shown.

  As shown in Table 1, the polarizing plates produced in Comparative Example 1 and Comparative Example 2 using the cooling roll 23 that was mirror-finished and had a surface roughness Rz of 0.1 μm both had wave curls. . On the other hand, none of the polarizing plates produced in Example 1 and Example 2 using the cooling roll 23 which was surface-finished with a rough grindstone and had a surface roughness Rz of 0.4 μm produced wave curl. It was.

DESCRIPTION OF SYMBOLS 1 ... Polarizing film, 2 ... 1st transparent resin film, 3 ... 2nd transparent resin film, 4 ... Laminated body before hardening, 5 ... Polarizing plate, 11 ... 1st coating machine , 12... Gravure roll provided in the first coating machine, 13... Second coating machine, 14... Gravure roll provided in the second coating machine, 16. ... Nip roll for bonding,
23 …… Contact body (cooling roll), 24 …… Guide roll for conveyance, 25, 26 …… Nip roll before winding, 28 …… Guide roll, 30 …… Product roll,
a, b, c, d, e: Amplitude measurement position, L: Wavelength, A: Amplitude.

Claims (4)

While transporting a polarizing film made of polyvinyl alcohol resin in a certain direction, a transparent resin film is superimposed on the laminated film via an ultraviolet curable adhesive to form a laminate, and the resulting laminate is arcuate along the transport direction. A method for producing a polarizing plate, wherein the adhesive is cured by irradiating with ultraviolet rays from the opposite side of the surface of the laminated body that is in close contact with the contact body, the contact body having a convex curved surface formed on the surface Because
The convex curved surface of the contact body has a surface roughness in the range of 0.4 to 1.2 μm expressed by the maximum height Rz of the contour curve, and a coefficient of static friction with the surface of the laminated body in close contact therewith. Is in the range of 0.2 to 1.0.   A transparent resin film is laminated on both sides of the polarizing film via an ultraviolet curable adhesive to form a laminate, and one transparent resin film of the laminate is brought into close contact with the contact body, and ultraviolet light is transmitted from the other transparent resin film side. The manufacturing method according to claim 1, wherein the adhesive is cured by irradiation.   The manufacturing method according to claim 1, wherein the contact body having the convex curved surface is a metal roll and has a surface temperature adjusting function.   The obtained polarizing plate is adhered to a liquid crystal cell to constitute a liquid crystal panel, and a surface opposite to a surface adhered to the liquid crystal cell is in close contact with the contact body. The manufacturing method in any one of.

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