JP2012208187A - Method for manufacturing polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent heat unevenness which easily occurs in a polarizing plate, in a method for manufacturing a polarizing plate in which transparent resin films are stuck to a polarizing film through an ultraviolet curable adhesive and followed by irradiating ultraviolet rays to cure the ultraviolet curable adhesive.SOLUTION: In a method for manufacturing a polarizing plate 5 in which transparent resin films 2 and 3 are stuck to a polarizing film 1 composed of a polyvinyl alcohol-based resin through an ultraviolet curable adhesive to form a laminate 4 and followed by irradiating with ultraviolet rays emitted from an ultraviolet irradiation device 16 to cure the adhesive, a wavelength filter 18 which can cut light having a wavelength of 400 nm or more is disposed on the side from which light from the ultraviolet irradiation device 16 is emitted, that is, between the ultraviolet irradiation device 16 and the laminate 4, and the light having a wavelength of 400 nm or more is substantially blocked, thereby irradiating with ultraviolet rays having only a wavelength of substantially 400 nm or less to the laminate 4 to cure the adhesive.

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, the polarizing plate produced by using an ultraviolet curable adhesive and irradiating it with ultraviolet rays in this way is “heat unevenness” on the transparent resin film surface irradiated with ultraviolet rays by the heat generated from the ultraviolet irradiation device. There was a problem of causing a minute deformation called “reducing” and impairing the appearance of the polarizing plate. For example, when the light from a fluorescent lamp is reflected on the surface of the polarizing plate, the heat unevenness occurs when an image of the fluorescent lamp is displayed as it is if the polarizing plate has no heat unevenness. In the polarizing plate, the unevenness (unevenness) is observed as many fine white spots. When a polarizing plate having heat unevenness is applied to a liquid crystal display device, a similar white spot is generated in a displayed image. Therefore, it is desired to produce a polarizing plate that does not cause heat unevenness.

  In JP 2009-134190 A (Patent Document 2), a polarizing film and a transparent resin film are each continuously conveyed in a long shape, and the transparent resin film is bonded to the polarizing film via an adhesive. And a method of producing a polarizing plate by polymerizing and curing an adhesive while adhering the obtained laminate to a convex curved surface formed in an arc shape along its conveying direction, typically a roll. Yes. A typical example of the adhesive is an ultraviolet curable adhesive, and paragraph 0021 describes that the above roll acts as a cooling roll whose surface temperature is set to 20 to 25 ° C. Yes. If the method of irradiating ultraviolet rays while adhering to the cooling roll in this way is adopted, it is expected that the above-described thermal unevenness that is likely to occur in a polarizing plate using an ultraviolet curable adhesive is also suppressed. However, even if a method of closely contacting the cooling roll is adopted, heat unevenness may still occur depending on the irradiation intensity of ultraviolet rays and the conveyance speed of the polarizing plate.

JP 2004-245925 A JP 2009-134190 A

  Therefore, the problem of the present invention is that a transparent resin film is bonded to a polarizing film via an ultraviolet curable adhesive, and the ultraviolet curable adhesive is cured by irradiating the ultraviolet ray there, to produce a polarizing plate, The purpose is to develop and provide a method in which heat unevenness hardly occurs in a polarizing plate.

  As a result of earnest research to solve such problems, the ultraviolet light irradiated to the laminate in which the transparent resin film is bonded to the polarizing film via the ultraviolet curable adhesive is substantially composed of only a wavelength of 400 nm or less. As a result, the inventors have found that it is effective to complete the present invention.

  That is, according to the present invention, a transparent resin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin via an ultraviolet curable adhesive, and the above adhesive is cured by irradiating ultraviolet rays thereon, and a polarizing plate is formed. There is provided a method for producing a polarizing plate, wherein the adhesive is cured by irradiating an ultraviolet ray substantially having only a wavelength of 400 nm or less.

  In order to obtain ultraviolet light having substantially only a wavelength of 400 nm or less, for example, light emitted from an ultraviolet light source is passed through a wavelength filter capable of cutting light having a wavelength of 400 nm or more, and light having a wavelength of 400 nm or more is substantially obtained. It is possible to adopt a method of blocking automatically. In the production method of the present invention, a transparent resin film is bonded to both surfaces of a polarizing film via an ultraviolet curable adhesive, and the ultraviolet curable adhesive is cured by irradiating ultraviolet rays from one transparent resin film side. Even in this case, it can be applied effectively.

  Further, the production method of the present invention continuously conveys a polarizing film and a transparent resin film as disclosed in the above-mentioned Patent Document 2 (Japanese Patent Laid-Open No. 2009-134190), respectively, and the polarizing film After laminating a transparent resin film via an ultraviolet curable adhesive, the resulting laminate is wound around and closely adhered to a contact body having a convex curved surface formed in an arc shape along its conveying direction. The present invention can also be effectively applied to a method of curing an ultraviolet curable adhesive by irradiating ultraviolet rays from the opposite side of the body to the contact body. The contact body used here is typically composed of a roll, and in that case, the axis of the roll is set so that the direction perpendicular to the width direction of the convex curved surface of the roll is the transport direction of the laminate. It arrange | positions so that it may orthogonally cross in the conveyance direction of the said laminated body.

  In this way, the polarizing film and the transparent resin film are each continuously conveyed in a long shape, and the laminate obtained by bonding the transparent resin film to the polarizing film via an ultraviolet curable adhesive is used as the outer peripheral surface of the roll. Also in the method of irradiating ultraviolet rays in a state of being wound and closely attached, a polarizing plate in which two transparent resin films are used and the transparent resin films are bonded to both surfaces of the polarizing film can be produced. In that case, the transparent resin film is bonded to both surfaces of the polarizing film via the above adhesive, and one transparent resin film side of the obtained laminate is wound around the outer peripheral surface of the roll, and the other is adhered. Irradiation of ultraviolet rays is performed from the transparent resin film side.

  According to the present invention, a polarizing plate in which generation of heat unevenness is suppressed while adopting a method of adopting a UV curable adhesive, irradiating it with UV and curing it, and bonding a polarizing film and a transparent resin film. Can be manufactured.

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 graph showing the light emission spectrum (curve A) of the metal halide lamp used as an ultraviolet light source, and the transmittance | permeability spectrum (curve B) of the wavelength filter similarly used for the cut | disconnection of the light of wavelength 400nm or more.

  With reference to FIG. 1, in this invention, the transparent resin films 2 and 3 are bonded to the polarizing film 1 via the ultraviolet curable adhesive, and it is set as the laminated body 4, and the ultraviolet-ray irradiation apparatus 16 is used for the laminated body 4 from the ultraviolet irradiation device 16. Is applied to cure the adhesive, and the polarizing plate 5 is manufactured.

  For bonding the polarizing film 1 and the transparent resin films 2 and 3, nip rolls 21 and 22 for bonding are used. 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 the illustrated example, the laminated body 4 after bonding is in close contact with the contact body 23 having a convex curved surface along the conveying direction, and ultraviolet rays are emitted from the ultraviolet irradiation device 16 disposed on the opposite side of the laminated body 4. Will be irradiated. 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.

  And the ultraviolet-ray irradiated to the laminated body 4 shall consist only of a wavelength of 400 nm or less substantially. In the illustrated example, a wavelength filter 18 capable of cutting light having a wavelength of 400 nm or more is disposed between the ultraviolet irradiation device 16 and the laminate 4 on the side from which the ultraviolet irradiation device 16 emits light. The emitted light is passed through the wavelength filter 18 so as to substantially block light having a wavelength of 400 nm or more, and the laminate 4 is irradiated with ultraviolet rays substantially having only a wavelength of 400 nm or less. ing.

  As will be described later, a mercury lamp, a metal halide lamp, or the like is used as the light source for the ultraviolet irradiation device 16, and such a general ultraviolet light source contains a large amount of ultraviolet light having a wavelength of 400 nm or less, but its wavelength region is wide from the ultraviolet region to the visible region. Therefore, when the light source is turned on, white or purple color is exhibited. When such a normal ultraviolet light source is used, light having a wavelength of 400 nm or more is substantially blocked through the wavelength filter 18 as shown. On the other hand, for example, there is a light source that emits only ultraviolet light having a wavelength of 400 nm or less, such as an excimer laser light source, and such a light source can be used. However, since such a light source that emits only ultraviolet light having a wavelength of substantially 400 nm or less is generally expensive, an ultraviolet light source that also generates visible light is used, and light having a wavelength of 400 nm or more is passed through the wavelength filter 18 as shown. It is practical to adopt a form that substantially blocks the above.

  Of course, using the polarizing film and the transparent resin film cut into a sheet, the production method of the present invention is used, and they are bonded via an ultraviolet curable adhesive, and the above adhesive is cured by irradiating ultraviolet rays there. In addition, the present invention can be applied in the form of a single wafer for manufacturing a polarizing plate, but particularly in industrial production, it is applied to a continuous production method as shown in FIG. Further, the ultraviolet irradiation method is not limited to the form of irradiation as shown in the drawing, preferably in close contact with the contact body 23 constituted by a roll. For example, the ultraviolet irradiation device 16 of the laminated body 4 is Of course, a mode in which ultraviolet rays are irradiated without arranging a special support or contact on the opposite side is also included in the present invention.

  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 proceed to the description on the method for manufacturing the polarizing plate.

[Polarized film]
A polarizing film consists of polyvinyl alcohol-type resin, and this polyvinyl alcohol-type resin is obtained by saponifying polyvinyl acetate type 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 laminated 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 The apparatus is configured such that the polarizing plate 5 obtained is wound around the product roll 30 through the nip rolls 25 and 26 before winding and 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.

  The first transparent resin film 2 is applied to the surface to be bonded to the polarizing film 1 in advance after the adhesive is applied from the first coating machine 11, and then the adhesive application surface is on one side of the polarizing film 1. Bonded. On the other hand, the second transparent resin film 3 is coated with the adhesive from the second coating machine 13 in advance on the surface to be bonded to the polarizing film 1, and then the adhesive coating surface of the polarizing film 1. Bonded to the other side.

  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.

  As for the 1st transparent resin film 2 and the 2nd transparent resin film 3 which apply | coated the adhesive agent, the adhesive agent coating surface is bonded to the polarizing film 1, respectively, and it is sandwiched by the nip rolls 21 and 22 for bonding, and is in a thickness direction. Pressurized to form a three-layered laminate 4 and conveyed to the contact body 23. The contact body 23 has a convex curved surface formed in an arc shape along the transport direction (longitudinal direction) of the laminate 4. And the laminated body 4 is conveyed, closely_contact | adhering to the convex curve of the contact body 23, the ultraviolet-ray irradiation from the ultraviolet irradiation device 16 is received in the process, and an adhesive agent is polymerized and hardened. 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, it is effective from the viewpoint of reducing the influence of heat generated by the irradiation of ultraviolet rays, that the contact body 23 is composed of a metal roll, and has a temperature adjusting function and acts as a cooling roll. The temperature adjusting function can be provided by a system 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.

  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. At this time, a wavelength filter 18 capable of cutting light having a wavelength of 400 nm or more is disposed between the ultraviolet irradiation device 16 on the side where the light is emitted, that is, between the ultraviolet irradiation device 16 and the laminate 4. The light to be passed is passed through the wavelength filter 18 so as to substantially block light having a wavelength of 400 nm or more, so that the laminate 4 is irradiated with ultraviolet rays having only a wavelength of 400 nm or less. 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 material of the wavelength filter 18 is not particularly limited, but from the viewpoint of heat resistance, a material obtained by forming a dielectric film or a metal film on a glass substrate by a vacuum deposition method, an ion assist deposition method, a sputtering method or the like is preferable. As the wavelength filter 18, an appropriate commercially available product that can cut light having a wavelength of 400 nm or more can be used. In particular, the average value of the transmittance of light having a wavelength between 250 nm and 400 nm is used. 80% or more, especially 85% or more, and the average value of the transmittance of light in the wavelength range of 400 nm or more and at least 500 nm is less than 5%, more preferably 2% or less, especially 1% or less. .

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. 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 . In the case of adopting a form in which the laminated body 4 is irradiated with ultraviolet rays in close contact with the contact body 23 as shown in the figure, while the laminated body 4 passes through the contact body 23, this accumulated light quantity is 10 to 2,000 mJ. It is particularly preferable to achieve / cm ² in order to sufficiently polymerize and cure the adhesive. 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 the line speed is set to 10 to 50 m so that the integrated light quantity is 10 to 2,000 mJ / cm ² while applying a tension of 100 to 800 N in the transport direction (longitudinal direction). It is preferable to set within a range of about / min. The distance between the ultraviolet irradiation device 16 and the laminate 4 is not particularly limited, but the distance from the ultraviolet light source constituting the ultraviolet irradiation device 16 to the laminate 4 so that the integrated light amount is 10 to 2,000 mJ / cm ^2. (When the laminated body 4 is brought into close contact with the contact body 23 as shown in FIG. 1), it is preferable that the shortest distance between the two is set within a range of about 10 to 500 mm. 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.

[Other description]
In the present invention, as described above, the transparent resin films 2 and 3 can be bonded to one side or both sides of the polarizing film 1 to form the polarizing plate 5, but preferably the polarizing film 1 as described above. Transparent resin films 2 and 3 are bonded to both sides of the film. On the other hand, for a mode in which a transparent resin film is bonded to only one side of the polarizing film 1 to form a polarizing plate, those skilled in the art can easily carry out the description regarding one transparent resin film from the above description. It will be understood as much as possible.

  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 laminate 4 is continuously wound around the outer peripheral surface of the cooling roll 23 whose surface temperature is set to 23 ° C., the triacetyl cellulose film side that is the second transparent resin film 3 is in close contact with the laminate 4. In minutes, it was conveyed with a tension of 600 N in the longitudinal direction.

  An ultraviolet irradiation device 16 (GS Yuasa Co., Ltd.) is disposed on the opposite side (the amorphous polyolefin resin film side which is the first transparent resin film 2) of the laminate 4 conveyed while closely contacting the cooling roll 23. Made). And the ultraviolet-ray radiate | emitted from 2 metal halide lamps with which it was passed was passed through the wavelength filter 18, and was irradiated to the laminated body 4, and the adhesive agent was hardened. The shortest distance from the lamp in the ultraviolet irradiation device 16 to the laminate 4 was set to 200 mm. The wavelength filter 18 used here was obtained from Keihin Optical Film Industry Co., Ltd., and had an average light transmittance of 88% between wavelengths 250 nm and 400 nm, and an average light transmittance between wavelengths 400 nm and 500 nm. The rate was 1%.

  The emission spectrum of the metal halide lamp used as the ultraviolet light source from 250 nm to 500 nm is shown by a thick curve A in FIG. 2, and the transmittance spectrum of the wavelength filter 18 from 250 nm to 800 nm is shown by the thin curve B in FIG. Indicated. In FIG. 2, the horizontal axis represents the wavelength (nm) common to A and B, the left vertical axis corresponding to the curve A represents the emission intensity of the metal halide lamp, and the right vertical axis corresponding to the curve B represents the transmittance (%). Represents. The light emission intensity of the lamp was expressed as a relative value with the intensity at the wavelength giving the maximum value being 100.

When the output of the ultraviolet irradiation device 16 is 120 W, the integrated light quantity in the wavelength range of 200 to 400 nm is 510 mJ / cm ² , and the ambient temperature near the cooling roll 23 of the laminate 4 when irradiated with ultraviolet rays is 110 ° C. there were. After the ultraviolet irradiation, the conveying guide roll 24 and the pre-winding nip rolls 25 and 26 are passed in this order, and the amorphous polyolefin resin film 2 is provided on one side of the polarizing film 1 and the triacetyl cellulose film is provided on the other side. 3 were bonded to obtain a polarizing plate 5 having a thickness of about 174 μm, which was wound around a product roll 30. When the light from the fluorescent lamp was reflected on the obtained polarizing plate and visually observed, an image of the fluorescent lamp was reflected as it was, and no thermal unevenness was observed.

[Example 2]
In Example 1, instead of “Zeonor film” which is an amorphous polyolefin resin film, “Diafoil” which is a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm and a width of 1,330 mm obtained from Mitsubishi Plastics, Inc. "Zeonor film" which is an amorphous polyolefin resin film used as the first transparent resin film 2 in Example 1 instead of the triacetyl cellulose film "Fujitac TD80". Was used as the second transparent resin film 3, and the output of the ultraviolet irradiation device 16 was 140 W. Other than that, a polarizing plate was produced in the same manner as in Example 1. At this time, the integrated light amount in the wavelength range of 200 to 400 nm irradiated on the laminate 4 is 630 mJ / cm ² , and the ambient temperature near the cooling roll 23 of the laminate 4 when irradiated with ultraviolet rays is 132 ° C. there were. When the light from the fluorescent lamp was reflected on the obtained polarizing plate and visually observed, an image of the fluorescent lamp was reflected as it was, and no thermal unevenness was observed.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the laminate 4 was irradiated with ultraviolet rays irradiated from the ultraviolet irradiation device 16 without passing through the wavelength filter 18. At this time, the cumulative amount of light in the wavelength range of 200 to 400 nm irradiated on the laminate 4 is 510 mJ / cm ² , and the ambient temperature in the vicinity of the cooling roll 23 of the laminate 4 when irradiated with ultraviolet rays is 223 ° C. It was. When the light from the fluorescent lamp was reflected on the obtained polarizing plate and visually observed, many fine white spots were observed in the image of the fluorescent lamp, and thermal unevenness occurred.

[Comparative Example 2]
A polarizing plate was produced in the same manner as in Example 2 except that the laminate 4 was irradiated with ultraviolet rays irradiated from the ultraviolet irradiation device 16 without passing through the wavelength filter 18. At this time, the cumulative amount of light in the wavelength range of 200 to 400 nm irradiated on the laminate 4 is 630 mJ / cm ² , and the ambient temperature in the vicinity of the cooling roll 23 of the laminate 4 when irradiated with ultraviolet rays is 265 ° C. It was. When the light from the fluorescent lamp was reflected on the obtained polarizing plate and visually observed, many fine white spots were observed in the image of the fluorescent lamp, and thermal unevenness occurred.

1 …… Polarizing film,
2 …… First transparent resin film,
3. Second transparent resin film,
4 ... laminate before curing,
5 ... Polarizing plate,
11 …… First coating machine,
12 ... The gravure roll that the first coating machine has,
13. Second coating machine,
14: Gravure roll provided in the second coating machine,
16 …… UV irradiation equipment,
18 …… Wavelength filter,
21, 22, ... nip rolls for bonding,
23 …… Contact body (cooling roll),
24 …… Conveying guide roll,
25, 26 ... nip roll before winding,
28 …… Guide roll,
30 …… Product roll,
A: Emission spectrum of metal halide lamp,
B: Transmittance spectrum of wavelength filter.

Claims (5)

A transparent resin film is bonded to a polarizing film made of a polyvinyl alcohol resin via an ultraviolet curable adhesive, and the adhesive is cured by irradiating with ultraviolet rays, whereby a polarizing plate is produced.
A method for producing a polarizing plate, wherein the adhesive is cured by irradiating an ultraviolet ray having substantially only a wavelength of 400 nm or less.   The manufacturing method according to claim 1, wherein the light emitted from the ultraviolet irradiation device is passed through a wavelength filter capable of cutting light having a wavelength of 400 nm or more, and the ultraviolet light in which light having a wavelength of 400 nm or more is substantially blocked is irradiated.   The manufacturing method of Claim 1 or 2 which pastes a transparent resin film through the said adhesive agent on both surfaces of a polarizing film, respectively, and irradiates the said ultraviolet-ray from one transparent resin film side.   Each of the polarizing film and the transparent resin film is continuously conveyed in a long shape, and after the transparent resin film is bonded to the polarizing film via the adhesive, the obtained laminate is an axis orthogonal to the conveying direction. The manufacturing method in any one of Claims 1-3 which wraps and adheres to the outer peripheral surface of the roll which has this, and irradiates the said ultraviolet-ray from the opposite side to the said roll of this laminated body.   The polarizing film and the two transparent resin films are each continuously conveyed in a long shape, and the transparent resin film is bonded to both surfaces of the polarizing film via the adhesive, and one of the obtained laminates The manufacturing method according to claim 4, wherein the transparent resin film side is wound around and closely adhered to the outer peripheral surface of the roll, and the ultraviolet ray is irradiated from the other transparent resin film side.

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