WO2013051598A1 - Method for manufacturing polarizer - Google Patents

Abstract

A method for manufacturing a polarizer, said method being characterized by including the following steps: a step in which a polarizing film is fabricated by subjecting a polyvinyl-alcohol resin film to a dyeing process, a boric-acid process, and a uniaxial stretching process; a step in which an active-energy-ray-curable adhesive is applied to one surface of a transparent film or transparent films; a step in which the surface(s) of the transparent film(s) to which the adhesive was applied is/are bonded to one or both surfaces of the polarizing film by sandwiching with bonding rolls, thereby fabricating a laminate; and a step in which a polarizer is fabricated by exposing said laminate to active-energy rays. This method for manufacturing a polarizer is further characterized in that the bonding rolls in the laminate-fabrication step apply a pressure in the 0.2-1.2 MPa range.

Description

Manufacturing method of polarizing plate

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

Polarizing films are widely used as dichroic dyes adsorbed and oriented on polyvinyl alcohol resin films. Iodine polarizing films using iodine as a dichroic dye and dichroic direct dyes as dichroic Dye-type polarizing films used as pigments are known. These polarizing films are usually used as polarizing plates by laminating a transparent film such as a triacetyl cellulose film on one side or both sides via an adhesive.

As a method of laminating a transparent film on one or both sides of a polarizing film, after applying an active energy ray-curable resin to the surface of the transparent film in advance, the polarizing film and the transparent film are sandwiched between a pair of bonding rolls. Next, there is a method of irradiating active energy rays to bond and cure (for example, Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 1), Japanese Patent Application Laid-Open No. 2009-134190 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2011-95560. Gazette (see Patent Document 3).

JP 2004-245925 A JP 2009-134190 A JP 2011-95560 A

In a polarizing plate in which a polarizing film and a transparent film coated with an active energy ray-curable adhesive on one side are bonded, air bubbles of about 100 μm are mixed between the polarizing film and the transparent film. There is. This bubble is accumulated in a place just before the active energy ray-curable adhesive that does not fit between the polarizing film and the transparent film is sandwiched between the bonding rolls, and a phenomenon called “liquid dam” occurs. As a result, air is caught between the surface of the polarizing film opposite to the side where the “liquid dam” occurs and the transparent film (the polarizing film is pushed by the swelling of the “liquid dam”, and the polarizing film It is thought that this occurs because the surface opposite to the side where the “liquid dam” is formed and the transparent film come into contact with each other before bonding, and air is caught. This is a phenomenon that did not occur when a conventional water-based pressure-sensitive adhesive was used, and is a particular problem due to the use of an active energy ray-curable adhesive.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is a polarizing plate in which a polarizing film and a transparent film coated with an active energy ray-curable adhesive on one side are bonded. Then, it is to provide a method capable of producing a polarizing plate in which bubbles are hardly generated between the polarizing film and the transparent film.

The present invention includes a step of producing a polarizing film by subjecting a polyvinyl alcohol resin film to dyeing treatment, boric acid treatment and uniaxial stretching treatment, and a step of applying an active energy ray-curable adhesive to one side of the transparent film; , A process of producing a laminate by laminating the transparent film on one side or both sides of the polarizing film with a laminating roll, and irradiating the laminate with active energy rays And a manufacturing method of a polarizing plate including a step of manufacturing a polarizing plate, wherein the pressing pressure of the bonding roll is within a range of 0.2 to 1.2 MPa in the step of manufacturing the laminate. Features.

According to the production method of the present invention, there is a polarizing plate in which a polarizing film and a transparent film coated with an active energy ray-curable adhesive on one side are bonded, and there are bubbles between the polarizing film and the transparent film. Manufacture of a polarizing plate that is less likely to occur is provided.

It is a figure which shows typically an example of the whole apparatus for performing the manufacturing method of the polarizing plate of this invention.

The method for producing a polarizing plate of the present invention includes: [1] a step of producing a polarizing film by subjecting a polyvinyl alcohol resin film to dyeing treatment, boric acid treatment and uniaxial stretching treatment; and [2] active on one side of the transparent film. A step of applying an energy ray curable adhesive; and [3] a laminated body in which the transparent film is bonded to one or both sides of the polarizing film with the adhesive-coated surface sandwiched between bonding rolls. And [4] irradiating the laminate with active energy rays to produce a polarizing plate. The polarizing plate production method of the present invention is characterized in that, in the step [3], the pressing pressure of the laminating roll is in the range of 0.2 to 1.2 MPa. Thereby, air becomes difficult to be caught between the polarizing film and the transparent film, and a polarizing plate in which bubbles are not easily generated between the polarizing film and the transparent film can be manufactured.

When the pressing pressure of the laminating roll is less than 0.2 MPa, the pressing pressure is insufficient and the film transport state becomes unstable and air bubbles are likely to be mixed. Also, the pressing pressure of the laminating roll is 1 When the pressure exceeds 2 MPa, a liquid dam is generated and bubbles are mixed. The pressing pressure of the bonding roll is preferably in the range of 0.5 to 1.2 MPa. The pressing pressure of this bonding roll can be measured, for example, as an instantaneous pressure in a two-sheet type prescale made by Fuji Film. The pressure of pressing against the bonding roll is usually applied to the bearing members at both ends of the bonding roll.

Here, FIG. 1 is a diagram schematically showing an example of the entire apparatus for performing the polarizing plate manufacturing method of the present invention. Hereinafter, with reference to FIG. 1, the whole manufacturing method of the polarizing plate of this invention is demonstrated in detail.

[1] Step of Producing Polarizing Film In the method for producing a polarizing plate of the present invention, first, a polarizing film is produced by subjecting a polyvinyl alcohol-based resin film to a dyeing treatment, boric acid treatment and uniaxial stretching treatment. Specifically, the polarizing film used in the present invention is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith (for example, ethylene-vinyl acetate copolymer). Polymer). Other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like. The degree of saponification of the polyvinyl alcohol resin is 85 mol% or more, preferably 90 mol% or more, more preferably 98 to 100 mol%. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 to 10000, preferably 1500 to 5000. These polyvinyl alcohol resins may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used.

A film obtained by forming such a polyvinyl alcohol resin is used as an original film of a polarizing film. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a conventionally known appropriate method. The film thickness of the raw film made of polyvinyl alcohol resin is not particularly limited, but is, for example, about 10 to 150 μm. Usually, it is supplied in the form of a roll, the thickness is in the range of 20 to 100 μm, preferably in the range of 30 to 80 μm, and the industrially practical width is in the range of 500 to 6000 mm. Alternatively, a polyester film such as an olefin film or a PET film may be used as a base material, and a polyvinyl alcohol resin may be applied on both surfaces or one surface thereof.

The commercially available polyvinyl alcohol film (vinylon VF-PS # 7500, Kuraray / OPL film M-7500, manufactured by Nihon Gosei) has a thickness of 75 μm (vinylon VF-PS # 6000, manufactured by Kuraray, vinylon VF-PE #). (6000, manufactured by Kuraray) has a thickness of 60 μm, (vinylon VF-PE # 5000, manufactured by Kuraray) has a thickness of 50 μm, and (vinylon VF-PE # 3000, manufactured by Kuraray) has a thickness of 30 μm. .

The polarizing film is usually a process of dyeing a polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye (dyeing process), and a polyvinyl alcohol resin film adsorbed with the dichroic dye is boric acid. It is manufactured through a step of treating with an aqueous solution (boric acid treatment step) and a step of washing with water after the treatment with the boric acid aqueous solution (water washing treatment step).

In the production of the polarizing film, the polyvinyl alcohol-based resin film is usually uniaxially stretched, but this uniaxial stretching may be performed before the dyeing treatment step or during the dyeing treatment step, It may be performed after the dyeing process. When uniaxial stretching is performed after the dyeing treatment step, the uniaxial stretching may be performed before the boric acid treatment step or during the boric acid treatment step. Of course, uniaxial stretching can be performed in these plural stages.

The uniaxial stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially 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.

The dyeing of the polyvinyl alcohol-based resin film with the dichroic dye in the dyeing process is performed, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, for example, iodine, a dichroic dye or the like is used. Examples of dichroic dyes include C.I. I. Dichroic direct dyes composed of disazo compounds such as DIRECT RED 39, and dichroic direct dyes composed of compounds such as trisazo and tetrakisazo are included. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, 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 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing an aqueous dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution, usually, 1 × ¹⁰ -4 ~ ¹⁰ parts by weight per 100 parts by weight of water, preferably 1 × ^{10 -3} ~ 1 parts by weight, particularly preferably 1 × 10 ^{- 3} to 1 × 10 ⁻² parts by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. When a dichroic dye is used as the dichroic dye, 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 1800 seconds. is there.

The boric acid treatment step is performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye 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 in the dyeing process described above, the boric acid-containing aqueous solution used in this boric acid treatment process preferably contains potassium iodide. In this case, 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 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 40 ° C. or higher, preferably 50 to 85 ° C., more preferably 55 to 80 ° C.

In the subsequent washing process, the polyvinyl alcohol-based resin film after the boric acid treatment described above is washed with water, for example, by immersing it in water. The temperature of water in the water washing treatment is usually 4 to 40 ° C., and the immersion time is usually 1 to 120 seconds. A method of spraying water in the form of a spray during or before and after the washing process, or spraying water from the slit-shaped ejection part and filling the film strongly may be appropriately selected. After the water washing treatment, a drying treatment is usually performed to obtain a polarizing film. A method such as blowing off water with an air knife or the like in the previous stage of the drying treatment, or sucking out moisture on the surface with a water absorption roll may be appropriately employed. The drying process is preferably performed using, for example, a hot air dryer or a far infrared heater. The temperature for the drying treatment is usually 30 to 100 ° C., preferably 50 to 90 ° C. The drying treatment time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

Thus, the polyvinyl alcohol resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, boric acid treatment and water washing treatment to obtain a polarizing film. The thickness of this polarizing film is usually in the range of 3 to 50 μm.

In addition, the film which has not only the said method but the polarizing function produced by another method is employ | adopted as a polarizing film.

[2] A process of applying an active energy ray-curable adhesive to a transparent film (transparent film)
Examples of the material constituting the transparent film used in the present invention include cycloolefin resins, cellulose acetate resins, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate resins, and acrylic resins. And film materials that have been widely used in the art, such as polypropylene.

The cycloolefin resin is a thermoplastic resin (also referred to as a thermoplastic cycloolefin resin) having a monomer unit made of a cyclic olefin (cycloolefin), such as norbornene or a polycyclic norbornene monomer. The cycloolefin-based resin may be a hydrogenated product of the above-mentioned cycloolefin ring-opening polymer or a ring-opening copolymer using two or more cycloolefins, and has a cycloolefin, a chain olefin, and a vinyl group. An addition polymer with an aromatic compound or the like may be used. Those having a polar group introduced are also effective.

When using a copolymer of a cycloolefin and a chain olefin or / and an aromatic compound having a vinyl group, examples of the chain olefin include ethylene and propylene, and examples of the aromatic compound having a vinyl group include Examples include styrene, α-methylstyrene, and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). In particular, when a terpolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group is used, the amount of the monomer unit composed of cycloolefin can be made relatively small as described above. In such a terpolymer, the unit of monomer composed of a chain olefin is usually 5 to 80 mol%, and the unit of monomer composed of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

Cycloolefin-based resins may be commercially available products such as Topas (manufactured by Ticona), Arton (manufactured by JSR), ZEONOR (manufactured by Nippon Zeon), ZEONEX (manufactured by Nippon Zeon ( Co., Ltd.), Apel (manufactured by Mitsui Chemicals, Inc.), Oxis (OXIS) (manufactured by Okura Kogyo Co., Ltd.) and the like can be suitably used. When such a cycloolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, for example, commercially available cycloolefin resin films such as Essina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa Film (manufactured by Optes Co., Ltd.), etc. You may use goods.

The cycloolefin resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be given to the cycloolefin-based resin film. Stretching is usually performed continuously while unwinding a film roll, and in a heating furnace, the roll traveling direction (film longitudinal direction), the direction perpendicular to the traveling direction (film width direction), or both Stretched. As the temperature of the heating furnace, a range from the vicinity of the glass transition temperature of the cycloolefin resin to the glass transition temperature + 100 ° C. is usually employed. The stretching ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin-based resin film is in a roll-wound state, the films tend to adhere to each other and easily cause blocking. Therefore, the cycloolefin-based resin film is usually rolled after the protective film is bonded. In addition, since the cycloolefin resin film generally has poor surface activity, the surface to be bonded to the polarizing film is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment. Is preferred. Among these, plasma treatment that can be carried out relatively easily, particularly atmospheric pressure plasma treatment, and corona treatment are preferable.

The cellulose acetate-based resin is a cellulose part or a completely esterified product, and examples thereof include a film made of cellulose acetate ester, propionate ester, butyrate ester, and mixed ester thereof. More specifically, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like can be given. As such a cellulose ester resin film, an appropriate commercially available product, for example, Fujitac TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac TD80UZ (manufactured by Fuji Film Co., Ltd.) KC8UX2M (manufactured by Konica Minolta Opto), KC8UY (manufactured by Konica Minolta Opto) Fujitac TD60UL (manufactured by Fuji Film), KC4UYW (manufactured by Konica Minolta Opto), KC6UAW (Konica Minolta Opto) KC2UAW (manufactured by Konica Minolta Opto Co., Ltd.) and the like can be suitably used.

Further, as the transparent film, a cellulose acetate-based resin film imparted with retardation characteristics is also preferably used. Commercially available cellulose acetate resin films with such retardation characteristics include WV BZ 438 (Fuji Film Co., Ltd.), KC4FR-1 (Konica Minolta Opto Co., Ltd.), and KC4CR-1 (Konica Minolta). Opt Co., Ltd.), KC4AR-1 (Konica Minolta Opto Co., Ltd.) and the like. Cellulose acetate is also called acetyl cellulose or cellulose acetate.

These cellulose acetate-based films are easy to absorb water, and the moisture content of the polarizing plate may affect the end talmi of the polarizing plate. The moisture content during the production of the polarizing plate is preferably closer to the equilibrium moisture content in the storage environment of the polarizing plate, for example, a clean room production line or a roll storage warehouse, and depends on the configuration of the laminated film. About 5%, more preferably 2.5 to 3.0%. The numerical value of the moisture content of this polarizing plate was measured by the dry weight method and is a change in weight after 105 ° C./120 minutes.

In the present invention, the transparent film has a function as a retardation film, a function as a brightness enhancement film, a function as a reflection film, a function as a transflective film, a function as a diffusion film, a function as an optical compensation film, etc. It can have an optical function. In this case, for example, by laminating an optical functional film such as a retardation film, a brightness enhancement film, a reflection film, a transflective film, a diffusion film, and an optical compensation film on the surface of the transparent film, such a function is achieved. In addition, the transparent film itself can be given such a function. Further, the transparent film may have a plurality of functions such as a diffusion film having the function of a brightness enhancement film.

For example, the above-mentioned transparent film is subjected to a stretching process described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, or the like, or a process described in Japanese Patent No. 3168850 can be used as a retardation film. The function of can be provided. The retardation characteristics of the retardation film can be appropriately selected, for example, such that the front retardation value is in the range of 5 to 100 nm and the thickness direction retardation value is in the range of 40 to 300 nm. Further, two or more layers having different central wavelengths of selective reflection are formed in the transparent film by forming micropores by a method as described in Japanese Patent Application Laid-Open Nos. 2002-169025 and 2003-29030. By superimposing these cholesteric liquid crystal layers, a function as a brightness enhancement film can be imparted.

If a metal thin film is formed on the transparent film by vapor deposition or sputtering, a function as a reflective film or a transflective film can be imparted. By coating the transparent film described above with a resin solution containing fine particles, a function as a diffusion film can be imparted. Moreover, the function as an optical compensation film can be provided by coating and aligning liquid crystalline compounds, such as a discotic liquid crystalline compound, on said transparent film. Moreover, you may make the transparent film contain the compound which expresses retardation. Further, various optical functional films may be directly bonded to the polarizing film using an appropriate adhesive. Examples of commercially available optical functional films include brightness enhancement films such as DBEF (manufactured by 3M, available from Sumitomo 3M Co., Ltd. in Japan), and viewing angle improvements such as WV film (manufactured by Fuji Film Co., Ltd.). Film, Arton Film (manufactured by JSR Corporation), Zeonoor Film (manufactured by Optes Corporation), Essina (manufactured by Sekisui Chemical Co., Ltd.), VA-TAC (manufactured by Comic Minolta Opto Corporation), Sumikalite (Sumitomo) (Chemical Co., Ltd.) etc. can be mentioned.

The thickness of the transparent film used in the present invention is preferably thin, but if it is too thin, the strength is lowered and the processability is poor. On the other hand, when it is too thick, problems such as a decrease in transparency and a longer curing time after lamination occur. Therefore, a suitable thickness of the transparent film is, for example, 5 to 200 μm, preferably 10 to 150 μm, more preferably 10 to 100 μm.

In order to improve the adhesion between the adhesive and the polarizing film and / or the transparent film, the polarizing film and / or the transparent film may be subjected to corona treatment, flame treatment, plasma treatment, ultraviolet treatment, primer coating treatment, saponification treatment, etc. A surface treatment may be applied.

Further, the transparent film may be subjected to surface treatments such as anti-glare treatment, anti-reflection treatment, hard coat treatment, antistatic treatment, and antifouling treatment individually or in combination of two or more. The transparent film and / or the transparent film surface protective layer may contain a UV absorber such as a benzophenone compound or a benzotriazole compound, or a plasticizer such as a phenyl phosphate compound or a phthalate compound.

(Active energy ray-curable adhesive)
Examples of the active energy ray-curable adhesive include an adhesive made of an epoxy resin composition containing an epoxy resin that is cured by irradiation with active energy rays from the viewpoint of weather resistance, refractive index, durability, and the like. However, the present invention is not limited to this, and various active energy ray-curable adhesives (organic solvent adhesives, hot melt adhesives, solventless adhesives) that have been used in the manufacture of polarizing plates. Etc.) can be adopted. These include acrylic compositions, acrylamide compositions, epoxy acrylate compositions, urethane compositions, vinyl compositions, and the like. Examples of the curing reaction include curing by a polymerization reaction such as radical polymerization, cationic polymerization, anionic polymerization, and thermal polymerization.

An epoxy resin means a compound having two or more epoxy groups in a molecule. From the viewpoint of weather resistance, refractive index, cationic polymerizability, and the like, the epoxy resin contained in the curable epoxy resin composition that is an adhesive is an epoxy resin that does not contain an aromatic ring in the molecule (see, for example, Patent Document 1). It is preferable that Examples of such epoxy resins include hydrogenated epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

The hydrogenated epoxy resin is obtained by a method of glycidyl etherifying a nuclear hydrogenated polyhydroxy compound obtained by selectively subjecting a polyhydroxy compound, which is a raw material of an aromatic epoxy resin, to a nuclear hydrogenation reaction under pressure in the presence of a catalyst. Obtainable. Examples of the aromatic epoxy resin include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, and hydroxy Examples include novolak-type epoxy resins such as benzaldehyde phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol. Of the hydrogenated epoxy resins, hydrogenated bisphenol A glycidyl ether is preferred.

The alicyclic epoxy resin means an epoxy resin having at least one epoxy group bonded to the alicyclic ring in the molecule. The “epoxy group bonded to an alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula. In the following formula, m is an integer of 2 to 5.

A compound in which a group in the form of removing one or more hydrogen atoms in (CH ₂ ) _m in the above formula is bonded to another chemical structure can be an alicyclic epoxy resin. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy resins, an epoxy resin having an oxabicyclohexane ring (m = 3 in the above formula) or an oxabicycloheptane ring (m = 4 in the above formula) exhibits excellent adhesion. Therefore, it is preferably used. Although the alicyclic epoxy resin used preferably below is specifically illustrated, it is not limited to these compounds.

(A) Epoxycyclohexylmethyl epoxycyclohexanecarboxylates represented by the following formula (I):

(Wherein R ¹ and R ² each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(B) Epoxycyclohexanecarboxylates of alkanediol represented by the following formula (II):

(Wherein R ³ and R ⁴ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and n represents an integer of 2 to 20).

(C) Epoxycyclohexyl methyl esters of dicarboxylic acid represented by the following formula (III):

(Wherein, R ⁵ and R ⁶ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and p represents an integer of 2 to 20).

(D) Epoxycyclohexyl methyl ethers of polyethylene glycol represented by the following formula (IV):

(Wherein R ⁷ and R ⁸ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and q represents an integer of 2 to 10).

(E) Epoxycyclohexyl methyl ethers of alkanediols represented by the following formula (V):

(Wherein R ⁹ and R ¹⁰ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and r represents an integer of 2 to 20).

(F) Diepoxy trispiro compound represented by the following formula (VI):

(Wherein R ¹¹ and R ¹² each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(G) Diepoxy monospiro compound represented by the following formula (VII):

(Wherein R ¹³ and R ¹⁴ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(H) Vinylcyclohexene diepoxides represented by the following formula (VIII):

(Wherein R ¹⁵ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).
(I) Epoxycyclopentyl ethers represented by the following formula (IX):

(Wherein R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(J) Diepoxytricyclodecanes represented by the following formula (X):

(Wherein R ¹⁸ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).
Among the alicyclic epoxy resins exemplified above, the following alicyclic epoxy resins are commercially available or similar, and are more preferably used because they are relatively easy to obtain.

(A) Esterified product of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (7-oxa-bicyclo [4.1.0] hept-3-yl) methanol [formula (I) In which R ¹ = R ² = H]
(B) 4-methyl-7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (4-methyl-7-oxa-bicyclo [4.1.0] hept-3-yl) methanol Ester compound of [In the formula (I), R ¹ = 4-CH ₃ , R ² = 4-CH ₃ compound],
(C) Esterified product of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and 1,2-ethanediol [in the formula (II), R ³ = R ⁴ = H, n = 2 Compound],
(D) (7-oxabicyclo [4.1.0] hept-3-yl) methanol and adipic acid ester compound [in the formula (III), R ⁵ = R ⁶ = H, p = 4 compound] ,
(E) (4-Methyl-7-oxabicyclo [4.1.0] hept-3-yl) esterified product of methanol and adipic acid [in formula (III), R ⁵ = 4-CH ₃ , R ⁶ = 4-CH ₃ , p = 4 compound]
(F) Etherified product of (7-oxabicyclo [4.1.0] hept-3-yl) methanol and 1,2-ethanediol [in the formula (V), R ⁹ = R ¹⁰ = H, r = Compound of 2].

In addition, examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. More specifically, 1,4-butanediol diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerin triglycidyl ether; trimethylolpropane triglycidyl ether; polyethylene glycol diglycidyl ether; propylene Diglycidyl ether of glycol; Polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin Examples thereof include glycidyl ether.

The epoxy resin which comprises the adhesive agent which consists of an epoxy-type resin composition may be used individually by 1 type, and may use 2 or more types together. The epoxy equivalent of the epoxy resin used in this composition is usually in the range of 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, the flexibility of the composite polarizing plate after curing may be reduced, or the adhesive strength may be reduced. On the other hand, when it exceeds 3000 g / equivalent, compatibility with other components contained in the adhesive may be lowered.

In this adhesive, cationic polymerization is preferably used as a curing reaction of the epoxy resin from the viewpoint of reactivity. Therefore, it is preferable to mix | blend a cationic polymerization initiator with the curable epoxy resin composition which is an active energy ray hardening-type adhesive agent. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction. Hereinafter, a cationic polymerization initiator that generates a cationic species or a Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”.

The method of curing the adhesive by irradiating with active energy rays using a cationic photopolymerization initiator enables curing at room temperature, reducing the need to consider the distortion due to heat resistance or expansion of the polarizing film, and between the films Is advantageous in that it can be bonded well. In addition, since the photocationic polymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy resin.

Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, benzenediazonium hexafluoroborate, and the like. Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis (diphenylsulfonio) diphenyl sulfide bis ( Hexafluorophosphate), 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide, bis (hexafluoroantimonate), 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio ] Diphenyl sulfide bis (hexafluorophosphate), 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7 -[Di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate, 4- (p-tert-butylphenyl) Carbonyl) -4′-diphenylsulfonio-diphenyl sulfide, hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio-diphenyl sulfide, tetrakis (pentafluorophenyl) borate, etc. Is mentioned.

Examples of the iron-allene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II). -Tris (trifluoromethylsulfonyl) methanide and the like.

Commercial products of these photocationic polymerization initiators can be easily obtained. For example, “Kayarad PCI-220” and “Kayarad PCI-620” (Nippon Kayaku Co., Ltd. )), “UVI-6990” (manufactured by Union Carbide), “Adekaoptomer SP-150” and “Adekaoptomer SP-170” (manufactured by ADEKA Corporation), “CI-5102”, “ "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" and "CIP-2064S" (above, Nippon Soda Co., Ltd.), "DPI-101", "DPI-102" , “DPI-103”, “DPI-105”, “MPI-103”, “MPI-105”, “BBI-101”, “BBI-1” 2 ”,“ BBI-103 ”,“ BBI-105 ”,“ TPS-101 ”,“ TPS-102 ”,“ TPS-103 ”,“ TPS-105 ”,“ MDS-103 ”,“ MDS-105 ” "DTS-102" and "DTS-103" (manufactured by Midori Chemical Co., Ltd.), "PI-2074" (manufactured by Rhodia), and the like.

The photocationic polymerization initiator may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength.

The amount of the cationic photopolymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and preferably 15 parts by weight or less based on 100 parts by weight of the epoxy resin. When the blending amount of the cationic photopolymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy resin, curing becomes insufficient, and mechanical strength and adhesive strength tend to decrease. Moreover, when the compounding quantity of a photocationic polymerization initiator exceeds 20 weight part with respect to 100 weight part of epoxy resins, the hygroscopic property of hardened | cured material will become high because the ionic substance in hardened | cured material will increase, and durability performance. May be reduced.

When using a photocationic polymerization initiator, the curable epoxy resin composition may further contain a photosensitizer as necessary. By using a photosensitizer, the reactivity of cationic polymerization is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

Specific examples of the photosensitizer include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o Benzophenone derivatives such as methyl benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, and 4,4′-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; 2 -Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone; and others, α, α-diethoxyacetophene Non, benzyl, fluorenone, xanthone, uranyl compounds, halogen compounds, and the like. A photosensitizer may be used individually by 1 type and may use 2 or more types together. The photosensitizer is preferably contained within a range of 0.1 to 20 parts by weight in 100 parts by weight of the curable epoxy resin composition.

The epoxy resin contained in the adhesive is cured by photocationic polymerization, but may be cured by both photocationic polymerization and thermal cationic polymerization. In the latter case, it is preferable to use a photocationic polymerization initiator and a thermal cationic polymerization initiator in combination.

Examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide. These thermal cationic polymerization initiators can be easily obtained as commercial products. For example, “Adeka Opton CP77” and “Adeka Opton CP66” (manufactured by ADEKA Corporation), “CI” are available under the trade names. -2639 "and" CI-2624 "(Nippon Soda Co., Ltd.)," Sun-Aid SI-60L "," Sun-Aid SI-80L "and" Sun-Aid SI-100L "(Made by Sanshin Chemical Industry Co., Ltd.) Etc.

The active energy ray-curable adhesive may further contain a compound that promotes cationic polymerization, such as oxetanes and polyols.

Oxetanes are compounds having a 4-membered ring ether in the molecule, such as 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3 -Ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, phenol novolac oxetane and the like. These oxetanes can be easily obtained as commercial products. For example, all of them are trade names such as “Aron Oxetane OXT-101”, “Aron Oxetane OXT-121”, “Aron Oxetane OXT-211”. “Aron Oxetane OXT-221” and “Aron Oxetane OXT-212” (above, manufactured by Toagosei Co., Ltd.). These oxetanes are usually contained in the curable epoxy resin composition in a proportion of 5 to 95% by weight, preferably 30 to 70% by weight.

As the polyols, those having no acidic groups other than phenolic hydroxyl groups are preferable. For example, polyol compounds having no functional groups other than hydroxyl groups, polyester polyol compounds, polycaprolactone polyol compounds, polyol compounds having phenolic hydroxyl groups, polycarbonates A polyol etc. can be mentioned. The molecular weight of these polyols is usually 48 or more, preferably 62 or more, more preferably 100 or more, and preferably 1000 or less. These polyols are usually contained in the curable epoxy resin composition in a proportion of 50% by weight or less, preferably 30% by weight or less.

Active energy ray-curable adhesives include ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, leveling agents, plasticizers, antifoaming agents, etc. Additives can be blended. Examples of the ion trapping agent include powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, and titanium-based inorganic compounds, and examples of the antioxidant include hindered phenol-based antioxidants. Etc.

Active energy ray-curable adhesives can be used as solventless adhesives that are substantially free of solvent components, but each coating method has an optimum viscosity range, A solvent may be included. It is preferable to use a solvent that dissolves the epoxy resin composition and the like well without degrading the optical performance of the polarizing film. For example, hydrocarbons represented by toluene, esters represented by ethyl acetate, and the like. And organic solvents such as The viscosity of the active energy ray-curable adhesive used in the present invention is preferably 80 mPa · s or less, and more preferably 50 mPa · s or less. This is because when the viscosity of the active energy ray-curable adhesive exceeds 80 mPa · s, the lower limit of the thickness where bubbles do not enter tends to be thick. In order to obtain sufficient adhesive strength, the viscosity of the active energy ray-curable adhesive is preferably 1 mPa · s or more, and more preferably 10 mPa · s or more. In addition, the said viscosity points out the viscosity measured with the liquid temperature of 25 degreeC with the E-type viscosity meter.

In the example shown in FIG. 1, the transparent films 2 and 3 that are continuously drawn out from the state wound in a roll shape have an active energy ray curable adhesive on one side by the adhesive coating devices 11 and 12, respectively. Applied. The method of applying the adhesive to the transparent film is not particularly limited, and various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Of these, taking into consideration the thin film coating, the degree of freedom of the pass line, the wideness, etc., gravure rolls are preferable as the adhesive coating apparatuses 11 and 12. Examples of commercially available coating apparatuses include MCD (microchamber doctor) manufactured by Fuji Kikai Co., Ltd.

When applying an adhesive using a gravure roll as the adhesive application device 11 or 12, the thickness of the applied adhesive (application thickness) is preferably 2.0 μm or more, more preferably 2. 5-4 μm. The coating thickness of the adhesive is adjusted by the draw ratio, which is the speed ratio of the gravure roll to the line speed of the transparent film. Generally, by adjusting the draw ratio (gravure roll speed / line speed) to 0.5 to 10, the coating thickness of the adhesive can be adjusted to about 0.1 to 10 μm. More specifically, the line speed of the transparent films 2 and 3 is set to 10 to 100 m / min, the gravure roll is rotated in the direction opposite to the conveying direction of the transparent films 2 and 3, and the speed of the gravure roll is set to 5 to 1000 m / min. By doing so, the coating thickness of the adhesive can be adjusted to 0.1 to 10 μm.

After preparation, the adhesive is usually at a predetermined temperature within the range of 15 to 40 ° C. ± 5 ° C. (for example, when the predetermined temperature is 30 ° C., 30 ° C. ± 5 ° C.), preferably ± 3 ° C., more preferably It is applied in an environment adjusted to ± 1 ° C.

[3] Bonding step Next, as described above with respect to the major features of the present invention, the surface of the polarizing film on which one side or both sides are coated with an active energy ray-curable adhesive is sandwiched between the bonding rolls. To make a laminate. In the manufacturing method of the polarizing plate of this invention, the transparent film may be bonded only to either one surface of the polarizing film mentioned above, and may be bonded to both surfaces. When pasted on both sides, each transparent film may be the same or different.

In the example shown in FIG. 1, the transparent films 2 and 3 that are continuously drawn out from a state wound in a roll shape have an active energy ray curable adhesive on one side by the adhesive coating devices 11 and 12, respectively. Applied. And the transparent film 2 and 3 are respectively laminated | stacked through the said adhesive agent by the bonding rolls 5a and 5b on both surfaces of the polarizing film 1 extended | drawn continuously similarly to the said transparent films 2 and 3, and the laminated body 4 is formed. Produced. At this time, as described above, the pressing pressure of the bonding roll is set within the range of 0.5 to 1.2 MPa.

In the present invention, one of the pair of bonding rolls 5a and 5b has a tapered outer peripheral shape whose diameter decreases from the center to the end (that is, the radius of the center is larger than the radius of the end). It may be a roll. In this case, it is preferable that the bonding roll which is not a crown roll is a flat roll whose diameter is substantially uniform. The pair of bonding rolls may be flat rolls.

The shape of the crown roll is preferably designed so that the distance between the crown roll and the flat roll is substantially uniform in a state where pressing is performed in the bonding step. Here, the space | interval of a crown roll and a flat roll is a space | interval of the outer periphery which the said crown roll and the said flat roll oppose in the cross section containing the axis | shaft of the said crown roll and the axis | shaft of the said flat roll. Normally, the crown roll and the flat roll are arranged so that the axis of the crown roll and the axis of the flat roll are parallel when no pressure is applied.

For example, when the bonding roll 5a is a metal flat roll and the bonding roll 5b is a rubber crown roll, pressure is applied to the bearing member of the flat roll in the direction of the crown roll. In this state, the crown roll is less bent, but if the shape of the crown roll is designed so that the distance between the crown roll and the flat roll is substantially uniform, the laminated body Can be uniformly pressurized. Even when the crown roll is pressed in the flat roll direction, the same effect can be obtained. Further, both the flat roll and the crown roll may be pressed in directions close to each other.

When a crown roll is used, the ratio of the difference between the diameter of the center portion and the diameter of the end portion is 0.0020 to 0.0500% with respect to the length of the crown roll (length in the axial direction). Is preferred. More preferably, the content is 0.0020 to 0.020%. Usually, in such a ratio range, the shape of the crown roll can be designed so that the distance between the crown roll and the flat roll is uniform in a state where pressing is performed in the bonding step.

Further, when a crown roll is used, the tapered outer peripheral shape is preferably an arc shape. Here, the taper-shaped outer peripheral shape of the crown roll being arc-shaped means that the cross section of the crown roll on the surface including the axis of the tapered outer peripheral shape is an arc. When the shaft member of the flat roll is pressed in the bonding process, the flat roll often bends so that the outer peripheral shape becomes an arc shape, and the outer peripheral shape of the opposing crown roll has a radius of curvature similar to that. It is because it can make the space | interval at the time of the press of the opposing bonding roll (crown roll and flat roll) uniform by making it arcuate, and can bond a polarizing film and a transparent film with a uniform pressure. .

The diameter of the bonding roll is not particularly limited, but the diameter in the case of a flat roll is preferably 50 to 400 mm. In the case of a crown roll, the diameter of the end is preferably 50 to 400 mm. In addition, the diameter of each of a pair of bonding roll may be the same, and may differ. The width of the bonding roll is 300 to 3000 mm.

The material of the bonding roll includes metal and rubber. It is preferable that one of the pair of bonding rolls is a metal roll and the other is a rubber roll. Furthermore, it is more preferable that the flat roll is made of metal and the crown roll is made of rubber.

In the conventional bonding roll, the upper bonding roll to be pressed is usually made of rubber, and the lower bonding roll is made of metal. This is because the lower laminating roll is made of metal, and the lower laminating roll is not deformed when pressed because the lower laminating roll is made of metal because the drive motor is attached to the lower laminating roll. It is because it is easy to maintain the peripheral speed of a bonding roll constant. However, in this case, in order to easily adjust the curl, it is preferable that the (upper) bonding roll to be pressed is made of metal, and the other (lower) bonding roll is made of rubber.

As the base material of the metal roll, various known materials can be used, preferably stainless steel, and more preferably SUS304 (stainless steel containing 18% Cr and 8% Ni). The surface of the metal roll is preferably subjected to chrome plating.

The material of the rubber roll is not particularly limited, and examples thereof include NBR (nitrile rubber), Titan, urethane, silicon, EPDM (ethylene-propylene-diene rubber), and preferably NBR, Titan, and urethane. The hardness of the rubber roll is not particularly limited, but is usually 60 to 100 °, preferably 85 to 95 °. In addition, the hardness of a rubber roll can be measured with the hardness meter based on JISK6253. As a commercially available hardness meter, for example, a rubber hardness meter “Type-A” manufactured by Asuka Corporation is used. Specifically, the resistance of the surface of the rubber roll when the surface is pressed with a stick or the like is measured with a hardness meter.

In addition, although the example bonded by a pair of bonding roll was shown in FIG. 1, it is not restrict | limited to this, The structure which provided a pair of backup roll so that a pair of bonding roll might be pinched | interposed It may be. Further, the backup roll may be arranged only on one of the pair of rolls.

[4] Step of irradiating active energy ray to laminate In the subsequent step, the laminate obtained as described above is irradiated with active energy ray to obtain a polarizing plate. In the example shown in FIG. 1, the laminate 4 is then conveyed while being in close contact with the outer peripheral surface of the roll 13. In the example shown in FIG. 1, first active energy ray irradiation devices 14 and 15 installed at positions facing the outer peripheral surface of the roll 13, and second and subsequent activities installed further downstream in the transport direction. Energy beam irradiation devices 16, 17, and 18 and a nip roll 19 for conveyance are provided in order along the conveyance direction. In this way, in the process of transporting the laminate 4 in close contact with the outer peripheral surface of the roll 13, the active energy rays are irradiated from the first active energy ray irradiation devices 14, 15 toward the outer peripheral surface of the roll 13, and the adhesive Is cured by polymerization. The second and subsequent active energy ray irradiating devices 16, 17, and 18 arranged on the downstream side in the transport direction are devices for completely polymerizing and curing the adhesive, and may be added or omitted as necessary. it can. Finally, the laminate 4 passes through the conveyance nip roll 19 and is wound around the winding roll 20 as a polarizing plate.

The roll 13 forms a convex curved surface having a mirror-finished outer peripheral surface. The roll 37 is conveyed while the laminate 37 is in close contact with the surface, and the adhesive is polymerized and cured by the active energy ray irradiation devices 14 and 15 in the process. . The diameter of the roll 13 is not particularly limited when the adhesive is polymerized and cured and the laminate 4 is sufficiently adhered. The roll 13 may be driven or rotated according to the movement of the line of the laminate 4 or may be fixed so that the laminate 4 slides on the surface. Further, the roll 13 may act as a cooling roll for dissipating heat generated in the laminate 4 at the time of polymerization and curing by irradiation with active energy rays. In that case, the surface temperature of the roll 13 acting as a cooling roll is preferably set to 4 to 30 ° C.

The light source used for polymerizing and curing the adhesive by irradiation with active energy rays is not particularly limited, but is preferably a light source having an emission distribution at a wavelength of 400 nm or less. Examples of such a light source include 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, and a metal halide lamp.

The light irradiation intensity to the active energy ray-curable adhesive is determined for each composition of the adhesive and is not particularly limited, but is preferably 10 to 5000 mW / cm ² . When the light irradiation intensity to the resin composition is less than 10 mW / cm ² , the reaction time becomes too long, and when it exceeds 5000 mW / cm ² , adhesion occurs due to heat radiated from the lamp and heat generated during polymerization of the composition. There is a possibility that yellowing of the epoxy resin composition as a constituent material of the agent or deterioration of the polarizing film may occur. The irradiation intensity is preferably an intensity in a wavelength region effective for activation of the photocationic polymerization initiator, more preferably an intensity in a wavelength region of a wavelength of 400 nm or less, and further preferably a wavelength region of a wavelength of 280 to 320 nm. Strength.

The irradiation time of the active energy ray to the active energy ray-curable adhesive is controlled for each composition to be cured and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 55 mJ / cm ² or more, preferably is preferably set to be 10 ~ 5000mJ / cm ^2. When the integrated light amount to the adhesive is less than 10 mJ / cm ² , the generation of active species derived from the initiator is not sufficient, and the adhesive is not sufficiently cured. On the other hand, when the integrated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

In the present invention, the laminate is irradiated with active energy rays to polymerize and cure the adhesive, but polymerization curing by heating may be used in combination.

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

<Example 1>
(Preparation of polarizing film)
As an original film of polyvinyl alcohol, a long polyvinyl alcohol film “OPL film M-7500 (manufactured by Nippon Gosei Co., Ltd.)” having a polymerization degree of 2400, a saponification degree of 99.9 mol%, a thickness of 75 μm, and a width of 3000 mm was used.

First, the film was sufficiently swollen by immersing it in a swelling tank containing pure water at 30 ° C. for 80 seconds while keeping the tension state of the film so that the raw film did not loosen. The inlet / outlet roll speed ratio accompanying the swelling in the swelling tank was 1.2. After draining with a nip roll, it was immersed in a water immersion tank containing 30 ° C. pure water for 160 seconds. The draw ratio in the machine direction in this tank was 1.09 times.

Next, uniaxial stretching was performed at a draw ratio of about 1.5 times while being immersed in a dyeing tank containing an aqueous solution of 0.02 / 2.0 / 100 in weight ratio of iodine / potassium iodide / water. Then, while being immersed in a boric acid bath containing an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 12 / 3.7 / 100 at 55.5 ° C. for 130 seconds, the cumulative draw ratio from the original fabric is 5 Uniaxial stretching was performed until it became 7 times. Then, it was immersed at 40 ° C. for 60 seconds in a boric acid bath containing an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 9 / 2.4 / 100.

Further, it is washed with pure water at 8 ° C. for about 16 seconds in a water washing tank, and then sequentially passed through a drying furnace at about 60 ° C. and then a drying furnace at about 85 ° C., and the residence time in these drying furnaces is 160 in total. Drying was performed for a second. Thus, a polarizing film having a thickness of 28 μm on which iodine was adsorbed and oriented was obtained.

(Preparation of polarizing plate)
As the transparent film, a cycloolefin resin film “ZEONOR” (manufactured by ZEONOR) having a thickness of 60 μm and a triacetylcellulose film “KC8UX2MW” (manufactured by Konica Minolta) having a thickness of 80 μm were prepared. An epoxy resin composition (“KR series” manufactured by ADEKA, viscosity: 44 mPa · s, including a cationic polymerization initiator), which is an ultraviolet curable adhesive, is applied to each of these surfaces using an adhesive coating device. Worked. At this time, the line speed of the polarizing film laminate in the adhesive coating apparatus is 25 m / min, the gravure roll is rotated in the direction opposite to the conveying direction of the laminated material, and the thickness of the adhesive layer is 2.9 μm, 2 0.7 μm.

Next, the cycloolefin resin film on the upper surface of the polarizing film and the triacetyl cellulose film on the lower surface are pressed by a pair of nip rolls (bonding rolls) each having a diameter of 300 mm through the epoxy resin composition. Bonding was performed at a pressure of 1.0 MPa.

The polarizing film on which the above two types of transparent films are bonded is transferred at a line speed of 25 m / min while applying a tension of 600 N / m in the longitudinal direction, and the total integrated light amount (light irradiation intensity in the wavelength region of wavelengths 280 to 320 nm). ) Was irradiated with ultraviolet rays (UVB) of about 250 mJ / cm ² (measurement value: measured by UV Power Pack II manufactured by FusionUV).

In the obtained polarizing plate, no large bubbles of about 100 μm were visually observed between the polarizing film and the transparent film.

<Example 2>
A polarizing plate was produced in the same manner as in Example 1 except that the pressing pressure of the bonding roll was 0.8 MPa. About the obtained polarizing plate, the big bubble about 100 micrometers was not observed visually between the polarizing film and the transparent film.

<Comparative Example 1>
A polarizing plate was produced in the same manner as in Example 1 except that the pressing pressure of the bonding roll was 1.5 MPa. About the obtained polarizing plate, the big bubble about 100 micrometers was observed visually between the polarizing film and the transparent film.

<Comparative example 2>
A polarizing plate was produced in the same manner as in Example 1 except that the pressing pressure of the bonding roll was 0.1 MPa. At the bonding roll part, the film conveyance state became unstable, and wrinkles and bubbles were observed.

DESCRIPTION OF SYMBOLS 1 Polarizing film, 2, 3 transparent film, 4 laminated body, 5a, 5b bonding roll, 11, 12 adhesive coating apparatus, 13 roll, 14, 15 1st active energy ray irradiation apparatus, 16, 17, 18 Second and subsequent active energy ray irradiation devices, 19 nip rolls, 20 take-up rolls.

Claims (1)

1. A step of producing a polarizing film by subjecting the polyvinyl alcohol resin film to a dyeing treatment, a boric acid treatment and a uniaxial stretching treatment;
   Applying an active energy ray-curable adhesive to one side of the transparent film;
   A step of producing a laminate by laminating the transparent film on one or both sides of the polarizing film with the adhesive-coated surface sandwiched between the laminating rolls;
   Irradiating the laminate with active energy rays and producing a polarizing plate, comprising the steps of:
   A method for producing a polarizing plate, wherein in the step of producing the laminate, the pressing pressure of the laminating roll is in the range of 0.2 to 1.2 MPa.

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