KR101956412B1 - Method for manufacturing polarizer - Google Patents

Abstract

The present invention provides a method for producing a polarizing film, comprising the steps of: preparing a polarizing film by subjecting a polyvinyl alcohol-based resin film to a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment; a step of applying an active energy ray- A step of bonding a transparent film to the one side or both sides of the film by sandwiching the side to which the adhesive is applied between the bonding rolls to produce a laminate; and a step of producing a polarizer plate by irradiating the laminate with an active energy ray, Wherein the pressing pressure of the bonding roll is in the range of 0.2 to 1.2 MPa in the step of producing the laminate.

Description

METHOD FOR MANUFACTURING POLARIZER [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a polarizing plate useful as one of optical components constituting a liquid crystal display or the like.

The polarizing film is widely used as a polyvinyl alcohol-based resin film in which a dichromatic dye is adsorbed and oriented, and an iodine-based polarizing film using iodine as a dichromatic dye or a dye-based polarizing film using a dichromatic direct dye as a dichromatic dye Film and the like are known. These polarizing films are usually polarized by bonding a transparent film such as a triacetylcellulose film to one or both sides thereof with an adhesive.

As a method of laminating a transparent film on one side or both sides of a polarizing film, an active energy ray-curable resin is applied to the surface of the transparent film in advance, and then the polarizing film and the transparent film are bonded by sandwiching them between a pair of bonding rolls, Then, there is a method of curing the adhesive by irradiating an active energy ray (for example, Japanese Patent Application Laid-Open No. 2004-245925 (Patent Document 1), Japanese Patent Application Laid-Open No. 2009-134190 (Patent Document 2) Open Patent Publication No. 2011-95560 (Patent Document 3), etc.).

Japanese Patent Application Laid-Open No. 2004-245925 Japanese Patent Application Laid-Open No. 2009-134190 Japanese Patent Laid-Open No. 11-95560

In a polarizing plate in which a polarizing film and a transparent film coated with an adhesive of an active energy ray-curable type on one side are bonded to each other, bubbles of about 100 탆 may be mixed between the polarizing film and the transparent film. This bubble causes a phenomenon called " liquid dam " in which an active energy ray-curable adhesive that has not yet entered the gap between the polarizing film and the transparent film is gathered at a position just before the adhesive roll is sandwiched, (The " liquid dam " is pushed up and the polarizing film is pressed so that the surface opposite to the side where the " liquid dam " of the polarizing film is formed and the transparent film are bonded to each other So that the air is introduced by the contact beforehand). This is a phenomenon that does not occur when a conventional water-based pressure-sensitive adhesive is used, and it is a specific problem due to the use of an active energy ray-curable adhesive.

An object of the present invention is to provide a polarizing plate in which a polarizing film and a transparent film coated with an adhesive of an active energy ray curing type on one side are bonded to each other and bubbles are generated between the polarizing film and the transparent film And a method for producing a polarizing plate which is difficult to produce.

The present invention provides a method for producing a polarizing film, comprising the steps of: preparing a polarizing film by subjecting a polyvinyl alcohol-based resin film to a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment; a step of applying an active energy ray- A step of attaching the transparent film to the one side or both sides of the polarizing film by sandwiching the side to which the adhesive is applied between the bonding rolls to produce a laminate; and a step of producing a polarizer by irradiating the laminate with an active energy ray Wherein the pressing pressure of the bonding roll is in the range of 0.2 to 1.2 MPa in the step of manufacturing the laminated body.

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

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing an example of a whole apparatus for carrying out the method for producing a polarizing plate of the present invention. Fig.

A polarizing plate manufacturing method of the present invention comprises the steps of: (1) subjecting a polyvinyl alcohol-based resin film to a dyeing treatment, a boric acid treatment and a uniaxial stretching treatment to produce a polarizing film; and [2] (3) a step of bonding a transparent film to the one side or both sides of the polarizing film by sandwiching the side to which the adhesive is applied between the bonding rolls to produce a laminate; and [4] basically includes a step of irradiating the laminate with an active energy ray to produce a polarizing plate. The polarizing plate manufacturing method of the present invention is characterized in that, in the step of [3], the pressing pressure of the bonding roll is set within a range of 0.2 to 1.2 MPa. This makes it difficult for air to enter between the polarizing film and the transparent film, thereby making it possible to produce a polarizing plate in which bubbles are less likely to occur between the polarizing film and the transparent film.

When the pressing pressure of the joining roll is less than 0.2 MPa, since the pressing pressure is insufficient, the conveying condition of the film becomes unstable and bubbles are easily mixed, and when the pressing pressure of the joining roll exceeds 1.2 MPa, So that air 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 the bonding roll can be measured as an instantaneous pressure in, for example, a two-sheet type free scale manufactured by Fuji Film. The pressurizing pressure for this joining roll is usually applied to the bearing members at both ends of the joining roll.

Here, FIG. 1 is a diagram schematically showing an example of the entire apparatus for carrying out the method for producing a polarizing plate of the present invention. Hereinafter, with reference to Fig. 1, the entire production process of the polarizing plate of the present invention will be described in detail.

[1] Step of producing polarizing film

In the method for producing a polarizing plate of the present invention, a polarizing film is first produced by subjecting a polyvinyl alcohol-based resin film to a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment. Concretely, the polarizing film used in the present invention is one obtained by orienting a dichromatic dye on a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetic acid-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith (for example, ethylene-vinyl acetate copolymer). Other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group. The degree of saponification of the polyvinyl alcohol-based resin is 85 mol% or more, preferably 90 mol% or more, and 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-based resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like modified with aldehydes may be used.

Such a film of a polyvinyl alcohol-based resin is used as a original film of a polarizing film. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a conventionally known appropriate method. The thickness of the original film containing the polyvinyl alcohol-based resin is not particularly limited, but is, for example, about 10 to 150 mu m. Usually, it is supplied in a roll form and has a thickness in the range of 20 to 100 mu m, preferably 30 to 80 mu m, and an industrially practical width of 500 to 6000 mm. It may also be a polyester film such as an olefin film or a PET film as a substrate and a polyvinyl alcohol resin applied to both sides or one side thereof.

(Vinylon VF-PS # 7500, manufactured by Kuraray Co., Ltd. / OPL film M-7500, manufactured by Nippon Gosei Co., Ltd.) (Vinylon VF-PE # 3000, manufactured by Kuraray Co., Ltd.) having a thickness of 60 mu m, a disk thickness of 50 mu m (Vinylon VF-PE # 5000, Kuraray Co., The thickness of the disk is 30 mu m or the like.

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

In producing the polarizing film, the polyvinyl alcohol-based resin film is usually uniaxially stretched. This uniaxial stretching may be performed before the dyeing process, during the dyeing process, or after the dyeing process. In the case of performing uniaxial stretching 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, it is also possible to perform uniaxial stretching in these plural steps.

The uniaxial stretching may be uniaxially stretched between different rolls of the main yarn, or uniaxially stretched by using a heat roll. In addition, it may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which stretching is performed in a state of being swollen with a solvent. The stretching magnification is usually about 3 to 8 times.

The dyeing by the dichroic dye of the polyvinyl alcohol-based resin film in the dyeing treatment step is carried out, for example, by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, for example, iodine, a dichroic dye and the like are used. The dichroic dyes include, for example, Si. children. Dichroic direct dyes including disazo compounds such as C. I. DIRECT RED 39, dichromatic direct dyes including compounds such as trisazo, tetrakisazo, and the like. The polyvinyl alcohol-based resin film is preferably subjected to immersion treatment with water before the dyeing treatment.

When iodine is used as the dichroism dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally 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 dichroism dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 占 폚, and the immersion time (dyeing time) for 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 in which a polyvinyl alcohol-based resin film is dipped in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually water, and 100 parts by weight of 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, particularly preferably 1 × 10 ^-3 to 1 × 10 ^{- 2} are parts by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. When a dichroic dye is used as the dichroism dye, the dye aqueous solution used for dyeing usually has a temperature of 20 to 80 캜, and the dipping time (dyeing time) for the aqueous solution is usually 10 to 1,800 seconds.

The boric acid treatment step is carried out by immersing a polyvinyl alcohol-based resin film stained with a dichroic dye in an aqueous solution containing boric acid. 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 above-described dyeing process, it is preferable that the boric acid-containing aqueous solution used in the boric acid treatment step 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 immersing time in the boric acid-containing aqueous solution is usually 60 to 1200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 40 占 폚 or higher, preferably 50 to 85 占 폚, and more preferably 55 to 80 占 폚.

In the subsequent water washing treatment step, the polyvinyl alcohol resin film after the boric acid treatment is subjected to water washing treatment, for example, by immersion in water. The temperature of water in the water washing treatment is usually 4 to 40 占 폚, and the immersion time is usually 1 to 120 seconds. A method in which water is sprayed in a spray form during or before or during the water washing treatment, or water is sprayed from the slit-like spray portion to strongly contact the film may be appropriately selected. After the washing treatment, the drying treatment is usually carried out to obtain a polarizing film. In the previous stage of the drying treatment, a method of spraying water with an air knife or the like, or a method of absorbing moisture on the surface with an absorbing roll may be suitably employed. The drying treatment is preferably carried out using a hot-air dryer, a far-infrared heater, or the like. The temperature of the drying treatment is usually 30 to 100 占 폚, preferably 50 to 90 占 폚. The drying treatment time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

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

In addition, not limited to the above method, a film having a polarizing function manufactured by a separate method is also employed as the polarizing film.

[2] Step 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 a cycloolefin resin, a cellulose acetate resin, a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, a polycarbonate resin Resins, acrylic resins, polypropylene, and the like, which are conventionally widely used in the field.

The cycloolefin-based resin is a thermoplastic resin (also referred to as a thermoplastic cycloolefin-based resin) having a unit of a monomer containing a cyclic olefin (cycloolefin), such as norbornene or a polycyclic norbornene monomer. The cycloolefin resin may be a hydrogenated product of a ring-opening polymer of the cycloolefin or a ring-opening copolymer using two or more cycloolefins, or an addition polymer with a cycloolefin, a chain olefin, or an aromatic compound having a vinyl group. It is also effective that a polar group is introduced.

When a copolymer of a cycloolefin and an aromatic compound having a chain or olefin and / or a vinyl group is used, examples of the chain olefin include ethylene and propylene. Examples of the aromatic compound having a vinyl group include styrene, Substituted styrene, and the like. In such a copolymer, the unit of the monomer containing the cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). Especially when a terpolymer of a cycloolefin, a chain olefin and an aromatic compound having a vinyl group is used, the unit of the monomer containing the cycloolefin can be a relatively small amount as described above. In such a terpolymer, the unit of the monomer containing a chain olefin is usually 5 to 80 mol%, and the unit of the monomer containing an aromatic compound having a vinyl group is usually 5 to 80 mol%.

Examples of the cycloolefin resin include commercially available products such as Topas (manufactured by Ticona), Aton (manufactured by JSR Corporation), Zeonor (manufactured by Nippon Zeon Co., Ltd.) ZEONEX (manufactured by Nippon Zeon Co., Ltd.), APEL (manufactured by Mitsui Chemicals, Inc.), and OXIS (manufactured by Okura Corporation) can be preferably used. When the cycloolefin resin is formed into a film, known methods such as a solvent casting method and a melt extrusion method are suitably used. Further, a preformed cycloolefin such as, for example, Essen (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonor film (manufactured by Optesis) A commercially available product of a film made of a resin can also be used.

The cycloolefin-based resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be imparted to the cycloolefin-based resin film. The stretching is usually carried out while unwinding the film roll, and is stretched by a heating furnace in the direction of advancement of the roll (longitudinal direction of the film), in the direction perpendicular to the progressing direction (width direction of the film), or both. The temperature of the heating furnace is usually in the range of the glass transition temperature + 100 deg. C in the vicinity of the glass transition temperature of the cycloolefin-based resin. The magnification of the stretching is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin-based resin film is in the roll-wound state, since the films tends to adhere to each other and blockiness tends to occur, roll-winding is usually carried out after the protective film is bonded. Since the cycloolefin-based resin film generally has a low surface activity, the surface to be bonded to the polarizing film is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame (flame) treatment and saponification treatment . Among them, a plasma treatment, particularly an atmospheric pressure plasma treatment and a corona treatment, which can be carried out relatively easily, is preferable.

As the cellulose acetate based resin, a cellulose ester partially or completely esterified product includes, for example, cellulose acetate ester, propionic ester, butyric acid ester, mixed ester thereof and the like. More specifically, a triacetylcellulose film, a diacetylcellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film and the like can be given. Examples of such a cellulose ester based resin film include commercially available products such as Fuji Tack TD80 (manufactured by Fuji Film), Fuji Tack TD80UF (manufactured by Fuji Film), Fuji Tack TD80UZ (manufactured by Fuji Film Co., Ltd.) , KC8UYW (manufactured by Konica Minolta Opto), KC8UY (manufactured by Konica Minolta Opto), Fujitack TD60UL (manufactured by Fuji Film), KC4UYW (manufactured by Konica Minolta Opto), KC6UAW KC2UAW (manufactured by Konica Minolta Opto Co., Ltd.), and the like can be preferably used.

Also, as the transparent film, a cellulose acetate resin film imparted with a retardation property is also preferably used. Examples of commercial products of the cellulose acetate based resin film to which such retardation properties are imparted include WV BZ 438 (manufactured by Fuji Film), KC4FR-1 (manufactured by Konica Minolta Opto Co., Ltd.), KC4CR-1 (Konica Minolta Opto Co., , KC4AR-1 (manufactured by Konica Minolta Opto), and the like. Acetate cellulose is also referred to as acetylcellulose or cellulose acetate.

These cellulose acetate films are easily absorbed, and the moisture content of the polarizing plate sometimes affects the end sagging of the polarizing plate. The moisture content at the time of production of the polarizing plate is preferably as close as possible to the storage environment of the polarizing plate, for example, the equilibrium moisture content in a production line of a clean room or a storage room of a winding roll, and depends on the composition of the laminated film. , And more preferably 2.5 to 3.0%. The numerical value of the moisture content of the polarizing plate was measured by a dry weight method, and the change in weight after 105 ° C / 120 minutes.

In the present invention, the transparent film can have an optical function such as a function as a retardation film, a function as a luminance enhancement film, a function as a reflection film, a function as a transflective film, a function as a diffusion film, and an optical compensation film . In this case, for example, it is possible to have such a function by laminating an optical functional film such as a retardation film, a luminance enhancement film, a reflection film, a transflective film, a diffusion film, or an optical compensation film on the surface of a transparent film In addition to this, the transparent film itself may be provided with such a function. In addition, a plurality of functions such as a diffusion film having the function of a brightness enhancement film may be provided in the transparent film.

For example, the stretching process described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, and the like are performed on the above-mentioned transparent film, or the process described in Japanese Patent No. 3168850 is performed to give a function as a retardation film can do. The retardation property in the retardation film can be appropriately selected, for example, in the range of the front retardation value of 5 to 100 nm and the thickness retardation value of 40 to 300 nm. Further, by forming fine holes in the above-mentioned transparent film by the method described in Japanese Patent Application Laid-Open Nos. 2002-169025 and 2003-29030, or by forming fine holes having different center wavelengths of selective reflection 2 By superimposing the cholesteric liquid crystal layer above the layer, a function as a brightness enhancement film can be given.

When a metal thin film is formed on the above-mentioned transparent film by vapor deposition, sputtering or the like, a function as a reflective film or a transflective film can be given. By coating the above-mentioned transparent film with a resin solution containing fine particles, a function as a diffusion film can be imparted. Further, by coating a liquid crystal compound such as a discotic liquid crystal compound and orienting the above-mentioned transparent film, a function as an optical compensation film can be imparted. Further, the transparent film may contain a compound exhibiting a retardation. Further, various optical functional films may be directly bonded to the polarizing film by using a suitable adhesive. Examples of the commercially available optical functional film include a luminance enhancement film such as DBEF (available from 3M Company, Japan, available from Sumitomo 3M Ltd.), a WV film (manufactured by Fuji Film Co., Ltd.) (Manufactured by Shin-Etsu Chemical Co., Ltd.), VA-TAC (manufactured by Konica Minolta Opto Co., Ltd.) ), And Sumikarite (manufactured by Sumitomo Chemical Co., Ltd.).

The thickness of the transparent film used in the present invention is preferably small, but if it is too thin, the strength is lowered and the workability is lowered. On the other hand, if the thickness is too large, the transparency may deteriorate or the curing time required after lamination may be increased. Therefore, the suitable thickness of the transparent film is, for example, 5 to 200 占 퐉, preferably 10 to 150 占 퐉, and more preferably 10 to 100 占 퐉.

A surface treatment such as a corona treatment, a flame treatment, a plasma treatment, an ultraviolet treatment, a primer coating treatment or a saponification treatment is applied to the polarizing film and / or the transparent film in order to improve the adhesion between the adhesive and the polarizing film and / .

The transparent film may be subjected to surface treatment such as antiglare treatment, anti-reflection treatment, hard coating treatment, antistatic treatment and antifouling treatment, either singly or in combination of two or more. The transparent protective film and / or the transparent film surface protective layer may contain an ultraviolet absorber such as a benzophenone-based compound or a benzotriazole-based compound or a plasticizer such as a phenylphosphate-based compound or a phthalic acid ester compound.

(Active energy ray curable adhesive)

As an active energy ray curable adhesive, an adhesive containing an epoxy resin composition containing an epoxy resin which is cured by irradiation with an active energy ray from the viewpoints of weather resistance, refractive index and durability can be mentioned. However, the present invention is not limited thereto. Various active energy ray curable adhesives (organic solvent adhesives, hot melt adhesives, solventless adhesives, etc.) conventionally used in the production of polarizing plates can be employed. Among these, an acrylic composition, an acrylamide composition, an epoxy acrylate composition, a urethane composition, a vinyl composition and the like are included. Examples of the curing reaction include radical polymerization, cation polymerization, anion polymerization, and thermal polymerization.

The epoxy resin means a compound having two or more epoxy groups in the molecule. From the viewpoints of weatherability, refractive index, cationic polymerizability and the like, the epoxy resin contained in the curable epoxy resin composition which is an adhesive is preferably an epoxy resin containing no aromatic ring in the molecule (see, for example, Patent Document 1) . As such epoxy resins, hydrogenated epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins and the like can be exemplified.

The hydrogenated epoxy resin can be obtained by a method of glycidyl etherification of a nuclear hydrogenated polyhydroxy compound obtained by selectively subjecting a polyhydroxy compound as a raw material of an aromatic epoxy resin to a nuclear hydrogenation reaction under pressure in the presence of a catalyst . 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; Novolak type epoxy resins such as phenol novolak epoxy resin, cresol novolak epoxy resin, and hydroxybenzaldehyde phenol novolac epoxy resin; Glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and epoxy polyvinylphenols. The epoxy resin may be used alone or in combination of two or more. Of hydrogenated epoxy resins, hydrogenated glycidyl ethers of bisphenol A are preferred.

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

The compound in which one or more hydrogen atoms of the (CH ₂ ) _m in the above formula are removed from other groups in the chemical structure may be an alicyclic epoxy resin. (CH ₂ ) _m may be suitably substituted with a straight chain alkyl group such as methyl group or ethyl group. Among the alicyclic epoxy resins, an epoxy resin having an oxabicyclohexane ring (wherein m = 3 in the above formula) or an oxabicycloheptane ring (in which m = 4 in the above formula) exhibits excellent adhesiveness, . Hereinafter, the alicyclic epoxy resin which is preferably used is specifically exemplified, but the present invention is not limited thereto.

(a) epoxycyclohexylmethyl epoxycyclohexanecarboxylates represented by the following formula (I):

(Wherein R ¹ and R ² represent, independently of each other, a hydrogen atom or a straight chain alkyl group having 1 to 5 carbon atoms).

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

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

(c) epoxycyclohexylmethyl esters of dicarboxylic acids represented by the following formula (III):

(Wherein R ⁵ and R ⁶ are each independently of the other a hydrogen atom or a straight chain alkyl group of 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 are, independently of each other, a hydrogen atom or a straight chain alkyl group of 1 to 5 carbon atoms, and q represents an integer of 2 to 10).

(e) epoxycyclohexyl methyl ethers of alkane diols represented by the following formula (V):

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

(f) a diepoxy trispyro compound represented by the following formula (VI):

(Wherein R < ¹¹ > and R < ¹² > independently represent a hydrogen atom or a straight chain alkyl group of 1 to 5 carbon atoms).

(g) a diepoxy monospiro compound represented by the following formula (VII):

(Wherein R ¹³ and R ¹⁴ represent, independently of each other, a hydrogen atom or a straight chain alkyl group having 1 to 5 carbon atoms).

(h) vinylcyclohexene epoxides represented by the following formula (VIII):

(Wherein R ¹⁵ represents a hydrogen atom or a straight chain alkyl group having 1 to 5 carbon atoms).

(i) epoxycyclopentyl ethers represented by the following formula (IX):

(Wherein R ¹⁶ and R ¹⁷ represent, independently of each other, a hydrogen atom or a straight chain alkyl group having 1 to 5 carbon atoms).

(j) diepoxytricyclodecane compounds represented by the following formula (X):

(Wherein R ¹⁸ represents a hydrogen atom or a straight chain alkyl group of 1 to 5 carbon atoms).

Among the above-exemplified alicyclic epoxy resins, the following alicyclic epoxy resins are more preferably used because they are commercially available, or as analogues thereof, and are relatively easy to obtain.

(A) an ester of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (7-oxa-bicyclo [4.1.0] hept- ¹ = compound of R < ² > = H]

(B) An esterified product of 4-methyl-7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (4-methyl- [In the formula (I), a compound of R ¹ = 4-CH ₃ and R ² = 4-CH ₃ ]

(C) an esterified product of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and 1,2-ethanediol [compound of formula (II) wherein R ³ = R ⁴ = H, n = 2] ,

Compounds of formula (III) wherein R ⁵ = R ⁶ = H, p = 4], (D) (7-oxabicyclo [4.1.0] hept-3-yl) methanol and adipic acid [

(E) (R ⁴ = CH ₃ , R ⁶ = CH ₃ ) in the formula (III) with an esterified product of (4-methyl- 4-CH ₃ , p = 4]

(F) (7- oxabicyclo [4.1.0] hept-3-yl) ether in the cargo [formula (V) of methanol and 1,2-ethanediol, R ⁹ = R ¹⁰ = a H, r = 2 compound].

Examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. More specifically, diglycidyl ether of 1,4-butanediol; Diglycidyl ether of 1,6-hexanediol; Triglycidyl ether of glycerin; Triglycidyl ether of trimethylolpropane; Diglycidyl ether of polyethylene glycol; Diglycidyl ether of propylene glycol; And polyglycidyl ethers of polyether polyols 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.

The epoxy resin constituting the adhesive containing the epoxy resin composition may be used alone or in combination of two or more. 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. If the epoxy equivalent is less than 30 g / equivalent, the flexibility of the composite polarizer after curing may be lowered or the adhesive strength may be lowered. On the other hand, if 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 incorporate a cationic polymerization initiator into the curable epoxy resin composition which is an active energy ray curable adhesive. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation of an active energy ray such as visible light, ultraviolet ray, X-ray or electron ray to initiate the polymerization reaction of the epoxy group. Hereinafter, the cationic polymerization initiator for generating a cationic species or Lewis acid by irradiation of an active energy ray to initiate the polymerization reaction of the epoxy group is referred to as " photo cationic polymerization initiator ".

The method of curing the adhesive by irradiation of an active energy ray using a photo cationic polymerization initiator enables curing at room temperature and reduces the need to take into account distortion due to heat resistance or expansion of the polarizing film, It is advantageous in that it can be bonded. Further, since the photo cationic polymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with an epoxy resin.

Examples of the photo cationic polymerization initiator include aromatic diazonium salts; Onium salts such as aromatic iodonium salts and aromatic sulfonium salts; Iron-arene complexes and the like.

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

The aromatic sulfonium salts include, for example, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4'-bis ( Diphenylsulfone bis (hexafluorophosphate), 4,4'-bis [di (? - hydroxyethoxy) phenylsulfonio] diphenylsulfide bis (hexafluoroantimonate) (P-toluyl) sulfonyl] diphenylsulfide bis (hexafluorophosphate), 4,4'-bis [di (? - hydroxyethoxy) phenylsulfonio] (P-toluyl) sulfonium] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenyl Diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfone-diphenylsulfide hexafluorophosphate, And the like can be mentioned diphenyl sulfide tetrakis (pentafluorophenyl) borate-antimonate, 4- (p-tert- butylphenyl-carbonyl) -4'-di (p- toluyl) Pony O.

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

Commercially available products of these cationic photopolymerization initiators can be easily obtained. For example, "Kayarad PCI-220" and "Kayarad PCI-620" (trade names, manufactured by Nippon Kayaku Co., , "Adeka Optomer SP-150" and "Adeka Optomer SP-170" (manufactured by Adeka Corporation), "CI-6990" (manufactured by Union Carbide Corporation) DPI-101 "," CIP-2082S "and" CIP-2064S "(manufactured by Nippon Soda Co., Ltd.)," CIT- DPI-103, DPI-105, MPI-103, MPI-105, BBI-101, BBI-102, BBI- 105, TPS-101, TPS-102, TPS-103, TPS-105, MDS-103, MDS-105, DTS- (Manufactured by Midori Kagaku Co., Ltd.) and " PI-2074 " (manufactured by Rhodia).

The cationic photopolymerization initiator may be used singly or as a mixture of two or more thereof. Among them, an aromatic sulfonium salt is preferably used because it has an ultraviolet ray absorbing property even in a wavelength range of 300 nm or more and is therefore excellent in curability and can provide a cured product having good mechanical strength and adhesive strength.

The compounding amount of the photo cationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and more preferably 15 parts by weight or less, based on 100 parts by weight of the epoxy resin. If the blending amount of the photo cationic polymerization initiator is less than 0.5 part by weight based on 100 parts by weight of the epoxy resin, the curing becomes insufficient and the mechanical strength and the adhesive strength tend to be lowered. If the compounding amount of the photo cationic polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy resin, the amount of the ionic substance in the cured product increases to increase the hygroscopicity of the cured product.

When a photo cationic polymerization initiator is used, the curable epoxy resin composition may further contain a photosensitizer, if necessary. By using a photosensitizer, the reactivity of the cationic polymerization is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfate compound, a redox compound, an azo compound and a diazo compound, a halogen compound, a light reducing pigment and the like.

More specific examples of the photosensitizer include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and?,? -Dimethoxy-? -Phenylacetophenone; Benzophenone derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, and 4,4'-bis (diethylamino) benzophenone; Thioxanthone derivatives such as 2-chlorothioxanthone, and 2-isopropylthioxanthone; Anthraquinone derivatives such as 2-chloro anthraquinone, and 2-methyl anthraquinone; Acridone derivatives such as N-methyl acridone, and N-butyl acridone; Other examples include?,? - diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compound, and halogen compound. The photosensitizer may be used alone or in combination of two or more. It is preferable that the photosensitizer is contained in the 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 from photo cation polymerization, but may also be cured by both photo cation polymerization and thermal cation polymerization. In the latter case, a photo cationic polymerization initiator and a thermal cationic polymerization initiator are preferably used in combination.

Examples of the thermal cationic polymerization initiator include a benzylsulfonium salt, a thiophenium salt, a thioronium salt, a benzylammonium salt, a pyridinium salt, a hydrazinium salt, a carboxylic acid ester, a sulfonic acid ester, and an amine imide. These thermal cationic polymerization initiators can be easily obtained as commercial products, and examples thereof include "ADEKA OPTON CP77" and "ADEKA OPTON CP66" (trade names, manufactured by Adeka Kagaku Co., Ltd.) CI-2639 "and" CI-2624 "(manufactured by Nippon Soda Co., Ltd.)," Sun Aid SI-60L "," Sun Aid SI-80L "and" Sun Aid SI- Manufactured by Kabushiki Kaisha).

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

The oxetanes are compounds having a 4-membered ring ether in the molecule, and examples thereof include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxy (3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) ox Cetane, phenol novolac oxetane, and the like. These oxetanes are commercially available as commercially available products, and examples thereof include "AARON oxetane OXT-101", "AARON oxetane OXT-121", "AARON oxethane OXT-211" , "Aronoxetan OXT-221" and "Aronoxetan OXT-212" (all manufactured by Toagosei Co., Ltd.). These oxetanes are contained in the curable epoxy resin composition in an amount of usually 5 to 95% by weight, preferably 30 to 70% by weight.

As the polyol, it is preferable that an acid group other than the phenolic hydroxyl group is not present. For example, a polyol compound having no functional group other than the hydroxyl group, a polyester polyol compound, a polycaprolactone polyol compound, a polyol compound having a phenolic hydroxyl group , Polycarbonate polyol, and the like. The molecular weight of these polyols is usually 48 or more, preferably 62 or more, more preferably 100 or more, and further preferably 1000 or less. These polyols are usually contained in a proportion of not more than 50% by weight, preferably not more than 30% by weight, in the curable epoxy resin composition.

Additives such as an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a leveling agent, a plasticizer, and an antifoaming agent may be further added to the active energy ray curable adhesive. Examples of the ion trap agent include inorganic compounds such as powdery bismuth, antimony, magnesium, aluminum, calcium, titanium and mixtures thereof. Examples of the antioxidant include hindered phenol antioxidants have.

The active energy ray-curable adhesive can be used as a solvent-free adhesive agent substantially not containing a solvent component. However, since each coating method has an optimum viscosity range, a solvent may be added for viscosity adjustment. As the solvent, it is preferable to use a solvent which dissolves an epoxy resin composition or the like well without lowering the optical performance of the polarizing film. For example, organic solvents such as hydrocarbons typified by toluene and esters typified by ethyl acetate . 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. When the viscosity of the active energy ray-curable adhesive exceeds 80 mPa · s, the lower limit of the thickness at which bubbles are not mixed tends to be thickened. Further, in order to obtain sufficient adhesive strength, the viscosity of the active energy ray-curable adhesive is preferably 1 mPa · s or more, more preferably 10 mPa · s or more. Further, the viscosity refers to a viscosity measured at a liquid temperature of 25 캜 by an E-type viscometer.

In the example shown in Fig. 1, the transparent films 2 and 3, which are continuously unwound from the roll-wound state, are coated with an active energy ray-curable adhesive on one side by adhesive coating devices 11 and 12, respectively do. The method of coating the adhesive on the transparent film is not particularly limited, but various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Among them, a gravure roll is preferable as the adhesive applicators 11 and 12 in consideration of the thin film coating, the degree of freedom of the pass line, and the correspondence to the wide width. A commercially available coating apparatus includes an MCD (micro chamber doctor) manufactured by Fuji Machinery Co., Ltd. and the like.

In the case where the adhesive is applied using a gravure roll as the adhesive applicators 11 and 12, the thickness (coating thickness) of the applied adhesive is preferably 2.0 m or more, and more preferably 2.5 to 4 m. The coating thickness of the adhesive is adjusted in accordance with the draw ratio, which is the velocity ratio of the gravure roll to the line speed of the transparent film. In general, by adjusting the draw ratio (speed / line speed of the gravure roll) to 0.5 to 10, the coating thickness of the adhesive can be adjusted to about 0.1 to 10 mu m. More specifically, the gravure roll is rotated in the direction opposite to the conveying direction of the transparent film (2, 3) with the line speed of the transparent film (2, 3) set at 10 to 100 m / 1000 m / min, the coating thickness of the adhesive can be adjusted to 0.1 to 10 탆.

After the adhesive is produced, it is preferable that the adhesive is heated to a predetermined temperature within a range of usually 15 to 40 ° C ± 5 ° C (for example, 30 ° C ± 5 ° C when the predetermined temperature is 30 ° C) Is applied under an environment adjusted to ± 1 ° C.

[3] Bonding process

Next, as described above with respect to the major feature of the present invention, a transparent film is bonded to one side or both sides of a polarizing film by sandwiching the side coated with an active energy ray-curable adhesive between the bonding rolls to produce a laminate do. In the method for producing a polarizing plate of the present invention, the transparent film may be bonded to only one of the above-mentioned polarizing films, or may be bonded to both sides. When bonded to both sides, the respective transparent films may be the same or different kinds.

In the example shown in Fig. 1, the transparent films 2 and 3, which are continuously unwound from the roll-wound state, are coated with an active energy ray-curable adhesive on one side by adhesive coating devices 11 and 12, respectively do. The transparent films 2 and 3 are superimposed on the both sides of the polarizing film 1 which has been continuously released in the same manner as the transparent films 2 and 3 by the bonding rolls 5a and 5b through the adhesive The laminate 4 is produced. At this time, the pressing pressure of the bonding roll is set within the range of 0.5 to 1.2 MPa as described above.

In the present invention, one of the pair of bonding rolls 5a and 5b may be a crown roll having a tapered outer circumferential shape in which the diameter decreases from the central portion to the end portion (that is, the radius of the central portion is larger than the radius of the end portion) . In this case, it is preferable that the bonding roll on the side other than the crown roll is a flat roll having a substantially uniform diameter. Further, the pair of bonding rolls may all be flat rolls.

It is preferable that the shape of the crown roll is designed such that the gap between the crown roll and the flat roll is substantially uniform in a state where the pressing is performed in the joining step. Here, the interval between the crown roll and the flat roll is the interval between the opposite outer circumferences of the crown roll and the flat roll in the cross section including the axis of the crown roll and the axis of the flat roll. Normally, the crown roll and the flat roll are arranged such that the axis of the crown roll and the axis of the flat roll are parallel to each other in a state where the pressing is not performed.

For example, when the joining roll 5a is a metal flat roll and the joining roll 5b is a crown roll made of rubber, pressure is applied to the bearing member of the flat roll in the direction of the crown roll. If the shape of the crown roll is designed so that the gap between the crown roll and the flat roll is substantially uniform, the laminate can be pressed uniformly. The same effect can also be obtained when the crown roll is pressed in the direction of the flat roll. Further, both of the flat roll and the crown roll may be pressed in a direction in which they are 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 preferably 0.0020 to 0.0500% with respect to the length (axial length) of the crown roll. And more preferably 0.0020 to 0.020%. Normally, in such a ratio range, it is possible to design the shape of the crown roll so that the gap between the crown roll and the flat roll becomes uniform in a state where the pressing is performed in the joining step.

In the case of using a crown roll, it is preferable that the tapered outer circumferential shape of the crown roll is an arc shape. Here, the tapered outer circumferential shape of the crown roll is an arc shape, which means that the cross-section of the crown roll on the surface including the tapered outer circumferential axis is an arc. When the shaft member of the flat roll is pressed in the joining step, the flat roll is often bent so that the outer circumferential shape becomes an arc shape, and the outer circumferential shape of the opposing crown roll is formed into an arc shape having the same radius of curvature, This is because it is possible to make the distance between pressing rolls (crown rolls and flat rolls) opposed to each other uniform, and to bond the polarizing film and the transparent film at a uniform pressure.

The diameter of the joining roll is not particularly limited, but the diameter in the case of a flat roll is preferably 50 to 400 mm. The diameter of the end portion in the case of a crown roll is preferably 50 to 400 mm. The diameter of each of the pair of bonding rolls may be the same or different. The width of the bonding roll is 300 to 3000 mm.

The material of the joining roll may be metal or rubber. It is preferable that one of the pair of bonding rolls is a metal roll and the other is a rubber roll. It is more preferable that the flat roll is made of metal and the crown roll is made of rubber.

In the conventional joining roll, the joining roll on the upper side which is normally pressed is made of rubber, and the joining roll on the lower side is made of metal. This is because the lower joining roll is made of metal so that the lower joining roll is not deformed at the time of pressurization and the main speed of the joining roll is easily kept constant Because. However, in this case, in order to facilitate the adjustment of the curling, it is preferable that the bonding roll (upper side) to be pressed is made of metal and the other (lower side) 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% of Cr and 8% of Ni). The surface of the metal roll is preferably subjected to a chromium plating treatment.

The material of the rubber roll is not particularly limited, but NBR (nitrile rubber), titan, urethane, silicone, EPDM (ethylene-propylene-diene rubber) and the like are preferable, and NBR, Titan and urethane are preferable. The hardness of the rubber roll is not particularly limited, but is usually 60 to 100 °, preferably 85 to 95 °. The hardness of the rubber roll can be measured by a hardness meter according to JIS K6253. As a commercially available hardness meter, for example, a rubber hardness meter "Type-A" manufactured by Asuka Co., Ltd. is used. Specifically, the resistance of the surface of the rubber roll when the surface is pressed by a rod or the like is measured with a hardness meter.

1 shows an example of joining with a pair of joining rolls. However, the present invention is not limited thereto, and a pair of joining rolls may be interposed and a pair of backup rolls may be further provided. Further, a backup roll may be disposed on only one side of the pair of rolls.

[4] Step of irradiating the laminate with active energy rays

In the subsequent step, the laminate obtained as described above is irradiated with an active energy ray to obtain a polarizing plate. In the example shown in Fig. 1, the laminate 4 is then conveyed while closely contacting the outer circumferential surface of the roll 13. In the example shown in Fig. 1, the first active energy ray irradiating devices 14 and 15 provided at positions facing the outer circumferential surface of the roll 13, and the second and subsequent active energy ray irradiating devices The apparatuses 16, 17, 18 and the transporting nip roll 19 are arranged in order along the transport direction. Thus, in the course of transporting the layered product 4 while closely contacting the outer peripheral surface of the roll 13, active energy rays are irradiated from the first active energy ray irradiating device 14 or 15 toward the outer peripheral surface of the roll 13 , And the adhesive is polymerized and cured. Further, the second and subsequent active energy ray irradiating devices 16, 17, and 18 disposed on the downstream side in the carrying direction are devices for fully polymerizing and curing the adhesive agent, and can be added or omitted as necessary. Finally, the layered product 4 passes through the transporting nip roll 19 and is wound on the winding roll 20 as a polarizing plate.

The roll 13 constitutes a convex curved surface whose outer circumferential surface is mirror-finished and is conveyed while adhering the laminated body 4 to the surface thereof. During the process, the active energy ray irradiating devices 14 and 15 polymerize and cure the adhesive . The diameter of the rolls 13 is not particularly limited in order to polymerize and cure the adhesive and sufficiently adhere the layered product 4. [ The roll 13 may be driven or rotated to move the line of the laminate 4, or may be fixed so that the laminate 4 slides on the surface. The roll 13 may also serve as a cooling roll for dissipating the heat generated in the laminate 4 at the time of polymerization curing by irradiation of active energy rays. In this case, the surface temperature of the roll 13 to be used as the cooling roll is preferably set to 4 to 30 占 폚.

The light source used for polymerizing and curing the adhesive by irradiation of an active energy ray is not particularly limited, but is preferably a light source having a light emission distribution at a wavelength of 400 nm or less. Examples of such light sources include low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps, chemical lamps, black light lamps, microwave excited mercury lamps, and metal halide lamps.

The light irradiation intensity for the active energy ray-curable adhesive is not particularly limited, as determined depending on the composition of the adhesive, but is preferably 10 to 5000 mW / cm ² . If the light irradiation intensity to the resin composition is less than 10 mW / cm ² , the reaction time becomes too long, and if it exceeds 5,000 mW / cm ² , heat radiated from the lamp and heat generated during polymerization of the composition, There is a possibility that yellowing of the epoxy resin composition or the like or deterioration of the polarizing film may occur. The irradiation intensity is preferably the intensity in the wavelength range effective for activation of the photo cationic polymerization initiator, more preferably the intensity in the wavelength range of 400 nm or less, more preferably the wavelength range of 280 to 320 nm .

The irradiation time of the active energy ray for the active energy ray-curable adhesive is controlled for each composition to be cured and is not particularly limited. However, the total amount of light to be displayed as the product of irradiation intensity and irradiation time is 55 mJ / cm ² or more, preferably 10 To 5000 mJ / cm < ² >. If the integrated amount of light for the adhesive is less than 10 mJ / cm ² , the generation of the active species derived from the initiator is not sufficient and the curing of the adhesive becomes insufficient. On the other hand, when the accumulated light quantity exceeds 5000 mJ / cm ² , the irradiation time becomes very long, which is disadvantageous for the improvement of the productivity.

In the present invention, the adhesive is polymerized and cured by irradiating the laminate with an active energy ray, but polymerization curing by heating may also be used in combination.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

≪ Example 1 >

(Production of polarizing film)

As the original film of polyvinyl alcohol, a long polyvinyl alcohol film "OPL film M-7500 (manufactured by Nippon Gosei)" having a degree of polymerization of 2400, a degree of saponification of 99.9 mol%, a thickness of 75 μm and a width of 3000 mm was used.

First, the original film was immersed in a swelling tank containing pure water at 30 DEG C for 80 seconds while keeping the tension of the film so that the original film was not loosened, thereby sufficiently swelling the film. The ratio of the roll speed at the inlet to the exit due to swelling in the swelling bath was 1.2. After dewatering in a nip roll, it was immersed in a water immersion tank containing pure water at 30 DEG C 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 immersing in a dyeing bath containing an aqueous solution of iodine / potassium iodide / water in a weight ratio of 0.02 / 2.0 / 100. Thereafter, uniaxial stretching was carried out by soaking in a boric acid bath containing an aqueous solution of 12 / 3.7 / 100 by weight of potassium iodide / boric acid / water at 55.5 DEG C for 130 seconds, until the cumulative stretching magnification from the disk reached 5.7. Thereafter, it was immersed in a boric acid bath containing an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 9 / 2.4 / 100 at 40 ° C for 60 seconds.

Then, the substrate was rinsed with pure water at 8 DEG C for about 16 seconds in a water bath, and then dried at about 60 DEG C and then at about 85 DEG C successively, and the retention time in the drying furnace was set to 160 seconds Drying was carried out. Thus, a polarizing film having a thickness of 28 mu m in which iodine was adsorbed and oriented was obtained.

(Production of polarizing plate)

As a transparent film, a cycloolefin resin film "ZEONOR" (manufactured by Nippon Zeon Co., Ltd.) having a thickness of 60 μm and a triacetyl cellulose film "KC8UX2MW" (manufactured by Konica Minolta Co., Ltd.) having a thickness of 80 μm were prepared (KR series, manufactured by Adeka Co., Ltd., viscosity: 44 mPa 占 퐏; including a cationic polymerization initiator), which is an ultraviolet curable adhesive, was coated on one side thereof using an adhesive applicator. At this time, the gravure roll was rotated in the direction opposite to the conveying direction of the laminated material with the line speed of the polarizing film laminate in the adhesive coating device set at 25 m / min, and the thickness of the adhesive layer was set to 2.9 탆 and 2.7 탆.

Next, the cycloolefin resin film was applied to the upper surface of the polarizing film, and the triacetyl cellulose film was attached to the lower surface thereof with a pair of nip rolls (bonding rolls) each having a diameter of 300 mm through the epoxy resin composition, respectively, MPa.

The polarizing film to which the two types of transparent films were bonded was fed at a line speed of 25 m / min while applying a tensile force of 600 N / m in the longitudinal direction to obtain a total accumulated light quantity (of light intensity in a wavelength range of 280 to 320 nm Ultraviolet ray (UVB) of about 250 mJ / cm ² (measurement value by UV Power Fuck II manufactured by Fusion UV) was irradiated.

With respect to the obtained polarizing plate, no large bubbles of about 100 mu m 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 set to 0.8 MPa. With respect to the resulting polarizing plate, no large bubbles of about 100 mu m were visually observed 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. With respect to the obtained polarizing plate, a large bubble of about 100 mu m was visually observed 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. The conveying state of the film was unstable in the joining roll portion, and wrinkles and bubbles were observed.

1: polarizing film
2, 3: Transparent film
4:
5a, 5b:
11, 12: Adhesive coating device
13: roll
14, 15: first active energy ray irradiating device
16, 17, 18: active energy ray irradiator
19: Nip roll
20: winding roll

Claims (1)

A step of producing a polarizing film by performing a dyeing treatment, a boric acid treatment and a uniaxial stretching treatment on a polyvinyl alcohol based resin film,
A step of applying an active energy ray-curable adhesive to one side of the transparent film,
A step of superimposing the transparent film on both sides of the polarizing film through the adhesive and joining the transparent film between the pair of bonding rolls to manufacture a laminated body;
And a step of irradiating the laminate with an active energy ray to manufacture a polarizing plate,
Among the pair of joining rolls, the joining rolls to be pressed are made of metal, the other joining rolls are made of rubber,
In the step of applying the active energy ray-curable adhesive material, the viscosity of the adhesive is in the range of 10 mPa · s to 50 mPa · s and the coating thickness is in the range of 2.0 to 4 μm,
Wherein the pressing pressure by the pair of bonding rolls is in the range of 0.2 to 1.2 MPa in the step of producing the laminate.

Images