TWI591389B - Method for manufacturing polarizing plate - Google Patents

Description

Method for manufacturing polarizing plate

The present invention relates to a method of manufacturing a polarizing plate which is used as one of optical parts constituting a liquid crystal display device or the like.

The polarizing film is widely used as a dichroic dye to be adsorbed to a polyvinyl alcohol resin film, and an iodine-based polarizing film containing iodine as a dichroic dye and a dichroic dye as a dichroic dye are known. The dye is a polarizing film or the like. These polarizing films are usually laminated on a single surface or both surfaces of a transparent film such as a triacetyl cellulose film through a bonding agent to form a polarizing plate.

As a method of applying a single-sided or two-area transparent film to 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 laminated by a pair of bonding rolls. Then, the active energy ray is irradiated to the splicing and hardening. (For example, refer to Japanese Laid-Open Patent Publication No. 2004-245925 (Patent Document 1), JP-A-2009-134190 (Patent Document 2), and JP-A-2011- Japanese Patent Publication No. 95560 (Patent Document 3). [Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-245925

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-134190

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2011-95560

In the polarizing plate in which the polarizing film is bonded and the transparent film of the active energy ray-curable bonding agent is applied to one surface, bubbles of about 100 μm may be mixed between the polarizing film and the transparent film. It is recognized that the bubble is an active energy ray-curable bonding agent which cannot enter between the polarizing film and the transparent film, and accumulates in the place before the pinch of the bonding roller, causing a phenomenon called "liquid dam". Therefore, the polarizing film is caused to bite air between the opposite surface on the side of the "liquid bank" and the transparent film (the expansion of the liquid bank) presses the polarizing film, and the opposite side of the side of the "liquid bank" is formed on the polarizing film. The transparent film is in contact with the film before it is bonded, and bites into the air). This is a phenomenon which is not caused when a conventional water-based adhesive is used, but is a problem unique to the use of an active energy ray-curing type bonding agent.

The present invention has been made to solve the above problems, and an object of the invention is to provide a method for producing a polarizing plate, which is a polarizing plate in which a polarizing film and a transparent film coated with an active energy ray-curable bonding agent on one side are bonded, wherein the polarizing film and the transparent film are transparent. Air bubbles are less likely to occur between the films.

The present invention relates to a method for producing a polarizing plate, comprising the steps of performing a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment on a polyvinyl alcohol-based resin film to form a polarizing film; and applying an active energy ray-hardening joint on one side of the transparent film. a step of coating the surface of the transparent film coated with the bonding agent on the one surface or both sides of the polarizing film, and laminating the bonding film to form a laminate And a step of irradiating the laminated body with an active energy ray to form a polarizing plate, wherein the pressing force of the bonding roller in the step of forming the laminated body is in a range of 0.2 to 1.2 MPa.

According to the manufacturing method of the present invention, a method for producing a polarizing plate, which is a polarizing plate in which a polarizing film and a transparent film coated with an active energy ray-curable bonding agent on one side are bonded, wherein a polarizing film and a transparent film are provided Bubble polarizers are less likely to occur.

1‧‧‧ polarizing film

2, 3‧‧‧ transparent film

4‧‧‧Layered body

5a, 5b‧‧‧ affixing rolls

11, 12 ‧ ‧ cement coating device

13‧‧‧ Roll

14, 15‧‧‧1st active energy ray irradiation device

16, 17, ‧ ‧ ‧ after 2nd active energy ray irradiation device

19‧‧‧Pinch roller

20‧‧‧Winding roller

Fig. 1 is a view showing an example of the entire apparatus for carrying out the method for producing a polarizing plate of the present invention.

The method for producing a polarizing plate of the present invention basically comprises the steps of: [1] performing a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment on a polyvinyl alcohol-based resin film to prepare a polarizing film; and [2] coating a single side of the transparent film. a step of preparing an active energy ray-curable bonding agent; [3] the step of coating the surface of the transparent film coated with the bonding agent on the one surface or both sides of the polarizing film with a bonding roll to form a laminated body And [4] a step of irradiating the above-mentioned laminated body with an active energy ray to prepare a polarizing plate. In the method for producing a polarizing plate of the present invention, in the step (3), the pressing force of the bonding roller is in the range of 0.2 to 1.2 MPa. Thereby, air can be hardly trapped between the polarizing film and the transparent film, and the bubble polarizing plate is less likely to occur between the polarizing film and the transparent film.

The pressing force of the bonding roller is less than 0.2 MPa, due to the push extrusion When the force is not sufficient, the transport state of the film is unstable, and bubbles are easily mixed. Further, when the pressing force of the bonding roller is more than 1.2 MPa, the liquid bank is mixed and bubbles are mixed. The pressing force of the bonding roller is preferably in the range of 0.5 to 1.2 MPa. The pressing force of the bonding roller can be measured, for example, by an instantaneous force in a two-piece pressure measuring sheet (Prescale) made of Fujifilm. The nip pressure with respect to the bonding roller is usually a shaft receiving member applied to both ends of the bonding roller.

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

[1] Step of making a polarizing film

In the method for producing a polarizing plate of the present invention, first, a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment are performed on a polyvinyl alcohol-based resin film to prepare a polarizing film. The polarizing film used in the present invention is specifically a drug which adsorbs and aligns a dichroic dye in a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin. Polyvinyl acetate-based resin In addition to polyvinyl acetate of a single polymer of vinyl acetate, for example, a copolymer of vinyl acetate and other monomers copolymerizable therewith (for example, an ethylene-vinyl acetate copolymer) may be mentioned. Wait. Other monomers copolymerizable with vinyl acetate may, for example, be 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-based resin is 85 mol% or more, more preferably 90 mol% or more, and still more desirably 98 to 100 mol%. The average degree of polymerization of the polyvinyl alcohol-based resin is usually from 1,000 to 10,000, more preferably from 1,500 to 5,000. These polyvinyl alcohol-based resins may be modified, and for example, aldehyde-modified polyethylene formaldehyde, polyvinyl acetaldehyde, polyvinyl butyral or the like may be used. A film made of such a polyvinyl alcohol-based resin is used as a raw material film of a polarizing film. The film forming method of the polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a conventionally known method. The film thickness of the raw material film composed of the polyvinyl alcohol-based resin is not particularly limited, but is, for example, about 10 to 150 μm. The thickness is usually supplied in the range of 20 to 100 μm, more preferably 30 to 80 μm, and the industrially practical width is in the range of 500 to 6000 mm. Further, a polyester film such as an olefin film or a PET film may be used as a substrate, and a polyvinyl alcohol resin may be applied to both surfaces or one surface thereof.

A film made of such a polyvinyl alcohol-based resin is used as a raw material film of a polarizing film. The method for producing a film made of a polyvinyl alcohol-based resin is not particularly limited, and a film can be produced by a conventionally known method. The thickness of the film of the raw material film composed of the polyvinyl alcohol-based resin is not particularly limited, and is, for example, about 10 to 150 μm. The thickness in the form of a roll is usually 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 1500 to 6000 mm. In addition, a polyester resin such as an olefin-based film or a PET film may be used as a substrate, and a polyvinyl alcohol-based resin may be applied to the surface or one side thereof.

Commercially available polyvinyl alcohol-based film (Vinylon VF-PS #7500, Kuraray/OPL film M-7500, manufactured by Nippon Synthetic Co., Ltd.) has a raw material thickness of 75 μm, (Vinylon VF-PS#6000, Kuraray) , Vinylon VF-PE #6000, made from Kuraray) raw material thickness 60 μm, (Vinylon VF-PE #5000, Kuraray) The thickness of the raw material is 50 μm, (Vinylon VF-PE #3000, manufactured by Kuraray), and the thickness of the raw material is 30 μm.

The polarizing film is usually a step of adsorbing a dichroic dye by dyeing a polyvinyl alcohol-based resin film to a dichroic dye (dyeing step), and a polyvinyl alcohol-based resin film having a dichroic dye adsorbed thereon as boric acid. The aqueous solution treatment step (boric acid treatment step) and the step of washing with the aqueous boric acid solution followed by water washing (water washing treatment step) are carried out.

Further, in the production of the polarizing film, the polyvinyl alcohol-based resin film is usually uniaxially stretched, and the uniaxial stretching may be performed before the dyeing treatment step, or may be carried out in the dyeing treatment step or after the dyeing treatment step. The uniaxial stretching is carried out after the dyeing treatment step, which may be carried out before the boric acid treatment step or in the boric acid treatment step. Of course, uniaxial stretching can be performed at these complex stages.

Uniaxial extension allows for uniaxial extension between rolls of varying speeds or uniaxial extension with hot rolls. Further, it may be a dry stretching which is extended in the atmosphere, or may be a wet stretching which is extended in a state of being swollen by a solvent. The stretching ratio is usually from 3 to 8 times.

In the dyeing treatment step, the polyvinyl alcohol-based resin film is dyed by a dichroic dye, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, for example, iodine, a dichroic dye or the like is used. The dichroic dye contains, for example, a dichroic direct dye composed of a bisazo compound such as C.I. Direct Red 39, a dichroic direct dye composed of a compound such as trisazo or tetrazo. Further, the polyvinyl alcohol-based resin film is preferably subjected to water immersion treatment before the dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing the impregnated polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in the 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. In the case where 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 the aqueous solution is usually 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as a dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is generally employed. The content of the dichroic dye of the aqueous solution is usually from 1 × 10 ^-4 to 10 parts by weight, more preferably from 1 × 10 ^-3 to 1 part by weight, particularly preferably from 1 × 10 ^-3 to 100 parts by weight per 100 parts by weight of water. 1 × 10 ^-2 parts by weight. The aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. In the case where a dichroic dye is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 80 ° C, and the immersion time (dyeing time) of the aqueous solution is usually 10 to 1800 seconds.

The boric acid treatment step is carried out by immersing the polyvinyl alcohol-based resin film dyed with the dichroic dye in an aqueous solution containing boric acid. The amount of boric acid containing an aqueous solution of boric acid is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. In the case where iodine is used as the dichroic dye in the dyeing treatment step, the aqueous solution containing boric acid used in the boric acid treatment step preferably contains potassium iodide. In this case, the amount of potassium iodide in the aqueous solution containing boric acid is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. Water soluble in boric acid The immersion time in the liquid is usually from 60 to 1200 seconds, more preferably from 150 to 600 seconds, more preferably from 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 40 ° C or higher, more preferably 50 to 85 ° C, still more preferably 55 to 80 ° C.

Then, in the water washing treatment step, the boric acid-treated polyvinyl alcohol-based resin film is subjected to a water washing treatment by, for example, immersing in water. The temperature of the water to be washed is usually 4 to 40 ° C, and the immersion time is usually 1 to 120 seconds. In the water washing treatment, it is preferable to use a spray-like spray water or a method of spraying water from a slit-shaped discharge portion to strongly rinse the film. After the water washing treatment, a drying treatment is usually carried out to obtain a polarizing film. In the stage before the drying treatment, a method in which air is blown off by an air knife or the like, or surface water is absorbed by a suction roll can be suitably used. The drying treatment is suitably carried out, for example, using a hot air dryer, a far infrared heater or the like. The temperature of the drying treatment is usually from 30 to 100 ° C, preferably from 50 to 90 ° C. The drying treatment time is usually from 60 to 600 seconds, more preferably from 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 water washing treatment to obtain a polarizing film. The thickness of the polarizing film is usually in the range of 3 to 50 μm.

Further, it is not limited to the above method, and a film having a polarizing function which is produced by another method may be used as the polarizing film.

[2] Step of coating an active energy ray-curable bonding agent on a transparent film

(transparent film)

The material constituting the transparent film used in the present invention is, for example, a cycloolefin resin, a cellulose acetate resin, such as polyethylene terephthalate or poly As the polyester resin such as ethylene naphthalate or polybutylene terephthalate, a polycarboxylate resin, an acrylic resin, or polypropylene, a film material which has been widely used in the prior art can be used.

The cycloolefin-based resin is a thermoplastic resin (also referred to as a thermoplastic cycloolefin resin) having a unit of a monomer composed of a cyclic olefin (cycloolefin) such as a norbornene or a polycyclic norbornene-based monomer. . The cycloolefin resin may be a ring-opening polymer of the above cycloolefin or a hydrogenated product of a ring-opening copolymer of two or more kinds of cycloolefins, or a cycloolefin, a chain olefin, or an aromatic compound having a vinyl group. Addition polymer. Moreover, it is also effective to introduce a polar base.

In the case of using a copolymer of a cyclic olefin and a chain olefin or/and an aromatic compound having a vinyl group, the chain olefin may, for example, be ethylene or propylene, and examples of the aromatic compound having a vinyl group include benzene. Ethylene, α-methylstyrene, nuclear alkyl-substituted styrene, and the like. In such a copolymer, the unit of the monomer composed of the cyclic olefin may be 50 mol% or less (more desirably 15 to 50 mol%). In particular, in the case of using a terpolymer of a cyclic olefin, a chain olefin, and an aromatic compound having a vinyl group, the unit of the monomer composed of the cyclic olefin may be in a small amount as described above. In such a terpolymer, a unit of a monomer composed of a chain olefin is usually 5 to 80 mol%, and a unit of a monomer having a vinyl aromatic compound is usually 5 to 80 mol%.

For the cycloolefin-based resin, a commercially available product such as Topas (manufactured by Ticona Co., Ltd.), Arton (manufactured by JSR Co., Ltd.), ZEONOR (manufactured by Nippon Zeon Co., Ltd.), and ZEONEX (Japanese ZEON shares) can be used. Manufactured by Ltd., APL (manufactured by Mitsui Chemicals, Inc.), OXIS (manufactured by Okura Industrial Co., Ltd.), etc. When such a film of a cycloolefin resin is used as a film, a conventional method such as a solvent cast film method or a melt extrusion method is suitably used. In addition, for example, a film made of a film of a cycloolefin-based resin prepared in advance, such as a scenamel (manufactured by Sekisui Chemical Co., Ltd.), a SCA40 (manufactured by Sekisui Chemical Co., Ltd.), or a ZEONOR film (manufactured by Optes Co., Ltd.), can be used. Sale.

The cycloolefin-based resin film may be a uniaxially stretched or a biaxially stretched. Any phase difference value which can be imparted to the cycloolefin-based resin film can be imparted by stretching. The stretching is generally performed while continuously winding up the film roll, and is extended in the heating furnace toward the traveling direction of the roll (the longitudinal direction of the film), the direction perpendicular to the traveling direction (the width direction of the film), or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cycloolefin-based resin film to the glass transition temperature + 100 °C. The stretching ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times.

When the cycloolefin-based resin film is wound into a roll, the film tends to be agglomerated after being adhered to each other. Therefore, the protective film is usually bonded and then wound into a roll. Further, since the cycloolefin resin film generally has poor surface activity, it is preferred to subject the surface to be bonded to the polarizing film to a surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment or saponification treatment. Among them, it is suitable for plasma processing which is easy to implement, especially atmospheric piezoelectric slurry treatment and corona treatment.

The cellulose acetate-based resin refers to a partially or fully esterified cellulose, and examples thereof include acetate, propionate, butyrate of cellulose. A film composed of such a mixed ester or the like. More specifically, for example, a triacetyl cellulose film, a diethyl fluorene cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, or the like can be given. Such a cellulose ester-based resin film can be suitably used in a commercially available product, for example, Fujitac TD80 (manufactured by Fujifilm Co., Ltd.), Fujitac TD80UF (manufactured by Fujifilm Co., Ltd.), and Fujitac TD80UZ (manufactured by Fujifilm Co., Ltd.). KC8UX2M (Konica Minolta Opto Co., Ltd.), KC8UY (Konica Minolta Opto Co., Ltd.), Fujitac TD60UL (made by Fujifilm Co., Ltd.), KC4UYW (Konica Minolta Opto Co., Ltd.), KC6UAW (Konica Minolta Opto) Co., Ltd.), KC2UAW (manufactured by Konica Minolta Opto Co., Ltd.), etc.

Further, as the transparent film, a cellulose acetate resin film which imparts a phase difference is also suitably used. For example, WV BZ 438 (made by Fujifilm Co., Ltd.), KC4FR-1 (Konica Minolta Opto Co., Ltd.), and KC4CR-1 (Konica Minolta) are commercially available as a commercial product of the cellulose acetate-based resin film. Opto Co., Ltd.), KC4AR-1 (manufactured by Konica Minolta Opto Co., Ltd.), and the like. Cellulose acetate is also known as acetaminophen, cellulose acetate.

These cellulose acetate-based films are easily absorbed by water, and the moisture content of the polarizing plate affects the relaxation of the ends of the polarizing plates. The water content at the time of manufacturing the polarizing plate is closer to the storage environment of the polarizing plate. For example, the balance of the moisture content of the production line of the clean room and the storage warehouse of the roll is better, although it is also related to the composition of the laminated film, but the moisture rate is, for example. To the extent of 2.0 to 3.5%, more preferably 2.5 % to 3.0%. The numerical value of the moisture content of the polarizing plate was measured by the dry weight method and was a change in weight after 105 ° C / 120 minutes.

In the present invention, the transparent film can have a function as a retardation film, a function as a luminance enhancement film, a function as a reflective film, a function as a semi-transmissive reflective film, a function as a diffusion film, a function as an optical compensation film, and the like. Optical functions such as optical functions. In this case, for example, an optical functional film such as a surface layer retardation film of a transparent film, a brightness enhancement film, a reflective film, a transflective film, a diffusion film, or an optical compensation film may have such a function. It is also possible to impart such a function to the transparent film itself. Further, the transparent film may have a plurality of functions such as a diffusion film having a function as a luminance enhancement film.

For example, the above-mentioned transparent film is subjected to the stretching treatment as described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, or the like, or the processing described in Japanese Patent No. 3168850, whereby the function as a retardation film can be imparted. The phase difference characteristic of the retardation film can be, for example, a range in which the front phase difference value is 5 to 100 nm, the thickness direction phase difference is 40 to 300 nm, or the like. Further, in the above transparent film, fine pores are formed by a method as described in JP-A-2002-169025 or JP-A-2003-29030, or the center wavelengths of the selective selective reflection are different. Two or more layers of the cholesteric liquid crystal layer can provide a function as a brightness enhancement film.

When the transparent film is formed into a metal thin film by vapor deposition, sputtering, or the like, it can be provided as a reflective film or a semi-transmissive reflective film. Applying a resin solution containing fine particles to the transparent film, thereby imparting diffusion The function of the film. In addition, a liquid crystal compound such as a discotic liquid crystalline compound is applied to the transparent film to be aligned, thereby imparting a function as an optical compensation film. Moreover, the transparent film may contain a compound exhibiting a phase difference. Further, various optical functional films can be directly bonded to the polarizing film using a suitable bonding agent. For the commercially available product of the optical functional film, for example, a brightness improving film such as DBEF (available from Sumitomo 3M Co., Ltd., manufactured by 3M Company), and a viewing angle improving film such as WV film (made by Fujifilm Co., Ltd.), Arton film (manufactured by JSR Co., Ltd.), ZEONOR film (manufactured by Optes Co., Ltd.), Escena (manufactured by Sekisui Chemical Co., Ltd.), VA-TAC (manufactured by Konica Minolta Opto Co., Ltd.), SUMICALITE (Sumitomo Chemical Co., Ltd.) A phase difference film such as a company).

The thickness of the transparent film used in the present invention is preferably thin, and when it is too thin, the strength is lowered and the workability is deteriorated. On the other hand, when it is too thick, there arises a problem that the transparency is lowered, and the curing time required after lamination is lengthened. Therefore, a suitable thickness of the transparent film is, for example, 5 to 200 μm, more desirably 10 to 150 μm, and still more desirably 10 to 100 μm.

In order to improve the bonding property between the bonding agent 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. Surface treatment such as processing.

Further, the transparent film may be used alone or in combination of two or more kinds to perform surface treatment such as anti-glare treatment, anti-reflection treatment, hard coating treatment, antistatic treatment, and anti-stain treatment. Moreover, transparent film and / or transparent film surface protection The layer may contain a plasticizer such as a UV absorber such as a diphenylketone compound or a benzotriazole compound, a phenyl phosphate compound or a phthalate compound.

(active energy ray hardening type bonding agent)

The active energy ray-curable bonding agent is composed of an epoxy resin-based resin composition containing an epoxy resin which is cured by irradiation with an active energy ray, from the viewpoints of weather resistance, refractive index, durability, and the like. Adhesive. However, the present invention is not limited thereto, and various active energy ray-curable bonding agents (organic solvent-based bonding agents, hot-melt-based bonding agents, solvent-free bonding agents, and the like) used in the production of conventional polarizing plates can be used. The acrylic composition, the acrylamide-based composition, the epoxy acrylate-based composition, the urethane-based composition, and the vinyl-based composition are contained. Further, curing by a polymerization reaction such as radical polymerization, cationic polymerization, anionic polymerization, or thermal polymerization may be mentioned.

The epoxy resin refers to a compound having two or more epoxy groups in the molecule. From the viewpoints of weather resistance, refractive index, cationic polymerizability, and the like, the epoxy resin contained in the curable epoxy resin composition of the bonding agent is preferably an epoxy resin containing no aromatic ring in the molecule (for example, refer to the patent literature) 1). Examples of such an epoxy resin include a hydrogenated epoxy resin, an alicyclic epoxy resin, and an aliphatic epoxy resin.

The nuclear hydrogenation polyhydroxy compound can be obtained by selectively performing a nuclear hydrogenation reaction under pressure in the presence of a catalyst to obtain a nuclear hydrogenation polyhydroxy compound ring by a polyhydroxy compound of a raw material of an aromatic epoxy resin under pressure. A method of oxypropyl etherification to obtain a hydrogenated epoxy resin. The aromatic epoxy resin may, for example, be a diglycidyl ether of bisphenol A or a diepoxypropyl ether of bisphenol F. And bisphenol epoxy resin such as bisphenol S diepoxypropyl ether; phenol novolak epoxy resin, cresol novolac epoxy resin, and phenolic epoxy resin such as hydroxybenzaldehyde phenol novolac epoxy resin A resin; a glycidyl ether of tetrahydroxyphenylmethane; a glycidyl ether of tetrahydroxydiphenyl ketone; and a polyfunctional epoxy resin such as epoxidized polyvinyl phenol. More preferably, the hydrogenated epoxy resin is a glycidyl ether of hydrogenated bisphenol A.

The alicyclic epoxy resin refers to an epoxy resin having one or more epoxy groups bonded to an alicyclic ring in the molecule. The "epoxy group bonded to the alicyclic ring" means the oxygen atom -O- of the bridge of the structure shown by the following formula. In the following formula, m is an integer of 2 to 5.

The group in which the form of one or a plurality of hydrogen atoms in the above formula (CH ₂ ) _m is bonded to a compound having another chemical structure can be an alicyclic epoxy resin. One or a plurality of hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. In the alicyclic epoxy resin, since it exhibits good adhesion, it is preferred to use an epoxy resin having an oxabicyclohexane ring (the above formula m=3) and an oxabicycloheptane ring (described above). Epoxy resin of the formula m=4). Hereinafter, the alicyclic epoxy resin which is preferably used is specifically exemplified, but is not limited to these compounds.

(a) Epoxycyclohexanecarboxylic acid epoxycyclohexyl methyl ester represented by the following formula (I): (wherein R ¹ and R ² independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(b) an epoxycyclohexanecarboxylic acid ester of an alkanediol represented by the following formula (II):

The hydrogen atoms independently of each other or 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) Epoxycyclohexylmethyl esters of dicarboxylic acids represented by the following formula (III): (wherein R ⁵ and R ⁶ independently of each other 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 ether of polyethylene glycol represented by the following formula (IV): (wherein R ⁷ and R ⁸ each independently 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) an epoxycyclohexyl methyl ether of an alkanediol 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) a diepoxytrispirocyclic compound represented by the following formula (VI): (wherein R ¹¹ and R ¹² independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(g) a diepoxymonospirocyclic compound represented by the following formula (VII): (wherein R ¹³ and R ¹⁴ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(h) a vinylcyclohexene diepoxide 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 of the following formula (IX): (wherein R ¹⁶ and R ¹⁷ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms).

(j) a dicyclooxytricyclodecane 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 the like, and it is preferred to use them because of their ease of use and the like.

(A) an ester of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid with (7-oxa-bicyclo[4.1.0]heptan-3-yl)methanol [in the formula (I), a compound of 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 [in the formula (I), R ¹ =4-CH ₃ , R ² =4-CH ₃ compound], (C) 7-oxabicyclo[4.1 .0] an ester of heptane-3-carboxylic acid with 1,2-ethanediol [in the formula (II), a compound of R ³ =R ⁴ =H, n=2], (D) (7-oxygen) An ester of heterobicyclo[4.1.0]heptan-3-yl)methanol with adipic acid (in the formula (III), R ⁵ =R ⁶ =H, p=4 compound], (E)(4-A An ester of benzyl-7-oxabicyclo[4.1.0]heptan-3-yl)methanol with adipic acid [in the formula (III), R ⁵ =4-CH ₃ , R ⁶ =4-CH ₃ ,p a compound of =4, (F) (7-oxabicyclo[4.1.0]heptan-3-yl)methanol and an etherified product of 1,2-ethanediol [in the formula (V), R ⁹ =R ¹⁰ =H, compound of r=2].

Further, the aliphatic epoxy resin may, for example, be a polyepoxypropyl ether of an aliphatic polyol or an alkylene oxide adduct thereof. More specifically, it may be a di-epoxypropyl ether of 1,4-butanediol; a di-epoxypropyl ether of 1,6-hexanediol; a triepoxypropyl ether of glycerol; a trihydroxyl Triepoxypropyl ether of methyl propane; diepoxypropyl ether of polyethylene glycol; diepoxypropyl ether of propylene glycol; addition of aliphatic polyols such as ethylene glycol, propylene glycol and glycerol Polyepoxypropyl ether of a polyether polyol obtained by using two or more kinds of alkylene oxides (ethylene oxide or propylene oxide).

The epoxy resin constituting the bonding agent made of the epoxy resin composition may be used alone or in combination of two or more. Used by the composition The epoxy equivalent of the epoxy resin is usually from 30 to 3,000 g/equivalent, more preferably from 50 to 1,500 g/equivalent. When the epoxy equivalent is less than 30 g/equivalent, there is a possibility that the flexibility of the composite polarizing plate after curing is lowered and the joint strength is lowered. On the other hand, when it exceeds 3,000 g / equivalent, there is a possibility that the compatibility with other components contained in the bonding agent is lowered.

Among the binders, from the viewpoint of reactivity, it is preferred to use a cationic polymerization for the hardening reaction of the epoxy resin. Therefore, as the curable epoxy resin of the active energy ray-curable bonding agent, it is preferred to incorporate a cationic polymerization initiator. The cationic polymerization initiator is irradiated with an active energy ray such as visible light, ultraviolet rays, X-rays, electron beams or the like to generate a cationic species or a Lewis acid, and initiates polymerization of an epoxy group. Hereinafter, a cationic polymerization initiator which generates a cationic species or a Lewis acid by the irradiation of an active energy ray and initiates polymerization of an epoxy group is referred to as a "photocationic polymerization initiator".

The method of curing the bonding agent by irradiation with an active energy ray using a photocationic polymerization initiator can be hardened at room temperature to reduce the necessity of considering the heat resistance of the polarizing film or bending due to expansion, and can be used in the film. It is advantageous to have a good joint between them. Further, the photocationic polymerization initiator is subjected to a catalyst action by light, and is excellent in storage stability and workability even when it is mixed with an epoxy resin.

The photocationic polymerization initiator may, for example, be an aromatic diazonium salt; an onium salt such as an aromatic onium salt or an aromatic onium salt; an iron-arene complex or the like.

Examples of the aromatic diazonium salt include benzene diazonium hexafluoroantimonate and hexafluorophosphorus. Acid benzene diazonium salt, benzene diazonium hexafluoroborate, and the like. Further, examples of the aromatic onium salt include diphenylphosphonium sulfonium (pentafluorophenyl)borate, diphenylphosphonium hexafluorophosphate, diphenylphosphonium hexafluoroantimonate, and bis(4-fluorophosphate). Nonylphenyl) phosphonium salt and the like.

Examples of the aromatic onium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, and bis(hexafluorophosphoric acid) 4,4. '-Bis(diphenylfluorene)diphenyl sulfide, bis(hexafluoroantimonate) 4,4'-bis[bis(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide, bis(hexafluoro) Phosphate) 4,4'-bis[bis(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide, hexafluoroantimonic acid 7-[bis(p-tolyl)purine]-2-isopropylsulfuric acid Thioxanthone, tetrakis(pentafluorophenyl)borate 7-[bis(p-tolyl)purine]-2-isopropylthioxanthone, 4-phenylcarbonyl-4'-hexafluorophosphate Diphenyl sulfonium-diphenyl sulfide, hexafluoroantimonate 4-(p-butylphenylcarbonyl)-4'-diphenylanthracene-diphenyl sulfide, tetrakis(pentafluorophenyl)borate 4 -(p-T-butylphenylcarbonyl)-4'-bis(p-tolyl)indole-diphenyl sulfide.

Further, examples of the iron-aromatic complex include, for example, xylene hexafluoroantimony-cyclopentadienyl iron (II), cumene hexafluoro-cyclopentadienyl iron (II), and xylene-cyclopentane. Iron (II)-tris(trifluoromethylsulfonyl)methanide (xylene-cyclopentadienyliron(II) tris(trifluoromethylsulfonyl)methanide).

Commercially available products of the photocationic polymerization initiators can be easily obtained, and for example, "KAYALITE PCI-220" and "KAYALITE PCI-620" (the above are manufactured by Nippon Kayaku Co., Ltd.) are listed under the respective trade names; UVI-6990" (made by Union Carbide Corporation), "ADEKA OPTOMER SP-150" and "ADEKA OPTOMER SP-170" (above ADEKA Co., Ltd.); "CI-5102", "CIT-1370", "CIT-1682", "CIP-1866S", "CIP-2048S" And "CIP-2064S" (above is made by Japan Soda Co., Ltd.); "DPI-101", "DPI-102", "DPI-103", "DPI-105", "MPI-103", "MPI" -105", "BBI-101", "BBI-102", "BBI-103", "BBI-105", "TPS-101", "TPS-102", "TPS-103", "TPS-105" "MDS-103", "MDS-105", "DTS-102" and "DTS-103" (manufactured by Green Chemical Co., Ltd.); "PI-2074" (manufactured by Rhodia Co., Ltd.).

The photocationic polymerization initiator may be used alone or in combination of two or more. Among them, the aromatic onium salt has an ultraviolet absorbing property in a wavelength region of 300 nm or more, and is excellent in curability, and can provide a cured product having good mechanical strength and joint strength. Therefore, an aromatic onium salt is preferably used.

The blending amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, more preferably 1 part by weight or more, and more desirably 15 parts by weight or less based on 100 parts by weight of the epoxy resin. When the amount of the photocationic polymerization initiator is less than 0.5 part by weight based on 100 parts by weight of the epoxy resin, the curing is insufficient, and the mechanical strength and the joint strength tend to be lowered. In addition, when the amount of the photocationic polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy resin, the ionic substance in the cured product increases, the hygroscopic property of the cured product becomes high, and the durability is lowered. The possibility.

In the case of using a photocationic polymerization initiator, a hardenable epoxy resin The composition may further contain a photosensitizer as needed. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and joint strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo and a diazo compound, a halide, a photoreductive dye, and the like.

More specific examples of the photosensitizer include, for example, benzoin methyl ether, benzoin isopropyl ether, and benzoin derivatives such as α,α-dimethoxy-α-phenylacetophenone; diphenyl ketone, 2, 4-dichlorodiphenyl ketone, methyl phthalate benzoate, 4,4'-bis(dimethylamino)diphenyl ketone and 4,4'-bis(diethylamino) Diphenyl ketone derivatives such as diphenyl ketone; thioxanthone derivatives such as 2-chlorothiazinone and 2-isopropylthioxanthone; 2-chloroindole and 2-methylindole Anthracene derivatives; acridone derivatives such as N-methylacridone and N-butylacridone; others such as α,α-diethoxyacetophenone, diphenylethylenedione, Fluorenone, Xanthone, uranium compounds, halides, and the like. The photosensitizer may be used alone or in combination of two or more. The photosensitizer is preferably contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the curable epoxy resin composition.

The epoxy resin contained in the bonding agent is hardened by photocationic polymerization, and can be hardened by both photocationic polymerization and thermal cationic polymerization. In the latter case, it is preferred to use a photocationic polymerization initiator and a thermal cationic polymerization initiator together.

The thermal cationic polymerization initiator may, for example, be a benzyl sulfonium salt, a thiophenium salt, a thiolanium salt, a benzyl ammonium salt, a pyridinium salt, a hydrazinium salt, a carboxylic acid ester or a sulfonate. , amine imine and the like. These thermal cationic polymerization initiators can be easily obtained as a commercial product, and, for example, "Adeka opton CP77" and "Adeka opton CP66" (above, ADEKA Co., Ltd.), "CI- 2639" and "CI-2624" (the above are made by Japan's Soda Co., Ltd.), "Sunaid SI-60L" and "Sunaid SI-80L" and "Sunaid SI-100L" (the above are Sanxin Chemical Industry Co., Ltd.) Limited company system) and so on.

The active energy ray-curable bonding agent may contain a compound which promotes cationic polymerization such as oxetane or polyol.

The oxetane is a compound having a 4-membered cyclic ether in the molecule, and examples thereof include 3-ethyl-3-hydroxymethyloxetane and 1,4-bis[(3-ethyl-3-). Oxecyclobutyl)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxetane, bis[(3-ethyl-3-oxetanyl) Methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, phenol novolac oxetane, and the like. These oxetane can be easily obtained as a commercial product, and can be exemplified by the respective trade names "Aron oxetane OXT-101", "Aron oxetane OXT-121", "Aron oxetane OXT-211", "Aron oxetane OXT-221" and "Aron oxetane OXT-212" (manufactured by Toagosei Co., Ltd.). The oxetanes usually have a ratio of 5 to 95% by weight, preferably 30 to 70% by weight, based on the curable epoxy resin composition.

The polyol is preferably one which does not have an acidic group other than a phenolic hydroxyl group, for example, a polyol compound having no functional group other than a hydroxyl group, a polyester polyol compound, a polycaprolactone polyol compound, and a phenolic hydroxyl group. A polyol compound, a polycarbonate polyol, or the like. The molecular weight of these polyols is usually 48 or more, more preferably 62 or more, still more preferably 100 or more, and still more preferably 1,000 or less. These polyols usually contain 50% by weight or less, and more preferably 30% by weight or less, in the curable epoxy resin composition.

In the active energy ray-curable bonding agent, an ion trapping agent, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow regulator, a leveling agent, a plasticizer, and a defoaming agent may be further blended. Additives such as agents. The ion scavenger may, for example, be a powdery lanthanoid, lanthanide, magnesium, aluminum, calcium, titanium or inorganic compound such as these mixed systems, and examples of the antioxidant include hindered phenol antioxidants.

As the active energy ray-curable bonding agent, a solventless bonding agent which does not substantially contain a solvent component can be used, and a solvent for adjusting the viscosity can be contained in order to have a suitable viscosity range for each coating method. The solvent is preferably an organic solvent such as a hydrocarbon represented by toluene or an ester represented by ethyl acetate, which does not lower the optical characteristics of the polarizing film and can dissolve the epoxy resin composition well. The viscosity of the active energy ray-curing bonding agent used in the present invention is preferably 80 mPa. Below s, more ideally 50mPa. s below. This is due to the activity of the active energy ray-curing cement more than 80mPa. In the case of s, the lower limit of the thickness at which bubbles cannot be mixed tends to increase. In addition, in order to obtain sufficient joint strength, the viscosity of the active energy ray hardening type bonding agent is preferably 1 mPa. Above s, more ideally 10mPa. s above. In addition, the viscosity refers to the viscosity measured at a liquid temperature of 25 ° C using an E-type viscosity meter.

In the example shown in Fig. 1, the transparent films 2 and 3 which are continuously pulled out from the state of the roll are coated with the active energy ray-curable bonding agent on the single side thereof by the bonding agent coating devices 11 and 12. . The method of applying the adhesive to the transparent film is not particularly limited, and for example, various coatings such as a doctor blade, a wire bar, a slit coating method, a comma coater, and a gravure coating method can be used. Cloth way. Among them, the bonding agent coating devices 11 and 12 are preferably crown rolls in consideration of film coating, degree of freedom of path lines, wide correspondence, and the like. For example, MCD (Micro Chamber Doctor) manufactured by Fuji Machinery Co., Ltd., which is a commercial coating device.

When the crown roll is used as the bonding agent coating apparatuses 11 and 12 and the bonding agent is applied, the thickness (coating thickness) of the applied bonding agent is preferably 2.0 μm or more, more preferably 2.5 to 4 μm. The coating thickness of the bonding agent is adjusted in accordance with the ratio of the ratio of the speed of the crown roller to the line speed of the transparent film. In general, the draw ratio (speed/linear velocity of the crown roll) is adjusted to 0.5 to 10, and the coating thickness of the adjustable bond is about 0.1 to 10 μm. More specifically, the linear speed of the transparent films 2, 3 is 10 to 100 m/min, and the crown roll is rotated in the opposite direction to the conveying direction of the transparent films 2, 3, and the speed of the crown roll is 5 to 1000 m/min. The coating thickness of this adjustable bonding agent is about 0.1 to 10 μm.

After the bonding agent is prepared, it is usually at a predetermined temperature of 15 to 40 ° C ± 5 ° C (for example, 30 ° C ± 5 ° C when the temperature is 30 ° C), more preferably ± 3 ° C, more preferably adjusted Coating in an environment of ±1 °C.

[3] bonding step

Then, one of the major features of the present invention is as described above in the polarizing film. On one side or both sides, the surface of the transparent film coated with the active energy ray-curable bonding agent is sandwiched by a bonding roll to form a laminated body. In the method for producing a polarizing plate of the present invention, the transparent film may be bonded only to either side of the polarizing film or may be bonded to both surfaces. In the case of bonding to both sides, each of the transparent films may be of the same type or different types.

The example shown in Fig. 1 is a transparent film continuously discharged from the state of a roll, and one side of 2 and 3 is coated with an active energy ray-hardening type on one surface thereof by the bonding agent coating apparatuses 11 and 12. Adhesive. Then, the polarizing film which is continuously discharged in the same manner as the above-mentioned transparent film 2, 3 is formed, and the laminated body 4 is produced by superposing the transparent film by the bonding rolls 5a, 5b by the bonding rolls 5a, 5b, respectively. At this time, the pressing pressure of the bonding is in the range of 0.5 to 1.2 MPa, which is the same as described above.

In the present invention, in one of the pair of bonding rollers 5a, 5b, the diameter gradually 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), and may also have a tapered outer circumference. A crown roll of the shape. In this case, the roller on the side of the non-coronal roll is desirably a lithographic roll having a substantially uniform diameter. In addition, a pair of bonding rolls can be the same as a lithographic roll.

The shape of the crown roll is preferably designed such that the interval between the crown roll and the lithographic roll is substantially uniform in the state of being pinched in the bonding step. Here, the distance between the crown roll and the lithographic roll means the interval between the crown roll and the lithographic roll in the cross section of the shaft including the crown roll and the lithographic roll. Further, generally, in the state where the crown roll and the lithographic roll are not nip, the axis of the crown roll and the axis of the lithographic roll are arranged in parallel.

For example, in the case where the bonding roller 5a is a metal lithographic roller and the bonding roller 5b is a rubber crown roller, pressure is applied to the direction of the crown roller with respect to the bearing member of the lithographic roller. In the state in which the nip is performed, the crown roll is bent, and the shape of the crown roll can be uniformly applied so that the space between the crown roll and the lithographic roll is substantially uniform, so that the laminated body can be uniformly pressed. Further, the same effect can be obtained even in the case of nip in the direction of the lithographic roll of the crown roll. Further, both the lithographic roll and the crown roll can be sandwiched in the direction in which they approach each other.

In the case of using a crown roll, the ratio of the difference between the diameter of the central portion and the diameter of the end portion is preferably 0.0020 to 0.0500% with respect to the length of the crown roll (the length in the axial direction). More preferably, it is 0.0020 to 0.020%. Generally, in such a ratio range, the shape of the crown roll can be designed to make the interval between the crown roll and the lithographic roll uniform in the state of being pinched in the bonding step.

Further, in the case of using a crown roller, the tapered outer peripheral shape is preferably an arc shape. Here, the tapered outer circumferential shape of the crown roller is an arc shape, and the cross section including the surface of the tapered outer circumferential shape of the crown roller is an arc. In the case of clamping the shaft member of the lithographic roll in the laminating step, the outer peripheral shape of the lithographic roll is mostly an arc-shaped curved shape, and the outer peripheral shape of the opposite crown roller has an arc of the same degree of curvature radius. In the shape, the interval between the laminating roller (coronal roller and the lithographic roller) can be made uniform, and the polarizing film and the transparent film can be bonded at a uniform pressure.

The diameter of the bonding roller is not particularly limited, but the diameter of the lithographic roller is smaller. Ideally 50 to 400mm. Further, the diameter of the end portion of the crown roller is preferably 50 to 400 mm. In addition, the respective diameters of the pair of bonding rolls may be the same or different. The width of the bonding roller is 300 to 3000 mm.

The material of the bonding roller can be metal or rubber. Preferably, one of the pair of bonding rolls is a metal roll, and the other is a rubber roll. Further, it is more preferable that the lithographic roll is made of metal and the crown roll is made of rubber.

The bonding roller on the upper side where the conventional bonding roller is usually pressed is made of rubber, and the bonding roller on the lower side is made of metal. This is because the lower side of the bonding roller is attached with a drive motor to control the rotation speed, and the lower side of the bonding roller is made of metal, the lower side of the bonding roller does not deform when squeezed, and the circumferential speed of the bonding roller is easy. Maintain a certain. However, in this case, in order to facilitate the adjustment of the bending, it is preferable that the bonding roller (upper side) is made of metal, and the other (lower side) bonding roller is made of rubber.

The base material of the metal roll can be made of various conventional materials, and is preferably stainless steel, more preferably SUS304 (a stainless steel containing 18% of Cr and 8% of Ni). It is preferable to carry out chrome plating treatment on the surface of the metal roll.

The material of the rubber roll is not particularly limited, and examples thereof include NBR (nitrile rubber), Titan, urethane, polyfluorene oxide, and EPDM (ethylene-propylene-diene rubber), and more preferably NBR. Titan, ethyl urethane. The hardness of the rubber roller is not particularly limited and is usually from 60 to 100 °, more preferably from 85 to 95 °. Further, the hardness of the rubber roll can be measured by a hardness tester according to JIS K6253. For the commercially available hardness meter, for example, a rubber hardness meter "A type" manufactured by ASKA Corporation or the like is used. Specifically, when the surface was pressed with a rod, the surface resistance of the rubber roller was measured by a durometer.

In addition, in the first figure, an example in which a pair of bonding rolls are attached is exemplified, Further, the present invention is not limited thereto, and a pair of back-up rolls may be further provided so as to sandwich a pair of bonding rolls. Further, the auxiliary roller may be disposed only on one of the pair of rollers. .

[4] Step of irradiating the laminated body with active energy rays

In the subsequent step, the laminated body obtained as described above is irradiated with an active energy ray to obtain a polarizing plate. In the example shown in Fig. 1, the laminated body 4 is conveyed while being in close contact with the outer peripheral surface of the roller 13. In the example shown in Fig. 1, the first active energy ray irradiation devices 14 and 15 which are provided at positions facing the outer circumferential surface of the roller 13 are provided in the order of the transport direction; the first active energy ray irradiation is performed. The second and subsequent active energy ray irradiation devices 16, 17, 18 provided on the downstream side in the transport direction of the devices 14, 15 and the nip roller 19 for transport. In the process of transporting the laminated body 4 while being in close contact with the outer peripheral surface of the roller 13, the active energy rays are applied to the outer peripheral surface of the roller 13 from the first active energy ray irradiation devices 14 and 15, and the bonding agent is polymerized and cured. Further, the second and subsequent active energy ray irradiation devices 16, 17, and 18 disposed on the downstream side in the transport direction are devices for completely polymerizing and hardening the bonding agent, and may be added or omitted as necessary. Finally, the laminated body 4 is taken up as a polarizing plate on the take-up roll 20 by the nip roller 19 for conveyance.

The outer circumferential surface of the roller 13 is formed as a convex curved surface of the mirror surface, and the surface thereof is conveyed while being in close contact with the laminated body 4, and the bonding agent is polymerized and hardened by the active energy ray irradiation devices 14 and 15 in the process. The diameter of the roller 13 is not particularly limited as long as the bonding agent is polymerized and hardened and the laminated body 4 is sufficiently adhered. The roller 13 can follow the movement of the line of the laminated body 4, or can be rotationally driven or fixed, and the laminated body 4 can slide over the surface. And by active energy When the wire is irradiated and polymerized and hardened, the roller 13 can also function as a cooling roll for dissipating heat generated by the laminated body 4. In this case, the surface temperature of the cooling roll is desirably set to 4 to 30 °C.

The light source used for the polymerization hardening of the bonding agent by irradiation with the active energy ray is not particularly limited, but is preferably a light source having a light-emitting distribution having a wavelength of 400 nm or less. Such a light source may, for example, be a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, or a metal halide lamp.

The light irradiation intensity of the active energy ray-curable adhesive is determined by the composition of each of the bonding agents, and is not particularly limited, and is preferably from 10 to 5,000 mW/cm ² . When the light irradiation intensity of the resin composition is less than 10 mW/cm ² , the reaction time becomes too long, and when it exceeds 5000 mW/cm ² , the bonding agent may be generated due to heat radiated from the lamp and heat generation during polymerization of the composition. The yellowing of the epoxy resin composition or the like of the constituent material and the deterioration of the polarizing film. Further, the irradiation intensity is preferably an intensity of a wavelength region in which the photocationic polymerization initiator is activated, more preferably a wavelength region having a wavelength of 400 nm or less, and more preferably a wavelength region having a wavelength of 280 to 320 nm.

The irradiation time of the active energy ray of the active energy ray-curable bonding agent is controlled according to the composition of each curing, and is not particularly limited, but the cumulative light amount indicating the total of the irradiation intensity and the irradiation time is preferably set to 55 mJ/ More than cm ^{2 is} more preferably 10 to 5000 mJ/cm ² . When the cumulative amount of the above-mentioned bonding agent is less than 10 mJ/cm ² , the occurrence of the active species from the initiator is insufficient, and the curing of the bonding agent is insufficient. On the other hand, when the cumulative amount of light exceeds 5000 mJ/cm ² , the irradiation time becomes very long, which is disadvantageous for improving productivity.

In the present invention, the layered body is irradiated with an active energy ray and the bonding agent is polymerized and cured, but it may be used in combination with heat polymerization.

[Examples]

The invention is illustrated in more detail below by way of examples, but the invention is not limited to the examples.

<Example 1>

(production of polarizing film)

A raw material film of polyvinyl alcohol was a long-length polyvinyl alcohol film "OPL film M-7500 (manufactured by Nippon Synthetic Co., Ltd.) having a polymerization degree of 2,400, a saponification degree of 99.9 mol%, a thickness of 75 μm, and a width of 3000 mm.

First, the film was kept in a state of tension without loosening the raw material film, and immersed in a swelling tank of pure water at 30 ° C for 80 seconds to sufficiently swell the film. With the swelling of the swelling tank, the ratio of the speed of the inlet to the outlet was 1.2. After the nip rolls were dehydrated, they were immersed in a water dipping tank of pure water at 30 ° C for 160 seconds. In this groove, the stretching ratio in the machine direction was 1.09 times.

Then, it was immersed in a dyeing tank containing an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.02/2.0/100, and one-axis extension was carried out at a stretching ratio of about 1.5 times. Then, in a boric acid bath in which an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 12 and 3.7/100 was placed, the mixture was immersed at 55.5 ° C for 130 seconds, and the axial stretching was performed from the cumulative stretching ratio of the raw material to 5.7 times. Then, it was immersed at 40 ° C for 60 seconds in a boric acid bath in which an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 9/2.4/100 was placed.

Further, in a water washing tank, washing with pure water at 8 ° C for about 16 seconds, Then, it was passed through a drying oven at about 60 ° C in a drying oven at about 85 ° C in that order, and the residence time in the drying ovens was 160 seconds in total, and drying was carried out. Thus, a polarizing film having a thickness of 28 μm in which iodine was adsorbed and aligned was obtained.

(production of polarizing plate)

A cycloolefin-based resin film "ZEONOR" (manufactured by Nippon Zeon Co., Ltd.) having a thickness of 60 μm as a transparent film, and a triacetone cellulose film "KC8UX2MW" (manufactured by Konica Minolta Opto Co., Ltd.) having a thickness of 80 μm were prepared. In the surface, an epoxy resin composition ("KR series" manufactured by Adeka Co., Ltd., viscosity: 44 mPa‧s, containing a cationic polymerization initiator) was applied to each of the adhesive coating apparatuses. At this time, in the bonding agent coating apparatus, the linear velocity of the polarizing film laminate was 25 m/min, and the crown roller was rotated in the opposite direction to the conveyance direction of the laminate. The thickness of the bonding layer was 2.9 μm and 2.7 μm.

Then, the cycloolefin-based resin film is placed on the surface of the polarizing film and the polyethylene oxide film is passed through the lower surface of the polarizing film, and the epoxy resin composition is passed through each other to have a diameter of 300 mm. A pair of nip rolls (bonding rolls) were attached at a pressing force of 1.0 MPa.

The polarizing film of the above-mentioned two kinds of transparent films was applied while moving at a linear velocity of 25 m/min while applying a tension of 25 N/m in the longitudinal direction, and the total accumulated light amount (the cumulative amount of light irradiation intensity in a wavelength region of a wavelength of 280 to 320 nm) was irradiated. ) is ultraviolet rays (UVB) of about 250 mJ/cm ² (measured from a measuring instrument: UV Power Puck II manufactured by FusionUV Co., Ltd.).

In the obtained polarizing plate, bubbles of a size of about 100 μm were not 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 force of the bonding roller was 0.8 MPa. In the obtained polarizing plate, bubbles of a size of about 100 μm were not 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 force of the bonding roller was 1.5 MPa. In the obtained polarizing plate, bubbles having a size of about 100 μm were 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 force of the bonding roller was 0.1 MPa. The conveyance state of the film of the bonding roll portion was unstable, and wrinkles and air bubbles were observed.

1‧‧‧ polarizing film

2, 3‧‧‧ transparent film

4‧‧‧Layered body

5a, 5b‧‧‧ affixing rolls

11,12‧‧‧Adhesive coating device

13‧‧‧ Roll

14, 15‧‧‧1st active energy ray irradiation device

16, 17, 18‧‧‧2nd active energy ray irradiation device

19‧‧‧Pinch roller

20‧‧‧Winding roller

Claims (1)

A method for producing a polarizing plate, comprising: a step of performing a dyeing treatment, a boric acid treatment, and a uniaxial stretching treatment on a polyvinyl alcohol-based resin film to form a polarizing film; and applying a viscosity of 10 mPa·s to one side of the transparent film to a step of an active energy ray-curable bonding agent of 50 mPa s; a step of superposing the transparent film on the both sides of the polarizing film through the bonding agent, sandwiching and laminating the bonding film to form a laminated body; and laminating the laminated layer a step of irradiating an active energy ray to form a polarizing plate; wherein, in the step of applying the active energy ray-curable bonding agent, the coating thickness of the bonding agent is in a range of 2.0 μm to 4 μm; in the step of fabricating the laminated body, The pressing force of the bonding roller is in the range of 0.2 to 1.2 MPa.