JP2008065160A - Manufacturing method of polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a polarizing plate by which a liquid crystal is protected from ultraviolet ray, the need of a drying furnace is eliminated, and production speed and productivity are drastically improved. <P>SOLUTION: The method of producing the polarizing plate is characterized in that a protective film (A) having ultraviolet non-transmitting property on one surface of a polarizer is stuck to a protective film (B) having ultraviolet transmitting property on another surface respectively through an ultraviolet curing type adhesive, and the stuck film is irradiated with ultraviolet ray from the side of the protective film (B) to cure the ultraviolet curing type adhesive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate in which a protective film is bonded to the front and back of a polarizer using an ultraviolet curable adhesive, and more particularly to a method for producing a polarizing plate having ultraviolet impermeability.

  Polarizers are used in optical elements such as liquid crystal display elements and glasses. In particular, for polarizing plates used in liquid crystal display elements, the upper and lower sides of the liquid crystal elements are sandwiched between polarizing plates, and light from a light emitting diode (LED) or cold cathode fluorescent tube from the backlight side is used as the polarizing performance of the polarizing plate. The screen is displayed by transmitting or blocking using the polarization behavior of the liquid crystal display. When manufacturing this polarizing plate, in general, a protective film is bonded to the front and back of a polarizer that is dyed with iodine on a uniaxially stretched polyvinyl alcohol resin for the purpose of improving the strength and water resistance of the polarizing plate. In general, the protective film is combined with an ultraviolet absorber for the purpose of preventing the polarizer and liquid crystal from being exposed to ultraviolet rays and degrading the quality (Patent Document 1).

As the protective film for the polarizing plate, an acetylcellulose-based film having excellent optical transparency such as triacetylcellulose (TAC) or cellulose acetate propionate (CAP) whose surface is saponified is usually used. When an acetylcellulose-based film is used as a protective film, a hydrophilic adhesive is used because both the polyvinyl alcohol-based polarizer and the protective film are hydrophilic. On the other hand, in recent years, it has been proposed to use a norbornene resin film as a protective film instead of an acetyl cellulose film. The norbornene-based resin film has excellent properties such as low moisture permeability and almost no retardation in the oblique direction. However, there is a problem that sufficient adhesive strength is not exhibited when a hydrophilic adhesive (for example, polyvinyl alcohol-based adhesive) used for bonding a polyvinyl alcohol-based polarizer and an acetylcellulose-based film is used. there were.
Furthermore, the hydrophilic adhesive requires a drying furnace for removing moisture in the adhesive, and there is a problem that the production speed is affected by the drying speed.

Japanese Patent Laying-Open No. 2005-010329

  An object of this invention is to provide the manufacturing method of the polarizing plate which protects a liquid crystal from an ultraviolet-ray, does not require a drying furnace, and can improve a production speed and productivity significantly.

  The present inventors pay attention to the fact that one of the protective films to be bonded to the front and back of the polarizer contains a UV absorber, but the other protective film does not contain a UV absorber. Surprisingly, UV irradiation from the outside of the protective film that does not contain UV absorbers also cures the UV curable adhesive applied between the polarizer and the protective film that contains UV absorbers. The present inventors have found that a polarizing plate without any problem can be obtained, and have reached the present invention.

That is, the present invention
(1) A protective film (A) having ultraviolet opaqueness on one side of the polarizer and a protective film (B) having ultraviolet transparent on the other side are bonded via an ultraviolet curable adhesive, respectively. The manufacturing method of the polarizing plate characterized by irradiating an ultraviolet-ray from the outer side of the said protective film (B), and hardening the said ultraviolet curing adhesive.
(2) The method for producing a polarizing plate according to (1), wherein the protective film (B) has a light transmittance of 80% or more at a wavelength of 365 nm.
(3) The method for producing a polarizing plate according to (1) or (2), wherein the protective film (A) has a maximum light transmittance of 15% or less in an ultraviolet region of 200 nm to 380 nm.
(4) The method for producing a polarizing plate according to any one of (1) to (3), wherein the protective film (A) or (B) has a retardation.
(5) The method for producing a polarizing plate according to any one of (1) to (4), wherein the protective film (A) and / or (B) is a norbornene resin film.

The method of the present invention uses an ultraviolet curable adhesive. There is a problem that a drying furnace is required to evaporate the water contained in the polyvinyl alcohol adhesive when the polarizer and the protective film are bonded using the conventional polyvinyl alcohol adhesive, and the production speed does not increase. there were. In this invention, it has the effect that the improvement of production speed and productivity can be improved significantly. In particular, it is suitable when a norbornene-based resin film having low moisture permeability and difficult to remove moisture is used as a protective film.
Moreover, since the ultraviolet curing adhesive disposed on the front and back of the polarizer can be cured simultaneously by ultraviolet irradiation from one side, it is advantageous in terms of cost. Furthermore, it is possible to provide a polarizing plate having excellent optical properties as compared with the case where an adhesive is used.

The best mode for carrying out the present invention will be specifically described below.
The polarizer used in the method for producing a polarizing plate of the present invention is not particularly limited, and conventionally known polarizers can be used. In particular, a uniaxially stretched film of a polyvinyl alcohol resin is dyed with iodine. Those are preferred.

  In addition, the protective film to be bonded to the front and back of the polarizer is not particularly limited in material, and conventionally known acetylcellulose-based films excellent in optical transparency such as TAC and CAP, norbornene-based resin films, etc. Can be used. Among these, it is preferable to use a norbornene-based resin film because it has lower moisture permeability than the acetylcellulose-based film and is excellent in optical anomaly.

  The norbornene-based resin for forming the above-described norbornene-based film is known. For example, the product name “Arton” manufactured by JSR, the product name “Zeonor” manufactured by Zeon Japan, and the product name “manufactured by Mitsui Chemicals” APEL "and the like. These norbornene resins may be used alone or in combination of two or more. The norbornene-based resin film may be a film obtained by forming a norbornene-based resin into a film by a known method such as a casting method or a melt extrusion method.

  Moreover, what has a phase difference can be used as a protective film (A) or (B). By using a film showing retardation as the protective film (A) or (B), the step of further laminating a retardation plate on the protective film is omitted, thereby further simplifying the process and reducing the cost. . The method for imparting a retardation to the protective film may be a known method, a uniaxial retardation film obtained by stretching the film in the longitudinal direction or the transverse direction, and a biaxial property obtained by stretching the film in the longitudinal direction and the transverse direction. Examples thereof include a stretched film such as a retardation film, and a liquid crystal coating type viewing angle compensation film in which a liquid crystal such as a discotic liquid crystal is tilted on a protective film.

In the present invention, as the above-described protective film, a protective film (A) having ultraviolet impermeability on one side of the polarizer and a protective film (B) having ultraviolet transmissivity on the other side are used. There is a need.
Here, UV opaqueness does not mean that UV rays are not transmitted at all, but means that UV rays are blocked to such an extent that polarizers and liquid crystals do not deteriorate. Specifically, UV rays of 200 nm to 380 nm are used. The maximum value of the light transmittance in the region is preferably 15% or less. The protective film (A) having such properties can be produced by blending an ultraviolet absorber in the raw material resin.

On the other hand, the protective film (B) having ultraviolet transparency means a film such as an ordinary transparent protective film not containing an ultraviolet absorber, and specifically, light transmittance at a wavelength of 365 nm. Is preferably 80% or more.
That is, chemical lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps and the like used for curing UV-curable adhesives mainly generate light in the wavelength range of 300 nm to 400 nm, and in particular, general metal halide lamps and high-pressure mercury lamps. The ultraviolet ray generated in is the largest amount of irradiation with a wavelength of 360 nm to 370 nm. Therefore, if the light transmittance at 365 nm, which is the central wavelength, is 80% or more, the ultraviolet curable type in which most of the light irradiated from the ultraviolet lamp passes through the protective film (B) and is applied to both sides of the polarizer. The adhesive can be cured. In addition, when using a polarizing plate as a liquid crystal display element, in order to prevent the ultraviolet-ray from external light from deteriorating a liquid crystal, it is preferable to arrange | position a protective film (A) to the external light side from a liquid crystal.

  The ultraviolet absorber blended in the protective film (A) described above is not particularly limited. For example, 2,2′-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy- 4-methoxybenzophenone, 2,2 ', 4-trihydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxy-2 ' Methoxybenzophenone, 2,2 ', 4-trihydroxy-4'-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2', 4-trihydroxy-4'-ethoxybenzophenone, Ben, such as 2,2'-dihydroxy-4,4'-diethoxybenzophenone Phenone UV absorber, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5) '-Methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-amyl-5'-isobutylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3' -Isobutyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-isobutyl-5'-propylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy- 3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzoto , 2- -, and the like [2'-hydroxy-5 '(1,1,3,3-tetramethylbutyl) phenyl] benzotriazole ultraviolet absorbers such as benzotriazole. These can be used alone or in combination of two or more.

  The ultraviolet curable adhesive used in the method for producing a polarizing plate of the present invention is not particularly limited as long as it is cured by irradiating ultraviolet rays and is transparent after curing. Examples of the ultraviolet curable compound that is the main component of the ultraviolet curable adhesive include, for example, a radical polymerization system, a compound having an acrylic group, a methacryl group, an allyl group, etc. as a functional group, and a photocation reaction system, an epoxy group. And a compound having a functional group. As more specific examples, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, neopentyl glycol Monofunctional acrylates such as acrylic acid benzoic acid mixed esters, polyethylene glycol diacrylates such as triethylene glycol diacrylate, tetraethylene glycol diacrylate, polypropylene glycol diacrylates such as dipropylene glycol diacrylate, tripropylene glycol diacrylate Acrylate, other, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate Multifunctional such as bisphenol A ethylene oxide modified diacrylate, bisphenol A propylene oxide modified diacrylate, dimethylol tricyclodecane diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate An acrylate etc. are mentioned. In addition to these, an oligomer having an acrylic group such as ethylene oxide-modified acrylate, propylene oxide-modified acrylate, epoxy acrylate, urethane acrylate, or a photo-curable epoxy resin synthesized from a compound having a hydroxyl group can also be used. . These can be used alone or in combination of two or more.

  In addition, it is preferable that 2-10 weight% of hardening initiators are normally mix | blended with the above-mentioned ultraviolet curable adhesive. There are two types of curing initiators: a photoradical polymerization initiator and a photocationic polymerization initiator. Examples of the photo-radical polymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-diphenylethane-1-one, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene. , Anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1 -(4-Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethyl Oxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. Is mentioned.

Photocationic polymerization initiators include, for example, aryl diazonium compounds as described in US Pat. No. 3,708,296, aromatic onium salts of Group VIa elements as described in US Pat. No. 4,058,400, US An aromatic onium salt of Group Va element described in Japanese Patent No. 4069055, a dicarbonyl chelate of Group IIIa-Va element described in US Pat. No. 4,086,091, and US Pat. No. 4,139,655 Described thiopyrylium salts, Group VIa elements having MF ₆ anion (where M is selected from P, As and Sb) as described in US Pat. No. 4,161,478, as described in US Pat. No. 4,231,951. Triarylsulfonium complex salts, aromatic iodonium complex salts and aromatic sulfones described in U.S. Pat. No. 4,256,828 A nitro complex salt can be mentioned. Suitable photocationic polymerization catalysts are polyarylsulfonium complex salts, aromatic sulfonium or iodonium salts of halogen-containing complex ions, and aromatic onium salts of group IIIa, Va and VIa elements. Some of these salts are, for example, Fc-508 or FX-512 (manufactured by 3M Company, polyarylsulfonium hexafluorophosphate) or UVE-1014 (General Electric, manufactured by Company, polyarylsulfonium). Hexafluoroantimony salt), SP-170, SP-150 (manufactured by Asahi Denka Co., Ltd., polyarylsulfonium hexafluorophosphate and hexafluoroantimonate) and are available from the market. it can. These curing initiators can be used alone or in combination of two or more.

  Moreover, it is also possible to mix a well-known additive with an ultraviolet curable adhesive. Known additives include viscosity modifiers for adjusting viscosity, various solvents, ionic conductive agents, conductive conductivity additives such as conductive metal oxide fine particles, and light diffusing fine particles whose refractive index and refractive index are different from each other. And the like, and the like.

Next, the manufacturing method of the polarizing plate of this invention is demonstrated concretely, referring drawings.
FIG. 1 is a schematic cross-sectional view of a polarizing plate obtained by the method for producing a polarizing plate of the present invention, and a protective film (A) 4, a protective film ( B) It has a structure in which 5 is bonded. FIG. 2 is a schematic view for explaining a method for producing a polarizing plate of the present invention.
As is clear from FIG. 2, the protective film (A) 4 having ultraviolet impermeability on the upper surface of the polarizer 2 and the protective film (B) 5 having ultraviolet transmissivity on the lower surface are continuously supplied. The coating thickness of the UV curable adhesive 3 is 0.1 to 5 μm, preferably 0.5, using a commonly used adhesive application device 10 such as a roll coater, bar coater, gravure roll, spray, adhesive supply nozzle or the like. The surface of the polarizer 2 on the both sides of the polarizer 2 or the protective film (A) 4 and the protective film (B) 5, or the polarizer 2 and the protective film (A) 4 and the protective film so as to have a thickness of ˜2 μm. After applying between the films (B) 5, pressurizing with a pinch roll 6 and pasting, the protective film (A) 4 / adhesive 3 / polarizer 2 / adhesive 3 / protective film (B) 5 It is set as the laminated body of a structure.
Next, the laminate is sent to the ultraviolet irradiation chamber (7) and irradiated with ultraviolet rays by the ultraviolet generator 8 installed outside the protective film (B) 5, that is, below the protective film (B) 5 in FIG. Then, the polarizing plate of the present invention is obtained by curing the ultraviolet curable adhesive 3 and winding it with the winding roll 9.
The conditions of ultraviolet irradiation differ depending on the type and composition of the ultraviolet curable adhesive 3, but the integrated light amount is preferably in the range of 500 to 2500 mJ / cm ² . Furthermore, it is preferable to perform ultraviolet irradiation after heating the laminate to about 40 to 120 ° C. in advance.
In order to enhance the adhesion between the protective films 4 and 5 and the polarizer 2, the surface of the protective film or the polarizer is modified in advance by a known corona treatment, plasma treatment, UV treatment, flame treatment, or the like. More preferably.

Furthermore, the polarizing plate obtained by the production method of the present invention includes an antiglare layer, a hard coat layer, an antireflection layer, a low reflection layer, a reflection layer, an antifouling layer, an antifogging layer, and a phosphorescent layer as necessary. In addition, one or more functional layers such as a light diffusion layer and an electroluminescence layer can be laminated.
The polarizing plate obtained by the production method of the present invention thus obtained is adhered to at least one side of a spectacle lens such as sunglasses or eyesight correction glasses as a polarizing plate to be used on at least one side of a liquid crystal panel. It is preferably applied as a polarizing plate.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. The obtained polarizing plate was evaluated by the following method.
<Measurement of light transmittance>
The light transmittance in the ultraviolet region of the protective films (A) and (B) was measured using “U-3500 type spectrophotometer” manufactured by Hitachi, Ltd. The maximum transmittance of the protective film (A) in the ultraviolet region of 200 to 380 nm is abbreviated as UVa, and the transmittance of the protective film (B) at 365 nm is abbreviated as UVb.
<Measurement of peel strength>
Peel strength between the polarizer and the protective film of the polarizing plate _(A) (T _A), and the peel strength between the polarizer and the protective film (B) of the polarizing plate (T _B) is manufactured by Shimadzu Corporation tensile tester "Autograph Using DCS5000, JIS K6854-4 adhesive-peeling adhesion strength test method-part 4: Measured according to the floating roller method at a tensile speed of 300 mm / min.

[Example 1]
Similar to the method shown in FIG. 2, a benzotriazole ultraviolet absorber as the protective film A is 0.3 above a polarizer (25 μm) obtained by dyeing a film made of a uniaxially stretched polyvinyl alcohol resin with iodine. A norbornene-based resin film (thickness 80 μm, UVa: 12%) blended in weight% is uniaxially stretched as a protective film B and no UV absorber is blended to give a retardation. A film (thickness 80 μm, UVb: 91%) is arranged, and an ultraviolet curable adhesive (main component is 2-hydroxyethyl acrylate, 2,2-dimethoxy-2-diphenylethane-1-one as a photocuring initiator) 5 wt% added and prepared) was applied so that the coating thickness was 2 μm, then pressed with a pinch roll and pasted, and a protective film ( ) / To obtain an adhesive / polarizer / adhesive / protective film (B) laminate having a structure. Next, ultraviolet rays are irradiated from the protective film B side with a metal halide lamp so that the illuminance is 160 mW / cm ² , the integrated light quantity is 1500 mJ / cm ² , and the irradiation distance is 180 mm. Curing was performed to obtain the polarizing plate of the present invention. The resulting polarizing plate has a peel strength (T _A ) of 18 N / m and a peel strength (T _B ) of 46 N / m between the polarizer and each protective film, and the properties as a polarizing plate are practically sufficient. It was a thing.

[Example 2]
A polarizing plate was obtained in the same manner as in Example 1 except that triacetyl cellulose (thickness: 80 μm, UVa: 5%) containing an ultraviolet absorber was used as the protective film A. The resulting polarizing plate has a peel strength (T _A ) of 19 N / m and a peel strength (T _B ) of 21 N / m between the polarizer and each protective film, and the properties as a polarizing plate are practically sufficient. It was a thing.

[Example 3]
The same as Example 1 except that triacetyl cellulose (thickness 80 μm, UVa: 5%) blended with UV absorber as protective film A and polycarbonate (thickness 100 μm, UVb: 88%) as protective film B were used. Thus, a polarizing plate was obtained. The obtained polarizing plate has a peel strength (T _A ) of 23 N / m and a peel strength (T _B ) of 25 N / m between the polarizer and each protective film, and the properties as a polarizing plate are practically sufficient. It was a thing.

[Comparative Example 1]
An attempt was made to obtain a polarizing plate in the same manner as in Example 1 except that the position of the ultraviolet generator in FIG. 2 was changed to the upper side of the laminate passage surface (the upper side of the protective film (A)). Was not cured, and the desired polarizing plate was not obtained.

[Comparative Example 2]
Although an attempt was made to obtain a polarizing plate in the same manner as in Example 2 except that the position of the ultraviolet generator in FIG. 2 was changed to the upper side of the laminate passage surface (the upper side of the protective film (A)), an ultraviolet curable adhesive was obtained. Was not cured, and the desired polarizing plate was not obtained.

[Comparative Example 3]
Although an attempt was made to obtain a polarizing plate in the same manner as in Example 3 except that the position of the ultraviolet generator in FIG. 2 was changed to the upper side of the laminate passage surface (the upper side of the protective film (A)), an ultraviolet curable adhesive was obtained. Was not cured, and the desired polarizing plate was not obtained.

  As described above, according to the present invention, since a drying furnace is unnecessary as compared with the case of using a polyvinyl alcohol-based adhesive, the production speed is greatly increased, and the improvement in productivity is improved. A method of manufacturing a board is provided. The polarizing plate obtained by the present invention is useful as an optical element such as a liquid crystal display element and glasses.

It is typical sectional drawing of the polarizing plate manufactured by this invention. It is a schematic diagram explaining the manufacturing method of the polarizing plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Polarizer 3 UV curable adhesive 4 Protective film (A)
5 Protective film (B)
6 Pinch roll 7 Ultraviolet irradiation chamber 8 Ultraviolet generator 9 Winding roll 10 Adhesive application device

Claims (5)

A protective film (A) having ultraviolet impermeability on one side of the polarizer and a protective film (B) having ultraviolet transmissivity on the other side are bonded via an ultraviolet curable adhesive, and then the protective film. (B) A method for producing a polarizing plate, comprising irradiating ultraviolet rays from the outside to cure the ultraviolet curable adhesive. The method for producing a polarizing plate according to claim 1, wherein the protective film (B) has a light transmittance of 80% or more at a wavelength of 365 nm. The method for producing a polarizing plate according to claim 1 or 2, wherein the protective film (A) has a maximum light transmittance of 15% or less in an ultraviolet region of 200 nm to 380 nm. The said protective film (A) or (B) has a phase difference, The manufacturing method of the polarizing plate of Claims 1-3 characterized by the above-mentioned. The said protective film (A) and / or (B) are norbornene-type resin films, The manufacturing method of the polarizing plate of Claims 1-4 characterized by the above-mentioned.

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