KR20100023749A - Polarizing plate - Google Patents

Abstract

PURPOSE: A polarizing plate is provided to reduce thickness and improve mechanical strength by laminating a polarizing polyethyleneterephthalate resin film through an adhesive layer. CONSTITUTION: A polarizing film is composed of the PVA(PolyVinyl Alcohol) resin. A first polyethyleneterephthalate resin film is laminated in one side of the polarizing film through an adhesive layer. A second polyethyleneterephthalate group resin film is laminated in the other side of the polarizing film through the adhesive layer. The thickness of the first or the second polyethyleneterephthalate group resin film is 20um or 50um.

Description

Polarizer {POLARIZING PLATE}

This invention relates to the polarizing plate in which the polyethylene terephthalate-type resin film of 20 micrometers-50 micrometers thickness is laminated | stacked on both surfaces of the polarizing film which consists of polyvinyl alcohol-type resins.

The polarizing plate is a cellulose acetate transparent protective film typified by a transparent protective film, for example, triacetyl cellulose, on one or both surfaces of a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. It is a laminated structure. This is bonded as an adhesive to a liquid crystal cell through another optical film as needed, and it is set as the component part of a liquid crystal display device.

BACKGROUND ART Liquid crystal display devices are rapidly expanding in use as thin display screens such as liquid crystal televisions, liquid crystal monitors, and personal computers. In particular, the market expansion of liquid crystal television is remarkable, and the demand for cost reduction is also very strong. As a polarizing plate for liquid crystal television, the thing which laminated | stacked the triacetyl cellulose film (TAC film) using the water-based adhesive on both surfaces of the polarizing film containing a polyvinyl alcohol-type resin film conventionally is used, and an adhesive is provided on one side of the polarizing plate. Retardation film is bonded through.

As a retardation film laminated | stacked on a polarizing plate, the stretched processed article of a polycarbonate-type resin film, the stretched processed article of a cycloolefin resin film, etc. are used, but for the liquid crystal television, cycloolefin resin with very little retardation unevenness at high temperature. The retardation film containing a film is used abundantly. Regarding the bonded product of such a retardation film containing a polarizing plate and a cycloolefin resin film, it is conceivable to reduce the number of components to be configured or to simplify the manufacturing process in order to improve productivity and reduce product cost. For example, Patent Document 1 (Japanese Patent Laid-Open No. Hei 8-43812) discloses a laminated structure of a cycloolefin-based (norbornene-based) resin film / polarizing film / TAC film having a phase difference function.

In addition, Patent Document 2 (Japanese Patent Laid-Open No. 2005-70140), Patent Document 3 (Japanese Patent Laid-Open No. 2005-l81817) and Patent Document 4 (Japanese Patent Laid-Open No. 2005-208456) include polyvinyl chloride. Joining the polarizing film and cycloolefin type protective film which consist of alcohol type resin with a urethane type water-based adhesive agent is described.

In large screen liquid crystal television applications, the necessity as a thin wall-mounted television is presently present, but the following point becomes a problem with respect to the components used for a liquid crystal panel.

(1) Corresponding to the thin large screen of the liquid crystal panel, it is necessary to reinforce the panel strength.

(2) Corresponding to the thinning of the liquid crystal television, the thickness of the member to be used is required.

(3) The gap between the liquid crystal panel and the backlight system on the back becomes narrow, and it is necessary to prevent circular irregularities and Newton rings caused by contact between the liquid crystal panel and the backlight system.

This invention is made | formed in order to solve the said subject, The objective is providing the polarizing plate which can fully reinforce the intensity of a liquid crystal panel, responding to the thickness reduction of the liquid crystal panel applied.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to solve such a subject, the 1st polyethylene terephthalate-type resin film of 20 micrometers-50 micrometers thickness is laminated | stacked on one side of the polarizing film which consists of polyvinyl alcohol-type resins, The polarizing plate on which the second polyethylene terephthalate film having a thickness of 20 μm to 50 μm is laminated on the other side of the polarizing film was found to have excellent mechanical strength despite the reduction in thickness, thereby completing the present invention.

That is, the present invention provides a polarizing film made of polyvinyl alcohol-based resin, a stretched first polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on one side of the polarizing film through an adhesive layer; It provides a polarizing plate having a second polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on the other side of the polarizing film through an adhesive layer.

In the polarizing plate of the present invention, it is preferable that the first polyethylene terephthalate resin film has a hard coating layer having surface irregularities laminated on the side opposite to the surface on which the polarizing film is laminated.

The first polyethylene terephthalate resin film is preferably biaxially stretched or uniaxially stretched, and the second polyethylene terephthalate resin film is preferably uniaxially stretched or not stretched.

The second polyethylene terephthalate-based resin film may have a pressure-sensitive adhesive layer laminated on the side opposite to the surface on which the polarizing film is laminated.

According to the polarizing plate of this invention, the improvement and thickness reduction of the mechanical strength of the liquid crystal panel applied can be achieved simultaneously. Moreover, the liquid crystal display device using the polarizing plate of this invention is applicable suitably to the liquid crystal display device for large screen liquid crystal televisions, especially the liquid crystal display device for wall-mounted liquid crystal televisions.

<Mode for carrying out the invention>

The polarizing plate of the present invention comprises a polarizing film made of polyvinyl alcohol-based resin, a stretched first polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on one side of the polarizing film via an adhesive layer; And a second polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on the other side of the polarizing film through an adhesive layer. Hereinafter, each structural member is demonstrated in detail.

(Polarizing film)

Specifically, the polarizing film used for the polarizing plate of this invention adsorbs and orients a dichroic dye to the uniaxially stretched polyvinyl alcohol-type resin film. Polyvinyl alcohol-type resin is obtained by saponifying a polyvinyl acetate type resin. As polyvinyl acetate type resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate, for example, an ethylene-vinyl acetate copolymer, etc. are mentioned. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamide which has an ammonium group, etc. are mentioned, for example.

The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. These polyvinyl alcohol-based resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of 1000 to 10000, preferably in the range of 1500 to 5000.

What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, It can form into a film by a conventionally well-known appropriate method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 10-150 micrometers.

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

In addition, although polyvinyl alcohol-type resin film is uniaxially stretched at the time of manufacture of a polarizing film, this uniaxial stretching may be performed before a dyeing process, may be performed in a dyeing process, or may be performed after a dyeing process. When uniaxial stretching is performed after a dyeing process, this uniaxial stretching may be performed before a boric acid treatment process, or may be performed during a boric acid treatment process. It is also possible to uniaxially stretch in these multiple steps. Uniaxial stretching may allow a circumferential speed to extend uniaxially between different rolls, and may make it uniaxially stretch using a thermal roll. Moreover, it may be dry stretching which extends | stretches in air | atmosphere, or it may be wet extending | stretching which extends | stretches in the state swollen with a solvent. The draw ratio is usually about 3 to 8 times.

Dyeing by the dichroic dye of the polyvinyl alcohol-type resin film in a dyeing process is performed by immersing a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. As a dichroic dye, iodine, a dichroic dye, etc. are used, for example. Dichroic dyes include, for example, dichroic direct dyes containing a disazo compound such as C. I. DIRECT RED 39, dichroic direct dyes containing a compound such as tris azo and tetrakis azo. In addition, it is preferable that the polyvinyl alcohol-based resin film be immersed in water before the dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. When iodine is used as a 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 using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing aqueous solution dichroic dye is employ | adopted normally. The content of the dichroic dye in this aqueous solution is usually water, and 100 parts by weight of 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, particularly preferably 1 × 10 ^-3 to 1 × 10 ^-2 parts by weight. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. When using a dichroic dye as a dichroic dye, the temperature of the dye aqueous solution used for dyeing is 20-80 degreeC normally, and also the immersion time (dyeing time) in this aqueous solution is 10-1800 second normally.

The boric acid treatment step is performed by immersing the polyvinyl alcohol-based resin film dyed with a dichroic dye in an aqueous solution containing boric acid. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. In the case where iodine is used as the dichroic dye in the dyeing treatment step described above, the boric acid-containing aqueous solution used in the boric acid treatment step preferably contains potassium iodide. In this case, the amount of potassium iodide in boric-acid containing aqueous solution is 0.1-15 weight part normally per 100 weight part of water, Preferably it is 5-12 weight part. Immersion time in boric acid containing aqueous solution is 60-1200 second normally, Preferably it is 150-600 second, More preferably, it is 200-400 second. The temperature of the boric acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

In the subsequent water washing process, the water washing process is performed by immersing the polyvinyl alcohol-type resin film after boric acid treatment mentioned above in water, for example. The temperature of the water in a water washing process is 5-40 degreeC normally, and immersion time is 1-120 second normally. After a water washing process, a drying process is normally given and a polarizing film is obtained. A drying process is performed using a hot air dryer, a far-infrared heater, etc. preferably, for example. The temperature of a drying process is 30-100 degreeC normally, Preferably it is 50-80 degreeC. The time of the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

In this way, 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 this polarizing film is in the range of 5-40 micrometers normally. As for the polarizing plate of this invention, the 1st polyethylene terephthalate-type resin film extended | stretched through the adhesive bond layer was laminated | stacked on one side of such a polarizing film, and the 2nd polyethylene terephthalate-type resin film was laminated | stacked via the adhesive bond layer on the other side. .

(1st polyethylene terephthalate resin film)

The 1st polyethylene terephthalate-type resin film used for the polarizing plate of this invention is extending | stretching a polyethylene terephthalate-type resin film, The thickness is 20-50 micrometers. It is preferable that the 1st polyethylene terephthalate resin film is uniaxially stretched or biaxially stretched for the reason of thickness reduction and mechanical strength.

Here, in this invention, the polyethylene terephthalate which comprises the said polyethylene terephthalate system resin film is resin in which 80 mol% or more of a repeating unit is comprised from ethylene terephthalate, and may also contain another copolymerization component. As another copolymerization component, isophthalic acid, p- (beta)-oxyethoxy benzoic acid, 4.4'- dicarboxydiphenyl, 4,4'- dicarboxy benzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid Dicarboxylic acid components such as 5-sodium sulfoisophthalic acid and 1,4-dicarboxycyclohexane; For example, diol components, such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, the ethylene oxide adduct of bisphenol A, polyethyleneglycol, polypropylene glycol, polytetramethylene glycol, are mentioned. These dicarboxylic acid components and diol components can be used in combination of 2 or more type as needed. Moreover, it is also possible to use together oxycarboxylic acids, such as p-oxybenzoic acid, with the said dicarboxylic acid component and a diol component. Such other copolymerization components may include compounds containing small amounts of amide bonds, urethane bonds, ether bonds, carbonate bonds, and the like.

As a manufacturing method of a polyethylene terephthalate, what is called direct polymerization method which directly reacts terephthalic acid and ethylene glycol (and other dicarboxylic acid and / or other diol as needed); Any production method, such as a so-called transesterification reaction, in which a dimethyl ester of terephthalic acid and ethylene glycol (and a dimethyl ester of another dicarboxylic acid and / or other diol, if necessary) are transesterified, may be applied. In addition, a polyethylene terephthalate can contain a well-known additive as needed. For example, it may contain a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver and the like. However, since transparency is necessary for optical use, it is preferable to keep the addition amount of an additive to the minimum.

The method for producing the uniaxially stretched first polyethylene terephthalate resin film, which is used in the present invention, is not particularly limited, but the polyethylene terephthalate, which is a raw material resin, is melted and the non-oriented film extruded into a sheet is glass transitioned. After transverse stretching by a tenter at the temperature more than temperature, the method of performing a heat setting process is mentioned. By performing a uniaxial stretching process, a polyethylene terephthalate resin film with higher mechanical strength can be obtained. The stretching temperature is 80 to 130 ° C, preferably 90 to 120 ° C, and the stretching ratio is 2.5 to 6 times, preferably 3 to 5.5 times. When a draw ratio becomes low, a polyethylene terephthalate-type resin film may not show sufficient mechanical strength.

Moreover, from a viewpoint of reducing the distortion of the orientation main axis in a polyethylene terephthalate-type resin film, it is preferable to loosen | cure a film to a longitudinal direction before performing a heat setting process after the above-mentioned horizontal stretching. The temperature for relaxation treatment is 90 to 200 ° C, preferably 120 to 180 ° C. Although the amount of relaxation varies depending on the lateral stretching conditions, it is preferable to set the amount of relaxation and the temperature so that the thermal contraction rate at 150 ° C. of the film after the relaxation treatment is 2% or less.

The temperature of heat setting treatment is 180-250 degreeC normally, Preferably it is 200-245 degreeC. The heat fixation treatment is usually performed by fixing the end of the film and holding the film at the temperature for 1 second to 10 minutes, preferably for 3 seconds to 1 minute. After the heat setting treatment, it is preferable to perform the relaxation treatment so that the relaxation ratio in the width direction of the film is 1 to 10% (preferably 2 to 5%). In this way, the distortion of the orientation main axis is reduced, and a uniaxially stretched polyethylene terephthalate resin film excellent in heat resistance is obtained. In this invention, the polyethylene terephthalate film whose distortion maximum value of an orientation principal axis is 10 degrees or less, More preferably, it is 8 degrees or less, More preferably, it is 5 degrees or less, is used preferably. When the distortion maximum value of an orientation main axis is large, when the polarizing plate using such a polyethylene terephthalate-type resin film is bonded to the liquid crystal display screen of a liquid crystal display device, there exists a tendency for coloring defect to become large. In addition, the distortion maximum value of the orientation main axis of the polyethylene terephthalate system resin film mentioned above can be measured, for example using a retardation film inspection apparatus RETS system (made by Otsuka Denshi Co., Ltd.).

As described above, a uniaxially stretched polyethylene terephthalate resin film can be obtained. The biaxially stretched polyethylene terephthalate resin film can be obtained by performing the longitudinal stretching treatment following the lateral stretching.

In the present invention, the thickness of the first polyethylene terephthalate resin film is 20 to 50 µm, preferably 30 to 40 µm. If the thickness is thin, the handling of the film is difficult, and when a thick polyethylene terephthalate film is used, the advantage of thinning is lost.

The first polyethylene terephthalate resin film may have a hard coating layer (also referred to as an anti-glare layer) having fine surface irregularities on the surface on the opposite side to the surface adhered to the polarizing film. It is preferable that the haze of the polyethylene terephthalate type resin film provided with the hard-coat layer which has such a fine surface asperity is 3 to 40% of range. In addition, the haze of a polyethylene terephthalate-type resin film is defined as ratio of the diffusivity with respect to total light transmittance, and can be measured with a commercially available haze meter as prescribed | regulated to JISK7136.

As a method of forming a hard-coat layer on the surface of a polyethylene terephthalate-type resin film, the method of coating the coating liquid which mixed the inorganic fine particle or organic fine particle with the resin binder on the surface of a polyethylene terephthalate-type resin film, etc. are mentioned, for example. It is not limited to this. As the inorganic fine particles, silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate and the like can be used as representative ones. As the organic fine particles, heat resistant resin particles such as crosslinked polyacrylic acid particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicone resin particles, and polyimide particles can be used.

It is preferable that the resin binder for disperse | distributing an inorganic fine particle or organic fine particle is selected from the material used as a high hardness (hard) coating. As the resin binder, an ultraviolet curable resin, a thermosetting resin, an electron beam curable resin or the like can be used, but an ultraviolet curable resin is preferably used from the viewpoint of productivity, hardness and the like. As ultraviolet curable resin, what is marketed can be used. For example, single or 2 or more types of polyfunctional acrylates, such as trimethylolpropane triacrylate and pentaerythritol tetraacrylate, and "Irgacure 907" and "Irgacure 184" (above, Ciba specialty -A mixture with photoinitiators, such as Chemicals Corporation make) and "Lucirine TPO" (made by BASF Corporation), can be made into an ultraviolet curable resin. For example, when using an ultraviolet curable resin, after disperse | distributing an inorganic fine particle or organic fine particle to an ultraviolet curable resin, and obtaining a composition, it apply | coats the said composition on a polyethylene terephthalate resin film and irradiates an ultraviolet-ray, and hard-coats A hard coating layer in which inorganic fine particles or organic fine particles are dispersed in a resin can be formed.

Moreover, as another method of providing an anti-glare function to a polyethylene terephthalate-type resin film, the method of containing an inorganic fine particle or organic microparticles | fine-particles in a polyethylene terephthalate-type resin film itself is mentioned.

Moreover, surface treatments, such as a hard coating process and an antistatic process, may be given to the surface on the opposite side to the surface which sticks with the polarizing film in the said polyethylene terephthalate system resin film. Moreover, the coating layer containing a liquid crystalline compound, its high molecular weight compound, etc. may be formed. Moreover, even if a polyethylene naphthalate film is used instead of a polyethylene terephthalate film, substantially the same effect is acquired.

A first polyethylene terephthalate-based resin film used in the present invention, if is preferable that the retardation value R ₀ 1000 nm or more, and more preferably not less than 3000 nm. This is because when the polyethylene terephthalate resin film having a small in-plane retardation value R ₀ is used, coloring on the front side tends to be remarkable. In addition, the upper limit of the retardation value R ₀ side of the polyethylene terephthalate-based resin film used in the present invention is sufficient to up to 10000 nm.

The first polyethylene terephthalate-based resin film having the above-described characteristics is generally excellent in mechanical properties, solvent resistance, scratch resistance, cost, and the like, and can be particularly preferably used in the polarizing plate of the present invention.

(2nd polyethylene terephthalate resin film)

The thickness of the 2nd polyethylene terephthalate resin film used for the polarizing plate of this invention is 20-50 micrometers, Preferably it is 30-40 micrometers from the same viewpoint as a 1st polyethylene terephthalate resin film. It is preferable that the 2nd polyethylene terephthalate resin film is uniaxially stretched or unstretched (unstretched) in order to avoid the image quality deterioration (interference nonuniformity) by a large phase difference. As the unstretched polyethylene terephthalate resin film, an unoriented film extruded into the above sheet form can be used.

The polyethylene terephthalate used in the second polyethylene terephthalate resin film, the method for producing the film, and various characteristics of the film (maximum distortion of the orientation main axis, haze, in-plane retardation value R _0, etc.) are the first polyethylene terephthalate resin. It may be the same as a film, and may differ.

Next, the manufacturing method of the polarizing plate of this invention is demonstrated. The polarizing plate of this invention bonds a 1st and 2nd polyethylene terephthalate-type resin film, respectively, through the adhesive agent on both surfaces of the above-mentioned polarizing film. The adhesive for bonding the first polyethylene terephthalate resin film and the adhesive for bonding the second polyethylene terephthalate resin film may be the same kind of adhesive or different kinds of adhesives. As an adhesive agent, the thing of the water system, ie, the thing which melt | dissolved the adhesive component in water, or the thing disperse | distributed to water is mentioned. By using an aqueous adhesive agent, the adhesive bond layer formed between a polarizing film and a polyethylene terephthalate type resin film can be made thin. As an aqueous adhesive agent used preferably, the adhesive composition containing polyvinyl alcohol-type resin or a urethane resin as a main component is mentioned.

When polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified Modified polyvinyl alcohol-based resins such as polyvinyl alcohol and amino group-modified polyvinyl alcohol may be used. When polyvinyl alcohol-type resin is used as an adhesive component, the said adhesive agent is normally manufactured as an aqueous solution of polyvinyl alcohol-type resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

In order to improve adhesiveness, it is preferable to add curable components, such as glyoxal and a water-soluble epoxy resin, and a crosslinking agent to the adhesive agent containing polyvinyl alcohol-type resin as a main component. As water-soluble epoxy resin, epichlorohydrin is made to react with the polyamide amine obtained by reaction of polyalkylene polyamines, such as diethylene triamine and triethylene tetramine, and dicarboxylic acids, such as adipic acid, for example. The polyamide polyamine epoxy resin obtained can also be used preferably. As a commercial item of such a polyamide polyamine epoxy resin, "Sumirez resin 650" (made by Sumika Chemtex), "Sumirez resin 675" (manufactured by Sumika Chemtex), "WS-525" ( Nippon PMC Co., Ltd.) etc. are mentioned. The addition amount of these curable components and a crosslinking agent (when all are added) is 1-100 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resins, Preferably it is 1-50 weight part. When the addition amount of the curable component and the crosslinking agent is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving the adhesion tends to be small, and when the addition amount of the curable component and the crosslinking agent is large, the adhesive layer This is because it tends to be vulnerable.

Moreover, when using urethane resin as a main component of an adhesive agent, the mixture of the polyester-type ionomer type urethane resin and the compound which has glycidyloxy group is mentioned as an example of a suitable adhesive composition. The polyester ionomer-type urethane resin here is a urethane resin which has a polyester frame | skeleton, and a small amount of ionic component (hydrophilic component) is introduce | transduced in it. Such ionomer-type urethane resin is suitable as an aqueous adhesive, since it is emulsified directly in water, without using an emulsifier, and becomes an emulsion. The polyester ionomer-type urethane resin itself is well-known, for example, Unexamined-Japanese-Patent No. 7-97504 describes as an example of the polymer dispersing agent for disperse | distributing a phenolic resin in an aqueous medium, and also mentioned above Japanese Unexamined Patent Application Publication No. 2005-70140 (Patent Document 2) and Japanese Unexamined Patent Application Publication No. 2005-208456 (Patent Document 4) disclose a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group. As an adhesive agent, the aspect which bonds a cycloolefin resin film to the polarizing film which consists of polyvinyl alcohol-type resin is disclosed.

As a method of bonding the 1st and 2nd polyethylene terephthalate resin films mentioned above to a polarizing film using an adhesive agent, it may be generally known, for example, the casting method, the Mayer coating method, the gravure coating method. And a method in which an adhesive is applied to the adhesive surface of the polarizing film and / or the film bonded thereto by a comma coating method, a doctor blade method, a die coating method, an immersion coating method, a spraying method, or the like, and the two are overlapped. . The casting method is a method in which a film, which is a coated object, moves in a substantially vertical direction, a substantially horizontal direction, or in an inclined direction between them, while expanding an adhesive onto a surface thereof.

After apply | coating an adhesive agent, these films are bonded by bonding together a polarizing film and the polyethylene terephthalate type resin film bonded to it with a nip roll etc. Moreover, after dripping an adhesive agent between a polarizing film and a polyethylene terephthalate type resin film, the method of making this laminated body pass between a roll and a roll, pressurizing, and spreading it uniformly is also employ | adopted. As a material of a roll, a metal, rubber | gum, etc. can be used. These rolls may be the same material or different materials.

Moreover, in order to improve adhesiveness, the adhesive surface of a polarizing film and / or a polyethylene terephthalate resin film is surface-treated, such as a plasma process, a corona treatment, an ultraviolet irradiation process, a flame (flame) process, saponification process, etc. suitably. You may. As a saponification process, the method of immersing in alkaline aqueous solution, such as sodium hydroxide and potassium hydroxide, is mentioned.

The adhesive layer is formed by laminating the first and second polyethylene terephthalate resin films on the polarizing film through an adhesive, respectively, and then drying and curing the adhesive. This drying process is performed by spraying hot air, for example, and the temperature is normally in the range of 40-100 degreeC, Preferably it exists in the range of 60-100 degreeC. In addition, a drying time is 20 to 1200 second normally.

The thickness of the adhesive bond layer after drying is 0.001-5 micrometers normally, Preferably it is 0.01-2 micrometers, More preferably, it is 0.01-1 micrometer. When the thickness of an adhesive bond layer is less than 0.001 micrometer, there exists a possibility that adhesive may become inadequate, and when the thickness of an adhesive bond layer exceeds 5 micrometers, there exists a possibility that the appearance defect of a polarizing plate may arise.

After bonding, curing at least half a day, usually for one day or more at a temperature of room temperature or less may be sufficient to obtain sufficient adhesive strength. Such curing is typically carried out in a rolled state. Preferable curing temperature is the range of 30-50 degreeC, More preferably, it is 35-45 degreeC. When curing temperature exceeds 50 degreeC, what is called a "winding knot" tends to arise in a roll winding state. In addition, the humidity at the time of curing may be appropriate, and the relative humidity may be in the range of 0 to 70%. The curing time is usually 1 to 10 days, preferably 2 to 7 days.

Moreover, in this invention, a photocurable adhesive agent can also be used as an adhesive agent. As a photocurable adhesive agent, the mixture of a photocurable epoxy resin, a photocationic polymerization initiator, etc. are mentioned, for example. In this case, a photocurable adhesive agent is hardened by irradiating an active energy ray. The light source of the active energy ray is not particularly limited, but an active energy ray having a luminescence distribution at a wavelength of 400 nm or less is preferable, and specifically, 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 A mercury lamp, a metal halide lamp, etc. are preferable here.

Light irradiation intensity to a photocurable adhesive agent is suitably determined by the composition of this photocurable adhesive agent, Although it does not specifically limit, It is preferable that irradiation intensity of the wavelength range effective for activation of a polymerization initiator is 0.1-6000 mW / cm <^2> . . If the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and if 6000 mW / cm ² or less, the yellowing or polarizing film of the epoxy resin due to heat generation during curing of the heat and photocurable adhesive radiated from the light source Less likely to cause deterioration. The light irradiation time to the photocurable adhesive is not particularly limited as it is controlled for each photocurable adhesive to be cured, but the accumulated light amount expressed as a product of the irradiation intensity and the irradiation time is 10 to 10000 mJ / m ² . It is preferable to be set. If the accumulated light amount to the photocurable adhesive agent is 10 mJ / m ² or more, a sufficient amount of active species derived from a polymerization initiator can be generated to reliably advance the curing reaction, and if it is 10000 mJ / m ² or less, the irradiation time is too long. Good productivity can be maintained without lengthening.

When hardening a photocurable adhesive agent by irradiation of an active energy ray, it is preferable to perform hardening on the conditions which the various functions of the polarizing plate called polarization degree, transmittance | permeability, and color of a polarizing film, and transparency of a polyethylene terephthalate-type resin film do not fall. Do.

In the polarizing plate of this invention, it is preferable that a 2nd polyethylene terephthalate-type resin film has an adhesive layer on the outer surface (surface opposite to the side bonded to a polarizing film). Such an adhesive layer can be used for bonding with a liquid crystal cell, or bonding with the optical functional film mentioned later. As an adhesive used for an adhesive layer, a conventionally well-known appropriate adhesive can be used without a restriction | limiting especially, For example, an acrylic adhesive, a urethane type adhesive, a silicone type adhesive etc. are mentioned. Especially, an acrylic adhesive is used preferably from a viewpoint of transparency, adhesive force, reliability, rework property, etc. The pressure-sensitive adhesive layer can be provided by using such an adhesive in the form of an organic solvent solution, for example, by applying a die coater, a gravure coater, or the like on a second polyethylene terephthalate resin film, and drying it. In addition, it can be provided also by the method of transferring the sheet-like adhesive formed on the plastic film (it is called a separator film) to which the mold release process was performed to the 2nd polyethylene terephthalate type resin film. Although there is no restriction | limiting in particular also about the thickness of an adhesive layer, It is preferable to exist in the range of 2-40 micrometers generally.

When the above-mentioned pressure-sensitive adhesive layer is formed, the optical functional film may be laminated on the polarizing plate of the present invention through the pressure-sensitive adhesive layer. As an optical functional film, the optical compensation film in which the liquid crystalline compound was apply | coated and orientated on the surface of a base material, the reflective polarizing film which transmits the polarized light of a specific kind, and reflects the polarized light which shows the opposite property, polycar A retardation film containing a carbonate resin, a retardation film containing a cyclic polyolefin resin, an antiglare function film having a concave-convex shape on the surface, a film with a surface antireflection function, a reflection film having a reflection function on the surface, and a reflection function Semi-transmissive reflective film etc. which have a transmissive function are mentioned. As a commercial item corresponded to the optical compensation film by which the liquid crystalline compound was apply | coated and orientated on the base material surface, "WV film" (Fuji Film Co., Ltd. product), "NH film" (Shin Nippon Sekiyu Co., Ltd. product), "NR Film "(new Nippon Seki Oil Co., Ltd. product) etc. are mentioned. As a commercial item which corresponds to the reflection type polarizing film which permeate | transmits a specific kind of polarized light and reflects the polarized light which shows the opposite property, it is "DBEF" (3M company make, Sumitomo 3M Co., Ltd. in Japan), for example. Available). Moreover, as a commercial item corresponding to the retardation film containing cyclic polyolefin type resin, it is "Aton film" (made by JSR Corporation), "Esshina" (made by Sekisui Chemical Industries, Ltd.), "Zeo", for example. NOR FILM "(made by Optes Corporation) etc. are mentioned.

The liquid crystal display device can be obtained by bonding the polarizing plate of this invention to a liquid crystal cell through an adhesive layer. The polarizing plate of this invention is normally bonded by the liquid crystal cell so that the 2nd polyethylene terephthalate resin film side may face a liquid crystal cell. The liquid crystal display device provided with the polarizing plate of this invention has sufficient mechanical strength, responding to thinning. About the other structure of a liquid crystal display device, the suitable structure of a conventionally well-known liquid crystal display device can be employ | adopted, and what is specifically limited also about the other structural members (light diffuser plate, a backlight, etc.) which a liquid crystal display device normally has is common. no.

When applying the polarizing plate of this invention to a liquid crystal display device, the polarizing plate of this invention may be used as a "back side polarizing plate", and may be used as a "front side polarizing plate." "Back side polarizing plate" means the polarizing plate arrange | positioned at the backlight side of the liquid crystal cell when mounted in a liquid crystal display device, and "front side polarizing plate" means the visual recognition side of the liquid crystal cell when mounted in a liquid crystal display device. It means the polarizing plate arranged.

<Example>

Although an Example is given to the following and this invention is demonstrated in more detail, this invention is not limited to these Examples. In addition, unless otherwise indicated,% and the part which show content-usage-amount in an example are a basis of weight. In the following examples, the in-plane retardation value R ₀ of the stretched film refers to a value measured using KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.). In addition, haze refers to the value measured using the haze meter HM-150 type (made by Murakami Shikisai Kijutsu Co., Ltd.) based on JISK7136. The distortion maximum value of an orientation main axis points out the value measured using the retardation film inspection apparatus RETS system (made by Otsuka Denshi Co., Ltd.).

<Example 1>

A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was immersed in pure water at 30 ° C., and then immersed at 30 ° C. in an aqueous solution having a weight ratio of 0.02 / 2/100 of iodine / potassium iodide / water. I was. Then, it was immersed at 56.5 degreeC in the aqueous solution whose weight ratio of potassium iodide / boric acid / water is 12/5/100. Subsequently, after wash | cleaning with pure water of 8 degreeC, it dried at 65 degreeC and obtained the polarizing film by which the iodine adsorption-orientated to polyvinyl alcohol. Stretching was mainly carried out in an iodine dyeing and boric acid treatment step, and the total draw ratio was 5.3 times.

A uniaxially stretched polyethylene terephthalate-based resin film having a thickness of 40 μm (distortion maximum value of orientation principal axis: 2 degrees, in-plane retardation value R ₀ : 3800 nm) was prepared, and a corona treatment was applied to the adhesive surface thereof. Separately, a biaxially stretched polyethylene terephthalate film having a thickness of 40 µm and a haze of 17% (a distortion maximum value of the orientation main axis: 2 degrees, an in-plane retardation value R ₀ : 3800 nm) was prepared, and a corona treatment was applied to the adhesive surface thereof. .

Next, the uniaxially-stretched and biaxially-stretched polyethylene terephthalate-based resin films were bonded to both surfaces of the polarizing film through a photocurable adhesive such that its corona treated surface became an adhesive surface, and then bonded by irradiating with ultraviolet rays to obtain a polarizing plate. . This polarizing plate is lighter in comparison with a normal polarizing plate and has a higher bursting strength.

The embodiments and examples disclosed herein are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is disclosed by the claims rather than the foregoing description, and is intended to include any modifications within the scope and meaning equivalent to the claims.

According to the polarizing plate of this invention, the improvement and thickness reduction of the mechanical strength of the liquid crystal panel applied can be achieved simultaneously. Moreover, the liquid crystal display device using the polarizing plate of this invention is applicable suitably to the liquid crystal display device for large screen liquid crystal televisions, especially the liquid crystal display device for wall-mounted liquid crystal televisions.

Claims (4)

Polarizing film which consists of polyvinyl alcohol-type resin, An elongated first polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on one side of the polarizing film through an adhesive layer; A second polyethylene terephthalate-based resin film having a thickness of 20 μm to 50 μm, laminated on the other side of the polarizing film through an adhesive layer. Polarizing plate having a. The polarizing plate according to claim 1, wherein the first polyethylene terephthalate resin film has a hard coating layer having surface irregularities laminated on a surface opposite to a surface on which the polarizing film is laminated. The polarizing plate according to claim 1 or 2, wherein the first polyethylene terephthalate resin film is biaxially stretched or uniaxially stretched, and the second polyethylene terephthalate resin film is uniaxially stretched or not stretched. The polarizing plate according to any one of claims 1 to 3, wherein the second polyethylene terephthalate resin film has a pressure-sensitive adhesive layer laminated on a surface opposite to a surface on which the polarizing film is laminated.