KR101708944B1 - A liquid crystal display device - Google Patents

Abstract

In the present invention, the front-side polarizing plate 20 is laminated on the visual side of the liquid crystal cell 10 through the first pressure-sensitive adhesive layer 41 and the rear-side polarizing plate 30 is laminated on the opposite side through the second pressure- And a backlight unit 60 is disposed on the outer side thereof to provide a liquid crystal display device. The back side polarizing plate 30 is provided with a first transparent protective film 32 / a polarizing film 31 / a second transparent protective film 33 / a third pressure sensitive adhesive layer 43 / a retardation film 35, and the retardation film 35 has a three-layer structure in which a skin layer 37 including a rubber particle-containing acrylic resin composition is formed on both surfaces of a core layer 36 containing a styrene resin . The first pressure sensitive adhesive layer 41, the second pressure sensitive adhesive layer 42 and the third pressure sensitive adhesive layer 43 all have a storage elastic modulus at 50 ° C of not less than 0.01 MPa and not more than 0.1 MPa. According to the present invention, there is provided a liquid crystal display device in which warpage of a liquid crystal panel is small and display unevenness is small even after being placed under a humid environment.

Description

[0001] The present invention relates to a liquid crystal display (LCD)

The present invention relates to a liquid crystal display in which warpage of a liquid crystal panel is reduced.

BACKGROUND ART [0002] Liquid crystal display devices are rapidly spreading as an information display device such as a cellular phone, a portable information terminal, a computer monitor, and a television, taking advantage of its low power consumption, low voltage operation, light weight and thinness. With the development of liquid crystal technology, liquid crystal display devices of various modes have been proposed, and problems of liquid crystal display such as response speed, contrast, and narrow viewing angle have been solved. However, since a polarizing plate is used in a liquid crystal display device, when the liquid crystal panel is placed under a humid environment, the liquid crystal panel is warped due to absorption of water by the polarizing plate, and display irregularity occurs.

JP 2007-292966-A proposes to improve the warpage of the liquid crystal panel under high temperature and high humidity by adjusting the dimensional change rate of the polarizing plate bonded to both surfaces of the liquid crystal cell. In JP 2003-50313-A, it is proposed to improve the warp of the liquid crystal panel under a humid environment by using a polarizing plate on which a pressure-sensitive adhesive layer showing specific clip characteristics is formed. However, in these improvements, the polarizing plate needs to be subjected to a pretreatment such as a heat treatment, or the display irregularity due to warping of the liquid crystal panel after put under a humid environment is insufficient.

On the other hand, a retardation film including a three-layer structure in which a skin layer containing a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer containing a styrene resin and which provides negative intrinsic birefringence, There is also an attempt to apply them to a liquid crystal display device in combination. For example, in JP 2009-258589-A, a transparent protective film is bonded to one side of a polarizing film through an adhesive, and on the other side of the polarizing film, a pressure-sensitive adhesive layer is laminated on both surfaces of the core layer containing the styrene- Layer structure in which a skin layer containing a (meth) acrylic resin composition containing rubber particles is formed on a polarizing plate to form a composite polarizing plate, which is applied to a liquid crystal display device. In JP 2009-258589-A, the pressure-sensitive adhesive layer for bonding the three-layered retardation film to a polarizing film is formed from a high-elastic pressure-sensitive adhesive exhibiting a storage elastic modulus of at least 0.1 MPa at a temperature of 80 캜, Respectively.

An object of the present invention is to provide a liquid crystal display device in which warpage of a liquid crystal panel is small and display unevenness is small even after being placed under a moist heat environment. The present inventors firstly laminated a transparent protective film on one side of a polarizing film with an adhesive and laminating a biaxial retardation film having a positive intrinsic birefringence on the other side of the polarizing film through an adhesive, A composite polarizer comprising a three-layer structure retardation film laminated with a skin layer comprising a (meth) acrylic resin composition containing rubber particles on both surfaces of a core layer containing a styrene resin through the pressure-sensitive adhesive layer And provides an excellent viewing angle characteristic when applied to an IPS mode liquid crystal display, and has filed a patent (JP 2010-217870-A). However, the durability under a harsh environment, such as a humid environment, where a practical site is assumed, has not yet been satisfied.

As a result of further studies, it has been found that when the composite polarizer proposed in JP 2010-217870-A is disposed on the rear side of the liquid crystal cell and another polarizer is disposed on the front side (viewing side) of the liquid crystal cell, Sensitive adhesive layer for bonding the liquid crystal cell to the rear-side polarizing plate and the pressure-sensitive adhesive layer for bonding the rear-side polarizing plate to the liquid crystal cell, and the pressure-sensitive adhesive layer for bonding the biaxial retardation film and the three- Is effective in suppressing warpage of the liquid crystal panel after being placed under a humid environment and is effective in improving display unevenness. The present invention has been accomplished based on these findings.

That is, the present invention includes the following.

[1] A liquid crystal display device comprising: a liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween; a front polarizer on the viewer side of the liquid crystal cell through a first pressure sensitive adhesive layer; Side polarizing plate laminated through the pressure-sensitive adhesive layer, and a backlight unit disposed outside the rear-side polarizing plate,

The front-side polarizing plate has a polarizing film and a pair of transparent protective films disposed on both sides thereof, and is laminated on the liquid crystal cell through the first pressure-sensitive adhesive layer on the side of the one transparent protective film,

The back side polarizing plate includes a polarizing film, a first transparent protective film disposed on one side of the polarizing film, a second transparent protective film disposed on the other side of the polarizing film, And a retardation film laminated on the liquid crystal cell through the second pressure-sensitive adhesive layer on the retardation film side,

The retardation film includes a three-layer structure in which a skin layer containing a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer containing a styrene resin,

Wherein the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the third pressure-sensitive adhesive layer all have storage elastic moduli at 50 DEG C in the range of 0.01 MPa to 0.1 MPa.

[2] A liquid crystal display device as described in [1] above, wherein the transparent protective film positioned on the liquid crystal cell side of the front polarizing plate has a retardation in the thickness direction of -10 to 10 nm.

[3] The liquid crystal display device according to [1] or [2], wherein the transparent protective film positioned on the liquid crystal cell side of the front polarizing plate comprises a cellulose resin or a polyolefin resin.

[4] The liquid crystal display according to any one of [1] to [3] above, wherein the second transparent protective film constituting the back side polarizing plate, that is, the side between the polarizing film and the retardation film, , Wherein the retardation of in-plane retardation is in the range of 30 to 150 nm, and the in-plane slow axis direction, the in-plane fast axis direction, and the thickness direction when the refractive index n _x, n _y and n _z, respectively, to have a range of refractive index anisotropy of less than 2 have greater than 1 Nz coefficient defined by equation (1),

Wherein the retardation film constituting the back side polarizing plate has an in-plane retardation in the range of 20 to 120 nm and an Nz coefficient defined by the following equation (1) is in the range of more than -2 to less than -0.5.

&Quot; (1) "

_{Nz = (n x -n z)} / (n x -n y)

In addition, the in-plane slow axis direction and the in-plane fast axis direction are perpendicular to each other in the plane.

According to the present invention, since the warpage of the liquid crystal panel is small even after being placed under a humid environment, it is possible to provide a liquid crystal display device with less display unevenness.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional schematic diagram showing a layer structure of a liquid crystal display device according to the present invention. FIG.

1, a liquid crystal display device according to the present invention includes a liquid crystal cell 10, a front polarizing plate 20 laminated on the viewer side of the liquid crystal cell through a first pressure sensitive adhesive layer 41, Side polarizing plate 30 laminated via the second pressure-sensitive adhesive layer 42 on the side opposite to the liquid crystal cell 10 and a backlight unit 60 disposed on the outside of the back-side polarizing plate (i.e., on the opposite side to the liquid crystal cell 10) . A front side polarizing plate 20 laminated via a first pressure sensitive adhesive layer 41 on the visual side of the liquid crystal cell and a back side polarizing plate 20 laminated on the opposite side of the liquid crystal cell through a second pressure sensitive adhesive layer 42, And the liquid crystal panel 50 is formed of the polarizing plate 30.

The front polarizing plate 20 disposed on the viewing side of the liquid crystal cell 10 includes a polarizing film 21 and a pair of transparent protective films 22 and 23 laminated on both sides thereof with an adhesive (not shown) Lt; / RTI > The back side polarizing plate 30 disposed on the side opposite to the viewing side of the liquid crystal cell 10 (i.e., on the side of the backlight unit 60) includes a polarizing film 31, A first transparent protective film 32 laminated via an adhesive (not shown) on the other side of the polarizing film and a second transparent protective film 33 laminated via an adhesive (not shown) on the other side of the polarizing film And a retardation film 35 is laminated on the liquid crystal cell side of the second transparent protective film 33 through the third pressure sensitive adhesive layer 43. This retardation film 35 is a three-layer structure in which skin layers 37 and 37 including a (meth) acrylic resin composition containing rubber particles are formed on both surfaces of a core layer 36 containing a styrene- .

The liquid crystal panel 50 and the backlight unit 60 are combined to form a liquid crystal display device. However, when the liquid crystal display device is placed under a moist heat environment, the liquid crystal panel 50 is warped and a part of the liquid crystal panel 50 The backlight unit 60 may be brought into contact with the backlight unit 60 in an unusual manner or may be in contact with the backlight unit 60 in an extreme case. The liquid crystal panel 50 is fixed by a case or a gold frame so as not to collapse to the viewer side. When the liquid crystal display device is placed under a moist heat environment, the liquid crystal panel 50 is warped and part of the liquid crystal panel 50 Sometimes comes into contact with the case or the gold frame in which it is fixed, thereby causing display unevenness.

Therefore, in the present invention, the first pressure sensitive adhesive layer 41 for bonding the front side polarizing plate 20 to the liquid crystal cell 10, the second pressure sensitive adhesive layer 41 for bonding the rear side polarizing plate 30 to the liquid crystal cell 10, And the third pressure sensitive adhesive layer 43 for bonding the transparent protective film 33 and the retardation film 35 constituting the rear side polarizing plate 30 to each other at a storage elastic modulus G ' To less than 0.1 MPa. This relation of the first pressure-sensitive adhesive layer a storage elastic modulus at 50 ℃ G ₁ of 41 ", a second adhesive layer (42) 50 ℃ the storage elastic modulus G ₂ in the", and the third adhesive layer 43, And G < ₃ >, respectively, when the storage elastic modulus at 50 DEG C is G < ₃ >.

&Quot; (2) "

0.01 MPa < = G < ₁ &_gt;

&Quot; (3) "

0.01 MPa? G ₂ '? 0.1 MPa

&Quot; (4) "

0.01 MPa? G ₃ '? 0.1 MPa

Hereinafter, each member constituting the liquid crystal display device of the present invention will be described in detail with reference to the reference numerals attached to Fig.

[Liquid crystal cell]

The liquid crystal cell 10 has two cell substrates 11 and 12 and a liquid crystal layer 15 sandwiched between these substrates. Although the cell substrates 11 and 12 are generally made of glass, they may be plastic substrates. In addition, the liquid crystal cell 10 itself in the liquid crystal display device of the present invention can be composed of various ones used in this field.

[Polarizing Film]

The polarizing films 21 and 31 constituting the front-side polarizing plate 20 and the back-face-side polarizing plate 30 are usually formed by a process of uniaxially stretching a polyvinyl alcohol-based resin film, a step of stretching a polyvinyl alcohol- A step of adsorbing the dichroic dye by dyeing, a step of treating the polyvinyl alcohol-based resin film adsorbed with the dichroic dye with an aqueous solution of boric acid, and a step of washing with water after treatment with an aqueous solution of boric acid.

The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehyde may be used. The polymerization degree of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, and preferably about 1,500 to 5,000.

Such a polyvinyl alcohol-based resin is used as an original film of a polarizing film. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. The film thickness of the polyvinyl alcohol-based resin original film is, for example, about 10 to 150 mu m, preferably about 10 to 100 mu m.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. In the case of uniaxial stretching after dyeing, the uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. Of course, uniaxial stretching may be performed at a plurality of steps shown here. As the uniaxial stretching, there can be used a method of uniaxially stretching between rolls having different circumferential speeds, a method of uniaxially stretching using a heat roll, or the like. The uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or by wet stretching in which the polyvinyl alcohol based resin film is stretched by using a solvent such as water. The stretching magnification is usually about 3 to 8 times.

The dyeing by the dichroic dye of the polyvinyl alcohol-based resin film can be performed by, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. Specific examples of the dichroic dye include iodine and dichromatic organic dyes. It is also preferable that the polyvinyl alcohol-based resin film is subjected to a treatment in which it is immersed in water and subjected to swelling before dyeing.

When iodine is used as the dichroism dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally used.

The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 占 폚. The immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually used. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The dye aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dichroic organic dye aqueous solution used for dyeing is usually about 20 to 80 캜. The immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be carried out by dipping the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The content of boric acid in the aqueous solution containing boric acid is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The immersing time in the aqueous solution containing boric acid is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C, and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 占 폚. The immersion time is usually about 1 to 120 seconds.

After washing with water, drying treatment is carried out to obtain a polarizing film. The drying treatment can be performed using a hot-air dryer or a far-infrared heater. The temperature of the drying treatment is usually about 30 to 100 占 폚, preferably 50 to 80 占 폚. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the water content in the polarizing film is reduced to a practical degree. The water content thereof is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost and may be damaged or broken after drying. If the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

As described above, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced. The thickness of the obtained polarizing film may be, for example, about 5 to 40 탆.

[Transparent protective film located on the side far from the liquid crystal cell]

The transparent protective films 22 and 32 located on the side farther from the liquid crystal cell 10 in the front side polarizing plate 20 and the back side polarizing plate 30 are made of a material excellent in transparency, mechanical strength, thermal stability, . As such a material, for example, an acrylic resin typified by methyl methacrylate resin, a chain polyolefin resin typified by polypropylene resin, a cyclic polyolefin resin, a cellulose resin, a polyethylene terephthalate resin, Polybutylene terephthalate resin, polyvinyl chloride resin, styrene resin, acrylonitrile-styrene copolymer resin, acrylonitrile-butadiene styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin , Polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polysulfone resins, polyether sulfone resins, polyarylate resins, polyamideimide resins, polyimide resins Based resins and the like.

These resins may be used alone or in combination of two or more.

A resin obtained by subjecting any of these polymers to polymer modification may be used as a material for a transparent protective film. Examples of polymer modification include copolymerization, crosslinking, molecular end modification, stereoregularity control, mixing involving reactions between different polymers, and the like.

Among these resins, a methacrylate-based resin, a polypropylene-based resin, a cellulose-based resin, or a polyethylene terephthalate-based resin is preferably used as the material of the transparent protective films 22 and 32 located farther from the liquid crystal cell 10 do.

The methyl methacrylate resin is a polymer containing 50% by weight or more of methyl methacrylate units. The content of the methyl methacrylate unit is preferably 70% by weight or more, and may be 100% by weight. The polymer having a methyl methacrylate unit of 100% by weight is obtained by polymerizing methyl methacrylate alone.

The methyl methacrylate resin can be usually obtained by polymerizing a monofunctional monomer having methyl methacrylate as a main component under the coexistence of a radical polymerization initiator and a chain transfer agent. In some cases, a monofunctional monomer is copolymerized with a component copolymerizable with methyl methacrylate. In some cases, a small amount of a polyfunctional monomer is copolymerized depending on the purpose.

Examples of monofunctional monomers that can be copolymerized with methyl methacrylate include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate Methacrylic acid esters other than methyl methacrylate such as 2-hydroxyethyl methacrylate; Acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate and 2-ethylhexyl acrylate; Acrylic acid hydroxyalkyl esters such as hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Substituted styrenes such as vinyltoluene and? -Methylstyrene; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; And unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. Each of these monomers may be used alone or in combination with one or more other monomers.

Examples of the polyfunctional monomer copolymerizable with methyl methacrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (Meth) acrylate and the like, or both terminal hydroxyl groups of an oligomer thereof are esterified with acrylic acid or methacrylic acid; Esterification of both terminal hydroxyl groups of propylene glycol or its oligomer with acrylic acid or methacrylic acid; Those obtained by esterifying a hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate or butanediol di (meth) acrylate with acrylic acid or methacrylic acid; Bisphenol A, an alkylene oxide adduct of bisphenol A, or both terminal hydroxyl groups of halogen substituents thereof esterified with acrylic acid or methacrylic acid; Trimethylol propane, pentaerythritol, etc., esterified with acrylic acid or methacrylic acid; An epoxy group of glycidyl acrylate or glycidyl methacrylate is added to a terminal hydroxyl group of a compound having two or more hydroxyl groups; A dibasic acid such as succinic acid, adipic acid, terephthalic acid, phthalic acid or a halogen substituent thereof, or an alkylene oxide adduct of these with ring-opening epoxy groups of glycidyl acrylate or glycidyl methacrylate; Allyl (meth) acrylate; And aromatic divinyl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used when copolymerizing a polyfunctional monomer.

It is also possible to use a modified resin obtained by reacting the methacrylic acid-based resin with a functional group. Examples of the reaction of such a functional period include a condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of 2- (hydroxymethyl) acrylate, a condensation reaction between a carboxyl group of acrylic acid and methyl 2- (hydroxymethyl) And a dehydration condensation reaction in a polymer chain with a hydroxyl group.

Commercially available methyl methacrylate resins can be easily obtained. Examples of commercially available products include "Sumipex" sold under the trade name of Sumitomo Chemical Co., Ltd., "Acrifet" sold by Mitsubishi Rayon Co., Ltd., "Sumitomo" sold by Asahi Kasei Co., Delpet "," Parafet "sold by Kuraray Co., Ltd., and" Arc Review "sold by Nihon Shokubai Co., Ltd.

The polypropylene resin is a polymer of a chain olefin monomer containing propylene as a main component, and is usually a chain olefin resin in which at least 80% by weight of the repeating units are composed of propylene. The polypropylene resin may be a homopolymer of propylene, or may be a copolymer obtained by copolymerizing propylene with a comonomer copolymerizable therewith in an amount of 1 to 20% by weight, preferably 3 to 10% by weight.

When a copolymer containing propylene as a main component is used, ethylene, 1-butene and 1-hexene are preferable as comonomers copolymerizable with propylene. Among them, a polypropylene resin having a comparatively excellent transparency can be obtained, and therefore it is preferable that ethylene is copolymerized in an amount of 1 to 20% by weight, preferably 3 to 10% by weight. When the copolymerization ratio of ethylene is 1% by weight or more, transparency is enhanced. On the other hand, when the copolymerization ratio of ethylene exceeds 20% by weight, the melting point of the resin is lowered, and the heat resistance required for the transparent protective film may be impaired.

The content of the component soluble in xylene at 20 캜 (abbreviation of CXS component: CXS component: cold xylene soluble) is preferably 1% by weight or less, more preferably 0.5% by weight or less. Among the polypropylene-based resins, a homopolymer of propylene having a CXS component of 1% by weight or less, more preferably 0.5% by weight or less is one of preferred examples.

A polypropylene resin can be easily obtained from commercial products. Examples of commercially available products include "Prime Polypro" sold by Prime Polymer Co., Ltd., "Novatec" and "Wintech" sold by Nippon Polypro Corporation, Sumitomo Chemical Co., And "Sun aroma" sold by Sun Aroma Co., Ltd., and so on.

The cellulose resin may be an organic acid ester or a mixed organic acid ester of cellulose in which some or all of the hydrogen atoms in the hydroxyl group of the cellulose are substituted with an acetyl group, a propionyl group and / or a butyryl group. Examples thereof include acetate esters of cellulose, propionic acid esters, butyric acid esters, and mixed esters thereof. Among them, triacetylcellulose, diacetylcellulose, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

The polyethylene terephthalate resin is a resin in which 80 mol% or more of the repeating units are composed of ethylene terephthalate, and may contain other dicarboxylic acid component and / or other diol component. Examples of other dicarboxylic acid components include isophthalic acid, 4,4'-dicarboxy diphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, 1,4-dicarboxycyclohexane, and the like. Examples of other diol components include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. .

These other dicarboxylic acid components and other diol components may be used in combination of two or more as necessary. Hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-beta-hydroxyethoxybenzoic acid may be used in combination. As other copolymerization components, a dicarboxylic acid component or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may also be used.

Examples of the method for producing the polyethylene terephthalate resin include a method of directly polycondensing terephthalic acid and ethylene glycol (and other dicarboxylic acids or other diols as necessary), a method of directly polycondensing a dialkyl ester of terephthalic acid and ethylene glycol (And optionally other diol esters) of terephthalic acid (and optionally other dicarboxylic acids) in the presence of a catalyst in the presence of a catalyst And the like are used. In addition, if necessary, further solid phase polymerization may be carried out to increase the molecular weight or decrease the low molecular weight component.

In the method of forming the above-mentioned resin on the transparent protective film for the polarizing plate, the method according to each resin can be appropriately selected. For example, there are a solvent casting method in which a resin dissolved in a solvent is cast in a metal band or a drum and dried to remove the solvent, a method in which the resin is heated and kneaded at a temperature not lower than its melting temperature, A melt extrusion method for obtaining a film, or the like can be used. In the melt extrusion method, a single layer film may be extruded, or a multilayer film may be simultaneously extruded.

A commercially available product of these resins can be easily obtained. Examples of commercially available films include "Techolloi" sold under the trade name of Sumitomo Chemical Co., Ltd., "Acrylite" sold by Mitsubishi Rayon Co., Ltd. under the trade names of methyl methacrylate resin film, And "Acryprene" sold by Asahi Kasei Co., Ltd., "Terra Grass" sold by Asahi Kasei Co., Ltd., "Paragraph" and "Comogras" sold by Kuraray Co., And "Arc Review". In the case of the polyethylene terephthalate-based resin film, there are "Nova Clear" sold by Mitsubishi Chemical Corporation under the trade name, and "A-PET sheet" sold by Deijin Kasei Co., In the case of the polypropylene type resin film, "PILMAX CPP film" sold by FILMAX Co., Ltd., "SUNTOX" sold by Suntox Co., Ltd., and TOCELLO Co., Ltd. are sold Which is sold from Toyobo Co., Ltd., which is sold by Tohcello Co., Ltd., Toyobo Pyrene Film, which is sold by Toyo Boseki Co., Ltd., and Treffan sold by Toray Film Co., Nippon Poly Ace ", and" Daiko FC "sold by Fujimura Kagaku Co., Ltd., and the like. Further, in the case of the cellulose-based resin film, "Fujikata TD" sold by Fuji Film Co., Ltd. and "Konica Minolta TAC Film KC" sold by Konica Minolta Opt Co., Ltd. are available.

It is possible to impart haze to the transparent protective film 22 disposed on the side far from the liquid crystal cell 10 and serving as a viewer side to exhibit anti-glare properties. Examples of the method for imparting haze include a method in which inorganic fine particles or organic fine particles are mixed into a raw material resin constituting a transparent protective film to form a film, and a method in which a resin mixed with fine particles and a resin Layer film, or a three-layer film made of a resin mixed with fine particles as an outer layer; a method of coating a coating liquid formed by mixing inorganic fine particles or organic fine particles with a curable binder resin on one side of the film, A method of installing a layer is used.

Examples of the inorganic fine particles used for imparting haze include silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, . Examples of the organic fine particles include crosslinked polyacrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicone resin particles and polyimide particles.

When haze is given to the transparent protective film, it is preferable that the haze value is in the range of 6 to 45%. If the haze value of the transparent protective film is less than 6%, a sufficient antiglare effect may not be exhibited. On the other hand, if the haze value exceeds 45%, the screen of the liquid crystal display device on which the transparent protective film is disposed may become cloudy, resulting in deterioration of image quality. Haze is a value defined as a ratio of diffusion transmittance to total light transmittance, and can be measured using a haze meter available in accordance with JIS K 7136. As a commercially available haze meter, for example, there is "HM-150 ", etc., which is commercially available from Mitsubishi Chemical Corporation. In the measurement of the haze value, it is preferable to use a measurement sample in which the film surface is bonded to the glass substrate so that the antiglare surface becomes the surface, for example, by using an optically transparent pressure-sensitive adhesive in order to prevent the film from warping.

A functional layer including a conductive layer, a hard coating layer, a low reflective layer, and the like is formed on the outer side of each of the transparent protective film 22 that is disposed on the viewer side and the transparent protective film 32 that is disposed on the side remote from the liquid crystal cell, Can be installed. As the coating liquid containing the binder resin constituting the antiglare layer, a resin composition capable of exhibiting such function may be selected.

[Transparent protective film positioned on the liquid crystal cell side]

The resin constituting the transparent protective films 23 and 33 located on the side closer to the liquid crystal cell 10 from the polarizing films 21 and 31 in the front side polarizing plate 20 and the back side polarizing plate 30 shown in Fig. As the material, the same materials as those described for the transparent protective films 22 and 32 located on the side far from the liquid crystal cell 10 can be used. Of these, a polyolefin-based resin including a cellulose resin or a chain polyolefin resin or a cyclic polyolefin resin is preferably used because it is easy to control the retardation value and is easily available.

The cyclic polyolefin-based resin referred to herein is obtained by polymerizing an alicyclic olefin such as norbornene or another cyclopentadiene derivative (sometimes referred to as "norbornene monomer") in the presence of a catalyst. When such a cyclic polyolefin-based resin is used, a transparent protective film having a predetermined retardation value described later tends to be easily obtained. Norbornene is a compound in which one carbon-carbon bond of a norbornane is a double bond, and is named bicyclo [2,2,1] hept-2-ene according to the IUPAC nomenclature. Examples of the norbornene derivatives include 3-substituted, 4-substituted, and 4, 5-di-substituted with the double bond position of the norbornene at the 1,2-position. Further, dicyclopentadiene or dimethanooctahydronaphthalene may be used as a monomer constituting the cyclic polyolefin-based resin.

The cyclic polyolefin-based resin may or may not have a norbornane ring in its constituent unit. Examples of the norbornene monomer forming the cyclic polyolefin-based resin having no norbornane ring in the constituent unit include ring-opening 5-membered rings, typically norbornene, dicyclopentadiene, 1- or 4 -Methylnorbornene, 4-phenylnorbornene, and the like. When the cyclic polyolefin-based resin is a copolymer, the arrangement of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer.

As the cyclic polyolefin-based resin, for example, ring-opening metathesis polymerization is carried out using cyclopentadiene and olefins or norbornene or a derivative thereof obtained by the Diels-Alder reaction from (meth) acrylic acid or its esters as monomers, A resin obtained by the addition; A resin obtained by performing ring-opening metathesis polymerization of dicyclopentadiene and tetracyclododecene or a derivative thereof obtained by the Diels-Alder reaction from olefins or (meth) acrylic acid or its esters as monomers, followed by hydrogenation; Norbornene, tetracyclododecene, derivatives thereof, and cyclic olefin monomers are subjected to ring-opening metathesis polymerization in the same manner as described above, followed by hydrogenation; And resins obtained by addition-copolymerizing a cyclic olefin such as norbornene, tetracyclododecene, or a derivative thereof with an aromatic compound having a chain olefin and / or vinyl group.

The cyclic polyolefin-based resin can easily obtain a commercially available product. Examples of commercially available products are sold by TOPAS ADVANCED POLYMERS GmbH under the trade name of "TOPAS" sold by Polyplastics Co., Ltd. and JSR Co., Ltd. under the trade name of TOPAS ADVANCED POLYMERS GmbH "Zeonor" and "Zeonex" sold by Nippon Zeon Co., Ltd. and "Arpel" sold by Mitsui Chemicals, Inc. are available. Films of these cyclic polyolefin resins and stretched films thereof are also commercially available, and examples thereof include "Zeonor film" sold by Nippon Zeon Co., Ltd., "Aton film" sold by JSR Corporation, And "Essener" sold by Sekisui Chemical Co., Ltd.

Typical examples of the chain polyolefin-based resin are a polyethylene-based resin and a polypropylene-based resin. Among them, preferred is a homopolymer of propylene or a copolymer mainly composed of propylene copolymerized with a comonomer copolymerizable therewith, for example, ethylene at a ratio of 1 to 20% by weight, preferably 3 to 10% by weight do.

In a method of forming a film on a film from a cellulose-based resin, a polyolefin-based resin or the like, a method depending on each resin can be appropriately selected. For example, there are a solvent casting method in which a resin dissolved in a solvent is cast in a metal band or a drum and the solvent is dried to remove the film to obtain a film, a method in which the resin is heated to a temperature not lower than its melting temperature and kneaded and extruded from the die, A melt extrusion method for obtaining a film can be used. Among them, a melt extrusion method is preferably used for the polyolefin-based resin from the viewpoint of productivity. On the other hand, the cellulose based resin is generally formed by a solvent casting method.

The liquid crystal cell 10 of the front-side polarizing plate 20 can be prevented from deteriorating when the liquid crystal cell 10 is in the in-plane switching (IPS) mode, It is preferable that the thickness direction retardation Rth of the transparent protective film 23 located on the side of the transparent protective film 23 is in the range of -10 to 10 nm. The thickness direction retardation Rth is a value obtained by multiplying the value obtained by subtracting the refractive index in the thickness direction from the average refractive index in the plane multiplied by the thickness of the film, and is expressed by the following equation (5). The in-plane retardation Re is a value obtained by multiplying the refractive index difference in the plane by the thickness of the film, and is represented by the following equation (6). From these relationships, the Nz coefficient defined by Equation (1) may be expressed by Equation (7).

Equation (5)

Rth = _{[(n x + n y / 2} -n z × d]

&Quot; (6) "

_{Re = (n x -n y)} × d

&Quot; (7) "

Nz = Rth / Re + 0.5

(Where n _x , n _y and n _z are as defined above, n _x is the refractive index in the in-plane slow axis direction, n _y is the refractive index in the in-plane fast axis direction (direction perpendicular to the slow axis in the plane) n _z is the refractive index in the thickness direction, and d is the thickness of the film)

Here, the retardation value may be a value at an arbitrary wavelength in the range of about 500 to 650 nm near the center of visible light, but in this specification, the retardation value at a wavelength of 590 nm is standard. The thickness direction retardation Rth and the in-plane retardation Re can be measured using various commercially available retardation systems.

As a method for controlling the retardation Rth in the thickness direction of the resin film within the range of -10 to 10 nm, there is a method of minimizing the distortion remaining in the thickness direction when the film is produced. For example, in the above-mentioned solvent casting method, a method of relaxing residual shrinkage distortion in the thickness direction, which occurs when the flexible resin solution is dried, by heat treatment, or the like can be used. On the other hand, in the melt extrusion method described above, the distance from the die to the cooling drum is minimized in order to prevent the resin film from being stretched between the extrusion and the cooling of the die, and at the same time, And a method of controlling the speed so that the film is not stretched can be used. Also, in the same manner as in the solvent casting method, a method of relaxing the residual strain in the obtained film by heat treatment can also be used.

[Transparent protective film (33) positioned on the liquid crystal cell side from the polarizing film of the back side polarizing plate]

The transparent protective film 33 located on the side closer to the liquid crystal cell 10 from the polarizing film 31 in the back side polarizing plate 30 used in the present invention preferably includes a polyolefin resin.

Here, the polyolefin resin is a resin containing a constituent unit derived from an olefin such as a chain olefin such as ethylene or propylene, or an alicyclic olefin such as norbornene or other cyclopentadiene derivatives as described above. The polyolefin-based resin may be a copolymer using two or more kinds of monomers. As for the cyclic polyolefin-based resin and the chain-like polyolefin-based resin which are examples of the polyolefin-based resin, the same explanation as that in the above [transparent protective film located on the liquid crystal cell side] is applied. Among them, as the polyolefin-based resin, a cyclic polyolefin-based resin, which is a resin mainly containing a constituent unit derived from an alicyclic olefin, is preferably used.

As the transparent protective film 33, a film containing a mixed resin containing at least two polyolefin resins or a film containing a mixed resin of a polyolefin resin and another thermoplastic resin may be used. For example, as the mixed resin containing two or more kinds of polyolefin resins, a mixture of the cyclic polyolefin resin and the chain polyolefin resin as described above can be mentioned. When a mixed resin of a polyolefin resin and another thermoplastic resin is used, the other thermoplastic resin is appropriately selected depending on the purpose. Specific examples include polyvinyl chloride resins, cellulose resins, polystyrene resins, acrylonitrile / butadiene / styrene copolymer resins, acrylonitrile / styrene copolymer resins, (meth) acrylic resins, polyvinyl acetate resins, Based resin, a polycarbonate-based resin, a modified polyphenylene ether-based resin, a polybutylene terephthalate-based resin, a polyethylene terephthalate-based resin, a polyphenylene sulfide-based resin, a poly A polyether ether ketone resin, a polyarylate resin, a liquid crystal resin, a polyamideimide resin, a polyimide resin, and a polytetrafluoroethylene resin. These thermoplastic resins may be used alone or in combination of two or more.

When a mixed resin of a polyolefin resin and another thermoplastic resin is used, the content of the other thermoplastic resin is usually about 50% by weight or less, preferably about 40% by weight or less based on the whole resin. When the content of other thermoplastic resin is within this range, a film having a small absolute value of photoelastic coefficient, exhibiting good wavelength dispersion characteristics, and excellent durability, mechanical strength and transparency can be obtained.

The film containing the polyolefin resin may contain other components such as a residual solvent, a stabilizer, a plasticizer, an antioxidant, an antistatic agent, an ultraviolet absorber and the like as needed within a range not impairing the object of the present invention. In addition, a leveling agent may be contained in order to reduce the surface roughness.

The transparent protective film 33 constituting the back-surface-side polarizing plate 30 includes the above-mentioned polyolefin-based resin, its in-plane retardation Re is in the range of 30 to 150 nm, and the Nz It is preferable that the refractive index anisotropy is in the range of more than 1 and less than 2. The refractive index anisotropy in which the Nz coefficient is in the range of more than 1 and less than 2 means that the following formula (8) is satisfied.

&Quot; (8) "

_{1 <(n x -n z)} / (n x -n y) <2

The polyolefin-based resin film having the refractive index anisotropy as described above can be obtained by known all-axis stretching, transverse direction uniaxial stretching in the tenter, simultaneous biaxial stretching, sequential biaxial stretching, or the like. In order to obtain a desired retardation value, It is possible not only to appropriately adjust the stretching speed but also to appropriately select various temperatures such as the preheating temperature at the time of stretching, the stretching temperature, the heat setting temperature, the cooling temperature, and the like.

The stretched polyolefin-based resin film used as the transparent protective film 33 preferably has a thickness in the range of 20 to 80 mu m, more preferably 40 to 80 mu m. When the thickness of the film is less than 20 탆, handling of the film is difficult, and a predetermined retardation value tends to be difficult to develop. On the other hand, when the thickness exceeds 80 탆, the workability is deteriorated, The weight of the polarizing plate may be increased.

[Bonding of Polarizing Film and Protective Film]

The polarizing film 21 and the transparent protective films 22 and 23 are bonded to each other at the front polarizing plate 20 and the polarizing film 31 and the transparent protective films 32 and 33 are bonded to each other at the rear polarizing plate 30 Adhesives are usually used. The thickness of the adhesive layer for bonding the polarizing film and the transparent protective film may be about 0.01 to 30 mu m, preferably 0.01 to 10 mu m, more preferably 0.03 to 5 mu m. When the thickness of the adhesive layer is in this range, no peeling or peeling occurs between the transparent protective film and the polarizing film to be laminated, and an adhesive force with no practical problem is obtained.

For forming the adhesive layer, an appropriate adhesive may be appropriately used depending on the kind and purpose of the adherend, and an anchor coating agent may be used if necessary. Examples of the adhesive include a solvent type adhesive, an emulsion type adhesive, a pressure-sensitive adhesive, a re-wetting adhesive, a polycondensation adhesive, a solventless adhesive, a film-type adhesive and a hot-melt type adhesive.

As one of preferred adhesives, an aqueous adhesive, that is, an adhesive component is dissolved or dispersed in water. Examples of the water-soluble adhesive component include a polyvinyl alcohol-based resin. Examples of the adhesive component dispersible in water include urethane-based resins having a hydrophilic group. The waterborne adhesives can be prepared by mixing these adhesive components with water, together with further additives that are optionally blended. Examples of a commercially available polyvinyl alcohol-based resin that can be an aqueous adhesive include "KL-318" (trade name) which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co.,

The water-based adhesive may contain a crosslinking agent if necessary. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts and the like. When a polyvinyl alcohol resin is used as an adhesive component, an aldehyde compound including glyoxal, a methylol compound including methylolmelamine, a water-soluble epoxy resin and the like are preferably used as a crosslinking agent.

Here, the water-soluble epoxy resin can be obtained, for example, by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylene triamine or triethylene tetramine with a dicarboxylic acid such as adipic acid, Amide epoxy resin. Examples of commercially available water-soluble epoxy resins include "Sumirez Resin 650 (30)" (trade name) sold by Sumika-Chemtech Co., Ltd.

The polarizing plate can be obtained by applying an aqueous adhesive to the bonding surface of the polarizing film and / or the transparent protective film, bonding them together, and then performing a drying treatment. Prior to adhesion, it is also effective to increase the wettability of the transparent protective film by subjecting the transparent protective film to easy adhesion treatment such as saponification treatment, corona discharge treatment or plasma treatment. The drying temperature may be, for example, about 60 to 100 占 폚. After the drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 占 폚 for about 1 to 10 days is preferable in further increasing the adhesive force.

Another preferable adhesive is a curable adhesive composition containing an epoxy compound which is cured by irradiation with an active energy ray or by heating. The curable epoxy compound has at least two epoxy groups in the molecule. In this case, the polarizing film and the transparent protective film can be adhered to each other by irradiating or heating the coating layer of the adhesive composition with an active energy ray to cure the curable epoxy compound contained in the adhesive. The curing of the epoxy compound is generally carried out by cationic polymerization of the epoxy compound. From the viewpoint of productivity, this curing is preferably carried out by irradiation of active energy rays.

From the viewpoints of weatherability, refractive index, cationic polymerizability, etc., it is preferable that the epoxy compound contained in the curable adhesive composition does not contain an aromatic ring in the molecule. Examples of the epoxy compound that does not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, aliphatic epoxy compounds, and the like. The epoxy compound preferably used in such a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline thereof will also be described here.

The hydrogenated epoxy compound may be a product obtained by glycidyl etherating a nuclear hydrogenated polyhydroxy compound obtained by subjecting an aromatic polyhydroxy compound as a raw material of an aromatic epoxy compound to a nuclear hydrogenation reaction selectively in the presence of a catalyst and under pressure . Examples of the aromatic polyhydroxy compound as a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F and bisphenol S; Novolak type resins such as phenol novolak resin, cresol novolak resin and hydroxybenzaldehyde phenol novolak resin; And multifunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. The glycidyl etherification can be carried out by subjecting the aromatic polyhydroxy compound to a nuclear hydrogenation reaction and then reacting the resultant nucleus-hydrogenated polyhydroxy compound with epichlorohydrin. As preferred hydrogenated epoxy compounds, glycidyl ethers of hydrogenated bisphenol A can be mentioned.

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

A compound in which one or more hydrogen atoms in (CH ₂ ) _m in this formula are bonded to other chemical structures may be an alicyclic epoxy compound. Further, one or a plurality of hydrogen atoms in (CH ₂ ) _m forming an alicyclic ring may be appropriately substituted with a straight chain alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m = 3 in the above formula) or oxabicycloheptane ring (m = 4 in the above formula) is preferable because it exhibits excellent adhesiveness Lt; / RTI &gt; Specific examples of the alicyclic epoxy compound are given below. Here, the name of the compound is first given, and then the corresponding formula is shown, and the compound name and the corresponding formula are given the same reference numerals.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-

B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,

C: Ethylene bis (3,4-epoxycyclohexanecarboxylate),

D: bis (3,4-epoxycyclohexylmethyl) adipate,

E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,

F: diethylene glycol bis (3,4-epoxycyclohexylmethyl ether),

G: Ethylene glycol bis (3,4-epoxycyclohexylmethyl ether)

H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispyro [5.2.2.5.2.2] heneic acid,

I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,

J: 4-vinylcyclohexene dioxide,

K: limonene dioxide,

L: bis (2,3-epoxycyclopentyl) ether,

M: dicyclopentadiene dioxide and the like.

The aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; Diglycidyl ether of 1,4-butanediol; Diglycidyl ether of 1,6-hexanediol; Triglycidyl ether of glycerin; Triglycidyl ether of trimethylolpropane; A polyglycidyl ether of a polyether polyol (for example, a diglycidyl ether of polyethylene glycol) obtained by adding an alkylene oxide (ethylene oxide or propylene oxide) to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol or glycerin, And the like.

In the curable adhesive composition, only one epoxy compound may be used alone, or two or more epoxy compounds may be used in combination. Among these, the epoxy compound preferably contains an alicyclic epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.

The epoxy compound used in the curable adhesive composition usually has an epoxy equivalent in the range of 30 to 3,000 g / equivalent, and the epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent. When an epoxy compound having an epoxy equivalent of less than 30 g / equivalent is used, there is a possibility that the flexibility of the polarizing plate after curing is lowered or the adhesive strength is lowered. On the other hand, in a compound having an epoxy equivalent of more than 3,000 g / equivalent, the compatibility with other components contained in the adhesive composition may be lowered.

From the viewpoint of reactivity, cationic polymerization is preferably used as a curing reaction of an epoxy compound. For this purpose, it is preferable to incorporate a cationic polymerization initiator into the curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating of an active energy ray such as visible light, ultraviolet ray, X-ray and electron beam, and initiates polymerization reaction of the epoxy group. From the viewpoint of workability, it is preferable that the cationic polymerization initiator is given a potential. Hereinafter, a cationic polymerization initiator for generating a cationic species or a Lewis acid by irradiation of an active energy ray and initiating a polymerization reaction of an epoxy group is referred to as a "photo cationic polymerization initiator ", and a cationic species or a Lewis acid is generated by heat, The cationic polymerization initiator for initiating the polymerization reaction is referred to as "thermal cationic polymerization initiator ".

The method of curing the adhesive composition by irradiation of an active energy ray using a photo cationic polymerization initiator enables curing at room temperature and reduces the necessity of considering the heat resistance or distortion caused by expansion of the polarizing film, It is advantageous in that the polarizing film can be favorably adhered. The photo cationic polymerization initiator acts catalytically in light, so that it is excellent in storage stability and workability even when mixed with an epoxy compound.

Examples of the photo cationic polymerization initiator include aromatic diazonium salts; Onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-arene complexes. The compounding amount of the photo cationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, more preferably 15 parts by weight or less, based on 100 parts by weight of the epoxy compound.

If the blending amount of the photo cationic polymerization initiator is less than 0.5 part by weight based on 100 parts by weight of the epoxy compound, the curing becomes insufficient and the mechanical strength and the adhesive strength of the cured product tend to be lowered.

On the other hand, if the blending amount of the photo cationic polymerization initiator exceeds 20 parts by weight based on 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, thereby increasing the hygroscopic property of the cured product and possibly lowering the durability.

When a photo cationic polymerization initiator is used, the curable adhesive composition may further contain a photosensitizer, if necessary. The use of a photosensitizer improves the reactivity of the cationic polymerization and improves the mechanical strength and adhesive strength of the cured product. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfate, an oxidation-reduction compound, an azo compound, a diazo compound, a halogen compound, a light reducing pigment and the like. When the photosensitizer is blended, the amount is preferably within a range of 0.1 to 20 parts by weight based on 100 parts by weight of the curable adhesive composition.

Examples of the thermal cationic polymerization initiator include benzylsulfonium salts, thiophenium salts, thiolium salts, benzylammonium salts, pyridinium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters and amine imides.

The curable adhesive composition containing an epoxy compound is preferably cured by photo cationic polymerization as described above, but may be cured by thermal cationic polymerization in the presence of the thermal cationic polymerization initiator described above. Alternatively, photo cationic polymerization and thermal cationic polymerization May be used in combination. When the photo cationic polymerization and the thermal cationic polymerization are used in combination, it is preferable that both of the photo cationic polymerization initiator and the thermal cationic polymerization initiator are contained in the curable adhesive composition.

In addition, the curable adhesive composition may further contain a compound that promotes cationic polymerization such as an oxetane compound or a polyol compound. The oxetane compound is a compound having a 4-membered ring ether in the molecule. When the oxetane compound is compounded, the amount thereof is usually 5 to 95% by weight, preferably 5 to 50% by weight in the curable adhesive composition. The polyol compound may be an alkylene glycol or oligomer thereof, such as ethylene glycol, hexamethylene glycol, polyethylene glycol, etc., polyester polyol, polycaprolactone polyol, polycarbonate polyol and the like. When the polyol compound is compounded, the amount thereof is usually 50% by weight or less, preferably 30% by weight or less, in the curable adhesive composition.

The curable adhesive composition may contain other additives such as an ion trap agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, a defoaming agent, etc. &Lt; / RTI &gt; Examples of the ion trap agent include inorganic compounds including a powdery bismuth system, antimony system, magnesium system, aluminum system, calcium system, titanium system, and mixtures thereof. Examples of the antioxidant include, And hindered phenol-based antioxidants.

The curable adhesive composition containing an epoxy compound is coated on the adhesive surface of the polarizing film or the transparent protective film or both of the adhesive surfaces thereof and then bonded on the surface coated with the adhesive and irradiated with an active energy ray or heated to be uncured The polarizing film and the transparent protective film can be adhered to each other. As a coating method of the adhesive, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

This curable adhesive composition can basically be used as a solvent-free adhesive agent substantially not containing a solvent. However, since each coating method has an optimum viscosity range, a solvent may be added for viscosity adjustment. The solvent is preferably an organic solvent that dissolves each component including the epoxy compound well without lowering the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, esters typified by ethyl acetate, and the like are used .

When the adhesive composition is cured by irradiation of an active energy ray, various kinds of the above-mentioned active energy rays can be used, but ultraviolet rays are preferably used since they are easy to handle and easily control the amount of irradiation light. The irradiation intensity or irradiation amount of the active energy ray, for example, ultraviolet rays is preferably adjusted so that a suitable productivity is maintained within a range that does not affect various optical performances including the polarization degree of the polarizing film and various optical performances including transparency and retardation characteristics of the transparent protective film Is appropriately determined.

When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, the thermal cationic polymerization initiator compounded in the curable adhesive composition is heated at a temperature not lower than a temperature at which cation species or Lewis acid is generated, and the specific heating temperature is, for example, about 50 to 200 ° C.

[Phase difference film]

The retardation film 35 disposed on the liquid crystal cell 10 side of the back side polarizing plate 30 has a structure in which the core layer 36 contains a styrene resin and a (meth) acrylic resin composition containing rubber particles on both surfaces thereof The skin layers 37 and 37 are formed.

The styrene-based resin constituting the core layer 36 may be a homopolymer of styrene or a derivative thereof, or may be a binary or a copolymer of styrene or a derivative thereof and another copolymerizable monomer. Here, the styrene derivative is a compound in which other groups are bonded to styrene, and examples thereof include alkyls such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, Substituted styrenes into which benzene nuclei of styrene such as styrene, hydroxystyrene, tert-butoxystyrene, vinylbenzoic acid, o-chlorostyrene, p-chlorostyrene and the like have been introduced with groups such as hydroxyl groups, alkoxy groups, carboxyl groups, . JP 2003-50316-A or JP 2003-207640-A may also be used. The styrene resin is preferably a copolymer of styrene or a styrene derivative with at least one monomer selected from acrylonitrile, maleic anhydride, methyl methacrylate and butadiene. The styrene resin constituting the core layer 36 is preferably heat-resistant, and its glass transition temperature (hereinafter referred to as "Tg") is generally 100 ° C or higher. The more preferable Tg of the styrene type resin is 120 DEG C or more.

The thickness of the core layer 36 including the styrene-based resin is preferably set to be 10 to 100 mu m. When the thickness is less than 10 mu m, a sufficient retardation value may not be easily developed by stretching. On the other hand, when the thickness exceeds 100 탆, the impact strength of the film tends to be weak, and the change in retardation due to external stress tends to increase. When applied to a liquid crystal display device, white fall off easily occurs, The display performance tends to be deteriorated.

The skin layers 37 and 37 disposed on both surfaces of the core layer 36 containing the styrene resin include a (meth) acrylic resin composition in which rubber particles are blended with a (meth) acrylic resin. Examples of the (meth) acrylic resin include a homopolymer of an alkyl methacrylate or an alkyl acrylate, a copolymer of an alkyl methacrylate and an alkyl acrylate, and the like. Specific examples of the methacrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate and propyl methacrylate. Specific examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate and propyl acrylate. As such (meth) acrylic resins, those commercially available as general-purpose (meth) acrylic resins can be used. Examples of the (meth) acrylic resin include those referred to as impact resistant (meth) acrylic resins, and those referred to as high heat resistant (meth) acrylic resins having a glutaric anhydride structure or a lactone ring structure in the main chain.

The rubber particles to be blended in the (meth) acrylic resin are preferably of acrylic type. The acrylic rubber particles are rubber-elastic particles obtained by polymerizing an acrylic acid alkyl ester such as butyl acrylate or 2-ethylhexyl acrylate as a main component in the presence of a polyfunctional monomer. Such particles having rubber elasticity may be formed as a single layer, or may be a multilayer structure having at least one rubber elastic layer. As the acrylic rubber particles having a multi-layer structure, those having rubber elastic particles as described above as a nucleus and covering the periphery thereof with a hard methacrylic acid alkyl ester polymer and hard rubbery methacrylic acid alkyl ester polymers as nuclei , Those covered with an acrylic polymer having rubber elasticity as described above, those covered with an acrylic polymer having rubber elasticity around its hard nucleus and covered with a hard alkyl methacrylate polymer . These rubber particles usually have an average diameter of particles formed of an elastic layer in the range of about 50 to 400 nm.

The content of the rubber particles in the (meth) acrylic resin composition constituting the skin layer 37 is usually about 5 to 50 parts by weight per 100 parts by weight of the (meth) acrylic resin. (Meth) acrylic resin and acrylic rubber particles are commercially available in the form of a mixture thereof, so that a commercially available product can be used. Examples of commercially available (meth) acrylic resins containing acrylic rubber particles include "HT55X" and "Technoloy S001" sold by Sumitomo Chemical Co., Such a (meth) acrylic resin composition generally has a Tg of 160 DEG C or lower, but preferably has a Tg of 120 DEG C or lower, more preferably 110 DEG C or lower.

It is preferable that the skin layers 37 and 37 including the (meth) acrylic resin composition in which rubber particles, preferably acrylic rubber particles, are blended have a thickness of 10 to 100 mu m. If the thickness is less than 10 탆, film formation tends to become difficult. On the other hand, if the thickness exceeds 100 m, the retardation of the (meth) acrylic resin layer tends to be negligible.

As described above, in the retardation film (35) used in the present invention, the core layer (36) containing a styrene series resin preferably has a Tg of 120 DEG C or higher, and the (meth) acrylic resin composition It is preferable that the skin layer 37 has a Tg of 120 DEG C or less, more preferably 110 DEG C or less. It is preferable that the Tg of the core layer 36 and the styrene-based resin layer 36 are not overlapped with each other so that the core layer 36 containing the styrene-based resin has a higher Tg than the skin layer 37 containing the (meth) acrylic resin composition containing the rubber particles.

In order to produce the retardation film 35 used in the present invention, for example, a (meth) acrylic resin composition in which a styrene resin and rubber particles are blended is co-extruded to form a film having a three-layer structure, . Alternatively, a single layer film may be produced, followed by heat fusion by heat lamination, followed by stretching.

In this retardation film 35, a three-layer structure in which skin layers 37 and 37 containing a (meth) acrylic resin composition containing rubber particles are formed on both surfaces of a core layer 36 containing a styrene- do. In this three-layer structure, the skin layers 37 and 37 disposed on both sides usually have substantially the same thickness. By adopting such a three-layer structure, the skin layers 37 and 37 including the (meth) acrylic resin composition containing the rubber particles function as a protective layer, and the mechanical strength and chemical resistance are excellent.

In the retardation film 35 constructed as described above, in-plane retardation is imparted by stretching. The stretching can be performed by a known all-axis stretching, transverse uniaxial stretching in a tenter, simultaneous biaxial stretching, sequential biaxial stretching, or the like, and stretching can be performed so as to obtain a desired retardation value.

The retardation film 35 used in the present invention preferably has an in-plane retardation Re in the range of 20 to 120 nm and an Nz coefficient defined by the above-mentioned formula (1) is in the range of more than -2 to less than -0.5 Do. And an index of refraction anisotropy whose Nz coefficient is in a range of more than -2 to less than 0.5 means that the following expression (9) is satisfied.

&Quot; (9) &quot;

_{-2 <(n x -n z)} / (n x -n y) <- 0.5

[Preparation of rear side polarizing plate]

The back side polarizing plate 30 is constituted by laminating the retardation film 35 on the transparent protective film 33 side through the third pressure sensitive adhesive layer 43. [ The method of laminating the retardation film 35 is not particularly limited, but usually the third pressure sensitive adhesive layer 43 is formed on the surface of the transparent protective film 33 or the retardation film 35 first. The pressure-sensitive adhesive layer can be formed not only by applying a pressure-sensitive adhesive solution containing a base polymer as described above to the transparent protective film 33 or the retardation film 35, and drying the applied pressure-sensitive adhesive solution, (Pressure-sensitive adhesive with a separator) provided on the release-treated surface of the support film (separator) and bonding it to the surface of the transparent protective film 33 or the retardation film 35 on the pressure-sensitive adhesive layer side . As another method, a method of forming a pressure-sensitive adhesive layer on the separator and then transferring it onto the polarizing transparent protective film 33 or onto the retardation film 35 may be used. The pressure sensitive adhesive layer thus formed may be laminated with a separator containing a resin film treated with a releasing agent such as a silicone.

When the pressure-sensitive adhesive layer is formed on the surface of the transparent protective film 33 or the retardation film 35, the pressure-sensitive adhesive layer may be formed on the surface of the transparent protective film 33 or the retardation film 35, The same treatment may be carried out on the surface of the pressure sensitive adhesive layer bonded to the transparent protective film 33 or the retardation film 35. [

The joining of the transparent protective film 33 and the retardation film 35 is performed by a conventionally known technique. For example, a joining roll or the like is used to cause the retardation film of the retardation film to be orthogonal to the polarization transmission axis of the polarizing film Or by a method in which the slow axis of the retardation film is bonded to the polarized light transmission axis of the polarizing film at a predetermined angle.

[Pressure-sensitive adhesive layer]

The first pressure sensitive adhesive layer 41 is laminated on the transparent protective film 23 to be the liquid crystal cell side of the front side polarizing plate 20 described above and on the retardation film 35 serving as the liquid crystal cell side of the back side polarizing plate 30, The pressure-sensitive adhesive layer 42 is laminated. The transparent protective film 33 and the retardation film 35 constituting the back-surface-side polarizing plate 30 are bonded through the third pressure-sensitive adhesive layer 43 as described above. The first pressure sensitive adhesive layer 41 and the second pressure sensitive adhesive layer 42 are provided on both sides of the liquid crystal cell 10 to bond the front polarizer 20 and the back polarizer 30 to each other.

The pressure-sensitive adhesive for forming each pressure-sensitive adhesive layer may be one having an excellent optical transparency and being appropriately provided with an adhesive property including wettability, cohesiveness and adhesiveness, but further preferably excellent durability and the like are preferably used. Specifically, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferably used as the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer.

The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin containing an acrylic acid alkyl ester such as butyl acrylate, ethyl acrylate, isooctyl acrylate, or 2-ethylhexyl acrylate as a main monomer. A polar monomer is usually copolymerized with the acrylic resin. A polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group. Here, the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group may be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. Concrete examples of the polar monomer include a carboxyl group-containing monomer represented by (meth) acrylic acid, a hydroxyl group-containing monomer typified by 2-hydroxypropyl (meth) acrylate or 2-hydroxyethyl (meth) (Meth) acrylamide, an epoxy group-containing monomer typified by 2-N, N-dimethylaminoethyl (meth) acrylate and glycidyl (meth) acrylate.

A crosslinking agent is usually mixed with an acrylic resin in the acrylic pressure-sensitive adhesive.

As typical examples of the crosslinking agent, there can be mentioned isocyanate compounds having at least two isocyanate groups (-NCO) in the molecule.

The pressure-sensitive adhesive may further contain various additives. Preferred examples of the additive include silane coupling agents and antistatic agents. The silane coupling agent is effective in enhancing adhesion to glass. The antistatic agent is effective in reducing or preventing the generation of static electricity. Generally, when a polarizing plate is attached to a liquid crystal cell through a pressure-sensitive adhesive layer, a surface protective film (separator) covering and adhered to the pressure-sensitive adhesive layer is peeled and bonded to the liquid crystal cell until that time. The orientation of the liquid crystal in the liquid crystal cell may be defective due to the static electricity generated when the liquid crystal cell is deflected. This phenomenon may cause display failure of the liquid crystal display device. As a means for reducing or preventing the generation of such static electricity, it is effective to incorporate an antistatic agent into a pressure-sensitive adhesive.

[Storage elastic modulus of pressure-sensitive adhesive]

In the present invention, the first pressure sensitive adhesive layer 41, the second pressure sensitive adhesive layer 42 and the third pressure sensitive adhesive layer 43 all have a storage elastic modulus at 50 占 폚 in a range of 0.01 MPa or more and 0.1 MPa or less. By constituting all the pressure-sensitive adhesive layers relatively smoothly as described above, even if the liquid crystal display device is exposed to a humid environment, the stress applied to the liquid crystal cell due to the dimensional change of the polarizing plate can be alleviated, and warping of the liquid crystal panel is suppressed. If the storage elastic modulus at 50 占 폚 of any one of the pressure-sensitive adhesive layers exceeds 0.1 MPa, the stress applied to the liquid crystal cell due to the dimensional change of the polarizing plate can not be sufficiently relaxed and the warp of the liquid crystal panel This may increase the display irregularity. On the other hand, if the storage modulus of elasticity is less than 0.01 MPa, a sufficient adhesive force tends to be hardly obtained. Various methods are used to adjust the storage elastic modulus at 50 DEG C from 0.01 MPa or more to less than 0.1 MPa, but a desired storage elastic modulus can be achieved by adjusting the amount of the crosslinking agent, for example.

The pressure-sensitive adhesive layers 41, 42 and 43 are prepared by preparing a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component as described above is dissolved in an organic solvent, directly applying the pressure-sensitive adhesive composition on the surface of the film on which the pressure- The pressure-sensitive adhesive composition described above is applied to the release-treated surface of the base film containing the resin film subjected to the releasing treatment by the coating method and the solvent is dried to remove the pressure-sensitive adhesive layer, and the pressure- And the like. When the pressure-sensitive adhesive layers 41, 42, and 43 are formed on the surface of the target film by a direct coating method of the former, a resin film (also referred to as a separator) subjected to release treatment is bonded to the surface thereof, It is customary to attach and protect surfaces. The latter transfer method is widely used in view of the handling property of the pressure sensitive adhesive composition which is an organic solvent solution. In this case, the release treated base film used for forming the pressure sensitive adhesive layer for the first time is adhered to the pressure sensitive adhesive layer formation surface, .

[Backlight unit]

The backlight unit (60) includes at least a light source member for supplying display light to the liquid crystal cell (10). This light source member is of a type called a sidelight type comprising a light guide plate and a light source disposed on one side or opposite side of the light guide plate or a light source arranged on a plurality of light sources and a light It may be of a type called a direct type comprising a diffusion plate. In any form, a light reflection layer is usually provided in the form of a sheet or a coating layer on the back surface (away from the liquid crystal cell 10) of the light source member. In addition, optical members such as a light-condensing sheet and a diffusion film may be arranged in one layer or a plurality of layers on the light emission side (the side facing the liquid crystal cell 10) of the light source member. The backlight unit 60 itself has the components described above and can have any arbitrary configuration used in this field.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, parts and% indicating the content or amount are based on the weight unless otherwise specified. The measurement of each physical property in the following examples was carried out by the following method.

(1) retardation value and Nz coefficient

The in-plane retardation was measured by irradiating light having a wavelength of 590 nm at a temperature of 23 DEG C using a phase difference meter "KOBRA-21ADH" based on a parallel Nicol rotation method manufactured by Oji Keisoku KK At the same time, thickness direction retardation or Nz coefficient was measured.

(2) Storage elastic modulus of pressure-sensitive adhesive

The storage elastic modulus (G ') of the pressure-sensitive adhesive was obtained by preparing a cylindrical specimen having a diameter of 8 mm and a thickness of 1 mm from the pressure-sensitive adhesive to be measured and measuring the dynamic viscoelasticity (dynamic analyzer RDA II: manufactured by REOMETRIC) The strain was measured using a twist shear method with a frequency of 1 Hz at an initial strain of 1 N and a temperature of 50 ° C.

In the following examples, the following two types of pressure-sensitive adhesive sheets were used.

(3) Adhesive sheet A:

A pressure-sensitive adhesive layer containing an acrylic copolymer mainly composed of butyl acrylate and an isocyanate crosslinking agent was formed to a thickness of 25 占 퐉 on a release-treated surface of a polyethylene terephthalate film (referred to as "separator & A commercially available pressure sensitive adhesive with a separator. The pressure-sensitive adhesive layer had a storage elastic modulus of 0.04 MPa at 50 占 폚.

(4) Adhesive sheet B:

An acrylic copolymer mainly composed of butyl acrylate, an ultraviolet ray curable component and an isocyanate crosslinking agent were placed on the release treated surface of a polyethylene terephthalate film (referred to as "separator" A pressure-sensitive adhesive having a pressure-sensitive adhesive layer having a thickness of 25 占 퐉 which is cured by curing and which is also commercially available. The storage modulus of the pressure-sensitive adhesive layer was 0.97 MPa at 50 占 폚.

Example 1

(a) Preparation of aqueous adhesive

3 parts of a carboxyl group-modified polyvinyl alcohol ("KL-318 ", available from Kuraray Co., Ltd.) was dissolved in 100 parts of water. To the aqueous solution was added a polyamide epoxy resin (SumikaChemex Co., Quot; Sumirez Resin 650 (30) ", an aqueous solution having a solid concentration of 30%) was added to prepare an aqueous adhesive.

(b) Production of retardation film

(Manufactured by NOVA Chemical Co., Ltd .; "DIRACK D332" (trade name), Tg = 131 DEG C) as a core layer and about 20% of acrylic rubber particles having an average particle diameter of 200 nm (Tg = 105 deg. C), which is used in a "Technoloy SO01" (trade name) marketed by Sumitomo Chemical Co., Ltd.) as a skin layer, Thereby obtaining a resin three-layer film having a skin layer formed thereon. This three-layer resin film was stretched to prepare a retardation film. The in-plane retardation of this retardation film was 55.0 nm and the Nz coefficient was -1.1.

(c) Transparent protective film

Saponification treatment was performed on a triacetyl cellulose film "TD80UL" (trade name) obtained from Fuji Film Co., Ltd., and the liquid crystal cell 10 of each of the front-side polarizing plate 20 and the rear- And the transparent protective films 22 and 32 disposed on the side farther from the transparent protective films 22 and 32, respectively. In addition, "KC4UEW" (trade name), a triacetyl cellulose film having a thickness of 40 μm obtained from Konica Minolta Opto, had a retardation in the in-plane retardation of 0.7 nm and a retardation in the thickness direction of -0.1 nm. This was subjected to a saponification treatment to form a transparent protective film 23 disposed on the liquid crystal cell 10 side of the front side polarizing plate 20. Further, the cyclic polyolefin-based resin film having a thickness of 35.8 占 퐉 obtained from Nippon Zeon Co., Ltd. had an in-plane retardation of 76.2 nm and an Nz coefficient of 1.37. This was used as the second transparent protective film 33 disposed between the polarizing film 31 in the rear side polarizing plate 30 and the retardation film 35.

(d) Production of polarizer

A triacetyl cellulose film "TD80UL" having a thickness of 80 mu m was bonded to one side of a polarizing film having a thickness of about 28 mu m in which iodine was adsorbed and oriented on a polyvinyl alcohol film through the water-based adhesive prepared in (a) And a triacetyl cellulose film "KC4UEW" having a thickness of 40 μm was bonded to the other side with the same water-based adhesive, and then dried at 80 ° C. for 5 minutes to prepare a front polarizing plate 20.

A triacetyl cellulose film "TD80UL" having the same thickness as the above was bonded to one side of the same polarizing film as described above through the same water-based adhesive as above, and the other side was coated with the same water- Of a cyclic polyolefin-based resin film were bonded and then dried at 80 DEG C for 5 minutes. The retardation film produced in the step (b) was applied onto the annular polyolefin based resin film (second transparent protective film 33) through the pressure-sensitive adhesive sheet A (with the separator peeled off) Axis so as to be orthogonal to each other, thereby producing the back-surface-side polarizing plate 30.

(e) Production of Polarizer with Adhesive Layer

The side of the triacetyl cellulose film "KC4UEW" (transparent protective film 23) having a thickness of 40 μm of the front side polarizing plate 20 prepared in the above (d) and the side of the retardation film 35 of the back side polarizing plate 30 , Respectively, to prepare a polarizing plate with a pressure-sensitive adhesive layer.

Of these, the polarizing plate with front side attached to the pressure-sensitive adhesive layer was oriented in the longitudinal direction, and the polarizing plate on the back side with the pressure-sensitive adhesive layer had the absorption axis in the short direction, About 40 cm in length].

(f) Fabrication and evaluation of liquid crystal display device

VIERA (model number: Viera TH-L32X1) of the IPS mode of the IPS mode manufactured by Panasonic Co., Ltd. [32 inches diagonal (about 81 cm), width about 71 cm x about 40 cm in length] And the polarizing plates above and below the liquid crystal cell were peeled off. In place of these original polarizing plates, the polarizing plate with a pressure-sensitive adhesive layer prepared in (e) was applied to the front side (viewing side) and the back side (backlight side) The separator was peeled off from each of the pressure-sensitive adhesive layers and joined at the side of the pressure-sensitive adhesive layer, thereby fabricating the liquid crystal panel 50. At this time, the absorption axis of the front-side polarizing plate 20 was arranged so as to be parallel to the alignment direction when the voltage of the liquid crystal molecules in the liquid crystal cell 10 was zero (black display). A backlight 60 was further attached to the liquid crystal panel to provide a liquid crystal display device. The backlight of this liquid crystal display device was turned on, and after 30 minutes, the contrast ratio at a position of an azimuth angle of 135 DEG and a polar angle of 60 DEG (using an EZ contrast 88XL for a display) manufactured by ELDIM White luminance / black luminance) was measured. Here, the azimuth angle is an angle when the right side of the screen is 0 ° and the counterclockwise direction is positive as viewed from the viewer side, the azimuth angle of 135 ° means the left upper direction of the screen and the polar angle means the tilt from the normal direction of the screen . As a result, the contrast ratio was 326.

(g) Humid environmental test of liquid crystal panel

The liquid crystal panel 50 produced in the step (f) was placed in an environment at a temperature of 40 DEG C and a relative humidity of 95% for 96 hours and taken out. The liquid crystal panel was left for one day under an environment of a temperature of 22 DEG C and a relative humidity of 55%. When the IPS mode liquid crystal display device was assembled again using this liquid crystal panel, the backlight was turned on, and the screen was observed one hour later, no display unevenness was observed.

Comparative Example 1 (corresponding to Example 4 of JP 2010-217870-A)

A liquid crystal panel 50 was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet B was used as the first pressure-sensitive adhesive layer 41 of the front side polarizing plate and the second pressure-sensitive adhesive layer 42 of the back side polarizing plate, The apparatus was assembled and evaluated in the same manner. The contrast ratio was the same as in Example 1, but as a result of the moist heat environment test, display irregularity was observed after 1 hour from lighting of the backlight.

Comparative Example 2

A liquid crystal panel 50 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive sheet B was used as the first pressure-sensitive adhesive layer 41 of the front-side polarizing plate, and the liquid crystal display was assembled and evaluated in the same manner. The contrast ratio was the same as in Example 1, but as a result of the moist heat environment test, display irregularity was observed after 1 hour from lighting of the backlight.

Comparative Example 3

A liquid crystal panel 50 was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet B was used as the second pressure-sensitive adhesive layer 42 of the back-side polarizing plate, and the liquid crystal display was assembled and evaluated in the same manner. The contrast ratio was the same as in Example 1, but as a result of the moist heat environment test, display irregularity was observed after 1 hour from lighting of the backlight.

The composition of the three pressure-sensitive adhesive layers and the results of the wet heat environment test are summarized in Table 1 for the Examples and Comparative Examples.

10 ... ... Liquid crystal cell
11, 12 ... ... Cell substrate
15 ... ... Liquid crystal layer
20 ... ... The front-
21 ... ... Polarizing film
22, 23 ... ... Transparent protective film
30 ... ... The back-
31 ... ... Polarizing film
32, 33 ... ... Transparent protective film
35 ... ... Phase difference film
36 ... ... Core layer
37 ... ... Skin layer
41 ... ... The first pressure-
42 ... ... The second pressure-
43 ... ... Third pressure-sensitive adhesive layer
50 ... ... Liquid crystal panel
60 ... ... Backlight unit

Claims (5)

A liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween,
A front polarizing plate laminated on the viewing side of the liquid crystal cell through a first pressure sensitive adhesive layer,
A back side polarizer laminated through a second pressure sensitive adhesive layer on the side opposite to the viewing side of the liquid crystal cell,
And a backlight unit disposed outside the back-side polarizing plate,
The front-side polarizing plate has a polarizing film and a pair of transparent protective films disposed on both sides thereof, and is laminated on the liquid crystal cell through the first pressure-sensitive adhesive layer on the side of the one transparent protective film,
The back side polarizing plate includes a polarizing film, a first transparent protective film disposed on one side of the polarizing film, a second transparent protective film disposed on the other side of the polarizing film, And a retardation film laminated on the liquid crystal cell through a second pressure-sensitive adhesive layer on the retardation film side,
The retardation film includes a three-layer structure in which a skin layer containing a (meth) acrylic resin composition containing rubber particles is formed on both surfaces of a core layer containing a styrene resin,
Wherein the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the third pressure-sensitive adhesive layer all have storage elastic moduli at 50 DEG C in the range of 0.01 MPa to 0.1 MPa. The liquid crystal display device according to claim 1, wherein the transparent protective film located on the liquid crystal cell side of the front polarizing plate has a retardation in the thickness direction of -10 to 10 nm. The liquid crystal display device according to claim 1, wherein the transparent protective film located on the liquid crystal cell side of the front side polarizing plate comprises a cellulose resin or a polyolefin resin. The liquid crystal display device according to claim 2, wherein the transparent protective film positioned on the liquid crystal cell side of the front side polarizing plate comprises a cellulose resin or a polyolefin resin. The polarizing plate according to any one of claims 1 to 4, wherein the second transparent protective film constituting the back-side polarizing plate comprises a polyolefin-based resin, the in-plane retardation thereof is in the range of 30 to 150 nm, axis (遲相軸) direction, the in-plane fast axis (進相軸) direction, and when the refractive index in the thickness direction with n _x, n _y and n _z, respectively, to greater than 1, the Nz coefficient defined by equation (1) is less than 2 Of the refractive index anisotropy,
Wherein the retardation film constituting the back side polarizing plate has an in-plane retardation in the range of 20 to 120 nm and an Nz coefficient defined by the following equation (1) is in the range of more than -2 to less than -0.5.
&Quot; (1) &quot;
_{Nz = (n x -n z)} / (n x -n y)

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