KR101685715B1 - A liquid crystal display device - Google Patents

Abstract

The present invention is a liquid crystal display device comprising a liquid crystal cell 10 having two cell substrates 11 and 12 and a liquid crystal layer 15 sandwiched therebetween and a first pressure sensitive adhesive layer 40 laminated via a first pressure sensitive adhesive layer 40 on the viewer side of the liquid crystal cell A back side polarizing plate 30 laminated through a second pressure sensitive adhesive layer 50 on the opposite side of the viewer side of the liquid crystal cell and a back light plate 30 disposed outside the back side polarizing plate 30, Unit-side polarizing plate 20 and the back-side polarizing plate 30 are respectively provided with polarizing films 21 and 31 and transparent protective films 25 and 26 disposed on both sides thereof; With 35 and 36, and provides a front-side polarization plate 20 of the water content W ₁ and the water content W ₂ ratio W ₁ / W ₂ is between the range of less than 1.0, 1.2 of the back polarizing plate 30, a liquid crystal display device .

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.

An object of the present invention is to provide a liquid crystal display device in which warping of a liquid crystal panel is small even after being placed under a moist heat environment and display unevenness is not present. As a result of intensive studies to achieve these objects, the present inventors have found that adjusting the ratio of the moisture content of the front-side polarizing plate to the moisture content of the rear polarizing plate suppresses warping of the liquid crystal panel after being placed under a humid environment, The present invention has been accomplished on the basis of these findings.

That is, the present invention includes the following.

[1] A liquid crystal display comprising: a liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween, a front polarizing plate laminated through a first pressure sensitive adhesive layer on the viewer side of the liquid crystal cell, And a backlight unit disposed on the outer side of the rear-side polarizing plate, wherein the front-side polarizing plate and the rear-side polarizing plate each have a polarizing film and a liquid crystal layer disposed on both sides of the polarizing film the transparent protective film has, and the front-side polarization plate of the water content W ₁ and the rear polarizing plate of the water content ratio W ₂ with W ₁ / W ₂ is in the range of less than 1.0, 1.2, the liquid crystal display device.

[2] The liquid crystal display according to [1], wherein the transparent protective film positioned on the liquid crystal cell side of each of the front side polarizing plate and the back side polarizing plate has a retardation value in the thickness direction in the range 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 each of the front side polarizing plate and the back side polarizing plate comprises a cellulose resin or a polyolefin resin.

[4] The transparent protective film positioned on the side farther from the liquid crystal cell of each of the front polarizer and the back polarizer in any one of [1] to [3] And has a thickness larger than the total thickness of the pressure-sensitive adhesive layer.

[5] The polarizing film of any one of [1] to [4], wherein the polarizing film of each of the front-side polarizing plate and the back-polarizing plate and the transparent protective film disposed on both surfaces thereof contain a polyvinyl alcohol-based resin and a water- Wherein the liquid crystal display device is bonded to the liquid crystal display device through an aqueous adhesive.

[6] The polarizing film of any one of [1] to [4], wherein the polarizing film of each of the front side polarizing plate and the back side polarizing plate and the transparent protective film disposed on both sides thereof, And the curable adhesive composition containing the curable adhesive composition.

[7] The liquid crystal display device according to [6], wherein the epoxy compound comprises an epoxy compound having at least one epoxy group bonded to an alicyclic ring.

According to the present invention, it is possible to provide a liquid crystal display device in which the warpage of the liquid crystal panel is small even after it is placed under a humid environment and therefore, there is no display unevenness.

1 is a schematic cross-sectional view showing a layer structure of a liquid crystal display device according to the present invention.

1, the liquid crystal display device of the present invention comprises a liquid crystal cell 10, a front side polarizing plate 20 laminated through a first pressure sensitive adhesive layer 40 on the viewer side of the liquid crystal cell, Side polarizer 30 laminated through the second pressure-sensitive adhesive layer 50 on the side opposite to the liquid crystal cell 10 and a backlight unit 70 disposed on the outside of the back-side polarizer (i.e., opposite to the liquid crystal cell 10) . A front side polarizing plate 20 laminated through a first pressure sensitive adhesive layer 40 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 50, And the liquid crystal panel 60 is formed of the polarizing plate 30.

The front side polarizing plate 20 disposed on the viewing side of the liquid crystal cell 10 has a polarizing film 21 and transparent protective films 25 and 26 laminated on both sides thereof with an adhesive (not shown) .

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 70) also includes a polarizing film 31 and an adhesive (not shown) And a transparent protective film 35, 36 laminated through the transparent protective film 35, 36.

The liquid crystal panel 60 and the backlight unit 70 are combined to form a liquid crystal display device. However, when the liquid crystal display device is placed under a humid environment, the liquid crystal panel 60 is warped, There is a case in which a part is abnormally brought close to the backlight unit 70 or, in an extreme case, it is brought into contact with the backlight unit 70 to cause display irregularity. In addition, when the liquid crystal display device is placed under a moist heat environment, the liquid crystal panel 60 is warped, and a part of the liquid crystal panel 60 There is a case where the display is brought into contact with the case or the gold frame fixing it to cause display unevenness.

In the present invention the water content of the front-side polarizing plate 20 is set to W _1, and by the water content of the back side polarizing plate 30 to the W _2, and of the two non-W ₁ / W ₂ is such that the range between 1.0 1.2 . Relationship between the water content of the water content W ₂ W ₁ and the rear-side polarizing plate 30 of the front-side polarizing plate (20) above, corresponds to that both satisfy the formula a.

<Formula a>

That is, it is very important that the moisture content W ₁ of the front-side polarizing plate 20 is made larger than the moisture content W ₂ of the rear-side polarizing plate 30. Thus, it has been found that warping of the liquid crystal panel 60 can be suppressed even after being placed under a humid environment, display irregularity is not recognized, and a liquid crystal display device having excellent display quality can be obtained.

The thicknesses of the transparent protective films 25 and 35 located on the side farther from the liquid crystal cell 10 are set to be located on the liquid crystal cell 10 side with respect to the front side polarizing plate 20 and the back side polarizing plate 30, It is also effective to increase the total thickness of the transparent protective films 26, 36 and the pressure-sensitive adhesive layers 40, 50 to be adhered thereto. By increasing the thickness of the transparent protective films 25 and 35 located on the side farther from the liquid crystal cell 10 with respect to the front side polarizing plate 20 and the back side polarizing plate 30 as described above, It is possible not only to improve handling properties in handling a polarizing plate of a large size of more than 32 inches (about 81 cm) diagonally, but also to improve the handling property of the liquid crystal panel 60, Is effective for suppressing warpage of the warp yarns.

Hereinafter, each member constituting the liquid crystal display device of the present invention will be described in detail in order with reference to the reference numerals given in 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 of the liquid crystal display device of the present invention can be composed of various ones employed in this field.

[Polarizing Film]

The polarizing films 21 and 31 constituting the front side polarizing plate 20 and the back side polarizing plate 30 are usually formed by a process of uniaxially stretching a polyvinyl alcohol based resin film and a step of stretching the polyvinyl alcohol based resin film to a dichroic dye A step of adsorbing a dichroic dye by dyeing, a step of treating a polyvinyl alcohol resin film adsorbed with a 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 saponification degree 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 占 퐉, preferably about 10 to 100 占 퐉.

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 where uniaxial stretching is carried out after dyeing, this uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. Of course, uniaxial stretching can also be performed at a plurality of steps shown here. For uniaxial stretching, a method of uniaxial stretching between rolls having different main speeds, a method of uniaxial stretching using a heat roll, or the like can be adopted. 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 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 dichroic 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 in which a polyvinyl alcohol-based resin film is dipped in an aqueous solution containing a water-soluble dichroic organic dye is employed. 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 占 폚. The immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

After the dyeing with the dichroic dye, the boric acid treatment 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 aqueous solution containing boric acid 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 boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 占 폚 or higher, preferably 50 to 85 占 폚, and more preferably 60 to 80 占 폚.

After the boric acid treatment, the polyvinyl alcohol-based resin film is usually washed with water. 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. The moisture content in the polarizing film is reduced to a practically acceptable level by the drying treatment. The water content thereof is usually about 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost, which may be damaged or broken after drying. When 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 25 and 35 located on the side farther from the liquid crystal cell 10 in each of the front side polarizing plate 20 and the back side polarizing plate 30 are made of a material excellent in transparency, mechanical strength, heat 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 transparent protective film material. The polymer modification includes, for example, copolymerization, crosslinking, molecular terminal modification, stereoregularity control, mixing involving the reaction between dissimilar polymers, and the like.

Of 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 25 and 35 located farther from the liquid crystal cell 10 .

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 obtained by polymerizing a monofunctional monomer containing methyl methacrylate as a main component in the presence of a radical polymerization initiator and a chain transfer agent. In some cases, a monofunctional monomer may be copolymerized with a component copolymerizable with methyl methacrylate. If desired, a small amount of a polyfunctional monomer may be copolymerized.

Examples of monofunctional monomers that can be copolymerized with methyl methacrylate include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethyl methacrylate Methacrylic acid esters other than methyl methacrylate such as hexyl and 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. These monomers may be used alone or in combination of two or more.

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 and tetraethylene glycol Esters of both terminal hydroxyl groups of ethylene glycol or oligomers thereof with acrylic acid or methacrylic acid, such as di (meth) acrylate; Esterification of both terminal hydroxyl groups of propylene glycol or its oligomer with acrylic acid or methacrylic acid; Esterified with acrylic acid or methacrylic acid, such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate and butanediol di (meth) acrylate; Bisphenol A, an alkylene oxide adduct of bisphenol A, or both terminal hydroxyl groups of these halogen substituents are esterified with acrylic acid or methacrylic acid; Esters of polyhydric alcohols such as trimethylolpropane and pentaerythritol 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; Dicarboxylic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid and halogen substituents thereof, or an alkylene oxide adduct thereof with ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate; Allyl (meth) acrylate; And aromatic divinyl compounds such as divinylbenzene. When a polyfunctional monomer is copolymerized, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used.

The modified resin may be used by carrying out a reaction between the functional groups of the methyl methacrylate resin. Examples of the reaction between these functional groups include a condensation reaction between a methyl ester group of methyl acrylate and a hydroxyl group of 2- (hydroxymethyl) acrylate in a polymer chain, a reaction between a carboxyl group of acrylic acid and methyl 2- (hydroxymethyl) And a dehydration condensation reaction in the 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., "Achrifet" sold by Mitsubishi Rayon Co., Ltd., "Aspirin" 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 usually a chain olefin resin in which 80% by weight or more of the repeating units is 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 or 1-hexene is preferable as a comonomer copolymerizable with propylene. Among them, a polypropylene resin having a comparatively high transparency can be obtained. 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 占 폚 (abbreviation for CXS component: CXS component: CXS is 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 content of 1% by weight or less and further 0.5% by weight or less is one of preferred examples.

The polypropylene-based resin can easily obtain a commercially available product. Examples of commercially available products include "Prime Polypro" sold by Prime Polymer Co., Ltd., "Novatech" and "Wintech" sold by Nippon Polypropylene Co., Ltd., Sumitomo Chemical Co., And "Sun aroma", which is sold by Sun Aroma Co., Ltd.

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, mixed esters thereof, and the like. 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 adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol have.

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, if necessary, other dicarboxylic acids or other diols), a method of directly polycondensing a dialkyl ester of terephthalic acid and ethylene glycol (And optionally other diol esters) of terephthalic acid (and other dicarboxylic acids if necessary) in the presence of a catalyst (for example, a dialkyl ester of a dicarboxylic acid or other diol) And a method of polycondensation in the presence of a catalyst. Further, if necessary, further solid phase polymerization may be carried out to increase the molecular weight or decrease the low molecular weight component.

The method of forming the resin as the transparent protective film for a polarizing plate can be appropriately selected in accordance with the method according to each resin. 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 removed by drying to obtain a film, a method in which the resin is heated to a temperature not lower than its melting temperature, A melt extrusion method for obtaining a film can be used. In the melt extrusion method, the single layer film may be extruded or the multilayer film may be extruded at the same time.

It is possible to easily obtain a commercially available film of these resins. Examples of commercially available films include methylcellulose based methyl methacrylate resin films such as "Techolloi" sold under the trade name of Sumitomo Chemical Co., Ltd., "Acrylite" commercially available from Mitsubishi Rayon Co., And "Acryprene" sold by Asahi Kasei Co., Ltd., "Terra Grass" sold by Asahi Kasei Co., "Paragraph" and "Comogras" sold by Kuraray Co., Ltd., And "Arc Review". Polyethylene terephthalate based resin films include "Nova Clear" sold by Mitsubishi Kagaku Co., Ltd. and "A-PET sheet" sold by Deijin Kasei Co., Ltd. under trade names. Polypropylene resin films can be produced by using the "FILMAX CPP film" marketed by FILMAX under the trade name "SunTox" sold by Suntox Co., Ltd., the " "Toyobo Pyrene Film" sold by Toyobo Co., Ltd., "Toraypan" sold by Toray Film Co., Ltd., "Nippon Polytech Co., Ltd. sold by Nippon Poly Ace Co., Ace ", and" Daiko FC, "which is sold by Fumamura Kagaku Co., Ltd. Further, as the cellulose resin film, "Fujikit TD" sold by Fuji Film Co., Ltd. and "Konica Minolta TAC Film KC" sold by Konica Minolta Opto Co., Ltd. are available.

The transparent protective film 25 disposed on the side farther from the liquid crystal cell 10 and serving as the viewing side can be imparted with haze and 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 not mixed with fine particles A method of forming a three-layered film by forming a two-layer film or a resin mixed with fine particles as an outer layer, a method of coating a coating liquid comprising inorganic fine particles or organic fine particles mixed with a curable binder resin on one side of the film, A method of providing an antiglare layer and the like are adopted.

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 imparted 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 in which the transparent protective film is disposed may become cloudy, resulting in deterioration of image quality. The haze is a value defined as a ratio of the diffusion transmittance to the total light transmittance and can be measured using a commercially available haze meter in accordance with JIS K7136. Examples of the commercially available haze meter include "HM-150 ", which is commercially available from Murakami Co., Ltd., Saijiju Co., In measuring the haze value, it is preferable to use a measurement sample in which, for example, an optically transparent pressure-sensitive adhesive is used and the film surface is bonded to the glass substrate so that the antiglare surface is the surface, in order to prevent the film from being warped.

A functional layer including a conductive layer, a hard coating layer, and a low reflective layer is formed on the outside of each of the transparent protective film 25 that is disposed on the viewer side and the transparent protective film 35 that is disposed on the side far 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 expressing these functions may be selected.

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

In the liquid crystal cell 10 described above in the resin material constituting the transparent protective films 26 and 36 located on the liquid crystal cell 10 side in the front side polarizing plate 20 and the back side polarizing plate 30 shown in Fig. The transparent protective films 25 and 35 may be the same as those described above. Of these, a polyolefin-based resin including a cellulose resin, a chain polyolefin resin and 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, for example, cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives 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 is easily obtained.

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

The cyclic polyolefin-based resin can easily obtain a commercially available product. Examples of commercially available products are sold under the trade names of TOPAS ADVANCED POLYMERS GmbH in Japan and TOPAS in Japan and sold by JSR Co., "Zeonor" and "Zeonex" sold by Nippon Zeon Co., Ltd., and "Apel" sold by Mitsui Chemicals, Inc. are available.

Typical examples of the chain polyolefin-based resin are a polyethylene-based resin and a polypropylene-based resin. Among them, a copolymer obtained by copolymerizing propylene homopolymer or propylene as a main component and a comonomer copolymerizable therewith, for example, ethylene at a ratio of 1 to 20% by weight, preferably 3 to 10% by weight is preferably used do.

The method of forming a film from a cellulose-based resin, a polyolefin-based resin, or the like into a film can be suitably selected in accordance with the method according to each resin. 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 removed by drying to obtain a film, a method in which the resin is heated to a temperature not lower than its melting temperature, A melt extrusion method for obtaining a film can be used. Among them, the melt extrusion method is preferably employed 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.

When the liquid crystal cell 10 is in an in-plane switching (IPS) mode, in order to prevent the wide viewing angle characteristic inherent to the IPS mode liquid crystal cell from being impaired, the transparent protective film 26, and 36, the retardation Rth in the thickness direction is preferably in the range of -10 to 10 nm. The retardation Rth in the thickness direction 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 (b). 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 formula (c).

<Expression b>

<Formula c>

In the formula, n _x is the refractive index in the x-axis direction (in-plane slow axis direction) in the film plane, n _y is the y axis direction (in-plane fast axis direction, (direction perpendicular to the x axis), n _z is the refractive index in the z-axis direction (thickness direction) perpendicular to the film surface, 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 retardation Rth in the thickness direction and the retardation Re in the plane can be measured by using various commercially available retardation systems.

As a method of 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 solvent casting method, a method of relaxing the residual shrinkage distortion in the thickness direction, which occurs when the casting resin solution is dried, by heat treatment, or the like can be adopted. On the other hand, in the melt extrusion method, the distance from the die to the cooling drum is minimized in order to prevent the resin film from being stretched between the extrusion of the die and cooling, and at the same time, the extrusion amount and the rotation speed of the cooling drum A method of controlling the film so as not to be stretched, and the like. Further, 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 employed.

[Bonding of Polarizing Film to Protective Film]

The polarizing film 21 and the transparent protective films 25 and 26 in the front side polarizing plate 20 and the polarizing film 31 and the transparent protective films 35 and 36 in the back side polarizing plate 30 An adhesive is usually used. The thickness of the adhesive layer for bonding the polarizing film and the transparent protective film can be about 0.01 to 30 mu m, preferably 0.01 to 10 mu m, more preferably 0.05 to 5 mu m. When the thickness of the adhesive layer is within 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.

In forming the adhesive layer, an appropriate adhesive may be suitably 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 moisture-resisting 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 water-based adhesive can be prepared by mixing such an adhesive component with water, together with further additives which are optionally compounded. 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 aqueous adhesive may contain a crosslinking agent as required. 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-based 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. An example of a commercially available water-soluble epoxy resin is "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 the adhesion, it is also effective to increase the wettability of the transparent protective film by performing 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, about 30 to 50 ° C for about 1 to 10 days is preferable for further increasing the adhesive strength.

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 an active energy ray to the coating layer of the adhesive composition, and curing 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. Further, from the viewpoint of productivity, this curing is preferably carried out by irradiation of active energy rays.

From the standpoint of weatherability, refractive index, cationic polymerizability, etc., the epoxy compound contained in the curable adhesive composition preferably 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, JP 2004-245925-A publication, but an outline thereof will also be given here.

The hydrogenated epoxy compound may be a glycidyl etherified product of 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, bispale F and bisphenol S; Novolak type resins such as phenol novolak resins, cresol novolac resins and hydroxybenzaldehyde phenol novolac resins; 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 obtained 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 crosslinked 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 of (CH ₂ ) _m in this formula are bonded to other chemical structures may be an alicyclic epoxy compound. Further, one or more hydrogen atoms of (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 (wherein m = 3 in the above formula) or an oxabicycloheptane ring (in which m = 4 in the above formula) has excellent adhesiveness is preferable . Specific examples of the alicyclic epoxy compound are shown 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; Polyglycidyl ethers of polyether polyols (for example, diglycidyl ethers of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin .

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 them, 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 within a range of 30 to 3,000 g / equivalent, and the epoxy equivalent is preferably in a 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, as a compound having an epoxy equivalent of more than 3,000 g / equivalent, there is a possibility that compatibility with other components contained in the adhesive composition is lowered.

From the viewpoint of reactivity, cationic polymerization is preferably used as a curing reaction of an epoxy compound. To this end, 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 ray, 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 need to consider the heat resistance or distortion caused by the expansion of the polarizing film, It is advantageous in that the polarizing film can be favorably adhered. Further, since the cationic photopolymerization initiator acts catalytically in the light, 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 mixing 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 compounding 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 compounding amount of the photo cationic polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy compound, the ionic substances in the cured product are increased, so that the hygroscopic property of the cured product is increased.

When a photo cationic polymerization initiator is used, the curable adhesive composition may further contain a photosensitizer, if necessary. By using a photosensitizer, the reactivity of the cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfate, 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, its 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.

On the other hand, examples of thermal cationic polymerization initiators include benzylsulfonium salts, thiophenium salts, thioronium salts, benzylammonium, pyridinium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters, amine imides and the like.

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, and photo cationic polymerization and thermal cation 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.

Further, the curable adhesive composition may further contain a compound that promotes cation 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 or the like, a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol or the like. When the polyol compound is compounded, its amount is usually 50% by weight or less, preferably 30% by weight or less, in the curable adhesive composition.

In addition, 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, And the like. Examples of the ion trap agent include inorganic compounds including powdery bismuth, antimony, magnesium, aluminum, calcium, titanium, and mixtures thereof. Examples of the antioxidant include, for example, And hindered phenol-based antioxidants.

The curable adhesive composition containing an epoxy compound is coated on the bonding surface of the polarizing film or the transparent protective film or both of the bonding surfaces thereof and then bonded to the coated surface with the adhesive, The adhesive layer can be cured to bond the polarizing film and the transparent protective film. As the coating method of the adhesive, various coating methods such as a doctor blade, a wire bar, a die coater, a comb coat, and a gravure coater can be adopted.

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

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 ray is adjusted so that the appropriate 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 cationic species and Lewis acid are generated, and the specific heating temperature is, for example, about 50 to 200 캜.

[Pressure-sensitive adhesive layer]

The first pressure sensitive adhesive layer 40 is laminated on the transparent protective film 26 to be the liquid crystal cell side of the front side polarizing plate 20 described above and on the transparent protective film 36 to be the liquid crystal cell side of the back side polarizing plate 30 The second pressure sensitive adhesive layer 50 is laminated. These pressure-sensitive adhesive layers 40 and 50 are provided on both sides of the liquid crystal cell 10 to bond the front-side polarizing plate 20 and the back-surface-side polarizing plate 30, respectively.

The pressure-sensitive adhesive for forming each of the pressure-sensitive adhesive layers may also be referred to as a pressure-sensitive adhesive, and may be any of those having excellent optical transparency and excellent adhesive properties including proper wettability, cohesiveness and adhesiveness, but further preferably excellent durability do. Specifically, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferably used as a pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer.

The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin containing acrylic acid alkyl ester such as butyl acrylate, ethyl acrylate, isooctyl acrylate and 2-ethylhexyl acrylate as main monomers. A polar monomer is usually copolymerized with the acrylic resin. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group, and the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group. The polar functional group is a carboxyl group, a hydroxyl group, an amide group, And so on. Specific examples of the polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, ) Acrylate, and glycidyl (meth) acrylate.

The acrylic pressure sensitive adhesive is usually blended with a crosslinking agent together with an acrylic resin. As typical examples of the crosslinking agent, there can be mentioned isocyanate compounds having at least two isocyanato groups (-NCO) in the molecule.

The pressure-sensitive adhesive may further contain various additives. Preferred examples of the additive include a silane coupling agent and an antistatic agent. The silane coupling agent is effective for enhancing adhesion to glass. Antistatic agents are 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 then, The resulting static electricity causes a defective orientation of the liquid crystal in the liquid crystal cell, and this phenomenon may cause display failure of the liquid crystal display device. As means for reducing or preventing the generation of such static electricity, it is effective to incorporate an antistatic agent into the pressure-sensitive adhesive.

The pressure-sensitive adhesive layers 40 and 50 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 and directly applying the pressure-sensitive adhesive composition on the transparent protective films 26 and 36 of the polarizing plate, 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 coating process or by the coating method, and the solvent is dried to form a pressure-sensitive adhesive layer, 36 by a transfer method.

In the case where the pressure-sensitive adhesive layers 40 and 50 are formed on the transparent protective films 26 and 36 by the former direct coating method, a resin film (also referred to as a separator) subjected to release treatment is bonded to the surface thereof, The surface of the pressure-sensitive adhesive layer is usually adhered and protected. From the viewpoint of handling property of the pressure-sensitive adhesive composition which is an organic solvent solution, the latter transfer method is widely adopted. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer for the first time becomes a separator It is also suitable in that it is.

[Moisture Content of Polarizer]

In the present invention, the water content by W ₁ and the rear-side water content ratio W ₂ W ₁ / W ₂ the range between 1.0 1.2, the polarizing plate 30 of Figure 1 with reference to the front-side polarization plate 20. The By the relationship between the water content W ₂ of the front-side polarization plate 20, the water content W ₁ and the rear-side polarizing plate 30 in this range, due to the light supplied from the backlight unit 70 at the time of lighting the liquid crystal panel 60 The temperature of the liquid crystal panel 60 rises sharply, and the balance between the polarizers 20 and 30 when the liquid evaporates and shrinks becomes better, and the warp of the liquid crystal panel 60 is suppressed.

The method of adjusting the water content of the polarizing plate is not particularly limited, and any method may be employed. For example, when the water content is lowered, a method of heat-treating the polarizing plate in a drying oven or the like is preferably adopted. When the moisture content is increased, a method of humidifying the polarizing plate in a moist heat oven or the like is preferably adopted. These treatments may be carried out by using a polarizing plate in the form of a roll, a polarizing plate in the form of a sheet, or a combination of a process in the roll-polarizing plate and a sheet-like polarizing plate.

[Thickness of each member constituting the polarizing plate]

The thickness of the transparent protective film 25 located on the side farther from the liquid crystal cell 10 with respect to the front side polarizing plate 20 is set to be larger than the thickness of the transparent protective film 26 located on the liquid crystal cell 10 side, The thickness of the transparent protective film 35 located farther from the liquid crystal cell 10 is set to be larger than the total thickness of the liquid crystal cell 10 Of the transparent protective film 36 and the second pressure-sensitive adhesive layer 50 adhered thereto. By thus increasing the thickness of the transparent protective films 25 and 35 located on the far side from the liquid crystal cell 10 with respect to each of the front side polarizing plate 20 and the back side polarizing plate 30, Not only can the transparency protective film 26, 36 located on the side of the liquid crystal panel (the side of the transparent protective film 26, 36) be thinned, 60 of the present invention.

It is preferable that the transparent protective films 26 and 36 located on the liquid crystal cell 10 side of the polarizers 20 and 30 have a thickness in the range of about 20 to 50 mu m. The thickness of each of the pressure-sensitive adhesive layers 40 and 50 to be adhered thereto can be set in the range of about 10 to 30 占 퐉. The transparent protective films 25 and 35 located on the side farther from the liquid crystal cell 10 of the polarizers 20 and 30 are transparent protective films 26 and 36 whose thicknesses are located on the liquid crystal cell 10 side, Preferably at least 30 占 퐉 or more, more preferably at least 10 占 퐉, more preferably at least 30 占 퐉. Further, as described above, the transparent protective film 25 located on the side farther from the liquid crystal cell of the front-side polarizing plate 20 has a thickness larger than that of the transparent protective film 26 on the liquid crystal cell side and the first pressure- Side polarizing plate 30 and the transparent protective film 35 located on the side farther from the liquid crystal cell of the rear-side polarizing plate 30 than the total thickness of the transparent protective film 36 on the liquid crystal cell side, The thickness of the second pressure-sensitive adhesive layer 50 is set to be larger than the total thickness of the second pressure-sensitive adhesive layer 50. The thicknesses of the transparent protective films 26 and 36 located on the liquid crystal cell side are respectively about 40 μm and the thicknesses of the first pressure sensitive adhesive layer 40 and the second pressure sensitive adhesive layer 50 are respectively about 25 μm, The thickness of the transparent protective films 25 and 35 located on the side farther from the transparent protective film 25 is about 80 μm, respectively.

[Backlight unit]

The backlight unit 70 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 sidelight type which is constituted by a light guide plate and a light source disposed on one side or opposite side of the light guide plate or a light diffusion type light source which is arranged on a plurality of light sources and on the side (toward the liquid crystal cell 10) It can be of the form called direct type which consists of plates. Regardless of the type, a light reflecting 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-converging sheet and a diffusion film may be disposed 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 70 itself may have any of the components described herein and adopted in this field.

<Examples>

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

(1) Measurement of thickness:

Was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation and thickness direction retardation:

In-plane retardation and thickness direction retardation at a wavelength of 590 nm were measured at a temperature of 23 캜 using a phase difference meter "KOBRA-21ADH " based on a parallel Nicol rotation method manufactured by Oji Keisoku KK.

(3) Measurement of the moisture content of the polarizing plate:

The polarizing plate (before forming the pressure-sensitive adhesive layer) cut to a size of 150 mm × 150 mm was left in a drying oven kept at 105 ± 1 ° C. for 60 minutes and then left in the drying oven before the weight in the drying oven (Weight after drying), the value calculated by the following formula was regarded as the water content of the polarizing plate.

Example 1

(Preparation of aqueous adhesive)

3 parts of "KL-318" (trade name), a carboxyl group-modified polyvinyl alcohol obtained from Kuraray Co., Ltd., was dissolved in 100 parts of water. To the aqueous solution was added a water-soluble polyamide epoxy 1.5 parts of a resin "Sumirez Resin 650 (30)" (trade name, aqueous solution having a solid content concentration of 30%) was added to prepare an aqueous adhesive.

(Production of polarizing plate)

"TD80UL" (trade name), which is a triacetyl cellulose film having a thickness of 80 μm obtained from Fuji Film Co., Ltd., was saponified to form transparent protective films 25, 35 disposed on the side far from the liquid crystal cell. Further, "KC4UEW" (trade name), a triacetyl cellulose film having a thickness of 40 μm obtained from Konica Minolta Opto, had a retardation in the plane of 0.7 nm and a retardation in the thickness direction of -0.1 nm. This was subjected to saponification treatment to form transparent protective films (26, 36) arranged on the liquid crystal cell side.

The transparent protective film having the thickness of 80 占 퐉 was bonded to one surface of a polarizing film having a thickness of about 28 占 퐉 in which iodine was adsorbed and aligned on a polyvinyl alcohol film through the aqueous adhesive prepared above, , And then dried at 80 DEG C for 5 minutes to prepare a polarizing plate.

(Production of a polarizing plate with a pressure-sensitive adhesive layer)

Using the polarizing plate prepared above, a pressure-sensitive adhesive sheet having a thickness of 25 占 퐉 was bonded to the surface of a transparent protective film having a thickness of 40 占 퐉 to prepare a polarizing plate having a pressure-sensitive adhesive layer. The polarizing plate having the pressure-sensitive adhesive layer was cut into a wide 32-inch size (diagonal 32 inches (about 81 cm) wide, about 71 cm in width and about 40 cm in length) with the absorption axis in the longer direction and the absorption axis in the shorter direction Respectively. These polarizers exhibited good handling properties at the time of handling.

(Fabrication and Evaluation of Liquid Crystal Display)

(Manufactured by Panasonic Corporation), IPS mode wide 32 type (diagonal 32 inches, width of about 71 cm x about 40 cm in length) liquid crystal television "VIERA" (model number: VIERA TH- L32X1) was peeled off to peel off the polarizing plates on the upper and lower sides of the liquid crystal cell. The polarizing plate with the pressure-sensitive adhesive layer prepared above was attached to the front side (viewing side) and the back side (backlight side) State, so that the liquid crystal panel 60 was manufactured. 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). The ratio of the water content W ₁ of the front side polarizing plate to the water content W ₂ of the back side polarizing plate was 1.05, so that the water content was high in the front side polarizing plate 20 and the water content was low in the rear side polarizing plate 30 Respectively. The liquid crystal panel 60 was allowed to stand for 96 hours under an environment of a temperature of 40 占 폚 and a relative humidity of 95% and then taken out and left for one day under an environment of a temperature of 22 占 폚 and a relative humidity of 55%. When the IPS mode liquid crystal display device was assembled again using this liquid crystal panel, and the backlight was turned on and observed after 1 hour, no display irregularity was observed.

Example 2

(Production of polarizing plate)

Except that the transparent protective films 25 and 35 disposed on the side farther from the liquid crystal cell were changed to "KC8UX" (trade name), which is a triacetyl cellulose film having a thickness of 80 μm obtained from Konica Minolta Opto, To prepare a polarizing plate.

(Production of a polarizing plate with a pressure-sensitive adhesive layer)

Using the polarizing plate prepared above, a pressure-sensitive adhesive sheet was bonded to the surface of a transparent protective film having a thickness of 40 탆 to prepare a polarizing plate having a pressure-sensitive adhesive layer. The polarizing plate having the pressure-sensitive adhesive layer was cut into a wide 32-inch size (diagonal 32 inches (about 81 cm) wide, about 71 cm in width and about 40 cm in length) with the absorption axis in the longer direction and the absorption axis in the shorter direction Respectively. These polarizers exhibited good handling properties at the time of handling.

(Fabrication and Evaluation of Liquid Crystal Display)

A liquid crystal panel 60 was produced in the same manner as in Example 1 except that the polarizing plate with the pressure-sensitive adhesive layer thus prepared was used. At this time, the ratio of the moisture content of the front-side polarizing plate 20 to that of the back-side polarizing plate 30 (moisture content W ₁ of the front-side polarizing plate / moisture content W ₂ of the rear-side polarizing plate) Respectively. The liquid crystal panel 60 was allowed to stand for 96 hours under an environment of a temperature of 40 占 폚 and a relative humidity of 95% and then taken out and left for one day under an environment of a temperature of 22 占 폚 and a relative humidity of 55%. The IPS mode liquid crystal display device was reassembled by using this liquid crystal panel, and the backlight was turned on and observed after 1 hour. However, there was a slight display irregularity, but no problem in terms of visibility.

Comparative Example 1

Example 2 and using a polarizing plate, the same pressure-sensitive adhesive is attached and the front-side polarization plate 20, is disposed to the low water content the higher the water content, the back side polarizing plate 30, but the (front-side polarizing plate of the water content W ₁ / And the ratio of the water content W ₂ of the rear side polarizing plate to the rear side polarizing plate was 1.31, and the liquid crystal display device was assembled and similarly evaluated. As a result, when the backlight was observed one hour after lighting, the display was not uniform.

The water content ratio W ₁ / W ₂ of the polarizing plate in the above Examples and Comparative Examples, the thickness of the protective film and the pressure-sensitive adhesive layer constituting the polarizing plate, and the evaluation results are summarized in Table 1 below.

10: liquid crystal cell
11, 12: cell substrate
15: liquid crystal layer
20: front polarizer
21: polarizing film
25, 26: Transparent protective film
30: back side polarizer
31: polarizing film
35, 36: transparent protective film
40: first pressure-sensitive adhesive layer
50: second pressure-sensitive adhesive layer
60: liquid crystal panel
70: Backlight unit

Claims (7)

A liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween,
A front polarizing plate laminated on the viewer 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 visible side of the liquid crystal cell,
And a backlight unit disposed outside the back-surface-side polarizer,
The front side polarizing plate and the back side polarizing plate each have a polarizing film and a transparent protective film disposed on both sides thereof,
The water content of the front-side polarization plate W ₁ and the back side polarizing plate of the water content ratio W ₂ with W ₁ / W ₂ of 1.05 in the range of 1.2 or more liquid crystal display device described below. The liquid crystal display device according to claim 1, wherein the transparent protective film positioned on the liquid crystal cell side of each of the front side polarizing plate and the back side polarizing plate has a retardation value in the thickness direction in the range of -10 to 10 nm. The liquid crystal display device according to claim 1 or 2, wherein the transparent protective film positioned on the liquid crystal cell side of each of the front side polarizing plate and the back side polarizing plate comprises a cellulose resin or a polyolefin resin. The liquid crystal display according to any one of claims 1 to 3, wherein the transparent protective film located on the side farther from the liquid crystal cell of the front polarizing plate is formed to have a thickness smaller than the total thickness of the transparent protective film positioned on the liquid crystal cell side and the first pressure- Having a large thickness,
Wherein the transparent protective film positioned on the side farther from the liquid crystal cell of the back side polarizing plate has a thickness larger than the total thickness of the transparent protective film positioned on the liquid crystal cell side and the second pressure sensitive adhesive layer adhered thereto. The polarizing film of claim 1 or 2, wherein the polarizing film of each of the front side polarizing plate and the back side polarizing plate and the transparent protective film disposed on both sides thereof are bonded via an aqueous adhesive containing a polyvinyl alcohol resin and a water-soluble epoxy resin And the liquid crystal display device is bonded. The polarizing plate according to claim 1 or 2, wherein the polarizing film of each of the front side polarizing plate and the rear side polarizing plate, and the transparent protective film disposed on both surfaces of the polarizing film are curable adhesive compositions containing an epoxy compound curable by irradiation of an active energy ray And the liquid crystal display device is bonded to the liquid crystal display device. The liquid crystal display device according to claim 6, wherein the epoxy compound comprises an epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.

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