JP2011248178A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device having a small warpage of a liquid crystal panel and showing little display irregularity even after being left to stand in a humid and hot environment.SOLUTION: The liquid crystal display device is manufactured by stacking a front polarizing plate 20 on a viewing side of a liquid crystal cell 10 with a first adhesive layer 41, stacking a back side polarizing plate 30 on the other side with a second adhesive layer 42, and disposing a backlight unit 60 outside the back side polarizing plate. The back side polarizing plate 30 has a layer structure of, from the backlight unit 60 side, a first transparent protective film 32/polarizing film 31/second transparent protective film 33/third adhesive layer 43/retardation film 35. The retardation film 35 has a three-layer structure comprising a core layer 36 made of a styrene resin and skin layers 37 made of an acrylic resin composition containing rubber particles, applied on both faces of the core layer 36. All of the first adhesive layer 41, the second adhesive layer 42 and the third adhesive layer 43 are configured to have storage moduli at 50°C of 0.01 MPa or more and 0.1 MPa or less.

Description

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

  In recent years, liquid crystal display devices have been rapidly used as information display devices such as mobile phones, personal digital assistants, computer monitors, and televisions by taking advantage of low power consumption, low voltage operation, light weight and thinness. It has become widespread. 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 are being solved. However, since a polarizing plate is used in the liquid crystal display device, when the liquid crystal panel is placed in a humid heat environment, the liquid crystal panel warps due to water absorption by the polarizing plate, and display unevenness occurs. Is a problem.

  Japanese Unexamined Patent Publication No. 2007-292966 (Patent Document 1) 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 sides of the liquid crystal cell. Has been. Japanese Patent Laid-Open No. 2003-50313 (Patent Document 2) uses a polarizing plate on which a pressure-sensitive adhesive layer exhibiting specific creep characteristics is used to improve the warpage of a liquid crystal panel in a humid heat environment. Has been proposed. However, in these improvements, it is necessary to subject the polarizing plate to a pretreatment such as a heat treatment, or the display unevenness due to the warp of the liquid crystal panel after being placed in a humid heat environment is insufficient.

  On the other hand, a retardation film having a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both surfaces of a core layer made of styrene resin, and gives negative intrinsic birefringence There is also an attempt to apply this to a liquid crystal display device in combination with a polarizing plate. For example, in JP 2009-258589 A (Patent Document 3), a transparent protective film is bonded to one surface of a polarizing film via an adhesive, and an adhesive layer is interposed to the other surface of the polarizing film. Then, a retardation film having a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is bonded to both surfaces of a core layer made of the above-mentioned styrene-based resin is bonded to a composite polarized light. It is described that it is a plate and this is applied to a liquid crystal display device. In Patent Document 3, a pressure-sensitive adhesive layer for laminating the above three-layer retardation film on a polarizing film is formed from a highly elastic pressure-sensitive adhesive having a storage elastic modulus of 0.1 MPa or more at a temperature of 80 ° C. This improves the durability against temperature changes.

JP 2007-292966 A JP 2003-050313 A JP 2009-258589 A

  An object of the present invention is to provide a liquid crystal display device in which the warp of the liquid crystal panel is small and display unevenness is small even after being placed in a humid heat environment. The inventors first laminated a transparent protective film on one surface of the polarizing film via an adhesive, and the other surface of the polarizing film has a biaxial position with a positive intrinsic birefringence via an adhesive. From the (meth) acrylic resin composition containing the rubber particles on both sides of the core layer made of the above-mentioned styrenic resin through the lamination of the phase difference film and the adhesive layer on the outside of the biaxial retardation film It was found that a composite polarizing plate formed by laminating a retardation film having a three-layer structure with a skin layer formed gives excellent viewing angle characteristics particularly for an IPS mode liquid crystal display device. As a patent application.

  As a result of further research, the composite polarizing plate proposed in Japanese Patent Application No. 2009-290785 was placed on the back side of the liquid crystal cell, and another polarizing plate was placed on the front side (viewing side) of the liquid crystal cell. , An adhesive layer for adhering the front side polarizing plate and the liquid crystal cell, an adhesive layer for adhering the rear side polarizing plate and the liquid crystal cell, and the biaxial retardation film in the back side polarizing plate and the above three-layer structure Adjusting the storage elastic modulus at 50 ° C for each pressure-sensitive adhesive layer for adhering the retardation film suppresses the warpage of the liquid crystal panel after being placed in a humid heat environment and improves display unevenness. As a result, the present invention has been completed.

  That is, according to the present invention, a liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween, and a front side polarizing plate laminated on the viewing side of the liquid crystal cell via the first adhesive layer A back side polarizing plate laminated via 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 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 via the first pressure-sensitive adhesive layer on one transparent protective film side. The back side polarizing plate includes a polarizing film, a first transparent protective film disposed on one surface of the polarizing film, a second transparent protective film disposed on the other surface of the polarizing film, On the second transparent protective film A retardation film laminated on the opposite side of the polarizing film via a third pressure-sensitive adhesive layer, and laminated on the liquid crystal cell via the second pressure-sensitive adhesive layer on the phase difference film side The retardation film has a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both surfaces of a core layer made of a styrene resin; and the first The pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the third pressure-sensitive adhesive layer all provide a liquid crystal display device having a storage elastic modulus at 50 ° C. in the range of 0.01 MPa to 0.1 MPa. .

  In the liquid crystal display device of the present invention, the transparent protective film located on the liquid crystal cell side of the front-side polarizing plate preferably has a thickness direction retardation in the range of −10 to 10 nm. Moreover, it is preferable to comprise the transparent protective film located in this liquid crystal cell side with a cellulose resin or polyolefin resin.

In these liquid crystal display devices, the second transparent protective film constituting the back-side polarizing plate, that is, the transparent protective film located between the polarizing film and the retardation film (and therefore closer to the liquid crystal cell than the polarizing film) , made of a polyolefin resin, there-plane retardation in a range of 30 to 150 nm, the in-plane slow axis direction, refractive index in the in-plane fast axis direction and a thickness direction, respectively n _x, n _y and n _z When the following formula (1):
_{Nz = (n x -n z)} / (n x -n y) (1)
The retardation film having a refractive index anisotropy in the range of Nz coefficient defined by 1 and less than 2 and constituting the back side polarizing plate has an in-plane retardation in the range of 20 to 120 nm. It is preferable that the Nz coefficient defined by the above formula (1) has a refractive index anisotropy in the range of more than −2 and less than −0.5. Note that the in-plane slow axis direction and the in-plane fast axis direction are orthogonal to each other in the plane.

  According to the present invention, it is possible to provide a liquid crystal display device in which the warp of the liquid crystal panel is small even after being placed in a moist heat environment, and thus display unevenness is small.

It is a cross-sectional schematic diagram which shows the layer structure of the liquid crystal display device which concerns on this invention.

  Referring to FIG. 1, the liquid crystal display device of the present invention includes a liquid crystal cell 10, a front-side polarizing plate 20 laminated on the viewing side of the liquid crystal cell via a first adhesive layer 41, and the viewing of the liquid crystal cell. Back side polarizing plate 30 laminated on the opposite side to the second adhesive layer 42, and a backlight disposed outside the back side polarizing plate (that is, opposite to the liquid crystal cell 10) A unit 60 is provided. The liquid crystal cell 10, the front polarizing plate 20 laminated on the viewing side of the liquid crystal cell via the first adhesive layer 41, and the second adhesive layer 42 on the opposite side of the liquid crystal cell were laminated. A liquid crystal panel 50 is formed with the back side polarizing plate 30.

  The front-side 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 surfaces via an adhesive (not shown). ing. The back-side polarizing plate 30 disposed on the side opposite to the viewing side of the liquid crystal cell 10 (that is, the backlight unit 60 side) is a polarizing film 31 and one surface thereof (surface far from the liquid crystal cell). A first transparent protective film 32 laminated via an adhesive (not shown); a second transparent protective film 33 laminated via an adhesive (not shown) on the other surface of the polarizing film; Further, a retardation film 35 is laminated on the liquid crystal cell side of the second transparent protective film 33 via a third pressure-sensitive adhesive layer 43. The retardation film 35 has a three-layer structure in which skin layers 37 and 37 made of a (meth) acrylic resin composition containing rubber particles are formed on both surfaces of a core layer 36 made of a styrene resin. .

  A liquid crystal display device is configured by combining the liquid crystal panel 50 and the backlight unit 60. When the liquid crystal display device is placed in a humid heat environment, the liquid crystal panel 50 warps, and a part of the liquid crystal panel 50 is formed. However, the display unit may become abnormally close to the backlight unit 60 or may come into contact in an extreme case, resulting in display unevenness. In addition, the liquid crystal panel 50 is fixed with a housing or a metal frame so as not to fall down on the viewing side. When the liquid crystal display device is placed in a humid heat environment, the liquid crystal panel 50 is warped, and the liquid crystal panel 50. Some of them contacted the case or the metal frame which fixed it, and the display nonuniformity might be caused.

Therefore, in the present invention, a first pressure-sensitive adhesive layer 41 for bonding the front-side polarizing plate 20 to the liquid crystal cell 10, a second pressure-sensitive adhesive layer 42 for bonding the back-side polarizing plate 30 to the liquid crystal cell 10, and All of the third pressure-sensitive adhesive layer 43 for bonding the transparent protective film 33 and the retardation film 35 constituting the back-side polarizing plate 30 have a storage elastic modulus G ′ at 50 ° C. of 0.01 MPa or more and 0.1 MPa or less. It is composed of a relatively soft material within the range. This relationship indicates that the storage elastic modulus of the first pressure-sensitive adhesive layer 41 at 50 ° C. is G ₁ ′, the storage elastic modulus of the second pressure-sensitive adhesive layer 42 at 50 ° C. is G ₂ ′, and the third pressure-sensitive adhesive layer 43. the storage modulus at a 50 ° C. as a G ₃ ', corresponds to all of the following equation (2) to (4).

0.01 MPa ≦ G ₁ ′ ≦ 0.1 MPa (2)
0.01 MPa ≦ G ₂ ′ ≦ 0.1 MPa (3)
0.01 MPa ≦ G ₃ ′ ≦ 0.1 MPa (4)

  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 includes two cell substrates 11 and 12 and a liquid crystal layer 15 sandwiched between the substrates. The cell substrates 11 and 12 are generally often made of glass, but 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 types employed in this field.

[Polarized film]
The polarizing films 21 and 31 constituting the front-side polarizing plate 20 and the rear-side polarizing plate 30 are usually formed by uniaxially stretching a polyvinyl alcohol-based resin film, by dyeing the polyvinyl alcohol-based resin film with a dichroic dye. It is manufactured through a step of adsorbing a chromatic dye, a step of treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with an aqueous boric acid solution.

  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 another monomer 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 resin is usually about 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 aldehydes can be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The film thickness of the polyvinyl alcohol resin raw film is, for example, about 10 to 150 μm, preferably about 10 to 100 μm.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can also be performed in a plurality of stages shown here. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. Uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. 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. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, 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 immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually 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. This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic organic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, 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 performed by a method of immersing the dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution 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, the boric acid-containing aqueous solution preferably 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 immersion 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 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of 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 ° C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to a practical level. The moisture content 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 polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

  As described above, a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced. The resulting polarizing film can have a thickness of, for example, about 5 to 40 μm.

[Transparent protective film located far from the liquid crystal cell]
In each of the front side polarizing plate 20 and the back side polarizing plate 30, the transparent protective films 22 and 32 positioned on the side far from the liquid crystal cell 10 are materials excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. Preferably it consists of. As such a material, for example, an acrylic resin having a methyl methacrylate resin as a representative example, a chain polyolefin resin having a polypropylene resin as a representative example, a cyclic polyolefin resin, a cellulose resin, and 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 resin Examples include resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polysulfone resins, polyether sulfone resins, polyarylate resins, polyamideimide resins, polyimide resins, and the like.

  These resins can be used alone or in combination of two or more. Moreover, resin which performed arbitrary polymer modification | denaturation with respect to these resin can also be used as the material for transparent protective films. Examples of the polymer modification include copolymerization, crosslinking, molecular terminal modification, stereoregularity control, and mixing including a case involving a reaction between different polymers.

  Among the above resins, a methyl methacrylate resin, a polypropylene resin, a cellulose resin, or a polyethylene terephthalate resin is preferably used as a material for the transparent protective films 22 and 32 located on the side far 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 methyl methacrylate units is preferably 70% by weight or more, and may be 100% by weight. A polymer having a methyl methacrylate unit of 100% by weight is obtained by polymerizing methyl methacrylate alone.

  The methyl methacrylate-based resin can be usually obtained by polymerizing a monofunctional monomer mainly composed of methyl methacrylate in the presence of a radical polymerization initiator and a chain transfer agent. A component that can be copolymerized with methyl methacrylate may be blended in the monofunctional monomer and copolymerized, and a small amount of the polyfunctional monomer may be copolymerized if desired.

  Monofunctional monomers that can be copolymerized with methyl methacrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxy methacrylate. Methacrylic acid esters other than methyl methacrylate such as ethyl; acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, and 2-ethylhexyl acrylate Hydroxyacrylates such as hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate Unsaturated alkyl acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; acrylonitrile; Examples thereof include unsaturated nitriles such as methacrylonitrile; unsaturated anhydrides such as maleic anhydride and citraconic anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. These monomers may be used alone or in combination of two or more.

  Examples of polyfunctional monomers that can be copolymerized with methyl methacrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth). Acrylate or ester of both end hydroxyl groups of ethylene glycol or its oligomer, such as acrylate; Propylene glycol or its oligomer end of hydroxyl groups esterified with acrylic or methacrylic acid; Neopentyl glycol A dihydric alcohol esterified with acrylic acid or methacrylic acid, such as di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di (meth) acrylate; Phenol A, alkylene oxide adducts of bisphenol A, or those obtained by esterifying the hydroxyl groups at both ends with acrylic acid or methacrylic acid; trimethylolpropane, and polyhydric alcohols such as pentaerythritol with acrylic acid or Those esterified with methacrylic acid; those obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl group of a compound having two or more hydroxyl groups; succinic acid, adipic acid, terephthalic acid, phthalic acid, and these Dibasic acids such as halogen-substituted products, or these alkylene oxide adducts obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate; allyl (meth) acrylate; And aromatic divinyl compounds. When copolymerizing a polyfunctional monomer, among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

  A resin modified by conducting a reaction between functional groups of a methyl methacrylate resin can also be used. Examples of such a reaction between functional groups include, for example, demethanol condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, and a carboxyl group of acrylic acid and 2 Examples thereof include a dehydration condensation reaction within a polymer chain with a hydroxyl group of methyl (hydroxymethyl) acrylate.

  A commercially available product can be easily obtained for the methyl methacrylate resin. Examples of commercial products are “Sumipex” sold by Sumitomo Chemical Co., Ltd., “Acrypet” sold by Mitsubishi Rayon Co., Ltd., and Asahi Kasei Co., Ltd. "Delpet", "Parapet" sold by Kuraray Co., Ltd., and "Acryviewer" sold by Nippon Shokubai Co., Ltd.

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

  When a copolymer containing propylene as a main component is used, the comonomer copolymerizable with propylene is preferably ethylene, 1-butene, or 1-hexene. Especially, since the polypropylene resin which is comparatively excellent in transparency is obtained, what copolymerized ethylene in the ratio of 1-20 weight%, preferably 3-10 weight% is preferable. By setting the copolymerization ratio of ethylene to 1% by weight or more, an effect of increasing transparency appears. 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 a component soluble in xylene at 20 ° C. (CXS component: CXS is an abbreviation of cold xylene soluble) is preferably 1% by weight or less and preferably 0.5% by weight or less. More preferred. Among the polypropylene-based resins, a propylene homopolymer having a CXS component of 1% by weight or less, and further 0.5% by weight or less is one suitable example.

  As the polypropylene resin, a commercially available product can be easily obtained. Examples of commercial products are “Prime Polypro” sold by Prime Polymer Co., Ltd., “Novatech” and “Wintech” sold by Nippon Polypro Co., Ltd., Sumitomo Chemical Co., Ltd. "Sumitomo Noblen" sold by the company, "San Aroma" sold by Sun Allomer.

  The cellulose resin may be an organic acid ester or mixed organic acid ester of cellulose in which part or all of the hydrogen atoms in the hydroxyl group of cellulose are substituted with an acetyl group, a propionyl group, and / or a butyryl group. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Of these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

  Polyethylene terephthalate resin is a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain other dicarboxylic acid components and / or other diol components. Examples of other dicarboxylic acid components include isophthalic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 1,4 -Dicarboxycyclohexane etc. are mentioned. Examples of other diol components include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  These other dicarboxylic acid components and other diol components can be used in combination of two or more if necessary. Hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid can also be used in combination. As other copolymer components, dicarboxylic acid components or diol components containing a small amount of amide bond, urethane bond, ether bond, carbonate bond, etc. can also be used.

  Polyethylene terephthalate resin can be produced by directly polycondensing terephthalic acid and ethylene glycol (and other dicarboxylic acids or other diols as required), dialkyl esters of terephthalic acid and ethylene glycol (and as required) A method of polycondensation of a dialkyl ester of another dicarboxylic acid or other diol) while performing an ester exchange reaction, an ethylene glycol ester of terephthalic acid (and other dicarboxylic acid if necessary) (and other diol if necessary) For example, a method in which an ester) is polycondensed in the presence of a catalyst is employed. Furthermore, if necessary, additional solid phase polymerization can be performed to increase the molecular weight or reduce the low molecular weight components.

  As a method for forming the resin as described above on the transparent protective film for the polarizing plate, a method corresponding to each resin may be appropriately selected. For example, a solvent cast method in which a resin dissolved in a solvent is cast on a metal band or drum, and the solvent is removed by drying to obtain a film. The resin is heated above its melting temperature, kneaded and extruded from a die. A melt extrusion method for obtaining a film by cooling can be used. In the melt extrusion method, a single layer film can be extruded or a multilayer film can be coextruded.

  Commercially available products of these resin films can be easily obtained. Examples of commercially available films include methyl methacrylate resin films, each with the trade name “Technoloy” sold by Sumitomo Chemical Co., Ltd. and “Acrylic” sold by Mitsubishi Rayon Co., Ltd. "Light" and "Acryprene", "Delagrass" sold by Asahi Kasei Co., Ltd., "Paragrass" and "Comogras" sold by Kuraray Co., Ltd., and "Acryviewer" sold by Nippon Shokubai and so on. For polyethylene terephthalate resin films, there are “Novaclear” sold by Mitsubishi Chemical Co., Ltd. and “A-PET sheet” sold by Teijin Chemicals Ltd., respectively. For polypropylene resin films, “FILMAX CPP film” sold by FILMAX, “Santox” sold by Sun Tox Co., Ltd. "Tosero", "Toyobo Pyrene Film" sold by Toyobo Co., Ltd., "Trephan" sold by Toray Film Processing Co., Ltd., "Nihon Polyace" sold by Nippon Polyace Co., Ltd. "Dazai FC" sold by Futamura Chemical Co., Ltd. Cellulosic resin films include “Fujitac TD” sold by Fuji Film Co., Ltd. and “Konica Minolta TAC Film KC” sold by Konica Minolta Opto Co., Ltd.

  The transparent protective film 22 disposed on the side far from the liquid crystal cell 10 and serving as the viewing side can be imparted with haze to exhibit antiglare 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, a resin mixed with fine particles by multilayer extrusion, and fine particles are mixed. A method of forming a two-layer film from a resin that has not been mixed, or forming a three-layer film by using a resin in which fine particles are mixed as an outer layer, a coating in which inorganic fine particles or organic fine particles are mixed with a curable binder resin on one side of the film A method of coating the liquid and curing the binder resin to provide an antiglare layer is employed.

  Examples of inorganic fine particles used for imparting haze include silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate, and the like. 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, the haze value is preferably in the range of 6 to 45%. When the haze value of the transparent protective film is less than 6%, a sufficient antiglare effect may not appear. 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 be whitened, resulting in a reduction in image quality. Haze is a value defined as the ratio of diffuse transmittance to total light transmittance, and can be measured using a commercially available haze meter in accordance with JIS K 7136. An example of a commercially available haze meter is “HM-150” sold by Murakami Color Research Laboratory. In measuring the haze value, in order to prevent warping of the film, for example, an optically transparent adhesive is used, and a measurement sample in which the film surface is bonded to a glass substrate so that the antiglare surface is the surface is used. Is preferred.

  A functional layer that is disposed on the side far from the liquid crystal cell and includes a conductive layer, a hard coat layer, a low reflection layer, and the like on the outer side of the transparent protective film 22 on the viewing side and the transparent protective film 32 on the backlight side Can be provided. As the coating liquid containing the binder resin constituting the antiglare layer, a resin composition capable of expressing these functions can also be selected.

[Transparent protective film located on the liquid crystal cell side]
In the front-side polarizing plate 20 and the back-side polarizing plate 30 shown in FIG. 1, the resin material constituting the transparent protective films 23 and 33 located closer to the liquid crystal cell 10 than the polarizing films 21 and 31 is the liquid crystal cell. The same thing as having described the transparent protective films 22 and 32 located in the side far from 10 can be used. Among these, since the retardation value is easily controlled and easily available, a cellulose resin or a polyolefin resin including a chain polyolefin resin or a cyclic polyolefin resin is preferably used.

  The cyclic polyolefin resin here 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. It is. When such a cyclic polyolefin-based resin is used, a transparent protective film having a predetermined retardation value described later can be easily obtained. Norbornene is a compound in which one carbon-carbon bond of norbornane is a double bond, and it is named bicyclo [2,2,1] hept-2-ene according to the IUPAC nomenclature. As examples of norbornene derivatives, there are 3-substituted, 4-substituted, 4,5-disubstituted, etc., where the double bond position of norbornene is 1,2-position. Furthermore, dicyclopentadiene, dimethanooctahydronaphthalene, and the like can also be used as monomers constituting the cyclic polyolefin resin.

  The cyclic polyolefin-based resin may or may not have a norbornane ring in its structural unit. Examples of the norbornene-based monomer that forms a cyclic polyolefin-based resin having no norbornane ring as a structural unit include, for example, those that become a 5-membered ring by ring opening, typically norbornene, dicyclopentadiene, 1- or 4- Examples thereof include methyl norbornene and 4-phenyl norbornene. When the cyclic polyolefin resin is a copolymer, the arrangement state of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. It may be a polymer.

  Examples of the cyclic polyolefin resin include ring-opening metathesis polymerization using cyclopentadiene and olefins or (meth) acrylic acid or esters thereof as a monomer with norbornene or a derivative thereof obtained by Diels-Alder reaction. Resin obtained by addition; ring-opening metathesis polymerization from dicyclopentadiene and olefins or (meth) acrylic acid or esters thereof by tetracyclododecene or its derivative obtained by Diels-Alder reaction, followed by Resin obtained by hydrogenation; at least two monomers selected from norbornene, tetracyclododecene, their derivatives, and other cyclic olefin monomers are similarly copolymerized by ring-opening metathesis, followed by Resins obtained by hydrogenation; resins obtained by addition copolymerization of aromatic compounds having chain olefins and / or vinyl groups with cyclic olefins such as norbornene, tetracyclododecene, or derivatives thereof It is done.

  As the cyclic polyolefin-based resin, a commercially available product can be easily obtained. Examples of commercial products are “TOPAS” produced by TOPAS ADVANCED POLYMERS GmbH under the trade name, and sold in Japan by Polyplastics Co., Ltd. “Arton” from JSR Co., Ltd. "Zeonor" and "Zeonex" sold by Nippon Zeon Co., Ltd., and "Appel" sold by Mitsui Chemicals. These cyclic polyolefin-based resin films and stretched films thereof are also commercially available. For example, they are all sold under the trade name “ZEONOR FILM” sold by Nippon Zeon Co., Ltd., and JSR Corp. There are “Arton Film” and “Essina” sold by Sekisui Chemical Co., Ltd.

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

  As a method for forming a film from a cellulose resin, a polyolefin resin, or the like, a method corresponding to each resin may be selected as appropriate. For example, a solvent cast method in which a resin dissolved in a solvent is cast on a metal band or drum, and the solvent is removed by drying to obtain a film. The resin is heated above its melting temperature, kneaded and extruded from a die. A melt extrusion method for obtaining a film by cooling with a cooling drum can be used. Among these, for the polyolefin-based resin, the melt extrusion method is preferably employed from the viewpoint of productivity. On the other hand, a cellulose resin is generally formed into a film by a solvent casting method.

  When the liquid crystal cell 10 is in an in-plane switching (IPS) mode, the liquid crystal cell 10 is positioned on the liquid crystal cell 10 side of the front-side polarizing plate 20 so as not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. The transparent protective film 23 preferably has a thickness direction retardation Rth 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 in-plane average refractive index, and is represented by the following formula (5). The in-plane retardation Re is a value obtained by multiplying the in-plane refractive index difference by the film thickness, and is represented by the following formula (6). From these relationships, the Nz coefficient previously defined in equation (1) can also be expressed as in equation (7) below.

Rth = _{[(n x + n y) /} 2-n z ] × d (5)
_{Re = (n x -n y)} × d (6)
Nz = Rth / Re + 0.5 (7)

Wherein, n _x, n _y and n _z is a as defined above, n _x is a refractive index in the in-plane slow axis direction, n _y is slow in-plane fast axis direction (in-plane the refractive index of the direction) perpendicular to the axis, n _z is a 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 used as a standard. Thickness direction retardation Rth and in-plane retardation Re can be measured using various commercially available phase difference meters.

  Examples of a method for controlling the thickness direction retardation Rth of the resin film within a range of −10 to 10 nm include a method for minimizing distortion remaining in the thickness direction when the film is produced. For example, in the above-described solvent casting method, a method of relaxing residual shrinkage strain in the thickness direction generated when the cast resin solution is dried by heat treatment can be employed. On the other hand, in the melt extrusion method described above, the distance from the die to the cooling drum is reduced as much as possible in order to prevent the resin film from being extruded from the die and cooled, and the extrusion amount and the rotation of the cooling drum are also reduced. A method of controlling the speed so that the film is not stretched can be adopted. Moreover, the method of relieving the distortion which remains in the obtained film by heat processing similarly to the solvent casting method is also employable.

[Transparent protective film 33 positioned closer to the liquid crystal cell than the polarizing film of the back side polarizing plate]
In the back side polarizing plate 30 used by this invention, it is preferable that the transparent protective film 33 located in the side near the liquid crystal cell 10 from the polarizing film 31 consists of polyolefin resin. Here, the polyolefin resin is a resin composed of a structural unit derived from a chain olefin such as ethylene or propylene, or an alicyclic olefin such as norbornene or other cyclopentadiene derivatives, as described above. is there. The polyolefin resin may be a copolymer using two or more kinds of monomers. For the cyclic polyolefin resin and the chain polyolefin resin, which are examples of the polyolefin resin, the same explanation as in the section of [Transparent protective film located on the liquid crystal cell side] applies. Among these, as the polyolefin-based resin, a cyclic polyolefin-based resin that is a resin mainly containing a structural unit derived from an alicyclic olefin is preferably used.

  The transparent protective film 33 may be a film made of a mixed resin containing two or more kinds of polyolefin resins, or a film made of a mixed resin of a polyolefin resin and another thermoplastic resin. For example, examples of the mixed resin containing two or more types of polyolefin resins include a mixture of the cyclic polyolefin resin and the chain polyolefin resin as described above. When using a mixed resin of a polyolefin-based resin and another thermoplastic resin, an appropriate one is appropriately selected as the other thermoplastic resin according to the purpose. Specific examples include polyvinyl chloride resin, cellulose resin, polystyrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, (meth) acrylic resin, polyvinyl acetate resin, polyvinyl chloride. Vinylidene resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyether Examples include ether ketone resins, polyarylate resins, liquid crystalline resins, polyamideimide resins, polyimide resins, and polytetrafluoroethylene resins. These thermoplastic resins can 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 and preferably about 40% by weight or less based on the entire resin. By setting the content of other thermoplastic resins within this range, a film having a small absolute value of the photoelastic coefficient, good wavelength dispersion characteristics, and excellent durability, mechanical strength, and transparency is obtained. be able to.

  A film comprising a polyolefin-based resin contains other components such as residual solvent, stabilizer, plasticizer, anti-aging agent, antistatic agent, and ultraviolet absorber as necessary, as long as the object of the present invention is not impaired. It may be. Moreover, a leveling agent can be contained in order to reduce the surface roughness.

The transparent protective film 33 constituting the back-side polarizing plate 30 is made of the above-described polyolefin-based resin, and has an in-plane retardation Re in the range of 30 to 150 nm. The Nz coefficient defined by the above formula (1) Preferably has a refractive index anisotropy in the range of more than 1 and less than 2. The Nz coefficient having a refractive index anisotropy in the range of more than 1 and less than 2 is represented by the following formula (8)
_{1 <(n x -n z)} / (n x -n y) <2 (8)
Means satisfying.

  The polyolefin resin film having refractive index anisotropy as described above can be obtained by known longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, etc., and a desired retardation value. In addition to appropriately adjusting the stretching ratio and the stretching speed so as to obtain a temperature, various temperatures such as a preheating temperature during stretching, a stretching temperature, a heat setting temperature, a cooling temperature, and the pattern may be appropriately selected.

  The stretched polyolefin resin film used as the transparent protective film 33 preferably has a thickness in the range of 20 to 80 μm, and more preferably in the range of 40 to 80 μm. When the thickness of the film is less than 20 μm, it is difficult to handle the film, and the predetermined retardation value tends to be difficult to develop. On the other hand, when the thickness exceeds 80 μm, the workability In addition, the transparency may be lowered, or the weight of the obtained polarizing plate may be increased.

[Adhesion between polarizing film and protective film]
Usually, an adhesive is used for joining the polarizing film 21 and the transparent protective films 22 and 23 in the front polarizing plate 20 and joining the polarizing film 31 and the transparent protective films 32 and 33 in the rear polarizing plate 30. . The adhesive layer for joining the polarizing film and the transparent protective film can have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.03 to 5 μm. If the thickness of the adhesive layer is within this range, the adhesive layer having no practical problem can be obtained without floating or peeling between the transparent protective film and the polarizing film to be laminated.

  In forming the adhesive layer, an appropriate adhesive can be used as appropriate according to the type and purpose of the adherend, and an anchor coating agent can be used as necessary. Examples of the adhesive include a solvent-type adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet-adhesive, a polycondensation-type adhesive, a solventless-type adhesive, a film-type adhesive, and a hot-melt-type adhesive. Can be mentioned.

  One preferred adhesive is an aqueous adhesive, that is, an adhesive component in which the adhesive component is dissolved or dispersed in water. Examples of adhesive components that can be dissolved in water include polyvinyl alcohol resins. An example of an adhesive component that can be dispersed in water is a urethane resin having a hydrophilic group. The water-based adhesive can be prepared by mixing such an adhesive component with water together with an additional additive added as necessary. Examples of commercially available polyvinyl alcohol resins that can be used as water-based adhesives include “KL-318” (trade name), which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

  The water-based adhesive can contain a crosslinking agent as necessary. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts. When a polyvinyl alcohol resin is used as an adhesive component, an aldehyde compound such as glyoxal, a methylol compound such as methylol melamine, a water-soluble epoxy resin, or the like is preferably used as a crosslinking agent. Here, the water-soluble epoxy resin is, for example, a polyamide obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. It can be an epoxy resin. Examples of commercially available water-soluble epoxy resins include “Smiles Resin 650 (30)” (trade name) sold by Sumika Chemtex Co., Ltd.

  A polarizing plate can be obtained by applying a water-based adhesive on the adhesive surface of the polarizing film and / or the transparent protective film, bonding them together, and then subjecting them to a drying treatment. Prior to adhesion, it is also effective to give the transparent protective film an easy adhesion treatment such as a saponification treatment, a corona discharge treatment, or a plasma treatment to enhance wettability. A drying temperature can be about 60-100 degreeC, for example. After the drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days is preferable for further enhancing the adhesive force.

  Another preferred adhesive is a curable adhesive composition containing an epoxy compound that is cured by irradiation with active energy rays or heating. Here, the curable epoxy compound has at least two epoxy groups in the molecule. In this case, the adhesion between the polarizing film and the transparent protective film is performed by irradiating an active energy ray to the coating layer of the adhesive composition or heating it to apply a curable epoxy compound contained in the adhesive. It can be carried out by a curing method. Curing of the epoxy compound is generally performed by cationic polymerization of the epoxy compound. Further, from the viewpoint of productivity, this curing is preferably performed by irradiation with active energy rays.

  From the viewpoint of weather resistance, refractive index, cationic polymerizability, etc., the epoxy compound contained in the curable adhesive composition is preferably one that does not contain an aromatic ring in the molecule. Examples of epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. The epoxy compound suitably 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 is also described here.

  The hydrogenated epoxy compound is a glycidyl compound obtained by subjecting an aromatic polyhydroxy compound, which is a raw material of an aromatic epoxy compound, to a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction in the presence of a catalyst and under pressure. It can be etherified. Examples of the aromatic polyhydroxy compound that is a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenol novolac resins, cresol novolac resins, and hydroxybenzaldehyde phenol novolac resins. And novolak type resins; polyhydroxy compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. A glycidyl ether can be obtained by performing a nuclear hydrogenation reaction on such an aromatic polyhydroxy compound and reacting the resulting hydrogenated polyhydroxy compound with epichlorohydrin. Suitable hydrogenated epoxy compounds include hydrogenated glycidyl ether of bisphenol A.

  An 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 bridged oxygen atom —O— in the structure represented by the following formula, and 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 removed and bonded to another chemical structure can be an alicyclic epoxy compound. Further, one or more hydrogen atoms in (CH ₂ ) _m forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m = 3 in the above formula) or an oxabicycloheptane ring (m = 4 in the above formula) has excellent adhesion. It is preferably used from the indication. Specific examples of the alicyclic epoxy compound are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
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-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] henicosane,
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 can 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; ethylene Polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol such as glycol, propylene glycol, and glycerin Can be mentioned.

  In the curable adhesive composition, the epoxy compound may be used alone or in combination of two or more. Among these, the epoxy compound preferably includes an alicyclic epoxy compound having at least one epoxy group bonded to the 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 this 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 exceeding 3,000 g / equivalent, compatibility with other components contained in the adhesive composition may be lowered.

  From the viewpoint of reactivity, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For that purpose, it is preferable to mix | blend a cationic polymerization initiator with the curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction. From the viewpoint of workability, it is preferable that the cationic polymerization initiator is provided with latency. Hereinafter, a cationic polymerization initiator that generates a cationic species or Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”, and generates a cationic species or a Lewis acid by heat. The cationic polymerization initiator that initiates the polymerization reaction of the epoxy group is referred to as “thermal cationic polymerization initiator”.

  The method of curing the adhesive composition by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at room temperature, reducing the need to consider the heat resistance of the polarizing film or distortion due to expansion, This is advantageous in that the transparent protective film and the polarizing film can be favorably bonded. In addition, since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.

  Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less. When the blending amount of the cationic photopolymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy compound, curing becomes insufficient, and the mechanical strength and adhesive strength of the cured product tend to decrease. On the other hand, when the blending amount of the cationic photopolymerization initiator exceeds 20 parts by weight with respect to 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, resulting in an increase in the hygroscopic property of the cured product and durability performance. May be reduced.

  When using a photocationic polymerization initiator, the curable adhesive composition may further contain a photosensitizer as necessary. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. When mix | blending a photosensitizer, it is preferable to make the quantity into the range of 0.1-20 weight part with respect to 100 weight part of curable adhesive compositions.

  On the other hand, examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide.

  The curable adhesive composition containing the epoxy compound is preferably cured by photocationic polymerization as described above, but can be cured by thermal cationic polymerization in the presence of the above-mentioned thermal cationic polymerization initiator. Cationic polymerization and thermal cationic polymerization can be used in combination. When photocationic polymerization and thermal cationic polymerization are used in combination, the curable adhesive composition preferably contains both a photocationic polymerization initiator and a thermal cationic polymerization initiator.

  The curable adhesive composition may further contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound. An oxetane compound is a compound having a 4-membered ring ether in the molecule. When mix | blending an oxetane compound, the quantity is 5 to 95 weight% normally in a curable adhesive composition, Preferably it is 5 to 50 weight%. The polyol compound may be alkylene glycol including ethylene glycol, hexamethylene glycol, polyethylene glycol or the like, or an oligomer thereof, polyester polyol, polycaprolactone polyol, polycarbonate polyol and the like. When a polyol compound is blended, the 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 have other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, as long as the adhesiveness is not impaired. Agents, flow modifiers, plasticizers, antifoaming agents, and the like. Examples of the ion trapping agent include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Examples of the antioxidant include And hindered phenolic antioxidants.

  After applying the curable adhesive composition containing the epoxy compound to the adhesive surface of the polarizing film or the transparent protective film, or to the adhesive surface of both of them, it is bonded to the adhesive-coated surface and activated energy. The polarizing film and the transparent protective film can be bonded by curing the uncured adhesive layer by irradiating the wire or heating. As an adhesive coating method, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.

  This curable adhesive composition can basically be used as a solvent-free adhesive that does not substantially contain a solvent, but each coating system has an optimum viscosity range, so that the viscosity is adjusted. For this purpose, a solvent may be contained. The solvent is preferably an organic solvent that dissolves each component including an epoxy compound well without degrading the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, etc. Esters can be used.

  When the adhesive composition is cured by irradiation with active energy rays, the above-mentioned various types of active energy rays can be used, but since the handling is easy and the amount of irradiation light is easy to control, ultraviolet rays are not emitted. Preferably used. Active energy rays such as ultraviolet irradiation intensity and dose do not affect various optical performance including polarization degree of polarizing film, and various optical performance including transparency and retardation characteristics of transparent protective film. Within a range, it is determined as appropriate so that moderate productivity is maintained.

  When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator compounded in the curable adhesive composition generates cationic species and Lewis acid, 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 core layer 36 made of a styrene resin, and a skin layer made of a (meth) acrylic resin composition containing rubber particles on both sides thereof. 37, 37 are formed.

  The styrenic resin constituting the core layer 36 may be a homopolymer of styrene or a derivative thereof, or may be a binary or higher copolymer of styrene or a derivative thereof and another copolymerizable monomer. There can also be. Here, the styrene derivative is a compound in which another group is bonded to styrene, such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, Alkyl styrene such as p-ethyl styrene, hydroxy styrene, tert-butoxy styrene, vinyl benzoic acid, o-chloro styrene, p-chloro styrene, benzene nucleus of styrene, hydroxyl group, alkoxy group, carboxyl group, And substituted styrene introduced with a group such as halogen. A terpolymer as disclosed in JP-A-2003-50316 or JP-A-2003-207640 can also be used. The styrene resin is preferably a copolymer of styrene or a styrene derivative and at least one monomer selected from acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. The styrenic resin constituting the core layer 36 is preferably heat-resistant, and generally has a glass transition temperature (referred to as “Tg”) of 100 ° C. or higher. A more preferable Tg of the styrene resin is 120 ° C. or more.

  The core layer 36 made of styrene resin is desirably set so that its thickness is 10 to 100 μm. When the thickness is less than 10 μm, a sufficient retardation value may not easily be exhibited by stretching. On the other hand, if the thickness exceeds 100 μm, the impact strength of the film tends to be weak and the retardation change due to external stress tends to increase, and white spots are likely to occur when applied to a liquid crystal display device. , Display performance is likely to deteriorate.

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

  The rubber particles blended in the (meth) acrylic resin are preferably acrylic. Acrylic rubber particles are particles having rubber elasticity obtained by polymerizing in the presence of a polyfunctional monomer mainly composed of an alkyl acrylate ester such as butyl acrylate or 2-ethylhexyl acrylate. Such rubber elastic particles 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 multilayer structure, particles having rubber elasticity as described above are used as cores, and the periphery thereof is covered with a hard alkyl methacrylate ester polymer, or a hard alkyl methacrylate ester polymer. The core is covered with an acrylic polymer having rubber elasticity as described above, and the hard core is covered with an acrylic polymer having rubber elasticity, and the periphery is further covered with a hard methacrylic polymer. Examples thereof include those covered with an acid alkyl ester polymer. These rubber particles generally 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. Since the (meth) acrylic resin and acrylic rubber particles are commercially available in a state where they are mixed, commercially available products thereof can be used. Examples of commercially available (meth) acrylic resins containing acrylic rubber particles include “HT55X” and “Technoloy S001” sold by Sumitomo Chemical Co., Ltd. Such a (meth) acrylic resin composition generally has a Tg of 160 ° C. or lower, but a preferable Tg is 120 ° C. or lower, and further 110 ° C. or lower.

  The skin layers 37 and 37 made of a (meth) acrylic resin composition containing rubber particles, preferably acrylic rubber particles, are desirably 10 to 100 μm in thickness. If the thickness is less than 10 μm, film formation tends to be difficult. On the other hand, if the thickness exceeds 100 μm, 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 made of a styrene resin preferably has a Tg of 120 ° C. or higher, while a (meth) acrylic resin in which rubber particles are blended. The skin layer 37 made of the composition preferably has a Tg of 120 ° C. or lower, more preferably 110 ° C. or lower. It is preferable that the core layers 36 made of styrene resin have a higher Tg than the skin layer 37 made of (meth) acrylic resin composition containing rubber particles, so that the Tg of both does not overlap. .

  In order to manufacture the retardation film 35 used in the present invention, for example, a film having a three-layer structure is formed by coextrusion of a styrene resin and a (meth) acrylic resin composition containing rubber particles. And then stretching. In addition, after each single-layer film is produced, heat fusion can be performed by heat lamination and the film can be stretched.

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

  The retardation film 35 configured as described above is given in-plane retardation by stretching. Stretching can be performed by known longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, and the like, and may be performed so as to obtain a desired retardation value.

In the retardation film 35 used in the present invention, the in-plane retardation Re is in the range of 20 to 120 nm, and the Nz coefficient defined by the formula (1) is in the range of more than −2 and less than −0.5. It preferably has refractive index anisotropy. The refractive index anisotropy in which the Nz coefficient exceeds −2 and is less than −0.5 is expressed by the following formula (9):
_{-2 <(n x -n z)} / (n x -n y) <- 0.5 (9)
Means satisfying.

[Manufacture of back side polarizing plate]
The back side polarizing plate 30 is configured by laminating a retardation film 35 on the surface of the transparent protective film 33 via a 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 first formed on the surface of the transparent protective film 33 or the retardation film 35. Such a pressure-sensitive adhesive layer can be formed by a method of applying a pressure-sensitive adhesive solution mainly composed of the base polymer as described above to the transparent protective film 33 or the retardation film 35 and drying the support, and a support subjected to a release treatment. A method in which a pressure-sensitive adhesive layer is formed on a release treatment surface of a film (separator) (adhesive with a separator) is prepared, and this is bonded to the surface of the transparent protective film 33 or the retardation film 35 on the pressure-sensitive adhesive layer side. Can also be formed. 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 35 or the retardation film 35 may be employed. it can. A separator made of a resin film that has been treated with a release agent such as silicone may be laminated on the pressure-sensitive adhesive layer thus formed.

  Furthermore, when forming an adhesive layer on the surface of the transparent protective film 33 or the retardation film 35, adhesiveness is improved on the adhesive layer formation surface of the transparent protective film 33 or the retardation film 35 as needed. For example, a corona treatment may be performed, and the same process may be performed on the surface of the adhesive layer bonded to the transparent protective film 33 or the retardation film 35.

  The pasting of the transparent protective film 33 and the retardation film 35 is performed by a conventionally known technique. For example, the retardation phase of the retardation film is delayed with respect to the polarization transmission axis of the polarizing film using a pasting roll or the like. It is performed by a method of laminating so that the axes are orthogonal or parallel, or a method of laminating so that the slow axis of the retardation film is at a predetermined angle with respect to the polarization transmission axis of the polarizing film.

[Adhesive layer]
The first pressure-sensitive adhesive layer 41 is laminated on the transparent protective film 23 on the liquid crystal cell side of the front polarizing plate 20 described above, and the retardation film 35 on the liquid crystal cell side of the rear polarizing plate 30. A second pressure-sensitive adhesive layer 42 is laminated on the top. Furthermore, the transparent protective film 33 and the phase difference film 35 which comprise the back side polarizing plate 30 are stuck through the 3rd adhesive layer 43 as above-mentioned. The 1st adhesive layer 41 and the 2nd adhesive layer 42 are provided in order to paste the front side polarizing plate 20 and the back side polarizing plate 30 on both sides of the liquid crystal cell 10, respectively.

  The pressure-sensitive adhesive forming each pressure-sensitive adhesive layer may be any material as long as it has excellent optical transparency and has been appropriately imparted with pressure-sensitive adhesive properties including wettability, cohesiveness, and adhesiveness. Those excellent in the above are preferably used. Specifically, an adhesive containing an acrylic resin (acrylic adhesive) is preferably used as the adhesive forming the adhesive layer.

  The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of an acrylic acid alkyl ester such as butyl acrylate, ethyl acrylate, isooctyl acrylate, or 2-ethylhexyl acrylate. This acrylic resin is usually copolymerized with a polar monomer. The 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 is a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. sell. Specific examples of the polar monomer include a carboxyl group-containing monomer having (meth) acrylic acid as a representative example, and a hydroxyl group having a representative example of 2-hydroxypropyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate. Monomers, amide group-containing monomers typically represented by (meth) acrylamide, 2-N, N-dimethylaminoethyl (meth) acrylate, epoxy group-containing monomers typically represented by glycidyl (meth) acrylate, and the like.

  The acrylic pressure-sensitive adhesive usually contains a crosslinking agent together with the acrylic resin. A typical example of the crosslinking agent is an isocyanate compound having at least two isocyanato groups (—NCO) in the molecule.

  Various additives may be further blended in the adhesive. Suitable additives include silane coupling agents and antistatic agents. A silane coupling agent is effective in increasing the adhesive strength with glass. Antistatic agents are effective in reducing or preventing the generation of static electricity. In general, when attaching a polarizing plate to a liquid crystal cell via an adhesive layer, the surface protective film (separator) that has been temporarily protected by covering the adhesive layer is peeled off and then attached to the liquid crystal cell. The static electricity generated when the surface protective film is peeled off causes the alignment failure of the liquid crystal in the liquid crystal cell, and this phenomenon may cause the display failure of the liquid crystal display device. As a means for reducing or preventing the generation of static electricity, it is effective to add an antistatic agent to the adhesive.

[Storage modulus of 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 ° C. in the range of 0.01 MPa or more and 0.1 MPa or less. Consists of things. In this way, all the pressure-sensitive adhesive layers are made of a relatively soft material to relieve the stress applied to the liquid crystal cell due to the dimensional change of the polarizing plate even when the liquid crystal display device is exposed to a humid heat environment. And warpage of the liquid crystal panel is suppressed. When the storage elastic modulus at 50 ° C. of any pressure-sensitive adhesive layer exceeds 0.1 MPa, the stress applied to the liquid crystal cell due to the dimensional change of the polarizing plate cannot be sufficiently relaxed, and when it is placed in a humid heat environment. The warpage of the liquid crystal panel becomes large, which may cause display unevenness. On the other hand, when the storage elastic modulus is less than 0.01 MPa, sufficient adhesive strength tends to be difficult to obtain. Various methods can be adopted to bring the storage elastic modulus at 50 ° C. to 0.01 MPa or more and less than 0.1 MPa. For example, by adjusting the amount of the crosslinking agent, a desired storage elastic modulus can be achieved. it can.

  The pressure-sensitive adhesive layers 41, 42, and 43 are prepared as a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component described above is dissolved in an organic solvent, and this is applied to the surface of the film on which the pressure-sensitive adhesive layer is to be formed. Apply the above-mentioned pressure-sensitive adhesive composition to the release treatment surface of the base film made of a resin film that has been subjected to a release treatment, either by direct application and drying to remove the solvent, and then remove the solvent by drying. Then, it can be formed by a transfer method in which a pressure-sensitive adhesive layer is adhered to the surface of a film intended for this. When the pressure-sensitive adhesive layers 41, 42, and 43 are formed on the surface of the target film by the former direct coating method, a resin film (also referred to as a separator) that has been subjected to a release treatment is bonded to the surface and used. Usually, the surface of the pressure-sensitive adhesive layer is temporarily protected. The latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition that is an organic solvent solution. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also advantageous from the point that it can be used as a separator after being adhered to the pressure-sensitive adhesive layer forming 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 arranged in a form called a side light type composed of a light guide plate and a light source arranged on one side surface or two opposite side surfaces, or on a plurality of light sources and on the side (toward the liquid crystal cell 10). It is possible to use a type called a direct type composed of a light diffusing plate. In any form, the light reflecting layer is usually provided in the form of a sheet or a coating layer on the back surface (the side far from the liquid crystal cell 10) of the light source member. Further, one or more optical members such as a light collecting sheet and a diffusion film may be further arranged on the light emitting side of the light source member (the side facing the liquid crystal cell 10). The backlight unit 60 itself has the members described here, and can have any configuration employed in this field.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, the parts and% representing the content or amount used are based on weight unless otherwise specified. In addition, each physical property in the following examples was measured by the following method.

(1) Retardation value and Nz coefficient Using a phase difference meter “KOBRA-21ADH” based on the parallel Nicol rotation method manufactured by Oji Scientific Instruments Co., Ltd., applying light with a wavelength of 590 nm at a temperature of 23 ° C. While measuring the retardation, thickness direction retardation or Nz coefficient was measured.

(2) Storage elastic modulus of adhesive The storage elastic modulus (G ') of an adhesive is a dynamic viscoelasticity measuring device (8 mm in diameter x 1 mm in thickness) prepared from a pressure-sensitive adhesive to be measured. Using Dynamic Analyzer RDA II (manufactured by REOMETRIC), the initial strain was set to 1N by the torsional shear method with a frequency of 1 Hz, and the measurement was performed at 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-based crosslinking agent on a release treatment surface of a polyethylene terephthalate film (referred to as “separator”) having a thickness of 38 μm that has been subjected to a release treatment. Is a commercially available pressure-sensitive adhesive with a separator having a thickness of 25 μm. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.04 MPa at 50 ° C.

(4) Adhesive sheet B:
An acrylic copolymer mainly composed of butyl acrylate, an ultraviolet curable component, and an isocyanate-based crosslinking agent on a release treatment surface of a 38 μm-thick polyethylene terephthalate film (referred to as “separator”) that has been subjected to a release treatment. A commercially available pressure-sensitive adhesive with a separator, in which a hard pressure-sensitive adhesive layer having a thickness of 25 μm cured by ultraviolet irradiation is formed. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.97 MPa at 50 ° C.

[Example 1]
(A) Preparation of aqueous adhesive 3 parts of carboxyl group-modified polyvinyl alcohol [“KL-318” obtained from Kuraray Co., Ltd.] is dissolved in 100 parts of water, and a polyamide which is a water-soluble epoxy compound is dissolved in the aqueous solution. An aqueous resin was prepared by adding 1.5 parts of an epoxy resin [Sumirez Resin 650 (30) obtained from Sumika Chemtex Co., Ltd., aqueous solution with a solid content concentration of 30%].

(B) Production of Retardation Film Styrene-maleic anhydride copolymer resin ["Dylark D332" (trade name), Tg = 131 ° C, sold by Nova Chemical Co., Ltd.] is used as the core layer, and the average particle size is 200 nm. A methacrylic resin (resin used in “Technoloy S001” (trade name) sold by Sumitomo Chemical Co., Ltd., Tg = 105 ° C.) containing about 20% acrylic rubber particles as a skin layer Three-layer coextrusion was performed to obtain a resin three-layer film in which skin layers were formed on both sides of the core layer. This resin three-layer film was stretched to produce a retardation film. This retardation film had an in-plane retardation of 55.0 nm and an Nz coefficient of -1.1.

(C) Transparent protective film “TD80UL” (trade name), which is a 80 μm-thick triacetyl cellulose film obtained from FUJIFILM Corporation, is subjected to saponification treatment, and the front side polarizing plate 20 and the back side polarizing plate 30 The transparent protective films 22 and 32 are disposed on the side far from the liquid crystal cell 10. “KC4UEW” (trade name), a 40 μm thick triacetylcellulose film obtained from Konica Minolta Opto, Inc., had an in-plane retardation of 0.7 nm and a thickness direction retardation of −0.1 nm. It was. This was subjected to saponification treatment to obtain a transparent protective film 23 disposed on the liquid crystal cell 10 side of the front side polarizing plate 20. Furthermore, the cyclic polyolefin resin film having a thickness of 35.8 μm obtained from Nippon Zeon Co., Ltd. had an in-plane retardation of 76.2 nm and an Nz coefficient of 1.37. This was made into the 2nd transparent protective film 33 arrange | positioned between the polarizing film 31 and the phase difference film 35 in the back side polarizing plate 30. FIG.

(D) Preparation of polarizing plate The above-described thickness of 80 μm is formed on one surface of a polarizing film having a thickness of about 28 μm in which iodine is adsorbed and oriented on the polyvinyl alcohol film through the aqueous adhesive prepared in (a) above. The triacetyl cellulose film “TD80UL” was bonded to the other side, and the above-mentioned 40 μm thick triacetyl cellulose film “KC4UEW” was bonded to the other surface through the same water-based adhesive. The front side polarizing plate 20 was produced by drying for 5 minutes.

  Also, the same 80 μm thick triacetyl cellulose film “TD80UL” is pasted on one side of the same polarizing film as above using the same aqueous adhesive as above, and the same on the other side. The above-described cyclic polyolefin resin film having a thickness of 35.8 μm was bonded through an aqueous adhesive, and then dried at 80 ° C. for 5 minutes. Furthermore, on the cyclic polyolefin resin film (second transparent protective film 33), the retardation film produced in the above (b) is passed through the pressure-sensitive adhesive sheet A (with the separator removed). The back side polarizing plate 30 was produced by bonding so that the phase axis was orthogonal to the absorption axis of the polarizing film.

(E) Production of polarizing plate with pressure-sensitive adhesive layer The front side polarizing plate 20 produced in (d) above has a 40 μm-thick triacetyl cellulose film “KC4UEW” (transparent protective film 23) side, and the back side polarizing plate. The above-mentioned pressure-sensitive adhesive sheet A was bonded to the 30 retardation film 35 side to prepare a polarizing plate with a pressure-sensitive adhesive layer. Among these, a wide 32 type size [diagonal of 32 inches (about 32 inches diagonal)] with the absorption axis from the front side polarizing plate with the adhesive layer as the longitudinal direction and the absorption axis from the back side polarizing plate with the adhesive layer as the short direction. 81 cm) and a width of about 71 cm × length of about 40 cm].

(F) Manufacture and Evaluation of Liquid Crystal Display Device Panasonic Corporation's IPS mode wide 32 type [32 inches diagonal (about 81 cm) width 71 cm x length 40 cm] LCD TV “VIERA” (model number: VIERA TH -L32X1) is disassembled, and the upper and lower polarizing plates of the liquid crystal cell are peeled off. Instead of the original polarizing plate, the polarizing plate with the adhesive layer prepared in (e) above is replaced with the front side (viewing side) of the liquid crystal cell and The separator was peeled off from each pressure-sensitive adhesive layer so as to be in a crossed Nicol state on the back side (backlight side), and bonded on the pressure-sensitive adhesive layer side to produce a 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 no voltage was applied to the liquid crystal molecules in the liquid crystal cell 10 (black display). A backlight 60 was further attached to the liquid crystal panel to obtain a liquid crystal display device. 30 minutes after turning on the backlight of this liquid crystal display device, the contrast ratio at an azimuth angle of 135 ° and a polar angle of 60 ° is measured using an “EZ Contrast 88XL” viewing angle characteristic measurement and evaluation device for 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 when viewed from the viewing side is positive. The azimuth angle 135 ° means the upper left direction of the screen, and the polar angle is , Meaning the tilt from the normal direction of the screen. As a result, the contrast ratio was 326.

(G) Wet heat environment test of liquid crystal panel The liquid crystal panel 50 produced in the above (f) was placed in an environment of a temperature of 40 ° C. and a relative humidity of 95% for 96 hours, then taken out, and the temperature was 22 ° C. and the relative humidity was 55. % Environment for 1 day. When this liquid crystal panel was used to reassemble the IPS mode liquid crystal display, the backlight was turned on and the screen was observed 1 hour later, no display unevenness was found.

[Comparative Example 1]
A liquid crystal panel 50 was produced in the same manner except that the adhesive sheet B was used as the first adhesive layer 41 of the front side polarizing plate and the second adhesive layer 42 of the back side polarizing plate in Example 1. Further, a liquid crystal display device was assembled and evaluated in the same manner. The contrast ratio was the same as that in Example 1, but as a result of the wet heat environment test, display unevenness was observed 1 hour after the backlight was turned on.

[Comparative Example 2]
As the first pressure-sensitive adhesive layer 41 of the front-side polarizing plate in Example 1, a liquid crystal panel 50 was produced in the same manner except that the pressure-sensitive adhesive sheet B was used, and a liquid crystal display device was assembled and evaluated in the same manner. . The contrast ratio was the same as that in Example 1, but as a result of the wet heat environment test, display unevenness was observed 1 hour after the backlight was turned on.

[Comparative Example 3]
As the second pressure-sensitive adhesive layer 42 of the back-side polarizing plate in Example 1, a liquid crystal panel 50 was produced in the same manner except that the pressure-sensitive adhesive sheet B was used, and a liquid crystal display device was assembled and evaluated in the same manner. . The contrast ratio was the same as that in Example 1, but as a result of the wet heat environment test, display unevenness was observed 1 hour after the backlight was turned on.

  About the above Example and the comparative example, the structure of three adhesive layers and the result of the wet heat environment test were put together in Table 1.

10 ... Liquid crystal cell,
11, 12 ... cell substrate,
15 …… Liquid crystal layer
20 …… Front-side polarizing plate,
21 …… Polarizing film,
22, 23 ... Transparent protective film,
30 …… Back polarizing plate,
31: Polarizing film,
32, 33 ... Transparent protective film,
35 ... retardation film,
36 …… Core layer,
37 …… Skin layer,
41 …… First adhesive layer,
42 …… Second adhesive layer,
43 …… Third adhesive layer,
50 ... LCD panel,
60 …… Backlight unit.

Claims (4)

A liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween,
A front-side polarizing plate laminated via a first pressure-sensitive adhesive layer on the viewing side of the liquid crystal cell,
A back side polarizing plate laminated via 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 surfaces thereof, and is laminated on the liquid crystal cell via the first pressure-sensitive adhesive layer on one transparent protective film side. Has been
The back side polarizing plate includes a polarizing film, a first transparent protective film disposed on one surface of the polarizing film, a second transparent protective film disposed on the other surface of the polarizing film, and A retardation film laminated on a side opposite to the polarizing film of the second transparent protective film via a third pressure-sensitive adhesive layer, and on the phase difference film side via the second pressure-sensitive adhesive layer Are stacked on the liquid crystal cell,
The retardation film has a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both surfaces of a core layer made of a styrene resin, and the first adhesive All of the adhesive layer, the second adhesive layer, and the third adhesive layer have a storage elastic modulus at 50 ° C. in the range of 0.01 MPa or more and 0.1 MPa or less. .   2. 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 has a thickness direction retardation 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 is made of a cellulose resin or a polyolefin resin. Said 2nd transparent protective film which comprises the said back side polarizing plate consists of polyolefin resin, and the in-plane retardation exists in the range of 30-150 nm, an in-plane slow axis direction, an in-plane fast axis direction and when the refractive index in the thickness direction, respectively, and n _x, n _y and n _z, wherein:
_{Nz = (n x -n z)} / (n x -n y)
The refractive index anisotropy in which the Nz coefficient defined by is in the range of more than 1 and less than 2;
The retardation film constituting the back-side polarizing plate has an in-plane retardation in a range of 20 to 120 nm, and an Nz coefficient defined by the above formula is in a range of more than −2 and less than −0.5. The liquid crystal display device according to claim 1, having refractive index anisotropy.

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