JP5964628B2 - Polarizing plate and liquid crystal display device - Google Patents

Description

  The present invention relates to a polarizing plate and a liquid crystal display device using the polarizing plate.

  A liquid crystal display device using a liquid crystal display panel as a display element is rapidly expanding its use as a thin display device such as a liquid crystal television, a liquid crystal monitor, and a personal computer. In particular, the market for liquid crystal televisions is remarkably expanding, and with this, there is a strong demand for cost reduction. A liquid crystal display device such as a liquid crystal television is configured by incorporating various members such as a backlight into a liquid crystal panel including a liquid crystal cell and a polarizing plate as constituent members.

  A polarizing plate is usually a transparent protective film, for example, cellulose acetate represented by triacetylcellulose, with an adhesive layer on one or both sides of a polarizing film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. It is the structure which bonded the protective film which consists of a resin. This is bonded to the liquid crystal cell with an adhesive via another optical film as necessary, to obtain a component part of the liquid crystal display device.

  However, a polarizing plate using a film made of a cellulose acetate-based resin as a protective film is derived from the high moisture permeability and water absorption rate of the protective film, which is a component of the polarizing plate, in a severe environment such as high temperature and high humidity. The performance as a board may change.

  Then, the technique which uses a polyethylene terephthalate film as a protective film as a technique which can solve the said subject is proposed. Polyethylene terephthalate film has characteristics such as low moisture permeability and low water absorption, so it can be expected to have high durability against severe environmental changes such as high temperature and high humidity, and has excellent mechanical strength and is relatively inexpensive. Therefore, in recent years, the liquid crystal display device has an advantage in terms of reduction in thickness and cost.

  However, on the other hand, when a polarizing plate using a polyethylene terephthalate film as a protective film is mounted on a liquid crystal display device, the oblique direction derived from its high retardation value compared to a general triacetyl cellulose film as a protective film. Color unevenness (also called interference unevenness or rainbow unevenness) is conspicuous and inferior in visibility. With respect to this problem, for example, in Japanese Patent Application Laid-Open No. 2009-109993 (Patent Document 1), a liquid crystal display device in which a polarizing plate using a polyethylene terephthalate film as a protective film and a polarizing plate provided with an antiglare layer with a controlled haze value is combined. A method of reducing color unevenness by configuring the above is disclosed. However, in this method, the antiglare film to be applied is limited, and when an antiglare film having a small haze is used, the reduction in color unevenness is insufficient.

  Therefore, as a more effective technique, a technique for improving the visibility by setting the optical characteristics of the polyethylene terephthalate film within a predetermined range is disclosed (for example, JP 2010-286539 A (Patent Document 2) and No. 2011-1112928 (Patent Document 3)). However, when effective in-plane retardation value is reduced by suppressing color unevenness, the problem is that the polarizing plate is deformed in a high temperature environment due to the decrease in the mechanical strength of the polyethylene terephthalate film. It was necessary to achieve both improved visibility and durability.

JP 2009-10993 A JP 2010-286539 A JP 2011-1112928 A

  Therefore, an object of the present invention is a polarizing plate having a polyethylene terephthalate film as a protective film, and has excellent color visibility when mounted on a liquid crystal display device, and is excellent even in harsh environments such as high temperature conditions. An object of the present invention is to provide a polarizing plate with little deformation. Another object of the present invention is to provide a liquid crystal display device having excellent visibility and environmental resistance using the polarizing plate.

According to the present invention, a polarizing film made of a polyvinyl alcohol resin and a polarizing plate in which a stretched polyethylene terephthalate film is laminated on one side of the polarizing film via an adhesive layer, the stretched polyethylene terephthalate film is a surface. the following retardation values 400nm inner and the slow axis direction of the refractive index n _x in the _plane, the refractive index in a direction perpendicular to the slow axis in the plane n _y, the refractive index in the thickness direction n _z and _when, and characterized by _(n x -n z) _/ is in _(n x -n _{y) n z} coefficient expressed by 7 or more and a tensile elastic modulus at 80 ° C. is not less than 800MPa A polarizing plate is provided.

  The stretched polyethylene terephthalate film may be provided with antiglare properties, or may have an antiglare layer on the surface opposite to the surface to be bonded to the polarizing film.

  Moreover, the surface on the opposite side to the stretched polyethylene terephthalate film in the said polarizing film can be equipped with a protective film or an optical compensation film through an adhesive bond layer.

  In this polarizing plate, the adhesive layer is preferably composed of a cured product layer of an ultraviolet curable resin composition containing an epoxy compound.

  As described above, when a protective film or an optical compensation film is laminated, the polarizing plate of the present invention has an adhesive layer on the surface opposite to the surface on which the polarizing film in the protective film or the optical compensation film is laminated. Can be provided.

  Furthermore, according to this invention, a liquid crystal display device provided with the liquid crystal panel by which the polarizing plate provided with the said adhesive layer was bonded to the liquid crystal cell via the adhesive layer is provided.

The polarizing plate of the present invention is a polarizing plate having a polyethylene terephthalate film as a protective film, having an in-plane retardation value of 400 nm or less, an _Nz coefficient of 7 or more, and a tensile elastic modulus at 80 ° C. of 800 MPa or more. By selecting a stretched polyethylene terephthalate film, it is possible to provide a polarizing plate with little color unevenness when mounted on a liquid crystal display device and excellent visibility, and with little deformation even under harsh environments such as high temperature conditions. be able to. Moreover, according to this invention, the liquid crystal display device which is excellent in visibility and environmental resistance using the said polarizing plate can be provided.

<Polarizing plate>
The polarizing plate of the present invention comprises a stretched polyethylene terephthalate film laminated on one side of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer. This stretched polyethylene terephthalate film has an in-plane retardation value of 400 nm or less, an _Nz coefficient of 7 or more, and a tensile elastic modulus at 80 ° C. of 800 MPa or more. Hereinafter, the polarizing plate of the present invention will be specifically described.

(Polarizing film)
Although the polarizing film used for this invention is not specifically limited, Usually, the process of uniaxially stretching a polyvinyl alcohol-type resin film by a well-known method, By dyeing a polyvinyl alcohol-type resin film with a dichroic dye , A process of adsorbing a dichroic dye, a process 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. .

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with 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. This polyvinyl alcohol resin may be modified, for example, polyvinyl formal and polyvinyl acetal modified with aldehydes can be used. Moreover, the polymerization degree of polyvinyl alcohol-type resin is 1000-10000 normally, and 1500-5000 are preferable.

  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 the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The film thickness of a polyvinyl alcohol-type raw film can be 10-150 micrometers, for example.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or may be wet stretching in which stretching is performed in a state where a solvent is used and the polyvinyl alcohol-based resin film is swollen. The draw ratio is usually 3 to 8 times.

  As a method of dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to 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 0.01 to 1 part by weight per 100 parts by weight of water. Moreover, content of potassium iodide is 0.5-20 weight part normally per 100 weight part of water. The temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually 20 to 1800 seconds.

On the other hand, when a dichroic 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 dye is usually employed. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ⁻⁴ to 10 parts by weight and preferably 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually 10 to 1800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can usually be performed by immersing the dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution.

  The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight and 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 amount of potassium iodide in the boric acid-containing aqueous solution is usually 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 60 to 1200 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, and preferably 50 to 85 ° 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 immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually 5 to 40 ° C. Moreover, the immersion time is usually 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The thickness of the polarizing film is usually 5 to 40 μm. The drying treatment can be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually 30 to 100 ° C, preferably 50 to 80 ° C. The time for the drying treatment is usually 60 to 600 seconds, and preferably 120 to 600 seconds.

  By the drying treatment, the moisture content of the polarizing film is reduced to a practical level. The moisture content is usually 5 to 40% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost, and the polarizing film may be damaged or broken after drying. Moreover, when a moisture content exceeds 40 weight%, it may be inferior to the thermal stability of a polarizing film.

(Stretched polyethylene terephthalate film)
As the stretched polyethylene terephthalate film used in the present invention, one or more polyethylene terephthalate-based resins are formed by melt extrusion, one or more uniaxially stretched films formed by transverse stretching, or the film is stretched longitudinally after film formation, One or more biaxially stretched films formed by transverse stretching. In the present invention, a biaxially stretched product is preferably used from the viewpoints of efficiently imparting necessary optical performance and productivity and low cost.

  The polyethylene terephthalate resin means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain other dicarboxylic acid components and 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, and 1, 4-dicarboxycyclohexane etc. are mentioned.

  Examples of the other diol component 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 may be used alone or in combination with a plurality of different types. In addition, hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid can be used in combination. Further, as other copolymerization component, a dicarboxylic acid component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like, or a diol component may be used.

  Polyethylene terephthalate resin can be produced by direct polycondensation of terephthalic acid and ethylene glycol (and other dicarboxylic acids or other diols as required), dialkyl esters of terephthalic acid and ethylene glycol (and if necessary) A transesterification reaction with a dialkyl ester of another dicarboxylic acid or other diol), and a polycondensation, and an ethylene glycol ester of terephthalic acid (and other dicarboxylic acids as required) A method of polycondensation of other diol esters) is employed.

  The polyethylene terephthalate resin can contain an additive as necessary. Examples of the additive include an ultraviolet absorber, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improving agent. The addition amount is preferably kept in a range that does not adversely affect the optical properties.

  The polyethylene terephthalate resin can be made into a transparent and homogeneous polyethylene terephthalate film with high mechanical strength by forming into a film and stretching. The production method is not particularly limited as long as the effects of the present invention are not impaired, but a biaxially stretched product is preferable as described above. For example, the method described below is adopted.

  First, the polyethylene terephthalate-based resin is molded into pellets, dried, and supplied to a melt-extrusion apparatus, heated to a melting point or higher and melted. Next, the melted resin is extruded from a die, brought into close contact with a cooling drum by an electrostatic application method or the like, and cooled and solidified to obtain a substantially amorphous unstretched film. The melting temperature is determined according to the melting point of the polyethylene terephthalate resin to be used and the extruder, and is not particularly limited, but is usually 250 to 350 ° C.

  Next, when obtaining a biaxially stretched film, the unstretched film is usually first stretched in the extrusion direction at a temperature equal to or higher than the glass transition temperature. The stretching temperature is usually 70 to 150 ° C, preferably 80 to 130 ° C, and more preferably 90 to 120 ° C. Moreover, a draw ratio is 1.0-3.0 times normally, and it is preferable that it is 1.1-2.0 times. This longitudinal stretching may be performed once, or may be performed in multiple steps as necessary. Usually, even when stretching is performed a plurality of times, the total stretching ratio is preferably within the above range.

  When obtaining a biaxially stretched film, transverse stretching is usually performed by a tenter after the longitudinal stretching treatment. This stretching temperature is usually 70 to 150 ° C, preferably 80 to 130 ° C, and more preferably 90 to 120 ° C. Moreover, a draw ratio is 2.0-6.0 times normally, and it is preferable that it is 2.5-5.5 times.

  Thereafter, heat treatment and relaxation treatment as necessary can be performed. The heat treatment temperature is usually 150 to 250 ° C, preferably 180 to 245 ° C, and more preferably 200 to 230 ° C. The heat treatment time is usually 1 to 600 seconds, preferably 1 to 300 seconds, and more preferably 1 to 60 seconds. Moreover, the temperature of a relaxation process is 100-230 degreeC normally, It is preferable that it is 110-210 degreeC, and it is more preferable that it is 120-180 degreeC. Moreover, the relaxation amount is usually 0.1 to 20%, preferably 1 to 10%, more preferably 2 to 5%.

  The method of heat treatment or relaxation treatment is not particularly limited, but each stepwise treatment in a plurality of temperature ranges can reduce the distribution of physical properties in the width direction of the film, and dimensional stability. It is preferable in terms of improvement.

The polarizing plate of the present invention, as such stretched polyethylene terephthalate film, the film thickness d, the slow axis direction of the refractive index n _x in the _plane, the refractive index in the direction perpendicular to the slow axis in the plane n _y , the refractive index in the thickness direction is taken as _{n z, (n x -n y} ) an in-plane phase difference _{R 0} as defined in × d is 400nm or less, _{and, (n x -n z) /} (n x _{N z} coefficient defined by -n _y) is used as 7 or more. By employing a stretched polyethylene terephthalate film having such optical performance, it is possible to effectively reduce color unevenness in a liquid crystal display device equipped with such a polarizing plate. The smaller R ₀ is, the better the color unevenness is, preferably 300 nm or less, and more preferably 250 nm or less. On the other hand, the higher the _Nz coefficient, the better the color unevenness, and more preferably 10 or more. When R ₀ exceeds 400 nm, or when the _Nz coefficient is less than 7, color unevenness tends to increase in a liquid crystal display device equipped with such a polarizing plate.

The R ₀ and N _z coefficients can be measured using, for example, a retardation film / optical material inspection apparatus RETS manufactured by Otsuka Electronics Co., Ltd.

  Moreover, as a stretched polyethylene terephthalate film in the present invention, a film having a tensile elastic modulus at 80 ° C. of 800 MPa or more is used. By employing a stretched polyethylene terephthalate film having such optical performance, it is possible to obtain a polarizing plate that is less likely to be deformed even under a severe environment such as a high temperature condition.

  The tensile elastic modulus can be measured using a general tensile testing machine, for example, Autograph AG-1 manufactured by Shimadzu Corporation, and a test piece having an appropriate size is cut to a predetermined size. Tensile tests can be performed in a drying oven maintained at temperature. The tensile modulus is defined as the slope of the elastic region in the stress-strain diagram obtained by a tensile test of the material. When the stress is σ and the strain is ε, E represented by σ = Eε is the longitudinal elastic modulus. It becomes a tensile elastic modulus.

In the stretched polyethylene terephthalate film of the present invention, any known technique can be used without limitation in order to control the R ₀ , N _z coefficient and tensile modulus within a specific range. For example, stretching in the stretching process of the polyethylene terephthalate film It can be controlled by adjusting conditions such as temperature, stretch ratio, and relaxation treatment. In addition, these optimum conditions differ depending on the resin constituting the film, and therefore, the obtained stretched film may be measured and appropriately determined so as to have preferable characteristics. Further, the stretched polyethylene terephthalate film has a variation in R ₀ and N _z coefficients as represented by bowing in the width direction. About such a stretched polyethylene terephthalate film, only the width range which has the target performance can also be selectively used as needed.

  The thickness of the stretched polyethylene terephthalate film used for the polarizing plate of the present invention is not particularly limited as long as the effects of the present invention are not impaired, but is preferably in the range of 15 to 100 μm, and in the range of 20 to 80 μm. More preferably, it is within. When the thickness of the stretched polyethylene terephthalate film is less than 15 μm, it tends to be inferior in mechanical strength or difficult to handle (inferior in handleability), and when the thickness exceeds 100 μm, This is not preferable because it tends to be difficult to perform and the cost tends to increase.

  Furthermore, in the stretched polyethylene terephthalate film used in the present invention, various functional layers other than the above can be laminated on one side or both sides as long as the effects of the present invention are not hindered. Examples of the laminated functional layer include a conductive layer, a smoothing layer, an easy-sliding layer, an anti-blocking layer, and an easy-adhesion layer. Especially, since this stretched polyethylene terephthalate film is laminated | stacked through a polarizing film and an adhesive bond layer, it is preferable that the easily bonding layer is laminated | stacked.

  The component constituting the easy-adhesion layer is not particularly limited. For example, a polyester resin, a urethane resin, or an acrylic resin having a polar group in the skeleton and a relatively low molecular weight and a low glass transition temperature. Resin etc. are mentioned. Moreover, a crosslinking agent, an organic or inorganic filler, a surfactant, a lubricant, and the like can be contained as necessary.

  The method of forming the functional layer into a stretched polyethylene terephthalate film is not particularly limited, but for example, a method of forming a film after all stretching steps have been completed, a step of stretching a polyethylene terephthalate resin, For example, a method of forming between the longitudinal stretching and the transverse stretching process, a method of forming immediately before or after being bonded to the polarizing film, and the like are employed. Among these, from the viewpoint of productivity, a method in which a polyethylene terephthalate-based resin is formed after being longitudinally stretched and then stretched laterally is preferably employed.

(Give antiglare properties to stretched polyethylene terephthalate film)
When the stretched polyethylene terephthalate film is used on the viewing side of the polarizing plate, it is preferable that antiglare property (haze) is imparted. As a method for imparting antiglare properties, for example, a method of mixing inorganic fine particles or organic fine particles into the polyethylene terephthalate resin to form a film, or a method of producing the multilayer film, inorganic fine particles or organic fine particles are present on one side. A method of forming a stretched film from an unstretched film having a mixed layer, and a surface of the stretched polyethylene terephthalate film opposite to the surface to be bonded to the polarizing film are mixed with inorganic fine particles or organic fine particles in a curable binder resin. For example, a method of coating the coating solution and curing the binder resin to provide an antiglare layer is employed.

  Examples of the inorganic fine particles include silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, and calcium phosphate. 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.

  The haze value of the stretched polyethylene terephthalate film imparted with antiglare property is preferably in the range of 1 to 45%. If the haze value is less than 1%, a sufficient antiglare effect may not appear. On the other hand, if it exceeds 45%, the screen of the liquid crystal display device using this film may be whitened, resulting in a decrease in image quality. The haze value can be measured using a haze / transmittance meter HM-150 (manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7136. In measuring the haze value, in order to prevent warping of the film, for example, a measurement sample in which the film surface is bonded to a glass substrate using an optically transparent adhesive so that the antiglare property-imparting surface becomes the surface. Is preferably used.

  In addition, when a stretched polyethylene terephthalate film is used on the backlight side of the polarizing plate, the antiglare property may not be given. In this case, the haze value is usually less than 6%.

  On the stretched polyethylene terephthalate film with antiglare properties, functions other than the antiglare layer, such as a conductive layer, a hard coat layer, a low reflection layer, a smoothing layer, a slippery layer, and an antiblocking layer Layers can be stacked. Moreover, as a resin composition (coating liquid) for forming the antiglare layer, a resin composition having any of these functions can also be selected.

  When a functional layer such as the antiglare layer is laminated on the surface of the stretched polyethylene terephthalate film opposite to the surface to be bonded to the polarizing film, the functional layer of the stretched polyethylene terephthalate film is closely adhered to the functional layer. In order to improve the property, a coating layer similar to the above can be formed.

(Adhesive layer)
The adhesive layer with which the polarizing plate of this invention is provided is a layer which bears adhesion | attachment with a polarizing film and a protective film. As this adhesive, for example, a composition using a polyvinyl alcohol resin or a urethane resin as a main component and dissolved in water, or a water-based adhesive dispersed in water, a photocurable resin and a photocationic polymerization initiator, etc. Solvent-free photo-curing adhesives containing, among others, from the viewpoint of improving productivity by making it possible to improve the adhesion between the polarizing film and the stretched polyethylene terephthalate film and eliminate the need for a drying step An adhesive comprising a cured layer of a solventless ultraviolet curable resin composition containing an epoxy compound and a cationic polymerization initiator is preferred.

  As the epoxy compound, an alicyclic epoxy compound can be preferably used. By using an ultraviolet curable resin composition containing an alicyclic epoxy compound as an adhesive, the adhesion between the polarizing film and the stretched polyethylene terephthalate film is improved and the durability of the polarizing plate in a harsh environment is further improved. Can do.

  When an ultraviolet curable resin composition containing an epoxy compound is used as an adhesive, after laminating a polarizing film and a stretched polyethylene terephthalate film through the adhesive, the adhesive is cured by irradiating ultraviolet rays. Thereby, the adhesive bond layer which consists of a hardened | cured material layer of the said ultraviolet curable resin composition is formed.

  Examples of the ultraviolet light source to be irradiated include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a super high pressure mercury lamp, a black light lamp, and a metal halide lamp having a light emission distribution at a wavelength of 400 nm or less. Moreover, the irradiation intensity and irradiation amount of ultraviolet rays are determined by the ultraviolet curable resin composition and the irradiation time, sufficiently activate the cationic polymerization initiator, and adversely affect the cured adhesive layer and film. Is appropriately selected within a range that does not give the

  The thickness of the adhesive layer made of the ultraviolet curable resin composition is usually 0.1 to 20 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 5 μm. If the thickness is less than 0.1 μm, the adhesive force between the polarizing film and the protective film laminated by the cured adhesive layer may be insufficient, and if the thickness exceeds 20 μm, the adhesive layer Curing may not proceed sufficiently, or even if cured, the flexibility of the film may deteriorate due to its thickness.

  The adhesive is also used in the case of laminating a transparent resin film such as a protective film or an optical compensation film on the surface opposite to the surface on which the stretched polyethylene terephthalate film of the polarizing film described later is laminated. About the adhesive agent in this case, the same kind as what is used when laminating | stacking the said extending | stretching polyethylene terephthalate film may be used, and a different thing may be used, respectively. When the transparent resin film is provided, it is preferable to simultaneously bond both sides of the polarizing film from the viewpoint of productivity. If an appropriate adhesive strength is obtained, the process is simpler if the same kind of adhesive is used. preferable.

(Protective film, optical compensation film)
The polarizing plate of the present invention includes a transparent resin film such as a protective film or an optical compensation film laminated via an adhesive layer on the surface opposite to the surface on which the stretched polyethylene terephthalate film of the polarizing film is laminated. May be.

  As the protective film, for example, a transparent resin film such as a cellulose resin film made of triacetyl cellulose (TAC), an olefin resin film, an acrylic resin film, a polycarbonate resin film, or a polyester resin film is used. it can. Examples of the optical compensation film include those obtained by stretching the transparent resin film to give refractive index anisotropy, those containing an optical anisotropy imparting additive, and those having an optically anisotropic layer formed on the surface. Is mentioned.

  The film thickness of the transparent resin film such as the protective film or the optical compensation film is usually about 10 to 200 μm, preferably 20 to 120 μm. Moreover, when using the said transparent resin film as an optical compensation film, what is necessary is just to set the optical characteristic to an appropriate value according to the viewing angle characteristic requested | required of the applied liquid crystal display device.

  Moreover, an optical functional film can be laminated | stacked on these protective films or optical compensation films, or an optical functional layer can also be coated. Examples of the optical functional film and the optical functional layer include an antiglare layer, a conductive layer, a hard coat layer, and an antireflection layer.

(Adhesive layer)
The polarizing plate of the present invention is for bonding the polarizing plate to other members such as a liquid crystal cell on the outer surface of a transparent resin film such as a protective film or an optical compensation film laminated on the opposite side of the stretched polyethylene terephthalate film. It can have an adhesive layer. As the pressure-sensitive adhesive used for such a pressure-sensitive adhesive layer, a conventionally known appropriate pressure-sensitive adhesive can be used without particular limitation, and examples thereof include an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. Among these, an acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability, and the like. The pressure-sensitive adhesive layer can be provided by a method in which such a pressure-sensitive adhesive is used, for example, in the form of an organic solvent solution, which is applied to a base film with a die coater or a gravure coater, and dried. Can be provided also by a method of transferring a sheet-like pressure-sensitive adhesive formed on a plastic film (referred to as a separate film) to the base film. Although there is no restriction | limiting in particular also about the thickness of an adhesive layer, Generally it is preferable to exist in the range of 2-40 micrometers.

<Liquid crystal display device>
The polarizing plate formed as described above can peel the release film from the pressure-sensitive adhesive layer and paste it on a liquid crystal cell to obtain a liquid crystal panel. This liquid crystal panel can be applied to a liquid crystal display device.

  The polarizing plate of the present invention can be used, for example, as a polarizing plate disposed on the light emitting side in a liquid crystal display device. The light emitting side refers to the side opposite to the backlight side of the liquid crystal display device based on the liquid crystal cell. When the polarizing plate of the present invention is adopted as the polarizing plate on the light emitting side, an antiglare layer and a hard coat layer are provided on the surface opposite to the surface laminated with the polarizing film of the stretched polyethylene terephthalate film of the polarizing plate. Preferably, at least one layer selected from an antireflection layer and an antistatic layer is provided. The polarizing plate disposed on the back side (backlight side) of the liquid crystal display device may be the polarizing plate of the present invention or a conventionally known polarizing plate.

  A liquid crystal cell constituting a liquid crystal display device is a member in which liquid crystal is sealed between two transparent substrates in order to switch the amount of transmitted light, and has a function of changing the alignment state of the liquid crystal by applying a voltage. Depending on the alignment state of the liquid crystal layer enclosed in the liquid crystal layer and the alignment state of the liquid crystal layer when a voltage is applied between the electrodes, there are various types such as twisted nematic (TN) mode and vertical alignment (VA) mode. is there. The polarizing plate of the present invention can be effectively applied to liquid crystal cells of various modes widely used in general liquid crystal display devices.

  The backlight constituting the liquid crystal display device may also be one widely used for general liquid crystal display devices. For example, it is composed of a diffuser plate and a light source arranged behind it, and the light from the light source is uniformly diffused by the diffuser plate and then emitted to the front side, or a light guide plate And a light source placed on the side of the light source. Once the light from the light source is taken into the light guide plate, the light is uniformly emitted to the front side. And so on. As a light source in the backlight, a cold cathode fluorescent lamp that emits white light using a fluorescent tube, a light emitting diode (LED), or the like can be employed.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In these examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. Evaluation was performed as follows.

<R ₀ , N _z coefficient>
The R ₀ and N _z coefficients of the stretched polyethylene terephthalate film were measured with a retardation film / optical material inspection apparatus RETS manufactured by Otsuka Electronics Co., Ltd.

<Tensile modulus>
The tensile elastic modulus of the stretched polyethylene terephthalate film was determined using Autograph AG-1 manufactured by Shimadzu Corporation. The measurement was performed by cutting a stretched polyethylene terephthalate film into a 20 mm × 100 mm test piece, holding both ends of the short side of the test piece with a chuck, and placing it in a drying oven controlled at 80 ° C. ± 2 ° C. for 5 minutes. Thereafter, it was pulled at a speed of 5 mm / min.

<Example 1>
(A) Production of Polarizing Film A polyvinyl alcohol film having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% and a thickness of 60 μm was immersed in pure water at 30 ° C., and then a weight ratio of iodine / potassium iodide / water. Was immersed in an aqueous solution of 0.04 / 1.5 / 100. Then, it is immersed in an aqueous solution having a potassium iodide / boric acid / water weight ratio of 12 / 3.6 / 100 at 56.5 ° C. for 130 seconds, and further, potassium iodide / boric acid / water has a weight ratio of 12 / 3.6. It was immersed in a 1.5 / 100 aqueous solution at 30 ° C. for 60 seconds. Subsequently, it was washed with pure water at 10 ° C. and then dried in a drying furnace at 60 ° C. and 85 ° C. for a total of 160 seconds to obtain a polarizing film having a thickness of 23 μm in which iodine was adsorbed and oriented on polyvinyl alcohol.

(B) a tensile modulus at Preparation 80 ° C. of the pressure-sensitive adhesive polarizing plate with the 920MPa, _{R 0} is 160 nm, oriented polyethylene terephthalate film of _{N z} coefficient 12.0 (thickness 38 [mu] m), corona treatment on its bonding surface Then, an ultraviolet curable adhesive composition containing an alicyclic epoxy compound was applied to the corona-treated surface with a thickness of 2.5 μm. Further, after the corona treatment was applied to the bonding surface of the optical compensation film made of a stretched norbornene resin having a thickness of 50 μm, the ultraviolet curable adhesive composition containing the alicyclic epoxy compound was thickened on the corona treatment surface as described above. The coating thickness was 2.5 μm.

  Subsequently, the stretched polyethylene terephthalate film on one side of the polarizing film prepared in (a) above, and the optical compensation film made of the stretched norbornene-based resin on the other side, respectively, are bonded via the coating surface of the adhesive composition. Was applied, and ultraviolet rays were irradiated from the side of the optical compensation film made of a stretched norbornene resin to cure the adhesive on both sides to obtain a polarizing plate. Further, an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm is provided on the outer surface of the optical compensation film of the polarizing plate, and a separate film subjected to a release treatment is bonded to the outer surface of the pressure-sensitive adhesive layer to obtain a polarizing plate with an adhesive. It was.

(C) Durability test of polarizing plate The polarizing plate with the adhesive prepared in (b) above was cut into a size of 200 mm × 300 mm, and the polarizing plate from which the separate film was peeled was bonded to the glass plate through the adhesive layer. A sample for durability test was prepared. Next, the endurance test was performed by putting the test sample in an oven maintained at 80 ° C. for 500 hours. The sample after the test was visually evaluated. The evaluation results are shown in Table 1.

(D) Production of liquid crystal display device The light emitting side polarizing plate was peeled off from the liquid crystal panel of a commercially available liquid crystal television equipped with a liquid crystal panel having a liquid crystal cell of vertical alignment mode, and instead, the adhesive produced in (b) above. What peeled off the separate film from the polarizing plate with an adhesive was affixed on the adhesive layer side in the same absorption axis direction as the original polarizing plate. The obtained liquid crystal panel was assembled with a configuration of backlight / light diffusion plate / diffusion sheet / liquid crystal panel to produce a liquid crystal display device, and a white image was displayed and visually observed. The evaluation results are shown in Table 1.

<Examples 2-4, Comparative Examples 1-3>
Instead of the stretched polyethylene terephthalate film used in Example 1 (b) above, a stretched polyethylene terephthalate film (thickness 38 μm) having the characteristics shown in Table 1 was used. A polarizing plate with an adhesive was prepared. Further, the polarizing plate was subjected to an endurance test at 80 ° C. in the same manner as in Example 1 (c), and the appearance was visually evaluated after the test. In addition, a liquid crystal display device was produced using the polarizing plate in the same manner as in Example 1 (d), and a white image was displayed and observed visually. The evaluation results are shown in Table 1.

As can be seen from the results in Table 1, the color of the stretched polyethylene terephthalate film in the polarizing plate in which the R ₀ is 400 nm or less and the _Nz coefficient is 7 or more is the color in the liquid crystal display device equipped with the polarizing plate. There was little unevenness and an effect of excellent visibility was recognized. In addition, the polarizing plate of this example in which a stretched polyethylene terephthalate film having a tensile elastic modulus at 80 ° C. of 800 MPa or more was laminated had a good appearance without peeling even after the durability test.

<Example 5>
In Example 1, the original polarizing plate on the light incident side was also peeled off, and instead of the polarizing plate with the adhesive produced in (b) above, the original polarizing plate on the light incident side was peeled off instead of the original polarizing plate. A liquid crystal display device was produced in the same manner as in Example 1 except that the liquid crystal display device was attached in the same absorption axis direction as that of the polarizing plate on the pressure-sensitive adhesive layer side. The visibility was good.

Claims (6)

A polarizing film made of a polyvinyl alcohol-based resin, and a polarizing plate in which a stretched polyethylene terephthalate film is laminated on one side of the polarizing film via an adhesive layer,
Oriented polyethylene terephthalate film, the following phase difference value is 400nm in the plane, and the slow axis direction of the in-plane refractive index n _x, the refractive index in a direction perpendicular to the slow axis in the plane n _y, thickness the refractive index in the direction when the _{n z,} has _(n x -n z) _/ is a _(n x -n _{y) n z} coefficient expressed by seven or more, a tensile modulus at 80 ° C. 800 MPa A polarizing plate characterized by the above.   2. The polarizing plate according to claim 1, wherein the stretched polyethylene terephthalate film has an antiglare property or is provided with an antiglare layer on a surface opposite to a surface bonded to the polarizing film.   The polarizing plate according to claim 1, wherein a protective film or an optical compensation film is provided on a surface opposite to the surface on which the stretched polyethylene terephthalate film is laminated in the polarizing film via an adhesive layer.   The polarizing plate according to claim 1, wherein the adhesive layer is formed of a cured layer of an ultraviolet curable resin composition containing an epoxy compound.   5. The polarizing plate according to claim 3, further comprising a pressure-sensitive adhesive layer laminated on a surface opposite to the surface on which the polarizing film is laminated in the protective film or the optical compensation film.   A liquid crystal display device comprising a liquid crystal panel, wherein the polarizing plate according to claim 5 is bonded to a liquid crystal cell via the adhesive layer.