JP2012013764A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

The present invention relates to a thin polarizing plate, which, when applied to a liquid crystal display device, has excellent display quality by suppressing warpage of the liquid crystal panel and light leakage caused thereby even under a high temperature environment. A liquid crystal display device using the same is provided.
A polarizing plate 10 in which a polarizing film 11 having a thickness of 10 μm or less and a protective film 12 are laminated, and a test piece having a length Lt1 in the width direction cut out from the polarizing plate 10 is 20 ° C. Assuming that the length in the width direction after heating from 84 to 84 ° C. in 1 minute and then maintaining at 84 ° C. for 4 hours is Lt2, the absolute value of the dimension expansion / contraction ratio St in the width direction calculated by the following formula (1) Is a polarizing plate and a liquid crystal display device using the same.
St = {(Lt2−Lt1) / Lt1} × 100 Formula (1)
[Selection] Figure 1

Description

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

  A polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. The polarizing plate usually has a configuration in which a protective film is laminated on both sides or one side of a polarizing film as disclosed in JP 2009-181042 A (Patent Document 1) and JP 2002-6133 A (Patent Document 2). It has become.

  2. Description of the Related Art In recent years, liquid crystal display devices and polarizing plates, which are constituent members thereof, are required to be thinner and lighter with the development of mobile devices such as notebook personal computers and mobile phones, and further development of large televisions. In addition, since the liquid crystal display device may be used in an environment that tends to be high temperature such as a vehicle, heat resistance is also demanded.

JP 2009-181042 A JP 2002-6133 A

  The polarizing film in the conventional polarizing plate is produced by stretching and dyeing a polyvinyl alcohol resin film raw material, and is usually subjected to crosslinking treatment with a crosslinking agent such as boric acid after dyeing.

  However, the polarizing plate produced in this way is likely to shrink in the stretching direction due to stretching relaxation of the polarizing film and shrinkage in the direction perpendicular to the stretching direction due to the progress of the crosslinking reaction in a high temperature environment. When applied to the above, there may be a problem in the display quality such as warpage of the liquid crystal panel and light leakage caused by it.

  The present invention is a thin polarizing plate, and when applied to a liquid crystal display device, a polarizing plate having good display quality by suppressing warpage of the liquid crystal panel and light leakage caused by the liquid crystal panel even under a high temperature environment, and the use thereof An object of the present invention is to provide a liquid crystal display device.

  The present invention comprises a polarizing film comprising a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented, uniaxially stretched, and a protective film bonded to one surface of the polarizing film. I will provide a. In the polarizing plate of the present invention, the polarizing film has a thickness of 10 μm or less. In the polarizing plate of the present invention, the test piece cut out from the polarizing plate is heated from 20 ° C. to 84 ° C. over 1 minute and then left in an environment maintained at 84 ° C., and the width of the test piece accompanying the change in the environment In the measurement test of the dimensional expansion and contraction rate in the direction, the length in the width direction of the test piece at 20 ° C. before the temperature rise is Lt1, and the length in the width direction of the test piece after being left for another 4 hours after the temperature rise is Lt2. Then, the dimension expansion / contraction rate St in the width direction calculated by the following formula (1) satisfies the relationship of the following formula (2). The width direction is perpendicular to the uniaxial stretching direction in the plane of the polarizing film.

St = {(Lt2−Lt1) / Lt1} × 100 Formula (1)
−0.3 ≦ St ≦ 0.3 Formula (2)
In the polarizing plate of the present invention, the saponification degree of the polyvinyl alcohol resin is preferably 98 mol% or more.

  Furthermore, the present invention provides a liquid crystal display device using the polarizing plate.

  According to the polarizing plate of the present invention, it is possible to configure a liquid crystal display device in which warpage of the liquid crystal panel, light leakage due to the liquid crystal panel, and color unevenness are suppressed even at high temperatures. In addition, according to the liquid crystal display device of the present invention, the liquid crystal display device can be configured to be thin, and even at high temperatures, warpage of the liquid crystal panel, light leakage and color unevenness due to the warpage can be suppressed.

It is a schematic sectional drawing which shows the fundamental layer structure of the polarizing plate which concerns on this invention. It is a flowchart which shows a preferable example of the manufacturing method of the polarizing plate which concerns on this invention. In a present Example, it is a schematic sectional drawing which shows the layer structure of the polarizing plate with a phase difference manufactured in order to implement light leakage evaluation.

Hereinafter, the polarizing plate of the present invention will be described in detail with reference to the drawings.
<Configuration of polarizing plate>
FIG. 1 is a schematic sectional view showing a basic layer structure of a polarizing plate according to the present invention. The polarizing plate 10 includes a polarizing film 11 and a protective film 12 that is bonded to one surface of the polarizing film 11. The polarizing film 11 is a polarizing film made of a polyvinyl alcohol resin having a dichroic dye adsorbed and oriented and uniaxially stretched, and has a thickness of 10 μm or less.

  The test piece cut out from the polarizing plate 10 is heated from 20 ° C. to 84 ° C. over 1 minute and then left in an environment where the test piece is maintained at 84 ° C., and the dimensional expansion / contraction ratio in the width direction of the test piece as the environment changes is measured. In this test, when the length in the width direction of the test piece at 20 ° C. before the temperature rise is Lt1, and the length in the width direction of the test piece after standing for 4 hours after the temperature rise is Lt2, the following formula ( The dimension expansion / contraction ratio St in the width direction calculated in 1) satisfies the relationship of the following formula (2). The direction of uniaxial stretching in the plane of the polarizing film 11 and the width direction in which the length is measured in the test for measuring the dimensional expansion / contraction rate are perpendicular.

St = {(Lt2−Lt1) / Lt1} × 100 Formula (1)
−0.3 ≦ St ≦ 0.3 Formula (2)
(Dimension stretch rate measurement)
The polarizing plate is cut with a super cutter into a width of 2 mm and a length of 50 mm so that the direction of the stretching axis is the long axis. The length in the width direction of the obtained strip-shaped test piece is measured using a thermomechanical analyzer (model TMA / 6100, manufactured by SII Nano Technology Co., Ltd.). This measurement is carried out in the tension / load control mode. After leaving the test piece in a room at 20 ° C. for a sufficient time, the initial length in the width direction (Lt1) of the test piece is measured, and then the inside of the sample room is measured. The temperature is set from 20 ° C. to 84 ° C. over 1 minute, and the temperature in the sample chamber is set to 84 ° C. after the temperature rise. After standing for 4 hours after the temperature rise, the length (Lt2) in the width direction of the test piece is measured under an environment of 84 ° C. In this measurement, the static load is 19.6 mN, and a SUS probe is used as a pulling jig. The dimension expansion / contraction ratio St is calculated from the measured value based on the formula (1). In the polarizing plate of the present invention, the dimensional expansion / contraction ratio St is set to −0.3 to 0.3, preferably −0.25 to 0.25 as shown in the formula (3). If the absolute value of the dimensional expansion / contraction ratio is larger than 0.3, there is a concern that warpage occurs when a polarizing plate is bonded to the liquid crystal cell and heat treatment is performed.

(Polarizing film)
As the polarizing film 11, a film made of a uniaxially stretched polyvinyl alcohol resin and adsorbed and oriented with a dichroic dye is used.

  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-based resin is preferably 98.0 mol% or more. If the saponification degree is less than 98.0 mol%, sufficient optical performance may not be obtained.

  The saponification degree as used herein is a unit ratio (mol%) representing the ratio of the acetate group contained in the polyvinyl acetate resin, which is a raw material for the polyvinyl alcohol resin, to a hydroxyl group by the saponification step. Is a numerical value defined by the following formula. It can be determined by the method defined in JIS K 6726 (1994).

Saponification degree (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
The higher the degree of saponification, the higher the proportion of hydroxyl groups, that is, the lower the proportion of acetate groups that inhibit crystallization. Further, the polyvinyl alcohol resin used in the present invention may be a modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol-based resins modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide, etc. . The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, and more preferably 1500 to 10,000.

  In the above-mentioned polyvinyl alcohol resin, additives such as a plasticizer and a surfactant may be added as necessary. As the plasticizer, polyols and condensates thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol resin.

  A film obtained by forming such a polyvinyl alcohol-based resin constitutes the polarizing film 111 according to the present invention. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. For example, it is formed by applying a polyvinyl alcohol resin solution obtained by dissolving polyvinyl alcohol resin powder in a good solvent on one surface of the substrate film and evaporating the solvent. By forming the resin layer to be the polarizing film 11 in this way, a thin polarizing film can be formed. Or the raw film which consists of polyvinyl alcohol-type resin as a resin layer used as the polarizing film 11 can also be used.

  The polarizing film 11 is uniaxially stretched. The draw ratio of uniaxial stretching is preferably more than 5 times, more preferably more than 5 times and not more than 17 times. The polarizing film 11 is generally manufactured through uniaxial stretching of a resin layer made of a polyvinyl alcohol resin, dyeing with a dichroic dye, crosslinking with a crosslinking agent, and then washing and drying.

  Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One type of these dichroic dyes may be used, or two or more types may be used in combination.

  Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

  The thickness of the polarizing film 11 is 10 micrometers or less, Preferably it is 1-8 micrometers. If the thickness of the polarizing film 11 exceeds 10 μm, the polarizing plate becomes thick.

(Protective film)
The protective film 12 may be a simple protective film having no optical function, or may be a protective film having an optical function such as a retardation film or a brightness enhancement film. The material of the protective film 12 is not particularly limited. For example, a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, Examples thereof include films that have been widely used in the art, such as polyester resin films, polycarbonate resin films, acrylic resin films, and polypropylene resin films made of a resin such as polybutylene terephthalate.

  Examples of the cyclic polyolefin-based resin include appropriate commercial products such as Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Nippon ZEON ( ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cyclic polyolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, pre-filmed cyclic polyolefins such as Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa (registered trademark) film (manufactured by Optes Co., Ltd.), etc. A commercial product of a film made of a resin may be used.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. An arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film by stretching. Stretching is usually performed continuously while unwinding the film roll, and is stretched in the heating furnace in the roll traveling direction, the direction perpendicular to the traveling direction, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 ° C. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

  Since the cyclic polyolefin resin film generally has poor surface activity, the surface to be bonded to the polarizing film 11 is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment. Is preferred. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  Examples of the cellulose acetate-based resin film include commercially available products such as Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark). TD80UZ (Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.) are preferably used. be able to.

  A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve viewing angle characteristics. Moreover, in order to provide a phase difference, what stretched the cellulose acetate type-resin film may be used. The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film 11. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  The thickness of the protective film 12 is preferably as thin as possible from the demand for thinning, is preferably 88 μm or less, and more preferably 48 μm or less. On the other hand, if it is too thin, the strength is lowered and the processability is poor, and therefore it is preferably 5 μm or more.

  The protective film 12 and the polarizing film 11 are bonded through, for example, an unillustrated adhesive layer or pressure-sensitive adhesive layer. In order to improve the adhesion, the surface of the protective film 12 and / or the polarizing film 11 is appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. Also good. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

(1) Adhesive layer The adhesive used for bonding of the polarizing film 11 and the protective film 12 includes, for example, a water-based adhesive using a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, or the like. . When a cellulose acetate film hydrophilized by a saponification process or the like is used as the protective film 12, a polyvinyl alcohol resin aqueous solution is suitably used as an aqueous adhesive for bonding to the polarizing film 11. Polyvinyl alcohol resins used as adhesives include polyvinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as other single quantities copolymerizable with vinyl acetate. And polyvinyl alcohol copolymers obtained by saponifying the copolymer with the polymer, and further modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive. When such a water-based adhesive is used, the adhesive layer obtained therefrom is usually 1 μm or less.

  Moreover, a photocurable adhesive can also be used as an adhesive at the time of bonding the polarizing film 11 and the protective film 12. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

(2) Adhesive layer The adhesive used for laminating the polarizing film 11 and the protective film 12 is usually based on an acrylic resin, a styrene resin, a silicone resin, etc., and there are an isocyanate compound and an epoxy compound. And a composition to which a crosslinking agent such as an aziridine compound is added. Furthermore, it can also be set as the adhesive layer which contains a light-diffusion agent and shows light diffusibility.

  The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm, but it is preferably applied thinly, and more preferably 3 to 25 μm, as long as the workability and durability characteristics are not impaired. When it is 3 to 25 μm, it has good processability and is also suitable for suppressing the dimensional change of the polarizing film. When the pressure-sensitive adhesive layer is less than 1 μm, the tackiness is lowered, and when it exceeds 40 μm, problems such as the pressure-sensitive adhesive protruding easily occur.

(Other optical layers)
The polarizing plate of the present embodiment having the above-described configuration can be used by stacking other optical layers in practical use. Moreover, the said protective film 12 may have a function of these optical layers. Examples of other optical layers include a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties, a film with an antiglare function having an uneven shape on the surface, and a surface antireflection function. Examples thereof include an attached film, a reflective film having a reflective function on the surface, a transflective film having both a reflective function and a transmissive function, a viewing angle compensation film, and a light diffusion film that diffuses light.

  Commercially available products corresponding to reflective polarizing films that transmit certain types of polarized light and reflect polarized light that exhibits the opposite properties include DBEF (available from 3M, Sumitomo 3M Co., Ltd.), APF (Available from 3M, available from Sumitomo 3M Limited). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate and oriented, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). Commercial products corresponding to retardation films made of cyclic polyolefin resins include Arton (registered trademark) film (manufactured by JSR Corporation), Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), Zeonor ( Registered trademark) film (manufactured by Optes Co., Ltd.). These optical layers are preferably disposed on the surface of the protective film 12 opposite to the surface bonded to the polarizing film 11. The protective film 12 and these optical layers can be bonded through the same adhesive layer or pressure-sensitive adhesive layer as described in the bonding of the protective film 12 and the polarizing film 11 described above.

<Production method of polarizing plate>
FIG. 2 is a flowchart showing an example of a method for producing a polarizing plate of the present invention. As shown in FIG. 2, the manufacturing method of the polarizing plate of this invention is a resin layer formation process (S10) which forms the resin layer which consists of polyvinyl alcohol-type resin on one surface of a base film, and makes it a laminated film, A polarizing film forming treatment step (S20) in which a polarizing film is applied to the resin layer to form a polarizing film, and a protective film is bonded to a surface opposite to the base film side of the polarizing film. A process (S30) and the base film peeling process (S40) which peels a base film from a laminated film are provided in this order. The polarizing film forming treatment step (S20) includes a uniaxial stretching step (S21) for uniaxially stretching the laminated film, a dyeing step (S22) for dyeing the resin layer with a dichroic dye, and a crosslinking step (S23). . In the polarizing film forming treatment step (S20), the uniaxial stretching step (S21) and the dyeing step (S22) are not limited to this order, and the uniaxial stretching step (S21) may be performed after the dyeing step (S22). The uniaxial stretching step (S21) and the dyeing step (S22) may be performed simultaneously.

[Base film]
As a material for the base film used in the above manufacturing method, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like is used. Specific examples of such thermoplastic resins include cellulose ester resins such as cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins. , (Meth) acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the base film preferably includes at least one selected from the group consisting of cellulose ester resins, polyolefin resins, cyclic polyolefin resins, and (meth) acrylic resins.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of such a cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UZ (Fuji Film ( Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), and the like.

  Examples of the polyolefin resin include polyethylene and polypropylene. When a base film made of polypropylene is used, it is preferable because it can be stably stretched at a high magnification. As the cyclic polyolefin resin, a norbornene resin is preferably used. Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as cyclic polyolefin resins. As specific examples, Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), ZEONEX (ZEONEX) (Registered trademark) (manufactured by ZEON CORPORATION) and Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, as the (meth) acrylic resin, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  Arbitrary appropriate additives other than said thermoplastic resin may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. . The content of the thermoplastic resin exemplified above in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97%. % By weight. This is because, if the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  Although the thickness of a base film can be determined suitably, generally 1-500 micrometers is preferable from the point of workability | operativity, such as intensity | strength and a handleability, 1-300 micrometers is more preferable, Furthermore, 5-200 micrometers is preferable. As for the thickness of a base film, 5-150 micrometers is the most preferable.

  The base film may be subjected to corona treatment, plasma treatment, flame treatment or the like on at least the surface on which the resin layer is formed in order to improve the adhesion with the resin layer. Moreover, in order to improve adhesiveness, you may form thin layers, such as a primer layer, in the surface at the side by which the resin layer of a base film is formed.

[Resin layer forming process]
In the resin layer forming step (S10) shown in FIG. 2, a solution containing a polyvinyl alcohol-based resin is applied on one surface of the base film to form a resin layer. The polyvinyl alcohol resin to be used is as described above.

  Known coating methods for solutions containing polyvinyl alcohol resins include wire bar coating, roll coating such as reverse coating and gravure coating, spin coating, screen coating, fountain coating, dipping and spraying. These methods can be selected as appropriate and employed. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. The drying time is, for example, 5 to 30 minutes.

  In the resin layer forming step (S10), it is also possible to form the resin layer by sticking a raw film made of polyvinyl alcohol resin on one surface of the base film.

[Polarization film process]
(Uniaxial stretching process)
In the uniaxial stretching step (S21) shown in FIG. 2, the laminated film composed of the base film and the resin layer is uniaxially stretched so that the draw ratio is preferably more than 5 times the original length of the laminated film. More preferably, the film is uniaxially stretched so that the draw ratio is more than 5 times and not more than 17 times. If the draw ratio is 5 times or less, the resin layer made of the polyvinyl alcohol-based resin is not sufficiently oriented, and as a result, the polarization degree of the polarizing film may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the laminated film is easily broken at the time of drawing, and at the same time, the thickness of the laminated film becomes unnecessarily thin, and the workability and handling properties in the subsequent process may be reduced. The stretching process in the uniaxial stretching step (S21) is not limited to stretching in one stage, and can be performed in multiple stages. When performing in multiple stages, the stretching process is performed so that the stretching ratio is preferably more than 5 times for all stages of the stretching process.

  In the uniaxial stretching step (S21) in the present invention, the longitudinal stretching treatment performed in the longitudinal direction of the laminated film is preferable. Examples of the longitudinal stretching method include an inter-roll stretching method, a compression stretching method, and a stretching method using a tenter. The stretching process is not limited to the longitudinal stretching process, and may be an oblique stretching process or the like.

  In addition, as the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but the use of the dry stretching method is preferable because the temperature at which the laminated film is stretched can be selected from a wide range.

(Dyeing process)
In the dyeing step (S22) shown in FIG. 2, the resin layer of the laminated film is dyed with a dichroic dye. The dichroic dye used is as described above.

  A dyeing process is performed by immersing the whole laminated film which consists of a substrate film and a resin layer, for example in the solution (dyeing solution) containing the above-mentioned dichroic dye. As the staining solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. As a solvent for the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

  When iodine is used as the dichroic dye, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 10% by weight in the dyeing solution. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80 by weight. , Particularly preferably in the range of 1: 7 to 1:70.

  The immersion time of the laminated film in the dyeing solution is not particularly limited, but is usually preferably in the range of 15 seconds to 15 minutes, and more preferably 1 minute to 3 minutes. Moreover, it is preferable that it is in the range of 10-60 degreeC, and, as for the temperature of a dyeing | staining solution, it is more preferable that it exists in the range of 20-40 degreeC.

  In the dyeing step, the dichroic dye is adsorbed on the resin layer made of the polyvinyl alcohol resin of the laminated film to orient the dichroic dye. The dyeing step (S22) can be performed before, simultaneously with, or after the uniaxial stretching step (S21). From the viewpoint of satisfactorily orienting the dichroic dye adsorbed on the resin layer made of the polyvinyl alcohol-based resin, lamination is performed. It is preferable to carry out after performing a uniaxial stretching process (S21) to a film.

(Crosslinking process)
In the polarizing film forming process step (S20) shown in FIG. 2, when the uniaxial stretching step (S21) and the dyeing step (S22) are completed, a crosslinking step (S23) is performed. The crosslinking step (S23) can be performed, for example, by immersing the laminated film in a solution containing a crosslinking agent (crosslinking solution).

  As the crosslinking solution, a solution obtained by dissolving the above-described crosslinking agent in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1 to 10 weight%, and it is more preferable that it is 2 to 6 weight%.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The iodide content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

  The immersion time of the laminated film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, and more preferably from 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking solution exists in the range of 10-80 degreeC.

  A bridge | crosslinking process (S23) can also perform a bridge | crosslinking process and a dyeing process (S22) simultaneously by mix | blending a crosslinking agent in a dyeing | staining solution. Preferably, the crosslinking step (S23) and the uniaxial stretching step (S21) are not performed simultaneously. When the stretching process is performed during the cross-linking step (S23), a neck-in of the laminated film is likely to occur.

(Other processes)
In the polarizing film forming treatment step (S20), it is preferable to finally perform a washing step and a drying step. As the washing step, a water washing treatment can be performed. A water washing process can be normally performed by immersing the laminated film which passed through the uniaxial stretching process (S21), the dyeing process (S22), and the bridge | crosslinking process (S23) in pure water, such as ion-exchange water and distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 5 to 240 seconds.

  In the washing step, washing treatment with an iodide solution and water washing treatment may be combined, and a solution in which liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like is appropriately blended may be used.

  It is preferable to perform a drying process after the washing process. Any appropriate method (for example, natural drying, ventilation drying, heat drying) can be adopted as the drying step. For example, the drying temperature in the case of heat drying is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. Through the above polarizing film forming treatment step (S20), the resin layer has a function as a polarizing film. In this specification, the resin layer that has undergone the polarizing film forming step (S20) is also referred to as a polarizing film.

[Protective film bonding process]
In the protective film bonding step (S30) shown in FIG. 2, the protective film 12 is bonded to the surface of the polarizing film 11 opposite to the surface on the base film side. Examples of the method of bonding the protective film 12 include a method of bonding the polarizing film 11 and the protective film 12 with an adhesive, and a method of bonding the polarizing film 11 and the protective film 12 with an adhesive. The pressure-sensitive adhesive and adhesive that can be used are as described above.

  When using an aqueous adhesive, after laminating the polarizing film 11 and the protective film 12, the laminated film is dried in order to remove water contained in the aqueous adhesive. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If the temperature is lower than 30 ° C., the polarizing film surface and the protective film surface tend to peel off. If it exceeds 90 ° C., the optical performance may be deteriorated by heat. The drying time can be 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

  After drying, it may be further cured at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C. for about 12 to 600 hours. The temperature at the time of curing is generally set lower than the temperature adopted at the time of drying.

  For applying the adhesive to the polarizing film 11 or the protective film 12, a conventionally known method can be used, for example, casting method, Mayer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating. Examples thereof include a method of applying an adhesive to the adhesive surface of the polarizing film 11 and / or the protective film 12 by a method, a dip coating method, a spraying method, or the like. In the casting method, the polarizing film 11 or the protective film 12 that is an object to be coated is moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two, and the adhesive is allowed to flow down on the surface to spread. It is a method to make it.

  After the adhesive is applied to the surface of the polarizing film 11 or the protective film 12, the polarizing film 11 and the protective film 12 are bonded together by being sandwiched by a nip roll or the like through the adhesive application surface. Also, after the adhesive film is dropped between the polarizing film 11 and the protective film 12 in a state where the polarizing film 11 and the protective film 12 are overlapped, the laminated film is pressed with a roll or the like to be uniformly spread. It can be preferably used. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, after dripping an adhesive agent between a polarizing film and a protective film, the method of passing this laminated film between rolls and pressurizing and spreading is preferably employed. In this case, these rolls may be made of the same material or different materials. The thickness of the adhesive layer after being bonded using the nip roll or the like before drying or curing is preferably 5 μm or less and 0.01 μm or more.

  When a photocurable resin is used as an adhesive, the photocurable adhesive is cured by irradiating active energy rays after bonding the polarizing film 11 and the protective film 12. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / it is preferable that the cm ^2. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the epoxy is generated by the heat radiated from the light source and the heat generated when the photo-curable adhesive is cured. There is little risk of yellowing of the resin or deterioration of the polarizing film. The light irradiation time to the photocurable adhesive is not particularly limited and is applied according to the photocurable adhesive to be cured, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time. Is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more and 2 μm or less, more preferably 0.01 μm or more and 1 μm or less.

  When curing a photocurable adhesive by irradiation with active energy rays, curing should be performed under conditions that do not deteriorate the functions of the polarizing plate, such as the degree of polarization of the polarizing film, the transmittance and hue, and the transparency of the protective film 12. Is preferred.

  In the method of bonding the polarizing film 11 and the protective film 12 with the pressure-sensitive adhesive, the pressure-sensitive adhesive layer may be provided on the surface of the protective film 12, and then bonded to the polarizing film 11. After providing the agent layer, the protective film 12 may be bonded here.

  The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a solution containing each component including the above-mentioned base polymer is applied to the surface of the protective film 12 or the surface of the polarizing film 11 and dried. After forming the layer, the protective film 12 and the polarizing film 11 may be bonded together, or after forming the pressure-sensitive adhesive layer on the separator, it may be transferred and laminated on the protective film 12 surface or the polarizing film 11 surface. Good. Further, when the pressure-sensitive adhesive layer is formed on the surface of the protective film 12 or the polarizing film 11, if necessary, the protective film 12 or the surface of the polarizing film 11, or one or both of the pressure-sensitive adhesive layers, for example, corona treatment May be applied.

[Base film peeling process]
In the manufacturing method of the polarizing plate of this invention, as shown in FIG. 2, a base film peeling process (S40) is performed after the protective film bonding process (S30) which bonds the polarizing film 11 and the protective film 12. As shown in FIG. In the base film peeling step (S40), the base film is peeled from the laminated film. The peeling method of a base film is not specifically limited, It can peel by the method similar to the peeling process of the peeling film performed with a normal polarizing plate with an adhesive. After the protective film bonding step (S30), the protective film may be peeled off as it is, or after the protective film is wound up in a roll shape after the bonding step (S30), it may be peeled off while being unwound in the subsequent step. .

<Configuration of liquid crystal display device>
The polarizing plate according to the present invention is suitable as a constituent member of a liquid crystal display device. The liquid crystal display device according to the present invention can be manufactured in accordance with a conventionally known method. That is, the liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a polarizing plate, and other components such as a lighting system as necessary, and further assembling a driving circuit. There is no limitation in particular except the point which uses the polarizing plate concerning this invention, and it applies to the former. As the liquid crystal cell, any type such as a TN type or an STN type can be used.

  A liquid crystal display device can be configured by disposing a polarizing plate on one side or both sides of a liquid crystal cell and further using a backlight or a reflection plate as appropriate in an illumination system. In such a liquid crystal display device, at least one of the polarizing plates disposed on one side or both sides of the liquid crystal cell is a polarizing plate according to the present invention. When providing polarizing plates on both the viewing side and the back side, they may be the same or different. In addition to the above, the liquid crystal display device can be configured by combining appropriate elements such as a diffusion plate, an antireflection film, a protective plate, a prism array, and a lens array sheet.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

[Example 1]
(Base film)
An unstretched random polypropylene (PP) film (melting point: 138 ° C.) having a thickness of 110 μm was used as the base film.

(Formation of primer layer)
Polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%, trade name: Z-200) is dissolved in 95 ° C. hot water to a concentration of 3% by weight in aqueous solution. Adjusted. The resulting aqueous solution was mixed with 5 parts by weight of a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumirez (registered trademark) resin 650) with respect to 6 parts by weight of polyvinyl alcohol powder. The obtained mixed aqueous solution was coated on a substrate film subjected to corona treatment and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(Formation of resin layer)
Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98 to 99 mol%) was dissolved in 95 ° C. hot water to prepare a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. The obtained aqueous solution was applied onto the primer layer and dried at 80 ° C. for 20 minutes to produce a three-layer laminated film comprising a base film, a primer layer, and a resin layer. At this time, the thickness of the resin layer was 7.9 μm.

(Polarized film processing process)
The laminated film was stretched 5.8 times by free end uniaxial stretching in the longitudinal direction at a heating temperature of 120 to 136 ° C. using a tenter device to obtain a stretched film. Thereafter, the stretched film was immersed in a warm bath at 60 ° C. for 60 seconds, immersed in a mixed aqueous solution of iodine and potassium iodide at 30 ° C. for 300 seconds, and then the excess iodine solution was washed away with 10 ° C. pure water. Next, it was immersed in a mixed aqueous solution of boric acid and potassium iodide at 76 ° C. for 600 seconds. Thereafter, it was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 50 ° C. for 300 seconds to obtain a polarizing film with a base film.

(Protective film bonding process, base film peeling process)
After applying a polyvinyl alcohol-based adhesive on the surface opposite to the surface on the base film side of the polarizing film with the base film, a protective film (manufactured by Konica Corporation, film thickness 40 μm, TAC) is bonded, A polarizing plate comprising four layers of a protective film, a polarizing film, a primer layer, and a base film was obtained. The base film was peeled from the obtained polarizing plate to obtain the polarizing plate of Example 1. At this time, the thickness of the polarizing film was 4.5 μm.

(Dimension stretch rate measurement)
The measurement test of the dimensional expansion / contraction rate of the polarizing plate of Example 1 was performed as described above, the lengths Lt1 and Lt2 in the width direction were measured, and the amount of change Lt2−Lt1 and the dimensional expansion / contraction rate St were calculated. Table 1 shows the results.

(Warpage measurement)
In the polarizing plate of Example 1, an acrylic pressure-sensitive adhesive layer was provided on the surface from which the base film was peeled off, and was cut into 72 mm × 40 mm so that the stretching axis direction was the short side direction. After bonding to the TFT surface of a 6 mm liquid crystal cell, it was allowed to stand in an oven at 85 ° C. for 72 hours. After taking out from the oven, one end of the liquid crystal cell was pressed to check whether the liquid crystal cell was warped. Table 1 shows the results.

(Light leakage evaluation)
In the polarizing plate of Example 1, an acrylic pressure-sensitive adhesive layer, a phase difference plate (manufactured by Sekisui Chemical Co., Ltd., Essina), and an acrylic pressure-sensitive adhesive layer are provided in this order on the surface from which the substrate film has been peeled off, and polarized light with retardation is provided. A plate was made. FIG. 3 is a schematic cross-sectional view showing the layer configuration of the polarizing plate with retardation. As shown in FIG. 3, the retardation polarizing plate 20 has a configuration in which an acrylic pressure-sensitive adhesive layer 21, a phase difference plate 22, an acrylic pressure-sensitive adhesive layer 23, a polarizing film 24, and a protective film 25 are laminated in this order. Two polarizing plates 20 with a phase difference of 72 mm × 40 mm were prepared for the viewing side and for the back side.

  When viewed from the protective film 25 side, the polarizing plate with retardation for viewing side is 45 counterclockwise that the absorption axis (stretching axis) direction of the polarizing film 24 makes with respect to the long side direction of the polarizing plate with retardation. The retardation plate 22 was laminated so that the slow axis direction of the retardation film 22 was 0 ° with respect to the long side direction of the retardation film.

  When viewed from the protective film 25 side, the polarizing plate with retardation on the back side has an absorption axis (stretching axis) direction of the polarizing film 24 of 45 ° counterclockwise with respect to the long side direction of the polarizing plate with retardation. Thus, the retardation plate 22 was laminated so that the slow axis direction of the retardation plate 22 was 90 ° with respect to the long side direction of the polarizing plate with retardation.

  About the obtained two polarizing plates with retardation, non-alkali glass (Corning Co., Ltd., Eagle 2000) so that the polarizing plate with retardation on the viewing side and the polarizing plate with retardation on the back side are crossed Nicols. A sample for evaluation was attached to the front and back. The obtained sample for evaluation was allowed to stand in an oven at 85 ° C. for 72 hours, and after taking out, placed on the backlight so that the polarizing plate with retardation on the back side was in contact with the backlight, and observed the light leakage situation. did. Table 1 shows the results.

[Example 2]
In Example 1, an unstretched homopolypropylene (PP) film (melting point: 163 ° C.) was used as the base film, the thickness of the resin layer before stretching was 14 μm, and the heating temperature during stretching was 140 to 160. A polarizing plate of Example 2 was obtained in the same manner as in Example 1 except that the temperature was changed to ° C. At this time, the thickness of the polarizing film was 6.8 μm. As with Example 1, the polarizing plate of Example 2 was subjected to dimensional expansion / contraction measurement, warpage measurement, and light leakage evaluation. Table 1 shows the results.

[Example 3]
In Example 2, the polarizing plate of Example 3 was obtained in the same manner as in Example 2 except that the draw ratio in the polarizing film forming treatment step was 5.5 times. At this time, the thickness of the polarizing film was 7.0 μm. For the polarizing plate of Example 3, similarly to Example 1, the dimensional stretch ratio measurement, the warpage measurement, and the light leakage evaluation were performed. Table 1 shows the results.

[Comparative example]
A polyvinyl alcohol film having a thickness of 75 μm made of polyvinyl alcohol having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more is uniaxially stretched about 5 times in a dry manner and further kept at a tension state at 60 ° C. After being immersed in pure water for 1 minute, it was immersed in a mixed aqueous solution of iodine and potassium iodide at 28 ° C. for 60 seconds. Thereafter, it was immersed in a mixed aqueous solution of boric acid and potassium iodide at 72 ° C. for 300 seconds. At this time, neck-in was observed in the width direction of the film. Subsequently, it was washed with pure water at 10 ° C. for 5 seconds and then dried at 90 ° C. for 180 seconds (again, neck-in was observed in the width direction) to obtain a polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol.

  Separately, in 100 parts by weight of water, 3 parts by weight of Kuraray Poval 117H (manufactured by Kuraray Co., Ltd.), 3 parts by weight of Goseifamer Z-200 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), zinc chloride (Nacalai Tesque Co., Ltd.) Soldered from 0.1) 0.18 parts by weight and 1.4 parts by weight of Glyoxal (sold from Nacalai Tesque) were dissolved to prepare a polyvinyl alcohol resin adhesive.

  A protective film (made by Konica Corporation, film thickness: 40 μm, product name: TAC) subjected to saponification treatment is bonded to one surface of the previously obtained polarizing film with a nip roll through the adhesive. did. Thereafter, it was dried at 50 ° C. for 300 seconds to obtain a polarizing plate of a comparative example. At this time, the thickness of the polarizing film was 28 μm.

  For the polarizing plate of the comparative example, the dimensional expansion / contraction rate measurement, the warpage measurement, and the light leakage evaluation were performed in the same manner as in Example 1. Table 1 shows the results.

  In light leakage evaluation, light leakage could not be confirmed in Examples 1 to 3, whereas light leakage was confirmed on the four sides in Comparative Example. From the results shown in Table 1, as can be seen in Examples 1 to 3, the polarizing film has a thickness of 10 μm or less, and the absolute value of the dimensional stretch rate St of the test piece cut out from the polarizing plate is 0.3 or less. In FIG. 5, it can be seen that warpage of the liquid crystal cell and light leakage could be suppressed. In addition, since light leakage can be suppressed as described above, the application of the polarizing plate to a liquid crystal display device is expected to suppress color unevenness in the device.

  DESCRIPTION OF SYMBOLS 10 Polarizing plate, 11, 24 Polarizing film, 12, 25 Protective film, 20 Retardation polarizing plate, 21, 23 Acrylic adhesive layer, 22 Retardation plate.

Claims (3)

A polarizing film made of a polyvinyl alcohol-based resin having a dichroic dye adsorbed and oriented, and uniaxially stretched;
A polarizing plate having a protective film bonded to one surface of the polarizing film,
The polarizing film has a thickness of 10 μm or less,
The test piece cut out from the polarizing plate was heated from 20 ° C. to 84 ° C. over 1 minute and then left in an environment maintained at 84 ° C., and the dimensional expansion / contraction ratio in the width direction of the test piece accompanying the change in the environment In the test for measuring the length in the width direction of the test piece at 20 ° C. before the temperature rise is Lt1, and the length in the width direction of the test piece after being left for another 4 hours after the temperature rise is Lt2. Then, the dimensional expansion / contraction ratio St calculated by the following formula (1) satisfies the relationship of the following formula (2), and the width direction is perpendicular to the direction of the uniaxial stretching in the plane of the polarizing film. ,Polarizer.
St = {(Lt2−Lt1) / Lt1} × 100 Formula (1)
−0.3 ≦ St ≦ 0.3 Formula (2)   The polarizing plate of Claim 1 whose saponification degree of the said polyvinyl alcohol-type resin is 98 mol% or more.   A liquid crystal display device using the polarizing plate according to claim 1.

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