WO2017047407A1

WO2017047407A1 - Composite polarizing plate and liquid crystal panel using same

Info

Publication number: WO2017047407A1
Application number: PCT/JP2016/075808
Authority: WO
Inventors: 寿和松本
Original assignee: 住友化学株式会社
Priority date: 2015-09-18
Filing date: 2016-09-02
Publication date: 2017-03-23
Also published as: TW201720644A; TWI681874B; JPWO2017047407A1

Abstract

Provided is a composite polarizing plate that experiences little reduction in degree of polarization at high temperatures. Also provided is a liquid crystal panel that has high heat resistance. A composite polarizing plate in which the following are laminated, in order: a first protective film; a first polarizing film that has a thickness of 15 μm or less; and a second polarizing film that has a thickness of 15 μm or less. The absorption axis of the first polarizing film and the absorption axis of the second polarizing film are approximately parallel.

Description

Composite polarizing plate and liquid crystal panel using the same

The present invention relates to a composite polarizing plate excellent in durability and a liquid crystal panel using the same.

In recent years, liquid crystal display devices have been rapidly used as information display devices such as mobile phones, personal digital assistants, computer monitors, and televisions by taking advantage of low power consumption, low voltage operation, light weight, and thinness. It has become widespread. With the development of liquid crystal technology, liquid crystal display devices of various modes have been proposed, and problems of liquid crystal display such as response speed, contrast, and narrow viewing angle are being solved. Under such circumstances, liquid crystal display devices have also been developed in fields where high durability is required such as in-vehicle applications. However, for a severe endurance test at a temperature of 95 ° C., there is a problem that the polarization degree is greatly lowered in a polarizing plate dyed with a conventional polyvinyl alcohol resin with iodine.

Japanese Patent Application Laid-Open No. 2002-072162 (Patent Document 1) discloses a configuration in which two polarizing plates are used on the light emission side of a projection display device. The polarizing plates are spatially separated. When a cooling gas is passed between two polarizing plates or a sapphire or crystal with high thermal conductivity is sandwiched between two polarizing plates, the refractive index is placed at the interface of the air layer or quartz. There is a problem that reflection due to the difference is large and the light use efficiency is lowered.

JP-A-10-133196 (Patent Document 2) discloses a composite polarizing plate obtained by directly laminating polarizing plates with improved heat resistance for a liquid crystal projector. However, a polarizing plate in which a triacetyl cellulose film is disposed as a protective layer on both sides of a polarizing film having a thickness of 20 to 30 μm has a large shrinkage force when the heat is applied. Problems such as peeling of the plate may occur. Further, when a material such as glass having a thermal conductivity of 0.8 W / m · K or more is used as the protective layer of the polarizing film, there is a problem that processing such as cutting is not easy and production efficiency is low. For these reasons, there is also a problem that it is difficult to provide functionality by providing a surface treatment layer on the surface of the composite polarizing plate.

JP 2002-072162 A JP-A-10-133196

An object of the present invention is to provide a composite polarizing plate that has a small decrease in polarization degree at high temperatures and is excellent in heat resistance and durability. Another object of the present invention is to provide a liquid crystal panel having high heat resistance.

That is, according to the present invention, the first protective film, the first polarizing film having a thickness of 15 μm or less, and the second polarizing film having a thickness of 15 μm or less are laminated in this order, and the absorption axis of the first polarizing film and the first polarizing film A composite polarizing plate in which the absorption axis of the polarizing film of 2 is substantially parallel is provided.

Further, according to the present invention, there is also provided a composite polarizing plate in which the second protective film is laminated on the surface opposite to the surface on which the first polarizing film is laminated.

In this composite polarizing plate, the single transmittance of the first polarizing plate having the first polarizing film and the first protective film is the single transmittance of the second polarizing plate having the second polarizing film and the second protective film. Preferably, the difference between the thickness of the first polarizing film and the thickness of the second polarizing film is 5 μm or less. Moreover, the composite polarizing plate which provides an adhesive layer on the surface on the opposite side to the surface where the 2nd polarizing film of the 2nd protective film was laminated | stacked in order to bond to a liquid crystal panel is also provided.

The second protective film preferably contains at least one selected from the group consisting of a cellulose resin, a polyolefin resin, and an acrylic resin, and preferably has a thickness direction retardation value of −10 to 10 nm.

Further, according to the present invention, a composite polarizing plate having a third protective film between the first polarizing film and the second polarizing film is also provided.

The third protective film is made of a cellulose-based resin, has an in-plane retardation value Re (590) at a wavelength of 590 nm of 10 nm or less, and an absolute value of a thickness direction retardation value Rth (590) at a wavelength of 590 nm is 10 nm or less. It is preferable that

The present invention also provides a liquid crystal panel in which the above-mentioned composite polarizing plate is laminated on at least one of the liquid crystal cells via an adhesive.

According to the present invention, a composite polarizing plate and a liquid crystal panel excellent in heat resistance and durability can be obtained by laminating two polarizing films having a thickness of 15 μm or less.

It is an example of the cross-sectional schematic diagram which shows the layer structure of the composite polarizing plate which concerns on this invention. It is an example of the cross-sectional schematic diagram which shows the layer structure of the composite polarizing plate which concerns on this invention. It is an example of the cross-sectional schematic diagram which shows the layer structure of the composite polarizing plate which concerns on this invention.

Referring to FIG. 1, the layer configuration of the composite polarizing plate 10 according to the present invention will be described. The composite polarizing plate 10 according to the present invention is configured by laminating a first protective film 12A, a first polarizing film 11A, and a second polarizing film 11B in this order. It is preferable that the 2nd protective film 12B is laminated | stacked on the surface on the opposite side to the surface where 11 A of 1st polarizing films in the 2nd polarizing film 11B were laminated | stacked. It is also useful to form the surface treatment layer 20 on the surface of the first protective film 12A opposite to the bonding surface of the first polarizing film 11A.

2, the composite polarizing plate 10 according to the present invention includes a first protective film 12A, a first polarizing film 11A, a third protective film 15, and a second polarizing film 11B laminated in this order. Configured. It is preferable that the 2nd protective film 12B is laminated | stacked on the surface on the opposite side to the surface where the 3rd protective film 15 was laminated | stacked in the 2nd polarizing film 11B. It is also useful to form the surface treatment layer 20 on the surface of the first protective film 12A opposite to the bonding surface with the first polarizing film 11A.

In the composite polarizing plate of the present invention, the first polarizing film 11A and the second polarizing film 11B are arranged so that their absorption axes are substantially parallel. In the present specification, the term “substantially parallel” means that the angle between the two is not strictly limited to 0 °, and for example, is within a range of 0 ± 5 °, preferably within a range of 0 ± 3 °.

Hereinafter, a laminated body including the first protective film 12A and the first polarizing film 11A is referred to as a first polarizing plate, and a laminated body including the second polarizing film 11B and the second protective film 12B is referred to as a second polarizing film. Sometimes called a polarizing plate. The third protective film 15 is included in either the first polarizing plate or the second polarizing plate. That is, the composite polarizing plate 10 of the present invention preferably has a layer configuration in which a first polarizing plate and a second polarizing plate are laminated.

In order to suppress the contraction force of the polarizing plate in a high temperature environment, the thickness of both the first polarizing film and the second polarizing film is set to 15 μm or less. Further, since the single transmittance of the first polarizing plate is smaller than the single transmittance of the second polarizing plate, the single transmittance of the composite polarizing plate can be further increased.

Furthermore, it is preferable that the difference between the thickness of the first polarizing film and the thickness of the second polarizing film is 5 μm or less. The second protective film preferably contains at least one selected from the group consisting of a cellulose resin, a polyolefin resin, and an acrylic resin. In addition, the thickness direction retardation value of the second protective film is preferably −10 to 10 nm.

In the composite polarizing plate 10, an adhesive layer 14 may be laminated on the second polarizing film or the second protective film. A composite polarizing plate can be bonded to a liquid crystal cell through the pressure-sensitive adhesive layer 14 to obtain a liquid crystal panel. Usually, although a polarizing plate is bonded on both surfaces of a liquid crystal cell, the composite polarizing plate of this invention is used suitably for the visual recognition side of a liquid crystal display device, a back surface side, or both.

The third protective film 15 is made of a cellulose resin film, has an in-plane retardation value Re (590) of 10 nm or less at a wavelength of 590 nm, and an absolute value of a thickness direction retardation value Rth (590) at a wavelength of 590 nm. Is preferably 10 nm or less.

In the composite polarizing plate of the present invention, although the degree of polarization of each polarizing plate may be lowered after being placed in a high temperature environment, the two polarizing plates are laminated in paranicol. As a result, a decrease in the degree of polarization can be suppressed.

Hereinafter, each member constituting the composite polarizing plate and the liquid crystal panel according to the present invention will be described in detail with reference to the reference numerals attached to FIG. 1 and FIG.

[Polarized film]
The first polarizing film 11A and the second polarizing film 11B constituting the composite polarizing plate 10 are usually a step of uniaxially stretching a polyvinyl alcohol-based resin film, and by staining the polyvinyl alcohol-based resin film with a dichroic dye. Produced through a step of adsorbing a dichroic dye, a step of crosslinking a polyvinyl alcohol resin film adsorbed with a dichroic dye with a boric acid aqueous solution, and a step of washing with water after the crosslinking treatment with a boric acid aqueous solution. be able to.

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

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

A film obtained by forming such a polyvinyl alcohol resin is used as an original film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The film thickness of the polyvinyl alcohol resin raw film is, for example, about 10 to 100 μm, preferably about 10 to 50 μm.

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

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

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. The immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

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

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

The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of immersing a boric acid-treated polyvinyl alcohol resin film in water. A solution containing potassium iodide may be used for washing with water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying process is performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature for the drying treatment is usually about 30 to 100 ° C., preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to a practical level. The water content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

As described above, a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol resin film can be produced.

Further, the stretching, dyeing, boric acid treatment, water washing step, and drying step of the polyvinyl alcohol resin film in the production process of the polarizing film may be performed in accordance with, for example, the method described in JP2012-159778A. . In the method described in this document, it is also useful to use a method of forming a polyvinyl alcohol resin layer to be a polarizing film by coating a polyvinyl alcohol resin on a base film.

It is also preferable to reduce the contraction force of the polarizing film itself from the viewpoint of suppressing a decrease in the degree of polarization under a high temperature environment and from the viewpoint of maintaining a good appearance. In order to suppress the shrinkage force of the polarizing film under a high temperature environment, the thickness of the polarizing film is preferably 12 μm or less. The thickness of the polarizing film is usually 3 μm or more in that good optical properties can be imparted.

The thickness difference between the thickness of the first polarizing film 11A and the thickness of the second polarizing film 11B is preferably 5 μm or less. More preferably, it is 3 μm or less. Thus, by using a polarizing film with a small thickness difference, the behavior of dimensional change under a high temperature environment can be matched between the first polarizing film 11A and the second polarizing film 11B. Therefore, it is thought that the crack of the polarizing film which generate | occur | produces due to the difference in the stress by the thermal contraction difference of two polarizing films is suppressed.

The polarizing film preferably has a shrinkage force of 2 N or less per 2 mm width in the absorption axis direction when held at a temperature of 80 ° C. for 240 minutes. If the shrinkage force is greater than 2N, the amount of dimensional change under a high temperature environment increases, and the shrinkage force of the polarizing film increases, so that the polarizing film tends to be easily cracked or peeled off. The shrinkage force of the polarizing film tends to be 2N or less when the draw ratio is lowered and the thickness of the polarizing film is reduced.

The difference in shrinkage force per 2 mm width in the absorption axis direction between the two polarizing films is preferably 1 N or less, and more preferably 0.5 N or less. As will be described later, in the composite polarizing plate of the present invention, it is preferable that the single transmittance of the second polarizing plate is larger than the single transmittance of the first polarizing plate. The magnitude of the contraction force may be different. For example, the difference in contraction force may be 0.1 N or more.

[First protective film 12A]
12 A of 1st protective films used for the composite polarizing plate 10 can be comprised with a transparent resin film. In particular, it is preferable to use a material that is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. In this specification, the transparent resin film means a resin film having a single transmittance of 80% or more in the visible light region.

As the first protective film 12A, a conventional protective film forming material in this field, such as a cellulose resin, a chain polyolefin resin, a cyclic polyolefin resin, an acrylic resin, a polyimide resin, a polycarbonate resin, and a polyester resin A film formed from a widely used material can be used. As a material constituting the protective film 12A, for example, a cellulose resin is preferable.

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

These resins may contain appropriate additives as long as the transparency is not impaired. Additives such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact aids , Matting agents, antibacterial agents, fungicides and the like. A plurality of these additives may be used in combination.

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

These resin films can be easily obtained as commercial products. Examples of commercially available films include “Fujitac (registered trademark) TD” sold by Fuji Film Co., Ltd. and Konica Minolta Co., Ltd., respectively, as cellulose resin films. Konica Minolta TAC Film KC ”.

[Surface treatment layer 20 of first protective film 12A]
12 A of 1st protective films may have the surface treatment layer 20 in the surface on the opposite side to the surface bonded by 11 A of 1st polarizing films. Examples of the surface treatment layer 20 include a hard coat layer having a fine surface irregularity shape. The hard coat layer preferably has a pencil hardness higher than H. If the pencil hardness is H or smaller, the surface is likely to be scratched, and if the pencil hardness is scratched, the visibility of the liquid crystal display device is deteriorated. The pencil hardness is determined in accordance with JIS K 5600-5-4: 1999 “General test methods for coating materials—Part 5: Mechanical properties of coating film—Section 4: Scratch hardness (pencil method)”. It is represented by the hardness of the hardest pencil that does not cause scratches when scratched with a pencil.

The first protective film 12A having the surface treatment layer 20 preferably has a haze value in the range of 0.1 to 45%, more preferably in the range of 5 to 40%. When the haze value is larger than 45%, the reflection of external light can be reduced, but the black display screen is reduced. On the other hand, when the haze value is less than 0.1%, sufficient antiglare performance cannot be obtained, and external light is reflected on the screen, which is not preferable. Here, the haze value is determined according to JIS K 7136: 2000 “Plastics—How to determine haze of transparent material”.

The hard coat layer with fine surface irregularities forms a method of forming a coating film containing organic fine particles or inorganic fine particles on the surface of the resin film, or a coating film containing or not containing organic fine particles or inorganic fine particles. Then, it can be formed by a method of pressing against a roll having an uneven shape, such as an embossing method. Such a coating film can be formed by, for example, a method of applying a coating liquid (curable resin composition) containing a binder component made of a curable resin and organic fine particles or inorganic fine particles to the surface of the resin film. .

As the inorganic fine particles, for example, silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate and the like can be used. Further, as the organic fine particles, resin particles such as crosslinked polyacrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicone resin particles, or polyimide particles should be used. Can do.

The binder component for dispersing inorganic fine particles or organic fine particles may be selected from materials having high hardness (hard coat). As the binder component, a photocurable resin, a thermosetting resin, an electron beam curable resin, and the like can be used. From the viewpoint of productivity and the hardness of the surface treatment layer 20 to be obtained, a photocurable resin is preferable. . As a photocurable resin, what is marketed can be used suitably. For example, polyfunctional acrylates such as trimethylolpropane triacrylate and pentaerythritol tetraacrylate are used singly or in combination of two or more, and “Irgacure (registered trademark) 907” and “Irgacure (registered trademark) 184” are used. Alternatively, a photopolymerization initiator such as “Lucirin (registered trademark) TPO” (both trade names sold by BASF) can be mixed to obtain a photocurable resin. When a photocurable resin is used, a resin composition obtained by dispersing inorganic fine particles or organic fine particles therein is applied onto a resin film and irradiated with light, whereby inorganic fine particles or organic fine particles are present in the binder resin. A dispersed hard coat layer can be formed.

As the polyfunctional acrylate constituting the photocurable resin, in addition to the above-described monomer types such as trimethylolpropane triacrylate and pentaerythritol tetraacrylate, urethane acrylate, polyol (meth) acrylate, or alkyl having two or more hydroxyl groups An oligomer type one such as a (meth) acrylic oligomer having a group can also be used.

The urethane acrylate here is prepared using, for example, (meth) acrylic acid and / or (meth) acrylic ester, polyol, and diisocyanate. Specifically, urethane is prepared by preparing hydroxy (meth) acrylate with at least one hydroxyl group remaining from (meth) acrylic acid and / or (meth) acrylic acid ester and polyol, and reacting it with diisocyanate. Acrylate can be produced. These (meth) acrylic acid and / or (meth) acrylic acid ester, polyol, and diisocyanate may be used singly or in combination of two or more. Moreover, you may add various additives according to the objective.

Examples of the (meth) acrylic acid ester used for the production of urethane acrylate include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth). (Meth) acrylic acid alkyl esters such as butyl acrylate; (meth) acrylic acid cycloalkyl esters such as (meth) acrylic acid cyclohexyl.

Similarly, the polyol used for the production of urethane acrylate is a compound having at least two hydroxyl groups in the molecule. Specific examples include ethylene glycol, trimethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,9 -Nonanediol, 1,10-decane glycol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol ester of hydroxypivalic acid, cyclohexanedimethylol, 1,4-cyclohexanediol, spiroglycol, tricyclodecane dimethylol, hydrogenated bisphenol A, ethylene oxide added bisphenol A, propylene oxide added bisphenol A, trimethylol ethane, tridimethyl Rupuropan, glycerin, 3-methylpentane-1,3,5-triol, pentaerythritol, dipentaerythritol, tripentaerythritol, and the like glucose ethers.

Similarly, the diisocyanate used in the production of urethane acrylate can be various aromatic, aliphatic or alicyclic diisocyanates. Specific examples include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 1,5-naphthalene diisocyanate, diphenyl-4,4′-diisocyanate, 3,3′-dimethyldiphenyl-4. , 4′-diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4′-diisocyanate, and hydrogenated compounds of these having an aromatic ring.

Specific examples of polyol (meth) acrylate that can be a polyfunctional acrylate include pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, Examples include 1,6-hexanediol di (meth) acrylate. These may be used alone or in combination. Furthermore, you may add various additives as needed. The polyol (meth) acrylate preferably comprises pentaerythritol triacrylate and pentaerythritol tetraacrylate. These may be a copolymer or a mixture.

Furthermore, as the (meth) acryl oligomer having an alkyl group containing two or more hydroxyl groups that can be another polyfunctional acrylate, for example, a (meth) acryl oligomer having a 2,3-dihydroxypropyl group or a 2-hydroxyethyl group And (meth) acrylic oligomers having 2,3-dihydroxypropyl groups.

Specific examples of the photopolymerization initiator constituting the photocurable resin include 2,2-dimethoxy-2-phenylacetophenone, acetophenone, benzophenone, xanthone, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′- Dimethoxybenzophenone, benzoinpropyl ether, benzyldimethyl ketal, N, N, N ′, N′-tetramethyl-4,4′-diaminobenzophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- Examples include 1-one and other thioxanthone compounds.

The photo-curable resin can be used in a state dissolved in a solvent as necessary. As the solvent, various organic solvents including ethyl acetate and butyl acetate can be used.

The photocurable resin may contain a leveling agent, and examples thereof include a fluorine-based or silicone-based leveling agent. Examples of the silicone leveling agent include reactive silicone, polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. Preferred are reactive silicone and siloxane leveling agents. By using a reactive silicone leveling agent, the surface of the hard coat layer is provided with slipperiness, and excellent scratch resistance can be maintained for a long period of time. On the other hand, when a siloxane-based leveling agent is used, film forming ability can be improved.

Examples of the leveling agent for reactive silicone include those having a siloxane bond and an acryloyl group or a hydroxyl group. Specific examples include the following copolymers.
(A) a copolymer of dimethylsiloxane / 3-acryloyl-2-hydroxypropoxypropylsiloxane / 2-acryloyl-3-hydroxypropoxypropylsiloxane,
(B) a copolymer of dimethylsiloxane / hydroxypropylsiloxane / tri (ω-isocyanatoalkyl) isocyanuric acid / aliphatic polyester,
(C) Copolymer of dimethylsiloxane / polyalkylene glycol alkylsiloxane having acrylate at the end / polyalkylene glycol alkylsiloxane having a hydroxyl group at the end.

Specific examples of commercially available reactive silicones are all trade names of “GRANDIC (registered trademark) PC-4100” sold by DIC Corporation, and “BYK-” sold by Big Chemie Japan Corporation. UV3500 "," BYK-UV3750 "," BYK-370 "," BYK-371 "," BYK-375 ", and" BYK-377 ".

By using an acrylic binder component (binder resin) as exemplified above, the adhesion to the protective film is improved, the mechanical strength is improved, and the surface treatment layer 20 that can effectively prevent surface scratches. Can be formed.

When providing a hard coat layer having a fine surface irregular shape by the embossing method, an uncured hard coat layer is formed on a resin film, and the hard coat layer is pressed against the mold on which the fine irregular shape is formed. The layer is cured and the shape of the mold is transferred to the hard coat layer. The transfer to the mold-shaped hard coat layer is preferably carried out by embossing, and as the embossing, a UV embossing method using an ultraviolet curable resin which is a kind of a photocurable resin is preferable. When the fine surface irregularity shape is formed by the embossing method, the hard coat layer may or may not contain inorganic or organic fine particles.

In the UV embossing method, an ultraviolet curable resin layer is formed on the surface of the protective film and cured while pressing the ultraviolet curable resin layer against the concave and convex surface of the mold so that the concave and convex surface of the mold becomes an ultraviolet curable resin. Transferred to the layer. Specifically, an ultraviolet curable resin is applied on a resin film, and the applied ultraviolet curable resin is in close contact with the uneven surface of the mold, and then the ultraviolet ray is irradiated from the resin film side to cure the ultraviolet ray. The shape of the mold is transferred to the ultraviolet curable resin by curing the curable resin and then peeling the resin film on which the cured ultraviolet curable resin layer is formed from the mold. The kind in particular of ultraviolet curable resin is not restrict | limited, For example, what was mentioned above can be used. Further, instead of the ultraviolet curable resin, a visible light curable resin that can be cured with visible light having a wavelength longer than that of ultraviolet light may be used by appropriately selecting a photopolymerization initiator.

The thickness of the surface treatment layer 20 is not particularly limited, but is preferably in the range of 2 to 30 μm, more preferably 3 to 30 μm. When the thickness of the surface treatment layer 20 is less than 2 μm, it is difficult to obtain sufficient hardness and the surface tends to be easily damaged. On the other hand, when the thickness is larger than 30 μm, the film tends to break or the first protective film 12A curls due to curing shrinkage of the surface treatment layer and tends to reduce productivity.

As described above, haze is preferably imparted to the first protective film 12A by the hard coat layer, but with the formation of the hard coat layer, the haze is generated by dispersing inorganic or organic fine particles in the protective film. It may be given. Specific examples of the inorganic or organic fine particles used for this purpose are the same as those listed above.

The first protective film 12A has various additional surface treatments such as antistatic treatment, antifouling treatment, or antibacterial treatment in addition to the antiglare treatment (haze imparting treatment) that also serves as a hard coat layer. It may be applied, and a coating layer made of a liquid crystalline compound or a high molecular weight compound thereof may be formed. In addition to the surface treatment, the antistatic function may be imparted to other portions of the polarizing plate such as an adhesive layer.

[Second protective film 12B]
The second protective film 12B may be the same film as the first protective film 12A or a different film.
The second protective film 12B preferably contains a cellulose resin, a polyolefin resin, or an acrylic resin because the retardation value is easily controlled and easily available. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.

As the cellulose resin, the same resin as the first protective film 12A can be used.

The cyclic polyolefin resin is obtained by polymerizing cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives in the presence of a catalyst. When such a cyclic polyolefin resin is used, a protective film having a predetermined retardation value to be described later is easily obtained.

As the cyclic polyolefin-based resin, for example, ring-opening metathesis polymerization is performed from cyclopentadiene and olefins or (meth) acrylic acid or esters thereof using norbornene obtained by Diels-Alder reaction or a derivative thereof as a monomer. Resin obtained by hydrogenation; ring-opening metathesis polymerization using dicyclopentadiene and olefins or (meth) acrylic acid or esters thereof by tetracyclododecene or a derivative thereof obtained by Diels-Alder reaction, Resin obtained by subsequent hydrogenation; at least two monomers selected from norbornene, tetracyclododecene, their derivatives, and other cyclic olefin monomers are similarly copolymerized by ring-opening metathesis, Resin obtained by subsequent hydrogenation; resin obtained by addition copolymerization of a cyclic olefin such as norbornene, tetracyclododecene, or a derivative thereof with a chain olefin and / or an aromatic compound having a vinyl group Can be mentioned.

As the cyclic polyolefin resin, a commercially available product can be easily obtained. Examples of commercial products are “TOPAS” produced by TOPAS ADVANCED POLYMERS GmbH and sold by Polyplastics Co., Ltd. in Japan, and “Arton” (registered by JSR Corporation). Trademark) ”,“ ZEONOR (registered trademark) ”and“ ZEONEX (registered trademark) ”sold by Nippon Zeon Co., Ltd., and“ APEL (registered trademark) ”sold by Mitsui Chemicals, Inc.

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

The polypropylene resin may contain an alicyclic saturated hydrocarbon resin. By containing the alicyclic saturated hydrocarbon resin, the retardation value can be easily controlled. The content of the alicyclic saturated hydrocarbon resin is advantageously 0.1 to 30% by weight relative to the polypropylene resin, and more preferably 3 to 20% by weight. When the content of the alicyclic saturated hydrocarbon resin is less than 0.1% by weight, the effect of controlling the retardation value cannot be sufficiently obtained, while when the content exceeds 30% by weight, the protective film Therefore, there is a concern that the alicyclic saturated hydrocarbon resin may bleed out over time.

The acrylic resin is typically a polymer containing 50% by weight or more of methyl methacrylate units. The content of methyl methacrylate units is preferably 70% by weight or more, and may be 100% by weight.

As a method for forming a film from the resin as described above, a method corresponding to each resin may be appropriately selected. For example, the above-described solvent casting method, melt extrusion method, or the like can be employed. Among these, for polyolefin resins and acrylic resins, the melt extrusion method is preferably employed from the viewpoint of productivity. On the other hand, a cellulose resin is generally formed into a film by a solvent casting method.

When the liquid crystal cell is in an in-plane switching (IPS) mode, the second protective film 12B has a thickness direction retardation value so as not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. Rth is preferably in the range of −10 to 10 nm. The retardation value Rth in the thickness direction is a value obtained by multiplying the value obtained by subtracting the refractive index in the thickness direction from the in-plane average refractive index, and is defined by the following formula (a). The in-plane retardation value Re is a value obtained by multiplying the in-plane refractive index difference by the film thickness, and is defined by the following formula (b).
Rth = [(n _x + _ny ) / 2−n _z ] × d (a)
Re = (n _x −n _y ) × d (b)

Wherein, n _x is a refractive index in x-axis direction in the film plane (in-plane slow axis direction), n _y is a y-axis direction (in-plane fast axis direction in the film plane, the plane In the direction perpendicular to the x-axis), _nz is the refractive index in the z-axis direction (thickness direction) perpendicular to the film surface, and d is the thickness of the film.

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

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

[Third protective film 15]
As the third protective film 15, a resin film similar to the first protective film 12A can be used. The third protective film 15 may be the same film as the first protective film 12A or may be a different film. As the 3rd protective film 15, since control of a phase difference value is easy and acquisition is also easy, a cellulose resin is preferable. As the cellulose resin film, the same film as the first protective film 12A can be used.

In order to suppress a decrease in the degree of polarization of the composite polarizing plate due to depolarization by the third protective film 15, the third protective film 15 has an in-plane retardation value Re (590) of 10 nm or less at a wavelength of 590 nm, The absolute value of the thickness direction retardation value Rth (590) at a wavelength of 590 nm is preferably 10 nm or less.

As a method for controlling the retardation value Rth in the thickness direction of the third protective film within a range of 10 nm or less, a method similar to that for the second protective film may be used.

[Bonding of polarizing film and protective film]
Bonding of the first polarizing film 11A and the first protective film 12A, bonding of the second polarizing film 11B and the second protective film 12B, and the first polarizing film 11A and the third protective film 15 Or bonding with the 2nd polarizing film 11B and the 3rd protective film 15 can be performed with an adhesive agent or an adhesive.
In this specification, the first polarizing film 11A and the second polarizing film 11B are collectively referred to as a polarizing film, and the first protective film 12A, the second protective film 12B, and the third protective film 15 Are sometimes simply referred to as protective films.
The adhesive layer for bonding the polarizing film and the protective film can have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm. If the thickness of the adhesive layer is within this range, the protective film and the polarizing film to be laminated do not float or peel off, and an adhesive force having no practical problem can be obtained. The pressure-sensitive adhesive layer for bonding the polarizing film and the protective film can have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, more preferably 10 to 25 μm.

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

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

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

A polarizing plate can be obtained by applying a water-based adhesive to the adhesive surface of the polarizing film and / or the protective film to be bonded thereto, and bonding them together, followed by drying treatment. Prior to adhesion, it is also effective to subject the protective film to easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment to enhance wettability. The drying temperature can be about 50 to 100 ° C., for example. After drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days is preferable in order to further increase the adhesive strength.

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

From the viewpoint of weather resistance, refractive index, cationic polymerizability, etc., the epoxy compound contained in the curable adhesive composition is preferably one that does not contain an aromatic ring in the molecule. Examples of epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. An epoxy compound suitably used for such a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline is also described here.

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

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

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

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] henicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide
K: Limonene dioxide
L: bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxide and the like.

The aliphatic epoxy compound can be an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; diglycidyl ether of 1,4-butanediol; diglycidyl ether of 1,6-hexanediol; triglycidyl ether of glycerin; triglycidyl ether of trimethylolpropane; ethylene Polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol such as glycol, propylene glycol, and glycerin Can be mentioned.

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

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

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

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

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

When using a photocationic polymerization initiator, the curable adhesive composition may further contain a photosensitizer as necessary. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. When a photosensitizer is blended, the amount is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the curable adhesive composition. Further, a sensitizing aid such as a naphthoquinone derivative may be used for improving the curing rate.

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

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

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

In addition, the curable adhesive composition may have other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, as long as the adhesiveness is not impaired. Agents, flow modifiers, plasticizers, antifoaming agents, and the like. Examples of the ion trapping agent include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Examples of the antioxidant include And hindered phenolic antioxidants.

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

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

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

When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator compounded in the curable adhesive composition generates cationic species and Lewis acid, and the specific heating temperature is, for example, about 50 to 200 ° C. .

[Lamination of first polarizing plate and second polarizing plate]
For the lamination of the first polarizing plate and the second polarizing plate, the same adhesive as that used for bonding the polarizing film and the protective film can be used. As another form, it is also preferable to use an adhesive for lamination of the first polarizing plate and the second polarizing plate.

[Adhesive layer 13]
The pressure-sensitive adhesive layer 13 used for laminating the first polarizing plate and the second polarizing plate is excellent in optical transparency and excellent in adhesive properties including appropriate wettability, cohesiveness, adhesiveness and the like. Although what is necessary is just, what is further excellent in durability etc. is preferable. Specifically, the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 13 is preferably a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive).

The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of alkyl acrylate such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate. This acrylic resin is usually copolymerized with a polar monomer. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group. Here, the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group. The group can be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. Specific examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl ( Examples include meth) acrylate and glycidyl (meth) acrylate.

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

Various kinds of additives may be further added to the adhesive. Suitable additives include silane coupling agents and antistatic agents. A silane coupling agent is effective in increasing the adhesive strength with glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

The pressure-sensitive adhesive layer 13 is prepared by preparing a pressure-sensitive adhesive composition in which the above pressure-sensitive adhesive component is dissolved in an organic solvent, and bonding surfaces (polarizing film or protective film) of two polarizing plates to be bonded to each other. Apply the above-mentioned pressure-sensitive adhesive composition to the release treatment surface of the base film made of a resin film that has been subjected to a release treatment by applying directly to any of the above, or drying the solvent. It can be formed by removing the pressure-sensitive adhesive layer, sticking it to one of the bonding surfaces (polarizing film or protective film) of the two polarizing plates, and transferring the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer 13 is formed by the former direct coating method, a resin film (also called a separator) that has been subjected to a release treatment is bonded to the surface, and the pressure-sensitive adhesive layer surface is temporarily protected until use. It is customary. The latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition that is an organic solvent solution. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also advantageous in that it can be used as a separator after being attached to a polarizing plate.

Prior to laminating the two polarizing plates via an adhesive or pressure-sensitive adhesive, it is also useful to perform corona treatment or plasma treatment on the polarizing film surface, protective film surface, and pressure-sensitive adhesive surface to be bonded in advance. .

[Adhesive layer 14]
The pressure-sensitive adhesive layer 14 formed on the surface of the second protective film 12B opposite to the bonding surface with the second polarizing film 11B is excellent in optical transparency, moderate wettability, cohesiveness, Any material may be used as long as it has excellent adhesive properties including adhesiveness, but materials having excellent durability and the like are preferably used. Specifically, an adhesive containing an acrylic resin (acrylic adhesive) is preferably used as the adhesive forming the adhesive layer. Specifically, the same material as the pressure-sensitive adhesive 13 can be used.

The pressure-sensitive adhesive layer 14 may contain various additives in the same manner as the pressure-sensitive adhesive layer 13. In particular, the pressure-sensitive adhesive layer 14 preferably contains an antistatic agent. In general, when attaching a polarizing plate to a liquid crystal cell via an adhesive layer, the surface protective film (separator) that has been temporarily protected by covering the adhesive layer is peeled off and then attached to the liquid crystal cell. The static electricity generated when the surface protective film is peeled off causes the alignment failure of the liquid crystal in the liquid crystal cell, and this phenomenon may cause the display failure of the liquid crystal display device. As a means for reducing or preventing the generation of static electricity, it is effective to add an antistatic agent to the adhesive.

When laminating the second protective film 12B and the pressure-sensitive adhesive layer 14, it is also useful to perform corona treatment, plasma treatment, etc. on the surface where the second protective film 12B and the pressure-sensitive adhesive layer 14 are laminated. is there.

[Production method of composite polarizing plate]
Although it does not restrict | limit especially as a method to manufacture the composite polarizing plate of this invention, For example, the 1st polarizing film A which laminated | stacked the 1st protective film 12A and the 1st polarizing film 11A, and the 2nd protective film The 2nd polarizing plate B which laminated | stacked 12B and the 2nd polarizing film 11B is manufactured. Next, the pressure-sensitive adhesive layer 13 is formed on the polarizing film of the first polarizing plate A or the second polarizing plate B. When the first polarizing plate A and the second polarizing plate B thus produced are bonded together by a roll-to-roll through the pressure-sensitive adhesive layer 13, the composite polarizing plate 10 is obtained. In this case, the first polarizing film 11A and the second polarizing film 11B are directly bonded via an adhesive layer or an adhesive layer. Furthermore, the composite polarizing plate with an adhesive is obtained by forming the adhesive layer 14 on the second protective film 12B. The composite polarizing plate with the pressure-sensitive adhesive can be bonded to the liquid crystal cell via the pressure-sensitive adhesive 14.

In addition, as a method for producing the composite polarizing plate of the present invention, for example, the first polarizing film A ′ and the second polarizing film in which the first protective film 12A, the first polarizing film 11A, and the third protective film 15 are laminated. A second polarizing plate B ′ in which the protective film 12B and the second polarizing film 11B are laminated is manufactured. Next, the pressure-sensitive adhesive layer 13 is formed on the third protective film 15 of the first polarizing plate A ′ or the polarizing film of the second polarizing plate B ′. When the first polarizing plate A ′ and the second polarizing plate B ′ thus produced are bonded together by a roll-to-roll through the adhesive 13, the composite polarizing plate 10 is obtained. Furthermore, the composite polarizing plate with an adhesive is obtained by forming the adhesive layer 14 on the second protective film 12B. The composite polarizing plate with the pressure-sensitive adhesive can be bonded to the liquid crystal cell via the pressure-sensitive adhesive layer 14.

Also, a method of producing the composite polarizing plate 10 by laminating the first polarizing plate A (or A ′) and the second polarizing plate B (or B ′) with a solvent-free adhesive by roll-to-roll. Preferably used.

When a composite polarizing plate is produced by laminating two polarizing plates as described above, the single transmittance of the first polarizing plate is preferably 38.0 to 43.0%, and 40.0 to 42. More preferably, it is 5%. The single transmittance of the second polarizing plate is preferably 40.0 to 45.0%, more preferably 41.0 to 43.0%. Moreover, it is preferable that both the polarization degree of a 1st polarizing plate and the polarization degree of a 2nd polarizing plate are 99.90% or more, and it is more preferable that it is 99.95% or more.

Thus, in the composite polarizing plate of the present invention, the single transmittance of the second polarizing plate is preferably larger than the single transmittance of the first polarizing plate. The difference between the single transmittance of the first polarizing plate and the single transmittance of the second polarizing plate is preferably 0.1% or more, more preferably more than 0.2%, 0.4 % Or more. The upper limit of the difference is not particularly limited, but is usually 5% or less, preferably 2% or less, and more preferably 1% or less.

In addition, it is preferable to use a method in which all the films constituting the composite polarizing plate 10 are laminated with a water-based adhesive or a solventless adhesive at a time.

The polarization degree of the composite polarizing plate obtained by the above production method is preferably 99.95% or more, more preferably 99.99% or more, and further preferably 99.995% or more. Moreover, the composite polarizing plate of this invention suppresses the fall of a polarization degree even after the heat test put into 95 degreeC oven for 1000 hours. For example, the polarization degree of the composite polarizing plate after the heat test can be 99.95% or more, or 99.99% or more. From another viewpoint, the magnitude of the degree of polarization reduction before and after the heat resistance test can be 0.010% or less, preferably 0.005% or less in the composite polarizing plate of the present invention, More preferably, it may be 0.003% or less.

[Liquid Crystal Cell]
The liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the substrates. In general, the cell substrate is often made of glass, but may be a plastic substrate. In addition, the liquid crystal cell itself used in the liquid crystal panel of the present invention can be composed of various types employed in this field.

[LCD panel]
A liquid crystal panel can be produced by bonding the composite polarizing plate 10 to a liquid crystal cell via the pressure-sensitive adhesive layer 14. Usually, although a polarizing plate is bonded on both surfaces of a liquid crystal cell, the composite polarizing plate of this invention is used suitably for the visual recognition side of a liquid crystal display device, a back surface side, or its both surfaces.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, the parts and% representing the content or amount used are based on weight unless otherwise specified. In addition, each physical property in the following examples was measured by the following method.

(1) Measurement of thickness:
Measurement was performed using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation value and thickness direction retardation value:
Using the phase difference meter “KOBRA (registered trademark) -WPR” based on the parallel Nicol rotation method manufactured by Oji Scientific Instruments Co., Ltd., the in-plane retardation value at the wavelength of 590 nm and the thickness direction position at a temperature of 23 ° C. The phase difference value was measured.

(3) Measurement of contraction force of polarizing film:
A piece of 2 mm wide × 50 mm long was cut with a super cutter manufactured by Sugano Seiki Co., Ltd. so that the absorption axis direction of the polarizing film was the long axis. The obtained strip-shaped polarizing film was used as a shrinkage force measurement sample. The sample for measuring the shrinkage force was set in a thermomechanical analyzer (“TMA / 6100” manufactured by Hitachi High-Tech Science Co., Ltd.) with a distance between chucks of 10 mm, and the specimen was left in a room at 20 ° C. for a sufficient time. The room temperature was raised from 20 ° C. to 80 ° C. over 1 minute, and the temperature in the sample chamber was set to be maintained at 80 ° C. after the temperature rise. After allowing the temperature to rise for 4 hours, the contraction force in the long side direction of the measurement sample was measured in an environment at 80 ° C. In this measurement, the static load was 0 mN, and a SUS probe was used as the jig.

(4) Measurement of polarization degree and single transmittance of polarizing plate:
The measurement was performed using a spectrophotometer with an integrating sphere [“V7100” manufactured by JASCO Corporation, 2-degree field of view; C light source].

[Production Example 1] Production of Polarizing Film 1 A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 4 times by dry stretching, and the tension state is further increased. The sample was immersed in pure water at 40 ° C. for 40 seconds while being kept, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds to perform the dyeing treatment. went. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption polarizing film having a thickness of 7 μm was obtained. It was 1.7N when the contractive force of the obtained polarizing film was measured.

[Production Example 2] Production of Polarizing Film 2 A 30 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 4 times by dry stretching, and the tension state is further increased. The sample was immersed in pure water at 40 ° C. for 40 seconds while being kept, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds to perform the dyeing treatment. went. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption polarizing film with a thickness of 12 μm was obtained. It was 2.0N when the contraction force of the obtained polarizing film was measured.

[Production Example 3] Production of Polarizing Film 3 Acetacetyl group-modified polyvinyl alcohol powder having an average polymerization degree of 1100 and a saponification degree of 99.5 mol% [trade name “GOHSEFIMAR (registered trademark)” manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Z-200 "] was dissolved in hot water at 95 ° C to prepare a 3% strength aqueous solution. As a crosslinking agent, a water-soluble polyamide epoxy resin (trade name “Smiles Resin (registered trademark) 650” manufactured by Taoka Chemical Industry Co., Ltd., an aqueous solution having a solid content of 30%) as a crosslinking agent was added to this aqueous solution as a solid content of 6 parts of polyvinyl alcohol. The mixture was mixed at a ratio of 5 parts per to make a primer coating solution. And after corona-treating a base film (thickness 110 μm, polypropylene film having a melting point of 163 ° C.), a primer coating solution was applied to the corona-treated surface using a micro gravure coater. Thereafter, it was dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

Next, polyvinyl alcohol powder having an average polymerization degree of 2400 and a saponification degree of 98.0 to 99.0 mol% (trade name “PVA124” obtained from Kuraray Co., Ltd.) was dissolved in hot water at 95 ° C. to obtain 8% A polyvinyl alcohol aqueous solution having a concentration was prepared. The obtained aqueous solution was coated on the primer layer of the base film using a lip coater at room temperature and dried at 80 ° C. for 20 minutes to obtain a laminated film consisting of the base film / primer layer / polyvinyl alcohol layer. Produced.

Next, the obtained laminated film was subjected to free end longitudinal uniaxial stretching at a temperature of 160 ° C. by 5.8 times. The total thickness of the laminated stretched film thus obtained was 28.5 μm, and the thickness of the polyvinyl alcohol layer was 5.0 μm.

The resulting laminated stretched film was dyed by immersing it in an aqueous solution having a water / iodine / potassium iodide weight ratio of 100 / 0.35 / 10 at 26 ° C. for 90 seconds, and then washed with 10 ° C. pure water. Next, this laminated stretched film was immersed in an aqueous solution having a water / boric acid / potassium iodide weight ratio of 100 / 9.5 / 5 at 76 ° C. for 300 seconds to crosslink the polyvinyl alcohol. Subsequently, the substrate was washed with pure water at 10 ° C. for 10 seconds, and finally dried at 80 ° C. for 200 seconds. By the above operation, a polarizing laminated film in which a polarizing film 3 having a thickness of 5 μm composed of a polyvinyl alcohol layer on which iodine was adsorbed and oriented was formed on a polypropylene base film was produced. It was 1.45 N when the obtained polarizing film was peeled from the base material and the shrinkage force was measured.

[Production Example 4] Production of Polarizing Film 4 A 60 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched by about 4 times by dry stretching, and the tension state is further increased. The sample was immersed in pure water at 40 ° C. for 40 seconds while being kept, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds to perform the dyeing treatment. went. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption polarizer having a thickness of 23 μm was obtained. It was 3.1N when the contraction force of the obtained polarizing film was measured.

[Production Example 5] Preparation of aqueous adhesive 3 parts by weight of carboxyl group-modified polyvinyl alcohol [trade name “KL-318” obtained from Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water, and a water-soluble epoxy was dissolved in the aqueous solution. 1.5 parts by weight of a resin-based polyamide epoxy additive [trade name “Smileise Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30 wt%] was added. A water-based adhesive was prepared.

[Production Example 6] Preparation of adhesive comprising curable epoxy resin composition Bis (3,4-epoxycyclohexylmethyl) as an epoxycyclohexylmethyl ester of dicarboxylic acid corresponding to the above formula D, which is an alicyclic epoxy resin. ) 100 parts of adipate, 25 parts of hydrogenated bisphenol A diglycidyl ether as the hydrogenated epoxy resin, and 4,4′-bis (diphenylsulfonio) diphenyl sulfide bis (hexafluorophosphate) 2 as the photocationic polymerization initiator After mixing 2 parts, defoaming was performed to obtain an adhesive A composed of a curable epoxy resin composition. The photocationic polymerization initiator was blended as a 50% by mass propylene carbonate solution.

[Adhesives A and B]
The following two types of pressure-sensitive adhesives were prepared.
Adhesive A: Sheet-like adhesive having a thickness of 25 μm [“P-3132” manufactured by Lintec Corporation]
Adhesive B: Sheet-like adhesive having a thickness of 15 μm [“P-0082” manufactured by Lintec Corporation]

[Protective films A, B, C]
The following three types of protective films were prepared.
Protective film A: Triacetyl cellulose film with hard coat manufactured by Konica Minolta, Inc .; 25KCHCN-TC (thickness 32 μm)
Protective film B: Triacetyl cellulose film manufactured by Konica Minolta, Inc .; KC2CT (thickness 20 μm, in-plane retardation value at wavelength 590 nm = 1.2 nm, thickness direction retardation at wavelength 590 nm = 1.3 nm)
Protective film C: Cyclic polyolefin resin film manufactured by ZEON Corporation; ZF14-013 (thickness 13 μm, in-plane retardation value at wavelength 590 nm = 0.8 nm, thickness direction retardation at wavelength 590 nm = 3.4 nm)

[Production Example 7]
(Preparation of polarizing plate A-1)
The protective film A was saponified. The protective film A and the polarizing film 1 were adhered with a water-based adhesive so that the triacetyl cellulose surface of the protective film A became a bonding surface with the polarizing film 1 to obtain a polarizing plate A-1. The single transmittance of the polarizing plate A-1 was 42.0%.

[Production Example 8]
(Preparation of polarizing plate B-1)
The protective film B was saponified. The protective film B and the polarizing film 1 were bonded with a water-based adhesive so that the triacetyl cellulose surface of the protective film B became a bonding surface with the polarizing film 1 to obtain a polarizing plate B-1. The single transmittance of the polarizing plate B-1 was 42.5%.

[Production Example 9]
(Preparation of polarizing plate C-1)
One surface of the protective film C was subjected to corona treatment. The protective film C and the polarizing film 1 were bonded with an aqueous adhesive so that the corona-treated surface of the protective film C became a bonding surface with the polarizing film 1 to obtain a polarizing plate C-1. The single transmittance of the polarizing plate C-1 was 42.3%.

[Production Example 10]
(Preparation of polarizing plate D-1)
The protective film A was saponified. The protective film A and the polarizing film 2 were bonded with a water-based adhesive so that the triacetyl cellulose surface of the protective film A became a bonding surface with the polarizing film 2 to obtain a polarizing plate D-1. The single transmittance of the polarizing plate D-1 was 42.0%.

[Production Example 11]
(Preparation of polarizing plate E-1)
The protective film B was saponified. The protective film B and the polarizing film 2 were bonded with a water-based adhesive so that the triacetyl cellulose surface of the protective film B became a bonding surface with the polarizing film 2 to obtain a polarizing plate E-1. The single transmittance of the polarizing plate E-1 was 42.5%.

[Production Example 12]
(Preparation of polarizing plate F-1)
One surface of the protective film C was subjected to corona treatment. The protective film C and the polarizing film 2 were bonded with a water-based adhesive so that the corona-treated surface of the protective film C became a bonding surface with the polarizing film 2 to obtain a polarizing plate F-1. The single transmittance of the polarizing plate F-1 was 42.3%.

[Production Example 13]
(Preparation of polarizing plate G-1)
The protective film A was subjected to saponification treatment, and one surface of the protective film C was subjected to corona treatment. Three films were bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film A, the polarizing film 2, and the corona-treated surface of the protective film C were bonded to each other, and a polarizing plate G-1 was obtained. . The single transmittance of the polarizing plate G-1 was 42.3%.

[Production Example 14]
(Preparation of polarizing plate H-1)
The protective film A was saponified. It protects so that the triacetyl-cellulose surface of the protective film A may become a bonding surface on the opposite surface (polarizing film surface) of the base material film of the polarizing laminated film produced in the manufacture example 3 in which the polarizing film 3 is formed. Film A was bonded with a water-based adhesive, and only the base film was peeled off to obtain polarizing plate H-1. The single transmittance of the polarizing plate H-1 was 41.2%.

[Production Examples 15 to 22]
Polarizers I-1 to P-1 were produced in the same manner except that the water-based adhesive used in Production Examples 7 to 14 was changed to an adhesive made of the curable epoxy resin composition. The pasting was performed by irradiating with an ultraviolet ray using an ultraviolet irradiation device with a belt conveyor (lamp: Fusion D lamp, integrated light quantity 1500 mJ / cm ² ) and leaving it at room temperature for 1 hour.

The single transmittance of the manufactured polarizing plate was as follows.
In addition, the inside of () shows the polarizing plate produced with the water-system adhesive of the same structure.

Production Example 15 Polarizing plate I-1 (Polarizing plate A-1): Single transmittance is 42.0%
Production Example 16 Polarizing plate J-1 (Polarizing plate B-1): Single transmittance is 42.5%
Production Example 17 Polarizing plate K-1 (Polarizing plate C-1): Single transmittance is 42.3%
Production Example 18 Polarizing plate L-1 (Polarizing plate D-1): Single transmittance is 42.0%
Production Example 19 Polarizing plate M-1 (Polarizing plate E-1): Single transmittance is 42.5%
Production Example 20 Polarizing plate N-1 (Polarizing plate F-1): Single transmittance is 42.3%
Production Example 21 Polarizing plate O-1 (polarizing plate G-1): single transmittance is 42.3%
Production Example 22 Polarizing plate P-1 (Polarizing plate H-1): Single transmittance is 41.2%

[Production Example 23]
(Preparation of polarizing plate Q-1)
A polarizing plate was produced in the same manner except that the polarizing film 1 in the polarizing plate A-1 was changed to the polarizing film 4. The single transmittance of the polarizing plate Q-1 was 42.0%.

[Production Example 24]
(Preparation of polarizing plate R-1)
A polarizing plate was produced in the same manner except that the polarizing film 1 in the polarizing plate B-1 was changed to the polarizing film 4. The single transmittance of the polarizing plate R was 42.5%.

[Production Example 25]
(Preparation of polarizing plate A-2)
The protective films A and B were subjected to saponification treatment. The protective film A, the polarizing film 1 and the protective film B are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film A and the triacetylrose surface of the protective film B become the bonding surface with the polarizing film 1. A polarizing plate A-2 was obtained. The single transmittance of the polarizing plate A-2 was 42.0%.

[Production Example 26]
(Preparation of polarizing plate B-2)
The protective film B was saponified. The protective film B and the polarizing film 1 were bonded with a water-based adhesive so that the triacetylulose surface of the protective film B became a bonding surface with the polarizing film 1 to obtain a polarizing plate B-2. The single transmittance of the polarizing plate B-2 was 42.5%.

[Production Example 27]
(Preparation of polarizing plate C-2)
One surface of the protective film C was subjected to corona treatment. The protective film C and the polarizing film 1 were bonded with an aqueous adhesive so that the corona-treated surface became a bonding surface with the polarizing film 1 to obtain a polarizing plate C-2. The single transmittance of the polarizing plate C-2 was 42.3%.

[Production Example 28]
(Preparation of polarizing plate D-2)
The protective films A and B were subjected to saponification treatment. The protective film A, the polarizing film 2 and the protective film B are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film A and the triacetylrose surface of the protective film B become the bonding surface with the polarizing film 2. A polarizing plate D-2 was obtained. The single transmittance of the polarizing plate D-2 was 42.0%.

[Production Example 29]
(Preparation of polarizing plate E-2)
The protective film B was saponified. The protective film B and the polarizing film 2 were bonded with a water-based adhesive so that the triacetylulose surface of the protective film B became a bonding surface with the polarizing film 2 to obtain a polarizing plate E-2. The single transmittance of the polarizing plate E-2 was 42.5%.

[Production Example 30]
(Preparation of polarizing plate F-2)
One surface of the protective film C was subjected to corona treatment. The protective film C and the polarizing film 2 were bonded with a water-based adhesive so that the corona-treated surface of the protective film C became a bonding surface with the polarizing film 2 to obtain a polarizing plate F-2. The single transmittance of the polarizing plate F-2 was 42.3%.

[Production Example 31]
(Preparation of polarizing plate G-2)
The protective film A was subjected to saponification treatment, and one surface of the protective film C was subjected to corona treatment. The protective film A, the polarizing film 2 and the protective film C are pasted with a water-based adhesive so that the triacetyl cellulose surface of the protective film A and the corona-treated surface of the protective film C become the bonding surface with the polarizing film 2. Thus, polarizing plate G-2 was obtained. The single transmittance of the polarizing plate G-2 was 42.3%.

[Production Example 32]
(Preparation of polarizing plate H-2)
The protective film A and the protective film B were saponified. Only the base film was peeled from the polarizing laminate film produced in Production Example 3 to obtain a polarizing film 3. The triacetylcellulose surface of the protective film A subjected to the saponification treatment, the polarizing film 3 and the protective film B were adhered with an aqueous adhesive to obtain a polarizing plate H-2. The single transmittance of the polarizing plate H-2 was 41.2%.

[Production Examples 33 to 40]
Polarizers I-2 to P-2 were similarly prepared except that the water-based adhesive used in Production Examples 25 to 32 was changed to an adhesive made of a curable epoxy resin composition. The pasting was performed by irradiating with an ultraviolet ray using an ultraviolet irradiation device with a belt conveyor (lamp: Fusion D lamp, integrated light quantity 1500 mJ / cm ² ) and leaving it at room temperature for 1 hour.

The single transmittance of the manufactured polarizing plate was as follows.
In addition, the inside of () shows the polarizing plate produced with the water-system adhesive of the same structure.

Production Example 33 Polarizing plate I-2 (Polarizing plate A-2): Single transmittance is 42.0%
Production Example 34 Polarizing plate J-2 (Polarizing plate B-2): Single transmittance is 42.5%
Production Example 35 Polarizing plate K-2 (Polarizing plate C-2): Single transmittance is 42.3%
Production Example 36 Polarizing plate L-2 (polarizing plate D-2): Single transmittance is 42.0%
Production Example 37 Polarizing plate M-2 (Polarizing plate E-2): Single transmittance is 42.5%
Production Example 38 Polarizing plate N-2 (polarizing plate F-2): Single transmittance is 42.3%
Production Example 39 Polarizing plate O-2 (polarizing plate G-2): Single transmittance is 42.3%
Production Example 40 Polarizing plate P-2 (Polarizing plate H-2): Single transmittance is 41.2%

[Production Example 41]
(Preparation of polarizing plate Q-2)
A polarizing plate was produced in the same manner except that the polarizing film 1 in the polarizing plate A-2 was changed to the polarizing film 4. The single transmittance of the polarizing plate Q-2 was 42.0%.

[Production Example 42]
(Preparation of polarizing plate R-2)
A polarizing plate was produced in the same manner except that the polarizing film 1 in the polarizing plate B-2 was changed to the polarizing film 4. The single transmittance of the polarizing plate R-2 was 42.5%.

[Example 1]
The polarizing film 1 in the polarizing plate A-1 and the polarizing film 1 in the polarizing plate B-1 were bonded together using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film B side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

The produced composite polarizing plate was cut into a 40 mm square and bonded to Corning Eagle XG to produce a sample for heat resistance evaluation. The sample thus prepared was put into an oven at 95 ° C. for 1000 hours. The degree of polarization after the heat test was 99.996%.

[Example 2]
The polarizing film 1 in the polarizing plate A-1 and the polarizing film 1 in the polarizing plate C-1 were bonded using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 3]
The polarizing film 2 in the polarizing plate D-1 and the polarizing film 2 in the polarizing plate E-1 were bonded together using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film B side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

The produced composite polarizing plate was cut into a 40 mm square and bonded to Corning Eagle XG to produce a sample for heat resistance evaluation. The sample thus prepared was put into an oven at 95 ° C. for 1000 hours. The degree of polarization after the heat test was 99.997%.

[Example 4]
The polarizing film 2 in the polarizing plate D-1 and the polarizing film 2 in the polarizing plate F-1 were bonded using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 5]
The polarizing film 1 in the polarizing plate A-1 and the polarizing film 2 in the polarizing plate F-1 were bonded using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 6]
The polarizing film 2 in the polarizing plate D-1 and the polarizing film 1 in the polarizing plate C-1 were bonded together using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 7]
The polarizing film 3 in the polarizing plate H-1 and the polarizing film 1 in the polarizing plate C-1 were bonded together using an adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, the surface of the polarizing film to be bonded and the surface of the pressure-sensitive adhesive were previously subjected to corona treatment. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.997%, and the single transmittance was 37.9%.

[Example 8]
A composite polarizing plate was produced in the same manner except that the polarizing plate A-1 of Example 1 was changed to the polarizing plate I-1 and the polarizing plate B-1 was changed to the polarizing plate J-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 9]
A composite polarizing plate was prepared in the same manner except that the polarizing plate A-1 of Example 2 was changed to the polarizing plate I-1 and the polarizing plate C-1 was changed to the polarizing plate K-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 10]
A composite polarizing plate was produced in the same manner except that the polarizing plate D-1 of Example 3 was changed to the polarizing plate L-1 and the polarizing plate E-1 was changed to the polarizing plate M-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 11]
A composite polarizing plate was produced in the same manner except that the polarizing plate D-1 of Example 4 was changed to the polarizing plate L-1, and the polarizing plate F-1 was changed to the polarizing plate N-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 12]
A composite polarizing plate was prepared in the same manner except that the polarizing plate A-1 of Example 5 was changed to the polarizing plate I-1 and the polarizing plate F-1 was changed to the polarizing plate N-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 13]
A composite polarizing plate was prepared in the same manner except that the polarizing plate D-1 of Example 6 was changed to the polarizing plate L-1, and the polarizing plate C-1 was changed to the polarizing plate K-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 14]
A composite polarizing plate was prepared in the same manner except that the polarizing plate H-1 of Example 7 was changed to the polarizing plate P-1 and the polarizing plate C-1 was changed to the polarizing plate K-1. The polarization degree of the composite polarizing plate was 99.997%, and the single transmittance was 37.9%.

[Example 15]
The protective film B in the polarizing plate A-2 and the polarizing film 1 in the polarizing plate B-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film B side which is the outermost layer of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 16]
The protective film B in the polarizing plate A-2 and the polarizing film 1 in the polarizing plate C-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The composite polarization degree was 99.998%, and the single transmittance was 38.6%.

[Example 17]
The protective film B in the polarizing plate D-2 and the polarizing film 2 in the polarizing plate E-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film B side which is the outermost layer of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 18]
The protective film B in the polarizing plate D-2 and the polarizing film 2 in the polarizing plate F-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 19]
The protective film B in the polarizing plate A-2 and the polarizing film 2 in the polarizing plate F-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 20]
The protective film B in the polarizing plate D-2 and the polarizing film 1 in the polarizing plate C-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 21]
The protective film B in the polarizing plate H-2 and the polarizing film 1 in the polarizing plate C-2 were bonded using the adhesive B so that the absorption axes of the polarizing plates were parallel to each other. At this time, a corona treatment was performed in advance on the protective film surface, the polarizing film surface, and the pressure-sensitive adhesive surface to be bonded. Adhesive A was bonded to the protective film C side of the composite polarizing plate thus obtained. The corona treatment was performed in advance on the protective film surface and the pressure-sensitive adhesive surface even when the pressure-sensitive adhesive A was bonded. The composite polarization degree was 99.997%, and the single transmittance was 37.9%.

[Example 22]
A composite polarizing plate was produced in the same manner except that the polarizing plate A-2 of Example 15 was changed to the polarizing plate I-2 and the polarizing plate B-2 was changed to the polarizing plate J-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 23]
A composite polarizing plate was produced in the same manner except that the polarizing plate A-2 of Example 16 was changed to the polarizing plate I-2 and the polarizing plate C-2 was changed to the polarizing plate K-2. The composite polarization degree was 99.998%, and the single transmittance was 38.6%.

[Example 24]
A composite polarizing plate was produced in the same manner except that the polarizing plate D-2 of Example 17 was changed to the polarizing plate L-2 and the polarizing plate E-2 was changed to the polarizing plate M-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 25]
A composite polarizing plate was prepared in the same manner except that the polarizing plate D-2 of Example 18 was changed to the polarizing plate L-2 and the polarizing plate F-2 was changed to the polarizing plate N-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 26]
A composite polarizing plate was prepared in the same manner except that the polarizing plate A-2 of Example 19 was changed to the polarizing plate I-2 and the polarizing plate F-2 was changed to the polarizing plate N-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 27]
A composite polarizing plate was produced in the same manner except that the polarizing plate D-2 of Example 20 was changed to the polarizing plate L-2 and the polarizing plate C-2 was changed to the polarizing plate K-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

[Example 28]
A composite polarizing plate was produced in the same manner except that the polarizing plate H-2 of Example 21 was changed to the polarizing plate P-2 and the polarizing plate C-2 was changed to the polarizing plate K-2. The composite polarization degree was 99.997%, and the single transmittance was 37.9%.

[Comparative Example 1]
Adhesive A was bonded onto the protective film C in the polarizing plate G-1. When bonding the pressure-sensitive adhesive A, the protective film surface and the pressure-sensitive adhesive surface were previously subjected to corona treatment. The polarization degree of the polarizing plate G-1 was 99.993%.

The produced polarizing plate was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning, to produce a sample for heat resistance evaluation. The sample thus prepared was put into an oven at 95 ° C. for 1000 hours. The degree of polarization after the heat test was 99.94%.

[Comparative Example 2]
Adhesive A was bonded onto the protective film C in the polarizing plate O-1. When bonding the pressure-sensitive adhesive A, the protective film surface and the pressure-sensitive adhesive surface were previously subjected to corona treatment. The degree of polarization of the polarizing plate O-1 was 99.993%.

[Comparative Example 3]
A composite polarizing plate was prepared in the same manner except that the polarizing plate A-1 of Example 1 was changed to the polarizing plate Q-1, and the polarizing plate B-1 was changed to the polarizing plate R-1. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

The produced composite polarizing plate was cut into a 40 mm square and bonded to Corning Eagle XG to produce a sample for heat resistance evaluation. The sample thus prepared was put into an oven at 95 ° C. for 1000 hours. The degree of polarization after the heat test was 99.996%, but peeling occurred in a region within 1 mm from the end of the polarizing plate.

[Comparative Example 4]
Adhesive A was bonded onto the protective film C in the polarizing plate G-2. When bonding the pressure-sensitive adhesive A, the protective film surface and the pressure-sensitive adhesive surface were previously subjected to corona treatment. The polarization degree of the polarizing plate G-2 was 99.993%.

[Comparative Example 5]
Adhesive A was bonded onto the protective film C in the polarizing plate O-2. When bonding the pressure-sensitive adhesive A, the protective film surface and the pressure-sensitive adhesive surface were previously subjected to corona treatment. The polarization degree of the polarizing plate O-2 was 99.993%.

[Comparative Example 6]
A composite polarizing plate was prepared in the same manner except that the polarizing plate A-2 of Example 15 was changed to the polarizing plate Q-2 and the polarizing plate B-2 was changed to the polarizing plate R-2. The polarization degree of the composite polarizing plate was 99.998%, and the single transmittance was 38.6%.

Tables 1 and 2 show the layer structure of the composite polarizing plate produced in each example. Table 3 shows the results of Examples and Comparative Examples.

According to the present invention, a composite polarizing plate and a liquid crystal panel having excellent heat resistance can be obtained.

DESCRIPTION OF SYMBOLS 10 Composite polarizing plate 11A 1st polarizing film 11B 2nd polarizing film 12A 1st protective film 12B 2nd

protective films

13 and 14 Adhesive layer 15 3rd protective film 20 Surface treatment layer

Claims

The first protective film, the first polarizing film having a thickness of 15 μm or less, and the second polarizing film having a thickness of 15 μm or less are laminated in this order, and the absorption axis of the first polarizing film and the absorption of the second polarizing film A composite polarizing plate whose axis is substantially parallel.
The composite polarizing plate according to claim 1, wherein the difference between the thickness of the first polarizing film and the thickness of the second polarizing film is 5 µm or less.
The composite polarizing plate according to claim 1 or 2, wherein a second protective film is laminated on a surface of the second polarizing film opposite to the surface on which the first polarizing film is laminated.
The single transmittance of the first polarizing plate having the first polarizing film and the first protective film is smaller than the single transmittance of the second polarizing plate having the second polarizing film and the second protective film. 3. The composite polarizing plate according to 3.
The composite polarizing plate according to claim 3 or 4, wherein the second protective film contains at least one selected from the group consisting of a cellulose resin, a polyolefin resin, and an acrylic resin.
6. The composite polarizing plate according to claim 3, wherein the second protective film has a thickness direction retardation value of −10 to 10 nm.
The composite polarizing plate according to any one of claims 3 to 6, wherein an adhesive layer is laminated on a surface of the second protective film opposite to the surface on which the second polarizing film is laminated.
The composite polarizing plate according to any one of claims 1 to 7, further comprising a third protective film between the first polarizing film and the second polarizing film.
The third protective film is made of a cellulose resin film, the in-plane retardation value Re (590) at a wavelength of 590 nm is 10 nm or less, and the thickness direction retardation value Rth (590) at a wavelength of 590 nm is 10 nm. The composite polarizing plate according to claim 8, wherein:
A liquid crystal panel in which the composite polarizing plate according to any one of claims 1 to 9 is disposed on at least one surface of a liquid crystal cell.