JP6455545B2 - Set of polarizing plates - Google Patents

Description

  The present invention relates to a set of polarizing plates.

  Liquid crystal display devices are used in various display devices by taking advantage of low power consumption, operation at low voltage, light weight and thinness. A liquid crystal panel constituting a liquid crystal display device has a configuration in which a pair of polarizing plates are laminated on both surfaces of a liquid crystal cell.

  In particular, in a liquid crystal panel for mobile use, a polarizing plate disposed on the back side of a liquid crystal cell may include a brightness enhancement film in order to reduce power consumption while improving screen brightness. The brightness enhancement film is a film having a property of reflecting linearly polarized light having a predetermined polarization axis or circularly polarized light in a predetermined direction and transmitting other light when backlight light of the liquid crystal display device or reflected light thereof is incident.

  However, when the back side polarizing plate is provided with a brightness enhancement film, the liquid crystal panel is warped even in a room temperature environment due to different polarizing plate members disposed above and below the liquid crystal cell. There is a problem that a problem occurs when the backlight unit or the cover glass is bonded. In recent years, the thickness of the glass substrate constituting the liquid crystal cell has been reduced, which has spurred this problem.

  For example, in Patent Document 1, by changing the thickness of the triacetyl cellulose film bonded to each polarizer between the polarizing plate arranged on the viewing side and the polarizing plate arranged on the back side, A method for reducing the warpage of a liquid crystal panel in a room temperature environment is disclosed.

  However, there is still much room for improvement in reducing warpage in a room temperature environment. Furthermore, the above Patent Document 1 has not studied warping in a high temperature environment in consideration of actual use, and the polarizing plate described in Patent Document 1 has a problem that warpage is large in a severe environment. I have it.

JP 2002-2072111 A

  An object of the present invention is to reduce the warpage of a liquid crystal panel in a normal temperature environment and reduce the warpage of the liquid crystal panel in a high temperature environment and reduce defects during actual use while facilitating the manufacture of a liquid crystal display device. And

[1] A set of polarizing plates comprising a viewing side polarizing plate disposed on the viewing side of the liquid crystal cell and a back side polarizing plate disposed on the back side of the liquid crystal cell,
The visual recognition side polarizing plate includes a first protective film, a first polarizer, and a second protective film in this order,
The back side polarizing plate includes a third protective film, a second polarizer, and a brightness enhancement film in this order,
The difference obtained by subtracting the thickness of the back side polarizing plate from the thickness of the viewing side polarizing plate is 13 μm or less,
A set of polarizing plates in which a difference obtained by subtracting the thickness of the second polarizer from the thickness of the first polarizer is more than 0 μm and not more than 5 μm.
[2] The thickness of the first polarizer is 7 μm or more and 15 μm or less,
The set of polarizing plates according to [1], wherein the thickness of the second polarizer is 4 μm or more and 12 μm or less.
[3] The set of polarizing plates according to [1] or [2], wherein the thickness of the viewing side polarizing plate and the thickness of the back side polarizing plate are both 100 μm or less.
[4] A liquid crystal panel having the set of polarizing plates according to any one of [1] to [3].

  According to the set of polarizing plates of the present invention, it is possible to reduce the warpage of the liquid crystal panel in a high temperature environment while reducing the warpage of the liquid crystal panel in a normal temperature environment.

It is sectional drawing which shows an example of the set of the polarizing plate of this invention. It is sectional drawing which shows an example of the visual recognition side polarizing plate which comprises the set of the polarizing plate of this invention. It is sectional drawing which shows an example of the back side polarizing plate which comprises the set of the polarizing plate of this invention. It is sectional drawing which shows an example of the liquid crystal panel of this invention. It is a top view which shows the position which measured the curvature amount of the glass sample.

  The polarizing plate set and the liquid crystal panel of the present invention will be described with reference to the drawings as appropriate. The set of polarizing plates of the present invention has a viewing side polarizing plate disposed on the viewing side of the liquid crystal cell and a back side polarizing plate disposed on the back side of the liquid crystal cell.

  In one embodiment, the polarizing plate of the present invention has the member shown in FIG. The set of polarizing plates shown in FIG. 1 has a viewing side polarizing plate 1 and a back side polarizing plate 2. The viewing-side polarizing plate 1 includes a first protective film 20, a first polarizer 10, a second protective film 21, and a first pressure-sensitive adhesive layer 40 in this order. The back side polarizing plate 2 includes a brightness enhancement film 30, a third pressure-sensitive adhesive layer 42, a second polarizer 11, a third protective film 22, and a second pressure-sensitive adhesive layer 41 in this order. The 1st adhesive layer 40 and the 2nd adhesive layer 41 can be an adhesive layer for bonding each polarizing plate to a liquid crystal cell, and will be finally integrated in a liquid crystal display device. Therefore, in the present invention, the thickness of the pressure-sensitive adhesive layer is included in the thickness of the polarizing plate.

  Moreover, as shown in FIG.2 and FIG.3, until it bonds the set of the polarizing plate of this invention to a liquid crystal cell, on the 1st adhesive layer 40 and the 2nd adhesive layer 41, it is a separator. 50 and the separator 51 are preferably temporarily bonded, and the protective film 60 and the protective film 61 are temporarily bonded to the first protective film 20 and the brightness enhancement film 30, respectively. preferable. Since the separators 50 and 51 and the protective films 60 and 61 are peeled off during the manufacturing process of the liquid crystal display device, the separators 50 and 51 are not finally incorporated into the liquid crystal display device. Therefore, in the present invention, the thicknesses of the separator and the protective film are not included in the thickness of the polarizing plate. Specifically, the thickness of each polarizing plate constituting the set of polarizing plates of the present invention is the thickness of the viewing side polarizing plate, for example, the arrow 100 shown in FIG. For example, the arrow 200 shown in FIG. 3 is the thickness of the back side polarizing plate.

  In FIG. 1, an adhesive layer or a pressure-sensitive adhesive layer for bonding the polarizer and the protective film is omitted. That is, for example, an adhesive layer or a pressure-sensitive adhesive layer (not shown) exists between the first protective film 20 and the first polarizer. The viewing side polarizing plate and the back side polarizing plate may include arbitrary layers other than those illustrated in FIG.

  In the set of polarizing plates of the present invention, the difference obtained by subtracting the thickness of the back side polarizing plate from the thickness of the viewing side polarizing plate is 13 μm or less, preferably −2 to 13 μm, more preferably −2 to 10 μm. More preferably, it is 1-10 micrometers. Further, in the set of polarizing plates of the present invention, the difference obtained by subtracting the thickness of the second polarizer of the back side polarizing plate from the thickness of the first polarizing plate of the viewing side polarizing plate exceeds 0 μm and is 10 μm or less. It is preferably more than 0 μm and 7 μm, more preferably more than 0 μm and 5 μm or less, and may be 1 μm or more. The thickness of the first polarizer is preferably larger than the thickness of the second polarizer.

  Thus, by having a thickness difference between the polarizing plate and the polarizer, it is possible to suppress the warpage of the liquid crystal panel in a normal temperature environment while reducing the warpage of the liquid crystal panel in a high temperature environment. The reason for this is not clear, but it is considered that in combination with the difference in the thickness of the polarizer as will be described later, it is possible to align the moisture in and out of each member constituting the polarizing plate in a room temperature environment. Also, in a high temperature environment, when the brightness enhancement film is a stretched film, the contraction force of the rear side polarizing plate and the contraction force of the viewing side polarizing plate can be made comparable in a high temperature environment, and the liquid crystal panel It is considered that the warpage of the sheet can be reduced.

In the set of polarizing plates of the present invention, the moisture content of the viewing side viewing side polarizing plate and the moisture content of the back side polarizing plate are preferably 5% or less, and may be 3% or less. In this specification, the moisture content of the polarizing plate is a value measured by a loss on drying method. Specifically, the weight (weight before drying) when left in an environment of temperature 23 ° C. and humidity 55% for 3 days is measured, and then the weight when left in an environment of 105 ° C. for 1 hour (after drying) Is a value calculated based on the following equation. The moisture content of the viewing side polarizing plate is preferably larger than the moisture content of the back side polarizing plate, and may be 0.2% or more.

Moisture content = 100 × [(weight before drying) − (weight after drying)] / weight before drying

  Further, the sum of the thickness of the viewing side polarizing plate and the thickness of the back side polarizing plate is preferably 200 μm or less, and more preferably 170 μm or less. Although a minimum is not limited, Usually, it is 100 micrometers or more. By setting it as the said range, control of the water | moisture content to enter / exit a polarizing plate is easy.

  Each member which comprises the set of the polarizing plate of this invention is demonstrated. Hereinafter, the first polarizer and the second polarizer may be collectively referred to as a polarizer, and the first protective film, the second protective film, and the third protective film are collectively referred to as a protective film. Sometimes the first adhesive layer, the second adhesive layer, and the third adhesive layer are collectively referred to as an adhesive layer, and the separator and the protective film are collectively referred to as a surface protective film. There is.

(Polarizer)
The polarizer used in the present invention is usually a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, a dichroic dye It is manufactured through a step of treating the polyvinyl alcohol-based resin film adsorbed with boric acid aqueous solution and a step of washing with water after the treatment with boric acid aqueous solution.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

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

What formed the polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer. The method for forming a polyvinyl alcohol-based resin can be formed by a known method. The film thickness of the polyvinyl alcohol-based raw film is preferably about 5 to 35 μm, more preferably 5 to 20 μm, considering that the thickness of the obtained polarizer is 15 μm or less. When the film thickness of the original film is 35 μm or more, it is necessary to increase the draw ratio when producing the polarizer, and the dimensional shrinkage of the obtained polarizer tends to increase.
On the other hand, when the film thickness of the raw film is 5 μm or less, the handling property at the time of stretching is lowered, and there is a tendency that problems such as cutting are likely to occur during production.

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

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

  As a method of dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C.
Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1800 seconds.

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

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

  The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight and preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight and preferably about 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 about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C or higher, preferably 50 to 85 ° C, and 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 immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. Further, the immersion time is usually about 1 to 120 seconds.

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

By the drying process, the moisture content of the polarizer is reduced to a practical level. The water content is usually 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizer is lost, and the polarizer may be damaged or broken after drying.
On the other hand, if the moisture content exceeds 20% by weight, the thermal stability of the polarizer may be inferior.

  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 polarizer may be performed in accordance with, for example, the method described in JP2012-159778A. . In the method described in this document, a polyvinyl alcohol resin layer to be a polarizer is formed by coating a polyvinyl alcohol resin on a base film.

  It is also effective to reduce the contraction force of the polarizer itself, and the thickness of the first polarizer is preferably 15 μm or less, more preferably 7 to 15 μm, and further preferably 10 to 13 μm. preferable. Similarly, the thickness of the second polarizer is preferably 15 μm or less, more preferably 4 to 12 μm, and even more preferably 5 to 10 μm.

(Protective film)
The protective film is composed of a resin film and can be composed of 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.

The resin for forming the protective film is not particularly limited. For example, methyl methacrylate resin, polyolefin resin, cyclic olefin resin, polyvinyl chloride resin, cellulose resin, styrene resin, acrylonitrile.・ Butadiene / styrene resins, acrylonitrile / styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, Examples thereof include films made of polyethylene terephthalate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, and the like.
These resin films are a film formed from a raw material resin, a uniaxially stretched film obtained by transverse stretching after film formation, a biaxially stretched film obtained by longitudinally stretching after film formation and then transversely stretching, etc. be able to.

  These resins can be used alone or in combination of two or more. These resins can also be used after any appropriate polymer modification. Examples of the polymer modification include copolymerization, crosslinking, molecular terminal modification, stereoregularity control, and reaction between different polymers. Modifications such as mixing including the case involving the.

  Among these, as the material for the protective film, it is preferable to use a methyl methacrylate resin, a polyethylene terephthalate resin, a polyolefin resin, or a cellulose resin. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.

  The methyl methacrylate resin is a polymer containing 50% by weight or more of methyl methacrylate units. The content of methyl methacrylate units is preferably 70% by weight or more, and may be 100% by weight. The polymer having a methyl methacrylate unit of 100% by weight is a methyl methacrylate homopolymer obtained by polymerizing methyl methacrylate alone.

  This methyl methacrylate resin can be usually obtained by polymerizing a monofunctional monomer mainly composed of methyl methacrylate in the presence of a radical polymerization initiator. In the polymerization, a polyfunctional monomer and a chain transfer agent can coexist if necessary.

  The monofunctional monomer that can be copolymerized with methyl methacrylate is not particularly limited. For example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methacrylic acid 2 -Methacrylic acid esters other than methyl methacrylate such as ethylhexyl and 2-hydroxyethyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-acrylate Acrylic esters such as ethylhexyl and 2-hydroxyethyl acrylate; methyl 2- (hydroxymethyl) acrylate, methyl 3- (hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, And hydroxyalkyl acrylates such as 2- (hydroxymethyl) butyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; vinyltoluene and α-methylstyrene Substituted styrenes; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide it can. Such monomers may be used alone or in combination of two or more.

  The polyfunctional monomer that can be copolymerized with methyl methacrylate is not particularly limited. For example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate , The hydroxyl groups at both ends of ethylene glycol or its oligomers such as tetraethylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, and tetradecaethylene glycol di (meth) acrylate were esterified with acrylic acid or methacrylic acid Propylene glycol or its oligomers with both terminal hydroxyl groups esterified with acrylic acid or methacrylic acid; Neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate Lilate and hydroxyl group of dihydric alcohol such as butanediol di (meth) acrylate esterified with acrylic acid or methacrylic acid; Bisphenol A, alkylene oxide adduct of bisphenol A, or both terminal hydroxyl groups of these halogen-substituted products Esterified with acrylic acid or methacrylic acid; polyhydric alcohols such as trimethylolpropane and pentaerythritol esterified with acrylic acid or methacrylic acid, and terminal hydroxyl groups of these polyhydric alcohols with glycidyl acrylate or glycidyl methacrylate Epoxy group ring-opening addition; succinic acid, adipic acid, terephthalic acid, phthalic acid, dibasic acids such as halogen substitution products, and alkylene oxide adducts Those with an epoxy group of glycidyl acrylate or glycidyl methacrylate by ring-opening addition; allyl (meth) acrylate; and aromatic divinyl compounds such as divinylbenzene and the like. Among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

  As the methyl methacrylate resin, those modified by a reaction between functional groups copolymerized with the resin are also used. As the reaction, for example, demethanol condensation reaction in the polymer chain of a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, or a carboxyl group of acrylic acid and 2- (hydroxymethyl) acrylic Examples thereof include a dehydration condensation reaction within a polymer chain of a hydroxyl group of methyl acid.

  The polyethylene terephthalate resin means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may contain other dicarboxylic acid components and diol components. Other dicarboxylic acid components are not particularly limited, and examples thereof include isophthalic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, and adipic acid. , Sebacic acid, 1,4-dicarboxycyclohexane and the like.

  Other diol components are not particularly limited, but propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol Etc.

  These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. Further, hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid can be used in combination. In addition, as other copolymerization component, a dicarboxylic acid component or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used.

  Polyethylene terephthalate resin can be produced by direct polycondensation of terephthalic acid and ethylene glycol (and other dicarboxylic acids or other diols as required), dialkyl esters of terephthalic acid and ethylene glycol (and if necessary) A transesterification reaction with a dialkyl ester of another dicarboxylic acid or other diol), and a polycondensation, and an ethylene glycol ester of terephthalic acid (and other dicarboxylic acids as required) For example, a method of polycondensation of other diol ester) in the presence of a catalyst is employed. Furthermore, if necessary, solid-state polymerization can be performed to improve the molecular weight or reduce the low molecular weight components.

  The cyclic polyolefin-based resin is obtained by polymerizing cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives in the presence of a catalyst. Use of such a cyclic polyolefin-based resin is preferable because a protective film having a predetermined retardation value described later can be 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; ring-opening metathesis copolymerization of at least two monomers selected from norbornene, tetracyclododecene, derivatives thereof, and other cyclic olefin monomers, Resins obtained by hydrogenation; resins obtained by addition copolymerization of aromatic compounds having chain olefins and / or vinyl groups with cyclic olefins such as norbornene, tetracyclododecene, or derivatives thereof Can be mentioned.

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

  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, There is a concern that the alicyclic saturated hydrocarbon resin bleeds out from the protective film over time.

  Cellulosic resins are those in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are substituted with acetyl groups, propionyl groups and / or butyryl groups. Further, it refers to a cellulose organic acid ester or a cellulose mixed organic acid ester. Examples include cellulose acetates, propionic acid esters, butyric acid esters, and mixed esters thereof. Among these, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like are preferable.

As a method of using a methyl methacrylate resin, a polyethylene terephthalate resin, a polyolefin resin, and a cellulose resin as a second protective film for adhering to a polarizer, a method corresponding to each resin is appropriately selected. Well, not particularly limited.
For example, a resin dissolved in a solvent is cast onto a metal band or drum, and a solvent casting method for obtaining a film by drying and removing the solvent, and the resin is heated and kneaded to a temperature higher than its melting temperature and extruded from a die, A melt extrusion method for obtaining a film by cooling is employed. In this melt extrusion method, a single layer film may be extruded or a multilayer film may be simultaneously extruded.

  The film used as the protective film can be easily obtained as a commercial product, and if it is a methyl methacrylate-based resin film, the trade name is Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acrylite (registered trademark), Acriprene (registered trademark) (Mitsubishi Rayon Co., Ltd.), Delagras (registered trademark) (Asahi Kasei Co., Ltd.), Paragrass (registered trademark), Comogras (registered trademark) (manufactured by Kuraray Co., Ltd.), Registered trademark) (manufactured by Nippon Shokubai Co., Ltd.). If it is a polyolefin-type resin film, ZEONOR (registered trademark) (Nippon Zeon Co., Ltd.), Arton (registered trademark) (JSR Co., Ltd.), etc. are mentioned by a brand name, respectively. If it is a polyethylene terephthalate-type resin film, Novaclear (trademark) (made by Mitsubishi Chemical Corporation), a Teijin A-PET sheet (made by Teijin Chemicals Ltd.), etc. are mentioned by a brand name, respectively. For polypropylene resin films, FILMAX CPP film (manufactured by FILMAX), Santox (registered trademark) (manufactured by Sun Tox Co., Ltd.), Tosero (registered trademark) (manufactured by Tosero Co., Ltd.), Toyobo Pyrene Film (Registered trademark) (manufactured by Toyobo Co., Ltd.), Treffan (registered trademark) (manufactured by Toray Film Processing Co., Ltd.), Nihon Polyace (manufactured by Nippon Polyace Co., Ltd.), and Dazai (registered trademark) FC (Futamura Chemical Co., Ltd.) Manufactured). In the case of cellulose-based resin films, Fujitac (registered trademark) TD (manufactured by Fuji Film Co., Ltd.), KC2UA and Konica Minolta TAC film KC (manufactured by Konica Minolta Co., Ltd.) and the like can be mentioned.

  The protective film and protective film used in the present invention can be provided with antiglare properties (haze). The method for imparting antiglare properties is not particularly limited. For example, a method of mixing inorganic fine particles or organic fine particles into the raw material resin to form a film, the multilayer extrusion described above, and the like. A method of forming a two-layer film from a resin in which fine particles are mixed and a resin in which fine particles are not mixed in the other, or a method of forming a three-layer film with the resin mixed with particles on the outside, and inorganic on one side of the film A method of coating a coating solution obtained by mixing fine particles or organic fine particles with a curable binder resin, curing the binder resin, and providing an antiglare layer is employed.

  Moreover, a protective film can also contain an additive as needed. Examples of the additive include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improver.

  The thickness of the protective film is usually about 1 to 50 μm and preferably 10 to 40 μm from the viewpoints of strength and handleability.

  The protective film is preferably subjected to saponification treatment, corona treatment, plasma treatment or the like prior to bonding with the polarizer.

  The first protective film can further be provided with functional layers such as a conductive layer, a hard coat layer, and a low reflection layer. Moreover, the resin composition which has these functions can also be selected for the binder resin which comprises the said glare-proof layer.

(Brightness enhancement film)
In the back side polarizing plate, a brightness enhancement film is disposed on the side far from the liquid crystal cell in the second polarizer. The thickness of the brightness enhancement film is preferably 35 μm or less, and more preferably 30 μm or less.

  As the brightness enhancement film, a polarization conversion element having a function of separating outgoing light from a light source (backlight) into transmitted polarized light, reflected polarized light, or scattered polarized light is used. Such a brightness enhancement film can improve the output efficiency of linearly polarized light by using retroreflected light from a reflected or scattered polarized backlight.

  Examples of the brightness enhancement film include anisotropic reflective polarizers. An example of the anisotropic reflective polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction. Examples of the anisotropic multiple thin film include trade names “APF” and “DBEF” manufactured by 3M. An example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ / 4 plate. An example of such a composite is a product name “PCF” manufactured by Nitto Denko Corporation. An example of the anisotropic reflective polarizer is a reflective grid polarizer. Examples of the reflective grid polarizer include metal grid reflective polarizers that perform fine processing on metal and emit reflected polarized light even in the visible light region. Of these, a brightness enhancement film comprising an anisotropic multiple thin film is preferred.

  You may form a functional layer in the surface on the opposite side to the bonding surface with the polarizing plate of a brightness improvement film. Examples of the functional layer include a hard coat layer, an antiglare layer, a light diffusing layer, and a retardation layer having a retardation value of ¼ wavelength, thereby improving adhesion to the backlight tape. And the uniformity of the displayed image can be improved.

(Surface protection film)
The separator is a film that is temporarily bonded to protect the surface of the viewing side polarizing plate and the back side polarizing plate until they are bonded to the liquid crystal cell. The separator is usually composed of a thermoplastic resin film having a release treatment on one side, and the release treatment surface is bonded to the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer. The thermoplastic resin constituting the separator can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, and the like. When the third pressure-sensitive adhesive layer provided in advance on the brightness enhancement film is provided, the surface of the third pressure-sensitive adhesive layer is also temporarily protected on the surface until the second polarizer is bonded. Therefore, the same separator as above can be stuck. The thickness of the separator is, for example, 10 to 50 μm.

  The protect film is composed of a resin film and an adhesive layer laminated thereon. A protect film is a film for protecting the surface of a visual recognition side polarizing plate and a back side polarizing plate, for example, can be temporarily bonded on a 1st protective film or a brightness improvement film. Usually, for example, after a polarizing plate with a protective film is bonded to a liquid crystal cell, the adhesive layer of the protective film is peeled off and removed. For this reason, the adhesive layer which a protective film has is not included in the thickness of a polarizing plate in this specification.

  The resin constituting the resin film is, for example, a thermoplastic resin such as a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate resin. Can do. Polyester resins such as polyethylene terephthalate are preferable. The resin film may have a single-layer structure or a multi-layer structure, but is preferably a single-layer structure from the viewpoints of manufacturability and manufacturing cost. About the adhesive layer which a protective film has, the description about the below-mentioned 1st adhesive layer and 2nd adhesive layer is quoted.

(First pressure-sensitive adhesive layer, second pressure-sensitive adhesive layer)
An adhesive layer can be laminated on the surface of the polarizing plate. A polarizing plate can be bonded to a liquid crystal cell through the said adhesive layer. In FIG. 1, the 1st adhesive layer 40 and the 2nd adhesive layer 41 correspond to this. The thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive is preferably 5 to 25 μm. More preferably, it is 10-25 micrometers.

  Examples of the pressure-sensitive adhesive that forms the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, and modified polyolefins. A polymer having a base polymer such as an epoxy-based polymer, a fluorine-based polymer, a natural rubber, a synthetic rubber, or the like can be appropriately selected and used. As the pressure-sensitive adhesive, those having excellent optical transparency, moderate wettability, cohesiveness and adhesive pressure-sensitive adhesive properties, and excellent weather resistance and heat resistance are particularly preferable.

  Various other additives may be blended in the adhesive. Examples of the additive include a silane coupling agent and an antistatic agent.

  The first adhesive layer and the second adhesive layer preferably have a storage elastic modulus of 0.01 to 0.1 MPa at 23 to 80 ° C., more preferably 0.02 to 0.06 MPa. preferable. “Showing a storage elastic modulus of 0.01 to 0.1 MPa at 23 to 80 ° C.” means that the storage elastic modulus takes a value in the above range at any temperature within this range. Since the storage elastic modulus usually decreases gradually as the temperature rises, if both the storage elastic modulus at 23 ° C. and 80 ° C. are within the above range, the pressure-sensitive adhesive layer has a storage elastic modulus within the above range at a temperature in this range. It can be seen that the rate is shown. The storage elastic modulus of the pressure-sensitive adhesive layer can be measured by a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC.

(Production method of polarizing plate)
The manufacturing method of the visual recognition side polarizing plate and back side polarizing plate which comprise the polarizing plate of this invention is demonstrated. The members described above can be bonded to each other by, for example, laminating via an adhesive layer or an adhesive layer.

(Lamination of polarizer and protective film)
The lamination of the protective film and the polarizer is preferably performed by, for example, a method in which the protective film and the polarizer are integrated using an adhesive. The thickness of the adhesive layer formed from the adhesive is preferably 0.01 to 35 μm, more preferably 0.01 to 10 μm, and still more preferably 0.01 to 5 μm. If it is this range, neither a float nor peeling will arise between a protective film and a polarizer, and the adhesive force which does not have a practical problem will be obtained.

  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. Etc. Moreover, an adhesive layer can also be provided through an anchor coat layer as necessary.

  A preferable adhesive is a water-soluble adhesive. This water-soluble adhesive includes, for example, one having a polyvinyl alcohol resin as a main component. A commercially available thing may be used for a water-soluble adhesive, and what mixed the solvent and the additive in the commercially available adhesive may be used. Examples of commercially available polyvinyl alcohol resins that can be water-soluble adhesives include KL-318 manufactured by Kuraray Co., Ltd.

  The water-soluble adhesive can contain a crosslinking agent. As a kind of crosslinking agent, an amine compound, an aldehyde compound, a methylol compound, an epoxy compound, an isocyanate compound, a polyvalent metal salt, and the like are preferable, and an epoxy compound is particularly preferable. Examples of commercially available cross-linking agents include Glyoxal, and Sumire Resin 650 (30) manufactured by Taoka Chemical Co., Ltd.

  Another preferred adhesive is an active energy ray-curable adhesive made of a resin composition that is cured by irradiation with active energy rays. Examples of the active energy ray-curable adhesive layer include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, and those containing a binder resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomer. As a photoinitiator, what contains the substance which generate | occur | produces active species like a radical, a cation, or an anion by irradiation of active energy rays like an ultraviolet-ray can be mentioned. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a cationic photopolymerization initiator can be preferably used.

  When using an active energy ray-curable adhesive, after bonding a polarizer and a protective film, a drying step is performed as necessary, and then the active energy ray-curable adhesive is irradiated by irradiating active energy rays. A curing step for curing is performed. The light source of the active energy ray is not particularly limited, but ultraviolet light having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low pressure mercury lamp, the medium pressure mercury lamp, the high pressure mercury lamp, the ultrahigh pressure mercury lamp, the chemical lamp, the black light lamp, the micro A wave excitation mercury lamp, a metal halide lamp, etc. can be used.

  The adhesive may contain an additive. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent.

(Lamination of polarizer and brightness enhancement film)

  It is preferable to use an adhesive layer for bonding the polarizer and the brightness enhancement film. In FIG. 1, the third pressure-sensitive adhesive layer corresponds to this. The thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive is preferably 3 to 20 μm. More preferably, it is 3-10 micrometers.

  Examples of the pressure-sensitive adhesive layer that bonds the polarizer and the brightness enhancement film include acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy, fluorine A polymer having a base polymer such as rubber, such as rubber, natural rubber and synthetic rubber can be appropriately selected and used. As the pressure-sensitive adhesive, those having excellent optical transparency, moderate wettability, cohesiveness and adhesive pressure-sensitive adhesive properties, and excellent weather resistance and heat resistance are particularly preferable.

  Various other additives may be blended in the adhesive. Examples of the additive include a silane coupling agent and an antistatic agent.

  The third adhesive layer preferably has a storage elastic modulus of 0.10 to 1.0 MPa at 23 to 80 ° C., and more preferably 0.15 to 0.8 MPa. When the storage elastic modulus at 23 to 80 ° C. is 0.10 to 1.0 MPa, the contraction force of the polarizer under the wet heat environment can be relaxed, and the warpage of the liquid crystal panel can be reduced more effectively. As a method for setting the storage elastic modulus of the third pressure-sensitive adhesive layer to 0.10 to 1.0 MPa, it is effective to blend a urethane acrylate oligomer in a normal pressure-sensitive adhesive composition. Preferably, such a urethane acrylate oligomer blended and then cured by irradiation with energy rays exhibits a high storage elastic modulus.

  The shape of the polarizing plate of the present invention is not particularly limited, but may be rectangular. When a polarizing plate is manufactured by a roll-to-roll method, it can be cut into a predetermined shape. The polarizing plate of the present invention may have a rectangular shape with a diagonal of 15 inches or less, a rectangular shape with a diagonal of 3 inches or more, or a rectangular shape with a diagonal of 7 inches or more.

(Liquid crystal panel manufacturing method)
A liquid crystal panel can be obtained by bonding the set of polarizing plates of the present invention to both surfaces of the liquid crystal cell. The pasting is preferably performed via the first pressure-sensitive adhesive layer of the viewing-side polarizing plate and the second pressure-sensitive adhesive layer of the back-side polarizing plate. The liquid crystal panel of the present invention can be suitably applied to a liquid crystal display device. The viewing side polarizing plate is preferably bonded so that its absorption axis is substantially parallel to the short side direction of the liquid crystal cell, and the back side polarizing plate has its absorption axis substantially parallel to the long side direction of the liquid crystal cell. It is preferable to bond so that it may become. In the present specification, “substantially parallel” means, for example, that the angle formed is 0 ± 5 °, preferably 0 ± 1 °.

  Since the entrance and exit of moisture to the viewing side polarizing plate and the back side polarizing plate can be controlled and the effects of the present invention can be further enhanced, the production of the liquid crystal panel is, for example, in an environment of temperature 18 to 28 ° C. and relative humidity 40 to 70%. It is preferable to carry out with.

  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. According to the set of polarizing plates of the present invention, even when the thickness of the liquid crystal cell is 0.4 mm or less, warpage can be significantly reduced. In the present invention, the thickness of the liquid crystal cell includes the thickness of the liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not prescribed | regulated by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified. The evaluation methods used in the examples are as follows.

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

(2) In-plane retardation Re and thickness direction retardation Rth:
It measured with the light of wavelength 590nm in 23 degreeC using the phase difference meter based on a parallel Nicol rotation method, and KOBRA-WPR by Oji Scientific Instruments.
(3) Storage elastic modulus:
The storage elastic modulus (G ′) of the pressure-sensitive adhesive was prepared by preparing a cylindrical test piece having a diameter of 8 mm and a thickness of 1 mm made of the pressure-sensitive adhesive to be measured, and measuring a dynamic viscoelasticity measuring device (Dynamic Analyzer RDA II: manufactured by REOMETRIC Co., Ltd.). ), The initial strain was set to 1 N by the torsional shear method with a frequency of 1 Hz, and the measurement was performed under the conditions of a temperature of 23 ° C. or a temperature of 80 ° C.

Each member was prepared as follows.
(Polarizer A)
A 30 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further kept in a pure water at 60 ° C. while maintaining tension. After being immersed for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, it was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a 12 μm thick polarizer in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(Polarizer B)
A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further maintained at 60 ° C. while maintaining the tension state. After being immersed in pure water for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a 7 μm-thick polarizer in which iodine was adsorbed and oriented on a polyvinyl alcohol film.

(Polarizer C)
A polyvinyl alcohol film having a thickness of 20 μm (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched by about 4.9 times by dry stretching, and further, while maintaining the tension state, After immersing in pure water of 1 ° C. for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer having a thickness of 8 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(Adhesive layer A)
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was laminated on a release-treated surface of a polyethylene terephthalate film (separator) having a thickness of 38 μm subjected to the release treatment was used. No urethane acrylate oligomer is blended in the acrylic adhesive.
The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

(Adhesive layer B)
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 15 μm was laminated on a release-treated surface of a polyethylene terephthalate film (separator) having a thickness of 38 μm subjected to the release treatment was used. No urethane acrylate oligomer is blended in the acrylic adhesive.
The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

(Adhesive layer C)
A release treatment surface of a polyethylene terephthalate film (separator) with a thickness of 38 μm obtained by releasing an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate-based crosslinking agent to a copolymer of butyl acrylate and acrylic acid. Then, it was coated with a die coater so that the thickness after drying was 5 μm and dried to obtain an adhesive sheet on which an adhesive layer was laminated. The storage elastic modulus of the pressure-sensitive adhesive layer obtained by removing the release film from the pressure-sensitive adhesive sheet was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

(Protective film)
The following protective films were prepared.
Protective film A: a triacetyl cellulose film (manufactured by Konica Minolta, Inc.) having a thickness of 20 μm. In-plane retardation value at wavelength 590 nm = 1.2 nm, thickness direction retardation value at wavelength 590 nm = 1.3 nm)
Protective film B: A cycloolefin resin film (manufactured by Nippon Zeon Co., Ltd.) having a thickness of 13 μm. In-plane retardation value at a wavelength of 590 nm = 0.8 nm, thickness direction retardation value at a wavelength of 590 nm = 3.4 nm, thickness direction retardation value at a wavelength of 483 nm = 3.5 nm, thickness direction retardation at a wavelength of 755 nm Value = 2.8 nm.
Protective film C: A cycloolefin-based resin film (manufactured by Nippon Zeon Co., Ltd.) having a thickness of 23 μm.
Protective film D: A triacetyl cellulose film having a surface with a thickness of 32 μm subjected to a hard coat treatment (25KCHC-TC, manufactured by Toppan Tomoegawa Optical Film Co., Ltd.). The water vapor transmission rate was 400 g / (m ² · 24 hr).

(Brightness enhancement film)
A brightness enhancement film (trade name: ADVanceD PolarizeD Film, Version 3 manufactured by 3M Co., Ltd.) having a thickness of 26 μm was used.

(Water-based adhesive)
3 parts of carboxyl group-modified polyvinyl alcohol (KL-318 manufactured by Kuraray Co., Ltd.) is dissolved in 100 parts of water, and a polyamide-epoxy additive that is a water-soluble epoxy compound (manufactured by Sumika Chemtex Co., Ltd.) is dissolved in the aqueous solution. Of Sumirez Resin (registered trademark) 650 (30), aqueous solution having a solid content of 30%] was added 1.5 parts to obtain an aqueous adhesive.

(Production Example 1: Viewing-side polarizing plate A)
A protective film B was bonded to one side of the polarizer A via an aqueous adhesive. A protective film D was bonded to the other surface of the polarizer A through an aqueous adhesive. The pressure-sensitive adhesive layer A laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer A in the protective film B. The thickness of the viewing side polarizing plate A was 77 μm.

(Production Example 2: Viewing-side polarizing plate B)
A protective film C was bonded to one surface of the polarizer A via an aqueous adhesive. A protective film D was bonded to the other surface of the polarizer A through an aqueous adhesive. The pressure-sensitive adhesive layer A laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer A in the protective film C. The thickness of the viewing side polarizing plate B was 87 μm.

(Production Example 3: Viewing Side Polarizing Plate C)
The protective film A was bonded to one side of the polarizer B via an aqueous adhesive. A protective film D was bonded to the other surface of the polarizer B via an aqueous adhesive. The pressure-sensitive adhesive layer A laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer B in the protective film A. The thickness of the viewing side polarizing plate C was 79 μm.

(Production Example 4: Back Side Polarizing Plate A)
The protective film B was bonded to one side of the polarizer B via a water-based adhesive. The pressure-sensitive adhesive layer C laminated on the release film was bonded to the surface opposite to the bonding surface with the protective film B in the polarizer B. The pressure-sensitive adhesive layer B laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer B in the protective film B. The release film on the pressure-sensitive adhesive layer C was peeled off, and a brightness enhancement film was bonded thereto. The thickness of the back side polarizing plate A was 66 μm.

(Production Example 5: Back side polarizing plate B)
The protective film A was bonded to one side of the polarizer B via an aqueous adhesive. The pressure-sensitive adhesive layer C laminated on the release film was bonded to the surface opposite to the bonding surface with the protective film A in the polarizer B. The pressure-sensitive adhesive layer A laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer B in the protective film A. The release film on the pressure-sensitive adhesive layer C was peeled off, and a brightness enhancement film was bonded thereto. The thickness of the back side polarizing plate A was 78 μm.

(Production Example 6: Back-side polarizing plate C)
The protective film A was bonded to one side of the polarizer B via an aqueous adhesive. The pressure-sensitive adhesive layer C laminated on the release film was bonded to the surface opposite to the bonding surface with the protective film A in the polarizer B. The pressure-sensitive adhesive layer B laminated on the release film was bonded to the surface opposite to the bonding surface with the polarizer B in the protective film A. The release film on the pressure-sensitive adhesive layer C was peeled off, and a brightness enhancement film was bonded thereto. The thickness of the back side polarizing plate A was 73 μm.

(Production Example 7: Viewing-side polarizing plate D)
A viewing-side polarizing plate D was produced in the same manner as in Production Example 1 except that the polarizer C was used instead of the polarizer A. The thickness of the viewing side polarizing plate D was 73 μm.

(Production Example 8: Viewing-side polarizing plate E)
A viewing-side polarizing plate E was produced in the same manner as in Production Example 2 except that the polarizer C was used instead of the polarizer A. The thickness of the viewing side polarizing plate E was 83 μm.

(Production Example 9: Back-side polarizing plate D)
A back-side polarizing plate D was produced in the same manner as in Production Example 4 except that the polarizer C was used instead of the polarizer B. The thickness of the back side polarizing plate D was 67 μm.

(Production Example 10: Back-side polarizing plate E)
A back-side polarizing plate E was produced in the same manner as in Production Example 5 except that the polarizer C was used instead of the polarizer B. The thickness of the back side polarizing plate E was 79 μm.

(Production Example 11: Back-side polarizing plate F)
A back-side polarizing plate F was produced in the same manner as in Production Example 6 except that the polarizer C was used instead of the polarizer B. The thickness of the back side polarizing plate F was 74 μm.

(Example 1 (comparison) )
The viewing side polarizing plate A and the back side polarizing plate A were cut into a rectangular shape having a long side direction of 155.25 mm and a short side direction of 95.9 mm. In addition, about the visual recognition side polarizing plate, it cut | judged so that the absorption-axis direction might become parallel to a short side direction, and about the back side polarizing plate, it cut | judged so that the absorption-axis direction might become parallel to a long-length direction.

(Panel warpage under normal temperature)
The release film on the pressure-sensitive adhesive layer A is peeled off from the cut viewing-side polarizing plate A, and a 0.2 mm-thick alkali-free glass (corresponding to a liquid crystal cell substrate, long side direction 160 mm, short) It was bonded to one surface of a rectangle having a side direction of 102 mm. The release film on the pressure-sensitive adhesive layer B was peeled off from the cut back-side polarizing plate A, and the other surface of the alkali-free glass was bonded via the pressure-sensitive adhesive layer B. Thus, the laminated body which consists of a viewing side polarizing plate A / glass plate / back side polarizing plate A was obtained. Then, the autoclave process was performed with respect to the laminated body. The absorption axis of each polarizing plate was orthogonal. In any of the examples, the moisture content of the viewing-side polarizing plate was 1.13%, the moisture content of the back-side polarizing plate was 0.6%, and the difference between the two was 0.53%.

The laminate was allowed to stand for 24 hours in an environment having a temperature of 23 ° C. and a humidity of 55% RH. Thereafter, the laminate was placed on a measurement table of a two-dimensional measuring device (manufactured by Nikon Corporation, NEXIV (registered trademark) VMZ-R4540) such that the viewing side polarizing plate A was on the upper side.
Next, the surface of the measurement table was focused, and the height from the reference focus was measured by focusing on each of the 25 points on the surface of the laminated body. The difference between the maximum value and the minimum value at the 25 measurement points was defined as the amount of warpage. The results are shown in Table 1 below. FIG. 5 is a schematic diagram showing measurement points of the warpage amount. 70 is a “measurement point”, 71 is a polarizing plate, and 72 is a glass plate. Twenty-five “measurement points” are points in a region about 7 mm inside from the end of the polarizing plate, and are arranged at intervals of about 20 mm in the short side direction and at intervals of about 35 mm in the long side direction.

(Panel warpage in high temperature environment)
In producing the laminate, a laminate comprising the viewing side polarizing plate A / glass plate / back side polarizing plate A was obtained in the same manner except that non-alkali glass having a thickness of 0.4 mm was used. In any of the examples, the moisture content of the viewing-side polarizing plate was 1.13%, the moisture content of the back-side polarizing plate was 0.6%, and the difference between the two was 0.53%.

The laminate was allowed to stand for 250 hours in an environment having a temperature of 85 ° C. and a humidity of 5% RH. Thereafter, the laminate was placed on a measurement table of a two-dimensional measuring device (manufactured by Nikon Corporation, NEXIV (registered trademark) VMZ-R4540) such that the viewing side polarizing plate A was on the upper side.
Next, in the same manner as the measurement of the warp of the panel in the normal temperature environment, the surface of the measuring table is focused, and the focus is set on each of the 25 points on the surface of the laminated body. The height of was measured. The difference between the maximum value and the minimum value at the 25 measurement points was defined as the amount of warpage. The results are shown in Table 1 below.

(Example 2 (Comparative) to Example 3 (Comparative) and Example 4, Comparative Examples 1 to 2)
The combination of the viewing side polarizing plate and the back side polarizing plate was shown in Table 1 below, and the warpage of the panel in a normal temperature environment and the warpage of the panel in a high temperature environment were measured. The results are summarized in Table 1 below. In Examples 1-4, the magnitude | size of the curvature of the liquid crystal panel was 0.4 mm or less also in the normal temperature environment and the high temperature environment. In Comparative Examples 1 to 3, the warpage of the liquid crystal panel exceeded 0.4 mm in either a normal temperature environment or a high temperature environment.

(Example 5 (comparative) to Example 9 (comparative), Example 10 and Example 11 (comparative) to Example 13 (comparative) )
The combination of the viewing side polarizing plate and the back side polarizing plate is shown in Table 2 below, and when the warpage of the panel under normal temperature environment and the warpage of the panel under high temperature environment are measured, Even in a high temperature environment, the warpage of the liquid crystal panel is 0.4 mm or less.

  According to the set of polarizing plates of the present invention, it is possible to reduce the warpage of the liquid crystal panel in a room temperature environment while reducing the warpage of the liquid crystal panel in a high temperature environment.

DESCRIPTION OF SYMBOLS 1 View side polarizing plate 2 Back side polarizing plate 10 1st polarizer 11 2nd polarizer 20 1st protective film 21 2nd protective film 22 3rd protective film 30 Brightness enhancement film 40 1st adhesive Layer 41 Second pressure-sensitive adhesive layer 42 Third pressure-sensitive adhesive layer 50, 51 Separator 60, 60 Protective film 70 Measurement location 71 Polarizing plate 72 Glass plate 100 View-side polarizing plate thickness 200 Back-side polarizing plate thickness

Claims (4)

A set of polarizing plates comprising a viewing side polarizing plate disposed on the viewing side of the liquid crystal cell and a back side polarizing plate disposed on the back side of the liquid crystal cell,
The visual recognition side polarizing plate includes a first protective film, a first polarizer, and a second protective film in this order,
The back side polarizing plate includes a third protective film, a second polarizer, and a brightness enhancement film in this order,
The difference obtained by subtracting the thickness of the back side polarizing plate from the thickness of the viewing side polarizing plate is −1 μm or more and 0 μm or less.
A set of polarizing plates, wherein a difference obtained by subtracting the thickness of the second polarizer from the thickness of the first polarizer is more than 0 μm and not more than 10 μm. The thickness of the first polarizer is 7 μm or more and 15 μm or less,
The set of polarizing plates according to claim 1, wherein the thickness of the second polarizer is 4 μm or more and 12 μm or less.   The set of polarizing plates according to claim 1 or 2, wherein both the thickness of the viewing side polarizing plate and the thickness of the back side polarizing plate are 100 µm or less.   A liquid crystal panel comprising the set of polarizing plates according to claim 1.

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