JP7226473B2 - A set of polarizers and a liquid crystal panel - Google Patents

Description

The present invention relates to a set of polarizing plates and a liquid crystal panel.

2. Description of the Related Art Liquid crystal display devices are used in various display devices, taking advantage of their features such as low power consumption, low voltage operation, light weight and thin profile. A liquid crystal panel constituting a liquid crystal display device has a structure in which a pair of polarizing plates are laminated on both sides of a liquid crystal cell.

Japanese Patent Laying-Open No. 2013-37115 (Patent Document 1) discloses that the polarizing film included in the optical layered body on the front side is 5 μm thicker than the polarizing film included in the optical layered body disposed on the side opposite to the front side. A method of suppressing the warping of liquid crystal panels in a high-temperature environment is presented by increasing the thickness as described above and laminating the polarizing film and the reflective polarizing film included in the optical laminate arranged on the side opposite to the front side. ing. These methods were effective when using a liquid crystal cell with a large thickness (for example, 0.5 mm or more, further 0.7 mm or more) and a reflective polarizing film with a large thickness (for example, 50 μm or more). However, in recent years, each member constituting the polarizing plate has become thin and weak in stiffness, and in addition, for a thin liquid crystal cell, the suppression of warpage of the liquid crystal panel in a high temperature environment has been insufficient.

JP 2013-37115 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a set of polarizing plates that can reduce warpage of a liquid crystal panel in a high-temperature environment.

[1] having a front-side polarizing plate arranged on the viewing side of the liquid crystal cell and a back-side polarizing plate arranged on the back side of the liquid crystal cell,
A laminate obtained by bonding the front-side polarizing plate and the back-side polarizing plate to a glass plate so that the absorption axis of the front-side polarizing plate and the absorption axis of the back-side polarizing plate are orthogonal to each other is heated at 85°C. At least one protective film in the polarizing plate on the side where the laminate warps in a convex shape has a tensile elastic modulus in the direction of the transmission axis of the polarizing plate at 85 ° C. and a polarizing plate absorption at 85 ° C. A set of polarizing plates satisfying the following formula (1), where Et and Ea are the tensile elastic moduli in the axial direction, respectively.
Ea/Et≧0.95 (1)
[2] The polarized light according to [1], wherein each of the front-side polarizing plate and the back-side polarizing plate has a polarizer made of a polyvinyl alcohol-based resin film, and the thickness of each of the polarizers is 15 μm or less. set of boards.
[3] The polarizing plate according to [1] or [2], wherein the difference between the thickness of the polarizer included in the front-side polarizing plate and the thickness of the polarizer included in the back-side polarizing plate is 5 μm or less. set.
[4] A liquid crystal panel comprising a set of polarizing plates according to any one of [1] to [3] and a liquid crystal cell, wherein the liquid crystal cell has a thickness of 0.4 mm or less.

According to the polarizing plate set of the present invention, it is possible to reduce the warpage of the liquid crystal panel in a high-temperature environment.

1 is a cross-sectional view showing an example of a set of polarizing plates of the present invention; FIG. 1 is a cross-sectional view showing an example of a liquid crystal panel of the present invention; FIG. It is a schematic cross section of the evaluation sample after heat treatment. FIG. 5 is a plan view showing positions where the amount of warpage of the evaluation sample was measured;

A set of polarizing plates and a 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 front-side polarizing plate arranged on the viewing side of the liquid crystal cell and a back-side polarizing plate arranged 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 polarizers shown in FIG. 1( a ) has a front polarizer 100 and a back polarizer 200 . In the front-side polarizing plate 100, the protective film 10 is laminated on one side of the polarizer 2 with an adhesive layer 30 interposed therebetween, and the protective film 11 is laminated on the other side of the polarizer 2 with an adhesive layer 21 interposed therebetween. It is Furthermore, an adhesive layer 20 is laminated on the protective film 11 .

The back-side polarizing plate 200 has a protective film 12 laminated on one surface of the polarizer 2 with an adhesive layer 32 interposed therebetween, and a brightness enhancement film on the other surface of the polarizer 2 with an adhesive layer 21 interposed therebetween. 40 are laminated. Furthermore, an adhesive layer 20 is laminated on the protective film 12 .

Also, the set of polarizing plates shown in FIG. In the front-side polarizing plate 101, the protective film 10 is laminated on one side of the polarizer 2 with an adhesive layer 30 interposed therebetween, and the protective film 11 is laminated on the other side of the polarizer 2 with an adhesive layer 31 interposed therebetween. It is Furthermore, an adhesive layer 20 is laminated on the protective film 11 .

The back-side polarizing plate 201 has a protective film 12 laminated on one surface of the polarizer 2 with an adhesive layer 31 interposed therebetween, and a brightness enhancement film 40 laminated on the protective film 12 with an adhesive layer 22 interposed therebetween. ing. Furthermore, an adhesive layer 20 is laminated on the other surface of the polarizer 2 .

In the set of polarizing plates shown in FIG. 1, the adhesive layer 20 may be, for example, an adhesive layer for laminating the polarizing plate to the liquid crystal cell.

In the set of polarizing plates of the present invention, the shapes of the front-side polarizing plate and the back-side polarizing plate are not particularly limited, but may be rectangular. When the shape of the polarizing plate is a rectangle having long sides and short sides, the absorption axis of the front-side polarizing plate is preferably parallel to the short sides, and the absorption axis of the back-side polarizing plate is parallel to the long sides. is preferably

In the set of polarizing plates of the present invention, when the laminate including the front-side polarizing plate and the back-side polarizing plate is heated, the protective film of the polarizing plate on the side that warps in a convex shape is the same as the polarizing plate at 85 ° C. When the tensile elastic modulus of the plate in the direction of the transmission axis and the tensile elastic modulus of the polarizing plate in the direction of the absorption axis at 85° C. are Et and Ea, respectively, the following formula (1) is satisfied. The tensile modulus can be measured by the method described in Examples below.

Ea/Et≧0.95 (1)

Ea/Et is more preferably 1.05 or more, even more preferably 1.10 or more. Ea/Et may be 2.5 or less.

If the edge of the laminate warps toward the front side polarizer, the polarizing plate on the side that warps in a convex shape is the back side polarizer. The warped side polarizing plate is the front side polarizing plate. A specific description will be given with reference to FIG. FIG. 3 shows a schematic cross-section of a laminated body in which a front-side polarizing plate 400 and a back-side polarizing plate 401 are attached to a glass plate 70 after being heat-treated. In FIG. 3(a), the polarizing plate on the convex warp side refers to the front side polarizing plate 400, and in FIG. Point to 401. The convex warped polarizing plate may be the front side polarizing plate or the back side polarizing plate. Since the back-side polarizing plate often includes a stretched polarizer and a similarly stretched brightness enhancement film, when the absorption axis direction of the back-side polarizing plate is the long side direction, The shrinkage force when the back-side polarizing plate is heated is often greater than that of the front-side polarizing plate.

The shape of the polarizing plate and the shape of the glass plate when attached to the glass plate are not particularly limited, but a rectangular shape is preferable, and in this case, the front side polarizing plate and the back side polarizing plate can have the same size. . When the polarizing plate is attached to the glass plate, the absorption axis of the front-side polarizing plate and the absorption axis of the back-side polarizing plate are perpendicular to each other. At this time, when the polarizing plate has a rectangular shape, the absorption axis of the front-side polarizing plate is preferably parallel to the short sides, and the absorption axis of the back-side polarizing plate is preferably parallel to the long sides.

The thickness of the glass plate can be, for example, 100 μm or more and 400 μm or less. When the thickness is within such a range, it is easy to determine which of the front-side polarizing plate and the back-side polarizing plate is the concavely warped polarizing plate.

The polarizing plate on the convex warp side may have protective films on both sides of the polarizer. In this case, at least one of the protective films preferably satisfies the formula (1). More preferably, the protective film laminated on the near side satisfies formula (1), and more preferably both protective films satisfy formula (1). Of course, one protective film may satisfy formula (1) and the other protective film may not satisfy formula (1).
The protective film here refers to a film laminated on a polarizer via an adhesive layer or pressure-sensitive adhesive layer.

The tensile elastic modulus Et in the transmission axis direction at 85° C. is preferably 500 MPa or more and 10000 MPa or less, and may be 1000 MPa or more and 8000 MPa or less. The tensile elastic modulus Ea in the absorption axis direction at 85° C. is preferably 500 MPa or more and 10000 MPa or less, may be 1000 MPa or more and 8000 MPa or less, or may be 2000 MPa or more and 8000 MPa or less.

Each member constituting the polarizing plate set of the present invention will be described.

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

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers that can be copolymerized. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

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

A film obtained by forming a polyvinyl alcohol-based resin is used as a raw film for a polarizer. A known method can be used to form a film from the polyvinyl alcohol-based resin. Considering that the thickness of the resulting polarizer is 15 μm or less, the film thickness of the polyvinyl alcohol base film is preferably about 5 to 35 μm, more preferably 5 to 20 μm. When the film thickness of the raw film is 35 μm or more, it is necessary to increase the draw ratio when manufacturing the polarizer, and the dimensional shrinkage of the resulting polarizer tends to increase.
On the other hand, when the film thickness of the raw film is 5 μm or less, the handleability during stretching tends to deteriorate, and problems such as cutting tend to occur during production.

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

In the uniaxial stretching, the film may be uniaxially stretched between rolls having different circumferential speeds, or may be uniaxially stretched using hot rolls. The uniaxial stretching may be dry stretching in which the film is stretched in the atmosphere, or may be wet stretching in which the polyvinyl alcohol resin film is stretched in a swollen state using a solvent. The draw ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye is employed. Specifically, iodine and dichroic dyes are used as dichroic dyes. The polyvinyl alcohol resin film is preferably immersed in water before being dyed.

When iodine is used as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually adopted. 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. Also, 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.
The immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of dyeing by immersing 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, 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 aid. The temperature of the dichroic dye aqueous 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.

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, 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, 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, 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, more preferably 60 to 80°C.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the water washing process is usually about 5 to 40.degree. Also, the immersion time is usually about 1 to 120 seconds.

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

The drying process reduces the moisture content of the polarizer to a practical level. Its moisture content is usually 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the flexibility of the polarizer may be lost and the polarizer may be damaged or broken after drying.
Moreover, when the moisture content exceeds 20% by weight, the thermal stability of the polarizer may deteriorate.

Further, stretching, dyeing, boric acid treatment, water washing, and drying of the polyvinyl alcohol-based resin film in the manufacturing process of the polarizer may be performed, for example, according to the method described in JP-A-2012-159778. . In the method described in this document, a polyvinyl alcohol-based resin layer that serves as a polarizer is formed by coating a base film with a polyvinyl alcohol-based resin.

Reducing the shrinkage force of the polarizer itself is also effective in reducing warpage in a high-temperature environment, and the thickness of the polarizers provided in both the front-side polarizing plate and the back-side polarizing plate is preferably 15 μm or less. , 4 to 13 μm, more preferably 5 to 10 μm.

The difference between the thickness of the polarizer provided on the front-side polarizing plate and the thickness of the polarizer provided on the back-side polarizing plate is preferably 5 μm or less, and may be 3 μm or less. When the protective film of the polarizing plate on the side warped in a convex shape satisfies the formula (1), by reducing the thickness difference of the polarizer in this way, the influence on the warping of the liquid crystal panel in a high-temperature environment is further reduced. be able to.

(Protective film)
The protective film is composed of a resin film, and may 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, a transparent resin film means a resin film having a single transmittance of 80% or more in the visible light range.

When the protective films are laminated on both sides of the polarizer, the same protective films or different protective films may be used. Moreover, the protective film for the front-side polarizing plate and the protective film for the back-side polarizing plate may be the same or different.

The resin that forms the protective film is not particularly limited, but examples include methyl methacrylate resins, polyolefin resins, cyclic olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, and acrylonitrile.・Butadiene/styrene resin, acrylonitrile/styrene resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate resin, Films made of polyethylene terephthalate-based resins, polysulfone-based resins, polyethersulfone-based resins, polyarylate-based resins, polyamideimide-based resins, polyimide-based resins, and the like can be mentioned.

These resins can be used alone or in combination of two or more. In addition, these resins can be used after being subjected to any appropriate polymer modification, and the polymer modification includes, for example, copolymerization, cross-linking, molecular terminal modification, stereoregularity control, and reaction between different polymers. Modifications such as mixing, including the case involving

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

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

This methyl methacrylate resin can usually be obtained by polymerizing a monofunctional monomer containing methyl methacrylate as a main component in the presence of a radical polymerization initiator. In the polymerization, a polyfunctional monomer and a chain transfer agent may coexist as required.

Monofunctional monomers that can be copolymerized with methyl methacrylate are not particularly limited, but examples include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, and 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 Acrylate esters such as ethylhexyl and 2-hydroxyethyl acrylate; methyl 2-(hydroxymethyl)acrylate, methyl 3-(hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and 2-( Hydroxyalkyl acrylates such as butyl hydroxymethyl)acrylate; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Substituted styrenes such as vinyltoluene and α-methylstyrene. 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. Such monomers may be used alone or in combination of two or more.

Polyfunctional monomers that can be copolymerized with methyl methacrylate are not particularly limited, and examples thereof include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. , tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, and tetradecaethylene glycol di(meth)acrylate, etc. Both terminal hydroxyl groups of ethylene glycol or its oligomers are esterified with acrylic acid or methacrylic acid. Propylene glycol or its oligomer with both terminal hydroxyl groups esterified with acrylic acid or methacrylic acid; Neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, butanediol di(meth)acrylate, etc. Those obtained by esterifying the hydroxyl groups of dihydric alcohols with acrylic acid or methacrylic acid; Bisphenol A, alkylene oxide adducts of bisphenol A, or those obtained by esterifying both terminal hydroxyl groups of these halogen-substituted products with acrylic acid or methacrylic acid; Esterified polyhydric alcohols such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid, and those obtained by ring-opening addition of epoxy groups of glycidyl acrylate or glycidyl methacrylate to terminal hydroxyl groups of these polyhydric alcohols; succinic acid , adipic acid, terephthalic acid, phthalic acid, dibasic acids such as halogen-substituted products thereof, and alkylene oxide adducts thereof obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate; acrylates; and aromatic divinyl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

Methyl methacrylate-based resins may also be modified by reaction between functional groups copolymerized in the resin. Examples of the reaction include intrachain demethanol condensation reaction between a methyl ester group of methyl acrylate and a hydroxyl group of 2-(hydroxymethyl)methyl acrylate, or a carboxyl group of acrylic acid and 2-(hydroxymethyl)acrylic acid. Intra-polymer chain dehydration-condensation reaction of hydroxyl groups of methyl acid can be mentioned.

A polyethylene terephthalate-based resin means a resin in which 80 mol % or more of repeating units is composed of ethylene terephthalate, and may contain other dicarboxylic acid component and diol component. Other dicarboxylic acid components include, but are not limited to, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, and adipic acid. , sebacic acid, and 1,4-dicarboxycyclohexane.

Other diol components include, but are not limited to, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adducts 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. Hydroxycarboxylic acids such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid can also be used in combination. As another copolymerization component, a dicarboxylic acid component containing a small amount of amide bond, urethane bond, ether bond, carbonate bond, or the like, or a diol component may be used.

Methods for producing polyethylene terephthalate-based resins include direct polycondensation of terephthalic acid and ethylene glycol (and optionally other dicarboxylic acids or other diols), dialkyl esters of terephthalic acid and ethylene glycol (and optionally a dialkyl ester of another dicarboxylic acid or other diol), followed by polycondensation, and ethylene glycol ester of terephthalic acid (and optionally other dicarboxylic acid) (and (Other diol esters) in the presence of a catalyst. Further, if necessary, solid state polymerization can be performed to improve the molecular weight or reduce the low molecular weight components.

Cyclic polyolefin resins are obtained, for example, by polymerizing cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives in the presence of a catalyst. The use of such a cyclic polyolefin resin is preferable because a protective film having a predetermined retardation value, which will be described later, can be easily obtained.

As the cyclic polyolefin resin, for example, norbornene or a derivative thereof obtained by Diels-Alder reaction from cyclopentadiene and olefins or (meth)acrylic acid or its esters is subjected to ring-opening metathesis polymerization as a monomer, followed by Resin obtained by hydrogenation; tetracyclododecene obtained by Diels-Alder reaction from dicyclopentadiene and olefins or (meth)acrylic acid or its esters, or its derivative, is subjected to ring-opening metathesis polymerization, and A resin obtained by subsequent hydrogenation; obtained by similarly ring-opening metathesis copolymerization of at least two monomers selected from norbornene, tetracyclododecene, derivatives thereof, and other cyclic olefin monomers, followed by hydrogenation. Resins: resins obtained by addition-copolymerizing linear olefins and/or aromatic compounds having a vinyl group to cyclic olefins such as norbornene, tetracyclododecene, or derivatives thereof, and the like.

Typical examples of chain polyolefin-based resins are polyethylene-based resins and polypropylene-based resins. Among them, a homopolymer of propylene or a copolymer composed mainly of propylene and copolymerized with a comonomer such as ethylene that can be copolymerized in an amount of 1 to 20% by weight, preferably 3 to 10% by weight. It is preferably used.

The polypropylene-based resin may contain an alicyclic saturated hydrocarbon resin. By containing the alicyclic saturated hydrocarbon resin, it becomes easier to control the retardation value. The content of the alicyclic saturated hydrocarbon resin is advantageously 0.1 to 30% by weight, more preferably 3 to 20% by weight, based on the polypropylene resin. If the content of the alicyclic saturated hydrocarbon resin is less than 0.1% by weight, the effect of controlling the retardation value is not sufficiently obtained, while if the content exceeds 30% by weight, the protective film There is a concern that the alicyclic saturated hydrocarbon resin may bleed out over time.

Cellulose-based resins are obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, softwood pulp), and some or all of the hydrogen atoms in the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups and/or butyryl groups. It also refers to cellulose organic acid esters or cellulose mixed organic acid esters. Examples thereof include cellulose acetate, propionate, butyrate, and mixed esters thereof. Among them, triacetyl cellulose film, diacetyl cellulose film, cellulose acetate propionate film, cellulose acetate butyrate film and the like are preferable.

A method for forming a second protective film for adhering a methyl methacrylate-based resin, a polyethylene terephthalate-based resin, a polyolefin-based resin, and a cellulose-based resin to a polarizer may be selected appropriately according to each resin. Well, not particularly limited.
For example, a solvent casting method in which a resin dissolved in a solvent is cast onto a metal band or drum and the solvent is removed by drying to obtain a film; A melt extrusion method is employed in which the film is obtained by cooling. The melt extrusion method may be extrusion of a single layer film or coextrusion of multilayer films.

Films used as protective films can be easily obtained commercially, and methyl methacrylate-based resin films are respectively trade names of Sumipex (manufactured by Sumitomo Chemical Co., Ltd.), Acrylite (registered trademark), Acryprene (registered trademark) (manufactured by Mitsubishi Rayon Co., Ltd.), Delaglas (registered trademark) (manufactured by Asahi Kasei Corporation), Paraglas (registered trademark), Comoglas (registered trademark) (manufactured by Kuraray Co., Ltd.), and Acryvure (manufactured by Kuraray Co., Ltd.) (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) and the like. Examples of polyolefin resin films include trade names such as Zeonor (registered trademark) (Nippon Zeon Co., Ltd.) and Arton (registered trademark) (JSR Corporation). Examples of polyethylene terephthalate resin films include Novaclear (registered trademark) (manufactured by Mitsubishi Chemical Corporation) and Teijin A-PET Sheet (manufactured by Teijin Chemicals Ltd.). For polypropylene resin films, FILMAX CPP film (manufactured by FILMAX Co., Ltd.), Santox (registered trademark) (manufactured by Sun Tox Co., Ltd.), Tohcello (registered trademark) (manufactured by Tohcello Co., Ltd.), Toyobo Pylen Film (registered trademark) (manufactured by Toyobo Co., Ltd.), Torayfan (registered trademark) (manufactured by Toray Advanced Film Co., Ltd.), Nihon Polyace (manufactured by Nippon Polyace Co., Ltd.), and Taiko (registered trademark) FC (Futamura Chemical Co., Ltd.) made) and the like. Cellulose resin films include FUJITAC (registered trademark) TD (manufactured by Fuji Film Co., Ltd.), KC2UA and Konica Minolta TAC Film KC (manufactured by Konica Minolta Co., Ltd.).

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

Moreover, the protective film can also contain an additive as needed. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light stabilizers, and impact modifiers.

The thickness of the protective film is usually about 1 to 50 μm from the viewpoint of strength and handling.

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

Functional layers such as a conductive layer, a hard coat layer, and a low-reflection layer can be further provided on the protective film of the front-side polarizing plate. A resin composition having these functions can also be selected as the binder resin constituting the antiglare layer.

A protective film that satisfies formula (1) can also be produced, for example, by stretching a resin film. The stretching method is not particularly limited as long as it is a manufacturing method using a sheet film. It can be a biaxially stretched film or the like obtained by stretching. The draw ratio can be, for example, 1.01 or more and 5.00 or less, and may be 1.01 or more and 3.00 or less.

(brightness enhancement film)
The back-side polarizing plate preferably has a brightness enhancement film on the far side of the polarizer from the liquid crystal cell. The thickness of the brightness enhancement film is preferably 35 μm or less, more preferably 30 μm or less. The thickness of the brightness enhancement film is usually 10 μm or more.

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

Brightness enhancement films include, for example, anisotropic reflective polarizers. An anisotropic reflective polarizer includes an anisotropic multilayer thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction. An example of an anisotropic multi-layer thin film is the product name "APF" manufactured by 3M. As an anisotropic reflective polarizer, there is a composite of a cholesteric liquid crystal layer and a λ/4 plate. An example of such a composite is the trade name "PCF" manufactured by Nitto Denko Corporation. An anisotropic reflective polarizer includes a reflective grid polarizer. As the reflective grid polarizer, there is a metal grid reflective polarizer that emits reflected polarized light even in the visible light region by finely processing a metal. Among them, a brightness enhancement film composed of an anisotropic multiple thin film is preferable.

A functional layer may be formed on the surface of the brightness enhancement film opposite to the surface bonded to the polarizing plate. Examples of the functional layer include a hard coat layer, an antiglare layer, a light diffusion layer, a retardation layer having a retardation value of 1/4 wavelength, etc., which improves adhesion with the backlight tape. and the uniformity of the displayed image can be improved.

(Adhesive layer)
A pressure-sensitive adhesive layer can be laminated on the surface of the polarizing plate. A polarizing plate can be attached to a liquid crystal cell through the pressure-sensitive adhesive layer. In FIG. 1, the adhesive layer 20 corresponds to this.
The thickness of the adhesive layer formed from the adhesive is preferably 5 to 25 μm, more preferably 10 to 25 μm.

The pressure-sensitive adhesive layer for bonding the front-side polarizing plate to the liquid crystal cell and the pressure-sensitive adhesive layer for bonding the back-side polarizing plate to the liquid crystal cell may be the same or different. You can use things.

Also, the brightness enhancement film and the protective film or polarizer can be laminated with an adhesive layer. In FIG. 1, the adhesive layers 21 and 22 correspond to this. The thickness of the adhesive layer formed from the adhesive is preferably 1 to 20 μm, more preferably 1 to 10 μm.

Examples of adhesives that form the adhesive layer include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride copolymers, modified polyolefins, epoxy systems, fluorine systems, natural rubbers, It is possible to appropriately select and use a polymer having a rubber-based polymer such as synthetic rubber as a base polymer. As the pressure-sensitive adhesive, it is particularly preferable to use a pressure-sensitive adhesive that exhibits excellent optical transparency, appropriate wettability, cohesiveness, and adhesive properties, and is excellent in weather resistance, heat resistance, and the like.

In addition to this, the adhesive may contain various additives. Additives include silane coupling agents and antistatic agents.

(adhesive layer)
Lamination of the protective film and the polarizer and lamination of the brightness enhancement film and the polarizer can be performed by, for example, a method of integrating them 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, still more preferably 0.01 to 5 μm. Within this range, there is no lifting or peeling between the protective film or the brightness enhancement film and the polarizer, and practically acceptable adhesive strength can be obtained.

Examples of adhesives include solvent-based adhesives, emulsion-based adhesives, pressure-sensitive adhesives, remoistening adhesives, polycondensation-based adhesives, solvent-free adhesives, film-like adhesives, and hot-melt adhesives. etc. Moreover, an adhesive layer can be provided via an anchor coat layer as needed.

Preferred adhesives include water-soluble adhesives. This water-soluble adhesive includes, for example, a polyvinyl alcohol-based resin as a main component. A commercially available water-soluble adhesive may be used, or a commercially available adhesive mixed with a solvent or an additive may be used. Commercially available polyvinyl alcohol resins that can be used as water-soluble adhesives include, for example, KL-318 manufactured by Kuraray Co., Ltd., and the like.

The water-soluble adhesive can contain a cross-linking agent. As the types of cross-linking agents, amine compounds, aldehyde compounds, methylol compounds, epoxy compounds, isocyanate compounds, polyvalent metal salts and the like are preferable, and epoxy compounds are particularly preferable. Examples of commercially available cross-linking agents include glyoxal, Sumilase Resin 650 (30) manufactured by Taoka Kagaku Kogyo Co., Ltd., and the like.

Another preferred adhesive is an active energy ray-curable adhesive composed of a resin composition that is cured by irradiation with an active energy ray. Active energy ray-curable adhesives include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, those containing a binder resin and a photoreactive cross-linking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from photopolymerizable monomers. Photopolymerization initiators include substances that generate active species such as radicals, cations, or anions upon irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, one containing a photocurable epoxy-based monomer and a photocationic polymerization initiator can be preferably used.

When using an active energy ray-curable adhesive, after laminating the polarizer and the protective film, a drying process is performed as necessary, and then the active energy ray-curable adhesive is removed by irradiating with an active energy ray. Perform a curing step for curing. The light source of the active energy ray is not particularly limited, but ultraviolet rays having a light emission distribution at a wavelength of 400 nm or less are preferable. A wave-excited mercury lamp, a metal halide lamp, or the like can be used.

The adhesive may contain additives. Additives include ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, flow modifiers, plasticizers, antifoaming agents and the like.

(Cured layer of active energy ray-curable resin composition)
The cured layer of the active energy ray-curable resin composition is useful as a protective layer for protecting the surface of the polarizer. Since the cured layer of the active energy ray-curable resin composition can be made thinner than a normal protective film, it is effective in thinning the polarizing plate.

The thickness of the cured layer of the active energy ray-curable resin composition is preferably 0.01 to 20 μm, more preferably 0.01 to 10 μm, still more preferably 0.01 to 5 μm.

As the active energy ray-curable resin composition forming the cured layer of the active energy ray-curable resin composition, the same active energy ray-curable adhesive can be used. The active energy ray-curable resin composition and the active energy ray-curable adhesive may be the same or different.

(Manufacturing method of polarizing plate)
The members described above can be laminated together, for example, by laminating them via an adhesive layer or a pressure-sensitive adhesive layer. A method of manufacturing a polarizing plate using a release film is also useful.

Hereinafter, the method for manufacturing the front-side polarizing plate and the back-side polarizing plate that constitute the polarizing plate of the present invention will be described by taking the set of polarizing plates shown in FIG. 1(a) as an example.

(Manufacturing method of front-side polarizing plate)
A peeling film, a polarizer 2, and a protective film 10 are prepared, and the protective film is attached to one surface of the polarizer with an adhesive, and is attached to the other surface of the polarizer with a volatile liquid. A release film is laminated. Of course, the bonding of the protective film and the polarizer and the lamination of the release film and the polarizer may be performed sequentially.

A volatile liquid is, for example, water or a mixture of water and a hydrophilic liquid. The hydrophilic liquid is preferably one that does not remain after the heat treatment in the second step. Examples include formic acid and acetic acid. Additives such as antistatic agents may be added to the volatile liquid.

The resin that forms the release film is not particularly limited, but examples include methyl methacrylate resins, polyolefin resins, cyclic olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, and acrylonitrile.・Butadiene/styrene resin, acrylonitrile/styrene resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate resin, Films made of polyethylene terephthalate-based resins, polysulfone-based resins, polyethersulfone-based resins, polyarylate-based resins, polyamideimide-based resins, polyimide-based resins, and the like can be mentioned.

In laminating the protective film to the polarizer, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and canopy treatment are applied to the bonding surface of the polarizer and/or the protective film in order to improve adhesiveness. Easy-adhesion treatment such as hardening treatment can be performed. It is also useful to subject the release film to the same treatment as the protective film in order to improve the wettability of the volatile liquid.

When an active energy ray-curable adhesive is used as the adhesive, the adhesive is cured by irradiating it with an active energy ray and then heat-treated to volatilize and remove the volatile liquid. When a water-based adhesive is used as the adhesive, the volatile liquid is volatilized and removed by heat treatment while adhering the polarizer and the protective film. It is preferable to use a water-based adhesive in that the process can be simplified.

The drying temperature is preferably 30-90°C. If the temperature is less than 30°C, it takes a long time to dry, which may cause poor appearance. Also, if the drying temperature exceeds 90° C., the heat may deteriorate the polarizing performance of the polarizer. The drying time can be about 10 to 1000 seconds, preferably 60 to 750 seconds, more preferably 150 to 600 seconds from the viewpoint of productivity.

By laminating the release film on the polarizer with a layer made of a volatile liquid interposed therebetween, the heating temperature in this step can be increased, for example, to about 60° C. to 90° C. or less. That is, even if the heating temperature is set high, in addition to being able to suppress breakage of the polarizer, the high-temperature heating makes it possible to obtain a single-sided protective polarizing plate with a small shrinkage rate of the polarizer and high dimensional stability. . By reducing the shrinkage rate of the single-sided protective polarizing plate, it is possible to further reduce warping of the liquid crystal panel when the polarizing plate is used to fabricate the liquid crystal panel.

In order to volatilize the volatile liquid used for laminating the polarizer and the release film by heating, the moisture permeability of at least one of the protective film and the release film is preferably 400 g/m ² · 24 hr or more, and 420 g /m ² ·24 hr or more is more preferable. When the water vapor permeability is within this range, the volatile liquid can be efficiently removed by volatilization in the subsequent second step, so productivity can be further enhanced.

The release film is peeled off from the single-sided protective polarizing plate, and the protective film 11 is laminated on the polarizer 2 of the single-sided protective polarizing plate via an adhesive layer. Furthermore, by forming the adhesive layer 20 on the protective film 11, a front-side polarizing plate consisting of the adhesive layer 20/protective film 11/adhesive layer 21/polarizer 2/adhesive layer 30/protective film 10 is obtained. be done.

(Manufacturing method of back side polarizing plate)
A release film, a polarizer 2, and a protective film 12 are prepared by a method similar to the method for manufacturing the front-side polarizing plate, and the protective film 12 is attached to one surface of the polarizer 2 via an adhesive, A release film is laminated on the other surface of the polarizer 2 via a volatile liquid. After bonding the polarizer 2 and the protective film 12 and removing the volatile liquid, the release film is peeled off to obtain a single-sided protective polarizing plate.

On the polarizer 2 in the single-sided protective polarizing plate, the brightness enhancement film 40 is laminated via the adhesive layer, and the adhesive layer 20 is laminated on the protective film 12, whereby the adhesive layer 20 / protective film 12 / adhesive A rear-side polarizing plate composed of agent layer 32/polarizer 2/adhesive layer 21/brightness enhancement film 40 is obtained.

The shape of the polarizing plate of the present invention is not particularly limited, but may be a rectangle or a rectangle having long sides and short sides. When the polarizing plate is manufactured by the 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.

(Method for manufacturing liquid crystal panel)
A liquid crystal panel can be obtained by laminating a set of polarizing plates of the present invention on both sides of a liquid crystal cell. It is preferable to perform lamination via the pressure-sensitive adhesive layer of the front-side polarizing plate and via the pressure-sensitive adhesive layer of the back-side polarizing plate. Moreover, it is preferable that the front-side polarizing plate is laminated on the viewing side of the liquid crystal cell, and the back-side polarizing plate is laminated on the back side of the liquid crystal cell. The liquid crystal panel of the present invention can be suitably applied to liquid crystal display devices. The front-side polarizing plate is preferably attached so that its absorption axis is substantially parallel to the short-side direction of the liquid crystal cell, and the back-side polarizing plate is attached so that its absorption axis is substantially parallel to the long-side direction of the liquid crystal cell. It is preferable to laminate so that In this specification, "substantially parallel" means, for example, that the angle formed is 0±5°, preferably 0±1°.

A liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the substrates. Cell substrates are generally made of glass in many cases, but may be plastic substrates. 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 if 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 the thickness of the pair of substrates sandwiching the liquid crystal layer.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not defined by these examples. In the examples, percentages and parts representing contents or amounts used are based on weight unless otherwise specified. The evaluation methods used in the examples are as follows.

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

(2) Tensile modulus A test piece having a width of 15 mm and a length of 150 mm was cut out from the film. Next, the upper and lower grips of a tensile tester equipped with a constant temperature bath [AUTOGRAPH (registered trademark) AG-1S tester manufactured by Shimadzu Corporation] are held so that the distance between the grips is 100 mm. Both ends were clamped and pulled at a tensile speed of 50 mm/min in an environment of 85°C to create a stress-strain curve, and the tensile modulus at 85°C was calculated.

(3) Moisture Permeability Moisture permeability was measured based on JIS Z 0208. The temperature and humidity conditions were 40 degrees and 90% RH.

(4) Determination of the polarizing plate on the side warped in a convex shape and measurement of the amount of warpage in a high temperature environment An evaluation sample having a configuration of back side polarizing plate / glass plate / front side polarizing plate was placed in an environment of 85 ° C. After standing still for 250 hours, it was placed on the measurement table of a two-dimensional measuring instrument with the front side polarizing plate facing upward. As a two-dimensional measuring device, "NEXIV (registered trademark) VMR-12072" manufactured by Nikon Corporation was used. Next, the surface of the measuring table was focused, and using that as a reference, 25 points on the surface of the sample for evaluation were focused, and the height from the reference focus was measured. The difference between the maximum and minimum heights at the 25 measurement points is the amount of warpage, and the warpage of the edge of the evaluation sample on the front side polarizing plate side is plus warp, and the back side polarizing plate side is for evaluation. A warp in which the edge of the sample was warped was taken as a negative warp. In the case of plus warp, the polarizing plate on the convexly warped side is the rear side polarizing plate, and in the case of the negative warp, the polarizing plate on the convexly warped side is the front side polarizing plate.

Specifically, the point 80 shown in FIG. 4 was used as the measurement point. The 25 points shown in FIG. 4 are points in a region 7 mm inward from the edge of the polarizing plate, and are provided at intervals of about 20 mm in the short side direction and at intervals of about 35 mm in the long side direction. In FIG. 4, reference numeral 402 denotes a polarizing plate, and 70 denotes a glass plate.

[Production Example 1] Production of polarizer A polyvinyl alcohol film having a thickness of 20 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol % or more) was uniaxially stretched by dry stretching to about 4 times, and then kept in a tensioned state. After immersing it in pure water at 40° C. for 40 seconds, it was then immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.052/5.7/100 at 28° C. for 30 seconds for dyeing treatment. rice field. After that, it was immersed in an aqueous solution of potassium iodide/boric acid/water at a weight ratio 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 was dried at 60°C for 50 seconds and then at 75°C for 20 seconds while maintaining a tension of 300N. A polarizer having a thickness of 7 μm was obtained.

[Production Example 2] Preparation of water-based adhesive Dissolve 3 parts by weight of carboxyl group-modified polyvinyl alcohol [trade name "KL-318" obtained from Kuraray Co., Ltd.] in 100 parts by weight of water, and add water-soluble epoxy to the aqueous solution. 1.5 parts by weight of a resin, a polyamide epoxy additive [trade name "Sumireze Resin (registered trademark) 650 (30)" obtained from Taoka Chemical Co., Ltd., an aqueous solution with a solid concentration of 30% by weight] was added. to prepare a water-based adhesive.

[Protective Films A, B, C, D and Release Film E]
The following five types of protective films and two types of release films were prepared.
Protective film A: 25KCHCN-TC. A film obtained by saponifying a triacetyl cellulose film with a hard coat layer manufactured by Toppan Printing Co., Ltd. The thickness was 32 μm, and the moisture permeability was 450 g/m ² ·24 hr.
Protective film B: ZT12. A cyclic polyolefin resin film manufactured by Zeon Corporation. The thickness is 20 μm, and it is manufactured by horizontal uniaxial stretching.
Protective film C: Zerotack (registered trademark). A film obtained by saponifying a triacetyl cellulose film manufactured by Konica Minolta, Inc. The thickness was 20 μm.
Protective film D: ZF14-023. A cyclic polyolefin resin film manufactured by Zeon Corporation. The thickness was 23 μm.
Release film E: Polymethyl methacrylate resin film manufactured by Sumitomo Chemical Co., Ltd. The thickness was 80 μm, and the moisture permeability was 50 g/m ² ·24 hr.

[Example 1]
[Preparation of front-side polarizing plate A]
While the polarizer obtained in Production Example 1 was continuously transported, the protective film A was continuously unwound from the protective film A roll, and the release film E was continuously unwound from the release film E roll. Next, a water-based adhesive is injected between the polarizer and the protective film A, and pure water is injected between the polarizer and the release film E, and passed through a bonding roll to pass the protective film A / water-based adhesive / A laminate film composed of polarizer/pure water/release film E was used. Subsequently, the laminated film is conveyed and heat-treated at 80° C. for 300 seconds in a drying oven to dry the water-based adhesive and to evaporate and remove the pure water present between the polarizer and the release film E. , a single-sided protective polarizing plate with a release film was obtained. The release film E was peeled off from the release film-attached single-side protective polarizing plate to obtain a single-side protective polarizing plate.

On the polarizer of the single-sided protective polarizing plate, an adhesive layer [trade name "#L2" manufactured by Lintec Corporation. The thickness was 5 μm. ], and further, the protective film B was laminated on the pressure-sensitive adhesive layer so that the stretching direction of the protective film B and the absorption axis direction of the polarizing plate were the same. After that, an adhesive layer [trade name “#KT” manufactured by Lintec Corporation] was applied to the protective film B. The thickness was 20 μm. ] was laminated. Thus, a front-side polarizing plate A comprising protective film A/aqueous adhesive layer/polarizer/adhesive layer/protective film B/adhesive layer was produced.

[Preparation of back side polarizing plate D]
While the polarizer obtained in Production Example 1 was continuously transported, the protective film C was continuously unwound from the protective film C roll, and the release film E was continuously unwound from the release film E roll. Next, a water-based adhesive is injected between the polarizer and the protective film C, and pure water is injected between the polarizer and the release film E, and the protective film C / water-based adhesive / is passed through a bonding roll. A laminate film composed of polarizer/pure water/release film E was used. Subsequently, the laminated film is conveyed and heat-treated at 80° C. for 300 seconds in a drying oven to dry the water-based adhesive and to evaporate and remove the pure water present between the polarizer and the release film E. , a single-sided protective polarizing plate with a release film was obtained. The release film E was peeled off from the release film-attached single-side protective polarizing plate to obtain a single-side protective polarizing plate.

A 15 μm-thick acrylic adhesive (a non-carrier film with a separator film manufactured by Lintec Corporation) is applied onto the polarizer of the single-sided protective polarizing plate, and a brightness enhancement film (trade name of 3M Co., Ltd.) is applied on the adhesive layer. "Advanced Polarized Film, Version 3. The thickness was 26 μm.]) was laminated. In this way, a back-side polarizing plate D composed of brightness enhancement film/adhesive layer/polarizer/water-based adhesive layer/protective film C/adhesive layer was produced.

[Preparation of sample for evaluation]
The front-side polarizing plate A was cut into a rectangular shape with a transmission axis direction of 155.25 mm and an absorption axis direction of 95.90 mm, and a rear-side polarizing plate D was cut with a size of 155.25 μm in the absorption axis direction and 95.90 mm in the transmission axis direction. It was cut into a rectangular shape. Next, a glass plate with a thickness of 0.4 mm (manufactured by Corning, product number: EAGLE XG (registered trademark)) is prepared, and the absorption axis of the front-side polarizing plate and the absorption axis of the back-side polarizing plate are perpendicular to each other. The front-side polarizing plate and the back-side polarizing plate were attached to a glass plate via respective adhesive layers.

The amount of warp in the obtained evaluation sample was measured in a high-temperature environment. Table 1 shows the results. The convex warped polarizing plate is the front polarizing plate, and the protective film B has a tensile elastic modulus of 1794 MPa in the transmission axis direction of the front polarizing plate at 85 ° C., and the absorption axis of the front polarizing plate. The directional tensile modulus was 2190 MPa. The protective film A had a tensile modulus of elasticity of 3563 MPa in the direction of the transmission axis of the front-side polarizing plate and a tensile modulus of elasticity of 3010 MPa in the direction of the absorption axis of the front-side polarizing plate at 85°C.

[Example 2]
Prepared in the same manner as front-side polarizing plate A except that protective film B was changed to protective film D, consisting of protective film A / water-based adhesive layer / polarizer / adhesive layer / protective film D / adhesive layer A front-side polarizing plate B was produced.
As for the rear-side polarizing plate, the rear-side polarizing plate D used in Example 1 was used. Then, an evaluation sample was produced in the same manner as in Example 1, except that the front-side polarizing plate A was changed to the front-side polarizing plate B of this example.

The amount of warp in the obtained evaluation sample was measured in a high-temperature environment. Table 1 shows the results. The polarizing plate on the convex warp side is the front polarizing plate, and the protective film D has a tensile elastic modulus of 2053 MPa in the transmission axis direction of the front polarizing plate at 85 ° C., and the absorption axis of the front polarizing plate. The directional tensile modulus was 2058 MPa. The protective film A had a tensile elastic modulus of 3563 MPa in the transmission axis direction of the front-side polarizing plate and a tensile elastic modulus of 3010 MPa in the absorption axis direction of the front-side polarizing plate at 85°C.

[Comparative Example 1]
The protective film A/water-based adhesive layer/polarizer was prepared in the same manner as the front-side polarizing plate A, except that the stretching direction of the protective film B and the transmission axis direction of the polarizing plate were laminated in the same direction. A front-side polarizing plate C composed of /adhesive layer/protective film B/adhesive layer was produced.
As for the rear-side polarizing plate, the rear-side polarizing plate D used in Example 1 was used. Then, an evaluation sample was produced in the same manner as in Example 1, except that the front-side polarizing plate A was changed to the front-side polarizing plate C of this example.

The amount of warp in the obtained evaluation sample was measured in a high-temperature environment. Table 1 shows the results. The convex warped polarizing plate is the front polarizing plate, and the protective film B has a tensile elastic modulus of 2190 MPa in the transmission axis direction of the front polarizing plate at 85 ° C., and the absorption axis of the front polarizing plate. The directional tensile modulus was 1794 MPa. The protective film A had a tensile elastic modulus of 3563 MPa in the transmission axis direction of the front-side polarizing plate and a tensile elastic modulus of 3010 MPa in the absorption axis direction of the front-side polarizing plate at 85°C.

As shown in Table 1, when the tensile elastic moduli Et and Ea of the protective film in the polarizing plate on the side warped in a convex shape satisfy Ea/Et≧0.95, the amount of warpage in a high-temperature environment can be reduced. rice field.

The polarizing plate set of the present invention is useful because it can reduce the warpage of the liquid crystal panel in a high-temperature environment.

2 Polarizer 10, 11, 12 Protective film 20, 21, 22 Adhesive layer 30, 31, 32 Adhesive layer 40 Brightness enhancement film 402 Polarizing plate 100, 101, 400 Front side polarizing plate 200, 201, 401 Rear side polarization Plate 300 Liquid crystal cell 70 Glass plate 80 Measurement point

Claims (6)

Having a front-side polarizing plate arranged on the viewing side of the liquid crystal cell and a back-side polarizing plate arranged on the back side of the liquid crystal cell,
the absorption axis of the front-side polarizing plate is parallel to the short side,
the absorption axis of the back-side polarizing plate is parallel to the long side,
A laminate obtained by bonding the front-side polarizing plate and the back-side polarizing plate to a glass plate so that the absorption axis of the front-side polarizing plate and the absorption axis of the back-side polarizing plate are orthogonal to each other is heated at 85°C. When heated for 250 hours at, the polarizing plate on the side where the laminate warps in a convex shape is the front side polarizing plate,
In the back-side polarizing plate, a protective film is laminated on one surface of the polarizer via an adhesive layer, and a brightness enhancement film is laminated on the other surface of the polarizer via an adhesive layer ,
At least one of the protective films in the front-side polarizing plate has a tensile modulus of elasticity in the transmission axis direction of the polarizing plate at 85°C and a tensile elastic modulus in the direction of the polarizing plate absorption axis at 85°C of Et and Ea, respectively. A set of polarizers that satisfies formula (1).
2.5≧Ea/Et≧0.95 (1) Both the front-side polarizing plate and the back-side polarizing plate are polyvinyl alcohol-based resin films.
2. The polarizer according to claim 1, wherein each of the polarizers has a thickness of 15 μm or less.
set of polarizing plates. 3. The set of polarizing plates according to claim 2, wherein each of said polarizers has a thickness of 13 [mu]m or less. Large difference between the thickness of the polarizer provided on the front-side polarizing plate and the thickness of the polarizer provided on the back-side polarizing plate
4. The set of polarizing plates according to any one of claims 1 to 3, having a thickness of 5 μm or less. The shape of the front-side polarizing plate and the back-side polarizing plate is a rectangular shape with a diagonal of 15 inches or less.
A set of polarizing plates according to any one of claims 1 to 4. A liquid crystal cell comprising the set of polarizing plates according to any one of claims 1 to 5 and a liquid crystal cell,
A liquid crystal panel having a thickness of 0.4 mm or less.

Images