JP6759715B2 - Set of polarizing plate for IPS mode - Google Patents

Description

The present invention relates to a set of polarizing plates for IPS mode and an IPS mode liquid crystal display device using the same.

In recent years, low power consumption, low voltage operation, lightweight and thin liquid crystal displays have rapidly become widespread as information display devices such as mobile phones, personal digital assistants, computer monitors, and televisions. With the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and problems of liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved.

As the opportunities for mobile phones and mobile information terminals to be used outdoors increase, when external light such as sunlight is strong, the liquid crystal display device equipped with a conventional liquid crystal cell and a conventional polarizing plate sets the external light. There was a problem that the LCD screen was hard to see due to the strong reflection of the light.

As such measures, a low reflection layer is provided on the surface of the viewing side polarizing plate to reduce external light reflection, or a circular polarizing plate is used for the viewing side polarizing plate to reduce external light reflection. It is customary to do so.

However, the visibility of the low-reflection layer alone is significantly reduced in an environment where the illuminance of external light exceeds 5000 lux. Further, in the IPS mode liquid crystal, the in-plane retardation value is usually 250 nm to 380 nm, and it is difficult to arrange a circular polarizing plate as a viewing side polarizing plate.

Japanese Unexamined Patent Publication No. 2005-128494

An object of the present invention is to provide a set of polarizing plates for a specific IPS mode liquid crystal cell capable of ensuring good visibility even in an environment where the illuminance of external light exceeds 5000 lux, and an IPS mode liquid crystal display device using the same. To do.

[1] A set of polarizing plates for bonding to both sides of an IPS mode liquid crystal cell having an in-plane retardation value of 400 nm to 500 nm, which comprises a viewing side polarizing plate and a back surface side polarizing plate.
The viewing side polarizing plate has a first polarizer and a λ / 4 plate, and has
The back side polarizing plate has a second polarizer and a λ / 2 plate.
The absorption axis of the first polarizing element of the viewing-side polarizing plate and the absorption axis of the second polarizer of the back-side polarizing plate are substantially orthogonal to each other .
Before SL lambda / 4 plate is arranged between the first polarizer and the liquid crystal cell,
The angle formed by the absorption axis of the first polarizer of the viewing-side polarizing plate and the slow axis of the λ / 4 plate is approximately 45 ° .
Before SL lambda / 2 plate is arranged between the second polarizer and the liquid crystal cell,
The angle formed by the absorption axis of the backside polarizing plate and the slow axis of the λ / 2 plate is approximately 45 °.
The slow axis of the λ / 4 plate and the slow axis of the λ / 2 plate are substantially parallel.
The Nz coefficient of the λ / 4 plate and the Nz coefficient of the λ / 2 plate are both −0.5 or more and 0.5 or less.
A set of polarizing plates in which the slow axis of the λ / 4 plate is arranged substantially parallel to the initial orientation direction of the IPS mode liquid crystal cell.
[2] The λ / 4 plate and the λ / 2 plate are three layers in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer made of a styrene resin. The set of polarizing plates according to [1], which is a retardation film having a structure.
[3] The set of polarizing plates according to [2], wherein the glass dislocation temperature of the core layer is 120 ° C. or higher, and the glass dislocation temperature of the skin layer is 120 ° C. or lower.
[4] An IPS mode liquid crystal display device in which a set of polarizing plates according to any one of [1] to [3] is arranged in an IPS mode liquid crystal cell having an in-plane retardation value of 400 nm to 500 nm.
[5] The IPS mode liquid crystal display device according to [4], wherein the size of the IPS mode liquid crystal display device is 15 inches or less diagonally.

According to the set of polarizing plates of the present invention, it is possible to provide a liquid crystal display device capable of suppressing reflection of external light and ensuring good visibility even in an environment with strong external light such as outdoors. ..

It is the schematic sectional drawing which shows the example of the preferable layer structure in the set of the polarizing plate which concerns on this invention. It is the schematic which shows the example of the preferable axis structure in the IPS liquid crystal display device which concerns on this invention.

Hereinafter, the set of the polarizing plate according to the present invention and the liquid crystal panel using the same will be described with reference to the drawings as appropriate, but the present invention is not limited to these embodiments.

FIG. 1 shows a schematic cross-sectional view of an example of a preferable layer structure in the polarizing plate according to the present invention. The polarizing plate of the present invention will be described with reference to FIG. The set of polarizing plates shown in FIG. 1 includes a polarizing plate 30 on which a λ / 434 plate is laminated on one side of the polarizing plate 30, and a polarizing plate on the back surface having a λ / 2 plate 54 on one side of the polarizing plate 50. It includes those in which the brightness improving film 60 is laminated on the other surface of the polarizing plate 50.

[Each member constituting the viewing side polarizing plate and the back side polarizing plate]
The visible side polarizing plate and the back side polarizing plate of the present invention include a polarizing plate 30 and a polarizing plate 50.

[Polarizer]
The first polarizer 32 and the second polarizer 52 usually adsorb the dichroic dye by uniaxially stretching the polyvinyl alcohol-based resin film and dyeing the polyvinyl alcohol-based resin film with the dichroic dye. It is produced through a step of treating a polyvinyl alcohol-based resin film on which a dichroic dye 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 the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-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 and polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film for the first polarizer 32 and the second polarizer 52. The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. The film thickness of the polyvinyl alcohol-based raw film is not particularly limited, but is, for example, about 10 μm to 150 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Moreover, uniaxial stretching may be performed in these a plurality of steps.

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

As a method of dyeing the polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye is adopted. Specifically, iodine or a dichroic dye is used as the dichroic dye. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. The iodine content 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. 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 immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye and dyeing is usually adopted. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water, preferably about 1 × 10 ^-3 to 1 part by weight. 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.

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, 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, 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., more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the 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 washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

After washing with water, a drying treatment is performed to obtain a first polarizer 32 and a second polarizer 52. 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, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

By the drying treatment, the moisture content of the first polarizer 32 and the second polarizer 52 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 first polarizer 32 and the second polarizer 52 is lost, and the first polarizer 32 and the second polarizer 52 are damaged after drying. It may break or break. On the other hand, if the water content exceeds 20% by weight, the thermal stability of the first polarizer 32 and the second polarizer 52 may be inferior.

As described above, a polarizer in which the dichroic dye is adsorbed and oriented on the polyvinyl alcohol-based resin film can be produced.

Further, the stretching, dyeing, boric acid treatment, washing step, and drying step of the polyvinyl alcohol-based resin film in the polarizing element manufacturing step may be performed according to the method described in, for example, Japanese Patent Application Laid-Open No. 2012-159778. .. In the method described in this document, it is also useful to use a method of forming a polyvinyl alcohol-based resin layer as a polarizer by coating a base film with a polyvinyl alcohol-based resin.

In order to suppress the contractile force of the polarizer in a high temperature environment, the thickness of the polarizer is preferably 15 μm or less, and more preferably 12 μm or less. The thickness of the polarizer is usually 3 μm or more in that good optical characteristics can be imparted.

By using a polarizer that suppresses the contraction force in a high temperature environment, it is possible to suppress the phase difference change due to the distortion of the λ / 2 plate and the λ / 4 plate due to the contraction of the polarizer, and it was used for the liquid crystal display device. Sometimes it can be a polarizing plate with small display unevenness.

When the polarizer is held at a temperature of 80 ° C. for 240 minutes, the contractile force per width 2 mm in the absorption axis direction is preferably 2N / 2 mm or less. If this shrinkage force is larger than 2N / 2 mm, the amount of dimensional change in a high temperature environment becomes large, and the shrinkage force of the polarizer becomes large, so that the λ / 2 plate and the λ / 4 plate are easily distorted, and further. Tends to be prone to cracking in the polarizer. The contractile force of the polarizer tends to be 2N / 2 mm or less when the draw ratio is reduced and the thickness of the polarizer is reduced. The method for measuring the contraction force follows the method of the examples described later.

A protective film is preferably laminated on at least one surface of the polarizer, and protective films may be provided on both sides. The protective films 31a, 31b, 51a, 51b can be made of a transparent resin film. In particular, it is preferable to use a material having excellent transparency, mechanical strength, thermal stability, moisture shielding property, and the like. In the present specification, the transparent resin film means a resin film having a simple substance transmittance of 80% or more in the visible light region.

Omission of the protective films 31b and 51b by allowing the λ / 4 plate 34 and the λ / 2 plate 54 to serve as protective films is also an effective means for thinning the polarizing plate. Similarly, omitting the protective film 51a by giving the brightness improving film 60 a role as a protective film is also an effective means for thinning the polarizing plate.

Examples of the protective films 31a, 31b, 51a, 51b include cellulose-based resins, chain polyolefin-based resins, cyclic polyolefin-based resins, acrylic-based resins, polyimide-based resins, polycarbonate-based resins, polyester-based resins, and the like. A film formed from a material widely used as a material for forming the above can be used.

Appropriate additives may be added to these resins as long as the transparency is not impaired. Additives include, for example, antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, fungicides, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact resistant aids. , Matters, antibacterial agents, fungicides and the like. A plurality of kinds of these additives may be used in combination.

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

Further, as the protective film 31a, a retardation plate obtained by stretching the film may be used to improve visibility when the screen is viewed through polarized sunglasses. It is desirable from the viewpoint of improving visibility of an angle between the absorption axis of the polarizer and the slow axis of the lambda / 4 plate as the retardation plate is arranged substantially 45 °. Further, when stacking the elongated polarizing element is preferred because it produced polarizing plate in a roll-to-roll the angle formed with respect to the long side direction of the long is stretched to approximately 45 ° or 135 °.

[Surface treatment layer 35 of protective film 31a]
The protective film 31a may have a surface treatment layer 35 on a surface opposite to the surface to be bonded to the polarizer 32. Examples of the surface treatment layer 35 include a hard coat layer having a fine surface uneven shape. The hard coat layer preferably has a pencil hardness higher than H. If the pencil hardness is H or less, the surface is easily scratched, and if the pencil is scratched, the visibility of the liquid crystal display device deteriorates. Pencil hardness is determined according to JIS K 5600-5-4: 1999 "General paint test method-Part 5: Mechanical properties of coating film-Section 4: Scratch hardness (pencil method)", and each hardness It is expressed by the hardness of the hardest pencil that does not cause scratches when scratched with a pencil.

The protective film 31a having the surface treatment layer 35 preferably has a haze value in the range of 0.1 to 45%, more preferably in the range of 5 to 40%. When the haze value is in a region larger than 45%, the reflection of external light can be reduced, but the black screen is less tight. Further, if the haze value is less than 0.1%, sufficient antiglare performance cannot be obtained and external light is reflected on the screen, which is not preferable. Here, the haze value is determined according to JIS K 7136: 2000 "How to determine the haze of a plastic-transparent material".

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

In addition to the above-mentioned antiglare treatment (haze imparting treatment) that also serves as a hard coat layer, the protective film 31a is subjected to various additional surface treatments such as an antireflection layer, an antistatic treatment, an antifouling treatment, or an antibacterial treatment. It may be applied, and a coat layer made of a liquid crystal compound or a high molecular weight compound thereof may be formed. In particular, when an antireflection layer of 3% or less is formed, it is preferably used because visibility can be maintained even at 10,000 Lux or more. In addition to the surface treatment, the antistatic function may be imparted to other parts of the polarizing plate, such as an adhesive layer.

[Protective films 31b, 51b]
As the protective films 31b and 51b, a cellulosic resin or a cyclic polyolefin resin is preferable because the retardation value can be easily controlled and easily obtained.

The cellulosic resin may be an organic acid ester or mixed organic acid ester of cellulosic, in which a part or all of hydrogen atoms at the hydroxyl group of cellulose are substituted with an acetyl group, a propionyl group and / or a butyryl group. For example, those composed of acetic acid ester of cellulose, propionic acid ester, butyric acid ester, mixed ester thereof and the like can be mentioned. Of these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

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. When such a cyclic polyolefin resin is used, a protective film having a predetermined retardation value described later can be easily obtained.

As the cyclic polyolefin resin, for example, ring-opening metathesis polymerization is carried out from cyclopentadiene and olefins or (meth) acrylic acid or esters thereof using norbornene or a derivative thereof obtained by a deal alder reaction as a monomer, followed by ring-opening metathesis polymerization. Resin obtained by hydrogenation; ring-opening metathesis polymerization is performed using tetracyclododecene or a derivative thereof obtained by a deal alder reaction from dicyclopentadiene and olefins or (meth) acrylic acid or esters thereof as a monomer. Resin obtained by subsequent hydrogenation; at least two monomers selected from norbornene, tetracyclododecene, derivatives thereof, and other cyclic olefin monomers are similarly ring-opened metathesis copolymerized and subsequently obtained by hydrogenation. Resins: Resins obtained by addition-copolymerizing a cyclic olefin such as norbornene, tetracyclododecene, or a derivative thereof with an aromatic compound having a chain olefin and / or a vinyl group.

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

The retardation value Rth in the thickness direction is preferably 10 nm or less in order to suppress a decrease in the degree of polarization due to depolarization of the protective films 31b and 51b. The retardation value Rth in the thickness direction is a value obtained by multiplying the value obtained by subtracting the refractive index in the thickness direction from the average refractive index in the plane by the thickness of the film, and is defined by the following equation (a). Further, the in-plane retardation value Re is preferably 10 nm or less. The in-plane retardation value Re is a value obtained by multiplying the in-plane refractive index difference by the thickness of the film, and is defined by the following equation (b).
Rth = [(n _x + n _y ) /2- _nz ] × d (a)
Re = (n _{x −} n _y ) × d (b)

In the equation, n _x is the refractive index in the in-plane x-axis direction (in-plane slow-phase axial direction), and n _y is the in-plane y-axis direction (in-plane advancing axial direction, in-plane). Is the refractive index in the direction orthogonal to the x-axis), n _z is the refractive index in the z-axis direction (thickness direction) perpendicular to the film surface, and d is the thickness of the film.

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

As a method of controlling the in-plane and thickness direction retardation value Rth of the resin film within the range of 10 nm or less, there is a method of minimizing the distortion remaining in the in-plane and thickness directions when the film is produced. .. For example, in the solvent casting method, a method of relaxing the residual shrinkage strain in the in-plane and thickness directions generated when the cast resin solution is dried by heat treatment can be adopted. On the other hand, in the melt extrusion method, in order to prevent the resin film from being extruded from the die and stretched during cooling, the distance from the die to the cooling drum is shortened as much as possible, and the extrusion amount and the rotation speed of the cooling drum are reduced. A method of controlling the film so that the film is not stretched can be adopted. Further, as in the solvent casting method, a method of alleviating the strain remaining on the obtained film by heat treatment can also be adopted.

[λ / 4 plate 34]
The λ / 4 plate 34 is preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture shielding property, and the like. The material of the λ / 4 plate may be composed of the resin forming the protective film, but it is preferable to use a styrene-based material. Styrene-based materials are desirable in that they satisfy the refractive index relational expression nz> nx ≧ ny, but their brittleness makes them unsuitable for use alone. Therefore, in the present invention, a retardation film having a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer made of a styrene resin is used. Is preferable.
The retardation film is also preferable because it has a positive wavelength dispersibility.

Here, the positive wavelength dispersibility means that the following equation (c) is satisfied. The numbers in parentheses are the measurement wavelengths (unit: nm) of the phase difference value.

Re (450)> Re (590)> Re (650) (c)

Further, in the present invention, the retardation value of the λ / 4 plate means that the retardation value Re is 120 nm to 160 nm when the measurement wavelength is 590 nm. In the present invention, the λ / 4 plate has an Nz coefficient defined by the following formula (d) in the range of -0.5 to 0.5, preferably in the range of -0.2 to 0.2. is there.

Nz = (nx-nz) / (nx-ny) = Re / Rth + 0.5 (d)

An appropriate additive may be blended in the λ / 4 plate as long as the transparency is not impaired. Additives include, for example, antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, fungicides, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact resistant aids. , Matters, antibacterial agents, fungicides and the like. A plurality of kinds of these additives may be used in combination.

The styrene-based resin constituting the core layer can be a homopolymer of styrene or a derivative thereof, or a binary or more copolymer of styrene or a derivative thereof and another copolymerizable monomer. You can also do it. Here, the styrene derivative is a compound in which another group is bonded to styrene, and is, for example, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, and the like. Alkyl styrene such as p-ethylstyrene, hydroxyl group, alkoxy group, carboxyl group, halogen on the benzene nucleus of styrene such as hydroxystyrene, tert-butoxystyrene, vinyl benzoic acid, o-chlorostyrene, p-chlorostyrene. Examples thereof include substituted styrene in which and the like have been introduced. A ternary copolymer as disclosed in JP-A-2003-90912 and JP-A-2004-167823 can also be used. The styrene resin is preferably a copolymer of styrene or a styrene derivative and at least one monomer selected from acrylonitrile, maleic anhydride, methyl methacrylate and butadiene. The styrene-based resin of the core layer is preferably composed of a heat-resistant resin, and its Tg is generally 100 ° C. or higher. A more preferable Tg of the styrene resin is 120 ° C. or higher.

It is desirable that the core layer made of a styrene resin is set so that its thickness is 10 to 100 μm. If the thickness is less than 10 μm, it may be difficult to develop a sufficient retardation value by stretching. On the other hand, if the thickness exceeds 100 μm, the impact strength of the film tends to be weakened, and the retardation change due to external stress tends to be large, so that white spots are likely to occur when applied to a liquid crystal display device. Display performance tends to deteriorate.

The skin layers arranged on both sides of the core layer made of the styrene resin are made of a (meth) acrylic resin composition in which rubber particles are mixed with the (meth) acrylic resin.
Here, examples of the (meth) acrylic resin include homopolymers of methacrylic acid alkyl esters or acrylic acid alkyl esters, copolymers of methacrylic acid alkyl esters and acrylic acid alkyl esters, and the like. Specific examples of the alkyl methacrylate ester include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of the alkyl acrylate ester include methyl acrylate, ethyl acrylate, and propyl acrylate. .. As such a (meth) acrylic resin, a commercially available general-purpose (meth) acrylic resin can be used. Some of the (meth) acrylic resins are called impact-resistant (meth) acrylic resins, and high heat-resistant (meth) acrylic resins having a glutaric anhydride structure or a lactone ring structure in the main chain. Also includes what is called.

The rubber particles blended in the (meth) acrylic resin are preferably acrylic particles. Acrylic rubber particles are particles having rubber elasticity obtained by polymerizing an acrylic acid alkyl ester such as butyl acrylate or 2-ethylhexyl acrylate as a main component in the presence of a polyfunctional monomer. The particles having rubber elasticity may be formed of a single layer, or may be a multilayer structure having at least one rubber elastic layer. As the acrylic rubber particles having a multi-layer structure, those having the above-mentioned particles having rubber elasticity as nuclei and covering them with a hard methacrylic acid alkyl ester polymer, and hard methacrylic acid alkyl ester polymers are used. The core is made of an acrylic polymer having rubber elasticity as described above, and the hard core is covered with an acrylic polymer having rubber elasticity, and the periphery thereof is hard methacrylic acid. Examples thereof include those covered with an alkyl ester polymer. In these rubber particles, the average diameter of the particles formed by the elastic layer is usually in the range of about 50 to 400 nm.

The content of the rubber particles in the (meth) acrylic resin composition constituting the skin layer is usually about 5 to 50 parts by weight per 100 parts by weight of the (meth) acrylic resin. Since the (meth) acrylic resin and the acrylic rubber particles are commercially available in a mixed state, the commercially available products can be used. Examples of commercially available (meth) acrylic resins containing acrylic rubber particles include "HT55X" and "Technoloy (registered trademark) S001" sold by Sumitomo Chemical Co., Ltd. Such a (meth) acrylic resin composition generally has a Tg of 160 ° C. or lower, and the preferred Tg is 120 ° C. or lower, more preferably 110 ° C. or lower.

It is desirable that the skin layer made of the (meth) acrylic resin composition containing the rubber particles, preferably the acrylic rubber particles, has a thickness of 10 to 100 μm. If the thickness is made less than 10 μm, film formation tends to be difficult. On the other hand, when the thickness exceeds 100 μm, the retardation of this (meth) acrylic resin layer tends to be non-negligible.

As described above, in the retardation film used in the present invention, the core layer made of a styrene resin preferably has a Tg of 120 ° C. or higher, while the (meth) acrylic resin composition containing rubber particles. The skin layer made of a substance preferably has a Tg of 120 ° C. or lower, more preferably 110 ° C. or lower. It is preferable that the Tg of both does not overlap, and the core layer made of a styrene resin has a higher Tg than the skin layer made of a (meth) acrylic resin composition containing rubber particles.

In order to produce the retardation film used in the present invention, for example, a styrene resin and a (meth) acrylic resin composition containing rubber particles may be co-extruded and then stretched. In addition, a method in which each single-layer film is produced, then heat-fused by heat lamination and stretched is also possible.

This retardation film has a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer made of a styrene resin. In this three-layer structure, the skin layers arranged on both sides are usually made to have substantially the same thickness. By forming the three-layer structure in this way, the skin layer made of the (meth) acrylic resin composition containing the rubber particles acts as a protective layer, and has excellent mechanical strength and chemical resistance.

The retardation film constructed as described above is given in-plane retardation by stretching. Stretching can be performed by known longitudinal uniaxial stretching, tenter horizontal uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, etc., and may be stretched so as to obtain a desired retardation value.

For example, when the first polarizer 32 (long shape) has an absorption axis in the longitudinal direction thereof, stretching treatment is performed so that the slow axis is in a direction of approximately 45 °. By doing so, the first polarizer 32 (polarizing filter) and the λ / 4 plate 34 can be continuously laminated roll-to-roll. As a result, the manufacturing process can be significantly shortened.

In the present invention, the thicknesses of the first layer and the second layer constituting the resin multilayer film are illustrated, but this is a value before stretching, and in the retardation film after stretching, each layer The lower limit of the thickness may be slightly lower than the above-mentioned value. However, it is more preferable to have the thickness in the above range even after stretching.

[λ / 2 plate 54]
As the λ / 2 plate 54, a retardation film made of the same material as that exemplified in the λ / 4 plate 34 can be used. The materials formed by the λ / 2 plate 54 and the λ / 4 plate 34 may be the same or different.

Further, in the present invention, the retardation value of the λ / 2 plate means that the retardation value Re is 200 nm to 300 nm when the measurement wavelength is 590 nm. In the present invention, the λ / 2 plate has an Nz coefficient in the range of −0.5 to 0.5, preferably in the range of −0.2 to 0.2.

For example, when the second polarizer 52 (long shape) has an absorption axis in the longitudinal direction thereof, stretching treatment is performed so that the slow axis is in a direction of approximately 45 °. By doing so, the second polarizer 52 (polarizing filter) and the λ / 2 plate 54 can be continuously laminated roll-to-roll. As a result, the manufacturing process can be significantly shortened.

[Brightness improving film 60]
The brightness improving film 60 is also called a reflective polarizer, and a polarization conversion element having a function of separating the emitted light from a light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light is used. As described above, by arranging the brightness improving film 60 on the polarizing plate 50, the emission efficiency of the linearly polarized light emitted from the polarizing plate 50 is improved by utilizing the retrolight which is reflected polarized light or scattered polarized light. Can be done.

The brightness improving film 60 can be, for example, an anisotropic reflection polarizer. An example of an anisotropic reflective polarizer is an anisotropic multilayer thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is a DBEF manufactured by 3M. Japanese Unexamined Patent Publication No. 4-268505, etc.). Another example of the anisotropic reflection polarizer is a composite of a cholesteric liquid crystal layer and a λ / 4 plate, and a specific example thereof is a PCF manufactured by Nitto Denko (Japanese Patent Laid-Open No. 11-231130, etc.). Yet another example of the anisotropic reflection polarizer is a reflection grid polarizer, a specific example of which is a metal lattice reflection polarizer (USA) in which metal is finely processed to emit reflected polarized light even in the visible light region. (Patent No. 6288840, etc.), a film obtained by adding fine metal particles into a polymer matrix and stretching it (Japanese Patent Laid-Open No. 8-184701).

Even if an optical layer such as a hard coat layer, an antiglare layer, a light diffusing layer, and a retardation layer having a retardation value of 1/4 wavelength is provided on the surface of the brightness improving film 60 opposite to the polarizing plate 50. Good. By forming the optical layer, the adhesion to the backlight tape and the uniformity of the displayed image can be improved. The thickness of the brightness improving film 61 can be about 10 to 100 μm, but is preferably 10 to 50 μm, more preferably 10 to 30 μm from the viewpoint of thinning the polarizing plate.

[Adhesion of each layer]
It is preferable that an arbitrary suitable adhesive layer or adhesive layer is provided between the members constituting the polarizing plate of the present invention. Further, in order to attach the polarizing plate to the liquid crystal cell, it is preferable to provide an adhesive layer on the surface of the polarizing plate. In the present embodiment, for example, an adhesive can be provided on the outside of the λ / 4 plate 34, and an adhesive layer can be provided on the outside of the λ / 2 plate 54. Examples of the adhesive forming the adhesive layer include water-based adhesives and active energy ray-curable adhesives that are cured by irradiation with ultraviolet rays or electron beams. Examples of the active energy ray-curable adhesive include a composition containing a radically polymerizable compound such as an acrylic compound and a composition containing a cationically polymerizable compound such as an epoxy compound. Each of these compositions preferably contains a radical polymerization initiator or a cationic polymerization initiator. As the pressure-sensitive adhesive, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferable.

[LCD cell]
The liquid crystal cell has a pair of substrates and a liquid crystal layer as a display medium sandwiched between the substrates. A color filter and a black matrix are provided on one of the substrates (color filter substrate). On the other substrate (active matrix substrate), a switching element (typically a TFT) that controls the electro-optical characteristics of the liquid crystal, a scanning line that gives a gate signal to the switching element, a signal line that gives a source signal, and a pixel. An electrode is provided. The color filter may be provided on the active matrix substrate side. The distance between the substrates (cell gap) is controlled by a spacer. An alignment film made of, for example, polyimide is provided on the side of the substrates in contact with the liquid crystal layer.

As the drive mode of the liquid crystal cell for arranging the set of the polarizing plates of the present invention, an IPS (In-Plane Switching) mode in which the in-plane retardation value is 400 to 500 nm at a wavelength of 590 nm is adopted. Since the liquid crystal cell itself has an in-plane retardation value close to 3λ / 4 wavelength in this way, it is possible to arrange a circular polarizing plate as a viewing side polarizing plate, and it is possible to significantly reduce the reflection of external light. it can.

As a method of adjusting the in-plane phase difference of the liquid crystal cell to 400 to 500 nm at a wavelength of 590 nm, it can be produced by adjusting the thickness of the liquid crystal of the liquid crystal cell. For example, a liquid crystal cell having a desired in-plane phase difference value can be produced by adjusting the thickness of the liquid crystal of the liquid crystal cell to about 1 to 6 μm.

[Liquid crystal display device]
The liquid crystal display device of the present invention includes the set of polarizing plates of the present invention and the liquid crystal cell. The liquid crystal display device of the present invention is particularly preferably used for small and medium-sized liquid crystal display devices because it has excellent visibility even outdoors where external light is strong. For example, it is suitable when the size of the liquid crystal display device is 15 inches or less diagonally.

The shaft configuration of each member in the liquid crystal display device of the present invention will be described with reference to FIG.

For convenience of explanation, the initial orientation direction of the liquid crystal cell used in the present invention is defined as 0 °, and the angle in the counterclockwise direction when the back side polarizing plate is viewed from the viewing side polarizing plate is defined as positive. .. The slow axes of the λ / 4 plate 34 and the λ / 2 plate 54 are arranged at approximately 0 ° with respect to the initial orientation direction.
Further, the absorption axis of the first polarizing element of the viewing side polarizing plate is arranged at approximately 135 ° with respect to the initial orientation direction, and the absorption axis of the second polarizer of the back side polarizing plate is in the initial orientation direction. On the other hand, it is arranged at approximately 45 °. Here, when it is described as approximately what °, it means that the value is within the range of ± 5 °, and preferably it is within the range of ± 2 °.

In the present invention, the initial orientation direction of the liquid crystal cell means the orientation direction of the liquid crystal molecules in the initial state in which the driving voltage is not applied to the liquid crystal cell.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. In the examples, the part and% indicating the content or the amount used are based on weight unless otherwise specified. As for the angle, counterclockwise is positive. The physical properties in the following examples were measured by the following methods.

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

(2) Measurement of in-plane retardation and thickness direction retardation:
In-plane lettering and thickness direction lettering at each wavelength at a temperature of 23 ° C using the phase difference meter "KOBRA (registered trademark) -WPR" manufactured by Oji Measuring Instruments Co., Ltd. based on the parallel Nicol rotation method. It was measured.

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

(4) Measurement of contractile force of polarizer Super cutter (Ogino Seiki Co., Ltd.) has a width of 2 mm and a length of 50 mm so that the direction in which the contractile force is measured (the direction of the absorber's absorption axis) is the long side. Cut with (manufactured by Seisakusho). The obtained strip-shaped chip was used as a test piece. The contraction force of the test piece was measured using a thermomechanical analyzer (manufactured by SII Nanotechnology Co., Ltd., model TMA / 6100). This measurement was carried out in a constant dimension mode, and the distance between chucks was set to 10 mm. After leaving the test piece in a room at 23 ° C. and 55% for 24 hours or more, the temperature setting in the sample room is raised from 23 ° C. to 80 ° C. in 1 minute, and after the temperature rise, the temperature in the sample room is maintained at 80 ° C. I set it up. After the temperature was raised and left for another 4 hours, the contraction force in the long side direction of the test piece was measured in an environment of 80 ° C. In this measurement, the static load was 0 mN, and a probe made by SUS was used as the jig.

[Production Example 1] Preparation of Polarizer A polyvinyl alcohol film having a thickness of 30 μm (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 4 times by dry stretching to maintain a tense state. After immersing it in pure water at 40 ° C. for 40 seconds, it is immersed in an aqueous solution with a weight ratio of iodine / potassium iodide / water of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds for dyeing. It was. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, while holding at a tension of 300 N, the iodine was adsorbed and oriented on the polyvinyl alcohol film by drying at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds. An absorption type polarizer having a thickness of 12 μm was obtained. The contractile force of the obtained polarizer was measured and found to be 2.0 N / 2 mm.

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

[Adhesives A and B]
The following two types of adhesive adhesive A: Sheet-like adhesive with a thickness of 25 μm [“P-3132” manufactured by Lintec Corporation]
Adhesive B: Sheet-shaped adhesive with a thickness of 5 μm [“NCF # L2” manufactured by Lintec Corporation]
I prepared.

[Protective films A, B, C, D]
The following three types of protective films were prepared.
Protective film A: Triacetyl cellulose film with hard coat manufactured by Konica Minolta Co., Ltd .; 25KCHCN-TC (thickness 32 μm)
Protective film B: Triacetyl cellulose film manufactured by Konica Minolta Co., Ltd .; KC2UA (thickness 25 μm)
Protective film C: Cyclic polyolefin resin film manufactured by Nippon Zeon Corporation; ZF14-013 (thickness 13 μm, in-plane retardation value at wavelength 590 nm = 0.8 nm, thickness direction retardation at wavelength 590 nm = 3.4 nm)
Protective film D: Antireflection film made of triacetyl cellulose-based resin manufactured by Toppan TOMOEGAWA Optical Products Co., Ltd .; 40KSPLR (thickness 44 μm, Y value 1.1% according to JIS-Z8701-1982)

[Brightness improvement film A]
The following brightness improving films were prepared.
Brightness improving film A: Brightness improving film with a thickness of 26 μm (trade name "Advanced Polarized Film, Version 3" made by 3M)

[Making λ / 4 plate]
Styrene-maleic anhydride-based copolymer resin [“Dairak (registered trademark) D332” (Tg = 131 ° C.) manufactured by Nova Chemical Co., Ltd.] is used as the core layer, and about 20% of acrylic rubber particles with an average particle size of 200 μm are blended. Acrylic resin [resin (Tg = 105 ° C) used in "Technoloy (registered trademark) S001" manufactured by Sumitomo Chemical Co., Ltd.] is used as a skin layer, and three layers are coextruded to increase the thickness of the core layer. A resin three-layer film having a thickness of 72 μm formed on both sides thereof at 60 μm was obtained. This resin three-layer film was stretched twice at 142 ° C. to obtain a negative retardation film having an in-plane retardation of 140 nm and an Nz coefficient of 0.0 at a wavelength of 590 nm.

[Making λ / 2 plate]
Styrene-maleic anhydride-based copolymer resin [“Dairak (registered trademark) D332” (Tg = 131 ° C.) manufactured by Nova Chemical Co., Ltd.] is used as the core layer, and about 20% of acrylic rubber particles with an average particle size of 200 μm are blended. Acrylic resin [resin (Tg = 105 ° C) used in "Technoloy (registered trademark) S001" manufactured by Sumitomo Chemical Co., Ltd.] is used as a skin layer, and three layers are coextruded to increase the thickness of the core layer. A resin three-layer film having a thickness of 72 μm formed on both sides thereof at 60 μm was obtained. This resin three-layer film was stretched four times at 142 ° C. to obtain a negative retardation film having an in-plane retardation of 260 nm and an Nz coefficient of 0.0 at a wavelength of 590 nm.

[Preparation of polarizing plate A]
The protective film A was subjected to a saponification treatment, and the surface of the protective film C to be bonded to the polarizer was subjected to a corona treatment. A polarizing plate is formed by adhering the protective film A, the polarizer and the protective film C with an aqueous adhesive so that the triacetyl cellulose surface of the protective film A and the corona-treated surface of the protective film C are bonded surfaces to the polarizer. I got A.

[Preparation of polarizing plate B]
The protective film B was subjected to a saponification treatment, and the surface of the protective film C to be bonded to the polarizer was subjected to a corona treatment. A polarizing plate was obtained by adhering the protective film B, the polarizer and the protective film C with an aqueous adhesive so that the corona-treated surfaces of the protective film B and the protective film C were bonded surfaces to the polarizer. Adhesive B was attached to the protective film B side of the polarizing plate B. At this time, the bonding surfaces of the protective film B and the adhesive B were subjected to corona treatment. Finally, the brightness improving film A was bonded to the pressure-sensitive adhesive B surface of the polarizing plate to obtain a polarizing plate B.

[Making a pseudo liquid crystal cell]
Non-alkali glass manufactured by Corning Inc .: Two sheets of Eagle XG (thickness 0.7 mm, length 157 mm × width 98 mm) with adhesive B bonded were prepared. At this time, corona treatment was performed on the bonded surfaces of the glass and the adhesive. Next, the previously prepared λ / 4 plate was bonded to the adhesive B surface of the two glasses, and at this time, the λ / 4 plate and the adhesive B surface were subjected to corona treatment. Further, the adhesive B was bonded to the λ / 4 plate surface of the two pieces of glass. At this time as well, the λ / 4 plate and the adhesive B surface were subjected to corona treatment. A λ / 4 plate was further attached to the adhesive B surface on one piece of glass. At this time as well, the λ / 4 plate and the adhesive B surface were subjected to corona treatment.
Finally, a pseudo liquid crystal cell was produced by laminating the λ / 4 surface of one glass and the adhesive B surface of another glass. At this time, corona treatment was performed on the λ / 4 plate surface and the bonding surface of the adhesive B. All λ / 4 plates were manufactured so that the slow axis direction was parallel to the long side direction of the glass.

It is assumed that the initial orientation direction of the pseudo liquid crystal cell is parallel to the short side direction of the glass, and the pseudo liquid crystal cell is assumed to be a liquid crystal cell when a driving voltage is applied (in the case of white display). ..

Furthermore, using Hi-McKee blue (MO-150-MC-BL) manufactured by Zebra Co., Ltd. on one of the glass surfaces of the manufactured pseudo liquid crystal cell, it appears in Doraemon ("Doraemon" by Fujiko F. Fujio. I drew a portrait of a cat-shaped robot (published by Shogakukan).

[Backlight]
Google Inc. The liquid crystal panel was taken out from Nexus 7 (registered trademark) manufactured by the manufacturer, and only the backlight was turned on to obtain a backlight.

[Example 1]
(Preparation of Visualizing Plate 1)
Adhesive B was attached to the protective film C surface of the polarizing plate A. At this time, the protective film C surface and the adhesive B bonding surface were subjected to corona treatment. Next, a λ / 4 plate was laminated on the pressure-sensitive adhesive B surface of the produced polarizing plate A. At this time, corona treatment was performed on the bonded surfaces of the adhesive B and the λ / 4 plate. The angle between the polarizing element absorption axis of the polarizing plate and the λ / 4 plate is 45 ° (when the protective film A surface of the polarizing plate is viewed as the upper surface, 45 ° counterclockwise from the polarizing element absorption axis of the polarizing plate. The slow axis of the λ / 4 plate was arranged so as to be °). Further, the adhesive A was attached to the λ / 4 plate surface of the polarizing plate A. Also at this time, the λ / 4 plate of the polarizing plate A and the bonding surface of the pressure-sensitive adhesive A were subjected to corona treatment. In this way, the viewing side polarizing plate 1 was produced.

(Preparation of backside polarizing plate 1)
The back side polarizing plate 1 was produced in the same manner as the viewing side polarizing plate except that the polarizing plate A was changed to the polarizing plate B and the λ / 4 plate was changed to the λ / 2 plate. That is, when the angle between the slow axis and the absorption axis and lambda / 2 plate of a polarizer having the polarizing plate B is viewed protective film B from -45 ° (protective film C, absorbing polarizers polarizing plate having The slow axis of the λ / 2 plate was arranged so as to be 45 ° clockwise with respect to the axis.) The λ / 2 plate was arranged on the protective film C via the adhesive B. Next, the pressure-sensitive adhesive A was laminated on the λ / 2 plate.

The produced visible side polarizing plate 1 and the back side polarizing plate 1 were cut into a size of 155 mm in length × 96 mm in width. In this case, the absorption axis of a polarizer polarizing plate having when viewed each polarizing plate protective film A (viewing-side polarizing plate 1) or a protective film B (rear-side polarizing plate 1) plane as a top surface, longitudinal direction It was cut so as to be 45 ° with respect to each other.

A pseudo-liquid crystal panel was produced by laminating a viewing-side polarizing plate 1 on a glass surface on which a portrait of Doraemon of a pseudo-liquid crystal cell was drawn and a back-side polarizing plate 1 on the glass surface on the opposite side. At this time, the shaft configuration was as shown in FIG. 2 (b).

The pseudo liquid crystal panel thus produced was placed on the produced backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even at 7500 Lux.

[Example 2]
A pseudo liquid crystal panel was produced in the same manner except that the protective film A of the viewing side polarizing plate 1 of Example 1 was changed to the protective film D.

The pseudo liquid crystal panel thus produced was placed on the produced backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even at an illuminance of 10000 Lux.

[Comparative Example 1]
Google Inc. When the upper and lower polarizing plates were peeled off from the Nexus 7 (registered trademark) liquid crystal panel manufactured by Nexus 7 and the in-plane retardation value of the liquid crystal cell was measured at a wavelength of 590 nm, it was 355 nm. Next, the polarizing plate A was attached to the visible side of the taken out liquid crystal cell via the adhesive A, and the polarizing plate B was attached to the back surface side via the adhesive A to prepare a liquid crystal panel. The liquid crystal panel thus produced was mounted on the Nexus 7, and an image of Doraemon was displayed on the screen to confirm whether it could be visually recognized under external light. As a result, the visibility was remarkably lowered at an illuminance of 5000 Lux, and it became difficult to identify the image.

According to the set of polarizing plates of the present invention, it is possible to provide a liquid crystal display device capable of suppressing reflection of external light and ensuring good visibility even in an environment with strong external light such as outdoors. So useful.

10 Visible side polarizing plate 20 Back side polarizing plate 30, 50 Polarizing plate 31a, 31b, 51a, 51b Protective film 35 Surface treatment layer 32 First polarizer 52 Second polarizer 34 λ / 4 plate 54 λ / 2 plate 61 in the slow axis 3 crystal cell of the brightness enhancement film 60 liquid crystal cell 1 intake Osamujiku 2 lambda / 4 plate in the initial alignment direction 4 lambda / 2 retardation axis 5 intake Osamujiku

Claims (5)

A set of polarizing plates for bonding to both sides of an IPS mode liquid crystal cell having an in-plane retardation value of 400 nm to 500 nm, which comprises a viewing side polarizing plate and a back surface side polarizing plate.
The viewing side polarizing plate has a first polarizer and a λ / 4 plate, and has
The back side polarizing plate has a second polarizer and a λ / 2 plate.
The absorption axis of the first polarizing element of the viewing-side polarizing plate and the absorption axis of the second polarizer of the back-side polarizing plate are substantially orthogonal to each other .
Before SL lambda / 4 plate is arranged between the first polarizer and the liquid crystal cell,
The angle formed by the absorption axis of the first polarizer of the viewing-side polarizing plate and the slow axis of the λ / 4 plate is approximately 45 ° .
Before SL lambda / 2 plate is arranged between the second polarizer and the liquid crystal cell,
The angle formed by the absorption axis of the backside polarizing plate and the slow axis of the λ / 2 plate is approximately 45 °.
The slow axis of the λ / 4 plate and the slow axis of the λ / 2 plate are substantially parallel.
The Nz coefficient of the λ / 4 plate and the Nz coefficient of the λ / 2 plate are both −0.5 or more and 0.5 or less.
A set of polarizing plates in which the slow axis of the λ / 4 plate is arranged substantially parallel to the initial orientation direction of the IPS mode liquid crystal cell. The λ / 4 plate and the λ / 2 plate have a three-layer structure in which a skin layer made of a (meth) acrylic resin composition containing rubber particles is formed on both sides of a core layer made of a styrene resin. The set of polarizing plates according to claim 1, which is a retardation film. The set of polarizing plates according to claim 2, wherein the glass transition temperature of the core layer is 120 ° C. or higher, and the glass transition temperature of the skin layer is 120 ° C. or lower. An IPS mode liquid crystal display device in which a set of polarizing plates according to any one of claims 1 to 3 is arranged in an IPS mode liquid crystal cell having an in-plane retardation value of 400 nm to 500 nm. The IPS mode liquid crystal display device according to claim 4, wherein the size of the IPS mode liquid crystal display device is 15 inches or less diagonally.

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