JP6699513B2 - Polarizing plate set and IPS mode liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a polarizing plate and an IPS mode liquid crystal display device using the polarizing plate.

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

  When external light such as sunlight is strong in mobile phones and personal digital assistants as they are used outdoors, liquid crystal display devices equipped with a conventional liquid crystal cell and a conventional polarizing plate will not emit the external light. There is a problem that the liquid crystal screen is hard to see due to strong reflection.

  As a countermeasure against this problem, a low reflection layer is provided on the surface of the viewing-side polarizing plate to reduce the reflection of external light, or a circular polarizing plate is used as the viewing-side polarizing plate to reduce the reflection of external light. It is customary to

  However, with only the above-mentioned low reflection layer, the visibility is remarkably deteriorated 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 dispose a circularly polarizing plate as the viewing side polarizing plate.

JP, 2005-128498, A

  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 laminating on both surfaces of an IPS mode liquid crystal cell having an in-plane retardation value of 100 nm to 200 nm, comprising a viewing side polarizing plate and a back side polarizing plate,
The absorption axis of the viewing side polarizing plate and the absorption axis of the back side polarizing plate are substantially orthogonal to each other,
The viewing side polarizing plate has a polarizer and a λ/4 plate,
The angle formed by the absorption axis of the viewing side polarizing plate and the slow axis of the λ/4 plate is approximately 45°,
A set of polarizing plates in which the slow axis of the λ/4 plate is arranged in a relationship substantially orthogonal to the initial alignment direction of the IPS mode liquid crystal cell.
[2] The set of polarizing plates according to [1], wherein the viewing-side polarizing plate includes a positive C plate arranged between the liquid crystal cell and the λ/4 plate.
[3] The set of polarizing plates according to [1], wherein the viewing side polarizing plate includes a positive C plate arranged between the polarizer of the viewing side polarizing plate and the λ/4 plate.
[4] The set of polarizing plates according to [2] or [3], wherein the positive C plate has a retardation value in the thickness direction of −50 nm to −150 nm.
[5] An IPS mode liquid crystal display device in which the polarizing plate set according to any one of [1] to [4] is arranged in an IPS mode liquid crystal cell having an in-plane retardation value of 100 nm to 200 nm.
[6] The IPS mode liquid crystal display device according to [5], wherein the size of the IPS mode liquid crystal display device is 15 inches or less on a diagonal.

  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 where the external light is strong such as outdoors. .

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

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

  1(a) and 1(b) are schematic cross-sectional views showing examples of preferable layer configurations in a polarizing plate according to the present invention. The polarizing plate of the present invention will be described with reference to FIGS. The polarizing plate set shown in FIGS. 1A and 1B is a viewing side polarizing plate 10 in which a λ/4 plate 34 and a positive C plate 35 are laminated on one surface of a polarizing plate 30, and a rear side polarizing plate. 20 includes a polarizing plate 50 having a brightness enhancement film 61 laminated on one surface thereof.

[Each member that constitutes the viewing-side polarizing plate and the back-side polarizing plate]
The viewing 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 polarizers 32 and 52 are usually a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, and an adsorption of the dichroic dye. It is manufactured through a step of treating the obtained polyvinyl alcohol-based resin film with a boric acid aqueous solution, and a step of washing with water after the treatment with the boric acid aqueous solution.

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

  The degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may 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 from such a polyvinyl alcohol-based resin is used as a raw film for the polarizers 32 and 52. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and the film can be formed by a known method. The 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 the dyeing of the dichroic dye, at the same time as the dyeing, or after the dyeing. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed at these plural stages.

  In the uniaxial stretching, stretching may be performed uniaxially between rolls having different peripheral speeds, or uniaxial stretching may be performed using a heat roll. The uniaxial stretching may be dry stretching in which the stretching is performed in the atmosphere, or wet stretching in which 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 the dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye is adopted. Specifically, iodine or a dichroic dye is used as the dichroic dye. The polyvinyl alcohol 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 and dyeing is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40°C. 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 employed. The content of the dichroic dye in this aqueous solution is usually about 1×10 ⁻⁴ to 10 parts by weight, and preferably about 1×10 ⁻³ to 1 part by weight, per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing 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 the dichroic dye can be usually 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 polyvinyl alcohol-based resin film treated with boric acid in water. The temperature of water in the water washing treatment is usually about 5 to 40°C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain the polarizers 32 and 52. The drying treatment 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 contents of the polarizers 32 and 52 are reduced to a practical level. The water 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 polarizers 32 and 52 may be lost, and the polarizers 32 and 52 may be damaged or broken after being dried. If the moisture content exceeds 20% by weight, the thermal stability of the polarizers 32 and 52 may be poor.

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

  Further, the stretching, dyeing, boric acid treatment, water washing, and drying steps of the polyvinyl alcohol-based resin film in the process of manufacturing the polarizer may be performed according to the method described in JP 2012-159778 A, for example. . As in the method described in this document, it is also effective to use a method of forming a polyvinyl alcohol resin layer serving as a polarizer by coating a polyvinyl alcohol resin on a base film.

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

  By using a polarizer whose contraction force is suppressed in a high temperature environment, it is possible to suppress the phase difference change due to the distortion of the λ/2 plate or the λ/4 plate due to the contraction of the polarizer, and it was used for the liquid crystal display device. In some cases, the polarizing plate can have a small display unevenness.

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

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

  The protective film 31b can be omitted by making the positive C plate 35 and the λ/4 plate 34 serve as a protective film, and can be omitted, which is an effective means for thinning the polarizing plate. Similarly, the protective film 51a may be omitted by making the brightness enhancement film 61 serve as a protective film, which is an effective means for thinning the polarizing plate.

  As the protective films 31a, 31b, 51a, 51b, cellulose-based resin, chain polyolefin-based resin, cyclic polyolefin-based resin, acrylic resin, polyimide-based resin, polycarbonate-based resin, polyester-based resin, etc. A film formed of a material that is widely used as a material for forming the film can be used.

  Appropriate additives may be added to these resins as long as the transparency is not impaired. Examples of additives include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retarders, stabilizers, processing aids, plasticizers, impact resistance aids. , Matting agents, antibacterial agents, antifungal agents and the like. Plural 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 resin dissolved in a solvent is cast on a metal band or drum, a solvent casting method for obtaining a film by drying and removing the solvent, heating the resin to a temperature above its melting temperature, kneading and extruding from a die. Alternatively, a melt extrusion method in which a film is obtained by cooling can be used. In the melt extrusion method, a single layer film can be extruded or a multilayer film can be coextruded.

  Further, as the protective film 31a, a retardation plate obtained by stretching the film for improving the visibility when viewing the screen through the polarized sunglasses may be used. From the viewpoint of improving visibility, it is desirable to dispose the retardation plate of the λ/4 plate as the retardation plate so that the angle formed by the absorption axis of the polarizing film is about 45°. In addition, when laminated with a long polarizing film, it is preferable that the angle formed with respect to the long direction of the long sheet is stretched to about 45° or 135° because a polarizing plate can be produced by roll-to-roll.

[Surface Treatment Layer 36 of Protective Film 31a]
The protective film 31a may have a surface treatment layer 36 on the surface opposite to the surface bonded to the polarizer 32. Examples of the surface treatment layer 36 include a hard coat layer having a fine surface irregular shape. The hard coat layer preferably has a pencil hardness higher than H. When the pencil hardness is H or lower, scratches are easily formed on the surface, and when scratched, the visibility of the liquid crystal display device is deteriorated. The pencil hardness is calculated according to JIS K 5600-5-4:1999 "General test method for paints-Part 5: Mechanical properties of coating film-Section 4: Scratch hardness (pencil method)". It is the hardness of the hardest pencil that does not cause scratches when scratched with a pencil.

  The haze value of the protective film 31a having the surface treatment layer 36 is preferably in the range of 0.1 to 45%, more preferably 5 to 40%. When the haze value is larger than 45%, the reflection of external light can be reduced, but the tightness of the screen for black display is reduced. Further, when the haze value is less than 0.1%, sufficient antiglare performance cannot be obtained and external light is reflected on the screen, which is not preferable. Here, the haze value is determined according to JIS K 7136:2000 “Plastic-Method for determining haze of transparent material”.

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

  The protective film 31a may be subjected to various additional surface treatments such as an antireflection layer, an antistatic treatment, an antifouling treatment, or an antibacterial treatment, in addition to the antiglare treatment (haze imparting treatment) that also serves as a hard coat layer. It may be applied, and a coat layer composed of a liquid crystal compound or a high molecular weight compound thereof may be formed. In particular, when an antireflection layer having a reflectance of 3% or less is formed, it can be used preferably even at 10,000 Lux or more because the visibility is not impaired. The antistatic function may be applied to other portions of the polarizing plate, such as the pressure-sensitive adhesive layer, other than the surface treatment.

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

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

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

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

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

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

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

  Here, the retardation value may be a value at any wavelength in the range of about 500 to 650 nm, which is near the center of visible light, but in this specification, the retardation value at a wavelength of 590 nm is standard. The retardation value Rth in the thickness direction and the in-plane retardation value Re can be measured by using various commercially available retarders.

  As a method for controlling the retardation value Rth in the plane and in the thickness direction of the resin film within the range of 10 nm or less, there is a method of minimizing distortion that remains in the plane and in the thickness direction when the film is produced. .. For example, in the solvent casting method, a method of relaxing residual shrinkage strain in the plane and in the thickness direction caused by drying the cast resin solution by heat treatment can be adopted. On the other hand, in the above-mentioned 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. A method of controlling the film so that the film is not stretched can be adopted. Further, similarly to the solvent casting method, a method of relaxing the strain remaining in the obtained film by heat treatment can be adopted.

[λ/4 plate 34]
It is particularly preferable that the λ/4 plate 34 is made of a material having excellent transparency, mechanical strength, thermal stability, moisture shielding property, and the like. For example, polyolefin resins such as chain polyolefin resins (polypropylene resins) and cyclic polyolefin resins (norbornene resins); cellulose resins such as cellulose ester resins such as cellulose triacetate and cellulose diacetate; Examples thereof include polyester resins; polycarbonate resins; (meth)acrylic resins; polystyrene resins; liquid crystal compositions; or mixtures and copolymers thereof. Among these, a film made of a polycarbonate-based resin and a liquid crystal composition is preferably used because it has a positive wavelength dispersibility.

Here, the positive wavelength dispersion means that the following formula (c) is satisfied. The number in parentheses is the measurement wavelength (unit: nm) of the phase difference value.

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

Further, in the present invention, the phase difference value of the λ/4 plate means that the phase difference value Re is 120 nm to 160 nm at the measurement wavelength of 590 nm. In the present invention, the λ/4 plate preferably has an Nz coefficient defined by the following formula (d) in the range of 0.8 to 1.2. The range is more preferably 0.95 to 1.05.

Nz=Re/Rth+0.5 (d)

  Appropriate additives may be added to the λ/4 plate as long as the transparency is not impaired. Examples of additives include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retardation reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids. , Matting agents, antibacterial agents, antifungal agents and the like. A plurality of these additives may be used in combination.

The polycarbonate-based resin refers to aromatic polycarbonate. Polycarbonate-based resins include, for example, a method of reacting a dihydric phenol and a carbonate precursor by an interfacial polycondensation method or a melt transesterification method; a method of polymerizing a carbonate prepolymer by a solid-state transesterification method; and a cyclic carbonate compound. It can be obtained by a method of polymerizing by a ring-opening polymerization method.

  Examples of the dihydric phenol include bisphenol A, 2,2-bis{(4-hydroxy-3-methyl)phenyl}propane, 2,2-bis(4-hydroxyphenyl)butane and 2,2-bis(4-hydroxy). Phenyl)-3-methylbutane, 2,2-bis(4-hydroxyphenyl)-3,3-dimethylbutane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4 -Hydroxyphenyl)-3,3,5-trimethylcyclohexane and α,α'-bis(4-hydroxyphenyl)-m-diisopropylbenzene obtained from at least one divalent phenol selected from the group consisting of Copolymers or copolymers are preferable, and in particular, a homopolymer of bisphenol A, and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and bisphenol A, 2,2-bis{( A copolymer with at least one dihydric phenol selected from 4-hydroxy-3-methyl)phenyl}propane and α,α′-bis(4-hydroxyphenyl)-m-diisopropylbenzene is preferably used. .

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples thereof include phosgene, diphenyl carbonate or dihaloformate of dihydric phenol.

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

  It is preferable to carry out a stretching treatment in order to impart a predetermined retardation value to the film thus formed. For stretching, any optimum stretching method such as uniaxial stretching/sequential biaxial stretching/simultaneous biaxial stretching can be adopted.

  The liquid crystal composition preferably has a liquid crystal phase that is a nematic phase (nematic liquid crystal). The mechanism of exhibiting liquid crystallinity of the liquid crystal material may be lyotropic or thermotropic. The alignment state of the liquid crystal material is preferably homogeneous alignment. As the liquid crystal material, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

  When used as a λ/4 plate in the present invention, it is preferably a cured layer of a liquid crystal composition. Specifically, when the liquid crystal composition contains a liquid crystal monomer, the liquid crystal monomer preferably contains a polymerizable monomer and/or a crosslinkable monomer. The alignment state of the liquid crystalline monomer can be fixed by polymerizing or crosslinking the liquid crystalline monomer. After aligning the liquid crystal monomers, for example, by polymerizing or cross-linking the liquid crystal monomers, the alignment state can be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed retardation layer, for example, the transition to the liquid crystal phase, the glass phase, or the crystal phase due to the temperature change peculiar to the liquid crystal compound does not occur. As a result, the retardation layer can be a layer that is not affected by temperature changes and has extremely excellent stability.

  Examples of the liquid crystal monomer include LC242 manufactured by BASF, trade name E7 manufactured by Merck, and LC-Silicon-CC3767 traded by Wacker-Chem. These liquid crystalline monomers may be used alone or in combination of two or more.

  The temperature range in which the liquid crystalline monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40 to 120°C, more preferably 50 to 100°C, and most preferably 60 to 90°C.

  The liquid crystal cured layer can be set so as to function most appropriately as a λ/4 plate. In other words, the thickness can be set so as to obtain desired optical characteristics. The thickness of the retardation layer is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and particularly preferably 0.5 to 5 μm.

  Any appropriate method can be adopted as a method for producing a film exhibiting optical anisotropy by applying and orienting a liquid crystal composition. For example, a method of forming a liquid crystal cured layer by subjecting the surface of a substrate film such as a polyethylene terephthalate film to an alignment treatment and applying a coating liquid containing the above liquid crystal composition to the surface is applied. The coating liquid may contain a polymerization initiator, a crosslinking agent, a surfactant, a solvent and the like. Any appropriate alignment treatment can be adopted as the alignment treatment. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment are mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an oblique vapor deposition method and a photo-alignment treatment. The rubbing treatment is preferable. The orientation treatment may be performed directly on the surface of the base material film, or by forming any suitable orientation film (typically, a silane coupling agent layer, a polyvinyl alcohol layer or a polyimide layer) on the base material film. It may be applied to the alignment film. When the rubbing treatment is applied, it is preferable to apply it directly to the surface of the base film.

  The alignment direction of the alignment treatment can be set according to the desired angle. By performing the alignment treatment, the liquid crystal material can be aligned according to the alignment direction of the base film, so that the slow axis of the formed liquid crystal cured layer is substantially the same as the alignment direction of the base film. Therefore, for example, when the polarizer 32 (long shape) has an absorption axis in the longitudinal direction, the alignment treatment is performed in the direction of an angle of approximately 135° with respect to the longitudinal direction of the substrate (long shape). By thus forming the liquid crystal cured layer, the polarizer 32 (polarizing plate) and the λ/4 plate 34 can be continuously laminated by roll-to-roll. As a result, the manufacturing process can be significantly shortened.

[Positive C plate 35]
The positive C plate used in the present invention refers to a retardation film having positive uniaxiality in which n _x and n _y are substantially equal and having an optical axis in the film normal direction. In terms of refractive index, the retardation film has a relationship of n _x ≈n _y <n _z .

  The in-plane retardation Re of the positive C plate 35 is preferably 20 nm or less, and more preferably 10 nm or less. The retardation value Rth in the thickness direction is preferably −50 nm to −150 nm. More preferably, it is -170 nm to -120 nm.

The material and the form of the positive C plate 35 are not particularly limited as long as they have the above optical characteristics. For example, a retardation film made of a birefringent polymer film and a retardation film having a retardation layer formed by coating or transferring a low molecular weight or high molecular weight liquid crystalline compound on a transparent support are both used. be able to. Moreover, each can also be laminated and used.

The retardation film made of the birefringent polymer film having the above optical properties is a method of stretching a polymer film in the thickness direction of a film by applying a predetermined tension while heating a heat-shrinkable film and heating the film, or vinylcarbazole. It can be easily formed by a method of applying a system polymer and drying. Further, as the retardation layer formed from the liquid crystal compound having the above optical properties, a cholesteric discotic liquid crystal compound or composition containing a chiral structural unit is fixed after orienting its helical axis substantially perpendicular to the substrate. Examples of the layer include a layer formed by solidifying, a layer formed by orienting a rod-shaped liquid crystal compound or composition having a positive refractive index anisotropy substantially perpendicular to a substrate and then fixing the composition. The rod-shaped liquid crystal compound may be a low molecular compound or a high molecular compound. Further, not only one retardation layer but also a plurality of retardation layers may be laminated to form a retardation layer having the above optical characteristics. Further, the retardation layer may be configured such that the entire laminate of the support and the retardation layer satisfies the above optical characteristics. As the rod-shaped liquid crystal compound to be used, those having a nematic liquid crystal phase, a smectic liquid crystal phase, or a lyotropic liquid crystal phase state in a temperature range where the orientation is fixed are preferably used. A liquid crystal exhibiting a smectic A phase or B phase, which can obtain uniform vertical alignment without fluctuation, is preferable. These phases are preferable in that the birefringence is larger than that of the nematic liquid crystal phase and the thickness of the film can be reduced. In particular, in the presence of an additive, for a rod-shaped liquid crystal compound that is in the above liquid crystal state in an appropriate orientation temperature range, a layer is formed using a composition containing the additive and the rod-shaped liquid crystal compound. Is also preferable.

  Examples of the rod-shaped liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenylesters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. Preferred are phenyldioxane, tolnes and alkenylcyclohexylbenzonitriles. In addition to the above low-molecular liquid crystal molecules, high-molecular liquid crystal molecules can be used. As the liquid crystal molecule, those having a partial structure capable of causing a polymerization or a crosslinking reaction by an actinic ray, an electron beam, heat or the like are preferably used. The number of the partial structures is 1 to 6, preferably 1 to 3.

  When the retardation layer formed by fixing the rod-shaped liquid crystalline compound in the aligned state is included, it is preferable to use the retardation layer formed by orienting the rod-shaped liquid crystalline compound in a substantially vertical orientation and fixed in that state. preferable. Substantially vertical means that the angle between the film surface and the director of the rod-shaped liquid crystal compound is in the range of 70° to 90°. These liquid crystalline compounds may be obliquely aligned, or may be so arranged that the tilt angle is gradually changed (hybrid alignment). Even in the case of oblique orientation or hybrid orientation, the average tilt angle is preferably 70° to 90°, more preferably 80° to 90°, most preferably 85° to 90°.

  The retardation layer formed from a rod-shaped liquid crystalline compound is a rod-shaped liquid crystalline compound, and if desired, a coating liquid containing a polymerizable initiator, an air interface vertical alignment agent and other additives described below is formed on a support. It can be formed by applying it on the formed vertical alignment film, vertically aligning it, and fixing the alignment state. When it is formed on a temporary support, it can also be produced by transferring the retardation layer on the support. Further, not only one retardation layer but also a plurality of retardation layers may be laminated to form a retardation layer exhibiting the above optical characteristics. Further, the retardation layer may be configured such that the entire laminate of the support and the retardation layer satisfies the above optical characteristics.

  In the present invention, a positive C plate layer formed of a liquid crystal compound may be formed on the λ/4 plate 34 in an overlapping manner.

[Brightness enhancement film 61]
The brightness enhancement film 61 is also called a reflection-type polarizer, and a polarization conversion element having a function of separating 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 enhancement film 61 on the polarizing plate 50, it is possible to improve the emission efficiency of the linearly polarized light emitted from the polarizing plate 50 by using the return light that is the reflected polarized light or the scattered polarized light. You can

  The brightness enhancement film 61 can be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflection polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is 3M DBEF ( JP-A-4-268505). Another example of the anisotropic reflection polarizer is a composite of a cholesteric liquid crystal layer and a λ/4 plate, a specific example of which is PCF manufactured by Nitto Denko (Japanese Patent Laid-Open No. 11-231130). Still another example of the anisotropic reflection polarizer is a reflection grid polarizer, and a specific example thereof is a metal grating reflection polarizer (US in which a metal is finely processed to emit reflection polarization even in a visible light region). Patent No. 6288840), and a film obtained by adding fine metal particles to a polymer matrix and stretching (Japanese Patent Laid-Open No. 8-184701).

  An optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, or a retardation layer having a retardation value of ¼ wavelength may be provided on the surface of the brightness enhancement film 61 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 enhancement film 61 can be about 10 to 100 μm, but is preferably 10 to 50 μm, and more preferably 10 to 30 μm from the viewpoint of thinning the polarizing plate.

[Adhesion of each layer]
It is preferable that any appropriate pressure-sensitive adhesive layer or adhesive layer is provided between each member constituting the polarizing plate of the present invention. For example, a pressure-sensitive adhesive layer is preferably provided on the surface of the polarizing plate in order to bond the polarizing plate to the liquid crystal cell. In the present embodiment, for example, an adhesive layer can be provided outside the λ/4 plate 34 and an adhesive layer can be provided outside the protective film 51b.

  Examples of the adhesive forming the adhesive layer include a water-based adhesive and an active energy ray-curable adhesive that is 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. It is preferable that each of these compositions contains a radical polymerization initiator or a cationic polymerization initiator. The pressure-sensitive adhesive is preferably a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive).

[Liquid crystal cell 60]
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 substrate (color filter substrate). On the other substrate (active matrix substrate), a switching element (typically a TFT) that controls electro-optical characteristics of 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 And electrodes are 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 between the substrates, which is in contact with the liquid crystal layer.

  An IPS (In-Plane Switching) mode having an in-plane retardation value of 100 to 200 nm at a wavelength of 590 nm is adopted as a driving mode of the liquid crystal cell for disposing the polarizing plate set of the present invention. Since the liquid crystal cell itself has an in-plane retardation value close to λ/4 wavelength, it becomes possible to dispose a circularly polarizing plate as a viewing side polarizing plate, and to significantly reduce reflection of external light. become able to.

  A method for adjusting the in-plane retardation of the liquid crystal cell to 100 nm to 200 nm at a wavelength of 590 nm can be prepared by adjusting the thickness of the liquid crystal of the liquid crystal cell. For example, a liquid crystal cell having a desired in-plane retardation value can be manufactured by adjusting the thickness of the liquid crystal of the liquid crystal cell to about 1 to 2 μm.

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

  The axial structure 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 alignment direction of the liquid crystal cell used in the present invention is defined as 0°, and the counterclockwise angle when viewing the back side polarizing plate from the viewing side polarizing plate is defined as positive. The slow axis of the λ/4 plate 34 is arranged at approximately −90° with respect to the initial alignment direction. Further, the absorption axis of the viewing side polarizing plate is arranged at approximately −45° with respect to the initial alignment direction, and the absorption axis of the back side polarizing plate is arranged at approximately 45° with respect to the initial alignment direction. When the term "approximately" is used here, it means that the value is within a range of ±5°, preferably within a range of ±2°.

  In the present invention, the initial alignment direction of the liquid crystal cell means an alignment direction of liquid crystal molecules in an initial state in which a driving voltage is not applied to the liquid crystal cell, and the initial alignment angle is an angle formed with respect to a long side of the liquid crystal cell. Is preferably about 45°.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, parts and% representing contents or amounts used are based on weight unless otherwise specified. Regarding the angle, the counterclockwise direction is positive. In addition, the measurement of each physical property in the following examples was performed by the following method.

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

(2) Measurement of in-plane retardation and thickness direction retardation:
Using a phase difference meter “KOBRA (registered trademark)-WPR” manufactured by Oji Scientific Instruments Co., Ltd., which is based on the principle of parallel Nicols rotation, at the temperature of 23° C., the in-plane retardation and the thickness direction retardation at each wavelength are measured. It was measured.

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

(4) Measurement of the contraction force of the polarizer A super cutter with a width of 2 mm and a length of 50 mm (Ogino Seiki Co., Ltd.) is used so that the direction in which the contraction force is measured (the absorption axis direction of the polarizer) is the long side of the polarizer It was cut at the factory. The obtained strip-shaped chip was used as a test piece. The shrinkage force of the test piece was measured using a thermomechanical analyzer (manufactured by SII Nano Technology Co., Ltd., model TMA/6100). This measurement was performed in the constant dimension mode, and the chuck distance was 10 mm. After leaving the test piece in a chamber at 23° C. and 55% for 24 hours or more, the temperature inside the sample chamber is raised from 23° C. to 80° C. in 1 minute, and after that, the temperature inside the sample chamber is maintained at 80° C. Was set. After the temperature was raised, the mixture was allowed to stand for another 4 hours, and then the shrinkage 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 SUS probe was used for the jig.

[Production Example 1] Production of Polarizer A polyvinyl alcohol film having a thickness of 30 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched by about 4 times by dry stretching, and the tension state is maintained. As it is, it is immersed in pure water at 40° C. for 40 seconds, and then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.052/5.7/100 at 28° C. for 30 seconds to perform a dyeing treatment. It was Then, it was immersed in an aqueous solution having a potassium iodide/boric acid/water weight ratio of 11.0/6.2/100 at 70° C. for 120 seconds. Then, after washing with pure water at 8° C. for 15 seconds, it is dried at 60° C. for 50 seconds and then at 75° C. for 20 seconds while maintaining the tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption type polarizer having a thickness of 12 μm was obtained. The shrinkage 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.] was dissolved in 100 parts by weight of water, and a water-soluble epoxy was added to the aqueous solution. 1.5 parts by weight of a polyamide-epoxy-based additive, which is a resin [trade name "SUMIREZ RESIN (registered trademark) 650(30)" obtained from Taoka Chemical Industry Co., Ltd., an aqueous solution having a solid content of 30% by weight) is added. Then, a water-based adhesive was prepared.

[Adhesives A and B]
The following two types of adhesives were prepared.
Adhesive A: Sheet-like adhesive having a thickness of 25 μm [“P-3132” manufactured by Lintec Corporation]
Adhesive B: 5 μm thick sheet-like adhesive [“NCF #L2” manufactured by Lintec Co., Ltd.]

[Protective film A, B, C, D]
The following three types of protective films were prepared.
Protective film A: hard coated triacetyl cellulose film manufactured by Konica Minolta; 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 Co., Ltd.; 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 resin manufactured by Toppan TOMOEGAWA Optical Products; 40K SPLR (thickness 44 μm, Y value 1.1% according to JIS-Z8701-1982)

[Brightness enhancement film A]
The following brightness enhancement films were prepared.
Brightness Enhancement Film A: 26 μm thick brightness enhancement film (3M product name “Advanced Polarized Film, Version 3)

[Production of λ/4 plate 1]
After forming a polyvinyl alcohol film (thickness 0.1 μm) on the surface of a base film (triacetyl cellulose film, thickness 80 μm), use a rubbing cloth to make polyvinyl alcohol in the direction of −45° with respect to the longitudinal direction of the substrate. The surface of the film was rubbed to prepare a base film having an alignment film.

Next, 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name Paliocolor LC242) and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by Ciba Specialty Chemicals, trade name Irgacure (registered trademark) 907, 0.5 g of a benzotriazole-based UV absorber (containing 1%) was dissolved in 40 g of toluene to prepare a coating solution. Then, the coating liquid was applied to the surface of the alignment substrate obtained above by a bar coater, and the liquid crystal was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with light of 20 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a retardation layer on the substrate. The thickness of the obtained retardation layer was 1 μm, and the in-plane retardation value was 139.8 nm at a wavelength of 590 nm.

[Production of λ/4 plate 2]
A resin film [“Zeonor Film (registered trademark)” manufactured by Nippon Zeon Co., Ltd.] hydrogenated on a ring-opening polymer of a norbornene-based monomer was longitudinally uniaxially stretched. The thickness of the obtained retardation film was 18 μm, and the in-plane retardation value was 137.2 nm at a wavelength of 590 nm.

[Preparation of positive C plate 1]
A commercially available vertical alignment film (JALS-204R, manufactured by Japan Synthetic Rubber Co., Ltd.) was diluted 1:1 with methyl ethyl ketone on the surface of a substrate film (triacetyl cellulose film, thickness 80 μm), and then applied with a wire bar coater ( Coating amount 2.4 ml/m ² ). Immediately, it was dried with warm air of 120° C. for 120 seconds.

Next, 3.8 g of the following rod-like liquid crystal compound, 0.06 g of a photopolymerization initiator (Irgacure (registered trademark) 907, manufactured by Ciba-Geigy), and a sensitizer (Kayacure (registered trademark) DETX, manufactured by Nippon Kayaku Co., Ltd.) A solution was prepared by dissolving 0.02 g and 0.002 g of the following air interface side vertical aligning agent in 9.2 g of methyl ethyl ketone. This solution was applied to the alignment film side of the film having the alignment film formed thereon with a wire bar and heated at 100° C. for 2 minutes to align the rod-shaped liquid crystal compound. Next, the rod-shaped liquid crystal compound was cross-linked by UV irradiation for 20 seconds at 80° C. with a 120 W/cm ² high pressure mercury lamp, and then allowed to cool to room temperature to prepare a retardation layer having the characteristics of a positive C plate. The thickness of the obtained retardation layer was 0.6 μm, and the retardation value in the thickness direction was −109.4 nm at a wavelength of 590 nm.

Rod-shaped liquid crystal compound

Air interface side vertical aligner:
Exemplified compound (II-4) described in Japanese Patent Application No. 2003-119959

[Preparation of positive C plates 2-3]
Positive C plates 2 to 3 were prepared in the same manner as the positive C plate 1. The retardation value was set to a desired retardation value by adjusting the thickness.

Phase difference value Rth(590)=−91.2 nm in the thickness direction of the positive C plate 2,
Retardation value Rth(590)=−69.1 nm in the thickness direction of the positive C plate 3,

[Production of Polarizing Plate A]
The protective film A was subjected to saponification treatment, and the surface of the protective film C to be attached to the polarizer was subjected to corona treatment. The protective film A and the polarizer and the protective film C are adhered with a water-based adhesive so that the triacetyl cellulose surface of the protective film A and the corona-treated surface of the protective film C become the bonding surface with the polarizer, I got A.

[Production of Polarizing Plate B]
The protective film B was subjected to saponification treatment, and the surface of the protective film C to be attached to the polarizer was subjected to corona treatment. The protective film B and the polarizer and the protective film C were adhered with a water-based adhesive so that the corona-treated surfaces of the protective film B and the protective film C were the surfaces to be bonded to the polarizer, to obtain a polarizing plate. The adhesive B was attached to the protective film B side of the polarizing plate B. At this time, corona treatment was performed on the bonding surfaces of the protective film B and the adhesive B. Finally, the brightness enhancement film A was attached to the adhesive B side of the polarizing plate to obtain a polarizing plate B.

[Preparation of pseudo liquid crystal cell]
Two sheets of a non-alkali glass manufactured by Corning Co., Ltd.: Eagle XG (thickness 0.7 mm, length 157 mm×width 98 mm) and an adhesive B adhered thereto were prepared. At this time, corona treatment was performed on the bonding surface of the glass and the adhesive. Next, the previously prepared λ/4 plate 1 was attached to the adhesive B side of one piece of glass. Also in this case, the λ/4 plate 1 and the pressure-sensitive adhesive B surface were subjected to corona treatment. Finally, one surface of the λ/4 plate of the glass to which the λ/4 plate 1 was bonded and the other side of the pressure-sensitive adhesive B of the glass were bonded to form a pseudo liquid crystal cell. At this time, corona treatment was performed on one surface of the λ/4 plate and the bonding surface of the adhesive B. The λ/4 plate 1 was manufactured so that the slow axis direction was −45° when the long side direction of the glass was 0°.

  It is assumed that the initial alignment direction of the pseudo liquid crystal cell is 45° in the long side direction of the glass, and the pseudo liquid crystal cell is a liquid crystal cell when a drive voltage is applied (in the case of white display). There is.

  Furthermore, by using High Mackey blue (MO-150-MC-BL) manufactured by Zebra Co., Ltd. on one glass surface of the manufactured pseudo liquid crystal cell, Doraemon (Fujiko F. Fujio's "Doraemon" appears. A cat-shaped robot, published by Shogakukan).

[Backlight]
Google Inc. A liquid crystal panel was taken out from Nexus 7 (registered trademark) manufactured by and the backlight was obtained by turning on only the backlight.

[Example 1]
(Production of viewing side polarizing plate 1)
The adhesive B was attached to the protective film C surface of the polarizing plate A. At this time, corona treatment was applied to the protective film C surface and the adhesive B bonding surface. Next, the λ/4 plate 1 was laminated on the pressure-sensitive adhesive B side of the produced polarizing plate A. At this time, the adhesive surfaces of the adhesive B and the λ/4 plate 1 were subjected to corona treatment.
The angle between the absorption axis of the polarizing plate and the λ/4 plate 1 is 45° (when viewing the protective film C from the protective film A, λ/is set to be 45° counterclockwise with respect to the absorption axis of the polarizing plate. The slow axis of 4 plate 1 was arranged.).
Further, the pressure-sensitive adhesive B was attached to one surface of the λ/4 plate of the polarizing plate A. Also at this time, corona treatment was performed on one surface of the λ/4 plate of the polarizing plate A and the bonding surface of the adhesive B. Next, the positive C plate 1 was attached to the adhesive B side of the polarizing plate A. Also at this time, corona treatment was performed on the pressure-sensitive adhesive B side and the bonding surface of the positive C plate 1.
Finally, the pressure sensitive adhesive A was attached to the surface of the positive C plate 1 of the polarizing plate A. Also at this time, the corona treatment was performed on the positive C plate 1 surface and the adhesive A bonding surface. In this way, the viewing side polarizing plate 1 was produced.

(Preparation of back side polarizing plate 1)
The pressure-sensitive adhesive A was attached to the protective film C side of the polarizing plate B to prepare the back side polarizing plate 1. At this time, corona treatment was applied to the protective film C surface and the adhesive A bonding surface.

  The visible side polarizing plate 1 and the back side polarizing plate 1 thus produced were cut into a size of 155 mm in length×96 mm in width. At this time, when the protective film A of the viewing-side polarizing plate 1 is viewed as the upper surface, the absorption axis of the viewing-side polarizing plate is cut so as to be parallel to the short side direction to protect the back-side polarizing plate 1. The film was cut so that the absorption axis of the back-side polarizing plate 1 was parallel to the long side direction when the film B surface was viewed as the top surface.

  The viewing-side polarizing plate 1 was attached to the glass surface on which the portrait of Doraemon of the pseudo-liquid crystal cell was drawn, and the back-side polarizing plate 1 was attached to the glass surface on the opposite side to produce a pseudo-liquid crystal panel. At this time, the shaft configuration was as shown in FIG.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 2]
A pseudo liquid crystal panel was produced in the same manner as in Example 1 except that the positive C plate 1 was changed to the positive C plate 2.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 3]
A pseudo liquid crystal panel was produced in the same manner as in Example 1 except that the positive C plate 1 was changed to the positive C plate 3.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 4]
A pseudo liquid crystal panel was produced in the same manner as in Example 1 except that the protective film A of the viewing side polarizing plate 1 was changed to the protective film D.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Example 5]
A pseudo liquid crystal panel was produced in the same manner as in Example 4 except that the positive C plate 1 was changed to the positive C plate 2.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Example 6]
A pseudo liquid crystal panel was produced in the same manner as in Example 4 except that the positive C plate 1 was changed to the positive C plate 3.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Example 7]
(Production of viewing side polarizing plate 2)
The adhesive B was attached to the protective film C surface of the polarizing plate A. At this time, corona treatment was applied to the protective film C surface and the adhesive B bonding surface. Then, the positive C plate 1 was attached to the adhesive B side of the produced polarizing plate A. Also at this time, corona treatment was performed on the pressure-sensitive adhesive B side and the bonding surface of the positive C plate 1. Further, the adhesive B was attached to the surface of the positive C plate 1 of the polarizing plate A. Also at this time, corona treatment was performed on the positive C plate 1 surface of the polarizing plate A and the bonding surface of the adhesive B. Next, the λ/4 plate 1 was attached to the adhesive B side of the polarizing plate A. At this time, the adhesive surfaces of the adhesive B and the λ/4 plate 1 were subjected to corona treatment. The angle between the absorption axis of the polarizing plate and the λ/4 plate 1 is 45° (when viewing the protective film C from the protective film A, λ/ The slow axis of 4 plate 1 was arranged.)
Finally, the pressure sensitive adhesive A was attached to one surface of the λ/4 plate of the polarizing plate A. Also at this time, corona treatment was performed on one surface of the λ/4 plate and the bonding surface of the adhesive A. In this way, the viewing side polarizing plate 2 was produced.

  The viewing-side polarizing plate 2 and the back-side polarizing plate 1 thus produced were cut into a size of 155 mm length×96 mm width. At this time, when the protective film A of the viewing-side polarizing plate 2 is viewed as the upper surface, the absorption axis of the viewing-side polarizing plate is cut so as to be parallel to the short side direction to protect the back-side polarizing plate 1. The film was cut so that the absorption axis of the back-side polarizing plate 1 was parallel to the long side direction when the film B surface was viewed as the top surface.

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

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 8]
A pseudo liquid crystal panel was produced in the same manner as in Example 7 except that the positive C plate 1 was changed to the positive C plate 2.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 9]
A pseudo liquid crystal panel was produced in the same manner as in Example 7 except that the positive C plate 1 was changed to the positive C plate 3.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 7500 Lux.

[Example 10]
A pseudo liquid crystal panel was produced in the same manner as in Example 7 except that the protective film A of the viewing side polarizing plate 2 was changed to the protective film D.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Example 11]
A pseudo liquid crystal panel was produced in the same manner as in Example 10 except that the positive C plate 1 was changed to the positive C plate 2.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Example 12]
A pseudo liquid crystal panel was produced in the same manner as in Example 10 except that the positive C plate 1 was changed to the positive C plate 3.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux.

[Examples 13 to 24]
Pseudo liquid crystal panels were produced in the same manner as in Examples 1 to 12 except that the λ/4 plate 1 was changed to the λ/4 plate 2. The correspondence relationship between the numbers of the respective examples is as shown in the table below.

  The pseudo liquid crystal panel manufactured in this manner was placed on the manufactured backlight, and it was confirmed whether Doraemon could be visually recognized. When the visibility was confirmed under external light, the visibility was good even with 10,000 Lux in all the pseudo liquid crystal panels.

[Comparative Example 1]
Google Inc. The in-plane retardation value of the liquid crystal cell was measured at a wavelength of 590 nm by peeling off the upper and lower polarizing plates from the Nexus 7 (registered trademark) liquid crystal panel manufactured by K.K. Next, the polarizing plate A was attached to the viewing side of the taken out liquid crystal cell via the adhesive A, and the polarizing plate B was attached to the back side via the adhesive A to prepare a liquid crystal panel. The liquid crystal panel thus manufactured 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 the external light. As a result, the visibility was remarkably reduced at 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 Viewing-side polarizing plate 20 Back-side polarizing plate 30, 50 Polarizing plate 31a, 31b, 51a, 51b Protective film 36 Surface treatment layer 32, 52 Polarizer 34 λ/4 plate 35 Positive C plate 61 Brightness improving film 60 Liquid crystal cell 1 Absorption axis of polarizing plate 2 Slow axis of λ/4 plate 3 Initial alignment direction of liquid crystal cell 5 Absorption axis of polarizing plate

Claims (5)

An IPS mode liquid crystal display device in which a viewing side polarizing plate and a back side polarizing plate are respectively attached to both surfaces of an IPS mode liquid crystal cell having an in- plane retardation value of 100 nm to 200 nm,
The absorption axis of the viewing side polarizing plate and the absorption axis of the back side polarizing plate are substantially orthogonal to each other,
The viewing side polarizing plate has a polarizer and a λ/4 plate,
The λ/4 plate and the polarizer are stacked in this order from the liquid crystal cell,
The angle formed by the absorption axis of the viewing side polarizing plate and the slow axis of the λ/4 plate is about 45°,
An IPS mode liquid crystal display device in which a slow axis of the λ/4 plate is arranged in a relationship substantially orthogonal to an initial alignment direction of the IPS mode liquid crystal cell. The IPS mode liquid crystal display device according to claim 1, wherein the viewing side polarizing plate includes a positive C plate arranged between the liquid crystal cell and the λ/4 plate. The IPS mode liquid crystal display device according to claim 1, wherein the viewing side polarizing plate includes a positive C plate disposed between the polarizer of the viewing side polarizing plate and the λ/4 plate. The IPS mode liquid crystal display device according to claim 2, wherein the positive C plate has a retardation value in the thickness direction of −50 nm to −150 nm. The IPS mode liquid crystal display device according to claim 1, wherein the size of the IPS mode liquid crystal display device is 15 inches or less on a diagonal .

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