JP2019219433A - Polarizing plate set and IPS mode liquid crystal display device using the same - Google Patents

Abstract

An object of the present invention is to provide a set of polarizing plates for a specific IPS mode liquid crystal cell which can ensure good visibility even in an environment where external light is strong, and to provide an IPS mode liquid crystal display device using the same. The liquid crystal cell includes a viewing-side polarizing plate and a back-side polarizing plate, and is used to form a liquid crystal panel by bonding to both surfaces of a liquid crystal cell. In the liquid crystal cell, the absorption axis of the viewing-side polarizing plate and the absorption axis of the back-side polarizing plate are orthogonal to each other. The viewing-side polarizing plate includes a λ / 4 plate between the polarizer and the liquid crystal cell. The angle between the absorption axis of the polarizing plate and the slow axis of the λ / 4 plate is approximately 45 °, and the viewing side polarizing plate includes a retardation film between the polarizer and the λ / 4 plate, The angle between the absorption axis of the polarizing plate and the slow axis of the retardation film is substantially parallel or substantially orthogonal, and the slow axis of the λ / 4 plate and the initial alignment direction of the IPS mode liquid crystal cell are substantially orthogonal. There is a set of polarizing plates. [Selection diagram] FIG.

Description

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

  2. Description of the Related Art In recent years, light-weight and thin liquid crystal displays that operate with low power consumption, operate at low voltage, and are thin have rapidly spread as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. With the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and the problems of liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved. Patent Literature 1 describes a technique for preventing light leakage and coloring when viewed from an oblique direction using a retardation film.

  As described above, the chances of using a liquid crystal display outdoors as a mobile phone or a portable information terminal increase, and when external light such as sunlight is strong, the conventional liquid crystal display has a strong reflection of external light and a liquid crystal screen. However, there was a problem that he could not see.

To address this problem, 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 as the viewing-side polarizing plate to reduce external light reflection. Is usually done.

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

JP 2005-128498 A

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

[1] A set of polarizing plates comprising a viewing-side polarizing plate and a back-side polarizing plate, which are used to form a liquid crystal panel by bonding to both surfaces of a liquid crystal cell,
The liquid crystal cell is 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 is orthogonal to the absorption axis of the back-side polarizing plate,
The viewing side polarizing plate includes a positive A plate between a polarizer and a liquid crystal cell, and an angle between an absorption axis of the viewing side polarizing plate and a slow axis of the positive A plate is approximately 45 °,
The viewing side polarizing plate includes a retardation film between the polarizer and the positive A plate, the angle between the absorption axis of the viewing side polarizing plate and the slow axis of the retardation film is substantially parallel or substantially parallel. Orthogonal
A set of polarizing plates, wherein the slow axis of the positive A plate and the initial alignment direction of the IPS mode liquid crystal cell are substantially orthogonal.
[2] The set of polarizing plates according to [1], further including a positive C plate between the liquid crystal cell and the positive A plate.
[3] The polarizing plate set according to [2], wherein the positive C plate has a retardation value in a thickness direction of −50 nm to −250 nm.
[4] An IPS mode liquid crystal display device in which the set of polarizing plates according to any one of [1] to [3] is arranged in an IPS mode liquid crystal cell having a front phase difference value of 100 nm to 200 nm.
[5] The IPS mode liquid crystal display device according to [4], wherein the IPS mode liquid crystal display device is for small and medium sized devices.

  The liquid crystal display device provided with the set of polarizing plates of the present invention can suppress reflection of external light, and thus has good visibility even in an environment with strong external light such as outdoors.

It is an outline sectional view showing the example of the preferred layer composition of the set of the polarizing plate concerning the present invention. It is the schematic which shows the example of the preferable axis | shaft structure of the IPS liquid crystal display device concerning this invention.

  Hereinafter, a set of a polarizing plate according to the present invention and a 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 is a schematic cross-sectional view showing an example of a preferred layer configuration in a set of polarizing plates according to the present invention. The set of the polarizing plate of the present invention will be described with reference to FIG. In the set of polarizing plates shown in FIG. 1, the viewing-side polarizing plate 10 has a configuration in which a retardation film 36, a positive A plate 34, and a positive C plate 35 are stacked on one surface of a polarizing plate 30. The rear polarizing plate 20 is obtained by laminating a brightness enhancement film 61 on one surface of the polarizing plate 50. The viewing side polarizing plate 10 can be arranged on the viewing side of the liquid crystal cell, and the back side polarizing plate 20 can be arranged on the back side of the liquid crystal cell.

  The viewing side polarizing plate 10 includes a positive A plate 34 between the polarizer 32 and the liquid crystal cell, and includes a retardation film 36 between the polarizer 32 and the positive A plate 34. In other words, the viewing-side polarizing plate 10 includes a positive A plate 34 on the back side of the polarizer 32, and includes a retardation film 36 between the polarizer 32 and the positive A plate 34.

[Each member constituting the viewing side polarizing plate and the back side polarizing plate]
The viewing side polarizing plate 10 and the back side polarizing plate 20 of the present invention include a polarizing plate 30 and a polarizing plate 50.

[Polarizer]
The polarizers 32 and 52 generally include a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye, and a step of adsorbing the dichroic dye. The polyvinyl alcohol-based resin film is manufactured through a step of treating 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-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of another monomer copolymerizable with vinyl acetate, and the like. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified. 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 of such a polyvinyl alcohol-based resin is used as a raw film of the polarizers 32 and 52. The method of forming the polyvinyl alcohol-based resin 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, simultaneously with, or after the dyeing of the dichroic dye. When the uniaxial stretching is performed after the dyeing, the uniaxial stretching may be performed before or during the boric acid treatment. Further, uniaxial stretching may be performed in these plural stages.

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

  As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye is employed. As the dichroic dye, specifically, iodine or a dichroic dye is used. The polyvinyl alcohol-based resin film is preferably subjected to a dipping treatment 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 the film 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. Further, 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 the 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, 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 aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. The immersion time (dyeing time) in the 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 aqueous solution containing boric acid 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 by, for example, immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water in the water washing process is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

  After the water washing, a drying treatment is performed, and the polarizers 32 and 52 are obtained. 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 time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  By the drying treatment, the water content of the polarizers 32 and 52 is reduced to a practical level. The water content is usually 5 to 20% by weight, preferably 8 to 15% by weight. If the water content is less than 5% by weight, the polarizers 32 and 52 lose flexibility, and the polarizers 32 and 52 may be damaged or broken after drying. When the water content exceeds 20% by weight, the thermal stability of the polarizers 32 and 52 may be poor.

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

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

  In order to suppress the shrinkage force of the polarizer 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 in that good optical characteristics can be imparted.

  By using a polarizer with a reduced contraction force in a high temperature environment, it is possible to suppress the phase difference change due to the distortion of the retardation film or the λ / 4 plate due to the contraction of the polarizer. In addition, a polarizing plate with small display unevenness can be obtained.

  When the polarizer is kept at a temperature of 80 ° C. for 240 minutes, the contraction force in the absorption axis direction per 2 mm in width is preferably 2 N / 2 mm or less. If the contraction force is larger than 2N / 2 mm, the dimensional change in a high-temperature environment increases, and the contraction force of the polarizer increases. The child tends to crack easily. The shrinking force of the polarizer tends to be 2 N / 2 mm or less when the stretching ratio is reduced or when the thickness of the polarizer is reduced.

  It is preferable that protective films are laminated on both surfaces of the polarizers 32 and 52. 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, heat stability, moisture shielding property, and the like. In the present specification, a transparent resin film refers to a resin film having a single transmittance of 80% or more in a visible light region.

  It is also an effective means to reduce the thickness of the protective film 31b by using a positive C plate or a positive A plate as an alternative. Similarly, for the protective film 51a, it is also effective to reduce the brightness enhancement film 61 as an alternative.

  As the protective films 31a, 31b, 51a, 51b, conventional protective films in the field such as cellulose resin, chain polyolefin resin, cyclic polyolefin resin, acrylic resin, polyimide resin, polycarbonate resin, polyester resin, etc. A film formed from a material widely used as a material for forming the film can be used.

  These resins may contain appropriate additives as long as the transparency is not impaired. Additives include, for example, 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, fungicides and the like. A plurality of these additives may be used in combination.

  As a method of forming a film from the above resin, any optimal method may be appropriately selected. For example, a resin dissolved in a solvent is cast on a metal band or drum, and a solvent casting method is used to obtain a film by drying and removing the solvent.The resin is heated to a temperature higher than its melting temperature, kneaded and extruded from a die. For example, a melt extrusion method of 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 co-extruded.

[Surface treatment layer 37 of protective film 31a]
The protective film 31a may have a surface treatment layer 37 on the surface opposite to the surface to be bonded to the polarizer 32. As the surface treatment layer 37, for example, a hard coat layer having a fine surface unevenness is used. 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 scratched, the visibility of the liquid crystal display device is deteriorated. The 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)". It is represented by the hardness of the hardest pencil that does not scratch when scratched with a pencil.

  The protective film 31a having the surface treatment layer 37 preferably has a haze value 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 black display screen is reduced. On the other hand, 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”.

  A hard coat layer having a fine surface unevenness is formed on the surface of the resin film by a method of forming a coating film containing organic fine particles or inorganic fine particles, 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 provided with 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 composed of a curable resin and organic fine particles or inorganic fine particles on the surface of a resin film. .

  The protective film 31a has 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) also serving as a hard coat layer. Or a coating layer made of a liquid crystal compound or a high molecular weight compound thereof. In particular, when an antireflection layer having a reflectance of 3% or less of external light on the surface is formed, even if it is 10,000 Lux or more, visibility is not impaired, so that it is preferably used. The antistatic function may be provided to other parts of the polarizing plate, such as an adhesive layer, other than the surface treatment.

[Protective films 31b, 51b]
As a material for forming the protective films 31b and 51b, a cellulose-based resin or a cyclic polyolefin-based resin is preferable because the control of the retardation value is easy and the material is easily available.

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

  The cyclic polyolefin-based resin is obtained, for example, by polymerizing a cyclic olefin monomer such as norbornene and another cyclopentadiene derivative in the presence of a catalyst. When such a cyclic polyolefin-based resin is used, a protective film having a predetermined retardation value described later is easily obtained.

  As the cyclic polyolefin-based resin, for example, from cyclopentadiene and an olefin or (meth) acrylic acid or an ester thereof, a ring-opening metathesis polymerization is carried out using norbornene or a derivative thereof obtained by a Diels-Alder reaction as a monomer, followed by A resin obtained by hydrogenation; ring-opening metathesis polymerization using tetracyclododecene or a derivative thereof obtained by a Diels-Alder reaction from dicyclopentadiene and an olefin or (meth) acrylic acid or an ester thereof as a monomer, A 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. Resins obtained by hydrogenation; resins obtained by addition copolymerization of a cyclic olefin such as norbornene, tetracyclododecene, or a derivative thereof with an aromatic compound having a chain olefin and / or a vinyl group. No.

  As a method of forming a film from the above resin, any optimal method may be appropriately selected. For example, a resin dissolved in a solvent is cast on a metal band or drum, and a solvent casting method is used to obtain a film by drying and removing the solvent.The resin is heated to a temperature higher than its melting temperature, kneaded and extruded from a die. For example, a melt extrusion method of 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 co-extruded.

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

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

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

  As a method for controlling the in-plane and thickness direction retardation values Rth of the resin film within a range of 10 nm or less, there is a method of minimizing distortion remaining in the in-plane and thickness direction when producing the film. . For example, in the solvent casting method, a method in which the residual shrinkage strain in the plane and in the thickness direction generated when the cast resin solution is dried can be alleviated by heat treatment. On the other hand, in the melt extrusion method, in order to prevent the resin film from being extruded from the die and being stretched before being cooled, the distance from the die to the cooling drum is reduced as much as possible, and the amount of extrusion and the rotation speed of the cooling drum are reduced. Can be adopted such that the film is not stretched. Further, similarly to the solvent casting method, a method in which strain remaining in the obtained film is relaxed by heat treatment can be adopted.

[Retardation film 36]
The retardation film 36 is mainly used for improving light leakage of the polarizing plate in an oblique view. As the retardation film to be used, known films can be used. For example, Re at a wavelength of 590 nm disclosed in Japanese Patent No. 5569773 is 30 to 150 nm, and an Nz coefficient defined by the following formula (c) Has a refractive index anisotropy of more than 1 and less than 2, a Re of 20 to 120 nm at a wavelength of 590 nm, an Nz coefficient of more than -2, and a refraction of less than -0.5. Laminated retardation film obtained by laminating a second retardation film having anisotropic anisotropy, Re at a wavelength of 590 nm disclosed in Japanese Patent No. 5391818 is 100 to 300 nm, and the Nz coefficient is 0.1 to 0.7. A retardation film, Re = 50 to 210 nm at a wavelength of 590 nm disclosed in Japanese Patent No. 3880996, and an Nz coefficient of about 1 (0.8 to 1. ), And a second retardation film in which Re at a wavelength of 590 nm is substantially zero (0 nm to 20 nm) and Rth is -500 to -10 nm. No. 4907993 and Patent No. 5383594 disclose a first retardation film having an Nz coefficient of 1 or more, and a second retardation film having Re of about zero at a wavelength of 590 nm and Rth having a negative value. A laminated retardation film or the like can be used.

Nz = Rth / Re + 0.5 (c)

  The retardation film 36 may be arranged such that its slow axis is substantially perpendicular or substantially perpendicular to the absorption axis of the polarizer 32 or 52. With such an arrangement, light leakage of the polarizing plate can be effectively suppressed.

[Positive A plate 34]
The positive A plate can be a retardation film having a relationship of nx> ny ≒ nz in terms of refractive index. ny ≒ nz includes the case where ny and nz are substantially equal, in addition to the case where ny and nz are completely equal. Specifically, if the magnitude of the difference between ny and nz is within 0.005, it can be said that ny and nz are substantially equal. The positive A plate includes a λ / 4 plate. In particular, the positive A plate 34 is preferably made of a material having excellent transparency, mechanical strength, heat stability, moisture shielding properties, and the like. Examples of the material of the positive A plate include polyolefin resins such as chain polyolefin resins (eg, polypropylene resins) and cyclic polyolefin resins (eg, norbornene resins); cellulose esters such as cellulose triacetate and cellulose diacetate. Cellulosic resins such as resin; polyester resin; polycarbonate resin; (meth) acrylic resin; polystyrene resin; liquid crystal composition; or a mixture or copolymer thereof. Among them, a film made of a polycarbonate resin, a polystyrene resin, and a liquid crystal composition is preferably used because it has a positive wavelength dispersion. Also, a film made of a cyclic polyolefin-based resin is preferably used because it has a substantially flat wavelength dispersibility.

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

Re (450)> Re (590)> Re (650) (d)

Here, the flat wavelength dispersion means that the following expression (e) is satisfied. The number in parentheses is the measurement wavelength (unit: nm) of the phase difference value. ≒ indicates that the relative difference from Re (590) is 10% or less.

Re (450) ≒ Re (590) ≒ Re (650) (e)

  In the present invention, the retardation value of the λ / 4 plate may be a retardation value Re of 120 nm to 160 nm at a measurement wavelength of 590 nm.

  In the present invention, when a film made of a polycarbonate resin or a liquid crystal composition is used, the Nz coefficient of the λ / 4 plate is preferably in the range of 0.8 to 1.2. More preferably, it is in the range of 0.95 to 1.05. When a film made of a polystyrene resin is used, the Nz coefficient is preferably in the range of -0.5 to 0.5. More preferably, it is in the range of -0.2 to 0.2. When a film made of a cyclic polyolefin-based resin is used, it is preferably in the range of 0.8 to 2.0. More preferably, it is in the range of 0.95 to 1.8.

  An appropriate additive may be blended in the positive A plate as long as the transparency is not impaired. Additives include, for example, 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, fungicides and the like. A plurality of these additives may be used in combination.

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

  As a method of forming a film from the above resin, any optimal method may be appropriately selected. For example, a resin dissolved in a solvent is cast on a metal band or drum, and the solvent is dried and the solvent is cast to obtain a film by removing the solvent.The resin is heated to its melting temperature or higher, kneaded and extruded from a die. For example, a melt extrusion method of 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 co-extruded.

  It is preferable to carry out a stretching treatment in order to give a predetermined retardation value to the film thus formed. For stretching, any suitable 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 of a nematic phase (nematic liquid crystal). The mechanism for expressing the liquid crystallinity of the liquid crystal material may be lyotropic or thermotropic. The alignment state of the liquid crystal material is preferably a 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.

  The positive A plate is preferably a cured layer of a liquid crystal material. Specifically, when the liquid crystal material is a liquid crystal monomer, it is preferably a polymerizable monomer and / or a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking the liquid crystal monomer. After the liquid crystal monomer is oriented, 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, a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to the liquid crystal compound does not occur. As a result, the retardation layer can be a layer having excellent stability, which is not affected by a change in temperature.

  Any appropriate liquid crystal monomer can be employed as the liquid crystal monomer. For example, polymerizable mesogen compounds described in JP-T-2002-533742 (WO 00/37585), EP 358208 (US Pat. No. 5,211,877), EP 66137 (US Pat. No. 4,388,453), WO 93/22397, EP 0261712, DE195504224, DE44040817, GB2280445 and the like can be used. Specific examples of such a polymerizable mesogen compound include, for example, trade name LC242 of BASF, trade name E7 of Merck, and trade name LC-Silicon-CC3767 of Wacker-Chem.

  The temperature range in which the liquid crystal monomer exhibits liquid crystal properties varies depending on the 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 liquid crystal cured 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 in which optical anisotropy is developed by coating and orientation of the liquid crystal composition. For example, there is a method in which an alignment treatment is performed on the surface of a base film such as a polyethylene terephthalate film, and the liquid crystal composition is applied to the surface to form a liquid crystal cured layer. Any appropriate orientation treatment can be adopted as the orientation treatment. Specifically, a mechanical alignment treatment, a physical alignment treatment, and a chemical alignment treatment may be mentioned. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include a magnetic field orientation treatment and an electric field orientation treatment. Specific examples of the chemical alignment treatment include an oblique deposition method and a photo-alignment treatment. Preferably, it is a rubbing treatment. The orientation treatment may be performed directly on the surface of the base 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 film. It may be applied to an alignment film. When a rubbing treatment is performed, it is preferable to perform the rubbing treatment directly on the surface of the base film.

  The alignment direction of the alignment treatment can be set according to the desired angle. By performing the orientation treatment, the liquid crystal material can be oriented in accordance with the orientation direction of the substrate film, so that the slow axis of the formed liquid crystal cured layer becomes substantially the same as the orientation direction of the substrate film. Therefore, for example, when the polarizer 32 (elongated) has an absorption axis in its longitudinal direction, the orientation treatment is performed in a direction at an angle of about 135 ° with respect to the longitudinal direction of the substrate (elongated). By forming the cured liquid crystal layer in this manner, the polarizer 32 (polarizing plate) and the positive A plate 34 can be continuously laminated on a roll-to-roll basis. As a result, the manufacturing process can be significantly reduced.

  The liquid crystal composition can be typically obtained by dissolving or dispersing the liquid crystal material in a solvent. As the solvent, any appropriate solvent can be adopted depending on the type of the liquid crystal material and the like. Specific examples include toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve. These solvents can be used alone or in combination of two or more.

  The content of the liquid crystal material in the liquid crystal composition can be appropriately set according to the type of the liquid crystal material, the thickness of a target layer, and the like. The content of the liquid crystal material is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and most preferably 15 to 30% by weight.

  The liquid crystal composition may further contain any appropriate additive as needed. Specific examples of the additive include a polymerization initiator and a crosslinking agent. These are particularly preferably used when a liquid crystal monomer is used as the liquid crystal material. Specific examples of the polymerization initiator include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Specific examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate crosslinking agent. These may be used alone or in combination of two or more. Further, specific examples of the additives include an antioxidant, a denaturant, a surfactant, a dye, a pigment, a discoloration inhibitor, and an ultraviolet ray blocking agent. These may be used alone or in combination of two or more. Examples of the anti-aging agent include phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds. Examples of the modifying agent include glycols, silicones and alcohols. The surfactant is used, for example, to smooth the surface of the optical film, and specific examples thereof include silicone-based, acrylic-based, and fluorine-based surfactants.

Any appropriate method can be adopted as a method for applying the liquid crystal composition. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, a spray coating method, and the like. The coating amount of the liquid crystal composition can be appropriately set according to the concentration of the coating liquid, the thickness of the target layer, and the like. For example, when the liquid crystal material concentration of the liquid crystal composition is 20% by weight, the coating amount is preferably 0.03 to 0.17 ml, more preferably 0.05 to 0.1, per area (100 cm ² ) of the transparent protective film. 0.15 ml, most preferably 0.08-0.12 ml.

  Next, the liquid crystal material is oriented according to the orientation direction of the substrate film surface. The alignment of the liquid crystal material is performed by processing at a temperature at which the liquid crystal material to be used exhibits a liquid crystal phase. By performing such a temperature treatment, the liquid crystal material assumes a liquid crystal state, and the liquid crystal material is oriented according to the orientation direction of the substrate surface. Thereby, birefringence occurs in the layer (coating layer) formed by coating, and a liquid crystal cured layer is formed.

  The temperature of the temperature treatment can be appropriately determined according to the type of the liquid crystal material. Preferably it is 40-120 degreeC, More preferably, it is 50-100 degreeC, Most preferably, it is 60-90 degreeC. The processing time of the temperature treatment is preferably 30 seconds or more, more preferably 1 minute or more, particularly preferably 2 minutes or more, and most preferably 4 minutes or more. When the processing time is shorter than 30 seconds, the liquid crystal material may not sufficiently take a liquid crystal state. On the other hand, the processing time is preferably 10 minutes or less, more preferably 8 minutes or less, and most preferably 7 minutes or less. If the treatment time exceeds 10 minutes, the additive may sublime.

When a liquid crystal monomer is used as the liquid crystal material, it is preferable that the coating layer is further subjected to a polymerization treatment or a crosslinking treatment. By performing the polymerization treatment, the liquid crystal monomer is polymerized, and the liquid crystal monomer is fixed as a repeating unit of the polymer molecule. By performing the crosslinking treatment, the liquid crystal monomer forms a three-dimensional network structure, and the liquid crystal monomer is fixed as a part of the crosslinked structure. As a result, the alignment state of the liquid crystal material is fixed. A polymer or a three-dimensional network structure formed by polymerizing or crosslinking a liquid crystal monomer is “non-liquid crystal”. Therefore, in the formed retardation layer, for example, a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to liquid crystal molecules does not occur. The specific procedure of the polymerization treatment or the crosslinking treatment can be appropriately selected depending on the type of the polymerization initiator or the crosslinking agent used. For example, when a photopolymerization initiator or a photocrosslinking agent is used, light irradiation may be performed, and when an ultraviolet polymerization initiator or a UV crosslinking agent is used, ultraviolet irradiation may be performed. The irradiation time, irradiation intensity, total irradiation amount, and the like of light or ultraviolet light can be appropriately set according to the type of liquid crystal material, the type of substrate and the type of alignment treatment, the characteristics desired for the liquid crystal cured layer, and the like.

  Styrene resins are desirable in that they satisfy the relational expression of refractive index nz> nx ≧ ny, but are not suitable for use alone due to their brittleness. Therefore, in the present invention, a phase difference 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 surfaces of a core layer made of a styrene resin is used. Is preferred.

  The styrene-based resin constituting the core layer can be a homopolymer of styrene or a derivative thereof, or a binary or higher copolymer of styrene or a derivative thereof and another copolymerizable monomer. You can also. Here, the styrene derivative is a compound in which another group is bonded to styrene, for example, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, Alkyl styrene such as p-ethyl styrene, hydroxy styrene, tert-butoxy styrene, vinyl benzoic acid, o-chlorostyrene, p-chlorostyrene, hydroxyl group, alkoxy group, carboxyl group, halogen And the like. Ternary copolymers 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 resin of the core layer is preferably made of a heat-resistant resin, and its Tg is generally 100 ° C. or higher. The more preferable Tg of the styrene resin is 120 ° C. or higher.

  The core layer made of a styrene-based resin is desirably set to have a thickness of 10 to 100 μm. If the thickness is less than 10 μm, a sufficient retardation value may not be easily developed by stretching. On the other hand, if the thickness exceeds 100 μm, the impact strength of the film tends to be weak, and the change in retardation value due to external stress tends to be large, so that white spots and the like tend to occur when applied to a liquid crystal display device. , Display performance is apt to decrease.

The skin layers disposed 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 a (meth) acrylic resin.
Here, examples of the (meth) acrylic resin include a homopolymer of an alkyl methacrylate or an alkyl acrylate, and a copolymer of an alkyl methacrylate and an alkyl acrylate. Specific examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, and propyl acrylate. . As such a (meth) acrylic resin, those commercially available as general-purpose (meth) acrylic resins can be used. Some of the (meth) acrylic resins are referred to as impact-resistant (meth) acrylic resins, and other high heat-resistant (meth) acrylic resins having a glutaric anhydride structure or a lactone ring structure in the main chain. Also included is what is called.

  The rubber particles blended in the (meth) acrylic resin are preferably acrylic. The acrylic rubber particles are particles having a rubber elasticity obtained by polymerizing in the presence of a polyfunctional monomer, mainly containing an alkyl acrylate such as butyl acrylate or 2-ethylhexyl acrylate. Such rubber elastic particles may be formed in a single layer, or may be a multilayer structure having at least one rubber elastic layer. Acrylic rubber particles having a multilayer structure include particles having rubber elasticity as a nucleus as described above, and a periphery thereof covered with a hard alkyl methacrylate polymer, a hard alkyl methacrylate polymer. A core and its circumference covered with an acrylic polymer having rubber elasticity as described above, and the periphery of a hard core is covered with an acrylic polymer having rubber elasticity, and further around the hard rigid methacrylic acid Those covered with an alkyl ester-based polymer are exemplified. These rubber particles usually have an average diameter of particles formed in the elastic layer 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 state of mixing them, 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 less, and the preferred Tg is 120 ° C. or less, and more preferably 110 ° C. or less.

  It is desirable that the skin layer made of a (meth) acrylic resin composition containing rubber particles, preferably acrylic rubber particles, has a thickness of 10 to 100 μm. If the thickness is reduced to less than 10 μm, film formation tends to be difficult. On the other hand, when the thickness exceeds 100 μm, the retardation value of the (meth) acrylic resin layer tends to be not negligible.

  As described above, in the retardation film used in the present invention, the core layer made of a styrene-based resin preferably has a Tg of 120 ° C. or more, while a (meth) acrylic resin composition containing rubber particles is included. The Tg of the skin layer made of a material is preferably 120 ° C. or lower, more preferably 110 ° C. or lower. It is preferable that the Tg of the two does not overlap, and that the core layer made of the styrene resin has a higher Tg than the skin layer made of the (meth) acrylic resin composition containing the 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, it is also possible to use a method in which a single-layered film is produced, then heat-sealed by heat lamination, and stretched.

  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 usually have substantially the same thickness. With such a three-layer structure, the skin layer made of the (meth) acrylic resin composition containing the rubber particles functions as a protective layer, and has excellent mechanical strength and chemical resistance.

  The in-plane retardation is imparted to the retardation film configured as described above by stretching. The stretching can be performed by known longitudinal uniaxial stretching, tenter horizontal uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like, and may be performed so as to obtain a desired retardation value.

  For example, when the polarizer 32 (elongated) has an absorption axis in the longitudinal direction, the stretching treatment is performed so that the slow axis is in a direction of approximately 45 °. By doing so, 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 reduced.

  As the cyclic polyolefin-based resin, the same one as described above may be used. When used as a retardation film, in-plane retardation is imparted by stretching. The stretching can be performed by known longitudinal uniaxial stretching, tenter horizontal uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like, and may be performed so as to obtain a desired retardation value.

  For example, when the polarizer 32 (elongated) has an absorption axis in the longitudinal direction, the stretching treatment is performed so that the slow axis is in a direction of approximately 45 °. By doing so, the polarizer 32 (polarizing plate) and the positive A plate 34 can be continuously laminated on a roll-to-roll basis. As a result, the manufacturing process can be significantly reduced.

[Positive C plate 35]
In the present invention, when a λ / 4 plate 34 having an Nz coefficient of 0.5 or more is used, it is preferable to further use a positive C plate.

The positive C plate to be used in the present invention, n _x and n _y is referred to a retardation film having an optical axis in the film normal direction at substantially equal positive uniaxial. Expressed in refractive index, a phase difference film having the relationship of _{n x ≒ n y <n z} . nx ≒ ny includes the case where nx and ny are substantially equal, in addition to the case where nx and ny are completely equal. Specifically, if the difference between nx and ny is within 0.005, it can be said that nx and ny are substantially equal.

  The positive C plate 35 preferably has an in-plane retardation value Re of 20 nm or less at a wavelength of 590 nm, more preferably 10 nm or less. The retardation value Rth in the thickness direction is preferably -50 nm to -250 nm at a wavelength of 590 nm. More preferably, it is -70 nm to -200 nm.

  The material and form of the positive C plate 35 are not particularly limited as long as it has the above-mentioned optical characteristics. For example, a retardation film made of a birefringent polymer film, a retardation film having a retardation layer formed by applying or transferring a low-molecular or high-molecular liquid crystalline compound on a transparent support, and the like are used. be able to. In addition, they can be used by laminating them.

A retardation film made of a birefringent polymer film having the above-mentioned optical properties is obtained by bonding a heat-shrinkable film and applying a predetermined tension while heating, and stretching the polymer film in the thickness direction of the film. It can be easily formed by a method of applying and drying a system polymer. Further, as the retardation layer formed from the liquid crystal compound having the above optical characteristics, a cholesteric discotic liquid crystal compound containing a chiral structural unit is formed by orienting the helical axis substantially perpendicular to the substrate and then fixing the cholesteric discotic liquid crystal compound. And a layer formed by aligning a rod-shaped liquid crystal compound having a positive refractive index anisotropy substantially perpendicularly to a substrate and then fixing the same. 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 exhibiting the above-mentioned optical characteristics. Further, the retardation layer may be configured so that the above-mentioned optical characteristics are satisfied by the entire laminate of the support and the retardation layer. As the rod-like liquid crystal compound to be used, a compound having a nematic liquid crystal phase, a smectic liquid crystal phase, and a lyotropic liquid crystal phase within a temperature range in which the alignment is fixed is suitably used. A liquid crystal exhibiting a smectic A phase and a B phase capable of obtaining 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, in a proper alignment temperature range, for a rod-like liquid crystal compound that is in the above liquid crystal state, a layer is formed using a composition containing the additive and the rod-like liquid crystal compound. Is also preferred.

Examples of the rod-shaped liquid crystalline compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines , Phenyldioxane, tolan and alkenylcyclohexylbenzonitrile are preferably used. Not only low molecular liquid crystal molecules as described above but also high molecular liquid crystal molecules can be used. As the liquid crystal molecules, those having a partial structure capable of causing a polymerization or a crosslinking reaction by actinic rays, electron beams, heat, or the like are suitably used. The number of the partial structures is 1 to 6, preferably 1 to 3.

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

  The retardation layer formed from the rod-shaped liquid crystalline compound is produced by applying and orienting a liquid crystal composition to develop optical anisotropy and curing, similarly to the method for producing a positive A plate using a liquid crystal material. can do.

  In the present invention, a positive C plate layer formed from a liquid crystalline compound may be formed on the positive A plate.

[Brightness improving film 61]
The brightness enhancement film 61 is also called a reflective polarizer, and uses a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmitted polarized light, reflected polarized light, or scattered polarized light. As described above, by arranging the brightness enhancement film 61 on the polarizing plate 50, it is possible to improve the emission efficiency of 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. Can be.

  The brightness enhancement film 61 can be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example is 3M DBEF ( JP-A-4-268505). Another example of the anisotropic reflective 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 (JP-A-11-231130). Still another example of the anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer that applies fine processing to metal and emits reflected polarized light even in the visible light region (US Patent No. 6288840), and a film obtained by adding metal fine particles into a polymer matrix and stretching the film (Japanese Patent Application Laid-Open No. 8-184701).

  An optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, and a retardation layer having a retardation value of １ ／ wavelength may be provided on the surface of the brightness enhancement film 61 opposite to the polarizing plate 50. Good. The formation of the optical layer can improve the adhesion to the backlight tape and the uniformity of the displayed image. The thickness of the brightness enhancement 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 making the polarizing plate thinner.

[Adhesion of each layer]
Any appropriate pressure-sensitive adhesive layer or adhesive layer is provided between the members constituting the polarizing plate of the present invention. For example, an adhesive layer is provided for attaching a polarizing plate to a liquid crystal cell.

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

  In the present invention, as the driving mode of the liquid crystal cell, an IPS (In-Plane Switching) mode having an in-plane phase difference value of 100 to 200 nm at a wavelength of 590 nm is employed. By setting the front phase difference value close to the λ / 4 wavelength in this way, it is possible to arrange a circularly polarizing plate on the viewing side polarizing plate, and it is possible to greatly reduce the reflection of external light.

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

[Liquid crystal display]
The liquid crystal display of the present invention includes a liquid crystal panel. In the liquid crystal panel, the set of the polarizing plates is bonded to the liquid crystal cell. The set of polarizing plates 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 strong. When used for small and medium-sized applications, the size of the viewing-side polarizing plate and the back-side polarizing plate constituting the set of polarizing plates can be 15 inches or less on a diagonal.

  The axis configuration of the liquid crystal display device of the present invention will be described with reference to FIG. For convenience of description, the initial alignment direction of the liquid crystal cell used in the present invention is defined as 0 °, and when viewing the rear-side polarizing plate 20 from the viewing-side polarizing plate 10, the counterclockwise angle is defined as positive. Will be explained. The slow axis of the positive A plate 34 is arranged at approximately 90 °. Further, it is preferable that the absorption axis of the viewing side polarizing plate 10 is arranged at about -45 ° and the absorption axis of the back side polarizing plate 20 is arranged at about 45 °. The slow axis of the retardation film 36 is arranged at -45 ° or 45 °. Here, when the angle is substantially described, it indicates that the value is within the range of ± 5 °.

  In other words, the absorption axis of the viewing-side polarizing plate is orthogonal to the absorption axis of the back-side polarizing plate. The angle between the absorption axis of the viewing side polarizing plate and the slow axis of the positive A plate is approximately 45 °. The angle between the absorption axis of the viewing side polarizing plate and the slow axis of the retardation film is substantially parallel or substantially orthogonal.

  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 where no driving voltage is applied to the liquid crystal cell.

  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 percentages representing the content or amount used are based on weight unless otherwise specified. As for the angle, the counterclockwise direction is positive. The phase difference value means a value at a wavelength of 590 nm unless otherwise specified. In addition, the measurement of each physical property in the following examples was performed by the following method.

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

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

[Production Example 1] Production of polarizer A polyvinyl alcohol film having a thickness of 30 µm (average degree of polymerization: about 2400, degree of saponification of 99.9 mol% or more) was uniaxially stretched about 4 times by dry stretching, and the tension was further maintained. After being immersed in pure water at 40 ° C. for 40 seconds, the dyeing treatment is performed by immersing in an aqueous solution of iodine / potassium iodide / water having a weight ratio of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds. Was. Then, it was immersed in an aqueous solution of potassium iodide / boric acid / water having a weight ratio of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after being washed with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption polarizer having a thickness of 12 μm was obtained. When the contraction force in the absorption axis direction of the obtained polarizer was measured, it was 2.0 N per 2 mm in width.

[Production Example 2] Preparation of water-based adhesive 3 parts by weight of a 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) was added. Thus, an aqueous adhesive was prepared.

[Adhesive A, B]
The following two types of pressure-sensitive adhesives A: 25 μm-thick sheet-like pressure-sensitive adhesive [“P-3132” manufactured by Lintec Corporation]
Adhesive B: 5 μm thick sheet adhesive [“NCF # L2” manufactured by Lintec Corporation]
Was prepared.

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

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

[Preparation of retardation film]
Retardation film 1: Cyclic polyolefin resin film manufactured by Zeon Corporation; ZT12 series (in-plane retardation value: 90.2 nm, retardation value in thickness direction: 79 nm) and retardation film 2: Styrene manufactured by Zeon Corporation A series resin-containing film; ZI04 series (in-plane retardation value: 60.7 nm, retardation value in thickness direction −91.1 nm) was prepared. The pressure-sensitive adhesive B was bonded to the retardation film 1. At this time, a corona treatment was performed on the bonding surfaces of the retardation film 1 and the adhesive B. Next, the retardation film 2 was bonded to the surface of the adhesive B opposite to the surface on which the retardation film 1 was laminated. Also in this case, the corona treatment was performed on the bonding surfaces of the retardation film 2 and the adhesive B. Upon lamination, the retardation films 1 and 2 were laminated so that the slow axes of the retardation films 1 and 2 were parallel. Thus, a retardation film was produced.

[Preparation of λ / 4 plate 1]
A polyvinyl alcohol film (0.1 μm in thickness) was formed on the surface of a substrate film (triacetyl cellulose film, 80 μm in thickness). Using a rubbing cloth, the surface of the polyvinyl alcohol film was rubbed in a direction at -45 ° with respect to the longitudinal direction of the substrate to produce a base film provided with 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 907, benzotriazole-based ultraviolet light) 0.5 g of an absorbent (containing 1% of an absorbent) was dissolved in 40 g of toluene to prepare a coating liquid. Then, the coating liquid was applied to the surface of the alignment film obtained above by a bar coater, and then heated and dried at 90 ° C. for 2 minutes to align the liquid crystal. 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 alignment film. The thickness of the obtained retardation layer was 1 μm, and the in-plane retardation value Re (590) was 139.8 nm.

[Preparation of λ / 4 plate 2]
A styrene-maleic anhydride-based copolymer resin (“Dylark (registered trademark) D332” (Tg = 131 ° C.) manufactured by Nova Chemical Co., Ltd.) is used as a core layer, and about 20% of acrylic rubber particles having an average particle size of 200 μm are compounded. The methacrylic resin (the resin (Tg = 105 ° C.) used for “Technoloy (registered trademark) (registered trademark) S001” manufactured by Sumitomo Chemical Co., Ltd.) is used as a skin layer, and three layers are co-extruded. A three-layer resin film having a layer thickness of 60 μm and a skin layer having a thickness of 72 μm on each side was obtained. This three-layer resin film was stretched twice at 142 ° C. to obtain a negative retardation film having an in-plane retardation value of 140 nm and an Nz coefficient of 0.0.

[λ / 4 plate 3, 4]
As the λ / 4 plate 3, a cyclic polyolefin-based resin film manufactured by Zeon Corporation; ZD12 series (in-plane retardation value: 140.1 nm, Nz coefficient: 1.1) was prepared.
As the λ / 4 plate 4, a cyclic polyolefin-based resin film manufactured by Zeon Corporation; ZD12 series (in-plane retardation value: 140.8 nm, Nz coefficient: 1.62) was prepared.

[Preparation of positive C plate 1]
A commercially available vertical alignment film (JALS-204R, manufactured by Nippon 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 ). The coating film was immediately dried with hot air at 120 ° C. for 120 seconds to obtain an alignment film.

Next, 3.8 g of the following rod-shaped liquid crystal compound, 0.06 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy), 0.02 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.), and the following air: A solution was prepared by dissolving 0.002 g of the interface side vertical alignment agent in 9.2 g of methyl ethyl ketone. This solution was applied on an alignment film with a wire bar, and heated at 100 ° C. for 2 minutes to align the rod-shaped liquid crystal compound. Next, UV irradiation was performed at 80 ° C. for 20 seconds using a 120 W / cm ² high pressure mercury lamp to polymerize the rod-shaped liquid crystal compound. Thereafter, the resultant was allowed to cool to room temperature to produce 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 Rth (590) in the thickness direction was −109.4 nm.

Rod-shaped liquid crystal compound:

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

[Preparation of positive C plates 2 to 8]
Positive C plates 2 to 8 were produced in the same manner as the positive C plate 1. The retardation value was controlled by adjusting the thickness.

Retardation value Rth (590) of positive C plate 2 in the thickness direction = −91.2 nm,
Retardation value Rth (590) of positive C plate 3 in the thickness direction = −69.1 nm,
The retardation value Rth (590) in the thickness direction of the positive C plate 4 = -99.2 nm,
Retardation value Rth (590) of positive C plate 5 in the thickness direction = -122.6 nm,
The retardation value Rth (590) in the thickness direction of the positive C plate 6 = -161.4 nm,
Retardation value Rth (590) of positive C plate 7 in the thickness direction = −180.1 nm,
Retardation value Rth (590) of positive C plate 8 in the thickness direction = −203.7 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. The protective film A, the polarizer, and the protective film C are adhered 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 become the bonding surfaces with the polarizer. Plate A was obtained. The layer constitution of the polarizing plate A was protective film A / polarizer / protective film C.

[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. The protective film B, the polarizer, and the protective film C were adhered with an aqueous adhesive such that the corona-treated surfaces of the protective films B and C became the surfaces to be bonded to the polarizer. The adhesive B was bonded to the protective film B side. At this time, the surface to which the protective film B and the adhesive B were bonded was subjected to corona treatment. Finally, the brightness enhancement film A was bonded to the surface of the pressure-sensitive adhesive B to obtain a polarizing plate B. The layer constitution of the polarizing plate B was protective film C / polarizer / protective film B / adhesive layer B / brightness improving film A.

[Production of pseudo liquid crystal cell]
Two sheets of a non-alkali glass manufactured by Corning: Eagle XG (0.7 mm thick, 157 mm long × 98 mm wide) bonded with an adhesive B were prepared. Next, the λ / 4 plate 1 prepared above was bonded to the surface of the adhesive B on one glass. Finally, one side of the λ / 4 plate and the surface of the pressure-sensitive adhesive B on the other glass were bonded to produce a pseudo liquid crystal cell. When laminating each layer, corona treatment was performed on the laminating surface. The layer configuration of the pseudo liquid crystal cell was glass / adhesive B / λ / 4 plate 1 / adhesive B / glass. The λ / 4 plate 1 was manufactured such 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 ° with respect to the long side direction of the glass, and the pseudo liquid crystal cell is a liquid crystal cell when a driving voltage is applied (white display). I assume.

[Backlight]
Google Inc. The liquid crystal panel was taken out from Nexus7 manufactured by Nissan Corp., and the rest was used as a backlight.

[Example 1]
(Preparation of viewing side polarizing plate 1)
The pressure-sensitive adhesive B was bonded to the protective film C of the polarizing plate A. Next, a retardation film was laminated on the adhesive B surface such that the retardation film 1 side was the adhesive B side. The angle between the absorption axis of the polarizing plate and the slow axis of the retardation film was 90 °. Next, the pressure-sensitive adhesive B was bonded to the surface of the retardation film.
The λ / 4 plate 1 was laminated on the adhesive B surface. The angle between the absorption axis of the polarizing plate and the slow axis of the λ / 4 plate 1 is 45 ° (when viewing the protection film C from the protection film A, the slow axis of the λ / 4 plate 1 45 ° clockwise from the axis).
Further, the adhesive B was bonded to one surface of the λ / 4 plate. Next, the positive C plate 1 was bonded to the adhesive B surface.
Finally, the adhesive A was bonded to one surface of the positive C plate. Thus, the viewing side polarizing plate 1 was produced. When laminating each layer, corona treatment was performed on the lamination surface. The layer configuration of the viewing side polarizing plate 1 is as follows: protective film A / polarizer / protective film C / adhesive B / retardation film / adhesive B / λ / 4 plate 1 / adhesive B / positive C plate 1 / adhesive A.

(Preparation of back side polarizing plate 1)
The pressure-sensitive adhesive A was bonded to the surface of the protective film C of the polarizing plate B to prepare a rear-side polarizing plate 1. At this time, the surface of the protective film C and the surface to which the pressure-sensitive adhesive A was bonded were subjected to corona treatment.

  The viewing-side polarizing plate 1 and the rear-side polarizing plate 1 were cut into a size of 155 mm (length) × 96 mm (width). At this time, when each polarizing plate is viewed with the surface of the protective film A or the protective film B as the upper surface, the absorption axis of the polarizing plate is 90 ° with respect to the long side direction, and the viewing side polarizing plate 1 is 90 ° with respect to the long side direction. It was cut so as to be 0 °.

On one of the glass surfaces of the fabricated pseudo liquid crystal cell, using Zebra Co., Ltd. Hi-Mackey Blue (MO-150-MC-BL), shokupanman (animation produced by Nippon Television Network Co., Ltd. A portrait of a friend of justice with a bread-shaped head that appeared in the book, author: Takashi Yanase).

  The viewing-side polarizing plate 1 was bonded to the glass surface of the pseudo liquid crystal cell on which the portrait of Shokupanman was drawn, and the rear polarizing plate 1 was bonded to the opposite glass surface to produce a pseudo liquid crystal panel. The axial configuration of each layer was the axial configuration shown in FIG.

  The pseudo liquid crystal panel produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 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 produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 3]
A pseudo liquid crystal panel was manufactured 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 produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 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 produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under external light in the frontal direction and in an oblique field of view (at an azimuth angle of 135 ° and a polar angle of 60 °).

[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 produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 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 produced in this manner was placed on a backlight, and it was confirmed whether Shokupanman was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 7]
(Preparation of viewing side polarizing plate 2)
The pressure-sensitive adhesive B was bonded to the protective film C of the polarizing plate A. Next, a retardation film was laminated on the adhesive B surface such that the retardation film 1 side was the adhesive B side. The angle between the absorption axis of the polarizing plate and the slow axis of the retardation film was 90 °. Next, the pressure-sensitive adhesive B was bonded to the surface of the retardation film.
Next, the λ / 4 plate 2 was laminated on the adhesive B surface. The angle between the absorption axis of the polarizing plate and the slow axis of the λ / 4 plate 2 is 45 ° (when viewing the protection film C from the protection film A, the slow axis of the λ / 4 plate 2 45 ° clockwise from the axis).
Further, an adhesive A was bonded to two surfaces of the λ / 4 plate. Thus, the viewing side polarizing plate 2 was produced. When laminating each layer, corona treatment was performed on the lamination surface. The layer configuration of the viewing side polarizing plate 2 was protective film A / polarizer / protective film C / adhesive B / retardation film / adhesive B / λ / 4 plate 2 / adhesive A.

  The prepared viewing side polarizing plate 2 and back side polarizing plate 1 were cut into a size of 155 mm (length) × 96 mm (width). At this time, when each polarizing plate is viewed with the protective film A or the protective film B surface as the upper surface, the absorption axis of the polarizing plate is 90 ° with respect to the long side direction, the viewing-side polarizing plate 2 is 90 °, and the back-side polarizing plate 1 is It was cut so as to be 0 °.

On one glass surface of the fabricated pseudo liquid crystal cell, using a high Mackie blue (MO-150-MC-BL) manufactured by Zebra Corporation, Mr. Batako (animation produced by Nippon Television Network Co., Ltd. "Soreike! Anpanman") A portrait of a fairy who works at the appearing bakery, author: Takashi Yanase).

  A viewing-side polarizing plate 2 was bonded to a glass surface on which a portrait of Mr. Batako of the pseudo-liquid crystal cell was drawn, and a rear-side polarizing plate 1 was bonded to the opposite glass surface to produce a pseudo liquid crystal panel. The axial configuration of each layer was the axial configuration shown in FIG.

  The pseudo liquid crystal panel produced in this manner was placed on a backlight, and it was confirmed whether Mr. Batako could visually recognize the panel. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 8]
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 produced in this manner was placed on a backlight, and it was confirmed whether Mr. Batako could visually recognize the panel. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 9]
(Preparation of viewing side polarizing plate 3)
The pressure-sensitive adhesive B was bonded to the protective film C of the polarizing plate A. Next, a retardation film was laminated on the adhesive B surface such that the retardation film 1 side was the adhesive B side. The angle between the absorption axis of the polarizing plate and the slow axis of the retardation film was 90 °. Next, the pressure-sensitive adhesive B was bonded to the surface of the retardation film.
Next, the λ / 4 plate 3 was laminated on the adhesive B surface. The angle between the absorption axis of the polarizing plate and the slow axis of the λ / 4 plate 3 is 45 ° (when viewing the protection film C from the protection film A, the slow axis of the λ / 4 plate 3 45 ° clockwise from the axis).
Further, the adhesive B was bonded to the three surfaces of the λ / 4 plate. Next, the positive C plate 1 was bonded to the adhesive B surface.
Finally, the adhesive A was bonded to one surface of the positive C plate. Thus, the viewing side polarizing plate 3 was produced. When laminating each layer, corona treatment was performed on the lamination surface. The layer configuration of the viewing side polarizing plate 3 is as follows: protective film A / polarizer / protective film C / adhesive B / retardation film / adhesive B / λ / 4 plate 3 / adhesive B / positive C plate 1 / adhesive Layer A.

  The prepared viewing side polarizing plate 3 and back side polarizing plate 1 were cut into a size of 155 mm (length) × 96 mm (width). At this time, when each polarizing plate is viewed with the protective film A or the protective film B surface as the upper surface, the absorption axis of the polarizing plate is 90 ° with respect to the long side direction, the viewing-side polarizing plate 3 is 90 °, and the back-side polarizing plate 1 is It was cut so as to be 0 °.

Melonpanna-chan (Nippon Television Network Co., Ltd.'s animation "Soreike! Anpanman") was used on one glass surface of the fabricated pseudo liquid crystal cell using Hi-Mackey Blue (MO-150-MC-BL) manufactured by Zebra Corporation. A portrait of a justice ally with a melon-pan head appearing, author: Takashi Yanase).

  The viewing-side polarizing plate 3 was bonded to the glass surface of the pseudo-liquid crystal cell on which the portrait of Melonpanna-chan was drawn, and the rear-side polarizing plate 1 was bonded to the opposite glass surface to produce a pseudo liquid crystal panel. The axial configuration of each layer was the axial configuration shown in FIG.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. When visibility was confirmed under external light in a frontal direction and an oblique field of view (at an azimuth angle of 135 ° and a polar angle of 60 °), the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 10]
A pseudo liquid crystal panel was produced in the same manner as in Example 9 except that the positive C plate 1 was changed to the positive C plate 4.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 11]
A pseudo liquid crystal panel was produced in the same manner as in Example 9, except that the positive C plate 1 was changed to the positive C plate 5.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 12]
A pseudo liquid crystal panel was produced in the same manner as in Example 9, except that the protective film A of the viewing side polarizing plate 3 was changed to the protective film D.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 13]
A pseudo liquid crystal panel was produced in the same manner as in Example 12, except that the positive C plate 1 was changed to the positive C plate 4.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 14]
A pseudo liquid crystal panel was produced in the same manner as in Example 12, except that the positive C plate 1 was changed to the positive C plate 5.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Melonpanna could be visually recognized. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 15]
(Preparation of Viewing Side Polarizing Plate 4)
The pressure-sensitive adhesive B was bonded to the protective film C of the polarizing plate A. Next, a retardation film was laminated on the adhesive B surface such that the retardation film 1 side was the adhesive B side. The angle between the absorption axis of the polarizing plate and the slow axis of the retardation film was 90 °. Next, the pressure-sensitive adhesive B was bonded to the surface of the retardation film.
Next, the λ / 4 plate 4 was laminated on the surface of the pressure-sensitive adhesive B. The angle between the absorption axis of the polarizing plate and the slow axis of the λ / 4 plate 4 is 45 ° (when viewing the protection film C from the protection film A, the slow axis of the λ / 4 plate 4 45 ° clockwise from the axis).
Further, an adhesive B was bonded to four surfaces of the λ / 4 plate. Next, the positive C plate 6 was bonded to the adhesive B surface.
Finally, the adhesive A was stuck on the surface of the positive C plate 6. Thus, the viewing side polarizing plate 4 was produced. When laminating each layer, corona treatment was performed on the lamination surface. The layer configuration of the viewing side polarizing plate 4 is as follows: protective film A / polarizer / protective film C / adhesive B / retardation film / adhesive B / λ / 4 plate 4 / adhesive B / positive C plate 6 / adhesive Layer A.

  The prepared viewing side polarizing plate 4 and back side polarizing plate 1 were cut into a size of 155 mm (length) × 96 mm (width). At this time, when each polarizing plate is viewed with the protective film A or the protective film B surface as the upper surface, the absorption axis of the polarizing plate is 90 ° with respect to the long side direction, the viewing-side polarizing plate 4 is 90 °, and the back-side polarizing plate 1 is. It was cut so as to be 0 °.

On one of the glass surfaces of the fabricated pseudo liquid crystal cell, using Zebra Corporation Hi-Mackey Blue (MO-150-MC-BL), Kavao-kun (animation produced by Nippon Television Network Co., Ltd. I drew a portrait of a hippo boy who goes to the school that appeared, the original author: Takashi Yanase).

  The viewing-side polarizing plate 4 was bonded to the glass surface of the pseudo liquid crystal cell on which a portrait of Kavao-kun was drawn, and the rear polarizing plate 1 was bonded to the opposite glass surface to produce a pseudo liquid crystal panel. The axial configuration of each layer was the axial configuration shown in FIG.

  The pseudo liquid crystal panel produced in this manner was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 16]
A pseudo liquid crystal panel was produced in the same manner as in Example 15 except that the positive C plate 6 was changed to the positive C plate 7.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 17]
A pseudo liquid crystal panel was produced in the same manner as in Example 15 except that the positive C plate 6 was changed to the positive C plate 8.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 7,500 Lux.

[Example 18]
A pseudo liquid crystal panel was produced in the same manner as in Example 15, except that the protective film A of the viewing side polarizing plate 3 was changed to the protective film D.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 19]
A pseudo liquid crystal panel was produced in the same manner as in Example 18, except that the positive C plate 6 was changed to the positive C plate 7.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under the external light in the front direction and in the oblique visual field (at an azimuth angle of 135 ° and a polar angle of 60 °). As a result, the visibility was good even when the illuminance of the external light was 10,000 Lux.

[Example 20]
A pseudo liquid crystal panel was produced in the same manner as in Example 18, except that the positive C plate 6 was changed to the positive C plate 8.

  The pseudo liquid crystal panel thus produced was placed on a backlight, and it was confirmed whether Cavao-kun was visible. The visibility was confirmed under external light in the frontal direction and in an oblique field of view (at an azimuth angle of 135 ° and a polar angle of 60 °).

[Comparative Example 1]
Google Inc. Nexus7 (registered trademark) Nishokupanman and Dokin-chan (a girl who falls in love with Shokupanman from Nippon Television Network Co., Ltd.'s anime "Soreike! Anpanman", author: Takashi Yanase) It was confirmed that it was visible under light. As a result, when the illuminance of the external light was 5000 Lux, the visibility was significantly reduced even in the front, making it difficult to identify the image. In addition, Google Inc. The upper and lower polarizers were separated from a Nexus 7 (registered trademark) liquid crystal panel, and the in-plane retardation value of the liquid crystal cell was measured. The in-plane retardation value was 355 nm at a wavelength of 590 nm.

REFERENCE SIGNS LIST 1 absorption axis of viewing side polarizing plate 2 slow axis of retardation film 3 slow axis of positive A plate 4 initial alignment direction of liquid crystal cell 5 absorption axis of back side polarizing plate 10 viewing side polarizing plate 20 back side polarizing plate 30 Polarizing plate 36 Phase difference film 34 Positive A plate 35 Positive C plate 50 Polarizing plate 61 Brightness improving film 32, 52 Polarizer 31a, 31b, 51a, 51b Protective film 37 Surface treatment layer

Claims (5)

It is a set of polarizing plates used for forming a liquid crystal panel, which comprises a viewing side polarizing plate and a back side polarizing plate, and is bonded to both surfaces of the liquid crystal cell, respectively.
The liquid crystal cell is 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 is orthogonal to the absorption axis of the back-side polarizing plate,
The viewing side polarizing plate includes a positive A plate between a polarizer and a liquid crystal cell, and an angle between an absorption axis of the viewing side polarizing plate and a slow axis of the positive A plate is approximately 45 °,
The viewing side polarizing plate includes a retardation film between the polarizer and the positive A plate, the angle between the absorption axis of the viewing side polarizing plate and the slow axis of the retardation film is substantially parallel or substantially parallel. Orthogonal
A set of polarizing plates, wherein the slow axis of the positive A plate and the initial alignment direction of the IPS mode liquid crystal cell are substantially orthogonal.   The set of polarizing plates according to claim 1, further comprising a positive C plate between the liquid crystal cell and the positive A plate.   The set of polarizing plates according to claim 2, wherein a retardation value in a thickness direction of the positive C plate is from -50 nm to -250 nm.   An IPS mode liquid crystal display device comprising the IPS mode liquid crystal cell having an in-plane retardation value of 100 nm to 200 nm, wherein the set of polarizing plates according to claim 1 is arranged.   5. The IPS mode liquid crystal display device according to claim 4, wherein the IPS mode liquid crystal display device is for small and medium sized devices.

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