JP2012145735A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device showing high contrast in a frontal direction, and to provide a thin and inexpensive liquid crystal panel capable of giving the liquid crystal display device.SOLUTION: The liquid crystal panel includes, successively from a viewing side, a first polarizing plate, an IPS (in-plane switching) mode liquid crystal cell, and a second polarizing plate. Each of the first polarizing plate and the second polarizing plate includes a polarizer. The first polarizing plate and/or the second polarizing plate include a protective layer laminated on a face opposite to the liquid crystal cell side of the polarizer. The polarizer satisfies the relationship of 0.030≤R≤0.040 where Ris expressed by R=nx-ny with nx representing a refractive index within a plane of the polarizer in a direction where the refractive index reaches the maximum at a wavelength of 1000 nm, and ny representing a refractive index in a direction perpendicular to the direction where the refractive index reaches the maximum.

Description

  The present invention relates to a liquid crystal panel and a liquid crystal display device.

  A liquid crystal display device (hereinafter referred to as LCD) is a device that displays characters and images using the electro-optical characteristics of liquid crystal molecules. The LCD normally uses a liquid crystal panel in which polarizing plates are arranged on both sides of the liquid crystal cell. For example, in the normally black method, a black image can be displayed in a state where no voltage is applied. The LCD has a problem that the contrast in the front and oblique directions is low.

  As a method of improving the front contrast of the liquid crystal display device, there is a method of improving the contrast of the polarizing plate, that is, the ratio of the single transmittance and the orthogonal transmittance of the polarizing plate. As a method for improving the contrast of the polarizing plate, a method using a polarizer obtained by stretching at a high stretch ratio is generally known. However, in such a polarizer, as the draw ratio is increased, stretch breakage or the like occurs, so that workability deteriorates and productivity is low.

  On the other hand, as the use of liquid crystal display devices expands, there is an increasing demand for thinning and low cost of liquid crystal display devices, and thinning and low cost of polarizing plates, which are essential components of liquid crystal display devices. Is desired. In order to meet such a demand, a polarizing plate in which a protective layer is provided only on one side of a polarizer has been proposed (Patent Document 1). However, since PVA polarizers are poor in mechanical properties and optical durability, in a polarizing plate provided with a protective layer only on one side, the dimensional change of the polarizer and deterioration of the optical characteristics are likely to occur. Such a problem is remarkable in a humidified environment.

Japanese Patent Laid-Open No. 10-186133

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a liquid crystal display device with high contrast in the front direction, and a thin and inexpensive liquid crystal capable of realizing the liquid crystal display device. To provide a panel.

The liquid crystal panel of the present invention includes a first polarizing plate, an IPS mode liquid crystal cell, and a second polarizing plate in this order from the viewing side, and the first polarizing plate and the second polarizing plate include: Each polarizer includes a polarizer, and the first polarizer and / or the second polarizer includes a protective layer laminated on a surface of the polarizer opposite to the liquid crystal cell, and the polarizer includes: 0.030 ≦ R _pva ≦ 0.040 is satisfied. Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny.
In a preferred embodiment, the dichroic ratio DR of the polarizer is 160 or more.
In a preferred embodiment, an antiglare layer is formed on the viewing side of the first polarizing plate.
In a preferred embodiment, a conductive treatment is performed on the liquid crystal cell side of the polarizer.
According to another aspect of the present invention, a liquid crystal display device is provided. This liquid crystal display device includes the above-described liquid crystal panel.

In the liquid crystal panel of the present invention, the contrast in the front direction can be improved by setting R _pva of the polarizer contained in the polarizing plate to 0.030 ≦ R _pva ≦ 0.040.

It is a schematic sectional drawing of the liquid crystal panel in preferable embodiment of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these specific embodiments.

<A. Overview of LCD panel>
FIG. 1 is a schematic cross-sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. The liquid crystal panel 100 includes a first polarizing plate 10, an IPS mode liquid crystal cell 20, and a second polarizing plate 10 ′ in this order from the viewing side. The first polarizing plate 10 includes a polarizer 11, and the second polarizing plate 10 ′ includes a polarizer 11 ′. The first polarizing plate 10 includes a protective layer 12 laminated on the surface of the polarizer 11 opposite to the liquid crystal cell 20, and the second polarizing plate 10 ′ includes the liquid crystal cell 20 of the polarizer 11 ′. Includes a protective layer 12 'laminated on the opposite surface. The protective layer may be included in only one of the first polarizing plate 10 and the second polarizing plate 10 ′ (preferably, the first polarizing plate 10 and the second polarizing plate as in the illustrated example). All of the plates 10 'include protective layers 12, 12'). Preferably, the absorption axis of the polarizer 11 included in the first polarizing plate 10 and the absorption axis of the polarizer 11 ′ included in the second polarizing plate 10 ′ are disposed so as to be substantially orthogonal. Practically, any appropriate adhesive layer (not shown) is disposed between the polarizers 11 and 11 ′ and the liquid crystal cell, and between the polarizers 11 and 11 ′ and the protective layers 12 and 12 ′. Is done.

  Preferably, as shown in FIG. 1, the protective layers 12 and 12 'are disposed only on one side of the polarizers 11 and 11'. With such a configuration, the influence of the retardation of the protective layer is small, and a decrease in transmittance due to interface reflection can be suppressed, so that desired optical characteristics can be easily adjusted. Further, the thickness of the polarizing plate can be reduced, and the liquid crystal display device can be thinned.

  In the liquid crystal panel of the present invention, an antiglare layer may be formed on the viewing side of the first polarizing plate. Preferably, the first polarizing plate includes a protective layer, and the antiglare layer is formed on the viewing side of the protective layer.

  The liquid crystal panel of the present invention may have a retardation layer between the first polarizing plate and the liquid crystal cell or between the second polarizing plate and the liquid crystal cell. Any appropriate retardation film can be used as the retardation layer. The optical properties (for example, refractive index ellipsoid), the number, the arrangement order when a plurality of retardation films are used, and the like can be appropriately selected depending on the purpose and application.

<B. Liquid crystal cell>
The liquid crystal cell preferably includes a pair of substrates and a liquid crystal layer as a display medium sandwiched between the pair of substrates. One substrate (active matrix substrate) includes a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal. Provided. The other substrate (color filter substrate) is provided with a color filter.

  The color filter may be provided on the active matrix substrate. Alternatively, when an RGB three-color light source (which may further include a multicolor light source) is used as the illumination means of the liquid crystal display device as in the field sequential method, the color filter can be omitted. The distance (cell gap) between the two substrates is controlled by a spacer. For example, an alignment film made of polyimide is provided on the side of each substrate in contact with the liquid crystal layer. Alternatively, for example, when the initial alignment of liquid crystal molecules is controlled using a fringe electric field formed by a patterned transparent electrode, the alignment film can be omitted.

  The driving mode of the liquid crystal cell is an in-plane switching (IPS) mode. The IPS mode uses voltage-controlled birefringence (ECB) effect to generate liquid crystal molecules that are homogeneously aligned in the absence of an electric field, for example, between a counter electrode and a pixel electrode formed of metal. The substrate is made to respond with an electric field parallel to the substrate (also called a transverse electric field). More specifically, for example, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol.2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), in the normally black method, the alignment direction of the liquid crystal cell when no electric field is applied is aligned with the absorption axis of the polarizer on one side, so that the upper and lower polarizing plates are If they are arranged orthogonally, the display is completely black without an electric field. When an electric field is present, the transmittance according to the rotation angle can be obtained by rotating the liquid crystal molecules while keeping them parallel to the substrate. The IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode using a V-shaped electrode or a zigzag electrode. Specific examples of the liquid crystal used in the IPS mode include nematic liquid crystal.

  The homogeneously aligned liquid crystal molecule refers to a liquid crystal molecule in which the alignment vector of the liquid crystal molecule is aligned in parallel and uniformly with respect to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecule. In the present specification, the case where the alignment vector is slightly inclined with respect to the substrate plane, that is, the case where the liquid crystal molecules have a pretilt is also included in the homogeneous alignment. When the liquid crystal molecules have a pretilt, the pretilt angle is preferably 20 ° or less from the viewpoint of maintaining high contrast and obtaining good display characteristics.

  As the nematic liquid crystal, any appropriate nematic liquid crystal can be adopted depending on the purpose. For example, the nematic liquid crystal may have a positive or negative dielectric anisotropy. A specific example of a nematic liquid crystal having positive dielectric anisotropy is a product name “ZLI-4535” manufactured by Merck. A specific example of a nematic liquid crystal having a negative dielectric anisotropy is a product name “ZLI-2806” manufactured by Merck & Co., Inc. Further, the difference between the ordinary light refractive index (no) and the extraordinary light refractive index (ne) of the nematic liquid crystal, that is, the birefringence (ΔnLC) can be arbitrarily set according to the response speed, transmittance, etc. of the liquid crystal. It is preferable that it is 0.05-0.30.

  As the liquid crystal cell, the one mounted on a commercially available liquid crystal display device may be used as it is. As a commercially available liquid crystal display device including an IPS mode liquid crystal cell, for example, a 20V type wide liquid crystal television manufactured by Hitachi, Ltd., trade name “Wooo”; -1 "; 17-inch TFT liquid crystal display manufactured by Nanao Corporation, trade name" FlexScan L565 "and the like.

<C. Polarizing plate>
The first polarizing plate and the second polarizing plate used in the present invention can each include a polarizer and a protective layer.

The transmittance of the first polarizing plate and the second polarizing plate is preferably 38.3% to 44.3%, more preferably 39.2% to 44.2%, and particularly preferably 41. From 1% to 44.2%, most preferably from 41.7% to 44.2%. When the transmittance is in such a range, a liquid crystal display device with high contrast in the front direction can be obtained. In addition, the transmittance | permeability of a polarizing plate can be calculated | required from the following formula | equation.
Transmittance = (k ₁ + k ₂ ) / 2
Here, k ₁ is the transmission axis of the transmittance of the polarizing plate, k ₂ is the absorption axis direction of the transmittance of the polarizing plate.

  The degree of polarization of the first polarizing plate and the second polarizing plate is preferably 99% or more, more preferably 99.5% or more, particularly preferably 99.7% or more, and most preferably It is 99.8% or more. When the degree of polarization is in such a range, a liquid crystal display device having high front contrast can be obtained.

As a specific method for measuring the degree of polarization, the parallel transmittance (T ₀ ) and orthogonal transmittance (T ₉₀ ) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(T ₀ -T ₉₀ ) / (T ₀ + T ₉₀ )} ^1/2 × 100. Here, the parallel transmittance T ₀ is a transmittance value of a parallel laminated polarizer obtained by superimposing two identical polarizers so that their absorption axes are parallel to each other, and the orthogonal transmittance T ₉₀ is the same. This is a transmittance value of an orthogonal laminated polarizer obtained by superposing two polarizers so that their absorption axes are orthogonal to each other. Further, these transmittances are Y values obtained by correcting the visibility with the 2-degree field of view (C light source) of JlS Z 8701-1982. The degree of polarization can be measured using a spectrophotometer V7100.

<C-1. Polarizer>
The polarizer satisfies 0.030 ≦ R _pva ≦ 0.040. Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny. The first polarizer and the second polarizer may have R _pva in the above range, and may be the same polarizer or different polarizers. R _pva is preferably 0.030 ≦ R _pva ≦ 0.039, more preferably 0.030 ≦ R _pva ≦ 0.035. By satisfying these characteristics, the polarizer can have excellent dimensional stability and optical durability in a humidified environment. As a result, even when the polarizer is used for a polarizing plate provided with a protective layer only on one side of the polarizer, dimensional change and optical characteristics are hardly deteriorated, and dimensional stability and optical durability that are practically acceptable. Can be realized. Therefore, the liquid crystal panel of the present invention can provide a liquid crystal display device that can be thinned without reducing productivity and that has improved contrast in the front direction.

Preferably, the polarizer has a moisture content of 14% by weight or less, more preferably 13% by weight or less, and still more preferably 12% by weight or less. In the present invention, the weight moisture content is measured as follows: The film to be measured is cut into a size of 100 mm × 100 mm to form a sample film, and the initial weight of the sample film is measured. Subsequently, the sample film is dried at 120 ° C. for 2 hours, the dry weight is measured, and the weight moisture content is determined by the following formula. In the following formula, the initial weight and the dry weight are average values obtained by measuring three times, respectively.
Moisture content (% by weight) = [(initial weight−dry weight) / initial weight] × 100
It is presumed that these characteristics are satisfied by increasing the amount of crystals that do not contribute to the orientation in the polarizer (typically, low orientation). When the value of R _pva and the weight moisture content satisfy the above ranges, the polarizer can have excellent dimensional stability and optical durability in a humidified environment without increasing the amount of boric acid. As a result, even when the polarizer is used for a polarizing plate provided with a protective layer only on one side of the polarizer, dimensional change and optical characteristics are hardly deteriorated, and dimensional stability and optical durability that are practically acceptable. Can be realized.

The polarizer preferably has a dichroic ratio DR of 160 or more, more preferably 165 to 185, and particularly preferably 175 to 185. When the dichroic ratio DR is within such a range, a liquid crystal panel and a liquid crystal display device with high front contrast can be obtained. The dichroic ratio DR can be obtained from the following equation.
Dichroic ratio DR = log (0.919 / k ₂ ) / log (0.919 / k ₁ )
Here, k ₁ is the transmission axis of the transmittance of the polarizer, k ₂ is the absorption axis direction of the transmittance of the polarizer, the constant 0.919 is the interfacial reflectance.

  The polarizer preferably contains a polyvinyl alcohol (PVA) resin containing a dichroic substance such as iodine or a dichroic dye as a main component.

  The iodine content of the polarizer is preferably 1.8% by weight to 5.0% by weight, and more preferably 2.0% by weight to 4.0% by weight. By setting the iodine content in the above range, a polarizing plate having a transmittance in a preferable range can be obtained, and a liquid crystal display device having high contrast in the front direction can be obtained.

  The boric acid content of the polarizer is preferably 0.5 wt% to 3.0 wt%, more preferably 1.0 wt% to 2.8 wt%, particularly preferably in terms of boron. 1.5 to 2.6% by weight. As described above, according to the present invention, a polarizer having excellent dimensional stability and optical durability in a humidified environment can be obtained without increasing the amount of boric acid.

  The polarizer may preferably further contain potassium. The potassium content is preferably 0.2% by weight to 1.0% by weight, more preferably 0.3% by weight to 0.9% by weight, and particularly preferably 0.4% by weight to 0.00%. 8% by weight. By making potassium content into the said range, the polarizing plate which has the transmittance | permeability of a preferable range and has high polarization degree can be obtained.

  The PVA resin can be obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The saponification degree of the PVA resin is preferably 95.0 mol% to 99.9 mol%. The saponification degree can be determined according to JIS K 6726-1994. By using a PVA resin having a saponification degree in the above range, a polarizer having excellent durability can be obtained.

  As the average degree of polymerization of the PVA-based resin, an appropriate value can be selected according to the purpose. The average degree of polymerization is preferably 1200 to 3600. The average degree of polymerization can be determined according to JIS K 6726-1994.

  The thickness of the polarizer is not particularly limited, and an appropriate thickness can be adopted depending on the purpose. The thickness is typically about 1 μm to 80 μm.

  The polarizer preferably has a conductive treatment on one surface. The polarizer that has been subjected to the conductive treatment is preferably arranged with its treated surface facing the liquid crystal cell. If the polarizer is subjected to a conductive treatment, for example, peeling charging at the time of rework can be prevented, and charging of the liquid crystal display device can be removed. The conductive treatment can be performed, for example, by corona treatment, plasma treatment, or primer coating. Examples of the primer used for the conductive treatment include an aqueous solution or an aqueous dispersion of a conductive polymer. Specific examples of the conductive polymer include polyaniline, polythiophene, polyethyleneimine, and allylamine compounds. Of these, polyaniline or polythiophene is preferable.

<C-2. Protective layer>
As said protective layer, it forms with the arbitrary appropriate films which can be used as a protective layer of a polarizing plate. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Preferably, the protective layer includes a cellulose acetate film. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

The protective layer preferably has a linear expansion coefficient α in a direction parallel to the transmission axis of the polarizer of the protective layer smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. By using such a protective layer, the crack durability can be improved. In one embodiment, the linear expansion coefficient α of the protective layer is preferably 4.5 × 10 ⁻⁵ / ° C. or less, and is −5.0 × 10 ⁻⁵ / ° C. to 4.5 × 10 ^−5. more preferably from / ° C., more preferably from ^{-4.5 × 10 -5 /℃~4.0×10 -5 / ℃} .

  As the protective layer of the polarizing plate, it is sufficient that at least one of the linear expansion coefficient in the TD direction and the linear expansion coefficient in the MD direction is smaller than the linear expansion coefficient in the transmission axis direction of the polarizer. Formed with any suitable film that can be used. What is necessary is just to arrange | position such a film so that the linear expansion coefficient of the direction parallel to the transmission axis of a polarizer may become smaller than the linear expansion coefficient of the transmission axis direction of a polarizer. The specific example of the material used as the main component of the film is as described above. Preferably, the film is a film mainly composed of a cellulose resin, a polyester resin or a polyimide resin, more preferably a triacetyl cellulose resin, a polyethylene terephthalate resin, a polyethylene naphthalate resin or a polyimide resin as a main component. It is a film. Preferably, the protective layer is a stretched film.

  The protective layer may be a transparent resin layer containing particles. The transparent resin layer containing the particles includes a transparent binder resin and particles. Any appropriate resin can be used as the transparent binder resin. Specifically, the resin exemplified as the main component of the film used as the protective layer may be used. Any appropriate particles can be used as the particles, and the particles may be inorganic particles or resin particles. The average particle diameter of the particles is preferably 0.05 μm to 2.0 μm.

  The protective layer may be subjected to any appropriate surface treatment on the surface. For example, as the protective layer, a commercially available polymer film subjected to surface treatment can be used as it is. Alternatively, a commercially available polymer film can be used after any surface treatment. Examples of the surface treatment include an antiglare treatment, a diffusion treatment (antiglare treatment), an antireflection treatment (antireflection treatment), a hard coat treatment, and an antistatic treatment. The protective layer included in the first polarizing plate is preferably subjected to anti-glare treatment on the viewing side to form an anti-glare layer. The anti-glare treatment is performed for the purpose of preventing the external light from being reflected on the surface of the polarizing plate and obstructing the viewing of the light transmitted through the polarizing plate. It is performed by providing a fine uneven structure on the surface of the protective layer by a roughening method by a processing method, a blending method of transparent fine particles). The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

<D. Adhesive layer>
In preferable embodiment, the said polarizer is affixed on the other member (a protective layer, a liquid crystal cell, and a phase difference layer as needed) which comprises a liquid crystal panel through an contact bonding layer. As the material for forming the adhesive layer, an appropriate adhesive and / or anchor coat agent can be selected according to the type and application of the adherend. Specific examples of adhesives include solvent-based adhesives, emulsion-type adhesives, pressure-sensitive adhesives, rehumidifying adhesives, polycondensation-type adhesives, solventless adhesives, and film-like adhesives according to the classification by shape. Agents, hot melt adhesives, and the like. According to the classification by chemical structure, synthetic resin adhesives, rubber adhesives, and natural product adhesives can be mentioned. The adhesive includes a viscoelastic substance (also referred to as an adhesive) that exhibits an adhesive force that can be sensed by pressure contact at room temperature.

  Preferably, the material forming the adhesive layer is a pressure-sensitive adhesive (also referred to as an acrylic pressure-sensitive adhesive) having an acrylic polymer as a base polymer. It is because it is excellent in transparency, adhesiveness, weather resistance, and heat resistance. The thickness of the acrylic pressure-sensitive adhesive layer can be appropriately adjusted according to the material and application of the adherend, but is usually 5 μm to 50 μm.

<E. Manufacturing method of liquid crystal panel>
The liquid crystal panel used in the present invention can be produced, for example, by sequentially laminating the above components (polarizer, protective layer, and retardation layer as necessary) in a liquid crystal cell. For example, the 1st laminated body (1st polarizing plate) in which the polarizer and the protective layer were laminated | stacked, and the 2nd laminated body (2nd polarizing plate) in which the polarizer and the protective layer were laminated | stacked. And then, the first and second laminates may be bonded to a liquid crystal cell.

  A polarizer using a conventional PVA-based resin is inferior in dimensional stability. Therefore, in a polarizing plate in which a protective layer is provided only on one side, the dimensional change of the polarizer is likely to occur. For example, curling occurs in the polarizing plate. Therefore, lamination with other members such as a liquid crystal cell becomes difficult, resulting in poor productivity. However, since the polarizer used in the liquid crystal panel used in the present invention is excellent in dimensional stability particularly in a humidified environment, the protective layer is on one side like the first polarizing plate and the second polarizing plate. Even in a form in which only the layers are stacked, it is possible to suppress the occurrence of curling due to the dimensional change of the polarizer. Thereby, the productivity at the time of laminating | stacking the polarizing plate which has a protective layer only on one side with another member improves. More specifically, it is possible not only to improve productivity when supplying a polarizing plate as a single sheet, but also to continuously laminate a polarizing plate having a protective layer only on one side, which has been difficult in the past. . That is, even when a polarizing plate having a protective layer only on one side is prepared in a roll state and laminated with other members, the occurrence of curling of the polarizing plate is suppressed, so that continuous lamination is possible. , Productivity is significantly improved. Moreover, since the polarizing plate which has a protective layer only on one side is thin, the said polarizing plate can be prepared in a long roll state, and can be laminated | stacked with another member. As a result, it is possible to reduce the work time required for switching the polarizing plate in the lamination step. Furthermore, by reducing the number of protective layers included in the liquid crystal panel, the influence on the display characteristics due to the optical characteristics of the protective layer can be suppressed, and the liquid crystal display device can be reduced in thickness and cost. Can do.

  Any appropriate method can be adopted as a method of laminating each component of the liquid crystal panel. Typically, it is laminated via any suitable adhesive layer. As a material for forming the adhesive layer, the materials described in the above section D can be used.

<F. Liquid crystal display>
The liquid crystal display device of the present invention includes the liquid crystal panel. FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It should be noted that the ratios of the vertical, horizontal, and thickness of each component shown in FIG. The liquid crystal display device 200 includes a liquid crystal panel 100 and a backlight unit 30 disposed on one side of the liquid crystal panel 100. In the illustrated example, the case where the direct type is adopted as the backlight unit is shown, but this may be a side light type, for example.

  When the direct method is adopted, the backlight unit 30 preferably includes a light source 31, a reflection film 32, a diffusion plate 33, a prism sheet 34, and a brightness enhancement film 35. When the sidelight system is adopted, preferably, the backlight unit further includes a light guide plate and a light reflector in addition to the above configuration. In addition, as long as the optical member illustrated in FIG. 2 has the effect of the present invention, a part of the optical member such as an illumination method of a liquid crystal display device or a driving mode of a liquid crystal cell can be omitted or other The optical member can be replaced.

  The liquid crystal display device may be a transmissive type that irradiates light from the back side of the liquid crystal panel to view the screen, or a reflective type that irradiates light from the viewing side of the liquid crystal panel to view the screen. good. Alternatively, the liquid crystal display device may be a transflective type having both transmissive and reflective properties.

  The liquid crystal display device of the present invention is used for any appropriate application. Applications include, for example, personal computer monitors, notebook computers, copiers and other OA devices, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable game machines and other portable devices, video cameras, televisions, microwave ovens, etc. Household electrical equipment, back monitors, car navigation system monitors, car audio and other in-vehicle equipment, display equipment such as commercial store information monitors, security equipment such as monitoring monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, each analysis method used in the Example is as follows.
(1) R _pva
About the polarizer used by the Example and the comparative example, it measured using the near infrared phase difference measuring apparatus KOBRA-31X100 / IR (wavelength 1000nm, 23 degreeC) by the Oji Scientific Instruments company.

(2) Dichroic ratio DR of polarizer
For the polarizers used in the examples and comparative examples, the transmittance k _{1 in} the transmission axis direction and the transmittance k ₂ in the absorption axis direction were measured using a spectrophotometer V7100, and the dichroic ratio DR was calculated from the following equation. Calculated:
Dichroic ratio DR = log (0.919 / k ₂ ) / log (0.919 / k ₁ )
Here, the constant 0.919 is the interface reflectance.
(3) Panel contrast The liquid crystal panel obtained in each example or comparative example is incorporated into a backlight unit so that the first polarizing plate is on the viewing side and the second polarizing plate is on the backlight side, and a liquid crystal display is provided. A device was made. About the obtained liquid crystal display device, contrast was computed in SR-UL1R made from Topcon.

[Reference Example 1]
A PVA resin film having a polymerization degree of 2400, a saponification degree of 99.7 mol%, and a thickness of 75 μm was prepared. The film was stretched 3 times in the film transport direction while being dyed in an aqueous iodine solution at 30 ° C., and then the total draw ratio was 4% by weight boric acid at 60 ° C. and 5% by weight potassium iodide aqueous solution. The film was stretched to be 6 times the original length. Furthermore, the stretched film was washed by immersing it in a 2 wt% potassium iodide aqueous solution at 30 ° C. for several seconds. The obtained stretched film was dried at 90 ° C. to obtain a polarizer (1). The obtained polarizer (1) had an R _pva of 0.035 and a dichroic ratio DR of 173.3.

[Reference Example 2]
A polarizer (2) was obtained in the same manner as in Reference Example 1 except that drying was performed at 80 ° C. R _pva of the obtained polarizer (2) was 0.038, and the dichroic ratio DR was 172.6.

[Reference Example 3]
A polarizer (3) was obtained in the same manner as in Reference Example 1 except that drying was performed at 70 ° C. The obtained polarizer (3) had an R _pva of 0.039 and a dichroic ratio DR of 172.6.

[Reference Example 4]
A polarizer (5) was obtained in the same manner as in Reference Example 1 except that drying was performed at 60 ° C. R _pva of the obtained polarizer (4) was 0.042, and the dichroic ratio DR was 171.4.

[Reference Example 5]
A polarizer (6) was obtained in the same manner as in Reference Example 1 except that drying was performed at 50 ° C. The obtained polarizer (5) had an R _pva of 0.043 and a dichroic ratio DR of 171.7.

[Reference Example 6]
A polarizer (7) was obtained in the same manner as in Reference Example 1 except that drying was performed at 40 ° C. The obtained polarizer (6) had an R _pva of 0.046 and a dichroic ratio DR of 173.3.

[Example 1]
A protective layer was laminated on one surface of the polarizer (1) obtained in Reference Example 1 using a PVA adhesive and dried at 40 ° C. for 2 minutes. Next, an adhesive was laminated on the other surface of the polarizer (1) to obtain a first polarizing plate (102 μm) containing the first polarizer. Moreover, the 2nd polarizing plate (102 micrometers) containing a 2nd polarizer was obtained like the 1st polarizing plate.
The polarizing plates on both sides were peeled from a liquid crystal cell of a commercially available liquid crystal television on which an IPS mode liquid crystal display element was mounted. A first polarizing plate was attached to one side of the liquid crystal cell so that the first polarizer and the liquid crystal cell were opposed to each other. Next, a second polarizing plate was attached to the other side of the liquid crystal cell so that the second polarizer and the liquid crystal cell face each other. At this time, the liquid crystal panel was manufactured by pasting so that the absorption axis of the second polarizer and the absorption axis of the first polarizer were orthogonal to each other. Table 1 shows the panel contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Example 2]
A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer (2) obtained in Reference Example 2 was used. Table 1 shows the panel contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Example 3]
A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer (3) obtained in Reference Example 3 was used. Table 1 shows the panel contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Comparative Example 1]
A liquid crystal panel was obtained in the same manner as in Example 1 except that the polarizer (4) obtained in Reference Example 4 was used. Table 1 shows the panel contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Comparative Example 2]
A liquid crystal panel was produced in the same manner as in Example 1 except that the polarizer (5) obtained in Reference Example 5 was used. Table 1 shows the panel contrast contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Comparative Example 3]
A liquid crystal panel was obtained in the same manner as in Example 1 except that the polarizer (6) obtained in Reference Example 6 was used. Table 1 shows the panel contrast of the obtained liquid crystal panel, the R _{pva of} the polarizer used in the liquid crystal panel, and the dichroic ratio DR.

[Evaluation]
The liquid crystal panels of Examples 1 to 3 of the present invention using a polarizer having an R _pva of 0.040 or less are compared to the liquid crystal panels of Comparative Examples 1 to 3 using a polarized light having an R _pva of more than 0.040. Showed high contrast.

  As described above, since the liquid crystal panel of the present invention exhibits a high front contrast when used in a liquid crystal display device, it is extremely useful for improving the display characteristics of, for example, a liquid crystal television, a personal computer monitor, and a mobile phone. .

DESCRIPTION OF SYMBOLS 10 1st polarizing plate 10 '2nd polarizing plate 11, 11' Polarizer 12, 12 'Protective layer 20 Liquid crystal cell 30 Backlight unit 31 Light source 32 Reflective film 33 Diffusion plate 34 Prism sheet 35 Brightness enhancement film 100 Liquid crystal panel 200 Liquid crystal display device

Claims (5)

A first polarizing plate, an IPS mode liquid crystal cell, and a second polarizing plate are provided in this order from the viewing side,
The first polarizing plate and the second polarizing plate each include a polarizer,
The first polarizing plate and / or the second polarizing plate includes a protective layer laminated on a surface of the polarizer opposite to the liquid crystal cell;
Liquid crystal panel in which the _polarizer satisfies 0.030 ≦ R _pva ≦ 0.040:
Here, R _pva is, when the wavelength is 1000 nm, the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer is nx, and the refractive index in the direction orthogonal to the direction in which the refractive index is maximum is ny. , R _pva = nx−ny.   The liquid crystal panel according to claim 1, wherein the dichroic ratio DR of the polarizer is 160 or more.   The liquid crystal panel according to claim 1, wherein an antiglare layer is formed on a viewing side of the first polarizing plate.   The liquid crystal panel according to claim 1, wherein a conductive treatment is performed on the liquid crystal cell side of the polarizer.   A liquid crystal display device comprising the liquid crystal panel according to claim 1.

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