JP2007328217A - Liquid crystal panel and liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display apparatus from which the light leaks little, looking at a screen from any direction of 360 degrees in an inclined direction. <P>SOLUTION: The liquid crystal display apparatus is provided with: a liquid crystal cell; a 1st polarizing plate disposed on one side of the liquid crystal cell; and a 2nd polarizing plate disposed on the other side of the liquid crystal cell. The 1st polarizing plate includes a 1st polarizer and a 1st phase difference layer disposed on the liquid crystal cell side of the 1st polarizer, the 2nd polarizing plate includes a 2nd polarizer and a 2nd phase difference layer disposed on the liquid crystal cell side of the 2nd polarizer, and a liquid crystal panel is used, wherein the refractive index ellipsoid of the 1st phase difference layer shows a relation of nx > ny ≥ nz, the index ellipsoid of the 2nd phase difference layer shows a relation of nx = ny > nz, and the transmittance of the 1st polarizing plate (T<SB>1</SB>) is larger than the transmittance (T<SB>2</SB>) of the 2nd polarizing plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel including two polarizing plates having different transmittances.

A liquid crystal display device (hereinafter referred to as LCD) is an element 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. When displaying a black image, the LCD has a problem that light from the backlight leaks to the viewer side in an oblique direction, which causes a decrease in the contrast ratio in the oblique direction. In order to solve this problem, a liquid crystal panel using a retardation film is disclosed (for example, see Patent Document 1). However, the market demands further improvements in the performance of LCDs. One of them is a liquid crystal display that can draw characters and images clearly in any direction from 360 ° in an oblique direction. A device is sought.
Japanese Patent No. 3648240

  An object of the present invention is to provide a liquid crystal display device in which light leakage is small no matter which direction the screen is viewed from 360 ° in an oblique direction.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by a liquid crystal panel shown below, and have completed the present invention.

The liquid crystal panel of the present invention comprises at least a liquid crystal cell, a first polarizing plate disposed on one side of the liquid crystal cell, and a second polarizing plate disposed on the other side of the liquid crystal cell, The first polarizing plate includes a first polarizer and a first retardation layer disposed on the liquid crystal cell side of the first polarizer, and the second polarizing plate includes a second polarizer And a second retardation layer disposed on the liquid crystal cell side of the second polarizer, and the refractive index ellipsoid of the first retardation layer satisfies nx> ny ≧ nz. The refractive index ellipsoid of the second retardation layer shows a relationship of nx = ny> nz, and the transmittance (T ₁ ) of the _first polarizing plate is the same as that of the second polarizing plate. It is larger than the transmittance (T ₂ ).

In a preferred embodiment, the difference (ΔT = T ₁ −T ₂ ) between the transmittance (T ₁ ) of the _first polarizing plate and the transmittance (T ₂ ) of the second polarizing plate is 0. 1% to 6.0%.

  In a preferred embodiment, the liquid crystal cell includes liquid crystal molecules aligned in a homeotropic alignment.

  In a preferred embodiment, the first polarizing plate is disposed on the viewing side of the liquid crystal cell, and the second polarizing plate is disposed on the side opposite to the viewing side of the liquid crystal cell.

  In a preferred embodiment, the first polarizer and the second polarizer have a polyvinyl alcohol resin containing iodine as a main component.

In a preferred embodiment, the iodine content of the second polarizer and (I _2), the iodine content of the first polarizer a difference between _{(I 1) (ΔI = I} 2 -I 1) is, 0.1% by weight to 2.6% by weight.

  In a preferred embodiment, the iodine content of the first polarizer and the second polarizer is 1.8 wt% to 5.0 wt%.

  In a preferred embodiment, the slow axis direction of the first retardation layer is substantially perpendicular to the absorption axis direction of the first polarizer.

In a preferred embodiment, the in-plane retardation value (Re ₁ [590]) at a wavelength of 590 nm of the first retardation layer is 50 nm to 200 nm.

  In a preferred embodiment, the first retardation layer is a retardation film (A) containing a norbornene resin.

In a preferred embodiment, a thickness direction retardation value (Rth ₂ [590]) at a wavelength of 590 nm of the second retardation layer is 100 nm to 400 nm.

  In a preferred embodiment, the second retardation layer contains a retardation film (B) containing a polyimide resin or a cellulose resin, or a retardation film containing a polyimide resin and a cellulose resin. It is a laminated body (C) with a phase difference film.

  According to another aspect of the present invention, a liquid crystal display device is provided. The liquid crystal display device includes the liquid crystal panel.

  In the liquid crystal panel of the present invention, two polarizing plates having different transmittances are arranged in a specific positional relationship, and each polarizing plate includes a retardation layer showing a specific refractive index ellipsoid. When the screen is viewed from any direction of 360 ° in an oblique direction compared to the liquid crystal panel, a liquid crystal display device with less light leakage can be provided.

<Definition of terms and symbols>
The definitions of terms and symbols in this specification are as follows.
(1) Transmittance of polarizing plate The transmittance (T) is a Y value of tristimulus values based on the 2-degree field of JlS Z 8701-1995.
(2) Refractive index (nx, ny, nz):
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), and “ny” is the direction orthogonal to the slow axis in the plane (ie, the fast axis direction). “Nz” is the refractive index in the thickness direction.
(3) In-plane retardation value:
The in-plane retardation value (Re [λ]) is an in-plane retardation value at a wavelength λ (nm) at 23 ° C. Re [λ] is obtained by Re [λ] = (nx−ny) × d where the thickness of the sample is d (nm). Re ₁ [λ] and Re ₂ [λ] represent in-plane retardation values of the first and second retardation layers, respectively.
(4) Thickness direction retardation value:
The thickness direction retardation value (Rth [λ]) is a thickness direction retardation value at 23 ° C. and a wavelength λ (nm). Rth [λ] is obtained by Rth [λ] = (nx−nz) × d where the thickness of the sample is d (nm). Note that Rth ₁ [λ] and Rth ₂ [λ] represent the retardation values in the thickness direction of the first and second retardation layers, respectively.
(5) Birefringence in the thickness direction:
The birefringence index (Δn _xz [λ]) in the thickness direction is a value calculated by the formula: Rth [λ] / d. Here, Rth [λ] represents a retardation value in the thickness direction at a wavelength λ (nm) at 23 ° C., and d represents a thickness (nm) of the film.
(6) Nz coefficient:
The Nz coefficient is a value calculated by the formula: Rth [590] / Re [590].
(7) In this specification, the description “nx = ny” or “ny = nz” includes not only the case where they are completely the same, but also the case where they are substantially the same. Therefore, for example, the description of nx = ny includes the case where Re [590] is less than 10 nm.
(8) In this specification, “substantially orthogonal” includes a case where an angle formed by two optical axes is 90 ° ± 2 °, and preferably 90 ° ± 1 °. “Substantially parallel” includes a case where an angle formed by two optical axes is 0 ° ± 2 °, and preferably 0 ° ± 1 °.

<A. Overview of LCD panel>
The liquid crystal panel of the present invention includes at least a liquid crystal cell, a first polarizing plate disposed on one side of the liquid crystal cell, and a second polarizing plate disposed on the other side of the liquid crystal cell. The first polarizing plate includes a first polarizer and a first retardation layer disposed on the liquid crystal cell side of the first polarizer, and the second polarizing plate includes a second polarizer. And a second retardation layer disposed on the liquid crystal cell side of the second polarizer. The refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny ≧ nz, and the refractive index ellipsoid of the second retardation layer shows a relationship of nx = ny> nz. The transmittance (T ₁ ) of the _first polarizing plate is larger than the transmittance (T ₂ ) of the second polarizing plate. Such a liquid crystal panel has a light leakage in an oblique direction as compared with a conventional liquid crystal panel (typically, the transmittance of two polarizing plates arranged on both sides of a liquid crystal cell is the same). It has the feature of being small.

  As described above, two polarizing plates having different transmittances are arranged in a specific positional relationship, and each polarizing plate includes a phase difference layer showing a specific refractive index ellipsoid, so that in an oblique direction, The ability to provide a liquid crystal display device with small light leakage no matter which direction the screen is viewed from 360 ° is a finding that has been found for the first time by the present inventors, and is an unexpectedly excellent effect. According to the estimation by the present inventors, the reason why the light leakage is reduced in all directions is that the optical compensation of the liquid crystal cell by the retardation layer and the optical compensation by adjusting the transmittance of the polarizing plate. This is thought to be because they complement each other in directions that are difficult to compensate.

The difference (ΔT = T ₁ −T ₂ ) between the transmittance (T ₁ ) of the _first polarizing plate and the transmittance (T ₂ ) of the second polarizing plate is preferably 0.1% to 6 0.0%, more preferably 0.1% to 4.5%, particularly preferably 0.2% to 3.0%, and most preferably 0.3% to 2.5%. . By using two polarizing plates having a difference in transmittance within the above range, a liquid crystal display device with even smaller oblique light leakage can be obtained.

  FIG. 1 is a schematic cross-sectional view of a liquid crystal panel in a preferred embodiment of the present invention. It should be noted that for the sake of easy understanding, the ratio of the vertical, horizontal, and thickness of each component shown in FIG. 1 is different from the actual ratio. A liquid crystal panel 100 of FIG. 1 includes a liquid crystal cell 10, a first polarizing plate 51 disposed on one side of the liquid crystal cell 10, and a second polarizing plate 52 disposed on the other side of the liquid crystal cell 10. Is provided. The first polarizing plate 51 includes a first polarizer 21, a first retardation layer 31 disposed on the liquid crystal cell side of the first polarizer 21, and a liquid crystal cell side of the first polarizer 21. Includes a first protective layer 41 disposed on the opposite side. The second polarizing plate 52 includes a second polarizer 22, a second retardation layer 32 disposed on the liquid crystal cell side of the second polarizer 22, and a liquid crystal cell side of the second polarizer 22. Includes a second protective layer 42 disposed on the opposite side. In the illustrated example, a configuration is shown in which the first polarizing plate 21 is disposed at the top of the liquid crystal cell and the second polarizing plate 22 is disposed at the bottom of the liquid crystal cell. The configuration may be reversed upside down.

  Practically, an arbitrary adhesive layer (not shown) may be disposed between the constituent members of the liquid crystal panel in order to join adjacent optical members. In this specification, the “adhesive layer” refers to a layer that joins surfaces of adjacent optical members and integrates them with practically sufficient adhesive force and adhesion time. Examples of the material for forming the adhesive layer include an adhesive and an anchor coat agent. The adhesive layer may have a multilayer structure in which an anchor coat layer is formed on the surface of an adherend and an adhesive layer is formed thereon. Further, it may be a thin layer (also referred to as a hairline) that cannot be visually recognized.

<B. Liquid crystal cell>
Any appropriate liquid crystal cell may be employed as the liquid crystal cell used in the present invention. Examples of the liquid crystal cell include an active matrix type using a thin film transistor and a simple matrix type used in a super twist nematic liquid crystal display device.

  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 active 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 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 liquid crystal cell preferably includes liquid crystal molecules aligned in a homeotropic alignment. In this specification, “homeotropic alignment” means a state in which the alignment vector of liquid crystal molecules is aligned perpendicularly (in the normal direction) to the substrate plane as a result of the interaction between the alignment-treated substrate and the liquid crystal molecules. Means things. The homeotropic alignment includes a case where the alignment vector of the liquid crystal molecules is slightly inclined with respect to the normal direction of the substrate, that is, the case where the liquid crystal molecules have a pretilt. When the liquid crystal molecules have a pretilt, the pretilt angle (angle from the substrate normal) is preferably 5 ° or less. By setting the pretilt angle in the above range, a liquid crystal display device with a high contrast ratio can be obtained.

  In the liquid crystal cell, the refractive index ellipsoid preferably exhibits a relationship of nz> nx = ny. As the liquid crystal cell in which the refractive index ellipsoid shows a relationship of nz> nx = ny, according to the drive mode classification, for example, a vertical alignment (VA) mode, a twisted nematic (TN) mode, a vertical alignment type, An electric field control birefringence (ECB) mode, an optical compensation birefringence (OCB) mode, and the like can be given. In the present invention, the driving mode of the liquid crystal cell is particularly preferably a vertical alignment (VA) mode.

  The VA mode liquid crystal cell utilizes a voltage-controlled birefringence effect, and makes liquid crystal molecules aligned in a homeotropic alignment respond to the substrate with an electric field in a normal direction in the absence of an electric field. Specifically, as described in, for example, Japanese Patent Application Laid-Open No. 62-210423 and Japanese Patent Application Laid-Open No. 4-153621, in the case of a normally black method, liquid crystal molecules are formed on a substrate in the absence of an electric field. Therefore, when the upper and lower polarizing plates are arranged orthogonally, a black display can be obtained. On the other hand, in the presence of an electric field, the liquid crystal molecules operate so as to tilt in a 45 ° azimuth direction with respect to the absorption axis of the polarizing plate, whereby the transmittance increases and white display is obtained.

  The VA mode liquid crystal cell can be multi-domained by using a substrate having slits formed on electrodes or a substrate having projections formed on the surface as described in JP-A-11-258605, for example. It may be what you did. Such a liquid crystal cell is, for example, an ASV (Advanced Super View) mode manufactured by Sharp Corporation, a CPA (Continuous Pinheal Alignment) mode manufactured by the same company, an MVA (Multi-domain Vertical Alignment mode) manufactured by Fujitsu Limited, or the like. PVA (Patterned Vertical Alignment) mode manufactured by Co., Ltd., EVA (Enhanced Vertical Alignment) mode manufactured by the same company, SURVIVAL (Super Ranged Viewing by Vertical Alignment), etc. manufactured by Sanyo Electric Co.

Rth _LC [590] of the liquid crystal cell in the absence of an electric field is preferably −500 nm to −200 nm, more preferably −400 nm to −200 nm. The Rth _LC [590] is appropriately set depending on the birefringence of the liquid crystal molecules and the cell gap. The cell gap (substrate interval) of the liquid crystal cell is usually 1.0 μm to 7.0 μm.

  As the liquid crystal cell, the one mounted on a commercially available liquid crystal display device may be used as it is. Commercially available liquid crystal display devices including VA mode liquid crystal cells include, for example, Sharp Corporation liquid crystal television product name “AQUIS series”, Sony liquid crystal television product name “BRAVIA series”, and SUMSUNG 32V type wide display. Liquid crystal television product name “LN32R51B”, Nanao Co., Ltd. liquid crystal television product name “FORIS SC26XD1”, AU Optronics liquid crystal television product name “T460HW01”, and the like.

<C. Polarizing plate>
The first polarizing plate used in the present invention includes a first polarizer and a first retardation layer disposed on the liquid crystal cell side of the first polarizer. The second polarizing plate includes a second polarizer and a second retardation layer disposed on the liquid crystal cell side of the second polarizer. Preferably, the first polarizing plate is disposed on the viewing side of the liquid crystal cell, and the second polarizing plate is disposed on the side opposite to the viewing side of the liquid crystal cell. Preferably, the absorption axis direction of the first polarizing plate is substantially orthogonal to the absorption axis direction of the second polarizing plate. The thickness of the polarizing plate is usually 20 μm to 300 μm. By setting it as the thickness of the said range, the polarizing plate excellent in mechanical strength can be obtained.

The transmittance (T ₁ ) of the first polarizing plate is preferably 41.1% to 44.3%, more preferably 41.4% to 44.3%, and particularly preferably 41.7%. % To 44.2%, and most preferably 42.0% to 44.2%. By setting T ₁ in the above range, it is possible to obtain a liquid crystal display device in which light leakage in an oblique direction is further reduced.

The transmittance (T ₂ ) of the second polarizing plate is preferably 38.3% to 43.3%, more preferably 38.6% to 43.2%, and particularly preferably 38.9. % To 43.1%, most preferably 39.2% to 43.0%. By setting T ₂ in the above range, it is possible to obtain a liquid crystal display device in which light leakage in an oblique direction is further reduced.

  As a method for increasing or decreasing the transmittance of the polarizing plate, for example, when a polarizer mainly composed of a polyvinyl alcohol resin containing iodine is used for the polarizing plate, the content of iodine in the polarizer The method of preparing is mentioned. Specifically, if the iodine content in the polarizer is increased, the transmittance of the polarizing plate can be lowered, and if the iodine content in the polarizer is decreased, the transmittance of the polarizing plate is increased. can do. This method can be applied to the production of a roll-shaped polarizing plate and the production of a polarizing plate for each leaf. The polarizer will be described later.

  The degree of polarization (P) of the first polarizing plate and / or the second polarizing plate is preferably 99% or more, more preferably 99.5% or more, and further preferably 99.8%. is there. By setting P in the above range, it is possible to obtain a liquid crystal display device in which light leakage in an oblique direction is further reduced.

The degree of polarization can be measured using a spectrophotometer [product name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.]. As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(H ₀ −H _{90 ) / (H 0 + H 90} )} can be determined from ^1/2 × 100. The parallel transmittance (H ₀ ) is a value of transmittance of a parallel laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are orthogonal to each other. These transmittances are Y values of tristimulus values based on the 2-degree field of JlS Z 8701-1995.

<D. Polarizer>
In this specification, the “polarizer” refers to one that converts natural light or polarized light into linearly polarized light. Any appropriate polarizer can be selected. Preferably, the polarizer has a function of separating incident light into two orthogonal polarization components, transmitting one polarization component, and absorbing, reflecting, and / or scattering the other polarization component.

  The first polarizer and the second polarizer used in the present invention are preferably composed mainly of a polyvinyl alcohol resin containing iodine. The first and second polarizers can usually be obtained by stretching a polymer film containing as a main component a polyvinyl alcohol-based resin containing iodine. Such a polarizer is excellent in optical characteristics.

The relationship between the iodine content (I ₁ ) of the first polarizer and the iodine content (I ₂ ) of the second polarizer is preferably I ₂ > I ₁ . The difference (ΔI = I ₂ −I ₁ ) between the iodine content (I ₂ ) of the _second polarizer and the iodine content (I ₁ ) of the first polarizer is preferably 0.1 weight. % To 2.6% by weight, more preferably 0.1% to 2.0% by weight, particularly preferably 0.1% to 1.4% by weight, and most preferably 0.15%. % By weight to 1.2% by weight. By setting the relationship of the iodine content of each polarizer within the above range, a polarizing plate having a transmittance relationship in a preferable range can be obtained, and a liquid crystal display device with small light leakage in an oblique direction can be obtained.

  The iodine content of the first polarizer and the second polarizer is preferably 1.8 wt% to 5.0 wt%, more preferably 2.0 wt% to 4.0 wt%. is there. The iodine content of the first polarizer is preferably 1.8% to 3.5% by weight, more preferably 1.9% to 3.2% by weight, and particularly preferably 2.% by weight. 0% by weight to 2.9% by weight. The iodine content of the second polarizer is preferably 2.3 wt% to 5.0 wt%, more preferably 2.5 wt% to 4.5 wt%, and particularly preferably 2. wt%. 5% to 4.0% by weight. By setting the iodine content of each polarizer in the above range, a polarizing plate having a transmittance in a preferable range can be obtained, and a liquid crystal display device with small light leakage in an oblique direction can be obtained.

  Preferably, the first polarizer and the second polarizer 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.

  Preferably, the first polarizer and the second polarizer further contain boron. The boron content is preferably 0.5 wt% to 3.0 wt%, more preferably 1.0 wt% to 2.8 wt%, and particularly preferably 1.5 wt% to 2. wt%. 6% by weight. By setting the boron content in the above range, a polarizing plate having a transmittance in a preferable range and a high degree of polarization can be obtained.

  The polyvinyl alcohol resin can be obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The saponification degree of the polyvinyl alcohol 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 polyvinyl alcohol 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 polyvinyl alcohol-based resin, an appropriate value can be appropriately 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.

  Any appropriate forming method can be adopted as a method for obtaining the polymer film containing the polyvinyl alcohol resin as a main component. Examples of the molding method include the method described in JP 2000-315144 A [Example 1].

  The polymer film containing the vinyl alcohol polymer as a main component preferably contains a plasticizer and / or a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As said surfactant, a nonionic surfactant is mentioned, for example. The content of the plasticizer and the surfactant is preferably more than 1 and 10 parts by weight with respect to 100 parts by weight of the vinyl alcohol polymer. The polyhydric alcohol and the surfactant are used for the purpose of further improving the dyeability and stretchability of the polarizer.

  A commercially available film can be used as it is as the polymer film containing the polyvinyl alcohol resin as a main component. Examples of the polymer film mainly composed of a commercially available polyvinyl alcohol-based resin include, for example, “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., “Toselo Vinylon Film” manufactured by Tosero Co., Ltd., Nippon Synthetic Chemical Industry Product name “Nippon Vinylon Film”, etc., may be mentioned.

  An example of a method for manufacturing a polarizer will be described with reference to FIG. FIG. 2 is a schematic view showing the concept of a typical production process of a polarizer used in the present invention. For example, a polymer film 301 mainly composed of a polyvinyl alcohol-based resin is fed from a feeding unit 300 and immersed in a swelling bath 310 containing pure water and a dyeing bath 320 containing an aqueous iodine solution, and rolls 311 having different speed ratios. , 312, 321 and 322, swelling treatment and dyeing treatment are performed while tension is applied in the longitudinal direction of the film. Next, the film subjected to the swelling treatment and the dyeing treatment is immersed in the first crosslinking bath 330 containing potassium iodide and the second crosslinking bath 340, and is rolled with rolls 331, 332, 341 and 342 having different speed ratios. While tension is applied in the longitudinal direction of the film, a crosslinking treatment and a final stretching treatment are performed. The film subjected to the crosslinking treatment is immersed in a washing bath 350 containing pure water by rolls 351 and 352 and subjected to a washing treatment. The water-washed film is dried by the drying means 360, so that the moisture content is adjusted to, for example, 10% to 30%, and is wound by the winding unit 380. The polarizer 370 can be obtained by stretching the polymer film containing the polyvinyl alcohol-based resin as a main component to 5 to 7 times the original length through these steps.

  In the dyeing step, the amount of iodine added to the dyeing bath for obtaining a polarizing plate having excellent optical properties is preferably 0.01 parts by weight to 0.15 parts by weight with respect to 100 parts by weight of water. More preferably, it is 0.01 weight part-0.05 weight part. When the amount of iodine added to the dyeing bath is increased within the above range, a polarizing plate having a low transmittance can be obtained as a result. Moreover, when the addition amount of the iodine of a dyeing bath is reduced in said range, a polarizing plate with a high transmittance | permeability can be obtained as a result.

  The amount of potassium iodide added to the dyeing bath is preferably 0.05 parts by weight to 0.5 parts by weight, more preferably 0.1 parts by weight to 0.3 parts by weight with respect to 100 parts by weight of water. It is. By setting the amount of potassium iodide to be in the above range, a polarizing plate having a preferable range of transmittance and a high degree of polarization can be obtained.

  In the dyeing step, the amount of potassium iodide added to the first crosslinking bath and the second crosslinking bath for obtaining a polarizing plate having excellent optical properties is preferably 0.1% with respect to 100 parts by weight of water. 5 to 10 parts by weight, more preferably 1 to 7 parts by weight. The amount of boric acid added in the first crosslinking bath and the second crosslinking bath is preferably 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight. By setting the amounts of potassium iodide and boric acid to be in the above ranges, a polarizing plate having a preferable range of transmittance and a high degree of polarization can be obtained.

<E. First retardation layer>
The first retardation layer used in the present invention is disposed between the first polarizer and the liquid crystal cell. The first retardation layer is preferably bonded to the first polarizer through an adhesive layer. The slow axis direction of the first retardation layer is preferably substantially orthogonal to the absorption axis direction of the first polarizer.

  The refractive index ellipsoid of the first retardation layer has a relationship of nx> ny ≧ nz. In this specification, the “retardation layer” refers to a transparent layer having a retardation in the plane and / or in the thickness direction. The first retardation layer may be a layer having a single-layer retardation, or may be a laminate composed of a plurality of layers. The thickness of the first retardation layer is preferably 0.5 μm to 200 μm. The transmittance (T [590]) at a wavelength of 590 nm of the first retardation layer is preferably 90% or more.

  The in-plane and / or thickness direction retardation value of the first retardation layer at a wavelength of 590 nm is 10 nm or more. In this specification, “shows a relationship of nx> ny ≧ nz” indicates a relationship of nx> ny = nz (also referred to as positive uniaxiality), or a relationship of nx> ny> nz (negative biaxial) (Also called sex).

Re ₁ [590] of the _first retardation layer is 10 nm or more, preferably 50 nm to 200 nm. When the refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny = nz, Re ₁ [590] is preferably 90 nm to 190 nm, and more preferably 110 nm to 170 nm. When the refractive index ellipsoid of the first retardation layer shows a relationship of nx>ny> nz, Re ₁ [590] is preferably 70 nm to 170 nm, and more preferably 90 nm to 150 nm. By setting Re ₁ [590] in the above range, a liquid crystal display device with small light leakage in an oblique direction can be obtained.

Rth ₁ [590] of the _first retardation layer can be appropriately set. When the refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny = nz, Re ₁ [590] and Rth ₁ [590] are substantially equal. In this case, the first retardation layer preferably satisfies the formula: | Rth ₁ [590] −Re ₁ [590] | <10 nm.

When the refractive index ellipsoid of the first retardation layer shows a relationship of nx>ny> nz, Rth ₁ [590] is larger than Re ₁ [590]. In this case, the difference between Rth ₁ [590] and Re ₁ [590] (Rth ₁ [590] −Re ₁ [590]) is preferably 10 nm to 100 nm, and more preferably 20 nm to 80 nm. The Rth ₁ [590] By setting as described above, it is possible to obtain a small liquid crystal display device of light leakage in oblique directions.

  The Nz coefficient of the first retardation layer can be set as appropriate. When the refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny = nz, the Nz coefficient is preferably more than 0.9 and less than 1.1. When the refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny> nz, the Nz coefficient is preferably 1.1 to 3.0, and more preferably 1.1 to 2. 0. By setting the Nz coefficient in the above range, a liquid crystal display device with a small light leakage in an oblique direction can be obtained.

  As the material for forming the first retardation layer, any appropriate material can be adopted as long as the refractive index ellipsoid shows a relationship of nx> ny ≧ nz. As the first retardation layer, for example, a retardation film containing a thermoplastic resin such as norbornene-based resin, polycarbonate-based resin, cellulose-based resin, or polyester-based resin can be used. The retardation film preferably contains 60 to 100 parts by weight of a thermoplastic resin with respect to 100 important parts of the total solid content.

  The first retardation layer is preferably a retardation film (A) containing an upper norbornene resin. The norbornene-based resin has a feature that the absolute value (C [590]) of the photoelastic coefficient is small. In this specification, the “norbornene-based resin” refers to a (co) polymer obtained by using a norbornene-based monomer having a norbornene ring as a part or all of a starting material (monomer). The “(co) polymer” represents a homopolymer or a copolymer (copolymer).

C [590] of the norbornene-based resin is preferably from ^{1 × 10 -12 m 2 / N~20} × 10 -12 m 2 / N, more preferably ^{1 × 10 -12 m 2 / N~10} × 10 ⁻¹² m ² / N. If a retardation film having an absolute value of the photoelastic coefficient in the above range is used, a liquid crystal display device with small optical unevenness can be obtained.

In the norbornene-based resin, a norbornene-based monomer having a norbornene ring (having a double bond in the norbornane ring) is used as a starting material. In the state of the (co) polymer, the norbornene-based resin may or may not have a norbornane ring in the structural unit. In the (co) polymer state, the norbornene-based resin having a norbornane ring as a structural unit is, for example, tetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] dec-3-ene, 8-methyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene, 8-methoxycarbonyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene and the like. A norbornene-based resin having no norbornane ring as a structural unit in the (co) polymer state is, for example, a (co) polymer obtained using a monomer that becomes a 5-membered ring by cleavage. Examples of the monomer that becomes a 5-membered ring by cleavage include norbornene, dicyclopentadiene, 5-phenylnorbornene, and derivatives thereof. When the norbornene-based resin is a copolymer, the arrangement state of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. It may be.

  Examples of the norbornene resin include (a) a resin obtained by hydrogenating a ring-opening (co) polymer of a norbornene monomer, and (b) a resin obtained by addition (co) polymerization of a norbornene monomer. The ring-opening copolymer of the norbornene-based monomer is a resin obtained by hydrogenating a ring-opening copolymer of one or more norbornene-based monomers and α-olefins, cycloalkenes, and / or non-conjugated dienes. Include. The resin obtained by addition copolymerization of the norbornene monomer includes a resin obtained by addition copolymerization of one or more norbornene monomers with α-olefins, cycloalkenes and / or non-conjugated dienes.

  A resin obtained by hydrogenating the ring-opening (co) polymer of the norbornene monomer is subjected to a metathesis reaction of the norbornene monomer or the like to obtain a ring-opening (co) polymer. It can be obtained by hydrogenation. Specifically, for example, the method described in paragraphs [0059] to [0060] of JP-A-11-116780, the method described in paragraphs [0035] to [0037] of JP-A-2001-350017, and the like. Can be mentioned. The resin obtained by addition (co) polymerization of the norbornene monomer can be obtained, for example, by the method described in Example 1 of JP-A No. 61-292601.

  The weight average molecular weight (Mw) of the norbornene resin is preferably 20,000 to 500,000 as measured by gel permeation chromatography (polystyrene standard) using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the norbornene-based resin is preferably 120 ° C to 170 ° C. If it is said resin, it has the outstanding thermal stability and the film excellent in the drawability can be obtained. The glass transition temperature (Tg) is a value calculated by the DSC method according to JIS K7121.

  The retardation film (A) containing the norbornene resin can be obtained by any appropriate forming method. Preferably, the retardation film (A) containing the norbornene-based resin is obtained by subjecting a polymer film formed into a sheet shape by a solvent casting method or a melt extrusion method to a longitudinal uniaxial stretching method, a lateral uniaxial stretching method, It is produced by stretching by a biaxial stretching method or a longitudinal and lateral sequential biaxial stretching method. The stretching method is preferably a lateral uniaxial stretching method. This is because it becomes possible to produce a roll of a polarizing plate in which the slow axis of the retardation film (A) and the absorption axis of the polarizer are orthogonal, and the productivity of the polarizing plate can be greatly improved. The temperature at which the polymer film is stretched (stretching temperature) is preferably 120 ° C to 200 ° C. Moreover, the magnification (drawing ratio) for stretching the polymer film is preferably more than 1 and 4 times or less.

  As the polymer film containing the norbornene resin, a commercially available film can be used as it is. Alternatively, a commercially available film subjected to secondary processing such as stretching and / or shrinking can be used. As a polymer film containing a commercially available norbornene resin, for example, Arton series (trade name; ARTON F, ARTON FX, ARTON D) manufactured by JSR Corporation, or Zeonore series (trade name: ZEONOR Corporation) manufactured by Optes Co., Ltd. ZF14, ZEONOR ZF16) and the like.

  The retardation film used as the first retardation layer may further contain any appropriate additive. Examples of the additive include a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizer, a crosslinking agent, and a thickener. Etc. The content of the additive is preferably more than 0 and 10 parts by weight or less with respect to 100 parts by weight of the main resin.

<F. Second retardation layer>
The second retardation layer used in the present invention is disposed between the second polarizer and the liquid crystal cell. The second retardation layer is preferably bonded to the second polarizer through an adhesive layer. In the second retardation layer, the refractive index ellipsoid shows a relationship of nx = ny> nz (also referred to as negative uniaxiality). The second retardation layer may be a single layer having a phase difference or may be a laminate composed of a plurality of layers. The thickness of the second retardation layer is preferably 0.5 μm to 200 μm. The transmittance (T [590]) at a wavelength of 590 nm of the second retardation layer is preferably 90% or more.

Re ₂ [590] of the _second retardation layer is less than 10 nm, preferably 5 nm or less, and more preferably 3 nm or less. By setting Re ₂ [590] in the above range, a liquid crystal display device with small light leakage in an oblique direction can be obtained.

Rth ₂ [590] of the _second retardation layer can be appropriately set according to the retardation value in the thickness direction of the liquid crystal cell. The Rth ₂ [590] is preferably 100 nm to 400 nm, more preferably 120 nm to 350 nm, and particularly preferably 150 nm to 300 nm. By the Rth ₂ [590] within the above range, it is possible to obtain a small liquid crystal display device of light leakage in oblique directions.

  As the material for forming the second retardation layer, any appropriate material can be adopted as long as the refractive index ellipsoid shows a relationship of nx = ny> nz. As the second retardation layer, for example, a retardation film containing a thermoplastic resin such as a polyimide resin, a cellulose resin, a norbornene resin, a polycarbonate resin, or a polyamide resin may be used. These retardation films preferably contain 60 to 100 parts by weight of a thermoplastic resin with respect to 100 important parts of the total solid content.

  The second retardation layer is preferably a retardation film (B) containing a polyimide resin or a cellulose resin, or a retardation film containing a polyimide resin and a retardation film containing a cellulose resin. It is a laminated body (C). In the laminate (C), it is preferable that a retardation film containing a polyimide resin is bonded to a retardation film containing a cellulose resin via an adhesive layer.

[Polyimide resin]
When the polyimide resin is formed into a sheet by the solvent casting method, the refractive index ellipsoid shows a relationship of nx = ny> nz because the molecules are likely to be spontaneously oriented during the evaporation process of the solvent. The film can be made very thin. The thickness of the retardation film containing the polyimide resin is preferably 0.5 μm to 10 μm, and more preferably 1 μm to 5 μm. The birefringence ( _Δnxz [590]) in the thickness direction of the retardation film containing the polyimide resin is preferably 0.01 to 0.12, more preferably 0.02 to 0.08. . Such a polyimide resin can be obtained, for example, by the method described in US Pat. No. 5,344,916.

  Preferably, the polyimide resin has a hexafluoroisopropylidene group and / or a trifluoromethyl group. More preferably, the polyimide resin has at least a repeating unit represented by the following general formula (I) or a repeating unit represented by the following general formula (II). Since polyimide resins containing these repeating units are excellent in solubility in general-purpose solvents, film formation by a solvent casting method is possible. Furthermore, a thin layer of the polyimide resin can be formed on a substrate having poor solvent resistance such as a triacetyl cellulose film without excessively eroding the surface.

In the above general formulas (I) and (II), G and G ′ are a covalent bond, CH ₂ group, C (CH ₃ ) ₂ group, C (CF ₃ ) ₂ group, C (CX ₃ ) ₂ group (here X is a halogen.), Each independently from the group consisting of CO, O, S, SO ₂ , Si (CH ₂ CH ₃ ) ₂ and N (CH ₃ ) groups. Represents a group selected, and may be the same or different.

  In the above general formula (I), L is a substituent, and e represents the number of substitutions. L is, for example, a halogen, an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, a phenyl group, or a substituted phenyl group, and in a plurality of cases, they are the same or different. e is an integer from 0 to 3.

  In the general formula (II), Q is a substituent, and f represents the number of substitutions. Q is, for example, selected from the group consisting of hydrogen, halogen, alkyl group, substituted alkyl group, nitro group, cyano group, thioalkyl group, alkoxy group, aryl group, substituted aryl group, alkyl ester group, and substituted alkyl ester group And when Q is plural, they are the same or different. f is an integer from 0 to 4, and g and h are integers from 1 to 3, respectively.

  The said polyimide resin can be obtained by reaction of tetracarboxylic dianhydride and diamine, for example. As the repeating unit of the above general formula (I), for example, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl is used as a diamine, and a tetracarboxylic acid having at least two aromatic rings. It can be obtained by reaction with dianhydride. As the repeating unit of the above general formula (II), for example, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride is used as a tetracarboxylic dianhydride, and this is combined with an aromatic ring. It can be obtained by reacting with at least two diamines. The reaction may be, for example, chemical imidization that proceeds in two stages or thermal imidization that proceeds in one stage.

  Any appropriate tetracarboxylic dianhydride may be selected. Examples of the tetracarboxylic dianhydride include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride. 2,3,3 ′, 4-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 2,2′-dibromo-4,4 ′, 5 , 5′-biphenyltetracarboxylic dianhydride, 2,2′-bis (trifluoromethyl) -4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4 '-Biphenyltetracarboxylic dianhydride, 4,4'-bis (3,4-dicarboxyphenyl) ether dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-bis (3 4-dicarboxyl Yl) sulfonic acid dianhydride, bis (2,3-carboxyphenyl) methane dianhydride, bis (3,4-carboxyphenyl) diethyl silane dianhydride, and the like.

  Any appropriate diamine may be selected. Examples of the diamine include 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 4,4′-diaminobiphenyl, 4,4′-diaminophenylmethane, 4,4 ′-( 9-fluorenylidene) -dianiline, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 4,4′-diaminodiphenyl ether, 3,4′- Examples include diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenylthioether, and the like.

  The above polyimide-based resin is a polyethylene oxide standard weight average molecular weight (Mw) using a dimethylformamide solution (a solution obtained by adding 10 mM lithium bromide and 10 mM phosphoric acid to make a 1 L dimethylformamide solution). However, it is preferably 20,000 to 180,000. The imidization rate is preferably 95% or more. The imidation rate can be determined from an integral intensity ratio between a proton peak derived from polyamic acid, which is a polyimide precursor, and a proton peak derived from polyimide.

  The retardation film containing the polyimide resin can be obtained by any appropriate molding method. Preferably, the retardation film containing the polyimide resin is produced by molding into a sheet shape by a solvent casting method.

[Cellulosic resin]
Arbitrary appropriate things can be employ | adopted for the said cellulose resin. The cellulose resin is preferably a cellulose organic acid ester or a cellulose mixed organic acid ester in which some or all of the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups, and / or butyl groups. Examples of the cellulose organic acid ester include cellulose acetate, cellulose propionate, and cellulose butyrate. Examples of the cellulose mixed organic acid ester include cellulose acetate propionate and cellulose acetate butyrate. The cellulose resin can be obtained, for example, by the method described in JP-A-2001-188128 [0040] to [0041].

  The weight average molecular weight (Mw) of the cellulose resin is preferably 20,000 to 1,000,000, as measured by gel permeation chromatography (polystyrene standard) using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the cellulose resin is preferably 110 ° C to 185 ° C. The glass transition temperature (Tg) can be determined by a DSC method according to JIS K7121. If it is said resin, it has the outstanding thermal stability and the film excellent in mechanical strength can be obtained.

  The retardation film containing the cellulose resin can be obtained by any appropriate forming method. Preferably, the retardation film containing the cellulose-based resin is produced by molding into a sheet shape by a solvent casting method. As the retardation film, a commercially available film can be used as it is. Alternatively, a commercially available film subjected to secondary processing such as stretching and / or shrinking can be used. As a polymer film containing a commercially available cellulose resin, for example, Fuji Photo Film Co., Ltd. Fujitac series (trade name: ZRF80S, TD80UF, TDY-80UL), Konica Minolta Opto Co., Ltd. trade name “KC8UX2M” Or the like.

  The retardation film used as the second retardation layer may further contain any appropriate additive. Examples of the additive include a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizer, a crosslinking agent, and a thickener. Etc. The content of the additive is preferably more than 0 and 10 parts by weight or less with respect to 100 parts by weight of the main resin.

  The second retardation layer may be a liquid crystal composition. When a liquid crystal composition is used, the retardation layer includes a solidified layer or a cured layer of a liquid crystal composition containing a rod-like liquid crystal compound aligned in a planar alignment, or a discotic liquid crystal compound aligned in a columnar alignment. It includes a solidified layer or a cured layer of the liquid crystal composition. If a liquid crystal compound is used, a thin retardation film can be obtained because the birefringence in the thickness direction is large.

  A retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition containing a rod-like liquid crystal compound aligned in the planar arrangement can be obtained, for example, by the method described in JP-A No. 2003-287623. In addition, a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition containing a discotic liquid crystal compounded soil aligned in the columnar arrangement can be obtained, for example, by the method described in JP-A-9-117983. it can.

<G. Protective layer>
The 1st and 2nd polarizing plate used for this invention is each provided with the 1st protective layer and the 2nd protective layer on the opposite side to the liquid crystal cell side of each polarizer. The first and second protective layers are used, for example, to prevent the polarizer from contracting or expanding or to prevent deterioration due to ultraviolet rays. The first and second protective layers may be the same or different.

  Any appropriate layer can be adopted as the protective layer. The thickness of the protective layer is preferably 20 μm to 100 μm. The transmittance (T [590]) at a wavelength of 590 nm of the protective layer is preferably 90% or more.

  Any appropriate material can be adopted as the material for forming the protective layer. Preferably, the protective layer is a polymer film containing a cellulose resin, a norbornene resin, or an acrylic resin. The polymer film containing the cellulose resin can be obtained, for example, by the method described in Example 1 of JP-A-7-112446. The polymer film containing the norbornene resin can be obtained, for example, by the method described in JP-A-2001-350017. The polymer film containing the acrylic resin can be obtained, for example, by the method described in Example 1 of JP-A-2004-198952.

  The protective layer may have a surface treatment layer on the side opposite to the side provided with the polarizer. The surface treatment layer can be appropriately treated according to the purpose. Examples of the surface treatment layer include treatment layers such as hard coat treatment, antistatic treatment, antireflection treatment (also referred to as antireflection treatment), and diffusion treatment (also referred to as antiglare treatment). These surface treatment layers are used for the purpose of preventing the screen from being soiled or damaged, or preventing the display image from becoming difficult to see due to the reflection of indoor fluorescent light or sunlight on the screen. In general, the surface treatment layer is formed by fixing a treatment agent for forming the treatment layer on the surface of a base film. The base film may also serve as the protective layer. Further, the surface treatment layer may have a multilayer structure in which, for example, a hard coat treatment layer is laminated on an antistatic treatment layer.

  As the protective layer, a commercially available polymer film provided with a surface treatment layer can be used as it is. Alternatively, a commercially available polymer film can be used after any surface treatment. Examples of the diffusion treatment (antiglare treatment) include AG150, AGS1, and AGS2 manufactured by Nitto Denko Corporation. Examples of the antireflection treatment (anti-reflection treatment) include ARS and ARC manufactured by Nitto Denko Corporation. Examples of the commercially available film subjected to the hard coat treatment and the antistatic treatment include “KC8UX-HA” manufactured by Konica Minolta Opto Co., Ltd. Examples of the commercially available surface treatment layer that has been subjected to the antireflection treatment include ReaLook series manufactured by NOF Corporation.

<H. Liquid crystal display>
The liquid crystal display device of the present invention includes the liquid crystal panel. FIG. 3 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, for the sake of easy understanding, the ratio of the vertical, horizontal, and thickness of each component shown in FIG. 3 is different from the actual one. The liquid crystal display device 200 includes at least a liquid crystal panel 100 and a backlight unit 80 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 type is adopted, the backlight unit 80 preferably includes at least a light source 81, a reflection film 82, a diffusion plate 83, a prism sheet 84, and a brightness enhancement film 85. When the sidelight method is adopted, preferably, the backlight unit further includes at least a light guide plate and a light reflector in addition to the above-described configuration. It should be noted that the optical member illustrated in FIG. 3 may be partially omitted depending on the application, such as the illumination method of the liquid crystal display device and the driving mode of the liquid crystal cell, as long as the effects of the present invention are exhibited. 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, OA equipment such as personal computer monitors, notebook computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Home appliances, back monitors, car navigation system monitors, car audio and other in-vehicle equipment, exhibition equipment such as commercial store information monitors, security equipment such as monitoring monitors, nursing monitors, medical monitors, etc. Nursing care / medical equipment.

  Preferably, the use of the liquid crystal display device of the present invention is a television. The screen size of the television is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, and particularly preferably a wide 32 type (687 mm × 412 mm) or more. .

The present invention will be further described using the above examples and comparative examples. In addition, this invention is not limited only to these Examples. In addition, each analysis method used in the Example is as follows.
(1) Transmittance of polarizing plate:
The transmittance (T) is the Y value of the tristimulus value based on the 2-degree field of JlS Z 8701-1995.
(2) Measuring method of each element (I, K) content:
Each element content was calculated | required with the analytical curve created beforehand using the standard sample from the X-ray intensity measured on the following conditions by the fluorescent X-ray analysis on the circular sample of diameter 10mm.
・ Analyzer: X-ray fluorescence analyzer (XRF) manufactured by Rigaku Denki Kogyo Co., Ltd. Product name “ZSX100e”
-Counter cathode: Rhodium-Spectral crystal: Lithium fluoride-Excitation light energy: 40 kV-90 mA
・ Iodine measurement line: I-LA
・ Potassium measurement line: K-KA
Quantitative method: FP method 2θ angle peak: 103.78 deg (iodine), 136.847 deg (potassium)
Measurement time: 40 seconds (3) Measuring method of phase difference values (Re [λ], Rth [λ]), Nz coefficient, T [590]:
Measurement was performed at 23 ° C. using a trade name “KOBRA21-ADH” manufactured by Oji Scientific Instruments. In addition, the value measured using the Abbe refractometer [Atago Co., Ltd. product name "DR-M4"] was used for the average refractive index.
(4) Measuring method of thickness:
When the thickness was less than 10 μm, measurement was performed using a thin film spectrophotometer [manufactured by Otsuka Electronics Co., Ltd., “instant multiphotometry system MCPD-2000”]. When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “KC-351C type”.
(5) Method for measuring molecular weight of polyimide resin:
Polyethylene oxide was calculated as a standard sample by a gel permeation chromatograph (GPC) method. The equipment, instruments and measurement conditions are as follows.
Sample: A sample was dissolved in an eluent to prepare a 0.1 wt% solution.
-Pretreatment: After standing for 8 hours, it was filtered through a 0.45 µm membrane filter.
・ Analyzer: “HLC-8020GPC” manufactured by Tosoh Corporation
・ Column: Tosoh GMH _XL + GMH _XL + G2500H _XL
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
Eluent: Dimethylformamide (added with 10 mM lithium bromide and 10 mM phosphoric acid to make up to 1 L dimethylformamide solution)
-Flow rate: 0.8 ml / min.
・ Detector: RI (differential refractometer)
-Column temperature: 40 ° C
・ Injection volume: 100 μl
(6) Method for measuring molecular weight of norbornene resin:
Polystyrene was calculated as a standard sample by the gel permeation chromatograph (GPC) method. Specifically, it measured with the following apparatuses, instruments, and measurement conditions. The sample is
Measurement sample: The sample was dissolved in tetrahydrane to give a 0.1% by weight solution, allowed to stand overnight, and then filtered using a 0.45 μm membrane filter.
・ Analyzer: “HLC-8120GPC” manufactured by TOSOH
Column: TSKgel Super HM-H / H4000 / H3000 / H2000
Column size: 6.0 mmI. D. × 150mm
-Eluent: Tetrahydrofuran-Flow rate: 0.6 ml / min.
・ Detector: RI (differential refractometer)
-Column temperature: 40 ° C
・ Injection volume: 20 μl
(7) Measuring method of glass transition temperature:
Using a differential scanning calorimeter [Seiko Co., Ltd. product name “DSC-6200”], it was determined by a method according to JIS K 7121 (1987) (measurement method of plastic transition temperature). Specifically, a 3 mg powder sample was heated twice (heating rate: 10 ° C./min) in a nitrogen atmosphere (gas flow rate: 80 ml / min) and measured twice, and the second data was adopted. The calorimeter corrected the temperature using a standard material (indium).
(8) Measuring method of absolute value (C [590]) of photoelastic coefficient:
Using a spectroscopic ellipsometer [product name “M-220” manufactured by JASCO Corporation], the sample (size 2 cm × 10 cm) is sandwiched at both ends and stress (5 to 15 N) is applied to the phase difference at the center of the sample. The value (23 ° C./wavelength 590 nm) was measured and calculated from the slope of the function of stress and retardation value.
(9) Measuring method of light leakage amount of liquid crystal display device in oblique direction:
After 30 minutes have passed since the backlight was turned on in a dark room at 23 ° C., an azimuth angle of 0 ° to 360 ° of the display screen when displaying a black image using the product name “EZ Contrast 160D” manufactured by ELDIM, The Y value of the XYZ display system at a polar angle of 60 ° was measured. The long side of the liquid crystal panel was set to an azimuth angle of 0 °, and the normal direction was set to a polar angle of 0 °.
(10) color shift of the liquid crystal display device (.DELTA.a ^* b ^*) of the measuring method:
After 30 minutes have passed since the backlight was turned on in a dark room at 23 ° C, the polar angle of the screen displaying the black image was 60 ° and the azimuth was 0 ° to 360 ° using the product name “EZ Contrast 160D” manufactured by ELDIM. defined by CIE1976L ^* a ^* b ^* color space in was measured color coordinates a ^* and b ^*. The color shift amount (Δa ^* b ^* ) in the oblique direction was calculated from the equation: {(a ^* ) ² + (b ^* ) ² } ^1/2 .

Production of Polarizer [Reference Example 1]
A polymer film (trade name “VF-PS # 7500”, manufactured by Kuraray Co., Ltd.) having a 75 μm-thick polyvinyl alcohol resin as a main component is placed in 5 baths under the following conditions [1] to [5] in the longitudinal direction of the film. The film was immersed while applying tension, and stretched so that the final stretching ratio was 6.2 times the original film length. The stretched film was dried in an air circulation drying oven at 40 ° C. for 1 minute to produce a polarizer A.
<Conditions>
[1] Swelling bath: 30 ° C. pure water.
[2] Dye bath: An aqueous solution at 30 ° C. containing 0.032 parts by weight of iodine with respect to 100 parts by weight of water and 0.2 parts by weight of potassium iodide with respect to 100 parts by weight of water.
[3] First cross-linking bath: 40 ° C. aqueous solution containing 3% by weight of potassium iodide and 3% by weight of boric acid.
[4] Second crosslinking bath: 60 ° C. aqueous solution containing 5% by weight of potassium iodide and 4% by weight of boric acid.
[5] Washing bath: A 25 ° C. aqueous solution containing 3% by weight of potassium iodide.

[Reference Example 2]
Polarizer B was produced under the same conditions and method as in Reference Example 1 except that the amount of iodine added under condition [2] was 0.031 parts by weight with respect to 100 parts by weight of water in the dye bath.

[Reference Example 3]
A polarizer C was produced under the same conditions and method as in Reference Example 1 except that the amount of iodine added under condition [2] was 0.027 parts by weight with respect to 100 parts by weight of water in the dye bath.

Preparation of first retardation layer [Reference Example 4]
Using a tenter stretching machine, a polymer film containing a norbornene-based resin having a thickness of 100 μm [trade name “Zeonor ZF14-100” manufactured by Optes Co., Ltd.] was fixed using a tenter stretching machine (fixed end lateral uniaxial stretching method, fixing the longitudinal direction, width The film was stretched 2.7 times in an air circulating constant temperature oven at 150 ° C. by the method of stretching in the direction) to obtain a retardation film A. In this retardation film (A), the refractive index ellipsoid shows a relationship of nx>ny> nz, and the thickness is 35 μm, T [590] = 91%, Re [590] = 120 nm, Rth [590] = 160 nm, Nz The coefficient was 1.33 and C [590] = 5.1 × 10 ⁻¹² m ² / N.

Preparation of second retardation layer [Reference Example 5]
2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride in a reaction vessel (500 mL) equipped with a mechanical stirrer, Dean-Stark device, nitrogen inlet tube, thermometer and condenser tube [Clariant Japan Co., Ltd.] 17.77 g (40 mmol) and 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl [Wakayama Seika Kogyo Co., Ltd.] 12.81 g (40 mmol) added. Subsequently, a solution in which 2.58 g (20 mmol) of isoquinoline was dissolved in 275.21 g of m-cresol was added, and the mixture was stirred at 23 ° C. for 1 hour (600 rpm) to obtain a uniform solution. Next, the reaction vessel was heated using an oil bath so that the temperature in the reaction vessel became 180 ± 3 ° C., and stirred for 5 hours while maintaining the temperature to obtain a yellow solution. After further stirring for 3 hours, heating and stirring were stopped, and the mixture was allowed to cool to room temperature.

  Acetone was added to the yellow solution in the reaction vessel to completely dissolve the gel to prepare a diluted solution (7% by weight). When this diluted solution was gradually added to 2 L of isopropyl alcohol while stirring, a white powder was precipitated. This powder was collected by filtration and poured into 1.5 L of isopropyl alcohol for washing. Further, the same operation was repeated once again for washing, and then the powder was collected again by filtration. This was dried for 48 hours in an air circulation type constant temperature oven at 60 ° C., and then dried at 150 ° C. for 7 hours to obtain a polyimide powder of the following structural formula (III) in a yield of 85%. The polyimide had a polymerization average molecular weight (Mw) of 124,000 and an imidation ratio of 99.9%.

The polyimide powder was dissolved in methyl isobutyl ketone to prepare a 15% by weight polyimide solution. This polyimide solution was uniformly cast in the form of a sheet by a slot die coater on the surface of a triacetylcellulose film (thickness 80 μm). Next, the film is put into a multi-chamber air circulation drying oven, and the solvent is evaporated while gradually raising the temperature from a low temperature of 80 ° C. for 2 minutes, 135 ° C. for 5 minutes, and 150 ° C. for 10 minutes. And the laminated body (C) provided with a 3.7-micrometer-thick polyimide layer and a triacetyl-cellulose film was obtained. In the laminate (C), the refractive index ellipsoid showed a relationship of nx = ny> nz, and T [590] = 90%, Re [590] = 1 nm, and Rth [590] = 210 nm. The optical properties of the polyimide layer portion of the laminate (C) were Rth [590] = 150 nm and Δn _xz = 0.04.

Production of first polarizing plate [Reference Example 6]
On one side of the polarizer A obtained in Reference Example 1, via a water-soluble adhesive mainly composed of a polyvinyl alcohol-based resin (trade name “GOHSEIMER Z200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) The retardation film A obtained in Reference Example 4 was stuck so that the slow axis direction of the retardation film A was orthogonal to the absorption axis direction of the polarizer A. Next, on the other side of the polarizer A, a polymer film containing a cellulose resin having a thickness of 80 μm [trade name “TD80UF” manufactured by Fuji Photo Film Co., Ltd.] is interposed through the water-soluble adhesive. Sticked. The characteristics of the polarizing plate A1 produced in this way are shown in Table 1 below.

[Reference Example 7]
A polarizing plate B1 was produced in the same manner as in Reference Example 6 except that the polarizer B obtained in Reference Example 2 was used in place of the polarizer A. The characteristics of the polarizing plate B1 are shown in Table 1 below.

[Reference Example 8]
A polarizing plate C1 was produced in the same manner as in Reference Example 6 except that the polarizer C obtained in Reference Example 3 was used in place of the polarizer A. The characteristics of the polarizing plate C1 are shown in Table 1 below.

[Reference Example 9]
On one side of the polarizer A obtained in Reference Example 1, via a water-soluble adhesive mainly composed of a polyvinyl alcohol-based resin (trade name “GOHSEIMER Z200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) The laminate C obtained in Reference Example 5 was stuck so that the triacetyl cellulose film side of the laminate C was opposed to the polarizer A. Next, on the other side of the polarizer A, a polymer film containing a cellulose resin having a thickness of 80 μm [trade name “TD80UF” manufactured by Fuji Photo Film Co., Ltd.] is interposed through the water-soluble adhesive. Sticked. The characteristics of the polarizing plate A2 thus produced are shown in Table 1 below.

[Reference Example 10]
A polarizing plate B2 was produced in the same manner as in Reference Example 9 except that the polarizer B obtained in Reference Example 2 was used in place of the polarizer A. The characteristics of the polarizing plate B2 are shown in Table 1 below.

[Reference Example 11]
A polarizing plate C2 was produced in the same manner as in Reference Example 9 except that the polarizer C obtained in Reference Example 3 was used in place of the polarizer A. The characteristics of the polarizing plate C2 are shown in Table 1 below.

Preparation of liquid crystal cell [Reference Example 12]
Take out the liquid crystal panel from a commercially available liquid crystal display device [BenQ 32-inch liquid crystal television product name “DV3250”] including the VA mode liquid crystal cell, and remove all the optical films such as polarizing plates placed above and below the liquid crystal cell. It was. The front and back of the glass plate of this liquid crystal cell was washed to obtain liquid crystal cell A.

Preparation of the liquid crystal panel and a liquid crystal display device Example 1
On the viewing side of the liquid crystal cell A prepared in Reference Example 12, the polarizing plate C1 prepared in Reference Example 8 as the first polarizing plate, the retardation film A side as the liquid crystal cell side, and the absorption axis of the polarizing plate C1 It was stuck via an acrylic pressure-sensitive adhesive (thickness 20 μm) so that the direction was substantially parallel to the long side direction of the liquid crystal cell A. Next, on the opposite side (backlight side) of the liquid crystal cell A, the polarizing plate A2 produced in Reference Example 9 is used as the second polarizing plate, the laminate C side is the liquid crystal cell side, and the polarizing plate It was stuck via an acrylic pressure-sensitive adhesive (thickness 20 μm) so that the absorption axis direction of A1 was substantially perpendicular to the long side direction of the liquid crystal cell A. At this time, the absorption axis direction of the first polarizing plate and the absorption axis direction of the second polarizing plate are substantially perpendicular to each other. This liquid crystal panel A was combined with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device A. The characteristics of the obtained liquid crystal display device A are shown in Table 2 below. FIG. 4 is a luminance contour diagram when the black image is displayed in the liquid crystal display device according to the first embodiment.
When the liquid crystal display device A displays a black image,
Average value of Y values of polar angle 60 °, azimuth angle 0 ° to 360 ° = 0.84
Maximum Y value of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 1.15
Minimum Y value of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 0.42
Difference between maximum and minimum Y values of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 0.73
Polar angle 60 °, the azimuth angle 0 ° ~360 ° Δa ^* b ^* of the mean = 2.26
Maximum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 4.35
Minimum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 0.10
Met.

[Example 2]
A liquid crystal panel B and a liquid crystal display device B were produced in the same manner as in Example 1 except that the polarizing plate B1 produced in Reference Example 7 was used as the first polarizing plate. The characteristics of the obtained liquid crystal display device B are shown in Table 2 below.

[Comparative Example 1]
In the same manner as in Example 1, except that the polarizing plate A1 prepared in Reference Example 6 was used as the first polarizing plate, and the polarizing plate C2 prepared in Reference Example 11 was used as the second polarizing plate. A liquid crystal panel H and a liquid crystal display device H were produced. The characteristics of the obtained liquid crystal display device H are shown in Table 2 below. FIG. 5 is a luminance contour diagram when the black image is displayed in the liquid crystal display device of Comparative Example 1.
When the liquid crystal display device H displays a black image,
Average value of Y values of polar angle 60 °, azimuth angle 0 ° to 360 ° = 1.13
Maximum Y value of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 1.86
Minimum Y value of polar angle 60 °, azimuth angle 0 ° to 360 ° = 0.55
Difference between maximum value and minimum value of Y value at polar angle of 60 ° and azimuth angle of 0 ° to 360 ° = 1.31
Average value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 4.14
Maximum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 6.02
Minimum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 2.14
Met.

[Comparative Example 2]
In the same manner as in Example 1, except that the polarizing plate A1 prepared in Reference Example 6 was used as the first polarizing plate, and the polarizing plate B2 prepared in Reference Example 10 was used as the second polarizing plate. A liquid crystal panel I and a liquid crystal display device I were produced. The characteristics of the obtained liquid crystal display device I are shown in Table 2 below.

[Comparative Example 3]
A liquid crystal panel J and a liquid crystal display device J were produced in the same manner as in Example 1 except that the polarizing plate C2 produced in Reference Example 11 was used as the second polarizing plate. The characteristics of the obtained liquid crystal display device J are shown in Table 2 below.

[Comparative Example 4]
In the same manner as in Example 1 except that the polarizing plate B1 prepared in Reference Example 7 was used as the first polarizing plate, and the polarizing plate B2 prepared in Reference Example 10 was used as the second polarizing plate. A liquid crystal panel K and a liquid crystal display device K were produced. The characteristics of the obtained liquid crystal display device K are shown in Table 2 below.

[Evaluation]
FIG. 6 shows changes in luminance (Y value) at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° on a screen displaying a black image in the liquid crystal display devices of Example 1 and Comparative Example 1. FIG. 7 shows the change in the color shift amount (Δa ^* b ^* ) at the polar angle of 60 ° and the azimuth angle of 0 ° to 360 ° on the screen displaying the black image in the liquid crystal display devices of Example 1 and Comparative Example 1. is there. Compared with the liquid crystal display device of the first comparative example, the liquid crystal display device of the first embodiment has a significantly smaller amount of change depending on the azimuth angle of the Y value and Δa ^* b ^*. It can be seen that light leakage in the oblique direction and color shift are extremely small.

In the liquid crystal display device including the liquid crystal panel of the present invention, as shown in Examples 1 and 2, the transmittance (T ₁ ) of the first polarizing plate is larger than the transmittance (T ₂ ) of the second polarizing plate. As a result, the luminance (light leakage in the oblique direction) when displaying a black image can be remarkably reduced as compared with the conventional liquid crystal display device. On the other hand, the liquid crystal display device of Comparative Examples 1 to 4, or those transmittance of the first polarizing plate (T ₁₎ and the transmittance of the second polarizing plate and (T ₂₎ are equal, or the first transmittance of the polarizing plate (T ₁₎ is, but is smaller than the transmittance of the second polarizing plate (T _2), the light leakage of the oblique directions, was very large.

  As described above, since the liquid crystal panel of the present invention can reduce light leakage in an oblique direction when used in a liquid crystal display device, it is extremely useful for improving display characteristics of, for example, a liquid crystal television, a personal computer monitor, and a mobile phone. is there.

It is a schematic sectional drawing of the liquid crystal panel in preferable embodiment of this invention. It is a schematic diagram which shows the concept of the typical manufacturing process of the polarizer used for this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It is a brightness | luminance contour map at the time of displaying the black image of the liquid crystal display device of Example 1. FIG. It is a brightness | luminance contour map at the time of displaying the black image of the liquid crystal display device of the comparative example 1. This is a change in luminance (Y value) at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° on a screen displaying a black image in the liquid crystal display devices of Example 1 and Comparative Example 1. This is a change in the amount of color shift (Δa ^* b ^* ) at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° on a screen displaying a black image in the liquid crystal display devices of Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 21 1st polarizer 22 2nd polarizer 31 1st phase difference layer 32 2nd phase difference layer 41 1st protective layer 42 2nd protective layer 42
51 First polarizing plate 51
52 Second Polarizing Plate 80 Backlight Unit 81 Light Source 82 Reflective Film 83 Diffuser Plate 84 Prism Sheet 85 Brightness Enhancement Film 100 Liquid Crystal Panel 301 Polymer Film Mainly Containing Polyvinyl Alcohol Resin 300 Feeding Section 310 Swelling Bath 320 Dyeing Bath 311, 312, 321, 322, 331, 332, 341, 342 Roll 330 First cross-linking bath 340 Second cross-linking bath 350 Washing bath 360 Drying means 370 Polarizer 380 Winding unit

Claims (13)

A liquid crystal cell;
A first polarizing plate disposed on one side of the liquid crystal cell;
And at least a second polarizing plate disposed on the other side of the liquid crystal cell,
The first polarizing plate includes a first polarizer, and a first retardation layer disposed on the liquid crystal cell side of the first polarizer,
The second polarizing plate includes a second polarizer, and a second retardation layer disposed on the liquid crystal cell side of the second polarizer,
The refractive index ellipsoid of the first retardation layer shows a relationship of nx> ny ≧ nz,
The refractive index ellipsoid of the second retardation layer shows a relationship of nx = ny> nz,
The transmittance (T ₁ ) of the _first polarizing plate is a liquid crystal panel that is larger than the transmittance (T ₂ ) of the second polarizing plate. The difference (ΔT = T ₁ −T ₂ ) between the transmittance (T ₁ ) of the _first polarizing plate and the transmittance (T ₂ ) of the second polarizing plate is 0.1% to 6.0. The liquid crystal panel according to claim 1, which is%.   The liquid crystal panel according to claim 1, wherein the liquid crystal cell includes liquid crystal molecules aligned in a homeotropic alignment.   The said 1st polarizing plate is arrange | positioned at the visual recognition side of the said liquid crystal cell, and the said 2nd polarizing plate is arrange | positioned at the opposite side to the visual recognition side of the said liquid crystal cell. LCD panel.   5. The liquid crystal panel according to claim 1, wherein each of the first polarizer and the second polarizer has a polyvinyl alcohol-based resin containing iodine as a main component. The difference (ΔI = I ₂ −I ₁ ) between the iodine content (I ₂ ) of the _second polarizer and the iodine content (I ₁ ) of the first polarizer is 0.1 wt% to The liquid crystal panel according to claim 5, which is 2.6% by weight.   The liquid crystal panel according to claim 5 or 6, wherein iodine content of the first polarizer and the second polarizer is 1.8 wt% to 5.0 wt%.   The liquid crystal panel according to claim 1, wherein a slow axis direction of the first retardation layer is substantially orthogonal to an absorption axis direction of the first polarizer. The liquid crystal panel according to claim 1, wherein an in-plane retardation value (Re ₁ [590]) at a wavelength of 590 nm of the first retardation layer is 50 nm to 200 nm.   The liquid crystal panel according to claim 1, wherein the first retardation layer is a retardation film (A) containing a norbornene-based resin. The second retardation value in the thickness direction at a wavelength of 590nm of the retardation layer (Rth ₂ [590]) is a 100 nm to 400 nm, the liquid crystal panel according to any one of claims 1 to 10.   The second retardation layer is a retardation film (B) containing a polyimide resin or a cellulose resin, or a laminate of a retardation film containing a polyimide resin and a retardation film containing a cellulose resin. The liquid crystal panel according to claim 1, wherein the liquid crystal panel is (C). A liquid crystal display device comprising the liquid crystal panel according to claim 1.