TW202004282A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

A liquid crystal panel (101) is provided with a liquid crystal cell (20), a first polarizer (30), a second polarizer (40), and an optically anisotropic element (50). The liquid crystal cell is provided with a liquid crystal layer including liquid crystal molecules in a homogeneous alignment in the absence of an electric field, and a color filter (22) disposed on a first principal surface of the liquid crystal layer. The slow-axis direction (53) of the optically anisotropic element (50) and the absorption axis direction (45) of the second polarizer are parallel. The thickness-direction retardation of the optically anisotropic element and the thickness-direction retardation of the color filter of the liquid crystal cell satisfy a predetermined relationship for each of a wavelength of 550 nm and a wavelength of 650 nm.

Description

Liquid crystal panel and liquid crystal display device

The invention relates to a liquid crystal panel provided with an optically anisotropic element between a liquid crystal cell and a polarizer. Furthermore, the present invention relates to a liquid crystal display device using the above liquid crystal panel.

The liquid crystal panel includes a liquid crystal cell between a pair of polarizers. The liquid crystal cell is provided with a liquid crystal layer between a pair of substrates. In a general liquid crystal cell, a color filter is provided on a substrate (color filter substrate) arranged on the viewing side of the liquid crystal layer, and a substrate arranged on the light source side ( A TFT (thin-film transistor, thin film transistor) substrate) is provided with pixel electrodes, TFT elements, and the like.

In the liquid crystal cell of the horizontal electric field effect (IPS, In-Plane Switching) method, in the state of no electric field, the liquid crystal molecules are aligned in a direction substantially parallel to the substrate surface, and the liquid crystal molecules are applied to the substrate surface by the application of the horizontal electric field Rotate in parallel planes to control light transmission (white display) and shadowing (black display). Like the IPS method, the liquid crystal panel in the horizontal electric field method in which liquid crystal molecules are aligned in parallel in the absence of an electric field has excellent viewing angle characteristics.

The liquid crystal display device of the IPS method is based on the alignment direction of the liquid crystal molecules in the state of no electric field of the liquid crystal cell (hereinafter referred to as the "initial alignment direction"), and the absorption axis direction of the polarizer disposed on the front and back of the liquid crystal cell The relationship is roughly divided into O mode and E mode. In the O mode, the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell is parallel to the initial alignment direction of the liquid crystal. In the E mode, the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell is orthogonal to the initial alignment direction of the liquid crystal.

When the IPS liquid crystal display device is viewed from an oblique direction at an angle of 45 degrees (azimuth angle 45 degrees, 135 degrees, 225 degrees, 315 degrees) with respect to the absorption axis of the polarizer, the light leakage of the black display is large, Easy to reduce the contrast or color shift. The light leakage is caused by the angle formed by the polarizer disposed on the front and back of the liquid crystal cell in the "apparent absorption axis direction" shifting from 90° when viewed from the oblique direction.

For the purpose of reducing light leakage when viewing from an oblique direction, a method of disposing an optically anisotropic element (retardation plate) between a liquid crystal cell and a polarizer is proposed. For example, Patent Document 1 proposes to arrange an optically anisotropic element having a refractive index anisotropy of nx>nz>ny between a liquid crystal cell and a polarizer. nx is the refractive index in the direction of the in-plane slow phase axis, ny is the refractive index in the direction of the in-plane progressive phase axis, and nz is the refractive index in the thickness direction (normal direction).

From the viewpoint of compensating the angular deviation of the apparent absorption axis direction of the polarizer, it is more ideal that the retardation of the optically anisotropic element is 1/2 of the wavelength, and Nz=(nx-nz)/(nx -Ny) indicates that the Nz coefficient is 0.5 (refer to Poincare sphere in FIG. 5). The retardation of the optically anisotropic element varies according to the wavelength. In the optical compensation of a liquid crystal display device using an optically anisotropic element, optical design is generally performed in such a way that leakage light of green light (wavelength near 550 nm) with higher visual sensitivity is reduced. Therefore, in order to compensate for the angular deviation of the apparent axial direction of the polarizer, it is sufficient to use an optically anisotropic element with a retardation at a wavelength of 550 nm of about 275 nm.

In addition to the apparent axial deviation of the polarizer, the characteristics of other optical elements will also cause light leakage during black display. For example, Patent Document 2 proposes to consider the birefringence of a triacetyl cellulose (TAC) film provided on the surface of the polarizer on the liquid crystal cell side as a protective film to adjust the optical characteristics of the optical anisotropic element used for optical compensation . In Patent Document 3, as a protective film provided on the surface of the polarizer, it is proposed to use a low birefringence film such as an original norbornene-based resin film. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 4-371903 [Patent Document 2] Japanese Patent Laid-Open No. 2001-258041 [Patent Document 3] Japanese Patent Laid-Open No. 2004-4641

[Problems to be solved by the invention]

The in-plane retardation of the color filter provided on the substrate of the liquid crystal cell is approximately 0, but it has a retardation of several nm to several tens of nm in the thickness direction. As described above, when the optical element disposed between the polarizer and the liquid crystal cell has birefringence, by adjusting the optical characteristics of the optically anisotropic element by considering its optical characteristics, light leakage when viewed from the oblique direction can be further reduced .

As described above, the optical compensation of the liquid crystal panel is optimized for green (higher than 550 nm wavelength) light with higher visual sensitivity. Therefore, in black display, light with a wavelength shifted from the optimal value by a large amount of light leaks, and the picture is colored to be recognized. In terms of optical design, it is difficult to make the hue when viewed from the oblique direction completely neutral. Therefore, when displaying in black, the screen is slightly colored and recognized depending on the wavelength of light with light leakage. Blue (near wavelength 450 nm) has a lower visual sensitivity than red (near wavelength 650 nm), so the hue of black display tends to prefer the blue color.

According to the research of the present inventors and others, in the case of a liquid crystal panel with a specific structure, considering the influence of the retardation in the thickness direction of the color filter, the design of the optical anisotropic element is performed in such a way as to minimize the green light leakage, It is found that there is a tendency that the light leakage of red light is large, and the black-displayed picture is recognized in the hue of red when viewed from the oblique direction. Specifically, the following problem was found, when the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell is orthogonal to the direction of the slow phase axis of the optical anisotropic element, if the color filter is considered The effect of retardation in the thickness direction and optical design in such a way that the green light leakage becomes smaller, also tends to suppress the red light leakage. On the other hand, in the case where the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell is parallel to the direction of the retardation axis of the optical anisotropic element, if the influence of the thickness direction delay of the color filter is considered, Green light leakage becomes the smallest way for optical design, then red light leakage is larger, and black display is easy to become the hue of the red system.

The object of the present invention is to provide an image display device in a liquid crystal panel in which the absorption axis direction of the light source side polarizer is parallel to the retardation axis direction of the optical anisotropic element, and the self-tilt is reduced in consideration of the influence of the color filter Light leakage in black display during direction recognition and reduced red coloration in black display are excellent in visibility. [Technical means to solve the problem]

The liquid crystal panel of the present invention includes: a liquid crystal cell including a liquid crystal layer including liquid crystal molecules aligned in parallel in a state without an electric field, and a color filter disposed on a first main surface (viewing side) of the liquid crystal layer; first polarized light The device is arranged on the first main surface (viewing side) of the liquid crystal cell; and the second polarizer is arranged on the second main surface (light source side) of the liquid crystal cell. The direction of the absorption axis of the first polarizer is orthogonal to the direction of the absorption axis of the second polarizer.

The color filter has at least a green transmission area and a red transmission area. The green transmission region of the color filter preferably has a thickness direction retardation Ct ₅₅₀ of 50 nm or less at a wavelength of 550 nm. The red region of the color filter preferably has a thickness direction retardation Ct ₆₅₀ with a wavelength of 650 nm of 50 nm or less. Both Ct ₅₅₀ and Ct ₆₅₀ are greater than zero. Ct ₅₅₀ and Ct ₆₅₀ may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more.

The liquid crystal panel of the present invention includes an optically anisotropic element disposed between the first polarizer and the second polarizer. The direction of the slow phase axis of the optically anisotropic element is parallel to the direction of the absorption axis of the second polarizer. Wavelength 650 nm of the optically anisotropic element of the front retardation Re ₆₅₀ retardation Rt in the thickness direction of the ratio Rt _{650 650} / Re ₆₅₀ of 0.2 to 0.8.

Preferably, the thickness direction retardation Rt ₆₅₀ (nm) of the optical anisotropic device at a wavelength of 650 nm and the thickness direction retardation Ct ₆₅₀ (nm) of the wavelength of 650 nm at the red transmission region of the color filter satisfy the following formula (1a) ) Or (2a): Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+116...(1a) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+116...(2a).

The liquid crystal panel of the first embodiment of the present invention is in the O mode, and the alignment direction (initial alignment direction) of the liquid crystal molecules in the liquid crystal cell in an electric field-free state is parallel to the absorption axis direction of the second polarizer. In the O-mode liquid crystal panel, an optically anisotropic element is arranged between the liquid crystal cell and the first polarizer, that is, on the viewing side of the liquid crystal cell.

In the first embodiment, it is preferable that the retardation Rt ₅₅₀ (nm) in the thickness direction of the wavelength of the optical anisotropic element at 550 nm and the retardation Ct ₅₅₀ (nm) in the thickness direction of the wavelength of 550 nm in the green transmission region of the color filter satisfy The following formula (3a): 0.97(Ct ₅₅₀ )+73≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+205...(3a).

The liquid crystal panel of the second embodiment of the present invention is in the E mode, and the initial alignment direction of the liquid crystal molecules of the liquid crystal cell is orthogonal to the absorption axis direction of the second polarizer. In the E-mode liquid crystal panel, an optically anisotropic element is arranged between the liquid crystal cell and the second polarizer, that is, on the light source side of the liquid crystal cell.

In the second embodiment, it is preferable that the retardation Rt ₅₅₀ (nm) in the thickness direction of the wavelength 550 nm of the optical anisotropic element and the retardation Ct ₅₅₀ (nm) in the thickness direction of the wavelength 550 nm of the green transmission region of the color filter satisfy The following formula (8a): 0.69(Ct ₅₅₀ )+70≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+200...(8a).

The liquid crystal display device of the present invention includes a light source disposed on the second main surface side of the liquid crystal panel. [Effect of invention]

According to the present invention, it is possible to provide a liquid crystal display device which is optically designed by considering the birefringence of a color filter, can reduce black brightness when viewed from an oblique direction, suppresses red coloration of black display, and has excellent visibility.

[Overview of the entire LCD panel] FIG. 1 is a conceptual diagram showing the configuration of the arrangement of optical elements in the liquid crystal panel 101 of the first embodiment. 2 is a schematic cross-sectional view of a liquid crystal display device 201 including a liquid crystal panel 101 and a light source 110. 3 is a conceptual diagram showing the configuration of the arrangement of optical elements in the liquid crystal panel 102 of the second embodiment. 4 is a schematic cross-sectional view of a liquid crystal display device 202 including a liquid crystal panel 102 and a light source 110.

The liquid crystal panel includes a first polarizer 30 disposed on the first main surface (viewing side) of the liquid crystal cell 20 and a second polarizer 40 disposed on the second main surface (light source side) of the liquid crystal cell 20. The absorption axis direction 35 of the first polarizer 30 is orthogonal to the absorption axis direction 45 of the second polarizer 40.

The liquid crystal panel 101 and the liquid crystal display device 201 of the first embodiment are in the O mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the light source 110 side of the liquid crystal cell 20 and the initial alignment direction 11 of the liquid crystal molecules of the liquid crystal layer 10 parallel. The liquid crystal panel 102 and the liquid crystal display device 202 of the second embodiment are in the E mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the light source 110 side of the liquid crystal cell 20 and the initial alignment direction 11 of the liquid crystal molecules of the liquid crystal layer 10 Orthogonal.

The liquid crystal panel of the present invention includes an optically anisotropic element between the first polarizer 30 and the second polarizer 40. The O-mode liquid crystal panel 101 of the first embodiment includes an optically anisotropic element 50 between the liquid crystal cell 20 and the first polarizer 30. The E-mode liquid crystal panel 102 of the second embodiment includes an optically anisotropic element 60 between the liquid crystal cell 20 and the second polarizer 40. In either form, the absorption axis direction 45 of the second polarizer 40 is parallel to the retardation axis directions 53, 63 of the optically anisotropic elements 50, 60.

In addition, in this specification, the term "orthogonal" refers not only to the situation of complete orthogonality, but also includes substantially orthogonality, and its angle is generally within the range of 90±2°, preferably 90±1°, more preferably 90 ±0.5 range. Similarly, the term "parallel" refers to not only perfect parallel, but also substantially parallel, and its angle is generally within ±2°, preferably within ±1°, and more preferably within ±0.5°.

[LCD unit] The liquid crystal cell 20 includes a liquid crystal layer 10 between the first substrate 21 and the second substrate 25. A color filter 22 is provided on the first substrate 21 (color filter substrate) disposed on the viewing side of the liquid crystal layer. The color filter 22 has at least a green transmission region 22G and a red transmission region 22R. The second substrate 25 (TFT substrate) disposed on the light source side of the liquid crystal layer 10 is provided with a switching element (generally a TFT element) for controlling the alignment direction of the liquid crystal.

In the green transmission region 22G of the color filter 22, a green filter having a relatively high transmittance for light near a wavelength of 500 to 600 nm is provided. The green filter preferably has a maximum transmittance near a wavelength of 500 to 600 nm. The transmittance of the green transmission region at a wavelength of 550 nm is, for example, 30% or more. The transmittance of the wavelength 450 nm in the green transmission region is preferably 10% or less. The transmittance of the green transmission region at a wavelength of 650 nm is preferably 10% or less, and more preferably 5% or less.

In the red transmission region 22R, a red filter having a relatively high transmittance for visible light with a longer wavelength than the wavelength of 600 nm is provided. The transmittance at a wavelength of 650 nm in the red transmission region is, for example, 30% or more. The transmittance at a wavelength of 550 nm and the transmittance at a wavelength of 450 nm in the red transmission region are preferably 10% or less, and more preferably 5% or less.

The color filter 22 may include regions other than the green transmission region 22G and the red transmission region 22R, and generally includes the blue transmission region 22B. The blue transmission region 22B is provided with a blue filter having a relatively high transmittance for visible light having a shorter wavelength than the wavelength of 500 nm. The transmittance of the wavelength 450 nm in the blue transmission region is, for example, 30% or more. The transmittance at a wavelength of 550 nm and the transmittance at a wavelength of 650 nm in the blue transmission region are preferably 10% or less, and more preferably 5% or less.

The color filter may further have a light-transmitting region having a relatively high light transmittance relative to a specific wavelength region other than the above. It is preferable that a black matrix is provided at the boundary between adjacent transmission regions.

The liquid crystal layer 10 includes liquid crystal molecules aligned in parallel under the state of no electric field. The so-called parallel alignment of liquid crystal molecules refers to the state in which the alignment vectors of the liquid crystal molecules are aligned parallel and uniformly with respect to the plane of the substrate. Furthermore, the alignment vector of the liquid crystal molecules may also be slightly tilted (pretilt) relative to the substrate plane. The pretilt angle of the liquid crystal cell is generally 3° or less, preferably 1° or less, and more preferably 0.5° or less.

Examples of liquid crystal cells including liquid crystal molecules aligned in parallel in an electroless state include lateral electric field effect (IPS) mode, fringe-field switching (FFS) mode, and ferroelectric liquid crystal (FLC). Mode etc. As the liquid crystal molecules, nematic liquid crystal or smectic liquid crystal can be used. Generally speaking, nematic liquid crystals are used in the IPS mode and FFS mode liquid crystal cells, and smectic liquid crystals are used in the FLC mode liquid crystal cells.

[Polarizer] The first polarizer 30 is disposed on the first main surface side of the liquid crystal cell 20, and the second polarizer 40 is disposed on the second main surface side. The polarizer converts natural light or arbitrary polarized light into linear polarized light. As the first polarizer 30 and the second polarizer 40, any appropriate polarizer can be used according to the purpose. For example, hydrophilic polymers such as adsorbed dichroic substances such as iodine and dichroic dyes on polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films can be cited. Uniaxially stretched film, polyene-based alignment film such as polyvinyl alcohol dehydration treatment or polyvinyl chloride dehydrochlorination treatment, etc.

Among these polarizers, from the viewpoint of having a high degree of polarization, a polychromatic substance such as iodine or a dichroic dye adsorbed to polyvinyl alcohol or partially formalized polyvinyl alcohol can be preferably used. A polyvinyl alcohol (PVA, polyvinyl alcohol) polarizer with a vinyl alcohol film and oriented in a specific direction. For example, a PVA-based polarizer can be obtained by performing iodine dyeing and stretching on a polyvinyl alcohol-based film.

As the PVA-based polarizer, a thin polarizer with a thickness of 10 μm or less can also be used. Examples of thin polarizers include those described in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, WO2010/100917 manual, Patent No. 4691205, and Patent No. 4571481. Thin polarizing film. Such a thin polarizer is obtained by, for example, a manufacturing method including a step of extending a PVA-based resin layer and an extending resin base material in a state of a laminate, and a step of iodine dyeing.

[Optical Anisotropic Element] The optically anisotropic elements 50 and 60 are in-plane refractive index nx in the direction of the retardation axis, in-plane refractive index ny in the direction of the advancement axis, and refractive index nz in the thickness direction satisfying nx>nz>ny . The polarizers 30 and 40 arranged above and below the liquid crystal cell 20 are arranged in such a way that the absorption axis directions 35 and 45 are orthogonal, but if the liquid crystal panel is viewed from the oblique direction, the apparent absorption axis of the polarizers 30 and 40 is The angle formed by the direction is greater than 90° (offset from orthogonal polarized light), so light leakage occurs.

By disposing a phase difference film satisfying nx>nz>ny between the liquid crystal cell 20 and the polarizers 30 and 40, the apparent axial shift of the polarizer can be compensated, and light leakage when viewing the picture from the oblique direction can be reduced. In particular, the black brightness at an angle of 45 degrees (azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees) relative to the absorption axis of the polarizer decreases, and the contrast improves.

In the O-mode liquid crystal panel 101 of the first embodiment, an optically anisotropic element 50 is arranged between the liquid crystal cell 20 and the first polarizer 30 on the viewing side. In the E-mode liquid crystal panel 102 of the second embodiment, an optically anisotropic element 60 is arranged between the liquid crystal cell 20 and the second polarizer 40 on the light source side.

The front retardation Re _{550 of the} optical anisotropic elements 50 and 60 at a wavelength of 550 nm is preferably 150 to 400 nm, more preferably 180 to 370 nm, and still more preferably 200 to 350 nm. The thickness direction retardation Rt _{550 of the} optical anisotropic device at a wavelength of 550 nm is preferably from 75 to 200 nm, more preferably from 90 to 185 nm, and even more preferably from 100 to 175 nm. In addition, the front retardation Re and the thickness direction retardation Rt use the in-plane retardation axis direction refractive index nx, the in-plane advancement axis direction refractive index ny, and the thickness direction refractive index nz are defined as follows: Re = (Nx-ny) × d Rt = (nx-nz) × d.

The range of Re and Rt of the optically anisotropic element considering the retardation in the thickness direction of the color filter will be described in detail below.

The optically anisotropic elements 50 and 60 preferably have an Nz coefficient defined by Nz=(nx-nz)/(nx-ny) of 0.2 to 0.8. According to the above definitions of Re and Rt, it can also be expressed as Nz=Rt/Re. In this specification, the Nz coefficient is calculated based on the refractive index at a wavelength of 650 nm. That is, Nz coefficient and retardation Re ₆₅₀ retardation Rt in the thickness direction of the ratio Rt _{650 650} / Re ₆₅₀ is a wavelength of 650 nm positive. Therefore, the optically anisotropic element preferably has Rt ₆₅₀ /Re ₆₅₀ of 0.2 to 0.8. In addition, in the retardation film produced by extending the polymer film, generally, the Nz coefficient calculated from the refractive index at a wavelength of 550 nm is substantially the same as the Nz coefficient calculated from the refractive index at a wavelength of 650 nm.

The Nz coefficient of the optically anisotropic element is more preferably 0.3 to 0.7, further preferably 0.4 to 0.6. There is a tendency that the closer the Nz coefficient is to 0.5, the lower the light leakage in a wider viewing angle range.

Examples of the material constituting the optically anisotropic element include polycarbonate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate resins, polyphenols, and poly Ether resins such as ether resins, sulfur resins such as polyphenylene sulfide, polyimide resins, cyclic polyolefin (polynorbornene) resins, polyamide resins, polyolefins such as polyethylene or polypropylene Resins, cellulose esters, etc. Liquid crystal materials can also be used as materials for optically anisotropic elements.

In the case of using a polymer material, by extending or shrinking the polymer film in at least one direction, the molecular alignment in a specific direction can be improved, thereby manufacturing an optically anisotropic element (retardation film). In the state where the polymer film and the heat-shrinkable film are stacked, one side extends in one direction, and the other side uses the shrinking force of the heat-shrinkable film to shrink the film in a direction orthogonal to the extension direction, thereby obtaining nx>nz>ny Anisotropic optical anisotropic element of refractive index.

The thickness of the optically anisotropic element can be appropriately selected according to the material and the like constituting the optically anisotropic element. When using polymer materials, the thickness of the optically anisotropic element is generally about 3 μm to 200 μm. In the case of using liquid crystal materials, the thickness of the optically anisotropic element (thickness of the liquid crystal layer) is generally about 0.1 μm to 20 μm.

The optical anisotropic element only needs to have specific Re and Rt, and the material, thickness and manufacturing method of the optical anisotropic element are not limited to the above.

[Optical Compensation Principle of Optical Anisotropic Element] In the present invention, by setting the optical characteristics of the optical anisotropic element according to the birefringence of the color filter, the apparent axial direction of the polarizer can be optically compensated Both the offset and the influence of the birefringence of the color filter obtain a liquid crystal display device with less light leakage when viewed from an oblique direction and a neutral hue of black display. Specifically, the optical characteristics of the optical anisotropic element are set in such a manner that the thickness direction of the green transmission region 22G of the color filter 22 at a wavelength of 550 nm is delayed by Ct ₅₅₀ and the optical anisotropic elements 50 and 60 The thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm satisfies a specific relationship; and the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm in the red transmission region 22R of the color filter 22 and the wavelength 650 nm at the wavelength of the optically anisotropic elements 50, 60 The thickness direction delay Rt ₆₅₀ satisfies a specific relationship.

<Optical compensation when the birefringence of the color filter is not considered> First, referring to FIG. 5, the principle of using an optically anisotropic element having a refractive index anisotropy of nx>nz>ny to compensate the apparent axial shift of the polarizer will be described. In FIG. 5, the Poincaré sphere is used to explain the situation where the apparent axial direction deviation of the polarizers 30 and 40 of the O-mode liquid crystal panel 101 shown in FIG. 1 is compensated by the optical anisotropic element 50.

The light passing through the light source side polarizer 40 is linearly polarized. When the liquid crystal display device is viewed from the front, the light passing through the polarizer is represented by a point P ₀ on the equator of the Poincare sphere. The absorption axis direction 35 of the viewing side polarizer 30 is orthogonal to the absorption axis direction 45 of the light source side polarizer 40, so light passing through the viewing side polarizer 30 is represented by a point P ₁ on the equator of the Poincaré sphere.

The initial alignment direction 11 of the liquid crystal molecules in the liquid crystal cell 20 is parallel to the absorption axis direction 45 of the polarizer 40, so the polarization state of the light transmitted through the polarizer 40 does not change after passing through the liquid crystal cell. That is, the polarization state of the light transmitted through the liquid crystal cell does not move from the point P ₀ on the Poincare sphere. Light passing through P ₀ of the liquid crystal cell 20 of, and transmitted light 30 of the P visible side polarizer member ₁ mutually linearly orthogonal to the polarization, it is fully absorbed by the viewer side polarizer 30 light transmitted through the liquid crystal cell 20, the can achieve black display.

If the liquid crystal display device is viewed from the direction of the azimuth angle 45° and the slope (polar angle) θ based on the normal direction of the screen based on the absorption axis direction of the polarizer, the apparent axis of the light source side polarizer 40 ₀ from direction P to P _'0, the visible side of the polarization axis direction of the member 30 of an apparent from the _{mobile. 1} to P P' _1. The greater the polar angle θ, the greater the change in the apparent axial direction of the polarizer.

The light 40 P _'0 and the light 30 transmitted through the viewer side polarizer P' is _absent orthogonal relation via a light source side polarizer, so that light leakage generation of black display. In order to prevent light leakage caused by such apparent axial shift, it is necessary to make the polarization state of the light after passing through the liquid crystal cell 20 to be linearly polarized light P _A orthogonal to the light P′ ₁ passing through the viewing side polarizer 30 .

In the O-mode liquid crystal panel 101 shown in FIG. 1, the absorption axis direction 45 of the light source side polarizer 40 is parallel to the initial alignment direction 11 of the liquid crystal cell 20, so the apparent initial alignment direction 11 when viewed from the oblique direction It moves in the same way as the absorption axis direction 45 of the light source side polarizer. Therefore, the polarization state of the light transmitted through the polarizer 40 does not change after passing through the liquid crystal cell, and does not move from the point P′ ₀ on the Poincare sphere.

The light transmitted through the liquid crystal cell 20 enters the optically anisotropic element 50. The optically anisotropic element 50 with an Nz coefficient of 0.5 does not change in the direction of the apparent optical axis no matter what angle it is viewed from, and there is a slow phase axis on the line connecting P ₀ and P ₁ . The front retardation (retardation of light with respect to the normal direction) Re of the optical anisotropic element 50 is 1/2 of the wavelength λ. In the case of Nz = 0.5, even if the transmission direction of light changes, the apparent delay will not change, and is fixed at λ/2. The retardation of λ/2 corresponds to the phase difference π, so the light P′ ₀ transmitted through the liquid crystal cell 20 rotates clockwise on the Poincaré sphere around the axis P ₀ -P ₁ by passing through the optical anisotropic element 50 180 °, is moved to the point P _A.

As described above, P _A linearly polarized light 30 transmitted through the system and the viewer side polarizer P 'perpendicular to the linearly polarized light _1, it polarization state by the optically anisotropic element 50 is changed by the light of P _A viewer side polarizer 30 Absorption, black display can be achieved.

As shown in FIG. 6, in the O-mode liquid crystal panel 106 where the absorption axis direction 45 of the second polarizer 40 is orthogonal to the retardation axis direction 53 of the optical anisotropic element 50, the polarized light by the optical anisotropic element 50 The state transition becomes a half-turn clockwise on the Poincaré ball, so as shown by the single-dot chain line in Figure 5, the trajectory on the Poincaré ball passes through the southern hemisphere. Since the rotation angle is 180 °, so that the case of the liquid crystal panel shown in the same manner as in FIG. 1, the polarization state of light transmitted through the optical anisotropy of the element 50 is represented by a point on the Poincare sphere P _A, and when the viewing-side polarizer The piece 30 absorbs, so a black display can be realized.

In the E-mode liquid crystal panel 102 shown in FIG. 3, the initial alignment direction 11 of the liquid crystal molecules of the liquid crystal cell 20 is orthogonal to the absorption axis direction 45 of the light source side polarizer 40, so the apparent appearance when viewed from the oblique direction The initial alignment direction 11 is offset from the absorption axis direction 45 of the light source side polarizer 40 by 90°. Therefore, the optical anisotropic element 60 is arranged between the light source side polarizer 40 and the liquid crystal cell 20, so that the linearly polarized light P′ ₀ transmitted through the light source side polarizer 40 is moved to the Poincare sphere by the optical anisotropic element 60 the point P _A. Thus, from the light source side of the polarizer 40 linearly polarized light P _'0, after linearly polarized light is converted into P _A by the optically anisotropic element 60 enters the liquid crystal cell 20, whereby the polarization state of light transmitted through the liquid crystal cell is not from the P _The change in _A is absorbed by the polarizer 30 on the viewing side, so that a black display can be realized.

As shown in FIG. 7, in the E-mode liquid crystal panel 107 in which the absorption axis direction 45 of the second polarizer 40 is orthogonal to the retardation axis direction 63 of the optical anisotropic element 60, the optical anisotropic element 60 is used The point where the transition of the polarization state on the Poincaré sphere becomes the northern or southern hemisphere is different, but the principle of optical compensation is the same as that of the liquid crystal panel 102 shown in FIG. 3.

As described above, when the effect of the birefringence of the color filter is not considered, the optical design of the optical anisotropic element does not depend on the optical axis direction of the optical anisotropic element and the optical axis direction of the polarizer The angle (parallel or orthogonal), and the angle formed by the initial alignment direction of the liquid crystal cell and the optical axis direction of the polarizer (O mode or E mode).

<Retardation in the thickness direction of the color filter> As described above, the retardation in the plane of the color filter 22 provided on the viewing side of the liquid crystal layer 10 in the liquid crystal cell 20 is approximately 0, but the thickness direction has several nm to several Ten nm delay. In the green transmission region 22G, the retardation in the thickness direction relative to the light near the wavelength with the highest transmittance of 550 nm affects the visibility. For the same reason, in the red transmission region 22R, the retardation in the thickness direction of light at a wavelength near 650 nm with a high transmittance affects visibility. Therefore, when evaluating the retardation in the thickness direction of the color filter, it is appropriate to use the thickness direction retardation Ct ₅₅₀ with a wavelength of 550 nm for the green transmission region (green color filter), and for the red transmission region (red Color filter), using the thickness direction retardation Ct ₆₅₀ with a wavelength of 650 nm for evaluation.

In order to suppress light leakage when viewed from an oblique direction, it is preferable that the retardation in the thickness direction of the color filter is small. The thickness direction retardation Ct ₅₅₀ of the wavelength of 550 nm in the green transmission region is preferably 50 nm or less, more preferably 40 nm or less, further preferably 35 nm or less, and particularly preferably 30 nm or less. The thickness direction retardation Ct ₆₅₀ of the red region of the color filter at a wavelength of 650 nm is preferably 50 nm or less, more preferably 40 nm or less, further preferably 35 nm or less, and particularly preferably 30 nm or less. The retardation in the thickness direction of the color filter is preferably 0, but it is difficult to make the retardation in the thickness direction of the color filter completely zero. Therefore, Ct ₅₅₀ and Ct _{650 are} greater than zero. Ct ₅₅₀ and Ct ₆₅₀ may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more.

<Principle of optical compensation considering the birefringence of the color filter> First, referring to FIG. 8A, the influence of the thickness direction delay of the color filter of the O-mode liquid crystal panel 101 shown in FIG. 1 and its optical consideration The compensation is explained. When the case where the visibility from the oblique direction, the polarization state of light after transmitted through the liquid crystal layer 10 of liquid crystal cell 20 _'0 represented by point P on the Poincare sphere, and this does not consider the case of birefringent color filters (FIG. 5) Same.

The light transmitted through the liquid crystal layer enters the color filter 22. The front retardation of the color filter is approximately 0, and has a specific thickness retardation, so it can be approximated as a negative C plate with a refractive index anisotropy of nx=ny>nz. Effect of light due to the oblique direction of the thickness direction retardation of the negative C plate of the polarization state changes from a point on the meridian along the Poincare sphere P _'0 south moved to the point P _C.

As in the case of FIG. 5, when the phase difference of the optical anisotropic element is π (the case of 180° rotation on the Poincaré sphere), the polarization state of the light passing through the optical anisotropic element is shown in FIG. 8A the point P _'A represents, located in the northern hemisphere of the Poincare sphere. In order to make the light 50 after transmitted through the optically anisotropic element of the linearly polarized light of a point on the equator represents P _A, it is necessary that the optically anisotropic element caused by the rotation angle of the Poincare sphere is greater than 180 °. That is, if the influence of the birefringence of the color filter is considered, in the O-mode liquid crystal panel 101 shown in FIG. 1, in order to make the light passing through the optical anisotropic element 50 linearly polarized, it is necessary to make the optical anisotropy The phase difference of the opposite element 50 is greater than π.

8B shows the state of optical compensation of the O-mode liquid crystal panel 106 of FIG. 6 in which the absorption axis direction 45 of the second polarizer 40 is orthogonal to the retardation axis direction 53 of the optical anisotropic element 50. The polarization state of the light after passing through the color filter 22 approaching as the negative C plate is the same as the case of FIG. 8A, and is represented by the point P _C of the southern hemisphere of the Poincare sphere. When the phase difference of the optically anisotropic element of π is the case, if the point P _C from the half turn in the clockwise direction of rotation on the Poincare sphere is rotated 180 °, it reaches the point in the northern hemisphere of P _'A by the equator. In order for the light passing through the optical anisotropic element 50 to be linearly polarized light represented by the point P _A on the equator, the rotation angle on the Poincaré sphere caused by the optical anisotropic element must be less than 180°. That is, if the influence of the birefringence of the color filter is considered, in the O-mode liquid crystal panel 106 shown in FIG. 6, in order to make the light passing through the optical anisotropic element 50 linearly polarized, it is necessary to make the optical anisotropy The phase difference of the opposite element 50 is less than π.

9A shows the state of optical compensation of the liquid crystal panel 107 in the E mode of FIG. 7 in which the absorption axis direction 45 of the second polarizer 40 is orthogonal to the slow phase axis direction 63 of the optical anisotropic element 60. As in the case of FIGS. 8A and 8B, if the light _PL after passing through the liquid crystal cell passes through the color filter 22 approaching as a negative C plate, the polarization state changes and goes south along the meridian on the Poincare sphere. In order that the light transmitted through the color filters after the linearly polarized light 30 is absorbed by the P _A and visible side polarizer, it is necessary that on the northern hemisphere of the Poincare sphere of light transmitted through the liquid crystal cell after the P _L.

As in the case of FIG. 5, the phase difference of the optical anisotropic element is π. If the linearly polarized light P′ ₀ passing through the polarizer on the light source side is moved to the point P on the Poincare sphere by the optical anisotropic element _A, the polarization state of light transmitted through the liquid crystal cell does not change from the P _A. However, the light after passing through the liquid crystal cell goes south along the meridian on the Poincare sphere due to the retardation of the thickness direction of the color filter, so the light after passing through the color filter becomes elliptically polarized light in the southern hemisphere, which is not recognized The light absorbed by the side polarizer 30 is recognized as light leakage.

In the E-mode liquid crystal panel 107 shown in FIG. 7, as shown in FIG. 9A, by making the phase difference of the optical anisotropic element 60 smaller than π (so that the optical anisotropic element is caused on the Poincare sphere The angle of rotation is less than 180°) and can be properly optically compensated. The polarization state of light transmitted through the phase difference is less than π of the optically anisotropic element is represented by a point on the southern hemisphere of the Poincare sphere P _R. Polarization state due to the influence of the retardation of the liquid crystal layer 10 is converted to the axis P _A -P _'1 in the clockwise direction of rotation as the center on the Poincare sphere, so that the polarization state of light after transmitted through the liquid crystal layer 10 by the Poincare The point P _L on the northern hemisphere of the ball indicates. As described above, if the light P _L after passing through the liquid crystal cell passes through the color filter 22, it travels south along the meridian on the Poincaré sphere and reaches the point P _A on the equator. Thus, the light transmitted through the color filter after P _A suitable visible side is absorbed by the polarizer 30, so as to prevent light leakage.

9B shows the state of optical compensation of the liquid crystal panel 102 in the E mode of FIG. 3 in which the absorption axis direction 45 of the second polarizer 40 is parallel to the slow phase axis direction 63 of the optical anisotropic element 60. In the liquid crystal panel 102, if the phase difference of the optical anisotropic element 60 is greater than π (the rotation angle on the Poincare sphere due to the optical anisotropic element is greater than 180°), the optical anisotropic element is transmitted after the polarization state of light of a point located on the southern hemisphere of the Poincare sphere P _R. Later, as in the case of FIG. 9A, by moving through the liquid crystal layer 10 to the point P _L on the northern hemisphere, by passing through the color filter 22 to reach the point P _A on the equator, so after passing through the color filter P _A suitable light absorbed by the viewer side polarizer 30.

As described above, in order to compensate optically by the optical anisotropic element in a manner that counteracts the effect of the birefringence of the color filter, it is necessary to adjust the phase of the optical anisotropic element according to the magnitude of the retardation in the thickness direction of the color filter difference. When the absorption axis direction of the light source side polarizer is parallel to the retardation axis direction of the optically anisotropic element, that is, the O-mode liquid crystal panel 101 shown in FIG. 1 (refer to FIG. 8A), and shown in FIG. 3 In the E-mode liquid crystal panel 102 (see FIG. 9B), in order to perform appropriate optical compensation, it is necessary to make the phase difference of the optically anisotropic element greater than π (make the retardation greater than λ/2). On the other hand, in the case where the absorption axis direction of the light source side polarizer is orthogonal to the retardation axis direction of the optically anisotropic element, that is, the O-mode liquid crystal panel 106 shown in FIG. 6 (see FIG. 8B), and In the E-mode liquid crystal panel 107 shown in FIG. 7 (see FIG. 9A), in order to perform appropriate optical compensation, it is necessary to make the phase difference of the optical anisotropic element smaller than π (to make the retardation smaller than λ/2).

[Optical Design of Optical Anisotropic Components] In the following, the research results of the inclusion optical simulation on the preferable optical characteristics of the optical anisotropic element corresponding to the retardation in the thickness direction of the color filter of the liquid crystal cell are described.

In the optical simulation, the LCD monitor simulator "LCD MASTER Ver.8.1.0.3" manufactured by Shintec is used, and the extended function of the LCD Master is used to obtain the black display in the direction of azimuth angle 45° and polar angle 60° The brightness, and the chromaticity of the CIE1976 color space of the black display (u', v').

In the simulation of the O-mode liquid crystal display device, as shown in FIG. 2, the light source side polarizer 40 is sequentially stacked from the light source 110 side, the IPS liquid crystal cell 20 having the color filter 22 on the viewing side of the liquid crystal layer 10, and the optical The anisotropic element 50 and the polarizer 30 on the viewing side are used as a simulation model. In the simulation of the E-mode liquid crystal display device, as shown in FIG. 4, the light source side polarizer 40, the optical anisotropic element 60, and the color filter on the viewing side of the liquid crystal layer 10 are sequentially stacked from the light source 110 side The IPS liquid crystal cell 20 of 22 and the polarizer 30 on the viewing side are used as a simulation model.

In the simulation, the front retardation of the liquid crystal layer of the IPS liquid crystal cell was set to 339 nm, and the pretilt angle was set to 0°. The Nz coefficient of the optically anisotropic element is set to 0.5, the retarded wavelength dispersion is set to Re ₆₅₀ /Re ₅₅₀ =Rt ₆₅₀ /Rt ₅₅₀ =0.95, and Rt _{650 is} changed to various values. The color filter changes the retardation Ct _{550 in} the thickness direction of the wavelength 550 nm in the green transmission region, and the retardation Ct _{650 in} the thickness direction of the wavelength 650 nm in the red transmission region in the range of 0 to 60 nm according to the 5 nm scale.

In the O-mode liquid crystal panel, the chromaticity of black display when Ct ₆₅₀ and Rt _{650 are} changed to various values is shown in FIGS. 10A and 10B. In the E-mode liquid crystal panel, the chromaticity of the black display when Ct ₆₅₀ and Rt _{650 are} changed to various values is shown in FIGS. 11A and 11B.

10A is a simulation result of the liquid crystal panel 101 (see FIG. 8A for the principle of optical compensation) in which the absorption axis direction 45 of the light source side polarizer 40 is parallel to the retardation axis direction 53 of the optical anisotropic element 50 as shown in FIG. 1. FIG. 10B is a simulation result of the liquid crystal panel 106 (see FIG. 8B for the principle of optical compensation) in which the absorption axis direction 45 of the light source side polarizer 40 is orthogonal to the retardation axis direction 53 of the optical anisotropic element 50 as shown in FIG. 6. 11A is a simulation result of the liquid crystal panel 107 (see FIG. 9A for the principle of optical compensation) in which the absorption axis direction 45 of the light source side polarizer 40 is orthogonal to the slow phase axis direction 63 of the optical anisotropic element 60 as shown in FIG. 7. 11B is a simulation result of the liquid crystal panel 102 in which the absorption axis direction 45 of the light source side polarizer 40 is parallel to the retardation axis direction 63 of the optical anisotropic element 60 as shown in FIG. 3 (refer to FIG. 9B for the principle of optical compensation).

As shown in FIGS. 10B and 11A, when the absorption axis direction of the light source side polarizer is orthogonal to the retardation axis direction of the optical anisotropic element, it is found that the thickness direction of the red transmission region of the color filter is retarded As Ct ₆₅₀ becomes larger, the maximum value of u′ when the retardation of Rt ₆₅₀ changes in the thickness direction of the optical anisotropic element tends to be smaller. In addition, in the range of Ct ₆₅₀ from 0 to 60 nm, regardless of the value of the retardation Rt _{650 in} the thickness direction of the optically anisotropic element, u'will not exceed 0.35. That is, when the absorption axis direction of the light source side polarizer is orthogonal to the retardation axis direction of the optical anisotropic element, the O-mode liquid crystal panel 106 shown in FIG. 6 and the E-mode liquid crystal shown in FIG. 7 When any one of the panels 107 is viewed from the oblique direction, the black-displayed picture is not significantly colored red.

On the other hand, as shown in FIGS. 10A and 11B, when the absorption axis direction of the light source side polarizer is parallel to the retardation axis direction of the optically anisotropic element, it is found that The thickness direction retardation Ct ₆₅₀ becomes larger, so that the thickness direction of the optical anisotropic element retards the maximum value of u′ when the Rt ₆₅₀ changes. In addition, in FIGS. 10A and 11B, compared with FIGS. 10B and 11A, u′ depends on the thickness direction retardation Ct ₆₅₀ of the red transmission region of the color filter and the thickness direction retardation Rt _{650 of the} optical anisotropic element. The earth changed, and it was found to exceed 0.35.

From these results, it can be seen that the O-mode liquid crystal panel 101 shown in FIG. 1 and the E-mode shown in FIG. 3 when the absorption axis direction of the light source side polarizer is parallel to the slow phase axis direction of the optically anisotropic element Any one of the liquid crystal panels 102 is affected by the birefringence of the red transmission area of the color filter, and when viewed from the oblique direction, the black display is colored red. That is, in a liquid crystal panel in which the absorption axis direction of the light source side polarizer is parallel to the retardation axis direction of the optically anisotropic element, when the optical compensation is performed considering the effect of the birefringence of the color filter, the reduction In addition to the small green light leakage to improve the contrast, the optical design of the optically anisotropic element needs to be carried out in a manner that reduces the coloration of the black display caused by the red light leakage.

<First embodiment: Optical design of O-mode liquid crystal panel> (Adjustment of chromaticity) FIG. 12 is based on the simulation results of the O-mode liquid crystal panel 101 shown in FIG. 1, and the chromaticity of the black display becomes a specific value Conditional drawing. The horizontal axis is the thickness direction retardation Ct ₆₅₀ of the wavelength 650 nm of the red transmission region of the color filter, and the vertical axis is the thickness direction retardation Rt ₆₅₀ of the optical anisotropic element at the wavelength 650 nm. At each Ct ₆₅₀ , the point where the chromaticity u'of the black display in the direction of the azimuth angle 45° and the polar angle 60° becomes 0.35 is indicated by a black circle mark and a black triangle mark. When Rt ₆₅₀ is located between the black circle mark and the black triangle mark, u'exceeds 0.35, and the black display is colored red and is recognized. When Rt ₆₅₀ is on the upper side of the black circle mark or on the lower side of the black triangle mark, u'does not reach 0.35, which can suppress the red coloration of black display.

It can be understood from FIG. 12 that both the upper limit side and the lower limit side of the boundary of u′=0.35 can be approached with a straight line. The straight line in the graph is represented by the following formula (1) and formula (2): Rt ₆₅₀ = 0.37 (Ct ₆₅₀ ) +116... (1) Rt ₆₅₀ = -0.44 (Ct ₆₅₀ ) +116... (2 ).

Therefore, the red-transmissive region 22R of the color filter 22 has a thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm, and the wavelength anisotropy element 50 has a thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm that satisfies the following formula (1a) or (2a) In this case, u'becomes 0.35 or less, and black display with reduced red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+116...(1a) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+116...(2a).

The white-coated circle mark and the white-coated triangle mark in FIG. 12 indicate the point where the chromaticity u′ of the black display becomes 0.314. When Rt ₆₅₀ is located between the white circle mark and the black circle mark, u'is 0.314～0.35, and when Rt ₆₅₀ is located above the white circle mark, u'is less than 0.314 . Similarly, when Rt ₆₅₀ is located between the white triangle mark and the black triangle mark, u'is 0.314 to 0.35, and when Rt ₆₅₀ is positioned lower than the white triangle mark, u'is less than 0.314.

The boundary of u'=0.314 represented by the white circle mark can be approximated by a straight line parallel to the above formula (1): Rt ₆₅₀ = 0.37(Ct ₆₅₀ )+121. The boundary of u'=0.314 represented by the white triangle mark can be approximated by a straight line parallel to the above formula (2): Rt ₆₅₀ =-0.44(Ct ₆₅₀ )+108.

Therefore, the retardation Ct _{650 in} the thickness direction of the wavelength 650 nm in the red transmission region of the color filter and the retardation Rt _{650 in} the thickness direction of the wavelength 650 nm of the optical anisotropic element satisfy the following formula (1b) or (2b) In this case, u'becomes 0.314 or less, and black display with a further reduction in red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+121...(1b) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+108...(2b).

Based on the above results, it can be said that in the O-mode liquid crystal panel shown in FIG. 1, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (1c) or (2c), black display with a reduced red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+C ₁ ...(1c) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+C ₂ ...(2c).

As described above, when u'=0.35 is used as the boundary, C _{1 in} equation (1c) is 116 nm, and C _{2 in} equation (2c) is 116 nm. In other words, in the case where the condition is set in a manner satisfying u′≦0.35, it is sufficient to set C ₁ =116 nm and C ₂ =116 nm as in the above formula (1a) and formula (2a). From the same point of view, when the condition is set in such a way that u'≦0.314 is satisfied, it is sufficient to set C ₁ =121 nm and C ₂ =108 nm as in the above formula (1b) and formula (2b). In order to further reduce the u'of the black display, it is sufficient to set C ₁ larger and C ₂ smaller.

C _{1 in} formula (1c) can be any number above 116. C ₁ may also be 116 nm, 121 nm, 124 nm, 126 nm, 128 nm, 130 nm, 132 nm, 134 nm, 136 nm, 138 nm, or 140 nm. Similarly, C _{2 in} formula (2c) may be any number below 116. C ₂ may also be 116 nm, 112 nm, 108 nm, 105 nm, 102 nm, 100 nm, 98 nm, 96 nm, 94 nm, 92 nm, or 90 nm.

From the viewpoint of reducing the chromaticity u'of black display when viewed from the oblique direction, if the Rt _{650 of the} optical anisotropic element 50 at a wavelength of 650 nm satisfies the above formula (1c) or (2c), the upper limit or The lower limit is not particularly limited. However, as will be described below, if the range of Rt _{550 for} reducing the black brightness and the wavelength dispersion Rt ₆₅₀ /Rt ₅₅₀ of the retardation of the optical anisotropic element 50 are considered, the upper and lower limits of Rt ₆₅₀ will naturally be determined.

(Adjustment of Brightness) As described above, by adjusting the Rt _{650 of the} optically anisotropic element according to the thickness direction retardation Ct _{650 of the} color filter, red light leakage is suppressed, thereby reducing the u'of black display. On the other hand, in order to reduce the amount of light leakage (black brightness) at the time of black display, it is preferable to perform optical design in such a manner that the light leakage of green light having a higher specific visual sensitivity is reduced.

FIG. 13 is a graph obtained by plotting the condition that the black brightness becomes a specific value according to the simulation result of the O-mode liquid crystal panel 101 shown in FIG. 1. The horizontal axis is the thickness direction retardation Ct _{550 at} the wavelength of 550 nm in the green transmission region of the color filter, and the vertical axis is the thickness direction retardation Rt _{550 at} the wavelength 550 nm of the optically anisotropic element. For each Ct ₅₅₀ , the black brightness in the direction of the azimuth angle 45° and the polar angle 60° has the same Ct ₅₅₀ , and it is a half of the point of the liquid crystal display device that does not use the optical anisotropic element is marked with a black circle And the black triangle mark indicates. In the case where Rt ₅₅₀ is located between the blackened round mark and the blackened triangular mark, the black brightness when viewed from the oblique direction is reduced to less than half compared to the case without an optically anisotropic element.

As can be understood from FIG. 13, compared with the case where the optical anisotropic element is not used, both the upper limit side and the lower limit side of the boundary of the region where the black brightness becomes 1/2 can be approached with a straight line. The straight line in the graph is represented by the following formula (3) and formula (4): Rt ₅₅₀ = 0.97 (Ct ₅₅₀ ) + 73... (3) Rt ₅₅₀ = 0.49 (Ct ₅₅₀ ) + 205 ... (4).

Therefore, the retardation Ct _{550 in} the thickness direction of the wavelength 550 nm of the green transmission region 22G of the color filter 22 and the retardation Rt _{550 in} the thickness direction of the wavelength 550 nm of the optical anisotropic element 50 satisfy the following formula (3a) When compared with the case where no optical anisotropic element is used, the black luminance in the oblique direction becomes 1/2 or less. 0.97(Ct ₅₅₀ )+73≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+205...(3a).

The white-coated circle mark and the white-coated triangle mark in FIG. 13 indicate that the black brightness becomes 1/5 of the black brightness of the liquid crystal display device that does not use the optically anisotropic element. In the case where Rt ₅₅₀ is located between the white-coated round mark and the white-coated triangular mark, the black brightness is reduced to less than 1/5 compared to the case without an optically anisotropic element.

The boundary indicated by the white circle mark can be approximated by a straight line parallel to the above formula (3): Rt ₅₅₀ = 0.97 (Ct ₅₅₀ ) + 98. The boundary indicated by the white triangle mark can be approximated by a straight line parallel to the above formula (4): Rt ₅₅₀ = 0.49 (Ct ₅₅₀ ) + 180. Therefore, when the retardation Ct _{550 in} the thickness direction of the wavelength 550 nm in the green transmission region of the color filter and the retardation Rt _{550 in} the thickness direction of the wavelength 550 nm of the optical anisotropic element satisfy the following formula (3b), and Compared with the case where no optical anisotropic element is used, the black brightness can be reduced to less than 1/5, and a display with higher contrast can be realized. 0.97(Ct ₅₅₀ )+98≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+180...(3b).

Based on the above results, it can be said that in the O-mode liquid crystal panel shown in FIG. 1, when Ct ₅₅₀ and Rt ₅₅₀ satisfy the following formula (3c), the influence of the birefringence of the color filter can be eliminated and the tilt direction can be achieved The display with reduced black brightness. 0.97(Ct ₅₅₀ )+C ₃ ≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+C ₄ ...(3c)

As described above, when the black brightness is set to be 1/2 or less of the black brightness of the liquid crystal display device not using the optical anisotropic element, as in the above formula (3a), C ₃ = 73 nm, C ₄ = 205 nm. From the same point of view, when the black brightness is set to 1/5 or less of the black brightness of the liquid crystal display device that does not use an optically anisotropic element, as in the above formula (3b), C ₃ =98, C ₄ = 180 nm. In order to further reduce the black brightness in the oblique direction, it is sufficient to set C _{3 to a} large value, and to set C _{4 to a} small value. C _{3 in} formula (3c) can be any number above 73. C ₃ may also be 73 nm, 88 nm, 98 nm, 108 nm, 113 nm, 118 nm, 123 nm, or 128 nm. Similarly, C _{4 in} formula (3c) can be any number below 205. C ₄ can also be 205 nm, 190 nm, 180 nm, 173 nm, 168 nm, 163 nm, 158 nm, 153 nm, or 148 nm.

As shown in FIG. 13, the greater the thickness direction delay Ct _{550 of} the color filter, the greater the optimal value of Rt ₅₅₀ of the optically anisotropic element for reducing the black brightness when viewed from the oblique direction. This can also be understood according to the principle of optical compensation shown in FIG. 8A. The color filter of the thickness direction retardation larger Ct _550, this corresponds to P '(P _C of greater latitude) from ₀ to P _C of greater FIG 8A. P _C deviates significantly from the latitude of the equator, then in order to make the light transmitted through the optical anisotropy of the element 50 moves to the equator on the Poincare sphere, it is necessary that the retardation of the optically anisotropic element increases. Therefore, as shown in FIG. 13, the larger Ct ₅₅₀ is, the larger Rt ₅₅₀ must be in order to reduce the black luminance.

(Both black brightness reduction and chromaticity are combined) In order to reduce the black brightness when viewed from the oblique direction, the Ct ₅₅₀ is retarded according to the thickness direction of the color filter to set the Rt of the optically anisotropic element in a manner satisfying the above formula (3c) ₅₅₀ , and the Rt _{650 of the} optically anisotropic element may be set in a manner satisfying the above formula (1c) or (2c). However, Rt ₅₅₀ and Rt ₆₅₀ cannot be individually set, and Rt ₆₅₀ /Rt ₅₅₀ is a fixed value corresponding to the wavelength dispersion of the retardation of the optically anisotropic element.

For example, when the Ct ₅₅₀ retardation in the thickness direction of the green transmission region of the color filter is 10 nm, if the Rt ₅₅₀ of the optically anisotropic element is 130 nm, the black brightness when viewed from the oblique direction is small, and Achieve high-contrast display. As set in the above simulation, when the optically anisotropic element has a wavelength dispersion of Rt ₆₅₀ /Rt ₅₅₀ =0.95, if Rt ₅₅₀ =130 nm, then Rt ₆₅₀ =124 nm.

Since the materials of the red color filter and the green color filter are different, the Rth of the two is different. In some cases, the Ct _{650 of the} red color filter is greater than the Ct ₅₅₀ of the green color filter. For example, if the retardation Ct _{650 in} the thickness direction of the red transmission region 22R of the color filter 22 is 30 nm, then in the case of Rt ₆₅₀ = 124 nm, neither of the above formulas (1a) and (1b) is satisfied In addition, the chromaticity u′ when viewed from the oblique direction exceeds 0.35, and the black display is colored red and is recognized.

It can be understood from the above example that in the O-mode liquid crystal panel shown in FIG. 1, even if the optical design of the optical anisotropic element is performed in such a manner that the black brightness becomes smaller, the chromaticity u'of the black display becomes larger, Black shows the coloring of red. On the other hand, consider the retardation in the thickness direction of the color filter Ct ₅₅₀ and Ct ₆₅₀ , and the retardation wavelength dispersion Rt ₆₅₀ /Rt _{550 of the} optical anisotropic element to satisfy the above formula (3c) (here, C ₃ is 73 nm or more, C ₄ is 205 nm or less), and satisfies the above formula (1c) or (2c) (here, C ₁ is 116 nm or more, C ₂ is 116 nm or less) to set the optical anisotropic element The thickness direction can be delayed.

In addition, the wavelength dispersion Rt ₆₅₀ /Rt ₅₅₀ retarded in the thickness direction of the retardation film is generally substantially equal to the wavelength dispersion Re ₆₅₀ /Re ₅₅₀ retarded in the front side, and is in the range of 0.8 to 1.2. Considering the general range of wavelength dispersion, when Ct ₆₅₀ is above 10 nm, Rt ₅₅₀ satisfies equation (3c), and Rt ₆₅₀ satisfies equation (2c) rarely. Therefore, it is preferable to set the retardation of the optically anisotropic element such that Rt ₅₅₀ satisfies the above formula (3c) and Rt ₆₅₀ satisfies the above formula (1c).

The front retardation Re ₅₅₀ and Re _{650 of the} optical anisotropic element 50 may be set so that Rt ₅₅₀ and Rt ₆₅₀ fall within the above range. As described above, the ratio of the thickness direction retardation Rt of the optical anisotropic element 50 to the front retardation Re is Nz=Rt/Re of 0.2 to 0.8, so under this constraint, the thickness direction retardation Rt of the optical anisotropic element ₅₅₀ and Rt ₆₅₀ and the Nz coefficient set the positive retardation Re ₅₅₀ and Re ₆₅₀ .

Specifically, the front retardation Re _{650 of the} optical anisotropic element 50 at a wavelength of 650 nm is preferably about twice the Rt ₆₅₀ . Therefore, Re ₆₅₀ preferably satisfies the following formula (1d) or (2d). Re ₆₅₀ ≧0.74(Ct ₆₅₀ )+C ₁₁ ...(1d) Re ₆₅₀ ≦-0.88(Ct ₆₅₀ )+C ₁₂ ...(2d).

C ₁₁ is twice that of C ₁ , specifically, C ₁₁ is 232 nm or more. C ₁₁ may also be 232 nm, 236 nm, 242 nm, 248 nm, 252 nm, 256 nm, 260 nm, 264 nm, 268 nm, 272 nm, 276 nm, or 280 nm. C ₁₂ is twice that of C ₂ , specifically, C ₁₂ is 232 nm or less. C ₁₂ can also be 232 nm, 224 nm, 216 nm, 210 nm, 204 nm, 200 nm, 196 nm, 192 nm, 188 nm, 184 nm, or 180 nm. Considering the delayed wavelength dispersion of the optical anisotropic element, Re _{650 of} the optical anisotropic element 50 preferably satisfies the above formula (1d).

The front retardation Re _{550 of the} optical anisotropic element 50 at a wavelength of 550 nm is preferably about twice the Rt ₅₅₀ . Therefore, Re ₅₅₀ preferably satisfies the following formula (3d): 1.94 (Ct ₅₅₀ ) + C ₁₃ ≦ Re ₅₅₀ ≦ 0.98 (Ct ₅₅₀ ) + C ₁₄ ... (3d).

C ₁₃ is twice that of C ₃ , specifically, C ₁₃ is 146 nm or more. C ₁₃ may also be 145 nm, 175 nm, 185 nm, 215 nm, 225 nm, 235 nm, 245 nm, or 255 nm. C ₁₄ is twice that of C _4. Specifically, C ₁₄ is 410 nm or less. C ₁₄ may also be 410 nm, 380 nm, 360 nm, 345 nm, 335 nm, 325 nm, 315 nm, 305 nm, or 295 nm.

<Second Embodiment: Optical Design of E-mode LCD Panel> FIG. 14 is a graph obtained by plotting the condition that the chromaticity of the black display becomes a specific value according to the simulation result of the E-mode liquid crystal panel 102 shown in FIG. 3. As in FIG. 12, the point where the chromaticity u'of the black display in the direction of the azimuth angle 45° and the polar angle 60° becomes 0.35 is indicated by the black circle mark and the black triangle mark, and the black display color The point where the degree u'becomes 0.314 is indicated by a white circle mark and a white triangle mark.

As in the case of FIG. 12, the boundary of u′=0.35 in FIG. 14 can also be approximated by a straight line expressed by the following formula (6) and formula (7): Rt ₆₅₀ =0.37(Ct ₆₅₀ )+116...(6) Rt ₆₅₀ = -0.44 (Ct ₆₅₀ ) + 120... (7).

Therefore, in the liquid crystal panel 102, the thickness direction retardation Ct _{650 at} the wavelength 650 nm of the red transmission region 22R of the color filter 22 and the thickness direction retardation Rt _{650 at} the wavelength 650 nm of the optical anisotropic element 50 satisfy the following In the case of formula (6a) or (7a), u'becomes 0.35 or less, and a black display with a reduced red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+116...(6a) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+120...(7a).

Furthermore, equation (6) is the same as equation (1) for the liquid crystal panel 101 of the O mode. Equation (7) is expressed by a straight line parallel to Equation (2) of the liquid crystal panel 101 of the O mode. In FIG. 14, as a reference, a straight line of formula (2) is indicated by a broken line.

The boundary of u'=0.314 represented by the white circle mark can be approximated by a straight line parallel to the above formula (6): Rt ₆₅₀ = 0.37(Ct ₆₅₀ )+121. The boundary of u'=0.314 represented by the white triangle mark can be approximated by a straight line parallel to the above formula (2): Rt ₆₅₀ =-0.44(Ct ₆₅₀ )+108.

Therefore, the retardation Ct _{650 in} the thickness direction of the wavelength 650 nm in the red transmission region of the color filter and the retardation Rt _{650 in} the thickness direction of the wavelength 650 nm of the optical anisotropic element satisfy the following formula (6b) or (7b) In this case, u'becomes 0.314 or less, and black display with a further reduction in red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+121...(6b) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+108...(7b).

Based on the above results, it can be said that in the E-mode liquid crystal panel 102 shown in FIG. 3, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (6c) or (7c), black display with a reduced red tone can be realized. Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+C ₆ ...(6c) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ )+C ₇ ...(7c).

When the conditions are set in a way that satisfies u'≦0.35, as in the above equations (6a) and (7a), C ₆ =116 nm and C ₇ =120 nm are sufficient to satisfy u′≦ When the conditions are set by the 0.314 method, as in the above equations (6b) and (7b), C ₆ =121 nm and C ₇ =108 nm may be used. In order to further reduce the u'of the black display, it is sufficient to set C ₆ larger and C ₇ smaller.

C _{6 in} formula (6c) can be any number above 116. C ₆ can be the same value as C ₁ above, C ₆ can also be 116 nm, 118 nm, 121 nm, 124 nm, 126 nm, 128 nm, 130 nm, 132 nm, 134 nm, 136 nm, 138 nm, Or 140 nm. Similarly, C _{7 in} formula (7c) can be any number below 120. C ₇ may be the same value as C ₂ above, or 121 nm, 116 nm, 112 nm, 108 nm, 105 nm, 102 nm, 100 nm, 98 nm, 96 nm, 94 nm, 92 nm, or 90 nm. Considering the delayed wavelength dispersion of the optical anisotropic element, the Rt _{650 of} the optical anisotropic element 60 preferably satisfies the above formula (6c).

From the viewpoint of reducing the chromaticity u'of black display when viewed from the oblique direction, the Rt _{650 of the} optical anisotropic element 60 at a wavelength of 650 nm satisfies the above formula (6c) or (7c), the upper limit Or the lower limit is not particularly limited. However, regarding the first embodiment, as described above, if the range of Rt _{550 for} reducing black brightness and the wavelength dispersion of retardation Rt ₆₅₀ /Rt _{550 of the} optical anisotropic element 60 are considered, the upper and lower limits of Rt ₆₅₀ Naturally will be decided.

FIG. 15 is a graph plotting the condition that the black luminance becomes a specific value according to the simulation results of the E-mode liquid crystal panel 102 shown in FIG. 3. As in FIG. 13, the black brightness in the direction of azimuth angle 45° and polar angle 60° becomes one half of the dots of the liquid crystal display device that does not use the optically anisotropic element are marked with black circles and black triangles It shows that the point where the black brightness becomes 1/5 of the liquid crystal display device that does not use an optically anisotropic element is indicated by a white circle mark and a white triangle mark.

As in the case of FIG. 13, in FIG. 15, compared with the case where the optical anisotropic element is not used, the boundary of the region where the black brightness becomes 1/2 can be approximated by a straight line. The straight line in the graph is represented by the following formula (8) and formula (9) show: Rt ₅₅₀ = 0.69 (Ct ₅₅₀ ) + 70... (8) Rt ₅₅₀ = 1.35 (Ct ₅₅₀ ) + 200 ... (9).

Therefore, in the liquid crystal panel 102, the thickness direction retardation Ct _{550 at} the wavelength 550 nm of the green transmission region 22G of the color filter 22 and the thickness direction retardation Rt _{550 at} the wavelength 550 nm of the optical anisotropic element 50 satisfy the following formula In the case of (8a), compared with the case where no optical anisotropic element is used, the black luminance becomes 1/2 or less. 0.69(Ct ₅₅₀ )+70≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+200...(8a).

The point represented by the white triangle mark can be approximated by a straight line parallel to the above formula (8): Rt ₅₅₀ = 0.69 (Ct ₅₅₀ ) + 98. The point indicated by the white circle mark can be approximated by a straight line parallel to the above formula (9): Rt ₅₅₀ = 1.35 (Ct ₅₅₀ ) + 180. Therefore, in the case where Ct ₅₅₀ and Rt ₅₅₀ satisfy the following formula (8b), the black luminance becomes 1/5 or less compared to the case where the optical anisotropic element is not used. 0.69(Ct ₅₅₀ )+98≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+171...(8b).

Based on the above results, it can be said that in the E-mode liquid crystal panel 102 shown in FIG. 3, when the Ct ₅₅₀ and Rt ₅₅₀ satisfy the following formula (8c), the influence of the birefringence of the color filter can be eliminated, and A display with reduced black brightness when viewed obliquely. 0.69(Ct ₅₅₀ )+C ₈ ≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+C ₉ ...(8c).

When the black luminance in the oblique direction is 1/2 or less when the optical anisotropic element is not used, it is sufficient to set C ₈ =70 nm and C ₉ =200 nm as in the above formula (8a). From the same point of view, when the black brightness in the oblique direction is 1/5 or less when no optical anisotropic element is used, as in the above formula (8b), C ₃ =98 and C ₄ =171 nm That's it. In order to further reduce the black brightness in the oblique direction, it is sufficient to set C _{8 to a} large value, and to set C _{9 to a} small value.

C _{8 in} formula (8c) can be any number above 70. C ₈ may also be 78 nm, 88 nm, 98 nm, 108 nm, 113 nm, 118 nm, 123 nm, or 128 nm. Similarly, C _{9 in} formula (8c) can be any number below 200. C ₉ may also be 200 nm, 190 nm, 180 nm, 173 nm, 168 nm, 163 nm, 158 nm, 153 nm, or 148 nm.

As shown in FIG. 15, the greater the thickness direction delay Ct _{550 of} the color filter, the greater the optimal value of Rt ₅₅₀ of the optically anisotropic element for reducing the black brightness when viewed from the oblique direction. This can also be understood according to the principle of optical compensation shown in FIG. 9B.

In the E-mode liquid crystal panel 102 shown in FIG. 3, in order to reduce the black brightness when viewed from the oblique direction, the retardation of Ct ₅₅₀ according to the thickness direction of the color filter is set to satisfy the above formula (8c) to set the optical direction Rt _{550 of the} anisotropic element, and Rt _{650 of the} optically anisotropic element may be set in a manner satisfying the above formula (6c) or (7c).

As with the description of the example of the O-mode liquid crystal panel, if the wavelength dispersion Rt ₆₅₀ /Rt _{550 of the} optically anisotropic element is considered, when the Ct ₆₅₀ is 10 nm or more, Rt ₅₅₀ satisfies the formula (8c) And, Rt ₆₅₀ rarely meets equation (7c). Therefore, it is preferable to set the retardation of the optical anisotropic element 60 such that Rt ₅₅₀ satisfies the above formula (8c) and Rt ₆₅₀ satisfies the above formula (6c).

The front retardation Re ₅₅₀ and Re _{650 of the} optical anisotropic element 60 may be set so that Rt ₅₅₀ and Rt ₆₅₀ fall within the above range. The front retardation Re _{650 of the} optical anisotropic element 60 at a wavelength of 650 nm is preferably about twice the Rt ₆₅₀ . Therefore, Re ₆₅₀ preferably satisfies the following formula (6d) or (7d): Re ₆₅₀ ≧0.74 (Ct ₆₅₀ ) + C ₁₆ ... (6d) Re ₆₅₀ ≦-0.88 (Ct ₆₅₀ ) + C ₁₇ ... ( 7d).

C ₁₆ is twice that of C ₆ , specifically, C ₁₆ is 232 nm or more. C ₁₆ can also be 232 nm, 236 nm, 242 nm, 248 nm, 252 nm, 256 nm, 260 nm, 264 nm, 268 nm, 272 nm, 276 nm, or 280 nm. C ₁₇ is twice that of C ₇ , specifically, C ₁₇ is 240 nm or less. C ₁₂ can also be 240 nm, 232 nm, 224 nm, 216 nm, 210 nm, 204 nm, 200 nm, 196 nm, 192 nm, 188 nm, 184 nm, or 180 nm. Considering the delayed wavelength dispersion of the optical anisotropic element, Re _{650 of} the optical anisotropic element 60 preferably satisfies the above formula (6d).

The front retardation Re _{550 of the} optical anisotropic element 60 at a wavelength of 550 nm is preferably about twice the Rt ₅₅₀ . Therefore, Re ₅₅₀ preferably satisfies the following formula (8d): 1.38 (Ct ₅₅₀ ) + C ₁₈ ≦ Re ₅₅₀ ≦ 2.70 (Ct ₅₅₀ ) + C ₁₉ ... (8d).

C ₁₈ is twice that of C ₈ , specifically, C ₁₈ is 140 nm or more. C ₁₈ may also be 155 nm, 175 nm, 185 nm, 215 nm, 225 nm, 235 nm, 245 nm, or 255 nm. C ₁₉ is twice that of C ₉ , specifically, C ₁₉ is 400 nm or less. C ₁₉ may also be 400 nm, 380 nm, 360 nm, 345 nm, 335 nm, 325 nm, 315 nm, 305 nm, or 295 nm.

[Arrangement of each optical member] As described above, in the liquid crystal panel 101 of the first embodiment, the optically anisotropic element 50 disposed on the viewing side of the liquid crystal cell 20 corresponds to the thickness direction retardation Ct _{550 of the} color filter 22 and Ct ₆₅₀ has optical design with specific optical characteristics. The liquid crystal panel 102 of the second embodiment is optically designed so that the optically anisotropic element 60 disposed on the light source side of the liquid crystal cell 20 corresponds to Ct ₅₅₀ and Ct ₆₅₀ and has specific optical characteristics.

The liquid crystal panel 101 of the first embodiment may be provided with an optically isotropic film as a polarizer for protection between the polarizer 30 on the viewing side and the optically anisotropic element 50 or between the polarizer 40 on the light source side and the liquid crystal cell 20 membrane. The liquid crystal panel 102 of the second embodiment may be provided with an optically isotropic film as a polarizer for protection between the polarizer 30 on the viewing side and the liquid crystal cell 20 or between the polarizer 40 on the light source side and the optical anisotropic element 60 membrane. By providing a polarizer protective film on the surface of the polarizer, the durability of the polarizer can be improved.

The optical isotropic film used as the protective film of the polarizer refers to a light that has passed through either the normal direction and the oblique direction and has not substantially converted its polarization state. Specifically, in the optically isotropic film, the front retardation Re is preferably 10 nm or less, and the thickness direction retardation Rt is preferably 20 nm or less. The front retardation of the optical isotropic film is more preferably 5 nm or less. The retardation in the thickness direction of the optical isotropic film is more preferably 10 nm or less, and further preferably 5 nm or less.

The liquid crystal panel may include an optical layer or other members other than the above. For example, it is preferable to provide a polarizer protective film on the outer surfaces of the polarizers 30 and 40 (the surface not facing the liquid crystal cell 20). The polarizer protective film provided on the outer surface of the polarizer may be optically isotropic or may have optical anisotropy. On the other hand, the polarizer protective film provided on the surface of the viewing side polarizer 30 on the liquid crystal cell 20 side and the light source side polarizer 40 on the liquid crystal cell 20 side is required to be optically isotropic as described above.

The liquid crystal panel 101 of the first embodiment is preferably between the viewing side polarizer and the liquid crystal cell 20, does not include optical anisotropic elements other than the optical anisotropic element 50, and is on the light source side polarizer 40 and the liquid crystal cell Between 20, it is preferable not to include an optically anisotropic element. The liquid crystal panel 102 of the second embodiment is preferably between the light source side polarizer and the liquid crystal cell 20, and preferably does not include an optical anisotropic element other than the optical anisotropic element 60, and is on the viewing side polarizer 30 and the liquid crystal cell Between 20, it is preferable not to include an optically anisotropic element.

A liquid crystal panel is formed by laminating a liquid crystal cell and the above-mentioned optical members. In the formation process, each member may be sequentially laminated on the liquid crystal cell individually, or a plurality of members may be laminated in advance. The stacking order of these optical components is not particularly limited. The polarizer and the optically anisotropic element may be laminated to form a laminated polarizing plate in advance, and the laminated polarizing plate may be bonded to the liquid crystal cell via an adhesive (not shown). As described above, a polarizer protective film may also be provided on the surface of the polarizer. Between the polarizer and the optically anisotropic element, an optical isotropic film can also be provided as a polarizer protective film.

In the lamination of each member, an adhesive or an adhesive can be preferably used. As an adhesive or an adhesive, acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride polymers can be appropriately selected and used. , Modified polyolefin, epoxy polymer, fluorine polymer, rubber polymer, etc. as the base polymer.

[Liquid crystal display device] The liquid crystal display device is formed by arranging the light source 110 on the second main surface side (the polarizer 40 side) of the liquid crystal panel. A brightness enhancing film (not shown) can also be provided between the liquid crystal panel and the light source. The brightness enhancement film can also be integrated with the polarizer on the light source side. For example, those in which the brightness enhancement film is bonded to the outer surface (surface on the light source side) of the second polarizer through the adhesive layer can be used. In addition, a polarizer protective film may also be provided between the polarizer and the brightness enhancing film.

10‧‧‧Liquid crystal layer 11‧‧‧Initial alignment direction 20‧‧‧Liquid crystal cell 21‧‧‧Color filter substrate 22‧‧‧TFT substrate 22B‧‧‧Blue transmission area 22G‧‧‧Green transmission area 22R ‧‧‧ Red transmission area 25‧‧‧TFT substrate 30‧‧‧ Polarizer 35‧‧‧ Absorption axis (direction) 40‧‧‧ Polarizer 45‧‧‧ Absorption axis (direction) 50‧‧‧ Optical anisotropy Element (phase difference plate) 53‧‧‧Phase phase axis (direction) 60‧‧‧Optical anisotropic element (phase difference plate) 63‧‧‧Phase phase axis (direction) 101‧‧‧LCD panel 102‧‧‧ 106‧‧‧ crystal panel The liquid crystal panel of the liquid crystal panel 110‧‧‧ 107‧‧‧ source 201‧‧‧ liquid crystal display device liquid crystal display device 202‧‧‧ P ₀ ‧‧‧ point P ₁ ‧‧‧ point P _'0 ‧‧ ‧ light P _'1 ‧‧‧ light P _A ‧‧‧ point P' _A ‧‧‧ point P _C ‧‧‧ point P _L ‧‧‧ light P _R ‧‧‧ point polar angle θ‧‧‧

FIG. 1 is a conceptual diagram of the configuration of the liquid crystal panel (O mode) of the first embodiment. 2 is a schematic cross-sectional view of the liquid crystal display device (O mode) of the first embodiment. 3 is a conceptual diagram of the configuration of the liquid crystal panel (E mode) of the second embodiment. 4 is a schematic cross-sectional view of a liquid crystal display device (E mode) of a second embodiment. FIG. 5 is an explanatory diagram illustrating a state of optically compensating the apparent axial deviation of the polarizer by the optical anisotropic element using the Poincare sphere. 6 is a conceptual diagram of the configuration of a liquid crystal panel (O mode) of a reference example. 7 is a conceptual diagram of a configuration of a liquid crystal panel (E mode) of a reference example. 8A and 8B are explanatory diagrams illustrating the state of optical compensation of an O-mode liquid crystal panel using a Poincaré sphere. 9A and 9B are explanatory diagrams illustrating the state of optical compensation of the E-mode liquid crystal panel using Poincaré balls. 10A and B are the simulation results of the chromaticity of the black display of the O-mode liquid crystal display device. 11A and B are the simulation results of the chromaticity of the black display of the E mode liquid crystal display device. 12 is a graph obtained by plotting the condition that the chromaticity u′ of the black display of the O-mode liquid crystal display device becomes a specific value. 13 is a graph obtained by plotting the condition that the brightness of the black display of the O-mode liquid crystal display device becomes a specific value. 14 is a graph obtained by plotting the condition that the chromaticity u′ of the black display of the E-mode liquid crystal display device becomes a specific value. 15 is a graph obtained by plotting the condition that the brightness of the black display of the liquid crystal display device of the E mode becomes below a specific value.

10‧‧‧Liquid crystal layer

11‧‧‧Initial alignment direction

20‧‧‧LCD unit

30‧‧‧ Polarizer

35‧‧‧absorption axis (direction)

40‧‧‧ Polarizer

45‧‧‧absorption axis (direction)

50‧‧‧Optical anisotropic element (phase difference plate)

53‧‧‧Phase axis (direction)

101‧‧‧ LCD panel

Claims (7)

A liquid crystal panel comprising: a liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in parallel in a state without electric field, and a color arranged on the first main surface of the liquid crystal layer and having at least a green transmission region and a red transmission region Filter; the first polarizer, which is arranged on the first main surface of the liquid crystal cell; the second polarizer, which is arranged on the second main surface of the liquid crystal cell; and the optical anisotropic element, which is arranged on the first Between a polarizer and a second polarizer; and the direction of the absorption axis of the first polarizer is orthogonal to the direction of the absorption axis of the second polarizer, and the direction of the slow phase axis of the optical anisotropic element is the same as the second polarizer The absorption axis direction of the device is parallel. In the above optically anisotropic device, the ratio of the front retardation Re ₆₅₀ at a wavelength of 650 nm to the thickness direction retardation Rt ₆₅₀ is Rt ₆₅₀ /Re ₆₅₀ from 0.2 to 0.8, and the green transmission area of the color filter Medium, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm is greater than 0 and below 50 nm. In the red transmission region of the above color filter, the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm is greater than 0 and below 50 nm, the liquid crystal cell The alignment direction of the liquid crystal molecules in an electric field-free state is parallel to the absorption axis direction of the second polarizer, the optical anisotropic element is disposed between the liquid crystal cell and the first polarizer, the optical anisotropy The thickness direction retardation Rt ₅₅₀ (nm) of the device at a wavelength of 550 nm and the above Ct ₅₅₀ (nm) satisfy the following formula (3a): 0.97(Ct ₅₅₀ )+73≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+205...(3a ) The above Rt ₆₅₀ (nm) and the above Ct ₆₅₀ (nm) satisfy the following formula (1a) or (2a): Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+116...(1a) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ ) +116...(2a). The liquid crystal panel according to claim 1, wherein the Rt ₅₅₀ and the Ct ₅₅₀ satisfy the following formula (3b): 0.97(Ct ₅₅₀ )+98≦Rt ₅₅₀ ≦0.49(Ct ₅₅₀ )+180...(3b). The liquid crystal panel according to claim 1 or 2, wherein the above Rt ₆₅₀ and the above Ct ₆₅₀ satisfy the following formula (1b) or (2b): Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+121...(1b) Rt ₆₅₀ ≦-0.44 (Ct ₆₅₀ ) + 108... (2b). A liquid crystal panel comprising: a liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in parallel in a state without electric field, and a color arranged on the first main surface of the liquid crystal layer and having at least a green transmission region and a red transmission region Filter; the first polarizer, which is arranged on the first main surface of the liquid crystal cell; the second polarizer, which is arranged on the second main surface of the liquid crystal cell; and the optical anisotropic element, which is arranged on the first Between a polarizer and a second polarizer; and the direction of the absorption axis of the first polarizer is orthogonal to the direction of the absorption axis of the second polarizer, and the direction of the slow phase axis of the optically anisotropic element is The absorption axis directions of the two polarizers are parallel. For the above optical anisotropic element, the ratio of the front retardation Re ₆₅₀ at a wavelength of 650 nm to the thickness direction retardation Rt ₆₅₀ is Rt ₆₅₀ /Re ₆₅₀ from 0.2 to 0.8. For the above color filter In the green transmission region, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm is 50 nm or less. For the red transmission region of the color filter above, the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm is greater than 0 and is 50 nm or less. The alignment direction of the liquid crystal molecules in an electric field-free state is orthogonal to the absorption axis direction of the second polarizer, the optical anisotropic element is disposed between the liquid crystal cell and the second polarizer, the optical anisotropy The thickness direction retardation Rt ₅₅₀ (nm) of the device at a wavelength of 550 nm and the above Ct ₅₅₀ (nm) satisfy the following formula (8a): 0.69(Ct ₅₅₀ )+70≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+200...(8a ) The above Rt ₆₅₀ (nm) and the above Ct ₆₅₀ (nm) satisfy the following formula (6a) or (7a): Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+116...(6a) Rt ₆₅₀ ≦-0.44(Ct ₆₅₀ ) +120...(7a). The liquid crystal panel according to claim 4, wherein the Rt ₅₅₀ and the Ct ₅₅₀ satisfy the following formula (8b): 0.69 (Ct ₅₅₀ )+98≦Rt ₅₅₀ ≦1.35(Ct ₅₅₀ )+171...(8b). The liquid crystal panel according to claim 4 or 5, wherein the Rt ₆₅₀ and the Ct ₆₅₀ satisfy the following formula (6b) or (7b): Rt ₆₅₀ ≧0.37(Ct ₆₅₀ )+121...(6b) Rt ₆₅₀ ≦-0.44 (Ct ₆₅₀ ) + 108... (7b). A liquid crystal display device comprising: the liquid crystal panel according to any one of claims 1 to 6; and a light source arranged on the second main surface side of the liquid crystal panel.

Images