KR20210016618A - Liquid crystal panel and liquid crystal display - Google Patents

Abstract

The liquid crystal panel 101 includes a liquid crystal cell 20, a first polarizer 30, a second polarizer 40, and an optically anisotropic element 50. The liquid crystal cell includes a liquid crystal layer containing liquid crystal molecules homogeneously aligned in an electric field state, and a color filter 22 disposed on a first main surface of the liquid crystal layer. The slow axis direction 53 of the optically anisotropic element 50 and the absorption direction axis 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 at each of a wavelength of 550 nm and a wavelength of 650 nm.

Description

Liquid crystal panel and liquid crystal display

The present invention relates to a liquid crystal panel including an optically anisotropic element between a liquid crystal cell and a polarizer. Further, the present invention relates to a liquid crystal display device using the liquid crystal panel.

The liquid crystal panel includes a liquid crystal cell between a pair of polarizers. A liquid crystal cell has a liquid crystal layer between a pair of substrates, and in a general liquid crystal cell, a color filter is provided on a substrate (color filter substrate) disposed on the viewer side of the liquid crystal layer, and a substrate disposed on the light source side (TFT substrate) There are provided pixel electrodes, TFT elements, and the like.

In the in-plane switching (IPS) liquid crystal cell, the liquid crystal molecules are homogeneously aligned in a direction substantially parallel to the substrate surface in an electric field, and the liquid crystal molecules are moved in a plane parallel to the substrate surface by applying an electric field in the transverse direction. By rotating, transmission of light (white display) and shielding (black display) are controlled. Like the IPS method, a horizontal electric field type liquid crystal panel in which liquid crystal molecules are homogeneously aligned in an electric field state has excellent viewing angle characteristics.

In the IPS type liquid crystal display device, the orientation direction of liquid crystal molecules in the fieldless state of the liquid crystal cell (hereinafter sometimes referred to as "initial orientation direction") and the absorption axis direction of the polarizers disposed on the front and back of the liquid crystal cell Based on the relationship with, it is largely 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 and the initial alignment direction of the liquid crystal are parallel. In the E mode, the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell and the initial alignment direction of the liquid crystal are orthogonal.

In the IPS system liquid crystal display device, when visually recognized from an oblique direction at an angle of 45 degrees with respect to the absorption axis of the polarizer (azimuth angles 45 degrees, 135 degrees, 225 degrees, and 315 degrees), the light leakage of the black display is large, and the contrast is reduced. Deterioration or color shift is likely to occur. This light leakage is due to the fact that the angle formed by the "appearance absorption axis direction" of the polarizers arranged on the front and back of the liquid crystal cell deviates from 90° when visually recognized in the oblique direction.

For the purpose of reducing light leakage during visual recognition in the oblique direction, a method of disposing an optically anisotropic element (phase difference plate) between a liquid crystal cell and a polarizer has been proposed. For example, in Patent Document 1, it is proposed to arrange an optically anisotropic element having a refractive index anisotropy of nx>nz>ny between a liquid crystal cell and one polarizer. nx is the refractive index in the in-plane slow axis direction, ny is the refractive index in the in-plane fast axis direction, and nz is the refractive index in the thickness direction (normal direction).

From the viewpoint of compensating the deviation of the angle in the direction of the absorption axis on the appearance of the polarizer, the optical anisotropic element has a retardation of 1/2 of the wavelength, and the Nz coefficient represented by Nz = (nx-nz)/(nx-ny) is 0.5 Ideally (see the Poincaré sphere in Fig. 5). The retardation of an optically anisotropic element depends on the wavelength. In optical compensation of a liquid crystal display device using an optically anisotropic element, generally, optical design is performed so that light leakage of green light (with a wavelength around 550 nm) having high non-visibility is reduced. Therefore, in order to compensate for the deviation of the angle in the axial direction on the appearance of the polarizer, an optically anisotropic element having a retardation of about 275 nm at a wavelength of 550 nm may be used.

In addition to the shift in the axial direction on the appearance of the polarizer, the characteristics of other optical elements may also cause light leakage during black display. For example, in Patent Document 2, it is proposed to adjust the optical properties of an optically anisotropic element for optical compensation in consideration of the birefringence of a triacetylcellulose (TAC) film provided as a protective film on the surface of the liquid crystal cell side of the polarizer. . In Patent Document 3, it is proposed to use a low birefringence film such as a norbornene resin film as a protective film provided on the surface of a polarizer.

Japanese Patent Laid-Open Publication No. Hei 4-371903 Japanese Patent Laid-Open Publication No. 2001-258041 Japanese Patent Laid-Open Publication No. 2004-4641

The color filter provided on the substrate of the liquid crystal cell has an in-plane retardation of approximately 0, but 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, light leakage when visually recognized in the oblique direction is prevented by adjusting the optical characteristics of the optically anisotropic element in consideration of its optical characteristics. It can be further reduced.

As described above, the optical compensation of the liquid crystal panel is optimized for green light with high visibility (around 550 nm wavelength). Therefore, during black display, light of a wavelength having a large deviation in optical design from the optimum value leaks, and the screen is colored and visually recognized. Due to the optical design, it is difficult to make the color completely neutral when viewed from an oblique direction, and therefore, in black display, the screen is slightly colored and visually recognized according to the wavelength of light that caused light leakage. Since blue (near wavelength 450 nm) has a lower visibility than red (near wavelength 650 nm), the color of the black display tends to be blue.

According to the review of the present inventors, in a liquid crystal panel of a specific configuration, when the optical anisotropic element is designed so that green light leakage is minimized in consideration of the influence of the thickness direction retardation of the color filter, the light leakage of red light is large. , It was found that the screen of black display when viewed from an oblique direction tends to be visually recognized with a red color. Specifically, when the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell and the slow axis direction of the optically anisotropic element are orthogonal, green light leakage is small in consideration of the effect of the retardation in the thickness direction of the color filter. If the optical design is performed so that it may be formed, the leakage of red light tends to be suppressed. On the other hand, when the absorption axis direction of the polarizer disposed on the light source side of the liquid crystal cell and the slow axis direction of the optical anisotropic element are parallel, the green light leakage is minimized in consideration of the effect of the retardation in the thickness direction of the color filter. When optical design was performed, the problem that red light leakage is large, and black display tends to become a red color has been discovered.

In the present invention, in a liquid crystal panel in which the absorption axis direction of the light source side polarizer and the slow axis direction of the optically anisotropic element are arranged in parallel, the light leakage of the black display when viewed from the oblique direction is reduced by considering the effect of the color filter. In addition, it is an object of the present invention to provide an image display device having excellent visibility by reducing the coloring of red in black display.

The liquid crystal panel of the present invention is a liquid crystal cell comprising a liquid crystal layer containing liquid crystal molecules homogeneously aligned in an electric field state, a color filter disposed on a first main surface (viewer side) of the liquid crystal layer, and a first liquid crystal cell. A first polarizer disposed on the main surface (viewer side), and a second polarizer disposed on the second main surface (light source side) of the liquid crystal cell. The absorption axis direction of the first polarizer and the absorption axis direction of the second polarizer are orthogonal.

The color filter has at least a green transmission region and a red transmission region. It is preferable that the green transmission region of the color filter has a thickness direction retardation Ct ₅₅₀ of 50 nm or less at a wavelength of 550 nm. It is preferable that the red region of the color filter has a thickness direction retardation Ct ₆₅₀ of 50 nm or less at a wavelength of 650 nm. 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 axis of the optically anisotropic element is parallel to the direction of the absorption axis of the second polarizer. In the optically anisotropic element, the ratio Rt ₆₅₀ /Re ₆₅₀ of the front retardation Re ₆₅₀ and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm is 0.2 to 0.8.

The thickness direction retardation Rt ₆₅₀ (nm) at the wavelength of 650 nm of the optically anisotropic element and the thickness direction retardation Ct ₆₅₀ (nm) at the wavelength of 650 nm of the red transmission region of the color filter satisfy the following equation (1a) or (2a). It is desirable to make it.

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 O mode, and the orientation direction (initial orientation direction) of the liquid crystal molecules in the electric field state of the liquid crystal cell and the absorption axis direction of the second polarizer are parallel. In the liquid crystal panel of the O mode, an optically anisotropic element is disposed between the liquid crystal cell and the first polarizer, that is, on the visible side of the liquid crystal cell.

In the first embodiment, the thickness direction retardation Rt ₅₅₀ (nm) at a wavelength of 550 nm of the optically anisotropic element and the thickness direction retardation Ct ₅₅₀ (nm) at a wavelength of 550 nm of the green transmission region of the color filter are expressed by the following equation (3a). It is desirable to meet.

_{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 and the absorption axis direction of the second polarizer are orthogonal. In the liquid crystal panel of the E mode, an optically anisotropic element is disposed 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, the thickness direction retardation Rt ₅₅₀ (nm) at a wavelength of 550 nm of the optically anisotropic element and the thickness direction retardation Ct ₅₅₀ (nm) at a wavelength of 550 nm of the green transmission region of the color filter are expressed by the following equation (8a). It is desirable to meet.

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.

According to the present invention, by performing optical design in consideration of the birefringence of a color filter, it is possible to reduce the black luminance when visually recognized in the oblique direction, and suppress the coloring of red in the black display, thereby providing excellent visibility. A display device can be provided.

1 is a conceptual diagram of a configuration of a liquid crystal panel (O mode) according to a first embodiment.
2 is a schematic cross-sectional view of a liquid crystal display device (O mode) according to the first embodiment.
3 is a conceptual diagram of a configuration of a liquid crystal panel (E mode) according to a second embodiment.
4 is a schematic cross-sectional view of a liquid crystal display device (E mode) according to a second embodiment.
Fig. 5 is an explanatory view taken along a Poincaré sphere of optical compensation for a shift in the axial direction of an apparent polarizer by an optically anisotropic element.
6 is a conceptual diagram of a 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.
Fig. 8 is an explanatory diagram of a state of optical compensation in a liquid crystal panel in an O mode along a Poincare sphere.
Fig. 9 is an explanatory view of a state of optical compensation in an E mode liquid crystal panel along a Poincaré sphere.
10 is a simulation result of the chromaticity of a black display of a liquid crystal display in an O mode.
Fig. 11 is a simulation result of the chromaticity of a black display of a liquid crystal display in E mode.
12 is a graph plotting conditions under which the chromaticity u'of the black display of the liquid crystal display in the O mode becomes a predetermined value.
13 is a graph plotting conditions under which the luminance of a black display in an O mode liquid crystal display becomes a predetermined value.
14 is a graph plotting conditions under which the chromaticity u'of the black display of the liquid crystal display of the E mode becomes a predetermined value.
15 is a graph plotting conditions under which the luminance of a black display in an E mode liquid crystal display device is equal to or less than a predetermined value.

[Overview of the entire LCD panel]

1 is a configuration conceptual diagram showing an arrangement of optical elements in a liquid crystal panel 101 according to a 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 configuration conceptual diagram showing 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 a first main surface (viewer side) of the liquid crystal cell 20 and a second polarizer 40 disposed on a second main surface (light source side) of the liquid crystal cell 20. Equipped. The absorption axis direction 35 of the first polarizer 30 and the absorption axis direction 45 of the second polarizer 40 are orthogonal to each other.

The liquid crystal panel 101 and the liquid crystal display 201 of the first embodiment are in O mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the side of the light source 110 of the liquid crystal cell 20 , The initial alignment directions 11 of liquid crystal molecules in the liquid crystal layer 10 are parallel. The liquid crystal panel 102 and the liquid crystal display 202 of the second embodiment are in the E mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the side of the light source 110 of the liquid crystal cell 20 , The initial alignment directions 11 of liquid crystal molecules in the liquid crystal layer 10 are 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 liquid crystal panel 101 in the O mode of the first embodiment includes an optically anisotropic element 50 between the liquid crystal cell 20 and the first polarizer 30. The liquid crystal panel 102 of the E mode of the second embodiment includes an optically anisotropic element 60 between the liquid crystal cell 20 and the second polarizer 40. In any form, the absorption axis direction 45 of the second polarizer 40 and the slow axis directions 53 and 63 of the optical anisotropic elements 50 and 60 are parallel.

In addition, "orthogonal" in this specification includes not only completely orthogonal, but also substantially orthogonal, and the angle is generally in the range of 90±2°, preferably 90±1°, more preferably It is in the range of 90±0.5. Similarly, "parallel" includes not only completely parallel, but also substantially parallel, and the angle is generally within ±2°, preferably within ±1°, and more preferably within ±0.5°. to be.

[Liquid crystal cell]

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 viewer side of the liquid crystal layer. The color filter 22 has at least a green transmissive region 22G and a red transmissive region 22R. On the second substrate 25 (TFT substrate) arranged on the light source side of the liquid crystal layer 10, a switching element (generally a TFT element) or the like for controlling the alignment direction of the liquid crystal is provided.

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

A red filter having a relatively high transmittance for visible light having a wavelength longer than 600 nm is provided in the red transmission region 22R. 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 a transmittance at a wavelength of 450 nm in the red transmission region is 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 a blue transmission region 22B. In the blue transmission region 22B, a blue filter having a relatively high transmittance for visible light having a wavelength shorter than 500 nm is provided. The transmittance at a wavelength of 450 nm in the blue transmission region is, for example, 30% or more. The transmittance at a wavelength of 550 nm and a transmittance at a wavelength of 650 nm in the blue transmission region is preferably 10% or less, and more preferably 5% or less.

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

The liquid crystal layer 10 contains liquid crystal molecules homogeneously aligned in an electric field state. The homogeneous alignment liquid crystal molecules are those in which the alignment vectors of the liquid crystal molecules are aligned in parallel and constant with respect to the substrate plane. Further, the alignment vector of the liquid crystal molecules may be slightly inclined with respect to the plane of the substrate (pretilt). 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 containing liquid crystal molecules homogeneously aligned in an electroless state include in-plane switching (IPS) mode, fringe field switching (FFS) mode, and ferroelectric liquid crystal (FLC) mode. As a liquid crystal molecule, nematic liquid crystal, smectic liquid crystal, etc. are used. In general, nematic liquid crystals are used for liquid crystal cells in IPS mode and FFS mode, and smetic liquid crystals are used for liquid crystal cells in FLC mode.

[Polarizer]

The first polarizer 30 is disposed on the side of the first main surface of the liquid crystal cell 20, and the second polarizer 40 is disposed on the side of the second main surface. The polarizer converts natural light or arbitrary polarized light into linear polarized light. As the first polarizer 30 and the second polarizer 40, any suitable polarizer may be employed depending on the purpose. For example, a dichroic substance such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially foamed polyvinyl alcohol-based film, and an ethylene/vinyl acetate copolymer-based partial saponification film, and uniaxially stretched. And polyene-based oriented films such as dehydration treatment products of polyvinyl alcohol and dehydrochloric acid treatment products of polyvinyl chloride.

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

As the PVA-based polarizer, a thin polarizer having a thickness of 10 μm or less can also be used. As a thin polarizer, for example, a thin type described in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, a pamphlet WO2010/100917, Japanese Patent Publication No. 4691205, Japanese Patent No. 44751481, etc. A polarizing film is mentioned. Such a thin polarizer is obtained, for example, by a manufacturing method including a step of stretching a PVA-based resin layer and a resin substrate for stretching in the state of a laminate, and a step of iodine dyeing.

[Optical anisotropic device]

The optically anisotropic elements 50 and 60 are retardation films in which the refractive index nx in the in-plane slow axis direction, the refractive index ny in the fast axis direction in the plane, and the refractive index nz in the thickness direction satisfy nx>nz>ny. The polarizers 30 and 40 arranged above and below the liquid crystal cell 20 are arranged so that the absorption axis directions 35 and 45 are orthogonal, but when the liquid crystal panel is visually recognized in an oblique direction, the appearance of the polarizers 30 and 40 Since the angle formed by the direction of the absorption axis of is larger than 90° (a shift from cross Nicole occurs), light leakage occurs.

By disposing a retardation film satisfying nx>nz>ny between the liquid crystal cell 20 and the polarizers 30 and 40, the deviation of the axis on the appearance of the polarizer is compensated, and the screen is visually recognized in the oblique direction. Light leakage can be reduced. In particular, the black luminance at an angle of 45 degrees with respect to the absorption axis of the polarizer (azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees) is reduced, and the contrast is improved.

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

The front retardation Re ₅₅₀ of the optically anisotropic elements 50 and 60 at a wavelength of 550 nm is preferably 150 to 400 nm, more preferably 180 to 370 nm, and even more preferably 200 to 350 nm. The thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm of the optically anisotropic element is preferably 75 to 200 nm, more preferably 90 to 185 nm, and even more preferably 100 to 175 nm. In addition, the front retardation Re and the thickness direction retardation Rt are defined below using the refractive index nx in the slow axis direction in the plane, the refractive index ny in the fast axis direction in the plane, and the refractive index nz in the thickness direction.

Re=(nx-ny)×d

Rt=(nx-nz)×d

The ranges of Re and Rt of the optically anisotropic element in consideration of the retardation in the thickness direction of the color filter will be described later.

The optically anisotropic elements 50 and 60 preferably have an Nz coefficient of 0.2 to 0.8 defined by Nz=(nx-nz)/(nx-ny). Based on the above definitions of Re and Rt, it may also be represented by Nz=Rt/Re. In this specification, the Nz coefficient is calculated based on the refractive index of a wavelength of 650 nm. That is, the Nz coefficient is the ratio Rt ₆₅₀ /Re ₆₅₀ of the front retardation Re ₆₅₀ and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm. Therefore, it is preferable that the optically anisotropic element has an Rt ₆₅₀ /Re ₆₅₀ of 0.2 to 0.8. In addition, in a retardation film produced by stretching a polymer film, the Nz coefficient calculated based on the refractive index at a wavelength of 550 nm and the Nz coefficient calculated based on the refractive index at a wavelength of 650 nm are generally substantially the same.

The Nz coefficient of the optically anisotropic element is more preferably 0.3 to 0.7, and still more preferably 0.4 to 0.6. The closer the Nz coefficient is to 0.5, the more the light leakage tends to decrease over a wide viewing angle range.

Materials constituting the optically anisotropic element include polycarbonate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate resins, sulfone resins such as polysulfone and polyethersulfone, and polyphenylene sulfide. Sulfide-based resins, polyimide-based resins, cyclic polyolefin-based (polynorbornene-based) resins, polyamide resins, polyolefin-based resins such as polyethylene and polypropylene, and cellulose esters. As the material of the optically anisotropic element, a liquid crystal material can also be used.

When a polymer material is used, by stretching or contracting the polymer film in at least one direction, molecular orientation in a predetermined direction can be improved, and an optically anisotropic element (phase difference film) can be produced. Optical having a refractive index anisotropy of nx> nz> ny by shrinking the film in a direction orthogonal to the stretching direction while stretching in one direction while a polymer film and a heat-shrinkable film are laminated. An anisotropic element is obtained.

The thickness of the optically anisotropic element can be appropriately selected depending on the material constituting the optically anisotropic element, and the like. When a polymer material is used, the thickness of the optically anisotropic element is generally about 3 μm to 200 μm. When a liquid crystal material is used, the thickness of the optically anisotropic element (the thickness of the liquid crystal layer) is generally about 0.1 μm to 20 μm.

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

[Optical compensation principle according to optical anisotropic elements]

In the present invention, by setting the optical characteristics of the optically anisotropic element according to the birefringence of the color filter, both the deviation in the apparent axial direction of the polarizer and the influence due to the birefringence of the color filter are optically compensated, and in the oblique direction. There is little light leakage when visually recognized, and a liquid crystal display device in which the color of black display is neutral is obtained. Specifically, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm in the green transmission region 22G of the color filter 22 and the thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm in the optical anisotropic elements 50 and 60 are predetermined. Satisfying the relationship; In addition, 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 thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm of the optical anisotropic elements 50 and 60 are predetermined relationships. The optical properties of the optically anisotropic element are set so as to satisfy.

<Optical compensation when the color filter's birefringence is not considered>

First, with reference to FIG. 5, a principle of compensating for a shift in the axial direction of an apparent polarizer using an optically anisotropic element having a refractive index anisotropy of nx>nz>ny will be described. In FIG. 5, a state in which the optical anisotropic element 50 compensates for the deviation in the axial direction of the polarizers 30 and 40 in the liquid crystal panel 101 in the O mode shown in FIG. 1 by using a Poincare sphere. have.

The light transmitted through the light source side polarizer 40 is linearly polarized light, and when the liquid crystal display device is visually recognized from the front, the light transmitted through the polarizer is indicated by a point P ₀ on the equator of the Poincare sphere. Since the absorption axis direction 35 of the viewer side polarizer 30 and the absorption axis direction 45 of the light source side polarizer 40 are orthogonal, the light passing through the viewer side polarizer 30 is a point on the equator of the Poincare sphere. It is represented by P ₁ .

Since 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, the polarization state of the light transmitted through the polarizer 40 is transmitted through the liquid crystal cell. It does not change afterwards. That is, the polarization state of light that has passed through the liquid crystal cell does not move from the point P ₀ on the Poincare sphere. Since the light (P ₀ ) transmitted through the liquid crystal cell 20 and the light (P ₁ ) transmitted through the viewer-side polarizer 30 are linearly polarized light that is orthogonal to each other, all of the light transmitted through the liquid crystal cell 20 is visually recognized. It is absorbed by the side polarizer 30, and a black display can be realized.

When the liquid crystal display device is visually recognized in the direction of an azimuth angle of 45° based on the absorption axis direction of the polarizer and an inclination (polar angle) θ based on the normal direction of the screen, the apparent axial direction of the light source side polarizer 40 is, from P ₀ P 'apparent in the axial direction of movement to _0, and the visual side polarizer 30 is in the P ₁ P' moves to _one. The larger the pole angle θ is, the greater the change in the axial direction on the appearance of the polarizer increases.

Since "light (P passing through the ₍₀ and the visual side polarizer _{30: 1)} P light), which is transmitted through the light source-side polarizer 40 is not an orthogonal relationship, light leakage occurs in a black display. In order to prevent light leakage due to this apparent axial displacement of the same, the polarization state of the light after passing through the liquid crystal cell 20, the visual side polarizer light (P _'1) and perpendicular to the straight line of 30 is transmitted through It is necessary to make it polarized light (P _A ).

In the liquid crystal panel 101 of the mode shown in Fig. 1, since the absorption axis direction 45 of the light source side polarizer 40 and the initial alignment direction 11 of the liquid crystal cell 20 are parallel, it should be visually recognized in the oblique direction. The apparent initial orientation direction 11 at the time moves similarly to the absorption axis direction 45 of the light source side polarizer. Therefore, the polarization state of the light transmitted through the polarizer 40, the Poincare sphere does not change after the liquid crystal cell transmission does not move from a point P _'0 above.

The light transmitted through the liquid crystal cell 20 enters the optically anisotropic element 50. In the optically anisotropic element 50 having an Nz coefficient of 0.5, the apparent optical axis direction does not change even when visually recognized from any angle, and a slow axis exists on the line connecting P ₀ and P ₁ . The frontal retardation (retardation for light in the normal direction) Re of the optically anisotropic element 50 is 1/2 of the wavelength ?. In the case of Nz=0.5, even if the transmission direction of light changes, the apparent retardation does not change, and is constant at λ/2. Since the retardation of λ/2 corresponds to the phase difference π, the light (P' ₀ ) that has passed through the liquid crystal cell 20 is transmitted through the optically anisotropic element 50, so that the axis (P ₀ -P ₁ ) Rotate 180° clockwise on the Poincaré sphere around, and move to point P _A.

As described above, since the linearly polarized light (P _A ) is a linearly polarized light orthogonal to the light (P′ ₁ ) transmitted by the viewer-side polarizer 30, the light whose polarization state is changed by the optically anisotropic element 50 (P _A ) is absorbed by the visual side polarizer 30, and black display can be realized.

As shown in FIG. 6, in the liquid crystal panel 106 of the O mode in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 53 of the optical anisotropic element 50 are orthogonal to each other, the optically anisotropic element Since the transformation of the polarization state according to (50) is counterclockwise on the Poincaré sphere, the trajectory on the Poincaré sphere passes through the southern hemisphere as indicated by the dashed-dotted line in Fig. 5. Since the rotation angle is 180°, similar to the case of the liquid crystal panel shown in FIG. 1, the polarization state of the light transmitted through the optically anisotropic element 50 is represented by a point P _A on the Poincare sphere, and the polarizer 30 on the viewer side Because it is absorbed by, black display can be realized.

In the liquid crystal panel 102 of the E mode shown in FIG. 3, since the initial alignment direction 11 of the liquid crystal molecules in the liquid crystal cell 20 is orthogonal to the absorption axis direction 45 of the light source side polarizer 40, When visually recognized in the oblique direction, the apparent initial alignment direction 11 and the absorption axis direction 45 of the light source side polarizer 40 deviate from 90°. Therefore, the optical anisotropy of the light source-side polarizer 40 and place an optically anisotropic element (60) between the liquid crystal cell 20, linearly polarized light transmitted through the light source-side polarizer 40 (P _'0), the device ( 60) to the point P _A on the Poincaré sphere. In this way, the linearly polarized light P′ ₀ from the light source side polarizer 40 is converted into linearly polarized light P _A by the optically anisotropic element 60 and then incident on the liquid crystal cell 20 to cause liquid crystal Since the polarization state of the light transmitted through the cell does not change in P _A and is absorbed by the viewer-side polarizer 30, a black display can be realized.

As shown in FIG. 7, in the liquid crystal panel 107 of the E mode in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 63 of the optical anisotropic element 60 are orthogonal to each other, the optically anisotropic element Although the trajectory in the Poincaré sphere of the conversion of the polarization state by (60) is different in that it becomes the northern or southern hemisphere, the principle of optical compensation is similar to that of the liquid crystal panel 102 shown in FIG. 3.

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

<Color filter thickness direction retardation>

As described above, the color filter 22 provided on the visible side of the liquid crystal layer 10 in the liquid crystal cell 20 has an in-plane retardation of approximately 0, but has a retardation of several nm to several tens of nm in the thickness direction. Have. In the green transmission region 22G, the retardation in the thickness direction with respect to the light having the highest transmittance in the vicinity of the wavelength 550 nm affects the visibility. For similar reasons, in the red transmission region 22R, the retardation in the thickness direction for light having a high transmittance in the vicinity of a wavelength of 650 nm affects visibility. Therefore, when evaluating the retardation in the thickness direction of the color filter, for the green transmission region (green color filter), the thickness direction retardation Ct ₅₅₀ with a wavelength of 550 nm is used, and for the red transmission region (red color filter), It is appropriate to perform evaluation using the thickness direction retardation Ct ₆₅₀ with a wavelength of 650 nm.

In order to suppress light leakage when visually recognized in the oblique direction, the thickness direction retardation of the color filter is preferably smaller. The thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm in the green transmission region is preferably 50 nm or less, more preferably 40 nm or less, still more preferably 35 nm or less, and particularly preferably 30 nm or less. The thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm in the red region of the color filter is preferably 50 nm or less, more preferably 40 nm or less, still more preferably 35 nm or less, and particularly preferably 30 nm or less. Although the retardation in the thickness direction of the color filter is ideally 0, it is difficult to completely set the retardation in the thickness direction of the color filter to 0. Thus, 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 color filter>

First, with reference to FIG. 8A, the influence of the retardation in the thickness direction of the color filter in the liquid crystal panel 101 of the O mode shown in FIG. 1 and optical compensation in consideration of this will be described. If the case of viewing from an oblique direction and obtain a liquid crystal layer 10, polarization state of the light after passing through the liquid crystal cell 20 Poincare is represented by the point P _'0 above, does not take into account the double refraction of the color filter (Fig. 5 ) Is similar to

The light transmitted through the liquid crystal layer enters the color filter 22. The color filter can approximate as a negative C plate having a refractive index anisotropy of nx = ny> nz since the front retardation is approximately 0 and has a predetermined thickness direction retardation. In an oblique direction to the light, the polarization state is changed by the influence of the retardation in the thickness direction of the negative C plate, and along the meridians of the upper south Poincare sphere in point P _'0 moves to the point P _C.

If also the similar to the case of Figure 5, the phase difference of the optically anisotropic element π (if rotated 180 ° on the Poincaré sphere), which is transmitted through the optically anisotropic element polarization state appears as a point P _'A of Figure 8A, the Poincare sphere It is located in the northern hemisphere. In order to make the light after passing through the optically anisotropic element 50 into linearly polarized light represented by the point P _A on the equator, it is necessary to increase the rotation angle of the Poincare sphere by the optically anisotropic element more than 180°. That is, considering the influence of the birefringence of the color filter, in the liquid crystal panel 101 of the O mode shown in FIG. 1, in order to make the light after passing through the optical anisotropic element 50 linearly polarized, the optical anisotropic element 50 It is necessary to make the phase difference larger than π.

FIG. 8B is a view of optical compensation in the liquid crystal panel 106 in the O mode of FIG. 6 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 53 of the optical anisotropic element 50 are orthogonal. It is showing the appearance. The polarization state of light after passing through the color filter 22 approximated as a negative C plate is represented by a point P _C in the southern hemisphere of the Poincare sphere, similar to the case of Fig. 8A. If the retardation of the optically anisotropic element is a π, when point 180 ° rotation on the Poincare sphere from P _C in the counterclockwise direction, beyond the equator and reaches the point P 'in the _A hemisphere. In order to make the light after passing through the optically anisotropic element 50 linearly polarized light represented by the point P _A on the equator, it is necessary to make the rotation angle of the Poincare sphere by the optically anisotropic element smaller than 180°. That is, considering the influence of the birefringence of the color filter, in the liquid crystal panel 106 of the O mode shown in FIG. 6, in order to make the light after passing through the optical anisotropic element 50 linearly polarized, the optical anisotropic element 50 It is necessary to make the phase difference smaller than π.

9A is a view of optical compensation in the liquid crystal panel 107 in the E mode of FIG. 7 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 63 of the optical anisotropic element 60 are orthogonal. It is showing the appearance. Similar to the case of FIGS. 8A and 8B, when the light P _L after passing through the liquid crystal cell passes through the color filter 22, which is approximated as a negative C plate, the polarization state changes and descends south along the meridian on the Poincaré sphere. . In order to absorb the light after passing through the color filter by the viewer-side polarizer 30 as linearly polarized light P _A , the light P _L after passing through the liquid crystal cell needs to be located in the northern hemisphere above the Poincare sphere.

Similar to the case of FIG. 5, when the phase difference of the optically anisotropic element is π, and the linearly polarized light (P' ₀ ) transmitted through the light source side polarizer is moved to the point P _A on the Poincare sphere by the optical anisotropic element, the liquid crystal cell The polarization state of light that has passed through does not change in P _A. However, since the light after passing through the liquid crystal cell descends along the meridian on the Poincare sphere due to the influence of the retardation in the thickness direction of the color filter, the light after passing through the color filter becomes elliptical polarized light located in the southern hemisphere, Light that is not absorbed by the viewer-side polarizer 30 is visually recognized as light leakage.

In the liquid crystal panel 107 of the E mode shown in Fig. 7, as shown in Fig. 9A, the phase difference of the optically anisotropic element 60 is made smaller than π (the rotation angle on the Poincare sphere by the optical anisotropic element is smaller than 180°. By doing), appropriate optical compensation becomes possible. The polarization state of light transmitted through an optically anisotropic element having a phase difference of less than π is represented by a point P _R on the southern hemisphere of the Poincaré sphere. Since the polarization state is changed by the influence of the phase difference of the liquid crystal layer 10 and rotates on the Poincaré sphere clockwise around the axis (P _A -P' ₁ ), the polarization of light after passing through the liquid crystal layer 10 The state is represented by the point P _L on the northern hemisphere of the Poincaré sphere. As described above, when light P _L after passing through the liquid crystal cell passes through the color filter 22, it moves south along the meridian on the Poincare sphere and reaches the point P _A on the equator. Therefore, the light P _A after passing through the color filter is appropriately absorbed by the visual side polarizer 30, and light leakage can be prevented.

9B is a view of optical compensation in the liquid crystal panel 102 of the E mode of FIG. 3 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 63 of the optical anisotropic element 60 are parallel Represents. In the liquid crystal panel 102, if the phase difference of the optically anisotropic element 60 is greater than π (the rotation angle on the Poincare sphere by the optically anisotropic element is greater than 180°), the polarization state of the light transmitted through the optically anisotropic element is Poincare It is located at point P _R above the southern hemisphere of the sphere. Then, similar to the case of Fig. 9A, by passing through the liquid crystal layer 10, moving to the point P _L on the northern hemisphere, and passing through the color filter 22, reaching the point P _A on the equator. Therefore, the light P _A after passing through the color filter is appropriately absorbed by the visible side polarizer 30.

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

[Optical Design of Optically Anisotropic Device]

Hereinafter, preferable optical characteristics of the optically anisotropic element according to the retardation in the thickness direction of the color filter of the liquid crystal cell will be described by mixing the results of examination by optical simulation.

For the optical simulation, using the LCD MASTER Ver.8.1.0.3, a simulator for liquid crystal displays manufactured by Syntech Co., Ltd., using the extended function of the LCD Master, the luminance of the black display in the directions of 45° azimuth and 60° polar angle, And chromaticity (u', v') in the CIE1976 color space of black display was obtained.

In the simulation of the liquid crystal display device of the O mode, as shown in FIG. 2, from the light source 110 side, the light source side polarizer 40, and the IPS liquid crystal including the color filter 22 on the visible side of the liquid crystal layer 10 The cell 20, the optically anisotropic element 50, and the visual side polarizer 30 were stacked in order as a simulation model. In the simulation of the liquid crystal display device in the E mode, as shown in FIG. 4, from the light source 110 side, the light source side polarizer 40, the optical anisotropic element 60, and the color filter ( The IPS liquid crystal cell 20 provided with 22), and the thing which laminated|stacked the view-side polarizer 30 in order was made into 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°. In the optically anisotropic element, the Nz coefficient was 0.5, the retardation wavelength dispersion was Re ₆₅₀ /Re ₅₅₀ =Rt ₆₅₀ /Rt ₅₅₀ =0.95, and Rt ₆₅₀ was changed to various values. The color filters, and change the blue transmission region ₅₅₀ in the thickness direction retardation Ct, Ct ₆₅₀ and the thickness direction retardation at a wavelength of 650nm of the red transmission region at a wavelength of 550nm, the interval in the range of 5nm to 60nm ~ 0.

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

10A is a liquid crystal panel 101 in which the absorption axis direction 45 of the light source side polarizer 40 and the slow axis direction 53 of the optical anisotropic element 50 are parallel as shown in FIG. Fig. 8A) is the simulation result. 10B is a liquid crystal panel 106 in which the absorption axis direction 45 of the light source side polarizer 40 and the slow axis direction 53 of the optical anisotropic element 50 are orthogonal to each other (with respect to the optical compensation principle), as shown in FIG. 8B) is the simulation result. 11A is a liquid crystal panel 107 in which the absorption axis direction 45 of the light source side polarizer 40 and the slow axis direction 63 of the optical anisotropic element 60 are orthogonal as shown in FIG. Fig. 9A) is the simulation result. FIG. 11B is a liquid crystal panel 102 in which the absorption axis direction 45 of the light source side polarizer 40 and the slow axis direction 63 of the optical anisotropic element 60 are parallel as shown in FIG. 3 (the optical compensation principle 9B) is a simulation result.

10B and 11A, when the absorption axis direction of the light source side polarizer and the slow axis direction of the optical anisotropic element are orthogonal, as the thickness direction retardation Ct ₆₅₀ of the red transmission region of the color filter increases When the thickness direction retardation Rt ₆₅₀ of the anisotropic element was changed, the maximum value of u'tended to decrease. In addition, in the range of 0 to 60 nm in which Ct ₆₅₀ was in the range of 0 to 60 nm, u'did not exceed 0.35 regardless of the value of the thickness direction retardation Rt ₆₅₀ of the optically anisotropic element. That is, when the absorption axis direction of the light source side polarizer and the slow axis direction of the optically anisotropic element are orthogonal, both of the liquid crystal panel 106 in the O mode shown in Fig. 6 and the liquid crystal panel 107 in the E mode shown in Fig. 7 Also, when visually recognized in the oblique direction, it can be seen that the black-displayed screen is not significantly colored in red.

On the other hand, as shown in Figs. 10A and 11B, when the absorption axis direction of the light source side polarizer and the slow axis direction of the optically anisotropic element are parallel, the thickness direction retardation Ct ₆₅₀ of the red transmission region of the color filter increases. , When the thickness direction retardation Rt ₆₅₀ of the optically anisotropic element was changed, the maximum value of u'tended to increase. In Figs. 10A and 11B, compared to Figs. 10B and 11A, u'is greatly changed depending 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. In addition, a case exceeding 0.35 was also observed.

From these results, when the absorption axis direction of the light source side polarizer and the slow axis direction of the optically anisotropic element are parallel, the liquid crystal panel 101 in the O mode shown in Fig. 1 and the liquid crystal panel 102 in the E mode shown in Fig. 3 It can be seen that the black display is colored red at the time of visual recognition in the oblique direction due to the influence of the birefringence of the red transmission region of the color filter in all of. That is, in a liquid crystal panel in which the absorption axis direction of the light source side polarizer and the slow axis direction of the optical anisotropic element are parallel, when optical compensation is performed in consideration of the effect of birefringence of the color filter, green light leakage is reduced to improve contrast. In addition, it turns out that it is necessary to perform optical design of the optically anisotropic element so as to reduce the coloring of the black display caused by red light leakage.

<First Embodiment: Optical Design of a Liquid Crystal Panel in O Mode>

(Adjustment of chromaticity)

12 is a graph plotting conditions under which the chromaticity of a black display becomes a predetermined value based on the simulation result of the liquid crystal panel 101 in the O mode shown in FIG. 1. The horizontal axis is the thickness direction retardation Ct ₆₅₀ at the wavelength of 650 nm in the red transmission region of the color filter, and the vertical axis is the thickness direction retardation Rt ₆₅₀ at the wavelength 650 nm of the optically anisotropic element. The point at which the chromaticity u'of the black display becomes 0.35 in the direction of the azimuth angle of 45° and the polar angle of 60° in each Ct ₆₅₀ is indicated by a black circle and a black triangle. When Rt ₆₅₀ is between the black circle and the black triangle, u'exceeds 0.35, and the black display is colored in red to be visually recognized. When Rt ₆₅₀ is higher than the black circle or lower than the black triangle, u'is less than 0.35, and red coloring of the black display is suppressed.

As can be understood from Fig. 12, the boundary of u'= 0.35 can be approximated by a straight line on both the upper limit side and the lower limit side. The straight line in the graph is represented by the following formula (1) and formula (2).

Rt ₆₅₀ =0.37(Ct ₆₅₀ )+116 ... (One)

Rt ₆₅₀ =-0.44 (Ct ₆₅₀ ) +116… (2)

Therefore, 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 thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm in the optical anisotropic element 50 are the following equation (1a) Alternatively, when (2a) is satisfied, u'becomes 0.35 or less, and black display with reduced red color can be realized.

Rt ₆₅₀ ≥0.37 (Ct ₆₅₀ )+116… (1a)

Rt ₆₅₀ ≤-0.44 (Ct ₆₅₀ )+116… (2a)

The white circles and white triangles in Fig. 12 indicate the point where the chromaticity u'of the black display becomes 0.314. When Rt ₆₅₀ is between the white circle and the black circle, u'is 0.314 to 0.35, and when it is above the white circle, u'is less than 0.314. Similarly, if Rt ₆₅₀ is between a white triangle and a black triangle, u'is 0.314 to 0.35, and if it is lower than the white triangle, u'is less than 0.314.

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

Therefore, when the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm in the red transmission region of the color filter and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm of the optical anisotropic element satisfy the following formula (1b) or (2b) Thus, it is possible to realize black display in which u'becomes 0.314 or less, and the color of red is further reduced.

Rt ₆₅₀ ≥0.37 (Ct ₆₅₀ )+121… (1b)

Rt ₆₅₀ ≤-0.44 (Ct ₆₅₀ )+108… (2b)

From the above results, in the liquid crystal panel of the O mode shown in Fig. 1, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (1c) or (2c), it is possible to realize a black display with reduced red color. can do.

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 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 of setting the conditions so as to satisfy u'≦0.35, it is sufficient to set C ₁ =116 nm and C ₂ =116 nm as in the above equations (1a) and (2a). From a similar point of view, in the case of setting the conditions to satisfy u'≦0.314, C ₁ =121 nm and C ₂ =108 nm may be used as in the above equations (1b) and (2b). In order to further reduce u'of the black display, it is sufficient to set C ₁ large and C ₂ small.

C ₁ in formula (1c) may be any number of 116 or more. C ₁ may 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 equation (2c) can be any number up to 116. C ₂ may 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 the black display when visually recognized in the oblique direction, Rt ₆₅₀ at a wavelength of 650 nm of the optically anisotropic element 50 is the upper limit thereof, if it satisfies the above formula (1c) or (2c). Or the lower limit is not particularly limited. However, as described later, considering the range of Rt ₅₅₀ for reducing black luminance, and the wavelength dispersion Rt ₆₅ 0/Rt ₅₅₀ of retardation of the optically anisotropic element 50, the upper and lower limits of Rt ₆₅₀ are determined by themselves. All.

(Adjustment of luminance)

As described above, by adjusting Rt ₆₅₀ of the optically anisotropic element according to the thickness direction retardation Ct ₆₅₀ of the color filter, it is possible to suppress red light leakage and reduce the black display u'. On the other hand, in order to reduce the amount of light leakage (black luminance) at the time of black display, it is preferable to perform optical design so that light leakage of green light with high visibility is reduced.

13 is a graph plotting conditions under which black luminance becomes a predetermined value based on the simulation result of the liquid crystal panel 101 in the O mode shown in FIG. 1. The horizontal axis is the thickness direction retardation Ct ₅₅₀ at a 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 optical anisotropic element. At each Ct ₅₅₀ , the black luminance in the direction of the azimuth angle 45° and the polar angle 60° has the same Ct ₅₅₀ , and the point that becomes half of the liquid crystal display device not using an optically anisotropic element is represented by a black circle and a black triangle. . When Rt ₅₅₀ is between the black circle and the black triangle, the black luminance when viewed from the oblique direction is reduced to less than half as compared to the case where the optical anisotropic element is not provided.

As can be understood from Fig. 13, the boundary of a region in which the black luminance is 1/2 compared to the case where an optically anisotropic element is not used can be approximated by a straight line on both the upper and lower limits. 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 thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm in the green transmission region 22G of the color filter 22 and the thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm in the optical anisotropic element 50 are the following formula (3a) When) is satisfied, the black luminance in the oblique direction is 1/2 or less compared to the case where the optical anisotropic element is not used.

_{0.97 (Ct 550) + 73≤Rt 550} ≤0.49 (Ct 550) +205 ... (3a)

The white circles and white triangles in Fig. 13 indicate that the black luminance becomes 1/5 of the black luminance of a liquid crystal display device not using an optically anisotropic element. When Rt ₅₅₀ is between a white circle and a white triangle, the black luminance is reduced to 1/5 or less compared to the case in which the optically anisotropic element is not provided.

The boundary represented by a white circle can be approximated by a straight line parallel to Equation (3): Rt ₅₅₀ =0.97(Ct ₅₅₀ )+98. The boundary represented by a white triangle can be approximated by a straight line parallel to Equation (4) above: Rt ₅₅₀ =0.49 (Ct ₅₅₀ )+180. Therefore, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm in the green transmission region of the color filter and the thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm of the optical anisotropic element are, When the following formula (3b) is satisfied, the black luminance is reduced to 1/5 or less compared to the case where the optically anisotropic element is not used, and a high-contrast display can be realized.

0.97(Ct ₅₅₀ )+98≤Rt ₅₅₀ ≤0.49(Ct ₅₅₀ )+180 ... (3b)

From the above results, in the liquid crystal panel of the O mode shown in Fig. 1, Ct ₅₅₀ and Rt ₅₅₀ When the following formula (3c) is satisfied, the influence of the birefringence of the color filter can be canceled, and it can be said that a display in which the black luminance in the oblique direction is reduced can be realized.

0.97(Ct ₅₅₀ )+C ₃ ≤Rt ₅₅₀ ≤0.49(Ct ₅₅₀ )+C ₄ … (3c)

As described above, in the case where the black luminance is 1/2 or less of the black luminance of a liquid crystal display device not using an optically anisotropic element, as in the above formula (3a), C ₃ =73 nm and C ₄ =205 nm do. From a similar point of view, when the black luminance is 1/5 or less of the black luminance of a liquid crystal display device that does not use an optically anisotropic element, as in the above formula (3b), C ₃ =98 and C ₄ =180 nm do. In order to further reduce the black luminance in the oblique direction, it is sufficient to set C ₃ large and C ₄ small. C ₃ in formula (3c) may be any number of 73 or more. C ₃ may be 73 nm, 88 nm, 98 nm, 108 nm, 113 nm, 118 nm, 123 nm or 128 nm. Similarly, C ₄ in equation (3c) can be any number up to 205. C ₄ may 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 larger the thickness direction retardation Ct ₅₅₀ of the color filter is, the larger the optimum value of Rt ₅₅₀ of the optically anisotropic element for reducing the black luminance when visually recognized in the oblique direction increases. This can be understood from the principle of optical compensation shown in Fig. 8A. The thickness direction retardation Ct ₅₅₀ of the color filter is large, and corresponds to the one in Fig. 8A greater the distance P _'0 and P _c (to the latitude of the large P _C). As the south latitude of P _C is significantly out of the equator, it is necessary to increase the phase difference of the optically anisotropic element in order to move the light after passing through the optically anisotropic element 50 in the orbit of the Poincare sphere. Therefore, as shown in FIG. 13, as Ct ₅₅₀ is larger, it is necessary to increase Rt ₅₅₀ in order to reduce black luminance.

(Both black luminance reduction and chromaticity)

In order to reduce the black luminance when visually recognized in the oblique direction, Rt ₅₅₀ of the optically anisotropic element is set to satisfy the above equation (3c) according to the thickness direction retardation Ct ₅₅₀ of the color filter, and the above equation (1c ) Or (2c) is satisfied by setting Rt ₆₅₀ of the optically anisotropic element. However, Rt ₅₅₀ and Rt ₆₅₀ cannot be set individually, and Rt ₆₅₀ /Rt ₅₅₀ is a constant value according to wavelength dispersion of retardation of an optically anisotropic element.

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

Since the red color filter and the green color filter have different materials, Rth of both is different, and Ct ₆₅₀ of the red color filter may be larger than Ct ₅₅₀ of the green color filter. For example, if the thickness direction retardation Ct ₆₅₀ in the red transmission region 22R of the color filter 22 is 30 nm, in the case of Rt ₆₅₀ = 124 nm, neither of the above equations (1a) and (1b) is satisfied, The chromaticity u'when visually recognized from the oblique direction exceeds 0.35, and the black display is colored red for visual recognition.

As can be understood from the above example, in the liquid crystal panel of the O mode shown in Fig. 1, even if the optical design of the optically anisotropic element is performed so that the black luminance decreases, the chromaticity u'of the black display increases, and the black display turns red. It may be colored. On the other hand, considering the thickness direction retardation Ct ₅₅₀ and Ct ₆₅₀ of the color filter, and the wavelength dispersion Rt ₆₅₀ /Rt ₅₅₀ of the retardation of the optically anisotropic element, the above formula (3c) is satisfied (however, C ₃ is 73 nm. Above, C ₄ is 205 nm or less), and also satisfies the above formula (1c) or (2c) (however, C ₁ is 116 nm or more and C ₂ is 116 nm or less), and the thickness direction retardation of the optically anisotropic element Just set the date.

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

The front retardation Re ₅₅₀ and Re ₆₅₀ of the optically anisotropic element 50 may be set so that Rt ₅₅₀ and Rt ₆₅₀ fall within the above range. As described above, since the ratio Nz=Rt/Re of the thickness direction retardation Rt to the front retardation Re is 0.2 to 0.8, the optical anisotropic element 50 has a thickness direction retardation Rt ₅₅₀ and The frontal retardation Re ₅₅₀ and Re ₆₅₀ are determined according to the Rt ₆₅₀ and Nz coefficients.

Specifically, the front retardation Re ₆₅₀ at a wavelength of 650 nm of the optically anisotropic element 50 is preferably about twice that of 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 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 may 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 wavelength dispersion of the retardation of the optically anisotropic element, it is preferable that Re ₆₅₀ of the optically anisotropic element 50 satisfies the above formula (1d).

The front retardation Re ₅₅₀ of the optically anisotropic element 50 at a wavelength of 550 nm is preferably about twice that of Rt ₅₅₀ . Therefore, it is preferable that Re ₅₅₀ 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 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 , and specifically, C ₁₄ is 410 nm or less. C ₁₄ may 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 Liquid Crystal Panel>

14 is a graph plotting conditions under which the chromaticity of black display becomes a predetermined value based on the simulation result of the liquid crystal panel 102 in the E mode shown in FIG. 3. Similar to FIG. 12, in the direction of azimuth angle of 45° and polar angle of 60°, the point at which the chromaticity u'of the black display becomes 0.35 is indicated by a black circle and a black triangle, and the point where the chromaticity u'of the black display becomes 0.314 is indicated. It is represented by white circles and white triangles.

Similar to the case of Fig. 12, the boundary of u'= 0.35 in Fig. 14 can be approximated by a straight line represented by the following equations (6) and (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 a wavelength of 650 nm in the red transmission region 22R of the color filter 22 and the thickness direction retardation Rt at a wavelength of 650 nm of the optical anisotropic element 50 _{When 650} satisfies the following formula (6a) or (7a), u'becomes 0.35 or less, and black display with reduced red color can be realized.

Rt ₆₅₀ ≥0.37 (Ct ₆₅₀ )+116… (6a)

Rt ₆₅₀ ≤-0.44 (Ct ₆₅₀ )+120… (7a)

In addition, Formula (6) is the same as Formula (1) regarding the liquid crystal panel 101 in O mode. Equation (7) is represented by a straight line parallel to Equation (2) for the liquid crystal panel 101 in the O mode. In Fig. 14, for reference, the straight line of Equation (2) is indicated by a dotted line.

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

Therefore, when the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm in the red transmission region of the color filter and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm of the optically anisotropic element satisfy the following equation (6b) or (7b) , u'becomes 0.314 or less, and a black display in which the red color is further reduced can be realized.

Rt ₆₅₀ ≥0.37 (Ct ₆₅₀ )+121… (6b)

Rt ₆₅₀ ≤-0.44 (Ct ₆₅₀ )+108… (7b)

From the above results, in the liquid crystal panel 102 of the E mode shown in Fig. 3, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (6c) or (7c), a black display with reduced red color can be realized. I can say that I can.

Rt ₆₅₀ ≥0.37(Ct ₆₅₀ )+C ₆ … (6c)

Rt ₆₅₀ ≤-0.44 (Ct ₆₅₀ )+C ₇ … (7c)

When the conditions are set to satisfy u'≤ 0.35, C ₆ =116 nm and C ₇ =120 nm can be used as in Equations (6a) and (7a) above, and u'≤ 0.314 is satisfied. In the case of setting the conditions, it is sufficient to set C ₆ =121 nm and C ₇ =108 nm as in the above equations (6b) and (7b). In order to further reduce u'of the black display, C ₆ is set larger and C ₇ is set smaller.

C ₆ in formula (6c) may be any number of 116 or more. C ₆ may be a numerical value equivalent to the aforementioned C _1, and C ₆ may 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 equation (7c) can be any number up to 120. C ₇ may be a numerical value equivalent to that of C ₂ described above, and may be 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. In consideration of the wavelength dispersion of the retardation of the optically anisotropic element, it is preferable that Rt ₆₅₀ of the optically anisotropic element 60 satisfies the above formula (6c).

From the viewpoint of reducing the chromaticity u'of the black display when visually recognized in the oblique direction, Rt ₆₅₀ at a wavelength of 650 nm of the optically anisotropic element 60 is the upper limit thereof, if it satisfies the above formula (6c) or (7c). Or the lower limit is not particularly limited. However, as described above with respect to the first embodiment, considering the range of Rt ₅₅₀ for reducing black luminance, and the wavelength dispersion Rt ₆₅₀ /Rt ₅₅₀ of retardation of the optically anisotropic element 60, the upper limit of Rt ₆₅₀ And the lower limit is set by itself.

15 is a graph plotting conditions under which black luminance becomes a predetermined value based on the simulation result of the liquid crystal panel 102 in the E mode shown in FIG. 3. Similar to FIG. 13, the point at which the black luminance in the direction of the azimuth angle of 45° and the polar angle of 60° becomes half of that of a liquid crystal display device not using an optically anisotropic element is represented by a black circle and a black triangle, and the black luminance is optically anisotropic. A point that is 1/5 of a liquid crystal display device that does not use an element is indicated by a white circle and a white triangle.

Similar to the case of Fig. 13, in Fig. 15, the boundary of the area where the black luminance is 1/2 can be approximated by a straight line compared to the case where the optical anisotropic element is not used, and the straight line in the graph is the following equation (8 ) And formula (9).

Rt ₅₅₀ =0.69(Ct ₅₅₀ )+70… (8)

Rt ₅₅₀ =1.35(Ct ₅₅₀ )+200… (9)

Accordingly, in the liquid crystal panel 102, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm in the green transmission region 22G of the color filter 22 and the thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm of the optical anisotropic element 50 this When the following formula (8a) is satisfied, the black luminance becomes 1/2 or less compared to the case where the optically anisotropic element is not used.

0.69(Ct ₅₅₀ )+70≤Rt ₅₅₀ ≤1.35(Ct ₅₅₀ )+200… (8a)

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

0.69(Ct ₅₅₀ )+98≤Rt ₅₅₀ ≤1.35(Ct ₅₅₀ )+171... (8b)

From the above results, in the liquid crystal panel 102 of the E mode shown in Fig. 3, when Ct ₅₅₀ and Rt ₅₅₀ satisfy the following equation (8c), the influence of the birefringence of the color filter is canceled, and visual recognition in the oblique direction It can be said that the display with reduced black luminance can be realized.

0.69(Ct ₅₅₀ )+C ₈ ≤Rt ₅₅₀ ≤1.35(Ct ₅₅₀ )+C ₉ … (8c)

In the case where the black luminance in the oblique direction is 1/2 or less of the case where an optically anisotropic element is not used, C ₈ =70 nm and C ₉ =200 nm may be used as in the above formula (8a). From a similar viewpoint, in the case where the black luminance in the oblique direction is 1/5 or less in the case of not using an optically anisotropic element, C ₃ =98 and C ₄ =171 nm may be used as in the above equation (8b). In order to further reduce the black luminance in the oblique direction, C ₈ may be set larger and C ₉ may be set smaller.

C ₈ in formula (8c) may be any number of 70 or more. C ₈ may be 78 nm, 88 nm, 98 nm, 108 nm, 113 nm, 118 nm, 123 nm or 128 nm. Similarly, C ₉ in equation (8c) can be any number up to 200. C ₉ may 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 larger the thickness direction retardation Ct ₅₅₀ of the color filter is, the larger the optimum value of Rt ₅₅₀ of the optically anisotropic element for reducing the black luminance when visually recognized in the oblique direction increases. This can be understood from the principle of optical compensation shown in Fig. 9B.

In the liquid crystal panel 102 of the E mode shown in Fig. 3, in order to reduce the black luminance when visually recognized in the oblique direction, the optical fiber to satisfy the above formula (8c) according to the thickness direction retardation Ct ₅₅₀ of the color filter. Rt ₅₅₀ of the anisotropic element may be set, and Rt ₆₅₀ of the optically anisotropic element may be set so as to satisfy the above formula (6c) or (7c).

Similar to the explanation for the example of the liquid crystal panel in the O mode, considering the wavelength dispersion Rt ₆₅₀ / Rt ₅₅₀ of the optically anisotropic element, when Ct ₆₅₀ is 10 nm or more, Rt ₅₅₀ satisfies Equation (8c), and Rt ₆₅₀ Few things satisfy this equation (7c). Therefore, it is preferable to set the retardation of the optically anisotropic element 60 so 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 optically 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 optically anisotropic element 60 at a wavelength of 650 nm is preferably about twice that of Rt ₆₅₀ . Therefore, it is preferable that Re ₆₅₀ 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 may 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 , and specifically, C ₁₇ is 240 nm or less. C ₁₂ may 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. In consideration of the wavelength dispersion of the retardation of the optically anisotropic element, it is preferable that Re ₆₅₀ of the optically anisotropic element 60 satisfies the above formula (6d).

The front retardation Re ₅₅₀ of the optically anisotropic element 60 at a wavelength of 550 nm is preferably about twice that of Rt ₅₅₀ . Therefore, it is preferable that Re ₅₅₀ 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 , and specifically, C ₁₈ is 140 nm or more. C ₁₈ may 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 , and specifically, C ₁₉ is 400 nm or less. C ₁₉ may 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, the liquid crystal panel 101 of the first embodiment corresponds to the thickness direction retardation Ct ₅₅₀ and Ct ₆₅₀ of the color filter 22, and the optically anisotropic element 50 disposed on the visible side of the liquid crystal cell 20 Optical design is performed so that) has a predetermined optical characteristic. 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 has predetermined optical characteristics corresponding to Ct ₅₅₀ and Ct ₆₅₀ . .

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

The optically isotropic film used as a polarizer protective film indicates that the polarization state thereof is not substantially changed even with respect to light passing through any direction of the normal direction and the oblique direction. Specifically, the optical isotropic film preferably has a front retardation Re of 10 nm or less, and a thickness direction retardation Rt of 20 nm or less. The frontal 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 still more preferably 5 nm or less.

The liquid crystal panel may include an optical layer other than the above or other members. For example, it is preferable that a polarizer protective film is provided on the outer surfaces of the polarizers 30 and 40 (surfaces that do not face 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 side of the liquid crystal cell 20 side of the viewer side polarizer 30 and the side of the liquid crystal cell 20 of the light source side polarizer 40 is required to be optically isotropic as described above.

It is preferable that the liquid crystal panel 101 of the first embodiment does not contain an optically anisotropic element other than the optically anisotropic element 50 between the visual side polarizer and the liquid crystal cell 20, and the light source side polarizer 40 and the liquid crystal cell It is preferable not to include an optically anisotropic element between (20). It is preferable that the liquid crystal panel 102 of the second embodiment does not contain an optically anisotropic element other than the optically anisotropic element 60 between the light source side polarizer and the liquid crystal cell 20, and the visual side polarizer 30 and the liquid crystal It is preferable that an optically anisotropic element is not included between the cells 20.

A liquid crystal panel is formed by laminating a liquid crystal cell and each of the optical members. In the formation process, each member may be sequentially stacked separately on the liquid crystal cell, or a stack of several members may be used. The order of lamination of these optical members is not particularly limited. A polarizer and an optically anisotropic element may be laminated to form a laminated polarizing plate in advance, and this laminated polarizing plate may be bonded to a liquid crystal cell via an adhesive (not shown). As described above, a polarizer protective film may be provided on the surface of the polarizer. An optical isotropic film may be provided as a polarizer protective film between the polarizer and the optically anisotropic element.

For lamination of each member, an adhesive or an adhesive is preferably used. Examples of adhesives and pressure-sensitive adhesives include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorine polymers, rubber polymers, etc. It can be appropriately selected and used.

[Liquid crystal display device]

A liquid crystal display device is formed by arranging the light source 110 on the second main surface side (polarizer 40 side) of the liquid crystal panel. A brightness enhancing film (not shown) may be provided between the liquid crystal panel and the light source. The brightness improving film may be provided integrally with the light source side polarizer. For example, what made the luminance enhancing film bonded to the outer surface (surface on the side of the light source) of the second polarizer through an adhesive layer can be used. Moreover, a polarizer protective film may be provided between a polarizer and a brightness improvement film.

20 liquid crystal cell
21 color filter substrate
22 TFT substrate
10 liquid crystal layer
11 Initial orientation direction
30, 40 polarizer
35, 45 absorption axis (direction)
50, 60 optical anisotropic element (phase difference plate)
53, 63 Slow axis (direction)
101, 102 liquid crystal panel
110 light source
201, 202 liquid crystal display

Claims (7)

A liquid crystal cell comprising a liquid crystal layer including liquid crystal molecules homogeneously aligned in an electric field state, and a color filter disposed on a first main surface of the liquid crystal layer and having at least a green transmission region and a red transmission region;
A first polarizer disposed on a first main surface of the liquid crystal cell;
A second polarizer disposed on a second main surface of the liquid crystal cell; And
A liquid crystal panel having an optically anisotropic element disposed between the first polarizer and the second polarizer,
The absorption axis direction of the first polarizer and the absorption axis direction of the second polarizer are orthogonal,
The slow axis direction of the optical anisotropic element and the absorption axis direction of the second polarizer are parallel,
In the optically anisotropic element, the ratio Rt ₆₅₀ /Re ₆₅₀ of the front retardation Re ₆₅₀ and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm is 0.2 to 0.8,
In the green transmission region of the color filter, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm is greater than 0 and 50 nm or less,
In the red transmission region of the color filter, the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm is greater than 0 and 50 nm or less,
The orientation direction of the liquid crystal molecules in the electric field state of the liquid crystal cell and the absorption axis direction of the second polarizer are parallel,
The optically anisotropic element is disposed between the liquid crystal cell and the first polarizer,
The thickness direction retardation Rt ₅₅₀ (nm) and the Ct ₅₅₀ (nm) at a wavelength of 550 nm of the optically anisotropic element satisfy the following equation (3a),
_{0.97 (Ct 550) + 73≤Rt 550} ≤0.49 (Ct 550) +205 ... (3a)
A liquid crystal panel in which the Rt ₆₅₀ (nm) and the 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 method of claim 1,
A liquid crystal panel in which Rt ₅₅₀ and Ct ₅₅₀ satisfy the following formula (3b):
0.97(Ct ₅₅₀ )+98≤Rt ₅₅₀ ≤0.49(Ct ₅₅₀ )+180 ... (3b). The method according to claim 1 or 2,
A liquid crystal panel, wherein Rt ₆₅₀ and 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 cell comprising a liquid crystal layer including liquid crystal molecules homogeneously aligned in an electric field state, and a color filter disposed on a first main surface of the liquid crystal layer and having at least a green transmission region and a red transmission region;
A first polarizer disposed on a first main surface of the liquid crystal cell;
A second polarizer disposed on a second main surface of the liquid crystal cell; And
A liquid crystal panel having an optically anisotropic element disposed between the first polarizer and the second polarizer,
The absorption axis direction of the first polarizer and the absorption axis direction of the second polarizer are orthogonal,
The slow axis direction of the optical anisotropic element and the absorption axis direction of the second polarizer are parallel,
In the optically anisotropic element, the ratio Rt ₆₅₀ /Re ₆₅₀ of the front retardation Re ₆₅₀ and the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm is 0.2 to 0.8,
In the green transmission region of the color filter, the thickness direction retardation Ct ₅₅₀ at a wavelength of 550 nm is 50 nm or less,
In the red transmission region of the color filter, the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm is greater than 0 and 50 nm or less,
The orientation direction of the liquid crystal molecules in the electric field state of the liquid crystal cell and the absorption axis direction of the second polarizer are orthogonal,
The optically anisotropic element is disposed between the liquid crystal cell and the second polarizer,
The thickness direction retardation Rt ₅₅₀ (nm) and the Ct ₅₅₀ (nm) at a wavelength of 550 nm of the optically anisotropic element satisfy the following equation (8a),
0.69(Ct ₅₅₀ )+70≤Rt ₅₅₀ ≤1.35(Ct ₅₅₀ )+200… (8a)
A liquid crystal panel in which the Rt ₆₅₀ (nm) and the 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 method of claim 4,
A liquid crystal panel in which Rt ₅₅₀ and Ct ₅₅₀ satisfy the following formula (8b):
0.69(Ct ₅₅₀ )+98≤Rt ₅₅₀ ≤1.35(Ct ₅₅₀ )+171... (8b). The method according to claim 4 or 5,
A liquid crystal panel in which Rt ₆₅₀ and 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 disposed on the second main surface side of the liquid crystal panel.

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