JP2019215461A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

To realize light leakage-free display when viewed from a diagonal direction.SOLUTION: A liquid crystal panel (101) comprises a liquid crystal cell (20), a first polarizer (30), a second polarizer (40), and an optical anisotropic element (50). A slow axis direction (53) of the optical anisotropic element (50) and an absorption axis direction (45) of the second polarizer are parallel to each other. The thickness direction retardation of the optical anisotropic element and the thickness direction retardation of a color filter (22) of the liquid crystal cell satisfy a prescribed relationship in both a wavelength 550 nm and a wavelength 650 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid crystal panel including an optically anisotropic element between a liquid crystal cell and a polarizer. The present invention also 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 includes a liquid crystal layer between a pair of substrates. In a general liquid crystal cell, a color filter is provided on a substrate (color filter substrate) disposed on the viewing side of the liquid crystal layer and disposed on the light source side. A pixel electrode, a TFT element, and the like are provided on a substrate (TFT substrate).

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

  In the IPS mode liquid crystal display device, the alignment direction of liquid crystal molecules in a state where no electric field is applied to the liquid crystal cell (hereinafter, sometimes referred to as “initial alignment direction”) and the absorption of polarizers arranged on the front and back of the liquid crystal cell. O mode and E mode are roughly classified based on the relationship with the axial direction. 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 is orthogonal to the initial alignment direction of the liquid crystal.

  In the IPS mode liquid crystal display device, when viewed from an oblique direction at an angle of 45 degrees (azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees) with respect to the absorption axis of the polarizer, light leakage of black display is prevented. It is large and the contrast is easily lowered and the color shift is apt to occur. This light leakage is caused by the fact that the angle formed by the “apparent absorption axis direction” of the polarizers disposed on the front and back of the liquid crystal cell is deviated from 90 ° when viewed from an oblique direction.

  A method of arranging an optically anisotropic element (retardation plate) between a liquid crystal cell and a polarizer has been proposed for the purpose of reducing light leakage when viewed from an oblique direction. For example, Patent Document 1 proposes that an optically anisotropic element having a refractive index anisotropy of nx> nz> ny is disposed 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 apparent deviation of the angle in the absorption axis direction of the polarizer, the optically anisotropic element has a retardation of 波長 of the wavelength, and Nz = (nx−nz) / (nx−ny). It is ideal that the Nz coefficient represented by is 0.5 (see Poincare sphere in FIG. 5). The retardation of the optically anisotropic element varies depending on the wavelength. In optical compensation of a liquid crystal display device using an optically anisotropic element, in general, optical design is performed so that light leakage of green light (having a wavelength of about 550 nm) with high relative visibility is reduced. Therefore, in order to compensate for the apparent axial angle deviation of the polarizer, an optically anisotropic element having a retardation at a wavelength of 550 nm of about 275 nm may be used.

  In addition to the apparent axial displacement of the polarizer, the characteristics of other optical elements can also cause light leakage during black display. For example, in Patent Document 2, in consideration of the birefringence of a triacetyl cellulose (TAC) film provided as a protective film on the surface of the polarizer on the liquid crystal cell side, the optical characteristics of the optical anisotropic element for optical compensation are disclosed. It has been proposed to adjust. In Patent Document 3, it is proposed to use a low birefringence film such as a norbornene-based resin film as a protective film provided on the surface of a polarizer.

JP-A-4-371903 JP 2001-258041 A JP-A-2004-4641

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

  As described above, the optical compensation of the liquid crystal panel is optimized for green light (wavelength around 550 nm) having high relative luminous efficiency. Therefore, at the time of black display, light having a wavelength with a large optical design deviation from the optimum value leaks, and the screen is colored and visually recognized. Due to the optical design, it is difficult to make the hue when viewed from an oblique direction completely neutral, so when displaying black, the screen is visually colored slightly depending on the wavelength of the light that caused light leakage. . Since blue (around 450 nm) has lower relative luminous efficiency than red (around 650 nm), the hue of black display tends to prefer blue.

  According to the study of the present inventors, in a liquid crystal panel having a specific configuration, an optically anisotropic element is designed so that green light leakage is minimized in consideration of the influence of retardation in the thickness direction of a color filter. In this case, it was found that the leakage of red light was large, and the screen of black display when viewed from an oblique direction tended to be viewed with a reddish hue. Specifically, when the absorption axis direction of the polarizer arranged on the light source side of the liquid crystal cell is orthogonal to the slow axis direction of the optically anisotropic element, the influence of the retardation in the thickness direction of the color filter is considered. If the optical design is performed so that the green light leakage is reduced, the red light leakage tends to be suppressed. On the other hand, if the absorption axis direction of the polarizer arranged on the light source side of the liquid crystal cell is parallel to the slow axis direction of the optically anisotropic element, consider the influence of retardation in the thickness direction of the color filter. When the optical design was made so that the green light leakage was minimized, there was a problem that the red light leakage was large and the black display was likely to have a red hue.

  The present invention relates to 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, when viewed from an oblique direction in consideration of the effect of the color filter. An object of the present invention is to provide an image display device which is excellent in visibility by reducing light leakage in black display and reducing red coloring in black display.

  A liquid crystal panel according to the present invention includes a liquid crystal cell including a liquid crystal layer containing liquid crystal molecules homogeneously aligned in an electric field-free state, and a color filter disposed on a first main surface (viewing side) of the liquid crystal layer. The liquid crystal cell includes a first polarizer disposed on a principal surface (viewing side) and a second polarizer disposed on a second principal 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 to each other.

The color filter has at least a green transmission region and a red transmission region. The green transmission region of the color filter preferably has a thickness direction retardation Ct ₅₅₀ of 50 nm or less at a wavelength of 550 nm. The red region of the color filter preferably has a thickness direction retardation Ct _{650 at} a wavelength of 650 nm of 50 nm or less. Ct ₅₅₀ and Ct ₆₅₀ are both greater than zero. Ct ₅₅₀ and Ct ₆₅₀ can 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 slow axis direction of the optically anisotropic element is parallel to the absorption axis direction of the second polarizer. The optically anisotropic element has a ratio Rt ₆₅₀ / Re ₆₅₀ of the front retardation Re ₆₅₀ and the thickness direction retardation Rt _{650 at} a wavelength of 650 nm of 0.2 to 0.8.

The thickness direction retardation Rt ₆₅₀ (nm) at a wavelength of 650 nm of the optical anisotropic element and the thickness direction retardation Ct ₆₅₀ (nm) at a wavelength of 650 nm of the red transmission region of the color filter are expressed by the following formula (1a) or (2a). It is preferable to satisfy.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) +116 (1a)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) +116 (2a)

  The liquid crystal panel of the first embodiment of the present invention is in the O mode, and the alignment direction (initial alignment direction) of the liquid crystal molecules in the state of no electric field of the liquid crystal cell is parallel to the absorption axis direction of the second polarizer. In the O-mode liquid crystal panel, an optically anisotropic element is disposed between the liquid crystal cell and the first polarizer, that is, on the viewing side of the liquid crystal cell.

In the first embodiment, the retardation Rt ₅₅₀ (nm) in the thickness direction at a wavelength of 550 nm of the optically anisotropic element and the retardation Ct ₅₅₀ (nm) in the thickness direction at a wavelength of 550 nm in the green transmission region of the color filter are represented by the following formula (3a). Is preferable.
0.97 (Ct ₅₅₀ ) + 73 ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) +205 (3a)

  The liquid crystal panel of the second embodiment of the present invention is in the E mode, and the initial alignment direction of the liquid crystal molecules of the liquid crystal cell is orthogonal to the absorption axis direction of the second polarizer. In the E-mode liquid crystal panel, an optically anisotropic element is 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 optical 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 formula (8a). ) Is preferably satisfied.
0.69 (Ct ₅₅₀ ) + 70 ≦ Rt ₅₅₀ ≦ 1.35 (Ct ₅₅₀ ) +200 (8a)

  A liquid crystal display device according to 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 the color filter, it is possible to reduce black luminance when viewed from an oblique direction, suppress red coloring of black display, and have excellent visibility. A liquid crystal display device can be provided.

It is a composition conceptual diagram of the liquid crystal panel (O mode) of a first embodiment. It is a typical sectional view of a liquid crystal display (O mode) of a first embodiment. It is a composition conceptual diagram of the liquid crystal panel (E mode) of a second embodiment. It is typical sectional drawing of the liquid crystal display device (E mode) of 2nd embodiment. It is explanatory drawing by the Poincare sphere of the mode of optical compensation of the shift | offset | difference of the apparent axial direction of a polarizer with an optically anisotropic element. It is a composition conceptual diagram of the liquid crystal panel (O mode) of a reference example. It is a composition conceptual diagram of the liquid crystal panel (E mode) of a reference example. It is explanatory drawing by the Poincare sphere of the state of the optical compensation in an O mode liquid crystal panel. It is explanatory drawing by the Poincare sphere of the state of the optical compensation in the liquid crystal panel of E mode. It is the simulation result of the chromaticity of the black display of the liquid crystal display device of O mode. It is a simulation result of the chromaticity of the black display of the liquid crystal display device of E mode. It is the graph which plotted the conditions from which the chromaticity u 'of black display of an O mode liquid crystal display device becomes a predetermined value. It is the graph which plotted the conditions from which the brightness | luminance of the black display of an O mode liquid crystal display device becomes a predetermined value. It is the graph which plotted the conditions from which the chromaticity u 'of black display of an E mode liquid crystal display device becomes a predetermined value. It is the graph which plotted the condition where the brightness | luminance of the black display of the liquid crystal display device of E mode becomes below a predetermined value.

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

  The liquid crystal panel includes a first polarizer 30 disposed on a first principal surface (viewing side) of the liquid crystal cell 20 and a second polarizer 40 disposed on a second principal surface (light source side) of the liquid crystal cell 20. . 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 device 201 of the first embodiment are in the O mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the light source 110 side of the liquid crystal cell 20 and the initial state of the liquid crystal molecules in the liquid crystal layer 10. The orientation direction 11 is parallel. The liquid crystal panel 102 and the liquid crystal display device 202 of the second embodiment are in the E mode, and the absorption axis direction 45 of the second polarizer 40 disposed on the light source 110 side of the liquid crystal cell 20 and the initial liquid crystal molecules in the liquid crystal layer 10. The orientation direction 11 is orthogonal.

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

  In this specification, the term “orthogonal” includes not only a case where they are completely orthogonal but also a case where they are substantially orthogonal, and the angle is generally in a range of 90 ± 2 °, preferably 90 ± 1 °. °, more preferably 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 °, more preferably Is within ± 0.5 °.

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

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

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

  The color filter may further include a light transmission region having a relatively high light transmittance for a specific wavelength region other than the above. A black matrix is preferably provided at the boundary between adjacent transmission regions.

  The liquid crystal layer 10 includes liquid crystal molecules that are homogeneously aligned in a state of no electric field. The homogeneously aligned liquid crystal molecules are those in which the alignment vectors of the liquid crystal molecules are aligned in parallel and uniformly with respect to the substrate plane. The alignment vector of the liquid crystal molecules may be slightly inclined with respect to the substrate plane (pretilt). The pretilt angle of the liquid crystal cell is generally 3 ° or less, preferably 1 ° or less, more preferably 0.5 ° or less.

  Examples of the liquid crystal cell including liquid crystal molecules which are homogeneously aligned in an electroless state include an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, and a ferroelectric liquid crystal (FLC) mode. As the liquid crystal molecule, nematic liquid crystal, smectic liquid crystal, or the like is used. In general, nematic liquid crystals are used for IPS mode and FFS mode liquid crystal cells, and smectic liquid crystals are used for FLC mode liquid crystal cells.

[Polarizer]
The first polarizer 30 is disposed on the first main surface side of the liquid crystal cell 20, and the second polarizer 40 is disposed on the second main surface side. A polarizer converts natural light or arbitrary polarized light into linearly polarized light. Any appropriate polarizer may be adopted as the first polarizer 30 and the second polarizer 40 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 formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. And a uniaxially oriented film, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride, and the like.

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

  As the PVA-based polarizer, a thin polarizer having a thickness of 10 μm or less can be used. Examples of the thin polarizer include those described in, for example, JP-A-51-069694, JP-A-2000-338329, WO2010 / 100917, pamphlet No. 4691205, Japanese Patent No. 4751481, and the like. Thin polarizing film. Such a thin polarizer is obtained, for example, by a production method including a step of stretching a PVA-based resin layer and a stretching resin base material in the state of a laminate, and a step of iodine staining.

[Optically anisotropic element]
In the optically anisotropic elements 50 and 60, the in-plane refractive index nx in the slow axis direction, the in-plane refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction satisfy nx>nz> ny. It is a retardation film. The polarizers 30 and 40 disposed above and below the liquid crystal cell 20 are disposed so that the absorption axis directions 35 and 45 are orthogonal to each other. However, when the liquid crystal panel is viewed from an oblique direction, the polarizers 30 and 40 appear to be apparent. Since the angle formed by the absorption axis direction becomes larger than 90 ° (deviation from crossed Nicols occurs), light leakage occurs.

  By disposing a retardation film that satisfies nx> nz> ny between the liquid crystal cell 20 and the polarizers 30 and 40, when the visual axis of the polarizer is displaced, the screen is viewed obliquely. Light leakage is reduced. In particular, the black luminance at 45 degrees (azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees) with respect to the absorption axis of the polarizer is reduced, and the contrast is improved.

  In the O-mode liquid crystal panel 101 of the first embodiment, the optically anisotropic element 50 is disposed between the liquid crystal cell 20 and the first polarizer 30 on the viewing side. In the E-mode liquid crystal panel 102 of the second embodiment, an optical 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 still more preferably 200 to 350 nm. The retardation Rt ₅₅₀ in the thickness direction at a wavelength of 550 nm of the optically anisotropic element is preferably from 75 to 200 nm, more preferably from 90 to 185 nm, even more preferably from 100 to 175 nm. The front retardation Re and the thickness direction retardation Rt are determined by using the in-plane slow axis direction refractive index nx, the in-plane fast axis direction refractive index ny, and the thickness direction refractive index nz. Defined below.
Re = (nx−ny) × d
Rt = (nx−nz) × d

  The range 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 in detail.

The optically anisotropic elements 50 and 60 preferably have an Nz coefficient defined by Nz = (nx−nz) / (nx−ny) of 0.2 to 0.8. Based on the above definitions of Re and Rt, it can also be expressed as Nz = Rt / Re. In this specification, the Nz coefficient is calculated based on the refractive index at a wavelength of 650 nm. That is, the Nz coefficient is a 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, the optically anisotropic element preferably has an Rt ₆₅₀ / Re ₆₅₀ of 0.2 to 0.8. In general, 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 substantially the same.

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

  Examples of the material constituting the optically anisotropic element include polycarbonate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate resins, sulfone resins such as polysulfone and polyether sulfone, and sulfides such as polyphenylene sulfide. Resins, polyimide resins, cyclic polyolefin (polynorbornene) resins, polyamide resins, polyolefin resins such as polyethylene and polypropylene, and cellulose esters. A liquid crystal material can also be used as the material of the optically anisotropic element.

  When a polymer material is used, by stretching or shrinking the polymer film in at least one direction, the molecular orientation in a predetermined direction can be increased to produce an optically anisotropic element (retardation film). While the polymer film and the heat-shrinkable film are laminated, the film is shrunk in the direction perpendicular to the stretching direction by using the shrinkage force of the heat-shrinkable film while stretching in one direction, thereby obtaining nx> nz> An optically anisotropic element having a refractive index anisotropy of ny is obtained.

  The thickness of the optically anisotropic element can be appropriately selected according to 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 by optical anisotropic element]
In the present invention, by setting the optical characteristics of the optical anisotropic element in accordance with the birefringence of the color filter, both the apparent axial deviation of the polarizer and the influence of the birefringence of the color filter are optically affected. Thus, a liquid crystal display device with little light leakage when viewed from an oblique direction and a neutral hue of black display can be 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 of the optically anisotropic elements 50 and 60 satisfy a predetermined relationship; In addition, the optical direction is determined so that 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 optically anisotropic elements 50 and 60 satisfy a predetermined relationship. The optical characteristics of the anisotropic element are set.

<Optical compensation without considering birefringence of color filter>
First, with reference to FIG. 5, the principle of compensating for the apparent axial deviation of a polarizer using an optically anisotropic element having a refractive index anisotropy of nx>nz> ny will be described. FIG. 5 illustrates how the optically anisotropic element 50 compensates for the apparent axial displacement of the polarizers 30 and 40 in the O-mode liquid crystal panel 101 shown in FIG. 1 using Poincare spheres. Yes.

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

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 does not change after transmission through the liquid crystal cell. That is, the polarization state of the light transmitted through the liquid crystal cell does not move from the point P ₀ on the Poincare sphere. Since the light P ₀ transmitted through the liquid crystal cell 20 and the light P ₁ transmitted through the viewing side polarizer 30 are linearly polarized light, all of the light transmitted through the liquid crystal cell 20 is absorbed by the viewing side polarizer 30. Therefore, black display can be realized.

When the liquid crystal display device is viewed from the direction of the azimuth angle of 45 ° with respect to the absorption axis direction of the polarizer and the inclination (polar angle) θ with respect to the normal direction of the screen, the apparent axis of the light source side polarizer 40 The direction moves from P ₀ to P ′ ₀ , and the apparent axial direction of the viewing side polarizer 30 moves from P ₁ to P ′ ₁ . As the polar angle θ increases, the change in the apparent axial direction of the polarizer increases.

Since the light P ′ ₀ transmitted through the light source side polarizer 40 and the light P ′ ₁ transmitted through the viewing side polarizer 30 are not orthogonal to each other, light leakage of black display occurs. In order to prevent light leakage due to such apparent axial misalignment, the polarization state of the light transmitted through the liquid crystal cell 20 is orthogonal to the light P ′ ₁ transmitted through the viewing side polarizer 30. it is necessary to linearly polarized light P _a.

In the O-mode liquid crystal panel 101 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 to each other, an apparent initial stage when viewed from an oblique direction. The alignment direction 11 moves in the same manner as the absorption axis direction 45 of the light source side polarizer. For this reason, the polarization state of the light transmitted through the polarizer 40 does not change after passing through the liquid crystal cell, and does not move from the point P ′ ₀ on the Poincare sphere.

The light transmitted through the liquid crystal cell 20 enters the optical anisotropic element 50. The optically anisotropic element 50 having an Nz coefficient of 0.5 does not change the apparent optical axis direction when viewed from any angle, and has a slow axis on the line connecting P ₀ and P _1. . The front retardation (retardation with respect to light in the normal direction) Re of the optically anisotropic element 50 is ½ of the wavelength λ. When Nz = 0.5, the apparent retardation does not change even if the light transmission direction changes, and is constant at λ / 2. Since the retardation of λ / 2 corresponds to the phase difference of π, the light P ′ ₀ transmitted through the liquid crystal cell 20 is transmitted through the optically anisotropic element 50, and the Poincare sphere is centered on the axis P ₀ −P _1. over by 180 ° clockwise rotation moves to point _{P a.}

As described above, the linearly polarized light P _A, since the viewing side polarizer 30 is linearly polarized perpendicular to the light P _'1 that transmits light P _A the polarization state is changed by the optical anisotropic device 50 is visible It is absorbed by the side polarizer 30 and a black display can be realized.

As shown in FIG. 6, in the O-mode liquid crystal panel 106 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 53 of the optically anisotropic element 50 are orthogonal, the polarization by the optically anisotropic element 50 Since the state is changed counterclockwise on the Poincare sphere, the trajectory on the Poincare sphere passes through the southern hemisphere as shown by the dashed line in FIG. Since the rotation angle is 180 °, as in the case of the liquid crystal panel shown in FIG. 1, the polarization state of light transmitted through the optical anisotropic device 50 is represented in terms P _A on the Poincare sphere, viewing side polarizer Therefore, black display can be realized.

In the E-mode liquid crystal panel 102 shown in FIG. 3, the initial alignment direction 11 of the liquid crystal molecules in the liquid crystal cell 20 is orthogonal to the absorption axis direction 45 of the light source side polarizer 40. There is a deviation from 90 ° between the initial alignment direction 11 and the absorption axis direction 45 of the light source side polarizer 40. For this reason, the optically anisotropic element 60 is disposed between the light source side polarizer 40 and the liquid crystal cell 20, and the linearly polarized light P ′ ₀ transmitted through the light source side polarizer 40 is reflected on the Poincare sphere by the optical anisotropic element 60. It is moved to the point _{P a.} Thus, the linearly polarized light P _'0 from the light source side polarizer 40, by entering the liquid crystal cell 20 after it is converted to linearly polarized light P _A by the optical anisotropic device 60, the light transmitted through the liquid crystal cell polarization state for not change from P _a, is absorbed by the viewing side polarizer 30, it is possible to realize a black display.

  As shown in FIG. 7, in the E-mode liquid crystal panel 107 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 63 of the optically anisotropic element 60 are orthogonal, the polarization by the optically anisotropic element 60 The principle of optical compensation is the same as that of the liquid crystal panel 102 shown in FIG. 3, although the point of the change of the state on the Poincare sphere is different in whether it is the northern hemisphere or the southern hemisphere.

  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 based on the angle (parallel between the optical axis direction of the optically anisotropic element and the optical axis direction of the polarizer). Or orthogonal) and the angle between the initial alignment direction of the liquid crystal cell and the optical axis direction of the polarizer (whether it is O mode or E mode).

<Thickness direction retardation of color filter>
As described above, the in-plane retardation of the color filter 22 provided on the viewing side of the liquid crystal layer 10 in the liquid crystal cell 20 has a retardation of several nm to several tens nm in the thickness direction. ing. In the green transmission region 22G, the thickness direction retardation with respect to light having a wavelength of about 550 nm, which has the highest transmittance, affects the visibility. For the same reason, in the red transmissive region 22R, the retardation in the thickness direction with respect to light having a high transmittance near the wavelength of 650 nm affects the visibility. Therefore, when evaluating the retardation in the thickness direction of the color filter, the retardation in the thickness direction Ct ₅₅₀ having a wavelength of 550 nm is used for the green transmission region (green color filter) and the red transmission region (red color filter) is used. It is appropriate to perform evaluation using a thickness direction retardation Ct ₆₅₀ having a wavelength of 650 nm.

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

<Principle of optical compensation considering color filter birefringence>
First, with reference to FIG. 8A, the influence of retardation in the thickness direction of the color filter in the O-mode liquid crystal panel 101 shown in FIG. 1 and optical compensation considering this will be described. When viewed from an oblique direction, the polarization state of light transmitted through the liquid crystal layer 10 of the liquid crystal cell 20 is represented by a point P ′ ₀ on the Poincare sphere when the birefringence of the color filter is not taken into consideration (FIG. Same as 5).

The light transmitted through the liquid crystal layer enters the color filter 22. The color filter can be approximated as a negative C plate having a refractive index anisotropy of nx = ny> nz because the front retardation is substantially 0 and has a predetermined thickness direction retardation. Light oblique direction, due to the influence of the thickness-direction retardation of the negative C plate, the polarization state is changed, then south from the point P _'0 along the meridian on the Poincare sphere, moves to point P _C.

As in the case of FIG. 5, when the phase difference of the optically anisotropic element is π (when rotated 180 ° on the Poincare sphere), the polarization state of the light transmitted through the optically anisotropic element is as shown in FIG. 8A. represented by P _'a, located northern hemisphere of the Poincare sphere. The light after passing through the optical anisotropic device 50, in order to linearly polarized light represented by point P _A on the equator, larger than 180 ° the rotation angle on the Poincare sphere by the optical anisotropic element There is a need. That is, in consideration of the influence of birefringence of the color filter, in the O-mode liquid crystal panel 101 shown in FIG. 1, in order to make the light after passing through the optical anisotropic element 50 linearly polarized light, the optical anisotropic element The phase difference of 50 needs to be larger than π.

FIG. 8B shows a state of optical compensation in the O-mode liquid crystal panel 106 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 to each other. The polarization state of the light after passing through the color filter 22 to be approximated as a negative C plate, as in the case of FIG. 8A, expressed in terms P _C in the southern hemisphere of the Poincare sphere. If the phase difference of the optically anisotropic element is a [pi, when is 180 ° rotated counterclockwise on the Poincare sphere from the point P _C, reaching past the equator northern hemisphere point P _'A. The light after passing through the optical anisotropic device 50, in order to linearly polarized light represented by point P _A on the equator is smaller than 180 ° rotation angle on the Poincare sphere by the optical anisotropic element There is a need. That is, in consideration of the influence of the birefringence of the color filter, in the O-mode liquid crystal panel 106 shown in FIG. 6, in order to make the light transmitted through the optical anisotropic element 50 linearly polarized light, the optical anisotropic element It is necessary to make the phase difference of 50 smaller than π.

FIG. 9A shows the state of optical compensation in the E-mode liquid crystal panel 107 of FIG. 7 in which the absorption axis direction 45 of the second polarizer 40 and the slow axis direction 63 of the optically anisotropic element 60 are orthogonal to each other. As in the case of FIGS. 8A and 8B, when the liquid crystal cell light P _L after transmission is transmitted through the color filter 22 to be approximated as a negative C plate, the polarization state is changed, south along the meridian on the Poincare sphere To do. As linearly polarized light P _A light after passing through the color filter, in order to absorb the viewing side polarizer 30 is required to a liquid crystal cell light P _L after transmission is positioned northern hemisphere on the Poincare sphere.

As in FIG. 5 moves, the phase difference of the optically anisotropic element [pi, the linearly polarized light P _'0 passing through the light source side polarizing element, the optical anisotropic element to a point P _A on the Poincaré sphere If is, the polarization state of light transmitted through the liquid crystal cell does not change from P _a. However, the light after passing through the liquid crystal cell goes south along the meridian on the Poincare sphere due to the influence of the thickness direction retardation of the color filter, so the light after passing through the color filter becomes elliptically polarized light located in the southern hemisphere. The light that is not absorbed by the viewing side polarizer 30 is viewed as light leakage.

In the E mode liquid crystal panel 107 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 optically anisotropic element is 180 °). Therefore, appropriate optical compensation becomes possible. The polarization state of the light phase difference has passed through the small optical anisotropic device than π is expressed in terms P _R on the southern hemisphere of the Poincare sphere. Since the polarization state is converted by the influence of the phase difference of the liquid crystal layer 10 and rotates clockwise on the Poincare sphere about the axis P _A -P ′ ₁ , the polarization state of the light transmitted through the liquid crystal layer 10 is Poincare. represented by the point P _L above the northern hemisphere of the sphere. As described above, when the liquid crystal cell light P _L after transmission is transmitted through the color filter 22, and 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 adequately absorbed by the viewing side polarizer 30, light leakage can be prevented.

FIG. 9B shows a state of optical compensation in the E-mode liquid crystal panel 102 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. . In the liquid crystal panel 102, if the phase difference of the optical anisotropic element 60 is larger than π (the rotation angle on the Poincare sphere by the optical anisotropic element is larger than 180 °), the optical anisotropic element is transmitted. the polarization state of the light is located at a point P _R on the southern hemisphere of the Poincare sphere. Thereafter, as in the case of FIG. 9A, the light passes through the liquid crystal layer 10 to move to the point P _L on the northern hemisphere, and passes through the color filter 22 to reach the point P _A on the equator. light P _a after passing through the filter is properly absorbed by the viewing side polarizer 30.

  As described above, in order to perform optical compensation by using the optically anisotropic element so as to cancel the influence of the birefringence of the color filter, the optical anisotropic element is required to have a thickness direction retardation in accordance with the thickness of the color filter. It is necessary to adjust the phase difference. 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 O-mode liquid crystal panel 101 (see FIG. 8A) shown in FIG. 1 and the E shown in FIG. In the mode liquid crystal panel 102 (see FIG. 9B), in order to perform appropriate optical compensation, the phase difference of the optically anisotropic element needs to be larger than π (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 O-mode liquid crystal panel 106 shown in FIG. 6 (see FIG. 8B) and FIG. In the E mode liquid crystal panel 107 (see FIG. 9A), it is necessary to make the phase difference of the optically anisotropic element smaller than π (retardation smaller than λ / 2) in order to perform appropriate optical compensation. is there.

[Optical design of optically anisotropic elements]
Below, the preferable optical characteristic of the optical anisotropic element according to the thickness direction retardation of the color filter of a liquid crystal cell is demonstrated with the examination result by optical simulation.

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

  In the simulation of the O-mode liquid crystal display device, as shown in FIG. 2, from the light source 110 side, the light source side polarizer 40, the IPS liquid crystal cell 20 having the color filter 22 on the viewing side of the liquid crystal layer 10, 50 and the viewing side polarizer 30 were sequentially laminated to form a simulation model. In the simulation of the E-mode liquid crystal display device, as shown in FIG. 4, an IPS liquid crystal cell including a color filter 22 on the viewing side of the light source side polarizer 40, the optically anisotropic element 60, and the liquid crystal layer 10 from the light source 110 side. 20 and the viewing side polarizer 30 were laminated in order as a simulation model.

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

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

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

As shown in FIGS. 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, the thickness direction retardation Ct ₆₅₀ of the red transmission region of the color filter is large. As the result, the maximum value of u ′ when the thickness direction retardation Rt ₆₅₀ of the optically anisotropic element was changed tended to decrease. Further, when Ct ₆₅₀ was in the range of 0 to 60 nm, u ′ did not exceed 0.35 regardless of the value of retardation Rt _{650 in} the thickness direction 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, any of the O mode liquid crystal panel 106 shown in FIG. 6 and the E mode liquid crystal panel 107 shown in FIG. In FIG. 5, it can be seen that the black display screen is not remarkably colored when viewed from an oblique direction.

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 optical anisotropic element are parallel, the thickness direction retardation Ct of the red transmission region of the color filter is obtained. _{As 650} increases, the maximum value of u ′ when the thickness direction retardation Rt ₆₅₀ of the optical anisotropic element is changed tends to increase. Also, in FIGS. 10A and 11B, compared to FIGS. 10B and 11A, 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, u 'Has changed significantly, sometimes exceeding 0.35.

  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 O-mode liquid crystal panel 101 shown in FIG. 1 and the E-mode liquid crystal shown in FIG. In any of the panels 102, the black display is colored red when viewed from an oblique direction due to the effect of birefringence in the red transmission region of the color filter. In other words, 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 parallel, when performing optical compensation in consideration of the birefringence of the color filter, the green light It can be seen that in addition to improving the contrast by reducing the leakage, it is necessary to optically design the optically anisotropic element so as to reduce the coloring of the black display due to the red light leakage.

<First Embodiment: Optical Design of O-Mode Liquid Crystal Panel>
(Adjustment of chromaticity)
FIG. 12 is a graph plotting conditions under which the chromaticity of black display becomes a predetermined value based on the simulation result of the O-mode liquid crystal panel 101 shown in FIG. The horizontal axis represents the thickness direction retardation Ct ₆₅₀ at a wavelength of 650 nm in the red transmission region of the color filter, and the vertical axis represents the thickness direction retardation Rt ₆₅₀ at a wavelength of 650 nm of the optical anisotropic element. In each Ct ₆₅₀ , points where the chromaticity u ′ of black display is 0.35 in the directions of azimuth angle 45 ° and polar angle 60 ° are indicated by black circles and black triangles. . When Rt ₆₅₀ is between a black circle and a black triangle, u ′ exceeds 0.35 and the black display is colored red and viewed. When Rt ₆₅₀ is above the black circle or below the black triangle, u ′ is less than 0.35, and the red coloration of 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 formulas (1) and (2).
Rt ₆₅₀ = 0.37 (Ct ₆₅₀ ) +116 (1)
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 of the optically anisotropic element 50 are expressed by the following formula (1a) or (2a). Is satisfied, u ′ becomes 0.35 or less, and black display with reduced redness can be realized.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) +116 (1a)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) +116 (2a)

A white circle and a white triangle in FIG. 12 indicate points where the chromaticity u ′ for black display is 0.314. When Rt ₆₅₀ is between the white circle and the black circle, u ′ is 0.314 to 0.35, and when Rt ₆₅₀ is above the white circle, u ′ Is smaller than 0.314. Similarly, when Rt ₆₅₀ is between the white triangle and the black triangle, u ′ is 0.314 to 0.35, and is lower than the white triangle. Has u ′ smaller than 0.314.

The boundary of u ′ = 0.314 indicated by a white circle can be approximated by a straight line parallel to the above equation (1): Rt ₆₅₀ = 0.37 (Ct ₆₅₀ ) +121. The boundary of u ′ = 0.314 indicated by the white triangle can be approximated by a straight line parallel to the above equation (2): Rt ₆₅₀ = −0.44 (Ct ₆₅₀ ) +108.

Therefore, 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 formula (1b) or (2b). In addition, u 'becomes 0.314 or less, and black display with further reduced red tint can be realized.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) +121 (1b)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) +108 (2b)

From the above results, in the O-mode liquid crystal panel shown in FIG. 1, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (1c) or (2c), a black display with reduced redness can be realized. I can say that.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) + C ₁ (1c)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) + C ₂ (2c)

As described above, when u ′ = 0.35 is used as the boundary, C ₁ in the formula (1c) is 116 nm, and C ₂ in the formula (2c) is 116 nm. In other words, when the condition is set so as to satisfy u ′ ≦ 0.35, C ₁ = 116 nm and C ₂ = 116 nm may be set as in the above formulas (1a) and (2a). From the same point of view, when setting the conditions so as to satisfy u ′ ≦ 0.314, C ₁ = 121 nm and C ₂ = 108 nm may be used as in the above formulas (1b) and (2b). . In order to further reduce the black display u ′, C ₁ may be set larger and C ₂ may be set smaller.

C ₁ in formula (1c) can be any number greater than or equal to 116. 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 formula (2c) can be any number below 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 black display when viewed from an oblique direction, Rt _{650 at} a wavelength of 650 nm of the optical anisotropic element 50 satisfies the above formula (1c) or (2c). The upper limit or lower limit is not particularly limited. However, as will be described later, in consideration of the range of Rt ₅₅₀ for reducing the black luminance and the retardation wavelength dispersion Rt ₆₅₀ / Rt ₅₅₀ of the optically anisotropic element 50, the upper limit and the lower limit of Rt ₆₅₀ are naturally determined. It is done.

(Adjustment of brightness)
As described above, by adjusting Rt _{650 of the} optically anisotropic element according to the thickness direction retardation Ct ₆₅₀ of the color filter, red light leakage can be suppressed and u ′ of black display can be reduced. On the other hand, in order to reduce the amount of light leakage (black luminance) during black display, it is preferable to perform optical design so that the light leakage of green light with high relative visibility is reduced.

FIG. 13 is a graph plotting conditions under which the black luminance becomes a predetermined value based on the simulation result of the O-mode liquid crystal panel 101 shown in FIG. The horizontal axis represents 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 represents the thickness direction retardation Rt ₅₅₀ at a wavelength of 550 nm of the optical anisotropic element. In each Ct ₅₅₀ , the black luminance in the direction of the azimuth angle of 45 ° and the polar angle of 60 ° has the same Ct ₅₅₀ and is half that of a liquid crystal display device using no optical anisotropic element. Are indicated by black circles and black triangles. When Rt ₅₅₀ is between a black circle and a black triangle, the black luminance when viewed from an oblique direction is less than half compared to the case where no optically anisotropic element is provided. Reduced.

As can be understood from FIG. 13, the boundary of the region where the black luminance is ½ compared to the case where no optically anisotropic element is used 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 formulas (3) and (4).
Rt ₅₅₀ = 0.97 (Ct ₅₅₀ ) +73 (3)
Rt ₅₅₀ = 0.49 (Ct ₅₅₀ ) +205 (4)

Accordingly, when the thickness direction retardation Ct _{550 at the} wavelength of 550 nm in the green transmission region 22G of the color filter 22 and the thickness direction retardation Rt _{550 at} the wavelength of 550 nm of the optically anisotropic element 50 satisfy the following expression (3a). The black luminance in the oblique direction is 以下 or less as compared with the case where no optically anisotropic element is used.
0.97 (Ct ₅₅₀ ) + 73 ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) +205 (3a)

A white circle and a white triangle in FIG. 13 indicate that the black luminance is 1/5 of the black luminance of a liquid crystal display device that does not use an optically anisotropic element. When Rt ₅₅₀ is between the white circle and the white triangle, the black luminance is reduced to 1/5 or less as compared with the case where no optically anisotropic element is provided.

The boundary indicated by the white circle can be approximated by a straight line parallel to the above equation (3): Rt ₅₅₀ = 0.97 (Ct ₅₅₀ ) +98. The boundary indicated by white triangles can be approximated by a straight line parallel to the above equation (4): Rt ₅₅₀ = 0.49 (Ct ₅₅₀ ) +180. Therefore, when the retardation Ct _{550 in} the thickness direction at a wavelength of 550 nm in the green transmission region of the color filter and the retardation Rt ₅₅₀ in the thickness direction at a wavelength of 550 nm of the optically anisotropic element satisfy the following expression (3b), Compared with the case where the isotropic element is not used, the black luminance is reduced to 1/5 or less, and a display with high contrast can be realized.
0.97 (Ct ₅₅₀ ) + 98 ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) +180 (3b)

From the above results, in the O-mode liquid crystal panel shown in FIG. 1, when Ct ₅₅₀ and Rt ₅₅₀ satisfy the following expression (3c), the influence of the birefringence of the color filter is canceled, and the black black in the oblique direction It can be said that display with reduced luminance can be realized.
0.97 (Ct ₅₅₀ ) + C ₃ ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) + C ₄ (3c)

As described above, when the black luminance is ½ or less of the black luminance of the liquid crystal display device that does not use the optically anisotropic element, C ₃ = 73 nm, C ₄ as in the above equation (3a). = 205 nm may be set. From the same viewpoint, when the black luminance is set to 1/5 or less of the black luminance of the liquid crystal display device that does not use the optically anisotropic element, C ₃ = 98, C ₄ as in the above equation (3b). = 180 nm may be set. In order to further reduce the black luminance in the oblique direction, C ₃ may be set large and C ₄ may be set small. C ₃ in formula (3c) can be any number greater than or equal to 73. 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 formula (3c) can be any number below 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, the larger the optimum value of Rt ₅₅₀ of the optical anisotropic element for reducing the black luminance when viewed from the oblique direction. This can also be understood from the principle of optical compensation shown in FIG. 8A. The thickness-direction retardation Ct ₅₅₀ of the color filter is large, in Figure 8A, which corresponds to the distance P _'0 and Pc is large (high latitude of P _C). Higher latitude of P _C is out of the large equator, the light after passing through the optical anisotropic device 50 to move on the equator of the Poincare sphere, it is necessary to increase the phase difference of the optically anisotropic element . Therefore, as shown in FIG. 13, as Ct ₅₅₀ is larger, Rt ₅₅₀ needs to be increased in order to reduce the black luminance.

(Both black luminance reduction and chromaticity compatible)
In order to reduce the black luminance when viewed from an oblique direction, Rt _{550 of the} optical anisotropic element is set so as to satisfy the above formula (3c) according to the thickness direction retardation Ct ₅₅₀ of the color filter. And Rt _{650 of the} optically anisotropic element may be set so as to satisfy the above formula (1c) or (2c). However, Rt ₅₅₀ and Rt ₆₅₀ cannot be set individually, and Rt ₆₅₀ / Rt ₅₅₀ is a constant value according to the wavelength dispersion of retardation of the optical 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} optical anisotropic element is 130 nm, the black luminance when viewed from an oblique direction is small, and the high contrast Display is feasible. As set in the above simulation, when the optical anisotropic element has a wavelength dispersion of Rt ₆₅₀ / Rt ₅₅₀ = 0.95, if Rt ₅₅₀ = 130 nm, then Rt ₆₅₀ = 124 nm.

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

As can be understood from the above example, in the O-mode liquid crystal panel shown in FIG. 1, the chromaticity u ′ of black display increases even when the optical anisotropic element is optically designed to reduce the black luminance. The black display may be colored red. On the other hand, considering the thickness direction retardations Ct ₅₅₀ and Ct _{650 of} the color filter and the wavelength dispersion Rt ₆₅₀ / Rt ₅₅₀ of the retardation of the optical anisotropic element, the above formula (3c) is satisfied (however, , C ₃ is 73 nm or more, C ₄ is 205 nm or less), and satisfies the above formula (1c) or (2c) (where C ₁ is 116 nm or more and C ₂ is 116 nm or less) The thickness direction retardation of the optically anisotropic element may be set.

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 a general chromatic dispersion range, when Ct ₆₅₀ is 10 nm or more, Rt ₅₅₀ satisfies the formula (3c) and Rt ₆₅₀ rarely satisfies the formula (2c). Therefore, it is preferable to set the retardation of the optical anisotropic element so that Rt ₅₅₀ satisfies the above formula (3c) and Rt ₆₅₀ satisfies the above formula (1c).

The front retardation Re ₅₅₀ and Re ₆₅₀ of the optically anisotropic element 50 may be set so that Rt ₅₅₀ and Rt ₆₅₀ are in the above range. As described above, in the optically anisotropic element 50, the ratio Nz = Rt / Re of the retardation in the thickness direction Rt to the front retardation Re is 0.2 to 0.8. Front retardations Re ₅₅₀ and Re ₆₅₀ are determined according to the thickness direction retardations Rt ₅₅₀ and Rt _{650 of} the isotropic element and the Nz coefficient.

Specifically, the front retardation Re ₆₅₀ of the optically anisotropic element 50 at a wavelength of 650 nm 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 the _{C 1,} in particular _{C 11} is more than 232 nm. 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 the _{C 2,} in particular _{C 12} is less than 232 nm. 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 retardation of the optically anisotropic element, Re ₆₅₀ of the optically anisotropic element 50 preferably 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, Re ₅₅₀ preferably satisfies the following formula (3d).
1.94 (Ct ₅₅₀ ) + C ₁₃ ≦ Re ₅₅₀ ≦ 0.98 (Ct ₅₅₀ ) + C ₁₄ (3d)

C ₁₃ is twice the _{C 3,} in particular _{C 13} is more than 146 nm. 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 the _{C 4,} in particular _{C 14} is 410nm 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>
FIG. 14 is a graph plotting conditions under which the chromaticity of black display becomes a predetermined value based on the simulation result of the E-mode liquid crystal panel 102 shown in FIG. As in FIG. 12, the black display chromaticity u ′ in the direction of azimuth angle 45 ° and polar angle 60 ° is 0.35, indicated by black circles and black triangles. The point at which the chromaticity u ′ of the image becomes 0.314 is indicated by a white circle and a white triangle.

As in the case of FIG. 12, the boundary of u ′ = 0.35 in FIG. 14 can be approximated by straight lines 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 _{650 at} a wavelength of 650 nm of the optically anisotropic element 50 are represented by the following formula (6a). ) Or (7a), u ′ becomes 0.35 or less, and black display with reduced redness can be realized.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) +116 (6a)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) +120 (7a)

  Expression (6) is the same as expression (1) for the O-mode liquid crystal panel 101. Expression (7) is expressed by a straight line parallel to Expression (2) regarding the O-mode liquid crystal panel 101. In FIG. 14, the straight line of Formula (2) is shown by the dotted line for reference.

The boundary of u ′ = 0.314 indicated by a white circle can be approximated by a straight line parallel to the above equation (6): Rt ₆₅₀ = 0.37 (Ct ₆₅₀ ) +121. The boundary of u ′ = 0.314 indicated by the white triangle can be approximated by a straight line parallel to the above equation (2): Rt ₆₅₀ = −0.44 (Ct ₆₅₀ ) +108.

Accordingly, 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 expression (6b) or (7b). In addition, u 'becomes 0.314 or less, and black display with further reduced red tint 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 E mode liquid crystal panel 102 shown in FIG. 3, when Ct ₆₅₀ and Rt ₆₅₀ satisfy the following formula (6c) or (7c), black display with reduced redness can be realized. It can be said.
Rt ₆₅₀ ≧ 0.37 (Ct ₆₅₀ ) + C ₆ (6c)
Rt ₆₅₀ ≦ −0.44 (Ct ₆₅₀ ) + C ₇ (7c)

When the conditions are set so as to satisfy u ′ ≦ 0.35, C ₆ = 116 nm and C ₇ = 120 nm as in the above formulas (6a) and (7a), and u ′ ≦ 0 When the condition is set so as to satisfy .314, C ₆ = 121 nm and C ₇ = 108 nm may be set as in the above formulas (6b) and (7b). In order to further reduce the black display u ′, C ₆ should be set large and C ₇ should be set small.

C ₆ in formula (6c) can be any number greater than or equal to 116. C ₆ may be a numerical value equivalent to C ₁ described above, 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. Good. Similarly, C ₇ in formula (7c) can be any number up to 120. C ₇ It may be a numerical value equivalent to 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. Considering the wavelength dispersion of 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 black display when viewed from an oblique direction, Rt _{650 at} a wavelength of 650 nm of the optical anisotropic element 60 satisfies the above formula (6c) or (7c). The upper limit or lower limit is not particularly limited. However, as described above with respect to the first embodiment, in consideration of the range of Rt ₅₅₀ for reducing the black luminance and the wavelength dispersion Rt ₆₅₀ / Rt ₅₅₀ of the retardation of the optical anisotropic element 60, the upper limit of Rt ₆₅₀ and The lower limit is determined by itself.

  FIG. 15 is a graph plotting the conditions under which the black luminance becomes a predetermined value based on the simulation result of the E-mode liquid crystal panel 102 shown in FIG. As in FIG. 13, the black luminance in the direction of azimuth angle 45 ° and polar angle 60 ° is half that of a liquid crystal display device that does not use an optically anisotropic element. A point where the black luminance is 1/5 of a liquid crystal display device using no optically anisotropic element is indicated by a white circle and a white triangle.

As in the case of FIG. 13, also in FIG. 15, the boundary of the region where the black luminance becomes ½ can be approximated by a straight line as compared with the case where the optically anisotropic element is not used. It is represented by the following formula (8) and formula (9).
Rt ₅₅₀ = 0.69 (Ct ₅₅₀ ) +70 (8)
Rt ₅₅₀ = 1.35 (Ct ₅₅₀ ) +200 (9)

Therefore, in the liquid crystal panel 102, the thickness direction retardation Ct ₅₅₀ at 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 optically anisotropic element 50 are represented by the following equation (8a). When the condition (1) is satisfied, the black luminance is 以下 or less as compared with the case where the optically anisotropic element is not used.
0.69 (Ct ₅₅₀ ) + 70 ≦ Rt ₅₅₀ ≦ 1.35 (Ct ₅₅₀ ) +200 (8a)

The point indicated by the white triangle can be approximated by a straight line parallel to the above equation (8): Rt ₅₅₀ = 0.69 (Ct ₅₅₀ ) +98. The point indicated by the white circle can be approximated by a straight line Rt ₅₅₀ = 1.35 (Ct ₅₅₀ ) +180 parallel to the above-described equation (9). Therefore, when Ct ₅₅₀ and Rt ₅₅₀ satisfy the following formula (8b), the black luminance is 1/5 or less compared to the case where no optically anisotropic element is used.
0.69 (Ct ₅₅₀ ) + 98 ≦ Rt ₅₅₀ ≦ 1.35 (Ct ₅₅₀ ) +171 (8b)

From the above results, in the E-mode liquid crystal panel 102 shown in FIG. 3, when Ct ₅₅₀ and Rt ₅₅₀ satisfy the following formula (8c), the influence of the birefringence of the color filter is canceled and the oblique direction is observed. It can be said that display with reduced black luminance when visually recognized can be realized.
0.69 (Ct ₅₅₀ ) + C ₈ ≦ Rt ₅₅₀ ≦ 1.35 (Ct ₅₅₀ ) + C ₉ (8c)

When the black luminance in the oblique direction is ½ or less of the case where no optically anisotropic element is used, C ₈ = 70 nm and C ₉ = 200 nm may be used as in the above equation (8a). From the same viewpoint, when the black luminance in the oblique direction is set to 1/5 or less of the case where the optically anisotropic element is not used, C ₃ = 98, C ₄ = 171 nm as in the above formula (8b). And it is sufficient. In order to further reduce the black luminance in the oblique direction, C ₈ should be set large and C ₉ should be set small.

C ₈ in the 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 formula (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, as the thickness direction retardation Ct ₅₅₀ of the color filter is larger, the optimum value of Rt ₅₅₀ of the optical anisotropic element for reducing the black luminance when viewed from an oblique direction is increased. This can also be understood from the principle of optical compensation shown in FIG. 9B.

In the E mode liquid crystal panel 102 shown in FIG. 3, in order to reduce the black luminance when viewed from an oblique direction, the above formula (8c) is satisfied according to the thickness direction retardation Ct ₅₅₀ of the color filter. Is set to Rt ₅₅₀ of the optically anisotropic element, and Rt _{650 of the} optically anisotropic element is set so as to satisfy the above formula (6c) or (7c).

Similarly to the description of the example of the O-mode liquid crystal panel, when considering the wavelength dispersion Rt ₆₅₀ / Rt ₅₅₀ of the optically anisotropic element, when Ct ₆₅₀ is 10 nm or more, Rt ₅₅₀ satisfies the formula (8c), Rt ₆₅₀ rarely satisfies the formula (7c). Therefore, it is preferable to set the retardation of the optical anisotropic element 60 so that Rt ₅₅₀ satisfies the above formula (8c) and Rt ₆₅₀ satisfies the above formula (6c).

The front retardations Re ₅₅₀ and Re ₆₅₀ of the optically anisotropic element 60 may be set so that Rt ₅₅₀ and Rt ₆₅₀ are in 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, Re ₆₅₀ preferably satisfies the following formula (6d) or (7d).
Re ₆₅₀ ≧ 0.74 (Ct ₆₅₀ ) + C ₁₆ (6d)
Re ₆₅₀ ≦ −0.88 (Ct ₆₅₀ ) + C ₁₇ (7d)

C ₁₆ is twice the _{C 6,} in particular _{C 16} is more than 232 nm. 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 the _{C 7,} in particular _{C 17} is less than 240 nm. 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 retardation of the optically anisotropic element, Re ₆₅₀ of the optically anisotropic element 60 preferably 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, Re ₅₅₀ preferably satisfies the following formula (8d).
1.38 (Ct ₅₅₀ ) + C ₁₈ ≦ Re ₅₅₀ ≦ 2.70 (Ct ₅₅₀ ) + C ₁₉ (8d)

C ₁₈ is twice the _{C 8,} in particular _{C 18} is 140nm 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 the _{C 9,} in particular _{C 19} is 400nm 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 optical members]
As described above, in the liquid crystal panel 101 of the first embodiment, the optical anisotropic element 50 disposed on the viewing side of the liquid crystal cell 20 corresponding to the thickness direction retardations Ct ₅₅₀ and Ct ₆₅₀ of the color filter 22 is predetermined. The optical design is performed so as to have the following optical characteristics. The liquid crystal panel 102 according to 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 has an optical isotropy as a polarizer protective film between the viewing side polarizer 30 and the optically anisotropic element 50 or between the light source side polarizer 40 and the liquid crystal cell 20. A film may be provided. The liquid crystal panel 102 of the second embodiment is optically isotropic as a polarizer protective film between the viewing side polarizer 30 and the liquid crystal cell 20 or between the light source side polarizer 40 and the optical anisotropic element 60. A film may be provided. By providing a polarizer protective film on the surface of the polarizer, the durability of the polarizer can be enhanced.

  The optically isotropic film used as a polarizer protective film does not substantially change the polarization state of light transmitted in any of the normal direction and the oblique direction. Specifically, the optically isotropic film preferably has a front retardation Re of 10 nm or less, and preferably has a thickness direction retardation Rt of 20 nm or less. The front retardation of the optical isotropic film is more preferably 5 nm or less. The thickness direction retardation of the optical isotropic film is more preferably 10 nm or less, and further preferably 5 nm or less.

  The liquid crystal panel may include an optical layer other than the above and other members. For example, a polarizer protective film is preferably 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 surface of the viewing side polarizer 30 on the liquid crystal cell 20 side and the light source side polarizer 40 on the liquid crystal cell 20 side is required to be optically isotropic as described above.

  The liquid crystal panel 101 according to the first embodiment preferably does not include an optically anisotropic element other than the optically anisotropic element 50 between the viewing side polarizer and the liquid crystal cell 20. Preferably, no optically anisotropic element is included between the cells 20. The liquid crystal panel 102 of the second embodiment preferably does not include an optically anisotropic element other than the optically anisotropic element 60 between the light source side polarizer and the liquid crystal cell 20. It is preferable that no optically anisotropic element is included between the cells 20.

  A liquid crystal panel is formed by laminating a liquid crystal cell and each of the above optical members. In the formation process, each member may be stacked separately on the liquid crystal cell, or a member in which several members are stacked in advance may be used. The order of stacking 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. Between the polarizer and the optically anisotropic element, an optical isotropic film may be provided as a polarizer protective film.

  For laminating the members, an adhesive or a pressure-sensitive adhesive is preferably used. Adhesives and adhesives are based on acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorine polymers, rubber polymers, etc. A polymer can be appropriately selected and used.

[Liquid Crystal Display]
By disposing the light source 110 on the second principal surface side (the polarizer 40 side) of the liquid crystal panel, a liquid crystal display device is formed. A brightness enhancement film (not shown) may be provided between the liquid crystal panel and the light source. The brightness enhancement film may be provided integrally with the light source side polarizer. For example, a film obtained by bonding a brightness enhancement film to the outer surface (surface on the light source side) of the second polarizer via an adhesive layer can be used. Moreover, the polarizer protective film may be provided between the polarizer and the brightness enhancement film.

Reference Signs List 20 liquid crystal cell 21 color filter substrate 22 TFT substrate 10 liquid crystal layer 11 initial alignment direction 30, 40 polarizer 35, 45 absorption axis (direction)
50,60 Optically anisotropic element (retardation 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 containing liquid crystal molecules that are homogeneously aligned in an electric field; and a color filter disposed on the 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 the second main surface of the liquid crystal cell; and a liquid crystal panel comprising 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 to each other,
The slow axis direction of the optically anisotropic element and the absorption axis direction of the second polarizer are parallel,
The optically anisotropic element has a ratio Rt ₆₅₀ / Re ₆₅₀ of front retardation Re ₆₅₀ and thickness direction retardation Rt _{650 at} a wavelength of 650 nm of 0.2 to 0.8,
The green transmission region of the color filter has a thickness direction retardation Ct _{550 at} a wavelength of 550 nm of greater than 0 and less than or equal to 50 nm.
The red transmission region of the color filter has a thickness direction retardation Ct _{650 at} a wavelength of 650 nm of greater than 0 and less than or equal to 50 nm.
The alignment direction of the liquid crystal molecules in the non-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) of the optically anisotropic element at a wavelength of 550 nm and the Ct ₅₅₀ (nm) satisfy the following formula (3a):
0.97 (Ct ₅₅₀ ) + 73 ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) +205 (3a)
The 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 liquid crystal panel according to claim 1, wherein the Rt ₅₅₀ and the Ct ₅₅₀ satisfy the following formula (3b).
0.97 (Ct ₅₅₀ ) + 98 ≦ Rt ₅₅₀ ≦ 0.49 (Ct ₅₅₀ ) +180 (3b) The liquid crystal panel according to claim 1 or 2, wherein the Rt ₆₅₀ and the 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 containing liquid crystal molecules that are homogeneously aligned in an electric field; and a color filter disposed on the 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 the second main surface of the liquid crystal cell; and a liquid crystal panel comprising 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 to each other,
The slow axis direction of the optically anisotropic element and the absorption axis direction of the second polarizer are parallel,
The optically anisotropic element has a ratio Rt ₆₅₀ / Re ₆₅₀ of front retardation Re ₆₅₀ and thickness direction retardation Rt _{650 at} a wavelength of 650 nm of 0.2 to 0.8,
The green transmission region of the color filter has a thickness direction retardation Ct _{550 at} a wavelength of 550 nm of 50 nm or less,
The red transmission region of the color filter has a thickness direction retardation Ct _{650 at} a wavelength of 650 nm of greater than 0 and less than or equal to 50 nm.
The alignment direction of the liquid crystal molecules in the non-electric field state of the liquid crystal cell is orthogonal to the absorption axis direction of the second polarizer,
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 formula (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 liquid crystal panel according to claim 4, wherein the Rt ₅₅₀ and the Ct ₅₅₀ satisfy the following formula (8b).
0.69 (Ct ₅₅₀ ) + 98 ≦ Rt ₅₅₀ ≦ 1.35 (Ct ₅₅₀ ) +171 (8b) The liquid crystal panel according to claim 4 or 5, wherein the Rt ₆₅₀ and the capacitor 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 claim 1; and a light source disposed on a second main surface side of the liquid crystal panel.