JPH09197445A - Color liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress changes in colors when the angle of visual field is increased by forming a liquid crystal layer in such a manner that the thickness of the layer in a blue pixel is smaller than the thickness of the layer in a green pixel and red pixel. SOLUTION: A color filter 13 is disposed on the surface of a transparent substrate 10A in such a manner that areas B, G, R which transmit blue, green and red light, respectively, are arranged in stripes in the direction perpendicular to the figure. Thickness of the color filter 13 in these areas is decreased in the order of areas B, G, R. The transparent substrates 10A and 10B are disposed parallel to each other with the alignment layers facing, and a liquid crystal layer 16 is formed between these substrates. The thickness of the liquid crystal layer 16 is the smallest in the area B and it increases along the area G and the region R. Optical phase difference plates 11A and 11B are disposed on the outside of the transparent substrates 10A and 10B, respectively, and further, polarizing plates 12A and 12B are disposed outside to form a cross Nicol prism. Thus, by increasing the thickness of the liquid crystal layer 16 in the order of the areas B, G, R, changes in colors when the angle of visual field is changed can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal panel, and more particularly to a color liquid crystal panel provided with an optical compensation plate.

[0002]

2. Description of the Related Art When a line of sight of a liquid crystal panel is tilted from a normal line of a substrate, black may become whitish or gray may become black depending on the tilting direction. In a normal twisted nematic (TN) type liquid crystal panel, when it is tilted in three directions, black becomes whitish, and when it is tilted in the remaining one direction, gray is black.

In order to improve the viewing angle characteristics of a liquid crystal panel,
A technique for providing an optical compensation plate in parallel with a substrate has been developed. In particular, a method (optical phase difference compensation method) in which an optically negative uniaxial optical compensation plate having a main optical axis in the direction of the normal to the substrate surface is inserted between the transparent substrate and the polarizing plate is known. Proposed.

By using the optical phase difference compensation method, it is possible to improve the viewing angle characteristics in the direction in which black becomes whitish. However, the viewing angle characteristic deteriorates in the direction in which the gray color becomes darker. For example, in the case of a display screen for a personal computer, since the screen is rarely viewed from below, it is sufficient in practical use to improve the viewing angle characteristics in the three directions.

[0005]

When the optical phase difference compensation method is used, the viewing angle characteristics in three directions can be improved, but the angle (viewing angle) formed between the viewing line and the substrate normal direction is increased. Then, a phenomenon occurs that the achromatic color becomes colored.

An object of the present invention is to provide a color liquid crystal panel in which a color change does not easily occur even if the viewing angle is increased.

[0007]

According to one aspect of the present invention, a pair of transparent substrates arranged to face each other, a liquid crystal layer sandwiched between the transparent substrates, and the liquid crystal layer side of the pair of transparent substrates. A transparent electrode formed on the surface of each of the pixels to define a pixel, and arranged for each of the pixels, and imparts a color of blue, green, or red to the light passing through each of the pixels. On the liquid crystal layer side surface of the pair of transparent substrates, and a color imparting unit that defines a blue pixel that transmits, a green pixel that transmits mainly green light, and a red pixel that transmits mainly red light, respectively. An alignment film formed so as to cover the transparent electrode and making the liquid crystal layer in a twist alignment state, and a thickness of the liquid crystal layer in the blue pixel is larger than a thickness of the liquid crystal layer in the green pixel and the red pixel. Each pixel to be thin Gap length providing means for defining the thickness of the liquid crystal layer in the liquid crystal layer, and a main optical axis provided on the surface of the transparent substrate and having a substantially normal direction in the substrate surface, and the refractive index in the normal direction is the substrate Provided is a color liquid crystal panel having an optically negative uniaxial optical compensation plate having a refractive index smaller than the in-plane direction refractive index.

By making the thickness of the liquid crystal layer of the blue pixel smaller than the thickness of the liquid crystal layer of the green pixel and the red pixel, it is possible to suppress color change when the viewing angle is increased. According to another aspect of the present invention, there is provided a color liquid crystal panel, wherein a product Δnd of a thickness d of the liquid crystal layer in the blue pixel and a refractive index anisotropy Δn of a liquid crystal material in the liquid crystal layer is 330 to 420 nm. To be done.

Δnd of the liquid crystal layer of the blue pixel is set to 330 to 42
By setting the thickness to 0 nm, it is possible to further suppress the color change when the viewing angle is increased. According to another aspect of the present invention, there is provided a color liquid crystal panel in which the thickness of the liquid crystal layer in the red pixel is thicker than the thickness of the liquid crystal layer in the green pixel.

By making the thicknesses of the liquid crystal layers of the blue, green and red pixels different from each other, it is possible to further suppress the color change when the viewing angle is increased. According to another aspect of the present invention, the color imparting unit is provided on a liquid crystal layer side surface of one transparent substrate of the pair of transparent substrates, and an area corresponding to the blue pixel, the green pixel and the red pixel. In, there is provided a color liquid crystal panel having a thickness peculiar to the color of the corresponding pixel and also serving as the gap length providing means.

When the thickness of the color providing means corresponding to each pixel of blue, green and red is set to a thickness unique to the color of each pixel, the thickness of the liquid crystal layer of each pixel also becomes the thickness unique to that color. Become.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION When the viewing angle characteristics of a color liquid crystal panel using the conventional optical phase difference compensation method were investigated, it was found that white becomes yellow and black becomes blue as the viewing angle is increased. When the wavelength characteristics of the transmittance in the oblique direction of this liquid crystal panel were measured, the transmittance for light of the blue wavelength (near 450 nm) when displaying white was smaller than the transmittance for red and green light. I found out.

When the optical phase difference compensation method is used, a normal TN is used.
It is considered that the variation of the transmittance in the oblique direction with respect to the wavelength is larger than that of the type liquid crystal panel. In order to suppress coloring when the viewing angle is increased, it is considered effective to reduce the variation of the transmittance in the oblique direction with respect to the wavelength.

FIG. 1 is a sectional view of a color liquid crystal panel according to an embodiment of the present invention. The color filter 13 is arranged on the surface of the transparent substrate 10A. Symbols B, G, in the figure
R represents regions that transmit blue light, green light, and red light, respectively. Each of the areas B, G, and R has a striped shape extending in the direction perpendicular to the paper surface. Also, color filter 1
The thickness of each region of 3 becomes thinner in the order of regions B, G, and R.

Stripe-shaped transparent electrodes 14A corresponding to the respective areas B, G and R are formed on the surface of the color filter 13. Further, an alignment film 15A is formed so as to cover the surfaces of the color filter 13 and the transparent electrode 14A.

A plurality of stripe-shaped transparent electrodes 14B extending in the lateral direction of the figure are formed on the surface of the transparent substrate 10B. An alignment film 15B is formed so as to cover the surfaces of the transparent substrate 10B and the transparent electrode 14B.

The transparent substrates 10A and 10B are arranged in parallel so that the surfaces of the alignment films face each other, and the liquid crystal layer 16 is interposed therebetween.
Is sandwiched. The intersection of one transparent electrode 14A and one transparent electrode 14B constitutes one pixel. The thickness of the liquid crystal layer 16 is the thinnest in the region B, and increases in the order of the region G and the region R.

Optical retardation plates 11A and 11B are arranged on the outer surfaces of the transparent substrates 10A and 10B, respectively. Further, polarizing plates 12A and 12B are arranged on the outer side thereof so as to form a crossed Nicols.

Next, the alignment directions of the alignment films 15A and 15B of the liquid crystal panel of FIG. 1 will be described with reference to FIG. FIG.
As shown in (A), the alignment film 50 causes the liquid crystal molecules 51 to have their major axes inclined (pretilt).
When constrained, the direction of the vector 52 obtained by vertically projecting the vector from the end on the alignment film side in the long axis direction of the liquid crystal molecule 51 toward the end on the rising side to the alignment film 50 is the in-plane alignment direction of the substrate. Call.

FIG. 2B is a plan view of the liquid crystal panel shown in FIG. 1 viewed from the transparent substrate 10B side. As shown in FIG. 2B, the in-substrate orientation direction 30A of the alignment film 15A and the in-substrate orientation direction 30B of the alignment film 15B are orthogonal to each other. The liquid crystal molecules in the liquid crystal layer 16 are 10
As the position approaches the B side, the tip of the arrow in the substrate in-plane orientation direction 30A is twisted in a direction (clockwise in the drawing) overlapping the rear end of the arrow in the substrate in-plane orientation direction 30B.

The direction of the vector sum of the vector in the opposite direction of the in-plane orientation direction 30A of the substrate and the in-plane orientation direction of the substrate 30B is defined as the upper side, and the opposite side is defined as the lower side.
The direction of the vector sum of 0A and 30B is defined as the right side, and the opposite side is defined as the left side.

FIGS. 3A and 3B show calculation results of CIE chromaticity of the color liquid crystal panels shown in FIGS. 1 and 2 in the white display state and the black display state, respectively. The right side vertex of the closed curve in the figure corresponds to red, the lower side vertex corresponds to blue, and the tip of the region protruding toward the upper left side corresponds to green.

The liquid crystal material used in the simulation is
ZLI-4792 (birefringence 0.09)
4), the retardation values of the optical compensating plates 11A and 11B in the direction of the visual angle of 30 ° are both 26 nm, the regions B and G,
The thickness of the liquid crystal layer 16 in R is 4.0 μm,
It is 5.0 μm and 5.5 μm. The applied voltage in the white display state is 1.6V, and the applied voltage in the black display state is 5.0V.

Points P ₀ and P _{80 in} FIG. 3A indicate CIE chromaticity at a viewing angle of 0 ° and 80 °, respectively, when the line of sight is tilted upward. Note that points Q ₀ and Q ₈₀ in the figure respectively represent CIE chromaticity at a viewing angle of 0 ° and 80 ° when the thickness of the liquid crystal layer 16 is constant at 5 μm. The curves connecting the points P ₀ and P ₈₀ and the points Q ₀ and Q ₈₀ respectively show the loci of CIE chromaticity when the viewing angle is changed from 0 ° to 80 °.

In the case of the liquid crystal panel shown in FIG. 1, the point P ₀ and the point P ₈₀ substantially coincide with each other, and the CIE chromaticity hardly changes even when the viewing angle is changed. On the other hand, when the thickness of the liquid crystal layer 16 is constant, when the viewing angle is increased from 0 °, the CIE chromaticity changes from the point Q ₀ to the point Q _{80 as} shown by the curve in the figure.

Points R ₀ and R ₈₀ in FIG. 3B are 0 ° viewing angles of the liquid crystal panel of FIG. 1 when the line of sight is tilted upward.
And CIE chromaticity at 80 ° and points S ₀ and S ₈₀
Shows CIE chromaticity at a viewing angle of 0 ° and 80 ° when the thickness of the liquid crystal layer is fixed at 5 μm. In the black display state, as in the white display state, the change in CIE chromaticity of the liquid crystal panel of FIG. 1 is smaller than that when the thickness of the liquid crystal layer is uniform.

As described above, by increasing the thickness of the liquid crystal layer in each region in the order of the regions B, G, and R, it is possible to suppress the color change when the viewing angle is changed. Table 1
Indicates the degree of color change due to an increase in viewing angle when the thickness of the liquid crystal layer in the regions B, G and R is variously changed.
The thickness of the liquid crystal layer is shown in unit of μm. The degree of color change ΔC is

[0028]

## EQU1 ## ΔC = ((x _i −x ₀ ) ² + (y _i −y ₀ ) ² ) ^1/2 is defined. Where x _i and y _i are C at each viewing angle
Color coordinates of IE chromaticity, x ₀ and y ₀ are C when the viewing angle is 0 °
Indicates the color coordinates of the IE chromaticity. That is, if the color change is large, ΔC becomes large. The numerical values used for the calculation are the same as those used in FIG.

[0029]

[Table 1]

When the thickness of the liquid crystal layer in the regions R and G is both 5.0 μm, the thickness of the region B is from 5.0 μm to 4.
When the thickness is as thin as 5 μm and 4.0 μm, color change is suppressed in most of the line-of-sight directions. When the thickness of the region B is 3.5 μm, the color change is suppressed in the horizontal direction of white display, but the color change is slightly large in the upper direction and black display.

When the thicknesses of the liquid crystal layers in the regions R, G and B are 5.5 μm, 5.0 μm and 4.0 μm, respectively,
The thickness of the liquid crystal layer in each of the regions R, G, and B is 5.0.
The color change in the upward direction in white display is slightly larger than that in the case of μm, 5.0 μm, and 4.0 μm, but the color change in the horizontal direction is suppressed.

As can be seen from Table 1, the thickness of the liquid crystal layer in the region B is preferably about 4 μm. Since the refractive index anisotropy Δn of the liquid crystal material used for the calculation is 0.094, more generally, the product Δnd of the refractive index anisotropy Δn of the liquid crystal layer in the region B and the thickness d of the liquid crystal layer is 376 nm
It is preferable that A preferable range of Δnd of the liquid crystal layer in the region B is 330 to 420 nm.

In the above embodiment, the retardation value in the direction of 30 ° from the normal line of the optical retardation plate is 28 nm, but other retardation values may be used. A preferred range of the retardation value in the direction of 30 ° from the normal line of the optical retardation plate will be 18 to 35 nm. Further, in FIG. 1, the case where the optical retardation plates 11A and 11B are arranged outside both of the transparent substrates 10A and 10B has been described, but they may be arranged only on one of them.

Although a simple matrix type liquid crystal panel is shown in FIG. 1, the above embodiment can be applied to an active matrix type liquid crystal panel using thin film transistors.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0036]

As described above, according to the present invention,
It is possible to suppress color change when the viewing angle is changed in the color liquid crystal panel.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal panel according to an exemplary embodiment of the present invention.

FIG. 2 is a perspective view of an alignment film and liquid crystal molecules for explaining an in-plane alignment direction of a substrate, and a diagram showing a vertical and horizontal relationship between the in-plane alignment direction of a liquid crystal panel.

FIG. 3 is a graph showing changes in CIE chromaticity when the viewing angle is changed in the liquid crystal panel of FIG. 1 and a conventional liquid crystal panel.

[Explanation of symbols]

 10A, 10B Transparent substrate 11A, 11B Optical retardation plate 12A, 12B Polarizing plate 13 Color filter 14A, 14B Transparent electrode 15A, 15B Alignment film 16 Liquid crystal layer 30A, 30B, 52 Substrate in-plane alignment direction 50 Alignment film 51 Liquid crystal molecule

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Tanuma 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited within Fujitsu Limited

Claims (4)

[Claims] 1. A pair of transparent substrates arranged to face each other, a liquid crystal layer sandwiched between the transparent substrates, and a plurality of pixels each formed on the surface of the pair of transparent substrates on the liquid crystal layer side. A transparent electrode that defines the pixel is arranged for each pixel, and the light transmitted through each pixel is blue.
A color imparting unit that imparts a color of green or red and that defines a blue pixel that transmits blue light, a green pixel that transmits green light, and a red pixel that transmits red light; and a pair of the transparent substrates. An alignment film is formed on the surface of the liquid crystal layer side so as to cover the transparent electrodes, and makes the liquid crystal layer in a twist alignment state, and the thickness of the liquid crystal layer in the blue pixel is the green pixel and the green pixel. Gap length providing means for defining the thickness of the liquid crystal layer in each pixel so as to be thinner than the thickness of the liquid crystal layer in the red pixel, and provided on the surface of the transparent substrate and in a direction substantially normal to the substrate surface. A liquid crystal panel having an optically negative uniaxial optical compensation plate having a main optical axis of, and having a refractive index in the normal direction smaller than the refractive index in the in-plane direction of the substrate. 2. The color liquid crystal panel according to claim 1, wherein the product Δnd of the thickness d of the liquid crystal layer in the blue pixel and the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer is 330 to 420 nm. . 3. The color liquid crystal panel according to claim 1, wherein a thickness of the liquid crystal layer in the red pixel is larger than a thickness of the liquid crystal layer in the green pixel. 4. The color imparting means is provided on the liquid crystal layer side surface of one of the pair of transparent substrates,
The color according to any one of claims 1 to 3, which has a thickness unique to a color of a corresponding pixel in a region corresponding to the blue pixel, the green pixel, and the red pixel, and also serves as the gap length providing unit. LCD panel.