JP2003215559A - Thin film transistor liquid crystal display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor liquid crystal display panel in which color variation in gradation display is suppressed and which realizes widening of a viewing angle and heightening of contrast. <P>SOLUTION: A nematic liquid crystal layer 12 with twist deformation is interposed between a thin film transistor substrate 4 and a counter electrode substrate 10. Crossed Nicol polarizing plates 19a, 19b are arranged corresponding to the rubbing directions of both substrates. Negative uniaxial liquid crystal optical films are disposed between the thin film transistor substrate 4 and the polarizing plate 19a on the substrate and between the counter electrode substrate 10 and the polarizing plate 19b on the substrate. At the same time, the liquid crystal film has a hybrid orientation structure in which the directors of the liquid crystal in the liquid crystal film continuously vary from the respective substrate sides to the respective polarizing plate sides and are fixed. The liquid crystal films are arranged so as to make the respective liquid crystal orientation directions coincide with the rubbing directions of the respective substrates. The cell thickness depths of respective red, green and blue pixels are adjusted so as to be mutually different by forming differences in the level of coloring layers among film thicknesses of red, green and blue coloring layers formed on the counter electrode substrate 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TFT type liquid crystal display panel using a thin film transistor (hereinafter referred to as "TFT"), and an image display application device using the same.

[0002]

2. Description of the Related Art Hereinafter, referring to FIG. 4 and FIG.
The panel structure of the FT type liquid crystal display panel will be described. First, FIG. 4 shows a sectional view of a panel structure of a conventional TFT type liquid crystal display panel.

In FIG. 4, an array chip 2, a pixel electrode 18, an alignment film 3 and the like are formed on a glass substrate 1, and a TFT
The substrate 4 is produced. Further, on the glass substrate 5, black matrices 6a and 6b, colored layers 7a, 7b and 7c,
The counter electrode substrate 10 is manufactured by forming the counter electrode 8 and the alignment film 9.

After rubbing the TFT substrate 4 and the counter electrode substrate 10, spherical bead spacers 14 are evenly dispersed on the counter electrode substrate 10 to form a cell gap, or on the counter electrode substrate 10. In advance, the conical spacers 13 with acrylic columns are formed. The bead spacer 14 is omitted in FIG.

Then, the TFT substrate 4 and the counter electrode substrate 10
After alignment curing of and with the sealing resin 11, they are cut into a predetermined size, and the liquid crystal 12 is injected into the liquid crystal panel. In addition, 15 has shown the electroconductive resin. Liquid crystal optical films 22a and 22b and polarizing plates 19a and 19 are provided on the outer surfaces of the glass substrates 1 and 5, respectively.
b is attached.

FIG. 5 is a perspective view showing an optical arrangement of each element in the panel structure as shown in FIG. 20a
Reference numerals 20b and 20b indicate rubbing axis directions in the TFT substrate 4 and the counter electrode substrate 10, respectively. The axis intersecting angle of the rubbing axes on each substrate is set to 90 °.

Reference numerals 21a and 21b denote absorption axis directions of the polarizing plates 19a (on the TFT substrate 4 side) and 19b (on the counter electrode substrate 10 side), respectively. Further, 23a and 23b are respectively the liquid crystal optical film 22a (TFT
The optical axis directions of the substrate 4 side) and 22b (counter electrode substrate 10 side) are shown. Where 20a, 21a, and 23
a, or 20b, 21b, and 23b are arranged in the same direction.

[0008]

In recent years, a liquid crystal display (Liquid Crystal Display) has been used.
Is accelerating to large high definition,
Due to high color reproduction and improvement of high-speed response technology, excellent display performance comparable to that of CRTs is being realized. In particular, it is considered that the viewing angle, which has been the most important issue of LCD until now, has been overcome to a considerable extent by the development of a novel optical film material and the improvement of the cell process technology.
In the future, it is expected that display performance and higher display quality will be required as a multimedia display compatible with text and animation for the digital society.

As a conventional wide viewing angle technique, an optical phase film is arranged in a predetermined axis direction on both surfaces of a glass of a liquid crystal panel from the viewpoints of high contrast wide field display, realization of a simple process construction method and cost reduction. Compensation technology was adopted. However, with this method, when the LCD is viewed from the oblique viewing angle direction, a phenomenon occurs in which the screen changes to yellow in achromatic display, especially in halftone display, resulting in extremely poor image quality and large display quality. It was accompanied by side effects that deteriorated.

A method for reducing the optical retardation of the liquid crystal cell has been often used as a remedy for the improvement. However, since the transmittance of the liquid crystal panel becomes small, the backlight of the light source is kept in order to maintain the brightness of the LCD. It is necessary to increase the power consumption of the light lamp or to add a prism sheet to collect light on the front of the LCD and separately adopt a countermeasure, and there has been a strong demand for establishment of a solution method without the above-mentioned side effects. .

FIG. 6 shows the viewing angle-chromaticity change amount obtained from the uniform chromaticity diagram for the chromaticity change amount when the conventional liquid crystal display panel is viewed from the front while tilting to the left and right. . Here, ΔU ′ in FIG. 6A is a value obtained by subtracting the uniform chromaticity coordinate value U ′ (θ = 0 °) in the front direction from the uniform chromaticity coordinate value U ′ (θ = θ °) at an oblique viewing angle. Indicates. 6B shows a value obtained by subtracting the uniform chromaticity coordinate value V ′ (θ = 0 °) in the front direction from the uniform chromaticity coordinate value V ′ (θ = θ °) at the oblique viewing angle.

As shown in FIGS. 6 (a) and 6 (b),
As the angle of view increases, both ΔU ′ and ΔV ′ change in the positive direction, and as a result, the image is colored yellow, resulting in a large loss of image visibility.

Various technical approaches have been taken in order to solve this problem, but an appropriate solution is still caused because of an increase in assembly process, reliability problems and other deterioration of display performance (trade-off). Currently, no means have been extracted.

In order to solve the above-mentioned problems, it is an object of the present invention to provide a thin film transistor type liquid crystal display panel having high visibility by improving the color shift that occurs in halftone display.

[0015]

In order to achieve the above object, a thin film transistor type liquid crystal display panel according to the present invention comprises a thin film transistor substrate having a thin film transistor array group and a counter electrode substrate having a transparent electrode film formed thereon. The nematic liquid crystal layer is sandwiched in a twisted array, and a crossed Nicol polarizing plate is disposed in the rubbing direction of the thin film transistor substrate and the counter electrode substrate, and between the thin film transistor substrate and the polarizing plate on the thin film transistor substrate,
And a negative uniaxial liquid crystal optical film respectively disposed between the counter electrode substrate and the polarizing plate on the counter electrode substrate, and the liquid crystal optical film is such that the liquid crystal directors thereof are from the thin film transistor substrate side and the counter electrode substrate side respectively. A thin film transistor type liquid crystal having a fixed hybrid alignment structure that continuously changes to the polarizing plate side, and is arranged so that the liquid crystal alignment azimuth and the rubbed azimuth of the thin film transistor substrate and the counter electrode substrate match. In a display panel, a colored layer formed on a counter electrode substrate is used to form a color layer step between the thicknesses of red, green, and blue layers, so that the cell thickness of each pixel of red, green, and blue is different. It is characterized by being adjusted.

With such a configuration, in the halftone display when the liquid crystal panel is viewed from the right and left viewing angle directions, each R,
The amount of change in chromaticity can be minimized by the combination of the retardation of the liquid crystal layer of the G and B pixels and the retardation of the liquid crystal optical film, which is generated by the optical compensation, and which has a wavelength-transmittance characteristic. Therefore, it is possible to suppress the yellow coloring that has conventionally occurred, and it is possible to realize a good display image that does not pose a problem in practical use.

Further, in the thin film transistor type liquid crystal display panel according to the present invention, the film thickness difference of the colored layer is 0 ≦ (Dg−Dr) ≦ 0.2 between the red layer thickness Dr and the green layer thickness Dg, respectively.
μm and between the green layer thickness Dg and the blue layer thickness Db, 0 ≦ (Db−
Dg) ≦ 0.2 μm, and an angle θ ′ formed by the liquid crystal rubbing orientation direction in the liquid crystal optical film and the nematic liquid crystal rubbing orientation in the liquid crystal layer is −3 ° ≦ θ ′ ≦ + 3 °. And the twist angle φ of the liquid crystal layer is within the range of 85 ° ≦ φ ≦ 95 °, and the refractive indices at the orthogonal axis coordinates (X, Y, Z) of the liquid crystal optical film are Nx, Ny, and Nz, respectively. , D is the film thickness of the film, and Rth = (Nz− (Nx + Ny) / 2) * D is the optical retardation in the thickness direction of the film, then −90 nm ≦ Rth ≦ −110 nm is satisfied,
Front phase difference Re 'at wavelength λ = 550 nm
It is preferable that (550) is adjusted so that Re ′ (550) ≦ 20 nm.

In order to achieve the above object, the image display application device according to the present invention is characterized by using the above-mentioned thin film transistor type liquid crystal display panel. With such a configuration, in the halftone display when the liquid crystal panel is viewed from the left and right viewing angle directions, the wavelength-transmittance caused by the optical compensation of the retardation of the liquid crystal layer of each R, G, and B pixel and the retardation of the liquid crystal optical film. The amount of change in chromaticity can be minimized by combining the characteristics.
Therefore, it is possible to provide an image display application device that can suppress the yellow coloring that has conventionally occurred and can realize a good display image that does not pose a problem in practical use.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thin film transistor type liquid crystal display panel according to embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional configuration diagram of a thin film transistor type liquid crystal display panel according to an embodiment of the present invention.

In FIG. 1, the liquid crystal cell structure formed by the TFT substrate 4 and the counter electrode substrate 10 is the liquid crystal display panel of the conventional example shown in FIG. 4 except for the colored layer 7 formed on the counter electrode substrate 10. The configuration is the same as that of FIG. 4, and the same elements as those of FIG.

In the present embodiment, the counter electrode substrate 1
0, a red layer 7a, a green layer 7b, and a blue layer 7c having different layer thicknesses are formed. When the red layer is Dr, the green layer is Dg, and the blue layer is Db in each color thickness, 0 ≦ (Dg-Dr) ≦
The film thickness is configured to satisfy the relationship of 0.2 μm and 0 ≦ (Db−Dg) ≦ 0.2 μm. The optical arrangement of each element of the TFT type liquid crystal display panel in this embodiment is the same as that of the conventional liquid crystal display panel.

FIG. 2 shows the amount of change in chromaticity when the thin film transistor type liquid crystal display panel according to the present embodiment is viewed from the front while tilting in the left-right direction.
The amount of change in chromaticity is shown, as in FIG.

As shown in FIG. 2A, ΔU 'hardly changes even when the angle of view greatly changes, and the color change is smaller than that in the conventional configuration shown in FIG. 6A. It is clear that it has been greatly improved.

In addition, FIG. 3A shows the difference in the layer thickness (Dg-Dr) between the red layer and the green layer for the white display, the black display, and the halftone display, and shows the chromaticity change amount in the horizontal viewing angle direction. FIG. 4 is a characteristic diagram expressed using uniform chromaticity coordinates U ′ and V ′.
(B) is the difference in layer thickness between the green layer and the blue layer (Db-
Dg) is a characteristic view showing the chromaticity change amount in the left-right viewing angle direction for each of white display, black display, and halftone display using uniform chromaticity coordinates U ′ and V ′.

As is clear from FIG. 3A, (Dg
It can be seen that as the value of −Dr) increases, ΔU ′ decreases in the white display and halftone display states, but changes significantly in the black display state.

Here, since the display image of the LCD is centered on the halftone region, it is assumed that the larger the value of (Dg-Dr), the better the display image can be obtained. But,
Increasing the step difference between colors deteriorates the original liquid crystal panel alignment controllability or alignment stability, so 0 ≦ (Dg−Dr) ≦ 0.2 μm results in the optimum step configuration. .

Further, since ΔV 'cannot be considered to depend on the value of (Dg-Dr) in any display state, its characteristic diagram is omitted.

On the other hand, as is clear from FIG. 3 (b),
As the value of (Db-Dg) increases, ΔU ′ decreases in the halftone display state, but it does not change in the white display state and the black display state.
However, as the optimum step configuration, 0 ≦ (Db−D
g) ≦ 0.2 μm. Further, ΔV ′ is not considered to depend on the value of (Db−Dg) in any display state, and therefore its characteristic diagram is omitted.

From the above characteristic diagram, by controlling the relative film thickness steps of the red layer 7a, the green layer 7b, and the blue layer 7c formed on the counter electrode substrate 10, a conventional liquid crystal display panel can be obtained. It can be seen that it is possible to suppress the image coloring phenomenon with respect to the change in the viewing angle during the halftone display.

[0030]

EXAMPLES In practice, a liquid crystal display panel having the structure shown in FIG. 1 was produced. Here, an angle θ ′ formed by the rubbing orientation direction of the film liquid crystal and the rubbing orientation direction of the nematic liquid crystal in the liquid crystal layer is within a range of −3 ° ≦ θ ′ ≦ + 3 °,
The twist angle φ of the liquid crystal layer is in the range of 85 ° ≦ φ ≦ 95 °, and the orthogonal axis coordinates (X, Y, Z) of the liquid crystal optical film.
Let Nx, Ny, and Nz be the respective refractive indices at, and D be the film thickness of the film, and let Rth = (Nz− (Nx + Ny) / 2) * be the optical retardation in the film thickness direction.
When D, it satisfies −90 nm ≦ Rth ≦ −110 nm and the phase difference (Re ′ (550)) in the front direction at the wavelength λ = 550 nm is Re ′ (550) ≦ 20.
It was adjusted to be nm. As a result, it has been possible to realize a high-performance liquid crystal display panel with excellent high-contrast wide viewing angle characteristics and very little color change.

Specifically, the cell thickness d in the blue pixel is 4.2 μm and the refractive index anisotropy Δn is 0.085 (λ = 55).
0 nm) and the twist angle φ was 85 ° ≦ φ ≦ 95 °. Further, the optical retardation Rth in the thickness direction of the liquid crystal optical film is -90 nm ≦ Rth ≦ −110n.
m, and the front phase difference at the wavelength λ = 550 nm is Re
(550) = 20 nm. The applied voltage of the liquid crystal was set such that the white voltage VW was 0V and the black voltage VB was 5V.

The resulting TFT type liquid crystal display panel is shown in FIG.
Further, as shown in FIG. 3, coloring in the halftone display in the horizontal viewing angle direction can be suppressed, and a high-quality image with high contrast and wide viewing angle can be provided.

[0033]

As described above, according to the thin film transistor type liquid crystal display panel of the present invention, the arrangement of the liquid crystal optical film on the TFT substrate or the counter electrode substrate and the relative arrangement of the red, green and blue colored layers of the counter electrode substrate. By using a different film thickness step configuration, it is possible to suppress the coloring phenomenon in the left and right viewing angles, which was particularly conspicuous in the past in halftone display.
It is possible to provide a high-quality display image with high contrast and a wide viewing angle.

[Brief description of drawings]

FIG. 1 is a sectional view of a thin film transistor type liquid crystal display panel according to an embodiment of the present invention.

FIG. 2 is a view angle-uniform chromaticity change characteristic diagram of a thin film transistor type liquid crystal display panel according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram of film thickness step-uniform chromaticity change characteristic in a thin film transistor type liquid crystal display panel according to an embodiment of the present invention.

FIG. 4 is a sectional view of a conventional thin film transistor type liquid crystal display panel.

FIG. 5 is a perspective view showing an optical arrangement in a conventional thin film transistor type liquid crystal display panel.

FIG. 6 is a view angle-uniform chromaticity change characteristic diagram of a conventional thin film transistor type liquid crystal display panel.

[Explanation of symbols] 1,5 glass substrate 2a, 2b array chip 3,9 Polyimide alignment film 4 TFT substrate 6a, 6b Black matrix layer 7, 7a, 7b, 7c Colored layer 8 Counter electrode 10 Counter electrode substrate 11 Seal resin 12 LCD Spacer with 13 pillars 14 Bead spacer 15 Conductive resin 18 pixel electrodes 19a, 19b Polarizing plate 22a, 22b Liquid crystal optical film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09F 9/35 G09F 9/35 (72) Inventor Yasuhiro Hayashi 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. In-house F-term (reference) 2H091 FA02Y FA11 FD04 FD09 FD12 FD24 GA13 LA03 LA11 LA12 LA13 LA15 LA18 LA19 2H092 JA24 JA42 JB13 JB32 JB38 KB04 KB12 KB22 KB25 MA13 PA08 PA10 QA07 CA07 CA24 CA02 CA02 CA07 CA24

Claims (3)

[Claims] 1. A nematic liquid crystal layer is twisted and sandwiched between a thin film transistor substrate having a thin film transistor array group and a counter electrode substrate having a transparent electrode film formed thereon, and the thin film transistor substrate and the counter electrode substrate are rubbed. A crossed nicols polarizing plate is arranged in the azimuth direction, and the negative uniaxial property is provided between the thin film transistor substrate and the polarizing plate on the thin film transistor substrate and between the counter electrode substrate and the polarizing plate on the counter electrode substrate, respectively. A liquid crystal optical film, wherein the liquid crystal optical film has a fixed hybrid alignment structure in which the liquid crystal director continuously changes from the thin film transistor substrate and the counter electrode substrate side to the polarizing plate side in each. , Its liquid crystal alignment direction and the thin film transistor substrate and In the thin film transistor type liquid crystal display panel in which the counter electrode substrate is arranged so as to match the rubbing-processed orientation, in the colored layer formed on the counter electrode substrate, red, green, and between the film thicknesses of the blue layers. A thin film transistor type liquid crystal display panel, wherein red, green and blue pixels are adjusted to have different cell thicknesses by forming color layer steps. 2. The thickness difference of the colored layer between the red layer thickness Dr and the green layer thickness Dg is 0 ≦ (Dg−Dr) ≦ 0.2.
μm and between the green layer thickness Dg and the blue layer thickness Db, 0 ≦ (Db−
Dg) ≦ 0.2 μm, and the angle θ ′ between the liquid crystal rubbing orientation direction in the liquid crystal optical film and the nematic liquid crystal rubbing orientation in the liquid crystal layer is −3 ° ≦ θ ′ ≦ + 3. And the twist angle φ of the liquid crystal layer is in the range of 85 ° ≦ φ ≦ 95 °, and the refractive indices at the orthogonal axis coordinates (X, Y, Z) of the liquid crystal optical film are Nx and Ny, respectively. , Nz, the film thickness of the film is D, and the optical retardation in the film thickness direction is Rth = (Nz− (Nx + Ny) / 2) * D, −90 nm ≦ Rth ≦ −110 nm is satisfied, and the wavelength λ = 550 nm. Phase difference Re 'in the front direction at
The thin film transistor type liquid crystal display panel according to claim 1, wherein (550) is adjusted so that Re ′ (550) ≦ 20 nm. 3. An image display application device using the thin film transistor type liquid crystal display panel according to claim 1.