Liquid-crystal display device and electronic equipment

Details Liquid-crystal display device and electronic equipment Liquid-crystal display device and electronic equipment

2000-06-06

2003-09-02

Kim, Robert H. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S145000, C349S106000, C349S108000, C349S109000

Reexamination Certificate

active

06614498

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a liquid-crystal display device having sub-pixels thereof, corresponding to three different colors and arranged in a delta pattern, and to electronic equipment incorporating the liquid-crystal display device.
BACKGROUND ART
Liquid-crystal display devices find widespread use in electronic equipment, such as small computers, digital cameras, and portable telephones. Such a liquid-crystal display device typically includes a pair of opposing substrates with a liquid crystal encapsulated therebetween, and electrodes formed on each of opposing surfaces of the substrates. The two electrodes and the liquid crystal sandwiched therebetween constitute pixels arranged in a matrix. When a voltage is selectively applied across the electrodes constituting the pixel, the liquid crystal changes its alignment, controlling the quantity of light transmitted therethrough, and thereby presenting a dot.
To present a color display in the liquid-crystal display device, one pixel is divided into three sub-pixels respectively corresponding to the primary colors of R (red), G (green), and B (blue). These sub-pixels placed in a predetermined pattern are arranged in a matrix. The coloring of each sub-pixel is typically performed through a color filter formed on one of the substrates.
Known as the arrangements of the color sub-pixels, i.e., the arrangement of color layers in the color filter in the liquid-crystal display device are an RGB stripe pattern shown in
FIG. 15
, an RGB mosaic pattern shown in
FIG. 16
, an RGGB mosaic pattern shown in
FIG. 17
, and an RGB delta pattern shown in FIG.
18
. In these figures, “R”, “G”, and “B” represent colors provided by respective sub-pixels. Specifically, “R” represents red, “G” represents green, and “B” represents blue.
The RGB stripe pattern shown in
FIG. 15
, also called a trio pattern, is useful for presenting a data display for texts and lines. The resolution thereof is lower than those of other patterns.
The RGB mosaic pattern shown in
FIG. 16
presents a difference in display quality between a rightward rising slant line and a leftward rising slant line, thereby generally presenting slant line noise over an entire image. Particularly, when the number of sub-pixels is small, the noise becomes conspicuous.
The RGGB mosaic pattern shown in
FIG. 17
is said to present a high resolution because the number of “G” sub-pixels providing a high visibility is large. But the score through subjective assessment tests is not necessarily high. Furthermore, if a viewing distance is small, the coarseness of an image stands out, because the number of “B” and “R” sub-pixels is small.
The RGB delta pattern shown in
FIG. 18
presents a horizontal resolution 1.5 times as good as that of the RGB mosaic pattern. The RGB delta pattern shown in
FIG. 18
is said to have a drawback in the presentation of the outline of an image, compared with the RGGB mosaic pattern, because of a poor slant component of the resolution thereof. However, the subjective assessment tests give the highest score to the RGB delta pattern.
Given the same density of the sub-pixels, the comparison of the patterns shows that the RGB delta pattern providing a high horizontal resolution is considered as an adequate pattern for resulting in a high-definition and high-quality image.
The following two wiring patterns are known to connect sub-pixels to conductor lines (such as data lines or scanning lines) for driving the sub-pixels in the RGB delta pattern. Specifically, there are two wiring patterns: a wiring pattern (hereinafter referred to as a type
1
) in which a single data line
212
is connected to the pixel electrodes
234
of two colors of the three sub-pixels of the three RGB colors as shown in
FIG. 19
, and a wiring pattern (hereinafter referred to as a type
2
) in which each line is connected to the pixel electrode
234
of only a single color sub-pixel of the three RGB color sub-pixels as shown in FIG.
20
. In these figures, the conductor line is a data line. As shown, a short line
220
d, connecting each data line
212
to each pixel electrode
234
, represents an active element, such as a TFT (Thin-Film Transistor) or a TFD (Thin-Film Diode).
In the type
1
wiring pattern (see FIG.
19
), among the two sub-pixels for two colors sharing one data line
212
, a variation in the potential of the sub-pixel for one color is affected by the potential of the sub-pixel for the other color. For this reason, a so-called vertical cross-talk occurs, and as a result, streak-like non-uniformity (sujimura in Japanese) occurs in a display screen. The display quality is thus degraded.
This problem is resolved by adopting the type
2
wiring pattern (see
FIG. 20
) in which one data line
212
handles one color. In the type
2
wiring pattern, however, if the potential of a data line
212
adjacent to a given sub-pixel varies, the potential of that sub-pixel also varies. For this reason, a so-called horizontal cross-talk occurs, creating a streak non-uniformity, and leading to a degradation in the display quality.
It is an object of the present invention to provide a liquid-crystal display device which achieves a high display quality by preventing the streak non-uniformity in the display screen arising from the vertical cross-talk and the streak non-uniformity in the display screen arising from the horizontal cross-talk, and to provide electronic equipment incorporating the liquid-crystal display device.
DISCLOSURE OF THE INVENTION
The streak non-uniformity is first discussed in detail before discussing the present invention.
Specifically, the streak non-uniformity in the display screen, arising from the vertical cross-talk in the type
1
wiring pattern shown in
FIG. 19
, is a phenomenon, which is that a dark row and a light row alternately occur every other row, when a single color pattern (solid pattern) of cyan, magenta, or yellow, i.e., respectively complementary color of “R”, “G”, or “B” is presented.
Now discussed is the liquid-crystal display device in a normally white mode with a white display (off) presented with no voltage applied. When a cyan display is presented, an “R” sub-pixel is in black (on), and a “G” sub-pixel and a “B” sub-pixel are in white (off). Data needs to be written to the “R” sub-pixels only.
In the type
1
wiring pattern, the data line is
212
{circle around (
1
)} is connected to the pixel electrodes
234
of the “R”
0
and “G” sub-pixels, the data line
212
{circle around (
2
)} is connected to the pixel electrodes
234
of the “G” and “B” sub-pixels, and the data line
212
{circle around (
3
)} is connected to the pixel electrodes
234
of the “B” and “R” sub-pixels.
The pixel electrode
234
of the “G” sub-pixel in the even rows are connected to the data line
212
{circle around (
1
)} only. When data is written to the “R” sub-pixels in the odd rows through the data line
212
{circle around (
1
)}, a difference between the potential of the “G” sub-pixels connected to the data line
212
{circle around (
1
)} and the potential of the data line
212
{circle around (
1
)} becomes large. For this reason, the potential of the “G” sub-pixels in the even rows is pulled to the writing potential to the “R” sub-pixels as shown in FIG.
21
{circle around (
1
)}. This is one type of vertical cross-talks.
Since the pixel electrodes
234
of the “G” sub-pixels in the odd rows are connected to only the data line
212
{circle around (
2
)} while the data line
212
{circle around (
2
)} is not connected to the “R” sub-pixels, a difference between the potential of the “G” sub-pixels connected to the data line
212
{circle around (
2
)} and the potential of the data line
212
{circle around (
2
)} remains small. For this reason, the potential of the “G” sub-pixels is almost unaffected by the writing voltage to the “R” sub-pixels as shown in FIG.
21
{circle around (
2
)}.
As a result, the root-mean-square value of the voltage applied to the “G” sub-pixels in the even rows becomes lower than the root-mean-square value of the voltage applied to t

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