Plasma address electrooptical device

Details Plasma address electrooptical device Plasma address electrooptical device

2000-08-04

2003-09-30

Ton, Toan (Department: 2871)

Liquid crystal cells, elements and systems

Particular excitation of liquid crystal

Plasma excitation

C313S517000

Reexamination Certificate

active

06628348

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a plasma address electrooptical device that controls the display of electrooptical elements by use of plasma discharge.
DESCRIPTION OF THE RELATED ART
Similar to the plasma display panel (PDP), a plasma address electrooptical device (plasma address liquid crystal display; PALC) is utilized as the major component of a large-sized flat panel display device.
An example of a plasma address electrooptical device utilizing a discharge plasma switch to drive a liquid crystal cell will now be explained.
FIG. 5
is a partial perspective view showing the plasma address electrooptical device according to the prior art. Actually, hundreds of liquid crystal drive electrodes and discharge cells are arranged in the device, but the drawing shows only a portion of them as an example.
As shown in
FIG. 5
, the plasma address electrooptical device
100
comprises liquid crystal cells
101
and plasma cells
102
mounted on a common dielectric layer
103
. The plasma cell
102
comprises a plurality of discharge cells
105
formed between a dielectric layer
103
and a lower substrate
104
. A plurality of grooves are formed to the surface of the lower substrate
104
facing the dielectric layer
103
, and each discharge cell
105
is defined by a groove being sealed by the discharge layer
103
. A gas capable of being ionized by discharge is sealed inside each discharge cell
105
, and a pair of plasma electrodes
106
and
107
is formed to the bottom of each cell. When voltage is imposed to the discharge cell
105
utilizing one of the pair of plasma electrodes
106
and
107
as anode and the other as cathode, the gas sealed inside the discharge cell
105
is ionized, and discharge plasma is generated.
On the other hand, the liquid crystal cell
101
comprises a liquid crystal layer
109
mounted between the upper substrate
108
and the dielectric layer
103
. A plurality of liquid crystal drive electrodes
110
arranged parallel to one another are formed on the surface of the upper substrate
108
facing the liquid crystal layer
109
. The liquid crystal drive electrodes
110
are arranged so as to cross the grooves (discharge cells
105
) formed on the lower substrate
104
, and individual pixels are each defined on the crossed areas.
The displaying method according to this plasma address electrooptical device is explained with reference to FIG.
6
.
As shown in FIG.
6
(
a
), by discharging one discharge cell (not shown) corresponding to a selected data sequence, charged particles are stored to the charged particle storage portion
111
formed on the surface of the dielectric layer
103
facing the discharge cell, so that the potentials of the stored portion are 0 V. By simultaneously imposing voltage data corresponding to the selected data sequence to the plurality of liquid crystal drive electrodes
110
, the discharge cells function as switching elements for the liquid crystal layer
109
. Therefore, the amount of electric charge corresponding to the data sequence is stored to the charged particle storage portion
111
on the surface of the dielectric layer
103
facing the discharge cell, and the electric field corresponding to one data sequence is applied to the liquid crystal cell, the status of which is maintained. This procedure is repeated for the number of discharge cells, and the voltage imposed to each liquid crystal drive electrode
110
is maintained until the same discharge cell is discharged for the next frame. Thereafter, until the data for the next frame is transmitted (FIG.
6
(
d
)), as shown in FIG.
6
(
b
) and FIG.
6
(
c
), data voltage corresponding to other discharge cell portions is imposed thereto, with the liquid crystal drive voltage being reversed. Every time the display is changed, the voltage imposed to the liquid crystal drive electrode
110
is reversed between positive and negative polarities. According to the example shown in
FIG. 6
, the device is driven so that voltage is imposed only to the pixel corresponding to red (R).
According to such plasma address electrooptical device, display leakage (hereinafter called “cross talk”) tends to occur to adjacent pixels in the display sequence corresponding to the same discharge cell. In other words, although liquid crystal drive voltage is imposed to the liquid crystal drive electrode that corresponds to only one pixel constituting one data point, as a result, cross talk is observed on the display. When cross talk occurs, the display grade of the device reduces greatly. For example, if colored images are to be displayed, one pixel, in other words, one liquid crystal drive electrode is allocated to one of the colors, R (red), G (green) or B (blue), and a colored filter is mounted on the pixel. If cross talk occurs when only red is to be displayed on the screen, as shown in the example of
FIG. 6
(when electric field is applied to only the pixel corresponding to R, and no electric field is applied to pixels corresponding to adjacent pixels G and B), display leakage is observed to portions of adjacent pixels G and B. As a result, clear red color cannot be displayed on the screen, and the color purity is reduced.
As shown in
FIG. 6
, 30 V is the amount of voltage needed to be imposed to the liquid crystal drive electrode in order to apply an electric voltage of 1 V/&mgr;m to the inner area of the liquid crystal layer. In other words, since the sum thickness of the liquid crystal layer and the dielectric layer is 30 &mgr;m, when 30 V is imposed to the liquid crystal drive electrode and charged particles are stored to the charged particle storage portion on the surface of the dielectric layer facing the discharge cell so that the electric potential thereof becomes 0 V, an electric field of 1 V/&mgr;m is applied to the interior of the liquid crystal layer.
The amount of leakage of an image to the adjacent pixels is hereinafter called the cross talk width. That is, as shown in
FIG. 7
, a center line shown by a chain single-dashed line is supposed to exist between pixels. The cross talk width refers to the length from the center line to the area of the adjoining pixel that is influenced by the information of a pixel. The intensity of display at the cross talk portion is hereinafter called the cross talk intensity. In other words, when a display of a pixel is leaked to adjacent pixels, the similarity of the display of the pixel and the display of the display leakage area is called the cross talk intensity. Actually, the cross talk intensity is expressed as strong when the display of a pixel is black and the display leakage area also displays black, and expressed as weak when the display of a pixel is black and the display leakage area displays a lighter color, such as gray.
Until now, cross talk was considered to be caused by the electric field that has been generated by the voltage imposed to the liquid crystal drive electrode and which protruded (leak out) beyond the intended electrode region. However, the amount of leakage of the electric field or the mechanism of the leakage was still mainly unknown, since it involved the structure of the device or the behavior of the discharged particles being stored.
Examples of the methods for restraining the cross talk proposed heretofore are explained in the following.
Japanese Patent Application Laid-Open Publication No. 8-123360 discloses a method for restraining cross talk caused by the thickness of the dielectric layer, by providing in advance a correction arithmetic process by a correction circuit to the data sequence signal that is to be applied to the liquid crystal drive electrode.
Moreover, Japanese Patent Application Laid-Open Publication No. 10-148820 discloses a method for restraining cross talk by arranging electrode groups in parallel with the liquid crystal drive electrodes on the surface of the dielectric layer facing the discharge cell. By arranging electrode groups, the ununiformity of charge density vanishes, and the fringe electrical field of adjacent liquid crystal drive electrodes is reduced, wh

Affiliated with

Also associated with

Rating

Plasma address electrooptical device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Plasma address electrooptical device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasma address electrooptical device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3034800