Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Plasma excitation
Reexamination Certificate
1993-09-15
2003-03-25
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Plasma excitation
C313S584000
Reexamination Certificate
active
06538707
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electro-optical device using an ionizable gaseous medium as an address element and, more specifically to an image display device adapted to drive an electro-optical material layer by making use of plasma.
2. Description of Related Art
To assure that a liquid crystal display has high resolution and high contrast, there is generally carried out a method in which active elements such as transistors, etc. are provided for every display pixels so as to drive them (which method is so called an active matrix addressing system).
In this case, however, since it is necessary to provide a large number of semiconductor elements such as thin film transistors, the yield is not good particularly when the display area is enlarged, giving rise to problems and the cost is increased.
Thus, as the means for solving this problem, Buzaku et al have proposed in the Japanese Laid Open Application No. 217396/89 publication (corresponding to U.S. Pat. No. 4,896,149 and U.S. Pat. No. 5,077,553) a method of utilizing discharge plasma in place of semiconductor elements such as MOS transistors or thin film transistors, etc. as an active element.
The configuration of an image display device for driving a liquid crystal so as to make use of discharge plasma will be briefly described below.
In this image display device, as shown in
FIG. 11
, a liquid crystal layer
101
serves as an electro-optic material layer and adjacent plasma chambers
102
are arranged under a thin dielectric sheet
103
comprised of glass, etc.
The plasma chambers
102
are constituted by forming a plurality of channels
105
parallel to each other in a glass substrate or base plate
104
. These chambers are filled with ionizable gas. Further, pairs of electrodes
106
and
107
parallel to each other are provided in respective channels
105
. The electrodes
106
and
107
function as an anode and a cathode for ionizing gas within the plasma chambers
102
so as to generate discharge plasma.
On the other hand, the liquid crystal layer
101
is held by the dielectric sheet
103
and a transparent base plate
108
. On the surface at the liquid crystal layer
101
side of the transparent base plate
108
, transparent electrodes
109
are formed. These transparent electrodes
109
are perpendicular to the plasma chambers
102
constituted by the channels
105
. The portions where the transparent electrodes
109
and the plasma chambers
102
intersect with each other correspond to respective picture elements.
In the above-mentioned image display device, by switching and scanning in sequence the plasma chambers
102
where plasma discharge is carried out, and by applying signal voltages to the transparent electrodes
109
on the liquid crystal layer
101
side in synchronism with the switching scan operation, these signal voltages correspond to respective picture elements. The liquid crystal layer
101
is thus driven.
Accordingly, the channels
105
, i.e, plasma chambers
102
respectively correspond to one scanning lines, and the discharge region is divided every scanning unit.
Meanwhile, in image display devices utilizing discharge plasma as described above, it is considered that an increased display area is more easily realized as compared to image display devices using semiconductor elements, but various problems remain in putting image display devices utilizing discharge plasma into practice.
For example, forming channels
105
for constituting respective chambers
102
at the surface portion of the glass substrate
104
serving as a transparent dielectric substrate results in considerable difficulty in manufacturing. Particularly, forming channels
105
at a high density is very difficult.
Further, in the case where there is adopted a structure such that plasma chambers
102
are respectively constituted by channels
105
, liquid crystal layer
102
sections corresponding to the projected portions or the glass substrate
104
, which partition respective plasma chambers
102
, become ineffective and portions are not driven. In addition, at the portions where the wall surfaces of respective channels
105
are formed as a slanting surface or a curved surface, the direction or the polarized state, etc. of a transmitted light is disturbed. This is a problem so as to obtain suitable luminance control, etc.
There is the possibility that the existence of the channels
105
exerts unfavorable large influences on the contrast and the transmissivity (or transmission factor) in the case where an image display is carried out.
Further, in order to scan plasma discharge, a drive circuit having a high voltage (about 150 to 500 volts) is necessarily required. For this reason, the drive circuit unit becomes large, and the cost is also increased.
Furthermore, when an attempt is made to drive the previously described image display device in accordance with the interlaced scanning system, inconveniences such as described below take place.
In conventional PALCs, when an interlaced drive is normally carried out, respective pixels are scanned only every other field (33 mill seconds, e.g., in the case of the NTSC system). At this time, when a moving pictorial image is displayed, images before one field are left within a screen for every other line. For this reason, particularly, at the end portion of a pictorial image, disagreeable fading-out occurs, so the picture quality may be substantially degraded. In addition, because of the inversion of the polarity of the liquid crystal, flicker of two frame periods takes place.
So as to solve this problem, in the same manner as in liquid crystal devices of the TFT System, it is possible to adopt, e.g., a method of converting an interlaced scanning to a sequential scanning by an image processing, a method of inputting a signal of one line to two scanning lines which combination is changed every field, or the like.
In any case, however, there results a great load on the drive circuit such that a line memory is required, and/or the writing time every line becomes one half. This causes the cost of the device to be increased.
SUMMARY OF THE INVENTION
In order to eliminate the above noted drawbacks, it is an object of the present invention to provide an electro-optical device such as an image display device which has excellent image qualities and is easily assembled into the device.
Another object of the invention is to provide an electro-optical device in which an operable voltage drive circuit can be used, thereby permitting the cost of the device to be reduced.
A further object of the invention is to provide an electro-optical device capable of eliminating, without alteration of the drive circuit, degradation of the dynamic resolution (resolution of a moving picture) when an interlaced operation is carried out.
In accordance with the present invention, there is provided an electro-optical device comprising a first substrate, a second substrate opposed to the first substrate, an electro-optical material layer, and a discharge chamber. The first substrate has a plurality of nonoverlapping first electrodes on a major surface thereof. The second substrate has a plurality of nonoverlapping second electrodes. The first and second electrodes are disposed spaced apart in the vertical and horizontal directions, respectively. The electro-optical material layer is disposed in contact with the first electrodes of the first substrate. The discharge chamber is disposed between the electro-optical material layer and the second substrate and is filled with an ionizable gas. The discharge chamber has a plurality of scanning units. Each scanning unit comprises a discharge region of a localized volume of ionized gas so that at least two scanning units are formed in a continuous space.
The inventive device may include a dielectric material layer disposed between the electro-optical material layer and the discharge chamber.
Preferably, the discharge region of all scanning units is formed as a continuous space.
Further, the inventive device may incl
Parker Kenneth
Sonnenschein Nath & Rosenthal
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