Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-03
2001-07-10
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000, C345S092000, C345S904000
Reexamination Certificate
active
06259424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement of a display matrix substrate used in a liquid crystal display apparatus for displaying an image, a production method of the display matrix substrate and a display matrix circuit used for the display matrix substrate.
2. Description of the Related Art
Generally, a liquid crystal has a mobility like a liquid while maintaining a certain molecular arrangement like a solid. This molecular arrangement is readily changed responsive to an intensity of an electric field applied thereto. The change of the molecular arrangement brings a change of the optical characteristics of the liquid crystal. As an apparatus employing such a liquid crystal, there is well known a liquid crystal image display apparatus (referred to as liquid crystal display apparatus).
In the liquid crystal display apparatus, the liquid crystal is enclosed between a common electrode and a matrix substrate having pixel electrodes disposed to face the common electrode, wherein the pixel electrodes can be individually controlled. The optical characteristic of the liquid crystal interposed between the respective electrodes and the common electrode is changed responsive to an intensity of electric field applied across the common electrode and each of the corresponding pixel electrodes by selectively applying a data signal to the respective pixel electrodes.
This type of the liquid crystal display apparatus is further classified into two types, a transmission type and a reflection one. The transmission type liquid crystal apparatus has a capability of reducing a production cost of the apparatus because of a simple structure thereof. On the other hand, it has a drawback of less brightness of a displayed image because downsizing a display pane of the apparatus brings an increase of a ratio of an area occupied by switching transistors for selectively driving the pixel electrodes and wirings, resulting in a decrease of a vignetting factor. Thus, the brightness of the displayed image is decreased.
On the other hand, in the reflection type liquid crystal apparatus as disclosed in the Japanese Patent Publication 57-39422 and Japanese Patent Laid-open Publication 4-338721, the switching transistors and the wirings can be provided under reflective pixel electrodes. Thus, it is possible to obtain a bright image without a decrease of the vignetting factor even when the display panel is downsized.
Accordingly, it is suitable for a magnifying projection type liquid crystal display apparatus to employ the reflection type display panel having small dimensions with a high density.
Next, a description is given of the reflection type liquid crystal display apparatus equipped with MOS type transistors a conceivable one of the liquid crystal display apparatuses.
FIG. 17
shows a block diagram of a circuit for operating pixels arranged in a matrix form in a conceivable liquid crystal display apparatus; and
FIG. 18
is a sectional view of a unit pixel of a display matrix substrate shown in FIG.
17
.
In
FIG. 17
, a reference character
1
designates a switching element of a MOS transistor. A plurality of the switching elements
1
are vertically and horizontally disposed in matrix on a glass plate or a silicon substrate (not shown). A pixel electrode
2
and a capacitor
3
for storing electric charges, of which one of terminals is commonly used with the pixel electrode
2
, are connected to a source
8
or a drain
7
of the switching element
1
. In this case the pixel electrode
2
is connected to the source
8
. A gate line Xi for selectively supplying a selection signal is connected to a gate electrode
4
of the switching element
1
, and a signal line Yj for supplying a video signal is connected to either the drain
7
or the source
8
which is not connected to the pixel electrode
2
. To the gate line Xi, the selection signal is applied from an X direction scanning circuit Xscn. And to the signal line Yj, the selection signal is applied from a Y direction scanning circuit Yscn.
To each of the pixel electrodes
2
, there is provided a transparent common electrode (referred to as common electrode)
5
so as to face each of the pixel electrodes
2
, and a liquid crystal
6
is enclosed between the common electrode
5
and the pixel electrodes
2
. Thus, a pixel is formed with every pixel electrode
2
.
Upon an operation of the switching element
1
, when a selection signal is applied to the gate electrode
4
through the gate line Xi, the switching element
1
of the MOS transistor is turned on. Thus, the video signal passes the switching element
1
through the signal line Yj, and is simultaneously applied to the pixel electrode
2
and the capacitor
3
, resulting is that the capacitor
3
is charged.
Here, an electrical potential of the pixel electrode
2
is maintained responsive to an amount of the electric charges stored in the corresponding capacitor
3
even when the selection signal from the gate line Xi becomes zero, i.e., in a non-selection mode.
During this time, the liquid crystal
6
undergoes an electrical potential applied across the pixel electrode
2
and the common electrode
5
. Thereby, a light transmittance of the liquid crystal
6
is modulated. Thus, the electric signal (the video signal) can be converted to a modulated optical signal by controlling an intensity of the electrical potential applied across the pixel electrode
2
and the common electrode
5
.
Accordingly, an image can be formed by disposing such unit pixels in matrix on a display panel and by vertically and horizontally scanning both the gate signal and the video signal. As a scanning method mentioned above, all the switching elements
1
along the gate line Xi arranged in an X direction are turned on. Thus, the video signal is applied to the pixel electrodes
2
, and the capacitors
3
are simultaneously charged thereby. And the following gate lines Xi are successively turned on by being scanned with the gate signal in a Y direction.
Next, the description is given of a structure of the unit pixel, referring to FIG.
18
.
The switching element
1
made of the MOS transistor as mentioned above, has the gate electrode
4
, the drain
7
, and the source
8
. The gate electrode
4
is provided on a substrate
10
made of a single crystal silicon through a gate oxide layer
9
. The gate electrodes
4
disposed in the X direction are formed as the gate line Xi by using, for instance, polycrystal silicon (FIG.
17
). Further, the drain
7
is connected to the signal line Yj extending in the Y direction (FIG.
17
).
Next to the source
8
, the capacitor
3
for storing the electric charges is formed by causing an insulation layer made of Si0
2
to be interposed between the substrate
10
and a capacitor electrode
11
, and the capacitor electrode
11
is connected to the source
8
. The pixel electrode
2
is formed, for instance, across an insulation layer
13
over the switching element
1
and the capacitor
3
. The pixel electrode
2
and the source
8
are electrically connected through a cutout
14
(enclosed by a broken line in
FIG. 18
) defined in a thickness direction for an electrical connection.
The pixel electrode
2
is made of such a material as aluminum having a high reflectivity for a read light.
A transparent glass plate
16
coated with the transparent common electrode
5
thereon is provided over the surface of the display matrix substrate
15
formed with the various elements mentioned above so that the transparent common electrode
5
faces the surface of the display matrix substrate
15
leaving a little clearance L
1
therebetween. On both surfaces of the transparent common electrode
5
and the pixel electrode
2
, there are respectively provided alignment layers
17
,
18
, and the liquid crystal
6
is enclosed between the pixel electrodes
2
and the transparent common electrode
5
, resulting in a liquid crystal panel. Thus, the reflection type liquid crystal display apparatus is produced. An incident light
19
coming from an u
Anderson Kill & Olick P.C.
Said Mansour M.
Shalwala Bipin
Victor Company of Japan Ltd.
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