Computer graphics processing and selective visual display system – Display driving control circuitry – Physically integral with display elements
Reexamination Certificate
1998-09-02
2001-07-03
Hjerpe, Richard (Department: 2774)
Computer graphics processing and selective visual display system
Display driving control circuitry
Physically integral with display elements
Reexamination Certificate
active
06256024
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal display (LCD) element, and more particularly relates to an active matrix type liquid crystal display element having a driving circuit unit and pixel unit formed combinedly that is capable of accepting a digital signal having a signal level lower than a power source voltage level of a horizontal driving circuit system.
2. Description of Related Art
Recently, the trend that LCD monitors separated from notebook type personal computers (referred to as personal computer hereinafter) being used as desktop type monitors has grown in response to the development of thin LCD monitors of reduced power consumption. The internal circuit of a personal computer is structured so that digital signals are processed. On the other hand, a CRT monitor is driven by analog signals, therefore the input output I/F (interface) is an analog I/F. However, because a LCD itself of a-Si uses mainly a source driver IC of a digital I/F, A/D conversion should be performed again somewhere, such conversion is very inefficient as a total system.
As for the state of the art of the driving circuit combined type LCD, while a sampling system of an analog video signal as shown in
FIG. 5
is developed, a circuit having a digital I/F has not been realized. Herein, the system in accordance with the conventional example shown in
FIG. 5
is described. Between a signal line
101
for transmission of a analog video signal and column lines
102
-
1
and
102
-
n,
n transfer gates
103
-
1
to
103
-
n
are connected.
These transfer gates
103
-
a
to
103
-
n
are turned on (becomes conductive) at the rising edge of sampling pulses &phgr;
1
, &phgr;
2
, . . . , &phgr;n supplied successively from the H shift register
104
to sample an analog video signal, and supplies successively it to column lines
102
-
1
to
102
-
n.
On the other hand, m row lines
105
-
1
to
105
-
m
are driven successively by the V shift register
106
.
On respective intersection points of n column lines
102
-
1
to
102
-
n
and m row lines
105
-
1
to
105
-
m,
a thin film transistor (TFT) is provided. A source electrode of the thin film transistor
107
is connected to a column line
102
-
1
to
102
-
n,
a gate electrode is connected to a row line
105
-
1
to
105
-
n
respectively. A drain electrode of the thin film transistor
107
is connected to the transparent pixel electrode of pixels respectively arranged two dimensionally in the form of a matrix.
The system in accordance with the conventional example having the structure described herein above is advantageous to a small sized LCD of, for example, the view finder of a video camera or the light bulb of a projector in that a full color (full analog) display is realized with a relatively simple structure. However, application to a large sized or medium sized LCD results in a significant disadvantage.
(1) Use of a large sized LCD panel inevitably leads to use of large capacity video line and source line (column line), and a large power is consumed when signals are charged/discharged rapidly. Further, an analog buffer for driving such load results in very large EMI (Electromagnetic Interference) source, and set design is difficult.
(2) It is considered in order to cope with the problem (1) that an analog signal is divided into a multiplicity of divided signals and divided analog signals are supplied, however it is very difficult to eliminate the dispersion between channels of a multiplicity of divided analog signals. Further, the system will be a very complex and large system.
(3) Point-successive sampling timing and phase control of video signals are very difficult and the image quality inevitably becomes poor due to ghost.
For the reason described herein above, a large sized driving circuit combined LCD has not been realized up to today. In the field of a-Si (amorphous silicon) LCD, heretofore a method in which a silicone LSI is mounted near a panel using mounting method of TAB (Tape Automated Bonding) and a signal is supplied is employed. However, cost of silicon LSI and mounting cost of a silicon LSI results directly in the increased panel cost.
SUMMARY OF THE INVENTION
The present invention is accomplished in view of such problem, it is the object of the present invention to provide a driving circuit combined type liquid crystal display element which is capable of simplifying the interface with a personal computer and accepting digital input.
The liquid crystal display element is a liquid crystal display element having a driving circuit unit and pixel unit formed combinedly which is capable of accepting a digital signal input having a signal level lower than a power source voltage level of a horizontal driving circuit system provided with a pulse generation means for generating a sampling pulse which samples in time series an input digital signal correspondingly to a pixel, a sampling means for sampling the input digital signal in response to the sampling pulse, a level conversion means for converting a digital signal sampled by the sampling means to a signal having a signal level sufficient for subsequent processing, and a D/A conversion means for generating an analog signal based on a digital signal which was level converted by the level conversion means.
In the above-mentioned liquid crystal display element, the driving circuit unit including a system for sampling digital signals, a system for converting the level of sampled digital signals, and a system for converting digital signals to analog signals and the pixel unit are formed combinedly. The the level of input digital signals with a small amplitude is converted to the power source voltage level of the horizontal driving circuit, and the liquid display element is thereby rendered capable of accepting digital signal input having a small amplitude from the outside.
REFERENCES:
patent: 5414443 (1995-05-01), Kanatani et al.
patent: 6057897 (2000-05-01), Ichikawa et al.
patent: 6078368 (2000-06-01), Ichikawa et al.
Hjerpe Richard
Kananen Ronald P.
Laneau Ronald
Rader Fishman & Grauer
Sony Corporation
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