Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-11-27
2002-06-11
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S058000, C345S098000, C345S100000
Reexamination Certificate
active
06404414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electro-optical device such as a liquid crystal device that uses a liquid crystal device substrate, and a projection display device that employs the same. More particularly, this invention relates to the structure of a type of liquid crystal device and electro-optical device in which reset potentials are applied to respective data lines before image signals are supplied to the data lines.
2. Description of Related Art
Of the liquid crystal device substrates employed for a liquid crystal device, the one having a built-in driving circuit has a pixel section
11
in which pixel areas
40
are defined by a plurality of scanning lines
20
and a plurality of data lines
30
arranged in a matrix pattern on a substrate
10
as shown in the block diagram of FIG.
15
. Each pixel area
40
has a pixel switching TFT
50
(thin film transistor) connected to the scanning line
20
and the data line
30
, a liquid crystal cell, and a holding capacitor formed between itself and a capacitor line
29
. Formed in the area outside (the area around) the pixel section
11
on the substrate
10
are a data side driving circuit section
60
for supplying image signals to each of the plurality of data lines
30
and a scanning side driving circuit section
70
for supplying scan signals to each of the plurality of scanning lines
20
. Of these driving circuit sections
60
and
70
, the data side driving circuit section
60
has an X-shift register
610
and a sampling circuit
620
equipped with a TFT functioning as an analog switch, so that image signals are supplied to each of the data lines
20
via an image signal line
630
.
In a liquid crystal device that employs a liquid crystal device substrate
1
configured as described above, for example, in order to implement a so-called inversion driving system in which image signals invert the polarity of data signals for each line according to the potential of a counter electrode or invert the polarity of the voltage applied to liquid crystal, the image signals supplied to the data lines
30
(a source electrode of the TFT
50
) are written to the liquid crystal cell via the TFT
50
while the polarity thereof is inverted for each horizontal scanning period as illustrated in
FIG. 16A
; hence, the potential of the pixel electrode of the pixel switching TFT changes as shown in FIG.
16
B. This means that the polarity of the image signals is inverted for each horizontal scanning period; therefore, the potential of the pixel electrode greatly changes and the charge and discharge from the data lines
30
to the image signal line
620
is accordingly repeated. Such charge and discharge seldom affects the quality of display if the display conforms to the NTSC standard because the sampling rate is relatively low; however, if the display based on HDTV or double speed NTSC is carried out, the charge and discharge leads to the generation of noise because the sampling rate is higher.
To avoid the problem set forth above, a configuration has been proposed wherein a reset driving circuit
80
, which is equipped with two series of reset signal lines
81
and
82
for applying reset potentials to the respective data lines
30
before supplying the image signals to the data lines
30
by utilizing a horizontal retrace line zone or the like and a reset potential supply ON/OFF switching circuit
83
, are provided in the area outside the pixel section
11
as shown in
FIG. 15
, so that the charge and discharge from the data lines
30
is almost completed beforehand by the reset potentials. In the liquid crystal device substrate
1
, which has this configuration, a reset potential having a predetermined polarity is applied from the reset signal lines
81
and
82
just before image signals are supplied to the data lines
30
as shown in FIG.
16
C. Thus, since the charge and discharge from the data lines
30
can be mostly completed before image signals are supplied to the data lines
30
, the potential of the pixel electrode changes less with time as illustrated in
FIG. 16D
, making it possible to restrain the charge and discharge from the data lines
30
. This in turn makes it possible to prevent the fluctuation of the potential at the image signal line
630
, so that the generation of noises in display can be controlled.
When bonding the liquid crystal device substrate
1
to a counter substrate (not shown) with a predetermined cell gap secured between the substrates, a sealant containing a cell gap material is applied considerably inward from the outer periphery of the liquid crystal device substrate
1
because a counter substrate
5
is smaller than the liquid crystal device substrate
1
as shown in FIG.
15
and
FIG. 17
, and the liquid crystal device substrate
1
and the counter substrate
5
are bonded by a sealing layer
90
composed of the sealant, the inner area thereof being provided as a liquid crystal sealing area
12
. In an example shown in
FIG. 17
, the sealing layer
90
is formed slightly outside the reset signal lines
81
and
82
in the area outside the pixel section
11
. In the area where the sealing layer
90
is formed, the process for forming the scanning lines
20
or the like is directly used to form many dummy patterns
15
in parallel to match the geometric shapes of the data lines on the opposite side, so that these parts are seemingly flat in the entire panel, and the sealant is applied thereto.
SUMMARY OF THE INVENTION
In the conventional configuration wherein the reset potentials are applied to the respective data lines
30
before the image signals are supplied to the data lines
30
so as to perform the charge and discharge from the data lines
30
by the reset potentials, since the pixels arranged laterally are reset at the same time; therefore, signals (electric charges) circulate to other data lines
30
via the reset signal lines
81
and
82
depending on the display pattern in the preceding frame. Such signal circulation appears in terms of a lateral cross talk in display, presenting a problem of deterioration in display quality. These kinds of problems could be prevented by setting time constants of the reset signal lines
81
and
82
sufficiently higher than time constants of the data lines
30
; hitherto, however, there has been only one method available by which the width of the data lines
30
is increased to make the time constants of the data lines
30
side relatively smaller, and the method is not adequate to securely prevent the signals from circulating.
Accordingly, the present invention has been made to solve the problem described above and it is an object of the invention to provide a configuration that increases the time constant itself of a reset signal line to prevent signals from circulating from the data lines via the reset signal line, thereby to improve the quality of display in a type of liquid crystal device in which reset potentials are applied to respective data lines before image signals are supplied to the data lines, and also in a type of a projection display that employs the same.
To solve the problem described above, according to the present invention, there is provided a liquid crystal device equipped with: a pair of substrates with liquid crystal sealed in therebetween; a pixel section which is mounted on one of the substrates and is composed of a plurality of data lines to which image signals are supplied, a plurality of scanning lines which cross the plurality of scanning lines and to which scanning signals are supplied, a first switching element connected to the respective data lines and scanning lines, and a pixel electrode connected to the first switching element; and a reset driving circuit provided with a second switching element for supplying a reset signal, which has been supplied to a reset signal conductor, to the data lines prior to the supply of an image signal in the area around the pixel section, and a capacitor which is connected to the second switching element and which stores electr
Kovalick Vincent E.
Oliff & Berridg,e PLC
Seiko Epson Corporation
Shalwala Bipin
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