Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-10-09
2004-05-04
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000, C345S204000, C345S205000, C345S206000
Reexamination Certificate
active
06731260
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention relates to a display device using an optical member such as liquid crystal, and more particularly to a display device having a drive circuit therein.
b) Description of the Related Art
A liquid crystal display devices (LCD) formed by adhering a pair of plates having predetermined electrode wiring mutually with a small gap therebetween and charging a liquid crystal into the gap to form a capacitor having the liquid crystal as a dielectric layer to form pixels, or an organic electroluminescence (EL) display device using organic EL capable of controlling an amount of emission by a quantity of electric current are used extensively as displays in the fields of OA equipment and AV equipment in view of advantages of being compact, thin, and low in power consumption. Especially, an active matrix LCD, which is formed with a thin film transistor (TFT) connected as a switching element to each pixel capacitor in order to control writing and retention of a display signal voltage, can display high resolution images are now standard.
FIG. 11
is a plan view showing the entire LCD, in which reference numeral
1
is a TFT substrate positioned at the back of the drawing,
2
is a counter substrate positioned toward this side of the drawing, and
3
is an edge sealing material for adhering the substrate
1
with the substrate
2
and made of a thermosetting adhesive agent such as an epoxy resin or a resin which is cured by irradiation of UV light. A small gap is formed between the TFT substrate
1
and the counter substrate
2
by a spacer (not shown), and the sealing material
3
is partly cut away to form an injection hole
31
. The liquid crystal is injected into the gap through the injection hole
31
, and the injection hole
31
is tightly sealed with a sealing material
32
.
The TFT substrate
1
has TFT formed using polycrystalline silicon (p-Si) as a channel layer on the substrate. The substrate
1
has thereon a display area
4
, which has a plurality of gate lines GL and drain lines DL arranged to intersect to one another and pixel electrodes PX formed at the intersections and connected to pixel TFTs SE to form one of pixel capacitors, a gate driver
5
formed around the display area
4
to supply a scanning signal to the pixel TFTs SE, a drain driver
6
which mainly comprises a bidirectional shift register and an analog switch and supplies a display signal voltage to the pixel TFTs SE in synchronization with scanning of the gate driver
5
, and a control circuit
7
which changes the shifting direction of the shift register to switch the operation directions of the drivers
5
,
6
. These drivers
5
,
6
are formed of p-Si TFTs having the same configuration as the display area
4
. Since the p-Si TFT has a sufficient operation speed, it can configure not only the pixel TFTs SE but also the peripheral drivers for driving them. Thus, a driver built-in LCD having such drivers incorporated into the display panel can be provided. Such TFTs are covered with a flattening insulating film of acrylic resin, SOG (spin on glass), BPSG (Boro-Phospho Silicate Glass) or the like. The pixel electrodes PX are formed on the flattening insulating film in the display area
4
, and connected to the pixel TFTs SE through contact holes formed in the flattening insulating film. Reference numeral
8
denotes signal-input terminals of such drivers.
The counter substrate
2
has a common electrode
9
, which forms the other of the pixel capacitors, formed entirely to correspond with the display area
4
. Although
FIG. 11
shows circuitry on the front side of the substrate
2
, the circuitry may be formed on the back side to oppose the TFT substrate
1
. The pixel capacitors are formed to comprise the liquid crystal and the common electrode
9
divided by the pixel electrodes. The common electrode
9
is partly extended to a corner of the substrate
2
to form a second counter electrode (common electrode) connection terminal
91
. The TFT substrate
1
has a counter electrode signal input terminal
81
for the common electrode
9
. The counter electrode signal input terminal
81
is routed to a first counter electrode connection terminal
83
formed on an area corresponding (oppose) to the counter electrode connection terminal
91
by a route line
82
. And, the first and second counter electrode connection terminals
83
,
91
are mutually adhered with a conductive adhesive agent
92
.
FIG. 12
is a partly enlarged plan view of an LCD. Gate driver
5
comprises a vertical shift register
51
and a buffer portion
52
which are formed along the vertical side in the drawing. Drain driver
6
comprises a horizontal shift register
61
formed along the horizontal side in the drawing and a sampling portion
62
consisting of analog switches corresponding to respective columns. The analog switches are controlled to turn on/off by the respective output phases of the horizontal shift register
61
to sample a display signal voltage from the original image signal which is externally supplied in synchronization with a dot cycle allocated to each column in each horizontal cycle and output to each column.
The epoxy resin or UV resin used for the sealing material
3
may contain water content which survives after drying when applied, atmosphere water content, impurity ions, or the like, and the flattening insulating film as the base of the sealing material
3
may be polarized. Thus, TFTs below the flattening insulating film cause a back channel effect, and an operation threshold voltage varies. Therefore, in the configuration that the sealing material
3
is formed to cover the areas of the gate driver
5
and the drain driver
6
as shown in
FIG. 11
, a logical circuit such as the shift register is located just below the sealing material
3
. When the operation characteristics of the respective TFT elements are changed, malfunction may occur, possibly resulting in equipment failure.
Further, even if the characteristics of the TFT elements are only slightly changed, when the curved portion of the outer edge line of the sealing material
3
is formed to locate on the drain driver
6
as shown in
FIG. 12
, the respective output phases of the drain driver
6
differ in operation between those in the area just below the sealing material
3
and those in the area not below the sealing material
3
. As a result, the display characteristics are different between the columns of the display area
4
corresponding to the output phases below the sealing material
3
and those in the area other than the sealing material
3
on the side of the gate driver
5
, the display characteristics also differ between the rows with the corresponding phases of the gate driver
5
just below the sealing material
3
and those in the area not below the sealing material
3
. In the drawing, the shaded (with lines rising toward the right side) area in the display area
4
has the corresponding shift register
51
or
61
of the gate driver
5
or the drain driver
6
in the area just below the sealing material
3
, and the area not shaded has the corresponding shift registers
51
,
61
in the area other than the sealing material
3
. The area not shaded is free from being changed the display characteristics, while the hatched area has the display characteristics varied. Thus, the shaded area is seen different from the other area. A large stress is applied to the outside edge of the curved portion of the sealing material
3
to affect on the characteristics of the TFT elements positioned below it. Therefore, the area having the phases of the corresponding drivers
5
,
6
on the curved portion of the sealing material
3
is seen different from the other area. Thus, the mixed presence of the areas with different display characteristics in the display area
4
results in degrading the display quality.
If the control circuit
7
is defective in operation, the operating directions of the drivers
5
,
6
cannot be changed, and general versatility of the LCD having drivers therein is
Hirai Kyoko
Jinno Yushi
Hogan & Hartson LLP
Kovalick Vincent E.
Sanyo Electric Co,. Ltd.
Shalwala Bipin
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