Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-04-20
2002-04-16
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S082000, C315S169300
Reexamination Certificate
active
06373453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix display device in which a thin film luminescent element such as an EL (electroluminescence) element or LED (light emitting diode) element, that emits light by application of a driving current to an organic semiconductor film, is driven and controlled by a thin film transistor (hereinafter referred to as a TFT).
2. Description of the Related Art
Active matrix display devices using current-controlled luminescent elements such as EL elements or LED elements have been disclosed. Since luminescent elements used in display devices of this type are self-luminescent, backlights are not required, unlike in liquid crystal display devices, and the viewing angle dependence is small, all of which are advantageous.
FIG. 13
is a block diagram of an active matrix display device which uses organic thin-film EL elements of the charge-injection type as described above. In an active matrix display device
1
A shown in the drawing, on a transparent substrate
10
, a plurality of scanning lines gate, a plurality of data lines sig extending in the direction orthogonal to the direction of extension of the scanning lines gate, a plurality of common feeders corn which run parallel to the data lines sig, and a plurality of pixels
7
which are formed in a matrix by the data lines sig and the scanning lines gate are arrayed. A data side drive circuit
3
and a scanning side drive circuit
4
are formed for data lines sig and scanning lines gate, respectively. Each of the pixels
7
includes a conduction control circuit
50
to which scanning signals are supplied through the scanning line gate and a thin film luminescent element
40
which emits light in response to picture signals supplied from the data line sig through the conduction control circuit
50
. In this example, the conduction control circuit
50
includes a first TFT
20
in which scanning signals are supplied to a gate electrode through the scanning line gate, a storage capacitor cap for retaining picture signals supplied from the data line sig through the first TFT
20
, and a second TFT
30
in which picture signals retained by the storage capacitor cap are supplied to a gate electrode. The second TFT
30
and the thin film luminescent element
40
are connected in series between an opposing electrode op (which will be described later in detail) and the common feeder com. The thin film luminescent element
40
emits light in response to a driving current applied from the common feeder com when the second TFT
30
is ON, and the emission is retained by the storage capacitor cap for a predetermined period of time.
With respect to the active matrix display device
1
A having the configuration described above, as shown in FIG.
14
and FIGS.
15
(A) and
15
(B), in any pixel
7
, the first TFT
20
and the second TFT
30
are formed using an island-like semiconductor film. The first TFT
20
has a gate electrode
21
as a portion of the scanning line gate. In the first TFT
20
, the data line sig is electrically connected to one of the source and drain regions through a contact hole of a first interlayer insulating film
51
, and a drain electrode
22
is electrically connected to the other of the source and drain regions. The drain electrode
22
extends toward the region in which the second TFT
30
is formed, and a gate electrode
31
of the second TFT
30
is electrically connected to this extension through a contact hole of the first interlayer insulating film
51
. In the second TFT
30
, an interconnecting electrode
35
is electrically connected to one of the source and drain regions through a contact hole of the first interlayer insulating film
51
, and a pixel electrode
41
of the thin film luminescent element
40
is electrically connected to the interconnecting electrode
35
through a contact hole of a second interlayer insulating film
52
.
As is clear from the FIG.
14
and FIGS.
15
(B) and
15
(C), the pixel electrode
41
is formed independently in each pixel
7
. On the upper layer side of the pixel electrode
41
, an organic semiconductor film
43
and the opposing electrode op are deposited in that order. Although the organic semiconductor film
43
is formed in each pixel
7
, it may be formed in a strip so as to extend over a plurality of pixels
7
. As is seen from
FIG. 13
, the opposing electrode op is formed not only on a display area
11
in which pixels
7
are arrayed, but also over substantially the entire surface of the transparent substrate
10
.
Again, in FIG.
14
and FIG.
15
(A), the common feeder com is electrically connected to the other one of the source and drain regions of the second TFT
30
through a contact hole of the first interlayer insulating film
51
. An extension
39
of the common feeder com opposes an extension
36
of the gate electrode
31
of the second TFT
30
with the first interlayer insulating film
51
as a dielectric film therebetween to form the storage capacitor cap.
However, in the active matrix display device
1
A, since only the second interlayer insulating film
52
is interposed between the opposing electrode op facing the pixel electrode
41
and the data line sig on the same transparent substrate
10
, which is different from a liquid crystal active matrix display device, a large amount of capacitance parasitizes the data line sig and the load on the data side drive circuit
3
increases.
SUMMARY OF THE INVENTION
Therefore, as shown in
FIG. 13
,
FIG. 14
, and FIGS.
16
(A),
16
(B), and
16
(C), the present inventor suggests that by providing a thick insulating film (bank layer bank, a shaded region in which lines that slant to the left are drawn at a large pitch) between the opposing electrode op and the data line sig and the like, the capacitance that parasitizes the data line sig is decreased. At the same time, the present inventor suggests that by surrounding a region in which the organic semiconductor film
43
is formed by the insulating film (bank layer bank), when the organic semiconductor film
43
is formed of a liquid material (discharged liquid) discharged from an ink jet head, the discharged liquid is blocked by the bank layer bank and the discharged liquid is prevented from spreading to the sides. However, if such a configuration is adopted, a large step bb is formed due to the existence of the thick bank layer bank, the opposing electrode op formed on the upper layer of the bank layer bank is easily disconnected at the step bb. If such disconnection of the opposing electrode op occurs at the step bb, the opposing electrode op in this portion is insulated from the surrounding opposing electrode op, resulting in a dot defect or line defect in display. If disconnection of the opposing electrode op occurs along the periphery of the bank layer bank that covers the surface of the data side drive circuit
3
and the scanning side drive circuit
4
, the opposing electrode op in the display area
11
is completely insulated from a terminal
12
, resulting in disenabled display.
Accordingly, it is an object of the present invention to provide an active matrix display device in which, even when parasitic capacitance is suppressed by forming a thick insulating film around an organic semiconductor film, disconnection or the like does not occur in the opposing electrode formed on the upper layer of the thick insulating film.
In order to achieve the object described above, in the present invention, an active matrix display device includes a display area having a plurality of scanning lines on a substrates a plurality of data lines extending in the direction orthogonal to the direction of extension of the scanning lines, and a plurality of pixels formed in a matrix by the data lines and the scanning lines. Each of the pixels is provided with a thin film luminescent element having a conduction control circuit which includes a TFT in which scanning signals are supplied to a gate electrode through the scanning lines, a pixel electrode, an organic semiconductor film de
Oliff & Berridg,e PLC
Piziali Jeff
Shalwala Bipin
LandOfFree
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