Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2002-03-22
2003-11-04
Ton, Toan (Department: 2871)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S505000, C313S509000, C315S169300
Reexamination Certificate
active
06642651
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to active matrix display devices which control thin film luminescent devices, such as electroluminescent (EL) devices emitting light by a driving current flowing in an organic semiconductive film, and light-emitting diode (LED) devices using thin film transistors (hereinafter referred to as TFTs).
2. Description of Related Art
Active matrix display devices using current-control-type luminescent devices, such as EL devices or LED devices, have been proposed. The fact that luminescent devices used in such types of display devices have self-luminescent functions provides advantages, such as obviating installation of a backlight, whereas backlights are essential for liquid crystal display devices, and providing a wider viewing angle.
FIG. 22
is a block diagram of an active matrix display device using charge-injection-type organic EL devices. In the active matrix display device
1
A shown in the drawing, a plurality of scanning lines gate, a plurality of data lines sig extending in a direction perpendicular to a direction of extension of the scanning lines gate, a plurality of common feed lines com extending along the data lines sig, and a plurality of pixels
7
in a matrix formed by the data lines sig and the scanning lines gate, are formed on a transparent substrate
10
.
A data line driving circuit
3
and a scanning line driving circuit
4
are provided for the data lines sig and the scanning lines gate, respectively. Each pixel
7
is provided with a conduction control circuit
50
for supplying scanning signals from a scanning line gate, and a thin film luminescent device
40
emitting based on image signals supplied from a data line sig through the conduction control circuit
50
.
In this example, the conduction control circuit
50
has a first TFT
20
for supplying scanning signals from the scanning line gate to a gate electrode; a holding capacitor cap for holding image signals supplied from the data line sig through the first TFT
20
; and a second TFT
30
for supplying the image signals held in the holding capacitor cap to the gate electrode. The second TFT
30
and the thin film luminescent device
40
are connected in series between an opposite electrode op (described below) and a common feed line com. The thin film luminescent device
40
emits light by a driving current from the common feed line com when the second TFT
30
is in an ON mode, and this emitting mode is maintained by a holding capacitor cap for a predetermined time.
In such a configuration of an active matrix display device
1
A, as shown in
FIGS. 23
,
24
(A), and
24
(B), the first TFT
20
and the second TFT
30
are formed of islands of a semiconductive film in each pixel
7
. The first TFT
20
is provided with a gate electrode
21
as a part of a scanning line gate. In the first TFT
20
, one source-drain region is electrically connected to a data line sig through a contact hole in a first insulating interlayer
51
, and the other region is connected to a drain electrode
22
. The drain electrode
22
extends towards the region of the second TFT
30
, and this extension is electrically connected to a gate electrode
31
of the second TFT
30
through a contact hole in the first insulating interlayer
51
. One source-drain region of the second TFT
30
is electrically connected to a relay electrode
35
through a contact hole of the first insulating interlayer
51
, and the relay electrode
35
is electrically connected to a pixel electrode
41
of the thin film luminescent device
40
through a contact hole in a second insulating interlayer
52
.
Each pixel electrode
41
is independently formed in each pixel
7
, as shown in
FIGS. 23
,
24
(B), and
24
(C). An organic semiconductive film
43
and an opposite electrode op are formed above the pixel electrode
41
in that order. Although the organic semiconductive film
43
is formed in each pixel
7
, a stripe film may be formed over a plurality of pixels
7
. The opposite electrode op is formed not only in a display section
11
including pixels
7
, but also over the entire surface of the transparent substrate
10
.
With reference to FIGS.
23
and
24
(A) again, the other source-drain region of the second TFT
30
is electrically connected to the common feed line com through a contact hole in the first insulating interlayer
51
. An extension
39
of the common feed line com faces an extension
36
of the gate electrode
31
in the second TFT
30
separated by the first insulating interlayer
51
as a dielectric film to form a holding capacitor cap.
In the active matrix display device
1
A, however, only the second insulating interlayer
52
is disposed between the opposite electrode op facing the pixel electrode
41
and the data line sig on the same transparent substrate
10
, which is unlike liquid crystal active matrix display devices; hence, a large capacitance is formed in the data line sig, and the data line driving circuit
3
is heavily loaded.
Accordingly, as shown in
FIGS. 22
,
23
,
25
(A),
25
(B), and
25
(C), the present inventors propose a reduction in parasitic capacitance in the data line sig by providing a thick insulating film (a bank layer bank; the region shaded with lines slanting downward to the left at a wide pitch) between the opposite electrode op and the data line sig. Furthermore, the present inventors propose that the region for forming the organic semiconductive film
43
be surrounded with the insulating film (bank layer bank) to block a solution discharged from an ink-jet head and to prevent bleeding of the solution towards sides in the formation of the organic semiconductive film
43
.
When the entire bank layer bank is formed of a thick inorganic material in adoption of such a configuration, a problem of a prolonged film forming time arises. When the thick inorganic film is patterned, the pixel electrode
41
may be damaged due to overetching. On the other hand, when the bank layer bank is formed of an organic material, such as a resist, the organic semiconductive film
43
may deteriorate at the boundary between the organic semiconductive film
43
and the bank layer bank by the effects of the solvent components contained in the organic material in the bank layer bank.
Since formation of a thick bank layer bank causes formation of a large step difference bb, the opposite electrode op formed above the bank layer bank readily breaks on the step difference bb. Such breakage of the opposite electrode op due to the step difference bb causes insulation of the opposite electrode op from the neighboring opposite electrodes op to form point or linear defects in the display. When the opposite electrode op breaks along the outer periphery of the bank layer bank which covers the surfaces of the data line driving circuit
3
and the scanning line driving circuit
4
, the opposite electrode op in the display section
11
is completely insulated from a terminal
12
and thus no image is displayed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention in view of the above problems to provide an active matrix display device, without damage of thin film luminescent devices, having a thick insulating film satisfactorily formed around an organic semiconductive film in the thin film luminescent devices.
It is another object of the present invention to provide an active matrix display device without breakage of an opposite electrode formed on a thick insulating film which is formed around an organic semiconductive film to reduce parasitic capacitance.
The present invention for solving the above-mentioned problems is characterized by an active matrix display device comprising a display region including a plurality of scanning lines on a substrate, a plurality of data lines extending in a direction perpendicular to a direction of extension of the scanning lines, and a plurality of pixels arranged in a matrix bounded by the data lines and the scanning lines; each of the pixels being provided with a thin film luminesce
Duong Tai
Oliff & Berridg,e PLC
Seiko Epson Corporation
Ton Toan
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