Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2002-01-22
2004-05-11
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S206000, C345S087000, C345S076000, C345S092000, C345S093000, C345S089000, C315S169100, C315S169300, C313S483000, C313S498000, C313S500000, C313S502000, C313S503000, C313S506000, C257S350000, C257S351000, C257S408000
Reexamination Certificate
active
06734839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix display device wherein the drive of a thin film luminescent element such as an electroluminescent element (hereinafter referred to as an “EL element”) or a light emitting diode element (hereinafter referred to as an “LED element”), which emits light when drive current passes through a luminescent thin film such as an organic semiconductor film, is controlled by a thin film transistor (hereinafter referred to as a “TFT”).
2. Description of the Related Art
An active matrix display device has been proposed which employs a current-controlled luminescent element such as an EL element or an LED element. All these luminescent elements are self-luminescent, making them advantageous in that they do not need a backlight that is required in the case of a liquid crystal display device and that they depend less on viewing angles.
FIG. 4
is a block diagram of an active matrix display device employing an EL element that emits light by means of a charge-injection type organic semiconductor thin film. Disposed on a transparent substrate
10
of an active matrix display device
1
A are a plurality of scanning lines gate, a plurality of data lines sig extendedly provided in such a direction that they intersect with the direction in which the scanning lines gate are extendedly provided, a plurality of common feeder lines com parallel to the data lines sig, and pixels
7
formed in a matrix by the data lines sig and the scanning lines gate. A data side drive circuit
3
and a scanning side drive circuit
4
are configured for the data lines sig and the scanning lines gate. Provided for each pixel
7
are a conduction control circuit
50
to which scanning signals are supplied via the scanning lines gate, and a thin film luminescent element
40
that emits light in accordance with image signals supplied from the data lines sig via the conduction control circuit
50
. The conduction control circuit
50
is constituted by a first TFT
20
in which scanning signals are supplied to a gate electrode thereof via the scanning lines gate, a retention capacitor cap that retains image signals supplied from the data lines sig via the first TFT
20
, and a second TFT
30
in which the image signals retained by the retention capacitor cap are supplied to a gate electrode thereof. The second TFT
30
and the thin film luminescent element
40
are connected in series between an opposing electrode op and the common feeder lines com to be discussed hereinafter. When the second TFT
30
is placed in an ON state, drive current passes through the common feeder lines com, causing the thin film luminescent element
40
to emit light, and the luminescent state is retained by the retention capacitor cap for a predetermined period of time.
FIG. 5
is a top plan view showing one of the pixels included in the active matrix display device shown in FIG.
4
. FIGS.
6
(A), (B), and (C) are a sectional view taken at the line A-A′, a sectional view taken at the line B-B′, and a sectional view taken at the line C-C′ of
FIG. 5
, respectively.
In the active matrix display device
1
A having such a configuration, the first TFT
20
and the second TFT
30
are formed in the same process by utilizing island-like semiconductor films in every pixel
7
as shown in FIG.
5
and FIGS.
6
(A) and (B). The first TFT
20
has a gate electrode
21
configured as a part of the scanning line gate. In the first TFT
20
, the data line sig is electrically connected via a contact hole of a first interlayer insulating film
51
to one end of a source and drain region, while a drain electrode
22
is electrically connected to the other end thereof. The drain electrode
22
is extendedly provided toward the region where the second TFT
30
is formed. A gate electrode
31
of the second TFT
30
is electrically connected to the extendedly provided portion via a contact hole of the first interlayer insulating film
51
. A relay electrode
35
is electrically connected to one end of the source and drain region of the second TFT
30
via the contact hole of the first interlayer insulating film
51
. A pixel electrode
41
of the thin film luminescent element
40
is electrically connected to the relay electrode
35
via a contact hole of a second interlayer insulating film
52
.
As can be seen from FIG.
5
and FIGS.
6
(B) and (C), the pixel electrode
41
is formed independently for each pixel
7
. On the upper layer side of the pixel electrode
41
, an organic semiconductor film
43
and the opposing electrode op are laminated in this order. The opposing electrode op is formed so that it covers at least a display section
11
.
Referring back to FIG.
5
and FIG.
6
(A), the common feeder line com is electrically connected to the other end of the source and drain region of the second TFT
30
via the contact hole of the first interlayer insulating film
51
. An extendedly provided portion
39
of the common feeder line com opposes an extendedly provided portion
36
of the gate electrode
31
of the second TFT
30
, with the first interlayer insulating film
51
sandwiched therebetween as a dielectric film thereby to form the retention capacitor cap.
The active matrix display device
1
A provides a great advantage in that the opposing electrode op deposited on the transparent substrate
10
obviates the need for laminating an opposing substrate, differentiating itself from an active matrix liquid crystal display device. However, the thin film luminescent element
40
is simply covered by the thin opposing electrode op, so that moisture or oxygen intrudes into the organic semiconductor film
43
by diffusing and transmitting through the opposing electrode op, leading to a danger of deteriorated luminous efficiency, a higher drive voltage (shift of a threshold voltage to a higher voltage side), and deteriorated reliability of the thin film luminescent element
40
. To prevent the entry of the moisture or oxygen, the conventional active matrix display device
1
A has been employing a method wherein at least the display section
11
is covered by an opposing substrate, and the outer periphery of the opposing substrate has been sealed. This method, however, inevitably sacrifices the advantage over the liquid crystal display device.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an active matrix display device capable of protecting a thin film luminescent element from moisture, etc. by means of a simple structure.
The active matrix display device in accordance with the present invention has the following configuration.
The active matrix display device has a display section on a substrate, the display section being formed by a plurality of scanning lines, a plurality of data lines intersecting the scanning lines, and a plurality of pixels formed in a matrix by the data lines and the scanning lines, each of the pixels having a conduction control circuit including a thin film transistor to which a scanning signal is supplied to a gate electrode thereof via the scanning lines, a pixel electrode formed for each pixel, a luminescent thin film deposited on an upper layer side of the pixel electrode, and a thin film luminescent element equipped with an opposing electrode which is formed at least on an entire surface of the display section on an upper layer side of the luminescent thin film, and the thin film luminescent element emitting light in accordance with image signals supplied from the data lines via the conduction control circuit, wherein: a protective film is formed on the upper layer side of the opposing electrode, which covers at least a region where the opposing electrode is formed.
According to the configuration, the thin film luminescent element can be protected against moisture, etc., that is diffused or transmitted through the opposing electrode since the protective film is formed on the upper layer side of the opposing electrode of the thin film luminescent element. Hence, it is possible
Hjerpe Richard
Oliff & Berridg,e PLC
Seiko Epson Corporation
Zamani Ali
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