Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2003-02-11
2004-12-28
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S504000, C345S076000, C315S169300
Reexamination Certificate
active
06836069
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an organic EL (electroluminescence) display unit and, more particularly, to an active-matrix organic EL display unit including a TFT (thin-film transistor) area and a luminescence area receiving therein an organic EL element.
(b) Description of the Related Art
An organic EL device emits light with a spontaneous electroluminescence function wherein positive holes injected from an anode and electrons injected from a cathode are recombined in an organic El film by applying an electric field to the organic EL film. The recombination energy generated by the recombination allows a fluorescent substance or phosphor in the organic EL film to generate electroluminescence. Examples of an organic EL display unit having such an organic EL device include an active-matrix organic EL display unit, wherein a plurality of pixel elements are arranged in a matrix on a glass substrate. Each pixel element includes a TFT area receiving therein a TFT and a luminescence area receiving therein an organic EL element driven by the associated TFT which functions as an active element.
FIG. 13
shows in a sectional view an example of a single pixel of the active-matrix organic EL display unit. The pixel element includes a TFT
20
and an associated organic EL element
40
both formed on a transparent insulator substrate (not shown). The TFT
20
includes source/drain regions formed in a p-type amorphous silicon layer
80
, formed on the transparent insulator substrate with an intervention of a SiO
2
underlying layer
60
, a gate insulation film
10
, and a gate electrode
12
connected to an aluminum electrode
14
. The TFT area is covered by an edge cover film
30
made of resin. The luminescence area receiving therein the organic EL element
40
include an organic planarizing film
21
formed on the underlying SiO
2
film
60
with an intervention of the gate insulation film
10
and inter-layer dielectric films
16
and
18
, and a transparent electrode
22
, an organic EL film
24
and an aluminum cathode
26
, which are consecutively formed on the organic planarizing film
21
.
The organic planarizing film
21
is used to alleviate the irregularity on the top surface of the interlayer dielectric film
18
. The transparent electrode
22
formed on the organic planarizing film
21
is connected to the TFT
20
via a contact plug
28
. The edge cover film
30
, which alleviates the irregularity on the surface of the transparent electrode
22
has a window
32
whereat a junction is formed between the organic EL film
24
and the transparent electrode
22
. The aluminum cathode
26
covers the entire surface of the organic EL display unit as a topmost layer. The edge cover film
30
is subjected to a tapering processing at the edge thereof adjacent to the window
32
formed in the edge cover film
30
for exposing the luminescence area. The taper processing protects the organic EL film
24
against a crack at the edge
34
of the window
32
, thereby preventing a short-circuit failure between the transparent electrode
22
and the aluminum cathode
16
.
In the conventional active-matrix organic EL display unit shown in
FIG. 13
, the organic planarizing film
21
is formed for planarization after the TFTs
20
are formed on the glass substrate. In addition, the tapering processing is conducted for planarization of the irregularity on the top of the TFT
20
caused by the thickness of the transparent electrode
22
after the transparent electrode
22
and the contact plug of the aluminum electrode
14
are formed. This process is conducted for prevention of the aluminum cathode
26
from being damaged or broken at the step difference and for prevention of a short-circuit failure between the transparent electrode
22
and the aluminum cathode
26
caused by the thinner structure of the organic EL film
24
.
The conventional active-matrix organic EL display unit shown in
FIG. 13
has a drawback wherein degassing from the organic planarization film
21
degrades the organic EL film
24
. In fabrication of the organic EL display unit, a wet processing conducted after forming the contact plug of the transparent electrode
22
causes moisture absorption in the organic planarizing film
21
, which later discharges the moisture therefrom and degrades the organic EL film
24
.
In order to solve the above problem in the conventional organic EL display unit, it may be considered to merely omit the organic planarizing film
21
. However, the omission of the organic planarizing film
21
, as shown in
FIG. 14
, necessitates a larger thickness of the edge cover film
30
for planarizing the surface of the TFT area. The larger thickness generates a larger step difference between the TFT area and the luminescence area, and a larger taper angle &thgr; at the edge of the edge cover film
30
near the window
32
, which causes a short-circuit failure between the transparent electrode
22
and the aluminum cathode
26
. Thus, omission of the organic planarizing film should not be employed.
In view of the above problem in the conventional organic EL display unit, it is an object of the present invention to provide an active-matrix organic EL display unit which is capable of solving the degassing problem to prevent degradation of the organic EL film and preventing a short-circuit failure between the transparent electrode and the aluminum cathode in the vicinity of the edge of the edge cover film.
The present invention provides an organic electroluminescence (EL) display unit including: a transparent insulator substrate, and a plurality of pixels formed thereon and each including a TFT area and a luminescence area, the TFT area receiving therein a TFT and including an edge cover film covering the TFT, the luminescence area having an organic EL element and a window formed in the edge cover film for exposing therefrom the organic EL element, an edge of the edge cover film adjacent to the window having a taper angle equal to or smaller than 30 degrees.
In accordance with the organic EL display unit of the present invention, the smaller taper angle equal to or smaller than 30 degrees prevents a short-circuit failure between electrodes of the organic EL element without degrading the organic EL film. The smaller taper angle may be obtained by a step alleviating film formed in the luminescence area and/or a tapering processing for the edge of the edge cover film as by using a post-baking treatment.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.
REFERENCES:
patent: 5684365 (1997-11-01), Tang et al.
patent: 6147451 (2000-11-01), Shibata et al.
patent: 6501227 (2002-12-01), Koyama
patent: 6590346 (2003-07-01), Hadley et al.
patent: 6597121 (2003-07-01), Imura
patent: 6665044 (2003-12-01), Jacobsen et al.
patent: 2002/0047120 (2002-04-01), Inukai
patent: 2000164875 (2000-06-01), None
McGuireWoods LLP
Patel Vip
Samsung SDI & Co., Ltd.
Zimmerman Glenn D.
LandOfFree
Organic EL display device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Organic EL display device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Organic EL display device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3292407