Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2000-09-25
2003-10-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S504000, C313S506000
Reexamination Certificate
active
06633134
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an active-matrix-driven organic electroluminescence (EL) display device and, more particularly, to such an organic EL display device having a multilayer substrate.
(b) Description of Related Art
Recently, active-matrix-driven organic EL display devices are intensively developed. The active-matrix-driven organic EL display device has a plurality of unit pixels arranged in a two-dimensional array on a supporting substrate for utilizing the EL phenomenon in an organic thin film.
FIG. 1
shows an equivalent circuit diagram of a general active-matrix-driven organic EL display device (hereinafter referred to as simply organic EL display device) such as described in JP Patent Publication No. 8-234683. The organic EL display device includes a plurality of unit pixels
50
each having first and second TFTs
56
and
57
and a storage capacitor
58
, a plurality of data lines
54
each disposed for the unit pixels
50
arranged in a column direction (Y-direction) and a plurality of scan lines
53
each disposed for the unit pixels
50
arranged in a row direction (X-direction). Each scan line
53
is supplied with scan signals by a scan driver (Y-driver)
51
and connected to gates of the first TFTs
56
in the unit pixels
50
. Each data line
54
is supplied with data signals by a data driver (X-driver)
52
and connected to the drain of the first TFT
56
in each of the unit pixels
50
. The source of the first TFT
56
is connected to the gate of the second TFT
57
and a first terminal of the storage capacitor
58
which has a second terminal connected to the ground. The drain of the second TFT
57
is connected to a cathode of an organic EL element or pixel EL element
41
, the anode of which is connected to a common source line.
FIG. 2
shows a cross section of the unit pixel
50
in a conventional organic EL display device such as shown in FIG.
1
. The unit pixel
50
includes a glass substrate
64
, and a p-type active Si (p-Si) film
61
implementing source/drain regions, a gate insulator film
62
, and a gate electrode
65
, which are consecutively formed on the glass substrate
64
to configure the second TFT. Source and drain electrodes
63
are formed on the gate insulator film
62
and connected to the active p-Si film
61
through via holes. The unit pixel
50
also includes a planarization (insulator) film
66
covering the TFTs, and an organic EL element or pixel EL element including an anode
68
made of ITO, an organic thin film
91
and a cathode
92
, which are consecutively formed on the planarization film
66
. The anode
68
is connected to the source of the second TFT. It is to be noted that the first TFT, the storage capacitor and other interconnects (not depicted) are also formed overlying the glass substrate
64
.
FIG. 3
shows another conventional organic EL display device in cross section, and
FIG. 4
shows a schematic perspective view thereof. This type of organic EL display device is described in a JP Utility Model Publication No. 4-31299. In the organic EL display device, an EL panel
110
mounting thereon organic EL elements and a TFT panel
120
mounting thereon TFTs, storage capacitors and interconnects are bonded together, with the electrodes of the EL panel
110
and the corresponding electrodes of the TFT panel
120
being connected by metallic bumps
136
The EL panel
110
includes an EL substrate
111
, and a transparent anode
112
, a first insulator film
113
, a ZnS luminescent film
114
, a second insulator film
115
and a metallic cathode
116
, which are consecutively formed on the EL substrate
111
. The TFT panel
120
includes an EL substrate
121
, and a gate electrode
122
, a gate insulator film
123
, an amorphous Si (a-Si) film
124
and a channel protective film
125
, which are consecutively formed on the TFT substrate
111
. Source electrode
130
and drain electrode
131
are also formed on the TFT substrate
121
. In
FIG. 4
, the TFT panel
120
mounts thereon the EL panel
110
. The can terminals
132
for the scan lines
53
are disposed at both the sides of the TFT panel
121
, whereas data terminals
133
for the data lines
54
are disposed at both the top and bottom of the TFT panel
121
. Ground terminals
134
and anode terminals
135
for the transparent electrode (anode) are disposed at the corner areas of the TFT panel
121
.
In the conventional organic EL display devices, the screen size of the display device substantially defines the size of the glass substrate
111
. Thus, a larger-screen display panel necessitates employment of a larger glass substrate, on which TFTs are fabricated. A larger glass substrate requires a larger fabrication facility including deposition and exposure systems and raises the fabrication costs for the organic EL display device. In addition, the large, number of unit pixels, formed on the large glass substrate etc., suffer from a lower ratio of the number of non-defective products to the number of total products due to the irregularities on the large glass substrate in the fabrication process.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an active-matrix-driven organic EL display device which is capable of reducing the dimensions of the substrate on which TFTs are fabricated as well as reducing the fabrication costs therefor by raising the ratio of the number of non-defective products to the number of total products.
The present invention provides an active-matrix-driven organic electroluminescence (EL) display device including first and second substrates, a plurality of unit pixels each including a pixel EL element and a pixel circuit, the pixel EL elements being arranged in a matrix on a front surface of the first substrate, a plurality of scan lines each disposed for a corresponding row of the unit pixels, a plurality of data lines each disposed for a corresponding column of the unit pixels, a drive circuit for driving the scan lines and the data lines to activate the pixel EL elements through respective the pixel circuits, the second substrate mounting thereon the drive circuit, the scan lines, the data lines and the pixel circuits, the first substrate mounting thereon the second substrate at a rear surface of the first substrate.
In accordance with the organic EL display device of the present invention, since the pixel circuit for driving a corresponding pixel EL element of a unit pixel is disposed outside the pixel area, the dimensions of the substrate mounting thereon the pixel circuit can be reduced compared to the dimensions of the substrate in the conventional organic EL display device, the MOSFETs in the pixel circuit can be fabricated at lower costs and with higher ratio of the number of non-defected products to the number of total products.
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.
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Kondo Yuji
Kota Atsushi
Dinh Trinh Do
Hayes & Soloway P.C.
NEC Corporation
Wong Don
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