Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-05-01
2003-09-16
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S079000, C345S209000
Reexamination Certificate
active
06621228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to EL display apparatus for displaying images or the like using an electroluminescent (hereinafter abbreviated as “EL”) layer.
2. Description of the Related Art
Attention has been paid for years to EL display apparatus of a basic configuration as shown in
FIG. 15
as a self-luminescent type flat display apparatus. The basic configuration of an EL display apparatus includes an electrically insulating transparent substrate
1
such as made of glass, strip-shaped transparent electrodes
2
arranged as extending parallel with each other on the glass substrate
1
, a dielectric material layer
3
covering the transparent electrodes
2
, and an EL layer of an inorganic material formed on the dielectric material layer
3
. On this structure are further stacked a dielectric material layer
5
and strip-shaped back face electrodes
6
arranged as extending parallel with each other on the dielectric material layer
5
. The transparent electrodes
2
and the back face electrodes
6
are each formed as a group of parallel fine wires and extend perpendicularly to each other.
FIG. 16
shows an applied voltage-luminance characteristic of the EL layer
4
shown in FIG.
15
. The EL layer
4
is formed by doping zinc sulfide (ZnS) as an inorganic fluorescent substance with an activator such as manganese (Mn). When the applied voltage reaches about 180 V, luminescence begins to occur and its luminance grows higher with rising voltage. When a voltage higher than a given voltage, for example about 230 V, is applied, the EL layer
4
gives off light at a sufficient luminance. Thus, the EL layer
4
needs to be driven by application of a relatively high voltage of about 200 V for its luminescence to occur.
EL display apparatus of the type shown in
FIG. 15
are adapted to display an image on the glass substrate
1
side. In this case, the transparent electrodes
2
on the glass substrate
1
side serve as data side electrodes, while the back face electrodes
6
serves as scanning side electrodes. The points of intersection of the transparent electrodes
2
on the data side and the back face electrodes
6
on the scanning side each form a pixel. Thus, a display panel has a plurality of such pixels arranged in a matrix pattern.
FIG. 17
shows a change in characteristics with time in the case where each electrode is driven by application of a symmetric waveform and that in the case where each electrode is driven by application of an a symmetric waveform for comparison. As seen from the characteristic resulting from the application of the asymmetric waveform plotted by one-dot chain line, the luminance varies in a direction such as to become lower than the initial characteristic. Application of a symmetric waveform causes a change plotted by the two-dot chain line to occur and hence can avoid such deterioration in performance involved in the case of application of an asymmetric waveform.
FIG. 18
schematically illustrates an electric circuit configuration of a driving circuit of a conventional EL display apparatus. The driving circuit configuration shown is basically equivalent to that disclosed in Japanese Examined Patent Publication JP-B2 6-34152 (1994) invented by Applicant of the instant application. Such a driving circuit provided in an EL display panel of the structure shown in
FIG. 15
includes a data side driving IC
11
as a semiconductor integrated circuit for driving the transparent electrodes
2
as data side electrodes, and a scanning side driving IC
12
for driving back face electrodes
6
as scanning side electrodes. The data side driving IC
11
incorporates a shift register latch
13
, and switching devices each comprising a pull-up element
14
and a pull-down element
15
. Similarly, the scanning side driving IC
12
incorporates a shift register latch
16
, and switching devices each comprising a pull-up element
17
and a pull-down element
18
. The pull-up elements
14
and pull-down elements
15
of the data side driving IC
11
form an output circuit adapted to drive data electrodes
19
. The pull-up elements
17
and pull-down elements
18
of the scanning side driving IC
12
form a driving circuit adapted to drive scanning electrodes
20
.
The source electrodes of the pull-up elements
14
in the data side driving IC
11
are connected to a common line and applied with a positive modulating voltage of +Vm. Similarly, the source electrodes of the pull-down elements
15
are connected to a common line and are grounded to assume a GND potential. The drain electrode of each pair of pull-up element
14
and pull-down element
15
is connected to each data electrode
19
. The data electrodes
19
consist of, for example, n electrodes X
1
, X
2
, X
3
, . . . , Xn, each of which are applied with a modulating voltage of Vm by the associated pull-up element
14
or pull-down element
15
in response to an image signal. The source electrodes of the pull-up elements
17
in the scanning side driving IC
12
are connected to a common line and supplied with a high positive voltage from a positive voltage supply circuit
21
, which is also indicated at Pd
1
. The source electrodes of the pull-down elements
18
are connected to a common line and supplied with a high negative voltage from a negative voltage supply circuit
22
, which is also indicated at Nd
1
. A diode
23
is provided between the positive voltage supply circuit
21
and the source electrodes of the pull-up elements
17
. A diode
24
is provided between the negative voltage supply circuit
22
and the source electrodes of the pull-down elements
18
. The diode
23
has an anode side connected to the positive voltage supply circuit
21
and a cathode side connected to the source electrodes of the pull-up elements
17
. The cathode side of the diode
23
is also connected to the cathode side of a diode
25
, and the anode side of the diode
25
is connected to the ground potential GND through a switching circuit
28
(Nd
2
). The diode
24
has an anode side connected to the source electrodes of the pull-down elements
18
and a cathode side connected to the negative voltage supply circuit
22
. The anode side of the diode
24
is also connected to the anode side of a diode
26
, and the cathode side of the diode
26
is connected to the ground potential GND through a switching circuit
27
(Pd
2
).
FIG. 19
schematically illustrates the configuration of a power supply circuit for generating a write voltage, which is a high voltage required to drive the EL display panel
10
shown in
FIG. 18. A
switching device
30
causes current on the primary side of a transformer
31
to be interrupted or passed. A pair of windings are provided on the secondary side of the transformer
31
, and diodes
32
and
33
and capacitors
34
and
35
associated with the windings provide a smoothed positive voltage of +Vw and a smoothed negative voltage of −Vw. An output of the positive side diode
32
on its cathode side associated with the capacitor
34
is supplied to the anode of a diode
36
, and the cathode side of the diode
36
is connected to the output side of transistors
39
and
40
controlled by a control circuit
38
. When the transistors
39
and
40
are operated by the control circuit
38
so that a positive modulating voltage of +Vm is obtained from the output side thereof, an output of Vw+Vm as a positive write voltage is obtained on the cathode side of the diode
36
.
The voltages of Vm and Vw, respectively, are established within the following ranges. Vm is a voltage for controlling the occurrence of luminescence of the EL display panel
10
and can assume any predetermined value lower than the luminescence initiating voltage. Vw is established to assume a value such that the sum of Vw and Vm is higher than the luminescence initiating voltage of the EL display panel
10
thereby ensuring a sufficient luminescence intensity.
FIG. 20
shows driving waveforms at different portions of data electrodes and scanning e
Harada Shigeyuki
Kiyohara Atsushi
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
Vu David
LandOfFree
EL display apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with EL display apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and EL display apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3057689