Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-07-13
2004-06-29
Wu, Xiao (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S076000, C345S084000, C345S085000, C345S090000, C345S092000, C315S169100, C315S169300, C315S175000, C349S039000, C349S042000
Reexamination Certificate
active
06756951
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a display apparatus using a display panel comprising spontaneous light emitting devices such as organic electroluminescence devices or the like and relates to a driving circuit for the display apparatus.
2. Description of Related Art
An organic electroluminescence (hereinafter, abbreviated to “EL”) device is known as a spontaneous light emitting element for realizing a thin display apparatus of a low electric power consumption.
FIG. 1
is a diagram schematically showing the structure of the EL element.
As shown in
FIG. 1
, the EL element is made in a manner that an organic functional layer
102
of at least one layer comprising an electron transport layer, a light emitting layer, a hole transport layer, and the like and a metal electrode
103
are laminated over a transparent substrate
100
made of a glass plate or the like on which a transparent electrode
101
has been formed.
FIG. 2
is an equivalent circuit diagram electrically showing characteristics of the EL element.
As shown in
FIG. 2
, the EL element can be represented by a capacitive component C and a component E of diode characteristics which is coupled in parallel with the capacitive component.
When a direct current is applied across the transparent electrode
101
and the metal electrode
103
by applying a plus voltage to an anode of the transparent electrode
101
and applying a minus voltage to a cathode of the metal electrode
103
, charges are accumulated in the capacitive component C. When the applied voltage exceeds a barrier voltage or a light emission threshold voltage that is peculiar to the EL element, a current starts flowing from the electrode (on the anode side of the diode component E) into the organic functional layer serving as a light emitting layer, so that the organic functional layer
102
emits light at intensity which is proportional to the current.
FIG. 3
is a diagram schematically showing the structure of an EL display apparatus for displaying an image by using an EL display panel formed by arranging a plurality of EL elements in a matrix shape.
In
FIG. 3
, cathode lines (metal electrodes) B
1
to B
n
serving as the first to nth display lines and m anode lines (transparent electrodes) A
1
to A
m
arranged so as to cross the cathode lines B
1
to B
n
are formed on an ELDP
10
as an EL display panel. EL elements E
11
to E
nm
having the structure as mentioned above are formed at the cross points of the cathode lines B
1
to B
n
and anode lines A
1
to A
m
, respectively. Each of the EL elements E
11
to E
nm
corresponds to one pixel of an ELDP
10
.
A light emission control circuit
1
converts supplied image data of one picture plane (n rows, m columns) into pixel data groups D
11
to D
nm
corresponding to the respective pixels of the ELDP
10
, namely, the EL elements E
11
to E
nm
and sequentially supplies those data every row to an anode line driving circuit
2
as shown in FIG.
4
.
For example, the pixel data D
11
to D
1m
correspond to m data bits for designating whether each of the EL elements E
11
to E
1m
belonging to the first display line of the ELDP
10
is allowed to execute the light emission or not. When each data bit is at the logic level “1”, it indicates “light emission”. When each data bit is at the logic level “0”, it indicates “non-light emission”.
The light emission control circuit
1
supplies a scanning line selection control signal for sequentially scanning each of the first to nth display lines of the ELDP
10
to a cathode line scanning circuit
3
synchronously with supplying timings of the pixel data of one row as shown in FIG.
4
.
The anode line driving circuit
2
first extracts all of the data bits at the logic level “1” designating “light emission” from the m data bits in the pixel data groups. The anode line driving circuit
2
subsequently selects all of the anode lines belonging to the “column” corresponding to each of the extracted data bits from the anode lines A
1
to A
m
, connects a constant current source only to the selected anode lines, and supplies a predetermined pixel drive current i.
The cathode line scanning circuit
3
alternatively selects the cathode line corresponding to the display line shown by the scanning line selection control signal from the cathode lines B
1
to B
n
, sets the selected cathode line to a ground potential, and applies a predetermined high potential V
cc
to each of the other cathode lines. The high potential V
cc
is set to almost the same value as that of the voltage across the EL element (voltage which is determined on the basis of a charge amount into the parasitic capacitor C) at the time when the EL element emits the light at a desired luminance.
The anode line driving circuit
2
allows the light-emission drive current to flow between the “column” to which the constant current source is connected and the display line set to the ground potential by the cathode line scanning circuit
3
. The EL element formed so as to cross the display line and the “column” emits the light in accordance with the light-emission drive current. Since no current flows between the display line set to the high potential V
cc
by the cathode line scanning circuit
3
and the “column” to which the constant current source is connected, the EL element arranged to cross the display line and the “column” is maintained in the “non-light emission” state.
When the operation as mentioned above is executed on the basis of the pixel data groups D
11
to D
1m
, D
21
to D
2m
, . . . , and D
n1
to D
nm
, a light emission pattern of one field according to the supplied image data, namely, an image is displayed on the screen of the ELDP
10
.
In recent years, to realize a large screen size of the display panel, it is necessary to increase the number of display lines, namely, the number of cathode lines B and increase the number of anode lines A, thereby realizing a highly fine screen. Since a circuit scale of each of the anode line driving circuit
2
and cathode line scanning circuit
3
also enlarges due to an increase in number of anode lines A and number of cathode lines B, therefore, there is a fear of deterioration of the yield in association with an increase in chip area when both of those circuits
2
and
3
are formed in one IC. To avoid it, there is an idea of constructing each of the anode line driving circuit
2
and cathode line scanning circuit
3
by a plurality of IC chips.
If the anode line driving circuit
2
is made of a plurality of IC chips, there however can be a case that the current amounts of light-emission drive currents to be supplied to the anode lines differ among the IC chips due to a variation occurred in the manufacturing process, or the like. Consequently, there is a problem that regions of difference luminance values are formed on the screen of the ELDP
10
due to the difference of the light-emission drive currents.
OBJECTS AND SUMMARY OF THE INVENTION
The invention has been made to solve the problems and it is an object of the invention to provide a display apparatus and a driving circuit of a display panel, in which even when an anode line driving circuit is made of a plurality of IC chips, light emission luminance values on the display panel can be uniformed.
According to the invention, there is provided a display apparatus comprising: a display panel made by forming a light emitting element as one pixel in each cross portion of a plurality of first electrode lines and a plurality of second electrode lines arranged so as to cross each of the first electrode lines; and a driving unit for performing light-emission driving of the display panel, wherein the driving unit is made of a plurality of driving circuits having a plurality of light-emission drive current sources each for generating a light-emission drive current to allow the light emitting device to emit the light and supplying the light-emission drive current to the first electrode line, and at least one of the plurality of driving circuits is provided with a dri
Ishizuka Shinichi
Ochi Hideo
Sakamoto Tsuyoshi
Tsuchida Masami
Abdulselam Abbas
Morgan & Lewis & Bockius, LLP
Pioneer Corporation
Wu Xiao
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