Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-10-11
2003-02-11
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S505000
Reexamination Certificate
active
06518709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color organic EL (electro-luminescent) display which is under development as a thin flat panel display and a driving method thereof and, in particular, relates to a color organic EL display and a driving method thereof where improved display quality is promoted.
2. Description of the Related Art
A color organic EL display receives much attention as a color thin flat panel display similar to a liquid crystal display device (LCD) and a plasma display.
FIG. 1
illustrates a schematic cross sectional view showing an EL element and the principle of its luminescence.
An EL element has the following constitution. A transparent electrode
122
made of indium tin oxide (ITO) is formed as a positive electrode on a transparent substrate
121
made of glass or film. Further, an organic hole injection layer
123
and an organic luminescence layer
124
are stacked subsequently on the ITO electrode
122
and a metal layer
125
is formed as a negative electrode on these layers. Here, the organic luminescence layer
124
emits luminescence toward the side of the transparent substrate
121
, when a voltage is applied between the ITO electrode
122
and the metal electrode
125
.
Further, as the constitution of an organic EL element, there are other ones such as a constitution where only an organic luminescence layer is formed between two electrodes, a constitution where an organic hole injection and transportation layer, an organic luminescence layer and an organic electron injection and transportation layer are formed subsequently between two electrodes, and a constitution where an organic hole injection layer, an organic hole transportation layer, an organic luminescence layer, and an organic electron transportation layer are formed subsequently between two electrodes.
As patterns for use in arrangement of sub pixels, there are a stripe pattern, a mosaic pattern and a delta pattern, for example.
FIG. 2
is a schematic view of the conventional stripe pattern,
FIG. 3
is a schematic view of the conventional delta pattern and
FIG. 4
is a schematic view of the conventional mosaic pattern.
In the conventional stripe pattern, as shown in
FIG. 2
, a plurality of first electrodes
101
extending in the column direction are formed. This first electrode
101
corresponds to the ITO electrode
122
. The length of each first electrode
101
in the horizontal direction (the row direction) is about one third of the length of one pixel in the horizontal direction. A plurality of second electrodes
104
extending in the row direction are formed above the first electrode
101
via an organic luminescence layer and the like. The second electrode
104
corresponds to the metal electrode
125
. The width of each second electrode
104
is about the same length as the length of one pixel in the vertical direction (the column direction). The number of the first electrodes
101
is the same as the number of displaying columns and the number of the second electrodes
104
is the same as number of displaying rows. Here, luminescent color from the organic luminescence layer formed between the first electrode
101
and the second electrode
104
is unified at every column and repeated as the sequence of red(R) green (G) and blue (B) in the row direction.
In this stripe pattern, a single sub pixel exists at the cross section of the first electrode
101
and the second electrode
104
. A single main pixel is composed of three color sub pixels arranged in the row direction.
This stripe pattern is preferable to display an image having many column lines and row lines such as a table since sub pixels having the same luminescent color are continuously arranged in the column direction.
Further, in the conventional delta pattern, as shown in
FIG. 3
, the first electrodes
111
, extending in the column direction, is formed so that the number of the electrodes is one and a half times of the number of displaying columns. Each of the first electrodes
111
has a charge injection portion
112
and a wiring portion
113
which are formed alternatively. The lengths in the horizontal and vertical directions of the charge injection portion
112
are a half of the lengths in the horizontal and vertical directions of the pixel, respectively. The charge injection portion
112
has a regular square shape or a similar one. The length in the vertical direction of the wiring portion
113
is a half of that of a pixel and the length in the horizontal direction is extremely narrow in comparison with that of the charge injection portion
112
. The numbers of the charge injection portions
112
and the wiring portions
113
are the same as the number of displaying rows per the single electrode
111
. Further, the charge injection portion
112
and the wiring portion
113
are arranged alternatively in the row direction. A plurality of the second electrodes
114
are formed above the first electrode
111
via an organic luminescence layer and the like. The second electrode
114
extends in the row direction. The number of the second electrodes
114
is the same as that of displaying rows. The first electrode
111
corresponds to the ITO electrode
122
and the second electrode
104
corresponds to the metal electrode
125
.
In this delta pattern, a single pixel is composed of the charge injection portions
112
for two colors adjacent to each other in the row direction and the charge injection portion
112
for another different luminescent color, which is provided directly above or directly under them. Namely, a single pixel is composed of three charge injection portions
112
which are located at each peak of “&Dgr;” or its reversed shape.
The delta pattern is preferable to display a natural image or a moving image since there is more irregularity of arrangement of sub pixels in comparison with the stripe pattern.
Further, in the conventional mosaic pattern, as shown in
FIG. 4
, the first electrode
101
and the second electrode
104
are arranged in a manner similar to the stripe pattern in FIG.
2
. But, location of luminescent color of an organic luminescence layer formed between two electrodes is shifted every sub pixel at every one row in the regulated direction. Therefore, the same luminescent color can be obtained every three rows if one pays his/her attention to a series of the first electrode
101
. In this mosaic pattern, a single pixel is composed of sub pixels for three colors arranged in the row direction.
The mosaic pattern provides advantages of both the stripe pattern and the delta pattern. In Japanese Patent Laid-open Publication Nos. Hei. 7-248482 and Hei. 10-78590, color LCDs having the mosaic pattern are disclosed.
In the conventional stripe pattern, however, there is a problem where display quality is different between a vertical line and a horizontal line when an image except a white line with emitting luminescence having the same intensity from three sub pixels is displayed, because sub pixels for three colors are arranged adjacently in order in the row direction, while sub pixels having the same color are continuously arranged in the column direction. Namely, there is different display quality between a vertical line and a horizontal line since a horizontal line is displayed as a fine dot line in case of displaying other color's line except white, though both vertical and horizontal lines are displayed as continuous line in case of displaying a white line.
Further, in the conventional delta pattern, a vertical line is displayed in a zigzag fashion contrary to the stripe pattern. This deteriorates the display quality and is not appropriate to display an image including many vertical and horizontal lines such as a table.
Further, in the conventional mosaic pattern, a series of the first electrode
101
includes sub pixels for three colors. Namely, three colors are illuminated by a single first electrode
101
. Thus, the order of outputting signal for each color needs to be changed every one displaying row and signal proces
Iketsu Yuichi
Kitazume Eiichi
Dinh Trinh Do
NEC Corporation
Wong Don
Young & Thompson
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