Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2000-01-20
2002-03-05
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169300, C313S491000
Reexamination Certificate
active
06353292
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a plasma display panel (PDP), and more particularly to a color plasma display panel in which a white color temperature is increased based on improvements of sustain electrodes.
2. Description of the Related Art
Recently, in the field of display apparatuses, a complexity of information to be displayed, a size of a display panel and a definition of a display panel are increasing rapidly. Therefore, an improvement of a display quality of a PDP is required. The PDP is being developed at a rapid pace because the PDP has advantageous characteristics, for example, no-flicker, ease of achieving a large panel, a high brightness and a long lifetime. There are two types of AC-PDPs. One type has two electrodes which create a selection-discharge (an address-discharge) and a sustain-discharge between the two electrodes. The other type has three electrodes, the third electrode of which creates address-discharges. In a gray-scale color PDP, the phosphors placed in discharge-cells are excited by an ultraviolet light generated by discharges. The phosphors are degraded by ionic bombardments simultaneously generated by the discharges. In the PDP having two electrodes, the phosphors are directly bombard by the ions. This may results in a short lifetime of the phosphors. To avoid the short lifetime of the phosphors, three electrodes generating a surface discharge are generally used in the color PDP. There are types of PDPs having the three electrodes. One type has the third electrode on the same substrate as that on which the first and the second electrodes are provided and the other type has the third electrode on a separate substrate which is opposite to the substrate having the first and the second electrodes. There are two types of PDPs having the three electrodes provided on the same substrate. One type has the third electrode deposited on the first and the second electrodes and the other type has the third electrode deposited under the first and the second electrodes. Furthermore, in a transmission type PDP, a light emitted from the phosphor can be seen through the phosphor, and in a reflection type PDP, a light reflected from the phosphor can be seen. Discharge cells are separated from adjacent discharge cells by separators. Each discharge cell may be sealed by surrounding separators. Otherwise, separators may be provided in only one direction of each discharge cell and each cell is isolated in another direction by an action of an electric field generated by proper gaps between the electrodes.
FIG. 1
shows a plan view of a PDP of one example according to the prior art. Two sustain electrodes, such as an X-electrode
101
(the first electrode) and Y-electrodes
102
to
106
(the second electrodes) are deposited on a substrate. Address electrodes
107
to
116
(the third electrodes) are provided on another substrate. Then, these two substrates are sealed together. Separators
117
to
127
are created perpendicular to a surface of the substrates. Separators
117
to
127
are also perpendicular to the X-electrode
101
and the Y-electrodes
102
to
106
and parallel to the address electrodes
107
to
116
. Each of the X-electrode
101
and the Y-electrodes
102
to
106
has a transparent electrode in part. This PDP is the reflection-type PDP. Therefore, a light reflected from the phosphor can be seen.
FIG. 2
shows a cross section in a direction parallel to the address electrodes
107
to
116
of the PDP shown in FIG.
1
. The PDP comprises a front glass substrate
201
and a rear glass substrate
202
. Sustain electrodes which comprise the X-electrode and the Y-electrodes are deposited on the front glass substrate
201
. The X-electrode has a transparent electrode
203
and a bus electrode
204
. The Y-electrode has a transparent electrode
205
and a bus electrode
206
. The transparent electrodes
203
and
205
are made up of an ITO which is a transparent conductive film of mainly indium oxide because they must transmit a light reflected from a phosphor. A resistance of the bus electrodes
204
,
206
and
208
is needed to be low to prevent a voltage drop caused by the electrode resistance. Therefore, the bus electrodes
204
,
206
and
208
are made up of chrome or copper. The X-electrode and the Y-electrodes are covered with a dielectric layer
209
. Furthermore, a magnesium oxide protection layer
210
is provided on the dielectric layer
209
. A surface of the protection layer
210
is a discharge surface. The address electrode
211
is deposited on the rear glass substrate
202
perpendicular to the X-electrode and the Y-electrodes which are deposited on the front glass substrate
201
.
FIG. 3
shows a cross section in a direction parallel to the X-electrodes
101
of the PDP shown in FIG.
1
. Separators
310
,
311
,
312
and
313
are deposited between address electrodes
307
,
308
and
309
. A red phosphor
314
, a green phosphor
315
and a blue phosphor
316
are deposited on the address electrodes between the separators. The front glass substrate
301
and the rear glass substrate
302
are assembled so that tips of the separators
310
to
313
are sealed to a magnesium oxide layer
306
.
FIG. 4
show a plan view of sustain electrodes for red, green and blue phosphors. A sustain electrode pair comprises an X-electrode
1
and a Y-electrode
1
. The X-electrode
1
comprises a bus electrode
401
and a transparent electrode
402
. The Y-electrode
1
comprises a bus electrode
403
and a transparent electrode
404
. A sustain discharge is created at a slit
413
between the X-electrode
1
and the Y-electrode
1
. This slit
413
is referred to as a positive slit
1
. A slit
415
is also referred to as a positive slit
2
. A sustain discharge is not created at a slit
414
between the X-electrode
2
and the Y-electrode
1
. This slit
414
is referred to as an opposite slit
2
. A red phosphor is deposited between separators
409
and
410
and a red light is emitted from the positive slit
1
between separators
409
and
410
when a sustain discharge is created at the positive slit
1
. A green phosphor is deposited between separators
410
and
411
, and a blue phosphor is deposited between separators
411
and
412
. A green light and a blue light are also emitted from the positive slit
1
when a sustain discharge is created at the positive slit
1
. Address electrodes not shown in
FIG. 4
are provided parallel to the separators.
FIG. 5
shows a relationship among a sustain electrode size, a discharge current value and a brightness.
FIG. 5
(A) shows a relationship between the sustain electrode size and the discharge current value. A solid line
501
shows a case where each sustain electrode provided for the red, green and blue phosphor cells has the same width. In this case, each discharge current at the red, green and blue phosphor cells has the same value despite the sustain electrode size. As a result, each ultraviolet ray generated by a discharge to excite the red, green and blue phosphor cells has the same strength.
However, each luminous efficiency and maximum brightness of the red, green and blue phosphors are different from each other. Therefore, a brightness of a particular color is lower than those of other colors even if each phosphor is excited by the ultra violet ray having the same strength generated by the discharge having the same strength. As a result, a white color temperature is reduced and this results in a degradation of a display quality.
For example,
FIG. 5
(B) shows a relationship between the sustain electrode size and the brightness. As described above, in case that each sustain electrode provided for the red, green and blue phosphor cells has the same width, the red, green and blue phosphor cells are excited by ultraviolet rays having the same strength. A blue brightness
511
, a red brightness
512
and a green brightness
513
are different from each other. The blue brightness
511
is the lowest of the three. As a result, the wh
Hirose Tadatsugu
Kameyama Shigeki
Kishi Tomokatsu
Takamori Takahiro
Fujitsu Limited
Staas & Halsey , LLP
Vu David
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