Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-02-04
2003-06-10
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100
Reexamination Certificate
active
06577070
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an AC type plasma display panel used for displaying images in a television receiver and a billboard.
BACKGROUND ART
FIG. 11
is a partially broken perspective view illustrating a schematic configuration of a conventional AC type plasma display panel (hereinafter, simply referred to as “a panel”).
FIG. 12
is a cross sectional view of
FIG. 11
taken along the line B—B in an arrow direction.
As is shown in
FIG. 11
, the conventional AC type plasma display panel
80
is provided with a front substrate
82
and a back substrate
83
opposing each other and separated by a discharge space. On the front substrate
82
, a plurality of pairs of stripe-shaped scanning electrodes
86
and sustaining electrodes
87
are arranged substantially in parallel and covered with a dielectric layer
84
and a protective coating
85
. A plurality of stripe-shaped address electrodes
88
are formed substantially in parallel on the back substrate
83
in the direction perpendicular to the scanning electrode
86
and the sustaining electrode
87
. Stripe-shaped barriers
89
are arranged between the address electrodes
88
. Phosphors
90
are formed between the barriers
89
so as to cover the address electrodes
88
. Spaces surrounded by the surface substrate
82
, the back substrate
83
and the barriers
89
form discharge cells
91
. The spaces in the discharge cells
91
are filled with gases radiating ultraviolet light due to discharge.
As is shown in
FIG. 12
, the phosphor
90
includes a blue phosphor
90
b
, a green phosphor
90
g
and a red phosphor
90
r,
and one of these three colors of phosphors is formed in each discharge cell. Thus, the discharge cell provided with the blue phosphor
90
b
constitutes a blue discharge cell
91
b
, the discharge cell provided with the green phosphor
90
g
constitutes a green discharge cell
91
g,
and the discharge cell provided with the red phosphor
90
r
constitutes a red discharge cell
91
r.
Next, a method for displaying an image data on the conventional panel
80
is described.
When driving the panel
80
, one field period is divided into subfields having the weight of emission period based on a binary system so that gradation is displayed by a combination of subfields for light emission. For example, when one field is divided into eight subfields, 256 gradation levels can be displayed. The subfield includes an initialization period, an address period and a sustain period.
In order to display an image data, signal waveforms that are different in each period, i.e., the initialization period, the address period or the sustain period, are applied to the electrodes.
In the initialization period, for example, a positive polarity pulse voltage with respect to the address electrode
88
is applied to all the scanning electrodes
86
so as to store wall charge on the protective coating
85
and the phosphors
90
.
In the address period, while a negative polarity pulse is being applied to the scanning electrodes
86
so as to scan the scanning electrodes
86
sequentially, a positive polarity pulse (a write voltage) is applied to the address electrodes
88
. A discharge (a write discharge) occurs in the discharge cell
91
at the intersection of the scanning electrode
86
and the address electrode
88
, generating charged particles. This is called a write operation.
In the subsequent sustain period, AC voltage that is sufficient to sustain the discharge is applied between the scanning electrode
86
and the sustaining electrode
87
for a certain period. Discharge plasma generated at the intersection of the scanning electrode
86
and the address electrode
88
excites the phosphor
90
so as to emit light while applying this AC voltage between the scanning electrode
86
and the sustaining electrode
87
. Where light emission is not desired, it may be possible not to apply the pulse to the scanning electrodes
86
in the address period.
In these conventional panels described above, for the purpose of obtaining white similar to that with chromaticity coordinates of a standard white light source, the width of the discharge cell
91
(that is, the distance between barriers
89
on both sides constituting the discharge cell
91
) is different from that with the other two colors (JP 9-115466 A). Specifically, the discharge cell
91
b
having the blue phosphor
90
b
is the widest, and the green discharge cell
91
g
and the red discharge cell
91
r
are narrower than the blue discharge cell
91
b
. The reason for this configuration is as follows. The luminous efficiency of the blue phosphor
90
b
is lower than those of the green phosphor
90
g
and the red phosphor
90
r.
Therefore, when all the widths of blue, green and red discharge cells are the same, the maximum input signal input into the discharge cells of respective colors cannot obtain the desired chromaticity and color temperature. For example, the chromaticity obtained from synthesizing the three colors deviates from the white range or its color temperature is low. Accordingly, the width of the discharge cell
91
is made different from that with the other two colors so that the maximum input signal input into the discharge cells of respective colors can obtain the desired white.
However, the above-described configuration has a problem in that the discharge starting voltage of the blue discharge cell
91
b
is different from those of the other two discharge cells
91
g
and
91
r.
FIG. 13
shows write voltages necessary to perform a write discharge in a stable manner when a constant voltage is applied to the scanning electrodes
86
in the write operation in the address period (complete lighting write voltages) with respect to the discharge cells of respective colors. As is described above, in the conventional panel, the discharge cells have necessary write voltages that are different from color to color. As a result, as is clearly shown in the figure, the discharge cells have complete lighting write voltages that are considerably different depending on their colors. Thus, applying the same write voltage to all the discharge cells causes problems of an unstable write discharge, erroneous discharge or discharge flicker, leading to an improper display.
In order to perform a stable write operation, it is necessary that the write voltage to be applied to the address electrodes
88
is changed depending on colors of the discharge cells in accordance with the complete lighting write voltage of the discharge cells of respective colors. However, this complicates the voltage control, raising the cost of the apparatus.
DISCLOSURE OF INVENTION
It is an object of the present invention to solve the problems above and to provide an AC type plasma display panel that achieves a stable write discharge even when blue, green and red discharge cells have different widths from each other, as well as prevents erroneous discharge and discharge flicker so as to realize a proper display.
In order to achieve the above-mentioned object, the present invention has the following configuration.
An AC type plasma display panel in accordance with the first configuration of the present invention includes two substrates opposing each other with barriers interposed therebetween, a plurality of discharge cells surrounded by the two substrates and the barriers, and a phosphor formed in each of the discharge cells. A width of the discharge cell in which the phosphor having at least one color of a plurality of colors is formed is different from a width of the discharge cell in which the phosphor having another color is formed. The AC type plasma display panel has a function of making complete lighting write voltages of the discharge cells in which the phosphors of respective colors are formed substantially uniform. “The complete lighting write voltage” in the present invention means a write voltage necessary to cause a write discharge in all of the desired discharge cells in a write operation in an address period followed by a sustain operation. Since the complete lighting write v
Aoto Koji
Hirao Kazunori
Kiriyama Kenji
Shino Taichi
Tahara Yoshihito
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Vu Jimmy T.
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