U.S. patent number RE41,832 [Application Number 12/389,281] was granted by the patent office on 2010-10-19 for method for driving a gas-discharge panel.
This patent grant is currently assigned to Hitachi Plasma Patent Licensing Co., Ltd. Invention is credited to Kenji Awamoto, Yasunobu Hashimoto, Seiichi Iwasa, Yasushi Yoneda.
United States Patent |
RE41,832 |
Hashimoto , et al. |
October 19, 2010 |
Method for driving a gas-discharge panel
Abstract
When performing the line-sequential addressing for setting the
state of each of the cells arranged in rows and columns that
constitute a display screen, discharge is generated that has
intensity in accordance with display data corresponding to each of
all cells belonging to the selected row for each selection of the
row. Thus, the priming effect in the following discharge is
generated.
Inventors: |
Hashimoto; Yasunobu (Kawasaki,
JP), Yoneda; Yasushi (Kawasaki, JP),
Awamoto; Kenji (Kawasaki, JP), Iwasa; Seiichi
(Kawasaki, JP) |
Assignee: |
Hitachi Plasma Patent Licensing
Co., Ltd (Tokyo, JP)
|
Family
ID: |
18232729 |
Appl.
No.: |
12/389,281 |
Filed: |
February 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11335899 |
Jan 20, 2006 |
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Reissue of: |
09427934 |
Oct 27, 1999 |
06680718 |
Jan 20, 2004 |
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Foreign Application Priority Data
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Nov 20, 1998 [JP] |
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10-330447 |
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Current U.S.
Class: |
345/63; 345/60;
315/169.4; 345/66; 345/690; 345/67; 345/204; 315/169.1 |
Current CPC
Class: |
G09G
3/2935 (20130101); G09G 3/2932 (20130101); G09G
3/2927 (20130101); G09G 2310/0213 (20130101); G09G
2310/066 (20130101); G09G 2300/0413 (20130101) |
Current International
Class: |
G09G
3/28 (20060101) |
Field of
Search: |
;345/60,63,66,67,68,76,77,204,690 ;315/169.1,169.4 |
References Cited
[Referenced By]
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'98, pp. 15-27. cited by other.
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Primary Examiner: Tran; My-Chau T
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP
Parent Case Text
.Iadd.This is a Divisional application of U.S. Reissue application
Ser. No. 11/335,899, filed Jan. 20, 2006, which is a Reissue of
U.S. application Ser. No. 09/427,934, filed Oct. 27, 1999, now U.S.
Pat. No. 6,680,718, and is a co-pending application of U.S.
application Ser. No. 12/388,870, and is also related to Reissue
application Ser. No. 12/684,818, filed Jan. 8, 2010 and Reissue
application Ser. No. 12/684,811, filed Jan. 8, 2010, the contents
of which are incorporated herein by reference..Iaddend.
Claims
What is claimed is:
.[.1. A method for driving a gas-discharge panel in which
line-sequential addressing is performed for setting a state of
cells arranged in rows and columns, the method comprising
generating a discharge in all cells of a selected row, irrespective
of a state to be set in each of the cells for each selection of the
row in addressing, an intensity of the discharge in each of the
cells of the selected row being set in accordance with state
setting data corresponding to each of the cells of the selected
row..].
.[.2. The method according to claim 1, wherein the intensity is set
to either a first intensity for cells to be lit during the
line-sequential addressing by applying a voltage in the cells to be
lit to achieve restart of a discharge in a light sustaining
operation or a second intensity for cells not to be lit during the
line-sequential addressing by applying a voltage in the cells not
to be lit to prohibit restart of a discharge in the light
sustaining operation..].
.[.3. The method according to claim 1, wherein the gas-discharge
panel includes scanning electrodes for selecting respective rows
and data electrodes for selecting respective columns crossing the
rows at respective cells, the scanning electrodes and the data
electrodes being covered with a dielectric layer for providing wall
voltage, a discharge space being continuous over an entire length
of each of the columns, the method further comprising: applying a
preparation pulse to the cells of the selected row before
performing the addressing to set a wall voltage of each cell to a
predetermined level to perform an addressing preparation;
generating the discharge in a first intensity for cells to be lit
during the line-sequential addressing by applying a voltage in the
cells to be lit to increase a wall charge level set after the
applied preparation pulse to achieve restart of the discharge in a
light sustaining operation; and generating the discharge in a
second intensity for cells not to be lit during the line-sequential
addressing by applying a voltage in the cells not to be lit to
decrease a wall charge level set after the applied preparation
pulse to prohibit restart of the discharge in the light sustaining
operation..].
.[.4. The method according to claim 3, further comprising: biasing
each of the data electrodes to a first potential or a second
potential in accordance with the state setting data of one row
synchronizing with a row selection by an independent potential
control with respect to each of the scanning electrodes..].
.[.5. A method for driving a gas-discharge panel in which
line-sequential addressing is performed for setting a state of
cells arranged in rows and columns so as to constitute a display
screen, the method comprising generating a discharge in all cells
of a selected row, irrespective of a state to be set in each of the
cells for each selection of the row in addressing, an intensity of
the discharge in each of the cells of the selected row being set in
accordance with state setting data corresponding to each of the
cells of the selected row..].
.[.6. A method for driving a gas-discharge panel having a display
screen including cells arranged in rows and columns, a scanning
electrode for selecting a corresponding row and a data electrode
for selecting a corresponding column crossing at a corresponding
cell, one of the scanning electrode and the data electrode being
covered with a dielectric layer for providing wall voltage, a
discharge space being continuous over an entire length of each of
the columns, the method comprising: performing line-sequential
addressing to control the wall voltage of all cells of the screen
in accordance with binary display data and sustaining by applying
an alternating voltage to all cells of a selected row, repeatedly;
and generating a discharge having either a first or a second
intensity depending on the display data corresponding to each of
the cells of the selected row for each selection of the row in the
addressing..].
.[.7. The method according to claim 6, further comprising: applying
a preparation pulse to the cells of the selected row before
performing the addressing so as to perform an addressing
preparation for setting the wall voltage of each cell to a
predetermined level; generating the discharge having a first
intensity for cells to be lit in the addressing so as to make a
level of the wall voltage set in the addressing preparation
increase to a sufficient level to regenerate a discharge in a light
sustaining operation; and generating the discharge having a second
intensity for cells not to be lit in the addressing so as to make
the level of the wall voltage set in the addressing preparation
decrease to a level such that a discharge cannot restart in the
sustaining operation..].
.[.8. The method according to claim 7, further comprising: biasing
each of the data electrodes to a first potential or a second
potential in accordance with the display data of one row
synchronizing with the row selection by an independent potential
control with respect to each of the scanning electrodes..].
.[.9. The method according to claim 7, further comprising: applying
a voltage to an electrode gap of the cells generating a discharge
in the addressing, in the addressing preparation the voltage
increasing from a first set value to a second set value, so as to
adjust the wall voltage of the electrode gap by generating plural
discharges or a continuous discharge in a rising period of the
voltage..].
.[.10. The method according to claim 6, further comprising:
applying a preparation pulse to the cells of the selected row
before performing the addressing so as to perform an addressing
preparation for setting the wall voltage of each cell to a
predetermined level; generating the discharge having a first
intensity for cells to be lit in the addressing so as to make a
level of the wall voltage set in the addressing preparation
maintain a sufficient level to regenerate a discharge in a light
sustaining operation; and generating the discharge having a second
intensity for cells not to be lit in the addressing so as to make
the level of the wall voltage set in the addressing preparation
decrease to a level such that a discharge cannot restart in the
sustaining operation..].
.[.11. The method according to claim 10, further comprising:
biasing each of the data electrodes to a first potential or a
second potential in accordance with the display data of one row
synchronizing with the row selection by an independent potential
control with respect to each of the scanning electrodes..].
.[.12. The method according to claim 10, further comprising:
applying a voltage to an electrode gap of the cells generating a
discharge in the addressing, in the addressing preparation the
voltage increasing from a first set value to a second set value, so
as to adjust the wall voltage of the electrode gap by generating
plural discharges or a continuous discharge in a rising period of
the voltage..].
.[.13. The method according to claim 6, further comprising: biasing
each of the data electrodes to a first potential or a second
potential in accordance with the display data of one row
synchronizing with the row selection by an independent potential
control with respect to each of the scanning electrodes..].
.[.14. The method according to claim 6, wherein the discharge is
generated one time in the cells of the selected row in the
addressing..].
.[.15. The method according to claim 6, wherein the row selection
is performed in a order such that in a second row selection and
after the second row selection the discharge in a former row
selection become effective as a priming discharge..].
.[.16. The method according to claim 6, further comprising:
dividing the rows of the screen into a group of odd rows and a
group of even rows; addressing each group by time sharing; and
applying a voltage to all cells of the latter group between the
addressing of the former group and the addressing of the latter
group, so as to generate a priming discharge..].
.[.17. The method according to claim 6, further comprising:
disposing one or more auxiliary electrodes that are similar to the
scanning electrode at the outside of the screen in a row direction;
and applying a voltage to the one or more auxiliary electrodes in
the addressing for generating a priming discharge before a first
row selection..].
.[.18. The method according to claim 17, further comprising:
dividing the rows of the screen into a group of odd rows and a
group of even rows; addressing each group by time sharing; and
applying a voltage to the one or more auxiliary electrodes close to
the row that is selected first in the latter group between the
addressing of the former group and the addressing of the latter
group, so as to generate the priming discharge..].
.[.19. A display device comprising: a gas-discharge panel having a
display screen including cells arranged in rows and columns, and
having a structure in which a scanning electrode for selecting a
corresponding row and a data electrode for selecting a
corresponding column cross each other at a corresponding cell, at
least one of the scanning electrode and data electrode is covered
with a dielectric layer for providing a wall voltage, and a
discharge space is continuous over an entire length of each of the
columns; a drive circuit performing line-sequential addressing to
control the wall voltage of all cells of the display screen in
accordance with binary display data, and sustaining by applying the
alternating voltage to all cells of a selected row, wherein the
drive circuit generates a discharge having either a first intensity
or a second intensity depending on the display data corresponding
to each of the cells of the selected row for each selection of the
row as the addressing..].
.[.20. The display device according to claim 19, further
comprising: a drive circuit that applies a voltage to an electrode
gap of the cells generating a discharge in the addressing, in an
addressing preparation, the voltage increasing from a first set
value to a second set value, the drive circuit adjusting the wall
voltage of the electrode gap by generating plural discharges or a
continuous discharge in a rising period of the voltage as the
addressing preparation..].
.[.21. A method for driving a gas-discharge panel in which
point-sequential addressing is performed for setting a state of
cells arranged in rows and columns, the method comprising:
generating a discharge in a selected cell, irrespective of a state
to be set in the cell for each selection in the addressing, an
intensity of the discharge in the cell being set in accordance with
state setting data corresponding to the cell..].
.[.22. A method for driving a gas-discharge panel in which a
plurality of discharge cells each having a memory function produced
by a wall charge are arranged in a matrix, the method comprising:
applying a predetermined preparation pulse to all of the discharge
cells arranged in the matrix, simultaneously, so as to set a wall
charge of each of the discharge cells to a predetermined level;
addressing to make the discharge cells of the matrix forming the
wall charge perform line-sequential addressing discharges;
displaying by applying a predetermined sustain pulse to the
discharge cells arranged in the matrix, so as to make the addressed
discharge cells perform sustain discharges; and the addressing
including generating a discharge in the discharge cells of the
matrix, wherein a discharge of a first intensity is generated in
the discharge cells to be addressed by applying a voltage producing
a discharges having a level sufficient to store sufficient wall
charge for restarting the discharges in the displaying, while a
discharge of a second intensity is generated in the discharge cells
not to be addressed, the second intensity lowering a level of the
wall charge set in the applying to a level that disables restarting
the discharge in the displaying..].
.[.23. A method for driving a gas-discharge panel in which a
plurality of discharge cells, each having a memory function
produced by a wall charge, are arranged in a matrix, the method
comprising: applying a preparation pulse, simultaneously to all of
the discharge cells arranged in the matrix to set a wall charge of
each of the discharge cells to a first level; and addressing the
discharge cells to perform line-sequential addressing discharges,
the addressing including generating a first intensity discharge or
a second intensity discharge in the discharge cells of the matrix,
wherein a first intensity discharge is generated in the discharge
cells to be lit by applying a voltage in the discharge cells to be
lit to increase the wall charge level to a second level greater
than the first level set after the applied preparation pulse to
achieve restart of a discharge in a light sustaining operation and
a second intensity discharge is generated in the discharge cells
not to be lit by applying a voltage in the discharge cells not to
be lit to lower a wall charge level to a third level less than the
first level set after the applied preparation pulse to prohibit
restart of a discharge in the light sustaining operation..].
.[.24. A method for driving a gas-discharge panel having a display
screen including cells arranged in rows and columns, a scanning
electrode for selecting a corresponding row and a data electrode
for selecting a corresponding column crossing at a corresponding
cell, the scanning electrode making a main electrode pair with a
third electrode at respective corresponding cells, at least two of
the two electrodes making the main electrode pair and the data
electrode being covered with a dielectric layer for providing wall
voltage, the method comprising: performing an addressing
preparation to initialize the wall voltage of all cells of the
screen, performing line-sequential addressing to control the wall
voltage of all cells of the screen in accordance with binary
display data and sustaining by applying an alternating voltage to
all cells of a selected row, repeatedly; applying a voltage to at
least one of electrode gaps of the cells generating a discharge in
the addressing, in the addressing preparation the voltage
increasing from a first set value to a second set value, so as to
adjust the wall voltage of the electrode gap by generating plural
discharges or a continuous discharge in a rising period of the
voltage; and setting the voltage to be applied to the electrode gap
to which the increasing voltage is applied higher than the second
set value irrespective of a value of display data, when a scanning
pulse for selecting a corresponding row is applied to the scanning
electrode in the addressing..].
.[.25. The method according to claim 24, wherein the electrode gap
to which the increasing voltage is applied is the electrode gap of
the main electrode pair..].
.[.26. The method according to claim 24, wherein a discharge space
of the gas-discharge panel is continuous over an entire length of
each of the columns..].
.Iadd.27. A method for driving a plasma display panel in which an
address electrode and a pair of main electrodes including a scan
electrode define a display cell, and displaying a frame which
includes a plurality of subfields, at least one subfields having an
addressing preparation period and an addressing period, the method
comprising: applying a voltage changing with time between the
address electrode and the scan electrode in the addressing
preparation period and attained voltage of the voltage is equal to
or less than the discharge starting voltage between the address
electrode and the scan electrode; applying an address voltage to
the address electrode and a scan voltage to the scan electrode
during the addressing period, wherein the voltage between the
address electrode and the scan electrode during the addressing
period is greater than the attained voltage during the addressing
preparation period..Iaddend.
.Iadd.28. A method for driving a plasma display panel in which an
address electrode and a pair of main electrodes including a scan
electrode define a display cell, and displaying a frame which
includes a plurality of subfields, at least one subfields having an
addressing preparation period and an addressing period, the method
comprising: applying a first voltage changing to positive direction
and a second voltage changing to negative direction to the scan
electrode applying an address pulse to address electrode and a scan
pulse to the scan electrode wherein attained voltage between the
main electrodes during applying the first voltage is greater than
discharge start voltage between the main electrodes, and attained
voltage between the main electrodes during applying the second
voltage which is less than the discharge starting
voltage..Iaddend.
.Iadd.29. A method according to claim 27, wherein the amount of the
wall voltage between the address electrode and the scan electrode
is equal to 0v after the voltage is applied in the addressing
preparation period..Iaddend.
.Iadd.30. A method according to claim 27, wherein the amount of the
wall voltage between the address electrode and the scan electrode
is equal to 0 volts after the voltage changing with time is applied
in the addressing preparation period when the attained voltage of
the ramp voltage with time is equal to the discharge starting
voltage between the address electrode and the scan
electrode..Iaddend.
.Iadd.31. A method according to claim 27, wherein the voltage
applied to the address electrode is relatively positive to the
voltage applied to the scan electrode in the addressing preparation
period..Iaddend.
.Iadd.32. A method according to claim 27, wherein the voltage
applied to the address electrode is relatively positive to the
voltage applied to the scan electrode in the addressing
period..Iaddend.
.Iadd.33. A method according to claim 27, wherein the voltage
changing with time includes ramp waveform, obtuse waveform and
step-like waveform..Iaddend.
.Iadd.34. A method according to claim 27, wherein during the
addressing period the pulse width applied to the address electrode
is not greater than 1 .mu.s..Iaddend.
.Iadd.35. A method according to claim 28, wherein the first voltage
attains to positive voltage and the second voltage attains to
negative voltage..Iaddend.
.Iadd.36. A method according to claim 28, wherein a polarity of
voltage applied between the pair of main electrodes when the first
voltage is applied are opposite to a polarity of voltage applied
between the pair of main electrodes when the second voltage is
applied..Iaddend.
.Iadd.37. A method according to claim 28, wherein a polarity of
voltage applied between the address electrode and the scan
electrode when the first voltage is applied are opposite to a
polarity of voltage applied between the address electrode and the
scan electrode when the second voltage is applied..Iaddend.
.Iadd.38. A method according to claim 27, wherein during the
addressing preparation period adjustment of wall voltage is
performed for both the electrode gap between the main electrodes
and the electrode gap between the address electrode and the scan
electrode..Iaddend.
.Iadd.39. A method for driving a plasma display panel in which
addressing is performed for cells arranged in rows and columns to
be lit, the method comprising: applying at least a pulse changing
voltage with time to cause discharge in the cell before the
addressing is performed; applying an addressing pulse to the cells
to be lit; wherein the pulse applied in the cell before the
addressing has voltage which is not greater than the discharge
start voltage in the cell..Iaddend.
.Iadd.40. A method for driving a plasma display panel according to
claim 42, wherein the pulse changing voltage with time is ramp
waveform, obtuse waveform, or step-like waveform..Iaddend.
.Iadd.41. A method for driving a plasma display panel according to
claim 39, wherein the addressing pulse has pulse width of 1 .mu.s
which enables the addressing..Iaddend.
.Iadd.42. A method for driving a plasma display panel according to
claim 39, wherein the addressing pulse is applied to each one of
every two rows..Iaddend.
.Iadd.43. A method for driving a plasma display panel according to
claim 39, wherein the discharge caused by the pulse changing
voltage with time supplies priming particle to the cell..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for driving a
gas-discharge panel such as a plasma display panel (PDP) or a
plasma addressed liquid crystal (PALC), and a display device using
the gas-discharge panel.
A plasma display panel is coming into wide use as a large screen
display device for a television set taking advantage of
commercialization of color display. Along with the expansion of the
market, requirement for reliability of operation has become more
rigorous.
2. Description of the Prior Art
As a color display device, an AC type plasma display panel having
three-electrode surface discharging structure is commercialized.
This device has a pair of main electrodes for sustaining discharge
disposed for each row of matrix display, and an address electrode
for each column. Diaphragms for suppressing discharge interference
between cells are disposed like a stripe. A discharge space is
continuous over the entire length of each column. This AC type
plasma display panel utilizes a memory function performed by wall
charge on a dielectric layer covering the main electrodes on
occasion of displaying. Namely, one pair of main electrodes is
assigned to a scanning electrode and the address electrode is
assigned to a data electrode for addressing by a line-sequential
format for controlling the charging state of each cell
corresponding to the display contents. After that, a sustaining
voltage (Vs) having alternating polarities is applied to all pairs
of the main electrodes simultaneously. Thus, a cell voltage (Vc)
that is a sum of the wall voltage (Vw) and the applied voltage can
exceeds a discharge starting voltage (Vf) only in a cell having a
wall discharge above a predetermined quantity, so that the surface
discharge occurs along the surface of the substrate for each
application of the sustaining voltage. By shortening the period of
applying the sustaining voltage, continuous displaying state can be
observed.
Concerning a display of sequential images like a television, the
addressing and the sustaining are repeated. In general, in order to
prevent fluctuations of the display, preparation of addressing is
performed for making the charged stale uniform over the entire
screen, after sustaining of an image and before addressing of the
next image.
In the conventional addressing, the charged quantity of the wall
charge (wall voltage) is altered by generating the addressing
discharge in either the cell to be lighted or the cell not to be
lighted. In the writing address format, the wall charge remaining
in the display screen is erased as preparation for addressing, and
the addressing discharge is generated only in the cell to be
lighted, so that an adequate quantity of wall charge is generated
in the cell. In the erasing address format, an adequate quantity of
wall charge is generated in all cells as preparation of addressing,
and then the addressing discharge is generated only in the cell not
to be lighted, so that the wall charge in the relevant cell is
erased.
SUMMARY OF THE INVENTION
In the above-mentioned line-sequential addressing, the charge that
contributes to the priming effect helping the addressing discharge
occur easily is a space charge remaining after generated by the
discharge for the preparation of addressing and a space charge
generated by addressing discharge in the cell in the upstream side
of the row selection (scanning). However, if the cell in the
upstream side is not required to generate the addressing discharge
(like a cell not to be lighted in the write addressing format),
only the space charge remaining after generated at the stage of the
preparation for addressing can contribute to the priming effect
since the addressing discharge is not generated in the upstream
side. Since the space charge decreases along with time passing, the
remaining quantity of the space charge will be smaller, as the
addressing is coming to an end, so that delay of discharging
becomes larger. For this reason, in a cell of a row that is
selected at relatively late timing, there was a case where the
addressing discharge cannot occur within the row selection period
(scanning period for one row) defined by a scan pulse width,
resulting in a display defect. An example of the display defect is
a "black noise" in which a part or a whole of the upper edge of a
belt cannot be lighted, when the belt is displayed in the lower
portion of the screen that is scanned vertically. Especially, in
the structure in which the discharge space is defined by a
diaphragm having a stripe pattern for each column, movement of the
space charge generating the priming effect can occur only in each
column, resulting in a display defect.
A method for improving the above-mentioned problem is proposed in
Japanese Unexamined Patent Publication 9-6280(A), in which a
priming discharge for forming the space charge is generated in the
row to be selected before applying the scanning pulse that selects
the row. The priming discharge is generated in all cells of the row
regardless of the display contents, so that the addressing
discharge almost surely occurs.
However, in the conventional driving method, since a priming pulse
for generating the priming discharge is applied to the next row to
be selected at the same time as application of the scanning pulse
to the selected row, it is difficult to optimize the pulse width
and the peak value, so that the control becomes complicated. In
addition, since the pulse width should be set to a little larger
for ensuring generation of the priming discharge, the priming pulse
should be applied for each row, and the time necessary for the
addressing becomes longer. If the timing for applying the pulse is
shifted between rows, the row selection period becomes a sum of the
priming pulse width and the scanning pulse width, so that the time
necessary for the addressing becomes even longer.
The object of the present invention is to improve the reliability
of the addressing while suppressing enlargement of the time
necessary for the addressing.
In the present invention, while addressing for controlling the
state of the cell in accordance with the state setting data such as
display data, it is not selected whether the addressing discharge
exists or not, but the quantity of addressing discharge (movement
of the electric charge). Namely, a voltage sufficient for
generating addressing discharge above the minimum value regardless
of the display contents is applied to all of the cells to be
addressed. The intensity of the electric discharge depends on the
applied voltage.
For example, when the line-sequential addressing is adopted, the
space charge that contributes to the priming effect in the row that
will be selected next is generated in all of the cells included in
the selected row. Therefore, the addressing discharge can be
certainly generated for any display pattern by performing the row
selection in the order that makes the distance between the nth
selected row and the (n+1)th selected row within a predetermined
range so that the space charge generated by the addressing
discharge becomes effective. If the scanning pulse width is
shortened in accordance with increase of the probability of the
addressing discharge, the display can be speed up.
The wall voltage can be varied by the addressing discharge in the
addressing of the gas-discharge panel in which each cell is charged
by the wall charge. Therefore, the wall voltage (the target value)
before change is set so that the wall voltage after change becomes
the desired value.
FIGS. 1A and 1B show the change in the wall voltage in the
addressing of the AC type plasma display panel to which the present
invention is applied.
The variation of the wall voltage can be adjusted by setting the
intensity of the discharge. However, the variation of the electrode
potential will vary either in the direction from a high level to a
low level or the opposite direction. Therefore, the combination of
lighting or not lighting and the intensity of the discharge
includes two patterns as described below.
In the case of writing address format, the wall voltage Vw between
main electrodes is set to a value Vw1 within a non-lighting range
in which the sustaining discharge cannot be generated as a
preprocess of the addressing process. The non-lighting range means
a range in which the cell voltage does not exceeds the discharge
starting voltage even if the sustaining voltage having the same
polarity with the wall voltage Vw is applied. The lower limit of
the non-lighting range is the threshold value Vth2 having the
negative polarity, and the upper limit of the non-lighting range is
the threshold value Vth1 having the positive polarity. In the
addressing process, a strong addressing discharge is generated for
the selected cell (the cell to be lightened), and the wall voltage
Vw is changed to a value in the lighting range in which the
sustaining discharge can be generated in the polarity opposite to
the previous polarity. In the non-selected cell (the cell not to be
lightened), a weak addressing discharge is generated for the
priming. In this case, the wall voltage Vw is changed from the
value Vw1 into a lower value (zero in the figure).
In the case of erasing address format, the wall voltage Vw between
main electrodes is set to a value Vw2 within a lighting range in
which the sustaining discharge can be generated as a preprocess of
the addressing process. In the addressing process, a strong
addressing discharge is generated for the non-selected cell, and
the wall voltage Vw is changed from the value Vw2 into a value in
the non-lighting range (zero in the figure). In the selected cell,
a weak addressing discharge is generated for the priming. In this
case, the wall voltage Vw is changed from the value Vw2 into a
value Vw2' in the lighting-range.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B show variations of the wall voltage in the
addressing of the AC type plasma display panel to which the present
invention is applied.
FIG. 2 is a schematic drawing of a plasma display device in
accordance with the present invention.
FIG. 3 is a perspective view showing the inner structure of the
plasma display panel.
FIG. 4 is a diagram showing a structure of the field.
FIG. 5 shows voltage waveforms in a first example of the drive
sequence.
FIG. 6 shows voltage waveforms in a second example of the drive
sequence.
FIG. 7 shows voltage waveforms in a third example of the drive
sequence.
FIG. 8 shows voltage waveforms in a fourth example of the drive
sequence.
FIG. 9 is a schematic diagram of the main electrode arrangement in
accordance with a second embodiment.
FIG. 10 shows voltage waveforms in a fifth example of the drive
sequence.
FIG. 11 shows voltage waveforms in a sixth example of the drive
sequence.
FIGS. 12A-12C show voltage waveforms of the addressing preparation
period.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 is a schematic drawing of a plasma display device 100 in
accordance with the present invention.
The plasma display device 100 includes an AC type plasma display
panel 1 that is of a thin-type and matrix-type color display device
and a driving unit 80 for selectively lighting a plurality of cells
C that make up a screen ES having m columns and n rows. The plasma
display device 100 is used for a wall-hung television set or a
monitor of a computer set.
The plasma display panel 1 has main electrodes X, Y that makes up
electrodes pairs and are arranged in parallel for generating
sustaining discharge (or also called display discharge). The main
electrodes X, Y and address electrodes A cross each other in each
cell C so as to form the three-electrode plane discharge structure.
The main electrodes X, Y extend in the row direction (the
horizontal direction) of the screen ES, and the main electrode Y is
used for a scanning electrode that selects cells C row by row in
addressing. The address electrodes A extend in the column direction
(the vertical direction), and are used for a data electrode that
select cells C row by row. The area where the group of the main
electrodes and the group of the address electrodes in the
substrates surface becomes the display area (i.e., the screen
ES).
The driving unit 80 includes a controller 81, a data processing
circuit 83, a power source circuit 84, an X-driver 85, a scan
driver 86, a Y-common driver 87, and an address driver 89. The
driving unit 80 is disposed at the rear side of the plasma display
panel 1. Each driver and the electrodes of the plasma display panel
1 are connected electrically by a flexible cable (not shown). The
driving unit 80 is provided with field data DF indicating intensity
levels (gradation level) of colors R, G and B of each pixel from an
external equipment such as a TV tuner or a computer, as well as
various synchronizing signals.
The field data DF are temporarily stored in a frame memory 830 in
the data processing circuit 83, and then are converted into
subfield data Dsf. The subfield data Dsf are stored in the frame
memory 830 and transferred to the address driver 89 at proper time.
The value of each bit of the subfield data Dsf is information
indicating whether the cell is required to be lightened or not in
the subfield for realizing the gradation mentioned below. More
specifically, it is information indicating whether the addressing
discharge is strong or weak.
The X-driver 85 applies the driving voltage to all of the main
electrodes X simultaneously. The electric commonality of the main
electrodes X can be realized not only by the illustrated linkage on
the panel in FIG. 2 but by wiring inside the X-driver 85 or by
wiring of the connection cable. The scan driver 86 applies the
driving voltage to the main electrode Y of the selected row in
addressing. The Y-common driver 87 applies the driving voltage to
all of the main electrodes Y simultaneously in sustaining. In
addition, the address driver 89 applies the driving voltage to the
total m of address electrodes A in accordance with the sub field
data Dsf for generating the first or second intensity of addressing
discharge. These drivers are supplied with a predetermined electric
power by the power source circuit 84 via wiring conductors (not
shown).
FIG. 3 is a perspective view showing the inner structure of the
plasma display panel 1.
In the plasma display panel 1, a pair of main electrodes X, Y is
arranged for each row on the inner side of a glass substrate 11
that is a base material of the front side substrate structure. The
row is an array of cells in the horizontal direction in the screen.
Each of the main electrodes X, Y includes a transparent conductive
film 41 and a metal film (a bus conductor) 42, and is coated with a
dielectric layer 17 that is made of low melting point glass and has
thickness of approximately 30 microns. The surface of the
dielectric layer 17 is provided with a protection film 18 made of
magnesia (Mg0) having thickness of approximately several thousands
angstroms. The address electrodes A are arranged on the inner
surface of a glass substrate 21 that is a base material of the rear
side substrate structure, and is coated with a dielectric layer 24
having thickness of approximately 10 microns. A diaphragm 29 having
linear band shape of 150 micron height is disposed between the
address electrodes A on the dielectric layer 24. Discharge spaces
30 are defined by these diaphragms 29 in the row direction for each
subpixel (small lighting area), and the gap size of the discharge
spaces 30 is defined. Three fluorescent layers 28R, 28G, 28B for
red, green and blue colors are disposed so as to cover the inner
wall of the rear side including the upper portion of the address
electrode A and the side wall of the diaphragm 29. The discharge
space 30 is filled with a discharge gas containing neon as the main
ingredient and xenon. The fluorescent layers 28R, 28G, 28B are
locally pumped to emit light by ultraviolet light emitted by the
xenon gas on discharge. A pixel includes three subpixels aligned in
the row direction. A structure in each subpixel is the cell
(display element) C. Since the arrangement pattern of the diaphragm
29 is a stripe pattern, each part of the discharge space 30
corresponding to each column is continuous in the column direction
over all rows.
A method for driving the plasma display panel 1 in the plasma
display device 100 will be explained as follows. First,
reproduction of the gradation will be explained generally, and then
driving sequence that is unique to the present invention will be
explained in detail.
FIG. 4 shows a structure of the field.
The gradation is reproduced by controlling lighting with binary
data in displaying a television image. Therefore, each field f of
the sequential input image is divided into, for example, eight
subframes sf1, sf2, sf3, sf4, sf5, sf6, sf7 and sf8 (the numerical
subscripts represent display order). In other words, each field f
that makes up the frame is replaced with eight subframes sf1-sf8.
Each frame is divided into eight when reproducing a non-interlace
image such as an output of a computer. Weights are assigned so that
the relative ratio of the intensity in these subfields sf1-sf8
becomes approximately 1:2:4:8:16:32:64:128 for setting the number
of sustaining discharge. Since 256 steps of intensity can be set by
combination of light/non-light of each subfield for each color, R,
G, B, the number of color that can be displayed becomes 256.sup.3.
It is not necessary to display subfields sf1-sf8 in the order of
the weight of intensity. For example, optimizing can be performed
in such a way that the subfield sf8 having a large weight is
disposed at the middle of the field period Tf.
The subfield period Tsf.sub.j that is assigned to each subfield
sf.sub.j (j=1-8) includes a preparation period TR for adjusting
charge by the ramp voltage, an address period TA for forming a
charge distribution corresponding to a display contents and a
sustain period TS for sustaining the lightened state so as to
ensure the intensity corresponding to the gradation level In each
subfield period Tsf.sub.j, lengths of the preparation period TR and
the address period TA are constant regardless of the weight of the
intensity, while the larger the weight of the intensity, the longer
the length of the sustain period TS becomes. Namely, the
eight-subfield periods Tsf.sub.j corresponding to one field f are
different from each other.
FIG. 5 is a diagram of voltage waveforms showing a first example of
the drive sequence. In this figure, main electrodes X, Y are
denoted with a suffix (1, 2, . . . n) representing the arrangement
order of the corresponding row, and the address electrodes A are
denoted with a suffix (1-m) representing the arrangement order of
the corresponding column. Other figures explained below will be in
the same way.
The drive sequence that is repeated in every subfield is generally
explained as follows.
In the preparation period TR, all of address electrodes A1-Am are
supplied with the pulse Pra1 and the opposite polarity pulse Pra2
in sequence, all of the main electrodes X1-Xn are supplied with the
pulse Prx1 and the opposite polarity pulse Prx2 in sequence, and
all of the main electrodes Y1-Yn are supplied with the pulse Pry1
and the opposite polarity pulse Pry2 in sequence. The pulse
application means to bias the electrode temporarily to a different
potential from the reference potential (e.g., the grand level). In
this example, pulses Pra1, Pra2, Prx1, Prx2, Pry1 and Pry2 are ramp
voltage pulses having a rate of change that generates minute
discharge. The pulses Pra1, Prx1 have the negative polarity, while
the pulse Pry1 has the positive polarity. Application of the pulses
Pra2, Prx2 and Pry2 having ramp waveforms enable the wall voltage
to be adjusted into the value corresponding to the subtract of the
discharge starting voltage and the pulse amplitude. The pulses
Pra1, Prx1 and Pry1 are applied so that the "former lightened cell"
that was lightened in the former subfield and the "former
non-lightened cell" that was not lightened in the former subfield
generate appropriate wall voltage.
In the address period TA, the scanning pulse Py is applied to the
main electrodes Y1-Yn in the arrangement order. At the same time
with this row selection, an address pulse Pa having the polarity
opposite to the scanning pulse Py and the peak value corresponding
to the subfield data Dsf of the selected row is applied to the
address electrodes A1-Am. Namely, strong discharge is generated in
the selected cell, while weak discharge is generated in the
non-selected cell. When the scanning pulse Py and the address pulse
Pa are applied, discharge occurs between the address electrode A
and the main electrode Y, which becomes a trigger for generating
discharge between the main electrodes X and Y. These sequential
discharges, i.e., the addressing discharge, are related to a
discharge starting voltage Vf.sub.AY between the address electrode
A and main electrode Y (hereinafter, referred to as an electrode
gap AY) and a discharge starting voltage Vf.sub.XY between the main
electrodes X, Y (hereinafter, referred to as an electrode gap XY).
Therefore, in the above-mentioned preparation period TR, adjustment
of the wall voltage is performed for both the electrode gap XY and
the electrode gap AY. The wall voltage between the electrode gaps
AY may be a value such that the discharge cannot occur before
applying the scanning pulse Py to the main electrode Y.
In the sustain period TS, a sustain pulse Ps having a predetermined
polarity (plus polarity in the illustrated example) is applied to
all of the main electrodes Y1-Yn at first. Then, the sustain pulse
Ps is applied to the main electrodes X1-Xn and the main electrodes
Y1-Yn alternately.
In this example, the final sustain pulse Ps is applied to the main
electrodes X1-Xn. When the sustain pulse Ps is applied, a surface
discharge will occur in the cell that is lighted this time and has
remaining wall charge in the address period TA. Every time when the
surface discharge occurs, the polarity of the wall voltage between
electrodes changes. All of the address electrodes A1-Am are biased
to the same polarity as the sustain pulse Ps in order to prevent
unnecessary discharge in the sustain period TS.
The wall voltage of the electrode gap XY at the end of the
preparation period TR is represented by Vw1 (X side is positive),
while the minimum value of the wall voltage of the electrode gap XY
when the cell is lighted in the sustain period TS is represented by
V.sub.TH (absolute value without polarity). In the plasma display
panel 1, the main electrodes X, Y are arranged symmetrically with
respect to the surface discharge gap. Therefore, the threshold
levels Vth1, Vth2 shown in FIGS. 1A and 1B have relationship such
that Vth1=V.sub.TH and Vth2=-V.sub.TH. Concerning the selected
cell, the strong addressing discharge makes the wall voltage of the
electrode gap XY change from Vw1 to -V.sub.TH or below. Concerning
the non-selected cell, a weak addressing discharge makes the wall
voltage of the electrode gap XY changes to a value higher than
-V.sub.TH and lower than V.sub.TH (preferably zero or a value
nearly equal to zero).
In order to control the addressing discharge, wall voltage is
preferably adjusted in the preparation process as explained In
Japanese Patent Application No. 10-157107. Usage of the ramp wave
in the preparation process makes the adjustment of the wall voltage
easy. When plural minute discharges occur continuously or
continuous discharges occur by applying the ramp wave voltage, the
sum of the applied voltage and the wall voltage during discharge is
maintained at the value almost equal to the discharge starting
voltage. Therefore, a subtraction from the discharge starting
voltage of the peak voltage (pulse amplitude) of the ramp wave
becomes (i.e., yields) the wall voltage after the ramp wave is
applied. Compared with a rectangular wave, the ramp wave has less
quantity of light emission. It is also advantageous in reducing the
background intensit.
The voltage waveform used for the preparation process is not
limited to a ramp wave. Only the requirement is that the voltage
between the electrodes increases simply from the first set value to
the second set value, while plural minute discharges can occur
continuously or continuous discharges can occur. For example, the
ramp waveform can be replaced with an obtuse waveform or a
step-like waveform shown in FIG. 12. Alternatively, the voltage
waveform may be a combination of plural waveforms selected from the
ramp waveform, the obtuse waveform and the step-like waveform.
An example of the applied voltages is explained as follows. The
discharge starting voltage of the electrode gap XY is 220 volts,
the discharge starting voltage of the electrode gap AY is 170
volts. Hereinafter, concerning the polarity of the applied voltage
and the wall voltage, the X side is regarded as positive in the
electrode gap XY, while the A side is regarded as positive in the
electrode gap AY.
In the preparation period TR, the widths of the pulses Pra1, Prx1
and Pry1 is 70 .mu.s, the rate of potential change of the electrode
gap XY is -4.2V/.mu.s and the final voltage thereof is -300V, the
ratio of voltage change of the electrode gap AY is -2.8V/.mu.s and
the final voltage thereof is -200V. The wall voltage at the end of
the pulse application is 80V for the electrode gap XY and 30V for
the electrode gap AY. The widths of the pulses Pra2, Prx2 and Pry2
are 25 .mu.s, the rate of potential change of the electrode gap XY
is 6.8V/.mu.s and the final voltage is 170V.
The rate of potential change of the electrode gap AY is 6.8V/.mu.s
and the final voltage is 170V. The wall voltage at the end of the
pulse application is 50V for the electrode gap XY and 0V for the
electrode gap AY.
In the address period TA, the address electrode potential of the
strong addressing discharge is 80V, the address electrode potential
of the weak addressing discharge is 0V, and the potential of the
main electrode X is 80V. The potential of the main electrode Y when
the scanning pulse is applied is -140V, while the potential of the
main electrode Y when the scanning pulse is not applied is 0V. The
wall voltage of the electrode gap XY at the end of the strong
addressing discharge is -120V, while the wall voltage of the
electrode gap XY at the end of the weak addressing discharge is
0V.
In the sustain period TS, the amplitude of the sustain pulse Ps is
170V, and the address electrode potential is 85V. In this case, the
minimum value of the wall voltage for generating the sustaining
discharge is 70V.
In the conventional technique, addressing of a row needs 3 .mu.s.
However, in this example, since the addressing discharge in the
upstream side of row selection contributes to the priming in the
downstream, the address pulse Pa having the pulse width of 1 .mu.s
enables stable addressing.
FIG. 6 is a diagram of the voltage waveform showing a second
example of the drive sequence. This example is an erasing address
format, in which the strong discharge occurs in the non-selected
cell.
In the preparation period TR, the pulse having the ramp waveform is
applied in the same way as the example shown in FIG. 5, so that the
wall voltage of the electrode gap XY is controlled to the target
value of the preparation process.
In the address period TR, a weak addressing discharge is generated
in the selected cell when applying the scanning pulse. The
intensity of discharge is set to the value such that the wall
voltage of the electrode gap XY after addressing discharge remains
within the lighting range. In the non-selected cell, a strong
addressing discharge is generated when applying the scanning pulse,
so that the wall voltage of the electrode gap XY is changed to a
value within the non-lighting range. The intensity of the discharge
when applying the scanning pulse is controlled by the potential of
the address electrode in the same way as the example shown in FIG.
5.
The wall voltage of the electrode gap XY at the end of the
preparation period is set to Vw2 (X side is positive), and the
minimum value of the wall voltage of the electrode gap XY for the
cell to be lightened in the sustain period TS is set to V.sub.TH
(absolute value). For the selected cell, the wall voltage of the
electrode gap XY is changed by the weak addressing discharge in the
range from Vw2 to Vth or more. For the non-selected cell, the wall
voltage of the electrode gap XY is changed by the strong addressing
discharge to a value higher than -V.sub.TH and lower than V.sub.TH
(preferably zero or a value nearly equal to zero).
An example of the applied voltages is explained as follows. The
discharge starting voltage of the electrode gap XY is 220 volts,
the discharge starting voltage of the electrode gap AY is 170
volts. Hereinafter, concerning the polarity of the applied voltage
and the wall voltage, the X side is regarded as positive in the
electrode gap XY, while the A side is regarded as positive in the
electrode gap AY.
In the preparation period TR, the widths of the pulses Pra1, Prx1
and Pry1 are 70 .mu.s, the rate of potential change of the
electrode gap XY is -6.0V/.mu.s and the final vote thereof is 420V,
the ratio of the voltage change of the electoral gap AY is
-3.6V/.mu.s and the final voltage thereof is -250V. The wall
voltage at the end of the pulse application is 200V for the
electrode gap XY and 80V for the electrode gap AY. The widths of
the pulses Pra2, Prx2 and Pry2 are 25 .mu.s, the rate of potential
change of the electrode gap XY is 2.0V/.mu.s and the final voltage
is 50V. The rate of potential change of the electrode gap AY is
5.2V/.mu.s and the final voltage is 130V. The wall voltage at the
end of the preparation period is 170V for the electrode gap XY and
40V for the exclude gap AY.
The rate of potential change of the electrode gap AY is 5.2V/.mu.s
and the final voltage is 130V. The wall voltage at the end of the
preparation period is 170V for the electrode gap XY and 40V for the
electrode gap AY.
In the address period TA, the address electrode potential of the
strong addressing discharge is 40V, the address electrode potential
of the weak addressing discharge is 0V, and the potential of the
main electrode X is 0V. The potential of the main electrode Y when
the scanning pulse is applied is -100V, while the potential of the
main electrode Y when the scanning pulse is not applied is 0V. The
wall voltage of the electrode gap XY at the end of the weak
addressing discharge is 120V, while the wall voltage of the
electrode gap XY at the end of the strong addressing discharge is
0V.
In the sustain period TS, the amplitude of the sustain pulse Ps is
170V, and the address electrode potential is 85V. In this case, the
minimum value of the wall voltage for generating the sustaining
discharge is 70V.
In this example too, since the addressing discharge at the upstream
side of the row selection contributes to the priming in the
downstream, the address pulse Pa having the pulse width of 1 .mu.s
enables stable addressing.
FIG. 7 is a diagram of the voltage waveform showing a third example
of the drive sequence.
In the addressing, the row selection is not required to perform in
the arrangement order. Namely, it is only required that the space
charge supplied by the addressing discharge in a certain row is
within a distance range that can contribute to the priming effect
for the later addressing discharge. In FIG. 7, even rows and odd
rows are selected alternately, and the each group of even or odd
rows is scanned by the arrangement order from the upper to the
lower. When switching from the odd row to the even row, the row
selection is performed by skipping two rows. Sufficient priming
effect was obtained by the row selection with skipping two rows in
the 25 inches and SXGA screen.
FIG. 8 is a diagram of the voltage waveform showing a fourth
example of the drive sequence.
The rows constituting the screen are divided into the group of odd
rows and the group of even rows. The preparation periods TR1, TR2
and the address periods TA1, TA2 are assigned to each group. The
sustain period TS is common to both groups.
Dividing the address process into two, the potential of the main
electrode X of the selected row can be different from the potential
of the main electrode X of the non-selected row that is adjacent to
the selected row, so that the propagation of the space charge
generated by the addressing discharge along the row direction is
controlled.
The second preparation period TR2 is provided for the following
purposes. One purpose is to readjust the potential of the even rows
since the state of the wall charge of the even rows is disturbed a
little by the addressing discharge of the odd rows (the first
address process). Another purpose is to supply the priming particle
to the addressing discharge of the head of the even row (the second
address process).
In the preparation period TR2, only the charges of the even rows
are controlled without disturbing the state of the wall charge of
the odd rows. For this reason, the pulse applied to the even rows
in the preparation period TR2 is the same as the first preparation
period TR1, while the pulse applied to the main electrodes X, Y of
the odd rows in the preparation period TR2 is the same as the
pulses Pra1 and Pra2 applied to the address electrodes A1-Am. Thus,
the applied voltage of the electrode gap AY and the electrode gap
XY within the cell of the odd rows in the preparation period TR2
becomes zero, so that the state of the wall charge cannot be
disturbed.
FIG. 9 is a schematic drawing of the main electrode arrangement of
a second embodiment. FIG. 10 shows voltage waveforms of a fifth
example of the drive sequence.
In the above-mentioned first to fourth examples, supply of the
priming particle to the first addressing discharge in the subfield
is performed by the discharge in the preparation process. In order
to ensure the supply of the priming particle, it is more effective
to generate the priming discharge after the preparation process and
before starting the addressing. For example, the outside of the
screen ES in the row direction is provided with an auxiliary main
electrode (an electrode for priming) that is similar to the main
electrodes X, Y so as to generate priming discharge by the
auxiliary main electrode. In the example shown in FIG. 9, the
auxiliary main electrodes DY1, DX1 are disposed at the outside of
the main electrodes Y1, X1 of the first row, and the auxiliary main
electrodes DY2, DX2 are disposed at the outside of the main
electrodes Yn, Xn of the final row. As shown in FIG. 10, the pulse
Pp is applied to the auxiliary main electrode DY1 so as to generate
the priming, then the scanning is started from the main electrode
Y1 that is closest to the auxiliary main electrode DY1 in the
screen. Though the peak value of the pulse Pp is the same as the
scanning pulse Py, the pulse width is set longer than the scanning
pulse P so as to increase the discharge probability. The
arrangement of the pair of auxiliary main electrodes makes the
pairs of main electrodes at the first and final rows adjacent to
the main electrodes at both sides in the same way as the other pair
of main electrodes. Therefore, the discharge condition is uniformed
and the display quality is increased.
FIG. 11 is a diagram of the voltage waveform showing a sixth
example of the drive sequence.
In the above-mentioned fourth example, the second preparation
period TR2 is provided. However, the second preparation period TR2
can be eliminated when the disturbance of the charge state of the
even rows by the address process of the odd rows is sufficiently
small. It is preferable that in order to supply the priming
particle to the first addressing discharge of the latter half of
the address process, the pair of auxiliary main electrodes may be
used so as to generate the priming discharge before the latter half
of the address process. The priming discharge can be generated just
before the address process of the odd row.
When the addressing is performed independently for the odd rows and
for even rows as explained in the fourth and sixth examples, the
main electrodes X of the odd rows can be common and controlled by
the first driver, while the main electrodes X of the even rows can
be common and controlled by the second driver.
In the above-mentioned embodiments, the target to be driven is the
plasma display panel 1 having structure in which the main
electrodes X, Y and the address electrode A are covered with the
dielectric material. However, the present invention can be also
applied to the structure in which either electrode making up a pair
is covered with the dielectric material. For example, even in the
structure that has no dielectric material for covering the address
electrode A, or the structure in which one of the main electrodes
X, Y is exposed to the discharge space 30, the sufficient wall
voltage can be generated in the electrode gaps XY, AY. The
polarity, the value, the application time and the rate of rising
change of the applied voltage are not limited to the examples. The
the present invention can be applied not only to display devices
including the plasma display panel, PALC, but also to gas-discharge
devices having other structure without utilizing the memory
function by the wall charge. The gas-discharge is not necessarily
required to be for display.
* * * * *