U.S. patent number RE43,083 [Application Number 12/043,881] was granted by the patent office on 2012-01-10 for gas dischargeable panel.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Toru Ando, Hidetaka Higashino, Naoki Kosugi, Ryuichi Murai, Nobuaki Nagao, Masaki Nishimura, Hiroyuki Tachibana, Yusuke Takata.
United States Patent |
RE43,083 |
Nishimura , et al. |
January 10, 2012 |
Gas dischargeable panel
Abstract
A gas discharge panel includes a first substrate and a second
substrate. A plurality of display electrode pairs which are each
made up of a sustain electrode and a scan electrode are formed on
the first substrate, and the first substrate and the second
substrate are set facing each other with a plurality of barrier
ribs in between so as to form a plurality of cells. In this gas
discharge panel, at least one of the sustain electrode and the scan
electrode includes: a plurality of line parts; and a discharge
developing part which makes a gap between adjacent line parts
smaller in areas corresponding to channels between adjacent barrier
ribs than in areas corresponding to the barrier ribs.
Inventors: |
Nishimura; Masaki (Kadoma,
JP), Higashino; Hidetaka (Kadoma, JP),
Murai; Ryuichi (Kadoma, JP), Takata; Yusuke
(Kadoma, JP), Nagao; Nobuaki (Kadoma, JP),
Ando; Toru (Ibaraki, JP), Kosugi; Naoki (Kadoma,
JP), Tachibana; Hiroyuki (Ibaraki, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
|
Family
ID: |
27344378 |
Appl.
No.: |
12/043,881 |
Filed: |
August 16, 2001 |
PCT
Filed: |
August 16, 2001 |
PCT No.: |
PCT/JP01/07049 |
371(c)(1),(2),(4) Date: |
August 29, 2003 |
PCT
Pub. No.: |
WO02/17345 |
PCT
Pub. Date: |
February 28, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
10344654 |
Aug 29, 2003 |
7009587 |
Mar 7, 2006 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Aug 18, 2000 [JP] |
|
|
2000-248369 |
Aug 30, 2000 [JP] |
|
|
2000-260395 |
Oct 11, 2000 [JP] |
|
|
2000-310413 |
|
Current U.S.
Class: |
345/67; 345/63;
345/66; 313/584; 315/169.4; 313/585; 345/68; 313/586; 345/69;
345/60; 313/583; 313/587; 315/169.1 |
Current CPC
Class: |
H01J
11/24 (20130101); H01J 11/12 (20130101); H01J
11/32 (20130101); G09G 3/2927 (20130101); H01J
2211/323 (20130101); G09G 2300/0426 (20130101); H01J
2211/245 (20130101); G09G 3/2022 (20130101) |
Current International
Class: |
G09G
3/28 (20060101); H01J 17/49 (20060101); G09G
3/10 (20060101) |
Field of
Search: |
;345/43,60-69,205,206,211,214 ;315/169.1-169.4,167,168
;313/492,495,504,583-587 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1200554 |
|
Dec 1998 |
|
CN |
|
0 939 420 |
|
Sep 1999 |
|
EP |
|
1 052 670 |
|
Nov 2000 |
|
EP |
|
03-187125 |
|
Aug 1991 |
|
JP |
|
04-036931 |
|
Feb 1992 |
|
JP |
|
05-290744 |
|
Nov 1993 |
|
JP |
|
8250030 |
|
Sep 1996 |
|
JP |
|
8315735 |
|
Nov 1996 |
|
JP |
|
11-133914 |
|
May 1999 |
|
JP |
|
11-212515 |
|
Aug 1999 |
|
JP |
|
11-250810 |
|
Sep 1999 |
|
JP |
|
11-297212 |
|
Oct 1999 |
|
JP |
|
11-297214 |
|
Oct 1999 |
|
JP |
|
2000-106090 |
|
Apr 2000 |
|
JP |
|
2000-294149 |
|
Oct 2000 |
|
JP |
|
2000-323045 |
|
Nov 2000 |
|
JP |
|
2001-143623 |
|
May 2001 |
|
JP |
|
2001-250484 |
|
Sep 2001 |
|
JP |
|
WO 97/20301 |
|
Jun 1997 |
|
WO |
|
Other References
Chinese Patent Application No. 200810108723.8 Office Action dated
Aug. 16, 2010, 9 pages. cited by other.
|
Primary Examiner: Dharia; Prabodh M
Claims
What is claim is:
1. A gas discharge panel in which phosphor layers corresponding to
three colors of red, green, and blue are formed one by one in a
plurality of cells, with a plurality of display electric pairs made
.[.up.]. of a sustain electrode and a scan electrode arranged so as
to cross the plurality of cells, .[.the improvement.]. .Iadd.said
panel .Iaddend.comprising: the sustain electrodes having a
plurality of separated line parts in each cell; the scan electrodes
having a plurality of separated line parts in each cell; and a
connector part connecting at least two line parts of the plurality
of line parts of the sustain electrode and scan electrode in each
cell; wherein the plurality of line parts, with adequate connector
part in each cell are relatively spaced to form a main discharge
gap that only requires a single peak discharge current waveform for
driving the sustain electrode and scan electrode.
2. The gas discharge panel of claim 1, wherein a width of each of
the plurality of cells, measured in the same direction that each of
the plurality of line parts extend, is determined according to
luminance of a phosphor layer formed in the cell.
3. The gas discharge panel of claim 1, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and a distance between two adjacent line parts decreases as
a distance from the main discharge gap increases.
4. The gas discharge panel of claim 1, wherein in each cell which
requires a lowest discharge firing voltage among the plurality of
cells, the connector part is positioned between two adjacent line
parts that are closest to each other.
5. The gas discharge panel of claim 1, wherein in each cell which
requires a highest discharge firing voltage among the plurality of
cells, the connector part is positioned between two adjacent line
parts that are farthest from each other.
6. The gas discharge panel of claim 1, wherein the sustain
electrode and the scan electrode are each formed using a metal
material.
7. The gas discharge panel of claim 6, wherein the metal material
includes Ag.
8. The gas discharge panel of claim 1, wherein the sustain
electrode and the scan electrode occupy less than 40% of a cell
area of each of the plurality of cells.
9. The gas discharge panel of claim 1, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and a distance between the connector part and the main
discharge gap increases in an order of red, green, and blue.
10. The gas discharge panel of claim 1, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and in each cell which requires a lower drive voltage among
the plurality of cells, the connector part is positioned farther
from the main discharge gap.
11. The gas discharge panel of claim 1, wherein projections are
formed on facing sides of two adjacent line parts that are closest
to the main discharge gap among the plurality of line parts.
12. A gas discharge display device comprising: the gas discharge
panel of claim 1 wherein a first substrate on which the plurality
of sustain electrodes and the plurality of scan electrodes are
formed is set facing a second substrate on which a plurality of
address electrodes are formed; and a drive circuit which drives the
plurality of sustain electrodes, the plurality of scan electrodes,
and the plurality of address electrodes.
13. The gas discharge display device of claim 12, wherein the drive
circuit applies a voltage whose waveform has a gentle slope, in a
set-up period.
14. A gas discharge panel in which a plurality of display electrode
pairs made up of a sustain electrode and a scan electrode are
arranged to cross a plurality of cells, the improvement comprising:
the sustain electrode having a plurality of separated line parts in
each cell; the scan electrode having a plurality of separated line
parts in each cell; and a discharge accelerating part located
between line parts of the sustain electrodes and/or the scan
electrodes in a plurality of cells.[.;.]..Iadd., .Iaddend. wherein
the plurality of line parts, with the discharge accelerating part
are spaced relatively to form a main discharge gap in each cell so
that only a single peak discharge current waveform is needed for
driving the sustain electrode and scan electrode in each cell.
15. The gas discharge panel of claim 14, wherein size of each of
the plurality of cells is determined according to luminance of a
phosphor layer formed in the cell.
16. The gas discharge panel of claim 14, wherein the discharge
accelerating part is shaped like any one of a triangle, a
quadrilateral, a cannon-ball, and a letter T.
17. The gas discharge panel of claim 14, a distance between
adjacent line parts decreases as a distance from the main discharge
gap increases.
18. The gas discharge panel of claim 14, wherein the sustain
electrode and the scan electrode are each formed using a metal
material.
19. The gas discharge panel of claim 18, wherein the metal material
includes Ag.
20. A gas discharge display device comprising: the gas discharge
panel of claim 14.Iadd.; .Iaddend. wherein a first substrate on
which the plurality of sustain electrodes and the plurality of scan
electrodes are formed is set facing a second substrate on which a
plurality of address electrodes are formed; and a drive circuit
which drives the plurality of sustain electrodes, the plurality of
scan electrodes, and the plurality of address electrodes.
21. The gas discharge display device of claim 20, wherein the drive
circuit applies a voltage whose waveform has a gentle slope, in a
set-up period.
.Iadd.22. A gas discharge panel in which a plurality of display
electrode pairs that are each made up of a sustain electrode and a
scan electrode are arranged so as to cross a plurality of cells
arranged along a longitudinal direction of the gas discharge panel,
a main discharge gap existing between a sustain electrode and a
scan electrode in each pair, wherein: the sustain electrode and the
scan electrode each have (a) a plurality of line parts and (b) a
connector part which connects at least two line parts out of the
plurality of line parts in each of the plurality of
cells..Iaddend.
.Iadd.23. The gas discharge panel of claim 22, wherein a plurality
of barrier ribs are provided to separate the display electrodes in
the longitudinal direction, and each connector part is provided in
a cell sandwiched between two adjacent barrier ribs..Iaddend.
.Iadd.24. The gas discharge panel of claim 22, wherein the sustain
electrode and the scan electrode occupy less than 40% of a cell
area of each of the plurality of cells..Iaddend.
.Iadd.25. The gas discharge panel of claim 22, wherein in each
sustain electrode and each scan electrode each, line parts other
than a line part that is closest to the main discharge gap are
wider than the line part that is closest to the main discharge
gap..Iaddend.
.Iadd.26. The gas discharge panel of claim 22, wherein the sustain
electrode and the scan electrode each have two, three or four line
parts..Iaddend.
.Iadd.27. A gas discharge display device comprising the gas
discharge panel of claim 22, wherein a first substrate and a second
substrate have been set to face each other, the plurality of
display electrode pairs being formed on the first substrate, a
plurality of address electrodes being formed on the second
substrate, and a drive device, which drives the plurality of
display electrode pairs and the plurality of address electrodes,
has been connected to the gas discharge panel..Iaddend.
.Iadd.28. The gas discharge display device of claim 27, wherein a
voltage whose waveform has a gentle slope is applied to the scan
electrode in a set-up period..Iaddend.
.Iadd.29. The gas discharge display device of claim 28, wherein a
voltage change of the slope is in a range of .+-.10
V/.mu.s..Iaddend.
.Iadd.30. A gas discharge panel in which a plurality of display
electrode pairs that are each made up of a sustain electrode and a
scan electrode are arranged so as to cross a plurality of cells, a
main discharge gap existing between a sustain electrode and a scan
electrode in each pair, wherein the sustain electrode and the scan
electrode each have (a) a plurality of line parts and (b) one or
more projections each of which projects toward the main discharge
gap from a side of a line part that faces toward the main discharge
gap..Iaddend.
.Iadd.31. The gas discharge panel of claim 30, wherein the sustain
electrode and the scan electrode each have at least two projections
that face each other via the main discharge gap..Iaddend.
.Iadd.32. The gas discharge panel of claim 30, wherein the sustain
electrode and the scan electrode each have a connector part which
connects at least two adjacent line parts out of the plurality of
line parts in each of the plurality of cells..Iaddend.
.Iadd.33. The gas discharge panel of claim 32, wherein phosphor
layers of red, green, and blue are formed one by one in a plurality
of cells, the sustain electrode and the scan electrode each have at
least three line parts, and a distance between the connector part
and the main discharge gap in each cell increases in an order of
red, green, and blue..Iaddend.
.Iadd.34. The gas discharge panel of claim 32, wherein some of the
plurality of cells differ from the remaining cells in a cell width
along the longitudinal direction, the sustain electrode and the
scan electrode each have at least three line parts, and in each
cell, the connector part is closer to the main discharge gap as the
cell width is smaller..Iaddend.
.Iadd.35. The gas discharge panel of claim 32, wherein phosphor
layers of red, green, and blue are formed one by one in a plurality
of cells, the sustain electrode and the scan electrode each have at
least three line parts, and in cells corresponding to phosphor
layers of one of red, green, and blue, the connector part is closer
to the -main discharge gap as a luminance of phosphor is
smaller..Iaddend.
.Iadd.36. The gas discharge panel of claim 32, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and in each cell which requires a lower drive voltage if the
connector is not provided, the connector part is positioned farther
from the main discharge gap..Iaddend.
.Iadd.37. The gas discharge panel of claim 32, wherein a plurality
of barrier ribs are provided to separate the display electrodes in
the longitudinal direction, and each connector part is provided in
a cell sandwiched between two adjacent barrier ribs..Iaddend.
.Iadd.38. The gas discharge panel of claim 32, wherein the
connector part is provided in a central part of a
cell..Iaddend.
.Iadd.39. The gas discharge panel of claim 32, wherein the
plurality of display electrode pairs are arranged along a row
direction of the panel, and a line part of a scan electrode or a
sustain electrode in each of two display electrode pairs that are
adjacent in the row direction is shared by the two display
electrode pairs..Iaddend.
.Iadd.40. The gas discharge panel of claim 32, wherein in each
sustain electrode and in teach scan electrode, the connector part
branches as the connector part is farther from the main discharge
gap..Iaddend.
.Iadd.41. The gas discharge panel of claim 32, wherein in each
sustain electrode and in each scan electrode, the connector part
includes a discharge developing part that is provided along a
longitudinal direction of the display electrodes in a
cell..Iaddend.
.Iadd.42. The gas discharge panel of claim 32, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and the line parts are connected by the connector part in a
straight line along a width direction thereof..Iaddend.
.Iadd.43. The gas discharge panel of claim 30, wherein the sustain
electrode and the scan electrode each have a projection that
projects from a side of a line part toward a side of another line
part among the plurality of line parts..Iaddend.
.Iadd.44. The gas discharge panel of claim 30, wherein in each
cell, a length of the projection in the longitudinal direction of
the line parts is 50% or less of a cell width in the longitudinal
direction..Iaddend.
.Iadd.45. The gas discharge panel of claim 30, wherein in each
cell, a length of the projection in the longitudinal direction of
the line parts is 20% or less of a cell width in the longitudinal
direction..Iaddend.
.Iadd.46. The gas discharge panel of claim 30, wherein the
projection is in a shape of a triangle, a quadrilateral, wave, or a
letter T..Iaddend.
.Iadd.47. The gas discharge panel of claim 30, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and a line part among the line parts has two projections
that project from two sides thereof toward sides of adjacent line
parts that face the two sides thereof, respectively..Iaddend.
.Iadd.48. The gas discharge panel of claim 43, wherein a distance
between the projection and a line part facing the projection is
equal to or less than the main discharge gap..Iaddend.
.Iadd.49. The gas discharge panel of claim 43, wherein a distance
between the projection and a line part facing the projection is
equal to or less than a half of the main discharge
gap..Iaddend.
.Iadd.50. The gas discharge panel of claim 43, wherein a plurality
of barrier ribs are provided to separate the display electrodes in
the longitudinal direction, and each projection is provided in a
cell sandwiched between two adjacent barrier ribs..Iaddend.
.Iadd.51. The gas discharge panel of claim 43, wherein a plurality
of barrier ribs are provided to separate the display electrodes in
the longitudinal direction, the line parts are arranged so as to
cross the barrier ribs, and one or more line parts among the line
parts have a wide projection which is larger than each barrier rib
in width, and each wide projection is provided at a region where a
line part crosses a barrier rib such that each wide projection
overlaps with the barrier rib and protrudes into a
cell..Iaddend.
.Iadd.52. The gas discharge panel of claim 32, wherein the sustain
electrode and the scan electrode each are a metal
electrode..Iaddend.
.Iadd.53. The gas discharge panel of claim 52, wherein the metal
electrode either has a layered structure of Cr/Cu/Cr or is made of
one or more materials selected from a group consisting of Ag, Pt,
Au, Al, Ni and Cr..Iaddend.
.Iadd.54. The gas discharge panel of claim 53, wherein the sustain
electrode and the scan electrode occupy less than 40% of a cell
area of each of the plurality of cells..Iaddend.
.Iadd.55. The gas discharge panel of claim 54, wherein in each
sustain electrode and each scan electrode each, line parts other
than a line part that is closest to the main discharge gap are
wider than the line part that is closest to the main discharge
gap..Iaddend.
.Iadd.56. The gas discharge panel of claim 55, wherein the sustain
electrode and the scan electrode each have two, three or four line
parts..Iaddend.
.Iadd.57. The gas discharge panel of claim 56, wherein the sustain
electrode and the scan electrode each have at least three line
parts, and a distance between any two adjacent line parts is
narrower as the two adjacent line parts are farther from the main
discharge gap..Iaddend.
Description
This application is a 371 of PCT/JP01/07049, filed Aug. 16,
2001.
1. Technical Field
The present invention relates to a gas discharge panel such as a
plasma display panel.
2. Background Art
Plasma display panels (PDPs) are one type of gas discharge panel.
PDPs enable large-screen slimline televisions to be produced
relatively easily, and so are receiving attention as
next-generation display panels. Currently, sixty-inch models have
already been commercialized.
FIG. 26 is a partial sectional perspective view showing a main
construction of a typical surface discharge AC (alternating
current) PDP. In the drawing, the z direction is a direction along
the thickness of the PDP, whilst the xy plane is a plane that is in
parallel with the panel plane of the PDP. As illustrated, this PDP
1 is roughly made up of a front panel FP and a back panel BP which
are set with their main surfaces facing each other.
A front panel glass 2 serves as a substrate for the front panel FP.
A plurality of pairs of display electrodes 4 and 5 (scan electrode
4 and sustain electrode 5) are formed on one main surface of the
front panel glass 2, so as to extend in the x direction. Surface
discharge is performed between display electrodes 4 and 5 which
form a pair. As one example, the display electrodes 4 and 5 are
made by mixing Ag with glass.
Power is supplied to the scan electrodes 4 independently of each
other. Meanwhile, the sustain electrodes 5 are all connected to the
same potential.
The main surface of the front panel glass 2 on which the display
electrodes 4 and 5 have been arranged is coated with a dielectric
layer 6 made of an insulating material and a protective layer 7, in
this order.
A back panel glass 3 serves as a substrate for the back panel BP. A
plurality of stripe address electrodes 11 are aligned with fixed
intervals on one main surface of the back panel glass 3, so as to
extend in they direction. The address electrodes 11 are made by
mixing Ag with glass.
The main surface of the back panel glass 3 on which the address
electrodes 11 have been arranged is coated with a dielectric layer
10 made of an insulating material. Barrier ribs 8 are arranged in
the gaps between the adjacent address electrodes 11, on the
dielectric layer 10. Phosphor layers 9R, 9G, and 9B corresponding
to the colors of red (R), green (G), and blue (B) are formed on the
side faces of the adjacent barrier ribs 8 and on the dielectric
layer 10 between these adjacent barrier ribs 8.
In FIG. 26, the phosphor layers 9R, 9G, and 9B are shown as having
the same width in the x direction. However, to balance the
luminance of each of these phosphors, a phosphor layer of a
specific color may be formed wider in the x direction than other
phosphor layers.
The front panel FP and the back panel BP with the above
constructions are set facing each other so that the display
electrodes 4 and 5 and the address electrodes 11 intersect at right
angles.
The front panel FP and the back panel BP are then sealed along
their edges, using a sealing material such as a glass frit. Hence
the inside of the front panel FP and back panel BP is hermetically
sealed.
A discharge gas (filler gas) which includes Xe is enclosed in the
sealed inside of the front panel FP and back panel BP, at a
predetermined pressure (conventionally around 40 kPa to 66.5
kPa).
Here, the spaces partitioned by the dielectric layer 6, phosphor
layers 9R, 9G, and 9B, and adjacent barrier ribs 8 between the
front panel FP and the back panel BP are discharge spaces 12. Also,
the areas where the pairs of display electrodes 4 and 5 cross over
the address electrodes 11 with the discharge spaces 12 therebetween
are cells for image display (not illustrated). FIG. 27 shows a
matrix that is formed by the plurality of pairs of display
electrodes 4 and 5 (N lines) and the plurality of address
electrodes 11 (M lines) in the PDP.
This PDP is driven in the following way. In each cell, discharge is
initiated between the address electrode 11 and one of the display
electrodes 4 and 5.
Discharge between the display electrodes 4 and 5 causes ultraviolet
light of a short wavelength (Xe resonance lines with a wavelength
of about 147 nm) to be generated.
This ultraviolet light excites the phosphor layers 9R, 9G, and 9B
to emit visible light. Hence an image is displayed.
A method of driving a conventional PDP is explained in greater
detail below, with reference to FIGS. 28 and 29.
FIG. 28 is a block conceptual diagram of an image display device
(PDP drive device) that uses a conventional PDP. FIG. 29 shows one
example of drive waveforms that are applied to the electrodes of
the panel.
As shown in FIG. 28, the PDP display device includes a frame memory
100, an output processing circuit 110, an address electrode drive
device 120, a sustain electrode drive device 130, and a scan
electrode drive device 140, for driving the PDP. The scan electrode
drive device 140, the sustain electrode drive device 130, and the
address electrode drive device 120 are respectively connected to
the scan electrodes 4, the sustain electrodes 5, and the address
electrodes 11. They are also connected to the output processing
circuit 110.
This being so, the PDP is driven as follows. Image information is
input in the frame memory 100 from outside. This image information
is introduced from the frame memory 100 into the output processing
circuit 110, based on timing information. After this, the output
processing circuit 110 instructs the scan electrode drive device
140, the sustain electrode drive device 130, and the address
electrode drive device 120 to apply pulse voltages to the
electrodes 4, 5, and 11, according to the image information and the
timing information. This produces an image display.
As shown in FIG. 29, the PDP drive method produces an image display
through a sequence of a set-up period, a write period, a sustain
period, and an erase period.
The NTSC standard for television images stipulates a frame rate of
60 frames per second. PDPs are fundamentally only capable of two
display states, ON and OFF. Accordingly, a method is employed in
which a field that is an illumination time period of each color of
red (R), green (G), and blue (B) is divided into a plurality of
sub-fields and the ON and OFF states in each sub-field are combined
to express a gray scale.
FIG. 30 shows a method of dividing into such sub-fields, to express
256 gray levels for each color in a conventional AC PDP. Here, the
sub-fields are weighed with the numbers of sustain pulses applied
in the discharge sustain period in the ratio of 1, 2, 4, 8, 16, 32,
64, and 128. Combinations of this eight-bit binary express a
256-level gray scale.
To drive the PDP, a set-up pulse is applied to the scan electrodes
4 in each sub-field, to set-up a wall charge in the cells in the
panel. Following this, a scan pulse and a write pulse are applied
respectively to a scan electrode 4 and sustain electrode 5 at the
top in the y direction (on the top line of the display), to perform
write discharge. As a result, a wall charge is accumulated on the
dielectric layer 6 in the cells corresponding to the scan electrode
4 and sustain electrode 5.
In the same manner, a scan pulse and a write pulse are applied to
each pair of scan electrode 4 and sustain electrode 5 that follows,
to accumulate a wall charge on the dielectric layer 6 in the cells
corresponding to the pair. This is repeated for all pairs of
display electrodes 4 and 5, thereby writing one screen of latent
image.
After this, the address electrodes 11 are grounded, and a sustain
pulse is applied alternately to the scan electrodes 4 and the
sustain electrodes 5 to perform sustain discharge. In the cells
where a wall charge has been accumulated on the dielectric layer 6,
discharge takes place as a result of the potential on the
dielectric layer 6 exceeding a discharge firing voltage.
Accordingly, sustain discharge is performed in the cells selected
by the write pulse, while the sustain pulse is being applied
(sustain period). During this sustain discharge period, discharge
is initiated between the address electrode 11 and one of the
display electrodes 4 and 5 in each cell. Discharge between the
display electrodes 4 and 5 causes ultraviolet light of a short
wavelength (Xe resonance lines, a wavelength of about 147 nm) to be
generated. This ultraviolet light excites the phosphor layers 9R,
9G, and 9B to emit visible light. This produces an image
display.
After this, a narrow erase pulse is applied to cause incomplete
discharge. As a result, the wall charge is erased to clear the
displayed image.
Today, electrical products are desired to consume as little power
as possible. Accordingly, there have been expectations for the
reduction of power consumption when driving a PDP. Due to the
recent increases in the size and resolution of PDPs, the power
consumption for PDPs tends to increase. This heightens the needs
for technologies that achieve lower power consumption. Also, PDPs
are fundamentally expected to exhibit stable image display
performance.
For this reason, it is desirable to reduce power consumption for
PDPs while maintaining stable driving performance and high panel
luminance. In other words, it is desirable to improve illumination
efficiency for PDPs.
To improve illumination efficiency, research has been done on the
areas such as the improvement of conversion efficiency from
ultraviolet to visible light in a phosphor. However, still more
improvements in illumination efficiency are to be desired.
In conventional panels, the following structure is used for display
electrodes, in order to improve panel luminance when displaying
images. Each display electrode is formed by providing a bus line of
metal electrode on a wide strip-shaped transparent electrode,
thereby expanding the electrode area. This being so, to suppress an
increase of discharge current caused by this structure or to reduce
the number of processing steps by omitting the transparent
electrode, various techniques have been proposed. One example is an
electrode structure in which the electrode is divided into a
plurality of parts to have openings (e.g. Japanese Patent No.
2734405). However, when such a structure is used, the following
problem arises. Since discharge grows gradually while jumping from
one electrode part to another, the drive voltage needs to be raised
to spread the discharge as far as the outermost electrode part.
In addition, to secure the current supply path even if the divided
electrode parts are partially disconnected and also to reduce the
overall resistance of the electrode, it may be desirable to
electrically connect the divided electrode parts. For instance,
connectors of about 50 .mu.m in width can be provided above the
barrier ribs to connect the divided electrode parts to each other.
According to this method, however, the precision of bonding the
front panel FP and the back panel BP together becomes strict around
10-20 .mu.m, which makes stable production more difficult.
Furthermore, if fewer connectors are used, the overall resistance
of the electrode increases. This causes a voltage drop, thereby
making it difficult to drive the PDP.
DISCLOSURE OF INVENTION
The present invention was conceived in view of the problem
described above, and aims to provide a gas discharge panel that has
favorable display performance with high luminance and illumination
efficiency.
Also, the present invention aims to provide a gas discharge panel
which uses a display electrode structure divided into a plurality
of parts without an increase in drive voltage. Furthermore, the
present invention aims to provide a gas discharge panel that defies
disconnections of divided electrode parts, has low-resistance
electrodes, and is easy to drive.
The stated object can be achieved by a gas discharge panel
including a first substrate and a second substrate, a plurality of
display electrode pairs which are each made up of a sustain
electrode and a scan electrode being formed on the first substrate,
and the first substrate and the second substrate being set facing
each other with a plurality of barrier ribs in between so as to
form a plurality of cells, wherein at least one of the sustain
electrode and the scan electrode includes: a plurality of line
parts; and a discharge developing part which makes a gap between
adjacent line parts smaller in areas corresponding to channels
between adjacent barrier ribs than in areas corresponding to the
barrier ribs.
The stated object can also be achieved by a gas discharge panel in
which phosphor layers corresponding to three colors of red, green,
and blue are formed one by one in a plurality of cells, and a
plurality of display electrode pairs that are each made up of a
sustain electrode and a scan electrode are arranged so as to cross
the plurality of cells, wherein a width of each of the plurality of
cells is determined according to luminance of a phosphor layer
formed in the cell, the sustain electrode and the scan electrode
each have (a) a plurality of line parts and (b) a connector part
which connects at least two line parts out of the plurality of line
parts in each of the plurality of cells, and a distance between the
plurality of line parts, a main discharge gap, and a position of
the connector part are set so that a discharge current waveform
when driving the sustain electrode and the scan electrode has a
single peak.
With this construction, each of the display electrodes 4 and 5 are
made up of a plurality of line parts and at least one connector
part. Such a display electrode has a smaller area than a
conventional strip-shaped display electrode, with it being possible
to decrease the electrode capacitance needed for discharge. In
general, if a display electrode is simply made up of a plurality of
separate line parts, discharge takes place in a discrete fashion.
As a result, the discharge current waveform tends to have a
plurality of peaks. This increases the discharge firing voltage,
thereby causing an increase in power consumption. According to the
present invention, on the other hand, the discharge current
waveform has a single peak as explained above, and so the panel can
be driven with a lower voltage. Therefore, the power consumption
can be reduced when compared with the conventional panel. This
benefits favorable illumination efficiency (drive efficiency).
Also, since the discharge current waveform has a single peak, a
voltage drop which could affect the panel luminance or the
illumination efficiency does not occur. Furthermore, stable
discharge can be performed even if a rise time of a drive pulse
becomes unstable. Thus, the gas discharge panel of the present
invention can express a gray scale by pulse modulation with
stability.
When the cell width differs for each of the colors of red, green,
and blue, the discharge firing voltage differs too. This makes it
difficult to produce a stable image display. This problem
associated with different cell widths can be solved if the above
display electrode structure is used. This further increases the
effects of the present invention (i.e. high illumination efficiency
and stable image display).
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view of display electrodes that are the first
embodiment of the present invention.
FIG. 2 shows changes in discharge current in each of when connector
parts are provided and when connector arts are not provided.
FIG. 3 shows changes in luminance when the widths of line parts are
varied.
FIG. 4 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 5 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 6 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 7 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 8 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 9 is a plan view of display electrodes that are a modification
to the first embodiment.
FIG. 10 is a plan view of display electrodes that are the second
embodiment of the present invention.
FIG. 11 is a plan view of display electrodes that are a
modification to the second embodiment.
FIG. 12 is a plan view of display electrodes that are a
modification to the second embodiment.
FIG. 13 shows shapes of pulses that are applied during ramp
discharge.
FIG. 14 is a plan view of display electrodes that are a
modification to the second embodiment.
FIG. 15 is a plan view of display electrodes that are a
modification to the second embodiment.
FIG. 16 shows discharge current waveforms when connector parts and
line parts are combined in different patterns.
FIG. 17 is a plan view of display electrodes that are the third
embodiment of the present invention.
FIG. 18 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 19 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 20 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 21 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 22 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 23 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 24 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 25 is a plan view of display electrodes that are a
modification to the third embodiment.
FIG. 26 is a partial sectional perspective view showing a main
construction of a typical surface discharge AC PDP.
FIG. 27 is a graph showing a matrix which is formed by a plurality
of pairs of display electrodes (N lines) and a plurality of address
electrodes (M lines) in the PDP.
FIG. 28 is a block conceptual diagram of an image display device
that uses a conventional PDP.
FIG. 29 shows an example of drive waveforms which are applied to
the electrodes (scan electrodes, sustain electrodes, and address
electrodes) in the PDP.
FIG. 30 shows a method of dividing into sub-fields, when the
conventional AC PDP expresses a 256-level gray scale for each
color.
BEST MODE FOR CARRYING OUT THE INVENTION
An overall construction of a PDP to which the embodiments of the
present invention relate is roughly the same as that of the
conventional PDP described earlier. The features of the present
invention mainly lie in a structure of a display electrode and its
vicinity. Accordingly, the following description focuses on the
display electrode.
(First Embodiment)
1-1. Structure of a Display Electrode
FIG. 1 is a plan view of a display electrode pattern which is the
first embodiment of the present invention.
In this embodiment, the phosphor layers 9 are formed such that
phosphor materials of the three primary colors are applied in the x
direction in the order of, for example, red, green, and blue (RGB),
so as to extend in the y direction. An area where one pair of
display electrodes 4 and 5 intersect one address electrode 11 is a
discharge cell. Three cells of red, green, and blue which are
adjacent in the x direction constitute one pixel X, as shown in
FIG. 1.
The panel of the first embodiment is characterized in that at least
one of the scan electrode 4 and the sustain electrode 5 which form
each pair is divided into three parts. A part that is closest to
the other electrode of the pair is a line part 4a (5a). The
distance between the line part 4a (5a) and the other electrode is a
main discharge gap Dgap. The main discharge gap Dgap represents the
shortest distance between the scan electrode 4 and the sustain
electrode 5. Discharge starts in this main discharge gap Dgap, and
spreads throughout the scan electrode 4 and the sustain electrode
5. A part that is located far from the main discharge gap Dgap is a
line part 4b (5b) which is a discharge end part that defines the
spreading range of the discharge. A part that connects the line
part 4a (5a) to the line part 4b (5b) is a connector part 4ab (5ab)
which is a discharge developing part. This connector part is
provided in each cell.
The connector part 4ab (5ab) is formed so that the gap between the
line parts 4a and 4b (5a and 5b) is smaller in the areas
corresponding to channels between adjacent barrier ribs 8 than in
the areas corresponding to the barrier ribs 8 (in the present
example, the gap between the line parts 4a and 4b (5a and 5b) in
the areas corresponding to the channels between adjacent barrier
ribs 8 is 0).
Cells that are adjacent in the x direction have the same line parts
4a and 4b (5a and 5b) but have separate connector parts 4ab
(5ab).
Here, it is desirable to situate the connector part 4ab (5ab) at
the center of each cell. In this way, a margin for displacements
which may occur when bonding the front panel FP and the back panel
BP together can be obtained.
If the construction of the back panel BP is not perpendicular to
the barrier ribs 8, displacements in the direction along the
barrier ribs 8 can be ignored. On the other hand, a margin for
displacements in the x direction is determined by the width of the
connector part 4ab (5ab).
Suppose a connector part that is perpendicular to the scan
electrode 4 is provided in the area corresponding to the barrier
rib 8, as in the case of Japanese Patent No. 2734405 mentioned
earlier. Since the width of the connector part and the width of the
barrier rib 8 are both about 50 .mu.m, a displacement of around
10-20 .mu.m can result in a change in characteristics.
In view of this, the width of the connector part 4ab (5ab) is set
to be at least 100 .mu.m smaller than the smallest distance Wcell
between adjacent barrier ribs 8 in FIG. 1. This provides a margin
of about .+-.50 .mu.m for displacements in the x direction.
The use of the same line part 4a (5a) across the adjacent cells in
the x direction has the following two effects. The first effect is
to decrease the resistance of the line part 4a (5a). A construction
of providing a separate discharge starting part for each individual
cell is known as exemplified by Unexamined Japanese Patent
Application Publication No. H08-250030. According to such a
construction, however, the resistance of each discharge starting
part increases. This causes a voltage drop, which increases the
discharge firing voltage.
The second effect is to facilitate the bonding of the front panel
FP and the back panel BP. As is clear from FIG. 1, there is no need
to consider displacements of the line parts 4a and 4b (5a and
5b).
In the first embodiment, the widths Pr, Pg, and Pb of the cells in
the x direction corresponding to the three colors of red, green,
and blue are not uniform, as shown in FIG. 1 (i.e.,
Pr.ltoreq.Pg.ltoreq.Pb). The reason for this is given below. The
phosphor layers 9R, 9G, and 9B for the three colors of red, green,
and blue have different luminance.
Accordingly, to balance the luminance between the red, green, and
blue cells, a cell corresponding to a phosphor layer which has
relatively low luminance (the blue cell in the present example) is
formed wider to increase the cell area, thereby ensuring sufficient
luminance.
It should be noted here that although the luminance of the blue
phosphor is usually lowest among the three colors of red, green,
and blue, this may not be the case depending on specifications of a
PDP.
In each cell between two adjacent barrier ribs 8, the scan
electrode 4 (sustain electrode 5) is made up of two thin line parts
4a and 4b (5a and 5b) and a connector part 4ab (5ab) that
electrically connects these two line parts.
The two line parts 4a and 4b (5a and 5b) are coupled together at
both ends of the scan electrode 4 (sustain electrode 5) (not
illustrated), so that the same voltage is applied to the two line
parts.
As one example, the size of each part is the following. The cell
width P in the y direction is 1.08 mm. The main discharge gap Dgap
is 80 .mu.m. The line part width in the y direction is 40 .mu.m.
The distance between the two line parts 4a and 4b (5a and 5b) is 80
.mu.m. Each of the display electrodes 4 and 5 is made using a metal
material (e.g. Ag or Cr/Cu/Cr). The use of Ag as the metal material
allows the reflectivity to increase and the loss of visible light
to be suppressed, and so contributes to higher illumination
efficiency.
The above size and position of each part of the display electrode
are determined so that the discharge current waveform when driving
the PDP has a single peak to thereby deliver excellent illumination
efficiency. To determine such a display electrode pattern that
makes the discharge current waveform have a single peak, a method
of varying the main discharge gap Dgap, the distance between the
line parts, the position of the connector part, and the like while
checking the waveform may be employed.
1-2. Specific Effects of the First Embodiment
When a display electrode in a PDP has a plurality of line parts,
usually a plurality of peaks occur in discharge current waveform.
FIGS. 2A and 2B show a display electrode structure which includes
only line parts and no connector parts and a discharge current
waveform for this structure, respectively. FIGS. 2C and 2D show a
display electrode structure which includes connector parts of the
present invention and a discharge current waveform for this
structure, respectively.
In both cases, discharge starts in the main discharge gap Dgap. The
discharge that starts in the main discharge gap Dgap, i.e., the gap
between the line parts 4a and 5a, grows spatially with time and
eventually spreads throughout the display electrodes 4 and 5.
In FIG. 2A, the display electrodes 4 and 5 to which a discharge
current is supplied each have a discrete structure, that is, a
structure of being separated into isolated parts. Therefore, the
discharge grows in a discrete fashion. As a result, a plurality of
peaks appear in the discharge current waveform as shown in FIG.
2B.
The line parts such as 4b and 4d (5b and 5d) that are far from the
main discharge gap Dgap perform discharge through the use of the
priming of the discharge of the inner line part. This being so, if
there is a substantial distance between line parts, the priming
effect is difficult to reach. Unless strong discharge is generated,
the discharge cannot reach the outermost line part. Hence the drive
voltage needs to be raised.
In FIG. 2C, on the other hand, the growth of discharge is more
continuous as can be understood from FIG. 2D, because the connector
part 4c (5c) that connects the line parts 4a and 4b (5a and 5b) is
present. The discharge that starts at the line part 4a (5a) grows
through the connector part 4c (5c) to the line part 4b (5b). This
growth is continuous, and so a lower drive voltage than that of
FIG. 2A is sufficient.
The inventors found through experimentation that the voltage
required by the structure of FIG. 2C was 3 to 5V lower than that
required by the structure of FIG. 2A. Meanwhile, there was no
substantial difference in panel luminance.
Each of the display electrodes 4 and 5 can be formed using a metal
electrode or a transparent electrode whose major component is a
metal oxide. To decrease resistance, however, it is desirable to
form at least the line parts 4a and 4b (5a and 5b) using a metal
electrode.
Here, the display electrode may be formed using a material which
mainly contains silver. The use of silver enables the reflectivity
to increase and the loss of visible light to be suppressed, thereby
contributing to a higher visible light utilization ratio.
Discharge at a given peak of discharge current tends to be greatly
affected by discharge that took place at its preceding peak of
discharge current (priming effects by residual ions, metastable
particles, and the like). In more detail, some discharge is
affected by its preceding discharge in such a way that the voltage
waveform deforms or the rise time of the drive pulse changes. Also,
the luminance or the illumination efficiency changes due to a
voltage drop and the like. Thus, if the discharge current waveform
has a plurality of peaks, the gray scale control tends to become
unstable. This poses a significant obstacle to producing a
favorable full-color moving image display on a television receiver
or similar.
According to the first embodiment, on the other hand, there is only
one discharge current peak. Hence stable sustain discharge can be
performed when compared with the case where a plurality of peaks
occur. This enables the gray scale control by pulse modulation to
be exercised with stability, with it being possible to ensure
excellent display performance.
In the first embodiment, the discharge current waveform has a
single peak. Accordingly, the discharge illumination waveform has a
single peak, too.
In the first embodiment, the above display electrode pattern is
applied to a construction where the cell width in the x direction
differs for each color of red, green, and blue. By doing so,
variations in discharge firing voltage among the three colors of
red, green, and blue are eliminated. As a result, a stable image
display can be produced.
FIG. 3A is a graph showing the correlation between the widths of
the line parts 4a, 4b, 5a, and 5b and the panel luminance. The
widths of the line parts 4a, 4b, 5a, and 5b are denoted by W4a,
W4b, W5a, and W5b respectively.
FIG. 3A shows measurement values when various parameters are set
such that the connector part width is 40 .mu.m, the distance
between the line parts is 290 .mu.m, the main discharge gap Dgap is
80 .mu.m, and the cell width Wcell is 360 .mu.m as shown in FIG.
3B.
As illustrated, the panel luminance begins to drop when the width
W4b (W5b) of the line part 4b (5b) where the discharge
substantially ends becomes 120 .mu.m or more. This drop in panel
luminance is mainly caused by a decrease in opening ratio due to
the widened line part. Which is to say, the panel luminance depends
on the cell opening ratio, i.e., the ratio of the line part area to
the cell area.
When the width W4b (W5b) of the line part 4b (5b) which is the
discharge end part is 120 .mu.m, the line part 4b (5b) occupies
about 40% of the cell area. Therefore, it is desirable to limit the
area of the line part 4b (5b) to less than 40% of the cell area, in
view of FIGS. 3A and 3B.
This factor needs to be taken into consideration when determining
the width of each line part.
Thus, the PDP of the first embodiment achieves excellent display
performance and illumination efficiency, by forming the display
electrode 4 (5) from the line parts 4a and 4b (5a and 5b) and the
connector part 4ab (5ab) to thereby reduce the electrode area and
also ensure a single-peak discharge current waveform.
In this specification, a single-peak discharge current waveform may
include such a discharge current waveform that has a peak other
than the maximum peak but its value is no more than 10% of the
value of the maximum peak.
1-3. Manufacturing Method for the PDP
One example method for manufacturing the PDP of the first
embodiment is explained below. This manufacturing method is also
applicable to PDPs of the other embodiments which are described
later.
1-3-1. Manufacture of the Front Panel
A front panel glass is made of soda lime glass and has a thickness
of about 2.6 mm. Display electrodes are formed on this front panel
glass. A method of forming display electrodes using metal
electrodes which include a metal material (Ag) (thick film
formation method) is shown below as one example.
A photoresist (photodegradable resin) is mixed with a metal (Ag)
powder and an organic vehicle to create a photosensitive paste.
This photosensitive paste is applied to one main surface of the
front panel glass, and a mask having a desired display electrode
pattern is placed on top of that. Light is applied onto the mask to
develop and bake (a baking temperature of around 590-600.degree.
C.). In this way, a line width as small as about 30 .mu.m can be
realized when compared with a conventional screen printing method
whose limit is a line width of 100 .mu.m. Here, other metal
materials such as Pt, Au, Ag, Al, Ni, Cr, tin oxide, and indium
oxide may instead be used.
Also, the electrode formation is not limited to the above method.
For instance, electrodes may be formed by depositing an electrode
material using evaporation, sputtering, or the like and then
executing etching.
Next, a protective layer with a thickness of about 0.3 to 1 .mu.m
is formed on a dielectric layer using evaporation, CVD
(chemical-vapor deposition), or the like. Magnesium oxide (MgO) is
preferably used for the protective layer.
This completes the front panel.
1-3-2. Manufacture of the Back Panel
A back panel glass is made of soda lime glass and has a thickness
of about 2.6 mm. A conductive material whose major component is Ag
is applied to one main surface of the back panel glass in stripes
at a predetermined pitch using screen printing, to form address
electrodes with a thickness of about 5 .mu.m. Here, to keep with
the requirements for a 40-inch NTSC or VGA television, the distance
between the adjacent address electrodes is set to be no greater
than around 0.4 mm.
Following this, a lead glass paste is applied to the entire surface
of the back panel glass on which the address electrodes have been
arranged, so as to assume a thickness of about 20 to 30 .mu.m. The
result is baked to form a dielectric film.
Next, barrier ribs with a height of about 60 to 100 .mu.m are
formed in the gaps between the adjacent address electrodes on the
dielectric film, using the same lead glass material as the
dielectric film. The barrier ribs can be formed, for example, by
repeatedly screen-printing a paste which includes the above glass
material and then baking it.
Once the barrier ribs have been formed, the phosphor inks of the
three colors of red (R), green (G), and blue (B) are applied one at
a time to the side faces of the barrier ribs and the exposed
surface of the dielectric film between the barrier ribs. The result
is dried and baked to form phosphor layers.
Examples of phosphor materials typically used for PDPs are given
below: Red phosphor: (Y.sub.xGd.sub.1-x)BO.sub.3:EU.sup.3+ Green
phosphor: Zn.sub.2SiO.sub.4:Mn.sup.3+ Blue phosphor:
BaMgAl.sub.10O.sub.17:Eu.sup.3+ (or
BaMgAl.sub.14O.sub.23:Eu.sup.3+)
A powder with an average particle diameter of about 3 .mu.m may be
used for each phosphor material. Though there are several methods
for applying phosphor ink, this embodiment employs a known meniscus
method that expels phosphor ink from a fine nozzle while forming a
meniscus (a cross-linking due to surface tension). This method has
an advantage of evenly applying phosphor ink to desired parts.
However, it should be obvious that the present invention is not
limited to this method. Other methods such as screen printing are
also applicable.
This completes the back panel.
Though the front panel glass and the back panel glass are made of
soda lime glass in this embodiment, this is a mere example of
material that can be used for the front panel glass and the back
panel glass, which may be formed from other materials.
1-3-3. Completion of the PDP
The front panel and the back panel manufactured in this way are
sealed together using sealing glass. Following this, the discharge
spaces are evacuated to produce a high vacuum (around
1.1.times.10.sup.-4 Pa), and discharge gas such as an Ne--Xe
mixture, an He--Ne--Xe mixture, or an He--Ne--Xe--Ar mixture is
introduced into the discharge spaces at a predetermined pressure
(e.g. 2.7.times.10.sup.5 Pa).
1-4. Modifications to the First Embodiment
The first embodiment describes the case where one connector part
4ab (5ab) is provided in each cell, but this is not a limit for the
invention. For instance, two connector parts 4ab (5ab) may be
provided in each cell, as shown in FIG. 4 (modification 1-1). This
allows a wider discharge space to be used for discharge.
In the first embodiment, the discharge which starts at the line
part 4a (5a) grows through the connector part 4ab (5ab) and
eventually reaches the line part 4b (5b).
However, it is difficult for the discharge to reach a space that is
far from all of the line part 4a (5a), the line part 4b (5b), and
the connector part 4ab (5ab), since the electric field strength of
the space is low. This causes the illumination intensity to
decrease. To minimize such a space, a plurality of connector parts
4ab (5ab) are provided in this modification. In so doing, a wider
space can be used for discharge, with it being possible to increase
the panel luminance.
Another effect produced by this modification is to strengthen the
current supply capacity of the connector part 4ab (5ab). By
providing two connector parts 4ab (5ab) in each cell as shown in
FIG. 4, the current supply capacity is doubled when compared with
the display electrode structure of FIG. 1. This facilitates the
growth of discharge, and enables the PDP to be driven with a lower
voltage. The priming increases due to these factors, thereby easing
the growth of discharge.
Note here that the shape of the connector part 4ab (5ab) may be
other than a straight line.
Also, the widths of the line parts 4a and 4b (5a and 5b) may not be
the same. For example, one line part (4b (5b) in this example) may
be set wider than the other line part, as shown in FIG. 5
(modification 1-2).
In general, the electric resistance of the scan electrode 4
(sustain electrode 5) can be reduced by widening the electrode
area. However, this causes the light emitted from a phosphor
excited by ultraviolet light due to discharge to be blocked, which
results in a drop in luminance.
On the other hand, if the electrode area is widened, the electric
resistance decreases and the flow of current is eased. In addition,
the discharge area in the discharge space widens. Accordingly, the
discharge current increases, which contributes to higher
luminance.
These factors indicate that the maximum luminance can be obtained
depending on the display electrode area.
On the whole, it is desirable to maximize the electrode area to
decrease the resistance, within a range where the maximum luminance
can be obtained. This being so, by increasing the electrode area in
a part which has low luminance in the discharge space, the blockage
of visible light can be effectively minimized.
The discharge starts at the line part 4a (5a) and grows towards the
line part 4b (5b). Therefore, the line part 4a (5a) and its
vicinity illuminate for a longest time, and so has high luminance.
Meanwhile, the line part 4b (5b) has relatively low luminance.
Accordingly, by widening the area of the line part 4b (5b) which
has low luminance, it is possible to decrease the resistance while
maintaining the panel luminance.
According to this modification, the electrode area is widened to an
appropriate extent to reduce the electric resistance. This assists
in a favorable flow of current, with it being possible to improve
the panel luminance. Here, it is preferable to widen a line part
which is relatively far from the main discharge gap Dgap, in order
to reduce the power required to start the discharge.
FIG. 6 shows another arrangement of a pair of display electrodes
(modification 1-3). In the drawing, two cells adjacent in the y
direction correspond to an X electrode, a Y electrode, and an X
electrode arranged in this order, where the two X electrodes share
the same Y electrode.
Here, Y electrodes 5A and 5B at the center are paired respectively
with an upper X electrode 4A and a lower X electrode 4B. The Y
electrodes 5A and 5B act as a single Y electrode electrically.
Also, a discharge accelerating part 4p (5p) which is in parallel
with the line parts 4a and 4b (5a and 5b) may be provided in each
cell so as to intersect the connector part 4ab (5ab) at the right
angle, as shown in FIG. 7 (modification 1-4).
According to this modification, the discharge which starts at the
line part 4a (5a) spreads in the y direction along the connector
part 4ab (5ab), and at the same time spreads in the x direction
along the discharge accelerating part 4p (5p). Thus, the discharge
effectively spreads in the discharge space between the line parts
4a and 4b (5a and 5b), as a result of which the luminance of the
entire cell increases.
Also, this modification produces a phenomenon in which the
discharge grows in the order of the line part 4a (5a), the
discharge accelerating part 4p (5p), and the line part 4b (5b).
This has an effect of widening the discharge space, with it being
possible to improve the luminance.
Similar effects can be obtained by a display electrode pattern
shown in FIG. 8 (modification 1-5). In the drawing, the connector
part 4ab (5ab) is divided into two parts to spread towards the line
part 4b (5b).
Also, a projection may be formed on one side of the line part 4a
(5a) facing the other display electrode of the pair so as to extend
from the connector part 4ab (5ab), as shown in FIG. 9 (modification
1-6). This being the case, the discharge is performed between these
facing projections. According to this construction, the discharge
starts between the projections extending from the connector parts
4ab and 5ab, with it being possible to reduce the power required to
start the discharge.
(Second Embodiment)
2-1. Structure of a Display Electrode
The second embodiment is fundamentally based on the first
embodiment, but is characterized in that a display electrode is
made up of three or more line parts 4a, 4b, . . . and connector
parts 4ab, 4b , . . . which are arranged in he y direction in a
straight line to connect the line parts.
FIG. 10 shows an example of the display electrode structure of the
second embodiment. In the drawing, the scan electrode 4 (sustain
electrode 5) has three line parts 4a-4c (5a-5c) that are connected
by connector parts 4ab and 4bc (5ab and 5b) arranged in a straight
line in the y direction. The distance Dab between the line parts 4a
and 4b (5a and 5b) is equal to the distance Dbc between the line
parts 4a and 4c (5a and 5c). It is preferable for Dab and Dbc to be
larger than the main discharge gap Dgap, to increase the opening
ratio. As a result, high luminance can be obtained, and the voltage
can be further reduced.
As one example, the size of each part is set as follows. The pixel
pitch is 1080 .mu.m, the line part width is 40 .mu.m, the main
discharge gap Dgap is 80 .mu.m, and the distance between adjacent
line parts is 100 .mu.m.
The panel of the second embodiment is characterized in that two or
more connector parts 4ab, 4bc, . . . (5ab, 5bc, . . . ) are formed
for the display electrode 4 (5) in each cell, so as to be situated
in the display area of the cell sandwiched by the adjacent barrier
ribs 8. In FIG. 10, the connector parts 4ab and 4bc (5ab and 5bc)
are provided for the scan electrode 4 (sustain electrode 5) in each
cell. In other words, two connector parts are provided for the scan
electrode 4 (sustain electrode 5) in each cell.
It is desirable to position the connector parts 4ab and 4bc (5ab
and 5bc) at the center of each cell. In this way, a margin for
displacements which may occur when sealing the front panel FP and
the back panel BP together can be obtained. Suppose a connector
part is positioned perpendicular to the x direction as in the case
of Japanese Patent No. 2734405. Since the connector part width is
50 .mu.m and the barrier rib width is about 60 .mu.m, a
displacement of around 10-20 .mu.m can result in a change in
characteristics. On the other hand, if a connector part is
positioned at the center of the cell as in this embodiment, a
margin corresponding to the difference between the cell width and
the connector part width is secured. Suppose the pixel pitch is
1080 .mu.m.times.1080 .mu.m. When the cell width in the x direction
is about 300 .mu.m and the connector part width is 40 .mu.m, then a
margin of about 260 .mu.m (.+-.130 .mu.m) can be secured.
Such an effort of securing a margin for displacements which can
occur in the sealing process may be dispensed with if a connector
part is placed irrespective of the cell width or is placed only
once in several tens of cells. However, such a regular arrangement
may appear to be some kind of pattern to the human eye when looked
at from the display plane side. Conversely, a completely random
arrangement is inefficient in terms of design. According to the
present invention, the connector part pitch is high, so that the
electric resistance of the whole display electrode is reduced and
the connector parts will not appear to form some kind of pattern to
the human eye.
Note that the size of each part in the second embodiment can be
determined in the same way as the first embodiment.
The display electrode structure shown in FIG. 10 delivers the same
effects as the first embodiment. Which is to say, the discharge
current waveform has a single peak, and the drive voltage is
reduced.
2-2. Modifications to the Second Embodiment
The second embodiment describes the case where the connector parts
4ab, 4bc, . . . (5ab, 5bc, . . . ) are arranged in a straight line
to connect the line parts 4a, 4b, 4c, . . . (5a, 5b, 5c, . . . ).
However, the present invention is not limited to such. For
instance, the line parts may be connected by the connector parts so
as to form a mesh, as shown in FIG. 11 (modification 2-1). In the
drawing, cells A, B, and C correspond to the red, green, and blue
phosphor layers, respectively. This being so, the green phosphor
layer corresponding to cell B has higher luminance than the blue
phosphor layer corresponding to cell C, and cell C is set wider
than cell B. In general, when the cell width is smaller, the
movement of electrons is restricted by the barrier ribs on both
sides, which makes it difficult for the discharge to grow in the
direction away from the main discharge gap Dgap. Therefore, to
effectively spread the discharge from the main discharge gap Dgap,
it is desirable to provide a connector part closer to the main
discharge gap Dgap when the cell width is smaller. By doing so, the
discharge characteristics such as the discharge voltage can be made
uniform, even when the cell pitch is not uniform.
As shown in FIG. 11, it is desirable to provide a connector part
closer to the main discharge gap Dgap, when the luminance of the
corresponding phosphor layer is relatively high (cell B in this
example). Meanwhile, it is desirable to provide a connector part
farther from the main discharge gap Dgap, when the luminance of the
corresponding phosphor layer is relatively low (cell A and cell C
in this example).
The reason for this is given below. In the cell which is wider in
the x direction (cell C), the capacitance of the display electrode
4 (5) near the main discharge gap Dgap which is necessary for
starting the discharge is larger than in the cell which is narrower
in the x direction (cells A and B). This being so, if the connector
part is located farther from the main discharge gap Dgap, this
capacitance can be reduced when compared with the case where the
connector part is located nearer the main discharge gap Dgap. In
addition, a larger amount of visible light can be obtained at the
start of the discharge.
In the narrower cell, on the other hand, the cell area is smaller
and so the influence of the capacitance of the display electrode is
relatively low. Therefore, the connector part can be positioned
more freely. As one example, the connector part 4ab (5ab) may be
provided in the cell with sufficient phosphor luminance (cell B),
whereas the connector part 4bc (5bc) may be provided in the cell
which needs to ensure a certain amount of phosphor light emission
(cell A).
This modification is made in consideration of these factors, with
it being possible to improve the luminance and the illumination
efficiency.
Similar effects can be delivered by a display electrode structure
shown in FIG. 12 (modification 2-2). In this modification, the
distance Dab between the line parts 4a and 4b (5a and 5b) is not
equal to the distance Dbc between the line parts 4a and 4c (5a and
5c).
This being so, a connector part is provided between the line parts
with a larger distance (Dab in FIG. 12) in cells A and B which each
have a smaller cell area. Meanwhile, a connector part is provided
between the line parts with a smaller distance in cell C which has
a larger cell area.
This structure where Dab and Dbc are different allows visible light
to be extracted more effectively onto the display plane.
Here, there may be a concern that the operating voltage could
differ in each cell when the connector part is placed in a
different position in each cell. If Dab and Dbc are the same as in
FIG. 10, varying the position of the connector part for each cell
hardly causes a variation in operating voltage of each cell.
However, if Dab and Dbc are different as in FIG. 12, the cell which
has the connector part positioned between the line parts with the
larger distance (cell A in FIG. 12) can be driven with a voltage
which is several volts lower. This causes a variation for each
cell.
Also, the drive voltage of each cell can change by several volts
due to the factors relating to the volume of the discharge space,
such as the cell area and the shape of the phosphor layer.
Accordingly, for a cell which requires a high drive voltage like
cells A and B shown in FIG. 12, an electrode structure which can be
driven with a lower voltage is adopted to thereby suppress a
variation in drive voltage for each cell.
In FIG. 12, cell C has a large cell area whilst cell A has a small
cell area. In this way, the luminance of the three colors of red,
green, and blue is appropriately balanced to produce a white color
with a desired color temperature. Usually the blue cell is widened
to increase the blue luminance so as to produce a white color with
a high color temperature. In such a case, the drive voltage of cell
C becomes lower than the drive voltage of cell A. Accordingly, the
connector part 4ab (5ab) is provided between the line parts 4a and
4b (5a and 5b) in cell A, to decrease the drive voltage. As a
result, the drive voltage of cell A can be made roughly equal to
the drive voltage of cell C.
Though each of the display electrode 4 and 5 has three line parts
in this example, it should be obvious that the display electrode
may have more than three line parts.
Also, the distance between the line parts 4a and 4b (5a and 5b) is
set larger than the distance between the line parts 4a and 4c (5a
and 5c) in this modification. Accordingly, the connector part 4ab
(5ab) is longer than the connector part 4bc (5bc). In so doing, a
large amount of visible light can be produced in the discharge
which occurs near the main discharge gap Dgap. By adopting the
display electrode structure of the present invention to a drive
method which applies a voltage of a waveform having a slope (see
FIG. 13) to the scan electrodes in the set-up period, stable write
discharge can be performed. As one example, the voltage change of
the slope is preferably .+-.10 V/.mu.s.
The above effect can be achieved for the following reason.
In general, the sloped voltage applied in the set-up period is
extremely weak. Therefore, even if the discharge voltage differs
for each cell, a wall charge can be accumulated close to the
discharge firing voltage in every cell. This wall charge can be
used to help the write discharge occur. However, since this
discharge generated in the set-up period is weak, it will not grow
throughout the cell if the electrode structure is discrete. This
makes it difficult to accumulate a sufficient wall charge, with
there being a danger that a discharge failure may occur to thereby
induce a degradation in image.
According to the modification 2-2, however, the weak discharge
generated in the main discharge gap Dgap can be easily spread to
the outermost line part of the cell due to the presence of the
connector part. As a result, a sufficient wall charge is
accumulated, with it being possible to perform stable write
discharge.
The details of ramp discharge are described in "Plasma Display
Device Challenges", ASIA DISPLAY 98, pp.15-27.
Also, the position of the connector part may be changed according
to the discharge characteristics of the phosphor. In doing so, it
is possible to ensure uniform write discharge characteristics of
each cell.
The modification 2-2 may be further modified to include four line
parts, as shown in FIG. 14. When the number of line parts is
increased in this way, the number of gaps between line parts
increases too. Hence the connector parts can be positioned more
freely.
Basically, it is desirable to position the connector part far from
the main discharge gap Dgap in the cell which is relatively wide in
the x direction, as explained earlier. As for the remaining cells,
the positions of the connector parts can be adjusted to some
extent, as shown in FIG. 15 (modification 2-3). In the drawing, the
display electrodes 4 and 5 each have four line parts, and two
connector parts are provided for each of the display electrodes 4
and 5 in each cell. Here, the cell which has a high discharge
firing voltage, such as cell A, has such a display electrode
structure that reduces the drive voltage. On the other hand, the
cell which has a low discharge firing voltage, such as cell C, has
such a display electrode structure that requires a high drive
voltage.
When Dab>Dbc>Dcd as shown in FIG. 15, connector parts are
positioned between line parts 4a and 4b (5a and 5b) and between
line parts 4a and 4c (5a and 5c) in cell A, whilst connector parts
are located between line parts 4b and 4c (5a and 5c) and between
line parts 4c and 4d (5c and 5d) in cell C.
In other words, when a cell has a higher discharge firing voltage,
the total length of connector parts provided in the cell is
greater.
By so doing, variations in drive voltage between cells can be
suppressed.
This modification also applies to a case where each display
electrode has more than four line parts.
2-2. Specific Effects of the Second Embodiment
Effects of providing the connector parts 4ab and 4bc (5ab and 5bc)
in each cell in the second embodiment are explained below.
FIGS. 16A and 16B relate to a comparative example. FIG. 16A shows a
display electrode structure which is made up of only line parts,
while FIG. 16B shows a discharge current waveform for this display
electrode structure.
FIG. 16C shows a display electrode structure which includes the
connector parts 4ab and 4bc (5ab and 5bc) of the second embodiment,
while FIG. 16D shows a discharge current waveform for this display
electrode structure.
FIG. 16E shows a display electrode structure which includes the
connector parts 4ab and 4bc (5ab and 5bc) of the modification 2-1,
while FIG. 16F shows a discharge current waveform for this display
electrode structure.
In all cases, the discharge starts in the main discharge gap Dgap
that is the smallest gap between the pair of display electrodes.
This discharge expands with time, and eventually spreads throughout
the cell including the line part 4c (5c).
In the case of FIG. 16A, the line parts 4a-4c (5a-5c) to which a
discharge current is supplied are simply positioned in a discrete
manner. Accordingly, the discharge grows in a discrete fashion too,
as a result of which a plurality of peaks appear in discharge
current waveform as shown in FIG. 16B. Since the electrode
structure is discrete, the electric field strength of the discharge
space is discrete. Therefore, a relatively high drive voltage is
needed for the discharge which is generated in the main discharge
gap Dgap to spread to the line part 4b (5b) and to the line part 4c
(5c).
In the case of FIG. 16C, on the other hand, the discharge current
waveform has a single peak as shown in FIG. 16D. Since the
connector parts 4ab and 4bc (5ab and 5bc) are provided to connect
the line parts 4a-4c (5a-5c), the discharge grows continuously.
This is because the electric field strength of the discharge space
has been made continuously high by providing the connector parts
4ab and 4bc (5ab and 5b). As a result, the drive voltage can be
reduced (the inventors found through experimentation that an
illumination voltage of about 200V was reduced by about 5V).
In the case of FIG. 16E, the display electrode structure is more
discrete than that of FIG. 16C. As a result, the peak of the
discharge current deforms a little as shown in FIG. 16F, which
causes the drive voltage to increase. Nevertheless, the discharge
current waveform of FIG. 16F can be regarded as having a single
peak, when compared with that of FIG. 16B. Also, the illumination
voltage is reduced by about 3V. Further, the length of connector
parts provided in each cell in FIG. 16E is shorter than that in
FIG. 16C, which increases the opening ratio and thereby improves
the panel luminance.
(Third Embodiment)
3-1. Structure of a Display Electrode
In the first and second embodiments, a display electrode is made up
of at least two line parts and at least one connector part which
electrically connects the line parts, when the red cell, the green
cell, and the blue cell have different widths in the x
direction.
In the third embodiment, the display electrode 4 (5) includes three
line parts 4a-4c (5a-5c) and projection parts 4aq and 4bq (5aq and
5bq) which are each provided on one side of any of the line parts
4a and 4b (5a and 5b) as a discharge developing part, as shown in
FIG. 17. Here, the projection parts 4aq and 4bq (5aq and 5bq) have
a rectangular shape, and are formed so as to extend in the y
direction.
These projection parts 4aq and 4ba (5aq and 5bq) are formed such
that the gap between adjacent line parts (e.g. 4a and 4b (5a and
5b)) is smaller in the areas corresponding to the channels between
adjacent barrier ribs 8 than in the areas corresponding to the
barrier ribs 8.
As one example, the size of each part is as follows. The line part
width in the y direction is about 10-100 .mu.m, and preferably
about 25-60 .mu.m. The distance between adjacent line parts
excluding the projection parts 4aq and 4bq (5aq and 5bq) is about
100-200 .mu.m, and preferably 50-100 .mu.m. The projection part
width in the x direction is no greater than 50% of the cell width
in the x direction, and preferably no greater than 20% of the cell
width in the x direction. Also, the projection part length in the y
direction is such that the distance between the projection part and
its facing line part is preferably no greater than the main
discharge gap Dgap, and more preferably no greater than half the
main discharge gap Dgap (e.g. 40 .mu.m or less when the main
discharge gap Dgap is 80 .mu.m).
3-2. Specific Effects of the Third Embodiment
The following is known through experimentation. Suppose the display
electrode 4 (5) has a plurality of line parts. This being so, when
the distance between adjacent line parts is greater, the luminance
and the illumination efficiency increase. On the other hand, if the
distance between adjacent line parts is widened, a sudden increase
in discharge firing voltage Vf may occur, as in the case of
widening the main discharge gap Dgap. This poses a significant
obstacle to implementation of panels.
This can be explained as follows. When the distance between
adjacent line parts is widened, the discharge at the discharge
firing voltage Vf starts only in the line part that is closest to
the main discharge gap Dgap. To spread this discharge throughout
the cell, a higher voltage is needed.
In view of this problem, the third embodiment provides the
aforementioned projection parts 4aq and 4bq (5aq and 5bq) on the
sides of the line parts 4a and 4b (5a and 5b), in order to locally
reduce the distance between adjacent line parts. This helps the
discharge which is generated near the main discharge gap Dgap
spread throughout the cell even with a low voltage. In so doing,
the rate of luminance change caused by a change in discharge
voltage can be suppressed, and the discharge firing voltage Vf can
be decreased.
This discharge voltage reduction effect produced by the provision
of the projection parts 4aq and 4bq (5aq and 5bq) greatly depends
on the main discharge gap Dgap and the distance between adjacent
line parts. If the distance between each projection part and its
facing line part is no greater than the main discharge gap Dgap,
the effect becomes particularly high. This effect is further
enhanced if the distance between the projection part and the facing
line part is no greater than 50% of the main discharge gap
Dgap.
When the display electrode is only made up of line parts, the
discharge current suddenly changes during the growth of discharge
from he main discharge gap Dgap. This causes a drop in the
potential of the electrode. Here, if line parts of the same
polarity are connected by a connector part, all connected line
parts tend to suffer some voltage drop during the discharge.
According to the third embodiment, however, the projection parts
4aq and 4bq (5aq and 5bq) are provided to the line parts, so that
the line parts of the same polarity are not directly connected. As
a result, a voltage drop hardly affects the outer line parts. In
other words, the spread of the voltage drop is stopped at the line
part 4a (5a) that is closest to the main discharge gap Dgap.
Accordingly, the discharge spreads to the outermost line part more
easily than in the first and second embodiments, with it being
possible to deliver a further reduction in voltage.
The third embodiment also has an effect of improving the cell
opening ratio, by providing the projection parts instead of the
connector parts.
Thus, the display electrode structure of the third embodiment
enables the distance between adjacent line parts to be widened
while maintaining the same discharge voltage, when compared with a
display electrode structure which is only made up of line parts.
Hence PDPs having high luminance and high illumination efficiency
can be realized.
3-3. Modifications to the Third Embodiment
The third embodiment describes the case where the projection parts
4aq and 4bq (5aq and 5bq) are each provided on only one side of one
of the line parts 4a and 4b (5a and 5b), but this is not a limit
for the present invention. For example, the projection parts 4bq
(5bq) may be provided on both sides of the line parts 4b (5b)
towards the adjacent line parts 4a and 4c (5a and 5c), as shown in
FIG. 18 (modification 3-1). In this case, the line part width is
about 10-100 .mu.m, and preferably about 25-60 .mu.m. The distance
between adjacent line parts is about 10-200 .mu.m, and preferably
50-100 .mu.m. The projection part length in the x direction is no
greater than 50% of the cell width, and preferably no greater than
20% of the cell width. Also, the distance between each projection
part and its facing line part is preferably no greater than the
main discharge gap Dgap, and more preferably no greater than half
the main discharge gap Dgap.
When a display electrode includes line parts, a larger distance
between adjacent line parts contributes to higher luminance and
higher illumination efficiency. However, if the distance between
adjacent line parts is widened, a sudden increase in discharge
firing voltage Vf may occur, as in the case of widening the main
discharge gap Dgap. This poses a significant obstacle to
implementation of panels.
This can be explained as follows. When the distance between
adjacent line parts is widened, the discharge at the discharge
firing voltage Vf starts only in the line part that is closest to
the main discharge gap Dgap. To spread this discharge throughout
the cell, a higher voltage is necessary.
In view of this problem, the modification 3-1 provides the
aforementioned projection parts in the gaps between adjacent line
parts, in order to locally shorten the distance between adjacent
line parts. Also, by forming such projection parts that cross over
the line parts, the discharge which occurs in the main discharge
gap Dgap spreads to the outer line parts more easily when compared
with the case where the projection parts are provided only on one
side of the line parts. Hence the rate of luminance change caused
by discharge voltage can be suppressed, and the discharge firing
voltage Vf can be decreased.
Thus, according to the display electrode structure of the
modification 3-1, high luminance and high illumination efficiency
can be achieved with a lower voltage, when compared with the
conventional display electrode structure which is only made up of
line parts.
Here, the shape of the projection parts is not limited to a
rectangle. Other shapes such as a triangle, a quadrilateral, a
cannon-ball, and a letter T are applicable, too. FIG. 19 shows a
display electrode structure having triangular projection parts 4bq
and 4cq (5bq and 5cq) (modification 3-2). According to this
modification, discharge expands between the top of the triangle of
each projection part and its facing line part.
Basically, it is desirable to provide the projection parts at the
center of the gaps between the adjacent barrier ribs 8. However,
this is not a limit for the present invention. For example, the
projection parts 4bq and 4cq may be provided so as to overlap the
barrier ribs 8 when looked from the above, as shown in FIG. 20
(modification 3-3). Here, the projection part width is a little
larger than the barrier rib width.
In doing so, the discharge voltage can be decreased, and the
opening ratio can be increased. This allows the discharge to occur
near the phosphor on the barrier ribs and then spread in the x
direction. Hence high luminance can be produced.
Suppose the third embodiment is applied to a case where the red
cell, the green cell, and the blue cell have different widths in
the x direction. In such a case, a structure shown in FIG. 21 may
be employed (modification 3-4). In the cell which has the smallest
cell width, the projection part 4bq (5bq) is provided on the line
part 4b (5b) near the main discharge gap Dgap. In the cell which
has moderate luminance, the projection part 4cq (5cq) is provided
on the line part 4c (5c) far from the main discharge gap Dgap. In
the cell which has the largest cell width, no projection part is
provided.
As an alternative, the positions of the projection parts may be
determined so as to ensure uniform discharge characteristics such
as discharge voltage between the cells.
Also, the third embodiment can be combined with the structure of
the second embodiment which realizes ramp discharge (modification
3-5). In FIG. 22, the distance between adjacent line parts is
smaller when the line parts are farther from the main discharge gap
Dgap. This being so, projection parts 4ab (5ab) are provided to the
line part 4a (5a). This structure exhibits the effect of the third
embodiment. In addition, the discharge generated at the main
discharge gap Dgap at the start of the discharge is effectively
used for visible light, which enables ramp discharge to be carried
out efficiently.
Also, the projection parts may have a large wavelike shape as shown
in FIG. 23 (modification 3-6). This structure has the same effects
as the modification 3-2.
Also, T-shaped projection parts 4aq (5aq) may be provided as shown
in FIG. 24 (modification 3-7). By doing so, the effective electrode
area of the line part 4a (5a) near the main discharge gap Dgap can
be widened. Thus, the spatial extent of the discharge in the main
discharge gap Dgap caused by the discharge firing voltage Vf is
increased. This suppresses a sudden luminance change around the
discharge firing voltage Vf and decreases the discharge firing
voltage Vf itself. Furthermore, the T shape of the projection parts
4aq (5aq) helps the discharge spread in the x direction. As a
result, the discharge spreads evenly throughout the cell, which
benefits high luminance and illumination efficiency.
Luminance caused by discharge in a surface discharge PDP is
centered around the main discharge gap. Accordingly, it is
important to increase the opening ratio near the main discharge
gap, to improve luminance and illumination efficiency. In a
conventional surface discharge PDP, a transparent electrode
material is used for a display electrode near the main discharge
gap, so that the opening ratio near the main discharge gap need not
be increased. However, when using a line part that is made from a
metal thin film or the like, the opening ratio near the main
discharge gap significantly affects the luminance and the
illumination efficiency.
FIG. 25 shows another modification to the third embodiment. In the
drawing, each display electrode is formed by arranging a plurality
of line parts which are each shaped like a zigzag. Here, the turns
of the zigzag are gentler when the line part is farther from the
main discharge gap. In this case too, the distance between adjacent
line parts is smaller in the areas corresponding to the channels
between the adjacent barrier ribs than in the areas corresponding
to the barrier ribs. Accordingly, these line parts serve as
discharge developing parts. This structure produces the same
effects as the structure shown in FIG. 19.
A metal thin film Cr/Cu/Cr is used as an electrode material in this
embodiment, though the invention should not be limited to this. The
same effects can be achieved by using a thick film electrode that
is formed by patterning, through printing or similar, a metal thin
film of Pt, Au, Ag, NiCr, or the like or a paste in which a metal
powder of Ag, Ag/Pd, Cu, Ni, or the like is dispersed in an organic
vehicle, and then baking the result.
Also, the same effects can be delivered by using a transparent
electrode material for the projection parts. This further increases
the opening ratio, which contributes to higher luminance and higher
illumination efficiency.
Also, a transparent electrode may be used for an electrode which
has connector parts as in the first and second embodiments or for
an electrode which has projection parts as in the third embodiment.
A transparent electrode typically has a large line resistance, and
so discharge develops slowly in the cell. Accordingly, the
discharge developing effects of the connector parts or projection
parts become more prominent.
Also, the projection parts may not be integrated with the scan
electrode or sustain electrode. Instead, they may be electrically
connected with the scan electrode or sustain electrode.
Also, an electrode structure that combines the connector parts and
the projection parts is applicable.
INDUSTRIAL APPLICABILITY
The present invention can be used for a television, and in
particular for a high-definition television that produces a
high-resolution image.
* * * * *