Gas discharge panel and method for driving the same

A monolithic gas discharge display panel includes a plurality of pairs of sustaining electrodes provided on a first substrate, a plurality of write electrodes separated from the pairs of sustaining electrodes by a dielectric layer and arranged to intersect the sustaining electrodes, and an insulating layer provided on the write electrodes and the dielectric layer for providing a leakage current from the insulating layer to the write electrodes. A second substrate spaced from and in parallel relation to the first substrate forms a gap between the insulating layer and the second substrate, the gap being filled with a discharge gas. A method of driving such a monolithic gas discharge panel prevents damage to the insulating layer means by applying a write voltage to the write electrodes which is of a positive potential with respect to the sustaining voltage applied to the sustaining electrodes and which relies on an internal decoding function of the panel to simplify driving circuitry and to eliminate the need for certain erase pulses.

BACKGROUND OF THE INVENTION 
The present invention relates to a gas discharge panel for data display and 
a method for driving same. In particular, a novel panel structure and 
driving method attain long life of an AC surface discharge or monolithic 
type gas discharge panel and stable operation with a wide operating 
margin. 
In gas discharge panels, known as plasma display panels, surface discharge 
or monolithic type display panels utilize lateral discharges between 
adjacent electrodes. Basically, as is disclosed in U.S. Pat. No. 
3,646,384, issued to F. M. Lay, in a monolithic gas discharge panel of 
this type the electrodes are disposed only on one substrate of a pair of 
substrates and are separated by a dielectric layer or layers. The 
electrodes on opposite sides of the dielectric layer are arranged to 
intersect and the intersections define discharge cells. The pair of 
substrates oppose each other and define a gap or space which is filled 
with a discharge gas. This structure provides the advantages of 
alleviating the requirement of an accurate gap spacing and the realization 
of multi-color displays which are created by coating the internal surface 
of the non-electrode bearing substrate with an ultraviolet ray excitation 
type phosphor. With the structure of the conventional panel, however, 
satisfactory panel life and operating margin could not be attained because 
the dielectric layer become damaged due to a concentration of the 
discharge current at portions of the dielectric layer corresponding to 
edges of the electrodes. Therefore, Japanese Unexamined Patent Publication 
No. 57-78751, having a common inventor with the present patent, proposes a 
panel structure which is improved by separating the functions of write 
cells and display cells in order to elongate the life of the panel. The 
conventional panel structure can be understood from a plan view of 
electrode layout, as shown in FIG. 1, and a partial sectional view as 
shown in FIG. 2. 
With respect to FIGS. 1 and 2, longitudinal sustaining electrode pairs 2, 3 
are provided on the rear side or electrode-bearing glass substrate 1 which 
functions as an electrode supporting substrate. The sustaining electrodes 
2, 3 have protrusions 2a, 3a of a comb or tooth-like structure, the 
protrusions on adjacent electrodes forming pairs, and discharge cells Dc 
are defined by each pair of the comb or tooth-like protrusions 2a, 3a. 
Write or address electrodes 5 are disposed laterally on a vacuum-deposited 
layer 4 which is formed of boron silicate glass and which separates the 
write or address electrodes 5 from the sustaining electrode pairs 2, 3. A 
layer 6 of boron silicate glass is vacuum-deposited over the wirte or 
address electrodes 5 and a surface protection layer 7 of MgO is formed 
over the boron silicate glass layer 6. Write or address cells Wc are 
defined at the intersecting points of the write electrodes 5 and any one 
of the sustaining electrodes 2, 3. An upper or front glass substrate 8 
opposes the electrode bearing substrate 1. A seal is formed between the 
edges of the electrode-bearing substrate 1 and the upper glass substrate 
8, the gap 9 between the substrates is evacuated, and a discharge gas is 
introduced into the gap 9 between them, thus completing a panel. 
Discharges are generated at the write cells Wc when a voltage higher than a 
discharge start voltage is applied to the write cells Wc. Thereafter, a 
sustaining voltage which is lower than the discharge start voltage is 
repeatedly applied alternately to the corresponding sustaining electrodes 
2 and 3 so that the write discharge is transferred to the adjacent display 
cell Dc in order to continuously sustain the discharges. By separating a 
picture element into two kinds of cells, i.e., write cells and display 
cells, the amount of time during which the concentration of current is 
located at the display cell Dc is decreased. Further, the large voltage 
necessary to generate a discharge is not applied to the display cell. 
As described above, the panel structure disclosed in the Japanese 
Unexamined Patent Publication No. 57-78751, can extend service life by 
alleviating damage to the dielectric layer. However, a comparatively thick 
dielectric layer 6 (about 6 .mu.m) and a surface protection layer 7 (about 
0.5 .mu.m) are formed on the address or write electrodes 5 in this panel, 
and therefore wall charges, generated by the discharges, accumulate on the 
portions of the surface protection layer corresponding to the positions of 
the write electrodes. The accumulation of such abnormal wall charges 
produces defective displays or improper discharges. 
When discharges are generated at the write cells, charges are accumulated 
on the surface of surface protection layer 7 correspnding to the relevant 
write cells Wc and the areas near such cells. The amount of charge which 
accumulates on the surface protection layer 7 at positions corresponding 
to the write cells Wc gradually increases as discharges occur at the 
display cells Dc until an abnormal field, resulting from the accumulation 
of excess wall charges, in cooperation with an external field, such as a 
sustaining voltage, induces an accidental discharge at the area near the 
relevant write cells. 
SUMMARY OF THE INVENTION 
A primary object of the present invention is to provide a surface discharge 
type gas discharge panel which assures longer life and stable operation. 
Another object of the present invention is to provide a panel structure 
which reduces the accumulation of excessive charges on the portions of a 
surface protection layer corresponding to write cells in a surface 
discharge panel comprising an electrode arrangement defining separate 
write or address cells and display cells. 
It is a further object of the present invention to provide a panel 
structure which minimizes the influence of the adjacent picture elements 
on one another and thereby realizes high display resolution. 
It is a further object of the present invention to improve a method for 
driving a panel in order to transfer the discharge spots from the write 
cells to the display cells and to stabilize the operation of the panel. 
It is a further object of the present invention to provide a method of 
selectively driving a panel having a plurality of picture elements 
arranged in matrix form to provide a wide operating margin and utilize an 
internal decoding function of a panel. 
A gas discharge display panel according to the present invention comprises 
an upper substrate and a lower or electrode-bearing substrate. Sustaining 
electrode pairs are formed on the electrode-bearing substrate, and a 
dielectric layer is formed over the sustaining electrodes. Write or 
address electrodes are formed on the dielectric layer and arranged to 
intersect the sustaining electrodes and an insulating layer is formed over 
the write electrodes and the dielectric layer; the upper and lower 
substrates thus oppose each other across a discharge space or gap. A seal 
is provided around the edges of the substrates and a discharge gas is 
back-filled into the discharge space after the discharge space is 
evacuated. 
The presence of the write electrodes under the insulating layer causes the 
insulating layer to have discontinuities which allow excess charges formed 
on the insulating layer to leak away or dissipate. Particularly, excess 
charges leak to the write electrodes in the form of leakage current. In 
one embodiment, the insulating layer is formed as a film having a 
thickness of 1 .mu.m or less; excessive charges which accumulate on the 
insulating layer are automatically exhausted or leaked to the lower write 
electrodes through the discontinuities in the relatively thin insulating 
layer. Accordingly, the generation of abnormal discharges resulting from 
an accumulation of excessive charges can be prevented. 
The present invention also relates to a method for driving a plasma display 
panel, including applying a write voltage, which has a positive potential 
value relative to one sustaining electrode of a sustaining electrode pair, 
to a write electrode, thereby to generate a discharge at the write cell 
defined by the intersection of the sustaining electrode pair and the write 
electrode. This driving method alleviates damage to and deterioration of 
the thin insulating layer because the portion of the thin insulating layer 
formed on the write electrode is not influenced by the impact of ions. The 
method also involves maintaining the potential of the write electrode at a 
positive potential value with respect to the potential of the sustaining 
electrode voltage while discharges are sustained at the display cells. 
Moreover, the method of the present invention involves applying write 
pulses having a positive polarity to the write cells, so that discharges, 
accompanied by generation of wall charges, are generated at the rising 
edge of such write pulses, and so that self-discharges created by the 
voltage difference of the accumulated wall charge are generated at the 
falling edge of said write pulse and transferred to the display cells by 
the energization of the sustaining electrodes which form display cells 
with the write electrodes, to which write pulses are applied at the timing 
of said self-discharges. According to this driving method, since wall 
charges automatically disappear with the self-discharges at the write 
cells, it is not necessary to perform the operation of erasing the write 
cells. 
Other characteristics of the present invention will be understood from the 
following detailed description with reference to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to FIGS. 3 and 4, a plurality of pairs of sustaining 
electrodes 11 are arranged in a longitudinal direction on the lower glass 
substrate 10, the lower glass substrate 10 functioning as an electrode 
supporting substrate. Write or address electrodes 13, extending in a 
lateral direction, and separator electrodes 14, also extending in a 
lateral direction, are separated from the sustaining electrodes by a 
dielectric layer 12 made of a low melting point glass. In accordance with 
the present invention, an insulating layer 15 several thousand Angstroms 
(.ANG.) thick is formed on the write electrodes 13 and separator 
electrodes 14 of the upper layer. The preferred structure for the 
insulating layer 15 is a single layer of magnesium oxide (MgO); however, 
the insulating layer 15 may comprise plural layers. A gas space 17, 
defined between the surface of the insulating layer 15 and an upper glass 
substrate 16, is evacuated and filled with a discharge gas, i.e., a gas 
capable of being ionized. 
Each sustaining electrode pair 11 comprises two adjacent sustaining 
electrodes, e.g., X1, Y1 and X2, Y2, as is further apparent from FIG. 4, 
and each sustaining electrode pair 11 is widened comb-like discharge 
portions x and y. The write electrodes 13, e.g., W1, W2, are transverse to 
the sustaining electrodes 11 and intersect the sustaining electrodes in the 
approximate area of the discharge portions x and y. Separator electrodes 
14, for use in a floating condition, are parallel to the write electrodes 
but do not intersect the discharge portions x and y. Thus, write cells Wc 
are defined by, for example, the intersecting point of the write 
electrodes W1, W2 and the sustaining electrodes X1, X2, and display cells 
Dc are defined by the area between the discharge portions x and y. Each 
adjacent write cell and display cell form a picture element or one dot. 
The insulating layer 15 can be formed, e.g., by an electron beam 
vacuum-deposition method, in a thickness of, for example, 5000 .ANG.. In 
addition, the electrodes 11, 13 and 14, may be formed of triple-layer 
conductors of chromium (Cr)--copper (Cu)--chromium (Cr), which are 
deposited on the respective substrate 10 and dielectric layer 12 by a 
conventional patterned photolithographic method. 
The panel strucutre of the present invention causes excessive charges which 
are accumulated on portions of the surface of the insulating layer 15 
corresponding to the intersections of write electrodes 13 and sustaining 
electrodes 11, to easily leak to the write electrodes 13 through pin holes 
or other discontinuities, such as crevices, in the insulating layer 15. 
Accordingly, excess charges do not accumulate on the surface of the 
insulating layer 15 and misdischarges, as described above, can be 
prevented. 
The number of manufacturing steps and man-hours required to produce a panel 
can be reduced with respect to the time required to produce the 
conventional double-layer structure having a dielectric layer 6 and a 
surface protection layer 7. Further, the lower dielectric layer 12 can be 
manufactured by a thick film manufacturing technique, thereby reducing the 
manufacturing cost. 
The thickness of the upper thin insulating layer 15 in the present 
invention is 1 .mu.m or less, because the formation of an insulating film 
of such thickness allows the charges accumulated on the surface of the 
insulating layer 15 to leak to the write electrodes 13 through 
discontinuities in the insulating film. It is also possible to form the 
insulating layer 15 of a double-layer by providing a low melting point 
glass or an alumina oxide layer of approximately 0.5 .mu.m under a MgO 
surface layer of 0.5 .mu.m. Further, the surface layer (not shown) in 
double-layer structure can be an alkali earth metal, such as calcium oxide 
(CaO) or strontium oxide (SrO), as well as MgO. The material for the 
unexposed layer of the insulating layer 15 can be one of a variety of 
oxides having a resistivity which is varied by doping or mixing a small 
quantity of a metal element in the selected oxide. 
In the preferred embodiment the insulating layer 15 has discontinuities, 
e.g., crevices or a porous structure, which permit a leakage of the 
excessive charges to flow from the surface of the insulating layer 15 to 
the write electrodes 13. However, in an alternative structure, the 
accumulation of charges can be removed by exposing the write electrode 13 
to the gas discharge space. This structure, however, has the disadvantage 
that panel operating characteristics become unstable because the write 
electrodes 13 are formed over the insulating layer of MgO and the 
insulating layer is contaminated during the manufacturing process of the 
write electrodes 13. Consequently, it is desirable to coat the entire 
surface with a thin magnesium oxide film after the write electrodes 13 and 
the separator electrodes 14 are formed on the dielectric layer 12. 
A method for driving the gas discharge panel, as described above, will be 
explained by referring to the driving voltage waveforms of FIG. 5 and the 
electrode arrangement of FIG. 4. In FIG. 5, VXs and VWs are waveforms of 
voltages to be applied to a selected one of the sustaining electrodes 11 
and a selected one of the write electrodes 13, e.g., sustaining electrode 
X1 and write electrode W1, respectively. VXns and VWns are waveforms of 
voltages to be applied to non-selected sustaining electrodes 11, e.g., X2, 
X3, and non-selected write electrodes 13, e.g., W2, W3; VY is a waveform of 
a voltage to be applied in common to the Y side sustaining electrodes 11, 
e.g., Y1-Y3. As can be seen from FIG. 5, a sustaining voltage Vs of, for 
example, -120 V, is applied to the selected sustaining electrode X1, while 
a write voltage Vw of +80 V is applied to the write electrode W1; the 
combination of the sustaining and write voltages is set to be higher than 
the voltage necessary to initiate a discharge and a discharge is generated 
at the write cell Wc11 defined at the intersecting points of these 
electrodes. This write discharge is accompanied by the generation of wall 
charges on the surface of the insulating layer at a position corresponding 
to the write cell Wc11. The wall charges accumulate so as to extend over 
the surface of the insulating layer 15 to the approximate position of 
display cell Dc11. Therefore, when a sustaining pulse SP with the voltage 
Vs is applied to the other sustaining electrode Y1, a discharge is 
generated at the display cell Dc11. The discharge creates wall charges in 
a similar form as the first write discharge. Thereafter, the sustaining 
pulse SP is repeatedly applied across all sustaining electrode pairs, as 
shown by the waveforms VXs and VY, to generate a continuous discharge in 
the display cell Dc11. This discharge can be erased by applying a voltage 
pulse of -120 V of a short duration to sustaining electrode X1. 
The accumulation of wall charges on the portion of the surface of the 
insulating layer 15 corresponding to the position of the selected write 
electrode W1 when the write discharge and display discharges are generaed 
is as follows. First, when the write discharge is generated, the write 
electrode W1 has a positive potential and therefore it attracts the 
electrons which are generated by the discharge; the discharge also creates 
positively charged ions. Accordingly, the surface of the thin insulating 
layer corresponding to the pertinent write electrode is not damaged 
because the positively charged ions do not impact or bombard this portion 
of the insulating layer. The negative charges (electrons) which accumulate 
on the surface of the insulating layer 15 gradually leak to the write 
electrode 13 via discontinuities in the insulating layer and finally 
disappear. When the display discharge is generated, the write electrode W1 
has a zero potential and thus is positive with respect to the negative 
sustaining pulse applied to the discharge sustaining electrode pair X, Y. 
Therefore, the portion of the surface of the insulating layer 15 
corresponding to write electrode W1 is not bombarded by ions generated by 
display discharges. When the driving waveforms shown in FIG. 5 are used, 
the portions of the surface of the insulating layer corresponding to the 
write electrodes 13 are not damaged by ion bombardment and the lifetime of 
a panel is extended. 
The write voltage VW applied to the write electrode 13 and the sustaining 
voltage VS applied to the X sustaining electrode 11 have opposite 
polarities in the case of the above embodiment. The write voltage and the 
sustaining voltage can also have the same polarity, in which case, the 
write voltage VW is selected to have a smaller amplitude than the 
sustaining voltage VS, and the write voltage is always positive with 
respect to the sustaining voltage. 
According to the panel structure and driving method of the present 
invention, long life and a higher operating margin of surface discharge 
type gas discharge panel can be attained. Further, a multi-color display 
can be realized when a gas which releases a large amount of ultraviolet 
rays when ionized during discharge, such as a combination of He and Xe, is 
used as the discharge gas and the internal surface of the glass substrate 
16 is coated with a phosphor which emits light when energized by 
ultraviolet rays. 
In a gas discharge panel where the write cells and display cells are 
separated, it is convenient to provide an internal decoding function by 
using multiple connections of the sustaining electrodes 11 in order to 
simplify the addressing circuitry for selecting each picture element or 
display cell. Namely, as shown in FIGS. 6(a)-(d), the number of terminals 
of the sustaining electrodes 11 to be selected and driven can be reduced 
by dividing all of the sustaining electrode pairs into a plurality of 
groups, connecting in common the X sustaining electrode of each sustaining 
electrode pair in each group and connecting in common, between the 
plurality of groups, corresponding ones of the Y sustaining electrodes of 
each sustaining electrode pair in each group. The method of the present 
invention relates to an improved driving method for addressing a surface 
discharge panel having an internal decoding function and an insulating 
layer 15 which permits a leakage current. 
FIGS. 6(a)-(d) illustrate the method of writing in discharge cells in an 
example of the display panel having a 9.times.7 dot structure, wherein 
nine sustaining electrode pairs are divided into three groups, each group 
including three electrode pairs. First, as shown in FIG. 6(a), the 
sustaining electrode X1 of the first group and the write electrode W1 are 
selected and a write voltage exceeding the voltage necessary to initiate a 
discharge is applied across them, and write discharges, as indicated by 
circles, are generated in the write cells in the group of electrodes 
corresponding to the intersecting points of these electrodes. Next, as 
shown in FIG. 6(b), one sustaining electrode group X1 and one sustaining 
electrode group Y2 are selected and a sustaining voltage is applied across 
them, thereby transferring the discharge to the display cell indicated by a 
double-circle, where the discharge is maintained by the inherent memory of 
the display device. When writing in the first line of the first group is 
completed, the sustaining electrode group X2 and the first write electrode 
W1 are selected and discharges are generated at the write cells in the 
write cells of the group indicated by the circles shown in FIG. 6(c). 
Thereafter, as shown in FIG. 6(d), a discharge can be generated at a 
desired display cell, as indicated by the double-circle, by selecting the 
sustaining electrode group Y3 and the sustaining electrode X2 of the 
second group and applying a sustaining voltage. After writing is conducted 
in the third group of the first line, writing is carried out in each group 
of the second line, and data is sequentially written into all areas of the 
discharge panel. 
In accordance with the present invention, a special driving voltage 
waveform which eliminates the operation of erasing non-selected write 
cells in each group is used in the line addressing of each group. FIGS. 
7(a)-(d) show examples of the driving voltage waveforms, wherein Ws is a 
voltage waveform to be applied to the selected write electrode, Xs is a 
voltage waveform to be applied to the selected sustaining electrode group, 
Ys is a voltage waveform to be applied to the selected Y sustaining 
electrode group, and Yn is a voltage waveform to be applied to the 
non-selected Y sustaining electrode group. In FIGS. 7(e)-(g), SWc is a 
voltage waveform to be applied to the selected write cells as a 
combination of Ws and Xs, SDc is a voltage waveform to be applied to the 
selected display cells as a combination of Xs and Ys, and NDc is a voltage 
waveform to be applied to the half-selected display cells as a combination 
of Xs and Yn. 
As seen from FIG. 7, when a positive write voltage pulse WP with peak value 
Vw is applied to the selected write electrode W1 while the first sustaining 
electrode group X1 is set to a sustaining voltage--Vs, discharges are 
generated at the write cells Wc between these electrodes and wall charges 
are accumulated on the surface layer 15. Thus, a wall voltage VQ indicated 
by the dotted line in the waveform diagram SWc is generated. When the write 
voltage pulse WP falls and the voltage difference between the write and 
sustaining electrodes goes to zero, a re-discharge occurs. The 
re-discharge is generated by the wall voltage VQ generated by the write 
discharge, and the re-discharge in turn generates space charges. Selective 
application of the sustaining voltage pulse SPS across the other sustaining 
electrode, in conjunction with the space charges, creates discharges in the 
selected display cells. The discharges are accompanied by the generation of 
wall charge VQ, shown as SDc in FIG. 7(f). In this case, since the write 
cell and display cell use one sustaining electrode in common, accumulation 
of wall charges created by the write discharge and adhering to the portion 
of the surface of the insulating layer corresponding to pertinent 
sustaining electrode expands toward the portion of the surface of the 
insulating layer corresponding to the display cell, also helping 
generating of the first display discharge. Accordingly, a transfer of the 
discharge from the write cell to the display cell can be realized through 
a combination of the space charges generated by the re-discharge in the 
write cell at the falling edge of the write pulse and the wall charge 
generated during the write discharge. It is important that the wall charge 
generated by the write discharge is sufficient to cause the self-discharge, 
and that the selective sustaining voltage pulse SPS is applied to the 
display cell at the same time that the re-discharge occurs. 
When writing is carried out in selected display cells, the timing of the 
sustaining voltage pulse SPS is advanced to coincide with the falling of 
the write pulse as indicated by the waveform Ys in FIG. 7(c). In addition, 
although not indicated in FIG. 7, it may be advantageous to delay or 
eliminate the sustaining pulse SP of waveform Yn corresponding to the 
advanced pulse of waveform Ys. Therefore, wall charges generated by the 
write discharge automatically disappear or erase in the non-selected 
display cells at the falling edge of the write voltage pulse and an 
erasing operation is not necessary for the non-selected cells. To realize 
self-erasing, it is only necessary that wall charges sufficient to cause a 
self-discharge are generated by the first write voltage pulse, and that the 
sustaining voltage to be applied to the non-selected display cells after 
the fall of the write pulse is delayed or omitted. 
The self-redischarge phenomena caused by the wall charge will now be 
described in more detail. FIG. 8(a) shows a cross-sectional view of the 
structure of write cells cut along the line 8--8' in FIG. 4. When the 
write voltage pulse is applied and the write electrode W3 has a positive 
potential relative to the sustaining electrode, electrons and ions adhere 
to the surface layer 15 in the polarity shown in FIG. 8(a) after the 
generation of the write discharge; these electrons and ions become the 
wall charges. Thereafter, when the write pulse falls and the write 
electrode W3 and the sustaining electrode X2 are at the same potential, 
the voltage distribution on the surface layer 15 depends only on the wall 
charges. FIG. 8(b) indicates the changes of such a surface potential. In 
FIG. 8(b), curve A indicates a voltage distribution depending on the 
electrode voltage when the write voltage is applied before the discharge 
occurs, dotted line B indicates a voltage distribution when the electrode 
voltage is cancelled by the wall charge due to the write discharge, and 
curve C indicates a voltage distribution depending only on the wall charge 
after the electrode potential is removed. The generation of the wall charge 
mainly depends on the rising waveform of the write voltage pulse and the 
panel structure, and the self-discharge occurs when a voltage difference 
VQ' of the wall charge exceeds the discharge voltage Vf. Particularly, in 
the panel structure shown in FIG. 3, the generation of wall charges is 
directly related to the thickness of the surface layer 15. When the 
surface layer is too thick, the surface voltage distribution is 
gently-sloped and the voltage difference of the wall charge which causes 
self-discharge is not easily generated. But, when the surface layer 15 is 
formed as a vacuum-deposited film having a thickness of, e.g., 2000-5000 
.ANG., the voltage distribution at the surface of the insulating layer 15 
changes sharply corresponding to the edges of the electrodes and the 
voltage distribution of the wall charge also changes sharply, reflecting 
the above distribution. As a result, self-discharges due to an avalanche 
phenomenon readily occur at the area where the voltage distribution 
changes sharply, and the phenomenon is enhanced when the surface layer is 
thinner. 
According to experiments by the inventors of the present invention, it has 
been confirmed that if the dielectric layer 12 covering the sustaining 
electrode pair 11 is 6 .mu.m thick, the self-discharge phenomenon occurs 
at the falling edge of write pulse when the thickness of the insulating 
layer 15 is 1 .mu.m thick (10,000 .ANG.) or less. The write pulse employed 
in the experiments has a peak value of, e.g., 110 V, and a duration of 8 
.mu.s. 
Meanwhile, it is effective, for preventing an accumulation of excessive 
charges on portions of the surface layer corresponding to the write 
electrode, to make the wall charge voltage distribution change abruptly by 
forming the insulating layer 15 of MgO with discontinuities. Namely, since 
a write voltage of single polarity is always applied to the write 
electrodes, the remaining wall charges are accumulated in accordance with 
the number of times a write pulse is applied to the write electrode. When 
an excess amount of charges are accumulated, they become the cause of 
accidental misdischarges, but, in the panel structure of the present 
invention, excess wall charges leak to the write electrode through 
discontinuities in the insulating layer. 
In such a panel structure, where the write electrode is disposed on the 
sustaining electrode pair and is covered with a thin insulating layer, it 
is difficult to protect the write electrodes, and the insulating layer may 
be damaged by intensified discharges during writing. In view of preventing 
damage to the write electrodes, it is desirable to apply write voltage 
pulses having a polarity which makes the write electrode side become 
positive, thereby protecting the write electrode from damage by ions 
during the discharge. 
According to the driving method of the present invention, wherein 
discharges are selectively transferred to the display cell from the write 
cell using the write discharge, accompanied by the generation of wall 
charges and the re-discharge generated by the wall charge, an improved 
operating margin for a surface discharge type panel and a decoding 
function can be obtained. For example, in a 16.times.24 display cell panel 
with a display cell pitch of 0.5 mm, the sustaining voltage margin ranged 
from 115 V to 130 V and the margin of the write voltage to be applied in 
combination with the sustaining voltage ranged from 105 V to 120 V. 
The selective transfer of a discharge from a write cell to a display cell 
accompanied by self-erasing may also be achieved without connecting the 
sustaining electrode pairs in groups. For example, a system of addressing 
one line at a time can be made to conform to the system of addressing each 
line in a group, if all of the sustaining electrodes are all connected in 
common and the Y sustaining electrode of each pair is individually 
addressed (i.e., a structure where the panel as a whole corresponding to 
one group). 
On the other hand, when multiple connections of the sustaining electrodes 
are employed, it is advantageous to employ the following driving method 
for further lowering the cost of driving circuitry. Namely, the write 
discharge at the write cell Wc is generated by a voltage difference 
between voltages applied to the selective write electrode Ws and the 
selective X sustaining electrode Xs. Accordingly, if an address voltage to 
be applied to the write cell is supplied from the sustaining electrode side 
with a large amplitude, the amplitude of a half-select voltage to be 
applied from the write electrode side may be reduced. In FIG. 7, writing 
with a lower write voltage Vw" can be attained by increasing the amplitude 
of the voltage applied to the selected sustaining electrode group from 
(-Vs) to (-Vw') when the write pulse WP is applied. Thus, a write 
electrode driver (amplifier) can be formed with an integrated transistor 
array, the write driver as well as the write electrodes having a low 
withstand or breakdown voltage, and the cost of the circuit as a whole can 
be lowered. 
In this case, a drive circuit having a higher breakdown voltage is required 
for the X side sustaining electrodes, but the number of elements to be 
driven, as compared with the number of sustaining electrodes, can be 
reduced through the use of multiple connections of the sustaining 
electrode pairs, i.e., by connecting the sustaining electrodes in groups. 
Therefore, the need to increase the breakdown voltage of the X side drive 
elements can substantially be neglected. 
When the driving method of the present invention is employed, it is 
convenient to use an asymetrical sustaining voltage waveform on the X and 
Y sustaining electrodes. That is, not only is the address timing 
asymmetrical, but also the normal sustaining period and the sustaining 
voltage Vs are applied to the X sustaining electrodes with a larger 
amplitude than the sustaining voltage for the Y sustaining electrodes. 
Additionally, in driving a surface discharge type panel where the write and 
display functions are separated, it is desirable to select a write 
electrode addressing sequence so that each subsequent write electrode 
which is addressed is on the opposite side of a previously addressed write 
electrode from the display cells associated with the previously addressed 
write electrode. This addressing sequence is effective for preventing 
display cell data written previously from being erased by the write 
discharges generated by a write electrode adjacent to the cells displaying 
the previously written data. For example, there is a coupling effect 
between the write discharge for display data written in write cell 
WC.sub.21, by selecting the write electrode W.sub.2 of the second line in 
FIG. 4, and the adjacent display cell DC.sub.31. The coupling effect 
between write cell WC.sub.21 and display cell DC.sub.31, separated by a 
distance d2, is larger than the coupling effect of the same write cell 
with display cell DC.sub.11, which are separated by a larger distance d1. 
Accordingly, if data is stored in display cell DC.sub.31, i.e., if the 
display cell is in discharge, mis-erasing may occur due to the write 
discharge generated during the addressing of write electrode W.sub.2. 
However, if the address scanning is carried out so as to progress 
sequentially downward, as seen in FIG. 4, the risk of miserasing is 
reduced since the distance between the write cell of selected line and the 
display cell addressed previously, e.g., d1, is larger than the distance 
between the write cell and the unaddressed display cell, e.g., d2, and 
thus the operating margin increases. 
Several alternative electrode arrangements will be described. FIG. 9 shows 
an electrode structure where the sustaining electrodes are formed in a 
straight stripe pattern; the comb-like protrusions defining the display 
cells shown in FIG. 4 are eliminated. The write electrode 35 and discharge 
suppressing electrode or separator electrode 36 are arranged to cross the 
straight sustaining electrode pair 32, 33. In this case, the write cell Wc 
is defined at the intersecting point of the write electrode 35, and the one 
sustaining electrode 32 of the electrode pair and the display cell Dc is 
defined by the portion of the sustaining electrode pair adjacent to the 
write electrode 35 and the separator electrode 36. The upper surface of 
the write electrode 35 and separator electrode 36 is, of course, covered 
with a thin insulating layer 15 (not shown). According to the electrode 
arrangement of FIG. 9, the pitch of electrode pair can be reduced since 
the comb-like protrusions for defining the display cells are eliminated 
from the sustaining electrodes, and the density of the display cells can 
be increased. Thus, a higher resolution display can be attained. 
In the electrode arrangement of FIG. 9, a write discharge is generated when 
a write voltage is applied to the write cell Wc. The write discharge 
generates wall charges which are accumulated on the surface insulating 
layer 15 (not shown), and the wall charge extends along the surface to the 
portion of the insulating layer 15 corresponding to the display cells Dc. 
However, the charges reaching the surface of the insulating layer in the 
portion thereof corresponding to the discharge suppressing electrode 36, 
which works as a capacitor with the sustaining electrode 35, are prevented 
from extending further. Accordingly, any influence between adjacent display 
cells caused by the movement of the wall charge along the direction of 
sustaining electrodes 32 can be prevented by means of the discharge 
suppressing electrodes 36. Of course, the discharge suppressing electrodes 
have a function similar to that of the separator electrode 14 shown in FIG. 
4 and can be used effectively for separation between adjacent display 
cells. 
FIG. 10 shows another electrode arrangement for attaining separation 
between the adjacent display cells in the direction along the write 
electrodes. In the electrode arrangement of FIG. 10, the write electrodes 
35 have branching segments 37 which extend between adjacent display cells. 
The position of the branching segments 37 is shifted away from the center 
of adjacent display cells so that it overlaps the edge of the sustaining 
electrode which does not form the write cell, and operates as an 
electrostatic barrier along the write electrode direction for preventing 
mis-erasure between the adjacent display cells. 
FIG. 11 shows the arrangement of write electrode 38 having a meander 
pattern, wherein the pertinent write electrode 38 is parallel to the 
sustaining electrodes 11 between the adjacent display cells and functions 
as an electrostatic barrier between the adjacent display cells. The write 
electrode 38 of the embodiment of FIG. 11 has first portions arranged to 
intersect the sustaining electrodes 11 and second portions arranged to be 
substantially parallel to the sustaining electrodes 11. In this case, the 
write cells Wc are alternately arranged on opposite sides of the display 
cell Dc. 
As will be understood from the above description, the insulating layer 15 
covering the write electrode is formed to allow the leakage of excessive 
charges from the surface of the insulating layer to the write electrodes. 
Therefore, unstable operation due to separation of write and display cell 
functions can be eliminated. Moreover, since damage of a thin surface 
insulating layer is alleviated by selecting the polarity of the voltage to 
be applied to the write electrode, long life can be attained. The 
employment of such a surface insulating layer makes possible the transfer 
of discharges from the write cell to the display cell, which is 
accompanied by the self-erasing operation. Accordingly, a large operating 
margin can be obtained with a simple addressing operation. Therefore, the 
present invention is very effective for realizing an improved AC driving 
surface discharge type or monolithic type gas discharge display panel.