Zigzag shifting self-transfer type display device

A display device wherein a plurality of discharge cells exploiting the d.c. discharge and having the memory function are separated into a group of cells to be used only for the transfer of discharge and a group of cells to be used for the transfer of discharge and for the display of characters etc., and wherein the self-transfer of discharge is done while the discharge is shifting zigzag among the cells of both the groups.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This inventin relates to a flat display device which replaces a cathode ray 
tube, and more particularly to a display device which employs optical 
elements having the memory function. 
2. Description of the Prior Art 
Heretofore, cathode ray tubes have been mainly used in a television set, 
the output device of a computer, the display device of a measuring 
instrument, etc., but flat display devices have been investigated and 
developed in compliance with the request for, e.g., the miniaturization of 
the device. These devices are so constructed and operated that a large 
number of light emitting elements such as electric bulbs, 
electroluminescence elements, light emitting diodes and discharge 
elements; optical modulator elements made of liquid crystal or the like; 
or elements whose optical states are changed by inputs (in this 
specification, the above-mentioned elements are generically named "optical 
elements") are principally arranged on a plane in the form of a matrix, 
and that a picture is displayed by applying electric signals to the 
individual optical elements and thus changing the optical states of the 
optical elements constituting a picture frame. 
As one of the expedients for obtaining a bright picture with such flat 
display device, it is known to employ as the optical elements ones which 
have the memory function as will be described later. 
In the case of driving such flat display device, the fundamental driving 
method has the disadvantage that the number of driving circuits and the 
number of connections between the driving circuits and electrodes are 
enormous. By way of example, consider a character display device of 32 
characters .times. 8 lines and of 7 .times. 9 dots per character. At this 
time, the number of driving circuits and the number of connections become 
close to 300. When the number of driving circuits is so large, the cost 
rises, and when the number of connections is so large, the reliability 
lowers. 
There has been published a self-transfer type display device which employs 
optical elements having the memory function in order to enhance the 
brightness and which adopts means stated hereunder in order to diminish 
the number of driving circuits and the number of connections. For the sake 
of simplicity, the optical elements shall be hereinbelow termed the 
"cells." 
FIG. 1 schematically shows the connections between cells and electrodes in 
a prior-art device. Here, the cells a.sub.w, a.sub.1, a.sub.2, a.sub.3, . 
. . have the memory function. The cell in each of display devices having 
hitherto been published has an equivalent circuit in which a capacitor and 
a discharge element are connected in cascade as shown in FIG. 2a, one in 
which a resistance and a discharge element are connected in cascade as 
shown in FIG. 2b, or one in which a resistance exhibited by a discharge 
element itself (for example, the abnormal glow-discharge region) is 
employed without using the external resistance in FIG. 2b as shown in FIG. 
2c. Alternatively, the cell is an electroluminescence element, a light 
emitting diode of the P-N-P-N structure, or the like. 
As illustrated in FIG. 3, such cell has a hysteresis characteristic in the 
brightness versus the electric variable value x (for example, voltage 
amplitude, current amplitude, pulse interval, pulse width, or pulse 
period). There is a region in which two states B.sub.1 and B.sub.o or more 
states of brightness exist with respect to a certain value (light emission 
maintaining value) x.sub.S of the variable value. Here, x.sub.E denotes 
the minimum value for maintaining the light emission (minimum light 
emission maintenance voltage), and x.sub.W the minimum value for starting 
the light emission (minimum discharge starting voltage). 
The cell of the self-transfer type display device requires (1) to have the 
memory property as described above and (2) to have coupling means between 
the cells. In the following explanation, the discharge cell shown in FIG. 
2c will be referred to as such cell. It is a matter of course, however, 
that the invention is applicable to any cells fulfilling the 
above-mentioned two conditions (for example, the cells in FIGS. 2a and 
2b). 
FIG. 4 illustrates a characteristic obtained in such a way that ionization 
means, for example, coupling holes are provided between the cells, i.e., 
between a.sub.w and a.sub.1, between a.sub.1 and a.sub.2, between a.sub.2 
and a.sub.3, . . . in the prior-art device shown in FIG. 1, and that the 
values of the discharge starting voltage x.sub.W at which the cells 
emitting no light are put into the light emission are plotted versus the 
distance between the cell emitting light and the cell not emitting light. 
In this case, x.sub.W1 and x.sub.W5 denote the discharge starting voltages 
of the first and fifth cells, respectively, x.sub.S denotes the light 
emission maintaining voltage, and x.sub.E denotes the minimum light 
emission maintaining voltage. 
In the panel provided with the coupling means between the cells as 
described above, every fourth ones of cathodes K.sub.1, K.sub.2, K.sub.3 . 
. . of the respective cells a.sub.1, a.sub.2, a.sub.3 . . . are connected 
to cathode lines as shown in FIG. 1. Voltages V.sub.K.phi.1, 
V.sub.K.phi.2, V.sub.K.phi.3 and V.sub.K.phi.4, V.sub.KW, and V.sub.A of 
waveforms shown in FIG. 5 are respectively applied to the four phases of 
cathode lines K.sub..phi.1, K.sub..phi.2, K.sub..phi.3 and K.sub..phi.4, a 
writing cathode line K.sub.W, and an anode line A. Here, those parts in 
the voltage waveform V.sub.KW which are indicated by marks X change in 
dependence on contents to be displayed. First, using the voltage indicated 
by the mark X, the writing cell a.sub.W is caused to emit light, to 
perform the writing. Subsequently, using the four phases of cathode pulse 
voltages V.sub.K.phi.1 .about.V.sub.K.phi.4, the point of light emission 
is sequentially transferred. In FIG. 5, both E.sub.A1 and E.sub.A2 
designate anode voltages. The voltage E.sub.A2 is applied in superposition 
on the voltage E.sub.A1 in order to facilitate the shift or transition of 
the discharge (the same applies in the following description). At the time 
when a desired cell is caused to emit light, the transfer (whose direction 
is indicated by an arrow in the figure) is stopped and the display is 
performed. Among the cells in FIG. 1, those a.sub.2, a.sub.3, a.sub.4, 
a.sub.6 . . . which are hatched do not execute the display even when they 
emit light, and execute only the transfer. On the other hand, the cells 
a.sub.1 a.sub.5, a.sub.9, . . . act as the cells for the display 
(hereinafter, termed "dots") and also effect the transfer action. 
According to the self-transfer type display device of FIG. 1 thus 
constructed, however the cathode electrodes K.sub.N ( N = 1, 2, . . . ) 
may increase, the number of lead-out electrodes may be 6. In contrast, in 
the conventional matrix panel, the number of lead-out electrodes increases 
with the number of cathode electrodes K.sub.N. 
In the case of the four-phase drive illustrated in FIG. 1, the interval of 
the displaying cells in the direction of self-transfer, i.e., the dot 
pitch (for example, the interval between the cells a.sub.1 and a.sub.5) 
l.sub.d becomes four times larger than the pitch of the cells (for 
example, the interval between the cells a.sub.5 and a.sub.6) l.sub.c. The 
pitch of the cells has its lower limit determined by the precision of 
fabrication, etc. Regarding, for example, the AC type plasma cell shown in 
FIG. 2a, the limit of the pitch l.sub.c of the cells is 0.4 mm at the 
present. For this reason, in the case of the prior-art device which is 
subjected to the four-phase drive in the electrode arrangement of FIG. 1, 
the limit of the dot pitch l.sub.d at the display becomes 1.6 mm. In the 
case where, on account of the response speed of the cells, a dispersion in 
the characteristics, etc., the number of drive phases of the cathodes need 
be increased to five or more, the dot pitch becomes still greater. 
In the case of performing a character display of the desk top type, a value 
of 0.7-1 mm is required as the dot pitch l.sub.d at the display. The 
prior-art self-transfer type display device has therefore been 
inappropriate for a display device of the desk top type in spite of the 
fact that it is high in brightness and small in the number of driving 
circuits as well as the number of connections. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a display device which is 
useable as a desk top type display panel and whose brightness is high. 
Another object of this invention is to provide a display device in which 
driving circuits are simple and the number of connections is small. 
In order to accomplish such objects, this invention creates a structure 
wherein a first set of electrodes are driven by n phases (n denotes an 
integer satisfying n .gtoreq. 2), a second set of electrodes intersecting 
with the first set of electrodes are driven by m phases (m denotes an 
integer satisfying m .gtoreq. 2), and the transfer of discharge by cells 
is carried out zigzag relative to a desired direction of transfer 
(hereinafter, termed the "principal self-transfer direction"). 
In this case, the operation corresponds to a drive by m .times. n phases in 
the case of the prior-art device. For this reason, the dot pitch l.sub.d 
at the display in the self-transfer direction is m .times. n .times. 
l.sub.c in the prior-art device, whereas the dot pitch l.sub.d at the 
display in the principal self-transfer direction becomes m .times. l.sub.c 
under substantially equal operating conditions in this invention. For 
example, in the case where m = n - 2, according to this invention the dot 
pitch at the display in the principal self-transfer direction becomes a 
half of that in the prior-art device (of course, the cell pitches in the 
invention and the prior art are equal). 
Hereunder, in order to simplify the explanation, the case of m = n = 2 will 
be referred to. However, this invention is not restricted thereto, but it 
is generally applicable to cases where m .gtoreq. 2 and n .gtoreq. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 6 is a diagram showing an example of the connections between cells and 
electrodes which constitute the self-transfer type display device 
according to this invention. 
As in the case of FIG. 1, symbols a.sub.w, a.sub.1, a.sub.2, a.sub.3, . . . 
represent the cells all of which have the memory function and among which 
those a.sub.2, a.sub.3, a.sub.4, a.sub.6, a.sub.7, a.sub.8, . . . are 
employed for only the transfer and those a.sub.1, a.sub.5, a.sub.9, . . . 
are employed for both the transfer and the display. Here, means of 
ionization coupling are provided between the cells a.sub.w and a.sub.1, 
between the cells a.sub.1 and a.sub.2, between the cells a.sub.2 and 
a.sub.3, between the cells a.sub.3 and a.sub.4, between the cells a.sub.4 
and a.sub.5, . . . The degree of coupling is made smaller between the 
cells a.sub.1 and a.sub.4, between the cells a.sub.3 and a.sub.6, between 
the cells a.sub.5 and a.sub.8, between the cells a.sub.7 and a.sub.10, . . 
. than between the cells (between the cells a.sub.w and a.sub.1, between 
the cells a.sub.1 and a.sub.2, . . . ) as illustrated by partition plates 
P in the figure. The first set of electrodes (first anode electrode 
A.sub.U and second anode electrode A.sub.L) are arranged substantially in 
parallel with the principal self-transfer direction, while the second set 
of electrodes (K.sub..phi.1, K.sub..phi.2) are provided in a direction 
substantially orthogonal to the first set of electrodes. 
FIG. 7, shows waveforms of appled voltages to the cathodes in two phases, 
V.sub.K.phi.1 and V.sub.K.phi.2 ; waveforms of applied voltages to the 
anodes in two phases, V.sub.AU and V.sub.AL ; and a waveform V.sub.KW of 
an applied voltage to a "write in" cathode K.sub.W. Parts indicated by 
marks X in the waveform V.sub.KW change depending on contents to be 
displayed. By applying the voltages of such waveforms, the point of light 
emission written in the writing cell a.sub.w is sequentially transferred 
to the cells a.sub.1, a.sub.2, a.sub.3, a.sub.4 . . . zigzag and advances 
in the principal self-transfer direction (a direction shown by an arrow in 
FIG. 6) as a whole. 
As also seen from FIG. 7, according to this invention, the electrodes being 
substantially parallel to the principal self-transfer direction and the 
electrodes intersecting therewith are respectively driven by the waveforms 
of at least two phases at the transfer (provided that the writing 
electrode shall now be involved in the number of phases). 
The waveforms illustrated in FIG. 7 are of a typical case, and different 
waveforms of the applied voltages V.sub.K.phi.1 and V.sub.K.phi.2 are 
shown in FIG. 8(a). In this case, when the difference between the minimum 
light-emission voltage x.sub.W and the minimum light-emission maintaining 
voltage x.sub.E of the cell adjoining the cell which is emitting light, 
that is, the value of (x.sub.W1 - x.sub.E) is small, it is possible to 
make E.sub.K2 = E.sub.K1 and E.sub.A2 = E.sub.A1 as illustrated in FIG. 
8(b). Herein, V.sub.KW is put into E.sub.K1 = E.sub.K2 when the cell is 
caused to emit light, and it is made below the aforecited value or made 
zero when the cell is not caused to emit light. When the degree of 
coupling between the cells a.sub.w and a.sub.1, between the cells a.sub.4 
and a.sub.5, between the cells a.sub.8 and a.sub.9, between the cells 
a.sub.12 and a.sub.13 . . . is particularly high, the operation of the 
transfer between these cells is sometimes conducted more stably in such a 
way that at .tau..sub.1 sec after the applied voltage of the preceding 
cell has been made below the minimum light-emission maintaining voltage 
x.sub.E, the voltage of the succeeding cell is made at least the minimum 
light-emission starting voltage x.sub.W1 of the cell adjoining the cell 
which is emitting light. The waveforms of the applied voltages to the 
cathodes in that case are ilustrated in FIG. 8(c). When the degree of 
coupling between the cells a.sub.2 and a.sub.3, between the cells a.sub.6 
and a.sub.7, between the cells a.sub.10 and a.sub.11, . . . is low, the 
operation of the transfer between these cells is conducted more stably in 
such a way that before making the applied voltage of the preceding cell 
below the value x.sub.E, the voltage of the succeeding cell is made at 
least the value x.sub.W1. The applied voltages to the cathodes in that 
case are illustrated in FIG. 8(d). Of course, these driving methods can be 
adopted in combination. 
FIG. 9 is a block diagram showing an example of a driving device in the 
case of performing the character display by the use of the display device 
of the construction of the cells and the electrodes as shown in FIG. 6. An 
input signal applied to a terminal 1 is stored in a memory 2, and is 
thereafter converted into an information indicative of an actual character 
by a character generator 3. It is delivered to the "write in" cathode line 
K.sub.W of the display device 10 via a "write in" cathode driving circuit 
4. In this case, the part indicated by the mark X in the waveform V.sub.KW 
shown in FIG. 7 changes in dependence on the output of the character 
generator 3. Anode driving circuits 6 and 7 and cathode driving circuits 8 
and 9 generate the voltage waveforms V.sub.AU, V.sub.AL, V.sub.K.phi.1 and 
V.sub.K.phi.2 shown in FIG. 7 in dependence on signals supplied from a 
timing circuit 5, respectively. 
FIG. 10 shows an embodiment of the construction of the display device of 
this invention at the time when, on the basis of the electrode arrangement 
shown in FIG. 6, the first and second anode electrodes A.sub.U and 
A.sub.L, and the cathode electrodes K.sub.1, K.sub.2, K.sub.3 . . . are 
respectively arranged on identical planes. The self-transfer type display 
device shown in FIG. 10 has two arrays of cells. 
The display device of FIG. 10 is composed of a transparent insulating 
material 11, a phosphor sheet 12, first anode electrodes 13-1 and 13-2, 
second anode electrode 14-1 and 14-2, a spacer 15 which is provided with 
grooves 15-1 of joined rectangles and through-holes 15-2, cathode 
electrodes 16-1, 16-2 . . . , "write in" cathode electrodes 17-1 and 17-2, 
and an insulating substrate 18. The cells are tightly closed by sealing 
therein a gas whose principal constituent is a rare gas such as xenon. 
The discharge occurs between the cathode electrodes 16, 17 and the first 
anode electrodes 13 or the second anode electrodes 14 through the 
penetrating holes 15-2 of the spacer 15. In this case, the coupling 
between the cells is done by the grooves 15-1 formed in the spacer 15. In 
the case of sealing Ne gas or the like and exploiting the visible light 
emission of the gas itself, the phosphor sheet 12 is unnecessary. With the 
construction as shown in FIG. 10, all of the electrodes 13, 14, 16 and 17, 
the spacer 15 and the phosphor sheet 12 can be efficiently fabricated by 
the thick film printing. 
Now, description will be made of an embodiment in the case where the 
electrodes A.sub.U and A.sub.L are arranged on planes different from each 
other. 
FIGS. 11(a) and 11(b) are an explanatory view in which the upper and lower 
cells are illustrated on the sheet of paper with a slight shift relative 
to each other and to which an electrode arrangement is added, and a 
sectional view in the vertical direction, respectively. In this case, the 
second anode electrodes A.sub.L and a "write in" anode electrode A.sub.W 
are disposed on the lower side, the cathode electrodes K.sub.1, K.sub.2, 
K.sub.3 . . . in the middle, and the first anode electrodes A.sub.U on the 
upper side. Likewise to the case of FIG. 6, ionization coupling means are 
provided between the cells a.sub.w and a.sub.1, the cells a.sub.1 and 
a.sub.2, the cells a.sub.2 and a.sub.3, the cells a.sub.3 and a.sub.4, . . 
. In the embodiment of FIGS. 11(a) and 11(b), in order to raise the 
response speed of the writing cell a.sub.w, a "keep alive" cell a.sub.KA 
which is coupled with the cell a.sub.w ionization-wise is provided. When 
the transfer cells are stacked in two stages as in the present embodiment, 
the proportion of occupying areas of the display cells on the surface to 
be viewed (in this case, the upper surface) can be enhanced. 
FIG. 12 shows a display device based on the construction of the cells and 
the electrodes as shown in FIG. 11(a) and 11(b), by taking as an example a 
case where the cells are of three arrays. The display device shown in FIG. 
12 is composed of a transparent insulating material 11, a phosphor sheet 
12, first anode electrodes (A.sub.U) 13-1, 13-2 and 13-3, a first spacer 
15-1, cathode electrodes (K.sub..phi.1, K.sub..phi.2) 16-1, 16-2 . . . , 
"keep alive" cathode electrodes (K.sub.KA) 19-1, 19-2 and 19-3, a second 
spacer 15-2, second anode electrodes (A.sub.L) 14-1, 14-2 and 14-3, "write 
in" anode electrodes (A.sub.W-1, A.sub.W-2, A.sub.W-3) 20-1, 20-2 and 
20-3, and an insulating substrate 18. The cells are tightly closed by 
sealing therein a gas whose principal constituent is a rare gas such as 
xenon. 
Here, the pitch of the cathode electrodes 16 is set at a half of each of 
the pitches of the first anode electrodes 13, the second anode electrodes 
14, and through-holes 151 and 152 of the respective first and second 
spacers 15-1 and 15-2. Through-holes 131 of the first anode electrodes and 
the through-holes 151 of the first spacer, and through-holes 141 of the 
second anode electrodes and the through-holes 152 of the second spacer are 
respectively set so that the corresponding through-holes may be coaxial. 
In addition, the through-holes 151 of the first spacer and the 
through-holes 131 of the first anode electrodes are set so as to oppose to 
the through-holes 152 of the second spacer and the through-holes 141 of 
the second anode electrodes under the state under which they shift to each 
other by the pitch of the cathode electrodes in the principal 
selt-transfer direction as illustrated by a one-dot chain line L. 
In the present embodiment, the ionization coupling between the upper group 
of cells (a.sub.1, a.sub.2, a.sub.5, a.sub.6, a.sub.9, a.sub.10 . . . in 
FIG. 11(a) and 11(b)) and the lower group of cells (a.sub.w, a.sub.3, 
a.sub.4, a.sub.7, a.sub.8 . . . in FIGS. 11(a) and 11(b)) is done by 
providing through-holes 161 in the cathode electrodes. The ionization 
coupling between the cells of the upper group of cells (between a.sub.1 
and a.sub.2, a.sub.5 and a.sub.6, a.sub.9 and a.sub.10, . . . in FIG. 
11(a) and 11(b)) and between the cells of the lower group of cells 
(between a.sub.KA and a.sub.W, a.sub.3 and a.sub.4, a.sub.7 and a.sub.8, . 
. . in FIGS. 11(a) and 11(b)) is achieved by disposing the respective two 
cells in the identical hole of the spacer. 
That is, the through-hole 151-1 provided in the spacer 15-1 hold in common 
the through-hole 161-1 and the through-hole 161-2 provided in the cathode 
electrodes, and it acts as a coupling hole which causes the cell on the 
upper side and the cell on the lower side to produce the discharge and 
which also transfers the discharge. 
In the panel thus constructed, the pitch of the display cells in the 
principal self-transfer direction coincides with the pitch of the holes of 
the first or second spacer, and becomes double the pitch of the holes of 
the cathodes. In consequence, the display dot pitch decreases to 1/2 as 
compared with that in the prior-art device shown in FIG. 1 (the display 
dot pitch is four times as large as the cathode pitch). By making the 
cathode pitch 0.5 mm or less and employing the structure of FIG. 10 or 
FIG. 12, the display dot pitch can be made 1 mm or less, and the display 
suitable for the desk top type becomes possible. 
When, as each cathode electrode in FIG. 12, an unperforated narrow metal 
sheet or a fine metal wire is used instead of the perforated broad metal 
sheet, the cathode electrode pitch can be made still smaller, and the 
display dot pitch can be made smaller accordingly. The coupling between 
the upper group of cells and the lower group of cells in this case is 
effected through clearances which are formed on both the sides of the 
cathodes. 
In the case of performing the display of characters etc. of a large number 
of lines, the number of electrodes to be derived from the panel can be 
further reduced by employing means for decreasing lead-out electrodes for 
the writing cells a.sub.Wi (i = 1, 2, . . . ) as will be stated hereunder. 
By way of example, an electrode arrangement in the case of performing the 
character display of 3 lines is shown in FIG. 13. In the figure, only a 
group of cells into which information are written by the "write in" 
cathode electrode K.sub.W1 are illustrated, and groups of cells by the 
"write in" cathode electrodes K.sub.W2 and K.sub.W3 are not illustrated. 
In this case, the writing cells A.sub.Wij are constructed by the writing 
cathode electrodes K.sub.Wi (i = 1, 2 and 3) and the writing anode 
electrodes A.sub.Wj (j = 1, 2, 3, . . . and 7). By connecting the 
electrodes of the writing cells in the form of a matrix in this manner, 
the number of lead-out electrodes becomes a half or less as compared with 
that in the case of the fundamental construction of FIGS. 11(a) and 11(b). 
An example of waveforms at this time is shown in FIG. 14. Desired writing 
can be carried out by shifting the writing times of the writing cells 
A.sub.W1j, A.sub.W2j and A.sub.W3j. 
By way of example, the number of lead-out electrodes required in the case 
of performing a character display wherein 32 characters .times. 8 lines = 
256 characters and 1 character = 5 .times. 7 dots is 216 in a conventional 
XY-matrix panel and is 60 in the panel employing the fundamental 
construction of FIGS. 11(a) and 11(b), whereas it is 19 in the panel 
employing the construction of FIG. 13. In this manner, according to the 
present embodiment, it becomes possible to make the number of electrodes 
below one-tenth without rendering the dot pitch at the display very large. 
Therefore, a bright display device which is suitable for the desk top type 
and in which the numbers of driving circuits and connections are small is 
provided. 
By holding both the voltages V.sub.K.phi.1 and V.sub.K.phi.2 at E.sub.K1 at 
the display as illustrated by broken lines BL in the waveforms of FIG. 7 
and FIG. 14, it is possible to simultaneously use two cells (for example, 
the cells a.sub.W and a.sub.1, a.sub.4 and a.sub.5, a.sub.8 and a.sub.9, 
a.sub.12 and a.sub.13, . . . in FIG. 6) for the display. By alternately 
lighting up the two cells (a.sub.W and a.sub.1, a.sub.4 and a.sub.5, 
a.sub.8 and a.sub.9, a.sub.12 and a.sub.13, . . . ) at the display, it is 
possible to establish a state in which apparently the two dots are 
emitting light. Even when the cathodes are changed to read as anodes and 
the anodes as cathodes in the above description, substantially the same 
operation is attained. 
Although, in the above, the display panels employing the optical elements 
have been set forth, this invention is not restricted thereto. For 
example, this invention is also applicable to an image pickup panel or a 
memory panel employing charge coupled devices (the so-called CCD's). In 
sum, if (1) elements to be employed have the memory function of at least 
two values and (2) coupling means can be provided between the elements, a 
panel to which this invention is applied can be fabricated.