U.S. patent number 3,622,829 [Application Number 04/778,279] was granted by the patent office on 1971-11-23 for improvements in fluorescent screen display panels.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Masanori Watanabe.
United States Patent |
3,622,829 |
Watanabe |
November 23, 1971 |
IMPROVEMENTS IN FLUORESCENT SCREEN DISPLAY PANELS
Abstract
A display panel useful for realizing a very thin panel-shaped
letter or figure display device or a panel-shaped TV set, wherein
the small region of the fluorescent screen may be illuminated by
the bombardment of charged particles; the control electrode, formed
by providing a plurality of parallel metal electrode sheets on one
principal surface of the insulating substrate, a plurality of
parallel metal electrode sheets on the other principal surface
orthogonal to the direction of arrangement of said former metal
electrode sheets and holes penetrating through the insulating
substrate at the part where said metal electrode sheets intersect
across the insulating substrate, being made to contact the
discharge plasma generated between the discharge electrodes;
electrons or ions being taken out of the discharge plasma by
applying a signal voltage to said metal electrodes of the control
electrode and made to pass through the holes selectively, the
transparent electrode comprising the fluorescent screen being
provided on the side opposite to said discharge plasma with respect
to said control electrode in parallel with said electrodes; and the
electrons or ions passing through said holes being accelerated and
made to collide with the fluorescent screen by the high voltage
applied to said transparent electrode.
Inventors: |
Watanabe; Masanori (Osaka,
JA) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JA)
|
Family
ID: |
27466011 |
Appl.
No.: |
04/778,279 |
Filed: |
November 22, 1968 |
Foreign Application Priority Data
|
|
|
|
|
Nov 28, 1967 [JA] |
|
|
42/77143 |
Nov 28, 1967 [JA] |
|
|
42/77144 |
Nov 28, 1967 [JA] |
|
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42/77145 |
Nov 28, 1967 [JA] |
|
|
42/77147 |
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Current U.S.
Class: |
313/491;
315/169.4; 345/66 |
Current CPC
Class: |
H01J
17/498 (20130101); H01J 3/025 (20130101) |
Current International
Class: |
H01J
3/02 (20060101); H01J 17/49 (20060101); H01J
3/00 (20060101); H01j 001/62 (); H01j 063/04 () |
Field of
Search: |
;313/108,109.5
;315/169,169TV ;178/7.5D,7.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kominski; John
Assistant Examiner: Demeo; Palmer C.
Claims
What is claimed is:
1. A display panel comprising a panel-shaped discharge tube filled
with low-pressure inert gas; a transparent electrode provided on
one inner surface of said tube; a fluorescent screen applied on
said transparent electrode; control electrode means spaced in
parallel with said one inner surface of said discharge tube; and a
pair of spaced discharge electrodes for producing a plasma by
ionizing said inert gas, said discharge electrodes being placed in
a space opposite to said fluorescent screen, said space being
defined by said control electrode means and the opposite inner
surface of said discharge tube; said control electrode means
comprising an insulating substrate having a plurality of holes
formed therein, a plurality of first parallel metal electrode
sheets on one surface of said insulating substrate and a plurality
of second parallel metal electrode sheets on the opposite surface
of said substrate which are orthogonal to said first metal
electrode sheets, said holes being formed in and through said
insulating substrate at the intersections of said first and second
metal electrode sheets, both sheets having apertures in
correspondence with said holes in said insulating substrate; and
further comprising means applying a signal voltage in sequence to
said metal electrode sheets of said control electrode means while
applying a high voltage between said transparent electrode and each
of said discharge electrodes.
2. A display panel according to claim 1, further comprising a
subsidiary electrode disposed in parallel with and between said
control electrode means and said opposite inner surface of said
discharge tube.
3. A display panel according to claim 1, wherein one of said
discharge electrodes is a thermionic cathode.
4. A display panel comprising a panel-shaped discharge tube filled
with low-pressure inert gas; a transparent electrode provided on
one inner surface of said tube; a fluorescent screen applied on
said transparent electrode; control electrode means spaced in
parallel with said one inner surface of said discharge tube; and a
pair of spaced discharge electrodes for producing a plasma by
ionizing said inert gas, said discharge electrodes being placed in
a space opposite to said fluorescent screen, said space being
defined by said control electrode means and the opposite inner
surface of said discharge tube; said control electrode means
comprising an insulating substrate having a plurality of holes
formed therein, a plurality of first parallel metal electrode
sheets on one surface of said insulating substrate and a plurality
of second parallel metal electrode sheets on the opposite surface
of said substrate which are orthogonal to said first metal
electrode sheets, said holes being formed in and through said
insulating substrate at the intersections of said first and second
metal electrode sheets, both sheets having apertures in
correspondence with said holes in said insulating substrate,
wherein a portion of each of said first and second electrode sheets
extends into said holes in said insulating substrate; and further
comprising means applying a signal voltage in sequence to said
metal electrode sheets of said control electrode means while
applying a high voltage between said transparent electrode and each
of said discharge electrodes.
5. A display panel comprising a panel-shaped discharge tube filled
with low-pressure inert gas; a fluorescent screen applied on one
inner surface of said discharge tube; an electrode provided on said
fluorescent screen; control electrode means spaced in parallel with
said one inner surface of said discharge tube; and a pair of spaced
discharge electrodes for producing a plasma by ionizing said inert
gas, said discharge electrodes being placed in a space opposite to
said fluorescent screen, said space being defined by said control
electrode means and the opposite inner surface of said discharge
tube; said control electrode means comprising an insulating
substrate having a plurality of holes formed therein, a plurality
of first parallel metal electrode sheets on one surface of said
insulating substrate and a plurality of second parallel metal
electrode sheets on the opposite surface of said substrate which
are orthogonal to said first metal electrode sheets, said holes
being formed in and through said insulating substrate at the
intersections of said first and second metal electrode sheets, both
sheets having apertures in correspondence with said holes in said
insulating substrate; and further comprising means applying a
signal voltage in sequence to said metal electrode sheets of said
control electrode means while applying a high voltage between said
electrode provided on said fluorescent screen and each of said
discharge electrodes.
6. A display panel according to claim 5, further comprising a
subsidiary electrode disposed in parallel with and between said
control electrode means and said opposite inner surface of said
discharge tube.
7. A display panel according to claim 5, wherein one of said
discharge electrodes is a thermionic cathode.
8. A display panel comprising a panel-shaped discharge tube filled
with low-pressure inert gas; a fluorescent screen applied on one
inner surface of said discharge tube; an electrode provided on said
fluorescent screen; control electrode means spaced in parallel with
said one inner surface of said discharge tube; and a pair of spaced
discharge electrodes for producing a plasma by ionizing said inert
gas, said discharge electrodes being placed in a space opposite to
said fluorescent screen, said space being defined by said control
electrode means and the opposite inner surface of said discharge
tube; said control electrode means comprising an insulating
substrate having a plurality of holes formed therein, a plurality
of first parallel metal electrode sheets on one surface of said
insulating substrate and a plurality of second parallel metal
electrode sheets on the opposite surface of said substrate which
are orthogonal to said first metal electrode sheets, said holes
being formed in and through said insulating substrate at the
intersections of said first and second metal electrode sheets, both
sheets having apertures in correspondence with said holes in said
insulating substrate, wherein a portion of each of said first and
second electrode sheets extends into said holes in said insulating
substrate; and further comprising means applying a signal voltage
in sequence to said metal electrode sheets of said control
electrode means while applying a high voltage between said
electrode provided on said fluorescent screen and each of said
discharge electrodes.
9. A display panel comprising a flat panel-shaped discharge tube
filled with low-pressure inert gas; a transparent sheet electrode
provided on one longitudinal inner surface of said tube; a
fluorescent screen coated on said transparent electrode; control
electrode means parallelely spaced from said inner surface and said
screen; a mesh-type subsidiary electrode spaced from said control
electrode means; opposed cathode and anode discharge electrodes;
and a plasma space for ionized inert gas opposite to said screen
and defined by said subsidiary electrode, said discharge electrodes
and a second longitudinal inner surface of said tube; said control
electrode means comprising an insulating substrate having a
plurality of holes formed therein, a plurality of first parallel
metal electrode sheets on one surface of said substrate, and a
plurality of second parallel metal electrode sheets on the opposite
surface of said substrate which are arranged orthogonally to said
first sheets, said holes being arranged in a matrix penetrating
through said substrate at the intersections of said first and
second sheets, both sheets having apertures therein in
correspondence with said holes; and wherein said display panel is
further provided with means for biasing the potential of said
subsidiary electrode below the potential of said anode discharge
electrode, means for biasing the potentials of said control
electrode sheets below the potential of said subsidiary electrode,
and a high-voltage supply connected between said transparent sheet
electrode and said cathode and anode electrodes.
10. A display panel comprising a flat panel-shaped discharge tube
filled with low-pressure inert gas; a transparent sheet electrode
provided on one longitudinal inner surface of said tube; a
fluorescent screen coated on said transparent electrode; control
electrode means parallelely spaced from said inner surface and said
screen; a mesh-type subsidiary electrode spaced from said control
electrode means; opposed cathode and anode discharge electrodes;
and a plasma space for ionized inert gas opposite to said screen
and defined by said subsidiary electrode, said discharge electrodes
and a second longitudinal inner surface of said tube; said control
electrode means comprising an insulating substrate having a
plurality of holes formed therein, a plurality of first parallel
metal electrode sheets on one surface of said substrate, and a
plurality of second parallel metal electrode sheets on the opposite
surface of said substrate which are arranged orthogonally to said
first sheets, said holes being arranged in a matrix penetrating
through said substrate at the intersections of said first and
second sheets, both sheets having apertures therein in
correspondence with said holes, wherein a portion of each of said
first and second electrode sheets extend into said holes in said
insulating substrate; and wherein said display panel is further
provided with means for biasing the potential of said subsidiary
electrode below the potential of said anode discharge electrode,
means for biasing the potentials of said control electrode sheets
below the potential of said subsidiary electrode, and a
high-voltage supply connected between said transparent sheet
electrode and said cathode and anode electrodes.
11. A display panel according to claim 10, further provided with
scanning means for supplying information signals to said first and
second electrode sheets.
Description
This invention relates to a plasma display panel in which electrons
or ions emitted from the surface of the discharge plasma, which is
the source of the charged particles, are accelerated and made to
bombard the fluorescent material to illuminate the panel
selectively, and more particularly to a TV set or a letter display
device.
Today, cathode-ray tubes are widely used in display devices
including TV sets. The characteristics of the cathode-ray tube
include easiness in obtaining high brightness, possibility of
changing from low to high brightness continuously and obtain a
so-called halftone, possibility of obtaining high resolution and so
forth.
However, since in a cathode-ray tube the cathode ray is
accelerated, deflected and made to bombard the fluorescent screen
for illumination, the electron gun, the deflection yoke, etc. must
be arranged in sequence on or around the same axis. Accordingly,
the device necessarily becomes large in length and large in volume.
Further, even if the cathode-ray tube is constructed in a panel
form, the construction is limited by the presence of the electron
gun and the deflection means.
Recently, the need for a display pane wherein said deficiencies are
obviated has become great. As such a display panel, many devices
utilizing the electroluminescence or gas discharge phenomena have
been studied and proposed. The device utilizing electroluminescence
is still in the developmental stage since sufficient brightness for
practical use has not yet been obtained. A study on the device
utilizing gas discharge has been reported in Th. J. de Boer: Ninth
National Symposium on Information Display: p. 193 (1968), B. M.
Arora, D. L. Bitzer, H. G. Slottow and R. H. Wilson: Eighth
National Symposium on Information Display: p. 1 (1967).
The report of Boer will be described briefly with reference to FIG.
1. Platinum wires 3, 4 are set on both sides of the insulating
substrate 2 comprising a large number of regularly arranged holes 1
in a way that the wires may pass the center of said holes 1 and the
periphery is sealed airtight by closely adhering the glass plates
5, 6 on both sides. Here, the directions of the platinum wires 3, 4
are orthogonal to each other. The inside of the device is filled
with an inert gas like neon, argon, etc. with appropriate pressure.
When the DC voltage is applied selectively to the mutually
orthogonal platinum wires 3, 4, the gas in the cell at the
intersection is ionized and made to illuminate.
The device reported by M. B. Arora et al. is almost the same in
structure and principle of operation as the one by Boer.
The deficiencies of said display devices include the spread of the
order of several hundred microseconds present in the time lag
between the application of the discharge voltage with the
initiation of discharge. For example, since according to the
American TV standard system, the frame number is 30 per second, the
number of scanning lines is 525 per frame and the number of the
effective scanning lines is 491 per frame, the linear scanning time
is 63.5 microseconds and the effective linear scanning time is 52.7
microseconds. According to the British TV standard system, the
number of frames is 25 per second, the number of scanning lines is
405 per frame, the number of effective scanning lines is 379 per
frame. Thus, the linear scanning time is 98.8 microseconds and the
effective linear scanning time is 82.0 microseconds. Further,
according to the European TV standard system, since the number of
frames is 25 per second, the number of scanning lines is 625 per
frame and the number of effective scanning lines is 584 per frame,
the linear scanning time is 64.0 microseconds and the effective
linear scanning time is 53.0 microseconds. Accordingly, since in
either one of these TV standard systems, the effective linear
scanning time is less than 100 microseconds, a several hundred
microsecond time lag is too large for effective use in any of the
above TV systems. Further, since the brightness depends on the
discharge time, it is technically difficult to realize brightness
modulation due to the large jitter.
An object of this invention is to provide a panel form or thin
display device.
Another object of the invention is to provide a device having a
short response time, i.e. a device having good response
characteristics comparable to or better than those of conventional
TV sets.
A further object of the invention is to provide a device in which
brightness comparable to that of conventional TV sets is obtained
and the brightness can be changed by a signal.
A yet further object of the invention is to provide a thin TV set
which can be hung on the wall.
A yet further object of the invention is to provide a light TV set
having a large panel or image display screen.
Other objects, features and advantages of the present invention
will be readily apparent from the following detailed description of
certain preferred embodiments taken in conjunction with the
accompanying drawings, in which:
FIG. 1 is a diagram for illustrating the main parts of the display
panel utilizing gas discharge as present by Th. J. de Boer;
FIG. 2 is a diagram illustrating the structure of an embodiment of
this invention;
FIG. 3 is a diagram illustrating the control electrode of the
device shown in FIG. 2;
FIG. 4 illustrates the operation of the device shown in FIG. 2;
FIGS. 5 and 6 show the characteristics of the control electrode
shown in FIG. 3;
FIG. 7 is a diagram for explaining Paschen's law; and
FIG. 8 shows a perspective view of an embodiment of this
invention.
Referring to FIG. 2, the structure of a panel-shaped display device
according to this invention will be described. In the figure, 11 is
the panel-shaped discharge tube, at least one principal wall of
which is made of a transparent insulating material like glass, 12
is a glass plate mount against the inner wall of said principal
wall of the discharge tube 11, 13 is a transparent electrode formed
of conductive filmlike tin oxide film adhered to the surface of
said glass plate 12, 14 is a fluorescent screen formed by applying
fluorescent material like zinc sulfide on the transparent electrode
13, and 15 is a control electrode arranged adjacently to the
fluorescent film 14 in parallel with the glass plate 12. As shown
in FIG. 3 which shows a magnified part of the control electrode,
the control grid 15 comprises the first grid electrode 17 on one
surface of the insulating substrate 16 and the second grid
electrode 18 on the other surface; both grid electrodes being
formed by arranging a plurality of metal electrode sheets in
parallel with each other. The direction of the array of the second
set of grid elements 18a, 18b,... 18n,... is orthogonal to that of
the first set of grid elements 17a, 17b,... 17m,... At the part
where the metal electrode sheets 17a, 17b,... 17m,... and 18a,
18b,... 18n,... composing the first and second grid electrodes 17
and 18, respectively, intersect, small holes 19 penetrating through
the electrodes and the insulating substrate 16 are provided. As
material for the insulating substrate 16, glass is preferable. The
reference numeral 20 indicates the grid or mesh subsidiary
electrode placed adjacently to the control electrode 15 in parallel
therewith on the side opposite to the transparent electrode 13 of
the control electrode 15. The numerals 21 and 22 indicate discharge
electrodes. When DC or AC voltage is applied between the two, a
glow discharge is generated and plasma 23 results. The discharge
tube 11 is filled with inert gas or a mixture of such gas and other
kinds of gas of the order of 10.sup.-.sup.2 Torr in pressure.
The numeral 24 indicates a power supply, e.g. a DC power supply,
whose cathode and anode are connected to the electrodes 21 and 22,
respectively, and 25 is a DC bias power supply whose cathode is
connected to the subsidiary electrode 20 and whose anode is
connected to the electrode 22 or the anode of the DC power supply
24. By said DC bias power supply 25, a potential lower than that of
the electrode 22 is given. The reference numerals 26 and 27
indicate DC bias power supplies whose anodes are both connected to
the subsidiary electrode 20 or the cathode of the DC bias power
supply 25. The cathode of the DC bias power supply 26 is connected
to the first grid electrode 17 of the control electrode by way of
the resistor 28. The other DC bias power supply 27 is connected to
the second grid electrode 18 of the control electrode 15 through
the resistor 29. The numerals 30, 31 designate signal input
terminals. Pulsed signals are fed from the terminal 30 to the first
grid electrode 17 of the control electrode 15 and from the terminal
31 to the second grid electrode 18 of the control electrode 15. The
sheets of electrodes elements composing the first and second
electrodes 17 and 18 comprise individual input terminals, but they
are represented by said signal input terminals 30, 31 in FIG. 2.
The numeral 32 indicates a high-tension DC power supply the cathode
thereof being connected to the subsidiary electrode 20 and the
anode being connected to the transparent electrode 13.
In another embodiment, shown in FIG. 4, a portion 170 of each
element of the grid electrode 17 and a portion 180 of each element
of the grid electrode 18 extends into the holes 19. This feature
improves the control of the electron flow by reducing the surface
charge caused by electrons adhering to the surface of the
insulating substrate 16 defining the hole 19.
Now, the operation of said device when the fluorescent film is
bombarded with electrons will be explained.
Since the discharge voltage is applied between the electrodes 21
and 22 by the DC power supply 24, a glow discharge is generated and
the gas present between said electrodes 21 and 22 is ionized to
form the plasma 23. If the electrode 21 to which the cathode of the
DC power supply 24 is connected is a thermionic cathode, the plasma
23 can be formed with a voltage between less than 100 volts and
about several tens of volts.
The plasma 23 fills the space surrounded by the walls of the
discharge tube 11 and the subsidiary electrode 20 and electrons and
ions distribute with substantially uniform density. The subsidiary
electrode 20 is maintained by the DC bias source 25 at a potential
slightly lower than than of the electrode 22 to which the anode of
the DC power supply 24 is connected. At the same time, part of the
plasma 23 flows into the side of the control electrode 15 through
the gaps or meshes of the subsidiary electrode 20. By suitably
selecting the gap width when the subsidiary electrode 20 is
grid-shaped, and the size of the mesh when it is mesh-shaped, the
potential, the density and the electron temperature of the plasma
passing through the electrode 20 can easily be made more uniform
than these of the plasma 23 located between the electrodes 21 and
22.
The first grid electrode 17 of the control electrode 15 is supplied
by the DC bias source 26 with a potential lower than that of the
subsidiary electrode 20. Since the potential of the plasma passing
through the subsidiary electrode 20 is nearly equal to that of the
electrode 20, there will occur no constant flow of electron current
onto grid electrode 17. Similarly, since the second grid electrode
18 is supplied with a potential lower than that of the subsidiary
electrode 20 by the DC bias source 27, the electron current does
not flow into the electrode 18 either. Therefore, in the quiescent
state electrons will not flow into the side of the fluorescent
screen 14 through the holes 19 provided in the control electrode
15.
To obtain an image on screen 14, a pulse signal with positive
polarity is applied from the input signal terminal 30 to the M
electrode of the metal electrode sheets composing the first grid
electrode 17 of the control electrode 15. The potential of the M
electrode will instantaneously become higher than that of the
subsidiary electrode 20 due to the pulse signal. This state is
shown in FIG. 4.
Then, the electrons in the plasma 23, particularly the electrons
which passed through the subsidiary electrode 20, are attracted to
the M electrode and the electron current flows in. Since a large
number of holes 19 are provided at the M electrode, part of the
electrons enter the holes 19.
The, the semicylindrical electron sheath is formed around the M
electrode, and a self-convergent electron current flows. A unique
relation holds among the plasma density, the thickness of the
electron sheath and the potential difference between the electrode
and the plasma. According to the theory of plasma technology, the
relation
holds, where n denotes the plasma density, d denotes the thickness
of the electron sheath, V denotes the potential difference between
the electrode and the plasma, m.sub.e indicates the electron mass,
e the elementary charge and v.sub.e the mean velocity of the
electron. The electrons at the plasma surface move in a way to
satisfy the above equation, and the electron sheath is formed
around the electrodes to which the signal is applied.
Since the potential of the second grid electrode 18 is maintained
lower than that of the subsidiary electrode 20 by the DC bias
source 27, the electron current flowing into the holes 19 of said M
electrode is reflected by the electric field formed by said
electrode 18 and never enters into the fluorescent screen 14. In
such a state, a pulse signal of positive polarity is applied from
the signal input terminal 31 to the N electrode of the metal
electrode sheets composing the second grid electrode 18. The
potential of the N electrode becomes instantaneously higher than
that of the subsidiary electrode 20 while the pulse is present.
Since the first and second grid electrodes 17 and 18 are arranged
orthogonally to each other, the electron current flows through the
common hole (M, N) of the M and N electrodes, whose potential is
higher than that of the subsidiary electrode 20, from the side of
the subsidiary electrode 20 to the side of the fluorescent screen
14.
A high potential is applied to the transparent electrode 13 by the
DC high-tension power supply 32. The electric field formed by the
transparent electrode 13 acts as an accelerating electric field for
electrons. Therefore, the electric current which passed through
said hole (M, N) travels while being accelerated in a beam form and
finally collides with the fluorescent screen 14. The atoms in the
small region of the fluorescent screen 14 where the electron
current hits are excited and emit light in the form of a spot.
Then, if a pulse signal is fed to the (N+1) electrode of the second
grid electrode 18 while maintaining the potential of the M metal
electrode sheet of the first grid electrode 17 above that of the
subsidiary electrode 20, the electron current passes through the
common hole (M, N+1) only while the pulse is present, and the small
region of the fluorescent screen 14 at a position corresponding to
the hole (M, N+1) is illuminated. Thus, if a pulse signal is fed to
the metal electrode sheets composing the first and second grid
electrodes 17 and 18, the fluorescent screen 14 can be scanned by
the electric current.
If the amplitude of the pulse signal is controlled, the quantity of
the electron current, which passes selectively through the holes 19
of the control electrode 15 while the pulse signal is applied, is
controlled. The relation between the signal voltage and the
electron current in this state is shown in FIGS. 5 and 6. FIG. 5
shows an example of the relation when the potential of the second
grid electrode 18 of the control electrode 15 is maintained equal
to that of the subsidiary electrode 20 and a signal voltage is
applied to the first grid electrode 17. The abscissa shows the
potential difference between the first grid electrode 17 and the
subsidiary electrode 20 when a signal voltage is applied to the
electrode 17. The ordinate shows the relative value of the electron
current corresponding to the potential difference. FIG. 6 shows an
example of the relation when a signal voltage is applied to the
second grid electrode 18 while maintaining the potential of the
first grid electrode 17 of the control electrode 15 equal to that
of the subsidiary electrode 20. The abscissa shows the potential
difference between the second grid electrode 18 and the subsidiary
electrode 20 and the ordinate shows the relative value of the
electron current. As is evident from the figure, the electron
current flows in correspondence to the signal voltage fed to the
control electrode 15. In particular, a linear relation holds
between the signal voltage fed to the second grid electrode 18 of
the control electrode 15 and the electron current passing through
the holes 19 of the control electrode.
Accordingly, the fluorescent screen 14 emits light with a
brightness corresponding to the amplitude of the pulse signal. If
the pulse signal is changed with time, the brightness of the
fluorescent screen 14 changes with position, and letters or figures
can be displayed.
In this embodiment the wall of the discharge tube 11 is made
transparent only at its area mounting the glass plate 12, the
transparent electrode 13 and the fluorescent screen 14 and may be
made of opaque at the other area thereof. Further, another
embodiment of the present display panel arrangement may be made in
the form of the fluorescent screen 14 and the transparent electrode
13 which are mounted onto the tube 11 without such an intermediate
glass plate 12.
If the transparent electrode 13 is provided on the face of the
discharge tube 11 and the luminescent screen 14 is applied on the
opposite side of the electrode 13, the luminescent efficiency
increases since the electrons or ions hit the luminescent screen 14
directly. Conversely, if the luminescent screen is adhered directly
to the face of the discharge tube 11 and the transparent electrode
is provided thereon, the electrons can pass through the transparent
electrode to make the screen illuminate, but ions cannot. In the
method of bombarding the luminescent screen 14 with ions, the
luminescent screen 14 may be damaged (so-called ion spot) due to
the large mass of ions. Therefore, it may be said that the method
of using electrons is more preferable because of the easiness of
acceleration and the lace of danger of damaging the luminescent
screen 14.
A particular construction of the discharge tube 11 is as follows:
the insulating substrate 16 of the control electrode 15 is a glass
plate of 1-2 mm. in thickness, the first grid electrode 17 and the
second grid electrode 18 are formed of low-resistivity material
like Cu, Al, Au, Ag, etc. of 0.005-0.1 mm. in thickness, the hole
provided at the insulating substrate 16 is 0.25-1 mm. in diameter,
the holes provided at the first and second grid electrodes 17 and
18 are 0.2-0.8 mm. in diameter, the thickness of the transparent
electrode 13 is of the order of m.mu.-.mu., and the gap between the
transparent electrode 13 and the control electrode 15 is 1-2 mm.,
the potential difference between the two electrodes 13 and 15 is
2-5 kv., and the thickness of the discharge tube 11 is 10 to
several tens of millimeters.
Though a high-tension voltage is applied between the transparent
electrode 13 and the subsidiary electrode 20, discharge will never
occur between the transparent electrode 13 and the subsidiary
electrode 20 or the control electrode 15. This is because the
property of such gas discharge is expressed by Paschen's law.
Namely, the spark voltage Vs of the uniform electric field becomes
a function of the product of the gas pressure P and the electrode
gap distance d. The spark voltage Vs decreases as said product Pd
increases and assumes a minimum value at a certain value. As the
product Pd increases further, the spark voltage Vs increases. Such
relation holds true over the wide range of the product Pd of gas
pressure P 10.sup.-.sup.2 -2,400 mm. Hg, electrode gap distance d
5.times. 10.sup.-.sup.4 -20 cm. and gas temperature
-15.degree.-860.degree. C. Some examples of the minimum spark
voltage Vs min and the product Pd of the gas pressure and the
electrode gap distance will be shown in the following table.
##SPC1##
The above table is derived from the "Electric Engineering Handbook"
published by the Institute of Electrical Engineers of Japan. In the
table, the values in the case of helium, neon and argon are shown
with respect to the use of the cathode of aluminum.
According to the above fact, when the gas pressure P and the
electrode gap distance d between the discharge electrodes 21, 22
are determined so as to ensure the minimum spark voltage Vs of the
Paschen's law, the transparent electrode 13, the control electrode
15 and the subsidiary electrode 20 are arranged very close to each
other without causing electrical discharge therebetween even if a
certain large potential difference is produced therebetween. For
example, in the case of argon gas, providing a gas pressure of
10.sup.-.sup.2 mm. Hg and the discharge electrode distance 100 mm.
(between the electrodes 21, 22), the product Pd is equal to 1 mm.
Hg.sup.. mm. Although this product value differs from that of the
table (12 mm. Hg.sup.. mm.), the electrical discharge is easily
occurrable with a thermionic cathode as the discharge electrode 21.
As to the control electrode 15 and the accelerating electrode 13,
the electrode distance is set to be 1-2 mm., so that the product Pd
is equal to 1-2 mm. Hg.sup.. mm. which remarkably differs from the
table value, and the spark initiation voltage also becomes very
high.
If a pulse signal of positive polarity lasting for a time interval
equal to one level scanning period of the TV signal is applied in
sequence to each metal electrode sheet of the first grid electrode
17 composing the control electrode and the video signal of one
level scanning period is divided and distributed to the metal
electrode sheet composing the second grid electrode 18, the
transmitted image is reproduced.
Since the electrons are taken out of the plasma 23 by the electric
field formed by selectively applying the pulse signal of positive
polarity to the first and second grid electrodes 17 and 18 of the
control electrode 15, the response time is quite short. Since the
electrons which passed through the holes 19 of the control
electrode 15 are accelerated by the electric field formed by the
transparent electrode 13, the time lag between the arrival of the
signal and the illumination of the small region of the luminescent
screen 14 at the corresponding position is hardly noticeable. When
a signal, such as a TV signal, whose amplitude changes constantly
is applied to the device, the device operates in a proper
manner.
FIG. 8 shows an example of the completed device. The electronic
device of the TV set is installed into the base 101 or the column
102 and the image-reproducing discharge tube 104 is installed in
the panel-shaped case 103.
* * * * *