U.S. patent number 3,629,654 [Application Number 04/880,676] was granted by the patent office on 1971-12-21 for removable electrode display device.
This patent grant is currently assigned to The National Cash Register Company. Invention is credited to John L. Janning.
United States Patent |
3,629,654 |
Janning |
December 21, 1971 |
REMOVABLE ELECTRODE DISPLAY DEVICE
Abstract
An electroluminescent display device formed by superimposing a
first substrate upon a second substrate, forming a cell between the
surfaces of the two substrates. A common transparent electrode is
deposited on the outside surface of one of the two substrates
overlying the entire cell formed by the superimposed substrates. A
conductive pattern electrode, having a desired configuration, is
placed in intimate contact (e.g., pressure contact) against the
outside surface of the other substrate. Information is displayed by
applying an alternating voltage of sufficient magnitude and
frequency between the two electrodes, resulting in the ignition of
an excitable gas contained within the formed cell, the illumination
produced corresponding to the configuration of the conductive
pattern electrode. The conductive pattern electrode is removable,
since it is retained against the outside surface of the cell only
by a pressure contact; therefore, the type of information to be
displayed can be easily varied simply by removing the conductive
pattern electrode and placing another in its place. The various
designs of removable electrode patterns which can be employed are
endless and can encompass Arabic numerals, alphabetic characters,
and other designs.
Inventors: |
Janning; John L. (Dayton,
OH) |
Assignee: |
The National Cash Register
Company (Dayton, OH)
|
Family
ID: |
25376825 |
Appl.
No.: |
04/880,676 |
Filed: |
November 28, 1969 |
Current U.S.
Class: |
315/166; 313/520;
345/76; 313/582 |
Current CPC
Class: |
H01J
11/00 (20130101) |
Current International
Class: |
H01J
17/49 (20060101); H05b 037/00 () |
Field of
Search: |
;313/109.5,18A,18R,201
;315/169R,169TV,246 ;340/336,343,344 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hossfeld; Raymond F.
Claims
What is claimed is:
1. A low-cost gaseous electroluminescent device comprising:
first and second transparent elements, each having an inside
surface and an outside surface, with said inside surfaces facing
each other and being spaced apart a distance of approximately 0.010
inch;
means for hermetically sealing said elements to form a chamber
therebetween;
an ionizable gas filling said chamber;
a continuous coating of transparent, electrically conductive
material contacting the outside surface of the first element to
form a coating electrode thereon;
a movable character electrode means;
means for positioning said character electrode means to contact the
outside surface of said second element; and a source of AC
potential connected to said character electrode means and said
coating electrode to ionize said gas to produce an illumination
conforming to the shape of the character electrode means.
2. The device as claimed in claim 1 in which said means for
positioning said character electrode means comprises:
a disc made of electrically insulating material and rotatably
mounted on a shaft; and
drive means for rotating said disc;
said character electrode means comprising: conductor character
elements located on one face of said disc and means for connecting
said elements to said source of AC potential;
said disc being positioned relative to the outside surface of the
second transparent element so that a selected character element on
said disc will be moved by said drive means to contact said outside
surface of the second transparent element and thereby ionize said
gas to produce an illumination conforming to the shape of the
selected character element.
3. The device as claimed in claim 1 in which said movable character
electrode means comprises:
a flat planar insulating card having character-forming electrodes
on one face thereof, with said electrodes being connected to said
source of AC potential;
said means for positioning said character electrode means being
holding means (like springs) for holding said card with the face
having said character-forming electrodes thereon against the
outside surface of the second transparent element to ionize the gas
to produce an illumination conforming to the shape of the
character-forming electrodes which are connected to the source of
AC potential.
4. The device as claimed in claim 1 in which said first and second
transparent elements are first and second tubes with each tube
having one closed end and one open end, said second tube being
smaller in diameter than the first tube and placed within the first
tube in concentric relationship therewith, with said open ends
being aligned and sealed together to form said chamber, with the
inside surface of the first tube and the outside surface of the
second tube forming the inside surfaces of said chamber;
said movable character electrode means being positioned inside said
second tube with said electrode means in contact with the inside
surface of the second tube.
5. The device as claimed in claim 1 in which said first and second
transparent elements are made of glass having a wall thickness of
approximately 0.030 inch;
said gas being composed of more than 99 percent neon and less than
1 percent of nitrogen and argon;
said source of AC potential being approximately 450 volts having
pulses of two microseconds' duration with fifteen microseconds'
duration between successive pulses.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an electroluminescent display cell
having a permanent electrode and a movable electrode.
Electroluminescent display devices which produce illumination
corresponding to a particular pattern upon the application of an
electrical potential across the electroluminescent display device
are well known. Devices of this type are exemplified in U.S. Pat.
No. 3,127,535, issued Mar. 31, 1964, on the application of Harold
T. Westerheim, and in British Pats. Nos. 1,161,832 and
1,161,833.
A continuing problem, applicable to most electroluminescent display
devices, has been the inability to provide a structure that can be
readily and reproducibly fabricated. Another expensive problem
found in the prior art devices is the fact that the entire display
device must be replaced upon the deterioration of the electrodes, a
problem which is particularly prevalent when the electrodes are
internal to the cell. These and other undesirable features found in
most prior art devices have been eliminated in the instant
invention.
It is therefore an object of the present invention to provide a
novel electroluminescent display cell which permits the easy
replacement of the electrode which determines the design of the
configuration to be displayed, a feature which also obviates the
necessity of replacing the entire display cell in the event of
electrode failure.
Another object of the invention is to provide an electroluminescent
display cell in which the type of information to be displayed is
not permanently affixed to the cell, thereby resulting in a display
cell capable of being utilized for displaying different types and
kinds of information.
A further object of the invention is to provide a structure which
is capable of easy manufacture.
Display cells fabricated in accordance with the teachings of this
invention allow for automated production, since no special
cavities, or designs or any sort, need be placed on the cell's wall
surfaces for outlining the character to be displayed.
SUMMARY OF THE INVENTION
This invention permits the display of variable information, since
the information to be displayed is not restricted to the display
cell.
One form of the invention features a display cell formed by the
assembly of two elements -- i.e., two transparent flat plates --the
plates assembled in such a manner that there is formed between the
two inner faces a cell for the containment of a gaseous medium. One
exterior side of the assembly serves as the front side; i.e., the
side which will be exposed to a viewer. A transparent common
electrode is deposited on the front side, completely overlying the
cell formed within the assembly. On the other exterior side of the
assembly-- i.e., the rear side-- is placed a movable character
electrode. The character electrode may be an insulating card
containing conductive character electrodes with the desired design
configuration. The movable character electrode is affixed to the
rear side of the display cell by conventional means, such as spring
means, which also facilitates the removal of the character
electrode. The illumination necessary for viewing the character to
be displayed is provided by the application of an alternating
potential between the common electrode and the movable character
electrode. This causes ignition to occur within the gas-containing
cell, thus providing illumination conforming to the configuration
of the movable electrode.
A second form of the invention features a display cell of tubular
construction, resulting in a display cell having somewhat the shape
of a conventional vacuum tube. This form of the invention utilizes
a transparent electrode deposited on the exterior surface of the
outside tube, which is the surface exposed to a viewer. The movable
electrode may be an internal electrode plug, or may take the form
of copper-clad electrodes on Mylar film, or may be any other
material, having electrodes thereon, which may be inserted within
the inside opening of the tubular cell.
Both forms of the invention are extremely versatile, in that the
information to be displayed can be changed simply by the
replacement of the movable electrode. The invention also lessens
the occurrence of cell replacement; e.g., if any spots were to
occur on the glass plates, the problem could be obviated simply by
moving the movable electrode to a clear spot on the glass.
Defective cells are easily replaced, since it is necessary only to
replace the glass housing, leaving the character electrodes
intact.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood by referring to the
following drawings.
FIG. 1 is an exploded isometric view of one embodiment of the
display assembly in accordance with the invention.
FIG. 2 is an isometric view of another form of the embodiment shown
in FIG. 1.
FIG. 3 is a front view of the display assembly in use with a
circular electrode pattern-containing disc.
FIG. 3a is a cross-sectional view taken along the line 3a of FIG. 3
to show more details of a conventional means for rotating the
disc.
FIG. 4 is a isometric view of still another form of the
invention.
FIG. 5 is a plan view of the embodiment illustrated in FIG. 4.
FIG. 6 illustrates the different form of construction that the
embodiment in FIG. 4 can take.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For a better understanding of the invention, reference is now made
to FIG. 1, which illustrates one form of the invention. The display
assembly 20 is composed of first, second, and third plates, 21, 22,
and 23, each having first and second sides, the first sides being
those sides facing the transparent electrode 25. The plates in the
completed structure are held together by conventional means such as
glass solder or glass cement, thereby resulting in an airtight
structure. The plate 22 is nothing more than a spacer, having a
central opening therethrough, spacing the plate 21 from the plate
23, and also forming a uniform cell within the assembled structure.
The plate 23 has a hole formed therein for the purpose of receiving
a conduit 24. The conduit 24 provides means by which the cell,
formed between the plates 21 and 23, is evacuated of air, and also
provides the means by which the cell is filled with an
electroluminescent material-- i.e., gas--after which the conduit 24
is sealed. The first plate, 21, has attached to its outside surface
(first side) a transparent conductive electrode 25 of a material
such as cadmium oxide, tin oxide, thin gold, or any other suitable
conductive material. The transparent conductive electrode 25 may be
deposited on the glass surface by conventional methods such as
metal deposition or other well-known coating techniques. The
electrode 25 serves as the common electrode for the display of FIG.
1.
Two pressure-applying nonconducting elements (leaf springs), which
are cemented onto the outside surface (second side) of the rear
plate 23, provide sufficient pressure to retain a pattern electrode
card 30 in intimate contact with the outside surface (second side)
of the glass plate 23. Electrodes 32 having a particular
configuration are coated on or imbedded in the insulating card 30,
each electrode being connected to its own input terminal, the
terminals shown generally at 31. Although the electrodes 32 in FIG.
1 are shown as a seven-bar matrix, it is apparent that the
electrode pattern could have any desired configuration, such as
numeric, alphabetic, alphanumeric, etc., the only requirement being
that the pattern electrodes overlie the gas cell. The electrodes 32
are connected to a source 31a of AC potential via a conventional
character selector 31b; and the transparent conductive electrode 25
is also connected to the AC source 31a.
It can be seen that the transparent electrode 25 is capacitively
coupled to the cell formed within the glass structure, due to the
external positioning of the electrode 25, thereby being separated
from the cell by the glass dielectric forming the structure.
Similarly, the electrodes 32 are also capacitively coupled to the
cell.
Looking at the display 60 of FIG. 2, it can be seen that the
embodiment of FIG. 1 can take another form. In FIG. 2, a hermetic
chamber is formed by the two substrates, the plates 61 and 62. The
chambers can be conventionally etched on the second side of the
plate 61 and on the first side of the plate 62. When assembled and
sealed, the chambers on the plates 61 and 62 are in full registry,
thereby defining a cell capable of maintaining a pressurized gas.
The gas is introduced into the structure through a conduit 69. If
desired, the chamber need be formed on only one of the two plates.
A transparent film electrode 63, which functions as the common
electrode for the display device 60, is deposited conventionally on
the outside surface (first side) of the plate 61. Electrodes 65 and
66 are coated on or imbedded in an insulating card 64, each
electrode connected to an input terminal 67. The electrode
character card 64 is held against the outside surface (second side)
of the plate 62 by springs 68, thereby placing the character
electrodes 65 and 66 in intimate contact with the plate 62. The
electrodes 63, 65, and 66 may be energized in the same manner as
those shown in FIG. 1.
In operation, the display devices of FIGS. 1 and 2 are similar.
Therefore, only the operation of the embodiment shown in FIG. 1
need be described. The movable insulating card 30, containing the
character electrodes 32, is placed in contact with the outside
surface of the rear plate 23. Application of an alternating
potential between selected terminals 31 of the character electrodes
32 and the common transparent electrode 25 causes an electron
multiplication process to occur within the cell. This
multiplication process proceeds until breakdown occurs; i.e., a
gaseous discharge occurs within the cell. The ionization will be
limited and will conform to the configuration of the character
electrodes. The parameters involved in producing the ionization for
the desired illumination include the potential applied across the
cell, the distance between the electrodes 25 and 32, and the
pressure of the gas contained in the cell. The ionization provides
the illumination conforming to the shape of the electrode patterns,
necessary for viewing by an observer. The ionization occurring
within the cell also provides the display cell with a memory,
because the ionization occurring within the cell results in the
deposition of charged particles on the inner cell wall surfaces of
the plates 21 and 23. Positive charges are deposited on the inner
cell wall surface capacitively coupled to the electrode to which
negative potential is being applied, and electrons are deposited on
the inner cell wall surface capacitively coupled to the electrode
to which a positive potential is being applied. These charges are
trapped on the cell walls because of the capacitive coupling effect
exerted by the glass cell walls. It can then be seen that the
deposited wall charge has a polarity which is opposite to that of
the potential initiating the ionization. Therefore, on the
succeeding reverse cycle, the wall charge will be additive to the
applied potential, thereby insuring ignition on the succeeding
reverse cycle and also lowering the criticality of maintaining the
applied potential at one specific value. In other words, after the
first ionization, the voltage necessary to sustain the ignition can
be of a magnitude which is equal to the original applied potential
less the wall charge. By proper selection of the desired character
electrodes, any type of character can be displayed.
FIG. 3 illustrates means by which information may serially be
displayed. Electrodes 33 are deposited on a circular insulating
disc 34, the disc being rotatably mounted on a shaft 35, which can
be rotated by any conventional stepping mechanism. The insulating
disc 34 is resilient and applies pressure against the outside
surface of the rear plate 23, thereby retaining the electrode
patterns in intimate contact with the glass surface. Rotating
contacts are connected to each character and are located on the
rear surface of the assembly 20. The rotating contacts may be
connected to an electrical source by any conventional means.
One such conventional means is shown in FIG. 3a. Each electrode
(like 33) is provided with an electrical contact 80, which is
suitably secured to the rear surface of the disc 34 as shown, and a
conductor 82, passing through the disc, connects the electrode
(like 33) with its associated contact 80. A stationary electrode
84, connected to an AC source, completes the electrical connection
to the selected electrode when the electrode (like 33) is
positioned in the topmost position (like the character 3 in FIG.
3), where the character contacts the assembly 20.
A conventional stepping mechanism for rotating the disc 34 is shown
in FIGS. 3 and 3a. The disc 34 has teeth 90 on a portion of its
periphery, which teeth are driven by a driving gear 92 associated
with a conventional stepping motor 94. The motor 94 rotates the
disc 34 so as to position the selected character to the topmost
position (like the character 3 shown in FIG. 3), where the selected
character contacts the assembly 20, and its associated contact 80
engages the stationary contact 84 to energize the assembly 20. A
conventional character select means (not shown) may be used for
energizing the stepping motor 94.
Illustrated in FIG. 4 is a single character display 39 featuring
tubular construction. The display cell 39 is fabricated from two
glass tubes 41 and 42. The tube 42, having an outside diameter less
than that of the tube 41, is placed inside of the tube 41, the
tubes being in concentric relationship with respect to each other.
The concentric relationship is further insured by spacer tips 51.
The tube 41 is open at both ends, and the tube 42 is closed at one
end and open at the other. One open end of the tube 41 is sealed to
the exterior surface of the tube 42, as shown at 42a in FIG. 5,
thereby forming an annular chamber between the inside wall of the
outside tube 41 and the outside wall of the inside tube 42.
Evacuation means are connected to the remaining open end of the
tube 41. The chamber is evacuated of air and is then filled with an
electroluminescent material such as gas. The tube 41 is then
sealed, resulting in the formation of a tip 43.
The outside of the tube 41 is coated with a transparent conductive
common electrode 40 over its entire cylindrical surface. The
transparent electrode can be of a material such as cadmium oxide,
tin oxide, thin gold, or any other material which can be deposited
and which will adhere to the outside glass surface of the tube 41.
Coating of the electrode can be accomplished by conventional
methods such as metal deposition techniques. A metallic band 50,
such as gold, is positioned over the transparent conductor at the
lower end of the tube 41, the band being utilized to insure a
better contact with the spring-loaded contact 48. The contact 48
and the pins 47 are connected to an energizing source like the one
shown in FIG. 1.
The movable electrodes for the display are on a separate substrate
44, which may be in the form of a plug. As one skilled in the art
can see, there are many possible ways to fabricate such an
electrode plug, such as copper-clad electrodes on Mylar, one piece
molded plugs with electrodes potted in place, and thin-film
electrodes on various flexible substrate forms. In order to
complete the display assembly, the electrode plug is inserted into
an opening 45 of the tube 42. The outer dimensions are such that
the plug 44 will place the electrode patterns 46 into contact with
the inside glass surface of the tube 42. By way of example only,
the electrode pattern on the plug 44 is shown to consist of a
seven-bar matrix in which leads are brought out to the pin
electrodes 47 for insertion into a suitable socket. The electrodes
46 can consist of any suitable material, such as gold, and may be
deposited on the plug by any conventional method.
FIG. 6 illustrates the fact that the device of FIG. 4 need not be
restricted to tubular construction. The device 70 is fabricated
from two rectangular members 71 and 72. The member 71 is placed
inside the member 72, thereby forming a chamber between the inside
surface of the tube 72 and the outside surface of the member 71.
The member 71 is closed at one end and open at the other; the
member 72 is open at both ends. The two open ends are sealed
together, and evacuation means are connected to the open end of the
member 72 for the evacuation of air from the chamber and also for
the introduction of an electroluminescent material into the
chamber, after which the open end of the member 72 is closed. A
rectangular card 73, containing character electrodes 74, is placed
in intimate contact with the inside surface of the member 71. Each
electrode 74 is connected to its own input terminal 75 for
connection to a suitable energizing source. Uniform spacing between
the members 71 and 72 is insured by spacer tips 76. The outer
surface of the member 72 has a transparent conductor coating
thereon (as was done with the FIG. 4 embodiment), and a metallic
band 77 is positioned over the coating to insure a good contact
with an energizing source like the one shown in FIG. 1. Although
only one character 74 is shown, a plurality of characters, one on
each side surface of the card 73, could be displayed.
The operation of the embodiments shown in FIGS. 4 and 6 is similar
to that shown in FIG. 1, in that, when voltage of a sufficient
magnitude is applied between selected character electrodes and the
common transparent electrode 40, (as shown in the FIG. 1
embodiment) a discharge will be created in the chamber in the area
immediately adjacent to the selected character electrodes. The
discharge will be limited to the area adjacent to the selected
electrodes by the selection of suitable applied energizing
potential, gas pressure, and distance between common and character
electrodes.
In order to aid those skilled in the art in the practice of the
present invention, the following information is given by way of
exemplification only. In the embodiment illustrated in FIG. 6, the
spacing between the tubes was 0.010 inch and can range up to 0.015
inch, with a wall thickness of approximately 0.030 inch. The gas
mixture consisted of 99.7 percent neon, 0.2 percent nitrogen, and
0.1 percent argon and was at a pressure of 140 millimeters of
mercury. The operating voltage was 475 volts AC, having
two-microsecond pulses with 15 microseconds spacing. Reducing the
tube wall thickness reduces the required operating voltage
significantly; or, inversely, increasing the tube wall thickness
increases the operating voltage.
* * * * *