U.S. patent number 3,924,228 [Application Number 05/538,990] was granted by the patent office on 1975-12-02 for electrostatically actuated display panel.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to George W. Goodrich.
United States Patent |
3,924,228 |
Goodrich |
December 2, 1975 |
Electrostatically actuated display panel
Abstract
An electrostatically actuated character generating display panel
is disclosed. The display panel embodies one or more flexible
membrane sections disposed in a predetermined pattern in an
electric field generated between a transparent window and a closely
spaced parallel support substrate. By electrically charging the
individual membrane sections, electrostatic forces are generated
which displace the charged sections either to or away from the
window. The space between the window and the substrate is filled
with a contrasting colored, high dielectric opaque fluid which
normally occludes the membrane sections when they are displaced
towards the substrate. When the electrostatic forces displace the
membrane sections against the window, the membrane displaces the
opaque fluid and the contacting portion of the membrane section
becomes visible through the window. Selectively charging individual
membrane sections in the pattern, indicative of the character to be
formed, selectively displaces the charged membrane sections against
the window and the desired character is visually formed.
Alternatively, a message imprinted upon a single segment can
similarly be made to appear or disappear.
Inventors: |
Goodrich; George W. (Bloomfield
Hills, MI) |
Assignee: |
The Bendix Corporation
(Southfield, MI)
|
Family
ID: |
24149289 |
Appl.
No.: |
05/538,990 |
Filed: |
January 6, 1975 |
Current U.S.
Class: |
345/48;
359/292 |
Current CPC
Class: |
G09F
9/372 (20130101) |
Current International
Class: |
G09F
9/37 (20060101); G08B 005/36 () |
Field of
Search: |
;340/324R,324M,336,366R,366B,378R ;350/161 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trafton; David L.
Attorney, Agent or Firm: Ignatowski; James R.
Claims
What is claimed is:
1. An electrostatically actuated display panel comprising:
a composite base having at least one electrically conductive planar
surface and a thin surface layer of insulating material disposed
over said conductive surface,
at least one electrically isolated, electrically conductive,
flexible membrane section having a predetermined color, said
membrane section having at one end a predetermined contact region
fixedly attached to said composite base on the side having said
layer of insulating material and electrically isolated from said
conductive surface, the opposite end of said at least one membrane
section being free to move under the influence of electrostatic
forces;
means for conducting an electrical charge to said at least one
membrane section;
a composite planar window disposed parallel to said composite base
and separated therefrom by a predetermined distance slightly
greater than the thickness of said membrane section, said composite
window having a thin layer of transparent electrically conductive
material disposed along the surface of said window adjacent to said
composite base;
means rigidly supporting said composite window from said composite
base and forming a peripherial fluid seal between said composite
base and said composite window; and
a low conductivity high dielectric constant fluid, having a color
contrasting to the color of said at least one membrane section,
filling in the space between said composite window, and said
composite base, said fluid having an opacity sufficient to occlude
viewing of said at least one membrane section when said membrane
section is disposed against the surface of said composite base.
2. The display panel of claim 1 wherein said at least one
electrically conductive flexible membrane section comprises a thin
sheet of flexible material having a length substantially longer
than its width, said sheet of flexible material having said
predetermined contact region at one end, an imprinted region at the
end opposite to said one end, and a hinge region disposed between
said electrical contact region and said imprinted region.
3. The display panel of claim 2 wherein only said imprinted region
has said predetermined color, said contact region and said hinge
region having a color blending with the color of said opaque
fluid.
4. The display panel of claim 2 wherein said thin sheet of flexible
material is porous to said opaque fluid.
5. The display panel of claim 4 wherein said thin sheet of flexible
material is nonconductive, said membrane section further includes
conductive material embedded in said thin sheet of material to
render said material conductive.
6. The display panel of claim 4 wherein said thin sheet of flexible
material is nonconductive, said membrane sections further include a
thin layer of conductive material disposed over at least one
surface of said thin sheet.
7. The display panel of claim 4 wherein said thin sheet further
includes a thin layer of insulator material disposed over surface
of said membrane sections.
8. The display panel of claim 4 wherein said at least one membrane
section is only one membrane section and said imprinted region has
a predetermined message printed thereon.
9. The display panel of claim 4 wherein said at least one membrane
section is a plurality of membrane sections electrically isolated
from each other, each of said membrane sections having a message
printed on said imprinted regions and wherein said means for
conducting independently conducts an electrical charge to each of
said plurality of membrane sections.
10. The display panel of claim 2 wherein said at least one membrane
section comprises a plurality of electrically isolated,
electrically conductive, flexible membrane sections disposed along
the surface of said composite base in at least one predetermined
character forming pattern, and said means for conducting
independently conducts an electrical charge to each of said
membrane sections.
11. The display panel of claim 10 wherein said at least one
predetermined character forming pattern comprises at least seven of
said electrically conductive flexible membrane sections arranged to
form a block numeral eight.
12. The display panel of claim 11 wherein said character forming
pattern further includes an eighth electrically conductive flexible
membrane section within the block numeral eight to form a
period.
13. The display panel of claim 10 wherein said at least one
character forming pattern comprises a plurality of character
forming patterns linearly disposed along a straight line.
14. The display panel of claim 10 wherein said at least one
character forming pattern comprises a plurality of character
forming patterns disposed in a multi line matrix.
15. The display panel of claim 1 wherein said composite window
further includes a thin, transparent layer of insulating material
disposed over the transparent conductive material.
16. The display panel of claim 15 wherein said layer of insulating
material disposed along the surface of said composite window
comprises a plurality of small isolated islands of insulating
material systematically disposed over the transparent conductive
material, and said layer of insulating material disposed along the
surface of said composite base also comprises a plurality of small
isolated islands of insulating material systematically disposed
along said conductive surface, further wherein each island of
insulating material disposed along said composite window and said
composite base are separated from all adjacent islands by a
distance sufficiently small to support said flexible membrane
sections in electrical isolation from said conductive material and
said conductive surface respectively.
17. The display panel of claim 1 wherein said composite base
includes a rigid metal plate wherein said conductive surface is one
surface of said metal plate.
18. The display panel of claim 17 wherein said metal plate further
includes a plurality of holes therethrough, one hole being disposed
in the contact region of each membrane section, said means for
conducting an electrical charge to each membrane section is a
plurality metal conductor wire having a diameter smaller than the
diameter of said holes and a length substantially longer than the
thickness of said metal plate, one of said metallic conductor wires
concentrically disposed in each of said holes with one end of said
conductor wires flush with the surface of said insulating material
and in electrical contact with said contact regions and insulating
material disposed between said metal plate and said conductor
wires, electrically insulating said wires from said metal
plate.
19. The display panel of claim 1 wherein said composite base
includes a rigid plate of insulator material and said conductive
surface is a thin layer of conductive material disposed over the
surface of said rigid plate of insulator material on the side
adjacent to said composite window.
20. The display panel of claim 13 wherein said composite base
includes a base substrate of insulator material and said conductive
surface comprises a plurality of conductive islands disposed over
the surface of said base substrate, each of said conductive islands
being associated with at least one of said character forming
patterns.
21. The display panel of claim 14 wherein said composite base
includes a base substrate of insulator material and said conductive
surface comprises a plurality of conductive islands disposed over
the surface of said base substrate, each of said conductive islands
being associated with at least one of said character forming
patterns.
22. The display panel of claim 10 wherein:
said character forming pattern is a multi element dot type matrix
having a predetermined number of elements systematically arranged
along two axes angularly disposed to each other,
said composite base includes a base substrate of insulator material
and said conductive surface comprises a plurality of electrically
isolated conductive stripes disposed parallel to one of said two
axes, said plurality of conductive stripes equal to the number of
elements in said multi element matrix along the other of said two
axes,
said membrane sections comprise a plurality of narrow membrane
sections disposed parallel to said other axis, said plurality of
membrane sections equal in number of elements in said multi element
matrix along said one axis.
23. The display panel of claim 1 wherein said predetermined
distance is of the order of 0.01 centimeter.
24. The display panel of claim 1 wherein said opaque fluid
comprises a mixture of ethyl acetate and oil soluble dye.
25. An electrostatically actuated display panel system
comprising:
a composite base having an electrically conductive planar surface
and a thin surface layer of insulating material disposed over said
conductive surface;
a plurality of thin electrically isolated electrically conductive
flexible membrane sections disposed along the surface of said
composite base having said insulating material in at least one
predetermined character forming pattern, each of said membrane
sections having along one edge a predetermined contact region
fixedly attached to said composite base and an imprinted region at
the opposite end having a predetermined color, each of said
membrane electrically isolated from said conductive surface;
means for independently conducting an electrical charge to each of
said membrane sections;
a composite window disposed parallel to said composite substrate
and separated therefrom by a predetermined distance slightly
greater than the thickness of said membrane sections, said
composite window having a thin layer of transparent electrically
conductive material disposed along the surface of the composite
adjacent to said composite substrate;
a peripheral support means rigidly positioning said composite
window with respect to said composite substrate and providing a
peripheral fluid seal therebetween;
a low conductivity, high dielectric constant fluid having a color
contrasting to the color of said imprinted region, filling in the
space between said composite window and said composite substrate,
said fluid having an opacity sufficient to occlude the viewing of
said imprinted region when said membrane sections are disposed
against the surface of said composite substrate;
a source of electrical power having at least two outputs of
different electrical potentials, one of said outputs providing
electrical power to the conductive surface of said composite base
substrate, the other output providing electrical power to the
conductive material disposed along the surface of said transparent
window; and
control logic means electrically connected to the means for
conducting an electrical charge to each of said membrane sections
for generating electrical signals charging predetermined membrane
sections in response to input signals indicative of character to be
generated.
26. The display panel system of claim 25 wherein:
said source of electrical power is an AC source of electrical power
wherein the potential of said two outputs alternate at a
predetermined frequency, and wherein the potential of the signals
generated by said control logic means synchronously alternate with
two outputs of the AC power source to maintain the relationship
between the potentials applied to the conductive surface of said
composite base and the conductive material disposed along the
surface of said transparent window, and signals applied to the
membrane sections.
27. The display panel system of claim 25 wherein said membrane
sections are porous to said opaque fluid.
28. The display panel system of claim 25 wherein said composite
window further includes a thin transparent layer of insulating
material deposited over the transparent conductive material.
29. The display panel system of claim 28 wherein said layer of
insulating material deposited along the surface of said composite
window comprises a plurality of small isolated islands of
insulating material systematically disposed over the transparent
conductive material, and said layer of insulating material disposed
along the surface of said composite base also comprises a plurality
of small isolated islands of insulating material systematically
disposed along said conductive surface, further, wherein each
island of insulating material disposed along said composite window
and said composite base are separated from all adjacent islands by
a distance sufficiently small to support said membrane sections in
electrical isolation from said conductive material and said
conductive surface respectively.
30. The display panel system of claim 25 wherein said at least one
predetermined character forming pattern comprises at least seven
linear electrically conductive flexible membrane sections arranged
to form a block numeral eight, and further includes an eighth
electrically conductive flexible membrane section within the block
numeral eight to form a period.
31. The display panel of claim 25 wherein said at least one
character forming pattern comprises a plurality of character
forming patterns disposed along a straight line.
32. The display panel of claim 31 wherein the conductive planar
surface of said composite base comprises a plurality of
electrically isolated conductive islands disposed along said
straight line of character forming patterns with at least one of
said islands being disposed under each of said patterns;
further, wherein corresponding membrane section in each of said
character forming patterns are electrically connected in parallel
to said control logic means; and
wherein said logic control means includes:
means for generating electrical signals indicative of the character
to be generated for each of said character forming patterns in a
predetermined sequence; and
means for applying to each of said islands, one at a time, in said
same predetermined sequence and in synchronization said electrical
signals, said one output from the source of electrical power while
simultaneously applying to all other islands, said other output
from the source of electrical power.
33. The display panel system of claim 25 wherein said at least one
character forming pattern comprises a plurality of character
forming patterns systematically disposed along the surface of said
composite base in a multi line matrix of character forming
patterns.
34. The display panel of claim 33 wherein the conductive planar
surface of said composite base comprises a plurality of
electrically isolated conductive planar islands in a multi line
matrix corresponding to the multi line matrix of character forming
patterns, each of said islands being associated with a
corresponding character forming pattern;
further, wherein corresponding membrane sections in each of said
character forming patterns are electrically connected in parallel
to said control logic means; and
wherein said logic control means further includes:
means for generating electrical signals indicative of the character
to be generated for each of said character forming patterns in a
predetermined sequence; and
means for applying to each of said islands, one at a time, in said
same predetermined sequence and in synchronization with said
electrical signals, said one output from the source of electrical
power while simultaneously applying to all other islands said other
output from the source of electrical power.
35. The display panel system of claim 33 wherein said multi line
matrix has the character forming patterns disposed at the
intersections of two interlaced sets of parallel lines angularly
disposed to each other;
said conductive planar surface of said composite base comprises a
plurality of electrically isolated conductive stripes disposed
parallel to one of said two sets of lines, one of said parallel
stripes corresponding with the patterns lying along each line in
said one set of lines;
further, wherein corresponding sections of each character forming
pattern lying along each line of the other set of parallel lines
are electrically connected in parallel; and
wherein said logic control means further includes;
means for generating electrical signals indicative of the
characters to be generated for each character forming pattern in a
first predetermined sequence;
means for applying said electrical signals to the parallel
connected membrane sections of the patterns lying along said other
set of parallel lines in a second predetermined sequence, said
second predetermined sequence applying said signals to the line of
patterns containing the pattern in which the character is to be
generated; and
means for applying to the conductive stripes, said one output from
the source of electrical power in a third predetermined sequence
while simultaneously applying to all other stripes said other
output from source of electrical power, said third predetermined
sequence applying said one output to the conductive stripe
associated with the line of patterns having the pattern in which
the character is to be generated.
36. The display panel of claim 35 wherein said two interlaced sets
of parallel lines are angularly disposed at right angles to each
other.
37. The display panel system of claim 25 wherein:
said character forming pattern is a multi element dot type matrix
having a predetermined number of elements systematically arranged
at the intersections of two sets of parallel lines angularly
disposed to each other;
said conductive planar surface of said composite base comprises a
plurality of electrically isolated conductive stripes, each of said
plurality of conductive stripes corresponding to one line in one of
said two sets of parallel lines;
said membrane sections comprises a second plurality of narrow
membrane sections, each narrow membrane section corresponding to
one line in the other of said two sets of parallel lines; and
said logic control means comprises:
means for generating in a predetermined sequence a first set of
electrical signals indicative of the elements in the matrix to be
displaced to form the desired character, said first predetermined
sequence of electrical signals being applied to the narrow membrane
section containing the element to be displaced in a like
sequence;
means for generating in a predetermined sequence a second set of
electrical signals applied to said conductive stripes, said second
set of signals applying to each conductive stripe an electrical
signal having a potential approximately equal to potential of said
one output while simultaneously applying to all other conductive
stripes said other output from said source of electrical power,
further, wherein said first and said second set of electrical
signals are synchronously generated to apply both sets of signals
to each element in the matrix, in a predetermined order.
38. The display panel system of claim 37 wherein said multi line
element matrix is a five by seven element array arranged in the
form of a parallelogram.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the field of visual communications and,
in particular, to passive display panel producing alpha numerical
characters by electrostatically moving selected flexible membrane
sections against the surface of a transparent window displacing an
opaque fluid disposed therebetween and forming visible
characters.
2. Prior Art
Display panels may be roughly categorized as luminous or passive
dependent upon whether they are self luminous or require ambient
light to relay the information to the recipient. Luminous display
panels, such as cathode ray tubes, arrays of light emitting diodes,
and plasma panels have found wide acceptance in both industry and
general public use. The deficiency of luminous display panels is
the tendency of the information displayed to be washed out, and
even lost under intense ambient illumination. In contrast, passive
display panels transmit the information to the recipient by means
of reflected ambient light and visibility increases with increased
ambient illumination. Passive display panels have practical
application where the ambient illumination may vary from intense
daylight to subdued conditions.
Passive display panels range in form from the time honored score
boards found in baseball parks to the more recent electronically
activated liquid crystal displays and includes various types of
panels in which the information is made visible by displacing an
opaque fluid filling the space between a transparent window and the
desired information. The displacement of the opaque fluid is
generally accomplished by moving the information bearing member
into physical contact with the window. The physical contact
displaces the fluid from between the window and member and the
information, otherwise occluded by the opaque fluid, becomes
visible. The prior art teaches the displacement of information or
character bearing members by mechanical, pneumatic, fluidic and
electromagnetic forces. G. A. Wearham, in U.S. Pat. Nos. 1,780,733
and 1,782,328 teaches the displacement of the member by both
mechanical and fluidic means. J. M. Cunnien, in U.S. Pat. No.
3,162,849 introduces the concept of using electromagnetic means for
moving the character bearing member. These early displays are
confined to simple on/off devices and were incapable of generating
individual characters of various forms in any one given location on
the face of the panel.
Many of the present applications for display panels require high
character densities which may be changed upon command and the
simple on/off configurations of the prior art are incapable of
meeting this requirement.
An initial attempt to overcome this problem is disclosed in my
earlier U.S. Pat. No. 3,812,490, "Flexible Membrane Display Panel
for Generating Characters Visible in Ambient Light". This device
uses a magnetized flexible membrane disposed in an opaque fluid a
short distance from a window. The membrane is selectively deflected
to form the desired characters by a matrix of small electromagnets
formed on a magnetically susceptible substrate disposed behind the
magnetized membrane on the side opposite the window. This
electromagnetically activated display panel represents one solution
to the problem.
The prior art further reveals that others have attempted to use
electrostatic forces to activate passive display panels. W. R.
Aiken in U.S. Pat. No. 3,304,549 discloses a "Composite Signaling
Device" in which a matrix of hinged vanes representing various
segments of a character are displaced by electrostatic forces from
a horizontal to vertical position making them visible through a
transparent window. In an alternate configuration, as disclosed by
Dahms et al, a hinged vane or flag is systematically deflected to
one or the other side of V-shaped grooves to form the desired
character. The opposite sides of the vanes and opposite sides of
the V-shaped grooves have the same contrasting colors. The vanes
are arranged so that each face of vane has the same color as the
adjacent face of the groove, so that when the vane is deflected to
one side, the exposed face of the vane and the exposed surface of
the V groove have the same color, and when the vane is deflected to
the other side, the opposite side of the vane and the other face of
the groove are exposed, displaying the contrasting color. In both
of these types of displays, the vane is required to move through a
considerable distance and relatively high electrostatic voltages
are required. Electrostatic deflection of a reflective membrane for
light modulators has also been used with large screen television
displays. Typical examples of such devices are disclosed by P.
Kendall, Jr. et al, U.S. Pat. No. 3,796,480, as well as my own U.S.
Pat. No. 3,746,785.
SUMMARY OF THE INVENTION
The invention is an electrostatically actuated passive display
panel. The panel comprises a plurality of electrically isolated
conductive membrane sections systematically disposed along the
surface of a support structure in a predetermined pattern. A
transparent window having an electrically conductive internal
surface is disposed parallel to the support structure and proximate
the conductive membrane sections so that a distance of
approximately 0.01 centimeter separates the window from the
adjacent surfaces of the membrane section. The space between the
window and the membrane sections is filled with a low conductivity,
high dielectric constant, colored fluid having sufficient opacity
to occlude the membrane section when viewed through the window. One
end of each membrane section is fixedly attached to the support
structure and the opposite end is free to move under the influence
of internally generated electrostatic forces. Under the influence
of electrostatic forces, the free ends of the membrane sections
contact the inner surface of the transparent window. The free end
of each membrane section has a region imprinted with a color
contrasting to the color of the fluid so that when the free end is
in contact with the window, the contrasting color of the imprinted
region is visible therethrough. Means are further provided for
generating an electric field between the conductive surface
disposed along the inner surface of the window and the support
structure and for individually conducting an electrical charge to
each electrically isolated membrane section. Selectively charging
individual membrane sections with electrical signals, having a
polarity the same as that applied to the support structure, will
generate an electrostatic field and therefor an electrostatic force
between the window and the charged membrane sections. The
attractive electrostatic force urges the free ends of the charged
membrane sections away from the support structure and into contact
with the window, displacing the opaque fluid and rendering the
region imprinted with the contrasting color to be visible.
Reversing the polarity of the charge on the individual membrane
sections so that it will have the same charge as on the window will
return their free ends to their original position along the support
substrate.
In a preferred embodiment, the membrane sections are arranged in
the familiar seven bar alpha numerical pattern, including an eighth
membrane section for generating a period or decimal point. The
invention may be embodied in an elementary form containing only a
single membrane section with an imprinted message or a single alpha
numerical pattern. The display may also take more complex forms
having a plurality of patterns arranged in linear or in two
dimensional matrices. The electrical power and potentials required
for activation of the electrostatically activated display panel are
well within the state of the art of solid state logic and switching
devices, and may be either AC or DC.
The object of the invention is a passive electrostatically
activated display panel compatible with state of the art logic
circuitry and components having a high character density. A further
object of the invention is a multiple character passive display
panel relatively simple and inexpensive to make. Still another
objective of the invention is a multiple character passive display
panel using no exotic or expensive components or manufacturing
techniques. Another object is a display panel which may be matrix
addressed or multiplexed. These and other objectives will become
evident from a reading of the following detailed description of the
preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exaggerated cross section view of a preferred
embodiment of the electrostatically activated display panel to show
the individual elements and construction details.
FIG. 2 is a plan view of the membrane sections arranged in the
familar seven bar alpha numerical pattern.
FIG. 3 is a plan view of an alternate embodiment of the composite
base having the leads to the individual membrane sections along a
common edge.
FIG. 4 is a cross section of the alternate embodiment shown in FIG.
3.
FIG. 5 is a cut away perspective illustrating a multi character
embodiment of the display panel.
FIG. 6 is a plan view of an alternate embodiment of a composite
substrate for a display panel capable of being multiplexed.
FIG. 7 is a plan view of an alternate embodiment of a composite
substrate for a panel capable of being matrix addressed.
FIG. 8 is a plan view of a composite base having a single membrane
section with a printed message.
FIG. 9 is a plan view of a composite base having an alternate
configuration for the membrane sections.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The details of the preferred embodiment of the electrostatically
activated membrane panel is discussed with reference to the
exaggerated cross sectional view of FIG. 1. This cross sectional
view shows the basic elements and these physical relationships to
each other. Referring to FIG. 1, the body of the display panel
comprises a composite transparent window 10, a composite membrane
support base 12 and a spacer body 14. The composite window 10,
composite base 12 and spacer body 14 form a structure having an
internal cavity completely filled with a low conductivity opaque
fluid 16. The composite window 10 comprises a window 18, such as
glass or any other suitable transparent material and has a
transparent conductive coating 20 of any type known in the art
which is applied along the inner surface of the window 18. The
transparent conductive coating 20, for example, may be a tin oxide
coating, such as the commercially available NESA coating or a
transparent vapor-deposited metalic film. The conductive coating 18
is further overlaid with an insulation material 22. When the
conductivity of the insulating material 22 is approximately equal
to the conductivity of the opaque fluid 16, the insulating material
may be in the form of a continuous layer disposed over the
conductive coating 20. However, when the conductivity of the
insulating material is substantially less than that of the opaque
fluid, the insulating material may be disposed over the conductive
coating 20 in the form of a plurality of isolated islands such as
would be obtained by evaporating silicon monoxide or other
insulating material through a fine mesh screen. The spacing between
the isolated islands being sufficiently small to prevent the
conductive deflectable membrane sections 28 from contacting the
conductive coating 20 between the islands.
The composite membrane support base 12 in the illustrated
embodiment of FIG. 1 comprises a metal plate 24 overlaid with an
insulating material 26. Like the composite window, when the
conductivity of the insulating material 26 is approximately equal
to the conductivity of the opaque fluid 16, the insulating material
may be in the form of a thin continuous layer disposed over the
internal surface of the metal plate 24. However, when the
conductivity of the insulating material is substantially less than
the conductivity of the opaque fluid, the insulating material may
be disposed along the surface of the metal plate in the form of a
plurality of isolated islands. The island configuration of the
insulating material on the composite window and composite base
permits the opaque fluid, having the higher conductivity, to be in
electrical contact with conductive surfaces of the window and the
base and enhances the establishment of a more uniform electrical
field therebetween. In alternate embodiments, to be discussed
hereinafter, the composite base 12 may be made from an insulating
material with a conductive coating disposed along the surface
thereof. Attached to the insulating material 26 are a plurality of
electrically isolated deflectable membrane sections 28 which will
be discussed in detail with reference to FIG. 2. Electrical contact
to each individual membrane section 28 is made by a like plurality
of conductor elements, illustrated as pins 30 making electrical
contact with each membrane section and passing through the metal
plate 24 and insulating material 26 to the external surface of the
display panel. By this means each membrane section 28 may be
individually charged by an electrical potential applied to the
associated pin 30. Insulator grommets 32 are provided for
electrical isolation between each pin 30 and the metal plate
24.
The spacer body 14 is made from an insulating material and provides
a circumferential fluid seal between the composite window 10 and
the composite support plate 12. The thickness of the spacer body 14
is selected so that the separation between the inner surface 34 of
insulation layer 22 and the upper surface 36 of the membrane
sections 28, indicated as dimension "A", is approximately 0.01
centimeter.
The opaque fluid 16 is a high dielectric constant, low
conductivity, colored fluid such as ethyl acetate, colored with a
commercial oil soluble dye.
Electrical power is applied to the transparent conductive layer 20
and the metal plate from a source of electrical power illustrated
as battery 38. Electrical power is also applied to each of the
membrane sections 28 via pins 30 and connecting leads from a
control logic circuit 40. The control logic circuit 40 has an input
indicative of the character to be formed. This input may be a
manual input from a keyboard, or an electrical signal from an
external source (not shown). The various types of inputs and the
manner in which they are generated are well known in the art and
need not be discussed for an understanding of the invention. The
control logic circuit may be powered from the same source as the
display panel, as shown, or may be powered by an independent
electrical source. The control logic circuit is of conventional
form and in response to an input indicative of a specific character
outputs electrical signals on the leads connected to the pins 30.
In the preferred embodiment, the output signals from the control
logic are bipolar electrical signals having either a magnitude and
polarity the same as that applied to the transparent conductive
layer 20 or the magnitude and polarity the same as that applied to
the metal plate 24 from the electrical power source.
The details of the membane sections 28 are discussed with reference
to FIG. 2. This illustrated embodiment comprises eight electrically
isolated membrane sections 28. Seven of the sections are arranged
to define the elements of a typical seven bar alpha numerical
character and the eighth section is a period or decimal point. The
use of this pattern to generate both letters and numerals is well
known and need not be further discussed. The membrane sections 28
may be a thin metal foil such as 2 um thick aluminum foil or made
from a thin sheet or film of a suitable plastic material, as
polyester or polyvinyl chloride, heavily loaded with conducting
particles, such as carbon black, so that each section is
electrically conductive and assumes a common electrical potential
when charged. Alternatively, the plastic film may be metalized,
using conventional metal deposition methods, such as vapor
deposition to provide the desired electrical conductivity. In cases
where the electrical charge leaking from the individual sections
may otherwise cause life limiting electrolysis of the opaque fluid
16, a thin insulating layer may be deposited over the conductive
surfaces of the individual membrane sections as a barrier to
electronic exchange to ions in the fluid.
Each membrane section 28, forming the alpha numerical character, is
comprised of three regions, as illustrated. The first region,
arbitrarily defined by the crosshatched area, is electrical contact
region 42, which is fixedly attached to the insulating material 26
and in electrical contact with the associated pin 30. This may be
accomplished using a conductive epoxy or by depositing a thin layer
of indium or an indium alloy in the contact region of each membrane
section 28 and affecting a cold indium weld between the layer of
insulating material 26 and the contact region 42 of the membrane
section. The second region, defined by the diagonal bar pattern, is
the hinge region 44 and is that segment of the membrane which flexs
when the section is subjected to electrostatic forces. The third
region is the imprinted region 46 which is imprinted with a color
contrasting to the color of the opaque fluid 16. For example, if
the opaque fluid is white, the imprinted region would be black and
vice versa. Obviously, other contrasting color combinations
including the use of fluorescent colors on the imprinted regions
could also be used if so desired. To improve the sharpness of the
generated character, the hinge region 44 and contact region 42 may
be colored to blend in with the color of the opaque fluid.
Alternatively, an opaque mask deposited on the inside surface of
the window could be used to occlude the hinge and contact regions
of the sections. The surface of the membrane sections 28 may be
continuous or porous. A porous membrane would permit fluid to flow
through the membrane reducing its resistance to movement thereby
increasing the response time of display panel.
The operation of the display panel is as follows:
An electrostatic potential difference is established between the
transparent conductive coating 20 disposed over the inner surface
of the composite window 10 and the metal plate 24 by means of the
source of electrical power supply, such as battery 38. Information
indicative of the character to be displayed is input into the
control logic 40 which generates electrical signals communicated to
the respective pins 30 on the display panel. The pins in electrical
contact with the membrane sections 28, which form the input
character, receive electrical signal having approximately the same
magnitude and polarity as the potential the metal plate 24. The
membrane sections forming the input character assume the potential
communicated to their respective pins and are subjected to an
electrostatic force urging the free imprinted region 46 of the
membrane sections towards the composite window 10. Under the
influence of these electrostatic forces, the imprinted region of
the membrane sections contact the transparent insulation material
22 overlaying the conductive layer 20 and displaces the opaque
fluid 16 from therebetween. With the opaque fluid 16 so displaced,
the imprinted region 46 of each membrane section in contact with
the transparent insulation material 22 becomes visible through the
composite window 10 and the input character is formed.
The remaining membrane sections receive signals from the control
logic which have approximately the same magnitude and polarity as
potential on the conductive coating 20 and are held against the
insulation material 26 overlaying the metal plate 24 by
electrostatic forces generated between the membrane sections and
the support substrate.
The electrical potentials required to displace the membrane
sections against the window appear to be well within the output
capabilities of state of the art solid state logic circuitry.
Buffer or interface amplifiers to increase voltage or current
levels are not required. The force of attraction per unit area
between two parallel conductors can be derived from the energy
stored in a capacitor. The electrostatic force F.sub.A is defined
by the equation: ##EQU1## Where F.sub.A = the force per unit area
between two parallel conductors (dynes/cm.sup.2)
V = the potential difference between the two parallel conductors
(volts)
x = the distance between the conductors (cm)
and
k = the dielectric constant of the medium between the conductors
(opaque fluid).
The dielectric constant of distilled water is 80, for glycol
(C.sub.2 H.sub.6 O.sub.2) 38 and furfural (C.sub.5 H.sub.4 O.sub.2)
is 42. If we assume a dielectric constant k=50, V=10 volts
x=x.times.0.01 cm, then the electrostatic force F.sub.A =20
dynes/cm.sup.2 which is higher than a force experimentally known to
be adequate to displace the membrane section against the window.
Therefore, a display panel built in accordance with the disclosed
principles will work.
While the electrical power supply has been illustrated as a DC
source of electrical power and the operation of the panel discussed
in terms of DC operation, the display panel is also operable with
alternating (AC) potentials. The requirement for AC operation is
that all applied potentials including the signals to the membrane
sections be changed in a synchronous manner so that the directions
of the electrostatic forces are unchanged. AC operation of the
panel is desirable because it significantly reduces the
electrolysis of the opaque fluid and increases the life of the
panel.
An alternate embodiment of the composite base eliminating the pins
30 protruding therethrough for electrical contact to the membrane
sections is shown in FIGS. 3 and 4. In this embodiment, electrical
conductors 48 are deposited on an insulator substrate 50 made from
glass or one of the commercially available plastics. The conductors
originate from a common edge of the substrate, indicated as edge
52, and individually terminate at a location under one of the
contact regions 42 of the associated membrane sections 28 (shown in
phantom). The conductors 48 may be formed on the insulator
substrate 50 using any of the methods well known in the art, such
as vapor deposition, silk screening, etc. The conductors 48 are
overlaid with a thin film of insulating material 54 such as silicon
monoxide, except for the contact area 56 under the contact regions
42 of the membrane sections. The entire surface area of the support
substrate 50, again, with the exception of contact areas 56, is
overlaid with a conductive film 58 which in turn is covered with
insulator material 60. The membrane sections 28 are attached to the
composite substrate 12 in the desired positions and in electrical
contact with the individual conductors 48 using any of the methods
well known in the art. The membrane sections may be attached to the
composite substrate using a conductive epoxy or a thin layer of
indium 62 over the area on the composite substrate 12, defined by
the contact region 42 of each membrane section 28.
FIG. 9 illustrates an alternate configuration of the deflectable
membrane sections 28 forming the alpha numerical character. In this
configuration, the hinge region 72 is connected to the narrow ends
of the imprinted region 74 and are substantially longer than they
are wide to provide increased flexibility of the hinge. The hinge
region may be colored to blend in with the color of the opaque
fluid, as discussed with reference to FIG. 2, or a mask having the
same color as the opaque fluid may be imprinted on composite window
10 to occlude the hinge region of the individual sections 28. The
dashed lines 76 outline the areas on the composite window to be
masked when this latter concept is employed. The areas 78 (diagonal
lines) indicate the areas to which a conductive epoxy or other
bonding agent is applied to attach the membrane sections to the
composite substrate 12. The operation of the display panel is the
same as discussed with reference to FIG. 1.
Although the display panel has been illustrated and described in
FIGS. 1 through 4 as having only a single alpha numerical
character, it is obvious that the concept can be extended to a
multiple character panel, as shown in FIG. 5. The numbers used to
identify the elements illustrated in FIG. 5 are the same as used in
FIGS. 1 through 4.
The multi character panel may be activated using any of the methods
presently available in the art including multiplex or matrix
address techniques which require fewer leads between the display
panel and the control logic.
To multiplex a multi character panel, such as illustrated in FIG.
5, the structure of the composite base may be made as shown on FIG.
6. In this illustration the insulator substrate 50 and electrical
conductors 48 depicted in FIG. 3 are understood but not shown to
simplify the drawing. The continuous conductive film 58 is
segmented into a plurality of electrically isolated conductive
islands 64 which may be individually charged by means of the logic
control 66. The corresponding sections 28 of each character on the
multi character display are electrically connected in parallel to
the logic control 66. The parallel electrical connections of the
corresponding sections may be made during the fabrication of the
composite base 12 or be made externally, as shown. The operation of
the multiplexed panel is as follows:
All of the islands 64 are initially electrically biased to the same
potential as the window, with the exception of the addressed island
associated with the character, the position of whose membrane
sections are to be set. The potential of the island being addressed
is different from that of the window to generate an electric field,
as discussed relative to FIG. 1. All the sections are then charged
for a short fraction of one clock cycle with a polarity opposite
that of the window, i.e., the nominal potential applied to the
conductive film on the composite base. Because the window and the
nonaddressed islands have the same electrical potential, the
sections associated with the nonaddressed islands are attracted to
the closest electrode, be it the window or the composite base. For
the remainder of the clock cycle, the sections to be displaced
towards the window remain at the potential of the addressed island
and the sections to be displaced against the composite base are
biased to the potential of the window. The sections at the window
potential and associated with the nonaddressed islands will not
move since there is no field gradient between the window and the
islands and the sections will float electrically. Only the sections
associated with the addressed island will be attracted to the
composite substrate. The sections to be displaced against the
window are charged to the potential of the addressed island. The
sections associated with the nonaddressed islands, as discussed
above, are attracted to the nearest electrodes and, therefore, will
retain their initial position, either against the window or against
the composite base. The sections associated with the addressed
island will be displaced against the window by electrostatic
forces. By serially addressing the islands associated with each
character on the panel, multiplexed operation may be achieved.
Logic controls for performing the required function and generating
the required potentials are well within the state of the art. The
location of the island being addressed can be determined from a
pair of shift registers and the sections being driven in parallel
from a third shift register device. The information indicative of
the characters to be displayed is serially generated and loaded
into the section shift register device. When the section shift
register is loaded, the island location shift registers are indexed
to the next sequential island location and both signals are
simultaneously applied to the panel.
For matrix operation, the structure of the composite substrate 12
may be made as shown on FIG. 7. Again, the substrate 50 and
conductors 48 are not shown to simplify the drawing. The continuous
conductive film 53 is segmented into a plurality of electrically
isolated conductive stripes 68 disposed in a plurality of rows
which may be individually charged by a logic control 70. Each
conductive stripe 68 being associated with one row of characters on
the multi character display panel. The characters are divided
according to columns and corresponding sections 28 in each
character in each column are electrically connected in parallel.
The parallel electrical connection between corresponding sections
in each column can be made during the fabrication of the composite
substrate or made externally as shown. Although only four
characters are illustrated, two in each row, and two in each
column, the concept is readily extended to many rows and columns
having many characters each.
The matrix operation of the display panel is similar to the
multiplex operation. Initially, all the rows 68 are charged to the
potential of the window except the row containing the character
whose sections are to be charged. The information indicative of the
sections to be displaced either towards or away from the window is
applied to the respective leads on the column containing character.
Obviously, the characters in the unaddressed columns will not
change, and for the reasons discussed with reference to multiplex
configurations, only the sections in the addressed column which are
in the character in the activated row will change. All other
characters will remain unchanged. By sequentially switching the
activation of the individual rows and columns in a predeterminable
order, each character can be changed in accordance with the signals
generated by the logic control. It would be obvious to one skilled
in the art that the conductive stripes 68 could be disposed along
the columns and that the parallel connection of the like character
sections could be made along the rows without departing from the
intent of the invention.
Having described the invention in terms of a panel having alpha
numerical characters, it is recognized that other types of
character patterns may be equally employed within the spirit of the
invention.
One such character pattern is the conventional 5 by 7 dot matrix in
which the characters are formed by activating predetermined dots
within the matrix. In this embodiment, the conductive film on the
composite substrate is segmented into a plurality of electrically
isolated conductive stripes, one stripe for each row of dots in the
pattern. The membrane sections take the form of a plurality of
parallel stripes angularly disposed to the conductive stripes; one
parallel membrane section for each column in the dot pattern. The
intersections between the conductive stripes and the parallel
membrane sections represent dots in the pattern. From the prior
discussion with reference to FIG. 6 and 7, it is readily seen that
by matrix addressing each row of conductive stripes and each column
of membrane section in a predeterminable sequence the membrane
sections at selected intersections can be deflected into contact
with the window to form the desired character.
In contrast to the multi character panels of FIGS. 5, 6 and 7, the
principles of the electrostatic display panel may be embodied in a
simple on/off type display having a predetermined message imprinted
on a single moveable membrane, such as shown in FIG. 8. It is
understood that this type of display may have more than one
moveable membrane and more than one printed message. The operation
of the display panel illustrated in FIG. 8 is the same as the
character forming configuration discussed with reference to FIGS. 1
and 2 and need not be repeated here. One skilled in the art will
immediately conceive other embodiments based on the disclosed
principles of operation. The embodiments illustrated and discussed
are merely to present the invention in several of its many forms
and are not intended to limit the scope of the invention.
* * * * *