Electromagnetic-wave modulating, movable electrode, capacitor elements

• US 5,519,565 A
• Filed: 05/24/1993
• Issued: 05/21/1996
• Est. Priority Date: 05/22/1992
• Status: Expired due to Term

• Current Assignee: NEW Visual Media Group LLC
• Original Assignee: Dielectric Systems International, Inc.
• Inventors: Slater, Mark S., Kalt, Charles G.
• Primary Examiner(s): Ledynh, Bot L.
• Application Number:
  US08/066,949
• Time in Patent Office: 1,093 Days
• Field of Search: 361/280, 361/281, 361/283, 359/230, 359/223, 359/291, 359/231, 73/514, 73/517 R, 73/518, 345/48, 345/84, 345/85
• US Class Current: 361/280
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements
• CPC Class Codes: G09F 13/0472 Traffic signs
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: H01G 5/04 using variation of effective area of electrode

Abstract

Inventive electromagnetic-wave-modulating capacitors with movable electrodes are low-cost, low-energy, reliable and fast-acting elements for employment in highly transparent, conductive fixed electrodes and are incorporated, among others, in reflective display pixels for large and small-scale video displays, including full-color displays where multiple such capacitors are aligned in a single pixel. Further embodiments, not necessarily with a transparent electrode, are assemblable into array antennas deployable in outer space; provide digitally controllable or responsive such variable capacitors; and in mechanically active applications can be constituted as accelerometers, or in microrobotics. Constructions with ultra-thin electrodes have special advantages.

Claims

1. A reflective display pixel for a reflective display constituted by a matrix of said reflective display pixels, said reflective display pixel having:

i) a reflectance-controlled pixel area extending across a light path to a viewer;

ii) a light-modulating capacitor comprising;

a) a transparent dielectric member having opposed faces and extending across and throughout said pixel area;

b) a transparent electrode extending across one face of said dielectric member throughout said display area, said transparent electrode having a light transmissivity of at least 80 percent and a conductivity expressed as a resistivity of not more than 100 ohms per square;

c) an active, light-modulating electrode movable to and from a position extending into said pixel area on the other face of said dielectric member said light-modulating electrode having a conductive electrode surface to contact said other face of said dielectric member;

said active, light-modulating electrode being movable in response to changes in an electric potential difference applied between said active movable electrode and said transparent electrode to extend across said light path and modulate light traveling therealong; and

iii) reflectance means extending across said light path in said pixel area on an opposite side of said light-modulating capacitor remote from said viewer said reflectance means being visually related to said light-modulating active movable electrode for reflectance control of said pixel area;

wherein the appearance of said pixel area to said viewer can be selectively comprised by said light-modulating electrode in combination with said reflectance means, and wherein light reflected from said reflectance means traverses said transparent electrode two times, traveling therethrough on both an incident and a reflected path.

2. A reflective display pixel as claimed in claim 1 wherein said reflectance means comprises a reflective background and a second said light-modulating capacitor having a second active, light-modulating electrode movable to extend across said light path, said second active movable electrode and said background being cooperative to provide a variable reflectance, wherein said first and second active, light-modulating movable electrodes and said background have different visual characteristics one from another whereby said appearance of said pixel area can be selectively composed from said first and second active, light-modulating movable electrodes and said background.

3. A reflective display pixel as claimed in claim 2 further comprising a sheet-like, transparent substrate having one and another opposed substrate surfaces extending across said light path and supporting said first light-modulating capacitor to extend across one substrate surface and said second light-modulating capacitor to extend across said other substrate surface.

4. A reflective display pixel as claimed in claim 3 further comprising third and fourth said movable active electrode light-modulating capacitors disposed on said opposed surfaces of said transparent substrate to share said pixel area respectively with said first and said second active, movable electrodes.

5. A reflective display pixel as claimed in claim 4 further comprising active electrodes which are activatable selectively to display selected intensities of the achromatic colors black and white and three primary, chromatic, mixing colors.

6. A reflective display pixel as claimed in claim 2 wherein each said light modulating capacitor has a plurality of active, movable, light-modulating electrodes selectively movable to traverse said pixel area in response to applied electric potential differences.

7. A reflective display pixel as claimed in claim 6 wherein each said active movable electrode comprises a flexible plastic leaf having an anchored portion and a movable portion extensible across said pixel area, said plastic leaf having a metallized surface engageable with said dielectric member.

8. A reflective display pixel as claimed in claim 1 wherein said active movable electrode is tapered in its direction of movement to be displaceable, in a voltage controlled manner, by a distance related to the applied voltage.

9. A reflective display pixel as claimed in claim 1 wherein said transparent electrode comprises indium tin oxide.

10. A reflective display pixel as claimed in claim 1 wherein said fixed electrode light transmissivity is at least 90% and said conductivity is expressed as a resistivity of no more than 70 ohms per square.

11. A reflective display pixel according to claim 1 wherein said light-modulating electrode comprises a plastic lamina prestressed into a coiled configuration, said coiled configuration light-modulating electrode uncoiling into engagement with said other surface of said dielectric member when said potential difference is applied.

12. A reflective display pixel as claimed in claim 11 wherein each said active movable electrode comprises a flexible plastic leaf having an anchored portion and a movable portion extensible across said pixel area, said plastic leaf having a metallized surface engageable with said dielectric member.

13. A display pixel capable of displaying a selected one of at least three visually distinct color states, each said color state being selected from chromatic and achromatic colors, said display pixel having a plurality of light-modulating capacitive elements each said light-modulating capacitive element comprising:

a) a laminar translucent dielectric member having opposed first and second surfaces;

b) a fixed electrode engaged with said first dielectric member surface; and

c) a movable light-modulating electrode having a conductive electrode surface to contact said second dielectric member surface;

wherein each said movable light-modulating eletrode is selectively movable into engagement with said second surface of said dielectric member in response to a potential difference between said movable electrode and said respective fixed electrode and is retracted in the absence of said potential difference, each said element being adapted to modulate light striking said element and wherein each said light-modulating capacitive element further comprises;

d) a further light-modulating element cooperative with said movable light-modulating element and capable of modulating light transmitted through said dielectric member;

each said light-modulating capacitive element displaying one of said visually distinct states.

14. A display pixel as claimed in claim 13 further comprising a sheet-like, transparent substrate having one and another opposed substrate surfaces extending across said display pixel and supporting a first one of said light-modulating capacitive elements to extend across one said substrate surface and said second light-modulating capacitive element to extend across said other substrate surface.

15. A reflective display pixel as claimed in claim 14 wherein each said movable electrode comprises a flexible plastic leaf having an anchored portion and a movable portion extensible across said pixel area, said plastic leaf having a metallized surface engageable with said dielectric member.

16. A reflective display pixel as claimed in claim 14 wherein said active movable electrode is tapered in its direction of movement to be displaceable, in a voltage controlled manner, by a distance related to the applied voltage.

17. A reflective display pixel as claimed in claim 14 further comprising third and fourth said movable active electrode light-modulating capacitors disposed on said opposed surfaces of said transparent substrate to share said pixel area respectively with said first and said second active, movable electrodes.

18. A reflective display pixel as claimed in claim 17 further comprising active electrodes which are activatable selectively to display selected intensities of the achromatic colors black and white and three primary, chromatic, mixing colors.

19. A reflective display pixel as claimed in claim 13 wherein said transparent electrode comprises indium tin oxide.

20. A reflective display pixel according to claim 13 wherein said light-modulating electrode comprises a plastic lamina prestressed into a coiled configuration, said coiled configuration light-modulating electrode uncoiling into engagement with said other surface of said dielectric member when said potential difference is applied.

21. A reflective display pixel as claimed in claim 20 wherein each said active movable electrode comprises a flexible plastic leaf having an anchored portion and a movable portion extensible across said pixel area, said plastic leaf having a metallized surface engageable with said dielectric member.

22. A generally flat, electronically driven, full-color moving video screen comprising a matrix of reflective display pixels, each said display pixel being capable of displaying a selected one of at least three visually distinct color states, each said color state being selected from chromatic and achromatic colors, said display pixel having a plurality of light-modulating capacitive elements each said light-modulating capacitive element comprising:

a) a laminar translucent dielectric member having opposed first and second surfaces;

b) a fixed electrode engaged with said first dielectric member surface; and

c) a movable light-modulating electrode having a conductive electrode surface to contact said second dielectric member surface;

wherein each said movable light-modulating eletrode is selectively movable into engagement with said second surface of said dielectric member in response to a potential difference between said movable electrode and said respective fixed electrode and is retracted in the absence of said potential difference, each said element being adapted to modulate light striking said element and wherein each said light-modulating capacitive element further comprises;

d) a further light-modulating element cooperative with said movable light-modulating element and capable of modulating light transmitted through said dielectric member;

each said light-modulating capacitive element displaying one of said visually distinct states.

23. A generally flat, electronically driven, monochrome moving video screen comprising a matrix of reflective display pixels, each said pixel comprising:

i) a reflectance-controlled pixel area extending across a light path to a viewer;

ii) a light-modulating capacitor comprising;

a) a transparent dielectric member having opposed faces and extending across and throughout said pixel area;

b) a transparent electrode extending across one face of said dielectric member throughout said display area, said transparent electrode having a light transmissivity of at least 80 percent and a conductivity expressed as a resistivity of not more than 100 ohms per square;

c) an active, light-modulating electrode movable to and from a position extending into said pixel area on the other face of said dielectric member said light-modulating electrode having a conductive electrode surface to contact said other face of said dielectric member;

said active, light-modulating electrode being movable in response to changes in an electric potential difference applied between said active movable electrode and said transparent electrode to extend across said light path and modulate light traveling therealong; and

iii) reflectance means extending across said light path in said pixel area on an opposite side of said light-modulating capacitor remote from said viewer said reflectance means being visually related to said light-modulating active movable electrode for reflectance control of said pixel area;

wherein the appearance of said pixel area to said viewer can be selectively comprised by said light-modulating electrode in combination with said reflectance means, and wherein light reflected from said reflectance means traverses said transparent electrode two times, traveling therethrough on both an incident and a reflected path.

24. A digitally responsive, electromagnetic-wave-modulating capacitor comprising a movable active electrode, a dielectric member and a control electrode, said capacitor having an active condition in which said electrodes and said dielectric member are held in capacitative, laminar engagement by electrostatic attraction generated by a potential difference applied between said electrodes in a manner enabling said capacitor to extend across an electromagnetic wave path and modulate said electromagnetic wave and having a relaxed condition in which said potential difference is not applied, said movable electrode is retracted away from said electromagnetic wave path and said electromagnetic wave is not so modulated, wherein at least one of said electrodes has at least one lateral edge which is stepped to taper in a direction away from said retracted position to be digitally responsive to changes in said applied potential difference.

25. A digitally responsive, electromagnetic-wave-modulating capacitor according to claim 24 wherein said control electrode is fixed and has a pair of symmetrically disposed stepped lateral edges tapering in said direction away from said retracted position.

26. A low-cost, sensitive, reliable accelerometer for sensing acceleration and providing an electrical output, said accelerometer comprising a variable capacitance element having:

a) a laminar dielectric member having opposed first and second surfaces;

b) a control electrode engaged with said first dielectric member surface in activated condition of said capacitative element; and

c) an active, movable, electrode having a conductor surface engageable with said second dielectric member surface in response to an activation potential difference applied between said electrodes;

said accelerometer being disposed in a movable or moving system to sense acceleration of said system, and being coupled in electric circuit to provide a control output responsive to a sensed acceleration.

27. An accelerometer according to claim 26, for activating an automobile airbag, comprising at least two pairs of said variable capacitative elements mounted for movement in opposed directions along an axis, said pairs of variable capacitative elements being mounted approximately orthogonally in a plane including an intended direction of travel of said automobile, said accelerometer including an oscillator circuit coupled with said variable capacitance elements to sense capacitances changes produced by acceleration and provide a control output.

28. A variable capacitative element comprising:

a) a laminar dielectric member having opposed first and second surfaces;

b) a control electrode capacitatively engaged with said first dielectric member surface in activated condition of said capacitative element; and

c) an active, movable, electrode, having a conductor surface capacitatively engageable with said second dielectric member surface in response to an activation potential difference applied between said electrodes;

said active, movable electrode being selectively movable between an extended position for electromagnetic wave modulation and a retracted position and being formed of a flexible plastic material having a thin, metallized conductor surface, being said surface capacitatively engageable with said dielectric member, said active movable electrode being prestressed to adopt said retracted position in a relaxed state, and having a thickness not exceeding about 2 microns.

29. A variable capacitative element according to claim 28 wherein said movable electrode is a metallized plastic film heat-treated to form a coil, said metallized conductor surface being outwardly, convexly exposed from said coil for engagement with said dielectric member.

30. A method of manufacturing a video display matrixed from a plurality of light-modulating, capacitative pixels each having a light-modulating, movable active electrode, said method comprising:

a) assembling a plurality of sheet-like layered materials into a laminated structure, said sheet-like layered materials including;

i) a fixed electrode layer;

ii) a dielectric layer capacitatively engaging said dielectric layer; and

iii) an active, light-modulating, movable electrode layer having a plurality of adjacent, active electrodes each said active, movable electrode being prestressed to adopt a retracted, inactive configuration, said active movable electrodes being advanceable from said retracted position by application of a potential difference between said fixed electrode and said metallization;

and;

b) forming said active, light-modulating, movable electrode layer from a sheet of metallized plastic material supported on said laminated structure with said metallization toward said structure and said plastic material exposed outwardly, by;

iv) cutting partial outlines of said movable electrodes in said metallized plastic sheet in a pattern providing a movable portion and a fixed portion of each said active, movable electrode, said cutting being only a partial incision along the cut outline, whereby the movable electrode portions of said sheet remains in place during said cutting step, and said cut outlines including a common outline between adjacent movable electrode portions,; and

v) curing said laminated structure with said metallized plastic sheet bearing said cut electrode outlines exposed outwardly to be heated, in an oven to cause said plastic material in said movable electrode portions to shrink and break away along said outlines;

whereby, on cooling, said movable electrodes adopt said retracted configuration.

31. A method of manufacturing a video display according to claim 30 further comprising:

c) applying an electrically conductive adhesive to said dielectric layer in predetermined areas for secural of said fixed portions of said active movable electrodes; and

d) securing said sheet of metallized plastic material to said dielectric by means of said adhesive areas, said adhesive areas being registered with said fixed active movable electrode portions.