Micro-electromechanical based bistable color display sheets

• US 6,201,633 B1
• Filed: 06/07/1999
• Issued: 03/13/2001
• Est. Priority Date: 06/07/1999
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bringans, Ross, Floyd, Philip Don, Thornton, Robert, Schuylenbergh, Koenraad Van, Fulks, Ronald T., Maeda, Patrick Y., Kubby, Joel A., Peeters, Eric, Pan, Feixia, Sun, Decai, Vo, Tuan Anh, Ho, Jackson, Apte, Raj B., Fork, David, Connell, G. A. Neville
• Primary Examiner(s): MAI, HUY KIM
• Application Number:
  US09/326,876
• Time in Patent Office: 645 Days
• Field of Search: 359/290, 359/291, 359/292, 359/296, 359/316, 359/317, 359/318, 359/227, 359/230, 359/254
• US Class Current: 359/296
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: H04N 5/66 Transforming electric information into light information scanning details H04N3/00
• CPC Class Codes: H04N 5/7416 involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• CPC Class Codes: H04N 9/30 using solid-state colour display devices
• CPC Class Codes: H04N 9/3102 using two-dimensional electronic spatial light modulators micromechanical modulators as such G02B26/0833; liquid crystal modulators as such G02F1/13

Abstract

A micro-electromechanical bistable shutter display device is provided capable of being implemented for both small screen, high resolution devices and for large billboard-type displays. The micro-electromechanical shutter assembly has bi-stability characteristics which allow the use of only a holding voltage to maintain an image. The micro-electromechanical shutter assembly includes a shutter having petal-like shutter segments covering reflective or transmittive films. To expose the film in a particular shutter assembly, its shutter segments are moved from the horizontal to a vertical position using electrostatic attraction forces to “collapse” the torsionally-hinged shutter segments. The shutter assembly can have a number of segments, as long as the resulting shutter assembly shape can be stacked to form a dense 2D array.

Claims

1. A micro-electromechanical shutter assembly comprising:

a transparent face plate layer provided to protect the shutter assembly from environmental effects;

a first conductive layer located below the transparent face plate, patterned with vertical sidewalls which define a cavity;

a second conductive layer located below the first conductive layer patterned in the shape of a shutter including shutter segments suspended by springs, the shutter formed near the bottom of the cavity;

a spacer layer located below the second conductive layer;

an electrically insulating bottom layer located below the spacer layer, whereby the spacer layer defines a gap between the second conductive layer and the bottom layer;

a third conductive layer located on the electrically insulating bottom layer;

an electrical terminal which provides a selectively actuated bias voltage to the sidewalls;

first address signal lines in operative connection with the shutter assembly, to provide selectively actuated first address signals to the shutter assembly; and

second address signal lines in operative connection with the third conductive layer to provide selective actuated second address signals to the third conductive layer.

2. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter is bistable.

3. The micro-electromechanical shutter assembly according to claim 1 wherein the bottom layer carries pixilated RGB color films.

4. The micro-electromechanical shutter assembly according to claim 1 wherein the sidewalls are optically reflective and coated with a thin insulating layer.

5. The micro-electromechanical shutter assembly according to claim 1 wherein the spring uses a folded beam structure.

6. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter assembly is formed in single crystal silicon.

7. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter assembly is configured by a lithographic process.

8. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter assembly is formed as at least one of a square configuration with two or four shutter segments, a rectangular configuration with two or four shutter segments, and a hexagon configuration with six shutter segments.

9. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter assembly is configured to receive the bias voltage when, the bias voltage is larger than a voltage supplied by the second address lines, and wherein the shutter assembly is further configured such that the smaller address voltage from the second address lines is sufficient to move a selected shutter segment from a first stable position to a second stable position when the larger bias voltage is being applied to the shutter assembly.

10. The micro-electromechanical shutter assembly according to claim 1 wherein the shutter segments are individually controllable from a first stable position to a second stable position.

11. A method of forming a micro-electromechanical shutter assembly comprising:

patterning a first conductive layer with vertical sidewalls which form a cavity;

patterning a second conductive layer located below the vertical sidewalls into the form of a shutter, the shutter having at least two shutter segments connected to a shutter body through springs which allow for movement of the segments;

forming a spacer layer below the second conductive layer;

providing an electrically insulating bottom layer below the spacer layer such that a gap is formed between the second conductive layer and the bottom layer;

forming an electrode terminal on the first conductive layer in order to supply a bias voltage, the bias voltage causing at least one of the shutter segments to move from a horizontal position at substantially 0 degrees to a vertical position at substantially 90 degrees; and

forming addressing lines on at least one of the shutter and bottom layer to supply addressing signals, the addressing signals selectively causing at least one of the shutter segments in the vertical position at substantially 90 degrees to be moved to the horizontal position at substantially 0 degrees.

12. The method according to claim 11 further comprising configuring an array of shutter assemblies for use in at least one of a reflective, projection, and transflective display device.

13. The method according to claim 11 wherein the step of forming the shutter with moving segments allows for display of a grey scale image.

14. A shutter assembly array for use in a display device, the shutter assembly array comprising:

a plurality of shutter assemblies including,

a transparent face plate layer provided to protect the shutter assemblies from environmental effects,

a first conductive layer located below the transparent face plate, patterned with vertical sidewalls which define a cavity,

a second conductive layer located below the first conductive layer patterned in the shape of a shutter including shutter segments suspended by springs, the shutter formed near the bottom of the cavity,

a spacer layer located below the second conductive layer, and

an electrically insulating bottom layer located below the spacer layer, whereby the spacer layer defines a gap between the second conductive layer and the bottom layer;

an electrical terminal which provides a selectively actuated bias voltage to each shutter assembly, wherein the first conductive layer of each shutter assembly is common to each other shutter assembly of the array;

row address lines connected to the shutters of each shutter assembly of the array, to provide row address signals to selected shutter assemblies of the array; and

column address lines carried on the bottom layer of each shutter assembly of the array, to provide column address signals to selected shutter assemblies of the array.

15. The shutter assembly array according to claim 14 wherein the display device is one of a reflective, projection, and transreflective display.

16. The shutter assembly array according to claim 14 wherein the display device using the shutter assembly array displays grey scale images.

17. A micro-electromechanical shutter assembly display comprising:

a conductive cavity having substantially planar conductive sidewalls;

a plurality of shutter segments located within the cavity, the shutter segments being substantially perpendicular to the sidewalls when in a first position;

a conductive electrode film located below the shutter segments, in a position substantially parallel to the shutter segments in the first position;

wherein when no voltage is applied the sidewalls, shutter segments and the conductive electrode film of the shutter segments remain in the first position;

wherein when a critical bias voltage is applied between the sidewall and shutter segments the shutter segments are moved to a second position substantially parallel and into contact with the sidewalls; and

wherein when the critical bias voltage is applied between the sidewall and shutter segments, and a critical segments voltage is applied to selected shutter segments, the selected shutter segments are maintained or moved to the first position, and the shutter segments which were not selected are maintained or moved to the second position.

19. The method according to claim 17 wherein use of the array in one of the reflective, projection and transreflective display device results in a passive matrix type display.

20. The micro-electromechanical shutter assembly display according to claim 17, wherein at a certain segments voltage an address torque is larger than a bias torque at small angles, and a stable shutter position is consequently created at ⊖

=0, and wherein said certain segments voltage for which this happens is substantially smaller than the bias voltage.

21. The micro-electromechanical shutter assembly display according to claim 17 wherein the shutter assembly display includes a plurality of shutter assemblies arranged and controlled to create an image upon application of predetermined bias and shutter voltages.

22. The micro-electromechanical shutter assembly display according to claim 17 wherein a holding voltage is used to maintain an image, without the requirement of a refreshing voltage, whereby there is substantially zero power consumption while an image is being displayed and substantially all power consumption is associated with the switching from one image to another.

23. The micro-electromechanical shutter assembly display according to claim 17 is a passive display.

24. The micro-electromechanical shutter assembly display according to claim 17 wherein the shutter assembly may be as small as several inches across to over 30 feet across.

18. The micro-electromechanical shutter assembly display according to claimed 17

wherein the display is configured as an array of shutter assemblies for use in at least one of a reflective projection, and transflective display device and

wherein when an image is displayed on one of the reflective and projection displays, the image is maintained through a step of maintaining a holding voltage, whereby a refresh current is not required and therefore substantially no power is being consumed while displaying an image whereby power consumption occurs substantially only during switching of images.