WO1986001627A1

WO1986001627A1 - Array of electrostatically actuated binary devices

Info

Publication number: WO1986001627A1
Application number: PCT/US1985/001586
Authority: WO
Inventors: George R. Simpson; Herbert W. Sullivan
Original assignee: Simpson George R; Sullivan Herbert W
Priority date: 1984-08-21
Filing date: 1985-08-19
Publication date: 1986-03-13
Also published as: EP0190331A1; JPS61503057A

Abstract

An electromechanical binary element is provided for uses such as display arrays. The binary element has a moveable flap having at least a conductive surface. The flap is electrostatically controllable between a position removed from a stator member having stationary electrodes, and a position overlying the stator member to modify the light reflective or transmissive character of the binary element when used as a display. The conductive surface of the flap is electrically isolated from the stationary electrodes. Stationary electrodes having a plurality of discrete conductive regions are provided to facilitate the control of elements in an array. Connection of a source of electrical potential between stationary electrode regions provides electrostatic force to attract the flap.

Description

ARRAY OF ELECTROSTATICALLY ACTUATED BINARY DEVICES

Background of the Invention This invention relates to electrostatically controllable electromechanical binary devices for use as an array in visual displays, switching matrices, memories, and the- like.

The prior art contains various examples of electrostatic display elements. One type of device such as is shown in U.S, 1,984,683 and 3,553,364 includes light valves having flaps extending parallel with the approaching light, with each flap electrostatically divertable to an oblique angle across the light path for either a transmissive or reflective display. U.S. 3,897,997 discloses an electrode which is electrostatically wrapped about a curved fixed electrode to affect the light reflective character of the fixed electrode. Further prior art such as is described in ELECTRONICS, 7 December 1970, pp. 78-83 and I.B.M. Technical Disclosure Bulletin, Vol. 13, No. 3, August 1970, uses an electron gun to electrostatically charge selected portions of a deformable material and thereby alter its light transmissive or reflective properties.

Additional instruction in the area of electrostatically controlled elements useable for display purposes can be gained from the following U.S. patents:

4,336,536 Kalt et al 4,266,339 Kalt 4,234,245 Toda et al

4,229,075 Ueda et al 4,208,103 Kalt et al 4,160,5-83 Ueda et al 4,160,582 Yasuo 4,105,294 Peck

4,094,590 Kalt 4,065,677 Micheron et al 3,989,357 Kalt 3,897,997 Kalt 888,241 Kuhlmann

The present invention proceeds from material disclosed in Simpson U.S. 4,248,501, and Simpson et al 4,235,522, the disclosure of which is incorporated herein by reference. Of background interest are: .R. Aiken: "An Electrostatic Sign - The Distec System", Society for Information Display, June 1972, pp, 108-9;

J.L. Bruneel et al: "Optical Display Device Using Bistable Elements", Applied Physics

Letters, Vol. 30, no. 8, 15 April 1977, pp. 382-3; and

R.T. Gallagher: "Microshutters Flip to Form Characters in Dot-Matrix Display", Electronics, 14 July 1983, pp, 81-2. This application relates in subject matter to our copending U.S. applications SN 642,997, 642,996, and 683,619. The disclosures of these applications are incorporated herein by reference. Sum ary of the Invention The present invention provides an electrostatically controllable electromechanical binary device for light reflective or light transmissive display arrays, switching matrices, memories, and the like. Each element in the array can be controlled individually. The- invention will be described in the context of use as a visual display, including black and white and multi-color alpha-numeric and pictorial displays.

A display element (pixel) of the invention has a stator including stationary electrodes and an adjacent moveable flap electrostatically controllable between a position removed from the stationary electrodes and an uncurled position overlying the stationary electrodes. In a preferred embodiment, the stator has a flat surface normal to the light path, with a curled flap, when attracted, uncurling to roll adjacent to and covering the stationary electrodes on the flat stator surface. The invention may also take the form of a curved stator about which a normally planar flap is wrapped when attracted. The display element can control light transmission or can affect light reflection qualities for a light reflective device. It is two-state or binary. It can be latched in either state.

Non-conductive means is provided between the stationary electrodes and the curled flap which can, for example, take the form of an insulative layer on either the stationary electrodes or the curled flap. Particular embodiments of dielectric insulators and external circuitry are provided to avoid operational difficulties arising from residual electric polarization of the dielectric insulators. Embodiments of stators having multiple discrete conductive electrode regions or segments are provided to enable selective individual control of elements within a display array. Each segment of an electrode can be addressed separately to cause, for example, selected elements within an array to become actuated, or to cause selected elements to remain actuated while other elements are de-actuated.

Brief Description of the Drawings Figure 1 is a perspective view of an embodiment of a display element.

Figure 2 is a perspective view of another embodiment of a display element.

Figure 3 is a perspective view of a light reflective embodiment.

Figure 4 is a perspective view of a light transmissive embodiment.

Figure 5 is a perspective view of another embodiment. Figure 6 is a schematic view illustrating another embodiment of a display element along with a suitable circuit.

Figure 7 is a schematic view illustrating another embodiment of a display element along with a suitable circuit.

Figure 8 is a schematic view of an array of multiple display elements according to Figure 6 along with a suitable circuit for address of individual display elements. Figure 9 is an exploded perspective view of another embodiment of a display element along with a suitable circuit. Detailed Description As shown in the drawings, the display elements of the invention can be of several configurations which can be incorporated into varied . display arrays.

Figure 1 depicts a display element (pixel) 10 of the invention having a stator 15 comprising stationary electrodes 12A, 12B which are overlain by a layer of insulative material 14. A moveable curled flap 16 having at least a surface which is electrically conductive has a portion 18 adjacent one end fixed with respect to the stator 15 and a free portion 20 at the other end controllable between a curled position removed from the stationary electrodes and an uncurled position overlying the stationary electrodes. The moveable flap 16 is electrostatically controlled by means of a source of electrical potential V and a control switch 24. When the potential V is connected, electrodes 12A and 12B become oppositely charged. The resulting electrostatic attraction forces cause the conductive flap 16 to uncurl and roll into a position overlying the stationary electrodes 12A, 12B as shown by dotted lines 26. When the potential V is disconnected and the electrodes connected together, the electrostatic forces decrease and a bias imparted to the material of the flap provides the restitution force to cause the free portion 20 to re-curl to its relaxed, curled position removed from the stationary electrodes 12A, 12B.

The curled flap 16 can be a thin metallic foil or can be a polymeric film such as polyethylene terephthalate having a thin conductive surface coating such as vacuum deposited aluminum. The stator 15 can comprise a rigid substrate of polymeric insulating material upon which conductive areas are deposited by printed circuit techniques to form stationary electrodes 12A and 12B. The conductive flap is electrically isolated from the stator electrodes. Figure 2 shows an embodiment in which the insulative layer 14 forms the inner surface of the curled flap 16.

The display element 10 can be used for either a light reflective or light transmissive display device. A reflective device is illustrated in Figure 3. As seen in Figure 3, when flap 16 is curled away from the stator 15, the viewer sees the light reflected from the area 32, consisting of light reflecting off the exposed stator 15 and insulative layer 14, as well as off the exposed portion of inner surface 34 of the flap 16. When the flap 16 is flattened to a position overlying, the stator 15, as shown by dotted lines 26, the viewer sees only the light reflected from outer surface 36 of the moveable electrode. As a light reflective device, the element ιo can be used in a variety of displays such as in a black and white or a multi-color array. For example, in a black and white display the insulative material layer 14 can be black, the inner surface 34 of the flap 16 can be black, and the outer surface 36 of the flap white. In the curled state, no light is reflected and area 32 appears to be black. When the flap 16 is uncurled or flattened, light is reflected from the white surface. Similarly, in a colored display the exposed surfaces in one state of the device can be of one color with the exposed surfaces in the other state of another color.

The display element 10 also can be a light gate for a light transmissive device such as is shown in Figure 4. The light source 40 is on the opposite side of the device from the viewer who sees the transmitted light emanating from area 44. As a light gate device, light is transmitted through a stator 15 comprising translucent stationary electrodes 12A, 12B and a translucent insulative layer 14. In the flattened condition, an opaque flap 16 blocks the light. In a multi-color display, the curled condition reveals a color of light transmitted through either a clear or colored stator 15. The flap 16 can be opaque, to constitute a color light gate device, or translucent and colored to effect a change of color of the transmitted light.

In addition, other embodiments of devices can be constructed for other light conditions or display effects. For example, a combination reflective and transmissive display can be constructed for use in varying light conditions by use of a translucent reflective coating on the surfaces of the stator 15 and flap 16 whereby the device can be used in a reflective mode when the light source 40 is off, or in a transmissive mode when the light source is on. In constructing operating embodiments of the invention, several operating variables are to be considered in selecting the materials for use in the electrodes, the insulative layer, and the substrate. Copending U.S. application S/N 642,997 discloses details of manufacturing techniques. With respect to the moveable flap, the material used must be capable of retaining the correct curl size for the particular use. Other considerations include the mass, since a lower mass moveable flap will have a lower inertia to respond more quickly to a given electrostatic force. A further consideration is the stiffness of the material, which also affects the electrostatic force needed to uncurl the material to effect flattening. In general, a moveable flap can be formed either of a metal or of a conductive polymeric material. In one large scale embodiment. beryllium copper 25 (BeCu 25) foil, 0.0001 inches thick, was curled by wrapping it about a 0.25 inch mandrel and heat treating it to set the curl. The resulting curled sheet was chemically etched into an array of 0.5 inch by 0.5 inch moveable flaps.

Altenatively, polymeric film can be provided with a conductive surface coating such, as vacuum deposited metal. A translucent polymer film can be provided with a translucent thin deposited conductive layer such as gold or indium-tin oxide. Polymeric flap materials can be provided with the curl bias by heat forming or can be a laminate of two or more plies bonded together while stressed unequally to form a curl bias. Stationary electrodes can be formed of a conductive material such as metal foil for a reflective display, or of a translucent layer of indium-tin oxide on a translucent substrate for a light transmissive display. The electrode regions can be formed by printed circuit techniques such as photo-etching, selective deposition, or can be printed using conductive ink materials. The insulative layer 14 also can be chosen from many materials. Polymeric materials are preferred. The electrostatic display elements of the present invention do not electrically connect the conductive flap to the source of electric potential to effect uncurling. The conductive flap is electrically isolated from the stator electrodes and from the source of potential. It is a "floating" electrode. The opposing polarity of the energized stator electrodes establishes a charge on the conductive flap or the conductive coating to attract the flap to uncurl and roll over the stator. A further embodiment of the invention is illustrated in Figure 5 where a biasing power source 54 and an incremental drive power source 56 are used to control the moveable electrode 16. The biasing power source 54, set at V volts, is at a voltage potential just below that needed to effect the uncurling of the flap 16. The incremental drive source, set at V volts, adds sufficient further potential when added to the bias potential to cause the flap to uncurl and overlie the stator 15. The use of a bias voltage continually applied across the electrodes, requiring only the switching of the Δ. V incremental voltage to effect a change of position of the moveable flap, can be highly advantageous in a display system. For example, a high voltage power supply can provide the bias voltage for all elements in the array. A smaller incremental potential is all that is necessary to control the elements with the attendant cost savings resulting from the ability to use lower voltage switching devices.

The advantages of this biasing effect are also realizable when a liquid layer is present between the moveable and stationary electrodes. Surface tension forces of the liquid provide a portion of the attractive force acting on the moveable electrode. The liquid thus acts in a manner similar to a bias voltage. Suitable liquids include silicone oil and petroleum oils and derivatives.

The embodiment of Figure 5 also can be operated with an excess of bias voltage sufficient by itself to maintain the flap 16 in a flattened position adjacent the stator 15. In this embodiment, the incremental drive voltage 56 is of opposite polarity, sufficient to decrease the electrostatic charge to a level which allows the flap to^" re-curl to a position removed from the stator. This embodiment also can take the form of a sufficiently charged electret insulative layer with the incremental drive source 56 of reverse polarity. This is advantageous in that in the quiescent state, with no Δ V potential applied, the moveable flap is flattened against the stator, rendering the moveable flap less subject to accidental physical damage.

Figure 6 illustrates a display element including a stator substrate having a plurality of discrete conductive regions 66-69, and a moveable curled flap 65. This embodiment provides independently addressable conductive control electrode regions 66-68 and common electrode region 69 to facilitate control of a particular display element in an array of display elements. In the illustrated embodiment of a four region stationary electrode, for example, an electrical potential, the sum of VI and V2, can be applied between common electrode region 69 and independently selected X electrode region 66, Y electrode region 67, or hold-down electrode region

68. Only when the common, X, Y, and hold-down regions all are energized will the moveable flap 65 fully flatten. Once fully flattened, the hold-down electrode region 68, while energized, provides sufficient electrostatic .force to latch the flap 65 in its flattened state regardless of whether the X or Y electrode regions remain energized. To release the flap 65 from its flattened state, all of the hold-down electrode 68 and the X and Y electrode regions must be de-energized, and the common electrode 69 must be switched to the lower voltage VI.

When only the common electrode region 69 and the X electrode region 66 are energized, the moveable flap 65 partially will uncurl. If, in addition to energization of the appropriate X electrode region 66, the appropriate Y electrode region 67 also is energized, the flap 65 will uncurl further. Hold-down electrode region 68 will complete the uncurling of the flap 65 to a fully flattened and latched condition. It should be noted that uncurling can not be effected by a conductive segment which is not immediately adjacent to the curled end portion of the flap. Therefore, the Y electrode region 67 can not cause uncurling until the X electrode region 66 has been energized to cause partial uncurling.

In order that the moveable electrode be attracted by the electrostatic field of a particular stationary electrode region, the flap must be proximate that region. This proximity can be achieved by causing the flap partially to overlie the particular region. One manner of. achieving the condition of partial overlying is to shape the stationary regions such that the demarcations between regions are not parallel to the curl axis of the flap. Thus, the flap partially^' overlies the adjacent electrode region and thereby is located within the domain of the electrostatic field of that adjacent region when it is subsequently energized. By sub-dividing the conductive surface of flap 65 into regions 61-63 by creating gaps of chevron shape in the conductive coating angled opposite to the angle of the demarcations of the stationary electrode regions 66-68, progressive uncurling of the flap is promoted. The operation of the X, Y, hold-down configuration of Figure 6 is illustrated in the circuit schematic where drive voltage VI plus V2 can be applied between the common electrode 69 and any or all of the other regions of the stationary electrode, x region 66, Y region 67, or hold-down region 68, by means of switches X, Y, or H, respectively. When switch X activates the X region 66, the flap 65 uncurls partially and activation of the Y region 67 by switch Y provides further uncurling. Switch H activates the hold-down region 68 to flatten fully and latch the flap 65 even if the switches X and Y subsequently de-energize the X and Y regions 66 and 67. Deactivation is achieved by switches X, Y, and H being connected to common electrode 69.

Figure 7 illustrates a variation of the display element of Figure 6 in which the X, Y, and hold-down electrodes (66A, 66B, 67A, 67B, 68A, 68B) are divided and positioned on each side of a central common electrode 69. The electrode halves are electrically connected together and to the appropriate control switch, X, Y, and H. The symmetry of the configuration of Figure 7 promotes even uncurling of- the flap 65. An electret having a permanent charge can be substituted -for common electrode 69 in the embodiments of Figures 6 and 7. Permanently polarized polyethylene terephthalate is a suitable electret ^• material.

Display elements having segmented stationary electrodes such as are illustrated in Figures 6 and 7, permits use of the elements in a display array in which each element of the array selectively can be actuated without 'affecting the state of the remainder of the elements in the array. Such a display array is illustrated in Figure 8 in which a plurality of display elements 81, 82, 83, and 84, each similar to that of Figure 6, are assembled in columns and rows to form a display array. The flaps are not shown. Each stator has a common electrode region 69, an X region, a Y region, and a hold down region H. All X regions in the first column are connected via a common lead to switch XI, and all X regions in the second ^■ column are connected to switch X2. Similarly, all Y regions in the first row are connected to switch Yl and all Y regions in the second row are connected to switch Y2. All hold-down regions are connected in common to switch H. Thereby, each element 81-84 can be actuated selectively by selection of the appropriate switches, and latched down by the closure of hold-down switch H.

As an example of the operation of the array in Figure 8, in order to actuate element 83 (XI, Y2), hold-down switch H and switch XI are closed to connect the hold-down and the X electrode regions in the first column to the potential VI plus V2, and switch Y2 is closed to connect the Y electrode regions in the second row to the potential VI plus V2. Since the element 83 is the only element in the array with both its X and Y electrode regions energized, it alone is caused to uncurl fully. Closure of hold-down switch H will latch element 83 in the flattened state when the X and Y electrode regions subsequently are deactivat- ed. Since a flap can be affected only by.a stationary electrode region immediately adjacent the curled portion, the circuitry required to control an array of elements is simplified.

The display elements illustrated in Figures 6 and 7 have two independently controllable stationary electrode regions (X, Y) in addition to the hold-down region..Increasing the number of independently controllable conductive regions in each display element permits a significant increase in the number of elements in an array without a concomitant increase in the number of switch devices required. Specifically, in order to address a particular element in an array having a number of elements N, each element having a number of independently controllable conductive regions d, the number of switch elements S required is

For example, for an array of N = 390,625 individually controlled picture elements, a single conductive region per element would require 390,625 switches, or one switch per element. If each element has two conductive regions, such as in Figure 8, 1250 switches are needed to control and address each element individually. If the elements have four regions, only 100 switches are required. The switch devices and all other switch devices referred to in this specification can be mechanical or electronic switches such as semiconductor elements. Their function is to apply potential between a common electrode and the control electrode of the element to be controlled.

Figure 9 illustrates an X, Y hold-down pixel embodiment which is randomly addressable in either the flattened or curled state without disturbing the state of other pixels in the array. The conductive flap 100 is arranged to overlie a stator having five electrode regions separated by gaps of chevron shape. Region 101 is a common electrode which is electrically in common with the common electrode regions of all elements in the array. Electrode 102 is a latch or hold-down electrically in common with electrode 105 and with all other hold-dpwns in the array. The X electrode is 103, and 104 is the Y electrode.

In operation, in order to cause the curled flap 100 to change its state from a curled to a fully flattened condition without changing other elements in the array, hold-down electrodes 102 and 105 are connected through switch 106 to one side of a potential which is the sum of Vl and V2. Common region 101 is switched on by connection to the other side of Vl. The curl 100 advances to the intersection between regions 102 and 103. The element is now ready to be addressed by connecting X electrode region 103 and Y electrode region 104 to Vl by appropriate switches. The curl 100 will advance and latch over hold-down region 105. The X and Y electrode regions 103 and 104 now can be turned off.

In order to cause the curled flap 100 to change state from the flattened to curled state without changing the state of other elements in the array, all electrodes 104, the Y electrodes, in the entire array are switched on (that is to the one side of VI). Then, hold-down electrodes 102 and 105 are switched to the lower potential of Vl alone. Now all X electrodes are turned on. This resets the array for individual addressing of elements without having changed the state of any element. Thus, all X and Y electrodes are on and all H electrodes are off. To address a particular pixel in the array, the X electrodes in the particular row are turned off and all Y electrodes in the particular column are turned off. The pixel at the intersection will curl up. Although the present invention has been illustrated and described using a planar stator and curled flap, it is apparent that it is applicable to a curved or cylindrical stator and a flap which tends to straighten itself into a planar element.

Claims

WHAT IS CLAIMED IS:

1) An electrostatically actuated binary element comprising: a stator member having at least two electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator member, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical stress to bias the flap into a curled condition proximate the fixed end, the stress being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between the stator electrode regions to cause the flap to uncurl and to overlie the stator member.

2) The element of claim 1 wherein the flap is a metal foil.

3) The element of claim 1 wherein the flap is a sheet of polymeric material having a conductive coating.

4) The element of claim 3 wherein the conductive coating is only on the surface of the flap remote from the stator member.

5) The element of claim 1 wherein the stator electrode regions extend from beneath the lap, when curled, along the stator member in the direction of uncurling the flap. 6) The element of claim 1 wherein the stator member includes a common electrode region extending from the vicinity of the fixed end of the flap along the direction of uncurling of the flap, and a plurality of discrete electrode regions arranged as a linear series progressing along the direction of uncurling, the electrical potential being connectable between the common electrode region and any of the discrete regions.

7) The element of claim 1 wherein the stator member includes a common electrode extending beneath the flap, when curled, and plurality of independent electrode regions arranged as a linear series progressing along the stator member in the direction of uncurling, the electrical potential being connectable between adjacent electrode regions.

8) The element of claim 6 wherein the discrete electrode regions are each divided in half and the halves arranged on the stator member symmetrically on either side of the common electrode region.

9) The element of claim 6 wherein the common electrode region is an electret having a permanent electrostatic charge.

10) An electrostatically actuated binary element comprising: a stator member having at least four electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator member. the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical stress to bias the flap into a curled condition proximate the fixed end, at least one of the stator electrode regions extending from beneath the flap, when curled, along the stator member in the direction of uncurling of the flap to thereby serve as a common electrode, at least three others of the stator electrode regions being discrete and arranged as a linear series progressing along the direction of uncurling, the mechanical stress of the flap being insufficient to overcome the electrostatic force acting, on the flap when an electrical potential is ^■applied between the common electrode and a discrete electrode region proximate the curl of the flap to cause the flap to uncurl to overlie the energized discrete electrode regions.

11) An array of electrostatically actuated binary elements arranged in columns and rows, each element comprising; a stator member having at least four electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator member, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical stress to bias the flap into a curled condition proximate the fixed end. at least one of the stator electrode regions extending from beneath the flap, when curled, along the stator member in the direction of uncurling of the flap to thereby serve as a common electrode, at least three others of the stator electrode regions being discrete and arranged as a linear series of first, second, and last regions progressing along the direction of uncurling, the mechanical stress of the flap being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between the common electrode and a discrete electrode region proximate the curl of the flap to cause the flap to uncurl to overlie the energized discrete electrode regions,

^■ all of the first stator electrode regions of each row of elements being electrically connected together, all of the second stator electrode regions of each column being electrically connected together, and all of the last stator electrodes of all elements being electrically connected together.

12) An electrostatically actuated binary element comprising; a stator member having at least two electrode regions, and an electrostatically attractable flexible flap having at least a conductive surface and having one end fixed with respect to the stator member, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical bias away from the stator, the bias being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between the stator electrode regions.

13) The element of claim 12 -wherein the flap is a metal foil.

14) The element of claim 12 wherein the flap is a sheet of polymeric material having a conductive coating.

15 ) The element of claim 14 wherein the conductive coating is only on the surface of the flap remote from the stator member.

16) The element of claim 12 wherein the stator electrode regions extend from beneath the flap along the stator member.

17) The element of claim 12 wherein the stator member includes a common electrode region extending from the vicinity of the fixed end of the flap and a plurality of discrete electrode regions arranged as a linear series progressing away from the fixed end, the electrical potential being connectable between the common electrode region and any of the discrete regions.

18) The element of claim 12 wherein the stator member includes a common electrode extending beneath the flap and a plurality of discrete electrode regions arranged as a linear series progressing along the stator member away from the fixed end, the electrical potential being connectable between adjacent electrode regions. 19) The element of claim 18 wherein the discrete electrode regions are each divided in half and the halves arranged on the stator member symmetrically on either side of the common electrode region.

20) The element of claim 18 wherein the common electrode region is an electret having a permanent electrostatic charge.

21) An electrostatically actuated binary element comprising; a stator member having at least four electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator member, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical stress to bias the flap away from the stator, at least one of the stator electrode regions extending from beneath the flap, when curled, along the stator member to thereby serve as a common electrode, at least three others of the stator electrode regions being discrete and arranged as a linear series, the mechanical stress of the flap being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between the common electrode and a discrete electrode region proximate the flap to cause the flap to overlie the energized discrete electrode regions. 22) An array of electrostatically actuated binary elements arranged in columns and rows, each element comprising; a stator member having at least four electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator member, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical stress to bias the flap away from the stator, at least one of the stator electrode regions extending from beneath the flap, when curled, along the stator member to thereby serve as a common electrode, at least three others of the stator electrode regions being discrete and arranged as a linear series of first, second, and last regions, the mechanical stress of the flap being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between the common electrode and a discrete electrode region proximate the flap to cause the flap to overlie the energized discrete electrode regions, all of the first stator electrode regions of each row of elements being electrically connected together, all of the second stator electrode regions of each column being electrically connected together, and all of the last stator electrodes of all elements being electrically connected together. 23) An electrostatically actuated binary element comprising; a stator member having in a linear series at least a first common, a latching, a first address, a second address, and a second common discrete electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical bias away from the stator member, the bias of the flap being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between adjacent electrode regions of the stator member to cause the flap to overlie the energized electrode regions.

24) An array of electrostatically actuated binary elements arranged in columns and rows, each element comprising; a stator member having in a linear series at least a first common, a latching, a first address, a second address, and a second common discrete electrode regions, and a flexible flap having at least a conductive surface and having one end fixed with respect to the stator, the conductive surface of the flap being electrically isolated from the electrode regions of the stator member, the flap having a permanent mechanical bias away from the stator member. the bias of the flap being insufficient to overcome the electrostatic force acting on the flap when an electrical potential is applied between adjacent electrode regons of the stator member to cause the flap to overlie the energized electrode regions, all of the common electrode regions of all elements of the array being electrically connected together, and to a common input lead, all of the latch electrode regions of all elements of the array being electrically connected together, and to a latch input lead, all of the first address electrode regions of all elements in each column of the array being electrically connected together and to an input lead for each column, all of the second address electrode regions in each row of the array being electrically connected together and to an input lead for each row.