EP0192702A1

EP0192702A1 - Array of electrostatically actuated binary shutter devices

Info

Publication number: EP0192702A1
Application number: EP19850904349
Authority: EP
Inventors: George R. Simpson; Herbert W. Sullivan
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-08-21
Filing date: 1985-08-19
Publication date: 1986-09-03
Also published as: WO1986001626A1; JPS61503056A

Abstract

Des dispositifs binaires disposés en panneaux et actionnés électrostatiquement, possèdent des volets ou battants pouvant être attirés pour effectuer un changement d'état. Une pluralité de volets peut être utilisée pour chaque dispositif. Plusieurs régions à électrodes permettent la commande en X, Y du dispositif et d'autres électrodes enclenchent les dispositifs dans l'état activé.Binary devices arranged in panels and actuated electrostatically, have flaps or leaves which can be attracted to effect a change of state. A plurality of flaps can be used for each device. Several electrode regions allow X, Y control of the device and other electrodes engage the devices in the activated state.

Description

ARRAY OF ELECTROSTATICALLY ACTUATED BINARY SHUTTER 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 defor able 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 4,160,583 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:

W.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 is related in subject matter to our copending U.S. application SN 642,752, 642,997, and 683,619. The disclosures of these applcations are incorporated herein by reference. Summary of the Invention The present invention provides an electrostatically controllable electromechanical binary device for use in display arrays, switching arrays, memories, and the like. The invention will be' described in the context of a visual display wherein each element in the array can be controlled individually to enable the production of a variety of visual displays, including black and white and multi-color alpha-numeric and pictorial displays.

A display element (pixel) of the invention has upper and lower parallel, spaced stators each including stationary electrodes and an interposed hinged moveable flap or shutter electrostatically controllable between a first position generally parallel with the stators and a second position generally perpendicular to the stators. In a preferred embodiment, the stators have flat surfaces normal to the light path, with a hinged flap or shutter, controllable electrostatically between positions normal to and parallel to the light path. The display element can control light transmission or can affect light reflection qualities for a light reflective device. It is useable as an alpha-numeric display for such applications as watches and calculators. It is two-state or binary. It can be latched in either state.

The display elements or pixels of the present invention are provided with conductive electrode regions for purposes of individual pixel addressing and latching. When used as an array of pixels one of the regions is designated as an X electrode, and another is designated as a Y electrode. All X electrodes in a row are connected together as are Y electrodes in a column. That pixel at the intersection of the column and the row is actuated to change status. Further electrode regions, designated hold-down, serve to latch the actuated pixel in the actuated status after the X and Y electrodes are de-energized. Arrays of a myriad of small pixels or binary elements, each independently addressable, are producible with a variety of known techniques such as selective deposition, photo-etching, direct printing with conductive inks, etc. A method of manufacture is disclosed in our copending application SN 642,997.

Brief Description of Drawings Figure 1 is a cross-sectional, elevational view taken along line I-I of Figure 2 showing a portion of an array of display elements according to the present invention.

Figure 2 is a plan view of a portion of an array of display elements according to Figure 1.

Figure 3 is a perspective view of a further embodiment of a display element of the present invention.

Figure 4 is a perspective view of a portion of an array of display elements showing a further embodiment of the present invention.

Figure 5 is a plan view of a portion of an array of display elements showing a further embodiment of the present invention.

Figure 6 is a cross-sectional, elevational view of a display element according to a further embodiment of the present invention. Figure 7 is a cross-sectional, elevational view of a display element according to a further embodiment of the present invention. Detailed Description Figures 1 and 2 illustrate a portion of an array which is a basic execution of the present invention. A first insulative substrate 10 of glass or plastic has formed thereon a plurality of parallel conductive stripes YlO, Yll, Y12, etc. A second insulative substrate 12 has formed thereon a similar plurality of parallel conductive stripes X20, X21, X22, etc. The two sets of stripes are orthogonal to each other. A thin membrane 14 extends between and parallel to the substrates. The membrane 14 contains a plurality of flaps or shutters 31-39 freed on three sides by a slot 16. The fourth side provides a torsional hinge for the shutter. The flaps or shutters are located at the crossings-over of the two sets of stripes.

Connection of stripes YlO and X21 across a source of electrical potential will establish an electrical field only in the vicinity of the intersection of those two stripes, namely, at shutter 32. Since no field is established at any other intersection in the array, no shutter other than shutter 32 is subjected to an electrical field. If the dielectric constant of membrane 14 and hence shutter 32 differs significantly from that of the air between the substrates 10 and 12, the electrical field will exert a force on shutter 32. Since the shutter is hinged, it will move toward alignment with the field. The shutter 32 will open as is shown in Figures 1 and 2.

If membrane 14 is opaque and if one or both of the substrates 10, 12, and one or both of the sets of conductive X, Y stripes are transparent, the open shutter 32 will allow the passage of light or will alter the reflection of impinged light to change the appearance of the pixel area occupied by shutter 32. By appropriate selection of X and Y conductive stripes particular shutters will be opened to create a pattern of pixels for a character or other graphic.

Figure 3 illustrates a pixel 340 of an embodiment in which the large, single shutters of

Figures 1 and 2 are replaced by a plurality of narrow shutters 341-345 which hinge on the small torsional straps or webs 347 which remain after cutting slots in the membrane 314 to define the shutters. Because each shutter 341-345 is narrow, the electrical force required to open the shutters is less than in the embodiment of Figures 1 and 2. Figure 3 shows a portion of an X stripe, X 320.

The shutters can be cut from a membrane of a polymer such as polyethylene terephthalate (PET) sold as MYLAR. PET film has a dielectric constant on the order of 6 to 9 which differs significantly from that of air. Conversely, the shutters can be conductive or have a conductive surface layer, as for example, aluminum vapor deposited onto a PET film. Either high dielectric or conductive shutters will swing toward alignment with the electrical field.

Figure 4 illustrates in perspective a portion of a pixel array which is a variation of that of Figures 1 and 2 wherein the X conductive stripes are eliminated and their function taken by a conductive surface coating on the membrane 414 in which the shutters are formed.

The membrane 414 is PET film upon which aluminum is vapor deposited. Gaps 452 are etched to divide the membrane into parallel stripes, X21, X22, etc. of the remaining aluminum. The shutters 432-436 are cut along these stripes such that all shutters in each X column of the array are electrically connected through the aluminum coating. The Y stripes YlO, Yll, etc. are formed as before on a substrate 10 spaced away from the shutters to accomodate the swing. Figure 4 shows shutter 432 opened as a result of application of an electrical potential between the conductive stripe for row X21, which includes shutter 432, and the conductive stripe for column YlO.

In each of the embodiments of Figures 1 through 4, the shutters tend to align with the electrical field when addressed. Closure is effected by a restorative mechanical bias or spring effect of the hinge or strap. This mechanical bias opposes the effect of the electrical field. The opened shutter will assume an open angle which is the resultant of the opposing strengths of the electrical field and the restorative mechanical bias.

Figure 5 shows a portion of a pattern of the conductive stripes. This kind of pattern can be used for both the X and the Y conductors for the previously described embodiments. The Y conductor pattern is shown in figure 5. Electrodes 531, 532, 533, etc. are ^' each connected to a lead YlO and are each energized when lead YlO is connected to a source of electrical potential. Similarly, electrodes 534-536 are connected to Yll and 537-539 to Y12. Separated from each of the electrodes 531-539 by a chevron shaped gap are electrodes 550, each of which is connected to a lead HD and the leads HD are connected in common. The electrodes 550 serve as latches. When a particular pixel is addressed by selective connection of the appropriate X and Y leads, the corresponding shutter swings open. If the leads HD are energized, the electrode 550 of the addressed pixel will maintain the selected shutter open thereby allowing the energization of the X and Y leads to be extinguished. This latching capability allows pixels to be addressed sequentially, while latching open each pixel as it is addressed. Since each character or graphic can be created and preserved by latching, a plurality or line of characters can be created one at a time and will persist until erased by extinction of the voltage provided to the leads HD.

Figure 6 is a sectional schematic view showing the hold-down or latch electrodes and the X and Y electrodes for a pixel having a shutter 632 cut from a membrane 614. The upper substrate 610 carries the X electrode and two latch electrode areas, LD and LU. The lower substrate 612 carries the Y electrode and two latch electrode areas, LD and LU. Before and after address of the pixel, the lower latch electrodes are connected to one side of a voltage source (arbitrarily designated (-) negative) and the upper latch electrodes are connected to the opposite side ^• of the voltage source (designated (+) positive). The shutter 632 remains essentially closed. Connection of the X electrode to the positive will have but small effect until the Y electrode is connected concurrently to the negative, at which event the shutter 632 will fly open as shown. Extinction of the X and Y drive voltages will no longer affect the shutter since it will remain latched open due to the continued connection of the latch electrodes to the voltage source. The gaps between the several electrode areas are of chevron shape as is shown in Figure 5. This assures that during opening, the edge of the shutter encounters the field of the next electrode area before leaving the previous electrode area.

Figure 7 shows an embodiment in which the X, Y, and latch up (LU) electrodes are located on upper stator 710. The membrane 714, including the shutters, is provided with a conductive surface such as vapor deposited aluminum. A latch-down electrode LD may be provided on lower stator 712 or may be located on membrane 714 adjacent the edge of the shutter aperture. The latch-down electrode is desired if the array is also to be addressed in reverse, that is, selective closing of open shutters.

To address selected shutters, all latch-down electrodes LD in the array are turned off, that is, switched to the potential of the shutters. All latch-up electrodes LU in the array are energized. Energization of the particular X row and Y column will cause the selected shutter (732 in Figure 7) to swing open and to latch open as it reaches proximity to latch-up electrode LU, allowing extinction of the X and Y drive. Reverse addressing can be accomplished to swing closed shutters that are open. Energization of latch-down electrodes LD latches closed all shutters that were closed or are closed by reverse addressing.

A configuration such as is shown in Figure 7, wherein the shutter is positively latched either open or closed by latch electrodes, is stable and is not much affected by external forces such as acceleration, vibration, shock, or static discharge. Latch elect¬ rodes which make use of permanently charged electrets function in the absence of power thereby sustaining the status of the array.

Electrode patterns of the types described in connection with Figures 5-7 also may be formed on the shutters and their membrane. Thus, the electrodes can be on one or both stators, on one stator and the shutters, or on all three.

The elements illustrated in Figures 6 and 7 have two independently controllable stationary electrode regions (X, Y) in addition to the hold-down regions. 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 d

S = d\ 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, 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 se iconduct- or elements. Their function is to apply potential between a common electrode and the control electrode of the element to be controlled.

While the invention has been described in terms of a visual display, essentially the array is a field of binary gating elements, either open or closed, either reflective of light or not, either a hole or not. Consequently, the array can be used as a memory for computer purposes. Once programmed with selected pixels open or closed, the status will. remain unchanged until a change is desired. In that form it is a read-write memory capable of editing or erasure.

For simplicity, the invention has been described showing planar stators. Curved or cylindrical surfaces may be employed to dispose electrode regions proximate the edge of the shutter as it is driven open or closed. Similarly, the invention has been described with shutters having a mechanical bias or spring effect for closure. No bias is needed for shutters which are driven closed as by reverse addressing.

Claims

WHAT IS CLAIMED IS:

1) An electrostatically actuated binary element comprising; a pair of parallel stator members each having plural electrode regions, and an electrostatically attractable, hing.ed shutter member, the shutter member having a permanent mechanical bias toward a closed position generally parallel with the stators, the bias being insufficient to overcome the electrostatic force acting on the shutter when an electrical potential is applied between stator electrode regions proximate said shutter to cause the shutter to be attracted toward the opened position generally normal to the stators.

2) The binary element of claim 1 wherein the shutter member is of a material having a high dielectric constant.

3) The binary element of claim 1 wherein the shutter member has at least an electrically conductive surface.

4) The binary element of claim 2 or claim 3 wherein the shutter member comprises a plurality of parallel shutter members.

5) An electrostatically actuated binary element comprising; a stator member having an electrode region, and an electrostatically attractable, hinged shutter member having closed and opened positions. the shutter member having at least a conductive surface and having a permanent mechanical bias toward a closed position generally parallel with the stator, the bias being insufficient to overcome the electrostatic force acting on the shutter when an electrical potential is applied between the stator electrode region and the conductive surface of the shutter to cause the shutter to be attracted toward an opened position generally normal to the stator.

6) The binary element of claim 5 wherein the stator member has at least two electrode regions, one being proximate the edge of the shutter when opened.

7) The binary element of claims 1 or 6 wherein the stator electrode regions are separated by a gap of chevron shape.

8) The binary element of claim 6 wherein the conductive surface of the shutter is separated by a gap of chevron shape into. at least two electrode regions.

9) The binary element of claim 1 wherein the stator members each have at least two electrode regions, one electrode region of each stator being proximate the shutter when opened.

10) An array of columns and rows of electrostatically actuated binary elements, each element comprising; a pair of parallel stator members each having plural electrode regions, and an electrostatically attractable, hinged shutter. the shutter member having a permanent mechanical bias toward a closed position generally parallel with the stators, the bias being insufficient to overcome the electrostatic force acting on the shutter when an electrical potential is applied between stator electrode regions proximate said shutter to cause the shutter to be attracted toward the opened position generally normal to the stators.

11) An array of columns and rows of electrostatically actuated binary elements, each element comprising; a stator member having an electrode region, and an electrostatically attractable, hinged shutter member having closed and opened positions, the shutter member having at least a conductive surface and having a permanent mechanical bias toward a closed position generally parallel with the stator, the bias being insufficient to overcome the electrostatic force acting on the shutter when an electrical potential is applied between the stator electrode region and the conductive surface of the shutter to cause the shutter to be attracted toward an opened position generally normal to the stator.

12) The array of claim 10 wherein, at the location of each binary element, each of the pair of stator members have first, second, and third electrode regions separated by gaps of chevron shape, all of the first and third electrode regions of each stator member being electrically connected together and to an input lead for each stator, the second electrode regions of one stator for all elements in a column being connected together and to an input lead for the column. 13) An array of columns and rows of electrostat¬ ically actuated binary elements, the array comprising a pair of parallel first and second stator members each having a plurality of parallel conductive stripes, the conductive stripes of the first stator member being orthogonal to, and spaced from, the stripes of the second stator member, electrostatically attractable, hinged shutter members located between the stator members at the crossings-over of the conductive stripes of the first and second stator members, the shutter members each having a permanent mechanical bias toward a position parallel with the stator members, the bias being insufficient to overcome the electrostatic force acting upon a shutter member located at the crossing-over of an orthogonal, spaced apart pair of conductive stripes between which on electric potential has been established.

14) An electrostatically actuated binary element comprising; a stator member having a plurality of discrete electrode regions, and an electrostatically attractable, hinged shutter member moveable between a closed and an opened position, the electrode regions being arranged to attract the shutter member progressively toward the open position.

15) The binary element of claim 14 wherein the shutter member has at least a conductive surface and wherein the stator member electrode regions comprise a first addressable electrode region, a second addressable electrode region, and a latch electrode region, whereby establishment of an electrical potential between the shutter member conductive surface and the stator electrode regions progressively attracts the shutter toward the opened position.

16) The binary element of claim 15 having a further latch electrode to latch the shutter in the closed position.

17) An electrostatically actuated binary element comprising; a pair of generally parallel stator members, each having at least two latch electrode regions and an addressable electrode region, and an electrostatically attractable, hinged shutter member located between the stator members and moveable between closed and open positions.

18) An array of columns and rows of binary elements according to claim 15 or claim 17 wherein all the first addressable electrode regions of a row of elements are electrically connected together and to an input lead for that row, all the second addressable electrode regions of a column of elements are electrically connected together and to an input lead for that column, and all of the latch electrodes are connected together and to an input lead.

19) An array of columns and rows of electrostatically actuated binary elements, the array comprising a stator member having a plurality of parallel conductive stripes, and a planar member having at least a conductive surface, the conductive surface being divided into a plurality of parallel conductive stripes, the conductive stripes of the planar member being spaced away from and orthogonal to the conductive stripes of the stator to form crossings-over, and electrostatically attractable hinged shutters located at the crossings-over and moneable between a position generally parallel with the stator and a position generally perpendicular to the stator member.

20) The binary element of claim 15 wherein, the latch electrode region is at least partially charged using a permanently charged electret material. ^"

21) The binary element of claim 17 wherein one or more of the latch electrode regions are at least partially charged using a permanently charged electret material.

22) The binary element of claim 13 wherein the shutter member is of a material having a high dielectric constant.

23) The binary element of claim 13 wherein the shutter member has at least an electrically conductive surface.

24) The binary element of claim 22 or claim 23 wherein the shutter member comprises a plurality of parallel shutter members.