WO2008085717A1

WO2008085717A1 - Shutter system

Info

Publication number: WO2008085717A1
Application number: PCT/US2007/088724
Authority: WO
Inventors: Hanlon Paul James Beatty; Moni George Matthew
Original assignee: Annulex Inc.
Priority date: 2006-12-21
Filing date: 2007-12-21
Publication date: 2008-07-17
Also published as: WO2008080117A2; WO2008080117A3

Abstract

In one embodiment, the invention provides a system. The system comprises at least one shutter which includes nanosize particles that can be excited to produce light; and a driving mechanism to drive the shutter.

Description

APPLICATION FOR LETTERS PATENT

For SHUTTER SYSTEM

Inventors:

Paul Hanlon James Beatty Moni George Matthew

Hahn and Moodley LLP

P.O. Box 52050

Minneapolis

MN 55402

Attorney's Docket No. 56.P002PCT

SHUTTER SYSTEM

FIELD

Embodiments of the invention relate to systems for displays and electro-optical shutters.

BACKGROUND

A shutter is a device that can control the passage of light through an aperture by selectively opening and closing the aperture.

A display device is a device for the presentation of information. Several technologies exist for the fabrication of display devices. Examples include liquid crystal displays (LCD) and thin film transistor displays (TFT).

SUMMARY

Embodiments of the present invention disclose a shutter which includes transparent nanosize fluorescent materials to produce a bistable multiplexed electronic display, or just a basic shutter system using particles.

The shutters may be fabricated in accordance with various technologies. In accordance with various embodiments, the shutter may be a MEMS-based shutter, an LCD shutter, particle shutter, or an electro-optic shutter such as a Lead LanthanumZirconate, Titanate (PLZT) shutter.

Moreover, the shutters, including ones based on particles, can be used also with colors generated simply by a reflecting layer, either by itself or in combination with a transparent phosphor.

In one embodiment, the shutter comprises black particles that move in a gas from a transparent electrode onto a coplanar black one to reveal reflected and/or emissive colors.

In another embodiment, black particles move laterally between electrodes having perpendicular planes to reveal reflected and/or emissive colors as a multiplexed (passive) addressed display. One of the improvements claimed here for particle shutters is the use of a transparent conductor on the opposing substrate, or an electret as the substrate or laminated to it, for the case of perpendicular electrodes. With an opposite polarity to the particles, these can prevent charged particles from accumulating on the other substrate rather than on the perpendicular side electrode. An additional improvement in the particle shutter is to have an insulating dielectric layer protrude over the planar electrode lengthening the path for dielectric breakdown of the gas, and so safeguard against this at the closest distance between electrodes. Alternatively, the fill pressure may be increased sufficiently to prevent gas breakdown, or use is made of a gas with higher breakdown strength than air.

Another feature of the laterally moving particles in a display is for an analog gray scale. Particles move out with increasing voltage first from areas of the planar electrode nearest the perpendicular side electrode. This gradual and reversible movement has been modeled on a computer using particles having a 2.8 micron diameter, charged to IfC, and surrounded on their surface by aerosil particles of about 8 to 16 nm diameter to reduce Van der Waals' forces.

Thus, enhanced brightness, contrast and color gamut are possible compared to previous systems. In the preferred embodiments, fast response speeds are provided by use of particles moving in a gas, or micro electromechanical system (MEMS) shutters.

In the following embodiments of this invention, a system is described for designing and manufacturing, comprising a means for illumination and associated optics, a means of fast shutter action of input or output electromagnetic radiation, a means for achieving desired spectral characteristics and luminance, and a means of integrating these into a display sub-assembly with driving electronics, , desiccant and connections. Illumination may be from the back or front of a display panel, and if necessary configured to some angle and range of wavelengths by optics. Thus, for example, in the case of quantum dot (QD) phosphors their excitation may be by any wavelengths shorter than those they emit, and typically in the violet to longer wave ultra violet to obtain the best efficiency of photoluminescence.

Illumination may comprise low pressure mercury discharge lamps (HgLs), with some 66% of their radiation at a wavelength of 254 nm, for direct excitation of phosphor inside the lamp or patterned on sub-pixels of a display. Alternatively, phosphor on the lamp may convert the radiation into longer wavelength UV/violet light at around 390 nm for the purpose of more efficient excitation of QDs. Using LEDs producing UV may not be so efficient to produce the exciting radiation, nor so efficient for producing the display emission.

Alternatively, the illumination may comprise efficient visible emitting light LEDs producing narrow band red, green and blue (RGB) when used in combination with a color filter behind the shutter. In this way, a wide color gamut is possible as with similarly illuminated LCDs, but with vastly greater transmittance due to the smaller attenuation of the shutters, particularly those using particles.

Optics may include a collimator sheet at the rear of the display panel placed in front of a tubular HgL, or a parabolic reflector around the lamp, so as to ensure optimal illumination of exciting radiation into the shutter cavity and associated phosphor or filters. Thus, for example, violet radiation can be gathered into just an upward direction onto QDs that then convert the wavelengths to RGB light emitted in all directions as a Lambertian emitter. This would apply for those displays say in signage where observers are looking upwards from below and would see the required visible light but would not see the violet light. This is necessary since a unique property of QDs and similar nanosize phosphors is their optical transparency.

Various types of shutters may be used, as defined earlier, and including the particle shutter device having charged particles of a powder deflected electrostatically in a unique sideways motion to achieve higher contrast, wider viewing angle, faster response, less temperature dependence and higher transmittance than for LCDs. This is mainly since there are no polarizers and there is a large aperture area.

Other shutters that can be used in combination with the means for illumination and generating colors disclosed in this invention are those based on MEMS technologies. As examples, MEMS devices of note include one based on using a flap with a torsion bar made of a carbon fiber as devised at the Thompson Lab of Cornell University as a micro mirror. Another is made by Pixtronix, Inc. used in conjunction with external color LEDs lit sequentially.

Some of these would have advantages of low voltages and mechanical return of the shutter to its former state in the absence of applied voltage, whereas particles require an opposed polarity. However, whereas some of these MEMS devices may be used as displays, often these are mirror projection ones rather than for direct view transmissive or reflective use, nor do they comprise all the varied features and options as envisaged in the present systems invention. An LCD can also be used as shutter for near-UV violet light placed behind it and a standard phosphor placed in front of it. For example See US Patent 6,191,834 Bl by Screen Technology Limited. Although luminance increases of about 3 x are claimed compared to conventional back lit LCDs, the phosphor particle size is such as to scatter ambient light which washes out the display preventing easy readability, by lowering the contrast and also reducing the color gamut. However, an improvement here is an absorbing contrast enhancement filter, although display luminance is reduced by its absorption.

Further examples of shutters using liquid crystals include those for stereoscopic TV such as from 3DTV & Tektronix. Others have been used for welding goggles by SAF-PRO, or for color television using sequential color liquid crystal shutters.

Other aspects of the invention will be apparent from the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic drawing of a display system, in accordance with one embodiment of the invention.

Figure 2 shows a schematic drawing of a particle shutter display in reflective mode using QD,s, in accordance with one embodiment of the invention.

Figure 3 shows a schematic drawing of a particle shutter display in reflective mode using QD,s, in accordance with one embodiment of the invention.

Figure 4 shows a HgL with reflectors for a transmissive display using QDs, in accordance with one embodiment of the invention.

Figure 5 illustrates directional excitation of quantum dots in a particle shutter display.

Figure 6 shows the orthogonal columns and rows for an RGB triad pixel in a matrix display.

Figure 7 shows a plan view of the column insulator, in accordance with one embodiment of the invention, with a gap for desiccant to access the pixels.

Figure 8 shows a schematic drawing of an electroplated film side electrode, in accordance with one embodiment of the invention. Figure 9 shows a schematic drawing of a further embodiment of an electroplated film side electrode, in accordance with one embodiment of the invention.

Figure 10 shows a schematic drawing of an electrode configuration comprising interdigitated co- planar electrodes, in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown only in block diagram form in order to avoid obscuring the invention.

Reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearance of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

Although the following description contains many specifics for the purposes of illustration, one skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present invention. Similarly, although many of the features of the present invention are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the invention is set forth without any loss of generality to, and without imposing limitations upon, the invention. In the following embodiments, the color generating films are incorporated into the various shutter devices on the inside of one of the substrates containing them closest to the shutter action. This avoids effects of parallax on viewing angle. In some cases, the color generating films may be located on the outside surface of one of the substrates if the substrates are of extremely thin dimensions. Examples of the latter include LCDs made on 12 micron thick plastic by Kent Displays, Inc.

In one embodiment of this invention, color generator films include absorption filters patterned by photoresist into sub-pixels of RGB as for LCDs, and using LEDs at edges of a light guide or diflfuser for the backlight. Alternatively, in another embodiment they can comprise QDs patterned for RGB using special high aspect ratio photoresist techniques known to those in the field to achieve sufficient quantity of QDs without excessive concentration which otherwise diminishes their quantum efficiency. QDs are known to have greater resilience to prolonged excitation by UV or near UV light compared with say organic fluorescent dyes. However, certain precautions are necessary to ensure optimal QD efficiency is maintained without concentration quenching when QDs are too close together or on a surface, as taught by patents held by Evident Technologies, Inc. and Sandia National Laboratories.

In still another embodiment of this invention, patterned RGB reflectors are also included for a reflective mode of operation requiring only ambient light including sunlight to produce a brilliant display. This can be used in combination with the RGB QDs enabling also reflection of rearward emitted light from the QDs and therefore a brighter display system by virtue of both reflected light, forward emitted fluorescent light and reflected fluorescent light. In a further embodiment, conventional powder phosphors may be employed with a UV backlight means of illumination, but in this case there will be some scattering of ambient light as for other displays using such phosphors (plasma displays, cathode ray tubes and vacuum fluorescent displays). However, contrast enhancement absorbance filters well known in the art can be applied. Normally, such filters attenuate not only reflected ambient light twice but emitted light once. However, if a particle shutter device is used there is the advantage of greater transmission for the exciting illumination compared to a conventional LCD and filters, and therefore the ability to override the absorption of emitted light to make the display brighter than competing phosphor display technologies, yet also having sufficient contrast (on- to off- luminance).

An LCD may be used for the shutter as taught in US patent 6,191,834, but then ideally the system should use a QD or nanophosphor for the emissive layer to prevent scattering of ambient light and avoid the need for a highly attenuating absorbing contrast enhancement filter. In fact, any type of suitable LCD may be used including by way of example standard twisted nematic, supertwisted nematic, bistable twisted nematic as at Nemoptic or ZBD Displays, Ltd.,, bistable cholesteric at Kent Displays, Inc. , polymer dispersed LCDs from Raychem/Taliq, & ferroelectric LCDs as at Displaytech Inc., & CRL in the UK.

Examples of fast electro-optic shutters are ones using the ceramic PLZT as in US Patents 5,631,735 & 5,029,989; some are sold by Furuchi in Japan. Slower electro-optic shutters include for example those using a liquid medium from Research Frontiers, Inc., of Long Island, NY or their licensees. The resulting display sub-assembly comprises the shutter using, top and bottom substrates of rigid glass or flexible polymers, transparent conducting film for a single planar electrode, epoxy edge seal, desiccant , edge connectors such as heat seal connectors, and a means of driving electronics to address the arrays of shutters.

In terms of addressing the display, a plurality of column electrodes on one substrate cross a plurality of row electrodes orthogonally disposed on the opposite substrate. At the intersection, sufficient potential and hence electric field is obtained to activate the shutter once a certain threshold is reached. This enables multiplexed passive addressing without the need for more expensive thin film transistors (TFTs). Low sheet resistance transparent electrodes such as those using gold, silver and ITO from Delta Technologies, Inc. can help avoid delays due to the RC time constant. Certain MEMS shutters can operate at low voltages for advantages regarding driver chips, but others operate at higher voltages than LCDs. Lower voltage shutters are ideal, but this may be a trade-off with performance in terms of speed, temperature range, viewing angle and brightness. Details of driving electronics for passive multiplexed driving or active matrix driving with inorganic or organic thin film transistors are well known to those skilled in the art and producers of the shutters mentioned.

The following embodiments of this invention are examples of assembled component items for the display system.

Figure 1 shows a schematic drawing of a display system in accordance with one embodiment of the invention. The system comprises illumination means (1) which is combined with optics means (3) to provide input radiation to a display sub-assembly (2). As will be seen, the display sub-assembly (2) comprises via a plurality of shutters (4) (only one of which is shown in Figure 1) and electronics (5). Shutters may be selected on the basis of actuating voltage, speed, contrast (transmission to light in the on-state compared to transmission in the off-state) and ease of fabrication, including suitable pixel size for sufficient resolution and area. The shutters are arranged in rows and columns. Each shutter may define a pixel of the display. In some cases the shutters may be grouped in groups of three, wherein each shutter in a group defines a sub-pixel for a particular primary color. Shutters may comprise particle shutters (6) that use particles (, MEMS-based shutters (7) (6) or various types of LCD shutters (8) ,or electo-optic shutters (9) such as the PLZT.

The electronics (5) comprises a driving mechanism for selectively driving the shutters. As one of ordinary skill in the art would understand, the driving mechanism will include connectors, addressing logic etc. Thus, shutters are known that exist without color generating films on their substrates, but in this invention those additions are made to the shutters to form the system. 15).

In Figure 2, substrates (13) enclose rectangular RGB sub-pixel cavities (16) filled with dry gas such as air as one example for a reflective system using a particle shutter. Epoxy forms a seal (15) at the periphery of the display and desiccant (12) keeps the device dry. Color generators such as patterned RGB QDs (11) and reflectors (8) are disposed on one substrate, and charged black insulating particles (5) moved by electrostatic forces occupy the planar transparent electrode (19) on the other substrate. Walls of a patterned insulating spacer (20) are coated with aluminum to form a side electrode (21). An insulating layer of baked photoresist (22) can be 2.5 to 6 microns thick, and preferably 3 microns, located on the opposing conducting planar electrode isolating it from the side electrode, and may also have at least two gaps of some 30 microns to allow access to desiccant (12) for removing any water from reaching the sub-pixel cavities.

Also, ideally the insulating layer (22) should protrude some 1 to 4 microns over the planar electrode, and preferably, 2 microns to prevent gas breakdown at the highest applied voltages. In this way, the shortest breakdown path is along the thickness of the insulator and its sideways intrusion over the planar electrode e.g. 3 + 2 = 5 microns. At a total applied voltage difference of 50 volts this gives an electric field of 10V/micron which is below the 17 V/micron breakdown of air following Paschen's Curve of breakdown voltage as a function of the product of pressure and distance. It is possible some sharp edges or conducting contaminant particles might double the local field to 20 V/micron .This will require an increase of the dielectric thickness to at least 3.5 microns and protrusion over the planar electrode of at least 2.3 microns. As a further precaution, or alternatively, the dry gas may be one having a higher breakdown strength such as carbon monoxide (4V/micron over one cm at normal pressure, compared to 3V/micron for air).

Advantageously, the photoresist can be patterned to interlock mechanically with the spacer (20) above it as a snap fit, or use a thermoplastic to seal the mating surfaces and better contain the particles (5). A further alternative is to have a slight curve on a relatively rigid substrate that flattens out when sealed with the epoxy at the edges and thus keeps pressed against the opposing surface. A layer of adhesive is also possible if it can be kept from deposited particles prior to curing. A few particles mixed in with such adhesive may be acceptable however provided most of the particles within the aperture area of the planar electrode are not captured. This should be possible as particles can be added as only two uniform monolayers using dispersing equipment comprising a vacuum chamber into which air and particles are admitted. Aerosil particles coat the charged particles to prevent aggregation and allow good flow. An electric field may be used to attract particles only onto the device electrode held at a suitable polarity and potential.

An important feature of the particle shutter device (PSD) and embodiment of this invention is the ability for analog gray scale whereby particles residing on the planar electrode nearer the side electrode move at lower voltages than those nearer the center of the planar electrode. Thus, only a few particles are moved at low voltages leaving most of the planar electrode covered for a dark shade of gray, higher voltage moves more particles for lighter shades of gray. This has been shown also with software modeling the electrostatic fields. Optimization is accomplished by dividing the applied voltage above and below ground to avoid particles nearer the center of the planar electrode being attracted only upwards towards the top cover plate that is at ground potential. Voltages and the cavity gap are chosen to maintain an electric field below the threshold needed to release charged particles attracted to the planar electrode by image forces etc. and is typically 3MV/cm. Voltage on the side electrode however can be higher to ensure sufficient field above this threshold at the larger distances involved. For example, in a 14 micron high cavity, maximum voltage can be up to + 51 V on the side electrode and -101 V on the planar electrode. Precise values will depend also on the charge imparted to the black particles during manufacture.

Figure 3 is an example of atransmissive mode of operation for a system.. Items are numbered as in the previous Figures including a mercury lamp HgL (1) emitting either 254 nm via a silica/quartz bulb or preferably, for greater efficiency of the conversion to visible light by the QDs, 390 nm through a special lamp phosphor such as that developed at Greenwich University (A.Vecht et al, J.Appl. Phys.Oct.1, 1998, Vol.84, Iss. 7, pp. 3827-3829).

In Figure 4, the long wavelength/violet light can be gathered and emitted in a direction parallel to the side electrode/spacers by a collimating sheet such as products manufactured by Wavefront Technology Inc., Fusion Optix Inc.and Reflexite Display Optics, or by using a parabolic reflector (23) at the back of the lamp. If a lamp phosphor is used to convert to 390 nm on the inside of the lamp, this can have a longitudinal aperture allowing some directionality and also capturing the radiation reflected back to the inside of the lamp. Once again, numbers retain their designation but item 24 is a filter either for violet light or sharp edge-absorption filters to prevent excitation of QDs in the off-state by sunlight. Thus, for example, this would cut off blue and green ambient light on red emitting QDs.

However, in a preferred embodiment using a PSD, one would reverse the positions of observer and the lamp so that the QDs are only excited by the lamp and the particles prevent excitation by sunlight in the off-state.

Advantageously, the directionality can then be upward to avoid observers seeing any violet light mixed with RGB from the QDs e.g. for signage displays where viewers observe from only the sides or below. Figure 5 shows this embodiment of the invention with a PSD, using the same item numbers as previously so QDs are (11) and particles are (5). In the case of shorter wavelength exciting radiation, the substrate furthest from the lamp can be more attenuating to UV than the substrate nearer to the lamp. Using QDs ensures directional excitation light is converted to Lambertian emission in all directions. Similarly, for shop window signage or e- books, excitation light can be directed downwards for observers who will be looking at the display only from above for a vertical orientated display. Conversely, certain e-books reader devices may be orientated horizontally in which case upward excitation light can be provided. These directional excitation systems avoid any visibility of violet light without need for filters. Having the QDs facing the excitation source and using the particles to block emitted visible light rather than excitation light ensures complete use of the excitation without need for its collimation parallel to the cavities.

Figure 6 shows the plan view layout of the matrix display of which cross sections have been discussed. Again, QDs are item (11), transparent column electrodes are (19) and aluminum rows are (25). Thus, at the cross-over of rows and columns the electric field exceeds the threshold for release of the charged particles.

Figure 7 shows another plan view with detail of the 2 to 3 micron thick insulating layer separating side electrodes from the transparent column electrodes. The two gaps of about 30 microns are to allow access of the sub-pixel cavities to the desiccant.

Regarding patterning of QDs and any pixel reflectors, it is assumed these are particulate materials capable of dispersion within photoresist and subsequent wet chemical etching to obtain the desired resolution. QDs are compatible with similar UV cured epoxy for producing inorganic LEDs excited into various visible colors by a blue or near UV LED. For the PSD, high aspect ratio materials are preferred in order to obtain sufficient QD material whilst maintaining a low concentration sufficient to avoid concentration quenching effects. Often, to maintain quantum efficiency, the colloidal QDs may have wider band gap shells, and also an outer 'skin' of organic materials; in some cases they may be joined at specific intervals along the backbone of a polymer as taught by work at Sandia National Laboratories.

Likewise, the colored reflectors may comprise reflective pigment particles similarly suspended in a photoresist. Alternatively, they may be made from patterned thin films including dielectric layers, or deposited by electrophoresis, electroplating and screen or ink jet printing.

In the case of a PSD, black insulating particles (S) are given an electrostatic charge prior to adding them to the sub-pixel cavities. This charge can be by use of an air ionizer, corona point discharge, or by tribo-charging using a paddle or other means. Details of the particles are given in the associated patent application.

Particles have been coated uniformly over large areas. In one example, an area in excess of a 4 inch diameter was coated using a fine particle dispersing machine such as the PD-10 from Ankersmid. This apparatus may be scaled up for larger display panels. These particles were made into a double monolayer for coating the planar electrode with sufficient obscurity for good contrast, yet avoiding overfilling of the cavities and side wall electrodes which would reduce transmittance in the on-state. Additionally, a suitable voltage on the planar electrode during coating help direct and retain such particles. In another embodiment, thick film electrodes are used. Figure 8 shows use of an electroplated metal film deposited over a photolithographically etched thin metal film. Substrate (13) is coated with the unpatterned conductive film (26) such as ITO on its inner side held at an opposite polarity to the particles deflecting any upward moving stray particles, and that is then coated with a thin inorganic or polymer insulator (27) of about 0.5 to 4 micron thickness respectively. Suitable inorganic dielectric films with high dielectric breakdown include various oxides including silicon oxynitride, tantalum oxide, aluminum oxideand others known to those skilled in the art. On that insulator is deposited a thin film some 0.5 to 1.5 microns thick of suitable metal (28), including copper or gold, that can be etched into the desired pattern for the side electrodes, and is and used to enable electrodeposition of a thicker metal film (29,) having a thickness of 10 -25 microns, and preferably 19 microns in the case of straight sided walls. This substitutes for the metal coating of the insulating spacer of the previous embodiments. The dielectric insulator (22) is deposited as a photoresist or ink jet deposited film that subsequently may be baked on the opposing covering the patterned ITO electrode (19).

Ideally, it should project some 1 to 4 microns into the pixel aperture area to prevent discharge of the cavity gas close between electrodes in closest proximity. An additional safety feature would be to use carbon monoxide as the cavity filling gas which has a slightly higher breakdown voltage. Another preventive measure against gas breakdown would be to fill with gas at higher pressure up to 50% above atmospheric pressure. After filling with the charged particles, desiccant and sealing adhesive the two substrates are brought together to produce the encapsulated shutter or display. Patterns may be of various shapes including stripes to produce either a basic shutter or matrix display.

An alternative to the conductive transparent electrode for controlling the stray particles and further embodiment of this invention is use of an electret for the substrate or laminate one to it having a polarity opposite to that of the particles.

Yet another embodiment of this invention is to bias the applied voltage with some alternating current to wriggle the particles across the top substrate should they land there and become immobile. However, normally the spherical particles are capable of rolling motion and will make their way to the side electrodes.

Figure 9 shows a preferred embodiment of the electroplated thick metal film electrode. Here, the particles are contained within cells by the walls of the thick metal film by 'spurs' (30) separated from the opposing cell by less than the diameter of the charged particle, say 2 microns for 2.8 micron diameter particles.

Another embodiment, shown in Figure 10, comprises interdigitated coplanar electrodes of which one set are black (31) and accommodate particles in the optically off-state, and the other set are transparent (32). Such electrodes can occupy approximately 50% of the total area leaving 50% between them for the other set of electrodes which can be transparent using for example indium tin oxide . This also allows high optical transmission being the product of the transmission for the transparent electrode and the aperture ratio i.e. typically 85% x 50% = 42%. Other aspects of this embodiment including the charged particles and gas cavity are the same as in the preceding embodiments. Thus, black particles move laterally across from black to transparent electrodes in response to opposed polarities on the electrodes. Electrode widths must be consistent with the flight distances outlined above being on the order of 19 to 45 microns. The electrodes can be etched in conductive thin films or printed by any means. Ideally, a thin width of black insulator say 10 microns wide may be placed overlapping the gap between each black and transparent electrode to reduce leakage of light in the optically off state. The black electrodes may be produced from patterning conductive carbon by itself or over indium tin oxide using various means of printing known to those skilled in the art. Alternatively, transparent conductive electrodes may be coated on top of black insulator where the width of that insulator covers the gap between the interdigitiated electrodes.

Other embodiments for this system include elements from the allied application including use of corrugated or zig zag perpendicular side electrodes for greater area to accommodate particles thus maintaining viewing angles, and mid-pixel spacer side electrodes to reduce the operating voltage.

Examples have been given for a Particle Shutter but the components identified may be used also with other types of electro-mechanical or electro-optic shutters in a similar way as will be understood by those skilled in the art. While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative and not restrictive of the broad invention and that this invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art upon studying this disclosure. In an area of technology such as this, where growth is fast and further advancements are not easily foreseen, the disclosed embodiments may be readily modifiable in arrangement and detail as facilitated by enabling technological advancements without departing from the principals of the present disclosure.

Claims

CLAIMS:

1. A system, comprising: at least one shutter which includes nanosize particles that can be excited to produce light; and a driving mechanism to drive the shutter.

2. The system of claim 1, wherein the nanosize particles are fluorescent.

3. The system of claim 1, wherein the particles are transparent.

4. The system of claim 1, wherein the at least one shutter comprises a particle shutter.

5. The system of claim 1, wherein the at least one shutter comprises a MEMS- based shutter.

6. The system of claim 1, wherein the at least one shutter comprises a LCD shutter.

7. The system of claim 1, wherein the at least one shutter comprises an electro-optic shutter.

8. The system of claim 1, comprising a plurality of shutters arranged in rows and columns to form a display.

9. The system of claim 4, wherein the shutter further comprises black particles that can be displaced laterally with respect to a transparent planar electrode to open the shutter.

10. The system of claim 9, wherein the shutter further comprises a substrate opposite the transparent planar electrode, the substrate being at least coated with an electret.

11. The system of claim 9, further comprising side electrodes that are transverse to the transparent electrode to cause the lateral displacement of the black particles under electrostatic forces.

12. The system of claim 11, further comprising an insulating dielectric to insulate the side electrodes from the planar transparent electrode.

13. The system of claim 12, wherein the substrate, the transparent planar electrode, and the side electrodes together define a cavity into which a part of the insulating dielectric projects.

14. The system of claim 13, wherein the insulating dielectric is recessed to allow the ingress of a desiccant into the cavity.

15. The system of claim 9, wherein the black particles are of a single color.

16. The system of claim 4, wherein the particle shutter comprises interdigitated electrodes.

17. The system of claim 16, wherein particle shutter comprises a black dielectric insulator between the interdigitated electrodes.