SPATIALLY-DISTRIBUTED ILLUMINATION SOURCES

BACKGROUND

Technical Field

[1002] The present application relates to thermal management and, more particularly, to micro-scale devices that generate ions and electrical fields to motivate flow of fluids, such as air, as part of a thermal management solution to dissipate heat or improve thermal uniformity of spatially-distributed illumination sources.

Related Art

[1003] Backlit displays are ubiquitous in consumer electronics with applications ranging from cellular phones to computer monitors and large- screen, high definition televisions. In the context of television displays, one popular display technology uses a multiplicity of liquid crystal light

transmissive elements arranged to form a two-dimensional array referred to as a liquid crystal display or "LCD." Selective control of the individual elements allows the LCD to spatially (and typically chromatically) modulate transmission of light from the backlighting illumination source to present images viewable at the front of the display. The design and physics of LCD panels and various light treatment film layers are well-known in the art and the following description is directed primarily towards thermal solutions for such displays and their illumination source.

[1004] In general, light can distributed over the backlit surface of the display using light guides and/or diffusers from edge-positioned illumination sources or from illumination sources distributed over a substantial portion of the two-dimensional extent of the display and diffused over the backside thereof. In the former case, the display may be characterized as "edge-lit," while in the latter case, the display may be characterized as "direct-lit." In either case, the spatially distributed nature of the illumination sources and the localized heat generated thereby creates thermal management challenges. [1005] In the context of edge-lit, large-panel television displays, one exemplary illumination source is a generally one-dimensional array of light- emitting diodes (LEDs). A typical LED edge-lit large-panel television can employ hundreds of LED packages, each dissipating hundreds of milliwatts and collectively generating substantial and highly localized thermal loads.

[1006] In some cases, the significant heat generated by LEDs may be spread or transferred to heat sinks and/or the television chassis itself for passive cooling, e.g., radiative and/or by convective air flow through vents formed in a rearward surface of the display housing. Unfortunately, many factors may complicate a thermal management solution. For example, design imperatives to scale to large screen sizes and extremely thin form factors, may drive illuminator configurations to large thermal loads at spatially distributed point sources with minimal standoff distances. In some cases, bill of material (BOM) cost considerations may drive designs toward smaller numbers of higher power LEDs or toward single-edge illuminator designs, each with potential hot spotting issues. In any case, thermal loading can become a significant design consideration as heat generated by illumination sources is highly localized, typically at one or more edges of the display. This intense localized thermal load may affect the optical characteristics or other performance characteristics of the display. For example, allowable LED array density, operating power or brightness levels of individual LEDs, and even useful life or chromatic characteristics of an individual LED may be adversely affected by thermal management designs that are unable to adequately dissipate heat.

[1007] Passive convection and radiative cooling have typically been used to address thermal loads in television displays since fans or other mechanical air movers can produce undesirable acoustic effects or other performance interference. However, passive cooling techniques may prove inadequate for some designs, particularly those that pack higher power and/or larger numbers of thermal point sources in ever tighter volumes to illuminate ever larger displays. In addition to challenges created by higher-powered and/or denser arrays of LEDs or other illumination sources, an increasing trend toward flush-mounted televisions and displays presents additional passive cooling challenges as flow through the traditional rearward facing passive cooling vents may be obstructed or severely restricted with the display mounted or positioned in close proximity to a wall or other surface.

[1008] Accordingly, improved thermal management solutions are sought to afford greater flexibility in the design of flat panel televisions and other displays, to improve performance and/or cost effectiveness of the distributed illumination sources employed in such televisions and displays, and to facilitate mounting and/or integration options for such televisions and displays.

SUMMARY

[1009] In some cases, active thermal management using forced air convective cooling may be a necessary or desirable thermal management solution to facilitate designs of certain flat panel televisions and other displays. Indeed, active thermal management solutions that employ an

electrohydrodynamic (EHD) air mover may be particularly adaptable to, and attractive for, the localized thermal management challenges of very large, extremely thin display panels, particularly those that employ an edge-lit illuminator design in which size, brightness, form-factor or bill of material considerations result in localized thermal load(s) for which conventional passive techniques are inadequate.

[1010] In particular, it has been discovered that a display apparatus having at least one laterally elongate array of discrete illumination sources may be cooled using an electrohydrodynamic (EHD) fluid mover. EHD cooling can reduce the temperature of the discrete illumination sources, provide more uniform temperature across the elongate array and display area, reduced power consumption, and provide greater flexibility of illumination design and display mounting. This may reduce overall device lifetime costs, device size or volume, and may improve electronic device performance or user

experience.

[1011] In some embodiments in accordance with the present invention, a display apparatus includes a two-dimensional array of transmissive display elements, at least one laterally elongate array of discrete illumination sources, and an electrohydrodynamic (EHD) fluid mover. During operation each of the discrete illumination sources constitutes a thermal point source thermally coupled via one or more thermal spreader paths to an elongate set of one or more heat transfer surfaces spanning at least a substantial portion of the lateral extent of the array. The electrohydrodynamic (EHD) fluid mover has a lateral extent generally coextensive with the elongate set of heat transfer surfaces and is positioned with respect thereto such that when energized, the electrohydrodynamic fluid mover motivates fluid flow over the elongate set of heat transfer surfaces in a flow direction transverse to a major lateral extent thereof, thereby dissipating heat evolved at the thermal point sources.

[1012] In some cases, during operation, the EHD fluid mover maintains a substantially uniform thermal profile throughout the laterally elongate array of discrete illumination sources. In some cases, temperature at a hottest operating one of the discrete illumination sources and at a coolest operating one of the discrete illumination sources differs by no more that about 5%. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform intensity of emitted light at each of the discrete illumination sources throughout the laterally elongate array. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform power dissipation at each of the discrete illumination sources throughout the laterally elongate array. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform chromatic characteristics of light supplied from each of the discrete illumination sources throughout the laterally elongate array.

[1013] In some embodiments, the discrete illumination sources of the laterally elongate array are series coupled between power supply terminals, and during operation, the EHD fluid mover maintains through active cooling, substantially uniform voltage drop at each of the discrete illumination sources throughout the laterally elongate array. In some embodiments, the discrete illumination sources of the laterally elongate array are light emitting diodes (LEDs) or groupings of thereof. In some embodiments, either or both of illumination power and chromatic character of light emitted by individual ones of the LEDs when powered is temperature dependent. In some

embodiments, the transmissive display elements include addressable liquid crystal cells arranged in a matrix.

[1014] In some embodiments, the laterally elongate array of discrete illumination sources is positioned adjacent a first edge of the two-dimensional array of transmissive display elements and the display apparatus further includes a light guide and diffuser assembly positioned to distribute light from the discrete illumination sources over the two-dimensional array of

transmissive display elements. In some embodiments, the display apparatus further includes at least a second laterally elongate array of discrete

illumination sources, positioned adjacent a second edge of the two- dimensional array of transmissive display elements; and a second

electrohydrodynamic (EHD) fluid mover having a lateral extent generally coextensive with a second elongate set of heat transfer surfaces thermally coupled to the discrete illumination sources of the second laterally elongate array and positioned with respect thereto such that when energized, the second electrohydrodynamic fluid mover motivates fluid flow over the second elongate set of heat transfer surfaces in a flow direction transverse to a major lateral extent thereof, thereby dissipating heat evolved at the thermal point sources of the second elongate set. In some cases, the first and second edges are opposing edges of the two-dimensional array of transmissive display elements.

[1015] In some embodiments, the discrete illumination sources of the laterally elongate array are arranged as a linear array. In some embodiments, the heat transfer surfaces include heat transfer fins introduced along the lateral extent thereof and oriented generally along a flow path from or to the EHD fluid mover.

[1016] In some embodiments, the display apparatus further includes a fluid flow path from an inlet ventilation boundary through the EHD fluid mover, over the heat transfer surfaces and to an outlet ventilation boundary, and the total fluid flow path length from inlet to outlet ventilation boundary extends a distance that is no greater than about 10% of a major or minor dimension of the two-dimensional array of transmissive display elements. In some cases, notwithstanding increasing scale of the two-dimensional array of transmissive display elements, total length of the fluid flow path from inlet to outlet ventilation boundary remains substantially fixed.

[1017] In some cases, relative to a coordinate system consistent with positioning or mounting of the display apparatus for operation, the laterally elongate array of discrete illumination sources is positioned adjacent bottom edge of the two-dimensional array of transmissive display elements; a substantially entirety of the inlet ventilation boundary is provided at a generally downward facing surface of the display apparatus; and a substantially entirety of the outlet ventilation boundary is provided closely proximate to the inlet ventilation boundary on at least one major two-dimensional surface of the display apparatus. In some cases, a substantial entirety of the inlet ventilation boundary is provided on a front surface of the display apparatus. In some cases, a substantial entirety of the inlet ventilation boundary is provided on a rear surface of the display apparatus.

[1018] In some cases, relative to a coordinate system consistent with positioning or mounting of the display apparatus for operation, the laterally elongate array of discrete illumination sources is positioned adjacent upper edge of the two-dimensional array of transmissive display elements; a substantially entirety of the outlet ventilation boundary is provided at a generally upward facing surface of the display apparatus; and a substantially entirety of the inlet ventilation boundary is provided closely proximate to the outlet ventilation boundary on at least one major two-dimensional surface of the display apparatus In some cases, a substantially entirety of the inlet and outlet ventilation boundaries are provided on opposing major two-dimensional surface of the display apparatus.

[1019] In some cases, relative to a coordinate system consistent with positioning or mounting of the display apparatus for operation, neither the inlet nor the outlet ventilation boundaries are provided on the rear two-dimensional surface of the display apparatus. [1020] In some cases, the display apparatus is flush mounted to a wall surface such that negligible volume is available to support effective cooling of the display apparatus by forced or unforced convective air flow between the rear two-dimensional surface and the wall.

[1021 ] In some embodiments in accordance with the present invention, an actively cooled illumination source includes an elongate array of discrete illumination elements and an electrohydrodynamic (EHD) fluid mover. The elongate array of discrete illumination elements has a length-to-width ratio of at least 40::1 , wherein each of the discrete illumination elements, during operation, constitutes a thermal point source and wherein the thermal point sources are distributed along elongate array. The electrohydrodynamic (EHD) fluid mover has a lateral extent generally coextensive with the length of the elongate array and is positioned with respect thereto such that when energized, the electrohydrodynamic fluid mover motivates fluid flow

throughout the substantial entirety of its lateral extent in a direction transverse to the elongate length of the array, thereby dissipating heat evolved at the thermal point sources.

[1022] In some embodiments, the EHD fluid mover has a thickness of less than about 1 cm in a dimension orthogonal to its lateral extent, and the lateral extent of the EHD fluid mover is greater than about 25cm. In some

embodiments, EHD fluid mover electrode geometries are configured such that transverse to a central portion of the elongate array, the central portion constituting at least 80% of the entirety of its lateral extent, the fluid flow motivated by the EHD fluid mover is of substantially uniform velocity. In some embodiments, an electrohydrodynamic (EHD) fluid mover a ratio of fluid flow velocity, velocity _max :: velocity _av erage, over the lateral extent of the EHD fluid mover is no greater than 3::1 . In some embodiments, EHD fluid mover electrode geometries are configured such that along its lateral extent, velocities of fluid flow motivated by the EHD fluid mover are tailored to a spatial variation in thermal load along the elongate array.

[1023] In some embodiments, the actively cooled illumination source further includes one or more thermal spreader paths coupled between the thermal point sources and an elongate set of one or more heat transfer surfaces spanning at least a substantial portion of the lateral extent of the array. In some embodiments, quantity of heat transfer into fluid flow transversely motivated over the one or more heat transfer surfaces by the EHD fluid mover is spatially differentiated in general correspondence with a spatial variation in thermal load along the elongate array. In some

embodiments, a spatially varied density, surface area or geometry of heat transfer fins provides at least a substantial portion of the spatial differentiation in quality of heat transfer into the fluid flow.

[1024] In some embodiments, the discrete illumination elements of the elongate array are arranged as a 1 -wide, generally-linear array. In some embodiments, the discrete illumination elements of the elongate array are arranged as an N-wide, M-long tessellation, wherein a ratio M::N is greater than about 10::1 . In some cases, the discrete illumination elements of the N- wide, M-long tessellation are distributed over a generally planar elongate surface. In some cases, the discrete illumination elements of the N-wide, M- long tessellation are distributed over a generally curved elongate surface.

[1025] In some embodiments, the actively cooled illumination source is configured as an illuminator for a display apparatus that further comprises an array of transmissive display elements and a light guide and diffuser assembly positioned to distribute light from the discrete illumination elements over a major surface of the array of transmissive display elements. In some embodiments, the actively cooled illumination source is configured as an illuminator for a display apparatus, wherein the major surface is generally planar. In some embodiments, the actively cooled illumination source is configured as an illuminator for a display apparatus, wherein the major surface is curved in a least one dimension; and wherein at least the diffuser is conformal with the curved major surface.

[1026] In some embodiments in accordance with the present invention, a display apparatus includes a two-dimensional array of transmissive display elements, a two-dimensional array of discrete illumination sources, a diffuser and an electrohydrodynamic (EHD) fluid mover. During operation, each of the discrete illumination sources constitutes a thermal point source. The diffuser is positioned to distribute light from the discrete illumination elements over a major surface of the array of transmissive display elements. The

electrohydrodynamic (EHD) fluid mover has a lateral extent generally coextensive with either a major or minor dimension of the two-dimensional array of discrete illumination sources and is positioned with respect thereto such that when energized, the electrohydrodynamic fluid mover motivates fluid flow over heat transfer surfaces thermally coupled to at least respective ones of the discrete illumination sources, thereby dissipating heat evolved at the thermal point sources.

[1027] In some cases, during operation, the EHD fluid mover maintains a substantially uniform thermal profile throughout the two-dimensional array of discrete illumination sources of discrete illumination sources. In some cases, temperature at a hottest operating one of the discrete illumination sources and at a coolest operating one of the discrete illumination sources differ by no more that about 5%. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform intensity of emitted light at each of the discrete illumination sources throughout the two- dimensional array. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform power dissipation at each of the discrete illumination sources throughout the two-dimensional array. In some cases, during operation, the EHD fluid mover maintains through active cooling, substantially uniform chromatic characteristics of light supplied from each of the discrete illumination sources throughout the two- dimensional array.

[1028] In some embodiments in accordance with the present invention, an apparatus includes an array of discrete illumination sources and an

electrohydrodynamic (EHD) fluid mover. During operation, each of the discrete illumination sources constitutes a thermal point source thermally coupled via one or more thermal spreader paths to an elongate set of one or more heat transfer surfaces spanning at least a substantial portion of the lateral extent of the array. The electrohydrodynamic (EHD) fluid mover has a lateral extent generally coextensive with the elongate set of heat transfer surfaces and is positioned with respect thereto such that when energized, the electrohydrodynamic fluid mover motivates fluid flow over the elongate set of heat transfer surfaces in a flow direction transverse to a major lateral extent thereof, thereby dissipating heat evolved at the thermal point sources.

[1029] In some embodiments, the apparatus further includes a fluid flow path from an inlet ventilation boundary through the EHD fluid mover, over the heat transfer surfaces and to an outlet ventilation boundary closely proximate to the inlet ventilation boundary, wherein the EHD fluid mover is configured to operate intermittently to allow heated fluid exiting through the outlet ventilation boundary to at least partially dissipate between successive operational cycles.

[1030] In some embodiments in accordance with the present invention, an electronic display device includes a first elongate illumination source and an electrohydrodynamic (EHD) air moving device comprising first and second electrodes energizable to motivate a fluid flow along a flow path to provide convective transfer of heat generated by the elongate illumination source. In some embodiments, the elongate illumination source comprises an array of discrete light emitting elements. . In some embodiments, the elongate illumination sources comprises one of a linear array and an arcuate array of LEDs. In some embodiments, the elongate illumination source comprises at least one of a CCFL tube and a fluorescent tube.

[1031] In some embodiments, the electronic display device further includes a diffusion panel arranged to distribute light from the elongate illumination source across a display area of the display device. In some embodiments, the electronic display device further includes a heat transfer structure extending between a heated region adjacent the elongate illumination source and the fluid flow. In some cases, the heat transfer structure includes at least one of a heat spreader, a heat pipe, a radiator and a heat transfer surface. In some cases, the elongate illumination source is thermally coupled to an electrode of the EHD device. In some cases, the flow path is arranged to also conduct heat from a source other than the elongate illumination source within a housing of the electronic display device to the environment. [1032] In some cases, the housing defines an inlet boundary and an outlet boundary of the flow path. In some cases, at least one of the inlet boundary and the outlet boundary substantially coincides with an edge portion of at least one of a display area, a display area bezel, and a housing of the electronic display device. In some cases, at least one of the inlet boundary and the outlet boundary is at least partially defined by a bezel surrounding the display area. In some cases, at least one of the inlet boundary and the outlet boundary is defined along one of the top, bottom, and side of the display device. In some cases, one of the inlet boundary and the outlet boundary is at least partially defined by a front facing bezel adjacent a display area of the display device and the other of the inlet boundary and the outlet boundary is defined on a lateral surface of the display device. In some cases, the inlet and outlet boundaries are arranged substantially outside of a major rearmost portion of a housing of the display device so as not to be obstructed by abutment of the major rearmost portion of the display device against a supporting surface. In some cases, the inlet and outlet boundaries are defined, without regard to order, in at least one of top and bottom surfaces, opposed side lateral surfaces, top and front surfaces, bottom and front surfaces, and side and front surfaces of the display device.

[1033] In some embodiments, the electronic display device further includes a second elongate illumination source in thermal communication with the flow path. In some embodiments, the electronic display device further includes a second EHD air moving device along the flow path. In some embodiments, the electronic display device further includes a supplemental air impeller operable to supplement the air flow during periods of increased thermal loading above a predetermined thermal threshold. In some embodiments, the supplemental air impeller is one of a fan and an EHD air moving device. In some cases, the thermal loading threshold is determined, at least in part, by at least one of display temperature and spectral output.

[1034] In some embodiments, at least one of the inlet and outlet boundaries substantially coincides with a location of a speaker grille. In some cases, acoustic agitation of air adjacent the speaker serves to aid in diffusion of exhausted air into the environment.

[1035] In some embodiments, the electronic display device further includes an ozone reducing material positioned within the flow path. In some embodiments, the electronic display device further includes an ozone- shielding material over an ozone sensitive surface positioned within the flow path. In some embodiments, the electronic display device further includes an RF shield between the EHD air moving device and an RF sensitive

component of the display device.

[1036] In some embodiments in accordance with the present invention, a display device includes a first elongate illumination source and a first electrohydrodynamic (EHD) air mover comprising first and second electrodes energizable to motivate a fluid flow along a flow path extending one of across and along a substantial portion of the length of the first elongate illumination source, wherein an inlet boundary and an outlet boundary of the flow path are defined by other than a major rearward surface of a housing of the display device.

[1037] In some embodiments, at least one of the inlet and outlet boundaries is defined in a forward surface of the housing. In some

embodiments, at least one of the inlet and the outlet boundaries is defined by a gap between an edge of a display area and a bezel surrounding a display area. In some embodiments, the inlet and outlet boundaries are defined at substantially opposed portions of the display housing such that the air flow extends across a major dimension of the display housing. In some

embodiments, the display device further includes a second EHD air mover, wherein the first EHD air mover is positioned to draw air into the inlet boundary and the second EHD air mover is positioned to expel air from the outlet boundary. In some embodiments, the second EHD air mover is energizable to motivate a fluid flow along a flow path extending one of across and along a substantial portion of the length of the second elongate illumination source. [1038] These and other embodiments will be understood with reference to the description, drawings and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[1039] The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. Drawings are not necessarily to scale; rather, emphasis has instead been placed upon illustrating the structural and fabrication principles of the described embodiments.

[1040] FIG. 1 is a graphic depiction of certain basic principles of electrohydrodynamic (EHD) fluid flow in a corona discharge type device.

[1041] FIG. 2 depicts an illustrative high voltage power supply

configuration in which emitter and collector electrodes of an illustrative EHD fluid mover are energized to motivate fluid flow past heat transfer surfaces (e.g., heat transfer fins thermally coupled to an elongate array of discrete illumination elements) in accordance with some embodiments of the present invention.

[1042] FIGS. 3A and 3B are rear perspective views of a display device illustrating an exemplary placement of inlet and outlet ventilation boundaries and (in the case of interior view FIG. 3B) an exemplary EHD motivated flow path past elongate arrays of discrete illumination elements and through the display device, all in accordance with some embodiments of the present invention.

[1043] FIG. 3C is an alternative rear perspective interior view in

correspondence with FIG. 3A, in which an alternative inlet-to-outlet flow path is provided in accordance with some embodiments of the present invention.

[1044] FIG. 4 is still another alternative rear perspective interior view of a display device, wherein exemplary EHD motivated flow are along a major dimension of elongate arrays of discrete illumination elements in accordance with some embodiments of the present invention and wherein an alternative placement of inlet and outlet ventilation boundaries is depicted.

[1045] FIGS. 5A and 5B are front and rear perspective views of an integral bracket and heat spreader assembly for an elongate array of light emitting diode (LED) illumination elements consistent with features illustrated in FIGS. 3B, 4 and 9A for respective EHD air mover cooled edge-lit embodiments of a display device in accordance with some embodiments of the present invention.

[1046] FIG. 6 is a simplified side cross-sectional view of an edge-lit configuration for a display device in accordance with some embodiments of the present invention, in which thermal management of the display (generally) and of an elongate array of light emitting diode (LED) illumination elements (more specifically) is facilitated using an EHD air mover.

[1047] FIG. 7 is a simplified side cross-sectional view of an alternative direct-lit configuration for a display device in accordance with some

embodiments of the present invention, in which thermal management of the display (generally) and of a two-dimensional array of light emitting diode (LED) illumination elements (more specifically) is facilitated using an EHD air mover.

[1048] FIGS. 8A and 8B are respective edge-on side and perspective views of an illustrative, flat panel display style, electronics device in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a total device depth typically less than about 10 mm.

[1049] FIG. 9A is an interior view (generally in correspondence with flat panel display device of FIGS. 8A and 8B) illustrating positional relations between components and ventilating air flows. FIGS. 9B and 9C depict, in illustrative cross-sections of the flat panel display device, opposing

electrostatically operative portions of respective EHD air movers in

accordance with some embodiments of the present invention. [1050] The use of the same reference symbols in different drawings indicates similar or identical items.

MODE(S) FOR CARRYING OUT THE INVENTION

[1051] As will be appreciated, many of the designs and techniques described herein have particular applicability to the thermal management challenges of densely-packed devices and small form-factors typical of modern consumer electronics. Indeed, some of the EHD fluid/air mover designs and techniques described herein facilitate active thermal

management in electronics whose thinness or industrial design precludes or limits the viability of mechanical air movers such as fans, blowers, etc. In some cases, even if fans, blowers, etc. were tolerable, it may be difficult to provide duct work to channel fan or blower motivated air flows past spatially- distributed illumination sources or, in the alternative, to provide effective heat transfer paths from the spatially-distributed illumination sources to fan or blower motivated air flows.

[1052] In some embodiments, EHD fluid/air movers may be fully integrated in an operational system such as a high-definition television, flat panel display or pad-type computer to provide thermal management of a spatially- distributed illumination source thereof. In other embodiments, EHD fluid/air movers may take the form of a thermally managed illuminator subassembly. In still other embodiments, EHD fluid/air movers may take the form of subassemblies or enclosures adapted for use in providing such systems, illuminators or subassemblies with EHD motivated flows.

[1053] Although much of the description herein focuses on thermal management solutions for flat panel displays and, in particular, edge-lit LED illuminator arrays, it will be appreciated that additional applications of the described techniques are also envisioned. In particular, applications to direct-lit, transmissive displays and to displays that employ other illuminator device technologies or even heat-generating emissive display elements are all envisioned. Furthermore, applications to the general field of spatially distributed (1 D and 2D) illuminators, such as for commercial, residential or architectural lighting, are also envisioned and, based on the description herein, will be appreciated by persons of ordinary skill in the art.

[1054] In general, a variety of scales, geometries and other design variations are envisioned for EHD air movers, together with a variety of positional interrelationships between a given EHD air mover and the spatially distributed illumination sources and/or associated heat transfer surfaces. For purposes of illustration, we focus on certain exemplary embodiments and certain surface profiles and positional interrelationships with other

components. For example, in much of the description herein, opposing planar collector electrodes are formed on interior surfaces of an enclosure or on an exposed surface of a display component and arranged as parallel surfaces proximate to a corona discharge-type emitter wire that is displaced from leading portions of the respective collector electrodes. Nonetheless, other embodiments may employ other electrostatically operative surface

configurations or other ion generation techniques and will nonetheless be understood in the descriptive context provided herein.

[1055] In the present application, some aspects of embodiments illustrated and described herein are referred to as electrohydrodynamic fluid accelerator devices, also referred to as "EHD devices," "EHD fluid accelerators," "EHD air movers," and the like. For purposes of illustration, some embodiments are described relative to particular EHD device configurations in which a corona discharge at or proximate to an emitter electrode operates to generate ions that are accelerated in the presence of electrical fields, thereby motivating fluid flow. While corona discharge-type devices provide a useful descriptive context, it will be understood (based on the present description) that other ion generation techniques may also be employed. For example, in some embodiments, techniques such as silent discharge, AC discharge, dielectric barrier discharge (DBD), or the like, may be used to generate ions that are in turn accelerated in the presence of electrical fields and motivate fluid flow.

[1056] Using heat transfer surfaces that, in some embodiments, take the form of heat transfer fins, heat dissipated by one or more spatially distributed illumination sources (e.g., an array of LEDs) and optionally additional electronics (e.g., microprocessors, graphics units, etc.) and/or other components can be transferred to the EHD motivated fluid flow and

exhausted from an enclosure through a ventilation boundary. Typically, when a thermal management system is integrated into an operational environment, heat transfer paths (often implemented as heat spreaders, heat pipes or using other thermal transport technologies) are provided to transfer heat from where it is dissipated (or generated) to a location (or locations) within the enclosure where air flow motivated by an EHD device (or devices) flows over heat transfer surfaces. EHD air mover designs described herein deliver spatially distributed air flow at the heat generating illumination sources and therefore allow heat transfer into the motivated airflow to occur closely proximate to the heat sources.

[1057] For illustration, heat transfer fins are depicted with respect to certain exemplary embodiments. However, as will be appreciated based on the description herein, in some embodiments, conventional arrays of heat sink fins need not be provided and EHD motivated fluid flow over exposed interior surfaces, whether proximate a heat source (such as an edge-lit LED array, emitters arranged in a direct-lit configuration, an elongate fluorescent illuminator or other spatially distributed illumination source) or removed therefrom, may provide sufficient heat transfer. In each case, provision of ozone catalytic or reactive surfaces/materials on heat transfer surfaces may be desirable. Typically, heat transfer surfaces, field shaping surfaces and dominant ion collecting surfaces of a collector electrode present differing design challenges and, relative to some embodiments, may be provided using different structures or with different surface conditioning. However, in some embodiments, a single structure may be both electrostatically operative (e.g., to shape fields or collect ions) and provide heat transfer into an EHD motivated fluid flow.

[1058] Note that, in some unventilated embodiments, EHD motivated fluid flow may be circulated within an enclosure, which in turn, may radiatively or convectively transfer heat to the ambient environment. In this way, hotspots on the exterior surface of the enclosure can be eliminated or at least mitigated even without significant airflow through a ventilation boundary. Of course, in some embodiments, EHD motivated flow(s) may be employed both to manage localized hotspots and to exhaust heat by forced convective heat transfer to an air flow that transits a ventilation boundary.

Electrohydrodynamic (EHD) Fluid Acceleration, Generally

[1059] Basic principles of electrohydrodynamic (EHD) fluid flow are well understood in the art and, in this regard, an article by Jewell-Larsen, N. et al., entitled "Modeling of corona-induced electrohydrodynamic flow with COMSOL multiphysics" (in the Proceedings of the ESA Annual Meeting on Electrostatics 2008) (hereafter, "the Jewell-Larsen Modeling article"), provides a useful summary. Likewise, U.S. Patent 6,504,308, filed October 14,1999, naming Krichtafovitch et al. and entitled "Electrostatic Fluid Accelerator" describes certain electrode and high voltage power supply configurations useful in some EHD devices. U.S. Patent 6,504,308, together with sections I (Introduction), II (Background), and III (Numerical Modeling) of the Jewell-Larsen Modeling article are hereby incorporated by reference herein for all that they teach.

[1060] EHD fluid mover designs described herein can include one or more corona discharge-type emitter electrodes. In general, such corona discharge electrodes include a portion (or portions) that exhibit(s) a small radius of curvature and may take the form of a wire, rod, edge or point(s). Other shapes for the corona discharge electrode are also possible; for example, the corona discharge electrode may take the shape of barbed wire, wide metallic strips, and serrated plates or non-serrated plates having sharp or thin parts that facilitate ion production at the portion of the electrode with the small radius of curvature when high voltage is applied. In general, corona

discharge electrodes may be fabricated in a wide range of materials. For example, in some embodiments, compositions such as described in U.S. Patent 7,157,704, filed December 2, 2003, entitled "Corona Discharge

Electrode and Method of Operating the Same" and naming Krichtafovitch et al. as inventors may be employed. U.S. Patent 7,157,704 is incorporated herein for the limited purpose of describing materials for some emitter electrodes that may be employed in some corona discharge-type embodiments. In general, a high voltage power supply creates the electric field between corona discharge electrodes and collector electrodes.

[1061] Basic principles of operation will be understood based on a simple two electrode system. Referring to the illustration in FIG. 1 , a high-intensity electric field between a first electrode 10 (often termed the "corona electrode," the "corona discharge electrode," the "emitter electrode" or just the "emitter") and a second electrode 12 creates conditions for EHD fluid acceleration. Fluid molecules, such as surrounding air molecules, near the emitter discharge region 11 become ionized and form a stream 14 of ions 16 that accelerate in the electric field toward second electrode 12, colliding with neutral fluid molecules 22 in the process. As a result, momentum is imparted to the neutral fluid molecules 17, inducing a corresponding movement of fluid molecules 17 in a generally downstream fluid flow direction, denoted by arrow 13, toward second electrode 12. Second electrode 12 may be variously referred to as the "accelerating," "attracting," "target" or "collector" electrode. While stream 14 of ions 16 is attracted to, and generally neutralized by, second electrode 12, the momentum imparted to neutral fluid molecules 17 carries them past second electrode 12. The result is EHD motivated fluid flow.

[1062] In general, EHD fluid mover designs described herein include ion collection surfaces positioned downstream of one or more corona discharge electrodes. Often, ion collection surfaces of an EHD fluid mover portion include leading surfaces of generally planar collector electrodes extending downstream of the corona discharge electrode(s). In some cases, a collector electrode may do double-duty as heat transfer surfaces. In some cases, a fluid permeable ion collection surface may be provided.

[1063] In general, collector electrode surfaces may be fabricated of any suitable conductive material, such as aluminum or copper. Alternatively, as disclosed in US Patent 6,919,698 to Krichtafovitch, collector electrodes (referred to therein as "accelerating" electrodes) may be formed of a body of high resistivity material that readily conducts a corona current, but for which a result voltage drop along current paths through the body of high resistivity collector electrode material provides a reduction of surface potential, thereby damping or limiting an incipient sparking event. Examples of such relatively high resistance materials include carbon filled plastic, silicon, gallium arsenide, indium phosphide, boron nitride, silicon carbide, and cadmium selenide. US Patent 6,919,698 is incorporated herein for the limited purpose of describing materials for some collector electrodes that may be employed in some embodiments. Note that in some embodiments described herein, a surface conditioning or coating of high resistivity material (as contrasted with bulk high resistivity) may be employed.

[1064] FIG. 2 depicts (in schematic form) an EHD air mover design suitable for use in some embodiments of the present invention. A high voltage power supply 98 is coupled between an emitter electrode 91 and collector electrodes 92 to generate an electric field and in some cases ions that motivate fluid flow 99 in a generally downstream direction. In the illustration, emitter electrode 91 is coupled to a positive high voltage terminal of power supply 98 (illustratively +3.5 KV, although specific voltages and, indeed, any supply voltage waveforms may be matters of design choice) and collector electrodes 92 are coupled to a local ground. See previously incorporated U.S. Patent 6,508,308 for a description of suitable designs for power supply 98. Given the substantial voltage differential and short distances involved (perhaps 1 mm or less) between emitter electrode 91 and leading surfaces of collector electrodes 92, an intense electrical field is developed which imposes a net downstream motive force on positively charged ions (or particles) in the fluid. Field lines illustrate (generally) spatial aspects of the resulting electric field and spacing of the illustrated field lines is indicative of intensity.

[1065] As will be understood by persons of ordinary skill in the art, corona discharge principles may be employed to generate ions in the intense electric field closely proximate the surface of a corona-discharge type emitter electrode. Thus, in corona discharge type embodiments in accord with

FIG. 2, fluid molecules (such as surrounding air molecules) near emitter electrode 91 become ionized and the resulting positively charged ions are accelerated in the electric field toward collector electrodes 92, colliding with neutral fluid molecules in the process. As a result of these collisions, momentum is transferred from the ions to neutral fluid molecules, inducing a corresponding movement of fluid molecules in a net downstream direction. While the positively charged ions are attracted to, and neutralized by, collector electrodes 92, the neutral fluid molecules move past collector electrodes 92 at an imparted velocity (as indicated by fluid flow 99).

[1066] Notwithstanding the descriptive focus on corona discharge type emitter electrode configurations, persons of ordinary skill in the art will appreciate that ions may be generated by other techniques such as silent discharge, AC discharge, dielectric barrier discharge (DBD), or the like, and once generated, may, in turn, be accelerated in the presence of electrical fields to motivate fluid flow as described herein. For avoidance of doubt, emitter electrodes need not be of a corona discharge type in all embodiments. Also for avoidance of doubt, power supply voltage magnitudes, polarities and waveforms (if any) described with respect to particular embodiments are purely illustrative and may differ for other embodiments.

[1067] Some embodiments described herein will be further understood in light of certain surfaces provided upstream of emitter electrode 91 to shape the electric previously described electric field and/or to provide a barrier to upstream migration of ions. For example, relative to the illustration of FIG. 2, dielectric surfaces 93 are provided on which positive charge (such as from ions generated at a corona discharge type instance of emitter electrode 91 or elsewhere) tends to accumulate. Because dielectric surfaces 93 do not provide an attractive path to ground, a net positive charge tends to

accumulate and thereafter operates electrostatically to repel like charges. As a result, dielectric surfaces 93 are electrostatically operative as a barrier to upstream ion migration. Upstream dielectric surfaces 93 also tend to electrostatically mask any otherwise attractive paths to ground, thereby shaping the previously described electric field in the primarily downstream direction toward collector electrodes 92. [1068] To improve performance, an air gap may be provided between leading edges of collector electrodes 92 and adjacent portions of dielectric surfaces 93. For example, in some embodiments, an air gap may be provided in the form of a shallow trench formed in dielectric surfaces 93 as illustrated in FIG. 2. In some embodiments, a berm in the dielectric surface may be provided to collect charge and further shape the electric field. Optionally, in some embodiments, one or more conductive paths 94 to ground may be provided further upstream of dielectric surfaces 93 to capture ions that may nonetheless migrate upstream. In some ventilated device embodiments, such a conductive path 94 to ground may be provided proximate an inlet vent.

Display Panels and Illumination Sources, Generally

[1069] FIGS. 3A and 3B are rear perspective views of a display device illustrating an exemplary placement of inlet and outlet ventilation boundaries and (in the case of interior view FIG. 3B) an exemplary EHD motivated flow path past elongate arrays of discrete illumination elements and through the display device. With reference to FIG. 3A, an inlet ventilation boundary 64 may be defined in a lower portion of a housing of display apparatus 60, and an outlet ventilation boundary 68 may be defined in an upper portion of the housing such that the air flow (indicated by arrows) travels a major dimension of the display device. In some embodiments, inlet and outlet ventilation boundaries may be positioned entirely outside of a rearward-most surface of the display housing to facilitate direct wall mounting. Alternatively, in some embodiments, flow paths may extend between any number of the sides, top or bottom, front or back, and transition surfaces therebetween.

[1070] Turning to the interior view of FIG. 3B, a chassis supports a two- dimensional array of transmissive display elements that is typically

sandwiched between a front-side display surface and light guides, diffuser panels, polarizers, etc. (collectively shown as display 62). Laterally elongate arrays 50 of discrete illumination sources (typically LEDs) are configured in a dual edge-lit configuration along top and bottom edge portions of display 62. Instances of EHD air mover 66 are positioned and energizable to generate an airflow (indicated by arrows) to provide forced convective transfer of heat generated by respective arrays 50 into the environment.

[1071] In some implementations, lateral extent of EHD air mover

instances 66 (or at least the cross-section of the air flow generated thereby) is substantially coextensive with the elongate arrays 50 of LEDs (or other spatially distributed illumination source) for which they provide thermal management. In the illustration of FIG. 3B, ventilating airflow motivated by EHD air movers 66 travels past lower-edge instances of the illuminator arrays and traverses a back-side of display 62 en route to upper-edge instances of the illuminator arrays. Of course, various heat spreaders, heat pipes, cooling fins, or other heat transfer structures and surfaces may be used in

combination with EHD air movers 66 to effectively transfer heat from the discrete illumination sources into the EHD motivated flow. In some

embodiments, the chassis itself can be thermally conductive to conduct and distribute heat from the various supported components to be transferred into the EHD motivated air flow.

[1072] Although a pair of EHD air mover subassemblies 66 is illustrated, larger or smaller numbers of subassemblies may be employed a given design. In some embodiments such as illustrated in FIG. 3C, shorter paths may be provided between inlet and outlet ventilation boundaries. EHD air movers may be provided at opposing top and bottom edges of a display. While some embodiments may provide EHD motivated air flow for thermal management of spatially distributed illumination sources at opposing (e.g., top and bottom) edges of display 62, other embodiments may illuminate at opposing side edges or at a single edge (though typically with higher power illuminators and commensurate increases in localized thermal loads). In general, EHD motivated air flow transverse to a lateral extent of elongate arrays 50 of LEDs (or other spatially distributed illumination source) is preferred; however, in some embodiments such as illustrated in FIG. 4, EHD air mover

subassemblies 66' may motivate air flow along a lateral extent of an elongate array 50 of LEDs (or other spatially distributed illumination source). [1073] With illustrative reference to FIG. 3C, in some embodiments, the flow path of a given EHD air mover 66 may be generally confined to a thermal envelope of the associate elongate array 50 of discrete illumination source, e.g., to an extreme upper or lower portion of the display housing. For example, elongate array 50 may be thermally coupled via an integral bracket/spreader to a closely proximate elongate set heat transfer surfaces spanning at least a substantial portion of the lateral extent of array 50. For example, in some cases, the thermal spreader paths and heat transfer surfaces can be formed as portions of assembly 58 (illustrated and described herein with reference to FIGS. 5A and 5B). In this example, EHD air mover 66 may motivate air flow over a relatively shorter flow path across the heat transfer surfaces. The inlets and outlets of the flow path can be defined in any suitable combination of display housing surfaces, e.g., front bezel portions, top or bottom surfaces, or lateral surfaces. While potentially less desirable for wall mounted installations, inlet or outlet boundaries may also be defined on a generally rearward facing portion of the display device.

[1074] With illustrative reference to FIG. 4, in some embodiments, the flow path of a given EHD air mover 66' may instead coincide with a lateral extent the elongate array 50 for which it provides thermal management. For example, in some embodiments, instances of an elongate array 50 of discrete illumination sources (e.g., LEDs) are provided along at least one edge of the display area and a corresponding EHD device 66' is positioned so as to transport air substantially along the length of the elongate array 50. In such embodiments, inlet and outlet ventilation boundaries may be defined such that air travels laterally along a top- or bottom-mounted elongate array 50 (as illustrated) or vertically along a side-mounted instances of an elongate array. EHD motivated air flow may be drawn in and exhausted at any suitable location defined on a housing of the display device 60". For example, an inlet can be centrally located relative to the arrays 50 while the outlets are peripherally located relative to the arrays 50 or display area.

[1075] As a general proposition, any number of additional heat transfer surfaces or heat transfer structures may be provided, e.g., in the form of cooling fins, heat spreaders, and the like. To mitigate effects of any ozone produced by the EHD device, it may be desirable in some embodiments to provide surfaces exposed to the air flow (including heat transfer surfaces) with an ozone reducing catalyst surface, e.g., manganese dioxide, or to include a mechanism for in-situ application of materials such as silver to electrode surfaces of the EHD air mover itself. Similarly, it may be advantageous to shield, encapsulate or otherwise protect various display apparatus

components from ozone, e.g., an LCD display, diffuser, or other optically sensitive components. In some cases, the flow path may itself e defined to confine air flow in a way that limits ozone exposure of selected or sensitive display apparatus components.

[1076] FIGS. 5A and 5B depict (in greater detail) front and rear

perspective views of the elongate array 50 instances previously described, including an integral bracket and heat spreader assembly 58 suitable for positioning an elongate array of light emitting diode (LED) illumination elements consistent with features illustrated in FIGS. 3B, 4 and 9A for respective EHD air mover cooled edge-lit illuminator configurations.

[1077] More specifically, in some embodiments, laterally elongate array 50 includes a plurality of discrete illumination sources 52, e.g., light emitting diodes LEDs, each of which constitutes a thermal point source. In a particular embodiment, the array 50 includes an essentially one-dimensional array of one hundred (100) 1 Watt LEDs cooled by about 7 cubic feet per minute (cfm) of air flow motivated by an EHD air mover such as illustrated and described herein. Discrete illumination sources 52 are thermally coupled via one or more thermal spreader paths 54, e.g., a substrate or thermal interface material, to an elongate set of one or more heat transfer surfaces 56 spanning at least a substantial portion of the lateral extent of array 50. Support bracket 58 may also serve as a heat transfer surface. Heat transfer surfaces are positioned to be exposed to the air flow generated by an EHD device as described herein.

[1078] In some embodiments, heat transfer surfaces 56 define fins extending through or around a chassis or other support structure to which support bracket 58 may be affixed. In a particular embodiment, thermal spreader path 54 conducts heat to support bracket 58 and to heat transfer surfaces 56. Support bracket 58 in turn conducts heat to a display chassis. Air flow from the EHD device then cools the heat transfer surfaces 56 and optionally the display chassis.

[1079] FIGS. 6 and 7 provide simplified side cross-sectional views of display devices with exemplary illuminator configurations EHD motivated air flow for thermal management. The illustrations are not to scale, but rather emphasis seek to illustrate variations for edge-lit and direct-lit illumination configurations. In particular, FIG. 6 depicts an edge-lit configuration for display device 60 in which thermal management of the display (generally) and of an elongate array of light emitting diode (LED) illumination elements 52 (more specifically) is facilitated using an EHD air mover 66. Light is provided from the individual illumination elements 52 (only one is visible in the edge-on view of FIG. 6, but the additional elements will be understood) to a back-side surface of transmissive display elements 603 using an optical assembly 601 that employs light guides, diffusers, polarizers etc. to deliver a generally uniform distribution of appropriately conditioned light. Suitable assemblies are well known in the art and facilitate the edge-lit illuminator configurations in many high-definition televisions and large panel displays. In such designs, EHD air mover configurations described herein (e.g., EHD air mover 66) may be used to manage the substantial and highly localized thermal load created by edge-positioned array of perhaps 100 LEDs.

[1080] FIG. 7 depicts an alternative direct-lit configuration for a display device 70 in which thermal management of a two-dimensional array of light emitting diode (LED) illumination elements distributed over the backside of a display is facilitated using an EHD air mover 76. As before, only a subset of the illumination elements 52 are visible in the edge-on view of FIG. 7, but will nonetheless be understood by persons of ordinary skill in the art. Light is provided from the individual illumination elements 52 to a back-side surface of transmissive display elements 603 using an optical assembly 701 that employs diffusers, polarizers etc. to deliver a generally uniform distribution of appropriately conditioned light. Again, suitable assemblies are well known in the art. EHD air mover configurations described herein (e.g., EHD air mover 66) may be used to manage the substantial and highly localized thermal load created by the back-side array of perhaps 100 LEDs that may constitute illumination elements 52. Although the illustration of FIG. 7

assumes back-side illumination of transmissive display elements, it will understood that analogous EHD motivated air flows may be employed in the thermal management of an emissive display in which display elements themselves generate significant spatially distributed thermal load.

EHD Air Mover Designs for Large Panel, Edge-Lit Display

[1081] FIGS. 8A and 8B are respective edge-on side and perspective views of an illustrative, flat panel display style, consumer electronics device 1000 in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a body portion having total thickness d of less than about 10 mm. FIG. 8A illustrates exemplary inflows 1002 and outflows 1003 that may be motivated through the consumer electronics device by EHD air movers 1010 designed and packed within the limited interior in accord with some inventive concepts of the present inventions. In some implementations, available interior volumes and/or assemblies may allow only 5 mm or less of the total thickness d for EHD air mover 1010.

[1082] Of course, positions illustrated for inflow(s), outflow(s) and heat transfer surfaces 1020 are purely exemplary and, more generally, ventilation boundaries may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors. FIG. 9A depicts one embodiment generally in accord with FIGS. 8A and 8B, in which elongate, edge-positioned arrays of illumination sources (LED illuminators 1150) generate heat which, during operation, is convectively transferred by way of heat transfer surfaces 1020 into air flows (1002, 1003) motivated by EHD air movers 1010A, 1010B. In the illustrated configuration, bottom-mounted EHD air mover instances (1010A) force air into the enclosure at the bottom of consumer electronics device 1000, while top-mounted EHD air mover instances (1010B) exhaust air from the top.

[1083] FIGS. 9B and 9C illustrate (in cross-section), EHD air mover configurations for lower and upper portions of the display device in which electrostatically operative portions of the design are formed as, or on, surfaces within the device enclosure. In some cases, at least one of the electrostatically operative portions is formed as, or on, an interior surface of the enclosure itself. In some cases, at least one of the electrostatically operative portions is formed as, or on, a surface that overlays the display. In each case, by forming electrostatically operative portions as, or on, such surfaces, EHD fluid/air movers can be accommodated within very limited interior spaces.

[1084] For example, in flat panel display device 1000, total depth d of cross-sections 9B and 9C, may be less than about 10 mm. Recalling the perspective view of FIG. 9A and the upper and lower instances of EHD air movers depicted therein, FIG. 9B illustrates cross-section 9B in which a substantial entirety of the interior depth accommodates an instance of lower EHD air mover 101 OA. FIG. 9C likewise illustrates cross-section 9C in which display surface 1001 and an instance of upper EHD air mover 1010B are both accommodated within the depth of flat panel display device 1000. In the illustrated bottom-to-top air flow, instances of upper EHD air mover 1010B are accommodated in a volume behind display surface 1001 and, accordingly, electrostatically operative features thereof are more tightly packed than analogous features of lower EHD air mover 1010A. Nonetheless, design and operation of the respective air movers are largely analogous.

[1085] In the case of EHD air mover 101 OA (see FIG. 9B), electrostatically operative surfaces may be formed (at least partially) over subassembly structure. As previously explained, an exoskeletal structure (e.g., a partial subassembly enclosure) may provide relative positional fixation of collector electrodes 1192 and emitter electrode 1191 with respect to each other. In such cases, dielectric surfaces 1193 (e.g., polyimide film or tape) may lap over a portion of the exoskeletal structure 1111 and conformably extend in an upstream direction where they are provided on, or as part of, a surface of an EMI shield. Alternatively, planar collector electrodes 1192 may be formed as, or more directly on, opposing interior surfaces of enclosure 1109.

[1086] In some embodiments of flat panel display 1000, a conductive (e.g., metallic) tape or strip may be affixed to the interior surface of a generally non- conductive case or surface thereof and coupled to ground to define each of the collector electrodes 1192. In general, the conductive tape or strip may be cut to a shape and extent desired for collector electrode 1192. Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) layer or region may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode 1192. In some cases, the grounded conductive layer or region may be, or may be formed integrally with, enclosure 1109.

[1087] For EHD air mover 1010B (see FIG. 9C), a first instance of collector electrode 1192 is formed in any of the manners just described, while the second instance of collector electrode 1192 is formed on or as part of an EMI shield 1108 that isolates EHD air mover 1010B from display 1001.

Exoskeletal structure of an EHD subassembly (though provided in some embodiments) is omitted for simplicity of illustration. As before, a conductive (e.g., metallic) tape or strip may be affixed to an otherwise non-conductive exposed surface of EMI shield 1108 and coupled to ground to define the second collector electrode instance. Also as before, the conductive tape or strip may be cut to a shape and extent desired for collector electrode 1192. Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) interior layer or region of EMI shield 1108 may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode 1192.

[1088] For both EHD air mover 1010A and EHD air mover 1010B,

respective instances of collector electrodes 1192 and emitter electrode 1191 are coupled between terminals of a high voltage power supply (not specifically shown, but as generally explained relative to FIG. 2) to generate an electric field and (in corona discharge-type embodiment such as illustrated) the ions that motivate air flow in a generally upward downstream direction as illustrated. As in previously described designs, emitter electrode 1191 instances may, in some embodiments, be coupled to a positive high voltage terminal of a power supply (illustratively +3.5 KV, although specific voltages and, indeed, any supply voltage waveforms may be matters of design choice) while collector electrodes 1192 instances are coupled to a local ground.

Operation of EHD air movers 1010A and 1010B is substantially as described with reference to FIG. 2.

[1089] As with the collector electrodes, opposing instances of dielectric surfaces 1193 are provided on, or as part of, an exposed surface of EMI shield 1108 or enclosure 1109. These dielectric surfaces are electrostatically operative and contribute to field shaping in the respective EHD fluid mover while also providing a barrier to ion migration upstream. In particular, during operation of EHD air movers 101 OA and 1010B, respective dielectric surfaces 1193 accumulate charge (such as from positive ions generated at a corona discharge type instance of emitter electrode 1191 ). As a result, dielectric surfaces 1193 are electrostatically operative as a barrier to upstream ion migration and tend to electrostatically mask any otherwise attractive paths to ground, such as enclosure 1109 itself or (particularly in the case of EHD air mover 101 OA) parts of display 1001 or other electronic components not specifically shown. In this way, respective dielectric surfaces 1193 shape the electric fields established by EHD air movers 101 OA and 1010B in the primarily downstream direction (upward in FIGS. 11A and 11 B) toward respective instances of collector electrodes 1192.

[1090] Additional ion migration barriers may be provided. For example, in the illustrations of FIG. 9B and 9C, an additional ion repelling barrier 1195 is introduced as a dielectric mesh, grid, grate or other air permeable curtain across a substantial upstream cross-section of the EHD motivated flow. As before, barrier 1195 accumulates charge (again from positive ions generated at corona discharge type instances of emitter electrode 1191 or elsewhere) and operates as an electrostatic barrier to upstream ion migration. In the configuration illustrated, conductive paths 1194 to ground are provided to capture ions that may nonetheless migrate upstream past barrier 1195.

[1091] Although available interior volumes and tolerances are, in general, implementation and design dependent, it should be clear from the illustrations and description herein that a thin flat panel display device may afford 5 mm or less of its total depth d for EHD air mover 1010B or 1010A.

[1092] In the configurations depicted, a unidirectional air flow entering

(1002) at the bottom of flat panel display 1001 and exiting (1003) at the top thereof is provided and EHD air movers instances are positioned to motivate air flow for respective positions upstream of heat transfer fins 1120 thermally coupled to elongate edge positioned arrays of illumination sources (LED illuminators 1150) that generate a substantial portion of heat to be exhausted from enclosure 1109. Although such flow and such positioning places EHD air mover 1010B in the more tightly constrained depth behind display 1001 , it allows ozone reducing materials (e.g., ozone reducing catalyst or reactive material) to be placed downstream of both air movers on surfaces, such as the heat transfer fins 1120 themselves (or heat spreaders, LED illuminator assemblies, etc.) whose heated surfaces tend to increase efficacy of the ozone reduction.

Other Embodiments

[1093] While the techniques and implementations of the EHD devices discussed herein have been described with reference to exemplary

embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the appended claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, the particular embodiments, implementations and techniques disclosed herein, some of which indicate the best mode contemplated for carrying out these embodiments, implementations and techniques, are not intended to limit the scope of the appended claims.