PORTABLE LIGHTING SYSTEMS INCORPORATING DEFORMABLE LIGHT SHEETS

Abstract

In accordance with certain embodiments, illumination systems include a flexible light sheet that may be wound within and unwound from, or folded within and unfolded from, a storage unit having a power source for powering light-emitting elements on the light sheet.

Description

FIELD OF THE INVENTION

In various embodiments, the present invention generally relates to electronic devices, and more specifically to array-based electronic devices.

BACKGROUND

Portable lights that incorporate conventional illumination sources typically represent a compromise between portability and functionality. Incandescent and halogen lamps are fragile, generate significant amounts of heat, and consume a relatively large volume. Furthermore, they generally function as point sources that emit light at high intensity from a small volume, whereas in many applications it is desirable to distribute a significantly lower intensity over a relatively large area to provide more even illumination and reduce glare. Such goals may be achieved (at least in part) via the use of optics and diffusers, but these typically increase the volume, reduce the efficiency, and increase the cost—all undesirable traits for portable lighting.

Solid-state illumination sources such as light-emitting diodes (LEDs) are not as fragile as conventional illumination sources, but LEDs pose challenges in terms of heat dissipation and light distribution. LEDs themselves are relatively small but typically are driven at a relatively high current to achieve high light intensity per LED. This high drive current leads to two disadvantages. First, the heat from the LED must be managed. This is typically accomplished with a thermal-management system, either passive or active, which may include use of a metal-clad printed circuit board (MCPCB), heat sinks, fans, or the like. These tend to be relatively large and expensive, decreasing the portability and adoption of such portable lighting sources. The second disadvantage is that the light is still emitted with high intensity from a small volume, resulting in undesirably limited light-distribution patterns and high glare. As mentioned above, these may be addressed but typically at the expense of portability and cost.

Common to all of these illumination sources are constraints based on their physical size and structure. They are relatively rigid, or formed on rigid circuit boards, which limits, for example, the ability to vary the two-dimensional conformation of a luminaire (or other lighting system) based on them. While various semi-flexible systems have been manufactured using a large number of relatively small rigid circuit boards attached to a flexible backing, these only have flexibility in one direction and have a relatively high risk of damage if they are flexed or bent in the opposite direction. The large number of electrical connections between the circuit boards, which are flexed and stressed during operation, also leads to potential reliability issues. Finally, such approaches are relatively costly because of the large number of separate circuit boards and connections that are required.

In view of the foregoing, a need exists for systems and techniques enabling the low-cost design and manufacture of compact reliable portable lighting systems having broad light distributions, low glare with the ability to produce different light-distribution patterns, and the ability to create conformationally variable (e.g., foldable, rollable, and/or bendable) illumination systems.

SUMMARY

In accordance with certain embodiments of the present invention, lighting systems incorporate light sheets that may be deployed in an open conformation for illumination of at least a portion of their surroundings and, when not in use, compressed, rolled, folded, or otherwise placed into a more compact conformation for portability. Lighting systems in accordance with embodiments of the invention may incorporate a storage unit for storage of the light sheet between deployments thereof, and the storage unit may incorporate thereon or therein a power source for supplying power to the light sheet. The light sheet may be flexible and preferably contains thereon an array of light-emitting elements interconnected with thin conductive traces.

In an aspect, embodiments of the invention feature an illumination device that includes or consists essentially of a flexible light sheet, a storage unit, a winding mechanism, and a power source. The flexible light sheet includes or consists essentially of (i) a flexible substrate, (ii) a plurality of light-emitting elements disposed over the substrate, and (iii) a plurality of conductive traces disposed on the substrate and electrically interconnecting the plurality of light-emitting elements. The storage unit is configured to accept and contain the light sheet in a rolled configuration therewithin. The light sheet is wound around an axis (e.g., a central axis) of the storage unit when contained therewithin. The storage unit is also configured to dispense at least a portion (i.e., some or all) of the light sheet therefrom via unwinding of the light sheet from the rolled configuration. The winding mechanism is utilized for winding and/or unwinding the light sheet around the axis of the storage unit. The power source is disposed within and/or on the storage unit and is utilized to supply power to at least an unrolled portion of the light sheet and thereby illuminating the light-emitting elements of at least the unrolled portion.

Embodiments of the invention may incorporate one or more of the following in any of a variety of combinations. The light sheet may be at least partially wound around an outer surface of the storage unit. The winding mechanism may include or consist essentially of a hand crank and/or a spring. The winding mechanism may be motorized. When the light sheet is extended from the storage unit, the thickness of the light sheet may be 5 mm or less. The light sheet may include an array of optical elements (e.g., lenses) disposed over the light-emitting elements. The array of optical elements may include or consist essentially of separate and discrete optical elements each associated with one or more light-emitting elements, or the array of optical elements may include or consist essentially of a unified layer or slab of material defining optical elements each disposed over, or otherwise associated with, one or more light-emitting elements. A water-resistant or waterproof coating may be disposed over the light-emitting elements of the light sheet. The coating may substantially conform to the non-planar topography of the light-emitting elements (and, e.g., other elements such as conductive traces) thereunder. The top surface of the coating may be planar notwithstanding the non-planar topography of the light-emitting elements (and, e.g., other elements such as conductive traces) thereunder. The power source may include or consist essentially of a battery disposed within the storage unit (e.g., at or proximate the axis around which the light sheet is wound), a solar cell and/or capacitor (e.g., a super-capacitor) disposed on an outer surface of the storage unit, and/or a connector configured for connection to an external source of power (e.g., an AC outlet). The light sheet may be configured to be wound within the storage unit to a radius of curvature of 50 mm or less.

The light-emitting elements may include or consist essentially of bare-die light-emitting diodes (and/or bare-die lasers) and/or packaged light-emitting diodes (and/or packaged lasers). The light-emitting elements may emit substantially white light, which may have a correlated color temperature is in the range of 2000 K to 10,000 K. A stiffener may be disposed along at least a portion (i.e., part or all or substantially all) of a leading edge of the light sheet (i.e., the edge of the light sheet emerging first out of the storage unit during unwinding and/or the edge of the light sheet disposed farthest away from the storage unit when the light sheet is fully unwound). A rotary electrical joint may be disposed within the storage unit, and the rotary electrical joint may be configured to preserve electrical contact between the light sheet and the power source during winding and unwinding of the light sheet. The power source may include or consist essentially of a battery (e.g., a flexible battery), a capacitor (e.g., a flexible capacitor), or a solar cell (e.g., a flexible solar cell) disposed on a surface of the light sheet opposite the light-emitting elements. The illumination device may also include, disposed within the storage unit, (i) drive circuitry configured to convert power from the power source for use by the light-emitting elements, (ii) control circuitry configured to control at least one emission characteristic of the light-emitting elements, and/or (iii) communication circuitry configured to transmit information to or from the illumination device.

When the light sheet is fully extended from the storage unit, a trailing edge of the light sheet may remain mechanically anchored within or on the storage unit. In some cases, only the unrolled portion of the light sheet is illuminated, and a rolled portion of the light sheet disposed within the storage unit is unilluminated. The illumination device may have an ingress protection rating of at least IP 65, as specified by International Protection Marking in International Electrotechnical Commission (IEC) standard 60529. The light sheet may include thereon one or more fasteners for positioning of the light sheet when the light sheet is at least partially extended. The one or more fasteners may include or consist essentially of a hook, a hook-and-loop fastener, a hole, a clamp, a grommeted hole (i.e., a hole with a grommet disposed partially or entirely therearound), and/or a magnet. The storage unit may include thereon one or more fasteners for positioning of the light sheet when the light sheet is at least partially extended. The one or more fasteners may include or consist essentially of a hook, a hook-and-loop fastener, a hole, a clamp, a grommeted hole, and/or a magnet. The plurality of light-emitting elements disposed over the substrate may form a fixed pattern in the shape of one or more symbols and/or letters.

In another aspect, embodiments of the invention feature an illumination device that includes or consists essentially of a flexible light sheet, a storage unit, one or more sensors, and a power source. The flexible light sheet includes or consists essentially of (i) a flexible substrate, (ii) a plurality of light-emitting elements disposed over the substrate, and (iii) a plurality of conductive traces disposed on the substrate and electrically interconnecting the plurality of light-emitting elements. The flexible light sheet includes at least one crease in a first direction for folding therealong. The light sheet may also include one or more creases in directions other than the first direction for folding therealong. The storage unit is configured to (i) accept and contain the light sheet in a folded configuration therewithin, and (ii) dispense at least a portion of (i.e., some or all of) the light sheet therefrom via unfolding of the light sheet from the folded configuration. The one or more sensors are each associated with a crease (and some or all creases may have multiple sensors associated therewith), and are configured to detect if the light sheet is folded or unfolded along the associated crease. The power source is disposed within and/or on the storage unit and responsive to the one or more sensors. The power source supplies power to an unfolded portion of the light sheet and thereby illuminates only the light-emitting elements of the unfolded portion, light-emitting elements on a folded portion of the light sheet remaining unilluminated.

Embodiments of the invention may incorporate one or more of the following in any of a variety of combinations. When the light sheet is extended from the storage unit, a thickness of the light sheet may be 5 mm or less. The light sheet may include an array of optical elements (e.g., lenses) disposed over the light-emitting elements. The array of optical elements may include or consist essentially of separate and discrete optical elements each associated with one or more light-emitting elements, or the array of optical elements may include or consist essentially of a unified layer or slab of material defining optical elements each disposed over, or otherwise associated with, one or more light-emitting elements. A water-resistant or waterproof coating may be disposed over the light-emitting elements of the light sheet. The coating may substantially conform to a non-planar topography of the light-emitting elements thereunder, or the top surface of the coating may be planar notwithstanding a non-planar topography of the light-emitting elements thereunder. The power source may include or consist essentially of a battery disposed within the storage unit (e.g., at or proximate the axis around which the light sheet is wound), a solar cell and/or capacitor (e.g., a super-capacitor) disposed on an outer surface of the storage unit, and/or a connector configured for connection to an external source of power (e.g., an AC outlet). The light-emitting elements may include or consist essentially of bare-die light-emitting diodes (and/or bare-die lasers) and/or packaged light-emitting diodes (and/or packaged lasers). The light-emitting elements may emit substantially white light, which may have a correlated color temperature in the range of 2000 K to 10,000 K.

A stiffener may be disposed along at least a portion of a leading edge of the light sheet. The power source may include or consist essentially of a battery (e.g., a flexible battery), a capacitor (e.g., a flexible capacitor), or a solar cell (e.g., a flexible solar cell) disposed on a surface of the light sheet opposite the light-emitting elements. The illumination device may also include, disposed within the storage unit, (i) drive circuitry configured to convert power from the power source for use by the light-emitting elements, (ii) control circuitry configured to control at least one emission characteristic of the light-emitting elements, and/or (iii) communication circuitry configured to transmit information to or from the illumination device. When the light sheet is fully extended from the storage unit, a trailing edge of the light sheet may remain mechanically anchored within or on the storage unit. The illumination device may have an ingress protection rating of at least IP 65, as specified by International Protection Marking in International Electrotechnical Commission (IEC) standard 60529. The light sheet may include thereon one or more fasteners for positioning of the light sheet when the light sheet is at least partially extended. The one or more fasteners may include or consist essentially of a hook, a hook-and-loop fastener, a hole, a clamp, a grommeted hole (i.e., a hole with a grommet disposed partially or entirely therearound), and/or a magnet. The storage unit may include thereon one or more fasteners for positioning of the light sheet when the light sheet is at least partially extended. The one or more fasteners may include or consist essentially of a hook, a hook-and-loop fastener, a hole, a clamp, a grommeted hole, and/or a magnet. The plurality of light-emitting elements disposed over the substrate may form a fixed pattern in the shape of one or more symbols and/or letters.

These and other objects, along with advantages and features of the invention, will become more apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. Reference throughout this specification to “one example,” “an example,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present technology. Thus, the occurrences of the phrases “in one example,” “in an example,” “one embodiment,” or “an embodiment” in various places throughout this specification are not necessarily all referring to the same example. Furthermore, the particular features, structures, routines, steps, or characteristics may be combined in any suitable manner in one or more examples of the technology. As used herein, the terms “about,” “approximately,” and “substantially” mean±10%, and in some embodiments, ±5%. The term “consists essentially of” means excluding other materials that contribute to function, unless otherwise defined herein. Nonetheless, such other materials may be present, collectively or individually, in trace amounts.

Herein, two components such as light-emitting elements and/or optical elements being “aligned” or “associated” with each other may refer to such components being mechanically and/or optically aligned. By “mechanically aligned” is meant coaxial or situated along a parallel axis. By “optically aligned” is meant that at least some light (or other electromagnetic signal) emitted by or passing through one component passes through and/or is emitted by the other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:

FIGS. 1A and 1B are an isometric view (FIG. 1A) and a cross-sectional view (FIG. 1B) of an illumination system with a wound light sheet, in accordance with various embodiments of the invention;

FIGS. 2A-2C are schematic illustrations of an illumination system with a foldable light sheet, in accordance with various embodiments of the invention;

FIG. 3 is a schematic illustration of an illumination system with a foldable light sheet, in accordance with various embodiments of the invention;

FIG. 4 is an isometric view of an illumination system featuring a light sheet integrated on an electronic device in accordance with various embodiments of the invention;

FIGS. 5A and 5B are side views of an illumination system having a stand to facilitate directional illumination in accordance with various embodiments of the invention;

FIG. 6 is an isometric view of an illumination system featuring a light sheet incorporated within a case in accordance with various embodiments of the invention;

FIG. 7 is an isometric view of an illumination system featuring a light sheet connected to a power source within a holder in accordance with various embodiments of the invention;

FIGS. 8A and 8B depict an illumination system featuring a light sheet conforming to an object such as a camping stove, in accordance with various embodiments of the invention;

FIGS. 8C and 8D depict illumination systems in which light sheets pop up (FIG. 8C) or are unrolled (FIG. 8D) from a storage unit in accordance with various embodiments of the invention;

FIG. 9A is a circuit diagram of a portion of a light sheet in accordance with various embodiments of the invention;

FIGS. 9B and 9C are schematic plan views of light sheets in accordance with various embodiments of the invention;

FIG. 10A is a schematic plan view of an extended light sheet in accordance with various embodiments of the invention;

FIGS. 10B and 10C are schematic cross-sectional views of portions of coated light sheets in accordance with various embodiments of the invention;

FIG. 10D is a schematic cross-sectional view of a wound light sheet in accordance with various embodiments of the invention;

FIGS. 10E-10H are schematic cross-sectional views of illumination systems in accordance with various embodiments of the invention;

FIGS. 11A and 11B are schematic cross-sectional views of portions of illumination systems incorporating vias for electrical interconnection in accordance with various embodiments of the invention;

FIGS. 12A-12C are schematic views of illumination systems incorporating shaped light sheets or shaped arrangements of light-emitting elements in accordance with various embodiments of the invention; and

FIG. 13 is a schematic cross-sectional view of a portion of an illumination system incorporating optical elements in accordance with various embodiments of the invention.

DETAILED DESCRIPTION

Various embodiments of the present invention feature a thin light sheet that does not require any additional heat sinking or thermal management. In some embodiments, the light sheet may also be flexible and may be curved or folded to achieve one or more specific characteristics or attributes, for example, to permit manufacture of a compact, foldable system and/or to achieve a specific light-distribution pattern.

FIGS. 1A and 1B depict exemplary lighting devices in accordance with embodiments of the present invention, although alternative devices or systems with similar functionality are also within the scope of the invention. As depicted, the lighting devices include or consist essentially of one or more flexible light sheets 110, which include a flexible substrate 165 on which is formed an array of light-emitting elements (LEEs) 140. In some embodiments of the present invention, light sheet 110 includes or consists essentially of an array of LEEs 140 electrically coupled by conductive elements formed on a flexible substrate, for example as described in U.S. patent application Ser. No. 13/799,807, filed Mar. 13, 2013 (the '807 application), or U.S. patent application Ser. No. 13/970,027, filed Aug. 19, 2013 (the '027 application), the entire disclosure of each of which is incorporated by reference herein. In some embodiments of the present invention, light sheet 110 is relatively thin, for example having a total thickness in the range of about 0.5 mm to about 3 mm. In some embodiments of the present invention, light sheet 110 does not require any additional thermal management or heat sinking.

FIGS. 1A-1B show an isometric view and a cross-sectional view of a lighting device 100 in accordance with various embodiments of the present invention. Lighting device 100 includes flexible light sheet 110 that may be rolled up into a drum 170. In some embodiments, flexible light sheet 110 may be rolled up into and unrolled out of the drum 170 using a winding handle 177, as shown, while in other embodiments light sheet 110 may be rolled and unrolled by other means, for example by manually wrapping light sheet 110 around drum 170, or by means of a motor that wraps light sheet 110 into or around drum 170, or by means of a spring-loaded mechanism, similar to that of a window shade. During storage, light sheet 110 is rolled into drum 170, while during operation all or a portion of light sheet 110 may be unrolled or extended from drum 170.

The large number of relatively small LEEs 140 that are distributed over the substrate 165 provides uniformly distributed light emission from a relatively large surface with relatively low glare.

FIGS. 1A and 1B depict an edge stiffener 175 along all or substantially all of the leading edge of light sheet 110; however, this is not a limitation of the present invention, and in other embodiments an edge stiffener 175 may be formed along one or more portions of the leading edge of light sheet 110, while other embodiments may not include any edge stiffener 175. In some embodiments, edge stiffener 175 may include one or more hooks, holes, snaps or the like (not shown in FIGS. 1A and 1B) that may be used as an attachment point to the leading edge of light sheet 110, for example to support lighting device 100 when unrolled and extended. In some embodiments, light sheet 110 may include one or more hooks, holes, snaps, or the like (not shown in FIGS. 1A and 1B) that may be used as an attachment point to one or more portions of light sheet 110, for example to support lighting device 100 when unrolled and extended. In some embodiments, drum 170 may include one or more hooks, holes, snaps or the like (not shown in FIGS. 1A and 1B) that may be used as an attachment point to drum 170, for example to support lighting device 100 when unrolled and extended.

FIG. 1B shows a battery 180 positioned within drum 170 and inside rolled-up light sheet 110. One or more optional drive boards 187, containing a drive circuit to power or partially power light sheet 110, or control boards, containing a control circuit to control various characteristics of light sheet 110, or communication boards to provide communication to and/or from lighting device 100, may also be positioned within drum 170. In some embodiments of the present invention, drive, communication, and/or control circuitry may be formed on light sheet 110 rather than on boards separate and discrete from lights sheet 110. In some embodiments of the present invention, battery 180 is a non-rechargeable battery, while in other embodiment battery 180 is rechargeable. In some embodiments of the present invention, battery 180 may be charged by connection to a primary power source, for example the AC mains system, while in other embodiments battery 180 may be charged by other means, for example by a solar cell, by an internal generator (for example a wind-up generator), by energy harvesting (for example by shaking or moving lighting system 100), by connection to an external charging source, or the like. In some embodiments, light sheet 110 may have one or more solar cells, formed on the side opposite LEEs 140, which may be used to charge battery 180. In some embodiments of the present invention, all or a portion of drum 170 may be covered with one or more solar cells that may be used to charge battery 180.

In some embodiments of the invention, drum 170 contains a rotary electrical joint that maintains electrical contact between light sheet 110 (and the LEEs 140 thereon) and a power source such as battery 180 and/or other control or communication elements while enabling free rotation of portions of the light sheet 110 as it is wound in or on drum 170 and unwound from drum 170. For example, the rotary electrical joint may feature a stationary conductive component that contacts the inside or outside of a rotating conductive component (e.g., a conductive ring) that rotates as light sheet 110 is wound or unwound. Suitable rotary joint configurations are well-known in the art.

In some embodiments of the present invention, light sheet 110 may be energized or de-energized using a switch located on drum 170 or on light sheet 110. In some embodiments of the present invention, the light intensity from light sheet 110 may be variable, for example LEEs 140 may be dimmable, to permit modification of the light level emitted by lighting device 100. In various embodiments, only a portion of the light sheet 110 is unrolled from drum 170 and only that unrolled portion is illuminated in order to, e.g., prevent excessive heat build-up and/or power consumption that might result from illuminating the LEEs 140 of the rolled portion of light sheet 110 remaining within drum 170. For example, movement of the rotary joint mentioned above may be utilized to measure (or “meter”) the amount of light sheet 110 exiting the drum 170 during unrolling, and then only those LEEs 140 (e.g., exposed rows, strings, or groups of LEEs 140, which may be individually addressable) are illuminated. Such embodiments enable the selection of a particular illumination level and/or area based on the current needs of the user, who may adjust the amount of illumination simply by rolling and unrolling light sheet 110 into and out of drum 170. In embodiments of the invention featuring foldable lighting devices (as described below), portions of the light sheet 110 that are unfolded from a storage unit or other container may be selectively illuminated in a similar fashion. For example, mechanical, magnetic, or piezoelectric sensors may be utilized at the folding joints in the light sheet 110 to signal when a particular portion or panel of light sheet 110 is deployed (e.g., unfolded), and then only the LEEs 140 on such portion(s) may be illuminated.

In some embodiments of the present invention, lighting device 100 may be water-resistant or waterproof. In some embodiments of the present invention, lighting system 100 may be dust-resistant or dirt-resistant. In some embodiments, lighting device 100 may be configured to protect light sheet 110, for example to provide mechanical protection, protection from dust, water, etc. One method for rating different levels of environmental protection is an IP rating as specified by International Protection Marking in International Electrotechnical Commission (IEC) standard 60529, providing classification of degrees of protection provided by enclosures for electrical equipment, the entirety of which is hereby incorporated by reference herein. In some embodiments, lighting device 100 may have any IP rating, for example from IP00 to IP 69k, or any other IP rating. In some embodiments of the present invention, lighting device 100 has an IP 65 rating or an IP 66 rating or an IP 67 rating or an IP 68 rating. In some embodiments, drum 170 may be constructed from metal or plastic, for example aluminum, steel, acrylic, polystyrene, polyester, or the like. In some embodiments, light sheet 100 may be conformally coated or encapsulated with a transparent or partially transparent material to create a water-resistant or waterproof coating on light sheet 110. In some embodiments, the transparent material has a transmittance to a wavelength of light emitted by LEEs 140 of at least 75%, at least 85%, or at least 95%.

In some embodiments of the present invention, light sheet 110 may have dimensions in the range of about 75 mm to about 300 mm wide and in the range of about 15 cm to about 1000 cm long; however, the dimensions of light sheet 110 are not a limitation of the present invention, and in other embodiments light sheet 110 may have different dimensions. In some embodiments, light sheet 110 has a width of about 15 cm and a length of about 2 m. In some embodiments, light sheet 110 has a width of about 30 cm and a length of about 1 m. Light sheet 110 is shown as having a rectangular shape in FIGS. 1A and 1B; however, this is not a limitation of the present invention, and in other embodiments light sheet 110 may have any shape, for example a trapezoid, a triangle, a circle or the like. In some embodiments, drum 170 may have a diameter in the range of about 25 mm to about 300 mm; however, the diameter of drum 170 is not a limitation of the present invention, and in other embodiments drum 170 may have a different diameter.

FIGS. 2A-2C show a lighting device 200, which is a variation on lighting device 100 shown in FIGS. 1A-1B. LEEs 140 are not shown in FIGS. 2A-2C for simplicity. While lighting device 100 incorporates a roll-up light sheet 110, lighting device 200 incorporates folding light sheet panels 210. FIG. 2B shows four light sheet panels 210 making up lighting device 200; however, this is not a limitation of the present invention, and in other embodiments lighting device 200 may incorporate fewer or more light sheet panels 210. In some embodiments of the present invention, the panels 210 are substantially rigid, while in other embodiments panels 210 are flexible.

FIG. 2B shows one embodiment of the present invention in which the lighting device 200 is suspended from a hook, nail or other wall-mounted feature. In some embodiments, a mounting fixture, for example a hole within light sheet 110 or an optional edge stiffener 175 (FIG. 1A, but not shown in FIGS. 2A-2C) may be used to attach lighting device 200 to the wall-mounted feature. FIG. 2C shows one embodiment of the present invention, in which lighting device 200 rests on a surface and forms a desk lamp. In this embodiment, the light-emitting surfaces of panels 210 are facing outwards; however, this is not a limitation of the present invention, and in other embodiments the light-emitting surfaces of panels 210 may face inwards.

As discussed herein, in some embodiments of the present invention a battery or other power source may be incorporated in drum 170. While drum 170 is shown as a cylinder in FIGS. 1A and 1B, this is not a limitation of the present invention, and in other embodiments drum 170 may have other shapes. For example, drum 150 may have a cross-sectional square shape (as shown in FIGS. 2A and 2C), a cross-sectional triangular shape, a cross-sectional hexagonal shape, or any other shape.

In some embodiments, other elements may be incorporated into lighting devices of the present invention. For example, in some embodiments a lighting device may incorporate a two-way radio, a receiving radio, a flashlight, a first aid kit, and/or a storage compartment, for example for money, matches, lighter, rope, minor or the like, a knife, or other items.

FIG. 3 shows another embodiment of the present invention, identified as lighting device 300. In this embodiment, instead of being rolled, as with lighting device 100, lighting device 300 is folded like a concertina or accordion. LEEs 140 are not shown in FIG. 3 for simplicity. In lighting device 300, light sheet 110 is coupled to a housing 310. In some embodiments of the present invention, the housing 310 may include one or more batteries 180 and/or one or more drive, communication, or control boards 187 or other features, as discussed herein. In some embodiments of the present invention, one or more solar cells or energy harvesting devices may be incorporated in or on housing 310 or on substrate 165.

In some embodiments of the present invention, the relatively thin nature of the light sheet, as well the ability to operate with no additional thermal management, may permit the incorporation of lighting devices into equipment or structures inaccessible to conventional solid-state lighting because of size and/or heat limitations.

FIG. 4 shows one embodiment of the present invention in which a light sheet-based lighting device is integrated into a mobile phone or other electronic device. FIG. 4 shows an electronic device 410, light sheet 110, and LEEs 140. It is often desirable for mobile phones, as well as other electronic devices such as tablets, phablets, laptop computers, remote controls, radios, etc., to have a thin form factor. In some embodiments of the present invention, the light sheet may have a thickness in the range of about 0.5 mm to about 2 mm and may be incorporated by mating the light sheet to a portion of electronic device 410, for example the case of a cell phone or tablet, or it may be incorporated by building it into the structure of the device itself. In some embodiments of the present invention, light sheet 110 may be mated to a portion of electronic device 410 by lamination, glue, adhesive, or the like. In some embodiments of the present invention, conductive traces as formed on substrate 165 (for example, as described in the '807 and '027 applications) may be formed on a portion of electronic device 410, eliminating the need for substrate 165. In some embodiments of the present invention, light sheet 110 may be controlled in part by electronic device 410. For example, in some embodiments of the present invention, light sheet 110 may flash or blink or change intensity upon receiving an incoming call or text or email. In some embodiments, the indication may be different to signal different events. In some embodiments of the present invention, light sheet 110 may be turned on or off by electronic device 410. In some embodiments of the present invention, the intensity of light emitted by light sheet 110 may be controlled by electronic device 410.

In some embodiments of the present invention, electronic device 410 may incorporate a stand, for example a stand 510, as shown in FIGS. 5A and 5B, to permit positioning of electronic device and light sheet 110 to provide illumination in one or more directions. For example, FIG. 5A shows illumination in a down direction, while FIG. 5B shows relatively lateral illumination. However, the illumination directions shown in FIGS. 5A and 5B are not limitations of the present invention, and in other embodiments the illumination direction may be upwards or in any direction.

FIG. 6 shows an embodiment of the present invention in which light sheet 110 is incorporated into a case 610, for example an equipment case. Light sheet 110 may be relatively thin and be relatively easily incorporated into the lid, sides and/or bottom of case 610, permitting uniform, low-glare illumination of the interior of case 610 without consuming a large amount of space within case 610 and without generating a significant amount of heat within case 610.

FIG. 7 shows another embodiment of the present invention, in which battery 180 or an alternate power source is contained within a holder 710 and is attached to light sheet 110 through a connecting cord 730 and an optional connector 720. In some embodiments of the present invention, optional connector 720 may permit separation of connecting cord 730 from holder 710. In some embodiments of the present invention, connector 720 is a waterproof connector. In some embodiments of the present invention, light sheet 110 incorporates an attachment feature 740, for example a hole or hook or hook and loop fastener or the like to permit positioning of lighting element 750. In some embodiments of the present invention, lighting element 750 includes or consists essentially of one or more light sheets 110. In some embodiments of the present invention, lighting element 750 includes or consists essentially of a light sheet 110 protected by one or more coatings or encapsulations, for example to achieve a water-resistant or waterproof lighting element 750, or to achieve a certain IP rating, for example IP 65, IP66, IP67 or IP68. In some embodiments, the coating may include one or more of the following: silicone, PDMS, polyurethane, acrylic, or the like. In some embodiments of the present invention, the coating may be flexible, while in other embodiments the coating may be substantially rigid. In some embodiments, the coating may be a conformal or substantially conformal coating, while in other embodiments the coating may not be conformal, for example it may be molded over one or more portions of light sheet 110, presenting a flat or substantially flat exterior surface. In some embodiments of the present invention, a flat exterior surface may be desirable, for example to facilitate cleaning.

FIGS. 8A and 8B show another embodiment of the present invention that includes a flexible light sheet 110 that may be formed or conformed to a container or other object. For example, in some embodiments of the present invention, light sheet 110 may be conformed around a water bottle, a camping stove (identified as 840 in FIGS. 8A and 8B), a fishing pole case, tent case, storage case, food case, or the like. In some embodiments, light sheet 110 may be wrapped around an object like a tree or a pole. In some embodiments, light sheet 110 is coated or encapsulated to protect LEEs 140 and substrate 165, as described herein. In some embodiments of the present invention, light sheet 110 includes one or more closure elements to aid in fixing light sheet 110 to the object. For example, in some embodiments of the present invention, ends of light sheet 110 may be affixed to each other to position light sheet 110 by magnets, clamps, hook and loop closures, bungee cords, cable ties, rope or string, or the like. In some embodiments of the present invention, holder 710, which may include a battery or other power source, as described herein, may be formed into a shape that fits adjacent to a portion of the object. For example, in FIGS. 8A and 8B, holder 710 has a shape substantially similar to the bottom of camping stove 840, permitting it to fit compactly into the bottom of camping stove 840. In some embodiments heat generated by LEEs 140 on light sheet 110 may be used to further advantage, for example to provide heat to gas in camping stove 840 to ensure a sufficient vapor pressure of gas for operation of camping stove 840.

FIGS. 8C and 8D show additional embodiments of the present invention, incorporating either a pop-up (FIG. 8C) or roll up (FIG. 8D) light sheet 110. The lighting device of FIG. 8C includes a pop-up light sheet 110 in a base 860. In some embodiments of the present invention, base 860 holds the power source for light sheet 110 as well as the light sheet 110. During storage, the top 865 is pushed down, moving light sheet 110 into base 860 where it is protected and resulting in a relatively compact size for storage. In operation, top 865 is extended, exposing light sheet 110. In some embodiments of the present invention, light sheet 110 is energized when top 865 is extended, while in other embodiments light sheet 110 may be energized by a separate switch or other means.

In the lighting device of FIG. 8D, the light sheet 110 is rolled up and stored inside holder 870, which may also in some embodiments contain the power source for light sheet 110. During operation, as shown in FIG. 8D, light sheet is removed from base 870. In some embodiments, during operation light sheet 110 may be flat or substantially flat, while in other embodiments light sheet 110 may be curved or otherwise shaped to achieve a specific spatial light distribution pattern.

In some embodiments of the present invention, light sheet 110 typically includes or consists essentially of an array of LEEs 140 electrically coupled by conductive elements formed on a flexible substrate, for example, as described in the '807 and '027 applications.

FIG. 9A depicts an exemplary circuit topology, in accordance with embodiments of the present invention, which features conductive elements 960, at least two power conductors 910, 920, multiple LEEs 140, and control elements (CEs) 940. In some embodiments, LEEs 140 may be configured in a regular periodic array, for example a substantially square or rectangular array, where LEEs 140 are separated by pitch (or “spacing”) 923 in the one direction (for example vertical direction) by pitch 925 in a substantially orthogonal direction. In some embodiments, pitch 925 is the same as or substantially the same as pitch 923. While the geometrical layout and pitches 923 and 925 are described in connection with the circuit schematic shown in FIG. 9A, such geometry, layout, and pitches are not limitations of the present invention, and in other embodiments the physical layout of the circuit elements may be different than the circuit topology shown in FIG. 9A. Additionally, other embodiments may have different circuit topologies, for example LEEs 140 may be electrically coupled in parallel, in a combination of series and parallel, or any other arrangement. In some embodiments, more than one group of electrically connected LEEs 140 may be electrically coupled to one CE 940, while other embodiments may not require any CEs 140. The specific circuit topology is not a limitation of the present invention.

The spacing between LEEs 140 shown in the structures of FIGS. 1A, 4, and 7 is constant or substantially constant; however, this is not a limitation of the present invention, and in other embodiments the spacing between LEEs 140 may vary. In some embodiments, the light sheet 110 may include two or more regions, each having the same or substantially the same spacing between LEEs 140, but with different spacing in different regions. In other embodiments, the spacing between various pairs or groups of LEEs 140 may be different.

In the examples shown in the figures, substrate 165 is substantially covered with an array of LEEs 140; however, in some embodiments, one or more portions of substrate 165 may not be populated with LEEs 140.

In some embodiments, all LEEs 140 in the lighting system may be driven at the same or substantially the same current; however, this is not a limitation of the present invention, and in other embodiments different LEEs 140 or different groups of LEEs 140 may be driven at different currents.

In some embodiments, all LEEs 140 in the lighting system may have the same optical characteristics, for example luminous or radiant flux, CCT, CRI, R9, spectral power distribution, light distribution pattern, angular color uniformity or the like; however, this is not a limitation of the present invention, and in other embodiments different LEEs 140 or different groups of LEEs 140 may have different optical characteristics.

FIG. 9A shows two power conductors 910 and 920, which may be used to provide power to strings 950 of LEEs 140. Each string 950 may include two or more electrically coupled LEEs 140. LEEs 140 in string 950 may be electrically coupled in series, as shown in FIG. 9A; however, this is not a limitation of the present invention, and in other embodiments other examples of electrical coupling may be utilized, for example LEEs in parallel or in any combination of series and parallel connections. FIG. 9A shows CE 940 connected in series with LEEs 140 of string 950; however, this is not a limitation of the present invention, and in other embodiments CE 940 may have different electrical coupling between power conductors 910, 920, or may be absent altogether. For example, in some embodiments CE 940 may be separately electrically coupled to power conductors 910, 920 and to the LEE string 950, while in other embodiments each CE 940 may be electrically coupled to two or more strings. The number of strings electrically coupled to each CE 940 is not a limitation of the present invention. Combinations of structures described herein, as well as other electrical connections, all fall within the scope of the present invention. Power conductors 910, 920 may be used to provide power to strings 950, for example AC power, DC power, or power modulated by any other means.

Referring to FIGS. 9B and 9C that depict schematics of exemplary light sheets 110, a light sheet 110 may feature an array of LEEs 140 each electrically coupled between conductive traces 960, and power conductors 910 and 920 providing power to conductive traces 960 and CEs 940, all of which are disposed over a substrate 165. As utilized herein, a “wiring board” refers to a substrate for LEEs with or without additional elements such as conductive traces or CEs. A wiring board may also be referred to as a light sheet or a circuit board. FIG. 9B shows a portion of light sheet 110. In the exemplary embodiment depicted in FIG. 9B, power conductors 910, 920 are spaced apart from each other and light-emitting strings (or simply “strings”) 950 are connected in parallel across power conductors 910, 920. In some embodiments, for example as shown in FIG. 9B, strings 950 do not cross (i.e., intersect) each other. In other words, power conductors 910, 920 are oriented in one direction and strings 950 are oriented such that they span power conductors 910, 920 in a different direction. As shown in FIG. 9B, strings 950 are substantially perpendicular to power conductors 910, 920. However, this is not a limitation of the present invention, and in other embodiments at least some segments (i.e., portions connecting two or more LEEs 140), or even the entire strings 950, may define a line (not necessarily a straight line) that is not perpendicular to power conductors 910, 920 yet is (at least for an entire string 950) not parallel to power conductors 910, 920. In other embodiments strings 950 may intersect, for example one string 950 splitting into two or more strings 950, or two or more strings 950 joining to form a reduced number of strings 950. In some embodiments conductive elements may cross over each other without being electrically coupled, and in some embodiments strings 950 may cross over or under each other without being electrically coupled. In some embodiments all or a portion of one or more strings 950 may be outside of power conductors 910, 920. Various examples of string geometries and conformations utilized in embodiments of the present invention are described in the '807 and '027 applications.

As shown, LEEs 140 are positioned across substrate 165 in a regular periodic array, although this is not a limitation of the present invention, and in other embodiments LEEs 140 may occupy any positions on light sheet 110. Power conductors 910 and 920 provide power to each LEE string, for example the string 950 encircled by the dashed line in FIG. 9B. Each LEE string 950 typically includes multiple conductive traces 960 that interconnect multiple LEEs 140, as well as one or more CEs 940, which in FIG. 9B is in series with LEEs 140. String 950 shown in FIG. 9B is a folded string, i.e., a string that has three segments electrically coupled in series but positioned as three adjacent segments. A string segment is a portion of a string spanning all or a portion of the region between power conductors 910 and 920 in FIG. 9B. In light sheet 110, some string segments may include LEEs 140 while others do not. However, in other embodiments the distribution and position of LEEs 140 along conductive elements 960 and string segments may be different. In some embodiments, a string 950 may be a straight string, i.e., a string with no folds, as shown in FIG. 9C. In the example of FIG. 9C, string 950 does not include a CE 940. One end of string 950 is electrically coupled to power conductor 910, while the other end of string 950 is electrically coupled to power conductor 920. As will be discussed, the number of segments in a string 950 is not a limitation of the present invention. Various examples of straight and folded strings utilized in embodiments of the present invention are detailed in the '807 and '027 applications.

FIGS. 9A and 9B illustrate three aspects in accordance with embodiments of the present invention. The first is the multiple strings 950 that are powered by the set of power conductors 910, 920. The second is the positional relationship between the locations of LEEs 140 and CE 940, which is disposed between the conductive traces 960 and between power conductors 910,920, such that the pitch between LEEs 140 is not disrupted by the placement or position of CE 940. The third is the inclusion of a CE 940 in each string of series-connected LEEs 140. Combinations of these three aspects enable light sheet 110 to be economically manufactured in very long lengths, for example in a roll-to-roll process, and cut to specified lengths, forming light sheets, while maintaining the ability to tile, or place light sheets adjacent to each other (e.g., in the length direction), with no or substantially no change in pitch between LEEs 140 or in the optical characteristics across the joint between two adjacent light sheets, as discussed in more detail in the '807 and '027 applications.

In an exemplary embodiment, CE 940 is configured to maintain a constant or substantially constant current through LEEs 140 of string 950. For example, in some embodiments, a constant voltage may be applied to power conductors 910, 920, which may, under certain circumstances may have some variation, or the sum of the forward voltages of LEEs 140 in different strings may be somewhat different, for example as a result of manufacturing tolerances, or the component and/or operational values of the element(s) within CE 940 may vary, for example as a result of manufacturing tolerances or changes in operating temperature, and CE 940 acts to maintain the current through LEEs 140 substantially constant in the face of these variations. In other words, in some embodiments the input to the light sheet is a constant voltage that is applied to power conductors 910, 920, and CEs 940 convert the constant voltage to a constant or substantially constant current through LEEs 140. The design of CE 940 may be varied to provide different levels of control or variation of the current through LEEs 140. In some embodiments, CEs 940 may control the current through LEEs 140 to be substantially constant with a variation of less than about ±25%. In some embodiments, CEs 940 may control the current through LEEs 140 to be substantially constant with a variation of less than about ±15%. In some embodiments, CEs 940 may control the current through LEEs 140 to be substantially constant with a variation of less than about ±10%. In some embodiments, CEs 940 may control the current through LEEs 140 to be substantially constant with a variation of less than about ±5%.

In some embodiments, CEs 940 may, in response to a control signal, act to maintain a constant or substantially constant current through LEEs 140 until instructed to change to a different constant or substantially constant current, for example by an external control signal. In some embodiments, as detailed herein, all CEs 940 on a sheet may act in concert, that is maintain or change the current through all associated LEEs 140; however, this is not a limitation of the present invention, and in other embodiments one or more CEs 940 may be individually instructed and/or energized.

In some embodiments LEEs 140 may include or consist essentially of light-emitting diodes (LED) or lasers. In some embodiments, light emitted from light sheet 110 is in the form of an array of bright spots, or light-emission points, resulting in a pixelated pattern. However, this is not a limitation of the present invention, and in other embodiments light sheet 110 includes different types of light emitters, for example organic LEDs (OLEDs). In some embodiments, light sheet 110 may emit light homogeneously or substantially homogeneously, for example light sheet 110 may include an array of LEEs 140 behind an optic or diffuser that spreads the light from LEEs 140 homogeneously or substantially homogeneously. In some embodiments, light sheet 110 may include one or more OLEDs emitting homogeneously or substantially homogeneously over light sheet 110.

In the embodiment depicted in FIG. 9B, LEEs 140 are distributed substantially uniformly over light sheet 110; however, this is not a limitation of the present invention, and in other embodiments, LEEs 140 may have a non-uniform distribution. As will be understood, the distributions of LEE 140 on light sheet 110 shown in FIG. 9B are not limitations of the present invention, and other embodiments may have other distributions of LEEs 140. In some embodiments, one or more portions of light sheet 110 may be unpopulated with LEEs 140. In some embodiments, the distribution of LEEs 140 on light sheet 110 is specifically chosen to achieve one or more characteristics, for example optical, electrical, thermal or the like, as described herein. In some embodiments, the distribution of LEEs 140 on light sheet 110 may be chosen to create a certain decorative look.

In some embodiments, light sheet 110 may also be cut to length, as discussed in more detail in the '807 and '027 applications. For example, in some embodiments of the present invention light sheet 110 may be cut between strings 950.

In some embodiments, light sheet 110 does not require any additional thermal management or heat-sinking, i.e., the heat generated by LEEs 140 is at least partially accommodated by the structure of light sheet 110 itself, for example substrate 165 and/or conductive elements 960 and/or power conductors 910, 920.

As utilized herein, the term “light-emitting element” (LEE) refers to any device that emits electromagnetic radiation within a wavelength regime of interest, for example, visible, infrared or ultraviolet regime, when activated, by applying a potential difference across the device or passing a current through the device. Examples of light-emitting elements include solid-state, organic, polymer, phosphor-coated or high-flux LEDs, laser diodes or other similar devices as would be readily understood. The emitted radiation of an LEE may be visible, such as red, blue or green, or invisible, such as infrared or ultraviolet. An LEE may produce radiation of a continuous or discontinuous spread of wavelengths. An LEE may feature a phosphorescent or fluorescent material, also known as a light-conversion material, for converting a portion of its emissions from one set of wavelengths to another. In some embodiments, the light from an LEE includes or consists essentially of a combination of light directly emitted by the LEE and light emitted by an adjacent or surrounding light-conversion material. An LEE may include multiple LEEs, each emitting essentially the same or different wavelengths. In some embodiments, a LEE is an LED that may feature a reflector over all or a portion of its surface upon which electrical contacts are positioned. The reflector may also be formed over all or a portion of the contacts themselves. In some embodiments, the contacts are themselves reflective. Herein “reflective” is defined as having a reflectivity greater than 65% for a wavelength of light emitted by the LEE on which the contacts are disposed. In some embodiments, an LEE may include or consist essentially of an electronic device or circuit or a passive device or circuit. In some embodiments, an LEE includes or consists essentially of multiple devices, for example an LED and a Zener diode for static-electricity protection. In some embodiments, an LEE may include or consist essentially of a packaged LED, i.e., a bare LED die encased or partially encased in a package. In some embodiments, the packaged LED may also include a light-conversion material. In some embodiments, the light from the LEE may include or consist essentially of light emitted only by the light-conversion material, while in other embodiments the light from the LEE may include or consist essentially of a combination of light emitted from an LED and from the light-conversion material. In some embodiments, the light from the LEE may include or consist essentially of light emitted only by an LED.

One or more non-LEE devices such as Zener diodes, transient voltage suppressors (TVSs), varistors, etc., may be placed on each light sheet to protect the LEEs 140 from damage that may be caused by high-voltage events, such as electrostatic discharge (ESD) or lightning strikes. In one embodiment, conductive trace segments shown in FIG. 9B or 9C between the LEE strings 950 may be used for placement of a single protection device per light sheet, where the device spans the positive and negative power traces, for example power conductors 910, 920. These trace segments also serve to provide a uniform visual pattern of lines in the web direction, which may be more aesthetically pleasing than a light sheet with noticeable gaps between LEE strings 950. In a more general sense, in addition to conductive traces 960 that are part of string 950, additional conductive traces 960 that may or may not be electrically coupled to other strings 950 and/or power conductors 910, 920 may be formed on substrate 165, for example to provide additional power conduction pathways or to achieve a decorative or aesthetically pleasing look to the pattern on the light sheet or to provide a communication pathway to one or more CEs 940, for example to provide a control signal to the one or more CEs 940. These trace segments also serve to provide a uniform visual pattern of lines in the web direction, which may be more aesthetically pleasing than a light sheet with noticeable gaps between LEE strings 950.

In one embodiment, an LEE 140 includes or consists essentially of a bare semiconductor die, while in other embodiments LEE 140 includes or consists essentially of a packaged LED.

In some embodiments, LEE 140 may include or consist essentially of a “white die” that includes an LED that is integrated with a light-conversion material (e.g., a phosphor) before being attached to the light sheet, as described in U.S. patent application Ser. No. 13/748,864, filed Jan. 24, 2013, or U.S. patent application Ser. No. 13/949,543, filed Jul. 24, 2013, the entire disclosure of each of which is incorporated by reference herein.

In some embodiments, LEEs 140 may emit light in a relatively small wavelength range, for example having a full width at half maximum in the range of about 20 nm to about 200 nm. In some embodiments, all LEEs 140 may emit light of the same or substantially the same wavelength, while in other embodiments different LEEs 140 may emit light of different wavelengths. In some embodiments LEEs 140 may emit white light, for example that is perceived as white light by the eye. In some embodiments, the white light may be visible light with a spectral power distribution the chromaticity of which is close to the blackbody locus in the CIE 1931 xy or similar color space. In some embodiments, white light has a color temperature in the range of about 2000 K to about 10,000 K. The emission wavelength, full width at half maximum (FWHM) of the emitted light or radiation or other optical characteristics of LEEs 140 may not be all the same and are not a limitation of the present invention.

Advantageously, embodiments of the present invention produce light sheet 110 having controlled optical characteristics. In some embodiments of the present invention, it is advantageous to have multiple light sheets, each of which as a similar CCT (preferably the average CCT of each light sheet during manufacture or use), having a relatively narrow CCT distribution. One measure of white color temperature is defined as a MacAdam ellipse. A MacAdam ellipse represents a region of colors on a chromaticity chart, for example the CIE chromaticity diagram, and a one-step MacAdam ellipse represents the range of colors around the center of the ellipse that are indistinguishable to the average human eye, from the color at the center of the ellipse. The contour of a one-step MacAdam ellipse therefore represents barely noticeable differences of chromaticity.

Multiple-step MacAdam ellipses may be constructed that encompass larger ranges of color around the center point. While there are many recommendations as to how tight the color temperature uniformity should be (as measured by MacAdam ellipses or other units), a variation encompassed within a smaller step number of MacAdam ellipses (smaller ellipse) is more uniform than one encompassed within a larger step number of MacAdam ellipses (larger ellipse). For example, a four-step MacAdam ellipse encompasses about a 300K color temperature variation along the black body locus, centered at 3200K, while a two-step MacAdam ellipse encompasses about a 150K color temperature variation along the black body locus, centered at 3200K.

In some embodiments of the present invention, the variation in average CCT between different light sheets 110 is less than 4 MacAdam ellipses, or less than 3 MacAdam ellipses or less than 2 MacAdam ellipses.

Substrate 165 may include or consist essentially of a semicrystalline or amorphous material, e.g., polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, fiberglass, FR4, metal core printed circuit board, (MCPCB), and/or paper. Substrate 165 may include multiple layers, for example, a semicrystalline or amorphous material, e.g., PEN, PET, polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, and/or paper formed over a second substrate for example comprising, acrylic, aluminum, steel and the like. Depending upon the desired application for which embodiments of the invention are utilized, substrate 165 may be substantially optically transparent, translucent, or opaque. For example, substrate 165 may exhibit a transmittance or a reflectivity greater than 70% for optical wavelengths ranging between approximately 400 nm and approximately 700 nm. In some embodiments substrate 165 may exhibit a transmittance or a reflectivity of greater than 70% for one or more wavelengths emitted by LEE 140. Substrate 165 may also be substantially insulating, and may have an electrical resistivity greater than approximately 100 ohm-cm, greater than approximately 1×10⁶ ohm-cm, or even greater than approximately 1×10¹⁰ ohm-cm. In some embodiments substrate 165 may have a thickness in the range of about 10 μm to about 500 μm.

Conductive elements, e.g., power conductors 910, 920 and conductive traces 960, may be formed via conventional deposition, photolithography, and etching processes, plating processes, lamination, lamination and patterning, evaporation sputtering or the like or may be formed using a variety of different printing processes. For example, power conductors 910, 920 and conductive traces 960 may be formed via screen printing, flexographic printing, ink-jet printing, and/or gravure printing. Power conductors 910, 920 and conductive traces 960 may include or consist essentially of a conductive material (e.g., an ink or a metal, metal film or other conductive materials or the like), which may include one or more elements such as silver, gold, aluminum, chromium, copper, and/or carbon. Power conductors 910, 920 and conductive traces 960 may have a thickness in the range of about 50 nm to about 1000 μm. In some embodiments, the thickness of power conductors 910, 920 and conductive traces 960 may be determined by the current to be carried thereby. While the thickness of one or more of power conductors 910, 920 and conductive traces 960 may vary, the thickness is generally substantially uniform along the length of the trace to simplify processing. However, this is not a limitation of the present invention, and in other embodiments the thickness and/or material of power conductors 910, 920 and conductive traces 960 may vary. In some embodiments, all or a portion of power conductors 910, 920 and conductive traces 960 may be covered or encapsulated. In some embodiments, a layer of material, for example insulating material, may be formed over all or a portion of power conductors 910, 920 and conductive traces 960. Such a material may include, e.g., a sheet of material such as used for substrate 265, a printed layer, for example using screen, ink jet, stencil or other printing means, a laminated layer, or the like. Such a printed layer may include, for example, an ink, a plastic and oxide, or the like. The covering material and/or the method by which it is applied is not a limitation of the present invention.

In some embodiments of the present invention, all or a portion of substrate 165 and/or power conductors 910, 920 and/or conductive traces 960 may be covered by a layer having pre-determined optical properties. In some embodiments, the optical properties of substrate 165 or a coating material on substrate 165, for example reflectance, transmittance, and/or absorption, may be utilized to further control the optical characteristics of the lighting system. In some embodiments, substrate 165 or a coating on substrate 165 may be a diffuse reflector, while in other embodiments it may be a specular reflector, and in yet other embodiments it may be designed to have a relatively high absorbance for light emitted by LEEs 140. In some embodiments of the present invention, substrate 165 may have a reflectance of at least 80% or at least 90% or at least 95% to a wavelength of light emitted by LEEs 140. In some embodiments of the present invention, substrate 165 may be transparent or substantially transparent to a wavelength of light emitted by LEEs 140, for example having a transmittance of at least 80% or at least 90% or at least 95% to a wavelength of light emitted by LEEs 140. In some embodiments of the present invention, substrate 165 may be absorbing or substantially absorbing to a wavelength of light emitted by LEEs 140, for example having an absorbance of at least 60% or at least 70% or at least 80% to a wavelength of light emitted by LEEs 140. In some embodiments, substrate 165 or portions of substrate 165 may be configured to diffuse a wavelength of light emitted by LEEs 140. In some embodiments, substrate 165 may have two or more regions, where different regions have different optical characteristics. In some embodiments, the transmittance of a diffuse region is at least 50%, or at least 70% or at least 80%, or at least 90% to a wavelength of light emitted by LEEs 140. The remaining portion of substrate 165 in this embodiment has a reflecting surface, i.e., a surface reflective to a wavelength of light emitted by LEEs 140.

In one embodiment, conductive traces 960 are formed with a gap between adjacent conductive traces 960, and LEEs 140 and CEs 940 are electrically coupled to conductive traces 960 using conductive adhesive, e.g., an isotropically conductive adhesive and/or an ACA, as described in U.S. Pat. No. 8,384,121, filed on Jun. 29, 2011, the entire disclosure of which is incorporated herein by reference. ACAs may be utilized with or without stud bumps and embodiments of the present invention are not limited by the particular mode of operation of the ACA. For example, the ACA may utilize a magnetic field rather than pressure (e.g., the ZTACH ACA available from SunRay Scientific of Mt. Laurel, N.J., for which a magnetic field is applied during curing in order to align magnetic conductive particles to form electrically conductive “columns” in the desired conduction direction). Furthermore, various embodiments utilize one or more other electrically conductive adhesives, e.g., isotropically conductive adhesives, non-conductive adhesives, in addition to or instead of one or more ACAs. In other embodiments, LEEs 140 and CEs 940 may be attached to and/or electrically coupled to conductive traces 960 by other means, for example solder, reflow solder, wave solder, wire bonding, or the like. The method by which LEEs 140 and CEs 940 are attached to conductive traces 960 is not a limitation of the present invention.

CE 940 may be one component or multiple active and/or passive components. In one embodiment, power conductors 910, 920 provide a DC voltage or substantially DC voltage and CE 940 includes or consists essentially of a resistor, e.g. a current-limiting resistor. The choice of the resistance value may be a trade-off between a number of parameters and characteristics that may include, e.g., efficiency and current stability. In general, a larger resistance will result in reduced efficiency but greater current stability, while a smaller resistance will result in increased efficiency but reduced current stability. Variations in the current may result from variations in the input voltage (for example across power conductors 910, 920), variations in forward voltage of the LEEs 140 within the string, variations in the value of the current-limiting resistor, variations in current that may occur if one or more LEEs 140 in the string become short-circuited or the like. In the case of CE 940 including or consisting essentially of a resistor, in some embodiments CE 940 is a discrete resistor formed within or on conductive traces 960, such as a chip resistor, a bare-die resistor or surface mount device (SMD) resistor.

As discussed above, in embodiments where CE 940 includes or consists essentially of a resistor, there may be trade-offs between efficiency and current stability. While such trade-offs may be acceptable in certain products, other products may require relatively better current stability at higher efficiencies, and in these cases CE 940 may include or consist essentially of multiple components or a circuit element, as discussed above. In some embodiments CE 940 includes or consists essentially of a field-effect transistor (FET) and a resistor. In another embodiment CE 940 includes or consists essentially of two bipolar junction transistors (BJTs) and two resistors.

In some embodiments, the efficiency and current stability increase with the number of components, as does the cost. In some embodiments where CE 940 includes or consists essentially of multiple components, the components may be in discrete form (i.e., each component individually electrically coupled to conductive traces 960) or in hybrid form (where multiple separate components are mounted on a submount, which is then electrically coupled to conductive traces 960), or in monolithic form (where multiple components are integrated on a semiconductor chip, for example a silicon-based or other semiconductor-based integrated circuit). In some embodiments, CE 940 may be in bare-die form, while in other embodiments CE 940 may be packaged or potted or the like. In some embodiments, CE 940 may include or consist essentially of a bare-die integrated circuit. In some embodiments, the integrated circuit includes or consists essentially of multiple active and/or passive devices that are fabricated on a common semiconductor substrate.

In other embodiments, power conductors 910, 920 may provide AC power, or power modulated at different frequencies and in these embodiments CEs 940 may be selected accordingly or may be omitted. In one embodiment, power conductors 910, 920 may provide a standard line voltage, for example about 120 VAC or about 940 VAC or about 277 VAC, for example at about 50 Hz or about 60 Hz. In some embodiments, CEs 940 may accommodate a plurality of input types, and thus be so-called “universal” CEs 940, while in other embodiments different CEs 940 may be required for different input types. The actual component or components of CEs 940 are not limiting to this invention; however, in preferred embodiments of this invention, the positioning of CEs 940 does not disrupt the LEE pitch. In another embodiment of this invention, the positioning of CEs 940 is independent of LEE pitch. As discussed herein, CEs 940 and LEEs 230 may be electrically coupled to conductive traces 960 using a variety of means, for example solder, conductive adhesive or anisotropic conductive adhesive (ACA); however, the method of electrical coupling of CEs 140 and LEEs 230 is not a limitation of the present invention.

In some embodiments, driver 710 is a substantially constant voltage supply, the output of which is pulse-width modulated to permit dimming of LEEs 140 on light sheet 110. In some embodiments, driver 710 is a UL class 2 system having a voltage output not exceeding 60 V.

FIG. 10A shows another embodiment of the present invention. The lighting device 1000 of FIG. 10A includes or consists essentially of a light sheet covered with a protective coating, for example a conformal or non-conformal coating. FIG. 10B shows one example of substrate 165 and LEEs 140 coated with a non-conformal coating 1020, while FIG. 10C shows an example of substrate 165 and LEEs 140 coated with a conformal or substantially conformal coating 1030. In some embodiments, the lighting device 1000 may include one or more holes, for example grommeted holes 1010, or hook and loop fasteners for ease of mounting; however, this is not a limitation of the present invention, and in other embodiments the 1000 lighting device may be affixed to a structure by other means. In one embodiment, the lighting device 1000 may be nailed or stapled to a suitable surface, for example a wood or plastic wall of a temporary structure. FIG. 10A shows an example of a lighting device 1000 extended (e.g., laid flat or substantially flat or having a non-flat (yet unrolled) shape) for operation, while FIG. 10D shows an example of a lighting device 1000 rolled up for storage or transportation. In some embodiments of the present invention, lighting device 1000 may include one or more connectors 1040 (FIG. 10E) for, e.g., electrically connecting the lighting device 1000 to another similar or identical lighting device or to a source or external power. In some embodiments, connector 1040 may be a waterproof connector. As shown in FIG. 10E, conductive traces 1050 formed on substrate 165 may interconnect multiple LEEs 140 on substrate 165 as well as provide electrical coupling between connector 1040 and LEEs 140.

In some embodiments, the lighting device of FIG. 10A may be powered by one or more batteries or other power sources, as described herein, which may be contained in a separate unit, for example holder 710 (not shown in FIG. 10A). However, this is not a limitation of the present invention, and in other embodiments of the present invention the power source may be incorporated into the lighting device, as shown in FIGS. 10F and 10G. In some embodiments of the present invention, one or more solar cells or photovoltaic devices 1060 may be integrated with light sheet 110, and these may be used to provide power to light sheet 110, as shown in FIG. 10C. In some embodiments of the present invention, solar cell 1060 may be relatively thin and formed on the side of substrate 165 opposite that on which LEEs 140 are formed, as shown in FIG. 10F. In some embodiments of the present invention, solar cell 1060 may be flexible, while in other embodiments solar cell 1060 may be rigid or substantially rigid. In some embodiments of the present invention, the structure shown in FIG. 10F may be encapsulated or coated to protect solar cell 1060 and/or light sheet 110.

In some embodiments, a battery, capacitor, or super-capacitor, or combination of one or more of these, identified in FIG. 10G as 1070, may also be incorporated to form a system that incorporates a flexible battery having a relatively thin form factor that is formed on the side of substrate 165 opposite that on which LEEs 140 are formed, as shown in FIG. 10G. In some embodiments of the present invention, battery 1070 may be flexible, while in other embodiments battery 1070 may be rigid or substantially rigid. In some embodiments of the present invention, the structure shown in FIG. 10G may be encapsulated or coated to protect solar cell 1060 and/or light sheet 110.

In some embodiments, both a battery and a solar cell may be incorporated with a light sheet to form a system that may charge the battery with the solar cell when light is available, for example during daylight hours, and energize the light sheet when desired from the battery, when little or no external light is present. A schematic of such a system is shown in FIG. 10H, in which battery 1070 and solar cell 1060 are formed on the side of substrate 165 opposite that on which LEEs 140 are formed. In preferred embodiments, both battery 1070 and solar cell 1060 are flexible. In some embodiments of the present invention, the structure shown in FIG. 10H may be encapsulated or coated to protect solar cell 1060, battery 1070 and/or light sheet 110.

FIGS. 10F-10H do not show the specifics of how battery 1070 and/or solar cell 1060 and LEEs 140 are electrically coupled. In some embodiments of the present invention, elements on the front and back of substrate 165 (i.e., on opposite sides of substrate 165) may be electrically coupled through electrical vias in substrate 165. FIG. 11A shows an example of substrate 165 with a front conductive trace 960 and a back conductive trace 1120 electrically coupled through a via 1110. FIG. 10B shows one embodiment of the present invention illustrating one approach to electrically couple LEEs 140 to a battery 1070. In this embodiment, power is coupled from battery contact 1130 through via 1110 to conductive trace 960 and LEE 140. Other means may also be used to electrically couple elements on opposite sides of substrate 165, for example rivets, staples or the like, as described in the '807 and '027 applications.

In some embodiments, light sheet 110 may be incorporated into emergency warning signs. For example FIG. 12 shows another embodiment of the present invention in which a light sheet 110 is incorporated into a portable warning triangle 1200. In some embodiments, warning triangle 1200 may fold to a small volume and shape, or may be rolled up to occupy a small volume while not in use. In some embodiments of the present invention, light sheet 110 may be energized and de-energized to provide a blinking indication. In some embodiments of the present invention, light sheet 110 may be cut or formed into one or more shapes, symbols or letters, to provide additional information or indications. For example light sheet 110 may be shaped into an arrow, a stop sign, a cross, or other shapes. In some embodiments of the present invention, LEEs 140 on light sheet 110 may be positioned to form one or more shapes, symbols or letters. FIGS. 12B and 12C show examples of embodiments of the present invention incorporating symbols or letters.

FIG. 12B shows a roll-up lighting device, similar to that of FIG. 1A; however, light sheet 110 is configured to include arrow symbols 1210 that may be illuminated upon energizing LEEs 140. This lighting device includes a storage compartment, identified here as drum 170, and a flexible illuminated portion, identified as 1215, that may be stored in storage compartment 170. In one embodiment of the present invention, arrow symbols 1210 are formed using shaped light sheet 110, while in other embodiments of the present invention arrow symbols 1210 are formed using patterns of LEEs 140 on a light sheet 110 that may have a shape not conforming to that of the symbols 1210. FIG. 12C shows a roll-up lighting device, similar to that of FIG. 10D; however, light sheet 110 is configured to include letters 1220 that spell the word “DANGER” that may be illuminated upon energizing LEEs 140. In one embodiment of the present invention, letters 1220 are formed using shaped light sheet 110, while in other embodiments of the present invention letters 1220 are formed using patterns of LEEs 140 on a light sheet 110 that may have a shape not conforming to that of the letters 1220.

In some embodiments of the present invention, the protective layer, for example conformal coating 1030 or non-conformal coating 1020, may be shaped to incorporate one or more optical elements to control an optical characteristic of LEE 140. In some embodiments of the present invention, such an optical element may include a refractive or reflecting or Fresnel lens, and may be used to control the spatial light distribution pattern of light emitted by one or more LEEs 140, as described in U.S. Patent Application Publication No. 2013/0141909, filed Dec. 4, 2012, the entire disclosure of which is hereby incorporated herein by reference. In some embodiments of the present invention, the protective layer may include or consist essentially of one or more of silicone, PDMS, and polyurethane, and it may be molded, cast, embossed, or otherwise formed into one or more flexible optical elements as part of the coating or encapsulation process. FIG. 13 shows one example of an embodiment of the present invention having coating 1020 surrounding substrate 165 and LEEs 140. As shown, a portion of coating 1020 is formed into multiple optical elements 1310. In some embodiments of the present invention, each LEE 140 is associated with one optical element 1310, while in other embodiments each optical element 1310 is associated with more than one LEE 140. In other embodiments, each LEE 140 is associated with more than one optical element 1310. Manufacture of coating 1020 incorporating optical elements 1310 from flexible optically transparent (to a wavelength of light emitted by LEEs 140) material results in a flexible illumination device incorporating optical elements for altering optical characteristics of the light emitted by the LEEs 140. In some embodiments, each optical element 1310 has a height above the surrounding coating in the range of about 0.5 mm to about 5 mm. In some embodiments, the maximum thickness 1330 is in the range of about 1 mm to about 7 mm, or in the range of about 1.5 mm to about 5 mm.

In some embodiments of the present invention, the illuminating portion of a portable lighting system, for example the flexible illumination portion 1215 of FIG. 12B, is bendable or foldable in only one axis; however, this is not a limitation of the present invention, and in preferred embodiments, the flexible illumination portion is flexible or bendable in more than one direction, for example in two orthogonal or substantially orthogonal directions.

In some embodiments of the present invention, the flexible illumination portion has a radius of curvature, to which it may be deformed without damaging the system, of 50 mm or less, or of 25 mm or less or of 10 mm or less or of 5 mm or less in one direction. In some embodiments of the present invention, the flexible illumination portion has said radius of curvature in more than one direction, for example in two orthogonal or substantially orthogonal directions.

In some embodiments of the present invention, the flexible illumination portion has a thickness in the range of about 0.5 mm to about 5 mm, or in the range of about 1 mm to about 3 mm.

As described herein, lighting devices of the present invention are based on a light sheet that includes multiple conductive traces formed on a flexible substrate and that interconnect an array of LEEs. The combination of a thin flexible substrate (for example in the range of about 12 μm to about 200 μm), thin malleable conductive traces (for example aluminum or copper having a thickness in the range of about 5 μm to about 100 μm) formed on the flexible substrate and robust electrical and mechanical connections (for example using solder or adhesive) between the conductive traces and the electrical components (LEEs and current control elements and any other desired components) results in an robust system, both mechanically and electrically, capable of being flexed, bent and rolled without damage or failure. The small size of the components and the relatively thin substrate and conductive traces contribute to the ability to achieve relatively small radii of curvature without damage or failure.

In general in the above discussion the arrays of semiconductor dies, light emitting elements, optics, and the like have been shown as square or rectangular arrays; however this is not a limitation of the present invention and in other embodiments these elements may be formed in other types of arrays, for example hexagonal, triangular or any arbitrary array. In some embodiments these elements may be grouped into different types of arrays on a single substrate.

The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. In addition, having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. Accordingly, the described embodiments are to be considered in all respects as only illustrative and not restrictive.

Claims

1. An illumination device comprising: a flexible light sheet comprising (i) a flexible substrate, (ii) a plurality of light-emitting elements disposed over the substrate, and (iii) a plurality of conductive traces disposed on the substrate and electrically interconnecting the plurality of light-emitting elements;a storage unit configured to (i) accept and contain the light sheet in a rolled configuration therewithin, the light sheet being wound around an axis of the storage unit when contained therewithin, and (ii) dispense at least a portion of the light sheet therefrom via unwinding of the light sheet from the rolled configuration;a winding mechanism for at least one of winding or unwinding the light sheet around the axis of the storage unit; anddisposed within or on the storage unit, a power source for supplying power at least to an unrolled portion of the light sheet and thereby illuminating the light-emitting elements of at least the unrolled portion.

2. The illumination device of claim 1, wherein the winding mechanism comprises at least one of a hand crank, a motorized mechanism, or a spring mechanism.

3.-4. (canceled)

5. The illumination device of claim 1, wherein, when the light sheet is extended from the storage unit, a thickness of the light sheet is 5 mm or less.

6. The illumination device of claim 1, wherein the light sheet comprises an array of optical elements disposed over the light-emitting elements.

7. The illumination device of claim 1, further comprising a water-resistant or waterproof coating disposed over the light-emitting elements of the light sheet, the coating substantially conforming to a non-planar topography of the light-emitting elements thereunder.

8. The illumination device of claim 1, further comprising a water-resistant or waterproof coating disposed over the light-emitting elements of the light sheet, a top surface of the coating being planar notwithstanding a non-planar topography of the light-emitting elements thereunder.

9. The illumination device of claim 1, wherein the power source comprises at least one of a battery disposed within the storage unit, a solar cell disposed on an outer surface of the storage unit, or a connector configured for connection to an external source of power.

10.-11. (canceled)

12. The illumination device of claim 1, wherein the light sheet is configured to be wound within the storage unit to a radius of curvature of 50 mm or less.

13. The illumination device of claim 1, wherein the light-emitting elements comprise at least one of bare-die light-emitting diodes or packaged light-emitting diodes.

14. (canceled)

15. The illumination device of claim 1, wherein the light-emitting elements emit substantially white light.

16. The illumination device of claim 15, wherein a correlated color temperature of the substantially white light is in the range of 2000 K to 10,000 K.

17. The illumination device of claim 1, further comprising a stiffener disposed along at least a portion of a leading edge of the light sheet.

18. The illumination device of claim 1, further comprising a rotary electrical joint disposed within the storage unit, the rotary electrical joint being configured to preserve electrical contact between the light sheet and the power source during winding and unwinding of the light sheet.

19. The illumination device of claim 1, wherein the power source comprises at least one of a flexible battery, a flexible capacitor, or a flexible solar cell disposed on a surface of the light sheet opposite the light-emitting elements.

20. The illumination device of claim 1, further comprising, disposed within the storage unit, at least one of (i) drive circuitry configured to convert power from the power source for use by the light-emitting elements, (ii) control circuitry configured to control at least one emission characteristic of the light-emitting elements, or (iii) communication circuitry configured to transmit information to or from the illumination device.

21. The illumination device of claim 1, wherein, when the light sheet is fully extended from the storage unit, a trailing edge of the light sheet remains mechanically anchored within the storage unit.

22. The illumination device of claim 1, wherein only the unrolled portion of the light sheet is illuminated, a rolled portion of the light sheet disposed within the storage unit being unilluminated.

23. (canceled)

24. The illumination device of claim 1, further comprising one or more fasteners on the light sheet for positioning of the light sheet when the light sheet is at least partially extended.

25. (canceled)

26. The illumination device of claim 1, further comprising one or more fasteners on the storage unit for positioning of the light sheet when the light sheet is at least partially extended.

27. (canceled)

28. The illumination device of claim 1, wherein the plurality of light-emitting elements disposed over the substrate forms a fixed pattern in the shape of one or more symbols and/or letters.

29.-50. (canceled)

51. The illumination device of claim 1, wherein at least one light-emitting element is coupled to one or more of the conductive traces with an anisotropic conductive adhesive, the anisotropic conductive adhesive being activatable via application of at least one of pressure, heat, or a magnetic field.