[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 62/646,852 filed on March 22, 2018, the content of which is incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] The present disclosure relates generally to illumination devices. More particularly, it relates to illumination devices, such as backlights for electronic displays, comprising light guide plates.

Technical Background

[0003] Liquid crystal displays (LCDs) are light-valve based displays in which the display panel includes an array of individually addressable light valves. A backlight is used to produce an emissive image in the LCD displays. Backlights are either edge-lit or direct-lit. An edge-lit backlight, for example, includes a light emitting diode (LED) array edge-coupled to a light guide plate that emits light from its surface. A direct-lit backlight, for example, includes a two-dimensional (2-D) array of LEDs directly behind the LCD panel. Edge-lit backlights are typically thinner than direct-lit backlights, while direct-lit backlights enable improved dynamic contrast since LEDs in dark regions of the display may be turned off.

[0004] LCD displays are getting thinner and lighter. For 65 inch class LCD displays, a total thickness of about 5 millimeters is desirable. In addition, displays with dimmable zones are desirable to accentuate the visual content. A direct-lit backlight may include dimmable zones, which may be one-dimensional (l-D) or two- dimensional (2-D). In l-D dimming, the display is divided into strips that run along the entire width or length of the display, and the luminance of each strip may be individually controlled. In 2-D dimming, the display is divided into tiles, and the luminance of each tile may be individually controlled. [0005] The backlight is a major part of a LCD display structure and as such contributes to the thickness of the display. The backlight should provide the desired luminance, color spectrum, and luminance and color uniformity while including individually dimmable zones. The backlight should deliver this functionality over a long lifetime for a low cost and with low energy consumption. Accordingly, illumination devices, such as backlights, that provide the desired functionality while having a small thickness are disclosed herein.

SUMMARY

[0006] Some embodiments of the present disclosure relate to an illumination device.

The illumination device includes a first light guide plate, a second light guide plate, and a light source. The first light guide plate includes a light coupling edge extending between a first major surface and a second major surface of the first light guide plate. The second light guide plate includes a light coupling edge extending between a first major surface and a second major surface of the second light guide plate. The light coupling edge of the second light guide plate faces the light coupling edge of the first light guide plate. The light source faces the first major surface of the first light guide plate and the first major surface of the second light guide plate. The light source intersects the light coupling edge of the first light guide plate and the light coupling edge of the second light guide plate.

[0007] Yet other embodiments of the present disclosure relate to an illumination device. The illumination device includes a first composite light guide plate and a light source. The first composite light guide plate includes a first major surface and a second major surface opposite to the first major surface. The first composite light guide plate includes a first slab and a second slab coupled to the first slab. The first composite light guide plate includes a first light coupling edge including a first curved surface extending from the second major surface toward the first major surface. The light source faces the first major surface of the first composite light guide plate to couple light into the first composite light guide plate via the first light coupling edge.

[0008] Yet other embodiments of the present disclosure relate to an illumination device. The illumination device includes a first light coupler, a light guide plate, and a first light source. The first light coupler includes a first light coupling region and a second light coupling region. Each of the first and second light coupling regions include a major surface, an edge surface extending from the major surface, and a curved surface extending toward the edge surface and toward the major surface. The curved surface of the first light coupling region faces the curved surface of the second light coupling region. The light guide plate includes a first portion facing the edge surface of the first light coupling region, a second portion facing the edge surface of the second light coupling region, and a third portion extending between the first portion and the second portion and facing the curved surface of the first light coupling region and the curved surface of the second light coupling region. The first light source faces the major surface of the first light coupling region and the major surface of the second light coupling region.

[0009] The illumination devices disclosed herein may be used for backlights with dimmable zones that are suitable for small or large (e.g., 65 inch class) displays. The illumination devices may be thin (e.g., less than about 2 mm) while meeting the luminance, color, and luminance and color uniformity requirements of dimmable backlights using glass. The number of individually dimmable zones may be scaled based on the display and may be either l-D or 2-D. The illumination devices are efficient in terms of nits per watt of light source power with nearly 100% of the light from the light sources coupled into the light guide plates.

[00010] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[00011] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment s), and together with the description serve to explain principles and operation of the various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[00012] FIGS. 1 A-1C schematically depict an exemplary light guide plate;

[00013] FIG. 2 depicts a cross-sectional view of light coupling into the exemplary light guide plate of FIGS. 1 A-1C from a light source;

[00014] FIG. 3 schematically depicts an exemplary illumination device including the light guide plate of FIGS. 1 A-1C;

[00015] FIG. 4 schematically depicts another example of an illumination device including the light guide plate of FIGS. 1 A-1C;

[00016] FIG. 5 schematically depicts another example of an illumination device including the light guide plate of FIGS. 1 A-1C;

[00017] FIG. 6 schematically depicts another example of an illumination device including the light guide plate of FIGS. 1 A-1C;

[00018] FIG. 7 schematically depicts another example of an illumination device including the light guide plate of FIGS. 1 A-1C;

[00019] FIGS. 8A-8B schematically depict exemplary stacks for the illumination device of FIG. 7;

[00020] FIGS. 9A-9C schematically depict an exemplary composite light guide plate;

[00021] FIG. 10 schematically depicts an exemplary illumination device including the composite light guide plate of FIGS. 9A-9C;

[00022] FIG. 11 schematically depicts another example of an illumination device including the composite light guide plate of FIGS. 9A-9C;

[00023] FIGS. 12A-12C schematically depict another example of a composite light guide plate;

[00024] FIG. 13 schematically depicts an exemplary illumination device including the composite light guide plate of FIGS. 12A-12C;

[00025] FIGS. 14A-14B schematically depict exemplary light couplers for the illumination devices of FIGS. 15-18B;

[00026] FIG. 15 schematically depicts an exemplary illumination device including the light coupler of FIG. 14A;

[00027] FIG. 16 schematically depicts another example of an illumination device including the light coupler of FIG. 14 A;

[00028] FIGS. 17A-17B schematically depict another example of an illumination device including two light couplers of FIG. 14 A; [00029] FIGS. 18A-18B schematically depict another example of an illumination device including four light couplers of FIG. 14 A;

[00030] FIG. 19 schematically depicts another example of an illumination device including a reflective layer;

[00031] FIG. 20 schematically depicts another example of an illumination device including a reflective layer or stack;

[00032] FIG. 21 schematically depicts another example of an illumination device including a stack of the light guide plates of FIGS. 1 A-1C;

[00033] FIGS. 22A-22B schematically depict an exemplary illumination device for a large display; and

[00034] FIG. 23 schematically depicts an exemplary LCD display.

DETAILED DESCRIPTION

[00035] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[00036] Ranges can be expressed herein as from“about” one particular value, and/or to“about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent“about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[00037] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom, vertical, horizontal - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[00038] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[00039] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[00040] Referring now to FIGS. 1A-1C, an exemplary light guide plate 100 is schematically depicted. FIG. 1A is an enlarged side view of a light coupling edge of light guide plate 100, FIG. 1B is a top view of light guide plate 100, and FIG. 1C is a side view of light guide plate 100. Light guide plate 100 includes a first major surface 102, a second major surface 104 opposite to the first major surface 102, and an edge surface 110 extending between the first major surface 102 and the second major surface 104. Light guide plate 100 also includes a light coupling edge 106, 108 extending between the first major surface 102 and the second major surface 104 opposite to edge surface 110. The light coupling edge includes a flat surface 106 and a curved surface 108. The flat surface 106 extends from the first major surface 102 to the curved surface 108, and the curved surface 108 extends from the flat surface 106 to the second major surface 104.

[00041] Light guide plate 100 may be made of glass, Poly(methyl methacrylate) (PMMA), polycarbonate, ceramic, or another suitable material. In certain exemplary embodiments, light guide plate 100 may have a thickness as indicated at 112 between about 1 mm and 2 mm (e.g., 1.4 mm), a length as indicated at 114 between about 5 mm and 500 mm (e.g., 400 mm), and a width as indicated at 116 between about 5 mm and 200 mm (e.g., 78 mm). In other examples, thickness 112, length 114, and width 116 may have other suitable values based upon a particular application. [00042] FIG. 2 depicts a cross-sectional view including ray tracing of light coupling into the exemplary light guide plate 100 of FIGS. 1A-1C from a light source 120. In certain exemplary embodiments, light source 120 is a light emitting diode (LED). Light source 120 may be arranged relative to light guide plate 100 such that about half of the light from light source 120 is incident on the first major surface 102 of light guide plate 100. Therefore, light from half of the emitting surface of light source 120 may be efficiently coupled into light guide plate 100 while light from the other half of the emitting surface of light source 120 may be efficiently coupled into a second light guide plate (not shown). As illustrated in FIG. 2, the light propagation in light guide plate 100 can be redirected in a direction that is substantially normal to the light propagation direction from light source 120 into light guide plate 100. The light from light source 120 is incident on the first major surface 102 of light guide plate 100 and is redirected by the light coupling edge 106, 108 into the remainder of the volume of light guide plate 100. Light incident on the first major surface 102 of light guide plate 100 may also be redirected by the second major surface 104 into the remainder of the volume of light guide plate 100.

[00043] The top surface of light source 120 may be in optical communication with the first major surface 102 of light guide plate 100. The critical angle of incidence for which the rays remain trapped in glass (refractive index = 1.5) when exposed to air is 41.81°. Accordingly, the profile of curved surface 108 may be derived from a requirement that the incidence angle from anywhere in the half-width of light source 120 in this cross-sectional view is kept below 42.81° (i.e., the critical angle + 1° margin) for all rays which are incident from the half-width of the emitting surface of light source 120 to the light coupling edge in light guide plate 100 at the curved surface 108 and the flat surface 106 of the light coupling edge. In this example, the height of light guide plate 100 is 1.394 mm, and the height of the flat surface 106 of the light coupling edge is 0.301 mm for a 0.65 mm wide light source 120. This height of the flat surface 106 results in the confinement of 92% of the radiation from the half-width of light source 120 in the light guide plate 100. The flat surface 106 of the light coupling edge enables the use of glass of a thickness less than 2 mm to be used in the fabrication of 65” or larger class of backlights for displays. The flat surface 106 also allows two light guide plates to be placed edge to edge over a single light source to couple most of the light from the light source into the light guide plates as illustrated below with reference to FIG. 3.

[00044] FIG. 3 schematically depicts an exemplary illumination device 130.

Illumination device 130 includes a first light guide plate lOOa, a second light guide plate lOOb, and a light source 120. First light guide plate lOOa and second light guide plate lOOb are similar to light guide plate 100 previously described and illustrated with reference to FIGS. 1A-1C. First light guide plate lOOa includes a light coupling edge l06a, l08a extending between a first major surface l02a and a second major surface l04a of the first light guide plate lOOa. Second light guide plate lOOb includes a light coupling edge l06b, l08b extending between a first major surface l02b and a second major surface l04b of the second light guide plate lOOb. The light coupling edge l06b, l08b of the second light guide plate lOOb faces the light coupling edge l06a, l08a of the first light guide plate lOOa. Light source 120 faces the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb. Light source 120 intersects the light coupling edge l06a, l08a of the first light guide plate lOOa and the light coupling edge l06b, l08b of the second light guide plate lOOb to couple light indicated by arrows 121 into the first light guide plate lOOa and the second light guide plate lOOb.

[00045] The first light coupling edge of the first light guide plate lOOa includes a flat surface l06a extending from the first major surface l02a of the first light guide plate lOOa and a curved surface l08a extending from the flat surface l06a to the second major surface l04a of the first light guide plate lOOa. Likewise, the light coupling edge of the second light guide plate lOOb includes a flat surface l06b extending from the first major surface l02b of the second light guide plate lOOb and a curved surface l08b extending from the flat surface l06b to the second major surface l04b of the second light guide plate lOOb. The flat surface l06a of the first light guide plate lOOa faces the flat surface l06b of the second light guide plate lOOb. In some embodiments, flat surface l06a is parallel to flat surface l06b. In certain exemplary embodiments, flat surface l06a of the first light guide plate lOOa contacts the flat surface l06b of the second light guide plate lOOb. In other examples, there may be a gap between the flat surface l06a of the first light guide plate lOOa and the flat surface l06b of the second light guide plate lOOb. [00046] FIG. 4 schematically depicts an embodiment of another illumination device 140. Illumination device 140 includes first light guide plate lOOa, second light guide plate lOOb, and light source 120 as previously described and illustrated with reference to FIG. 3. In addition, illumination device 140 includes a printed circuit board (PCB) 142 and an illumination device structure 144, such as a housing. Light source 120 is electrically coupled to PCB 142 to receive power and control signals. PCB 142 is mechanically coupled to illumination device structure 144. PCB 142 may support a row of light sources aligned with light source 120 to couple light into light guide plates lOOa and lOOb via the light coupling edges of light guide plates lOOa and lOOb.

[00047] FIG. 5 schematically depicts an embodiment of another illumination device 150. Illumination device 150 includes first light guide plate lOOa, second light guide plate lOOb, and light source 120 as previously described and illustrated with reference to FIG. 3. In addition, illumination device 150 includes a stack 152. Stack 152 faces at least one of the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb. Stack 152 includes a patterned reflective layer 154, a scattering or diffuser layer 156, and a reflective layer 158.

[00048] Patterned reflective layer 154, scattering or diffuser layer 156, and reflective layer 158 are in optical communication with one another. In this example, the top of patterned reflective layer 154 is in optical communication with the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb. The top of scattering or diffuser layer 156 is also in optical communication with the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb at the locations where the material for patterned reflective layer 154 is not present. This may be accomplished by applying an index matching fluid, gel, or tape at the layer interfaces and by filling up the voids with index matching fluid or gel.

[00049] There are two possibilities for the light incident on the first major surface l02a of first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb: (a) if the light is incident on the patterned reflective layer 154, the light is reflected and continues to remain confined in the first light guide plate lOOa or the second light guide plate lOOb, and (b) if the light is incident at a place where there is no reflective material, the light propagates out of the first light guide plate lOOa or the second light guide plate lOOb and into the scattering or diffuser layer 156 where the light is scattered in all directions. The light scatter pattern may, in certain exemplary embodiments, be considered to be Lambertian. Some other scatter pattern such as Gaussian may also be produced depending on the scattering medium and the ratio of scattering particle size and the wavelength of light. Some of the light goes through the scattering or diffuser layer 156 without being scattered or is scattered toward the reflective layer 158. The light is then reflected by the reflective layer 158, and on the return path, the light is either again scattered by the scatting or diffuser layer 156 or the light continues to propagate either in the scattering or diffuser layer 156 or toward and into the first light guide plate lOOa or the second light guide plate lOOb where the light is not incident on the patterned reflective layer 154.

[00050] In certain exemplary embodiments, stack 152 may be a single stack present under the majority of the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb except for a small opening to make room for light source 120. In other examples, a first stack 152 may be present under the first light guide plate lOOa and a second stack 152 may be present under the second light guide plate lOOb with light source 120 between the two stacks.

[00051] FIG. 6 schematically depicts an embodiment of another illumination device 160. Illumination device 160 includes first light guide plate lOOa, second light guide plate lOOb, light source 120, and stack 152 as previously described and illustrated with reference to FIG. 5 and PCB 142 and illumination device structure 144 as previously described and illustrated with reference to FIG. 4. In addition, illumination device 160 includes a stack 162. Stack 162 faces at least one of the second major surface l04a of the first light guide plate lOOa and the second major surface l04b of the second light guide plate lOOb. In this example, stack 162 includes a diffuser layer 164, a brightness enhancement layer 166, and a dual brightness enhancement layer 168. In other examples, stack 162 may include a diffuser layer, a brightness enhancement layer, or a diffuser layer and a brightness enhancement layer.

[00052] Stack 162 may include spacers (not shown) between the layers 164, 166, and 168, and between the bottom layer 164 and the second major surface l04a of the first light guide plate lOOa and the second major surface l04b of the second light guide plate lOOb. For example, where PCB 142 has a thickness of 0.51 mm, light source 120 has a height of 0.36 mm, light guide plates lOOa and lOOb have a glass thickness of 1.4 mm, and stack 162 has a thickness of 1 mm, the thickness of illumination device 160 as measured between the bottom of PCB 142 to the top of the stack 162 is 3.27 mm.

[00053] In the embodiment depicted in FIG. 6, stack 162 is a single stack present over the second major surface l04a and the curved surface l08a of the first light guide plate lOOa and the second major surface l04b and the curved surface l08b of the second light guide plate lOOb. In other embodiments, however, a first stack 162 may be present over the first light guide plate lOOa, and a second stack 162 may be present over the second light guide plate lOOb.

[00054] FIG. 7 schematically depicts an embodiment of another illumination device 170. Illumination device 170 includes first light guide plate lOOa, second light guide plate lOOb, and light source 120 as previously described and illustrated with reference to FIG. 3. In addition, illumination device 170 includes a stack 172. Stack 172 faces at least one of the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb. Stack 172 includes a patterned scattering or diffuser layer 174 and a reflective layer 176.

[00055] In certain exemplary embodiments, patterned scattering or diffuser layer 174 may be formed by either coating a scattering or diffuser layer with a mask on the first major surface l02a of the first light guide plate lOOa and on the first major surface l02b of the second light guide plate lOOb or by micromachining the scattering or diffuser pattern on the first major surface l02a of the first light guide plate lOOa and on the first major surface l02b of the second light guide plate lOOb. In another example, patterned scattering or diffuser layer 174 may be formed from a scattering or diffuser film with laser patterned holes. The reflective layer 176 may be a film of high reflective material or a high reflective coating applied to the surface of scattering or diffuser layer 172 facing away from the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb.

[00056] Layers 174 and 176 are in optical communication with one another. Patterned scattering or diffuser layer 174 is in optical communication with the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb. This may, for example, be accomplished by applying index matching fluid, gel, or tape at the layer interfaces and by filling up all voids with index matching fluid or gel. There are three possibilities for the light incident on the first major surface l02a of the first light guide plate lOOa and on the first major surface l02b of the second light guide plate lOOb: (a) if the light is incident on the scattering or diffuser layer 172, the light is scattered and some of the scattered light escapes the second major surface l04a of the first light guide plate lOOa or the second major surface l04b of the second light guide plate lOOb, (b) if the light is incident at a place where there is no diffuser material 174 and no index matching material, the light is totally internally reflected and the light propagates within the first light guide plate lOOa or the second light guide plate lOOb, and (c) if the light is incident at a place where there is index matching tape, fluid, or gel, the light propagates out of the first light guide plate lOOa or the second light guide plate lOOb through first major surface l02a or first major surface l02b and is reflected at the reflective layer 176 below the scattering or diffuser layer 174 and reflected back in a direction toward second major surface l04a and second major surface l04b to contribute to the luminance from the second major surface l04a of the first light guide plate lOOa or the second major surface l04b of the second light guide plate lOOb.

[00057] In certain exemplary embodiments, stack 172 may be a single stack present under the majority of the first major surface l02a of the first light guide plate lOOa and the first major surface l02b of the second light guide plate lOOb except for a small opening to make room for light source 120. In other examples, a first stack 172 may be present under the first light guide plate lOOa and a second stack 172 may be present under the second light guide plate lOOb with light source 120 between the two stacks.

[00058] FIGS. 8A-8B schematically depict exemplary stacks l72a and l72b, respectively, for the illumination device of FIG. 7. Stack l72a or l72b may be used in place of stack 172 of illumination device 170. As depicted in FIG. 8 A, stack l72a includes a scattering or diffuser layer l74a including through-holes and a reflective layer l76a, where the through-holes in scattering or diffuser layer l74a are filled with a reflective material 178. As depicted in FIG. 8B, stack l72b includes a scattering or diffuser layer l74b having a varying thickness (i.e., optical density) and a reflective layer l76b. Scattering or diffuser layer l74b modifies the luminance distribution on the second major surface l04a of the first light guide plate lOOa and on the second major surface l04b of the second light guide plate lOOb. [00059] FIGS. 9A-9C schematically depict an exemplary composite light guide plate 200. FIG. 9A is an enlarged side view of a light coupling edge of composite light guide plate 200, FIG. 9B is a top view of composite light guide plate 200, and FIG. 9C is a side view of composite light guide plate 200. Composite light guide plate 200 includes a first major surface 202, a second major surface 204 opposite to the first major surface 202, and an edge surface 210 extending between the first major surface 202 and the second major surface 204. Composite light guide plate 200 includes a first slab 218 and a second slab 220 optically coupled to the first slab 218. The refractive indices of first slab 218 and second slab 220 may be equal (e.g., 1.5). In this example, first slab 218 is directly coupled to second slab 220. In other examples, an index matching material may be positioned between first slab 218 and second slab 220 and optically couple first slab 218 to second slab 220. In yet other examples, the interface between first slab 218 and second slab 220 may include a scattering and reflector stack to aid in producing luminance uniformity.

[00060] Composite light guide plate 200 also includes a light coupling edge 206, 208 extending between the first major surface 202 and the second major surface 204 opposite to edge surface 210. The light coupling edge includes a flat surface 206 and a curved surface 208. The flat surface 206 extends from the first major surface 202 to the curved surface 208, and the curved surface 208 extends from the flat surface 206 to the second major surface 204.

[00061] In this example, first slab 218 includes the first major surface 202 and the flat surface 206 of the light coupling edge. Second slab 220 includes the second major surface 204 and the curved surface 208 of the light coupling edge. In certain exemplary embodiments, first slab 218 may be made of glass and second slab 220 may also be made of glass. In other examples, first slab 218 may be made of glass and second slab 220 may be made of PMMA, polycarbonate, or ceramic. In yet other examples, first slab 218 may be made of PMMA, polycarbonate, or ceramic and second slab 220 may be made of glass.

[00062] First slab 218 may, for example, have a thickness as indicated at 213 between about 0.2 mm and 1 mm (e.g., 0.301 mm for a 0.65 mm wide light source 120). Second slab 220 may, for example, have a thickness as indicated at 212 between about 0.5 and 1.5 mm (e.g., 1.093 mm). In certain exemplary embodiments, composite light guide plate 200 may have a length as indicated at 214 between about 5 mm and 500 mm (e.g., 400 mm), and a width as indicated at 216 between about 5 mm and 200 mm (e.g., 78 mm). In other examples, thickness 212, thickness 213, length 214, and width 216 may have other suitable values based upon the particular application.

[00063] FIG. 10 schematically depicts an embodiment of another illumination device 230. Illumination device 230 includes a first composite light guide plate 200a and a second composite light guide plate 200b. Illumination device 230 also includes a light source 120 and a stack 152 as previously described and illustrated with reference to FIG. 5. First composite light guide plate 200a and second composite light guide plate 200b are similar to composite light guide plate 200 previously described and illustrated with reference to FIGS. 9A-9C. First composite light guide plate 200a includes a first slab 218a and a second slab 220a optically coupled to the first slab 218a. Second composite light guide plate 200b includes a third slab 218b and a fourth slab 220b optically coupled to the third slab 218b.

[00064] First composite light guide plate 200a includes a first light coupling edge 206a, 208a extending between a first major surface 202a and a second major surface 204a of the first composite light guide plate 200a. Second composite light guide plate 200b includes a second light coupling edge 206b, 208b extending between a first major surface 202b and a second major surface 204b of the second composite light guide plate 200b. The second light coupling edge 206b, 208b of the second composite light guide plate 200b faces the first light coupling edge 206a, 208a of the first composite light guide plate 200a.

[00065] Light source 120 faces the first major surface 202a of the first composite light guide plate 200a and the first major surface 202b of the second composite light guide plate 200b. Light source 120 intersects the first light coupling edge 206a, 208a of the first composite light guide plate 200a and the second light coupling edge 206b, 208b of the second composite light guide plate 200b to couple light into the first composite light guide plate 200a via the first light coupling edge 206a, 208a and to couple light into the second composite light guide plate 200b via the second light coupling edge 206b, 208b.

[00066] The first light coupling edge of the first composite light guide plate 200a includes a flat surface 206a of first slab 218a extending from the first major surface 202a of the first composite light guide plate 200a and a curved surface 208a of second slab 220a extending from the flat surface 206a to the second major surface 204a of the first composite light guide plate 200a. Likewise, the second light coupling edge of the second composite light guide plate 200b includes a flat surface 206b of third slab 218b extending from the first major surface 202b of the second composite light guide plate 200b and a curved surface 208b of fourth slab 220b extending from the flat surface 206b to the second major surface 204b of the second composite light guide plate 200b. The flat surface 206a of the first composite light guide plate 200a faces the flat surface 206b of the second composite light guide plate 200b. In some embodiments, the flat surface 206a is parallel with the flat surface 206b. In certain exemplary embodiments, flat surface 206a of the first composite light guide plate 200a contacts the flat surface 206b of the second composite light guide plate 200b. In other examples, there may be a gap between the flat surface 206a of the first composite light guide plate 200a and the flat surface 206b of the second composite light guide plate 200b.

[00067] FIG. 11 schematically depicts an embodiment of another illumination device 240. Illumination device 240 is similar to illumination device 230 previously described and illustrated with reference to FIG. 10, except that in illumination device 240 a single slab 218 is used in place of first slab 2l8a and third slab 2l8b. In this example, illumination device 230 includes a composite light guide plate including a first slab 218, a second slab 220a, and a third slab 220b. Illumination device 240 also includes a light source 120 and can further include a stack 152 as previously described and illustrated with reference to FIG. 5.

[00068] First slab 218 may be rectangular and includes a first major surface 202 and a second major surface 203 opposite to first major surface 202. Second slab 220a and third slab 220b are optically coupled to the second major surface 203 of first slab 218. Second slab 220a includes a first light coupling edge including a first curved surface 208a extending from a second major surface 204a of second slab 220a toward the first major surface 202 and the second major surface 203 of first slab 218. Likewise, third slab 220b includes a second light coupling edge including a second curved surface 208b extending from a third major surface 204b of third slab 220b toward the first major surface 202 and the second major surface 203 of first slab 218. The first curved surface 208a of second slab 220a faces the second curved surface 208b of third slab 220b. Light source 120 faces the first major surface 202 to couple light into the second slab 220a via the first light coupling edge and to couple light into the third slab 220b via the second light coupling edge.

[00069] FIGS. 12A-12C schematically depict an embodiment of another composite light guide plate 300. FIG. 12A is an enlarged side view of a light coupling edge of composite light guide plate 300, FIG. 12B is a top view of composite light guide plate 300, and FIG. 12C is a side view of composite light guide plate 300. Composite light guide plate 300 includes a first major surface 302, a second major surface 304 opposite to the first major surface 302, and an edge surface 310 extending between the first major surface 302 and the second major surface 304. Composite light guide plate 300 includes a first slab 318 and a second slab 320 optically coupled to the first slab 318 at an interface 319. The refractive index of first slab 318 may be greater (e.g., 1.8) than the refractive index of second slab 320 (e.g., 1.5).

[00070] Composite light guide plate 300 also includes a light coupling edge 306, 308 extending between the first major surface 302 and the second major surface 304 opposite to edge surface 310. The light coupling edge includes a flat surface 306 and a curved surface 308. The flat surface 306 extends from the first major surface 302 to the curved surface 308, and the curved surface 308 extends from the flat surface 306 to the second major surface 304.

[00071] In this embodiment, first slab 318 includes a portion of the first major surface 302 and the flat surface 306 and the curved surface 308 of the light coupling edge. In other examples, first slab 318 may also include a portion of the second major surface 304. Second slab 320 includes a portion of the first major surface 302 and the second major surface 304. In certain exemplary embodiments, first slab 318 may be made of glass and second slab 320 may also be made of glass. The refractive indices of glass in the first slab and in the second slab may be different. In other examples, first slab 318 may be made of glass and second slab 320 may be made of PMMA, polycarbonate, or ceramic. In yet other examples, first slab 318 may be made of PMMA, polycarbonate, or ceramic and second slab 320 may be made of glass.

[00072] In certain exemplary embodiments, composite light guide plate 300 may, for example, have a thickness as indicated at 312 between about 0.5 and 1.5 mm (e.g., 1.16 mm), a length as indicated at 314 between about 5 mm and 500 mm (e.g., 400 mm), and a width as indicated at 316 between about 5 mm and 200 mm (e.g., 78 mm). In other examples, thickness 312, length 314, and width 316 may have other suitable values based upon the particular application. Compared to composite light guide plates 100 and 200 previously described above with reference to FIGS. 1A-1C and 9A-9C, respectively, composite light guide plate 300 may have a reduced thickness and weight.

[00073] FIG. 13 schematically depicts an embodiment of another illumination device 330. Illumination device 330 includes a first composite light guide plate 300a and a second composite light guide plate 300b. Illumination device 330 also includes a light source 120 and a stack 152 as previously described and illustrated with reference to FIG. 5. First composite light guide plate 300a and second composite light guide plate 300b are similar to composite light guide plate 300 previously described and illustrated with reference to FIGS. 12A-12C. First composite light guide plate 300a includes a first slab 318a and a second slab 320a optically coupled to the first slab 3 l8a. Second composite light guide plate 300b includes a third slab 318b and a fourth slab 320b optically coupled to the third slab 318b.

[00074] First composite light guide plate 300a includes a first light coupling edge 306a, 308a extending between a first major surface 302a and a second major surface 304a of the first composite light guide plate 300a. Second composite light guide plate 300b includes a second light coupling edge 306b, 308b extending between a first major surface 302b and a second major surface 304b of the second composite light guide plate 300b. The second light coupling edge 306b, 308b of the second composite light guide plate 300b faces the first light coupling edge 306a, 308a of the first composite light guide plate 300a.

[00075] Light source 120 faces the first major surface 302a of the first composite light guide plate 300a and the first major surface 302b of the second composite light guide plate 300b. Light source 120 intersects the first light coupling edge 306a, 308a of the first composite light guide plate 300a and the second light coupling edge 306b, 308b of the second composite light guide plate 300b to couple light indicated by arrows 121 into the first composite light guide plate 300a via the first light coupling edge 306a, 308a and to couple light into the second composite light guide plate 300b via the second light coupling edge 306b, 308b.

[00076] The first light coupling edge of the first composite light guide plate 300a includes a flat surface 306a of first slab 318a extending from the first major surface 302a of the first composite light guide plate 300a and a curved surface 308a of first slab 3 l8a extending from the flat surface 306a to the second major surface 304a of the first composite light guide plate 300a. Likewise, the second light coupling edge of the second composite light guide plate 300b includes a flat surface 306b of third slab 318b extending from the first major surface 302b of the second composite light guide plate 300b and a curved surface 308b of third slab 318b extending from the flat surface 306b to the second major surface 304b of the second composite light guide plate 300b. The flat surface 306a of the first composite light guide plate 300a faces the flat surface 306b of the second composite light guide plate 300b. In certain exemplary embodiments, first slab 318a and third slab 318b may be combined into a single slab.

[00077] FIGS. 14A-14B schematically depict exemplary light couplers for the illumination devices of FIGS. 15-18B described below. FIG. 14A illustrates a cross- sectional view of a light coupler 400. Light coupler 400 includes a first light coupling region 418a and a second light coupling region 418b. Each of the first and second light coupling regions 418a and 418b includes a major surface 402a and 402b, an edge surface 4l0a and 410b extending from the major surface 402a and 402b, and a curved surface 408a and 408b extending toward the edge surface 4l0a and 410b and toward the major surface 402a and 402b, respectively. The curved surface 408a of the first light coupling region 418a faces the curved surface 408b of the second light coupling region 4l8b. In this example, each of the first and second light coupling regions 418a and 418b also includes a flat surface 406a and 406b extending from the major surface 402a and 402b to the curved surface 408a and 408b, respectively. The flat surface 406a of the first light coupling region 418a faces the flat surface 406b of the second light coupling region 418b. In certain exemplary embodiments, each of the first and second light coupling regions 418a and 418b may include a further major surface (not shown) opposite to major surface 402a and 402b extending between edge surface 4l0a and 410b and curved surface 408a and 408b, respectively.

[00078] FIG. 14B illustrates a cross-sectional view of a light coupler 401. Light coupler 401 is similar to light coupler 400 previously described and illustrated with reference to FIG. 14A, except that light coupler 401 is a formed as a single component. Light coupler 401 includes a first light coupling region 418a and a second light coupling region 418b formed as a single component. Each of the first and second light coupling regions 418a and 418b includes major surface 402, an edge surface 4l0a and 41 Ob extending from the major surface 402, and a curved surface 408a and 408b extending toward the edge surface 4l0a and 41 Ob and toward the major surface 402, respectively. The curved surface 408a of the first light coupling region 418a faces the curved surface 408b of the second light coupling region 418b. In certain exemplary embodiments, each of the first and second light coupling regions 418a and 418b may include a further major surface (not shown) opposite to major surface 402 extending between edge surface 4l0a and 410b and curved surface 408a and 408b, respectively. Light coupler 401 may be used in place of light coupler 400 of FIG. 14 A.

[00079] FIG. 15 schematically depicts an embodiment of another illumination device 430. Illumination device 430 includes a light coupler 400 (alternatively, 401) and a light guide plate 432. Illumination device 430 also includes a light source 120, and optionally a stack 152, as previously described and illustrated with reference to FIG. 5. Light coupler 400 was described with reference to FIG. 14 A. Light guide plate 432 includes a first portion 434a facing the edge surface 4l0a of the first light coupling region 418a and a second portion 434b facing the edge surface 410b of the second light coupling region 4l8b. Light guide plate 432 also includes a third portion 434c extending between the first portion 434a and the second portion 434b and facing the curved surface 408a of the first light coupling region 418a and the curved surface 408b of the second light coupling region 418b.

[00080] In this embodiment, there is first interfacial space 436a between first portion 434a of light guide plate 432 and light coupler 400, a second interfacial space 436b between second portion 434b of light guide plate 432 and light coupler 400, and a third interfacial space 436c between third portion 434c of light guide plate 432 and light coupler 400. The interfacial space 436a-436c may be filled with air, vacuum, or a combination of materials. Light source 120 faces the major surface 402a of the first light coupling region 418a and the major surface 402b of the second light coupling region 418b. Light coupler 400 couples light as indicated by arrows 121 into light guide plate 432 from light source 120.

[00081] FIG. 16 schematically depicts an embodiment of another illumination device 440. Illumination device 440 is similar to illumination device 430 previously described and illustrated with reference to FIG. 15, except that illumination device 430 includes an optical interface material within the interfacial space 436a and 436b. The optical interface material may be an index matching material.

[00082] FIGS. 17A-17B schematically depict an embodiment of another illumination device 450. FIG. 17A illustrates a top view and FIG. 17B illustrates a cross-sectional view of illumination device 450. Illumination device 450 is similar to illumination device 430 previously described and illustrated with reference to FIG. 15, except that illumination device 450 includes two light couplers and a light guide plate for two light couplers. Illumination device 450 includes a first light coupler 400a, a second light coupler 400b, and a light guide plate 452. In this example, light guide plate 452 includes a first portion 434a, a second portion 434b, and a third portion 434c extending between the first portion 434a and the second portion 434b. Light guide plate 452 also includes a fourth portion 434d facing the edge surface of the second light coupling region of the second light coupler 400b. In addition, light guide plate 452 includes a fifth portion 434e extending between the fourth portion 434d and the second portion 434b and facing the curved surface of the first light coupling region and the curved surface of the second light coupling region of the second light coupler 400b. A first light source l20a faces the major surface of the first light coupling region and the major surface of the second light coupling region of first light coupler 400a. A second light source l20b faces the major surface of the first light coupling region and the major surface of the second light coupling region of second light coupler 400b.

[00083] FIGS. 18A-18B schematically depict an embodiment of another illumination device 460. FIG. 18A illustrates a top view and FIG. 18B illustrates a cross-sectional view of illumination device 460. Illumination device 460 is similar to illumination device 450 previously described and illustrated with reference to FIGS. 17A-17B, except that illumination device 460 includes four light couplers and a light guide plate for four light couplers. Illumination device 460 includes a first light coupler 400a, a second light coupler 400b, a third light coupler 400c, a fourth light coupler 400d, and a light guide plate 462. In this embodiment, light guide plate 462 includes a first portion 434a, a second portion 434b, and a third portion 434c extending between the first portion 434a and the second portion 434b. Light guide plate 462 also includes a fourth portion 434d and a fifth portion 434e extending between the fourth portion 434d and the second portion 434b. In addition, light guide plate 462 also includes a sixth portion 434f facing the edge surface of the second light coupling region of the third light coupler 400c and a seventh portion 434g extending between the sixth portion 434f and the first portion 434a and facing the curved surface of the first light coupling region and the curved surface of the second light coupling region of the third light coupler 400c. Likewise, light guide plate 462 also includes an eighth portion 434h facing the edge surface of the second light coupling region of the fourth light coupler 400d and a ninth portion 434i extending between the eighth portion 434h and the fourth portion 434d and facing the curved surface of the first light coupling region and the curved surface of the second light coupling region of the fourth light coupler 400d. A light source l20a-l20d faces the major surface of the first light coupling region and the major surface of the second light coupling region of light couplers 400a-400d, respectively.

[00084] Light guide plate 462 includes a notch 464 in the second portion 434b. In certain exemplary embodiments, notch 464 is centered within second portion 434b. Notch 464 divides illumination device 460 into two zones. A first zone is formed to the left of notch 464 and includes light couplers 400a and 400c and a second zone is formed to the right of notch 464 and includes light couplers 400b and 400d. An inter zone layer 466 may be within the notch 464. In certain exemplary embodiments, inter-zone layer 466 may be an adhesive material or a piece of glass or plastic that defines the zones and that adds additional properties such as strengthening of the light guide plate 462 and/or for absorbing stray light. In other embodiments, zone boundaries may be defined by indentations, breaks, or structures in light guide plate 462 or by the addition of materials into light guide plate 462 by diffusion or other suitable mechanisms. Any physical void used to define a zone boundary may be filled with a combination of materials. While two zones are illustrated in FIGS. 18A- 18B, in other examples the number of zones may vary and the number of light couplers and light sources within each zone may vary.

[00085] FIG. 19 schematically depicts an embodiment of another illumination device 500. Illumination device 500 is similar to illumination device 150 previously described and illustrated with reference to FIG. 5, except that illumination device 500 includes a reflective layer 502. Illumination device 500 includes a first light guide plate lOOa, a second light guide plate lOOb, a light source 120, and a stack 152 as previously described. Reflective layer 502 is arranged on the curved surface l08a of the first light guide plate lOOa and on the curved surface l08b of the second light guide plate lOOb. Reflective layer 502 may also be arranged on a portion of second major surface l04a of the first light guide plate lOOa and on a portion of second major surface l04b of the second light guide plate lOOb.

[00086] Reflective layer 502 prevents light from escaping from along the curved surface l08a and the flat surface l06a of the first light guide plate lOOa and the curved surface l08b and the flat surface l06b of the second light guide plate lOOb. In addition, reflective layer 502 may reflect any light passing between first light guide plate lOOa and second light guide plate lOOb from light source 120 back into first light guide plate lOOa or second light guide plate lOOb. Reflective layer 502 may be optimized for reflectivity and absorptivity to maximize brightness homogenization of illumination device 500.

[00087] FIG. 20 schematically depicts an embodiment of another illumination device 510. Illumination device 510 is similar to illumination device 150 previously described and illustrated with reference to FIG. 5, except that illumination device 510 includes a reflective layer or stack 512. Illumination device 510 includes a first light guide plate lOOa, a second light guide plate lOOb, a light source 120, and a stack 152 as previously described. Reflective layer or stack 512 is arranged over the curved surface l08a of the first light guide plate lOOa and over the curved surface l08b of the second light guide plate lOOb. Reflective layer or stack 512 may also be arranged over a portion of second major surface l04a of the first light guide plate lOOa and over a portion of second major surface l04b of the second light guide plate lOOb. In certain exemplary embodiments, reflective layer or stack 512 is a stand-alone reflective layer. In other embodiments, reflective layer or stack 512 is a stack including a reflective layer and a scattering or diffuser layer.

[00088] Reflective layer or stack 512 prevents light from escaping from along the curved surface l08a and the flat surface l06a of the first light guide plate lOOa and the curved surface l08b and the flat surface l06b of the second light guide plate lOOb. In addition, reflective layer or stack 512 may reflect any light passing between first light guide plate lOOa and second light guide plate lOOb from light source 120 back into first light guide plate lOOa or second light guide plate lOOb. Reflective layer or stack 512 may be optimized for reflectivity and absorptivity to maximize brightness homogenization of illumination device 510. [00089] FIG. 21 schematically depicts an embodiment of another illumination device 520. Illumination device 520 is similar to illumination device 150 previously described and illustrated with reference to FIG. 5, except that illumination device 520 includes four light guide plates in a stacked configuration. Illumination device 520 includes a first light guide plate lOOa, a second light guide plate lOOb, a light source 120, and a stack 152 as previously described. In addition, illumination device 520 includes a third light guide plate lOOc stacked on first light guide plate lOOa and a fourth light guide plate lOOd stacked on second light guide plate lOOb.

[00090] In certain exemplary embodiments, a scattering or diffuser layer and/or a reflective layer (not shown) may be inserted between the first light guide plate lOOa and the third light guide plate lOOc and between the second light guide plate lOOb and the fourth light guide plate lOOd. Third light guide plate lOOc and fourth light guide plate lOOd prevent light from escaping from along the curved surface l08a and the flat surface l06a of the first light guide plate lOOa and the curved surface l08b and the flat surface l06b of the second light guide plate lOOb. In addition, third light guide plate lOOc and fourth light guide plate lOOd may prevent the escape of any light passing between first light guide plate lOOa and second light guide plate lOOb from light source 120.

[00091] FIGS. 22A-22B schematically depict an embodiment of another illumination device 600. Illumination device 600 may be used as a backlight for a large (e.g., 65 inch) display. In examples, illumination device 600 can have a length as indicated at 610 of about 0.8 m and a width as indicated at 612 of about 1.4 m. Illumination device 600 can be divided into six tiles 602 arranged in three columns and two rows. In various examples, each tile 602 may include a printed circuit board and have a length as indicated at 616 of about 0.4 m and a width as indicated at 614 of about 0.467 m. Each tile 602 can include three zones 604, where each zone is a l-D dimmable zone. As illustrated in FIG. 22B, each zone 604 can include two light guide plates 606 and a plurality of light sources (e.g., LEDs) 608 along the interface between the two light guide plates 606. Light guide plates 606 and light sources 608 may be configured similarly to any of the illumination devices previously described herein to form each zone 604.

[00092] FIG. 23 schematically depicts an exemplary LCD display 700. LCD display 700 includes a backlight 702 and a LCD panel 704. Backlight 702 supplies light to LCD panel 704 and may include any of the illumination devices previously described herein arranged in any suitable number of zones. LCD panel 704 includes a stack including a polarizer layer, a thin film transistor backplane, a liquid crystal layer, a color filter layer, an analyzer layer, and cover glass. In other examples, backlight 702 may be used to supply light to other types of displays or used as a stand-alone light source.

[00093] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.