Optical coupling device for coupling light into a display panel - Patents.com

Abstract

An optical coupling device for use in a display device, the optical coupling device including a transparent plate having a plurality of bridge structures configured to direct light from a light source positioned adjacent an edge surface of the transparent plate to a display panel attached to the transparent plate.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63 / 336,580, filed April 29, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] (Technical field) The present invention relates to a light coupling device for illuminating a display panel, and more particularly to a transparent plate having a plurality of bridge structures configured to couple light from one or more light sources through the transparent plate to an adjacent display panel. [Background technology]

[0003] Liquid crystal display (LCD) devices (e.g., televisions, computer monitors, etc.) are used in optical devices large and small. Several classes of LCD display devices are available. In one class, the display device includes a display panel and a backlight unit that illuminates the display panel. The display panel comprises liquid crystal material and other layers (various electrodes, color filters, etc.) disposed between two glass substrates. The backlight unit comprises a light guide plate and a light source. Light from the light source is coupled into the light guide plate, e.g., an edge surface of the light guide plate, extracted from the light guide plate, and redirected towards the display panel. By varying the properties of the liquid crystal material, the light from the backlight can be modulated to form an image that is emitted from the display panel. The image can be viewed from one side of the display panel.

[0004] The second category includes display devices in which an image can be viewed from both sides of the display device (dual-view transparent display devices). Such display devices are sometimes called transparent display devices. In transparent display devices, a liquid crystal material can be sandwiched between two transparent plates, and the liquid crystal layer acts as a light guide without the need for a separate backlight unit. By locally changing the light scattering properties of the liquid crystal material at pixel locations, the light trapped in the light guide plate by total reflection can be extracted from the light guide plate to form an image. This transparent liquid crystal display device has high transparency, does not require special light sources (such as polarized and / or collimated light sources), and provides dual-viewing of the displayed image. However, because the liquid crystal material functions as part of the light guide plate, this type of display may suffer from poor uniformity of display brightness, as well as limited display size. Summary of the Invention [Means for solving the problem]

[0005] Disclosed herein is a display device that can exhibit high brightness uniformity, which facilitates increasing the display size while allowing two-sided viewing of an image. More specifically, the display device includes at least one transparent plate, e.g., a transparent glass plate, from which a plurality of bridge structures extend and are configured to be attached to a display panel, e.g., by adhesive. The bridge structures are protrusions, e.g., columnar structures (e.g., formed of the transparent plate material), integral with the transparent plate, or a material, e.g., an optically clear adhesive, deposited on the transparent plate. The protrusions can have a regular, e.g., geometric, cross-sectional shape, such as a circular cross-sectional shape, an elliptical cross-sectional shape, or a polygonal cross-sectional shape, in a plane perpendicular to its longitudinal axis (and perpendicular to the first major surface of the transparent plate). The bridge structures can be discrete bridge structures, e.g., discrete features, e.g., individual drops of a material different from the material of the transparent plate. Such discrete features can be formed of a polymeric material or can be drops of an optically clear adhesive. In another embodiment, the bridge structures can be remnants of material removal or replacement from the surface of the transparent substrate itself. In yet another embodiment, the bridge structures can include protrusions from a layer, such as a layer of optically clear adhesive, coated on the transparent plate to bond the bridge structures together. A transparent plate with bridge structures can be used to couple light from a light source into a display panel, thereby illuminating the display panel.

[0006] Accordingly, in a first aspect, a light coupling device for coupling light from a light source into a display panel is disclosed, the light coupling device comprising a transparent plate including a first major surface and a second major surface opposite the first major surface, the transparent plate further comprising a plurality of edge surfaces connecting the first and second major surfaces. Extending from the second major surface of the transparent plate are a plurality of bridge structures, each bridge structure having a length L defined between a reference plane from which the plurality of bridge structures extend and a distal end of the bridge structure furthest from the reference plane, the length L being in a range of about 2 micrometers to about 200 micrometers.

[0007] In a second aspect, the plurality of edge surfaces include a first edge surface and a second edge surface opposite the first edge surface, e.g., parallel to the first edge surface, and the plurality of bridge structures include a first set of bridge structures positioned along a first axis extending between the first edge surface and the second edge surface, and a distance separating adjacent bridge structures of the first set of bridge structures along the first axis can decrease in a direction from the first edge surface toward the second edge surface.

[0008] In a third aspect, the plurality of bridge structures of the second aspect can include a second set of bridge structures positioned along the first axis, and a distance separating adjacent bridge structures of the second set of bridge structures can decrease in a direction from the second edge surface toward the first edge surface.

[0009] In a fourth aspect, the plurality of edge surfaces of the third aspect include a third edge surface and a fourth edge surface opposite the third edge surface, e.g., parallel to the third edge surface, and the plurality of bridge structures include a third set of bridge structures positioned along a second axis extending between the third edge surface and the fourth edge surface, and a distance separating adjacent bridge structures of the third set of bridge structures can decrease in a direction from the third edge surface toward the fourth edge surface.

[0010] In a fifth aspect, the plurality of bridge structures of the fourth aspect includes a fourth set of bridge structures positioned along the second axis, wherein the distance separating adjacent bridge structures of the fourth set of bridge structures decreases in a direction from the fourth edge surface toward the third edge surface.

[0011] In a sixth embodiment, the first edge surface can be orthogonal to the third edge surface.

[0012] In a seventh aspect, a cross-sectional shape of the bridge structures of the plurality of bridge structures in a plane parallel to the first main surface can include a circle, an ellipse, or a polygon.

[0013] In the seventh aspect, the maximum width of each bridge structure in a plane parallel to the first main surface can be in the range of about 10 micrometers to about 50 millimeters.

[0014] In a ninth aspect, the maximum width can vary along the length of each bridge structure.

[0015] In a tenth aspect, the maximum width of each bridge structure may be greater at the distal end than at the reference plane.

[0016] In an eleventh aspect, the plurality of bridge structures can include an optically clear adhesive.

[0017] In a twelfth embodiment, the optically clear adhesive can include a coating layer disposed on the second major surface of the transparent plate.

[0018] In a thirteenth aspect, the reference surface may be the second major surface of the transparent plate.

[0019] In a fourteenth aspect, the reference surface may be a surface of a transparent plate recessed from the second main surface.

[0020] In a fifteenth aspect, the reference surface of the twelfth aspect can include a concave surface of the coating layer.

[0021] In the sixteenth aspect, the maximum thickness of the transparent plate can be in the range of about 0.1 mm to about 5 mm.

[0022] In the seventeenth embodiment, the refractive index of the transparent plate can be in the range of about 1.35 to about 1.65.

[0023] In an eighteenth embodiment, the transparent plate can be attached to a glass substrate that is bonded to a plurality of bridge structures.

[0024] In a nineteenth aspect, the plurality of bridge structures can be disposed within a host material, and the refractive index of the host material can be at least about 10% less than the refractive index of the bridge structures.

[0025] In a twentieth embodiment, the refractive index of the bridge structure can differ from the refractive index of the transparent plate by less than about 10%.

[0026] The foregoing summary and the following detailed description present embodiments that are intended to provide an overview or framework for understanding the nature and features of the embodiments disclosed herein. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the present disclosure, and together with the description explain the principles and operation of the present disclosure. [Brief description of the drawings]

[0027] [Figure 1] FIG. 2 is a cross-sectional end view of a single-sided liquid crystal display device. [Diagram 2] 1 is a cross-sectional side view of an exemplary dual-view liquid crystal display device according to the present disclosure. [Diagram 3] 3 is an enlarged cross-sectional end view of a portion of the display device of FIG. 2 showing a bridge structure. [Figure 4] 1 is a cross-sectional end view of an exemplary dual-sided liquid crystal display device in which a bridge structure layer is applied to the surface of a transparent plate according to the present disclosure. [Diagram 5] 1 is a cross-sectional end view of an exemplary dual-view liquid crystal display device having a bridge structure on a surface of a transparent plate, the bridge structure comprising discrete members applied to the surface of the transparent plate, in accordance with the present disclosure. [Figure 6] 6 is an enlarged cross-sectional end view of a portion of the display device of FIG. 5 showing the discrete bridge structure layer applied to the transparent plate. [Figure 7] FIG. 2 is a cross-sectional end view of an exemplary dual-sided liquid crystal display device according to the present disclosure, in which a bridge structure layer is applied to the surface of a transparent plate, the bridge structure comprising discrete members applied to the surface of the transparent plate. [Figure 8] 6 is an enlarged cross-sectional end view of a portion of the display device of FIG. 5 showing a bridge structure layer applied to a transparent plate, the bridge structure layer comprising a base layer and a bridge structure. [Figure 9] 1 is a top view of an exemplary bridge structure cross-section in a plane parallel to the surface of the transparent plate. [Figure 10]1A is a cross-sectional end view of an exemplary bridge structure in which the width of the bridge structure varies along the length of the bridge structure. FIG. [Figure 11] 1 is a diagram of an exemplary transparent plate according to the present disclosure showing a pattern of bridge structures on the surface of the transparent plate and the varying spacing between the bridge structures as a function of distance from the light coupling side edge of the transparent plate. [Figure 12] 1 is a cross-sectional end view of an exemplary display device comprising a transparent plate with two light sources disposed along two light-coupling edge surfaces of the transparent plate illuminating a bridge structure. [Figure 13] 1 is a diagram of an exemplary transparent plate according to the present disclosure showing a pattern of bridge structures on the surface of the transparent plate and the varying spacing between the bridge structures as a function of distance from the two light-coupling side edges of the transparent plate. [Figure 14] 1 is a diagram of an exemplary transparent plate according to the present disclosure showing a pattern of bridge structures on the surface of the transparent plate and the varying spacing between the bridge structures as a function of distance from the three light-coupling side edges of the transparent plate. [Figure 15] 1 is a diagram of an exemplary transparent plate according to the present disclosure showing a pattern of bridge structures on the surface of the transparent plate and the varying spacing between the bridge structures as a function of distance from the four light-coupling side edges of the transparent plate. [Figure 16] FIG. 2 is a cross-sectional end view of an exemplary display device comprising two transparent plates attached to a display panel, each transparent plate illuminated with a light source disposed along a corresponding light-coupling edge surface of the transparent plate. [Figure 17] FIG. 2 is a cross-sectional end view of an exemplary display device comprising two transparent plates attached to a display panel, each illuminated with a light source disposed along opposing light-coupling edge surfaces of the transparent plates. [Figure 18] FIG. 2 is a cross-sectional end view of an exemplary display device comprising two transparent plates attached to a display panel, each transparent plate illuminated by two opposing light sources positioned along corresponding light-coupling edge surfaces of the transparent plates. [Figure 19]21 is a graph of normalized luminance obtained from the display device of FIG. 20 showing the luminance uniformity across the dimension of the display panel of the display device perpendicular to the light coupling edge surface. [Figure 20] FIG. 2 is a cross-sectional end view of an exemplary display device on which a dual-view display device without a bridge structure is modeled. [Figure 21] FIG. 21 is a graph of measured normalized luminance from the display device of FIG. 20 and modeled luminance for a comparable display device as a function of distance along the X-axis, showing good agreement between measured and modeled luminance across the X-dimension of the display panel of the display device perpendicular to the light coupling edge surface. [Figure 22] 1 is a cross-sectional end view of an exemplary display device with a display panel having a first transparent plate that includes a bridge structure and a second transparent plate that does not have a bridge structure. [Diagram 23] 23 is a graph showing the spacing between individual bridge structures along an X-axis orthogonal to the light-coupling edge surface of the display device of FIG. 22 as a function of the number of bridge structures along the X-axis. [Figure 24] 23 is a graph comparing the light intensity in a first image plane of the display device of FIG. 22 with the light intensity in the image plane of the display device of FIG. 20 as a function of distance along the X-axis. [Diagram 25] 23 is a graph comparing the light intensity in a second image plane of the display device of FIG. 22 with the light intensity in the image plane of the display device of FIG. 20 as a function of distance along the X-axis. [Figure 26] 23 is a graph comparing the light intensity at the centre of the liquid crystal material of the display device of FIG. 22 with the light intensity at the image plane of the display device of FIG. 20 as a function of distance along the X-axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0029] As used herein, the term "about" means that quantities, sizes, compositions, parameters, and other quantities and characteristics are not, or need not be, exact, but are approximate and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding, measurement errors, and the like, as well as other factors known to those of ordinary skill in the art.

[0030] 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 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 further be understood that the endpoints of each range are significant in relation to the other endpoint, and independently of the other endpoint.

[0031] Directional terms used herein, e.g., up, down, right, left, front, back, top, bottom, are merely used with reference to the figures and do not imply absolute orientation.

[0032] Unless expressly stated otherwise, no method described herein should be construed as requiring that its steps be performed in a particular order, nor should any apparatus be construed as requiring a particular orientation. Thus, if a method claim does not actually recite an order that its steps are to be followed, or if any apparatus claim does not actually recite an order or orientation for individual components, or if the claims or specification do not otherwise clearly state that the steps are to be limited to a particular order, or if no particular order or orientation for the apparatus components is recited, no order or orientation is to be implied in any respect. This applies to all possible implicit criteria for interpretation, including logical matters regarding the arrangement of steps, operational flow, order of components, or orientation of components, general meaning derived from grammatical constructions or punctuation, and the number or type of embodiments described in the specification.

[0033] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "an element" includes aspects having two or more such elements unless the context clearly dictates otherwise.

[0034] As used herein, the terms "exemplary," "example," or various forms thereof, mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" or "example" is not to be construed as preferred or advantageous over other aspects or designs. Moreover, examples are provided merely for clarity and understanding and are not meant to restrict or limit in any way the disclosed subject matter or relevant portions of this disclosure. It can be understood that countless additional or alternative examples of varying scope could have been presented, but have been omitted for the sake of brevity.

[0035] As used herein, the terms "comprises" and "including," and variations thereof, unless otherwise indicated, shall be construed as synonymous and non-limiting. A list of elements following the transitional phrase "comprises" or "including" is a non-exclusive list, such that there may be elements other than those specifically recited in the list.

[0036] As used herein, the terms "substantial," "substantially," and variations thereof, are intended to describe a described characteristic being equal or nearly equal to a value or description. For example, a "substantially planar" surface describes a surface that is planar or nearly planar. Furthermore, "substantially" is intended to indicate that two values ​​are equal or nearly equal. In some embodiments, "substantially" can describe values ​​that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0037] As used herein, the term "transparent" or variations thereof when used in the context of an article of manufacture (e.g., a plate, substrate, or other article or portion thereof) means that the transmittance of electromagnetic radiation (e.g., light) by the article material is about 50% or greater over 100 millimeters (mm) in the wavelength range of 400 nanometers (nm) to 700 nm as measured with an optical power meter.

[0038] 1 shows a liquid crystal transparent display device 10 configured to display an image. The display device 10 comprises a liquid crystal display panel 12 and a polarized backlight unit (BLU) 14. The BLU 14 is typically spaced apart from the display panel 12 by a gap. The display panel 12 includes a liquid crystal material 20 sandwiched between a first glass substrate 22 and a second glass substrate 24. The display panel 12 may further comprise a transparent electrode 26, a pixel electrode 28, and a thin film transistor 30 to facilitate control of the liquid crystal material at individual pixel locations. The display device 10 may further comprise a polarizer 18 positioned above the viewer-facing surface of the display panel.

[0039] The BLU 14 comprises a light source 32, for example formed of one or more light emitting diodes (LEDs), and a light guide plate (LGP) 34 configured to receive light from the light source 32 through at least one edge surface of the light guide plate (LGP) 34 and distribute the light to the adjacent surface of the display panel 12. The BLU 14 may further comprise a polarizer 36 positioned between the light source 32 and the LGP 34 to linearly polarize the light from the light source. The light coupled into the LGP 34 from at least one edge surface of the LGP 34 converts the illumination from the light source, for example a one-dimensional (1D) linear array of LEDs, into two-dimensional (2D) area illumination. Light can be extracted from the LGP 34 by adding a light extractor to one or both sides of the LGP that prevents total internal reflection of the light guided into the LGP. The extracted light then passes through the liquid crystal layer 20 where the phase of the light is modulated, and then passes through the polarizer 18 where the phase modulation is converted to intensity modulation. The viewed image is formed on one side of the display panel 12, as shown by viewer 38. Because the BLU is physically separated from the liquid crystal layer 20, this class of liquid crystal display allows for large display sizes. However, the separation of the BLU and the display panel can make it difficult to reduce the thickness of the display device. Additionally, the need for polarizers can limit the transparency of the display panel to less than about 50%.

[0040] Described herein is a liquid crystal display device that allows two-sided viewing of the display device, where a bridge structure is introduced into the transparent liquid crystal display device to couple light from one or more edge-lit transparent plates to illuminate the display panel on one side. The bridge structure is a protrusion that extends outward from the transparent plate and extends between the transparent plate and the display panel. The embodiments herein can allow two-sided viewing of images with high brightness uniformity. Such designs further enable thin and large displays. The width can range, for example, from about 25 millimeters (mm) to about 250 mm, and the length can range from about 15 mm to about 150 mm. The disclosed edge-lit transparent liquid crystal display does not require special light sources such as polarized light sources and / or collimated light sources (narrow output angular distribution).

[0041] FIG. 2 is a cross-sectional end view of an exemplary display device 100 including a transparent plate 102 attached to and optically coupled to a display panel 104 similar to display panel 12. The display panel 104 includes a first glass substrate 22 and a second glass substrate 24, as described above. A liquid crystal layer 20, e.g., a polymer dispersed liquid crystal (PDLC) material, is sandwiched between the first and second glass substrates. A typical PDLC material includes microdroplets of low molecular weight nematic liquid crystal dispersed in a polymer film. The polymer film can be, for example, poly(vinyl alcohol), poly(vinyl acetate), or an acrylic copolymer. The display panel 104 further includes a transparent electrode 26 (e.g., indium tin oxide, ITO) disposed on the first glass substrate 22, pixel electrodes 28 disposed on the second glass substrate 24, and thin film transistors 30 that facilitate control of the scattering properties of the liquid crystal material at individual pixel locations. Light from a light source 32, e.g., an array of LEDs, is coupled into the transparent plate 102 through an edge surface thereof, converting the light from the 1D light source into 2D surface illumination of the display panel 104. However, unlike the display device 10 shown in FIG. 1, no polarizer 18 is required, and the displayed image is formed by modifying the local light scattering properties of the liquid crystal material at each pixel location. Compared to the previous liquid crystal transparent display, the transparent liquid crystal display of FIG. 2 can have a higher transparency (e.g., about 50% or more) than the display device embodied in FIG. 1, for example, allowing two-sided viewing of the displayed image. As used hereinafter, the edge surface of the transparent plate through which the light from the light source 32 is coupled is referred to as the light coupling edge surface.

[0042] The transparent plate 102 functions to distribute light across the adjacent display panel surface, and therefore functions as a light guide plate. The material of the transparent plate 102 is selected to have a refractive index close to that of the adjacent liquid crystal display panel substrates, for example, within about 10% of the refractive index of the display panel substrates 22 and / or 24. For example, the transparent plate 102 can be a glass plate including a silicate glass, such as borosilicate glass, aluminoborosilicate glass, alkali aluminoborosilicate glass, alkali-free aluminoborosilicate glass, or any other suitable silicate glass, although non-silicate glasses are also contemplated within the transparency and refractive index constraints discussed above.

[0043] The refractive index of the transparent plate 102 can be in the range of about 1.35 to about 1.65 at 590 nm, for example, in the range of about 1.36 to about 1.65, in the range of about 1.38 to about 1.65, in the range of about 1.40 to about 1.65, in the range of about 1.45 to about 1.65, in the range of about 1.50 to about 1.65, in the range of about 1.55 to about 1.65, in the range of about 1.60 to about 1.65, in the range of about 1.35 to about 1.6, in the range of about 1.35 to about 1.55, in the range of about 1.35 to about 1.5, in the range of about 1.35 to about 1.45, in the range of 1.35 to about 1.40, in the range of about 1.35 to about 1.39, in the range of about 1.38 to about 1.38, in the range of about 1.37, or in the range of about 1.35 to about 1.36 (including all ranges and subranges therebetween).

[0044] The transparent plate 102 includes a first major surface 106, a second major surface 108 opposite the first major surface 106, and a number of bridge structures 110 that aid in coupling light from the transparent plate to the display panel 104. The first major surface 106 and the second major surface 108 may be parallel surfaces. The first major surface 106 may be a flat surface with no protrusions or recesses (depressions) formed therein. The first main surface 106 and the second main surface 108 define a maximum thickness Tm (see FIG. 3 ) therebetween that is in the range of about 0.1 mm to about 5 mm, for example, in the range of about 0.1 mm to about 4 mm, in the range of about 0.1 mm to about 3 mm, in the range of about 0.1 mm to about 2 mm, in the range of about 0.1 mm to about 1 mm, in the range of about 0.1 mm to about 0.5 mm, in the range of about 0.2 mm to about 5 mm, in the range of about 0.3 mm to about 5 mm, in the range of about 0.4 mm to about 5 mm, in the range of about 0.5 mm to about 5 mm, in the range of about 0.6 mm to about 5 mm, in the range of about 0.7 mm to about 5 mm, in the range of about 0.8 mm to about 5 mm, in the range of about 0.9 mm to about 5 mm, in the range of about 1 mm to about 5 mm, in the range of about 2 mm to about 5 mm, in the range of about 3 mm to about 5 mm, or in the range of about 4 mm to about 5 mm (including all ranges and subranges therebetween).

[0045] As further shown in FIGS. 2-3, the bridge structure 110 can be monolithically, e.g., integrally, formed such that the bridge structure 110 is continuous with and formed of the same material as the non-bridge structure portions of the transparent plate 102. As shown in FIGS. 2 and 3, the bridge structure 110 can be etched or molded into the transparent plate 102. For example, the transparent plate 102 can be patterned with a resist material and the transparent plate can be etched (e.g., acid etched or plasma etched) to create the bridge structure 110. In another embodiment, the transparent plate 102 can be patterned using photolithography and subsequently etched. Wet or dry etching (e.g., plasma etching) can be used. In some embodiments, the bridge structure can be machined into the transparent plate surface. The transparent plate 102 can be bonded to the display panel 104 with an adhesive 112. For example, the adhesive 112 can be disposed between the transparent plate 102 and the display panel 104, such as between a distal end of the bridge structure 110 and the display panel 104.

[0046] However, the bridge structures 110 can be deposited on the surface of the transparent plate 102, for example as discrete bridge structures 110. Thus, the bridge structures 110 can be formed from a material different from that of the transparent plate 102. FIG. 5 is a top view of the transparent plate 102 showing a plurality of discrete bridge structures 110 deposited on the second major surface 108, and FIG. 6 is an enlarged cross-sectional view of one such bridge structure. Deposition of the bridge structures 110 can be achieved, for example, by screen printing a transparent bridge structure on the surface (e.g., the second major surface 108) of the transparent plate 102 as shown in FIGS. 4-6. In another example, the bridge structures 110 can be inkjet printed on the surface.

[0047] The bridge structures 110 may comprise a sheet of material 114 including a base layer 116 of thickness Tb and a plurality of bridge structures 110 extending from a surface 118 of the base layer 116, as shown in Figures 7-8, and may be integral with the sheet of material 114. The sheet 114 may be formed, for example, by microreplication, in which case the bridge structures 110 may be embossed into the sheet 114. The sheet 114 may be a polymeric material, for example a transparent polymeric material.

[0048] If the bridge structure 110 is formed of a material different from that of the transparent plate (or display panel), for example, formed as a discrete bridge structure or deposited using a sheet 114, the refractive index of the bridge structure material should be close to that of the transparent plate (or display panel substrate), for example, within 10% of the refractive index of the transparent plate, for example, within about 8%, within about 6%, within about 5%, within about 4%, within about 3%, within about 2%, or within about 1%. The material 120 surrounding the bridge structure can be air or another material having a refractive index at least 10% lower, for example at least 12% lower, at least 14% lower, at least 16% lower, or at least 20% lower than that of the bridge structure material to preserve the light-guiding performance of both the transparent plate 102 and the bridge structure 110. For example, the surrounding material 120 can be a polymeric material selected to have a refractive index at least 10% lower than that of the bridge structure material. The materials of the transparent plate 102, bridge structure 110, and material 120 surrounding the bridge structure can be selected to be transparent at visible wavelengths (i.e., the absorption of electromagnetic radiation (e.g., light) by the material is 50% or less over 100 millimeters (mm) in the wavelength range of 400 nanometers (nm) to 700 nm as measured with an optical power meter at about 350 nm to about 700 nm). As mentioned above, the transparent plate 102 can be formed of a glass material.

[0049] The bridge structures 110 can have a variety of cross-sectional shapes and sizes. Figure 9 shows examples of cross-sectional shapes of the bridge structures 110 in a plane parallel to the first major surface 106 of the transparent plate 102. By way of example, the cross-sectional shape of the bridge structures can be circular (a), elliptical or oval (b), or polygonal (e.g., rectangular (c), square (d), hexagonal (e), octagonal (f), etc.). However, the individual bridge structures need not have a regular geometric cross-sectional shape, but instead may be irregularly shaped.

[0050] Each bridge structure disposed between the transparent plate and another article, e.g., a liquid crystal display panel, has a length L defined between a reference plane and a distal end 130 of the bridge structure furthest from the reference plane. When the bridge structure 110 is integral with the transparent plate, as shown in FIG. 3, the reference plane can be a concave surface 132 of the transparent plate 102. When the bridge structure 110 is a discrete feature deposited on the transparent plate 102, as shown in FIGS. 5-6, the reference plane is a major surface of the transparent plate from which the discrete bridge structure extends, e.g., the second major surface 108. Referring to FIG. 3, which shows the bridge structure 110 integral with the transparent plate, the concave surface of the transparent plate is the result of a subtractive process. That is, the transparent plate material has been removed or replaced, e.g., by an etching process, a machining process, an embossing process, or a different material replacement process. Thus, the length (e.g., height) L of the bridge structure 110 is a portion of the maximum thickness Tm of the transparent plate 102. Thus, the length L of the bridge structure that is integral with the transparent plate is determined from the concave surface 132 of the transparent plate to the distal end 130 that corresponds to the second major surface 108 of the transparent plate 102 .

[0051] On the other hand, as shown in FIG. 6, when the bridge structures are discrete and each bridge structure is deposited on the second major surface 108 of the transparent plate, the reference plane corresponds to the second major surface 108, and the length L of the bridge structure 110 is the distance from the reference plane (the second major surface 108) to the distal end 130 of the bridge structure that is furthest from the reference plane.

[0052] Further, as shown in Figures 7-8, when the bridge structure comprises a sheet of material (e.g., formed by a microreplication process), the reference plane is the surface of the base layer 116 from which the bridge structure extends, and the length L of the bridge structure is defined between the surface of the base layer 116 from which the bridge structure extends and the distal end 130 of the bridge structure (the end furthest from the reference plane). It can thus be seen that the definition of the reference plane from which the length L of the bridge structure is determined depends on the nature of the bridge structure, i.e., whether the bridge structure is integral with the transparent plate or deposited on the transparent plate. However, as is evident from the previous examples, it should also be understood that the absolute length L (relative to the reference plane) of the bridge structure can be equivalent in each of the situations described, the difference being what constitutes the reference plane.

[0053] The length L of the bridge structure defined between the reference plane and the distal end of the bridge structure can range from a few micrometers (eg, about 2 micrometers) to about 200 micrometers. The length L can be, for example, in the range of about 5 μm to about 200 μm, about 10 μm to about 200 μm, about 20 μm to about 200 μm, about 40 μm to about 200 μm, about 60 μm to about 200 μm, about 80 μm to about 200 μm, about 2 μm to about 180 μm, about 2 μm to about 160 μm, about 2 μm to about 140 μm, about 2 μm to about 120 μm, about 2 μm to about 100 μm, about 2 μm to about 80 μm, about 2 μm to about 60 μm, about 2 μm to about 40 μm, about 2 μm to about 20 μm, about 2 μm to about 10 μm, or about 2 μm to about 5 μm (including all ranges and partial ranges therebetween).

[0054] On the other hand, Figures 3, 6, and 8 show bridge structures with a uniform width (in a single plane perpendicular to the first major surface 106, which divides the transparent sheet into two halves of equal maximum width). For example, with reference to Figure 9(e), the width W of each bridge structure may vary along the length L of the bridge structure, as shown in Figure 10 (representing a unitary bridge structure). The maximum cross-sectional width Wm of the bridge structure in a plane parallel to the first main surface 106 of the transparent plate 102 is in the range of about 10 micrometers to about 50 mm, for example, in the range of about 10 μm to about 30 mm, in the range of about 10 μm to about 20 mm, in the range of about 10 μm to about 10 mm, in the range of about 10 μm to about 5 mm, in the range of about 10 μm to about 1 mm, in the range of about 10 μm to about 500 μm, in the range of about 10 μm to about 150 μm, in the range of about 10 μm to about 100 μm, in the range of about 10 μm to about 50 μm, or in the range of about 10 μm to about 25 μm. The thickness of the nanoparticles may be in the range of about 20 μm to about 50 mm, about 40 μm to about 50 mm, about 60 μm to about 5 mm, about 80 μm to about 50 mm, about 100 μm to about 50 mm, about 200 μm to about 50 mm, about 250 μm to about 50 mm, about 500 μm to about 50 mm, about 1 mm to about 50 mm, about 5 mm to about 50 mm, or about 10 mm to about 50 mm, or about 25 mm to about 50 mm (including all ranges and partial ranges therebetween).

[0055] Referring now to FIG. 11, the distribution of bridge structures 110 may be regular (e.g., aligned in rows and columns) on the transparent plate 102, as shown in FIG. 5, or the bridge structures may be randomly or pseudo-randomly distributed. To provide uniform or substantially uniform illumination of the display panel 104, the distribution of bridge structures may be varied as a function of distance from the edge where light from the light source is coupled out ("light-coupling edge surface"). For example, as shown in FIG. 11, the spacing dX between adjacent bridge structures in a direction perpendicular to the light-coupling edge surface 150a (i.e., from the light-coupling edge surface 150a toward the edge surface 150b) decreases with increasing distance from the light-coupling edge surface 150a to compensate for the attenuation of optical power with propagation distance. However, the display device is not limited to a single light source or a single light-coupling edge surface. As used herein, "adjacent bridge structures" refers to two bridge structures spaced apart from each other, with no other bridge structures disposed between the two bridge structures on an axis extending between the two adjacent bridge structures.

[0056] As an example, Fig. 12 shows a display device 100 with two light sources 32, one light source 32a disposed adjacent to a first light-coupling edge surface 150a, and a second light source 32b positioned adjacent to a second light-coupling edge surface 150b opposite the first light-coupling edge surface 150a. As shown in Fig. 13, the spacing dX between adjacent bridge structures of the display device 100 illuminated by the two light sources 32a, 32b decreases in the direction from the first light-coupling edge surface 150a to the second light-coupling edge surface 150b, i.e., in the direction perpendicular to the light-coupling edge surface 150a. Moreover, the spacing dX between adjacent bridge structures decreases in the direction from the second light-coupling edge surface 150b to the first light-coupling edge surface 150a. The effect of the spacing dX between adjacent bridge structures decreasing in two opposite directions is that the spacing dX between adjacent bridge structures in the direction from the first light-coupling edge surface 150a toward the second light-coupling edge surface 150b first decreases as the distance from the light-coupling edge surface 150a increases, and then increases as the distance from the first light-coupling edge surface 150a continues to increase. Similarly, the spacing dX between adjacent bridge structures in the direction from the second light-coupling edge surface 150b toward the first light-coupling edge surface 150a first decreases as the distance from the second light-coupling edge surface 150b increases, and then increases as the distance from the second light-coupling edge surface 150b continues to increase. As a result, the spacing dX between adjacent bridge structures is smallest in the central region of the transparent plate (along an axis perpendicular to the first and second light-coupling edge surfaces 150a, 150b) and increases as the distance from either the opposing first or second light-coupling edge surface decreases. The spacing dY between the bridge structures in a direction parallel to either the first or second optically coupling edge surface 150a or 150b (e.g., along an axis between and perpendicular to the third edge surface 150c and edge surface 150d) can remain substantially uniform.

[0057] The display device 100 may include a single light source 32, two light sources 32, or more than two light sources 32, each coupling light into a different light-coupling edge surface of the transparent plate. For example, Fig. 14 is a cross-sectional end view of a display device 100 in which the transparent plate 102 is illuminated with three light sources (e.g., three arrays of LEDs), with a first light source 32a adjacent to a first light-coupling edge surface 150a, a second light source 32b adjacent to a second light-coupling edge surface 150b, and a third light source 32c adjacent to a third light-coupling edge surface 150c. The first light source 32a couples light into the first light-coupling edge surface 150a, the second light source 32b couples light into the second light-coupling edge surface 150b, and the third light source 32c couples light into the third light-coupling edge surface 150c. The first and second light coupling edge surfaces 150a and 150b can be parallel edge surfaces, while the third light coupling edge surface can be orthogonal to either or both of the first and second light coupling edge surfaces 150a and 150b. As described above for the case where two light sources couple light into two parallel light coupling edge surfaces, the bridge structures 110 can be arranged such that the spacing dX between adjacent edge surfaces in a direction from the first light coupling edge surface 150a to the second light coupling edge surface 150b decreases as the distance from the first light coupling edge surface 150a increases, and the spacing dX between the bridge structures in a direction from the second light coupling edge surface 150b to the first light coupling edge surface 150a similarly decreases as the distance from the second light coupling edge surface 150b increases. As a result, the spacing dX between adjacent bridge structures is smallest at the center of the transparent plate (along an axis perpendicular to the first and second light-coupling edge surfaces 150a and 150b) and increases as the distance from the center increases (as the distance from the first or second light-coupling edge surface decreases). Similar to the case where a single light source couples light into the light-coupling edge surface, the spacing dY between adjacent bridge structures in a direction from the third light-coupling edge surface 150c (illuminated by the third light source 32c) toward the fourth edge surface 150d decreases as the distance from the third light-coupling edge surface 150c increases. The spacing dY between adjacent bridge structures along an axis between the third light-coupling edge surface 150c and the fourth edge surface 150d (e.g., an axis perpendicular to the third light-coupling edge surface 150c) is smallest near the fourth edge surface 150d.

[0058] FIG. 15 illustrates a case where four light sources couple light into the transparent plate 102, with each light source coupling light into a different edge surface. FIG. 15 illustrates a transparent plate 102 with four light-coupling edge surfaces 150a-150d and four light sources 32a-32d that couple light into the four light-coupling edge surfaces separately. That is, the first light source 32a couples light into the first light-coupling edge surface 150a, the second light source 32b couples light into the second light-coupling edge surface 150b, the third light source 32c couples light into the third light-coupling edge surface 150c, and the fourth light source 32d couples light into the fourth light-coupling edge surface 150d. The spacing dX between adjacent bridge structures in the direction from the first light-coupling edge surface 150a to the second light-coupling edge surface 150b decreases as the distance from the first light-coupling edge surface 150a increases. The spacing dX between adjacent bridge structures decreases in a direction from the second light-coupling edge surface 150b toward the first light-coupling edge surface 150a. Thus, along an axis perpendicular to the first and second light-coupling edge surfaces 150a and 150b from the first and second light-coupling edge surfaces 150a and 150b, the spacing dX between adjacent bridge structures is smallest in the central region of the transparent plate 102 and largest near the first and second light-coupling edge surfaces. That is, the spacing dX between adjacent bridge structures in a direction from the first light-coupling edge surface 150a toward the second light-coupling edge surface 150b decreases as the distance from the first light-coupling edge surface 150a increases, and then increases as the distance from the first light-coupling edge surface 150a continues to increase. Similarly, the spacing dX between adjacent bridge structures in a direction from the second light-coupling edge surface 150b toward the first light-coupling edge surface 150a decreases as the distance from the second light-coupling edge surface 150b increases, and then increases as the distance from the second light-coupling edge surface 150b continues to increase.

[0059] Similarly, the spacing dY between adjacent bridge structures in the direction from the third light-coupling edge surface 150c to the fourth light-coupling edge surface 150d along an axis perpendicular to the third and fourth light-coupling edge surfaces 150c and 150d decreases as the distance from the third light-coupling edge surface 150a increases. Furthermore, the spacing dY between adjacent bridge structures decreases in the direction from the fourth light-coupling edge surface 150d to the third light-coupling edge surface 150c along an axis perpendicular to the third and fourth light-coupling edge surfaces 150c and 150d. Thus, between the third light-coupling edge surface 150c and the fourth light-coupling edge surface 150b, the spacing dY between adjacent bridge structures along an axis perpendicular to the third and fourth light-coupling edge surfaces 150c and 150d is smallest in the central region of the transparent plate 102 and largest near the third and fourth light-coupling edge surfaces. That is, the spacing dY between adjacent bridge structures in the direction from the third light-coupling edge surface 150c toward the fourth light-coupling edge surface 150d decreases as the distance from the third light-coupling edge surface 150c increases, and then increases as the distance from the third light-coupling edge surface 150c continues to increase. Similarly, the spacing dY between adjacent bridge structures in the direction from the fourth light-coupling edge surface 150d toward the third light-coupling edge surface 150c decreases as the distance from the fourth light-coupling edge surface 150d increases, and then increases as the distance from the fourth light-coupling edge surface 150d continues to increase. As shown in FIG. 15, in the case of four light sources and four light-coupling edge surfaces (in the case of a rectangular transparent plate), the spacing between adjacent bridge structures is smallest in the central region of the transparent plate and largest in the peripheral region of the transparent plate, for example, as the distance from any one of the light-coupling edge surfaces decreases.

[0060] A display device according to the present disclosure can include two or more transparent plates 102. For example, Figure 16 shows a display device 200 with two transparent plates attached, where a first transparent plate 102a is attached to a first major surface 202 of a display panel 104 (e.g., glass substrate 22) and a second transparent plate 102b is attached to a second major surface 204 of the display panel 104 (e.g., glass substrate 24) opposite the first transparent plate 102a. Either the first transparent plate 102a or the second transparent plate 102b, or both, can be configured as described above with respect to Figures 3-15, including the pattern (e.g., spacing) of bridge structures associated with their distance from their respective light-coupling edge surfaces.

[0061] FIG. 16 is a cross-sectional end view of a display device 200 including a first light source 32a-1 adjacent a first light-coupling edge surface 150a-1 of a first transparent plate 102a and a second light source 32a-2 adjacent a second light-coupling edge surface 150a-2 of a second transparent plate 102b. Each transparent plate 102a, 102b includes a plurality of bridge structures as described above, with the spacing between adjacent bridge structures decreasing as the distance from the respective light-coupling edge surface to the bridge structure increases, for example as described with respect to FIG. 11. In the embodiment shown in FIG. 16, the light-coupling edge surfaces 150a-1, 150a-2 of each transparent plate 102a, 102b are positioned such that light from each light source initially propagates in the same direction. That is, the light sources are positioned adjacent the corresponding edge surfaces of each transparent plate, i.e., on the same side of the transparent plates. In the illustrated embodiment, the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge surface in the same direction for both transparent plates. That is, the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge surface of transparent plate 102a in a first direction, and the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge surface of the second transparent plate 102b in the same first direction. However, it will be apparent that the light-coupling edge surface of the second transparent plate 102b can be oriented perpendicular to the light-coupling edge surface of transparent plate 102a, such that the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge structure of the first transparent plate in the first direction, and the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge structure of the second transparent plate in a second direction that is perpendicular to the first direction.

[0062] Conversely, Figure 17 is a cross-sectional end view of a display device 200 including a first light source 32a-l adjacent to a first light-coupling edge surface 150a-1 of a first transparent plate 102a and coupling light into the first transparent plate 102a in a first direction, and a second light source 32b-2 coupling light into the second transparent plate 102b in a second direction opposite the first direction. Each transparent plate 102a, 102b includes a plurality of bridge structures, the spacing between adjacent bridge structures decreasing as the distance from the respective light-coupling edge surface to the bridge structures increases, as described with respect to Figure 11. More specifically, the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge surface of the first transparent plate 102a in the first direction, and the spacing between adjacent bridge structures decreases as a function of distance from the light-coupling edge surface of the second transparent plate 102b in a second direction opposite the first direction.

[0063] 18 is a cross-sectional end view of a display device 200 including a first light source 32a-1 adjacent a first light-coupling edge surface 150a-1 of a first transparent plate 102a and coupling light into the first transparent plate 102a in a first direction, and a second light source 32b-1 coupling light into the first transparent plate 102a in a second direction opposite the first direction. The first transparent plate 102a is thus illuminated as described for FIG. 13. That is, for the first transparent plate 102a, the spacing between adjacent bridge structures decreases as a function of distance from the first light-coupling edge surface of the first transparent plate 102a in the first direction, and the spacing between adjacent bridge structures decreases as a function of distance from a second light-coupling edge surface opposite the first light-coupling edge surface of the first transparent plate 102a in a second direction opposite the first direction. The display device 200 further comprises a third light source 32a-2 adjacent to the third light-coupling edge surface 150a-2 of the second transparent plate 102b and coupling light to the second transparent plate 102b in a first direction, and a fourth light source 32b-2 coupling light to the fourth light-coupling edge surface 150b-2 of the second transparent plate 102b in a second direction opposite the first direction. That is, each of the first transparent plate 102a and the second transparent plate 102b is illuminated identically. Furthermore, each transparent plate 102a, 102b comprises a plurality of bridge structures 110, the spacing between adjacent bridge structures decreasing as the distance from the respective light-coupling edge surface to the bridge structure increases, as described with respect to FIG. 13. In another embodiment, each transparent plate 102a, 102b may further comprise an additional light-coupling edge surface such that light from the additional light sources is coupled to the additional light-coupling edge surface. For example, each transparent plate 102a and 102b may be illuminated as described with respect to FIG. 14 or FIG.

[0064] From the above description, it will be apparent that many combinations of light sources disposed adjacent to the light-coupling edge surface of one or more transparent plates of a display device are contemplated. That is, a display device contemplated herein can include one or more transparent plates, the one or more transparent plates disposed adjacent to a respective major surface of a display panel. Each transparent plate can include one or more light sources, each light source disposed adjacent to a light-coupling edge surface of the respective transparent plate. Each transparent plate can include one or more light-coupling surfaces, with a light source positioned adjacent to each light-coupling edge surface. For example, there can be one, two, three, four, five or more light sources associated with each transparent plate of a display device, with each light source positioned adjacent to a respective light-coupling edge surface of the respective transparent plate (see, e.g., Figures 11, 13, 14, 15 and the description thereof). Each light source can include a plurality of light emitting devices, e.g., a plurality of LEDs arranged in a linear array. In addition, it will be further apparent that the orientation of second transparent plate 102b, including the light sources disposed adjacent the light-coupling surface of the second transparent plate, may be different than the orientation of the first transparent plate and the light sources adjacent the light-coupling edge surface of the first transparent plate, i.e., the light sources adjacent the light-coupling edge surface of second transparent plate 102b need not be positioned in exactly the same way as the light sources adjacent the light-coupling edge surface of first transparent plate 102a.

[0065] FIG. 19 is a graph showing the measured normalized luminance as a function of distance from the light-coupling edge surface for the display device 300 shown in FIG. 20 when the display panel is displaying a white screen (e.g., light output but no image). The display device 300 included a display panel 104 including a liquid crystal layer disposed between two glass substrates 22, 24, a first transparent plate 302a attached to a first (A) side (e.g., glass substrate 22) of the display panel 104, and a second transparent plate 302b attached to a second (B) side (e.g., glass substrate 24) opposite the first side of the display panel 104. The first transparent plate 302a and the second transparent plate 302b were attached to the respective sides of the display panel 104 by an adhesive layer 304 (OCA layer). A light source 32 having a Lambertian output was positioned adjacent to the light-coupling edge surface of the first transparent plate 302a. The transparent plates 302a and 302b did not include a bridge structure. The transparent plates 302a, 302b were 0.7 mm thick and had a refractive index of 1.50 at 550 nm. The liquid crystal material was 0.05 mm thick and had a refractive index of 1.60. The adhesive 304 was 0.125 mm thick and had a refractive index of 1.48 at 550 nm. The display panel had width and length dimensions of 40 mm and 120 mm, respectively. The data shows that the luminance uniformity of the display device 300 was very poor, only about 5%.

[0066] The luminance of display device 300 was also modeled. Figure 21 is a graph showing the modeled results (dashed line) along with the data from Figure 19. The data shows good agreement between the experimental (measured) and modeled results.

[0067] Another display device 400, shown in FIG. 22, was modeled. The display device 400 included a display panel 104 including a liquid crystal layer disposed between two glass substrates 22, 24 (see FIG. 1), a first transparent plate 102 attached to a first surface of the display panel 104 at a first (A) side of the display panel (e.g., glass substrate 22) by a plurality of bridge structures 110 formed from an optically clear adhesive, a second transparent plate 402 attached to a second (B) side of the display panel 12 (e.g., glass substrate 24) by a second layer 404 of optically clear adhesive but without bridge structures, and a light source 32 positioned adjacent to the light-coupling edge surface of the first transparent plate 102. The light source 32 included a plurality of LEDs, each LED having a Lambertian output, and was positioned to illuminate the light-coupling edge surface of the first transparent plate 102. The transparent plates 102, 402 had a thickness of 0.7 mm. The refractive index of the transparent plates 102 and 402 was 1.50 at 550 nm. The liquid crystal material had a thickness of 0.05 mm and a refractive index of 1.60. The optically clear adhesive layer 404 that attaches the second transparent plate 402 to the display panel 12 (i.e., the second glass substrate 24) had a thickness of 0.125 mm and a refractive index of 1.48 at 550 nm. The display panel had width and length dimensions of 40 mm and 120 mm, respectively.

[0068] The bridge structures of the transparent plate 102 of the display device 400 had a spacing between adjacent bridge structures that decreased as a function of distance from the light source (i.e., the light-coupling edge surface) in a first direction as shown in FIG. 8. The spacing between adjacent bridge structures in a direction perpendicular to the first direction was uniform. The bridge structures had a circular cross-sectional shape with a radius of 50 micrometers (μm) and a height of 50 μm, and the material 120 surrounding the bridge structures was air. FIG. 23 shows the spacing dX between adjacent bridge structures as a function of the cumulative number of bridge structures counted from the light-coupling edge surface in the direction of the opposite edge surface.

[0069] FIG. 24 shows the luminance (in watts) as a function of distance from the light-coupling edge surface for the display device viewed from the side facing the transparent plate 102 (side A) compared to side A (dashed line) of the display device 300, assuming the display device 400 displays a white screen (illuminated but not displaying an image). FIG. 25 shows the luminance (in watts) as a function of distance from the light-coupling edge surface for the display device 400 viewed from the side facing the transparent plate 402 (side B) compared to side B (dashed line) of the display device 300. FIG. 26 shows the luminance (in watts) as a function of distance from the light-coupling edge surface for the display device 400, at the center of the liquid crystal material thickness, compared to the display device 300 (dashed line). The data shows that the average luminance (or center luminance) of the display device 400 with bridge structures on sides A and B is similar to the display device 300 without the bridge structures, but the luminance uniformity of the display device 400 with the bridge structures is significantly higher than the display device 300 without the bridge structures.

[0070] The following table provides brightness uniformity data for sides A, B, and the center of the liquid crystal (LC) layer for display devices 300 and 400. The data shows that the use of a transparent plate with multiple bridge structures in the display device significantly improves brightness.

[0071] [Table 1]

[0072] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure, and therefore, the present disclosure is intended to cover all such modifications and variations provided they come within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0073] 22 First glass substrate 24 Second glass substrate 32 light source 100 display devices 102 Transparent plate 104 Display Panel 106 First main surface 108 Second main surface 110 Bridge structure 112 Adhesive

Claims

1. 1. A light coupling device for coupling light from a light source to a display panel, comprising: A transparent plate having a first main surface and a second main surface opposite to the first main surface, the transparent plate further having a plurality of edge surfaces connecting the first main surface and the second main surface; a plurality of bridge structures extending from the second major surface, each of the bridge structures having a length L in a range of about 2 micrometers to about 200 micrometers defined between a reference plane from which the plurality of bridge structures extend and a distal end of the bridge structure furthest from the reference plane; 1. An optical coupling device comprising:

2. 2. The optical coupling device of claim 1, wherein the plurality of edge surfaces includes a first edge surface and a second edge surface opposite the first edge surface, and the plurality of bridge structures includes a first set of bridge structures positioned along a first axis extending between the first edge surface and the second edge surface, and a distance separating adjacent bridge structures of the first set of bridge structures along the first axis decreases in a direction from the first edge surface toward the second edge surface.

3. 3. The optical coupling device of claim 2, wherein the plurality of bridge structures includes a second set of bridge structures positioned along the first axis, the distance separating adjacent bridge structures of the second set of bridge structures decreasing in a direction from the second edge surface toward the first edge surface.

4. 4. The optical coupling device of claim 3, wherein the plurality of edge surfaces includes a third edge surface and a fourth edge surface opposite the third edge surface, and the plurality of bridge structures includes a third set of bridge structures positioned along a second axis extending between the third edge surface and the fourth edge surface, a distance separating adjacent bridge structures of the third set of bridge structures decreasing in a direction from the third edge surface toward the fourth edge surface.

5. 5. The optical coupling device of claim 4, wherein the plurality of bridge structures includes a fourth set of bridge structures positioned along the second axis, the distance separating adjacent bridge structures of the fourth set of bridge structures decreasing in a direction from the fourth edge surface toward the third edge surface.

6. The optical coupling device of claim 5 , wherein the first edge surface is orthogonal to the third edge surface.

7. The optical coupling device according to claim 1 , wherein a cross-sectional shape of the bridge structures of the plurality of bridge structures in a plane parallel to the first main surface includes a circle, an ellipse, or a polygon.

8. 10. The optical coupling device of claim 1, wherein a maximum width of each of the bridge structures in a plane parallel to the first major surface ranges from about 10 micrometers to about 50 millimeters.

9. The optical coupling device of claim 8 , wherein the maximum width varies along the length of each of the bridge structures.

10. The optical coupling device of claim 9 , wherein the maximum width is greater at the distal end than at the reference surface.

11. The optical coupling device of claim 1 , wherein the plurality of bridge structures comprises an optically clear adhesive.

12. The optical coupling device of claim 11 , wherein the optically transparent adhesive comprises a coating layer disposed on the second major surface of the transparent plate.

13. The optical coupling device of claim 1 , wherein the reference surface is the second major surface of the transparent plate.

14. The optical coupling device of claim 1 , wherein the reference surface is a surface of the transparent plate recessed from the second major surface.

15. The optical coupling device of claim 12 , wherein the reference surface comprises a concave surface of the coating layer.

16. The optical coupling device of claim 1 , wherein the maximum thickness of the transparent plate is in the range of about 0.1 mm to about 5 mm.

17. 10. The optical coupling device of claim 1, wherein the refractive index of the transparent plate is in the range of about 1.35 to about 1.

65.

18. The optical coupling device of claim 1 , wherein the transparent plate is bonded to a glass substrate attached to the plurality of bridge structures.

19. 10. The optical coupling device of claim 1, wherein the plurality of bridge structures are disposed within a host material, the host material having a refractive index at least about 10% less than the refractive index of the bridge structures.

20. 10. The optical coupling device of claim 1, wherein the refractive index of the bridge structure differs from the refractive index of the transparent plate by less than about 10%.

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