WO2020205386A1

WO2020205386A1 - Illumination device including a laminate glass light guide plate and method for fabricating the illumination device

Info

Publication number: WO2020205386A1
Application number: PCT/US2020/024806
Authority: WO
Inventors: Jin Su Kim; Jun Ro Yoon
Original assignee: Corning Incorporated
Priority date: 2019-04-04
Filing date: 2020-03-26
Publication date: 2020-10-08

Abstract

A light guide plate includes a laminate glass and a first plurality of light extraction features. The laminate glass includes a core layer, a first clad layer on a first surface of the core layer, and a second clad layer on a second surface of the core layer opposite to the first surface. The first plurality of light extraction features are formed from the first clad layer.

Description

ILLUMINATION DEVICE INCLUDING A LAMINATE GLASS LIGHT GUIDE PLATE AND METHOD FOR FABRICATING THE ILLUMINATION DEVICE

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

Provisional Application Serial No. 62/829,392 filed on April 4, 2019, the content of which is relied upon and 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 including laminate glass light guide plates with light extraction features.

Technical Background

[0003] Due to the thin form factor and optical performance (i.e., point-to-areal illumination), edge-lit lighting using light guide plates (LGPs) has been expanding from display applications to luminaire, architecture, automotive (e.g., interior and glazing), and other applications. Compared to most display applications, these other applications may be exposed to harsher environments, such as greater temperature cycling, higher humidity, ultraviolet (UV) light exposure, high vibration, etc. Typical LGPs may be based on a polymer, such as poly methyl methacrylate (PMMA). Polymer based LGPs, however, may be vulnerable in harsh environments due to a high coefficient of thermal expansion (CTE), low hardness, low stiffness, water absorption, and low UV light resistance. Thus, polymer based LGPs may be limited in meeting the requirements of these other edge-lit lighting applications. In addition, light extraction patterning by laser or printing may be limited for polymer based LGPs, thus restricting design freedom and the optical characteristics of polymer based LGP edge-lit lighting.

SUMMARY

[0004] Some embodiments of the present disclosure relate to a light guide plate. The light guide plate includes a laminate glass and a first plurality of light extraction features. The laminate glass includes a core layer, a first clad layer on a first surface of the core layer, and a second clad layer on a second surface of the core layer opposite to the first surface. The first plurality of light extraction features are formed from the first clad layer.

[0005] Yet other embodiments of the present disclosure relate to an illumination device. The illumination device includes a laminate glass, a first plurality of light extraction features, and a light source. The laminate glass includes a core layer, a first clad layer on a first surface of the core layer, and a second clad layer on a second surface of the core layer opposite to the first surface. The first plurality of light extraction features are formed from the first clad layer. The light source is arranged to emit light into the core layer through a third surface of the core layer extending between the first surface and the second surface.

[0006] Yet other embodiments of the present disclosure relate to a method for fabricating an illumination device. The method includes masking a first clad layer of a laminate glass with a first mask, the laminate glass comprising a core layer between the first clad layer and a second clad layer. The method includes etching the first clad layer based on the first mask to form a first plurality of light extraction features.

[0007] The glass based edge-lit illumination devices and light guide plates disclosed herein may have several advantages over polymer based edge-lit illumination devices and light guide plates. For example, glass based edge-lit light guide plates may provide a thinner yet stronger structure, a more pristine surface, a higher hardness and scratch resistance, and a better dimensional stability due to a lower CTE and lower moisture absorption. In addition, glass based edge-lit guide plates may also provide a higher stiffness (which enables lower warp and design freedom for bezel-less luminaires), UV light resistance (i.e., less yellowing under sunlight exposure), and more durability in harsh environments (e.g., temperature, vibration, etc.). Further, by using laminate glass based edge-lit light guide plates, the shape of the light extraction features may be uniquely controlled, double sided illumination devices may be fabricated, and non-planar shaped illumination devices may be fabricated.

[0008] Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0009] It is to be understood that both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The accompanying drawings are included to provide further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a cross-sectional view of an exemplary light guide plate for single sided illumination;

[0011] FIG. 2 is a cross-sectional view of an exemplary light guide plate for double sided illumination;

[0012] FIG. 3 is a cross-sectional view of an exemplary single sided illumination device;

[0013] FIG. 4 is a cross-sectional view of an exemplary double sided illumination device;

[0014] FIG. 5 is a cross-sectional view of an exemplary non-planar illumination device;

[0015] FIG. 6 is a cross-sectional view of an exemplary single sided illumination device and illustrates light extraction from the illumination device;

[0016] FIG. 7 is a cross-sectional view of an exemplary double sided illumination device and illustrates light extraction from the illumination device;

[0017] FIGS. 8A-8C are perspective views of exemplary light guide plates;

[0018] FIGS. 9A-9D are cross-sectional views illustrating an exemplary method for fabricating an illumination device;

[0019] FIGS. 10A-10D are cross-sectional views illustrating another exemplary method for fabricating an illumination device; and

[0020] FIGS. 11A-11D are cross-sectional views illustrating an exemplary method for fabricating a non-planar light guide plate.

DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0024] 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.

[0025] 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.

[0026] As used herein, the term“liquidus viscosity” refers to the shear viscosity of a glass composition at the liquidus temperature of the glass composition.

[0027] As used herein, the term“liquidus temperature” refers to the highest temperature at which devitrification occurs in a glass composition.

[0028] As used herein, the terms“coefficient of thermal expansion” or“CTE” refer to the coefficient of thermal expansion of a glass composition averaged over a temperature range from about 20 degrees Celsius to about 300 degrees Celsius.

[0029] The term“substantially free,” when used herein to describe the absence of a particular oxide component in a glass composition, means that the component is absent from the glass composition or present in the glass composition in a trace amount of less than 0.2 mol %.

[0030] Throughout this disclosure, the concentrations of constituent components (e.g., S1O2, AI2O3, B2O3, and the like) are given in mole percent (mol %) on an oxide basis, unless otherwise specified. [0031] Referring now to FIG. 1, a cross-sectional view of an exemplary light guide plate 100 for single sided illumination is depicted. Light guide plate 100 may include a laminate glass including a core layer 102, a first clad layer 108 on a first surface 104 of the core layer 102, and a second clad layer 112 on a second surface 106 of the core layer 102 opposite to the first surface 104. Light guide plate 100 includes a plurality of light extraction features 110 formed from the first clad layer 108.

[0032] The core layer 102 includes a glass material, such as aluminosilicate, alkali- aluminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali- aluminoborosilicate, soda lime, or other suitable glasses. Non-limiting examples of commercially available glasses suitable for use as a core layer 102 include EAGLE XG®, Lotus™, Willow®, Iris™, and Gorilla® glasses from Coming Incorporated. In certain exemplary embodiments, the first clad layer 108 and the second clad layer 112 may include photosensitive glass (PSG), such as FOTOFORM®, available from Coming Incorporated. In this case, the first clad layer 108 and the second clad layer 112 have a first photosensitivity and the core layer 102 has a second photosensitivity less than the first photosensitivity. In certain exemplary embodiments, the second photosensitivity is zero photosensitivity (e.g., the photosensitivity of regular glasses). In other embodiments, the first clad layer 108 and the second clad layer 112 may include a glass having an etch rate in a reagent greater than (e.g., 10 times) an etch rate of the core layer 102 in the reagent. A suitable reagent may, for example, have a pH between 1.2 and 2.1.

[0033] Light extraction features 110 may be arranged in a pattern on the first surface 104 of the core layer 102. As used herein, the term“pattern” is intended to denote that the light extraction features 110 are present on the surface of the core layer 102 in any given pattern or design, which may, for example, be random or arranged, repetitive or non-repetitive, uniform or non-uniform. Each of the plurality of light extraction features 110 may, for example, have a width as indicated at 116 between about 30 micrometers and about 90 micrometers, a height as indicated at 117 between about 10 micrometers and about 30 micrometers, and a spacing as indicated at 118 between about 100 micrometers and about 250 micrometers. Each light extraction feature 110 may have a circular shape, a rectangular shape, a triangular shape, or another suitable shape.

[0034] FIG. 2 is a cross-sectional view of an exemplary light guide plate 120 for double sided illumination. Light guide plate 120 may include a laminate glass including a core layer 102, a first clad layer 108 on a first surface 104 of the core layer 102, and a second clad layer 112 on a second surface 106 of the core layer 102 opposite to the first surface 104 as previously described with reference to FIG. 1. Light guide plate 120 includes a first plurality of light extraction features 110 formed from the first clad layer 108 as previously described. Light guide plate 120 also includes a second plurality of light extraction features 114 formed from the second clad layer 112. Light extraction features 114 may be similar to light extraction features 110.

[0035] FIG. 3 is a cross-sectional view of an exemplary single sided illumination device 130. Illumination device 130 includes a light guide plate 100 as previously described and illustrated with reference to FIG. 1 and a light source 132. Light source 132 is arranged to emit light into the core layer 102 through a third surface 107 of the core layer 102 extending between the first surface 104 and the second surface 106. The light source 132 may include, for example, a light emitting diode (LED), a micro-LED, an organic LED (OLED), another suitable light source having a wavelength ranging from about 100 nanometers to about 750 nanometers, or a plurality of such light sources arranged in an array.

[0036] Light source 132 may be optically coupled to light guide plate 100. In certain exemplary embodiments, an optical adhesive (not shown) may be used to couple the light source 132 to the light guide plate 100. The optical adhesive (e.g., phenyl silicone) may have a refractive index greater than or equal to a refractive index of the light guide plate 100. As will be described below with reference to FIG. 6, illumination device 130 emits light from the first surface 104 of the core layer 102 when the light propagated within the core layer 102 due to total internal reflection is extracted out of the core layer 102 by the light extraction features 110.

[0037] FIG. 4 is a cross-sectional view of an exemplary double sided illumination device 140. Illumination device 140 includes a light guide plate 120 as previously described and illustrated with reference to FIG. 2 and a light source 132. Light source 132 is arranged to emit light into the core layer 102 through a third surface 107 of the core layer 102 extending between the first surface 104 and the second surface 106. The light source 132 may include, for example, an LED, a micro-LED, an OLED, another suitable light source having a wavelength ranging from about 100 nanometers to about 750 nanometers, or a plurality of such light sources arranged in an array.

[0038] Light source 132 may be optically coupled to light guide plate 120. In certain exemplary embodiments, an optical adhesive (not shown) may be used to couple the light source 132 to the light guide plate 120. The optical adhesive (e.g., phenyl silicone) may have a refractive index greater than or equal to a refractive index of the light guide plate 120. As will be described below with reference to FIG. 7, illumination device 140 emits light from the first surface 104 and the second surface 106 of the core layer 102 when the light propagated within the core layer 102 due to total internal reflection is extracted out of the core layer 102 by the first light extraction features 110 and the second light extraction features 114.

[0039] FIG. 5 is a cross-sectional view of an exemplary non-planar illumination device 150. Illumination device 150 includes a light guide plate 152, a first light source 132a, and a second light source 132b. Light guide plate 152 has a non-planar shape and includes a core layer 102, a first clad layer 108 on the first surface 104 of the core layer 102 from which light extraction features 110 are formed, and a second clad layer 112 on the second surface 106 of the core layer 102. In this embodiment, the core layer 102 has a non-planar shape. First light source 132a is arranged to emit light into the core layer 102 through a third surface 107 of the core layer 102 extending between the first surface 104 and the second surface 106. Second light source 132b is arranged to emit light into the core layer 102 through a fourth surface 109 of the core layer 102 extending between the first surface 104 and the second surface 106. Each of the first light source 132a and the second light source 132b may include, for example, an LED, a micro-LED, an OLED, another suitable light source having a wavelength ranging from about 100 nanometers to about 750 nanometers, or a plurality of such light sources arranged in an array.

[0040] In certain exemplary embodiments, each of the first light source 132a and the second light source 132b may be spaced apart from the light guide plate 152. In other embodiments, each of the first light source 132a and the second light source 132b may be physically coupled to the light guide plate 152. In certain exemplary embodiments, an optical adhesive (not shown) may be used to couple each light source 132a and 132b to the light guide plate 152. Lhe optical adhesive (e.g., phenyl silicone) may have a refractive index greater than or equal to a refractive index of the light guide plate 152. Illumination device 150 emits light from the first surface 104 of the core layer 102 when the light propagated within the core layer 102 due to total internal reflection is extracted out of the core layer 102 by the light extraction features 110.

[0041] FIG. 6 is a cross-sectional view of an exemplary single sided illumination device 160 and illustrates light extraction from the illumination device 160. Illumination device 160 includes a light guide plate 162, a printed circuit board (PCB) 163, and a light source 132. Light guide plate 162 includes a core layer 102, a first clad layer 108 on the first surface 104 of the core layer 102 from which light extraction features 110 are formed. In this example, the clad layer on the second surface 106 was excluded during fabrication of the laminate glass or has been removed (e.g., via etching). PCB 163 is in electrical communication with light source 132.

[0042] Light source 132 is arranged to emit light into the core layer 102 through a third surface 107 of the core layer 102 extending between the first surface 104 and the second surface 106. The light emitted into the core layer 102 by the light source 132 propagates through the core layer 102 due to total internal reflection as indicated by ray 164 until the light is extracted out of the core layer 102 due to light extraction features 110 as indicated by ray 166.

[0043] FIG. 7 is a cross-sectional view of an exemplary double sided illumination device 170 and illustrates light extraction from the illumination device 170. Illumination device 170 includes a light guide plate 172, a PCB 163, and a light source 132. Light guide plate 172 includes a core layer 102, a first clad layer 108 on the first surface 104 of the core layer 102 from which light extraction features 110 are formed, and a second clad layer 1112 on the second surface 106 of the core layer 102 from which light extraction features 114 are formed. PCB 163 is in electrical communication with light source 132.

[0044] Light source 132 is arranged to emit light into the core layer 102 through a third surface 107 of the core layer 102 extending between the first surface 104 and the second surface 106. A first portion of light emitted into the core layer 102 by the light source 132 propagates through the core layer 102 due to total internal reflection as indicated by ray 164 until the light is extracted out of the core layer 102 due to light extraction features 110 as indicated by ray 166. In addition, a second portion of light emitted into the core layer 102 by the light source 132 propagates through the core layer 102 due to total internal reflection as indicated by ray 174 until the light is extracted out of the core layer 102 due to light extraction features 114 as indicated by ray 176.

[0045] FIG. 8A is a perspective view of an exemplary light guide plate 200 including circular shaped light extraction features 204. Light guide plate 200 includes a core layer 202 and a clad layer on the upper surface of the core layer 202 from which light extraction features 204 are formed. Light extraction features 204 may be arranged in any suitable pattern, such as a random or arranged pattern, a repetitive or non-repetitive pattern, or a uniform or non-uniform pattern. In certain exemplary embodiments, the pattern may have a size-gradient for uniform light extraction over the entire upper surface of the core layer 202.

[0046] FIG. 8B is a perspective view of an exemplary light guide plate 220 including rectangular shaped light extraction features 224. Light guide plate 220 includes a core layer 202 and a clad layer on the upper surface of the core layer 202 from which light extraction features 224 are formed. Light extraction features 224 may be arranged in any suitable pattern, such as a random or arranged pattern, a repetitive or non-repetitive pattern, or a uniform or non-uniform pattern. In certain exemplary embodiments, the pattern may have a size-gradient for uniform light extraction over the entire upper surface of the core layer 202.

[0047] FIG. 8C is a perspective view of an exemplary light guide plate 240 including triangular shaped light extraction features 244. Light guide plate 240 includes a core layer 202 and a clad layer on the upper surface of the core layer 202 from which light extraction features 244 are formed. Light extraction features 244 may be arranged in any suitable pattern, such as a random or arranged pattern, a repetitive or non-repetitive pattern, or a uniform or non-uniform pattern. In certain exemplary embodiments, the pattern may have a size-gradient for uniform light extraction over the entire upper surface of the core layer 202.

[0048] While FIGS. 8A-8C illustrate three shapes that may be used for light extraction features, in other embodiments, the light extraction features may have another suitable shape or a combination of shapes. The light extraction features may also be arranged on the lower surface of the core layer 202. In this case, the light extraction features arranged on the lower surface of the core layer 202 may have the same shape or a different shape than the light extraction features arranged on the upper surface.

[0049] FIGS. 9A-9D are cross-sectional views illustrating an exemplary method for fabricating an illumination device. As illustrated in FIG. 9A at 300, the method may include fabricating a laminate glass including a core layer 102, a first clad layer 108 on a first surface 104 of the core layer 102, and a second clad layer 112 on a second surface 106 of the core layer 102 opposite to the first surface 104. In this embodiment, an etch rate of the first clad layer 108 and the second clad layer 112 in a reagent is greater than an etch rate of the core layer 102 in the reagent.

[0050] The first clad layer 108 may be directly fused to the first surface 104 of the core layer 102, and the second clad layer 112 may be directly fused to the second surface 106 of the core layer 102. The clad layers 108 and 112 may be fused to the core layer 102 without any additional materials, such as adhesives, polymer layers, coating layers, or the like being disposed between the core layer 102 and the clad layers 108 and 112. Thus, the first surface 104 of the core layer 102 may be directly adjacent to the first clad layer 108, and the second surface 106 of the core layer 102 may be directly adjacent to the second clad layer 112. In some embodiments, the core layer 102 and the clad layers 108 and 112 are formed via a fusion lamination process. Diffusive layers (not shown) may form between the core layer 102 and the first clad layer 108, or between the core layer 102 and the second clad layer 112, or both. [0051] In certain exemplary embodiments, the laminate glass may have a thickness of at least about 0.05 millimeters, at least about 0.1 millimeters, at least about 0.2 millimeters, at least about 0.3 millimeters, or at least about 0.5 millimeters In other embodiments, the laminate glass may have a thickness of at most about 12.5 millimeters, at most about 10 millimeters, at most about 5 millimeters, at most about 3 millimeters, at most about 1.5 millimeters, or at most about 0.5 millimeters. For example, the laminate glass may have a thickness between about 0.1 millimeters and about 12.5 millimeters. In certain exemplary embodiments, the clad layers 108 and 112 may each have a thickness between about 0.025 millimeters and about 0.25 millimeters.

[0052] In other embodiments, a ratio of a thickness of the core layer 102 to a thickness of the laminate glass is at least about 0.7, at least about 0.8, at least about 0.85, at least about 0.9, or at least about 0.95. The ratio of the thickness of the core layer 102 to the thickness of the clad layers 108 and 112 (e.g., the combined thickness) may be at least about 1, at least about 3, at least about 5, at least about 7, or at least about 9. In other embodiments, the ratio of the thickness of the core layer 102 to the thickness of the clad layers 108 and 112 is at most about 20, at most about 15, or at most about 10.

[0053] The core layer 102 includes a core glass composition. The clad layers 108 and 112 include a clad glass composition different from the core glass composition. In certain exemplary embodiments, the clad glass composition may include from about 45 mol % to about 60 mol % SiCE and from about 8 mol % to about 19 mol % AI2O3, a CTE between about 50x 10^_7/°C and about 95x 10^_7/°C, and a liquidus viscosity of at least about 50 Kilopascal. The clad glass composition may be substantially free of As and Cd and/or Pb. A degradation rate of the clad glass composition in a reagent may be at least 10 times greater than a degradation rate of the core glass composition in the reagent.

[0054] As illustrated in FIG. 9B at 320, the method includes masking the first clad layer 108 with a first mask 322. Masking of the first clad layer 108 may include applying a resist material to the first clad layer 108 to form the first mask 322. First mask 322 includes a pattern for defining where light extraction features are to be formed from first clad layer 108. In this embodiment, the method includes masking the surface of the second clad layer 112 with a solid second mask 324 for creating a light guide plate for single sided illumination (i.e., no light extraction features are to be formed from second clad layer 112). In other embodiments, the method may include masking the second clad layer 112 with a patterned second mask for creating a light guide plate for double sided illumination (i.e., light extraction features are to be formed from second clad layer 112). [0055] As illustrated in FIG. 9C at 340, the method includes etching the first clad layer 108 based on the first mask 322 to form a first plurality of light extraction features 110. Etching of the first clad layer 108 may include etching the first clad layer 108 to expose portions of the core layer 102. If the second clad layer 112 is masked with a patterned second mask, the method also includes etching the second clad layer 112 based on the second mask to form a second plurality of light extraction features (e g., light extraction features 114 of FIG. 2).

[0056] Etching of the first clad layer 108 and/or the second clad layer 112 may include contacting the laminate glass with a reagent for about 0.5 hours to about 10 hours, which causes exposed portions of clad layers 108 and/or 112 to be at least partially removed from the core layer 102. The reagent includes any suitable component capable of degrading or dissolving the exposed portions of clad layers 108 and/or 112. For example, the reagent may include an acid, a base, another suitable component, or a combination thereof. In some embodiments, the reagent may include an acid such as, for example, a mineral acid (e.g., HC1, HNO3, H2SO4, H3PO4, H3BO3, HBr, HCIO4, or HF), a carboxylic acid (e.g., CH3COOH), or a combination thereof. For example, in some embodiments, the reagent may include HC1 (e.g., 50 vol % HC1 in water) or HNO3. In some embodiments, the reagent may include a base such as, for example, LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2, or a combination thereof. After etching, the first mask 322 and the second mask 324 are removed.

[0057] As illustrated in FIG. 9D at 360, the method includes arranging a first light source 132a adjacent to a surface of the core layer 102 extending between the first clad layer 108 and the second clad layer 112. The method may also include arranging a second light source 132b adjacent to a surface of the core layer 102 extending between the first clad layer 108 and the second clad layer 112 opposite to the first light source 132a. In certain exemplary embodiments, the method may include optically coupling the first light source 132a and the second light source 132b to the core layer 102 via an optical adhesive (e.g., phenyl silicone).

[0058] FIGS. 10A-10D are cross-sectional views illustrating another exemplary method for fabricating an illumination device. As illustrated in FIG. 10A at 400, the method may include fabricating a laminate glass including a core layer 102, a first clad layer 108 on a first surface 104 of the core layer 102, and a second clad layer 112 on a second surface 106 of the core layer 102 opposite to the first surface 104. In this embodiment, the first clad layer 108 and the second clad layer 112 have a first photosensitivity and the core layer 102 has a second photosensitivity less than the first photosensitivity. The second photosensitivity may be zero photosensitivity.

[0059] The first clad layer 108 may be directly fused to the first surface 104 of the core layer 102, and the second clad layer 112 may be directly fused to the second surface 106 of the core layer 102. The clad layers 108 and 112 may be fused to the core layer 102 without any additional materials, such as adhesives, polymer layers, coating layers, or the like being disposed between the core layer 102 and the clad layers 108 and 112. Thus, the first surface 104 of the core layer 102 may be directly adjacent to the first clad layer 108, and the second surface 106 of the core layer 102 may be directly adjacent to the second clad layer 112. In some embodiments, the core layer 102 and the clad layers 108 and 112 are formed via a fusion lamination process. Diffusive layers (not shown) may form between the core layer 102 and the first clad layer 108, or between the core layer 102 and the second clad layer 112, or both.

[0060] In certain exemplary embodiments, the laminate glass may have a thickness of at least about 0.05 millimeters, at least about 0.1 millimeters, at least about 0.2 millimeters, at least about 0.3 millimeters, or at least about 0.5 millimeters. In other embodiments, the laminate glass may have a thickness of at most about 12.5 millimeters, at most about 10 millimeters, at most about 5 millimeters, at most about 3 millimeters, at most about 1.5 millimeters, or at most about 0.5 millimeters. For example, the laminate glass may have a thickness between about 0.1 millimeters and about 12.5 millimeters. In certain exemplary embodiments, the clad layers 108 and 112 may each have a thickness between about 0.025 millimeters and about 0.25 millimeters.

[0061] In other embodiments, a ratio of a thickness of the core layer 102 to a thickness of the laminate glass is at least about 0.7, at least about 0.8, at least about 0.85, at least about 0.9, or at least about 0.95. The ratio of the thickness of the core layer 102 to the thickness of the clad layers 108 and 112 (e.g., the combined thickness) may be at least about 1, at least about 3, at least about 5, at least about 7, or at least about 9. In other embodiments, the ratio of the thickness of the core layer 102 to the thickness of the clad layers 108 and 112 is at most about 20, at most about 15, or at most about 10.

[0062] The core layer 102 includes a core glass composition. The clad layers 108 and 112 include a clad glass composition different from the core glass composition. The core layer 102 may be formed from a core glass composition having a core photosensitivity. The first clad layer 108 may be formed from a first-clad glass composition having a first-clad photosensitivity different from the core photosensitivity. The second clad layer 112 may be formed from a second-clad glass composition having a second-clad photosensitivity that is also different from the core photosensitivity. In some embodiments, the first-clad glass composition and the second-clad composition may be identical. In other embodiments, the first-clad glass composition and the second-glad glass composition may be different. In such embodiments, the first-clad photosensitivity and the second-clad photosensitivity may be the same or different.

[0063] In some embodiments, any or all of the core glass composition, the first-clad glass composition, and the second-clad glass composition may be photosensitive glass compositions. Photosensitive glass compositions compose a class of glass materials that undergo a change in crystallinity properties when the photosensitive glass composition is exposed to radiation such as UV light, for example. In some photosensitive glass compositions, the change in crystallinity may result directly from the exposure to the radiation. In other photosensitive glass compositions, the exposure to the radiation may cause undetectable physical changes to the glass composition, such as the formation of nucleation centers. In such photosensitive glass compositions, once the nucleation centers are formed, the change to crystallinity may be completed by applying a heat treatment to the glass composition. The photosensitive glass compositions suitable for use herein may include, as non-limiting examples, alkaline-earth aluminoborosilicate glasses, zinc borosilicate glasses, and soda-lime glass. In certain exemplary embodiments, FOTOFORM®, available from Corning Incorporated, may be a suitable photosensitive glass composition for clad layers 108 and 112.

[0064] As illustrated in FIG. 10B at 420, the method includes masking the first clad layer 108 with a first mask 422. First mask 422 includes a pattern for defining where light extraction features are to be formed from first clad layer 108. The method includes exposing the first clad layer 108 to UV light 424 through the first mask 422. First mask 422 protects portions of first clad layer 108 from exposure to the UV light 424. In this embodiment, second clad layer 112 is not directly exposed to the UV light 424 for creating a light guide plate for single sided illumination (i.e., no light extraction features are to be formed from second clad layer 112). In other embodiments, the method may include masking the second clad layer 112 with a patterned second mask and exposing the second clad layer 112 to the UV light 424 for creating a light guide plate for double sided illumination (i.e., light extraction features are to be formed from second clad layer 112). During the UV exposure, the UV light 424 may have a wavelength of from about 100 nanometers to about 400 nanometers, for example from about 290 nanometers to about 330 nanometers. The UV exposure time may range from 5 seconds to several hours, such as from about 3 minutes to about 2 hours.

[0065] In some embodiments, the glass laminate may be heated after the exposure to the UV light. The heating may proceed at least until the portions of clad layer 108 that were exposed to the UV light exhibit a change in crystallinity. In some embodiments, the heating may be conducted at temperatures of from about 300 degrees Celsius to about 900 degrees Celsius, depending on the composition of the clad layer 108.

[0066] As illustrated in FIG. IOC at 440, the method includes etching the first clad layer 108 based on the first mask 422 to form a first plurality of light extraction features 110. Etching of the first clad layer 108 may include etching the first clad layer 108 to expose portions of the core layer 102 If the second clad layer 112 was masked with a patterned second mask and exposed to the UV light 424, the method also includes etching the second clad layer 112 based on the second mask to form a second plurality of light extraction features.

[0067] Etching of the first clad layer 108 may include removing the crystallized portions selectively from the clad layer 108 by taking advantages of one or both of a differential solubility or a differential etch-rate of the portions of clad layer 108 that were exposed to the UV light compared to portions of the clad layer 108 that were masked from the UV light. Removing the crystallized portions may include etching techniques such as immersion, ultrasonic etching, or spraying, for example, in a suitable etchant such as hydrofluoric acid, for example.

[0068] As illustrated in FIG. 10D, the method includes arranging a first light source 132a adjacent to a surface of the core layer 102 extending between the first clad layer 108 and the second clad layer 112. The method may also include arranging a second light source 132b adjacent to a surface of the core layer 102 extending between the first clad layer 108 and the second clad layer 112 opposite to the first light source 132a. In certain exemplary embodiments, the method may include optically coupling the first light source 132a and the second light source 132b to the core layer 102 via an optical adhesive (e.g., phenyl silicone).

[0069] FIGS. 11A-11D are cross-sectional views illustrating an exemplary method for fabricating a non-planar light guide plate. As illustrated in FIG. 11 A at 500, the method may include fabricating a laminate glass including a core layer 102, a first clad layer 108 on a first surface 104 of the core layer 102, and a second clad layer 112 on a second surface 106 of the core layer 102 opposite to the first surface 104 as previously described and illustrated with reference to FIG. 10A. In this embodiment, the first clad layer 108 and the second clad layer 112 have a first photosensitivity and the core layer 102 has a second photosensitivity less than the first photosensitivity. The second photosensitivity may be zero photosensitivity.

[0070] As illustrated in FIG. 1 IB at 520, the method includes masking the first clad layer 108 with a first mask 522. First mask 522 includes a pattern for defining where light extraction features are to be formed from first clad layer 108. The method includes exposing the first clad layer 108 to UV light 524 through the first mask 522. First mask 522 protects portions of first clad layer 108 from exposure to the UY light 524. In this embodiment, second clad layer 112 is not directly exposed to the UV light 524 for creating a light guide plate for single sided illumination (i.e., no light extraction features are to be formed from second clad layer 112). In other embodiments, the method may include masking the second clad layer 112 with a patterned second mask and exposing the second clad layer 112 to the UV light 524 for creating a light guide plate for double sided illumination (i.e., light extraction features are to be formed from second clad layer 112). During the UV exposure, the UV light 524 may have a wavelength of from about 100 nanometers to about 400 nanometers, for example from about 290 nanometers to about 330 nanometers. The UV exposure time may range from 5 seconds to several hours, such as from about 3 minutes to about 2 hours.

[0071] As illustrated in FIG. 11C at 540, the method includes hot forming the laminate glass to change the shape of the laminate glass. The laminate glass may be heated and manipulated to provide any suitable shape, such as an arch. In other embodiments, the method may include cold forming the laminate glass to change the shape of the laminate glass.

[0072] As illustrated in FIG. 11D at 560, the method includes etching the first clad layer 108 based on the first mask 522 to form a first plurality of light extraction features 110. Etching of the first clad layer 108 may include etching the first clad layer 108 to expose portions of the core layer 102. If the second clad layer 112 was masked with a patterned second mask and exposed to the UV light 525, the method also includes etching the second clad layer 112 based on the second mask to form a second plurality of light extraction features.

[0073] Etching of the first clad layer 108 may include removing the crystallized portions selectively from the clad layer 108 by taking advantages of one or both of a differential solubility or a differential etch-rate of the portions of clad layer 108 that were exposed to the UV light compared to portions of the clad layer 108 that were masked from the UV light. Removing the crystallized portions may include etching techniques such as immersion, ultrasonic etching, or spraying, for example, in a suitable etchant such as hydrofluoric acid, for example. Light sources (not shown) may be arranged adjacent to the non-planar light guide plate to fabricate a non-planar illumination device, such as illumination device 150 of FIG. 5.

[0074] 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.

Claims

What is claimed is:

1. A light guide plate comprising:

a laminate glass comprising a core layer, a first clad layer on a first surface of the core layer, and a second clad layer on a second surface of the core layer opposite to the first surface; and

a first plurality of light extraction features formed from the first clad layer.

2. The light guide plate of claim 1, further comprising:

a second plurality of light extraction features formed from the second clad layer.

3. The light guide plate of claim 1, wherein the first clad layer is directly fused to the first surface of the core layer and the second clad layer is directly fused to the second surface of the core layer.

4. The light guide plate of claim 1, wherein an etch rate of the first clad layer and the second clad layer in a reagent is greater than an etch rate of the core layer in the reagent.

5. The light guide plate of claim 1, wherein the first clad layer and the second clad layer comprise a first photosensitivity and the core layer comprises a second photosensitivity less than the first photosensitivity.

6. The light guide plate of claim 5, wherein the second photosensitivity is zero photosensitivity.

7. The light guide plate of claim 1, wherein the core layer comprises a non-planar shape.

8. The light guide plate of claim 1, wherein each of the first plurality of light extraction features comprise a circular shape, a rectangular shape, or a triangular shape.

9. The light guide plate of claim 1, wherein each of the first plurality of light extraction features comprise a width between 30 and 90 micrometers, a height between 10 and 30 micrometers, and a spacing between next nearest light extraction features between 100 and 250 micrometers.

10. An illumination device comprising:

a laminate glass comprising a core layer, a first clad layer on a first surface of the core layer, and a second clad layer on a second surface of the core layer opposite to the first surface;

a first plurality of light extraction features formed from the first clad layer; and a light source arranged to emit light into the core layer through a third surface of the core layer extending between the first surface and the second surface.

11. The illumination device of claim 10, further comprising:

12. The illumination device of claim 10, wherein the core layer comprises a non- planar shape.

13. The illumination device of claim 10, wherein the light source comprises a light emitting diode.

14. A method for fabricating an illumination device, the method comprising:

masking a first clad layer of a laminate glass with a first mask, the laminate glass comprising a core layer between the first clad layer and a second clad layer; and

etching the first clad layer based on the first mask to form a first plurality of light extraction features.

15. The method of claim 14, further comprising:

masking the second clad layer with a second mask; and etching the second clad layer based on the second mask to form a second plurality of light extraction features.

16. The method of claim 14, further comprising:

hot forming the laminate glass to change the shape of the laminate glass.

17. The method of claim 14, wherein masking the first clad layer of the laminate glass comprises applying a resist material to the first clad layer to form the first mask.

18. The method of claim 14, further comprising:

exposing the first clad layer to ultraviolet light through the first mask.

19. The method of claim 14, wherein etching the first clad layer comprises etching the first clad layer to expose portions of the core layer.

20. The method of claim 14, further comprising:

arranging a light source adjacent to a surface of the core layer extending between the first clad layer and the second clad layer.