WO2018144720A1

WO2018144720A1 - Light guide assemblies comprising optical manipulation features

Info

Publication number: WO2018144720A1
Application number: PCT/US2018/016430
Authority: WO
Inventors: Shenping Li; Wageesha Senaratne; Natesan Venkataraman
Original assignee: Corning Incorporated
Priority date: 2017-02-01
Filing date: 2018-02-01
Publication date: 2018-08-09
Also published as: CN110249176A; KR20190108622A; JP2020506525A; TW201835621A

Abstract

Disclosed herein are light guide assemblies comprising a glass substrate, a prismatic layer, and at least one modifying layer comprising an inorganic or inorganic-organic hybrid material. At least one light source may be optically coupled to an edge surface of the glass substrate to provide an optical assembly. Display and lighting devices comprising such light guide and optical assemblies are further disclosed.

Description

LIGHT GUIDE ASSEMBLIES COMPRISING OPTICAL MANIPULATION

FEATURES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S. Provisional Application Serial No. 62/453,075 filed on February 1 , 2017, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The disclosure relates generally to light guide assemblies and display or lighting devices comprising such assemblies, and more particularly to glass light guide plates comprising at least one optical manipulation feature.

BACKGROUND

[0003] Liquid crystal displays (LCDs) are commonly used in various electronics, such as cell phones, laptops, electronic tablets, televisions, and computer monitors. However, LCDs can be limited as compared to other display devices in terms of brightness, contrast ratio, efficiency, and viewing angle. For instance, to compete with other display technologies, there is a continuing demand for higher contrast ratio, color gamut, and brightness in conventional LCDs while also balancing power requirements and device size (e.g., thickness).

[0004] LCDs can comprise a backlight unit (BLU) for producing light that can then be converted, filtered, and/or polarized to produce the desired image.

BLUs may be edge-lit, e.g. , comprising a light source coupled to an edge of a light guide plate (LGP), or back-lit, e.g., comprising a two-dimensional array of light sources disposed behind the LCD panel. Back-lit BLUs may have the advantage of improved dynamic contrast as compared to edge-lit BLUs. For example, a display with a back-lit BLU can independently adjust the brightness of each LED to optimize the dynamic range of the brightness across the image. This is commonly known as local dimming. However, to achieve desired light uniformity and/or to avoid hot spots in back-lit BLUs, the light source(s) may be positioned at a distance from the LGP, thus making the overall display thickness greater than that of an edge-lit BLU. In traditional edge-lit BLUs, the light from each LED can spread across a large region of the LGP such that turning off individual LEDs or groups of LEDs may have only a minimal impact on the dynamic contrast ratio.

[0005] The local dimming efficiency of an LGP can be enhanced, for example, by providing one or more micro structures on the LGP surface. For instance, plastic LGPs, such as polymethyl methacrylate (PMMA) or methyl methacrylate styrene (MS) LGPs, can be fabricated with surface microstructures, e.g., microlenses, that may collimate or confine the light from each LED within a narrow band. In this way, it may be possible to adjust the brightness of the light source(s) along the edge of the LGP to enhance the dynamic contrast of the display. If LEDs are mounted on two opposing sides of the LGP, the brightness of pairs of LEDs can be adjusted to produce a brightness gradient along the bands of illumination that may further improve the dynamic contrast.

[0006] It may also be advantageous to modify a LGP to improve the uniformity of color and/or intensity of light extracted from the LGP. For instance, at least one surface of the LGP may be modified to include light extraction features that destroy total internal reflection (TIR) in the LGP. In some instances, the density of the light extraction features may increase with distance from the light source.

Techniques for surface modification of LGPs to form microstructures and/or light extraction features may include, for example, screen printing, inkjet printing, thermal imprinting, and laser imprinting. Laser imprinting may have certain advantages in terms of pattern control the patterning, e.g., using software, reduced processing time, repeatability, and manufacturing flexibility. Thermal imprinting may also have advantages in terms of improved control over feature shape, repeatability, and mass processing capability.

[0007] Glass LGPs may offer various improvements over plastic LGPs, e.g., in terms of their low light attenuation, low coefficient of thermal expansion, and high mechanical strength. As such, it may be desirable to use glass as an alternative material of construction for LGPs in order to overcome various drawbacks associated with plastics. For instance, due to their relatively weak mechanical strength and/or low stiffness, it can be difficult to make plastic LGPs that are both sufficiently large and thin to meet current consumer demands. Plastic LGPs may also necessitate a larger gap between the light source and LGP due to high coefficients of thermal expansion, which can reduce optical coupling efficiency and/or require a larger display bezel. Additionally, plastic LGPs may have a higher propensity to discolor over time and/or to absorb moisture and swell as compared to glass LGPs.

[0008] Due to the above-mentioned advantages, many display

manufacturers are replacing plastic LGPs with glass LGPs, e.g., to produce thinner displays. However, the BLU can still comprise other polymeric layers, such as brightness enhancing films (BEFs) or light diffusing layers, which may have one or more of the drawbacks mentioned above. Accordingly, it would be advantageous to provide BLU stacks comprising as few polymeric components as possible, e.g., by replacing at least one organic layer in the BLU with an inorganic or inorganic-organic hybrid layer. It would also be advantageous to provide a BLU comprising a glass LGP and having at least one of improved local dimming efficiency, improved light uniformity, and/or improved light extraction efficiency.

SUMMARY

[0009] The disclosure relates, in various embodiments, to Also disclosed herein are light guide assemblies comprising a glass substrate having a light emitting first major surface and an opposing second major surface; a prismatic layer comprising an organic, inorganic, or inorganic-organic hybrid material; and a first modifying layer positioned between the first major surface of the glass substrate and the prismatic layer. The first modifying layer can comprise an inorganic or inorganic- organic hybrid material and a refractive index n_M less than a refractive index n_G of the glass substrate.

[0010] According to various embodiments, the refractive index n_M of the first modifying layer may be less than a refractive index n_P of the prismatic layer. The light guide assembly may further comprise at least one adhesive layer, e.g., between the prismatic layer and the first modifying layer. A refractive index n_A of the adhesive layer may, in some embodiments, be less than a refractive index n_P of the prismatic layer and greater than the refractive index n_M of the first modifying layer. In other embodiments, the light guide assembly may not comprise an adhesive layer, e.g., an inorganic or inorganic-organic hybrid prismatic layer may be disposed directly on the first modifying layer.

[0011] According to certain embodiments, the light guide assembly may further comprise a second modifying layer disposed on the second major surface of the glass substrate, the second modifying layer comprising an inorganic or inorganic- hybrid material. A refractive index η_Μ· of the second modifying layer may be greater than or equal to the refractive index n_G of the glass substrate. The second modifying layer and/or second major surface of the glass substrate may comprise at least one light extraction feature, e.g., a plurality of light extraction features. A thickness of the first or second modifying layer may range, for example, from about 5 μιη to about 100 μιη.

[0012] Further disclosed herein are light guide assemblies comprising a glass substrate having a light emitting first major surface and an opposing second major surface; and a prismatic layer disposed on the first major surface of the glass substrate. The prismatic layer can comprise an inorganic or inorganic-organic hybrid material and a refractive index n_P less than a refractive index n_G of the glass substrate. In some embodiments, the light guide assembly may further comprise a second modifying layer disposed on the second major surface of the glass substrate, the second modifying layer comprising an inorganic or inorganic-hybrid material and a refractive index n_M greater than or equal to the refractive index n_G of the glass substrate. According to non-limiting embodiments, the second modifying layer can comprise a plurality of light extraction features and/or microstructures. Exemplary microstructures can include a periodic or non-periodic array of prisms, rounded prisms, or lenticular lenses.

[0013] Still further disclosed herein are optical assemblies comprising a light source optically coupled to an edge surface of any light guide assembly disclosed herein. The light source may, in some embodiments, have a maximum emission angle ©m satisfying the following equation: 9_m ≤ arcsin

In other words, if a light source with a maximum emission angle (0_m) is used, the refractive indexes of the glass substrate and the first modifying layer can satisfy the following equation: n_L ² _GP - n_L ² _I > sin(#_ffl) . Display, electronic, and lighting devices comprising such light guide and optical assemblies are also disclosed herein.

[0014] Additional features and advantages of the disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the methods as described herein, including the detailed description which follows, the claims, as well as the appended drawings. [0015] It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the

disclosure, and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure, 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 of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following detailed description can be further understood when read in conjunction with the following drawings, in which:

[0017] FIGS. 1 -5B illustrate exemplary configuration of light guide assemblies according to various embodiments of the disclosure; and

[0018] FIGS. 6A-D illustrate exemplary microstructured surfaces according to certain embodiments of the disclosure.

DETAILED DESCRIPTION

[0019] Disclosed herein are light guide assemblies comprising a glass substrate having a light emitting first major surface and an opposing second major surface; a prismatic layer comprising an organic, inorganic, or inorganic-organic hybrid material; and a first modifying layer positioned between the first major surface of the glass substrate and the prismatic layer. The first modifying layer can comprise an inorganic or inorganic-organic hybrid material and a refractive index n_M less than a refractive index n_G of the glass substrate. The light guide assemblies may further comprise an adhesive layer and/or second modifying layer.

[0020] Also disclosed herein are light guide assemblies comprising a glass substrate having a light emitting first major surface and an opposing second major surface; and a prismatic layer disposed on the first major surface of the glass substrate. The prismatic layer can comprise an inorganic or inorganic-organic hybrid material and a refractive index n_P less than a refractive index n_G of the glass substrate. The light guide assemblies may further comprise a second modifying layer. Still further disclosed herein are optical assemblies comprising a light source optically coupled to an edge surface of any light guide assembly disclosed herein. Devices comprising such light guide and optical assemblies are also disclosed herein, such as display, lighting, and electronic devices, e.g., televisions, computers, phones, tablets, and other display panels, luminaires, solid-state lighting, billboards, and other architectural elements, to name a few.

[0021] Various embodiments of the disclosure will now be discussed with reference to FIGS. 1 -6, which illustrate exemplary embodiments and aspects of light guide assemblies. The following general description is intended to provide an overview of the claimed devices, and various aspects will be more specifically discussed throughout the disclosure with reference to the non-limiting depicted embodiments, these embodiments being interchangeable with one another within the context of the disclosure.

[0022] FIG. 1 illustrates an exemplary light guide assembly 100 comprising a glass substrate 110, a prismatic layer 115, and a first modifying layer 120. The glass substrate 110 can have a light emitting first major surface 125, a light incident edge surface 130, and a second major surface 135 opposite the first major surface 125. The first modifying layer 120 may be disposed on the first major light emitting surface 125 of the glass substrate 110, and the prismatic layer 115 may be disposed on the first modifying layer 120. The first modifying layer 120 may be positioned between the glass substrate 110 and the prismatic layer 115. The prismatic layer 115 can comprise organic, inorganic or inorganic-organic hybrid materials. The first modifying layer 120 can comprise inorganic or inorganic-organic hybrid materials. Suitable materials for the prismatic layer 115 and first modifying layer 120 are discussed in more detail below.

[0023] As used herein, the term "disposed on" and variations thereof is intended to denote that a component or layer is located on a particular surface and in direct physical contact with that surface. For instance, first modifying layer 120 may be disposed on the first major surface 125 of the glass substrate 110 and in direct physical contact with that surface, e.g., without any additional layers or films positioned therebetween. As such, a component A disposed on a surface of component B is in direct physical contact with component B.

[0024] In some embodiments, at least one light source 140 may be optically coupled to the light-incident edge surface 130, e.g., positioned adjacent to the edge surface. As used herein, the term "optically coupled" is intended to denote that a light source is positioned at an edge of the LGP so as to introduce light into the LGP. A light source may be optically coupled to the LGP even though it is not in physical contact with the LGP. Additional light sources (not illustrated) may also be optically coupled to other edge surfaces of the LGP, such as adjacent or opposing edge surfaces.

[0025] A plurality of light extraction features 145 may be formed on the second major surface 135 or within the matrix of the glass substrate 110, e.g. , under the second major surface 135, as discussed in more detail below. A reflector 150 may be positioned adjacent to the second major surface 135 of the glass substrate 110 to recycle light back to the light guide assembly 100.

[0026] Referring to FIG. 2, a light guide assembly 100 can comprise a glass substrate 110 and a first modifying layer 120 disposed on the light emitting first major surface 125 of the glass substrate 110. A prismatic layer 115 may be positioned adjacent to the first modifying layer 120, e.g. , such that the first modifying layer 120 is positioned between the glass substrate 110 and the prismatic layer 115. Optionally, an adhesive layer 155 may be positioned between the prismatic layer 115 and the first modifying layer 120. For instance, the first modifying layer 120 may be disposed on the first major surface 125, adhesive layer 155 may be disposed on the first modifying layer 120, and the prismatic layer 115 may be disposed on the adhesive layer 155, in some non-limiting embodiments. In certain embodiments, the prismatic layer 115 may be laminated to the first modifying layer 120 by the adhesive layer 155. The prismatic layer 115 can comprise organic, inorganic or inorganic- organic hybrid materials. The first modifying layer 120 can comprise inorganic or inorganic-organic hybrid materials.

[0027] As used herein, the term "positioned adjacent" and variations thereof is intended to denote that a component or layer is located on or near a particular surface of a listed component, but not necessarily in direct physical contact with that surface. For instance, the prismatic layer 115 is depicted in FIG. 1 in direct physical contact with first modifying layer 120. However, in some embodiments, such as the embodiment depicted in FIG. 2, other layers or films (e.g., adhesive layer 155), or even a gap, may be present between these two components. In FIG. 1 , the prismatic layer 115 is disposed on the first modifying layer 120. In FIG. 2, the prismatic layer 115 is positioned adjacent the first modifying layer 120.

[0028] As such, a component A "positioned adjacent" a surface of component B may or may not be in direct physical contact with component B. In some embodiments, a component positioned adjacent a surface may be in direct physical contact with that surface. Similarly, a component A "positioned between" components B and C may be located between components B and C, but not necessarily in direct physical contact with these components. In certain

embodiments, a first component positioned between second components may be in direct physical contact with at least one of the second components.

[0029] A plurality of light extraction features 145 may be formed on the second major surface 135 or within the matrix of the glass substrate 110, e.g. , under the second major surface 135, as discussed in more detail below. Similar to FIG. 1 , a light source 140 may be positioned adjacent to the light incident edge surface 130 of the glass substrate 110 and a reflector 150 may be positioned adjacent to the second major surface 135 of the glass substrate 110.

[0030] With reference to FIG. 3, a light guide assembly 100 can comprise a glass substrate 110, a first modifying layer 120 disposed on the first major surface 125 of the glass substrate 110, a second modifying layer 120' disposed on the second major surface 135 of the glass substrate, and a prismatic layer 115 disposed on (illustrated) or positioned adjacent to (not illustrated) the first modifying layer 120. The first modifying layer 120 may be positioned between the glass substrate 110 and the prismatic layer 115. The prismatic layer 115 can comprise organic, inorganic or inorganic-organic hybrid materials. The first and second modifying layers 120, 120' can comprise inorganic or inorganic-organic hybrid materials.

[0031] A light source 140 may be positioned adjacent to the light incident edge surface 130 of the glass substrate 110 and a reflector 150 may be positioned adjacent to the second modifying layer 120'. According to additional embodiments, a plurality of light extraction features 145 may be formed on or in the second modifying layer 120' as discussed in more detail below.

[0032] Referring to FIG. 4, a light guide assembly 100 can comprise a glass substrate 110 and a prismatic layer 115 disposed on the light emitting first major surface 125 of the glass substrate 110. The prismatic layer 115 may comprise an inorganic or inorganic-organic hybrid material, as discussed in more detail below. A plurality of light extraction features 145 may be formed on the second major surface 135 or within the matrix of the glass substrate 110, e.g., under the second major surface 135, as discussed in more detail below. A light source 140 may be positioned adjacent to the light incident edge surface 130 of the glass substrate 110 and a reflector 150 may be positioned adjacent to the second major surface 135 of the glass substrate 110.

[0033] FIGS. 5A-B depict side views of a light guide assembly 100 as viewed from an edge surface 160 adjacent (e.g. , orthogonal) to the light incident surface 130 and from the light incident surface 130, respectively. The light guide assembly 100 can comprise a glass substrate 110, a prismatic layer 115 disposed on the light emitting first major surface 125 of the glass substrate 110, and a second modifying layer 120' disposed on the second major surface 135 of the glass substrate. As depicted in FIGS. 5A-B, the second modifying layer 120' may comprise a plurality of microstructures 165.

[0034] As used herein, the term "microstructures," "microstructured," and variations thereof is intended to refer to surface relief features of the modifying layer extending in a given direction (e.g., parallel or orthogonal to a direction of light propagation) and having at least one dimension (e.g., height, width, etc.) that is less than about 500 μιη, such as less than about 400 μιη, less than about 300 μιη, less than about 200 μιη, less than about 100 μιη, less than about 50 μιη, or even less, e.g., ranging from about 1 0 μιη to about 500 μιη, including all ranges and subranges therebetween. The microstructures may, in certain embodiments, have regular or irregular shapes, which can be identical or different within a given array.

[0035] While the configuration depicted in FIGS. 5A-B depicts a second modifying layer 120' including microstructures 165, it is to be understood that the second modifying layer 120' may not include microstructures 165, in some embodiments. Similarly, while the embodiment depicted in FIG. 3 is not described as having a microstructured second modifying layer 120', it is to be understood that the second modifying layer 120' may include microstructures, in non-limiting embodiments.

[0036] The prismatic layer 115 and second modifying layer 120' may comprise an inorganic or inorganic-organic hybrid material, as discussed in more detail below. A plurality of light extraction features 145 may be formed on or in the second modifying layer 120'. In some embodiments, light extraction features 145 may be disposed on top of microstructures 165, e.g., as illustrated in FIG. 5B. A light source 140 may be positioned adjacent to a light incident edge surface 130 of the glass substrate 110 and a reflector 150 may also be positioned adjacent to the second modifying layer 120' to recycle light back to the light guide assembly 100. [0037] Light from the light source 140 may spread quickly within the light guide assembly 100, which can make it challenging to effect local dimming (e.g., by turning off one or more light sources). However, by providing one or more microstructures that are elongated in the direction of light propagation (as indicated by the solid arrow in FIG. 5A), it may be possible to limit the spreading of the light such that each light source effectively illuminates only a narrow strip of the LGP. The illuminated strip may extend, for example, from the point of origin at the light incident edge surface 130 to a similar endpoint on an opposing edge surface 170. As such, using various microstructure configurations, it may be possible to collimate the light and effect 1 D local dimming of at least a portion of the light guide assembly 100 in a relatively efficient manner.

[0038] In certain embodiments, the light guide assembly can be configured such that it is possible to achieve 2D local dimming. For instance, one or more additional light sources can be optically coupled to an adjacent (e.g., orthogonal) edge surface, such as one or both of edge surfaces 160. One modifying layer may comprise microstructures extending in a light propagation direction, and another modifying layer (not illustrated) may comprise microstructures extending in a direction orthogonal to the light propagation direction. Thus, 2D local dimming may be achieved by selectively shutting off one or more of the light sources along each edge surface.

[0039] While FIG. 5B generally illustrates microstructures 165 of the same size and shape, which are evenly spaced apart at substantially the same pitch, it is to be understood that not all microstructures within a given array must have the same size and/or shape and/or spacing. Combinations of microstructure shapes and/or sizes may be used, and such combinations may be arranged in a periodic or non-periodic fashion. Additionally, while FIG. 5B illustrates microstructures 165 having a lenticular profile, the second modifying layer 120' can comprise any other suitable microstructures 165 with different profiles. For instance, FIGS. 6A-B illustrate microstructures comprising prisms 165A and rounded prisms 165B, respectively. As shown in FIG. 6C, the microstructures may also comprise lenticular lenses 165C. Of course, the depicted microstructures are exemplary only and are not intended to limit the appended claims. Other microstructure shapes are possible and intended to fall within the scope of the disclosure. Furthermore, while FIGS. 6A- C illustrate regular (or periodic) arrays, it is also possible to use an irregular (or non- periodic) array. For instance, FIG. 6D is an SEM image of a microstructured surface comprising a non-periodic array of prisms.

[0040] The size and/or shape of the microstructures 165 can also vary depending on the desired light output and/or optical functionality of the light guide assembly 100. For instance, different microstructure shapes may result in different local dimming efficiencies, also referred to as the local dimming index (LDI). The local dimming index may be determined, for example, using the methods set forth in Jung et al., "Local dimming design and optimization for edge-type LED backlight unit," SID Symp. Dig. Tech. Papers, 42(1 ), pp. 1430-1432 (June 201 1 ). By way of non-limiting example, a periodic array of prism microstructures may result in an LDI value up to about 70%, whereas a periodic array of lenticular lenses may result in an LDI value up to about 83%. Of course, the microstructure size and/or shape and/or spacing may be varied to achieve different LDI values. Different microstructure shapes may also provide additional optical functionalities. For instance, a prism array having a 90° prism angle may not only result in more efficient local dimming, but may also partially focus the light in a direction perpendicular to the prismatic ridges due to recycling and redirecting of the light rays.

[0041] With reference to FIG. 6A, prism microstructures 165A can have a prism angle Θ ranging from about 60° to about 120°, such as from about 70° to about 1 10°, from about 80° to about 100°, or about 90°, including all ranges and subranges therebetween. Referring to FIG. 6C, lenticular microstructures 165C can have any given cross-sectional shape (as illustrated by the dashed lines), ranging from semicircular, semi-elliptical, parabolic, or other similar rounded shapes. It should be noted that light extraction features are not illustrated in FIGS. 6A-C for purposes of simplified illustration, but such features may be present in non-limiting embodiments.

[0042] The second modifying layer 120' (with microstructures) may have an overall thickness d₂ and a "land" thickness t. The microstructures may comprise peaks p and valleys v, and the overall thickness may correspond to the height of the peaks p, whereas the land thickness may correspond to the height of the valleys v. According to various embodiments, it may be advantageous to provide a second modifying layer 120' having a land thickness t equal to zero or as close to zero as possible. When t is zero, the second modifying layer 120' may be discontinuous. For instance, the land thickness t may range from 0 to about 50 μιη, such as from about 1 μιη to about 40 μιη, from about 2 μιη to about 30 μιη, from about 5 μιη to about 20 μιη, or from about 10 μιη to about 15 μιη, including all ranges and subranges therebetween. In additional embodiments, the overall thickness d₂ of the second modifying layer 120' may range from about 10 μιη to about 100 μιη, such as from about 20 μιη to about 90 μιη, from about 30 μιη to about 80 μιη, from about 40 μιη to about 70 μιη, or from about 50 μιη to about 60 μιη, including all ranges and subranges therebetween.

[0043] With continued reference to FIGS. 6A-C, the microstructures may also have a width w, which can be varied as appropriate to achieve a desired aspect ratio. Variation of the land thickness t and overall thickness d₂ can also be used to modify the light output. In non-limiting embodiments, the aspect ratio (w/[d₂-t]) of the microstructures 165 can range from about 0.2 to about 8, such as from about 0.5 to about 7, from about 1 to about 6, from about 1.5 to about 5, from about 2 to about 4, or from about 2.5 to about 3, including all ranges and subranges therebetween.

According to some embodiments, the aspect ratio can range from about 2 to about 3, e.g., about 2, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3, including all ranges and subranges therebetween. The width w of the microstructures 165 can also range, for example, from about 1 μιη to about 500 μιη, such as from about 10 μιη to about 400 μιη, from about 20 μιη to about 300 μιη, from about 30 μιη to about 250 μιη, from about 40 μιη to about 200 μιη, or from about 50 μιη to about 100 μιη, including all ranges and subranges therebetween. It should also be noted that the

microstructures 165 may have a length L extending in the direction of light propagation or in a direction orthogonal to the propagation of light (see, e.g., dashed lines in FIGS. 6A-C). The length L of the microstructures 165 can vary as desired, e.g., depending on the dimensions of the glass substrate 110. According to various embodiments, the microstructures may have one or more discontinuities along their length L or width w.

[0044] A general direction of light emission from light source 140 is depicted in FIGS. 1-5 by a solid arrow. Light injected into the LGP may propagate along a length of the LGP due to total internal reflection (TIR), until it strikes an interface at an angle of incidence that is less than the critical angle. Total internal reflection (TIR) is the phenomenon by which light propagating in a first material (e.g., glass, plastic, etc.) comprising a first refractive index can be totally reflected at the interface with a second material (e.g., air, etc.) comprising a second refractive index lower than the first refractive index. TIR can be explained using Snell's law: W_j Sin^ ) = «₂ sin(^)

which describes the refraction of light at an interface between two materials of differing indices of refraction. In accordance with Snell's law, n₁ is the refractive index of a first material, n₂ is the refractive index of a second material, Θ, is the angle of the light incident at the interface relative to a normal to the interface (incident angle), and 0_r is the angle of refraction of the refracted light relative to the normal. When the angle of refraction (0_r) is 90°, e.g. , sin(0_r) = 1 , Snell's law can be expressed as:

< _c = < , = sin ¹(¾

The incident angle Θ, under these conditions may also be referred to as the critical angle Θ₀. Light having an incident angle greater than the critical angle (Θ, > Θ₀) will be totally internally reflected within the first material, whereas light with an incident angle equal to or less than the critical angle (Θ, < Θ₀) will be transmitted by the first material.

[0045] In the case of an exemplary interface between air (A?7= ) and glass ( 7₂=1 -5), the critical angle (Θ₀) can be calculated as 42°. Thus, if light propagating in the glass strikes the air-glass interface at an incident angle greater than 42°, all the incident light will be reflected from the interface at an angle equal to the incident angle. If the reflected light encounters a second interface comprising an identical refractive index relationship as the first interface, the light incident on the second interface will again be reflected at a reflection angle equal to the incident angle.

[0046] As used herein, "refractive index" refers to the refractive index of a material as measured near the peak of human eye response (e.g., about 550 nm). The refractive indices of the various components of the light guide assembly 100 may be chosen to increase the amount of light transmitted by the light guide assembly 100 in a direction normal or substantially normal to the light emitting surface 125 of the glass substrate 110, e.g., toward the viewer. For instance, in the non-limiting embodiments depicted in FIGS. 1-3, the first modifying layer 120 may have a refractive index n_M that is less than a refractive index n_G of the glass substrate 110 and the refractive index n_P of the prismatic layer 115. The refractive index n_P of the prismatic layer 115 may, in some embodiments, be greater than or equal to the refractive index n_G of the glass substrate 110. The adhesive layer 155, if present (FIG. 2), may have a refractive index n_A greater than the refractive index n_M of the first modifying layer 120, but less than the refractive index n_P of the prismatic layer 115, in some embodiments. The second modifying layer 120', if present (FIG. 3), may have a refractive index n_M- greater than or equal to the refractive index n_G of the glass substrate 110. In the non-limiting embodiments depicted in FIGS. 4-5, the refractive index n_P of the prismatic layer 115 may be less than the refractive index n_G of the glass substrate 110. The second modifying layer 120', if present (FIGS. 5A-B), may have a refractive index 7_M that is greater than or equal to a refractive index n_G of the glass substrate 110.

[0047] According to various embodiments, a refractive index n_G of the glass substrate 110 may range from about 1 .3 to about 1 .8, such as from about 1 .35 to about 1 .7, from about 1 .4 to about 1 .65, from about 1 .45 to about 1 .6, or from about 1 .5 to about 1 .55, including all ranges and subranges therebetween. In some embodiments, the first modifying layer 120 may have a refractive index less than that of the glass substrate 110, e.g., n_G may be at least about 1 % greater than n_M, such as at least about 2%, at least about 3%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, or at least about 25% greater than n_M, including all ranges and subranges therebetween, for instance, from about 1 % to about 25% greater than n_M. In non-limiting embodiments, n_M may range from about 1 to about 1 .78, such as from about 1 .1 to about 1 .75, from about 1 .2 to about 1 .7, from about 1 .3 to about 1 .6, or from about 1 .4 to about 1 .5, including all ranges and subranges therebetween.

[0048] According to additional embodiments, the second modifying layer 120' (with or without microstructures) may have a refractive index greater than that of the glass substrate 110, e.g., η_Μ· may be at least about 1 % greater than n_G, such as at least about 2%, at least about 3%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, or at least about 25% greater than n_G, including all ranges and subranges therebetween, for instance, from about 1 % to about 25% greater than n_G. In non-limiting embodiments, η_Μ· may range from about 1 .32 to about 2.1 , such as from about 1 .35 to about 2, from about 1 .4 to about 1 .9, from about 1 .5 to about 1 .8, or from about 1 .6 to about 1 .7, including all ranges and subranges therebetween. According to further embodiments, the second modifying layer 120' may have a refractive index equal to or substantially equal to that of the glass substrate 110, e.g., ^M- may be within about 1 % of n_G, such as within about 0.5%, within about 0.2%, or within about 0.1 % of n_G, including all ranges and subranges therebetween

[0049] According to certain embodiments, e.g., if the prismatic layer 115 is disposed on the first major surface 125 of glass substrate 110, the prismatic layer 115 may have a refractive index less than that of the glass substrate 100, e.g., n_G may be at least about 1 % greater than n_P, such as at least about 2%, at least about 3%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, or at least about 25% greater than n_P, including all ranges and subranges

therebetween, for instance, from about 1 % to about 25% greater than n_P. In some embodiments, e.g., if first modifying layer 120 is positioned between the prismatic layer 115 and the glass substrate 110, the prismatic layer 115 may have a refractive index greater than that of the glass substrate 110 and/or first modifying layer 120, e.g., n_P may be at least about 1 % greater than n_G and/or n_M, such as at least about 2%, at least about 3%, at least about 5%, at least about 10%, at least about 15%, at least about 20%, or at least about 25% greater than n_G and/or n_Ml including all ranges and subranges therebetween, for instance, from about 1 % to about 25% greater than n_G and/or n_M. According to further embodiments, the prismatic layer 115 may have a refractive index equal to or substantially equal to that of the glass substrate 110 and/or first modifying layer 120 and/or second modifying layer 120', e.g., n_P may be within about 1 % of n_G and/or n_M and/or n_M; such as within about 0.5%, within about 0.2%, or within about 0.1 % of n_G and/or n_M and/or n_M; including all ranges and subranges therebetween.

[0050] In some embodiments, light source 140 may be a Lambertian light source, such as a light emitting diode (LED). The light source 140 may, in certain embodiments, emit blue, UV, or near-UV light (e.g., approximately 100-500 nm). According to various embodiments, the maximum emission angle (0_m) of the light source (e.g., LED) and the refractive indices of the glass substrate and first modifying layer may be chosen to maximize coupling efficiency of light from the light source into the light guide assembly. For instance, for given refractive indices n_G and n_M of the glass substrate and first modifying layer, the light source may be chosen such that its maximum emission angle 0_m satisfies the following equation (1 ):

9_m ≤ arcsin (n_G ² - n_M ² ) ( 1 ) Similarly, for a given maximum emission angle 0_m, the glass substrate and first modifying layer refractive indices may be chosen such that the following equation (2) is satisfied:

n_G ² - n_M ² ≥ sin(0_m) (2)

As used herein, the term "maximum emission angle" is intended to refer to the largest angle of light emission relative to the normal of the emission source surface, for example, if the angular distribution of a planar LED output is Lambertian, the maximum emission angle may be about 80 degrees.

[0051] Referring again to FIGS. 1-5, the first modifying layer 120, second modifying layer 120', or the glass substrate 110 may comprise a plurality of light extraction features 145 formed on or under a surface thereof. For instance, the first modifying layer 120, second modifying layer 120', or the second major surface 135 of the glass substrate 110 may be patterned with a plurality of light extraction features 145. The light extraction features 145 may be distributed on a surface as textural features making up a roughened or raised surface, or may be distributed within and throughout the glass substrate 110, first modifying layer 120, second modifying layer 120', or portions thereof, e.g., as laser-damaged features. Light extraction features 145 may have any cross-sectional profile and can comprise at least one dimension (e.g., width, height, length, etc.) that is less than about 100 microns (μιη), such as less than about 75 μιη, less than about 50 μιη, less than about 25 μιη, less than about 10 μιη, or even less, including all ranges and subranges therebetween, e.g., ranging from about 1 μιη to about 100 μιη.

[0052] In various embodiments, the light extraction features 145 may comprise light scattering sites. According to various embodiments, the extraction features 145 may be patterned in a suitable density so as to produce substantially uniform light output intensity across the light emitting surface 125 of the glass substrate 110. In certain embodiments, a density of the light extraction features 145 proximate the light source 140 may be lower than a density of the light extraction features 145 at a point further removed from the light source 140, or vice versa, such as a gradient from one end to another, as appropriate to create the desired light output distribution across the light guide assembly 100.

[0053] Suitable methods for creating such light extraction features can include printing, such as inkjet printing, screen printing, microprinting, and the like, texturing, mechanical roughening, etching, injection molding, coating, laser damaging, or any combination thereof. Light extraction features 145 may, for example, be formed using the methods disclosed in co-pending and co-owned International Patent Application Nos. PCT/US201 3/063622 and

PCT/US2014/070771 , each incorporated herein by reference in their entirety. Non- limiting examples of suitable methods can also include, for instance, acid etching a surface, coating a surface with Ti0₂, and laser damaging the substrate or layer by focusing a laser on a surface or within the matrix.

[0054] Exemplary lasers include, but are not limited to, Nd:YAG lasers, C0₂ lasers, and the like. The operating parameters of the laser, such as laser power, pulse duration, pulse energy, and other variables may vary depending on the desired light extraction feature profile. In some embodiments, the pulse duration may range from about 1 to about 1000 microseconds (με), such as from about 5 to about 500 με, from about 10 με to about 200 με, from about 20 με to about 100 με, or from about 30 με to about 50 με, including all ranges and subranges

therebetween. The laser power may also range from about 1 to about 100 Watts (W), such as from about 5 to about 50 W, or from about 10 to about 35 W, including all ranges and subranges therebetween. The laser energy may range, for example, from about 0.01 to about 100 millijoules (mJ), such as from about 0.1 to about 10 mJ, from about 0.5 to about 5 mJ, or from about 1 mJ to about 2 mJ, including all ranges and subranges therebetween.

[0055] The glass substrate 110 can have any desired size and/or shape as appropriate to produce a desired light distribution. The major surfaces 125, 135 of glass substrate 110 may, in certain embodiments, be planar or substantially planar and/or parallel. The first and second major surfaces may also, in various

embodiments, have a radius of curvature along at least one axis. The glass substrate 110 may comprise four edges, or may comprise more than four edges, e.g. a multi-sided polygon. In other embodiments, the glass substrate 110 may comprise less than four edges, e.g., a triangle. By way of a non-limiting example, the glass substrate 110 may comprise a rectangular, square, or rhomboid sheet having four edges, although other shapes and configurations are intended to fall within the scope of the disclosure including those having one or more curvilinear portions or edges.

[0056] In certain embodiments, the glass substrate 110 may have a thickness of less than or equal to about 3 mm, for example, ranging from about 0.1 mm to about 2.5 mm, from about 0.3 mm to about 2 mm, from about 0.5 mm to about 1 .5 mm, or from about 0.7 mm to about 1 mm, including all ranges and subranges therebetween. The glass substrate 110 can comprise any material known in the art for use in display devices, including 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 glass light guide include, for instance, EAGLE XG^®, Lotus™, Willow^®, Iris™, and Gorilla^® glasses from Corning Incorporated.

[0057] Some non-limiting glass compositions can include between about 50 mol % to about 90 mol% Si0₂, between 0 mol% to about 20 mol% Al₂0₃, between 0 mol% to about 20 mol% B₂0₃, between 0 mol% to about 20 mol% P₂0₅, and between 0 mol% to about 25 mol% R_xO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1 . In some embodiments, R_xO - Al₂0₃ > 0; 0 < R_xO - AI2O3 < 15; x = 2 and R₂0 - Al₂0₃ < 15; R₂0 - Al₂0₃ < 2; x=2 and R₂0 - AI2O3 - MgO > -15; 0 < (R_xO - Al₂0₃) < 25, -1 1 < (R₂0 - Al₂0₃) < 1 1 , and -15 < (R₂0 - Al₂0₃ - MgO) < 1 1 ; and/or -1 < (R₂0 - Al₂0₃) < 2 and -6 < (R₂0 - Al₂0₃ - MgO) < 1 . In some embodiments, the glass comprises less than 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is < about 50 ppm, < about 20 ppm, or < about 10 ppm. In other embodiments, Fe + 30Cr + 35Ni < about 60 ppm, Fe + 30Cr + 35Ni < about 40 ppm, Fe + 30Cr + 35Ni < about 20 ppm, or Fe + 30Cr + 35Ni < about 10 ppm. In other embodiments, the glass comprises between about 60 mol % to about 80 mol% Si0₂, between about 0.1 mol% to about 15 mol% Al₂0₃, 0 mol% to about 12 mol% B₂0₃, and about 0.1 mol% to about 15 mol% R₂0 and about 0.1 mol% to about 15 mol% RO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1 .

[0058] In other embodiments, the glass composition can comprise between about 65.79 mol % to about 78.17 mol% Si0₂, between about 2.94 mol% to about 12.12 mol% Al₂0₃, between about 0 mol% to about 1 1 .16 mol% B₂0₃, between about 0 mol% to about 2.06 mol% Li₂0, between about 3.52 mol% to about 13.25 mol% Na₂0, between about 0 mol% to about 4.83 mol% K₂0, between about 0 mol% to about 3.01 mol% ZnO, between about 0 mol% to about 8.72 mol% MgO, between about 0 mol% to about 4.24 mol% CaO, between about 0 mol% to about 6.17 mol% SrO, between about 0 mol% to about 4.3 mol% BaO, and between about 0.07 mol% to about 0.1 1 mol% Sn0₂. [0059] In additional embodiments, the glass substrate 110 can comprise glass having an R_xO/AI₂0₃ ratio between 0.95 and 3.23, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2. In further embodiments, the glass may comprise an R_xO/AI₂0₃ ratio between 1 .18 and 5.68, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1 . In yet further embodiments, the glass can comprise an R_xO - Al₂0₃ - MgO between -4.25 and 4.0, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2. In still further embodiments, the glass may comprise between about 66 mol % to about 78 mol% Si0₂, between about 4 mol% to about 1 1 mol% AI2O3, between about 4 mol% to about 1 1 mol% B2O3, between about 0 mol% to about 2 mol% Li₂0, between about 4 mol% to about 12 mol% Na₂0, between about 0 mol% to about 2 mol% K₂0, between about 0 mol% to about 2 mol% ZnO, between about 0 mol% to about 5 mol% MgO, between about 0 mol% to about 2 mol% CaO, between about 0 mol% to about 5 mol% SrO, between about 0 mol% to about 2 mol% BaO, and between about 0 mol% to about 2 mol% Sn0₂.

[0060] In additional embodiments, the glass substrate 110 can comprise a glass material including between about 72 mol % to about 80 mol% Si0₂, between about 3 mol% to about 7 mol% Al₂0₃, between about 0 mol% to about 2 mol% B₂0₃, between about 0 mol% to about 2 mol% Li₂0, between about 6 mol% to about 15 mol% Na₂0, between about 0 mol% to about 2 mol% K₂0, between about 0 mol% to about 2 mol% ZnO, between about 2 mol% to about 10 mol% MgO, between about 0 mol% to about 2 mol% CaO, between about 0 mol% to about 2 mol% SrO, between about 0 mol% to about 2 mol% BaO, and between about 0 mol% to about 2 mol% Sn0₂. In certain embodiments, the glass can comprise between about 60 mol % to about 80 mol% Si0₂, between about 0 mol% to about 15 mol% Al₂0₃, between about 0 mol% to about 15 mol% B2O3, and about 2 mol% to about 50 mol% R_xO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1 , and wherein Fe + 30Cr + 35Ni < about 60 ppm.

[0061] In some embodiments, the glass substrate 110 can comprise a color shift Ay less than 0.05, such as ranging from about -0.005 to about 0.05, or ranging from about 0.005 to about 0.015 (e.g., about -0.005, -0.004, -0.003, -0.002, - 0.001 , 0, 0.001 , 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.01 1 , 0.012, 0.013, 0.014, 0.015, 0.02, 0.03, 0.04, or 0.05). In other embodiments, the glass substrate can comprise a color shift less than 0.008. According to certain embodiments, the glass substrate can have a light attenuation ch (e.g., due to absorption and/or scattering losses) of less than about 4 dB/m, such as less than about 3 dB/m, less than about 2 dB/m, less than about 1 dB/m, less than about 0.5 dB/m, less than about 0.2 dB/m, or even less, e.g., ranging from about 0.2 dB/m to about 4 dB/m, for wavelengths ranging from about 420-750 nm.

[0062] Attenuation may be characterized by measuring light transmission Τι_(λ) of an input source through a transparent substrate of length L and normalizing this transmission by the source spectrum Τ₀(λ). In units of dB/m the attenuation is given by α(λ) =-10/Ι_*^₁₀(ΤΊ_(λ)/ΤΊ_(λ)) where L is the length in meters and Τι_(λ) and ^"Π_(λ) are measured in radiometric units.

[0063] The glass substrate 110 may, in some embodiments, comprise glass that is chemically strengthened, e.g., by ion exchange. During the ion exchange process, ions within a glass sheet at or near the surface of the glass sheet may be exchanged for larger metal ions, for example, from a salt bath. The incorporation of the larger ions into the glass can strengthen the sheet by creating a compressive stress in a near surface region. A corresponding tensile stress can be induced within a central region of the glass sheet to balance the compressive stress.

[0064] Ion exchange may be carried out, for example, by immersing the glass in a molten salt bath for a predetermined period of time. Exemplary salt baths include, but are not limited to, KNO3, L1 NO3, NaNC , RbNC , and combinations thereof. The temperature of the molten salt bath and treatment time period can vary. It is within the ability of one skilled in the art to determine the time and temperature according to the desired application. By way of a non-limiting example, the temperature of the molten salt bath may range from about 400°C to about 800°C, such as from about 400°C to about 500°C, and the predetermined time period may range from about 4 to about 24 hours, such as from about 4 hours to about 10 hours, although other temperature and time combinations are envisioned. By way of a non- limiting example, the glass can be submerged in a KN0₃ bath, for example, at about 450°C for about 6 hours to obtain a K-enriched layer which imparts a surface compressive stress.

[0065] The first modifying layer 120 or second modifying layer 120' can comprise any inorganic or inorganic-organic hybrid material having a refractive index n_M or n_M- suitable for the desired application. Exemplary inorganic materials can include, for example, inorganic oxides such as silicon oxide, aluminum oxide, titanium oxides, zirconium oxides, rare earth metal oxides; other inorganic materials such as alkali silicates; and combinations thereof. As used herein, "inorganic- organic hybrid" materials are intended to include refer to composites comprising inorganic and organic constituents at the nanometer or molecular level, as opposed to a macroscopic (e.g., micrometer or millimeter) level. Exemplary inorganic-organic hybrid materials may include, for example, organosilicates, such as silsesquioxanes and polyoctachedral silsesquioxanes commercially available from Gelest, Hybrid Plastics, or Honeywell, and combinations thereof. Such inorganic-hybrid materials may, in certain embodiments, be UV curable, thermally curable, or photocurable. For example, in a non-limiting embodiment, the inorganic-organic hybrid material can be a photocurable organosilicate.

[0066] The total thickness of the first modifying layer 120 or second modifying layer 120' may range, in some embodiments, from about 5 μιη to about 100 μιη, such as from about 5 μιη to about 90 μιη, from about 10 μιη to about 80 μιη, from about 20 μιη to about 70 μιη, from about 30 μιη to about 60 μιη, or from about 40 μιη to about 50 μιη, including all ranges and subranges therebetween.

Deposition of an inorganic or inorganic-organic hybrid first or second modifying layer 120, 120' may be carried out, in some embodiments, using sputtering or vapor deposition techniques, e.g., chemical vapor deposition (CVD) or plasma-enhanced CVD (PECVD), as well as other techniques including dip coating, spin coating, roll coating, screen printing, and the like. According to some embodiments, an inorganic-organic hybrid material may be applied as a liquid, sol-gel, or low viscosity layer and may be subsequently cured, e.g., by UV, thermal, photo curing, or any combination thereof. The second modifying layer 120' may be provided with microstructures 165 using any suitable technique, such as patterning, imprinting, molding, etching, microreplicating, or otherwise shaping at least one surface to provide microstructures 165. In various embodiments, an inorganic-organic hybrid material may be cured before or during formation of the microstructures, e.g., by imprinting, microreplicating, or molding.

[0067] The adhesive layer 155, if present, may include any adhesive known in the art, e.g., optically clear adhesives (OCAs), such as those sold by 3M, and ionomer polymers, such as those sold by DuPont. Exemplary thicknesses for the adhesive layer can include, for example, a thickness ranging from about 5 μιη to about 500 μιη, from about 10 μιη to about 400 μιη, from about 25 μιη to about 300 μιη, from about 50 μιη to about 250 μιη, or from about 100 μιη to about 200 μιη, including all ranges and subranges therebetween.

[0068] The prismatic layer 115 can comprise any film or material known in the art capable of brightening light emitted from a LGP, e.g., modifying the angular distribution of the light such that it is normal or substantially normal (~90°C) to the light emitting surface of the glass substrate 110. Exemplary polymeric prismatic films include brightness enhancing films (BEFs) and dual brightness enhancing films (DBEFs), to name a few. A non-limiting example of a commercially available polymeric prismatic films is Vikuiti™ sold by 3M. In certain embodiments, the prismatic layer 115 can comprise an organic, inorganic, or inorganic-organic hybrid material as disclosed herein. Such a material may be patterned, imprinted, molded, etched, microreplicated, or otherwise shaped to provide a prismatic structure capable of brightening light emitted from the glass substrate.

[0069] In certain embodiments, various components of the light guide assembly 100, such as the glass substrate 110, first modifying layer 120, second modifying layer 120' and/or adhesive layer 155 (if present) can be transparent or substantially transparent. As used herein, the term "transparent" is intended to denote that the component has an optical transmission of greater than about 70% in the visible region of the spectrum (~420-750nm) for a transmission length of 500 mm or less. For instance, an exemplary transparent material may have greater than about 75% transmittance in the visible region, such as greater than about 80%, or greater than about 85% transmittance, including all ranges and subranges therebetween. In certain embodiments, an exemplary modifying layer 120, 120' may have an optical transmittance of greater than about 40% in the visible region over a transmission length of 500 mm or less, such as greater than about 50%, greater than about 60%, greater than about 70%, or greater than about 80% transmittance, including all ranges and subranges therebetween.

[0070] In some embodiments, an exemplary transparent material can comprise less than 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is < about 50 ppm, < about 20 ppm, or < about 10 ppm. In other embodiments, Fe + 30Cr + 35Ni < about 60 ppm, Fe + 30Cr + 35Ni < about 40 ppm, Fe + 30Cr + 35Ni < about 20 ppm, or Fe + 30Cr + 35Ni < about 10 ppm. According to additional embodiments, an exemplary transparent material can comprise a color shift Ay < 0.015 or, in some embodiments, a color shift < 0.008.

[0071] Color shift may be characterized by measuring variation in the x and y chromaticity coordinates of the extracted light along the length L of an LGP illuminated by standard white LED(s) such as the Nichia NFSW157D-E using the CIE 1931 standard for color measurements. The nominal color point of the LED(s) is chosen to be y=0.28 and x=0.29. For glass LGPs the color shift Ay can be reported as Ay = y(L₂)-y(L₁) where L₂ and l_i are Z positions along the panel or substrate direction away from the source launch and where

meters. Exemplary glass LGPs have Ay < 0.05, Ay < 0.01 , Ay< 0.005, Ay < 0.003, or Ay < 0.001 . If the LGP has no light extraction features it may be characterized by adding a small area of light extraction features at each measurement point Li and L₂.

[0072] The light guide assemblies disclosed herein can comprise at least one optical manipulation feature designed to direct light in a forward direction, e.g., toward the viewer. For instance, the optical manipulation feature may increase the amount of light transmitted by the light guide assembly 100 in a direction normal or substantially normal to the light emitting surface 125 of the glass substrate 110. The relative refractive indices of the prismatic layer n_P, modifying layer(s) n_M and/or n_M; and glass substrate n_G can similarly be engineered to promote the normal or substantially normal direction of light rays transmitted by the light guide assembly. The use of inorganic or inorganic-organic materials to replace one or more organic (e.g., polymeric) layers in the BLU stack may provide opportunities to create layers of varying refractive index, which may allow for a greater degree of light manipulation within the BLU stack.

[0073] The light guide assemblies disclosed herein may be used in various display devices including, but not limited to, LCDs. The optical components of an exemplary LCD may further comprise one or more diffusing, reflecting, prismatic, and/or polarizing films, a thin film transistor (TFT) array, a liquid crystal layer, and/or one or more color filters, to name a few components. The light guide assemblies disclosed herein may also be used in various illuminating devices, such as luminaires or solid state lighting devices.

[0074] It will be appreciated that the various disclosed embodiments may involve particular features, elements or steps that are described in connection with that particular embodiment. It will also be appreciated that a particular feature, element or step, although described in relation to one particular embodiment, may be interchanged or combined with alternate embodiments in various non-illustrated combinations or permutations.

[0075] It is also to be understood that, as used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to "a light source" includes examples having two or more such light sources unless the context clearly indicates otherwise. Likewise, a "plurality" or an "array" is intended to denote "more than one." As such, a "plurality of light extraction features" includes two or more such features, such as three or more such features, etc., and an "array of microstructures" includes two or more such microstructures, such as three or more such microstructures, and so on.

[0076] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, examples include 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 aspect. 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.

[0077] The terms "substantial," "substantially," and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a "substantially planar" surface is intended to denote a surface that is planar or approximately planar. Moreover, as defined above, "substantially similar" is intended to denote that two values are equal or approximately equal. In some embodiments, "substantially similar" may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0078] 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. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred. [0079] While various features, elements or steps of particular

embodiments may be disclosed using the transitional phrase "comprising," it is to be understood that alternative embodiments, including those that may be described using the transitional phrases "consisting" or "consisting essentially of," are implied. Thus, for example, implied alternative embodiments to an assembly that comprises A+B+C include embodiments where an assembly consists of A+B+C and

embodiments where an assembly consists essentially of A+B+C.

[0080] It will be apparent to those skilled in the art that various

modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Since modifications combinations, subcombinations and variations of the disclosed embodiments incorporating the spirit and substance of the disclosure may occur to persons skilled in the art, the disclosure should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1 . A light guide assembly comprising:

(a) a glass substrate comprising a light emitting first major surface and an opposing second major surface;

(b) a prismatic layer comprising an organic material, inorganic material, or inorganic-organic hybrid material; and

(c) a first modifying layer positioned between the first major surface of the glass substrate and the prismatic layer, the first modifying layer comprising:

an inorganic material or inorganic-organic hybrid material, and a refractive index n_M less than a refractive index n_G of the glass substrate.

2. The light guide assembly of claim 1 , wherein the refractive index n_M of the first modifying layer is less than a refractive index n_P of the prismatic layer.

3. The light guide assembly of claim 1 , further comprising an adhesive layer positioned between the prismatic layer and the first modifying layer.

4. The light guide assembly of claim 3, wherein a refractive index n_A of the adhesive layer is less than a refractive index n_P of the prismatic layer and greater than the refractive index n_M of the first modifying layer.

5. The light guide assembly of claim 1 , wherein the prismatic layer comprises an inorganic material or inorganic-organic hybrid material and wherein the prismatic layer is disposed on the first modifying layer.

6. The light guide assembly of claim 1 , further comprising at least one light extraction feature disposed on or under the second major surface of the glass substrate.

7. The light guide assembly of claim 1 , further comprising a second modifying layer disposed on the second major surface of the glass substrate, the second modifying layer comprising an inorganic material or inorganic-organic hybrid material.

8. The light guide assembly of claim 7, wherein the second modifying layer has a refractive index n_M- greater than or equal to a refractive index n_G of the glass substrate.

9. The light guide assembly of claim 7, wherein the second modifying layer comprises at least one light extraction feature.

10. The light guide assembly of claim 7, wherein the second modifying layer comprises a plurality of microstructures.

1 1 . The light guide assembly of claim 10, wherein the plurality of microstructures comprises a periodic or non-periodic array of prisms, rounded prisms, or lenticular lenses.

12. The light guide assembly of any one of the preceding claims, wherein a thickness of the first modifying layer or the second modifying layer ranges from about 10 μιη to about 100 μιη.

13. An optical assembly comprising a light source optically coupled to an edge surface of the light guide assembly of any one of the preceding claims.

14. The optical assembly of claim 13, wherein a maximum emission angle 0_m of the light source satisfies equation (1 ):

0_m ≤ arcsin (n_G ² - n¾) (1 ).

15. A light guide assembly comprising:

(a) a glass substrate comprising a light emitting first major surface and an opposing second major surface; and

(b) a prismatic layer disposed on the first major surface of the glass

substrate, wherein the prismatic layer comprises: an inorganic material or inorganic-organic hybrid material, and a refractive index n_P less than a refractive index n_G of the glass substrate.

16. The light guide assembly of claim 15, further comprising a second modifying layer disposed on the second major surface of the glass substrate, wherein the second modifying layer comprises an inorganic or inorganic-hybrid material and a refractive index η_Μ· greater than or equal to the refractive index n_G of the glass substrate.

17. The light guide assembly of claim 16, wherein the second modifying layer further comprises at least one light extraction feature.

18. The light guide assembly of claim 16, wherein the second modifying layer further comprises a plurality of micro structures.

19. The light guide assembly of claim 18, wherein the plurality of microstructures comprises a periodic or non-periodic array of prisms, rounded prisms, or lenticular lenses.

20. An optical assembly comprising a light source optically coupled to an edge surface of the light guide assembly of any one of claims 15-19.

21 . A display, lighting, or electronic device comprising the light guide assembly or optical assembly of any one of the preceding claims.