AND DEVICES COMPRISING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S. Provisional Application Serial No. 62/397441 filed September 21 , 2016, 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 edge-lit light guide plates and display or lighting devices comprising such light guide plates, and more particularly to glass light guide plates comprising an optical bonding layer, a diffusive light reflecting layer, and an optional light absorbing region.

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. Edge-lit BLUs may have the advantage of reduced display thickness as compared to back-lit BLUs. For example, to achieve desired light uniformity and/or to avoid hot spots in direct-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. [0005] Current consumer demands for electronic devices include thinner displays and/or narrower bezels around the display region. However, as LGPs become increasingly thinner to accommodate such displays, they may have reduced rigidity, making it difficult to produce LGPs that are both sufficiently large and thin to meet consumer requirements. This is particularly the case for plastic LGPs, which have lower mechanical strength and/or stiffness as compared to their glass counterparts.

[0006] In some instances, the rigidity of the LGP may be improved by laminating a rear reflector to a major surface of the LGP. However, such LGP- reflector laminate assemblies may also present some drawbacks in the case of edge-lit LGPs, such as the generation of a bright band near the edge of the LGP to which the light source is coupled. A potential solution to the bright band

phenomenon can include, for instance, increasing the gap between the LGP and the light source. However, increasing the gap between the light source and LGP can increase the size of the display bezel and/or reduce optical coupling efficiency.

Chamfering the light-incident edge of the LGP may also reduce the bright band effect, but the additional step of chamfering the LGP may increase the manufacturing and/or integration costs of the overall assembly, and the chamfer length may also necessitate a thicker bezel.

[0007] Accordingly, it would be advantageous to provide LGP assemblies having reduced thickness and/or improved rigidity while also avoiding or reducing the bright band effect. It would also be advantageous to provide edge-lit BLUs capable of producing a uniform distribution of light in terms of color and/or brightness across the viewing surface.

SUMMARY

[0008] The disclosure relates, in various embodiments, to light guide assemblies comprising a light guide plate having a light emitting major surface, an opposing major surface, and at least one light incident edge, and a diffusive light reflecting layer bonded to at least a portion of the opposing major surface of the light guide plate by an optical bonding layer, the optical bonding layer having a refractive index lower than a refractive index of the light guide plate. Also disclosed herein are light guide assemblies comprising a light guide plate having a light emitting major surface, an opposing major surface, and at least one light incident edge, a light reflecting layer bonded to at least a portion of the opposing major surface of the light guide plate by an optical bonding layer; and a light absorbing region proximate the at least one light incident edge of the light guide plate. Display, lighting, and electronic devices comprising such light guides are also disclosed herein.

[0009] In non-limiting embodiments, the diffusive light reflecting layer may be bonded to substantially all of the opposing major surface of the LGP. In other embodiments, the diffusive light reflecting layer may be bonded to a portion of the opposing major surface proximate the at least one light incident edge of the LGP, and a second light reflecting layer, which can be specular or diffusive, may be bonded to the remainder of the opposing major surface. A diffusive light reflecting band may have a width ranging from about 2 mm to about 15 mm. In various embodiments, the diffusive light reflecting layer may have at least one of a 3-dB scattering angle greater than or equal to about 80 degrees or a Sigma scattering parameter of greater than or equal to about 1 . According to additional embodiments, the diffusive light reflecting layer can have a reflectivity of at least about 90% at visible wavelengths.

[0010] The light absorbing region may comprise a light absorbing layer bonded to at least one of the light emitting major surface or opposing major surface of the light guide plate. In various embodiments, the light reflecting layer may be bonded to a first region of the opposing major surface of the light guide plate and the light absorbing layer is bonded to at least one of (i) a second region of the opposing major surface of the light guide plate proximate the at least one light incident edge or (ii) a third region of the light emitting major surface of the light guide plate proximate the at least one light incident edge. The light absorbing region may, for example, have a width ranging from about 2 mm to about 15 mm and/or an absorbance of at least about 80% at visible wavelengths.

[0011] In various embodiments, the at least one light incident edge of the light guide plate may comprise at least one chamfer. The refractive index of the optical bonding layer may, for example, be at least about 7% less than the refractive index of the light guide plate. In certain non-limiting embodiments, the optical bonding layer may have an optical transmission of at least about 30% at visible wavelengths over a length of about 500 mm or greater.

[0012] 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.

[0013] 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

[0014] The following detailed description can be further understood when read in conjunction with the following drawings.

[0015] FIGS. 1A-B illustrate exemplary light guide assemblies according to various embodiments of the disclosure;

[0016] FIGS. 2A-B illustrate exemplary light guide assemblies according to additional embodiments of the disclosure;

[0017] FIGS. 3A-B illustrate exemplary light guide assemblies according to further embodiments of the disclosure;

[0018] FIG. 4A-B are graphical depictions of light distribution across LGPs laminated with specular and diffusive reflectors, respectively;

[0019] FIG. 5 is a graphical depiction of brightness as function of distance from the light-incident edge for LGPs laminated with specular and diffusive reflectors;

[0020] FIGS. 6A-B are graphical depictions of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of distance between the light source and LGP for LGPs laminated with specular and diffusive reflectors, respectively;

[0021] FIGS. 7A-B are graphical depictions of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of distance between the light source and LGP for chamfered LGPs laminated with specular and diffusive reflectors, respectively; [0022] FIG. 8 is a graphical depiction of coupling efficiency as a function of distance between the light source and LGP for LGPs having varying chamfer heights;

[0023] FIG. 9 is a graphical depiction of scattered power as a function of polar angle for diffusive reflectors with varying Sigma scattering parameters;

[0024] FIG. 10 is a graphical depiction of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of distance between the light source and LGP for LGPs laminated to reflectors having varying Sigma scattering parameters;

[0025] FIG. 11 is a graphical depiction of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of diffusive band width for LGPs laminated with a specular reflector and a diffusive reflector band;

[0026] FIG. 12A-B are graphical depictions of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of absorbing band width for LGPs laminated with a specular reflector; and

[0027] FIGS. 12C is a graphical depiction of brightness difference between two positions (10 mm and 500 mm away from the light incident edge) as a function of absorbing band width for LGPs laminated with a diffusive reflector.

DETAILED DESCRIPTION

[0028] Disclosed herein are light guide assemblies comprising a light guide plate including a light emitting major surface, an opposing major surface, and a at least one light incident edge, and a diffusive light reflecting layer bonded to the opposing major surface of the light guide plate by an optical bonding layer, the optical bonding layer having a refractive index lower than a refractive index of the light guide plate.

[0029] Also disclosed herein are light guide assemblies comprising a light guide plate having a light emitting major surface, an opposing major surface, and at least one light incident edge, a light reflecting layer bonded to the opposing major surface of the light guide plate by an optical bonding layer; and a light absorbing region proximate the at least one light incident edge of the light guide plate.

[0030] Devices comprising such light guides 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.

[0031] Various embodiments of the disclosure will now be discussed with reference to FIGS. 1 -3, which illustrate exemplary embodiments 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.

[0032] FIGS. 1A-B illustrate various exemplary embodiments of light guide assemblies 100, 100' comprising a light guide plate (LGP) 110 or a chamfered LGP 110', respectively. The LGP 110, 110' may comprise a light emitting major surface 115 and an opposing major surface 120. The LGP 110, 110' may further comprise at least one light incident edge 125, to which a light source 105 may be optically coupled, in some embodiments. The light source 105 can have a height h that may vary depending, e.g., upon the thickness of the LGP 110, 110'. Although only one light incident edge 125 is illustrated in FIGS. 1-3, it is to be understood that the LGP may comprise more than one light incident edge, such as two, three, four, or more light incident edges. In some embodiments, at least one light source may be coupled to each edge of the LGP to form a light incident perimeter around the LGP. Further, as shown in FIG. 1 B, the light incident edge(s) 125 may comprise chamfered surface(s) 145, which may have a height H and which may form an angle Θ with the major surface(s) of the chamfered LGP 110'. The light guide assembly 100, 100' may further comprise a diffusive light reflecting layer 130, bonded to the major surface 120 by an optical bonding layer 135.

[0033] 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, e.g., the two components may be separated by a gap G as illustrated in FIGS. 1 -3, although a gap may also not be present in some embodiments. Additional light sources (not illustrated) may be optically coupled to other edge surfaces of the LGP, such as adjacent or opposing edge surfaces.

[0034] As shown in FIGS. 1A-B, the diffusive light reflecting layer 130 may cover all or substantially all of major surface 120. Alternatively, as shown in FIGS. 2A-B, diffusive light reflecting layer 130 may cover only a portion of major surface 120. For instance, a light reflecting layer 140, which may be specular or diffusive, without limitation, may cover a first region of major surface 120 and diffusive light reflecting layer 130 may cover a region proximate or adjacent to the light incident edge 125, e.g., forming a diffusive light reflecting band. Such a diffusive light reflecting band may have a width W _D extending from the light incident edge toward an opposing edge to a predetermined position along the LGP. While FIGS. 2A-B depict only one light source 105 optically coupled to one edge of the LGP, it is to be understood that multiple light sources can be coupled to one edge, or to more than one edge of the LGP. In such instances, the diffusive light reflecting band may be positioned proximate any edge optically coupled to a light source. For example, the LGP may comprise two or more light incident edges and a diffusive light reflective band may be positioned proximate each of the light incident edges.

[0035] In further embodiments, referring to FIGS. 3A-B, the light guide assembly 100, 100' can comprise a light absorbing region, such as a light absorbing layer 150, which may be positioned proximate or adjacent to light incident edge 125 e.g., forming a light absorbing band. Such a light absorbing band may have a width W _A extending from the light incident edge toward an opposing edge to a

predetermined position along the LGP. The absorbing layer 150 may be bonded to major surface 120 (as illustrated), to light emitting surface 115 (not illustrated), or both (not illustrated). While FIGS. 3A-B depict the light absorbing region as a separate layer, it is also possible for the LGP to be treated to create an integral light absorbing region, as discussed in more detail below. Further, while FIGS. 3A-B depict only one light source 105 optically coupled to one edge of the LGP, it is to be understood that multiple light sources can be coupled to one edge, or to more than one edge of the LGP. In such instances, the light absorbing band may be positioned proximate any edge optically coupled to a light source. For example, the LGP may comprise two or more light incident edges and a diffusive light reflective band may be positioned proximate each of the light incident edges.

[0036] The LGP 110, 110' can comprise any material known in the art for use in display devices. For example, the LGP may comprise a plastic such as polymethyl methacrylate (PMMA) or a glass, 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 LGP include, for instance, EAGLE XG ^® , Lotus™, Willow ^® , Iris™, and Gorilla ^® glasses from Corning

Incorporated.

[0037] Some non-limiting glass compositions can include between about 50 mol % to about 90 mol% Si0 ₂ , between 0 mol% to about 20 mol% Al ₂ 0 ₃ , between

0 mol% to about 20 mol% B ₂ 0 ₃ , and between 0 mol% to about 25 mol% R _x O, 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 _x O - Al ₂ 0 ₃ > 0; 0 < R _x O - Al ₂ 0 ₃ < 15; x = 2 and R ₂ 0 - Al ₂ 0 ₃ < 15; R ₂ 0 - Al ₂ 0 ₃ < 2; x=2 and R ₂ 0 - Al ₂ 0 ₃ - MgO > -15; 0 < (R _x O - Al ₂ 0 ₃ ) < 25, -1 1 < (R ₂ 0 - Al ₂ 0 ₃ ) < 1 1 , and -15 < (R ₂ 0 - Al ₂ 0 ₃ - MgO) < 1 1 ; and/or -

1 < (R ₂ 0 - Al ₂ 0 ₃ ) < 2 and -6 < (R ₂ 0 - Al ₂ 0 ₃ - MgO) < 1 , all values given in mole%. In some embodiments, the glass comprises less than about 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is less than about 50 ppm, less than about 20 ppm, or less than 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% Si0 ₂ , between about 0.1 mol% to about 15 mol% Al ₂ 0 ₃ , 0 mol% to about 12 mol% B ₂ 0 ₃ , and about 0.1 mol% to about 15 mol% R ₂ 0 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 .

[0038] In other embodiments, the glass composition can comprise between about 65.79 mol % to about 78.17 mol% Si0 ₂ , between about 2.94 mol% to about 12.12 mol% Al ₂ 0 ₃ , between about 0 mol% to about 1 1.16 mol% B ₂ 0 ₃ , between about 0 mol% to about 2.06 mol% Li ₂ 0, between about 3.52 mol% to about 13.25 mol% Na ₂ 0, between about 0 mol% to about 4.83 mol% K ₂ 0, 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% Sn0 ₂ .

[0039] In additional embodiments, the glass composition can comprise an R _x O/AI ₂ 0 ₃ 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 composition may comprise an R _x O/AI ₂ 0 ₃ 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 composition can comprise R _x O, Al ₂ 0 ₃ , and MgO in amounts (expressed in mol%) such that R _x O - Al ₂ 0 ₃ - MgO is 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 composition may comprise between about 66 mol % to about 78 mol% Si0 ₂ , between about 4 mol% to about 1 1 mol% Al ₂ 0 ₃ , between about 4 mol% to about 1 1 mol% B ₂ 0 ₃ , between about 0 mol% to about 2 mol% Li ₂ 0, between about 4 mol% to about 12 mol% Na ₂ 0, between about 0 mol% to about 2 mol% K ₂ 0, 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% Sn0 ₂ .

[0040] In additional embodiments, the glass composition can comprise between about 72 mol % to about 80 mol% Si0 ₂ , between about 3 mol% to about 7 mol% Al ₂ 0 ₃ , between about 0 mol% to about 2 mol% B ₂ 0 ₃ , between about 0 mol% to about 2 mol% Li ₂ 0, between about 6 mol% to about 15 mol% Na ₂ 0, between about 0 mol% to about 2 mol% K ₂ 0, 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% Sn0 ₂ . In certain embodiments, the glass composition can comprise between about 60 mol % to about 80 mol% Si0 ₂ , between about 0 mol% to about 15 mol% Al ₂ 0 ₃ , between about 0 mol% to about 15 mol% B ₂ 0 ₃ , and about 2 mol% to about 50 mol% R _x O, 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.

[0041] In some embodiments, the LGP 110, 110' can comprise a color shift Ay less than 0.030, such as ranging from about 0.005 to about 0.03 (e.g. , about 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.01 1 , 0.012, 0.013, 0.014, 0.015, 0.020, 0.025, or 0.030). In other embodiments, the LGP can comprise a color shift less than 0.015, such as less than 0.008. According to certain embodiments, the LGP can have a light attenuation (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. A refractive index of the LGP may, in various embodiments, 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.

[0042] The LGP 110, 110' may, in some embodiments, be 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 thereof. A corresponding tensile stress can be induced within a central region of the glass sheet to balance the compressive stress.

[0043] 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, KN0 ₃ , LiN0 ₃ , NaN0 ₃ , RbN0 ₃ , and combinations thereof. The temperature of the molten salt bath and treatment time period can vary depending on the desired depth and magnitude of the compressive stress layer. 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 KN0 ₃ bath, for example, at about 450°C for about 6 hours to obtain a K-enriched layer which imparts a surface compressive stress.

[0044] In certain embodiments, the LGP 110, 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. A length of the LGP 110, 110' may also vary depending on the application, e.g., as appropriate for small handheld devices or large displays such as billboards. For instance, a length of the LGP may as small as 1 mm, or may be as great as 10 m, or even greater. In some embodiments, the LGP length may range from about 10 mm to about 1 m, such as from about 50 mm to about 500 mm, from about 100 mm to about 400 mm, or from about 200 mm to about 300 mm, including all ranges and subranges therebetween.

[0045] The LGP 110, 110' can have any desired size and/or shape as appropriate to produce a desired light distribution. The major surfaces 115, 120 may, in certain embodiments, be planar or substantially planar and/or may be parallel or substantially parallel. The LGP 110, 110' may comprise four edges or may comprise more than four edges, e.g. a multi-sided polygon. In other

embodiments, the LGP 110, 110' may comprise less than four edges, e.g., a triangle. By way of a non-limiting example, the LGP 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.

[0046] In the case of a chamfered LGP 110', the chamfer dimensions may be chosen as appropriate to achieve the desired coupling efficiency, display configuration, and/or light distribution. In certain embodiments, the chamfer height H may range from about 0.01 mm to about 1 mm, such as from about 0.05 mm to about 0.9 mm, from about 0.1 mm to about 0.8 mm, from about 0.2 mm to about 0.7 mm, from about 0.3 mm to about 0.6 mm, or from about 0.4 mm to about 0.5 mm, including all ranges and subranges therebetween. The chamfer angle Θ may similarly vary depending on the LGP configuration, for example, from about 5° to about 60°, from about 8° to about 50°, from about 10° to about 45°, from about 15° to about 40°, from about 20° to about 30°, including all ranges and subranges therebetween.

[0047] The LGP and/or optical bonding layer may, in certain embodiments, be transparent or substantially transparent. As used herein, the term "transparent" is intended to denote that the LGP and/or optical bonding layer, at a thickness of 1 mm, has an optical transmission of greater than about 80% in the visible region of the spectrum (~420-750nm). For instance, an exemplary transparent material may have greater than about 85% transmittance in the visible light range, such as greater than about 90%, greater than about 95%, or greater than about 99% transmittance, including all ranges and subranges therebetween. In certain embodiments, an exemplary transparent material may have an optical transmittance of greater than about 30% in the visible wavelength range over a length of about 500 mm or greater, such as an optical transmittance greater than about 50%, greater than about 60%, or greater than about 70%, including all ranges and subranges therebetween.

[0048] In some embodiments, an exemplary transparent material can comprise less than about 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is less than about 50 ppm, less than about 20 ppm, or less than 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 Ay < 0.008.

[0049] Color shift may be characterized by measuring variation in the x and y chromaticity coordinates along the length L using the CIE 1931 standard for color measurements. For glass light-guide plates the color shift Ay can be reported as Ay=y(L ₂ )-y(L ₁ ) where L ₂ and U are Z positions along the panel or substrate direction away from the source launch and where meters. Exemplary LGPs or optical bonding layers may have Ay < 0.01 , Ay < 0.005, Ay < 0.003, or Ay < 0.001 .

[0050] Although not illustrated in FIGS. 1 -3, the light emitting surface 115 and/or the opposing major surface 120 of the LGP 110, 110' may be patterned with a plurality of light extraction features. As used herein, the term "patterned" is intended to denote that the plurality of light extraction features is present on or in the surface(s) of the LGP in any given pattern or design, which may, for example, be random or arranged, repetitive or non-repetitive, uniform or non-uniform. In other embodiments, the light extraction features may be located within the matrix of the LGP adjacent the surface, e.g., below the surface. For instance, the light extraction features may be distributed across the surface, e.g. as textural features making up a roughened or raised surface, or may be distributed within and throughout the substrate or portions thereof, e.g., as laser-induced features.

[0051] In various embodiments, the light extraction features optionally present on the surface(s) of the LGP may comprise light scattering sites. In other embodiments, the light extraction features optionally present on the surface(s) of the LGP may comprise refractive structures that break the total internal reflection condition of the LGP. Non-limiting examples of the shapes of these refractive features may include hemispherical, toroidal, or ellipsoidal shapes. According to various embodiments, the extraction features may be patterned in a suitable density so as to produce substantially uniform light output intensity across the light emitting surface of the LGP. In certain embodiments, a density of the light extraction features proximate the light source may be lower than a density of the light extraction features at a point further removed from the light source, or vice versa, such as a gradient from one end of the LGP to another, as appropriate to create the desired light output distribution across the LGP.

[0052] 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. Non-limiting examples of such methods include, for instance, acid etching a surface, coating a surface with Ti0 ₂ , and laser damaging the substrate by focusing a laser on a surface or within the LGP matrix. Light extraction features may also be produced using any of the methods disclosed in co-pending and co-owned International Patent Application Nos.

PCT/US2013/063622 and PCT/US2014/070771 , each incorporated herein by reference in their entirety.

[0053] The optical bonding layer 135 can comprise any material known in the art suitable for laminating the reflector and the glass or plastic LGP. For instance, in some embodiments, the optical bonding layer may comprise at least one material chosen from epoxies, photopolymers, urethanes, silicones, cyanoacrylates, polyester resin based materials, and like materials. Exemplary thicknesses of the optical bonding layer may range, e.g., from about 10 μιη to about 500 μιη, such as from about 20 μιη to about 400 μιη, from about 30 μιη to about 300 μιη, from about 40 μιη to about 200 μιη, or from about 50 μιη to about 100 μιη, including all ranges and subranges therebetween.

[0054] According to various embodiments, the optical bonding layer 135 may have a refractive index (Π ₀ Β) that is at least 7% less than the refractive index of the LGP (n _L cp)- In additional embodiments, n ₀ _¾ may be at least 10% less than n _L cp, such as at least 13% or at least 15% less than n _L cp, including all ranges and subranges therebetween. For example, in the case of a LGP having a refractive index of 1 .7, an optical bonding layer may have a refractive index less of than about 1 .6, such as ranging from about 1 .55 to about 1 .45, or even lower. By way of a non- limiting example, the refractive index of the optical bonding layer may be less than 1 .7, such as ranging from about 1 .3 to about 1 .65, from about 1 .35 to about 1 .6, from about 1 .4 to about 1 .55, or from about 1 .45 to about 1 .5, including all ranges and subranges therebetween. As discussed above, the optical bonding layer may be transparent at visible wavelengths. For instance, the optical bonding layer may have an optical transmittance of greater than about 30% in the visible wavelength range over a length, e.g., transmission distance, greater than or equal to 500 mm, such as greater than about 50%, greater than about 60%, or greater than about 70%, including all ranges and subranges therebetween.

[0055] As shown in FIGS. 1-3, the light guide assembly 100, 100' can include at least one light reflecting layer, such as diffusive light reflecting layer 130 and/or light reflecting layer 140. Reflecting layer 140 may be a specular reflector or a diffusive reflector. According to various embodiments, the diffusive light reflecting layer 130 can include materials chosen from polytetrafluoroethylene (PTFE) optical diffusing films, diffusive polystyrene films, diffusive acrylic polymer films, and white paper layers, to name a few. The light reflecting layer 140 may include, for example, materials such as organic or inorganic multi-layer optical films, metal foils, and like materials. The diffusive light reflecting layer 130 and/or light reflecting layer 140 may have a reflectance greater than or equal to about 90% at visible wavelengths, such as greater than or equal to about 92%, 95%, 96%, 97%, 98%, 99%, or 100%, including all ranges and subranges therebetween, e.g., ranging from 90% to 100% reflectance.

[0056] Whereas a specular reflector, e.g., light reflecting layer 140 may have a relatively smooth surface, a diffusive reflector such as light reflecting layer 130 may have, or may be treated to provide, a roughened surface. According to various embodiments, the diffusive light reflecting layer 130 may be a Lambertian reflector. In additional embodiments, the diffusive light reflective layer 130 may be characterized by a 3-dB scattering angle greater than or equal to about 80 degrees, such as greater than or equal to 85 degrees, 90 degrees, 95 degrees, 100 degrees, 105 degrees, 1 10 degrees, 1 15 degrees, 120 degrees, or any range or subrange therebetween, e.g., ranging from about 80 degrees to about 120 degrees. The diffusive light reflecting layer 130 may also be characterized by a Gaussian scattering function, with a Sigma scattering parameter greater than or equal to about 1 , such as ranging from about 2 to about 5, or from about 3 to about 4, including all ranges and subranges therebetween. [0057] As illustrated in FIGS. 1A-B, the diffusive light reflecting layer 130 may cover all or substantially all of major surface 120. Alternatively, as illustrated in FIGS. 2A-B, light reflecting layer 140 (e.g., specular or diffusive) may cover a first region of the major surface 120 and diffusive light reflecting layer 130 may cover a second region proximate the light incident edge 125. In some embodiments, the diffusive light reflecting layer 130 may extend from the light incident edge toward an opposing edge for a predetermined distance, e.g. , to form a diffusive band having a width W _D . Such a band may, in certain embodiments, having a width W _D ranging from about 2 mm to about 15 mm, such as from about 3 mm to about 12 mm, from about 4 mm to about 10 mm, from about 5 mm to about 8 mm, or from about 6 mm to about 7 mm, including all ranges and subranges therebetween. The diffusive light reflecting layer 130, if present in the form of a band proximate the light incident edge 125, may have any shape appropriate for providing the desired light distribution including, but not limited to, rectangular, square, and any other regular or irregular shapes, without limitation, such as shapes having curvilinear edges.

[0058] Referring to FIGS. 3A-B, the light guide assemblies 100, 100' may also comprise a light absorbing region proximate the light incident edge 125. Such an absorbing region may be present as a light absorbing layer 150, which may be present on the light emitting major surface 115 (not illustrated) or the opposing major surface 120 (as depicted). Suitable materials for such a light absorbing layer 150 may include, but are not limited to, carbon, carbon nanotubes, carbon black, carbon black filled polymers (e.g., acrylates, polypropylenes, epoxies, etc.), black pigments, and combinations thereof. Alternatively, or additionally, the LGP 110, 110' may be treated to create an integral light absorbing region, e.g., by exposing a portion of the LGP to short-wavelength UV light having a wavelength in the range of about 193 nm to about 250 nm. The LGP may be exposed to the selected wavelength for a time period sufficient to induce formation of color centers on or near the surface(s) of the LGP. The LGP and light source can then be positioned relative to each other such that the treated light absorbing regions are proximate the light source. Reflecting layer 140 may be a specular reflector or a diffusive reflector.

[0059] The absorbing region, e.g., light absorbing layer 150 and/or integral absorbing region, may have an absorbance greater than or equal to about 80% at visible wavelengths, such as greater than or equal to about 85%, 90%, 95%, 99%, or 100%, including all ranges and subranges therebetween, e.g. , ranging from 80% to 100% absorbance. In some embodiments, the light absorbing region may extend from the light incident edge toward an opposing edge for a predetermined distance, e.g., to form an absorbing band having a width W _A . Such a band may, in certain embodiments, having a width W _A ranging from about 2 mm to about 15 mm, such as from about 3 mm to about 12 mm, from about 4 mm to about 10 mm, from about 5 mm to about 8 mm, or from about 6 mm to about 7 mm, including all ranges and subranges therebetween. The light absorbing region may have any shape appropriate for providing the desired light distribution including, but not limited to, rectangular, square, and any other regular or irregular shapes, without limitation, such as shapes having curvilinear edges.

[0060] The LGPs disclosed herein may be used in various display devices including, but not limited to LCDs. Exemplary devices comprising such LGPs include televisions, computers, phones, tablets, and other display panels. According to various embodiments of the disclosure, display devices can comprise at least one of the disclosed LGPs 110, 110' coupled to at least one light source 105, which may emit blue, UV, or near-UV light (e.g., approximately 100-500 nm). In some embodiments, the light source 105 may be a Lambertian light source, such as a light emitting diode (LED).

[0061] The height h of the light source 105 may vary as desired, for instance, depending on the thickness of the LGP. According to non-limiting embodiments, the light source may have a height less than 5 mm, such as ranging from about 0.5 mm to about 5 mm, from about 1 mm to about 4 mm, or from about 2 mm to about 3 mm, including all ranges and subranges therebetween. In certain embodiments, the light source 105 may be positioned relative to the LGP 110, 110' such that a gap G exists between the two components. The distance of such a gap may range, for example, from about 0.01 mm to about 1 mm such as from about 0.05 mm to about 0.9 mm, from about 0.1 mm to about 0.8 mm, from about 0.2 mm to about 0.7 mm, from about 0.3 mm to about 0.6 mm, or from about 0.4 mm to about 0.5 mm, including all ranges in between.

[0062] The optical components of an exemplary LCD may further comprise a reflector, a diffuser, one or more prism films, one or more linear or reflecting polarizers, a thin film transistor (TFT) array, a liquid crystal layer, and one or more color filters, to name a few components. The LGPs disclosed herein may also be used in various illuminating devices, such as luminaires or solid state lighting devices, as well as architectural elements such as billboards.

[0063] 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.

[0064] 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" "or an array of light extraction features" includes two or more such features, such as three or more such features, and so on.

[0065] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value and/or "between" values. 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.

[0066] 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.

[0067] 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.

[0068] 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 a device that comprises A+B+C include embodiments where a device consists of A+B+C and embodiments where a device consists essentially of A+B+C.

[0069] 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.

[0070] The following Examples are intended to be non-restrictive and illustrative only, with the scope of the invention being defined by the claims.

EXAMPLES

Example 1 : Diffusive Light Reflecting Layer

[0071] FIG. 4A depicts the light distribution along a LGP without a chamfer (thickness = 2 mm; width = 10 mm; length = 502 mm; n _L cp = 1 .5) laminated to a specular rear reflector (96% reflectivity) by an optical bonding layer (thickness = 40 μιη; n ₀ _¾ = 1 -35). A light source (LED; height = 1 mm) is positioned at the center of the bottom edge of the LGP as illustrated and distanced from the LGP by a 0.1 mm gap. FIG. 4B similarly depicts the light distribution along a LGP without a chamfer laminated to a diffusive rear reflector with otherwise identical parameters. A bright band can be seen in FIG. 4A near the light incident edge (bottom edge) for the LGP laminated to a specular reflector. In contrast, FIG. 4B shows that the bright band at the bottom edge has been eliminated for the LGP laminated to a diffusive reflector. The contrast between FIGS. 4A-B can also be seen in FIG. 5, which graphically plots brightness as a function of distance from the light incident edge of the LGP for the specular reflector (A) and the diffusive reflector (B). It can be further appreciated from the plot in FIG. 5 that the LGP laminated to the specular reflector produced a bright band (increased brightness in the region near the LED as compared to the rest of the LGP) that extends approximately 100 mm from the light incident edge of the LGP.

[0072] An additional comparison between the specular and diffusive reflectors is presented in FIGS. 6A-B and FIGS. 7A-B, which plot the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) as a function of distance between the LGP and LED, where G=0 when the gap between the LED and LGP was eliminated. As the brightness difference approaches zero, the light output from the LGP becomes more uniform, e.g., the bright band effect is reduced or eliminated. FIG. 6A demonstrates the brightness comparison curves for a LGP without chamfer laminated to a specular reflector by optical bonding layers having varying refractive indices (n ₀ B = 1 -35 (C), n ₀ B = 1 -30 (D), n ₀ B = 1 -25 (E)). The brightness differences for such a LGP at G=0 were 23%, 16%, and 8% for n _OB = 1 .35, 1 .30, and 1 .25, respectively. FIG. 6B demonstrates the brightness comparison curves for a LGP without chamfer laminated to a diffusive reflector by optical bonding layers having varying refractive indices (n ₀ B = 1 -35 (F), n ₀ B = 1 -30 (G), n ₀ B = 1 -25 (H)). By replacing the specular reflector with a diffusive reflector, the brightness difference at G=0 dropped to 4.3%, 2.7%, and 0.9% for n ₀ B = 1 -35, 1 .30, and 1 .25, respectively. A similar comparison can be drawn for a chamfered LGP (chamfer height = 0.2 mm; chamfer angle = 45°) laminated to a specular reflector and a chamfered LGP laminated to a diffusive reflector, as shown in FIGS. 7A-B (n _OB = 1 .35 (I, L), n _OB = 1 .30 (J, M), n _OB = 1 .25 (K, N)).

[0073] For both cases illustrated in FIGS. 6A-B and FIGS. 7A-B, the brightness difference decreases as the gap between the LED and LGP increases. The brightness difference for the chamfered LGPs (FIGS. 7A-B) decreases slightly faster with the gap increase as compared to the LGPs without chamfer (FIGS. 6A- B). However, increasing the gap between the light source and LED may necessitate a wider bezel to mask the display components from user view. Moreover, as shown in FIG. 8, for both LGPs with and without chamfers (H = 0 mm (O), H = 0.3 mm (P), H = 0.5 mm (Q)), increasing the gap between the LED and LGP can also result in decreased light coupling efficiency.

[0074] FIG. 9 demonstrates scattered power for a diffusive reflector with different Sigma scattering parameters using the Gaussian function to characterize the scattering performance of the reflector. A Sigma parameter of 0 represents the angular distribution of specular reflection, whereas a Sigma parameter of 5 represents near-Lambertian angular distribution. Turning to FIG. 10, the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) is plotted as a function of distance between the LGP and LED for LGPs without chamfer laminated to a diffusive reflector with an optical bonding layer (n ₀ B = 1 -35). It can be appreciated from the plot that the brightness difference decreases from 28% to 6.4% when the Sigma parameter of the reflector increases from 0 (specular) to 1 , and further decreases to less than 5% when the Sigma parameter increases to 2 and higher (approaching Lambertian).

Example 2: Diffusive Light Reflecting Band

[0075] FIG. 11 plots the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) as a function of diffusive reflector band width for LGPs without chamfer laminated to a specular reflector with or without a diffusive reflector band proximate the light incident edge. The

reflector(s) were laminated to the LGP by optical bonding layers having varying refractive indices (n ₀ B = 1 -35 (R), n ₀ B = 1 -30 (S), n ₀ B = 1 -25 (T)). For all three cases, the brightness difference decreases as the width of the diffusive reflector band increases. For a LGP without the diffusive reflector band, the brightness difference was 22.8%, 14.8%, and 7.8% for n _OB = 1 .35, 1 .30, and 1 .25, respectively. The brightness difference dropped to below 5% when the diffusive reflector band width was greater than 8 mm, 5.8 mm, and 2.4 mm for n ₀ B = 1 -35, 1 .30, and 1 .25, respectively.

Example 3: Light Absorbing Band

[0076] FIG. 12A plots the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) as a function of light absorbing band width for LGPs without chamfer laminated to a specular reflector with or without a light absorbing band applied to the LGP proximate the light incident edge. The reflectors were laminated to the LGP by optical bonding layers having varying refractive indices (n ₀ B = 1 -35 (U), n ₀ _¾ = 1 -30 (V), n ₀ _¾ = 1 -25 (W)). For all three cases, the brightness difference decreases as the width of the light absorbing band increases. For a LGP without the light absorbing band, the brightness difference was 22.8%, 14.8%, and 7.8% for n ₀ B = 1 .35, 1 .30, and 1 .25, respectively. The brightness difference dropped to below 5% when then the diffusive reflector band width was greater than 5 mm, 4 mm, and 1 .7 mm for n ₀ _¾ = 1 -35, 1 .30, and 1 .25, respectively.

[0077] FIG. 12B plots the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) as a function of light absorbing band width for LGPs without chamfer laminated to specular reflectors with varying absorbance (a = 50% (X), a = 95% (Y), a = 100% (Z)) by an optical bonding layer with a refractive index of 1 .35. As can be appreciated from the plot, as the absorbance of the band decreases, the effectiveness of the band at reducing the bright band is degraded. For instance, at a band width of 8mm, the 50% absorbance band has a brightness difference of 1 1 %, whereas the 100% absorbance band has a brightness difference of 2%. However, the impact on brightness difference between 95% and 100% absorbance is relatively minimal.

[0078] FIG. 12C plots the brightness difference between two positions along the LGP (10 mm and 500 mm from the light incident edge) as a function of light absorbing band width for LGPs without chamfer laminated to a diffusive reflector. The reflectors were laminated to the LGP by optical bonding layers having varying refractive indices (n ₀ _¾ = 1 -35 (AA), n ₀ _¾ = 1 -30 (BB), n ₀ _¾ = 1 -25 (CC)). For a LGP without the light absorbing band, the brightness difference was 4%, 2.7%, and 0.9% for n ₀ B = 1 -35, 1 .30, and 1 .25, respectively. The brightness difference dropped to below 5% when the diffusive reflector band width was greater than 5 mm, 4 mm, and 1 .7 mm for n ₀ B = 1 -35, 1 .30, and 1 .25, respectively. By including a 6 mm light absorbing band, the brightness difference dropped to 2.5%, 1 .9%, and 0.7% for n ₀ B = 1 .35, 1 .30, and 1 .25, respectively. For all three cases, the brightness difference decreases as the width of the absorbing band increases. However, as compared to FIG. 12A (specular reflector), the difference is less pronounced because the brightness uniformity is already improved by the diffusive reflector.