WO2019217408A1 - Backlight unit with improved 2d local dimming - Google Patents

Abstract

Backlight units include a light guide plate having an array of unit zones, and an array of light sources positioned proximate the light guide plate. At least one light source is optically coupled to at least one corresponding unit zone in the array of unit zones, the at least one light source comprising a first emission edge or a first dominant emission direction positioned at an angle relative to a horizontal axis of the corresponding unit zone. Display and lighting devices comprising such backlight units are further disclosed.

Description

BACKLIGHT UNIT WITH IMPROVED 2D LOCAL DIMMING

FIELD OF THE DISCLOSURE

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 62/667,867 filed on May 7, 2018, the content of which is relied upon and incorporated herein by reference in its entirety.

[0002] The disclosure relates generally to backlight units and display or lighting devices comprising such backlight units, and more particularly to backlight units comprising a light guide plate having an array of unit zones and light sources positioned at an angle relative to at least one axis of the unit zones.

BACKGROUND

[0003] Liquid crystal displays (LCDs) are commonly used in various electronics, such as cell phones, laptops, electronic tablets, televisions, and computer monitors. 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.

[0004] Direct-lit BLUs may have the advantage of improved dynamic contrast as compared to edge-lit BLUs. For example, a display with a direct-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 direct-lit BLUs, the light source(s) may be positioned at a distance from the LGP and/or the diffuser film, thus making the overall display thickness greater than that of an edge-lit BLU. While edge-lit BLUs may be thinner, 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] Accordingly, it would be advantageous to provide thin BLUs having improved local dimming efficiency without negatively impacting the uniformity of light emitted by the BLU. It would also be advantageous to provide backlights having a thickness similar to that of edge-lit BLUs while also providing local dimming capabilities similar to that of direct-lit BLUs.

SUMMARY

[0006] The disclosure relates, in various embodiments, to backlight units comprising a light guide plate having an array of unit zones; and an array of quadrilateral light sources positioned proximate the light guide plate, wherein at least one quadrilateral light source is optically coupled to at least one corresponding unit zone in the array of unit zones, the at least one quadrilateral light source comprises a first emission edge, and the first emission edge is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°. Display and lighting devices comprising such backlight units are also disclosed herein.

[0007] According to various embodiments, the light guide plate may comprise glass. In certain embodiments, the at least one quadrilateral light source can be chosen from square and rectangular light sources. According to further embodiments, the at least one quadrilateral light source is a top-emitting LED or a side-emitting LED, such as a ring of side-emitting LEDs.

[0008] In certain embodiments, the first emission edge is positioned at a first angle ranging from about 40° to about 50°, such as about 45°. According to non-limiting embodiments, the at least one quadrilateral light source comprises a second emission edge, and the second emission edge is positioned at a second angle relative to a vertical axis of the corresponding unit zone, the second angle ranging from about 30° to about 60°, such a about 45°. The array of unit zones may include, for example, a grid of square unit zones, and each unit zone in the grid can comprise a corresponding quadrilateral light source. In certain embodiments, the light guide plate can comprise an array of holes, each hole positioned in a respective unit zone, and at least one quadrilateral source may be positioned in at least one hole in the array of holes. [0009] According to further embodiments, at least one major surface of the light guide plate can be patterned with light extraction features. In additional embodiments, the array of quadrilateral light sources can be positioned proximate a major surface of the light guide plate. A reflective layer can, in certain embodiments, be positioned proximate a major surface of the light guide plate. According to non- limiting embodiments, the reflective layer can be a patterned reflective layer. In additional embodiments, the backlight unit can further comprise at least one of a diffusing film, a prismatic film, and a reflective polarizing film.

[0010] Also disclosed herein are backlight units including a light guide plate comprising an array of unit zones; and an array of light sources positioned proximate the light guide plate, wherein at least one light source is optically coupled to at least one corresponding unit zone in the array of unit zones, wherein the at least one light source comprises a first dominant emission direction, and wherein the first dominant emission direction is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°. In certain embodiments, the at least one light source further comprises a second emission direction, wherein the second emission direction is positioned orthogonal to the first dominant emission direction, and the ratio of the optical flux emitted along the first dominant emission direction and the optical flux emitted along the second emission direction ranges from about 1.1 to about 1.7.

[0011] 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.

[0012] 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

[0013] The following detailed description can be further understood when read in conjunction with the following drawings.

[0014] FIG. 1 illustrates a light guide plate (LGP) comprising an array of unit zones and light sources;

[0015] FIGS. 2A-B illustrate exemplary quadrilateral light sources;

[0016] FIG. 3A illustrates a LGP including an exemplary unit zone comprising a round light source;

[0017] FIG. 3B illustrates a LGP including an exemplary unit zone comprising a square light source;

[0018] FIG. 3C illustrates a LGP including an exemplary unit zone comprising a square light source oriented at a 45° angle with respect to the horizontal axis of the unit zone; and

[0019] FIG. 4A illustrates a spatial luminance distribution for the configuration of FIG. 3A;

[0020] FIG. 4B illustrates a spatial luminance distribution for the configuration of FIG. 3B;

[0021] FIG. 4C illustrates a spatial luminance distribution for the configuration of FIG. 3C;

[0022] FIG. 5A is a plot of spatial luminance along the horizontal and diagonal axes of the light source as a function of distance for the distribution of FIG. 4A;

[0023] FIG. 5B is a plot of spatial luminance along the horizontal and diagonal axes of the light source as a function of distance for the distribution of FIG. 4B;

[0024] FIG. 5C is a plot of spatial luminance along the horizontal and diagonal axes of the light source as a function of distance for the distribution of FIG. 4C; [0025] FIG. 6 is a plot of luminance ratio along the horizontal and diagonal axes of the light source as a function of distance for FIGS. 5A-C; and

[0026] FIG. 7 is a radial plot of far field light intensity emitted from light sources corresponding to configurations shown in FIGS. 3A-C.

DETAILED DESCRIPTION

[0027] Disclosed herein are backlight units comprising a light guide plate having an array of unit zones; and an array of quadrilateral light sources positioned proximate the light guide plate, wherein at least one quadrilateral light source is optically coupled to at least one corresponding unit zone in the array of unit zones, the at least one quadrilateral light source comprises a first emission edge, and the first emission edge is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°.

[0028] Also disclosed herein are backlight units including a light guide plate comprising an array of unit zones; and an array of light sources positioned proximate the light guide plate, wherein at least one light source is optically coupled to at least one corresponding unit zone in the array of unit zones, wherein the at least one light source comprises a first dominant emission direction, and wherein the first dominant emission direction is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°.

[0029] Devices comprising such backlights 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.

[0030] Various embodiments of the disclosure will now be discussed with reference to FIGS. 1 -7, which illustrate exemplary backlights, components thereof and aspects thereof. 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. [0031] FIG. 1 illustrates a top view of an exemplary light guide plate (LGP) 100 comprising an array of unit zones 105, represented by dashed lines. For purposes of illustration only, light sources 110 are depicted in each unit zone and are visible, although in actual practice such light sources may, in certain embodiments, be disposed behind the LGP and not visible when viewed from the top. While the illustrated embodiment comprises a light source 110 in each unit zone, other embodiments are contemplated in which only certain unit zones comprise light sources. Additionally, alternative LGP configurations are intended to fall within the scope of the disclosure, including different unit zone and/or light source locations, sizes, shapes, and/or spacing. For instance, while the depicted embodiment includes a periodic or regular array of unit zones and light sources having the same size, shape, and spacing, other embodiments are contemplated in which the array is irregular or non-periodic.

[0032] Each light source 110 can have any size and/or shape as

appropriate to accommodate a desired light output including, but not limited to, quadrilateral shapes including squares, rectangles, parallelograms, or rhomboids, and other suitable shapes, which may be regular or irregular, including shapes having one or more curvilinear portions or edges. As used herein, the term

“quadrilateral” is used to refer to a light source with four light-emitting sides or edges, including quadrilateral shapes with rounded portions, e.g., squares or rectangles with rounded edges or corners. According to various embodiments, the light source 110 can comprise two or more light sources arranged to form a quadrilateral shape. For instance, as shown in FIGS. 2A-B, four light sources 110A-D may be arranged in a ring to form a square shape, or any other quadrilateral shape, as desired. Of course, any number of light sources can be arranged in configurations other than those depicted in FIGS. 2A-B to form a quadrilateral shape. For example, each of light sources 110A-D can comprise two or more light sources. One potential advantage of using more than one light source is to provide more light in one zone, thereby reducing the number of driving electronics associated with the number of the zones.

[0033] In certain embodiments, the light source 110 can be a top-emitting light emitting diode (LED), which predominantly emits light in a direction normal to or at high angles relative to a major surface of the LGP, such as at angles 60° or greater, e.g., 90°, relative to the horizontal plane of the LGP. Side-emitting LEDs may also be used, which direct a significant portion of light at high angles relative to the vertical (normal) plane of the LGP. By way of a non-limiting example, a side- emitting LED may direct at least 3x of light at angles of 30° or greater relative to the normal of the LED, such as 4x, 5x, 10x, or greater, e.g., ranging from about 3x to about 10x, including all ranges and subranges therebetween. An exemplary side- emitting LED can emit a majority of light at higher angles (e.g., approaching 70°). According to certain embodiments, the angular emission intensity distribution may be symmetrical about the normal of the LED. The light source, e.g., top-emitting or side-emitting LED, can emit red, green, blue, UV, or near-UV light, e.g., light having wavelengths ranging from about 100 nm to about 700 nm. For some non-limiting embodiments, infrared light can also be used.

[0034] The LGP 100 may have any dimensions, such as length L and width W, which can vary depending on the display or lighting application. In some embodiments, the length L can range from about 0.01 m to about 10 m, such as from about 0.1 m to about 5 m, from about 0.5 m to about 2.5 m, or from about 1 m to about 2 m, including all ranges and subranges therebetween. Similarly, the width W can range from about 0.01 m to about 10 m, such as from about 0.1 m to about 5 m, from about 0.5 m to about 2.5 m, or from about 1 m to about 2 m, including all ranges and subranges therebetween. Each unit zone 105 may also have an associated unit length Lo and unit width Wo, which can vary depending on the dimensions of the LGP 100 and the number and/or spacing of the light sources 110 along the LGP 100. The unit length Lo of a given unit zone 105 can be calculated, for example, by measuring the horizontal distance between the center of the light source 110 associated with that unit zone and the center of an immediately adjacent light source (e.g., to the right or the left). Similarly, the unit width Wo of the unit zone 105 can be calculated by measuring the vertical distance between the center of the light source 110 associated with that unit zone and the center of an immediately adjacent light source (e.g., above or below). For LGPs comprising unit zones all having the same dimensions, the unit length Lo can be calculated by dividing the length L of the LGP by the number of horizontal unit zones, and the unit width Wo can be calculated by dividing the width W of the LGP by the number of vertical unit zones. The length L and the width W of the LGP may, in some embodiments be substantially equal or they may be different. Similarly, the unit length Lo and the unit width Wo may be substantially equal or they may be different.

[0035] Of course, while a rectangular LGP 100 is illustrated in FIG. 1 , it is to be understood that the LGP may have any regular or irregular shape as appropriate to produce a desired light distribution for a chosen application. The LGP 100 may comprise four edges as illustrated in FIG. 1 , or may comprise more than four edges, e.g. a multi-sided polygon. In other embodiments, the LGP 100 may comprise less than four edges, e.g., a triangle. By way of a non-limiting example, the LGP may comprise a quadrilateral shape, such as a rectangular or square 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. According to various embodiments, the LGP 100 can comprise a 3 x 3 grid of horizontal and vertical unit zones, e.g., nine total unit zones. In other embodiments, the LGP 100 may comprise a greater number of unit zones, such as a 4 x 4 grid, a 5 x 5 grid, a 6 x 6 grid, and so forth without limitation. The LGP 100 can also comprise a 2 x 2 grid of unit zones in various embodiments. In still further embodiments, the LGP 100 can comprise a grid of unit zones with fewer or greater horizontal unit zones as compared to vertical unit zones, e.g., a 2 x 3 grid, a 3 x 2 grid, a 3 x 4 grid, a 4 x 3 grid, a 2 x 4 grid, a 4 x 2 grid, a 4 x 5 grid, a 5 x 4 grid, a 3 x

5 grid, a 5 x 3 grid, a 2 x 5 grid, a 5 x 2 grid, a 5 x 6 grid, a 6 x 5 grid, a 4 x 6 grid, a 6 x 4 grid, a 3 x 6 grid, a 6 x 3 grid, a 2 x 6 grid, a 6 x 2 grid, and so forth without limitation.

[0036] According to various embodiments, the LGP can comprise any transparent material used in the art for lighting and display applications. As used herein, the term“transparent” is intended to denote that the LGP has an optical transmission of greater than about 10% over a length of 500 mm in the visible region of the spectrum (~420-750nm). For instance, an exemplary transparent material may have greater than about 30% transmittance in the visible light range over a length of 500 mm, such as greater than about 50%, greater than about 80%, or greater than about 90% transmittance, including all ranges and subranges therebetween. A LGP having an optical transmission of greater than about 10% or 30% over a length of 500 mm can have an optical transmission of greater than about 79% or 89% over a length of 50 mm. In some embodiments, the light path in the

BLU can be about Lo 12, Wo / 2, or 1/2 -yJJl +W₀ ² depending on the direction, e.g., between about 10 mm and about 100 mm.

[0037] The optical properties of the LGP may be affected by the refractive index of the transparent material. According to various embodiments, the LGP may have a refractive index ranging 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 other embodiments, the LGP may have a relatively low level of light attenuation (e.g., due to absorption and/or scattering). The light attenuation (a) of the LGP may, for example, be less than about 5 dB/m for wavelengths ranging from about 420-750 nm. For instance, a may be less than about 4 dB/m, 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, including all ranges and subranges therebetween, e.g., from about 0.2 dB/m to about 5 dB/m.

[0038] The LGP may comprise polymeric materials, such as plastics, e.g., polymethyl methacrylate (PMMA), methylmethacrylate styrene (MS),

polydimethylsiloxane (PDMS), or other similar materials. The LGP can also comprise a glass material, such as aluminosilicate, alkali-aluminosilicate,

borosilicate, alkali-borosilicate, aluminoborosilicate, alkali-aluminoborosilicate, soda lime, or other suitable glasses. Non-limiting examples of commercially available glasses suitable for use as a glass light guide include, for instance, EAGLE XG^®, Lotus™, Willow^®, Iris™, and Gorilla^® glasses from Corning Incorporated. Soda lime glass may also be used in certain embodiments.

[0039] Some non-limiting glass compositions can include between about 50 mol % to about 90 mol% S1O2, between 0 mol% to about 20 mol% AI2O3, between 0 mol% to about 20 mol% B2O3, and between 0 mol% to about 25 mol% RxO, 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, RxO - AI2O3 > 0; 0 < R_xO - AI2O3 < 15; x = 2 and R2O— AI2O3 < 15; R2O— AI2O3 < 2; x=2 and R2O— AI2O3— MgO > -15; 0 < (RxO— AI2O3) < 25, -11 < (R2O - AI2O3) < 11 , and -15 < (R2O - AI2O3 - MgO) < 11 ; and/or - 1 < (R2O - AI2O3) < 2 and -6 < (R2O - AI2O3 - 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% S1O2, between about 0.1 mol% to about 15 mol% AI2O3, 0 mol% to about 12 mol% B2O3, and about 0.1 mol% to about 15 mol% RxO, 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.

[0040] In other embodiments, the glass composition can comprise between about 65.79 mol % to about 78.17 mol% S1O2, between about 2.94 mol% to about 12.12 mol% AI2O3, between about 0 mol% to about 11.16 mol% B2O3, between about 0 mol% to about 2.06 mol% L12O, between about 3.52 mol% to about 13.25 mol% Na20, between about 0 mol% to about 4.83 mol% K2O, 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 0.11 mol% Sn02.

[0041] In additional embodiments, the glass can comprise an R_XO/AI2O3 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 RxO/AhCb 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 RxO - AI2O3 - 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% S1O2, between about 4 mol% to about 11 mol% AI2O3, between about 4 mol% to about 11 mol% B2O3, between about 0 mol% to about 2 mol% L12O, between about 4 mol% to about 12 mol% Na20, between about 0 mol% to about 2 mol% K2O, 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. [0042] In additional embodiments, the glass can comprise between about 72 mol% to about 80 mol% S1O2, between about 3 mol% to about 7 mol% AI2O3, between about 0 mol% to about 2 mol% B2O3, between about 0 mol% to about 2 mol% L12O, between about 6 mol% to about 15 mol% Na20, between about 0 mol% to about 2 mol% K2O, 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% S1O2, between about 0 mol% to about 15 mol% AI2O3, between about 0 mol% to about 15 mol% B2O3, and about 2 mol% to about 50 mol% RxO, 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.

[0043] In some embodiments, the LGP can comprise a color shift Ay less than 0.015, such as ranging from about 0.005 to about 0.015 (e.g., about 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.011 , 0.012, 0.013, 0.014, or 0.015). In other embodiments, the LGP can comprise a color shift less than 0.008. 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 LGPs the color shift Ay can be reported as Ay=y(L2)-y(Li) where L2 and Li are Z positions along the panel or substrate direction away from the source launch and where L2- Li=0.5 meters. Exemplary LGPs have Ay < 0.01 , Ay < 0.005, Ay < 0.003, or Ay < 0.001. According to certain embodiments, the LGP can have a light attenuation CM (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.

[0044] The LGP may, in some embodiments, comprise glass that has been chemically strengthened, e.g., ion exchanged. 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.

[0045] 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, UNO3, NaN03, RbN03, 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 KNO3 bath, for example, at about 450°C for about 6 hours to obtain a K-enriched layer which imparts a surface compressive stress.

[0046] Referring to FIG. 3A, an exemplary LGP 200 is illustrated, which comprises a 3 x 3 grid of unit zones 205, each unit zone comprising a circular light source 210. Each light source 210 emits light symmetrically about the z-axis, which is perpendicular to the plane of the LGP. For a given unit zone, a horizontal distance d1 may be measured along the horizontal x-axis of the LGP from a point p1 at the edge of the light source to a point P1 at the edge of the unit zone, a vertical distance d2 may be measured along the vertical y-axis of the LGP from a point p2 at the edge of the light source to a point P2 at the edge of the unit zone, and a diagonal distance d3 may be measured along a diagonal v-axis of the LGP from a point p3 at the edge of the light source to a point P3 at the edge of the unit zone.

[0047] The distances d1 and d2 can be equal or substantially similar when the unit width Wo and unit length Lo are equal or substantially similar to each other, e.g., as illustrated in FIG. 3A. However, the distance d3 will always be longer than d1 or d2 in the case of circular light sources (ds = Vrfl² ÷ dl²). When the light emitted from the light source is the same in all directions, the same amount of light is spread over a longer distance d3 along the diagonal direction than the distances d1 , d2 along the horizontal or vertical directions. Consequently, the average luminance along the diagonal direction is lower than along the horizontal or vertical direction. The spatial luminance pattern produced by such a configuration is illustrated in FIG. 4A.

[0048] Referring to FIG. 3B, an exemplary LGP 200’ is depicted, which comprises a 3 x 3 grid of unit zones 205’, each unit zone comprising a square light source 210’. The square light source has a first emission edge e1’ and a second emission edge e2’ orthogonal to the first emission edge. The square light source 210’ is oriented such that the first emission edge e1’ is parallel to the horizontal x- axis extending along the unit length Lo of the unit zone 205’ (referred to herein as 0° horizontal orientation) and its second emission edge e2’ is parallel to the vertical y- axis extending along the unit width Wo of the unit zone (referred to herein as 0° vertical orientation).

[0049] The configuration of FIG. 3B suffers the same spatial luminance problem as the configuration depicted in FIG. 3A, but to a greater degree. The distances d1 and d2 can be equal or substantially similar when the unit width Wo and unit length Lo are equal or substantially similar to each other. However, the distance d3 will be longer than d1 or d2 (d3

Additionally, the square light source will emit less light along the diagonal direction than the horizontal or vertical direction. Thus, the average luminance along the diagonal direction is much lower than along the horizontal or vertical direction. The spatial luminance pattern produced by such a configuration is illustrated in FIG. 4B.

[0050] Referring to FIG. 3C, an exemplary LGP 200” is depicted, which comprises a 3 x 3 grid of unit zones 205”, each unit zone comprising a rotated square light source 210”. The square light source has a first emission edge e1” and a second emission edge e2” orthogonal to the first emission edge. The rotated light source 210” is oriented such that the first emission edge e1” is at an angle with respect to the horizontal x-axis extending along the unit length Lo of the unit zone 205” (a 45° horizontal orientation as depicted) and its second emission edge e2” is at an angle with respect to the vertical y-axis extending along the unit width Wo of the unit zone (a 45° vertical orientation as depicted). In various embodiments, the horizontal and vertical axes of the unit zone(s) can correspond to the horizontal and vertical axes of the LGP, e.g., the horizontal x-axis can extend along the length L of the LGP, and the vertical y-axis can extend along the width W of the LGP.

[0051] In the configuration of FIG. 3C, distance d3 is still greater than d1 and d2, as in the configurations of FIGS. 3A-B (d3 « y¾l1 ). However, the rotated square light source 210 emits more light along the diagonal direction than in the horizontal or vertical direction. As a result, the average luminance along the diagonal direction is closer to that along the horizontal or vertical direction. The spatial luminance pattern produced by such a configuration is illustrated in FIG. 4C. Further, by modifying the light source emission surface profile, it may be possible to make F3/d3 closer to F1/d1 or F2/d2, where F3, F 1 , and F2 represent the average optical flux along the diagonal direction, the horizontal direction, and the vertical direction, respectively. In various embodiments, the ratio of the light intensity emitted along the first dominant emission direction and the light intensity emitted along the second emission direction can range from about 1.1 to about 1.7, from about 1.2 to about 1.6, from about 1.3 to about 1.5, or from about 1.35 to about 1.45, including all ranges and subranges therebetween, where the first dominant emission direction is positioned at a first angle relative to a horizontal axis of the

corresponding unit zone, the first angle ranging from about 30° to about 60°, and the second emission direction is orthogonal to the first dominant emission direction.

Thus, the difference between the luminance along the diagonal direction and the luminance along the horizontal or vertical direction can be reduced even further for the configuration depicted in FIG. 3C.

[0052] FIGS. 4A-C illustrate two-dimensional spatial luminance

distributions for a single light source in the center unit zone, representing the configurations of FIG. 3A (round or circular light source), FIG. 3B (square light source, 0° orientation), and FIG. 3C (square light source, 45° orientation),

respectively. In each example, the unit zone has a unit width Wo = 90 mm and a unit length Lo = 90 mm. The light source is about 1.6 mm, located in a hole of 2 mm diameter. The light extraction pattern on the LGP is optimized to provide uniformity of greater than 75% when all light sources are turned on in the 3x3 unit zones.

However, when only the light source in one unit zone, such as the center unit zone, is turned on, the spatial luminance distributions vary, for instance between the horizontal and diagonal directions.

[0053] FIGS. 5A-C illustrate spatial luminance distributions at different horizontal (plot L(d1)) and diagonal (plot L(d3)) distances from the light source. FIG. 5A represents the configuration of FIG. 3A (round light source), FIG. 5B represents the configuration of FIG. 3B (square light source, 0° orientation), and FIG. 5C

represents the configuration of FIG. 3C (square light source, 45° orientation). As can be appreciated from the plots, for all cases, L(d3) < L(d1) when the horizontal distance X is between 30 mm and 45 mm, indicating that luminance is greater in the horizontal direction than in the diagonal direction at locations away from the light sources. For convenience, the horizontal distance X is measured from the center of the light sources, not from the emission surface of the light sources. However, the square light sources at 0° orientation (FIG. 5B) have a less favorable spatial distribution as compared to round light sources (FIG. 5A), whereas rotating the square light sources to a 45° orientation (FIG. 5B) improves the spatial distribution, even as compared to the configuration with round light sources. This is confirmed by FIG. 6, which plots the ratio of luminance along d1 to the luminance along d3 for each of the three configurations, where plot A ((thin solid line) represents round light sources, plot B (thin dashed line) represents square light sources at 0° orientation, and plot C (thick solid line) represents square light sources at 45° orientation. The ratio L(d1)/L(d3) is lowest and closest to 1 for plot C, indicating improved uniformity of spatial luminance distribution along the horizontal and diagonal directions for the rotated square light sources. Similar results are expected for spatial luminance distribution along the vertical and diagonal directions. In addition, the average luminance within the center zone, is higher in FIG. 4C than in FIG. 4A or FIG. 4B, indicating a better local dimming in the configuration of FIG. 3C than in the

configuration of FIG. 3A or FIG. 3B.

[0054] The light sources depicted in FIG. 3C can have light emitting edges e1” and e2” with the same or different dimensions, e.g., e1” > e2”, e1” < e2”, or e1” = e2”. While the light sources in FIG. 3C are rotated such that the first emission edge e1” is at an angle Q1 = 45° with respect to the horizontal axis of the unit zone, and the second emission edge e2” is at an angle Q2 = 45° with respect to the vertical axis, it is possible for the emission edge(s) to form different angles with respect to the horizontal and vertical axes, and the angles formed with the axes may or may not be equal, for example, Q1 > Q2, Q1 < Q2, or Q1 = Q2. In certain embodiments, Q1 and/or Q2 can range from about 30° to about 60°, such as from about 35° to about 55°, from about 40° to about 50°, or about 45°, including all ranges and subranges therebetween.

[0055] In some non-limiting embodiments, as depicted in FIG. 3C, the horizontal axis of the unit zone(s) can be parallel to the length L of the LGP (e.g., Lo parallel to L) and/or the vertical axis of the unit zone(s) can be parallel to the width W of the LGP (e.g., Wo parallel to W). Additionally, the spacing between light sources may vary, such that the unit length Lo and unit width Wo may or may not be equal. In some embodiments, Wo > Lo or, in other embodiments, Wo < Lo. According to various embodiments, Wo = Lo.

[0056] While FIG. 3C illustrates square unit zones of the same size and square light sources of the same size, it is to be understood that the unit zones and/or light sources can have different sizes and/or shapes, including multiple light sources arranged to form a quadrilateral shape as depicted, e.g., in FIGS. 2A-B. For instance, the light sources may not be square, e.g., rectangular light sources or any other quadrilateral shape. In some embodiments, the light sources may not have a quadrilateral shape. For instance, the light sources may have a first dominant emission direction, e.g., a direction in which the light source emits the highest light intensity.

[0057] FIG. 7 shows a radial plot of far field light intensity emitted from light sources corresponding to the configurations shown in FIGS. 3A-C, where plot A (thin solid line) represents round light sources, plot B (thin dashed line) represents square light sources at 0° orientation, and plot C (thick solid line) represents square light sources at 45° orientation. Plot A has a generally round shape which indicates a generally uniform light intensity emitted in all directions. In contrast, plot B indicates dominant emissions along directions d1 and d2 (e.g., along the X and Y axis of the unit zone). For plot C, the light sources are rotated such that they have a first dominant emission along direction d3, e.g., 45° relative to the X axis or the horizontal direction of the unit zone. The rotated light source has at least one second emission direction, e.g., along the X and/or Y axes (in the d1 and d2 direction). For the illustrated non-limiting embodiment, the ratio of the light intensity along the first dominant emission direction d3 and the light intensity along the second emission direction(s) d1 and/or d2 (along the X or Y axis) for plot C is about 1.3, but it can have other values disclosed herein, such as from about 1.1 to about 1.7, from about 1.2 to about 1.6, from about 1.3 to about 1.5, or from about 1.35 to about 1.45, including all ranges and subranges therebetween.

[0058] As such, a light source having a first dominant emission direction may have any variety of shapes, including but not limited to quadrilateral shapes.

The light source, regardless of shape, may be rotated as disclosed herein such that the first dominant emission direction is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°, such as from about 35° to about 55°, from about 40° to about 50°, or about 45°. Light sources of any shape having a first dominant emission direction can thus be incorporated into the configuration of FIG. 3C. Additionally, the multiple light sources 110A-D depicted in FIGS. 2A-B may be arranged to form any shape or configuration having a first dominant emission direction. Further, the light sources 110 depicted in FIG. 1 can have a quadrilateral shape and/or a first dominant emission direction.

[0059] A BLU as disclosed herein can comprise an array of light sources optically coupled to the LGP. As used herein, the term“optically coupled” is intended to denote that a light source is positioned at a surface 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 direct physical contact with the LGP. In a direct-lit

configuration, the light sources may be positioned proximate the LGP, such as located behind or underneath the LGP, e.g., optically coupled to a first or second major surface of the LGP. Alternatively, the LGP may comprise one or more recesses or holes in which the light sources can be placed. In certain embodiments, each unit zone can be optically coupled to a corresponding light source, for example, each unit zone can comprise a hole in which at least one light source is positioned.

[0060] Light injected into the LGP may propagate within 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:

n_x sin(^) = n₂ sin(^.)

which describes the refraction of light at an interface between two materials of differing indices of refraction. In accordance with Snell’s law, ni is the refractive index of a first material, ri2 is the refractive index of a second material, 0i 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:

0 = Q, = sin^_1(— )

ni

The incident angle 0i under these conditions may also be referred to as the critical angle 0_C. Light having an incident angle greater than the critical angle (0i > 0_C) will be totally internally reflected within the first material, whereas light with an incident angle equal to or less than the critical angle (0i < 0_C) will be transmitted by the first material.

[0061] In the case of an exemplary interface between air (ni= 1 ) and glass (/?₂=1.5), the critical angle (0_C) can be calculated as 41 °. Thus, if light propagating in the glass strikes the air-glass interface at an incident angle greater than 41 °, 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.

[0062] According to various embodiments, the first and/or second major surfaces of the LGP 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 under the surface 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. The light extraction features can, in various embodiments, be patterned to produce a gradient. In certain 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 LGP or portions thereof, e.g., as laser-damaged sites or features. 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 T1O2, and laser damaging the substrate by focusing a laser on a surface or within the substrate matrix.

[0063] In various embodiments, the light extraction features optionally present on the first or second major surface of the LGP may comprise light- scattering sites. According to various embodiments, the extraction features may be patterned in a suitable density so as to improve the uniformity of light intensity output 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, as appropriate to create the desired light output distribution across the LGP.

[0064] The LGP may be treated to create light extraction features according to any method known in the art, e.g., 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. For example, a surface of the LGP may be ground and/or polished to achieve the desired thickness and/or surface quality. The surface may then be optionally cleaned and/or the surface to be etched may be subjected to a process for removing contamination, such as exposing the surface to ozone. The surface to be etched may, by way of a non-limiting embodiment, be exposed to an acid bath, e.g., a mixture of glacial acetic acid (GAA) and ammonium fluoride (NFUF) in a ratio, e.g., ranging from about 1 : 1 to about 9:1. The etching time may range, for example, from about 30 seconds to about 15 minutes, and the etching may take place at room temperature or at elevated temperature. Process parameters such as acid

concentration/ratio, temperature, and/or time may affect the size, shape, and distribution of the resulting extraction features. It is within the ability of one skilled in the art to vary these parameters to achieve the desired surface extraction features.

[0065] In certain embodiments, the BLU can further comprise a reflective layer, which can be positioned proximate to a major surface of the LGP. According to various embodiments, the reflective layer may be patterned, e.g., comprising two or more regions with different optical properties such as different light reflectance or light transmittance. The reflective layer can comprise any combination of reflective components capable of reflective light or blocking the transmission of light, such as metals, dielectric materials, inks, polymers, inorganic particles, and the like, and transmissive components through which light can be transmitted, such as optically clear, translucent, and/or transparent materials, e.g., glasses, polymers, transparent oxides, and other like materials. The transmissive component can also represent air, an empty space or gap, or a lack of reflective component. For instance, in a patterned metallic coating, the metallic coating can represent the reflective

component and the discontinuities or gaps in the metallic coating can represent the transmissive component. The patterned reflective layer can any given pattern or design, which may, for example, be random or arranged, repetitive or non-repetitive, uniform or non-uniform. In some embodiments, the patterned reflective layer can comprise a gradient.

[0066] The rotated light source orientation disclosed herein, e.g., for light sources with a quadrilateral shape and/or first dominant emission direction, can be used in conjunction with various LGP and BLU configurations, which may include one or more additional components. Exemplary components can include, for instance, optical films such as diffusing films, prismatic films, and/or reflective polarizing films. Light extraction features and/or reflective layers can also be used in conjunction with the LGP.

[0067] For example, as disclosed in U.S. Provisional Application No.

62,452,470, entitled BACKLIGHT UNIT WITH 2D LOCAL DIMMING, which is incorporated herein by reference in its entirety, an exemplary BLU can comprise a LGP having an array of holes and a plurality of light extraction features. Light sources (rotated at the desired orientation) can be positioned in at least one of the holes in the array of holes. An optical layer can be positioned on a light-emitting major surface of the light guide plate. The optical layer can comprise a first region disposed over the at least one hole and a second region disposed over a portion of the light guide plate adjacent to the at least one hole and the first and second regions of the optical layer can have different optical properties, such as different diffuse reflectance or diffuse transmittance.

[0068] As disclosed in U.S. Provisional Application No. 62/549,576, entitled BACKLIGHT UNIT HAVING A LIGHT GUIDE PLATE, which is incorporated herein by reference in its entirety, an exemplary BLU can comprise a bottom reflector, a plurality of discrete light sources, and a patterned LGP having a first pattern of microstructures on its bottom surface and a second pattern of

microstructures on its top surface near or above the discrete light sources, and a third pattern of microstructures on its top, bottom, both surfaces away from the discrete light sources to extract light, and a patterned reflector having a first area and a second area, the first area being more reflective than the second area, and the second area being more transmissive than the first area. The discrete light sources (rotated at the desired orientation) may be located directly behind the patterned LGP. A first portion of the light output of the light sources can be coupled into the patterned LGP by the first pattern and the second pattern on the patterned LGP, can travel laterally in the patterned LGP due to the total internal reflection, and can be extracted out by the third pattern of microstructures, and a second portion of the dominant light output of the light sources can travel laterally between the bottom reflector and the patterned reflector due to multiple reflections at the reflective surfaces of the bottom reflector and the patterned reflector. Another exemplary BLU can comprise a bottom reflector, a plurality of discrete light sources (rotated at the desired orientation), and patterned LGP having a first pattern of microstructures on its top or bottom (or both) surfaces and away from the discrete light sources to extract light, and has a second pattern of microstructures on its bottom surface near or above the discrete light sources to redirect the light away from the discrete light source and reduce the absorption of the light by the discrete light source. The light sources can be located directly behind the patterned LGP, and the first pattern of microstructures have a base angle in the range of 25 and 65 degrees.

[0069] As disclosed in U.S. Provisional Application No. 62/551 ,375, entitled LIGHT GUIDES INCLUDING GRATINGS, which is incorporated herein by reference in its entirety, an exemplary BLU can comprise a LGP, a bottom reflector and a plurality of light sources (rotated at the desired orientation) located between the bottom reflector and the LGP. The LGP can include a pattern of first gratings on its first surface and pattern of second gratings on its second surface, and each of the second gratings may be aligned with a first grating. A pattern of light extraction features may be present on the first or second surface of the LGP. Light from each light source can be coupled into the LGP by a corresponding first grating such that a first portion of the light travels laterally in the LGP and is extracted out of the LGP by the light extraction features. Another exemplary BLU can comprise a LGP, having a pattern of light extraction features on its bottom surface or top surface and a pattern of first gratings on the bottom surface or top surface; and a plurality of light sources (rotated at the desired orientation) located between a bottom reflector and the LGP, wherein light from each light source is coupled into the LGP by a corresponding first grating such that a first portion of the light travels laterally in the LGP and is extracted out of the LGP by the light extraction features.

[0070] As disclosed in U.S. Provisional Application No. 62/551 ,493, entitled DIRECT-LIT BACKLIGHT UNIT WITH 2D LOCAL DIMMING, which is incorporated herein by reference in its entirety, an exemplary BLU can comprise a LGP having a first major surface, an opposing second major surface, and a plurality of light extraction features; a rear reflector positioned proximate the second major surface of the LGP; and a patterned reflective layer positioned proximate the first major surface of the LGP, the patterned reflective layer comprising at least one optically reflective component and at least one optically transmissive component. At least one light source (rotated at the desired orientation) can be optically coupled to the second major surface of the light guide plate.

[0071] As disclosed in U.S. Provisional Application No. 62/551 ,491 , entitled MULTILAYER REFLECTOR FOR DIRECT LIT BACKLIGHTS, which is incorporated herein by reference in its entirety, an exemplary BLU can comprise a LGP having a light emitting first major surface and an opposing second major surface; and a reflector positioned proximate first or second major surface of the substrate, the reflector comprising two or more layers of a reflective material with each of the layers having a first area and a second area, the first area being more reflective than the second area, and the second area being more transmissive than the first area. At least one light source (rotated at the desired orientation) can be optically coupled to the LGP, e.g., optically coupled to the second major surface through an optical adhesive layer. Another exemplary BLU can also comprise a LGP having a light emitting first major surface and an opposing major surface; a plurality of discrete light sources (rotated at the desired orientation); a reflector positioned proximate the second major surface; and a multi-layer patterned reflector positioned proximate the first major surface, each layer having a first area and a second area, the first area being more reflective than the second area, and the second area being more transmissive than the first area.

[0072] The BLUs disclosed herein may be used in various display devices including, but not limited to televisions, computers, phones, handheld devices, billboards, or other display screens. The BLUs disclosed herein may also be used in various illuminating devices, such as luminaires or solid state lighting devices.

[0073] 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.

[0074] 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 scattering features” includes two or more such features, such as three or more such features, etc., and an“array of holes” includes two or more such holes, such as three or more such holes, and so on. [0075] 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.

[0076] 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, “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.

[0077] 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.

[0078] 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, sub- combinations 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 backlight unit comprising: a light guide plate comprising an array of unit zones; and an array of quadrilateral light sources positioned proximate the light guide plate, wherein at least one quadrilateral light source is optically coupled to at least one corresponding unit zone in the array of unit zones, wherein the at least one quadrilateral light source comprises a first emission edge, and wherein the first emission edge is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°.

2. The backlight unit of claim 1 , wherein the light guide plate comprises glass.

3. The backlight unit of claim 1 , wherein the at least one quadrilateral light source is chosen from square and rectangular light sources.

4. The backlight unit of claim 1 , wherein the at least one quadrilateral light source is a square light source.

5. The backlight unit of claim 1 , wherein the at least one quadrilateral light source is a top-emitting LED.

6. The backlight unit of claim 1 , wherein the at least one quadrilateral light source is a ring of side-emitting LEDs.

7. The backlight unit of claim 1 , wherein the first angle ranges from about 40° to about 50°.

8. The backlight unit of claim 1 , wherein the first angle is about 45°.

9. The backlight unit of claim 1 , wherein the at least one quadrilateral light source comprises a second emission edge, and wherein the second emission edge is positioned at a second angle relative to a vertical axis of the corresponding unit zone, the second angle ranging from about 30° to about 60°.

10. The backlight unit of claim 1 , wherein the second angle is about 45°.

11. The backlight unit of claim 1 , wherein the array of unit zones comprises a grid of square unit zones.

12. The backlight unit of claim 1 , wherein the grid of square unit zones comprises a 3 x 3 grid, and wherein each unit zone in the grid comprises a corresponding quadrilateral light source.

13. The backlight unit of claim 1 , wherein the array of quadrilateral light sources is positioned proximate a major surface of the light guide plate.

14. The backlight unit of claim 1 , wherein the light guide plate comprises an array of holes, each hole having a respective unit zone, and wherein at least one quadrilateral light source is positioned in at least one hole in the array of holes.

15. The backlight unit of claim 1 , wherein at least one major surface of the light guide plate is patterned with light extraction features.

16. The backlight unit of claim 1 , further comprising a reflective layer positioned proximate a major surface of the light guide plate.

17. The backlight unit of claim 16, wherein the reflective layer is a patterned reflective layer.

18. A display or lighting device comprising the backlight unit of claim 1.

19. A backlight unit comprising: a light guide plate comprising an array of unit zones; and an array of light sources positioned proximate the light guide plate, wherein at least one light source is optically coupled to at least one corresponding unit zone in the array of unit zones, wherein the at least one light source comprises a first dominant emission direction, and wherein the first dominant emission direction is positioned at a first angle relative to a horizontal axis of the corresponding unit zone, the first angle ranging from about 30° to about 60°.

20. The backlight unit of claim 19, wherein the at least one light source further comprises a second emission direction, wherein the second emission direction is positioned orthogonal to the first dominant emission direction, and the ratio of the optical flux emitted along the first dominant emission direction and the optical flux emitted along the second emission direction ranges from about 1.1 to about 1.7.