WO2023215140A1

WO2023215140A1 - Display device including a backlight unit with chamfered diffuser plate

Info

Publication number: WO2023215140A1
Application number: PCT/US2023/019896
Authority: WO
Inventors: Tzu-Ling Niu
Original assignee: Corning Incorporated
Priority date: 2022-05-06
Filing date: 2023-04-26
Publication date: 2023-11-09
Also published as: TW202409685A

Abstract

A display device having a display panel and a backlight unit positioned behind the display panel relative to a viewer of the display panel, the backlight unit including a diffuser plate having first major surface and a second major surface, and an edge surface connecting the first major surface and the second major surface. The diffuser plate includes at least one chamfer surface intersecting the second major surface. A height of the chamfer surface is equal to or greater than about ½ a thickness of the diffuser plate, and a chamfer angle of the chamfer surface is equal to or less than about 50 degrees.

Description

DISPLAY DEVICE INCLUDING A BACKLIGHT UNIT WITH CHAMFERED DIFFUSER PLATE

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63/338991 filed on May 6, 2022, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to a display device having a display panel and a backlight unit for illuminating a display panel, and in particular, the backlight unit includes a diffuser plate having a chamfered edge surface configured to suppress light leakage from the diffuser plate.

BACKGROUND

[0003] Many display devices, particularly liquid crystal display (LCD) devices such as LCD televisions, include a border around the display panel. The border is typically formed by a black matrix material applied to one or both substrates of the display panel. A backlight unit (BLU) is placed behind the display panel, the backlight unit comprising a diffuser plate and optical films to provide uniform light distribution. A gap is provided between the diffuser plate and the frame of the display device to accommodate thermal expansion of the diffuser plate. This is particularly useful if the diffuser plate comprises a polymer material, as the polymer material is prone to dimensional changes owing to the heat generated by the light board of the backlight unit. Without a gap, the diffuser plate may contact the frame or other internal structure and cause distortion of the diffuser plate and possible distortion of the displayed image. The width of the border can be in a range of about 3 millimeters (mm) to about 4 or 5 mm and typically extends over the gap.

[0004] To provide a more immersive viewing experience, some display devices have minimal border width, for example on the order of about 1 mm, a so-called zero border display (ZBD) device. To provide a high contrast image, the ZBD device is usually combined with a direct- lit (back-lighted) backlight unit to provide zoned dimming of the displayed image. In some instances, the narrow width of the border in the ZBD device means the gap between the diffuser plate and the frame may not be covered. Thus, light that might leak from edges of the diffuser plate may exit the display device through the gap and be observable by a viewer of the display as a bright line.

SUMMARY

[0005] A display device is disclosed, comprising a display panel; and a backlight unit positioned behind the display panel relative to a viewer of an image on the display panel, the backlight unit comprising a backplane substrate comprising a plurality of light emitters and a diffuser disposed between the backplane substrate and the display panel, the diffuser comprising a diffuser plate including a first major surface, a second major surface, an edge surface extending between and joining the first major surface and the second major surface, and a thickness defined between the first major surface and the second major surface. The edge surface comprises a chamfer surface extending from the second major surface, the chamfer surface having a chamfer angle less than 50 degrees defined between the chamfer surface and a first plane coincident with the second major surface and a chamfer height greater than one half the thickness of the diffuser plate.

[0006] The chamfer surface may be a first chamfer surface, the edge surface further comprising a second chamfer surface intersecting the first chamfer surface. Additionally, the chamfer angle may be a first chamfer angle, the second chamfer surface comprising a second chamfer angle equal to or less than 50 degrees defined between the second chamfer surface and a second plane parallel with the first plane and intersecting the second chamfer surface where the second chamfer surface intersects the first chamfer surface.

[0007] In embodiments, the second chamfer surface may comprise a second chamfer height defined from the second plane, and a sum of the first chamfer height and the second chamfer height is equal to or greater than one half the thickness of the diffuser plate.

[0008] The edge surface may further comprise a first peripheral edge surface intersecting the chamfer surface, a second peripheral edge surface intersecting the first major surface, and an intermediate edge surface extending between the first peripheral edge surface and the second peripheral edge surface, the intermediate edge surface orthogonal to the first peripheral edge surface and the second peripheral edge surface. The second peripheral edge surface may be orthogonal to the first major surface. The first peripheral edge surface may be parallel to the second peripheral edge surface. [0009] In embodiments, a height of the second peripheral edge surface defined between the intermediate edge surface and the first major surface may be equal to or less than one half the thickness of the diffuser plate.

[0010] In embodiments, the chamfer surface may be a coated surface. For example, the chamfer surface may comprise a color conversion coating, a light absorbing coating, or a light reflecting surface. The light reflecting surface may comprise Ti, Ag, or Al. The chamfer surface may comprise a plurality of prisms. The chamfer surface may comprise a plurality of lenticular lenses. The chamfer surface may comprise a diffraction grating.

[0011] In embodiments, the diffuser plate may comprise one or more optical layers disposed on the first major surface, the one or more optical layers comprising at least one of a quantum dot film, a phosphor films, a diffuser film, or a brightness enhancement film. The one or more optical layers may be disposed on the first major surface or spaced apart from the first major surface. The one or more optical layers may be recessed from the edge surface. Alternatively, the one or more optical layers may extend past the edge surface.

[0012] In embodiments, the diffuser plate may comprise a glass material, for example a silicate glass, a borosilicate glass, an aluminoborosilicate glass, an alkali-containing aluminoborosilicate glass, an alkali-free borosilicate glass (having less than about 0. 1 weight% alkali metal), or any other glass material suitable as a diffuser plate in a backlight application.

[0013] Both the foregoing general description and the following detailed description present embodiments intended to provide an overview or framework for understanding the nature and character of the embodiments disclosed herein. The accompanying drawings are included to provide further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a cross-sectional view of a portion of an exemplary display device comprising a diffuser positioned with a gap between the diffuser and a frame of the display device, the display device further including a border that extends past the gap;

[0015] FIG. 2 is a cross-sectional view of an exemplary display device similar to the display device of FIG. 1 wherein the gap is made greater than the width of the border extending past the frame so that the gap is not fully covered by the border;

[0016] FIG. 3 is a cross-sectional view of another exemplary display device comprising a border of reduced width; [0017] FIG. 4 is a cross-sectional view of still another exemplary display device comprising a border of reduced width, shown without a chamfer surface;

[0018] FIG. 5 is a close-up cross-sectional view of a portion of the display device of FIG. 4 showing a light ray escaping from the diffuser and reflecting from a frame of the display device toward a viewer;

[0019] FIG. 6 is a cross-sectional view of a portion of an exemplary display device in accordance with embodiment of the present disclosure, wherein an edge surface of a diffuser plate comprising the diffuser include a chamfer surface;

[0020] FIG. 7 is a close-up cross-sectional view of a portion of the display device of FIG. 6 showing a light ray reflecting from the chamfer surface via total internal reflection;

[0021] FIG. 8 is a close-up cross-sectional view of a portion of another exemplary display device similar to the display device of FIG. 6, wherein the diffuser plate comprises a chamfer surface having a height equal to a thickness of the diffuser plate.

[0022] FIG. 9 is a close-up cross-sectional view of yet another exemplary display device similar to the display device of FIG. 7, wherein the diffuser plate comprises a plurality (e.g., two) chamfer surfaces;

[0023] FIG. 10 is a close-up cross-sectional view of a portion of another exemplary display device similar to the display device of FIG. 6, wherein the diffuser plate comprises an overhanging portion in addition to a chamfer surface, the overhanging portion extending past the chamfer surface;

[0024] FIG. 11 is a close-up cross-sectional view of a portion of still another exemplary display device similar to the display device of FIG. 10, wherein a portion of diffuser (e.g., optical layer) overhangs (extends past) the diffuser plate;

[0025] FIG. 12 is a close-up cross-sectional view of a portion of yet another exemplary display device similar to the display device of FIG. 10, wherein a portion of the diffuser (e.g., one or more optical layers) is recessed from an edge of the diffuser plate;

[0026] FIG. 13 is a close-up cross-sectional view of a portion of another exemplary display device similar to the display device of FIG. 6, wherein a portion of the diffuser (e.g., one or more optical layers) overhangs (extends past) the diffuser plate;

[0027] FIG. 14 is a close-up cross-sectional view of a portion of yet another exemplary display device similar to the display device of FIG. 8 wherein a portion of the diffuser (e.g., one or more optical layers) overhangs (extends past) the diffuser plate; [0028] FIG. 15 is a close-up cross-sectional view of a portion of yet another exemplary display device similar to the display device of FIG. 9 wherein a portion of the diffuser (e.g., one or more optical layers) overhangs (extends past) the diffuser plate;

[0029] FIG. 16 is a close-up cross-sectional view of a portion of still another exemplary display device similar to the display device of FIG. 6, wherein a portion of the diffuser (e.g., one or more optical layers) is recessed from an edge of the diffuser plate;

[0030] FIG. 17 is a close-up cross-sectional view of a portion of yet another exemplary display device similar to the display device of FIG. 8 wherein a portion of the diffuser (e.g., one or more optical layers) is recessed from an edge of the diffuser plate;

[0031] FIG. 18 is a close-up cross-sectional view of a portion of yet another exemplary display device similar to the display device of FIG. 9 wherein a portion of the diffuser (e.g., one or more optical layers) is recessed from an edge of the diffuser plate;

[0032] FIG. 19 is a close-up cross-sectional view of a portion of another exemplary display device similar to the display device of FIG. 6 wherein an edge surface of the diffuser plate comprises one or more of a plurality of prismatic or lenticular lens features, a diffraction grating, or a coating e.g., a polymer or metallic coating, a light absorbing material (e.g., a “black” ink or OCA containing a back light absorbing material such as carbon black), a reflective coating such as a vapor deposited metal (e.g., gold or silver) or a metal-containing ink, or multiple layers of TiO2 and/or SiO2, or a color conversion material;

[0033] FIG. 20 is a plot of brightness in nits as a function of distance in millimeters (mm) across a display panel from the border for a display device similar to the display device of FIG.

6 showing a decrease in the magnitude of a bright line (due to light escaping from the diffuser plate) as the height H of the chamfer surface increases at a viewing angle of 30 degrees;

[0034] FIG. 21 is a plot of brightness in nits as a function of distance in mm across a display panel from the border for a display device similar to the display device of FIG. 6 showing a decrease in the magnitude of a bright line (due to light escaping from the diffuser plate) as the height H of the chamfer surface increases at a view angle of 45 degrees.

DETAILED DESCRIPTION

[0035] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. However, this disclosure can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. [0036] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.

[0037] Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. Similarly, when values are expressed as approximations by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will 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.

[0038] Directional terms as used herein — for example, up, down, right, left, front, back, top, bottom — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0039] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus, specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0040] As used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise. [0041] The word “exemplary,” “example,” or various forms thereof are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” or as an “example” should not be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided solely for purposes of clarity and understanding and are not meant to limit or restrict the disclosed subject matter or relevant portions of this disclosure in any manner. It can be appreciated that a myriad of additional or alternate examples of varying scope could have been presented but have been omitted for purposes of brevity.

[0042] As used herein, the terms “comprising” and “including,” and variations thereof, shall be construed as synonymous and open-ended, unless otherwise indicated. A list of elements following the transitional phrases comprising or including is a non-exclusive list, such that elements in addition to those specifically recited in the list may also be present.

[0043] 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” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0044] FIG. 1 depicts a cross-sectional view of a portion of a display device 10, for example a display monitor (e.g., television, computer monitor, etc.). Display device 10 comprises a frame 12, a backlight unit 14 comprising a backplane (light board) 16 having a plurality of light emitters 18 (e.g., LEDs (e.g., blue LEDs, white LEDs), mini-LEDs, etc.) disposed thereon and a diffuser 20 comprising a diffuser plate 21 and one or more optical layers 22, a display panel 24 positioned forward of backlight unit 14, and a border 26 disposed around a periphery of display panel 24. Border 26 has a width W, and a peripheral edge 28 of diffuser plate 21 is separated from frame 12 by a gap 30. As shown, gap 30 is less than the width of the portion of border 26 that extends past frame 12, i.e., distance 32. The relative positions of the diffuser plate and the frame, by producing a gap 30 that is less than the distance 32, minimizes light that can leak from the backlight unit to the viewer. That is, the border overlaps diffuser plate 21 , thereby blocking light escaping from the edge of the diffuser plate (which light might reflect from an adjacent structure such as the frame) from further escaping from between the border and the diffuser plate and to be observed by a viewer as a bright light on the display panel.

[0045] In contrast, FIG. 2 illustrates a similar display device 10 wherein the gap 30 is made greater than the distance 32 the border extends past the frame. In such instances, light that may leak from the diffuser plate may be observable to a viewer of the display device (the viewer has line of sight in the gap 30 between the inside edge of the border and peripheral edge 28 of diffuser 20 (e.g., diffuser plate 21). [0046] Recent trends in display manufacture have included a so-called zero border display (ZBD) device, where the display panel border has minimal width W, for example equal to or less than about 1 millimeter. As shown in FIG. 3, gap 30 is significantly reduced to accommodate the greatly reduced border width W and avoid the presence of gap W between the inside edge of the border and the outer periphery of the diffuser 20, e.g., diffuser plate 21. [0047] Many modem display monitors employ plastic diffuser plates (e.g., poly(methyl methacrylate) due to their low cost, low weight, and good optical clarity. However, plastic diffuser plates also have high thermal expansion, and may expand more than gap 30 allows. In such instances the plastic diffuser plate can contact a frame member and develop stress that can warp the plastic diffuser plate and potentially cause optical distortions of the displayed image. On the other hand, making gap 30 large enough to accommodate thermal expansion of the plastic diffuser plate can facilitate the appearance of a dark band in visible from a direction normal to the display panel or light leakage visible at larger viewing angles by a viewer of the display.

[0048] FIG. 4 is a cross-sectional view of a ZBD device 100. ZBD device 100 may comprise an outer frame 104, a mid- frame 108 positioned within outer frame 104, for example attached to one or more interior surfaces of outer frame 104, a backlight unit 112 comprising a backplane substrate 116, a plurality of light emitters 120 disposed on backplane substrate 116, and a diffuser 124 comprising one or more optical layers 128 and a diffuser plate 132. The optical layers may be laminated to diffuser plate 132, or the optical layers may not be laminated to the diffuser plate. In some embodiments, the optical layers may be partially laminated. That is, edge portions of the optical layers may be laminated to the diffuser plate, whereas other portions of the optical layers may not be laminated to the diffuser plate, for example a central portion of the optical layers may not be laminated to the diffuser plate. In some instances, one or more peripheral edge portions of the optical layers may be laminated to the diffuser plate. The light emitters could be, for example, blue light emitting diodes (LEDs), white light emitting LEDs. The light emitters may be mini-LEDs. The one or more optical layers 128 may comprise, for example, a quantum dot film, a phosphor films, a diffuser film, a brightness enhancement film (BEF), or any combination thereof. The one or more optical layers 128 may have the same size as diffuser plate 132 such that the one or more optical layers 128 terminate at the edges of the diffuser plate. That is, the optical layers may not extend past the edges of the diffuser plate. Alternatively, the one or more optical layers 128 may have a size different than diffuser plate 132 such that the one or more optical layers 128 either overhang (e.g., are cantilevered from) or are receded from an edge of diffuser plate 132. Optical layers 128, when laminated to the diffuser plate, may be laminated to diffuser plate 132 by an adhesive 140, for example an optically clear adhesive (OCA).

[0049] Diffuser plate 132 comprises a first major surface 134 facing display panel 138 (e.g., an LCD panel) and a second major surface 136 opposite first major surface 134 and facing backplane substrate 116 (i.e., facing light emitters 120). A diffuser plate 132 thickness TDP is defined between first major surface 134 and second major surface 136. Diffuser plate 132 may be a polymer diffuser plate. However, in further embodiments, diffuser plate 132 may be a glass diffuser plate and comprise, as an example, a silicate glass, such as an alumino-silicate glass, an aluminoborosilicate glass, an alkali free aluminoborosilicate glass (comprising less than about 1 weight percent alkali metal), or any other glass suitable for use a diffuser plate. In some embodiments, the diffuser plate may comprise a ceramic material. For example, the diffuser plate may comprise a glass-ceramic material. ZBD device 100 further comprises a display panel border 152 disposed about a periphery of display panel 138. Border 152 may be, for example, an opaque (e.g., black) material, for example an ink or polymer material applied to one or both substrates comprising display panel 138. Mid-frame 108 may be positioned on outer frame 104 and may comprise any variety of shapes and/or sizes. For example, in the embodiment shown in FIG. 4, mid- frame 108 comprises a plurality of shelves for supporting components of the display device. For example, diffuser plate 132 may be supported by a first shelf 156 of mid-frame 108. Similarly, display panel 138 may be supported by a second shelf 160 of mid-frame 108 such that display panel 138 is spaced apart from diffuser 124 in a direction orthogonal to second major surface 136. That is, a gap 164 may be provided between diffuser 124 and display panel 138. First shelf 156 and second shelf 160 may be parallel. Accordingly, display panel 138 may be parallel with diffuser plate 132. Diffuser plate 132 may be attached to first shelf 156 by an adhesive 166. Similarly, display panel 138 may be attached to second shelf 160 by adhesive 166. Adhesive 166 may be an optically clear adhesive or another suitable adhesive. As shown in FIG. 4, ZBD device 100 may suffer from the same distinction as the display device 10 of FIG. 3. That is, because border 152 may have a minimal overall width W (e.g., less than about 1 mm), the edge gap 168 between diffuser plate 132 and mid- frame 108 can allow light propagating through the diffuser plate 132 and exiting therefrom to be visible to a viewer 172 as a bright line adjacent border 152. Viewer 172 may be positioned to view display panel 138 at a viewing angle (|) relative to a normal 173 to display panel 138. However, it should be noted that in some embodiments, ZBD device 100 may not include midframe 108, and the gap 168 may be formed between a peripheral edge surface of diffuser plate 132 and another structure of ZBD device 100, for example outer frame 104 or a bezel (not shown).

[0050] FIG. 5 is a close-up view of the gap 168 area of FIG. 4. Light ray 176 (for example, from light emitters 120) is shown entering diffuser plate 132 through second major surface 136, whereupon the light ray intersects edge surface 174 of diffuser plate 132 at an angle 0i relative to a normal 178 to edge surface 174 located at the intersection of light ray 176 and edge surface 174. In the embodiment of FIG. 5, edge surface 174 is orthogonal to first and second major surfaces 134 and 136. As depicted, angle Eh may be less than the critical angle, wherein the light ray does not totally internally reflect within the diffuser plate. Instead, light ray 176 is refracted at edge surface 174 and exits the diffuser plate into free space, e.g., gap 168. The critical angle refers to the angle of incidence 9 (e.g., 9i above) of a light ray traversing a first medium having a first index of refraction m and intersecting an interface between the first medium and a second medium having a second index of refraction m less than the first index of refraction beyond which the light ray is totally internally reflected at the interface. If the angle of incidence 9 is greater than the critical angle 9_C, defined as 9_C = arcsin(n2/ ), the light ray will be totally internally reflected by edge surface 174. Accordingly, refracted light ray 189 is shown exiting edge surface 174 and reflecting from mid- frame 198, becoming reflected light ray 182. Depending on specific angles of refraction and reflection, reflected light ray 182 may pass through gap 168 and be visible to viewer 172 as a bright line on the display panel.

[0051] FIG. 6 is a partial cross-sectional view of ZBD device 199 shown along one edge and comprising an improved diffuser 299. Diffuser 299 comprises a diffuser plate 292 including a first major surface 294 and a second major surface 296 opposite first major surface 294 and facing backplane substrate 116. An edge surface 298 of diffuser plate 292 joins first major surface 294 to second major surface 296. First major surface 294 and second major surface 296 define thickness TDP therebetween. First major surface 294 and second major surface 296 may be parallel surfaces. As shown in FIGS. 6 and 7, edge surface 298 comprises a chamfer surface 219. Chamfer surface 219 forms a chamfer angle a defined between chamfer surface 219 and a plane 212 co-planer with second major surface 296 of diffuser plate 292. Chamfer angle a may be an acute angle equal to or less than 59 degrees. A height H of chamfer surface 219 as measured from plane 214 (defined along a normal to plane 212) is greater than or equal to one half the thickness of diffuser plate 292, i.e., H >

TDP where H is the height of the chamfer surface and TDP is the thickness of diffuser plate 292 defined between the first and second major surfaces 294, 296. In some embodiments, the height H may be equal to the thickness TDP (see FIG. 8). Referring to FIG. 7, a second light ray 220 (from a light emitter 120) is depicted entering diffuser plate 202 through second major surface 206, where the light ray is refracted. The refracted light ray then intersects chamfer surface 210. Because of the presence of chamfer surface 210, second light ray 220 intersects the chamfer surface at an angle O2 relative to a normal 222 to chamfer surface 210, wherein angle 02 may be equal to or greater than the critical angle, whereupon second light ray 220 is totally internally reflected and does not exit the diffuser plate at the point of incidence on the chamfer surface, thereby reducing the probability the light ray will be visible to viewer 172. Other sources of light may be guided in and subsequently leak from diffuser plate 202 similar to second light ray 220, for example light produced by quantum dot wavelength conversion or light refracted by optical films.

[0052] In some embodiments, edge surface 208 may comprise a compound chamfer surface, wherein edge surface 208 of diffuser plate 132 comprises at least two chamfer surfaces. That is, as shown in FIG. 9, diffuser plate 202 may include a first chamfer surface 210a and a second chamfer surface 210b, the two chamfer surfaces comprising two respective chamfer angles. For example, FIG. 9 illustrates a diffuser plate edge surface 208 including first chamfer surface 210a having a first chamfer angle al equal to or less than 50 degrees relative to plane 212 and a first chamfer height Hl, and a second chamfer surface 210b comprising a second chamfer angle a2 equal to or less than 50 degrees relative to second plane 214 and a second chamfer height H2, wherein second plane 214 is parallel to plane 212 The sum of first chamfer height Hl and second chamfer height H2 is equal to or greater than one half the thickness of light guide plate TDP, i.e., (Hl + H2) > 1/2(TDP). For example, in the embodiment depicted in FIG. 9, Hl + H2 = TDP. In the embodiment of FIG. 9, H1+ H2 = H. However, Hl + H2 may be less than TDP.

[0053] The number of chamfer surfaces is not limited to two chamfer surfaces. For example, edge surface 208 may include n chamfer surfaces comprising n respective chamfer angles a_n, and wherein

where H_n represents the height of the individual chamfer surfaces from 1 to n and TDP represents the thickness of the diffuser plate. Thus, the sum of the n chamfer heights is equal to or greater than the thickness of the diffuser plate but less than or equal to TDP- Each chamfer angle _n is equal to or less than 50 degrees.

[0054] Edge surface 208 may comprise one or more chamfer surfaces that are recessed relative to the remainder of the edge surface such that an overhanging lip portion 221 extending outward from the chamfer surface is formed. In the embodiment of FIG. 10, edge surface 208 comprises a chamfer surface 210, a first peripheral edge surface 222, a second peripheral edge surface 224, and an intermediate edge surface 226 extending between and joining first peripheral edge surface 222 and second peripheral edge surface 224. Chamfer surface 210 forms an angle a equal to or less than 50 degrees relative to plane 212 (and a complementary angle P with second major surface 206, wherein = 180 - a). Height H of chamfer surface 210 is equal to or greater than one half TDP. Intermediate edge surface 226 may be orthogonal to each of first peripheral edge surface 222 and second peripheral edge surface 224. First peripheral edge surface 222 may be parallel to second peripheral edge surface 224. Further, first peripheral edge surface 222 and second peripheral edge surface 224 may each be orthogonal to first major surface 204. First peripheral edge surface 222 comprises a height Hpi and is recessed a recess distance 228 from second peripheral edge surface 224, thereby forming lip portion 221. A height Hp2 of lip portion 221 is defined between first major surface 204 and intermediate edge surface 226. In the embodiment of FIG. 10, TDP = H + Hpi + Hp2. It should be readily apparent that chamfer surface 210 could, in other embodiments, comprise more than one chamfer surface (e.g., be a compound chamfer surface comprising two or more chamfer surfaces) in accordance with equation (1).

[0055] In the preceding embodiments, the one or more optical layers 128 terminate at second peripheral edge surface 224. Alternatively, the one or more optical films may extend beyond (overhang) lip portion 221 (e.g., second peripheral edge surface 224). FIG. 11 depicts the edge surface 208 of FIG. 10, but with the one or more optical layers 128 extending outward from second peripheral edge surface 224 an overhang distance Fo. While shown attached to diffuser plate 132, as noted previously, optical layers 128 may, in some embodiments, be unattached to diffuser plate 132.

[0056] Similarly, the one or more optical layers 128 may terminate inward of second peripheral edge surface 224, as shown in FIG. 12. In the embodiment of FIG. 12, the one or more optical layers 128 terminate a recess distance Fr from second peripheral edge surface 224. [0057] It should be apparent that optical film termination variations as described above may be applied to other diffusers. For example, FIGS. 13-15 depict embodiments wherein the one or more optical films extend past diffuser plate 202. FIG. 13 illustrates a portion of a diffuser 200 wherein the height H of chamfer surface 210 is less than the thickness TDP of diffuser plate 202 but equal to or greater than one half TDP, and the one or more optical films overhang (extend past) the peripheral edge surface 230. FIG. 14 illustrates a portion of diffuser 200 wherein the height H of chamfer surface 210 is equal to the thickness TDP of diffuser plate 202 and the one or more optical layers 128 overhang (extend past) diffuser plate 202 by an overhang distance Fo. FIG. 15 depicts another diffuser 200 with a diffuser plate 202 comprising a first chamfer surface 210a with a first chamfer height of Hl and a first chamfer angle al, and a second chamfer surface 210b with a second chamfer height of H2 and a second chamfer angle a2, and wherein the sum of the first and second chamfer heights Hl + H2 is equal to the thickness TDP of diffuser plate 202 and each of the first and second chamfer angles al, a.2 is equal to or less than 50 degrees, and wherein the one or more optical layers 128 overhang (extend past) diffuser plate 202 by overhang distance Fo.

[0058] Similarly, FIGS. 16-18 depict embodiments wherein the one or more optical layers 128 are recessed from edge surface 208 by a recess distance Fr, i.e., before the intersection of first major surface 204 and edge surface 208. FIG. 16 illustrates a portion of a diffuser 200 wherein the height H of chamfer surface 210 is equal to or greater than on half TDP but less than thickness TDP of diffuser plate 202 and the one or more optical films are recessed from peripheral edge surface 230 by recess distance Fr. FIG. 17 illustrates a portion of diffuser 200 wherein the height H of chamfer surface 210 is equal to the thickness TDP of diffuser plate 202 and the one or more optical layers 128 are recessed from the intersection of first major surface 204 and edge surface 208 by recess distance Fr. FIG. 18 depicts another diffuser 200 comprising a first chamfer surface 210a with a first chamfer height of Hl and a first chamfer angle al, and a second chamfer surface 210b with a second chamfer height of H2 and a second chamfer angle a2, and wherein the sum of the chamfer heights Hl + H2 is equal to the thickness of diffuser plate 202 and each of the first and second chamfer angles al, a2 is equal to or less than 50 degrees, and wherein the one or more optical layers 128 are recessed from the intersection of first major surface 204 and edge surface 208 by recess distance Fr.

[0059] Referring now to FIG. 19, in some embodiments, chamfer surface 210 may comprise a surface layer 240 including, for example, a plurality of prismatic or lenticular lens features or a diffraction grating. This may be accomplished by engraving or etching the features directly into the chamfer surface or by applying a coating, for example a polymer coating having preformed features formed therein to the chamfer surface. In other embodiments, surface layer 240 may comprise a light absorbing material (e.g., a “black” ink or OCA containing a back light absorbing material such as carbon black), a reflective coating such as a vapor deposited metal (e.g., gold or silver) or a metal-containing ink, or multiple layers of TiO2 and/or SiO2. In some embodiments, surface layer 240 may comprise a color conversion material such as a quantum dot material, a phosphor material, or an organic light emitting diode material.

[0060] FIG. 20 shows brightness in nits as a function of position (distance from the border ) on the display panel in millimeters for a display device having a diffuser plate with a single chamfer surface (e.g., chamfer surface 210) when viewed at a 30-degree viewing angle <|) (wherein viewing angle <|) refers to the angle relative to a normal to the display panel surface facing the viewer, thus, a viewer viewing the display at an angle offset from the normal by 30 degrees. See FIG. 4). The diffuser plate was set at 0.7 mm, the chamfer angle a was fixed at 45 degrees, and the chamfer height H varied from 0.2 mm to 0.7 mm. The data show that as the chamfer height increased from 0.2 mm to 0.7 mm, the magnitude of the bright line decreased.

[0061] FIG. 21 is similar to the modeling of FIG. 20 with the exception the viewing angle was assumed to be 45 degrees. Again, the data show that as the chamfer height increased from 0.2 mm to 0.7 mm, the magnitude of the bright line decreased.

[0062] It will be apparent to those skilled in the art that various modifications and variations can be made to embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover such modifications and variations provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A display device, comprising: a display panel; a backlight unit comprising: a backplane substrate comprising a plurality of light emitters; a diffuser disposed between the backplane substrate and the display panel, the diffuser comprising a diffuser plate comprising a first major surface, a second major surface, an edge surface extending between and joining the first major surface and the second major surface, and a thickness defined between the first major surface and the second major surface; and wherein the edge surface comprises a chamfer surface extending from the second major surface, the chamfer surface comprising a chamfer angle less than 50 degrees defined between the chamfer surface and a first plane coincident with the second major surface and a chamfer height greater than one half the thickness of the diffuser plate.

2. The display device of claim 1, wherein the chamfer surface is a first chamfer surface, the edge surface further comprising a second chamfer surface intersecting the first chamfer surface.

3. The display device of claim 2, wherein the chamfer angle is a first chamfer angle, the second chamfer surface comprising a second chamfer angle equal to or less than 50 degrees defined between the second chamfer surface and a second plane parallel with the first plane and intersecting the second chamfer surface where the second chamfer surface intersects the first chamfer surface.

4. The display device of claim 3, wherein the second chamfer surface comprises a second chamfer height defined from the second plane, and a sum of the first chamfer height and the second chamfer height is equal to or greater than one half the thickness of the diffuser plate.

5. The display device of claim 1, wherein the edge surface further comprises a first peripheral edge surface intersecting the chamfer surface, a second peripheral edge surface intersecting the first major surface, and an intermediate edge surface extending between the first peripheral edge surface and the second peripheral edge surface, the intermediate edge surface orthogonal to the first peripheral edge surface and the second peripheral edge surface.

6. The display device of any one of claim 5, wherein a height of the second peripheral edge surface defined between the intermediate edge surface and the first major surface is equal to or less than one half the thickness of the diffuser plate.

7. The display device of claim 1, wherein the chamfer surface comprises a color conversion coating.

8. The display device of claim 1, wherein the chamfer surface comprises a light absorbing coating.

9. The display device of claim 1 , wherein chamfer surface comprises a light reflecting surface.

10. The display device of claim 9, wherein the light reflecting surface comprises Ti, Ag, or Al.

11. The display device of claim 1 , wherein the chamfer surface comprises a plurality of prisms.

12. The display device of claim 1, wherein the chamfer surface comprises a plurality of lenticular lenses.

13. The display device of claim 1, wherein the chamfer surface comprises a diffraction grating.

14. The display device of any one of claims 1 to 13, wherein the diffuser comprises one or more optical layers disposed on the first major surface, the one or more optical layers comprising at least one of a quantum dot film, a phosphor films, a diffuser film, or a brightness enhancement film.

15. The display device of claim 14, wherein the one or more optical layers are recessed from the edge surface.

16. The display device of claim 14, wherein the one or more optical layers extend past the edge surface.

17. The display device of any one of claims 1 to 16, wherein the diffuser plate comprises glass.