WO2024054357A1

WO2024054357A1 - Display tiling with reduced seam visibility

Info

Publication number: WO2024054357A1
Application number: PCT/US2023/031007
Authority: WO
Inventors: Alexander Lee CUNO; Dae Youn Kim; Kyung-Jin Lee; Shenping Li; Dong Keun Shin; Hong Yoon
Original assignee: Corning Incorporated
Priority date: 2022-09-08
Filing date: 2023-08-24
Publication date: 2024-03-14
Also published as: CN117672089A

Abstract

An optical display device including a base plate and a plurality of tiled LED boards disposed thereon. One or more of the base plate and/or the LED boards may be coated with one or more coating materials to adjust a relative reflectivity between the base plate and the LED boards to minimize the intensity of light reflected at the gap between the tiled LED boards due to reflectance at the base plate.

Description

DISPLAY TILING WITH REDUCED SEAM VISIBILITY

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 63/374956 filed on September 8, 2022, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to optical display devices, and in particular tiled optical display devices having reduced visibility at the gaps between individual display panels of the tiled optical display devices.

BACKGROUND

[0003] While large-area displays are highly desired, mass production of such large-area displays suffer from low production yields and high cost and represent technical challenges for emerging high-resolution Micro-LED (pLED) displays. A well-accepted, cost-effective approach for creating a large-area display is to tile multiple small format displays to form a large-area display.

[0004] One issue experienced by a tiled display is visible seam lines on the tiled display screen at the boundaries of adjacent small format displays that comprise the tiled display. To overcome this problem, various approaches have been proposed, such as overlapping the edge of small format displays, utilizing different optical devices to cover the seam lines in which the seam visibility is reduced by guiding light from adjacent light emitting areas to seam line areas through optical devices, and employing optical edge blending techniques in which, to camouflage the seam, electronic adjustment is applied to pixels in areas adjacent to a seam to adjust the brightness and/or pattern in that area.

SUMMARY

[0005] In a first aspect, an optical display device is disclosed, comprising a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface, a first substrate comprising a third major surface, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface. [0006] The optical display device may further comprise a second substrate comprising a fifth major surface, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap. A first surface portion of the third major surface adjacent to and extending along the gap may be coated with a second coating material different than the first coating material, and at least a portion of a second surface portion of the third major surface adjacent the first surface portion is coated with a third coating material different than the second coating material.

[0007] In a second aspect, a reflectivity of the first major surface coated with the first coating material of the optical display device of the first aspect is less than a reflectivity of the first surface portion coated with the second coating material.

[0008] In a third aspect, a reflectivity of the first major surface coated with the first coating material of the optical display device of the first aspect may be at least 50% less than a reflectivity of the first surface portion coated with the second coating material.

[0009] In a fourth aspect, a reflectivity of the first major surface coated with the first coating material of the optical display device of the first aspect, may be at least 75% less than a reflectivity of the first surface portion coated with the second coating material.

[0010] In a fifth aspect, a scattering factor n_e of the first surface portion coated with the second coating material of the optical display device of any one of the first through the fourth aspects, may be equal to or less than a scattering factor <J_S of the second surface portion coated with the third coating material.

[0011] In a sixth aspect, a reflectivity of the first surface portion coated with the second coating material of the optical display device of the first aspect, may be greater than a reflectivity of the second surface portion coated with the third coating material.

[0012] In a seventh aspect, a third surface portion of the fifth major surface adjacent to and extending along the gap of the optical display device of the first aspect may be coated with the second coating material, and at least a portion of the fourth surface portion of the fifth major surface adjacent the third surface portion is coated with the third coating material [0013] In an eighth aspect, the first surface portion of the optical display device of the seventh aspect may comprise a first chamfer surface and the third surface portion may comprise a second chamfer surface. [0014] In a ninth aspect, at least a portion of the second surface portion and at least a portion of the fourth surface portion of the optical display device of the eighth aspect may be coated with the second coating material.

[0015] In a tenth aspect, a width of the gap between the first edge surface and the second edge surface of the optical display device of the first aspect may increase in a direction from the third major surface toward the base plate.

[0016] In an eleventh aspect, a width of the gap between the first edge surface and the second edge surface of the optical display device of the first aspect may decrease in a direction from the third major surface toward the base plate.

[0017] In a twelfth aspect, the first edge surface of the optical display device of the first aspect may comprise an arcuate surface.

[0018] In a thirteenth aspect, the first edge surface and the second edge surface of the optical display device of any one of the first aspect through the twelfth aspects may be coated with the second coating material.

[0019] In a fourteenth aspect, the third major surface of the optical display device of any one of the first through the thirteenth aspect may comprise a plurality of light emitting diodes disposed thereon.

[0020] In a fifteenth aspect, an optical display device is disclosed, comprising a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface, a first substrate comprising a third major surface, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface, and a second substrate comprising a fifth major surface, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap. The third major surface may be coated with a second coating material different than the first coating material, a surface roughness of the first major surface coated with the first coating material may be equal to a surface roughness of the third major surface coated with the second coating material, and a reflectivity of the first major surface coated with the first coating material may be greater than a reflectivity of the third major surface coated with the second coating material.

[0021] In a sixteenth aspect, the third major surface of the optical display device of the fifteenth aspect may comprise a plurality of light emitting diodes disposed thereon. [0022] In a seventeenth aspect, the reflectivity of the first major surface coated with the first coating material of the optical display device of the fifteenth or the sixteenth aspects may be less than 2 times the reflectivity of the third major surface coated with the second coating material.

[0023] In an eighteenth aspect, the reflectivity of the first major surface coated with the first coating material of the optical display device of the seventeenth aspects may be in a range from about 5% to about 10%.

[0024] In a nineteenth aspect, an optical display device is disclosed, comprising a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface, a first substrate comprising a third major surface coated with a second coating material, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface, a second substrate comprising a fifth major surface coated with the second coating material, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap. A reflectivity of the first major surface coated with the first coating material may be greater than a reflectivity of the third major surface or the second major surface coated with the second coating material.

[0025] In a twentieth aspect, the reflectivity of the base plate of the optical display device of the nineteenth aspect may be less than 2 times the reflectivity of at least one of the third major surface or the fifth major surface coated with the second coating material.

[0026] In a twenty first aspect, at least one of the first edge surface or the second edge surface of the optical display device of the nineteenth or the twentieth aspects may be coated with the second coating material.

[0027] In a twenty second aspect, and one or more of the base plate, the first substrate or the second substrate of the optical display devices of any one of the preceding aspects may comprise glass.

[0028] In any of the preceding aspects, any one or more of the first substrate, the second substrate, or the base plate of the optical display devices disclosed herein may comprise glass, for example a silica-based glass, e.g., an aluminosilicate glass, such as an aluminoboro silicate glass. [0029] 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

[0030] FIG. 1 is a plot graphically illustrating the intensity of light reflected from an exemplary tiled display as a function of position across several tiles of the display, including across a gap between the several tiles;

[0031] FIG. 2 is a cross-sectional schematic view of an exemplary tiled display comprising a plurality of LED boards, a base plate to which LED boards 12 comprising light emitting diodes 16 disposed thereon are attached, and a cover fdter, and illustrates view angle;

[0032] FIG. 3 is a plot of the absolute value of Seam Visibility factor (SVF) as a function of base plate reflectivity Ruase Plate obtained from experiments;

[0033] FIG. 4 is a plot showing a Gaussian profile of surface scattering a from an exemplary tiled display as a function of scattering factor a in degrees;

[0034] FIG. 5A is a cross-sectional view of an exemplary tiled display according to embodiments of the present disclosure;

[0035] FIG. 5B is a close-up view of the exemplary tiled display of FIG. 5A;

[0036] FIG. 6 is a cross-sectional view of another exemplary tiled display according to embodiments of the present disclosure;

[0037] FIG. 7 is a cross-sectional view of an exemplary tiled display comprising chamfer surfaces according to embodiments of the present disclosure;

[0038] FIG. 8 is a cross-sectional view of another exemplary tiled display comprising chamfer surfaces according to embodiments of the present disclosure;

[0039] FIG. 9 is a cross-sectional view of still another exemplary tiled display comprising chamfer surfaces according to embodiments of the present disclosure;

[0040] FIG. 10 is a cross-sectional view of yet another exemplary tiled display comprising chamfer surfaces according to embodiments of the present disclosure;

[0041] FIG. 11 is a cross-sectional view of a exemplary tiled display comprising display tiles with angled edge surfaces defining a gap therebetween according to embodiments of the present disclosure; [0042] FIG. 12 is a cross-sectional view of another exemplary tiled display comprising display tiles with angled edge surfaces defining a gap therebetween according to embodiments of the present disclosure;

[0043] FIG. 13 is a cross-sectional view of another exemplary tiled display comprising display tiles with arcuate edge surfaces defining a gap therebetween according to embodiments of the present disclosure;

[0044] FIG. 14 is a schematic view of a lighting set-up for experiments conducted according to embodiments disclosed herein;

[0045] FIG. 15 is a plot showing corresponding intensity distributions for chamfer surface reflectivities over a range from 3% to 10%;

[0046] FIG. 16 is a plot showing optimal reflectivity Re of the (near-edge) chamfer surfaces for a viewing angle = 0 as a function of base plate surface reflectivity when all surfaces (base surface, substrate surfaces, edge surfaces, and chamfer surfaces) have an identical scattering factor;

[0047] FIG. 17 is a plot showing optimal reflectivity Re of the (near-edge) chamfer surfaces for a view angle = 0 as a function of the ratio of near-edge coated substrate and substrate surfaces scattering factors (o_c/o_s) when the reflections of base surface and substrate surfaces are 0% and 5%, respectively;

[0048] FIG. 18 is a plot showing modeled seam visibility factor SVF as a fraction of scattering factor for all surfaces of an exemplary tiled display for a normal viewing angle;

[0049] FIG. 19 is a plot showing optimal reflectivity of coated near-edge substrate surfaces as a function of the ratio of scattering factors (oe/c_s) (viewing angle = 0) when the reflections of the base surface and the substrate surfaces are 0% and 5%, respectively;

[0050] FIG. 20 a cross-sectional view of a representative tiled display device used for an experimental study on the effect of near-edge LED board coating on tiling seam visibility according to embodiments of the present disclosure;

[0051] FIG. 21 is a plot showing the reflection spectra of inks used to coat components of exemplary tiled display devices in according to embodiments of the present disclosure;

[0052] FIG. 22 is a cross-sectional view of a representative tiled device used as an experimental reference device according to embodiments of the present disclosure;

[0053] FIG. 23 is a plot showing the measured cross-sectional intensity distributions of the tiling seam for the reference tiled display of FIG. 22; [0054] FIG. 24 is a plot showing the measured cross-sectional intensity distributions of the tiling seam for the display device of FIG. 20; and

[0055] FIG. 25 is a plot showing curves of measured SVF as a function of viewing angle for the reference case (line with circles) of FIG. 22 and the case under experimental study (line with squares) of FIG. 20.

DETAILED DESCRIPTION

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The terms “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.

[0063] 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.

[0064] 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, within about 2% of each other, or within about 1 % of each other.

[0065] As used herein, the terms “gap” and “seam” are synonymous and refer to the region separating individual and immediately adjacent display panels, for example individual display panels (e.g., LED boards) disposed on a base plate.

[0066] The manufacture of large area displays, for example as might be used for signage (e.g., billboards or other broadly visible displays), is more easily accomplished by tiling multiple small displays together in vertical and/or horizontal arrays, wherein the image to be displayed can be segmented across the multiple displays. For example, multiple thin display panels can be arranged on a common base plate to form a larger tiled display. Still, a small gap may exist between adjacent edge surfaces of the individual display panels of the tiled display. While this gap may be on the order of a pixel width apart (e.g., about 50 micrometers or smaller), the human eye is capable of discerning such an image discontinuity, particularly when displayed in a regular geometric array (e.g., straight lines, for example a rectangular pattern of individual display panels).

[0067] One visible artifact from the existence of gaps (seams) between adjacent edges of individual display panels of a tiled display is the disparity in luminance between the individual display panels and the base plate to which the individual display panels are coupled. That is, seam visibility depends at least on the degree to which ambient light incident on the tiled display is reflected from the individual display panels compared to the light reflected from the base plate through the intervening gap(s) between the individual display panels.

[0068] Accordingly, in some embodiments, seam visibility can be decreased by adjusting reflectance of the individual display panels relative to the base plate to be greater than the reflectance of the base plate to which the individual display panels are mounted. This can be accomplished by modifying the reflectance of the individual display panels, modifying the reflectance of the base plate, or modifying both the individual display panels and the base plate. [0069] Seam visibility can be quantified by the following equation:

SVF = WG/(WFWHF) x A/Ib (1) where SVF represents the seam visibility factor, WG represents the distance between the adjacent light (e.g., LED) boards (e.g., the gap Gtherebetween - see FIG. 2), WFWHM represents the width of the cross-sectional intensity distribution of a tiled device image at the gap at one half the the maximum intensity A of the intensity distribution, and lb is the base intensity of the cross-sectional intensity distribution (e.g., spaced away from the gap).

[0070] FIG. 1 is a plot graphically illustrating several parameters of Equation (1), specifically lb, WFWHM, and A. The dip in the displayed curve represents the location of the gap G between LED boards.

[0071] The light scattering property of a surface relative to a coated surface can be described by a Gaussian scattering function represented by the following equation:

1(6) = I_o exp[-(0/c)²] (2) where 0 is the angle from the specular direction, 1(6) is radiance in the 6 direction, I_o is radiance in the specular direction, and <J is the scattering factor, which is the standard deviation of the Gaussian distribution. [0072] Referring now to FIG. 2, when the view angle p_v representing the angle between the line of sight of a person viewing the display (hereinafter “viewer”) and a normal to the surface of the display, which is the angle between the view direction and the display normal, is smaller than the critical view angle p_Vc, SVF can be approximated as

SVF « C (RLED Board - Rflase Plate X «)/RLED Board (3) where c represents a constant corresponding to the value of WG/WFWHM, represents

the reflectivity of the backplane substrate (which may include a plurality of light emitting diodes disposed thereon), Rsase Plate represents the reflectivity of the base plate to which the plurality of LED boards may be attached, and a represents a light escaping factor defined as the ratio of the light power emitted (escaping) from the base plate to the power of the light incident on the base plate surface. The greater the scattering factor, the less the light escaping factor a. The nearer SVF is to zero, the less visible the seam between LED boards.

[0073] In accordance with Equation (3), if the reflectivity RIFD Board of the LED board is equal to the reflectivity Rsase Plate of the base plate, SVF is zero for a 0-degree view angle p_v. However, as a practical matter, not all light reaching the base plate can be reflected back to reach the viewer at least because of scattering of light incident on the base plate. Consequently, some light may be trapped in the gap between LED boards and/or light may be reflected from the back plate at a non-normal angle. Light escaping at a non-normal angle may intersect side walls of the display panels. The light escaping factor a is relative to the scattering factor of the base surface, which is in turn relative to the base plate surface roughness and is defined as the outcoupling ratio from the seam geometry. A light escaping factor of 1.0 means 100% light is outcoupled without any loss of incoming light, while a light escaping value of 0.5 indicates a 50% light loss inside the gap due to absorption of scattered light at the side wall(s) defining the seam. The light escaping factor is expected to be the range of 0.5 to 1.0 assuming a Gaussian profile of scattered light.

[0074] FIG. 2 shows a cross-sectional schematic view of an exemplary tiled display 10 comprising a plurality of LED boards 12, abase plate 14 to which LED boards 12 comprising light emitting diodes 16 disposed thereon are attached, and a cover filter 18. Cover filter 18 can function to reduce surface reflection of the display, enhance contrast ratio, adjust displayed color of the display, and/or protect the display. The light boards may comprise glass, for example, and without limitation, a silicate glass such as an alkali-free borosilicate glass, or an alumino-borosilicate glass, or any other glass suitable for the manufacture of optical display devices. Similarly, in embodiments, the base plate may comprise a glass material, similar to or different from the glass of the LED boards. However, in further embodiments, the base plate and/or the LED boards may comprise a polymer material, for example a phenolic material.

[0075] A viewer of the tiled display is designated by the reference numeral 20 and is shown observing the tiled display at a view angle p_v relative to a normal 22 to the tiled display 10 (e.g., cover fdter 18). The figure illustrates light trapping within gap G due to scattering at the base plate surface. In this instance, the LED boards had a thickness t_s of 500 micrometers (pm) and a width WG of gap G between adjacent light boards was 50 pm. The critical view angle (Lc represents the angle within which light can escape the gap (e.g., clear the edges of the adjacent LED boards) and for the current example is approximately 3 ° ± 1 ° . Even though the reflectance RLED Board of the LED boards is equal to the reflectivity of the base plate Rsase Plate in this example, the seam remains visible (as if the surface of the base plate has a different surface roughness, thus a different scattering factor, which results in different reflectivity values).

[0076] For minimizing seam visibility when the view angle p_v is less than the critical view angle p_Vc, it can be estimated that the reflectivity of the base plate should be slightly greater than the reflectivity of the LED boards if the base plate and the LED boards have the same surface roughness (or same scattering factor).

[0077] Experiments were conducted by changing the reflectivity of the base plate to greater than 5%. Base plates used in the experiments were commercially available color chip plates with varying ranges of grey scale “color” and exhibited reflectivities of 5%, 8%, 11%, 18%, 24%, and 44%. Reflectivities were measured using a Konica-Minolta CM-2600d spectrophotometer. The LED boards were simulated by glass plates having a black coating and had reflectivites of 3.9% and 5.2%. In the instance of 3.9% reflectivity, the LED boards were coated with a thermally cured acrylic polymer containing carbon black powder and talc powder. The polymer was determined to contain C, O, F, Mg and Si in amounts by weight of about 23.6%, 68.2%, 2.4%, 2.7% and 3.1%, respectively, by Scanning Electron Microscopy with Energy Dispersive X-ray analysis (SEM-EDX). The coating was applied by spray coating. In the instance of LED boards with 5.2% reflectivity, the boards were coated with a thermally cured phenoxy resin comprising carbon black powder. The coating material was deposited on the LED boards by screen printing. The resin contained C, O, Si and Ca in amounts of about 26.3%, 71.6%, 0.85 and 1.13%, respectively, again determined by SEM-EDX. Edge surfaces of the LED boards were either coated or left bare (uncoated). The transmittance of the cover filter was 57%, the viewing angle was 0°, and there was a 50 pm gap (WG) between adjacent LED boards. The LED boards were illuminated by a 380-lux ambient light normal to the surface of the boards, measured by a Testo 540 light meter at the surface of the LED boards.

The light escaping factor a was assumed to be 0.5 and 1.0, respectively.

[0078] SVF was calculated as provided in Table 1, below.

Table 1

[0079] The data of Table 1 show that SVF was minimized when the reflectivity of the base plate was greater than the reflectivity of the LED boards. The absolute value of edge surface reflectivity does not play a significant role, but it is thought that edge surface roughness plays a major role in terms of SVF minimization.

[0080] The LED boards had a surface roughness after coating as indicated in Table 2. Surface roughness was measured using a confocal laser scanning microscope. Samples with an edge surface reflectivity of 4.0% were not edge coated.

Table 2

[0081] FIG. 3 is a plot of the absolute value of SVF as a function of base plate reflectivity Rfiase Plate obtained from the preceding experiments, where curve 20 represents an LED board reflectivity Board of 5.2% and abase plate reflectivity RsasePiate of 4.0%, curve 22 represents an LED board reflectivity Board of 5.2% and a base plate reflectivity RBase Plate of 5.2% ,

and curve 24 represents an LED board reflectivity RLED Board of 3.9% and a base plate reflectivity Rnase Plate of 4.0%. Range 26 represents the approximate base plate reflectivity over which SVF is essentially zero. The three lines 20, 22, and 24 come from the data in Table 1. The two dotted lines 28, 30 are theoretical predictions from Equation 3 for a = 1.0 and a = 0.5, respectively. FIG. 3 shows the inflection points of |SVF| (that is, where |SVF| ~ 0). The inflection point depends on the light escaping factor, a. If there is no scattering element in the seam region, e.g., a = 1, |SVF| ~ 0 comes close to R(Base Plate). If the seam region surfaces are rough, trapping of incoming light becomes more pronounced, and thus less light escapes. Based on experiments and theoretical estimation, the light escaping factor is in a range between 0.5 and 1.0, which corresponds to 5% < R(SVF=0) < 10% FIG. 4 is a plot showing a Gaussian profde of surface scattering as a function of scattering factor a in degrees. The shaded region depicts low to moderate scattering in the seam area.

[0082] To suppress seam visibility over a broader array of viewing angles, other display modifications may be made, either separately or in addition to the foregoing. In accordance with further aspects, different coatings having different reflectivities may be employed on the LED boards. FIG. 5 A is a cross-sectional view of a tiled display 100 and FIG. 5B is a closeup view of portion B from FIG. 5 A. Tiled display 100 comprises a base plate 102 including a first major surface 104 and a second major surface 106 opposite first major surface 104. First and second major surfaces 104, 106 may be parallel surfaces. First major surface 104 may comprise a first coating material 108 disposed thereon. First coating material 108 comprises a first reflectivity Rb and a first scattering factor Ob (see Equation (1)). Tiled display 100 further comprises a first LED board (substrate) 110 comprising a third major surface 112 and a fourth major surface 114 opposite third major surface 112. Third and fourth major surfaces 112, 114 may be parallel surfaces. Fourth major surface 114 of first LED board 110 is disposed on base plate first major surface 104 overtop first coating material 108. A first edge surface 116 of first LED board 110 is disposed between third major surface 112 and fourth major surface 114 and joins third major surface 112 and fourth major surface 114. First edge surface 116 may be orthogonal to third and fourth major surfaces 112, 114. While not shown, third major surface 112 may include aplurality of light emitting diodes (e.g., LEDs, microLEDs) disposed thereon. [0083] Tiled display 100 still further comprises a second LED board (substrate) 118 comprising a fifth major surface 120 and a sixth major surface 122 opposite fifth major surface 120. Fifth and sixth major surfaces 120, 122 may be parallel surfaces. Sixth major surface 122 is disposed on base plate first major surface 104 overtop first coating material 108. A second edge surface 124 is disposed between fifth major surface 120 and sixth major surface 122 and joins fifth major surface 120 and sixth major surface 122. Second edge surface 124 may be orthogonal to fifth and sixth major surfaces 120, 122. Similar to first substrate 110, fifth major surface 120 may include aplurality of light emitting diodes (e.g., LEDs, microLEDs) disposed thereon. First LED board 110 and second LED board 118 are arranged such that a gap G comprising a width WG separates first edge surface 116 from second edge surface 124. That is, first and second edge surfaces 116, 124 are adjacent edge surfaces separated by gap G. In this context, adjacent means first and second edge surfacesl l6, 124 are directly opposite one another with no intervening structure. Gap G may be a uniform gap, wherein first and second edge surfaces 116, 124 are parallel edge surfaces separated uniformly by width WG.

[0084] Referring now to FIG. 5B, in aspects, third major surface 112 may comprise a first surface portion 126 and a second surface portion 128 adjacent first surface portion 126. That is, first surface portion 126 may be a near-edge surface portion extending along gap G and having a uniform width W_ei extending from the intersection of third major surface 112 and first edge surface 116. Second surface portion 128 extends over the remainder of third major surface 112, for example from first surface portion 126 in a direction away from gap G. Similarly, fifth major surface 120 may comprise a third surface portion 130 and a fourth surface portion 132 adjacent third surface portion 130. Third surface portion 130 may likewise be a near-edge surface portion extending along gap G and having a uniform width W_e2 extending away from the intersection of fifth major surface 120 and second edge surface 124. In aspects, W_ei may be equal to W_e2. Fourth surface portion 132 may extend over the remainder of fifth major surface 120, for example from third surface portion 130 in a direction away from gap G.

[0085] Still referring to FIG. 5B, first surface portion 126 of third major surface 112 may be coated with a second coating material 134 and second surface portion 128 may be coated with a third coating material 136. Similarly, third surface portion 130 of fifth major surface 120 may be coated with second coating material 134 and fourth surface portion 132 of fifth major surface 120 may be coated with third coating material 136. Second coating material 134 comprises a second reflectivity Re and a second scattering factor n_e, and third coating material 136 comprises a third reflectivity Rs and a third scattering factor <J_S. In the embodiment of FIGS. 5A and 5B, first and second edge surfaces 116, 124 are uncoated.

[0086] FIG. 6 depicts a tiled display 200 similar to tiled display 100 of FIGS. 5A and 5B, with the exception that, in addition to near-edge surface portions 126, 130 of third and fifth major surfaces 112, 120 bordering first and second edge surfaces 116, 124, respectively, first and second edge surfaces 116, 124 may also be coated with second coating material 134 such that second coating material 134 extends continuously over first and third surface portions 126, 130 and over first and second edge surfaces 116, 124.

[0087] FIG. 7 illustrates a portion of another tiled display 300 similar to tiled display 100 shown in FIG. 5A-5B, with the exception that first surface portion 126 of third major surface 112 and third surface portion 130 of fifth major surface 120 each comprise a chamfer surface. For example, chamfer surface 140 of first surface portion 126 of third major surface 112 forms an angle a_ci relative to the plane of third major surface 112, while third surface portion 130 of fifth major surface 120 comprises a second chamfer surface 142 forming an angle a_C2 relative to the plane of fifth major surface 120. In the embodiment of FIG. 7, the entirety of first surface portion 126 comprises first chamfer surface 140 and the entirety of third surface portion 130 comprises the second chamfer surface 142. In the embodiment of FIG. 7, first surface portion 126 (e.g., first chamfer surface 140) and third surface portion 130 (e.g., second chamfer surface 142) are each coated with second coating material 134. At least a portion of second surface portion 128 and at least a portion of fourth surface portion 132 may also be coated with second coating material 134. For example, second coating material 134 coating at least a portion of second surface portion 128 and at least a portion of fourth surface portion 132 coats the respective at least a portion 128, 132 along a strip of the at least a portion 128, 132 parallel with gap G, wherein a width of the strip is designated in FIG. 7 as W_e. That is, at least a portion of an unchamfered portion of third major surface 112 and fifth major surface 120 are coated with second coating material 134. The width of the unchamfered surfaces coated with second coating material 134 taken parallel to third major surface 112 and fifth major surface 120 is designated W_c. At least a portion of second surface portion 128 and at least a portion of fourth surface portion 132 may each be coated with third coating material 136. In the embodiment shown in FIG. 7, at least a portion of second surface portion 128 and at least a portion of fourth surface portion 132 are coated with second coating material 134, and the remainder of second surface portion 128 and fourth surface portion 132 are coated with third coating material 136. [0088] FIG. 8 depicts still another tiled display 400 similar to the tiled display of FIG. 7, with the exception that, in addition to chamfer surfaces 140, 142 being coated with second coating material 134, first and second edge surfaces 116, 124 are also coated with second coating material 134.

[0089] FIG. 9 depicts another tiled display 500 similar to the tiled display of FIG. 8 with the exception that second surface portion 128 and fourth surface portion 132 are not coated with second coating material 134. In the embodiment of FIG. 9, first surface portion 126 and third surface portion 130 are comprised entirely of chamfer surface 140 and chamfer surface 142, respectively, and first chamfer surface 140 and second chamfer surface 142 are coated with second coating material 134. Second surface portion 128 and fourth surface portion 132 are coated with third coating material 136. First and second edge surfaces 116, 124 of first and second LED boards 110, 118 are uncoated. [0090] FIG. 10 depicts another tiled display 600 similar to tiled display 500, with the exception that first and second edge surfaces 116, 124 are coated with second coating material 134 in addition to chamfer surfaces 140, 142 being coated with second coating material 134.

[0091] FIGS. 11-13 show other embodiments of tiled displays incorporating engineered edges. That is, the light boards have edges exhibiting other than planar edge surfaces orthogonal to the major surfaces of the substrates. For example, FIG. 11 depicts atiled display device 700 similar to tiled display device 100 but comprising edge surfaces 116, 124 that slope downward from first and third major surfaces and outward (away from a centerline 125 of gap G) such that the width WG of gap G increases in a direction from third major surface 112 toward first major surface 104 of base plate 102 (in the direction of arrow 144). First and second edge surfaces 116, 124 form an angle ([> with first major surface 104 of base plate 102. Angle ([> (external to first and second edge surfaces 116, 124) is an acute angle in this embodiment. Although not shown, edge surfaces 116 and/or 124 may be fully or partially coated with second coating material 134.

[0092] FIG. 12 depicts atiled display device 800 similar to tiled display device 100 but where edge surfaces 116, 124 slope downward and inward such that the width WG of gap G decreases in a direction from third major surface 112 toward first major surface 104 of base plate 102 (in the direction of arrow 144). First and second edge surfaces form an obtuse angle ([> with first major surface 104 of base plate 102. Although shown without coatings, in further aspects edge surfaces 116 and/or 124 may be fully or partially coated with second coating material 134.

[0093] FIG. 13 depicts a tiled display device 900 similar to tiled display device 100 but where LED boards 110, 118 have arcuate (e.g., rounded, bullnose) edge surfaces. The edge surfaces 116, 124 may be fully or partially coated with first coating material 134, whereas the third and fourth major surfaces of LED boards 110, 118 may be fully or partially coated with third coating material 136.

[0094] The optimal reflectivity of the near-edge substrate surface coating (e.g., coating material 134 applied to first and third surface portions 126, 130) for suppressing tiling seam visibility can be expressed as,

Re = ((^(WG^^c+Wejj/CfeXOe/Osy-Rs - ((Cfb/Cf_c)-(W_G/(2(W_c + W_e))-(Oe/o_S)yRb, (4) where Re and n_e represent reflectivity and scattering factor of the near-edge substrate surface coating , respectively, for the first and third surface portions 126, 130, Rs and <J_S represent reflectivity and scattering factor of the second and fourth substrate surfaces 128, 132, Rb and Ob represent reflectivity and scattering factor of the coated base surface 104 in the gap G, WG is the width of gap G between the substrates, and W_c and W_e are widths of the substrate chamfer surfaces and/or the coated near-edge first and second surface portions 126, 130. The exponent y is a constant equal to 1.7 and Cfb is a correction factor for the tiling gap. This correction factor represents the portion of light reflected from base surface 104 (e.g., coating material first coating material 108) trapped in gap G between the LED boards relative to the gap width, LED board thickness t_s, chamfer angle a_c, and the base and edge surface properties. Accordingly, Cfb is less than 1. Cf_c is a correction factor that relates to chamfer angle and the ratio of W_c/W_e. [0095] To achieve effective suppression of tiling seam visibility for a wide range of viewing angles, the intensity of light reflected by the base plate surface should be less than the intensity of light reflected by the LED board surfaces (i.e., in the right side of Eq. (4), the second term should be much smaller than the first term). For example, in various embodiments, a reflectivity of the first major surface coated with the first coating material may be at least 50% less than a reflectivity of the first surface portion coated with the second coating material, such as at least 75% less than a reflectivity of the first surface portion coated with the second coating material.

[0096] For such cases where a wide range of viewing angles is desired, or when the viewing angle is greater than the critical viewing angle p_vc, Equation (4) becomes

Re = ((l+CW^CWc+Wejj/CfeXOe/Osr-Rs. (5)

[0097] As shown by Equation (4) and Equation (5), conditions needed for the second term to be much less than the first term can be achieved by (1) Rb — > 0; (2) Ob » o_e, and/or; (3) (W_c + We) » W_G.

[0098] Effective suppression of tiling seam visibility can also be demonstrated using a ray tracing method. The modeling setup for ray tracing is shown in FIG. 14 and comprises a tiled display device (tiled display device 600 shown) and three ambient light sources, a first, broad array light source 1000, a second light source 1002 arranged to illuminate the first chamfer surface 140 (upper chamfer surface in the figure) and a third light source 1004 arranged to illuminate the second chamfer surface 142 (lower chamfer surface in the figure). An observer 1006 of the display device was assumed to be arranged at a position normal to the display device along line 1008 extending through the gap between the display substrates.

[0099] The first case simulated was the schematic shown in FIG. 10, in which first coating material 134 covers both chamfer surfaces 140, 142 (W_e = 0) and the edge surfaces 116, 118. Table 3, below, gives the modeling parameters for this case.

Table 3

[0100] Modeled intensity distributions as collected by observer 1006 around the tiling seam area (0 ± 2 mm from the seam centerline) for the reflectivity of the chamfer surfaces varied from about 3% reflectivity to about 8% reflectivity with a step of between 1% and 2% when the base surface reflectivity Rb and scattering factor Ob were 5% and 0.57 degrees, respectively. FIG. 15 is a plot showing corresponding intensity distributions for chamfer surface reflectivities over a range from 3% to 10%. The data show tiling seam visibility varied with chamfer surface reflectivity, with the least tiling seam visibility achieved with a chamfer surface reflectivity slightly greater than about 5% (e.g., between about 5% and about 6%).

[0101] Figure 16 is a plot showing the optimal reflectivity Re of the (near-edge) chamfer surfaces, for a viewing angle = 0, as a function of base plate surface reflectivity when all surfaces (base surface, substrate surfaces, edge surfaces, and chamfer surfaces) have an identical scattering factor of 0.57 degrees. The line represents analytical results calculated from Equation (4), and the circles are ray-tracing modeling results.

[0102] FIG. 17 is a plot showing the optimal reflectivity Re of the (near-edge) chamfer surfaces, for a view angle = 0, as a function of the ratio of near-edge coated substrate and substrate surfaces scattering factors (O_C/Q_S) when the reflections of base surface and substrate surfaces are 0% and 5%, respectively. The analytical prediction (line) agrees with the results of the ray-tracing modeling (circles).

[0103] Satisfying Equation (4) or Equation (5) implies the light intensity observed by a viewer collected from the tiling gap area (gap + near-edge area) equals the light intensity from a noseam substrate surface with the same area. To evenly distribute light reflected from the near- edge LED board area over the tiling seam area, the reflected incident ambient light should be scattered into a certain solid angle, implying the near-edge LED board surface should have a certain scattering (e.g., scattering factor > 0). To determine the threshold for the scattering factor of the near-edge LED board surface, two example cases that satisfy Equation (5) and Equation (4), respectively, were modeled. The first case was with Rb = 0%, Re = 11%, and Rs = 5%, and the second case was with Rb = 2.5% Re = 8.5%, and Rs = 5%, For both cases, all surfaces (base surface, LED board surface, edge surface, chamfer surface and/or near-edge substrate surface) have an identical scattering factor. [0104] FIG. 18 is a plot showing the modeled seam visibility factor SVF as a fraction of scattering factor for all surfaces for a normal (i.e., 90 degree) viewing angle. Line 1100 and line 1102 represent the modeling results of the first and second cases, respectively. In the figure, line 1100 represents SVF for base plate surfaces and nearby-tiling -edge LED board surfaces having reflectivities of 0%, and 11%, respectively. Line 1102 represents SVF for base plate surfaces and nearby-tiling-edge LED board surfaces having reflectivities of 2.5%, and 8.5%, respectively. The squares represent SVF for light reflected from the tiling seam area of the first case (line 1100) for a scattering factor of 0 degrees, 0.29 degrees, 0.57 degrees, and 1.15 degrees from left to right. It can be seen that with an increase of scattering factor, the reflected light is more evenly distributed over the tiling seam area. Both cases show that when the scattering factor of the chamfer surface (or near-edge LED board surface) is larger than 1 degree, the reflected light can be evenly distributed over the tiling seam area.

[0105] The second case simulated is the schematic shown in FIG. 6, in which the tiling edges of the two substrates are without chamfers, and the widths W_ei, W_e2 of the near-edge substrate surface coatings are 50 pm. Table 4 gives the modeling parameters for this case.

Table 4

[0106] FIG. 19 is a plot showing the optimal reflectivity of the coated near-edge substrate surface as a function of the ratio of scattering factors (o_e/c_s) (viewing angle = 0) when the reflections of the base surface and the substrate surfaces are 0% and 5%, respectively. The optimal reflectivity derived from intensity distributions of light reflected from the tiling seam area achieved by ray-tracing modeling when the ratio of scattering factors (o_e/c_s) is 0.67, 0.82, 0.93, and 1.1, respectively, are shown as discrete points in FIG. 19. In most instances, a scattering factor n_e of the first surface portion coated with the second coating material should be equal to or less than a scattering factor <J_S of the second surface portion coated with the third coating material. For this case, using ray tracing, the correction factor C& was found to be 0.8. Like the first modeled case, the analytical result (line) of the second modeled case is in good agreement with the results of ray-tracing modeling (circles). [0107] FIG. 20 shows a cross-sectional view of the tiled device for the experimental study on the effect of near-edge LED board coating on tiling seam visibility. The tiled device with a gap width WG of 50 pm consisted of one base plate 102 and two glass substrates 110, 118 (0.4 mm thick Coming® Lotus NXT glass) that were cut by laser and represented two LED boards. There were no electronic devices (e.g., LEDs) on the substrates. The edge surfaces 116, 124 and near-edge substrate surfaces (area ~50 pm from the edge at the gap G) were coated with a black ink A (Media NM-M1) having a reflectivity of about 7.3% at 550 nm. Meanwhile, the other three edges of the substrate were without coating. The other areas of the substrate surfaces not coated with black ink A were coated with a black ink B (Media NM-G) having a reflectivity of about 4.8% at 550 nm Reflectivity was measured by spectrophotometry over the visible wavelength range. The reflectivity difference between the two inks was about 2.5%. The base plate surface was coated with black ink B. Figure 21 is a plot showing the reflection spectra of the inks A and B.

[0108] For comparison, seam visibility measurements were conducted on a reference case wherein two uncoated edges of the same two substrates were tiled facing each other with a tiling gap of about 50 pm. The base plate coating 108 was black ink A. Figure 22 is a cross- sectional view of the tiled device for the reference measurement.

[0109] FIG. 23 is a plot showing the measured cross-sectional intensity distributions of the tiling seam for the reference case and FIG. 24 shows the measured cross-sectional intensity distributions of the tiling seam for the case under study in which the tiling edge and nearby- tiling-edge substrate surfaces were coated with black ink B for a viewing angle from 0 degrees to about 50 degrees with a step of 10 degrees. FIG. 25 is a plot showing the curves of measured SVF as a function of viewing angle for the reference case (line with circles) and the case under study (line with squares) . The data show that tiling seam visibility can be suppressed by coating the near-edge substrate surface (e.g., LED board) with a material (e.g., black ink B) having a greater reflectivity than the coating material (e.g., black ink A) of the other areas of the substrate surface for viewing angles from about 10 degree to about 50 degrees. The lack of improvement in SVF at a normal viewing angle is believed to be a consequence of the base surface reflectivity not being close to zero (in the right side of Equation (4), i.e., the second term is not much smaller than the first term), which results in a lowering of SVF of the zeroviewing angle for the reference case.

[0110] To further reduce tiling seam visibility, the reflectivity difference between the coatings of the near-edge substrate surfaces and the remainder of the substrate surfaces can be increased, (e.g., the difference between the first and third substrate surfaces and the second and fourth substrate surfaces). For example, this experimental result was compared with previous modeling results on the optimal reflectivity of near-edge substrate surface coating, which is shown in FIG. 19. FIG. 19 shows the curve of the optimal reflectivity of near-edge substrate surface coating as a function of the ratio of scattering factors (oe/c_s) for a base surface reflectivity Rb = 0 and a substrate surface reflectivity of 5%. Assuming the ratio of scattering factors (o_e/c_s) is 1, the modeling results predict the optimal reflectivity difference between the nearby-tiling-edge substrate surface and the other substrate surface is about 5%. However, the reflectivity difference between the near-edge substrate surface and the other substrate surfaces is -2.5% in the experiment. This suggests further increasing the reflectivity of the near-edge substrate coating by about 2.5% to get optimal seam visibility mitigation when the same substrate surface coating is used.

[0111] 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. An optical display device, comprising: a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface; a first substrate comprising a third major surface, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface; a second substrate comprising a fifth major surface, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap; and wherein a first surface portion of the third major surface adjacent to and extending along the gap is coated with a second coating material different than the first coating material, and at least a portion of a second surface portion of the third major surface adjacent the first surface portion is coated with a third coating material different than the second coating material.

2. The optical display device of claim 1, wherein a reflectivity of the first major surface coated with the first coating material is less than a reflectivity of the first surface portion coated with the second coating material.

3. The optical display device of claim 1, wherein a reflectivity of the first major surface coated with the first coating material is at least 50% less than a reflectivity of the first surface portion coated with the second coating material.

4. The optical display device of claim 1, wherein a reflectivity of the first major surface coated with the first coating material is at least 75% less than a reflectivity of the first surface portion coated with the second coating material.

5. The optical display device of any one of claims 1 to 4, wherein a scattering factor n_e of the first surface portion coated with the second coating material is equal to or less than a scattering factor <J_S of the second surface portion coated with the third coating material.

6. The optical display device of claim 1, wherein a reflectivity of the first surface portion coated with the second coating material is greater than a reflectivity of the second surface portion coated with the third coating material.

7. The optical display device of claim 1, wherein a third surface portion of the fifth major surface adjacent to and extending along the gap is coated with the second coating material, and at least a portion of a fourth surface portion of the fifth major surface adjacent the third surface portion is coated with the third coating material

8. The optical display device of claim 7, wherein the first surface portion comprises a first chamfer surface and the third surface portion comprises a second chamfer surface.

9. The optical display device of claim 8, wherein at least a portion of the second surface portion and at least a portion of the fourth surface portion are coated with the second coating material.

10. The optical display device of claim 1, wherein a width of the gap between the first edge surface and the second edge surface increases in a direction from the third major surface toward the base plate.

11. The optical display device of claim 1, wherein a width of the gap between the first edge surface and the second edge surface decreases in a direction from the third major surface toward the base plate.

12. The optical display device of claim 1, wherein the first edge surface comprises an arcuate surface.

13. The optical display device of any one of claims 1 to 12, wherein the first edge surface and the second edge surface are coated with the second coating material.

14. The optical display device of any one of claims 1 to 13, wherein the third major surface comprises a plurality of light emitting diodes disposed thereon.

15. An optical display device, comprising: a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface; a first substrate comprising a third major surface, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface; a second substrate comprising a fifth major surface, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap; and wherein the third major surface is coated with a second coating material different than the first coating material, a surface roughness of the first major surface coated with the first coating material is equal to a surface roughness of the third major surface coated with the second coating material, and a reflectivity of the first major surface coated with the first coating material is greater than a reflectivity of the third major surface coated with the second coating material.

16. The optical display device of claim 15, wherein the third major surface comprises a plurality of light emitting diodes disposed thereon.

17. The optical display device of claim 15 or claim 16, wherein the reflectivity of the first major surface coated with the first coating material is less than 2 times the reflectivity of the third major surface coated with the second coating material.

18. The optical display device of claim 17, wherein the reflectivity of the first major surface coated with the first coating material is in a range from about 5% to about 10%.

19. The optical display device of any one of claims 15 to 18, wherein the first substrate and the second substrate comprise glass.

20. An optical display device, comprising: a base plate comprising a first major surface coated with a first coating material and a second major surface opposite the first major surface; a first substrate comprising a third major surface coated with a second coating material, a fourth major surface opposite the third major surface and disposed on the first coating material, and a first edge surface disposed between the third major surface and the fourth major surface; a second substrate comprising a fifth major surface coated with the second coating material, a sixth major surface opposite the fifth major surface and disposed on the first coating material, and a second edge surface disposed between the fifth major surface and the sixth major surface and extending adjacent the first edge surface such that the first edge surface and the second edge surface are separated by a gap; and wherein a reflectivity of the first major surface coated with the first coating material is greater than a reflectivity of the third major surface or the second major surface coated with the second coating material.

21. The optical display device of claim 20, wherein the reflectivity of the base plate is less than 2 times the reflectivity of at least one of the third major surface or the fifth major surface coated with the second coating material.

22. The optical display device of claim 20 or claim 21, wherein at least one of the first edge surface or the second edge surface is coated with the second coating material.