WO2023249823A1

WO2023249823A1 - Displays with reduced edge light leakage

Info

Publication number: WO2023249823A1
Application number: PCT/US2023/024908
Authority: WO
Inventors: Shenping Li; Lu Zhang
Original assignee: Corning Incorporated
Priority date: 2022-06-23
Filing date: 2023-06-09
Publication date: 2023-12-28
Also published as: TW202411748A; CN117642870A

Abstract

A display includes a backplane, a plurality of micro Light Emitting Diodes (micro-LEDs) electrically coupled to the backplane, an Optically Clear Adhesive (OCA) layer over the backplane and the plurality of micro-LEDs, and a glass layer over the OCA layer. The OCA layer includes a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.6. The glass layer includes a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0.

Description

DISPLAYS WITH REDUCED EDGE LIGHT LEAKAGE

CROSS-REFERENCE TO RELATED PPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63/354870 filed on June 23, 2022, the content of which is relied upon and incorporated herein by reference in its entirety

BACKGROUND

Field

[0002] The present disclosure relates generally to displays. More particularly, it relates to displays with reduced edge light leakage.

Technical Background

[0003] Large area displays may not be practical to manufacture on a single large area substrate. For example, the size of the display may be larger than what existing processing equipment can handle and/or the yield of large display sizes may be much lower than the yield of smaller display sizes. In these cases, manufacturing a display by tiling multiple small format displays is advantageous. The tiling of small format displays to create larger displays may apply to display technologies including light emitting diode (LED), micro-LED, organic light emitting diode (OLED), and liquid crystal display (LCD). A common problem of tiled displays is a noticeable seam of brighter light between the small format displays of the tiled display.

[0004] Micro-LEDs are small (e.g., typically less than about 100 micrometer by about 100 micrometer) light emitting components. They are inorganic semiconductor components producing high luminance up to 50 million nits. Therefore, micro-LEDs are particularly suitable for high resolution and large tiled displays. However, small format displays of a tiled large area micro-LED display should have low edge light leakage to prevent visible seams between the small format displays under expected viewing conditions.

SUMMARY

[0005] Some embodiments of the present disclosure relate to a display. The display includes a backplane, a plurality of micro Light Emitting Diodes (micro-LEDs) electrically coupled to the backplane, an Optically Clear Adhesive (OCA) layer over the backplane and the plurality of micro-LEDs, and a glass layer over the OCA layer. The OCA layer includes a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.6. The glass layer includes a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0.

[0006] Yet other embodiments of the present disclosure relate to a display. The display includes a glass substrate, an OCA layer over the substrate, a plurality of micro-LEDs over the OCA layer, and an encapsulation layer over the OCA layer and the plurality of micro-LEDs. The glass substrate includes a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0. The encapsulation layer includes a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 0.1 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.9.

[0007] Yet other embodiments of the present disclosure relate to a display. The display includes a substrate and a plurality of small format displays arranged on the substrate. Each small format display of the plurality of small format displays include a plurality of micro-LEDs, an OCA layer encapsulating the plurality of micro-LEDs, and a glass layer proximate the OCA layer. The OCA layer includes a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1. 1 and about 1.6. The glass layer includes a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0.

[0008] The displays disclosed herein reduce edge light leakage from the displays by adjusting the geometric parameters (e.g., thickness) and/or by adjusting the optical properties (e.g., refractive index and/or transmittance (or absorbance)) of the OCA and glass layers. Adjusting the geometric parameters and optical properties of the OCA and glass layers is simple and effective, and no additional components are used to suppress the edge light leakage from the displays. [0009] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0010] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1A is atop view of an exemplary large area display;

[0012] FIG. IB is a simplified cross-sectional view of the exemplary large area display of FIG. 1A;

[0013] FIG. 2A is atop view of an exemplary small format display;

[0014] FIGS. 2B and 2C are simplified cross-sectional views of the exemplary small format display of FIG. 2A;

[0015] FIG. 3A is a side view of an exemplary micro Light Emitting Diode (micro-LED);

[0016] FIG. 3B is a top view of an exemplary pixel including three micro-LEDs;

[0017] FIGS. 4A-4F are charts illustrating edge light leakage reduction and normal brightness reduction as various parameters of the display of FIGS. 2A-2C are modified;

[0018] FIG. 5 is a simplified cross-sectional view of another exemplary small format display; and

[0019] FIGS. 6A-6C are charts illustrating edge light leakage reduction and normal brightness reduction as various parameters of the display of FIG. 5 are modified.

DETAILED DESCRIPTION

[0020] 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 may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. [0021] 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 and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another 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.

[0022] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom, vertical, horizontal - are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0023] 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.

[0024] 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.

[0025] Large area displays are highly desired by consumers and public information systems. High cost and low production yields, however, are technical challenges for the mass production of such large area displays. This is particularly true for high resolution micro Light Emitting Diode (micro-LED) displays. One cost-effective approach for creating a large area display is to tile multiple small format displays to form a large area display. To protect the micro-LEDs and to enhance the mechanical properties of micro-LED displays, small format displays are typically encapsulated by cover glasses using Optically Clear Adhesive (OCA). One issue of a tiled display, however, is bright visible seam lines on the tiled displays at the boundaries of the adjacent small format displays caused by edge light leakage due to the encapsulation (e.g., OCA and glass layers) when the display is turned on.

[0026] Accordingly, disclosed herein are displays that suppress the edge light leakage of encapsulated micro-LED displays by adjusting the geometric parameters (e.g., thickness) and/or by adjusting the optical properties (e.g., refractive index and/or transmittance (or absorbance)) of the OCA and glass layers. Adjusting the geometric parameters and optical properties of the layers is simple and effective, and no additional components are used to suppress the edge light leakage from the displays.

[0027] Referring now to FIGS. 1A and IB, a top view and a simplified cross-sectional view of an exemplary large area display 100 is depicted, respectively. Large area display 100 includes a substrate 102 and a plurality of small format displays 104 arranged on the substrate 102. Each small format display 104 may be a micro-LED display, such as a top-emission micro-LED display or a bottom-emission micro-LED display. Between the edges of the adjacent small format displays 104 are seams 106. As described in more detail below with reference to FIGS. 2A-2C, light emitted from the small format displays 104 may leak out of the edges of the small format displays at seams 106, resulting in visible seams when the large area display 100 is turned on.

[0028] Substrate 102 may be a glass substrate, a printed circuit board, or another suitable substrate including circuitry for routing power and signals to each small format display 104 to control the operation of each micro-LED of each small format display 104. Substrate 102 may, for example, be attached to small format displays 102 using fasteners and/or an adhesive material. While in this embodiment, large area display 100 includes 16 small format displays arranged in four rows and four columns, in other embodiments, large area display 100 may include any suitable number of small format displays 104 arranged in any suitable numbers of rows and columns.

[0029] FIG. 2A is a top view of an exemplary small format display 200. In certain exemplary embodiments, small format display 200 may be used for each small format display 104 previously described and illustrated with reference to FIGS. 1A and IB. Small format display 200 includes a backplane 202 and a plurality of pixels 204 electrically coupled to the backplane 202. Each pixel 204 may include one, two, three, four, or more micro-LEDs to provide a monochrome or color display. Backplane 202 may be a glass substrate or printed circuit board including circuitry for routing power and signals to each pixel 204 to control the operation of each micro-LED of each pixel 204. Small format display 200 includes four edges 203, where light emitted by the display may leak out. While in this embodiment, small format display 202 includes 25 rows and 25 columns of pixels 204, in other embodiments, small format display 202 may include any suitable numbers of rows and columns of pixels.

[0030] FIGS. 2B and 2C are simplified cross-sectional views of the exemplary small format display 200 of FIG. 2A. In addition to backplane 202 and pixels 204, small format display 200 includes an OCA layer 206 and a glass layer (e.g., cover glass) 208. In this example, each pixel 204 includes a first (e.g., blue) micro-LED 204a, a second (e.g., green) micro-LED 204b, and a third (e.g., red) micro-LED 204c to provide a full color display. Thus, display 200 includes a plurality of micro-LEDs electrically coupled to the backplane 202. Each micro-LED 204a/204b/204c is electrically coupled to circuitry (not shown) on backplane 202 for controlling the operation of each micro-LED. In this embodiment, the plurality of micro-LEDs are top-emission micro-LEDs, such that the light emitted by the micro-LEDs passes through the top of the display 200. In certain exemplary embodiments, backplane 202 includes a glass substrate with an array of thin film transistors (TFTs) formed thereon, where each TFT is electrically coupled to a micro-LED. In other embodiments, backplane 202 includes a printed circuit board or another suitable substrate.

[0031] The OCA layer 206 may include phenyl silicone or another suitable material. The OCA layer 206 is proximate (e.g., over) the backplane 202 and the plurality of micro-LEDs (204a/204b/204c), such as directly contacting a top surface 205 of the backplane 202 and directly contacting and encapsulating the plurality of micro-LEDs. The glass layer 208 may include a glass such as aluminosilicate, alkali-aluminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali-aluminoboro silicate, soda lime, or other suitable glasses (e.g., Gorilla® glass, Ceramic Shield, EAGLE XG® glass). The glass layer 208 is proximate (e.g., over) the OCA layer 206, such as directly contacting a top surface 207 of the OCA layer 206. The glass layer 208 may be laminated to the backplane 202 and the plurality of micro-LEDs via the OCA layer 206 to protect the micro-LEDs and to enhance the mechanical properties of the display 200.

[0032] The OCA layer 206 and the glass layer 208 may cause edge light leakage through the edges 203 of the display 200 through four different ways. As illustrated in FIG. 2B at 210a, a first way that the OCA layer 206 and the glass layer 208 may cause edge light leakage through the edges 203 of the display 200 includes light that escapes from the side walls of the micro- LEDs and goes directly out of the edges of the OCA layer 206 and the glass layer 208. Because the OCA layer 206 has a higher refractive index than air, compared to a display without the OCA layer 206 and the glass layer 208, more light emits from the micro-LED side walls in a display including the OCA layer 206 and the glass layer 208. Thus, the OCA layer 206 and the glass layer 208 enhances the edge light leakage . As illustrated in FIG. 2B at 21 Ob, a second way that the OCA layer 206 and the glass layer 208 may cause edge light leakage through the edges 203 of the display 200 includes light that escapes from the side walls of the micro-LEDs and first goes to the top surface 209 of the glass layer 208, is then reflected by the interface between air and the glass layer 208 (e.g., mainly through Total Internal Reflection (TIR)), and then exits from the edges 203 of the display.

[0033] As illustrated in FIG. 2C at 210c, a third way that the OCA layer 206 and the glass layer 208 may cause edge light leakage through the edges 203 of the display 200 includes light emitted from the top surfaces of the micro-LEDs that goes directly out of the edges 203 of the OCA layer 206 and glass layer 208. As illustrated in FIG. 2C at 210d, a fourth way that the OCA layer 206 and the glass layer 208 may cause edge light leakage through the edges 203 of the display 200 includes light emitted from the top surfaces of the micro-LEDs and first goes to the top surface 209 of the glass layer 208, is then reflected by the interface between air and the glass layer 208 (e.g., mainly through TIR), and then exits from the edges 203 of the display. [0034] Accordingly, disclosed herein are displays to suppress the edge light leakage of micro-LED displays including an OCA layer 206 and a glass layer 208 by adjusting the geometric design (e.g., thicknesses of the OCA layer 206 and the glass layer 208) and the optical properties (e.g., refractive index and transmittance (or absorbance)) of the OCA layer 206 and the glass layer 208. By considering the performance of edge light leakage suppression and display brightness at the display normal, optimal designs can be determined by ray-tracing modeling. Transmittance may be defined as the ratio of the incident light falling on a body to that transmitted through the body. The transmittance of a body may be within a range between about 0 percent, where all incident light is blocked from passing through the body, to about 100 percent, where all incident light passes through the body. Refractive index may be defined as the ratio of the velocity of light in a vacuum to the velocity of light in a specified medium. The transmittance and refractive index of OCA and glass layers may be adjusted by adjusting the material properties of the OCA and glass layers.

[0035] In certain exemplary embodiments as further described below with reference to FIGS. 4A and 4D, to suppress edge light leakage from the display 200, the OCA layer 206 may have a thickness 212 between the top surface 205 of the backplane 202 and the top surface 207 of the OCA layer 207 within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance (over the OCA layer thickness at about 550 nanometers) within a range between about 40 percent and about 95 percent, and a refractive index (at about 550 nanometers) within a range between about 1.1 and about 1.6. In other embodiments, the thickness 212 of the OCA layer 206 may be within a range between about 0.01 millimeters and about 0.1 millimeters. In other embodiments, the transmittance of the OCA layer 206 may be within a range between about 80 percent and about 95 percent. In other embodiments, the refractive index of the OCA layer 206 may be within a range between about 1.2 and about 1.4. [0036] In certain exemplary embodiments as further described below with reference to FIGS. 4B, 4C, 4E, and 4F, to suppress edge light leakage, the glass layer 208 may have a thickness 214 between the top surface 207 of the OCA layer 206 and the top surface 209 of the glass layer 208 within a range between about 0.05 millimeters and about 2 millimeters, a transmittance (over the glass layer thickness at about 550 nanometers) within a range between about 40 percent and about 95 percent, and a refractive index (at about 550 nanometers) within a range between about 1.4 and about 2.0. In other embodiments, the thickness 214 of the glass layer 208 may be within a range between about 0. 1 millimeters and about 0.3 millimeters. In other embodiments, the transmittance of the glass layer 208 may be within a range between about 80 percent and about 95 percent. In other embodiments, the refractive index of the glass layer 208 may be within a range between about 1.5 and about 1.7.

[0037] FIG. 3A is a side view of an exemplary micro-LED 300. In certain exemplary embodiments, micro-LED 300 may be used for micro-LED 204a, 204b, and/or 204c within each pixel 204 as previously described and illustrated with reference to FIGS. 2A-2C. Micro- LED 300 includes contact pads 302 (e.g., metal pads), a bottom passivation layer 304, an active layer 306 (e.g., a Multiple Quantum Well (MQT) active layer), and a top passivation layer 308. The contact pads 302 are electrically coupled to the top surface 205 of the backplane 202. The bottom surface of the bottom passivation layer 304 contacts the contact pads 302. The top surface of the bottom passivation layer 304 contacts the bottom surface of the active layer 306. The top surface of the active layer 306 contacts the bottom surface of the top passivation layer 308. Each contact pad 302 may have a height 310 of about 1 micrometer and a width 312 of about 10 micrometers. The distance 314 between the contact pads 302 may be about 10 micrometers. The height 316 of the bottom passivation layer 304 may be about 2.2 micrometers, the height 318 of the active layer 306 may be about 0.6 micrometers, and the height 320 of the top passivation layer may be about 2.2 micrometers, such that the total height 322 may be about 5 micrometers. In other embodiments, micro-LED 300 may have other suitable dimensions.

[0038] FIG. 3B is a top view of an exemplary pixel 204 including micro-LEDs 204a, 204b, and 204c. Each micro-LED 204a, 204b, and 204c has a length 332 of about 30 micrometers and a width 334 of about 20 micrometers. The distance 330 between the micro-LEDs within the pixel 204 may be about 25 micrometers. In other embodiments, micro-LEDs 204a, 204b, and 204c and pixel 204 may have other suitable dimensions.

[0039] The following Table 1 includes display parameters and optical performance comparisons for several example top-emission displays, such as display 200 previously described and illustrated with reference to FIGS. 2A-2C including pixels 204 and micro-LEDs 204a, 204b, and 204c as previously described and illustrated with reference to FIGS. 3 A and 3B. Table 1 includes the thickness 214 of the glass layer 208, the transmittance of the glass layer 208, and the refractive index of the glass layer 208. Table 1 also includes the thickness 212 of the OCA layer 206, the transmittance of the OCA layer 206, and the refractive index of the OCA layer 206. Table 1 further includes the edge light leakage reduction and the normal brightness reduction for each example compared to a reference example.

TABLE 1: DISPLAY PARAMETERS AND OPTICAL PERFORMANCE COMPARISONS

[0040] As shown in Table 1, in the reference example, the thicknesses of the glass layer 208 and the OCA layer 206 are about 0.5 millimeters and about 0.1 millimeters, respectively. The transmittance s of the glass layer 208 and the OCA layer 206 are greater than about 99.97 percent and greater than about 98.5 percent, respectively. The refractive indices of the glass layer 208 and the OCA layer 206 are about 1.51 and about 1.49, respectively. This reference example is used as the reference for the 10 examples listed in Table 1 to illustrate the impact of different display parameters on the optical performance and edge light leakage of the 10 examples.

[0041] For the reference example, the brightness of the display with the OCA layer 206 and the glass layer 208 at the normal decreases by about 50 percent, and about 50 percent of the total output of light exits the display from the four edges of the display (edge light leakage) compared to a display without the OCA layer 206 and the glass layer 208. The edge light leakage reduction compared to the reference example may be defined as:

Edge light leakage reduction (%) = 100 • (P_e-r - Pe-n)/Pe-r where:

P_e-r is the total edge light leakage power of the reference example; and

Pe-_n is the total edge light leakage power of the example being compared to the reference example.

The normal brightness reduction compared to the reference example may be defined as: Normal brightness reduction (%) = 100 • (B_e-r - B_e-n)IB_e-r where:

B_e-r is the normal brightness of the reference example; and

B_e-n is the normal brightness of the example being compared to the reference example. [0042] As shown in Table 1, Example 1 includes all the same parameters as the reference example, except that the transmittance of the glass layer 208 is reduced from greater than about 99.97 percent to about 80 percent. Compared to the reference example, Example 1 has an edge light leakage reduction of about 59.5 percent. Reducing the transmittance of the glass layer 208, however, reduces the display brightness. Compared to the reference example, Example 1 has a normal brightness reduction of about 26.8 percent.

[0043] Example 2 includes all the same parameters as the reference example, except that the transmittance of the OCA layer 206 is reduced from greater than about 98.5 percent to about 80 percent. Compared to the reference example, Example 2 has an edge light leakage reduction of about 67.5 percent. Reducing the transmittance of the OCA layer 206, however, reduces the display brightness. Compared to the reference example, Example 2 has a normal brightness reduction of about 24.3 percent.

[0044] Example 3 includes all the same parameters as the reference example, except that the transmittance of the glass layer 208 is reduced from greater than about 99.97 percent to about 90 percent and the transmittance of the OCA layer 206 is reduced from greater than about 98.5 percent to about 90 percent. Compared to the reference example, Example 3 has an edge light leakage reduction of about 62.5 percent. Reducing the transmittance of the glass layer 208 and the OCA layer 206, however, reduces the display brightness. Compared to the reference example, Example 3 has a normal brightness reduction of about 24.0 percent.

[0045] In Examples 1, 2, and 3, the total transmittance of the OCA layer 206 and the glass layer 208 is reduced by about 20 percent from the reference example. In Example 1, the reduction in total transmittance is all due to the glass layer 208. In Example 2, the reduction in total transmittance is all due to the OCA layer 206. In Example 3, the reduction in total transmittance is equally due to the OCA layer 206 and the glass layer 208. Example 3 has the lowest normal brightness reduction, while the edge light leakage reduction of Example 3 is between the edge light leakage reduction of Examples 1 and 2.

[0046] Example 4 includes all the same parameters as the reference example, except that the transmittance of the glass layer 208 is reduced from greater than about 99.97 percent to about 80 percent and the thickness of the OCA layer 206 is variable. FIG. 4A is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the thickness of the OCA layer 206 for Example 4. The edge light leakage reduction versus the OCA layer thickness is indicated by line 402, and the normal brightness reduction versus the OCA layer thickness is indicated by line 404. As illustrated by line 402, the edge light leakage reduction decreases from about 65 percent to about 59 percent as the thickness of the OCA layer increases from about 0.02 millimeters to about 0.1 millimeters. As illustrated by line 404, the normal brightness reduction increases from about 26 percent to about 27 percent as the thickness of the OCA layer increases from about 0.02 millimeters to about 0.1 millimeters. Accordingly, as the thickness of the OCA layer decreases from about 0.1 millimeters to about 0.02 millimeters, the edge light leakage reduction improves by about 6 percent, while the normal brightness reduction worsens by about 1 percent.

[0047] Example 5 includes all the same parameters as the reference example, except that the transmittance of the glass layer 208 is reduced from greater than about 99.97 percent to about 80 percent, the thickness of the glass layer 208 is variable, and the refractive index of the OCA layer 206 is reduced from about 1.49 to about 1.40. FIG. 4B is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the thickness of the glass layer 208 for Example 5. The edge light leakage reduction versus the glass layer thickness is indicated by line 406, and the normal brightness reduction versus the glass layer thickness is indicated by line 408. As illustrated by line 406, the edge light leakage reduction decreases from about 80 percent to about 62 percent as the thickness of the glass layer increases from about 0.2 millimeters to about 0.5 millimeters. As illustrated by line 408, the normal brightness reduction is substantially insensitive to changes in the thickness of the glass layer. Accordingly, as the thickness of the glass layer decreases from about 0.5 millimeters to about 0.2 millimeters, the edge light leakage reduction improves by about 18 percent, while the normal brightness reduction is not substantially impacted.

[0048] Example 6 includes all the same parameters as the reference example, except that the transmittance of the glass layer 208 is reduced from greater than about 99.97 percent to about 90 percent, the thickness of the glass layer 208 is variable, and the transmittance of the OCA layer 206 is reduced from greater than about 98.5 percent to about 90 percent. FIG. 4C is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the thickness of the glass layer 208 for Example 6. The edge light leakage reduction versus the glass layer thickness is indicated by line 410, and the normal brightness reduction versus the glass layer thickness is indicated by line 412. As illustrated by line 410, the edge light leakage reduction decreases from about 82 percent to about 65 percent as the thickness of the glass layer increases from about 0.2 millimeters to about 0.5 millimeters. As illustrated by line 412, the normal brightness reduction is substantially insensitive to changes in the thickness of the glass layer. Accordingly, as the thickness of the glass layer decreases from about 0.5 millimeters to about 0.2 millimeters, the edge light leakage reduction improves by about 17 percent, while the normal brightness reduction is not substantially impacted.

[0049] Example 7 includes a thickness of the glass layer 208 of about 0.2 millimeters, a transmittance of the glass layer of about 90 percent, a refractive index of the glass layer of about 1.51, a thickness of the OCA layer 206 of about 0.06 millimeters, a transmittance of the OCA layer of about 90 percent, and a variable refractive index of the OCA layer. FIG. 4D is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the refractive index of the OCA layer 206 for Example 7. The edge light leakage reduction versus the OCA layer refractive index is indicated by line 414, and the normal brightness reduction versus the OCA layer refractive index is indicated by line 416. As illustrated by line 414, the edge light leakage reduction decreases from about 92 percent to about 82 percent as the OCA layer refractive index increases from about 1.30 to about 1.49. As illustrated by line 416, the normal brightness reduction increases from about 2 percent to about 24 percent as the OCA layer refractive index increases from about 1.30 to about 1.49. Accordingly, as the refractive index of the OCA layer decreases from about 1.49 to about 1.30, the edge light leakage reduction improves by about 10 percent, while the normal brightness reduction improves by about 22 percent.

[0050] Example 8 includes a thickness of the glass layer 208 of about 0.2 millimeters, a variable transmittance of the glass layer, a refractive index of the glass layer of about 1.51, a thickness of the OCA layer 206 of about 0.06 millimeters, a transmittance of the OCA layer greater than about 98.5 percent, and a refractive index of the OCA layer of about 1.40. FIG. 4E is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the transmittance of the glass layer 208 for Example 8. The edge light leakage reduction versus the glass layer transmittance is indicated by line 418, and the normal brightness reduction versus the glass layer transmittance is indicated by line 420. As illustrated by line 418, the edge light leakage reduction decreases from about 94 percent to about 88 percent as the glass layer transmittance is increased from about 60 percent to about 90 percent. As illustrated by line 420, the normal brightness reduction decreases from about 44 percent to about 14 percent as the glass layer transmittance increases from about 60 percent to about 90 percent. Accordingly, as the glass layer transmittance decreases from about 90 percent to about 60 percent, the edge light leakage reduction improves by about 6 percent, while the normal brightness reduction worsens by about 30 percent.

[0051] Example 9 includes a thickness of the glass layer 208 of about 0.2 millimeters, a transmittance of the glass layer of about 90 percent, a variable refractive index of the glass layer, a thickness of the OCA layer 206 of about 0.06 millimeters, a transmittance of the OCA layer of about 90 percent, and a refractive index of the OCA layer of about 1 .40. FIG. 4F is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the refractive index of the glass layer 208 for Example 9. The edge light leakage reduction versus the glass layer refractive index is indicated by line 422, and the normal brightness reduction versus the glass layer refractive index is indicated by line 424. As illustrated by line 422, the edge light leakage reduction increases from about 77 percent to about 93 percent as the glass layer refractive index increases from about 1.4 to about 1.9. As illustrated by line 424, the normal brightness reduction increases from about 13 percent to about 20 percent as the glass layer refractive index increases from about 1.4 to about 1.9. Accordingly, as the refractive index of the glass layer decreases from about 1.9 to about 1.4, the edge light leakage reduction worsens by about 16 percent, while the normal brightness reduction improves by about 7 percent.

[0052] Example 10 includes a thickness of the glass layer 208 of about 0.2 millimeters, a transmittance of the glass layer of about 90 percent, a refractive index of the glass layer of about 1.7, a thickness of the OCA layer 206 of about 0.06 millimeters, a transmittance of the OCA layer of about 90 percent, and a refractive index of the OCA layer of about 1.40. Compared to the reference example, Example 10 has an edge light leakage reduction of about 93.2 percent, and a normal brightness reduction of about 16.9 percent. Thus, by adjusting the geometric and optical parameters of the display, Example 10 provides a substantial reduction in edge light leakage with a relatively small penalty in normal brightness reduction.

[0053] In summary, there is a relationship between the display edge light leakage and the parameters of the glass layer and the OCA layer. There is a decrease in the edge light leakage with a decrease in the thickness of the glass layer, a decrease in the transmittance of the glass layer, and/or an increase in the refractive index of the glass layer. There is also a decrease in the edge light leakage with a decrease in the thickness of the OCA layer, a decrease in the refractive index of the OCA layer, and/or a decrease in the transmittance of the OCA layer. In addition, there is a relationship between the display normal brightness and the parameters of the glass layer and the OCA layer. There is an increase in the display brightness at the normal with a decrease in the refractive index of the glass layer and/or an increase in the transmittance of the glass layer. There is also an increase in the display brightness at the normal with a decrease in the thickness of the OCA layer, a decrease in the refractive index of the OCA layer, and/or an increase in the transmittance of the OCA layer. The display brightness at the normal is insensitive to the thickness of the glass layer when the transmittance of the glass layer is kept constant. There is a tradeoff between the edge light leakage and the normal brightness when varying transmittance of the OCA layer and/or the glass layer.

[0054] FIG. 5 is a simplified cross-sectional view of another example small format display 500. In certain exemplary embodiments, small format display 500 may be used for each small format display 104 previously described and illustrated with reference to FIGS. 1A and IB. Small format display 500 includes a glass substrate (e.g., cover glass) 508, an OCA layer 506a, a plurality of micro-LEDs (e.g., 504a/504b/504c), and an encapsulation layer 506b (e.g., an OCA layer, an opaque material layer, or a low transmission material layer). One pixel is illustrated in FIG. 5 including a first (e.g., blue) micro-LED 504a, a second (e.g., green) microLED 504b, and a third (e.g., red) micro-LED 504c. In this embodiment, the plurality of micro- LEDs are bottom-emission micro-LEDs, such that the light emitted by the micro-LEDs passes through the bottom of the display 500 as indicated at 520 and the contact pads 502 of each micro-LED are on the top of each micro-LED. In certain exemplary embodiments, the arrangement and dimensions of each pixel and the micro-LEDs 504a/504b/504c of each pixel is similar to the arrangement and dimensions of each pixel 204 and the micro-LEDs 204a/204b/204c previously described and illustrated with reference to FIGS. 3A and 3B. Each micro-LED 504a/504b/504c is electrically coupled to circuitry (not shown) for controlling the operation of each micro-LED. In certain exemplary embodiments, an array of thin film transistors (TFTs) may be formed on display 500, where each TFT is electrically coupled to a micro-LED.

[0055] The glass substrate 508 may include a glass such as aluminosilicate, alkalialuminosilicate, borosilicate, alkali-borosilicate, aluminoborosilicate, alkali- aluminoborosilicate, soda lime, or other suitable glasses (e.g., Gorilla® glass, Ceramic Shield, EAGLE XG® glass). The OCA layer 506a is proximate (e.g., over) a top surface 507 of the glass substrate 508. In certain exemplary embodiments, display 500 may include a silicon nitride layer (not shown) between the top surface of the glass substrate 508 and the bottom surface of the OCA layer 506a. The plurality of micro-LEDs are proximate (e.g., over) the OCA layer 506a, such as directly contacting a top surface 505 of the OCA layer. The encapsulation layer 506b is proximate (e.g., over) the OCA layer 506a and the plurality of micro-LEDs (e.g., directly contacting the top surface 505 of the OCA layer 506a and the plurality of micro-LEDs), such that the plurality of micro-LEDs are encapsulated by the encapsulation layer 506b. The OCA layer 506a and the encapsulation layer 506b may include the same material (e.g., phenyl silicone) or different materials.

[0056] As previously described with reference to display 200 of FIGS. 2A-2C, display 500 may also suffer from edge light leakage. Thus, in certain exemplary embodiments as further described below with reference to FIGS. 6A-6C, to suppress edge light leakage, the glass substrate 508 may have a thickness 514 between the bottom surface 509 and the top surface 507 of the glass substrate within a range between about 0.05 millimeters and about 2 millimeters, a transmittance (overthe glass substrate thickness at about 550 nanometers) within a range between about 40 percent and about 95 percent, and a refractive index (at about 550 nanometers) within a range between about 1.4 and about 2.0. In other embodiments, the thickness 514 of the glass substrate 508 may be within a range between about 0. 1 millimeters and about 0.3 millimeters. In other embodiments, the transmittance of the glass substrate 508 may be within a range between about 80 percent and about 95 percent. In other embodiments, the refractive index of the glass substrate 508 may be within a range between about 1.5 and about 1.7.

[0057] In certain exemplary embodiments, the OCA layer 506a may have a thickness 512a between the top surface 507 of the glass substrate 508 and the top surface 505 of the OCA layer of about 2 micrometers. In certain exemplary embodiments, to suppress edge light leakage, the encapsulation layer 506b may have a thickness 512b between the top surface 505 of the OCA layer 506a and the top surface 511 of the encapsulation layer 506b within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance (over the encapsulation layer thickness at about 550 nanometers) within a range between about 0.1 percent and about 95 percent, and a refractive index (at about 550 nanometers) within a range between about 1.1 and about 1.9. In other embodiments, the thickness 512b of the encapsulation layer 506b may be within a range between about 0.01 millimeters and about 0.1 millimeters. In other embodiments, the transmittance of the encapsulation layer 506b may be within a range between about 10 percent and about 50 percent. In other embodiments, the refractive index of the encapsulation layer 506b may be within a range between about 1.2 and about 1.4.

[0058] The following Table 2 includes display parameters for several example displays, such as display 500 previously described and illustrated with reference to FIG. 5. Table 2 includes the thickness 514 of the glass substrate 508, the transmittance of the glass substrate 508, and the refractive index of the glass substrate 508. Table 2 also includes the thickness 512a of the OCA layer 506a, the transmittance of the OCA layer 506a, and the refractive index of the OCA layer 506a. Table 2 further includes the thickness 512b of encapsulation layer 506b, the transmittance of the encapsulation layer 506b, and the refractive index of the encapsulation layer 506b.

TABLE 2: DISPLAY PARAMETERS

[0059] As shown in Table 2, in the reference example, the thicknesses of the glass substrate 508, the OCA layer 506a, and the encapsulation layer 506b are about 0.5 millimeters, about 2 micrometers, and about 20 micrometers, respectively. The transmittance s of the glass substrate 508, the OCA layer 506a, and the encapsulation layer 506b are greater than about 99.97 percent, greater than about 99 percent, and greater than about 99 percent, respectively. The refractive indices of the glass substrate 508, the OCA layer 506a, and the encapsulation layer 506b are about 1.51, about 1.55, and about 1.49, respectively. This reference example is used as the reference for the 3 examples listed in Table 2 to illustrate the impact of different display parameters on the optical performance and edge light leakage of the 3 examples.

[0060] As shown in Table 2, Example 1 includes all the same parameters as the reference example, except that the transmittance of the glass substrate 508 is variable. FIG. 6A is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the transmittance of the glass substrate 508 for Example 1. The edge light leakage reduction versus the transmittance of the substrate glass is indicated by line 602, and the normal brightness reduction versus the transmittance of the substrate glass is indicated by line 604. As illustrated by line 602, the edge light leakage reduction decreases from about 75 percent to about 45 percent as the transmittance of the substrate glass increases from about 70 percent to about 90 percent. As illustrated by line 604, the normal brightness reduction decreases from about 34 percent to about 14 percent as the transmittance of the substrate glass increases from about 70 percent to about 90 percent. Accordingly, as the transmittance of the glass substrate 508 decreases from about 90 percent to about 70 percent, the edge light leakage reduction improves by about 30 percent, while the normal brightness reduction worsens by about 20 percent.

[0061] Example 2 includes all the same parameters as the reference example, except that the transmittance of the glass substrate 508 is reduced from greater than about 99.97 percent to about 80 percent and the refractive index of the glass substrate is variable. FIG. 6B is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the refractive index of the glass substrate 508 for Example 2. The edge light leakage reduction versus the refractive index of the substrate glass is indicated by line 606, and the normal brightness reduction versus the refractive index of the substrate glass is indicated by line 608. As illustrated by line 606, the edge light leakage reduction increases from about 58 percent to about 95 percent as the refractive index of the substrate glass increases from about 1.4 to about 1.9. As illustrated by line 608, the normal brightness reduction increases from about 22.5 percent to about 29 percent as the refractive index of the substrate glass increases from about 1.4 to about 1.9. Accordingly, as the refractive index of the glass substrate 508 decreases from about 1.9 to about 1.4, the edge light leakage reduction worsens by about 37 percent, while the normal brightness reduction improves by about 6.5 percent.

[0062] Example 3 includes all the same parameters as the reference example, except that the transmittance of the glass substrate 508 is reduced from greater than about 99.97 percent to about 80 percent and the thickness of the glass substrate is variable. FIG. 6C is a chart illustrating the edge light leakage reduction and the normal brightness reduction versus the thickness of the glass substrate 508 for Example 3. The edge light leakage reduction versus the thickness of the substrate glass is indicated by line 610, and the normal brightness reduction versus the thickness of the substrate glass is indicated by line 612. As illustrated by line 610, the edge light leakage reduction decreases from about 78 percent to about 58 percent as the thickness of the substrate glass increases from about 0.2 millimeters to about 0.5 millimeters. As illustrated by line 612, the normal brightness reduction is substantially insensitive to changes in the thickness of the substrate glass. Accordingly, as the thickness of the glass substrate 508 decreases from about 0.5 millimeters to about 0.2 millimeters, the edge light leakage reduction improves by about 20 percent, while the normal brightness reduction is not substantially impacted.

[0063] In summary, the impact of the transmittance, refractive index, and thickness of the substrate glass on the edge light leakage and normal brightness of the bottom-emission microLED display 500 of FIG. 5 is similar to the impact of the transmittance, refractive index, and thickness of the glass layer on the edge light leakage and normal brightness for the top-emission micro-LED display 200 of FIGS. 2A-2C.

[0064] 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 comprising: a backplane; a plurality of micro Light Emitting Diodes (micro-LEDs) electrically coupled to the backplane; an Optically Clear Adhesive (OCA) layer over the backplane and the plurality of micro- LEDs, the OCA layer comprising a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.6; and a glass layer over the OCA layer, the glass layer comprising a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0.

2. The display of claim 1, wherein the plurality of micro-LEDs comprises a plurality of top-emission micro-LEDs.

3. The display of claim 1, wherein the OCA layer comprises a thickness within a range between about 0.01 millimeters and about 0. 1 millimeters.

4. The display of claim 1 , wherein the OCA layer comprises a transmittance within a range between about 80 percent and about 95 percent.

5. The display of claim 1, wherein the OCA layer comprises a refractive index within a range between about 1.2 and about 1.4.

6. The display of claim 1, wherein the glass layer comprises a thickness within a range between about 0.1 millimeters and about 0.3 millimeters.

7. The display of claim 1, wherein the glass layer comprises a transmittance within a range between about 80 percent and about 95 percent.

8. The display of claim 1, wherein the glass layer comprises a refractive index within a range between about 1.5 and about 1.7.

9. A display comprising: a glass substrate comprising a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0; an Optically Clear Adhesive (OCA) layer over the substrate; a plurality of micro Light Emitting Diodes (micro-LEDs) over the OCA layer; and an encapsulation layer over the OCA layer and the plurality of micro-LEDs, the encapsulation layer comprising a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 0.1 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.9.

10. The display of claim 9, wherein the plurality of micro-LEDs comprises a plurality of bottom-emission micro-LEDs.

11. The display of claim 9, wherein the encapsulation layer comprises a thickness within a range between about 0.01 millimeters and about 0.1 millimeters.

12. The display of claim 9, wherein the encapsulation layer comprises a transmittance within a range between about 10 percent and about 50 percent.

13. The display of claim 9, wherein the encapsulation layer comprises a refractive index within a range between about 1.2 and about 1.4

14. The display of claim 9, wherein the glass substrate comprises a thickness within a range between about 0.1 millimeters and about 0.3 millimeters.

15. The display of claim 9, wherein the glass substrate comprises a transmittance within a range between about 80 percent and about 95 percent.

16. The display of claim 9, wherein the glass substrate comprises a refractive index within a range between about 1.5 and about 1 .7.

17. A display comprising: a substrate; and a plurality of small format displays arranged on the substrate, wherein each small format display of the plurality of small format displays comprises: a plurality of micro Light Emitting Diodes (micro-LEDs); an Optically Clear Adhesive (OCA) layer encapsulating the plurality of micro- LEDs, the OCA layer comprising a thickness within a range between about 0.005 millimeters and about 0.2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.1 and about 1.6; and a glass layer proximate the OCA layer, the glass layer comprising a thickness within a range between about 0.05 millimeters and about 2 millimeters, a transmittance within a range between about 40 percent and about 95 percent, and a refractive index within a range between about 1.4 and about 2.0.

18. The display of claim 17, wherein the OCA layer comprises a thickness within a range between about 0.01 millimeters and about 0.1 millimeters, a transmittance within a range between about 80 percent and about 95 percent, and a refractive index within a range between about 1.2 and about 1.4.

19. The display of claim 17, wherein the glass layer comprises a thickness within a range between about 0.1 millimeters and about 0.3 millimeters, a transmittance within a range between about 80 percent and about 95 percent, and a refractive index within a range between about 1.5 and about 1.7.

20. The display of claim 17, wherein the plurality of micro-LEDs are arranged in pixels and each pixel comprises a blue micro-LED, a green micro-LED, and a red micro-LED.