Phosphor protection in micro-LED displays

Abstract

The present invention addresses the problem of a micro LED display using a phosphor. A method of protecting phosphor function in a micro LED display during lamination includes depositing a protective bank having a transparent material prior to phosphor coating. The method further includes using the protective bank as a barrier such that a top of the phosphor is lower than a top of the protective bank.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 413,708, filed on October 6, 2022, which is hereby incorporated by reference in its entirety.

[0003] Background and technical field

[0004] The present invention relates to micro LED displays using phosphors. Summary of the invention

[0005] The present invention relates to a method for protecting the phosphor function in a micro-LED display during lamination, the method comprising: assembling the display with micro-LEDs; adding a color conversion layer on top of the micro-LED device; covering the micro-LED with a passivation layer before the color conversion layer; depositing a protective dam with a transparent material before the phosphor coating; and making the protective dam act as a barrier so that the top of the phosphor coating is lower than the top of the protective dam.

[0006] The present invention relates to a method for protecting phosphor functionality in a micro-LED display during lamination, the method comprising: having a micro-LED display; depositing a transparent material coated on top of the entire active area after the phosphor coating; and allowing the transparent material to act as a physical barrier between the glass or filler interlayer and the phosphor coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing and other advantages of the present disclosure will become apparent by reading the following detailed description and referring to the accompanying drawings.

[0008] Figure 1 The problem to be solved is shown.

[0009] Figure 2 A micro-LED display sandwiched between glass and PVB layers is shown.

[0010] FIG. 3( a ) shows a cross section of a micro LED display with a protection bank.

[0011] FIG. 3( b ) shows a top view of a micro LED display with a protection bank.

[0012] FIG4( a ) shows a cross section of a micro LED display having a coating of a transparent material.

[0013] FIG4( b ) shows a top view of a micro LED display with a coating of a transparent material. DETAILED DESCRIPTION

[0014] Micro-LED displays can be used in automotive (windshields, windows, sunroofs), retail (windows, large glass shelves), signage, and regular glass.

[0015] Micro-LED displays that use phosphors and need to be laminated between glass face the problem of color point shift.

[0016] like Figure 1 As shown, the red arrows show the problem to be solved. The ability of the phosphor to convert blue light to white light is reduced during the lamination problem, so the display no longer displays the correct colors.

[0017] exist Figure 2 , a laminated stack is shown. The display is assembled with micro-LEDs or other micro-devices. A color conversion device is added on top of the micro-LEDs (or other micro-devices). The color conversion can be a phosphor or Qdot (quantum dots). The micro-LEDs can be covered with a passivation layer before the color conversion layer. The micro-LED display 201 is sandwiched between glass layers 200 and 204 and filler layers 203 and 205 (the filler layers can be PVB). During the lamination process, the phosphor 202 will be in contact with the top filler layer or glass. Pressure is applied, which squeezes the phosphor layer (making it thinner) and degrades the optical properties (causing color shift).

[0018] Here, phosphor is used as an example of color conversion, but the color conversion may also be another material.

[0019] When pressure and temperature are applied to the laminate stack, the filler layer and / or glass presses on the phosphor 202, which causes the phosphor to thin and reduces the number of phosphor particles participating in the down conversion. Therefore, the resulting color is blue-shifted. To prevent this, solutions that reduce or eliminate the pressure on the phosphor can be implemented.

[0020] In one embodiment, a protective bank (transparent material) is used which can act as a barrier so that the top of the phosphor is lower than the top of the protective bank. The protective bank will act as a spacer so that the phosphor is physically protected from the lamination stack (glass, filler layers).

[0021] like Figure 3(a) and 3(a) As shown, a protective dam 300 (transparent material) can be deposited on the micro LED display 201 before or after the phosphor coating 202. The dam will be higher than the total height of the phosphor, so when the phosphor is applied, the phosphor will be below the dam. Therefore, when the display is laminated, the phosphor is below the top of the dam and is physically protected.

[0022] There may be a reflective layer beneath the microLED. A passivation layer may cover the microLED. The passivation layer may be patterned or a cover layer covering the display surface. The embankment may be a photosensitive material patterned around the microLED. In one case, the embankment is a blackout layer with an opening at the top of the microLED. Since the embankment may be a thick layer, this may result in light loss in the embankment layer. In another case, the embankment may be an isolation structure with a wall surrounding the microLED. The angle of the wall may be negative to direct light to the surface. In another related embodiment, one or more outer surfaces of the wall are covered by a reflective layer. In another related embodiment, one or more inner walls are covered by a reflective layer. This will improve light coupling into the phosphor. Moreover, it will direct light in a specific direction.

[0023] The bank layer may be patterned and hard baked to provide a better barrier.

[0024] In another related embodiment, the phosphor may be covered with a thick layer of transparent material so that the lamination stack does not physically affect the phosphor.

[0025] like Figure 4(a) and 4(b) As shown in , a transparent material 302 (e.g., SU8, photoresist, BCB) can be coated on top of the entire active area after the phosphor is coated. In another related embodiment, the material is patterned on top of the micro-LED or phosphor area. The protective layer can extend over the phosphor layer. The material will form a physical barrier between the glass or filler interlayer and the phosphor. When pressure is applied to the laminate stack, the phosphor will not thin or degrade.

[0026] In the case where the protective material 302 is patterned, one or more of the walls may be covered by a reflective layer. Additionally, the walls of the patterned structure may have angles that facilitate light extraction or light coupling.

[0027] Although the present disclosure is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown in the drawings by way of example and will be described in detail herein. However, it should be understood that the present disclosure is not intended to be limited to the specific forms disclosed. On the contrary, the present disclosure will cover all modifications, equivalents and alternative forms that fall within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A method for protecting phosphor functionality in a micro-LED display during lamination, the method comprising: Make the display assembled with micro LEDs; adding a color conversion layer on top of the micro-LED device; Covering the micro-LEDs with a passivation layer before the color conversion layer; depositing a protective bank having a transparent material before the phosphor coating; as well as The protection bank is made to act as a barrier so that the top of the phosphor coating is lower than the top of the protection bank.

2. The method of claim 1, wherein the display is sandwiched between a layer of glass and a layer of filler.

3. The method of claim 1, wherein the color conversion is phosphor or Qdot. The method according to claim 2 , wherein the filler layer is PVB.

5. The method of claim 1 , wherein the protective dam is deposited on the display before or after applying the phosphor, wherein the protective dam is higher than the total height of the phosphor coating so that when the phosphor coating is applied, the phosphor coating will be below the protective dam. The method of claim 1 , wherein there is a reflective layer beneath the micro-LEDs. 7 . The method of claim 6 , wherein the passivation layer is patterned and a bank layer of photosensitive material is patterned around the micro LEDs. The method of claim 7 , wherein the bank layer is a blanking layer having an opening at the top of the micro LED.

9. The method of claim 7, wherein the bank is an isolation structure having walls surrounding the micro LEDs, wherein an angle of the walls is negative to direct light to a surface.

10. The method of claim 9, wherein one or more outer surfaces of the wall are covered with a reflective layer.

11. The method of claim 9, wherein one or more inner walls are covered by a reflective layer.

12. A method of protecting phosphor functionality in a micro-LED display during lamination, the method comprising: Having the micro LED display; After the phosphor coating, a transparent material is deposited that coats on top of the entire active area; as well as The transparent material is made to act as a physical barrier between the glass or filler interlayer and the phosphor coating.

13. The method of claim 12, wherein the transparent material is patterned on top of the micro-LEDs and the transparent material extends over the phosphor coating.

14. The method of claim 12, wherein the transparent material is one of SU8, photoresist or BCB.

15. The method of claim 13, wherein the one or more walls are covered by a reflective layer and the walls of the patterned structure are angled to enhance light extraction or light coupling.

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