Displays with direct-lit backlight units

Patent metadata

Field	Value
Publication number	US-11022840-B2
Application number	US-201916409567-A
Country	US
Kind code	B2
Filing date	May 10, 2019
Priority date	Mar 3, 2017
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

An array of pixels in a display may be illuminated by a backlight having an array of light-emitting diodes in an array of respective cells. A reflector is used to reflect light from the light-emitting diodes through the array of pixels. Within the cells, the reflector has cross-sectional profiles that help distribute light emitted from the light-emitting diodes toward edges of the cells. A light diffuser layer for the backlight may have a partially reflective layer such as a thin-film interference filter with an angularly dependent transmission. Within each cell, the reflector may have cross-sectional profiles with portions that are parabolic or elliptical.

First claim

What is claimed is:

1. A display, comprising:
pixels configured to display images; and
a backlight configured to produce backlight illumination for the pixels, wherein the backlight comprises:
a two-dimensional array of light-emitting diode cells each of which includes at least one light-emitting diode that is configured to emit light, wherein the two-dimensional array of light-emitting diode cells is formed in a plane;
a reflector with a curved cross-sectional profile having a selected one of a parabolic shape and an elliptical shape, wherein the reflector reflects light through the array of pixels from the light-emitting diodes, wherein the cross-sectional profile is defined by an axis of symmetry that is substantially parallel to the plane so that the more of the light from the light-emitting diodes is directed toward the edges of the cells than toward the centers of the cells;
a microlens array layer between the pixels and the two-dimensional array of light-emitting diode cells;
a light diffuser layer between the two-dimensional array of light-emitting diode cells and the microlens array layer; and
a phosphor layer, wherein the light diffuser layer is interposed between the phosphor layer and the two-dimensional array of light-emitting diode cells.

2. The display defined in claim 1 wherein the backlight further comprises a first thin-film interference filter on the diffuser layer and a second thin-film interference filter on the phosphor layer.

3. The display defined in claim 2 wherein the light-emitting diodes comprise blue light-emitting diodes configured to emit blue light.

4. The display defined in claim 3 wherein the first thin-film interference filter is configured to partially transmit the blue light.

5. The display defined in claim 4 wherein the second thin-film interference filter is configured to transmit the blue light and reflect red and green light generated in the phosphor layer in response to the blue light.

6. The display defined in claim 5 wherein the backlight further comprises first and second prism films between the pixels and the microlens array layer.

7. The display defined in claim 6 wherein the backlight further comprises a reflective polarizer between the second prism film and the pixels.

8. A display, comprising:
a plurality of pixels;
a backlight configured to produce backlight illumination for the plurality of pixels, wherein the backlight comprises:
an array of light sources that are configured to emit light and that are arranged in a plurality of respective cells, wherein the array of light sources is formed in a plane; and
a reflector that reflects the light through the plurality of pixels from the light sources, wherein the reflector has a plurality of cross-sectional profiles in each cell, wherein each cross-sectional profile has a portion that is selected from the group consisting of: a parabolic portion and an elliptical portion, wherein each of the cross-sectional profiles is defined by an axis of symmetry that is oriented substantially parallel to the plane so that more of the light from the light sources is directed toward edges of the cells than toward centers of the cells;
a light diffuser layer interposed between the light sources and the array plurality of pixels;
an angularly dependent filter interposed between the light diffuser layer and the light sources; and
a layer of photoluminescent material, wherein the light diffuser layer is interposed between the layer of photoluminescent material and the light sources.

9. The display defined in claim 8 wherein the light sources comprise a two-dimensional array of the light sources that are arranged in a two-dimensional array of the respective cells.

10. The display defined in claim 9 wherein each light source has at least one light-emitting diode.

11. The display defined in claim 10 wherein the angularly dependent filter is a thin-film interference filter having an angularly dependent light transmission characteristic.

12. The display defined in claim 11 wherein the angularly dependent filter comprises a coating on the light diffuser layer.

13. The display defined in claim 12 wherein the reflector comprises a reflector selected from the group consisting of: a glossy white reflector, a diffusively reflective white reflector, or a specularly reflective white reflector.

14. The display defined in claim 12 wherein the reflector comprises a reflector selected from the group consisting of: a stack of thin-film dielectric layers forming a thin-film interference mirror, a cholesteric liquid crystal layer, and a stack of polymer films of alternating refractive index.

15. The display defined in claim 11 further comprising a printed circuit, wherein the light-emitting diodes are mounted to the printed circuit, wherein within each cell, the reflector has four straight edges surrounding a respective one of the light-emitting diodes, and wherein each point along each of the four edges is separated by a common distance from the printed circuit.

16. The display defined in claim 11 further comprising a printed circuit, wherein the light-emitting diodes are mounted to the printed circuit, wherein within each cell, the reflector has four corners and four curved edges each of which extends between a respective pair of the four corners, wherein each of the four curved edges has endpoints separated from the printed circuit by a first distance and a midpoint separated from the printed circuit by a second distance that is less than the first distance.

17. The display defined in claim 10 wherein the light-emitting diodes comprise blue light-emitting diodes.

18. The display defined in claim 9 wherein each light source comprises at least two light-emitting diodes.

19. A display, comprising:
an array of pixels; and
a backlight configured to produce backlight illumination for the array of pixels, wherein the backlight comprises:
a reflector forming a two-dimensional array of light-emitting diode cells in a plane, wherein each of the light-emitting diode cells includes at least one light-emitting diode that is configured to emit light, wherein the reflector reflects light through the array of pixels from the light-emitting diodes, wherein the reflector has at least three cross-sectional profiles in each cell, each of which has a portion that is parabolic, wherein each of the parabolic cross-sectional profiles is defined by an axis of symmetry that is oriented substantially parallel to the plane so that more of the light from the light-emitting diodes is directed toward edges of the light-emitting diode cells than toward centers of the light-emitting diode cells;
a light diffuser layer interposed between the array of pixels and the array of light-emitting diodes; and
a coating on the light-diffuser layer that forms a thin-film interference filter that has an angularly dependent transmission.

20. The display defined in claim 19 wherein the light-emitting diodes are configured to emit blue light.

21. The display defined in claim 20 further comprising a printed circuit, wherein the light-emitting diodes are mounted to the printed circuit, wherein within each cell the reflector has four corners and has four straight edges extending between the corners, and wherein each point along each of the four straight edges is separated by a common distance from the printed circuit.

22. The display defined in claim 20 further comprising a printed circuit, wherein the light-emitting diodes are moun

Assignees

• Apple Inc

Inventors

• Liu Rong
• Sun Yu P
• Hafidi Abdeslam
• Zweigle Erik A
• Qi Jun
• Gu Mingxia
• Yin Victor H
• Li Xiangtong
• Li Yanming
• Huang Yi
• Hong Ziruo

Classifications

• G02F1/133607

  the light controlling member including light directing or refracting elements, e.g. prisms or lenses · CPC title

• G02F1/133603 Primary

  with LEDs · CPC title

• G02F1/133606

  including a specially adapted diffusing, scattering or light controlling members · CPC title

• G02F1/133611

  including means for improving the brightness uniformity · CPC title

• G02F1/133614

  using photoluminescence, e.g. phosphors illuminated by UV or blue light · CPC title