High Dynamic Range Liquid Crystal Display

• US 20150198834A1
• Filed: 09/30/2014
• Published: 07/16/2015
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wu, Jiaying, Chen, Wei, Chen, Cheng, Qi, Jun, Zhong, John Z., Marcu, Gabriel, Riedel, William Mathews
• Granted Patent: US 9,541,794 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133614 using photoluminescence, e.g. phosphors illuminated by UV or blue light
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2413/13 Positive birefingence
• CPC Class Codes: G02F 2413/14 Negative birefingence

Abstract

A display may have a first stage such as a color liquid crystal display stage and a second stage such as a monochromatic liquid crystal display stage that are coupled in tandem so that light from a backlight passes through both stages. The dynamic range of the display may be enhanced by using the second stage to perform local dimming operations. The pixel pitch of the second stage may be greater than the pixel pitch of the first stage to ease alignment tolerances and reduce image processing complexity. The color stage and monochromatic stages may share a polarizer. A color filter in the color stage may have an array of red, green, and blue elements or an array of white, red, green, and blue elements. The color stage may be a fringe field display and the monochrome stage may be an in-plane switching display or a twisted nematic stage.

Claims

1. A display, comprising:

a color upper stage having white, red, green, and blue color filter elements;

a monochromatic lower stage; and

a backlight that supplies light that passes through the monochromatic lower stage before passing through the color upper stage, wherein the color upper stage has a first pixel pitch and wherein the monochromatic lower stage has a second pixel pitch that is greater than the first pixel pitch.

2. The display defined in claim 1 wherein the color upper stage comprises:

a thin-film transistor layer;

a color filter layer that includes the white, red, green, and blue color filter elements; and

a liquid crystal layer interposed between the thin-film transistor layer and the color filter layer.

3. The display defined in claim 1 wherein:

the color upper stage comprises;

a first thin-film transistor layer;

a color filter layer that includes the white, red, green, and blue color filter elements; and

a first liquid crystal layer between the first thin-film transistor layer and the color filter layer; and

the monochromatic lower stage comprises;

a second thin-film transistor layer;

a transparent substrate; and

a second liquid crystal layer between the second thin-film transistor layer and the transparent substrate.

4. The display defined in claim 3 wherein:

the color upper stage comprises a first upper polarizer and a first lower polarizer, wherein the first liquid crystal layer is between the first upper polarizer and the first lower polarizer; and

the monochromatic lower stage comprises a second upper polarizer and a second lower polarizer, wherein the second liquid crystal layer is between the second upper polarizer and the second lower polarizer.

5. The display defined in claim 4 wherein at least a selected polarizer of the first upper polarizer, the first lower polarizer, the second upper polarizer, and the second lower polarizer includes a negative birefringence compensation layer and a positive birefringence compensation layer.

6. The display defined in claim 3 wherein the color upper stage comprises a first polarizer and the monochromatic lower stage comprises a second polarizer, the display further comprising a common polarizer that is shared between the color upper stage and the monochromatic lower stage, wherein the first liquid crystal layer is between the first polarizer and the common polarizer and wherein the second liquid crystal layer is between the second polarizer and the common polarizer.

7. The display defined in claim 6 wherein the common polarizer comprises:

a polarizer layer;

first compensation films; and

second compensation films, wherein the polarizer layer is between the first compensation films and the second compensation films.

8. The display defined in claim 7 wherein the polarizer layer comprises a polyvinyl alcohol layer, wherein the first compensation films include positive and negative birefringence layers, and wherein the second compensation films include positive and negative birefringence layers.

9. The display defined in claim 1 wherein the backlight comprises a quantum dot structure.

10. The display defined in claim 9 wherein the backlight comprises a blue light source that supplies blue light to the quantum dot structure.

11. The display defined in claim 9 further comprising:

display circuitry that receives image data and splits the image data into a first channel supplied to the color upper stage and a second channel supplied to the lower monochromatic stage.

12. A two-stage display, comprising:

a color stage having pixels with a first pixel pitch;

a monochromatic stage having pixels with a second pitch that is greater than the first pitch; and

backlight structures that include a light source, that include a quantum dot structure that receives light from the light source, and that include a light guide plate that receives light from the quantum dot structure and provides backlight, wherein the color stage and monochromatic stage are coupled in tandem so that the backlight passes through both the color stage and the monochromatic stage.

13. The two-stage display defined in claim 12 wherein the color stage comprises:

a thin-film transistor layer;

a color filter layer that includes white, red, green, and blue color filter elements; and

a liquid crystal layer interposed between the thin-film transistor layer and the color filter layer.

14. The display defined in claim 12 further comprising a common polarizer that is shared between the color stage and the monochromatic stage.

15. The display defined in claim 14 wherein:

the color stage comprises;

a first thin-film transistor layer;

a color filter layer; and

a first liquid crystal layer between the first thin-film transistor layer and the color filter layer; and

the monochromatic lower stage comprises;

a second thin-film transistor layer;

a transparent substrate; and

a second liquid crystal layer between the second thin-film transistor layer and the transparent substrate.

16. The display defined in claim 15 wherein the common polarizer is interposed between the first thin-film transistor layer and the transparent substrate.

17. A two-stage display, comprising:

a color stage having a first layer of liquid crystal material and having pixels with a first pixel pitch;

a monochromatic stage having a second layer of liquid crystal material and having pixels with a second pixel pitch that is greater than the first pixel pitch;

a backlight that produces light, wherein the color stage and monochromatic stage are coupled in tandem so that the light from the backlight passes through both the color stage and the monochromatic stage, wherein the color stage has a first polarizer, and wherein the monochromatic stage has a second polarizer; and

a common polarizer that is shared by the color stage and the monochromatic stage.

18. The two-stage display defined in claim 17 wherein the backlight includes quantum dot structures, wherein the color stage has a color filter layer with white, red, green, and blue color filter elements, and wherein the pixels of the monochromatic stage comprise pixels selected from the group consisting of:

twisted nematic pixels and in-plane switching pixels.

19. A two-stage display, comprising:

a color stage having a first layer of liquid crystal material and having pixels with a first pixel pitch;

a monochromatic stage having a second layer of liquid crystal material and having pixels with a second pixel pitch that is greater than the first pixel pitch; and

a backlight that produces light, wherein the color stage and monochromatic stage are coupled in tandem so that the light from the backlight passes through both the color stage and the monochromatic stage, wherein;

the pixels of the color stage are fringe field switching pixels; and

the pixels of the monochromatic stage comprise pixels selected from the group consisting of;

twisted nematic pixels and in-plane switching pixels.

20. The two-stage display defined in claim 19 wherein the backlight includes quantum dot structures, wherein the display comprises a shared polarizer that forms part of the color stage and part of the monochromatic stage, and wherein the shared polarizer includes at least two negative birefringence layers.