Reflective Morphable Display Device and method of Feature Activation

• US 20100097549A1
• Filed: 10/20/2008
• Published: 04/22/2010
• Est. Priority Date: 10/20/2008
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ishikawa, Tomohiro, Polak, Robert D., Cady, Andrew N., Dean, Kenneth
• Granted Patent: US 8,040,475 B2
• Time in Patent Office: Days
• US Class Current: 349/115
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133618 for ambient light
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/13476 in which at least one liquid crystal cell or layer assumes a scattering state
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G02F 1/1391 Bistable or multi-stable liquid crystal cells G02F1/141 takes precedence
• CPC Class Codes: G02F 2201/44 Arrangements combining different electro-active layers, e.g. electrochromic, liquid crystal or electroluminescent layers
• CPC Class Codes: G02F 2201/58 Arrangements comprising a monitoring photodetector
• CPC Class Codes: G02F 2203/09 transflective

Abstract

Disclosed is reflective morphable display with multi-layered depth viewing, low power consumption and few components and a method of activating various features thereof. The disclosed display includes a bi-stable reflective cholesteric liquid display crystal (ChLCD) layered in combination with a display device such as an LCD and a quarter lambda (λ/4) retardation film layer. Linearly polarized light emerging from the front surface of a display device is circularly polarized by the λ/4 layer before entering the ChLCD layer. In its reflective state, the ChLCD layer receiving a portion of the ambient light having the same handedness of the ChLCD is reflected in a mirror-like manner. Also in its reflective state, when it receives light that is circularly polarized by the λ/4 retardation film layer, the ChLCD layer acts as a shutter. A display device with depth viewing is provided as the ChLCD layer pixelated so it is configured to display font and/or other indicia.

Claims

1. A display comprising:

a display device configured to transmit linearly polarized light in an on state and to absorb linearly polarized light in an off state;

a bi-stable cholesteric (ChLCD) layer configured to have a reflective state being a stable state, a lower transmissivity state being a stable state, and a high transmissivity state requiring power to maintain the high transmissivity state, the ChLCD layer being configured to reflect a circularly polarized light with a particular handedness in the reflective state;

a single quarter lambda layer positioned between the display and the cholesteric layer configured to change linearly polarized light to light being the circularly polarized light and to change the circularly polarized light transmitted to light being linearly polarized light.

2. The display of claim 1 wherein the display device is a liquid crystal display.

3. The display of claim 1 wherein the quarter lambda layer and the display device are configured to create an absorbing background for the ChLCD layer, wherein the bi-stable ChLCD layer is configured to provide always-on information

4. The display of claim 1 wherein the cholesteric layer is configured to display indicia.

5. The display of claim 1, wherein the cholesteric layer comprises at least one sub-layer containing cholesteric material having a bottom side facing the display and a top side, the sub-layer containing cholesteric material tuned to a particular colored reflective state and wherein a color filter layer is positioned on the top side.

6. The display of claim 1 wherein the cholesteric layer comprises at least one sub-layer containing cholesteric material having a bottom side facing the display and a top side, the sub-layer containing cholesteric material tuned to a red-colored reflective state, and wherein a notch filter layer is positioned on the top side and is configured to absorb light between a range of approximately 580-620 nm.

7. The display of claim 6 further comprising:

the display device including at least one chromatic filter that compensates for absorption of light by the notch filter.

8. The display of claim 7 further comprising:

at least one additional sub-layer containing cholesteric material positioned on the top side of the at least one sub-layer containing cholesteric material, said additional sub-layer containing cholesteric material is tuned to have a reflected state wavelength shorter than red wavelengths, wherein the notch filter layer is positioned between the at least one sub-layer and the additional sub-layer.

9. The display of claim 1 further comprising:

a keypad element adjacent the display device;

an absorptive polarizer layer configured to absorb light having a particular linear polarization, the absorptive polarizer layer positioned between the keypad element and the single quarter lambda layer.

10. The display of claim 9 further comprising:

a dual brightness enhancement film positioned between the keypad element and the absorptive polarizer layer.

11. A display comprising:

a keypad element;

a bi-stable cholesteric layer configured to have a reflective state being a stable state, a lower transmissivity state being a stable state and a high transmissivity state requiring power to maintain the high transmissivity state and configured to reflect a circularly polarized light with a particular handedness in the reflective state;

a single quarter lambda layer positioned between the keypad element and the cholesteric layer configured to change linearly polarized light transmitted from the keypad element to light being the circularly polarized light and to change the circularly polarized light transmitted from the cholesteric layer to linearly polarized light; and

an absorptive polarizer layer configured to absorb a particular linear light positioned between the keypad element and the a single quarter lambda layer.

12. The display of claim 11, wherein the cholesteric layer comprises at least one sub-layer containing cholesteric material having a bottom side facing the display and a top side, the sub-layer containing cholesteric material tuned to a particular colored reflective state and wherein a color filter layer is positioned on the top side.

13. The display of claim 11 further comprising:

a dual brightness enhancement film positioned between the keypad element and the absorptive polarizer layer.

14. A method of display including a display device configured to transmit linearly polarized light in an on state and to absorb linearly polarized light in an off state, the method comprising:

activating a bi-stable cholesteric layer configured to have a reflective state being a stable state, a lower transmissivity state being a stable state and a high transmissivity state requiring power to maintain the high transmissivity state and configured to reflect a circularly polarized light with a particular handedness in the reflective state, wherein activating the cholesteric layer changes the state of the cholesteric layer so that it is one of a reflective state, a high transmissivity state and a lower transmissivity state;

transmitting light through a single quarter lambda layer positioned between the display and the cholesteric layer, the single quarter lambda layer being configured to change linearly polarized light to the circularly polarized light and to change the circularly polarized light to linearly polarized light.

15. The method of claim 14, wherein by activating the cholesteric layer, the cholesteric layer is in at least one of a high transmissivity state and a lower transmissivity state, the method further comprising:

activating the display so that it transmits linearly polarized light; and

displaying indicia thereon the cholesteric layer in a first color.

16. The method of claim 14 wherein by activating the cholesteric layer, the cholesteric layer is in at least one of a high transmissivity state and a lower transmissivity state, the method further comprising:

deactivating the display so that it absorbs light; and

displaying indicia thereon the cholesteric layer in a second color.

17. The method of claim 14, further comprising:

changing the state of at least a portion of the cholesteric layer to the reflective state.

18. The method of claim 14, further comprising:

activating at least a portion of the cholesteric layer to at least one of high transmissivity state and lower transmissivity state so that the display is visible therethrough.

19. The method of claim 14 wherein a keypad element is adjacent the display, and the cholesteric layer and the single quarter lambda layer are layered with the keypad element, the method, further comprising:

activating a keypad element; and

transmitting light from the keypad element through an absorptive polarizer layer configured to absorb a particular linear light, the absorptive polarizer layer between the keypad element and the a single quarter lambda layer.

20. The method of claim 19, further comprising:

activating at least a portion of the cholesteric layer to at least one of high transmissivity state and lower transmissivity state so that the keypad element is visible therethrough.