Electronic device and LC shutter with diffusive reflective polarizer

• US 7,864,270 B2
• Filed: 02/08/2008
• Issued: 01/04/2011
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Polak, Robert, Ishikawa, Tomohiro, Zhuang, Jim
• Primary Examiner(s): ROJAS, OMAR R
• Application Number:
  US12/028,092
• Publication Number:
  US 20090201447A1
• Time in Patent Office: 1,061 Days
• Field of Search: None
• US Class Current: 349/97
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133602 Direct backlight
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2203/03 scattering
• CPC Class Codes: G02F 2203/04 wavelength independent
• CPC Class Codes: G02F 2203/09 transflective

Abstract

An electronic device (200) includes a display (202) and an LC shutter (204), at least a portion of which is operatively positioned over the display (202). The LC shutter (204) provides switching between a transparent state and a diffusive state with high image integrity, and high transmission in the transparent state. In one embodiment, the electronic device (200) further includes control logic (206) operatively coupled to the LC shutter (204) to provide control signals (212) to the LC shutter (204) to effect the transparent state. The LC shutter (204) includes a first dichroic polarizer (300), such as a broadband dichroic polarizer, an LC cell (304), and a diffusive reflective polarizer (307). The LC cell (304) is interposed between the first dichroic polarizer (300) and the diffusive reflective polarizer (307). Related methods are also set forth.

Claims

1. An LC shutter comprising:

a first dichroic polarizer;

a diffusive reflective polarizer;

an LC cell interposed between the first dichroic polarizer and the diffusive reflective polarizer;

a second dichroic polarizer interposed between the LC cell and the diffusive reflective polarizer; and

wherein the first dichroic polarizer is a broadband dichroic polarizer and the second dichroic polarizer is a passive narrowband dichroic polarizer, the LC cell operative to cause the LC shutter to operate in a visible diffusive state or a transparent state in response to application of a voltage.

2. The LC shutter of claim 1, further comprising a third dichroic polarizer that is a broadband dichroic polarizer, and wherein the diffusive reflective polarizer, the second dichroic polarizer, and the LC cell are interposed between the first dichroic polarizer and the third dichroic polarizer.

3. The LC shutter of claim 1, wherein the diffusive reflective polarizer comprises:

a polymer of a first kind; and

a polymer of a second kind which is immiscible with the polymer of a first kind;

wherein the diffusive reflective polarizer is such that there is a refractive index match between the polymer of a first kind and the polymer of a second kind along a first axis of the diffusive reflective polarizer and a refractive index mismatch between the polymer of a first kind and the polymer of a second kind along a second axis of the diffusive reflective polarizer.

4. The LC shutter of claim 3, wherein the diffusive reflective polarizer is transparent to incoming light polarized along the first axis and backward scattering to incoming light polarized along the second axis.

5. The LC shutter of claim 1, wherein the LC cell comprises:

a first substrate;

a second substrate; and

liquid crystal material interposed between the first substrate and the second substrate.

6. The LC shutter of claim 5, wherein the LC cell is operative to rotate polarization of incident light when a voltage is not applied to the LC cell.

7. An electronic device comprising:

a display operative to emit light; and

at least a portion of an LC shutter positioned over the display, and wherein the LC shutter further comprises;

a first dichroic polarizer;

a diffusive reflective polarizer;

an LC cell interposed between the first dichroic polarizer and the diffusive reflective polarizer;

a second dichroic polarizer interposed between the LC cell and the diffusive reflective polarizer; and

wherein the first dichroic polarizer is a broadband dichroic polarizer and the second dichroic polarizer is a passive narrowband dichroic polarizer.

8. The electronic device of claim 7, wherein the first dichroic polarizer is a broadband dichroic polarizer, and wherein the LC shutter further comprises a second dichroic polarizer that is a broadband dichroic polarizer, and wherein the diffusive reflective polarizer and the LC cell are interposed between the first dichroic polarizer and the second dichroic polarizer.

9. The electronic device of claim 7, wherein the LC shutter further comprises a third dichroic polarizer that is a broadband dichroic polarizer, and wherein the diffusive reflective polarizer, the second dichroic polarizer, and the LC cell are interposed between the first dichroic polarizer and the third dichroic polarizer.

10. The electronic device of claim 7, wherein at least a portion of the LC shutter is further operatively positioned over a keypad operative to emit light.

11. The electronic device of claim 7, further comprising a radio-telephone subsystem operatively coupled to the display.

12. The electronic device of claim 7, wherein the diffusive reflective polarizer comprises:

a polymer of a first kind; and

a polymer of a second kind which is immiscible with the polymer of a first kind;

wherein the diffusive reflective polarizer is such that there is a refractive index match between the polymer of a first kind and the polymer of a second kind along a first axis of the diffusive reflective polarizer and a refractive index mismatch between the polymer of a first kind and the polymer of a second kind along a second axis of the diffusive reflective polarizer.

13. The electronic device of claim 12, wherein the diffusive reflective polarizer is transparent to incoming light polarized along the first axis and backward scattering to incoming light polarized along the second axis.

14. The electronic device of claim 7, wherein the LC cell comprises:

a first substrate;

a second substrate; and

liquid crystal material interposed between the first substrate and the second substrate.

15. The electronic device of claim 14, wherein the LC cell is operative to rotate polarization of incident light when a voltage is not applied to the LC cell.