Transflective LC Display Having Narrow Band Backlight and Spectrally Notched Transflector

• US 20070247573A1
• Filed: 04/18/2007
• Published: 10/25/2007
• Est. Priority Date: 04/19/2006
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Watson, Philip E., Ouderkirk, Andrew J.
• Application Number:
  US11/736,812
• Publication Number:
  US 20070247573A1
• Time in Patent Office: Days
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination

Abstract

A transflective display includes a front polarizer, a transflector, and a liquid crystal (LC) panel disposed between the front polarizer and the transflector. The display also includes a backlight for illuminating the LC panel in the transmissive viewing mode. The backlight emits light over selected relatively narrow portions of the visible spectrum, and the transflector has a spectrally variable reflectivity to selectively transmit the light emitted by the backlight and substantially reflect other visible wavelengths. This combination can increase the efficiency of the transflective display by enhancing the display brightness in both the reflective mode and the transmissive mode.

Claims

1. A transflective display having a reflective viewing mode and a transmissive viewing mode, the display comprising:

a front polarizer;

a transflector;

a liquid crystal (LC) panel disposed between the front polarizer and the transflector; and

a backlight for illuminating the LC panel in the transmissive viewing mode;

wherein the backlight emits light over selected portions of the visible spectrum; and

wherein the transflector has a spectrally variable reflectivity to selectively transmit the light emitted by the backlight.

2. The display of claim 1, wherein the backlight includes a plurality of narrow band light sources.

3. The display of claim 2, wherein the plurality of narrow band light sources includes a first LED emitting substantially blue light, a second LED emitting substantially green light, and a third LED emitting substantially red light.

4. The display of claim 1, wherein the front polarizer is an absorptive polarizer.

5. The display of claim 1, wherein the transflector includes a reflective polarizer.

6. The display of claim 1, wherein the transflector has a first block axis and a first pass axis orthogonal to each other in a plane of the transflector, and the spectrally variable reflectivity is a reflectivity for light polarized along the first block axis of the reflective polarizer, such reflectivity being lower for wavelengths of light emitted by the backlight than for other visible wavelengths.

7. The display of claim 6, wherein the transflector substantially transmits visible light polarized along the first pass axis.

8. The display of claim 1, wherein the transflector has a first block axis and a second block axis orthogonal to each other in a plane of the transflector, and the spectrally variable reflectivity is a reflectivity for light polarized along the first block axis of the reflective polarizer, such reflectivity being lower for wavelengths of light emitted by the backlight than for other visible wavelengths.

9. The display of claim 8, wherein the transflector substantially reflects visible light polarized along the second block axis.

10. The display of claim 9, wherein the backlight includes a polarization scrambling layer to convert at least some light polarized along the second block axis to light polarized along the first block axis.

11. The display of claim 1, further comprising:

a back polarizer disposed between the LC panel and the transflector.

12. The display of claim 11, wherein the back polarizer is an absorptive polarizer.

13. The display of claim 1, further comprising:

an absorptive polarizer between the transflector and the backlight.

14. The display of claim 1, wherein the backlight emits polarized light.

15. The display of claim 1, wherein the selected portions of the visible spectrum comprise one or more distinct bands whose full width at half maximum (FWHM) is no greater than 50, 35, or 20 nm.

16. The display of claim 1, wherein the spectrally variable reflectivity includes a high reflectivity with one or more low reflectivity notches therein for at least one polarization state, each notch having a FWHM no greater than 50, 35, or 20 nm.

17. The display of claim 1, wherein the spectrally variable reflectivity of the transflector changes as a function of incidence angle.

18. The display of claim 1, wherein the light emitted by the backlight is at least partially collimated.

19. The display of claim 18, wherein the light emitted by the backlight has a full angular width at half-maximum intensity no greater than 40°

or 20°

in at least one dimension.

20. The display of claim 1, wherein the backlight emits light of different colors in a temporal sequence.

21. The display of claim 1, wherein the backlight emits light of different colors in a spatial array.