Transflective displays with reflective polarizing transflector

• US 6,262,842 B1
• Filed: 01/24/2000
• Issued: 07/17/2001
• Est. Priority Date: 06/26/1995
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Weber, Michael F., Ouderkirk, Andrew J., Wortman, David L., Cull, Brian D.
• Primary Examiner(s): CHANG, AUDREY Y
• Application Number:
  US09/490,879
• Time in Patent Office: 540 Days
• Field of Search: 359/495, 359/487, 359/497, 359/498, 359/599, 349/62, 349/96, 349/19
• US Class Current: 359/485.02
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• 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 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A transflector is described which increases efficiency and brightness under both ambient and supplemental lighting conditions in visual display applications. In one embodiment, the transflector includes a reflective polarizing element that reflects one polarization of light and transmits the other. In an alternate embodiment, the transflector includes a reflective polarizing element and a diffusing element such that the transflector diffusely reflects light of one polarization and transmits the other. The transflector is useful for both reflective and transflective liquid crystal displays.

Claims

1. A reflective display, comprising

a light modulator provided to selectively alter a polarization state of polarized light passing through the light modulator, the light modulator having a viewer side and a back side;

a reflective polarizer positioned on the back side of the light modulator to reflect light having a first polarization state and to transmit light having a second polarization state; and

a rear dichroic polarizer positioned between the light modulator and the reflective polarizer to allow at least a portion of light reflected by the reflective polarizer to be transmitted back through the light modulator,

further including a front dichroic polarizer positioned on the viewer side of the light modulator.

2. A reflective display, comprising

a light modulator provided to selectively alter a polarization state of polarized light passing through the light modulator, the light modulator having a viewer side and a back side;

a reflective polarizer positioned on the back side of the light modulator to reflect light having a first polarization state and to transmit light having a second polarization state; and

a rear dichroic polarizer positioned between the light modulator and the reflective polarizer to allow at least a portion of light reflected by the reflective polarizer to be transmitted back through the light modulator,

wherein a high reflectivity axis of the reflective polarizer forms an angle of about 0°

with a transmission axis of the rear dichroic polarizer.

3. A reflective display, comprising

a light modulator provided to selectively alter a polarization state of polarized light passing through the light modulator, the light modulator having a viewer side and a back side;

a reflective polarizer positioned on the back side of the light modulator to reflect light having a first polarization state and to transmit light having a second polarization state; and

a rear dichroic polarizer positioned between the light modulator and the reflective polarizer to allow at least a portion of light reflected by the reflective polarizer to be transmitted back through the light modulator,

further comprising a diffusing element disposed between the reflective polarizer and the rear dichroic polarizer, wherein the diffusing element includes elliptical diffusers.

4. A transflective display, comprising:

a transmissive light modulator having a viewer side and a back side, the light modulator provided to selectively alter a polarization state of polarized light passing through the light modulator;

a supplemental light source disposed on the back side of the light modulator;

a reflective polarizer positioned between the light modulator and the supplemental light source, the reflective polarizer disposed to reflect light having a first polarization state and to transmit light having a second polarization state; and

an absorber disposed between the supplemental light source and the reflective polarizer to absorb a portion of light passing through the absorber and to transmit a portion of light passing through the absorber,

wherein an image is generated by the light modulator when either ambient light is incident on the viewer side of the light modulator or under supplemental lighting conditions when light is generated by the supplemental light source.

5. The display of claim 4, wherein the absorber is a dichroic polarizer.

6. The display of claim 4, wherein the display image exhibits an increased contrast under ambient light compared to the transflective display without the absorber disposed between the supplemental light source and the reflective polarizer.

7. The display of claim 4, further including a front dichroic polarizer positioned on the viewer side of the light modulator.

8. The display of claim 4, wherein the reflective polarizer comprises a plurality of layers.

9. The display of claim 8, wherein a refractive index difference between at least two adjacent layers along a first in-plane axis of the reflective polarizer is greater than a refractive index difference between the at least two adjacent layers along a second in-plane axis of the reflective polarizer.

10. The display of claim 4, wherein the display image reverses between ambient light and supplemental lighting conditions.

11. The display of claim 4, wherein the display image has an appearance of dark pixels on a diffusely lit background under both ambient light and supplemental lighting conditions.

12. The display of claim 4, further comprising a diffusing element disposed between the reflective polarizer and the absorber.

13. The display of claim 12, wherein the diffusing element includes elliptical diffusers.

14. The display of claim 12, wherein the diffusing element substantially maintains the polarization of light reflected by the reflective polarizer.