High contrast front projection screen

• US 20070139766A1
• Filed: 12/20/2005
• Published: 06/21/2007
• Est. Priority Date: 12/20/2005
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Radcliffe, Marc, Manoj, Nirmal
• Application Number:
  US11/312,939
• Publication Number:
  US 20070139766A1
• Time in Patent Office: Days
• US Class Current: 359/459
• 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 1/13478 based on selective reflection
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G03B 21/604 Polarised screens

Abstract

A front projection screen and a projection system incorporating same are disclosed. The front projection screen includes a plurality of cholesteric liquid crystal layers and one or more retarder layers. Each cholesteric liquid crystal layer has a reflectance curve characterized by a reflectance peak and a reflectance full width at half maximum. The reflectance peaks of at least two cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers are located at different wavelengths. A retardance full width at half maximum of a first retarder layer in the one or more retarder layers encloses the reflectance full width at half maxima of two or more cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers.

Claims

1. A front projection screen comprising a plurality of cholesteric liquid crystal layers and one or more retarder layers, each cholesteric liquid crystal layer having a reflectance curve characterized by a reflectance peak and a reflectance full width at half maximum, the reflectance peaks of at least two cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers being at different wavelengths, wherein a retardance full width at half maximum of a first retarder layer in the one or more retarder layers encloses the reflectance full width at half maxima of two or more cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers.

2. The front projection screen of claim 1, wherein the retardance full width at half maximum of the first retarder layer encloses the reflectance full width at half maxima of the cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers

3. The front projection screen of claim 1, wherein the first retarder layer is substantially a half-wave retarder at the reflectance peaks of the cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers.

4. The front projection screen of claim 1, wherein the one or more retarder films have substantially a same retardance profile.

5. The front projection screen of claim 1, wherein the reflectance peaks of the plurality of the cholesteric liquid crystal layers are located at three or more distinct wavelengths.

6. The front projection screen of claim 1 further comprising a light absorbing layer.

7. The front projection screen of claim 1 further comprising a light diffusing layer.

8. The front projection screen of claim 1, wherein at least one of the plurality of cholesteric liquid crystal layers is optically diffusive.

17. A front projection display comprising a projector and the front projection screen of claim 1, the projector being capable of projecting an image at a plurality of distinct wavelength ranges, the plurality of cholesteric liquid crystal layers having reflectance peaks within each of the plurality of distinct wavelength ranges.

18. The front projection display of claim 17, wherein the plurality of distinct wavelength ranges includes wavelength ranges in the blue, green, and red regions of the electromagnetic spectrum.

9. A front projection screen comprising a plurality of cholesteric liquid crystal layers and one or more retarder layers, a first cholesteric liquid crystal layer in the plurality of cholesteric liquid crystal layers having a first reflectance peak at an m^th order half-wave retardance peak of a retarder layer in the one or more retarder layers, a second cholesteric liquid crystal layer in the plurality of cholesteric liquid crystal layers having a second reflectance peak at an n^th order half-wave retardance peak of a retarder layer in the one or more retarder layers, the first reflectance peak being at a different wavelength than the second reflectance peak, n being different than m.

10. The front projection screen of claim 9, wherein the m^th and n^th order half-wave retardance peaks are from a same retarder layer.

11. The front projection screen of claim 9, wherein at least one of the m^th and n^th orders is higher than a zeroth order.

12. The front projection screen of claim 9, wherein a retardance full width at half maximum of the m^th order half-wave retardance peak encloses a reflectance full width at half maximum of the first reflectance peak.

13. The front projection screen of claim 9, wherein a retardance full width at half maximum of the n^th order half-wave retardance peak encloses a reflectance full width at half maximum of the second reflectance peak

14. The front projection screen of claim 9, wherein the plurality of cholesteric liquid crystal layers have a same handedness.

15. The front projection screen of claim 9, wherein at least two cholesteric liquid crystal layers in the plurality of cholesteric liquid crystal layers have reflectance peaks at substantially a same wavelength.

16. The front projection screen of claim 9 further comprising a light absorbing layer.

19. A front projection screen comprising a plurality of cholesteric liquid crystal layers and one or more retarder layer, each cholesteric liquid crystal layer having a reflectance curve characterized by a reflectance peak and a reflectance full width at half maximum, at least one of the one or more retarder layers having a plurality of half-wave retardance peaks within the reflectance full width at half maximum of a cholesteric liquid crystal layer in the plurality of cholesteric liquid crystal layers.

20. The front projection screen of claim 19, wherein the reflectance peaks of the plurality of the cholesteric liquid crystal layers are located at three or more distinct wavelengths.

21. A front projection display comprising a projector and the front projection screen of claim 19, the projector being capable of projecting an image at a plurality of distinct wavelength ranges, the plurality of cholesteric liquid crystal layers having reflectance peaks within each of the plurality of distinct wavelength ranges.

22. A front projection screen comprising at least three groups of optical layers, each group including a retarder layer disposed between two cholesteric liquid crystal layers having a same handed-ness, each group reflecting light in a wavelength region in which the other groups transmit light.

23. The front projection screen of claim 22, wherein the reflectance peaks of the two cholesteric liquid crystal layers in a group of optical layers are located at substantially a same wavelength.

24. The front projection screen of claim 22, wherein the retarder in each group is substantially a half-wave retarder at the reflectance peaks of the two cholesteric liquid crystal layers in the group.

25. The front projection screen of claim 22, wherein at least one group of optical layers forms a stack of the optical layers.

26. The front projection screen of claim 22, wherein a first group in the at least three groups of optical layers reflects light in a blue region of the electromagnetic spectrum and transmits light elsewhere in the visible, a second group in the at least three groups of optical layers reflects light in a green region of the electromagnetic spectrum and transmits light elsewhere in the visible, and a third group in the at least three groups of optical layers reflects light in a red region of the electromagnetic spectrum and transmits light elsewhere in the visible.

27. The front projection screen of claim 22, wherein a cholesteric liquid crystal layer in a group is optically diffusive.

28. The front projection screen of claim 22 further comprising a light absorbing layer.

29. The front projection screen of claim 22, wherein in a group of optical layers each of the two cholesteric liquid crystal layers has a reflectance curve characterized by a reflectance peak and a reflectance full width at half maximum, and wherein the retarder layer in the group has a plurality of half-wave retardance peaks within the reflectance full width at half maximum of each of the two cholesteric liquid crystal layers.

30. The front projection screen of claim 22, wherein in a group of the at least three groups of optical layers each of the two cholesteric liquid crystal layers has a reflectance curve characterized by a reflectance peak and a reflectance full width at half maximum, and wherein the retarder layer in the group has a retardance profile characterized by a plurality of half-wave retardance peaks, each retardance peak having a corresponding retardance full width at half maximum, and wherein the reflectance full width at half maximum of each cholesteric liquid crystal layer in the group is enclosed within a retardance full width at half maximum of the retarder layer in the group.

31. The front projection screen of claim 22, wherein a retarder layer in a group comprises a multilayer optical film capable of reflecting light by optical interference, wherein the multilayer optical film comprises alternating first and second layers.

32. A front projection screen comprising at least three groups of optical layers, each group reflecting light in a wavelength region in which the other groups transmit light, each of at least two groups including a retarder layer disposed between two cholesteric liquid crystal layers having a same handed-ness, at least one group including a multilayer optical film comprising alternating first and second layers, wherein the multilayer optical film reflects light by optical interference.

33. A front projection screen comprising:

a first group of optical layers substantially reflecting light in a first wavelength region in the visible and substantially transmitting light elsewhere in the visible;

a second group of optical layers substantially reflecting light in a second wavelength region in the visible and substantially transmitting light elsewhere in the visible, the second region being different than the first region, each of the first and second groups including a retarder layer disposed between two cholesteric liquid crystal layers having a same handed-ness; and

a colored reflective layer substantially reflecting light in a third wavelength region in the visible and substantially absorbing light elsewhere in the visible, the third region being different than the first and the second regions.

34. The front projection screen of claim 33, wherein the colored reflective layer comprises pigments and/or dyes dispersed in a binder.