Polarizing turning film with multiple operating orientations

• US 20070133226A1
• Filed: 12/13/2005
• Published: 06/14/2007
• Est. Priority Date: 12/13/2005
• Status: Abandoned Application

• Current Assignee: Rohm and Haas Denmark Finance A/S
• Original Assignee: Eastman Kodak Company
• Inventors: Mi, Xiang-Dong
• Application Number:
  US11/300,659
• Publication Number:
  US 20070133226A1
• Time in Patent Office: Days
• US Class Current: 362/607
• CPC Class Codes: G02B 27/288 Filters employing polarising elements, e.g. Lyot or Solc filters G02B5/3016 takes precedence
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements

Abstract

This invention relates to a light redirecting article that redirects light toward a target angle, the light redirecting article having an input surface for accepting incident illumination over a first range of incident angles when in a first position and over a second range of incident angles when in a second position: the output surface having a number of light redirecting structures, each having a first exit surface sloping away from normal in one direction as defined by a first base angle β1, wherein the first exit surface redirects illumination with the light redirecting article in the first position, and a second exit surface sloping away from normal, in the opposite direction relative to the first exit surface, wherein the second exit surface redirects illumination with the light redirecting article in the second position and wherein first and second base angles β1 and β2 are unequal.

Claims

1. A light redirecting article for redirecting light toward a target angle, the light redirecting article comprising:

(a) an input surface for accepting incident illumination over a first range of incident angles when the light redirecting article is in a first position and over a second range of incident angles when the light redirecting article is in a second position;

(b) an output surface comprising a plurality of light redirecting structures each light redirecting structure having

(i) a first exit surface sloping away from normal in one direction as defined by a first base angle β

1 relative to the input surface, wherein the first exit surface redirects illumination with the light redirecting article in the first position, and

(ii) a second exit surface sloping away from normal, in the opposite direction relative to the first exit surface, as defined by a second base angle β

2 relative to the input surface, wherein the second exit surface redirects illumination with the light redirecting article in the second position,

wherein first and second base angles β

1 and β

2 are unequal; and

wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position;

the light redirecting article provides an output light that is within +/−

5 degrees of the target angle.

2. The light-redirecting article of claim 1 wherein the second position is rotated 180 degrees from the first position and in the same incident plane.

3. The light-redirecting article of claim 1 wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position the output light further has a transmittance of one polarization in excess of 85 percent.

5. The light redirecting article of claim 3 wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position, the output light has a transmittance of less than 55 percent for the orthogonal polarization.

6. The light redirecting article of claim 3 wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position, the output light has a transmittance of less than 50 percent for the orthogonal polarization.

7. The light redirecting article of claim 1 comprising a material having a refractive index greater than 1.6.

8. The light redirecting article of claim 1 wherein the light redirecting article is fabricated from at least two materials having different indices of refraction.

9. The light redirecting article of claim 1 wherein for at least one of the first and second exit surfaces, there is more than one slope.

10. The light redirecting article of claim 1 wherein there is curvature over at least some portion of at least one of the first and second exit surfaces.

11. The light redirecting article of claim 1 wherein at least one light redirecting structure is truncated.

12. The light redirecting article of claim 1 wherein the light redirecting article can be utilized with two different light guide plates having two different principal angles of incident illumination.

13. The light redirecting article of claim 1 wherein the target angle is normal with respect to the plane of the light redirecting article.

14. The light redirecting article of claim 1 wherein a plurality of the light redirecting structures are substantially parallel and extend from one edge of the output surface to the other.

15. The light redirecting article of claim 1 wherein the light redirecting structures are extended in an arcuate pattern.

4. The light redirecting article of claim I wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position, the output light further has a transmittance of one polarization in excess of 90 percent.

16. A display apparatus comprising:

(a) an illumination source for emitting illumination over a range of angles;

(b) a light redirecting article for redirecting light toward a target angle, the light redirecting article comprising;

(i) an input surface for accepting incident illumination over a first range of incident angles when the light redirecting article is in a first position and over a second range of incident angles when the light redirecting article is in a second position;

(ii) an output surface comprising a plurality of light redirecting structures each light redirecting structure having

a first exit surface sloping away from normal in one direction as defined by a first base angle β

1 relative to the input surface, wherein the first exit surface redirects illumination with the light redirecting article in the first position, and

a second exit surface sloping away from normal, in the opposite direction relative to the first exit surface, as defined by a second base angle β

2 relative to the input surface, wherein the second exit surface redirects illumination with the light redirecting article in the second position,

wherein first and second base angles β

1 and β

2 are unequal; and

wherein for incident illumination over the first range of incident angles when the light redirecting article is in the first position and over the second range of incident angles when the light redirecting article is in the second position;

the light redirecting article provides an output light that is within +/−

5 degrees of the target angle; and

(c) a light gating device for forming an image by modulating the output light from the light redirecting article.

17. The display apparatus of claim 16 further comprising a pair of crossed polarizers, wherein the light redirecting structures are elongated in an elongation direction and wherein each of the crossed polarizers is oriented either substantially parallel or substantially perpendicular to the elongation direction of the light redirecting article.

18. The display apparatus of claim 16 further comprising a half wave plate and a pair of crossed polarizers, wherein the light redirecting structures are elongated in an elongation direction and wherein each of the crossed polarizers is substantially oriented at +/−

45 degrees relative to the elongation direction of the light redirecting article.