Higher transmission light control film

• US 9,335,449 B2
• Filed: 10/13/2008
• Issued: 05/10/2016
• Est. Priority Date: 10/16/2007
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Gaides, Gary E., Epstein, Kenneth A.
• Primary Examiner(s): Kianni, Kaveh C
• Application Number:
  US12/682,640
• Publication Number:
  US 20100214506A1
• Time in Patent Office: 2,766 Days
• Field of Search: 349/61
• US Class Current: 1/1
• CPC Class Codes: G02B 2207/123 Optical louvre elements, e.g. for directional light blocking
• CPC Class Codes: G02B 5/0263 with positional variation of the diffusing properties, e.g. gradient or patterned diffuser
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 5/3066 involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle

Abstract

A light control film, and light collimating assemblies and liquid crystal displays incorporating such light control films are described. The light control film includes alternating transmissive and absorptive regions, where the refractive index of each transmissive region is greater than the refractive index of each absorptive region. The absorptive regions form interfaces at angles that are close to the perpendicular to the light control film. A portion of the incident light intercepting the absorptive region undergoes Total Internal Reflection, and is transmitted through the film. The axial brightness of light passing through the film is increased, the brightness is more uniform within the viewing angle, and the viewing cutoff angle is sharpened.

Claims

1. A light control film, comprising:

a light input surface and a light output surface opposite the light input surface;

alternating transmissive and absorptive regions disposed between the light input surface and the light output surface, each transmissive region having an index of refraction N1, and each absorptive region having an index of refraction N2, where N1−

N2 is not less than 0.005;

a first interface between a transmissive region and an adjacent absorptive region; and

an interface angle θ

1 defined by the first interface and a direction perpendicular to the light output surface, where θ

1 is not greater than 3 degrees.

2. The light control film of claim 1, wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at greater than 80% of the maximum brightness measured at any angle less than 10 degrees from the direction perpendicular to the light output surface.

3. The light control film of claim 1, wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at greater than 80% of the maximum brightness measured at any angle less than 20 degrees from the direction perpendicular to the light output surface.

4. The light control film of claim 1, wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at greater than 90% of the maximum brightness measured at any angle less than 10 degrees from the direction perpendicular to the light output surface.

5. The light control film of claim 1, wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at greater than 90% of the maximum brightness measured at any angle less than 20 degrees from the direction perpendicular to the light output surface.

6. The light control film of claim 1, further comprising a polar viewing cutoff angle, and wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at less than 10% of the maximum brightness measured at any angle greater than the polar viewing cutoff angle.

7. The light control film of claim 6, wherein light incident to the light input surface exits the light output surface with a maximum brightness in a direction perpendicular to the light output surface, and exits the light output surface at less than 5% of the maximum brightness measured at any angle greater than the polar viewing cutoff angle.

8. The light control film of claim 1, wherein N1−

N2 is less than 0.1.

9. The light control film of claim 1, wherein N1−

N2 is between 0.007 and 0.06.

10. The light control film of claim 1, wherein each absorptive region comprises an optically absorptive material selected from a pigment, a dye, or a combination thereof.

11. The light control film of claim 10, wherein the optically absorptive material is a carbon black pigment.

12. The light control film of claim 1, wherein each of the transmissive and absorptive regions comprise a radiation cured (meth)acrylate polymer.

13. The light control film of claim 1, wherein the transmissive region has a second interface with a second adjacent absorptive region, and an interface angle θ

2 defined by the second interface and a direction perpendicular to the light output surface, where θ

2 is not greater than 3 degrees.