Higher transmission light control film comprising a transmissive region and an absorptive region each having a different index of refraction

• US 9,804,311 B2
• Filed: 04/06/2016
• Issued: 10/31/2017
• 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): Lee, Paul
• Application Number:
  US15/092,033
• Publication Number:
  US 20160216420A1
• Time in Patent Office: 573 Days
• 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 collimated lighting assembly, comprising:

a light control film, comprising;

a light input surface;

transmissive and absorptive regions, the transmissive region having an index of refraction N1, and the absorptive region having an index of refraction N2, where N1−

N2 is not less than 0.005,

wherein a first interface between the transmissive region and the absorptive region makes an angle not greater than 3 degrees with a direction perpendicular to the input surface; and

a light source emitting light toward the light input surface.

2. The collimated lighting assembly of claim 1, further comprising a prismatic film disposed between the light source and the light control film.

3. The collimated lighting assembly of claim 1, further comprising a reflective polarizer disposed between the light source and the light control film.

4. The collimated lighting assembly of claim 3, wherein the reflective polarizer is laminated to the light control film.

5. The collimated lighting assembly of claim 3, further comprising a prismatic film disposed between the light source and the reflective polarizer.

6. The light control film of claim 1, wherein the transmissive region has a second interface with a second absorptive region, and the second interface makes an angle of not greater than 3 degrees with the direction perpendicular to the input surface.

7. A liquid crystal display, comprising:

a light control film, comprising;

alternating transmissive and absorptive regions disposed laterally within a plane defined by a light input surface and a light output surface opposite the light input surface, an index of refraction of each absorptive region being less than an index of refraction of each transmissive region by at least 0.005;

a first interface between a transmissive region and a first adjacent absorptive region defining an interface angle θ

₁ measured from a direction perpendicular to the plane of the film, wherein θ

₁ is not greater than 3 degrees;

a light source emitting light toward the light input surface; and

a liquid crystal display module receiving light from the light output surface.

8. The liquid crystal display of claim 7, further comprising a prismatic film disposed between the light source and the light control film.

9. The liquid crystal display of claim 7, further comprising a reflective polarizer disposed between the light source and the light control film.

10. The liquid crystal display of claim 9, wherein the reflective polarizer is laminated to the light control film.

11. The liquid crystal display of claim 9, further comprising a prismatic film disposed between the light source and the reflective polarizer.

12. The light control film of claim 7, 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.