Luminance control film

• US 6,091,547 A
• Filed: 04/30/1997
• Issued: 07/18/2000
• Est. Priority Date: 09/27/1994
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Gardiner, Mark Edward, O'Neill, Mark Brian, Wortman, David Lee
• Primary Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/846,955
• Time in Patent Office: 1,175 Days
• Field of Search: 359/625, 359/619, 359/640, 359/569, 359/574, 359/621, 359/622, 359/628, 40/442, 345/139, 385/129
• US Class Current: 359/625
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: G02B 5/008 Surface plasmon devices diffractive gratings with a pitch less than or comparable to the wavelength G02B5/1809; surface plasmons in integrated optics G02B6/1226; optical analysis of materials by means of surface plasmons G01N21/553
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Abstract

The luminance control film includes a periodic array of optical structures which are small with respect to the wavelength of light. Scattering and diffractive effects result in improved off-axis illumination intensity in comparison with brightness enhancement optical devices having larger scale optical structures.

Claims

1. A luminance control film assembly comprising:

a first luminance control film, and a second luminance control film;

said first luminance control film having a first prism axis;

said second luminance control film having a second prism axis;

wherein, said first prism axis and said second prism axis are not parallel, thereby forming a crossing angle theta;

each of said first and said second luminance control films having a body portion having a first surface and a second surface;

each of said first surfaces having a linear array of prisms characterized by pitch less than 30 micrometers whereby diffractive effects will cause a soft luminance dropoff as a viewer moves off a central viewing axis;

each of said second surfaces being planar;

said first luminance control film stacked on said second luminance control film such that the prisms of said first surface of said first luminance control film are proximate said second surface of said second luminance control film.

2. The luminance control film assembly of claim 1 wherein theta is greater than 45 degrees and less than 135 degrees.

3. The luminance control film assembly of claim 1 wherein theta is 90 degrees.

4. An optical assembly for providing illumination comprising:

a light source having a reflectivity greater than zero and emitting light;

a luminance control film assembly located proximate said light source;

said luminance control film assembly having a first luminance control film, and having a second luminance control film;

said first luminance control film having a first prism axis and said second luminance control film having a second prism axis;

wherein, said first prism axis and said second prism axis are not parallel, thereby forming a crossing angle theta;

each of said first and second luminance control film having a body portion, each of said body portion having a first surface and having a second surface;

each of said first surfaces having a linear array of prisms characterized by pitch less than 30 micrometers;

each of said second surfaces being planar;

said first luminance control film stacked on said second luminance control film such that the prisms of said first surface of said first luminance control film are proximate said second surface of said second luminance control film;

said second surface of said first luminance control film proximate said light source.

5. An optical assembly for displaying information to a viewer, comprising:

a light source having a reflectivity greater than zero;

a display panel;

a luminance control film assembly located between said light source and said display panel;

said luminance control film assembly including a first luminance control film and a second luminance control film each of said luminance control films having a structured surface and said luminance control films being crossed at an angle theta, where theta is greater than 45 degrees and less than 135 degrees;

at least one of said luminance control films having structures of a size such that diffractive effects will cause a soft luminance dropoff as a viewer moves off a central viewing axis.

6. The optical assembly of claim 5 wherein theta is 90 degrees.