Brightness enhancement film with soft cutoff

• US 5,917,664 A
• Filed: 02/05/1996
• Issued: 06/29/1999
• Est. Priority Date: 02/05/1996
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: O'Neill, Mark B., Cobb, Sanford Jr.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Robinson, Mark A.
• Application Number:
  US08/596,792
• Time in Patent Office: 1,240 Days
• Field of Search: 359/831, 359/834, 359/836, 359/837, 359/454, 359/455, 359/459, 359/625, 359/628, 359/639, 359/640, 359/463, 349/57, 349/62, 349/67
• US Class Current: 359/831
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet

Abstract

A brightness enhancement film has a plurality of linear prisms. The prisms are disposed in pairs, each pair having first and second prisms and each prism has a prism angle and a valley angle. Either the prism angles or the valley angles, but not both, are equal.

Claims

1. A film for enhancing the apparent on axis brightness of a light source said film comprising first and second surfaces, said first surface being a structured surface having a plurality of linear prisms thereon, said prisms being disposed in side by side pairs, each pair having first and second prisms, and each prism having a prism angle and a valley angle wherein either said prism angles or said valley angles of each pair but not both are equal.

2. A film according to claim 1 wherein said prism angles are equal.

3. A film according to claim 1 wherein said valley angles are equal.

4. A backlight for use with a display said backlight comprising:

a light source;

a light pipe positioned to receive light from said light source; and

a film for enhancing the apparent on axis brightness of said backlight, said film comprising first and second surfaces, said first surface being a structured surface having a plurality of linear prisms thereon, said prisms being disposed in side by side pairs, each pair having first and second prisms, and each prism having a prism angle and a valley angle wherein either said prism angles or said valley angles of each pair but not both are equal.

5. A backlight according to claim 4 wherein said prism angles are equal.

6. A backlight according to claim 4 wherein said valley angles are equal.

7. A backlight according to claim 4 further comprising a diffuser between said light pipe and said film.

8. A electronic display comprising:

a light source;

a light pipe positioned to receive light from said light source;

a film for enhancing the apparent on axis brightness of said backlight, said film comprising first and second surfaces, said first surface being a structured surface having a plurality of linear prisms thereon, said prisms being disposed in side by side pairs, each pair having first and second prisms, and each prism having a prism angle and a valley angle wherein either said prism angles or said valley angles of each pair but not both are equal; and

an liquid crystal display module.

9. A display according to claim 8 wherein said prism angles are equal.

10. A backlight according to claim 8 wherein said valley angles are equal.

11. A backlight according to claim 8 further comprising a diffuser between said light pipe and said film.