Back-lit display

• US 4,874,228 A
• Filed: 01/03/1989
• Issued: 10/17/1989
• Est. Priority Date: 03/24/1987
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Miller, Richard A., Aho, Kenneth A., Melby, Jeffrey J.
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): Hagarman, Sue
• Application Number:
  US07/292,762
• Time in Patent Office: 287 Days
• Field of Search: 362/299, 362/301, 362/303, 362/304, 362/309, 362/327, 362/347, 362/348, 362/349, 362/339, 362/31, 362/255, 362/256, 362/23, 362/26, 362/29, 350/338, 350/339 D, 350/345
• US Class Current: 349/62
• CPC Class Codes: A01N 37/26 containing the group; Thio analogues thereof
• CPC Class Codes: F21S 43/315 using total internal reflection
• CPC Class Codes: F21S 43/40 characterised by the combination of reflectors and refractors
• CPC Class Codes: F21V 7/00 Reflectors for light sources characterised by cooling arrangements F21V29/505
• CPC Class Codes: F21V 7/0091 using total internal reflection
• CPC Class Codes: F21Y 2103/00 Elongate light sources, e.g. fluorescent tubes
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• 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 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G09F 13/0422 Reflectors
• CPC Class Codes: G09F 13/14 Arrangements of reflectors therein
• CPC Class Codes: G09F 2013/145 curved reflectors

Abstract

A back-lit display utilizes a light transmissive film having a smooth surface and a structured surface. The structured surface has a series of triangular prisms running parallel or concentric to one another. A reflector is placed adjacent to the smooth surface so that light entering the film at an angle that is close to parallel to the smooth surface will emerge from the film at a predetermined angle with respect to the incoming beam. A display, that could be a liquid crystal display, is positioned so that light reflected by the film passes through it.

Claims

1. A back-lit display comprising:

a housing defining an optical cavity having an optical window;

a light reflecting film in said optical cavity, said light reflecting film having first and second major surfaces, said first surface being a structured surface having a plurality of triangular prisms thereon and said second surface being a smooth surface, and a light reflecting means adjacent said second surface for reflecting light approaching said second surface from said first surface;

a first light source positioned so that light rays approach said film in a direction that is almost parallel to said second surface of said film; and

display means in said optical window.

2. The back-lit display of claim 1 wherein said display means includes a liquid crystal display.

3. The back-lit display of claim 1 further comprising light diffusing means between said reflective film and said display means.

4. The back-lit display of claim 1 wherein said light source is positioned so that light rays approach said film in a direction that makes an angle of no more than 20°

with said second surface.

5. The back-lit display of claim 1 further comprising a second light source positioned so that light rays approach said film in a direction that is almost parallel to said second surface of said film, said first and second light source being positioned adjacent opposite ends of said film.

6. The back-lit display of claim 5 wherein said display means includes a liquid crystal display.

7. The back-lit display of claim 5 further comprising light diffusing means between said reflective film and said display means.

8. The back-lit display of claim 5 wherein both of said light sources are positioned so that light rays approach said film in a direction that makes an angle of no more than 20°

with said second surface.

9. The back-lit display of claim 8 wherein said display means includes a liquid crystal display.

10. The back-lit display of claim 9 further comprising light diffusing means between said reflective film and said display means.

11. The back-lit display of claim 1 wherein said light source is positioned adjacent one end of said film and said film curves so that said end of said film adjacent said light source is more distant from said display means than the opposite end of said film.

12. The back-lit display of claim 11 wherein said display means includes a liquid crystal display.

13. The back-lit display of claim 11 further comprising light diffusing means between said reflective film and said display means.

14. The back-lit display of claim 11 wherein said light source is positioned so that light rays approach said film in a direction that makes an angle of no more than 20°

with said second surface.

15. The back-lit display of claim 14 wherein said display means includes a liquid crystal display.

16. The back-lit display of claim 15 further comprising light diffusing means between said reflective film and said display means.

17. The back-lit display of claim 1 wherein said light source comprises:

a light reflecting film having first and second major surfaces, said first surface being a structured surface having a plurality of triangular prisms thereon and said second surface being a smooth surface and a light reflecting means adjacent said second surface for reflecting light approaching said second surface from said first surface; and

a light emitting means positioned so that light rays approach said light source reflecting film in a direction that is almost parallel to said second surface of said light source reflecting film.

18. The back-lit display of claim 17 wherein said display means includes a liquid crystal display.