Plane light source unit

• US 5,126,882 A
• Filed: 11/10/1988
• Issued: 06/30/1992
• Est. Priority Date: 11/12/1987
• Status: Expired due to Term

• Current Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Original Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Inventors: Oe, Makoto, Chiba, Ithussei
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): Dang, Hung Xuan
• Application Number:
  US07/269,723
• Time in Patent Office: 1,328 Days
• Field of Search: 350/167, 350/330, 350/334, 350/338, 350/345
• US Class Current: 359/619
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• 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 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• 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 6/0071 with elongated shape, e.g. tube
• CPC Class Codes: G02B 6/04 formed by bundles of fibres G02B6/24 takes precedence

Abstract

A plane light source unit is provided which comprises a first element having a light incident face at least at one side end thereof and a first light emitting surface extending perpendicularly to the light incident face, the first element further having a reflecting layer provided on a surface thereof opposite to the first light emitting surface, and a second element having a light incident surface which receives the light emitted by the first element and a second light emitting surface through which light is emitted in a predetermined direction, the first light emitting surface and/or the opposite surface of the first element having a directive function to cause incident light through the light incident face to emit through the first light emitting surface in a direction oblique to the direction of the light, the second element having a large number of prism units formed on the light incident surface thereof. The plane light source unit is advantageously used as a backlighting means for a liquid crystal display device or the like.

Claims

1. A plane light source unit, comprising a first element having a light incident face at lest at one side end thereof and a first light emitting surface extending perpendicularly to said light incident face, said first element further having a reflecting layer provided on a surface thereof opposite to said first light emitting surface, and a second element having a light incident surface which receives the light emitted by said first element and a second light emitting surface through which light is emitted in a predetermined direction, at least one of said first light emitting surface and the opposite surface of said first element comprising means having a directive function to cause incident light through said light incident face to emit through said first light emitting surface in two preferential directions oblique to, and on opposite sides of, a normal line thereof, said second element having a large number of prism units formed on said light incident surface thereof, each prism unit having at least one surface positioned for effecting total reflection of the light received by said second element,

wherein the direction of substantially all of the light emitting from said second element makes an angle ranging from 0 degrees to 20 degrees with respect to a normal line of said first light emitting surface of said first element.

2. A plane light source unit according to claim 1, wherein either said first light emitting surface or the opposite surface of said first element has a large number of lens units formed thereon which contribute to the directive function.

3. A plane light source unit according to claim 2, wherein said large number of lens units are convex cylindrical lenticular lenses.

4. A plane light source unit according to claim 2, wherein said large number of lens units are concave cylindrical lenticular lenses.

5. A plane light source unit according to claim 2, wherein said large number of lens units are triangular pole-shaped lenticular lenses.

6. A plane light source unit according to claim 2, wherein said large number of lens units are polygonal pole-shaped lenticular lenses.

7. A plane light source unit according to claim 2, wherein said large number of lens units are anisotropic lenticular lenses.

8. A plane light source unit according to claim 1, wherein said first light emitting surface and/or the opposite surface of said first element has a mat finished surface which extends substantially in parallel to a plane of said reflecting layer and contribute to the directive function.

9. A plane light source unit according to claim 8, wherein a haze of said first element on which said mat finished surface is formed is equal to or greater than 30 percent.

10. A plane light source unit according to claim 1, wherein said first element has a pair of light incident surfaces at two opposing side ends thereof.

11. A plane light source unit according to claim 1, wherein said first element is made of an acrylic resin material.

12. A plane light source unit according to claim 1, wherein said first element is made of a polycarbonate resin material.

13. A plane light source unit according to claim 1, wherein said second element is made of an acrylic resin material.

14. A plane light source unit according to claim 1, wherein said second element is made of a polycarbonate resin material.

15. A plane light source unit according to claim 1, wherein the direction of light emitting from said first element makes an angle equal to or greater than 45 degrees and smaller than 90 degrees with respect to a normal line of said first light emitting surface of said first element.