Plane light source unit

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 emitting 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.

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Claims

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..Iadd.

16. A plane light source unit, comprising a first element having a light incident face at least 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 a preferential direction oblique to 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..Iaddend..Iadd.17. A plane light source unit, comprising a first element having a light incident face at least 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 a roughened surface having a directive function to cause incident light through said light incident face to emit through said first light emitting surface in a preferential direction oblique to 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..Iaddend.
Referenced Cited
U.S. Patent Documents
1535985 August 1925 Clark
2855523 January 1958 Berger
3740119 June 1973 Sakurai et al.
3840695 October 1974 Fischer
4043636 August 23, 1977 Eberhardt et al.
4126383 November 21, 1978 Doriguzzi et al.
4714983 December 22, 1987 Lang
4798448 January 17, 1989 Van Raalte
4958911 September 25, 1990 Beiswenger et al.
Foreign Patent Documents
0167721 November 1985 EPX
58-159517 September 1983 JPX
Other references
  • IBM Technical Disclosure Bulletin, vol. 29, No. 11, Apr. 1987, pp. 4838-4839, New York, N.Y., "Backlighting for liquid crystal display".
Patent History
Patent number: RE35704
Type: Grant
Filed: Jun 29, 1994
Date of Patent: Dec 30, 1997
Assignee: Mitsubishi Rayon Co., Ltd. (Tokyo)
Inventors: Ithussei Chiba (Tokyo), Makoto Oe (Tama)
Primary Examiner: Hung X. Dang
Application Number: 8/267,380
Classifications
Current U.S. Class: By Surface Composed Of Lenticular Elements (359/619); 359/36; 359/40
International Classification: G02B 2700; G02F 11335;