Plane light source unit

• US 5,711,589 A
• Filed: 04/10/1996
• Issued: 01/27/1998
• Est. Priority Date: 06/22/1993
• 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: Chiba, Issei, Oe, Makoto
• Primary Examiner(s): Husar, Stephen F.
• Application Number:
  US08/630,467
• Time in Patent Office: 657 Days
• Field of Search: 362/31, 362/32, 362/26, 362/330
• US Class Current: 362/620
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• 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 6/004 Scattering dots or dot-like elements, e.g. microbeads, scattering particles, nanoparticles
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

A plane light source unit which may be advantageously used as a backlighting means for a liquid crystal display device, and which includes a transparent light guide having a side end surface as a light incident surface, a surface perpendicular to the light incident surface as a light emitting surface, and a light reflecting layer provided on an opposite surface to the light emitting surface; and a second element having a large number of prism units formed on the light emitting surface of the transparent light guide which receives the light emitted from the transparent light guide and emits the light in a predetermined direction; wherein at least one of the light emitting surface and the opposite surface of said transparent light guide has a directional light emitting function which emits the incident light from the light incident surface of the transparent light guide in an oblique direction to the incident light and has a regulation function which makes the luminance of the light through the light emitting surface uniform over the whole surface thereof.

Claims

1. A plane light source unit, comprising:

a transparent light guide having a side end surface as a light incident surface, a surface perpendicular to the light incident surface as a light emitting surface, and a light reflecting layer provided on an opposite surface to the light emitting surface; and

a second element having a large number of prism units provided on the light emitting surface of the transparent light guide which receives light emitted from the transparent light guide and at least either one of surfaces provided on each of said prism units providing a total reflection of the light emitted from the transparent light guide whereby each of said prism units emits the light in a predetermined direction;

wherein at least one of the light emitting surface and the opposite surface of the transparent light guide has a directional light emitting function which emits incident light from the light incident surface of the transparent light guide as a directional light having an angle of 60°

-70°

with respect to a line perpendicular to the light incident surface of the transparent light guide and has a regulation function which makes a luminance of the light through the light emitting surface uniform over a whole surface thereof;

the transparent light guide having roughened surface with the directional light emitting function opposite to the light emitting surface, the roughened surface having flat areas which form a surface of total reflection so that the ratio of the flat areas to the total area increases as the distance from the light incident surface decreases, so that the transparent light guide regulates the luminance of the light to be uniform over the entire light emitting surface.

2. A plane light source unit as claimed in claim 1;

wherein the transparent light guide is produced by injection molding.

3. A plane light source unit as claimed in claim 1;

wherein the haze value of the roughened surface formed on the transparent light guide is not less than 30%.

4. A plane light source unit as claimed in claim 1;

wherein the transparent light guide comprises an acrylic resin.