Mitsubishi Rayon Company, Limited

Makoto Oe

Issei Chiba

Ithussei Chiba

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.

Plane light source unit

A box-type planar light-source device has incorporated therein a linear light source and is provided with a reflecting surface and a multi-prism sheet. The reflecting surface has such function that a major portion of a light reflected by the reflecting surface is obliquely incident upon the multi-prism sheet. The multi-prism sheet has its inner surface formed with a group of prisms so arranged as to extend in parallel relation to the light source and having such function that the light incident directly or obliquely in reflection outgoes in concentration toward a predetermined direction. Accordingly, so as to eliminate portion by the fact that the light outgoing at an angle separated from the normal direction converges at the dark portion. A dark-portion removing sheet for eliminating a dark portion at a location immediately above the light source is arranged on the side of the front face of the multi-prism sheet. An illumination apparatus can satisfactorily exhibit its optical performance by incorporation of the planar light-source device as illumination apparatuses of various display devices. The display devices include an internal-illumination type display device, a liquid-crystal display device, a display device mounted to an automatic vending machine, an observation device for a film, or an illumination apparatus mounted to a wall surface of a building.

Planar light-source device and illumination apparatus using the same

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.

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Kawasaki, Japan

Makoto Oe