Enplas Corporation

Yasuhiro Koike

Other

Hiromi Sasako

Kayoko Watai

Kayoko Masaki

Tsuyoshi Ishikawa

Takayuki Arai

An improved surface light source device applicable to back lighting of a liquid display. In the surface light source device, a plate-shaped optical block ( ) is disposed along an emitting surface of a plate-shaped optical member ( ), to which illumination light is to be supplied from a primary light source ( ), and has on at least one of its outer and inner sides a directivity modifying surface for modifying directivity of illumination light emitted from the emitting surface. Directivity modifying surface occupies at least part of the whole area of the optical block except a predetermined range (AR ) from a position aligning to the incidence surface of the plate-shaped optical member ( ). The optical block ( ) and the plate-shaped optical member ( ) may be held in a unitary form by a holding mechanism formed integrally with the optical block ( ) and/or the plate-shaped optical member ( ). One end of a reflection member about the primary light source ( ) may be pinched between the optical block ( ) and the plate-shaped optical member ( ).

Surface light source device

A surface light source device has a narrowed visual field and increased brightness. The surface light source device can be applied to a liquid crystal display. The back side of a fluorescent lamp is covered with silver foil. Light emitted from the lamp enters a wedge-shaped light guide plate through its incident surface. The light guide plate is designed so that directional light exits from the guide plate. When the light is guided toward a thin-walled end surface through the light guide plate, the light is scattered, reflected, and undergoes other action. Collimated light flux gradually exits from the exiting surface. The light flux passes through two prism sheets successively. As a result, the direction of propagation of the light is restricted in two dimensions. The light flux of increased brightness is directed to the liquid crystal panel. V-shaped channels formed in the prism faces of the two prism sheets PS,, PS,are arrayed in two mutually perpendicular directions while facing outward. The prismatic vertical angles of the two sheets PS,, PS,have various desirable combinations of values. For example, where the first sheet PS1 is disposed vertical to the lamp, the vertical angles of the two sheets PS,, PS,are preferably 90&deg; and 70&deg;, respectively.

Surface light source device and liquid crystal display

In a surface light source device of side light type applied to a liquid crystal display or the like, particularly, a surface light source device of side light type with emitting directivity, irregularities in luminance of output light are prevented from occurring in the vicinity of an incidence surface. In a surface light source device of side light type 10, a diffusible area M1 to diffusely reflect illumination light and an absorptive area (on a reflection sheet 11) to restrain the illumination light from reflection from bands in the vicinity of the incidence surface oppositely with the emitting surface of a light guide plate 12 with emitting directivity. It is thereby possible to reduce irregularities in output light luminance occurring in the vicinity of the incidence surface T. A light reflection member 18 may be arranged so as to extend over an edge EU of the emitting surface of the light guide plate 12, with directivity of illumination light emitted from the the emitting surface being modified. A light blocking material may be arranged on a side end surface of a light control member 13 to prevent illumination light emitted from a light source from being directly incident. Illumination light incident on the edge EU of the light guide plate may be blocked by a light blocking member 18. The diffusible area may be formed by roughening a surface opposite with the emitting surface.

Surface light source device of side light type

In a surface light source device of side light type applied to a liquid crystal display device, etc., more specifically a surface light source device of side light type having a directivity emitting characteristic, a bright-and-dark-band contrast which is generated in a vicinity of an incidence surface is prevented. In a surface light source device of side light type, light diffusible areas composed on main-and-supplementary diffusible areas are formed on a slanted surface and an emitting surface of a light guide plate having a directivity emitting characteristic. A silver sheet is fixed to a projected portion of a prism sheet along an upper edge, and an illumination light which arrives at the upper edge from a fluorescent lamp is blocked so that the strong brightening of the upper edge is prevented. An illumination light form a lower edge is blocked by a reflector or a frame and reflected diffusively. The light diffusible area may be formed on one of the slanted surface and the emitting surface. Moreover, the light diffusible area may be formed on an additional element such as a reflection sheet.

Surface light source device of side light type with belt-like diffusible

A wedge-shaped light scattering guide plate 10 employed in a surface light source device of side-light type has a width equal to the length of a primary light source element. An incidence end surface 11 is formed as a matte surface (rough surface) by a matting process. The incidence end surface 11 is provided with roughness which is uniform or increases toward end portions. The roughened incidence end surface 11 produces scattered light in the vicinity of the incidence end surface, especially at both side end portions. The scattered light contributes to elimination of variation in luminance which tends to occur in the vicinity of the incidence end surface 11. A light diffusing plate may be interposed between the primary light source element and the light scattering guide plate.

A method of generating a dual light flux, and a surface light source device for use in a display with a dual preferential viewing direction. Light of a fluorescent lamp is introduced from a light incidence surface to inside of a wedge shape light scattering guide with exiting directivity. While this light is led toward an end surface, it is emitted from a light outgoing surface as an illuminating light flux with exiting directivity to reach a prism sheet as a primary light flux. V-shape grooves giving a prism vertical angle of 90.degree. are formed to face inward and perpendicular to the lamp on the inner surface of the prism sheet, while V-shape grooves giving a prism vertical angle 64.degree. are formed parallel to the lamp on the outer surface of the prism sheet.

Surface light source device of dual light flux generation

In a surface light source device of side light type, occurrence of irregularities in luminance is prevented in the vicinity of an incidence surface 10 of a light guide plate 1. A light source element 2 is disposed on a lateral side of the light guide plate 1 and the light introduced into the light guide plate 1 through the incidence surface 10 is emitted through an emission surface 11. The light comes outside after undergoing the action of an additional element 3 (such as a priority traveling direction correcting action) and is applied to, for example, back lighting in a liquid crystal display. A reflection sheet such as a silver foil is disposed along a rear surface 12. The rear surface 12 is treated in various manners in order to reflect the light toward the emission surface 11. Another reflection sheet 20 is disposed as a reflector surrounding the light source element 2 from the back side. A case 4 partially projects inward along the incidence surface 10 to form light shielding walls 8, 9. The shielding walls 8, 9 are adapted to prevent light emitted from the light source element 2 from intruding through gaps G1 to G4 between the elements, or through an end surface of an end edge portion 3a of the additional element.

Growing community of inventors

Tokyo, Japan

Hiromi Sasako