Enplas Corporation

Other

Yasuhiro Koike

Kayoko Watai

Tsuyoshi Ishikawa

Kazuaki Yokoyama

Hiromi Sasako

Takayuki Arai

Kayoko Masaki

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

A light regulation element regulates both the travelling direction and diffusion state of a light emitted from a surface light source device. Lights from a cylindrical light source,such as a cold cathode tube is introduced in a light guide,. The light guide,has an emission surface,on the side opposite to a reflection element,, and a light regulation element,is arranged in opposition to the emission surface,. Protrusions,are formed on one surface or both surfaces of the light regulation element,. Coated on the surface on the light emission side of the light regulation element,is a light diffusion layer,. The turbidity of the light diffusion layer,falls within a range from 1900 cm,to 2400 cm,. The light emitted from the emission surface,of the light guide penetrates the light regulation element,, thereby causing the light travelling direction to be regulated. Then, the light whose travelling direction has been regulated penetrates the light diffusion layer,, thereby causing a light diffusion. The light diffusion layer,is formed, for example, by mixing fine particles of a glass having a light penetrability or of a synthetic resin such as acryl and silicone, or fine hollow particles of glass, acryl resin or the like, or air bubbles in a coating material having a light penetrability.

Light regulation device

An effective radiation region of a rod-type light source,having circumferences of electrodes,A and,B has a length AR. A light diffusible surface,D (or,D&prime;) is formed on the rear surface (or emitting surface) of a light guide plate,to which a light is supplied from the rod-type light source,The light diffusible surface,D (,D&prime;) has an emission quantity suppressing region AR,emission quantity promoting region AR,and light quantity control region AR,The emission quantity suppressing region AR,is formed in the vicinity of an incidence surface of the light guide plate,so as to have a dimension nearly equal to AR. The emission quantity promoting region AR,is formed in the vicinities of both the ends of the emission quantity suppressing region AR,The emission quantity promoting region AR,is formed so as to have light scattering power which is increased locally near the incidence surface. The light quantity control region AR,is formed so that light scattering power is increased gradually according to a distance from the incidence surface. The emission quantity suppressing region AR,prevents excessive light emission, and the emission quantity promoting region AR,supplements insufficient light emission in the circumferences of the electrodes,A and,B.

Surface light source device of side light type

A surface light source device using a light conducting member, in which a multiplicity of concave portions are formed on an opposite surface of a light emitting surface of the light conducting member and the concave portions are arranged to have specific shapes to obtain a bright surface light source with a uniform brightness. A light diffusing material is fulfilled within the concave portions of the light conducting member so that a more uniform brightness can be obtained in an easy manner.

Surface light source device

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 surface light source device of side light type controls the intensity of light rays emitted therefrom. The surface light source device of side light type comprises a light scattering guide 20 having a light incidence surface 22, a light emission surface 23 and an inclined surface 25. The device further includes a primary light source L arranged around one side of the light incidence surface 22, a silver foil R surrounding the primary light source L, a prism sheet 4 arranged along the light emission surface 23, and a silver foil S arranged along the inclined surface 25. The inclined surface 25 of the light scattering guide 20 composed of three sections I, II and III. The section I is a convex cylindrical surface section having a radius of curvature of 330 mm. The tangential direction at the end of the guide on the side of the light incidence surface 22 is parallel to the light emission surface 23. The tangential direction at the boundary between the sections I and II is inclined at an angle 4.degree. with respect to the light emission surface 23. The sections II and III are straight sections whose inclinations are 4.degree. and 3.6.degree. with respect to the light emission surface 23, respectively. The distribution of emitted light intensity from the surface light source device has a higher luminance around its center. Various distributions of emitted light intensity are provided by varying the transition of inclinations of the inclined surface (particularly refer to FIG. 13).

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.

A surface illuminant device includes a light transmitter, light sources disposed adjacent to entrance ends of the light transmitter, and a reflecting sheet disposed below a lower surface of the light transmitter. The entrance ends of the light transmitter are configured as rough surfaces, and thereby unevenness of brightness of the surface illuminant device can be lessened.

Surface illuminant device

A transparent member having a multiplicity of prism-like convex portions which are aligned in parallel to each other and formed on at least one of surfaces of the member; the member is used to be disposed between a light emitting surface side of a surface light source device and a liquid crystal display device; and by using the member, it is possible to illuminate the liquid crystal display device in a bright and uniform manner and to prevent that any stripe pattern is appeared.

Prismatic member with coarsened portions or triangular prismatic and

A corner supply type plane light source device having a simple structure and capable of forming a uniform luminescent part with a small power consumption is disclosed. The corner supply type plane light source device comprises a flat-plate light-scattering light guide 1, diffusion reflective sheets 2, 4, and LEDs 3 disposed at corners. The light-scattering light guide 1 is composed of a material provided with a uniform scattering power, and the effective scattering irradiation parameter E and the correlation distance a satisfy the conditions of 9.ltoreq.E[cm.sup.-1 ].ltoreq.100 and 0.06.ltoreq.a[.mu.m].ltoreq.35. Turning on the LEDs 3, light is supplied from each corner. The LED radiation light having directivity immediately undergoes the scattering in the light-scattering light guide 1 and the propagation direction is expanded in the lateral and vertical directions, and also undergoes the internal reflection on the bottom 12 and sides 13, and diffusion reflection by the diffusion reflective sheets 2, 4. As a result, the light propagates throughout the entire light-scattering light guide 1. The light surpassing the critical conditions on the light exit surface 11 through this process is emitted from the light exit surface 11 to provide a light flux F. (Representative drawing) FIG. 4

Corner supply type plane light source device

A surface illuminate device illuminates a liquid crystal display panel by diffused light produced through a diffusing plate disposed on the front of an illuminant section. A prism sheet having many triangular prisms is disposed on the exit side of the diffusing plate so that the longitudinal direction of each prism is nearly parallel to the plane of polarization of a polarizing plate placed on the prism sheet side of the liquid crystal display panel. Thus, the surface illuminant device can provide bright illumination suitable for the backlight of the liquid crystal display panel.

Growing community of inventors

Hasuda, Japan

Kayoko Watai