Abstract: A substrate 12 consists of a transparent plastic made from polylactic acid as a material, and an optical disc 10 provided with the substrate 12 is heated up to a heat deflection temperature. As a result, the substrate 12 is softened, and pits 22 formed on a signal recording surface 20 of the substrate 12 are erased. Thus, data recorded on the optical disc 10 is unreadable, and even if the disc 10 is discarded, the optical disc 10 is never read carelessly in accordance with the disposal of the optical disc.

Abstract: On a data recording region, an aluminum reflective film is formed together with a reflective film forming a pattern on an outer circumferential side of the data recording region. Although aluminum identical to the material of the reflective film on the data recording region can be employed for the reflective film on the outer circumferential region, gold, titanium and the like can also be used. Therefore, an optical disk that has a unique pattern formed at an outer circumferential region that was not conventionally used can be fabricated at a low cost.

Abstract: An outer light collecting portion 10 which sticks out of a light emission surface 14 to the light emission direction at the same time when a light guide plate is formed by resin forming with a mold. An area of a surface for collecting outer light is larger than that of a conventional light guide plate so as to collect outer light effectively. Light from a light source which is incidence through a light incident surface 12 reflects from a light reflection surface 13 and two side surface 11 of a light guide plate 1, and is emitted as synthesized light having the even directivity from a light emission surface 14.

Abstract: The present invention provides a light guide plate and a surface light source using the light guide plate to improve the utilization efficiency of external light and light from an internal light source and to achieve thinner width of the light guide plate. In this invention, internal light emitted from an internal light source 3 is brought to the inside of the light guide plate 1 from an internal light collecting surface 16 in the light guide plate 1, and external light such as natural light is brought to the inside of the light guide plate 1 from an external light collecting portion 11. The light brought to the inside of the light guide plate reflects and is converged several times from a reflective plate 15 mounted to the outside of the light reflective surface 14 and three side end surfaces 12 and is emitted from the light emissive surface 13 of the light guide plate 1 to a diffusing plate 6.

Abstract: In a method of producing a lightguide plate for surface light source according to the present invention, a plate-shaped metal mold for defining the shape of a part of a cavity of a molding die and particularly, the shape of a light emitting surface of the lightguide plate for surface light source (a concavo-convex shape, a lenticular lens shape, etc.) is provided so as to be replaceable, to form a cavity having a desired shape by the replacement of the plate-shaped metal mold. Resin liquid is injected into the cavity, its resin liquid is solidified, and the resin is then released from the cavity. Consequently, a lightguide plate for surface light source having a desired shape and particularly, having its light emitting surface in a desired shape is produced.

Abstract: A disc is provided which includes a disc body of disc shape having a center hole. An information recording area is formed on one side surface of the disc body. The information recording area has information thereon read by reflection of laser light. The information recording area has an inner circumferential edge positioned adjacent to the center hole. The disc body has a radius ranging from 39 mm to 80 mm, the center hole has a radius ranging from 7.5 mm to 7.55 mm, and the inner circumferential edge of the information recording area being positioned to extend from a radius of 15 mm to 22 mm from the center of the disc body.

Abstract: A light guide plate is provided including a first lens portion comprising a plurality of recessed or projected lenticular unit lenses formed of the same resin as that of the light guide plate on a light emission surface. The plurality of lenticular unit lenses in the first lens portion are triangular prism portions whose respective vertexes have an angle of 125.degree. to 165.degree. and are so arranged that their respective ridge lines are nearly parallel to each other. Such construction makes it possible to set the number of lenticular lens sheets used to one or to further eliminate the necessity of the lenticular lens sheets, so that the cost of parts and the fabrication cost of the light guide plate can be reduced.