A guide plate having an emission face for light-output, a back face and an incidence end face for light-input is improved. The emission face is provided with a plurality of projections each of which includes a blunt top portion. The projections have shapes such as like domes or like ridges. Each dome-like projection has a diameter ranging, for example, from 50 .mu.m to 200 .mu.m and has a height ranging, for example, from 0.1 .mu.m to 50 .mu.m. The dome-like projections distribute with density such that one or more projections are allocated, for example, per box of 0.5 mm.times.0.5 mm. Ridge-like projections run so as to have a crossing angle, for example, 60 degrees or more with respect to the incidence end face. Ratio of repetition pitch of the ridge-like projections to their height falls within a range, for example, from 5000:1 to 1:1. Height of each ridge-like projection may fall within a range from 1 .mu.m to 100 .mu.m. The emission face may be further provided with light scattering pattern consisting of a plurality of scattering elements to scatter illumination light. The improved guide plate is employed in a surface light source device of side light type. The surface light source device may be applied to a LCD having a LCD panel, which is illuminated by the light source device.

A spread illuminating apparatus 1 according to the present invention includes a transparent substrate, a linear light source made up of a light reflector 16 as an optical path conversion portion and/or a light conductor 13 made of a linear transparent material and having optical path conversion portion at least, on either side and disposed closely along at least one side end surface 3 of a transparent substrate 2, and a dot-shaped light source 12 disposed on one end portion 14 of the light conductor 13. The light emitted from the dot-shaped light source 12 enters the light conductor 13/or reflected on the light reflector, and the light emitted from a surface 18 opposing to the transparent substrate 2 enters the transparent substrate 2, to thereby become a linear light source as a whole. Accordingly, since a fluorescent lamp which has been employed as a conventional light source is not used, impact resistance is improved, and illumination is enabled at a low voltage.

A backlight assembly is disclosed having a light pipe and at least one light source located at an edge of the light pipe. The light pipe has a back surface and a front surface opposite the back surface. The light pipe also has one or more light directing, diffusing, turning, or brightness enhancing film layers adjacent the front surface. The light pipe also has an integral surface diffuser microstructure molded, embossed, or otherwise replicated in the front surface of the light pipe.

An edge-lit illumination system comprising a light transmitting sheet (10) which has a surface treatment, capable of reflecting or scattering light, on at least one of its opposing surfaces (11, 12), a light source (13) positioned in proximity to, and adjacent to, an edge of this sheet, and a reflective surface (14) positioned adjacent to an edge of the sheet, at an obtuse angle (18) to the plane of the sheet and extending away from one surface of the sheet. The reflective surface is preferably disposed adjacent to the edge of the light transmitting sheet having the light source adjacent to it. The obtuse angle preferably ranges from 100 to 145 degrees. This invention gives an increase in the area of illumination across the light transmitting sheet.

A sheet light emitting apparatus, including a light guiding plate of a translucent material and having light receiving and light emitting surfaces, a light source disposed to face the light receiving surface, and a prism structure provided on the light receiving surface, the prism structure having plural kinds of prisms having different apex angles.