Abstract: There are provided a surface light source having uniform and high brightness independently whether the light source is small or large while using semiconductor light emitting devices (LEDs), and an electrically illuminated signboard using the surface light source, which is thin and capable of uniform display and which operates with low electricity consumption. LEDs (12) of a dome type are arranged on four corners at a bottom surface of a box body (11) of a tray shape whose bottom surface is quadrilateral, whose upper side is open, on an inner surface of which a light reflection member (11b) is provided, and whose side walls (11c) are inclined outward. The LEDs (12) are arranged so as to mainly irradiate a region between a vertical plane on a diagonal line (N) of the bottom surface and one side wall (11c), and the region irradiated by each of the LEDs (12) of the dome type arranged on the four corners rotates individually and sequentially in a specific direction (same direction) in the box body (11).

Abstract: LEDs (7) are arranged on at least opposite two corners of a bottom surface of a box body (11) of a tray shape whose bottom surface is quadrilateral, whose upper side is open, on an inner surface of which a light reflection member (11b) is provided, and whose side walls (11c) are inclined outward, so as to irradiate inside of the box body, wherein a plurality of LEDs (71) are arranged so that a region irradiated by each of the LEDs (71) rotates sequentially in a specific direction (same direction). As a result, there can be obtained a surface light source having high brightness and uniformity in an arbitrary size whether the light source is small or large while using semiconductor light emitting devices (LEDs), and an electrically illuminated signboard using the surface light source, which is thin and capable of uniform display and which operates with low electricity consumption.

Abstract: LEDs (7) are arranged on at least opposite two corners of a bottom surface of a box body (11) of a tray shape whose bottom surface is quadrilateral, whose upper side is open, on an inner surface of which a light reflection member (11b) is provided, and whose side walls (11c) are inclined outward, so as to irradiate inside of the box body, wherein a plurality of LEDs (71) are arranged so that a region irradiated by each of the LEDs (71) rotates sequentially in a specific direction (same direction). As a result, there can be obtained a surface light source having high brightness and uniformity in an arbitrary size whether the light source is small or large while using semiconductor light emitting devices (LEDs), and an electrically illuminated signboard using the surface light source, which is thin and capable of uniform display and which operates with low electricity consumption.