Abstract: An internally illuminated sign device according to an embodiment includes a sign panel and a lighting unit that applies light from the rear side to the sign panel. The sign panel includes a prism layer, an air layer disposed on an interface on the rear side of the prism layer, a first colored display layer of optical transparency disposed on the front side of the prism layer and having a predetermined shape, and a second colored display layer of optical transparency disposed on the rear side of the air layer in a shape visible the same as the first colored display layer. The second colored display layer is disposed at a position laid over the first colored display layer when the sign panel is seen in front.

Abstract: An optical layer for a light control type solar photovoltaic module, a light control type solar photovoltaic module, and a light control type solar photovoltaic panel have an excellent directionality to the sunlight are provided. An optical layer 4 for a light control type solar photovoltaic module includes an entrance surface 11 and an exit surface 12 and is arranged opposite photovoltaic cells 6 that convert light into electric energy.

Abstract: An optical layer for a light control type solar photovoltaic module, a light control type solar photovoltaic module, and a light control type solar photovoltaic panel having an excellent directionality to the sunlight are provided. An optical layer 4 for a light control type solar photovoltaic module includes an entrance surface 11 and an exit surface 12 and is arranged opposite photovoltaic cells 6 that convert light into electric energy. A number of prismatic optical elements are formed in at least one of the entrance surface 11 and the exit surface 12, each of the prismatic optical elements is on a common plane S1 defined by a common base shared by the prismatic optical elements adjacent to each other, and a prism axis 7 of each of the prismatic optical elements is inclined toward a predetermined direction with respect to a direction perpendicular to the common plane.