Abstract: The present invention is directed to a multi display device that can realize a large-sized screen by interconnecting a plurality of display elements. The multi display device comprises at least two flat display elements of which adjacent sides are closely contact each other to make a large-sized screen, housings receiving and supporting the display elements, respectively, light-compensating means for refracting display light from the display elements toward a center area of the adjacent sides thereof, thereby to minimize or remove the non-display area in the screen.

Abstract: Provided is an advertisement apparatus using a light switching device which transmits or shields light according as a power source or heat is supplied or not. The advertisement apparatus includes a light switching device transmitting light when a power source or heat is supplied thereto and shielding light of less than predetermined brightness when a power source or heat is not supplied thereto, or operating in a reverse manner, and an illuminator for illuminating an image onto the light switching device with light whose brightness is greater than the predetermined brightness. The light switching device can be used as the window of a building, and can present images of an advertisement using the illuminator for irradiating light from a projector, for example, to the light switching device. Therefore, the advertisement apparatus using a light switching device can be used for both indoor and outdoor advertising displays.