Patent ID: 8836889

Claim:
A transparent display device, comprising: a light guide plate formed with a plurality of concave patterns at the lower surface thereof to totally reflect polarized light entered in a lateral direction while transmitting natural light entered from a lower direction therethrough; a light source disposed in a lateral direction of the light guide plate to emit visible light including a first and a second polarized light; a first polarizing plate disposed at a lateral portion of the light guide plate to transmit either one of the first and second polarized lights through to the light guide plate; a liquid crystal panel arranged directly above an upper surface of the light guide plate without any intervening structure between a first substrate of the liquid crystal panel and the light guide plate, wherein the liquid crystal panel drives liquid crystals to change the phase of the polarized light; and a second polarizing plate on a second substrate of the liquid crystal panel, the second polarizing plate being arranged to control an amount of the polarized light according to the changed phase of the polarized light, wherein the natural light is entered from a lower surface of the light guide plate, and at this time the natural light is entered to the liquid crystal panel via a portion between the concave patterns of the light guide plate so that the transparent display device is maintained at a transparent state regardless of whether or not being displayed by the natural light and an object located at a lower portion of the light guide plate is allowed to be viewed by the user at the front side, wherein intervals D 1 and D 2 between the concave patterns formed in a second region P 2 of the plurality of concave patterns located away from the light source on the basis of a central portion of the lower surface of the light guide plate are formed narrower than the intervals D 1 and D 2 between the concave patterns formed in a first region P 1 thereof located adjacent to the light source, and wherein the plurality of concave patterns have an oval-shaped structure, and the concave patterns formed in the first region (P 1 ) of the plurality of concave patterns which is located near to the light source on the basis of a central portion of the light guide plate is 100-150 μm in horizontal length (L 1 ) and 50-150 μm in vertical length (L 2 ), and the concave patterns formed in the second region (P 2 ) which is located away from the light source 10 on the basis of a central portion of the light guide plate is 100-200 μm in horizontal length (L 1 ) and 50-150 μm in vertical length (L 2 ).