Patent ID: 8215818
Filing Date: 2012-07-10
Classification: G02F,H05B

Abstract:
1. A light box, for backlighting of liquid crystal displays, the light box comprising: a case having a bottom and an opening facing the bottom; at least a lightguide plate disposed in the case, the lightguide plate having two opposed main faces and at least two edges, and a light-diffusing optical structure formed on the main face proximate the bottom of the case for diffusing the light propagating in the lightguide plate; at least a printed circuit on the bottom side of the case parallel to the bottom of the case; a plurality of light-emitting diodes placed linearly along one of the edges of the lightguide plate, the light emitted by the light-emitting diodes entering the lightguide plate via one of the edges and being diffused by the light-diffusing optical structure; and at least two electric power supplies, wherein the plurality of light-emitting diodes are organized in at least two rows and a light-emitting diode in one row is supplied by one of the two electric power supplies and is immediately followed by a light-emitting diode in the other row supplied by another one of the at least two electric power supplies, thereby minimizing variations in uniformity of the illumination provided by the light box in case of failure of one of said rows of LEDs, wherein the printed circuit has a central hole, the printed circuit being coated, on the face facing the lightguide plate, with a translucent white film and with a diffusing opaque coating having a hole in the coating coaxial with the central hole of the printed circuit.