US Patent 7793448 Display module and illumination sign device using the same

A display module includes a first light guide plate, a first light shielding sheet disposed above the first light guide plate, a first light source positioned adjacent to the first light guide plate, a second light shielding sheet disposed under the first light guide plate, a second light guide plate disposed under the second light shielding sheet, and a second light source positioned adjacent to the second light guide plate. The first and second light sources emit different color light. The first light shielding sheet defines a first light transmitting pattern. The second light shielding sheet defines a second light transmitting pattern according to the first light transmitting pattern. An area of the second light transmitting pattern is less than that of the first light transmitting pattern.