Patent ID: 7585083

Claim:
A backlight for a display device comprising: a board; a plurality of light emitting diodes (LEDs) mounted on the board; and a light guiding plate comprising light reflecting grooves corresponding to respective LEDs, wherein the LEDs are disposed behind and spaced apart from a bottom surface of the light guiding plate at a predetermined distance, and wherein the light reflecting grooves are formed at an upper surface of the light guiding plate, each having a shape of a reversed-cone and the backlight satisfies the following equation d ≥ 6 ⁢ l ⁢ ⁢ tan ⁢ ⁢ θ 2 ⁢ ⁢ tan ⁢ ⁢ θ T - 5 ⁢ ⁢ tan ⁢ ⁢ θ where d is a thickness of the light guiding plate, l is a distance from a light emitting chip of each LED behind the light guiding plate to the bottom surface of the light guiding plate, θ is the largest angle formed between the main axis of the light reflecting groove and the directly upward proceeding light to be intercepted, and θ T is an angle formed between a cross-section of the light reflecting groove and the main axis thereof, wherein the light emitting chip of each LED is non-coplanar with any portion of the light guiding plate.