Patent ID: 7364337
Filing Date: 2008-04-29
Classification: G02B,H04M

Abstract:
1. A flexible backlight unit for a key of an input device, the key having a character shaped opening portion for enabling light transmission, the unit comprising: a light guide plate formed of flexible transparent resin and having a plurality of island-like light guide pattern portions in which a plurality of engraved or embossed patterns on a predetermined regular basis are formed in a plurality of requirement character shapes so that light can be diffused and scattered at uniform luminance from each necessary light emitting portion of a bottom surface of the key; and at least one light emitting unit installed at a side wall of the light guide plate, wherein a pattern density (D) required for one, which is intended for design, of the island-like light guide pattern portions is defined as in Equation below: where, S: Area of the light guide pattern portion at a position intended for design (mm D: Pattern density, A: Constant value (1.7E-7 to 2.0E-2), T: Thickness of the light guide plate (mm), L: Distance from the light emitting unit to the pattern (mm), θ: Angle between an extension line of a central line of the light emitting unit and an imaginary line connecting from the light emitting unit to the light guide pattern portion (radian value: 0 to π/2), S S S