Patent ID: 8471832

Claim:
A keypad assembly comprising: a switch board having at least one switch; a light guide panel mounted on the switch board and comprising contiguous upper and lower surfaces that has a constant level of reflectivity and extends along a length of the switch board, the upper surface of the light guide panel being flat throughout its entire length along an upper surface of the switch board, the light guide panel propagating light through an inside of the light guide panel and undergoing total internal reflection at each of the upper and lower surfaces of the light guide panel being in direct contact with an air layer; a light emitting device facing a second lateral surface of the light guide panel, the light emitting device coupling light to an inside of the light guide panel; a first light blocking member directly stacked on a first lateral surface of the light guide panel, the first light blocking member extending to the switch board and reflecting or absorbing incident light; and a second light blocking member directly stacked on the light emitting device and absorb incident light leaking toward the light emitting device, wherein the light guide panel includes a light extraction pattern arranged over said at least one switch and below a key button to change an incident angle of a portion of the light being propagated through the light guide panel and contacting the light extraction pattern to be smaller than a critical angle of total internal reflectivity and project out of the light guide panel and illuminate the key button; wherein light undergoes total internal reflection throughout an entire length of the light guide panel along the upper surface of the switch board except for the portion of the light contacting the light extraction pattern; and wherein the first light blocking member is continuously stacked on lateral surfaces of the light guide panel except for the second lateral surface so that the first light blocking member has a U-shaped strip along the lateral surfaces of the light guide panel.