Patent ID: 8362928

Claim:
A keypad assembly including a switch board having a plurality of dome switches, the keypad assembly comprising: a plurality of key buttons; a plurality of light emitting devices; a waveguide being disposed under the key buttons and having a predetermined refractive index such that lights emitted from the light emitting devices and entering the waveguide travels according to an internal total reflection condition; a plurality of reflecting patterns being disposed on an inner surface of the waveguide and being configured to reflect the light traveling within the waveguide toward the key buttons; and an auxiliary layer being disposed on an upper surface of the waveguide along an entirety of the upper surface of the waveguide including respective surfaces corresponding to a position of each of the plurality of key buttons, said auxiliary layer having a lower refractive index than the waveguide, and being configured to induce a constant total reflection condition for a traveling angle of light that is less than a total reflection angle threshold determined by a first interface of the auxiliary layer and the waveguide at the upper surface of the waveguide and a second interface of the waveguide and air at a lower surface of the waveguide; wherein the plurality of reflecting patterns being disposed in the waveguide are configured to change the traveling angle of light incident thereon to exceed a total reflection angle threshold; and wherein a plurality of protrusion members are disposed under the waveguide and the plurality of reflecting patterns; and wherein a plurality of dome switches on top of a switchboard are arranged below the waveguide and the protrusion members, and the plurality of dome switches are spaced apart from the waveguide and the protrusion members.