Patent ID: 8384979

Claim:
A writing device comprising: a stylus comprising a first light source operable for emitting light of a first wavelength; a second light source operable for emitting light of a second wavelength; a transparent first electrode layer; a second electrode layer; and a displaying layer sandwiched between the first and second electrode layers, the displaying layer consisting essentially of a photochromic material reversibly transformable between a first state where a part of the photochromic material is an electroluminescent material when portions of the displaying layer is illuminated by the light emitted from the stylus and a voltage is applied between the first and second electrodes, and a second state where the part of the photochromic material is transformed into a non-electroluminescent material when the displaying layer is illuminated by the light emitted from the second light source and the voltage is applied between the first and second electrodes, thereby portions of the displaying layer illuminated by the light emitted from the stylus displaying an illuminated movement track of the stylus, wherein the photochromic material of the displaying layer consists essentially of 1,2-diphenylethylene, and the first wavelength in a range from 520 nm to 650 nm, the second wavelength is in a range from 4 nm to 380 nm.