Disclosed herein is an optical device having a light source and a viscoelastic lightguide. Light from the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection. The viscoelastic lightguide may comprise a pressure sensitive adhesive. The optical device may be used in a variety of constructions wherein the device emits light being transported within the viscoelastic lightguide. Constructions include those used for signs, markings, illumination devices, display devices, keypad assemblies and tail light assemblies for vehicles.