US Patent 7948567 Optically writable display medium and optical writing method

An optically writable display medium includes an optical switching element and a display element. The optical switching element includes a charge transport layer sandwiched between an upper charge generating layer and a lower charge generating layer. The display element includes a display layer having memory properties and is provided on the optical switching element. The absorption wavelength region of the upper charge generating layer and the absorption wavelength region of the lower charge generating layer are substantially different from each other.