Patent ID: 6808778
Filing Date: 2004-10-26
Classification: G11B,G11C,Y10T

Abstract:
A method for multilevel recording onto an optical recording medium using a laser, the optical recording medium of the type comprising:an optically transparent substrate, said substrate made of a thermoplastic resin with a glass transition point (Tg) between 80Â° C. and 160Â° C.; a recording layer provided on said optically transparent substrate, said recording layer having a dye as a principle component, said recording layer having a virtual recording cell; a reflecting film, provided on the recording layer, said reflecting film comprising a metal having a coefficient of thermal conductivity of 300 k/WÂ·mâˆ’1Â·Kâˆ’1 or more and a film thickness at a recording mark of 50 nm or more; wherein information can be recorded on the recording medium by forming recording marks on the recording layer by irradiating the laser and the recorded information can be read by irradiating a read laser onto the recording mark, and wherein the virtual recording cell is specified in an arbitrary unit length in a direction of relative movement between the laser and the recording layer and in a unit width in a direction that intersects said direction of movement; the method for multilevel recording comprising the step of: forming recording marks in said virtual recording cell at any of at least five levels, said recording marks varying in size depending on one of modulation of irradiation time of the laser and modulation of irradiation power of the laser, resulting in multilevel recording of information.