Information recording medium and method for recording information to the same

A method for recording information as pits to an optical information recording medium comprising:

• a transparent disk-shape substrate on which pre-grooves are concentrically or helically formed with a depth of 1450-2050 angstroms;
• an optical absorbing layer with an absorbance of 0.7-0.9 made of a palladium phthalocyanine dye formed on a surface of said substrate;
• and a reflecting layer formed on said optical absorbing layer, which comprises steps of:
• forming a first FM carrier having a first center frequency and a first frequency band,
• forming at least one of a second FM carrier and a third pulse carrier;
• said second FM carrier having a second center frequency lower than said first center frequency and a second frequency band spaced from said first frequency band, said third pulse carrier having a pulse-repetition frequency lower than said second center frequency and a third frequency band spaced from said second frequency band,
• adding at least one of said second FM carrier and said third pulse carrier to said first FM carrier to form a frequency-division multiplex signal;
• and
• symmetrically clipping said frequency-division multiplex signal to form a limited waveform;
• irradiating a laser beam turning on and off in response to said limited waveform onto said optical absorbing layer of said optical information recording medium rotating at a linear velocity of 10.1-11.4 m/sec. along said pre-groove to form a plurality of pits each having a changed reflectivity being duty-cycle modulated in response to said limited waveform.