Information recording medium, information recording method and information recording apparatus

#The present invention relates to an information recording medium, an information recording method and an information recording apparatus which are capable of recording such information in real time by means of recording beams, for example, laser beams as digital information including pulse-frequency modulated analog signals of projected images and voice, data in electronic computers, facsimile signals and digital audio signals. More particularly, the present invention relates to a disk shaped recording medium using an erasable, phase-change type optical recording film.

#Conventional phase-change type optical disks have a recording film capable of fast erasure by crystallization that is materialized within a time substantially equal to the time required for a recording laser beam to pass on a point on a disk, for example. The conventional method of recording and erasing information to and from such an erasable recording film is to change the power of the laser beam between two levels higher than the reading power levels, these levels are a high power level and an intermediate power level. The advantage of this method is that the so-called overwriting (replacing old information with new without prior erasing) is possible. When such overwriting is repeated a plurality of times, however, the laser beam irradiates the recording film repeatedly in accordance with the recording information signal. This results in a high probability of allowing VFO recording marks to be repeatedly written to the same place in an area close to a preformat section in particular, and therefore variations in film thickness tend to occur locally because of recording film fluidization.

#According to Japanese Unexamined Patent Publication No. 150725/1991, a method that avoids the recording film from being repeatedly written at the same place involves shifting the data write start position each time data is written or at appropriate times when old data is overwritten, whereby mark-forming positions are properly distributed. Thus the overwriting cyclability of the optical disk are improved.

#FIG. 1 is a partial sectional view of a disk embodying the present invention.

#FIG. 2 is a diagram of an exemplary sector format according to an embodiment of the invention.

#FIG. 3 is a block diagram of an information recording apparatus according to an embodiment of the invention.

#A detailed description will subsequently be given of the preferred embodiments of the present invention.

#The recording film for use in the present invention is preferably a crystal-amorphous phase-change optical recording film capable of fast crystallization, a recording film utilizing an amorphous-amorphous change, a crystal-crystal phase-change (e.g. a change in the crystal system and particle size) recording film or a magneto-optic recording film. However, any other recording film which has a tendency to have waveform distortion at the beginning and/or the end of a recording area may also be used.

#In addition to the preformatted area and a gap area, a recording area such as the VFO/SYNC area and the user data area capable of recording information are provided. Moreover, the dummy area is provided on at least one of the leading or trailing sides located respectively before and after the recording area, and this dummy area serves to prevent information actually read from the data area from being damaged even though repeated overwriting causes the fluidization of the recording film. The damage is prevented because the distortion of the regenerative signal waveform resulting from the fluidization thereof is confined to the VFO area, the dummy signal and/or the buffer area.