Abstract: In order to perform simultaneous recording and reproduction, a large capacity of buffer memories were required. In addition, it was difficult to record data while reproducing data which was recorded by a different apparatus. The present invention has an objective of providing an information recording medium, a simultaneous recording and reproduction method, and an information recording and reproduction apparatus which guarantee simultaneous recording and reproduction. The simultaneous recording and reproduction is guaranteed by reproducing data recorded in an area having at least a minimum size fulfilling the simultaneous recording and reproduction condition which allows for four access operations, recording data in an area having at least the same size, and performing reproduction and recording alternately by switching reproduction to recording when the data amount in the reproduction buffer becomes full and switching recording to reproduction when the data amount in the recording buffer becomes empty.

Abstract: According to a recording method for a conventional rewritable disc, the latest data is recorded by rewriting data in an identical area. In the case of a disc of which the number of times of data rewrite is limited, this causes a problem that a defect block is easily generated. The present invention has an objective of providing an information recording medium, an information recording and reproduction method, and an information recording and reproduction system apparatus, by which data is recorded sequentially from an unallocated area after an entry sector number, and data recording is sequentially repeated from an inner portion to an outer portion.

Abstract: A glass body comprising an alkali-containing glass substrate and a silicon oxide layer formed on its surface for preventing diffusion of alkali metal ions from the glass substrate. Said silicon oxide layer contains hydrogen bonded to silicon.