Information recording medium and its manufacturing method

Abstract

It is an object to improve the recording transfer rate of a phase change recording medium, to reduce the producing costs of the medium, to greatly increase the degree of freedom for the selection of the substrate of the medium, particularly to provide a medium having a structure of Rc<Ra, and to increase the storage capacity of the medium. In order to accomplish this object, a medium, wherein the initial state is an amorphous state immediately after sputtering, has a structure having a unique short-range order. In addition, there is provided a medium wherein the distribution of the number of crystal grains with respect to grain sizes has a plurality of maximum values. Moreover, when a recording operation is carried out by laser beams, an amorphous state band part is formed between tracks. In addition, the thermal conductivity of a recording layer is in a unique range, and contains Kr or Xe in a specific range. Moreover, in the case of a medium of a single-sided double-layer structure having a plurality of recording layers, at least one of the recording layers has any one of the above described characteristics. Moreover, as a method for producing a recording layer having these characteristics, the bias voltage applied to a target during sputtering is set to be in a specific range. In addition, the ion density of plasma is set to be greater than a specific value. In addition, the recording layer is heated by means of a lamp while a thermal load on a substrate is suppressed. By the above described methods, the time required to crystallize the recording layer is decreased to improve the data transfer rate. In addition, by applying a rapid crystallization performance on an as-deposited amorphous material, the initial crystallizing step is omitted to reduce the producing costs. Moreover, by allowing a medium of Rc<Ra to be used from an as-deposited amorphous state, it is possible to increase the range for selecting the structure of the medium, and it is possible to improve the reflectance of a single-sided double-layer medium, so that it is possible to increase the storage capacity of the medium.

Dependencies are inferred from the claim text.