Hoya Corporation

Nippon Sheet Glass Company, Limited

Kensuke Matsuno

Takeo Watanabe

Masamichi Kezuka

Junji Kurachi

Koji Okuhata

Takao Miwa

Satoshi Jibiki

Junichi Hashimoto

A substrate for use as a disk substrate in a hard disk drive or the like, an information recording medium such as a magnetic disk, and a starting material glass plate which is a starting material of the substrate for information recording media. The forming conditions of the starting material glass plate are controlled such that the starting material glass plate has a long-wavelength waviness of not more than 6 nm. This starting material glass plate is polished so as to have a long-wavelength waviness of not more than 6 nm using CeOabrasive grains having a mean grain diameter of not less than 0.01 &#x3bc;m and a 90% diameter of the volume grain size distribution of not less than 0.02 &#x3bc;m. The resulting substrate for an information recording medium has an excellent planarity, can be obtained in a short time and with a low polishing amount, and the resulting information recording medium is able to cope with increased data zone recording density.

Substrate for information recording media and manufacturing method thereof, information recording medium, and starting material glass plate

There are provided a substrate for information recording media and a manufacturing method thereof, according to which the projection height of minute undulations formed on the substrate surfaces can be made more uniform, and variation in the projection density can be suppressed. First, chemical strengthening treatment is carried out on a glass substrate that has been prepared by processing a sheet-shaped starting material glass plate into a predetermined shape. Then, precision polishing is carried out on the glass substrate that has been subjected to the chemical strengthening treatment, such that a polishing amount in a thickness direction of the glass substrate is within a predetermined range. Finally, surface washing is carried out on the glass substrate that has been subjected to said precision polishing.

Substrate for information recording media and manufacturing method thereof, and information recording medium

There are provided a method of manufacturing a glass substrate for information recording media that allows the inner and outer peripheral edge surfaces of the glass substrate for information recording media to be smoothed easily and inexpensively, a glass substrate for information recording media manufactured using this method, and an information recording medium using this glass substrate. A donut-shaped glass disk for information recording media having an outer peripheral edge surface and an inner peripheral edge surface is prepared. At least one of the outer peripheral edge surface and the inner peripheral edge surface of the glass disk is smoothed by melt-heating to a temperature at or above the softening point of the glass by irradiating with at least one laser beam. As a result, at least one of the outer peripheral edge surface and the inner peripheral edge surface of the glass disk becomes smooth and rounded, and hence a polishing step used in a conventional method can be omitted, and moreover chamfering in a grinding step can also be omitted.

METHOD OF MANUFACTURING GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIA, GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIA MANUFACTURED USING THE METHOD, AND INFORMATION RECORDING MEDIUM USING THE GLASS SUBSTRATE

There is provided a glass substrate for magnetic recording media, which enables damage to a magnetic recording medium using the glass substrate to be prevented. The glass substrate is a donut-shaped glass substrate comprising major surfaces, an outer peripheral edge surface, an inner peripheral edge surface, and chamfered surfaces, each connecting between one of the major surfaces and one of the outer peripheral edge surface and the inner peripheral edge surface. Each of the chamfered surfaces comprises a conical surface part and an annular curved surface part connected to one another, and for each of the chamfered surfaces, a percentage ratio of a length of an outline of the annular curved surface part to a length of an outline of the chamfered surface in a cross section of the glass substrate including a central axis of the glass substrate is not less than a predetermined value.

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Yokkaichi, Japan

Kensuke Matsuno