Method of producing glass substrate for information recording medium

Abstract

The invention discloses a process for producing a glass substrate for an information recording medium by press-shaping a molten glass which gives a glass containing 0.1 to 30 mol% of TiO2, 1 to 45 mol% of CaO, 5 to 40 mol% of total of MgO and the above CaO, 3 to 30 mol% of total of Na2O and Li2O, 0 to 15 mol% of Al2O3 and 35 to 65 mol% of SiO2 and having properties of a liquidus temperature of 1360 DEG C or lower and a viscosity of at least 10 poise in a shaping-allowable temperature range, or by preparing a preform formed of a glass which contains 0.1 to 30 mol% of TiO2, 1 to 45 mol% of CaO, 5 to 40 mol% of total of MgO and the above CaO, 3 to 30 mol% of total of Na2O and Li2O, 0 to 15 mol% of Al2O3 and 35 to 65 mol% of SiO2 and has properties of a liquidus temperature of 1360 DEG C or lower and shaping the preform in the form of a disc by a re-heat pressing method. According to the above process, there can be mass-produced, with high productivity, high-quality glass substrates to be used for information recording media such as a magnetic disc, an optical disc, a magneto-optic disc, and the like.

Description

technical field [0001] This invention relates to the manufacturing method of the glass substrate for information recording media, and the method of manufacturing an information recording medium using the glass substrate obtained by this method. More specifically, the present invention relates to a method for manufacturing glass substrates that can be used in information recording media such as magnetic disks, optical disks, and magneto-optical disks with high quality, high productivity, and industrial scale, and by A method of manufacturing the above-mentioned information recording medium by providing a recording layer on the obtained glass substrate. technical background [0002] The main components of a magnetic recording device such as a computer are a magnetic recording medium and a magnetic recording and reproducing head. As the magnetic recording medium, there are known floppy disks and hard disks. Among them, an aluminum alloy can be used as a s...

AI Technical Summary

Problems solved by technology

[0010] However, for those chemically strengthened glass substrates disclosed in documents such as the above-mentioned JP-A-1-239036, the Young's modulus is about 80 GPa, which may be difficult to meet the strict requirements for hard disks in the future.

For those glasses that are chemically strengthened by conventional ion exchange methods, since they contain a large amount of alkali metal components, when used for a long time in a high temperature and humid environment, alkali metal ions will be released from the pinhole part of the magnetic film or The weak part of the magnetic film such as the peripheral part of the magnetic film or the part where the glass is exposed is precipitated, which causes corrosion or deterioration of the magnetic film, which is its disadvantage

[0011] In addition, for the crystallized glass disclosed in US Pat. No. 5,391,522 specification, although Young's modulus and heat resistance are slightly superior to the above-mentioned chemically strengthened glass substrates, the roughness is lower than that of chemically strengthened glass substrates. The substrate is poor, and the reduction of the flying height of the magnetic head is limited, so it cannot meet the requirements of high-level magnetic recording, which is its problem

[0012] In addition, when seeking high-speed rotation of a magnetic disk made of a conventional information recording medium glass substrate in order to achieve high-speed data, it is difficult to ensure the stability of the flying height (the distance between the magnetic head and the magnetic disk during playback recording).

[0013] On the other hand, the magnetic recording medium made of glassy carbon disclosed in Japanese Patent Laid-Open No. 3-273525 is superior to the above-mentioned chemically strengthened glass substrate or crystal in terms of heat resistance and light weight. glass substrate, but its surface has too many defects to allow high-density recording

In addition, since the Young's modulus of glassy carbon is very small, and its strength is also poor, it is necessary to increase the thickness of the substrate, and it is difficult to achieve thinning of the substrate, which is its problem.