Kabushiki Kaisha Ohara

Ohara, Inc.

Kousuke Nakajima

Naoyuki Goto

Junko Ishioka

Katsuhiko Yamaguchi

Takayuki Kishi

Toshitaka Yagi

Mariko Kataoka

Toshihide Nakajima

Kazuyoshi Nakamura

Takahisa Oonami

Glass-ceramics includes LiO, AlOand SiO, have an average crystal grain diameter of a predominant crystal phase of 90 nm or below and have crystal grain diameter distribution of 20 nm or below. The glass-ceramics can be manufactured by heat treating glass comprising LiO, AlOand SiOunder a temperature within a range from 650&#xb0; C. to 750&#xb0; C. and then further heat treating the glass under a temperature within a range from 700&#xb0; C. to 800&#xb0; C. for 100-200 hours.

Glass ceramics comprising beta-quartz or beta-quartz solid solution

Method for manufacturing glass-ceramics

A substrate having flatness of less than 230 nmPV and surface roughness at RMS of less than 0.20 nm. is obtained by a method comprising: a process of polishing an object to be polished with a polishing pad comprising at least one layer having compressibility of 5% or below in a base layer of the polishing pad.

Substrate and a method for polishing a substrate

Holding member for information storage disk and information storage disk drive device

A high rigidity glass-ceramic substrate is provided which contains, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of enstatite (MgSiO ), enstatite solid solution (MgSiO solid solution), magnesium titanate (MgTi O ) and magnesium titanate solid solution (MgTi O solid solution), has fine crystal grains (preferably globular crystal grains) of precipitated crystal phases, has excellent melting property of a base glass, high resistivity to devitrification, easiness in polishing, excellent smoothness in the surface after polishing and has high Young's modulus capable of coping with a high speed rotation.

High rigidity glass-ceramic substrate

A high rigidity glass-ceramic substrate is provided which contains, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of enstatite (MgSiO ), enstatite solid solution (MgSiO solid solution), magnesium titanate (MgTi O) and magnesium titanate solid solution (MgTi O solid solution), has fine crystal grains (preferably globular crystal grains) of precipitated crystal phases, has excellent melting property of a base glass, high resistivity to devitrification, easiness in polishing, excellent smoothness in the surface after polishing and has high Young's modulus capable of coping with a high speed rotation.

A glass-ceramic substrate for a magnetic information recording medium contains, as a main crystal phase or phases, one or more crystal phases selected from the group consisting of &bgr;-quartz (&bgr;-SiO ), &bgr;-quartz solid solution (&bgr;-SiO solid solution), &bgr;-spodumene (&bgr;-Li O.Al O .4SiO ), &bgr;-spodumene solid solution (&bgr;-Li O.Al O .4SiO solid solution), &bgr;-eucryptite (&bgr;-Li O.Al O .2SiO , a part of Li O being capable of being substituted by MgO and/or ZnO) and &bgr;-eucryptite solid solution (&bgr;-Li O.Al O .2SiO solid solution, a part of Li O being capable of being substituted by MgO and/or ZnO). Alternatively, the glass-ceramic contains, as a main crystal phase or phases, gahnite (ZnAl O ) and/or gahnite solid solution (ZnAl O solid solution). The glass-ceramic substrate has a high heat resisting property and a super flat surface capable of achieving a high recording density according to the perpendicular magnetic recording.

Glass-ceramic substrate for a magnetic information recording medium

A high rigidity glass-ceramic substrate for a magnetic information storage medium has a ratio of Young's modulus to specific gravity within a range from 37 to 63 and comprises Al O within a range from 10% to less than 20%. A predominant crystal phase of the glass-ceramic substrate consists of one or more crystals selected from the group consisting of &bgr;-quartz, &bgr;-quartz solid solution, enstatite, enstatite solid solution, forsterite and forsterite solid solution.

High rigidity glass-ceramic substrate for a magnetic information storage medium

A high rigidity glass-ceramic substrate for a magnetic information storage medium has a ratio of Young's modulus to specific gravity within a range from 37 to 63 and comprises Al,O,within a range from 10% to less than 20%. Predominant crystal phases of the glass-ceramic substrate consist of (1) cordierite or cordierite solid solution and (2) one or more crystals selected from the group consisting of Spinel crystal, Spinel crystal solid solution, enstatite, enstatite solid solution, &bgr;-quartz and &bgr;-quartz solid solution.

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Samukawa-machi, Japan

Kousuke Nakajima