Kabushiki Kaisha Ohara

Ohara, Inc.

Takayuki Kishi

Naoyuki Goto

Katsuhiko Yamaguchi

Junko Ishioka

Kousuke Nakajima

Toshitaka Yagi

The present invention provides an inorganic composition for use in information recording medium disc substrate and such, having an excellent surface property capable of sufficiently corresponding with a ramp load system for high density recording, a high degree of tolerability to high speed rotation, and high productivity at a low melting point. Specifically, this invention provides an inorganic composition containing one crystalline phase selected from the group consisting of &#x3b1;-quartz (&#x3b1;-SiO), lithium disilicate (LiSiO) and lithium monosilicate (LiSiO), or that contain at least a crystalline phase of lithium monosilicate (Li2SiO3), in which a mean particle diameter of a particle showing a crystalline phase contained in the inorganic composition is 1 &#x3bc;m or less, a ring flexural strength is 300 MPa or more, and a surface roughness (an arithmetic mean roughness) thereof after a polishing process is 10 &#x212b; or less.

Inorganic composition

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.

Growing community of inventors

Sagamihara, Japan

Takayuki Kishi