Kabushiki Kaisha Ohara

Kabushiki Kaisya Ohara

Ohara, Inc.

Yasuyuki Kawashima

Naoyuki Goto

Junko Ishioka

Katsuhiko Yamaguchi

Masashi Maekawa

Nobuo Kawasaki

Yoshio Karasawa

Provided are SiO&#x2014;AlO-based or LiO&#x2014;AlO&#x2014;SiO-based crystallized glass that solves the cause of cracking and fracture in forming it into large-size shaped articles, that has homogeneous inner quality and that may be produced stably at high efficiency; and a method for producing it. The crystallized glass contains components of SiOand AlO, wherein the crystal precipitation peak temperature width obtained in differential thermal analysis of amorphous glass, a precursor thereof, is at least 22&#xb0; C. Preferably, the total amount of the TiOcomponent and the ZrOcomponent in the crystallized glass is within a range of from 3.0 to less than 4.3%. FIG.is referred to.

Crystallized glass, and method for producing crystallized glass

There is provided a glass-ceramic which is suitable for use as a light filter. The glass-ceramic has Young's modulus (GPa) within a range from 95 to 120 and includes 5.3-8 weight percent of Al O , 0.5-3.5 weight percent of ZrO and 71-81 weight percent of SiO , based respectively on the total content of the oxides. The glass-ceramic preferably has, as its predominant crystal phases, (a) lithium disilicate (Li O. SiO ) and (b) at least one of &agr;-quartz (&agr;-SiO ) and &agr;-quartz solid solution (&agr;-SiO solid solution), has specific gravity within a range from 2.4 to 2.6 and has a coefficient of thermal expansion within a range from 65&times;10 /&deg; C. to 130&times;10 /&deg; C. within a temperature range from &minus;50&deg; C. to &plus;70&deg; C.

Glass-ceramics for a light filter

There is provided a glass-ceramic substrate which is suitable for use as a light filter. The glass-ceramic has a Young's modulus (GPa) within a range from 95 to 120 and includes 5.3 to 8 weight percent (expressed on an oxide basis) of Al O . Tile glass ceramic substrate preferably has, as its predominant crystal phases, (a) lithium disilicate (Li O&middot;2SiO ) and b) at least one of &agr;-quartz (&agr;-SiO ) and &agr;-quartz solid solution (&agr;-SiO solid solution), has a specific gravity within a range from 2.4 to 2.6 and has a coefficient of thermal expansion within a range from 65&times;10 /&deg; C. to 130&times;10 /&deg; C. within a temperature range from &minus;50&deg; C. to &plus;70&deg; C.

Glass-ceramics

A glass-ceramic suitable for use as a light filter includes, as a predominant crystal phase, lithium disilicate (Li O.2SiO ) or a combination of lithium disilicate and at least one crystal phase selected from the group consisting of &agr;-quartz (&agr;-SiO ), &agr;-quartz solid solution (&agr;-SiO solid solution), &agr;-cristobalite (&agr;-SiO ) and &agr;-cristobalite solid solution (&agr;-SiO solid solution). This substrate has Young's modulus (GPa)/specific gravity of 37 or over, surface roughness Ra (arithmetic mean roughness) of 5.0 &angst; or below, a coefficient of thermal expansion within a temperature range from &minus;50&deg; C. to &plus;70&deg; C. which ranges from &plus;65&times;10 /&deg; C. to &plus;130&times;10 /&deg; C. and bending strength of 400 MPa or over.

There is provided a glass-ceramic substrate for an information storage medium usable in an information storage device of the ramp loading system. The glass ceramic substrate has a Young's modulus (GPa)/specific gravity of or over and includes 5.3 to 8 weight percent (expressed on an oxide basis) of Al O . The glass ceramic substrate has, as its predominant crystal phases, lithium disilicate (Li O.2SiO ) and &agr;-quartz (&agr;-SiO ), has a coefficient of thermal expansion within a range from 65&times;10 /&deg; C. to 130&times;10 /&deg; C. within a temperature range from &minus;50&deg; C. to &plus;70&deg; C. and has a surface roughness (Ra) (arithmetic mean roughness) of 9 &angst; or below.

Glass-ceramic substrate for an information storage medium

A glass-ceramic substrate for an information storage medium includes, as a predominant crystal phase, lithium disilicate (Li,O&middot;2SiO,) or a combination of lithium disilicate and at least one crystal phase selected from the group consisting of &agr;-quartz (&agr;-SiO,), &agr;-quartz solid solution (&agr;-SiO,solid solution), &agr;-cristobalite (&agr;-SiO,) and &agr;-cristobalite solid solution (&agr;-SiO,solid solution). This substrate has Young's modulus (GPa)/specific gravity of 37 or over, surface roughness Ra (arithmetic mean roughness) of 5.0 &angst; or below, a coefficient of thermal expansion within a temperature range from &minus;50&deg; C. to &plus;70&deg; C. which ranges from &plus;65&times;10,/&deg; C. to &plus;130&times;10,/&deg; C. and bending strength of 400 MPa or over.

A method for manufacturing a magnetic disk substrate includes a step of polishing a glass-ceramic having a crystal phase consisting of crystal grains having an average diameter of less than 3 .mu.m with a polishing material having a grain diameter smaller than the diameter of the crystal grain. In one aspect of the invention, the glass-ceramic includes lithium disilicate (Li.sub.2 O--2SiO.sub.2) and alpha-quartz (alpha-SiO.sub.2) as predominant crystal phases and grown crystal grains of the alpha-quartz each have a globular grain structure consisting of aggregated particles and have a diameter within a range of 0.3 .mu.m-3.0 .mu.m.

Method for manufacturing a magnetic disk substrate

A method for detecting a defect in a glass-ceramic for magnetic disks includes steps of forming a colored glass-ceramic having Munsell value within the range of 0 to 7 in the CIE color system by subjecting to heat treatment a base glass comprising in weight percent:

Method for detecting a defect in a glass-ceramic for magnetic disks

A cordierite glass-ceramic having a cordierite crystal phase as a predominant crystal phase is obtained by melting a base glass consisting in weight percent of:

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Sagamihara, Japan

Yasuyuki Kawashima