Kabushiki Kaisha Ohara

Kabushiki Kaisya Ohara

Ohara, Inc.

Katsuhiko Yamaguchi

Naoyuki Goto

Junko Ishioka

Kousuke Nakajima

Toshitaka Yagi

Muneo Nakahara

Futoshi Ishizaki

Takayuki Kishi

Yasuyuki Kawashima

Tatsuya Senoo

Mariko Kataoka

Hisao Yatsuda

Kiyoyuki Momono

Goro Enomoto

Hideo Yasui

Hiroshi Shishido

It is an object of the present invention to provide a crystallized glass which has various properties required for employing the substrate for information recording medium of the next generation, and also has significantly low specific gravity; and a crystallized glass substrate for information recording medium. A crystallized glass containing, as a crystal phase, one or more selected from RAlOand RTiO(wherein R is one or more selected from Mg and Fe), the crystallized glass comprising the components of SiOof 50% to 70%, AlOof 10% to 26%, TiOof 1 to 15%, MgO of 2.5% to 25%, FeO of 0% to 8%, and ZnO of 0% to less than 2%, expressed in terms of mass percentage on an oxide basis, wherein the value of (AlO+MgO)/SiOis 0.30 or more and 0.65 or less, and a specific gravity is less than 2.63.

Crystallized glass and crystallized glass substrate for information recording medium

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 storage medium having a super flat surface comprises, as a predominant phase or phases, at least one crystal phase selected from the group consisting of lithium disilicate (Li O.2SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.57 &angst; and 3.62 &angst;), quartz (SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 &angst; to 3.41 &angst;), quartz solid solution (SiO solid solution, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 &angst; to 3.41 &angst;), cristobalite (SiO , having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 4.04 &angst; to 4.14 &angst;) and cristobalite solid solution (SiO solid solution, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 4.04 &angst; to 4.14 &angst;), has a coefficient of thermal expansion within a range from &plus;62&times;10&minus; /&deg; C. to &plus;130&times;10 /&deg; C. in a temperature range from &minus;50&deg; C. to &plus;70&deg; C., has Young's modulus within a range from 80 GPa to 150 GPa, has Vickers hardness within a range from 4.5 GPa to 15.0 GPa, has a specific gravity within a range from 2.2 to 2.8, has a surface roughness (Ra) after polishing within a range from 3 &angst; to 9 &angst; and contains Al O in the amount of 2% to less than 10%.

Glass-ceramic substrate for a magnetic information storage medium

A magnetic head has a slider made of a glass-ceramic substrate which has, as its predominant crystal phase, a mixed crystal of lithium disilicate (Li,O.2SiO,) and either or both of &agr;-quartz (&agr;-SiO,) and &agr;-cristobalite (&agr;-SiO,), the &agr;-quartz has a globular grain structure each globular crystal grain being made of aggregated particles and having a grain diameter within a range from 0.1 &mgr;m to 3.0 &mgr;m, the &agr;-cristobalite has a globular grain structure each globular grain having a grain diamter within a range from 0.1 &mgr;m to 1.0 &mgr;m, and surface roughness (Ra) of the glass-ceramic substrate after polishing is within a range from 5 &angst; to 50 &angst;.

Magnetic head having a slider made of a glass-ceramic

A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO,) and lithium disilicate (Li,O&middot;2SiO,) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.20 to less than 0.25, a grain diameter of crystal grains is within a range from 0.1 &mgr;m to 1.0 &mgr;m, surface roughness (Ra) of the substrate after polishing is within a range from 2 &angst; to 9 &angst;.

Glass-ceramic substrate for a magnetic disk

A glass-ceramic substrate for a magnetic head has as its predominant crystal phase a mixed crystal of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and either or both of .alpha.-quartz (.alpha.-SiO.sub.2) and .alpha.-cristobalite (.alpha.-SiO.sub.2), the .alpha.-quartz has a globular grain structure each globular crystral grain being made of aggregated particles and having a grain diameter within a range from 0.1 .mu.m to 3.0 .mu.m, the .alpha.-cristobalite has a globular grain structure each globular grain having a grain diamter within a range from 0.1 .mu.m to 1.0 .mu.m, and surface roughness (Ra) of the glass-ceramic substrate after polishing is within a range from 5 .ANG. to 50 .ANG..

Glass-ceramic substrate for a magnetic head and a method for

A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO.sub.2) and lithium disilicate (Li.sub.2.SiO.sub.2) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.25 to 0.35, a grain diameter of crystal grains is within a range from 0.1 .mu.m to 1.0 .mu.m, surface roughness (Ra) of the substrate after polishing is within a range from 2 .ANG. to 10 .ANG. and abrasion resistance index (Aa) of the substrate is within a range from 5 to 15.

A crystallized glass and a manufacturing method therefor are disclosed. The crystallized glass comprises .beta.-spodumene solid solution as the predominant crystal phase, and is produced by forming a melted raw glass, cooling and thereafter heat-treating it. The raw glass has a composition comprising, expressed in terms of weight percent: 52-65% SiO.sub.2 ; 8-15% Al.sub.2 O.sub.3 ; 0-4% P.sub.2 O.sub.5, 3-8% TiO.sub.2, and 0-4% ZrO.sub.2, wherein the following inequality is satisfied, 0.1&lt;(% of P.sub.2 O.sub.5 +% of ZrO.sub.2)/(% of TiO.sub.2)&lt;0.8; 0-10% ZnO, 0-10% MgO, and 0-5% BaO, wherein the following inequality is satisfied, &lt;(% of ZnO+% of MgO+% of BaO)&lt;15; 3-12% Li.sub.2 O; 0-4% K.sub.2 O; and As.sub.2 O.sub.3 and Sb.sub.2 O.sub.3, wherein the following inequality is satisfied, 0&lt;% of As.sub.2 O.sub.3 +% of Sb.sub.2 O.sub.3 &lt;2.

Crystallized glass and method for manufacturing the same

A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO.sub.2) and lithium disilicate (Li.sub.2 O . 2SiO.sub.2) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.25 to 0.35, a grain diameter of crystal grains is within a range from 0.1 .mu.m to 1.0 .mu.m, surface roughness (Ra) of the substrate after polishing is within a range from 2 .ANG. to 10 .ANG. and abrasion resistance index (Aa) of the substrate is within a range from 5 to 15.

A magnetic disk substrate is made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2). The crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles. Each globular grain has a size within a range from 0.3 .mu.m to 3 .mu.m. Surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG. which is an optimum range of surface roughness for the magnetic disk.

Magnetic disk substrate and method for manufacturing the same

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

Method for manufacturing a crystalized glass magnetic disk substrate

A glass-ceramic for a magnetic disk substrate in which the grain size can be controlled and the surface roughness after polishing is within the range from 15 .ANG. to 50 .ANG. is provided by heat treating a base glass including in weight percent:

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Sagamihara, Japan

Katsuhiko Yamaguchi