Kabushiki Kaisha Ohara

Junko Ishioka

Naoyuki Goto

Yasuyuki Kawashima

Kousuke Nakajima

Katsuhiko Yamaguchi

Masahiro Onozawa

Takayuki Kishi

Toshitaka Yagi

Michiko Ogino

Yoshio Mori

Mariko Kataoka

Glass has optical constants of a refractive index (nd) of 1.79 or over and an Abbe number (&#x3bd;d) of 27 or over and a specific gravity (D) of 3.20 or over and is free from devitrification in the interior of the glass in a reheat test. The glass has chemical durability according to the Powder Method (acid-proof property RA according to the Powder Method) which is Class 1.

Glass

An optical glass having optical constants of refractive index (nd) within a range from 1.49 to 1.54 and Abbe number (&#x3bd; d) within a range from 55 to 65 comprises, in mass %, 

Optical glass

An optical glass having a small photoelastic constant (&#x3b2;) suitable for parts for polarizing optical system and light polarization control elements and having a refractive index (nd) within a range from 1.60 to 1.68 and an Abbe number (&#x3bd; d) within a range from 40 to less than 65 comprises, as atoms constituting the optical glass, 

Optical glass having a small photoelastic constant

An optical glass having a positive anomalous dispersion comprises, in mass %, is free of PbO and AsOexcept for unavoidable mixing of these compounds as impurities, has optical constants of a refractive index (nd) within the range from 1.48 to less than 1.55 and an Abbe number (&#x3bd;d) within the range from 45 to 55, and has an anomalous dispersion (&#x394;&#x3b8;g,F) of +0.0010 or over.

Optical glass having an anomalous dispersion

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

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

An optical glass includes SiO ; PbO; B O ; not less than 0.1 mass % of TeO ; and not less than 0.4 mass % of Li O.

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 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 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 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.

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.

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Sagamihara, Japan

Junko Ishioka