Abstract: 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 (Li2O.2SiO2, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.57 Å and 3.62 Å), quartz (SiO2, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 Å to 3.41 Å), quartz solid solution (SiO2 solid solution, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 3.33 Å to 3.41 Å), cristobalite (SiO2, having an interplaner spacing of maximum peak intensity measured by an X-ray diffraction analysis within a range from 4.04 Å to 4.

Abstract: 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;-SiO2), &bgr;-quartz solid solution (&bgr;-SiO2 solid solution), &bgr;-spodumene (&bgr;-Li2O.Al2O3.4SiO2), &bgr;-spodumene solid solution (&bgr;-Li2O.Al2O3.4SiO2 solid solution), &bgr;-eucryptite (&bgr;-Li2O.Al2O3.2SiO2, a part of Li2O being capable of being substituted by MgO and/or ZnO) and &bgr;-eucryptite solid solution (&bgr;-Li2O.Al2O3.2SiO2 solid solution, a part of Li2O being capable of being substituted by MgO and/or ZnO). Alternatively, the glass-ceramic contains, as a main crystal phase or phases, gahnite (ZnAl2O4) and/or gahnite solid solution (ZnAl2O4 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.

Abstract: 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 37 or over and includes 5.3 to 8 weight percent (expressed on an oxide basis) of Al2O3. The glass ceramic substrate has, as its predominant crystal phases, lithium disilicate (Li2O.2SiO2) and &agr;-quartz (&agr;-SiO2), has a coefficient of thermal expansion within a range from 65×10−7/° C. to 130×10−7/° C. within a temperature range from −50° C. to +70° C. and has a surface roughness (Ra) (arithmetic mean roughness) of 9 Å or below.

Abstract: A negative thermal expansion glass ceramic having a negative coefficient of thermal expansion, which is a sufficiently large absolute value in a temperature range of −40° C. to +160° C. and a method for producing the same are provided. The negative thermal expansion glass ceramic has a coefficient of thermal expansion of −25 to −100×10−7/° C. in the temperature range of −40° C. to +160° C., and comprises main crystalline phases which are one or more types selected from a group consisting of &bgr;-eucryptite solid solution (&bgr;-Li2O.Al2O3.2SiO2 solid solution), &bgr;-eucryptite (&bgr;-Li2O.Al2O3.2SiO2), &bgr;-quartz solid solution (&bgr;SiO2 solid solution), and &bgr;-quartz (&bgr;-SiO2), wherein a total amount of crystals of the main crystalline phases can be 70 to 100% in mass percent.

Abstract: Glass for a light filter capable of preventing variation of refractive index in a band-pass filter has a coefficient of thermal expansion within a range from 90×10−7/° C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 75 GPa or over and Vickers hardness of 550 or over, and light transmittance for plate thickness of 10 mm of 90% or over within a wavelength range from 950 nm to 1600 nm.

Abstract: 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 Young's modulus (GPa)/specific gravity of 37 or over and includes 0 to less than 10 weight percent (expressed on oxide basis) of Al2O3. The glass-ceramic substrate has, as its predominant crystal phases, lithium disilicate (Li2O.2SiO2) and &agr;-quartz (&agr;-SiO2), has a coefficient of thermal expansion within a range from 65×10−7/° C. to 130×10−7/° C. wtihin a temperature range from −50° C. to +70° C. and has a surface roughness (Ra) (arithmetic mean roughness) of 9 Å or below.

Abstract: 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 (MgSiO3 solid solution), magnesium titanate (MgTi2O5) and magnesium titanate solid solution (MgTi2O5 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.

Abstract: There are provided low expansion transparent glass-ceramics obtained by heat treating a base glass produced at a relatively low melting temperature of 1530° C. or below. The glass-ceramics have an average linear thermal expansion coefficient within a range from +6×10−7/° C. to +35×10−7/° C., 80% transmittance wavelength (T80) of 700 nm or below, internal transmittance of 75% or over at light wavelength of 1550 nm, heat resisting temperature of 800° C. or over and Young's modulus of 90 GPa or over. The glass-ceramics comprise SiO2, Al2O3, MgO, CaO, BaO, ZnO, Li2O, TiO2 and ZrO2 and contain &bgr;-quartz or &bgr;-quartz solid solution as a predominant crystal phase. There are also provided optical waveguide elements and an arrayed waveguide grating (AWG) type planar lightwave circuit utilizing these glass-ceramics.

Abstract: 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 Al2O3 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.

Abstract: There is provided a glass-ceramic substrate for a magnetic information storage medium having a data zone and a landing zone capable of stably lifting a magnetic head in the landing zone and also capable of reducing the amount of lifting of the magnetic head in the data zone for realizing a high recording density. The landing zone has a multiplicity of projections or depressions formed by irradiation of laser beam. A CO2 laser or a laser diode pumped solid-state laser can be used for this purpose. The surface roughness (Ra) of a polished surface of the landing zone is within a range from 3 Å to 9 Å, height of the projections or depressions is within a range from 50 Å to 300 Å, surface roughness (Ra) of the projections or depressions is within a range from 10 Å to 50 Å and interval of the projections or depressions is within a range from 10 &mgr;m to 200 &mgr;m.

Abstract: There is provided a glass-ceramic substrate for a magnetic information storage medium having a data zone and a landing zone capable of stably lifting a magnetic head in the landing zone and also capable of reducing the amount of lifting of the magnetic head in the data zone for realizing a high recording density. The landing zone has a multiplicity of projections or depressions formed by irradiation of laser beam. A CO2 laser or a laser diode pumped solid-state laser can be used for this purpose. The surface roughness (Ra) of a polished surface of the landing zone is within a range from 3 Å to 9 Å, height of the projections or depressions is within a range from 50 Å to 300 Å, surface roughness (Ra) of the projections or depressions is within a range from 10 Å to 50 Å and interval of the projections or depressions is within a range from 10 &mgr;m to 200 &mgr;m.

Abstract: 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 Al2O3 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.

Abstract: 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 Al2O3 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.

Abstract: A luminous glass ceramic comprising a main crystallized phase of spinel or a solid solution of spinel including the components in weight %: SiO2 30-65 Al2O3  5-35 MgO  1-20 BaO 3-4 ZnO  5-35 TiO2  1-15 As2O3 + Sb2O3 0-3 wherein one or more rare earth elements are added to the glass ceramic in an amount of 0.1-30 wt %.

Abstract: 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 (Li2O.2SiO2) and either or both of &agr;-quartz (&agr;-SiO2) and &agr;-cristobalite (&agr;-SiO2), 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 Å to 50 Å.

Abstract: A luminous glass ceramic comprising, in percent by weight, the following components: SiO2  50-65 (%) P2O5   0-10 Al2O3  18-30 Li2O   2-6 MgO 0.2-6 ZnO   0-2 CaO   0-4 BaO 0.5-6 TiO2   1-4 ZrO2   1-4 As2O3 + Sb2O3   0-2 wherein a total amount of SiO2 and P2O5 is 50-70 wt. %, a ratio of P2O5 to SiO2 is 0-0.18, a ratio of Al2O3 to SiO2 is 0.30-0.55, one or more rare earth elements are added to the glass ceramic on an oxide basis of 0.1-30 wt. % to an total amount of other components, Na2O component, K2O component, and PbO component are not essentially contained, and the glass ceramic has a thermal shock resistance |&Dgr;t|° C.

Abstract: A glass-ceramic substrate for an information storage medium includes, as a predominant crystal phase, lithium disilicate (Li2O·2SiO2) or a combination of lithium disilicate and at least one crystal phase selected from the group consisting of &agr;-quartz (&agr;-SiO2), &agr;-quartz solid solution (&agr;-SiO2 solid solution), &agr;-cristobalite (&agr;-SiO2) and &agr;-cristobalite solid solution (&agr;-SiO2 solid solution). This substrate has Young's modulus (GPa)/specific gravity of 37 or over, surface roughness Ra (arithmetic mean roughness) of 5.0 Å or below, a coefficient of thermal expansion within a temperature range from −50° C. to +70° C. which ranges from +65×10−7/° C. to +130×10−7/° C. and bending strength of 400 MPa or over.

Abstract: A glass-ceramic substrate for a magnetic information storage medium includes, as predominant crystal phases, lithium disilicate (Li.sub.2 O.2SiO.sub.2) and at least one selected from a group consisting of .alpha.-quartz (.alpha.-SiO.sub.2), .alpha.-quartz solid solution (.alpha.-SiO.sub.2 solid solution), .alpha.-cristobalite (.alpha.-SiO.sub.2) and .alpha.-cristobalite solid solution (.alpha.-SiO.sub.2 solid solution) and has a coefficient of thermal expansion of +65 to +130.times.10.sup.-7 /.degree. C. at a temperature within a range from -50.degree. C. to +70.degree. C. and surface roughness (Ra) after polishing of 3 .ANG.-9 .ANG..

Abstract: 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..

Abstract: A transparent simulation disk for measuring flying height of a magnetic head (i.e., distance between a magnetic head and a magnetic disk such as a hard disk of a computer) in place of a magnetic disk is made of a SiO.sub.2 --R.sub.2 O (where R is Li, Na or K) glass or glass-ceramic having electric resistivity of 10.sup.8 -10.sup.14 .OMEGA.cm and abrasion of 90 or below.