Abstract: 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 Al2O3, 0.5-3.5 weight percent of ZrO2 and 71-81 weight percent of SiO2, based respectively on the total content of the oxides. The glass-ceramic preferably has, as its predominant crystal phases, (a) lithium disilicate (Li2O.2SiO2) and (b) at least one of &agr;-quartz (&agr;-SiO2) and &agr;-quartz solid solution (&agr;-SiO2 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 65×10−7/° C. to 130×10−7/° C. within a temperature range from −50° C. to +70° C.

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.

Abstract: Glass-ceramics for a light filter capable of preventing variation of refractive index in a band-pass filter have a coefficient of thermal expansion within a range from 95×10−7/°C. to 140×10−7/°C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 85 GPa and bending strength of 10 kg/mm2, and light transmittance for plate thickness of 10 mm of 60% or over within a wavelength range from 950 nm to 1600 nm. Predominant crystal phases of these glass-ceramics should preferably be (a) lithium disilicate and (b) one selected from the group consisting of &agr;-quartz, &agr;-quartz solid solution, &agr;-cristobalite and &agr;-cristobalite solid solution.

Abstract: 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 Al2O3. Tile glass ceramic substrate preferably has, as its predominant crystal phases, (a) lithium disilicate (Li2O·2SiO2) and b) at least one of &agr;-quartz (&agr;-SiO2) and &agr;-quartz solid solution (&agr;-SiO2 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 65×10−7/° C. to 130×10−7/° C. within a temperature range from −50° C. to +70° C.

Abstract: An information storage disk holding member for holding an information storage disk in position in an information storage disk drive device, the holding member being made of glass-ceramics in which a crystal phase is dispersed in a glass matrix. The holding member has specific rigidity (Young's modulus/specific gravity) of not greater than 37 GPa, specific gravity of not greater than 3.0, coefficient of thermal expansion within a range from −50° C. to +70° C. which is within a range from +35×10−7/° C. to +130×10−7/° C., Young's modulus within a range from 95 GPa to 130 GPa, specific gravity within a range from 2.40 to 2.60 and bending strength within a range from 400 MPa to 800 MPa.

Abstract: Glass-ceramics fo a light filter capable of preventing variation of refractive index in a band-pass filter have a coefficient of thermal expansion within a range from 95×10−7/°C. to 140×10−7/°C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 85 GPa and bending strength of 10 kg/mm2, and light transmittance for plate thickness of 10 mm of 60% or over within a wavelength range from 950 nm to 1600 nm. Predominant crystal phases of these glass-ceramics should preferably be (a) lithium disilicate and (b) one selected from the group consisting of &agr;-quartz, &agr;-quartz solid solution, &agr;-cristobalite and &agr;-cristobalite solid solution.

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: 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 Al2O3, 0.5-3.5 weight percent of ZrO2 and 71-81 weight percent of SiO2, based respectively on the total content of the oxides. The glass-ceramic preferably has, as its predominant crystal phases, (a) lithium disilicate (Li2O.2SiO2) and (b) at least one of &agr;-quartz (&agr;-SiO2) and &agr;-quartz solid solution (&agr;-SiO2 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 65×10−7/° C. to 130×10−7/° C. within a temperature range from −50° C. to +70° C.

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: 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 (MgSiO3), 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: A glass-ceramic substrate for an information storage medium made of a glass-ceramics having a crystal phase dispersed in a glass matrix has a ratio of crystal phase (the amount of crystal) in the glass-ceramics is within a range from 50 wt % to 70 wt % and crystal grains having an average crystal grain diameter within a range from 0.10 &mgr;m to 0.50 &mgr;m are exposed on the surface of the substrate. The glass-ceramics substrate has Young's modulus within a range from 95 GPa to 160 GPa, specific gravity within a range from 2.40 to 2.80, and a ratio of Young's modulus to specific gravity within a range from 39 GPa to 57 GPa. The glass-ceramic substrate has a surface microstructure in which respective crystal grains present in a surface portion of the substrate are fixed to the surface portion with half or more in volume of the respective crystal grains being exposed above the surface of the glass matrix.

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. to 120×10−7/° 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: 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. to 120×10−7/° C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 75GPa 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: Glass-ceramics for a light filter capable of preventing variation of refractive index in a band-pass filter have a coefficient of thermal expansion within a range from 95×10−7/°C. to 140×10−7/°C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 85 GPa and bending strength of 10 kg/mm2, and light transmittance for plate thickness of 10 mm of 60% or over within a wavelength range from 950 nm to 1600 nm. Predominant crystal phases of these glass-ceramics should preferably be (a) lithium disilicate and (b) one selected from the group consisting of &agr;-quartz, &agr;-quartz solid solution, &agr;-cristobalite and &agr;-cristobalite solid solution.

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 (MgSiO3), enstatite solid solution (MgSiO3 solid solution), magnesium titanate (MgTi2O) 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 glass-ceramics containing, as a predominant crystal phase or phases, at least one selected from the group consisting of &agr;-cristobalite, &agr;-cristobalite solid solution, &agr;-quartz and &agr;-quartz solid solution, containing substantially no lithium disilicate (Li2O·2SiO2), lithium silicate (Li2O·SiO2), &bgr;-spodumene, &bgr;-eucryptite, &agr;-quartz, mica or fluorrichterite, containing substantially no Cr ingredient or Mn ingredient, and having average linear thermal expansion coefficient within a range from +65×10−7/° C. to +140×10−7/° C. within a temperature range from −50° C. to +70° C., said predominant crystal phase or phases having an average crystal grain diameter of less than 0.10 &mgr;m. The glass-ceramics are suitable for use as a substrate for an information storage medium and also for use as a substrate for a light filter.

Abstract: Glass-ceramics fo a light filter capable of preventing variation of refractive index in a band-pass filter have a coefficient of thermal expansion within a range from 95×10−7/° C. to 140×10−7/° C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 85 GPa and bending strength of 10 kg/mm2, and light transmittance for plate thickness of 10 mm of 60% or over within a wavelength range from 950 nm to 1600 nm. Predominant crystal phases of these glass-ceramics should preferably be (a) lithium disilicate and (b) one selected from the group consisting of &agr;-quartz, &agr;-quartz solid solution, &agr;-cristobalite and &agr;-cristobalite solid solution.

Abstract: A glass-ceramic suitable for use as a light filter 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 (Li2O.2SiO2) and at least one selected from a 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) and has a coefficient of thermal expansion of +65 to +130×10−7/° C. at a temperature within a range from −50° C. to +70° C. and surface roughness (Ra) after polishing of 3 Å-9 Å.

Abstract: Glass-ceramics of a light filter capable of preventing variation of refractive index in a band-pass filter have a coefficient of thermal expansion within a range from 95×10−7/° C. to 140×10−7/° C. within a temperature range from −20° C. to +70° C. and, preferably, Young's modulus of 85 GPa and bending strength of 10 kg/mm2, and light transmittance for plate thickness of 10 mm of 60% or over within a wavelength range from 950 nm to 1600 nm. Predominant crystal phases of these glass-ceramics should preferably be (a) lithium disilicate and (b) one selected from the group consisting of &agr;-quartz, &agr;-quartz solid solution, &agr;-cristobalite and &agr;-cristobalite solid solution.