Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
  • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
  • C03B17/06—Forming glass sheets
  • C03B17/067—Forming glass sheets combined with thermal conditioning of the sheets
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
  • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
  • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
  • C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/14—Compositions for glass with special properties for electro-conductive glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/20—Compositions for glass with special properties for chemical resistant glass
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
  • H05K1/0306—Inorganic insulating substrates, e.g. ceramic, glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2204/00—Glasses, glazes or enamels with special properties
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/1271—Supports; Mounting means for mounting on windscreens
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
  • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/06—Thermal details
  • H05K2201/068—Thermal details wherein the coefficient of thermal expansion is important

Definitions

• the present invention relates to a glass plate and a process for producing the glass plate.
• radio appliances such as radars and portable telephones
• vehicles including motor vehicles and in buildings.
• radio appliances utilizing radio waves having frequencies in a high-frequency band microwaves to millimeter waves
• a gigahertz frequency band e.g., 3-300 GHz range
• High-frequency devices Circuit boards used in such radio appliances for high-frequency applications (hereinafter referred to as “high-frequency devices) generally employ insulating substrates such as resin substrates, ceramic substrates, and glass substrates. Such insulating substrates for use in high-frequency devices are required to attain reductions in transmission loss due to dielectric loss, conductor loss, etc., in order to ensure the properties of high-frequency signals, such as the quality and intensity thereof.
• Patent Literature 1 discloses an ultraviolet- and infrared-absorbing glass constituted from a soda-lime silica glass having a specific composition.
• Patent Literature 1 JP-A-2002-348143
• an object of the present invention is to provide a novel glass plate which is low in propagation loss and transmission loss in a high-frequency band and is usable as the substrates of high-frequency devices or as window materials, and to provide a process for producing the glass plate.
• the present invention relates to the following.
• the glass plate satisfies (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0004, where tan ⁇ 100 is a dielectric dissipation factor of the glass plate at 10 GHz after having been heated to (Tg+50)° C. and then cooled to (Tg ⁇ 150)° C. at 100° C./min.
• the glass plate according to 1 above having a relative permittivity at 10 GHz of ⁇ rA, wherein the glass plate satisfies 0.95 ⁇ ( ⁇ r100/ ⁇ rA) ⁇ 1.05, where ⁇ r100 is a relative permittivity of the glass plate at 10 GHz after having been heated to (Tg+50)° C. and then cooled to (Tg ⁇ 150)° C. at 100° C./min.
• the glass plate according to any one of 1 to 7 above which includes from 30 to 85% of SiO 2 as represented by mol % based on oxides.
• SiO 2 from 57 to 70%
• Al 2 O 3 +B 2 O 3 is from 20 to 40%
• Al 2 O 3 /(Al 2 O 3 +B 2 O 3 ) is 0.1 to 0.45
• Li 2 O from 0 to 5%
• SiO 2 from 55 to 80%
• Al 2 O 3 from 0 to 15%
• SiO 2 +Al 2 O 3 is from 55 to 90%
• MgO from 0 to 20%
• MgO+CaO is from 0 to 30%
• MgO+CaO+SrO+BaO from 0 to 30%
• Li 2 O from 0 to 20%
• the glass plate according to any one of 1 to 9 above which is for use as a substrate for a high-frequency device in which high-frequency signals having a frequency of 3.0 GHz or higher are handled.
• a melting/forming step in which raw materials for glass are melted to obtain a molten glass and the molten glass is formed into a plate shape
• a cooling step in which the molten glass formed into the plate shape is cooled to a temperature of (Tg ⁇ 300)° C. or lower with respect to the glass transition temperature Tg (° C.) to obtain a glass base plate, and
• a heat treatment step in which the obtained glass base plate is heated from the temperature of (Tg ⁇ 300)° C. or lower to a temperature in a range of from (Tg ⁇ 100)° C. to (Tg+50)° C., without being heated to a temperature exceeding (Tg+50)° C., and is then cooled again to (Tg ⁇ 300)° C. or lower,
• each heat treatment step extends until the temperature of the glass base plate exceeds (Tg ⁇ 300)° C., thereafter reaches a maximum temperature Temax (° C.) in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C., and then declines again to (Tg ⁇ 300)° C. or lower,
• a total time period in which the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. in a whole heat treatment step(s) is K (minutes) or longer, the K being represented by the following formula (1) using the maximum temperature Tmax (° C.) of the glass base plate in the whole heat treatment step(s), and
• each heat treatment step satisfies the following formula (2), where t 1 (minutes) is a time period in each heat treatment from a time when the temperature of the glass base plate lastly begins to decline from the maximum temperature Temax (° C.) to a time when the temperature of the glass base plate lastly passes (Tg ⁇ 110)° C.
• t 2 and the t 3 have a difference in time therebetween of 1 minute or more
• Te 2 and Te 3 satisfy the following formula (3).
• the glass plate according to the present invention shows little absorption of electromagnetic waves in a high-frequency band and can attain a high transmittance. Furthermore, using this glass plate in circuit boards makes it possible to provide practical high-frequency devices, such as electronic devices, reduced in propagation loss and transmission loss. Moreover, this glass plate, when used as window materials for vehicles, e.g., motor vehicles, and buildings, can propagate electromagnetic waves without causing considerable attenuation, in the case where millimeter-wave radars have been mounted in the vehicles or electronic appliances are used in the buildings.
• the glass plate according to this embodiment has a dielectric dissipation factor at 10 GHz of tan ⁇ A and a glass transition temperature of Tg° C., and this glass plate, after having been heated to (Tg+50)° C. and then cooled to (Tg ⁇ 150)° C. at 100° C./min, satisfies the relationship (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0004, where tan ⁇ 100 is a dielectric dissipation factor thereof.
• the dielectric dissipation factor (hereinafter sometimes referred to simply as “tan ⁇ ”) of a glass plate is a value represented by ⁇ ′′/ ⁇ ′ using complex permittivity, where ⁇ ′ is relative permittivity and ⁇ ′′ is dielectric loss.
• tan ⁇ The smaller the value of tan ⁇ , the lower the absorption of electromagnetic waves in the frequency band and the higher the attained transmittance.
• dielectric dissipation factor and relative permittivity are values measured at a measuring frequency of 10 GHz by the method as provided for in IEC 61189-2-721 (2015).
• values of tan ⁇ can be regulated by changing the glass composition.
• the present invention is based on a newly discovered method whereby values of tan ⁇ can be regulated without changing a glass composition. This makes it possible to obtain a glass which has a smaller value of tan ⁇ than conventional glasses even when having the same composition.
• Glasses differing in density are obtained by using different cooling rates in glass production. Specifically, a high cooling rate results in a vitreous state having a low density (sparse), while a low cooling rate results in a vitreous state having a high density (dense). It has been discovered that the density of the vitreous state correlates with the value of tan ⁇ in a high-frequency band.
• the glass plate in the case where the vitreous state is dense and has a high density, can have an increased transmittance for electromagnetic waves in a high-frequency band (can be reduced in the absorption of the electromagnetic waves), resulting in a smaller value of tan ⁇ in the high-frequency band.
• the term “high-frequency band” in this description is intended to mean frequencies of usually not shorter than 3.0 GHz, in particular, not shorter than 3.5 GHz, and actual tests were performed at 10 GHz.
• the glass plate according to this embodiment has a smaller value of tan ⁇ A in a high-frequency band than conventional glass plates having the same composition. This can be assessed in terms of the value of (tan ⁇ 100 ⁇ tan ⁇ A) described above. Specifically, in the case where a glass plate having a dielectric dissipation factor at 10 GHz of tan ⁇ A is heated to (Tg+50)° C. and then cooled to (Tg ⁇ 150)° C.
• the glass plate is deemed to be a glass plate obtained through cooling conducted at a cooling rate lower than 100° C./min and has a high density and high transparency.
• this glass plate can be regarded as having a considerably smaller value of tan ⁇ A than conventional glass plates having the same composition and as showing high transparency to electromagnetic waves in a high-frequency band.
• the tan ⁇ A of the glass plate satisfies the relationship (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0004 as stated above, the tan ⁇ A preferably satisfies (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0005, more preferably satisfies (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0006, from the standpoint of making the glass plate show higher transparency.
• the tan ⁇ A may satisfy (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.001, or may satisfy (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0008, or may satisfy (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0007, or may satisfy (tan ⁇ 100 ⁇ tan ⁇ A) ⁇ 0.0006.
• any two portions of the glass plate which are separated from each other by 40 mm or more have a difference in dielectric dissipation factor tan ⁇ at 10 GHz of preferably 0.0005 or less, more preferably 0.0004 or less, still more preferably 0.0003 or less.
• this glass plate can be regarded as having a narrow in-plane distribution of dielectric dissipation factor and can be regarded as a glass plate which had evenness in cooling rate and is homogeneous.
• differences in tan ⁇ are hence preferred.
• the term “any two portions separated from each other by 40 mm or more” means any two portions lying on the same plane and separated by 40 mm or more.
• dielectric dissipation factor tan ⁇ at 10 GHz there is no particular lower limit on the difference in dielectric dissipation factor tan ⁇ at 10 GHz between any two portions of the glass plate which are separated from each other by 40 mm or more, but the difference may be 0.0001 or more.
• the glass plate has a relative permittivity ⁇ rA at 10 GHz which satisfies the relationship 0.95 ⁇ ( ⁇ r100/ ⁇ rA) ⁇ 1.05, where ⁇ r100 is a relative permittivity at 10 GHz of the glass plate which has been heated to (Tg+50)° C. and then cooled to (Tg ⁇ 150)° C. at 100° C./min.
• the value represented by ( ⁇ r100/ ⁇ rA) is more preferably 0.98 or larger, still more preferably 0.99 or larger, and is more preferably 1.03 or smaller, still more preferably 1.02 or smaller, especially preferably 1.01 or smaller.
• the relative permittivity Fr of the obtained glass plate has a substantially constant value even when the glass plate has been produced using different cooling rates. Because of this, a reduction in loss in high-frequency devices can be attained without considerably changing the design of the devices.
• any two portions of the glass plate which are separated from each other by 40 mm or more have a difference in relative permittivity ⁇ rA at 10 GHz of preferably 0.05 or less, more preferably 0.04 or less, still more preferably 0.03 or less.
• this glass plate is a homogeneous glass plate which has a narrow in-plane distribution of relative permittivity and had evenness in cooling rate.
• differences in ⁇ rA are hence preferred.
• the difference may be 0.01 or more.
• the glass plate having such properties can be advantageously used as the substrates of high-frequency devices and as window materials.
• the high-frequency devices are more preferably ones in which high-frequency signals having a frequency of 3.0 GHz or higher, in particular 3.5 GHz or higher, are handled.
• the glass plate preferably includes SiO 2 in an amount of 30-85% as represented by mol % based on oxides.
• the glass plate is more preferably an alkali-free glass.
• the glass plate is more preferably a soda-lime glass.
• this glass plate In the case where the glass plate is for use as the substrate of a high-frequency device, this glass plate more preferably has the following composition as represented by mol % based on oxides.
• SiO 2 from 57 to 70%
• Al 2 O 3 +B 2 O 3 from 20 to 40%
• Li 2 O from 0 to 5%
• SiO 2 is a network-forming substance. In the case where the content thereof is 57% or higher, satisfactory glass-forming ability and satisfactory weatherability can be attained and devitrification can be inhibited. Such SiO 2 contents are hence preferred.
• the content of SiO 2 is more preferably 58% or higher, still more preferably 60% or higher, yet still more preferably 61% or higher. Meanwhile, in the case where the content of SiO 2 is 70% or less, satisfactory glass meltability can be attained; such SiO 2 contents are hence preferred.
• the content thereof is more preferably 68% or less, still more preferably 66% or less, yet still more preferably 65% or less, especially preferably 64% or less, most preferably 63% or less.
• Al 2 O 3 is a component effective in improving the weatherability, improving the Young's modulus, inhibiting the glass from suffering phase separation, reducing the coefficient of thermal expansion, and so on.
• the content of Al 2 O 3 is 5% or higher, the effects of the inclusion of Al 2 O 3 are sufficiently obtained; such Al 2 O 3 contents are hence preferred.
• the content of Al 2 O 3 is more preferably 6% or higher, still more preferably 7% or higher, yet still more preferably 8% or higher. Meanwhile, in the case where the content of Al 2 O 3 is 15% or less, the glass has satisfactory properties including meltability; such Al 2 O 3 contents are hence preferred.
• the content thereof is more preferably 14% or less, still more preferably 13% or less, yet still more preferably 12% or less.
• B 2 O 3 is a component which improves the meltability, and the content thereof is preferably 15% or higher.
• B 2 O 3 is also a component capable of lowering the dielectric dissipation factor in a high-frequency range.
• the content thereof is more preferably 16% or higher, still more preferably 17% or higher, yet still more preferably 17.5% or higher.
• the content of B 2 O 3 is preferably 24% or less, more preferably 23% or less, still more preferably 22% or less.
• the total content of Al 2 O 3 and B 2 O 3 is more preferably 20% or higher, especially preferably 25% or higher, from the standpoint of glass meltability. From the standpoint of heightening the low-dielectric-loss characteristics of the glass plate while maintaining the glass meltability, etc., the total content thereof is preferably 40% or less, more preferably 37% or less, still more preferably 35% or less, especially preferably 33% or less.
• MgO is a component which increases the Young's modulus without increasing the specific gravity, and can thereby heighten the specific modulus. MgO hence is effective in mitigating the problem of deflection and can improve the fracture toughness to heighten the glass strength. Furthermore, MgO is a component which improves the meltability also and can inhibit the glass from having too low a coefficient of thermal expansion. Although MgO may not be contained, the content of MgO, if it is contained, is preferably 0.1% or higher, more preferably 0.2% or higher, still more preferably 1% or higher, yet still more preferably 2% or higher.
• the content of MgO is preferably 10% or less, more preferably 9% or less, still more preferably 8% or less, yet still more preferably 7% or less, particularly preferably 6% or less, in particular 5% or less, especially preferably 4% or less, most preferably 3% or less.
• CaO is characterized by being next to MgO among the alkaline-earth metals in heightening the specific modulus and by not excessively lowering the strain point, and is a component which improves the meltability like MgO. Furthermore, CaO is a component characterized by being less prone to heighten the devitrification temperature than MgO. Although CaO may not be contained, the content of CaO, if it is contained, is preferably 0.1% or higher, more preferably 0.2% or higher, still more preferably 0.5% or higher, yet still more preferably 1% or higher, especially preferably 2% or higher.
• the content of CaO is preferably 10% or less, more preferably 8% or less, still more preferably 7% or less, yet still more preferably 6% or less, particularly preferably 5% or less, in particular 4% or less, especially preferably 3% or less.
• SrO is a component which improves the meltability without heightening the devitrification temperature of the glass.
• the content of SrO if it is contained, is preferably 0.1% or higher, more preferably 0.2% or higher, still more preferably 0.5% or higher, yet still more preferably 1% or higher, especially preferably 2% or higher.
• the content of SrO is desirably 10% or less, preferably 9% or less, more preferably 8% or less, still more preferably 7% or less, yet still more preferably 6% or less, particularly preferably 5% or less, in particular 4% or less, especially preferably 3% or less, most preferably 2.5% or less.
• BaO is a component which improves the meltability without heightening the devitrification temperature of the glass.
• the content of BaO if it is contained, is preferably 0.1% or higher, more preferably 0.2% or higher, still more preferably 1% or higher, especially preferably 2% or higher.
• the content of BaO is preferably 10% or less, more preferably 8% or less, still more preferably 5% or less, yet still more preferably 3% or less.
• ZnO is a component which improves the chemical resistance, but is prone to separate out and may heighten the devitrification temperature. Because of this, the content of ZnO is preferably 0.1% or less, more preferably 0.05% or less, still more preferably 0.03% or less, yet still more preferably 0.01% or less. Especially preferably, the glass composition contains substantially no ZnO.
• the term “containing substantially no ZnO” means that the content thereof is, for example, less than 0.01%.
• the molar ratio represented by ⁇ Al 2 O 3 /(Al 2 O 3 +B 2 O 3 ) ⁇ is preferably 0.1 or higher from the standpoint of enabling the glass to have improved acid resistance and excellent evenness with inhibited phase separation. From the standpoint of imparting an improved Young's modulus, that molar ratio is more preferably 0.3 or higher, still more preferably 0.33 or higher, yet still more preferably 0.35 or higher, especially preferably 0.38 or higher.
• molar ratio is preferably 0.45 or less, more preferably 0.4 or less, still more preferably 0.35 or less, yet still more preferably 0.3 or less.
• the contents of Al 2 O 3 , MgO, CaO, SrO, and BaO as represented by mol % based on oxides are respectively expressed by [Al 2 O 3 ], [MgO], [CaO], [SrO], and [BaO], then the value represented by ⁇ [Al 2 O 3 ] ⁇ ([MgO]+[CaO]+[SrO]+[BaO]) ⁇ is preferably larger than ⁇ 3, more preferably ⁇ 2 or larger, still more preferably ⁇ 1 or larger, especially preferably ⁇ 0.5 or larger, from the standpoint of acid resistance.
• the value represented by ⁇ [Al 2 O 3 ] ⁇ ([MgO]+[CaO]+[SrO]+[BaO]) ⁇ is preferably less than 2, more preferably 1.5 or less, still more preferably 1.0 or less, especially preferably 0.5 or less.
• the content molar ratio represented by ⁇ (SrO+BaO)/RO ⁇ is preferably 0.64 or higher, more preferably 0.7 or higher, still more preferably 0.75 or higher, especially preferably 0.8 or higher, from the standpoints of lowering the surface devitrification temperature and improving the glass production efficiency. Meanwhile, from the standpoint of reducing the raw-material cost in view of the fact that raw materials for SrO and BaO are expensive, the molar ratio is preferably 0.85 or less, more preferably 0.8 or less.
• the RO represents the total content of MgO, CaO, SrO, and BaO.
• R 2 O represents the total content of alkali metal oxides.
• alkali metal oxides include Li 2 O, Na 2 O, K 2 O, Rb 2 O, and Cs 2 O. Since Rb 2 O and Cs 2 O, among alkali metal oxides, are rarely contained in glasses, R 2 O usually means the total content of Li 2 O, Na 2 O, and K 2 O (Li 2 O+Na 2 O+K 2 O).
• the glass composition may not contain alkali metal oxides.
• inclusion of alkali metal oxides eliminates the need of excessive raw-material purification and makes it possible to obtain practical glass meltability and glass plate production efficiency and to regulate the coefficient of thermal expansion of the glass plate. Because of this, in the case where alkali metal oxides are contained, the total content thereof (R 2 O) is preferably 0.001% or higher, more preferably 0.002% or higher, still more preferably 0.003% or higher, especially preferably 0.005% or higher.
• the total content thereof is preferably 5% or less, more preferably 3% or less, still more preferably 1% or less, yet still more preferably 0.2% or less, particularly preferably 0.1% or less, especially preferably 0.05% or less.
• the content of Li 2 O, as one of the alkali metal oxides, is preferably from 0 to 5%, more preferably 0.1% or higher, still more preferably 0.2% or higher, and is more preferably 4% or less, still more preferably 3% or less.
• the content of Na 2 O is preferably from 0 to 5%, more preferably 0.1% or higher, still more preferably 0.2% or higher, and is more preferably 4% or less, still more preferably 3% or less.
• the content of K 2 O is preferably from 0 to 5%, more preferably 0.1% or higher, still more preferably 0.2% or higher, and is more preferably 4% or less, still more preferably 3% or less.
• Fe may be contained in order to reduce resistance values within a melting-temperature range, e.g., the resistance value at 1,500° C.
• the content thereof in terms of Fe 2 O 3 is preferably 0.01% or higher, more preferably 0.05% or higher.
• the content of Fe in terms of Fe 2 O 3 is preferably 1% or less, more preferably 0.5% or less, still more preferably 0.1% or less.
• the ⁇ -OH value which is an index to the water content of the glass, is preferably 0.05 mm ⁇ 1 or higher, more preferably 0.1 mm ⁇ 1 or higher, still more preferably 0.2 mm ⁇ 1 or higher, especially preferably 0.3 mm ⁇ 1 or higher, from the standpoint of attaining a reduced resistance value in a temperature range where raw materials for glass are melted, for example, at around 1,500° C., to make the glass suitable for melting by electric heating.
• the ⁇ -OH value is preferably 1.0 mm ⁇ 1 or less, more preferably 0.8 mm ⁇ 1 or less, still more preferably 0.6 mm ⁇ 1 or less, especially preferably 0.5 mm ⁇ 1 or less.
• the ⁇ -OH value in this description is a value determined by examining a glass sample for absorbance for light having wavelengths of from 2.75 to 2.95 ⁇ m and dividing a maximum absorbance ⁇ max by the thickness (mm) of the sample.
• the glass composition may contain at least one component selected from the group consisting of SnO 2 , Cl, and SO 3 for improving the refinability of the glass plate.
• the total content of these (SnO 2 +Cl+SO 3 ) may be from 0.01 to 1.0 mass % with respect to the total content of SiO 2 , Al 2 O 3 , RO, and R 2 O (SiO 2 +Al 2 O 3 +RO+R 2 O) as represented by mass % based on oxides, which is taken as 100%.
• the total content thereof is preferably 0.80 mass % or less, more preferably 0.50 mass % or less, still more preferably 0.30 mass % or less. Meanwhile, the total content thereof is preferably 0.02 mass % or higher, more preferably 0.05 mass % or higher, still more preferably 0.10 mass % or higher.
• the glass composition may contain at least one component (hereinafter referred to as “minor component”) selected from the group consisting of Sc 2 O 3 , TiO 2 , ZnO 2 , Ga 2 O 3 , GeO 2 , Y 2 O 3 , ZrO 2 , Nb 2 O 5 , In 2 O 3 , TeO 2 , HfO 2 , Ta 2 O 5 , WO 3 , Bi 2 O 3 , La 2 O 3 , Gd 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 for improving the acid resistance of the glass.
• the content of minor components is too high, the glass has reduced evenness and is prone to suffer phase separation. Consequently, the content of minor components, in terms of the total content thereof as represented by mol % based on oxides, is 1.0% or less. Only one of those minor components may be contained, or two or more thereof may be contained.
• the glass composition may be made to contain F for the purposes of improving the meltability, lowering the strain point, lowering the glass transition temperature, lowering the annealing point, etc.
• the content of F is preferably 1 mass % or less with respect to the total content of SiO 2 , Al 2 O 3 , RO, and R 2 O (SiO 2 +Al 2 O 3 +RO+R 2 O) as represented by mass % based on oxides, which is taken as 100%.
• this glass plate in the case where the glass plate is for use as a window material, this glass plate more preferably has the following composition as represented by mol % based on oxides.
• SiO 2 from 55 to 80%
• Al 2 O 3 from 0 to 15%
• SiO 2 +Al 2 O 3 from 55 to 90%
• MgO from 0 to 20%
• MgO+CaO from 0 to 30%
• MgO+CaO+SrO+BaO from 0 to 30%
• Li 2 O from 0 to 20%
• SiO 2 and Al 2 O 3 are components which contribute to an improvement in Young's modulus and thereby make it easy to ensure the strength required of window materials for use in building applications, motor vehicle applications, etc.
• the content of SiO 2 is preferably 55% or higher, more preferably 57% or higher, still more preferably 60% or higher, yet still more preferably 63% or higher, particularly preferably 65% or higher, especially preferably 68% or higher, most preferably 70% or higher.
• the content of SiO 2 is preferably 80% or less, more preferably 78% or less, still more preferably 75% or less, most preferably 74% or less.
• Al 2 O 3 is a component which is for ensuring weatherability and which prevents the glass plate from suffering thermal cracking due to too high an average coefficient of linear expansion.
• the content of Al 2 O 3 is preferably 0.01% or higher, more preferably 0.05% or higher, still more preferably 0.1% or higher.
• the content of Al 2 O 3 is preferably 15% or less, more preferably 10% or less, still more preferably 5% or less, yet still more preferably 1% or less, especially preferably 0.5% or less.
• the total content of SiO 2 and Al 2 O 3 is preferably from 55 to 90% from the standpoint of obtaining a satisfactory radio-wave transmittance. From the standpoints of ensuring weatherability and preventing the average coefficient of linear expansion from becoming too high, the total content thereof is more preferably 57% or higher, still more preferably 60% or higher, yet still more preferably 65% or higher, especially preferably 70% or higher, most preferably 72% or higher. Meanwhile, from the standpoint of keeping the T2 and the T4 low to render the glass easy to produce, the total content thereof is more preferably 85% or less, still more preferably 80% or less, yet still more preferably 78% or less, especially preferably 75% or less.
• B 2 O 3 is a component which improves the meltability and glass strength and heightens the radio-wave transmittance. Meanwhile, B 2 O 3 is a component which makes alkali elements prone to volatilize during melting/forming, leading to a decrease in glass quality. In addition, too high contents thereof reduce the average coefficient of linear expansion to render the glass difficult to physically strengthen. Because of these, the content of B 2 O 3 is preferably 15% or less, more preferably 10% or less, still more preferably 8% or less, yet still more preferably 5% or less, particularly preferably 3% or less, especially preferably 1% or less. Most preferably, the glass composition contains substantially no B 2 O 3 .
• the expression “containing substantially no B 2 O 3 ” means that the glass composition does not contain B 2 O 3 except for the case where B 2 O 3 has come into the glass as an unavoidable impurity.
• MgO is a component which accelerates the melting of the raw materials for glass and improves the weatherability. Meanwhile, from the standpoint of preventing devitrification to heighten the radio-wave transmittance, the content of MgO is preferably 20% or less, more preferably 15% or less, still more preferably 8% or less, yet still more preferably 4% or less, especially preferably 1% or less, most preferably 0.5% or less. MgO may not be contained.
• CaO, SrO, and BaO are components which lower the dielectric dissipation factor of the glass and can improve the meltability of the glass. One or more of these may be contained.
• CaO may not be contained.
• the content thereof is preferably 3% or higher, more preferably 6% or higher, still more preferably 8% or higher, yet still more preferably 10% or higher, especially preferably 110% or higher, from the standpoints that CaO reduces the dielectric loss of the glass to thereby improve the radio-wave transmittance and that CaO can further bring about an improvement in meltability (decreases in T2 and T4).
• the content of CaO is preferably 20% or less. From the standpoint of lower brittleness, the content thereof is more preferably 15% or less, still more preferably 14% or less, yet still more preferably 13% or less, especially preferably 12% or less.
• the content of SrO is preferably 15% or less, more preferably 8% or less, still more preferably 3% or less, yet still more preferably 1% or less, from the standpoints of avoiding an increase in the specific gravity of the glass and enabling the glass to retain the strength and low brittleness.
• the glass composition contains substantially no SrO.
• the expression “containing substantially no SrO” means that the glass composition does not contain SrO except for the case where SrO has come into the glass as an unavoidable impurity.
• the content of BaO is preferably 15% or less, more preferably 5% or less, still more preferably 3% or less, yet still more preferably 2% or less, especially preferably 1% or less, from the standpoints of avoiding an increase in the specific gravity of the glass and enabling the glass to retain the strength and low brittleness.
• the glass composition contains substantially no BaO.
• the expression “containing substantially no BaO” means that the glass composition does not contain BaO except for the case where BaO has come into the glass as an unavoidable impurity.
• the total content of MgO, CaO, SrO, and BaO may be 0% (none of these is contained). However, from the standpoint of lowering the glass viscosity during production to lower the T2 and T4 or from the standpoint of heightening the Young's modulus, the total content thereof is preferably higher than 0%, more preferably 0.5% or higher, still more preferably 5% or higher, yet still more preferably 8% or higher, especially preferably 10% or higher, most preferably 11% or higher.
• the total content thereof is preferably 30% or less, more preferably 17% or less, still more preferably 16% or less, yet still more preferably 15% or less, especially preferably 14% or less, most preferably 13% or less.
• the total content of MgO and CaO is preferably 30% or less, more preferably 25% or less, still more preferably 20% or less, yet still more preferably 15% or less, especially preferably 13% or less.
• the total content thereof may be 0% (neither is contained).
• the total content thereof is preferably 1% or higher, more preferably 2% or higher, still more preferably 5% or higher, yet still more preferably 8% or higher, especially preferably 10% or higher.
• Li 2 O is a component which improves the meltability of the glass and is also a component which renders the glass apt to have an increased Young's modulus, thereby contributing to an improvement in glass strength.
• Li 2 O may not be contained, the inclusion thereof makes chemical strengthening possible and is sometimes effective in heightening the radio-wave transmittance.
• the content of Li 2 O if it is contained, is preferably 0.1% or higher, more preferably 1% or higher, still more preferably 2% or higher, yet still more preferably 3% or higher, especially preferably 4% or higher. Meanwhile, too high Li 2 O contents might result in devitrification or phase separation during glass production to make the production difficult.
• the content thereof is preferably 20% or less, more preferably 16% or less, still more preferably 12% or less, yet still more preferably 8% or less, especially preferably 7% or less, most preferably 6.5% or less.
• Na 2 O and K 2 O are components which improve the meltability of the glass, and incorporating at least either of the two in an amount of 0.1% or larger makes it easy to regulate the T2 to 1,750° C. or lower and the T4 to 1,350° C. or lower. Meanwhile, too low total contents of Na 2 O and K 2 O might make the glass unable to have an increased average coefficient of linear expansion and to be thermally strengthened. Furthermore, by the inclusion of both Na 2 O and K 2 O, the weatherability can be improved while maintaining the meltability. There are cases where the inclusion thereof is effective also in heightening the radio-wave transmittance.
• Na 2 O may not be contained, the inclusion thereof renders chemical strengthening possible, besides having the effects shown above. Because of this, the content thereof is preferably 0.1% or higher, more preferably 1% or higher, still more preferably 3% or higher, yet still more preferably 5% or higher, especially preferably 6% or higher. Meanwhile, from the standpoint of preventing the glass plate from having too high an average coefficient of thermal expansion to become prone to suffer thermal cracking, the content of Na 2 O is preferably 20% or less, more preferably 16% or less, still more preferably 14% or less, yet still more preferably 12% or less, especially preferably 10% or less, most preferably 8% or less.
• K 2 O may not be contained, the inclusion thereof produces the effects shown above. Because of this, the content thereof is preferably 0.1% or higher, more preferably 0.9% or higher, still more preferably 2% or higher, yet still more preferably 3% or higher, especially preferably 4% or higher. Meanwhile, from the standpoint of preventing the glass plate from having too high an average coefficient of thermal expansion to become prone to suffer thermal cracking and from the standpoint of preventing the weatherability from decreasing, the content of K 2 O is preferably 20% or less, more preferably 16% or less, still more preferably 14% or less, yet still more preferably 12% or less, especially preferably 10% or less, most preferably 8% or less. Also from the standpoint of radio-wave transmittance, regulating the content of K 2 O so as to be within that range makes it possible to obtain a high radio-wave transmittance.
• the average coefficient of thermal expansion can be regulated to a desired value to render the glass plate suitable for use as window materials which satisfactorily match with other members, e.g., black ceramics and interlayers.
• R 2 O represents the total content of alkali metal oxides. Since Rb 2 O and Cs 2 O, among alkali metal oxides, are rarely contained in glasses, R 2 O usually means the total content of Li 2 O, Na 2 O, and K 2 O (Li 2 O+Na 2 O+K 2 O).
• Alkali metal oxides although the glass composition may not contain these, are components which lower the glass viscosity during glass production to lower the T2 and the T4. Because of this, the total content of alkali metal oxides, if these are contained, is preferably higher than 0%, more preferably 1% or higher, still more preferably 5% or higher, yet still more preferably 6% or higher, particularly preferably 8% or higher, in particular 10% or higher, especially preferably 11% or higher, most preferably 12% or higher. Meanwhile, from the standpoint of improving the weatherability, the total content thereof is preferably 20% or less, more preferably 19% or less, still more preferably 18.5% or less, yet still more preferably 18.0% or less, especially preferably 17.5% or less, most preferably 17.0% or less.
• the glass composition contains one or more alkali metal oxides
• Na 2 O is contained
• the molar ratio represented by (Na 2 O/R 2 O) is more preferably 0.01 or higher and is more preferably 0.98 or less, from the standpoint of sufficiently obtaining the effect of lowering the dielectric dissipation factor.
• That molar ratio is still more preferably 0.05 or higher, yet still more preferably 0.1 or higher, particularly preferably 0.2 or higher, especially preferably 0.3 or higher, most preferably 0.4 or higher.
• that molar ratio is still more preferably 0.8 or less, yet still more preferably 0.7 or less, especially preferably 0.6 or less, most preferably 0.55 or less.
• the glass composition contains one or more alkali metal oxides
• K 2 O is contained
• the molar ratio represented by (K 2 O/R 2 O) is more preferably 0.01 or higher and is more preferably 0.98 or less, from the standpoint of sufficiently obtaining the effect of heightening the radio-wave transmittance. That molar ratio is still more preferably 0.05 or higher, yet still more preferably 0.1 or higher, particularly preferably 0.2 or higher, especially preferably 0.3 or higher, most preferably 0.4 or higher. Meanwhile, that molar ratio is still more preferably 0.8 or less, yet still more preferably 0.6 or less, especially preferably 0.55 or less.
• the product (R 2 O ⁇ MgO, % 2 ) of the total content of alkali metal oxides (R 2 O, %) and the content of MgO (%) is made small.
• (R 2 O ⁇ MgO) is preferably 100% 2 or less, more preferably 80% 2 or less, still more preferably 66% 2 or less, yet still more preferably 60% 2 or less, particularly preferably 50% 2 or less, especially preferably 40% 2 or less, most preferably 30% 2 or less.
• that product is preferably 1% 2 or larger, more preferably 3% 2 or larger, still more preferably 5% 2 or less.
• ZrO 2 is a component which lowers the glass viscosity during melting to accelerate the melting and improves the heat resistance and chemical durability. Meanwhile, too high contents thereof may result in an increase in liquidus temperature. Because of this, the content of ZrO 2 is preferably 5% or less, more preferably 2.5% or less, still more preferably 2% or less, yet still more preferably 1% or less, especially preferably 0.5% or less. Most preferably, the glass composition contains substantially no ZrO 2 .
• the expression “containing substantially no ZrO 2 ” means that the glass composition does not contain ZrO 2 except for the case where ZrO 2 has come into the glass as an unavoidable impurity.
• the total content of some of the components described above which is represented by (SiO 2 +Al 2 O 3 +MgO+CaO+SrO+BaO+Li 2 O+Na 2 O+K 2 O) is preferably 85% or higher, more preferably 88% or higher, still more preferably 90% or higher, yet still more preferably 92% or higher, particularly preferably 95% or higher, especially preferably 98% or higher, most preferably 99.5% or higher, from the standpoint that such values of that total content not only make it possible to produce the glass plate from easily available raw materials for glass but also make it easy to ensure the weatherability of the glass plate. That total content may be 100%, and is more preferably 99.9% or less in view of cases where a colorant, a refining agent, etc. are added to the glass plate.
• the glass composition may contain at least one component selected from the group consisting of SnO 2 , Cl, and SO 3 for improving the refinability of the glass plate.
• the total content of these (SnO 2 +Cl+SO 3 ) may be from 0.01 to 1.0 mass % with respect to the total content of the main components SiO 2 , Al 2 O 3 , RO, and R 2 O (SiO 2 +Al 2 O 3 +RO+R 2 O) as represented by mass % based on oxides, which is taken as 100%.
• the total content thereof is preferably 0.80 mass % or less, more preferably 0.50 mass % or less, still more preferably 0.30 mass % or less. Meanwhile, the total content thereof is preferably 0.02 mass % or higher, more preferably 0.05 mass % or higher, still more preferably 0.10 mass % or higher.
• glass transition temperature Tg, T2, T4, devitrification temperature, Young's modulus, acid resistance, alkali resistance, coefficient of expansion (average coefficient of expansion), strain point, density, plate thickness, and principal-surface area of the glass plate are as follows.
• the glass transition temperature Tg is preferably 580° C. or higher, more preferably 600° C. or higher, from the standpoint of preventing the substrate from deforming in high-frequency device production steps. Meanwhile, from the standpoint of easily producing the glass plate, the Tg is preferably 750° C. or lower, more preferably 720° C. or lower. Values of glass transition temperature Tg are measured in accordance with JIS R 3103-3:2001.
• the T2 is preferably 1,950° C. or lower, more preferably 1,700° C. or lower, from the standpoint of easily producing the glass plate. Meanwhile, from the standpoint of reducing the convection of the molten glass to make the glass-melting apparatus less apt to be damaged, the T2 is preferably 1,500° C. or higher.
• the T4 is preferably 1,350° C. or lower, more preferably 1,300° C. or lower, from the standpoint of protecting the production apparatus. Meanwhile, from the standpoint that a decrease in the quantity of heat carried into the forming apparatus by the glass results in the necessity of increasing the quantity of heat to be inputted to the forming apparatus, the T4 is preferably 1,100° C. or higher.
• T2 and T4 are measured with a rotary high-temperature viscometer.
• the devitrification temperature is preferably 1,350° C. or lower, more preferably 1,300° C. or lower, from the standpoint that in glass-plate forming, such devitrification temperatures enable the members of the forming apparatus to have lowered temperatures and hence prolonged lives. Meanwhile, although there is no particular lower limit on devitrification temperature, the devitrification temperature may be 1,000° C. or higher, or may be 1,050° C. or higher.
• the devitrification temperature is determined by placing particles of a crushed glass on a dish made of platinum, heat-treating the glass particles for 17 hours in electric furnaces having constant temperatures, examining the heat-treated sample with an optical microscope to determine a highest temperature which has resulted in crystal precipitation in the surface and inside of the glass and a lowest temperature which has not resulted in crystal precipitation, and taking an average of the highest and the lowest temperatures as the devitrification temperature.
• the Young's modulus is preferably 50 GPa or higher, more preferably 55 GPa or higher, from the standpoint that such values of Young's modulus are effective in reducing the amount in which the glass plate deflects when used in high-frequency device production steps. Although there is no particular upper limit on Young's modulus, the Young's modulus may be 100 GPa or less. Values of Young's modulus are measured with an ultrasonic-pulse Young's modulus meter.
• the term “acid resistance” means the amount of glass components extracted per unit surface area when the glass plate is immersed in an aqueous acid solution (6 wt % HNO 3 +5 wt % H 2 SO 4 ; 45° C.) for 170 seconds.
• the extraction amount indicating the acid resistance is preferably 0.05 g/cm 2 or less, more preferably 0.03 g/cm 2 or less, from the standpoint of preventing the glass surfaces from being roughened when cleaned with an acid solution. Although there is no particular lower limit on extraction amount, the extraction amount may be 0.001 g/cm 2 or larger.
• alkali resistance means the amount of glass components extracted per unit surface area when the glass plate is immersed in an aqueous alkali solution (1.2 wt % NaOH; 60° C.) for 30 minutes.
• the extraction amount indicating the alkali resistance is preferably 0.10 g/cm 2 or less, more preferably 0.08 g/cm 2 or less, from the standpoint of preventing the glass surfaces from being roughened when cleaned with an alkali solution. Although there is no particular lower limit on extraction amount, the extraction amount may be 0.001 g/cm 2 or larger.
• the coefficient of expansion use is made of values of the average coefficient of thermal expansion measured with a thermodilatometer in the temperature range of from 50 to 350° C.
• the average coefficient of thermal expansion is preferably 20 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or higher, more preferably 25 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or higher, from the standpoint of more suitably regulating the difference in thermal expansion coefficient between the glass plate and each of other members in configuring, for example, a semiconductor package as a high-frequency device.
• the average coefficient of thermal expansion is preferably 60 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or less, more preferably 50 ⁇ 10 7 (K 1 ) or less.
• the strain point is preferably 500° C. or higher, more preferably 550° C. or higher, from the standpoint of heat resistance. Meanwhile, from the standpoint of facilitating relaxation, the strain point is preferably 800° C. or lower. Values of strain point are measured in accordance with JIS R 3103-2 (2001).
• the density is preferably 2.8 g/cm 3 or less from the standpoint of making the glass plate lightweight. Although there is no particular lower limit on density, the density may be 2.0 g/cm 3 or higher. Values of density are determined by the Archimedes method.
• the plate thickness is preferably 0.05 mm or larger, more preferably 0.1 mm or larger, still more preferably 0.3 mm or larger, from the standpoint of ensuring the strength required of substrates. Meanwhile, from the standpoints of thickness reduction, size reduction, improvement in production efficiency, etc., the plate thickness is preferably 2.0 mm or less, more preferably 1.5 mm or less, still more preferably 1.0 mm or less, yet still more preferably 0.7 mm or less, especially preferably 0.5 mm or less.
• the area of each principal surface of the glass plate is preferably 80 cm 2 or larger, more preferably 350 cm 2 or larger, still more preferably 500 cm 2 or larger, yet still more preferably 1,000 cm 2 or larger, even still more preferably 1,500 cm 2 or larger, and especially preferably 2,000 cm 2 or larger, 2,500 cm 2 or larger, 3,000 cm 2 or larger, 4,000 cm 2 or larger, 6,000 cm 2 or larger, 8,000 cm 2 or larger, 12,000 cm 2 or larger, 16,000 cm 2 or larger, 20,000 cm 2 or larger, and 25,000 cm 2 or larger in order of increasing preference.
• the area of the principal surface of the substrate is usually preferably 5,000,000 cm 2 or less.
• this glass plate has a narrow in-plane distribution of dielectric dissipation factor and is homogeneous. Because of this, the glass plate is suitable for use in producing large-area high-frequency devices and in windows for transmitting high-frequency waves, etc., unlike conventional glass plates.
• the area of the principal surface of the substrate is more preferably 100,000 cm 2 or less, still more preferably 80,000 cm 2 or less, yet still more preferably 60,000 cm 2 or less, especially preferably 50,000 cm 2 or less, particularly preferably 40,000 cm 2 or less, most preferably 30,000 cm 2 or less.
• glass transition temperature Tg, T2, T4, devitrification temperature, Young's modulus, acid resistance, alkali resistance, coefficient of expansion (average coefficient of expansion), strain point, density, plate thickness, and principal-surface area of the glass plate are as follows. Methods for determining these properties are the same as those used for determining the properties in the case of the use as substrates for high-frequency devices.
• the glass transition temperature Tg is preferably 500° C. or higher, more preferably 520° C. or higher, from the standpoint of performing glass bending. Meanwhile, the Tg is preferably 620° C. or lower, more preferably 600° C. or lower, from the standpoint of performing strengthening by air chilling.
• the T2 is preferably 1,550° C. or lower, more preferably 1,480° C. or lower, from the standpoint of easily producing the glass plate. Meanwhile, from the standpoint of reducing the convection of the molten glass to make the glass-melting apparatus less apt to be damaged, the T2 is preferably 1,250° C. or higher.
• the T4 is preferably 1,200° C. or lower, more preferably 1,100° C. or lower, from the standpoint of protecting the production apparatus. Meanwhile, from the standpoint that a decrease in the quantity of heat carried into the forming apparatus by the glass results in the necessity of increasing the quantity of heat to be inputted to the forming apparatus, the T4 is preferably 900° C. or higher.
• the devitrification temperature is preferably 1,100° C. or lower, more preferably 1,000° C. or lower, from the standpoint that in glass-plate forming, such devitrification temperatures enable the members of the forming apparatus to have lowered temperatures and hence prolonged lives. Meanwhile, although there is no particular lower limit on devitrification temperature, the devitrification temperature may be 900° C. or higher.
• the Young's modulus is preferably 50 GPa or higher, more preferably 55 GPa or higher, from the standpoint of attaining a reduced deflection amount. Although there is no particular upper limit on Young's modulus, the Young's modulus may be 100 GPa or less.
• the acid resistance is such that the extraction amount shown above is preferably 0.1 g/cm 2 or less, more preferably 0.05 g/cm 2 or less, from the standpoint of preventing the glass surfaces from being roughened when cleaned with an acid solution. Although there is no particular lower limit on extraction amount, the extraction amount may be 0.001 g/cm 2 or larger.
• the alkali resistance is such that the extraction amount shown above is preferably 0.20 g/cm 2 or less, more preferably 0.10 g/cm 2 or less, from the standpoint of preventing the glass surfaces from being roughened when cleaned with an alkali solution. Although there is no particular lower limit on extraction amount, the extraction amount may be 0.001 g/cm 2 or larger.
• the coefficient of thermal expansion use is made of values of the average coefficient of thermal expansion within the temperature range of from 50 to 350° C.
• the average coefficient of thermal expansion is preferably 60 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or higher, more preferably 70 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or higher, from the standpoint of facilitating strengthening by air chilling. Meanwhile, from the standpoint that too high average coefficients of thermal expansion result in poor thermal shock resistance, the average coefficient of thermal expansion is desirably 130 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or less, preferably 110 ⁇ 10 ⁇ 7 (K ⁇ 1 ) or less.
• the strain point is preferably 450° C. or higher, more preferably 500° C. or higher, from the standpoint of heat resistance. Meanwhile, from the standpoint of facilitating relaxation, the strain point is preferably 700° C. or lower. Values of strain point are measured in accordance with JIS R 3103-2 (2001).
• the density is preferably 2.8 g/cm 3 or less from the standpoint that too high densities make the glass plate too heavy and difficult to handle in conveyance. Although there is no particular lower limit on density, the density may be 2.0 g/cm 3 or higher.
• the plate thickness is preferably 1.0 mm or larger, more preferably 1.5 mm or larger, from the standpoint of ensuring the rigidity required of window materials. Meanwhile, from the standpoint of weight reduction, the plate thickness is preferably 6.0 mm or less, more preferably 5.0 mm or less.
• the area of each principal surface of the glass plate is preferably 350 cm 2 or larger, more preferably 500 cm 2 or larger, still more preferably 1,000 cm 2 or larger, even still more preferably 1,500 cm 2 or larger, and especially preferably 2,000 cm 2 or larger, 2,500 cm 2 or larger, 3,000 cm 2 or larger, 4,000 cm 2 or larger, 6,000 cm 2 or larger, 8,000 cm 2 or larger, 12,000 cm 2 or larger, 16,000 cm 2 or larger, 20,000 cm 2 or larger, and 25,000 cm 2 or larger in order of increasing preference.
• the area of the principal surface of the window material is usually 6,000,000 cm 2 or less. Even when having such a large area, this glass plate has a narrow in-plane distribution of dielectric dissipation factor and is homogeneous. Because of this, the glass plate is suitable for use in producing large-area high-frequency devices and in windows for transmitting high-frequency waves, etc., unlike conventional glass plates.
• the area of the principal surface of the window material is more preferably 100,000 cm 2 or less, still more preferably 80,000 cm 2 or less, yet still more preferably 60,000 cm 2 or less, especially preferably 50,000 cm 2 or less, particularly preferably 40,000 cm 2 or less, most preferably 30,000 cm 2 or less.
• both the tan ⁇ A and the ⁇ rA are small.
• the glass plate is rendered applicable to large-area high-frequency devices, windows for transmitting high-frequency waves, etc. unlike conventional glass plates.
• the tan ⁇ A is preferably 0.009 or less, more preferably 0.008 or less, 0.007 or less, 0.006 or less, and 0.005 or less in order of increasing preference, still more preferably 0.004 or less, especially preferably 0.0035 or less, particularly preferably 0.003 or less, most preferably 0.0025 or less.
• the tan ⁇ A is 0.0001 or larger, more preferably 0.0004 or larger, still more preferably 0.0006 or larger, yet still more preferably 0.0008 or larger, most preferably 0.001 or larger.
• the ⁇ rA is preferably 6.8 or less, more preferably 6.5 or less, 6.0 or less, 5.5 or less, 5.2 or less, and 4.9 or less in order of increasing preference, still more preferably 4.7 or less, especially preferably 4.5 or less, particularly preferably 4.4 or less, most preferably 4.3 or less.
• the ⁇ rA is 3.5 or higher, more preferably 3.6 or higher, still more preferably 3.7 or higher, especially preferably 3.8 or higher, particularly preferably 3.9 or higher, most preferably 4.0 or higher.
• the process of glass plate production according to this embodiment includes, in the following order: a melting/forming step in which raw materials for glass are melted to obtain a molten glass and the molten glass is formed into a plate shape; a cooling step in which the molten glass formed into the plate shape is cooled to a temperature of (Tg ⁇ 300)° C. or lower with respect to the glass transition temperature Tg (° C.) to obtain a glass base plate; and a heat treatment step in which the obtained glass base plate is heated from the temperature of (Tg ⁇ 300)° C. or lower to a temperature in a range of from (Tg ⁇ 100)° C. to (Tg+50)° C., without being heated to a temperature exceeding (Tg+50)° C., and is then cooled again to (Tg ⁇ 300)° C. or lower.
• the heat treatment step is conducted one, two, or three or more times.
• Each heat treatment step extends until the temperature of the glass base plate exceeds (Tg ⁇ 300)° C., thereafter reaches a maximum temperature Temax (° C.) in a range of from (Tg ⁇ 100)° C. to (Tg+50)° C., and then declines again to (Tg ⁇ 300)° C. or lower.
• a total time period in which the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. in the whole heat treatment step(s) is K (minutes) or longer, the K being represented by the following formula (1) using the maximum temperature Tmax (° C.) of the glass base plate in the whole heat treatment step(s).
• Each heat treatment step satisfies the following formula (2), where t 1 (minutes) is a time period in the step from a time when the temperature of the glass base plate lastly begins to decline from the maximum temperature Temax (° C.) to a time when the temperature of the glass base plate lastly passes (Tg ⁇ 110)° C.
• the melting/forming step which is a step for melting raw materials for glass to obtain a molten glass and forming the molten glass into a plate shape
• conventionally known methods can be used without particular limitations.
• One example of the step is shown below.
• Raw materials for glass are prepared so as to result in a desired composition of the glass plate.
• the raw materials are continuously introduced into a melting furnace and heated to preferably about 1,450 to 1,750° C. to obtain a molten glass.
• the raw materials are oxides, carbonates, nitrates, sulfates, hydroxides, halides such as chlorides, etc.
• the melting and refining steps include a step in which the molten glass comes into contact with platinum, fine platinum particles are sometimes released into the molten glass and undesirably come as a foreign substance into the glass plate being obtained.
• Use of raw-material nitrates has the effect of inhibiting the inclusion of platinum as a foreign substance.
• nitrates Usable as the nitrates are strontium nitrate, barium nitrate, magnesium nitrate, calcium nitrate, etc. It is more preferred to use strontium nitrate.
• the particle size of the raw materials use can suitably be made of raw materials ranging from a raw material composed of particles which have a large particle diameter of several hundred micrometers but do not remain undissolved to a raw material composed of particles which have a small particle diameter of about several micrometers and which neither fly off when conveyed nor aggregate to form secondary particles. It is also possible to use granules.
• the water content of each raw material can be suitably regulated in order to prevent the raw material from flying off.
• the melting conditions regarding ⁇ -OH value and the degree of oxidation-reduction of Fe (redox [Fe 2+ /(Fe 2+ +Fe 3+ )]) can be suitably regulated.
• a refining step for removing bubbles from the obtained molten glass may be conducted.
• a method of degassing by depressurization may be used, or degassing may be conducted by heating the molten glass to a temperature higher than the temperature used for melting the raw materials.
• SO 3 or SnO 2 may be used as a refining agent.
• Preferred SO 3 sources are sulfates of at least one element selected from Al, Li, Na, K, Mg, Ca, Sr, and Ba. More preferred are sulfates of alkali metals. Of these, Na 2 SO 4 is especially preferred because this sulfate is highly effective in enlarging bubbles and shows satisfactory initial solubility. Also sulfates of alkaline-earth metals may be used. Of these, CaSO 4 .2H 2 O, SrSO 4 , and BaSO 4 are more preferred because these sulfates are highly effective in enlarging bubbles.
• a refining agent in the method of degassing by depressurization it is preferred to use a halogen such as Cl or F.
• Preferred Cl sources are chlorides of at least one element selected from Al, Mg, Ca, Sr, and Ba. More preferred are chlorides of alkaline-earth metals. Of these, SrCl 2 .6H 2 O and BaCl 2 .2H 2 O are especially preferred because these chlorides are highly effective in enlarging bubbles and have low deliquescence.
• Preferred F sources are fluorides of at least one element selected from Al, Na, K, Mg, Ca, Sr, and Ba. More preferred are fluorides of alkaline-earth metals. Of these, CaF 2 is still more preferred because this fluoride is highly effective in enhancing the meltability of raw materials for glass.
• Tin compounds represented by SnO 2 evolve O 2 gas in glass melts.
• SnO 2 is reduced to SnO at temperatures not lower than 1,450° C. to evolve O 2 gas and thereby function to grow the bubbles.
• raw materials for glass are melted by heating to about 1,450 to 1,750° C. and, hence, the bubbles in the glass melt are more effectively enlarged.
• a forming step is conducted in which the molten glass, preferably the molten glass from which bubbles have been removed in the refining step, is formed into a plate shape to obtain a glass ribbon.
• a known method for forming a glass into a plate shape such as a float process in which a molten glass is poured onto a molten metal, e.g., tin, and thereby formed into a plate shape to obtain a glass ribbon, an overflow downdraw process (fusion process) in which a molten glass is caused to flow downward from a trough member, or a slit downdraw process in which a molten glass is caused to flow down through a slit.
• the molten glass may be subjected as such to the subsequent cooling step without being formed into a plate shape.
• the molten glass obtained in the forming step is cooled to a temperature of (Tg ⁇ 300)° C. or lower with respect to the glass transition temperature Tg (° C.) to obtain a glass base plate.
• Tg glass transition temperature
• any desired average cooling rate can be employed without particular limitations thereon.
• the average cooling rate is preferably 10° C./min or higher, more preferably 40° C./min or higher.
• the average cooling rate is preferably 1,000° C./min or less, more preferably 100° C./min or less.
• An average cooling rate from (Tg+50)° C. to (Tg ⁇ 100)° C. is preferably higher than 10° C./min, more preferably 15° C./min or higher.
• average cooling rate in the case where the center and edge portions of the glass plate differ in cooling rate, means an average value determined from refractive indexes.
• the cooling rates of the center and the edge portions can be determined by measuring the respective refractive indexes.
• a heat treatment step is conducted in which the obtained glass base plate is heated from the temperature of (Tg ⁇ 300) ° C. or lower to a temperature in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C., without being heated to a temperature exceeding (Tg+50)° C., and is then cooled again to (Tg ⁇ 300)° C. or lower.
• This heat treatment step may be conducted only once or may be conducted two or three or more times.
• Each heat treatment step extends until the temperature of the glass base plate exceeds (Tg ⁇ 300)° C., thereafter reaches a maximum temperature Temax (° C.) in a range of from (Tg ⁇ 100)° C. to (Tg+50)° C., and then declines again to (Tg ⁇ 300)° C. or lower.
• the heating rate from above the (Tg ⁇ 300)° C. to the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. is not particularly limited.
• the glass base plate Before the temperature of the glass base plate reaches the range of from (Tg ⁇ 100)° C. to (Tg+50)° C., the glass base plate may be repeatedly heated and cooled or may be held at a certain temperature.
• the total time period in which the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. in the whole heat treatment step(s) is K (minutes) or longer, the K being represented by the following formula (1) using the maximum temperature Tmax (° C.) of the glass base plate in the whole heat treatment step(s).
• the total time period in which the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. is the sum of the time period in the first heat treatment step when the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. and the time period in the second and any succeeding heat treatment steps when the temperature of the glass base plate is in the range.
• K (minutes) or longer an improvement in radio-wave transparency is attained.
• the total time period in which the temperature of the glass base plate is in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. is preferably (K+5) minutes or longer, more preferably (K+10) minutes or longer. Although there is no particular upper limit thereon, that total time period is preferably (K+60) minutes or shorter, more preferably (K+45) minutes or shorter, still more preferably (K+30) minutes or shorter, from the standpoint of heightening the production efficiency.
• the glass base plate is not particularly limited in temperature profile. That is, the glass base plate may be repeatedly heated and cooled in one heat treatment step so that, for example, the glass base plate is heated to a temperature in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C., subsequently cooled to a temperature higher than (Tg ⁇ 300)° C. but lower than (Tg+50)° C., and then heated again to a temperature in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C. Moreover, the glass base plate may be held at a certain temperature.
• the lower limit of that temperature range is (Tg ⁇ 100)° C. from the standpoint of improving the radio-wave transparency
• the lower limit is preferably (Tg ⁇ 90)° C. or higher, more preferably (Tg ⁇ 80)° C. or higher.
• the upper limit of that temperature range is (Tg+50)° C. from the standpoint of preventing the glass from deforming, the upper limit is preferably (Tg+40)° C. or lower, more preferably (Tg+35)° C. or lower.
• Each heat treatment step satisfies the following formula (2), where t 1 (minutes) is a time period in each heat treatment step from a time when the temperature of the glass base plate lastly begins to decline from the maximum temperature Temax (° C.) to a time when the temperature of the glass base plate lastly passes (Tg ⁇ 110)° C.
• Temax ° C.
• the highest temperature of the two or more values of Temax (° C.) is the Tmax (° C.).
• the glass base plate can have various temperature profiles, examples of which include: the aforementioned case where the glass base plate is heated to a temperature in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C., subsequently cooled to a temperature higher than (Tg ⁇ 300)° C. but lower than (Tg+50)° C., and then heated again to a temperature in the range of from (Tg ⁇ 100)° C. to (Tg+50)° C.; the case where the glass base plate is heated and cooled in the temperature range of from (Tg ⁇ 100)° C. to (Tg+50)° C. and thereby undergoes temperature changes; and the case where the glass base plate is held at a certain temperature in the temperature range of from (Tg ⁇ 100)° C. to (Tg+50)° C.
• Temperature profiles in the heat treatment step other than those described above are not particularly limited.
• Formula (3) indicates that the cooling rate at the time t 1 is not too high. In the case where the relationship of formula (3) is satisfied, a sufficient heat treatment period can be ensured. Such heat treatment step is hence preferred.
• the value represented by (Te 2 ⁇ Te 3 )/(t 3 ⁇ t 2 ) is more preferably 9 or smaller, still more preferably 8 or smaller. Although there is no particular lower limit thereon, that value may be 0.1 or larger from the standpoint of preventing the glass plate production from requiring too long a period.
• VC average cooling rate of the center of the glass base plate and an average cooling rate of an edge portion of the glass base plate in cooling from the maximum temperature Temax (° C.) to (Tg ⁇ 300)° C. or lower
• VC average cooling rate of the center of the glass base plate and an average cooling rate of an edge portion of the glass base plate in cooling from the maximum temperature Temax (° C.) to (Tg ⁇ 300)° C. or lower
• VE ° C./min
• the ratio represented by VC/VE is preferably as close to 1 as possible, because such values of the ratio make it possible to obtain a homogeneous glass plate.
• that ratio is preferably 0.8 or larger, more preferably 0.9 or larger, and is preferably 1.2 or less, more preferably 1.1 or less, most preferably 1.
• the glass base plate which has been cooled to (Tg ⁇ 300)° C. or lower in the heat treatment step is successively cooled to room temperature (e.g., 50° C. or lower), thereby obtaining the glass plate according to this embodiment.
• Conditions for the cooling to room temperature are not particularly limited.
• the average cooling rate from (Tg ⁇ 300)° C. to 50° C. is preferably 0.5° C./min or higher and is preferably 50° C./min or less. Meanwhile, natural cooling may be conducted without performing temperature control.
• a molten glass may be formed into a plate shape using a press forming method in which the glass is directly formed into a plate shape.
• this glass plate can be subjected to any desired treatments, processing, etc., such as, for example, strengthening by air chilling, chemical strengthening, and polishing.
• platinum crucible made of platinum or an alloy including platinum as a main component, as a melting tank and/or a refining tank.
• raw materials are prepared so as to result in the composition of a glass plate to be obtained, and the platinum crucible containing the raw materials is heated in an electric furnace preferably to about 1,450° C. to 1,700° C.
• a platinum stirrer is inserted thereinto to stir the contents for from 1 to 3 hours, thereby obtaining a molten glass.
• the molten glass may be poured, for example, onto a carbon plate or into a mold to form the molten glass into a plate shape or a block shape.
• the propagation loss of high-frequency signals can be reduced to improve the properties, e.g., quality and intensity, of the high-frequency signals.
• substrates constituted of this glass plate are suitable for use in high-frequency devices in which high-frequency signals of 3.0 GHz or higher are handled.
• the substrates are suitable also for use in high-frequency devices in which signals in various high-frequency bands are handled, such as signals having frequencies of 3.5 GHz or higher, 10 GHz or higher, 30 GHz or higher, 35 GHz or higher, etc.
• the high-frequency devices are not particularly limited. Examples thereof include high-frequency devices (electronic devices) such as semiconductor devices for use in communication appliances such as portable telephones, smartphones, portable digital assistants, and Wi-Fi appliances, surface acoustic wave (SAW) devices, radar components such as radar transceivers, and antenna components such as liquid-crystal antennas.
• high-frequency devices electronic devices
• semiconductor devices for use in communication appliances such as portable telephones, smartphones, portable digital assistants, and Wi-Fi appliances
• SAW surface acoustic wave
• radar components such as radar transceivers
• antenna components such as liquid-crystal antennas.
• this glass plate is suitable also for use as window materials for vehicles, e.g., motor vehicles, and buildings. This is because there are cases where those high-frequency devices in which high-frequency signals are handled are disposed in vehicles like millimeter-wave radars. Furthermore, there are frequently cases where high-frequency devices are used in buildings like communication appliances and base stations. Because of this, the glass plate is exceedingly useful in reducing the propagation loss of high-frequency signals in the window materials.
• this glass plate besides being a glass plate formed into a flat-plate shape by, for example, a float process or a fusion process, may be a bent glass plate obtained by forming the flat-plate-shaped glass plate into a curved shape by gravitational forming, press forming, etc.
• the glass plate can be deformed at will before use in accordance with where the glass plate is to be disposed.
• the glass constituting the glass plate is not particularly limited to soda-lime glass, aluminosilicate glass, alkali-free glass, etc., and an appropriate glass can be selected in accordance with applications.
• the glass may be a strengthened glass having a compression stress layer in the glass surfaces and a tensile stress layer in an inner portion of the glass.
• the strengthened glass use can be made of either a chemically strengthened glass or a glass strengthened by air chilling (physically strengthened glass).
• Raw material for glass were put in a platinum crucible so as to result in the composition which is Composition 1 shown in Table 1, and were melted by heating at 1,650° C. for 3 hours in an electric furnace, thereby obtaining a molten glass.
• a platinum stirrer was inserted into the platinum crucible and the contents were stirred therewith for 1 hour to homogenize the glass.
• the molten glass was poured onto a carbon plate and thereby formed into a plate shape (melting/forming step).
• the plate-shaped molten glass was introduced into an electric furnace having a temperature of about (Tg+50)° C. and the temperature was maintained for 1 hour. Thereafter, the glass was cooled to room temperature ° C. at an average cooling rate of 1° C./min to obtain glass base plates (cooling step).
• the glass base plates were heated to 630° C. at 10° C./min and held at 630° C. for the time periods shown in Table 2 in the row “Holding period (min)”. Thereafter, the glass base plates were cooled in the electric furnace from 630° C. to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 2 and then allowed to cool naturally to room temperature, thereby obtaining glass plates (heat treatment step).
• Examples 1 to 3 are Examples according to the present invention, and Example 4 is Comparative Example.
• the obtained glass plates were examined for the following properties by the methods shown below.
• each blank in the composition indicates that the raw material had not been added on purpose, and each of the blanks regarding the properties indicates that the property was not determined.
• Each glass was examined for viscosity to calculate T2 and T4. Specifically, a rotary high-temperature viscometer (RVM-550, manufactured by OPT Corp.) was used to determine the viscosity of the glass in accordance with ASTM C965-96 (2002). MIST717a was used as a reference to correct the viscosity of the glass, and the T2 and the T4 were calculated therefrom.
• RVM-550 rotary high-temperature viscometer
• Devitrification temperature was determined by placing particles of a crushed glass on a dish made of platinum, heat-treating the glass particles for 17 hours in electric furnaces having constant temperatures, examining the heat-treated sample with an optical microscope (Model ME600, manufactured by Nikon Corp.) to determine a highest temperature which had resulted in crystal precipitation in the surface and inside of the glass and a lowest temperature which had not resulted in crystal precipitation, and taking an average of the highest and the lowest temperatures as the devitrification temperature.
• an optical microscope Model ME600, manufactured by Nikon Corp.
• Young's modulus was measured with an ultrasonic-pulse Young's modulus meter (38DL-PAUS, manufactured by Olympus Co., Ltd.) in accordance with JIS R 1602 (1995).
• Acid resistance was determined by immersing a glass sample in an aqueous acid solution (6 wt % HNO 3 +5 wt % H 2 SO 4 ; 45° C.) for 170 seconds and evaluating the amount of glass components extracted per unit surface area (mg/cm 2 ).
• Alkali resistance was determined by immersing a glass sample in an aqueous alkali solution (1.2 wt % NaOH; 60° C.) for 30 minutes and evaluating the amount of glass components extracted per unit surface area (mg/cm 2 ).
• the coefficient of thermal expansion within the temperature range of from 50 to 350° C. was measured with a TMA (Model TD5000SA, manufactured by MAC Corp.) in accordance with JIS R 3102 (1995). An average of the resultant coefficients of linear expansion at 50-350° C. was determined as the average coefficient of thermal expansion.
• Density was determined in accordance with JIS Z 8807 (2012).
• the dielectric dissipation factor tan ⁇ A at 10 GHz of an obtained glass plate was measured with a resonator for 10 GHz (resonator for 10 GHz manufactured by OWED Company) by an SPDR method in accordance with IEC 61189-2-721 (2015).
• the glass plate was heated to (Tg+50)° C. and cooled to (Tg ⁇ 150)° C. at 100° C./min, and was then examined for dielectric dissipation factor tan ⁇ 100 at 10 GHz in the same manner.
• the relative permittivity ⁇ rA at 10 GHz of an obtained glass plate was measured with a resonator for 10 GHz (resonator for 10 GHz manufactured by OWED Company) by an SPDR method in accordance with IEC 61189-2-721 (2015).
• the glass plate was heated to (Tg+50)° C. and cooled to (Tg ⁇ 50)° C. at 100° C./min, and was then examined for relative permittivity ⁇ r100 at 10 GHz in the same manner.
• Example 1 Example 2
• Example 3 Example 4 Tmax (° C.) 630 630 630 630 Temax (° C.) 630 630 630 630 630 Holding period (min) 1550 210 75 30 Average cooling rate (° C./min) 0.1 1 10 500 ⁇ r100 4.49 4.49 4.49 tan ⁇ 100 0.0062 0.0062 0.0062 ⁇ rA 4.51 4.47 4.46 4.42 tan ⁇ A 0.0044 0.0050 0.0056 0.0066 ⁇ tan ⁇ 0.0018 0.0012 0.0006 ⁇ 0.0004 ⁇ r100/ ⁇ rA 1.00 1.00 1.01 1.02 t1 (min) 1600 160 16 0.32 Value of K in formula (1) 15 15 15 15 Value of left side of formula (2) 0.10 1.0 10.0 500.0
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 2 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 597° C. at 10° C./min and held at 597° C. for the time periods shown in Table 3 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 3.
• Examples 5 to 7 are Examples according to the present invention, and Example 8 is Comparative Example.
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 3 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 653° C. at 10° C./min and held at 653° C. for the time periods shown in Table 4 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 4.
• Examples 9 to 11 are Examples according to the present invention, and Example 12 is Comparative Example.
• Example 10 Example 11
• Example 12 Tmax (° C.) 653 653 653 653 Temax (° C.) 653 653 653 653 Holding period (min) 1550 210 75
• Average cooling rate (° C./min) 0.1 1 10 500 ⁇ r100 4.36 4.36 4.36 tan ⁇ 100 0.0029 0.0029 0.0029 ⁇ rA 4.34 4.35 4.36 4.37 tan ⁇ A 0.0018 0.0022 0.0025 0.0032 ⁇ tan ⁇ 0.0011 0.0007 0.0004 ⁇ 0.0003 ⁇ r100/ ⁇ rA 1.00 1.00 1.00 1.00 t1 (min) 1300 130 13 0.26 Value of K in formula (1) 15 15 15 15 Value of left side of formula (2) 0.10 1.0 10.0 500.0
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 4 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 675° C. at 10° C./min and held at 675° C. for the time periods shown in Table 5 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 5.
• Examples 13 to 15 are Examples according to the present invention, and Example 16 is Comparative Example.
• Example 16 Tmax (° C.) 675 675 675 675 Temax (° C.) 675 675 675 675 675 Holding period (min) 1550 210 75 30 Average cooling rate (° C./min) 0.1 1 10 500 ⁇ r100 4.86 4.86 4.86 tan ⁇ 100 0.0032 0.0032 0.0032 ⁇ rA 4.83 4.84 4.86 4.88 tan ⁇ A 0.0022 0.0025 0.0028 0.0034 ⁇ tan ⁇ 0.0010 0.0007 0.0004 ⁇ 0.0002 ⁇ r100/ ⁇ rA 1.01 1.00 1.00 1.00 t1 (min) 1600 160 16 0.32 Value of K in formula (1) 15 15 15 15 Value of left side of formula (2) 0.10 1.0 10.0 500.0
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 5 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 760° C. at 10° C./min and held at 760° C. for the time periods shown in Table 6 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 6.
• Examples 17 to 19 are Examples according to the present invention, and Example 20 is Comparative Example.
• Example 17 Example 18
• Example 19 Example 20 Tmax (° C.) 760 760 760 760 Temax (° C.) 760 760 760 760 760 760 Holding period (min) 1550 210 75 30 Average cooling rate (° C./min) 0.1 1 10 500 ⁇ r100 5.45 5.45 5.45 tan ⁇ 100 0.0063 0.0063 0.0063 ⁇ rA 5.42 5.44 5.44 5.46 tan ⁇ A 0.0044 0.005 0.0056 0.0067 ⁇ tan ⁇ 0.0019 0.0013 0.0007 ⁇ 0.0004 ⁇ r100/ ⁇ rA 1.01 1.00 1.00 1.00 t1 (min) 1600 160 16 0.32 Value of K in formula (1) 15 15 15 15 Value of left side of formula (2) 0.10 1.0 10.0 500.0
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 6 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 760° C. at 10° C./min and held at 760° C. for the time periods shown in Table 7 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 7.
• Examples 21 to 23 are Examples according to the present invention, and Example 24 is Comparative Example.
• Example 21 Example 22
• Example 23 Example 24 Tmax (° C.) 755 755 755 755 Temax (° C.) 755 755 755 755 Holding period (min) 1550 210 75 30 Average cooling rate (° C./min) 0.1 1 10 500 ⁇ r100 5.14 5.14 5.14 tan ⁇ 100 0.0053 0.0053 0.0053 0.0053 ⁇ rA 5.18 5.17 5.16 5.12 tan ⁇ A 0.0033 0.0040 0.0047 0.0058 ⁇ tan ⁇ 0.0020 0.0013 0.0006 ⁇ 0.0005 ⁇ r100/ ⁇ rA 0.99 0.99 1.00 1.00 t1 (min) 8650 865 86.5 1.73 Value of K in formula (1) 15 15 15 15 15 Value of left side of formula (2) 0.10 1.00 10.00 500.00
• Glass plates were obtained in the same manner as in Example 1, except that raw materials for glass were used so as to result in the composition shown as Composition 7 in Table 1, that in the subsequent heat treatment step, the glass base plates were heated to 700° C. at 10° C./min and held at 700° C. for the time periods shown in Table 8 in the row “Holding period (min)”, and that the glass base plates were cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 8.
• Examples 25 to 27 are Examples according to the present invention, and Example 28 is Comparative Example.
• Raw materials for glass were used so as to result in the composition shown as Composition 4 in Table 1, and a plate-shaped molten glass was obtained using a glass melting tank and a forming apparatus (melting/forming step).
• the plate-shaped molten glass which had been 700° C. was cooled to room temperature with an annealing apparatus at an average cooling rate of 50° C./min to obtain glass base plates having a size of 37 cm ⁇ 47 cm and a thickness of 1.1 mm (cooling step).
• glass plates were obtained in the same manner as in Example 1, except that the glass base plates were heated to the temperatures Tmax (° C.) shown in Table 9 at 10° C./min, held at the temperatures Tmax (° C.) for the time periods shown in Table 9 in the row “Holding period (min)”, and cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 9.
• Tmax ° C.
• Table 9 the temperatures shown in Table 9 at 10° C./min
• Tmax ° C.
• Tmax time periods shown in Table 9 in the row “Holding period (min)”
• the temperature of the electric furnace was regulated so that if the average cooling rate of the center of each glass base plate and the average cooling rate of an edge portion thereof were respectively expressed by VC (° C./min) and VE (° C./min), then the ratio represented by VC/VE was 1.1 or less.
• edge portion of the glass base plate means a position which is at a distance of 10 cm from an edge of the glass base plate.
• Table 9 further shows: the difference in tan ⁇ A between two portions which differed most in tan ⁇ A among the approximately central portion of the plate and the four portions near the corners; and the difference in ⁇ rA between two portions which differed most in ⁇ rA among those five portions.
• Raw materials for glass were used so as to result in the composition shown as Composition 6 in Table 1, and a plate-shaped molten glass was obtained using a glass melting tank and a forming apparatus (melting/forming step).
• the plate-shaped molten glass which had been 800° C. was cooled to room temperature with an annealing apparatus at an average cooling rate of 800° C./min to obtain glass base plates having a size of 37 cm ⁇ 47 cm and a thickness of 1.1 mm (cooling step).
• glass plates were obtained in the same manner as in Example 1, except that the glass base plates were heated to the temperatures Tmax (° C.) shown in Table 10 at 10° C./min, held at the temperatures Tmax (° C.) for the time periods shown in Table 10 in the row “Holding period (min)”, and cooled in the electric furnace to (Tg ⁇ 300)° C. at the average cooling rates shown in Table 10.
• Tmax ° C.
• Table 10 the temperatures shown in Table 10° C./min
• the temperature of the electric furnace was regulated so that if the average cooling rate of the center of each glass base plate and the average cooling rate of an edge portion thereof were respectively expressed by VC (° C./min) and VE (° C./min), then the ratio represented by VC/VE was 1.1 or less.
• edge portion of the glass base plate means a position which is at a distance of 10 cm from an edge of the glass base plate.
• the obtained glass plates were examined for relative permittivity and dielectric dissipation factor under the same conditions as in Example 1. An approximately central portion of each plate and four portions near the corners were thus examined and maximum values and minimum values of those properties were recorded. The results thereof are shown in Table 10.
• Table 10 further shows: the difference in tan ⁇ A between two portions which differed most in tan ⁇ A among the approximately central portion of the plate and the four portions near the corners; and the difference in ⁇ rA between two portions which differed most in ⁇ rA among those five portions.

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