CEILING GLASS AND USE THEREOF

Abstract

A sealing glass is provided that includes SiO.sub.2, Al.sub.2O.sub.3 having a content of less than 2% by weight, is free of PbO except for unavoidable impurities, a coefficient of linear thermal expansion (∝.sub.20-300 of more than 10*10.sup.−6/K, a dielectric constant (ε.sub.r) in the range from at least 7.10 to not more than 7.80 at a measurement frequency of 1 MHz and a temperature of 25° C., and a glass transition temperature (T.sub.g) in a range from 400 to 550° C.

Claims

1. A sealing glass comprising: SiO.sub.2; Al.sub.2O.sub.3 having a content of less than 2% by weight; free of PbO except for unavoidable impurities; a coefficient of linear thermal expansion (∝.sub.20-300) of more than 10*10.sup.−6/K; a dielectric constant (ε.sub.r) in the range from at least 7.10 to not more than 7.80 at a measurement frequency of 1 MHz and a temperature of 25° C.; and a glass transition temperature (T.sub.g) in a range from 400 to 550° C.

2. The sealing glass of claim 1, wherein the glass transition temperature (T.sub.g) is in a range of 450° C. to 500° C.

3. The sealing glass of claim 1, wherein the SiO.sub.2 has a content of at least 45% by weight and not more than 75% by weight.

4. The sealing glass of claim 1, further comprising a content of B.sub.2O.sub.3 of at least 2% by weight and not more than 20% by weight.

5. The sealing glass of claim 1, further comprising alkali metal oxides having a total content that is at least 10% by weight and not more than 40% by weight and Na.sub.2O having a content that is not more than 500 ppm.

6. The sealing glass of claim 1, further comprising Li.sub.2O in a contact of 0% to not more than 10% by weight.

7. The sealing glass of claim 1, further comprising K.sub.2O in a content of at least 5% by weight of and not more than 40% by weight.

8. The sealing glass of claim 1, consisting of two different alkali metal oxides.

9. The sealing glass of claim 8, wherein the two different alkali metal oxides are Li.sub.2O and K.sub.2O.

10. The sealing glass of claim 1, consisting of two different alkaline earth metal oxides.

11. The sealing glass of claim 1, consisting of two different oxides that act as alkaline earth metal oxide as components.

12. The sealing glass of claim 11, wherein the alkaline earth metal oxide are CaO and ZnO.

13. The sealing glass of claim 1, further comprising CaO having a content of 0% by weight to not more than 15% by weight.

14. The sealing glass of claim 1, further comprising ZnO having a content of 0% by weight to not more than 8% by weight.

15. The sealing glass of claim 1, further comprising a stability of the dielectric constant, determined by a ratio of $\frac{C}{C_0}$ where C.sub.0 is a capacitance in an initial state and C is the capacitance after a thermal stressing, where the ratio is less than 2 determined for the thermal stressing at 85° C.

16. The sealing glass of claim 15, wherein the thermal stressing takes place between 40 hours and 600 hours.

17. The sealing glass of claim 15, wherein the ratio is less than less than 1.2.

18. The sealing glass of claim 1, comprising in % by weight on an oxide basis: SiO.sub.2 from 45 to 75, B.sub.2O.sub.3 from 2 to 20, Li.sub.2O from 0 to 10, free of Na.sub.2O except for unavoidable traces, K.sub.2O from 5 to 40, CaO from 0 to 15, BaO from 0 to 16, ZnO from 0 to 8, F from 0 to 10, and a sum of alkali metal oxides in a range from at least 10% by weight to not more than 40% by weight, wherein the unavoidable traces of Na.sub.2O and PbO are in each case not more than 500 ppm by weight.

19. The sealing glass of claim 1, comprising, in % by weight on an oxide basis: SiO.sub.2 from 50 to 63, B.sub.2O.sub.3 from 5 to 18, Li.sub.2O from 1 to 10, free of Na.sub.2O except for unavoidable traces, K.sub.2O from 12 to 20, CaO from 1 to 15, BaO from 0 to 5, ZnO from 0 to 5, F from 0 to 5, and a sum of alkali metal oxides in a range from at least 13% by weight to not more than 30% by weight, wherein the unavoidable traces of Na.sub.2O and PbO are in each case not more than 500 ppm by weight.

20. The sealing glass of claim 1, comprising in % by weight on an oxide basis: SiO.sub.2 from 50 to 72, Al.sub.2O.sub.3 from 0 to 2, B.sub.2O.sub.3 from 2 to 20, Li.sub.2O from 0 to 5, free of Na.sub.2O except for unavoidable traces, K.sub.2O from 10 to 35, CaO from 0 to 7, BaO from 0 to 16, ZnO from 0 to 5, F from 0 to 8, and a sum of alkali metal oxides in a range from at least 15% by weight to not more than 35% by weight, wherein the unavoidable traces of Na.sub.2O and PbO are in each case not more than 500 ppm by weight.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] FIGS. 1a-1b show ToF-SIMS graphs of a potassium-containing glass to illustrate the formation of potassium enrichment.

DETAILED DESCRIPTION

[0086] The invention will be explained further below with the aid of examples. If contents do not add up to 100% by weight in the examples, this is attributable to usual measurement inaccuracies and/or the presence of possible traces and/or rounding errors.

[0087] An advantageous composition of a sealing glass according to the present disclosure is given by the following composition range on an oxide basis in % by weight: [0088] SiO.sub.2 from 45 to 75, preferably from 50 to 65, particularly preferably from 51 to 62, [0089] Al.sub.2O.sub.3 from 0 to 2, preferably free of Al.sub.2O.sub.3 except for unavoidable traces, [0090] B.sub.2O.sub.3 from 2 to 20, preferably from 5 to 18, particularly preferably from 8 to 17, [0091] Li.sub.2O from 0 to 10, preferably from 0 to 5, [0092] Na.sub.2O from 0 to 10, preferably free of Na.sub.2O except for unavoidable traces, [0093] K.sub.2O from 5 to 40, preferably from 8 to 34, particularly preferably from 14 to 34, [0094] CaO from 0 to 15, preferably from 0 to 13, [0095] BaO from 0 to 16, preferably from 0 to 10, particularly preferably free of BaO except for unavoidable traces, [0096] ZnO from 0 to 8, preferably from 0 to 5, [0097] F from 0 to 10, preferably from 0.5 to 8,

[0098] where the sum of the alkali metal oxides, ΣR.sub.2O, is in the range from at least 10% by weight to not more than 40% by weight, preferably from at least 15% by weight to not more than 35% by weight.

[0099] A further advantageous composition of a sealing glass according to the present disclosure is given by the following composition range on an oxide basis in % by weight: [0100] SiO.sub.2 from 50 to 63, preferably from 51 to 56, [0101] Al.sub.2O.sub.3 from 0 to 2, preferably free of Al.sub.2O.sub.3 except for unavoidable traces, [0102] B.sub.2O.sub.3 from 5 to 18, preferably from 7 to 11, [0103] Li.sub.2O from 1 to 10, preferably from 3 to 5, [0104] Na.sub.2O from 0 to 10, preferably from 0 to 0.5, particularly preferably free of Na.sub.2O except for unavoidable traces, [0105] K.sub.2O from 12 to 20, preferably from 15 to 18, [0106] CaO from 1 to 15, preferably from 5 to 15, more preferably from 10 to 15, particularly preferably from 11 to 14, very particularly preferably from 12 to 13, [0107] BaO from 0 to 5, preferably from 0 to 1, [0108] ZnO from 0 to 5, preferably from 2 to 4.5, particularly preferably from 2 to 4, [0109] F from 0 to 5, preferably from 0.1 to 2, particularly preferably from 0.5 to 1.5,

[0110] where the sum of the alkali metal oxides, ΣR.sub.2O, is in the range from at least 13% by weight to not more than 30% by weight, preferably from at least 14% by weight to not more than 26% by weight, particularly preferably from at least 16% by weight to not more than 24% by weight.

[0111] Sealing glasses which have compositions within the above composition range make it possible to achieve dielectric constants ε.sub.r in the range from at least 7.40 to not more than 7.80, preferably determined at a measurement frequency of 1 MHz and a temperature of 25° C.

[0112] The glass transition temperature, T.sub.g, of the sealing glasses having compositions within the above composition range is preferably in the range from 400° C. to 550° C., preferably from 450° C. to 500° C.

Example 1

[0113] In one embodiment, the sealing glass comprises the following components in % by weight on an oxide basis:

TABLE-US-00002 SiO.sub.2 55.6 Al.sub.2O.sub.3   0.030 B.sub.2O.sub.3  8.4 Li.sub.2O  4.1 K.sub.2O 15.9 CaO 11.9 ZnO  3.4 F   0.54.

[0114] In the case of the composition of the sealing glass as per example 1, the following properties are achieved:

[0115] Density 2.59 g/cm.sup.3

[0116] ∝.sub.20-300 10.22*10.sup.−6/K

[0117] Softening point 601° C.

[0118] Working point 792° C.

[0119] Dielectric constant ε.sub.r 7.5

[0120] T.sub.g 470° C.

[0121] The softening point is, for the purposes of the present disclosure, the temperature at which a glass, here the sealing glass according to embodiments, has a viscosity of 10.sup.7.6 dPas, and the working point is the temperature at which a glass, here the sealing glass according to embodiments, has a viscosity of 10.sup.−4 dPas.

Example 2

[0122] In a further embodiment, the sealing glass comprises the following components in % by weight on an oxide basis:

TABLE-US-00003 SiO.sub.2 54.1 Al.sub.2O.sub.3   0.023 B.sub.2O.sub.3  9.0 Li.sub.2O  4.1 K.sub.2O 16.6 CaO 11.9 ZnO  3.4 F   0.63.

[0123] In the case of the composition of the sealing glass as per example 2, the following properties are achieved:

[0124] Density 2.59 g/cm.sup.3

[0125] ∝.sub.20-300 10.4*10.sup.−6/K

[0126] Softening point 593° C.

[0127] Working point 777° C.

[0128] Dielectric constant ε.sub.r 7.5

[0129] T.sub.g 475° C.

Example 3

[0130] In another embodiment, the sealing glass comprises the following components in % by weight on an oxide basis:

TABLE-US-00004 SiO.sub.2 53.1 Al.sub.2O.sub.3   0.021 B.sub.2O.sub.3  9.3 Li.sub.2O  4.2 K.sub.2O 17.2 CaO 12.0 ZnO  3.5 F   0.68.

[0131] In the case of the composition of the sealing glass as per example 3, the following properties are achieved:

[0132] Density 2.59 g/cm.sup.3

[0133] ∝.sub.20-300 10.57*10.sup.−6/K

[0134] Softening point 588° C.

[0135] Working point 764° C.

[0136] Dielectric constant ε.sub.r 7.5

[0137] T.sub.g 470° C.

[0138] The sealing glass of examples 1 to 3 is in each case preferably free of Na.sub.2O and PbO except for unavoidable traces, where unavoidable traces of Na.sub.2O and PbO are in each case not more than 500 ppm by weight, where the sealing glass can additionally comprise secondary constituents and/or traces, for example in the form of refining agents, where the sum of the secondary constituents and/or traces is preferably less than 2% by weight in total.

[0139] Still another advantageous composition of a sealing glass according to the present disclosure is given by the following composition range on an oxide basis in % by weight: [0140] SiO.sub.2 from 50 to 72, preferably from 58 to 63, [0141] Al.sub.2O.sub.3 from 0 to 2, preferably free of Al.sub.2O.sub.3 except for unavoidable traces, [0142] B.sub.2O.sub.3 from 2 to 20, preferably from 13 to 18, [0143] Li.sub.2O from 0 to 5, preferably from 0 to 1, particularly preferably free of Li.sub.2O except for unavoidable traces, [0144] Na.sub.2O from 0 to 10, preferably from 0 to 5, particularly preferably free of Na.sub.2O except for unavoidable traces, [0145] K.sub.2O from 10 to 35, preferably from 15 to 35, particularly preferably from 15 to 20, [0146] CaO from 0 to 7, preferably from 0 to 1, particularly preferably free of CaO except for unavoidable traces, [0147] BaO from 0 to 16, more preferably from 0 to 5, particularly preferably from 0 to 1, particularly preferably free of BaO except for unavoidable traces, [0148] ZnO from 0 to 5, preferably from 0 to 1, particularly preferably free of ZnO except for unavoidable traces, [0149] F from 0 to 8, preferably from 5 to 8,

[0150] where the sum of the alkali metal oxides, ΣR.sub.2O, is in the range from at least 15% by weight to not more than 35% by weight, preferably from at least 17% by weight to not more than 34% by weight.

[0151] In the case of sealing glasses which have compositions within the above composition range, it is possible to achieve dielectric constants ε.sub.r in the range from at least 7.10 to not more than 7.80, preferably determined at a measurement frequency of 1 MHz and a temperature of 25° C.

[0152] The glass transition temperature, T.sub.g, of the sealing glasses having compositions within the above composition range is preferably in the range from 400° C. to 550° C.

Example 4

[0153] In a further embodiment, the sealing glass comprises the following components in % by weight on an oxide basis:

TABLE-US-00005 SiO.sub.2 54.3 Al.sub.2O.sub.3   0.016 B.sub.2O.sub.3 14.6 K.sub.2O 30.0 F   0.75.

[0154] In the case of the composition of the sealing glass as per example 2, the following properties are achieved:

[0155] Density 2.49 g/cm.sup.3

[0156] ∝.sub.20-300 11.3*10.sup.−6/K

[0157] Dielectric constant ε.sub.r 7.2

[0158] T.sub.g 531° C.

[0159] FIGS. 1a and 1b shows concentration curves determined by means of ToF-SIMS of particular ions in a potassium-containing glass to illustrate the potassium enrichment in surface layers of glass.

[0160] FIG. 1a, a first ToF-SIMS graph for a potassium-containing glass in the ground and polished state is shown. The intensity of the measurement signal in arbitrary units a. u. is plotted on the Y axis, while the sputtering time in seconds is plotted on the x axis, with a higher sputtering time indicating a greater penetration depth into the surface of the test specimen examined, here a potassium-containing glass.

[0161] The concentration curves 1, 2, 3, 4, 5 and 6 of the ions potassium K.sup.+, boron.sup.3+, Ba.sup.2+ (for .sup.137Ba.sup.2+), Al.sup.3+, Na.sup.+ and Li.sup.+ at the surface of a glass are shown here and designated accordingly.

[0162] In comparison, FIG. 1b shows the respective concentration curve after cleaning.

[0163] Although the surface of the specimen for FIG. 1a is polished and thus at least mildly cleaned, for the test specimen in FIG. 1b appropriate surface cleaning, for example as is carried out in the production of optical elements such as lenses, was undertaken. The surface of the test specimen on which the ToF-SIMS graph of FIG. 1b was based was thus exposed over a longer period of time to moisture in the form of an aqueous cleaning solution.

[0164] It can be seen that in the case of the glass under consideration in FIGS. 1a-1b after such a cleaning process there is enrichment 10 of potassium in a layer close to the surface, here corresponding to a sputtering time of about 700 seconds.

[0165] The inventors presume that the ability of potassium to form such an enriched layer on contacting of the surface of the glass could lead to the surprising positive effect of the stability of the glass properties, in particular the dielectric properties, even in the case of temperature stresses, in the case of the sealing glasses according to embodiments of the present disclosure. The formation of such a potassium-enriched layer could hinder the mobility of other ions and/or stabilize the polarizability of the glass network.

LIST OF REFERENCE NUMERALS

[0166] 1 Potassium concentration curve [0167] 11 Potassium enrichment [0168] 2 Boron concentration curve [0169] 3 .sup.137Barium concentration curve [0170] 4 Aluminum concentration curve [0171] 5 Sodium concentration curve [0172] 6 Lithium concentration curve