Radiopaque glass and uses thereof

Abstract

The amorphous, or at least partially crystalline, glass-based joining material is suitable for high-temperature applications, particularly in fuel cells and/or sensors. In addition to SiO.sub.2 and B.sub.2O.sub.3 as glass formers, the joining material similarly contains BaO and CaO, whereby the amount of Al.sub.2O.sub.3 is limited. The joining material has a coefficient of linear thermal expansion of at least 7.0.Math.10.sup.6 K.sup.1 in a range of 20 C. to 300 C. The joining material can be used for joining ferritic high-grade steels and/or chromium-containing alloys and/or ceramics, such as stabilized zirconium oxide and/or aluminium oxide.

Claims

1. A radiopaque glass having a refractive index n.sub.d of 1.48 to 1.56, which is free of PbO apart from at most impurities, said radiopaque glass having a composition comprising, in wt. % on an oxide basis: TABLE-US-00007 SiO.sub.2 35-75 B.sub.2O.sub.3 5-15 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-10 BaO 0.6-24 Cs.sub.2O 1-30 SnO.sub.2 >4-15 F 0.5 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

2. The radiopaque glass as defined in claim 1, wherein said composition comprises not more than 5 wt. % of F.

3. The radiopaque glass as defined in claim 1, wherein said composition comprises, in wt. % on an oxide basis: TABLE-US-00008 SiO.sub.2 38-70 B.sub.2O.sub.3 6-15 Al.sub.2O.sub.3 1-7 K.sub.2O 0-7 BaO 0.8-20 Cs.sub.2O 1-28 SnO.sub.2 >4-15 F 0.75-2.5 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

4. The radiopaque glass as defined in claim 1, wherein the sum of BaO+Cs.sub.2O+SnO.sub.2+F is 12 wt. %.

5. The radiopaque glass as defined in claim 1, wherein a molar ratio of SnO.sub.2 to F is at least 0.4.

6. The radiopaque glass as defined in claim 1, wherein a molar ratio of SnO.sub.2 to F is at most 0.85.

7. The radiopaque glass as defined in claim 1, wherein a molar ratio of Cs.sub.2O to the sum of BaO+Cs.sub.2O+SnO.sub.2 is at least 0.05.

8. The radiopaque glass as defined in claim 1, wherein a molar ratio of Cs.sub.2O to the sum of BaO+Cs.sub.2O+SnO.sub.2 is at most 0.48.

9. The radiopaque glass as defined in claim 1, further comprising at least one of the following components in the amount in wt. % based on oxide content as follows: TABLE-US-00009 ZrO.sub.2 0-2 ZnO 0-2 MgO 0-2 CaO 0-2 WO.sub.3 0-2 Nb.sub.2O.sub.5 0-2 HfO.sub.2 0-2 Ta.sub.2O.sub.5 0-2 Gd.sub.2O.sub.3 0-2 Sc.sub.2O.sub.3 0-2 Y.sub.2O.sub.3 0-2 Yb.sub.2O.sub.3 0-2 La.sub.2O.sub.3 0-2.

10. The radiopaque glass as defined in claim 1, which is, apart from at most impurities, free of at least one of Na.sub.2O, Li.sub.2O, MgO, CeO.sub.2, TiO.sub.2, La.sub.2O.sub.3 and ZrO.sub.2.

11. The radiopaque glass as defined in claim 1, which has a refractive index n.sub.d in the refractive index range between 1.48 and 1.56 and a relative aluminum equivalent thickness ALET (%) greater than or equal to a minimum value according to the following equation (I):
Min. relative ALET(%)=C*n.sub.dD, wherein C=11000 and D =16160.

12. The radiopaque glass as defined in claim 11, which has a refractive index n.sub.d in the refractive index range between 1.48 and 1.56 and a relative aluminum equivalent thickness ALET (%) smaller than or equal to a maximum value according to the following equation (II):
max. relative ALET(%)=A*n.sub.dB, wherein A=11430 and B=16230.

13. The radiopaque glass as defined in claim 1, which has a minimum relative ALET of 120% and a maximum relative ALET of 700% when n.sub.d is from 1.48 to <1.49; a minimum relative ALET of 260% and a maximum relative ALET of 1000% when n.sub.d is from 1.49 to <1.51; a minimum relative ALET of 520% and a maximum relative ALET of 1200% when n.sub.d is from 1.51 to <1.53; a minimum relative ALET of 780% and a maximum relative ALET of 1500% when n.sub.d is from 1.53 to <1.55; and a minimum relative ALET of 850%, and a maximum relative ALET of 1600% when n.sub.d is from 1.55 to 1.56.

14. The radiopaque glass as defined in claim 1, which has a minimum relative ALET of 120% and a maximum relative ALET of 760% when n.sub.d is from 1.48 to <1.49; a minimum relative ALET of 240% and a maximum relative ALET of 875% when n.sub.d is from 1.49 to <1.50; a minimum relative ALET of 360% and a maximum relative ALET of 990% when n.sub.d is from 1.50 to <1.51; a minimum relative ALET of 475% and a maximum relative ALET of 1105% when n.sub.d is from 1.51 to <1.52; a minimum relative ALET of 590% and a maximum relative ALET of 1220% when n.sub.d is from 1.52 to <1.53, a minimum relative ALET of 705% and a maximum relative ALET of 1335% when n.sub.d is from 1.53 to <1.54; a minimum relative ALET of 820% and a maximum relative ALET of 1450% when n.sub.d is from 1.54 to <1.55; and a minimum relative ALET of 935% and a maximum relative ALET of 1565% when n.sub.d is from 1.55 to 1.56.

15. The radiopaque glass as defined in claim 1, in which 95 wt. % has a composition consisting, in wt. % on an oxide basis, of: TABLE-US-00010 SiO.sub.2 35-75 B.sub.2O.sub.3 5-15 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-10 BaO 0.6-24 Cs.sub.2O 1-30 SnO.sub.2 >4-15 F 0.5 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

16. A glass for diagnostic purposes in humans or animals, said radioactive glass having a refractive index n.sub.d of 1.48 to 1.56, which is free of PbO apart from at most impurities, said radioactive glass having a composition comprising, in wt. % on an oxide basis TABLE-US-00011 SiO.sub.2 35-75 B.sub.2O.sub.3 5-15 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-10 BaO 0.6-24 Cs.sub.2O 1-30 SnO.sub.2 >4-15 F 0.5 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

17. A dental glass for treating cavities in teeth, or for a dental restoration, in humans or animals, said dental glass comprising a radiopaque glass having a refractive index n.sub.d of 1.48 to 1.56, which is free of PbO apart from at most impurities, said radiopaque glass having a composition comprising, in wt. % on an oxide basis TABLE-US-00012 SiO.sub.2 35-75 B.sub.2O.sub.3 5-15 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-10 BaO 0.6-24 Cs.sub.2O 1-30 SnO.sub.2 >4-15 F 0.5 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

18. The dental glass as defined in claim 17, in the form of a powder or particulate consisting of particles.

19. The dental glass as defined in claim 17, consisting of powder particles with surfaces that are silanized.

20. A polymer-based dental composition comprising a dental polymer and a dental glass as defined in claim 17.

21. A dental cement comprising a dental glass as defined in claim 17.

22. The dental cement as defined in claim 21, wherein it is a polymer-reinforced glass ionomer cement containing the dental glass, wherein the dental glass is in the form of an inert additive.

23. A cover or substrate glass for display technology or photovoltaics, said cover or said substrate glass comprising a lead-free radiopaque glass as defined in claim 1.

24. An embedding material for a radioactive material comprising a lead-free radiopaque glass as defined in claim 1.

25. An X-ray or cathode ray tube comprising a lead-free radiopaque glass as defined in claim 1.

26. An element for optical applications, comprising a lead-free radiopaque glass as defined in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which:

(2) FIG. 1 is a graph showing the correlation between relative ALET and refractive index, n.sub.d, for working examples of the radiopaque glass according to the invention; and

(3) FIG. 2 is a graph illustrating two linear equations for upper and lower limits of the relative ALET.

(4) FIG. 1 shows in graph form the advantageous correlation between refractive index and relative aluminium equivalent thickness (relative ALET) for the working examples:

(5) It is advantageous if, within the claimed refractive index range from 1.48 to 1.56, the refractive index is assigned a relative aluminium equivalent thickness ALET (in %), as may be described by the following equation:
relative ALET (%)=(15480 to 15900)*n.sub.d(23015 to 22695).

(6) According to a first advantageous variant of the invention, it is advantageous if the radiopaque glass with a refractive index n.sub.d in the refractive index range between 1.48 and 1.56 has a relative aluminium equivalent thickness ALET (%) which is greater than or equal to a minimum relative aluminium equivalent thickness (min. relative ALET) which is defined by the following equation:
min. relative ALET (%)=C*n.sub.dD, where C=11000 and D=16160.

(7) It is further advantageous if the radiopaque glass with a refractive index n.sub.d in the refractive index range between 1.48 and 1.56 has a relative aluminium equivalent thickness ALET (%) which is less than or equal to a maximum relative aluminium equivalent thickness (max. relative ALET) which is determined by the equation:
max. relative ALET (%)=A*n.sub.dB, where A=11430 and B=16230.

(8) For the radiopaque glasses, therefore, advantageously, every refractive index in the n.sub.d range 1.48 to 1.56 may be assigned an interval of the relative ALET which is bounded by a maximum relative ALET and a minimum relative ALET. A radiopaque glass according to the invention having a defined refractive index n.sub.d has a relative ALET which lies advantageously in the interval of the relative ALET, the interval being calculable by the equations stated above.

(9) According to this first advantageous variant, the assignment (n.sub.d; relative ALET) is made by the establishing of two linear equations which define the advantageous upper and lower limits of the relative ALET in the n.sub.d range from 1.48 to 1.56 for the glasses according to the invention. FIG. 2 shows the graphs of the linear equations. The graphs form what are called enveloping lines. In the region between the upper enveloping line (maximum) and the lower enveloping line (minimum), the advantageous range of the relative ALET, which is assigned to the n.sub.d range from 1.48 to 1.56, is located for the glasses according to the invention. As can be seen, the working examples are located between the enveloping lines.

(10) According to a second advantageous variant of the invention, in the refractive index range between 1.48 and 1.56, the assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is made via the statement of the following intervals:

(11) TABLE-US-00005 n.sub.d ALET min. and preferably ALET max. 1.48 to <1.49 120% and preferably 700% 1.49 to <1.51 260% and preferably 1000% 1.51 to <1.53 520% and preferably 1200% 1.53 to <1.55 780% and preferably 1500% 1.55 to 1.56 850%, and preferably 1600% preferably 910%

(12) What this means, to give an example, is as follows: a radiopaque glass having a composition in accordance with the invention and a refractive index which is within the n.sub.d range between 1.49 to <1.51 (e.g. n.sub.d=1.50) advantageously has a relative ALET which is at least 260% (corresponding to ALET min.). At maximum, the ALET of this glass may be preferably 1000% (corresponding to ALET max.). For radiopaque glasses which fall within other n.sub.d ranges, the other values indicated in each case for ALET min. and ALET max. are valid. ALET min. therefore defines a lower limit, and ALET max. an upper limit, for the relative ALET, referred to a defined n.sub.d range.

(13) According to an alternative advantageous variant, in the refractive index range between 1.48 and 1.56, the assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is made via the statement of the following intervals:

(14) TABLE-US-00006 n.sub.d ALET min. and preferably ALET max. 1.48 to <1.49 120% and preferably 760% 1.49 to <1.50 240% and preferably 875% 1.50 to <1.51 360% and preferably 990% 1.51 to <1.52 475% and preferably 1105% 1.52 to <1.53 590% and preferably 1220% 1.53 to <1.54 705% and preferably 1335% 1.54 to <1.55 820% and preferably 1450% 1.55 to 1.56 935% and preferably 1565%

(15) What this means, to give an example, is as follows: a radiopaque glass having a composition in accordance with the invention and a refractive index which is within the n.sub.d range between 1.48 to <1.49 (e.g. n.sub.d=1.485) advantageously has a relative ALET which is at least 120% (corresponding to ALET min.). At maximum, the ALET of this glass may be preferably 760% (corresponding to ALET max.). For radiopaque glasses which fall within other n.sub.d ranges, the other values indicated in each case for ALET min. and ALET max. are valid. ALET min. therefore defines a lower limit, and ALET max. an upper limit, for the relative ALET, referred to a defined n.sub.d range.

(16) For gathering the data, glass bulks were produced from the glass compositions of the working examples, and the associated parameters were ascertained: the relative aluminium equivalent thickness (in %) was determined by the technique described above. The refractive index n.sub.d was determined in a known way. The number of samples per working example was 2. Each parameter was measured multiply, and the average values were calculated for the refractive index and the X-ray absorption. Linear regression allows the correlation between index of refraction and radiopacity to be represented for the radiopaque glasses according to the invention with the radiopacifier system of SnO.sub.2, BaO, Cs.sub.2O and F, as shown in FIG. 1.

(17) For comparison, index of refraction and relative aluminium equivalent thickness are likewise plotted in FIG. 1 for the stated comparative examples, which are based on different radiopacifier systems. It can be seen that the working examples in the claimed refractive index range have a much higher X-ray absorption than the comparative examples (based on the respective refractive index). For the same index of refraction, X-ray absorption values achieved in the glasses according to the invention are substantially higherfor example, at n.sub.d=1.548, working example AB1 has a relative ALET of 1240%, while comparative example VB1 has only 763%, comparative example VB10 only 276%, and comparative example VB14 only 190%. In the low index of refraction range as well, at around 1.49, working example AB3 exhibits a relative ALET of 310%, whereas that of comparative example VB19 is only 80%. Accordingly, the X-ray visibility of the glasses according to the invention, and of a polymer-based dental composition produced using them, is significantly increased. Accordingly, for the same thickness, optical elements (e.g. glass protective elements, etc.), comprising the glass according to the invention absorb more X-radiation as known optical elements or else, for the same X-ray absorption, can be made thinner, thereby allowing a weight saving to be made.

(18) Especially in the case of glasses with low indices of refraction, it was hitherto difficult to raise the radiopacity, and possible only to raise it insufficiently, because increasing the proportion of radiopacifiers would have increased the index of refraction at the same time. With the radiopacifier system according to the invention, comprising SnO.sub.2, BaO, Cs.sub.2O and F, a significant rise in the radiopacity is achieved even at low indices of refraction, and, in the higher index of refraction range, the aluminium equivalent thickness is improved very greatly relative to the known glasses.

(19) In FIG. 2, working example AB15, in relation to the radiopacifier components Cs.sub.2O, BaO and SnO.sub.2, exhibits a similar composition and a similarly high relative ALET as working example AB7, but with a refractive index of 1.504 has a much lower refractive index than working example AB7 (n.sub.d=1.525). This is attributable to the advantageous influence of the inventive fluorine component, allowing the refractive index to be adjusted specificallyand in this particular case, to be lowered. As a result it is possible specifically to produce a glass having a high relative ALET and a comparatively low refractive index.

(20) A comparison of working examples AB13 and AB14, which are likewise shown in FIG. 2, makes it clear that through appropriate choice of the radiopacifiers in the radiopacifier system according to the invention, comprising SnO.sub.2, BaO, Cs.sub.2O and F, it is possible to produce glasses having approximately the same refractive index but having different relative ALETs.

(21) The invention may be additionally described by the following declarations as well: 1. Dental composition or dental material, comprising a radiopaque glass according to the invention as filler, for the treatment, more particularly for the filling, of cavities in human and/or animal teeth and/or for dental restoration. 2. Glass powder comprising powder particles composed of the radiopaque glass according to the invention. 3. Glass powder according to declaration 2, wherein the surfaces of the powder particles present are silanized. 4. Filler for polymer-based dental compositions for the treatment, more particularly filling, of cavities in human and/or animal teeth and/or for dental restoration, comprising the glass according to the invention. 5. Polymer-based dental composition comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. 6. Dental glass/polymer composite comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. 7. Dental glass/polymer composite according to declaration 6, wherein the dental polymer is preferably a UV-curable resin based on acrylate, methacrylate,2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)-phenyl]propane (bis-GMA), triethylene glycol dimethacrylate (TEGDMA or TEGMA, depending on what is meant here), urethane dimethacrylate (UDMA), alkanediol dimethacrylate or cyanoacrylate. 8. Dental glass/polymer glass ionomer cement comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. 9. Use of a radiopaque glass according to the invention as dental glass for producing a dental glass/polymer dental composition comprising dental polymer for the treatment, more particularly filling, of cavities in human and/or animal teeth and/or for dental restoration. 10. Use of a radiopaque glass according to the invention as glass powder. 11. Use according to declaration 10, wherein the surfaces of the powder particles present are silanized. 12. Use according to declaration 10 or 11 in a dental glass/polymer dental composition comprising dental polymer. 13. Use of a radiopaque glass according to the invention as radiopacifier in a polymer-based dental composition and/or as element for optical applications and/or as cover glass and/or substrate glass in display technology for cathode ray tubes (CRT) and/or as cover glass and/or substrate glass in photovoltaics and/or as lamp glass in X-ray tubes and/or as material for the embedding of radioactive materials.

(22) With the radiopacifier combination according to the invention (SnO.sub.2, BaO, Cs.sub.2O) and with the defined addition of fluorine it is possible to formulate a glass having on the one hand a desired index of refraction and on the other hand an extremely high X-ray absorption. In accordance with the invention, in the refractive index range from 1.48 to 1.56, it is possible to realize a range of the relative aluminium equivalent thickness from about 120% up to more than 1400%, e.g. up to 1600%.

(23) The examples also demonstrate that the refractive indices n.sub.d of the glass system according to the invention, particularly in a range from 1.48 to 1.56, can be adapted to the intended application without detriment to the necessary ALETs. As a result, the system can be used advantageously in particular as a filler in dental compositions, but also for other applications which impose high requirements on factors including the purity and/or the chemical resistance and temperature stability. The glass system can be produced at favourable cost on an industrial scale.

(24) The glass according to the invention, furthermore, is relatively easy to melt and therefore efficient to produce. Found in particular has been a glass system in which, through changes in the individual constituents within the stated limits, it is possible to adjust the refractive index in line with the requirements of the applicationfor example, requirements asked of a dental filling materialwith the resulting glass having an improved ALET. The variation of the possible refractive indices encompassed by the invention is relatively wide. This glass system permits especially rational industrial production of glasses within the glass system, especially since only a defined selection of raw materials need be held in stock, within which the proportions are varied in the stated amounts. Accordingly, the procedural regimes when melting the glasses within the glass system are also very similar.

(25) While the invention has been illustrated and described as embodied in a radiopaque glass and uses thereof, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.

(26) Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

(27) What is claimed is new and is set forth in the following appended claims.