Claims
- 1. Process for producing an optical fluorophosphate glass based on metaphosphates and fluorides of alkaline earth metals and of aluminum and on alkaline earth metal oxides having refractive indices n.sub.e between 1.515 and 1.546, Abbe values .nu..sub.e between 75.8 and 77.4 and positive anomalous partial dispersion values +.DELTA..nu..sub.e between 14.85 and 15.15; said glass having the following composition (in weight-%):
- ______________________________________ Mg 2.4-2.7 Ca 4.5-4.9 Sr 15.9-17.6 Ba 20.2-22.3 Al 5.6-6.2 P 8.8-9.7 F 22.0-24.3 O 15.7-17.4;______________________________________
- said glass being molten from a mixture which has the following composition (in weight-%):
- ______________________________________ Mg(PO.sub.3).sub.2 0.5-1 Ca(PO.sub.3).sub.2 1-2 Ba(PO.sub.3).sub.2 21-24 Al(PO.sub.3).sub.3 10-12,______________________________________
- wherein the total content of all metaphosphates is between 33 and 18 weight-%;
- ______________________________________ MgF.sub.2 6-7 CaF.sub.2 8-10 SrF.sub.2 15-18 AlF.sub.3 14-16______________________________________
- wherein the total content of all fluorides is between 45 and 48 weight-%;
- ______________________________________ BaO 11-13 SrO 5-7______________________________________
- wherein the total content of all oxides is between 16 and 20 weight-%; characterized in that said process is carried out according to the following steps:
- (a) heating the starting mixture at 860-900.degree. C. within a period of 100-130 minutes,
- (b) increasing the temperature within 5 minutes to 1150-1170.degree. C.,
- (c) subsequently stirring within a period of from 60 to 90 minutes,
- (d) reducing the melt temperature to 930-970.degree. C. at a reduced stirring speed, and
- (e) casting at a temperature of from 750 to 760.degree. C. in mold preheated to about 510.degree. C.
- 2. Process according to claim 1, characterized in that it is carried out according to the following steps:
- (a) heating the starting mixture in a platinum crucible at 880.degree. C. within a period of 120 minutes,
- (b) increasing the temperature within 5 minutes to 1160.degree. C.,
- (c) subsequently stirring at a stirrer speed of 180 revolutions per minute within a period of 90 minutes,
- (d) reducing the melt temperature to 950.degree. C. and decreasing the stirring speed to 80 revolutions per minute,
- (e) casting at a temperature of from 750 to 760.degree. C. in aluminum molds preheated to 510.degree. C.
- 3. Process according to claim 1, characterized in that the mixture has the following composition (in weight-%):
- ______________________________________ Mg(PO.sub.3).sub.2 0.8-0.9 Ca(PO.sub.3).sub.2 1.2-1.4 Ba(PO.sub.3).sub.2 21.2-23.4 Al(PO.sub.3).sub.3 10.5-11.6 MgF.sub.2 6.0-6.6 CaF.sub.2 8.2-9.1 SrF.sub.2 15.6-17.3 AlF.sub.3 14.1-15.6 BaO 11.5-12.7 SrO 5.9-6.6.______________________________________
- 4. Process according to claim 3, characterized in that the mixture has the following composition (in weight-%):
- ______________________________________ Mg(PO.sub.3).sub.2 0.80 Ca(PO.sub.3).sub.2 1.27 Ba(PO.sub.3).sub.2 22.31 Al(PO.sub.3).sub.3 11.00 MgF.sub.2 6.32 CaF.sub.2 8.64 SrF.sub.2 16.44 AlF.sub.3 14.88 BaO 12.10 SrO 6.24.______________________________________
Priority Claims (2)
| Number |
Date |
Country |
Kind |
| 3538491 |
Oct 1985 |
DEX |
|
| 3633445 |
Oct 1986 |
DEX |
|
Parent Case Info
This application is a division of application Ser. No. 07/268,635 filed Nov. 8, 1988, now U.S. Pat. No. 4,859,635, which is a file-wrapper-continuing application of application Ser. No. 07/059,925 filed June 9, 1987, now abandoned, which in turn is a continuation-in-part of Internatonal Application No. PCT/DE86/00428, filed Oct. 10, 1986, designating the United States of America.
The application relates to an optical fluorophosphate glass which exhibits anomalous positive partial dispersion and is based on alkaline earth metal metaphosphates, aluminum metaphosphate, alkaline earth metal fluorides, aluminum fluoride and alkaline earth metal oxides, and a process for its production.
For many purposes, the glasses used in the construction of precision optical instruments possess, in addition to well-tried combinations of optical parameters (n.sub.e /.nu..sub.e parameter pairs) and anomalous partial dispersion values, extreme values in their other physico-chemical properties too. It is the task of the glass chemist to develop optical glasses in which as large a number as possible of all other physical properties are optimized in predetermined manner, without adversely influencing or altering the already well-tried optical parameters. Since a modern formulation for optical glass is a multicomponent system, any detectable, i.e. measurable, improvement in individual parameters represents a further step in optimization of the specific material.
It is therefore the object of the present invention to provide an optical glass of this type in which, while retaining its extreme optical data (refractive index, Abbe value, anomalous partial dispersion), the physico-chemical properties of this glass and its technological conditions of production are so improved that reproducible large scale production can be carried out without difficulty, and the resulting glass can, in particular, be produced in large stria-free and bubble-free units.
In the following table, the optical and physico-chemical properties of a known glass are compared with the same properties of the glass according to the invention.
The first four stated parameters designate optical properties and have the following meanings:
+.DELTA..nu..sub.e =positive deviation from the "normal line", as illustrated graphically in, for example, the drawing of German Patent 1,496,563 or the corresponding U.S. Pat. No. 3,451,829 and explained in the associated text. This difference is designated as the "positive" anomalous partial dispersion value.
The lower six parameters designate physico-chemical properties, i.e.:
US Referenced Citations (8)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 2306174 |
Oct 1976 |
FRX |
Non-Patent Literature Citations (1)
| Entry |
| Chemical Abstracts, vol. 103, No. 10, Abstract No. 75254q. |
Divisions (1)
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Number |
Date |
Country |
| Parent |
268635 |
Nov 1988 |
|
Continuations (1)
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Number |
Date |
Country |
| Parent |
59925 |
Jun 1987 |
|
Patent Grant
4941907
