Claims
- 1. Durable visibly transparent clear microspheres less than about 2 millimeters in diameter, containing no more than about 5 weight-percent scattered crystallinity, and adapted for use as a reflective element in a pavement marking, said microspheres being formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________B.sub.2 O.sub.3 5-20TiO.sub.2 20-40BaO and/or SrO 10-35Alkali-metal oxide 0-15selected from Na.sub.2 O and K.sub.2 OSiO.sub.2 25-40All other ingredients 0-15;______________________________________
- said glass being essentially free of CaO, and containing no more than 10 weight-percent ZnO; and said glass having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
- 2. Microspheres of claim 1 which include at least 1 weight-percent of alkali-metal oxide.
- 3. Microspheres of claim 1 or 2 which include 0.5 to 5 weight-percent of a metal fluoride.
- 4. Microspheres of claim 3 in which the metal fluoride is sodium fluoride.
- 5. Microspheres of claim 1 which include at least 10 weight-percent B.sub.2 O.sub.3.
- 6. Durable visibly transparent clear microspheres between about 0.25 and 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________B.sub.2 O.sub.3 10-20TiO.sub.2 25-35BaO and/or SrO 15-25Alkali-metal oxide 2-10selected from Na.sub.2 O and K.sub.2 OSiO.sub.2 25-35NaF 1-3;______________________________________
- said glass being essentially free of CaO and containing no more than 10 weight-percent ZnO, having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
- 7. Pavement marking tape comprising a backing and a layer of microspheres of claim 1, 2, 4, 5, or 6 carried on the backing.
- 8. Durable visibly transparent clear microspheres less than about 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and adapted for use as a reflective element in a pavement marking, said microspheres being formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________B.sub.2 O.sub.3 10-20TiO.sub.2 20-40BaO and/or SrO 10-35Alkali-metal oxide 0-15selected from Na.sub.2 O and K.sub.2 OSiO.sub.2 20-40All other ingredients 0-15;______________________________________
- said glass being essentially free of CaO, and containing no more than 10 weight-percent ZnO; and said glass having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
- 9. Microspheres of claim 8 which include at least 1 weight-percent of alkali-metal oxide.
- 10. Microspheres of claim 8 which include at least 1 weight-percent K.sub.2 O.
- 11. Microspheres of claim 8, 9, or 10 which include 0.5 to 5 weight-percent of a metal fluoride.
- 12. Durable visibly transparent clear microspheres between about 0.25 and 2 millimeters in diameter, containing no more than 5 weight-percent scattered crystallinity, and formed from glass that consists essentially of ingredients as listed in the following table, in which percentages are given by weight:
- ______________________________________B.sub.2 O.sub.3 5-20TiO.sub.2 25-50BaO and/or SrO 15-25Alkali-metal oxide 2-15selected from Na.sub.2 O and K.sub.2 OSiO.sub.2 25-40All other ingredients 0-15;______________________________________
- said glass being essentially free of CaO and containing no more than 10 weight-percent ZnO, having an index of refraction between 1.6 and 1.9, and exhibiting a crush resistance of at least about 3500 kilograms per square centimeter.
- 13. Microspheres of claim 12 which include at least 1 weight-percent of K.sub.2 O.
- 14. Microspheres of claims 12 or 13 which include 0.5 to 5 weight-percent of a metal fluoride.
REFERENCE TO RELATED APPLICATIONS
This application is a continuation of prior application Ser. No. 101,646, filed Dec. 10, 1979 and now abandoned, which was a continuation of Ser. No. 922,533, filed July 7, 1978 now abandoned, which was a continuation-in-part of prior application Ser. No. 820,809, filed Aug. 1, 1979, and now both abandoned.
US Referenced Citations (10)
Foreign Referenced Citations (2)
Number |
Date |
Country |
400737 |
Apr 1966 |
AUX |
45-12504 |
May 1970 |
JPX |
Continuations (2)
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Number |
Date |
Country |
Parent |
101646 |
Dec 1979 |
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Parent |
922533 |
Jul 1978 |
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
820809 |
Aug 1977 |
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