Optical glass

• US 20030050177A1
• Filed: 06/18/2002
• Published: 03/13/2003
• Est. Priority Date: 07/03/2001
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Ohara
• Original Assignee: Kabushiki Kaisha Ohara
• Inventors: Uehara, Susumu
• Granted Patent: US 6,753,281 B2
• Time in Patent Office: Days
• US Class Current: 501/78
• CPC Class Codes: C03C 3/068 containing rare earths

Abstract

An optical glass has optical constants which are an refractive index (nd) of 1.70-1.75 and an Abbe number (νd) of 45.0-54.0; a glass transformation temperature (Tg) of 500-580° C. The glass has the following composition in mass percent of: SiO₂ more than 5 to 15%; B₂O₃ 20 to less than 30%; a total amount of SiO₂+B₂O₃ more than 25 to 40%; La₂O₃ more than 21 to less than 30%; Y₂O₃ more than 5 to 15%; Gd₂O₃ 0 to less than 10%; ZrO₂ 1-8%; Nb₂O₅ 0.1-5%; Ta₂O₅ more than 5 to 12%; a total amount of ZrO₂+Nb₂O₅+Ta₂O₅ 7-20%; ZnO 0-10%; CaO 0-10%; SrO 0-5%; BaO 0-10%; a total amount of ZnO+CaO+SrO+BaO 5-15%; Li₂O 1-8%; Sb₂O₃ 0-1%; and As₂O₃ 0-1%. Devitrification is not generated when the optical glass is kept at a temperature of 920° C. for two hours.

Claims

1. An optical glass comprising:

optical constants which are a refractive index (nd) in a range of 1.70 to 1.75 and an Abbe number (ν

d) in a range of 45.0 to 54.0;

a glass transformation temperature (Tg) in a range of 500 to 580°

C.;

more than 5 to 15 mass % of SiO₂;

20 to less than 30 mass % of B₂O₃;

a total amount of SiO₂+B₂O₃ being more than 25 to 40 mass %;

more than 21 to less than 30 mass % of La₂O₃;

more than 5 to 15 mass % of Y₂O₃;

0 to less than 10 mass % of Gd₂O₃;

1 to 8 mass % of ZrO₂;

0.1 to 5 mass % of Nb₂O₅;

more than 5 to 12 mass % of Ta₂O₅;

a total amount of ZrO₂+Nb₂O₅+Ta₂O₅ being 7 to 20 mass %;

0 to 10 mass % of ZnO;

0 to 10 mass % of CaO;

0 to 5 mass % of SrO;

0 to 10 mass % of BaO;

a total amount of ZnO+CaO+SrO+BaO being 5 to 15 mass %;

1 to 8 mass % of Li₂O;

0 to 1 mass % of Sb₂O₃; and

0 to 1 mass % of As₂O₃;

wherein devitrification is not generated when the glass is kept at a temperature of 920°

C. for two hours.

2. The optical glass as claimed in claim 1, wherein the devitrification is not generated when the optical glass is kept at a temperature of the glass transformation temperature (Tg)+80°

C. for 30 minutes.

3. The optical glass as claimed in claim 1, wherein the devitrification is not generated when the optical glass is kept at a temperature of the glass transformation temperature (Tg)+140°

C. for 30 minutes.

4. The optical glass as claimed in claim 1, wherein the optical glass is substantially free of a fluorine, a PbO, a WO₃ and an SnO₂ components.