Optical glass and process for the production of optical products
AssigneeHoya Corporation
InventorKazuo Tachiwana
Life of this patent
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Abstract
An optical glass having high-refractivity and low-dispersion optical properties and having a low glass transition point so that a heat-treating furnace can be operated for a long period of time. The optical glass has a refractive index nd of at least 1.875, an Abbe's number νd of at least 39.5 and a glass transition point Tg of 700° C. or lower, and contains at least one of La2O3, Gd2O3, Y2O3 or Yb2O3 and at least one of ZrO2, Ta2O5 or Nb2O5, with a weight ratio of the total content of La2O3, Gd2O3, Y2O3 and Yb2O3 to the total content of SiO2 and B2O3 of from 3.2 to 5 and the weight ratio of the total content of ZrO2, Ta2O5 and Nb2O5 to the total content of SiO2 and B2O3 is from 1.1 to 1.5.
Claims15
An optical glass which is a borosilicate glass comprising at least one selected from La2O3, Gd2O3, Y2O3 or Yb2O3 and at least one selected from ZrO2, Ta2O5 or Nb2O5, and 0 to 1% by weight WO3, wherein the weight ratio of the total content of La2O3, Gd2O3, Y2O3 and Yb2O3 to the total content of SiO2 and B2O3 is from 2 to 4, the weight ratio of the total content of ZrO2, Ta2O5 and Nb2O5 to the total content of SiO2 and B2O3 is from 1 to 2, and the total content of SiO2, B2O3, GeO2, ZnO, La2O3, Gd2O3, Y2O3, Yb2O3, ZrO2 and Ta2O5 to over 95% by weight, and the weight ratio of ZnO/(SiO2+B2O3) is more than 0 but less than 2, said optical glass having a refractive index nd of at least 1.875, an Abbe's number νd of at least 39.5 and a glass transition point Tg of 700° C. or lower.
Dependencies are inferred from the claim text.