Colorless p{11 o{11 {11 glass with anomalous dispersion in short wavelength region

Claim 2

The glass according to claim 1 consisting of from 50 to 70% P2O5, from 1 to 5% B2O3, from 2 to 5% Al2O3, wherein the sum of the amount of said B2O3 and Al2O3 is from 3 to 8% and from 0.5 to 2.5% TiO2, all percentages being by weight.

Claim 3

The glass according to claim 3 which as a Nu d of from 50.2 to 66.0 and a theta hg of from 0.443 to 0.493.

Claim 4

A colorless anomalous dispersion glass free of alkali metal oxides and having a large Abbe''s number consisting of, in percentages by weight, calculated as the component oxides of said glass, from 40.0 to 67.4% P2O5, from 1.5 to 3.6% B2O3 and from 1 to 9.0% Al2O3 as glossforming materials, wherein the sum of the amount of said B2O3 and Al2O3 is from 3 to 12.6%, said amount of Al2O3 and B2O3 preventing coloration in said glass; from 4.3 to 37.9% BaO, from 2.0 to 13.2% MgO, from 0 to 10.0% ZnO, from 0 to 9.5% SrO, from 0 to 6% CaO and from 0 to 2.5% As2O3 as glass modifiers, wherein the sum of said BaO, MgO, ZnO, SrO, CaO and As2O3 is from 20.0 to 57.0%; and from 0.05 to 3.0% based on the total weight of said glass-forming materials and glass modifiers, of TiO2, said amount of TiO2 providing an anomalous dispersion without decreasing the Abbe''s number of said glass, and said amounts of MgO, As2O3 and ZnO also serving to prevent coloration in said glass.

Claim 5

The glass according to claim 5 which has a Nu d of from 50.2 to 67.9 and a theta hg of from 0.436 to 0.503.

Claim 6

In an anomalous dispersion glass consisting essentially of P2O5 as a basic glass-forming material and TiO2 as an additive to obtain an anomalous dispersion, wherein large quantities of alkali metal oxides are added thereto to prevent coloration in said glass, resulting in a glass of poor stability and chemical durability, the improvement consisting of a colorless anomalous dispersion glass free of alkali metal oxides and having an Abbe''s number of from 45 to 70, a partial dispersion ratio theta hg of from 0.430 to 0.505, and good stability and chemical durability, said glass consisting of, in percentages by weight, calculated as the component oxides of said glass, from 38 to 70% P2O5, from 1.0 to 5.0 B2O3 and from 1 to 10% Al2O3 as glass -forming materials, wherein the sum of the amount of said B2O3 and Al2O3 is from 2 to 15%, said amount of Al2O3 and B2O3 preventing coloration in said glass; from 4 to 38% BaO, from 2 to 17% MgO, from 0 to 10% ZnO, from 0 to 8% CaO, from 0 to 10% SrO and from 0 to 3% As2O3 as glass modifiers, wherein the sum of the amount of said BaO, MgO, ZnO, CaO, SrO and As2O3 is 15 to 60%, said amount of MgO, As2O3 and ZnO also serving to prevent coloration in said glass; and from 0.05 to 4.0%, based on the total weight of said glass-forming materials and said glass modifiers, of TiO2, said amount of TiO2 providing an anomalous dispersion without decreasing the Abbe''s number of said glass.