Abstract: A clad glass composition that is excellent in devitrification resistance and that prevents the whole mother glass rod from devitrifying by preventing a core glass composition from devitrifying in forming a mother glass rod using a concentric crucible drawing method, is provided. The clad glass composition forms a clad of a mother glass rod for a gradient-index rod lens having a core/clad structure.

Abstract: The present invention provides a clad glass composition that is excellent in devitrification resistance and that prevents the whole mother glass rod from devitrifying by preventing a core glass composition from devitrifying in forming a mother glass rod using a concentric crucible drawing method. The clad glass composition forms a clad of a mother glass rod for a gradient-index rod lens having a core/clad structure. The clad glass composition includes the following components, indicated by mol %: 45 to 65% SiO2; 0.5 to 10% TiO2; 0 to 15% B2O3; 0 to 7% Al2O3; 0.1 to 10% Bi2O3; 0 to 5% Li2O; 5 to 30% Na2O; 0 to 10% K2O; 0 to 15% MgO; 0 to 10% CaO; 0 to 10% SrO; 0.

Abstract: A gradient-index rod lens is provided that is excellent in yield. The gradient-index rod lens has a core/clad structure and is obtained by providing a mother glass rod, which includes a core glass mother composition and a clad glass mother composition, with a refractive index distribution through ion exchange. The clad and the core each contains an alkali metal oxide but are substantially free from lead. The clad and the core each contains an alkali metal oxide and has a basic composition including components other than the alkali metal oxide, but they are different from each other in the basic composition. The clad glass mother composition has a higher thermal expansion coefficient and glass-transition temperature than those of the core glass mother composition. The difference of the thermal expansion coefficient between the clad glass mother composition and the core glass mother composition is larger than 2×10?7/° C. but smaller than 20×10?7/° C.

Abstract: It is an object of the present invention to provide a clad glass composition for graded-index rod lens for covering, during manufacturing, a preform glass composition lens of a graded-index rod lens that does not include PbO, in which the composition substantially does not include PbO, and expressed in mol % includes SiO2: 45 to 65, Na2O: 3 to 30, K2O: 0 to 10, MgO: 0 to 15, BaO: 0 to 20, where Na2O+K2O: 3 to 35 and MgO+BaO: 0 to 25, and furthermore includes B2O3: 0 to 15, ZnO: 0 to 10, TiO2: 0 to 10, Y2O3: 0 to 7, ZrO2: 0 to 7, Nb2O5: 0 to 7, In2O3: 0 to 7, La2O3: 0 to 7, Ta2O5: 0 to 10, where B2O3+ZnO+TiO2+Y2O3+ZrO2+Nb2O5+In2O3+La2to 20, and a content of at least one of TiO2 and La2O3 is substantially 0 mol %.

Abstract: A gradient-index rod lens is provided that is excellent in yield. The gradient-index rod lens has a core/clad structure and is obtained by providing a mother glass rod, which includes a core glass mother composition and a clad glass mother composition, with a refractive index distribution through ion exchange. The clad and the core each contains an alkali metal oxide but are substantially free from lead. The clad and the core each contains an alkali metal oxide and has a basic composition including components other than the alkali metal oxide, but they are different from each other in the basic composition. The clad glass mother composition has a higher thermal expansion coefficient and glass-transition temperature than those of the core glass mother composition. The difference of the thermal expansion coefficient between the clad glass mother composition and the core glass mother composition is larger than 2×10?7/° C. but smaller than 20×10?7/° C.

Abstract: The present invention provides a clad glass composition that is excellent in devitrification resistance and that prevents the whole mother glass rod from devitrifying by preventing a core glass composition from devitrifying in forming a mother glass rod using a concentric crucible drawing method. The clad glass composition forms a clad of a mother glass rod for a gradient-index rod lens having a core/clad structure. The clad glass composition includes the following components, indicated by mol %: 45 to 65% SiO2; 0.5 to 10% TiO2; 0 to 15% B2O3; 0 to 7% Al2O3; 0.1 to 10% Bi2O3; 0 to 5% Li2O; 5 to 30% Na2O; 0 to 10% K2O; 0 to 15% MgO; 0 to 10% CaO; 0 to 10% SrO; 0.

Abstract: It is an object of the present invention to provide a clad glass composition for graded-index rod lens for covering, during manufacturing, a preform glass composition lens of a graded-index rod lens that does not include PbO, in which the composition substantially does not include PbO, and expressed in mol % includes SiO2: 45 to 65, Na2O: 3 to 30, K2O: 0 to 10, MgO: 0 to 15, BaO: 0 to 20, where Na2O+K2O: 3 to 35 and MgO+BaO: 0 to 25, and furthermore includes B2O3: 0 to 15, ZnO: 0 to 10, TiO2: 0 to 10, Y2O3: 0 to 7, ZrO2: 0 to 7, Nb2O5: 0 to 7, In2O3: 0 to 7, La2O3: 0 to 7, Ta2O5: 0 to 10, where B2O3+ZnO+TiO2+Y2O3+ZrO2+Nb2O5+In2O3+La2O3+Ta2O5: 0 to 20, and a content of at least one of TiO2 and La2O3 is substantially 0 mol %.