An optical glass includes La.sup.3+, Zn.sup.2+, Nb.sup.5+, and Ti.sup.4+ as a cation configuring glass. La.sup.3+, Zn.sup.2+, Nb.sup.5+, and Ti.sup.4+ which satisfy 10 cat %≤La.sup.3+≤20 cat %, 10 cat %≤Zn.sup.2+≤60 cat %, 20 cat %≤Nb.sup.5+≤60 cat %, and 0 cat %≤Ti.sup.4+≤40 cat % expressed by cation %.

Molding a Li ion conductive sulfide glass construct into a flat preform shape using a mold having a molding surface of a material that is chemically inert in direct contact with a glass blank when heated can improve molding performance.

A production apparatus making continuously curved crystalline glass as a cover or container includes a melting device, a drainage device, a molding device, and a crystallizing device. The melting device melts glass raw material to form a glass melt. The drainage device drains the glass melt to the molding device. The molding device includes a rotating table and a plurality of molding molds thereon. Each molding mold can be moved toward or away from the drainage device by the rotating table. Each molding mold has a molding cavity. At least one part of the molding cavity includes a plane, and at least one part of the molding cavity includes a curved surface to extrude the glass melt with such different surface forms. The crystallizing device crystallizes the curved glass member to achieve the curved crystallized glass member. A method for manufacturing such glass is also provided.

A production apparatus making continuously curved crystalline glass as a cover or container includes a melting device, a drainage device, a molding device, and a crystallizing device. The melting device melts glass raw material to form a glass melt. The drainage device drains the glass melt to the molding device. The molding device includes a rotating table and a plurality of molding molds thereon. Each molding mold can be moved toward or away from the drainage device by the rotating table. Each molding mold has a molding cavity. At least one part of the molding cavity includes a plane, and at least one part of the molding cavity includes a curved surface to extrude the glass melt with such different surface forms. The crystallizing device crystallizes the curved glass member to achieve the curved crystallized glass member. A method for manufacturing such glass is also provided.

An optical glass includes La.sup.3+, Zn.sup.2+, Nb.sup.5+, and Ti.sup.4+ as a cation configuring glass. La.sup.3+, Zn.sup.2+, Nb.sup.5+, and Ti.sup.4+ which satisfy 10 cat %La.sup.3+20 cat %, 10 cat %Zn.sup.2+60 cat %, 20 cat %Nb.sup.5+60 cat %, and 0 cat %Ti.sup.4+40 cat % expressed by cation %.

A process deciding method in a method of manufacturing an optical element by heating and press-molding an optical material to mold the optical element using a molding die on which a release film is formed, includes a basicity degree identifying process in which a degree of basicity of the optical material is identified; and a removing process determining process of determining whether to perform one or both of first removing process in which an oxidizing substance is removed and a second removing process in which a basic substance is removed from at least one of a surface of the optical material and a surface of the release film by comparing the degree of basicity of the optical material identified in the basicity degree identifying process with a predetermined reference value, before press-molding the optical material.