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 %.

Provided is an optical glass containing glass-forming cations, the optical glass satisfying, expressed in cation percent, 10 cat %≤B.sup.3+≤50 cat %, 15 cat %≤La.sup.3+≤35 cat %, 20 cat %≤Nb.sup.5+≤50 cat %, and 15 cat %≤Ti.sup.4+≤25 cat %.

Provided is an optical glass containing glass-forming cations, the optical glass satisfying, expressed in cation percent, 10 cat %B.sup.3+50 cat %, 15 cat %La.sup.3+35 cat %, 20 cat %Nb.sup.5+50 cat %, and 15 cat %Ti.sup.4+25 cat %.

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 %.

An optical element molding mold set includes a first mold and a second mold that are opposite to each other, and a third mold that is located on an outer periphery of a cavity between the first mold and the second mold, and an inner peripheral surface of the third mold has different friction coefficients between one side and another side in an opposite direction of the first mold and the second mold.

A curved glass and a preparation method is provided. The preparation method for curved glass includes: melting a glass batch into a glass liquid, and clearing the glass liquid; introducing the cleared glass liquid into a mold cavity with a preset shape, and forming, by using a compression molding process, a glass product with a shape corresponding to that of the curved glass, where a size of the glass product is greater than a size of the curved glass; annealing the molded glass product; and processing the annealed glass product into the curved glass based on the shape and the size of the curved glass.

Various embodiments provide a mold including a pyrolytic carbon film disposed at a surface of the mold. Various embodiments relate to using a low pressure chemical vapor deposition process (LPCVD) or using a physical vapor deposition (PVD) process in order to form a pyrolytic carbon film at a surface of a mold.

An optical element molding mold set includes a first mold and a second mold that are opposite to each other, and a third mold that is located on an outer periphery of a cavity between the first mold and the second mold, and an inner peripheral surface of the third mold has different friction coefficients between one side and another side in an opposite direction of the first mold and the second mold.

A system for forming a glass article includes a mold assembly and a burner assembly. The mold assembly includes a mold body that defines an open cavity configured to receive a glass-containing material in a molten state. The mold assembly further includes a plunger configured to be actuated towards the mold body and into the open cavity to press the glass-containing material into a closed volume defined by the mold body and the plunger. The mold assembly further includes (i) first surfaces that define the closed volume and (ii) one or more pairs of second surfaces that make sliding contact when the plunger is actuated. The burner assembly is configured to form a solid lubricant on active surfaces of the mold assembly. The active surfaces include all the first surfaces and at least one second surface of each of the one or more pairs of second surfaces.

A curved glass and a preparation method is provided. The preparation method for curved glass includes: melting a glass batch into a glass liquid, and clearing the glass liquid; introducing the cleared glass liquid into a mold cavity with a preset shape, and forming, by using a compression molding process, a glass product with a shape corresponding to that of the curved glass, where a size of the glass product is greater than a size of the curved glass; annealing the molded glass product; and processing the annealed glass product into the curved glass based on the shape and the size of the curved glass.