GLASS, OPTICAL GLASS, GLASS MATERIAL FOR PRESS MOLDING AND OPTICAL ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide glass, optical glass, a glass material for press molding and an optical element, with the content of precious metals, e.g. platinum, reduced.SOLUTION: Glass has a refractive index nd of 1.75 or higher and a value ofβOH, defined by equation (1), meeting the relation of equation (2). (1)βOH=-[ln(B/A)]/t and (2)βOH≥181.39×nd-325.75×nd+194.85×nd-38.1, where t is the thickness (mm) of the glass used in measurement of the external transmittance; A is the external transmittance (%) at the wavelength of 2,500 nm when light enters in parallel with the thickness direction of the glass; and B is the external transmittance (%) at the wavelength of 2,900 nm when light enters in parallel with the thickness direction of the glass.