Phosphate Crown Glass
Phosphate Crown Glass is referred to as PK glass. The dispersion coefficient is similar to that of light crown glass but the refractive index is higher. In the nd-v diagram, it is located on the left side of the crown and barium crown glass, so it is also called low-dispersion optical glass together with the heavy phosphorous crown. Its chemical composition basically belongs to the K2O-P2O5 system containing oxides such as boron and magnesium. Phosphate glass volatilizes severely when melting, and it is difficult to eliminate streaks. Mainly used as a material for optical parts in optical componments, such as optical lenses.
By modifying the glass formula, the optical glass without lead, arsenic and cadmium and other radioactive elements is expressed by a prefix "H-" indicating its envioronment-friendly characteristics, for example: H-ZPK1
