Optical glass, precision press molding preform and manufacturing method of the same, optical element and manufacturing method of the same

摘要

The optical glass comprises equal to or greater than 5 mole percent of P₂O₅, has an Abbé number of equal to or greater than 58 and a glass transition temperature of equal to or less than 570 degree Celsius, and has an alkalinity resistance defined as a rate of weight reduction of equal to or less than 17 micrograms/(cm².hour) when the surface of said optical glass which has been optically polished is immersed in 0.01 mole/liter of NaOH aqueous solution at 50 degree Celsius.