PURPOSE: To prevent the corrosion of a metal, and to prevent the whitening of a plastic lens by using a cooling liquid of specified ratio of aminoalcohol as well as of polyhydric alcohol and of viscosity.
CONSTITUTION: A cooling liquid comprising 1-50weight% of aminoalcohol and 99-50weight% of polyhydric alcohol, whose viscosity at 30°C is not more than 60cPs, or preferably not more than 50cPs, is used. As aminoalcohol, such as triethanolamine, or diethanolamine is used, while ethylene glycol or diethylene glycol and the like is used as polyhydric alcohol. When the amount of aminoalcohol is less than 1weight%, the suppressing effect toward corrosion does not appear, while if it exceeds 50weight%, viscosity becomes too high. When the viscosity exceeds 60cPs, convection is not carried out smoothly, and cooling efficiency is reduced. The corrosion of an aluminum die-cast frame does not occur, and the whitening of a plastic lens is thus inhibited.
KANEGA FUMIAKI
MURANAKA MASAYUKI
YOSHIZAKI ISAO
HITACHI LTD