Patent ID: 8754019

Claim:
A pressure transmission medium, comprising: an ester which comprises two or more ring structures of an aromatic ring or a saturated naphthenic ring, wherein the ester is an ester of a carboxylic acid having an aromatic ring or a saturated naphthenic ring and an alcohol having an aromatic ring or a saturated naphthenic ring, and a kinematic viscosity of the ester at 40 degrees C. is less than 15 mm 2 /s; and wherein the ester is any one of esters selected from the group consisting of: an ester formed by a carboxylic acid having an ether bond and an alcohol having no ether bond; an ester formed by a carboxylic acid having no ether bond and an alcohol having an ether bond; and an ester formed by a carboxylic acid having an ether bond and an alcohol having an ether bond.