A compound represented by the formula AF(—COF)n, provided that AF and n have the following meanings. AF: a fluorinated adamantane residue which is an n-valent group having an n number of hydrogen atoms removed from adamantane (provided that when n is at least 2, the removed hydrogen atoms are hydrogen atoms bonded to different carbon atoms), wherein at least one of the remaining hydrogen atoms is substituted by a fluorine atom, and the remaining hydrogen atoms may be substituted by a C1-6 alkyl group or fluoroalkyl group, and n: an integer of from 1 to 4, provided the when n is 1, AF has at least one hydrogen atom.