Use fontforge. To convert from ipam.ttc to ipam.ttf

sudo apt install -yq fontforge
fontforge -lang=ff -c 'Open("ipam.ttc"); Generate("ipam.ttf"); Close();'

This command also print the font names.

Copyright (c) 2000-2014 by George Williams. See AUTHORS for Contributors.
 License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
 with many parts BSD <http://fontforge.org/license.html>. Please read LICENSE.
 Based on sources from 11:21 UTC 24-Sep-2017-ML-D.
 Based on source from git with hash: 
Warning: Mac and Windows entries in the 'name' table differ for the
  Family string in the language Japanese
  Mac String: IPAMincho
  Windows String: IPA明朝
Warning: Mac and Windows entries in the 'name' table differ for the
  Fullname string in the language Japanese
  Mac String: IPAMincho
  Windows String: IPA明朝