PURPOSE: To provide the titled ink which gives a clear handwriting which can be easily erased, by dissolving a developer contg. a phosphorus acid group and a colorless electron-donating org. compd. capable of developing color by said developer in a solvent which does not interfere with a color forming reaction.
CONSTITUTION: A developer (A) contg. a phosphorus acid group (e.g. phenylphosphonic acid) and a colorless electron-donating org. compd. (B) (e.g. Crystal Violet Lactone) capable of developing color by said developer are dissolved in a solvent (C) (e.g. benzyl alcohol) which does not interfere with a color forming reaction, to obtain the desired writing ink. When writing in this ink, a dense, clear handwriting can be obtd., which can be easily erased by an eraser contg. a desensitizing polar compd. such as an alcohol, a ketone, an ester or an ether (e.g. paper contg. an acetone soln. of dioctyl adipate).
YAMAGUCHI MAKOTO
IWATA MASAHIRO
