We provide an excellent thermochromic ink exhibiting anirreversible colored state at temperatures within a range of from-20.degree. to 60.degree. C. It is called ''friction friction gelink'' which is interesting materials. When the frictions generateheat by the rubber of the other end and the temperature increase is60 degree, the handwriting will disappear. If paper is put in thecircumstance of minus 18 degree, the handwriting also appears.