Abstract: There is provided a friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, a thermal conductivity of a friction portion of the friction body is set to be within 0.05 W/(m·K) to 50 W/(m·K).

Abstract: There is provided a friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, a thermal conductivity of a friction portion of the friction body is set to be within 0.05 W/(m·K) to 50 W/(m·K).

Abstract: The present invention provides the ballpoint pen that precludes the possibility of the pipe portion bending at the joint thereof can be provided even if the outer diameter D is small. In the ballpoint pen having a ballpoint pen tip at a front end thereof, the ballpoint pen tip rotatably accommodating a ball at a front end of a pipe made of metal, an outwardly projecting pipe portion having a uniform thickness throughout the length thereof is arranged at a front end of the ballpoint pen tip, and if a length of the pipe portion is L, an outer diameter of the pipe portion is D, a relational expression "L/D.ltoreq.4.0" is satisfied.