Friction body, writing instrument and writing instrument set

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, wherein

• when a friction coefficient between the friction body and the paper surface is defined as μ;
• a vertical load imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as W (N);
• a velocity at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as V (m/s);
• and
• a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm2),
• the friction body satisfies a relation of (μ×W×V)/A≧4.

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, wherein

• when a vertical load W imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 4.9 N;
• and
• a velocity V at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 0.5 m/s, and
• a friction coefficient between the friction body and the paper surface is defined as μ;
• and
• a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm2),
• the friction body satisfies a relation of μ/A≧1.5.

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,

• wherein when a friction coefficient between the friction body and the paper surface is defined as μ;
• a vertical load imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as W (N),
• a velocity at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as V (m/s);
• and
• a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm2),
• the friction body satisfies a relation of (μ×W×V)/A≧15.

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, wherein

• when a vertical load W imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 4.9 N;
• and
• a velocity V at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 0.5 m/s, and
• a friction coefficient between the friction body and the paper surface is defined as μ;
• and
• a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm2),
• the friction body satisfies a relation of μ/A≧6.