Thermochromic writing instrument

Abstract

Provided is a thermochromic writing instrument, including thermochromic ink; and a friction unit configured to cause handwriting in the thermochromic ink to undergo a thermochromic change by frictional heat. The thermochromic ink includes a metallic luster pigment added thereto. The thermochromic writing instrument is provided with an attachment hole to attach the friction unit. The friction unit includes an attachment portion to be inserted into the attachment hole and a friction portion in a convex curved surface shape projecting from the attachment hole. The friction portion has a volume Ve and the metallic luster pigment has a volume Vp, the volume Ve and the volume Vp satisfying 5 □ Ve/Vp □ 35, the friction portion 32 has a maximum outer diameter D and a projection length L, the diameter D and the length L satisfying 0.1 □ L/D □ 1.5, and a material for the friction unit 3 has a value of Shore A hardness in accordance with JIS K 7215 of Japan Industrial Standard measured immediately after starting contact with an indenter in a range of 60 or more and 85 or less and has a value (ΔHS) of the Shore A hardness defined by a following equation of 0 or more and less than 5, ΔHS=(Shore A Hardness Value immediately after Starting Contact with Indenter)−(Shore A Hardness Value 15 seconds after Starting Contact with Indenter).

Dependencies are inferred from the claim text.