US 12,275,269 B2
Thermochromic writing instrument
Takeshi Hashimoto, Tokyo (JP)
Assigned to Kabushiki Kaisha Pilot Corporation, Tokyo (JP)
Appl. No. 17/915,815
Filed by Kabushiki Kaisha Pilot Corporation, Tokyo (JP)
PCT Filed Mar. 24, 2021, PCT No. PCT/JP2021/012246
§ 371(c)(1), (2) Date Sep. 29, 2022,
PCT Pub. No. WO2021/200474, PCT Pub. Date Oct. 7, 2021.
Claims priority of application No. 2020-065330 (JP), filed on Mar. 31, 2020.
Prior Publication US 2023/0150294 A1, May 18, 2023
Int. Cl. B43K 29/02 (2006.01)
CPC B43K 29/02 (2013.01) 10 Claims
OG exemplary drawing
 
1. A thermochromic writing instrument, comprising: thermochromic ink; and a friction unit configured to cause handwriting in the thermochromic ink to undergo a thermochromic change by frictional heat, wherein
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 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 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).