	US 12,421,411 B2
	Aqueous ink composition for reversibly thermochromic writing instrument, and refill and aqueous ballpoint pen incorporating aqueous ink composition for reversibly thermochromic writing instrument
Naoto Masushige, Tokyo-to (JP); Mamiko Ogura, Tokyo-to (JP); and Itsuka Ohno, Tokyo-to (JP)
Assigned to KABUSHIKI KAISHA PILOT CORPORATION, Tokyo-to (JP)
Appl. No. 17/602,066
Filed by KABUSHIKI KAISHA PILOT CORPORATION, Tokyo-to (JP)
PCT Filed Mar. 30, 2020, PCT No. PCT/JP2020/014445 § 371(c)(1), (2) Date Apr. 12, 2022, PCT Pub. No. WO2020/209118, PCT Pub. Date Oct. 15, 2020.
Claims priority of application No. 2019-075890 (JP), filed on Apr. 11, 2019; and application No. 2019-076696 (JP), filed on Apr. 12, 2019.
Prior Publication US 2022/0251406 A1, Aug. 11, 2022
Int. Cl. C09D 11/50 (2014.01); B43K 1/08 (2006.01); B43K 7/02 (2006.01); B43K 29/02 (2006.01); C09D 11/17 (2014.01); C09D 11/18 (2006.01)

CPC C09D 11/50 (2013.01) [B43K 1/08 (2013.01); B43K 7/02 (2013.01); B43K 29/02 (2013.01); C09D 11/17 (2013.01); C09D 11/18 (2013.01)]

9 Claims

1. A reversibly thermochromic aqueous ink composition comprising:

a reversibly thermochromic microcapsule pigment in which a reversibly thermochromic composition comprising (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium to determine an occurrence temperature of a coloring reaction of the component (a) and the component (b) are encapsulated in a microcapsule comprising an organic resin;

an N-vinyl-2-pyrrolidone polymer having a degree of polymerization of 2 to 20;

glycerin; and

water,

wherein when contents (% by mass) of the reversibly thermochromic microcapsule pigment, the N-vinyl-2-pyrrolidone polymer, and the glycerin with respect to a total mass of the ink composition are P_MC, P_PVP, and P_G, respectively,

0.6≤P_MC/(P_PVP+P_G)≤43.0, and

0.3≤P_PVP/P_G≤3.3,

wherein the P_MCis 13 to 20% by mass and wherein a total of the P_MC, the P_PVP, and the P_Gis 24.0 to 41.0% by mass.