Thermochromic color-memorizing composition and thermochromic color-memorizing microcapsule pigment encapsulating same

1. Thermochromic color-memorizing composition comprising:

(a) an electron-donating color-developing organic compound;

(b) an electron-accepting compound; and

(c) an ester compound represented by the following formula (1) as a reaction medium which controls color reaction between said components (a) and (b):

(wherein, R represents an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group having 6 to 11 carbon atoms or a cycloalkyl group having 5 to 7 carbon atoms; Xs each independently represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom; Ys each independently represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom; and n represents 0 or 1).

2. The composition according to claim 1 , wherein, in said ester compound represented by said formula (1), said R represents an alkyl group having 6 to 16 carbon atoms or a cycloalkylalkyl group having 6 to 10 carbon atoms; said Xs represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms; and said Ys represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms.

3. The composition according to claim 1 , wherein said component (a) is a compound selected from the group consisting of phthalide compounds, fluoran compounds, styrynoquinoline compounds, diazarhodamine lactone compounds, pyridine compounds, quinazoline compounds and bisquinazoline compounds.

4. The composition according to claim 1 , wherein the ratio of said component (b) and that of said component (c) are, based on mass, 0.1 to 50 parts and 1 to 800 parts, respectively, with respect to 1 part of said component (a).

5. The composition according to claim 1 , which has a hysteresis width (ΔH) of 8° C. to 80° C.

6. Thermochromic color-memorizing microcapsule pigment encapsulating the thermochromic color-memorizing composition according to claim 1 .

7. Ink composition comprising:

the microcapsule pigment according to claim 6 ; and

a vehicle.

8. The ink composition according to claim 7 , comprising said thermochromic color-memorizing microcapsule pigment in an amount of 5 to 40% by mass with respect to the total mass of said ink composition.

9. Writing instrument comprising:

an axial barrel which stores the ink composition according to claim 7 ; and

a pen body which delivers said ink composition stored in said axial barrel.

10. The writing instrument according to claim 9 , further comprising a friction member.