Thermochromic color-memory composition and thermochromic color-memory microcapsule pigment encapsulating the same
The present invention provides a thermochromic color-memory composition including (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) an ester compound represented by the following formula (1) or (2), as a reaction medium which controls color reaction of the component (a) and the component (b); and a thermochromic color-memory microcapsule pigment encapsulating the thermochromic color-memory composition.
1. A thermochromic color-memory microcapsule pigment encapsulating a thermochromic color-memory 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) or (2), as a reaction medium which controls color reaction of the component (a) and the component (b):
wherein each R 1 independently represents a cycloalkyl group having 3 to 8 carbon atoms or a cycloalkylalkyl group having 4 to 9 carbon atoms, and each n1 independently represents an integer of 1 to 3; and
wherein R 2 represents an alkyl group having 3 to 17 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or a cycloalkylalkyl group having 5 to 8 carbon atoms, X represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a methoxy group, an ethoxy group, or a halogen atom, and n2 represents an integer of 1 to 3.
2. An ink composition comprising the thermochromic color-memory microcapsule pigment according to claim 1 , and a vehicle.
3. The ink composition according to claim 2 , comprising the thermochromic color-memory microcapsule pigment in an amount of 5 to 40% by mass with respect to the total mass of the ink composition.
4. A writing instrument comprising: an axial barrel which stores the ink composition according to claim 2 ; and a pen body which delivers the ink composition stored in the axial barrel.
5. The writing instrument according to claim 4 , further comprising a friction member.
6. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein in the ester compound represented by the formula (1), each R 1 independently represents a cycloalkyl group having 5 to 7 carbon atoms or a cycloalkylalkyl group having 5 to 8 carbon atoms.
7. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein in the ester compound represented by the formula (1), each R 1 independently represents a cyclohexyl group or a cycloalkylalkyl group having 7 or 8 carbon atoms.
8. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein in the ester compound represented by the formula (2), R 2 represents a linear alkyl group having 5 to 15 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a cycloalkylalkyl group having 6 to 8 carbon atoms.
9. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein in the ester compound represented by the formula (2), R 2 represents a linear alkyl group having 7 to 13 carbon atoms, a cyclohexyl group, or a cycloalkylalkyl group having 7 or 8 carbon atoms.
10. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein the component (a) is a compound selected from the group consisting of a phthalide compound, a fluoran compound, a styrylquinoline compound, a diazarhodamine lactone compound, a pyridine compound, a quinazoline compound, and a bisquinazoline compound.
11. The thermochromic color-memory microcapsule pigment according to claim 1 , wherein a composition ratios of the component (b) and the component (c) with respect to 1 part of the component (a) are 0.1 to 50 parts and 1 to 800 parts, respectively, on mass basis.
12. The thermochromic color-memory microcapsule pigment according to claim 1 , having a hysteresis width ΔH of 8° C. to 80° C.