Reversible thermochromic composition and reversible thermochromic microcapsule pigment containing the same

Abstract

[Problem] To provide: a reversible thermochromic composition that has excellent contrast between a colored state and a colorless state and also has excellent lightfastness; and a reversible thermochromic microcapsule pigment that encapsulates the reversible thermochromic composition. [Solution] A reversible thermochromic composition that includes (a) an organic electron-donating coloring compound, (b) a combination of compounds that have a specific structure and serve as electron-accepting compounds, and (c) a reaction medium that reversibly allows an electron transfer reaction to occur between component (a) and component (b) in a specific temperature range; and a reversible thermochromic microcapsule pigment that encapsulates the reversible thermochromic composition.

Description

[Technical Field]

[0001] The present invention relates to a reversible thermochromic composition and a reversible thermochromic microcapsule pigment encapsulating the same. More specifically, the present invention relates to a reversible thermochromic composition that becomes discolored at temperatures above its high-temperature discoloration point and becomes colored at temperatures below its low-temperature discoloration point, and to a reversible thermochromic microcapsule pigment encapsulating the same. [Background technology]

[0002] Conventionally, reversible thermochromic compositions have been disclosed that change color from a colored state to a decolored state, and the essential components of the compositions are an electron-donating organic color-forming compound, an electron-accepting compound, and a reaction medium that reversibly induces an electron donor-acceptor reaction between the electron-donating organic color-forming compound and the electron-accepting compound in a specific temperature range. For example, Patent Document 1 discloses the above-mentioned reversible thermochromic compositions, and in particular, discloses that the developer, which is an electron-accepting compound, is a compound having a specific structure, either alone or in combination of two or more types.

[0003] A reversible thermochromic composition is required to have high density in the colored state, low density in the decolorized state, and excellent contrast.Furthermore, it is required to have excellent light resistance when colored, that is, to suppress a decrease in color density over time even when exposed to light in the colored state. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-297277 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made based on the background art described above, and aims to provide a reversible thermochromic composition that has a high density in the colored state, a low density in the decolorized state, and excellent light resistance, and a reversible thermochromic microcapsule pigment containing the same. [Means for solving the problem]

[0006] The reversible thermochromic composition according to the present invention comprises: (a) an electron-donating color-forming organic compound; (b) a combination of a compound represented by formula (I) and a compound represented by formula (IIa) or (IIb) as an electron accepting compound; (c) a reaction medium that causes a reversible electron transfer reaction between component (a) and component (b) in a specific temperature range; The compound comprises: [ka] (In the formula, R 11 is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, L is a single bond, a linear or branched alkylene group having 1 to 3 carbon atoms, or an aryl-substituted alkylene group having 7 to 9 carbon atoms; R 12 and R 13 each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms, which may be substituted with a fluorine atom, a cyclic alkyl group having 3 to 7 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a halogen atom; R 14each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, a cyclic alkyl group having 3 to 7 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms which may be substituted with a halogen atom or a hydroxy group, an aryl-substituted alkyl group having 7 to 11 carbon atoms which may be substituted with a halogen atom or a hydroxy group, a hydroxy group, or a halogen atom; n12 and n13 each independently represent 0 to 3; n14 is 0 to 3) [ka] (In the formula, R a1 and R a2 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 17 carbon atoms which may be substituted with a fluorine atom (wherein a methylene (-CH-) group in the alkyl group may be replaced with an oxy (-O-) group or a carbonyl (-CO-) group), R a3 and R a4 each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms, which may be substituted with a fluorine atom or a hydroxy group, an alkenyl group having 2 to 4 carbon atoms, or a halogen atom; na3 and na4 each independently represent an integer of 0 to 2. [ka] (In the formula, R b1 and R b2 each independently represents a hydroxy group, a linear or branched alkoxy group having 1 to 9 carbon atoms, a linear or branched alkyl group having 1 to 10 carbon atoms which may be substituted with a fluorine atom, an alkenyl group having 2 to 10 carbon atoms, or a halogen atom; nb1 is 0 to 3, nb2 is 0 to 2)

[0007] The reversible thermochromic microcapsule pigment according to the present invention contains the above-mentioned reversible thermochromic composition encapsulated therein. The reversible thermochromic liquid composition according to the present invention comprises the above-mentioned reversible thermochromic microcapsule pigment and a vehicle. The reversibly thermochromic solid writing material or solid cosmetic according to the present invention comprises the above-mentioned reversibly thermochromic microcapsule pigment and an excipient. The reversible thermochromic molding resin composition according to the present invention comprises the above-mentioned reversible thermochromic microcapsule pigment and a molding resin. The reversible thermochromic laminate of the present invention comprises a support and a reversible thermochromic layer containing the above-mentioned reversible thermochromic microcapsule pigment. The writing implement according to the present invention contains a writing ink containing a reversible thermochromic microencapsulated pigment and a vehicle. [Effects of the Invention]

[0008] The present invention provides a reversible thermochromic composition that has a high density in the colored state, a low density in the decolorized state, an excellent contrast between the colored state and the decolorized state, and excellent light resistance, and a reversible thermochromic microcapsule pigment encapsulating the composition. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a reversibly thermochromic composition that is heat-discolorable. [Figure 2] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a heat-discolorable, reversible thermochromic composition having color memory properties. [Figure 3] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a reversibly thermochromic composition that develops color over time. DETAILED DESCRIPTION OF THE INVENTION

[0010] The reversible thermochromic composition of the present invention includes a thermally decolorizable (decolorizes when heated and develops color when cooled) reversible thermochromic composition containing at least three essential components: (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of components (a) and (b) occurs. The reversible thermochromic composition may be a thermally decolorizable (decolorizes upon heating and develops color upon cooling) reversible thermochromic composition having a relatively small hysteresis width (ΔH) (ΔH=1 to 7°C), such as those described in Japanese Patent Publication Nos. 51-44706, 51-44707, and 1-29398 (see Figure 1). The reversible thermochromic composition changes color around a certain temperature (color change point), exhibiting a decolorized state at temperatures above the high-temperature color change point and a colored state at temperatures below the low-temperature color change point, with only one of the two states existing at room temperature. The other state is maintained while the heat or cold required to achieve that state is applied, but returns to the state it exhibits at room temperature once the application of heat or cold is removed (see Figure 1).

[0011] Furthermore, reversible thermochromic compositions may also be used that exhibit a large hysteresis width (ΔH=8-70°C), as described in JP-B No. 4-17154, JP-A No. 7-179777, JP-A No. 7-33997, JP-A No. 8-39936, JP-A No. 2005-1369, etc., and that exhibit a color change along a curve plotting the change in color density with temperature, which follows significantly different paths when the temperature is increased from a temperature lower than the color change temperature range than when the temperature is decreased from a temperature higher than the color change temperature range, and that exhibit a colored state at temperatures below the complete color change temperature t1 or a discolored state at a temperature higher than the complete discoloration temperature t4, and that have color memory in a specific temperature range (the temperature range between the color change onset temperature t2 and the discoloration onset temperature t3 (a temperature range in which two phases are essentially maintained)) (see Figure 2).

[0012] The components (a), (b), and (c) will be specifically described below.

[0013] Component (a), i.e., the electron-donating organic color-forming compound, is the component that determines the color, and is a compound that donates electrons to component (b), which is the color developer, to develop color.

[0014] Examples of the electron-donating color-forming organic compound include a phthalide compound, a fluoran compound, a styrinoquinoline compound, a diazarhodamine lactone compound, a pyridine compound, a quinazoline compound, and a bisquinazoline compound.

[0015] Examples of the phthalide compound include a diphenylmethane phthalide compound, a phenylindolyl phthalide compound, an indolyl phthalide compound, a diphenylmethane azaphthalide compound, a phenylindolyl azaphthalide compound, and derivatives thereof. Among these, the phenylindolyl azaphthalide compound and derivatives thereof are preferred. Examples of fluoran compounds include aminofluoran compounds, alkoxyfluoran compounds, and derivatives thereof.

[0016] Examples of compounds that can be used as component (a) are listed below. 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-n-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-acetamido-4-diethylaminophenyl)-3-(1-propyl-2-methylindol-3-yl)-4-azaphthalide, 3,6-bis(diphenylamino)fluoran, 3,6-bis(N-phenyl-Np-tolylamino)fluoran, 3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluorane, 2-methyl-6-(N-ethyl-Np-tolylamino)fluoran, 3-chloro-6-cyclohexylaminofluoran, 2-methyl-6-cyclohexylaminofluoran, 2-chloroamino-6-di-n-butylaminofluoran, 2-(2-chloroanilino)-6-di-n-butylaminofluoran, 2-(3-trifluoromethylanilino)-6-diethylaminofluoran, 2-(3-trifluoromethylanilino)-6-di-n-pentylaminofluoran, 2-dibenzylamino-6-diethylaminofluoran, 2-(N-methylanilino)-6-(N-ethyl-Np-tolylamino)fluoran, 1,3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methoxy-6-diethylaminofluoran, 2-anilino-3-methyl-6-di-n-butylaminofluoran, 2-anilino-3-methoxy-6-di-n-butylaminofluoran, 2-xylidino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-Np-tolylamino)fluoran, 6-diethylamino-1,2-benzofluoran, 6-(N-ethyl-N-isobutylamino)-1,2-benzofluoran, 6-(N-ethyl-N-isopentylamino)-1,2-benzofluoran, 2-(3-methoxy-4-dodecoxystyryl)quinoline, 2-diethylamino-8-diethylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-di-n-butylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-diethylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-(N-ethyl-N-isoamylamino)-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-di-n-pentylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1′(3′H)-isobenzofuran]-3′-one, 4,5,6,7-tetrachloro-3-(4-dimethylamino-2-methoxyphenyl)-3-(1-n-butyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-(4-diethylamino-2-ethoxyphenyl)-3-(1-n-pentyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 3',6'-bis[phenyl(2-methylphenyl)amino]spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one, 3',6'-bis[phenyl(3-methylphenyl)amino]spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 3',6'-bis[phenyl(3-ethylphenyl)amino]spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one, 2,6-bis(2′-ethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-bis(2′,4′-diethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-bis(2,4-diethyloxyphenyl)-4-[4-bis(4-methyloxyphenyl)aminophenyl]pyridine, 2-(4′-dimethylaminophenyl)-4-methoxyquinazoline, 4,4'-Ethylenedioxy-bis[2-(4-diethylaminophenyl)quinazoline]

[0017] In addition, fluorans may be compounds having a substituent on the phenyl group forming the xanthene ring, or may be compounds that have a substituent on the phenyl group forming the xanthene ring and also have a substituent on the phenyl group forming the lactone ring (for example, an alkyl group such as a methyl group, or a halogen atom such as a chlorine atom), and that exhibit a blue or black color.

[0018] Component (b), ie, the electron accepting compound, is a compound that accepts electrons from component (a) and functions as a developer for component (a). Component (b) is a combination of a compound represented by formula (I) and a compound represented by formula (IIa) or (IIb).

[0019] The compound represented by formula (I) is: [ka] During the ceremony, R 11 is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and is preferably a hydrogen atom or a methyl group. L is a single bond, a linear or branched alkylene group having 1 to 3 carbon atoms, or an aryl-substituted alkylene group having 7 to 9 carbon atoms, preferably a single bond or an ethylene group, more preferably a single bond. In the present invention, the aryl group also includes an alkyl-substituted aryl group (for example, a tolyl group). The same applies to the aryl groups described below. R 12 and R 13 are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, which may be substituted with a fluorine atom, a cyclic alkyl group having 3 to 7 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, or a halogen atom, and are preferably a linear or branched alkyl group having 1 to 4 carbon atoms (more preferably a methyl group), a linear or branched alkoxy group having 1 to 3 carbon atoms (more preferably a methoxy group or an ethoxy group), a cyclohexyl group, or a halogen atom (more preferably a fluorine atom). R 14 each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, a cyclic alkyl group having 3 to 7 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms which may be substituted with a halogen atom or a hydroxy group, an aryl-substituted alkyl group having 7 to 11 carbon atoms which may be substituted with a halogen atom or a hydroxy group, a hydroxy group, or a halogen atom; Preferably, it is a linear or branched alkyl group having 1 to 4 carbon atoms, which may be substituted with a fluorine atom, a cyclic alkyl group having 3 to 7 carbon atoms, a linear or branched alkoxy group having 1 to 3 carbon atoms, an aryl-substituted alkyl group having 7 to 11 carbon atoms and substituted with a hydroxy group, or a hydroxy group; More preferably, it is a methyl group, an ethyl group, a cyclohexyl group, a methoxy group, an ethoxy group, a hydroxyphenyl-substituted propyl group, or a hydroxy group. More preferred is a hydroxyphenyl-substituted propyl group or a hydroxy group. n12 and n13 each independently represent 0 to 3, preferably 0 or 1, and more preferably 0. n14 represents 0 to 3, preferably 0 or 1. In a more preferred embodiment, the hydroxy group is located at the 4-position (para-position) of the benzene ring.

[0020] Specific examples of (I) include the following: 1-phenyl-1,1-bis(4-hydroxyphenyl)methane, 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane, 4,4′,4″-methylidynetrisphenol, 4,4'-[(4-hydroxyphenyl)methylene]bis(2-methylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2-cyclohexyl-5-methylphenol), 4,4′,4″-ethylidynetrisphenol, 4,4′,4″-ethylidinetris(2-methylphenol), 4,4'-[1-{4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene]bisphenol, 4,4'-[1-{4-[1-(4-hydroxy-3-methylphenyl)-1-methylethyl]phenyl}ethylidene]bis(2-methylphenol), 4,4'-[(3-ethoxy-4-hydroxyphenyl)methylene]bisphenol, 4,4'-[3-(5-cyclohexyl-4-hydroxy-2-methylphenyl)-3-phenyl)propylidene]bis(2-cyclohexyl-5-methylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2-isopropylphenol), 4,4'-[1-{4-[1-(3-fluoro-4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene]bisphenol, 4,4'-[3-(2,5-dimethyl-4-hydroxyphenyl)butylene]bis(2,5-dimethylphenol), 1,1,3-tris(4-hydroxyphenyl)propane, 1,2,2-tris(4-hydroxyphenyl)propane, 1,3,3-tris(4-hydroxyphenyl)butane, 1,4,4-tris(4-hydroxyphenyl)pentane, 2,2-bis(3-methyl-4-hydroxyphenyl)-1-(4-hydroxyphenyl)propane, 1-(3-methyl-4-hydroxyphenyl)-2,2-bis(4-hydroxyphenyl)propane, 1-(3-methyl-4-hydroxyphenyl)-3,3-bis(4-hydroxyphenyl)butane, 3,3-bis(3-methyl-4-hydroxyphenyl)-1-(4-hydroxyphenyl)butane, 1,1,3-tris(3-methyl-4-hydroxyphenyl)propane, 1,3,3-tris(3-methyl-4-hydroxyphenyl)butane, 4,4'-[4-(4-hydroxyphenyl)-sec-butylidene]bis(2-methylphenol)

[0021] The compound represented by formula (IIa) is: [ka] During the ceremony, R a1 and R a2are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 17 carbon atoms which may be substituted with a fluorine atom (wherein a methylene (-CH-) group in the alkyl group may be replaced with an oxy (-O-) group or a carbonyl (-CO-) group), Preferably, each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 11 carbon atoms which may be substituted with a fluorine atom, More preferably, R a1 and R a2 at least one of the above is a linear or branched alkyl group having 5 to 9 carbon atoms, More preferably, each independently, R a1 and R a2 One of the groups is a branched alkyl group having 5 to 9 carbon atoms, and the other is hydrogen or a methyl group. R a3 and R a4 are each independently a linear or branched alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom or a hydroxy group, an alkenyl group having 2 to 4 carbon atoms, or a halogen atom, and are preferably a linear or branched alkyl group having 1 to 4 carbon atoms (more preferably a methyl group) or a halogen atom (more preferably a fluorine atom). na3 and na4 each independently represent 0 to 2, preferably 0 or 1, and more preferably 0. In a more preferred embodiment, the hydroxy group is located at the 4-position (para-position) of the benzene ring.

[0022] Specific examples of (IIa) include the following: 1,1-bis(4-hydroxyphenyl) n-hexane, 1,1-bis(4-hydroxyphenyl) n-octane, 1,1-bis(4-hydroxyphenyl) n-decane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis(4-hydroxyphenyl)-2-ethylbutane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl) n-heptane, 2,2-bis(4-hydroxyphenyl) n-dodecane, 2,2-bis(4-hydroxyphenyl)-4-methylhexane, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,2-bis(4-hydroxy-3-methylphenyl)butane, 2,2-bis(4-hydroxy-3-isopropylphenyl)propane, 2,2-bis(3-fluoro-4-hydroxyphenyl)propane

[0023] The compound represented by formula (IIb) is: [ka] During the ceremony, R b1 and R b2 each independently represents a hydroxy group, a linear or branched alkoxy group having 1 to 9 carbon atoms, a linear or branched alkyl group having 1 to 10 carbon atoms which may be substituted with a fluorine atom, an alkenyl group having 2 to 10 carbon atoms, or a halogen atom; Preferably, it is a hydroxy group or a linear or branched alkyl group having 1 to 8 carbon atoms. More preferably, it is a hydroxy group or a linear or branched alkyl group having 3 to 6 carbon atoms. More preferred is a hydroxy group, an isobutyl group, a sec-butyl group, or a tert-butyl group. nb1 is 0 to 3, and preferably 1. nb2 is 0 to 2, and preferably 1. In a more preferred embodiment, the hydroxy groups are present at the 2-position (ortho-position) and 4-position (para-position) of one of the benzene rings.

[0024] Specific examples of (IIb) include the following: 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone, 2,4-dihydroxy-4′-n-propylbenzophenone, 2,4-dihydroxy-4′-n-butylbenzophenone, 2,4-dihydroxy-4′-isobutylbenzophenone, 2,4-dihydroxy-4′-sec-butylbenzophenone, 2,4-dihydroxy-4′-tert-butylbenzophenone, 2,4-dihydroxy-4′-n-hexylbenzophenone, 2,4-dihydroxy-2′,4′-dimethylbenzophenone, 2,4-dihydroxy-2′,4′,6′-trimethylbenzophenone, 2,4-dihydroxy-2′-methoxybenzophenone, 2,4-dihydroxy-4′-ethoxybenzophenone, 2,4-dihydroxy-2′,4′-dimethoxybenzophenone, 2,4-Dihydroxy-3',4'-diethoxybenzophenone

[0025] By combining the compound represented by formula (I) and the compound represented by formula (IIa) or (IIb) as component (b), the properties of each compound can be utilized, and a reversible thermochromic composition having high color density and excellent light resistance in the colored state can be provided.

[0026] Of the compounds represented by formula (IIa) and (IIb), the compound represented by formula (IIa) is preferred from the viewpoints of easy availability and excellent productivity. In other words, as component (b), a combination of the compound represented by formula (I) and the compound represented by formula (IIa) is preferred from the viewpoints of color density, light resistance, and productivity. Among the compounds represented by formula (I), R 11is a hydrogen atom or a methyl group, L is a single bond or an ethylene group, n12 and n13 are each 0, and n14 is 0 or 1. When n14 is 1, R 14 is a methyl group, an ethyl group, a methoxy group, an ethoxy group, a hydroxyphenyl-substituted propyl group, or a hydroxy group, and the hydroxy group is located at the 4-position (para-position) of the benzene ring. 11 is a hydrogen atom or a methyl group, L is a single bond, n12 and n13 are each 0, and n14 is 0 or 1, and when n14 is 1, R 14 is a hydroxyphenyl-substituted propyl group or a hydroxy group, and the hydroxy group is located at the 4-position (para position) of the benzene ring. As compared with the case where the compound represented by formula (I) is used alone as the component (b), the decolorization concentration of the reversible thermochromic composition can be maintained at the same level or can be reduced. Therefore, the compound represented by formula (IIa) to be combined with the compound represented by formula (I) is preferably R a1 and R a2 At least one of R is a linear or branched alkyl group having 5 to 9 carbon atoms, na3 and na4 are each 0, and the hydroxy group is located at the 4-position (para-position) of the benzene ring. a1 and R a2 One of the groups is a branched alkyl group having 5 to 9 carbon atoms, the other is a hydrogen atom or a methyl group, na3 and na4 are each 0, and the hydroxy groups are each located at the 4-position (para-position) of the benzene ring. That is, as the compound represented by formula (I), R 11 is a hydrogen atom or a methyl group, L is a single bond, n12 and n13 are each 0, and n14 is 0 or 1, and when n14 is 1, R 14 is a hydroxyphenyl-substituted propyl group or a hydroxy group, and the hydroxy group is located at the 4-position (para-position) of the benzene ring; and as compounds represented by formula (IIa), Ra1 and R a2 The most preferred combination is a compound in which one of the groups is a branched alkyl group having 5 to 9 carbon atoms, the other is a hydrogen atom or a methyl group, n3 and n4 are each 0, and the hydroxy group is located at the 4-position (para-position) of the benzene ring.

[0027] The mass ratio of the compound represented by formula (I): the compound represented by formula (IIa) is preferably in the range of 1:0.5 to 1:5, more preferably 1:1 to 1:3. When the mass ratio of the compound represented by formula (I) to the compound represented by formula (IIa) is within the above range, it is easy to obtain a reversible thermochromic composition having a large difference between the color density and the decolorized density, i.e., an excellent contrast between the colored state and the decolorized state. Furthermore, when the mass ratio of the compound represented by formula (I) to the compound represented by formula (IIa) is in the range of 1:1 to 1:3, the compound represented by formula (IIa) easily dissolves the compound represented by formula (I), further improving the color density of the reversible thermochromic composition, thereby obtaining a reversible thermochromic composition having an even more excellent contrast between the colored state and the decolorized state.

[0028] The component (c) of the reaction medium that reversibly induces an electron transfer reaction between the components (a) and (b) in a specific temperature range is described below. Examples of the component (c) include alcohols, esters, ketones, ethers, and acid amides. When the reversible thermochromic composition of the present invention is applied to microencapsulation and secondary processing, compounds having 10 or more carbon atoms are preferably used to stably retain the composition in the capsule, since low molecular weight compounds will evaporate out of the capsule when subjected to high heat treatment.

[0029] As the alcohol, aliphatic monohydric saturated alcohols having 10 or more carbon atoms are effective.

[0030] As the esters, esters having 10 or more carbon atoms are effective, and examples thereof include esters obtained from any combination of a monocarboxylic acid having an aliphatic, alicyclic or aromatic ring and a monohydric alcohol having an aliphatic, alicyclic or aromatic ring; esters obtained from any combination of a polycarboxylic acid having an aliphatic, alicyclic or aromatic ring and a monohydric alcohol having an aliphatic, alicyclic or aromatic ring; and esters obtained from any combination of a monocarboxylic acid having an aliphatic, alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic, alicyclic or aromatic ring.

[0031] Also effective are esters of saturated fatty acids and branched fatty alcohols, esters of unsaturated fatty acids or branched or substituted saturated fatty acids and branched fatty alcohols or fatty alcohols having 16 or more carbon atoms, and ester compounds selected from cetyl butyrate, stearyl butyrate, and behenyl butyrate.

[0032] Furthermore, in order to change color while exhibiting large hysteresis characteristics in the color density-temperature curve and to impart color memory depending on temperature changes, carboxylic acid ester compounds having a ΔT value (melting point-cloud point) of 5°C or more and less than 50°C, as described in Japanese Patent Publication No. 4-17154, can be exemplified.

[0033] Also effective are fatty acid ester compounds obtained from an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid, and fatty acid ester compounds having a total of 17 to 23 carbon atoms obtained from n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid having 10 to 16 carbon atoms.

[0034] As the ketones, aliphatic ketones having a total carbon number of 10 or more are effective, and examples thereof include aryl alkyl ketones having a total carbon number of 12 to 24.

[0035] As the ethers, aliphatic ethers having a total of 10 or more carbon atoms are effective.

[0036] Examples of the above alcohols, esters, ketones, ethers, and acid amides include the compounds described in JP-A-2020-100710.

[0037] Furthermore, the component (c) may be a compound represented by the following formula (1). [ka] [wherein R1 represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, and either X1 or X2 represents -(CH2) n OCOR2 or (CH2) n COOR2, the other represents a hydrogen atom; n represents an integer of 0 to 2; R2 represents an alkyl or alkenyl group having 4 or more carbon atoms; Y1 and Y2 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen atom; and r and p each independently represent an integer of 1 to 3. Among the compounds represented by formula (1), when R1 is a hydrogen atom, a reversible thermochromic composition having a wider hysteresis width can be obtained, which is preferable, and it is even more preferable that R1 is a hydrogen atom and m is 0. Among the compounds represented by formula (1), the compound represented by the following formula (2) is more preferred. [ka] (In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, and more preferably an alkyl group having 12 to 22 carbon atoms.)

[0038] Furthermore, the component (c) may be a compound represented by the following formula (3). [ka] (In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, m and n each independently represent an integer of 1 to 3, and X and Y each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom.)

[0039] Furthermore, the component (c) may be a compound represented by the following formula (4). [ka] (wherein X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen atom; m represents an integer of 1 to 3; and n represents an integer of 1 to 20).

[0040] Furthermore, the component (c) may be a compound represented by the following formula (5). [ka] (wherein R represents an alkyl or alkenyl group having 1 to 21 carbon atoms, and n represents an integer of 1 to 3).

[0041] Furthermore, the component (c) may be a compound represented by the following formula (6). [ka] (wherein X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; m represents an integer of 1 to 3; and n represents an integer of 1 to 20).

[0042] Furthermore, the component (c) may be a compound represented by the following formula (7). [ka] (In the formula, R represents an alkyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, a cycloalkyl group, or an alkenyl group having 4 to 22 carbon atoms; X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; and n represents 0 or 1.)

[0043] Furthermore, the component (c) may be a compound represented by the following formula (8). [ka] (wherein R represents an alkyl group having 3 to 18 carbon atoms or an aliphatic acyl group having 3 to 18 carbon atoms; X represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom; Y represents a hydrogen atom or a methyl group; and Z represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom).

[0044] Furthermore, the component (c) may be a compound represented by the following formula (9). [ka] (In the formula, R represents an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, or a cycloalkyl group; X represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; Y represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; and n represents 0 or 1.)

[0045] Furthermore, the component (c) may be a compound represented by the following formula (10). [ka] (In the formula, R represents any one of an alkyl group having 3 to 18 carbon atoms, a cycloalkylalkyl group having 6 to 11 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, and an alkenyl group having 3 to 18 carbon atoms; X represents any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a halogen atom; and Y represents any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, and a halogen atom.)

[0046] Furthermore, the component (c) may be a compound represented by the following formula (11). [ka] (wherein R represents a cycloalkyl group having 3 to 8 carbon atoms or a cycloalkylalkyl group having 4 to 9 carbon atoms, and n represents an integer of 1 to 3).

[0047] Furthermore, the component (c) may be a compound represented by the following formula (12). [ka] (In the formula, R 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 n represents an integer of 1 to 3.)

[0048] Examples of the compounds represented by formulas (2) to (12) include those described in JP 2020-100710 A Examples of the compounds include those described in the publication No.

[0049] Among the above-mentioned components (c), compounds having one or more aromatic rings are preferred because they provide excellent solubility of component (a) in the reversible thermochromic composition, and this makes it easier to prepare a reversible thermochromic composition with improved color density. Compounds represented by formulas (1) to (12) having two or more aromatic rings are more preferred.

[0050] Furthermore, reversible thermochromic compositions of the heat-coloring type (which develops color when heated and loses color when cooled) that use gallic acid esters (JP-B No. 51-44706, JP-A No. 2003-253149) or the like as electron-accepting compounds, and reversible thermochromic microcapsule pigments encapsulating such compositions can also be used (see Figure 3).

[0051] The reversible thermochromic composition of the present invention is a compatible solution containing the above-mentioned components (a), (b), and (c) as essential components. The proportion of each component depends on the concentration, discoloration temperature, discoloration form, and type of each component, but the mass ratio of component (a):component (b) that generally provides the desired properties is preferably in the range of 1:0.1 to 1:100, more preferably 1:0.1 to 1:50, and even more preferably 1:0.5 to 1:20. Furthermore, the mass ratio of component (a) to component (c) is preferably in the range of 1:5 to 1:100, more preferably 1:5 to 1:50, even more preferably 1:5 to 1:20, and particularly preferably 1:5 to 1:15. When the mass ratio of component (a) to component (c) is within the above range, it becomes easy to obtain a reversibly thermochromic composition having a large difference in density between the colored and decolored densities, i.e., an even more excellent contrast between the colored and decolored states.

[0052] Furthermore, the reversible thermochromic composition may contain various light stabilizers as required. The light stabilizer is included to prevent photodegradation of the reversibly thermochromic composition consisting of components (a), (b), and (c), and is blended in a proportion of 0.3 to 24 parts by mass, preferably 0.3 to 16 parts by mass, per part by mass of component (a). Among the light stabilizers, ultraviolet absorbers effectively block ultraviolet rays contained in sunlight and the like, preventing photodegradation caused by the excited state resulting from the photoreaction of component (a). Furthermore, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, and the like inhibit photooxidation reactions. The light stabilizers may be used alone or in combination of two or more.

[0053] The reversible thermochromic composition of the present invention is effective when used as is, but it can also be encapsulated in microcapsules to form a reversible thermochromic microcapsule pigment (hereinafter sometimes referred to as a "microcapsule pigment" or "pigment"), or dispersed in a thermoplastic resin or a thermosetting resin to form reversible thermochromic resin particles (hereinafter sometimes referred to as "resin particles"). The reversible thermochromic composition is preferably encapsulated in microcapsules to form a reversible thermochromic microcapsule pigment, because encapsulation in microcapsules makes it possible to form a chemically and physically stable pigment, and furthermore, the reversible thermochromic composition can maintain the same composition under various conditions of use, thereby achieving the same effects. Microencapsulation can be performed by any of the conventionally known methods, such as isocyanate-based interfacial polymerization, melamine-formalin-based or other in situ polymerization, liquid curing coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and is selected appropriately depending on the application. Furthermore, a secondary resin film can be provided on the surface of the microcapsules depending on the purpose to impart durability or modify the surface properties for practical use. The reversible thermochromic microcapsule pigment preferably has a mass ratio of inclusions to wall film of 7:1 to 1:1, and by having the mass ratio of inclusions to wall film within the above range, a decrease in color density and clarity during color development is prevented.A more preferred mass ratio is 6:1 to 1:1.

[0054] The average particle size of the reversible thermochromic microencapsulated pigment or resin particles is preferably 0.01 to 50 μm, more preferably 0.1 to 30 μm, and even more preferably 0.5 to 20 μm. If the average particle size of the microencapsulated pigment or resin particles exceeds 50 μm, dispersion stability and processing suitability will be poor when blended into ink, paint, or resin. On the other hand, if the average particle size is less than 0.01 μm, it will be difficult to achieve high-concentration color development. Furthermore, when the microencapsulated pigment or resin particles are used in inks for writing instruments, the average particle size is preferably in the range of 0.01 to 5 μm, more preferably 0.05 to 4 μm, even more preferably 0.1 to 3 μm, and particularly preferably 0.5 to 3 μm. If the average particle size of the pigment or resin particles exceeds 5 μm, it becomes difficult to obtain good ink dischargeability when used in writing instruments. On the other hand, if the average particle size is less than 0.01 μm, it becomes difficult to achieve high-density color development. The average particle size was measured by determining the particle area using image analysis particle size distribution measurement software (manufactured by Mountec Co., Ltd., product name: MacView), calculating the diameter equivalent to a circle with a projected area (Heywood diameter) from the area of ​​the particle area, and measuring the average particle size of particles equivalent to a sphere with the same volume using this value. Furthermore, if the particle size of all or the majority of particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to an equal volume sphere using the Coulter method using a particle size distribution analyzer (product name: Multisizer 4e, manufactured by Beckman Coulter, Inc.). Furthermore, the volumetric particle size and average particle size may be measured using a calibrated laser diffraction / scattering particle size distribution analyzer (manufactured by HORIBA, Ltd., product name: LA-300) based on values ​​measured using the above software or a measuring device using the Coulter method.

[0055] A reversible thermochromic composition, a reversible thermochromic colorant such as a reversible thermochromic microcapsule pigment or resin particles is dispersed in a vehicle containing water and / or an organic solvent and, if necessary, various additives to form an ink composition (hereinafter, sometimes referred to as "ink"), It can be used as a reversible thermochromic liquid composition such as printing ink used in screen printing, offset printing, process printing, gravure printing, coater printing, pad printing, etc.; paint used in brush coating, spray coating, electrostatic coating, electrodeposition coating, flow coating, roller coating, dip coating, etc.; inkjet ink; ultraviolet-curing ink; ink for writing instruments such as marking pens, ballpoint pens, fountain pens, and brush pens; ink for applicators; ink for stamps; paints; cosmetics; and coloring liquids for textiles.

[0056] The reversible thermochromic liquid composition may contain various additives. Examples of additives include resins, crosslinking agents, curing agents, drying agents, plasticizers, viscosity modifiers, dispersants, ultraviolet absorbers, antioxidants, light stabilizers, anti-settling agents, smoothing agents, gelling agents, antifoaming agents, matting agents, penetrating agents, pH adjusters, foaming agents, coupling agents, moisturizing agents, antifungal agents, preservatives, and rust inhibitors.

[0057] Examples of the vehicle for a writing instrument used in the ink for a writing instrument include an oil-based vehicle containing an organic solvent, and an aqueous vehicle containing water and, if necessary, an organic solvent. When the vehicle is an aqueous vehicle, the writing instrument ink may contain a water-soluble organic solvent that is compatible with water. The water-soluble organic solvent suppresses evaporation of water from the ink and prevents fluctuations in the specific gravity of the vehicle, maintaining good dispersion stability of the reversible thermochromic microencapsulated pigment, and stabilizing the structure of the polymer flocculant (described below) or the loose aggregates formed by the polymer flocculant and the dispersant. Examples of organic solvents include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0058] When a writing instrument ink contains a water-soluble organic solvent, the water-soluble organic solvent is preferably blended in an amount of 1 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 25% by mass, based on the total amount of the ink. If the blending ratio of the water-soluble organic solvent exceeds 40% by mass, the ink viscosity tends to increase. On the other hand, if the blending ratio is less than 1% by mass, the effect of suppressing water evaporation becomes poor.

[0059] When the writing instrument ink contains a water-soluble organic solvent and the hysteresis width (ΔH) of the reversible thermochromic microencapsulated pigment blended into the writing instrument ink is large, the specific gravity of the microencapsulated pigment is greater than 1, and when adjusting the specific gravity of the vehicle, using a water-soluble organic solvent with a specific gravity greater than that of water makes it easier to adjust the specific gravity. Therefore, it is preferable to use glycerin or the like with a specific gravity greater than 1.1 as the water-soluble organic solvent.

[0060] Writing instrument inks can be formulated with shear thinning agents, and inks containing shear thinning agents (shear thinning inks) can suppress aggregation and sedimentation of microencapsulated pigments and can also suppress bleeding of handwriting, resulting in the formation of good handwriting. Furthermore, when shear-thinning ink is stored in a ballpoint pen-shaped writing instrument, it can prevent ink leakage from the gap between the ball and the tip when the writing instrument is not in use, and it can prevent ink from flowing back when the writing tip is left facing upward (upright).

[0061] Examples of shear thinning agents include xanthan gum, welan gum, succinoglycan (average molecular weight: approximately 1,000,000 to 8,000,000), which is an organic acid-modified heteropolysaccharide whose constituent monosaccharides are glucose and galactose, alka gum, guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alkyl alginate esters, polymers having a molecular weight of 100,000 to 150,000 and containing alkyl esters of methacrylic acid as the main component, glucomannan, thickening polysaccharides having gelling ability extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, cross-linked acrylic acid polymers, inorganic Examples of surfactants include nonionic surfactants with an HLB value of 8 to 12, such as fine molecular weight polymers, polyglycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene lanolin / lanonin alcohol / beeswax derivatives, polyoxyethylene alkyl ethers / polyoxypropylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and fatty acid amides, salts of dialkyl or dialkenyl sulfosuccinic acid, mixtures of N-alkyl-2-pyrrolidone and anionic surfactants, and mixtures of polyvinyl alcohol and acrylic resins.

[0062] Furthermore, a polymer flocculant can be blended into the ink for the writing instrument. In the ink containing the polymer flocculant (flocculating ink), the microcapsule pigment forms loose aggregates via the polymer flocculant, which prevents the microcapsule pigments from coming into contact with each other and aggregating, thereby improving the dispersibility of the microcapsule pigment.

[0063] Examples of polymer flocculants include polyvinylpyrrolidone, polyethylene oxide, and water-soluble polysaccharides. Examples of water-soluble polysaccharides include tragacanth gum, guar gum, pullulan, cyclodextrin, and water-soluble cellulose derivatives. Furthermore, examples of water-soluble cellulose derivatives include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose. Among the above polymer flocculants, hydroxyethyl cellulose is preferred because of its excellent dispersibility.

[0064] The polymer flocculant is preferably blended in an amount of 0.1 to 1 mass %, more preferably 0.3 to 0.5 mass %, based on the total amount of ink. By blending within this range, the microencapsulated pigment forms loose aggregates, and the effect of improving the dispersibility of the pigment can be fully exerted.

[0065] Furthermore, the dispersibility of the microcapsule pigment can be improved by blending a dispersant into the ink for the writing instrument. In addition, a polymer flocculant and a dispersant can be used in combination. When both are used in combination, the dispersibility of the microencapsulated pigment can be improved, and the dispersibility of the loose aggregates of the microencapsulated pigment formed via the polymer flocculant can be further improved.

[0066] Examples of dispersants include synthetic resins such as polyvinylpyrrolidone, polyvinyl butyral, polyvinyl ether, styrene-maleic acid copolymer, ketone resin, hydroxyethyl cellulose and its derivatives, and styrene-acrylic acid copolymer, acrylic polymers, PO·EO adducts, and polyester amine oligomers. Among the above dispersants, acrylic polymer dispersants are preferred because they have excellent dispersibility for microencapsulated pigments, acrylic polymer dispersants having carboxy groups are more preferred, and acrylic polymer dispersants having a comb structure and having carboxy groups in the side chains are even more preferred. A particularly preferred dispersant is an acrylic polymer dispersant with a comb structure having multiple carboxy groups in the side chains, and a specific example is Solsperse 43000, a product name manufactured by Lubrizol Japan Co., Ltd. The dispersant is preferably blended in an amount of 0.01 to 2% by mass, more preferably 0.1 to 1.5% by mass, based on the total amount of ink. If the blending ratio of the dispersant exceeds 2% by mass, the microencapsulated pigment is likely to settle or float when subjected to external vibrations, etc. On the other hand, if the blending ratio is less than 0.01% by mass, the effect of improving dispersibility is less likely to be achieved.

[0067] Furthermore, by blending a water-soluble resin into the ink for a writing instrument, it is possible to impart adhesiveness and viscosity to the handwriting on the paper surface. Examples of water-soluble resins include alkyd resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, and dextrin. Among the above-mentioned water-soluble resins, polyvinyl alcohol is preferred because it provides excellent stability to the acrylic polymer dispersant, and partially saponified polyvinyl alcohol with a saponification degree of 70 to 89 mol % is more preferred because it provides excellent solubility in the ink even in the acidic range. The water-soluble resin is preferably blended in an amount of 0.3 to 3.0% by mass, more preferably 0.5 to 1.5% by mass, based on the total amount of the ink.

[0068] Furthermore, when the viscosity of the vehicle used in the writing instrument ink is low, adding a specific gravity adjuster can prevent the microencapsulated pigment from settling or floating up in the ink and becoming localized, thereby improving the dispersion stability of the microencapsulated pigment.

[0069] The dispersion stability of a pigment is maximized when the difference in specific gravity between the vehicle and the pigment is minimal, and the specific gravity adjuster brings the specific gravity of the vehicle closer to that of the pigment. The specific gravity of the vehicle depends on the specific gravity of the water-soluble substance dissolved in the vehicle and the amount added, so adding and dissolving a larger amount of a specific gravity adjuster with a larger specific gravity in the vehicle makes it possible to increase the specific gravity of the vehicle.

[0070] Examples of specific gravity adjusters include oxyacids of Group 6 elements having an atomic weight of 90 to 185 and salts thereof. Such a specific gravity adjuster can adjust the specific gravity of the vehicle to be closer to that of the pigment, which has a higher specific gravity, and can prevent the pigment from settling or floating up and becoming localized when subjected to external stimuli such as vibration, even while the ink has a low viscosity.

[0071] The oxygen acid and its salt are selected from the group consisting of oxygen acids of transition metal elements and their salts, and the oxygen acid ions are said to form tetrahedrons or octahedrons in which oxygen atoms are usually 4- or 6-coordinated to the metal atom or the like. The oxygen acid and its salt may be a polyacid and its salt, i.e., a polyacid acid salt. The polyacid includes an isopolyacid, a heteropolyacid, etc., and the polyacid acid salt includes an isopolyacid acid salt, a heteropolyacid acid salt, etc.

[0072] Examples of the specific gravity adjuster include a single oxygen acid and its salt, an isopoly acid and its salt, and a heteropoly acid and its salt. Examples of the single oxygen acid include molybdic acid and tungstic acid, and examples of the salt of the single oxygen acid include sodium molybdate, potassium molybdate, ammonium molybdate, sodium tungstate, potassium tungstate, ammonium tungstate, lithium tungstate, and magnesium tungstate. Examples of isopolyacids include metamolybdic acid, paramolybdic acid, metatungstic acid, paratungstic acid, and isotungstic acid. Furthermore, examples of isopolyacid salts include sodium metamolybdate, potassium metamolybdate, ammonium metamolybdate, sodium paramolybdate, potassium paramolybdate, ammonium paramolybdate, sodium metatungstate, potassium metatungstate, ammonium metatungstate, barium metatungstate, sodium paratungstate, and sodium isotungstate. Examples of heteropolyacids include molybdophosphoric acid, molybdosilicic acid, tungstophosphoric acid, and tungstosilicic acid, and examples of heteropolyacid salts include sodium molybdophosphate, sodium molybdosilicate, sodium tungstophosphate, and sodium tungstosilicate. The above oxygen acids and salts thereof can be used alone or in a suitable mixture of two or more.

[0073] Among the above-mentioned specific gravity adjusters, metatungstic acid, paratungstic acid, sodium metatungstate, potassium metatungstate, ammonium metatungstate, barium metatungstate, sodium paratungstate, sodium isotungstate, tungstophosphoric acid, tungstosilicic acid, sodium tungstophosphate, and sodium tungstosilicate are preferred, and sodium isotungstate, sodium metatungstate, and sodium paratungstate are more preferred. The above-mentioned sodium isotungstate, sodium metatungstate, and sodium paratungstate are not only highly safe but also have high specific gravities themselves, so that it is easy to adjust the liquid to have a high specific gravity depending on the amount added, and therefore they are preferably used.

[0074] The gravity adjuster is preferably blended in an amount of 2 to 20% by mass, more preferably 5 to 15% by mass, based on the total amount of ink. If the blending ratio of the gravity adjuster exceeds 20% by mass, the microcapsule pigment tends to aggregate. On the other hand, if the blending ratio is less than 2% by mass, the effect of adjusting the vehicle's specific gravity is reduced. The mass ratio of the microcapsule pigment to the specific gravity adjuster is preferably 1:0.05 to 4.0, more preferably 1:0.075 to 2.0, and even more preferably 1:0.1 to 1.5.

[0075] The vehicle containing the above-mentioned specific gravity adjuster is particularly effective for microencapsulated pigments with high specific gravities, and even though the ink has a low viscosity, it can suppress the pigment from settling in the ink when subjected to external stimuli such as vibration, thereby improving the dispersion stability of the microencapsulated pigment. The specific gravity of a microencapsulated pigment depends on the particle size, the components and their content encapsulated in the microcapsules, the components and film thickness of the capsule wall, the color state of the microencapsulated pigment, and the temperature. However, the specific gravity is preferably 1.05 to 1.20 when the microencapsulated pigment is fully colored and at 20°C relative to water. Such pigments exhibit a large hysteresis width (ΔH), can be decolorized by heating, and can maintain the decolorized state within a specific temperature range. However, pigments with a large hysteresis width (ΔH) often contain a compound with two or more aromatic rings in the molecule as component (c), which increases their specific gravity and makes them prone to settling and separation in ink, particularly when subjected to external stimuli such as vibration. However, the use of the specific gravity adjuster described above in inks is advantageous because it prevents the microencapsulated pigment from settling and localizing, improving the dispersion stability of the pigment, even while maintaining a low ink viscosity. Considering the dispersion stability of the pigment in the ink, the specific gravity of the microencapsulated pigment is preferably 1.10 to 1.20, and more preferably 1.12 to 1.15, when the microencapsulated pigment is in a fully colored state and is based on water at 20°C. The specific gravity of the microcapsule pigment can be measured by the following method.

[0076] (Method for measuring specific gravity of microcapsule pigments) 1. 30 ml of glycerin aqueous solution and 1 g of fully colored microcapsule pigment are placed in a screw cap bottle and mixed to obtain a microcapsule pigment dispersion. 2. 30 ml of the microcapsule pigment dispersion is adjusted to 20°C and centrifuged at 1000 rpm for 30 seconds. A refrigerated tabletop centrifuge (manufactured by Kokusan Co., Ltd., product name: H103N) can be used as the centrifuge. 3. Observe the microcapsule pigment dispersion. If most of the microcapsule pigment has settled to the bottom of the beaker, repeat steps 1 and 2 using an aqueous solution with a higher glycerin concentration than the glycerin aqueous solution used at this time, and observe the state of the dispersion. If it is confirmed that most of the microcapsule pigment is floating on the liquid surface, repeat steps 1 and 2 using an aqueous solution with a lower glycerin concentration than the glycerin aqueous solution used this time, and observe the state of the dispersion. The above series of operations is repeated until it is visually confirmed that the majority of the microencapsulated pigment does not float to the surface or settle, but that the glycerin aqueous solution is uniformly colored except for the surface and the area near the bottom of the screw cap bottle. When this state is observed, the specific gravity of the glycerin aqueous solution is measured and used as the specific gravity of the microencapsulated pigment. The specific gravity of the glycerin aqueous solution can be measured by the hydrometer method described in JIS K0061, Section 7.1, using an aqueous solution adjusted to 20°C.

[0077] Furthermore, the vehicle containing the above-mentioned specific gravity adjuster has a specific gravity in the range of 1.00 to 1.30 at 20°C when water is used as the reference substance, and the specific gravity is preferably 1.05 to 1.20, and more preferably 1.08 to 1.18. Furthermore, the specific gravity of the vehicle is preferably 0.90 to 1.20 times, and more preferably 0.95 to 1.10 times, the specific gravity of the pigment. When the specific gravity of the vehicle is within the above range and the ratio of the specific gravity of the vehicle to the specific gravity of the pigment is also within the above range, even when the ink is subjected to an external stimulus such as vibration, the pigment can be further prevented from settling and becoming localized in the ink, even though the ink has a low viscosity, thereby further improving the dispersion stability of the pigment.

[0078] When the vehicle for the writing instrument is an aqueous vehicle, the vehicle contains at least water, and the amount of water is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, based on the total amount of the ink.

[0079] Furthermore, when the writing instrument ink is used in a ballpoint pen, it is preferable to add to the ink a lubricant such as a higher fatty acid such as oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, a thiophosphite triester such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester), a polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoester, a polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diester, or a metal salt, ammonium salt, amine salt, or alkanolamine salt thereof to prevent wear of the ball seat.

[0080] In addition, additives such as wetting agents, resins, resin particles, pH adjusters, rust inhibitors, surfactants, wetting agents, antifoaming agents, viscosity adjusters, preservatives, and antifungal agents can also be added as needed.

[0081] The reversible thermochromic microencapsulated pigment is preferably blended in the writing instrument ink in an amount of 5 to 40% by mass, more preferably 10 to 40% by mass, and even more preferably 10 to 30% by mass, based on the total mass of the ink. By blending the microencapsulated pigment in the above range, the desired color density can be obtained and a decrease in ink outflow properties can be prevented.

[0082] The ink composition according to the present invention can be produced by any conventionally known method, specifically by blending the required amounts of the above-described components and mixing them with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or various dispersers such as a bead mill.

[0083] When the ink for a writing instrument according to the present invention is used in a ballpoint pen, its viscosity is measured at a rotation speed of 1 rpm (shear rate of 3.84 sec) in an environment of 20°C. -1When measured under the conditions of 100 rpm (shear rate 384 sec), the viscosity is preferably 1 to 2000 mPa·s, more preferably 3 to 1500 mPa·s, and even more preferably 500 to 1000 mPa·s, because this can prevent the sedimentation or aggregation of the microencapsulated pigment. -1 When measured under the conditions of (1), the viscosity is preferably 1 to 200 mPa·s, more preferably 10 to 100 mPa·s, and even more preferably 20 to 50 mPa·s, because this allows for good ink discharge from the pen tip of the ballpoint pen. By having the viscosity within the above range, it is possible to maintain high levels of dispersion stability of the microencapsulated pigment and free flow of the ink within the mechanism of the ballpoint pen. The viscosity was measured using a rheometer (TA Instruments, product name: Discovery HR-2, cone plate (diameter 40 mm, angle 1°)) at a rotation speed of 1 rpm (shear rate 3.84 sec) with the ink placed in a 20°C environment. -1 ), or rotation speed 100 rpm (shear rate 384 sec -1 ) are values ​​measured under the conditions.

[0084] When the writing instrument ink according to the present invention is used in a ballpoint pen, the surface tension thereof is preferably 20 to 50 mN / m, and more preferably 25 to 45 mN / m, in an environment of 20° C. Having a surface tension within the above range makes it easy to suppress bleeding of written lines and strike-through onto the paper surface, and also improves the wettability of the ink to the paper surface. The surface tension was measured using a surface tension measuring instrument (manufactured by Kyowa Interface Science Co., Ltd., product name: DY-300) by placing the ink in an environment of 20°C using a vertical plate method using a platinum plate.

[0085] When the writing instrument ink according to the present invention is used in a ballpoint pen, its pH is preferably 3 to 10, and more preferably 4 to 9. When the pH is within the above range, aggregation or sedimentation of the microencapsulated pigment contained in the ink can be suppressed at low temperatures. The pH was measured by placing the ink in an environment of 20°C using a pH meter (manufactured by DKK Toa Corporation, product name: IM-40S).

[0086] When the writing instrument ink according to the present invention is used in a marking pen, its viscosity, measured at 30 rpm in an environment of 20° C., is preferably 1 to 20 mPa·s, more preferably 1 to 10 mPa·s, and even more preferably 1 to 5 mPa·s. Having a viscosity within the above range can improve the fluidity of the ink and the dispersion stability of the microencapsulated pigment. The viscosity was measured by placing the ink in an environment of 20°C using a BL-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., product name: TVB-M type viscometer, L-type rotor).

[0087] When the writing instrument ink according to the present invention is used in a marking pen, the surface tension thereof is preferably 25 to 50 mN / m, more preferably 25 to 45 mN / m, and even more preferably 35 to 45 mN / m in an environment of 20° C. Having a surface tension within the above range makes it easy to suppress bleeding of written lines and strike-through onto the paper surface, and also improves the wettability of the ink to the paper surface. The surface tension was measured using a surface tension measuring instrument (manufactured by Kyowa Interface Science Co., Ltd., product name: DY-300) by placing the ink in an environment of 20°C using a vertical plate method using a glass plate.

[0088] When the writing instrument ink according to the present invention is used in a marking pen, its pH is preferably from 3 to 8, more preferably from 4 to 7, and even more preferably from 5 to 6. By keeping the pH within the above range, aggregation or sedimentation of the microencapsulated pigment contained in the ink at low temperatures can be suppressed. The pH was measured by placing the ink in an environment of 20°C using a pH meter (manufactured by DKK Toa Corporation, product name: IM-40S).

[0089] The ink for the writing implement is contained in a writing implement having a pen tip and an ink filling mechanism. Examples of writing implements include ballpoint pens, marking pens, fountain pens, brush pens, calligraphy pens, and other various writing implements.

[0090] The pen tip of the writing implement is not particularly limited, and pen tips with various types of tips can be used. Among the various types of tips, examples of ballpoint pen tips include tips in which a ball is held in a ball holding portion formed by deforming the area near the tip of a metal pipe by pressing it inward from the outer surface, tips in which a ball is held in a ball holding portion formed by cutting a metal material with a drill or the like, tips in which a resin ball receiving seat is provided inside a metal or plastic tip, and tips in which the ball held in the tip is urged forward by a spring body. The material of the ballpoint pen tip and ball is not particularly limited, and examples thereof include cemented carbide (super hard), stainless steel, ruby, ceramic, resin, rubber, and the like. The diameter of the ball is preferably 0.1 to 3.0 mm, more preferably 0.2 to 2.0 mm, and even more preferably 0.3 to 1.0 mm. The ball may also be subjected to a surface treatment such as a DLC coating.

[0091] Examples of marking pen tips include conventional porous members with interconnected pores, such as resin-processed fibers, fused heat-fusible fibers, and felt, which have a porosity selected from a range of approximately 30 to 70%, or extrusion-molded synthetic resin bodies with multiple ink outlet holes extending in the axial direction, and one end of which can be processed into a shape appropriate for the purpose, such as a bullet shape, a rectangle, or a chisel shape, for practical use.

[0092] Examples of fountain pen tips (pen bodies) include those made by cutting metal plates such as stainless steel plates or gold alloy plates into a tapered shape and then bending or curving them, or those made by molding resin into the shape of a pen tip. The pen bodies may also be provided with a slit in the center or a ball at the tip.

[0093] The ink filling mechanism may be, for example, an ink reservoir or ink occlusion body that can be directly filled with ink for a writing instrument. The ink container may be a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a metal tubular body, and the above-mentioned chip may be directly connected, or the ink container and chip may be connected via a connecting member. The ink occlusion body is a fiber bundle formed by bundling crimped fibers in the longitudinal direction, and is contained within a covering such as a plastic cylinder or film, with the porosity adjusted to a range of approximately 40 to 90%.

[0094] When filling a ballpoint pen with ink for a writing instrument, the structure and shape of the ballpoint pen itself are not particularly limited, and an example is a ballpoint pen that has an ink reservoir filled with shear-thinning ink inside the barrel, the ink reservoir communicating with a ballpoint pen tip having a ball attached to the tip, and further has a liquid plug tightly attached to the end face of the ink to prevent backflow.

[0095] The ink backflow preventive composition is filled into the ink reservoir at the rear end of the ink reservoir. The ink backflow preventive composition comprises a non-volatile liquid and / or a hardly-volatile liquid, examples of which include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, and fatty acid-modified silicone oil. The ink backflow preventive composition may be used alone or in combination of two or more kinds.

[0096] It is preferable to add a thickener to the ink backflow preventive composition to thicken it to a suitable viscosity. Examples of thickeners include clay-based thickeners such as silica with a hydrophobic surface treatment, fine particle silica with a methylated surface, aluminum silicate, swellable mica, hydrophobically treated bentonite or montmorillonite, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate, dextrin-based compounds such as tribenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, fatty acid dextrins, and cellulose-based compounds. Furthermore, the above-mentioned liquid ink backflow preventive composition and a solid ink backflow preventive composition can be used in combination.

[0097] The barrel itself can also be used as the ink filling mechanism, and an example of such a mechanism is a ballpoint pen in which ink is directly filled into the barrel and a ballpoint pen tip is attached to the front end of the barrel.

[0098] A ballpoint pen equipped with a ballpoint pen tip and an ink filling mechanism may further include an ink supply mechanism for supplying the ink filled in the ink filling mechanism to the pen tip.

[0099] The ink supply mechanism is not particularly limited, but examples include: (1) a mechanism that has an ink guide core made of a fiber bundle or the like as an ink flow regulator and supplies ink to the pen tip; (2) a mechanism that has a comb-shaped ink flow regulator and supplies ink to the pen tip through this; and (3) a mechanism that supplies ink to the pen tip via a pen core consisting of multiple disks arranged in parallel with comb-shaped intervals, with slit-shaped ink guide grooves that run vertically through the disks in the axial direction and wider ventilation grooves than the grooves, and an ink guide core that is arranged in the axial center to guide ink from the ink filling mechanism to the pen tip.

[0100] The material for the pen core is not particularly limited as long as it is a synthetic resin that can be injection molded into a structure in which multiple discs are arranged in a comb-like groove pattern. Examples of synthetic resins include general-purpose polycarbonate, polypropylene, polyethylene, and acrylonitrile-butadiene-styrene copolymer (ABS resin). In particular, acrylonitrile-butadiene-styrene copolymer (ABS resin) is preferably used because it has high moldability and is easy to obtain pen core performance.

[0101] When a ballpoint pen is provided with the ink supply mechanism, the ink occlusion body can be used as the ink filling mechanism in addition to the ink reservoir and barrel.

[0102] Specific examples of the configuration of a ballpoint pen that contains writing instrument ink include: (1) a ballpoint pen in which a ballpoint pen tip is connected to an ink container directly or via a connecting member, the writing instrument ink is filled, and a ballpoint pen refill formed by filling the end face of the ink with an ink backflow prevention material is contained in the barrel; (2) a ballpoint pen in which the barrel is directly filled with writing instrument ink and is provided with a mechanism for supplying ink to the pen tip using a comb-shaped ink flow regulator or an ink guide core made of a fiber bundle or the like as an ink flow regulator; (3) a ballpoint pen in which the barrel is directly filled with writing instrument ink and is provided with a mechanism for supplying ink to the pen tip via the above-mentioned pen core; and (4) a ballpoint pen in which the barrel contains an ink occlusion body made of a fiber bundle impregnated with writing instrument ink and is provided with a mechanism for supplying ink to the pen tip using an ink guide core made of a fiber bundle or the like as an ink flow regulator.

[0103] When filling a marking pen with ink for a writing instrument, the structure and shape of the marking pen itself are not particularly limited, and an example is a marking pen that has an ink reservoir filled with cohesive ink inside the barrel, and the ink reservoir is connected to the marking pen tip. The ink occlusion body may be directly connected to the tip, or may be connected to the ink occlusion body and the tip via a connecting member.

[0104] A marking pen equipped with a marking tip and an ink filling mechanism may further include an ink supply mechanism for supplying the ink filled in the ink filling mechanism to the pen tip.

[0105] The ink supply mechanism is not particularly limited, but examples include, in addition to the ink supply mechanism provided in the ballpoint pen described above, (4) a mechanism provided with an ink flow rate regulator using a valve mechanism, which supplies ink to the pen tip by opening the valve. The valve mechanism can be a conventional, general-purpose pumping type that opens when the tip is pressed, and is preferably set to a spring pressure that can be pressed and opened by the pressure of the writing pen.

[0106] When the marking pen is provided with an ink supply mechanism, the ink filling mechanism may be an ink reservoir that can be directly filled with writing instrument ink, in addition to the ink occlusion body described above. Also, the barrel itself may serve as the ink filling mechanism, and the writing instrument ink may be directly filled therein.

[0107] Specific configurations of marking pens that contain writing instrument ink include: (1) a marking pen in which an ink occlusion body made of a fiber bundle impregnated with writing instrument ink is contained in a barrel, and a marking pen tip made of a fiber processed body or a resin molded body with capillary gaps is connected to the barrel directly or via a connecting member so that the ink occlusion body and the tip are connected; (2) a marking pen in which the barrel is filled directly with writing instrument ink and is provided with a mechanism for supplying ink to the pen tip by using a comb-shaped ink flow regulator or an ink guide core made of a fiber bundle or the like as an ink flow regulator; and (3) a marking pen in which the writing instrument ink is directly contained in the barrel. Examples include: (4) a marking pen that is filled with ink and has a mechanism that supplies ink to the pen tip via the pen core; (5) a marking pen that is equipped with a marking pen refill in a barrel, the marking pen tip being made of a fiber processed body or a resin molded body with a capillary gap formed in an ink reservoir that contains an ink reservoir made of a fiber bundle impregnated with writing instrument ink, and the marking pen tip is connected directly or via a connecting member so that the ink reservoir and the tip are connected.

[0108] Furthermore, the ballpoint pen or marking pen may be in the form of a detachable ink cartridge, in which case the ink contained in the ink cartridge of the writing instrument can be replaced with a new cartridge after the ink is used up. Ink cartridges include those that double as the barrel that constitutes the writing instrument when connected to the writing instrument body, and those that cover and protect the barrel (rear barrel) after being connected to the writing instrument body. In the latter case, the ink cartridge may be used alone, or may be one in which the writing instrument body and ink cartridge are connected in the writing instrument before use, or one that is stored in the barrel in a disconnected state so that the user of the writing instrument can connect the ink cartridge in the barrel when using it to start use.

[0109] Furthermore, when a ballpoint pen or marking pen is directly filled with writing instrument ink, it is preferable to incorporate an agitator such as an agitating ball for agitating the ink into the ink reservoir or barrel into which the ink is filled, in order to facilitate redispersion of the microcapsule pigment. Examples of the shape of the agitator include a spherical body and a rod-shaped body. The material of the agitator is not particularly limited, and examples thereof include metal, ceramic, resin, and glass.

[0110] Furthermore, it is preferable that writing instruments such as ballpoint pens or marking pens be provided with a cap that is attached to cover the writing tip (tip tip) or with a retraction mechanism that allows the writing tip to protrude and retract from the writing instrument body (barrel), which can prevent the writing tip from drying out and becoming unable to write, or from becoming contaminated or damaged. A writing instrument with a retractable mechanism can be any writing instrument that has a structure in which the writing tip is stored in a barrel exposed to the outside air and the writing tip protrudes from the barrel opening when the retractable mechanism is activated.For example, a writing instrument with a retractable mechanism (retractable writing instrument) can be made by producing the above-mentioned ballpoint pen refill or marking pen refill, storing the refill in a barrel, and configuring it so that the writing tip protrudes from the barrel opening when the retractable mechanism is activated. Furthermore, when a writing instrument is provided with a retractable mechanism, it can also be a composite type retractable writing instrument (retractable ballpoint pen or retractable marking pen) that contains multiple ballpoint pen refills or marking pen refills in the barrel, and in which the writing tip of one of the refills is caused to retract from the barrel opening by activation of the retractable mechanism.

[0111] Examples of retraction mechanisms include: (1) a side-slide retraction mechanism in which an operating part (clip) that can move back and forth in the radial direction protrudes radially outward from the rear side wall of the barrel, and the writing tip is retracted from the front end opening of the barrel by sliding the operating part forward; (2) a rear-end knock retraction mechanism in which the operating part at the rear end of the barrel is pressed forward to cause the writing tip to retract from the front end opening of the barrel; (3) a side-knock retraction mechanism in which the operating part that protrudes from the outer surface of the barrel side wall is pressed radially inward to cause the writing tip to retract from the front end opening of the barrel; and (4) a rotary retraction mechanism in which the operating part at the rear of the barrel is rotated to cause the writing tip to retract from the front end opening of the barrel.

[0112] Furthermore, the shapes of ballpoint pens and marking pens are not limited to the configurations described above, and they may be equipped with tips of different shapes, or with pen tips that dispense ink of different colors, or they may be composite writing instruments (double-headed, retractable pen tip, etc.) that are equipped with tips of different shapes and dispense ink of different colors from each tip.

[0113] The handwriting obtained by writing on a surface to be written on using a writing instrument containing the above-mentioned ink for a writing instrument can be discolored by rubbing with a finger or by using a heating or cooling tool. Examples of heating tools include an electrically heated discoloring tool equipped with a resistance heating element such as a PTC element, a heat discoloring tool filled with a medium such as hot water, a heat discoloring tool using steam or laser light, and the application of a hair dryer. However, friction members and friction bodies are preferred because they can change color in a simple manner. Examples of cooling devices include electrically operated thermochromic devices using a Peltier element, thermochromic devices filled with a refrigerant such as cold water or ice chips, refrigerants, refrigerators, freezers, and the like.

[0114] As the friction member and friction body, an elastic body such as an elastomer or a plastic foam, which has a high elastic feel and can generate appropriate friction and frictional heat when rubbed, is preferred, but plastic molded bodies, stone, wood, metal, cloth, etc. can also be used. Although a general eraser used for erasing pencil marks may be used to rub the marks, eraser dust will be generated during the rubbing, and therefore the above-mentioned friction member and friction body which hardly generate eraser dust are preferably used. Examples of materials for the friction member and friction body include silicone resin, SEBS resin (styrene-ethylene-butadiene-styrene block copolymer), etc. Silicone resin tends to adhere to areas that have been erased by rubbing, and handwriting tends to be repelled when writing is repeated, so SEBS resin is more preferably used.

[0115] The friction member or friction body may be a separate component of any shape from the writing instrument, but by providing it in the writing instrument, the writing instrument can be made highly portable. Also, a writing instrument set can be obtained by combining a writing instrument with a friction member or friction body of any shape that is separate from the writing instrument.

[0116] In the case of a writing instrument with a cap, the location where the friction member or friction body is provided is not particularly limited. For example, the cap itself may be formed from a friction member, the barrel itself may be formed from a friction member, or if a clip is provided, the clip itself may be formed from a friction member, or the friction member or friction body may be provided at the tip (top) of the cap or the rear end of the barrel (the part where the writing tip is not provided), etc. When the writing implement is a retractable writing implement, the location where the friction member or friction body is provided is not particularly limited. For example, the barrel itself may be formed from a friction member, and if a clip is further provided, the clip itself may be formed from a friction member, or the friction member or friction body may be provided near the barrel opening, the rear end of the barrel (the part where the writing tip is not provided), or the knock portion.

[0117] The ink can also be used as a stamp ink. Water is used as the medium for the ink for stamping, but a water-soluble organic solvent can also be used if necessary. When a microcapsule pigment is used in a stamp ink, glycerin or propylene glycol is preferred among water-soluble organic solvents.

[0118] The water-soluble organic solvent is preferably blended in an amount of 30 to 60% by mass, more preferably 30 to 55% by mass, and even more preferably 40 to 50% by mass, based on the total amount of the ink. By blending the water-soluble organic solvent in the above range, the ink will not dry out or absorb moisture, making it easier to obtain a clear print. If the blending ratio of the water-soluble organic solvent exceeds 60% by mass, the moisture absorption tends to increase, causing the printed image to bleed or become mottled, making it difficult to obtain a clear printed image. On the other hand, if the blending ratio is less than 30% by mass, the printed surface dries out, causing the printed image to fade, making it difficult to obtain a clear printed image.

[0119] Furthermore, an organic solvent can also be used as the medium. Examples of organic solvents include castor oil fatty acid alkyl esters, cellosolve-based solvents, alkylene glycol-based solvents, ester-based solvents, hydrocarbon-based solvents, halogenated hydrocarbon-based solvents, alcohol-based solvents, ether-based solvents, ketone-based solvents, propionic acid-based solvents, highly polar solvents, and mixed solvents thereof.

[0120] Furthermore, the ink for stamping may contain a thickener, of which alkali-soluble acrylic emulsion is preferred. When an alkali-soluble acrylic emulsion is used as the thickener, the pH of the ink is preferably 6-11, more preferably 7-11, and even more preferably 7-10.

[0121] Furthermore, by adding a binder resin to the ink for stamping, it is possible to improve the adhesion of the printed image and adjust the viscosity of the ink. Examples of the binder resin include a resin emulsion, an alkali-soluble resin, and a water-soluble resin.

[0122] In addition, additives such as wetting agents, resins, resin particles, pH adjusters, rust inhibitors, surfactants, wetting agents, antifoaming agents, viscosity adjusters, preservatives, and antifungal agents can also be added as needed.

[0123] The reversible thermochromic microencapsulated pigment is preferably blended in the stamp ink in an amount of 10 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 10 to 30% by mass, based on the total amount of the ink. If the blending ratio of the microencapsulated pigment exceeds 40% by mass, the dispersion stability of the microencapsulated pigment in the ink tends to decrease. On the other hand, if the blending ratio is less than 10% by mass, the color density tends to decrease.

[0124] The above-mentioned ink for stamps can be used as ink for stamp pads and ink for stamps provided with a stamp material having continuous pores. For example, a stamp pad can be impregnated with ink to obtain a stamp pad that supplies ink to the printing surface of a stamp that comes into contact with it.Also, a stamp can be obtained by impregnating ink into a stamp material having continuous pores.

[0125] The stamp can form an image on various surfaces. Furthermore, the image formed by the stamp ink can be discolored by rubbing it with a finger or by applying the heating or cooling tool described above. The friction member and friction body described above are preferred as heating tools because they can be discolored in a simple manner.

[0126] The friction member or friction body may be a separate member of any shape from the stamp, but by providing it on the stamp, it can be made highly portable. Also, a stamp set can be obtained by combining a stamp with a separate friction member or friction body of any shape.

[0127] When applying or printing the reversible thermochromic liquid composition, the material of the support is not particularly limited and all materials are effective, such as paper, synthetic paper, fiber, fabric, synthetic leather, leather, plastic, glass, ceramic material, metal, wood, stone, etc. The shape of the support is not limited to a flat surface, but may be uneven. A reversible thermochromic laminate (reversible thermochromic printed matter) can be obtained by providing a reversible thermochromic layer containing a reversible thermochromic colorant on a support. In the case where a non-thermochromic colored layer (non-thermochromic image) is pre-formed on the support, the colored layer or image can be made to disappear or appear by the reversible thermochromic layer due to a change in temperature, further diversifying the manner of change.

[0128] Furthermore, the reversibly thermochromic colorant can be melt-blended with an excipient and molded to form a reversibly thermochromic solid molded article for application, which can be used as a solid writing material or a solid cosmetic. Examples of solid writing materials include crayons, pencil leads, mechanical pencil leads, solid gel markers, and the like. Examples of solid cosmetics include foundation, eyeliner, eyebrow pencil, eyeshadow, lipstick, etc.

[0129] Examples of excipients used in solid writing materials include waxes, gelling agents, clay minerals, and the like.

[0130] Among the excipients, it is preferable to contain at least one of polyolefin wax, sucrose fatty acid ester, and dextrin fatty acid ester, as these are likely to improve the density of the writing.

[0131] In order to provide a solid writing material with excellent mechanical strength and thermal discoloration properties, and to facilitate handling during production, the excipient preferably has a mass average molecular weight (Mw) of 2,000 to 50,000, more preferably 10,000 to 30,000, and more preferably a number average molecular weight (Mn) of 1,000 to 10,000. The mass average molecular weight and number average molecular weight are values ​​measured by gel permeation chromatography (GPC) using polystyrene as a standard.

[0132] The excipient is preferably blended in an amount of 0.2 to 70% by mass, more preferably 0.5 to 40% by mass, based on the total amount of the solid writing material. When the blending ratio of the excipient is within the above range, the shape of the solid writing material can be easily obtained, and the writing density of the solid writing material can easily be increased. If the blending ratio of the excipient exceeds 70% by mass, it becomes difficult to obtain a sufficient writing density, whereas if the blending ratio is less than 0.2% by mass, it becomes difficult to obtain a shape suitable for a writable core material.

[0133] Furthermore, by blending a filler into the solid writing material, it is possible to improve the strength of the solid writing material and adjust the writing feel. Among the above fillers, talc or calcium carbonate is preferred because it has excellent moldability and is less likely to impair thermochromic properties when a microcapsule pigment is used.

[0134] The filler is preferably blended in the range of 10 to 65% by mass based on the total amount of the solid writing material. If the blending ratio of the filler exceeds 65% by mass, the color development and writing feel tend to deteriorate. On the other hand, if the blending ratio is less than 10% by mass, the strength of the solid writing material tends to deteriorate.

[0135] Furthermore, by blending a binder resin into the solid writing material, the strength of the solid writing material can be improved. Among the binder resins, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol are preferred, and molding stability can be improved by using these resins in combination with polyester polyol. The binder resin is preferably blended in the range of 0.5 to 5% by mass based on the total amount of the solid writing material.

[0136] Furthermore, by incorporating a hindered amine compound into the solid writing material, it is possible to make afterimages of erased writing on the writing surface less visible, thereby ensuring rewritability without impairing the appearance of the writing surface and improving marketability.

[0137] In addition, additives such as viscosity adjusters, antifungals, preservatives, antibacterial agents, UV inhibitors, antioxidants, lubricants, and fragrances may also be added as needed.

[0138] The solid writing material may be used alone as a writing material, or may be used as an inner core with an outer shell covering the outer periphery to form a core-sheath structure (double core).

[0139] The shell may contain additives such as non-thermochromic colorants, antifungal agents, preservatives, antibacterial agents, ultraviolet absorbers, antioxidants, lubricants, and fragrances, if necessary.

[0140] The solid writing material can be used to write on various writing surfaces, and furthermore, since it uses a reversible thermochromic colorant, the handwriting written on the writing surface can be discolored by rubbing with a finger or by applying the above-mentioned heating or cooling tool. As the heating tool, the above-mentioned friction member and friction body are preferred because they can be discolored by a simple method.

[0141] The friction member or friction body may be a component of any shape that is separate from the solid writing body or the exterior of a solid writing implement in which the solid writing body is housed in an exterior container, but by providing it on the solid writing body or the exterior of a solid writing implement in which the solid writing body is housed in an exterior container, it can be made highly portable.Specific examples include a form in which the friction member is provided on an exterior in the shape of a pencil, crayon, or the like, made of wood or paper.Furthermore, a solid writing body set can be obtained by combining the solid writing body with a friction member or friction body of any shape that is separate from the solid writing body.

[0142] Furthermore, the reversible thermochromic colorant can be melt-blended with a thermoplastic resin, a thermosetting resin, wax, or the like to form pellets, powder, or paste, and used as a reversible thermochromic molding resin composition. The above-mentioned reversible thermochromic molding resin composition can be subjected to general-purpose injection molding, extrusion molding, blow molding, cast molding or the like to obtain molded articles in the form of three-dimensional objects of any shape, films, sheets, plates, filaments, rods, pipes and the like. Furthermore, by melt-blending it with a thermoplastic resin, toner and powder coatings can be obtained.

[0143] In addition, by blending a non-thermochromic colorant such as a general dye or pigment into the above-mentioned reversibly thermochromic liquid composition, solid molding for coating, or resin composition for molding, the color change behavior from color (1) to color (2) is exhibited.

[0144] On the above-mentioned molded body or laminate, a layer containing a light stabilizer and / or a transparent metallic luster pigment can be laminated to improve light resistance, or a top coat layer can be provided to improve durability. Examples of light stabilizers include ultraviolet absorbers, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, and ozone quenchers. Examples of transparent metallic luster pigments include pigments having a core material such as natural mica, synthetic mica, glass flakes, alumina, or transparent film flakes whose surface is coated with a metal oxide such as titanium oxide.

[0145] Specific examples of products using the reversible thermochromic composition and the microcapsule pigment or resin particles containing the same include the following. (1)Toys Dolls and animal-shaped toys, hair for dolls and animal-shaped toys, doll houses and furniture, clothes, doll accessories such as hats, bags, shoes, accessory toys, stuffed toys, drawing toys, toy picture books, puzzle toys such as jigsaw puzzles, building block toys, block toys, clay toys, fluid toys, tops, kites, musical instrument toys, cooking toys, gun toys, catching toys, background toys, toys imitating vehicles, animals, plants, buildings, food, etc. (2) Clothing Clothing such as T-shirts, sweatshirts, blouses, dresses, swimwear, raincoats, skiwear, footwear such as shoes and shoelaces, cloth accessories such as handkerchiefs, towels, wrapping cloths, gloves, ties, hats, scarves, mufflers, etc. (3) Indoor decorations Curtains, curtain strings, tablecloths, rugs, cushions, carpets, rugs, upholstery, seats, mats, picture frames, artificial flowers, photo frames, etc. (4) Furniture Bedding such as futons, pillows, mattresses, lighting fixtures, heating and cooling appliances, etc. (5) Ornaments Rings, bracelets, tiaras, earrings, hair clips, false nails, ribbons, scarves, watches, glasses, etc. (6) Stationery Writing implements, stamps, erasers, writing pads, rulers, notebooks, adhesive tape, etc. (7)Daily necessities Lipstick, eye shadow, foundation, eyeliner, eyebrow pencil, nail polish, hair dye, false nails, false nail paint, and other cosmetics, toothbrushes, etc. (8) Kitchen utensils Cups, plates, chopsticks, spoons, forks, pots, frying pans, etc. (9) Other Calendars, labels, cards, recording materials, various types of printed materials for preventing counterfeiting, picture books and other books, bags, packaging containers, embroidery thread, sports equipment, fishing tackle, coasters, musical instruments, hand warmers, ice packs, wallets and other bags, umbrellas, vehicles, buildings, temperature detection indicators, training tools, etc. [Example]

[0146] Examples are shown below. Unless otherwise specified, "parts" and "%" in the examples represent "parts by mass" and "% by mass", respectively.

[0147] <Example 101> Preparation of reversible thermochromic microencapsulated pigments As component (a), 6.5 parts of 2-(3-trifluoromethylanilino)-6-di-n-pentylaminofluoran (A-1), as component (b), 4 parts of 4,4'-[1-{4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene]bisphenol (I-1) and 6 parts of 1,1-bis(4-hydroxyphenyl)-2-ethylhexane (IIa-1) as component (c), and 25 parts of behenyl alcohol (C-1) and 25 parts of stearyl stearate (C-2) as component (c) were mixed and dissolved by heating to obtain a reversible thermochromic composition that changes color reversibly. This reversible thermochromic composition was added to a mixed solution consisting of 35 parts of an aromatic isocyanate prepolymer as a wall material and 40 parts of a cosolvent, and then emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution. After stirring while heating, 2.5 parts of a water-soluble aliphatic modified amine was added and stirring was continued to prepare a microcapsule dispersion. From the above microcapsule dispersion, a microcapsule pigment with an average particle size of 2.0 μm was obtained by centrifugation.

[0148] <Examples 102 to 106, 201 to 209 and Comparative Examples 101, 102, 201 to 209> A microcapsule pigment was obtained in the same manner as in Example 101, except that the types and amounts of components (a), (b), and (c) were changed to those shown in Table 1 or Table 2. The color tone of the obtained microcapsule pigment in the colored state is as shown in Tables 1 and 2, and the colored state changed to the decolored state. The values ​​for components (a), (b), and (c) in the table indicate "parts by mass," and the values ​​for the concentration retention rates indicate "%." [Table 1] [Table 2] Components (a), (b), and (c) in the table are the compounds shown below. A-1 2-(3-trifluoromethylanilino)-6-di-n-pentylaminofluoran A-2 6-(N-ethyl-N-isopentylamino)-1,2-benzofluoran A-3 2-Di-n-butylamino-8-di-n-pentylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidin-5,1'(3'H)-isobenzofuran]-3'-one A-4 1,3-dimethyl-6-diethylaminofluoran A-5 2-N-methylanilino-6-(N-ethyl-Np-tolylamino)fluoran A-6 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide A-7 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide A-8 3,6-bis(diphenylamino)fluoran A-9 3-(2-acetamido-4-diethylaminophenyl)-3-(1-propyl-2-methylindol-3-yl)-4-azaphthalide I-1 4,4'-[1-{4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene]bisphenol I-2 4,4',4"-Ethylidinetrisphenol I-3 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane I-4 4,4'-[4-(4-hydroxyphenyl)-sec-butylidene]bis(2-methylphenol) IIa-1 1,1-bis(4-hydroxyphenyl)-2-ethylhexane IIa-2 2,2-bis(4-hydroxyphenyl)propane IIa-3 1,1-bis(4-hydroxyphenyl)-2-methylpropane IIa-4 2,2-bis(4-hydroxyphenyl)hexafluoropropane IIb-1 2,4-Dihydroxy-4′-tert-butylbenzophenone C-1 Behenyl Alcohol C-2 Stearyl stearate C-3 4-benzyloxyphenylethyl caprate C-4 4-biphenylacetic acid cyclohexylmethyl

[0149] [Discoloration temperature measurement] Reversible thermochromic inks were prepared by mixing 40 parts of each microencapsulated pigment obtained in Examples 101-106, 201-209, and Comparative Examples 101, 102, and 201-209 with 52 parts of an ethylene-vinyl acetate copolymer resin emulsion, 5 parts of a thickener, and 3 parts of a leveling agent. A solid pattern was screen-printed on high-quality paper using the ink to obtain a sample for measuring the color change temperature. Each sample for measuring the color change temperature was placed in the measurement area of ​​a color-difference meter (Tokyo Denshoku Co., Ltd., product name: TC-3600). The sample area was heated and cooled at a rate of 2°C / min. The lightness value was measured as the color density at each temperature, and a color density-temperature curve was created. From the color density-temperature curve, the complete color development temperature t1, the color development start temperature t2, the color fade start temperature t3, the complete fade temperature t4, and ΔH (hysteresis width: (intermediate temperature between t3 and t4) - (intermediate temperature between t1 and t2)) were calculated. The results are shown in Tables 3 and 4 below. The values ​​in the table indicate "°C."

[0150] [Table 3]

[0151] [Table 4]

[0152] [Concentration measurement] Reversible thermochromic inks were prepared by mixing 40 parts of each of the microcapsule pigments obtained in Examples 101 to 106, 201 to 209 and Comparative Examples 101, 102, and 201 to 209, 52 parts of an ethylene-vinyl acetate copolymer resin emulsion, 5 parts of a thickener, and 3 parts of a leveling agent. A solid pattern was screen-printed on high-quality paper using the ink to obtain a sample for density measurement. The density measurement samples of Examples 101 to 106, 201 to 209 and Comparative Examples 101, 102, 201 to 209, which had been cooled to below t1 and brought to a fully colored state, were set in the measurement section of a fluorescent spectrodensitometer (manufactured by Konica Minolta, Inc., product name: FD-7 type), and the absolute density of the colored state (hereinafter referred to as "color density") was measured. Furthermore, the density measurement samples of Examples 101-106, 201-209 and Comparative Examples 101, 102, 201-209, which were heated to t4 or higher and completely bleached, were set in the measurement section of the above-mentioned spectrofluorimeter, and the absolute density of the bleached state (hereinafter referred to as "bleached density") was measured. The results obtained are shown in Tables 1 and 2.

[0153] [Lightfastness evaluation] A reversible thermochromic ink was prepared by mixing 40 parts of each of the microcapsule pigments of Examples 101 to 106, 201 to 209 and Comparative Examples 101, 102, and 201 to 209, 52 parts of an ethylene-vinyl acetate copolymer resin emulsion, 5 parts of a thickener, and 3 parts of a leveling agent. A solid pattern was screen-printed on high-quality paper using the ink to obtain a measurement sample. Each of the above measurement samples was cooled to below t1 to allow it to fully develop color, and then it was set in the measurement section of a fluorescence spectrodensitometer (manufactured by Konica Minolta, Inc., product name: FD-7 type) and the absolute density of the fully developed color (hereinafter referred to as "initial density") was measured. Next, each measurement sample whose concentration was measured was subjected to a xenon light resistance test at 170 w / m using a xenon light resistance tester (manufactured by Suga Test Instruments Co., Ltd., product name: Table Sun XT75) in a temperature environment not exceeding t3. 2 The plants were continuously irradiated with light at an irradiance of 1000 kJ / cm for 10 hours. After the light irradiation, each measurement sample was removed and cooled to below t1 to allow the sample to fully develop color. Then, each measurement sample was set in the measurement section of the above-mentioned fluorescence spectrodensitometer, and the absolute density in the fully developed state after the light irradiation (hereinafter referred to as "density after the light irradiation") was measured. The density retention rate [(density value after light irradiation) / (initial density value) × 100] was calculated from the initial density value and the density value after light irradiation. Note that a larger density retention rate indicates better light resistance. The results are shown in Tables 1 and 2.

[0154] Application example 1 Preparation of a reversible thermochromic writing implement (reversible thermochromic ballpoint pen) A reversible thermochromic liquid composition for a writing instrument ink was prepared by mixing 25 parts of the microcapsule pigment of Example 102 (previously cooled to -20°C or below to develop a black color), 0.3 parts of a shear thinning agent (xanthan gum), 10 parts of urea, 10 parts of glycerin, 0.5 parts of a nonionic penetrant (manufactured by San Nopco Ltd., product name: Nopco SW-WET-366), 0.1 parts of a modified silicone antifoaming agent (manufactured by San Nopco Ltd., product name: Nopco 8034), 0.5 parts of a phosphate ester surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Plysurf AL), 0.5 parts of a pH adjuster (triethanolamine), 0.2 parts of an antifungal agent (manufactured by Lonza Japan Co., Ltd., product name: Proxel XL-2), and 52.9 parts of water. The above-mentioned writing instrument ink was sucked and filled into an ink reservoir tube made of polypropylene pipe, and then connected to a ballpoint pen tip having a 0.5 mm diameter carbide ball at its tip via a resin holder. Next, a viscoelastic ink backflow preventive material (liquid stopper) mainly composed of polybutene was filled into the rear end of the ink reservoir tube to prepare a ballpoint pen refill. The above-mentioned refill was incorporated into the barrel to obtain a ballpoint pen (retractable ballpoint pen). The ballpoint pen has a tip attached to a ballpoint pen refill housed in a barrel exposed to the outside air, and the tip protrudes from the front opening of the barrel by operating a clip-shaped slide mechanism attached to the rear side wall of the barrel. SEBS resin is attached to the rear end of the barrel as a friction member. When the above ballpoint pen was used to write on a piece of paper to form black letters (handwriting), the handwriting was black at room temperature (25°C), and when the letters were rubbed with a friction member, the letters disappeared and became colorless, and this state could be maintained unless the paper was cooled to below -20°C. Furthermore, when the paper was placed in a freezer and cooled to below -20°C, the letters again turned black, and this color change behavior could be reproduced repeatedly.

[0155] Application example 2 Preparation of reversible thermochromic recording material (information display card) A reversible thermochromic liquid composition for printing ink was prepared by uniformly mixing 40 parts of the microcapsule pigment of Example 105 (previously cooled to -20°C or below to develop a black color) into an aqueous vehicle consisting of 50 parts of a urethane resin emulsion, 3 parts of a leveling agent, and 1 part of a thickener. A transparent anchor coat layer consisting of a urethane resin and an isocyanate-based curing agent was applied to the surface of a transparent polyester film (25 μm thick) with an adhesive layer on the backside as a support. The above-mentioned printing ink was solid-printed on top of this using a screen stencil, dried, and cured to form a reversible thermochromic layer. A transparent protective layer containing an epoxy acrylate oligomer, a polyester acrylate oligomer, and an acrylate monomer was then applied to the top layer, and polymerized by ultraviolet light to produce a reversible thermochromic recording material. The above-mentioned recording material was then attached to a white polyester film (188 μm thick) as a substrate and used in practical applications as an information display card. The reversible thermochromic recording material was once cooled to -20°C or below to allow the reversible thermochromic layer to completely develop a black color, after which character information was printed using a thermal printer equipped with a thermal head. The above recording material displayed clear white character information (cut-out characters) on a black background, and the white character information was visible as long as it was maintained at a temperature above -20°C and below 58°C. Furthermore, when the above recording material was cooled to below -20°C to completely change the reversible thermochromic layer to black, the white cut-out characters were no longer visible. From this state, white cut-out characters could be formed on the reversible thermochromic layer again using a thermal printer, and the above recording material could be reused many times.

[0156] Application example 3 Preparation of reversible thermochromic printed matter A reversible thermochromic liquid composition for offset printing ink was prepared by mixing 30 parts of the microcapsule pigment of Example 106 (previously cooled to -20°C or below to develop a black color), 5 parts of a red dye, and 65 parts of a linseed oil-based offset ink vehicle. The above offset printing ink was used to offset print both the front and back of high-quality paper as the printing medium, and the ink was dried and cured to form a date (thermochromic image). The thermochromic images on the front and back were formed so as not to overlap. Next, a non-color-changing black offset printing ink was used to offset print the paper, and the ink was dried and cured to form a border (non-color-changing image), producing a reversible thermochromic print. The reversible thermochromic printed matter described above is initially a notebook-style printed matter with black dates printed on it, but by rubbing the thermochromic image at any point on the surface with a friction member, the color can be changed to red by the frictional heat generated, and the changed color can be maintained at room temperature (25°C), making it useful for managing holiday schedules. Furthermore, the dates printed on the back of the changed areas do not change color due to the heat transferred when the thermochromic image on the surface is changed, allowing for accurate schedule management.

[0157] Application example 4 Fabrication of a doll toy with hair using reversible thermochromic composite fiber Five parts of the microcapsule pigment of Example 201, one part of a dispersant, 94 parts of nylon 12 with a melting point of 180°C, and 0.1 parts of a blue general pigment were melt-mixed in an extruder at 200°C to prepare a reversible thermochromic molding resin composition in pellet form for the core. The above pellets were fed into an extruder for forming the core, and nylon 12 natural pellets were fed into an extruder for forming the sheath. Using a composite fiber spinning device, the fibers were spun at 200°C through 18 nozzles so that the core:sheath volume ratio was 6:4, to prepare a reversible thermochromic composite fiber consisting of 18 single filaments with an outer diameter of 90 μm. The reversible thermochromic composite fiber was once cooled to below -20°C to allow the microencapsulated pigment to completely develop its color, and the reversible thermochromic composite fiber exhibited a purple color, a mixture of the red from the microencapsulated pigment and the blue from the general pigment. The reversible thermochromic composite fiber was implanted onto the head of a doll in the usual manner, and a doll toy with hair made of the reversible thermochromic composite fiber was produced. The hair of the toy doll did not change color at body temperature or the ambient temperature, but when heated above 59°C, it changed from purple to blue. When cooled below -20°C, it changed back to purple. This change was repeatable. Furthermore, by heating a portion of the hair with a hair dryer or other device, the color of the hair could be changed as desired by forming a pattern in which only the desired portion was decolorized. Furthermore, the discolored state could be maintained at room temperature (25°C), and after heating the entire hair to above 59°C to decolorize it, it was possible to cool it to below -20°C and return it to purple color.

[0158] Application example 5 Fabrication of a reversible thermochromic writing implement (reversible thermochromic marking pen) 20 parts of the microcapsule pigment of Example 202 (previously cooled to -20°C or below to develop a pink color) was mixed with a polymer flocculant (hydroxyethyl cellulose) [manufactured by Dow Chemical Japan, product name: CELLOSIZE A reversible thermochromic liquid composition for a writing instrument ink was prepared by mixing 0.4 parts of a cellulose acetate copolymer (EP-09), 0.4 parts of an acrylic polymer dispersant (manufactured by Lubrizol Japan Corp., product name: Solsperse 43000), 0.2 parts of a preservative (sodium 2-pyridinethiol 1-oxide) (manufactured by Lonza Japan Co., Ltd., product name: Sodium Omadine), 0.2 parts of a preservative (3-iodo-2-propynyl N-butylcarbamate) (manufactured by Lonza Japan Co., Ltd., product name: Glykasil 2000), 18 parts of glycerin, 0.2 parts of an antifoaming agent, 1 part of a pH adjuster (10% diluted phosphoric acid solution), 8 parts of a specific gravity adjuster (sodium polytungstate) (manufactured by Sometsu Co., Ltd., product name: SPT), and 46.6 parts of water in an aqueous vehicle. The ink reservoir, made of polyester sliver covered with a synthetic resin film, was impregnated with the above-mentioned writing instrument ink and housed in a barrel made of polypropylene resin. A resin-processed pen body (bullet-shaped) made of an extrusion-molded polyacetal resin with multiple ink outlet holes extending in the axial direction was attached to the tip of the barrel via a holder, and a cap was attached to produce a marking pen. SEBS resin was attached to the top of the cap as a friction member. When the marking pen was used to write on a piece of paper to form pink letters (handwriting), the handwriting was pink at room temperature (25°C), and when the letters were rubbed with a friction member, the letters disappeared and became colorless, and this state could be maintained unless the paper was cooled to below -20°C. Furthermore, when the paper was placed in a freezer and cooled to below -20°C, the letters again showed a color change behavior, turning pink, and this color change behavior could be reproduced repeatedly.

[0159] Application example 6 Fabrication of a reversible thermochromic writing implement (reversible thermochromic marking pen) 23 parts of the microcapsule pigment of Example 203 (previously cooled to -20°C or below to develop an orange color) was mixed with a polymer flocculant (hydroxyethyl cellulose) [manufactured by Dow Chemical Japan, product name: CELLOSIZE A reversible thermochromic liquid composition for a writing instrument ink was prepared by mixing 0.4 parts of an acrylic polymer dispersant (manufactured by Lubrizol Japan Corp., product name: Solsperse 43000), 0.4 parts of a preservative (sodium 2-pyridinethiol 1-oxide) (manufactured by Lonza Japan Co., Ltd., product name: Sodium Omadine), 0.2 parts of a preservative (sodium 2-iodo-2-propynyl N-butylcarbamate) (manufactured by Lonza Japan Co., Ltd., product name: Glykasil 2000), 30 parts of glycerin, 0.01 parts of an antifoaming agent, 0.03 parts of a pH adjuster (10% diluted phosphoric acid solution), and 45.76 parts of water in an aqueous vehicle. The ink reservoir, made of polyester sliver covered with a synthetic resin film, was impregnated with the above-mentioned writing instrument ink and housed in a barrel made of polypropylene resin. A resin-processed pen body (chisel type) made of polyester fiber was attached to the tip of the barrel via a resin holder, and a cap was attached to produce a marking pen. SEBS resin was attached to the rear end of the barrel as a friction member. When the marking pen was used to write on a piece of paper to form orange letters (handwriting), the handwriting was orange at room temperature (25°C), and when the letters were rubbed with a friction member, the letters disappeared and became colorless, and this state could be maintained unless the paper was cooled to below -20°C. Furthermore, when the paper was placed in a freezer and cooled to below -20°C, the letters again showed a discoloration behavior, turning orange, and this discoloration behavior could be reproduced repeatedly.

[0160] Application example 7 Preparation of a reversible thermochromic solid writing implement A mixture for the inner core was prepared by kneading 40 parts of the microcapsule pigment of Example 204, 35 parts of filler (talc), 10 parts of a diluent (side-chain crystalline polyolefin) [Toyokuni Oil Mills, product name: HS Crystal 4100], 10 parts of a diluent (polyolefin wax) [Sanyo Chemical Industries, Ltd., product name: SANWAX 131-P (softening point 110 ° C, penetration 3.5)], 2 parts of a styrene-acrylic acid copolymer, 2 parts of polyvinyl alcohol, and 1 part of a hindered amine light stabilizer in a kneader. Next, 69 parts of filler (talc), 10 parts of a sucrose fatty acid ester, 10 parts of the diluent (polyolefin wax), and 10 parts of an ethylene-vinyl acetate copolymer were kneaded in a kneader to prepare a mixture for the outer shell. The above-mentioned kneaded material for the inner core was wrapped around the outer surface of the kneaded material for the outer shell so that it would become the inner core, and compression-molded using a press to form a solid writing material with a core-sheath structure into an outer diameter of φ3 mm and a length of 60 mm (the inner core was φ2 mm and the outer shell thickness was 0.5 mm). Note that the above dimensions are set values, and the solid writing material was manufactured by cooling to -20°C after compression molding and returning to room temperature. The solid writing body was molded into a round outer shaft (wooden shaft) to obtain a pencil. Furthermore, a cylindrical friction body made of SEBS resin was fixed to the rear end of the pencil via a metal connecting member to produce a solid writing implement with a friction body (a pencil with a friction body). When the solid writing implement was used to write on paper to form green letters (handwriting), the handwriting was green at room temperature (25°C). When the letters were rubbed with the friction member, the letters faded and became colorless. This state could be maintained unless the paper was cooled to -20°C or below. Furthermore, when the paper was placed in a freezer and cooled to -20°C or below, the letters again turned green, a color change that could be repeatedly reproduced.

[0161] Application example 8 Preparation of a reversible thermochromic writing implement (reversible thermochromic ballpoint pen) A reversible thermochromic liquid composition for a writing instrument ink was prepared by mixing 25 parts of the microcapsule pigment of Example 206 (previously cooled to -20°C or below to develop a blue color), 0.3 parts of a shear thinning agent (xanthan gum), 10 parts of urea, 10 parts of glycerin, 0.5 parts of a nonionic penetrant (manufactured by San Nopco Ltd., product name: Nopco SW-WET-366), 0.1 parts of a modified silicone antifoaming agent (manufactured by San Nopco Ltd., product name: Nopco 8034), 0.5 parts of a phosphate ester surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Plysurf AL), 0.5 parts of a pH adjuster (triethanolamine), 0.2 parts of an antifungal agent (manufactured by Lonza Japan Co., Ltd., product name: Proxel XL-2), and 52.9 parts of water. The above-mentioned writing instrument ink was sucked and filled into an ink reservoir tube made of polypropylene pipe, and then connected to a ballpoint pen tip with a 0.5 mm diameter stainless steel ball at its tip via a resin holder. Next, a viscoelastic ink backflow preventer (liquid stopper) mainly composed of polybutene was filled into the rear end of the ink reservoir tube, and a tail plug was fitted to the rear of the pipe. The front and rear barrels were assembled, and a cap was attached. After that, the ballpoint pen was degassed by centrifugation, and a ballpoint pen was produced. An SEBS resin was attached to the rear end of the rear barrel as a friction member. When the above ballpoint pen was used to write on paper to form blue letters (handwriting), the handwriting was blue at room temperature (25°C), and when the letters were rubbed with a friction member, the letters disappeared and became colorless, and this state could be maintained unless the paper was cooled to below -20°C. Furthermore, when the paper was placed in a freezer and cooled to below -20°C, the letters again turned blue, and this color change behavior could be reproduced repeatedly.

[0162] Application example 9 Fabrication of reversible thermochromic stamps A reversible thermochromic liquid composition serving as a stamp ink was prepared by mixing 20 parts of the microcapsule pigment of Example 207 (previously cooled to -20°C or below to develop a blue color), 50 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (manufactured by Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 16.7 parts of water. The stamp ink was impregnated into a stamp material with continuous pores, and the stamp material was attached to a stamp base material so that the printing surface of the stamp material was exposed. A cap was then fitted to produce a stamp. The rear end of the stamp base material was fitted with SEBS resin as a friction member. When the above stamp was repeatedly pressed against the surface to be stamped (paper), the ink smoothly flowed out of the printing surface of the stamping material and transferred to the surface to be stamped, allowing for the continuous formation of clear prints without bleeding. The print was blue at room temperature (25°C), and when rubbed with a friction member, the print faded to a colorless state, a state that could be maintained unless cooled to -20°C or below. Furthermore, when the paper surface was placed in a freezer and cooled to -20°C or below, the print again turned blue, and this color change behavior could be reproduced repeatedly.

[0163] Application example 10 Preparation of reversible thermochromic printed material (reversible thermochromic T-shirt) 30 parts of the microcapsule pigment of Example 208 (previously cooled to -20°C or below to develop a red color) was uniformly mixed into an aqueous vehicle consisting of 60 parts of an acrylic emulsion (solid content 45%), 0.2 parts of an antifoaming agent, 1 part of a viscosity modifier, and 8.8 parts of water to prepare a reversible thermochromic liquid composition that is a printing ink. The above printing ink was printed onto a white T-shirt (made of cotton) as a support, using a 100-mesh screen to create a pattern of numerous hearts. The ink was then dried and hardened to form a reversible thermochromic layer, producing a reversible thermochromic printed material (reversible thermochromic T-shirt). At room temperature (25°C), numerous red heart patterns were visible on the surface of the T-shirt, and this did not change at body temperature or ambient temperature. However, when heated to above 58°C, the area where the heart patterns were printed became colorless and the red hearts were no longer visible. Furthermore, when cooled to below -20°C, the red hearts were visible again. This change could be repeated. Furthermore, by heating the T-shirt with an iron or other device, a portion of the heart pattern on the surface could be decolorized, forming a pattern in which only the desired heart pattern was decolorized, allowing the T-shirt pattern to be freely changed. This discolored state could be maintained at room temperature (25°C), and the entire T-shirt could be heated to above 58°C to completely decolorize the heart pattern, and then cooled to below -20°C to restore the color of the heart pattern.

[0164] Application example 11 Fabrication of reversible thermochromic plugs 2.5 parts of the microcapsule pigment of Example 209 (previously cooled to -20°C or below to develop a blue-green color) and 1.5 parts of an orange general pigment were stirred and mixed into an oil vehicle consisting of 12.5 parts of vinyl chloride-vinyl acetate copolymer, 38.3 parts of xylene, 45 parts of butyl acetate, and 0.2 parts of viscosity modifier to prepare a reversible thermochromic liquid composition, which is a paint used for spray painting. The above paint was spray-painted onto the plug portion (white) of a household electric cord as a support, and dried to provide a reversible thermochromic layer, thereby producing a reversible thermochromic plug. The reversible thermochromic plug is brown at room temperature (25°C), and once it turns orange at temperatures above 59°C, it will maintain that orange discoloration unless it is cooled to below -20°C. Therefore, it was possible to visually confirm the temperature history of the plug when it overheats and reaches a high temperature range of 59°C or higher. [Explanation of symbols]

[0165] t1 full color temperature t2 color development start temperature t3 decolorization start temperature t4 complete color erasure temperature T1 complete decolorization temperature T2 decolorization start temperature T3 color development temperature T4 full color temperature ΔH Hysteresis width

Claims

1. (a) an electron-donating color-forming organic compound; (b) a combination of a compound represented by formula (I) and a compound represented by formula (IIa) or (IIb) as an electron accepting compound; (c) a reaction medium that causes a reversible electron transfer reaction between the components (a) and (b) in a specific temperature range; and A reversible thermochromic composition comprising: 【Chemistry 1】 (In the formula, R １１ is a hydrogen atom or a methyl group, L is a single bond or an ethylene group; n12 and n13 are each 0; n14 is 0 or 1, When n14 is 1, R 14 is a methyl group, an ethyl group, a methoxy group, an ethoxy group, a hydroxyphenyl-substituted propyl group, or a hydroxy group; The hydroxy group is located at the 4-position of each benzene ring. 【Chemistry 2】 (In the formula, R ａ１ and R ａ２ one of which is a branched alkyl group having 5 to 9 carbon atoms, and the other is a hydrogen atom or a methyl group, na3 and na4 are each 0, The hydroxy group is located at the 4-position of each benzene ring. 【Transformation 3】 (In the formula, Rb1 is a linear or branched alkyl group having 3 to 6 carbon atoms, R b2 is a hydroxy group; nb1 is 1, nb2 is 1, The hydroxy groups are located at the 2nd and 4th positions of one of the benzene rings.

2. The composition according to claim 1, comprising, as component (b), a combination of a compound represented by formula (I) and a compound represented by formula (IIa).

3. In formula (I), L is a single bond and R １４ The composition of claim 1 or 2, wherein is a hydroxyphenyl-substituted propyl group or a hydroxy group.

4. The composition described in claim 2 or 3, wherein the mass ratio of the compound represented by formula (I): the compound represented by formula (IIa) is 1:0.5 to 1:

5.

5. A reversible thermochromic microcapsule pigment encapsulating the composition according to any one of claims 1 to 4.

6. A reversible thermochromic liquid composition comprising the reversible thermochromic microcapsule pigment according to claim 5 and a vehicle.

7. 7. The reversible thermochromic liquid composition according to claim 6, which is selected from the group consisting of printing ink, writing ink, applicator ink, stamp ink, inkjet ink, paint, ultraviolet-curable ink, coloring material, cosmetics, and textile coloring liquid.

8. A solid writing material or solid cosmetic comprising the reversible thermochromic microcapsule pigment according to claim 5 and an excipient.

9. A reversible thermochromic molding resin composition comprising the reversible thermochromic microcapsule pigment according to claim 5 and a molding resin.

10. A reversibly thermochromic molded article obtained by molding the reversibly thermochromic molding resin composition according to claim 9.

11. A reversible thermochromic laminate comprising a support and a reversible thermochromic layer comprising the reversible thermochromic microencapsulated pigment according to claim 5.

12. A writing implement containing the reversible thermochromic liquid composition according to claim 6.

13. A refill containing the reversible thermochromic liquid composition described in claim 6.

14. A writing instrument having the refill described in claim 13 housed within a barrel.

15. 15. The writing implement according to claim 12 or 14, further comprising a friction member that discolors writing made with the writing implement due to frictional heat.

Images