WO2020085358A1

WO2020085358A1 - Reversible thermochromic microcapsule pigment for ink and reversible thermochromic aqueous ink composition using same

Info

Publication number: WO2020085358A1
Application number: PCT/JP2019/041460
Authority: WO
Inventors: 真之三田; 格若木
Original assignee: 株式会社パイロットコーポレーション; パイロットインキ株式会社
Priority date: 2018-10-24
Filing date: 2019-10-23
Publication date: 2020-04-30
Also published as: JPWO2020085358A1

Abstract

[Problem] To provide a reversible thermochromic microcapsule pigment for ink that is rich in color forming properties and is capable of forming a high-definition reversible thermochromic image, a reversible thermochromic aqueous ink composition using the same, and an ink container accommodating the aqueous ink composition. [Solution] A reversible thermochromic microcapsule pigment for ink in which a reversible thermochromic composition including (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium for determining a temperature at which a color reaction of the components (a) and (b) occurs is enclosed in microcapsules, and the microcapsules are characterized by having a zeta potential of a positive or negative value in a microcapsule dispersion composed of only water and the microcapsules.

Description

Reversible thermochromic microcapsule pigment for ink, and reversible thermochromic aqueous ink composition using the same

The present invention relates to a reversible thermochromic microcapsule pigment. More specifically, the present invention relates to a reversible thermochromic water-based microcapsule pigment for ink, which is rich in color development and capable of forming a high-definition image. The present invention also relates to an ink composition using the microcapsule pigment, and an ink container containing the ink composition.

BACKGROUND ART Conventionally, an ink composition having a reversible thermochromic property has excellent vividness and can realize different colors depending on the temperature, and thus has been used in various writing instruments and printing devices.
In such an ink, a reversible thermochromic microcapsule pigment containing a reversible thermochromic component as a colorant is insoluble in an ink solvent, has high stability, and is highly sensitive to color reaction. Often used.

However, the reversible thermochromic microcapsule pigment has a larger particle size than general pigments and may form coarse aggregates in the ink, which may cause clogging of the ink flow path. Reversible thermochromic microcapsule pigment in ink because it is difficult to form a high-definition image because the ink ejection property from the ink ejection part deteriorates when the ink flow path becomes clogged, and the color development is rich. It is considered to suppress the aggregation of (See, for example, Patent Documents 1 and 2)

Patent Document 1 describes an ink composition for a writing instrument containing a reversible thermochromic microcapsule pigment, water, a water-soluble polysaccharide, and bentonite.
The ink composition for a writing instrument is excellent in the dispersibility of the reversible thermochromic microcapsule pigment, and suppresses the aggregation of the reversible thermochromic microcapsule pigment so that the ink ejection property from the ink ejection portion of the writing instrument is good. Is.

In addition, Patent Document 2 describes a reversible thermochromic ink composition for inkjet including a microcapsule pigment having a reversible thermochromic property as a colorant.
The reversible thermochromic ink composition for inkjet is excellent in ink releasability of the reversible thermochromic microcapsule pigment from the nozzle (ink ejection portion) of the printer head, rich in color development, and forms a high-definition printed image. It was made possible.

In the above patent document, it is possible to suppress aggregation of the reversible thermochromic microcapsule pigment to some extent. However, the effect of suppressing the aggregation is not sufficient, and the reversible thermochromic microcapsule pigment aggregates, the ink ejection property from the ink ejection portion is deteriorated, the color development is rich, and it is difficult to form a high-definition image. However, there was room for improvement.

JP 2012-97168 A JP 2012-158621A

The present invention has been made in view of the above, is excellent in dispersibility in ink, facilitates ink ejection from the ink ejection portion by improving the fluidity of the ink, is rich in color development, and has high-definition reversibility. A reversible thermochromic microcapsule pigment for ink, which is capable of forming a thermochromic image, a reversible thermochromic aqueous ink composition comprising the reversible thermochromic microcapsule pigment, and the aqueous ink composition The present invention provides an ink container containing the.

The present invention includes (a) an electron-donating color-developing 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. A reversible thermochromic microcapsule containing a reversible thermochromic composition comprising
Reversible heat for ink, characterized in that the microcapsules have a positive or negative zeta potential under conditions of 20 ° C. and a pH value of 7 in a microcapsule dispersion liquid consisting of water and the microcapsules only. The present invention relates to a color-changing microcapsule pigment.
Further, the present invention contains the reversible thermochromic microcapsule pigment for ink described above, water, and a dispersant,
The present invention relates to a reversible thermochromic water-based ink composition, wherein the dispersant has a functional group having a charge having a sign opposite to the zeta potential value of the microcapsule pigment in the structure.
The present invention also relates to an ink container containing the water-based ink composition described above.
The present invention also relates to an ink container set including a plurality of ink containers described above.

According to the present invention, the dispersibility in ink is excellent, the fluidity of the ink is good, the ink is easily ejected from the ink ejecting portion, the color development is rich, and a highly precise reversible thermochromic image can be formed. There is provided a reversible thermochromic microcapsule pigment for ink, a reversible thermochromic aqueous ink composition containing the same, and an ink container containing the aqueous ink composition.

It is explanatory drawing which shows the color change behavior of the microcapsule pigment (heat-decoloring type) which included the reversible thermochromic composition. It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment (heat-decoloring type) which encapsulated the reversible thermochromic composition which has color memory. It is a schematic diagram showing an example of composition of an ink jet printer.

Hereinafter, embodiments of the present invention will be described in detail. In the present specification, “parts”, “%”, “ratio”, etc. indicating the composition are based on mass unless otherwise specified.

The present invention relates to a reversible thermochromic microcapsule pigment for ink, and a reversible thermochromic aqueous ink composition containing the reversible thermochromic microcapsule pigment (hereinafter also referred to as “aqueous ink composition” or “ink composition”). ) Is related to. The present invention also relates to an ink container containing a water-based ink composition. Hereinafter, the reversible thermochromic microcapsule pigment and each component constituting the water-based ink composition will be described.

(Reversible thermochromic microcapsule pigment)
The reversible thermochromic microcapsule pigment of the present invention (hereinafter, also referred to as “microcapsule pigment”) comprises an electron-donating color-forming organic compound, an electron-accepting compound, and a reaction medium that determines the temperature at which a color reaction between the two occurs. The reversible thermochromic composition described below is included.

As the microcapsule pigment, a color change occurs before and after a predetermined temperature (color change point) as a boundary, which is described in JP-B-51-44706, JP-B-51-44707, and JP-B-1-29398. However, it exhibits a decolored state in the temperature range above the high-temperature side discoloration point, and a colored state in the temperature range below the low-temperature side discoloration point.There is only one specific state at room temperature in both states, and the other state. Is maintained as long as the heat or cold required to develop that state is applied, but returns to the state exhibited at room temperature when heat or cold is not applied, with a relatively small hysteresis width ( A microcapsule pigment containing a heat-decolorizable reversible thermochromic composition having ΔH = 1 ° C. to 7 ° C.) can be used (see FIG. 1).

Further, a reversible thermochromic composition exhibiting a large hysteresis characteristic, which is described in JP-A-2006-137886, JP-A-2006-188660, JP-A-2008-45062, JP-A-2008-280523 and the like. It is also possible to use a microcapsule pigment containing a substance. That is, the shape of the curve plotting the change in the coloring density due to the temperature change is significantly different between the case where the temperature is increased from the lower temperature side than the color change temperature range and the case where the temperature is decreased from the higher temperature side than the color change temperature range. The color changes along the path, and the color development state in the low temperature range below the complete color development temperature (t1) or the color development state in the high temperature range above the complete color removal temperature (t4) is in the specific temperature range [between t2 and t3. In the temperature range (substantially two-phase holding temperature range)], a microcapsule pigment including a reversible thermochromic composition having color memory can be used (see FIG. 2).

The hysteresis characteristics in the color density-temperature curve of the microcapsule pigment containing the reversible thermochromic composition having color memory will be described.
In FIG. 2, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to the temperature change progresses along the arrow. Here, A is a point indicating the density at a temperature t4 (hereinafter referred to as a complete erasing temperature) at which the completely erasing state is reached, and B is a temperature t3 at which the erasing is started (hereinafter referred to as an erasing starting temperature). Is a point showing the density at C, C is a point showing the density at a temperature t2 at which color development starts (hereinafter, referred to as a color development start temperature), and D is a temperature t1 at which a fully developed state is reached (hereinafter referred to as a complete color development temperature). ) Is a point indicating the concentration.
The color change temperature range is the temperature range between t1 and t4, and both the colored state and the decolored state can coexist, and the temperature range between t2 and t3, which is a region with a large difference in color density, is the substantial color change temperature range. Is.
Further, the length of the line segment EF is a scale showing the contrast of discoloration, and the length of the line segment HG passing through the midpoint of the line segment EF is a temperature width (hereinafter referred to as hysteresis width ΔH) showing the degree of hysteresis. However, if this ΔH value is small, only one specific state can exist in the normal temperature range of both states before and after discoloration. Further, if the ΔH value is large, it becomes easy to maintain each state before and after the color change.

The complete erasing temperature t4 is, for example, 50 ° C. or more and 90 ° C. or less, preferably 55 ° C. or more and 85 ° C. or less, and more preferably, when erasing by frictional heat generated by rubbing between the friction member and the writing surface. It is in the range of 60 ° C. or higher and 80 ° C. or lower, and the complete color development temperature t1 can be a temperature that can be obtained only in a freezer, a cold region, etc., and is, for example, 0 ° C. or lower, preferably −50 ° C. or higher and −5. C. or lower, more preferably -50.degree. C. or higher and -10.degree. C. or lower.

The electron-donating color-developing organic compound, electron-accepting compound and reaction medium are explained below. The electron-donating color-developing organic compound is a component that determines the color tone and is a compound that develops a color by donating an electron to the electron-accepting compound. Examples of the electron-donating color-developing 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. Of these, a phthalide compound and a fluoran compound are included. At least one selected from the group is preferred.

Examples of the phthalide compound include diphenylmethanephthalide compound, phenylindolylphthalide compound, indolylphthalide compound, diphenylmethaneazaphthalide compound, phenylindolylazaphthalide compound, and derivatives thereof. , Phenylindolyl azaphthalide compounds, and their derivatives are preferred. In addition, examples of the fluorane compound include an aminofluorane compound, an alkoxyfluorane compound, and derivatives thereof.

Examples of these compounds are shown below.
3,3-bis (p-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-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-propylindol-3-yl) -4-azaphthalide,
3,6-bis (diphenylamino) fluorane,
3,6-dimethoxyfluorane,
3,6-di-n-butoxyfluorane,
2-methyl-6- (N-ethyl-Np-tolylamino) fluorane,
3-chloro-6-cyclohexylaminofluorane,
2-methyl-6-cyclohexylaminofluorane,
2- (2-chloroamino) -6-dibutylaminofluorane,
2- (2-chloroanilino) -6-di-n-butylaminofluorane,
2- (3-trifluoromethylanilino) -6-diethylaminofluorane,
2- (3-trifluoromethylanilino) -6-dipentylaminofluorane,
2- (dibenzylamino) -6-diethylaminofluorane,
2- (N-methylanilino) -6- (N-ethyl-Np-tolylamino) fluorane,
1,3-dimethyl-6-diethylaminofluorane,
2-chloro-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methoxy-6-diethylaminofluorane,
2-anilino-3-methyl-6-di-n-butylaminofluorane,
2-anilino-3-methoxy-6-di-n-butylaminofluorane,
2-xylidino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6- (N-ethyl-Np-tolylamino) fluorane,
1,2-benz-6-diethylaminofluorane,
1,2-benz-6- (N-ethyl-N-isobutylamino) fluorane,
1,2-benz-6- (N-ethyl-N-isoamylamino) fluorane,
2- (3-methoxy-4-dodecoxystyryl) quinoline,
Spiro [5H- (1) benzopyrano [2,3-d] pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one, 2- (diethylamino) -8- (diethylamino) -4-methyl ,
Spiro [5H- (1) benzopyrano [2,3-d] pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one, 2- (di-n-butylamino) -8- (di -N-butylamino) -4-methyl,
Spiro [5H- (1) benzopyrano [2,3-d] pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one, 2- (di-n-butylamino) -8- (diethylamino ) -4-methyl,
Spiro [5H- (1) benzopyrano [2,3-d] pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one, 2- (di-n-butylamino) -8- (N -Ethyl-N-i-amylamino) -4-methyl,
Spiro [5H- (1) benzopyrano [2,3-d] pyrimidin-5,1 '(3'H) isobenzofuran] -3'-one, 2- (dibutylamino) -8- (dipentylamino) -4 -Methyl,
4,5,6,7-Tetrachloro-3- [4- (dimethylamino) -2-methoxyphenyl] -3- (1-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-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] xanthen] -3-one,
3 ′, 6′-bis [phenyl (3-ethylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9 ′-[9H] xanthen] -3-one,
2,6-bis (2'-ethyloxyphenyl) -4- (4'-dimethylaminophenyl) pyridine,
2,6-bis (2 ', 4'-diethyloxyphenyl) -4- (4'-dimethylaminophenyl) pyridine,
2- (4'-dimethylaminophenyl) -4-methoxy-quinazoline,
4,4 '-(ethylenedioxy) -bis [2- (4-diethylaminophenyl) quinazoline] and the like can be mentioned.

As the fluoranes, in addition to the compound having a substituent on the phenyl group forming a xanthene ring, a substituent on the phenyl group forming a lactone ring as well as a substituent on the phenyl group forming a xanthene ring (for example, , An alkyl group such as a methyl group, or a halogen atom such as a chloro group), and a compound exhibiting a blue color or a black color.

Examples of the electron-accepting compound include compounds having an active proton, pseudo-acidic compounds (a compound which is not an acid but acts as an acid in the composition to develop an electron-donating color-forming organic compound), and an electron vacancy. There is a group of compounds having pores. Examples of the compound having an active proton include compounds having a phenolic hydroxyl group, such as monophenols and polyphenols, and further substituents thereof include an alkyl group, an alkenyl group, an aryl group, an acyl group, an alkoxycarbonyl group, and a carboxy group. Examples thereof include compounds having an ester or amide group thereof, a halogen group, and the like, and phenol-aldehyde condensation resins such as bis type and tris type phenols. Further, it may be a metal salt of a compound having a phenolic hydroxyl group.

Specific examples of the electron-accepting compound include phenol, o-cresol, tert-butylcatechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenyl. Phenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcin, dodecyl gallate, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, bis (3-allyl- 4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4-isopropoxyphenylsulfone, 4-benzyloxyphenyl-4-hydroxyphenylsulfone, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis 4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) n-butane, 1,1-bis (4-hydroxyphenyl) n-pentane, 1,1-bis (4-hydroxyphenyl) n- Hexane, 1,1-bis (4-hydroxyphenyl) n-heptane, 1,1-bis (4-hydroxyphenyl) n-octane, 1,1-bis (4-hydroxyphenyl) n-nonane, 1,1 -Bis (4-hydroxyphenyl) n-decane, 1,1-bis (4-hydroxyphenyl) n-dodecane, 1,1-bis (4-hydroxyphenyl) -2-methylpropane, 1,1-bis ( 4-hydroxyphenyl) -3-methylbutane, 1,1-bis (4-hydroxyphenyl) -3-methylpentane, 1,1-bis (4-hydroxyphenyl) -2 3-dimethylpentane, 1,1-bis (4-hydroxyphenyl) -2-ethylbutane, 1,1-bis (4-hydroxyphenyl) -2-ethylhexane, 1,1-bis (4-hydroxyphenyl)- 3,7-Dimethyloctane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1-phenyl-1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) n-butane, 2,2-bis (4-hydroxyphenyl) n-pentane 2,2-bis (4-hydroxyphenyl) n-hexane, 2,2-bis (4-hydroxyphenyl) n-heptane, 2,2-bis ( 4-hydroxyphenyl) n-octane, 2,2-bis (4-hydroxyphenyl) n-nonane, 2,2-bis (4-hydroxyphenyl) n-decane, 2,2-bis (4-hydroxyphenyl) n-dodecane, 2,2-bis (4-hydroxyphenyl) ethyl propionate, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) -4 -Methylhexane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 9,9-bis (4-hydroxy-3-methylphenyl) ) Fluorene, 1,3-bis [2- (4-hydroxyphenyl) -2-propyl] benzene, bis (2-hydroxyphenyl) methane, 1,1 1- tris (4-hydroxyphenyl) ethane, 2,2-bis (3-methyl-4-hydroxyphenyl) butane, 4-t-butyl-2 ', may be mentioned 4'-dihydroxy benzophenone.

A compound having a phenolic hydroxyl group can exhibit the most effective thermochromic property, but aromatic carboxylic acids and aliphatic carboxylic acids having 2 to 5 carbon atoms, carboxylic acid metal salts, acidic phosphoric acid esters and their metals. It may be a compound selected from salts, 1,2,3-triazole and its derivatives.

Explain the reaction medium that determines the temperature at which the color reaction by the electron-donating organic compound and the electron-accepting compound occurs. Examples of the reaction medium include compounds such as alcohols, esters, ketones, ethers and acid amides. When using these compounds for microencapsulation and secondary processing, low-molecular weight compounds evaporate out of the capsule when subjected to high heat treatment, so in order to stably retain them in the capsule, the number of carbon atoms is 10 or more. Compounds of are preferably used.

As the alcohol, an aliphatic monovalent saturated alcohol having 10 or more carbon atoms is effective. Specific examples thereof include decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol and docosyl alcohol.

As the esters, esters having 10 or more carbon atoms are effective, and any combination of a monovalent carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic, alicyclic or aromatic ring. , An aliphatic, an alicyclic or aromatic ring-containing polyvalent carboxylic acid, and an ester, an aliphatic or an alicyclic ring obtained from any combination of an aliphatic, alicyclic or aromatic ring-containing monohydric alcohol Alternatively, there can be mentioned esters obtained from any combination of a monovalent carboxylic acid having an aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring. Specifically, ethyl caprylate, octyl caprylate, stearyl caprylate, myristyl caprate, docosyl caprate, 2-ethylhexyl laurate, n-decyl laurate, 3-methylbutyl myristate, cetyl myristate, isopropyl palmitate, Neopentyl palmitate, nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutyl stearate, 3,5,5-trimethylhexyl stearate, n-undecyl stearate, pentadecyl stearate, stearyl stearate, stearin Cyclohexyl methyl acid, isopropyl behenate, hexyl behenate, lauryl behenate, behenyl behenate, cetyl benzoate, ptert-butyl stearyl benzoate stearyl, diimiphthalate Stille, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelate, di- (n-nonyl) sebacate, 1,18-octadecyl Dyneopentyl methylene dicarboxylate, ethylene glycol dimyristate, propylene glycol dilaurate, propylene glycol distearate, hexylene glycol dipalmitate, 1,5-pentanediol distearate, 1,2,6-hexanetriol trimyristate, 1,4-cyclohexanediol didecyl, 1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprinate, xylene glycol distearate and the like can be mentioned.

Ester compounds selected from esters of saturated fatty acids and branched fatty alcohols and esters of unsaturated fatty acids or saturated fatty acids having a branched or substituted group and branched or having 16 or more carbon atoms are also effective. is there. Specifically, 2-ethylhexyl butyrate, 2-ethylhexyl behenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate, 3,5,5-trimethylhexyl laurate, 3,5,5-trimethylhexyl palmitate, 3,5,5-Trimethylhexyl stearate, 2-methylbutyl caproate, 2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate, 1-ethylpropyl stearate, 1-ethylpropyl behenate, 1-ethylhexyl laurate, 1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate, 2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyl laurate, 2-stearic acid stearate Met Butyl, 2-methylbutyl stearate, 3-methylbutyl stearate, 1-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutyl behenate, 1-methylheptyl stearate, 1-methylheptyl behenate, caproic acid 1 -Ethylpentyl, 1-ethylpentyl palmitate, 1-methylpropyl stearate, 1-methyloctyl stearate, 1-methylhexyl stearate, 1,1-dimethylpropyl laurate, 1-methylpentyl caprate, palmitic acid 2-methylhexyl, 2-methylhexyl stearate, 2-methylhexyl behenate, 3,7-dimethyloctyl laurate, 3,7-dimethyloctyl myristate, 3,7-dimethyloctyl palmitate, stearic acid 3, 7-Jime Ruoctyl, 3,7-dimethyloctyl behenate, stearyl oleate, behenyl oleate, stearyl linoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearyl erucate, isostearyl erucate, cetyl isostearate, isostearine. Acid stearyl, 2-methylpentyl 12-hydroxystearate, 2-ethylhexyl 18-bromostearate, isostearyl 2-ketomyristate, 2-ethylhexyl 2-fluoromyristate, cetyl butyrate, stearyl butyrate, behenyl butyrate, etc. To be

Furthermore, in order to exhibit a large hysteresis characteristic with respect to the color density-temperature curve and to change the color, and to impart the color memory property depending on the temperature change, the temperature of 5 ° C. or more and less than 50 ° C. described in JP-B-4-17154 is used. Carboxylic acid ester compound showing ΔT value (melting point-clouding point), for example, carboxylic acid ester containing substituted aromatic ring in molecule, ester of carboxylic acid containing unsubstituted aromatic ring and aliphatic alcohol having 10 or more carbon atoms A carboxylic acid ester having a cyclohexyl group in the molecule, a fatty acid having 6 or more carbon atoms and an unsubstituted aromatic alcohol or phenol, a fatty acid having 8 or more carbon atoms and a branched aliphatic alcohol or ester, a dicarboxylic acid and an aromatic alcohol, or Esters of branched aliphatic alcohols, dibenzyl cinnamate, heptyl stearate, didecyl adipate, Adipic acid dilauryl, dimyristyl adipate, dicetyl adipate, distearyl adipate, trilaurin, trimyristin, tristearin, dimyristin, distearate, and the like.

Fatty acid ester compound obtained from odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and aliphatic carboxylic acid having even-numbered carbons, n-pentyl alcohol or n-heptyl alcohol, and even aliphatic carboxylic acid having 10 to 16 carbon atoms A fatty acid ester compound having a total carbon number of 17 to 23 obtained from an acid is also effective. Specifically, n-pentadecyl acetate, n-tridecyl butyrate, n-pentadecyl butyrate, n-undecyl caproate, n-tridecyl caproate, n-pentadecyl caproate, n-nonyl caprylate, n-undecyl caprylate, N-Tridecyl caprylate, n-pentadecyl caprylate, n-heptyl caprate, n-nonyl caprate, n-undecyl caprate, n-tridecyl caprate, n-pentadecyl caprate, n-pentyl laurate, lauric acid n-heptyl, n-nonyl laurate, n-undecyl laurate, n-tridecyl laurate, n-pentadecyl laurate, n-pentyl myristate, n-heptyl myristate, n-nonyl myristate, n-myristate Undecyl, n-tridecyl myristate, N-Pentadecyl lithitate, n-pentyl palmitate, n-heptyl palmitate, n-nonyl palmitate, n-undecyl palmitate, n-tridecyl palmitate, n-pentadecyl palmitate, n-nonyl stearate, stearic acid n-Undecyl, n-tridecyl stearate, n-pentadecyl stearate, n-nonyl eicosanate, n-underci eicosanate, n-tridecyl eicosanate, n-pentadecyl eicosanate, n-nonyl behenate, n-behenate Examples include undecyl, n-tridecyl behenate, and n-pentadecyl behenate.

As ketones, aliphatic ketones having a total carbon number of 10 or more are effective. Specifically, 2-decanone, 3-decanone, 4-decanone, 2-undecanone, 3-undecanone, 4-undecanone, 5-undecanone, 2-dodecanone, 3-dodecanone, 4-dodecanone, 5-dodecanone, 2 -Tridecanone, 3-Tridecanone, 2-Tetradecanone, 2-Pentadecanone, 8-Pentadecanone, 2-Hexadecanone, 3-Hexadecanone, 9-Heptadecanone, 2-Pentadecanone, 2-Octadecanone, 2-Nonadecanone, 10-Nonadecanone, 2-Eicosanone , 11-eicosanone, 2-heneicosanone, 2-docosanone, lauron, stearone and the like.

Further, as the ketones, arylalkyl ketones having a total carbon number of 12 to 24, for example, n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n -Tetradecanophenone, 4-n-dodecaacetophenone, n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n- Nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, n-nonanophenone, 4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone, 4-n-cyclohexylacetophenone, 4-tert-butyl Propiophenone, n-heptaphenone, 4-n- Emissions chill acetophenone, phenyl ketone, benzyl -n- butyl ketone, 4-n-butyl acetophenone, n- hexanophenone, 4-isobutyl acetophenone, 1-acetonaphthone, 2-acetonaphthone, cyclopentyl phenyl ketone.

As the ethers, aliphatic ethers having a total carbon number of 10 or more are effective. Specifically, dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditridecyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecyl ether. Examples thereof include decyl ether, dioctadecyl ether, decanediol dimethyl ether, undecanediol dimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethyl ether, decanediol diethyl ether, and undecanediol diethyl ether.

Examples of acid amides include acetamide, propionic acid amide, butyric acid amide, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and oleic acid amide. , Erucamide, benzamide, caproic acid anilide, caprylic acid anilide, capric acid anilide, lauric acid anilide, myristic acid anilide, palmitic acid anilide, stearic acid anilide, behenic acid anilide, oleic acid anilide, erucic acid anilide, caproic acid N -Methylamide, caprylic acid N-methylamide, capric acid N-methylamide, lauric acid N-methylamide, myristic acid N-methylamide, palmitic acid N-methylamide, stearic acid N-methylamide De, behenic acid N-methylamide, oleic acid N-methylamide, erucic acid N-methylamide, lauric acid N-ethylamide, myristic acid N-ethylamide, palmitic acid N-ethylamide, stearic acid N-ethylamide, oleic acid N-ethylamide, Lauric acid N-butylamide, myristic acid N-butylamide, palmitic acid N-butylamide, stearic acid N-butylamide, oleic acid N-butylamide, lauric acid N-octylamide, myristic acid N-octylamide, palmitic acid N-octylamide , Stearic acid N-octylamide, oleic acid N-octylamide, lauric acid N-dodecylamide, myristic acid N-dodecylamide, palmitic acid N-dodecylamide, stearic acid N-dodecylamide, oleic acid Acid N-dodecyl amide, dilauric acid amide, dimyristic acid amide, dipalmitic acid amide, distearic acid amide, dioleic acid amide, trilauric acid amide, trimyristic acid amide, tripalmitic acid amide, tristearic acid amide, triolein Acid amide, succinic acid amide, adipic acid amide, glutaric acid amide, malonic acid amide, azelaic acid amide, maleic acid amide, succinic acid N-methylamide, adipic acid N-methylamide, glutaric acid N-methylamide, malonic acid N-methylamide , Azelaic acid N-methylamide, succinic acid N-ethylamide, adipic acid N-ethylamide, glutaric acid N-ethylamide, malonic acid N-ethylamide, azelaic acid N-ethylamide, succinic acid N-butylamide, adipic acid N -Butylamide, glutaric acid N-butylamide, malonic acid N-butylamide, adipic acid N-octylamide, adipic acid N-dodecylamide and the like.

Also, a compound represented by the following formula (1) can be used as a reaction medium.

In the formula, R ₁ represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, and _one of X ₁ and X ₂ is — (CH ₂ ) nOCOR ₂ or (CH ₂ ) nCOOR ₂ , the other. Represents a hydrogen atom, n represents an integer of 0 to 2, R ₂ represents an alkyl group or an alkenyl group having 4 or more carbon atoms, Y ₁ and Y ₂ represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, A methoxy group or a halogen atom is shown, and r and p are integers from 1 to 3.

Of the compounds represented by the formula (1), when R ₁ is a hydrogen atom, a reversible thermochromic composition having a wider hysteresis width can be obtained, which is preferable, and R ₁ is a hydrogen atom, and , M is more preferably 0. Among the compounds represented by formula (1), the compound represented by the following formula (2) is more preferably used.

R in the formula (2) represents an alkyl group or an 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.

Specific examples of the compound represented by the formula (2) include 4-benzyloxyphenylethyl octanoate, 4-benzyloxyphenylethyl nonanoate, 4-benzyloxyphenylethyl decanoate, and 4-benzyl undecanoate. Oxyphenylethyl, 4-benzyloxyphenylethyl dodecanoate, 4-benzyloxyphenylethyl tridecanoate, 4-benzyloxyphenylethyl tetradecanoate, 4-benzyloxyphenylethyl pentadecanoate, 4-benzylhexadecanoate Examples thereof include oxyphenylethyl, 4-benzyloxyphenylethyl heptadecanoate, and 4-benzyloxyphenylethyl octadecanoate.

Further, a compound represented by the following formula (3) can be used as a reaction medium.

In formula (3), R represents an alkyl group or an alkenyl group having 8 or more carbon atoms, m and n each represent an integer of 1 to 3, X and Y each represent a hydrogen atom, and an alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 4 carbon atoms or a halogen atom.

Specific examples of the compound represented by the formula (3) include 1,1-diphenylmethyl octanoate, 1,1-diphenylmethyl nonanoate, 1,1-diphenylmethyl decanoate, 1,1-diphenylmethyl undecanoate, 1,1-Diphenylmethyl dodecanoate, 1,1-Diphenylmethyl tridecanoate, 1,1-Diphenylmethyl tetradecanoate, 1,1-Diphenylmethyl pentadecanoate, 1,1-Diphenylmethyl hexadecanoate,

Heptadecanoic acid

1,1 Examples thereof include diphenylmethyl and 1,1-diphenylmethyl octadecanoate.

Furthermore, a compound represented by the following formula (4) can be used as a reaction medium.

In formula (4), 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. .

The compound represented by the formula (4) includes a diester of malonic acid and 2- [4- (4-chlorobenzyloxy) phenyl)] ethanol, and a diester of succinic acid and 2- (4-benzyloxyphenyl) ethanol. , A diester of succinic acid and 2- [4- (3-methylbenzyloxy) phenyl)] ethanol, a diester of glutaric acid and 2- (4-benzyloxyphenyl) ethanol, glutaric acid and 2- [4- ( 4-chlorobenzyloxy) phenyl)] ethanol diester, adipic acid 2- (4-benzyloxyphenyl) ethanol diester, pimelic acid 2- (4-benzyloxyphenyl) ethanol diester, suberic acid Of 2- (4-benzyloxyphenyl) ethanol with suberic acid and 2- 4- (3-methylbenzyloxy) phenyl)] ethanol diester, suberic acid and 2- [4- (4-chlorobenzyloxy) phenyl)] ethanol diester, suberic acid and 2- [4- (2 , 4-Dichlorobenzyloxy) phenyl)] ethanol diester, azelaic acid 2- (4-benzyloxyphenyl) ethanol diester, sebacic acid 2- (4-benzyloxyphenyl) ethanol diester, 1 , 10-decanedicarboxylic acid diester of 2- (4-benzyloxyphenyl) ethanol, 1,18-octadecanedicarboxylic acid diester of 2- (4-benzyloxyphenyl) ethanol, 1,18-octadecanedicarboxylic acid And 2- [4- (2-methylbenzyloxy) phenyl)] It can be exemplified diester of Nord.

Furthermore, a compound represented by the following formula (5) can be used as a reaction medium.

In the formula (5), R represents an alkyl group or an alkenyl group having 1 to 21 carbon atoms, and n represents an integer of 1 to 3.

Examples of the compound represented by the formula (5) include diesters of 1,3-bis (2-hydroxyethoxy) benzene and capric acid, diesters of 1,3-bis (2-hydroxyethoxy) benzene and undecanoic acid, 1 , 3-bis (2-hydroxyethoxy) benzene with lauric acid, 1,3-bis (2-hydroxyethoxy) benzene with myristic acid, 1,4-bis (hydroxymethoxy) benzene with butyric acid Diester of 1,4-bis (hydroxymethoxy) benzene and isovaleric acid, diester of 1,4-bis (2-hydroxyethoxy) benzene and acetic acid, 1,4-bis (2-hydroxyethoxy) Diester of benzene and propionic acid, 1,4-bis (2-hydroxyethoxy) benzene and valer , A diester of 1,4-bis (2-hydroxyethoxy) benzene and caproic acid, a diester of 1,4-bis (2-hydroxyethoxy) benzene and caprylic acid, 1,4-bis (2- Examples include diesters of hydroxyethoxy) benzene and capric acid, diesters of 1,4-bis (2-hydroxyethoxy) benzene and lauric acid, and diesters of 1,4-bis (2-hydroxyethoxy) benzene and myristic acid. it can.

Furthermore, a compound represented by the following formula (6) can be used as a reaction medium.

In formula (6), 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 1 To an integer of 20.

Examples of the compound represented by the formula (6) include a diester of succinic acid and 2-phenoxyethanol, a diester of suberic acid and 2-phenoxyethanol, a diester of sebacic acid and 2-phenoxyethanol, 1,10-decanedicarboxylic acid and 2 Examples include a diester of phenoxyethanol and a diester of 1,18-octadecanedicarboxylic acid and 2-phenoxyethanol.

Furthermore, a compound represented by the following formula (7) can be used as a reaction medium.

In formula (7), 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, and X represents a hydrogen atom or 1 to 4 carbon atoms. Is an alkyl group, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, and n is 0 or 1.

Examples of the compound represented by the formula (7) include decyl 4-phenylbenzoate, lauryl 4-phenylbenzoate, myristyl 4-phenylbenzoate, cyclohexylethyl 4-phenylbenzoate, octyl 4-biphenylacetate, and 4-biphenylacetic acid. Nonyl, decyl 4-biphenylacetate, lauryl 4-biphenylacetate, myristyl 4-biphenylacetate, tridecyl 4-biphenylacetate, pentadecyl 4-biphenylacetate, cetyl 4-biphenylacetate, cyclopentyl 4-biphenylacetate, cyclohexylmethyl 4-biphenylacetate Examples include hexyl 4-biphenylacetate and cyclohexylmethyl 4-biphenylacetate.

Furthermore, a compound represented by the following formula (8) can be used as a reaction medium.

In formula (8), R represents either an alkyl group having 3 to 18 carbon atoms or an aliphatic acyl group having 3 to 18 carbon atoms, and X is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or 1 carbon atom. Or 2 is an alkoxy group or a halogen atom, Y is a hydrogen atom or a methyl group, Z is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 or 2 carbon atoms. , Or a halogen atom.

Examples of the compound represented by the formula (8) include phenoxyethyl 4-butoxybenzoate, phenoxyethyl 4-pentyloxybenzoate, phenoxyethyl 4-tetradecyloxybenzoate, phenoxyethyl 4-hydroxybenzoate and dodecanoic acid. Examples thereof include esters and phenoxyethyl vanillic acid dodecyl ether.

Furthermore, a compound represented by the following formula (9) can be used as a reaction medium.

In formula (9), 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, and X represents a hydrogen atom, an alkyl group, or an alkoxy. A 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.

Examples of the compound represented by the formula (9) include benzoic acid ester of octyl p-hydroxybenzoate, benzoic acid ester of decyl p-hydroxybenzoate, p-methoxybenzoic acid ester of heptyl p-hydroxybenzoate and p-hydroxyl. Examples thereof include o-methoxybenzoic acid ester of dodecyl benzoate and benzoic acid ester of cyclohexylmethyl p-hydroxybenzoate.

Further, a compound represented by the following formula (10) can be used as a reaction medium.

In formula (10), R is either 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, or an alkenyl group having 3 to 18 carbon atoms. X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom, and Y is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or methoxy. Represents a group, an ethoxy group, or a halogen atom.

Examples of the compound represented by the formula (10) include phenoxyethyl ether of nonyl p-hydroxybenzoate, phenoxyethyl ether of decyl p-hydroxybenzoate, phenoxyethyl ether of undecyl p-hydroxybenzoate, and phenoxyethyl dodecyl vanillate. An example is ether.

Furthermore, a compound represented by the following formula (11) can be used as a reaction medium.

In the formula (11), 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.

Examples of the compound represented by the formula (11) include diesters of 1,3-bis (2-hydroxyethoxy) benzene and cyclohexanecarboxylic acid, and diesters of 1,4-bis (2-hydroxyethoxy) benzene and cyclohexanepropionic acid. An example is a diester of 1,3-bis (2-hydroxyethoxy) benzene and cyclohexanepropionic acid.

Furthermore, a compound represented by the following formula (12) can be used as a reaction medium.

In formula (12), 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, and X represents a hydrogen atom or 1 to 1 carbon atoms. 5 represents an alkyl group, a methoxy group, an ethoxy group, or a halogen atom, and n represents an integer of 1 to 3.

Examples of the compound represented by the formula (12) include a diester of 4-phenylphenol ethylene glycol ether and cyclohexanecarboxylic acid, a diester of 4-phenylphenol diethylene glycol ether and lauric acid, 4-phenylphenol triethylene glycol ether and cyclohexanecarboxylic acid. Acid diester, 4-phenylphenol ethylene glycol ether and octanoic acid diester, 4-phenylphenol ethylene glycol ether and nonanoic acid diester, 4-phenylphenol ethylene glycol ether and decanoic acid diester, 4-phenyl Examples thereof include diesters of phenol ethylene glycol ether and myristic acid.

Further, as the electron-accepting compound, a specific alkoxyphenol compound having a linear or side chain alkyl group having 3 to 18 carbon atoms is used (Japanese Patent Application Laid-Open Nos. 11-129623 and 11-5973), or a specific Using a hydroxybenzoic acid ester (Japanese Unexamined Patent Publication No. 2001-105732), using a gallic acid ester, etc. (Japanese Patent Publication No. 51-44706, Japanese Unexamined Patent Publication No. 2003-253149), a coloring type by heating (coloring by heating, It is also possible to apply a reversible thermochromic composition which is decolorized by cooling) and a reversible thermochromic microcapsule pigment (reversible thermochromic pigment) containing the reversible thermochromic composition.

The reversible thermochromic composition is a compatibilized solution containing an electron-donating color-developing organic compound, an electron-accepting compound and a reaction medium as essential components. The proportion of each component may be appropriately selected depending on the density, the color change temperature, the color change form, the type of each component, and the like. Generally, the component ratio for obtaining desired characteristics is such that the electron-accepting compound is 0.1 to 100 parts by mass, preferably 0.1 to 50 parts by mass, relative to 1 part by mass of the electron-donating color-forming organic compound. , More preferably 0.5 to 20 parts by mass, and the reaction medium is 5 to 200 parts by mass, preferably 5 to 100 parts by mass, more preferably 10 to 100 parts by mass.

The microcapsule pigment may further contain various light stabilizers, if necessary. The light stabilizer is contained in order to prevent photodegradation of the reversible thermochromic composition, and is 0.3 part by mass or more and 24 parts by mass or less, preferably 0 part by mass with respect to 1 part by mass of the electron-donating color-developing organic compound. It is contained in a proportion of not less than 3 parts by mass and not more than 16 parts by mass. Further, among the light stabilizers, the ultraviolet absorber effectively blocks ultraviolet rays contained in sunlight and the like to prevent photodegradation caused by an excited state due to a photoreaction of the electron-accepting compound. Further, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers and the like suppress the oxidation reaction due to light. The light stabilizers may be used alone or in combination of two or more.

The reversible thermochromic composition is used as a reversible thermochromic microcapsule pigment by being encapsulated in microcapsules. The microencapsulation methods include conventionally known interfacial polymerization method, in-situ polymerization method, submerged curing coating method, phase separation method from aqueous solution, phase separation method from organic solvent, melt dispersion cooling method, vaporization method. There are a medium suspension coating method, a spray drying method and the like, which are appropriately selected depending on the application. Further, the surface of the microcapsules may be provided with a secondary resin film depending on the purpose to impart durability or may be modified in surface characteristics for practical use. Further, the zeta potential of the microcapsule pigment can be changed by providing a secondary resin film or modifying the surface characteristics.

The content of the microcapsule pigment is preferably in the range of inclusion / wall film = 7/1 to 1/1 (mass ratio), and when the ratio of the wall film is within the above range, the color density and vividness at the time of color development are clear. It is possible to prevent deterioration of the property, and more preferably, inclusion / wall film = 6/1 to 1/1 (mass ratio).
The zeta potential of the microcapsule pigment can also be changed by adjusting the mass ratio of the inclusions of the microcapsule pigment and the wall film.

By encapsulating the reversible thermochromic composition in microcapsules, a chemically and physically stable pigment can be constructed.

The microcapsule pigment has a positive or negative zeta potential under the conditions of 20 ° C. and a pH value of 7.
Since the microcapsule pigment has a positive or negative zeta potential in the microcapsule pigment dispersion liquid consisting of only water and the microcapsule pigment, by combining the microcapsule pigment and the dispersant described below, It is possible to obtain a water-based ink composition which has good dispersibility of the microcapsule pigment and exhibits excellent ink fluidity. When the zeta potential is 0 mV, the dispersibility of the microcapsule pigment is reduced and aggregates are easily formed.

Although it is ideal to use pure water as the water, ion-exchanged water can also be used.
As the ion-exchanged water, ion-exchanged water produced by ion-exchanging distilled water and having an electrical conductivity of less than 1000 μS / m at 25 ° C. is used.
As a device for generating ion-exchanged water, it is possible to use an ion-exchanged water generation device such as (product name: pure water production device Autostill WA33, manufactured by Yamato Scientific Co., Ltd.).
Further, as the ion-exchanged water, ion-exchanged water having electric conductivity, which is generated by ion-exchanging tap water obtained by filtering impurities, can be used.
The tap water that is subjected to ion exchange may be tap water that has not been filtered.

The value of the zeta potential of the microcapsule pigment is 20 ° C. and the pH value of the microcapsule pigment dispersion liquid is 7 (pH value of 6.5 or more), considering that the microcapsule pigment has good dispersibility and thermal discoloration. A pH value of less than 7.5 is regarded as a pH value 7. More practically, a pH value of 6.8 or more and 7.2 or less is regarded as a pH value of 7.), and 0 <| ζ | ≦ 20 mV. It is preferable that 1 ≦ | ζ | ≦ 15 mV is more preferable. More preferably, 2 ≦ | ζ | ≦ 10 mV, and particularly preferably 3 ≦ | ζ | ≦ 10 mV.
In the present invention, when the number average value of 20 pieces of measurement data of zeta potential is in the range of −0.04 mV to 0.04 mV, the zeta potential value is considered to be substantially 0 mV.

The zeta potential of the microcapsule pigment is calculated from the streaming potential measured by the streaming potential method. For measuring the streaming potential and calculating the zeta potential, a product name: streaming potential measuring device Stabino PMX400, manufactured by Microtrac Bell Co., Ltd. is used.

When the value of the zeta potential is within the above range, the transfer of electrons between the components (a), (b), and (c) is affected in the thermochromic function of the components (a), (b), and (c). Is less likely to cause discoloration sensitivity, and it is less likely to cause residual color such as residual color when erasing.
Further, in the present invention, even if a microcapsule pigment and an additive having a high absolute value of zeta potential are combined in the ink composition, problems are less likely to occur. Therefore, various additives having different zeta potential values are used. There is a degree of freedom, and stable ink can be adjusted.

The microcapsule pigment preferably has a volume average particle diameter (median diameter) of 0.1 to 5 μm and does not include microcapsule pigment particles having a particle diameter of more than 8 μm. Such a microcapsule pigment has excellent tinting strength, and when it is used in an ink, the fluidity of the ink composition is good, so that it is possible to further improve the ink dischargeability and the image color developability.
It should be noted that if the microcapsule pigment particles having a particle size of more than 8 μm are not included, the microcapsule pigment particles having a particle size of more than 8 μm are likely to cause clogging. Is to do. Regarding the ink of the present invention which does not contain microcapsule pigment particles having a particle size of more than 8 μm, the microcapsule pigment particles having a particle size of more than 6 μm when the upper limit of the volume average particle size is 4 μm or less as described later. When the upper limit of the volume average particle diameter is 3 μm or less, it is preferable that the microcapsule pigment particles having a particle diameter of more than 4 μm are not included.

Since microcapsule pigments have a larger particle size than general pigments, clogging may occur in the ink flow path depending on the particle size. Further, when a microcapsule pigment having an excessively small particle diameter is used, clogging can be suppressed, but the coloring power of the microcapsule pigment is low, so that the color developability of an image tends to be deteriorated.
Further, even if the microcapsule pigment has a particle size that does not cause clogging and has sufficient coloring power, it is difficult to achieve good ink fluidity due to variations in the particle size, and high-definition It tends to be difficult to form an image.

Therefore, by setting the average particle diameter of the microcapsule pigment, and the particle diameter within the above range, the coloring power of the microcapsule pigment is improved, and the fluidity of the ink using the microcapsule pigment can be increased. It is easy to form a high-definition image with rich color development.
In particular, when an inkjet printer is used as an apparatus for forming an image, the inkjet printer includes an ink flow path having a small inner diameter and an ink ejection portion in the printer head, but the microcapsule pigment having the above-mentioned average particle diameter and particle diameter is In addition, clogging is less likely to occur in the ink flow path and the ink discharge portion, so that the ink dischargeability can be improved.
Further, when forming a high-definition image with an inkjet printer, fine ink droplets having a uniform diameter are ejected from the ink ejecting portion, so that the ink droplet landing accuracy on the surface to be printed is good. Although desirable, a microcapsule pigment having an average particle diameter and a particle diameter has a small variation in particle diameter, so uniform and fine ink droplets can be easily formed, and a high-definition printed image can be easily formed.

Considering that the coloring power and the ink dischargeability of the microcapsule pigment are good and the droplets having a uniform diameter are easily formed at the time of ink discharge, the microcapsule pigment has the upper limit of the volume average particle diameter. The thickness is preferably 4 μm or less, more preferably 3 μm or less. The upper limit value is specified as described above because it is possible to secure a substantial color density when the microcapsule pigment has a size of about 2 μm, but it is easier to secure the color density when the microcapsule pigment is larger. If present, it is not preferable from the viewpoints of continuous ejection stability, prevention of clogging, prevention of sedimentation, etc. Therefore, it is essential that the volume average particle diameter be 5 μm or less. For the same reason, the upper limit value is preferably 4 μm or less, more preferably 3 μm or less.
Furthermore, the lower limit of the volume average particle diameter is preferably 0.3 μm or more, more preferably 0.5 μm or more. In order to specify the lower limit as described above, it is necessary to be 0.1 μm or more from the viewpoint of color developability, and if it is less than that, it is difficult to obtain a sufficient color density. Further, for the same reason, the lower limit value is preferably 0.3 μm or more, more preferably 0.5 μm or more.

Specific examples of the microcapsule pigment contained in the ink composition include microcapsules having a volume average particle diameter (median diameter) of 0.1 to 5.0 μm and not containing microcapsule pigment particles having a particle diameter of more than 8 μm. A pigment, a volume average particle diameter of 0.3 to 5.0 μm, a microcapsule pigment not including microcapsule pigment particles having a particle diameter of more than 8 μm, a volume average particle diameter of 0.5 to 5.0 μm, Microcapsule pigment not containing microcapsule pigment particles having a particle size of more than 8 μm, microcapsule pigment having a volume average particle size of 0.1 to 4.0 μm and not containing microcapsule pigment particles having a particle size of more than 6 μm Microcapsule pigment particles having a volume average particle diameter of 0.3 to 4.0 μm and a particle diameter of more than 6 μm Not containing, microcapsule pigments having a volume average particle diameter of 0.5 to 4.0 μm and not having microcapsule pigment particles having a particle diameter of more than 6 μm, volume average particle diameters of 0.1 to 3 A microcapsule pigment which does not include microcapsule pigment particles having a particle diameter of 0.0 μm or more than 4 μm, and a microcapsule pigment particle having a volume average particle diameter of 0.3 to 3.0 μm and a particle diameter of more than 4 μm. Mention may be made of microcapsule pigments that do not contain, and microcapsule pigments that do not contain microcapsule pigment particles having a volume average particle size of 0.5 to 3.0 μm and a particle size exceeding 4 μm.

When forming a printed image with an inkjet printer using multicolor inks such as cyan, magenta, yellow, and black, or multicolor ink compositions of the same color with different discoloration temperatures, all inks are used. If it is not ejected satisfactorily, it becomes difficult to form a print image with high definition and a wide variety of hues, or a print image whose appearance changes due to temperature changes. However, by setting the average particle size and particle size of the microcapsule pigment contained in the ink composition of each color as described above, the colorability of each ink composition, the ink dischargeability, and the droplets having a uniform diameter at the time of ink discharge Since the formability is good, it is possible to form a high-definition printed image with excellent color development, or to form a printed image whose appearance changes with changes in temperature.

The particle diameter and the volume average particle diameter are measured by determining the particle area using image analysis type particle size distribution measurement software "MacView" manufactured by Mountech Co., Ltd., and the projected area circle equivalent diameter (from the area of the particle area) (Heywood diameter) is calculated, and is the value measured as the average particle diameter of particles corresponding to equal volume spheres.
If all or most of the particles have a particle size of more than 0.2 μm, a particle size distribution measuring device (Beckman Coulter, Inc., product name: Multisizer 4e) is used to obtain an equivalent volume sphere by the Coulter method. It is also possible to measure as the average particle diameter of the particles.
Furthermore, a laser diffraction / scattering particle size distribution measuring device (device name: LA-300, manufactured by Horiba, Ltd.) was calibrated based on standard samples or the values measured using a measuring device by the Coulter method. Alternatively, the volume-based particle diameter and the average particle diameter (median diameter) may be measured.

The shape of the microcapsule pigment may have a non-circular cross section as well as a circular cross section.

The microcapsule pigments may be used alone or in combination of two or more.
When using a mixture in which two or more kinds of microcapsule pigments are used in combination, it is preferable that the average particle diameter and the particle diameter of the mixture satisfy the above-mentioned ranges.

(Ink composition)
The ink composition according to the present invention contains at least a microcapsule pigment, water, and a dispersant, has excellent dispersibility of the microcapsule pigment, and has good fluidity of the ink to facilitate ink ejection from the ink ejection portion, It is rich in color development and can form a high-definition reversible thermochromic image.

The content of the microcapsule pigment is, for example, 3% by mass or more and 30% by mass or less, preferably 5% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 15%, based on the total mass of the ink composition. It is not more than mass%. When the content rate of the microcapsule pigment is within the above range, aggregation of the microcapsule pigment is suppressed, and the ink ejection property from the ink ejection portion is easily improved.

(Dispersant)
The dispersant has a functional group having a charge having a sign opposite to the zeta potential value of the microcapsule pigment in the ink composition in the structure.
The dispersant has a functional group strongly adsorbed to the surface of the microcapsule pigment, thereby preventing the microcapsule pigments from approaching each other and aggregating, increasing the dispersibility of the microcapsule pigment, and improving the ink fluidity. .
For this reason, clogging of the ink flow path due to the agglomerates of the microcapsule pigments is suppressed, and the ink ejection from the ink ejection portion is improved, so that it is possible to form a high-definition image with rich color development. .

Specific examples of the dispersant include a styrene-maleic acid copolymer and an alkali neutralized product thereof, an olefin-maleic acid copolymer and an alkali neutralized product thereof, as a substance having a functional group having a negative charge in its structure. Examples thereof include acrylic polymer compounds and synthetic resins such as styrene-acrylic acid copolymer.
Examples of the substance having a positively charged functional group in its structure include dialkylaminoacrylic acid esters such as dimethylaminoethyl acrylate and diethylaminoethyl acrylate, dialkylaminomethacrylic acid esters such as dimethylaminoethyl methacrylate, dimethylaminostyrene and diethylamino. Dialkylaminostyrenes such as styrene and methylethylaminostyrene and quaternary ammonium derivatives thereof, methacryloxyethyltrimethylammonium chloride, methacrylamidopropyltrimethylammonium chloride, 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, vinylbenzyltrimethylammonium chloride And other unsaturated vinyl monomers (cationic resin It can be mentioned copolymers of the illustrated ones) and as used in obtaining the John emulsion polymerization.

Among the dispersants, in consideration of improving the dispersibility of the microcapsule pigment, as the substance having a functional group having a negative charge in its structure, an olefin-maleic acid copolymer and its alkali-neutralized product are used. , And acrylic polymer compounds are preferable, and acrylic polymer compounds are particularly preferable. As the acrylic polymer compound, it is possible to use substances such as polyacrylic acid, acrylic acid-maleic acid copolymer, acrylic urethane copolymer, and alkali-neutralized products thereof, more preferably a carboxyl group. And an acrylic polymer compound having a comb structure having a carboxyl group in its side chain. A particularly preferred dispersant is an acrylic polymer compound having a comb structure having a plurality of carboxyl groups in its side chain, and specific examples thereof include product names: Sols Perth 43000, acrylic polymer compounds manufactured by Nippon Lubrizol Co., Ltd., and the like. Can be mentioned.

Further, as the substance having a functional group having a positive charge in its structure, dialkylaminoacrylic acid esters such as dimethylaminoethyl acrylate and diethylaminoethyl acrylate, and dialkylaminomethacrylic acid esters such as dimethylaminoethyl methacrylate are preferable.

The content of the dispersant is 0.01, based on the total mass of the ink composition, in consideration of suppressing excessive thickening of the ink composition and improving dispersibility of the microcapsule pigment. It is preferably contained in an amount of 2 to 2% by mass, more preferably 0.1 to 1.5% by mass.

(Additive)
The ink composition may contain the following components, if necessary. Specifically, ethylene glycol, propanediol, butanediol, pentanediol, diethylene glycol, glycerin, polyethylene glycol, polypropylene glycol, radical polymerizable compound, polyvinyl alcohol, polyvinylpyrrolidone, urethane resin, styrene-butadiene resin, alkyd resin, Sulfoamide resin, maleic acid resin, polyvinyl acetate resin, ethylene vinyl acetate resin, vinyl chloride-vinyl acetate resin, copolymer of styrene and maleic acid ester, styrene-acrylonitrile resin, cyanate-modified polyalkylene glycol, ester gum, xylene resin , Urea resin, urea aldehyde resin, phenol resin, alkylphenol resin, terpene phenol resin, rosin resin and its hydrogenated compounds, rosin phenol resin Fixing agent for polyvinyl alkyl ether, polyamide resin, polyolefin resin, nylon resin, polyester resin, cyclohexanone resin, water-soluble inorganic salt, surfactant, antiseptic agent, rust preventive, mildew proofing agent, antioxidant, ultraviolet ray Examples include conventionally known substances such as an absorber, a polymerization initiator, a chelating agent, a pH adjuster, a viscosity adjuster, and a shear thinning agent.
Among the above components, when a radical polymerizable compound and a radical polymerization initiator are used in the ink composition, when the printed image is irradiated with light, particularly UV light, the radical polymerizable compound is immediately polymerized to form an ink composition. Since the object quickly adheres to the surface to be printed, the fixability of the printed image can be further enhanced.

Radical polymerizable compounds include (meth) acrylates, (meth) acrylamides, aromatic vinyls, allyl compounds, N-vinyl compounds, vinyl esters (vinyl acetate, vinyl propionate, vinyl versatate, etc.), allyl Esters (allyl acetate, etc.), halogen-containing monomers (vinylidene chloride, vinyl chloride, etc.), vinyl ethers (methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxy vinyl ether, 2-ethylhexyl vinyl ether, methoxyethyl vinyl ether, cyclohexyl vinyl ether, chloro) Examples thereof include ethyl vinyl ether), vinyl cyanide ((meth) acrylonitrile etc.) and olefins (ethylene, propylene etc.). In the present specification, "(meth) acrylate" when referring to both or any of "acrylate" and "methacrylate" and "(meth)" when referring to both or any of "acrylic" and "methacryl" "Acrylic" may be described.

In addition, as the radical polymerization initiator, aromatic ketones, aromatic onium salt compounds, organic peroxides, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds , A compound having a carbon-halogen bond, and the like.

The viscosity of the ink composition can be adjusted to any value as long as the ink composition can be ejected well from the ink ejecting portion, but it is preferably 2 to 30 mPa when measured at a rotation speed of 30 rpm. · S is preferable, and 3 to 20 mPa · s is more preferable.
When the viscosity is set to the above-mentioned value, ink is easily ejected, rich in color developability, and a high-definition image is easily formed.
The viscosity can be measured at 20 ° C. using a BL type viscometer (product name: TVB-M type viscometer, L type rotor, manufactured by Toki Sangyo Co., Ltd.).

The surface tension of the ink composition is preferably 20 to 50 mN / m, and more preferably 20 to 35 mN / m. By setting the surface tension within the above numerical range, it becomes easy to enhance the permeability of the ink composition and improve the drying property of the image.
The surface tension is obtained by measuring the surface tension using a surface tension measuring instrument manufactured by Kyowa Interface Science Co., Ltd. in a 20 ° C. environment using a glass plate by the vertical plate method.

The pH value of the ink composition is preferably 4 to 8 at 20 ° C., more preferably 5 to 7 in consideration of improving the stability of the ink composition over time.

The aqueous ink composition according to the present invention can be produced by using various stirrers such as a propeller stirrer, a homodisper, or a homomixer, and various dispersers such as a bead mill.
As an example of a specific manufacturing method, there can be mentioned a manufacturing method in which a microcapsule pigment, water and an additive are mixed to prepare a microcapsule pigment dispersion liquid, and then the dispersant is mixed.
In addition, a manufacturing method in which the additives are mixed after mixing the microcapsule pigment, water and the dispersant can also be mentioned.

The water-based ink composition according to the present invention is used for a writing instrument and an inkjet printer printing machine.

(Writing instrument)
The ink composition of the present invention is preferably used for writing instruments.
As the writing instrument, a direct liquid type ballpoint pen, a marking pen, a fountain pen, etc. can be exemplified.
Further, as the writing instrument, various tips are attached to the writing tip, ink is directly stored inside the barrel (ink storage section), and a comb-shaped ink flow rate adjusting member (pen core) made of synthetic resin is interposed. Marking pens, ballpoint pens, and fountain pens having a structure can be mentioned.

Of the tips, for example, a fiber tip, a felt tip, a plastic tip, a writing brush, or the like can be applied as the marking pen tip, and as the ballpoint pen tip, the vicinity of the tip of the metal pipe is pressed and deformed inward from the outer surface. Chip that holds the ball in the ball holding part, chip that holds the ball in the ball holding part formed by cutting a metal material with a drill, etc., resin ball inside the metal or plastic chip A chip provided with a seat, or a ball held on the chip and biased forward by a spring body can be applied. As the ball, cemented carbide, stainless steel, ruby, ceramic, resin, rubber, etc. can be applied, and those having a diameter of 0.1 mm to 1.0 mm are preferably used.

As the fountain pen-shaped tip (pen body), a metal plate such as a stainless steel plate or a gold alloy plate that is cut into a tapered shape and is bent or curved, or a pen-shaped resin molded product can be applied. . The pen body may be provided with a slit at the center or a ball portion at the tip.

As the material of the pen core, any general-purpose polycarbonate, polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, or the like can be used as long as it is a synthetic resin that can be injection-molded into a structure in which a large number of discs are formed in a comb groove shape. However, an acrylonitrile-butadiene-styrene copolymer is preferable because it has particularly high moldability and can easily obtain pen core performance.

(inkjet printer)
The ink composition according to the present invention may be used in an inkjet printer.
The inkjet printer was not ejected from the ink containing portion containing the ink composition, the printer head, the ink supply channel for supplying ink from the ink containing portion to the printer head, and the nozzle (ink ejecting portion) of the printer head. An ink recovery channel for returning ink from the printer head to the ink supply channel is provided, and the ink is circulated through the ink supply channel, the printer head, and the ink recovery channel.

Inkjet printers prevent ink from accumulating in the ink flow path (ink supply flow path and ink recovery flow path) and the printer head due to ink circulation and agglomeration of the microcapsule pigments, and from the nozzles of the printer head. Ink ejection property is improved.

In consideration of suppressing the aggregation of the microcapsule pigment, it is preferable that the printer head be provided with a flow path for ink circulation in the printer head.
Since the printer head is provided with the above flow path, it is possible to easily circulate the ink in the printer head during the ink circulation and to suppress the ink retention in the printer head, so that the microcapsule pigment aggregates in the printer head. It is easy to suppress that.
The inkjet printer includes the above-mentioned mechanism, and the structure of the apparatus is not limited as long as ink circulation is possible, and may include a deaeration mechanism, a heating mechanism, and the like.

The ink ejection method of the printer head is a known method, for example, a charge control method in which ink is ejected by using electrostatic attraction, a drop-on-demand method (pressure pulse method) in which vibration pressure of a piezo element is used, or an electric method. An acoustic inkjet method in which a signal is converted into an acoustic beam to irradiate the ink and the ink is ejected by using radiation pressure, a thermal ink jet (Bubble Jet (registered trademark) that uses the pressure generated by heating the ink to form bubbles ) Method etc. can be adopted suitably.

-The nozzle of the printer head has an inner diameter that allows good ejection of the ink composition. The inner diameter preferably has an inner diameter of 10 μm to 100 μm, and more preferably has an inner diameter of 10 to 50 μm, in consideration of improving the color developability and fineness of the printed image. The more preferable inner diameter of the nozzle is 10 to 30 μm.

When the ink composition contains a radical polymerizable compound and a radical polymerization initiator, the inkjet printer preferably includes a UV light irradiation unit.
By irradiating the printed image formed by the ink composition with UV light, the radically polymerizable compound is polymerized and the ink composition is quickly fixed to the printed surface, so that the fixability of the printed image can be improved. .
Further, the ink container may be capable of mounting the ink container.

An example of the inkjet printer according to this embodiment will be described below with reference to the drawings.

FIG. 3 is a schematic diagram illustrating an example of the configuration of an inkjet printer including an ink circulation mechanism. The ink supply device 1 shown in FIG. 3 includes an ink container 2, a printer head 3, an ink supply channel 4a, a pump 5, a wiping means 6, and a head for returning ink to the ink supply channel 4a to circulate the ink. The flow path 4b (flow path on the left side of the printer head 3 in the drawing) is provided.
The printer head 3 is formed with an ink ejection portion 8 of a plurality of nozzles 7 for ejecting the ink composition 9 on one surface, and the ink composition 9 in the nozzle 7 is extruded by a piezoelectric element or the like, whereby The ink composition 9 is discharged from the ink discharge port 8. Further, the printer head 3 includes an ink intake port 3b for taking in the ink composition from the ink supply flow path 4a, an ink exhaust port 3a for exhausting the ink composition to the ink recovery flow path 4b, a plurality of nozzles 7, and an ink intake port. It has an internal flow path 3c that connects the inlet 3b and the ink discharge port 3a.

The ink circulation path is a path that circulates the ink composition 9 by connecting the ink intake port 3b and the ink discharge port 3a of the printer head 3 with an ink flow path. In FIG. 3, an ink supply flow path 4a, an internal flow path 3c of the printer head 3, and an ink recovery flow path 4b form an annular path to circulate the ink composition 9. While the printing is stopped, the ink composition 9 is circulated in the annular path in order to prevent the microcapsule pigments of the ink composition 9 from settling and aggregating the microcapsule pigments in the printer head 3. Is preferred. For the ink supply flow path 4a and the ink recovery flow path 4b, for example, pipes having a diameter of 1 to 10 mm can be used, and the material can be silicon pipes. The length of one round of the circulation path may be 800 mm to 10 m, further 1 to 9 m, and particularly 3 to 8 m.

The pump 5 is arranged on the upstream side of the printer head 3 in the ink supply flow path 4 a and supplies the ink composition 9 to the printer head 3. By supplying the ink composition 9 to the printer head 3 and circulating the ink composition 9 in the annular path, the ink composition 9 in the internal flow path 3c of the printer head 3 flows, and the ink composition in the printer head 3 flows. It is possible to prevent the microcapsule pigment components of Item 9 from settling and aggregating the microcapsule pigment components.

During ink jet printing, it is preferable to circulate the ink composition with a pump. Further, while the inkjet printing is stopped, it is preferable that a cap (not shown) is attached to the nozzle discharge portion to circulate the ink composition.

Reversible thermal discoloration by using an inkjet printer to form an appropriate printed image by spraying on any target object such as paper, synthetic paper, coated paper, plastic sheet, plastic, wood, metal, glass, etc., fabric, non-woven fabric, etc. Printed matter is obtained.

(Ink container)
The ink composition may be contained in an ink container.
The ink container is not particularly limited as long as it can contain the ink composition, and can be selected from various constituent materials and forms.
Examples of the constituent material include plastics such as polyethylene terephthalate (PET) and polypropylene (PP), various metals (including alloys), and polyethylene, ethylene vinyl acetate copolymer, and polyolefin such as polypropylene. it can. Further, the present invention is not limited to these, and may be a polymer obtained by blending or laminating the above-mentioned polymers in an appropriate ratio, a film thereof, or the like.
Examples of the form of the ink container include a pack, a bottle, a tank, a bottle, and a can.

The ink container may be provided with a plurality of ink storage chambers that are independent of each other, and each of the chambers may store a plurality of colors of ink composition so that the inks in the chambers have different colors.
Also, a plurality of ink containers can be combined to form an ink container set. The ink container set may be composed of the same color ink or plural colors of ink.
Further, the ink container may have a structure that allows it to be attached to an inkjet printer and supply the ink composition from the ink container to the ink flow path.

Examples will be described below. The following numerical values in the examples are numerical values obtained by measuring with the following measuring machine.
-Average particle diameter and particle diameter of the microcapsule pigment The average particle diameter in the present invention uses an average particle diameter (median diameter) on a volume basis, but in measuring the particle diameter, image analysis type particle size distribution measurement software (MacView, Mountec Co., Coulter method (electric detection zone method) particle size measuring device, laser diffraction / scattering type particle size distribution measuring device (device name: LA-300, manufactured by Horiba, Ltd.) can be used.
When the laser diffraction / scattering particle size distribution measuring device is used, the measurement is performed by a measuring device which is calibrated by another measuring device such as a standard sample or the Coulter method (electrical detection zone method).
If there is a difference in the numerical values obtained depending on the measuring machine, the numerical value obtained using the image analysis type particle size distribution measurement software will be given priority.
In this example, a laser diffraction / scattering particle size distribution measuring device (device name: LA-300, manufactured by Horiba, Ltd.) calibrated by the Coulter method (electrical detection zone method) was used to measure the volume. The average particle size (median size) and the particle size were measured. However, in Examples 6 and 14, the average particle size (median size) and the particle size on a volume basis were measured using image analysis type particle size distribution measurement software (MacView, manufactured by Mountech Co., Ltd.).

-Zeta potential of microcapsule pigment The zeta potential in the present invention can be measured by a measuring device such as a streaming potential measuring device (Stabino PMX400, manufactured by Microtrac Bell Co., Ltd.).
The above-mentioned measuring machine measures streaming potential, calculation of zeta potential, and measurement of pH value.
The zeta potential measuring device can be used as long as it can measure the zeta potential at a specific pH value by linking the zeta potential display and the pH meter.

-Measurement conditions of streaming potential Sample: Microcapsule pigment dispersion prepared according to the following: Sample amount during measurement: 10 ml
Sample temperature during measurement: 20 ℃
Measuring machine piston size: 400μm
Number of measurements: The same sample is repeatedly measured until a zeta potential of 20 is obtained when a pH value of 7 is measured by the measuring instrument. The number average value of the individual pieces is the zeta potential of the microcapsule pigment.
Although water is used as a measurement solvent, electricity of less than 1000 μS / m at 25 ° C. generated by pure water or an ion-exchanged water generator (product name: pure water production apparatus Autostill WA33, manufactured by Yamato Scientific Co., Ltd.). Ion-exchanged water having conductivity can be used.
In this example, ion-exchanged water produced by the ion-exchanged water producing device was used to measure the zeta potential at pH = 7 by a streaming potential measuring device.

(Preparation procedure of microcapsule pigment dispersion)
1. 10 g of the microcapsule pigment and 90 g of ion-exchanged water are mixed with stirring using a disper at a rotation speed of 2000 rpm for 15 minutes.
The mixture obtained in 2.1 is diluted 10 times with deionized water.
Sonicate the dilution obtained in 3.2 for 5 minutes. (Complete)

・ Viscosity of ink composition Product name: TVB-M type viscometer, L type rotor, manufactured by Toki Sangyo Co., Ltd.

Example 1
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution in which 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent were mixed as a wall film material was emulsified and dispersed in a 10% polyvinyl alcohol aqueous solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.71 μm, and the maximum particle size was 2.29 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 6.3 mV.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.10 parts and 79.08 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
As a result of measuring the viscosity of the water-based ink composition, it was 5.46 mPa · s at 20 ° C. and a rotation speed of 30 rpm.

The above water-based ink composition was contained in an ink container (fountain pen cartridge: product name IRF-12S, manufactured by Pilot Corporation).
The ink container was housed in a fountain pen (product name: Kakuno, manufactured by Pilot Corporation), and writing was performed on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
From the handwriting in the colored state, good coloring was visually recognized and the outline was clear.

Example 2
(Preparation of microcapsule pigment)
As component (a), 9 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthen-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution of the cresol novolac type epoxy resin 10.0 parts as a wall film material and 50.0 parts of a co-solvent was melted at a high temperature, emulsified and dispersed in a 10% gelatin aqueous solution to form fine droplets, and heated. After continuing the stirring, 5.0 parts of the water-soluble aliphatic modified amine was added, and the stirring was further continued to obtain a microcapsule pigment suspension.
After removing coarse particles from the suspension by a centrifuge, the suspension was filtered by a filter press to obtain a microcapsule pigment.
The volume average particle size of the microcapsule pigment was 0.71 μm, and the maximum particle size was 2.60 μm. (Median diameter)
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 6.9 was 18.3 mV.
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, preservative (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (glycolic acid) 0.20 parts and 78.98 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).

The above water-based ink composition was placed in a fountain pen of the same type as the fountain pen used in Example 1, and writing was performed on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
From the handwriting in the colored state, good coloring was visually recognized and the outline was clear.

Example 3
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.05 parts and 79.13 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).

Example 4
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0 20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (glycolic acid) 0 30 parts and 78.88 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).

The above water-based ink composition was placed in a fountain pen and written on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
From the handwriting in the colored state, good coloring was visually recognized and the outline was clear.

Example 5
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution in which 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent were mixed as a wall film material was emulsified and dispersed in a 10% polyvinyl alcohol aqueous solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 5.26 μm, and the maximum particle diameter was 7.69 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 4.8 mV.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.10 parts and 79.08 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).

The above water-based ink composition was placed in a fountain pen of the same type as the fountain pen used in Example 1, and writing was performed on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
Good color was visually recognized from the handwriting in the color-developed state, but some fading occurred and the outline was partially unclear.

Example 6
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution of 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a co-solvent as a wall film material was dissolved at a high temperature, emulsified and dispersed in an aqueous 12% polyvinyl alcohol solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.05 μm, and the maximum particle diameter was 0.61 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion liquid was 7.0 was 6.8 mV.

The above water-based ink composition was placed in a fountain pen of the same type as the fountain pen used in Example 1, and writing was performed on copy paper.
Magenta handwriting is visible on the copy paper at room temperature (25 ° C), and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state immediately after writing at -25 ° C (magenta color). It has returned to the state where the handwriting was formed).
The handwriting in the colored state had a clear outline, but the color was slightly pale.

Example 7
(Preparation of microcapsule pigment)
As component (a), 9 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthen-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution of 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a co-solvent as a wall film material was dissolved at a high temperature, emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 1.73 μm, and the maximum particle diameter was 9.94 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 2.8 mV.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.10 parts and 79.48 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).

Example 8
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 12.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.10 parts and 77.08 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The viscosity of the water-based ink composition was measured using a BL type viscometer (product name: TVB-M type viscometer, L type rotor, manufactured by Toki Sangyo Co., Ltd.). As a result, it was 6 at 20 ° C. and a rotation speed of 30 rpm. It was 0.74 mPa · s.

The water-based ink composition, a large number of discs are arranged in parallel with a comb-shaped gap between them, a slit-shaped ink guide groove longitudinally extending through the discs and a ventilation groove thicker than the groove are provided, Direct liquid type ball-point pen (product name: Hitec Point V5 that guides ink to a pen tip in the form of a ball-point pen through the pen core that has an ink guide core for guiding ink from the ink storage section to the pen tip at the shaft center. Grip, manufactured by Pilot Corporation, Inc.) and written on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
From the handwriting in the colored state, good coloring was visually recognized and the outline was clear.

Example 9
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 15.00 parts, preservative (pyridine-2-thiol 1-oxide, sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts, pH adjuster (citric acid) 0.10 parts and 74.08 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid.
An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
As a result of measuring the viscosity of the aqueous ink composition, it was 9.12 mPa · s at 20 ° C. and a rotation speed of 30 rpm.

A water-based ink composition, in which an ink occlusion body made of a fiber bundle is built in the barrel, and a marking pen tip made of a fusion-bonded body of heat-fusible fibers in which a capillary gap is formed is attached to the barrel. Then, the ink occlusion body of the marking pen in which the ink occlusion body and the chip were connected was impregnated, and writing was performed on copy paper.
Magenta handwriting is visible on copy paper at room temperature (25 ° C), and reversible thermochromic image (handwriting) is erased by heating to 60 ° C or higher, and at -25 ° C or lower immediately after writing. It returned to (a state in which magenta handwriting was formed).
From the handwriting in the colored state, good coloring was visually recognized and the outline was clear.

Example 10
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.0 parts, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10.0 parts, 2-hydroxy-3- (4-benzoyl) Phenoxy) -N, N, N-trimethyl-1-propanammonium chloride 1.0 part, ethylene glycol 5.0 parts, antifungal agent (product name: Proxel XL-2, manufactured by Zeneca Corporation) 0.2 part, 0.5 parts of antifoaming agent (silicon type, product name: SN deformer 381, manufactured by San Nopco Co., Ltd.), 0.10 parts of pH adjusting agent (phosphoric acid) and 60.3 parts of water are uniformly mixed to obtain a microcapsule pigment. A dispersion was obtained. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
As a result of measuring the viscosity of the water-based ink composition, it was 5.68 mPa · s at 20 ° C. and a rotation speed of 30 rpm.
The aqueous ink composition was contained in an ink container (polypropylene bottle).

(inkjet printer)
A printer head including an ink storage unit, a UV light irradiation unit for irradiating a print image with UV light, an ink supply channel for supplying ink from the ink storage unit to the printer head, and ink for the printer head An ink recovery flow path for returning the ink from the head to the ink supply flow path, and connecting the ink storage section, the printer head, the ink supply flow path, and the ink recovery flow path to the ink supply flow path, the printer head, and The water-based ink composition was stored in the ink storage portion using an inkjet printer that enables ink circulation through the ink recovery channel.

The printer head has a nozzle having an inner diameter of 25 μm, an ink inlet for taking in the ink composition from an ink supply channel, an ink outlet for discharging the ink composition to an ink recovery channel, a nozzle, and an ink inlet. , And a printer head internal flow path communicating with the ink discharge port.

The circulation mechanism connects the pump and the ink recovery channel between the ink storage section of the printer and the printer head between the ink storage section and the printer head to enable ink circulation. And The flow rate of the ink composition in the flow channel (hereinafter referred to as "ink flow rate") was controlled by a pump. The ink supply channel and the ink recovery channel were made of silicone rubber.

Printing on recording paper (copy paper) and UV light irradiation were performed using an inkjet printer to obtain a reversible thermochromic print.
During printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visually recognized at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state before erasing (magenta) at -25 ° C or lower. The state in which color printing was formed) was restored.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 11
(Preparation of microcapsule pigment)
As component (a), 9 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthen-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution which was dissolved at room temperature and mixed with 35.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent was emulsified and dispersed in an 8% polyvinyl alcohol aqueous solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 1.02 μm, and the maximum particle size was 3.91 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion liquid was 7.0 was 6.8 mV.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.0 parts, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10.0 parts, 2-hydroxy-3- (4-benzoyl) Phenoxy) -N, N, N-trimethyl-1-propanammonium chloride 1.0 part, ethylene glycol 5.0 parts, antifungal agent (product name: Proxel XL-2, manufactured by Zeneca Corporation) 0.2 part, 0.5 parts of antifoaming agent (silicon type, product name: SN deformer 381, manufactured by San Nopco Co., Ltd.), 0.10 parts of pH adjusting agent (phosphoric acid) and 60.3 parts of water are uniformly mixed to obtain a microcapsule pigment. A dispersion was obtained. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

(inkjet printer)
Using the inkjet printer used in Example 10, the aqueous ink composition was stored in the ink storage portion.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state before use (magenta color) at -25 ° C or lower. The state in which the print characters of (1) have been formed) has been restored.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 12
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution of 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a co-solvent as a wall film material was dissolved at a high temperature, emulsified and dispersed in an aqueous 12% polyvinyl alcohol solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.55 μm, and the maximum particle size was 1.55 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion liquid was 7.0 was 8.2 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state before use (magenta color) at -25 ° C or lower. The state in which the print characters of (1) have been formed) has been restored.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 13
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 5 was prepared.

(inkjet printer)
Using the inkjet printer used in Example 10, the ink composition was stored in the ink storage portion.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state before use (magenta color) at -25 ° C or lower. The state in which the print characters of (1) have been formed) has been restored.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, but some fading occurred, and the start point, end point, and contour were partially unclear.

Example 14
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 6 was prepared.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visually recognized on the printed matter at room temperature (25 ° C), and the reversible thermochromic image disappears when heated to 60 ° C or more, and the state before use (magenta color of -25 or less) It returned to the state where printed characters were formed).
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
In the color-developed state, the start point, the end point, and the outline were clear, but the color was slightly light.

Example 15
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 7 was prepared.

Example 16
(Preparation of microcapsule pigment and aqueous ink composition)
The microcapsule pigment of Example 10 and the aqueous ink composition were used.
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

(inkjet printer)
The ink composition was stored in the inkjet printer used in Example 10.

Recording was performed on a recording paper (coated paper, product name: Raicho Coat, manufactured by Chuetsu Chemical Industry Co., Ltd.) using the above inkjet printer to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to flow the ink in the ink flow path and the printer head.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state before use (magenta color) at -25 ° C or lower. The state in which the print of (1) was formed) was returned. The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 17
(Preparation of microcapsule pigment and aqueous ink composition)
The microcapsule pigment of Example 10 and the aqueous ink composition were used.
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

Printing was performed on a recording material (resin plate, thickness 5 mm, made of acrylic resin) using the above inkjet printer to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to flow the ink in the ink flow path and the printer head.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state immediately after printing at -25 ° C (magenta color printing is It has returned to the formed state).
The reversible thermochromic image was formed by setting the decolored recording material again in the ink jet printer and printing was carried out, and the printed material could be used repeatedly.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 18
(Preparation of microcapsule pigment and aqueous ink composition)
The microcapsule pigment of Example 10 and the aqueous ink composition were used.
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

The ink jet printer was used to print on the side wall of a recording material (polypropylene resin bottle) to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to flow the ink in the ink flow path and the printer head.
The reversible thermochromic image of magenta color is visually recognized at room temperature (25 ° C) in the printed matter, and the reversible thermochromic image disappears when hot water of 60 ° C or higher is poured, and the state immediately after printing (magenta color of -25 ° C or less). It returned to the state where the print was formed.
The reversible thermochromic image was formed by setting the decolored recording material again in the ink jet printer and printing was carried out, and the printed material could be used repeatedly.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 19
(Preparation of microcapsule pigment)
7- [2- (acetylamino) -4- (diethylamino) phenyl] -7- (2-methyl-1-propyl-1H-indol-3-yl) furo [3,4-b] as component (a) Pyridine-5 (7H) -one 3.0 parts, 1,1'-bis (4'-hydroxyphenyl) n-nonane 15.0 parts as component (b), 4-benzyloxy caprate as component (c) A solution in which a reversible thermochromic composition composed of 50.0 parts of phenylethyl was uniformly heated and dissolved, and 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent were mixed, Emulsified and dispersed in a 10% aqueous solution of polyvinyl alcohol to form fine droplets, continued stirring while heating, then add 2.5 parts of water-soluble aliphatic modified amine, and continue stirring to suspend microcapsule pigment A liquid was obtained.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.73 μm, and the maximum particle diameter was 2.60 μm. (Median diameter)
The completely decolorized temperature of the microcapsule pigment is 60 ° C., the completely developed temperature is −25 ° C., and the cyan color changes to colorless due to the temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 6.9 was 7.6 mV.

Printing was performed on a recording paper (copy paper) using the above inkjet printer to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to flow the ink in the ink flow path and the printer head.
A cyan color reversible thermochromic image is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C or higher. The state in which the print of (1) was formed) was returned.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 20
(Preparation of microcapsule pigment)
3.0 parts of 4- [2,6-bis (2-ethoxyphenyl) -4-pyridinyl] -N, N-dimethylbenzenamine as component (a) and 2,2-bis (4- as component (b) A reversible thermochromic composition composed of 9.0 parts of (hydroxyphenyl) hexafluoropropane and 50.0 parts of 4-benzyloxyphenylethyl caprate as the component (c) was uniformly dissolved by heating to produce an aromatic wall film material. A solution prepared by mixing 40.0 parts of a polyvalent isocyanate prepolymer and 50.0 parts of a cosolvent was emulsified and dispersed in a 10% polyvinyl alcohol aqueous solution to form fine droplets, and the mixture was stirred while heating and then water-soluble. 2.5 parts of a modified aliphatic aliphatic amine was added and stirring was continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.70 μm, and the maximum particle size was 2.60 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from yellow to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.2 was 7.4 mV.

(Preparation of water-based ink composition for inkjet)
Microcapsule pigment (pre-cooled and developed color) 10.0 parts, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10.0 parts, 2-hydroxy-3- (4-benzoyl) Phenoxy) -N, N, N-trimethyl-1-propanammonium chloride 1.0 part, ethylene glycol 5.0 parts, antifungal agent (product name: Proxel XL-2, manufactured by Zeneca Corporation) 0.2 part, 0.5 parts of antifoaming agent (silicon type, product name: SN deformer 381, manufactured by San Nopco Co., Ltd.), 0.10 parts of pH adjusting agent (phosphoric acid) and 60.3 parts of water are uniformly mixed to obtain a microcapsule pigment. A dispersion was obtained. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

Printing was performed on a recording paper (copy paper) using the above inkjet printer to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to flow the ink in the ink flow path and the printer head.
A yellow reversible thermochromic image is visually recognized at room temperature (25 ° C.) on the printed matter, and the reversible thermochromic image disappears when heated to 60 ° C. or higher. The state in which a color print image was formed) was restored.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 21
(Preparation of microcapsule pigment)
7.0 parts of 2- (2-chloroanilino) -6-di-n-butylaminofluorane as component (a) and 1,1'-bis (4'-hydroxyphenyl) n-dodecane 15 as component (b) 0.04 parts, and a reversible thermochromic composition composed of 50.0 parts of 4-benzyloxyphenylethyl caprate as the component (c) was uniformly heated and dissolved, and an aromatic polyvalent isocyanate prepolymer 40. A solution prepared by mixing 0 parts and 50.0 parts of a cosolvent was emulsified and dispersed in a 10% aqueous solution of polyvinyl alcohol to form fine droplets, and the mixture was stirred while heating, and then water-soluble aliphatically modified amine 2. 5 parts was added and stirring was continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.78 μm, and the maximum particle diameter was 2.60 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 60 ° C., the complete color development temperature is −25 ° C., and the color changes from black to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 7.7 mV. (

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of black color is visually recognized on the printed matter at room temperature (25 ° C), and the reversible thermochromic image disappears when heated to 60 ° C or higher, and immediately after printing (black color at -25 ° C or lower). The state in which the print of (1) was formed) was returned.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 22
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) 2,2-bis (4-hydroxyphenyl) hexafluoropropane (4.0 parts), 4,4 ′-(2-ethylhexylidene) bisphenol (11.0 parts), (c) component glutaric acid di-4 A reversible thermochromic composition consisting of 50.0 parts of benzyloxyphenylethyl was uniformly heated and dissolved, and 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent were mixed. The solution was emulsified and dispersed in a 10% aqueous solution of polyvinyl alcohol to form fine droplets, and the mixture was stirred while heating, then 2.5 parts of a water-soluble aliphatic modified amine was added, and the mixture was further stirred. To obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.92 μm, and the maximum particle size was 3.52 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 87 ° C., the complete color development temperature is −35 ° C., and the color changes from magenta to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 6.9 was 7.0 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
A reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 87 ° C or higher, and the state immediately after printing (magenta color) at -35 ° C or lower. The state in which the print of (1) was formed) was returned.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 23
(Preparation of microcapsule pigment)
As component (a), 6.0 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 10.0 parts of 1,1′-bis (4′-hydroxyphenyl) 2-ethylhexane as a component and 50.0 parts of n-nonyl palmitate as a component (c) was uniformly added. A solution in which 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent were mixed as a wall film material was emulsified and dispersed in a 10% polyvinyl alcohol aqueous solution to form fine droplets, and added. After continuing stirring while warming, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 1.02 μm, and the maximum particle diameter was 3.72 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 30 ° C. and a complete color development temperature of 18 ° C. The color changes from magenta to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 6.9 was 6.8 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visually recognized at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 30 ° C or more, and the state immediately after printing (magenta color of 18 ° C or less). It returned to the state where printed characters were formed).
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 24
(Preparation of microcapsule pigment)
As component (a), 9 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthen-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 10.0 parts of 1,1′-bis (4′-hydroxyphenyl) 2-ethylhexane as a component and 50.0 parts of 4-methylbenzyl laurate as a component (c) is uniformly added. A solution in which 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a co-solvent were mixed by heating and emulsified and dispersed in a 10% polyvinyl alcohol aqueous solution to form fine droplets, After continuing stirring while heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.87 μm, and the maximum particle size was 2.57 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 27 ° C and the complete color development temperature is -25 ° C, and the color changes from magenta to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion liquid was 7.0 was 7.5 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color is visible at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 27 ° C or higher, and the state immediately after printing (magenta color) at -25 ° C or lower. The state in which the print characters of (1) have been formed) has been restored.
From printing at room temperature, good color development was visually recognized, and the start point, end point, and outline were clear.

Example 25
(Preparation of microcapsule pigment)
A microcapsule pigment similar to that in Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.0 parts, organic pigment (pigment blue 15: 3) 0.2 part, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10 0.0 part, 2-hydroxy-3- (4-benzoylphenoxy) -N, N, N-trimethyl-1-propanammonium chloride 1.0 part, ethylene glycol 5.0 part, antifungal agent (product name: proxel XL-2, manufactured by Zeneca Co., Ltd.) 0.2 part, antifoaming agent (silicon type, product name: SN deformer 381, manufactured by San Nopco Co., Ltd.) 0.5 part, pH adjuster (phosphoric acid) 0.10 part and 60.1 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The aqueous ink composition was contained in the same ink bottle as the ink bottle used in Example 10.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
A purple reversible thermochromic image is visually recognized on the printed matter at room temperature (25 ° C), and the reversible thermochromic image changes to cyan color when heated to 60 ° C or higher, and immediately after printing at -25 ° C or lower (purple color). The state in which the print of (1) was formed) was returned.
From the print, good color development was visually recognized, and the start point, end point, and outline were clear.

Example 26
(Preparation of microcapsule pigment)
Preparation of Microcapsule Pigment A As component (a), 7- [2- (acetylamino) -4- (diethylamino) phenyl] -7- (2-methyl-1-propyl-1H-indol-3-yl) furo [ 3,4-b] Pyridin-5 (7H) -one 3.0 parts, 4,4 '-(2-ethylhexylidene) bisphenol 15.0 parts as component (b), and capric acid as component (c) A reversible thermochromic composition composed of 50.0 parts of 4-benzyloxyphenylethyl is uniformly dissolved by heating, and 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a cosolvent are mixed as a wall film material. The resulting solution was emulsified and dispersed in a 10% aqueous solution of polyvinyl alcohol to form fine droplets, and the mixture was continuously stirred while heating, then 2.5 parts of a water-soluble aliphatic modified amine was added, and the mixture was further stirred to prepare a microscopic solution. A capsule pigment suspension was obtained. Microcapsule pigment A was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment A was 0.69 μm, and the maximum particle diameter was 2.27 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment A is 60 ° C., the complete color development temperature is −25 ° C., and the cyan color changes to colorless due to the temperature change.
Preparation of Microcapsule Pigment B 9-Ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one as component (a) 6. A reversible thermochromic composition comprising 0 part, 10.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as the component (b), and 50.0 parts of 4-methylbenzyl palmitate as the component (c). Is uniformly heated and dissolved, and a solution obtained by mixing 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent is emulsified in a 10% polyvinyl alcohol aqueous solution to form fine droplets. After dispersing and continuing stirring with heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
Microcapsule pigment B was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment B was 0.73 μm, and the maximum particle size was 2.60 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment B is 40 ° C. and the complete color development temperature is 5 ° C., and the color changes from magenta to colorless due to temperature change.
The zeta potential of the microcapsule pigment mixture obtained by mixing the microcapsule pigment A and the microcapsule pigment B in a mass ratio of 1: 1 was measured, and as a result, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.1 was 7 It was 0.6 mV.

(Preparation of water-based ink composition)
5.0 parts of microcapsule pigment A (pre-cooled and developed color), 5.0 parts of microcapsule pigment B (pre-cooled and developed color), 14.0 parts of morpholinoethyl (meth) acrylate 10.0 parts of piperazinoethyl (meth) acrylate, 1.0 part of 2-hydroxy-3- (4-benzoylphenoxy) -N, N, N-trimethyl-1-propanammonium chloride, 5.0 parts of ethylene glycol, antifungal Agent (product name: Proxel XL-2, manufactured by Zeneca Co., Ltd.) 0.2 part, antifoaming agent (silicon type, product name: SN Deformer 381, manufactured by San Nopco Co., Ltd.) 0.5 part, pH adjuster (phosphoric acid) ) 0.10 parts and 60.3 parts of water were uniformly mixed to obtain a microcapsule pigment dispersion liquid. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
A purple reversible thermochromic image is visually recognized at room temperature (25 ° C), and the reversible thermochromic image changes to cyan when heated to 40 ° C or higher, and the reversible thermochromic image is heated to 60 ° C or higher. The discolored image disappeared, and the reversible thermochromic image changed to magenta at -5 ° C or lower and returned to the state immediately after printing (state where purple print was formed) at -25 ° C or lower.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 27
(Preparation of microcapsule pigment)
4.5 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthene-12,1 '(3H) -isobenzofuran] -3'-one as component (a), (b) As components, 4.0 parts of 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 4.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol, and as component (c) stearyl caprate 32. A reversible thermochromic composition consisting of 5 parts and 17.5 parts of stearyl laurate is uniformly heated and dissolved, and 40.0 parts of an aromatic polyisocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent are mixed. The resulting solution was emulsified and dispersed in a 10% aqueous solution of polyvinyl alcohol so as to form fine droplets, and the mixture was stirred while heating, then 2.5 parts of a water-soluble aliphatic modified amine was added, and the stirring was continued. To obtain a microcapsule pigment suspension Te.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.85 μm, and the maximum particle diameter was 2.85 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 37 ° C., the complete color development temperature is 28 ° C., and the color changes from magenta to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment dispersion liquid, the zeta potential was 7.2 mV when the pH value of the microcapsule pigment dispersion liquid was 6.8.

(Preparation of water-based ink composition)
Microcapsule pigment 10.0 parts, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10.0 parts, 2-hydroxy-3- (4-benzoylphenoxy) -N, N, N-trimethyl 1.0 part of -1-propaneammonium chloride, 5.0 parts of ethylene glycol, 0.2 part of antifungal agent (product name: Proxel XL-2, manufactured by Zeneca Co., Ltd.), antifoaming agent (silicon type, product name: SN deformer 381 (manufactured by San Nopco Ltd.) 0.5 part, pH adjuster (phosphoric acid) 0.10 part and water 60.3 parts were uniformly mixed to obtain a microcapsule pigment dispersion liquid. An aqueous ink composition was prepared by mixing 0.40 parts of the microcapsule pigment dispersion and an acrylic polymer dispersant (product name: Sols Perth 43000, manufactured by Nippon Luvsol Co., Ltd.).
The aqueous ink composition was contained in a bottle having the same form as the ink container used in Example 10.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
During printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of magenta color was visually recognized on the printed matter at room temperature (25 ° C), and the reversible thermochromic image was erased by heating at 37 ° C or higher, and immediately after printing at room temperature (25 ° C). It returned to the state (state in which the magenta print image was formed).
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 28
(Preparation of microcapsule pigment)
3.0 parts of 3 ', 6'-bis [phenyl (3-methylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one as component (a), Consists of 8.0 parts of 4,4 '-(2-methylpropylidene) bisphenol as component (b), 15.0 parts of 2-methylpentyl stearate and 35.0 parts of 2-ethylhexyl stearate as component (c). A reversible thermochromic composition was uniformly heated and dissolved, and a solution prepared by mixing 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a cosolvent as a wall film material was added to a 10% polyvinyl alcohol aqueous solution to give a fine solution. The mixture was emulsified and dispersed in the form of drops, and stirring was continued while heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and the stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.85 μm, and the maximum particle diameter was 2.85 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 10 ° C and the complete color development temperature is 5 ° C, and the color changes from blue to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.1 was 7.3 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of the printed matter is in a decolored state at room temperature (25 ° C), and the blue reversible thermochromic image is visually recognized by cooling to 5 ° C or lower, and by heating to 10 ° C or higher. The reversible thermochromic image returned to the decolorized state.
In the print that developed color after cooling, good color was visually recognized, and the start point, end point, and outline were clear.

Example 29
(Preparation of microcapsule pigment)
3.0 parts of 3 ', 6'-bis [phenyl (3-methylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one as component (a), Reversible thermal discoloration consisting of 8.0 parts of 4,4 '-(2-methylpropylidene) bisphenol as component (b), 30.0 parts of n-nonyl palmitate and 20.0 parts of decyl myristate as component (c) Solution of a hydrophilic composition uniformly heated and mixed with 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent to form fine droplets in a 10% aqueous polyvinyl alcohol solution. After emulsifying and dispersing as described above, stirring was continued while heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
A microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.83 μm, and the maximum particle size was 2.81 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 20 ° C., the complete color development temperature is 15 ° C., and the color changes from blue to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.1 was 7.5 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of the printed matter is in a decolored state at room temperature (25 ° C), and a blue reversible thermochromic image is visually recognized by cooling to 15 ° C or lower, and by heating to 20 ° C or higher. The reversible thermochromic image returned to the decolorized state.
From the print that developed color after cooling, good color development was visually recognized, and the start point, end point, and outline were clear.

Example 30
(Preparation of microcapsule pigment)
3.0 parts of 3 ', 6'-bis [phenyl (3-methylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one as component (a), Reversible thermochromic composition consisting of 8.0 parts of 4,4 '-(2-methylpropylidene) bisphenol as the component (b), 37.5 parts of stearyl caprate and 12.5 parts of cetyl caprate as the component (c). The solution was uniformly heated and dissolved, and a solution prepared by mixing 40.0 parts of an aromatic polyvalent isocyanate prepolymer as a wall film material and 50.0 parts of a cosolvent was formed into fine droplets in a 10% aqueous polyvinyl alcohol solution. After emulsification and dispersion, and stirring was continued while heating, 2.5 parts of water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.91 μm, and the maximum particle diameter was 3.01 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 30 ° C and the complete color development temperature is 25 ° C, and the color changes from blue to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 6.9 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
A reversible thermochromic image of blue is visually recognized at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 30 ° C or more, and a state immediately after printing (blue at room temperature (25 ° C) The state in which the print characters of (1) have been formed) has been restored.
From the print that developed color after heating, good color development was visually recognized, and the start point, end point, and outline were clear.

Example 31
(Preparation of microcapsule pigment)
3.0 parts of 3 ', 6'-bis [phenyl (3-methylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one as component (a), Consists of 8.0 parts of 4,4 '-(2-methylpropylidene) bisphenol as component (b), 25.0 parts of 3-methylbutyl behenate and 25.0 parts of 2-methylpentyl behenate as component (c). A reversible thermochromic composition was uniformly heated and dissolved, and a solution prepared by mixing 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a cosolvent as a wall film material was added to a 10% polyvinyl alcohol aqueous solution to give a fine solution. The mixture was emulsified and dispersed in the form of drops, and stirring was continued while heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and the stirring was further continued to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle diameter of the microcapsule pigment was 0.94 μm, and the maximum particle diameter was 3.15 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 40 ° C. and the complete color development temperature is 35 ° C., and the color changes from blue to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment dispersion, the zeta potential when the pH value of the microcapsule pigment dispersion was 7.0 was 6.8 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
A blue reversible thermochromic image is visually recognized at room temperature (25 ° C) on the printed matter, and the reversible thermochromic image disappears when heated to 40 ° C or higher, and a state immediately after printing (blue at room temperature (25 ° C)). The state in which the print characters of (1) have been formed) has been restored.
In the print that developed color after heating, good color was visually recognized, and the start point, end point, and outline were clear.

Example 32
(Preparation of microcapsule pigment)
3.0 parts of 3 ', 6'-bis [phenyl (3-methylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one as component (a), Reversible composition consisting of 8.0 parts of 4,4 '-(2-methylpropylidene) bisphenol as component (b), 45.0 parts of n-butyl myristate and 5.0 parts of n-butyl palmitate as component (c). The thermochromic composition was uniformly heated and dissolved, and a solution prepared by mixing 40.0 parts of an aromatic polyvalent isocyanate prepolymer and 50.0 parts of a cosolvent as a wall film material was added to a 10% polyvinyl alcohol aqueous solution to form microdroplets. The resulting emulsion was emulsified and dispersed, and the mixture was stirred while heating, 2.5 parts of a water-soluble aliphatic modified amine was added, and the mixture was further stirred to obtain a microcapsule pigment suspension.
The microcapsule pigment was obtained by filtering the suspension with a filter press.
The volume average particle size of the microcapsule pigment was 0.89 μm, and the maximum particle size was 2.93 μm. (Median diameter)
The complete decolorization temperature of the microcapsule pigment is 0 ° C., the complete color development temperature is −15 ° C., and the color changes from blue to colorless due to temperature change.
As a result of measuring the zeta potential of the microcapsule pigment, the zeta potential when the pH value of the microcapsule pigment dispersion liquid was 7.1 was 7.2 mV.

Recording paper (copy paper) was printed and UV light was irradiated using the inkjet printer to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The reversible thermochromic image of the printed matter is in a decolored state at room temperature (25 ° C), and when cooled to -15 ° C or less, a blue reversible thermochromic image is visually recognized and heated to 0 ° C or more. As a result, the reversible thermochromic image returned to a decolored state.
From the print that developed color after cooling, good color development was visually recognized, and the start point, end point, and outline were clear.

Example 33
(Preparation of microcapsule pigment and aqueous ink composition)
The cyan, magenta, yellow, and black aqueous ink compositions of Example 10, Example 19, Example 20, and Example 21 were used.

(Ink container)
The ink composition was contained in an ink bottle of the same form as the ink container used in Example 10 to prepare an ink container set consisting of magenta, cyan, yellow, and black ink bottles.

(inkjet printer)
The ink accommodating portion of the inkjet printer used in Example 10 was made to be capable of accommodating the above-described four-color ink compositions independently, and the ink accommodating portion accommodated each color independently.

Printing and UV light irradiation were performed on recording paper (copy paper) using the above inkjet printer to form a reversible thermochromic image to obtain a reversible thermochromic printed matter.
At the time of printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
At room temperature (25 ° C.), a reversible thermochromic image of a mixed color consisting of cyan, magenta, yellow, black, and two or more colors selected from the above four colors is visually recognized on the printed matter, and heated to 60 ° C. or more. As a result, the reversible thermochromic image disappeared and returned to a state immediately after printing (a state in which prints of cyan, magenta, yellow, black, etc. were formed) at -25 ° C.
The reversible thermochromic image was formed by setting the decolored recording sheet again in the ink jet printer and printing was performed, and the printed matter could be repeatedly used.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Example 34
(Preparation of microcapsule pigment and aqueous ink composition)
The aqueous ink compositions of Example 28, Example 29, Example 30, and Example 31 were used.

(Ink container)
Four types of water-based ink compositions were housed in an ink bottle of the same form as the ink container used in Example 10 to prepare an ink container set consisting of each ink bottle.

(inkjet printer)
The ink containing portion of the ink jet printer used in Example 10 was made to be able to contain four types of ink compositions independently, and each ink composition was contained independently in the ink containing portion.

After printing each of the water-based ink compositions on a recording paper (copy paper) using the above-mentioned inkjet printer so that they are recorded at different positions, the printed area is irradiated with UV light to form a reversible thermochromic image. Thus, a reversible thermochromic printed matter was obtained.
During printing, the circulation mechanism was operated to circulate the ink in the ink supply channel, the printer head, and the ink recovery channel.
The printed matter is at room temperature (25 ° C.), the prints formed with the ink compositions of Example 28 and Example 29 are in a decolored state, and the prints formed with the ink compositions of Example 30 and Example 31 are It was visually confirmed and confirmed to play a role as a temperature indicator.
From the printing in the color-developed state, good color was visually recognized, and the start point, the end point, and the contour were clear.

Comparative Example 1
(Preparation of microcapsule pigment)
As component (a), 9 parts of 9-ethyl- (3-methylbutyl) amino-spiro [12H-benzo [a] xanthen-12,1 '(3H) -isobenzofuran] -3'-one, (b) A reversible thermochromic composition consisting of 15.0 parts of 4,4 '-(2-ethylhexylidene) bisphenol as a component and 50.0 parts of 4-benzyloxyphenylethyl caprate as a component (c) was uniformly added. A solution of 20.0 parts of aromatic polyvalent isocyanate prepolymer, 10.0 parts of cresol novolac type epoxy resin, and 50.0 parts of cosolvent, which were dissolved at room temperature and used as a wall film material, was added to a 10% aqueous gelatin solution to form microdroplets. The resulting emulsion was emulsified and dispersed, and stirring was continued while heating, 5.0 parts of a water-soluble aliphatic modified amine was added, and the stirring was further continued to obtain a microcapsule pigment suspension.
After removing coarse particles from the suspension by a centrifuge, the suspension was filtered by a filter press to obtain a microcapsule pigment.
The volume average particle diameter of the microcapsule pigment was 0.86 μm, and the maximum particle diameter was 2.72 μm. (Median diameter)
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −25 ° C., and changes from magenta color to colorless due to temperature change.
When the zeta potential was measured when the pH value of the microcapsule dispersion was 7.0, the zeta potential was 0 mV. (Each zeta potential value of 20 data pieces is −0.04 to +0.04 mV, and the number average value thereof is less than 0.04 mV, which can be regarded as substantially 0 mV.)

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.00 parts, glycerin 10.00 parts, preservative (pyridine-2-thiol 1-oxide sodium salt, product name: Sodium omazine, manufactured by Lonza Japan Co., Ltd.) 0 20 parts, antiseptic (3-iodo-2-propynylbutyl carbamate, product name: Glycacil 2000, manufactured by Lonza Japan Co., Ltd.) 0.20 parts, antifoaming agent 0.02 parts and water 79.58 parts uniformly. By mixing, an aqueous ink composition was obtained.

The above water-based ink composition was placed in a fountain pen of the same type as the fountain pen used in Example 1, and writing was performed on copy paper.
Magenta handwriting is visible on the copy paper at room temperature (25 ° C), and the reversible thermochromic image disappears when heated to 60 ° C or higher, and the state immediately after writing at -25 ° C (magenta color). It has returned to the state where the handwriting was formed).
The handwriting in the colored state was extremely faint, and it was difficult to visually recognize the color and outline.

Comparative example 2
(Preparation of microcapsule pigment)
The same microcapsule pigment as in Comparative Example 1 was prepared.

(Preparation of water-based ink composition)
Microcapsule pigment (pre-cooled and developed color) 10.0 parts, morpholinoethyl (meth) acrylate 14.0 parts, piperazinoethyl (meth) acrylate 10.0 parts, 2-hydroxy-3- (4-benzoyl) Phenoxy) -N, N, N-trimethyl-1-propanammonium chloride 1.0 part, ethylene glycol 5.0 parts, antifungal agent (product name: Proxel XL-2, manufactured by Zeneca Corporation) 0.2 part, 0.5 parts of a defoaming agent (silicon type, product name: SN deformer 381, manufactured by San Nopco Ltd.) and 60.8 parts of water were uniformly mixed to obtain a water-based ink composition.

(inkjet printer)
The water-based ink composition was stored in the ink storage portion of the inkjet printer used in Example 10. At that time, since an aggregate of the microcapsule pigment was confirmed on the inner bottom of the accommodating portion, printing was not performed.

The formed image was evaluated as follows. The results obtained were as shown in Tables 1-4.
As described above, Comparative Example 2 was not evaluated because an image was not formed.

(Evaluation of color development)
The color developability of the image was visually observed.
A: Dark and clear.
B: The color is slightly light, but it is sufficiently visible.
C: Light color and difficult to see. There are practical problems.

(Evaluation of fineness)
The fineness of the image was visually observed.
A: There is no blur and the outline of the image is clear.
B: There is slight blurring or the outline of the image is slightly unclear, but there is no problem in practical use.
C: There is blurring or the outline of the image is unclear. There are practical problems.

t1 Full color development temperature of reversible thermochromic microcapsule pigment of heat bleaching type t2 Color development start temperature of reversible thermochromic microcapsule pigment of heat bleaching type t3 Decoloration of reversible thermochromic microcapsule pigment of heat bleaching type Starting temperature t4 Complete erasing temperature of heat-erasable reversible thermochromic microcapsule pigment ΔH Hysteresis width 1 Ink supply device 2 Ink container 3 Printer head 3a Ink discharge port 3b Ink intake 3c Internal flow path 4a Ink supply flow path 4b Ink collection flow path 5 Pump 6 Wiping means 7 Nozzle 8 Ink ejection port 9 Ink composition

Claims

A reversible composition comprising (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of the components (a) and (b) occurs. A reversible thermochromic microcapsule containing a thermochromic composition,
Reversible heat for ink, characterized in that the microcapsules have a positive or negative zeta potential under conditions of 20 ° C. and a pH value of 7 in a microcapsule dispersion liquid consisting of water and the microcapsules only. Color-changing microcapsule pigment.
The microcapsule pigment according to claim 1, wherein the zeta potential ζ is 0 <| ζ | ≦ 20 mV.
The microcapsule pigment according to claim 1 or 2, wherein the zeta potential ζ is 1 ≦ | ζ | ≦ 15 mV.
The microcapsule pigment according to any one of claims 1 to 3, which has a volume average particle diameter of 0.1 to 5 µm and a maximum particle diameter of 8 µm or less.
The microcapsule pigment according to any one of claims 1 to 4, which has a volume average particle diameter of 0.3 to 4 µm and a maximum particle diameter of 6 µm or less.
The microcapsule pigment according to any one of claims 1 to 5, which has a volume average particle diameter of 0.3 to 3 µm and a maximum particle diameter of 4 µm or less.
A microcapsule pigment according to any one of claims 1 to 6, water, and a dispersant,
The reversible thermochromic water-based ink composition, wherein the dispersant has a functional group having a charge having a sign opposite to the zeta potential value of the microcapsule pigment in the structure.
8. The dispersant according to claim 7, wherein the dispersant is selected from the group consisting of an olefin-maleic acid copolymer and its alkali neutralized product, an acrylic polymer compound, a dialkylaminoacrylic acid ester, and a dialkylaminomethacrylic acid ester. The described ink composition.
The ink composition according to claim 7 or 8, wherein the content of the dispersant is 0.01 to 2 mass% based on the total mass of the ink composition.
An ink container containing the ink composition according to any one of claims 7 to 9.
An ink container set including a plurality of ink containers according to claim 10.