Thermochromic microcapsule pigment composition, thermochromic aqueous ink composition containing the same, and aqueous writing instrument

Abstract

The present invention provides a thermochromic microcapsule pigment composition, a thermochromic aqueous ink composition, and a thermochromic aqueous writing instrument, all of which exhibit excellent color development and leave no residue of ink when the color fades. [Solution] A thermochromic microcapsule pigment composition containing an electron-donating compound, an electron-accepting compound, and a reaction medium, wherein the electron-donating compound contains three types of compounds, each having a specific structure, in a predetermined proportion; a thermochromic aqueous ink composition containing the thermochromic microcapsule pigment composition; and a thermochromic aqueous writing instrument containing the thermochromic aqueous ink composition.

Description

Technical Field

[0001] The present invention relates to a thermochromic microcapsule pigment composition, a thermochromic water-based ink composition containing the same, and a water-based writing instrument, and more specifically, relates to a thermochromic microcapsule pigment composition comprising an electron-donating compound (colorformer), an electron-accepting compound, and a reaction medium, which contains three types of electron-donating color-forming compounds having specific structures at a predetermined ratio as the electron-donating compound (colorformer), as well as a thermochromic water-based ink composition and a water-based writing instrument containing the same.

Background Art

[0002] A thermochromic composition is a substance that develops and fades color reversibly depending on temperature, and contains an electron-donating color-forming compound, an electron-accepting compound, and a reaction medium that reversibly causes the reaction between these two compounds in a specific temperature range as essential components. In order to produce a thermochromic water-based ink for applying such a thermochromic composition to a water-based writing instrument, a technique using a microcapsule pigment enclosing an electron-donating color-forming compound among the constituent elements of the thermochromic composition has been conventionally known, and writing instruments containing ink produced using the microcapsule pigment have the property of fading handwriting and are used in various fields.

[0003] The thermochromic microcapsule pigment used in thermochromic water-based inks has a problem of low visibility compared to commonly used black pigments or dyes due to the properties of the material. In order to improve this problem, the content of the black electron-donating color-forming compound or the content of microcapsules contained in the thermochromic microcapsule pigment is generally increased, but this type of method has a problem that it is difficult to highlight the characteristics of the thermochromic writing instrument due to the phenomenon that the residue becomes dark during color erasure. Therefore, there is a demand for the development of a microcapsule pigment suitable for a thermochromic writing instrument that enhances color developability and leaves no handwriting residue during color erasure, and an ink containing the same.

[0004] Conventionally, various technologies have been developed to enhance the characteristics of thermochromic writing instruments. Specifically, Patent Document 1 describes a thermochromic color-memory composition in which the color development and decolorization reversibly change depending on the temperature, by incorporating a specific fatty acid ester compound as a reaction medium into a microcapsule pigment, and a thermochromic microcapsule pigment containing this composition. Patent Document 2 also relates to a thermochromic color-memory microcapsule pigment, and describes a technology that increases the ΔH width and achieves thermochromic color memory by incorporating an electron-donating color-developing compound, an electron-accepting compound, a reaction medium that reversibly causes the reaction between these two compounds in a specific temperature range, and a color change temperature adjusting agent as essential components. Patent Document 3, relating to thermochromic writing instruments, describes a technology that increases the density of the writing and makes it easy to erase or change the color of the writing by incorporating a fluorane derivative of a specific structure as an electron-donating color-developing compound among the components of the thermochromic composition. However, in these conventional technologies, there is no known technique for improving color development while suppressing the generation of ink residue during erasure by incorporating three types of electron-donating color-developing compounds having a specific structure in specific proportions.

[0005] Therefore, the present inventors diligently conducted research to overcome the problems of the prior art described above, and as a result, they discovered that a thermochromic microcapsule pigment composition comprising an electron-donating compound (colorformer), an electron-accepting compound, and a reaction medium, containing three types of electron-donating color-developing compounds having a specific structure as the thermochromic compound in a predetermined proportion, as well as a thermochromic aqueous ink composition and aqueous writing instrument containing the same, exhibits excellent color development and leaves no residue of writing when the color fades, thus completing the present invention. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4219776 [Patent Document 2] Japanese Patent Publication No. 2001-152041 [Patent Document 3] Patent No. 7463157 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the main objective of the present invention is to provide a thermochromic microcapsule pigment composition that exhibits excellent color development and leaves no residue of ink marks when the color fades.

[0008] Another object of the present invention is to provide a thermochromic aqueous ink composition containing the thermochromic microcapsule pigment composition.

[0009] A further object of the present invention is to provide a thermochromic aqueous writing instrument containing the thermochromic aqueous ink composition. [Means for solving the problem]

[0010] According to one aspect of the present invention, the present invention provides a thermochromic microcapsule pigment composition comprising an electron-donating compound (colorformer), an electron-accepting compound, and a reaction medium, wherein the electron-donating compound (colorformer) comprises a compound of chemical formula 1, a compound of chemical formula 2, and a compound of chemical formula 3, and the compounds of chemical formula 1, chemical formula 2, and chemical formula 3 are present in amounts of 60-90% by weight, 1-20% by weight, and 1-20% by weight, respectively, based on the total weight of the electron-donating compound. [ka] (In the formula, X1 is a methyl group or a halogen atom, R1 is a linear or branched alkyl group having 1 to 8 carbon atoms. R2 is a linear alkyl group having 1 to 8 carbon atoms or an alkylphenyl group having 7 or 8 carbon atoms (however, the sum of the carbon atoms of R1 and R2 is 2 to 9). [ka] (In the formula, R3 is a linear or branched alkyl group having 1 to 9 carbon atoms.) R4 is a linear alkyl group having 1 to 9 carbon atoms or an alkylphenyl group having 7 to 9 carbon atoms. [ka] (In the formula, X2 and X3 are each independently linear or branched alkyl groups having 1 to 8 carbon atoms.)

[0011] The electron-donating compound according to the present invention is represented by the following chemical formulas 1 to 3, where chemical formula 1 is as follows: [ka]

[0012] In the above chemical formula 1, X1 is a methyl group or a halogen atom, where the halogen atom can be selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0013] In the above chemical formula 1, R1 is a linear or branched alkyl group having 1 to 8 carbon atoms, and R2 is a linear alkyl group having 1 to 8 carbon atoms or an alkylphenyl group having 7 or 8 carbon atoms. However, the sum of the carbon atoms of R1 and R2 is 2 to 9. The alkyl group can be selected from the group consisting of methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, n-pentyl group, isopentyl group, neo-pentyl group, tert-pentyl group, n-hexyl group, isohexyl group, neo-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, neo-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, neo-octyl group, tert-octyl group, n-nonyl group, isononyl group, neo-nonyl group, and tert-nonyl group. Examples of the C7 or C8 alkylphenyl group include a methylphenyl group, a dimethylphenyl group, or an ethylphenyl group.

[0014] Examples of compounds represented by chemical formula 1 according to the present invention include 3-(N-ethyl-4-methylphenylamino)-6-methyl-7-anilinofluoran, 3-[N-(n-butyl)-4-methylphenylamino]-6-methyl-7-anilinofluoran, and 3-[N-(n-pentyl)-4-methylphenylamino]-6- Examples include at least one compound selected from the group consisting of methyl-7-anilinofluoran (3-[N-(n-pentyl)-4-methylphenylamino]-6-methyl-7-anilinofluoran) and 3-[N-(benzyl)-4-methylphenylamino]-6-methyl-7-anilinofluoran (3-[N-(benzyl)-4-methylphenylamino]-6-methyl-7-anilinofluoran), preferably 3-(N-ethyl-4-methylphenylamino)-6-methyl-7-anilinofluoran.

[0015] Among the electron-donating compounds according to the present invention, the compound of Chemical Formula 2 is as follows. [Chemical Formula]

[0016] In the above Chemical Formula 2, R3 is a linear or branched alkyl group having 1 to 9 carbon atoms, and R4 is a linear alkyl group having 1 to 9 carbon atoms or an alkylphenyl group having 7 to 9 carbon atoms.

[0017] The alkyl group may be selected from the group consisting of methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, n-hexyl group, isohexyl group, neohexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, neoheptyl group, tert-heptyl group, n-octyl group, isooctyl group, neooctyl group, tert-octyl group, n-nonyl group, isononyl group, neononyl group, and tert-nonyl group. Examples of the alkylphenyl group having 7 to 9 carbon atoms include methylphenyl group, dimethylphenyl group, ethylphenyl group, trimethylphenyl group, and methylethylphenyl group.

[0018] Examples of compounds represented by chemical formula 2 according to the present invention include 9'-[ethyl(3-methylbutyl)amino]-3H-spiro[2-benzofuran-1], 9'-[N-isopropyl-N-isohexylamino]-3H-spiro[2-benzofuran-1], 9'-[Nn-propyl-N-tert-butylamino]-3H-spiro[2-benzofuran-1], and 9'-[N-methyl-N-nonylamino]-3H-spiro It may be at least one selected from the group consisting of [2-benzofuran-1] (9'-[N-methyl-N-nonylamino]-3H-spiro[2-benzofuran-1]), 9'-[N-ethyl-N-(4-tert-butylphenyl)amino]-3H-spiro[2-benzofuran-1] (9'-[N-ethyl-N-(4-tert-butylphenyl)amino]-3H-spiro[2-benzofuran-1]), and 9'-[N-neohexyl-N-ethylamino]-3H-spiro[2-benzofuran-1] (9'-[N-neohexyl-N-ethylamino]-3H-spiro[2-benzofuran-1]), preferably 9'-[ethyl(3-methylbutyl)amino]-3H-spiro[2-benzofuran-1].

[0019] Among the electron-donating compounds according to the present invention, the compound with chemical formula 3 is as follows: [ka]

[0020] In the above chemical formula 3, X2 and X3 are each independently linear or branched alkyl groups having 1 to 8 carbon atoms. Here, the alkyl group can be selected from the group consisting of methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, n-pentyl group, isopentyl group, neo-pentyl group, tert-pentyl group, n-hexyl group, isohexyl group, neo-hexyl group, tert-hexyl group, n-heptyl group, isoheptyl group, neo-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, neo-octyl group, and tert-octyl group.

[0021] Examples of compounds represented by chemical formula 3 according to the present invention include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-di-n-butylaminophenyl)-6-diethylaminophthalide, and 3,3-bis(p-diisopropylaminophenyl)-6-dimethylaminophthalide. It may be at least one selected from the group consisting of -dimethylaminophthalide, 3,3-bis(p-dihexylaminophenyl)-6-dimethylaminophthalide, and 3,3-bis(p-dimethylaminophenyl)-6-di-n-pentylaminophthalide, preferably 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide.

[0022] The thermochromic microcapsule pigment composition according to the present invention preferably contains 60-90% by weight, 1-20% by weight, and 1-20% by weight of compounds represented by chemical formulas 1, 2, and 3, respectively, based on the total weight of the electron-donating compounds in the capsules. More preferably, it can contain 70-90% by weight of the compound of chemical formula 1, 5-15% by weight of the compound of chemical formula 2, and 5-15% by weight of the compound of chemical formula 3. Most preferably, it can contain 80-90% by weight of the compound of chemical formula 1, 5-10% by weight of the compound of chemical formula 2, and 5-10% by weight of the compound of chemical formula 3. If the compound content falls outside the range and combination of the above compounds, it is difficult to achieve excellent color development, and residue remains when the ink is erased after writing, making it difficult to achieve the thermochromic aqueous ink composition and aqueous writing instrument that the present invention aims to realize.

[0023] In the thermochromic microcapsule pigment composition of the present invention, the composition contains an electron-accepting compound, the electron-accepting compound causing the electron-donating compound according to the present invention to develop color, and any compound that has been conventionally used for the color development of electron-donating chromogenic organic compounds can be used, and it is preferable to use a group of compounds having an active proton. Examples of compounds having an active proton include compounds having a phenolic hydroxyl group and phenol aldehyde condensation resins such as monophenol, bis-type, and tris-type phenols, but are not limited to these. Metal salts of compounds having a phenolic hydroxyl group can also be used.Examples include phenol, o-cresol, tertiary butylcatechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcinol, dodecyl gallate, 2,2-bis(4-hydroxyphenyl)propane, 4,4-dihydroxydiphenylsulfone, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)sulfide, 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-3-methylbutane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis( Examples include 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, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)ethylpropionate, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,2-bis(4-hydroxyphenyl)n-heptane, and 2,2-bis(4-hydroxyphenyl)n-nonane, and preferably 2,2-bis(4-hydroxy-3-methylphenyl)propane, but not limited thereto.

[0024] In the thermochromic microcapsule pigment composition of the present invention, the composition contains a reaction medium, the reaction medium being a component that reversibly exhibits a reaction between an electron-donating compound and an electron-accepting compound within a specific temperature range, and any conventionally used substance can be used, preferably at least one compound selected from the group consisting of alcohols, esters, ketones, ethers, fatty acids, hydrocarbons and azomethines, and more preferably an ester compound.For example, 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, n-heptyl laurate, lauric acid n-nonyl laurate, n-undecyl laurate, n-tridecyl laurate, n-pentadecyl laurate, n-pentyl myristate, n-heptyl myristate, n-nonyl myristate, n-undecyl myristate, n-tridecyl myristate, n-pentadecyl myristate, n-pentyl palmitate, n-heptyl palmitate, n-nonyl palmitate, n-undecyl palmitate, n-tridecyl palmitate, n-pentadecyl palmitate, n-stearate -Nonyl, n-undecyl stearate, n-tridecyl stearate, n-pentadecyl stearate, n-nonyl eicosanoate, n-undecyl eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, n-pentadecyl behenate, 4-benzyloxyphenylethyl octanoate, 4-benzyloxyphenylethyl nonanoate, 4-benzyloxyphenylethyl decanoate, It may be selected from the group consisting of 4-benzyloxyphenylethyl undecanoate, 4-benzyloxyphenylethyl dodecanoate, 4-benzyloxyphenylethyl tridecanoate, 4-benzyloxyphenylethyl tetradecanoate, 4-benzyloxyphenylethyl pentadecanoate, 4-benzyloxyphenylethyl hexadecanoate, 4-benzyloxyphenylethyl heptadecanoate, and 4-benzyloxyphenylethyl octadecanoate.

[0025] The thermochromic microcapsule pigment composition according to the present invention may further contain resin raw materials for microencapsulation and can be encapsulated by microencapsulation methods such as interfacial polymerization, interfacial polycondensation, in-situ polymerization, liquid curing coating, phase separation from aqueous solution, phase separation from organic solvent, melt-dispersion cooling, air suspension coating, and spray drying.

[0026] According to another aspect of the present invention, the present invention provides a thermochromic aqueous ink composition containing the thermochromic microcapsule pigment composition according to the present invention described above.

[0027] In the thermochromic aqueous ink composition of the present invention, the thermochromic microcapsule pigment composition is preferably contained in an amount of 0.1 to 15% by weight, and more preferably in an amount of 5 to 14% by weight, relative to the total weight of the thermochromic aqueous ink composition. If the content of the thermochromic microcapsule raw material composition is less than the above range, the color development will be significantly reduced, and if it exceeds the above range, the content in the ink will be high, which may result in poor writing performance over time.

[0028] In the thermochromic aqueous ink composition of the present invention, the color development state and decolorization state of the thermochromic aqueous ink composition can be evaluated by ΔL*(D65). L*(D65) represents the brightness of an object measured under a D65 standard light source. In the color development state, a smaller L*(D54) value indicates a darker blackness, and a larger ΔL*(D65) indicates a better decolorization state (residue). The thermochromic aqueous ink composition of the present invention is characterized in that ΔL*(D65) is 50 or more. In most conventional thermochromic aqueous inks, ΔL*(D65) is less than 50, in which case there is a possibility that residue will remain when the ink is decolorized after writing.

[0029] According to one experimental example of the present invention, in the case of a thermochromic aqueous ink composition containing the thermochromic microcapsule pigment composition according to the present invention (Example), the ΔL*(D65) in the colored state and the decolorized state was 50 or more, and no residue remained after decolorization. In contrast, in the case of a thermochromic aqueous ink composition that does not contain the thermochromic microcapsule pigment composition according to the present invention (Comparative Example 1), or an aqueous ink composition that has the same composition as the aqueous ink according to the present invention but has a different content of electron-donating compounds (Comparative Example 2), the ΔL*(D65) in the colored state and the decolorized state was less than 50, and it was confirmed that residue remained after decolorization (see Experimental Example). These results indicate that when the thermochromic microcapsule pigment composition according to the present invention is applied to a thermochromic aqueous ink composition and an aqueous writing instrument, it is possible to impart the effect of excellent color development and no residue remaining when the color is decolorized after writing.

[0030] In the thermochromic aqueous ink composition of the present invention, the thermochromic aqueous ink composition may further contain distilled water, a water-soluble solvent, a thickener, a lubricant, a preservative, and the like, in addition to the thermochromic microcapsule pigment composition.

[0031] According to another aspect of the present invention, the present invention provides a thermochromic aqueous writing instrument containing the aforementioned thermochromic aqueous ink composition.

[0032] In the thermochromic aqueous writing instrument of the present invention, the thermochromic aqueous writing instrument may be a ballpoint pen, a gel pen, or both a ballpoint pen and a gel pen, but is not limited thereto, and is applicable to any writing instrument to which a thermochromic aqueous ink composition can be applied. [Effects of the Invention]

[0033] As described above, the thermochromic aqueous ink composition produced using the thermochromic microcapsule pigment according to the present invention and the thermochromic aqueous writing instrument containing it have excellent color development and the effect of leaving no residue of writing when the color fades. [Brief explanation of the drawing]

[0034] [Figure 1] This figure shows the color development and decolorization states of the ink according to the example. [Figure 2] This figure shows the color development and decolorization state of the ink in Comparative Example 1. [Figure 3] This figure shows the color development and decolorization state of the ink in Comparative Example 2. [Figure 4] This figure shows the thermochromic aqueous ballpoint pen of the present invention. [Modes for carrying out the invention]

[0035] The present invention will be described in more detail below with reference to examples. However, these examples are merely illustrative of the present invention, and the technical scope of the present invention should not be construed as being limited by these examples.

[0036] Example: Production of an aqueous ink containing a thermochromic microcapsule pigment composition A thermochromic water-based ink consisting of the components listed in Table 1 below was manufactured.

[0037] 1) Production of thermochromic microcapsule pigment compositions A thermochromic microcapsule pigment composition consisting of electron-donating compounds, electron-accepting compounds, and a reaction medium corresponding to chemical formulas 1 to 3 was dissolved, then added to a mixed solution consisting of an aromatic isocyanate prepolymer and a prepared solvent as a wall film material, and emulsified and dispersed in an aqueous PVA solution to produce a microcapsule dispersion, thereby obtaining a thermochromic microcapsule pigment with an average particle size of 2 to 3 μm.

[0038] 2) Manufacture of a thermochromic aqueous black ink composition A ballpoint pen ink composition was produced by mixing and stirring the thermochromic microcapsule pigment composition obtained above with a thickener, humectant, lubricant, preservative, pH adjuster, etc.

[0039] [Table 1]

[0040] Comparative Example 1: Production of an aqueous ink containing a thermochromic microcapsule pigment composition A thermochromic aqueous ink consisting of the components shown in Table 2 below was manufactured. The manufacturing method was the same as in the examples, but the composition and their respective contents were set to be different.

[0041] [Table 2]

[0042] Comparative Example 2: Production of an aqueous ink containing a thermochromic microcapsule pigment composition Although the constituent components were the same as those in the examples, a water-based ink was manufactured by differently configuring the content of the compounds with chemical formulas 1 to 3 that constitute the electron-donating compound. The composition and content are shown in Table 3, and the manufacturing method was the same as in the examples.

[0043] [Table 3]

[0044] Experimental example: Confirmation of L*(D65) values ​​for the color development and decolorization states of thermochromic water-based inks. Images and L*(D65) values ​​were measured for both the colored and decolorized states, and the difference (ΔL) between these two L*(D65) values ​​was confirmed. The results are shown in Table 4 and Figures 1 to 3.

[0045] 1) Measurement of the L*(D65) value of the color development state Samples coated with the thermochromic aqueous ink prepared in the examples and comparative examples are prepared by applying the ink to ISO 14145 paper and allowing it to dry. Then, the spectrophotometer (Test Equipment: Color-eye 7000A (X-rite)) is set to SCI mode and D65 light source mode, and after calibration using the instrument's standard white plate, the sample is placed in the measuring instrument and the L*(D65) value is checked.

[0046] 2) Measurement of the L*(D65) value of the decolorized state The L*(D65) value of the sample whose color development was measured is decolorized at 70°C for 12 hours and then measured again using a spectrophotometer.

[0047] [Table 4]

[0048] As shown in Figures 1 to 3, in the case of an aqueous ink containing a fluorane-based compound commonly used as a thermochromic pigment (Comparative Example 1), and an aqueous ink with the same composition as the aqueous ink according to the present invention but with a different content of electron-donating compounds (Comparative Example 2), residue remained in both cases. In contrast, it was confirmed that no residue remained in the case of the aqueous ink according to the present invention (Example). Furthermore, since the ΔL*(D65) in the Example was 50 or more, while the ΔL*(D65) in Comparative Examples 1 and 2 was less than 50, it can be seen that when the aqueous ink according to the present invention is applied to an aqueous writing instrument, the effect of leaving no residue after writing can be achieved. [Explanation of Symbols]

[0049] 100 Thermochromic Water-Based Ballpoint Pens 110 Locking device 120 Friction body

Claims

1. A thermochromic microcapsule pigment composition containing an electron-donating compound, an electron-accepting compound, and a reaction medium, The electron-donating compound includes the compound represented by chemical formula 1, the compound represented by chemical formula 2, and the compound represented by chemical formula 3, A thermochromic microcapsule pigment composition characterized in that the compound represented by chemical formula 1, the compound represented by chemical formula 2, and the compound represented by chemical formula 3 are present in amounts of 60 to 90% by weight, 1 to 20% by weight, and 1 to 20% by weight, respectively, based on the total weight of the electron-donating compound. 【Chemistry 1】 (In the formula, X 1 This is a methyl group or a halogen atom, R 1 This is a linear or branched alkyl group having 1 to 8 carbon atoms. R 2 is a linear alkyl group having 1 to 8 carbon atoms or an alkylphenyl group having 7 or 8 carbon atoms (however, R 1 and R 2 The total number of carbon atoms is between 2 and 9. 【Chemistry 2】 (In the formula, R 3 This is a linear or branched alkyl group having 1 to 9 carbon atoms. R 4 (This refers to a linear alkyl group having 1 to 9 carbon atoms or an alkylphenyl group having 7 to 9 carbon atoms.) 【Transformation 3】 (In the formula, X 2 and X 3 are each independently a linear or branched alkyl group having 1 to 8 carbon atoms.)

2. The thermochromic microcapsule pigment composition according to claim 1, characterized in that the electron-accepting compound is at least one selected from the group consisting of inorganic acids, organic acids, aromatic carboxylic acids, aliphatic carboxylic acids, bisphenols, and triazoles.

3. The thermochromic microcapsule pigment composition according to claim 1, characterized in that the reaction medium is at least one selected from the group consisting of alcohols, esters, ketones, ethers, fatty acids, hydrocarbons, and azomethines.

4. A thermochromic aqueous ink composition comprising the thermochromic microcapsule pigment composition and ink vehicle described in claim 1.

5. The thermochromic aqueous ink composition according to claim 4, characterized in that the thermochromic microcapsule pigment composition is contained in an amount of 0.1 to 15% by weight relative to the total weight of the thermochromic aqueous ink composition.

6. The thermochromic aqueous ink composition according to claim 4, characterized in that the ΔL* (D65) of the thermochromic aqueous ink in the colored state and the decolorized state is 50 or more.

7. A thermochromic aqueous writing instrument comprising the thermochromic aqueous ink composition described in claim 4.

8. The thermochromic aqueous writing instrument according to claim 7, wherein the thermochromic aqueous writing instrument is a ballpoint pen, a gel pen, or both a ballpoint pen and a gel pen.

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