JP2012041459A - Reversible thermochromic aqueous ink composition, and writing utensil and writing utensil set using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermochromic aqueous ink composition which can suppress handwriting from lightening or deepening, especially lightening of handwriting with time in the erecting condition, or lightening of handwriting due to vibration caused at shipping or carrying does not occur so as to give favorable writing performances as well as smooth writing feelings; and a writing utensil and a writing utensil set using the composition.SOLUTION: The reversible thermochromic aqueous ink composition comprises: water; a water-soluble organic solvent; a reversible thermochromic microcapsule pigment having an average particle diameter of 0.1-2.0 μm and encapsulating a reversible thermochromic composition comprising (a) an electron-donating coloring organic compound, (b) an electron-accepting compound, and (c) a reactive medium which determines the occurrence temperature of the coloring reaction of the above both components; a comb-type polymeric dispersant having a carboxyl group on the side chain; an organic nitrogen-sulfur compound; and a water-soluble resin. There are also disclosed a writing utensil 1 using the ink composition, and a writing utensil set comprising the writing utensil and a friction body.

Description

  The present invention relates to a reversible thermochromic water-based ink composition, a writing instrument using the same, and a writing instrument set.

2. Description of the Related Art Conventionally, a filling type writing instrument in which an ink occlusion body is impregnated with a reversible thermochromic water-based ink composition capable of forming a handwriting whose color tone changes with temperature change and accommodated in a shaft cylinder has been disclosed (for example, Patent Document 1). reference).
In the reversible thermochromic water-based ink composition, the reversible thermochromic microcapsule pigment and the vehicle have a specific gravity difference so that the reversible thermochromic capsule pigment gradually aggregates and settles in the ink occlusion body, and the pen body faces downward (inverted state). Alternatively, the problem that the handwriting is lightened or darkened by the upward (upright state) state is solved, and a water-soluble polymer flocculant is blended in the ink. The above problem is solved by suspending the microcapsule pigment in a loosely aggregated state by a loose bridging action.
However, blending of the polymer flocculant can suppress the aggregation and sedimentation of the microcapsule pigment for a short period of time, but the lightening and darkening of the handwriting due to the specific gravity difference between the microcapsule pigment and the vehicle can be prevented for a long time. It is difficult to suppress completely, and in some cases, the handwriting is lightened with time in an upright state, or the handwriting is lightened by applying vibration during transportation or carrying in an upright state.

JP-A-11-335613

  The present invention can suppress the lightening and darkening of the handwriting, and in particular, the handwriting is lightened over time in the upright state, or the handwriting is generated by applying vibration during transportation or carrying in the upright state. An object of the present invention is to provide a reversible thermochromic water-based ink composition that does not lighten and has a smooth writing feeling, a writing instrument using the same, and a writing instrument set.

The present invention is intended to solve the problems of the conventional reversible thermochromic water-based ink composition and the writing instrument using the same, that is, water, a water-soluble organic solvent, and (b) an electron. The average particle size including a reversible thermochromic composition comprising a donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of the both occurs is 0. A reversible thermochromic water-based ink composition comprising a reversible thermochromic microcapsule pigment of 1 to 2.0 μm, a comb polymer dispersant having a carboxyl group in a side chain, an organic nitrogen sulfur compound, and a water-soluble resin. Is a requirement.
Further, the organic nitrogen sulfur compound is 2- (4-thiazoyl) -benzimidazole, 2- (thiocyanatomethylthio) -1,3-benzothiazole, 2-methyl-4-isothiazolin-3-one, 5-chloro- It is a compound selected from 2-methyl-4-isothiazolin-3-one, and the mass ratio of the comb-type polymer dispersant having a carboxyl group in the side chain and the organic nitrogen sulfur compound is 1: 1 to 1:10. That the pH of the ink composition is in the range of 3 to 8, that the pH of the ink composition is in the range of 3 to 8 and that is soluble in water, and the polyurethane emulsion has a pH of 5 to 9 Alternatively, it is required to contain an acrylic resin emulsion.
Furthermore, the writing instrument provided with the pen body which accommodates the said reversible thermochromic water-based ink composition in a shaft cylinder, and guide | leads out the ink composition in the said shaft cylinder is made into requirements.
Furthermore, the rear end of the pen body is in contact with an ink occlusion body composed of a fiber bundling body housed in a shaft cylinder, the ink occlusion body is impregnated with an ink composition, and the pen body is It is a requirement that it is a marking pen body and that it is provided with a friction member.
Furthermore, a writing instrument set including the writing instrument and a friction body is a requirement.

  The present invention can suppress the lightening and darkening of the handwriting, and in particular, the handwriting does not lighten over time in an upright state or the handwriting does not lighten by applying vibration during transportation or carrying. It is possible to provide a reversible thermochromic water-based ink composition having a writing performance and a smooth writing feeling, a writing tool using the same, and a writing tool set.

It is explanatory drawing which shows the discoloration behavior of a heat decoloring type reversible thermochromic microcapsule pigment. It is explanatory drawing which shows the discoloration behavior of the heat decoloring type reversible thermochromic microcapsule pigment having color memory. It is explanatory drawing which shows the discoloration behavior of a heat coloring type reversible thermochromic microcapsule pigment. It is explanatory drawing which shows one Example of the writing instrument of this invention. It is explanatory drawing which shows the other Example of the writing instrument of this invention. It is explanatory drawing which shows the other Example of the writing instrument of this invention.

The colorant contained in the ink composition includes (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of the two occurs. A microcapsule pigment in which a reversible thermochromic composition that is decolored by heating containing at least three essential components is encapsulated in microcapsules.
Examples of the reversible thermochromic composition include those described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc., at a predetermined temperature (discoloration point). Discolored before and after, decolored state in the temperature range above the high temperature side discoloration point, color development state in the temperature range below the low temperature side discoloration point, only one specific state exists in the normal temperature range among the two states, The other state is maintained as long as the heat or cold required to develop the state is applied, but when the heat or cold is no longer applied, the hysteresis width returns to the state exhibited in the normal temperature range. It has relatively small characteristics (ΔH = 1 to 7 ° C.) (see FIG. 1).

In addition, large hysteresis characteristics (ΔH _B = 8 to 50 ° C.) described in JP- _B -4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, and the like. ), That is, when the shape of the curve plotting the change in the color density due to the temperature change is lowering the temperature from the lower temperature side than the color changing temperature range, as opposed to increasing the temperature from the lower temperature side. In the specific temperature range, the color changes in a low temperature range below the complete color development temperature (t ₁ ) or the color erase state in the high temperature range above the complete color erase temperature (t ₄ ). A heat-erasable microcapsule pigment in which a reversible thermochromic composition having color memory in a temperature range between t _{2 and} t ₃ (substantially two-phase holding temperature range) is encapsulated in microcapsules Applicable (Fig. 2 Irradiation).

The hysteresis characteristic in the color density-temperature curve of the reversible thermochromic composition 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 proceeds along the arrow. Here, A is a point indicating a density at a temperature t ₄ (hereinafter referred to as a complete decoloring temperature) that reaches a completely decolored state, and B is a temperature t ₃ (hereinafter referred to as a decoloring start temperature). C is a point indicating a density at a temperature t ₂ at which color development starts (hereinafter referred to as a color development start temperature), and D is a temperature t ₁ at which a complete color development state is reached (hereinafter referred to as a complete color development state). This is a point indicating a density at a color development temperature).
Discoloration temperature region is a temperature range between the t ₁ and t _4, it is possible to exhibit any of the states of the colored state and the decolored state, between t ₂ and t ₃ is a region having a large difference in color density The temperature range is substantially the two-phase holding temperature range.
The length of the line segment EF is a scale indicating the discoloration contrast, and the length of the line segment HG passing through the midpoint of the line segment EF is a temperature width indicating the degree of hysteresis (hereinafter referred to as hysteresis width ΔH). If this ΔH value is small, only one specific state can exist in the normal temperature range among both states before and after the color change. Further, when the ΔH value is large, it is easy to maintain each state before and after the color change.

Specifically, as the reversible thermochromic composition having color memory, a complete color development temperature t ₁ can be obtained only in a freezing room, a cold district, etc., that is, −50 to 0 ° C., preferably −40 to − 5 ° C., more preferably −30 to −10 ° C., and the temperature at which the complete decoloring temperature t ₄ is obtained from a frictional heat generated by a friction body, a heating body such as a hair dryer, that is, 45 to 95 ° C., preferably 50 to 90
By specifying the temperature in the range of 60 ° C., more preferably in the range of 60 to 80 ° C., and specifying the ΔH value in the range of 40 to 100 ° C., it is possible to effectively function to maintain the color exhibited in the normal state (daily life temperature range).

Specific examples of the compounds (a), (b) and (c) are shown below.
Examples of the electron donating color-forming organic compound as component (a) of the present invention include diphenylmethane phthalides, phenyl indolyl phthalides, indolyl phthalides, diphenyl methane azaphthalides, and phenyl indolyl azaphthalides. , Fluorans, stylinoquinolines, diazarhodamine lactones and the like.
Examples of these compounds are given 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- (N-ethylanilino) phenyl] -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide,
3,6-diphenylaminofluorane,
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- (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-methyl-6-di-n-butylaminofluorane,
2-xylidino-3-methyl-6-diethylaminofluorane,
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) pyrimidine-5,1 '(3'H) isobenzofuran] -3'-one,
2- (diethylamino) -8- (diethylamino) -4-methyl-spiro [5H- (1) benzopyrano (2,3-g) pyrimidine-5,1 ′ (3′H) isobenzofuran] -3-one,
2- (Di-n-butylamino) -8- (di-n-butylamino) -4-methyl-spiro [5H- (1) benzopyrano (2,3-g) pyrimidine-5,1 '(3' H) Isobenzofuran] -3-one,
2- (Di-n-butylamino) -8- (diethylamino) -4-methyl-spiro [5H- (1) benzopyrano (2,3-g) pyrimidine-5,1 '(3'H) isobenzofuran] -3-one,
2- (Di-n-butylamino) -8- (N-ethyl-Ni-amylamino) -4-methyl-spiro [5H- (1) benzopyrano (2,3-g) pyrimidine-5,1 ' (3′H) isobenzofuran] -3-one,
2- (Dibutylamino) -8- (dipentylamino) -4-methyl-spiro [5H- (1) benzopyrano (2,3-g) pyrimidine-5,1 '(3'H) -isobenzofuran] -3 -On,
3- (2-methoxy-4-dimethylaminophenyl) -3- (1-butyl-2-methylindol-3-yl) -4,5,6,7-tetrachlorophthalide,
3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4,5,6,7-tetrachlorophthalide,
3- (2-ethoxy-4-diethylaminophenyl) -3- (1-pentyl-2-methylindol-3-yl) -4,5,6,7-tetrachlorophthalide,
4,5,6,7-Tetrachloro-3- [4- (dimethylamino) -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,
And 3 ', 6'-bis [phenyl (3-ethylphenyl) amino] -spiro [isobenzofuran-1 (3H), 9'-[9H] xanthen] -3-one.
Furthermore, there can be mentioned pyridine-based, quinazoline-based, bisquinazoline-based compounds and the like which are effective for developing a fluorescent yellow to red color, such as 4- [2,6-bis (2-ethoxyphenyl). -4-pyridinyl] -N, N-dimethylbenzenamine.

As the electron-accepting compound of component (b), a group of compounds having active protons, a group of pseudo-acidic compounds (a group of compounds that are not acids but act as an acid in the composition and cause component (a) to develop color), electrons There is a group of compounds having pores.
Examples of compounds having active protons include monophenols to polyphenols as compounds having phenolic hydroxyl groups, and alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxy groups and esters thereof as substituents. Alternatively, those having an amide group, a halogen group, etc., and bis-type and tris-type phenols, phenol-aldehyde condensation resins and the like can be mentioned. Moreover, the metal salt of the compound which has the said phenolic hydroxyl group may be sufficient.

Specific examples are given below.
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, resorcin, 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-methylbu 1,1-bis (4-hydroxyphenyl) -2-methylpropane, 1,1-bis (4-hydroxyphenyl) n-hexane, 1,1-bis (4-hydroxyphenyl) n-heptane, , 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-ethylhexane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) ethyl Propionate, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2 Bis (4-hydroxyphenyl) n- heptane, there is 2,2-bis (4-hydroxyphenyl) n- nonane.
The compound having a phenolic hydroxyl group can develop the most effective thermochromic property, but aromatic carboxylic acids and aliphatic carboxylic acids having 2 to 5 carbon atoms, carboxylic acid metal salts, acidic phosphate esters and their It may be a compound selected from metal salts, 1,2,3-triazole and derivatives thereof.

The component (c) of the reaction medium that causes the electron transfer reaction by the components (a) and (b) to occur reversibly in a specific temperature range will be described. Examples of the component (c) include esters, ketones, ethers, alcohols, and acid amides.
As the component (c), the color density-temperature curve has a large hysteresis characteristic (a curve plotting a change in color density due to a temperature change changes the temperature from the low temperature side to the high temperature side, and the high temperature side to the low temperature side). A carboxylic acid ester compound exhibiting a ΔT value (melting point-cloud point) of 5 ° C. or more and less than 50 ° C., which can form a reversible thermochromic composition exhibiting color memory, which changes color when changing to Carboxylic acid ester having a substituted aromatic ring in the molecule, carboxylic acid ester having an unsubstituted aromatic ring and an aliphatic alcohol ester having 10 or more carbon atoms, carboxylic acid ester having a cyclohexyl group in the molecule, 6 or more carbon atoms Fatty acid and unsubstituted aromatic alcohol or phenol ester, fatty acid having 8 or more carbon atoms and branched aliphatic alcohol or ester, dicarboxylic acid and aroma Ester of alcohol or branched aliphatic alcohol, dibenzyl cinnamate, heptyl stearate, didecyl adipate, dilauryl adipate, dimyristyl adipate, dicetyl adipate, distearyl adipate, trilaurin, trimyristin, tristearin, dimyristin, Distearin or the like is used.

Also, fatty acid ester compounds obtained from an odd aliphatic monohydric alcohol having 9 or more carbon atoms and an aliphatic carboxylic acid having an even number of carbon atoms, n-pentyl alcohol or n-heptyl alcohol and an even fat having 10 to 16 carbon atoms. A fatty acid ester compound having a total carbon number of 17 to 23 obtained from a group carboxylic 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 ristinate, 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 eicosanoate, n-undecyl eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-behenate Examples include undecyl, n-tridecyl behenate, and n-pentadecyl behenate.

As the ketones, aliphatic ketones having a total carbon number of 10 or more are effective, and 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, laurone, stearone and the like.
Further, arylalkyl ketones having 12 to 24 carbon atoms in total, such as n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n-tetradecano Phenone, 4-n-dodecanacetophenone, 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-butylpropiophenone, n-heptaphenone, 4-n-pentylacetophene Emissions, cyclohexyl phenyl ketone, benzyl -n- butyl ketone, 4-n-butyl acetophenone, n- hexanophenone, 4-isobutyl acetophenone, 1-acetonaphthone, 2-acetonaphthone, may be mentioned cyclopentyl phenyl ketone.

As ethers, aliphatic ethers having a total carbon number of 10 or more are effective, and include dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditrityl ether. Decyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecyl ether, dioctadecyl ether, decane diol dimethyl ether, undecane diol dimethyl ether, dodecane diol dimethyl ether, tridecane diol dimethyl ether, decane diol diethyl ether, undecane diol diethyl ether, etc. Can be mentioned.
As the alcohols, aliphatic monovalent saturated alcohols having 10 or more carbon atoms are effective. Decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl Alcohol, octadecyl alcohol, eicosyl alcohol, docosyl alcohol, etc. can be mentioned.
Acid amides include hexanoic acid amide, heptanoic acid amide, octanoic acid amide, nonanoic acid amide, decanoic acid amide, undecanoic acid amide, lauric acid amide, tridecanoic acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, Examples thereof include docosanoic acid amide.

〔式中、Ｒ_１は水素原子又はメチル基を示し、ｍは０〜２の整数を示し、Ｘ_１、Ｘ_２のいずれか一方は−（ＣＨ_２）_ｎＯＣＯＲ_２又は−（ＣＨ_２）_ｎＣＯＯＲ_２、他方は水素原子を示し、ｎは０〜２の整数を示し、Ｒ_２は炭素数４以上のアルキル基又はアルケニル基を示し、Ｙ_１及びＹ_２は水素原子、炭素数１〜４のアルキル基、メトキシ基、又は、ハロゲンを示し、ｒ及びｐは１〜３の整数を示す。〕
前記式（１）で示される化合物のうち、Ｒ_１が水素原子の場合、より広いヒステリシス幅を有する可逆熱変色性組成物が得られるため好適であり、更にＲ_１が水素原子であり、且つ、ｍが０の場合がより好適である。
なお、式（１）で示される化合物のうち、より好ましくは下記一般式（２）で示される化合物が用いられる。

式中のＲは炭素数８以上のアルキル基又はアルケニル基を示すが、好ましくは炭素数１０〜２４のアルキル基、更に好ましくは炭素数１２〜２２のアルキル基である。
前記化合物として具体的には、オクタン酸−４−ベンジルオキシフェニルエチル、ノナン酸−４−ベンジルオキシフェニルエチル、デカン酸−４−ベンジルオキシフェニルエチル、ウンデカン酸−４−ベンジルオキシフェニルエチル、ドデカン酸−４−ベンジルオキシフェニルエチル、トリデカン酸−４−ベンジルオキシフェニルエチル、テトラデカン酸−４−ベンジルオキシフェニルエチル、ペンタデカン酸−４−ベンジルオキシフェニルエチル、ヘキサデカン酸−４−ベンジルオキシフェニルエチル、ヘプタデカン酸−４−ベンジルオキシフェニルエチル、オクタデカン酸−４−ベンジルオキシフェニルエチルを例示できる。 Further, as the component (c), a compound represented by the following general formula (1) described in JP-A No. 2006-137886 is preferably used.

[Wherein, 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 represents — (CH ₂ ) _n OCOR ₂ or — (CH ₂ ) _n COOR ₂ , the other represents a hydrogen atom, n represents an integer of 0 to 2, R ₂ represents an alkyl or alkenyl group having 4 or more carbon atoms, Y ₁ and Y ₂ represent a hydrogen atom, 1 to 4 carbon atoms An alkyl group, a methoxy group, or halogen, and r and p each represent an integer of 1 to 3. ]
Among the compounds represented by the formula (1), when R ₁ is a hydrogen atom, it is preferable because a reversible thermochromic composition having a wider hysteresis width can be obtained, and R ₁ is a hydrogen atom, and , M is more preferably 0.
Of the compounds represented by the formula (1), a compound represented by the following general formula (2) is more preferably used.

R in the formula represents an alkyl group or alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, more preferably an alkyl group having 12 to 22 carbon atoms.
Specific examples of the compound include octanoic acid-4-benzyloxyphenylethyl, nonanoic acid-4-benzyloxyphenylethyl, decanoic acid-4-benzyloxyphenylethyl, undecanoic acid-4-benzyloxyphenylethyl, and dodecanoic acid. -4-benzyloxyphenylethyl, tridecanoic acid-4-benzyloxyphenylethyl, tetradecanoic acid-4-benzyloxyphenylethyl, pentadecanoic acid-4-benzyloxyphenylethyl, hexadecanoic acid-4-benzyloxyphenylethyl, heptadecanoic acid Examples thereof include -4-benzyloxyphenylethyl and octadecanoic acid-4-benzyloxyphenylethyl.

（式中、Ｒは炭素数８以上のアルキル基又はアルケニル基を示し、ｍ及びｎはそれぞれ１〜３の整数を示し、Ｘ及びＹはそれぞれ水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲンを示す。）
前記化合物として具体的には、オクタン酸１,１−ジフェニルメチル、ノナン酸１,１−ジフェニルメチル、デカン酸１,１−ジフェニルメチル、ウンデカン酸１,１−ジフェニルメチル、ドデカン酸１,１−ジフェニルメチル、トリデカン酸１,１−ジフェニルメチル、テトラデカン酸１,１−ジフェニルメチル、ペンタデカン酸１,１−ジフェニルメチル、ヘキサデカン酸１,１−ジフェニルメチル、ヘプタデカン酸１,１−ジフェニルメチル、オクタデカン酸１,１−ジフェニルメチルを例示できる。 Furthermore, the compound shown by following General formula (3) described in Unexamined-Japanese-Patent No. 2006-188660 can also be used as said (c) component.

(In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, m and n each represents an integer of 1 to 3, X and Y represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, carbon, respectively. (The alkoxy group of Formula 1-4 is shown, and a halogen.)
Specific examples of the compound include 1,1-diphenylmethyl octanoate, 1,1-diphenylmethyl nonanoate, 1,1-diphenylmethyl decanoate, 1,1-diphenylmethyl undecanoate, 1,1-dodecanoic acid 1,1- Diphenylmethyl, tridecanoic acid 1,1-diphenylmethyl, tetradecanoic acid 1,1-diphenylmethyl, pentadecanoic acid 1,1-diphenylmethyl, hexadecanoic acid 1,1-diphenylmethyl, heptadecanoic acid 1,1-diphenylmethyl, octadecanoic acid An example is 1,1-diphenylmethyl.

（式中、Ｘは水素原子、炭素数１乃至４のアルキル基、メトキシ基、ハロゲン原子のいずれかを示し、ｍは１乃至３の整数を示し、ｎは１乃至２０の整数を示す。）
前記化合物としては、マロン酸と２−〔４−(４−クロロベンジルオキシ）フェニル）〕エタノールとのジエステル、こはく酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、こはく酸と２−〔４−(３−メチルベンジルオキシ）フェニル）〕エタノールとのジエステル、
グルタル酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、グルタル酸と２−〔４−(４−クロロベンジルオキシ）フェニル）〕エタノールとのジエステル、アジピン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、ピメリン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、スベリン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、スベリン酸と２−〔４−(３−メチルベンジルオキシ）フェニル）〕エタノールとのジエステル、スベリン酸と２−〔４−(４−クロロベンジルオキシ）フェニル）〕エタノールとのジエステル、スベリン酸と２−〔４−(２，４−ジクロロベンジルオキシ）フェニル）〕エタノールとのジエステル、アゼライン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、セバシン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、１，１０−デカンジカルボン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、１，１８-オクタデカンジカルボン酸と２−（４−ベンジルオキシフェニル）エタノールとのジエステル、１，１８-オクタデカンジカルボン酸と２−〔４−(２−メチルベンジルオキシ）フェニル）〕エタノールとのジエステルを例示できる。 Furthermore, the compound shown by following General formula (4) described in Unexamined-Japanese-Patent No. 2008-280523 can also be used as said (c) component.

(Wherein, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen atom, m represents an integer of 1 to 3, and n represents an integer of 1 to 20)
Examples of the compound include a diester of malonic acid and 2- [4- (4-chlorobenzyloxy) phenyl)] ethanol, a diester of succinic acid and 2- (4-benzyloxyphenyl) ethanol, succinic acid and 2- [4- (3-methylbenzyloxy) phenyl)] diester with ethanol,
Diester of glutaric acid and 2- (4-benzyloxyphenyl) ethanol, diester of glutaric acid and 2- [4- (4-chlorobenzyloxy) phenyl)] ethanol, adipic acid and 2- (4-benzyloxy) Phenyl) ethanol diester, pimelic acid and 2- (4-benzyloxyphenyl) ethanol diester, suberic acid and 2- (4-benzyloxyphenyl) ethanol diester, 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 and 2- (4-benzene) Ndyloxyphenyl) ethanol, diester of sebacic acid and 2- (4-benzyloxyphenyl) ethanol, diester of 1,10-decanedicarboxylic acid and 2- (4-benzyloxyphenyl) ethanol, 1 , 18-octadecanedicarboxylic acid and 2- (4-benzyloxyphenyl) ethanol diester, 1,18-octadecanedicarboxylic acid and 2- [4- (2-methylbenzyloxy) phenyl)] ethanol diester it can.

（式中、Ｒは炭素数１乃至２１のアルキル基又はアルケニル基を示し、ｎは１乃至３の整数を示す。）
前記化合物としては、１，３−ビス（２−ヒドロキシエトキシ）ベンゼンとカプリン酸とのジエステル、１，３−ビス（２−ヒドロキシエトキシ）ベンゼンとウンデカン酸とのジエステル、１，３−ビス（２−ヒドロキシエトキシ）ベンゼンとラウリン酸とのジエステル、１，３−ビス（２−ヒドロキシエトキシ）ベンゼンとミリスチン酸とのジエステル、１，４−ビス（ヒドロキシメトキシ）ベンゼンと酪酸とのジエステル、１，４−ビス（ヒドロキシメトキシ）ベンゼンとイソ吉草酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンと酢酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとプロピオン酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンと吉草酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとカプロン酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとカプリル酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとカプリン酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとラウリン酸とのジエステル、１，４−ビス（２−ヒドロキシエトキシ）ベンゼンとミリスチン酸とのジエステルを例示できる。 Furthermore, a compound represented by the following general formula (5) can also be used as the component (c).

(In the formula, R represents an alkyl group or alkenyl group having 1 to 21 carbon atoms, and n represents an integer of 1 to 3).
Examples of the compound include a diester of 1,3-bis (2-hydroxyethoxy) benzene and capric acid, a diester of 1,3-bis (2-hydroxyethoxy) benzene and undecanoic acid, and 1,3-bis (2 -Hydroxyethoxy) benzene and lauric acid diester, 1,3-bis (2-hydroxyethoxy) benzene and myristic acid diester, 1,4-bis (hydroxymethoxy) benzene and butyric acid diester, 1,4 Diesters of bis (hydroxymethoxy) benzene and isovaleric acid, diesters of 1,4-bis (2-hydroxyethoxy) benzene and acetic acid, and 1,4-bis (2-hydroxyethoxy) benzene and propionic acid Diester, diester of 1,4-bis (2-hydroxyethoxy) benzene and valeric acid Diester of 1,4-bis (2-hydroxyethoxy) benzene and caproic acid, diester of 1,4-bis (2-hydroxyethoxy) benzene and caprylic acid, 1,4-bis (2-hydroxyethoxy) benzene And diester of capric acid, 1,4-bis (2-hydroxyethoxy) benzene and lauric acid, and 1,4-bis (2-hydroxyethoxy) benzene and myristic acid.

  Furthermore, as an electron-accepting compound, a specific alkoxyphenol compound having a linear or side chain alkyl group having 3 to 18 carbon atoms (Japanese Patent Laid-Open No. 11-129623), a specific hydroxybenzoic acid ester (Japanese Patent Laid-Open No. 2001-105732). Gazette), gallic acid ester (Japanese Patent Laid-Open No. 2003-253149) and the like, and a heat-colorable microcapsule pigment encapsulating a reversible thermochromic composition can also be applied (see FIG. 3).

The blending ratio of the components (a), (b), and (c) depends on the concentration, the color change temperature, the color change form, and the type of each component. In general, the component ratio at which a desired color change characteristic is obtained is as follows. (B) Component 1 is in the range of (b) Component 0.1-50, preferably 0.5-20, (c) Component 1-800, preferably 5-200. Part by mass).
Here, in the reversible thermochromic microcapsule pigment or the ink, a colorant such as a non-thermochromic dye or pigment is blended to change the color from color (1) to color (2). Changes can also be exhibited.

The microencapsulation of the reversible thermochromic composition includes interfacial polymerization method, interfacial polycondensation method, in situ polymerization method, submerged curing coating method, phase separation method from aqueous solution, phase separation method from organic solvent, melt dispersion There are a cooling method, an air suspension coating method, a spray drying method, and the like, which are appropriately selected according to the application.
Examples of the material of the capsule include epoxy resin, urea resin, urethane resin, and isocyanate resin.
Further, a secondary resin film may be provided on the surface of the microcapsule according to the purpose to impart durability, or the surface characteristics may be modified for practical use.

As the microcapsule pigment, those having an average particle diameter of 0.1 to 2.0 μm, preferably 0.1 to 1.8 μm, more preferably 0.1 to 1.5 μm are used.
The weight ratio of the reversible thermochromic composition to the microcapsule wall film is a reversible thermochromic composition: wall film = 7: 1 to 1: 1 (mass ratio), preferably 6: 1 to 1: 1. It is preferable to satisfy the range.
When the average particle diameter of the microcapsule pigment exceeds 2.0 μm, it is difficult to obtain a smooth writing feeling, and when the average value of the maximum outer diameter is less than 0.1 μm, it is difficult to exhibit high color density.
When the ratio of the reversible thermochromic composition to the wall film is larger than the above range, the thickness of the wall film becomes too thin, and the resistance to pressure and heat tends to decrease, and the ratio of the wall film to the reversible thermochromic composition When the value is larger than the above range, color density and sharpness during color development tend to be reduced.
The particle diameter is measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd .; LA-300), and the average particle diameter (median diameter) is calculated based on the numerical value. .

The reversible thermochromic microcapsule pigment can be blended in an amount of 5 to 40% by mass, preferably 10 to 40% by mass, and more preferably 15 to 35% by mass with respect to the total amount of the ink composition.
If it is less than 5% by mass, the color density is insufficient, and if it exceeds 40% by mass, the ink outflow is reduced and writing performance is impaired.

As a medium used for the ink, water and a water-soluble organic solvent are used.
Examples of the water-soluble organic solvent include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, and ethylene glycol monomethyl. Ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, N-methyl-2- Pyrrolidone, or the like is used.
Note that the microcapsule pigment encapsulating the reversible thermochromic composition having a large hysteresis width has a specific gravity of more than 1, so that the water-soluble organic solvent to be applied is preferably more than 1.1.
Glycerin is preferably used as the water-soluble organic solvent, and can be blended in an amount of 5 to 40% by weight, preferably 25 to 40% by weight, more preferably 30 to 35% by weight based on the total amount of the ink composition.

The comb polymer dispersant having a carboxyl group in the side chain improves long-term dispersion stability of the microcapsule pigment itself when used in combination with an organic nitrogen sulfur compound.
The comb polymer dispersant having a carboxyl group in the side chain is not particularly limited as long as it is a comb polymer compound having a plurality of carboxyl groups in the side chain, but a plurality of carboxyl groups in the side chain. An acrylic polymer compound having the formula:

The organic nitrogen sulfur compound further suppresses settling of the microcapsule pigment due to vibration when the ink composition is filled in a writing instrument and put to practical use.
This is for further improving dispersibility in which the microcapsule pigment is dispersed by the comb polymer dispersant having a carboxyl group in the side chain.
As the organic nitrogen sulfur compound, a compound selected from thiazole compounds, isothiazole compounds, benzothiazole compounds, and benzoisothiazole compounds is used.
Specific examples of the organic nitrogen sulfur compound include 2- (4-thiazoyl) -benzimidazole (TBZ), 2- (thiocyanatomethylthio) -1,3-benzothiazole (TCMTB), 2-methyl-4-isothiazoline- One or more compounds selected from 3-one and 5-chloro-2-methyl-4-isothiazolin-3-one are used, preferably 2- (4-thiazoyl) -benzimidazole (TBZ), 2 One or more compounds selected from -methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one are used.
As the organic nitrogen sulfur compound, manufactured by Permachem Asia Co., Ltd., trade names: Topside 88, 133, 170, 220, 288, 300, 400, 500, 600, 700Z, 800, 950, manufactured by Hokuko Sangyo Co., Ltd., trade names: Hokuster HP, E50A, Hokuside P200, 6500, 7400, MC, 369, and R-150.
The mass ratio of the comb-type polymer dispersant having a carboxyl group in the side chain and the organic nitrogen sulfur compound is 1: 1 to 1:10, preferably 1: 1 to 1: 5, and satisfies the above range. Thus, the dispersibility of the microcapsule pigment and the suppression of sedimentation of the microcapsule pigment due to vibration can be sufficiently expressed.

The water-soluble resin is added to provide adhesion to the paper surface and viscosity, and the above-described comb-type polymer dispersant having a carboxyl group in the side chain and stability of the organic nitrogen sulfur compound in the ink. It has a function to enhance.
Examples of the water-soluble resin include alkyd resin, acrylic resin, styrene maleic acid copolymer, cellulose derivative, polyvinyl pyrrolidone, polyvinyl alcohol, dextrin, and the like. 89% partially saponified polyvinyl alcohol is preferably used.
The amount of the water-soluble resin added can be 0.3 to 3.0% by weight, preferably 0.5 to 1.5% by weight in the ink.

The ink composition can suppress aggregation and sedimentation in a low temperature region of the reversibly thermochromic microcapsule pigment contained by adjusting the pH to 3 to 8, preferably 4 to 7, more preferably 5 to 6. .
When the pH exceeds 8, it tends to impair ink outflow properties when left in a low temperature range, that is, a temperature range where the ink freezes. The color developability becomes strong, and there may be a problem that a color residue is generated at the time of decoloring.
The water-soluble resin is preferably a water-soluble resin that is soluble in the ink composition when the pH of the ink composition is in the range of 3 to 8.

When the pH of the ink composition is in the range of 3 to 8, adding a polyurethane emulsion or acrylic resin emulsion having a pH of 5 to 9 is excellent in dispersion stability in the ink composition having a pH of 3 to 8. Fixing power is exhibited, and particularly, the fixing property is high even on a surface such as coated paper or a resin film that is difficult to permeate ink, and the handwriting is hardly peeled off by rubbing or the like.
Examples of the polyurethane emulsion having a pH of 5 to 9 include those manufactured by Avicia, trade names: NeoRez R-972, R-9637, R2105, R-966, R-967, R-985, R-986, R-989, R-9603, R-940, R9403, manufactured by DIC Corporation, trade names: Hydran AP-20, AP-40, APX-101H, CP-7020, Sanyo Chemical Co., Ltd., trade names: Uprene UXA-307, etc. It can be illustrated.
Examples of the acrylic resin emulsion having a pH of 5 to 9 include BASF, trade name: Jocril 1535, DIC Corporation, trade name: Boncoat R-3880-E, and the like.
The polyurethane emulsion or the acrylic resin emulsion can be added in an amount of 1 to 15% by weight, preferably 2 to 10% by weight in the ink composition as a solid content.
If it is less than 1% by weight, it is difficult to obtain the desired fixing property, and even if it exceeds 15% by weight, no further improvement in fixing property can be obtained, so no further addition is required.
The pH of the emulsion is preferably 5 or more and less than 9.
The pH of the ink composition and the resin emulsion is measured using a pH meter (manufactured by Toa DKK, product number: HM-20P, glass electrode type hydrogen ion concentration indicator).

The ink composition has a surface tension adjusted to 25 to 45 mN / m, preferably 30 to 45 mN / m, more preferably 30 to 40 mN / m.
By adjusting the surface tension within the above range, it is difficult to cause blurring when written, and the ink can be left in a temperature range below 0 ° C. where the ink freezes or even in a high temperature range, for example, 50 ° C. It is difficult to cause variations in handwriting density and writing width depending on the storage environment and use environment without impairing the flowability.
When the surface tension is less than 25 mN / m, the outflow property of the ink tends to be unstable, and the handwriting density becomes non-uniform. Further, when the surface tension exceeds 45 mN / m, line breakage is likely to occur, and the ink outflow amount decreases due to the storage environment and use environment described above, and the handwriting density decreases, and the writing width tends to vary. .

In addition, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin and other anticorrosives, urea, nonionic surfactants, reduced or non-reduced starch hydrolysates, trehalose, etc. Wetting agents such as saccharides, oligosaccharides, sucrose, cyclodextrin, glucose, dextrin, sorbit, mannitol, sodium pyrophosphate, antifoaming agents, fluorine surfactants and nonionic surfactants that improve ink permeability May be used.
Furthermore, a sodium salt of naphthalene sulfonic acid formalin condensate [manufactured by Kao, trade name: demole N] can also be used as a surfactant, and is preferably used together with glycerin.
In addition, the average particle diameter of a color changing from white to colorless in which a compound selected from crystalline esters, ethers, and ketones having a melting point in the range of −40 ° C. to + 95 ° C. is 0.1-2. By using a 0 μm reversible thermochromic microcapsule pigment in combination, a reversible thermochromic aqueous ink composition capable of forming a pastel handwriting can also be obtained.

The pen body is preferably a marking pen body, and examples thereof include a pen body made of fiber, felt, plastic, or the like.
The tip shape of the marking pen body may be either a bullet type or a chisel type.
In addition, a brush pen body and a ballpoint pen body can be used. As the brush pen body, a fiber bundling body in which fibers are closely bundled in the longitudinal direction, a plastic porous body having continuous pores, and a heat-sealing of synthetic resin fibers. Examples thereof include a resin processed body, and a soft resin or elastomer extrusion processed body.
As the ballpoint pen body, metal is cut to form a ball receiving seat and an ink lead-out portion inside, a plurality of inward protruding portions are provided on the inner surface near the tip of the metal pipe by pressing deformation from the outer surface, An ink outflow gap extending radially outward from the central portion between the inward protruding portions is exemplified.
The ball held by the ballpoint pen body has an outer diameter of 0.3 to 2.0 mm, preferably 0.4 to 1.5 mm, more preferably 0.5 to 0.5 mm, such as cemented carbide, stainless steel, ruby and ceramic. A 1.0 mm ball is effective.
The ballpoint pen body is provided with a resilient member that bounces the rear end of the ball forward. When not writing, the ball is pressed against the inner edge of the tip of the pen body to bring it into close contact. The ink can be made to flow backward by allowing it to retreat.
As the shaft cylinder, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon is preferably used.
In addition, as a structure of the writing instrument for containing the ink composition, a direct liquid writing instrument having a structure in which a valve mechanism is arranged in the shaft cylinder and the ink in the shaft cylinder is led to the pen body by opening the valve, Direct ink writing instruments with a structure in which ink is directly stored in the ink flow adjusting member composed of a comb groove-like ink flow adjusting member and a fiber bundle are included. A solid writing instrument having a structure in which the body is impregnated, the pen body is attached to the writing tip, and the rear end of the pen body is in contact with the ink occlusion body directly or via a connecting member is preferable.
The ink occlusion body is formed by converging crimped fibers in the longitudinal direction, and is configured to be included in a covering body such as a plastic cylinder or a film and to adjust the porosity to a range of approximately 40 to 90%. Is done. The fiber bundle may be one that has been processed by resin processing, heat sealing, or plasticizer.

The handwriting formed from the writing instrument containing the ink composition can be discolored by friction with a finger or application of a heating tool or a cooling tool.
Examples of the heating tool include an energization heating color changing tool equipped with a resistance heating element, a heating color changing tool filled with hot water, and a hair dryer. Preferably, a friction member or a friction body that can change color by a simple method is used. Is used.
The friction member or the friction body is preferably an elastic body such as an elastomer or a plastic foam which is rich in elasticity and can generate frictional heat by generating appropriate friction during friction. Wood, metal, and fabric may be used.
Although it is possible to rub the handwriting using an eraser, it is preferable to use a friction member as described above because erase scraps are generated during friction.
As the material of the friction member and friction body, silicone resin, SEBS resin (styrene ethylene butadiene styrene block copolymer), and polyester resin are preferably used. Since the handwriting tends to be repelled when writing repeatedly, SEBS resin and polyester resin are more preferably used.
The friction member may be an arbitrary-shaped member (friction body) that is separate from the writing instrument, but is excellent in portability by being fixed to the writing instrument.
In the case of a writing instrument having a cap, the location where the friction member is provided is not particularly limited. For example, when the cap itself is formed of a friction member, the shaft tube itself is formed of a friction member, or a clip is provided. The clip itself can be formed of a friction member, or the friction member can be provided at the tip end (top) of the cap or the rear end of the shaft cylinder (the portion where the writing tip is not provided).
In the case of a retractable writing instrument, the location where the friction member is provided is not particularly limited, but for example, the shaft cylinder itself is formed with a friction member, or when the clip is provided, the clip itself is formed with a friction member, A friction member can be provided in the vicinity of the shaft tube opening, the rear end portion of the shaft tube (the portion where the writing tip portion is not provided) or the knock portion.
Examples of the cooling / heating tool include a cooling / heating discoloration tool using a Peltier element, a cooling / heating discoloration tool filled with a coolant such as cold water and ice pieces, a refrigerator and a freezer.
Moreover, a writing instrument set can be obtained by combining the writing instrument and a friction body.

Examples of the water-based ink composition for reversible thermochromic writing instruments and the writing instrument using the same according to the present invention are shown below, but the present invention is not limited thereto.
In addition, the part in an Example shows a mass part.
The surface tension of the ink was measured with an automatic surface tension meter (CBVP-A3) manufactured by Kyowa Interface Science Co., Ltd. at a temperature of 20 ° C.

Example 1
Preparation of reversible thermochromic microcapsule pigment (a) 3.0 parts of 1,3-dimethyl-6-diethylaminofluorane as component (4) 4,4 '-(2-ethylhexane-1, 1- Diyl) Color comprising 3.0 parts of diphenol, 5.0 parts of 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane, and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c) A microcapsule pigment suspension containing a reversible thermochromic composition having a memory property was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.8 μm, a complete color erasing temperature of 60 ° C., and a complete color development temperature of −20 ° C., which changes from orange to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition 25.0 parts of the above microcapsule pigment (previously cooled to −20 ° C. or less to develop an orange color), comb polymer dispersant [manufactured by Nippon Lubrizol Co., Ltd. , Trade name: Solsperse 43000], 0.5 parts, organic nitrogen sulfur compound [made by Hokuko Chemical Co., Ltd., trade name: Hokuside R-150, 2-methyl-4-isothiazolin-3-one and 5-chloro-2 -Methyl-4-isothiazolin-3-one mixture] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part and water 37.98 parts were mixed. A reversible thermochromic aqueous ink composition was obtained.
The ink composition had a pH of 7.00 and a surface tension of 39.8 mN / m.

Production of filling-type writing instrument (see Fig. 4)
The ink composition 2 is impregnated with an ink occlusion body 2 in which a polyester sliver is coated with a synthetic resin film, and is stored in a shaft cylinder 4 made of polypropylene resin. A polyester fiber resin processing pen body 3 is placed at the end of the axis cylinder ( A cannonball type) assembled in a connected state via a holder 5, and a cap 6 was attached to obtain a filling pen 1 (marking pen).
A SEBS resin is attached as a friction member 7 to the rear end portion of the shaft cylinder.

An orange character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting has an orange color at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft cylinder, the character is discolored and becomes colorless, and this state is maintained at room temperature. By cooling to −20 ° C. or less, the original orange color was restored, and the discoloration behavior was reproduced repeatedly.

Example 2
Preparation of reversible thermochromic microcapsule pigment (a) 3.0 parts of 1,3-dimethyl-6-diethylaminofluorane as component (4) 4,4 '-(2-ethylhexane-1, 1- Diyl) Color comprising 3.0 parts of diphenol, 5.0 parts of 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane, and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c) A microcapsule pigment suspension containing a reversible thermochromic composition having a memory property was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.5 μm, a complete color erasing temperature of 60 ° C., and a complete color development temperature of −25 ° C., which changes from orange to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition 25.0 parts of the microcapsule pigment (previously cooled to −25 ° C. or less and colored orange), comb-type polymer dispersant [manufactured by Nippon Lubrizol Co., Ltd. , Trade name: Solsperse 43000], 0.5 parts, organic nitrogen sulfur compound [made by Hokuko Chemical Co., Ltd., trade name: Hokuside R-150, 2-methyl-4-isothiazolin-3-one and 5-chloro-2 -Methyl-4-isothiazolin-3-one mixture] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part and water 37.98 parts were mixed. A reversible thermochromic aqueous ink composition was obtained.
The ink composition had a pH of 7.00 and a surface tension of 39.8 mN / m.

Fabrication of filling-type writing instruments Impregnation of the ink composition in an ink occlusion body in which a polyester sliver is coated with a synthetic resin film, and the polyester composition is accommodated in a shaft cylinder made of polypropylene resin, and a polyester fiber resin processing pen at the tip of the axis cylinder Was assembled in a connected state via a (bullet type) holder, and a cap was attached to obtain a filling pen (marking pen).
A SEBS resin is mounted as a friction member on the rear end of the shaft tube.

An orange character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting has an orange color at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft cylinder, the character is discolored and becomes colorless, and this state is maintained at room temperature. By cooling to −25 ° C. or lower, the original orange color was restored, and the discoloration behavior was repeatedly reproduced.

Example 3
Preparation of reversible thermochromic microcapsule pigment (a) 3.0 parts of 1,3-dimethyl-6-diethylaminofluorane as component (4) 4,4 '-(2-ethylhexane-1, 1- Diyl) Color comprising 3.0 parts of diphenol, 5.0 parts of 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane, and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c) A microcapsule pigment suspension containing a reversible thermochromic composition having a memory property was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.1 μm, a complete color erasing temperature of 60 ° C., and a complete color development temperature of −30 ° C., which changes from orange to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition 25.0 parts of the above microcapsule pigment (previously cooled to −30 ° C. or less to develop an orange color), comb polymer dispersant [manufactured by Nippon Lubrizol Co., Ltd. , Trade name: Solsperse 43000], 0.5 parts, organic nitrogen sulfur compound [made by Hokuko Chemical Co., Ltd., trade name: Hokuside R-150, 2-methyl-4-isothiazolin-3-one and 5-chloro-2 -Methyl-4-isothiazolin-3-one mixture] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part and water 37.98 parts were mixed. A reversible thermochromic aqueous ink composition was obtained.
The ink composition had a pH of 7.00 and a surface tension of 39.8 mN / m.

Fabrication of filling-type writing instruments Impregnation of the ink composition in an ink occlusion body in which a polyester sliver is coated with a synthetic resin film, and the polyester composition is accommodated in a shaft cylinder made of polypropylene resin, and a polyester fiber resin processing pen at the tip of the axis cylinder Was assembled in a connected state via a (bullet type) holder, and a cap was attached to obtain a filling pen (marking pen).
A SEBS resin is mounted as a friction member on the rear end of the shaft tube.

An orange character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting has an orange color at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft cylinder, the character is discolored and becomes colorless, and this state is maintained at room temperature. By cooling to −30 ° C. or lower, the original orange color was restored, and the discoloration behavior was reproduced repeatedly.

Example 4
Preparation of reversible thermochromic microcapsule pigment (I) 2- (dibutylamino) -8- (dipentylamino) -4-methyl-spiro [5H- [1] benzopyrano [2,3-g] pyrimidine-5 as component (a) , 1 ′ (3′H) -isobenzofuran] -3-one 1.0 part, (b) component 4,4 ′-(2-ethylhexane-1,1-diyl) diphenol 3.0 part, A reversible thermochromic composition having color memory consisting of 5.0 parts of 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c) A microcapsule pigment suspension containing the product was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.4 μm, a complete color erasing temperature of 58 ° C., a complete color development temperature of −25 ° C., and changes from pink to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition 25.0 parts of the reversible thermochromic microcapsule pigment (previously cooled to -25 ° C. or less to develop a pink color), comb polymer dispersant [Nippon Louvre Zol Co., Ltd., trade name: Solsperse 43000] 0.5 part, organic nitrogen sulfur compound [Hokuko Chemical Co., Ltd., trade name: Hokuside 369] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35 0.0 part of silicone antifoaming agent and 37.98 parts of water were mixed to obtain a reversible thermochromic aqueous ink composition.
The ink composition had a pH of 6.98 and a surface tension of 40.0 mN / m.

Production of filling-type writing instrument (see Fig. 5)
The ink composition 2 is impregnated with an ink occlusion body 2 in which a polyester sliver is coated with a synthetic resin film, and is stored in a shaft cylinder 4 made of polypropylene resin. A polyester fiber resin processing pen body 3 is placed at the end of the axis cylinder ( A chisel-type) holder 5 was assembled in a connected state, and a cap 6 was attached to obtain a filling pen 1 (marking pen).
A SEBS resin is attached as a friction member 7 to the tip of the cap.

A pink character (handwriting) was formed by writing on the character printed on the paper surface using the marking pen.
The handwriting has a pink color at room temperature (25 ° C.). When the handwriting is rubbed with a friction body attached to the shaft tube, the handwriting is discolored and becomes colorless, and this state is maintained at room temperature. Then, by cooling to −25 ° C. or lower, the original pink color was restored, and the discoloration behavior was reproduced repeatedly.

Example 5
(I) 4.5 parts of 2- (2-chloroamino) -6-dibutylaminofluorane as component, 4,4 '-(2-ethylhexane-1,1-diyl) diphenol 3 as component (b) 0.02 parts, 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane 5.0 parts, (c) reversible color memory consisting of 50.0 parts 4-benzyloxyphenylethyl caprate A microcapsule pigment suspension containing the thermochromic composition was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.3 μm, a complete color erasing temperature of 56 ° C., a complete color development temperature of −25 ° C., and changes color from black to colorless with temperature change.

Preparation of reversible thermochromic water-based ink composition 30.0 parts of the reversible thermochromic microcapsule pigment (previously cooled to −25 ° C. or less to develop black color), comb polymer dispersant [Nippon Lubrizol Co., Ltd., trade name: Solsperse 43000], 0.5 parts, organic nitrogen sulfur compound [2- (4-thiazoyl) -benzimidazole, manufactured by Hokuko Chemical Co., Ltd., trade name: Hoxter HP, 2- (4 -Thiazoyl) -benzimidazole] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part, and water 32.98 parts are mixed to form a reversible thermochromic water-based ink. A composition was obtained.
The pH of the ink composition was 7.1, and the surface tension was 38.5 mN / m.

Production of direct liquid writing instrument (see Fig. 6)
Ink 8 (cooled in advance to −20 ° C. or less to cause the microcapsule pigment to develop a pink color and then allowed to stand at room temperature) and stirrer 9 (SUS-304 ferritic stainless steel ball, diameter 3 mm) Was incorporated in the shaft cylinder 4, the valve mechanism 10 was interposed, and the marking pen body 3 (chisel type) was attached via the holder 5 to obtain a direct liquid writing instrument 1 (marking pen).
The valve mechanism is composed of a valve seat, a valve body, and a metal spring that urges the valve body to press against the valve seat, and the valve opens with the pressure applied to the pen body during writing. is there.
A SEBS resin is attached as a friction member 7 to the rear end portion of the shaft cylinder.

A black character (handwriting) was formed by writing on the paper using the marking pen.
The handwriting is black at room temperature (25 ° C.), and when rubbed with a friction body attached to the cap, the handwriting is decolored and colorless, and this state is maintained at room temperature, By cooling to −25 ° C. or lower, the original black color was restored, and the discoloration behavior was reproduced repeatedly.

Comparative Example 1
Preparation of reversible thermochromic water-based ink composition 25.0 parts of reversible thermochromic microcapsule pigment prepared in Example 1 (previously cooled to -20 ° C. or less and colored orange), organic nitrogen sulfur compound [ Manufactured by Hokuko Chemical Co., Ltd., trade name: Hokuside R-150] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part, water 38.48 parts By mixing, a reversible thermochromic water-based ink composition was obtained.
The ink composition had a pH of 6.60 and a surface tension of 40.5 mN / m.

Production of Filling-Type Writing Instruments Built-in writing tools similar to Example 1 were used to obtain filling-type writing tools (marking pens).

Comparative Example 2
Preparation of reversible thermochromic water-based ink composition 25.0 parts of the reversible thermochromic microcapsule pigment prepared in Example 4 (previously cooled to -20 ° C. or less to develop a pink color), hydroxyethyl cellulose, 0. 5 parts, organic nitrogen sulfur compound [made by Hokuko Chemical Co., Ltd., trade name: Hokuside 369] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 parts, silicone-based antifoaming agent 0.02 part, 37.98 parts of water was mixed to obtain a reversible thermochromic water-based ink composition.
The ink composition had a pH of 6.60 and a surface tension of 40.4 mN / m.

Production of Filling-Type Writing Instruments Built-in writing tools similar to Example 2 were used to obtain filling-type writing tools (marking pens).

Comparative Example 3
Preparation of reversible thermochromic water-based ink composition 30.0 parts of reversible thermochromic microcapsule pigment prepared in Example 5 (previously cooled to -20 ° C. or less and colored black), hydroxyethylcellulose 0.5 Parts, organic nitrogen sulfur compound [2- (4-thiazoyl) -benzimidazole, manufactured by Hokuko Chemical Co., Ltd., trade name: Hoxter HP, 2- (4-thiazoyl) -benzimidazole] 1.0 part, polyvinyl alcohol 0.5 parts, 35.0 parts of glycerin, 0.02 part of agent, and 32.98 parts of water were mixed to obtain a reversible thermochromic water-based ink composition.
The pH of the ink composition was 6.90, and the surface tension was 39.8 mN / m.

Production of Filled Writing Instruments Built in a writing instrument similar to Example 5, a direct liquid writing instrument (marking pen) was obtained.

Comparative Example 4
Preparation of reversible thermochromic microcapsule pigment A reversible thermochromic microcapsule pigment was obtained in the same manner as in Example 1 except that the average particle size of the microcapsule pigment was adjusted to 2.5 μm.
The microcapsule pigment has a complete decolorization temperature of 60 ° C. and a complete color development temperature of −20 ° C., and changes from orange to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition Reversible thermochromic water-based ink was prepared in the same manner as in Example 1 except that the microcapsule pigment (previously cooled to −20 ° C. or less and colored orange) was used. A composition was prepared.

Production of Filling Type Writing Tool A filling type writing tool (marking pen) was prepared in the same manner as in Example 1 except that the reversible thermochromic aqueous ink composition was used.

An orange character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting has an orange color at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft cylinder, the character is discolored and becomes colorless, and this state is maintained at room temperature. By cooling to −20 ° C. or less, the original orange color was restored, and the discoloration behavior was reproduced repeatedly.

Comparative Example 5
Preparation of reversible thermochromic microcapsule pigment A reversible thermochromic microcapsule pigment was obtained in the same manner as in Example 4 except that the average particle size of the microcapsule pigment was adjusted to 2.3 μm.
The microcapsule pigment has a complete decolorization temperature of 58 ° C. and a complete color development temperature of −20 ° C., and changes from pink to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition Reversible thermochromic water-based ink composition by the same method as in Example 4 except that the microcapsule pigment (previously cooled to −20 ° C. or less and colored in pink) was used. An ink composition was prepared.

Production of Filling Type Writing Tool A filling type writing instrument (marking pen) was prepared by the same method as in Example 4 except that the reversible thermochromic aqueous ink composition was used.

Using the writing instrument, writing was made on paper to form pink letters (handwriting).
The handwriting has a pink color at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft tube, the character is discolored and becomes colorless, and this state is maintained at room temperature. By cooling to −20 ° C. or lower, the original pink color was restored, and the discoloration behavior was repeatedly reproduced.

Comparative Example 6
Preparation of reversible thermochromic microcapsule pigment A reversible thermochromic microcapsule pigment was obtained in the same manner as in Example 5 except that the average particle size of the microcapsule pigment was adjusted to 2.4 μm.
The microcapsule pigment has a complete decolorization temperature of 56 ° C. and a complete color development temperature of −20 ° C., and changes from black to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition Reversible thermochromic water-based ink was prepared in the same manner as in Example 5 except that the microcapsule pigment (previously cooled to -20 ° C or less and colored black) was used. A composition was prepared.

Production of Filled Writing Instruments A direct liquid writing instrument (marking pen) was prepared in the same manner as in Example 5 except that the reversible thermochromic aqueous ink composition was used.

A black character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting is black at room temperature (25 ° C.), and when the character is rubbed with a friction member attached to the shaft tube, the character is decolored and becomes colorless, and this state is maintained at room temperature. By cooling to −20 ° C. or lower, the original black color was restored, and the discoloration behavior was reproduced repeatedly.

  The following tests were carried out using the writing instruments obtained in the respective examples and comparative examples.

Vibration Test Using a writing instrument produced in Examples 1 to 5 and Comparative Examples 1 to 6, 10 lines of 20 cm are written on a report sheet.
Put the cap on the writing instrument and set it upright on the shaker (manufactured by Taitec Co., Ltd., reciprocating shaker) in the upright state (writing tip upward), and add vibration in the vertical direction at 284 rpm for 5 hours in an environment of 25 ° C. After that, 10 lines of 20 cm straight lines were written on the report paper and compared with the handwriting before the test.
Furthermore, after applying vibration in the vertical direction for 50 hours in a 40 ° C. environment assuming long-term aging, 10 lines of 20 cm straight lines were similarly written on the report paper and compared with the handwriting before the test.

The vibration test results are shown in the following table.

In addition, the evaluation regarding the symbol in a table | surface is as follows.
○: The handwriting is not faint compared to the initial, and has the same color density as the initial.
X: Fading was observed at the start of writing, and the handwriting density was lighter than in the initial stage.

Aging test Four writing instruments prepared in Example 1 and Comparative Example 1 are prepared. Using the writing instrument, write 10 lines of 20 cm straight lines on the report sheet.
Put the cap on the writing instrument you wrote and stand upright (writing tip upward), the first one at 25 ° C for 30 days, the second one at 25 ° C for 60 days, the third one at 50 ° C for 30 days, the fourth one at 50 ° C Leave for 60 days. After leaving each, 10 lines of 20 cm were written on the report paper and compared with the handwriting before the test.

The results of aging tests are shown in the following table.

In addition, the evaluation regarding the symbol in a table | surface is as follows.
○: The handwriting is not faint compared to the initial, and has the same color density as the initial.
X: Fading was observed at the start of writing, and the handwriting density was lighter than in the initial stage.

Writing Feeling Test Using the writing tools produced in Examples 1 to 5 and Comparative Examples 1 to 6, writing feelings were compared by writing 30 circles of 15 circles on a line.
The writing test was performed by five testers A to E.

The writing test results are shown in the following table.

In addition, the evaluation regarding the symbol in a table | surface is as follows.
A: Very smooth writing is possible.
○: Smooth writing is possible.
(Triangle | delta): It has normal writing feeling.

Example 6
Preparation of reversible thermochromic microcapsule pigment (a) 3.0 parts of 1,3-dimethyl-6-diethylaminofluorane as component (4) 4,4 '-(2-ethylhexane-1, 1- Diyl) Color comprising 3.0 parts of diphenol, 5.0 parts of 2,2-bis (4'-hydroxyphenyl) -hexafluoropropane, and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c) A microcapsule pigment suspension containing a reversible thermochromic composition having a memory property was obtained.
The suspension was centrifuged to isolate a reversible thermochromic microcapsule pigment.
The microcapsule pigment has an average particle size of 1.5 μm, a complete color erasing temperature of 60 ° C., and a complete color development temperature of −25 ° C., which changes from orange to colorless according to temperature change.

Preparation of reversible thermochromic water-based ink composition 25.0 parts of the microcapsule pigment (previously cooled to −25 ° C. or less and colored orange), comb-type polymer dispersant [manufactured by Nippon Lubrizol Co., Ltd. , Trade name: Solsperse 43000], 0.5 parts, organic nitrogen sulfur compound [made by Hokuko Chemical Co., Ltd., trade name: Hokuside R-150, 2-methyl-4-isothiazolin-3-one and 5-chloro-2 -Methyl-4-isothiazolin-3-one mixture] 1.0 part, polyvinyl alcohol 0.5 part, glycerin 35.0 part, silicone-based antifoaming agent 0.02 part and water 37.98 parts were mixed. A reversible thermochromic aqueous ink composition was obtained.
The ink composition had a pH of 7.00 and a surface tension of 39.8 mN / m.

Fabrication of filling-type writing instruments Impregnation of the ink composition in an ink occlusion body in which a polyester sliver is coated with a synthetic resin film, and the polyester composition is accommodated in a shaft cylinder made of polypropylene resin, and a polyester fiber resin processing pen at the tip of the axis cylinder A (bullet type) was assembled in a connected state via a holder, and a cap was attached to obtain a filling pen (marking pen).

Preparation of writing instrument set A writing instrument set was obtained by combining the above-mentioned filling type writing instrument and a rectangular SEBS resin friction body.
An orange character (handwriting) was formed by writing on the paper using the writing instrument.
The handwriting has an orange color at room temperature (25 ° C.), and when the character is rubbed with a friction body, the character is decolored and colorless, and this state is maintained at room temperature, and is −25 By cooling to below ℃, the original orange color was restored and the discoloration behavior was reproduced repeatedly.

t ₁ Complete color development temperature of reversible thermochromic microcapsule pigment with heat decoloring type t ₂ Color development start temperature of reversible thermochromic microcapsule pigment with heat decoloration type t ₃ Reversible thermochromic microcapsule pigment with heat decoloration type Decoloration start temperature of t ₄ Complete decolorization temperature of reversible thermochromic microcapsule pigment of heat decoloring type T ₁ Complete decoloration temperature of reversible thermochromic microcapsule pigment of ₁ heating color developing type T ₂ Reversible heat of color developing type of heat decoloring Discoloration start temperature of the color-changing microcapsule pigment T ₃ Color development start temperature of the reversible thermochromic microcapsule pigment of the ₃ heating color development type T ₄ Color development temperature of the reversible thermochromic microcapsule pigment of the heat development color type ΔH Hysteresis width 1 Writing instrument 2 Ink occlusion body 3 Pen body 4 Shaft cylinder 5 Holder 6 Cap 7 Friction member 8 Ink 9 Stirring body 10 Valve mechanism

Claims (11)

  Reversible thermal discoloration comprising water, a water-soluble organic solvent, (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction occurs. Reversible thermochromic microcapsule pigment having an average particle size of 0.1 to 2.0 μm encapsulating a functional composition, a comb-type polymer dispersant having a carboxyl group in a side chain, an organic nitrogen sulfur compound, Reversible thermochromic water-based ink composition comprising an adhesive resin.   The organic nitrogen sulfur compound is 2- (4-thiazoyl) -benzimidazole, 2- (thiocyanatomethylthio) -1,3-benzothiazole, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl The reversibly thermochromic water-based ink composition according to claim 1, which is a compound selected from -4-isothiazolin-3-one.   The reversible thermochromic water-based ink composition according to claim 1 or 2, wherein the mass ratio of the comb polymer dispersant having a carboxyl group in the side chain and the organic nitrogen sulfur compound is 1: 1 to 1:10.   The reversibly thermochromic water-based ink composition according to any one of claims 1 to 3, wherein the pH of the ink composition is in the range of 3 to 8.   The reversibly thermochromic water-based ink composition according to claim 4, wherein the ink composition is made of a water-soluble resin that is soluble in the pH range of 3 to 8.   The reversibly thermochromic water-based ink composition according to claim 4 or 5, comprising a polyurethane emulsion or an acrylic resin emulsion having a pH of 5 to 9.   A writing instrument comprising a pen body that houses the reversible thermochromic water-based ink composition according to any one of claims 1 to 6 in a shaft cylinder and derives the ink composition in the shaft cylinder.   8. The writing instrument according to claim 7, wherein a rear end of the pen body is in contact with an ink occlusion body composed of a fiber bundle housed in a shaft cylinder, and the ink occlusion body is impregnated with an ink composition.   The writing instrument according to claim 7 or 8, wherein the pen body is a marking pen body.   The writing instrument according to any one of claims 7 to 9, further comprising a friction member.   A writing instrument set comprising the writing instrument according to any one of claims 7 to 9 and a friction body.

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