Thermochromic ink composition for writing instruments and writing instrument containing the same

Abstract

To provide a thermochromic ink composition 2 for writing instruments, and a writing instrument 1 containing the composition, where the ink composition contains a medium, a heat-discolorable reversible thermochromic pigment in a colored state, and a heat-color-developable reversible thermochromic pigment in a discolored state, where the colors in the colored states of the heat-discolorable reversible thermochromic pigment and the heat-color-developable reversible thermochromic pigment are different, the complete discoloration temperature t4 of the heat-discolorable reversible thermochromic pigment is in the range of 40 to 95°C, the complete color-development temperature T4 of the heat-color-developable reversible thermochromic pigment is in the range of 40 to 95°C, and the complete discoloration temperature T1 is in the range of -50 to 5°C.SOLUTION: The invention provides a thermochromic ink composition for writing instruments, and a writing instrument containing the composition. The ink composition enables formation of written traces without limitation on the color of the written traces before or after color change and allowing the written traces rich in variations in color change.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a thermochromic ink composition for a writing instrument and a writing instrument containing the same. More specifically, the present invention relates to a thermochromic ink composition for a writing instrument that can change the color of handwriting and a writing instrument containing the same. [Background technology]

[0002] Conventionally, there have been disclosed a heat-discoloring, reversible thermochromic pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium for controlling the color reactions of (a) and (b) is encapsulated in a microcapsule, or a thermochromic ink composition for a writing instrument containing a heat-coloring, reversible thermochromic pigment and a normal color-unchanging colorant (see, for example, Patent Document 1). Although handwriting obtained with a writing implement containing the ink composition can be discolored by heating, in a system using a heat-discoloring, reversible thermochromic pigment, the color of the handwriting before discoloration is a mixture of the color of the heat-discoloring, reversible thermochromic pigment and the color of a normal colorant, and in a system using a heat-coloring, reversible thermochromic pigment, the color of the handwriting after discoloration is a mixture of the color of the heat-coloring, reversible thermochromic pigment and the color of a normal colorant, which places limitations on the color of the handwriting before or after discoloration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-206432 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a thermochromic ink composition for a writing instrument, which changes the color of handwriting in response to temperature changes of this type, and which has no restrictions on the color of handwriting before or after discoloration, and a writing instrument containing the same. [Means for solving the problem]

[0005] The present invention relates to a medium, a thermally-discolorable reversible thermochromic pigment that is decolorized by heating from a colored state and develops color by cooling from the decolorized state, and a thermally-colorable reversible thermochromic pigment that develops color by heating from a decolorized state and develops color by cooling from the colored state, wherein the thermally-discolorable reversible thermochromic pigment is in a colored state, and the thermally-colorable reversible thermochromic pigment is in a decolorized state, and the thermally-discolorable reversible thermochromic pigment and the thermally-colorable reversible thermochromic pigment are (A) A microcapsule pigment exhibiting hysteresis characteristics in a color density-temperature curve and exhibiting alternation between a colored state and a colorless state, wherein the microcapsule contains a reversible thermochromic composition comprising at least an electron-donating organic color-forming compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color reactions of (a) and (b). The heat-discoloring reversible thermochromic pigment begins to discolor when temperature t3 is reached during the temperature rise from the colored state and becomes completely colorless in a temperature range of temperature t4 or higher. The heat-discoloring reversible thermochromic pigment begins to color when temperature t2 is reached during the temperature fall from the colorless state and becomes completely colored in a temperature range of temperature t1 or lower, with temperature t4 being in the range of 40 to 95°C. The heat-coloring reversible thermochromic pigment begins to color when temperature T3 is reached during the temperature rise from the colorless state and becomes completely colored at temperatures T4 or higher, and becomes completely colored when the temperature falls from the colored state. In the process, the pigment begins to fade when it reaches temperature T2 and becomes completely faded when it reaches temperature T1, and exhibits hysteresis characteristics in which a colored state and a colorless state are selectively maintained in the temperature range between temperatures T2 and T3, temperature T4 being in the range of 40 to 95°C, and temperature T1 being in the range of -50 to 5°C, and the ink composition for a thermochromic writing instrument is characterized in that the color of the colored state of the heat-discoloring reversible thermochromic pigment and the color-developing reversible thermochromic pigment are different. Furthermore, the present invention also provides a writing instrument containing the thermochromic ink composition for a writing instrument, a writing instrument provided with a friction member, and the like. [Effects of the Invention]

[0006] The present invention can provide a thermochromic ink composition for a writing instrument that is capable of forming handwriting with a wide variety of color changes without any restrictions on the color of handwriting before or after color change, and a writing instrument containing the same. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a reversibly thermochromic composition that is heat-discolorable. [Figure 2] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a heat-discolorable, reversible thermochromic composition having color memory properties. [Figure 3] 1 is a graph illustrating the hysteresis characteristics in the color density-temperature curve of a reversibly thermochromic composition that develops color over time. [Figure 4] 1 is an explanatory diagram of an embodiment of a writing instrument containing a thermochromic writing instrument ink composition of the present invention. [Figure 5] FIG. 2 is an explanatory diagram of another embodiment of a writing instrument containing the thermochromic writing instrument ink composition of the present invention. [Figure 6] FIG. 2 is an explanatory diagram of another embodiment of a writing instrument containing the thermochromic writing instrument ink composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The reversible thermochromic pigments that can be used include a thermally decolorizable (discolors when heated and develops color when cooled) reversible thermochromic pigment containing a reversible thermochromic composition consisting of three components: an electron-donating organic color-forming compound, an electron-accepting compound, and an organic compound medium that reversibly induces a color-forming reaction between the two compounds; and a thermally colorable (develops color when heated and develops color when cooled) reversible thermochromic pigment containing a reversible thermochromic composition consisting of three components: an electron-donating organic color-forming compound, an electron-accepting compound, and an organic compound medium that reversibly induces a color-forming reaction between the two compounds. Among these, the reversible thermochromic pigment of the heat-discoloring type will be explained. The reversible thermochromic composition may be a heat-discoloring type (discolors upon heating and develops color upon cooling) reversible thermochromic composition having a relatively small hysteresis width (ΔH=1 to 7°C), such as those described in Japanese Patent Publication Nos. 51-44706, 51-44707, and 1-29398 (see FIG. 1 ), which undergoes a color change around a predetermined temperature (color change point), exhibiting a discolored state in a temperature range above the high-temperature color change point and a colored state in a temperature range below the low-temperature color change point, and of these two states, only one specific state exists in the room temperature range (normal living temperature range), and the other state is maintained while the heat or cold required to manifest that state is applied, but returns to the state exhibited in the room temperature range once the application of heat or cold is removed (see FIG. 1 ). In addition, the hysteresis width (ΔH) described in JP-B-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, JP-A-2006-137880, JP-A-2008-280523, WO 2010 / 131684, WO 2010 / 131684, WO 2012 / 046837, WO 2014 / 200053, WO 2015 / 119161, WO 2016 / 027664, WO 2017 / 022471, WO 2018 / 155583, etc. ) shows a relatively large characteristic in the range of 25°C to 80°C, that is, the shape of the curve plotting the change in color density with temperature change follows a significantly different path when the temperature is increased from a temperature lower than the color change temperature range than when the temperature is decreased from a temperature higher than the color change temperature range, and the color changes along a path that is colored in the low temperature range below the complete color change temperature (t1) or decolored in the high temperature range above the complete decolorization temperature (t4), and the reversible thermochromic composition can also be applied as a heat-discoloring type (discolors when heated and develops color when cooled) reversibly thermochromic composition that has color memory in a specific temperature range [a temperature range between t2 and t3 (a temperature range where two phases are substantially maintained)] (see Figure 2).

[0009] The hysteresis characteristics of the color density-temperature curve of the reversibly thermochromic composition will be described below. In Figure 2, the vertical axis represents color density and the horizontal axis represents temperature. Changes in color density due to temperature changes progress along the arrows. Here, A represents the density at temperature t4 (hereinafter referred to as the complete decolorization temperature) at which the color is completely removed, B represents the density at temperature t3 (hereinafter referred to as the decolorization onset temperature) at which decolorization begins, C represents the density at temperature t2 (hereinafter referred to as the color development onset temperature), and D represents the density at temperature t1 (hereinafter referred to as the complete color development temperature) at which the color is completely removed. The discoloration temperature range is the temperature range between t1 and t4, and can exhibit either a colored state or a decolored state. The temperature range between t2 and t3, which is the region with the largest difference in color density, is the actual discoloration temperature range. The length of the line segment EF is a measure of the contrast of the discoloration, and the length of the line segment HG passing through the midpoint of the line segment EF is the temperature range indicating the degree of hysteresis (hereinafter referred to as the hysteresis range ΔH). If this ΔH value is small, only one specific state can exist between the two states before and after the discoloration in the room temperature range. Furthermore, if the ΔH value is large, it is easier to maintain each state before and after the discoloration. Here, by having the complete decolorization temperature t4 in the range of 40 to 95°C, preferably 45 to 95°C, and more preferably 50 to 95°C, the color can be removed by a simple method such as rubbing with a finger or a friction material. Furthermore, if the complete color development temperature t1 is set to a temperature in the range of -50 to 5°C, preferably -50 to 0°C, and more preferably -50 to -5°C, which is not reached at normal living temperatures, the discolored state can be maintained at room temperature.

[0010] Components (a), (b) and (c) contained in the reversible thermochromic composition will be specifically described below. The component (A), ie, the electron-donating organic color former, is a component that determines the color, and is a compound that donates electrons to the component (B), which is a color developer, to develop color. Examples of the electron-donating color-forming organic compound include phthalide compounds, fluoran compounds, styrinoquinoline compounds, diazarhodamine lactone compounds, pyridine compounds, quinazoline compounds, and bisquinazoline compounds. Of these, phthalide compounds, fluoran compounds, styrinoquinoline compounds, and diazarhodamine lactone compounds are preferred. Examples of the phthalide compound include diphenylmethane phthalide compounds, phenylindolyl phthalide compounds, indolyl phthalide compounds, diphenylmethane azaphthalide compounds, phenylindolyl azaphthalide compounds, and derivatives thereof. Among these, phenylindolyl azaphthalide compounds and derivatives thereof are preferred. Examples of these compounds are shown below. 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-acetamido-4-diethylaminophenyl)-3-(1-propylindol-3-yl)-4-azaphthalide, 3,6-bis(diphenylamino)fluoran, 3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluorane, 2-methyl-6-(N-ethyl-Np-tolylamino)fluoran, 3-chloro-6-cyclohexylaminofluoran, 2-methyl-6-cyclohexylaminofluoran, 2-(2-chloroamino)-6-dibutylaminofluoran, 2-(2-chloroanilino)-6-di-n-butylaminofluoran, 2-(3-trifluoromethylanilino)-6-diethylaminofluoran, 2-(3-trifluoromethylanilino)-6-dipentylaminofluoran, 2-(dibenzylamino)-6-diethylaminofluoran, 2-(N-methylanilino)-6-(N-ethyl-Np-tolylamino)fluoran, 1,3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methoxy-6-diethylaminofluoran, 2-anilino-3-methyl-6-di-n-butylaminofluoran, 2-anilino-3-methoxy-6-di-n-butylaminofluoran, 2-xylidino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-(N-ethyl-Np-tolylamino)fluoran, 1,2-Benz-6-diethylaminofluoran, 1,2-Benz-6-(N-ethyl-N-isobutylamino)fluoran, 1,2-benz-6-(N-ethyl-N-isoamylamino)fluoran, 2-(3-methoxy-4-dodecoxystyryl)quinoline, spiro[5H-(1)benzopyrano(2,3-d)pyrimidin-5,1'(3'H)isobenzofuran]-3'-one, 2-(diethylamino)-8-(diethylamino)-4-methyl, spiro[5H-(1)benzopyrano(2,3-d)pyrimidin-5,1'(3'H)isobenzofuran]-3'-one, 2-(di-n-butylamino)-8-(di-n-butylamino)-4-methyl, spiro[5H-(1)benzopyrano(2,3-d)pyrimidin-5,1'(3'H)isobenzofuran]-3'-one, 2-(di-n-butylamino)-8-(diethylamino)-4-methyl, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidin-5,1'(3'H)isobenzofuran]-3'-one, 2-(di-n-butylamino)-8-(N-ethyl-Ni-amylamino)-4-methyl, spiro[5H-(1)benzopyrano(2,3-d)pyrimidin-5,1'(3'H)isobenzofuran]-3'-one, 2-(dibutylamino)-8-(dipentylamino)-4-methyl, 4,5,6,7-tetrachloro-3-[4-(dimethylamino)-2-methoxyphenyl]-3-(1-butyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-[4-(diethylamino)-2-ethoxyphenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-[4-(diethylamino)-2-ethoxyphenyl]-3-(1-pentyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-tetrachloro-3-[4-(diethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone, 3',6'-bis[phenyl(2-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one, 3',6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one, 3',6'-bis[phenyl(3-ethylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one, 2,6-bis(2′-ethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-bis(2′,4′-diethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2-(4′-dimethylaminophenyl)-4-methoxy-quinazoline, 4,4'-(Ethylenedioxy)-bis[2-(4-diethylaminophenyl)quinazoline] The following can be mentioned: In addition to the above-mentioned compounds having a substituent on the phenyl group forming the xanthene ring, fluorans may also be compounds that exhibit a blue or black color and have a substituent on the phenyl group forming the xanthene ring and also have a substituent on the phenyl group forming the lactone ring (for example, an alkyl group such as a methyl group, or a halogen atom such as a chloro group).

[0011] The component (ii), ie, the electron accepting compound, is a compound that accepts electrons from the component (i) and functions as a developer for the component (i). The electron-accepting compound may be a compound selected from a group of compounds having an active proton and derivatives thereof, a group of pseudo-acidic compounds (a group of compounds that are not acids but act as an acid in the composition to cause component (A) to develop color), a group of compounds having an electron vacancy, etc. Among these, a compound selected from a group of compounds having an active proton is preferred. Examples of compounds having an active proton and derivatives thereof include compounds having a phenolic hydroxyl group and metal salts thereof, carboxylic acids and metal salts thereof, preferably aromatic carboxylic acids, aliphatic carboxylic acids having 2 to 5 carbon atoms and metal salts thereof, acidic phosphate esters and metal salts thereof, as well as azole compounds and derivatives thereof, and 1,2,3-triazole and derivatives thereof. Among these, compounds having a phenolic hydroxyl group are preferred because they can exhibit effective thermochromic properties. The compounds having a phenolic hydroxyl group include a wide range of compounds, from monophenolic compounds to polyphenolic compounds, and further include bis- and tris-phenols, phenol-aldehyde condensation resins, etc. Among the compounds having a phenolic hydroxyl group, those having at least two benzene rings are preferred. Furthermore, these compounds may have a substituent, and examples of the substituent include an alkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, a carboxyl group and its ester or amide group, and a halogen group. Examples of metals contained in the metal salts of compounds having an active proton include sodium, potassium, calcium, zinc, zirconium, aluminum, magnesium, nickel, cobalt, tin, copper, iron, vanadium, titanium, lead, and molybdenum.

[0012] Specific examples are given below. Phenol, o-cresol, tertiary butyl catechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcinol, dodecyl gallate, 4,4-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl) sulfide, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane, 1 ,1-bis(4-hydroxyphenyl)n-butane, 1,1-bis(4-hydroxyphenyl)n-pentane, 1,1-bis(4-hydroxyphenyl)n-hexane, 1,1-bis(4-hydroxyphenyl)n-heptane, 1,1-bis(4-hydroxyphenyl)n-octane, 1,1-bis(4-hydroxyphenyl)n-nonane, 1,1-bis(4-hydroxyphenyl)n-decane, 1,1-bis(4-hydroxyphenyl)n-dodecane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis(4-hydroxyphenyl)n-butane, 1,1-bis(4-hydroxyphenyl)n-pentane, 1,1-bis(4-hydroxyphenyl)n-hexane, 1,1-bis(4-hydroxyphenyl)n-heptane, 1,1-bis(4-hydroxyphenyl)n-octane, 1,1-bis(4-hydroxyphenyl)n-nonane, 1,1-bis(4-hydroxyphenyl)n-decane, 1,1-bis(4-hydroxyphenyl)n-dodecane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis(4-hydroxyphenyl)-3-methylbutane, 1,1-bis(4-hydroxyphenyl)-3-methylpentane, 1,1-bis(4-hydroxyphenyl)-2,3-dimethylpentane, 1,1-bis(4-hydroxyphenyl)-2-ethylbutane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl)-3,7-dimethyloctane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1-phenyl-1,1-bi bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)n-butane, 2,2-bis(4-hydroxyphenyl)n-pentane, 2,2-bis(4-hydroxyphenyl)n-hexane, 2,2-bis(4-hydroxyphenyl)n-heptane, 2,2-bis(4-hydroxyphenyl)n-octane, 2,2-bis(4-hydroxyphenyl)n-nonane, 2,2-bis(4-hydroxyphenyl)n-decane, 2,2-bis(4-hydroxyphenyl)n-dodecane, 2,Examples include 2-bis(4-hydroxyphenyl)ethyl propionate, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 2,2-bis(4-hydroxyphenyl)-4-methylhexane, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, bis(2-hydroxyphenyl)methane, 1,1,1-tris(4-hydroxyphenyl)ethane, and 3,3-bis(3-methyl-4-hydroxyphenyl)butane. The compounds having a phenolic hydroxyl group are capable of exhibiting the most effective thermochromic properties, but compounds selected from aromatic carboxylic acids and aliphatic carboxylic acids having 2 to 5 carbon atoms, carboxylic acid metal salts, acidic phosphate esters and their metal salts, 1,2,3-triazole and its derivatives may also be used.

[0013] The component (iii) of the reaction medium that reversibly induces the electron donor / acceptor reaction between the components (i) and (ii) in a specific temperature range will now be described. Examples of the component (iii) include alcohols, esters, ketones, ethers, and acid amides. When component (c) is used for microencapsulation and secondary processing as described below, compounds with low molecular weights tend to evaporate outside the capsules when subjected to high heat treatment, so compounds with 10 or more carbon atoms are preferably used to ensure stable retention within the capsules. As the alcohol, aliphatic monohydric saturated alcohols having 10 or more carbon atoms are effective, and specific examples include decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, and docosyl alcohol.

[0014] As the esters, esters having 10 or more carbon atoms are effective, and examples thereof include esters obtained from any combination of a monocarboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring, esters obtained from any combination of a polycarboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring, and esters obtained from any combination of a monocarboxylic acid having an aliphatic and alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring. Specific examples include esters obtained from ethyl caprylate, octyl caprylate, stearyl caprylate, myristyl caprate, docosyl caprate, 2-ethylhexyl laurate, n-decyl laurate, 3-methylbutyl myristate, myristyl myristate, cetyl myristate, isopropyl palmitate, neopentyl palmitate, nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutyl stearate, and 3,5,5-trimethylhexyl stearate. , n-undecyl stearate, pentadecyl stearate, stearyl stearate, cyclohexylmethyl stearate, isopropyl behenate, hexyl behenate, lauryl behenate, behenyl behenate, cetyl benzoate, stearyl p-tert-butylbenzoate, dimyristyl phthalate, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelaate, di-(n-noni) sebacate 1,18-octadecylmethylenedicarboxylate dineopentyl, ethylene glycol dimyristate, propylene glycol dilaurate, propylene glycol distearate, hexylene glycol dipalmitate, 1,5-pentanediol distearate, 1,2,6-hexanetriol trimyristate, 1,4-cyclohexanediol didecyl, 1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprinate, xylene glycol distearate, and the like.

[0015] Also effective are esters of saturated fatty acids and branched fatty alcohols, esters of unsaturated fatty acids or branched or substituted saturated fatty acids and branched fatty alcohols or fatty alcohols having 16 or more carbon atoms, and ester compounds selected from cetyl butyrate, stearyl butyrate, and behenyl butyrate. Specifically, 2-ethylhexyl butyrate, 2-ethylhexyl behenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate, 3,5,5-trimethylhexyl laurate, 3,5,5-trimethylhexyl palmitate, 3,5,5-trimethylhexyl stearate, 2-methylbutyl caproate, 2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate, 1-ethylpropyl stearate, 1-ethylpropyl behenate, 1-ethylhexyl laurate xyl, 1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate, 2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyl laurate, 2-methylbutyl stearate, 2-methylbutyl stearate, 3-methylbutyl stearate, 1-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutyl behenate, 1-methylheptyl stearate, 1-methylheptyl behenate, 1-ethylpentyl caproate, 1-Ethylpentyl Palmitate, 1-Methylpropyl Stearate, 1-Methyloctyl Stearate, 1-Methylhexyl Stearate, 1,1-Dimethylpropyl Laurate, 1-Methylpentyl Caprate, 2-Methylhexyl Palmitate, 2-Methylhexyl Stearate, 2-Methylhexyl Behenate, 3,7-Dimethyloctyl Laurate, 3,7-Dimethyloctyl Myristate, 3,7-Dimethyloctyl Palmitate, 3,7-Dimethyloctyl Stearate, 3,7-Dimethyl Behenate Examples of suitable oleic acid copolymers include octyl oleate, stearyl oleate, behenyl oleate, stearyl linoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearyl erucate, isostearyl erucate, cetyl isostearate, stearyl isostearate, 2-methylpentyl 12-hydroxystearate, 2-ethylhexyl 18-bromostearate, isostearyl 2-ketomyristate, 2-ethylhexyl 2-fluoromyristate, cetyl butyrate, stearyl butyrate, and behenyl butyrate.

[0016] Furthermore, in order to cause a color change that exhibits large hysteresis characteristics in the color density-temperature curve and to impart color memory properties that depend on temperature changes, carboxylic acid ester compounds that exhibit a ΔT value (melting point-cloud point) of 5°C or more and less than 50°C, as described in Japanese Patent Publication No. 4-17154, such as carboxylic acid esters containing a substituted aromatic ring in the molecule, esters of carboxylic acids containing an unsubstituted aromatic ring and aliphatic alcohols having 10 or more carbon atoms, carboxylic acid esters containing a cyclohexyl group in the molecule, esters of fatty acids having 6 or more carbon atoms and unsubstituted aromatic alcohols or phenols, esters of fatty acids having 8 or more carbon atoms and branched aliphatic alcohols, esters of dicarboxylic acids and aromatic alcohols or branched aliphatic alcohols, dibenzyl cinnamate, heptyl stearate, didecyl adipate, dilauryl adipate, dimyristyl adipate, dicetyl adipate, distearyl adipate, trilaurin, trimyristin, tristearin, dimyristin, and distearin, etc.

[0017] Fatty acid ester compounds obtained from an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid, and fatty acid ester compounds having a total of 17 to 23 carbon atoms obtained from n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid having 10 to 16 carbon atoms are 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, n-heptyl laurate, n-nonyl laurate, n-undecyl laurate, n-tridecyl laurate, n-pentadecyl laurate, n-pentyl myristate, n-heptyl myristate, myristate Examples thereof include 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-nonyl stearate, n-undecyl stearate, n-tridecyl stearate, n-pentadecyl stearate, n-nonyl eicosanoate, n-undelci eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, and n-pentadecyl behenate.

[0018] As the ketones, aliphatic ketones having a total carbon number of 10 or more are effective, and examples thereof include 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, aryl alkyl ketones having a total carbon number of 12 to 24, for example, n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n-tetradecanophenone, 4-n-dodecaacetophenone, n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, n ... nophenone, 4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone, 4-n-cyclohexylacetophenone, 4-tert-butylpropiophenone, n-heptaphenone, 4-n-pentylacetophenone, cyclohexyl phenyl ketone, benzyl-n-butyl ketone, 4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone, 1-acetonaphthone, 2-acetonaphthone, cyclopentyl phenyl ketone, and the like.

[0019] As the ethers, aliphatic ethers having a total of 10 or more carbon atoms are effective, and examples thereof include dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditridecyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecyl ether, dioctadecyl ether, decanediol dimethyl ether, undecanediol dimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethyl ether, decanediol diethyl ether, and undecanediol diethyl ether.

[0020] Examples of acid amides include acetamide, propionic acid amide, butyric acid amide, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, benzamide, caproic acid anilide, caprylic acid anilide, capric acid anilide, lauric acid anilide, myristic acid anilide, palmitic acid anilide, stearic acid anilide, behenic acid anilide, oleic acid anilide, erucic acid anilide, and caproic acid N-methylamide. Caprylic acid N-methylamide, capric acid N-methylamide, lauric acid N-methylamide, myristic acid N-methylamide, palmitic acid N-methylamide, stearic acid N-methylamide, behenic acid N-methylamide, oleic acid N-methylamide, erucic acid N-methylamide, lauric acid N-ethylamide, myristic acid N-ethylamide, palmitic acid N-ethylamide, stearic acid N-ethylamide, oleic acid N-ethylamide, lauric acid N-butylamide, myristic acid N-butylamide, palmitic acid N-butylamide, stearic acid N-ethylamide Phosphoric acid N-butylamide, oleic acid N-butylamide, lauric acid N-octylamide, myristic acid N-octylamide, palmitic acid N-octylamide, stearic acid N-octylamide, oleic acid N-octylamide, lauric acid N-dodecylamide, myristic acid N-dodecylamide, palmitic acid N-dodecylamide, stearic acid N-dodecylamide, oleic acid N-dodecylamide, dilauric acid amide, dimyristic acid amide, dipalmitic acid amide, distearic acid amide, dioleic acid amide, trilauric acid amide, tri Myristic acid amide, tripalmitic acid amide, tristearic acid amide, trioleic acid amide, succinic acid amide, adipic acid amide, glutaric acid amide, malonic acid amide, azelaic acid amide, maleic acid amide, succinic acid N-methylamide, adipic acid N-methylamide, glutaric acid N-methylamide, malonic acid N-methylamide, azelaic acid N-methylamide, succinic acid N-ethylamide, adipic acid N-ethylamide, glutaric acid N-ethylamide, malonic acid N-ethylamide, azelaic acid N-ethylamide, succinic acid N-butylamide,Examples include adipic acid N-butylamide, glutaric acid N-butylamide, malonic acid N-butylamide, adipic acid N-octylamide, and adipic acid N-dodecylamide.

[0021] Furthermore, as the component (iii), a compound represented by the following general formula (1) can also be used. [ka] [wherein R1 represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, and either X1 or X2 represents -(CH2) n OCOR2 or -(CH2) n COOR2, the other represents a hydrogen atom, n represents an integer of 0 to 2, R2 represents an alkyl or alkenyl group having 4 or more carbon atoms, Y1 and Y2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen, and r and p represent integers of 1 to 3. Among the compounds represented by the formula (1), when R1 is a hydrogen atom, a reversible thermochromic composition having a wider hysteresis width can be obtained, which is preferable, and when R1 is a hydrogen atom and m is 0, it is even more preferable. Among the compounds represented by formula (1), compounds represented by the following general formula (2) are more preferably used. [ka] In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, and more preferably an alkyl group having 12 to 22 carbon atoms. Specific examples of the compound include 4-benzyloxyphenylethyl octanoate, 4-benzyloxyphenylethyl nonanoate, 4-benzyloxyphenylethyl decanoate, 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.

[0022] Furthermore, as the component (iii), a compound represented by the following general formula (3) can also be used. [ka] (In the formula, R represents an alkyl or alkenyl group having 8 or more carbon atoms, m and n each represent an integer of 1 to 3, and X and Y each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom.) Specific examples of the compound include 1,1-diphenylmethyl octanoate, 1,1-diphenylmethyl nonanoate, 1,1-diphenylmethyl decanoate, 1,1-diphenylmethyl undecanoate, 1,1-diphenylmethyl dodecanoate, 1,1-diphenylmethyl tridecanoate, 1,1-diphenylmethyl tetradecanoate, 1,1-diphenylmethyl pentadecanoate, 1,1-diphenylmethyl hexadecanoate, 1,1-diphenylmethyl heptadecanoate, and 1,1-diphenylmethyl octadecanoate.

[0023] Furthermore, a compound represented by the following general formula (4) can also be used as the component (iii). [ka] (In the formula, 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, a diester of succinic acid and 2-[4-(3-methylbenzyloxy)phenyl]ethanol, a diester of glutaric acid and 2-(4-benzyloxyphenyl)ethanol, a diester of glutaric acid and 2-[4-(4-chlorobenzyloxy)phenyl]ethanol, a diester of adipic acid and 2-(4-benzyloxyphenyl)ethanol, a diester of pimelic acid and 2-(4-benzyloxyphenyl)ethanol, a diester of suberic acid and 2-(4-benzyloxyphenyl)ethanol, a diester of suberic acid and 2-[4-(3-methylbenzyloxy)phenyl]ethanol, a diester of glutaric acid and 2-(4-benzyloxyphenyl)ethanol, a diester of adipic acid and 2-(4-benzyloxyphenyl)ethanol, a diester of pimelic acid and 2-(4-benzyloxyphenyl)ethanol, a diester of suberic acid and 2-[4-(3-methylbenzyloxy)phenyl]ethanol, a diester of adipic acid and 2-(4-benzyloxyphenyl) ... Examples thereof include the diester of suberic acid and 2-[4-(4-chlorobenzyloxy)phenyl]ethanol, the diester of suberic acid and 2-[4-(2,4-dichlorobenzyloxy)phenyl]ethanol, the diester of azelaic acid and 2-(4-benzyloxyphenyl)ethanol, the diester of sebacic acid and 2-(4-benzyloxyphenyl)ethanol, the diester of 1,10-decanedicarboxylic acid and 2-(4-benzyloxyphenyl)ethanol, the diester of 1,18-octadecanedicarboxylic acid and 2-(4-benzyloxyphenyl)ethanol, and the diester of 1,18-octadecanedicarboxylic acid and 2-[4-(2-methylbenzyloxy)phenyl]ethanol.

[0024] Furthermore, a compound represented by the following general formula (5) can also be used as the component (iii). [ka] (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, a diester of 1,3-bis(2-hydroxyethoxy)benzene and lauric acid, a diester of 1,3-bis(2-hydroxyethoxy)benzene and myristic acid, a diester of 1,4-bis(hydroxymethoxy)benzene and butyric acid, a diester of 1,4-bis(hydroxymethoxy)benzene and isovaleric acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and acetic acid, and the like. Examples include a diester of 4-bis(2-hydroxyethoxy)benzene and propionic acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and valeric acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and caproic acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and caprylic acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and capric acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and lauric acid, and a diester of 1,4-bis(2-hydroxyethoxy)benzene and myristic acid.

[0025] Furthermore, a compound represented by the following general formula (6) can also be used as the component (iii). [ka] (In the formula, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; m represents an integer of 1 to 3; and n represents an integer of 1 to 20.) Examples of the compound include a diester of succinic acid and 2-phenoxyethanol, a diester of suberic acid and 2-phenoxyethanol, a diester of sebacic acid and 2-phenoxyethanol, a diester of 1,10-decanedicarboxylic acid and 2-phenoxyethanol, and a diester of 1,18-octadecanedicarboxylic acid and 2-phenoxyethanol.

[0026] Furthermore, a compound represented by the following general formula (7) can also be used as the component (iii). [ka] (In the formula, R represents an alkyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, a cycloalkyl group, or an alkenyl group having 4 to 22 carbon atoms; X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; and n represents 0 or 1.) Examples of the compound include decyl 4-phenylbenzoate, lauryl 4-phenylbenzoate, myristyl 4-phenylbenzoate, cyclohexylethyl 4-phenylbenzoate, octyl 4-biphenylacetate, nonyl 4-biphenylacetate, decyl 4-biphenylacetate, lauryl 4-biphenylacetate, myristyl 4-biphenylacetate, tridecyl 4-biphenylacetate, pentadecyl 4-biphenylacetate, cetyl 4-biphenylacetate, cyclopentyl 4-biphenylacetate, cyclohexylmethyl 4-biphenylacetate, hexyl 4-biphenylacetate, and cyclohexylmethyl 4-biphenylacetate.

[0027] Furthermore, a compound represented by the following general formula (8) can also be used as the component (iii). [ka] (In the formula, R represents either an alkyl group having 3 to 18 carbon atoms or an aliphatic acyl group having 3 to 18 carbon atoms; X represents either a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom; Y represents either a hydrogen atom or a methyl group; and Z represents either a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom.) Examples of the compound include phenoxyethyl 4-butoxybenzoate, phenoxyethyl 4-pentyloxybenzoate, phenoxyethyl 4-tetradecyloxybenzoate, esters of phenoxyethyl 4-hydroxybenzoate with dodecanoic acid, and dodecyl ether of phenoxyethyl vanillate.

[0028] Furthermore, a compound represented by the following general formula (9) can also be used as the component (iii). [ka] (In the formula, R represents any one of an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, and a cycloalkyl group; X represents any one of a hydrogen atom, an alkyl group, an alkoxy group, and a halogen atom; Y represents any one of a hydrogen atom, an alkyl group, an alkoxy group, and a halogen atom; and n represents 0 or 1.) Examples of the compound include benzoate ester of octyl p-hydroxybenzoate, benzoate ester of decyl p-hydroxybenzoate, p-methoxybenzoate ester of heptyl p-hydroxybenzoate, o-methoxybenzoate ester of dodecyl p-hydroxybenzoate, and benzoate ester of cyclohexylmethyl p-hydroxybenzoate.

[0029] Furthermore, a compound represented by the following general formula (10) can also be used as the component (iii). [ka] (In the formula, R represents any one of an alkyl group having 3 to 18 carbon atoms, a cycloalkylalkyl group having 6 to 11 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, and an alkenyl group having 3 to 18 carbon atoms; X represents any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a halogen atom; and Y represents any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, and a halogen atom.) Examples of the compound include phenoxyethyl ether of nonyl p-hydroxybenzoate, phenoxyethyl ether of decyl p-hydroxybenzoate, phenoxyethyl ether of undecyl p-hydroxybenzoate, and phenoxyethyl ether of dodecyl vanillate.

[0030] Furthermore, a compound represented by the following general formula (11) can also be used as the component (iii). [ka] (In the formula, R represents a cycloalkyl group having 3 to 8 carbon atoms or a cycloalkylalkyl group having 4 to 9 carbon atoms, and n represents an integer of 1 to 3.) Examples of the compound include a diester of 1,3-bis(2-hydroxyethoxy)benzene and cyclohexanecarboxylic acid, a diester of 1,4-bis(2-hydroxyethoxy)benzene and cyclohexanepropionic acid, and a diester of 1,3-bis(2-hydroxyethoxy)benzene and cyclohexanepropionic acid.

[0031] Furthermore, a compound represented by the following general formula (12) can also be used as the component (iii). [ka] (In the formula, R represents an alkyl group having 3 to 17 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, or a cycloalkylalkyl group having 5 to 8 carbon atoms; X represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a methoxy group, an ethoxy group, or a halogen atom; and n represents an integer of 1 to 3.) Examples of the compound include a diester of 4-phenylphenol ethylene glycol ether and cyclohexanecarboxylic acid, a diester of 4-phenylphenol diethylene glycol ether and lauric acid, a diester of 4-phenylphenol triethylene glycol ether and cyclohexanecarboxylic acid, a diester of 4-phenylphenol ethylene glycol ether and octanoic acid, a diester of 4-phenylphenol ethylene glycol ether and nonanoic acid, a diester of 4-phenylphenol ethylene glycol ether and decanoic acid, and a diester of 4-phenylphenol ethylene glycol ether and myristic acid.

[0032] The proportions of the components of the reversible thermochromic composition vary depending on the concentration, discoloration temperature, discoloration form, and type of each component, but generally, the component ratios that provide the desired properties are in the range of 1 part of component (a) to 0.1 to 100, preferably 0.1 to 50, and more preferably 0.5 to 20, of component (b), and 1 to 800, preferably 5 to 200, and more preferably 10 to 100, of component (c) (all of the above proportions are in parts by mass).

[0033] Furthermore, various light stabilizers can be added as needed. The light stabilizer is contained to prevent photodegradation of the reversibly thermochromic composition consisting of components (A), (B), and (C), and is contained in a proportion of 0.3 to 24% by mass, preferably 0.3 to 16% by mass, per 1% by mass of component (A). Among the light stabilizers, the ultraviolet absorber effectively blocks ultraviolet rays contained in sunlight and the like, preventing photodegradation caused by the excited state due to the photoreaction of component (A). Furthermore, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, etc., inhibit oxidation reactions caused by light. The light stabilizers may be used alone or in combination of two or more.

[0034] The reversible thermochromic composition can be encapsulated in microcapsules and used as a reversible thermochromic microcapsule pigment (reversible thermochromic pigment). Microencapsulation can be performed by any of the known methods, such as interfacial polymerization, in situ polymerization, liquid curing coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and is appropriately selected depending on the intended use. Furthermore, a secondary resin film can be provided on the surface of the microcapsules depending on the intended purpose to impart durability or to modify the surface properties for practical use. Examples of resins constituting the microcapsules include urea resins, urethane resins, urea-urethane resins, epoxy resins, melamine resins, benzoguanamine resins, and isocyanate resins. The microcapsule pigment preferably has a mass ratio of inclusions / wall film of 7 / 1 to 1 / 1, and by having the wall film ratio within this range, it is possible to prevent a decrease in color density and clarity during color development, and more preferably, the mass ratio of inclusions / wall film is 6 / 1 to 1 / 1. By encapsulating the pigment in the microcapsules, a chemically and physically stable pigment can be obtained.

[0035] The average particle size of the reversible thermochromic microcapsule pigment is not particularly limited, but is preferably in the range of 0.1 to 5 μm, more preferably 0.3 to 5 μm, even more preferably 0.3 to 4 μm, and particularly preferably 0.5 to 3 μm. The average particle diameter was measured by determining the particle region using image analysis particle size distribution measurement software (manufactured by Mountec Co., Ltd., product name: MacView), calculating the diameter equivalent to a circle with a projected area (Heywood diameter) from the area of ​​the particle region, and measuring the average particle diameter of particles equivalent to a sphere with the same volume using this value. Furthermore, if the particle size of all or the majority of particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to an equal-volume sphere by the Coulter method using a particle size distribution analyzer (product name: Multisizer 4e, manufactured by Beckman Coulter, Inc.). Furthermore, the volumetric particle size and average particle size may be measured using a calibrated laser diffraction / scattering particle size distribution analyzer (manufactured by HORIBA, Ltd., product name: LA-960V2) based on values ​​measured using the above-mentioned software or a measuring device using the Coulter method.

[0036] Next, the reversible thermochromic pigment of the heat-coloring type will be described. The electron-donating organic color former (a) used in the reversible thermochromic composition is the same as the electron-donating organic color former used in the heat-discolorable reversible thermochromic pigment. As the electron-accepting compound (b), an alkoxyphenol compound represented by the following general formula (13) described in JP-A-11-129623 can be used. [ka] (R represents an alkyl group.) Examples of the compound include pn-propyloxyphenol, pn-butyloxyphenol, pn-pentyloxyphenol, pn-hexyloxyphenol, pn-heptyloxyphenol, pn-octyloxyphenol, pn-nonyloxyphenol, pn-decyloxyphenol, pn-undecyloxyphenol, pn-dodecyloxyphenol, pn-tridecyloxyphenol, pn-tetradecyloxyphenol, pn-pentyldecyloxyphenol, pn-hexyldecyloxyphenol, pn-heptyldecyloxyphenol, and pn-octyldecyloxyphenol.

[0037] Furthermore, as the electron-accepting compound, a hydroxybenzoic acid ester compound represented by the following general formula (14), which is described in JP-A No. 2001-105732, can also be used. [ka] (wherein R represents a linear or branched alkyl group having 13 to 22 carbon atoms, one or two of X, Y, and Z represent a hydroxyl group, and the remaining represent hydrogen). Examples of the compounds include 3-hydroxybenzoic acid tridecyl ester, 3-hydroxybenzoic acid tetradecyl ester, 3-hydroxybenzoic acid pentadecyl ester, 3-hydroxybenzoic acid hexadecyl ester, 3-hydroxybenzoic acid heptadecyl ester, 3-hydroxybenzoic acid octadecyl ester, 3-hydroxybenzoic acid nonadecyl ester, 3-hydroxybenzoic acid eicosyl ester, 3-hydroxybenzoic acid heneicosyl ester, 3-hydroxybenzoic acid docosyl ester, 4-hydroxybenzoic acid Tridecyl 4-hydroxybenzoate, tetradecyl 4-hydroxybenzoate, pentadecyl 4-hydroxybenzoate, hexadecyl 4-hydroxybenzoate, heptadecyl 4-hydroxybenzoate, octadecyl 4-hydroxybenzoate, nonadecyl 4-hydroxybenzoate, eicosyl 4-hydroxybenzoate, heneicosyl 4-hydroxybenzoate, docosyl 4-hydroxybenzoate, tridecyl 4-hydroxybenzoate, 3,4-dihydroxybenzoate, 3,4- Dihydroxybenzoic acid tetradecyl ester, 3,4-dihydroxybenzoic acid pentadecyl ester, 3,4-dihydroxybenzoic acid hexadecyl ester, 3,4-dihydroxybenzoic acid heptadecyl ester, 3,4-dihydroxybenzoic acid octadecyl ester, 3,4-dihydroxybenzoic acid nonadecyl ester, 3,4-dihydroxybenzoic acid eicosyl ester, 3,4-dihydroxybenzoic acid heneicosyl ester, 3,4-dihydroxybenzoic acid docosyl ester, 3,5-dihydroxybenzoic acid tridecyl ester Examples of hydroxybenzoic acid include 3,5-dihydroxybenzoic acid tetradecyl ester, 3,5-dihydroxybenzoic acid pentadecyl ester, 3,5-dihydroxybenzoic acid hexadecyl ester, 3,5-dihydroxybenzoic acid heptadecyl ester, 3,5-dihydroxybenzoic acid octadecyl ester, 3,5-dihydroxybenzoic acid nonadecyl ester, 3,5-dihydroxybenzoic acid eicosyl ester, 3,5-dihydroxybenzoic acid heneicosyl ester, and 3,5-dihydroxybenzoic acid docosyl ester.

[0038] Furthermore, as the electron-accepting compound, a gallic acid ester compound described in JP-A No. 2003-253149 can also be used. Examples of the compound include dodecyl gallate, tridecyl gallate, tetradecyl gallate, pentadecyl gallate, hexadecyl gallate, octadecyl gallate, eicosyl gallate, and behenyl gallate.

[0039] (c) Examples of reaction media that control the color reactions of (a) and (b) include hydrocarbons, halogenated hydrocarbons, sulfides, ethers, ketones, esters, acid amides, alcohols, waxes, etc. The hydrocarbons include chain hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, etc., and examples of saturated chain hydrocarbons include pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, and triacontane. Examples of unsaturated chain hydrocarbons include 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-heneicosene, 1-docosene, 1-tricosene, 1-tetracosene, 1-pentacosene, 1-hexacosene, 1-heptacosene, 1-octacosene, 1-nonacosene, and 1-triacontene. Examples of alicyclic hydrocarbons include cyclooctane, cyclododecane, n-pentadecylcyclohexane, n-octadecylcyclohexane, n-nonadecylcyclohexane, and decahydronaphthalene. Examples of aromatic hydrocarbons include dodecylbenzene, biphenyl, ethylbiphenyl, 4-benzylbenzene, phenyltolylmethane, diphenylethane, 1,3-diphenylbenzene, dibenzyltoluene, methylnaphthalene, 2,7-diisopropylnaphthalene, methyltetralin, and naphthylphenylmethane.

[0040] Examples of the halogenated hydrocarbons include 1-bromodecane, 1-bromoundecane, 1-bromododecane, 1-bromotridecane, 1-bromotetradecane, 1-chlorotetradecane, 1-bromopentadecane, 1-bromohexadecane, 1-chlorohexadecane, 1-iodohexadecane, 1-bromoheptadecane, 1-bromooctadecane, 1-chlorooctadecane, 1-iodooctadecane, 1-bromoeicosane, 1-chloroeicosane, 1-bromodocosane, and 1-chlorodocosane.

[0041] Examples of the sulfides include di-n-octyl sulfide, di-n-nonyl sulfide, di-n-decyl sulfide, di-n-dodecyl sulfide, di-n-tetradecyl sulfide, di-n-hexadecyl sulfide, di-n-octadecyl sulfide, octyldodecyl sulfide, diphenyl sulfide, dibenzyl sulfide, ditolyl sulfide, diethylphenyl sulfide, dinaphthyl sulfide, 4,4'-dichloro-diphenyl sulfide, and 2,4,5,4'-tetrachloro-diphenyl sulfide.

[0042] Examples of the ethers include aliphatic ethers having a total of 10 or more carbon atoms, such as dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditridecyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecyl ether, dioctadecyl ether, decanediol dimethyl ether, undecanediol dimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethyl ether, decanediol diethyl ether, and undecanediol diethyl ether. Examples of alicyclic ethers include s-trioxane. Examples of aromatic ethers include phenyl ether, benzyl phenyl ether, dibenzyl ether, di-p-tolyl ether, 1-methoxynaphthalene, and 3,4,5-trimethoxytoluene.

[0043] Examples of the ketones include aliphatic ketones having a total carbon number of 10 or more, such as 2-decanone, 3-decanone, 4-decanone, 2-undecanone, 3-undecanone, 4-undecanone, 5-undecanone, 6-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-nonadacanone, 2-eicosanone, 11-eicosanone, 2-heneicosanone, 2-docosanone, laurone, and stearone. Aryl alkyl ketones having a total carbon number of 12 to 24, for example, n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n-tetradecanophenone, 4-n-dodecaacetophenone, n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, n ... Examples of suitable acetophenones include nanophenone, 4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone, 4-n-cyclohexylacetophenone, 4-tert-butylpropiophenone, n-heptaphenone, 4-n-pentylacetophenone, cyclohexyl phenyl ketone, benzyl-n-butyl ketone, 4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone, 1-acetonaphthone, 2-acetonaphthone, and cyclopentyl phenyl ketone. Aryl aryl ketones, such as benzophenone, benzyl phenyl ketone, and dibenzyl ketone. Alicyclic ketones, such as cyclooctanone, cyclododecanone, cyclopentadecanone, and 4-tert-butylcyclohexanone, are also listed.

[0044] As the esters, esters having 10 or more carbon atoms are effective, and examples thereof include esters obtained from any combination of a monocarboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring, esters obtained from any combination of a polycarboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring, and esters obtained from any combination of a monocarboxylic acid having an aliphatic and alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring. Specific examples include esters obtained from ethyl caprylate, octyl caprylate, stearyl caprylate, myristyl caprate, stearyl caprate, docosyl caprate, 2-ethylhexyl laurate, n-decyl laurate, 3-methylbutyl myristate, cetyl myristate, isopropyl palmitate, neopentyl palmitate, nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutyl stearate, and 3,5,5-trimethylhexyl stearate. Cetyl, n-undecyl stearate, pentadecyl stearate, stearyl stearate, cyclohexylmethyl stearate, isopropyl behenate, hexyl behenate, lauryl behenate, behenyl behenate, cetyl benzoate, stearyl p-tert-butylbenzoate, dimyristyl phthalate, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelaate, di-(n-octyl)sebacate Examples include 1,18-octadecylmethylenedicarboxylate dineopentyl, ethylene glycol dimyristate, propylene glycol dilaurate, propylene glycol distearate, hexylene glycol dipalmitate, 1,5-pentanediol dimyristate, 1,2,6-hexanetriol trimyristate, 1,4-cyclohexanediol didecyl, 1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprinate, and xylene glycol distearate. Also effective are esters of saturated fatty acids and branched fatty alcohols, esters of unsaturated fatty acids or branched or substituted saturated fatty acids and branched fatty alcohols or fatty alcohols having 16 or more carbon atoms, and ester compounds selected from cetyl butyrate, stearyl butyrate, and behenyl butyrate.Specifically, 2-ethylhexyl butyrate, 2-ethylhexyl behenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate, 3,5,5-trimethylhexyl laurate, 3,5,5-trimethylhexyl palmitate, 3,5,5-trimethylhexyl stearate, 2-methylbutyl caproate, 2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate, 1-ethylpropyl stearate, 1-ethylpropyl behenate, 1-ethylhexyl laurate xyl, 1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate, 2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyl laurate, 2-methylbutyl stearate, 2-methylbutyl stearate, 3-methylbutyl stearate, 1-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutyl behenate, 1-methylheptyl stearate, 1-methylheptyl behenate, 1-ethylpentyl caproate, 1-Ethylpentyl Palmitate, 1-Methylpropyl Stearate, 1-Methyloctyl Stearate, 1-Methylhexyl Stearate, 1,1-Dimethylpropyl Laurate, 1-Methylpentyl Caprate, 2-Methylhexyl Palmitate, 2-Methylhexyl Stearate, 2-Methylhexyl Behenate, 3,7-Dimethyloctyl Laurate, 3,7-Dimethyloctyl Myristate, 3,7-Dimethyloctyl Palmitate, 3,7-Dimethyloctyl Stearate, 3,7-Dimethyl Behenate Examples include octyl oleate, stearyl oleate, behenyl oleate, stearyl linoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearyl erucate, isostearyl erucate, cetyl isostearate, stearyl isostearate, 2-methylpentyl 12-hydroxystearate, 2-ethylhexyl 18-bromostearate, isostearyl 2-ketomyristate, 2-ethylhexyl 2-fluoromyristate, cetyl butyrate, stearyl butyrate, and behenyl butyrate. Further examples include the carboxylic acid ester compounds disclosed in Japanese Patent Publication No. 4-17154, such as carboxylic acid esters containing a substituted aromatic ring in the molecule, esters of carboxylic acids containing an unsubstituted aromatic ring and aliphatic alcohols having 10 or more carbon atoms, carboxylic acid esters containing a cyclohexyl group in the molecule, esters of fatty acids having 6 or more carbon atoms and unsubstituted aromatic alcohols or phenols, esters of fatty acids having 8 or more carbon atoms and branched aliphatic alcohols or esters, esters of dicarboxylic acids and aromatic alcohols or branched aliphatic alcohols, dibenzyl cinnamate, heptyl stearate, didecyl adipate, dilauryl adipate, dimyristyl adipate, dicetyl adipate, distearyl adipate, trilaurin, trimyristin, tristearin, dimyristin, and distearin. Fatty acid ester compounds obtained from an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid, and fatty acid ester compounds having a total of 17 to 23 carbon atoms obtained from n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid having 10 to 16 carbon atoms are 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, n-heptyl laurate, n-nonyl laurate, n-undecyl laurate, n-tridecyl laurate, n-pentadecyl laurate, n-pentyl myristate, n-heptyl myristate, myristate Examples of suitable oleic acid esters include n-nonyl palmitate, 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-nonyl stearate, n-undecyl stearate, n-tridecyl stearate, n-pentadecyl stearate, n-nonyl eicosanoate, n-undelcino eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, and n-pentadecyl behenate.

[0045] Examples of the alcohols include aliphatic monohydric saturated alcohols such as decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, and docosyl alcohol; aliphatic unsaturated alcohols such as allyl alcohol and oleyl alcohol; alicyclic alcohols such as cyclopentanol, cyclohexanol, cyclooctanol, cyclododecanol, and 4-tert-butylcyclohexanol; aromatic alcohols such as 4-methylbenzyl alcohol and benzhydrol; and polyhydric alcohols such as polyethylene glycol.

[0046] Examples of the acid amides include the following compounds: acetamide, propionic acid amide, butyric acid amide, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, benzamide, caproic acid anilide, caprylic acid anilide, capric acid anilide, lauric acid anilide, myristic acid anilide, palmitic acid anilide, stearic acid anilide, behenic acid anilide, oleic acid anilide, erucic acid anilide, caproic acid N-methylamide, and caprylic acid. N-methylamide, capric acid N-methylamide, lauric acid N-methylamide, myristic acid N-methylamide, palmitic acid N-methylamide, stearic acid N-methylamide, behenic acid N-methylamide, oleic acid N-methylamide, erucic acid N-methylamide, lauric acid N-ethylamide, myristic acid N-ethylamide, palmitic acid N-ethylamide, stearic acid N-ethylamide, oleic acid N-ethylamide, lauric acid N-butylamide, myristic acid N-butylamide, palmitic acid N-butylamide, stearic acid N-ethylamide Phosphoric acid N-butylamide, oleic acid N-butylamide, lauric acid N-octylamide, myristic acid N-octylamide, palmitic acid N-octylamide, stearic acid N-octylamide, oleic acid N-octylamide, lauric acid N-dodecylamide, myristic acid N-dodecylamide, palmitic acid N-dodecylamide, stearic acid N-dodecylamide, oleic acid N-dodecylamide, dilauric acid amide, dimyristic acid amide, dipalmitic acid amide, distearic acid amide, dioleic acid amide, trilauric acid Amides, trimyristic acid amide, tripalmitic acid amide, tristearic acid amide, trioleic acid amide, succinic acid amide, adipic acid amide, glutaric acid amide, malonic acid amide, azelaic acid amide, maleic acid amide, succinic acid N-methylamide, adipic acid N-methylamide, glutaric acid N-methylamide, malonic acid N-methylamide, azelaic acid N-methylamide, succinic acid N-ethylamide, adipic acid N-ethylamide, glutaric acid N-ethylamide, malonic acid N-ethylamide, azelaic acid N-ethylamide,Examples include succinic acid N-butylamide, adipic acid N-butylamide, glutaric acid N-butylamide, malonic acid N-butylamide, adipic acid N-octylamide, and adipic acid N-dodecylamide.

[0047] Examples of waxes and medium-molecular-weight polymers include paraffin wax, microcrystalline wax, petrolactam, oxidized paraffin wax, and oxidized petrolactam, each having a melting point of 50 to 120°C. Examples include shellac, sugarcane wax, carnauba wax, candelilla wax, castor wax, hydrogenated beef tallow oil, hydrogenated fish oil, hydrogenated rapeseed oil, montan wax, palm wax, butterbur wax, hazel wax, and wool wax. Examples of waxes and medium-molecular-weight polymers include oxidized polyethylene wax, montanic acid wax, ethylene-vinyl acetate copolymer wax, ethylene-acrylic copolymer wax, and vinyl ether wax. Examples of waxes and medium-molecular-weight polymers include palm oil, babassu oil, liquid paraffin, polybutene, polybutadiene, and polystyrene oligomer.

[0048] Furthermore, as the component (c), an aliphatic hydrocarbon having 17 or more carbon atoms may be used; as the component (c), a hydrocarbon selected from chain hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons may be used in combination with a compound selected from alcohols, esters, ethers, ketones, and acid amides having a melting point of 50°C or higher; the hydrocarbon may be used in combination with a styrene-based compound having a softening point of 5°C or higher and a weight-average molecular weight of 200 to 100,000; the hydrocarbon may be used in combination with a styrene polymer having a softening point of -10°C or higher and a weight-average molecular weight of 200 to 100,000, and an alkoxyphenyl compound; or the hydrocarbon may be used in combination with a linear dibasic acid compound having 3 to 22 carbon atoms and an alcohol, ester, ether, ketone, acid amide, or aromatic hydrocarbon having a melting point of 50°C or higher.

[0049] The reversible thermochromic composition is a heat-coloring type reversible thermochromic microcapsule pigment (reversible thermochromic pigment) obtained by the same method as the heat-discoloring type reversible thermochromic pigment, and a pigment having the same average particle diameter as the heat-discoloring type reversible thermochromic pigment is used. The reversible thermochromic pigment of the heat-coloring type begins to develop color when it reaches temperature T3 as the temperature rises from a colorless state and becomes completely colored at temperatures equal to or higher than temperature T4. As the temperature drops from the colored state, it begins to lose color when it reaches temperature T2 and becomes completely colored when it reaches temperature T1. The temperature T4, which can be obtained by a simple method such as rubbing with a finger or a friction object, is in the range of 40 to 95°C, preferably 45 to 95°C, and more preferably 50 to 95°C. The temperature T1, which is not reached at normal living temperatures, is in the range of -50 to 5°C, preferably -50 to 0°C, and more preferably -50 to -5°C, which is not reached at normal living temperatures. This allows the discolored state to be maintained at room temperature (see Figure 3).

[0050] The heat-discolorable, reversible thermochromic pigment is in a colored state in the normal temperature range and functions as a colorant that makes handwriting visible when written. The handwriting is decolorized when heated to a complete decolorization temperature t4 in the range of 40 to 95°C. On the other hand, the heat-coloring type reversible thermochromic pigment is in a decolorized state in the normal temperature range and does not function as a colorant that makes handwriting visible during writing. The heat-discoloring, reversible thermochromic pigment that constitutes the initial handwriting disappears when heated, but the heat-coloring, reversible thermochromic pigment changes color when heated to the full color temperature T4, which is in the range of 40 to 95°C, and forms the handwriting. The written mark made with the heat-coloring type reversible thermochromic pigment loses color when the temperature reaches −50 to 5° C. (T1), and therefore the colored state can be maintained in the room temperature range. When the temperature t1 of the heat-discoloring reversible thermochromic pigment described above is less than 20°C, handwriting made with the heat-coloring reversible thermochromic pigment is visible at room temperature, but when the temperature t1 is above 20°C, handwriting made with a third color is a mixture of the heat-coloring reversible thermochromic pigment and the heat-discoloring reversible thermochromic pigment. To obtain the third color mark, the temperature must be below t1. The room temperature is a temperature range of 20°C or higher, more specifically, a temperature range of 20°C or higher and 25°C or lower. The heat-discoloring type reversible thermochromic pigment and the heat-coloring type reversible thermochromic pigment have different chromatic colors in the colored state, which gives the user a sense of surprise and the appeal of color change. The different colors are hue sections excluding the same hue section on the Munsell hue circle (10 hues), and in the case of hue sections adjacent to both sides of the same hue section, they are colors with a lightness difference of more than 3.0 and a saturation difference of more than 10.

[0051] The medium is an organic solvent, water, or a water-soluble organic solvent, and various additives may be added. The organic solvent can be any of the general-purpose organic solvents used in oil-based inks, but it is preferable to use a medium-boiling point solvent with a boiling point in the range of 95°C to 220°C, preferably 140°C to 200°C, as the main solvent (i.e., containing 50% or more). Examples of organic solvents within the above boiling point range include n-octane, isooctane, n-heptane, methylcyclohexane, ethylcyclohexane, toluene, xylene, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 3-methyl-1,3-butanediol, 1,3-butanediol, and hexylene glycol. Other examples of co-solvents that can be used include low-boiling solvents such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, ethylene glycol alkyl (C1-3) ether, ethylbenzene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, methyl lactate, ethyl lactate, dimethyl carbonate, propylene glycol methyl ether acetate, and ethylene glycol monoethyl ether acetate, and high-boiling solvents such as ethylene glycol monophenyl ether. Examples of the water-soluble organic solvent include ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0052] Examples of ink compositions for thermochromic writing instruments that comprise at least the reversible thermochromic pigment and a medium include shear thinning inks that contain a shear thinning agent, and aggregating inks that contain a water-soluble polymer aggregating agent to suspend microcapsule pigments in a loosely aggregated state.

[0053] By adding the shear thinning agent, aggregation and sedimentation of the reversible thermochromic pigment can be suppressed, and bleeding of handwriting can be suppressed, so that good handwriting can be formed. Furthermore, when the writing implement to be filled with the ink is in the form of a ballpoint pen, it is possible to prevent ink leakage from the gap between the ball and the tip when not in use, and to prevent ink from flowing back when the writing tip is left facing upward (upright state). Examples of the shear thinning agent include xanthan gum, welan gum, succinoglycan (average molecular weight of approximately 1,000,000 to 8,000,000), which is an organic acid-modified heteropolysaccharide whose constituent monosaccharides are glucose and galactose, guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alginic acid alkyl esters, polymers having a molecular weight of 100,000 to 150,000 and whose main component is an alkyl ester of methacrylic acid, glucomannan, thickening polysaccharides with gelling ability extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, crosslinkable acrylic acid polymers, inorganic fine particles, polyglycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, nonionic surfactants with an HLB value of 8 to 12 such as fatty acid amides, and salts of dialkyl or dialkenyl sulfosuccinic acid. Examples include a mixture of N-alkyl-2-pyrrolidone and an anionic surfactant, and a mixture of polyvinyl alcohol and an acrylic resin.

[0054] Examples of the water-soluble polymer flocculant include polyvinylpyrrolidone, polyethylene oxide, and water-soluble polysaccharides. Examples of the water-soluble polysaccharides include tragacanth gum, guar gum, pullulan, cyclodextrin, and water-soluble cellulose derivatives. Specific examples of the water-soluble cellulose derivatives include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose. In the ink composition of the present invention, any water-soluble polymer that exhibits a loose bridging action between microcapsulated pigment particles can be used, but among these, water-soluble cellulose derivatives function effectively.

[0055] Furthermore, the addition of a water-soluble resin can provide adhesion and viscosity to the paper surface. Examples of the water-soluble resin include alkyd resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, and dextrin, with polyvinyl alcohol being preferred. Furthermore, as the polyvinyl alcohol, a partially saponified polyvinyl alcohol having a saponification degree of 70 to 89 mol % is more preferably used because it is highly soluble in ink even in the acidic range. The amount of the water-soluble resin added to the ink is in the range of 0.3 to 3.0% by mass, preferably 0.5 to 1.5% by mass.

[0056] Furthermore, when the ink composition of the present invention is used by filling it into a ballpoint pen, it is preferable to add a lubricant such as a higher fatty acid such as oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, a thiophosphite triester such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester), a phosphate monoester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, a phosphate diester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, or a metal salt, ammonium salt, amine salt or alkanolamine salt thereof to prevent wear of the ball seat. Other additives that may be added include inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate; pH adjusters such as water-soluble amine compounds and other organic basic compounds; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, and saponin; preservatives or antifungal agents such as carbolic acid, 1,2-benzthiazolin-3-one sodium salt, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; wetting agents such as urea, nonionic surfactants, reduced or non-reduced starch hydrolysates, oligosaccharides such as trehalose, sucrose, cyclodextrin, glucose, dextrin, sorbitol, mannitol, and sodium pyrophosphate; antifoaming agents; dispersants; and fluorine-based surfactants and nonionic surfactants that improve the penetration of the ink.

[0057] The ink composition is used in practice by being filled into a writing instrument such as a ballpoint pen or a marking pen having a ballpoint pen tip or a marking pen tip attached to the writing tip.

[0058] When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited, and an example is a ballpoint pen that has an ink reservoir tube filled with shear-thinning ink inside the barrel, the ink reservoir tube communicating with a tip having a ball attached to the tip, and further having a liquid plug tightly attached to the end face of the ink to prevent backflow.

[0059] To explain the ballpoint pen tip in more detail, it is possible to use a tip in which the ball is held in a ball holding portion formed by pressing inward from the outer surface near the tip of a metal pipe, or a tip in which the ball is held in a ball holding portion formed by cutting a metal material with a drill or the like, a tip in which a resin ball receiving seat is provided inside a metal or plastic tip, or a tip in which the ball held in the tip is urged forward by a spring body, etc. The balls may be made of cemented carbide, stainless steel, ruby, ceramic, resin, rubber, etc. and have a diameter of about 0.3 to 3.0 mm, preferably 0.3 to 1.5 mm, and more preferably 0.4 to 1.0 mm.

[0060] The ink reservoir tube for containing the ink is made of a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon. The ink reservoir may be directly connected to the tip, or may be connected to the tip via a connecting member. Furthermore, the ink reservoir tube may be in the form of a refill, with the refill stored within the barrel, or the barrel itself with a tip attached to the tip may serve as the ink reservoir, with ink being filled directly into the barrel. The ballpoint pen obtained as described above may be a ballpoint pen with a cap or a retractable ballpoint pen, and its shape is not particularly limited. Any retractable ballpoint pen can be used as long as the writing tip provided on the ballpoint pen refill is stored inside the barrel and exposed to the outside air, and the writing tip protrudes from the barrel opening when the retractable mechanism is activated. Examples of the method of operating the retractable mechanism include a knock type, a rotation type, and a slide type. The knock type has a knock portion at the rear end of the barrel or on the side of the barrel, and by pressing the knock portion, the ballpoint pen tip is caused to protrude and retract from the opening at the front end of the barrel, or by pressing a clip portion provided on the barrel, the ballpoint pen tip is caused to protrude and retract from the opening at the front end of the barrel. The rotating type can be exemplified by a configuration having a rotating part at the rear of the barrel, and by rotating the rotating part, the ballpoint pen tip can be made to appear and disappear from the opening at the front end of the barrel. The sliding type can be exemplified by a configuration in which a sliding portion is provided on the side of the barrel, and the ballpoint pen tip is made to protrude and retract from the opening at the front end of the barrel by operating the sliding portion, or a configuration in which the ballpoint pen tip is made to protrude and retract from the opening at the front end of the barrel by sliding a clip portion provided on the barrel.

[0061] The rear end of the ink contained in the ink reservoir tube can be filled with an ink backflow preventive material. The ink backflow preventive composition comprises a non-volatile liquid or a hardly volatile liquid. Specific examples include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, and the like, and one or more of these can be used in combination.

[0062] The non-volatile liquid and / or the hardly-volatile liquid is preferably thickened to a suitable viscosity by adding a thickener. Examples of the thickener include clay-based thickeners such as silica whose surface has been hydrophobically treated, fine particle silica whose surface has been methylated, aluminum silicate, swellable mica, and hydrophobically treated bentonite or montmorillonite; fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate; dextrin-based compounds such as tribenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, and fatty acid dextrins; and cellulose-based compounds. Furthermore, the liquid ink backflow preventive material can be used in combination with a solid ink backflow preventive material.

[0063] Furthermore, when filling a marking pen with an ink composition, the structure and shape of the marking pen itself are not particularly limited, and examples include a marking pen in which an ink occlusion body made of a fiber bundle is built into the barrel, and a pen tip made of a fiber processed body with capillary gaps formed therein is attached to the barrel directly or via an intermediate member, and the ink occlusion body and the pen tip are connected, and the ink occlusion body is impregnated with cohesive ink, and a marking pen in which the pen tip and an ink reservoir tube are arranged via a valve body that opens when the pen tip is pressed, and ink is directly stored in the ink reservoir tube.

[0064] The pen tip is a porous material with interconnected pores, such as a resin-processed fiber body, a fused heat-melting fiber body, or a felt body, with a porosity selected from a range of approximately 30 to 70%, and one end is processed into a shape suitable for the purpose, such as a bullet shape, a rectangle, or a chisel shape, for practical use. The ink occlusion body is made by bundling crimped fibers in the longitudinal direction, and is contained within a covering such as a plastic cylinder or film, with the porosity adjusted to a range of approximately 40 to 90%. The valve body may be of a pumping type, but it is preferable that the valve body be set to a spring pressure that can be pressed and released by the pressure of the writing pen. The marking pen obtained as described above may be a marking pen with a cap or a retractable marking pen, and its shape is not particularly limited.

[0065] Furthermore, the shape of the ballpoint pen or marking pen is not limited to those described above, but may be a composite writing instrument (double-headed, retractable, etc.) equipped with pen tips of different shapes or pen tips that dispense ink of different colors.

[0066] The handwriting formed by the writing implement containing the ink composition can be discolored by rubbing with a finger or by applying a friction material. The friction body is preferably an elastic body such as an elastomer or plastic foam, which has a high elastic feel and can generate appropriate friction and frictional heat when rubbed, but it may also be a plastic molded body, stone, wood, metal, or fabric. Although it is possible to rub the handwriting using an eraser, the above-mentioned friction body is preferably used because the rub generates eraser dust. As the material for the friction body, silicone resin or SEBS resin (styrene ethylene butadiene styrene block copolymer), which is a styrene-based resin, is preferably used. However, since silicone resin tends to adhere to the erased part by friction and tends to repel handwriting when writing is repeated, SEBS resin is more preferably used. The friction body can be combined with a writing implement and a separate member (friction body) of any shape to obtain a writing implement set, but by fixing the friction member (friction body) to the writing implement, excellent portability is achieved. The location where the friction member is fixed is not particularly limited, but in the case of a ballpoint pen with a cap, it can be provided at the tip (top) of the cap or the rear end of the barrel (the part where the writing tip is not provided), and in the case of a retractable ballpoint pen, it can be provided at the tip or rear end of the barrel. Furthermore, a small protrusion of any shape may be provided on a part of the cap or on a part of the barrel to serve as a friction member. [Example]

[0067] Next, the thermochromic ink composition for a writing instrument of the present invention and the writing instrument containing the same will be described. In the examples, the formulations are in parts by mass. Example 1 Preparation of reversible thermochromic pigments that can be decolorized by heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 1.0 parts of 2-(dibutylamino)-8-(dipentylamino)-4-methyl-spiro[5H-[1]benzopyrano[2,3-g]pyrimidin-5,1'(3'H)-isobenzofuran]-3-one as component (a), 3.0 parts of 4,4'-(2-ethylhexane-1,1-diyl)diphenol and 5.0 parts of 2,2-bis(4'-hydroxyphenyl)-hexafluoropropane as components (b), and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c). The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.3 μm, a completely discolored temperature (t4) of 58° C., a completely colored temperature of −20° C. (t1), and reversibly changes color from pink to colorless with temperature change.

[0068] Preparation of reversible thermochromic pigments that change color upon heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition consisting of 3.0 parts of 3'6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one as component (a), 8.0 parts of dodecyl 4-hydroxybenzoate as component (b), 20.0 parts of octadecane as component (c), and 1.0 part of distearyl ketone as component (d). The suspension was centrifuged to isolate the reversible thermochromic microencapsulated pigment. The microcapsule pigment has an average particle size of 2.5 μm, a complete color development temperature (T4) of 42° C., a complete decolorization temperature (T1) of 3° C., and reversible color change from colorless to blue with temperature change.

[0069] Preparation of thermochromic writing instrument ink composition A thermochromic writing instrument ink composition was prepared, consisting of 15.0 parts of the heat-discoloring, reversible thermochromic pigment, 15.0 parts of the heat-coloring, reversible thermochromic pigment, 0.3 parts of xanthan gum (shear thinning agent), 10 parts of urea, 10 parts of glycerin, 0.5 parts of a phosphate ester surfactant, 0.6 parts of a nonionic penetrating agent, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of an antifungal agent, 0.5 parts of triethanolamine, and 47.4 parts of water.

[0070] Creation of writing implements (see Figure 4) The ink 2 (previously cooled to below -20°C to cause the heat-discoloring type reversible thermochromic pigment to develop a pink color) was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a 0.5 mm stainless steel ball at the tip via a resin relay member 4 (holder). Next, an ink backflow preventive body 6 (liquid stopper) was filled into the rear end of the polypropylene pipe, and a tail plug 7 was fitted to the rear of the pipe to form a refill 8. The refill was then placed in a barrel 9 (consisting of a front barrel and a rear barrel), and a cap 10 was attached, followed by degassing by centrifugation to obtain a writing instrument 1 (ballpoint pen). The rear portion of the rear barrel is fitted with a friction member 11 made of SEBS resin.

[0071] When the writing implement was used to write on writing paper, pink handwriting was formed using the heat-discolorable reversible thermochromic pigment, and the handwriting was retained at room temperature (20°C). When the handwriting was rubbed with the friction element attached to the writing instrument, the pink handwriting disappeared, but the heat-coloring type reversible thermochromic pigment developed color, turning the handwriting blue. When the friction was stopped and the handwriting was left to stand, the blue color was maintained at room temperature (20°C). When the handwriting was cooled to below -20°C, the heat-discoloring reversible thermochromic pigment turned pink, resulting in a purple color that was a mixture of pink and blue, and the handwriting was maintained at room temperature (20°C).

[0072] Example 2 Preparation of reversible thermochromic pigments that can be decolorized by heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 1.0 parts of 3'6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one as component (a), 3.0 parts of 4,4'-(2-ethylhexane-1,1-diyl)diphenol and 5.0 parts of 2,2-bis(4'-hydroxyphenyl)-hexafluoropropane as components (b), and 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c). The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.3 μm, a completely discolored temperature (t4) of 58° C., a completely colored temperature (t1) of −20° C., and reversibly changes color from blue to colorless with temperature change.

[0073] Preparation of reversible thermochromic pigments that change color upon heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition consisting of 3.0 parts of 2-(dibutylamino)-8-(dipentylamino)-4-methyl-spiro[5H-[1]benzopyrano[2,3-g]pyrimidin-5,1'(3'H)-isobenzofuran]-3-one as component (a), 8.0 parts of dodecyl 4-hydroxybenzoate as component (b), 20.0 parts of octadecane as component (c), and 1.0 part of distearyl ketone as component (d). The suspension was centrifuged to isolate the reversible thermochromic microencapsulated pigment. The microcapsule pigment has an average particle size of 2.5 μm, a complete color development temperature (T4) of 42° C., a complete decolorization temperature (T1) of 3° C., and reversible color change from colorless to pink with temperature change.

[0074] Preparation of thermochromic writing instrument ink composition A thermochromic writing instrument ink composition was prepared, consisting of 15.0 parts of the heat-discoloring, reversible thermochromic pigment, 15.0 parts of the heat-coloring, reversible thermochromic pigment, 0.3 parts of xanthan gum (shear thinning agent), 10 parts of urea, 10 parts of glycerin, 0.5 parts of a phosphate ester surfactant, 0.6 parts of a nonionic penetrating agent, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of an antifungal agent, 0.5 parts of triethanolamine, and 47.4 parts of water.

[0075] Creation of writing implements (see Figure 4) The ink 2 (previously cooled to -20°C or below to cause the heat-discoloring type reversible thermochromic pigment to develop a blue color) was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a 0.5 mm stainless steel ball at the tip via a resin relay member 4 (holder). Next, an ink backflow preventive body 6 (liquid stopper) was filled into the rear end of the polypropylene pipe, and a tail plug 7 was fitted to the rear of the pipe to form a refill 8. The refill was then placed in a barrel 9 (consisting of a front barrel and a rear barrel), and a cap 10 was attached, followed by degassing by centrifugation to obtain a writing instrument 1 (ballpoint pen). The rear portion of the rear barrel is fitted with a friction member 11 made of SEBS resin.

[0076] When the writing implement was used to write on writing paper, blue handwriting was formed using the heat-discolorable reversible thermochromic pigment, and the handwriting was retained at room temperature (20°C). When the handwriting was rubbed with the friction element attached to the writing instrument, the blue handwriting disappeared, but the heat-coloring type reversible thermochromic pigment developed color, turning the handwriting pink. When the friction was stopped and the handwriting was left to stand, the pink color remained at room temperature (20°C). When the handwriting was cooled to below -20°C, the heat-discoloring reversible thermochromic pigment turned blue, resulting in a purple color that was a mixture of blue and pink, and the handwriting was maintained at room temperature (20°C).

[0077] Example 3 Preparation of reversible thermochromic pigments that can be decolorized by heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory properties, consisting of 3.0 parts of 1,3-dimethyl-6-diethylaminofluoran as component (a), 5.0 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane as component (b), and 50.0 parts of 4-biphenyldecyl acetate as component (c). The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.0 μm, a completely discolored temperature (t4) of 47° C., a completely colored temperature (t1) of −10° C., and reversibly changes color from orange to colorless with temperature change.

[0078] Preparation of reversible thermochromic pigments that change color upon heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition consisting of 3.0 parts of 3'6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one as component (a), 8.0 parts of dodecyl 4-hydroxybenzoate as component (b), 20.0 parts of octadecane as component (c), and 1.0 part of distearyl ketone as component (d). The suspension was centrifuged to isolate the reversible thermochromic microencapsulated pigment. The microcapsule pigment has an average particle size of 2.5 μm, a complete color development temperature (T4) of 42° C., a complete decolorization temperature (T1) of 3° C., and reversible color change from colorless to blue with temperature change.

[0079] Preparation of thermochromic writing instrument ink composition A thermochromic writing instrument ink composition was obtained by mixing 13.0 parts of the heat-discoloring type reversible thermochromic pigment (previously cooled to -10°C or below to develop an orange color), 13.0 parts of the heat-coloring type reversible thermochromic pigment (previously cooled to 3°C or below to develop a color), 0.5 parts of hydroxyethyl cellulose, 0.2 parts of a comb-type polymer dispersant (manufactured by Lubrizol Japan Co., Ltd., trade name: Solsperse 43000), 1.0 part of an organic nitrogen-sulfur compound (manufactured by Hokko Chemical Industry Co., Ltd., trade name: Hokuside R-150, a mixture of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one), 0.5 parts of polyvinyl alcohol, 25.0 parts of glycerin, 0.02 parts of an antifoaming agent, and 46.78 parts of water.

[0080] Creation of writing implements (see Figure 5) The ink composition was impregnated into an ink absorbing body 12 made of polyester sliver covered with a synthetic resin film, and housed in a barrel 9 made of polypropylene resin. A marking pen tip 5 (bullet-shaped) made of polyester fiber was assembled and connected to the tip of the barrel via a relay member 4 (holder), and a cap 10 was attached to obtain a writing instrument 1 (marking pen). The cap has a friction member 11 made of SEBS resin attached to the top.

[0081] When the writing implement was used to write on writing paper, orange handwriting was formed using the heat-discolorable reversible thermochromic pigment, and the handwriting was retained at room temperature (20°C). When the handwriting was rubbed with the friction element attached to the writing instrument, the orange handwriting disappeared, but the heat-coloring type reversible thermochromic pigment developed color and the handwriting turned blue. When the friction was stopped and the handwriting was left to stand, the blue color was maintained at room temperature (20°C). When the handwriting was cooled to below -10°C, the heat-discoloring reversible thermochromic pigment turned orange, resulting in a pink color that was a mixture of orange and blue, and the handwriting was maintained at room temperature (20°C).

[0082] Example 4 Preparation of reversible thermochromic pigments that can be decolorized by heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 3.0 parts of 4-[2,6-bis(2-ethoxyphenyl)-4-pyridinyl]-N,N-dimethylbenzeneamine as component (a), 10.0 parts of 2,2-bis(4'-hydroxyphenyl)-hexafluoropropane as component (b), and 50.0 parts of 4(4-phenylpropyl)oxyphenylethyl octadecanoate as component (c). The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.0 μm, a completely discolored temperature (t4) of 61° C., a completely colored temperature (t1) of 28° C., and reversibly changes color from yellow to colorless with temperature change.

[0083] Preparation of reversible thermochromic pigments that change color upon heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition consisting of 3.0 parts of 3'6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one as component (a), 8.0 parts of dodecyl 4-hydroxybenzoate as component (b), 20.0 parts of nonadecane as component (c), and 1.0 part of distearyl ketone as component (d). The suspension was centrifuged to isolate the reversible thermochromic microencapsulated pigment. The microcapsule pigment has an average particle size of 2.5 μm, a complete color development temperature (T4) of 42° C., a complete decolorization temperature (T1) of −10° C., and reversible color change from colorless to blue with temperature change.

[0084] Preparation of thermochromic writing instrument ink composition A thermochromic writing instrument ink composition was prepared, consisting of 15.0 parts of the heat-discoloring, reversible thermochromic pigment, 15.0 parts of the heat-coloring, reversible thermochromic pigment, 0.3 parts of succinoglycan (shear thinning agent), 10 parts of urea, 5 parts of glycerin, 0.5 parts of a phosphate ester surfactant, 0.6 parts of a nonionic penetrating agent, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of an antifungal agent, 0.5 parts of triethanolamine, and 52.9 parts of water.

[0085] Making ballpoint pen refills The ink 2 (previously cooled to below -10°C to cause the heat-coloring type reversible thermochromic pigment to fade and the heat-coloring type reversible thermochromic pigment to develop a blue color) was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a 0.5 mm stainless steel ball at its tip via a resin relay member 4 (holder). Next, an ink backflow preventive (liquid plug) was filled into the rear end of the polypropylene pipe, and a tail plug was fitted onto the rear of the pipe to form a refill. The refill was incorporated into a barrel 9 to obtain a writing instrument 1 (retractable ballpoint pen) (see FIG. 6). The tip of the barrel is provided with a friction member 11 made of SEBS resin. The retractable ballpoint pen has a structure in which the writing tip provided on the ballpoint pen refill is stored inside the barrel while being exposed to the outside air, and the writing tip protrudes from the opening at the front end of the barrel by activation of a retraction mechanism (knock mechanism) provided at the rear end of the barrel. When the retractable mechanism of the writing instrument was activated to cause the ballpoint pen tip to protrude from the front end opening of the barrel, and writing was performed on writing paper, a yellow mark was formed using the heat-discoloring reversible thermochromic pigment, and the mark was retained at room temperature (20°C). When the handwriting is rubbed with a friction element attached to the writing instrument, the yellow handwriting disappears temporarily and the heat-coloring, reversible thermochromic pigment changes color, turning it blue, so that the blue handwriting is visible immediately after rubbing, but when the rubbing is stopped and the handwriting is left standing, the heat-discoloring, reversible thermochromic pigment changes color to yellow at room temperature (20°C), so that the yellow and blue become mixed and turn green, and the handwriting is maintained at room temperature (20°C).

[0086] Example 5 Preparation of reversible thermochromic pigments that can be decolorized by heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 3.0 parts of 4-[2,6-bis(2-ethoxyphenyl)-4-pyridinyl]-N,N-dimethylbenzeneamine as component (a), 10.0 parts of 2,2-bis(4'-hydroxyphenyl)-hexafluoropropane as component (b), and 50.0 parts of 4(4-phenylpropyl)oxyphenylethyl octadecanoate as component (c). The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.0 μm, a completely discolored temperature (t4) of 61° C., a completely colored temperature (t1) of 28° C., and reversibly changes color from yellow to colorless with temperature change.

[0087] Preparation of reversible thermochromic pigments that change color upon heating A microcapsule pigment suspension was obtained containing a reversible thermochromic composition consisting of 3.0 parts of 3'6'-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one as component (a), 8.0 parts of dodecyl 4-hydroxybenzoate as component (b), 20.0 parts of nonadecane as component (c), and 1.0 part of distearyl ketone as component (d). The suspension was centrifuged to isolate the reversible thermochromic microencapsulated pigment. The microcapsule pigment has an average particle size of 2.5 μm, a complete color development temperature (T4) of 42° C., a complete decolorization temperature (T1) of −10° C., and reversible color change from colorless to blue with temperature change.

[0088] Preparation of thermochromic writing instrument ink composition A thermochromic writing instrument ink composition was prepared, consisting of 15.0 parts of the heat-discoloring, reversible thermochromic pigment, 15.0 parts of the heat-coloring, reversible thermochromic pigment, 0.3 parts of succinoglycan (shear thinning agent), 10 parts of urea, 5 parts of glycerin, 0.5 parts of a phosphate ester surfactant, 0.6 parts of a nonionic penetrating agent, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of an antifungal agent, 0.5 parts of triethanolamine, and 52.9 parts of water.

[0089] Making ballpoint pen refills The ink 2 (previously cooled to below -10°C to cause the heat-coloring type reversible thermochromic pigment to fade and the heat-coloring type reversible thermochromic pigment to develop a blue color) was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a 0.5 mm stainless steel ball at its tip via a resin relay member 4 (holder). Next, an ink backflow preventive (liquid plug) was filled into the rear end of the polypropylene pipe, and a tail plug was fitted onto the rear of the pipe to form a refill. The refill was incorporated into a barrel 9 to obtain a writing instrument 1 (retractable ballpoint pen) (see FIG. 6). The tip of the barrel is provided with a friction member 11 made of SEBS resin. The retractable ballpoint pen has a structure in which the writing tip provided on the ballpoint pen refill is stored inside the barrel while being exposed to the outside air, and the writing tip protrudes from the opening at the front end of the barrel by activation of a retraction mechanism (knock mechanism) provided at the rear end of the barrel. When the retractable mechanism of the writing instrument was activated to cause the ballpoint pen tip to protrude from the front end opening of the barrel, and writing was performed on writing paper, a yellow mark was formed using the heat-discoloring reversible thermochromic pigment, and the mark was retained at room temperature (20°C). When the handwriting is rubbed with a friction element attached to the writing instrument, the yellow handwriting disappears temporarily and the heat-coloring, reversible thermochromic pigment changes color, turning it blue, so that the blue handwriting is visible immediately after rubbing, but when the rubbing is stopped and the handwriting is left standing, the heat-discoloring, reversible thermochromic pigment changes color to yellow at room temperature (20°C), so that the yellow and blue become mixed and turn green, and the handwriting is maintained at room temperature (20°C). [Explanation of symbols]

[0090] t1 Complete color development temperature of heat-discolorable, reversible thermochromic pigment t2 Color development start temperature of heat-discolorable reversible thermochromic pigment t3 Thermally decolorizable reversible thermochromic pigment decolorization temperature Complete decolorization temperature of t4 heat-decolorizing reversible thermochromic pigment T1 Complete decolorization temperature of reversible thermochromic pigments T2: Thermally colored, reversible thermochromic pigment fade starting temperature T3 Heat-coloring type reversible thermochromic pigment color development start temperature T4 Heat-Coloring Type Reversible Thermochromic Pigment Full Color Temperature ΔH Hysteresis width 1 writing implements 2 Ink 3 Ink reservoir 4 Relay parts 5 chips 6 Ink backflow prevention body 7 tail plug 8 Refills 9 Shaft tube 10 Caps 11 Friction member 12 Ink occlusion body

Claims

1. and a medium; a heat-discoloring reversible thermochromic pigment that is discolored by heating from a colored state and develops a color by cooling from the discolored state; and a heat-coloring reversible thermochromic pigment that is colored by heating from the discolored state and develops a color by cooling from the colored state, wherein the heat-discoloring reversible thermochromic pigment is in a colored state, and the heat-coloring reversible thermochromic pigment is in a discolored state. The heat-discoloring reversible thermochromic pigment and the heat-coloring reversible thermochromic pigment are microencapsulated pigments that exhibit hysteresis characteristics in a color density-temperature curve and exhibit alternating change between a colored state and a colorless state, and in the process of increasing temperature from a colored state, the heat-discoloring reversible thermochromic pigment is in a colored state, and the heat-coloring reversible thermochromic pigment is in a discolored state. ３ When the temperature reaches t ４ In the temperature range above, the color becomes completely colorless. In the process of decreasing the temperature from the colorless state, ２ When the temperature reaches t １ It becomes completely colored in the temperature range below t ４ is in the range of 40 to 95°C, and the temperature T ３ When the temperature reaches T ４ At this temperature, the color is completely developed, and as the temperature decreases from the colored state, ２ When the temperature reaches T １ When the temperature reaches T ２ and temperature T ３ The colored state and the colorless state are selectively maintained in the temperature range between the temperature T ４ is in the range of 40 to 95°C, and the temperature T １ and the color of the heat-discoloring type reversible thermochromic pigment and the heat-coloring type reversible thermochromic pigment in the colored state are different from each other.

2. A writing instrument containing the thermochromic writing instrument ink composition according to claim 1.

3. 3. The writing implement according to claim 2, further comprising a friction member.

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