Coating solution and applicator containing it, writing instrument, and applicator set

Abstract

The present invention provides a coating liquid that can prevent the thermal color change image, which exhibits tautomerism between a colored state and a colorless state upon application of heating or cold, from becoming irreversibly colored and thus becoming colorless, as well as a coating tool, writing instrument, and coating tool set containing the same. [Solution] A coating liquid that makes a thermally discolored image formed by an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reaction of (a) and (b) is encapsulated in a capsule wall film, wherein the coating liquid comprises a liquid substance that degrades the microcapsule wall film and an electron-accepting compound, and an applicator 1, a writing instrument, and an applicator set containing the same.

Description

Technical Field

[0001] The present invention relates to a coating liquid, a coating tool containing the same, a writing tool, and a coating tool set. More specifically, the present invention relates to a coating liquid that can make a thermochromic image that reversibly changes color from colored to colorless into an irreversible colored state, a coating tool containing the same, a writing tool, and a coating tool set.

Background Art

[0002] Conventionally, it has been disclosed that by applying a coating liquid containing resin particles having 70% or more by volume of all resin particles in the range of particle diameters of 0.5 to 5 μm onto erasable handwriting formed on paper with an eraser, the handwriting can be made non-erasable (see, for example, Patent Document 1). In addition, as a writing tool capable of forming erasable handwriting, there is disclosed a writing tool containing an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition composed of at least (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-forming reaction between (a) and (b) is encapsulated in a microcapsule wall film (see, for example, Patent Document 2). The handwriting (thermochromic image) formed by the writing tool is a thermochromic handwriting that changes color due to temperature changes, and can be discolored by frictional heat generated by rubbing with a friction body such as an elastomer, and is less likely to generate eraser dust like an eraser, so it is highly convenient.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention aims to provide a coating liquid that prevents the thermal color change image, which shows tautomorphism between a colored state and a colorless state upon application of heat or cold, from becoming colorless and remaining irreversibly colored, and a coating tool, writing instrument, and coating tool set containing the same. [Means for solving the problem]

[0005] The present invention provides a coating solution that makes a thermally discolored image formed by an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reactions of (a) and (b) is encapsulated in a capsule wall film, wherein the coating solution is required to contain a liquid substance that degrades the microcapsule wall film and an electron-accepting compound. Furthermore, the requirements include an applicator comprising: an applicator that houses the coating liquid in a container and is connected to the container and provides an applicator for dispensing the coating liquid; a writing instrument that contains an ink composition comprising a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium for controlling the color reaction of (a) and (b) is encapsulated in a capsule wall film; a writing instrument and applicator set comprising a writing instrument containing an ink composition comprising a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium for controlling the color reaction of (a) and (b) is encapsulated in a capsule wall film; and an applicator. [Effects of the Invention]

[0006] The present invention provides a coating liquid that can prevent a thermal color change image, which exhibits tautomorphism between a colored state and a colorless state upon application of heating or cold, from becoming irreversibly colored and thus becoming colorless, as well as an applicator, writing instrument, and applicator set containing the same. [Brief explanation of the drawing]

[0007] [Figure 1] This graph illustrates the hysteresis characteristics in the color density-temperature curve of a reversible thermochromic composition that decolorizes upon heating. [Figure 2] This graph illustrates the hysteresis characteristics in the color density-temperature curve of a reversible thermochromic composition that has color memory properties and heat-decolorizing properties. [Figure 3] This is a longitudinal cross-sectional diagram illustrating one embodiment of the applicator of the present invention. [Figure 4] This is a longitudinal cross-sectional diagram illustrating one embodiment of the writing instrument of the present invention. [Figure 5] This is a longitudinal cross-sectional diagram illustrating another embodiment of the writing instrument of the present invention. [Modes for carrying out the invention]

[0008] The present invention describes a coating liquid that makes the reversible thermochromic thermal discoloration image formed by an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-changing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-changing reactions of (a) and (b) is encapsulated in a capsule wall film, making the reversible thermochromic thermal discoloration image irreversible. The coating solution comprises a liquid substance that degrades the microcapsule wall film and an electron-accepting compound. The liquid substance that degrades the microcapsule wall film is a substance that degrades the wall film of a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition is encapsulated in the capsule wall film, the composition comprising (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reactions of (a) and (b), which is a coloring agent in the writing formed by applying the ink composition to a writing surface. The liquid substance is not particularly limited as long as it degrades the wall film. As the liquid substance that degrades the microcapsule wall membrane, alcohols having 1 to 6 carbon atoms, esters having 2 to 7 carbon atoms, ketones having 3 to 7 carbon atoms, amines having 2 to 7 carbon atoms, glycol ethers having 3 to 8 carbon atoms, etc. are used, preferably alcohols having 2 to 6 carbon atoms, esters having 3 to 6 carbon atoms, ketones having 3 to 6 carbon atoms, amines having 2 to 6 carbon atoms, glycol ethers having 3 to 7 carbon atoms are used, and more preferably alcohols having 2 to 4 carbon atoms, esters having 3 to 5 carbon atoms, ketones having 3 to 5 carbon atoms, amines having 2 to 5 carbon atoms, glycol ethers having 3 to 6 carbon atoms are used. Specifically, methanol, ethanol, propanol (n-propanol, iso-propanol), butyl alcohol (n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol), pentyl alcohol (n-pentyl alcohol, 2-pentyl alcohol, neopentyl alcohol), hexyl alcohol (1-hexanol, 2-hexanol, 3-hexanol), methyl formate, ethyl formate, triethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, diisopropyl ketone, monoethylamine, methyl ethyl Examples include amines, trimethylamine, butylamine, diethylamine, methylbutylamine, triethylamine, dipropylamine, methylhexylamine, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, aniline, pyridine, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol diethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and dipropylene glycol monoethyl ether.

[0009] The electron-accepting compound is an electron-accepting compound used in a reversible thermochromic composition comprising at least (a) an electron-donating chromogenic organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color reaction of (a) and (b). This compound is selected from the group of compounds having active protons and their derivatives, the group of pseudoacidic compounds (compounds that are not acids but act as acids in the composition to cause component (a) to develop color), the group of compounds having electron vacancies, etc., and among these, compounds selected from the group of compounds having active protons are used. Furthermore, the electron-accepting compound contained in the coating solution and the electron-accepting compound used in the reversible thermochromic composition may be the same or different.

[0010] Examples of applicators for containing the coating liquid include those having a storage body made of a fiber bundle inside a container (shaft cylinder), and an applicator made of a fiber processed body with capillary gaps formed therein attached to the container directly or via an intermediate member, with the storage body and the applicator connected; and those having an applicator and a container (shaft cylinder) arranged via a valve that is released when the applicator is pressed, with the coating liquid directly contained in the container.

[0011] Next, we will specifically describe an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reactions of (a) and (b) is encapsulated in a capsule wall film, and a writing instrument containing the same. As the aforementioned reversible thermochromic composition, a reversible thermochromic composition of the heat-decolorizing type (decolorizes upon heating and develops color upon cooling) is used, which comprises a reversible thermochromic composition consisting of three components: an electron-donating color-developing organic compound, an electron-accepting compound, and an organic compound medium that reversibly causes the color reaction between the two. As the aforementioned reversible thermochromic composition, a reversible thermochromic composition of the heat-decolorizing type (decolorizes when heated and develops color when cooled) can be applied, as described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc., which changes color before and after a predetermined temperature (color change point), exhibits a decolorized state in the temperature range above the high-temperature color change point and a colored state in the temperature range below the low-temperature color change point, and of the two states, only one specific state exists in the room temperature range (normal living temperature range), and the other state is maintained as long as the heat or cold required to bring about that state is applied, but returns to the state exhibited in the room temperature range when the application of such heat or cold is stopped, and which has a relatively small hysteresis width (ΔH=1~7℃) (see Figure 1). Furthermore, the hysteresis width (Δ) described in Japanese Patent Publication No. 4-17154, Japanese Patent Publication No. 7-179777, Japanese Patent Publication No. 7-33997, Japanese Patent Publication No. 8-39936, Japanese Patent Publication No. 2006-137880, Japanese Patent Publication No. 2008-280523, International Publication No. 2010 / 131684, International Publication No. 2010 / 131684, International Publication No. 2012 / 046837, International Publication No. 2014 / 200053, International Publication No. 2015 / 119161, International Publication No. 2016 / 027664, International Publication No. 2017 / 022471, International Publication No. 2018 / 155583, etc. H) exhibits a relatively large characteristic of 8°C to 80°C, meaning that the shape of the curve plotting the change in color density due to temperature changes follows a significantly different path when the temperature is increased from a temperature below the color change temperature range compared to when it is decreased from a temperature above the color change temperature range. Therefore, a reversible thermochromic composition that exhibits color memory in a specific temperature range [temperature range between t2 and t3 (effectively a two-phase retention temperature range)], where the colored state in the low temperature range below the complete color development temperature (t1) or the decolorized state in the high temperature range above the complete decolorization temperature (t4), can also be applied (see Figure 2).

[0012] The hysteresis characteristics in the color density-temperature curve of the aforementioned reversible thermochromic composition will be described. In Fig. 2, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to temperature change proceeds along the arrow. Here, A is a point indicating the density at the temperature t4 (hereinafter referred to as the complete decolorization temperature) at which the complete decolorization state is reached, B is a point indicating the density at the temperature t3 (hereinafter referred to as the decolorization start temperature) at which decolorization starts, C is a point indicating the density at the temperature t2 (hereinafter referred to as the color development start temperature) at which color development starts, and D is a point indicating the density at the temperature t1 (hereinafter referred to as the complete color development temperature) at which the complete color development state is reached. The discoloration temperature range is the temperature range between t1 and t4, and can exhibit either a colored state or a decolorized state. The temperature range between t2 and t3, where there is a large difference in color density, is the substantial discoloration temperature range. Also, the length of the line segment EF is a measure indicating the contrast of discoloration, and the length of the line segment HG passing through the midpoint of the line segment EF is the temperature width indicating the degree of hysteresis (hereinafter referred to as the hysteresis width ΔH). When this ΔH value is small, only a specific one of the two states in the normal temperature range can exist before and after discoloration. Also, when the ΔH value is large, it becomes easy to maintain each state before and after discoloration. Here, when the complete decolorization temperature t4 is in the range of 40 to 95 °C, preferably 45 to 95 °C, more preferably 50 to 95 °C, it can be decolorized by a simple method such as rubbing with a finger or rubbing with a friction body. Also, when the complete color development temperature t1 is set to a temperature that cannot be reached at normal living temperatures in the range of -50 to 5 °C, preferably -50 to 0 °C, more preferably -50 to -5 °C, the discolored state can be maintained in the normal temperature range.

[0013] The components (a), (b), and (c) contained in the reversible thermochromic composition will be specifically described below. The component (a), that is, the electron-donating color-forming organic compound, is a component that determines the color, and is a compound that donates electrons to the component (b), which is a developer, and develops color. Examples of the electron-donating color-forming organic compound include phthalide compounds, fluoran compounds, styrylnaphthyridine compounds, diazarhodamine lactone compounds, pyridine compounds, quinazoline compounds, bisquinazoline compounds, etc. Among these, phthalide compounds, fluoran compounds, styrylnaphthyridine 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 their derivatives. Among these, phenylindolyl azaphthalide compounds and their derivatives are preferred. These compounds are exemplified below. 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-acetamido-4-diethylaminophenyl)-3-(1-propylindol-3-yl)-4-azaphthalide, 3,6-bis(diphenylamino)fluorane, 3,6-dimethoxyfluorane, 3,6-di-n-butoxyfluorane, 2-methyl-6-(N-ethyl-Np-tolylamino)fluorane, 3-Chloro-6-cyclohexylaminofluorane, 2-methyl-6-cyclohexylaminofluorane, 2-(2-chloroamino)-6-dibutylaminofluorane, 2-(2-chloroanilino)-6-di-n-butylaminofluorane, 2-(3-trifluoromethylanilino)-6-diethylaminofluorane, 2-(3-trifluoromethylanilino)-6-dipentylaminofluorane, 2-(dibenzylamino)-6-diethylaminofluorane, 2-(N-methylanilino)-6-(N-ethyl-Np-tolylamino)fluorane, 1,3-dimethyl-6-diethylaminofluorane, 2-Chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methoxy-6-diethylaminofluorane, 2-anilino-3-methyl-6-di-n-butylaminofluorane, 2-anilino-3-methoxy-6-di-n-butylaminofluorane, 2-Xylidino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-Np-tolylamino)fluorane, 1,2-Benz-6-diethylaminofluorane, 1,2-Benz-6-(N-ethyl-N-isobutylamino)fluorane, 1,2-Benz-6-(N-ethyl-N-isoamylamino)fluorane, 2-(3-methoxy-4-dodecoxystyryl)quinoline, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,2-(diethylamino)-8-(diethylamino)-4-methyl, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,2-(di-n-butylamino)-8-(di-n-butylamino)-4-methyl, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,2-(di-n-butylamino)-8-(diethylamino)-4-methyl, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-5,1′(3′H)isobenzofuran]-3′-one,2-(di-n-butylamino)-8-(N-ethyl-Ni-amylamino)-4-methyl, Spiro[5H-(1)benzopyrano(2,3-d)pyrimidine-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-indole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-[4-(diethylamino)-2-ethoxyphenyl]-3-(1-ethyl-2-methyl-1H-indole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-[4-(diethylamino)-2-ethoxyphenyl]-3-(1-pentyl-2-methyl-1H-indole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-[4-(diethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indole-3-yl)-1(3H)-isobenzofuranone, 3′,6′-bis[phenyl(2-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 3′,6′-bis[phenyl(3-methylphenyl)amino]-spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 3′,6′-bis[phenyl(3-ethylphenyl)amino]-spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 2,6-bis(2′-ethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-Bis(2′,4′-diethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2-(4′-dimethylaminophenyl)-4-methoxyquinazoline, 4,4′-(ethylenedioxy)-bis[2-(4-diethylaminophenyl)quinazoline] Examples include: In addition to the aforementioned compounds having substituents on the phenyl group forming the xanthene ring, fluoranes may also be compounds exhibiting blue or black coloration, having substituents on the phenyl group forming the xanthene ring and also substituents (for example, alkyl groups such as methyl groups, halogen atoms such as chloro groups) on the phenyl group forming the lactone ring.

[0014] The aforementioned component (b), i.e., the electron-accepting compound, is a compound that accepts electrons from component (a) and functions as a color developer for component (a). The electron-accepting compounds include compounds selected from the group of compounds having active protons and their derivatives, the group of pseudoacidic compounds (compounds that are not acids but act as acids in the composition to cause component (a) to develop color), and the group of compounds having electron vacancies. Among these, compounds selected from the group of compounds having active protons are preferred. Examples of compounds having active protons and their derivatives include compounds having phenolic hydroxyl groups and their metal salts, carboxylic acids and their metal salts, preferably aromatic carboxylic acids, aliphatic carboxylic acids having 2 to 5 carbon atoms and their metal salts, acidic phosphate esters and their metal salts, as well as azol compounds and their derivatives, 1,2,3-triazoles and their derivatives. Among these, compounds having phenolic hydroxyl groups are preferred because they can exhibit effective thermal color change properties. The aforementioned compounds having phenolic hydroxyl groups broadly include monophenol compounds to polyphenol compounds, and further include bis-type and tris-type phenols, as well as phenol-aldehyde condensation resins. Among the compounds having phenolic hydroxyl groups, those having at least two benzene rings are preferred. These compounds may also have substituents, and examples of substituents include alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxyl groups and their esters or amide groups, halogen groups, and the like. Examples of metals included in the metal salt of the compound having the active proton include sodium, potassium, calcium, zinc, zirconium, aluminum, magnesium, nickel, cobalt, tin, copper, iron, vanadium, titanium, lead, and molybdenum.

[0015] Specific examples are given below. Phenol, o-cresol, tert-butylcatechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcinol, dodecyl gallate, 4,4-dihydroxydiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane, 1 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) Phenyl)-3-methylbutane, 1,1-bis(4-hydroxyphenyl)-3-methylpentane, 1,1-bis(4-hydroxyphenyl)-2,3-dimethylpentane, 1,1-bis(4-hydroxyphenyl)-2-ethylbutane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl)-3,7-dimethyloctane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1-phenyl-1,1-bis(4-hydroxyphenyl) 2,2-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)ethylpropionate, 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 compound having the phenolic hydroxyl group exhibits the most effective thermal color change 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-triazoles and their derivatives may also be used.

[0016] The component (c) of the reaction medium that causes the electron transfer reaction by the components (a) and (b) described above to occur reversibly in a specific temperature range will now be explained. Examples of component (c) include alcohols, esters, ketones, ethers, and acid amides. When using the aforementioned component (c) for microencapsulation and secondary processing described later, low molecular weight compounds tend to evaporate outside the capsule when subjected to high heat treatment. Therefore, compounds with 10 or more carbon atoms are preferably used to stably retain them inside the capsule. Effective alcohols include monohydric aliphatic saturated alcohols with 10 or more carbon atoms, specifically decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, and docosyl alcohol.

[0017] As for esters, esters with 10 or more carbon atoms are effective, and esters obtained from any combination of a monohydric carboxylic 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 polyhydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring, or any combination of a monohydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring Examples of esters obtained from these include, specifically, 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, p-tert-butyl stearyl benzoate, dimyristyl phthalate, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelaate, di-(n-nonyl) sebacate Examples include 1,18-octadecylmethylenedicarboxylic acid 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, etc.

[0018] Furthermore, ester compounds selected from saturated fatty acids and branched aliphatic alcohols, unsaturated fatty acids or branched or substituted saturated fatty acids and branched or aliphatic alcohols with 16 or more carbon atoms, cetyl butyrate, stearyl butyrate, and behenyl butyrate are also effective. 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-Dimethyloctyl behenate Examples include thiooctyl 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.

[0019] Furthermore, in order to exhibit large hysteresis characteristics with respect to the color density-temperature curve and change color, thereby providing color memory depending on temperature changes, carboxylic acid ester compounds exhibiting a ΔT value (melting point-cloud point) of 5°C or higher 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, trimiristine, tristearin, dimyristine, distearin, etc. are mentioned.

[0020] Fatty acid ester compounds obtained from an odd-numbered aliphatic monohydric alcohol with 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid, and fatty acid ester compounds with a total of 17 to 23 carbon atoms obtained from n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid with 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, myristic acid Examples 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-undersi eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, and n-pentadecyl behenate.

[0021] Effective ketones include aliphatic ketones with a total carbon number of 10 or more, such as 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, and stearone. Furthermore, arylalkyl ketones with a total carbon number of 12 to 24, such as n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n-tetradecanophenone, 4-n-dodecacetophenone, n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, n-nonylacetophenone Examples include nophenone, 4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone, 4-n-cyclohexylacetophenone, 4-tert-butylpropiophenone, n-heptaphenone, 4-n-pentylacetophenone, cyclohexylphenyl ketone, benzyl-n-butyl ketone, 4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone, 1-acetonaphthone, 2-acetonaphthone, and cyclopentylphenyl ketone.

[0022] As for ethers, aliphatic ethers with a total of 10 or more carbon atoms are effective, and examples 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.

[0023] Acid amides include acetamide, propionic acid amide, butyrate 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, Caprylic acid N-methylamide, capric acid N-methylamide, lauric acid N-methylamide, myristate acid N-methylamide, palmitic acid N-methylamide, stearate N-methylamide, behenic acid N-methylamide, oleic acid N-methylamide, erucate N-methylamide, laurate N-ethylamide, myristate acid N-ethylamide, palmitic acid N-ethylamide, stearate N-ethylamide, oleic acid N-ethylamide, laurate N-butylamide, myristate acid N-butylamide, palmitic acid N-butylamide, stear N-butylamide phosphate, N-butylamide oleate, N-octylamide laurate, N-octylamide myristate, N-octylamide palmitate, N-octylamide stearate, N-octylamide oleate, N-dodecylamide laurate, N-dodecylamide myristate, N-dodecylamide palmitate, N-dodecylamide stearate, N-dodecylamide oleate, dilaurate, dimyristateamide, dipalmitamide, distearate, dioleamide, trilaurate, 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 N-butylamide adipic acid, N-butylamide glutarate, N-butylamide malonate, N-octylamide adipic acid, and N-dodecylamide adipic acid.

[0024] Furthermore, the compound represented by the following general formula (1) can also be used as component (c) above. [ka] [In the formula, R1 represents a hydrogen atom or a methyl group, m represents an integer from 0 to 2, and either X1 or X2 is -(CH2)] n OCOR2 or -(CH2) n COOR2, the other side represents a hydrogen atom, n is an integer from 0 to 2, R2 represents an alkyl group or alkenyl group with 4 or more carbon atoms, Y1 and Y2 represent a hydrogen atom, an alkyl group with 1 to 4 carbon atoms, a methoxy group, or a halogen, and r and p are integers from 1 to 3. Among the compounds represented by formula (1) above, the case where R1 is a hydrogen atom is preferred because it yields a reversible thermochromic composition with a wider hysteresis width, and the case where R1 is a hydrogen atom and m is 0 is even more preferred. Furthermore, among the compounds represented by formula (1), the compound represented by the following general formula (2) is more preferably used. [ka] In the formula, R represents an alkyl 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 aforementioned compounds 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.

[0025] Furthermore, as component (c) above, 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 from 1 to 3, and X and Y represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a halogen, respectively.) Specific examples of the aforementioned compounds 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.

[0026] Furthermore, the compound represented by the following general formula (4) can also be used as component (c). [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 from 1 to 3; and n represents an integer from 1 to 20.) The aforementioned compounds include diesters of malonic acid and 2-[4-(4-chlorobenzyloxy)phenyl)]ethanol, succinic acid and 2-(4-benzyloxyphenyl)ethanol, succinic acid and 2-[4-(3-methylbenzyloxy)phenyl)]ethanol, glutaric acid and 2-(4-benzyloxyphenyl)ethanol, glutaric acid and 2-[4-(4-chlorobenzyloxy)phenyl)]ethanol, adipic acid and 2-(4-benzyloxyphenyl)ethanol, pimelic acid and 2-(4-benzyloxyphenyl)ethanol, suberic acid and 2-(4-benzyloxyphenyl)ethanol, and suberic acid and 2-[4-(3-methylbenzyloxy) Examples include diesters of 2-(4-(4-chlorobenzyloxy)phenyl)) ethanol, diesters of suberic acid and 2-(4-(2,4-dichlorobenzyloxy)phenyl)) ethanol, diesters of suberic acid and 2-(4-dichlorobenzyloxy)phenyl)) ethanol, diesters of azelaic acid and 2-(4-benzyloxyphenyl) ethanol, diesters of sebacic acid and 2-(4-benzyloxyphenyl) ethanol, diesters of 1,10-decanedicarboxylic acid and 2-(4-benzyloxyphenyl) ethanol, diesters of 1,18-octadecanedicarboxylic acid and 2-(4-benzyloxyphenyl) ethanol, and diesters of 1,18-octadecanedicarboxylic acid and 2-(4-methylbenzyloxy)phenyl)) ethanol.

[0027] Furthermore, the compound represented by the following general formula (5) can also be used as component (c). [ka] (In the formula, R represents an alkyl or alkenyl group having 1 to 21 carbon atoms, and n represents an integer from 1 to 3.) The aforementioned compounds include diesters of 1,3-bis(2-hydroxyethoxy)benzene and capric acid, diesters of 1,3-bis(2-hydroxyethoxy)benzene and undecanoic acid, diesters of 1,3-bis(2-hydroxyethoxy)benzene and lauric acid, diesters of 1,3-bis(2-hydroxyethoxy)benzene and myristic acid, diesters of 1,4-bis(hydroxymethoxy)benzene and butyric acid, diesters of 1,4-bis(hydroxymethoxy)benzene and isovaleric acid, diesters of 1,4-bis(2-hydroxyethoxy)benzene and acetic acid, Examples include diesters of 4-bis(2-hydroxyethoxy)benzene with propionic acid, 1,4-bis(2-hydroxyethoxy)benzene with valeric acid, 1,4-bis(2-hydroxyethoxy)benzene with caproic acid, 1,4-bis(2-hydroxyethoxy)benzene with caprylic acid, 1,4-bis(2-hydroxyethoxy)benzene with capric acid, 1,4-bis(2-hydroxyethoxy)benzene with lauric acid, and 1,4-bis(2-hydroxyethoxy)benzene with myristic acid.

[0028] Furthermore, the compound represented by the following general formula (6) can also be used as component (c). [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 from 1 to 3; and n represents an integer from 1 to 20.) Examples of the aforementioned compounds include diesters of succinic acid and 2-phenoxyethanol, diesters of suberic acid and 2-phenoxyethanol, diesters of sebacic acid and 2-phenoxyethanol, diesters of 1,10-decanedicarboxylic acid and 2-phenoxyethanol, and diesters of 1,18-octadecanedicarboxylic acid and 2-phenoxyethanol.

[0029] Furthermore, the compound represented by the following general formula (7) can also be used as component (c). [ka] (In the formula, R represents any of a C4 to C22 alkyl group, a cycloalkylalkyl group, a cycloalkyl group, or a C4 to C22 alkenyl group; X represents any of a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, or a halogen atom; and n represents 0 or 1.) Examples of the aforementioned compounds 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.

[0030] Furthermore, the compound represented by the following general formula (8) can also be used as component (c). [ka] (In the formula, R represents any of an alkyl group having 3 to 18 carbon atoms or an aliphatic acyl group having 3 to 18 carbon atoms; X represents any of 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 any of a hydrogen atom or a methyl group; and Z represents any of 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 aforementioned compounds include phenoxyethyl 4-butoxybenzoate, phenoxyethyl 4-pentyloxybenzoate, phenoxyethyl 4-tetradecyloxybenzoate, esters of phenoxyethyl 4-hydroxybenzoate and dodecanoic acid, and dodecyl ether of phenoxyethyl vanillate.

[0031] Furthermore, the compound represented by the following general formula (9) can also be used as component (c). [ka] (In the formula, R represents any of the following: an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, or a cycloalkyl group; X represents any of the following: a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; Y represents any of the following: a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; and n represents 0 or 1.) Examples of the aforementioned compounds include benzoic acid esters of octyl p-hydroxybenzoate, decyl p-hydroxybenzoate, p-methoxybenzoic acid ester of heptyl p-hydroxybenzoate, o-methoxybenzoic acid ester of dodecyl p-hydroxybenzoate, and benzoic acid ester of cyclohexylmethyl p-hydroxybenzoate.

[0032] Furthermore, the compound represented by the following general formula (10) can also be used as component (c). [ka] (In the formula, R represents any of the following: an alkyl group having 3 to 18 carbon atoms, a cycloalkylalkyl group having 6 to 11 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an alkenyl group having 3 to 18 carbon atoms; X represents any of the following: a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom; and Y represents any of the following: a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, or a halogen atom.) Examples of the aforementioned compounds 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.

[0033] Furthermore, the compound represented by the following general formula (11) can also be used as component (c). [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 from 1 to 3.) Examples of the aforementioned compounds include diesters of 1,3-bis(2-hydroxyethoxy)benzene and cyclohexanecarboxylic acid, diesters of 1,4-bis(2-hydroxyethoxy)benzene and cyclohexanepropionic acid, and diesters of 1,3-bis(2-hydroxyethoxy)benzene and cyclohexanepropionic acid.

[0034] Furthermore, the compound represented by the following general formula (12) can also be used as component (c). [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 from 1 to 3.) Examples of the aforementioned compounds include diesters of 4-phenylphenol ethylene glycol ether and cyclohexanecarboxylic acid, diesters of 4-phenylphenol diethylene glycol ether and lauric acid, diesters of 4-phenylphenol triethylene glycol ether and cyclohexanecarboxylic acid, diesters of 4-phenylphenol ethylene glycol ether and octanoic acid, diesters of 4-phenylphenol ethylene glycol ether and nonanoic acid, diesters of 4-phenylphenol ethylene glycol ether and decanoic acid, and diesters of 4-phenylphenol ethylene glycol ether and myristic acid.

[0035] The proportion of each component in the reversible thermochromic composition depends on the concentration, discoloration temperature, discoloration form, and type of each component, but generally, the component ratios that yield the desired properties are in the range of (a) 1 part of component, (b) 0.1 to 100 parts, preferably 0.1 to 50 parts, more preferably 0.5 to 20 parts, and (c) 1 to 800 parts, preferably 5 to 200 parts, more preferably 10 to 100 parts (all proportions are in parts by mass).

[0036] Furthermore, various light stabilizers can be added as needed. The aforementioned light stabilizers are included to prevent photodegradation of the reversible thermochromic composition consisting of components (a), (b), and (c), and are included in a ratio of 0.3 to 24% by mass, preferably 0.3 to 16% by mass, per 1% by mass of component (a). Furthermore, among the light stabilizers, the ultraviolet absorber effectively cuts ultraviolet rays contained in sunlight, etc., and prevents photodegradation caused by the excitation state due to the photoreaction of component (a). In addition, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, etc., suppress oxidation reactions caused by light. The aforementioned light stabilizers may be used alone or in combination of two or more types.

[0037] The aforementioned reversible thermochromic composition is encapsulated in microcapsules and used as a reversible thermochromic microcapsule pigment. Microencapsulation can be achieved using known methods such as interfacial polymerization, in situ polymerization, liquid curing coating, phase separation from aqueous solutions, phase separation from organic solvents, melt-dispersion-cooling, air suspension coating, and spray drying, and is selected appropriately depending on the application. Examples of resins that constitute the microcapsules include urea resin, urethane resin, urea-urethane resin, epoxy resin, melamine resin, benzoguanamine resin, and isocyanate resin. The microcapsule pigment is preferably in the range of encapsulation / wall film = 7 / 1 to 1 / 1 (mass ratio). By having the wall film ratio within this range, a decrease in color density and vividness during color development can be prevented. More preferably, the encapsulation / wall film ratio is 6 / 1 to 1 / 1 (mass ratio).

[0038] 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 using image analysis-based particle size distribution measurement software [Mountec Co., Ltd., product name: MacView] to determine the particle area, calculate the projected area circle equivalent diameter (Heywood diameter) from the area of ​​the particle area, and then measure the average particle diameter of particles equivalent to an equivolute sphere based on that value. Furthermore, if the particle size of all or most of the particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to equivolute spheres using the Coulter method with a particle size distribution analyzer [Beckman Coulter, Ltd., product name: Multisizer 4e]. Furthermore, volume-based particle diameter and average particle diameter may be measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., product name: LA-960V2) that has been calibrated based on the values ​​measured using the above-mentioned software or Coulter method measuring device.

[0039] The medium for the ink composition containing the reversible thermochromic microcapsule pigment is an organic solvent, water, water, and a water-soluble organic solvent, and various additives can be added. As the aforementioned organic solvent, a general-purpose one used for oil-based inks can be used, 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 in the range of 140°C to 200°C, as the main solvent (i.e., containing 50% or more). Examples of organic solvents within the aforementioned 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. In addition, low-boiling point 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, as well as high-boiling point solvents such as ethylene glycol monophenyl ether, can be used as auxiliary solvents. Examples of the aforementioned water-soluble organic solvents 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, sulforane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0040] Examples of ink compositions comprising at least the reversible thermochromic microcapsule pigment and a medium include printing ink compositions used in screen printing, offset printing, process printing, gravure printing, coaters, pad printing, etc., writing instrument ink compositions such as those for marking pens, ballpoint pens, fountain pens, and brush pens, and paints. Examples of the aforementioned ink compositions for writing instruments include shear-thinning ink compositions containing a shear-thinning agent, and coagulating ink compositions containing a water-soluble polymer flocculant in which microcapsule pigments are suspended in a loosely aggregated state.

[0041] By adding the aforementioned shear-reducing viscosity-imparting agent, aggregation and sedimentation of microcapsule pigments and resin particles can be suppressed, and bleeding of the handwriting can be suppressed, resulting in the formation of good handwriting. Furthermore, if the writing instrument filled with the ink composition 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 backflow when the writing tip is left upright. The aforementioned shear-thickening agent may include xanthan gum, gellan gum, succinoglycans (average molecular weight approximately 1 to 8 million) whose constituent monosaccharides are organic acid-modified heteropolysaccharides of glucose and galactose, guar gum, locust bean gum and its derivatives, hydroxyethylcellulose, alkyl alginates, polymers with a molecular weight of 100,000 to 150,000 mainly composed of alkyl esters of methacrylic acid, glucomannan, gelling polysaccharides extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or their derivatives, 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 sulfosuccinate. Examples include a mixture of N-alkyl-2-pyrrolidone and anionic surfactant, and a mixture of polyvinyl alcohol and acrylic resin.

[0042] Examples of the aforementioned water-soluble polymer flocculants include polyvinylpyrrolidone, polyethylene oxide, and water-soluble polysaccharides. Examples of the aforementioned water-soluble polysaccharides include tragacanth gum, guar gum, pullulan, cyclodextrin, and water-soluble cellulose derivatives. Specific examples of water-soluble cellulose derivatives include methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, and hydroxypropylmethylcellulose. In the ink composition of the present invention, any water-soluble polymer that exhibits a loose bridging effect between microcapsule pigment particles can be used, but water-soluble cellulose derivatives are particularly effective.

[0043] Furthermore, adding a water-soluble resin can impart 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, among the polyvinyl alcohols, partially saponified polyvinyl alcohol with a degree of saponification of 70-89 mol% is more preferably used because it is highly soluble even in acidic inks. The amount of the water-soluble resin added to the ink composition is preferably in the range of 0.3 to 3.0% by mass, more preferably 0.5 to 1.5% by mass.

[0044] Furthermore, when the ink composition is used by filling it into a ballpoint pen, it is preferable to add a lubricant such as a higher fatty acid like oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, thiophosphite triesters such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester), phosphate monoesters of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, phosphate diesters of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, or metal salts, ammonium salts, amine salts, or alkanolamine salts thereof to prevent wear of the ball bearing seat. Furthermore, pH adjusters such as inorganic salts like sodium carbonate, sodium phosphate, and sodium acetate, and organic basic compounds such as water-soluble amine compounds, rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitride, diisopropylammonium nitride, and saponins, preservatives or fungicides such as carbolic acid, sodium salt of 1,2-benzthiazolin 3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine may be added. Additionally, fluorinated surfactants or nonionic surfactants that improve ink penetration may be added.

[0045] The aforementioned ink composition is used by filling writing instruments such as ballpoint pens and marking pens, which have a ballpoint pen tip or marking pen tip attached to the writing end, into the writing instrument. When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited. For example, one could exemplified a ballpoint pen having an ink reservoir filled with a shear-reducing ink composition inside the barrel, the ink reservoir communicating with a tip to which a ball is attached, and a backflow prevention stopper tightly fitted to the end face of the ink.

[0046] To explain the ballpoint pen tip in more detail, the tip can be one in which a ball is held in a ball-holding portion formed by pressing the tip of a metal pipe inward from the outer surface, or one in which a ball is held in a ball-holding portion formed by cutting a metal material with a drill or the like, one in which a resin ball-receiving seat is provided inside a metal or plastic tip, or one in which the ball held in the tip is biased forward by a spring. Furthermore, the ball can be made of materials such as cemented carbide, stainless steel, ruby, ceramic, resin, or rubber, with a diameter of approximately 0.3 to 3.0 mm, preferably 0.3 to 1.5 mm, and more preferably 0.4 to 1.0 mm.

[0047] The ink container tube for holding the ink composition is, for example, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon. In addition to directly connecting the tip to the ink storage tube, the ink storage tube and the tip may also be connected via a connecting member. Furthermore, the ink reservoir may be in the form of a refill, with the refill housed inside the barrel, or the barrel itself, with a tip attached to its end, may be used as the ink reservoir, with ink directly filled into the barrel. The ballpoint pen obtained in the manner described above may be a ballpoint pen with a cap, or a retractable ballpoint pen, and its shape is not particularly limited. A retractable ballpoint pen can be used as long as the writing tip, which is attached to 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 operating methods for the retraction mechanism include knocking, rotating, and sliding mechanisms. The aforementioned retractable pen may be configured such that it has a retractable part at the rear end or side of the barrel, and the ballpoint pen tip extends and retracts from the front end opening of the barrel by pressing the retractable part, or by pressing a clip provided on the barrel to extend and retract the ballpoint pen tip from the front end opening of the barrel. The aforementioned rotary type may be exemplified by having a rotating part at the rear of the barrel, and by rotating the rotating part, the ballpoint pen tip can be extended and retracted from the opening at the front of the barrel. The aforementioned sliding mechanism may be exemplified by having a sliding part on the side of the barrel, and by operating the slide, the ballpoint pen tip can be extended and retracted from the opening at the front of the barrel, or by sliding a clip part provided on the barrel, the ballpoint pen tip can be extended and retracted from the opening at the front of the barrel.

[0048] An ink backflow prevention body can be filled into the rear end of the ink contained in the aforementioned ink storage tube. The aforementioned ink backflow prevention composition consists of a non-volatile liquid or a low-volatility liquid. Specifically, 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, etc., and one or more of these can be used in combination. The non-volatile liquid and / or non-volatile liquid is preferably thickened to a suitable viscosity by adding a thickening agent. Examples of the thickening agent include silica with a hydrophobic surface treatment, fine particle silica with a methylated surface treatment, aluminum silicate, swellable mica, clay-based thickening agents such as hydrophobic treated bentonite and montmorillonite, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate, tripenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, dextrin compounds such as fatty acid dextrins, and cellulose compounds. Furthermore, the liquid ink backflow prevention body and the solid ink backflow prevention body can be used in combination.

[0049] Furthermore, when filling a marking pen with an ink composition, the structure and shape of the marking pen itself are not particularly limited. For example, a marking pen may have an ink-absorbing body made of a fiber bundle built into the barrel, and a pen tip made of a fiber processed body with capillary gaps attached to the barrel directly or via an intermediate member, with the ink-absorbing body and the pen tip connected, and the ink-absorbing body being impregnated with an agglomerating ink composition. Another example is a marking pen in which the pen tip and an ink-containing tube are arranged via a valve that is released when the pen tip is pressed, and the ink is directly contained in the ink-containing tube.

[0050] The aforementioned pen tip is a porous material with interconnected pores, selected from materials such as resin-processed fibers, fused heat-meltable fibers, and felt, with a porosity generally ranging from 30% to 70%. One end is processed into a shape suitable for the purpose, such as a bullet shape, rectangle, or chisel shape, for practical use. The aforementioned ink-absorbing material is constructed by bundling crimped fibers in the longitudinal direction and embedding it in a covering such as a plastic cylinder or film, adjusting the porosity to approximately 40-90%. Furthermore, while the valve body can be of the pumping type, it is preferable that it be set to a spring pressure that allows it to be released by pressing with pen pressure. The marking pen obtained in the manner described above may be a marking pen with a cap, or a retractable marking pen, and its shape is not particularly limited.

[0051] Furthermore, the form of the ballpoint pen or marking pen is not limited to those described above, and may also be a multi-function writing instrument (such as a double-ended or retractable-tip type) equipped with pen tips of different shapes or pen tips that dispense ink compositions of different colors.

[0052] The writing produced by a writing instrument containing the aforementioned ink composition can be erased by friction with a finger, or by applying a friction object, a heating device, or a cooling device. Examples of the heating device include an electrically heated color-changing device equipped with a resistance heating element, a heated color-changing device filled with hot water, etc., and the use of a hair dryer. Preferably, a friction body that can change color by a simple method is used. The friction body is preferably an elastic material such as an elastomer or plastic foam that is highly elastic and can generate appropriate friction and frictional heat during friction, but it may also be a plastic molded body, stone, wood, metal, or fabric. While it is also possible to use an eraser to rub away the ink, this generates eraser residue, so it is preferable to use a friction material as described above. As the material of the friction body, silicone resin and styrene-based resins such as SEBS resin (styrene-ethylene-butadiene-styrene block copolymer) are preferably used. However, silicone resin tends to adhere to the area erased by friction, and the writing tends to be repelled when writing repeatedly, so SEBS resin is more preferably used. The aforementioned friction element can be obtained by combining a writing instrument with a separate component of any shape (friction element) to create a thermochromic learning tool set. However, attaching the friction element to the writing instrument provides superior portability. 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 at the rear end of the barrel (the part without a writing tip), and in the case of a retractable ballpoint pen, it can be provided at the tip of the barrel or at the rear end of the barrel. Furthermore, a small protrusion of any shape can be provided on part of the cap or part of the barrel to serve as a friction member. Examples of the aforementioned cooling devices include cooling devices that utilize a Peltier element, cooling devices filled with refrigerants such as cold water or ice chips, and applications of refrigerators and freezers.

[0053] The applicator may also be equipped with a writing instrument as an integral part of it. Examples include a double-ended applicator (writing and applicator) with a writing instrument at one end and an applicator at the other, and a retractable applicator (writing and applicator) that selectively extends the pen body of the writing instrument and the applicator body of the applicator from the tip of the barrel. The convenience of the applicator can be improved by equipping it with the aforementioned friction body. Furthermore, the writing instrument and the applicator can be combined to form a writing instrument and applicator set, and by equipping the writing instrument with a friction element, a highly convenient writing instrument and applicator set can be created.

[0054] The writing produced by a writing instrument containing the aforementioned ink composition changes color reversibly from a colored state to a colorless state upon heating, and from a colorless state to a colored state upon cooling. When the coating solution is applied to the colored handwriting, the liquid substance in the coating solution that degrades the microcapsule wall film degrades the wall film of the reversible thermochromic microcapsule pigment that forms the handwriting. At the same time, the electron-accepting compound contained in the coating solution acts on the reversible thermochromic composition consisting of components (a), (b), and (c) in the microcapsules. As a result, the proportion of component (b) in the reversible thermochromic composition increases, strengthening the intermolecular interaction between component (a) and component (b). This is presumed to prevent decolorization by heating, even if component (c), which contributes to decolorization, is present, thus maintaining the colored state. [Examples]

[0055] Examples are shown below, but the present invention is not limited to these examples. Note that the part in the example refers to the part by mass. Example 1 (see Figures 3 and 4) Preparation of application tools A coating solution was prepared by mixing 3.6 parts of ethanol and 0.4 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane. The coating liquid is impregnated into an ink-absorbing body 2 made of polyester sliver coated with a synthetic resin film, housed in a barrel 4 made of polypropylene resin, and an applicator 3 (chisel type) made of polyester fiber is assembled to connect to the tip of the barrel via a relay member 5 (holder), and a cap 6 is attached to obtain the applicator 1.

[0056] Preparation of reversible thermochromic microcapsule pigments A reversible thermochromic composition with color memory properties, consisting of (a) 2.0 parts of 4,5,6,7-tetrachloro-3-[4-(dimethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indole-3-yl)-1(3H)-isobenzofuranone as component, (b) 5.0 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane as component, and (c) 50.0 parts of 4-benzyloxyphenylethyl capric acid as component, was uniformly heated and dissolved. A solution was mixed with 30.0 parts of aromatic polyvalent isocyanate prepolymer as a wall material and 50.0 parts of a co-solvent. This solution was emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution to form fine droplets, and stirring was continued. Then, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was centrifuged to isolate the reversible thermochromic microcapsule pigment. The average particle size of the microcapsule pigment is 1.8 μm, the complete decolorization temperature (t4) is 55°C, and the complete color development temperature (t1) is -20°C. The pigment reversibly changes color from blue to colorless with temperature changes.

[0057] Preparation of ink compositions for writing instruments A writing instrument ink composition was prepared consisting of 22.5 parts of the aforementioned reversible thermochromic microcapsule pigment (pre-cooled to -20°C or below to develop a blue color), 0.3 parts of xanthan gum (shear viscosity reducing agent), 10 parts of urea, 10 parts of glycerin, 0.5 parts of phosphate ester surfactant, 0.6 parts of nonionic penetration agent, 0.1 part of modified silicone defoamer, 0.1 part of antifungal agent, 0.5 parts of triethanolamine, and 55.4 parts of water.

[0058] Manufacturing of writing instruments The ink composition 8 was suction-filled into a polypropylene resin pipe (ink storage tube 9), and connected to a ballpoint pen tip 10 holding a 0.5 mm stainless steel ball at its tip via a resin relay member 5 (holder). Next, an ink backflow prevention body 11 (liquid stopper) was filled into the rear end of the polypropylene pipe, and then a tail plug 12 was fitted to the rear of the pipe to form a refill 13. Furthermore, the refill was assembled into the barrel 4 (consisting of a front barrel and a rear barrel), the cap 6 was fitted on, and then degassed by centrifugal treatment to obtain a writing instrument 7 (ballpoint pen). Furthermore, SEBS resin is attached as a friction member 14 to the rear of the rear axle cylinder.

[0059] Using the aforementioned writing instrument, a blue thermally discolored image (handwriting) was formed on the paper. The aforementioned handwriting exhibited a blue color at room temperature (25°C). When the handwriting was rubbed with a friction material, the color disappeared, becoming colorless. This state could be maintained as long as the temperature was not cooled to below -20°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -20°C, the handwriting again showed a discoloration behavior, turning blue, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper with the aforementioned writing instrument to form a blue heat-discolored image (handwriting), and then applying the coating liquid to the handwriting using the applicator, the handwriting did not disappear even when rubbed with a friction tool.

[0060] Example 2 (see Figures 3 and 5) Preparation of application tools A coating solution was prepared by mixing 3.6 parts of ethyl acetate and 0.4 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane. The coating liquid is impregnated into an ink-absorbing body 2 made of polyester sliver coated with a synthetic resin film, housed in a barrel 4 made of polypropylene resin, and an applicator 3 (chisel type) made of polyester fiber is assembled to connect to the tip of the barrel via a relay member 5 (holder), and a cap 6 is attached to obtain the applicator 1.

[0061] Preparation of reversible thermochromic microcapsule pigments A reversible thermochromic composition with color memory properties, consisting of (a) 3.0 parts of 1,3-dimethyl-6-diethylaminofluorane as component, (b) 5.0 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane as component, and (c) 50.0 parts of 4-biphenyldecyl acetate as component, was uniformly heated and dissolved. A solution was mixed with 30.0 parts of aromatic polyvalent isocyanate prepolymer as a wall material and 50.0 parts of a co-solvent. This solution was emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution to form fine droplets, and stirring was continued. Then, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was centrifuged to isolate the microcapsule pigments. The average particle size of the microcapsule pigment is 2.0 μm, the complete decolorization temperature (t4) is 47°C, and the complete color development temperature (t1) is -10°C. The pigment reversibly changes color from orange to colorless with temperature changes.

[0062] Preparation of ink compositions for writing instruments A writing instrument ink composition was prepared consisting of 22.5 parts of the aforementioned reversible thermochromic microcapsule pigment (pre-cooled to -10°C or below to develop an orange color), 0.3 parts of xanthan gum (shear viscosity reducing agent), 10 parts of urea, 10 parts of glycerin, 0.5 parts of phosphate ester surfactant, 0.6 parts of nonionic penetration agent, 0.1 part of modified silicone defoaming agent, 0.1 part of antifungal agent, 0.5 parts of triethanolamine, and 55.4 parts of water.

[0063] Manufacturing of writing instruments The ink composition 8 was suction-filled into a polypropylene resin pipe (ink storage tube 9), and connected to a ballpoint pen tip 10 holding a 0.5 mm stainless steel ball at its tip via a resin relay member 5 (holder). Next, an ink backflow prevention device (liquid stopper) was filled into the rear end of the polypropylene pipe, and then a tail plug was fitted to the rear of the pipe to create a refill. The refill was incorporated into the barrel 4 to obtain a writing instrument 7 (retractable ballpoint pen). Furthermore, SEBS resin is provided as a friction member 13 at the tip of the shaft cylinder. The aforementioned retractable ballpoint pen has a structure in which the writing tip, provided on the ballpoint pen refill, is stored inside the barrel while exposed to the outside air, and the writing tip protrudes from the opening at the front of the barrel when a retractable mechanism (knock mechanism) provided at the rear end of the barrel is activated.

[0064] Using the aforementioned writing instrument, writing was done on paper to form an orange, heat-changed image (handwriting). The aforementioned handwriting was orange at room temperature (25°C), and when the handwriting was rubbed with a friction material, the handwriting disappeared and became colorless. This state could be maintained as long as the temperature was not cooled to below -10°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -10°C, the handwriting again showed a discoloration behavior, turning orange, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper with the aforementioned writing instrument to form an orange heat-discolored image (handwriting), and then applying the coating liquid to the handwriting using the applicator, the handwriting did not disappear even when rubbed with a friction tool.

[0065] Example 3 (see Figures 3 and 5) Preparation of application tools A coating solution was prepared by mixing 3.6 parts of dimethyl ketone and 0.4 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane. The coating liquid is impregnated into an ink-absorbing body 2 made of polyester sliver coated with a synthetic resin film, housed in a barrel 4 made of polypropylene resin, and an applicator 3 (chisel type) made of polyester fiber is assembled to connect to the tip of the barrel via a relay member 5 (holder), and a cap 6 is attached to obtain the applicator 1.

[0066] Preparation of reversible thermochromic microcapsule pigments A reversible thermochromic composition with color memory properties, consisting of (a) 4.5 parts of 2-(2-chloroanilino)-6-di-n-butylaminofluorane as component, (b) 8 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane as component, and (c) 50 parts of 4-benzyloxyphenylethyl capric acid as component, was uniformly heated and dissolved. A solution was mixed with 30.0 parts of aromatic polyvalent isocyanate prepolymer as a wall material and 50.0 parts of a co-solvent. This solution was emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution to form fine droplets, and stirring was continued. Then, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was centrifuged to isolate the microcapsule pigments. The average particle size of the microcapsule pigment is 2.0 μm, the complete decolorization temperature (t4) is 60°C, and the complete color development temperature (t1) is -20°C. The pigment reversibly changes color from black to colorless with temperature changes.

[0067] Preparation of ink compositions for writing instruments A writing instrument ink composition was prepared consisting of 22.0 parts of the aforementioned heat-decolorizing reversible thermochromic pigment (pre-cooled to -20°C or below to develop black color), 0.3 parts of succinoglycan (shear viscosity reducing agent), 10 parts of urea, 5 parts of glycerin, 0.5 parts of phosphate ester surfactant, 0.6 parts of nonionic penetration agent, 0.1 parts of modified silicone defoaming agent, 0.1 parts of antifungal agent, 0.5 parts of triethanolamine, and 60.9 parts of water.

[0068] Manufacturing of writing instruments The ink composition 8 was suction-filled into a polypropylene resin pipe (ink storage tube 9), and connected to a ballpoint pen tip 10 holding a 0.5 mm stainless steel ball at its tip via a resin relay member 5 (holder). Next, an ink backflow prevention device (liquid stopper) was filled into the rear end of the polypropylene pipe, and then a tail plug was fitted to the rear of the pipe to create a refill. The refill was incorporated into the barrel 4 to obtain a writing instrument 7 (retractable ballpoint pen). Furthermore, SEBS resin is provided as a friction member 13 at the tip of the shaft cylinder. The aforementioned retractable ballpoint pen has a structure in which the writing tip, provided on the ballpoint pen refill, is stored inside the barrel while exposed to the outside air, and the writing tip protrudes from the opening at the front of the barrel when a retractable mechanism (knock mechanism) provided at the rear end of the barrel is activated.

[0069] Using the aforementioned writing instrument, a black thermally discolored image (handwriting) was formed on the paper. The aforementioned handwriting was black at room temperature (25°C), and when the handwriting was rubbed with a friction material, the handwriting disappeared and became colorless. This state could be maintained as long as the temperature was not cooled to below -20°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -20°C, it exhibited a discoloration behavior where the handwriting turned black again, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper with the aforementioned writing instrument to form a black heat-discolored image (handwriting), and then applying the coating liquid to the handwriting using the applicator, the handwriting did not disappear even when rubbed with a friction tool.

[0070] Example 4 Preparation of application tools The coating solution obtained in Example 1 was impregnated into an ink-absorbing material and housed in one end of the barrel. An applicator (chisel type) made of polyester fiber was then attached to the tip via a connecting member (holder) and assembled in this manner. Furthermore, a refill obtained in Example 1 was attached to the other end of the barrel to obtain a double-ended applicator. Furthermore, the barrel is equipped with caps at both ends, and one of the caps has a SEBS resin piece attached to its top as a friction member.

[0071] Using the aforementioned applicator, writing was done on the paper to form a blue heat-changed image (handwriting). The aforementioned handwriting exhibited a blue color at room temperature (25°C). When the handwriting was rubbed with a friction material, the color disappeared, becoming colorless. This state could be maintained as long as the temperature was not cooled to below -20°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -20°C, the handwriting again showed a discoloration behavior, turning blue, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper using the applicator to form a blue heat-discolored image (handwriting), the coating liquid was applied to the handwriting, and the handwriting was rubbed with a friction tool, but the handwriting did not disappear.

[0072] Example 4 Manufacturing of writing instruments and applicator sets A writing instrument and a set of applicators were obtained by combining the applicator and writing instrument obtained in Example 2. Using the aforementioned writing instrument, writing was done on paper to form an orange, heat-changed image (handwriting). The aforementioned handwriting was orange at room temperature (25°C), and when the handwriting was rubbed with a friction material, the handwriting disappeared and became colorless. This state could be maintained as long as the temperature was not cooled to below -10°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -10°C, the handwriting again showed a discoloration behavior, turning orange, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper with the aforementioned writing instrument to form an orange heat-discolored image (handwriting), and then applying the coating liquid to the handwriting using the applicator, the handwriting did not disappear even when rubbed with a friction tool.

[0073] Example 5 Manufacturing of writing instruments and applicator sets A writing instrument and a set of applicators were obtained by combining the applicator and writing instrument obtained in Example 3. Using the aforementioned writing instrument, a black thermally discolored image (handwriting) was formed on the paper. The aforementioned handwriting was black at room temperature (25°C), and when the handwriting was rubbed with a friction material, the handwriting disappeared and became colorless. This state could be maintained as long as the temperature was not cooled to below -20°C. Furthermore, when the aforementioned paper was placed in a freezer and cooled to below -20°C, it exhibited a discoloration behavior where the handwriting turned black again, and this discoloration behavior could be repeatedly reproduced. Next, after writing on the paper with the aforementioned writing instrument to form a black heat-discolored image (handwriting), and then applying the coating liquid to the handwriting using the applicator, the handwriting did not disappear even when rubbed with a friction tool. [Explanation of symbols]

[0074] t1 Complete color development temperature of reversible thermochromic composition t2: Color development start temperature of reversible thermochromic composition t3: Decolorization start temperature of reversible thermochromic composition t4 Complete decolorization temperature of reversible thermochromic composition 1. Applicator 2. Ink absorber 3. Coating 4 shaft cylinder 5. Intermediate Member 6 caps 7 Writing instruments 8. Ink composition 9 Ink reservoir tubes 10 ballpoint pen tips 11. Ink backflow prevention element 12 tail plug 13 Refills 14 Friction Members

Claims

1. A coating liquid that makes a thermally discolored image formed by an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reactions of (a) and (b) is encapsulated in a capsule wall film, characterized in that the coating liquid comprises a liquid substance that degrades the microcapsule wall film and an electron-accepting compound.

2. An applicator comprising a container containing the coating liquid described in claim 1, and an applicator connected to the container for dispensing the coating liquid.

3. An applicator comprising a writing instrument containing an ink composition comprising a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium for controlling the color-developing reactions of (a) and (b) is encapsulated in a capsule wall film.

4. The aforementioned reversible thermochromic microcapsule pigment exhibits hysteresis characteristics with respect to the color density-temperature curve, and is a pigment that exhibits tautomorphism between a colored state and a colorless state, and in the process of the temperature rising from the colored state, the temperature t ３ When it reaches a certain temperature, it begins to lose its color, ４ At the above temperature range, it becomes completely colorless, and in the process of the temperature decreasing from the colorless state, temperature t ２ When it reaches a certain temperature, it begins to change color, １ The coloring becomes complete within the following temperature range, and the temperature t ２ and temperature t ３ It exhibits hysteresis properties in which the colored state and the colorless state are selectively maintained in the temperature range between t １ It is in the range of -50 to 5°C, and temperature t ４ The applicator according to claim 3, wherein the temperature is in the range of 40 to 95°C.

5. The applicator according to claim 3 or 4, comprising a friction element.

6. A writing instrument and applicator set comprising: a writing instrument containing an ink composition containing a reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-developing reactions of (a) and (b) is encapsulated in a capsule wall film; and an applicator according to claim 2.

7. The reversible thermochromic microcapsule pigment is a pigment that exhibits hysteresis characteristics with respect to the color density-temperature curve and shows the mutability between the colored state and the colorless state. In the process of temperature rising from the colored state, when the temperature reaches t ３ , it begins to fade, and in the temperature range above t ４ , it completely becomes colorless. In the process of temperature decreasing from the colorless state, when the temperature reaches t ２ , it begins to color, and in the temperature range below t １ , it completely becomes colored. It shows the hysteresis characteristic that the colored state and the colorless state are selectively retained in the temperature range between the temperature t ２ and the temperature t ３ . The temperature t １ is in the range of -50 to 5°C, and the temperature t ４ is in the range of 40 to 95°C. The writing instrument and coating tool set according to claim 6.

8. The writing instrument and applicator set according to claim 6 or 7, wherein the writing instrument is equipped with a friction element.

Images