Thermochromic stamp ink composition and stamp accommodating the same

Abstract

To provide a thermochromic stamp ink composition which not only affords convenience by enabling a stamp impression to be visually confirmed at the time of stamping and under ordinary usage conditions, but also makes it possible to easily check the history of the impression after decoloration by ultraviolet irradiation, and also to provide a stamp accommodating the thermochromic stamp ink composition.SOLUTION: A thermochromic stamp ink composition comprising a medium, a thermochromic material capable of changing from a colored state to a colorless state, and a fluorescent substance that generates fluorescence when irradiated with ultraviolet light, and a stamp 1 accommodating the thermochromic stamp ink composition.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a thermochromic ink composition for a stamp and a stamp containing the same. More specifically, the present invention relates to a thermochromic ink composition for a stamp that allows the history of an imprint to be confirmed and a stamp containing the same. [Background technology]

[0002] BACKGROUND ART Conventionally, stamps using ink compositions containing dyes that emit fluorescence when exposed to ultraviolet light have been disclosed (see, for example, Patent Document 1). The print image obtained by the stamp is not visible under sunlight or indoor light, but changes color when exposed to ultraviolet light, making it invisible or difficult to recognize, and therefore does not impair the appearance of the article.When exposed to ultraviolet light, the print image emits light in the visible light range, making it readable by visual inspection. However, since the print image cannot be visually recognized when stamped, there is a drawback in that it is not possible to confirm whether the desired print image has been formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-329258 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a thermochromic ink composition for stamps, which allows the print image to be visually confirmed when stamped and under normal use conditions, and also allows the history of the print image to be confirmed by ultraviolet light when the print image is erased, and a stamp containing the same. [Means for solving the problem]

[0005] The present invention requires an ink composition for a thermochromic stamp, which contains a medium, a thermochromic material that changes color from colored to colorless, and a fluorescent substance that emits fluorescence when irradiated with ultraviolet light. Furthermore, the thermochromic material is a microencapsulated pigment in which a reversible thermochromic composition comprising at least (a) an electron-donating organic color-forming compound, (b) an electron-accepting compound, and (c) a reaction medium for controlling the color-forming reactions of (a) and (b) is encapsulated in a microcapsule, and the pigment exhibits hysteresis characteristics in the color density-temperature curve, exhibiting alternation between a colored state and a colorless state, and the temperature ranges for maintaining both states are both in the room temperature range, and in the process of temperature rise from the colored state, the pigment begins to lose color when it reaches temperature t3, and completely loses color in a temperature range of t4 or higher, which is higher than temperature t3. The material becomes colorless, and in the process of decreasing temperature from the colorless state, it begins to become colored when it reaches temperature t2, which is lower than temperature t3, and becomes completely colored in the temperature range equal to or lower than temperature t1, which is lower than temperature t2. It exhibits hysteresis characteristics in which the colored state and the colorless state are selectively maintained in the temperature range between temperatures t2 and t3, and temperature t1 is in the range of -50 to 5°C and temperature t4 is in the range of 40 to 95°C. The material is made using a microcapsule pigment in which the fluorescent substance is encapsulated in microcapsules, or resin particles in which the fluorescent substance is dispersed in a thermoplastic or thermosetting resin. Furthermore, the present invention is also concerned with a stamp containing the thermochromic ink composition for stamps and a stamp provided with a friction member. [Effects of the Invention]

[0006] The present invention provides a thermochromic ink composition for stamps, which not only offers the convenience of allowing the print image to be visually confirmed when stamped and under normal use conditions, but also allows the image history to be easily confirmed by irradiating it with ultraviolet light after the print image has been erased, and a stamp 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 reversibly 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 stamp containing the thermochromic stamp ink composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The thermochromic material that changes color from colored to colorless may be a thermally discolorable reversible thermochromic material containing three components: an inorganic material such as Ag2HgI4 or Cu2HgI4, a liquid crystal, an electron-donating color-forming organic compound, an electron-accepting compound, and an organic compound medium that reversibly induces a color reaction between the two; or a thermally colorable reversible thermochromic material containing three components: an electron-donating color-forming organic compound, an electron-accepting compound, and an organic compound medium that reversibly induces a color reaction between the two. Among these, a reversible thermochromic material containing an electron-donating color-forming organic compound, an electron-accepting compound, and an organic compound medium that reversibly induces the color-forming reaction between the two will be described below. The reversible thermochromic material may be a reversible thermochromic composition of the thermal decolorization type (decolorized by heating and colored by cooling) containing at least three essential components: (i) an electron-donating color-forming organic compound, (ii) an electron-accepting compound, and (iii) a reaction medium that determines the temperature at which the color reaction between the two occurs. The reversible thermochromic composition may be a thermally decolorizable (decolorizes 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 decolorized 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, 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 ).

[0009] In addition, JP-B-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, JP-A-2005-1369, JP-A-2008-280523, etc., show a relatively large hysteresis width (ΔH) of 8°C to 80°C, that is, the shape of the curve plotting the change in color density due to temperature change is such that the temperature is increased from a lower temperature side than the discoloration temperature range. The color changes along significantly different paths depending on whether the temperature is increased from above the color-changing temperature range or decreased from a higher temperature than the color-changing temperature range, and the color develops in a low-temperature range below the complete color-changing temperature (t1) or the color fades in a high-temperature range above the complete fade temperature (t4). Reversible thermochromic compositions of the heat-discoloring type (discolors when heated and develops when cooled) that have color memory in a specific temperature range [the temperature range between t2 and t3 (a temperature range where two phases are essentially maintained)] can also be applied (see Figure 2).

[0010] 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, the complete color development temperature t1 is in the range of -50 to 5°C, preferably -50 to 0°C, and more preferably -50 to -5°C, and the complete decolorization temperature t4 is in the range of 40 to 95°C, preferably 45 to 95°C, and more preferably 50 to 95°C, which makes it easier to maintain the discolored state at room temperature.

[0011] 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] and the like. 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).

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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, may be used.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Furthermore, reversible thermochromic compositions of the heat-coloring type (which develops color upon heating and loses color upon cooling) can also be applied (see FIG. 3), using specific alkoxyphenol compounds having a linear or branched alkyl group with 3 to 18 carbon atoms as the electron-accepting compound (Japanese Patent Application Laid-Open Nos. 11-129623 and 11-5973), specific hydroxybenzoic acid esters (Japanese Patent Application Laid-Open No. 2001-105732), or gallic acid esters (Japanese Patent Application Laid-Open Nos. 51-44706 and 2003-253149).

[0034] 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).

[0035] 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.

[0036] The reversible thermochromic composition can be encapsulated in microcapsules to be used as a reversible thermochromic microcapsule pigment, or dispersed in a thermoplastic or thermosetting resin to be used as reversible thermochromic resin particles. 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.

[0037] The average particle size of the reversible thermochromic microcapsule pigment or reversible thermochromic resin particles 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.

[0038] The fluorescent material is a material that emits light when irradiated with ultraviolet light. Examples of fluorescent substances that emit light when exposed to ultraviolet light include fluorescent brighteners, ultraviolet fluorescent dyes, and ultraviolet fluorescent pigments. Preferably used are ultraviolet fluorescent dyes and ultraviolet fluorescent pigments that are colorless before exposure to ultraviolet light and emit light when exposed to ultraviolet light. Examples of the fluorescent brightening agent that can be used include oil-soluble fluorescent brightening agents based on coumarin, naphthalimide, oxazole, thiophene, stilbene, styrene biphenyl derivatives, and pyrazolone derivatives, as well as water-soluble fluorescent brightening agents obtained by adding a water-soluble polar group such as a sulfone group, a carboxyl group, an amide group, or a hydroxyl group to a styrene biphenyl derivative or pyrazolone derivative fluorescent brightening agent. Examples of the ultraviolet fluorescent dye include fluorescein, coumarin-based, oxazole-based, pyrazoline-based, thiadiazole-based, spiropyran-based, pyrenesulfonic acid-based, benzimidazole-based, and diaminostilbene-based dyes. The ultraviolet fluorescent pigments include copper-activated fluorescent materials such as ZnS:Cu and ZnS:Cu,Al, silver-activated fluorescent materials such as (ZnCd)S:Ag+In2O3, gold-activated fluorescent materials such as ZnS:Au and ZnS:Au,Cu, and manganese-activated fluorescent materials such as Zn2SiO4:Mn, Zn2SiO4:Mn,As, and BaAl. 12 O 19 :Mn, europium-activated fluorescent materials include Sr5(PO4)3Cl:Eu, Y2O2S:Eu, Y2O3:Eu, YVO4:Eu, (Y,Gd)BO3:Eu, Sr5(PO4)3Cl:Eu, and BaMgAl 10 O 17 :Eu, BaMgAl 14 O 23 :Eu, BaMg2Al 14 O 24:Eu, BaMgAl 16 O 27 :Eu, and terbium-activated fluorescent materials such as LaPO4:Tb and CeMgAl 11 O 19 :Tb, Gd2O2S:Tb, Y3Al5O 12 : Y3Al5O as a fluorescent material activated with Tb and Cerium 12 :Ce, Y2SiO3:Ce, Lu3Al5O 12 Examples of inorganic ultraviolet fluorescent pigments include fluorescent substances activated with ZnO:Zn, cadmium, bismuth, calcium sulfide, samarium, and lead. The fluorescent material is a material that emits light when irradiated with ultraviolet light, but in the case of a fluorescent material that also emits light when irradiated with blue light, the history of the printed image can be confirmed by irradiating it with light such as a blue LED. The blue light used has a peak emission wavelength in the range of 400 to 495 nm, and is primarily blue light.

[0039] The fluorescent substance can be contained in a medium, or can be used as a fluorescent microcapsule pigment in which the fluorescent substance is encapsulated in microcapsules, or as fluorescent resin particles in which the fluorescent substance is uniformly or locally dispersed in a thermoplastic or thermosetting resin, or can be contained in a reversible thermochromic microcapsule pigment, or can be contained in the wall film of a reversible thermochromic microcapsule pigment. The fluorescent microcapsule pigment, in which the fluorescent substance is encapsulated in microcapsules, has excellent dispersion stability in ink using an aqueous medium. The microencapsulation can be carried out by the same method as that for the reversible thermochromic microencapsulated pigment.

[0040] The content of the fluorescent substance is 0.01 to 30% by mass, preferably 0.05 to 20% by mass, and more preferably 0.1 to 10% by mass, based on the total amount of the ink composition. If the amount is less than 0.01% by weight, the effect of checking the history of the print image when irradiated with light using an irradiator is poor, and even if more than 30% by weight is added, the effect of checking the history of the print image when irradiated with light using an irradiator cannot be further improved, so no further addition is necessary.

[0041] The medium used is water and, if necessary, a water-soluble organic solvent. Examples of the water-soluble organic solvent include glycols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,3-butylene glycol, and ethylene glycol monomethyl ether, as well as lower alkyl ethers thereof, 2-pyrrolidone, N-vinylpyrrolidone, and urea. When using a reversible thermochromic microcapsule pigment that encapsulates a reversible thermochromic composition consisting of (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that reversibly induces an electron donor-acceptor reaction between the components (a) and (b) in a specific temperature range, glycerin and propylene glycol are preferably used as the water-soluble organic solvent.

[0042] If necessary, a thickener can also be added. Examples of the thickener include xanthan gum, welan gum, succinoglycan (average molecular weight: about 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 derivatives thereof, hydroxyethyl cellulose, alginic acid alkyl esters, polymers having a molecular weight of 100,000 to 150,000 and containing alkyl esters of methacrylic acid as the main component, glycomannan, thickening polysaccharides having gelling ability extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, cross-linked alginates, and the like. Examples include acrylic acid polymers, inorganic fine particles, polyglycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene lanolin / lanolin alcohol / beeswax derivatives, polyoxyethylene alkyl ethers / polyoxypropylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, nonionic surfactants with an HLB value of 8 to 12 such as fatty acid amides, and salts of dialkyl or dialkenyl sulfosuccinic acid, which can be used alone or in combination. As the thickener, an alkali-soluble acrylic emulsion is preferably used. When an alkali-soluble acrylic emulsion is used as the thickener, the pH of the ink composition is adjusted to 6 to 11, preferably 7 to 11, and more preferably 7 to 10.

[0043] Furthermore, a binder resin may be added to adjust the viscosity and fixation of the printed image. The binder resin is selected from a resin emulsion, an alkali-soluble resin, and a water-soluble resin. Examples of the resin emulsion include aqueous dispersions of polyacrylic acid ester, styrene-acrylic acid copolymer, polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, methacrylic acid-maleic acid copolymer, ethylene-methacrylic acid copolymer, α-olefin-maleic acid copolymer, polyester, polyurethane, etc. Examples of the alkali-soluble resin include styrene-maleic acid copolymer, ethylene-maleic acid copolymer, styrene-acrylic acid copolymer, etc. Examples of the water-soluble resin include polyvinyl alcohol, polyvinyl butyral, etc., and these can be used alone or in combination of two or more.

[0044] In addition, additives such as a pH adjuster, a preservative or antifungal agent, a solvent penetration improver, and an antifoaming agent may be added as needed. Examples of the pH adjuster include inorganic salts such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide, and sodium acetate, and organic basic compounds such as water-soluble amine compounds such as triethanolamine and diethanolamine. Examples of the antiseptic or antifungal agent include carbolic acid, sodium salt of 1,2-benzisothiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine. Examples of the penetration enhancer include fluorine-based surfactants and nonionic, anionic and cationic surfactants. The antifoaming agent includes dimethylpolysiloxane.

[0045] The ink composition is used as an ink composition for a stamp pad and an ink composition for a stamp having a stamp material having continuous pores. The ink composition for a stamp pad is impregnated into a stamp pad to obtain a stamp pad that supplies the ink composition to the printing surface of a stamp that comes into contact with it, or the ink composition for a stamp having a printing material with continuous pores is impregnated into the printing material of a stamp having a printing material with continuous pores to obtain a stamp. A stamp equipped with a printing material having interconnected pores is made by impregnating an ink composition into a rubber-like elastic body having interconnected pores, which is the printing material. When this stamp is pressed against a target surface, the ink composition is transferred to the target surface through the openings of the interconnected pores, thereby transferring the surface shape of the stamp. Areas where transfer is not desired are made recessed, or the openings are closed to prevent the ink composition from adhering to the target surface. The stamp material having continuous pores is housed in a stamp base material so that the stamp surface is exposed, and the exposed surface is preferably provided with a cap to prevent the ink composition from drying out when not in use or contamination due to accidental contact. In addition, an ink reservoir for supplying an ink composition to the printing material may be provided at the rear of the printing material having continuous pores.

[0046] The print formed by the ink composition can be erased by rubbing with a finger or by applying a heat or cold tool. Examples of the heating tool include an electrically heated color-changing tool equipped with a resistance heating element, a heated color-changing tool filled with hot water, or a hair dryer, but preferably, a friction member is used as a means capable of changing color in a simple manner. The friction member is preferably made of an elastic material such as an elastomer or plastic foam, which has a high elasticity and can generate frictional heat by generating appropriate friction when rubbed. Although it is possible to rub the print using an eraser, the rub generates eraser dust, so the above-mentioned friction member, which generates almost no eraser dust, is preferably used. The friction member is made of a material such as silicone resin, SEBS resin (styrene-ethylene-butylene-styrene block copolymer), polyester resin, or polyester elastomer. The friction member can be a stamp set obtained by combining a stamp with a friction body, which is a separate member of any shape, but providing the friction member on the stamp makes it more portable. Examples of the cooling and heating device include a cooling and heating device using a Peltier element, a cooling and heating device filled with a refrigerant such as cold water or ice chips, and a refrigerator or freezer. [Example]

[0047] Next, the thermochromic ink composition for stamps and the stamp containing the same of the present invention will be described. In the examples, the formulations are in parts by mass. Example 1 Preparation of microcapsule pigments A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 2.0 parts of 4,5,6,7-tetrachloro-3-[4-(dimethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone 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 component (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 1.8 μm, a completely decolorized temperature of 55° C., a completely colored temperature of −20° C., and reversibly changes color from blue to colorless with temperature change.

[0048] Preparation of thermochromic stamp ink composition A thermochromic stamp ink composition was obtained by mixing 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop a blue color), 2.5 parts of a fluorescent microcapsule pigment in which Zn2SiO4:Mn as a fluorescent substance is encapsulated in microcapsules, 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 14.2 parts of water.

[0049] Fabrication of the stamp (see Figure 4) The ink composition was impregnated into a stamp material 2 having continuous pores, and the stamp material was fixed to a stamp substrate 3 so that the printing surface of the stamp material was exposed, and a cap 5 was fitted to obtain a stamp. A friction member 4 made of SEBS resin is provided at the rear end of the stamp base material. When the stamp was used to impress on a target surface (paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming a blue print image which was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the blue print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted green light and was visible, making it possible to confirm the history. Furthermore, when light was irradiated using an illumination device that emits blue light using a blue LED, the decolorized print image lit up and was visible, allowing the history to be confirmed.

[0050] Example 2 Preparation of microcapsule pigments 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), 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c), and 1.0 parts of 1-[(2-nitro-4-methylphenyl)azo]-2-naphthalenol as a fluorescent substance. The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.3 μm, a completely decolorized temperature of 58° C., a completely colored temperature of −20° C., and reversibly changes color from pink to colorless with temperature change.

[0051] Preparation of thermochromic stamp ink composition A thermochromic stamp ink composition was obtained by mixing 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop a pink color), 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 16.7 parts of water.

[0052] Stamp creation The ink composition was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp substrate so that the printing surface of the stamp material was exposed, and a cap was fitted to obtain a stamp. The rear end of the stamp base material is provided with a friction member made of SEBS resin. When the stamp was used to impress a target surface (paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming a pink print image that was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the pink print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted red light and was visible, making it possible to confirm the history. Furthermore, when light was irradiated using an illumination device that emits blue light using a blue LED, the decolorized print image lit up and was visible, allowing the history to be confirmed.

[0053] Example 3 Preparation of microcapsule pigments 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), 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 2.0 μm, a completely decolorized temperature of 60° C., a completely colored temperature of −20° C., and reversibly changes color from orange to colorless with temperature change.

[0054] Preparation of thermochromic stamp ink composition A thermochromic stamp ink composition was obtained by mixing 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop an orange color), 1.0 part of fluorescent resin particles in which Y2O2S:Eu as a fluorescent substance was dispersed in the resin, 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 15.7 parts of water.

[0055] Stamp creation The ink composition was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp substrate so that the printing surface of the stamp material was exposed, and a cap was fitted to obtain a stamp. The rear end of the stamp base material is provided with a friction member made of SEBS resin. When the stamp was used to impress a target surface (paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming an orange print image that was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the orange print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted red light and was visible, making it possible to confirm the history. Furthermore, when light was irradiated using an illumination device that emits blue light using a blue LED, the decolorized print image lit up and was visible, allowing the history to be confirmed.

[0056] Example 4 Preparation of microcapsule pigments A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 2.0 parts of 4,5,6,7-tetrachloro-3-[4-(dimethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone 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 component (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 1.8 μm, a completely decolorized temperature of 55° C., a completely colored temperature of −20° C., and reversibly changes color from blue to colorless with temperature change.

[0057] Preparation of thermochromic stamp ink composition 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop a blue color), Lu3Al5O as a fluorescent material 12 A thermochromic stamp ink composition was obtained by mixing 2.0 parts of a fluorescent microcapsule pigment in which Ce is encapsulated in microcapsules, 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 14.2 parts of water.

[0058] Stamp creation The ink composition was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp substrate so that the printing surface of the stamp material was exposed, and a cap was fitted to obtain a stamp. The rear end of the stamp base material is provided with a friction member made of SEBS resin. When the stamp was used to impress on a target surface (paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming a blue print image which was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the blue print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted yellow light and was visible, making it possible to confirm the history. Furthermore, when light was irradiated using an illumination device that emits blue light using a blue LED, the decolorized print image lit up and was visible, allowing the history to be confirmed.

[0059] Example 5 Preparation of microcapsule pigments A microcapsule pigment suspension was obtained containing a reversible thermochromic composition with color memory, consisting of 2.0 parts of 4,5,6,7-tetrachloro-3-[4-(dimethylamino)-2-methylphenyl]-3-(1-ethyl-2-methyl-1H-indol-3-yl)-1(3H)-isobenzofuranone 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), 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c), and 0.5 parts of 7-[1',3',5'-triazine-4'-chloro-6'-(3''-diethylaminopropylamino)-2'-yl-amino]-3-phenylcoumarin as an oil-soluble fluorescent brightener. The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 1.8 μm, a completely decolorized temperature of 55° C., a completely colored temperature of −20° C., and changes color from blue to colorless with temperature change.

[0060] Preparation of thermochromic stamp ink composition A thermochromic stamp ink composition was obtained by mixing 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop an orange color), 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 16.7 parts of water.

[0061] Stamp creation The ink composition was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp substrate so that the printing surface of the stamp material was exposed, and a cap was fitted to obtain a stamp. The rear end of the stamp base material is provided with a friction member made of SEBS resin. When the stamp was used to imprint on a target surface (white paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming a blue print image that was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the blue print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted light and was visible, making it possible to confirm the history.

[0062] Example 6 Preparation of microcapsule pigments 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), 50.0 parts of 4-benzyloxyphenylethyl caprate as component (c), and 0.2 parts of 2,2'-(1,2-ethylenediyldi-4,1-phenylene)bisbenzoxazole as a fluorescent substance. The suspension was centrifuged to isolate the microencapsulated pigment. The microcapsule pigment has an average particle size of 2.3 μm, a completely decolorized temperature of 58° C., a completely colored temperature of −20° C., and reversibly changes color from pink to colorless with temperature change.

[0063] Preparation of thermochromic stamp ink composition A thermochromic stamp ink composition was obtained by mixing 20.0 parts of the microcapsule pigment (previously cooled to -20°C or below to develop a pink color), 50.0 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10.0 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based antifoaming agent, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 16.7 parts of water.

[0064] Stamp creation The ink composition was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp substrate so that the printing surface of the stamp material was exposed, and a cap was fitted to obtain a stamp. The rear end of the stamp base material is provided with a friction member made of SEBS resin. When the stamp was used to impress a target surface (paper), the ink composition smoothly flowed out from the printing surface of the stamping material and transferred to the target surface, forming a pink print image that was maintained at room temperature (25°C). When the print was rubbed with the friction element provided on the stamp, the pink print disappeared, and this state was maintained at room temperature (25°C). When the area where the print had been present was irradiated with light using an ultraviolet irradiator, the erased print emitted blue light and was visible, making it possible to confirm the history. Furthermore, when light was irradiated using an illumination device that emits blue light using a blue LED, the decolorized print image lit up and was visible, allowing the history to be confirmed. [Explanation of symbols]

[0065] t1 Complete color development temperature of heat-discoloring type reversible thermochromic composition t2 Color development start temperature of heat-discoloring type reversible thermochromic composition t3The starting temperature of discoloration of reversible thermochromic composition t4 Complete decolorization temperature of reversible thermochromic composition T1 Complete decolorization temperature of reversible thermochromic composition with heat coloring T2: The temperature at which the reversible thermochromic composition begins to fade T3 Color development start temperature of heat-coloring type reversible thermochromic composition T4 Complete color development temperature of reversible thermochromic composition ΔH Hysteresis width 1 stamp 2 Seal material 3 Stamp substrate 4 Friction members 5 Caps

Claims

1. An ink composition for a thermochromic stamp, comprising a medium, a thermochromic material that changes color from colored to colorless, and a fluorescent substance that emits fluorescence when irradiated with ultraviolet light.

2. The thermochromic material is a microencapsulated 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-forming reaction of (a) and (b) is encapsulated in a microcapsule, and the pigment exhibits hysteresis characteristics in a color density-temperature curve, exhibiting alternation between a colored state and a colorless state, and the temperature ranges for both states are both in the room temperature range, and in the process of temperature rise from the colored state, the pigment ３ When the temperature reaches t ３ Higher temperature t ４ In the temperature range above, the color becomes completely colorless. In the process of decreasing the temperature from the colorless state, ３ Lower temperature t ２ When the temperature reaches t ２ Lower temperature t １ The color is completely changed in the temperature range below the temperature t ２ and temperature t ３ The colored state and the colorless state are selectively maintained in the temperature range between t １ is in the range of -50 to 5°C, and the temperature t ４ 2. The ink composition for a thermochromic stamp according to claim 1, wherein the temperature is in the range of 40 to 95°C.

3. 3. The ink composition for a thermochromic stamp according to claim 1, wherein the ink composition comprises a microcapsule pigment in which the fluorescent substance is encapsulated in a microcapsule, or a resin particle in which the fluorescent substance is dispersed in a thermoplastic or thermosetting resin.

4. A stamp containing the thermochromic stamp ink composition according to claim 1 or 2.

5. 5. The stamp according to claim 4, further comprising a friction member.

Images