Learning tool, and learning tool set

Abstract

To provide a learning tool, which reduces cost, improves practicability and suitable for an intellectual training application, capable of hiding and revealing an answer portion without covering, with a reversible thermally discoloring material, all the answer portions of a plurality of learning tools, where questions and answers of the questions are displayed, and a learning tool set.SOLUTION: The present invention relates to a learning tool 1 and a learning tool set. The learning tool consists of: a learning sheet 2 in which a question display section 4 and an answer display section 5 corresponding to the question display section are provided on a surface of a sheet 3; and an answer hiding / revealing sheet 6 which is placed on the learning sheet. In the learning tool, the learning sheet includes a plurality of learning sheets with different contents of the question display sections and the answer display sections. In the answer hiding / revealing sheet, on a surface of a transparent sheet 7, a reversible thermally discoloring image 8 is provided which contains a reversible thermally discoloring material, of which the color is changed from a colored state to a colorless state by a temperature change, covering the answer display section in a case where the transparent sheet is placed on the learning sheet.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a learning tool and a learning tool set, and more particularly to a learning tool and a learning tool set on which questions and answers to the questions are displayed. [Background technology]

[0002] Conventionally, learning tools have been disclosed in which the answer portion of the learning tool, on which questions and the answers to the questions are displayed, is covered with a reversible thermochromic material that changes color from colored to colorless with a change in temperature (see, for example, Patent Documents 1 or 2). The learning tool allows answers that are invisible when the reversible thermochromic material is in a colored state to be made visible by making the reversible thermochromic material colorless by a simple means such as touch, thereby simplifying the structure of the learning tool and allowing the answers to be quickly confirmed. However, when a plurality of learning tools are used, it is necessary to cover the answer area of ​​each learning tool with a reversible thermochromic material, which is time-consuming and costly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Microfilm of Utility Model Application No. 61-99667 (Utility Model Application No. 63-4576) [Patent Document 2] Microfilm of Utility Model Application No. 62-195118 (Utility Model Application No. 1-97969) Summary of the Invention [Problem to be solved by the invention]

[0004] To provide a learning tool and a learning tool set which enable the concealment and reveal of the answer parts of a plurality of learning tools on which problems and answers to the problems are displayed without covering all of the answer parts with a reversible thermochromic material. [Means for solving the problem]

[0005] The present invention provides a learning tool comprising a learning sheet having a question display section and an answer display section corresponding to the question display section on the surface of the sheet, and an answer concealment sheet to be placed on the learning sheet, wherein the learning sheet comprises a plurality of learning sheets having different content for the question display section and the answer display section, and the answer concealment sheet is an answer concealment sheet having a reversible thermochromic image on the surface of a transparent sheet which contains a reversible thermochromic material that changes color from colored to colorless due to a change in temperature and which covers the answer display section when the transparent sheet is placed on the learning sheet. Further, the present invention is also applicable to a learning tool set comprising the learning tool and a friction body, a learning tool set comprising the learning tool and a writing implement equipped with a friction member, and the like. Effect of the Invention

[0006] To provide a learning tool and a learning tool set suitable for intellectual training purposes at low cost and with high practicality, which enables each answer part of a plurality of learning tools on which questions and answers to the questions are displayed to be concealed without covering all of them with a reversible thermochromic material. [Brief description of the drawings]

[0007] [Figure 1] 1 is a graph illustrating hysteresis characteristics in a color density-temperature curve of a heat-discolorable, reversible thermochromic composition. [Diagram 2] 1 is a graph illustrating the hysteresis characteristics in a color density-temperature curve of a reversible thermochromic composition having color memory properties. [Diagram 3] 1 is a graph illustrating hysteresis characteristics in a color density-temperature curve of a reversible thermochromic composition that develops color upon heating. [Figure 4] 1 is a top view showing an embodiment of a learning tool of the present invention. [Diagram 5] 5 is a top view showing a state in which an answer concealment sheet is placed on the top surface of one of the study sheets in FIG. 4. FIG. [Figure 6] FIG. 6 is a top view showing the state in which the reversible thermochromic image of the answer concealment sheet placed on the top surface of the learning sheet on one side of FIG. 5 has been erased. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The study sheet has, on its front surface, a question display section and an answer display section corresponding to the question display section. The material of the sheet is not particularly limited, and examples thereof include paper, synthetic paper, synthetic leather, leather, plastic, glass, ceramics, metal, wood, stone, etc., with paper and synthetic paper being preferred. The question display section and answer display section provided on the surface of the sheet are letters, symbols, pictures, sentences, etc. containing a non-discoloring colorant, and it is preferable that a plurality of question display sections and a plurality of answer display sections corresponding to the question display sections are formed on the surface of the sheet. The learning sheet includes a plurality of learning sheets each having a question display section and an answer display section with different contents. The answer display sections of the multiple study sheets are provided in the same position so that they can be covered with the reversible thermochromic image of the answer concealment sheet. The non-discoloring colorant may be a general dye or pigment, and the dye may be an acid dye, a basic dye, or a direct dye. Examples of the pigment that can be used include inorganic pigments such as carbon black and ultramarine, organic pigments such as azo pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, threne pigments, quinacridone pigments, anthraquinone pigments, threne pigments, diketopyrrolopyrrole pigments, dioxazine pigments, perylene pigments, perinone pigments, and isoindolinone pigments, and fluorescent pigments. The non-discoloring colorant is dispersed in a vehicle containing water and / or an organic solvent and, if necessary, various additives, to prepare a printing ink or inkjet ink for use in screen printing, offset printing, process printing, gravure printing, etc., and then printed to form a question display section and an answer display section on a sheet. The study sheet is composed of a plurality of study sheets each having a different content in the question display section and answer display section. The multiple learning sheets may be separate, or holes may be drilled in each learning sheet and the sheets may be joined together with a ring-shaped member, or the sheets may be bound together along one edge to form a booklet. By joining the learning sheets together or forming them into a booklet, a highly portable learning tool can be obtained.

[0009] The answer concealment sheet has a reversible thermochromic image on the surface of a transparent sheet, the image containing a reversible thermochromic material that changes color from colored to colorless due to a temperature change and covers the answer display section when the transparent sheet is placed on a learning sheet. The transparent sheet can be made of any material having transparency, but a transparent plastic sheet is preferably used. Specific examples of the material for the transparent sheet include plastic sheets such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polymethyl methacrylate, polyacrylate, polystyrene, polycarbonate, cellulose triacetate, cellulose diacetate, polyvinyl alcohol, and polyamide, and glass plates. Plastic sheets such as polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl chloride, which are highly flexible and have excellent safety, are preferably used. The transparent sheet may be formed by laminating sheets of the same material or by laminating sheets of different materials. The transparency may be colorless transparency, colored transparency, translucency, or colored translucency. The answer concealment sheet may be in the form of a plate, or in the form of a container or bag capable of containing the learning sheet. By forming the answer concealing sheet in a container or bag shape, it becomes possible to easily specify the positions of the answer indicating portion and the reversible thermochromic image. When the answer concealment sheet is in the shape of a container or bag, by providing a waterproof function to the opening, it can become a highly convenient learning tool that can be used in the bathroom, etc.

[0010] The reversible thermochromic image is a design or picture selected from geometric patterns such as circles, squares, rectangles, triangles, etc., and is made of a reversible thermochromic material. Examples of the reversible thermochromic material include inorganic materials such as Ag2HgI4 and Cu2HgI4, liquid crystals, resin particles containing a reversible thermochromic composition, and reversible thermochromic microencapsulated pigments (reversible thermochromic pigments) encapsulating a reversible thermochromic composition, and reversible thermochromic microencapsulated pigments are preferably used.

[0011] The reversible thermochromic composition may be a thermally decolorizable (decolorizing by heating and coloring by cooling) reversible thermochromic composition 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-forming reaction between the two occurs. The reversible thermochromic composition may be a reversible thermochromic composition of a heat-discoloring type (discolored by heating and colored by cooling) having a relatively small hysteresis width (ΔH) of 1 to 7° C., which is described in JP-B-51-44706, JP-B-51-44707, JP-B-1-29398, etc. and which changes color around a certain temperature (discoloration point), exhibits a discolored state in a temperature range above the high-temperature discoloration point, and exhibits a colored state in a temperature range below the low-temperature discoloration point, and of the 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 express that state is applied, but returns to the state exhibited in the room temperature range when the application of the heat or cold is removed (see FIG. 1).

[0012] In addition, hysteresis width (ΔH) described in 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. shows a relatively large characteristic of 8°C to 80°C, that is, the shape of the curve plotting the change in color density due to temperature change is as follows: A reversible thermochromic composition of the heat-discoloring type (discolors when heated and develops color when cooled) that has color memory in a specific temperature range [temperature range between t2 and t3 (temperature range where two phases are substantially maintained)], in which the color changes along a route that is significantly different when the temperature is lowered from a higher temperature side than the discoloration temperature range and the colored state is in a low temperature range below the complete color-developing temperature (t1) or in a decolored state is in a high temperature range above the complete decolorization temperature (t4) (see Figure 2).

[0013] The hysteresis characteristic in the color density-temperature curve of the reversible thermochromic composition will now 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 progresses along the arrow. Here, A is a point indicating the density at temperature t4 (hereinafter referred to as complete decolorization temperature) where a completely decolorized state is reached, B is a point indicating the density at temperature t3 (hereinafter referred to as decolorization onset temperature) where decolorization begins, C is a point indicating the density at temperature t2 (hereinafter referred to as color development onset temperature) where color development begins, and D is a point indicating the density at temperature t1 (hereinafter referred to as complete color development temperature) where a completely colored state is reached. 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 a large 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 a temperature range indicating the degree of hysteresis (hereinafter referred to as hysteresis range ΔH). If this ΔH value is small, only one of the two states before and after the discoloration can exist in the room temperature range. If the ΔH value is large, it is easy to maintain each state before and after the discoloration.

[0014] 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-forming compound, is a component that determines the color, and is a compound that develops color by donating electrons to the component (B), which is a color developer. Examples of the electron-donating color-forming organic compound include phthalide compounds, fluoran compounds, styrinquinoline compounds, diazarhodamine lactone compounds, pyridine compounds, quinazoline compounds, and bisquinazoline compounds. Of these, phthalide compounds, fluoran compounds, styrinquinoline 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 given below. 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethoxy-4-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-butoxyfluoran, 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] etc. can be mentioned. In addition to the above-mentioned compounds having a substituent on the phenyl group forming the xanthene ring, the fluorans may also be compounds that have a substituent on the phenyl group forming the xanthene ring and also have a substituent (e.g., an alkyl group such as a methyl group, or a halogen atom such as a chloro group) on the phenyl group forming the lactone ring, and exhibit a blue or black color.

[0015] The component (b), ie, the electron accepting compound, is a compound that accepts electrons from the component (a) and functions as a developer for the component (a). 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 which 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, and the like. 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 monophenol compounds to polyphenol compounds, and further include bis-type and tris-type phenols and phenol-aldehyde condensation resins. Among the compounds having a phenolic hydroxyl group, those having at least two benzene rings are preferred. In addition, 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, a halogen group, and the like. Examples of the metal contained in the metal salt of the compound having an active proton include sodium, potassium, calcium, zinc, zirconium, aluminum, magnesium, nickel, cobalt, tin, copper, iron, vanadium, titanium, lead, and molybdenum.

[0016] Some 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-butyl ... 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, 2,2-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, 3,3-bis(3-methyl-4-hydroxyphenyl)butane, etc. The compound having a phenolic hydroxyl group is capable of exhibiting the most effective thermal discoloration properties, but it may also be a compound 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.

[0017] The component (iii) of the reaction medium that reversibly induces an electron donor-acceptor reaction by the components (a) and (b) 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 the microencapsulation and secondary processing described below, compounds having a carbon number of 10 or more are preferably used in order to stably retain the component in the capsule, since low molecular weight compounds tend to evaporate outside the capsule when subjected to high heat treatment. As the alcohols, aliphatic monohydric saturated alcohols having 10 or more carbon atoms are effective, and specific examples thereof include decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, docosyl alcohol, etc.

[0018] As the esters, esters having 10 or more carbon atoms are effective, and examples thereof include esters obtained from any combination of a monovalent carboxylic acid having an aliphatic and an alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and an alicyclic or aromatic ring, esters obtained from any combination of a polyvalent carboxylic acid having an aliphatic and an alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and an alicyclic or aromatic ring, esters obtained from any combination of a monovalent carboxylic acid having an aliphatic and an alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and an alicyclic or aromatic ring, Specific examples of the esters include 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.

[0019] 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-ethylpropyl 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 of suitable oleic acid esters include ethyl octyl, 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-bromostearinate, isostearyl 2-ketomyristate, 2-ethylhexyl 2-fluoromyristate, cetyl butyrate, stearyl butyrate, and behenyl butyrate.

[0020] Furthermore, in order to change color while exhibiting a large hysteresis characteristic with respect to the color density-temperature curve and to impart color memory depending on temperature change, carboxylic acid ester compounds exhibiting a ΔT value (melting point-cloud point) of 5° C. or more and less than 50° C. as described in JP-B-4-17154 may be mentioned, 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, distearin, etc.

[0021] Fatty acid ester compounds obtained from an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an aliphatic carboxylic acid having an even number of carbon atoms, 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, myristic Examples of the glyceryl stearate 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-undelsyl eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, and n-pentadecyl behenate.

[0022] 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.

[0023] 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.

[0024] 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 of the amides include adipic acid N-butylamide, glutaric acid N-butylamide, malonic acid N-butylamide, adipic acid N-octylamide, and adipic acid N-dodecylamide.

[0025] Furthermore, as the component (iii), a compound represented by the following general formula (1) can also be used. [ka] [In the formula, 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 further when R1 is a hydrogen atom and m is 0, it is more preferable. Among the compounds represented by formula (1), it is more preferable to use a compound represented by the following general formula (2). [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 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.

[0026] 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.) 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.

[0027] 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, and a diester of malonic acid and 2-[4-(4-chlorobenzyloxy)phenyl]ethanol. Examples of such esters include a diester of 2-(4-benzyloxyphenyl)ethanol with suberic acid, a diester of 2-(4-(2,4-dichlorobenzyloxy)phenyl)ethanol with suberic acid, a diester of 2-(4-benzyloxyphenyl)ethanol with suberic acid, a diester of 2-(4-benzyloxyphenyl)ethanol with azelaic acid, a diester of 2-(4-benzyloxyphenyl)ethanol with sebacic acid, a diester of 1,10-decanedicarboxylic acid and 2-(4-benzyloxyphenyl)ethanol with 1,18-octadecanedicarboxylic acid, and a diester of 1,18-octadecanedicarboxylic acid and 2-(4-benzyloxyphenyl)ethanol with 2-[4-(2-methylbenzyloxy)phenyl)]ethanol.

[0028] 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 a diester of 1,4-bis(hydroxymethoxy)benzene and acetic acid. 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.

[0029] Furthermore, as the component (iii), a compound represented by the following general formula (6) can also be used. [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.

[0030] Furthermore, a compound represented by the following general formula (7) 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, a cycloalkylalkyl group, a cycloalkyl group, and an alkenyl group having 4 to 22 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 4 carbon atoms, and 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.

[0031] Furthermore, as the component (iii), a compound represented by the following general formula (8) can also be used. [ka] (In the formula, R represents any one of an alkyl group having 3 to 18 carbon atoms and an aliphatic acyl group having 3 to 18 carbon atoms; X represents any one of a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, and a halogen atom; Y represents any one of a hydrogen atom and a methyl group; and Z represents any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, and a halogen atom.) Examples of the compound include phenoxyethyl 4-butoxybenzoate, phenoxyethyl 4-pentyloxybenzoate, phenoxyethyl 4-tetradecyloxybenzoate, an ester of phenoxyethyl 4-hydroxybenzoate with dodecanoic acid, and dodecyl ether of phenoxyethyl vanillate.

[0032] Furthermore, as the component (iii), a compound represented by the following general formula (9) can also be used. [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 the benzoate ester of octyl p-hydroxybenzoate, the benzoate ester of decyl p-hydroxybenzoate, the p-methoxybenzoate ester of heptyl p-hydroxybenzoate, the o-methoxybenzoate ester of dodecyl p-hydroxybenzoate, and the benzoate ester of cyclohexylmethyl p-hydroxybenzoate.

[0033] Furthermore, as the component (iii), a compound represented by the following general formula (10) can also be used. [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.

[0034] Furthermore, as the component (iii), a compound represented by the following general formula (11) can also be used. [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.

[0035] Furthermore, as the component (iii), a compound represented by the following general formula (12) can also be used. [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 cyclohexane carboxylic acid, a diester of 4-phenylphenol diethylene glycol ether and lauric acid, a diester of 4-phenylphenol triethylene glycol ether and cyclohexane carboxylic 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.

[0036] Furthermore, reversible thermochromic compositions of the heat-coloring type (which develops color when heated and loses color when cooled) that use specific alkoxyphenol compounds having a straight-chain or side-chain alkyl group having 3 to 18 carbon atoms as the electron-accepting compound (JP Patent Publication Nos. 11-129623 and 11-5973), specific hydroxybenzoic acid esters (JP Patent Publication No. 2001-105732), or gallic acid esters (JP Patent Publication Nos. 51-44706 and 2003-253149) can also be applied (see FIG. 3).

[0037] The ratio of each component of the reversible thermochromic composition depends on the concentration, color change temperature, color change form, and type of each component, but generally, the component ratio that gives the desired properties is 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 the above ratios are parts by mass).

[0038] Furthermore, various light stabilizers can be added as necessary. The light stabilizer is contained in order to prevent photodegradation of the reversible thermochromic composition consisting of components (a), (b) and (c), and is contained in a ratio of 0.3 to 24 mass%, preferably 0.3 to 16 mass%, per 1 mass% of component (a). Among the light stabilizers, the ultraviolet absorber effectively blocks ultraviolet rays contained in sunlight and the like, and prevents photodegradation caused by the excited state due to the photoreaction of component (a). The antioxidant, singlet oxygen quencher, superoxide anion quencher, ozone quencher and the like suppress oxidation reactions caused by light. The light stabilizers may be used alone or in combination of two or more kinds.

[0039] The reversible thermochromic composition can be used as a reversible thermochromic microencapsulated pigment by being encapsulated in a microcapsule. Microencapsulation may be carried out 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, spray drying, etc., and may be appropriately selected depending on the application. Furthermore, a secondary resin film may be provided on the surface of the microcapsule depending on the purpose to impart durability or modify the surface properties for practical use. The microcapsule pigment preferably has a mass ratio of inclusions / wall film of 7 / 1 to 1 / 1. By having the wall film ratio within this range, it is possible to prevent a decrease in color density and vividness 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.

[0040] The reversible thermochromic microencapsulated pigment satisfies practical application when its particle size is in the range of 0.5 to 30 μm, preferably 0.5 to 20 μm, and more preferably 1.0 to 10 μm. The particle size and average particle size were measured by determining the particle area using Mountec's image analysis particle size distribution measurement software "Mac View", calculating the projected area circle equivalent diameter (Heywood diameter) from the area of ​​the particle area, and measuring the particle size and average particle size of the particles equivalent to an equal volume sphere using this value. In addition, if the particle size of all particles or the majority of particles exceeds 0.2 μm, it is also possible to measure the particle size and average particle size of the particles equivalent to an equal volume sphere by the Coulter method using a particle size distribution measurement device (Beckman Coulter, Inc., product name: Multisizer 4e). Furthermore, the volumetric particle size and average particle size (median size) may be measured using a laser diffraction / scattering particle size distribution analyzer (device name: LA-960V2, manufactured by HORIBA, Ltd.) calibrated based on values ​​measured using a measuring device based on the Coulter method.

[0041] The reversible thermochromic material can be dispersed in a vehicle containing water and / or an organic solvent and, if necessary, various additives, to prepare a printing ink or inkjet ink for use in screen printing, offset printing, process printing, gravure printing, etc., and then printed to form a reversible thermochromic image on the surface of a transparent sheet.

[0042] In the case where the reversible thermochromic microencapsulated pigment exhibits hysteresis characteristics with respect to the color concentration-temperature curve, and exhibits alternation between a colored state and a colorless state, and in the process of increasing temperature from a colored state, the pigment begins to lose color when it reaches temperature t3 and becomes completely colorless in a temperature range of t4 or higher, which is higher than temperature t3, and in the process of decreasing temperature from the colorless state, the pigment begins to become colored when it reaches temperature T2, which is lower than temperature T3, and becomes completely colored in a temperature range of t1 or lower, which is lower than temperature t2, by setting temperature t4 in the range of 30 to 90°C, preferably 30 to 80°C, and more preferably 30 to 70°C, the color changes due to body heat when touched with the hand, or due to frictional heat caused by rubbing with a finger or using a friction body, thereby enabling easy color change.

[0043] A transparent metallic gloss layer may be provided on the reversible thermochromic image to impart a metallic glossy color or to improve the light resistance of the reversible thermochromic composition. Examples of the transparent metallic luster pigment contained in the transparent metallic luster layer include pigments having a core material such as natural mica, synthetic mica, glass pieces, alumina, and transparent film pieces whose surface is coated with a metal oxide such as titanium oxide. Moreover, a transparent resin layer (protective layer) can be provided on the reversible thermochromic image. The transparent resin layer may contain light stabilizers such as ultraviolet absorbers, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, and ozone quenchers.

[0044] The reversible thermochromic image can be changed in color by touch, rubbing with fingers, applying hot or cold water, a friction body, a heat-changing tool, or a cold-heat-changing tool. The heating device may be an electrically heated discoloration device equipped with a resistance heating element or a heat discoloration device filled with hot water or the like, and the cooling device may be an electrically heated discoloration device using a Peltier element or a cold-heat discoloration device filled with a refrigerant such as cold water or ice chips, but it is preferable to use a friction body that can be discolored in a simple manner. The friction body is preferably an elastic body such as an elastomer or plastic foam, which has a high elastic feel and can generate appropriate friction and generate frictional heat when rubbed, but it may also be a plastic molded body, stone, wood, metal, or fabric. Although it is possible to use an eraser for friction, it is preferable to use a friction body such as that described above, since the friction generates eraser dust. Examples of the material of the friction body include silicone resin, SBS resin (styrene-butadiene-styrene copolymer), and SEBS resin (styrene-ethylene-butylene-styrene block copolymer). By combining the learning tool with the friction body, a learning tool set with excellent portability can be obtained. Furthermore, by combining the learning tool with a writing implement having a friction member, a learning tool set can be obtained that is highly portable and has improved convenience since it is possible to write on the learning sheet. The location where the friction member is fixed can be the tip (top) of the cap, or the tip (part where no writing tip is provided) of the barrel, or the like. The ink contained in the writing instrument may be a non-thermochromic ink, but by using ink that can be erased by heating, it is possible to make the writing instrument more convenient by allowing repeated writing. The colorant contained in the heat-decolorizable ink can be the thermochromic material described above. The writing implement may be a solid writing implement such as a pencil or a crayon. EXAMPLES

[0045] Examples are shown below, but the present invention is not limited to these examples. In the examples, "parts" refers to parts by weight. Example 1 (see Figures 4 to 6) Creating a study sheet On a sheet 3 made of synthetic paper, the numbers and symbols "2 x 2 = 4" were printed using a blue screen printing ink consisting of 5 parts blue pigment, 1 part viscosity modifier, 0.2 parts defoaming agent, and 93.8 parts water, and then dried to form a problem display section 4 consisting of the "2 x 2 =" part and an answer display section 5 consisting of the "4" part, thereby obtaining a learning sheet 2. Furthermore, the numbers and symbols "2×3=6" were printed and dried on another sheet 3 using the blue screen printing ink to form a problem display section 4 consisting of the "2×3=" part and an answer display section 5 consisting of the "6" part, thereby obtaining a learning sheet 2. The answer display sections of the two study sheets are formed in the same place (position) on the study sheets.

[0046] Creating an answer sheet An answer concealment sheet 6 was obtained by providing a reversible thermochromic image 8 containing a reversible thermochromic material that changes color from colored to colorless in response to a change in temperature on the surface of a polyester transparent sheet 7 so as to cover the answer display section when the transparent sheet is placed on the learning sheet. The reversible thermochromic image was formed using a reversible thermochromic screen printing ink consisting of 30 parts of a reversible thermochromic microcapsule pigment (t1: 27°C, t2: 30°C, t3: 31°C, t4: 35°C, changes color from blue to colorless) encapsulating a heat-discolorable reversible thermochromic composition consisting of 1 part of 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide as component (A), 5 parts of 4,4'-(2-ethylhexylidene)bisphenol as component (B), and 50 parts of decyl stearate as component (C), 50 parts of an acrylic resin emulsion (solid content 45%), 1 part of a viscosity modifier, 0.2 parts of an antifoaming agent, and 18.8 parts of water.

[0047] Making learning materials A learning tool 1 consisting of the plurality of learning sheets 2 and an answer concealment / reveal sheet 6 was obtained. When the answer concealing sheet was placed on top of one of the learning sheets, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated.

[0048] Example 2 Production of learning tool sets The learning tool of Example 1 was combined with a friction body made of SEBS resin to obtain a learning tool set. When the answer concealment sheet was placed on the top surface of one of the learning sheets of the learning tool set, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated.

[0049] Example 3 Creating a study sheet Two learning sheets were obtained in the same manner as in Example 1, and a hole was provided at one end of each sheet, and the two learning sheets were connected together with an openable and closable ring member.

[0050] Creating an answer sheet An answer concealment / revealing sheet was obtained in the same manner as in Example 1.

[0051] Making learning materials A learning tool comprising the plurality of learning sheets and an answer concealment / revealment sheet was obtained. When the answer concealing sheet was placed on top of one of the learning sheets, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated.

[0052] Example 4 Production of learning tool sets The learning tool of Example 3 was combined with a friction body made of SEBS resin to obtain a learning tool set. When the answer concealment sheet was placed on the top surface of one of the learning sheets of the learning tool set, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated.

[0053] Example 5 Creating a study sheet Two learning sheets obtained in the same manner as in Example 1 were glued at one side to obtain a learning sheet in the form of a booklet.

[0054] Creating an answer sheet An answer concealment / revealing sheet was obtained in the same manner as in Example 1.

[0055] Making learning materials A learning tool comprising the plurality of learning sheets and an answer concealment / revealment sheet was obtained. When the answer concealing sheet was placed on top of one of the learning sheets, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the reversible thermochromic image was rubbed with a finger, the image disappeared due to the frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated.

[0056] Example 6 Production of learning tool sets A learning tool set was obtained by combining the learning tool of Example 5 with a writing implement containing ink that can be erased by heating and having a friction member at the rear of the barrel. When the answer concealment sheet was placed on the top surface of one of the learning sheets of the learning tool set, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with the friction body of a writing implement, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Next, when the answer concealment sheet was placed on top of the other learning sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealment sheet and became invisible. Next, when the sheet was rubbed with the friction body of a writing implement, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 27°C, the reversible thermochromic image turned blue again and the answer display area became invisible. The phase change could be repeated. Furthermore, the writing implement was used to write letters and pictures on the study sheet.

[0057] Example 7 Creating a study sheet On a sheet of synthetic paper, the numbers and symbols "2 x 2 = 4" were printed using pink screen printing ink consisting of 5 parts pink pigment, 1 part viscosity modifier, 0.2 parts defoamer, and 93.8 parts water, and then dried to form a problem display section consisting of "2 x 2 =" and an answer display section consisting of "4", thereby obtaining a learning sheet. Furthermore, on another sheet, the numbers and symbols "2×3=6" were printed and dried using the pink screen printing ink to form a problem display section consisting of "2×3=" and an answer display section consisting of "6", thereby obtaining a learning sheet. The answer display sections of the two study sheets are formed in the same place (position) on the study sheets.

[0058] Creating an answer sheet An answer concealment sheet was obtained by providing a reversible thermochromic image containing a reversible thermochromic material that changes color from colored to colorless due to a change in temperature on the surface of a transparent polyethylene bag so as to cover the answer display section when the learning sheet was placed inside. The bag-shaped answer concealment sheet has a waterproof zipper at the opening. The reversible thermochromic image was formed using a reversible thermochromic screen printing ink consisting of 30 parts of a reversible thermochromic microcapsule pigment (t1: 31°C, t2: 34°C, t3: 37°C, t4: 42°C, changes color from pink to colorless) encapsulating a heat-discolorable reversible thermochromic composition consisting of 2 parts of 3-diethylamino-7,8-benzofuran as component (a), 5 parts of 4,4'-decylidenebisphenol as component (b), and 50 parts of myristyl myristate as component (c), 50 parts of an acrylic resin emulsion (solid content 45%), 1 part of a viscosity modifier, 0.2 parts of an antifoaming agent, and 18.8 parts of water.

[0059] Making learning materials A learning tool comprising the plurality of learning sheets and an answer concealment / revealment sheet was obtained. When one of the learning sheets was placed in the answer concealing sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when hot water of 42°C or higher was applied to the reversible thermochromic image, the image disappeared and the answer display section of the learning sheet became visible. Furthermore, when the temperature dropped below 31°C, the reversible thermochromic image turned pink again and the answer display area became invisible. The phase change could be repeated. Next, when the other learning sheet was placed in the answer concealing sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when hot water of 42°C or higher was applied to the reversible thermochromic image, the image disappeared and the answer display section of the learning sheet became visible. Furthermore, when the temperature dropped below 31°C, the reversible thermochromic image turned pink again and the answer display area became invisible. The phase change could be repeated.

[0060] Example 8 Production of learning tool sets The learning tool of Example 7 was combined with a friction body made of SEBS resin to obtain a learning tool set. When one of the learning sheets of the learning tool set was placed in the answer concealing sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 31°C, the reversible thermochromic image turned pink again and the answer display area became invisible. The phase change could be repeated. Next, when the other learning sheet was placed in the answer concealing sheet, the answer display portion of the learning sheet was concealed by the reversible thermochromic image of the answer concealing sheet and became invisible. Next, when the sheet was rubbed with a friction body, the image was erased by frictional heat, and the answer display portion of the learning sheet became visible. Furthermore, when the temperature dropped below 31°C, the reversible thermochromic image turned pink again and the answer display area became invisible. The phase change could be repeated. [Explanation of symbols]

[0061] t1 Complete color development temperature of heat-discolorable reversible thermochromic composition t2 Color development start temperature of heat-discolorable reversible thermochromic composition t3: The starting temperature of discoloration of reversible thermochromic composition that discolors when heated t4 Complete decolorization temperature of heat-decolorizing type reversible thermochromic composition T1 Complete decolorization temperature of heat-coloring type reversible thermochromic composition T2: The starting temperature of discoloration of a reversible thermochromic composition that develops color by heating T3: Color development start temperature of heat-coloring type reversible thermochromic composition T4 Complete color development temperature of heat-coloring type reversible thermochromic composition ΔH Hysteresis width 1. Learning materials 2 Support 3 Sheets 4 Question display area 5 Answer display area 6 Answer Sheet 7 Transparency Sheet 8 Reversible thermochromic image

Claims

1. A learning tool comprising a learning sheet having a question display section and an answer display section corresponding to the question display section on the surface of the learning sheet, and an answer concealment sheet to be placed on the learning sheet, wherein the learning sheet comprises a plurality of learning sheets having different question display sections and answer display sections, and the answer concealment sheet is an answer concealment sheet having a reversible thermochromic image on the surface of a transparent sheet which contains a reversible thermochromic material that changes color from colored to colorless in response to a temperature change and covers the answer display section when the transparent sheet is placed on the learning sheet.

2. A learning tool set comprising the learning tool according to claim 1 and a friction body.

3. A learning tool set comprising the learning tool according to claim 1 and a writing implement having a friction member.

4. 4. The set of learning tools according to claim 3, wherein said writing implement contains ink which can be erased by heating.

Images