Microcapsule pigment

Abstract

To provide a microcapsule pigment with superior redispersibility that exhibits reduced susceptibility to hard caking by forming the wall film of the microcapsule pigment from an isocyanate-based compound and a polymer containing a specific structural unit.SOLUTION: A microcapsule pigment comprises a core material and a wall film enclosing the core material. The wall film comprises an isocyanate-based compound and a polymer containing a specific structural unit.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a microencapsulated pigment having excellent redispersibility. [Background technology]

[0002] Conventionally, microcapsule pigments have been disclosed in which pigments with a high specific gravity such as titanium oxide or pigments with somewhat poor dispersibility such as carbon black are encapsulated in microcapsules. For example, Patent Document 1 discloses a microcapsule pigment in which a substance (core substance) containing a poorly water-soluble medium and carbon black is encapsulated in a shell layer (wall film) composed of a trimethylolpropane adduct of xylylene diisocyanate and hexamethylene diamine. Furthermore, a reversible thermochromic microcapsule pigment is disclosed that contains a reversible thermochromic composition having as essential components an electron-donating organic color-forming compound, an electron-accepting compound, and a reaction medium (desensitizer) that reversibly induces an electron donating / receiving reaction between the electron-donating organic color-forming compound and the electron-accepting compound in a specific temperature range, and that reversibly changes color from a colored state to a decolored state. For example, Patent Document 2 discloses a microcapsule granule in which a reversible thermochromic recording composition (core material) is contained in a film (wall film) composed of a polyisocyanate and a xylylenediamine.

[0003] The above-mentioned microencapsulated pigments may have poor dispersibility in liquid compositions or resin compositions, and in particular in low-viscosity liquid compositions, the microencapsulated pigments are prone to aggregation, and separation occurs due to the difference in specific gravity between the microencapsulated pigments and the vehicle, causing the microencapsulated pigments to form hard cakes over time. When the hard cakes are formed, there is a problem in that it becomes difficult to redisperse the microencapsulated pigments. Therefore, there is a demand for a microencapsulated pigment that is inhibited from forming a hard cake and has excellent redispersibility. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-122168 A [Patent Document 2] Japanese Patent Application Publication No. 7-40660 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made based on the background art described above, and aims to provide a microencapsulated pigment which is inhibited from forming hard cakes and has excellent redispersibility. [Means for solving the problem]

[0006] The present invention relates to a microcapsule pigment comprising a core substance and a wall film encapsulating the core substance, the wall film being composed of an isocyanate compound and a polymer containing at least one of a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II). [ka] (In the formula, n1 represents an integer of 0 or 1, and X1 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.) [ka] (In the formula, n2 represents an integer of 0 or 1, and X2 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.) Furthermore, the present invention requires a liquid composition comprising the microcapsulated pigment and a vehicle. The liquid composition is selected from the group consisting of printing ink, paint, inkjet ink, ultraviolet-curable ink, ink for writing instruments, ink for applicators, ink for stamps, paints, cosmetics, and coloring liquids for textiles, and the invention also requires that the liquid composition is a writing instrument containing the ink for writing instruments. A further feature is a solid writing material or a solid cosmetic material comprising the microencapsulated pigment and an excipient. The present invention also provides a molding resin composition containing a microencapsulated pigment and a molding resin, and a molded article obtained by molding the molding resin composition. Furthermore, the present invention requires a laminate comprising a support and a colored layer containing the microencapsulated pigment. Effect of the Invention

[0007] The present invention can provide a microcapsule pigment having excellent redispersibility and suppresses the formation of a hard cake by forming the wall film of the microcapsule pigment from an isocyanate compound and a polymer having specific structural units. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The microcapsulated pigment according to the present invention comprises a core substance and a wall film encapsulating the core substance, and the wall film is composed of an isocyanate compound described below and a polymer having specific structural units. Each component constituting the microcapsulated pigment according to the present invention will be described below.

[0009] The isocyanate compound according to the present invention is used as a wall film forming material for microcapsule pigments. The isocyanate compound is not particularly limited, and an aliphatic isocyanate compound or an aromatic isocyanate compound can be used, but an aromatic isocyanate compound is preferred. In addition, a compound having two or more isocyanate groups (-NCO) in one molecule is preferred, and specifically, a bifunctional diisocyanate compound, a trifunctional triisocyanate compound, and a tetrafunctional tetraisocyanate compound can be mentioned.

[0010] Examples of isocyanate compounds include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, diphenylmethane-4,4'-diisocyanate, hydrogenated diphenylmethane diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4 '-Diisocyanate, 1,4-Xylylene Diisocyanate, 1,3-Xylylene Diisocyanate, Tetramethyl-m-Xylylene Diisocyanate, Tetramethyl-p-Xylylene Diisocyanate, Hydrogenated Xylylene Diisocyanate, 4-Chloro-1,3-Xylylene Diisocyanate, 2-Methyl-1,3-Xylylene Diisocyanate, Diphenylpropane-4,4'-Diisocyanate, Diphenylhexafluoropropane-4,4'-Diisocyanate, Trimethylene Diisocyanate, Hexamethylene Diisocyanate, Trimethyl Diisocyanates such as hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, trans-1,4-cyclohexylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, lysine diisocyanate, diphenyl ether-4,4'-diisocyanate, 2,6-diisocyanatocaproic acid, and norbornane diisocyanate. Examples of the isocyanate compounds include triisocyanate compounds such as 4,4',4"-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, tris(isocyanatophenyl)thiophosphate, 1,6,11-undecane triyl triisocyanate, 4-(isocyanatomethyl)octane-1,8-diyl diisocyanate, 1,3,6-hexamethylene triisocyanate, and lysine triisocyanate; and tetraisocyanate compounds such as 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate. The isocyanate compounds can be used alone or in combination of two or more.

[0011] The isocyanate compound according to the present invention may be a polymer or adduct using the above-mentioned isocyanate compound. Examples of the polymer or adduct include a dimer of a diisocyanate compound, a trimer (biuret or isocyanurate) of a diisocyanate compound, an adduct obtained by adding a diisocyanate compound to a compound having three or more active hydrogen groups in one molecule (e.g., polyol, polyamine, polythiol, etc.), a formalin condensate of benzene isocyanate, and a polymer of an isocyanate compound having a polymerizable group such as methacryloyloxyethyl isocyanate.

[0012] Examples of polymers or adducts of isocyanate compounds include a dimer of 2,4-tolylene diisocyanate, a biuret or isocyanurate of hexamethylene diisocyanate, an isocyanurate of 2,4-tolylene diisocyanate and hexamethylene diisocyanate, a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylene diisocyanate, a trimethylolpropane adduct of 1,4-xylylene diisocyanate, a trimethylolpropane adduct of 1,3-xylylene diisocyanate, a hexanetriol adduct of 2,4-tolylene diisocyanate, polymethacryloyloxyethyl isocyanate, and polymethylene polyphenyl polyisocyanate.

[0013] The polymer according to the present invention is used as a curing agent acting on the isocyanate compound which is the wall film forming material, and contains at least one of a constitutional unit represented by the following formula (I) and a constitutional unit represented by the following formula (II). Such a polymer is a cationic macromolecule (cationic polymer) that exhibits cationic properties in an aqueous medium such as water.

[0014] [ka] (In the formula, n1 represents an integer of 0 or 1, and X1 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.) [ka] (In the formula, n2 represents an integer of 0 or 1, and X2 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.)

[0015] Regarding X1 or X2, Examples of hydrogen halides include hydrogen chloride (hydrochloric acid), hydrogen bromide, and hydrogen iodide. Examples of the carboxylic acid include acetic acid, propionic acid, and butyric acid. Examples of sulfate esters include methyl sulfate and ethyl sulfate. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, and 1-butanesulfonic acid. Examples of each can be given.

[0016] The microencapsulated pigment according to the present invention can have a surface positively charged by using a polymer containing at least one of the constituent units represented by the above formula (I) and the constituent units represented by the above formula (II). This generates electrostatic repulsion between the microencapsulated pigments, which can prevent the microencapsulated pigments from densely agglomerating together to form a hard cake, resulting in a microencapsulated pigment with excellent redispersibility.

[0017] The monomer that forms the constitutional unit represented by formula (I) includes allylamine or a salt thereof. An example of a monomer that forms the constitutional unit represented by formula (II) is diallylamine or a salt thereof.

[0018] As the polymer according to the present invention, a polymer having a structural unit represented by the above formula (I) can be used, and an example thereof is a polymer represented by the following formula (1). The polymer represented by the following formula (1) is an allylamine polymer or a polymer of an allylamine salt. [ka] (In the formula, n1 represents an integer of 0 or 1, X1 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and n represents a natural number.)

[0019] The mass average molecular weight of the polymer represented by formula (1) is in the range of 500 to 200,000, and n represents the degree of polymerization required to achieve a mass average molecular weight of 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 150,000, and more preferably 1,500 to 100,000.

[0020] The polymer according to the present invention is preferably a polymer in which n1 in formula (1) is 0 or 1 and X1 is any one of hydrochloric acid, acetic acid, and amidosulfuric acid, and more preferably a polymer in which n1 is 0 or 1 and X1 is hydrochloric acid. Such a polymer is excellent in the effect of positively charging the surface of the microencapsulated pigment and generating electrostatic repulsion between the microencapsulated pigments, and therefore it is easier to further prevent the microencapsulated pigments from densely agglomerating to form a hard cake, and it is easier to improve redispersibility.

[0021] Specific examples of the polymer represented by formula (1) include those manufactured by Nittobo Medical Co., Ltd., product names: PAA-01, PAA-03, PAA-05, PAA-08, PAA-15C, PAA-25, PAA-HCL-01, PAA-HCL-03, PAA-HCL-05, PAA-HCL-3L, PAA-HCl-10L, PAA-SA, and the like.

[0022] As the polymer according to the present invention, a polymer having a structural unit represented by the above formula (II) can be used, and an example thereof is a polymer represented by the following formula (2). The polymer represented by the following formula (2) is a diallylamine polymer or a diallylamine salt polymer. [ka] (In the formula, n2 represents an integer of 0 or 1, X2 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and n represents a natural number.)

[0023] The mass average molecular weight of the polymer represented by formula (2) is in the range of 500 to 200,000, and n represents the degree of polymerization required to achieve a mass average molecular weight of 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 150,000, more preferably 2,000 to 100,000, and even more preferably 5,000 to 50,000.

[0024] The polymer according to the present invention is preferably a polymer of formula (2) in which n2 is 0 or 1 and X2 is any one of hydrochloric acid, acetic acid, and amidosulfuric acid, and more preferably a polymer in which n2 is 0 or 1 and X2 is hydrochloric acid. Such a polymer is excellent in the effect of positively charging the surface of the microencapsulated pigment and generating electrostatic repulsion between the microencapsulated pigments, and therefore it is easier to further prevent the microencapsulated pigments from densely agglomerating to form a hard cake, and it is easier to improve redispersibility.

[0025] Specific examples of the polymer represented by formula (2) include products manufactured by Nittobo Medical Co., Ltd., product names: PAS-21 and PAS-21CL.

[0026] As the polymer according to the present invention, a polymer having both the constitutional unit represented by the above formula (I) and the constitutional unit represented by the above formula (II) can be used, and an example of the polymer according to the present invention is a polymer represented by the following formula (3). The polymer represented by the following formula (3) is a copolymer of allylamine or a salt of allylamine and diallylamine or a salt of diallylamine. [ka] (In the formula, n1 and n2 each independently represent an integer of 0 or 1, X1 and X2 each independently represent any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and m and n each independently represent a natural number.)

[0027] The mass average molecular weight of the polymer represented by formula (3) is in the range of 500 to 200,000, and m and n represent the degree of polymerization required for the mass average molecular weight to be 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 150,000, more preferably 5,000 to 150,000, and even more preferably 10,000 to 100,000.

[0028] As the polymer according to the present invention, a polymer in which, in formula (3), n1 and n2 are both 0, or n1 and n2 are both 1, and X1 and X2 are both either hydrochloric acid, acetic acid, or amidosulfuric acid is preferred, and a polymer in which n1 and n2 are both 1, and X1 and X2 are both hydrochloric acid or acetic acid is more preferred.

[0029] Specific examples of the polymer represented by formula (3) include those manufactured by Nittobo Medical Co., Ltd., product names: PAA-D11, PAA-D11-HCL, PAA-D41-HCL, PAA-D19-HCL, PAA-D19A, and the like.

[0030] The polymer according to the present invention may contain other structural units in addition to the structural unit represented by the above formula (I) and the structural unit represented by the above formula (II). Examples of other structural units include a structural unit represented by the following formula (III), a structural unit derived from acrylamide, and a structural unit derived from sulfur dioxide (sulfonyl group, -SO2-). [ka] (In the formula, X3 - represents a halide ion, a carboxylate ion, a sulfate ion, a sulfate ester ion, a phosphate ion, or a sulfonate ion, and R3 and R3' each independently represent an alkyl group having 1 to 3 carbon atoms.

[0031] X3 - Regarding Examples of halide ions include chloride ions, bromide ions, and iodide ions. Examples of carboxylate ions include acetate ion, propionate ion, butyrate ion, etc. Examples of sulfate ester ions include methyl sulfate ion and ethyl sulfate ion. Examples of sulfonate ions include methanesulfonate ion, ethanesulfonate ion, 1-propanesulfonate ion, and 1-butanesulfonate ion. Examples of each can be given.

[0032] Regarding R3 and R3′. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

[0033] An example of a polymer containing the structural unit represented by the above formula (III) as the other structural unit is a polymer represented by the following formula (4). [ka] (In the formula, n1 represents an integer of 0 or 1, X1 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and X3 - represents a halide ion, a carboxylate ion, a sulfate ion, a sulfate ester ion, a phosphate ion, or a sulfonate ion, R3 and R3' each independently represent an alkyl group having 1 to 3 carbon atoms, and m and n each independently represent a natural number.

[0034] The mass average molecular weight of the polymer represented by formula (4) is in the range of 500 to 200,000, and m and n represent the degree of polymerization required for the mass average molecular weight to be 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 100,000, more preferably 5,000 to 50,000, and even more preferably 10,000 to 20,000.

[0035] As the polymer according to the present invention, a polymer in which n1 is 0, R3 and R3' are each independently a methyl group or an ethyl group in the formula (4) is preferred, and a polymer in which n1 is 0, R3 and R3' are both methyl groups, and X3 - is a chloride ion, or n1 is 0, one of R3 and R3' is a methyl group and the other is an ethyl group, and X3 - is ethyl sulfate ion (C2H5SO4 - ) is more preferred.

[0036] A specific example of the polymer represented by formula (4) is PAA-1123 (product name, manufactured by Nittobo Medical Co., Ltd.).

[0037] An example of a polymer containing an acrylamide-derived structural unit as the other structural unit is a polymer represented by the following formula (5). [ka] (In the formula, n2 represents an integer of 0 or 1, X2 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and n represents a natural number.)

[0038] The mass average molecular weight of the polymer represented by formula (5) is in the range of 500 to 200,000, and m and n represent the degree of polymerization required for the mass average molecular weight to be 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 100,000, more preferably 2,000 to 50,000, and even more preferably 5,000 to 20,000.

[0039] The polymer according to the present invention is preferably a polymer of formula (5) in which n2 is 1 and X2 is any one of hydrochloric acid, acetic acid, and amidosulfuric acid, and more preferably a polymer in which n2 is 1 and X2 is hydrochloric acid.

[0040] A specific example of the polymer represented by formula (5) is PAS-2141CL (product name: manufactured by Nittobo Medical Co., Ltd.).

[0041] An example of a polymer containing a sulfur dioxide-derived structural unit (sulfonyl group, -SO2-) as another structural unit is a polymer represented by the following formula (6). [ka] (In the formula, n2 represents an integer of 0 or 1, X2 represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid, and n represents a natural number.)

[0042] The mass average molecular weight of the polymer represented by formula (6) is in the range of 500 to 200,000, and n represents the degree of polymerization required to achieve a mass average molecular weight of 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 50,000, more preferably 1,500 to 25,000, and further preferably 2,000 to 10,000.

[0043] The polymer according to the present invention is preferably a polymer of formula (6) in which n2 is 1 and X2 is any one of hydrochloric acid, acetic acid, and amidosulfuric acid, and more preferably a polymer in which n2 is 1 and X2 is hydrochloric acid or acetic acid.

[0044] Specific examples of the polymer represented by formula (6) include products manufactured by Nittobo Medical Co., Ltd., product names: PAS-92 and PAS-92A.

[0045] As the polymer according to the present invention, a polymer in which a primary amine of a polymer having a structural unit in which n1 is 0 in the above formula (I) is partially modified can also be used, and an example of such a polymer is the polymer represented by the following formula (7). [ka] (In the formula, R represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or an amino group, and m and n each independently represent a natural number.)

[0046] Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, and an isopropoxy group. Examples of each can be given.

[0047] The mass average molecular weight of the polymer represented by formula (7) is in the range of 500 to 200,000, and m and n represent the degree of polymerization required for the mass average molecular weight to be 500 to 200,000. The mass average molecular weight is preferably in the range of 1,000 to 150,000, more preferably 1,500 to 100,000, and further preferably 5,000 to 50,000.

[0048] Specific examples of the polymer represented by formula (7) include those manufactured by Nittobo Medical Co., Ltd., product names: PAA-U5000, PAA-U7030, PAA-AC5050A, PAA-N5000, PAA-N5050CL, and the like.

[0049] The mass average molecular weight of the polymer according to the present invention is a value calculated as polyethylene glycol by the GPC method (gel permeation chromatography method).

[0050] In the microencapsulated pigment according to the present invention, the blending amount of the polymer relative to the isocyanate-based compound is not particularly limited, but the blending amount of the polymer is preferably in the range of 1 to 30 parts by mass, more preferably in the range of 2 to 25 parts by mass, and even more preferably in the range of 3 to 20 parts by mass, relative to 100 parts by mass of the isocyanate-based compound. By blending the amount of the polymer relative to the isocyanate compound within the above range, it becomes easier to positively charge the surface of the microencapsulated pigment, making it easier to improve the redispersibility of the microencapsulated pigment.

[0051] The wall film of the microcapsule pigment according to the present invention is composed primarily of a urea resin (polyurea) or urea-urethane resin (polyureaurethane) formed by a polymerization reaction of an isocyanate compound, a polymer having specific structural units, and, if necessary, a compound having a hydroxyl group (-OH).

[0052] Examples of compounds having a hydroxy group (-OH), i.e., alcohol-based compounds, include polyols having two or more hydroxy groups, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, catechol, resorcinol, and hydroquinone. The alcohol-based compounds can be used alone or in combination of two or more.

[0053] The core material may be a coloring composition comprising a coloring material and a medium. Examples of the coloring composition include those in which a dye or pigment is dissolved or dispersed as a coloring material in an aqueous medium or an oil-based medium.

[0054] The dyes include acid dyes, basic dyes, direct dyes, oil-soluble dyes, disperse dyes, and the like. Examples of pigments include inorganic pigments, organic pigments, glittering pigments, fluorescent pigments, and phosphorescent pigments. In addition, a pigment dispersant can be used as necessary. Examples of pigment dispersants include anionic and nonionic surfactants; anionic polymers such as polyacrylic acid and styrene-acrylic acid; and nonionic polymers such as PVP and PVA.

[0055] Examples of the aqueous medium include water, such as tap water, ion-exchanged water, ultrafiltered water, and distilled water. Examples of oil-based media include esters such as monobasic acid esters, dibasic acid monoesters, dibasic acid diesters, partial esters or complete esters of polyhydric alcohols, aromatic hydrocarbons such as alkylbenzenes and alkylnaphthalenes, higher alcohols, ketones, ethers, and the like. The aqueous medium or oily medium can be used alone or in combination of two or more kinds.

[0056] As the coloring composition, a thermochromic material that changes color due to a change in temperature can also be used. This color change may be reversible or irreversible, but a reversible thermochromic material is preferred because it can repeatedly exhibit color changes due to temperature changes. Examples of thermochromic materials used as coloring compositions include coloring compositions that are at least composed of (a) an electron-donating organic color-forming compound as a coloring material and (b) an electron-accepting compound as a medium.Further examples include coloring compositions that are at least composed of a homogeneous compatible mixture of the (a) component as a coloring material, the (b) component as a medium, and (c) a reaction medium that determines the temperature at which the coloring reaction of the (a) component and the (b) component occurs, that is, reversible thermochromic compositions that are at least composed of the (a) electron-donating organic color-forming compound, the (b) electron-accepting compound, and the (c) reaction medium that determines the temperature at which the coloring reaction of the (a) component and the (b) component occurs.

[0057] As the reversible thermochromic composition, a reversible thermochromic composition of the heat-discoloring type having a relatively small hysteresis width (ΔH) (ΔH=1 to 7°C) described in JP-B-51-44706, JP-B-51-44707, JP-B-1-29398, etc. can be used. The heat-discoloring type means that the composition is decolored by heating and colored by cooling. This reversible thermochromic composition discolors around a predetermined temperature (discoloration point), and exhibits a discolored state in a temperature range above the high-temperature discoloration point and a colored state in a temperature range below the low-temperature discoloration point. 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 manifest that state is applied, but returns to the state exhibited in the room temperature range when the application of heat or cold is removed.

[0058] As the reversible thermochromic composition, a heat-discolorable reversible thermochromic composition having a large hysteresis width (ΔH=8 to 80° C.) described in JP-B-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, JP-A-2005-1369, etc. can be used. The heat-discolorable type means that the color disappears when heated and the color appears when cooled. This reversible thermochromic composition changes color along a path that is significantly different when the temperature is increased from a lower temperature side than the discoloration temperature range than when the temperature is decreased from a higher temperature side than the discoloration temperature range, and has color memory in a specific temperature range [the temperature range between the color development onset temperature t2 and the discoloration onset temperature t3 (temperature range in which two phases are essentially maintained)] in which the colored state is in a temperature range below the complete color development temperature t1, or the discolored state is in a high temperature range above the complete discoloration temperature t4.

[0059] In addition, when the reversible thermochromic composition having the above-mentioned color memory property is applied to the present invention, the reversible thermochromic composition can effectively function to retain the color exhibited under normal conditions (daily living temperature range) by specifying the complete color development temperature t1 to a temperature that can only be obtained in a freezer or a cold region, and the complete discoloration temperature t4 to a temperature range that can be obtained from frictional heat produced by a friction body or a familiar heating body such as a hair dryer, and specifying the ΔH value to be 40 to 100°C.

[0060] The temperature that can only be obtained in freezers, cold regions, etc. is in the range of -50 to 0°C, preferably -40 to -5°C, and more preferably -30 to -10°C. The temperature obtainable from a common heating element such as a hair dryer is in the range of 50 to 95°C, preferably 50 to 90°C, and more preferably 60 to 80°C.

[0061] As the reversible thermochromic composition, a heat-coloring type reversible thermochromic composition using a gallic acid ester, as described in JP-B-51-44706, JP-A-2003-253149, etc., can also be used. The heat-coloring type means that the color develops when heated and the color disappears when cooled.

[0062] The reversible thermochromic composition is a compatible solution containing the above components (A), (B), and (C) as essential components. The ratio of each component depends on the concentration, discoloration temperature, discoloration form, or type of each component, but the component ratio that generally provides the desired properties is in the range of 1 part by weight 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, more preferably 5 to 100, and even more preferably 10 to 100, of component (C) (all the above ratios are in parts by weight).

[0063] As the coloring composition, a photochromic material that changes color upon irradiation with light can also be used. This color change may be reversible or irreversible, but a reversible photochromic material is preferred because it can repeatedly exhibit color changes upon irradiation with light. An example of a photochromic material used as a coloring composition is a coloring composition in which a photochromic compound as a coloring material is dissolved in a medium, that is, a reversible photochromic composition consisting of at least a photochromic compound and a medium.

[0064] Examples of photochromic compounds include conventionally known spirooxazine derivatives, spiropyran derivatives, naphthopyran derivatives, etc. that develop color when irradiated with sunlight, ultraviolet light, or blue light with a peak emission wavelength in the range of 400 to 495 nm, and lose color when the irradiation is stopped. For example, the compounds described in JP 2021-120493 A and WO 2020 / 137469 A can be cited as examples. Furthermore, a photochromic compound having a photomemory property (color memory photochromic property) can also be used. Examples of such photochromic compounds include diarylethene derivatives, such as those described in JP-A-2021-120493.

[0065] Examples of the medium include various oligomers such as styrene-based oligomers, acrylic-based oligomers, terpene-based oligomers, and terpene-phenol-based oligomers. By dissolving the photochromic compound in various oligomers, it is possible to improve both the light resistance and color density, and further to adjust the color change sensitivity. The oligomers can be used alone or in combination of two or more.

[0066] Styrene oligomers are compounds having a styrene skeleton or hydrogenated products thereof, and examples thereof include low molecular weight polystyrene, styrene-α-methylstyrene copolymers, α-methylstyrene polymers, and α-methylstyrene-vinyltoluene copolymers. The acrylic oligomer may, for example, be an acrylic acid ester copolymer. The terpene oligomer is a compound having a terpene skeleton, and examples thereof include α-pinene polymer, β-pinene polymer, and d-limonene polymer. Terpene phenol oligomers are copolymers of cyclic terpene monomers and phenols, or hydrogenated copolymers thereof, such as α-pinene-phenol copolymers.

[0067] The reversible thermochromic material or the reversible photochromic material can be encapsulated in a microcapsule to form a reversible thermochromic microencapsulated pigment or a reversible photochromic microencapsulated pigment, which can be chemically and physically stable. Furthermore, the reversible thermochromic material or the reversible photochromic material can maintain the same composition under various conditions of use and can provide the same effects.

[0068] The microencapsulated pigment of the present invention may also contain various additives such as antioxidants, ultraviolet absorbers, infrared absorbers, dissolution aids, preservatives, and fungicides, provided that their functions are not adversely affected. When the microencapsulated pigment according to the present invention contains a reversible thermochromic microencapsulated pigment or a reversible photochromic microencapsulated pigment, it is also possible to make the microencapsulated pigment exhibit a color change behavior from color (1) to color (2) by incorporating a non-color-changing colorant such as a general dye or pigment into the microcapsules.

[0069] The microencapsulated pigment according to the present invention has an excellent redispersibility even when it contains a core substance with a high specific gravity. Microencapsulated pigments containing a core substance with a high specific gravity tend to settle over time and form a hard cake, but the microencapsulated pigment according to the present invention can suppress the formation of a hard cake due to settling over time.

[0070] Examples of microcapsule pigments encapsulating a core substance with a large specific gravity include microcapsule pigments encapsulating a coloring composition that uses titanium oxide, carbon black, or a luster pigment as a coloring material, and reversible thermochromic microcapsule pigments encapsulating a reversible thermochromic composition with a large hysteresis width (ΔH).

[0071] The microencapsulated pigment according to the present invention is preferably a reversible thermochromic microencapsulated pigment in which the component (c) in the reversible thermochromic composition is in the range of 60 to 90 mass % based on the total amount of the reversible thermochromic composition, the mass average molecular weight of component (c) is 250 or more, and the specific gravity of the reversible thermochromic microencapsulated pigment in a completely colored state at 20°C, relative to water, is 1.05 to 1.20. Such reversible thermochromic microencapsulated pigments have a reversible thermochromic function of becoming decolorized in a temperature range above the high-temperature discoloration point (complete discoloration temperature) and becoming colored in a temperature range below the low-temperature discoloration point (complete color development temperature), and also exhibit a large hysteresis width (ΔH) and can maintain a colored or decolored state in a specific temperature range, so they are widely used not only in the field of writing instruments but also in a wide range of other fields. However, reversible thermochromic microencapsulated pigments with a large hysteresis width (ΔH) often use a compound having two or more benzene rings in the molecule as component (c), which tends to increase the specific gravity and tend to settle over time to form a hard cake, making it difficult to redisperse them. The microcapsule pigment according to the present invention can be easily redispersed even when it contains a core substance with a large specific gravity because the wall film is composed of an isocyanate compound and the above-mentioned polymer. Furthermore, since the reversible thermochromic function of the reversible thermochromic composition is not easily impaired by the external environment, it is preferable to use the above-mentioned reversible thermochromic microcapsule pigment as the microcapsule pigment according to the present invention.

[0072] In consideration of the redispersibility of the microencapsulated pigment according to the present invention, it is more preferable that the component (C) in the reversible thermochromic composition is in the range of 65 to 85 mass % based on the total amount of the reversible thermochromic composition, the mass average molecular weight of component (C) is 250 or more, and the specific gravity of the reversible thermochromic microencapsulated pigment in a completely colored state at 20°C relative to water is 1.05 to 1.20 (preferably 1.10 to 1.20, more preferably 1.12 to 1.15). Further preferred is a reversible thermochromic microencapsulated pigment in which the component (c) in the reversible thermochromic composition is in the range of 70 to 85 mass % based on the total amount of the reversible thermochromic composition, the mass average molecular weight of component (c) is 250 or more, and the specific gravity of the reversible thermochromic microencapsulated pigment in a completely colored state at 20°C relative to water is 1.05 to 1.20 (preferably 1.10 to 1.20, more preferably 1.12 to 1.15). The specific gravity of the reversible thermochromic microencapsulated pigment can be measured by the following method.

[0073] (Method for measuring specific gravity of reversible thermochromic microencapsulated pigment) 1. Put 30 ml of glycerin aqueous solution and 1 g of fully colored reversible thermochromic microcapsule pigment into a screw tube bottle and mix to prepare a reversible thermochromic microcapsule pigment dispersion. 2. 30 ml of the above dispersion is adjusted to 20° C. and centrifuged at 1000 rpm for 30 seconds. A refrigerated tabletop centrifuge (manufactured by Kokusan Co., Ltd., product name: H103N) can be used as the centrifuge. 3. Observe the dispersion. When it is confirmed that most of the microencapsulated pigment has settled to the bottom of the beaker, repeat steps 1 and 2 using an aqueous solution with a higher glycerin concentration than the original glycerin aqueous solution, and observe the state of the dispersion. If it is confirmed that most of the microencapsulated pigment has floated to the liquid surface, repeat steps 1 and 2 using an aqueous solution with a lower glycerin concentration than the glycerin aqueous solution used at this time, and observe the state of the dispersion. The above series of operations is repeated until it is visually confirmed that most of the microencapsulated pigment is not sinking to the surface of the liquid or floating to the surface, but is uniformly colored in all areas of the glycerin aqueous solution except for the liquid surface and the bottom of the screw tube bottle. The specific gravity of the glycerin aqueous solution when this state is observed is measured and is regarded as the specific gravity of the reversible thermochromic microencapsulated pigment. The specific gravity of the glycerin aqueous solution can be measured by the hydrometer method described in JIS K0061, Section 7.1, using an aqueous solution adjusted to 20°C.

[0074] The microencapsulated pigment according to the present invention can be produced by a microencapsulation method. Examples of the microencapsulation method include an in situ polymerization method, a liquid hardening coating method, a phase separation method from an aqueous solution, a phase separation method from an organic solvent, a melting dispersion cooling method, an air suspension coating method, and a spray drying method. The microencapsulation method is appropriately selected depending on the application, and an interfacial polymerization method is preferable.

[0075] When the microcapsule pigment according to the present invention is produced by the interfacial polymerization method, the production method includes an emulsification step in which an oily component (oil phase) containing a core substance and an isocyanate compound as a wall film forming material is dispersed in an aqueous medium (aqueous phase) to prepare an emulsion, and a polymerization step in which the wall film forming material is polymerized at the interface between the oil phase and the aqueous phase to form the wall film of the microcapsule. The oil phase is added to the aqueous phase and emulsified using mechanical force, and then a polymer is added as a curing agent, and the temperature of the system is raised as necessary to cause interfacial polymerization at the interface between the oil phase and the aqueous phase, thereby forming microcapsules. In addition, desolvation can be performed simultaneously or after the end of the interfacial polymerization reaction. After the interfacial polymerization reaction and desolvation, the microcapsule pigment is separated from the aqueous phase, washed, and then dried, etc., to obtain the microcapsule pigment.

[0076] The aqueous medium is not particularly limited, but water, ion-exchanged water, or the like can be used.

[0077] The aqueous phase may contain a protective colloid such as a water-soluble polymer in advance. Examples of the water-soluble polymer include conventionally known anionic polymers, nonionic polymers, amphoteric polymers, etc., which can be appropriately selected and used. Preferred examples of the water-soluble polymer include polyvinyl alcohol, gelatin, and cellulose-based polymers.

[0078] The aqueous phase may contain a surfactant. Examples of the surfactant include anionic surfactants and nonionic surfactants, and those that do not cause precipitation or aggregation by acting with a protective colloid are preferred. Preferred surfactants include sodium alkylbenzenesulfonate such as sodium lauryl sulfate, dioctyl sodium sulfosuccinate, and polyalkylene glycols such as polyoxyethylene nonylphenyl ether.

[0079] Depending on the purpose, a secondary resin film may be further provided on the surface of the microencapsulated pigment according to the present invention to impart durability or to modify the surface properties for practical use.

[0080] In the microcapsule pigment according to the present invention, the mass ratio of the core substance to the wall film is preferably 7:1 to 1:1, and by having the mass ratio of the core substance to the wall film within the above range, a decrease in color density and vividness during color development is prevented.The mass ratio of the core substance to the wall film is more preferably 6:1 to 1:1.

[0081] The microcapsule pigment according to the present invention may be a microcapsule pigment having a wall film composed of a resin selected from urea resin, urethane resin, urea-urethane resin, epoxy resin, melamine resin, benzoguanamine resin, etc., on the surface of which a wall film composed of an isocyanate compound and the above-mentioned polymer is provided.

[0082] The average particle size of the microencapsulated pigment is not particularly limited, but is preferably in the range of 0.01 to 50 μm, more preferably 0.1 to 30 μm, and even more preferably 0.5 to 20 μm. If the average particle size exceeds 50 μm, the pigment will lack dispersion stability or processability when blended into ink, paint, or resin. On the other hand, if the average particle size is less than 0.01 μm, it will be difficult to exhibit high-concentration color development. When the microencapsulated pigment according to the present invention is used in a writing instrument ink described below, the average particle size is preferably in the range of 0.01 to 5 μm, more preferably 0.05 to 4 μm, even more preferably 0.1 to 3 μm, and particularly preferably 0.5 to 3 μm. If the average particle size exceeds 5 μm, it becomes difficult to obtain good ink dischargeability when used in a writing instrument. On the other hand, if the average particle size is less than 0.01 μm, it becomes difficult to exhibit high-concentration color development.

[0083] The average particle size was measured by determining the particle area using image analysis particle size distribution measurement software (manufactured by Mountec Corporation, product name: MacView), calculating the projected area equivalent circle diameter (Heywood diameter) from the area of ​​the particle area, and measuring the average particle size of particles equivalent to a sphere of equal volume using this value. If the particle size of all or the majority of the 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-300) based on values ​​measured using the above software or a measuring device using the Coulter method.

[0084] The microencapsulated pigment according to the present invention is dispersed in a vehicle containing at least one of water and an organic solvent and, if necessary, various additives to prepare an ink composition (hereinafter, sometimes referred to as "ink"), It can be used as a liquid composition such as printing ink used in screen printing, offset printing, process printing, gravure printing, coater, pad printing, etc.; paint used in brush coating, spray coating, electrostatic coating, electrocoating, flow coating, roller coating, dip coating, etc.; inkjet ink; ultraviolet-curing ink; ink for writing instruments such as marking pens, ballpoint pens, fountain pens, and brush pens; ink for applicators; ink for stamps; paints; cosmetics; and coloring liquid for textiles.

[0085] The liquid composition may contain various additives. Examples of additives include resins, crosslinking agents, curing agents, drying agents, plasticizers, viscosity modifiers, dispersants, UV absorbers, antioxidants, light stabilizers, anti-settling agents, smoothing agents, gelling agents, defoamers, matting agents, penetrating agents, pH adjusters, foaming agents, coupling agents, moisturizing agents, antifungal agents, preservatives, and rust inhibitors.

[0086] Examples of the writing vehicle used in the writing ink include an oil-based vehicle containing an organic solvent, and an aqueous vehicle containing water and, if necessary, an organic solvent. When the vehicle is an aqueous vehicle, the writing ink may contain a water-soluble organic solvent that is compatible with water. The water-soluble organic solvent suppresses the evaporation of water from the ink, prevents fluctuations in the specific gravity of the vehicle, and stably disperses the microencapsulated pigment in the ink.

[0087] Examples of organic solvents include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0088] When the writing instrument ink contains a water-soluble organic solvent, the content of the water-soluble organic solvent relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 1 to 40 mass%, more preferably 5 to 30 mass%, and even more preferably 10 to 25 mass%.

[0089] A thickener can be blended into the ink for writing instruments, which can suppress aggregation or sedimentation of the microencapsulated pigment and can also suppress bleeding of handwriting, thereby enabling the formation of good handwriting. As the thickener, any conventionally known substance can be used, but it is preferable to use a substance that can impart shear thinning properties to the ink composition (shear thinning agent). Ink containing a shear thinning agent (shear thinning ink) has high viscosity and is difficult to flow when left at rest or under low stress, but easily becomes less viscous when external stress is applied. Therefore, when not writing, it is possible to prevent ink leakage, separation or backflow of ink, and when writing, it is easy to improve the stability of ink ejection from the pen tip. In particular, when such an ink composition is used in a writing instrument (ballpoint pen) equipped with a ballpoint tip as the pen tip, the ink composition is stably held in the ballpoint pen because of its high viscosity when left stationary without shear stress. Therefore, when writing, a strong shear stress is applied to the ink composition due to the rotation of the ball, and the ink composition in the vicinity of the ball is more likely to have a lower viscosity, which can improve the ink discharge stability.

[0090] When the writing instrument ink contains a thickener, the content of the thickener relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.1 to 20% by mass.

[0091] Examples of shear thinning agents include water-soluble polysaccharides, polymers having a molecular weight of 100,000 to 150,000 that are primarily composed of alkyl esters of methacrylic acid, crosslinked poly-N-vinyl carboxylic acid amides, benzylidene sorbitol and its derivatives, benzylidene xylitol and its derivatives, alkali-thickening acrylic resins, crosslinked acrylic acid polymers, inorganic fine particles, nonionic surfactants with an HLB value of 8 to 12, and metal or amine salts of dialkyl sulfosuccinic acid. The shear thinning agents may be used alone or in combination of two or more.

[0092] Examples of water-soluble polysaccharides include xanthan gum, welan gum, zeta sea gum, diutan gum, macrophomopsis gum, succinoglycan, guar gum, locust bean gum and derivatives thereof, hydroxyethyl cellulose, alkyl alginates, glucomannan, agar, carrageenan, and other carbohydrates having gelling ability extracted from seaweed.

[0093] A dispersant can be blended into the writing ink to enhance the dispersibility of the microencapsulated pigment. Examples of dispersants include synthetic resins such as polyvinylpyrrolidone, polyvinyl butyral, polyvinyl ether, styrene-maleic acid copolymer, ketone resin, hydroxyethyl cellulose and its derivatives, styrene-acrylic acid copolymer, acrylic polymers, PO·EO adducts, and polyester amine oligomers. Among these dispersants, dispersants having at least one of an acidic group and a salt of an acidic group, that is, dispersants exhibiting anionic properties, are preferred. By using a dispersant exhibiting anionic properties, the dispersant is easily collected on the surface of the microencapsulated pigment positively charged by the polymer. Then, due to the ionic interaction between the microencapsulated pigment and the dispersant, the dispersant produces a loose bridging action between the microencapsulated pigments positively charged, and the microencapsulated pigment has the effect of forming a loose aggregate. This prevents the microencapsulated pigments from densely agglomerating, thereby preventing the microencapsulated pigments from forming a hard cake, and further improving the redispersibility.

[0094] Examples of the acidic group include a phosphoric acid group, a carboxy group, a sulfonic acid group, a phosphoric acid ester group, a sulfate ester group, a nitrate ester group, a phosphorous acid group, a phosphonic acid group, and a sulfinic acid group. Examples of the salt of the acidic group include a metal salt such as a potassium salt or a sodium salt of the above acidic group. These may be used alone or in combination of two or more in one molecule. Commercially available dispersants having at least one of an acidic group and a salt of an acidic group include, for example, the DISPER BYK series from BYK Japan K.K., the FLOWLEN series from Kyoeisha Chemical Co., Ltd., the ARON series from Toagosei Co., Ltd., the JONCRYL series from BASF Japan Ltd., and the Solsperse series from Lubrizol Japan Co., Ltd. As the dispersant, an acrylic polymer dispersant is preferred because it is easy to improve the redispersibility of the microencapsulated pigment, an acrylic polymer dispersant having a carboxy group is more preferred, and an acrylic polymer dispersant having a comb structure and a carboxy group in the side chain is even more preferred. A particularly preferred dispersant is an acrylic polymer dispersant having a comb structure and multiple carboxy groups in the side chains, and a specific example is Solsperse 43000 (manufactured by Lubrizol Japan Co., Ltd.).

[0095] When the writing ink contains a dispersant, the content of the dispersant relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.01 to 2 mass%, more preferably 0.1 to 1.5 mass%. By having the content within the above range, it becomes easy to improve the dispersibility of the microencapsulated pigment in the ink.

[0096] When the ink for a writing instrument is used in a writing instrument (ballpoint pen) equipped with a ballpoint pen tip, the ink for a writing instrument may be blended with a lubricant. The lubricant improves the lubricity between the ball seat provided inside the tip body and the ball provided at the front end of the tip body, making it possible to easily prevent wear of the ball seat and improve the writing feel.

[0097] Examples of lubricants include higher fatty acids such as oleic acid; nonionic surfactants having a long-chain alkyl group; polyether-modified silicone oils; thiophosphite triesters such as thiophosphite tri(alkoxycarbonylmethyl ester) and thiophosphite tri(alkoxycarbonylethyl ester); phosphate surfactants such as polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoesters, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diesters, or metal salts, ammonium salts, amine salts, and alkanolamine salts of these phosphate esters.

[0098] The writing instrument ink may also contain other additives, as necessary, such as polymer flocculants, water-soluble resins, specific gravity adjusters, surfactants, pH adjusters, wetting agents, resin particles, rust inhibitors, wetting agents, defoamers, viscosity adjusters, preservatives or antifungal agents, air bubble absorbers, defoamers, antioxidants, and ultraviolet absorbers.

[0099] In the ink for writing instruments, the content of the microencapsulated pigment relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 5 to 40 mass%, more preferably 10 to 40 mass%, and even more preferably 10 to 30 mass%. By having the content within the above range, the desired color density can be obtained and a decrease in ink outflow can be prevented.

[0100] The ink composition can be produced by any conventionally known method. Specifically, the ink composition can be produced by mixing the above-mentioned components in required amounts and stirring them with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or dispersing them with various dispersers such as a bead mill.

[0101] The viscosity of the ink for a writing instrument is preferably in the range of 1 to 30 mPa s, more preferably 1 to 20 mPa s, and even more preferably 1 to 10 mPa s, in an environment of 20° C. By having the viscosity within the above range, the stability and fluidity of the ink composition can be maintained at a high level. The viscosity can be measured, for example, using a BL type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., product name: TVB-M type viscometer with L type rotor) by placing the ink in an environment of 20°C and measuring the rotation speed at 30 rpm.

[0102] The pH of the writing instrument ink is preferably in the range of 3 to 10. By having the pH within the above range, it is possible to prevent the ink from becoming excessively viscous or from deteriorating. The pH value was measured by placing the ink in an environment of 20° C. using a pH meter (manufactured by DKK-TOA Corporation, product name: IM-40S).

[0103] Examples of writing instruments in which the writing instrument ink can be stored include various writing instruments such as ballpoint pens, marking pens, fountain pens, brush pens, and calligraphy pens.

[0104] When the writing instrument ink is used in a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited, and the ink may be used, for example, by filling a ballpoint pen refill or ballpoint pen equipped with a ballpoint pen tip and an ink filling mechanism.

[0105] A ballpoint pen tip is composed of a tip body and a ball provided at the front end of the tip body. Examples of ballpoint pen tips include a tip in which a ball is held by a ball holding portion formed by pressing and deforming the vicinity of the tip of a metal pipe body inward from the outer surface, a tip in which a ball is held by a ball holding portion formed by cutting a metal material with a drill or the like, a tip in which a resin ball receiving seat is provided inside a metal or plastic tip body, and a tip in which the ball held by the tip is biased forward by a spring body.

[0106] The material of the tip body and the ball is not particularly limited, and examples thereof include cemented carbide (super hard), stainless steel, ruby, ceramic, resin, rubber, etc. Furthermore, the ball can be subjected to a surface treatment such as a DLC coating.

[0107] The diameter of the ball is generally in the range of 0.2 to 3 mm, preferably 0.2 to 2 mm, more preferably 0.2 to 1.5 mm, and further preferably 0.2 to 1 mm.

[0108] An example of the ink filling mechanism is an ink reservoir that can be directly filled with ink. The ink reservoir may be a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a metallic tubular body.

[0109] A ballpoint pen refill (hereinafter sometimes referred to as a "refill") can be formed by connecting a ballpoint pen tip directly or via a connecting member to an ink container and directly filling the ink container with ink. A ballpoint pen can be formed by storing this refill in a barrel.

[0110] The rear end of the ink reservoir is filled with an ink backflow prevention body, which may be a liquid plug or a solid plug.

[0111] The liquid plug is made of a non-volatile liquid and / or a difficult-to-volatile liquid, examples of which include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefins, α-olefin oligomers or cooligomers, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, and the like. The non-volatile liquid and / or the hardly-volatile liquid can be used alone or in combination of two or more kinds.

[0112] It is preferable to add a thickener to the non-volatile liquid and / or the low-volatility liquid to thicken it to a suitable viscosity. Examples of thickeners include clay-based thickeners such as silica with a hydrophobic surface treatment, fine particle silica with a methylated surface, aluminum silicate, swellable mica, and hydrophobically treated bentonite or montmorillonite; fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate; dextrin-based compounds such as tribenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, and fatty acid dextrin; and cellulose-based compounds.

[0113] Examples of solid plugs include solid plugs made of polyethylene, polypropylene, polymethylpentene, and the like. As the ink backflow preventer, a solid plug and the above-mentioned liquid plug can be used in combination.

[0114] In addition, it is also possible to form a ballpoint pen equipped with a ballpoint pen tip and an ink filling mechanism by using the barrel itself as the ink filling mechanism, filling ink directly into the barrel, and attaching a ballpoint pen tip to the front end of the barrel.

[0115] When the ink filled in the ink filling mechanism has a low viscosity, a ballpoint pen having a ballpoint pen tip and an ink filling mechanism may further include an ink supply mechanism for supplying the ink filled in the ink filling mechanism to the pen tip.

[0116] The ink supply mechanism is not particularly limited, and examples include (1) a mechanism that has an ink guide core made of a fiber bundle or the like as an ink flow rate regulator and supplies ink to the pen tip through this, (2) a mechanism that has a comb-shaped ink flow rate regulator and supplies ink to the pen tip through this, and (3) a mechanism that supplies ink to the pen tip through a pen core consisting of a number of disks arranged in parallel with comb-shaped intervals, with slit-shaped ink guide grooves running vertically through the disks in the axial direction and wider air vent grooves than the grooves, and with an ink guide core located in the axial center to guide ink from the ink filling mechanism to the pen tip.

[0117] The material for the pen core is not particularly limited as long as it is a synthetic resin that can be injection molded into a structure in which multiple disks are arranged in a comb groove shape. Acrylonitrile-butadiene-styrene copolymer (ABS resin) is preferably used because it has high moldability and is easy to obtain pen core performance.

[0118] Specific examples of the configuration of a ballpoint pen that contains ink for writing instruments include: (1) a ballpoint pen having an ink container filled with ink within a barrel, to which a ballpoint pen tip is connected directly or via a connecting member, and in which an ink backflow prevention body is filled at the end face of the ink container; (2) a ballpoint pen in which ink is directly filled within the barrel and which is provided with a mechanism for supplying ink to the pen tip via a comb-shaped ink flow regulator or an ink guide core made of a fiber bundle or the like as an ink flow regulator; and (3) a ballpoint pen in which ink is directly filled within the barrel and which is provided with a mechanism for supplying ink to the pen tip via the above-mentioned pen core.

[0119] When the writing instrument ink is used in a marking pen, the structure and shape of the marking pen itself are not particularly limited, and the ink may be used, for example, by filling a marking pen refill or a marking pen equipped with a marking pen tip and an ink filling mechanism.

[0120] Examples of marking pen tips include conventional porous members with interconnected pores, such as resin-processed fibers, fused heat-fusible fibers, and felt, which have a porosity selected from a range of approximately 30 to 70%, or extrusion-molded synthetic resin bodies with multiple ink outlet holes extending in the axial direction, one end of which can be processed into a bullet shape, rectangular shape, chisel shape, or other shape suited to the purpose for which it is used.

[0121] An example of the ink filling mechanism is an ink occlusion body that can be filled with ink. The ink occlusion body is a fiber bundle in which crimped fibers are bundled in the longitudinal direction, and is placed inside a plastic cylinder or a covering such as a film, with the porosity adjusted to the range of approximately 40 to 90%.

[0122] A marking pen can be formed by housing an ink occlusion body impregnated with ink inside the barrel and connecting a marking pen tip to the barrel directly or via a connecting member so as to connect to the ink occlusion body.

[0123] Also, a marking pen refill (hereinafter sometimes referred to as a "refill") can be formed by storing an ink occlusion body impregnated with ink in an ink container and connecting a marking pen tip to the ink container directly or via a connecting member so as to be connected to the ink occlusion body. A marking pen can be formed by storing this refill in a barrel.

[0124] The ink reservoir may be, for example, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a tubular body made of metal.

[0125] A marking pen having a marking pen tip and an ink filling mechanism may further include an ink supply mechanism for supplying the ink filled in the ink filling mechanism to the pen tip.

[0126] The ink supply mechanism is not particularly limited, and examples thereof include, in addition to the ink supply mechanism provided in the ballpoint pen described above, (4) a mechanism provided with an ink flow rate regulator using a valve mechanism, which supplies ink to the pen tip by opening the valve. The valve mechanism can be of the conventional, general-purpose pumping type that opens when the tip is pressed, and is preferably set to a spring pressure that can be pressed and opened by the pressure of the writing pen.

[0127] When the marking pen is provided with an ink supply mechanism, the ink filling mechanism may be an ink reservoir that can be filled directly with ink, in addition to the ink occlusion body described above. Also, the barrel itself may serve as the ink filling mechanism, and ink may be filled directly.

[0128] Specific examples of the configuration of a marking pen that contains ink for a writing instrument include: (1) a marking pen in which an ink occlusion body consisting of a fiber bundle impregnated with ink is contained within a barrel, and a marking pen tip consisting of a fiber processed body or a resin molded body with capillary gaps formed therein is connected to the barrel directly or via a connecting member so that the ink occlusion body and the tip are connected; (2) a marking pen in which ink is directly filled into the barrel, and a mechanism is provided for supplying ink to the pen tip by using a comb-shaped ink flow regulator or an ink guide core consisting of a fiber bundle or the like as an ink flow regulator; (3) a marking pen in which ink is directly filled into the barrel, and a mechanism is provided for supplying ink to the pen tip via the above-mentioned pen core; and (4) a marking pen in which the tip and an ink container are connected via a valve mechanism that opens when the tip is pressed, and ink is directly filled into the ink container.

[0129] When the ballpoint pen or marking pen according to the present invention is one in which ink is directly filled, an agitator such as an agitating ball for agitating the ink can be built into the ink reservoir or barrel in which the ink is filled in order to facilitate redispersion of the microcapsule pigment. Examples of the shape of the agitator include a spherical body and a rod-shaped body. The material of the agitator is not particularly limited, and examples thereof include metal, ceramic, resin, and glass.

[0130] The writing instrument according to the present invention, such as a ballpoint pen or a marking pen, may be in the form of an ink cartridge as a removable structure. In this case, after the ink contained in the ink cartridge of the writing instrument is used up, the writing instrument can be used again by replacing it with a new ink cartridge.

[0131] The ink cartridges used may be those that double as the barrel that constitutes the writing instrument when connected to the main body of the writing instrument, or those that cover and protect the barrel (rear barrel) after being connected to the main body of the writing instrument. In the latter case, the ink cartridge may be used alone, or the writing instrument may have an ink cartridge connected to the main body of the writing instrument before use, or may be housed in the barrel in a disconnected state so that the user of the writing instrument can connect the ink cartridge in the barrel when using the writing instrument and start using it.

[0132] A writing instrument such as a ballpoint pen or marking pen according to the present invention can be made into a capped writing instrument by providing a cap that is attached to cover the pen tip (writing tip), thereby preventing the writing tip from being contaminated or damaged. In addition, writing instruments such as ballpoint pens or marking pens that contain a refill inside the barrel can be made into retractable writing instruments by providing a retraction mechanism inside the barrel that allows the writing tip to protrude and retract from the barrel, thereby preventing the writing tip from becoming contaminated or damaged.

[0133] Any retractable writing instrument can be used as long as the writing tip is housed within a barrel with the writing tip exposed to the outside air and the retractable mechanism is activated to cause the writing tip to protrude from the barrel opening. It may also be a composite type retractable writing instrument in which a plurality of refills are housed within the barrel, and the writing tip of any one of the refills is caused to protrude and retract from the barrel opening by operation of a retraction mechanism.

[0134] Examples of the retraction mechanism include: (1) a side-slide type retraction mechanism in which an operating part (clip) that can move in the front-rear direction protrudes radially outward from the rear side wall of the barrel, and the operating part is slid forward to cause the writing tip to appear and disappear from the front opening of the barrel; (2) a rear-end knock type retraction mechanism in which an operating part provided at the rear end of the barrel is pressed forward to cause the writing tip to appear and disappear from the front opening of the barrel; (3) a side-knock type retraction mechanism in which an operating part protruding from the outer surface of the side wall of the barrel is pressed radially inward to cause the writing tip to appear and disappear from the front opening of the barrel; and (4) a rotating type retraction mechanism in which an operating part at the rear of the barrel is rotated to cause the writing tip to appear and disappear from the front opening of the barrel.

[0135] The shape of the ballpoint pen or marking pen is not limited to the configuration described above, and it may be equipped with tips of different shapes, or with tips that dispense ink of different tones or hues, or it may be a composite writing instrument (double-ended or retractable tip, etc.) in which tips of different shapes are attached and the ink dispensed from each tip has a different color tone or hue.

[0136] When the microencapsulated pigment contains a reversible thermochromic microencapsulated pigment, the writing made on the surface to be written on using a writing instrument containing the writing instrument ink can be discolored by rubbing with a finger or by using a heating or cooling tool.

[0137] Examples of the heating device include an electrically-heated discoloring device equipped with a resistive heating element such as a PTC element, a heat discoloring device filled with a medium such as hot water, a heat discoloring device using steam or laser light, and the application of a hair dryer. However, friction members and friction bodies are preferred because they can change color in a simple manner. Examples of cooling devices include electrically-operated thermochromic devices using a Peltier element, thermochromic devices filled with a refrigerant such as cold water or ice chips, cooling agents, refrigerators, freezers, and the like.

[0138] As the friction member and friction body, elastic bodies such as elastomers and plastic foams that are rich in elasticity and can generate appropriate friction and generate frictional heat when rubbed are preferred, but plastic molded bodies, stone materials, wood, metals, fabrics, etc. can also be used. Note that, although a general eraser used for erasing pencil marks may be used to rub the marks, eraser shavings are generated during rubbing, the above-mentioned friction members and friction bodies that generate almost no eraser shavings are preferably used.

[0139] Examples of the material of the friction member and the friction body include silicone resin, styrene-ethylene-butadiene-styrene block copolymer (SEBS resin), etc. Silicone resin is likely to adhere to the part erased by rubbing, and handwriting tends to be repelled when writing is repeated, so SEBS resin is more preferably used.

[0140] The friction member or friction body may be a member of any shape that is separate from the writing instrument, but by providing it on the writing instrument, the writing instrument can be made highly portable. Also, a writing instrument set can be obtained by combining a writing instrument with a friction member or friction body of any shape that is separate from the writing instrument.

[0141] In the case of a writing instrument with a cap, the location where the friction member or friction body is provided is not particularly limited. For example, the cap itself may be formed from a friction member, the barrel itself may be formed from a friction member, and if a clip is provided, the clip itself may be formed from a friction member, or the friction member or friction body may be provided at the tip (top) of the cap or the rear end of the barrel (the part where the writing tip is not provided), etc.

[0142] In the case of a writing instrument equipped with a retractable mechanism, the location where the friction member or friction body is provided is not particularly limited, and for example, the barrel itself may be formed from a friction member, and if a clip is further provided, the clip itself may be formed from a friction member, or the friction member or friction body may be provided near the opening of the barrel, at the rear end of the barrel (the portion where the writing tip is not provided), or at the knock portion.

[0143] The ink composition according to the present invention can be used as an ink for stamps. The stamp vehicle used in the stamp ink may be an oil-based vehicle containing an organic solvent, or an aqueous vehicle containing water and, if necessary, an organic solvent.

[0144] Examples of the organic solvent include castor oil fatty acid alkyl esters, cellosolve-based solvents, alkylene glycol-based solvents, ester-based solvents, hydrocarbon-based solvents, halogenated hydrocarbon-based solvents, alcohol-based solvents, ether-based solvents, ketone-based solvents, propionic acid-based solvents, highly polar solvents, and mixed solvents thereof.

[0145] When the vehicle is an aqueous vehicle, the ink for stamping may contain a water-soluble organic solvent that is compatible with water. When the microencapsulated pigment contains a reversible thermochromic microencapsulated pigment, the water-soluble organic solvent is preferably glycerin or propylene glycol.

[0146] When the ink for stamping contains a water-soluble organic solvent, the content of the water-soluble organic solvent relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 30 to 60 mass%, more preferably 30 to 55 mass%, and even more preferably 40 to 50 mass%. By having the content within the above range, the ink does not dry out or absorb moisture, making it easier to obtain a clear print.

[0147] A thickener can be blended into the ink for stamping, which can suppress aggregation or sedimentation of the microencapsulated pigment and can also suppress bleeding of the printed image, making it possible to form a clear printed image. As the thickener, any known substance can be used, but an alkali-soluble acrylic emulsion is preferred. When an alkali-soluble acrylic emulsion is used as the thickener, the pH of the ink for stamping is preferably in the range of 6-11, more preferably 7-11, and even more preferably 7-10.

[0148] The stamp ink may also contain other additives, such as binder resins, surfactants, pH adjusters, wetting agents, resin particles, rust inhibitors, wetting agents, defoamers, viscosity adjusters, preservatives or antifungal agents, air bubble absorbers, defoamers, antioxidants, and ultraviolet absorbers, as required.

[0149] In the ink for stamps, the content of the microencapsulated pigment relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 10 to 40 mass%, more preferably 10 to 35 mass%, and even more preferably 10 to 30 mass%. If the content exceeds 40 mass%, the dispersion stability of the microencapsulated pigment in the ink tends to decrease. On the other hand, if the content is less than 10 mass%, the color density tends to decrease.

[0150] The ink for stamps can be used as ink for stamp pads and ink for stamps equipped with a printing material having continuous pores. For example, a stamp pad can be impregnated with ink to obtain a stamp pad that supplies ink to the printing surface of a stamp that is brought into contact with the stamp pad, or a stamp can be obtained by impregnating ink into the printing material of a stamp having continuous pores.

[0151] The stamp can form an image on various surfaces. Furthermore, when the microencapsulated pigment contains a reversible thermochromic microencapsulated pigment, the image formed on the surface using the stamp containing the ink for stamping can be discolored by rubbing with a finger or by the above-mentioned heating or cooling tool. The above-mentioned friction member and friction body are preferable as the heating tool, since they can be discolored by a simple method.

[0152] The above-mentioned friction member or friction body may be a member of any shape separate from the stamp, but by providing it on the stamp, it is possible to make the stamp highly portable. Also, a stamp set can be obtained by combining a stamp with a friction member or friction body of any shape separate from the stamp.

[0153] When the ink composition according to the present invention is used by printing or coating, the material of the substrate to be printed or coated is not particularly limited and all materials are effective, for example, paper, synthetic paper, fiber, cloth, synthetic leather, leather, plastic, glass, ceramic material, metal, wood, stone, etc. Cut. The shape of the support is not limited to a flat shape, but may be uneven.

[0154] A laminate (printed matter) can be obtained by providing a colored layer made of a liquid composition on a support. When the microcapsule pigment contains a reversible thermochromic microcapsule pigment or a reversible photochromic microcapsule pigment, a color-changing laminate (color-changing printed matter) can be obtained in which a color-changing layer made of a reversible thermochromic liquid composition or a reversible photochromic liquid composition is provided on a support. This laminate (printed matter) reversibly changes color due to temperature change or light irradiation. In addition, in the case of a support on which a non-color-changing colored layer (non-color-changing colored image) has already been formed, by providing a color-changing layer on the non-color-changing colored layer, the non-color-changing colored layer (non-color-changing colored image) can be concealed or revealed by the color-changing layer due to temperature changes or exposure to light, thereby further diversifying the manner of change.

[0155] The microencapsulated pigment according to the present invention can be melt-blended with an excipient and molded into a solid molding for application, which can be used as a solid writing material or a solid cosmetic material. Examples of solid writing materials include crayons, pencil leads, mechanical pencil leads, solid gel markers, and the like. Examples of solid cosmetics include foundation, eyeliner, eyebrow cream, eyeshadow, lipstick, etc.

[0156] Examples of excipients used in the solid writing material include wax, gelling agents, clay minerals, etc. Among the excipients, it is preferable to contain at least one selected from the group consisting of polyolefin wax, sucrose fatty acid ester, and dextrin fatty acid ester, since this easily improves the writing density.

[0157] The content of the excipient relative to the total mass of the solid writing material is not particularly limited, but is preferably in the range of 0.2 to 70% by mass, more preferably 0.5 to 40% by mass. When the content is within the above range, the shape of the solid writing material can be easily obtained, and the writing density of the solid writing material can easily be increased.

[0158] The solid writing material may also contain additives such as fillers, binder resins, viscosity modifiers, preservatives or antifungal agents, antibacterial agents, antioxidants, ultraviolet light inhibitors, lubricants, and fragrances, if necessary.

[0159] The solid writing material may be used alone as a writing material, or may be used as an inner core with an outer shell covering the outer periphery thereof to form a core-sheath structure (double core).

[0160] The solid writing material can be used to write on various writing surfaces. Furthermore, when the microencapsulated pigment contains a reversible thermochromic microencapsulated pigment, the writing made on the writing surface using the solid writing material can be discolored by rubbing with a finger or by the above-mentioned heating tool or cold tool. Since it can be discolored by a simple method, the above-mentioned friction member and friction body are preferable as the heating tool.

[0161] The friction member or friction body may be a member of any shape separate from the solid writing body or the exterior of the solid writing implement in which the solid writing body is housed in an exterior container, but by providing it on the exterior of the solid writing body or the solid writing implement, it can be made highly portable.Specific examples include a form in which the friction member is provided on an exterior in the shape of a pencil, crayon, etc., made of wood or paper.In addition, a solid writing body set can be obtained by combining the solid writing body with a friction member or friction body of any shape separate from the solid writing body.

[0162] The microencapsulated pigment according to the present invention can be melt-blended with thermoplastic resins, thermosetting resins, waxes, etc. to form pellets, powder, or paste, and used as a molding resin composition. Using the above-mentioned molding resin composition, molded articles in the form of three-dimensional objects of any shape, films, sheets, plates, filaments, rods, pipes, etc. can be obtained by general-purpose means such as injection molding, extrusion molding, blow molding, cast molding, etc. Moreover, by melt-blending it with a thermoplastic resin, a toner or powder coating material can be obtained.

[0163] In the above-mentioned liquid compositions, solid moldings for coating, and resin compositions for molding, when the microencapsulated pigment contains a reversible thermochromic microencapsulated pigment or a reversible photochromic microencapsulated pigment, it is possible to make them exhibit a color change behavior from colored (1) to colored (2) by blending a non-color-changing colorant such as a general dye or pigment.

[0164] Specific examples of products using the microencapsulated pigment according to the present invention include the following. (1)Toys Dolls and animal-shaped toys; hair for dolls and animal-shaped toys; doll houses and furniture, clothing, hats, bags, shoes and other doll accessories; accessory toys; stuffed toys; drawing toys; toy picture books; puzzle toys such as jigsaw puzzles; building block toys; building blocks; clay toys; fluid toys; tops; kites; musical instrument toys; cooking toys; gun toys; capture toys; background toys; mask toys; toys imitating vehicles, animals, plants, buildings, food, etc., (2) Clothing Clothing such as T-shirts, sweatshirts, blouses, dresses, swimsuits, raincoats, skiwear, etc.; footwear such as shoes; shoelaces; shoe components such as insoles, outsoles, midsoles, etc.; cloth personal items such as handkerchiefs, towels, wrapping cloths, etc.; gloves; ties; hats; sportswear, etc. (3) Indoor decorations Carpets, curtains, curtain strings, tablecloths, rugs, cushions, seat cushions, chair upholstery, seats, mats, picture frames, artificial flowers, photo frames, etc. (4) Furniture Bedding such as futons, pillows, mattresses, chairs, zaisu chairs, sofas, lighting equipment, heating and cooling equipment, etc. (5) Decorations Rings, bracelets, tiaras, necklaces, earrings, hair clips, false nails, ribbons, scarves, watches, glasses, key chains, etc. (6) Stationery Writing implements, stamps, erasers, writing pads, rulers, planners, notebooks, adhesive tape, etc. (7)Daily necessities Toiletries such as disposable diapers; bath supplies; toothbrushes; cooling or heat-retaining bags; hand warmers; thermometers; watering cans; buckets; cleaning equipment; cosmetics such as lipstick, eye shadow, foundation, eyeliner, eyebrows, nail polish, hair dye, and false nail paint, etc. (8) Kitchen utensils Cooking utensils, lunch boxes, water bottles, cups, plates, chopsticks, spoons, forks, pots, frying pans, coasters, trivets, placemats, etc. (9)Other Calendars, labels, cards, recording materials, various printed materials to prevent counterfeiting; picture books and other books; sporting equipment such as gloves, protectors, nets, etc.; bags; packaging containers; embroidery thread; fishing gear; musical instruments; ice packs; bags such as wallets; umbrellas; vehicles; buildings; temperature detection indicators; teaching equipment such as picture books and maps; pet supplies: medical or nursing supplies such as supports, bandages, bandages, etc., electronic devices such as smartphones, earphones, speakers, etc. EXAMPLES

[0165] Examples are shown below. In the examples, "parts" refers to "parts by mass" unless otherwise specified.

[0166] Example 1 A reversible thermochromic composition consisting of 2 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl) as component (A), 5 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and 3 parts of 1,1-bis(4-hydroxyphenyl)-2-ethylhexane as component (B), and 50 parts of 4-benzyloxyphenylethyl caprate as component (C) was added to a mixed solution consisting of 35 parts of aromatic isocyanate prepolymer and 40 parts of cosolvent as a wall film forming material, and then emulsified and dispersed in an 8% polyvinyl alcohol aqueous solution. After continuing to stir while heating, 2.5 parts of allylamine polymer (mass average molecular weight: 3,000) was added as a curing agent (polymer), and further stirring was continued to prepare a microcapsule dispersion. A reversible thermochromic microcapsule pigment was obtained from the above microcapsule dispersion by centrifugation. The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0167] Example 2 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine polymer (mass average molecular weight: 5,000) and the blending amount was changed to 4 parts. The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0168] Example 3 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine polymer (mass average molecular weight: 8,000) and the blending amount was changed to 1.5 parts. The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 61°C, and reversibly changed color from blue to colorless with temperature change.

[0169] Example 4 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine hydrochloride polymer (mass average molecular weight: 5,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0170] Example 5 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine hydrochloride polymer (mass average molecular weight: 15,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 61°C, and reversibly changed color from blue to colorless with temperature change.

[0171] Example 6 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine hydrochloride-diallylamine hydrochloride copolymer (mass average molecular weight: 20,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0172] Example 7 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to an allylamine acetate-diallylamine acetate copolymer (mass average molecular weight: 40,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0173] Example 8 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to a diallylamine polymer (mass average molecular weight: 5,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0174] Example 9 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to a diallylamine hydrochloride copolymer (mass average molecular weight: 50,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 61°C, and reversibly changed color from blue to colorless with temperature change.

[0175] Example 10 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to a diallylamine hydrochloride-sulfur dioxide copolymer (mass average molecular weight: 5,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 61°C, and reversibly changed color from blue to colorless with temperature change.

[0176] Example 11 A reversible thermochromic microencapsulated pigment was obtained in the same manner as in Example 1, except that the polymer was changed to a diallylamine acetate-sulfur dioxide copolymer (mass average molecular weight: 5,000). The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 61°C, and reversibly changed color from blue to colorless with temperature change.

[0177] Example 12 A composition consisting of 10 parts of azo-based red pigment and 10 parts of stearyl myristate was added to a mixed solution consisting of 30 parts of aromatic isocyanate prepolymer as a wall film forming material and 50 parts of cosolvent, and then emulsified and dispersed in a 6% polyvinyl alcohol aqueous solution. After continuing to stir while heating, 4 parts of allylamine acetate-diallylamine acetate copolymer (mass average molecular weight: 40,000) was added as a hardener (polymer), and further stirring was continued to prepare a microcapsule dispersion. A microcapsule pigment was obtained from the above microcapsule dispersion by centrifugation. The above microencapsulated pigment had a red color.

[0178] Comparative Example 1 A reversible thermochromic composition consisting of 2 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl) as component (A), 5 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane and 3 parts of 1,1-bis(4-hydroxyphenyl)-2-ethylhexane as component (B), and 50 parts of 4-benzyloxyphenylethyl caprate as component (C) was added to a mixed solution consisting of 35 parts of aromatic isocyanate prepolymer as a wall film forming material and 40 parts of cosolvent, and then emulsified and dispersed in an 8% polyvinyl alcohol aqueous solution. After continuing to stir while heating, 2.5 parts of xylylenediamine was added as a curing agent, and further stirring was continued to prepare a microcapsule dispersion. A reversible thermochromic microcapsule pigment was obtained from the above microcapsule dispersion by centrifugation. The above microcapsule pigment had a complete color development temperature t1 of -20°C and a complete decolorization temperature t4 of 62°C, and reversibly changed color from blue to colorless with temperature change.

[0179] Comparative Example 2 A composition consisting of 10 parts of azo red pigment and 10 parts of stearyl myristate was added to a mixed solution consisting of 30 parts of aromatic isocyanate prepolymer as a wall film forming material and 50 parts of co-solvent, and then emulsified and dispersed in a 6% polyvinyl alcohol aqueous solution, and the mixture was stirred while heating, and then 4 parts of xylylenediamine was added as a curing agent, and stirring was continued to prepare a microcapsule dispersion. A microcapsule pigment was obtained from the above microcapsule dispersion by centrifugation. The above microencapsulated pigment had a red color.

[0180] [Preparation of pigment dispersion] 20 parts of each of the microcapsule pigments obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were mixed into an aqueous vehicle consisting of 0.4 parts of an acrylic polymer dispersant (manufactured by Lubrizol Japan, product name: Solsperse 43000), 0.2 parts of a preservative (2-pyridinethiol 1-oxide sodium) (manufactured by Arcsada Japan, product name: Sodium Omadine), 0.2 parts of a preservative (3-iodo-2-propynyl N-butylcarbamate) (manufactured by Arcsada Japan, product name: Glycasil 2000), 24 parts of glycerin, 0.2 parts of an antifoaming agent, 6 parts of a specific gravity adjuster (sodium polytungstate) (manufactured by Sometu, product name: SPT), and 49 parts of water, to prepare a pigment dispersion as a test sample. Each of the microcapsulated pigments in Examples 1 to 11 and Comparative Example 1 was cooled to a temperature below the complete color development temperature t1 and used in a completely color-developed state.

[0181] [Viscosity measurement] For each of the pigment dispersions of Examples 1 to 12 and Comparative Examples 1 and 2, the viscosity was measured using a BL type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., product name: TVB-M type viscometer L type rotor) at room temperature (20°C) and a rotation speed of 30 rpm. The measurement results are shown in Table 1 below.

[0182] [Redispersibility test] 40 g of the pigment dispersions of Examples 1 to 12 and Comparative Examples 1 and 2 were placed in screw cap bottles (No. 7) and left to stand for 30 days in a thermostatic chamber set at 50° C. After 30 days, the bottles were removed from the thermostatic chamber and each screw cap bottle was shaken up and down to visually confirm the redispersion state of each pigment dispersion, and the redispersibility was evaluated according to the following criteria. The evaluation results are shown in Table 1 below, with an "A" being a pass. A: The microencapsulated pigment was easily redispersed by shaking. B: The microencapsulated pigment was not redispersed by shaking.

[0183] [Table 1]

[0184] Application example 1 Preparation of reversible thermochromic recording material (information display card) A reversible thermochromic liquid composition, which is a printing ink, was prepared by uniformly mixing 40 parts of the microcapsule pigment of Example 1 (which had been cooled in advance to -20°C or below to cause it to develop a blue color) into an aqueous vehicle consisting of 50 parts of a urethane resin emulsion, 3 parts of a leveling agent, and 1 part of a thickener. A transparent anchor coat layer consisting of a urethane resin and an isocyanate-based hardener was provided on the surface of a transparent polyester film (thickness 25 μm) with an adhesive layer on the back side as a support, and the above-mentioned printing ink was solid-printed on the upper layer using a screen plate, dried and hardened to provide a reversible thermochromic layer. Further, a transparent protective layer containing an epoxy acrylate oligomer, a polyester acrylate oligomer, and an acrylate monomer was provided on the upper layer, and the layer was irradiated with ultraviolet light to polymerize the layer, thereby producing a reversible thermochromic recording material. Next, the above-mentioned recording material was attached to a white polyester film (thickness 188 μm) as a substrate, and used practically as an information display card. The reversible thermochromic recording material was once cooled to -20°C or lower to allow the reversible thermochromic layer to completely develop a blue color, after which text information was printed on it using a thermal printer equipped with a thermal head. The above recording material displayed white character information (cut-out characters) clearly on a blue background, and the white character information was visible as long as it was kept in a temperature range of more than -20°C and less than 62°C. Furthermore, when the above recording material was cooled to -20°C or lower to cause the reversible thermochromic layer to completely turn blue, the white cut-out characters were no longer visible. From this state, white cut-out characters could be formed on the reversible thermochromic layer again using a thermal printer, and the above recording material could be used repeatedly many times. Since the microcapsule pigment used in the printing ink has excellent redispersibility, even after the printing ink has been stored for a long period of time, the microcapsule pigment does not densely aggregate and the formation of a hard cake is suppressed, and the microcapsule pigment is uniformly dispersed by stirring again. When a reversible thermochromic recording material was produced using the printing ink after the long period of storage in the same manner as above, the reversible thermochromic layer had a uniform concentration and no roughness due to poor dispersion of the microcapsule pigment was observed, and the same reversible thermochromic recording material as that produced using the printing ink before the long period of storage was obtained.

[0185] Application example 2 Preparation of reversible thermochromic printed matter (reversible thermochromic T-shirt) 30 parts of the microcapsule pigment of Example 4 (previously cooled to -20°C or below to develop a blue color) was uniformly mixed into an aqueous vehicle consisting of 60 parts of an acrylic emulsion (solid content 45%), 0.2 parts of an antifoaming agent, 1 part of a viscosity modifier, and 8.8 parts of water to prepare a reversible thermochromic liquid composition that is a printing ink. The above printing ink was printed on a white T-shirt (made of cotton) as a support using a 100 mesh screen to create a number of star patterns, and the ink was then dried and hardened to form a reversible thermochromic layer, producing a reversible thermochromic printed material (reversible thermochromic T-shirt). At room temperature (20°C), numerous blue stars were visible on the surface of the T-shirt, and this did not change at body temperature or the ambient temperature. However, when heated to 62°C or higher, the areas with the printed stars became colorless and the blue stars were no longer visible. When cooled to -20°C or lower, the blue stars were visible again. This change could be repeated. In addition, by heating the T-shirt with an iron or other device, a part of the star pattern on the surface of the T-shirt was decolorized, forming a pattern in which only the desired star pattern was decolorized, and it was possible to arbitrarily change the pattern of the T-shirt. Furthermore, the discolored state could be maintained at room temperature (20°C), and after heating the entire T-shirt to over 62°C to completely decolorize the star pattern, it was possible to cool it to below -20°C and cause the star pattern to recolor. The microencapsulated pigment used in the above printing ink has excellent redispersibility, so even after the printing ink has been stored for a long period of time, the microencapsulated pigment does not densely aggregate and the formation of a hard cake is suppressed, and the microencapsulated pigment is uniformly dispersed by stirring again. When a reversible thermochromic T-shirt was produced using the printing ink after long-term storage in the same manner as above, the reversible thermochromic layer had a uniform concentration and no roughness due to poor dispersion of the microencapsulated pigment was observed, and the T-shirt obtained was similar to that produced using the printing ink before long-term storage.

[0186] Application example 3 Fabrication of reversible thermochromic stamps A reversible thermochromic liquid composition serving as a stamp ink was prepared by mixing 20 parts of the microcapsulated pigment of Example 6 (previously cooled to -20°C or below to develop a blue color), 50 parts of glycerin, 1.5 parts of an alkali-soluble acrylic emulsion (manufactured by Rohm and Haas Japan Co., Ltd., product name: Primal DR73), 0.9 parts of triethanolamine, 10 parts of a 50% aqueous solution of polyvinylpyrrolidone, 0.2 parts of a silicone-based defoamer, 0.5 parts of a penetrating leveling agent, 0.2 parts of a preservative, and 16.7 parts of water. The above-mentioned ink for stamping was impregnated into a stamp material having continuous pores, and the stamp material was fixed to a stamp base material so that the printing surface of the stamp material was exposed, and a cap was fitted to produce a stamp. The rear end of the stamp base material was equipped with SEBS resin as a friction member. When the stamp was repeatedly pressed against the surface to be imprinted (paper), the ink smoothly flowed out from the printing surface of the printing material and transferred to the surface to be imprinted, and a clear print could be continuously formed without bleeding. The print was blue at room temperature (20°C), and when rubbed with a friction member, the print disappeared and became colorless, and this state could be maintained unless it was cooled to -20°C or lower. Furthermore, when the paper surface was placed in a freezer and cooled to -20°C or lower, the print turned blue again, and this color change behavior could be reproduced repeatedly. The stamp was left to stand for 30 days at room temperature (20°C), and then pressed against a piece of paper again at room temperature (20°C). The ink flowed smoothly from the surface of the stamp material and was transferred to the paper, resulting in a clear print similar to the initial print. This is because the microencapsulated pigment used in the stamp ink did not densely aggregate even after a long period of time, and the formation of a hard cake was suppressed.

[0187] Application example 4 Preparation of a reversible thermochromic writing implement (reversible thermochromic marking pen) 20 parts of the microcapsulated pigment of Example 9 (previously cooled to -20°C or lower to develop a blue color) was mixed into an aqueous vehicle consisting of 0.4 parts of an acrylic polymer dispersant (manufactured by Lubrizol Japan, product name: Solsperse 43000), 0.2 parts of a preservative (2-pyridinethiol 1-oxide sodium) (manufactured by Arcsada Japan, product name: Sodium Omadine), 0.2 parts of a preservative (3-iodo-2-propynyl N-butylcarbamate) (manufactured by Arcsada Japan, product name: Glykasil 2000), 24 parts of glycerin, 0.2 parts of a defoamer, 6 parts of a specific gravity adjuster (sodium polytungstate) (manufactured by SOMETU, product name: SPT), and 49 parts of water, to prepare a reversible thermochromic liquid composition that is an ink for writing instruments. The above-mentioned writing ink was impregnated into an ink occlusion body made of polyester sliver covered with a synthetic resin film, and housed in a barrel made of polypropylene resin. A resin-processed pen body (bullet-shaped) made of an extrusion molded product of polyacetal resin having multiple ink outlet holes extending in the axial direction was connected to the tip of the barrel via a holder, and a cap was attached to produce a marking pen. SEBS resin was attached to the top of the cap as a friction member. When the above marking pen was used to write on paper at room temperature (20°C), good blue handwriting (characters) with a consistent density and line width was obtained without any smudges. When the handwriting was rubbed with a friction member, the handwriting disappeared and became colorless, and this state could be maintained unless it was cooled to -20°C or lower. When the paper was placed in a freezer and cooled to -20°C or lower, the handwriting again turned blue, and this color change behavior could be reproduced repeatedly. The marking pen was left to stand for 30 days with the tip facing up at room temperature (20°C), and then written on paper at room temperature (20°C) again. As with the initial writing, there was no smudging and good blue writing (letters) with consistent density and line width was obtained. This is because the microencapsulated pigment used in the ink for writing instruments does not aggregate densely even after long periods of time, and the formation of hard cakes was suppressed.

[0188] Application example 5 Preparation of a reversible thermochromic writing implement (reversible thermochromic marking pen) 23 parts of the microcapsulated pigment of Example 11 (which had been cooled to -20°C or lower in advance to develop a blue color) was mixed into an aqueous vehicle consisting of 0.4 parts of an acrylic polymer dispersant (manufactured by Lubrizol Japan Co., Ltd., product name: Solsperse 43000), 0.2 parts of a preservative (sodium 2-pyridinethiol 1-oxide) (manufactured by Arcsada Japan Co., Ltd., product name: Sodium Omadine), 0.2 parts of a preservative (3-iodo-2-propynyl N-butylcarbamate) (manufactured by Arcsada Japan Co., Ltd., product name: Glycasil 2000), 30 parts of glycerin, and 46.2 parts of water, to prepare a reversible thermochromic liquid composition that is an ink for a writing instrument. The ink reservoir, which is made of polyester sliver covered with a synthetic resin film, is impregnated with the above-mentioned ink for writing instruments, and housed in a barrel made of polypropylene resin. A resin-processed pen body (chisel type) made of polyester fiber is attached to the tip of the barrel via a resin holder, and a cap is attached to make a marking pen. The rear end of the barrel is equipped with SEBS resin as a friction member. When the above marking pen was used to write on paper at room temperature (20°C), good blue handwriting (characters) with a consistent density and line width was obtained without any smudges. When the handwriting was rubbed with a friction member, the handwriting disappeared and became colorless, and this state could be maintained unless it was cooled to -20°C or lower. When the paper was placed in a freezer and cooled to -20°C or lower, the handwriting again turned blue, and this color change behavior could be reproduced repeatedly. The above marking pen was left to stand for 30 days with the tip facing up at room temperature (20°C), and when writing was again done on paper at room temperature (20°C) after 30 days, good blue writing (characters) with a consistent density and line width was obtained without any smearing, just like the initial writing. This is because the microencapsulated pigment used in the ink for writing instruments does not densely aggregate even after a long period of time, and the formation of a hard cake was suppressed.

Claims

1. A microcapsule pigment comprising a core substance and a wall film encapsulating the core substance, the wall film being composed of an isocyanate compound and a polymer containing at least one of a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II): 【Chemistry 1】 (In the formula, n1 represents an integer of 0 or 1, and X １ represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.) 【Chemistry 2】 (In the formula, n2 represents an integer of 0 or 1, and X ２ represents any one of hydrogen halide, carboxylic acid, sulfuric acid, sulfate ester, phosphoric acid, sulfonic acid, and amidosulfuric acid.)

2. A liquid composition comprising the microcapsulated pigment according to claim 1 and a vehicle.

3. 3. The liquid composition according to claim 2, which is selected from the group consisting of printing ink, paint, inkjet ink, ultraviolet curable ink, writing ink, coating ink, stamp ink, paint, cosmetics, and fiber coloring liquid.

4. A writing instrument containing the ink for writing instruments according to claim 3.

5. A solid writing material or solid cosmetic comprising the microcapsule pigment according to claim 1 and an excipient.

6. A molding resin composition comprising the microcapsulated pigment according to claim 1 and a molding resin.

7. A molded article obtained by molding the molding resin composition according to claim 6.

8. A laminate comprising a support and a colored layer comprising the microencapsulated pigment according to claim 1.

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