JP2002105361A - Reversible thermal color-changing and ultraviolet light- curing type ink and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermal color-changing and ultraviolet light- curing type ink capable of improving the solvent resistance of a reversible thermal color-changing composition contained in it for exhibiting a permanent reversible thermal color-changing function and also exhibiting a good color concentration on developing its color. SOLUTION: This reversible thermal color-changing and ultraviolet light- curing ink is obtained by containing the reversible thermal color-changing composition in it with a wall film at least containing a photo-polymerized composition, an aliphatic amine or an aromatic amine, and the above wall film consists of a reversible thermal color-changing microencapsulated pigment ionized by an acidic substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermochromic ultraviolet curable ink and a method for producing the same. More specifically, the present invention relates to a reversible thermochromic ultraviolet curable ink excellent in heat resistance and solvent resistance using a surface-modified reversible thermochromic microcapsule pigment and a method for producing the same.

[0002]

2. Description of the Related Art A reversible thermochromic ultraviolet curable ink has been disclosed in Japanese Patent Application Laid-Open No. Hei 7-324178, and a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition is used. Another object of the present invention is to eliminate the loss of the reversible thermochromic function due to the reversible thermochromic composition being exposed to a solvent. Generally, a reversible thermochromic UV curable ink is composed of a reversible thermochromic material, a base oligomer, a reactive monomer, and a photopolymerization composition comprising a photopolymerization initiator. Has a molecular weight of about 200 to 500, corresponds to an organic solvent used for general printing inks, and may deteriorate the reversible thermochromic composition. Regarding microencapsulation, a multicapsulated microcapsule having excellent solvent resistance and a method for producing the same are known. As the production method, production of a multicapsule by applying a polymerizable polymer film and a coacervate of a water-soluble resin is known. Method, or a method for producing multiple capsules by combining polymerizable polymer membranes. However, the application of coacervate complicates the process considerably, increases the cost, and increases the weight of the wall film, so that the relative weight of the core material in the microcapsules decreases and the color of the reversible thermochromic composition contained therein increases. Had a drawback that the color density of the toner decreased. Further, since formalin is used as a curing reagent, it has an unfavorable problem in terms of safety and health. On the other hand, the production method for combining polymerizable polymer membranes also often uses a melamine-formaldehyde resin, and is similar to the above-described method for producing a multicapsule by applying a coacervate of a polymerizable polymer membrane and a water-soluble resin. Have a problem.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to a reversible thermochromic composition which has improved solvent resistance, has a permanent reversible thermochromic function, and exhibits good color density during color formation. The present invention relates to a thermochromic UV-curable ink and a method for producing a reversible thermochromic UV-curable ink excellent in safety and health.

[0004]

According to the present invention, there is provided a reversible thermochromic ultraviolet curable ink comprising at least a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition and a photopolymerizable composition. The thermochromic microcapsule pigment contains a reversible thermochromic composition by a wall film containing at least an aliphatic amine or an aromatic amine, and the wall film is ionized by an acidic substance to be reversible thermochromic ultraviolet curing. Requires mold ink. Further, the reversible thermochromic composition comprises (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, (c) the (a),
It must be a composition comprising a reaction medium for controlling the temperature at which the color reaction of (b) occurs. Furthermore, a microcapsule using an aliphatic amine or an aromatic amine as a material for forming a wall film is treated with an acidic substance having a molecular weight of 1500 or less in an aqueous medium by acidifying the pH of the system to obtain a reversible thermochromic property. A method for producing a reversible thermochromic ultraviolet curable ink in which a microcapsule pigment is mixed with a photopolymerizable composition is required.

[0005] Among the photopolymerizable compositions contained in the reversible thermochromic ultraviolet curable ink, the reactive monomer is a liquid compound in which many compounds are very small, having a molecular weight of about 200 to 500, and these liquid compounds are In some cases, the reversible thermochromic function is impaired due to, for example, penetration into the inside of the reversible thermochromic microcapsule pigment in the ink. We have:
As a countermeasure, amines are used as a wall film material, and a microcapsule pigment whose wall film is ionized by an acidic substance is used. Regarding the production of the ionized microcapsule pigment, an aliphatic amine or an aromatic compound is used as a wall film forming material. Solvent resistance of reversible thermochromic microcapsule pigments is improved by treating microcapsules containing aromatic amines in an aqueous medium with an acidic substance having a molecular weight of 1500 or less and acidifying the pH of the system. And found that a remarkable effect can be obtained for the reactive monomer. As described above, it is conceivable to increase the film thickness in order to strengthen the wall film, but it is not preferable because the relative amount of the reversible thermochromic composition decreases. In the present invention, the wall film is ionized by an acidic substance, which is obtained by treating an acidic medium with an acidic substance having a molecular weight of 1500 or less in an aqueous medium to make the pH of the system acidic.
Preferably, the acidic substance used has a low molecular weight,
It is an acidic substance having a molecular weight of 1500 or less. The acidic substance used in the present invention is a water-soluble substance, and may be any of an organic substance and an inorganic substance as long as it lowers the pH of the system.

[0006] As described above, increasing the film thickness for the purpose of strengthening the wall film decreases the relative amount of the core substance. For example, (a) an electron-donating color-forming organic compound, B) an electron-accepting compound, (c) the above (a),
Regarding the application of the reversible thermochromic composition comprising a reaction medium for determining the temperature at which the color reaction of (b) occurs, the color density of the reversible thermochromic composition is higher than that of general dyes and pigments. And for the microencapsulation, the amount of wall film relative to the core material is particularly limited in order to maintain its effective color density high. In this regard, the acidic substance preferably has a low molecular weight, and the molecular weight of 1500 is used in the treatment of the present method.
The following acidic substances:

The acidic substance used in the present invention may be either an organic substance or an inorganic substance as long as it is substantially water-soluble as described above and lowers the pH of the system. To be specifically exemplified below, as the organic acid, formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, fluoroacetic acid, acetoacetic acid, diethylacetic acid, methoxyacetic acid,
Ethoxyacetic acid, cyclopentylacetic acid, cyclohexylacetic acid, phenylacetic acid, o-chlorophenylacetic acid, m-chlorophenylacetic acid, p-chlorophenylacetic acid, 2,4-dichlorophenylacetic acid, phenoxyacetic acid, o-chlorophenoxyacetic acid, m- Chlorphenoxyacetic acid, p-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,
4,5-trichlorophenoxyacetic acid, diphenylacetic acid,
o-tolylacetic acid, m-tolylacetic acid, p-tolylacetic acid, propionic acid, α-chloropropionic acid, 2,3-dicyclopropionic acid, α-bromopropionic acid, 2,3-dibromopropionic acid, butyric acid, isobutyric acid Butyric acid, α-chlorobutyric acid, α, β-dichlorobutyric acid, valeric acid, isovaleric acid, 5-
Chlorvaleric acid, benzoic acid, o-chlorobenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, 2,4-dichlorobenzoic acid, o-bromobenzoic acid, m-bromobenzoic acid,
p-bromobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, 2,4-dinitrobenzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, naphthoic acid, Acrylic acid, methacrylic acid, tiglic acid, sorbic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, 3-cyclohexene-1-carboxylic acid, pyruvic acid, nicotinic acid, cinnamic acid, α-chlorocinnamic acid, α-bromocinnamic leather Monocarboxylic acids such as acids,
Oxalic acid, malonic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid, diethylmalonic acid, malonic acid monomethyl ester, succinic acid, methylsuccinic acid, dimethylsuccinic acid, diethylsuccinic acid, dimethoxysuccinic acid,
Diethoxysuccinic acid, diacetosuccinic acid, chlorsuccinic acid, dichlorosuccinic acid, brosuccinic acid, dibromosuccinic acid, monomethyl succinate, glutaric acid, α-
Methyl glutaric acid, α-ethyl glutaric acid, dimethyl glutaric acid, adipic acid, 3-methyl adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,2
-Cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 4-nitrophthalic acid, diphenyldicarboxylic acid, diphthalic acid, dinicotinic acid, maleic acid,
Polycarboxylic acids such as ethylmaleic acid, diethylmaleic acid, chlormaleic acid, bromomaleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, tricarballylic acid, and aconit, glycolic acid, gluconic acid, glyceric acid, and lactic acid , Malic acid, citric acid, citramalic acid,
Tartronic acid, tartaric acid, itartaric acid, monomethyl tartrate, sodium bitartrate, potassium bitartrate, dihydroxytartaric acid, dihydroxymalonic acid, hydroxybutyric acid, dihydroxybutyric acid, hydroxyvaleric acid, diglycolic acid, citrazinic acid, tolovic acid, sialic acid,
o-hydroxybenzoic acid, m-hydroxybenzoic acid, p
-Hydroxycarboxylic acids such as hydroxybenzoic acid, protocatechuic acid, gallic acid, mandelic acid, p-chloromandelic acid, and benzylic acid; and other organic acids such as methyl sulfate, ethyl sulfate, methanesulfonic acid, and ethanesulfonic acid. , Ethanesulfinic acid, benzenesulfonic acid, p
-Toluene sulfonic acid, p-toluene sulfinic acid, xylene sulfonic acid, sulfobenzoic acid, naphthalene sulfonic acid, 2-naphthol-6-sulfonic acid, sulfanilic acid, dioxyacetone-1-phosphate, dimethyl phosphate,
Examples thereof include diethyl phosphate, diisopropyl phosphate, and dibutyl phosphate.

The inorganic acids include hydrochloric acid, chlorous acid, chloric acid, perchloric acid, sulfuric acid, sulfurous acid, sodium hydrogensulfite, sodium bisulfite, nitrous acid, nitric acid, hypophosphorous acid, phosphorous acid, phosphoric acid, Pyrophosphoric acid, monosodium phosphite,
Examples include sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen pyrophosphate, hydrobromic acid, bromic acid, boric acid and the like.

These acidic substances are used alone or in combination of two or more. As the target microcapsule, a microcapsule having an amino residue on the wall membrane and which becomes a cation under acidic conditions is used. Specific examples include microcapsules having an epoxy resin-amine curing agent system, a dichloride-amines system, and an isocyanates-amines system wall film prepared by an interfacial polymerization method or an in-situ polymerization method.

Next, a processing method will be described. An acidic substance is added to the stock solution of microcapsules prepared using the wall membrane material to lower the pH of the system. The effect is greater as the pH value is lower, and is preferably 3 or less. If it is inconvenient to lower the pH in the form of a stock solution, the microcapsules may be separated from the medium once, then dispersed in water and added. Although the reaction proceeds even at room temperature, it is preferable to heat the reaction to 40 to 100 ° C. because the reaction time becomes longer. The reaction is usually completed within tens of minutes to several hours. Further, the powdered microcapsules can be added to the medium containing the acidic substance. Specifically, an epoxy resin prepared by an interfacial polymerization method or an in-situ polymerization method-
Examples include microcapsules having an amine curing agent-based, dichloride-amines-based, and isocyanates-amines-based wall film.

As the acidic substance for lowering the pH of the system, a substance capable of lowering the pH of the system by adding a small amount thereof is suitably used in terms of productivity and work efficiency, and is used in the present invention. The acidic substance is preferably an acidic substance having an acid dissociation index (pKa) of 4 or less in an aqueous medium. Furthermore,
Among the above-mentioned acidic substances, inorganic acids are preferably used because organic acids are liable to be browned when the capsules are heat-treated, and are more expensive than inorganic acids. In particular, phosphoric acid is preferred as the inorganic acid because it is excellent in productivity, work efficiency, and safety.

The microcapsules used in the present invention are different from ordinary multi-capsules in that the additive substance forms a further layer on the wall film. It is considered to improve the barrier property against a hydrophobic resin or the like. In addition, the method is a very simple method as described above, and it goes without saying that ordinary encapsulation equipment can be used as it is,
If the dispersion medium is appropriate, the acidic substance can be added as it is following the encapsulation, which is very advantageous in terms of cost. Further, since the substance to be added is a low molecule, the viscosity of the system hardly changes and the workability is the same as that of the conventional method. The microcapsule pigment thus obtained is excellent in solvent resistance and monomer resistance, so that not only the range of materials used for UV-curable inks, particularly the range of use of reactive monomers, is expanded, but also the initial good. This is an effective countermeasure against the problem that the discoloration function deteriorates with time.

The reversible thermochromic composition encapsulated in the microcapsules comprises: (a) an electron-donating color-forming organic compound;
A composition containing three components of (b) an electron-accepting compound and (c) a reaction medium for determining the temperature at which a color reaction occurs between the two is suitably used. For example, Japanese Patent Publication No. Sho 51-4 proposed by the present applicant.
No. 4,706, JP-B-51-44707, JP-B-1-29398, and the like can be used.
The composition discolors before and after a predetermined temperature (discoloration point) as a boundary, exhibits a decolored state in a temperature range higher than the color change point, and a color developed state in a temperature range lower than the color change point. Only one particular state can exist in a region. That is, the other state is maintained while the heat or cold required for the state to appear is applied, but returns to the state exhibited in the normal temperature range when the application of the heat or cold disappears, the hysteresis width. Is a heat decoloring type reversible thermochromic composition showing a relatively small thermochromic behavior. In addition, Japanese Patent Publication Nos. 4-17154, 7-179777, 7-33997, and 8-399 proposed by the present applicant.
No. 36, which shows a large hysteresis characteristic, that is, the shape of the curve plotting the change in the coloring density due to the temperature change is opposite to the case where the temperature is increased from a lower temperature side than the color change temperature range. Discoloration follows a route that is significantly different from that when descending from the higher temperature side, and the color development state in the temperature range below the low temperature side discoloration point, or the decoloration state in the temperature range above the high temperature side discoloration point, It is also possible to use a heat-decoloring type thermochromic color-memory composition which can retain the alternation even after removing the application of the cold or heat required for the color change.

Further, Japanese Patent Application Laid-Open No. 11-1 proposed by the present applicant
No. 29623, JP-A-11-5973, etc., specific alkoxyphenol compounds having a straight-chain or side-chain alkyl group having 3 to 18 carbon atoms as the (b) electron-accepting compound contained in the composition Heat-colorable reversible thermochromic composition to which is applied, further, as the electron-accepting compound contained in the heat-colorable reversible thermochromic composition, 3
-Hydroxybenzoic acid tridecyl ester, 3-hydroxybenzoic acid tetradecyl ester, 3-hydroxybenzoic acid pentadecyl ester, 3-hydroxybenzoic acid hexadecyl ester, 3-hydroxybenzoic acid heptadecyl ester, 3-hydroxybenzoic acid octadecyl ester Ester, 3-hydroxybenzoic acid nonadecyl ester, 3-hydroxybenzoic acid eicosyl ester, 3-
Heneicosyl hydroxybenzoate, docosyl 3-hydroxybenzoate, tridecyl 4-hydroxybenzoate, tetradecyl 4-hydroxybenzoate, pentadecyl 4-hydroxybenzoate, hexa-4-hydroxybenzoate Decyl ester, 4-hydroxybenzoic acid heptadecyl ester,
Octadecyl 4-hydroxybenzoate, nonadecyl 4-hydroxybenzoate, eicosyl 4-hydroxybenzoate, heneicosyl 4-hydroxybenzoate, docosyl 4-hydroxybenzoate, 3,4-dihydroxy Tridecyl benzoate, tetradecyl 3,4-dihydroxybenzoate, pentadecyl 3,4-dihydroxybenzoate, hexadecyl 3,4-dihydroxybenzoate, heptadecyl 3,4-dihydroxybenzoate, Octadecyl 3,4-dihydroxybenzoate, nonadecyl 3,4-dihydroxybenzoate, eicosyl 3,4-dihydroxybenzoate, heneicosyl 3,4-dihydroxybenzoate, 3,4 Docosyl dihydroxybenzoate, tridecyl 3,5-dihydroxybenzoate, tetradecyl 3,5-dihydroxybenzoate, pentadecyl 3,5-dihydroxybenzoate, hexadecyl 3,5-dihydroxybenzoate Heptadecyl 3,5-dihydroxybenzoate, octadecyl 3,5-dihydroxybenzoate, nonadecyl 3,5-dihydroxybenzoate, eicosyl 3,5-dihydroxybenzoate, 3,5-dihydroxybenzoate Hydroxybenzoic acid esters such as acid eicosyl ester and 3,5-dihydroxybenzoic acid docosyl ester can also be used.

The proportion of each component of the reversible thermochromic composition depends on the concentration, the discoloration temperature, the discoloration form and the type of each component.
Component (b) ranges from 0.1 to 50, preferably from 0.5 to 20, component (c) from 1 to 200, and preferably from 5 to 100, relative to component (1). Parts by weight).

Next, the photopolymerizable composition will be described. The photopolymerizable composition is a reactive oligomer, a reactive monomer,
It comprises at least a photopolymerization initiator. Reactive oligomers include polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, oligo acrylate, alkyd acrylate,
Polyol acrylate and the like. Monofunctional monomers such as 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate as reactive monomers,
Examples thereof include bifunctional monomers such as 1,3-butanediol acrylate, neopentyl glycol acrylate, and 1,6-hexanediol acrylate, and polyfunctional monomers such as trimethylolpropane triacrylate and dipentaerythritol acrylate. As the photopolymerization initiator, acetophenone-based initiators such as acetophenone, 2-phenyl-2,2-dimethoxyacetophenone and 2-hydroxy-2,2-dimethoxyacetophenone;
Benzophenone, [4-[(4-methylphenyl) thio] phenyl] phenyl-methanone, Michler's ketone,
[4-phenylthiophenyl] benzohenone-based initiators such as phenyl-methanone, thioxanthone-based initiators such as thioxanthone, 2,4-diethylthioxanthone and isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl-
Acyl phosphine oxide initiators such as 2,4,6-trimethylbenzoylphenyl phosphine oxide;
Benzoin ether initiators, α-acyl oxime ester initiators and the like can be mentioned. The mixing ratio of each component in the reversible thermochromic ultraviolet curable ink having the above-described configuration is not particularly limited, but the base oligomer 100
Reversible thermochromic microcapsule pigment 1 based on parts by weight
Generally, 0 to 200 parts by weight, 10 to 500 parts by weight of a reactive monomer, and 0.1 to 100 parts by weight of a photopolymerization initiator are used.

In addition, photosensitizers, defoamers, leveling agents, ultraviolet absorbers, infrared absorbers, antistatic agents, thixotropic agents, viscosity modifiers, dispersants, extenders, penetrants, preservatives Various additives such as a polymerization inhibitor and a silane coupling agent, and general pigments can be added as required.

The reversible thermochromic UV-curable ink of the present invention is obtained by dispersing a dried product of a microcapsule pigment in a base oligomer, and then reacting a reactive monomer as a viscosity modifier.
Of course, a method of adding a photopolymerization initiator and other additives is also preferable, but the method is also suitable for a case where an ink is produced by a flushing method using a hydrous microcapsule pigment and a reactive oligomer. This is because the microcapsule pigment of the present invention has a small amount of amines used for forming a wall film by acid treatment, and the microcapsule pigment and the reactive oligomer are well kneaded under reduced pressure.
In an untreated system, addition of the microcapsule pigment and the reactive oligomer under reduced pressure occurs due to the remaining amines used in the production of the microcapsule pigment, and addition polymerization of the oligomer occurs, so that a desired ink cannot be obtained. The ink thus obtained is a microcapsule pigment that has been treated with an acid, so that it is stable over time, and the continuity of the reversible thermochromic function in ink storage is higher than that of an untreated system. It is excellent.

The reversible thermochromic UV-curable ink obtained as described above can be prepared by a conventionally known method, for example, printing means such as screen printing, offset printing, gravure printing, coater, tampo printing, transfer, and the like. A reversible thermochromic layer is provided on the support surface by means of brush coating, spray coating, flow coating, roller coating, dip coating, etc., and cured by irradiation with ultraviolet light to obtain a reversible thermochromic laminate.

The material and form of the support are not particularly limited. Examples of the material include plastic (plastic film), glass, metal, stone, porcelain, wood, synthetic paper, cloth, flocking or raised cloth, non-woven cloth, and the like. Synthetic leather, leather and the like can be mentioned. In addition, the shape of the laminate may be an uneven shape other than a planar shape. Specific examples include beverage containers, toys, artificial flowers, stationery, daily necessities, cosmetic tools, accessories, lighting equipment, sports equipment, printed matter, vehicles, clothing, footwear, indoor decorations, and the like. Further, the reversible thermochromic layer may be a design such as a combination of characters, symbols, patterns, and lines, or an image (design) having an appropriate shape. Further, a protective layer can be provided on the reversible thermochromic layer of the reversible thermochromic laminate.
When a layer containing a light stabilizer and / or a light-shielding pigment is provided on the reversible thermochromic layer, light resistance is improved.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reversible thermochromic UV-curable ink of the present invention has an epoxy resin-amine curing agent system, dichlorides-amines system, and isocyanates-amines system wall film. A microcapsule obtained by adding an acidic substance having a molecular weight of 1500 or less to an aqueous medium containing microcapsules, heating and stirring, and modifying the capsule surface,
It is obtained by mixing with a photopolymerizable composition. After forming a reversible thermochromic layer on the surface of the support with the ink, it is cured using a general-purpose ultraviolet irradiation device to obtain various laminates and printed matter.

[0022]

Examples of the present invention will be described below. Parts in Examples are parts by weight. Example 1 Production of reversible thermochromic microcapsule pigment (a) 1 part of 6-diethylamino-7,8-benzofluoran as an electron-donating color-forming organic compound, and (b) 1,1- as an electron-accepting compound After heating and dissolving a reversible thermochromic composition comprising 6 parts of bis (4-hydroxyphenyl) -n-decane, (c) 45 parts of butyl stearate and 5 parts of cetyl caprate as a reaction medium, aromatic polyvalent Mix 30 parts of isocyanate prepolymer and 40 parts of co-solvent,
An aqueous solution containing 5 parts of diethylenetriamine was emulsified and dispersed in an aqueous solution of polyvinyl alcohol, and an aqueous solution containing 5 parts of diethylenetriamine was added dropwise to form a wall film of a polyurea resin film composed of a polyvalent isocyanate / amine to obtain a reversible thermochromic microcapsule pigment dispersion. .
Phosphoric acid was added to 100 parts of the microcapsule dispersion to adjust the pH of the system to 2.5, heated at 70 ° C., and centrifuged to obtain a reversible thermochromic microcapsule pigment. The resulting microcapsule pigment was colorless at about 23 ° C. or higher and turned pink at about 18 ° C. or lower.

Preparation of reversible thermochromic UV-curable ink Dry substance 20 of the reversible thermochromic microcapsule pigment
Parts, dispersant 8 parts, epoxy acrylate oligomer 3
5.5 parts were mixed, and then 2-
2.5 parts of (hydroxy-5-tert-butylphenyl) benzotriazole were added to obtain a mixture. Separately, 5 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide was added as a photopolymerization initiator to 2 parts.
The mixture obtained by kneading the mixture obtained by heating and dissolving in 26 parts of -hydroxy, 1-chlorooxy, and 3-methacryloxypropane, and the above mixture, and further adding 3 parts of a sensitizer, an antifoaming agent, and a leveling agent, to perform reversible thermochromic discoloration. UV curable ink was obtained.

Preparation of Reversible Thermochromic Laminate Using a reversible thermochromic UV-curable ink, heart-shaped screen printing was performed on a transparent glass with a 100-mesh screen plate, followed by irradiation with a 160 W / cm metal halide lamp. Ultraviolet irradiation was performed at a distance of 20 cm and a line speed of 15 m / min to obtain a reversible thermochromic laminate (reversible thermochromic glass). The glass is 1
At 8 ° C. or lower, a pink heart pattern appeared as a printed image (reversible thermochromic image), and at 23 ° C. or higher, it became colorless.
In addition, this aspect change could be repeatedly performed by the temperature change. In addition, after applying a cross-cut cellophane tape (registered trademark) to the printed portion and performing an adhesiveness test for peeling it off, the printed portion did not peel off from the glass and had good adhesion to the substrate (glass). Was shown. Further, the obtained reversible thermochromic ultraviolet curable ink did not show any abnormality even after one month at 50 ° C., and retained the initial performance.

Example 2 Preparation of reversible thermochromic microcapsule pigment (a) 3 parts of 3-dibutylamino-6-methyl-7-anilinofluoran as an electron-donating color-forming organic compound,
(B) A reversible thermochromic composition comprising 6 parts of 1,1-bis (4-hydroxyphenyl) -2-methylpropane as an electron accepting compound, (c) 25 parts of stearyl caprate and 25 parts of cetyl alcohol as a reaction medium. After heating and dissolving the product, 10 parts of a cresol novolak type epoxy resin and 50 parts of a cosolvent are mixed, emulsified and dispersed in a 10% aqueous gelatin solution, and 50 parts of a 10% aqueous solution of a diethylenetriamine / epoxy resin adduct is dropped. Thus, a wall film of an epoxy resin film composed of epoxy / amine was formed to obtain a reversible thermochromic microcapsule dispersion. The pH of the system was adjusted to 2.0 by adding citric acid to 100 parts of the microcapsule dispersion, and stirring was continued at 70 ° C. for 30 minutes, followed by centrifugation to obtain a reversible thermochromic microcapsule pigment. . The obtained microcapsules were pigments which turned colorless at about 32 ° C. or higher and black at about 27 ° C. or lower.

Production of reversible thermochromic UV-curable ink 30 parts of the dried reversible thermochromic microcapsule pigment were mixed with 38.5 parts of a rosin-modified acrylate oligomer, and then 2- (3 -T-butyl-5-octyloxycarbonylethyl-2-hydroxyphenyl) -benzotriazole 2.5 parts was added to obtain a mixture. Separately, 5 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide as a photopolymerization initiator were heated and dissolved in 24 parts of EO-modified (n = 15) trimethylolpropane triacrylate, and the mixture was mixed with the mixture. And a defoaming agent and a leveling agent were further added to obtain a reversible thermochromic UV-curable ink.

Preparation of a Reversible Thermochromic Laminate Using the reversible thermochromic ultraviolet-curable ink, a screen is formed on a screen frame of an offset print pamphlet on which a person on a television screen is projected by an 80 mesh screen plate. After printing, UV irradiation was performed using a 120 W / cm metal halide lamp at an irradiation distance of 20 cm and a line speed of 7 m / min to obtain a reversible thermochromic laminate (reversible thermochromic print). The printing layer (reversible thermochromic layer) of the printed matter has a thickness of about 55 μm,
At 27 ° C. or lower, the color was black, and nothing appeared on the television screen. However, when the temperature was increased to 32 ° C. or higher, the color of the printed layer was erased, and the underlying human figure was visually recognized. In addition, this aspect change could be repeatedly performed by the temperature change. In addition, after applying a cross-cut cellophane tape to the printed portion and performing an adhesiveness test for peeling it off, the printed portion showed good adhesiveness to the substrate (paper) without peeling off from the pamphlet. . Further, the obtained reversible thermochromic UV-curable ink was cured at 50 ° C. for 1 hour.
No abnormality was observed after a lapse of months, and the initial performance was maintained.

Comparative Example 1 A microcapsule pigment was prepared in the same manner as in Example 1, except that phosphoric acid was not added to the reversible thermochromic microcapsule pigment dispersion of Example 1, and an ink was prepared using the pigment. did. After 2 weeks of the obtained ink at 50 ° C., a laminate similar to that of Example 1 was produced.
Even when cooled to 8 ° C. or lower, and even to about 0 ° C., the color density was not sufficient, and the color density was significantly lower than that of Example 1. This is presumably because, during the accelerated aging of the ink, the vehicle, especially the low molecular weight monomer component, passed through the microcapsule wall membrane and affected the color changing function of the reversible thermochromic composition.

Comparative Example 2 A microcapsule pigment was prepared in the same manner as in Example 2, except that citric acid was not added to the reversible thermochromic microcapsule pigment dispersion of Example 2, and an ink was prepared using the pigment. did. After two weeks of the obtained ink at 50 ° C., a laminate similar to that of Example 2 was prepared. The laminate did not have a sufficient color density even when cooled to 27 ° C. or lower, and even to about 10 ° C. As compared with Example 2, the color density was remarkably low, and it was not possible to hide the lower layer human image. This is presumably because, during the accelerated aging of the ink, the vehicle, especially the low molecular weight monomer component, passed through the microcapsule wall membrane and affected the color changing function of the reversible thermochromic composition.

[0030]

According to the present invention, a reversible thermochromic microencapsulated pigment obtained by ionizing a wall film containing at least an aliphatic amine or an aromatic amine with an acidic substance is used, so that the solvent contained in the reversible thermochromic composition is contained therein. Not only can improve the reversibility and show a permanent reversible thermochromic function,
It is possible to provide a reversible thermochromic UV-curable ink which shows a good color density at the time of color development. In addition, a microcapsule using an aliphatic amine or an aromatic amine as a material for forming a wall film is treated with an acidic substance having a molecular weight of 1500 or less in an aqueous medium to adjust the pH of the system to an acidic value, and then treated with a reversible thermochromic microcapsule. By the production method of mixing the capsule pigment and the photopolymerizable composition, it is possible to provide a reversible thermochromic ultraviolet curable ink excellent in low cost and safety and health.

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Claims (3)

[Claims] 1. A reversible thermochromic microcapsule pigment comprising at least a reversible thermochromic composition and a photopolymerizable composition, wherein the reversible thermochromic microcapsule pigment comprises: A reversible thermochromic ultraviolet curable ink comprising a wall film containing at least an aliphatic amine or an aromatic amine and containing a reversible thermochromic composition, wherein the wall film is ionized by an acidic substance. 2. The reversible thermochromic composition comprises (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound,
The reversible thermochromic UV-curable ink according to claim 1, which is a composition comprising (c) a reaction medium for controlling the temperature at which the color reaction of (a) and (b) occurs. 3. A microcapsule in which an aliphatic amine or an aromatic amine is used as a wall film-forming material is prepared by using an acidic substance having a molecular weight of 1500 or less in an aqueous medium to form a p-type capsule.
A method for producing a reversible thermochromic UV-curable ink, comprising mixing a reversible thermochromic microcapsule pigment treated with acidification of H and a photopolymerizable composition.