CN101970603A - Thermochromic composition and thermochromic microcapsules - Google Patents

Abstract

The invention provides a thermochromic composition which little suffers from residual color in the faded state and exhibits relatively large color difference on color change; and a process for production of the same. The invention relates to a thermochromic composition comprising an electron-donating color-developing organic compound, an electron-accepting compound and a desensitizer which is characterized in that the desensitizer is (1) a fatty acid methyl ester having 5 or more carbon atoms in total and/or (2) a fatty acid amide having 4 or more carbon atoms in total. A thermochromic composition having a desired color-temperature hysteresis can be produced by changing the blending ratio between the desensitizers (1) and (2) in incorporating both with the other components.

Description

Thermochromic composition and thermochromic microcapsules

technical field

The present invention relates to a thermochromic composition and thermochromic microcapsules. The invention also relates to methods of making thermochromic compositions.

Background technique

The thermochromic composition undergoes reversible color development and color loss due to temperature, and can be used, for example, in printed matters, inks, paints, packaging materials, recording materials, and the like. As a representative example of such a composition, there is a composition utilizing an electron transfer reaction between an electron-donating chromogenic organic compound (electron donor) and an electron-accepting compound (electron acceptor) (Patent Document 1, Patent Document 2, etc.) .

In general, in the heating-cooling cycle, the thermochromic composition can reversibly repeat color development-color loss or color loss-color development, but usually there is a temperature difference between the color development temperature and the color loss temperature (i.e. Temperature hysteresis ΔH). For example, as shown in Figure 1, when ΔH=0°C, it is Figure 1(b), and ΔH appears in Figure 1(a) and Figure 1(c). FIG. 1( a ) shows the case where the decolorization temperature is increased, and FIG. 1( c ) shows the case where the color development temperature is increased.

In this regard, as a technique for increasing the color change temperature hysteresis ΔH, it is known to use a specific fatty acid ester compound obtained from an odd-numbered aliphatic monohydric alcohol and an aliphatic carboxylic acid as a reaction medium, by combining the reaction medium and The homogeneously dissolved color-forming reaction components are contained in microcapsules, and a microcapsule pigment exhibiting a thermochromic characteristic with a hysteresis width (line segment HG) of 8°C to 30°C is obtained (Patent Document 3). Utilizing this microcapsule pigment, the following characteristics are effectively exhibited. Regarding the color concentration-temperature curve, it shows a hysteresis width (ΔH) of 8°C to 30°C, produces reversible discoloration from color development to color loss, and can be reciprocated in the normal temperature region. The ground-changing memory maintains both the color on the low-temperature side of the color-changing temperature and the color on the high-temperature side, applying heat or cold and heat as needed, and can reversibly reproduce any one color and maintain memory.

In addition, for example, a thermochromic color-memory microcapsule pigment containing (1) an electron-donating color-developing organic compound, (2) an electron-accepting compound, and (3) ) reaction medium at the temperature of the color reaction and (4) discoloration temperature regulator as four necessary components, the above-mentioned (4) discoloration temperature regulator is selected from ethers, esters, ketones, One or more compounds of amides and fatty acids, the relationship is: when the melting point is Y°C, relative to the melting point (X°C) of the component (3) satisfies (X+16)≤Y≤(X +100) °C relationship, the above four necessary ingredients are contained in the microcapsules, and the temperature-color concentration curve shows a hysteresis range (ΔH) of 5 °C to 80 °C, and the color will change below the trigger point on the low temperature side The temperature region between the low-temperature trigger point and the high-temperature trigger point is memorized and held in memory alternately with the color displayed in each region above the high-temperature trigger point (Patent Document 4).

In addition, a reversible thermochromic microcapsule pigment containing (1) an electron-donating color-developing organic compound, (2) an electron-accepting compound, and (3) a color-developing compound that determines the above-mentioned (1) and (2) has also been proposed. The reaction medium of the occurrence temperature of the color reaction and the (4) discoloration temperature regulator are four necessary components, and the above-mentioned (4) discoloration temperature regulator is selected from esters, alcohols, ketones, amides satisfying the following relationship One or two or more compounds among , hydrocarbons, and fatty acids, the relationship is: when the melting point is Y°C, relative to the melting point (X°C) of the component (3), satisfy X+30≤Y≤200 relationship, the above-mentioned four essential components are contained in microcapsules (Patent Document 5).

Patent Document 1: Japanese Patent Application Laid-Open No. 6-65568

Patent Document 2: Japanese Patent Publication No. 4-17154

Patent Document 3: Japanese Patent Application Laid-Open No. 7-33997

Patent Document 4: Japanese Unexamined Patent Publication No. 2001-152041

Patent Document 5: Japanese Patent Laid-Open No. 2002-12787

Contents of the invention

However, in these conventional techniques for controlling the temperature hysteresis of discoloration, there is a problem of large color residue (underdeveloped color) especially during decolorization. Therefore, even if a high color density is obtained, there is still room for further improvement in terms of color change and color difference.

Therefore, the main object of the present invention is to provide a thermochromic composition which has little color residue especially during decolorization and can express a large color change and color difference.

In order to solve the problems of the prior art, the inventors of the present invention conducted intensive studies, and as a result, found that the above object can be achieved by adopting a specific combination of components as an ink composition, and completed the present invention.

That is, the present invention relates to the following thermochromic composition and thermochromic microcapsules.

Item 1. A thermochromic composition characterized in that it contains an electron-donating color-developing organic compound, an electron-accepting compound, and a desensitizing agent, and as the above-mentioned desensitizing agent, it contains: One or both of fatty acid methyl esters and (2) fatty acid amides with a total of 4 or more carbon atoms.

Item 2. The thermochromic composition according to item 1 above, wherein the fatty acid methyl ester is methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate At least one of esters and methyl behenate.

Item 3. The thermochromic composition according to item 1 above, wherein the fatty acid amide is stearic acid amide, behenic acid amide, oleic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, and erucic acid amide at least one of the

Item 4. The thermochromic composition according to item 1 above, which has a discoloration temperature lag of less than 5°C.

Item 5. A thermochromic microcapsule comprising the composition described in Item 1 above contained in the microcapsule.

Item 6. A method for producing a thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound, and a desensitizing agent, wherein (1) the total number of carbon atoms In the case of fatty acid methyl ester having 5 or more carbon atoms and (2) fatty acid amide having 4 or more carbon atoms, the hysteresis can be changed by changing the compounding ratio of both, and a thermochromic composition having a desired color change temperature hysteresis can be obtained.

Item 7. The production method according to the above item 6, wherein the discoloration temperature lag is less than 5°C.

Invention effect

According to the thermochromic composition or microcapsules of the present invention, by using one or both of the prescribed fatty acid methyl ester and fatty acid amide as a desensitizing agent, it is possible to achieve a high color concentration and suppress color residue (decolorization concentration). It is lower, so that high color change and color difference can be achieved.

In addition, in the present invention, not only the discoloration color difference is large, but also sharp discoloration characteristics can be obtained. That is, the width from the discoloration start temperature (or decolorization start temperature) to the discoloration end temperature (or decolorization end temperature) is narrow, and a clear discoloration behavior can be obtained.

When both the predetermined fatty acid methyl ester and fatty acid amide are used as desensitizers, in addition to the above effects, the color change temperature hysteresis ΔH corresponding to the blending ratio of the two can be freely set. In particular, in the present invention, the above-mentioned ΔH can be arbitrarily set continuously or stepwise in the range from 0°C to a desired value (preferably 20°C or less, more preferably less than 5°C, most preferably 4.5°C or less) .

The thermochromic composition of the present invention can be used in various applications. For example, it is suitable for imparting thermochromic properties to various materials or products such as inks, printed matter, plastic moldings, packaging materials, recording materials, and fibers.

Description of drawings

Fig. 1 is a graph for explaining the presence or absence of discoloration temperature hysteresis in a thermochromic composition.

Fig. 2 is a graph showing an achromatic curve and a color development curve used in test examples.

Fig. 3 is an achromatic curve for explaining the decolorizing temperature t1 (and the color developing temperature t2) in the test example.

Detailed ways

·Thermochromic composition

The thermochromic composition of the present invention is a thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound, and a desensitizing agent, and is characterized in that, as the above-mentioned desensitizing agent, it contains (1) the total number of carbon atoms One of fatty acid methyl esters with 5 or more carbon atoms and (2) fatty acid amides with 4 or more carbon atoms, or both.

Electron-donating chromogenic organic compounds

The electron-donating color-developing organic compound (color-forming agent) is not limited as long as it reacts with the electron-accepting compound (color-developing agent) to develop color, and known or commercially available ones can be used. For example, the following compounds are preferably used. These compounds may be used singly or in combination of two or more.

(a) Fluorocarbons...2′-[(2-chlorophenyl)amino]-6′-(dibutylamino)-spiro[isobenzofuran-1(3H), 9′-(9H)xanthene t]-3-keto, 3-diethylamino-6-methyl-7-chlorofluorocarbon, 3-dimethylaminobenzo(a)-fluorocarbon, 3-amino-5-methylfluorocarbon Hydrocarbon, 2-methyl-3-amino-6,7-dimethylfluorene, 2-bromo-6-cyclohexylaminofluorene, 6′-(ethyl(4-methylphenyl)amino-2 ′-(N-methylphenylamino)-spiro(isobenzofuran 1(3H), 9′-(9H)xanthene)-3-one, 3,6-diphenylaminofluorene, etc.;

(b) Fluorenes...3,6-bis(diethylamino)fluorenespiro(9.3′)-4′-azabenzofuranone, 3,6-bis(diethylamino)fluorenespiro(9.3′) )-4',7'-diazabenzofuranone, etc.;

(c) Diphenylmethane benzofuranones...3,3-bis-(p-ethoxy-4-dimethylaminophenyl)benzofuranone, etc.;

(d) Diphenylmethane azabenzofuranones...3,3-bis-(1-ethoxy-4-diethylaminophenyl)-4-azabenzofuranone, etc.;

(f) Indolylbenzofuranones...3,3-bis(n-butyl-2-methylindol-3-yl)benzofuranone, 3,3-bis(1-ethyl-2 -Methylindol-3-yl)benzofuranone, etc.;

(g) Phenylindolylbenzofuranones...3-(1-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)benzofuranone wait;

(h) Phenylindolyl azabenzofuranones...3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole- 3-yl)-4-azabenzofuranone, 3-[2-ethoxy-4-(N-ethylanilino)phenyl-3-(1-ethyl-2-methylindole -3-yl)-4-azabenzofuranone, etc.;

(i) Styryl quinolines... 2-(3-methoxy-4-dodecyloxystyryl) quinoline, etc.;

(j) Pyridines...2,6-diphenyl-4-(6-dimethylaminophenyl)pyridine, 2,6-diethoxy-4-(4-diethylaminophenyl)pyridine wait;

(k) Quinazolines...2-(4-N-methylanilinophenyl)-1-phenoxyquinazoline, 2-(4-dimethylaminophenyl)-4-(1- Methoxyphenyloxy)quinazoline, etc.;

(l) Bisquinazolines...4,4'-(ethylenedioxy)-bis[2-(1-diethylaminophenyl)quinazoline], 4,4'-(ethylenedioxy Oxy)-bis[2-(1-di-n-butylaminophenyl)quinazoline], etc.;

(m) Ethylene phthalides...3,3-bis[1,1-bis-(p-dimethylaminophenyl)ethylene-3]benzofuranone, etc.;

(n) Ethylene azabenzofuranones...3,3-bis[1,1-bis-(p-dimethylaminophenyl)ethylidene-2]-4-azabenzofuranone, 3,3-bis[1,1-bis-(p-dimethylaminophenyl)ethylene-2]-4,7-diazabenzofuranone, etc.;

(o) Triphenylmethane benzofuranones... crystal violet lactone, malachite green lactone, etc.;

(p) Polyaryl methanol... Michler alcohol, crystal violet methanol, malachite green methanol, etc.;

(q) Leuco auramines...N-(2,3-dichlorophenyl) leuco auramine, N-benzoyl amine, N-acetyl amine, etc.;

(r) Rhodamine lactams...Rhodamine β-lactam, etc.;

(s) Indolines...2-(phenyliminoethylene)-3,3-dimethylindoline, etc.;

(t) Spiropyrans...N-3,3-trimethylindolebenzospiropyran, 8-methoxy-N-3,3-trimethylindolebenzospiropyran, etc.;

In addition, in the present invention, in addition to the above compounds, diazarhodamine lactones, xanthenes, and the like can also be used.

In the present invention, at least one of fluorocarbons among these electron-donating chromogenic organic compounds is preferably used. In particular, 2′-[(2-chlorophenyl)amino]-6′-(dibutylamino)-spiro[isobenzofuran-1(3H), 9′-(9H)xanthene]- At least one of 3-keto and 3,6-diphenylaminofluorene.

The content of the electron-donating color-developing organic compound can be appropriately set according to the type of the compound, etc., but is usually preferably about 0.1 to 50% by weight, particularly preferably about 0.8 to 15% by weight, in the thermochromic composition of the present invention. When the above-mentioned content is less than 0.1% by weight, there is a possibility that the density of color development may decrease. On the other hand, when the above-mentioned content exceeds 50% by weight, the base hair color may increase.

electron accepting compound

As the electron-accepting compound, known or commercially available compounds can be appropriately used without limitation. For example, the following compounds are preferably used. These compounds may be used singly or in combination of two or more.

(a) Phenols... bisphenol A or its derivatives, bisphenol S or its derivatives, p-phenylphenol, dodecylphenol, o-bromophenol, ethyl p-oxybenzoate, methyl gallate, phenolic Resin, etc.;

(b) Metal salts of phenols...Metal salts of phenols such as Na, K, Li, Ca, Zn, Al, Mg, Ni, Co, Sn, Cu, Fe, Ti, Pb, Mo, etc.;

(c) Aromatic carboxylic acids and aliphatic carboxylic acids with 2 to 5 carbon atoms... phthalic acid, benzoic acid, acetic acid, propionic acid, etc.;

(d) Metal salts of carboxylic acids...sodium oleate, zinc salicylate, nickel benzoate, etc.;

(e) Acidic phosphates... butyl acid phosphate, 2-ethylhexyl acid phosphate, dodecyl acid phosphate;

(f) Metal salts of acidic phosphates... Metal salts of Na, K, Li, Ca, Zn, Al, Mg, Ni, Co, Sn, Fe, Ti, Pb, Mo, etc. of acidic phosphates;

(g) Triazole compounds...1,2,3-triazole, 1,2,3-benzotriazole, etc.;

(h) Thiourea and its derivatives... diphenylthiourea, di-o-toluyl urea, etc.;

(i) Haloalcohols...2,2,2-Trichloroethanol, 1,1,1-Tribromo-2-methyl-2-propanol, N-3-pyridyl-N'-(1- Hydroxy-2,2,2-trichloroethyl)urea, etc.;

(j) Benzothiazoles...2-mercaptobenzothiazole, 2-(4'-morpholinodithio)benzothiazole, N-tert-butyl-2-benzothiazolylsulfenamide, 2- Zinc salt of mercaptobenzothiazole, etc.

In the present invention, among these electron-accepting compounds, at least one of phenols and metal salts thereof can be suitably used. Especially preferably at least one selected from 1) bisphenol A and its derivatives and 2) bisphenol S and its derivatives, most preferably 2,2-bis(4-hydroxyphenyl)propane and 1,1 - at least one of bis(4'-hydroxyphenyl)-1-phenylethane.

The content of the electron-accepting compound can be appropriately set according to the type of the compound, etc., but is usually preferably about 0.05 to 98% by weight, particularly preferably 0.5 to 77% by weight, in the thermochromic composition of the present invention. When the above-mentioned content is less than 0.05% by weight, a reduction in the color density may be caused. On the other hand, when the above-mentioned content exceeds 98% by weight, the base hair color may increase.

In addition, in the present invention, the relationship with the electron-donating color-developing organic compound is preferably 0.1-100 parts by weight of the electron-accepting compound, particularly preferably 0.5-20 parts by weight, relative to 1 part by weight of the electron-donating color-developing organic compound. parts by weight.

Desensitizer

As a desensitizing agent, one or both of (1) a fatty acid methyl ester having 5 or more carbon atoms and (2) a fatty acid amide having 4 or more carbon atoms is contained.

The total number of carbon atoms in the above-mentioned fatty acid methyl ester is 5 or more, preferably 8 or more, and more preferably 12 or more. When the total number of carbon atoms is less than 5, the boiling point may be low and volatilization may occur. In addition, the upper limit of the total number of carbon atoms is not limited, but usually about 23 can be used.

As above-mentioned fatty acid methyl ester, can use the carboxyl hydrogen atom of fatty acid (particularly straight-chain saturated monocarboxylic acid) and obtain by methyl substitution, for example, preferably use general formula R1-COOCH3 (wherein, R1 represents carbon atom The ester represented by the hydrocarbon group whose number is 3 or more). This ester can be obtained, for example, by esterification reaction of fatty acid and methanol. The above-mentioned R1 may be a group substituted with a substituent or may be unsubstituted. It is particularly preferred that R1 is an unsubstituted alkyl group, more preferably an unsubstituted linear alkyl group.

Preferred specific examples of the aforementioned fatty acid methyl esters include methyl butyrate, methyl valerate, methyl caproate, methyl caprylate, methyl caprate, methyl laurate, methyl myristate, palmitate at least one of methyl stearate, methyl stearate, methyl arachidate, methyl behenate, methyl tetracosanoate, and the like. Particularly preferred is at least one of methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate, and methyl behenate.

The total number of carbon atoms in the above fatty acid amide is 4 or more, preferably 8 or more, and more preferably 12 or more. When the total number of carbon atoms is less than 4, it may result in a low boiling point and easy volatilization. In addition, the upper limit of the total number of carbon atoms is not limited, and usually about 22 can be used.

As above-mentioned fatty acid amide, the OH group on the carboxyl group of fatty acid (particularly linear saturated monocarboxylic acid) can be used the substance obtained by amino substitution, for example, it is preferable to use the general formula R2-CONH2 (wherein R2 represents the number of carbon atoms is an amide represented by a hydrocarbon group of 3 or more). This amide (acid amide) can be obtained, for example, by reacting a fatty acid with ammonia, a primary amine, or the like. Examples of the above-mentioned R2 include the same groups as those for the above-mentioned R1. That is, the above-mentioned R2 may be a group substituted with a substituent or may be unsubstituted. It is particularly preferred that R2 is an unsubstituted alkyl group, especially preferably an unsubstituted straight-chain alkyl group.

Preferred specific examples of the above fatty acid amides include butyric acid amide, valeric acid amide, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oil amide, At least one of acid amide, arachidamide, behenamide, erucamide, and the like. Particularly preferred is at least one of stearic acid amide, behenic acid amide, oleic acid amide, lauric acid amide, erucic acid amide, myristic acid amide and palmitic acid amide.

In the present invention, one or both of the above-mentioned fatty acid methyl ester and fatty acid amide is contained as a desensitizing agent, but it is preferable to contain both of the above-mentioned fatty acid methyl ester and fatty acid amide as a desensitizing agent. When both are used, more accurate ΔH control can be realized. For example, by changing the components and compounding ratio of both, ΔH can be brought close to 0°C, preferably 0°C≦ΔH≦3°C. In addition, ΔH can be continuously changed by continuously changing the compounding ratio of both.

In the present invention, a system composed of one or both of the above-mentioned fatty acid methyl ester and fatty acid amide is preferably used as a desensitizing agent. However, other desensitizers may be used in combination within the range that does not interfere with the effects of the present invention. For example, the following desensitizers can also be used.

(a) Alcohols...n-hexadecanol, n-octanol, cyclohexanol, hexanediol, etc.;

(b) Esters...myristate, laurate, dioctyl phthalate, etc.;

(c) Ketones... methylhexyl ketone, benzophenone, stearyl ketone, etc.;

(d) Ethers... butyl ether, diphenyl ether, distearyl ether, etc.;

(e) Fatty acids with 6 or more carbon atoms...lauric acid, stearic acid, 2-oxymyristic acid, etc.;

(f) Aromatic compounds...Diphenylmethane, dibenzyltoluene, propylbiphenyl, isopropylnaphthalene, 1,1,3-trimethyl-3-tolyl-indane, dodecylbenzene, etc. ;

(g) Mercaptans...n-decyl mercaptan, n-myristyl mercaptan, n-stearyl mercaptan, isohetyl mercaptan, dodecyl benzyl mercaptan, etc.;

(h) Sulfides... Di-n-octyl sulfide, di-n-decyl sulfide, diphenyl sulfide, dimethylphenyl sulfide, etc.;

(i) Disulfides... di-n-octyl disulfide, di-n-decyl disulfide, diphenyl disulfide, dinaphthalene disulfide, etc.;

(j) Sulfoxides... diethyl sulfoxide, tetramethylenecarboxide, diphenyl sulfoxide, etc.;

(k) Sulfones...diethylsulfone, dibutylsulfone, diphenylsulfone, dibenzylsulfone, etc.;

(l) Aimines...benzylidene laurylamine, p-methoxybenzylidene laurylamine, benzylidene-p-anisidine, etc.;

(m) Fatty acid primary amine salts... stearylamine oleate, myristylamine stearate, stearylamine behenate, etc.

The content (total amount) of the desensitizing agent can be appropriately set according to the type of the compound, etc., and is generally preferably about 1 to 99% by weight, particularly preferably 19 to 99% by weight, and further preferably Preferably it is 60 to 95% by weight. When the above content is less than 1% by weight, it may cause an increase in base hair color. In addition, if the above-mentioned content exceeds 99% by weight, it may result in a decrease in the density of color development.

In addition, the compounding ratio in the case of using both of the fatty acid methyl ester and fatty acid amide is not limited, but usually it is preferably set within the range of (former):(latter)=1:0.1 to 0.3 (weight ratio). Within this range, ΔH can be brought close to 0°C.

other ingredients

In the thermochromic composition of the present invention, ultraviolet absorbers, infrared absorbers, antioxidants, non-thermochromic pigments, non-thermochromic dyes, fluorescent whitening agents, and surfactants may be added to the composition as needed. , defoamer, leveling agent, solvent, thickener and other known additives.

Among the above-mentioned additives, as the ultraviolet absorber, any compound may be used as long as it can effectively absorb ultraviolet rays contained in sunlight or the like to prevent photodegradation caused by the excited state of the chromophoric material due to the photoreaction. Examples of ultraviolet absorbers include benzophenones, benzotriazoles, cyanoacrylates, triazines, salicylic acids, oxalic acid anilides, malonates, and benzoic acids. , cinnamic acid, dibenzoylmethane and other compounds. Among them, a benzotriazole-based ultraviolet absorber is preferable, and "Tinuvin 326" manufactured by Ciba Specialty Chemicals is preferable as a commercially available product. The content (total amount) of the ultraviolet absorber can be appropriately set depending on the type of the compound and the like, but is usually preferably about 0 to 96% by weight, particularly preferably 0 to 61% by weight, in the thermochromic composition of the present invention.

(2) Method for producing thermochromic composition

The thermochromic composition of the present invention can be prepared by injecting these components into known mixers such as a stirrer, a mixer, and a homogenizer, and mixing them uniformly. In this case, mixing is preferably performed while heating. The heating temperature is not limited, but usually about 120 to 180°C can be used.

In particular, the present invention provides a method for producing a thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound and a desensitizing agent, characterized in that:

When blending (1) fatty acid methyl ester with a total carbon number of 5 or more and (2) fatty acid amide with a total carbon number of 4 or more as the above-mentioned desensitizing agent, the hysteresis is changed by changing the ratio of the two, and the product having A thermochromic composition with desired color change temperature hysteresis.

That is, by changing the compounding ratio of (1) (2) above, it is possible to set ΔH according to the compounding ratio. Specifically, if the total amount of the above-mentioned (1) and (2) is taken as 100 parts by weight, by the range of 0 parts by weight<[the ratio of the above-mentioned (1) or the ratio of the above-mentioned (2)]<100 parts by weight Continuously changing, the desired ΔH can be obtained. In particular, as described above, it is preferably set within the range of (the compound of (1) above):(the compound of (2) above)=1:0.1 to 0.3 (weight ratio). Within this range, ΔH can be brought close to 0°C.

The present invention provides a method for producing a thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound, and a desensitizing agent. The method can control the color change temperature hysteresis ΔH. As the above-mentioned desensitizing agent, compound ( In the case of 1) a fatty acid methyl ester with a total of 5 or more carbon atoms and (2) a fatty acid amide with a total of 4 or more carbon atoms, the discoloration temperature lag ΔH is changed by changing the ratio of the two. The conditions of this method may be the same as those of the above-mentioned production method.

(3) Thermochromic microcapsules

The present invention provides thermochromic microcapsules containing the thermochromic composition described above in microcapsules. Except for using the thermochromic composition of the present invention as the content, the same structure as that of known microcapsules can be employed. For example, there may be mentioned microcapsules formed by enclosing contents containing a thermochromic composition with a wall membrane.

As content, a solvent (dissolution aid), an emulsifier, etc. may be contained as needed in addition to the thermochromic composition.

The content of the thermochromic composition is not limited, but usually, if the microcapsules are 100% by weight, it is preferably about 6 to 98% by weight, particularly preferably 50 to 95% by weight.

The solvent can be appropriately selected from known solvents as long as it can uniformly dissolve the thermochromic composition and the wall film raw material and does not hinder the thermochromic performance. A solvent that can be removed by a subsequent step is particularly preferable. For example, ester solvents (but not including the above-mentioned (1) (2) compounds), ketone solvents, ether solvents, glyceryl ether solvents, hydrocarbon solvents, aromatic solvents, nitrogen-containing solvents, silicon solvents, halogen-containing solvents, etc. These solvents may be used singly or in combination of two or more.

As the emulsifier, it is preferable to use an amphiphilic substance that adsorbs on the surface of oil droplets and stabilizes it when the content is emulsified in water. As these emulsifiers, known emulsifiers can be used. For example, water-soluble natural polymers, water-soluble synthetic polymers, surfactants, inorganic fine particles and the like can be cited. These emulsifiers can be used singly or in combination of two or more. The emulsifier can be appropriately selected according to the type of resin component constituting the wall film and the like. For example, when the resin component is an epoxy resin, proteins such as gelatin and casein are preferably used as emulsifiers in addition to polysaccharides such as gum arabic. Moreover, for example, when using a melamine formaldehyde resin as a resin component, it is preferable to use an ethylene maleic anhydride copolymer etc. as an emulsifier. Moreover, when polyurethane (isocyanate) is used as a resin component, gelatin, polyvinyl alcohol, etc. can be used.

As the wall film, it is generally preferable to use a resin-based wall film. As the resin, for example, various thermoplastic resins and thermosetting resins can be used. More specifically, epoxy resins, polyamide resins, acrylonitrile resins, polyurethane resins, polyurea resins, urea resins, melamine-formaldehyde resins, benzomelamine resins, butylated melamine resins, , Butylated urea resin, urea-melamine resin, etc. These resin components can be used alone or in combination of two or more. When producing microcapsules, these raw materials can be used to polymerize and microencapsulate.

(4) Method for producing thermochromic microcapsules

As a method for producing the thermochromic microcapsules of the present invention, it can be carried out according to known microencapsulation except for using the thermochromic composition of the present invention as a content. Examples of methods for microencapsulation include surface polymerization (polycondensation, polyaddition), in situ (insitu) polymerization, aggregation, in-liquid drying, spray drying, and the like.

Specifically, as an example of the method for producing microcapsules of the present invention, for example, microcapsules are suitably produced by a method including the following three steps. 1) In the first process, under the condition of presence or absence of solvent, the main raw materials (except crosslinking agent) capable of forming the film wall are mixed or dissolved with the thermochromic composition to prepare a solution; 2) In the second process, Add the obtained solution to an emulsifier aqueous solution to prepare an O/W emulsion; 3) The third step is to add a crosslinking agent or a solution thereof to the O/W emulsion. Hereinafter, each step will be described.

first process

In the first step, a solution is prepared by mixing or dissolving main raw materials capable of constituting a film wall (excluding the crosslinking agent) and the thermochromic composition in the presence or absence of a solvent.

As a thermochromic composition, what was demonstrated above was used. Usually, the usage-amount of a thermochromic composition is preferably 5-50 weight part with respect to 100 weight part of emulsifier aqueous solution, Especially preferably, it is 10-40 weight part. When the said usage-amount is less than 5 weight part, productivity may fall. On the other hand, when the amount used exceeds 50 parts by weight, emulsification may be difficult.

As the main raw material and the crosslinking agent, the components constituting the wall film described in (3) above can be used. In this case, it is particularly more preferable to set appropriately according to the method of microencapsulation. For example, in the case of microencapsulation by in situ polymerization, when the wall film is melamine resin, polyurea resin, etc., melamine, urea, etc. can be used as the main raw material and formalin can be used as the crosslinking agent. In the case of microencapsulation by the in situ polymerization method, when the wall film is a polyurethane resin or the like, an isocyanate compound can be used as a main raw material and a polyol can be used as a crosslinking agent. For example, in the case of microencapsulation by surface polymerization (polycondensation), when the wall film is epoxy resin or the like, an epoxy compound can be used as a main raw material and a polyamine compound can be used as a crosslinking agent. In the case of microencapsulation by surface polymerization (polycondensation), when the wall film is polyurethane resin, urea urethane resin, etc., it is possible to use isocyanate compound as the main raw material and polyamine compound, polyol, water, etc. agent. In the case of microencapsulation by surface polymerization (polycondensation), when the wall film is polyamide resin or the like, an acid chloride compound can be used as a main raw material and a polyamine compound can be used as a crosslinking agent. In the case of microencapsulation by surface polymerization (addition polymerization), when the wall film is an acrylic resin or the like, an acrylic compound can be used as a main raw material and a peroxy compound can be used as a crosslinking agent.

The usage amounts of the main raw material and the crosslinking agent are not particularly limited. The main raw material can be suitably set in the range of 1-50 weight part normally with respect to 100 weight part of emulsifier aqueous solution, Preferably it is 2-10 weight part. The crosslinking agent can be suitably set in the range of 0.5-25 weight part normally with respect to 100 weight part of emulsifier aqueous solutions, Preferably it is 1-5 weight part. When the amount of the main raw material or the crosslinking agent used is too small or too large, the reaction may become insufficient and the strength, heat resistance, etc. of the capsule (membrane) may decrease.

In the first step, a solvent may be used as necessary. As the solvent, those listed above can be used.

The usage-amount of a solvent is not limited, It can set suitably within the range of 0-100 weight part normally with respect to 100 weight part of emulsifier aqueous solution, Preferably it is 0-40 weight part.

second process

In the second step, the obtained solution is added to an aqueous emulsifier solution to prepare an O/W emulsion.

As the emulsifier aqueous solution, an aqueous solution obtained by dissolving the above-mentioned emulsifier in water can be used. The concentration of the emulsifier aqueous solution can be appropriately set according to the type of emulsifier, etc., but usually it is preferably 0.1 to 15% by weight, and particularly preferably 0.5 to 8% by weight. When the above concentration is less than 0.2% by weight, emulsification may be difficult. When the above-mentioned concentration exceeds 15% by weight, foaming may occur.

In the present invention, the preparation of the O/W emulsion can be carried out by known methods such as stirring method and membrane permeation method. The droplet diameter of the O/W emulsion at this time can be appropriately set within a range of about 0.1 to 20 μm.

third process

In the third step, a crosslinking agent or a solution thereof is added to the O/W emulsion. As the crosslinking agent, various crosslinking agents listed above can be used. As a solution of a crosslinking agent, for example, an aqueous solution of a crosslinking agent obtained by dissolving a crosslinking agent in water is preferably used. The concentration of the aqueous solution at this time is not limited, but it is usually preferably within a range of about 1 to 100% by weight. The method of adding the crosslinking agent is not particularly limited, but it is preferably added dropwise.

In addition, as a special example, when an isocyanate compound is used as a raw material for the wall film, an amine compound produced by a reaction between water and isocyanate in an aqueous emulsifier solution can be used as a crosslinking agent without newly adding a crosslinking agent.

After adding a crosslinking agent or a solution thereof, the crosslinking proceeds, and when the crosslinking is completed, desired microcapsules can be obtained in the form of a slurry. Thereafter, if necessary, the microcapsules are recovered in a solid state by a known solid-liquid separation method such as filtration or centrifugation. In addition, the microcapsules can also be washed as needed.

Example

Examples and comparative examples are shown below to further clarify the characteristics of the present invention. However, the present invention is not limited to the Examples.

Examples 1-14 and Comparative Examples 1-4

While heating each component shown in Table 1 at 120-180 degreeC, it mixed uniformly with the stirrer, and prepared each thermochromic composition.

Examples 15-25 and Comparative Examples 5-7

Using the materials shown in Table 2, the thermochromic compositions obtained in Examples 2-4 and 7-14 and Comparative Examples 5-7 were microencapsulated. Table 3 shows the corresponding relationship of the thermochromic composition.

First, the main resin agent (main raw material) and the thermochromic composition as the capsule wall film are uniformly mixed and dissolved using a dissolution aid (solvent) to obtain a solution. Next, the above-mentioned solution was added to the emulsifier aqueous solution heated at 30 to 60° C., while performing medium-shear stirring. Next, by performing high-shear stirring, an O/W emulsion (particle diameter of droplets: about 5 μm) was obtained from the above solution. Then, switch to low-shear stirring, and add a crosslinking agent aqueous solution dropwise to the above-mentioned O/W emulsion. After reacting at a temperature of 60-90° C. for 3-12 hours, cool to room temperature to obtain a slurry in which microcapsules are dispersed.

[Table 2]

Thermochromic composition (content) 10.0 Resin main agent TDI prepolymer*1 3.6 Dissolving aid Ethyl acetate 10.0 acetone 5.0 Emulsifier in water 4% - Gelatin in water 71.4 total 100.0

*1 Trimethylolpropane adduct of toluene diisocyanate

[table 3]

Embodiment 26～4l

In the microcapsules of Example 18 (ie, the thermochromic composition of Example 7), the color formers were changed as shown in Table 4.

Test example 1

The thermochromic properties of the thermochromic compositions and microcapsules obtained in Examples and Comparative Examples were examined.

<Production of samples>

In Examples 1 to 14 and Comparative Examples 1 to 4, 0.05 g of a thermochromic composition heated to 70 to 100° C. was dropped onto No. 5 filter paper, and impregnated by heating at 120° C. for 10 minutes to obtain the measured Color samples.

In Examples 15-41 and Comparative Examples 5-7, the microcapsule slurry cooled to room temperature was coated on No. 1 filter paper by the knife coating method, and dried at room temperature for 2 hours to obtain a sample for color measurement.

<Evaluation>

The color measurement of the sample was performed using a color difference meter (trade name "CR-300", manufactured by Minolta), and the color density was expressed by the color difference ΔE* from the white calibration plate.

As a measurement sequence, the color measurement was repeated by heating from -10°C at 1°C each time to the temperature at which the sample was completely decolorized. As shown by the solid line in FIG. 2 , the color difference ΔE* corresponding to the temperature (horizontal axis) is plotted to obtain an achromatic curve.

Cool the sample from the temperature at which the sample is completely decolorized to -10°C at 1°C each time, and repeat the color measurement. As shown by the dotted line in FIG. 2 , the color difference ΔE* was plotted against the temperature (horizontal axis) to obtain a color development curve.

In the above-mentioned achromatic curve and color development curve, as shown in Figure 3, the color change range of the maximum value (ΔE*max) and the minimum value (ΔE*min) of the color difference ΔE* of each curve is taken as ΔE, and each curve The temperature corresponding to [ΔE*min+(ΔE/2)] is used as the discoloration temperature (decolorization temperature t1, color development temperature t2). Here, although FIG. 3 is a diagram illustrating the achromatic curve, the color development curve also coincides with it.

Next, from the t1 and t2 obtained above, the discoloration temperature lag ΔH=|t2-t1| (absolute value) is obtained. The results are shown in Table 2.

As shown in Table 1, it can be seen that the thermochromic compositions shown in Examples 1-14 and Comparative Examples 1-4 all develop color to black at low temperature, and lose color and become colorless when heated above a specific temperature. The examples 1-6 of using the desensitizing agent A fatty acid methyl ester and the desensitizing agent B fatty acid amide alone, compared with the comparative examples 1 and 2 using the common desensitizing agent lauryl laurate or stearyl laurate, It has the same level of color density, and the undercolor (color residue) is suppressed to be low, showing good decolorization and color development performance. Examples 7 and 8 in which desensitizing agent A fatty acid methyl ester and desensitizing agent B fatty acid amide are used in combination, and comparative example 3 in which fatty acid amide is combined with general-purpose desensitizing agent lauryl laurate or stearyl laurate Compared with , 4, it has a high color concentration, and the background color is suppressed lower, showing good decolorization and color development performance. Compared with Comparative Examples 1-4, Examples 9 to 12 in which two kinds of desensitizing agent A fatty acid methyl esters and one or two kinds of desensitizing agent B fatty acid amides were used in combination also exhibited good decolorization and color development performance. In addition, Examples 13 and 14 in which an ultraviolet absorber was blended also exhibited favorable decolorization and color development performance compared with Comparative Examples 1 to 4.

From the results in Table 3, it can be seen that the encapsulated thermochromic compositions shown in Examples 15-25 and Comparative Examples 5-7 all develop black color at low temperature, and lose color and become colorless when heated above a specific temperature. . Examples 15-17 (capsules of Examples 2-4) using the desensitizer A fatty acid methyl ester alone, and comparative examples 5 and 6 ( Compared with the capsules of Comparative Examples 1 and 2), it has the same degree of color development density, and the bottom color (color residue) is suppressed to be low, showing good decolorization and color development performance. Examples 18-23 (capsules of Examples 7-12) using one or two desensitizer A fatty acid methyl esters and one or two desensitizer B fatty acid amides in combination, and the general desensitizer lauryl Compared with Comparative Example 7 (capsules of Comparative Example 3) in which fatty acid amide was combined with stearyl acid stearyl ester, it had the same degree of color development concentration, and the background color (color residue) was suppressed lower, showing good disappearance. Color hair color performance. In Examples 18 and 19 (capsules of Examples 7 and 8) using fatty acid methyl esters and two fatty acid amides in combination, compared with Examples 16 and 17 (capsules of Examples 3 and 4) using fatty acid methyl esters alone, The hysteresis of the discoloration temperature was narrowed by 4°C and 5°C, showing good discoloration behavior close to the decolorization and color development temperature. On the other hand, the difference in the color change hysteresis of Comparative Example 7 (capsule of Comparative Example 3) in which two types of fatty acid amides were combined in the general-purpose desensitizer and Comparative Example 6 (capsule of Comparative Example 2) using the general-purpose desensitizer alone At only 1°C, the hysteresis improvement effect of combining fatty acid amide with fatty acid methyl ester was not exhibited. In addition, Examples 24 and 25 (capsules of Examples 13 and 14) to which the ultraviolet absorber was added had good color development performance and color development and color function. The sample without UV absorber was exposed through Blue Scale 3 levels to see the bottom color (color difference ΔE=30 before and after exposure), but the color difference before and after exposure of Examples 24 and 25 were ΔE=8 and 11 respectively, and the light resistance was obtained. improve.

According to the results in Table 4, it can be seen that Examples 26-40, which are the same as Example 18 (capsules of Example 7) except for the color-forming agent, develop colors at low temperatures into various colors, and if heated above a specific temperature, all of them disappear. Color becomes colorless.

Claims (7)

1. A thermochromic composition, characterized in that: Contains electron-donating chromogenic organic compounds, electron-accepting compounds and desensitizers, As the desensitizing agent, one or both of (1) a fatty acid methyl ester having 5 or more carbon atoms and (2) a fatty acid amide having 4 or more carbon atoms is contained. 2. The thermochromic composition as claimed in claim 1, characterized in that: The fatty acid methyl ester is at least one of methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate and methyl behenate. 3. The thermochromic composition as claimed in claim 1, characterized in that: The fatty acid amide is at least one of stearic acid amide, behenic acid amide, oleic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide and erucamide. 4. The thermochromic composition as claimed in claim 1, characterized in that: The color change temperature lag is less than 5°C. 5. A thermochromic microcapsule, characterized in that: Formed by containing the composition according to claim 1 in microcapsules. 6. A method for producing a thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound and a desensitizing agent, characterized in that: When blending (1) fatty acid methyl ester with a total of 5 or more carbon atoms and (2) fatty acid amide with a total of 4 or more carbon atoms as the desensitizer, the hysteresis is changed by changing the ratio of the two to obtain A thermochromic composition having a desired color change temperature hysteresis. 7. The manufacturing method according to claim 6, characterized in that: The color change temperature lag is less than 5°C.

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