JP7297624B2 - Ink, method for producing the ink, and temperature indicator using the ink - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technology of a temperature indicator for checking temperature change of a temperature-controlled object, and more particularly to a temperature-sensing water-based ink for marking a temperature indicator, a manufacturing method of the water-based ink, and a temperature indicator using the water-based ink. It relates to indicators.

Perishable foods, frozen foods, and cold-preserved pharmaceuticals (eg, vaccines, biopharmaceuticals) are required to be kept within a predetermined temperature range without interruption during the distribution processes of production, transportation, storage, and sale. Therefore, conventionally, a method of constantly measuring and recording the temperature during the distribution process by installing a data logger capable of continuously recording time and temperature in a shipping container has often been adopted.

The method using data loggers has the advantage of being able to clarify when temperature troubles occur if there is temperature-induced damage to the product. However, this method is suitable for bulk management of a large amount of products, and has a weakness in terms of cost for individual management of individual products.

On the other hand, there is a method of using a temperature indicator instead of a data logger as a method of individually controlling the temperature of each product. A temperature indicator is a member that changes the color of a marker portion when the temperature exceeds or falls below a preset temperature so that the change in ambient temperature can be known. Although temperature indicators do not have the recording accuracy of data loggers, they are suitable for managing individual products because they are attached to individual products. A temperature sensing material is used in the color changing marker portion.

In addition, by making the temperature sensing material ink-like (i.e., using temperature sensing ink), various printing methods can be used as markings on the temperature indicator (eg, characters, symbols, one-dimensional barcodes, two-dimensional barcodes). (eg, gravure printing, screen printing, dispenser, inkjet printing) can be utilized.

Patent Document 1 discloses a homogeneous phase solution of an electron-donating color-forming organic compound, an electron-accepting compound, and a reaction medium for controlling the color reaction between the electron-donating color-forming organic compound and the electron-accepting compound. Disclosed is a reversible thermochromic writing oil-based ink composition comprising at least a microcapsule pigment encapsulating a reversible thermochromic composition comprising and an organic solvent.

Patent Document 2 discloses a temperature sensing material comprising a temperature indicating material containing a leuco dye, a developer and a decolorant, and a matrix material, wherein the matrix material is a non-polar material, and the melting point of the matrix material is is higher than the melting point of the temperature indicating material, and forms a phase separation structure in which the temperature indicating material is dispersed in the matrix material. Further, Patent Literature 2 discloses a temperature sensing ink containing the temperature sensing material and a solvent.

JP 2005-320485 A WO2018/110200

As noted above, the use of temperature sensitive inks allows for the use of various printing methods for marking the temperature indicators. Here, marking by inkjet printing is preferable from the viewpoint of the manufacturing cost of the temperature indicator. Moreover, from the viewpoint of environmental protection, it is preferable to use water-based ink.

It is clear that the technique described in Patent Literature 1 relates to oil-based ink compositions and not water-based inks. On the other hand, Patent Document 2 suggests the possibility of water-based ink. However, Patent Document 2 does not specifically disclose the dispersibility of the temperature sensing material in the water-based ink.

In other words, there is a demand for a temperature-sensing water-based ink in which it is easy to ensure and maintain the dispersibility of the temperature-sensing material in the ink (in other words, a temperature-sensing water-based ink with excellent stability).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a temperature-sensing water-based ink with excellent stability, a method for producing the temperature-sensing water-based ink, and a temperature indicator using the temperature-sensing water-based ink.

(I) One aspect of the present invention is an ink in which temperature sensing particles are dispersed in an aqueous dispersion medium,
An ink is provided in which the temperature-sensing particles include a temperature-sensing material containing a leuco dye, a developer, and a decolorant, and a surfactant.

(II) Another aspect of the present invention is a method for producing the above ink,
a temperature sensing material preparation step of mixing, melting, and solidifying the leuco dye, the color developer, and the color erasing agent to prepare the temperature sensing material;
an emulsion preparing step of preparing an emulsion of the temperature sensing material/surfactant by heating and stirring the temperature sensing material and the surfactant solution;
a suspension preparation step of preparing a suspension of temperature sensing particles/aqueous dispersion medium by stirring and mixing the heated emulsion and the heated aqueous dispersion medium, and then cooling to room temperature while stirring;
A method for producing an ink characterized by having

(III) Still another aspect of the present invention is a temperature indicator in which a marker is printed with a predetermined ink on a printing substrate,
A temperature indicator is provided, wherein the predetermined ink is the ink described above.

ADVANTAGE OF THE INVENTION According to this invention, the temperature-sensing water-based ink which is excellent in stability, the method of manufacturing the said temperature-sensing water-based ink, and the temperature indicator using the said temperature-sensing water-based ink can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows a temperature sensing material and the principle of its color change, (a) represents a decoloring state, (b) represents a developing state. FIG. 10 is a schematic diagram showing how the temperature detection material of the high temperature side detection type changes in color; FIG. 4 is a schematic diagram showing how a low temperature side detection type temperature detection material changes color; 1 is a schematic diagram showing a configuration example of a temperature-sensing water-based ink according to the present invention; FIG. It is a cross-sectional schematic diagram which shows an example of a temperature detection particle. It is a cross-sectional schematic diagram which shows another example of a temperature detection particle. It is process drawing which shows an example of the manufacturing method of the temperature detection ink which concerns on this invention. 4 is a photograph showing a color change of printed characters in a temperature indicator using the temperature-sensing water-based ink of Example 1. FIG.

The present invention can add the following improvements and changes to the ink (I) described above.
(i) In the temperature sensing particles, fine particles of the temperature sensing material, in which the leuco dye and the developer are dispersed in the decolorant matrix, are coated with the surfactant.
(ii) In the temperature sensing particles, the surfactant is also present inside the temperature sensing particles.
(iii) The temperature sensing particles have a median diameter of 0.1 μm or more and 100 μm or less.
(iv) The temperature sensitive water-based ink further comprises an additive.
(v) the additive is a water-soluble resin binder, a conductive agent and/or a leveling agent;
(vi) The temperature-sensing water-based ink includes a plurality of types of temperature-sensing particles having different color development start temperatures, and each of the plurality of types of temperature-sensing particles develops color at a predetermined temperature or lower. A temperature sensing particle comprising a sensing type temperature sensing material.
(vii) The temperature-sensing water-based ink includes a plurality of types of temperature-sensing particles having different color development start temperatures, and each of the plurality of types of temperature-sensing particles develops color at a predetermined temperature or higher. A temperature sensing particle comprising a sensing type temperature sensing material.
(viii) The temperature-sensing water-based ink contains a plurality of types of temperature-sensing particles having color development start temperatures different from each other, and the plurality of types of temperature-sensing particles are a low-temperature side detection type that develops at a predetermined temperature or lower. and temperature sensing particles containing a high-temperature-side sensing type temperature sensing material that develops color at a predetermined temperature or higher.

According to the present invention, the following improvements and changes can be made in the ink manufacturing method (II) described above.
(ix) After the suspension preparation step, the method further includes an additive mixing step of mixing an additive into the suspension.
(x) The step of preparing the temperature sensing material includes a pulverization process to granulate the temperature sensing material from lumps.

Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings. The present invention is not limited to the embodiments described here, and can be appropriately combined with known techniques or improved based on known techniques without departing from the technical idea of the invention. . The same reference numerals may be used for synonymous substances and processes (including cases where the difference is small).

[Temperature sensing material and its color change]
First, the temperature sensing material used in the present invention and its color change will be briefly described. FIG. 1 is a schematic diagram showing a temperature sensing material and the principle of its color change, where (a) represents a color-erased state and (b) represents a color-developed state.

The temperature sensing material 4 is a material whose color density reversibly changes with changes in temperature (increase/decrease in temperature), and as shown in FIG. Contains a developer 2 and a decolorizer 3 to control the temperature range of color change. The state in which the leuco dye 1 and the developer 2 are separated and dispersed in the decolorant 3 is the decolorized state (see FIG. 1(a)). and the color developer 2 are in a developed state (see FIG. 1(b)).

Next, the relationship between the temperature of the temperature sensing material 4 and color change will be briefly described with reference to FIGS. FIG. 2 is a schematic diagram showing color change of the high temperature side detection type temperature sensing material, and FIG. 3 is a schematic diagram showing color change of the low temperature side detection type temperature sensing material. In FIGS. 2 and 3, the vertical axis is color density, the horizontal axis is temperature, Ta is the color development start temperature, _{and T d is} the color disappearance start temperature.

In the high temperature side detection type temperature sensing material 4, it is preferable to use a material that is difficult to crystallize as the decolorizing agent 3. As shown in FIG. When the high-temperature side detection type temperature sensing material 4 is rapidly cooled from the temperature M in the molten state (the colorless state in which the leuco dye 1 and the color developer 2 are separated) to the color development start temperature T _{a or} less, the color disappears. The agent 3 is solidified in an amorphous state, and the leuco dye 1 and the developer 2 are frozen in a separated state (that is, in a decolorized state).

As shown in FIG. 2, when the temperature is gradually increased from this frozen state, the decolorizing agent 3 begins to crystallize at the color development start temperature T _a , and leuco crystals are formed along with rearrangement of molecules for crystallization. Dye 1 and developer 2 combine to develop color. The developing state is maintained while the decolorizing agent 3 is crystallized. When the temperature further rises, the crystals of the decolorizing agent 3 begin to melt at the decoloring start temperature T _d , and the leuco dye 1 and developer 2 separate and decolorize. That is, the color density change exhibits hysteresis with respect to temperature change.

Using such a property of color change, the presence or absence of color change can be detected by using a high-temperature side detection type temperature detection material 4 prepared so that the color development start temperature T _a is the upper limit temperature of the object to be temperature-controlled. It is possible to detect whether or not the temperature of the object to be temperature-controlled has reached the upper-limit control temperature from the presence or absence of color development.

On the other hand, in the low-temperature side detection type temperature sensing material 4, it is preferable to use a material that is difficult to solidify (a material that easily maintains a supercooled liquid phase) as the decolorant 3. When the low-temperature side detection type temperature sensing material 4 is slowly cooled from the molten state temperature M, the decolorizing agent 3 becomes a supercooled liquid phase and the decolorizing state (leuco dye 1 and developer 2 separate state).

As shown in FIG. 3, when further cooled from this supercooled liquid phase state, the decolorizing agent 3 begins to crystallize at the color development start temperature T _a , and along with the rearrangement of the molecules for crystallization The leuco dye 1 and developer 2 combine to develop color. After that, even if the temperature rises, the developing state is maintained while the decolorizing agent 3 is crystallized. When the temperature further rises, the crystals of the decolorizing agent 3 begin to melt at the decoloring start temperature T _d , and the leuco dye 1 and developer 2 separate and decolorize. That is, the color density change exhibits hysteresis with respect to temperature change.

Using such a property of color change, the presence or absence of color change can be detected by using a low-temperature side detection type temperature detection material 4 prepared so that the color development start temperature T _a is the lower limit temperature of the object to be temperature-controlled. It can be detected whether or not the temperature of the object to be temperature-controlled has reached the lower-limit control temperature from the presence or absence of color development.

[Temperature detection water-based ink]
Next, a temperature-sensing water-based ink according to one embodiment of the present invention will be described.

FIG. 4 is a schematic diagram showing a configuration example of temperature-sensing water-based ink. As shown in FIG. 4, the temperature-sensing water-based ink 100 includes an aqueous dispersion medium 20 and temperature-sensing particles 10 and/or 11 dispersed in the aqueous dispersion medium, and the temperature-sensing particles 10 and 11 contain a leuco dye. 1, a temperature sensing material 4 containing a developer 2 and a decolorant 3, and a surfactant 5. The temperature-sensing water-based ink 100 may further contain various additives (eg, water-soluble resin binder 30 and other additives 40) in order to meet the properties required according to the application.

From the viewpoint of ease of printing and print quality, the content of the temperature sensing particles 10 and 11 in the water-based temperature sensing ink 100 is preferably 5% by mass or more and 20% by mass or less. By setting the content of the temperature-sensing particles in the ink to 5% by mass or more, the color developability of the printed matter is enhanced and the visibility of the printed matter is improved. By setting the content of the temperature-sensing particles in the ink to 20% by mass or less, aggregation of the temperature-sensing particles can be suppressed. In the case of inkjet printing, it is more preferably 5% by mass or more and 10% by mass or less.

The content of the water-soluble resin binder 30 in the water-based temperature sensing ink 100 is preferably 1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 15% by mass or less. By setting the content of the water-soluble resin binder in the ink to 1% by mass or more, the abrasion resistance of the printed matter is improved, and peeling of the printed matter can be suppressed. By setting the content of the water-soluble resin binder in the ink to 30% by mass or less, it is possible to suppress an increase in the viscosity of the ink and enable more stable printing.

The temperature-sensing water-based ink 100 is not limited to one color development start temperature T _a (develops when the temperature is equal to or higher than a predetermined temperature, or when the temperature is lower than or equal to a predetermined temperature). A plurality of types of temperature sensing particles 10 and 11 having different color development start temperatures T _a may be included so as to indicate the temperature T _a . In other words, in the water-based temperature-sensing ink 100 of the present invention, each of the temperature-sensing particles 10 and 11 is independently coated with the surfactant 5, so even if a plurality of types of temperature-sensing particles are mixed, chemical have the advantage of not interfering with each other (exhibit different color development start temperatures T _a ).

For example, if two or more types of temperature sensing particles including a high temperature side sensing type temperature sensing material 4 that develops color at a predetermined temperature or higher are included, two or more temperatures can be sensed, and high temperature side temperature sensing resolution can be obtained. improves. Similarly, if two or more types of temperature sensing particles including the low temperature side sensing type temperature sensing material 4 that develops color at a predetermined temperature or less are included, the temperature sensing resolution on the low temperature side is improved. In addition, if both the temperature detection particles including the high temperature side detection type temperature detection material 4 and the temperature detection particles including the low temperature side detection type temperature detection material 4 are included, both the upper limit temperature and the lower limit temperature can be managed. can do.

The surfactant does not necessarily have to completely cover the surface of the temperature sensing particles. In the present invention, the term "coating" means that the surfactant surrounds most of the surface of the temperature sensing particle (for example, 60% or more of the total surface).

Moreover, although it is most desirable that the temperature sensing particles 10 and 11 are evenly dispersed in the aqueous dispersion medium 20, the temperature sensing particles 10 and 11 may be dispersed in a state of aggregation to some extent. In other words, the water-based temperature-sensing ink 100 of the present invention includes the temperature-sensing particles 10 and 11 dispersed in the water-based dispersion medium 20 in a state of aggregation to some extent.

(Temperature sensing particle)
FIG. 5A is a schematic cross-sectional view showing an example of temperature sensing particles, and FIG. 5B is a schematic cross-sectional view showing another example of temperature sensing particles. Note that both FIGS. 5A and 5B show an erased state. As shown in FIG. 5A, the temperature sensing particles 10 are composed of fine particles of a temperature sensing material 4 in which leuco dye 1 and developer 2 are dispersed in a matrix of decolorant 3, and surfactant 5 is coated around the fine particles. ing.

Further, as shown in FIG. 5B, in the temperature sensing particles 11, the surfactant 5 exists not only around the fine particles of the temperature sensing material 4 but also inside the temperature sensing particles. The temperature sensing particles 11 involve the surfactant 5 in the process of forming fine particles of the temperature sensing material 4, and/or a plurality of fine temperature sensing particles 10 aggregate/ It is thought that it is obtained by coalescing.

By coating the surface of the fine particles of the temperature sensing material 4 with the surfactant 5, when the water-based temperature sensing ink 100 is prepared, the water-soluble resin binder 30 and the additive 40 have no unwanted influence on the temperature sensing material 4 ( For example, unwanted chemical reactions can be suppressed.

It is preferable to adjust the particle size/particle size distribution of the temperature sensing particles 10 and 11 from the viewpoint of compatibility with various printing methods/printing apparatuses and from the viewpoint of ink storage stability. The particle size/particle size distribution of the temperature detection particles 10 and 11 can be measured by, for example, a particle size distribution measuring device, and the median diameter (also referred to as _D50 ) is preferably 0.1 μm or more and 100 μm or less, and 0.1 μm or more and 10 μm or less is more preferable. In the case of inkjet printing, the median diameter is more preferably 0.1 μm or more and 2 μm or less in order to suppress nozzle clogging.

(leuco dye)
The leuco dye 1 constituting the temperature sensing material 4 is an electron-donating compound, and known dyes for pressure-sensitive copying paper and heat-sensitive recording paper can be used. For example, triphenylmethanephthalide, fluorane, phenothiazine, indolylphthalide, leuco auramine, spiropyran, rhodaminelactam, triphenylmethane, triazene, spirophthalanexanthene, naphtholactam, Azomethine-based leuco dyes can be mentioned.

More specific examples include 9-(N-ethyl-N-isopentylamino)spiro[benzo[a]xanthene-12,3'-phthalide], 2-methyl-6-(Np-tolyl-N- Ethylamino)-fluorane 6-(diethylamino)-2-[(3-trifluoromethyl)anilino]xanthene-9-spiro-3'-phthalide, 3,3-bis(p-diethylaminophenyl)-6-dimethylamino phthalide, 2'-anilino-6'-(dibutylamino)-3'-methylspiro[phthalido-3,9'-xanthene], 3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl -2-methylindol-3-yl)-4-azaphthalide, 1-ethyl-8-[N-ethyl-N-(4-methylphenyl)amino]-2,2,4-trimethyl-1,2-dihydro spiro[11H-chromeno[2,3-g]quinoline-11,3′-phthalide], and the like.

Two or more leuco dyes 1 may be used in combination.

(developer)
The color developer 2 that constitutes the temperature sensing material 4 changes the chemical structure of the leuco dye 1 by combining with the electron-donating leuco dye 1 to develop color. A known developer for paper can be used. Further, the developer is not limited to the developer for pressure-sensitive copying paper or thermosensitive recording paper, and the developer 2 may be any compound that is an electron acceptor and can change the color of the leuco dye 1 .

For example, metal salts of carboxylic acid derivatives, metal salicylates, metal salicylates, sulfonic acids, sulfonates, phosphoric acids, metal phosphates, acid phosphates, acid phosphate metal salts, phosphites, nitrites Phosphate metal salts can be preferably used. Those having high compatibility with the leuco dye 1 and the decolorizing agent 3 described later are particularly preferable.

More specific examples include benzyl 4-hydroxybenzoate, 2,2'-biphenol, 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane, 2,2-bis(3-cyclohexyl-4 -hydroxyphenyl)propane, bisphenol A, bisphenol F, bis(4-hydroxyphenyl)sulfide, paraoxybenzoic acid ester, gallic acid ester, phenols such as 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1-bis(4-hydroxy-3-methylphenyl)cyclohexane, α,α,α'-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene.

Two or more color developers 2 may be used in combination. By combining a plurality of types of developers 2, the color density of the leuco dye 1 during development can be adjusted. The mixing ratio of the developer 2 to the leuco dye 1 can be appropriately selected according to the desired color density. For example, about 0.1 to 100 parts by weight of developer 2 may be mixed with 1 part by weight of leuco dye.

(Decoloring agent)
The decolorizing agent 3 constituting the temperature sensing material 4 is a compound capable of dissociating the bond between the leuco dye 1 and the developer 2, and controls the color development temperature between the leuco dye 1 and the developer 2. It is also a compound that can In general, within the temperature range in which the leuco dye 1 and the developer 2 combine to form a color, the decolorizer 3 is in a crystallized solid state. On the other hand, when the decolorizing agent 3 is in a melted liquid phase state, it exerts a function of dissociating the bond between the leuco dye 1 and the developer 2, resulting in a decolored state. Therefore, the state change temperature of the decolorizing agent 3 is important for controlling the developing temperature.

The decolorizing agent 3 is a material that does not change the chemical structure of the leuco dye 1 (that is, does not develop the color), and can dissociate the bond between the leuco dye 1 and the developer 2 (leuco dye 1 and the developer 2). The binding strength between the color developer 2 and the decoloring agent 3 is greater than the binding strength with the coloring agent 2). For example, hydroxy compounds, ester compounds, glycerol compounds, acetate compounds, peroxy compounds, carbonyl compounds, aromatic compounds, aliphatic compounds, halogen compounds, amino compounds, imino compounds, N-oxide compounds, hydroxylamine compounds, nitro compounds, azo compounds, diazo compounds, azide compounds, ether compounds, oil compounds, sugar compounds, peptide compounds, nucleic acid compounds, alkaloid compounds, and steroid compounds.

Specific examples of ester compounds include isopropyl myristate, diethyl sebacate, dimethyl adipate, decyl decanoate, diethyl phenylmalonate, diisobutyl phthalate, triethyl citrate, benzyl butyl phthalate, methyl nicotinate, phenylacetate 2- Phenyl ethyl, benzyl cinnamate, methyl acetoacetate, dimethyl succinate, dimethyl sebacate, monoolein, ethyl stearate, methyl palmitate, di-n-octyl phthalate, benzyl benzoate, diethylene glycol dibenzoate, propionic acid 2 -phenylethyl, butyl stearate, methyl myristate, methyl anthranilate, isopropyl palmitate, ethyl 4-fluorobenzoate, ethyl 2-bromopropionate, tristearin, ethyl 1,3-dibromobutyrate, dimethyl adipate, 2 -ethyl palmitate, diethyl terephthalate, phenyl stearate, methyl arachidate, methyl 4-chlorobenzoate, dimethyl dodecanedioate, diethyl formaminomalonate, methyl pentadecanoate, ethyl arachidate, ethyl benzilate, dicyclohexyl phthalate , Isobutyl 4-aminobenzoate, Butyl 4-hydroxybenzoate, Monoethyl fumarate, Methyl benzylate, Diphenyl phthalate, Phenyl benzoate, Methyl 3-nitrobenzoate, Methyl 3-hydroxy-2-naphthoate, Citric acid trimethyl, ethyl 4-aminobenzoate, methyl 4-nitrobenzoate, 2-naphthyl benzoate, dimethyl fumarate, adiphenine hydrochloride, ethyl 4-hydroxybenzoate, vinyl butyrate, methyl 4-iodobenzoate, propyl gallate , 1,4-diacetoxybenzene, diethyl allylmalonate, diethyl bromomalonate, diethyl ethoxymethylenemalonate, diethyl ethylmalonate, diethyl fumarate, diethyl maleate, diethyl malonate, diethyl phthalate, ethyl benzoate, 4- (dimethylamino) ethyl benzoate, ethyl nicotinate, benzyl laurate, benzyl acetate, methyl phenylacetate, phenyl acetate, diethyl succinate, tributyrin, diethyl methylmalonate, dimethyl oxalate, dibenzyl malonate, dimethyl maleate, terephthalate Methyl aldehyde, diallyl phthalate, benzyl bromoacetate, methyl phenylpropiolate, isobutyl benzoate, dibutyl sebacate, diethyl adipate, diethyl terephthalate, dipropyl phthalate, diisopropyl adipate, sorbitan tristearate, sorbitan monostearate, Stearate amide, glycerol monostearate, glycerol distearate, stearyl acrylate, dibenzyl phthalate, dimethyl nitroterephthalate, ethyl coumarin-3-carboxylate, benzyl p-benzyloxybenzoate, 4-chloro-3-nitrobenzoate methyl acid, dimethyl terephthalate, methyl 4-amino-2-methoxybenzoate, and dimethyl 5-aminoisophthalate.

Specific examples of glycerol compounds include tricaprin, tripalmitin, ethylene glycol dibenzoate, and triolein. Specific examples of acetate compounds include 4-diacetoxybutane, 1,1-ethanediol diacetate, benzal diacetate, 1,4-diacetoxybutane, diethylene glycol diacetate, vitamin K4, 2,5-diacetate, Acetoxytoluene, 1,1-ethanediol diacetate. Specific examples of aromatic compounds include m-tolyl acetate, 1,2-diacetoxybenzene, and valetamate bromide. Specific examples of amino compounds include ethyl anthranilate and 4-aminobutyl benzoate. Specific examples of imino compounds include methyl N-methylanthranilate. Specific examples of nitro compounds include ethyl 4-nitrobenzoate.

Specific examples of steroid compounds include cholesterol, cholesteryl bromide, β-estradiol, methylandrostenediol, pregnenolone, cholesterol benzoate, cholesterol acetate, cholesterol linoleate, cholesterol palmitate, cholesterol stearate, cholesterol oleate, 3-chloro cholestene, cholesterol hydrocinnamate, cholesterol laurate, cholesterol butyrate, cholesterol formate, cholesterol heptanoate, cholesterol hexanoate, cholesterol myristate, cholesterol propionate, cholesterol phenylacetate, cholesterol chloroformate, 2,4-dichloro cholesterol benzoate, cholesterol oleyl carbonate, cholesterol amyl carbonate, cholesterol n-octyl carbonate, estrone, ethinyl estradiol, estriol, estradiol benzoate, α-estradiol, β-estradiol 17-heptanoate, 2-methoxy- β-estradiol, androsterone, abiraterone, dehydroepiandrosterone, dehydroepiandrosterone acetate, ethisterone, 17β-hydroxy-17-methylandrosta-1,4-dien-3-one, methylandrostenediol, 16- dehydropregnenolone acetate, 11α-hydroxyprogesterone, 17α-hydroxyprogesterone caproate, 17α-hydroxyprogesterone acetate, megestrol acetate, cortisone acetate, cortisone, cortexolone, deoxycorticosterone acetate, hydrocortisone, 6α-methylprednisolone, Prednisolone, prednisone, β-cholestanol, cholesterol-5α,6α-epoxide, diosgenin, ergosterol, β-sitosterol, stigmasterol, β-sitosterol acetate.

Two or more decolorizing agents 3 may be used in combination. By combining multiple types of decolorizing agents 3, it is possible to adjust the discoloration temperature and the time required for discoloration.

(Surfactant)
The surfactant 5 constituting the temperature sensing particles 10, 11 is for dispersing the temperature sensing material 4 in the aqueous dispersion medium 20, and various ionic surfactants (anionic, cationic, amphoteric) and various nonionic surfactants are available.

Examples of anionic surfactants include those in which the hydrophilic groups are composed of carboxylate, sulfonate, sulfate ester, and phosphate ester types. Examples of cationic surfactants include those in which the hydrophilic groups are composed of amine salts, pyridinium salts and benzyl halide salts. Examples of amphoteric surfactants include those in which the hydrophilic groups are composed of carboxylate, sulfonate, sulfate ester, and phosphate ester types. can be used.

Examples of nonionic surfactants include those whose hydrophilic groups are composed of esters, ethylene oxide, ethers, amine amides, and sorbitol.

(Aqueous dispersion medium)
The water-based temperature-sensing ink 100 of the present invention preferably has a pH (potential of hydrogen) adjusted to 6 or more and 8 or less in order to suppress the influence on the color development/discoloration characteristics of the temperature-sensing material. . The water-based dispersion medium 20 is not particularly limited as long as the temperature-sensing water-based ink 100 is adjusted to have an appropriate liquidity. There may be.

(Additive)
(1) Water-Soluble Resin Binder The water-soluble temperature-sensing ink 100 preferably contains a water-soluble resin binder 30 to help adjust the viscosity and adhere the temperature-sensing particles 10 and 11 to the temperature indicator substrate. As the water-soluble resin binder 30, for example, acrylic resin, urethane resin, phenol resin, polyester, polyethylene oxide, styrene/maleic acid, polyvinyl alcohol, and polyacrylamide can be preferably used. The content of the water-soluble resin binder 30 in the water-based temperature sensing ink 100 is preferably 1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 15% by mass or less.

(2) Conductive agent When applying the temperature-sensing water-based ink to a charge control type inkjet printer, it is desirable to adjust the electrical resistivity of the ink to 2000Ωcm or less from the viewpoint of printing controllability. The temperature sensing water-based ink 100 of the present invention may also include a conductive agent as another additive 40 to adjust electrical resistivity.

Since the conductive agent used here must be dissolved in the aqueous dispersion medium 20, a water-soluble salt is preferable. For example, nitrate, perchlorate, tetraphenylborate, and ammonium ion salt are preferably used. can. More specific examples include lithium nitrate, sodium nitrate, ammonium nitrate, lithium perchlorate, sodium perchlorate, ammonium perchlorate, lithium tetraphenylborate, sodium tetraphenylborate, and ammonium tetraphenylborate. mentioned.

(3) Leveling agent The temperature sensing water-based ink 100 of the present invention may contain a leveling agent as another additive 40 to adjust print quality.

(Method for producing temperature-sensing water-based ink)
Next, a method for producing the temperature-sensing water-based ink 100 according to the present invention will be described.

FIG. 6 is a process drawing showing an example of the method for producing the temperature sensing ink according to the present invention. As shown in FIG. 6, first, the leuco dye, the developer, and the decolorant are mixed, melted, and solidified so that the desired color development start temperature T _a and decoloration start temperature T _d are obtained, and the temperature is detected. A temperature sensing material preparation step (S1) for preparing material 4 is performed. Melting is preferably carried out in the temperature range of 150-250°C.

The adjusted temperature sensing material 4 can be used in the next step as it is in the form of a lump, but the lump may be pulverized into granules. Although the pulverization process is not an essential process, it is preferable from the viewpoint of smooth progress of the next step. The temperature sensing material preparation step S1 shall include a pulverization process.

Next, an emulsion preparation step (S2) is performed in which the temperature detection material 4 and the solution of the surfactant 5 are heated, stirred and mixed to prepare an emulsion 6 of the temperature detection material/surfactant. The mass ratio of “temperature detection material: surfactant” is preferably “1:1” to “1:5”, and the temperature range where the temperature detection material 4 becomes droplets (for example, 80 to 100 °C). Also, the droplet size of the temperature sensing material 4 can be adjusted by the stirring speed. In other words, the stirring speed is controlled in order to control the droplet size of the temperature sensing material 4 (the size of the subsequent temperature sensing particles 10, 11).

Next, after stirring and mixing the emulsion 6 heated to the temperature range in which the temperature sensing material 4 becomes droplets and the aqueous dispersion medium 20 heated to the temperature range, the temperature sensing particles are cooled to room temperature while stirring. / A suspension preparation step (S3) for preparing a suspension 7 of an aqueous dispersion medium is performed. As described above, the aqueous dispersion medium 20 is preferably adjusted to pH 6 to 8, and may be pure water or a buffer solution. The mixing amount of the aqueous dispersion medium 20 is preferably such that the mass ratio of "emulsion:aqueous dispersion medium" is from "1:5" to "1:10". As for the method of mixing the emulsion 6 and the aqueous dispersion medium 20 , the aqueous dispersion medium 20 may be injected into the emulsion 6 or the emulsion 6 may be injected into the aqueous dispersion medium 20 .

In the suspension preparation step S3, when the emulsion 6 and the aqueous dispersion medium 20 are mixed, since the temperature sensing material 4 is hydrophobic, the droplets of the temperature sensing material 4 are coated with the surfactant 5. As a result, an emulsion dispersed in the aqueous dispersion medium 20 is obtained. When this emulsion is cooled, the droplets of temperature sensing material 4 are solidified, and suspension 7 in which temperature sensing particles 10 and 11 are dispersed in aqueous dispersion medium 20 is obtained.

Next, an additive mixing step (S4) of mixing various additives (a water-soluble resin binder 30, a conductive agent and/or a leveling agent) into the suspension 7 is performed. The additive mixing step S4 is not an essential step, but is preferably performed from the viewpoint of adjusting the printing controllability and printing quality of the ink. This completes the temperature-sensing water-based ink 100 .

Although not shown in FIG. 6, when producing a temperature-sensing water-based ink containing a plurality of types of temperature-sensing particles having different color development start temperatures, separately prepared suspensions 7 or temperature-sensing The water-based ink 100 may be appropriately mixed.

EXAMPLES The present invention will now be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples.

[Experiment 1]
(Production of Example 1)
2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthene] (manufactured by Yamada Kagaku Kogyo Co., Ltd., S- 205) was used. Octyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a developer. As the decolorizing agent, a mixture of methyl p-toluate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2-phenylethyl phenylacetate (manufactured by Tokyo Chemical Industry Co., Ltd.) at a mass ratio of "9:1" was used. .

A mass ratio of 3:3:100 of leuco dye:developer:decolorizer was mixed, melted and stirred at 190° C., and then solidified to prepare a bulk temperature sensing material. The resulting mass was manually pulverized in a mortar to prepare a granular temperature sensing material (temperature sensing material preparing step S1). This temperature sensing material is colorless (colorless) in an environment maintained at room temperature (25°C), but once cooled to 4°C or less, it develops black.

0.5 g of the prepared temperature sensing material and 2 g of surfactant (Demoll (registered trademark) EP manufactured by Kao Corporation) were weighed and mixed with heating and stirring using a magnetic stirrer (95°C, 600 rpm, 10 minutes) A temperature sensing material/surfactant emulsion was prepared (emulsion preparation step S2).

Next, the emulsion at 95°C and an aqueous phosphate buffer solution (concentration 0.1 mol/L, pH = 7.0, 20 g) heated to 95°C were stirred and mixed (95°C, 600 rpm, 10 minutes). Thereafter, the mixture was cooled to room temperature while being stirred to prepare a temperature sensing particle/aqueous dispersion medium suspension (suspension preparation step S3).

In the suspension preparation step S3, when the emulsion and the phosphate buffer aqueous solution (aqueous dispersion medium) are stirred and mixed, the temperature sensing material is hydrophobic and forms spherical droplets in order to minimize interfacial energy. The liquid droplets are dispersed in the phosphate buffer aqueous solution in such a manner that the surfactant coats the liquid droplets, forming an emulsion. When the emulsion is cooled, the temperature sensing material droplets solidify into a suspension of spherical temperature sensing particles dispersed in an aqueous phosphate buffer solution.

The particle size distribution of the temperature sensing particles in the resulting suspension was measured using a particle size distribution analyzer (Model LS-230, manufactured by Beckman Coulter, Inc.), confirming that the median diameter was approximately 1 μm. bottom.

Next, the resulting suspension was mixed with a water-soluble resin binder to prepare the temperature-sensing water-based ink of Example 1 (additive mixing step S4). Polyvinyl alcohol (PVA) was used as the water-soluble resin binder and mixed so that the content of the water-soluble resin binder in the water-based temperature sensing ink was 5% by mass.

(Evaluation of Example 1)
A temperature indicator was produced using the water-based temperature-sensing ink of Example 1, and an experiment was conducted to confirm printability and temperature-sensibility. A commercially available DOD (Drop On Demand) ink jet printer was used as the printing device, and commercially available art paper was used as the printing substrate. A temperature change test (cooled to 4°C after holding at 25°C for 10 minutes) was performed on the produced temperature indicator, and the color change of the printed characters was visually confirmed. When the sample was colorless when kept at 25°C and when it was cooled to 4°C and the printed characters could be identified, it was evaluated as "acceptable".

FIG. 7 is a photograph showing a change in color of printed characters in the temperature indicator using the water-based temperature-sensing ink of Example 1. FIG. As shown in Fig. 7, when kept at 25°C, the printed characters are colorless and cannot be identified, but when cooled to 4°C, the printed characters are developed and the printed characters can be identified. That is, Example 1 is evaluated as "acceptable". The components and evaluation results of the temperature-sensing water-based ink of Example 1 are summarized in Table 1 below.

[Experiment 2]
(Production and evaluation of Comparative Example 1)
A particulate temperature sensing material was prepared in the same manner as in Example 1. After that, the granular temperature sensing material was pulverized using a jet mill to prepare a powdery temperature sensing material. When the particle size distribution of the obtained powdery temperature sensing material was measured using a particle size distribution analyzer, it was confirmed that the median diameter was about 2 μm.

Next, 0.5 g of the powdered temperature sensing material was added to an aqueous phosphate buffer solution (concentration 0.1 mol/L, pH = 7.0, 22 g) heated to 95°C, stirred and mixed (95°C, 600 rpm, 20 minutes) After forming the emulsion, it was cooled to room temperature while stirring to prepare a suspension of temperature sensing particles/aqueous dispersion medium.

Next, the resulting suspension was mixed with a water-soluble resin binder to prepare a water-based temperature-sensing ink of Comparative Example 1. Polyvinyl alcohol was used as the water-soluble resin binder and mixed so that the content of the water-soluble resin binder in the water-based temperature sensing ink was 5% by mass.

Next, a temperature indicator was produced in the same manner as in Example 1 using the water-based ink for temperature detection of Comparative Example 1. The same temperature change test as in Example 1 (holding at 25° C. for 10 minutes and then cooling to 4° C.) was performed on the produced temperature indicator. As a result, the printed characters remained colorless both at 25°C and after cooling at 4°C. That is, Comparative Example 1 was evaluated as "failed". The components and evaluation results of the temperature-sensing water-based ink of Comparative Example 1 are also shown in Table 1.

In order to check the soundness of the temperature-sensing particles themselves, the water-based temperature-sensing ink of Comparative Example 1 was brush-painted on a printing substrate, and then subjected to the same temperature change test as in Example 1 (after holding at 25°C for 10 minutes, cooling to 4°C) was performed. As a result, it was colorless both at 25°C and at 4°C, but it was confirmed that the temperature sensing particles were coated on the printing substrate.

Considering the reason why the color did not develop against the temperature change, it is possible that the temperature sensing particles themselves deteriorated due to the physical pulverization process by the jet mill.

[Experiment 3]
(Production and evaluation of Example 2)
In the additive mixing step S4, the water-based temperature-sensing ink of Example 2 was prepared in the same manner as in Example 1, except that lithium nitrate was mixed so that the content of the conductive agent in the water-based temperature-sensing ink was 5% by mass. was made.

Next, a temperature indicator was produced using the water-based temperature sensing ink of Example 2. A commercially available charge control type ink jet printer was used as the printing device, and commercially available art paper was used as the printing substrate. The same temperature change test as in Example 1 (holding at 25° C. for 10 minutes and then cooling to 4° C.) was performed on the produced temperature indicator. As a result, Example 2 was evaluated as "pass". The components and evaluation results of the temperature-sensing water-based ink of Example 2 are also shown in Table 1.

[Experiment 4]
(Production and evaluation of Examples 3 and 4)
In the emulsion preparation step S2, the temperature-sensing water-based ink of Example 3 was prepared in the same manner as in Example 1, except that Demoll (registered trademark) NL manufactured by Kao Corporation was used as the surfactant. A water-based temperature-sensing ink of Example 4 was prepared in the same manner as in Example 2, except that Demoll (registered trademark) NL manufactured by Kao Corporation was used as the agent.

A temperature indicator was produced using the water-based temperature sensing ink of Example 3 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 4.

The same temperature change test as in Example 1 (holding at 25° C. for 10 minutes and then cooling to 4° C.) was performed on the produced temperature indicator, and the color change of the printed characters was visually confirmed. As a result, both Examples 3 and 4 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 3 and 4 are also shown in Table 1.

[Experiment 5]
(Production and evaluation of Examples 5 and 6)
3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (manufactured by Yamada Kagaku Kogyo Co., Ltd., Crystal Violet Lactone: CVL) was used as the leuco dye, and octyl gallate was used as the developer. Vitamin K4 (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a coloring agent.

In the temperature sensing material preparation step S1, leuco dye: developer: decoloring agent is mixed at a mass ratio of 2:2:100, melted and stirred at 180°C, and then solidified to prepare a bulk temperature sensing material. bottom. The resulting mass was manually crushed in a mortar to prepare a granular temperature sensing material. This temperature sensing material is colorless in an environment maintained at 25°C, but once heated to 40°C or higher, it develops a blue color.

Next, in the emulsion preparation step S2, 0.5 g of the temperature detection material and 2.5 g of a surfactant (Demoll (registered trademark) EP manufactured by Kao Corporation) were weighed and mixed with heating and stirring using a magnetic stirrer. (95°C, 600 rpm, 10 minutes) to prepare the temperature sensing material/surfactant emulsion.

Next, in the suspension preparation step S3, the emulsion at 95°C and the phosphate buffer aqueous solution (concentration 0.1 mol/L, pH = 7.0, 20 g) heated to 95°C were stirred and mixed (95°C, 600 rpm for 10 minutes). Thereafter, the mixture was cooled to room temperature while being stirred to prepare a temperature sensing particle/aqueous dispersion medium suspension. When the particle size distribution of the temperature sensing particles in the obtained suspension was measured using a particle size distribution analyzer, it was confirmed that the median diameter was about 1.5 μm.

Next, in the additive mixing step S4, the water-based temperature-sensing ink of Example 5 was prepared in the same manner as in Example 1, and the water-based temperature-sensing ink of Example 6 was prepared in the same manner as in Example 2.

A temperature indicator was produced using the water-based temperature sensing ink of Example 5 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 6.

A temperature change test (heated to 40°C after holding at 25°C for 10 minutes) was performed on the produced temperature indicator, and the color change of printed characters was visually confirmed. When it was colorless when kept at 25°C and developed when heated to 40°C and the printed characters could be identified, it was evaluated as "acceptable". As a result, both Examples 5 and 6 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 5 and 6 are also shown in Table 1.

[Experiment 6]
(Production and evaluation of Examples 7 and 8)
In the emulsion preparation step S2, the water-based temperature sensing ink of Example 7 was prepared in the same manner as in Example 5 except that DEMOLL (registered trademark) NL manufactured by Kao Corporation was used as the surfactant. A water-based temperature sensing ink of Example 8 was prepared in the same manner as in Example 2, except that Demol NL manufactured by Kao Corporation was used as the agent.

A temperature indicator was produced using the water-based temperature sensing ink of Example 7 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 8.

The same temperature change test as in Example 5 (holding at 25° C. for 10 minutes and then heating to 40° C.) was performed on the produced temperature indicator, and the color change of the printed characters was visually confirmed. As a result, both Examples 7 and 8 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 7 and 8 are also shown in Table 1.

[Experiment 7]
(Production and evaluation of Examples 9 and 10)
Example 5 except that a mixture of vitamin K4 (manufactured by Tokyo Chemical Industry Co., Ltd.) and propyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.) at a mass ratio of "1:1" was used as the decolorant. A granular temperature sensing material was prepared in the same manner. This temperature sensing material is colorless in an environment maintained at 25°C, but develops a blue color once heated to 50°C or higher.

Next, in the emulsion preparing step S2 and the suspension preparing step S3, a temperature sensing particle/aqueous dispersion medium suspension was prepared in the same manner as in Example 5. When the particle size distribution of the temperature sensing particles in the obtained suspension was measured using a particle size distribution analyzer, it was confirmed that the median diameter was about 1.5 μm.

Next, in the additive mixing step S4, the temperature-sensing water-based ink of Example 9 was prepared in the same manner as in Example 1, and the temperature-sensing water-based ink of Example 10 was prepared in the same manner as in Example 2.

A temperature indicator was produced using the water-based temperature sensing ink of Example 9 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 10.

A temperature change test (heated to 50°C after being held at 25°C for 10 minutes) was performed on the produced temperature indicator, and the color change of printed characters was visually confirmed. When it was colorless when kept at 25°C and developed when heated to 50°C and the printed characters could be identified, it was evaluated as "acceptable". As a result, both Examples 9 and 10 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 9 and 10 are also shown in Table 1.

[Experiment 8]
(Production and evaluation of Examples 11 and 12)
In the emulsion preparation step S2, the water-based temperature sensing ink of Example 11 was prepared in the same manner as in Example 5 except that DEMOLL (registered trademark) NL manufactured by Kao Corporation was used as the surfactant. A water-based temperature sensing ink of Example 12 was prepared in the same manner as in Example 2, except that Demol NL manufactured by Kao Corporation was used as the agent.

A temperature indicator was produced using the water-based temperature sensing ink of Example 11 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 12.

The same temperature change test as in Example 9 (holding at 25° C. for 10 minutes and then heating to 50° C.) was performed on the produced temperature indicator, and the color change of the printed characters was visually confirmed. As a result, both Examples 11 and 12 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 11 and 12 are also shown in Table 1.

[Experiment 9]
(Production and evaluation of Examples 13 and 14)
The water-based temperature-sensing ink of Example 1 and the water-based temperature-sensing ink of Example 9 were mixed at a mass ratio of 1:1 to prepare the water-based temperature-sensing ink of Example 13. Further, the water-based temperature-sensing ink of Example 4 and the water-based temperature-sensing ink of Example 12 were mixed at a mass ratio of "1:1" to prepare the water-based temperature-sensing ink of Example 14.

Since the water-based temperature-sensing inks of Examples 13 and 14 each contain two types of temperature-sensing materials, they are colorless in an environment maintained at 25°C, but appear black once cooled to 4°C or below. It becomes a temperature-sensitive water-based ink that develops blue once heated above 50°C.

A temperature indicator was produced using the water-based temperature sensing ink of Example 13 in the same manner as in Example 1, and a temperature indicator was produced in the same manner as in Example 2 using the water-based temperature sensing ink of Example 14.

A temperature change test (maintained at 25°C for 10 minutes, cooled to 4°C, and then heated to 50°C) was performed on the produced temperature indicator, and the color change of the printed characters was visually confirmed. When it was colorless when kept at 25°C, when it was cooled to 4°C and when heated to 50°C, it was evaluated as "pass" when printed characters could be identified, and otherwise evaluated as "fail". . As a result, Examples 13 and 14 were evaluated as "pass". The components and evaluation results of the temperature-sensing water-based inks of Examples 13 and 14 are also shown in Table 1.

The above-described embodiments and examples are described to aid understanding of the present invention, and the present invention is not limited only to the specific configurations described. For example, it is possible to replace part of the configuration of the embodiment with a configuration of common technical knowledge of a person skilled in the art, and it is also possible to add a configuration of common general technical knowledge of a person skilled in the art to the configuration of the embodiment. That is, in the present invention, deletion, replacement with another configuration, or addition of another configuration may be made to a part of the configurations of the embodiments and examples of the present specification without departing from the technical idea of the invention. It is possible.

1... leuco dye, 2... developer, 3... decolorant, 4... temperature sensing material, 5... surfactant,
10, 11... temperature detection particles, 20... aqueous dispersion medium, 30... water-soluble resin binder, 40... other additives,
100...Temperature detection water-based ink.

Claims (11)

An ink for inkjet printing,
The ink is a temperature-sensing water-based ink,
A temperature sensing material containing a leuco dye, a developer and a decolorant, temperature sensing particles containing a surfactant, an aqueous dispersion medium, and a conductive agent as an additive ,
The ink has an electrical resistivity of 2000 Ωcm or less,
In the temperature sensing particles, fine particles of the temperature sensing material in which the leuco dye and the developer are dispersed in a matrix of the color erasing agent are coated with the surfactant. An ink characterized in that the surfactant is also present inside . In the ink according to claim 1,
The ink, wherein the ink further contains a water-soluble resin binder and/or a leveling agent as the additive. In the ink according to claim 1 or claim 2 ,
An ink, wherein the temperature detection particles have a median diameter of 0.1 μm or more and 100 μm or less. In the ink according to any one of claims 1 to 3,
An ink characterized in that the ink has a pH of 6 or more and 8 or less. In the ink according to any one of claims 1 to 4 ,
including a plurality of types of temperature sensing particles having color development start temperatures different from each other;
An ink characterized in that each of the plurality of types of temperature sensing particles develops a color when the temperature drops below a predetermined temperature. In the ink according to any one of claims 1 to 4 ,
including a plurality of types of temperature sensing particles having color development start temperatures different from each other;
An ink characterized in that each of the plurality of types of temperature-sensing particles develops a color when it reaches a predetermined temperature or higher. In the ink according to any one of claims 1 to 4 ,
including a plurality of types of temperature sensing particles having color development start temperatures different from each other;
An ink according to claim 1, wherein the plurality of types of temperature sensing particles include both temperature sensing particles that develop color at a predetermined temperature or less and temperature sensing particles that develop color at a predetermined temperature or higher. A method for producing an ink ,
The ink is an ink containing a temperature sensing material containing a leuco dye, a developer and a decolorant, temperature sensing particles containing a surfactant, and an aqueous dispersion medium,
a temperature sensing material preparation step of mixing, melting, and solidifying the leuco dye, the color developer, and the color erasing agent to prepare the temperature sensing material;
an emulsion preparing step of preparing an emulsion of the temperature sensing material/surfactant by heating and stirring the temperature sensing material and the surfactant solution;
a suspension preparation step of preparing a suspension of temperature sensing particles/aqueous dispersion medium by stirring and mixing the heated emulsion and the heated aqueous dispersion medium, and then cooling to room temperature while stirring;
A method for producing an ink, comprising: In the method for producing the ink according to claim 8 ,
A method for producing an ink, further comprising an additive mixing step of mixing an additive into the suspension after the suspension preparation step. In the method for producing the ink according to claim 8 or 9 ,
A method for producing an ink, wherein the temperature sensing material preparation step includes a pulverization process for converting the temperature sensing material from lumps to granules. A temperature indicator having an ink marker printed on a printed substrate,
A temperature indicator, wherein the ink is the ink according to any one of claims 1 to 7 .

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