JP2022087590A - Irreversible thermosensitive color development ink and printer using the same - Google Patents

Abstract

To provide an irreversible thermosensitive color development ink which can be used in printing on a charging control type ink jet printer, and which can be discolored to a chromatic color by integration of a temperature and time when a temperature of a printing dot formed by printing becomes equal to or greater than a prescribed temperature, and provide a printer using the same.SOLUTION: An irreversible thermosensitive color development ink according to the present invention includes, a leuco dye, a developer, a decoloring agent and a solvent. At least one of the leuco dye, the developer and the decoloring agent is not microencapsulated. In the irreversible thermosensitive color development ink, volatility satisfies a relationship of the solvent>the decoloring agent>the leuco dye and the developer. By volatilization of the decoloring agent, the ink is developed to a chromatic color.SELECTED DRAWING: None

Description

The present invention relates to an irreversible heat-sensitive color-developing ink and a printing apparatus using the same.

With the need for quality control of foods and pharmaceuticals, it is required to control the temperature without interruption in the distribution process of production, transportation and consumption. For example, at the production stage of foods and pharmaceuticals, it is necessary to grasp whether or not necessary heat treatment (for example, heat treatment at around 60 ° C.) and sterilization treatment (for example, sterilization treatment at around 110 ° C.) are properly performed. Therefore, temperature control is performed. At the stage of transportation and consumption, for example, temperature control is performed to keep the product at a low temperature without interruption (cold chain).

In order to constantly measure and record the temperature during production and transportation, a data logger that can continuously record the time and temperature is often installed. As a result, if the necessary heat treatment or sterilization treatment is not performed, or if the product is damaged, the responsibility can be clarified. However, data loggers are unsuitable for individual product management due to their price and size.

When controlling the quality of individual products, relatively inexpensive temperature indicators may be used instead of data loggers. Although the temperature indicator is not as accurate as a data logger, it can be attached to individual products, and the surface is dyed when the temperature exceeds or falls below the preset temperature, so it is possible to know changes in the temperature environment. It is possible. However, temperature indicators are often unsuitable for application to mass-produced products from the viewpoint of price and sticking speed.

On the other hand, charge control type inkjet printers are used in a wide range of fields such as foods and electronic parts for printing the expiration date, expiration date, serial number, and the like. If an ink jet printer with charge control can print ink that changes color irreversibly with respect to temperature changes, it is more suitable for temperature control of mass-produced products than a temperature indicator from the viewpoint of price and printing speed.

Patent Document 1 discloses an erasable inkjet ink that can form a high-density image and is erased to a sufficiently invisible state. Specifically, Patent Document 1 contains a leuco dye, a water-insoluble color developer, and a solvent containing alcohol and water, and the amount of the water is 7% by mass or more and 25% by mass or less of the solvent. An erasable inkjet ink comprising the above is disclosed.

Patent Document 2 is characterized in that a benzoic anhydride derivative represented by a predetermined general formula is used as a sensitivity improving agent in a heat-sensitive recording material utilizing a color-developing reaction between a leuco dye and a color developer. Thermal recording materials are disclosed.

Japanese Unexamined Patent Publication No. 2012-224789 No. 2729253

In order for a charge-controlled inkjet printer to print ink that changes color irreversibly with temperature changes on mass-produced products at high speed, it is necessary to solve a plurality of problems as follows. For example, the ink printed by inkjet dries quickly and can form print dots. Further, it is mentioned that the printed dots have high adhesion to mass-produced products. Further, in order for the inkjet printer to print with high definition, it is possible to eject ink from an inkjet nozzle having a small diameter.

Further, in order to utilize the print dot as a temperature indicator, it is preferable that the change can be clearly visually recognized when the color changes with respect to the temperature change. Therefore, it is required that the color of the ink changes from colored to colored in an easy-to-understand manner, or changes from colorless to colored.

In addition, when managing products whose quality deteriorates depending on temperature and time, such as fresh foods and biopharmaceuticals, a time temperature indicator (Time-Temperature Indicator) that changes color by integrating time and temperature is used. .. In order to utilize the print dots as such a time temperature indicator, it is required that the ink changes its color by integrating the time and the temperature with respect to the temperature change.

Under such circumstances, the erasable inkjet ink disclosed in Patent Document 1 contains a solvent containing water as a main component. Therefore, it is assumed that the erasable inkjet ink does not have a sufficient drying speed when printing at high speed, and that high adhesion to plastics often used for mass-produced products cannot be obtained. Further, since this erasable inkjet ink is an ink that changes color from colored to colorless by heating, it is difficult to use it as a temperature indicator. Further, since this erasable inkjet ink does not take into consideration the color change due to the integration of time and temperature, it is difficult to use it as a time temperature indicator.

The heat-sensitive recording material disclosed in Patent Document 2 contains a solid material that is not completely dissolved in the solvent component in the material. Therefore, it is assumed that it is difficult for this heat-sensitive recording material to stably eject ink from an inkjet nozzle having a small diameter when applied to a charge control type inkjet printer. Further, this heat-sensitive recording material is characterized by a high color development speed, and it is difficult to use it as a time temperature indicator in which a color changes by integrating time and temperature.

The present invention has been made in view of the above problems, and can be printed by a charge control type inkjet printer, and when the printed dots formed by printing reach a predetermined temperature or higher, the color can be changed to a colored color by integrating the temperature and time. An object of the present invention is to provide a heat-sensitive color-developing ink and a printing apparatus using the same.

In order to solve the above problems, the irreversible heat-sensitive color-developing ink according to the present invention contains a leuco dye, a color developer, a decoloring agent and a solvent, and at least one of the leuco dye, the color developing agent and the decoloring agent. One is not microencapsulated and its volatileness satisfies the relationship of the solvent> the decoloring agent> the leuco dye and the color developer, and the decoloring agent volatilizes to become colored. It was configured to be colored.

According to the present invention, an irreversible heat-sensitive color-developing ink that can be printed by a charge-controlled inkjet printer and can change color by integrating the temperature and time when the printed dots formed by printing reach a predetermined temperature or higher, and the irreversible heat-sensitive color-developing ink. The printing apparatus used can be provided.

It is a schematic diagram which shows typically the inkjet head of the charge control type inkjet printer. It is a schematic cross-sectional view in the case where the print dot formed by printing the irreversible heat-sensitive color-developing ink according to this embodiment with a charge control type inkjet printer is placed in an environment of a predetermined temperature or lower. It is a schematic cross-sectional view in the case where the print dot formed by printing the irreversible heat-sensitive color-developing ink according to this embodiment with a charge control type inkjet printer is placed in an environment exceeding a predetermined temperature. It is a schematic diagram explaining an example of the printing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a schematic diagram explaining another example of the printing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a schematic diagram explaining another example of the printing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a schematic diagram explaining another example of the printing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a schematic diagram explaining an example of the writing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a schematic diagram explaining another example of the writing apparatus using the irreversible heat-sensitive color-developing ink according to this embodiment. It is a photograph which shows the time-temperature dependence of the print dot which used the irreversible heat-sensitive color-developing ink which concerns on Example 1. FIG. The figure shows a state after 1 minute has passed at 110 ° C. under normal pressure. It is a schematic diagram of FIG. 9A. It is a photograph which shows the time-temperature dependence of the print dot which used the irreversible heat-sensitive color-developing ink which concerns on Example 1. FIG. The figure shows a state after 10 minutes have passed at 110 ° C. under normal pressure. It is a schematic diagram of FIG. 9C. It is a photograph which shows the time-temperature dependence of the print dot which used the irreversible heat-sensitive color-developing ink which concerns on Example 2. FIG. The figure shows the state after 2 minutes have passed at 110 ° C. under normal pressure. It is a schematic diagram of FIG. 10A. It is a photograph which shows the time-temperature dependence of the print dot which used the irreversible heat-sensitive color-developing ink which concerns on Example 2. FIG. The figure shows the state after 20 minutes have passed at 110 ° C. under normal pressure. It is a schematic diagram of FIG. 10C.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, the common parts are designated by the same reference numerals and duplicated explanations will be omitted.

<Irreversible heat-sensitive color-developing ink>
The irreversible heat-sensitive color-developing ink according to one embodiment of the present invention (hereinafter, may be simply referred to as “ink”) contains a leuco dye, a color developer, a decoloring agent, and a solvent.
Further, in the ink according to the present embodiment, at least one of the leuco dye, the color developer and the decoloring agent is not microencapsulated.
Further, in the ink according to the present embodiment, the volatility satisfies the relationship of solvent> decoloring agent> leuco dye and coloring agent.
Then, the ink according to the present embodiment develops a color due to the volatilization of the decolorizing agent.
First, the leuco dye, the color developer, the decoloring agent, and the solvent in the ink according to the present embodiment will be described.

<Leuco dye>
Leuco dyes are electron donating compounds. As the leuco dye, conventionally known dyes for pressure-sensitive copying paper and heat-sensitive recording paper can be used. Leuco dyes include, for example, triphenylmethanephthalide, fluorane, phenothiazine, indolylphthalide, leucooramine, spiropyran, rhodamine lactam, triphenylmethane, triazene, and spirophphthalanxanthene. , Naftlactam type, azomethine type and the like can be used. Specific examples of leuco dyes include 2'-methyl-6'-(N-p-tolyl-N-ethylamino) spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one. , 9- (N-ethyl-N-isopentylamino) spiro [benzo [a] xanthene-12,3'-phthalide], 2-methyl-6- (Np-tolyl-N-ethylamino) -fluoran 6- (Diethylamino) -2-[(3-trifluoromethyl) anilino] xanthene-9-spiro-3'-phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3 -Bis (p-diethylaminophenyl) -6-dimethylaminophthalide, 2'-anilino-6'-(dibutylamino) -3'-methylspiro [phthalide-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-dihydrospiro [11H-chromeno [2,3-g] quinoline-11,3'-phthalide], 3- (1-ethyl-2methylindol-3-yl) -3- (4-Diethylamino-2-methylphenyl) -4-azaphthalide and the like can be mentioned.
As the leuco dye, any one selected arbitrarily from the above-mentioned exemplified compounds can be used, but two or more kinds may be used in combination.

<Color developer>
The color developer changes the structure of the leuco dye and causes color development by contacting with the electron-donating leuco dye. As the color developer, known ones used in thermal recording paper, pressure-sensitive copying paper, and the like can be used. Specific examples of the color developer include benzyl 4-hydroxybenzoate, 2,2'-biphenol, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane, and 2,2-bis (3-cyclohexyl-). 4-Hydroxyphenyl) propane, 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, α, α, α'-tris (4-hydroxyphenyl) ) -1-Ethyl-4-isopropylbenzene, bisphenol A, bisphenol F, bis (4-hydroxyphenyl) sulfide, paraoxybenzoic acid ester, gallic acid ester (for example, octyl peroxide) and other phenols. The color developer is not limited to these, and any compound that is an electron acceptor and can change the color of the leuco dye can be used. The color developer includes metal salts of carboxylic acid derivatives, salicylic acid and salicylic acid metal salts, sulfonic acids, sulfonates, phosphoric acids, phosphoric acid metal salts, acidic phosphoric acid esters, acidic phosphoric acid ester metal salts, and subphosphorus. Acids, phosphite metal salts and the like can be used. In particular, the color developer preferably has high compatibility with leuco dyes and decolorizing agents described later, and is preferably benzyl 4-hydroxybenzoate, 2,2'-bisphenol, and 4,4'-cyclohexylidenebis (2-). Cyclohexylphenol), 2,2-bis (3-cyclohexyl-4-hydroxyphenyl) propane, 2,2-bis (2-hydroxy-5-biphenylyl) propane, 4,4'-cyclohexylidenebis (o- Cresol), 2,2-bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, bisphenol P, 4,4'-(9-fluorenylidene) diphenol, bisphenol A, bisphenol M, 4,4'-thiodiphenol, bisphenol S, 4,4'-biphenol, 4,4'-oxydiphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-(1,3) -Dimethylbutylidene) diphenol, 4,4'-(2-ethylhexylidene) diphenol, 4,4'-etylidene bisphenol (bisphenol E), 4,4'-(2-hydroxybenzylidene) bis (2) , 3,6-trimethylphenol), 1,1'-methylenebis (2-naphthol), tetrabromobisphenol A, organic color-developing agents such as gallic acid esters are preferable.
As the color developer, any one selected arbitrarily from the above exemplified compounds can be used, but two or more thereof may be used in combination. The color density of the leuco dye at the time of coloration can be adjusted by combining two or more kinds of the color developer. The amount of the developer to be used is selected according to the desired color density. The amount of the developer to be used can be selected, for example, in the range of about 0.1 to 100 parts by mass with respect to 1 part by mass of the leuco dye.

<Discoloring agent>
The decoloring agent is a compound capable of dissociating the bond between the leuco dye and the color developer, and is a compound capable of controlling the color development temperature and time of the leuco dye and the color developer. In the temperature range in which the leuco dye immediately after the formation of the printed dots is in the decolorized state, the function of dissociating the bond between the leuco dye and the color developer is exhibited. On the other hand, for example, when the print dots formed by printing ink with a printing device such as an inkjet printer are exposed to a certain temperature or higher or heated to a temperature at which the decolorizing agent volatilizes (evaporates), the color is decolorized. Since the agent volatilizes and disappears from the printed dots, it indicates a state in which the leuco dye is colored (colored). This makes it possible to know that the control temperature has been exceeded. Therefore, the state change temperature of the decolorizing agent is important for controlling the temperature of the printing dots. In the present specification, "developing a color" means, for example, changing the color from a colorless transparent state to a colored state in the visible light region, and changing from a specific colored state to another colored state in the visible light region. It means to change the color. Here, the inkjet printer described above is preferably a charge control type inkjet printer as described later. As described above, when the charge control type inkjet printer is used, it is possible to realize a temperature indicator suitable for temperature control of mass-produced products from the viewpoint of price and printing speed.

For example, when the ink according to the present embodiment is regarded as normal below the control temperature and is regarded as abnormal when exposed to a temperature exceeding the control temperature for a certain period of time, the ink according to the present embodiment is used. The formed print dots need not develop color for a long time at a control temperature or lower. In such a case, the decolorizing agent in the print dots does not volatilize for a long time below the control temperature, and needs to volatilize in a certain time at a temperature exceeding the control temperature. Volatilization of the decolorizing agent contained in the ink according to the present embodiment must not occur even in the printing apparatus before forming the print dots when the temperature is below the control temperature. Therefore, it is preferable that the decolorizing agent used in the present embodiment has a high boiling point so that it hardly evaporates at a temperature of about room temperature under a normal pressure (for example, about 101 kPa) environment. Although it depends on the usage environment and the control temperature of the target product, the developing color temperature, that is, the temperature at which the decolorizing agent volatilizes from the printed dots is, for example, about 40 to 180 ° C. under normal pressure. More specifically, the color development time is preferably about several hours to several days when the normal pressure is 40 ° C., and about several minutes to several hours when the normal pressure is 100 ° C. As a decolorizing agent that realizes these developing colors and developing times, those having a boiling point of about 80 to 370 ° C. at normal pressure can be preferably used. By doing so, for example, in the production stage of foods and pharmaceuticals, are necessary heat treatments (for example, heat treatment at around 60 ° C.) and sterilization treatments (for example, sterilization treatments at around 110 ° C.) appropriately performed? It is possible to grasp whether or not.

If the volatilization of the decolorizing agent in the ink before printing can be suppressed, a decoloring agent having a boiling point of about 40 to 80 ° C. can be used, thereby lowering the color development temperature of the ink. Can be done. Therefore, the ink according to this embodiment can be used for temperature control of a product having a low control temperature. To suppress the volatilization of the decolorizing agent in the ink before printing, for example, a mechanism for cooling may be provided adjacent to the holding portion for holding the ink tank (ink container / ink cartridge) of the printing device such as an inkjet printer. This can be done by providing a mechanism for mixing the decolorizing agent with the mixed liquid containing the leuco dye, the developing agent and the solvent immediately before printing. These aspects will be described later.

As the decolorizing agent, a wide range of materials can be used as long as they can dissociate the bond between the leuco dye and the developing agent. If the polarity is low and the leuco dye does not show color developability and the polarity is high enough to dissolve the leuco dye and the developer, various materials can be decolorizing agents. Typical examples of the decolorizing agent include hydroxy compounds, ester compounds, peroxy compounds, carbonyl compounds, aromatic compounds, aliphatic compounds, halogen compounds, amino compounds, imino compounds, N-oxide compounds, and aliphatic amine compounds. Various organic compounds such as hydroxyamine compounds, nitro compounds, azo compounds, diazo compounds, azi compounds, ether compounds, oil and fat compounds, sugar compounds, peptide compounds, nucleic acid compounds, alkaloid compounds, and steroid compounds can be used.
As the decolorizing agent, those having a boiling point of about 80 to 370 ° C. at normal pressure and high volatility can be preferably used. Specific examples of the decolorizing agent include ethylamine, dibutylamine, triethylamine, tripropylamine, 3-aminopropyldiethoxymethylsilane, 3-aminopropyldimethoxymethylsilane, bis (hexamethylene) triamine, and bis (2-). Fats such as methoxyethyl) amines, 1,4-butanediol bis (3-aminopropyl) ethers, didecylmethylamine, N, N-didodecylmethylamine, di-n-octylamine, isophoronediamine, dibenzylamine Group amine compounds, hydroxyamine compounds such as ethanolamine, N, N-diethylethanolamine, N-ethyldiethanolamine, triethanolamine, and N-butyldiethanolamine can be used. The decoloring agent preferably contains these compounds from the viewpoint of compatibility with the leuco dye and the color developer. Of course, the decolorizing agent is not limited to these compounds, and any material can be used as long as it can dissociate the bond between the leuco dye and the developing agent.
As the decolorizing agent, any one selected arbitrarily from the above exemplified compounds can be used, but two or more thereof may be used in combination. By combining with a decolorizing agent, it is possible to adjust the method of discoloration with respect to the volatilization rate, the color development temperature, and the color development time.

<Solvent>
Since the ink according to this embodiment is applied to a charge control type inkjet printer and is assumed to be used for printing mass-produced products, it is preferable to use a solvent having a high drying speed. Further, the ink used for the charge control type inkjet printer needs to have a viscosity of about several mPa · s. Further, the ink according to the present embodiment needs to contain at least a leuco dye, a color developer, and a decoloring agent, and it is necessary to dissolve these materials. Examples of the solvent that satisfies these at the same time include alcohols such as methanol, ethanol and propanol, ketones such as acetone, methyl ethyl ketone, isopropyl methyl ketone and cyclohexanone, ethyl acetate, methyl acetate, ethyl propionate and methyl propionate. Examples thereof include esters, dimethyl ethers, ethers such as methanol, and the like.

In addition, a resin (binder material) having a low polarity may be dissolved in the ink in order to impart high adhesion to general-purpose plastics such as polypropylene, polyethylene, and polyethylene terephthalate, which are widely used as mass-produced products. In that case, an organic solvent having a low polarity is preferable as the solvent. Examples of such organic solvents include alcohols such as butanol and pentanol, ketones such as acetone, methyl ethyl ketone, isopropyl methyl ketone and cyclohexanone, and esters such as ethyl acetate, methyl acetate, ethyl propionate and methyl propionate. , Dimethyl ether, ethers such as tetrahydrofuran and the like.

In the ink according to the present embodiment, as described above, at least one of the leuco dye, the color developer and the decoloring agent is not microencapsulated. When microencapsulated, the particle size of the particles increases. Therefore, the more microencapsulated particles the ink contains, the more difficult it is for the particles to fly as intended in a charge-controlled inkjet printer that charges the ink droplets for printing, and it is possible to print high-definition characters. It tends to be difficult. In the ink according to the present embodiment, at least one of the leuco dye, the color developer and the decoloring agent is not microencapsulated, so that the charge control type inkjet is compared with the case where all of them are microencapsulated. High-definition characters can be printed when printed with a printer. From the viewpoint of printing higher-definition characters with a charge-controlled inkjet printer, it is preferable that all of the leuco dye, the developer and the decoloring agent are not microencapsulated.

Even when one or two of the leuco dye, the color developer and the decoloring agent contained in the ink according to the present embodiment are microencapsulated, for example, DOD (Drop On Demand) is used. ) When the ink is used in an inkjet printer, high-definition characters can be printed. In the DOD type inkjet printer, ink droplets are ejected / stopped by changing the volume of the piezo element (piezoelectric element) provided in the nozzle by energization or by opening and closing the solenoid valve provided in the nozzle by energization. Is controlled to print. That is, the DOD type inkjet printer can print without adding an electric charge to the ink droplets. Therefore, as described above, the DOD type inkjet printer can print high-definition characters even when one or two of the leuco dye, the developer and the decolorizer are microencapsulated. It can be carried out.

Further, as described above, the ink according to the present embodiment has volatility satisfying the relationship of solvent> decoloring agent> leuco dye and coloring agent. In this way, since the solvent has the highest volatility, the solvent can be quickly volatilized to form print dots after printing the ink on the target product with a printing device such as a charge control type inkjet printer. Since the volatileness of the decolorizing agent is higher than that of the leuco dye and the developing agent, the decolorizing agent becomes the leuco dye and the developing agent when the printed dots are exposed to a certain temperature or higher or heated. It volatilizes before the colorant and disappears from the printed dots. Therefore, the leuco dye and the color developer remaining in the print dots cause the print dots to develop a color by integrating the temperature and time. The details of the color development of the print dots will be described later.

<Pigments / Dyes>
As described above, the ink according to the present embodiment contains at least a leuco dye, a color developer, a decoloring agent and a solvent, but may contain materials other than these as long as the color development characteristics of the ink are not impaired. can.
For example, the ink according to the present embodiment may contain a pigment or a dye as long as the color development characteristics of the ink are not impaired. When a pigment or dye is contained, the color of the ink before color development (print dot color) and the color of the ink after color development (print dot color) can be arbitrarily changed. Any pigment or dye can be used as long as it is used for printing ink, but when used in an inkjet printer, a pigment having a finer particle size is preferable. The size of the pigment is preferably 500 nm or less, more preferably 100 nm or less. The size of the dye is preferably 50 nm or less, more preferably 10 nm or less.

<Binder material>
The ink according to this embodiment may contain a binder material. When the binder material is included, the adhesion of the print dots can be improved when the object to be printed on which the print dots are formed is a general-purpose plastic, metal, glass, film or the like.
As the binder material, any resin that is soluble in the solvent generally used in the fields of ink, paint, adhesive, etc. is used as long as the color development characteristics of the ink are not impaired. be able to. In the case of the present embodiment, for example, it is preferable to use a resin having low polarity as the main material of the binder material for the purpose of imparting high adhesion to general-purpose plastics widely used as mass-produced products. Examples of such low-polarity resins include styrene resin, styrene acrylic resin, acrylic resin, end-sealing epoxy resin, salt-vinegar bipolymer resin, butyral resin, various rosin-modified resins, phenol resin, novolak resin, and polyamide resin. , Polyester resin, Xylene resin, maleic acid resin, various cellulose resins and the like. As the binder material, the above-mentioned resins can be used alone or in combination of two or more so that the viscosity of the ink according to the present embodiment is within about several mPa · s. In addition to general-purpose plastics, metals, glass, and films, the ink according to this embodiment can be applied to various printing objects such as non-woven fabrics and paper. As the ink according to the present embodiment, a binder material having high adhesion to each printing object can be appropriately selected and used.

When the ink according to the present embodiment contains a binder material, the volatility preferably satisfies the relationship of solvent> decoloring agent> leuco dye and color developer> binder material. By doing so, the volatility of the binder material is the lowest and remains until the end, so that it is possible to prevent the print dots from being removed.

<Measurement of volatility>
In the present specification, the volatility of the solvent, the decoloring agent, the leuco dye and the color developer, and the binder material is determined by, for example, a method of measuring the vapor pressure using a pressure gauge or the like, an everyometer, or a differential scanning calorific value. The boiling point can be measured using a meter, or the amount of evaporation can be measured by a method such as a heat-drying moisture meter, but the present invention is not limited to these.

<Additives>
When the ink according to the present embodiment is used as an ink for a charge control type inkjet printer, if a highly conductive leuco dye and a color developer can be used, no conductive agent is required. On the other hand, when the ink cannot be sufficiently conductive with the leuco dye and the color developer, the conductivity can be imparted by adding the conductive agent. As the conductive agent, it is preferable to use a complex. The conductive agent needs to be dissolved in a solvent, and it is also important that it does not affect the color tone. Further, the conductive agent generally has a salt structure. Since this has a charge bias in the molecule, it is presumed that high conductivity can be exhibited.

As a result of the examination from the above viewpoints, the conductive agent preferably has a salt structure.
The salt-structured conductive agent is preferably one in which the cation has a tetraalkylammonium ion structure. The alkyl chain may be either linear or branched, and the larger the number of carbon atoms, the better the solubility in the solvent. However, the smaller the number of carbon atoms, the lower the resistance can be with a small addition rate. The practical number of carbon atoms when used in ink is about 2 to 8.
The salt-structured conductive agent is preferable because anions such as hexafluorophosphate ion and tetrafluoroborate ion have high solubility in a solvent.

Preferred conductive agents include, for example, tetraethylammonium hexafluorophosphate, tetrapropylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetrapentylammonium hexafluorophosphate, tetrahexylammonium hexafluorophosphate, and tetraoctylammonium. Hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetrapropylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetrapentylammonium tetrafluoroborate, tetrahexylammonium tetrafluoroborate, tetraoctylammonium tetrafluoroborate. Examples include lat.

Further, in the printed dots after drying with a solvent, the surface of the dots may not be smooth, and a uniform color density may not be developed with respect to the developed color state of the printed characters and marks. In such a case, the leveling agent can be suitably used as an additive. The leveling agent is effective in forming flat and small print dots by flattening the print dots or preventing the dots from spreading. As the leveling agent, for example, commonly used surfactants, lubricants, modder flows and the like can be used. Further, as the leveling agent, for example, silicone oil and its modified derivative, fluorine-based lubricant, lanolin, palm oil, carnauba wax and the like can be used.

In addition, in order to supplement the color development speed of the print dots and the adhesion to the substrate, the ink according to the present embodiment further contains a plasticizer, a surfactant, and the like, as long as the color development characteristics of the ink are not impaired. Lubricants, various adhesives, pressure-sensitive adhesives, softeners and the like may be added.
As described above, the ink according to this embodiment is assumed to be used as an ink for a charge control type inkjet printer, but it may also be applied to inks such as pens and stamps and paints for printing such as screen printing. can.

<Ink for charge-controlled inkjet printer>
As described above, the ink according to this embodiment is assumed to be applied to a charge control type inkjet printer. That is, the ink according to this embodiment is used as an ink for a charge control type inkjet printer.
Here, FIG. 1 is a schematic diagram schematically showing an inkjet head 11 of a charge control type inkjet printer 10.
As shown in FIG. 1, the inkjet head 11 of the charge control type inkjet printer 10 includes a nozzle 12, a charge electrode 13, a deflection electrode 14, and a gutter 15. The nozzle 12 is a device that ejects an ink solution as minute ink droplets 16 by changing the volume of the piezo element by energization. The charging electrode 13 is an electrode that applies a charge to the ejected ink droplet 16. The deflection electrode 14 is an electrode that controls the flight direction of the charged ink droplet 16 to land on the print target 17.

When the ink according to this embodiment is used as an ink for a charge control type inkjet printer, if the resistance at the time of solution is high, the ink droplet 16 tends not to fly straight and bends in the inkjet head 11 of the charge control type inkjet printer 10. be. Therefore, it is preferable that the charge control type inkjet printer ink has a resistivity of about 2 kΩ · cm or less in solution.

Further, since the print dot 2 after the ink droplet 16 has landed expresses a character or a code, it is necessary to regularly eject the ink droplet 16 from the ejection port having a diameter of about 40 to 100 μm of the nozzle 12. At that time, if a solid material having a diameter of about several μm such as an impurity is present in the ink, the ink droplet 16 does not fly straight and it becomes difficult to print high-definition characters. Therefore, it is preferable that the material in the ink is uniformly dissolved in the solvent. When the ink contains a pigment, it is preferable to use a pigment having a diameter as small as possible. As described above, the size of the pigment is preferably 500 nm or less.

<Print dot>
The ink according to this embodiment is printed on an object 17 to be printed by an inkjet printer (particularly, a charge control type inkjet printer) to form print dots 2, and then the decolorizing agent 5 (see FIGS. 2A and 2B) volatilizes. When the temperature rises above the predetermined temperature, the color is developed by integrating the temperature and time.

FIG. 2A is a schematic cross-sectional view when the print dots 2 formed by printing the ink according to the present embodiment with the charge control type inkjet printer 10 are placed in an environment of a predetermined temperature (control temperature) or lower. FIG. 2B is a schematic cross-sectional view when the print dots 2 formed by printing the ink according to the present embodiment with the charge control type inkjet printer 10 are placed in an environment exceeding a predetermined temperature (control temperature).

As shown in FIG. 2A, the ink (not shown) according to this embodiment is a solvent (not shown) which is a main component after printing on the base material 1 (printing object 17) with the charge control type inkjet printer 10. Is volatilized to form print dots 2. The formed print dot 2 contains a leuco dye 3, a color developer 4, and a decolorizing agent 5. When the ink according to this embodiment contains a binder material, the binder material (not shown) is included in the print dot 2. Since the print dot 2 contains a resin as a binder material, the print dot 2 can adhere to the base material 1 such as plastic with high adhesion.

The print dot 2 develops a color due to the structure of the leuco dye 3 by containing the leuco dye 3 which is an electron donating compound and the color developer 4 which is an electron accepting compound. On the other hand, the printed dot 2 has a characteristic of decolorizing when it contains a certain amount of the decolorizing agent 5, which is a compound capable of dissociating the bond between the leuco dye 3 and the developing agent 4.

As shown in FIG. 2A, when the print dot 2 is placed in an environment of a predetermined temperature (control temperature) or lower, the print dot 2 contains a certain amount of the decolorizing agent 5, so that the bond between the leuco dye 3 and the developing agent 4 is dissociated. It is in a decolorized state.
From this state, when the print dot 2 is placed in an environment exceeding a predetermined temperature (control temperature) at which the decolorizing agent 5 volatilizes, the decoloring agent 5 starts volatilizing, and when a certain time elapses at that temperature, the figure is shown. As shown in 2B, the leuco dye 3 and the color developer 4 are combined to develop a color due to the structure of the leuco dye 3.

At this time, if the leuco dye 3, the developer 4, and the decolorizing agent 5 contained in the print dot 2 are colorless or white materials (if the binder material is also included, the binder material is also colorless or white), the ink jet is used. The formed print dots 2 are colorless or white immediately after printing. When the temperature rises above a predetermined temperature at which the decolorizing agent 5 volatilizes due to heating or the like, the color develops depending on the leuco dye 3. As described above, the print dot 2 formed by using the ink according to the present embodiment can exhibit a function of irreversibly changing from colorless to colored in response to a temperature change, like a temperature indicator.

Further, at this time, at least one of the leuco dye 3, the color developer 4, and the decoloring agent 5 contained in the print dot 2 is a colored material (when the binder material is included, the binder material is a colored material). Or), if a colored material such as a dye is added to the ink, the print dot 2 immediately after formation becomes colored. When the temperature rises above a predetermined temperature at which the decolorizing agent 5 volatilizes due to heating or the like, the color develops in a color dependent on the leuco dye 3, and the colored print dots 2 can be changed to another colored.

The temperature and time at which the print dots 2 develop colors depend on the volatilization temperature and rate of the decolorizing agent 5. Since the volatilization rate of the decolorizing agent 5 increases as the temperature rises, the print dot 2 can be used as a time temperature indicator in which the color changes with the integration of time and temperature.

The volatilization temperature of the decolorizing agent 5 in the printing dot 2 is also affected by the leuco dye 3 and the developing agent 4 (when the binder material is included, the binder material is also affected). Further, the volatilization temperature of the decolorizing agent 5 in the print dot 2 largely depends on the boiling point of the decolorizing agent 5 and the saturated vapor pressure. Therefore, the temperature and speed at which the printing dots 2 develop are adjusted by using the decolorizing agent 5 having a suitable boiling point and saturated vapor pressure for the ink for the temperature and time conditions suitable for quality control of the printing object 17. can do.

<Printing equipment>
The ink according to this embodiment can be applied to any general printing apparatus used for offset printing, gravure printing, flexographic printing, letterpress printing, screen printing, on-demand printing and the like.
However, as described above, the ink according to the present embodiment develops color due to the volatilization of the decolorizing agent. In order to prevent unnecessary color development and appropriately monitor the control temperature, the printing device using the ink according to this embodiment prevents the decolorizing agent from volatilizing from the pre-printing ink in the device. It is preferable to adopt a configuration that does.
Therefore, a printing apparatus for printing using the ink according to the present embodiment will be described with reference to FIGS. 3 to 6. 3 to 6 are schematic views illustrating an example of a printing apparatus using ink according to the present embodiment. FIGS. 3 to 6 show printing devices having a configuration for preventing the decolorizing agent from volatilizing. The same reference numerals are given to the configurations common to each aspect, and detailed description thereof will be omitted.

<First aspect of printing device>
As shown in FIG. 3, the printing apparatus 30 according to the first aspect is a charge control type inkjet printer 10 provided with a first container holding unit 31 and a cooling unit 32. The first container holding portion 31 and the cooling portion 32 are provided in the printing apparatus main body 33.
The first container holding unit 31 holds the ink container A containing the ink according to the present embodiment. Further, the cooling unit 32 is provided adjacent to the first container holding unit 31 and cools the first container holding unit 31.

The printing apparatus main body 33 includes a main container 34 that mixes ink and supplies ink to the nozzle 12, and a solvent container 35 that contains a solvent.
The main container 34 and the ink container A held in the first container holding portion 31 are connected by an ink supply path 36 so that the ink in the ink container A can be supplied to the main container 34 through the ink supply path 36. It has become.
Further, the main container 34 and the gutter 15 in the inkjet head 11 are connected by a recovery path 37, and the ink droplet 16 collected by the gutter 15 can be supplied to the main container 34 through the recovery path 37. ..
Further, the main container 34 and the solvent container 35 are connected by a solvent supply path 38, and the solvent in the solvent container 35 can be supplied to the main container 34 through the solvent supply path 38.
The density and viscosity of the ink in the main container 34 are controlled, and the ink is appropriately replenished from the ink container A or the solvent is supplied from the solvent container 35 so as to be within a predetermined range. There is.
The main container 34 and the nozzle 12 are connected by an ink supply path 39, and the ink in the main container 34 can be supplied to the nozzle 12 through the ink supply path 39.
The nozzle 12 to which the ink is supplied ejects the ink droplet 16 from the ejection port.

As described above, the printing apparatus 30 includes a cooling unit 32 for cooling the first container holding unit 31, and therefore, by cooling the first container holding unit 31 with the cooling unit 32, the first container holding unit 31 is provided. The ink in the ink container A held in the container A can be cooled. Therefore, it is possible to prevent the solvent and the decoloring agent from volatilizing in the ink container A.
It is more preferable that the printing device 30 is provided with a cooling device (not shown) for cooling the main container 34. By doing so, the ink is more preferably cooled, and the volatilization of the solvent or the decoloring agent can be further prevented.

<Second aspect of printing device>
As shown in FIG. 4, the printing apparatus 40 according to the second aspect includes a charge control type inkjet printer 10 including a second container holding unit 41, a third container holding unit 42, and a main container 34. Is. The second container holding portion 41, the third container holding portion 42, and the main container 34 are provided in the printing apparatus main body 33.
The second container holding portion 41 holds the mixed liquid container B containing the mixed liquid containing the leuco dye, the color developer, and the solvent. The third container holding portion 42 holds the decolorizing agent container C containing the decolorizing agent. Further, the main container 34 is a container in which the mixed liquid supplied from the mixed liquid container B and the decolorizing agent supplied from the decolorizing agent container C are mixed to obtain the ink according to the present embodiment.

The main container 34 and the mixed liquid container B held by the second container holding portion 41 are connected by a mixed liquid supply passage 43, and the mixed liquid in the mixed liquid container B is transferred to the main container 34 through the mixed liquid supply passage 43. It can be replenished to.
Further, the main container 34 and the decolorizing agent container C held in the third container holding portion 42 are connected by a decolorizing agent replenishment path 44, and are in the decolorizing agent container C through the decolorizing agent replenishment path 44. The decolorizing agent can be replenished to the main container 34.

As described above, the printing apparatus 40 mixes the mixed liquid supplied from the mixed liquid container B and the decolorizing agent supplied from the decolorizing agent container C in the main container 34. As described above, since the printing apparatus 40 mixes the mixed liquid and the decoloring agent immediately before supplying the ink to the nozzle 12, it is possible to prevent the decolorizing agent from volatilizing in the main container 34.

<Third aspect of printing device>
As shown in FIG. 5, the printing device 50 according to the third aspect is different from the printing device 30 in that the DOD type inkjet printer 51 is used instead of the charge control type inkjet printer 10 of the printing device 30 according to the first aspect. ing. More specifically, the printing apparatus 50 is different from the printing apparatus 30 in that the DOD type inkjet head 52 is used instead of the inkjet head 11 of the printing apparatus 30 according to the first aspect. Other than that, the printing device 50 and the printing device 30 have a common configuration.

The DOD type inkjet head 52 ejects and stops ink droplets 16 by changing the volume of the piezo element provided in the nozzle 12 by energization or by opening and closing the solenoid valve provided in the nozzle 12 by energization. Control and print. That is, the DOD type inkjet printer 51 prints without applying an electric charge to the ink droplet 16.

Since the printing device 50 also includes a cooling unit 32 for cooling the first container holding unit 31, the ink container held by the first container holding unit 31 by cooling the first container holding unit 31 with the cooling unit 32. The ink in A can be cooled. Therefore, the printing apparatus 50 can prevent the solvent and the decoloring agent from volatilizing in the ink container A.
It is more preferable that the printing device 50 also has a cooling device (not shown) for cooling the main container 34. By doing so, the ink is more preferably cooled, and the volatilization of the solvent or the decoloring agent can be further prevented.

<Fourth aspect of printing device>
As shown in FIG. 6, the printing device 60 according to the fourth aspect is different from the printing device 40 in that the DOD type inkjet printer 51 is used instead of the charge control type inkjet printer 10 of the printing device 40 according to the second aspect. ing. More specifically, it differs from the printing apparatus 40 in that the DOD type inkjet head 52 is used instead of the inkjet head 11 of the printing apparatus 40 according to the second aspect. Other than that, the printing device 60 and the printing device 40 have a common configuration.

The printing apparatus 60 also mixes the mixed liquid supplied from the mixed liquid container B and the decolorizing agent supplied from the decolorizing agent container C in the main container 34. As described above, since the printing apparatus 60 also mixes the mixed liquid and the decoloring agent immediately before supplying the ink to the nozzle 12, it is possible to prevent the decolorizing agent from volatilizing in the main container 34.

As described above, the ink according to the present embodiment can be printed by the charge control type inkjet printer 10, but can also be printed by the DOD type inkjet printer 51.
Further, the ink container A, the mixed liquid container B, and the decolorizing agent container C described in the first to fourth aspects of the printing apparatus can be of a replaceable cartridge type.

<Writing device>
Next, a writing device capable of writing using the ink according to the present embodiment will be described with reference to FIGS. 7 and 8. 7 and 8 are schematic views illustrating an example of a writing apparatus using ink according to the present embodiment.
As described above, the ink according to the present embodiment develops color due to the volatilization of the decolorizing agent. In order to prevent unnecessary color development and appropriately monitor the control temperature, the writing apparatus using the ink according to this embodiment prevents the decolorizing agent from volatilizing from the ink before printing in the apparatus. It is preferable to adopt a configuration that does. 7 and 8 both show a writing device that employs a configuration that prevents the decolorizing agent from volatilizing. The same reference numerals are given to the configurations common to each aspect, and detailed description thereof will be omitted.

<First aspect of the writing device>
As shown in FIG. 7, the writing device 70 according to the first aspect includes an ink case 72 and a writing device cooling unit 73 in a substantially cylindrical outer case 71.
The ink case 72 contains the ink according to the present embodiment. The writing device cooling unit 73 is provided in the outer case 71 so as to cover the outer periphery of the ink case 72, and cools the ink case 72. As the cooling unit 73 for the writing device, for example, a cooling agent (cooling agent) that has been cooled or frozen in advance can be used. The outer case 71 and the ink case 72 may be made of any resin.

The ink case 72 is connected to the pen tip portion 74 so that the ink in the ink case 72 can be supplied to the pen tip portion 74. The outer case 71 may be provided with an observation window 75. By doing so, when the ink case 72 is made of a transparent material, the remaining amount of ink in the ink case 72 can be confirmed.

As described above, the writing device 70 includes a writing device cooling unit 73 for cooling the ink case 72. Therefore, the ink in the ink case 72 is cooled by cooling the ink case 72 with the writing device cooling unit 73. Can be cooled. Therefore, the writing device 70 can prevent the solvent and the decoloring agent from volatilizing in the ink case 72.

<Second aspect of writing device>
As shown in FIG. 8, the writing device 80 according to the second aspect includes a mixed liquid case 81, a decolorizing agent case 82, and a main case 83 in a substantially cylindrical outer case 71. ..
The mixed liquid case 81 contains a mixed liquid containing a leuco dye, a color developer and a solvent. The decolorizing agent case 82 contains a mixed solution containing the decolorizing agent. The main case 83 is connected to the mixed liquid case 81 and the decolorizing agent case 82, respectively. The main case 83 mixes the mixed liquid supplied from the mixed liquid case 81 and the decolorizing agent supplied from the decolorizing agent case 82 to obtain the ink according to the present embodiment, and supplies the ink to the pen tip portion 74. do.
The mixed liquid case 81, the decolorizing agent case 82, and the main case 83 may all be formed of any resin.

The writing device 80 mixes the mixed liquid supplied from the mixed liquid case 81 and the decolorizing agent supplied from the decolorizing agent case 82 in the main case 83. As described above, since the writing device 80 mixes the mixed liquid and the decoloring agent immediately before supplying the ink to the pen tip portion 74, it is possible to prevent the decolorizing agent from volatilizing in the main case 83.

Next, the irreversible heat-sensitive color-developing ink will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

<Making irreversible heat-sensitive color-developing ink>
As a leuco dye, 2'-methyl-6'-(N-p-tolyl-N-ethylamino) spiro [isobenzofuran-1 (3H), 9'-[9H] xanthene] -3-one (manufactured by Yamada Chemical Co., Ltd.) RED520) by 4 parts by weight, Tokyo Kasei Kogyo Co., Ltd. octyl eclipse by 8 parts by weight as a developer, N, N-diethylethanolamine having a boiling point of 162 ° C. as a decolorizing agent by 8 parts by weight, and a number average molecular weight as a binder material ( Mn) 10 parts by weight of a copolymer of polyvinyl alcohol and polyvinyl acetate of 10000 (number of repetitions of polyvinyl alcohol unit: number of repetitions of polyvinyl acetate unit ≈ 36:64, hydroxyl value is 285), 70 parts by weight of methyl ethyl ketone as a solvent Used part. Irreversible heat-sensitive color-developing ink was prepared by mixing these materials for about 1 hour.

The volatility of the solvent, the volatility of the decolorizing agent, the volatility of the leuco dye and the color developer, and the volatility of the binder material were determined by using a heat-drying moisture meter MS-70 to measure 1 g of each material at 110 ° C. It was verified by measuring the amount of evaporation when heated for a minute.
As a result, the volatility of the solvent was 99%, the volatility of the decolorizing agent was 20%, the volatility of the leuco dye and the color developer was 0.01 wt%, and the volatility of the binder material was 0 wt%.
It was confirmed that the volatility has a relationship of solvent> decolorizing agent> leuco dye and developing agent> binder material.

<Evaluation of temperature and time detection function>
The produced ink was filled in an inkjet printer UX type manufactured by Hitachi Industrial Equipment Systems Co., Ltd., and printed on a white polypropylene base material. The printed dots printed on the substrate were colorless in the initial state.
When it was allowed to stand in an environment of 20 ° C. for one week, it was confirmed that it remained colorless.
When the substrate on which the print dots were printed was allowed to stand in an environment of 110 ° C. under normal pressure, the color gradually began to develop in red after 1 minute (see FIGS. 9A and 9B), and completely became red after 10 minutes. It was confirmed to be colored (see FIGS. 9C and 9D). It is probable that this color development was caused by the volatilization of the decolorizing agent. Note that FIG. 9A is a photograph showing the time-temperature dependence of the print dots using the irreversible heat-sensitive color-developing ink according to the first embodiment. The figure shows a state after 1 minute has passed at 110 ° C. under normal pressure. 9B is a schematic diagram of FIG. 9A. FIG. 9C is a photograph showing the time-temperature dependence of the print dots using the irreversible heat-sensitive color-developing ink according to the first embodiment. The figure shows a state after 10 minutes have passed at 110 ° C. under normal pressure. 9D is a schematic diagram of FIG. 9C. After that, the substrate on which the print dots were printed was allowed to stand again in an environment of 20 ° C., but it was confirmed that the print dots once developed in red did not return to the original colorlessness and retained the red color.
On the other hand, as described above, when the substrate on which the print dots are printed is allowed to stand in an environment of 60 ° C. under normal pressure, it begins to develop a gradual red color after 1 day and completely develops a red color after 1 week. Was confirmed (not shown).

From the above, it was confirmed that the irreversible heat-sensitive color-developing ink according to Example 1 can be printed on a substrate by a charge control type inkjet printer. Further, it was confirmed that the print dots formed by printing in this way can be colored in color by integrating the temperature and time when the temperature rises above a predetermined temperature. Furthermore, it was confirmed that the discoloration of the printed dots once discolored was irreversible.

<Making irreversible heat-sensitive color-developing ink>
4 parts by weight of 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (CVL manufactured by Yamada Chemical Co., Ltd.) as a leuco dye, and 8 parts by weight of octyl eclipse acid produced by Tokyo Kasei Kogyo as a developer. A copolymer of polyvinyl alcohol and polyvinyl acetate having a number average molecular weight (Mn) of 10000 as a binder material containing 8 parts by weight of triethanolamine having a boiling point of 335 ° C as a decolorizing agent (number of repetitions of polyvinyl alcohol unit: Polyvinyl acetate unit) The number of repetitions ≈36: 64, the hydroxyl value was 285) by 10 parts by weight, and 70 parts by weight of methyl ethyl ketone was used as the solvent. Irreversible heat-sensitive color-developing ink was prepared by mixing these materials for about 1 hour.

Similar to Example 1, the volatility of the solvent, the volatility of the decolorizing agent, the volatility of the leuco dye and the color developer, and the volatility of the binder material were measured by a heat-drying moisture meter MS-70 with 1 g of each material. Was verified by measuring the amount of evaporation when heated at 110 ° C. for 1 minute.
As a result, the volatility of the solvent was 99%, the volatility of the decolorizing agent was 10%, the volatility of the leuco dye and the color developer was 0.01 wt%, and the volatility of the binder material was 0 wt%.
It was confirmed that the volatility has a relationship of solvent> decolorizing agent> leuco dye and developing agent> binder material.

<Evaluation of temperature and time detection function>
The produced ink was filled in an inkjet printer UX type manufactured by Hitachi Industrial Equipment Systems Co., Ltd., and printed on a white polypropylene base material. The printed dots printed on the substrate were colorless in the initial state.
When it was allowed to stand in an environment of 20 ° C. for one week, it was confirmed that it remained colorless.
When the substrate on which the print dots were printed was allowed to stand in an environment of 110 ° C. under normal pressure, the color gradually began to develop in blue after 2 minutes (see FIGS. 10A and 10B), and completely became blue after 20 minutes. It was confirmed to be colored (see FIGS. 10C and 10D). It is probable that this color development was caused by the volatilization of the decolorizing agent. FIG. 10A is a photograph showing the time-temperature dependence of the print dots using the irreversible heat-sensitive color-developing ink according to the second embodiment. The figure shows the state after 2 minutes have passed at 110 ° C. under normal pressure. 10B is a schematic diagram of FIG. 10A. FIG. 10C is a photograph showing the time-temperature dependence of the print dots using the irreversible heat-sensitive color-developing ink according to the second embodiment. The figure shows the state after 20 minutes have passed at 110 ° C. under normal pressure. 10D is a schematic diagram of FIG. 10C. After that, the substrate on which the print dots were printed was allowed to stand again in an environment of 20 ° C., but it was confirmed that the print dots once developed in blue did not return to the original colorlessness and retained the blue color.
On the other hand, as in the above, when the substrate on which the print dots were printed was allowed to stand in an environment of 60 ° C. under normal pressure, it began to develop a gradual blue color after 3 days and completely developed a blue color after 2 weeks. Was confirmed (not shown).

From the above, it was confirmed that the irreversible heat-sensitive color-developing ink according to Example 2 can also be printed on the substrate by the charge control type inkjet printer. Further, it was confirmed that the print dots formed by printing in this way can be colored in color by integrating the temperature and time when the temperature rises above a predetermined temperature. Furthermore, it was confirmed that the discoloration of the printed dots once discolored was irreversible.
Further, from the results of Example 2 and Example 1, by using decolorizing agents having different boiling points for the irreversible heat-sensitive color-developing ink, the discoloration temperature and time of the print dots formed by the charge control type inkjet printer can be adjusted. I was able to confirm that there was.

<Making irreversible heat-sensitive color-developing ink>
4 parts by weight of 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (CVL manufactured by Yamada Chemical Co., Ltd.) as a leuco dye, 8 parts by weight of octyl eclipse manufactured by Tokyo Kasei Kogyo as a color developer, As a decolorizing agent, 8 parts by weight of triethanolamine having a boiling point of 335 ° C. was used, and as a solvent, 80 parts by weight of methyl ethyl ketone was used. Irreversible heat-sensitive color-developing ink was prepared by mixing these materials for about 1 hour.
Volatility is the relationship of solvent> decolorizing agent> leuco dye and coloring agent as in Example 2.

<Evaluation of temperature and time detection function>
The produced ink was filled in an inkjet printer UX type manufactured by Hitachi Industrial Equipment Systems Co., Ltd., and printed on a white polypropylene base material. The printed dots printed on the substrate were colorless in the initial state.
When it was allowed to stand in an environment of 20 ° C. for one week, it was confirmed that it remained colorless.
When the substrate on which the print dots were printed was allowed to stand in an environment of 110 ° C. under normal pressure, it was confirmed that the color gradually began to develop in blue after 2 minutes and completely developed in blue after 20 minutes (). The photographs and schematic views were the same as those in FIGS. 10A to 10D). It is probable that this color development was caused by the volatilization of the decolorizing agent. After that, the substrate on which the print dots were printed was allowed to stand again in an environment of 20 ° C., but it was confirmed that the print dots once developed in blue did not return to the original colorlessness and retained the blue color.
On the other hand, as in the above, when the substrate on which the print dots were printed was allowed to stand in an environment of 60 ° C. under normal pressure, it began to develop a gradual blue color after 3 days and completely developed a blue color after 2 weeks. Was confirmed (not shown).
From the above, it was confirmed that even in the ink containing no binder material, the performance of printing dots to develop color depends on the temperature and time.

Although the irreversible heat-sensitive color-developing ink according to the present invention and the printing apparatus using the same have been described in detail with reference to embodiments and examples, the gist of the present invention is not limited thereto, and various modifications are made. Is included. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1 Base material 2 Printing dots 3 Leuco dye 4 Color developer 5 Decoloring agent 6 Binder material 10 Charge control type inkjet printer 11 Inkjet head 12 Nozzle 13 Charging electrode 14 Deflection electrode 15 Gutter 16 Ink droplet 17 Printing object 30, 40, 50, 60 Printing device 31 1st container holding part 32 Cooling part 33 Printing device main body 34 Main container 35 Dye container 41 2nd container holding part 42 3rd container holding part

Claims (10)

Contains leuco dyes, color developers, decolorants and solvents,
At least one of the leuco dye, the developer and the decolorizer is not microencapsulated and
The volatility satisfies the relationship of the solvent> the decolorizing agent> the leuco dye and the coloring agent.
An irreversible heat-sensitive color-developing ink characterized in that the decolorizing agent volatilizes to develop a colored color. In claim 1,
Including more binder material,
An irreversible heat-sensitive color-developing ink characterized in that the volatility satisfies the relationship of the solvent> the decolorizing agent> the leuco dye and the developing agent> the binder material. In claim 1,
An irreversible heat-sensitive color-developing ink, characterized in that print dots formed by printing the irreversible heat-sensitive color-developing ink with an inkjet printer develop a color when the temperature at which the decolorizing agent volatilizes. In claim 3,
An irreversible heat-sensitive color-developing ink, wherein the inkjet printer is a charge-controlled inkjet printer. In claim 1,
An irreversible heat-sensitive color-developing ink, characterized in that the decolorizing agent is an amino compound. In claim 1,
An irreversible heat-sensitive color-developing ink characterized by having a boiling point of the decolorizing agent of 80 to 370 ° C. In claim 1,
An irreversible heat-sensitive color-developing ink, wherein the solvent contains at least one of alcohols, ketones, esters, and ethers. In claim 1,
An irreversible heat-sensitive color-developing ink comprising at least one of a conductive agent, a leveling agent and a plasticizer. A printing apparatus for printing using the irreversible heat-sensitive color-developing ink according to any one of claims 1 to 8.
A first container holding portion for holding an ink container containing the irreversible heat-sensitive color-developing ink, and a first container holding portion.
A cooling unit provided adjacent to the first container holding portion and cooling the first container holding portion, and a cooling unit.
A printing apparatus characterized by being provided with. A printing apparatus for printing using the irreversible heat-sensitive color-developing ink according to any one of claims 1 to 8.
A second container holding portion that holds a mixed liquid container containing the mixed liquid containing the leuco dye, the color developer, and the solvent.
A third container holding portion for holding the decolorizing agent container containing the decolorizing agent, and
A main container that mixes the mixed liquid supplied from the mixed liquid container and the decoloring agent supplied from the decolorizing agent container to obtain the irreversible heat-sensitive color-developing ink.
A printing apparatus characterized by being provided with.

Images