JP6133702B2 - Ink jet ink, method for producing the same, and method for using the same - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is suitably used for printing and recording with an ink jet printer on the surface of food (including food pills, the same applies hereinafter), packaging materials for food wrapping, materials that have an opportunity to come into contact with food, and the like. In particular, the present invention relates to an ink-jet ink having improved drying properties with ethanol, a method for producing the same, and a method for using the same.

  In recent years, food and food packaging materials are required to display the production location, producer, production history, and the like, and the quality, such as the expiration date and the date of manufacture, has become necessary. Displaying these pieces of information can confirm safety and provide a sense of security and reliability for the product. In addition, the quality can be improved from such a viewpoint.

  On the other hand, processing characters, figures, designs, etc. on foods and related packaging materials is also an important factor for making a product that incentivizes purchase. When recording directly on food, it is naturally necessary to use ink made of edible materials, but when recording on food-related materials such as packaging, using edible ink materials is more A sense of security is obtained. From such a viewpoint, an ink composed of a material composed of a food material or a food additive is desired.

  Therefore, conventionally, inks made from food additives have been known as a countermeasure for foods. However, preparing inks from materials that can be taken orally has limitations on ink materials. In addition, since there are few types of such ink materials, it is difficult to prepare them in the same manner as general inkjet inks.

  That is, first, some inks mainly composed of water are known, but they are inferior in water resistance and cannot be used for objects that come into contact with water. There was a problem that there was too much concentration and the concentration was not sufficient.

For example, a green ink composition is known that contains shellac resin as a binder, ethanol and water as solvents, and iron chlorophyllin sodium or (and) copper chlorophyllin sodium as a colorant (see Patent Document 1).
In this ink, the colorant such as copper chlorophyllin used is a water-soluble pigment that does not have sufficient solubility in alcohol, so a large amount of water is used to increase the ink concentration. Is essential. For this reason, this ink is essentially composed mainly of water and is used by mixing a small amount of ethanol. In addition, some of the materials that were not allowed for food additives were used.
Therefore, although this ink is excellent in water resistance and is an inkjet ink suitable for printing on the food surface, it cannot be said that the above-mentioned problems have been solved yet as long as it is mainly composed of water.

An ink containing a bayberry extract or the like as an edible stabilizer is also known (see Patent Document 2).
This ink is intended to stabilize the light resistance of the pigment, and the composition of the ink is an ink that uses 70% by weight or more of the total ink, and the pigment and stabilizer are exclusively used for water. Since it has solubility, ethanol is used only about 20% by weight of the total ink.
Therefore, this ink is also an ink mainly composed of water, and the pigment, resin, etc. are easily dissolved by water.
In addition, when the object to be recorded is transparent, or conversely black or dark brown, the ink is transparent when printing with colored natural pigments that dissolve in the solvent. Therefore, problems such as a lack of opacity in the required printed portion and a failure to confirm the printing effect due to the underlying color are likely to occur.

Furthermore, a printing ink for an orally administered product obtained by blending a colorant component in an aqueous vehicle containing a water-soluble resin as a binder and further adding a wetting agent is also known (see Patent Document 3).
According to this ink, it is possible to extend the clean-up interval of printing equipment parts during printing, improve printing efficiency, and improve printing performance to ensure clearer printing. However, the ink is mainly water.

Unlike the above water-based ink, an ink composition using a water-insoluble solvent has also been proposed (see Patent Document 4).
Specifically, this ink composition is one in which Bengala is dispersed in a non-water-soluble solvent and has a low bleeding and a high printing density.
However, few water-insoluble solvents are allowed to be added to foods. For example, octane used in Examples of Patent Document 4 is not allowed to be added to foods except for the purpose of flavoring. . Moreover, since water-insoluble solvent is used as a solvent, it is difficult to impart conductivity.
Therefore, restrictions on the use of ink have not been sufficiently solved.

  In order to solve the above problems, the applicant of the present application has previously proposed an edible ink-jet ink for food use using charcoal pigment as a coloring material (see Patent Document 5).

Japanese Patent Laid-Open No. 53-127010 JP 09-302294 A JP 2001-31898 A JP 2007-106913 A JP 2010-248313 A

According to the above-mentioned ink filed earlier by the applicant of the present application, the ink can be made of a material that can be taken orally, and it can meet the demands of sufficient visibility, water resistance, etc. The material is charcoal pigment and is limited to black or gray ink.
Therefore, the ink is composed of materials that can be taken orally, and ink that can meet the requirements of sufficient visibility, water resistance, etc. is separately added with an ink composition different from the above ink using carbon powder pigment. The issue was to provide a new one.
Specifically, an object of the present invention is to provide an inkjet ink having sufficient visibility even when recorded on various foods, materials that come into contact with food, food packaging materials, and the like. It is another object of the present invention to form an opaque clear print record without a decrease in visibility due to being transparent like a dye even when the recording object is dark. In addition, when recorded on various foods, food contact materials, food packaging materials, etc., inks that have been recorded on foods and packaging materials that do not dissolve pigments and do not cause disgusting appearance even when wet. For the purpose of providing. In addition, it is intended to provide ink composed only of materials that are allowed to be added to foods and medicinal tablets, and packaging materials recorded with this ink. At this time, even if the food comes into contact or the recorded portion directly contacts the mouth, the object is to eliminate the concern about hygiene. Furthermore, it aims at making the ink after recording into the ink which is excellent in light resistance and abrasion resistance.

As a result of intensive studies in order to solve the above-described conventional problems, the present inventors, as a premise that ethanol is included for improving dryness, all can be taken orally, iron oxide, molecular weight By using 10,000 to 150,000 hydroxypropyl cellulose and water, an ink-jet ink in which iron oxide was dispersed in hydroxypropyl cellulose and a water ethanol solvent could be realized.
Further, in producing the ink, it has also been found that it is effective to employ two specific steps described later in order to obtain an iron oxide having excellent dispersibility stability.
Furthermore, the optimal usage method which uses the said ink was also discovered.

That is, the inkjet ink for tablets according to the present invention (hereinafter sometimes simply referred to as “inkjet ink”) includes iron oxide having an average particle size of 0.01 to 10 μm and hydroxypropyl having a molecular weight of 10,000 to 150,000. Cellulose and a solvent containing ethanol as a main component and water are essential components (except for those containing shellac resin as a component) .

In the method for producing an inkjet ink according to the present invention, iron oxide is dispersed in a first resin solution in which hydroxypropyl cellulose having a molecular weight of 10,000 to 150,000 is dissolved in a first solvent in which water and / or ethanol are essential. A first step of obtaining a dispersion, and a second solvent containing 50% by weight or more of ethanol based on hydroxypropyl cellulose having a molecular weight of 10,000 to 150,000 or both of the hydroxypropyl cellulose and a conductive agent. A second step of mixing the resin solution and the dispersion obtained in the first step, wherein the iron oxide is an inkjet ink in which iron oxide having an average particle size of 0.01 to 10 μm is dispersed (however, , Except for those containing shellac resin as a component) .

  The method of using the inkjet according to the present invention is characterized in that the inkjet ink is diluted with a diluent solvent containing ethanol, water and a conductive agent when the inkjet ink is used in an inkjet printer.

  In the following, “ink-jet ink” may be simply abbreviated as “ink” in the present invention. “Hydroxypropyl cellulose” may be simply abbreviated as “HPC”.

The ink according to the present invention can be widely used for food-related applications because iron oxide, HPC, ethanol and water, which are essential components, can be taken orally.
Specifically, for example, food or packaging materials recorded with this ink can be used with peace of mind in food packaging materials. Can be implemented. In particular, even when food is in direct contact with food, or when food is in contact with food or when the recorded portion is in direct contact with the mouth, hygiene concerns can be eliminated.
The ink according to the present invention is also excellent in water resistance because the solvent is mainly composed of ethanol, enabling clear printing with high visibility.
Specifically, for example, when recording is made on various foods, materials that come into contact with foods, food packaging materials, etc., sufficient visibility can be provided to the recorded portions. Further, even when the recording object is a dark color, an opaque and clear print record can be formed without causing a drop in visibility as in the case of using a transparent dye. And when it records on various foodstuffs, the material which touches foodstuffs, food packaging materials, etc., even if it gets wet, there is an advantage that a pigment does not elute and it does not give a disgusting appearance.
Since the ink according to the present invention further contains water as a solvent, it is useful as a conductive ink.

Moreover, according to the method for producing an ink according to the present invention, it is possible to produce an ink having very excellent iron oxide dispersion stability.
Specifically, in the method for producing an ink according to the present invention, first, HPC that is easily dissolved in water and ethanol is dissolved in a first solvent essentially containing water and / or ethanol to form a first resin solution. Iron oxide is easily dispersed in the first resin solution to form a dispersion. On the other hand, HPC for adjusting viscosity and an ethanol-soluble conductive agent are dissolved in a second solvent mainly composed of ethanol to form a second resin solution, and the dispersion is mixed with the second resin solution. Thereby, an ink in which iron oxide in the dispersion is stably dispersed can be obtained. By the way, in earnest examination when solving the problems of the present invention, it was found that adding a conductive agent to the dispersion causes a decrease in the dispersibility of iron oxide, but the method for producing an ink according to the present invention According to this, it is possible to effectively suppress a decrease in dispersibility of iron oxide due to the conductive agent.
In addition, since the addition amount can be increased by using a low molecular weight HPC, the dispersion stability of iron oxide can be improved, and an ink having a viscosity that can be stably discharged by an ink jet printer can be prepared. .

  According to the method of using the ink according to the present invention, the ink is used in an ink jet printer while appropriately diluting the ink with a diluting solvent containing ethanol, water and a conductive agent, so that severe continuous printing is performed with the ink jet printer. Even in this case, it is possible to prevent the ink from being concentrated in the printer and to maintain an appropriate conductivity. Thereby, long-term continuous printing performance can be stably continued without lowering the conductivity of the ink.

  Hereinafter, the ink according to the present invention, a method for producing the same, and a method for using the same will be described in detail. However, the scope of the present invention is not limited to these descriptions, and the gist of the present invention is impaired except for the following examples. Changes can be made as appropriate without departing from the scope.

〔ink〕
The ink of the present invention contains iron oxide, HPC, and a solvent mainly composed of ethanol and containing water as essential components.
The essential components in the ink of the present invention are generally recognized as those that can be taken orally, as will be described later.
As described above, since the ink of the present invention has an advantage that the essential component is made of only an orally ingestible material, in order to maintain this advantage, the ink of the present invention can be used even when it contains a component other than the essential component. It is desirable that the material be ingestible.
Therefore, all the materials exemplified below are based on selection that can be taken orally. However, it should not be construed that any material not recognized as an orally ingestible material is immediately excluded from the subject of the present invention.
In addition, whether or not it can be taken orally can be used as a rough standard based on whether it is listed in food additives, Japanese pharmacopoeia and pharmaceutical additive standards defined by the Food Sanitation Law.

<Iron oxide>
The ink according to the present invention uses iron oxide as an edible dye and an opaque material.
Preferred examples of the iron oxide include red iron sesquioxide showing red, yellow iron sesquioxide showing yellow, and black iron oxide showing black. All of these are allowed to be added to food or pharmaceutical products. In particular, iron sesquioxide showing red is preferable.
The iron sesquioxide, also called Bengala, is a material that has been used for coloring cosmetics and foods since ancient times, and is therefore a valuable material that provides a sense of security for use in foods. Since iron sesquioxide shows a clear red or brown color when refined, it is easy to obtain density and opacity when the ink is prepared. In addition, since iron sesquioxide does not exhibit magnetism at room temperature, it is relatively easy to achieve the miniaturization required for inkjet use, and iron oxide particles are not adsorbed to the equipment and equipment during ink preparation, making it easy to handle. .

As said iron oxide, an average particle diameter of 0.01-10 micrometers is preferable. If the average particle size of the iron oxide is larger than 10 μm, it may take too much time to disperse sufficiently in the ink, and there is a possibility that the characteristics of the HPC may be changed due to excessive heat. . If the average particle diameter of the iron oxide is smaller than 0.01 μm, there is a possibility that a problem of a decrease in printing density may occur.
An average particle diameter of 0.05 to 3 μm is more preferable. Such an ink containing iron oxide having an average particle diameter of 0.05 to 3 μm enables particularly good opacity and clear color reproduction. On the other hand, when the average particle diameter of iron oxide is larger than 3 μm, sedimentation occurs during storage of the ink, which may cause sedimentation or clogging of the ink in the printer piping system. Further, it is not preferable to make the average particle diameter finer than 0.05 μm because unnecessary dispersion energy is required, and it is not preferable in terms of inducing transparency.
Among them, those having an average particle diameter of 1 μm or less are particularly preferable.
Such adjustment of the average particle diameter can be performed by a horizontal sand mill.
In the present invention, the average particle diameter of iron oxide refers to a value measured with a light scattering type particle size distribution meter using laser light.

<HPC>
The HPC used in the present invention is a nonionic water-soluble polymer obtained by reacting with an etherifying agent such as propylene oxide after using cellulose such as pulp that exists widely in nature as a raw material, treating it with sodium hydroxide. (Cellulose ether).
HPC is recognized as an orally ingestible material. For example, it is used as a food additive in Europe and the United States. In recent years, it has been approved in Japan as a food additive based on the provisions of Article 10 of the Food Sanitation Law and a material that can be added to pharmaceuticals by the Japanese Pharmacopoeia. ing.
In the ink of the present invention, HPC acts as a dispersion stabilizer for iron oxide particles and a binder component of the ink, and has a low foaming property with respect to water.
In addition, HPC is soluble in both water and ethanol, and particularly has higher solubility in ethanol than other water-soluble and edible cellulose derivatives such as sodium carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC). Is expensive. Furthermore, it was found that the iron oxide particles are suitable for stable dispersion in a solvent because of its chemical structure and high solubility.

The HPC having a molecular weight of 10,000 to 150,000 is used. If it is this range, the iron oxide which is a pigment | dye can be disperse | distributed stably, and it will be easy to obtain the appropriate viscosity in an inkjet printer. On the other hand, when HPC having a molecular weight of less than 10,000 is used, it is difficult to stably disperse iron oxide particles and prepare a stable ink. On the other hand, if HPC having a molecular weight exceeding 150,000 is used, the viscosity of the HPC itself is too high, and the viscosity of the ink becomes excessively high, making it difficult to eject with an inkjet printer. In addition, since the viscosity of the dispersion is increased, a dispersion load is excessively applied during the dispersion treatment (because it needs to be used in a disperser for a long time), resulting in a reduction in work efficiency.
Incidentally, the HPC of the above molecular weight distribution has a viscosity of 2 to 10 mPa. Corresponding to s (20 ° C.).
In addition, the molecular weight as used in the field of this invention is computed from intrinsic viscosity (measured value) using the following formula (1) of Mark-Houwink-Sakurada (Mark Fwinck, Sakurada).

                    [Η] = KMα (1)

  In formula (1), [η] is the intrinsic viscosity, M is the molecular weight, K is a constant specific to the substance to be measured, and α is a constant specific to the substance to be measured. The constant K and the constant α are known in advance for each substance to be measured. The intrinsic viscosity [η] is obtained by measuring the viscosity of a plurality of solutions having different concentrations of the solvent and the concentration of the substance to be measured, and extrapolating from the plurality of measured viscosity values.

<Solvent>
In the ink of the present invention, the solvent is mainly composed of ethanol and contains water.
As the ethanol, fermented ethanol for food or denatured ethanol is known and can be suitably used in the present invention.
In the range which does not impair the effect of this invention, you may further contain solvents other than ethanol and water.

<Other additives>
The ink of the present invention may contain other additives such as a wetting agent, an emulsifier, and a conductive agent as long as the effects of the present invention are not impaired.

(Wetting agent)
Examples of the wetting agent include propylene glycol and glycerin.
The wetting agent serves to adjust ink drying properties and ink viscosity. Further, depending on the background of the recording material, the effect of adjusting the permeability is also suitable for the purpose of use.
The wetting agent may be used as part of the solvent described above.

(emulsifier)
Examples of the emulsifier include sorbitan fatty acid ester, glycerin fatty acid ester, sucrose fatty acid ester, and lecithin. These emulsifiers are edible and excellent in aqueous stability, and contribute to the dispersion stability of iron oxide in the ink.
Among these emulsifiers, nonionic surfactants have suitability for HLB of ink depending on the type of the recording object. Therefore, when the recording object is a packaging film, HLB 8 to 16 are also used as fats and oils. For foods with a lot of minutes, it is suitable for recording to make ink adjustments such as HLB1-2.

(Conductive agent)
The ink of the present invention can be used for both continuous type ink jet printers and on-demand type ink jet printers. However, in the case of inks used for continuous type ink jet printers, the electrical conductivity corresponding to the printer used is used. Adjustments are made. The conductive agent is used for adjusting the conductivity.
Examples of the conductive agent include sodium lactate, sodium acetate, sodium dehydroacetate, and sodium pantothenate. All of these can be taken orally. In particular, sodium acetate dissolves well in alcohol-containing solvents and can achieve the role of maintaining the conductivity of ink droplets in printers in a small amount. It is also effective in suppressing the decrease in stability as much as possible.
In addition, in tableted products where the print object has hygroscopicity, ink peeling and transfer are likely to occur, but sodium acetate has the characteristic that these symptoms are less likely to occur than other conductive agents. doing.
Further, the dispersion stability of iron oxide is more stable than the addition of other conductive agents. The combination of iron oxide and sodium acetate is good not only for the stability immediately after the addition, but also for the stability over time after the addition.

<Ink blending>
Iron oxide is related to the content of other components in the present invention, but is preferably contained in the ink in the range of 0.3 to 20% by weight of the total ink. Furthermore, Preferably it is 0.5 to 5 weight%.
If the content of iron oxide is less than 0.3% by weight, the print density becomes insufficient.
On the other hand, when the content of iron oxide exceeds 20% by weight, poor dispersion and continuous printability are deteriorated. In particular, the stability tends to deteriorate in continuous recording. In addition, the fluidity in the ink piping system in the printer is insufficient, and the content concentration of iron oxide in the ink discharged due to sedimentation of iron oxide particles is reduced, leading to a decrease in the density of printed matter. Further, as a problem that may occur, the ink flow path is blocked, and the discharge from the nozzle itself becomes difficult.

  In the present invention, HPC is preferably contained in the range of 0.1 to 10% by weight of the total ink, and more preferably in the range of 1 to 8% by weight. If the HPC content is less than 0.1% by weight, it may be difficult to obtain an ink having a viscosity that can be stably ejected by an ink jet printer, and sufficient adhesion to a recording object is difficult to obtain. There is a risk. On the other hand, if it exceeds 10% by weight, the viscosity of the ink becomes too high, the fluidity at low temperature is insufficient, and the stability during recording of the ink jet printer may be lowered.

A solvent can be used in 50 to 97 weight% of the range of the whole ink, for example.
In the present invention, the solvent is mainly composed of ethanol and contains water, and the content ratio thereof can be appropriately determined in consideration of the required drying property and water resistance of the ink.
The meaning that the solvent is mainly ethanol is basically 50% by weight or more of the whole solvent, but may be slightly less than 50% by weight as long as the effect of the present invention can be exhibited.
And as a content rate with respect to the whole ink of ethanol, 40 to 90 weight% of the whole ink is preferable, for example.
Moreover, although the content rate of water is related with content of another component, the range of 3-20 weight% of the whole ink is preferable, for example. If the water content is less than 3% by weight, it may be difficult to obtain stable iron oxide dispersion and conductivity during ink preparation. On the other hand, if the water content is more than 20% by weight, the drying property is lowered, and there is a possibility that the characteristic of “fast drying property” for ethanol ink cannot be obtained.

When the humectant, which is an optional component, is used in the range of 0 to 10% by weight of the entire ink, it is possible to appropriately permeate the recording object and adjust the drying. When the content of the wetting agent exceeds 10% by weight, there is a possibility that the intended improvement in drying property cannot be achieved.
The emulsifier is preferably used in an amount of 5% by weight or less based on the solubility in an alcohol solvent, and a sufficient effect can be obtained by using the emulsifier within the range.
Furthermore, although the addition amount of the said electrically conductive agent is related with content of another component, it is preferable that it is 0.2 to 2.0 weight% of the whole ink. By using within this range, the electrical conductivity of the ink can be appropriately set to about 0.3 m to 5 mS / cm. Adjustment within a small amount is preferable even within the above range. When the addition amount of the conductive agent exceeds 2.0% by weight, there is a possibility of causing aggregation of the dye.

[Manufacture of ink]
The ink of the present invention can be prepared by arbitrarily mixing the above essential components and other optional components, and the production method thereof is not particularly limited.
However, in order to obtain an iron oxide having excellent dispersion stability, a production method including the following first step and the following second step is preferable.
In particular, the conductive agent tends to reduce the dispersion stability of iron oxide, but the following production method can effectively suppress the decrease in the dispersion stability of iron oxide due to the conductive agent. This is presumably because the stable dispersion was first prepared and then mixed with the solution containing the conductive agent.

<First step>
In the first step, iron oxide is dispersed in a first resin solution in which HPC is dissolved in a first solvent essentially containing water and / or ethanol to obtain a dispersion.
HPC dissolves well in water and ethanol and stabilizes the dispersibility of iron oxide.

First, preparation of the first resin solution will be described.
The composition of the first solvent may be appropriately determined in consideration of the composition of the ink to be finally obtained in relation to the composition of the second solvent described later and the mixing ratio with the second solvent. Specifically, either water or ethanol may be used, but a mixed solvent of water and ethanol is preferable. In such a mixed solvent, the mutual ratio of water and ethanol is, for example, 90: 0 on a weight basis. ~ 30: 50 is preferred.
The content of HPC in the first resin solution may be appropriately determined in consideration of the composition of the ink to be finally obtained, the amount of HPC used in the second step described later, and the solubility of HPC. For example, it is preferable to select so that it may become 1-20 weight% of HPC with respect to the dispersion whole quantity mentioned later. If the HPC is less than 1% by weight, a sufficient concentration of iron oxide may not be dispersed. On the other hand, if the HPC exceeds 20% by weight, the viscosity of the first resin solution becomes excessive, which may cause clogging of the pipes of the disperser, making it impossible to perform sufficient dispersion treatment.

Next, description will be made on the point of obtaining a dispersion by dispersing iron oxide in the first resin solution.
The amount of iron oxide added is preferably in the range of 5 to 30% by weight of iron oxide, for example, with respect to the total amount of the dispersion. If the iron oxide is less than 5% by weight, it is necessary to add a large amount of dispersion in the ink preparation process in order to obtain an ink having a sufficient pigment concentration. Adjustment to an appropriate viscosity may be restricted, and in some cases, nozzle holes may be clogged. On the other hand, if it exceeds 30% by weight, the viscosity of the dispersion becomes excessive, which may cause clogging of the pipes of the disperser, the circulation during dispersion is insufficient, and sufficient dispersion treatment may not be performed.
Further, in relation to HPC in the first resin solution, for example, when 2 to 6 parts by weight of HPC is used with respect to 10 parts by weight of iron oxide, excellent dispersibility can be obtained. If the content of HPC with respect to iron oxide is less than 2 parts by weight, it may be difficult to sufficiently disperse iron oxide. On the other hand, if the content of HPC with respect to iron oxide exceeds 6 parts by weight, the viscosity at the time of dispersion becomes too high, which may cause problems such as a decrease in dispersion efficiency.
When dispersing in the first resin solution, a method of dispersing the iron oxide and the first resin solution with a high-speed agitator mill, a method of applying an impact with the ball mill between the iron oxide and the first resin solution with a reduced amount of solvent, etc. It can be appropriately selected and used. However, from the aspect of mixing with the first resin solution in dispersion, dispersion using a horizontal sand mill using zirconia beads or the like as a dispersion medium is preferable. A medialess disperser that does not use a dispersive medium is also an effective method for producing a dispersoid with less contamination (contamination or contamination). As such a medialess disperser, Nanomizer (Nanomizer), Starburst (Sugino Machine Co., Ltd.), Microfluidizer (Paurec Co., Ltd.), etc. can be used.

<Second step>
In the second step, a second resin solution in which both HPC or HPC and a conductive agent are dissolved in a second solvent containing 50% by weight or more of ethanol as a whole is mixed with the dispersion obtained in the first step. .
The composition of the second solvent only needs to contain 50% by weight or more of ethanol, and the composition of the ink to be finally obtained, the composition of the first solvent and the mixing ratio with the first solvent. It may be determined appropriately in consideration of the above. As the remainder of the solvent, water is preferable, and other solvents such as propylene glycol may be used.
The content of HPC and conductive agent in the second resin solution also takes into account the composition of the ink to be finally obtained, the amount of HPC used in the first step, and the solubility of HPC and conductive agent. May be determined as appropriate.
For example, HPC is preferably in a ratio of 1 to 10% by weight with respect to the total amount of the second resin solution. The conductive agent is preferably in a proportion of 0.2 to 2% by weight with respect to the total amount of the second resin solution. If the weight is less than 0.2%, sufficient conductivity cannot be imparted. In particular, ink droplets are insufficiently charged in a continuous ink jet printer, ink droplets cannot be deflected, and printing failure may occur. is there. If it exceeds 2% by weight, the ion concentration of the whole ink becomes excessive. When the ion concentration is excessive, the repulsive force between the dispersed particles is weakened, and there is a possibility that the iron oxide particles are aggregated.
The mixing ratio of the second resin solution and the dispersion is, for example, preferably from 95: 5 to 70:30 on a weight basis.

[Use of ink]
The ink of the present invention can be used in the same manner as conventional inkjet inks.
When used in an ink jet printer, the ink jet ink can be diluted with a diluting solvent containing ethanol, water and a conductive agent.
When used in an inkjet printer while diluting ink with a diluting solvent as appropriate, even when severe continuous printing is performed with an inkjet printer, it is possible to prevent ink concentration in the printer and maintain an appropriate electrical conductivity. . Thereby, long-term continuous printing performance can be stably continued without lowering the conductivity of the ink.

Since the ink of the present invention contains ethanol as a solvent main component, the drying property is superior to an ink mainly composed of water. Further, even a non-permeable material can form a recording portion having good water resistance, and depending on the recording system, high-speed variable information can be printed.
The subject of the present invention is a food that is safe even if you put it in your mouth, but it can also contain tablets that are restricted by health food or the Pharmaceutical Affairs Law. It is handled as a recording object.
The ink of the present invention can be particularly preferably used for a material that comes into contact with food directly or a packaging material for food. Examples of such packaging materials include plastic materials such as polypropylene, polyethylene, polyamide, and polyethylene terephthalate that have been surface-treated as necessary, or nonwoven fabrics and paper.

  Furthermore, since the ink of the present invention can be composed entirely of those whose ingestion is recognized by laws and regulations such as the Food Sanitation Law and the Pharmaceutical Affairs Law, food design, decoration, and display of high-grade data It is also effective for quality traceability. As the design and its data, a product name, production place, harvest date / time, producer, date, special symbol, character image, etc. can be recorded. These notations can also give reliability to the distribution form of the product as a reliable display method of the route.

  Examples of foods on which the ink of the present invention is recorded include gums, candies, biscuits, cookies, buns, and chocolates. Also, for example, it can be recorded in fruits such as oranges, apples, watermelons, melons, mangoes, strawberries, peaches, vegetables, processed meats, and the like. It is also possible to record in a tablet-like orally ingested product. In addition, packaging materials for packaging these foods are also subject to recording. Alternatively, it can be recorded on food packaging materials such as bread wraps, food trays, lunch boxes, packs, or chopsticks, toothpicks, skewers, etc.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples. Hereinafter, for convenience, “parts by weight” will be expressed as “parts” and “% by weight” will be expressed as “%”.

(Preparation of dispersion)
With the formulations shown in Table 1 and Table 2, dispersions 1-10 according to Preparation Examples 1-10 and dispersions 1A-9A according to Comparative Preparation Examples 1-9 were prepared.
In Tables 1 and 2, HPC (* 1) has a molecular weight of 40,000 and a 2% aqueous solution having a viscosity of 2.5 mPa.s. s (20 ° C.) hydroxypropylcellulose, HPC (* 2) has a molecular weight of 100,000 and a 2% aqueous solution having a viscosity of 4.0 mPa.s. s (20 ° C.) hydroxypropylcellulose, HPC (* 3) has a molecular weight of 300,000 and a 2% aqueous solution having a viscosity of 400 mPa.s. s (20 ° C) is hydroxypropylcellulose, CMC is sodium carboxymethylcellulose.

A specific preparation method is as described in detail below.
<Preparation Example 1>
3 parts of HPC having a molecular weight of 40,000 was dissolved in 87 parts of purified water, and 10 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Preparation Example 2>
Similarly, 6 parts of HPC having a molecular weight of 40,000 was dissolved in 74 parts of purified water, and 20 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 3>
Similarly, 7 parts of HPC having a molecular weight of 100,000 was dissolved in 73 parts of purified water, and 20 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 4>
Similarly, 6 parts of HPC having a molecular weight of 40,000 was dissolved in 74 parts of purified water, and 20 parts of yellow ferric oxide was added thereto and stirred to prepare a premix of yellow ferric oxide.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of yellow ferric oxide.

<Preparation Example 5>
Similarly, 6 parts of HPC having a molecular weight of 100,000 was dissolved in 74 parts of purified water, and 20 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 6>
Similarly, 6.4 parts of HPC having a molecular weight of 40,000 are dissolved in 72.1 parts of purified water, and 21.3 parts of iron sesquioxide and 0.2 part of sucrose fatty acid ester are added thereto and stirred. A premix of iron sesquioxide was prepared.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 21.3% dispersion of iron sesquioxide.

<Preparation Example 7>
Similarly, 5 parts of HPC having a molecular weight of 100,000 is dissolved in 74.8 parts of purified water. To this, 20 parts of iron sesquioxide and 0.2 part of sucrose fatty acid ester are added and stirred. A premix was prepared.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 8>
Similarly, 8 parts of HPC having a molecular weight of 40,000 were dissolved in a mixed solution of 52 parts of purified water and 20 parts of ethanol. To this, 20 parts of iron sesquioxide was added and stirred to prepare a premix of iron sesquioxide. .
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 9>
Similarly, 6 parts of HPC having a molecular weight of 40,000 was dissolved in a mixed solution of 44 parts of purified water and 30 parts of ethanol. To this, 20 parts of iron sesquioxide was added and stirred to prepare a premix of iron sesquioxide. .
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Preparation Example 10>
3 parts of HPC having a molecular weight of 40,000 was dissolved in 87 parts of purified water, and 10 parts of black iron oxide was added thereto and stirred to prepare a premix of black iron oxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% black iron oxide dispersion.

<Comparative Preparation Example 1>
3 parts of HPC having a molecular weight of 40,000 was dissolved in 87 parts of purified water, and 10 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Comparative Preparation Example 2>
3 parts of carboxymethyl cellulose (hereinafter referred to as CMC) was dissolved in 57 parts of purified water and 30 parts of ethanol, and 10 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Comparative Preparation Example 3>
8 parts of HPC having a molecular weight of 300,000 are dissolved in 67 parts of purified water, and 5 parts of glycerin fatty acid ester are mixed therewith. To this, 20 parts of iron sesquioxide was added and stirred to prepare a premix of iron sesquioxide.
This premix was subjected to a dispersion treatment in a bead mill for 2 hours to prepare a 20% dispersion of iron sesquioxide.

<Comparative Preparation Example 4>
3 parts of HPC having a molecular weight of 300,000 is dissolved in 82 parts of purified water, and 5 parts of glycerin fatty acid ester is mixed therewith. To this, 10 parts of yellow ferric oxide was added and stirred to prepare a premix of yellow ferric oxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of yellow ferric oxide.

<Comparative Preparation Example 5>
3 parts of HPC having a molecular weight of 40,000 was dissolved in 87 parts of ethanol, and 10 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Comparative Preparation Example 6>
3 parts of HPC having a molecular weight of 40,000 was dissolved in 87 parts of purified water, and 10 parts of edible red No. 3 aluminum lake was added thereto and stirred to prepare a premix of edible red No. 3 aluminum lake.
This premix was dispersed in a bead mill for 2 hours to prepare a 10% dispersion of edible red No. 3 aluminum lake.

<Comparative Preparation Example 7>
A mixed liquid of 85.5 parts purified water, 3 parts glycerin fatty acid ester, 1 part sucrose fatty acid ester, and 0.5 part sorbitan fatty acid ester was prepared. This mixed solution was added to 10 parts of iron sesquioxide to prepare a premix.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Comparative Preparation Example 8>
1 part of HPC having a molecular weight of 40,000 was dissolved in 89 parts of purified water, and 10 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 10% dispersion of iron sesquioxide.

<Comparative Preparation Example 9>
7.8 parts of HPC having a molecular weight of 40,000 was dissolved in 82.4 parts of purified water, and 9.8 parts of iron sesquioxide was added thereto and stirred to prepare a premix of iron sesquioxide.
This premix was dispersed for 2 hours in a bead mill to prepare a 9.8% dispersion of iron sesquioxide.

[Example: Production of inkjet ink]
<Example 1>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 40,000 in 77 parts of ethanol. While stirring 20 parts of the dispersion 1, the HPC solution was added thereto to sufficiently mix and disperse the dispersion 1 and the HPC solution. To this mixed dispersion, 1 part of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.
<Example 2>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 40,000 in 87 parts of ethanol. While stirring 10 parts of the dispersion 2, the HPC solution was added thereto, and the dispersion 2 and the HPC solution were sufficiently mixed and dispersed. To this mixed dispersion, 1 part of sodium lactate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 3>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 100,000 in 87 parts of ethanol. While stirring 10 parts of the dispersion 3, the HPC solution was added thereto to sufficiently mix and disperse the dispersion 3 and the HPC solution. To this mixed dispersion, 1 part of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 4>
An HPC solution was prepared by dissolving 3 parts of HPC having a molecular weight of 40,000 in 86 parts of ethanol. While stirring 10 parts of the dispersion 4, the HPC solution was added thereto, and the dispersion 4 and the HPC solution were sufficiently mixed and dispersed. To this mixed dispersion, 1 part of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a yellow inkjet ink.

<Example 5>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 100,000 in 82 parts of ethanol. While stirring 10 parts of the dispersion 5, 5 parts of the HPC solution and propylene glycol were added thereto, and the dispersion 5, the HPC solution, and propylene glycol were sufficiently mixed and dispersed. To this mixed dispersion, 1 part of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 6>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 40,000 in 86.7 parts of ethanol. While stirring 10 parts of the dispersion 6, the HPC solution was added thereto, and the dispersion 6 and the HPC solution were sufficiently mixed and dispersed. To this mixed dispersion, 1.3 parts of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 7>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 100,000 in ethanol of 86.2 parts. While stirring 10 parts of the dispersion 7, 0.5 part of the HPC solution and glycerin fatty acid ester were added thereto, and the dispersion 7, the HPC solution, and glycerin fatty acid ester were sufficiently mixed and dispersed. To this mixed dispersion, 1.3 parts of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 8>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 40,000 in 85.5 parts of ethanol. While stirring 10 parts of dispersion 8, 0.5 part of the HPC solution and glycerin fatty acid ester and 0.5 part of sorbitan fatty acid ester are added thereto, and dispersion 8 and the HPC solution, glycerin fatty acid ester and sorbitan fatty acid are added. The ester was thoroughly mixed and dispersed. To this mixed dispersion, 1.5 parts of sodium acetate was added to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 9>
An HPC solution was prepared by dissolving 2 parts of HPC having a molecular weight of 40,000 in 78.5 parts of ethanol. To this HPC solution, 3 parts of propylene glycol and 1.5 parts of sodium acetate were added and dissolved. While stirring 15 parts of Dispersion 9, the above-mentioned solution prepared by adding 3 parts of propylene glycol and 1.5 parts of sodium acetate to the HPC solution was added to the dispersion 9 and the HPC solution, propylene glycol. Then, a solution of sodium acetate was sufficiently mixed and dispersed to prepare an ink. This preparation solution was filtered through a filter having a pore size of 1 μm to obtain a reddish brown inkjet ink.

<Example 10>
A black inkjet ink was obtained in the same manner as in Example 1 except that the dispersion 1 in Example 1 was replaced with the dispersion 10.

<Example 11>
Preparation of the dispersion 1 of Example 1 was omitted, a premix of a mixed solution having a formulation substantially similar to that of Example 1 was prepared, and a bead mill dispersion of this premix was performed to prepare an ink dispersion. . This dispersion was filtered through a filter having a pore size of 1 μm to obtain an inkjet ink.

<Comparative Example 1>
In the same manner as in Example 1, an ink having the composition shown in Table 4 described later was prepared.
Specifically, 4 parts of HPC having a molecular weight of 40,000 was dissolved in 74.5 parts of purified water, and 0.5 part of glycerin fatty acid ester and 1 part of sodium acetate were mixed and dissolved therein. While stirring 20 parts of the dispersion 1A, the above mixed solution was added thereto and mixed and dispersed.
This mixed dispersion was filtered through a filter having a pore size of 1 μm to obtain an inkjet ink.

<Comparative Examples 2-9>
A mixed solution having the composition shown in Table 4 to be described later was prepared, and this mixed solution was added to and mixed with each of dispersions 2A to 9A to obtain inkjet inks according to Comparative Examples 2 to 9.

<Comparative Example 10>
A mixed solution having the composition shown in Table 4 to be described later was prepared, and this mixed solution was added to and mixed with dispersion 1A to obtain an inkjet ink according to Comparative Example 10.

[Performance evaluation]
About each ink of each said Examples 1-11 and Comparative Examples 1-10, the physical-property measurement and performance evaluation which are explained in full detail below were performed.
The results are shown in Tables 3 and 4 together with the formulations of Examples and Comparative Examples.
In Tables 3 and 4, HPC (* 1) has a molecular weight of 40,000, and the viscosity of a 2% aqueous solution is 2.5 mPa.s. s (20 ° C.) hydroxypropylcellulose, HPC (* 2) has a molecular weight of 100,000 and a 2% aqueous solution having a viscosity of 4.0 mPa.s. s (20 ° C.) hydroxypropylcellulose, HPC (* 3) has a molecular weight of 300,000 and a 2% aqueous solution having a viscosity of 400 mPa.s. s (20 ° C) is hydroxypropylcellulose, CMC is sodium carboxymethylcellulose.
In addition, “−” in Table 4 means that it is not worthy of evaluation or cannot be evaluated.

<Ink physical properties>
The average particle diameter of iron oxide in the ink was measured by the median diameter (d50) using a particle size distribution meter (UPA type) manufactured by Nikkiso Co., Ltd.
The viscosity (20 ° C., mPa · s) of the ink was measured using a viscometer (EH cone type RE-80L) manufactured by Toki Sangyo Co., Ltd.
The conductivity (mS / cm) was measured using a conductivity meter (ES-51) manufactured by Horiba.

<Redispersibility>
The original ink was sprinkled on an ink surface of about 1 gram which had been left to dry, and after shaking 20 times, evaluation was performed according to the following criteria in terms of re-dissolvability and the presence or absence of agglomerates by filtration.
○: Redispersibility is good.
X: The particle diameter increases and the film is in a completely aggregated state.

<Water resistance>
Presence or absence of ink dissolution when the printing surface of a recording object printed on paper for filtration of tempura oil was wetted with water by a continuous ink jet printer (model KGK JET CCS-3000 manufactured by Kishu Giken Kogyo Co., Ltd.) This was confirmed by coloring the water and coloring the tissue paper on which the printed surface was wiped, and evaluated according to the following criteria. Moreover, it printed also on the processed product of the corn starch compression-molded with the tableting machine, and confirmed the degree of the blur.
A: Water and tissue paper are not colored at all.
○: Water and tissue paper are slightly colored, but the printing can be read.
X: Printing completely disappears and is unreadable.

<Fixability>
Printed with a continuous ink jet printer (model KGK JET CCS-3000, manufactured by Kishu Giken Kogyo Co., Ltd.) on the processed product compression-molded by a tableting machine. The presence or absence of was evaluated according to the following criteria.
A: No peeling at all.
○: Slightly peeled off, but can be read.
X: The print is completely peeled off and cannot be read.

<Visibility>
Printing was performed in the same manner as in the evaluation of the fixing property, and it was confirmed whether or not it was legible by visual observation, and evaluated according to the following criteria.
A: There is no change immediately after printing.
◯: Printing is slightly missing but legible.
X: Unreadable.

<Printing performance in high temperature environment>
The state of the printing result when a printing test was performed with an ink jet printer in an environmental room maintained at 45 ° C. was evaluated according to the following criteria.
○: The printing state is good. There are no problems with inkjet printers.
X: Iron oxide particles deteriorate and aggregate at high temperatures, causing piping clogging.

<Printing performance in low temperature environment>
The state of the printing result when a printing test was performed with an ink jet printer in an environmental room maintained at 5 ° C. was evaluated according to the following criteria.
○: The printing state is good. There are no problems with inkjet printers.
X: The fluidity of the ink is increased and the piping and nozzles are clogged due to the low temperature.

<Continuous discharge property>
The ink prepared as described above was loaded into a continuous ink jet printer (model KGK JET CCS-3000 manufactured by Kishu Giken Kogyo Co., Ltd.), and troubles (nozzle clogging, defective printing, ink) occurred when continuously performing a printing test. Judgment was made according to the following criteria based on the presence or absence of droplet landing position abnormality or ejection pressure abnormality.
○: Each printing dot has landed correctly.
X: Dot lacks or does not land at a predetermined position.

[Consideration of results]
<Consideration about Examples>
Example 1 is an ink-jet ink containing 2% of iron sesquioxide, which can maintain stable dispersibility and is stable in ejection by a printer. Visibility was good, and fixing results by printing on tableted tablets, and good results without subsequent transfer were shown.
Example 2 also shows good results similar to Example 1. Sodium lactate used as a conductive agent has shown good results in fixability by printing on tableted tablets and subsequent transfer. However, compared to the one using sodium acetate, there is a subtle aspect of subtle quality.
In Example 3, although the molecular weight of HPC is 100,000, the viscosity of the ink can be maintained at an appropriate value, and good results are shown.
In Example 4, yellow ferric oxide was used instead of ferric oxide, but good results similar to those of ferric oxide were obtained.
In Example 5, propylene glycol was used, which has good redispersibility, in particular, good re-dissolvability, and good response to nozzle drying in a printer. On the other hand, in terms of water resistance, although there is no problem, there is a subtle negative aspect.
In Examples 6 and 7, in the preparation of the dispersion, sucrose fatty acid ester was added to promote dispersion, and although the particle diameter was subtle, it was aimed to reduce it.
In Example 7, glycerin fatty acid ester is further added in the second step to stabilize the ink.
In Examples 8 and 9, ethanol is mixed in the dispersion solvent, and in the case where the cooling efficiency of the disperser is not sufficient, the case where the temperature rise during dispersion is relatively high is handled. A dispersion intended to be used is used.
In Example 8, glycerin fatty acid and sorbitan fatty acid ester are added in appropriate amounts to further improve the stability of iron oxide.
In Example 9, propylene glycol was used, and redispersibility, in particular, resolubility was good, and the response to nozzle drying in a printer was good. On the other hand, in terms of water resistance, although there is no problem, there is a subtle negative aspect.
In Example 10, black iron oxide was used as the iron oxide, but it had excellent physical properties as in Example 1 and was capable of forming a good black printed matter.
In Example 11, ink was prepared in advance without obtaining a dispersion. However, although the dispersion time more than double the dispersion time when dispersing Dispersion 1 was applied, in the particle size distribution, The particle size appeared larger.

<Consideration about ink composition based on results of Comparative Examples 1-6>
Comparative Example 1 was an ink mainly composed of water, and caused poor fixing properties due to water resistance and slow drying.
In Comparative Example 2, CMC was used instead of HPC, and poor dispersion occurred due to insufficient solubility in ethanol.
In Comparative Example 3, since the molecular weight of HPC is large, it is difficult to match the suitability for the printer. The ink viscosity has increased.
In Comparative Example 4, the content of HPC was reduced because the molecular weight of HPC was large as in Comparative Example 3, but the viscosity could not be lowered, and stable ejection with a printer was difficult.
Comparative Example 5 uses a dispersion of an alcohol solution of HPC, and is not sufficiently dispersed. In addition, 2 parts or more of a conductive agent was added, and aggregation of the pigment due to excessive addition was also generated. There is no water at the time of dispersion, and even in the ink, there is no water, so the drying property is good, but it is agglomerated and does not form a sufficient ink.
In Comparative Example 6, an edible lake pigment was used, but problems of water resistance and bleeding were generated. In addition, compared with the light resistance of iron oxide, significant deterioration of light resistance (discoloration, discoloration) was observed.

<Consideration about manufacturing conditions of ink based on results of Comparative Examples 7 to 10>
In Comparative Example 7, a dispersion of iron sesquioxide was prepared with glycerin fatty acid ester, sucrose fatty acid ester, and sorbitan fatty acid ester without using HPC, and this dispersion was prepared into an ink with an HPC solution. In this case, the pigment aggregated during mixing with the dispersion.
In Comparative Example 8, the amount of HPC relative to iron sesquioxide is 1/10, and sufficient dispersion cannot be maintained. Therefore, aggregates were generated over time, and continuous stable ejection could not be obtained.
In Comparative Example 9, since the amount of HPC with respect to iron sesquioxide was as much as 8/10, there was a problem that the viscosity was increased by the preparation of the dispersion. When the ink is prepared by adjusting the concentration to use this dispersion, the viscosity becomes higher than the optimum value of the printer, and continuous stable ejection cannot be performed. Of course, poor distribution also occurred.
In Comparative Example 10, the amount of HPC exceeded 10% by weight with respect to the total amount of the second resin solution, and the viscosity was 20 mPa.s. As a result, the ink exceeded s, so that the ink could not be sufficiently discharged by the printer, and the evaluation of the printed sample could not be sufficiently performed.

  The ink of the present invention can be suitably used in food-related applications such as various foods, materials that come into contact with food, and recording on food packaging materials. The method for producing the ink of the present invention can be suitably used as a method for producing the ink, and the method for using the ink of the present invention can be suitably used as a method for using the ink.

Claims (8)

Iron oxide having an average particle diameter of 0.01 to 10 μm, hydroxypropyl cellulose having a molecular weight of 10,000 to 150,000, and a solvent mainly containing ethanol and containing water are essential components (however, shellac resin is used as a component) including excluding), tablets for inkjet inks. The inkjet ink for tablets according to claim 1, wherein the iron oxide is at least one selected from iron sesquioxide, yellow iron sesquioxide, and black iron oxide. Furthermore , the inkjet ink for tablets of Claim 1 or 2 containing a electrically conductive agent. The inkjet ink for tablets according to claim 3, wherein the conductive agent is sodium acetate. The content ratio of the iron oxide is 0.3 to 20% by weight, the content ratio of the hydroxypropylcellulose is 0.1 to 10% by weight, the content ratio of the ethanol is 40 to 90% by weight, The inkjet ink for tablets according to claim 3 or 4, wherein a content ratio of water is 3 to 20% by weight and a content ratio of the conductive agent is 0.1 to 2% by weight. A first step of obtaining a dispersion by dispersing iron oxide in a first resin solution in which hydroxypropyl cellulose having a molecular weight of 10,000 to 150,000 is dissolved in a first solvent essentially containing water and / or ethanol;
A second resin solution in which hydroxypropyl cellulose having a molecular weight of 10,000 to 150,000 or both of the hydroxypropyl cellulose and a conductive agent is dissolved in a second solvent containing 50% by weight or more of ethanol as a whole; and in the first step, A second step of mixing with the obtained dispersion, and an inkjet ink in which iron oxide having an average particle diameter of 0.01 to 10 μm is dispersed as the iron oxide (however, containing a shellac resin as a component) except) to produce a method of manufacturing a tablet for inkjet inks. In the said 1st process, the manufacturing method of the inkjet ink for tablets of Claim 6 using the said hydroxypropyl cellulose 2-6 weight part with respect to 10 weight part of said iron oxides. Use of the inkjet ink for tablets used by diluting the inkjet ink with a diluent solvent comprising ethanol, water and a conductive agent when the inkjet ink according to any one of claims 1 to 5 is used in an inkjet printer. Method.