JP2018141160A - Ink and method for manufacturing edible object using the same, and printing method for edible object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ink that is suitable for inkjet printing to apply marking to a surface of an oral product such as a tablet, a capsule, and a food.SOLUTION: Ink contains at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water soluble polymer having a viscosity-average molecular weight of 1,000-220,000, and the ink contains water of 50 wt.% or more of liquid constituting the ink as the dispersion medium, where the coloring material is activated carbon.SELECTED DRAWING: None

Description

  The present invention relates to an ink suitable for printing by an inkjet method, particularly for marking the surface of oral products such as tablets, capsules and foods.

  In order to prevent accidental ingestion, counterfeiting, and drug identification, it is common practice to print symbols, letters, numbers and / or patterns on the surface of solid preparations such as tablets, hard capsules, and soft capsules. Yes.

Conventionally, printing on the surface of these solid preparations has been performed by a plate-making method such as offset printing or gravure printing. For example, Patent Literature 1, Patent Literature 2, and Patent Literature 3 describe a method of transferring ink to a printing material in a stamp type by pressing a rubber roll surface against a printed material such as a tablet.
However, these plate-based methods are based on the premise that the printing surface has a certain degree of hardness, and that the surface is flat and has no irregularities. Satisfactory marking on a wide variety of tablets such as sugar-coated tablets and OD tablets (orally disintegrating tablets) has been difficult.

  Therefore, it is conceivable to employ a non-plate printing method such as an inkjet method or a UV laser method. In particular, according to the ink jet method, the surface to be printed is less restricted than the UV laser method, and printing can be performed on a wider range of objects.

  Inkjet systems are broadly classified into continuous types and on-demand types, and in either method, it is necessary to stably eject ink from thin nozzles. In the continuous type, ink particles ejected continuously are charged as necessary, and deflected in accordance with the amount of charge by a deflection electrode to bend the course and adhere to the print surface. At this time, the uncharged ink particles are collected and returned to the ink tank again. On the other hand, the on-demand type is a system that ejects ink only when necessary. The latter on-demand type has the advantage that the structure of the ink ejection mechanism is simpler and easier to miniaturize than the continuous type, but the ink tends to clog because the ink concentrates or settles while it is not ejected. Therefore, when a pigment is used as the ink coloring material, it is not easy to achieve satisfactory discharge performance and stable performance. In particular, in order to print on an edible body such as a tablet, it is necessary that all the components contained in the ink be ingested into the body, so that a conventionally known inkjet ink is used as it is. It ’s difficult. Here, the pigments that can be used in the edible body are limited, and include lake pigments and inorganic pigments. However, it is difficult to stably disperse these pigments as fine particles in an aqueous medium, and separation or precipitation in the liquid occurs over time, which induces clogging of the ink nozzles and is difficult to use for ink. It is. Further, in the case of a printing material such as a tablet, there are many cases where satisfactory adhesion to the ink component cannot be obtained because the surface may be coated. Furthermore, when selecting the material for the surface of the substrate, there are restrictions such as being edible, not inhibiting the effective expression of the active ingredients of the tablet, and having sufficient adhesion with the ink without problems. is there.

On the other hand, when a dye is used as the coloring material, there is a problem that satisfactory light resistance and water resistance cannot be obtained.
Patent Document 4 describes an ink formed by dispersing charcoal pigment and shellac resin or cellulose resin. However, since the upper limit of the pigment concentration in the ink is about 0.7% by weight, it seems that the printing contrast (colorability) cannot be sufficiently ensured. Further, it is disclosed that it is used for continuous ink jet, and it is estimated that it is difficult to prevent nozzle clogging when used for on-demand ink jet.

JP 2000-42089 A JP 2000-229847 A JP 2001-31898 A WO2014 / 014010A1 publication

  An object of the present invention is to provide an ink that can be used for marking on the surface of an edible body such as a tablet, a capsule, or a part of food, and is suitable for printing by an inkjet method.

  Therefore, as a result of intensive studies to achieve the above-mentioned object, the present inventors can use a specific color material, add a specific polymer material or adjust the dispersed particle size as appropriate, and can be taken in the body. An excellent ink that has excellent adhesion to the tablet surface with only the components, and has sufficient fixability and light resistance while enabling continuous ejection even in ink jet printing, and exhibits sufficient colorability. And completed the present invention.

That is, the present invention
(1) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000, and constituting the ink as the dispersion medium An ink comprising 50% or more water by weight of the liquid to be treated, wherein the colorant is activated carbon;
(2) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000, wherein the coloring material is activated carbon. The content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. ink,
(3) An ink containing at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a K value of 10 to 90, wherein the color material is activated carbon and water-soluble organic An ink having a solvent content of 5 to 30% by weight in the ink liquid and a water-soluble polymer content of 20 to 200 parts by weight with respect to 100 parts by weight of activated carbon;
(4) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a number average molecular weight (Mn) of 2,000 to 140,000, wherein the coloring material is It is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. Features ink,
(5) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a weight average molecular weight (Mw) of 4,000 to 500,000, wherein the coloring material is It is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. Features ink,
(6) An ink containing at least (i) a colorant, (ii) a dispersion medium, and (iii) a water-soluble polymer having a z-average molecular weight (Mz) of 10,000 to 1,000,000, The material is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. Ink, characterized by
(7) An ink containing at least (i) a color material and (ii) a dispersion medium, wherein the color material is activated carbon, and an average dispersed particle size of the activated carbon in the ink is 50 nm to 1 μm. Ink,
(8) The ink according to any one of (1) to (7), wherein the dispersion medium contains one or more of ethanol, isopropanol, polyethylene glycol, propylene glycol, and glycerin,

(9) The ink according to any one of (1) to (8), having a viscosity of 1.0 to 10.0 mPa · s and a surface tension of 30 to 38 mN / m,
(10) The ink according to any one of the above (1) to (9), which is an inkjet ink,
(11) The ink according to any one of (1) to (10), which is used as a marking ink on the surface of an orally ingested product,
(12) A method for producing an orally ingested product, wherein the ink according to any one of (1) to (11) is printed on a printing surface using an inkjet printing apparatus, and (13) the above ( A printing method comprising printing the ink according to any one of 1) to (11) on an orally ingested product using an inkjet printing apparatus.

  According to the present invention, only the components that can be ingested by the body have excellent adhesion to the tablet surface in particular, and adhesion, water resistance, light resistance, and scratch resistance while enabling continuous ejection even in ink jet printing. And an excellent ink having sufficient colorability can be obtained.

  The ink of the present invention is characterized by containing at least (i) a color material and (ii) a dispersion medium, and using activated carbon as the color material.

[Activated carbon]
Activated carbon is a black porous powder, and is generally used for deodorization, water purification, wastewater treatment, catalyst support, and the like using its pores. In particular, refined activated carbon is taken as medicinal charcoal, and is used to adsorb gas and toxic substances in the intestines and discharge them outside the body. In the present invention, activated carbon, which is not common as a color material, is used as a black color material.
Activated carbon is known as a carbon material having a very large specific surface area. By heating carbon materials such as wood, so-called charcoal such as Bincho charcoal is obtained (this process is called “carbonization”), but the specific surface area of charcoal (including powdered ones) is generally It is said to be 300 to 500 m ² / g. On the other hand, activated carbon has a specific surface area of 800 to 2000 m ² / g, more preferably 500 to 3000 m ² / g by treating charcoal at a high temperature close to 1000 ° C. It is known as having an extremely high adsorption performance because it is called “activation” or “activation reaction” that the specific surface area is increased to become activated carbon by being treated at a high temperature.

In general, activated carbon is made by reacting with a gas or a chemical at a high temperature using a carbon material such as coal or coconut shell as a raw material. There are known a chemical activation method in which a raw material is impregnated with a zinc chloride solution and heated under certain conditions, and a water vapor activation method in which the raw material and heated water vapor are activated at a temperature of 800 to 1000 ° C. The production method is not particularly limited.
Activated carbon is roughly classified into three types, that is, “coal-based”, “plant-based”, and “others” depending on the raw material, but can be used without any particular limitation in the present invention.

  Moreover, it can be roughly divided into powdered activated carbon and granular activated carbon depending on the shape. Powdered activated carbon refers to a powder having a particle size that passes through a sieve of 100 mesh (aperture 0.15 mm), and granular activated carbon refers to a particle size that does not pass through the sieve. Other special shapes include fibrous activated carbon and specially-shaped activated carbon (honeycomb shape, plate shape (sheet shape)). In the present invention, powdered activated carbon is preferably used because it is finer and has excellent dispersibility and colorability.

Although the physical property of the activated carbon used by this invention is not specifically limited, Generally, an average particle diameter is 1-100 micrometers, Most preferably, it is a 5-70 micrometers thing.
The specific surface area is not particularly limited, but is preferably 500 to 3000 m ² / g, particularly preferably 1000 to 2000 m ² / g.
The total pore volume is not particularly limited, but is preferably 0.3 to 5 ml / g, more preferably 0.5 to 4 ml / g, and most preferably 0.5 to 3 ml / g.

The average pore diameter is preferably 1 to 20 nm, particularly preferably 2 to 10 nm.
The pH of the activated carbon is preferably 3 to 8, particularly preferably 4.5 to 7.5.
The iron content in the activated carbon is preferably 0.03% by weight or less, particularly preferably 0.01% by weight or less.
The pH, average particle diameter, specific surface area, total pore volume, average pore diameter, and iron content are measured according to the method of JIS K 1474-91.

The activated carbon used in the present invention is 0.53% or less of chloride (as Cl) and 0.48 as sulfate (as SO4) in accordance with the methods described in JIS K 1474-91 and the official food additives. % Or less, zinc of 0.10% or less, and arsenic (as As ₂ O ₃ ) of 4.0 μg / g or less are suitable.
If it is in these ranges, since it conforms to the food additive standards, printing on the edible body is possible, and the influence of the impurities on the ink physical properties can be prevented.

The amount of the activated carbon is 0.1 to 10% by weight, preferably 0.5 to 8% by weight, more preferably 1 to 5% by weight in the ink liquid.
If it is less than 0.1% by weight, the concentration as a colorant is thin, and the marking performance of the object may not be sufficient. If it exceeds 10% by weight, it may be difficult to achieve continuous ejection due to poor temporal stability of the ink due to agglomeration of activated carbon, and further, the ejection performance from the nozzles decreases.

As described above, the activated carbon is a black powder or a granular material, but is not usually used as a coloring material. This is because in normal usage, the degree of blackness is not high and the dispersibility is not high. In contrast, in the present invention, surprisingly, the activated carbon is converted into an ink as a color material, thereby achieving sufficient coloring, achieving stable and fine dispersion applicable to inkjet printing, and also for oral administration. It can be used safely.
In the present invention, preferably, the specific polymer material described later is mixed, so that the activated carbon is 0.1 to 10% by weight, particularly 0.5 to 8% by weight as described above, and more particularly 0.5 to 8% by weight. Since it can be contained in the ink at a high concentration of 1 wt% to 5 wt% and a stable dispersion state can be maintained, it can also be used for a continuous ink jet printer.

First of all, we were able to obtain such an excellent ink, even if it is a material that is not normally used as a coloring material. This is largely due to the extensive study by the present inventors. In addition, the affinity between activated carbon and the surface of tablets and other edible bodies, which has not been a target of inkjet printing, is excellent. In particular, excellent ink performance could be obtained by being present in the ink in the finely dispersed state described below.
Furthermore, it is presumed that the combination of a specific water-soluble polymer and activated carbon described below expresses high color developability with a more excellent stable dispersion state.

(Water-soluble polymer)
The first form of the ink of the present invention is an ink containing at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000. In addition, the ink contains 50% by weight or more of water constituting the ink as a dispersion medium, and the coloring material is activated carbon. A second form of the ink of the present invention is an ink containing at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000. The color material is activated carbon, the content of the water-soluble organic solvent is 5% to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 with respect to 100 parts by weight of the activated carbon. The ink is characterized by being part by weight.
That is, the first and second forms of the ink of the present invention are characterized by containing a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000.
In general, in order to prepare a liquid composition in which solid fine particles such as pigments are dispersed in a liquid medium, a compound called a dispersant is added. These are compounds that have the function of stably dispersing solid fine particles such as pigments in a dispersion medium. Roughly speaking, these compounds are classified into relatively low molecular weight compounds called surfactants and higher molecular weight polymer compounds. Broadly divided.

Among these, high molecular compounds generally have many hydrophilic groups in the molecular chain, and water molecules are hydrated and dissolved therein, as well as long-chain aminoamides, acrylic acid / polycarboxylic acids and their salts. As the main structure, the adsorptive groups adsorbed on the solid fine particles include basic groups such as amides and amines, and acidic groups such as carboxy groups and phosphate groups and soluble types as neutralized salts.
In contrast to these general solid fine particle dispersion methods, in the present invention, activated carbon which is a solid fine particle is blended with a polymer which is water-soluble and has a viscosity average molecular weight of 1,000 to 220,000. It is a feature that it is stably dispersed. It is not restricted to what is known especially as a dispersing agent.

The water-soluble polymer has a viscosity average molecular weight of 1,000 to 220,000, preferably 2,000 to 100,000, more preferably 5,000 to 100,000, and most preferably 7,000 to 50,000. is there.
Viscosity average molecular weight is basically measured using the Polymer Vol. 38, no. 7, pp. According to the molecular weight measurement method described in 457-463 (July, 1981). That is, the following procedure.

(1) The sample is added to excess acetone and purified by precipitation. This operation is repeated twice and then dried under reduced pressure until there is no odor of acetone.
(2) An aqueous solution of the sample after purification is prepared, and the viscosity average molecular weight is determined using the Ubbelohde viscometer (water, 120 seconds) and the Mark-Kuhn-Houwink equation (Mark-Houwink-Sakurada equation). As the coefficients M and α of the Mark-Kuhn-Houwink equation, those described in the above-mentioned collection of polymer papers are used.
However, other methods can be used as long as the equivalent results can be obtained.

  In addition, since the numerical value of molecular weight has a measurement error etc., about 10% can be fluctuated. Therefore, the upper and lower ranges of about 10% of the numerical range described above can be used. The same applies to the number average molecular weight, weight average molecular weight, and z average molecular weight described later.

  As the water-soluble polymer used in the present invention, it is particularly preferable to use a nonionic polymer. As an indicator of polarity, there is an acid value. In the present invention, the acid value is preferably 30 mgKOH / g or less, more preferably 20 mgKOH / g or less, further preferably 5 mgKOH / g or less, and most preferably no acid value is detected (acid). The value is substantially 0 mg KOH / g). In this range, the printing properties such as the dispersion performance of activated carbon and the water resistance of the printed matter are particularly excellent.

The acid value is measured by a method based on DIN 53402, and more specifically as follows.
(1) Take a sample in a 0.9 to 1.3 g beaker and weigh it.
(2) Add 50 ml of acetone.
(3) Measure with an automatic potentiometric titrator using 0.1N NaOH aqueous solution. The result is the same regardless of which automatic potentiometric titrator is used.
(4) The amine value is obtained by the following calculation formula.

Acid value = [(ab) × 5.61] / E (mgKOH / g)

a: ml of 0.1 N NaOH required for titration b: ml of 0.1 N NaOH required for titration of blank E: weight of sample (g)
(5) Display: Display up to one decimal place.

  A third form of the ink of the present invention is an ink containing at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a K value of 10 to 90, wherein the color material is It is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. It is a characteristic ink. That is, it is characterized by containing a water-soluble polymer having a K value of 10 to 90. The K value of the water-soluble polymer is preferably 10 to 90, particularly preferably 10 to 60. More preferably, it is 15-40. Here, the K value is determined by measuring the viscosity according to the first method <2.53> of the viscosity measurement method in the 16th revised Japanese pharmacopoeia, and is obtained by the Fikentscher formula according to the method described in the column of “K value” described in the pharmacopoeia. It is a thing. In this range, the printed matter characteristics such as the dispersion performance of activated carbon and the water resistance of the printed matter are particularly excellent. Note that the K value may vary by about 10% due to measurement errors and the like. Therefore, the upper and lower ranges of about 10% of the above values may be used.

  Specifically, casein, water-soluble cellulose derivatives, polyvinyl pyrrolidone, polyvinyl methyl ether and the like are preferably used according to the surface material of the printed material.

  As the water-soluble cellulose derivative, a cellulose ether substituted with an alkyl group and a hydroxyalkyl group, or a cellulose ether substituted with a hydroxyalkyl group is preferably used.

  Particularly preferably, a nonpolar water-soluble polymer such as hydroxypropylcellulose (HPC), hydroxypropylmethylcellulose (HPMC), or polyvinylpyrrolidone is used. These can provide an ink having excellent dispersion stability when used in the ink of the present invention and excellent dischargeability in printing by an ink jet method, and also has fixing properties to a printing material. It also has excellent affinity with resin components used as tablet coating materials and capsule film materials. Further, it is preferable because an ink having excellent fixability can be obtained for various objects such as tablets.

These water-soluble cellulose derivatives, water-soluble polymers such as polyvinyl alcohol and polyvinyl pyrrolidone have good adhesion to the sugar-coated layer of the sugar-coated tablet, and can be suitably used when printing the sugar-coated tablet by inkjet. Among them, polyvinyl pyrrolidone is particularly excellent as a material having excellent fixing properties and a dispersion performance in a color material. Particularly, among polyvinyl pyrrolidones, those having a viscosity average molecular weight of 1,000 to 220,000 are preferable, those of 2,000 to 100,000 are more preferable, those of 5,000 to 100,000 are further preferable, and 7,000. Most preferred is ˜50,000.
When the viscosity average molecular weight is less than 2,000, dispersion becomes difficult and the dispersed particle size tends to be large. On the other hand, if it exceeds 220,000, the viscosity increases and a uniform dispersion may not be obtained.

The fourth form of the ink of the present invention contains at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a number average molecular weight (Mn) of 2,000 to 140,000. Ink, the coloring material is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 with respect to 100 parts by weight of the activated carbon. The ink is characterized by being -200 parts by weight. That is, it is characterized by containing a water-soluble polymer having a number average molecular weight (Mn) of 2,000 to 140,000.
The number average molecular weight (Mn) is preferably 2,500 to 100,000, more preferably 3,000 to 70,000. If it is less than 2,000, dispersion becomes difficult and the dispersed particle size tends to increase. On the other hand, if it exceeds 140,000, the viscosity increases and a uniform dispersion may not be obtained. In particular, it is 3,000 to 70,000, has the best dispersibility, and is excellent in printed material properties such as water resistance of the printed material.

The fifth form of the ink of the present invention contains at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a weight average molecular weight (Mw) of 4,000 to 500,000. Ink, the coloring material is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 with respect to 100 parts by weight of the activated carbon. The ink is characterized by being -200 parts by weight. That is, it is characterized by containing a water-soluble polymer having a weight average molecular weight (Mw) of 4,000 to 500,000.
Preferably, the weight average molecular weight (Mw) is 8,000 to 400,000, more preferably 10,000 to 200,000. If it is less than 4,000, dispersion becomes difficult and the dispersed particle size tends to increase. On the other hand, if it exceeds 500,000, the viscosity increases and a uniform dispersion may not be obtained. Particularly, the dispersibility is excellent at 10,000 to 200,000, and the printed matter characteristics such as water resistance of the printed matter are also excellent.

The sixth form of the ink of the present invention comprises at least (i) a color material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a z average molecular weight (Mz) of 10,000 to 1,000,000. The ink containing the colorant is activated carbon, the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 100 parts by weight of the activated carbon. 20 to 200 parts by weight of the ink. That is, it is characterized by containing a water-soluble polymer having a z-average molecular weight (Mz) of 10,000 to 1,000,000.
Preferably, the z average molecular weight (Mz) is 20,000 to 600,000, more preferably 30,000 to 300,000. If it is less than 10,000, dispersion becomes difficult and the dispersed particle size tends to increase. On the other hand, if it exceeds 1,000,000, the viscosity may increase and a uniform dispersion may not be obtained. In particular, it is 30,000 to 300,000, has the best dispersibility, and is excellent in printed material properties such as water resistance of the printed material.

  Here, these number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz) can be determined by gel permeation chromatography (GPC) as follows. In addition, even if it is another measuring method, if an equivalent value is calculated | required, it can be used.

Analytical instruments and measurement conditions:
Sample preparation: Weigh 20 mg of sample, add 10 ml of 0.1M NaNO ₃ / CH ₃ CN (= 80/20), dissolve by heating in a warm air dryer at 40 ° C for 1 hour, and a 0.45-μm filter Filtration and use for measurement.
Standard preparation: Weigh 2 mg of sample, add 0.1 ml of 0.1M NaNO ₃ / CH ₃ CN (= 80/20), dissolve by heating in a warm air dryer at 40 ° C for 1 hour, 0.45 µm Filter with a filter and measure.

GPC measuring device: Main system LC-20AT manufactured by Shimadzu Corporation
Controller CBM-20A
Degasser DGU-12A LC-10
Pump LC-20AP
Column oven CPO-10A
Detector: RI detector (RID detector RID-10A)

column:
TSKgel G3000PWXL (Tosoh) 7. 8mmI. D. × 300mm (Inner diameter (mm) × Length (mm)) Neutral column
TSKgel G6000PWXL (Tosoh) 7. 8mmI. D. × 300mm (Inner diameter (mm) × Length (mm)) Neutral column

Eluent: 0.1M NaNO ₃ aqueous solution / acetonitrile = 8/2
Flow rate: 1.0mL / min
Column temperature: 40 ° C
Injection volume: Sample; 100 μl, standard product: 100 μL

  The measurement is performed twice and the average value is adopted.

  In the second to sixth embodiments of the present invention, the amount of the water-soluble polymer added is 20 to 200 parts by weight with respect to 100 parts by weight of activated carbon. This range is also preferable in the first embodiment of the present invention. More preferably, it is 25-180 weight part, Most preferably, it is 30-150 weight part. If it is less than 20% by weight, it is difficult to sufficiently disperse the coloring material, and the dispersed particle diameter of the activated carbon in the dispersion medium becomes large. If the amount exceeds 200 parts by weight, the viscosity of the ink becomes high, so that it becomes difficult for the ink to be ejected from the nozzle, and the continuous ejection property is lowered.

  In the ink of the present invention, it has been found that by blending the specific water-soluble polymer described above, the activated carbon can be stably and finely dispersed and can be suitably used for ink jet printing. In addition, by blending this specific water-soluble polymer, the activated carbon color tone is excellent, the adhesion when printed on various printing objects such as tablets is improved, and the fixing to the printing object is good. Excellent black printing became possible without rubbing and disappearing. The mechanism for obtaining such an excellent effect is not completely clear, but it has good affinity with activated carbon, which is a porous fine powder, and is stabilized by the interaction with the polarity of the surface of the activated carbon. Guessed. At the same time, it is presumed that it has excellent affinity with the coating components on the surface of tablets and the like.

[Dispersion medium]
The dispersion medium of the present invention is not particularly limited as long as it is a liquid that can disperse activated carbon, and may be appropriately selected according to the application. However, by using water as a main component, in terms of safety and operability. An excellent ink can be obtained. The ink of the present invention can maintain stable dispersibility and continuous discharge in ink jet printing even when water is mainly used as a dispersion medium. When used for printing pharmaceutical edible bodies such as tablets, distilled water and water for injection are suitable. Here, “mainly comprising water” means that 50% by weight or more, more preferably 60% by weight or more of the liquid constituting the ink is water. That is, in the first embodiment of the present invention, 50% by weight or more of the liquid constituting the ink is water. Particularly preferably, the liquid component other than the specific water-soluble organic solvent described below has a composition that is substantially water.

(Water-soluble organic solvent)
In the present invention, it is desirable to include a specific water-soluble organic solvent as a liquid component other than water. When these water-soluble organic solvents are added, the head portion can be prevented from being clogged and the drying property of the ink can be adjusted when the ink-jet printing is used.
Specific examples of such water-soluble organic solvents include, for example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, trimethylolpropane, ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, diglycerin, 1,2-hexane Diol, 1,6-hexanediol, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,5-pentanediol, monoethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, monoethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, methyl lactate, lactic acid It is selected from ethyl and 1,3-dimethyl-2-imidazolidinone, and these can be used alone or in admixture of two or more. Particularly preferably, ethanol, isopropanol, polyethylene glycol, propylene glycol, glycerin and the like are suitable as food additives.

  In the second to sixth embodiments of the present invention, the addition amount of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid. This range is also preferable in the first embodiment of the present invention. More preferably, the content is 6 to 25% by weight, and if it is added more than that, the viscosity of the ink becomes high, and the stability of the ink and the ejectability from the nozzle may be lowered, or the drying speed may be slowed. Addition of less than 5% by weight may cause a problem in nozzle discharge, resulting in blurring or continuous discharge.

[Surface tension modifier]
In the present invention, a surface tension adjusting agent can be used as necessary. The surface tension adjusting agent is a component having the function of improving the discharge from the nozzle and adjusting the surface tension.
Specific examples of the surface tension adjusting agent include surfactants such as nonions and anions. Specifically, for example, alkylbenzene sulfonates, higher alcohol sulfates, higher fatty acid salts, higher alkyl dicarboxylates, alkyls. Anionic surfactants such as naphthalene sulfonate, alkyl sulfosuccinate, naphthalene sulfonate formalin condensate salt, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phosphate ester; for example, polyoxyethylene alkyl ether, polyoxy Ethylene alkyl phenyl ether, fatty acid monoglyceride, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, glycerin fatty acid ester Ether, nonionic surfactants such as polyoxyethylene-added acetylene glycol, silicone surfactants, fluorine surfactants, ethanol, water-soluble organic solvent such as isopropanol and the like.

In the ink of the present invention, nonionic surfactants such as sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, glycerin fatty acid ester, and polyoxyethylene-added acetylene glycol are suitable. Sucrose fatty acid esters such as monostearic acid esters and sucrose oligoesters and glycerin fatty acid esters such as triacetin can achieve the most preferable liquid properties.
The addition amount of the surface tension adjusting agent may be appropriately selected according to the required surface tension, but it is preferably 0.5 to 30% by weight, particularly preferably 1 to 20% by weight in the ink.

[Sugar and other additives]
Saccharides can be added for the purpose of improving dischargeability and adhesion. Examples of the sugar include monosaccharides, disaccharides, and polysaccharides.Specific examples include glucose, galactose, mannose, growth, talose, allose, altrose, idose, fructose, sorbose, tagatose, psicose, sucrose, maltose, Lactose, maltotriose, isomaltose, maltotetraose, isomaltotriose, isomalttetraose, panose, nigerose, kojibiose, lactose, palatinose, kestose, nistose, fructosylnystose, inulobiose, inurotriose, inurotetra Examples thereof include aose, isomalterose, maltosyl sucrose, maltotriosyl sucrose, maltopentaose, maltohexaose, maltoheptaose and the like. The sugar derivatives are preferably sugars obtained by reducing or oxidizing the above sugars, and specific examples include maltitol and sorbit.
The addition amount is preferably 1 to 20% by weight in the ink liquid, and has the function of improving fading when printing on a recording medium and stabilizing ejection.

  Further, in the ink of the present invention, orthophenylphenol, sodium orthophenylphenol, diphenyl, thiabendazole, and imazalil are preferable as the antifungal agent so as to have desired physical properties, and hypochlorite is used as the disinfectant. Sodium acid, hydrogen peroxide and ethanol are preferred. Moreover, additives, such as an antifoamer, a rust preventive agent, and a PH adjuster, can be mix | blended suitably.

In addition, the ink of the present invention is characterized by containing activated carbon as a color material, but other color materials may be contained within a range not impeding the performance of the present invention.
However, sufficient coloring can be obtained with activated carbon alone for edible printing applications described below.

  In addition, for the purpose of adjusting the viscosity of the ink and other purposes, other water-soluble polymers may be appropriately added within a range not impeding the performance of the present invention. Examples thereof include starch systems such as guar gum, locust bean gum, agar and methyl starch, gelatin, pullulan, xanthan gum, tragacanth gum and dextrin. In addition, other conventionally known dispersants may be appropriately added within a range not impeding the performance of the present invention.

[Preparation of ink]
A seventh aspect of the ink of the present invention is an ink containing at least (i) a color material and (ii) a dispersion medium, wherein the color material is activated carbon, and the average dispersed particle size of the activated carbon in the ink is 50. It is an ink characterized by being -500 nm.
That is, the activated carbon in the ink according to the twenty-sixth aspect of the ink of the present invention has an average dispersed particle size of 50 nm to 1 μm, preferably 50 to 800 nm, more preferably 50 to 700 nm, still more preferably 50 to 600 nm, still more preferably. It is 50-500 nm, More preferably, it is 100-450 nm, Most preferably, it is 150-400 nm. Within this range, the coloring power, dispersion stability, nozzle ejection property, and fixability to the printed material are the most excellent, but the average dispersed particle diameter is in the range of 50 to 500 nm, regardless of the above-mentioned ink jet device or nozzle. Each physical property is extremely excellent.

When the average dispersed particle size is less than 50 nm, aggregation is likely to occur due to van der Waals force between particles, and the temporal stability tends to be lowered. When the average dispersed particle diameter exceeds 1 μm, the coloring material is easily separated in the liquid, and precipitation may easily occur.
In addition to controlling the average particle diameter, it is preferable to suppress the amount of coarse particles. By adjusting so that 90% or more of all the activated carbon particles in the liquid have a dispersed particle diameter of 1 μm or less, more preferably 500 nm or less, an ink having further excellent physical properties can be obtained. Dispersion treatment may be performed until the size of all particles falls within this range, but the dispersion treatment is performed until the average particle diameter falls within the above range in order to prevent a large amount of particles that are too fine from being generated and re-aggregated. A method of removing coarse particles by a known method such as centrifugal separation or filter filtration is also suitable.

In addition, the measurement of the average dispersed particle diameter here and the dispersed particle diameter of all the particles is as follows.
Conditioning: Dilute the stock solution with ion-exchanged water so that it enters the defined concentration range.
Measuring instrument: Dynamic light scattering particle size distribution analyzer ("NIKKISO: Microlracwave-EX150")
Measurement time: 120 seconds

  In the first to sixth embodiments of the ink of the present invention described above, by setting the average dispersed particle diameter and the dispersed particle diameter of all the particles in the above-described range, it is possible to obtain an ink having further excellent physical properties. Further, the above-mentioned dispersion medium, water-soluble organic solvent, surface tension adjusting agent, saccharides and other additives are common in the twenty-sixth aspect of the ink of the present invention and can be preferably used. In particular, the presence of the water-soluble polymer used in any one or more of the first to sixth forms of the ink of the present invention described above makes it possible to make fine particles of the activated charcoal characterized in the seventh form of the ink of the present invention. A dispersed state can be obtained easily and stably.

The viscosity of the inks of the first to seventh embodiments of the present invention described above is 1.0 to 10.0 mPa · s. Preferably, it is 1.5 to 9.0 mPa · s, and particularly preferably 2.0 to 8.0 mPa · s.
When the viscosity is less than 1.0 mPa · s, a satellite phenomenon may occur or the nozzle may not become droplets. Conversely, when the viscosity exceeds 10.0 mPa · s, a satellite phenomenon may occur or ink droplets may not be formed. The satellite phenomenon refers to small droplets such as dust that are separated from the main droplets of the ejected ink droplets from the head nozzle.

The method for measuring the viscosity is as follows.
Conditioning: Stock solution
Measuring equipment: Conical plate type rotational viscometer ("TVE-20L type" (product number) manufactured by Toki Sangyo Co., Ltd.)
Measurement conditions: 50rpm
Measurement temperature: 25 ℃

The surface tension is preferably 28 to 40 mN / m, more preferably 30 to 38 mN / m, and particularly preferably 31 to 37 mN / m.
Further, when the surface tension is less than 28 mN / m, a phenomenon occurs in which the liquid droplets are ejected without sufficient droplets, and the same applies when the surface tension exceeds 40 mN / m.

The method for measuring the surface tension is as follows.
Conditioning: Stock solution
Measuring instrument: Automatic surface tension meter (plate method) (Kyowa Interface Science Co., Ltd. “CBVP-Z”)
Measurement temperature: 25 ℃

[Preparation of ink]
The ink of the present invention can be prepared by mixing the above-described components into an ink. The mixing method is not particularly limited. For example, after the activated carbon, the water-soluble polymer, and water are mixed and stirred, the activated carbon is dispersed in water by dispersing in a disperser such as a paint shaker, roll mill, ball mill, sand mill, or jet mill. Can be stabilized.

At this stage, the method of removing coarse particles and then adding the water-soluble organic solvent and the surface tension adjusting agent described above to form an ink is also suitable for ensuring a stable and good dispersion state.
Alternatively, it is possible to further improve the quality by subjecting the prepared ink to filter processing or the like by a known technique, or removing impurity ions.

[Printing method and application]
Printing can be performed on various objects using the ink of the present invention described above. Since the ink of the present invention can be prepared with only components that can be safely taken into the body, it can be suitably used for printing on pharmaceuticals such as tablets and capsules or printing on various foods. The printing method is not limited, and it may be used for offset printing and gravure printing methods that have been used for edible printing conventionally, but even when used for inkjet printing, it maintains stable ejection properties and is excellent. Performance can be demonstrated. That is, it can be used as an inkjet ink for printing using an inkjet printer, and can also be used as a marking ink on the surface of an edible body. The ink of the present invention is printed using an inkjet printer. An edible body can be produced by printing on the surface.
Since the printed matter obtained in this way is excellent in colorability and fixability, the ink of the present invention is used for various purposes such as prevention of counterfeiting, ensuring traceability, preventing accidental ingestion, improving discrimination, and imparting amusement properties. Printing on medicines, foods, etc. can be performed.

Hereinafter, the present invention will be described in detail with reference to examples. In the examples, all “parts” indicate parts by weight, and “%” indicates all parts by weight.
Table 1 shows the types of water-soluble polymers used in Examples and Comparative Examples and the measurement results of number average molecular weight, weight average molecular weight and z average molecular weight. The measurement was performed twice and the average value was adopted.

[Example 1]
The following components were blended and stirred for 1 hour at room temperature with a propeller stirrer.
Component amount (parts by weight (hereinafter referred to as parts))
Activated carbon 10.0
(Average particle diameter: 25 μm, average pore diameter: 2.8 nm)
Polyvinylpyrrolidone 8.5
(Viscosity average molecular weight: 40,000, K value 30, number average molecular weight 6,401, weight average molecular weight 27,739, z average molecular weight 71,598)
Water 81.5

Next, 150 g of 0.7 mm diameter glass beads were put into the pot for paint shaker, and shaken for 3 hours.
Coarse particles contained in this dispersion are removed and adjusted so that the dispersed particle diameter of 90% or more of all particles is 500 nm or less and the solid content concentration is 10% by weight to be “dispersion 1”. Ink formation was performed by the following method.

Component amount (parts)
Dispersion 1 (solid content 10%) 50.0
Glycerin 10.0
Ethanol 10.0
Fatty acid monoglyceride 3.0
Water 27.0
The mixture was stirred for 30 minutes to prepare an ink.
The obtained ink had an average dispersed particle size of 350 nm, a viscosity of 3.1 mPa · s, and a surface tension of 33 mN / m. Further, the obtained ink showed a uniform black color in appearance.
Furthermore, the above inks were examined for stability over time, ejection properties, fixing properties, light resistance, and water resistance according to the following methods. The results are shown in Table 1.

(A) Stability test over time The ink was put in a glass bottle and allowed to stand in a thermostatic chamber at 5 ° C. for 1 month, and then the presence or absence of color material separation, water floating and sedimentation was confirmed. The state in which separation of the coloring material, water floating and sedimentation occurred as little as possible was evaluated as abnormal.
In Table 1, “O” indicates no abnormality and “X” indicates abnormality.

(B) Ejectability test Using an inkjet printer (Qualicaps Co., Ltd.) and a droplet observation device, whether or not ink can be ejected from the head, whether or not droplets can be formed, and whether or not re-ejection can be performed after ejection has been stopped Was investigated.

(C) Fixability drying test Using a tablet immediately after printing with an ink jet printer as a sample, the printed portion of the sample was rubbed with a nonwoven fabric, and the presence or absence of ink extension and the presence or absence of ink transfer to the nonwoven fabric were investigated.

(D) Light resistance test About 0.5 mL of ink was applied to bar coater No. 5 was applied to white paper for color tone test, the ink was dried, and a sample for light resistance test was prepared. Place the sample in a photostability tester (LST-300D manufactured by Tokyo Rika Kikai Co., Ltd.), and after exposure at a total illumination of 1.2 million lux · hr, the sample before exposure using visual and spectral color difference meter (SE6000 manufactured by Nippon Denshoku Industries Co., Ltd.) The difference in color tone was investigated.

(E) Water resistance test A tablet having a wire diameter of about 0.1 mm and a size of about 0.5 mm square was printed on a tablet by an ink jet printer to prepare a sample for water resistance test. A sample was stored in an atmosphere in which a saturated solution of sodium chloride was placed in a desiccator to maintain a constant humidity (relative humidity of about 75%) for one week, and the presence or absence of bleeding on the printed part was examined.
(F) Coloring test The printed part of the sample after the test prepared in the test of (e) was visually confirmed to confirm whether the printing can be distinguished and the color tone. Black or dark gray (red when red color material is used) that can be clearly distinguished is marked with ◯, and others with x.

[Comparative Example 1]
Ink was prepared in the same manner as in Example 1, except that the activated carbon was replaced with the petrol and the polyvinyl pyrrolidone was replaced with gum arabic.
[Comparative Example 2]
Ink was produced in the same manner as in Example 1, except that the activated carbon was replaced with black iron oxide.

[Example 2]
The following components were blended and stirred for 1 hour at room temperature with a propeller stirrer.

Component amount Activated carbon 10.0
(Average particle size: 30 μm, average pore diameter: 2.1 nm)
Polyvinylpyrrolidone 10.0
(Viscosity average molecular weight: 25,000, K value 25, number average molecular weight 4,495, weight average molecular weight 18,291, z average molecular weight 51,018)
Water 80.0

Next, 150 g of 0.7 mm diameter glass beads were put into a paint shaker pot and shaken for 3 hours.
Coarse particles contained in this dispersion are removed and adjusted so that 90% or more of all particles have a dispersed particle diameter of 500 nm or less and a solid content concentration of 10% by weight (“Dispersion 2”). Ink was obtained by the following method.

Component amount (parts)
Dispersion 2 (solid content 10%) 50.0
Glycerin 10.0
Propylene glycol 10.0
Sucrose fatty acid ester 10.0
Water 20.0
The mixture was stirred for 30 minutes to prepare an ink.
The obtained ink had an average dispersed particle size of 250 nm, a viscosity of 2.5 mPa · s, and a surface tension of 32 mN / m. Further, the obtained ink showed a uniform black color in appearance.

[Example 3]
The following components were blended and stirred for 1 hour at room temperature with a propeller stirrer.

Component amount Activated carbon 10.0
(Average particle diameter: 35 μm, average pore diameter: 3.4 nm)
Polyvinylpyrrolidone 7.0
(Viscosity average molecular weight: 40,000, K value 30, number average molecular weight 6,401, weight average molecular weight 27,739, z average molecular weight 71,598)
Water 83.0

Next, 370 g of 0.5 mm diameter zirconia beads were placed in a paint shaker pot and shaken for 7 hours.
Coarse particles contained in this dispersion are removed and adjusted so that the dispersion particle diameter of 90% or more of all particles is 500 nm or less and the solid content concentration is 10% by weight to obtain dispersion 3. Made ink.

Component amount (parts)
Dispersion 3 (solid content 10%) 48.0
Sucrose fatty acid ester 10.9
Water 41.1

The mixture was stirred for 30 minutes to prepare an ink.
The obtained ink had an average dispersed particle size of 316 nm, a viscosity of 4.8 mPa · s, and a surface tension of 33 mN / m. Further, the obtained ink showed a uniform black color in appearance.

[Comparative Example 3]
Ink was prepared in the same manner as in Example 3, except that the activated carbon was replaced with a water-soluble black dye.

[Example 4]
The following components were blended and stirred for 1 hour at room temperature with a propeller stirrer.

Component amount Activated carbon 10.0
(Average particle diameter: 35 μm, average pore diameter: 3.4 nm)
Polyvinylpyrrolidone 7.0
(Viscosity average molecular weight: 25,000, K value 25, number average molecular weight 4,495, weight average molecular weight 18,291, z average molecular weight 51,018)
Water 83.0

Next, 370 g of 0.5 mm-diameter zirconia beads were placed in a paint shaker pot and shaken for 7 hours.
Coarse particles contained in this dispersion are removed and adjusted so that the dispersion particle diameter of 90% or more of all particles is 500 nm or less and the solid content concentration is 10% by weight to obtain dispersion 3. Made ink.

Component amount (parts)
Dispersion 4 (solid content 10%) 48.0
Propylene glycol 10.0
Sucrose fatty acid ester 8.7
Water 33.3

The mixture was stirred for 30 minutes to prepare an ink.
The obtained ink had an average dispersed particle size of 283 nm, a viscosity of 4.0 mPa · s, and a surface tension of 32 mN / m. Further, the obtained ink showed a uniform black color in appearance.

[Comparative Example 4]
In Example 4, except that the activated carbon was replaced with Bincho charcoal, an ink was prepared in the same manner. However, when the mixture was put into a propeller stirrer and stirred, the ink was vigorously thickened and gelled, and the fluidity was lost and uniform dispersion was achieved. Neither test was possible because no liquid could be obtained and no ink was formed.

[Comparative Example 5]
In Example 4, polyvinyl pyrrolidone (viscosity average molecular weight; 25,000, K value 25, number average molecular weight 4,495, weight average molecular weight 18,291, z average molecular weight 51,018) was converted to polyvinyl pyrrolidone (viscosity average molecular weight; The ink was prepared in the same manner except that it was replaced with 2.8 million, K value 120, number average molecular weight 142,948, weight average molecular weight 525,307, z average molecular weight 1,106,232). When the mixture was added and stirred, the viscosity increased to gel, the fluidity was lost, a uniform dispersion could not be obtained, and no ink could be formed, so neither test was possible.

  In Comparative Example 1 and Comparative Example 2, it was difficult to print with an ink jet printer due to poor dischargeability, and it was not possible to prepare a sample for a water resistance test. Further, in Comparative Example 3, the characters printed on the tablets were blurred due to the water resistance test, and it was difficult to distinguish the characters in the color development test, and the printing density was low.

  From the above Examples and Comparative Examples, it can be seen that the ink of the present invention using activated carbon as a coloring material and containing a water-soluble polymer has excellent characteristics as an inkjet ink.

  According to the present invention, it has excellent fixability on the tablet surface only with components that can be ingested by the body, and it has fixing property and light resistance while enabling continuous discharge even in ink jet printing, especially continuous type printing. An excellent ink provided, a printing method using the ink, and a method for producing an edible body can be provided.

Claims (13)

  An ink containing at least (i) a colorant, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000, and the liquid constituting the ink as the dispersion medium An ink comprising 50% by weight or more of water, wherein the color material is activated carbon.   An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000, wherein the coloring material is activated carbon and is water-soluble An ink characterized in that the content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon.   An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a K value of 10 to 90, wherein the coloring material is activated carbon and containing a water-soluble organic solvent An ink having an amount of 5 to 30% by weight in the ink liquid and a water-soluble polymer content of 20 to 200 parts by weight with respect to 100 parts by weight of activated carbon.   At least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a number average molecular weight (Mn) of 2,000 to 140,000, wherein the coloring material is activated carbon The content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. ink.   An ink containing at least (i) a colorant, (ii) a dispersion medium, and (iii) a water-soluble polymer having a weight average molecular weight (Mw) of 4,000 to 500,000, wherein the colorant is activated carbon The content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. ink.   An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a water-soluble polymer having a z-average molecular weight (Mz) of 10,000 to 1,000,000, wherein the coloring material is activated carbon The content of the water-soluble organic solvent is 5 to 30% by weight in the ink liquid, and the content of the water-soluble polymer is 20 to 200 parts by weight with respect to 100 parts by weight of the activated carbon. And ink.   An ink containing at least (i) a colorant and (ii) a dispersion medium, wherein the colorant is activated carbon, and the average dispersed particle size of the activated carbon in the ink is 50 nm to 1 μm, and is a water-soluble organic solvent An ink having a content of 5 to 30% by weight in the ink liquid and containing 20 to 200 parts by weight of a water-soluble polymer with respect to 100 parts by weight of activated carbon.   The ink according to any one of claims 1 to 7, wherein the dispersion medium contains one or more of ethanol, isopropanol, polyethylene glycol, propylene glycol, and glycerin.   The ink according to any one of claims 1 to 8, which has a viscosity of 1.0 to 10.0 mPa · s and a surface tension of 30 to 38 mN / m.   The ink according to any one of claims 1 to 9, which is an inkjet ink.   The ink according to any one of claims 1 to 10, which is used as a marking ink on the surface of an edible body.   An ink according to claim 1 is printed on a printing surface using an ink jet printing apparatus. A printing method comprising printing the ink according to any one of claims 1 to 11 on an orally ingested product by an ink jet printing apparatus.