JP6771138B2 - Ink and method of manufacturing edible material using it and method of printing edible material - Google Patents

Description

The present invention relates to inks 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, drug identification, etc., 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. There is.

Conventionally, printing on the surface of these solid preparations has been performed by a plate-printing method such as offset printing or gravure printing. For example, Patent Document 1, Patent Document 2, and Patent Document 3 describe a method of transferring ink to a printed matter in a stamp manner by pressing the surface of a rubber roll against a printed matter such as a tablet.
However, these plated methods are based on the premise that the printed surface has a certain degree of hardness and that the surface is flat and has no irregularities. Therefore, uncoated tablets that do not necessarily have these characteristics. It has not been easy to make satisfactory markings on a wide variety of tablets such as sugar-coated tablets and OD tablets (orally disintegrating tablets).

Therefore, it is conceivable to adopt a non-printing printing method such as an inkjet method or a UV laser method. In particular, the inkjet method has less restrictions on the surface to be printed than the UV laser method, and can print on a wider range of objects.

The inkjet method is roughly classified into a continuous type and an on-demand type, and in either method, it is necessary to stably eject ink from a thin nozzle. In the continuous type, the ink particles that are continuously ejected are charged as needed, and the ink particles are deflected according to the amount of charge by the deflection electrode to bend the course and adhere to the printed 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 method of ejecting 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 concentrates or settles while it is not ejected, and the nozzle is easily clogged. Therefore, when a pigment is used as the color material of the ink, it is not easy to achieve satisfactory ejection performance and performance stability. 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 can be ingested into the body without any problem, and the conventionally known inkjet ink is used as it is. It's difficult. Here, the pigments that can be used for edible bodies are limited, and examples thereof include lake pigments and inorganic pigments. However, it is difficult to stably disperse these pigments in an aqueous medium as fine particles, and separation or precipitation in the liquid occurs over time, which induces clogging of the ink nozzles and is therefore difficult to use in ink. Is. Further, in the case of a printed matter such as a tablet, since the surface thereof may be coated, it is often the case that satisfactory adhesion to the ink component cannot be obtained. Furthermore, when selecting the material for the surface of the printed matter, there are restrictions such as being edible, not hindering the expression of the effect of the active ingredient of the tablet, and having no problem with the affinity with the ink and having sufficient adhesion. 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 dispersed in a shellac resin or a cellulosic resin using a charcoal powder dye. However, since the pigment concentration in the ink is limited to about 0.7% by weight, it seems that sufficient print contrast (colorability) cannot be ensured. Further, it is disclosed that it is used for continuous type inkjet, and it is presumed that it is difficult to prevent the occurrence of nozzle clogging when used for on-demand type inkjet.

Japanese Unexamined Patent Publication No. 2000-24089 Japanese Unexamined Patent Publication No. 2000-229847 Japanese Unexamined Patent Publication No. 2001-31898 WO2014 / 014010A1 Gazette

An object of the present invention is to provide an ink that can be used for marking 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 diligent studies to achieve the above object, the present inventors can take it into the body by using a specific coloring material, adding a specific polymer material as appropriate, and adjusting the dispersed particle size. An excellent ink that has excellent adhesion to the tablet surface with only the components, has fixability and light resistance while enabling continuous ejection even in printing by the inkjet method, and exhibits sufficient colorability. Was completed and the present invention was reached.

That is, the present invention
An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a viscosity average molecular weight of 1,000 to 220,000, and the coloring material is activated carbon. Characteristic ink,
(2) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a K value of 10 to 90, wherein the coloring material is activated carbon.
(3) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a number average molecular weight (Mn) of 2,000 to 140,000, and the coloring material is activated carbon. Ink, characterized by being
(4) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a weight average molecular weight (Mw) of 4,000 to 500,000, and the coloring material is activated carbon. An ink characterized by being present.

(5) An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a z average molecular weight (Mz) of 10,000 to 1,000,000, wherein the coloring material is An ink characterized by being activated carbon.
(6) The ink contains at least (i) a coloring material, polyvinylpyrrolidone, and (ii) a dispersion medium, the coloring material is activated carbon, and the average dispersed particle size of the activated carbon in the ink is 50 nm to 1 μm. The ink is characterized by.

According to the present invention, only components that can be ingested in the body have excellent adhesion to the tablet surface, and adhesion, water resistance, light resistance, and scratch resistance can be achieved while enabling continuous ejection even in printing by an inkjet method. It is possible to obtain an excellent ink having sufficient colorability.

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

[Activated carbon]
Activated carbon is a black porous powder, and is generally used for deodorization, water purification, wastewater treatment, catalyst support, etc. by utilizing its pores. In particular, refined activated carbon is taken as medicinal charcoal and is used to adsorb gas and toxic substances in the intestine and discharge them from the body. In the present invention, activated carbon, which is not generally used as a coloring material, is used as a black coloring material.
Activated carbon is known as a carbon material having an extremely large specific surface area. By heating carbon materials such as wood, so-called charcoal such as Bincho charcoal can be obtained (this process is called "carbonization"), but the specific surface area of charcoal (including powdered ones) is generally known. It is said to be 300 to 500 m ² / g. By contrast, activated carbon, by treating at a high temperature even closer 1000 ° C. charcoal, carbon materials (in this way that a specific surface area of 800~2000m ² / g, yet reached 500~3000m ² / g Is known to have extremely high adsorption performance because its specific surface area increases when it is treated at a high temperature to become activated carbon (referred to as "activation" or "activation reaction").

Generally, activated carbon is made by reacting carbon substances such as coal and coconut shells with gas and chemicals at high temperature. A chemical activation method in which a raw material is impregnated with a zinc chloride solution and then heated under certain conditions, and a steam activation method in which the raw material and heated steam are activated at a temperature of 800 to 1000 ° C. are known. In the present invention, activated carbon is used. The manufacturing method is not particularly limited.
Activated carbon is roughly classified into three types depending on the raw material, that is, "coal-based", "plant-based", and "other", but can be used without particular limitation in the present invention.

Further, it can be roughly divided into powdered activated carbon and granular activated carbon according to the shape. The powdered activated carbon refers to a powder having a particle size that passes through a sieve of 100 Mesh (opening 0.15 mm), and the granular activated carbon refers to a powder having a particle size that does not pass through the sieve. In addition, there are fibrous activated carbon and specially molded activated carbon (honeycomb shape, plate shape (sheet shape)) as special shapes. In the present invention, it is preferable to use powdered activated carbon because it is finer and has excellent dispersibility and colorability.

The physical properties of the activated carbon used in the present invention are not particularly limited, but generally, the average particle size is 1 to 100 μm, particularly preferably 5 to 70 μm.
The specific surface area is also not particularly limited, but is preferably 500 to 3000 m ² / g, and particularly preferably 1000 to 2000 m ² / g.
The total pore volume is also 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 size, specific surface area, total pore volume, average pore diameter, and iron content are measured by the method of JIS K 1474-91.

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

The blending amount of the activated carbon is preferably 0.1% by weight to 10% by weight, preferably 0.5% by weight to 8% by weight, and more preferably 1% by weight to 5% by weight in the ink liquid.
If it is less than 0.1% by weight, the concentration as a colorant is low, 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 stability of the ink over time due to aggregation of activated carbon and further deterioration of ejection property from the nozzle.

Activated carbon is a black powder or granular material as described above, but is not usually used as a coloring material (coloring material). This is because the expression of blackness is not high and the dispersibility is not high under normal usage. On the other hand, in the present invention, surprisingly, by inking activated carbon as a coloring material, sufficient coloring is achieved, stable and fine dispersion applicable to inkjet printing is achieved, and also for oral administration. It can be used safely.
Further, in the present invention, preferably, by mixing a specific polymer material described later, activated carbon as a coloring material is used as a coloring material from 0.1% by weight to 10% by weight, particularly 0.5% by weight to 8% by weight, and further. Since it can be contained in the ink at a high concentration of 1% by weight to 5% by weight and a stable dispersed state can be maintained, it can also be used in a continuous type inkjet printer.

The reason why we were able to obtain such excellent ink is that even materials that are not normally used as coloring materials can be used for coloring purposes by performing proper dispersion without being bound by prejudice. This is largely due to the diligent studies of the present inventors. In addition, the affinity between the surface of tablets and other edible bodies, which has not been the subject of conventional inkjet printing, and activated carbon is excellent as a result. In particular, excellent ink performance could be obtained by allowing the ink to exist in a finely dispersed state, which will be described later.
Furthermore, it is presumed that the combination of the specific water-soluble polymer and activated carbon described below exhibits high color development as well as a more excellent and stable dispersed state.

[Water-soluble polymer]
The first form of the ink of the present invention is 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. The ink is characterized in that the coloring material is activated carbon. That is, it is characterized by containing a water-soluble polymer having a viscosity average molecular weight of 1,000 to 220,000. Generally, 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 having a function of stably dispersing solid fine particles such as pigments in a dispersion medium, and can be roughly classified into compounds having a relatively low molecular weight and called surfactants and high molecular weight compounds having a higher molecular weight. It is roughly divided.

Of these, polymer compounds generally have many hydrophilic groups in their molecular chains, and water molecules hydrate and dissolve in them, long-chain aminoamides, acrylic acids / polycarboxylic acids, and salts thereof. As an adsorbing group having a main structure and adsorbing on solid fine particles, there are a basic type such as amide and amine, and a soluble type as a neutralizing salt having an acidic group such as a carboxy group and a phosphoric acid group. In contrast to these general methods for dispersing solid fine particles, in the present invention, activated carbon which is a solid fine particle by blending a polymer which is water-soluble and has a viscosity average molecular weight of 1,000 to 220,000. Is characterized by stable dispersion. In particular, it is not limited to those known as dispersants.

The viscosity average molecular weight of the water-soluble polymer is 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. The measurement of viscosity average molecular weight is basically performed in Polymer Papers vol. 38, No. 7, pp. According to the method for measuring molecular weight described in 457-463 (July, 1981). That is, the procedure is as follows.

(1) The sample is added to excess acetone for precipitation purification. After repeating this operation twice, it is dried under reduced pressure until the odor of acetone disappears.
(2) An aqueous solution of the purified sample is prepared, and the viscosity average molecular weight is determined using the Ubbelohde viscometer (water, 120 seconds) and the Mark-Kuhn-Houwink formula (Mark-Houwink-Sakurada formula). For the coefficients M and α of the Mark-Kuhn-Houwink equation, those described in the above polymer papers are used.
However, any other method may be used as long as the same result can be obtained.

Since the numerical value of the molecular weight has a measurement error and the like, it may fluctuate by about 10%. Therefore, it does not matter if the range is above or below about 10% of the above-mentioned numerical range. The same applies to the number average molecular weight, the weight average molecular weight, and the z average molecular weight, which will be described later.

As the water-soluble polymer used in the present invention, it is particularly preferable to use a nonionic polymer. There is an acid value as an index of polarity, and 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 mgKOH / g). In this range, printing characteristics such as dispersion performance of activated carbon and water resistance of printed matter are particularly excellent.

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

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

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

A second form of the ink of the present invention is 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 It is an ink characterized by being activated carbon. 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 to 40. Here, the K value is obtained by measuring the viscosity by the first method <2.53> of the viscosity measurement method in the 16th revised Japanese Pharmacopoeia, and by using the Fikentscher formula according to the method described in the "K value" column described in the Pharmacopoeia. It is a thing. In this range, the printed matter properties such as the dispersion performance of activated carbon and the water resistance of the printed matter are particularly excellent. Since the K value has measurement errors, it can fluctuate by about 10%. Therefore, the range may be above or below about 10% of the above value.

As the above water-soluble polymer, specifically, casein, a water-soluble cellulose derivative, polyvinylpyrrolidone, polyvinylmethyl ether and the like are preferably used depending on the surface material of the printed matter.

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, non-polar water-soluble polymers such as hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), and polyvinylpyrrolidone are used. These can provide inks having excellent dispersion stability when used in the ink of the present invention, ejection property in printing by an inkjet method, and fixability on a printed matter. It also has an excellent affinity with resin components used as tablet coating materials and capsule film materials. Further, it is preferable because it is possible to obtain an ink having excellent fixability to various objects such as tablets.

These water-soluble cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, and other water-soluble polymers have good adhesion to the sugar-coated layer of sugar-coated tablets, and can be suitably used when printing on sugar-coated tablets by inkjet. Among them, polyvinylpyrrolidone is particularly good in fixing and has a dispersion performance in a coloring material. In particular, among polyvinylpyrrolidones, those having a viscosity average molecular weight of 1,000 to 220,000 are preferable, those having a viscosity average molecular weight of 2,000 to 100,000 are more preferable, those having a viscosity average molecular weight of 5,000 to 100,000 are further preferable, and 7,000. The most preferable one is ~ 50,000.
If the viscosity average molecular weight is less than 2,000, dispersion becomes difficult and the dispersed particle size tends to increase. On the other hand, if it exceeds 220,000, the viscosity may increase and a uniform dispersion may not be obtained.

A third form of the ink of the present invention contains 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. It is an ink characterized in that the coloring material is activated carbon. That is, it is characterized by containing a water-soluble polymer having a number average molecular weight (Mn) of 2,000 to 140,000.
Preferably, the number average molecular weight (Mn) is 2,500-100,000, more preferably 3,000-70,000. 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 may increase and a uniform dispersion may not be obtained. In particular, the value is 3,000 to 70,000, which has the best dispersibility and excellent printed matter properties such as water resistance of the printed matter.

A fourth form of the ink of the present invention contains 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. It is an ink, which is characterized in that the coloring material is activated carbon. 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 may increase and a uniform dispersion may not be obtained. In particular, it is 10,000 to 200,000, and has the best dispersibility and also excellent printed matter properties such as water resistance of the printed matter.

A fifth form of the ink of the present invention comprises 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. It is an ink contained and is characterized in that the coloring material is activated carbon. 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, and has the best dispersibility and also excellent printed matter properties such as water resistance of the printed matter.

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. It should be noted that other measurement methods can be used as long as the same value can be obtained.

Analytical instruments and measurement conditions:
Sample preparation: Weigh 20 mg of sample, add 10 ml of 0.1 M NaNO3 / CH3CN (= 80/20), heat to dissolve in a warm air dryer at 40 ° C for 1 hour, and filter with a 0.45 μm filter. And use it for measurement.
Standard product adjustment: Weigh 2 mg of the sample, add 10 ml of 0.1 M NaNO3 / CH3CN (= 80/20), heat at 40 ° C for 1 hour with a warm air dryer to dissolve, and use a 0.45 μm filter. 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) 7.8mm I. D. × 300 mm (inner diameter (mm) × length (mm)) Neutral column
TSKgel G6000PWXL (Tosoh) 7.8mm I. D. × 300 mm (inner diameter (mm) × length (mm)) Neutral column

Eluent: 0.1 M NaNO ₃ aqueous solution / acetonitrile = 8/2
Flow rate: 1.0 mL / 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.

The amount of the water-soluble polymer added is preferably 20 to 200 parts by weight, more preferably 25 to 180 parts by weight, and most preferably 30 to 150 parts by weight with respect to 100 parts by weight of the activated carbon. If it is less than 20% by weight, it is difficult to sufficiently disperse the coloring material, and the dispersed particle size of the activated carbon in the dispersion medium becomes large. If it 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.

It has been found that in the ink of the present invention, activated carbon can be stably and finely dispersed by blending the specific water-soluble polymer described above, and can be suitably used for inkjet printing. Moreover, by blending this specific water-soluble polymer, the color tone of activated carbon is excellently expressed, 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 is possible without rubbing and disappearing. The mechanism by which such an excellent effect is obtained is not completely clear, but it has a good affinity with activated carbon, which is a porous fine powder, and is stabilized by interaction with the polarity of the surface of activated carbon. Guess. At the same time, it is presumed that it has an excellent affinity with the coating component 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 capable of dispersing activated carbon, and may be appropriately selected depending on the intended use. However, by using water as the main component, in terms of safety and operability, It can be an excellent ink. Further, the ink of the present invention can maintain stable dispersibility and continuous ejection in inkjet printing even when water is mainly used as the dispersion medium. When used for printing a medicinal edible body such as a tablet, distilled water, water for injection, or the like is suitable. Here, the term "mainly water" means that 50% by weight or more, more preferably 60% by weight or more of the liquid constituting the ink is water. Particularly preferably, the composition is substantially water as a liquid component other than the specific water-soluble organic solvent described below.

[Water-soluble organic solvent]
In the present invention, it is desirable to contain a specific water-soluble organic solvent as a liquid component other than water. By adding these water-soluble organic solvents, it is possible to prevent clogging of the head portion and adjust the drying property of the ink when it is used for printing by an inkjet method.
Specific examples of such a water-soluble organic solvent include, for example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, trimethylolpropane, ethylene glycol monoethyl ether, and ethylene. Glycol Monobutyl ether, monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglucol, hexylene glycol, glycerin, diglycerin, 1,2-hexane Diol, 1,6-hexanediol, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,5-pentanediol, monoethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, monoethylene glycol monobutyl ether, diethylene glycol monomethyl Of 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, ethyl lactate, 1,3-dimethyl-2-imidazolidinone They are selected from among, and these can be used alone or in admixture of two or more. Particularly preferably, as a food additive, ethanol, isopropanol, polyethylene glycol, propylene glycol, glycerin and the like are suitable.

The amount of the water-soluble organic solvent added is preferably 5% to 30% by weight, preferably 6% to 25% by weight in the ink liquid, and if it is added more than that, the ink becomes highly viscous, and the stability of the ink and the nozzle The ejection property from the ink may be reduced, or the drying speed may be slowed down. If it is added in an amount of less than 5% by weight, a problem may occur in nozzle ejection, which may cause faintness or make continuous ejection impossible.

[Surface tension adjuster]
In the present invention, a surface tension adjusting agent can be used if necessary. The surface tension adjusting agent is a component having a function of improving discharge from a nozzle and adjusting the surface tension.
Specific examples of the surface tension adjusting agent include surfactants such as nonions and anions, and specifically, for example, alkylbenzene sulfonates, higher alcohol sulfates, higher fatty acid salts, higher alkyl dicarboxylates, and alkyls. Anionic surfactants such as naphthalene sulfonate, alkyl sulfosuccinate, sodium sulfonate formalin condensate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phosphate; eg polyoxyethylene alkyl ether, polyoxy Nonionic surfactants such as ethylene alkylphenyl 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, polyoxyethylene-added acetylene glycol, silicone type Examples thereof include water-soluble organic solvents such as surfactants, fluorosurfactants, ethanol and isopropanol.

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 preferable, and sucrose among them. 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 amount of the surface tension adjusting agent added may be appropriately selected according to the required surface tension, but is preferably 0.5 to 30% by weight, particularly preferably 1 to 20% by weight in the ink.

[Sugars and other additives]
Sugars can be added for the purpose of improving ejection properties and adhesion. Examples of sugars include monosaccharides, disaccharides, and polysaccharides, and specific examples thereof include glucose, galactose, mannose, growth, tarose, allose, altrose, idose, fructose, sorbose, tagatose, psicose, sucrose, maltos, and so on. Lactose, maltotriose, isomaltose, maltotetraose, isomalttriose, isomalttetraose, panose, nigerose, kojibiose, laccherose, palatinose, kestose, nistose, fructosyl nistose, inulobiose, inurotriose, inurotetraose Examples include ose, isomaltose, maltosyl sucrose, maltotriose sucrose, maltopentaose, maltohexaose, and maltoheptaose. Derivatives of these sugars are preferably sugars obtained by reducing or oxidizing the above sugars, and specific examples thereof include maltitol and sorbitol.
The amount added is preferably 1% by weight to 20% by weight in the ink liquid, and has a function of improving faintness when printed on the recording object and stabilizing ejection.

Further, the ink of the present invention preferably has orthophenylphenol, orthophenylphenol sodium, diphenyl, thiabendazole, and imazalyl as a fungicide, and hypochlorite as a bactericide, in order to have desired physical properties. Sodium acid, hydrogen peroxide and ethanol are preferred. Further, additives such as an antifoaming agent, a rust preventive agent, and a PH adjuster can be appropriately added.

Further, the ink of the present invention is characterized by containing activated carbon as a coloring material, but other coloring materials may be contained as long as the performance of the present invention is not impaired. However, for printing of edible materials, which will be described later, sufficient color development can be obtained with activated carbon alone.

Further, for the purpose of adjusting the viscosity of the ink and other purposes, other water-soluble polymers may be added as appropriate as long as the performance of the present invention is not impaired. Examples thereof include starch-based products such as guar gum, locust bean gum, agar and methyl starch, gelatin, pullulan, xanthan gum, tragant gum and dextrin. Further, other conventionally known dispersants may be added as appropriate as long as the performance of the present invention is not impaired.

[Making ink]
The sixth form of the ink of the present invention is an ink containing at least (i) a coloring material and (ii) a dispersion medium, the coloring 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 having a diameter of about 500 nm.
That is, the activated carbon in the ink according to the 26th form 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 to 500 nm, more preferably 100 to 450 nm, and most preferably 150 to 400 nm. In this range, the coloring power, dispersion stability, nozzle ejection property, and fixability to the printed matter are the best. Especially, the average dispersed particle size is in the range of 50 to 500 nm, regardless of the inkjet device or the nozzle. Each physical property is extremely excellent.

When the average dispersed particle size is less than 50 nm, agglomeration is likely to occur due to the van der Waals force between the particles, and the stability with time tends to decrease. When the average dispersed particle size exceeds 1 μm, the coloring material may be easily separated into the liquid and precipitation may easily occur.
Moreover, it is preferable not only to control the average particle size but also to suppress the amount of coarse particles. By adjusting so that 90% or more of the total particles of activated carbon in the liquid have a dispersed particle size of lμm or less, more preferably 500 nm or less, an ink having even better physical properties can be obtained. It is conceivable to carry out the dispersion treatment until the size of all particles falls within this range, but in order to prevent a large amount of too fine particles from being generated and reaggregating, the dispersion treatment is performed until the average particle size falls within the above range. A method of removing the coarse particles by a known method such as centrifugation or filter filtration is also preferable.

The measurement of the average dispersed particle size and the dispersed particle size of all the particles here is as follows.
Conditioning: Dilute the stock solution with ion-exchanged water so that it falls within the specified measurement concentration range.
Measuring equipment: Dynamic light scattering type particle size distribution measuring instrument ("NIKKISO: Microlracwave-EX150")
Measurement time: 120 seconds

Even in the first to fifth forms of the ink of the present invention described above, the ink having even better physical properties can be obtained by setting the range of the average dispersed particle diameter and the dispersed particle diameter of all the particles described above. Further, the above-mentioned dispersion medium, water-soluble organic solvent, surface tension adjusting agent, saccharide and other additives are common to the 26th form of the ink of the present invention and can be preferably used. Further, in particular, by allowing the water-soluble polymer used in any one or more forms of the ink of the present invention described above to be present, the fine activated carbon characterized by the sixth form of the ink of the present invention is present. A dispersed state can be easily and stably obtained.

Further, the viscosities of the inks of the first to sixth embodiments of the present invention described above are 1.0 to 10.0 mPa · s. It is preferably 1.5 to 9.0 mPa · s, and particularly preferably 2.0 to 8.0 mPa · s.
If the viscosity is less than 1.0 mPa · s, a satellite phenomenon may occur or droplets may not be formed from the nozzle. On the contrary, when the viscosity exceeds 10.0 mPa · s, the 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 ink droplets ejected from the head nozzle.

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

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 droplets are not sufficiently discharged from the nozzle, and the same applies when the surface tension exceeds 40 mN / m.

The method for measuring the surface tension is as follows.
Conditioning: Undiluted solution
Measuring equipment: Automatic surface tension meter (plate method) (Kyowa Interface Science Co., Ltd. "CBVP-Z")
Measurement temperature: 25 ° C

[Making ink]
In the production of the ink of the present invention, the above-mentioned components may be mixed to obtain an ink. The mixing method is not particularly limited, but for example, activated carbon, a water-soluble polymer, and water are mixed and stirred, and then dispersed with a disperser, for example, a paint shaker, a roll mill, a ball mill, a sand mill, a jet mill, or the like, and the activated carbon is put into water. It can be stabilized.

At this stage, the method of removing the 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 dispersed state.
Alternatively, the prepared ink can be filtered by a known technique, or impurity ions can be removed to further improve the quality.

[Printing method and application]
Using the ink of the present invention described above, printing can be performed on various objects. Since the ink of the present invention can be produced only with components that can be safely ingested in the body, it can be suitably used for printing on pharmaceuticals such as tablets and capsules, or printing on various foods, for example. The printing method is not limited, and it may be used for methods such as offset printing and gravure printing, which have been conventionally used for printing edible materials, but even when used for inkjet printing, it maintains stable ejection properties and is excellent. Can demonstrate the performance. That is, it can be used as an ink for inkjet for printing using an inkjet printing device, and can also be used as a marking ink for the surface of an edible body, and the ink of the present invention can be printed using the inkjet printing device. An edible material can be produced by printing on a surface.
Since the printed matter thus obtained has excellent colorability and fixability, the ink of the present invention can be used for various purposes such as prevention of counterfeiting, ensuring traceability, prevention of accidental ingestion, improvement of distinctiveness, and impartation of amusement property. It is possible to print on pharmaceuticals, foods, etc.

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

[Example 1]
The following components were blended and stirred with a propeller stirrer at room temperature for 1 hour.
Amount
(Weight part (hereinafter referred to as part))
Activated carbon 10.0
(Average particle size; 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

Then, 150 g of 0.7 mm diameter glass beads were placed in a paint shaker pot with respect to the obtained mixture and shaken for 3 hours.
The 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 liquid 1". Inking was performed by the following method.

Quantity (part)
Dispersion 1 (solid content 10%) 50.0
Glycerin 10.0
Ethanol 10.0
Fatty acid monoglyceride 3.0
Water 27.0
An ink was prepared by stirring with the above composition for 30 minutes.
The obtained ink had an average dispersed particle diameter of 350 nm, a viscosity of 3.1 mPa · s, and a surface tension of 33 mN / m. In addition, the obtained ink showed a uniform black color in appearance.
Further, the ink was examined for stability over time, ejection property, fixability, light resistance, and water resistance according to the following methods. The results are shown in Table 1.

(B) Stability test over time After putting the ink in a glass bottle and letting it stand in a constant temperature room at 5 ° C. for 1 month, it was confirmed whether or not the coloring material was separated, water floated, and settled. A state in which separation of coloring materials, water floating, and sedimentation occurred even a little was evaluated as abnormal.
In Table 1, the case where there is no abnormality is evaluated as ◯, and the case where there is an abnormality is evaluated as ×.

(B) Dischargeability test Using an inkjet printing machine (manufactured by Qualicaps Co., Ltd.) and a droplet observation device, whether ink can be ejected from the head, whether droplets can be formed, and whether re-ejection can be performed after the ejection is stopped. Was investigated.

(C) Fixability dryness test Using tablets immediately after printing with an inkjet printing machine as a sample, the printed part of the sample was rubbed with a non-woven fabric, and the presence or absence of ink spread and the presence or absence of ink transfer to the non-woven fabric were investigated.

(D) Light resistance test Approximately 0.5 mL of ink was applied to the 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 light stability tester (LST-300D manufactured by Tokyo Rika Kikai), expose it to a total illuminance of 1.2 million lux · hr, and then use a visual and spectroscopic color difference meter (SE6000 manufactured by Nippon Denshoku Kogyo) to prepare the sample before exposure. We investigated the difference in color tone with.

(E) Water resistance test A sample for water resistance test was prepared by printing letters with a wire diameter of about 0.1 mm and a size of about 0.5 mm square on a tablet with an inkjet printing machine. After storing the sample in a desiccator in a constant humidity state (relative humidity of about 75%) for 1 week with a saturated solution of sodium chloride, the presence or absence of bleeding in the printed area was investigated.
(F) Color development test The printed part of the sample after the test prepared in the test (e) was visually confirmed to confirm whether the printing could be discriminated and the color tone. Black or dark gray (red when a red color material is used) with good print discrimination was marked with 〇, and others were marked with x.

[Comparative Example 1]
Ink was prepared in the same manner except that activated carbon was used as a valve handle and polyvinylpyrrolidone was replaced with gum arabic in Example 1. [Comparative Example 2] Ink was prepared in the same manner except that the activated carbon was replaced with black iron oxide in Example 1.

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

Quantity (part)
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

Then, with respect to the obtained mixture, 150 g of 0.7 mm diameter glass beads were placed in a pot for a paint shaker and shaken for 3 hours.
The 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 (“dispersion liquid 2”). Ink was obtained by the following method.

Quantity (part)
Dispersion 2 (solid content 10%) 50.0
Glycerin 10.0
Propylene glycol 10.0
Sucrose fatty acid ester 10.0
Water 20.0
An ink was prepared by stirring with the above composition for 30 minutes.
The obtained ink had an average dispersed particle diameter of 250 nm, a viscosity of 2.5 mPa · s, and a surface tension of 32 mN / m. In addition, the obtained ink showed a uniform black color in appearance.

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

Quantity (part)
Activated carbon 10.0
(Average particle size; 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

Then, 370 g of 0.5 mm diameter zirconia beads were placed in a paint shaker pot with respect to the obtained mixture, and the mixture was shaken for 7 hours.
The 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, and the following is obtained. Inked.

Quantity (part)
Dispersion 3 (solid content 10%) 48.0
Sucrose fatty acid ester 10.9
Water 41.1

An ink was prepared by stirring with the above composition for 30 minutes.
The obtained ink had an average dispersed particle diameter of 316 nm, a viscosity of 4.8 mPa · s, and a surface tension of 33 mN / m. In addition, the obtained ink showed a uniform black color in appearance.

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

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

Quantity (part)
Activated carbon 10.0
(Average particle size; 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

Then, 370 g of 0.5 mm diameter zirconia beads were placed in a paint shaker pot with respect to the obtained mixture and shaken for 7 hours.
The 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, and the following is obtained. Inked.

Quantity (part)
Dispersion 4 (solid content 10%) 48.0
Propylene glycol 10.0
Sucrose fatty acid ester 8.7
Water 33.3

An ink was prepared by stirring with the above composition for 30 minutes.
The obtained ink had an average dispersed particle diameter of 283 nm, a viscosity of 4.0 mPa · s, and a surface tension of 32 mN / m. In addition, the obtained ink showed a uniform black color in appearance.

[Comparative Example 4]
In Example 4, the ink was prepared in the same manner except that the activated carbon was replaced with Bincho charcoal, but when the ink was put into a propeller stirrer and stirred, it violently thickened and gelled, lost fluidity and uniformly dispersed. Neither test was possible because no liquid could be obtained and no ink could be formed.

[Comparative Example 5]
In Example 4, polyvinylpyrrolidone (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 used as polyvinylpyrrolidone (viscosity average molecular weight; I tried to make ink in the same way 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), but with a propeller stirrer When it was charged and stirred, it thickened and gelled, lost its fluidity, and a uniform dispersion could not be obtained, and it could not be converted into ink, so neither test could be performed.

In Comparative Example 1 and Comparative Example 2, the ejection property was poor and printing by an inkjet printing machine was difficult, so that a sample for a water resistance test could not be prepared. Further, in Comparative Example 3, the characters printed on the tablet were blurred due to the water resistance test, 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 ink for an inkjet.

According to the present invention, only the components that can be ingested in the body have excellent fixability on the tablet surface, and the fixability and light resistance can be improved while enabling continuous ejection even in printing by an inkjet method, particularly a continuous type. It is possible to provide an excellent ink provided, a printing method using the same, and a method for producing an edible material.

Claims (6)

An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a viscosity average molecular weight of 1,000 to 220,000, characterized in that the coloring material is activated carbon. Inks (excluding those containing 1% by weight or more of clay minerals having a smectite structure) . An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a K value of 10 to 90, characterized in that the coloring material is activated carbon (smectite structure). Except for those containing 1% by weight or more of clay minerals) .
An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a polyvinylpyrrolidone having a number average molecular weight (Mn) of 2,000 to 140,000, and the coloring material is activated carbon. Characteristic inks (excluding those containing 1% by weight or more of clay minerals having a smectite structure) . An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) a polyvinylpyrrolidone having a weight average molecular weight (Mw) of 4,000 to 500,000, and the coloring material is activated carbon. Characteristic inks (excluding those containing 1% by weight or more of clay minerals having a smectite structure) . An ink containing at least (i) a coloring material, (ii) a dispersion medium, and (iii) polyvinylpyrrolidone having a z average molecular weight (Mz) of 10,000 to 1,000,000, wherein the coloring material is activated carbon. Inks characterized by this (excluding those containing 1% by weight or more of clay minerals having a smectite structure) . An ink containing at least (i) a coloring material, polyvinylpyrrolidone, and (ii) a dispersion medium, characterized in that the coloring material is activated carbon and the average dispersed particle size of the activated carbon in the ink is 50 nm to 1 μm. Ink (excluding those containing 1% by weight or more of clayey mineral having a smectite structure) .