Inkjet ink for tablets and tablet printed matter

Abstract

The purpose of the present invention is to provide: an inkjet ink which has improved fixability (transfer resistance) while maintaining excellent printing stability; and a tablet printed matter which is provided with a printed section printed by means of the inkjet ink. The inkjet ink according to the present embodiment contains an edible dye, a binder, and water and ethanol as solvents, and contains only a liquid binder as the binder.

Description

TECHNICAL FIELD

[0001] The present application relates to an inkjet ink for tablets and a tablet print. BACKGROUND

[0002] In an inkjet printing ink for printing on tablets (hereinafter, also simply referred to as "inkjet ink"), there are cases where, for example, by using a food dye such as a tar-based pigment as a coloring material, the inkjet ink is edible (for example, refer to Patent Document 1).

[0003] When a large number of tablets having a printed portion printed using the above inkjet ink (printing ink) are produced, since the printed tablets come into contact with each other, there are cases where the printing ink of one tablet is transferred to another tablet.

[0004] This causes a poor appearance of the tablet, leading to an increase in poor tablets and a decrease in productivity.

[0005] In order to suppress the unintended transfer of the printing ink, an inkjet ink having high drying properties or fixing properties of the ink is required, but by increasing the amount of a drying solvent in the ink, the drying of the nozzle liquid surface is promoted, and there are cases where the printing stability is decreased.

[0006] In addition, in order to solve the problem of the fixing properties of the ink, there is a method of using a solid or gel-like binder, but in the case where such a binder is added, there are cases where the printing quality such as the intermittent recovery properties is decreased.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: Japanese Patent No. 6389506 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] As described above, in the inkjet ink for tablets related to the prior art, there are few inkjet inks having excellent fixing properties (transfer resistance) of the ink while maintaining excellent printing stability. Specifically, in the inkjet ink for tablets related to the prior art, there are few inkjet inks in which all of the initial printing properties, continuous printing properties, intermittent recovery properties, and transfer resistance are excellent.

[0012] The present inventors have found that, in order to improve the above properties of the inkjet ink, it is necessary to add a liquid-like binder to the inkjet ink.

[0013] The present application was made in view of the above problems, and aims to provide an inkjet ink in which the fixing properties (transfer resistance) of the ink are improved while maintaining excellent printing stability, and a tablet print having a printed portion printed using the inkjet ink.

[0014] Means for solving the problems

[0015] To achieve the above object, one embodiment of the present application relates to an inkjet ink, characterized by containing an edible dye, a binder, water and ethanol as a solvent, and containing only a liquid binder as the binder.

[0016] In addition, to achieve the above object, one embodiment of the present application relates to a tablet print, characterized by having a printed portion printed using the above inkjet ink.

[0017] Effects of the Invention

[0018] According to one embodiment of the present application, it is possible to improve the fixing property (resistance to transfer) of the ink while maintaining excellent printing stability. BRIEF DESCRIPTION OF DRAWINGS

[0019] [ Figure 1 ] is a schematic cross-sectional view showing one example of a tablet (plain tablet) relating to an embodiment of the present application.

[0020] [ Figure 2 ] is a schematic cross-sectional view showing one example of a tablet (film-coated tablet) relating to an embodiment of the present application.

[0021] [ Figure 3 ] is one example of a printed image of a tablet (plain tablet) relating to an embodiment of the present application.

[0022] [ Figure 4 ] is one example of a printed image of a tablet (film-coated tablet) relating to an embodiment of the present application.

[0023] Explanation of Symbols

[0024] 1 Base material of tablet

[0025] 3 Printed image

[0026] 5 Plain tablet print

[0027] 7 Film-coating layer

[0028] 9 Film-coated tablet print

[0029] 11 Printed image of plain tablet (solid image)

[0030] 13 Printed image of film-coated tablet (two-dimensional bar code) DETAILED DESCRIPTION

[0031] Embodiments of the present application (hereinafter, referred to as "present embodiments") relate to an inkjet ink, for example, an inkjet ink capable of improving ink fixation (transfer resistance) while maintaining print stability of a printed image or the like applied to the surface of a medical tablet using an inkjet printing method. Hereinafter, the configuration of an inkjet ink (tablet inkjet ink) and a tablet (tablet printed matter) having a printed portion printed using the inkjet ink according to the present embodiments will be described in detail.

[0032] [Configuration of inkjet ink]

[0033] The inkjet ink according to the present embodiments is an edible inkjet ink containing at least a food dye (food coloring), a binder, and water and ethanol as solvents.

[0034] In addition, the inkjet ink according to the present embodiments contains only a liquid binder as the above binder for fixing the ink to the surface of a printed matter (for example, a solid preparation). Specifically, in the present embodiments, only a binder having a viscosity of 1000 mPa-s or less in a range of 0°C or higher and 50°C or lower of the temperature of the binder (hereinafter, also referred to as "liquid binder" for convenience) is used. Note that the "binder" in the present embodiments is also sometimes referred to as a coating agent.

[0035] In addition, the inkjet ink according to the present embodiments contains, for example, polyethylene glycol as the liquid binder.

[0036] In addition, the inkjet ink according to the present embodiments contains, for example, polyethylene glycol having an average molecular weight in a range of 280 or higher and 420 or lower as the liquid binder.

[0037] In addition, the inkjet ink according to the present embodiments contains, for example, propylene glycol as a wetting agent.

[0038] In addition, the inkjet ink according to the present embodiments contains, for example, a dye in a range of 1.0% or more and 5.0% or less with respect to the mass of the entire tablet inkjet ink, a binder in a range of 1.0% or more and 7.0% or less with respect to the mass of the entire tablet inkjet ink, and a wetting agent in a range of more than 0% and 28.0% or less with respect to the mass of the entire tablet inkjet ink.

[0039] In addition, the inkjet ink according to the present embodiments contains, for example, a dye in a range of 1.0% or more and 5.0% or less with respect to the mass of the entire tablet inkjet ink, a binder in a range of 1.0% or more and 7.0% or less with respect to the mass of the entire tablet inkjet ink, and a wetting agent in a range of more than 0% and 28.0% or less with respect to the mass of the entire tablet inkjet ink.

[0040] In addition, the dye of the inkjet ink according to the present embodiment is, for example, at least one selected from the group consisting of azo-based dyes, triphenylmethane-based dyes, and xanthene-based dyes.

[0041] In addition, the inkjet ink according to the present embodiment contains, for example, red No. 102 or yellow No. 4 as the azo-based dye, blue No. 1 as the triphenylmethane-based dye, and red No. 3 as the xanthene-based dye.

[0042] Hereinafter, each component of the inkjet ink according to the present embodiment will be described.

[0043] (Colorant)

[0044] As described above, the inkjet ink according to the present embodiment contains a food dye. The food dye used in the present embodiment is, for example, at least one selected from the group consisting of azo-based dyes, triphenylmethane-based dyes, and xanthene-based dyes.

[0045] In addition, as the azo-based dye, for example, red No. 102 or yellow No. 4 can be used.

[0046] In addition, as the triphenylmethane-based dye, for example, blue No. 1 can be used.

[0047] In addition, as the xanthene-based dye, for example, red No. 3 can be used.

[0048] In the inkjet ink according to the present embodiment, the blending ratio of the food dye, that is, the total content of the food dye with respect to the mass of the entire ink is preferably in the range of 1.0% by mass or more and 5.0% by mass or less, more preferably in the range of 1.0% by mass or more and 4.0% by mass or less, and further preferably in the range of 1.5% by mass or more and 3.0% by mass or less.

[0049] According to such a configuration, it is possible to impart good legibility to a printed image and to impart high printing stability. Note that, in the present embodiment, "printing stability" is a concept including initial printing performance, continuous printing performance, and intermittent recovery performance (printing recovery performance).

[0050] On the other hand, when the total content of the above-described food dye is less than 1.0% by mass, the entire printed color becomes pale, and the legibility of a printed image tends to decrease. In addition, when the total content of the above-described food dye exceeds 5.0% by mass, the solubility stability of the food dye becomes poor, and the pigment in the ink is precipitated or deposited in a solid form, which causes clogging of the nozzles of the inkjet head at the time of printing, and the printing stability, particularly, the intermittent recovery performance, can decrease.

[0051] Note that the inkjet ink of the present embodiment can contain a colorant (color material) other than the above-mentioned food dye. The colorant other than the above-mentioned food dye is not particularly limited as long as it is edible.

[0052] The colorant that can be added to the inkjet ink of the present embodiment can be appropriately selected from among conventionally known synthetic food dyes and natural food dyes, for example.

[0053] In addition, in the case where the inkjet ink of the present embodiment contains a color material other than the above-mentioned food dye as a food dye, the total content of the food dye is preferably in the range of 1.0% by mass or more and 5.0% by mass or less, more preferably in the range of 1.0% by mass or more and 4.0% by mass or less, and further preferably in the range of 1.5% by mass or more and 3.0% by mass or less. Thereby, the printed image can be imparted with good legibility, and the inkjet ink can be imparted with excellent printing stability, particularly intermittent recovery.

[0054] As the synthetic food dye, for example, tar-based dyes, natural dye derivatives, natural-based synthetic dyes, and the like can be exemplified. As the tar-based dyes, for example, food red No. 2, food red No. 3, food red No. 40, food red No. 102, food red No. 104, food red No. 105, food red No. 106, food yellow No. 4, food yellow No. 5, food blue No. 2, food red No. 2 aluminum lake, food red No. 3 aluminum lake, food red No. 40 aluminum lake, food yellow No. 4 aluminum lake, food 5 aluminum lake, food blue No. 1 aluminum lake, food blue No. 2 aluminum lake, and the like can be exemplified. As the natural dye derivatives, for example, norbixin potassium and the like can be exemplified. As the natural-based synthetic dyes, for example, β-carotene, riboflavin, and the like can be exemplified.

[0055] In addition, as natural food colorants, for example, anthocyanin-based colorants, carotenoid-based colorants, quinone-based colorants, chlorophyll-based colorants, flavonoid-based colorants, betalain-based colorants, monascus-based colorants, and other natural-origin colorants can be mentioned. As anthocyanin-based colorants, for example, red radish colorant, red cabbage colorant, red rice colorant, elderberry colorant, blueberry colorant, currant colorant, cranberry colorant, salmonberry colorant, perilla colorant, sim blueberry colorant, strawberry colorant, dark sweet cherry colorant, cherry colorant, hibiscus colorant, blueberry colorant, grape juice colorant, grape skin colorant, black currant colorant, blackberry colorant, blueberry colorant, plum colorant, European blueberry colorant, boysenberry colorant, mulberry colorant, purple sweet potato colorant, purple corn colorant, purple yam colorant, raspberry colorant, red currant colorant, loganberry colorant, and other anthocyanin-based colorants can be mentioned. As carotenoid-based colorants, for example, bixin colorant, gardenia yellow colorant, and other carotenoid-based colorants can be mentioned. As quinone-based colorants, for example, carmine colorant, alkanin colorant, lac colorant, and other quinone-based colorants can be mentioned. As flavonoid-based colorants, for example, safflower yellow colorant, sorghum colorant, onion colorant, and other flavonoid-based colorants can be mentioned. As betalain-based colorants, for example, betacyanin colorant can be mentioned. As monascus-based colorants, for example, monascus colorant, monascus yellow colorant can be mentioned. As other natural-origin colorants, for example, turmeric colorant, quassia colorant, gardenia red colorant, spirulina blue colorant, and the like can be mentioned.

[0056] (Binder)

[0057] As described above, the inkjet ink according to the present embodiment contains only a liquid binder as a binder for fixing the food dye to the surface of the printed matter. Specifically, the binder contained in the inkjet ink according to the present embodiment is, for example, polyethylene glycol (PEG). In addition, among polyethylene glycols, a polyethylene glycol having an average molecular weight in the range of 280 or more and 420 or less, and more preferably a polyethylene glycol having an average molecular weight in the range of 300 or more and 400 or less, is preferable as the binder in the present embodiment.

[0058] If the binder is configured as such, by being added to the inkjet ink together with the above-described solvent (water and ethanol), the inkjet ink is imparted with moderate viscosity (flowability), and the affinity (binding property) to the surface material of the tablet is improved, and thus the ink containing the above-described food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink according to the present embodiment can improve the legibility of the printed image, and can improve the ink fixation (resistance to transfer) of the printed image.

[0059] Note that when the average molecular weight of the polyethylene glycol is less than 280, the flowability of the inkjet ink is too high, and sometimes the affinity (binding property) with the tablet surface material cannot be sufficiently obtained. In addition, when the average molecular weight of the polyethylene glycol exceeds 420, the flowability of the inkjet ink is too low, and sometimes the affinity (binding property) with the tablet surface material cannot be sufficiently obtained.

[0060] In addition, in the inkjet ink according to the present embodiment, two or more kinds of binders having different average molecular weights can be used in combination. In the inkjet ink according to the present embodiment, for example, polyethylene glycol having an average molecular weight in the range of 380 or more and 420 or less (PEG 400) and polyethylene glycol having an average molecular weight in the range of 285 or more and 315 or less (PEG 300) can be used in combination as the binder. In the polyethylene glycols having different average molecular weights, the types of solvents in which each is easily dissolved are different. That is, in the inkjet ink according to the present embodiment, when two or more kinds of polyethylene glycols having different average molecular weights are used, the solubilities in water and ethanol used as the solvent are different, respectively. Therefore, in the present embodiment, by using two or more kinds of polyethylene glycols having different average molecular weights in combination as the binder, the maximum solubility (total solubility) in the solvent containing water and ethanol can be increased compared to the case where only one kind of polyethylene glycol is used as the binder. As a result, according to this configuration, the inkjet ink is given a moderate viscosity (flowability), and the affinity (binding property) with the tablet surface material is improved, and thus the ink containing the above-described food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink according to the present embodiment can improve the legibility of the printed image, and can improve the ink fixation (resistance to transfer) of the printed image.

[0061] In the inkjet ink according to the present embodiment, the blending ratio of the binder is preferably in the range of 1.0% by mass or more and 7.0% by mass or less, more preferably in the range of 1.0% by mass or more and 4.2% by mass or less, and further preferably in the range of 2.8% by mass or more and 4.2% by mass or less, with respect to the mass of the entire ink.

[0062] According to such a configuration, the above-described binder can more reliably exert the fixing effect on the ink, and the ink fixation (resistance to transfer) of the inkjet ink can be reliably improved. In addition, the inkjet ink can be given a moderate viscosity (flowability), and the inkjet ink according to the present embodiment can be given high printing stability, and in particular, intermittent recovery.

[0063] On the other hand, when the blending ratio of the binder is less than 1.0% by mass, the fixing effect of the ink is reduced, and it can be difficult to obtain the ink fixability (transfer resistance). In addition, when the blending ratio of the binder exceeds 7.0% by mass, the viscosity of the ink increases, and the solubility stability of the binder deteriorates, which causes the nozzle of the inkjet head to be clogged during printing, and thus the printing stability, particularly the intermittent recovery, can be reduced.

[0064] In addition, in the case where two or more kinds of binders having different average molecular weights are contained as the binder, when the blending ratio of the binders as a whole is less than 1.0% by mass, the fixing effect of the ink is reduced, and it can be difficult to obtain the ink fixability (transfer resistance). In addition, when the blending ratio of the binders as a whole exceeds 7.0% by mass, the viscosity of the ink increases, and the solubility stability of the binder deteriorates, which causes the nozzle of the inkjet head to be clogged during printing, and thus the printing stability, particularly the intermittent recovery, can be reduced.

[0065] Note that, in the inkjet ink according to the present embodiment, in the case where two or more kinds of binders having different average molecular weights are contained as the binder, the blending ratio of the binders can be 1.0% by mass or more in total.

[0066] In addition, in the case where two or more kinds of binders having different average molecular weights are contained as the binder, the blending ratio of the binder having a small average molecular weight can be greater than the blending ratio of the binder having a large average molecular weight. For example, the blending ratio of the binder having a small average molecular weight is preferably in the range of 1.1 times or more to 2.0 times or less, more preferably in the range of 1.1 times or more to 1.5 times or less, and further preferably in the range of 1.1 times or more to 1.3 times or less, of the blending ratio of the binder having a large average molecular weight.

[0067] In addition, in the case where two or more kinds of binders having different average molecular weights are contained as the binder, the blending ratio of the binder having a small average molecular weight can be greater than the blending ratio of the binder having a large average molecular weight. For example, the blending ratio of the binder having a small average molecular weight is preferably in the range of 1.1 times or more to 2.0 times or less, more preferably in the range of 1.1 times or more to 1.5 times or less, and further preferably in the range of 1.1 times or more to 1.3 times or less, of the blending ratio of the binder having a large average molecular weight.

[0068] According to such a configuration, the fixing effect of the binder on the ink can be more reliably exerted, and the fixability (transfer resistance) of the inkjet ink can be reliably improved.

[0069] (Solvent)

[0070] In addition to the above-mentioned edible dye and the above-mentioned binder, the inkjet ink according to the present embodiment contains a solvent (dispersion medium) for dissolving (dispersing) the edible dye and the binder. In the inkjet ink according to the present embodiment, as the solvent, it is sufficient to contain water (e.g., purified water) and ethanol.

[0071] In addition, the inkjet ink according to the present embodiment can further contain propylene glycol (PG) as the solvent. Propylene glycol functions as a wetting agent, and can prevent drying of the ink at the inkjet nozzle, imparting high printing stability, particularly excellent intermittent recovery, to the ink. In addition, ethanol has high volatility, and thus can improve the transfer resistance (drying property) of the inkjet ink.

[0072] In addition, in the inkjet ink according to the present embodiment, the blending ratio of each component of the above-mentioned solvent is not limited, but the blending ratio of ethanol, i.e., the amount of addition of ethanol, is preferably in the range of 6.5% by mass or more and 11.5% by mass or less with respect to the mass of the entire ink. According to such a configuration, the drying property of the inkjet ink is reliably improved. Thus, the inkjet ink can be imparted with more excellent transfer resistance.

[0073] On the other hand, when the amount of addition of ethanol is less than 6.5% by mass, the drying of the printed surface of the tablet surface is delayed, and sometimes, such a poor condition (transfer failure) occurs that, when the printed tablets contact each other, the un-dried ink adheres to the other tablet, causing contamination. On the other hand, when the amount of addition of ethanol exceeds 11.5% by mass, the drying of the ink at the inkjet nozzle occurs, causing clogging of the nozzle of the inkjet head at the time of printing, and thus the printing stability, particularly the intermittent recovery, can be reduced.

[0074] In addition, in the inkjet ink according to the present embodiment, in the case where propylene glycol is contained in the solvent, the blending ratio of the propylene glycol, i.e., the amount of addition of the propylene glycol, is preferably in the range of 0% by mass or more and 28.0% by mass or less with respect to the mass of the entire ink. According to such a configuration, the inkjet ink can be imparted with moderate tackiness (flowability), the drying of the ink at the inkjet nozzle can be prevented, and the ink can be imparted with high printing stability, particularly excellent intermittent recovery.

[0075] In addition, the amount of addition of propylene glycol is more preferably 10% by mass or more. Thereby, the inkjet ink can be imparted with moderate tackiness (flowability), the drying of the ink at the inkjet nozzle can be further prevented, and the ink can be further imparted with high printing stability, particularly excellent intermittent recovery.

[0076] Note that when the amount of propylene glycol added exceeds 28.0% by mass, the drying of the printed surface of the tablet surface is delayed, and sometimes, an adverse condition (poor transfer) occurs in which, when the printed tablets are in contact with each other, the un-dried ink adheres to the other tablet and causes contamination.

[0077] In addition, the inkjet ink according to the present embodiment can further contain at least one of glycerin or isopropyl alcohol as a solvent. Specifically, among the above-described solvents, either one of glycerin or isopropyl alcohol can be further contained, or both of glycerin and isopropyl alcohol can be further contained. Glycerin functions as a wetting agent like the above-described propylene glycol. In addition, since isopropyl alcohol is highly volatile like the above-described ethanol, the transfer resistance (drying property) of the inkjet ink can be improved. In addition to the above-described components, by further adding glycerin, isopropyl alcohol, or both of them to the solvent, the light resistance of the inkjet ink can be improved, and the inkjet ink can be endowed with properties corresponding to each component. In addition, by further containing these components in the solvent, the inkjet ink can be endowed with moderate tackiness (flowability), and the affinity (binding property) with the tablet surface material is further improved, so the fixing effect of the ink containing the above-described food dye can be further improved.

[0078] (Internal resin)

[0079] In addition to the above-described pigment and solvent, the inkjet ink according to the present embodiment can contain an internal resin. The internal resin that can be added to the inkjet ink according to the present embodiment is a resin-like substance that is edible and is a water-soluble powder, a slurry, or a flaky substance, as long as it is a substance that forms a film on the tablet surface by drying after printing. As the above-described internal resin, for example, polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), polyvinylpyrrolidone (PVP), high-molecular-weight polyethylene glycol (PEG) such as polyethylene glycol 4000 / polyethylene glycol 1540, shellac resin, methacrylic acid copolymer (product name: Eudragit S100), malt dextrin, erythritol, and the like can be listed.

[0080] (Flowing agent)

[0081] In addition to the above-mentioned pigment, solvent, or internally added resin, the inkjet ink according to the present embodiment can also contain a leveling agent. The leveling agent that can be added to the inkjet ink according to the present embodiment is only required to be a surface active agent that is edible and water-soluble. As the above-mentioned leveling agent, for example, polyglycerin fatty acid ester (e.g., di-stearate decaglycerin ester Q-182S manufactured by Taiyo Chemical Industry Co., Ltd., monolaurate decaglycerin ester Q-12S manufactured by the same company), sorbitan fatty acid ester (e.g., NIKKOL SL-10 manufactured by Nikko Chemicals Co., Ltd.), sucrose fatty acid ester (e.g., DK Ester F-110 manufactured by the first industrial Co., Ltd.), polysorbate (Emazole S-120 series manufactured by Kao Corporation), and the like can be exemplified.

[0082] (Fade inhibitor)

[0083] In addition to the above-mentioned pigment, solvent, or internally added resin, leveling agent, the inkjet ink according to the present embodiment can also contain a fade inhibitor. The fade inhibitor that can be added to the inkjet ink according to the present embodiment is only required to be a substance that is edible. As the above-mentioned fade inhibitor, for example, reducing isomaltulose or tri-potassium citrate, and the like can be exemplified.

[0084] By adding the above-mentioned fade inhibitor to the inkjet ink, the inkjet ink can be imparted with excellent light resistance.

[0085] [Printing method]

[0086] The printing method of the inkjet ink according to the present embodiment is not particularly limited, and can be printing using an inkjet device such as a commercially available inkjet printer. Thus, the inkjet ink according to the present embodiment is very useful because of its wide range of applications. For example, the inkjet ink according to the present embodiment can be printed by an inkjet device of the so-called drop-on-demand type using a piezoelectric element (piezoelectric ceramic) as an actuator, or can be printed by an inkjet device of another type.

[0087] As the inkjet device of the drop-on-demand type, for example, a device employing a thermal inkjet method that uses water vapor pressure generated by instantaneously heating a micro-heating element to a high temperature (200 to 300°C) to eject the inkjet ink, a device that ejects the inkjet ink by electrostatically vibrating an actuator, a device employing an ultrasonic method that uses cavitation phenomenon of ultrasonic waves, and the like can be exemplified. In addition, if the inkjet ink according to the present embodiment has a charging property, a device employing a continuous jet type (continuous method) can also be used.

[0088] [Tablet]

[0089] In the present embodiment, the inkjet ink according to the present embodiment can be used to print characters and images on the surface of, for example, a tablet. That is, the tablet according to the present embodiment can have a printed portion, i.e., a printed image, printed using the inkjet ink according to the present embodiment. According to the inkjet ink according to the present embodiment, for example, the light resistance of a printed image (e.g., printed image 3) applied to the surface of a medical tablet using an inkjet printing method can be improved. Hereinafter, the configuration of a tablet having a printed image printed using the inkjet ink according to the present embodiment will be described.

[0090] The tablet according to the present embodiment is, for example, a medical tablet. Here, the "medical tablet" includes, in addition to, for example, a plain tablet, a sugar-coated tablet, an enteric-coated tablet, an intraoral disintegrating tablet, and the like, a film-coated tablet having a water-soluble surface layer formed on the outermost surface of the tablet, and the like.

[0091] Figure 1 is a schematic cross-sectional view showing one example of a medical tablet (plain tablet) on which printing (character printing, image printing) has been performed. Figure 1 A plain tablet print 5 on which a printed image 3 of characters and the like has been printed on the upper surface of a substrate 1 of the tablet is shown in a cross-sectional view.

[0092] Figure 2 is a schematic cross-sectional view showing one example of a medical tablet (film-coated tablet) on which printing (character printing, image printing) has been performed. Figure 2 A film-coated tablet print 9 on which a printed image 3 of characters and the like has been printed on the upper surface of a substrate 1 of the tablet having a film-coated layer 7 formed on the surface is shown in a cross-sectional view.

[0093] Note that in the present embodiment, as shown in Figure 3 , a solid image can be printed as a plain tablet printed image 11, and as shown in Figure 4 , a two-dimensional bar code can be printed as a film-coated tablet printed image 13.

[0094] The active ingredient contained in the medical tablet is not particularly limited. For example, a substance effective for the prevention / treatment of various diseases (for example, a substance having a sleep-inducing action, a tranquilizer activity, an antibacterial activity, a depressant action, an antianginal activity, an analgesic action, an anti-inflammatory activity, a mental stabilizing action, a diabetes treatment activity, a diuretic action, an anticholinergic activity, an anti-gastric acid excess action, an antiepileptic action, an ACE inhibitory activity, a β-receptor antagonist or agonist activity, a narcotic action, an appetite suppressant action, an antiarrhythmic action, an antidepressant action, an anticoagulant activity, an antidiarrheal action, an antihistamine activity, an antimalarial action, an antitumor activity, an immunosuppressive activity, an antiparkinsonian action, an antipsychotic action, an antiplatelet activity, an antihyperlipidemic action, and the like), a substance having a cleaning action, a flavoring agent, a substance having a deodorizing action, and the like, but is not limited thereto.

[0095] As needed, the tablet according to the present embodiment can be combined with a carrier permitted for use in the active ingredient. For example, if it is a medical tablet, a pharmaceutically acceptable carrier can be combined. As the pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as formulation raw materials can be used, for example, an excipient, a lubricant, a binder, a disintegrant, a thickening agent, and the like can be appropriately combined in an appropriate amount. In addition, as needed, a preservative, an antioxidant, a coloring agent, a sweetening agent, and the like can be used.

[0096] In the present embodiment, a medical tablet as an example of a tablet is described, but the present application is not limited thereto. The printing object of the inkjet ink according to the present embodiment is not particularly limited, and for example, it can be printed on the surface of various tablets such as a tablet for administration to animals other than humans (pets, livestock, poultry, and the like), a tablet, a feed, a fertilizer, a cleaning agent, a lemon-flavored candy, or the like, or a food such as a tablet-shaped candy or a health food. In addition, the size of the printing object of the inkjet ink according to the present embodiment is not particularly limited, and it can be applied to tablets of various sizes.

[0097] (EFFECTS OF THE PRESENT EMBODIMENT)

[0098] (1) The inkjet ink according to the present embodiment contains a food dye, a binder, and water and ethanol as solvents, and contains only a liquid binder as the binder.

[0099] According to such a configuration, compared to the related art, it is possible to improve the fixing property (transfer resistance) of the ink while maintaining excellent printing stability.

[0100] (2) In the inkjet ink according to the present embodiment, the binder can be polyethylene glycol.

[0101] According to such a configuration, compared with the related art, since the inkjet ink is imparted with moderate viscosity (fluidity) and further improved affinity (binding property) with the surface material of the tablet, the ink containing the above-mentioned food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink of the present embodiment can further improve legibility of the printed image, and can further improve ink fixation (resistance to transfer) of the printed image.

[0102] (3) Further, in the inkjet ink according to the present embodiment, the average molecular weight of the polyethylene glycol can be in the range of 280 or more and 420 or less.

[0103] According to such a configuration, compared with the related art, since the inkjet ink is imparted with moderate viscosity (fluidity) and further improved affinity (binding property) with the surface material of the tablet, the ink containing the above-mentioned food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink of the present embodiment can further improve legibility of the printed image, and can further improve ink fixation (resistance to transfer) of the printed image.

[0104] (4) Further, the inkjet ink according to the present embodiment can further contain propylene glycol as a wetting agent.

[0105] According to such a configuration, compared with the related art, it is possible to prevent drying of the ink at the inkjet nozzle, and impart high printing stability, particularly excellent intermittent recovery, to the ink.

[0106] (5) Further, in the inkjet ink according to the present embodiment, when containing a wetting agent, the food dye can be blended in the range of 1.0% or more and 5.0% or less with respect to the mass of the entire inkjet ink for tablets, the binder can be blended in the range of 1.0% or more and 7.0% or less with respect to the mass of the entire inkjet ink for tablets, and the wetting agent can be blended in the range of 0% or more and 28.0% or less with respect to the mass of the entire inkjet ink for tablets.

[0107] According to such a configuration, compared with the related art, since the inkjet ink is imparted with moderate viscosity (fluidity) and further improved affinity (binding property) with the surface material of the tablet, the ink containing the above-mentioned food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink of the present embodiment can further improve legibility of the printed image, and can further improve ink fixation (resistance to transfer) of the printed image. Further, it is possible to prevent drying of the ink at the inkjet nozzle, and impart high printing stability, particularly excellent intermittent recovery, to the ink.

[0108] (6) In addition, the inkjet ink according to the present embodiment can contain a dye in a range of 1.0% or more and 5.0% or less with respect to the mass of the entire inkjet ink for tablets, and a binder in a range of 1.0% or more and 7.0% or less with respect to the mass of the entire inkjet ink for tablets, without containing a wetting agent.

[0109] According to such a configuration, compared with the related art, since the inkjet ink is imparted with moderate viscosity (flowability) and further improved affinity (binding property) with the surface material of the tablet, the ink containing the above-mentioned food dye can be fixed to the surface of the printed matter. Thus, the inkjet ink according to the present embodiment can further improve legibility of the printed image, and can further improve ink fixation (resistance to transfer) of the printed image.

[0110] (7) In addition, in the inkjet ink according to the present embodiment, as the food dye, at least one selected from the group consisting of an azo-based dye, a triphenylmethane-based dye, and a xanthene-based dye can be contained.

[0111] According to such a configuration, compared with the related art, legibility of the printed image can be further improved.

[0112] (8) In addition, in the inkjet ink according to the present embodiment, the azo-based dye can be Red No. 102 or Yellow No. 4, the triphenylmethane-based dye can be Blue No. 1, and the xanthene-based dye can be Red No. 3.

[0113] According to such a configuration, compared with the related art, legibility of the printed image can be further improved.

[0114] (9) The tablet printed matter according to the present embodiment has a printed image (one example of a printed portion) 3 printed with the above-mentioned inkjet ink.

[0115] According to such a configuration, compared with the related art, unintended transfer can be suppressed, and legibility of the printed image 3 and the like directly printed on the surface of the tablet and the like can be sufficiently improved. In addition, the printed image portion printed on the surface of the tablet can be imparted with edibility.

[0116] [Examples]

[0117] Hereinafter, the present application will be described in more detail by examples, but the present application is not limited to any of the examples.

[0118] [Examples 1 to 33 and Comparative Examples 1 to 12]

[0119] Hereinafter, the preparation steps of the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12 will be described.

[0120] [Manufacture of Inkjet Inks]

[0121] First, an ink for printing was prepared. The inkjet ink contains a pigment (food dye), a solvent, a binder (coating agent), a fading inhibitor in the following amounts. As the order of preparation, first, the binder and the fading inhibitor were added to the solvent to obtain a transparent base liquid. Next, the pigment was added to the transparent base liquid. In this way, the ink relating to the present embodiment was prepared. Hereinafter, the various components are described in detail.

[0122] In the present embodiment, purified water (ion exchange water), propylene glycol (PG), and ethanol were used as the solvent as needed. Specifically, purified water was added to propylene glycol (PG) and ethanol and stirred sufficiently to obtain a solvent (mixed solvent). In addition, a binder and a fading inhibitor were added to the above solvent as needed and stirred for about 1 hour to obtain a transparent base liquid. In the above transparent base liquid, a food dye, i.e., blue No. 1, and red No. 3, red No. 102, yellow No. 4, were added as pigments as needed to obtain the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12.

[0123] <Sample 1 (Comparative Example 1)>

[0124] With respect to the inkjet ink as a whole of Sample 1 (Comparative Example 1), the blending ratio of blue No. 1 as the pigment was set to 1.5 mass%, the blending ratio of purified water among the solvent was set to 63.0 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 28.0 mass%, and the blending ratio of polyvinylpyrrolidone (PVP) (molecular weight 45,000) as the binder was set to 1.0 mass%. Note that the polyvinylpyrrolidone (PVP) used as the binder in the present sample was a solid in a range of 0°C or higher and 50°C or lower in temperature.

[0125] In this way, the inkjet ink of Sample 1 (Comparative Example 1) was obtained.

[0126] <Sample 2 (Comparative Example 2)>

[0127] With respect to the inkjet ink as a whole of Sample 2 (Comparative Example 2), the blending ratio of polyvinylpyrrolidone (PVP) (molecular weight 45,000) among the binder was set to 0.5 mass%, the blending ratio of polyethylene glycol (PEG 400) was set to 0.5 mass%, and the same as Sample 1 (Comparative Example 1) except for this. Note that the polyethylene glycol (PEG 400) used as the binder in the present sample was a liquid in a range of 0°C or higher and 50°C or lower in temperature.

[0128] In this way, the inkjet ink of Sample 2 (Comparative Example 2) was obtained.

[0129] <Sample 3 (Comparative Example 3)>

[0130] The same as Sample 1 (Comparative Example 1) except that the binder was set to sodium salt of carboxymethyl cellulose (CMC-Na). Note that the sodium salt of carboxymethyl cellulose (CMC-Na) used as the binder in this sample was solid in a range of 0°C or higher and 50°C or lower in temperature.

[0131] Thus, the inkjet ink of Sample 3 (Comparative Example 3) was obtained.

[0132] <Sample 4 (Comparative Example 4)>

[0133] The blending ratio of the sodium salt of carboxymethyl cellulose (CMC-Na) among the binders was set to 0.5 mass% and the blending ratio of polyethylene glycol (PEG 400) was set to 0.5 mass% with respect to the entire inkjet ink of Sample 4 (Comparative Example 4), and the same as Sample 1 (Comparative Example 1) except for this.

[0134] Thus, the inkjet ink of Sample 4 (Comparative Example 4) was obtained.

[0135] <Sample 5 (Comparative Example 5)>

[0136] The blending ratio of polyvinyl alcohol-acrylic acid-methyl methacrylate copolymer (POVACOAT) as the binder was set to 1.0 mass% with respect to the entire inkjet ink of Sample 5 (Comparative Example 5), and the same as Sample 1 (Comparative Example 1) except for this. Note that the polyvinyl alcohol-acrylic acid-methyl methacrylate copolymer (POVACOAT) used as the binder in this sample was solid in a range of 0°C or higher and 50°C or lower in temperature.

[0137] Thus, the inkjet ink of Sample 5 (Comparative Example 5) was obtained.

[0138] <Sample 6 (Example 1)>

[0139] The blending ratio of polyethylene glycol (PEG 400) as the binder was set to 1.0 mass% with respect to the entire inkjet ink of Sample 6 (Example 1), and the same as Sample 1 (Comparative Example 1) except for this.

[0140] Thus, the inkjet ink of Sample 6 (Example 1) was obtained.

[0141] <Sample 7 (Example 2)>

[0142] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 48.0% by mass, the proportion of ethanol was set to 11.5% by mass, the proportion of propylene glycol (PG) was set to 28.0% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 1.0% by mass, and the proportion of reducing isomaltulose (denoted as "Isomalt" in the table) as the color fading inhibitor was set to 10.0% by mass, with respect to the entire inkjet ink of sample 7 (Example 2).

[0143] In this way, the inkjet ink of sample 7 (Example 2) was obtained.

[0144] <Sample 8 (Example 3)>

[0145] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 50.5% by mass, the proportion of ethanol was set to 11.5% by mass, the proportion of propylene glycol (PG) was set to 28.0% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 1.0% by mass, and the proportion of reducing isomaltulose as the color fading inhibitor was set to 7.5% by mass, with respect to the entire inkjet ink of sample 8 (Example 3).

[0146] In this way, the inkjet ink of sample 8 (Example 3) was obtained.

[0147] <Sample 9 (Example 4)>

[0148] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 53.0% by mass, the proportion of ethanol was set to 11.5% by mass, the proportion of propylene glycol (PG) was set to 28.0% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 1.0% by mass, and the proportion of reducing isomaltulose as the color fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 9 (Example 4).

[0149] In this way, the inkjet ink of sample 9 (Example 4) was obtained.

[0150] <Sample 10 (Example 5)>

[0151] The mixing ratio of blue No. 1 as the colorant was set to 1.5 mass% and the mixing ratio of purified water among the solvents was set to 55.5 mass%, the mixing ratio of ethanol was set to 11.5 mass%, the mixing ratio of propylene glycol (PG) was set to 28.0 mass%, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 1.0 mass%, and the mixing ratio of erythritol as the color fading inhibitor was set to 2.5 mass% with respect to the entire inkjet ink of sample 10 (Example 5).

[0152] In this way, the inkjet ink of sample 10 (Example 5) was obtained.

[0153] <Sample 11 (Example 6)>

[0154] The mixing ratio of blue No. 1 as the colorant was set to 1.5 mass% and the mixing ratio of purified water among the solvents was set to 58.0 mass%, the mixing ratio of ethanol was set to 11.5 mass%, the mixing ratio of propylene glycol (PG) was set to 28.0 mass%, and the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 1.0 mass% with respect to the entire inkjet ink of sample 11 (Example 6).

[0155] In this way, the inkjet ink of sample 11 (Example 6) was obtained.

[0156] <Sample 12 (Comparative Example 6)>

[0157] The mixing ratio of blue No. 1 as the colorant was set to 1.5 mass% and the mixing ratio of purified water among the solvents was set to 64.0 mass%, the mixing ratio of ethanol was set to 6.5 mass%, and the mixing ratio of propylene glycol (PG) was set to 28.0 mass% with respect to the entire inkjet ink of sample 12 (Comparative Example 6).

[0158] In this way, the inkjet ink of sample 12 (Comparative Example 6) was obtained.

[0159] <Sample 13 (Comparative Example 7)>

[0160] The mixing ratio of blue No. 1 as the colorant was set to 1.5 mass% and the mixing ratio of purified water among the solvents was set to 59.0 mass%, the mixing ratio of ethanol was set to 6.5 mass%, the mixing ratio of propylene glycol (PG) was set to 28.0 mass%, and the mixing ratio of erythritol as the color fading inhibitor was set to 5.0 mass% with respect to the entire inkjet ink of sample 13 (Comparative Example 7).

[0161] In this way, the inkjet ink of sample 13 (Comparative Example 7) was obtained.

[0162] <Sample 14 (Example 7)>

[0163] The proportion of blue No. 1 as the colorant was set to 1.5 mass% with respect to the entire inkjet ink of sample 14 (Example 7), the proportion of purified water among the solvents was set to 64.0 mass%, the proportion of ethanol was set to 6.5 mass%, the proportion of propylene glycol (PG) was set to 26.6 mass%, and the proportion of polyethylene glycol (PEG 400) as the binder was set to 1.4 mass%.

[0164] Thus, the inkjet ink of sample 14 (Example 7) was obtained.

[0165] <Sample 15 (Example 8)>

[0166] The proportion of blue No. 1 as the colorant was set to 1.5 mass% with respect to the entire inkjet ink of sample 15 (Example 8), the proportion of purified water among the solvents was set to 59.0 mass%, the proportion of ethanol was set to 6.5 mass%, the proportion of propylene glycol (PG) was set to 26.6 mass%, the proportion of polyethylene glycol (PEG 400) as the binder was set to 1.4 mass%, and the proportion of reduced isomaltulose as the color fading inhibitor was set to 5.0 mass%.

[0167] Thus, the inkjet ink of sample 15 (Example 8) was obtained.

[0168] <Sample 16 (Example 9)>

[0169] The proportion of blue No. 1 as the colorant was set to 1.5 mass% with respect to the entire inkjet ink of sample 16 (Example 9), the proportion of purified water among the solvents was set to 64.0 mass%, the proportion of ethanol was set to 6.5 mass%, the proportion of propylene glycol (PG) was set to 25.2 mass%, and the proportion of polyethylene glycol (PEG 300) as the binder was set to 2.8 mass%. Note that the polyethylene glycol (PEG 300) used as the binder in this sample is liquid in a range of 0°C or higher and 50°C or lower in temperature.

[0170] Thus, the inkjet ink of sample 16 (Example 9) was obtained.

[0171] <Sample 17 (Example 10)>

[0172] The mixing ratio of blue No. 1 as the colorant was set to 1.5% by mass, the mixing ratio of purified water among the solvents was set to 59.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 25.2% by mass, the mixing ratio of polyethylene glycol (PEG 300) as the binder was set to 2.8% by mass, and the mixing ratio of erythritol as the color fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 17 (Example 10).

[0173] Thus, the inkjet ink of sample 17 (Example 10) was obtained.

[0174] <Sample 18 (Example 11)>

[0175] The mixing ratio of blue No. 1 as the colorant was set to 1.5% by mass, the mixing ratio of purified water among the solvents was set to 59.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 25.2% by mass, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 2.8% by mass, and the mixing ratio of erythritol as the color fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 18 (Example 11).

[0176] Thus, the inkjet ink of sample 18 (Example 11) was obtained.

[0177] <Sample 19 (Example 12)>

[0178] The mixing ratio of blue No. 1 as the colorant was set to 1.5% by mass, the mixing ratio of purified water among the solvents was set to 59.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, the mixing ratio of polyethylene glycol (PEG 300) as the binder was set to 4.2% by mass, and the mixing ratio of erythritol as the color fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 19 (Example 12).

[0179] Thus, the inkjet ink of sample 19 (Example 12) was obtained.

[0180] <Sample 20 (Example 13)>

[0181] Relative to the entire inkjet ink of sample 20 (Example 13), the mixing ratio of Blue No. 1 as a pigment is set to 1.5 mass%, the mixing ratio of purified water in the solvent is set to 59.0 mass%, the mixing ratio of ethanol is set to 6.5 mass%, the mixing ratio of propylene glycol (PG) is set to 23.8 mass%, the mixing ratio of polyethylene glycol (PEG 400) as a binder is set to 4.2 mass%, and the mixing ratio of reduced isomaltulose as a fading inhibitor is set to 5.0 mass%.

[0182] In this way, the inkjet ink of Sample 20 (Example 13) was obtained.

[0183] <Sample 21 (Example 14)>

[0184] Relative to the entire inkjet ink of sample 21 (Example 14), the mixing ratio of Blue No. 1 as a pigment is set to 1.5 mass%, the mixing ratio of purified water in the solvent is set to 64.0 mass%, the mixing ratio of ethanol is set to 6.5 mass%, the mixing ratio of propylene glycol (PG) is set to 21.0 mass%, and the mixing ratio of polyethylene glycol (PEG 400) as a binder is set to 7.0 mass%.

[0185] In this way, the inkjet ink of Sample 21 (Example 14) was obtained.

[0186] <Sample 22 (Example 15)>

[0187] With respect to the entire inkjet ink of sample 22 (Example 15), the mixing ratio of Blue No. 1 as a pigment is set to 1.5 mass%, the mixing ratio of purified water in the solvent is set to 59.0 mass%, the mixing ratio of ethanol is set to 6.5 mass%, the mixing ratio of propylene glycol (PG) is set to 21.0 mass%, the mixing ratio of polyethylene glycol (PEG 400) as a binder is set to 7.0 mass%, and the mixing ratio of reduced isomaltulose as a fading inhibitor is set to 5.0 mass%.

[0188] In this way, the inkjet ink of Sample 22 (Example 15) was obtained.

[0189] <Sample 23 (Example 16)>

[0190] Relative to the entire inkjet ink of sample 23 (Example 16), the proportion of blue No. 1 as a pigment is set to 1.5 mass%, the proportion of purified water in the solvent is set to 64.0 mass%, the proportion of ethanol is set to 6.5 mass%, the proportion of propylene glycol (PG) is set to 14.0 mass%, and the proportion of polyethylene glycol (PEG 400) as a binder is set to 14.0 mass%.

[0191] Thus, the inkjet ink of sample 23 (Example 16) was obtained.

[0192] <Sample 24 (Example 17)>

[0193] With respect to the inkjet ink of sample 24 (Example 17) as a whole, the blending ratio of blue No. 1 as the colorant was set to 1.5 mass%, the blending ratio of purified water among the solvents was set to 59.0 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 14.0 mass%, the blending ratio of polyethylene glycol (PEG 400) as the binder was set to 14.0 mass%, and the blending ratio of erythritol as the color fading inhibitor was set to 5.0 mass%.

[0194] Thus, the inkjet ink of sample 24 (Example 17) was obtained.

[0195] <Sample 25 (Comparative Example 8)>

[0196] With respect to the inkjet ink of sample 25 (Comparative Example 8) as a whole, the blending ratio of blue No. 1 as the colorant was set to 1.5 mass%, the blending ratio of purified water among the solvents was set to 64.0 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 23.8 mass%, and the blending ratio of polyethylene glycol (PEG 4000) as the binder was set to 4.2 mass%. Note that the polyethylene glycol (PEG 4000) used as the binder in this sample is a solid in a range of 0°C or higher and 50°C or lower in temperature.

[0197] Thus, the inkjet ink of sample 25 (Comparative Example 8) was obtained.

[0198] <Sample 26 (Comparative Example 9)>

[0199] With respect to the inkjet ink of sample 26 (Comparative Example 9) as a whole, the blending ratio of blue No. 1 as the colorant was set to 1.5 mass%, the blending ratio of purified water among the solvents was set to 64.0 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 23.8 mass%, and the blending ratio of polyethylene glycol (PEG 1540) as the binder was set to 4.2 mass%. Note that the polyethylene glycol (PEG 1540) used as the binder in this sample is a solid in a range of 0°C or higher and 50°C or lower in temperature.

[0200] Thus, the inkjet ink of sample 26 (Comparative Example 9) was obtained.

[0201] <Sample 27 (Example 18)>

[0202] The mixing ratio of blue No. 1 as the colorant was set to 1.5% by mass, the mixing ratio of purified water among the solvents was set to 64.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, and the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, with respect to the entire inkjet ink of sample 27 (Example 18).

[0203] In this way, the inkjet ink of sample 27 (Example 18) was obtained.

[0204] <Sample 28 (Example 19)>

[0205] The mixing ratio of blue No. 1 as the colorant was set to 1.5% by mass, the mixing ratio of purified water among the solvents was set to 64.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, and the mixing ratio of polyethylene glycol (PEG 300) as the binder was set to 4.2% by mass, with respect to the entire inkjet ink of sample 28 (Example 19).

[0206] In this way, the inkjet ink of sample 28 (Example 19) was obtained.

[0207] <Sample 29 (Example 20)>

[0208] The mixing ratio of blue No. 1 as the colorant was set to 0.5% by mass, the mixing ratio of purified water among the solvents was set to 60.0% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the mixing ratio of reduced isomaltulose as the fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 29 (Example 20).

[0209] In this way, the inkjet ink of sample 29 (Example 20) was obtained.

[0210] <Sample 30 (Example 21)>

[0211] The mixing ratio of blue No. 1 as the colorant was set to 1.0% by mass, the mixing ratio of purified water among the solvents was set to 59.5% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the mixing ratio of reduced isomaltulose as the fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 30 (Example 21).

[0212] Thus, the inkjet ink of sample 30 (Example 21) was obtained.

[0213] <Sample 31 (Example 22)>

[0214] With respect to the inkjet ink of sample 31 (Example 22) as a whole, the blending ratio of blue No. 1 as the colorant was set to 1.5 mass%, the blending ratio of purified water among the solvents was set to 59.0 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 23.8 mass%, the blending ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2 mass%, and the blending ratio of erythritol as the color fading inhibitor was set to 5.0 mass%.

[0215] Thus, the inkjet ink of sample 31 (Example 22) was obtained.

[0216] <Sample 32 (Example 23)>

[0217] With respect to the inkjet ink of sample 32 (Example 23) as a whole, the blending ratio of blue No. 1 as the colorant was set to 3.0 mass%, the blending ratio of purified water among the solvents was set to 57.5 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 23.8 mass%, the blending ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2 mass%, and the blending ratio of erythritol as the color fading inhibitor was set to 5.0 mass%.

[0218] Thus, the inkjet ink of sample 32 (Example 23) was obtained.

[0219] <Sample 33 (Example 24)>

[0220] With respect to the inkjet ink of sample 33 (Example 24) as a whole, the blending ratio of blue No. 1 as the colorant was set to 4.0 mass%, the blending ratio of purified water among the solvents was set to 56.5 mass%, the blending ratio of ethanol was set to 6.5 mass%, the blending ratio of propylene glycol (PG) was set to 23.8 mass%, the blending ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2 mass%, and the blending ratio of erythritol as the color fading inhibitor was set to 5.0 mass%.

[0221] Thus, the inkjet ink of sample 33 (Example 24) was obtained.

[0222] <Sample 34 (Example 25)>

[0223] The mixing ratio of blue No. 1 as the colorant was set to 5.0% by mass, the mixing ratio of purified water among the solvents was set to 55.5% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the mixing ratio of reducing isomaltulose as the color-fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 34 (Example 25).

[0224] Thus, the inkjet ink of sample 34 (Example 25) was obtained.

[0225] <Sample 35 (Example 26)>

[0226] The mixing ratio of blue No. 1 as the colorant was set to 6.0% by mass, the mixing ratio of purified water among the solvents was set to 54.5% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 23.8% by mass, the mixing ratio of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the mixing ratio of reducing isomaltulose as the color-fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 35 (Example 26).

[0227] Thus, the inkjet ink of sample 35 (Example 26) was obtained.

[0228] <Sample 36 (Comparative Example 10)>

[0229] The mixing ratio of blue No. 1 among the colorants was set to 0.04% by mass, the mixing ratio of red No. 3 was set to 2.5% by mass, the mixing ratio of purified water among the solvents was set to 57.3% by mass, the mixing ratio of ethanol was set to 6.5% by mass, the mixing ratio of propylene glycol (PG) was set to 28.0% by mass, the mixing ratio of tri-potassium citrate (listed as “citric acid K” in the table) among the color-fading inhibitors was set to 5.0% by mass, and the mixing ratio of reducing isomaltulose was set to 0.7% by mass, with respect to the entire inkjet ink of sample 36 (Comparative Example 10).

[0230] Thus, the inkjet ink of sample 36 (Comparative Example 10) was obtained.

[0231] <Sample 37 (Comparative Example 11)>

[0232] The inkjet ink of Sample 37 (Comparative Example 11) was obtained in this way.

[0233] The inkjet ink of Sample 37 (Comparative Example 11) was obtained in this way.

[0234] <Sample 38 (Example 27)>

[0235] The inkjet ink of Sample 38 (Example 27) was obtained in this way.

[0236] The inkjet ink of Sample 38 (Example 27) was obtained in this way.

[0237] <Sample 39 (Example 28)>

[0238] The inkjet ink of Sample 39 (Example 28) was obtained in this way.

[0239] The inkjet ink of Sample 39 (Example 28) was obtained in this way.

[0240] <Sample 40 (Example 29)>

[0241] The inkjet ink of sample 40 (Example 29) was obtained in this way.

[0242] The inkjet ink of sample 40 (Example 29) was obtained in this way.

[0243] <Sample 41 (Example 30)>

[0244] The inkjet ink of sample 41 (Example 30) was obtained in this way.

[0245] The inkjet ink of sample 41 (Example 30) was obtained in this way.

[0246] <Sample 42 (Comparative Example 12)>

[0247] The inkjet ink of sample 42 (Comparative Example 12) was obtained in this way.

[0248] The inkjet ink of sample 42 (Comparative Example 12) was obtained in this way.

[0249] <Sample 43 (Example 31)>

[0250] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 59.0% by mass, the proportion of ethanol was set to 6.5% by mass, the proportion of propylene glycol (PG) was set to 23.8% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the proportion of erythritol as the color-fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 43 (Example 31).

[0251] Thus, the inkjet ink of sample 43 (Example 31) was obtained.

[0252] <Sample 44 (Example 32)>

[0253] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 54.0% by mass, the proportion of ethanol was set to 11.5% by mass, the proportion of propylene glycol (PG) was set to 23.8% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the proportion of erythritol as the color-fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 44 (Example 32).

[0254] Thus, the inkjet ink of sample 44 (Example 32) was obtained.

[0255] <Sample 45 (Example 33)>

[0256] The proportion of blue No. 1 as the colorant was set to 1.5% by mass, the proportion of purified water among the solvents was set to 45.5% by mass, the proportion of ethanol was set to 20.0% by mass, the proportion of propylene glycol (PG) was set to 23.8% by mass, the proportion of polyethylene glycol (PEG 400) as the binder was set to 4.2% by mass, and the proportion of erythritol as the color-fading inhibitor was set to 5.0% by mass, with respect to the entire inkjet ink of sample 45 (Example 33).

[0257] Thus, the inkjet ink of sample 45 (Example 33) was obtained.

[0258] Each of the inks of Examples 1 to 33 and Comparative Examples 1 to 12 described above was passed through a membrane filter to remove solid foreign matter in the liquid. Specifically, each of the inks was passed through a membrane filter (cellulose acetate membrane) having a pore diameter of 5.0 μm once, and then passed through a membrane filter (cellulose acetate membrane) having a pore diameter of 0.8 μm once, to thereby obtain a refined ink, respectively.

[0259] <Evaluation>

[0260] The above refined ink of the ink of each of the above examples and comparative examples was evaluated for printing stability and transferability (resistance to transfer) by the following method. The evaluation results are shown in Tables 1 to 4 described later together with the ink compositions of each of the above examples and comparative examples.

[0261] (Printing stability: initial printing property and continuous printing property)

[0262] A piezoelectric ceramic-driven drop-on-demand inkjet head having a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveying direction of the recording medium such as a tablet), and a total number of nozzles of 2,656 was used. Using the above inkjet head, a test pattern was printed immediately after nozzle maintenance was performed. Then, based on the printing condition of the test pattern, the legibility of the printed image produced with the failed ejection area was confirmed. The evaluation criteria are described below.

[0263] Note that the "initial printing property" in this evaluation refers to the printing property after printing has just started, and the "continuous printing property" refers to the printing property when a test pattern is printed after ink has been continuously ejected from the head for 30 minutes.

[0264] O: a case where the absence or skew of lines is 5% or less of the whole

[0265] Δ: a case where the absence or skew of lines is 20% or less of the whole

[0266] X: a case where the absence or skew of lines exceeds 20% of the whole

[0267] Note that if each of the evaluations of the initial printing property and the continuous printing property is "O" or "Δ", there is no problem in use, and thus it is set as pass.

[0268] (Printing stability: intermittent recovery property)

[0269] A piezoelectric ceramic-driven drop-on-demand inkjet head having a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveying direction of the recording medium such as a tablet), and a total number of nozzles of 1,280 was used, and after being left for a prescribed time (15 minutes to 60 minutes) without flushing, a test pattern was printed at a printing drop amount of 6 pl per drop, and it was confirmed that ink could be ejected from all the nozzles without failed ejection. Note that in Tables 1 to 4 below, the time until ink could be ejected was measured as the evaluation result of the intermittent printing property (intermittent recovery property / ejection stability). The evaluation criteria are described below.

[0270] O: 30 minutes or more

[0271] Δ: 20 minutes or more and less than 30 minutes

[0272] X: less than 20 minutes

[0273] In addition, if the evaluation of the intermittent recovery (discharge stability) test was "○" or "△", it was considered as passing because there was no problem in use.

[0274] (Transferability: Press test)

[0275] Using a piezoelectric ceramic-driven on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the direction in which recording media such as tablets are transported), and a total number of 1,280 nozzles, images were printed on the following tablets using the inkjet inks of the examples and comparative examples at a printing drop size of 6 pl per drop.

[0276] After 60 seconds of printing, warm air drying was performed for 5 seconds. A press test was then performed 60 seconds after printing. In this press test, a tablet attached to a digital dynamometer was brought into contact with the printed tablet for 0.9 to 1.0 seconds under a pressure of 9 to 10 N to confirm that the printed ink had not transferred. Note that in Tables 1 to 4, the transferred ink concentration was visually inspected as an evaluation of transfer resistance (drying properties). The evaluation criteria are as follows.

[0277] ◎: No ink transfer

[0278] ○: Ink transfer is minimal and difficult to visually confirm

[0279] △: Ink transfer is minimal and can be easily visually confirmed

[0280] ×: Ink color is transferred darkly

[0281] In addition, when the evaluation of transferability (transfer resistance) was "◎", "○", or "△", it was considered as passing because there was no problem in use.

[0282] The compositions and evaluation results of the inkjet inks of the Examples and Comparative Examples are shown in Tables 1 to 4. Note that "blank" in Tables 1 to 4 indicates that the substance was not used.

[0283] In addition, all units in Tables 1 to 4 are "mass %".

[0284]

[0285]

[0286]

[0287]

[0288] As shown in Tables 1 to 4, it is found that the evaluation results of the printing stability (initial printing property, continuous printing property, intermittent recovery property) of the inkjet inks of Examples 1 to 33 are "Δ" or more, and the inkjet inks have sufficient printing stability (initial printing property, continuous printing property, intermittent recovery property).

[0289] In addition, as shown in Tables 1 to 4, it is found that the evaluation results of the transferability (tablet drying property) of the inkjet inks of Examples 1 to 33 are "Δ" or more, and the inkjet inks have sufficient transferability (tablet drying property).

[0290] As described above, as long as the tablet inkjet ink containing the edible dye, the binder, and water and ethanol as the solvent, and only the binder having a viscosity of 1000 mPa-s or less in a range where the temperature of the binder is 0°C or higher and 50°C or lower is added as the binder, the inkjet ink having high printing stability and high ink fixation (resistance to transferability) and the tablet printed matter having a printed portion printed with the inkjet ink can be provided.

[0291] The scope of the present application is not limited to the exemplary embodiments described in the drawings, but includes all embodiments having equivalent effects to the object of the present application. Further, the scope of the present application is not limited to the combination of features of the application defined by the claims, but can be defined by all desired combinations of specific features among all disclosed features.

[0292] In addition, for example, the present application can adopt the following configurations. (1)

[0294] A tablet inkjet ink,

[0295] containing an edible dye, a binder, and water and ethanol as a solvent,

[0296] containing only a liquid binder as the binder. (2)

[0298] The tablet inkjet ink according to the above (1), wherein

[0299] The binder is polyethylene glycol. (3)

[0301] The tablet inkjet ink according to the above (2), wherein

[0302] The average molecular weight of the polyethylene glycol is in a range of 280 or more and 420 or less. (4)

[0304] The tablet inkjet ink according to any one of the above (1) to (3), wherein

[0305] propylene glycol as a wetting agent. (5)

[0307] The inkjet ink for tablets according to any one of (1) to (3) above, wherein

[0308] propylene glycol as a wetting agent,

[0309] only one liquid binder, polyethylene glycol, is contained as the binder. (6)

[0311] The inkjet ink for tablets according to (5) above, wherein

[0312] the average molecular weight of the polyethylene glycol is in the range of 280 or more and 420 or less,

[0313] the polyethylene glycol is blended in the range of 1.0% or more and 14.0% or less relative to the mass of the entire inkjet ink for tablets,

[0314] the ethanol is blended in the range of 6.5% or more and 20.0% or less relative to the mass of the entire inkjet ink for tablets,

[0315] the dye is at least one selected from triphenylmethane dyes and xanthene dyes, and does not contain an azo dye,

[0316] in the case where the triphenylmethane dye is blue No. 1, reduced isomaltulose as a fading inhibitor is further contained,

[0317] in the case where the xanthene dye is red No. 3, tri-potassium citrate as a fading inhibitor is further contained. (7)

[0319] The inkjet ink for tablets according to (6) above, wherein

[0320] only the edible dye, the binder, water and ethanol as the solvent, and the wetting agent are contained. (8)

[0322] The inkjet ink for tablets according to any one of (4) to (7) above, wherein

[0323] the dye is blended in the range of 1.0% or more and 5.0% or less relative to the mass of the entire inkjet ink for tablets,

[0324] the binder is blended in the range of 1.0% or more and 7.0% or less relative to the mass of the entire inkjet ink for tablets,

[0325] The wetting agent is blended in a range of more than 0% and 28.0% or less relative to the mass of the entire inkjet ink for tablets. (9)

[0327] The inkjet ink for tablets according to any one of (1) to (8) above, wherein

[0328] The dye is blended in a range of 1.0% or more and 5.0% or less relative to the mass of the entire inkjet ink for tablets,

[0329] The binder is blended in a range of 1.0% or more and 7.0% or less relative to the mass of the entire inkjet ink for tablets. (10)

[0331] The inkjet ink for tablets according to any one of (1) to (9) above, wherein

[0332] The dye is at least one selected from the group consisting of an azo-based dye, a triphenylmethane-based dye, and a xanthene-based dye. (11)

[0334] The inkjet ink for tablets according to (10) above, wherein

[0335] The azo-based dye is Red No. 102 or Yellow No. 4,

[0336] The triphenylmethane-based dye is Blue No. 1,

[0337] The xanthene-based dye is Red No. 3. (12)

[0339] The inkjet ink for tablets according to any one of (5) to (7) above, wherein

[0340] The polyethylene glycol is blended in a range of 1.0% or more and 14.0% or less relative to the mass of the entire inkjet ink for tablets,

[0341] The propylene glycol is blended in a range of 14.0% or more and 28.0% or less relative to the mass of the entire inkjet ink for tablets. (13)

[0343] The inkjet ink for tablets according to any one of (1) to (12) above, wherein

[0344] The dye is at least one selected from the group consisting of a triphenylmethane-based dye and a xanthene-based dye, and is not an azo-based dye,

[0345] In the case where the triphenylmethane-based dye is Blue No. 1, it further contains a reduced isomaltulose as a fading inhibitor,

[0346] In the case where the xanthene-based dye is Red No. 3, tri-potassium citrate is further contained as a fading inhibitor. (14)

[0348] The inkjet ink for tablets according to any one of (13) above, wherein

[0349] The reducing isomaltulose is blended in a range of 0.7% or more and 10.0% or less with respect to the mass of the entire inkjet ink for tablets. (15)

[0351] The inkjet ink for tablets according to any one of (5) to (7) above, wherein

[0352] contains only the edible dye, the binder, water and ethanol as the solvent, the wetting agent, and the fading inhibitor,

[0353] The dye is blended in a range of 1.0% or more and 5.0% or less with respect to the mass of the entire inkjet ink for tablets.

[0354] The polyethylene glycol is blended in a range of 1.0% or more and 7.0% or less with respect to the mass of the entire inkjet ink for tablets.

[0355] The propylene glycol is blended in a range of 14.0% or more and 28.0% or less with respect to the mass of the entire inkjet ink for tablets.

[0356] contains only Blue No. 1 and Red No. 3 as the dye,

[0357] contains reducing isomaltulose as a fading inhibitor for Blue No. 1,

[0358] contains tri-potassium citrate as a fading inhibitor for Red No. 3,

[0359] The reducing isomaltulose is blended in a range of 0.7% or more and 10.0% or less with respect to the mass of the entire inkjet ink for tablets. (16)

[0361] The inkjet ink for tablets according to any one of (5) to (7) above, wherein

[0362] The content of the polyethylene glycol is less than the content of the propylene glycol, or

[0363] The content of the polyethylene glycol is the same as the content of the propylene glycol. (17)

[0365] The inkjet ink for tablets according to (14) above, wherein

[0366] The content of the blue No. 1 is less than that of the red No. 3,

[0367] The content of the reduced isomaltulose is less than that of the tri-potassium citrate. (18)

[0369] A tablet print having a printed portion printed with the inkjet ink for tablets according to any one of (1) to (17) above.

Claims

1. An inkjet ink for tablets, containing an edible dye, a binder, and water and ethanol as solvents, containing only a liquid binder as the binder.

2. The inkjet ink for tablets according to claim 1, wherein the binder is polyethylene glycol.

3. The inkjet ink for tablets according to claim 2, wherein the average molecular weight of the polyethylene glycol is in the range of 280 or more and 420 or less.

4. The inkjet ink for tablets according to claim 2 or claim 3, further containing propylene glycol as a wetting agent.

5. The inkjet ink for tablets according to claim 1, further containing propylene glycol as a wetting agent, containing only a liquid binder, polyethylene glycol, as the binder, the average molecular weight of the polyethylene glycol is in the range of 280 or more and 420 or less, the polyethylene glycol is blended in the range of 1.0% or more and 14.0% or less relative to the mass of the entire inkjet ink for tablets, the ethanol is blended in the range of 6.5% or more and 20.0% or less relative to the mass of the entire inkjet ink for tablets, the dye is at least one selected from triphenylmethane-based dyes and xanthene-based dyes, and does not contain an azo-based dye, in the case where the triphenylmethane-based dye is blue No. 1, it further contains reduced isomaltulose as a fading inhibitor, in the case where the xanthene-based dye is red No. 3, it further contains tri-potassium citrate as a fading inhibitor.

6. The inkjet ink for tablets according to claim 5, wherein only the edible dye, the binder, water and ethanol as the solvents, and the wetting agent are contained.

7. The inkjet ink for tablets according to claim 5, wherein the dye is blended in the range of 1.0% or more and 5.0% or less relative to the mass of the entire inkjet ink for tablets, the binder is blended in the range of 1.0% or more and 7.0% or less relative to the mass of the entire inkjet ink for tablets, the wetting agent is blended in the range of more than 0% and 28.0% or less relative to the mass of the entire inkjet ink for tablets.

8. The inkjet ink for tablets according to claim 5, wherein the dye is blended in the range of 1.0% or more and 5.0% or less relative to the mass of the entire inkjet ink for tablets, the binder is blended in the range of 1.0% or more and 7.0% or less relative to the mass of the entire inkjet ink for tablets.

9. The inkjet ink for tablets according to claim 4, wherein the dye is at least one selected from azo-based dyes, triphenylmethane-based dyes, and xanthene-based dyes.

10. The inkjet ink for tablets according to claim 9, wherein the azo-based dye is red No. 102 or yellow No. 4, the triphenylmethane-based dye is blue No. 1, the xanthene-based dye is red No.

3.

11. The inkjet ink for tablets according to claim 5, wherein the polyethylene glycol is blended in the range of 1.0% or more and 14.0% or less relative to the mass of the entire inkjet ink for tablets, the polyethylene glycol is blended in the range of 1.0% or more and 14.0% or less relative to the mass of the entire inkjet ink for tablets, The propylene glycol is blended in a range of 14.0% or more and 28.0% or less relative to the mass of the entire inkjet ink for tablets.

12. The inkjet ink for tablets according to claim 5, wherein The dye is at least one selected from the group consisting of triphenylmethane-based dyes and xanthene-based dyes, and is not an azo-based dye, In the case where the triphenylmethane-based dye is blue No. 1, it further contains reductone as a fading inhibitor, In the case where the xanthene-based dye is red No. 3, it further contains tri-potassium citrate as a fading inhibitor.

13. The inkjet ink for tablets according to claim 12, wherein The reductone is blended in a range of 0.7% or more and 10.0% or less relative to the mass of the entire inkjet ink for tablets.

14. The inkjet ink for tablets according to claim 5, wherein Only the edible dye, the binder, water and ethanol as the solvent, the wetting agent, and the fading inhibitor are contained, The dye is blended in a range of 1.0% or more and 5.0% or less relative to the mass of the entire inkjet ink for tablets, The polyethylene glycol is blended in a range of 1.0% or more and 7.0% or less relative to the mass of the entire inkjet ink for tablets, The propylene glycol is blended in a range of 14.0% or more and 28.0% or less relative to the mass of the entire inkjet ink for tablets, Only blue No. 1 and red No. 3 are contained as the dye, The reductone is contained as a fading inhibitor of the blue No. 1, Tri-potassium citrate is contained as a fading inhibitor of the red No. 3, The reductone is blended in a range of 0.7% or more and 10.0% or less relative to the mass of the entire inkjet ink for tablets.

15. A tablet print having a printed portion printed using the inkjet ink for tablets according to claim 5.

Images