Tablet Inkjet Ink and Tablet Printed Matter

Abstract

An object of the present invention is to provide an inkjet ink that improves the fixing property (transfer resistance) of ink while maintaining excellent printing stability, and a tablet printed matter including a printed portion printed with the inkjet ink. 【Solution means】The inkjet ink according to the present embodiment contains an edible dye, an adhesive, water and ethanol as solvents, and only a liquid adhesive as the adhesive.

Description

Technical Field

[0001] The present invention relates to an inkjet ink for tablets and a tablet printed matter.

Background Art

[0002] There is an inkjet ink for printing on tablets (hereinafter, also simply referred to as "inkjet ink") that has edibility by using an edible dye such as a tar-based dye as a coloring material (for example, see Patent Document 1).

[0003] In mass-producing tablets provided with a printed portion printed with the above inkjet ink (printing ink), when the printed tablets come into contact with each other after printing, there may occur a phenomenon in which the printing ink of one tablet is transferred to the other tablet. This may cause poor appearance of the tablets, leading to an increase in defective tablets and a decrease in productivity.

[0004] In order to suppress the unintended transfer of the printing ink, an inkjet ink with high drying property and high ink fixing property of the ink is required. However, by increasing the amount of the drying solvent in the ink, the drying of the nozzle liquid surface is promoted, and the printing stability may decrease.

[0005] Also, in order to solve the problem of the fixing property of the ink, there is a method of using a solid or gel-like adhesive. However, when these adhesives are added, the printing quality such as intermittent restartability may decrease.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, among the inkjet inks for tablets according to the prior art, there were few that maintained excellent printing stability and had excellent ink fixing properties (transfer resistance). Specifically, among the inkjet inks for tablets according to the prior art, there were few that were excellent in all of initial printability, continuous printability, intermittent restartability, and transfer resistance. The present inventor has found that in order to improve the above performance of the inkjet ink, it is necessary to add a liquid adhesive to the inkjet ink.

[0008] The present invention has been made in view of such points, and an object thereof is to provide an inkjet ink that improves the fixing property (transfer resistance) of the ink while maintaining excellent printing stability, and a tablet printed matter including a printed portion printed with the inkjet ink.

Means for Solving the Problems

[0009] In order to achieve the above object, an inkjet ink according to one aspect of the present invention includes an edible dye, an adhesive, and water and ethanol as solvents, and is characterized by including only a liquid adhesive as the adhesive.

[0010] Further, in order to achieve the above object, a tablet printed matter according to one aspect of the present invention is characterized by including a printed portion printed using the above inkjet ink.

Effects of the Invention

[0011] According to one aspect of the present invention, it is possible to improve the fixing property (transfer resistance) of the ink while maintaining excellent printing stability.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] The inkjet ink according to an embodiment of the present invention (hereinafter referred to as "the present embodiment") relates to an inkjet ink that can improve the ink fixing property (transfer resistance) while maintaining the print stability of a printed image or the like applied by an inkjet printing method to the surface of a medical tablet, for example. Hereinafter, the configuration of the inkjet ink according to an embodiment of the present invention (inkjet ink for tablets) and a tablet (tablet printed matter) provided with a printed portion printed with the inkjet ink will be described in detail.

[0014] 〔Configuration of Inkjet Ink〕 The inkjet ink according to the present embodiment is an edible inkjet ink, and contains at least an edible dye (edible pigment), an adhesive, and water and ethanol as solvents.

[0015] Further, the inkjet ink according to the present embodiment contains only a liquid adhesive as the adhesive for fixing the ink to the surface of an object to be printed (for example, a solid preparation). Specifically, in the present embodiment, only an adhesive whose viscosity is 1000 mPa·s or less within the range where the temperature of the adhesive is 0°C or higher and 50°C or lower (hereinafter also referred to as "liquid adhesive" for convenience) is used. Note that the "adhesive" in the present embodiment may also be referred to as a coating agent.

[0016] Further, the inkjet ink according to the present embodiment contains, for example, polyethylene glycol as a liquid adhesive. Further, the inkjet ink according to the present embodiment contains, for example, polyethylene glycol having an average molecular weight in the range of 280 or more and 420 or less as a liquid adhesive.

[0017] In addition, the inkjet ink according to the present embodiment further contains, for example, propylene glycol as a wetting agent. In addition, in the inkjet ink according to the present embodiment, for example, the dye is blended in the range of 1.0% or more and 5.0% or less with respect to the total mass of the inkjet ink for tablets, the adhesive is blended in the range of 1.0% or more and 7.0% or less with respect to the total mass of the inkjet ink for tablets, and the wetting agent is blended in the range of more than 0% and 28.0% or less with respect to the total mass of the inkjet ink for tablets.

[0018] In addition, in the inkjet ink according to the present embodiment, for example, no wetting agent is blended, the dye is blended in the range of 1.0% or more and 5.0% or less with respect to the total mass of the inkjet ink for tablets, and the adhesive is blended in the range of 1.0% or more and 7.0% or less with respect to the total mass of the inkjet ink for tablets. In addition, the dye of the inkjet ink according to the present embodiment is, for example, at least one selected from azo dyes, triphenylmethane dyes, and xanthene dyes.

[0019] In addition, in the inkjet ink according to the present embodiment, for example, C.I. Food Red 102 or C.I. Food Yellow 4 is added as an azo dye, C.I. Food Blue 1 is added as a triphenylmethane dye, and C.I. Food Red 3 is added as a xanthene dye.

[0020] Hereinafter, each component constituting the inkjet ink according to the present embodiment will be described. (Colorant) 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 azo dyes, triphenylmethane dyes, and xanthene dyes.

[0021] In addition, as the azo dye, for example, C.I. Food Red 102 or C.I. Food Yellow 4 is used. In addition, as the triphenylmethane dye, for example, C.I. Food Blue 1 is used. In addition, as the xanthene dye, for example, Red No. 3 is used. In the inkjet ink according to this embodiment, the blending ratio of the food dye, that is, 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 even more preferably in the range of 1.5% by mass or more and 3.0% by mass or less, based on the mass of the entire ink.

[0022] With such a configuration, good visibility can be imparted to the printed image, and high printing stability can be imparted. In this embodiment, the "printing stability" is a concept including initial printability, continuous printability, and intermittent restartability (print restartability).

[0023] On the other hand, when the total content of the above food dye is less than 1.0% by mass, the overall printing color tends to be light and the visibility of the printed image tends to decrease. Further, when the total content of the above food dye exceeds 5.0% by mass, the dissolution stability of the food dye deteriorates, and the pigment in the ink may precipitate or settle as a solid, which may cause nozzle clogging of the inkjet head during printing, and the printing stability, particularly the intermittent restartability, may decrease.

[0024] Note that the inkjet ink according to this embodiment may contain pigments (color materials) other than the above food dyes. The pigments other than the above food dyes are not particularly limited as long as they are edible. The pigments that can be added to the inkjet ink according to this embodiment can be appropriately selected and added, for example, from conventionally known synthetic food pigments and natural food pigments.

[0025] In addition, when the inkjet ink according to the present embodiment contains a coloring material other than the above edible dyes as an edible dye, the total content of the edible dyes 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 even more preferably in the range of 1.5% by mass or more and 3.0% by mass or less. Thereby, good visibility can be imparted to the printed image, and excellent printing stability, particularly intermittent restartability, can be imparted to the inkjet ink.

[0026] Examples of the synthetic food colorants include tar dyes, natural pigment derivatives, natural synthetic pigments, etc. Examples of the tar dyes include 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, Aluminum Lake of Food Red No. 2, Aluminum Lake of Food Red No. 3, Aluminum Lake of Food Red No. 40, Aluminum Lake of Food Yellow No. 4, Aluminum Lake of Food Yellow No. 5, Aluminum Lake of Food Blue No. 1, Aluminum Lake of Food Blue No. 2, etc. Examples of the natural pigment derivatives include potassium norbixin, etc. Examples of the natural synthetic pigments include β-carotene, riboflavin, etc.

[0027] Examples of natural food colorants include, for example, anthocyanin pigments, carotenoid pigments, quinone pigments, chlorophyll pigments, flavonoid pigments, betaine pigments, Monascus pigments, and pigments derived from other natural products. Examples of anthocyanin pigments include, for example, red radish pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, cranberry pigment, salmonberry pigment, perilla pigment, sweet blueberry pigment, strawberry pigment, dark sweet cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, grape juice pigment, grape skin pigment, blackcurrant pigment, blackberry pigment, blueberry pigment, plum pigment, whortleberry pigment, boysenberry pigment, mulberry pigment, purple sweet potato pigment, purple corn pigment, purple yam pigment, raspberry pigment, redcurrant pigment, loganberry pigment, and other anthocyanin pigments. Examples of carotenoid pigments include, for example, annatto pigment, gardenia yellow pigment, and other carotenoid pigments. Examples of quinone pigments include, for example, cochineal pigment, shikonin pigment, lac pigment, and other quinone pigments. Examples of flavonoid pigments include, for example, safflower yellow pigment, safflower pigment, onion pigment, and other flavonoid pigments. Examples of betaine pigments include, for example, beet red pigment. Examples of Monascus pigments include, for example, red kojic pigment, red kojic yellow pigment. Examples of pigments derived from other natural products include, for example, turmeric pigment, licorice pigment, gardenia red pigment, spirulina blue pigment, etc.

[0028] (Adhesive) As described above, the inkjet ink according to this embodiment contains only a liquid adhesive as an adhesive for fixing an edible dye to the surface of an object to be printed. Specifically, the adhesive contained in the inkjet ink according to this embodiment is, for example, polyethylene glycol (PEG). Further, as the adhesive in this embodiment, among polyethylene glycols, polyethylene glycol having an average molecular weight in the range of 280 or more and 420 or less is preferable, and polyethylene glycol having an average molecular weight in the range of 300 or more and 400 or less is more preferable.

[0029] If the adhesive has such a configuration, by adding it to the inkjet ink together with the above solvents (water and ethanol), appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (binding property) with the tablet surface substance is enhanced. Therefore, the ink containing the above edible dye can be fixed to the surface of the object to be printed. As a result, the inkjet ink according to this embodiment can improve the visibility of the printed image and can also improve the ink fixing property (transfer resistance) of the printed image. In addition, when the average molecular weight of polyethylene glycol is less than 280, the fluidity of the inkjet ink may be too high, and the affinity (binding property) with the tablet surface substance may not be sufficiently obtained. Further, when the average molecular weight of polyethylene glycol exceeds 420, the fluidity of the inkjet ink may be too low, and the affinity (binding property) with the tablet surface substance may not be sufficiently obtained.

[0030] In addition, in the inkjet ink according to the present embodiment, as the adhesive, two or more types of adhesives having different average molecular weights may be used in combination. In the inkjet ink according to the present embodiment, as the adhesive, for example, polyethylene glycol (PEG400) having an average molecular weight in the range of 380 or more and 420 or less and polyethylene glycol (PEG300) having an average molecular weight in the range of 285 or more and 315 or less may be used in combination. In polyethylene glycols having different average molecular weights, the types of solvents in which they are easily dissolved are different. That is, in the inkjet ink according to the present embodiment, when two or more types of polyethylene glycols having different average molecular weights are used, the solubilities in water and ethanol used as the solvent are different. Therefore, in the present embodiment, by using in combination two or more types of polyethylene glycols having different average molecular weights as the adhesive, the maximum dissolved amount (total dissolved amount) in a solvent containing water and ethanol can be increased compared to the case where only one type of polyethylene glycol is used as the adhesive. As a result, with such a configuration, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (bonding property) with the surface substance of the tablet is enhanced, so that the ink containing the edible dye can be fixed on the surface of the object to be printed. Thereby, the inkjet ink according to the present embodiment can improve the visibility of the printed image and the ink fixing property (transfer resistance) of the printed image.

[0031] In the inkjet ink according to the present embodiment, the blending ratio of the adhesive 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 even more 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.

[0032] With such a configuration, the effect of fixing the ink by the above-mentioned adhesive can be more surely exhibited, and the ink fixing property (transfer resistance) of the inkjet ink can be surely improved. Further, an appropriate viscosity (fluidity) is imparted to the inkjet ink, and high printing stability, particularly intermittent restartability, can be imparted to the inkjet ink according to the present embodiment.

[0033] On the other hand, when the blending ratio of the adhesive is less than 1.0% by mass, the effect of fixing the ink is reduced, and it may be difficult to obtain the ink fixing property (transfer resistance). Further, when the blending ratio of the adhesive exceeds 7.0% by mass, it may cause clogging of the nozzles of the inkjet head during printing due to an increase in the ink viscosity and deterioration of the dissolution stability of the adhesive, and the printing stability, particularly the intermittent restartability, may decrease.

[0034] Further, when two or more types of adhesives having different average molecular weights are included as the adhesive, if the total blending ratio of the adhesives is less than 1.0% by mass, the effect of fixing the ink is reduced, and it may be difficult to obtain the ink fixing property (transfer resistance). Further, when the total blending ratio of the adhesives exceeds 7.0% by mass, it may cause clogging of the nozzles of the inkjet head during printing due to an increase in the ink viscosity and deterioration of the dissolution stability of the adhesive, and the printing stability, particularly the intermittent restartability, may decrease.

[0035] In the inkjet ink according to the present embodiment, when two or more types of adhesives having different average molecular weights are included as the adhesive, the blending ratio of the adhesives may be 1.0% by mass or more in total.

[0036] Further, when two or more types of adhesives having different average molecular weights are included as the adhesive, the blending ratio of the adhesive having a smaller average molecular weight may be larger than the blending ratio of the adhesive having a larger average molecular weight. For example, the blending ratio of the adhesive having a smaller average molecular weight is preferably in the range of 1.1 times or more and 2.0 times or less, more preferably in the range of 1.1 times or more and 1.5 times or less, and even more preferably in the range of 1.1 times or more and 1.3 times or less of the blending ratio of the adhesive having a larger average molecular weight.

[0037] Further, when two or more types of adhesives having different average molecular weights are included as the adhesive, the blending ratio of the adhesive having a large average molecular weight may be larger than the blending ratio of the adhesive having a small average molecular weight. For example, the blending ratio of the adhesive having a large average molecular weight is preferably in the range of 1.1 times or more and 2.0 times or less, more preferably in the range of 1.1 times or more and 1.5 times or less, and even more preferably in the range of 1.1 times or more and 1.3 times or less of the blending ratio of the adhesive having a small average molecular weight.

[0038] With such a configuration, the ink fixing effect by the above adhesive is more surely exhibited, and the fixability (transfer resistance) of the inkjet ink can be surely improved.

[0039] (Solvent) The inkjet ink according to the present embodiment contains a solvent (dispersion medium) for dissolving (dispersing) the edible dye and the adhesive in addition to the edible dye and the adhesive. The inkjet ink according to the present embodiment may contain water (for example, purified water) and ethanol as the solvent.

[0040] Further, the inkjet ink according to the present embodiment may further contain propylene glycol (PG) as the solvent. Propylene glycol functions as a wetting agent, prevents the ink from drying at the inkjet nozzle, and can impart high print stability, particularly excellent intermittent restartability, to the ink. Further, since ethanol has high volatility, the transfer resistance (drying property) of the inkjet ink can be improved.

[0041] Further, in the inkjet ink according to the present embodiment, the blending ratio of each component of the solvent is not limited, but the blending ratio of ethanol, that is, the addition amount 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. With such a configuration, the drying property of the inkjet ink is surely improved. Therefore, excellent transfer resistance can be imparted to the inkjet ink.

[0042] On the one hand, if the addition amount of ethanol is less than 6.5% by mass, the delay in drying of the printed surface on the tablet surface increases, which may cause problems (poor transfer) such as the undried ink adhering to the other tablet and becoming dirty when the printed tablets come into contact with each other. On the other hand, if the addition amount of ethanol exceeds 11.5% by mass, drying of the ink occurs at the inkjet nozzle, which may cause nozzle clogging of the inkjet head during printing and reduce printing stability, particularly the intermittent restartability.

[0043] Further, in the inkjet ink according to the present embodiment, when propylene glycol is contained in the solvent, the blending ratio of the propylene glycol, that is, the addition amount of 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. With such a configuration, appropriate viscosity (fluidity) can be imparted to the inkjet ink, drying of the ink at the inkjet nozzle can be prevented, and high printing stability, particularly excellent intermittent restartability, can be imparted to the ink.

[0044] Moreover, it is more preferable that the addition amount of propylene glycol is 10% by mass or more. Thereby, appropriate viscosity (fluidity) can be imparted to the inkjet ink, drying of the ink at the inkjet nozzle can be further prevented, and high printing stability, particularly excellent intermittent restartability, can be further imparted to the ink.

[0045] In addition, if the addition amount of propylene glycol exceeds 28.0% by mass, the delay in drying of the printed surface on the tablet surface increases, which may cause problems (poor transfer) such as the undried ink adhering to the other tablet and becoming dirty when the printed tablets come into contact with each other.

[0046] In addition, the inkjet ink according to this embodiment may further contain at least one of glycerin or isopropyl alcohol as a solvent. Specifically, in the above solvent, either one of glycerin or isopropyl alcohol may be further contained, or both glycerin and isopropyl alcohol may be further contained. Glycerin functions as a wetting agent in the same manner as the above-described propylene glycol. In addition, since isopropyl alcohol has high volatility like the above-described ethanol, the transfer resistance (drying property) of the inkjet ink can be improved. By further adding glycerin and isopropyl alcohol to the above components to the solvent, the light resistance of the inkjet ink can be improved, and performance according to each component can be imparted to the inkjet ink. Further, by further containing these components in the solvent, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (binding property) with the tablet surface substance is further enhanced, so that the fixing effect of the ink containing the above edible dye can be further improved.

[0047] (Internal additive resin) The inkjet ink according to this embodiment may contain an internal additive resin in addition to the above-described dyes and solvents. The internal additive resin that can be added to the inkjet ink according to this embodiment is an edible and water-soluble powder, paste, or flaky resin-like substance, and any substance that can form a film on the tablet surface by drying after printing may be used. Examples of the above internal additive resin include polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), polyvinyl pyrrolidone (PVP), high molecular weight polyethylene glycol (PEG) such as polyethylene glycol 4000 / polyethylene glycol 1540, shellac resin, methacrylic acid copolymer (product name: Eudragit S100), maltodextrin, erythritol, and the like.

[0048] (Leveling agent) The inkjet ink according to this embodiment may contain a leveling agent in addition to the above-described dyes, solvents, or internal resins. The leveling agent that can be added to the inkjet ink according to this embodiment may be an edible and water-soluble surfactant. Examples of the leveling agent include polyglycerol fatty acid esters (e.g., Decaglycerin distearate Q-182S, Decaglycerin monolaurate Q-12S manufactured by Sun Chemical Corporation), sorbitan fatty acid esters (e.g., NIKKOL SL-10 manufactured by Nikko Chemicals Co., Ltd.), sucrose fatty acid esters (e.g., DK ester F-110 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), polysorbates (Emasol S-120 series manufactured by Kao Corporation), and the like.

[0049] (Fading inhibitor) The inkjet ink according to this embodiment may contain a fading inhibitor in addition to the above-described dyes, solvents, internal resins, or leveling agents. The fading inhibitor that can be added to the inkjet ink according to this embodiment may be an edible substance. Examples of the fading inhibitor include reduced isomaltulose, tripotassium citrate, and the like. By adding the above fading inhibitor to the inkjet ink, excellent light resistance can be imparted to the inkjet ink.

[0050] 〔Printing method〕 The inkjet ink according to this embodiment is not particularly limited with respect to the printing method, and printing can be performed using an inkjet device such as a commercially available inkjet printer. Therefore, the inkjet ink according to this embodiment has a wide range of applications and is very useful. For example, the inkjet ink according to this embodiment can be printed with a so-called drop-on-demand inkjet device using a piezo element (piezoelectric ceramics) as an actuator, and can also be printed with other types of inkjet devices.

[0051] As a drop-on-demand type inkjet device, for example, a thermal inkjet device that ejects inkjet ink by the vapor pressure generated by instantaneously heating a micro heating element to a high temperature (200 to 300°C), an electrostatic type device that ejects inkjet ink by electrostatically vibrating an actuator, a device that employs an ultrasonic method using the cavitation phenomenon of ultrasonic waves, etc. can be mentioned. Further, if the inkjet ink according to this embodiment has chargeability, it is also possible to use a device that employs a continuous injection type (continuous method).

[0052] 〔Tablet〕 In this embodiment, the inkjet ink according to this embodiment may be printed or drawn on the surface of, for example, a tablet using the above-described printing method. That is, the tablet according to this embodiment only needs to have a printed portion, that is, a printed image, printed using the inkjet ink according to this embodiment. If it is the inkjet ink according to this embodiment, for example, the light resistance of a printed image (for example, printed image 3) applied to the surface of a medical tablet using the inkjet printing method can be improved. Hereinafter, the configuration of a tablet having a printed image printed with the inkjet ink according to the embodiment will be described.

[0053] The tablet according to this embodiment is, for example, a medical tablet. Here, the "medical tablet" includes, for example, plain tablets (naked tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, etc., and also film-coated tablets having a water-soluble surface layer formed on the outermost surface of the tablet.

[0054] FIG. 1 is a schematic cross-sectional view showing an example of a medical tablet (plain tablet) on which printing (printing, drawing) has been performed. In FIG. 1, a plain tablet print 5 having a printed image 3 such as characters printed on the upper surface of a tablet base material 1 is shown in a cross-sectional view.

[0055] FIG. 2 is a schematic cross-sectional view showing an example of a medical tablet (film-coated tablet) on which printing (letterpress printing, printing) has been performed. FIG. 2 shows, in cross-sectional view, a film-coated tablet print 9 in which a printed image 3 such as letters is printed on the upper surface of a tablet substrate 1 having a film coat layer 7 formed on the surface.

[0056] In addition, in the present embodiment, as shown in FIG. 3, a solid tablet printed image 11 may be printed as a solid image, or as shown in FIG. 4, a two-dimensional barcode may be printed as a film-coated tablet printed image 13.

[0057] The active ingredient contained in the medical tablet is not particularly limited. For example, substances effective for the prevention and treatment of various diseases (for example, substances having a sleep-inducing effect, a tranquilizer activity, an antibacterial activity, an antihypertensive effect, an antianginal activity, an analgesic effect, an anti-inflammatory activity, a psychotropic activity, a diabetes treatment activity, a diuretic effect, an anticholinergic activity, an anti-hyperacidity effect, an antiepileptic effect, an ACE inhibitory activity, a β-receptor antagonist or agonist activity, an anesthetic effect, an appetite suppressant effect, an antiarrhythmic effect, an antidepressant effect, an anticoagulant activity, an antidiarrheal effect, an antihistamine activity, an antimalarial effect, an antitumor activity, an immunosuppressive activity, an anti-Parkinson's disease effect, an antipsychotic effect, an antiplatelet activity, an antihyperlipidemic effect, etc.), substances having a cleaning effect, fragrances, substances having a deodorizing effect, etc., but are not limited thereto.

[0058] The tablet according to the present embodiment can be blended with a carrier acceptable for its use together with the active ingredient, if necessary. For example, in the case of a medical tablet, a pharmaceutically acceptable carrier can be blended. As the pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as formulation materials are used. For example, excipients, lubricants, binders, disintegrants, thickeners, etc. are blended in appropriate amounts as appropriate. In addition, additives such as preservatives, antioxidants, colorants, sweeteners, etc. can also be used, if necessary.

[0059] In this embodiment, a medical tablet has been described as an example, but the present invention is not limited thereto. The printing target of the inkjet ink according to this embodiment is not particularly limited. For example, it may be printed on the surfaces of various tablets such as tablets administered to animals other than humans (pets, livestock, poultry, etc.), feeds, fertilizers, detergents, tablet confections such as ramune candies, and foods such as supplements. Further, the inkjet ink according to this embodiment is not particularly limited with respect to the size of the printing target, and is applicable to tablets of various sizes.

[0060] (Effects of this embodiment) (1) The inkjet ink according to this embodiment contains an edible dye, an adhesive, and water and ethanol as solvents, and contains only a liquid adhesive as the adhesive. With such a configuration, compared with the prior art, it is possible to improve the fixing property (transfer resistance) of the ink while maintaining excellent printing stability.

[0061] (2) In the inkjet ink according to this embodiment, the adhesive may be polyethylene glycol. With such a configuration, compared with the prior art, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (binding property) with the tablet surface substance is further enhanced. Therefore, the ink containing the above edible dye can be fixed on the surface of the object to be printed. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and further improve the ink fixing property (transfer resistance) of the printed image.

[0062] (3) Further, in the inkjet ink according to this embodiment, the average molecular weight of polyethylene glycol may be in the range of 280 or more and 420 or less. With such a configuration, compared with the prior art, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (binding property) with the tablet surface substance is further enhanced. Therefore, the ink containing the above edible dye can be fixed on the surface of the object to be printed. As a result, the inkjet ink according to the present embodiment can further improve the visibility of the printed image and further improve the ink fixing property (transfer resistance) of the printed image.

[0063] (4) Further, the inkjet ink according to the present embodiment may further contain propylene glycol as a wetting agent. With such a configuration, compared with the prior art, drying of the ink at the inkjet nozzle can be prevented, and high printing stability, particularly excellent intermittent restartability, can be imparted to the ink.

[0064] (5) Further, when the inkjet ink according to the present embodiment contains a wetting agent, the edible dye is blended in the range of 1.0% or more and 5.0% or less based on the total mass of the inkjet ink for tablets, and the adhesive is blended in the range of 1.0% or more and 7.0% or less based on the total mass of the inkjet ink for tablets. The wetting agent may be blended in the range of 0% or more and 28.0% or less based on the total mass of the inkjet ink for tablets.

[0065] With such a configuration, compared with the prior art, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (binding property) with the tablet surface substance is further enhanced. Therefore, the ink containing the above edible dye can be fixed on the surface of the object to be printed. As a result, the inkjet ink according to the present embodiment can further improve the visibility of the printed image and further improve the ink fixing property (transfer resistance) of the printed image. Also, drying of the ink at the inkjet nozzle can be prevented, and high printing stability, particularly excellent intermittent restartability, can be imparted to the ink.

[0066] (6) Also, when the inkjet ink according to this embodiment does not contain a wetting agent, the dye may be blended within a range of 1.0% or more and 5.0% or less with respect to the total mass of the inkjet ink for tablets, and the adhesive may be blended within a range of 1.0% or more and 7.0% or less with respect to the total mass of the inkjet ink for tablets.

[0067] With such a configuration, compared with the prior art, appropriate viscosity (fluidity) is imparted to the inkjet ink, and the affinity (bonding property) with the tablet surface substance is further enhanced. Therefore, the ink containing the above edible dye can be fixed on the surface of the object to be printed. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and can further improve the ink fixing property (transfer resistance) of the printed image.

[0068] (7) Also, the inkjet ink according to this embodiment may contain at least one selected from azo dyes, triphenylmethane dyes, and xanthene dyes as edible dyes. With such a configuration, compared with the prior art, the visibility of the printed image can be further improved.

[0069] (8) Also, in the inkjet ink according to this embodiment, the azo dye may be Red No. 102 or Yellow No. 4, the triphenylmethane dye may be Blue No. 1, and the xanthene dye may be Red No. 3. With such a configuration, compared with the prior art, the visibility of the printed image can be further improved.

[0070] (9) The tablet printed matter according to this embodiment includes a printed image (an example of a printed portion) 3 printed with the above-described inkjet ink. With such a configuration, compared with the prior art, unintended transfer is suppressed, and the visibility of the printed image 3 etc. directly printed on the surface of the tablet etc. can be sufficiently improved. Furthermore, edibility can also be imparted to the printed image portion printed on the surface of the tablet.

[0071] [Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples in any way.

[0072] <Examples 1 to 33 and Comparative Examples 1 to 12> Hereinafter, the preparation procedures of the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12 will be described.

[0073] (Manufacture of Inkjet Ink) First, printing ink was prepared. The inkjet ink contains a dye (food dye), a solvent, an adhesive (coating agent), and a fading inhibitor in the contents described below. As the preparation order, first, the adhesive and the fading inhibitor were added to the solvent to obtain a transparent base liquid. Next, the dye was added to the transparent base liquid. Thus, the ink according to this example was prepared. Hereinafter, various components will be specifically described.

[0074] In this example, purified water (ion-exchanged water), propylene glycol (PG), and ethanol were used for the solvent as needed. Specifically, propylene glycol (PG) and ethanol were added to the purified water and stirred well to obtain a solvent (mixed solvent). Further, the adhesive and the fading inhibitor were added to the above-mentioned solvent as needed and stirred for about 1 hour to obtain a transparent base liquid. To the above-mentioned transparent base liquid, Food Blue No. 1, which is a food dye, and Red No. 3, Red No. 102, and Yellow No. 4 were added as needed to obtain the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12.

[0075] <Sample 1 (Comparative Example 1)> For the entire inkjet ink of Sample 1 (Comparative Example 1), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 63.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of polyvinylpyrrolidone (PVP) (molecular weight 45,000), which is an adhesive, was 1.0% by mass. Note that the polyvinylpyrrolidone (PVP) used as an adhesive in this sample is solid within the temperature range of 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 1 (Comparative Example 1) was obtained.

[0076] <Sample 2 (Comparative Example 2)> For the entire inkjet ink of Sample 2 (Comparative Example 2), the blending ratio of polyvinylpyrrolidone (PVP) (molecular weight 45,000) among the adhesives was 0.5% by mass, and the blending ratio of polyethylene glycol (PEG400) was 0.5% by mass. Otherwise, it was the same as Sample 1 (Comparative Example 1). Note that the polyethylene glycol (PEG400) used as an adhesive in this sample is liquid within the temperature range of 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 2 (Comparative Example 2) was obtained.

[0077] <Sample 3 (Comparative Example 3)> It was the same as Sample 1 (Comparative Example 1) except that the adhesive was sodium carboxymethyl cellulose (CMC-Na). Note that the sodium carboxymethyl cellulose (CMC-Na) used as an adhesive in this sample is solid within the temperature range of 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 3 (Comparative Example 3) was obtained.

[0078] <Sample 4 (Comparative Example 4)> For the entire inkjet ink of Sample 4 (Comparative Example 4), it was the same as Sample 1 (Comparative Example 1) except that the blending ratio of sodium carboxymethyl cellulose (CMC-Na) among the adhesives was 0.5% by mass and the blending ratio of polyethylene glycol (PEG400) was 0.5% by mass. Thus, the inkjet ink of Sample 4 (Comparative Example 4) was obtained.

[0079] <Sample 5 (Comparative Example 5)> For the entire inkjet ink of Sample 5 (Comparative Example 5), it was the same as Sample 1 (Comparative Example 1) except that the blending ratio of polyvinyl alcohol·acrylic acid·methyl methacrylate copolymer (POVACOAT), which is an adhesive, was 1.0% by mass. Note that the polyvinyl alcohol·acrylic acid·methyl methacrylate copolymer (POVACOAT) used as the adhesive in this sample is solid within the range where its temperature is 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 5 (Comparative Example 5) was obtained.

[0080] <Sample 6 (Example 1)> For the entire inkjet ink of Sample 6 (Example 1), it was the same as Sample 1 (Comparative Example 1) except that the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 1.0% by mass. Thus, the inkjet ink of Sample 6 (Example 1) was obtained.

[0081] <Sample 7 (Example 2)> For the entire inkjet ink of Sample 7 (Example 2), the blending ratio of Blue No. 1 as a pigment was 1.5% by mass, the blending ratio of purified water among the solvents was 48.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 1.0% by mass, and the blending ratio of reducing isomaltulose (described as "isomalt" in the table), which is a discoloration inhibitor, was 10.0% by mass. Thus, the inkjet ink of Sample 7 (Example 2) was obtained.

[0082] <Sample 8 (Example 3)> With respect to the entire inkjet ink of Sample 8 (Example 3), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 50.5% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, the mixing ratio of polyethylene glycol (PEG400), which is an adhesive, was 1.0% by mass, and the mixing ratio of reducing isomaltulose, which is a fading inhibitor, was 7.5% by mass. Thus, the inkjet ink of Sample 8 (Example 3) was obtained.

[0083] <Sample 9 (Example 4)> With respect to the entire inkjet ink of Sample 9 (Example 4), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 53.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, the mixing ratio of polyethylene glycol (PEG400), which is an adhesive, was 1.0% by mass, and the mixing ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 9 (Example 4) was obtained.

[0084] <Sample 10 (Example 5)> With respect to the entire inkjet ink of Sample 10 (Example 5), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 55.5% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, the mixing ratio of polyethylene glycol (PEG400), which is an adhesive, was 1.0% by mass, and the mixing ratio of reducing isomaltulose, which is a fading inhibitor, was 2.5% by mass. Thus, the inkjet ink of Sample 10 (Example 5) was obtained.

[0085] <Sample 11 (Example 6)> For the entire inkjet ink of Sample 11 (Example 6), the mixing ratio of Blue No. 1 as a dye was 1.5% by mass, the mixing ratio of purified water among the solvents was 58.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and the mixing ratio of polyethylene glycol (PEG400) as an adhesive was 1.0% by mass. Thus, the inkjet ink of Sample 11 (Example 6) was obtained.

[0086] <Sample 12 (Comparative Example 6)> For the entire inkjet ink of Sample 12 (Comparative Example 6), the mixing ratio of Blue No. 1 as a dye was 1.5% by mass, the mixing ratio of purified water among the solvents was 64.0% by mass, the mixing ratio of ethanol was 6.5% by mass, and the mixing ratio of propylene glycol (PG) was 28.0% by mass. Thus, the inkjet ink of Sample 12 (Comparative Example 6) was obtained.

[0087] <Sample 13 (Comparative Example 7)> For the entire inkjet ink of Sample 13 (Comparative Example 7), the mixing ratio of Blue No. 1 as a dye was 1.5% by mass, the mixing ratio of purified water among the solvents was 59.0% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and the mixing ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 13 (Comparative Example 7) was obtained.

[0088] <Sample 14 (Example 7)> For the entire inkjet ink of Sample 14 (Example 7), the mixing ratio of Blue No. 1 as a dye was 1.5% by mass, the mixing ratio of purified water among the solvents was 64.0% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 26.6% by mass, and the mixing ratio of polyethylene glycol (PEG400) as an adhesive was 1.4% by mass. Thus, the inkjet ink of Sample 14 (Example 7) was obtained.

[0089] <Sample 15 (Example 8)> With respect to the entire inkjet ink of Sample 15 (Example 8), the blending ratio of C.I. Blue 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 26.6% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 1.4% by mass, and the blending ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 15 (Example 8) was obtained.

[0090] <Sample 16 (Example 9)> With respect to the entire inkjet ink of Sample 16 (Example 9), the blending ratio of C.I. Blue 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 25.2% by mass, and the blending ratio of polyethylene glycol (PEG300) as an adhesive was 2.8% by mass. Note that the polyethylene glycol (PEG300) used as an adhesive in this sample is liquid within the range of 0°C or higher and 50°C or lower in temperature. Thus, the inkjet ink of Sample 16 (Example 9) was obtained.

[0091] <Sample 17 (Example 10)> With respect to the entire inkjet ink of Sample 17 (Example 10), the blending ratio of C.I. Blue 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 25.2% by mass, the blending ratio of polyethylene glycol (PEG300) as an adhesive was 2.8% by mass, and the blending ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 17 (Example 10) was obtained.

[0092] <Sample 18 (Example 11)> With respect to the entire inkjet ink of Sample 18 (Example 11), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 25.2% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 2.8% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 18 (Example 11) was obtained.

[0093] <Sample 19 (Example 12)> With respect to the entire inkjet ink of Sample 19 (Example 12), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG300), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 19 (Example 12) was obtained.

[0094] <Sample 20 (Example 13)> With respect to the entire inkjet ink of Sample 20 (Example 13), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 20 (Example 13) was obtained.

[0095] <Sample 21 (Example 14)> For the entire inkjet ink of Sample 21 (Example 14), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 21.0% by mass, and the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 7.0% by mass. Thus, the inkjet ink of Sample 21 (Example 14) was obtained.

[0096] <Sample 22 (Example 15)> For the entire inkjet ink of Sample 22 (Example 15), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 21.0% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 7.0% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 22 (Example 15) was obtained.

[0097] <Sample 23 (Example 16)> For the entire inkjet ink of Sample 23 (Example 16), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 14.0% by mass, and the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 14.0% by mass. Thus, the inkjet ink of Sample 23 (Example 16) was obtained.

[0098] <Sample 24 (Example 17)> For the entire inkjet ink of Sample 24 (Example 17), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 59.0% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 14.0% by mass, the mixing ratio of polyethylene glycol (PEG400), which is an adhesive, was 14.0% by mass, and the mixing ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 24 (Example 17) was obtained.

[0099] <Sample 25 (Comparative Example 8)> For the entire inkjet ink of Sample 25 (Comparative Example 8), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 64.0% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 23.8% by mass, and the mixing ratio of polyethylene glycol (PEG4000), which is an adhesive, was 4.2% by mass. Note that the polyethylene glycol (PEG4000) used as an adhesive in this sample is solid within the temperature range of 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 25 (Comparative Example 8) was obtained.

[0100] <Sample 26 (Comparative Example 9)> For the entire inkjet ink of Sample 26 (Comparative Example 9), the mixing ratio of Blue No. 1, which is a dye, was 1.5% by mass, the mixing ratio of purified water among the solvents was 64.0% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 23.8% by mass, and the mixing ratio of polyethylene glycol (PEG1540), which is an adhesive, was 4.2% by mass. Note that the polyethylene glycol (PEG1540) used as an adhesive in this sample is solid within the temperature range of 0°C or higher and 50°C or lower. Thus, the inkjet ink of Sample 26 (Comparative Example 9) was obtained.

[0101] <Sample 27 (Example 18)> For the entire inkjet ink of Sample 27 (Example 18), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, and the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass. Thus, the inkjet ink of Sample 27 (Example 18) was obtained.

[0102] <Sample 28 (Example 19)> For the entire inkjet ink of Sample 28 (Example 19), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, and the blending ratio of polyethylene glycol (PEG300), which is an adhesive, was 4.2% by mass. Thus, the inkjet ink of Sample 28 (Example 19) was obtained.

[0103] <Sample 29 (Example 20)> For the entire inkjet ink of Sample 29 (Example 20), the blending ratio of Blue No. 1, which is a dye, was 0.5% by mass, the blending ratio of purified water among the solvents was 60.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 29 (Example 20) was obtained.

[0104] <Sample 30 (Example 21)> For the entire inkjet ink of Sample 30 (Example 21), the blending ratio of Blue No. 1, which is a dye, was 1.0% by mass, the blending ratio of purified water among the solvents was 59.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 30 (Example 21) was obtained.

[0105] <Sample 31 (Example 22)> For the entire inkjet ink of Sample 31 (Example 22), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 31 (Example 22) was obtained.

[0106] <Sample 32 (Example 23)> For the entire inkjet ink of Sample 32 (Example 23), the blending ratio of Blue No. 1, which is a dye, was 3.0% by mass, the blending ratio of purified water among the solvents was 57.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 32 (Example 23) was obtained.

[0107] <Sample 33 (Example 24)> For the entire inkjet ink of Sample 33 (Example 24), the compounding ratio of Blue No. 1, which is a dye, was 4.0% by mass, the compounding ratio of purified water among the solvents was 56.5% by mass, the compounding ratio of ethanol was 6.5% by mass, the compounding ratio of propylene glycol (PG) was 23.8% by mass, the compounding ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the compounding ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 33 (Example 24) was obtained.

[0108] <Sample 34 (Example 25)> For the entire inkjet ink of Sample 34 (Example 25), the compounding ratio of Blue No. 1, which is a dye, was 5.0% by mass, the compounding ratio of purified water among the solvents was 55.5% by mass, the compounding ratio of ethanol was 6.5% by mass, the compounding ratio of propylene glycol (PG) was 23.8% by mass, the compounding ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the compounding ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 34 (Example 25) was obtained.

[0109] <Sample 35 (Example 26)> For the entire inkjet ink of Sample 35 (Example 26), the compounding ratio of Blue No. 1, which is a dye, was 6.0% by mass, the compounding ratio of purified water among the solvents was 54.5% by mass, the compounding ratio of ethanol was 6.5% by mass, the compounding ratio of propylene glycol (PG) was 23.8% by mass, the compounding ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the compounding ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 35 (Example 26) was obtained.

[0110] <Sample 36 (Comparative Example 10)> For the entire inkjet ink of Sample 36 (Comparative Example 10), the blending ratio of Blue No. 1 among the dyes was 0.04% by mass, the blending ratio of Red No. 3 was 2.5% by mass, the blending ratio of purified water among the solvents was 57.3% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, the blending ratio of tripotassium citrate (described as "K citrate" in the table) among the fading inhibitors was 5.0% by mass, and the blending ratio of reduced isomaltulose was 0.7% by mass. Thus, the inkjet ink of Sample 36 (Comparative Example 10) was obtained.

[0111] <Sample 37 (Comparative Example 11)> For the entire inkjet ink of Sample 37 (Comparative Example 11), the blending ratio of Blue No. 1 among the dyes was 0.7% by mass, the blending ratio of Red No. 102 was 1.4% by mass, the blending ratio of Yellow No. 4 was 0.4% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, the inkjet ink of Sample 37 (Comparative Example 11) was obtained.

[0112] <Sample 38 (Example 27)> For the entire inkjet ink of Sample 38 (Example 27), the blending ratio of Blue No. 1 among the dyes was 0.04% by mass, the blending ratio of Red No. 3 was 2.5% by mass, the blending ratio of purified water among the solvents was 57.3% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 25.2% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 2.8% by mass, the blending ratio of tripotassium citrate among the fading inhibitors was 5.0% by mass, and the blending ratio of reduced isomaltulose, which is a fading inhibitor, was 0.7% by mass. Thus, the inkjet ink of Sample 38 (Example 27) was obtained.

[0113] <Sample 39 (Example 28)> For the entire inkjet ink of Sample 39 (Example 28), the mixing ratio of Food Blue 1 among the dyes was 0.04% by mass, the mixing ratio of Food Red 3 was 2.5% by mass, the mixing ratio of purified water among the solvents was 57.3% by mass, the mixing ratio of ethanol was 6.5% by mass, the mixing ratio of propylene glycol (PG) was 23.8% by mass, the mixing ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, the mixing ratio of tripotassium citrate among the fading inhibitors was 5.0% by mass, and the mixing ratio of reduced isomaltulose was 0.7% by mass. Thus, the inkjet ink of Sample 39 (Example 28) was obtained.

[0114] <Sample 40 (Example 29)> For the entire inkjet ink of Sample 40 (Example 29), the mixing ratio of Food Blue 1 among the dyes was 0.7% by mass, the mixing ratio of Food Red 102 was 1.4% by mass, the mixing ratio of Food Yellow 4 was 0.4% by mass, the mixing ratio of purified water among the solvents was 53.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 25.2% by mass, the mixing ratio of polyethylene glycol (PEG400) as an adhesive was 2.8% by mass, and the mixing ratio of reduced isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 40 (Example 29) was obtained.

[0115] <Sample 41 (Example 30)> For the entire inkjet ink of Sample 41 (Example 30), the mixing ratio of Food Blue 1 among the dyes was 0.7% by mass, the mixing ratio of Food Red 102 was 1.4% by mass, the mixing ratio of Food Yellow 4 was 0.4% by mass, the mixing ratio of purified water among the solvents was 53.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 23.8% by mass, the mixing ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, and the mixing ratio of reduced isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 41 (Example 30) was obtained.

[0116] <Sample 42 (Comparative Example 12)> With respect to the entire inkjet ink of Sample 42 (Comparative Example 12), the blending ratio of Blue No. 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 65.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, and the blending ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 42 (Comparative Example 12) was obtained.

[0117] <Sample 43 (Example 31)> With respect to the entire inkjet ink of Sample 43 (Example 31), the blending ratio of Blue No. 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, and the blending ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 43 (Example 31) was obtained.

[0118] <Sample 44 (Example 32)> With respect to the entire inkjet ink of Sample 44 (Example 32), the blending ratio of Blue No. 1 as a dye was 1.5% by mass, the blending ratio of purified water among the solvents was 54.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, and the blending ratio of reducing isomaltulose as a fading inhibitor was 5.0% by mass. Thus, the inkjet ink of Sample 44 (Example 32) was obtained.

[0119] <Sample 45 (Example 33)> For the entire inkjet ink of Sample 45 (Example 33), the blending ratio of Blue No. 1, which is a dye, was 1.5% by mass, the blending ratio of purified water among the solvents was 45.5% by mass, the blending ratio of ethanol was 20.0% by mass, the blending ratio of propylene glycol (PG) was 23.8% by mass, the blending ratio of polyethylene glycol (PEG400), which is an adhesive, was 4.2% by mass, and the blending ratio of reducing isomaltulose, which is a fading inhibitor, was 5.0% by mass. Thus, an inkjet ink of Sample 45 (Example 33) was obtained.

[0120] Each of the inks of the above-described Examples 1 to 33 and Comparative Examples 1 to 12 was passed through a membrane filter to remove solid foreign matters in the liquid. Specifically, purified inks were obtained by passing through a membrane filter (cellulose acetate membrane) with a diameter of 5.0 μm once and then passing through a membrane filter (cellulose acetate membrane) with a diameter of 0.8 μm once.

[0121] <Evaluation> Regarding the purified inks using the inks of the above-described Examples and Comparative Examples, the printing stability and transferability (transfer resistance) were evaluated by the following method. The evaluation results are shown in Tables 1 to 4 described later together with the ink compositions of the above-described Examples and Comparative Examples.

[0122] (Printing stability: Initial printability and continuous printability) For the inkjet head, a piezoelectric ceramic-driven drop-on-demand type inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of a recording medium such as a tablet), and a total number of nozzles of 2,656 was used. Using the above-described inkjet head, a test pattern was printed immediately after performing nozzle maintenance. Then, from the printing status of the test pattern, the readability of the printed image due to the occurrence of non-ejection regions was confirmed. The evaluation criteria are as follows.

[0123] Note that the "initial printability" in this evaluation refers to the printability immediately after the start of printing, and the "continuous printability" refers to the printability when printing a test pattern after continuously discharging ink from the head for 30 minutes.

[0124] 〇: When the missing or bending of the line is 5% or less of the whole △: When the missing or bending of the line is 20% or less of the whole ×: When the missing or bending of the line exceeds 20% of the whole Note that if each evaluation of the initial printability and the continuous printability is "〇" or "△", it is considered qualified because there are no problems in use.

[0125] (Printing stability: intermittent restartability) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of the recording medium such as tablets), and a total nozzle number of 1,280, after leaving it without flushing for a specified time (15 minutes to 60 minutes), a test pattern was printed with a printing drop volume of 6 pl per drop, and it was confirmed that the ink was discharged without non-discharge from all nozzles. Note that in Tables 1 to 4 below, as the evaluation result of the intermittent printability (intermittent restartability / discharge stability), the standing time during which the ink can be discharged was measured. The evaluation criteria are as follows.

[0126] 〇: 30 minutes or more △: 20 minutes or more and less than 30 minutes ×: Less than 20 minutes Note that if the evaluation of the intermittent restartability (discharge stability) test is "○" or "△", it is considered qualified because there are no problems in use.

[0127] (Transferability: pressing test) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of the recording medium such as tablets), and a total nozzle number of 1,280, images were printed on the following tablets with the inkjet inks of the examples and each comparative example at a printing drop volume of 6 pl per drop.

[0128] The tablets were dried with warm air for 5 seconds while 60 seconds elapsed after printing, and a pressing test was carried out when 60 seconds had elapsed after printing. In this pressing test, the printed tablets were brought into contact with the tablets attached to a digital force gauge at a pressure of 9 to 10 N for 0.9 to 1.0 seconds, and it was confirmed that the printed ink did not transfer. In Tables 1 to 4, the concentration of the transferred ink was visually observed as the evaluation result of the transfer resistance (drying property). The evaluation criteria are as follows.

[0129] ◎: When there is no transfer of ink ○: When the transfer of ink is very slight and difficult to visually confirm △: When the transfer of ink is slight and visually confirmable (easy) ×: When the ink transfers darkly In addition, if the evaluation of the transferability (transfer resistance) is "◎", "○", or "△", it was considered qualified because there are no problems in use.

[0130] The compositions and evaluation results of the inkjet inks of each example and each comparative example are shown in Tables 1 to 4. In Tables 1 to 4, the "blank" part indicates that the substance is not used. Also, all units in Tables 1 to 4 are "mass%".

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3]

[0134] [Table 4]

[0135] As shown in Tables 1 to 4, in the inkjet inks of Examples 1 to 33, the evaluation results of printing stability (initial printability, continuous printability, intermittent restartability) were all "△" or higher, indicating that they had sufficient printing stability (initial printability, continuous printability, intermittent restartability). Also, as shown in Tables 1 to 4, in the inkjet inks of Examples 1 to 33, the evaluation results of transferability (tablet drying property) were all "△" or higher, indicating that they had sufficient transferability (tablet drying property).

[0136] As described above, for an inkjet ink for tablets containing an edible dye, an adhesive, and water and ethanol as solvents, and adding only an adhesive whose viscosity is 1000 mPa·s or less within the range where the temperature of the adhesive is 0°C or higher and 50°C or lower as the adhesive, it is possible to provide an inkjet ink having high printing stability and high ink fixing property (transfer resistance), and a tablet printed matter including a printed portion printed with the inkjet ink.

[0137] The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that bring about equivalent effects to those intended by the present invention. Further, the scope of the present invention is not limited to the combination of the features of the invention defined by the claims, but may be defined by any desired combination of specific features among all the disclosed respective features.

[0138] Also, for example, the present invention can take the following configurations. (1) An inkjet ink for tablets containing an edible dye, an adhesive, and water and ethanol as solvents, wherein the adhesive contains only a liquid adhesive as the adhesive. (2) The inkjet ink for tablets according to (1) above, wherein the adhesive is polyethylene glycol. (3) The inkjet ink for tablets according to (2) above, 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 any one of (1) to (3) above, further containing propylene glycol as a wetting agent. (5) The dye is blended within a range of 1.0% or more and 5.0% or less with respect to the mass of the entire inkjet ink for tablets. The adhesive is blended within a range of 1.0% or more and 7.0% or less with respect to the mass of the entire inkjet ink for tablets. The inkjet ink for tablets according to (4) above, wherein the wetting agent is blended within a range of more than 0% and 28.0% or less with respect to the mass of the entire inkjet ink for tablets. (6) The dye is blended within a range of 1.0% or more and 5.0% or less with respect to the mass of the entire inkjet ink for tablets. The inkjet ink for tablets according to any one of (1) to (4) above, wherein the adhesive is blended within a range of 1.0% or more and 7.0% or less with respect to the mass of the entire inkjet ink for tablets. (7) The inkjet ink for tablets according to any one of (1) to (6) above, wherein the dye is at least one selected from azo dyes, triphenylmethane dyes, and xanthene dyes. (8) The azo dye is Red No. 102 or Yellow No. 4. The triphenylmethane dye is Blue No. 1. The inkjet ink for tablets according to (7) above, wherein the xanthene dye is Red No. 3. (9) A tablet printed matter having a printed portion printed using the inkjet ink for tablets according to any one of (1) to (8) above.

Explanation of Signs

[0139] 1 Substrate of tablet 3 Printed image 5 Plain tablet printed matter 7 Film coat layer 9 Film-coated tablet printed matter 11 Plain tablet printed image (solid image) 13 Film-coated tablet printed image (2D barcode)

Claims

1. An inkjet ink for tablets, comprising an edible dye, an adhesive, water and ethanol as solvents, and a wetting agent, wherein the wetting agent contains propylene glycol, the adhesive contains only one kind of polyethylene glycol which is a liquid adhesive, the average molecular weight of the polyethylene glycol is in the range of 280 or more and 420 or less, the polyethylene glycol is formulated in the range of 1.0% or more and 14.0% or less based on the mass of the entire inkjet ink for tablets, the ethanol is formulated in the range of 6.5% or more and 20.0% or less based on the mass of the entire inkjet ink for tablets, the dye is at least one selected from triphenylmethane dyes and xanthene dyes and does not contain azo dyes, when the triphenylmethane dye is Blue No. 1, it further contains reduced isomaltulose as a fading inhibitor, when the xanthene dye is Red No. 3, it further contains tripotassium citrate as a fading inhibitor.

2. The inkjet ink for tablets according to Claim 1, comprising only the edible dye, the adhesive, water and ethanol as solvents, and the wetting agent.

3. The dye is formulated in the range of 1.0% or more and 5.0% or less based on the mass of the entire inkjet ink for tablets, the adhesive is formulated in the range of 1.0% or more and 7.0% or less based on the mass of the entire inkjet ink for tablets, the wetting agent is formulated in the range of more than 0% and 28.0% or less based on the mass of the entire inkjet ink for tablets.

4. The dye is formulated in the range of 1.0% or more and 5.0% or less based on the mass of the entire inkjet ink for tablets, the adhesive is formulated in the range of 1.0% or more and 7.0% or less based on the mass of the entire inkjet ink for tablets.

5. The polyethylene glycol is formulated in the range of 1.0% or more and 14.0% or less based on the mass of the entire inkjet ink for tablets, the propylene glycol is formulated in the range of 14.0% or more and 28.0% or less based on the mass of the entire inkjet ink for tablets.

6. The tablet inkjet ink according to any one of claims 1 to 5, wherein the reduced isomaltulose is blended in a range of 0.7% or more and 10.0% or less based on the total mass of the tablet inkjet ink.

7. Comprising only the edible dye, the adhesive, water and ethanol as the solvent, the wetting agent, and the fading inhibitor, The dye is blended in a range of 1.0% or more and 5.0% or less based on the total mass of the tablet inkjet ink, The polyethylene glycol is blended in a range of 1.0% or more and 7.0% or less based on the total mass of the tablet inkjet ink, The propylene glycol is blended in a range of 14.0% or more and 28.0% or less based on the total mass of the tablet inkjet ink, The dye contains only Food Blue No. 1 and Food Red No. 3, The fading inhibitor for Food Blue No. 1 contains reduced isomaltulose, The fading inhibitor for Food Red No. 3 contains tripotassium citrate, The tablet inkjet ink according to claim 1, wherein the reduced isomaltulose is blended in a range of 0.7% or more and 10.0% or less based on the total mass of the tablet inkjet ink.

8. A tablet printed matter provided with a printed portion printed using the tablet inkjet ink according to any one of claims 1 to 5.

Images