Inkjet ink for tablet and tablet printed material

Abstract

To provide an inkjet ink in which fixedness (transfer durability) of the ink is improved while maintaining excellent printing stability, and a tablet printed material including a printing portion printed with the inkjet ink.SOLUTION: The inkjet ink according to the present embodiment includes: an edible dye; an adhesive; and water and ethanol as a solvent; where the adhesive is only a liquid adhesive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink-jet ink for tablets and tablet prints. [Background technology]

[0002] Some inkjet printing inks (hereinafter simply referred to as "inkjet inks") for printing on tablets are edible by using food dyes such as tar-based pigments as coloring materials (see, for example, Patent Document 1).

[0003] When mass-producing tablets with printed sections printed with the above-mentioned inkjet ink (printing ink), the printed tablets may come into contact with each other, resulting in the printing ink of one tablet being transferred to another tablet. This can cause the tablets to have poor appearance, leading to an increase in defective tablets and a decrease in productivity.

[0004] In order to prevent unintended transfer of printing ink, inkjet inks with high ink drying and ink fixation properties are required, but increasing the amount of drying solvent in the ink can accelerate drying of the nozzle liquid surface, which can reduce printing stability.

[0005] In addition, one method of solving the problem of ink fixation has been to use a solid or gel adhesive, but adding such an adhesive can sometimes result in a decrease in print quality, such as intermittent resumption. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6389506 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, few ink-jet inks for tablets according to the prior art have excellent ink fixation properties (transfer resistance) while maintaining excellent printing stability. Specifically, few ink-jet inks for tablets according to the prior art have excellent initial printability, continuous printability, intermittent restartability, and transfer resistance. The present inventors have found that in order to improve the above-mentioned performance of ink-jet ink, it is necessary to add a liquid adhesive to the ink-jet ink.

[0008] The present invention has been made in consideration of these points, and aims to provide an inkjet ink that has improved ink fixation (transfer resistance) while maintaining excellent printing stability, and a tablet printed matter having a printed portion printed with the inkjet ink. [Means for solving the problem]

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

[0010] In addition, in order to achieve the above object, a printed tablet product according to one embodiment of the present invention is characterized by having 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 fixability (transfer resistance) of ink while maintaining excellent printing stability. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (plain tablet) according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (film-coated tablet) according to an embodiment of the present invention. [Figure 3]1 is an example of a printed image of a tablet (plain tablet) according to an embodiment of the present invention. [Figure 4] 1 is an example of a printed image of a tablet (film-coated tablet) according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] An 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 fixability (transfer resistance) while maintaining the print stability of, for example, printed images applied by inkjet printing to the surface of medical tablets. Hereinafter, the inkjet ink (inkjet ink for tablets) according to an embodiment of the present invention and the configuration of a tablet (printed tablet) having a printed portion printed with the inkjet ink will be described in detail.

[0014] [Configuration of inkjet ink] The inkjet ink according to this embodiment is an edible inkjet ink, and contains at least a food dye (food coloring), an adhesive, and water and ethanol as a solvent.

[0015] Furthermore, the inkjet ink according to this embodiment contains only a liquid adhesive as the adhesive for adhering the ink to the surface of a substrate (e.g., a solid formulation). Specifically, this embodiment uses only an adhesive (hereinafter, for convenience, also referred to as a "liquid adhesive") whose viscosity is 1000 mPa·s or less at a temperature in the range of 0°C to 50°C. Note that the "adhesive" in this embodiment may also be referred to as a coating agent.

[0016] The inkjet ink according to this embodiment contains, for example, polyethylene glycol as a liquid adhesive. The inkjet ink according to this 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] The inkjet ink according to this embodiment further contains, for example, propylene glycol as a wetting agent. Furthermore, in the inkjet ink according to this embodiment, for example, the dye is blended in a range of 1.0% to 5.0% by mass of the total inkjet ink for tablets, the adhesive is blended in a range of 1.0% to 7.0% by mass of the total inkjet ink for tablets, and the humectant is blended in a range of more than 0% to 28.0% by mass of the total inkjet ink for tablets.

[0018] Furthermore, the inkjet ink according to this embodiment does not contain a humectant, and contains a dye in a range of 1.0% to 5.0% by mass of the total inkjet ink for tablets, and a pressure-sensitive adhesive in a range of 1.0% to 7.0% by mass of the total inkjet ink for tablets. The dyes used in the inkjet ink according to this embodiment include, for example, azo dyes, trifluoromethyl-2- ... The dye is at least one selected from the group consisting of phenylmethane dyes and xanthene dyes.

[0019] In addition, the inkjet ink according to this embodiment may contain, for example, Red No. 102 or Yellow No. 4 as an azo dye, Blue No. 1 as a triphenylmethane dye, and Red No. 3 as a xanthene dye.

[0020] Each component constituting the inkjet ink according to this embodiment will be described below. (Coloring material) As described above, the inkjet ink according to this embodiment contains a food dye, which may be at least one selected from the group consisting of azo dyes, triphenylmethane dyes, and xanthene dyes.

[0021] As the azo dye, for example, Red No. 102 or Yellow No. 4 is used. Furthermore, as a triphenylmethane dye, for example, Blue No. 1 is used. Furthermore, for example, Red No. 3 is used as a xanthene dye. In the inkjet ink according to this embodiment, the blending ratio of the food dyes, i.e., the total content of the food dyes, is preferably in the range of 1.0% by mass to 5.0% by mass, more preferably in the range of 1.0% by mass to 4.0% by mass, and even more preferably in the range of 1.5% by mass to 3.0% by mass, relative to the mass of the entire ink.

[0022] This configuration can provide good visibility to the printed image and high printing stability. In this embodiment, "printing stability" is a concept that includes initial printability, continuous printability, and intermittent resumability (printing resumability).

[0023] On the other hand, if the total content of the food dyes is less than 1.0% by mass, the overall printed color tends to be lighter and the visibility of the printed image tends to decrease. Also, if the total content of the food dyes exceeds 5.0% by mass, the dissolution stability of the food dyes deteriorates, causing the pigments in the ink to precipitate or settle as a solid, which can cause nozzle clogging in the inkjet head during printing and reduce print stability, particularly intermittent restartability.

[0024] The inkjet ink according to this embodiment may contain a coloring material (coloring material) other than the above-mentioned food dyes. There are no particular restrictions on the coloring material other than the above-mentioned food dyes, as long as it is edible. The dye that can be added to the inkjet ink according to this embodiment can be appropriately selected from conventionally known synthetic food dyes and natural food dyes.

[0025] Furthermore, even when the inkjet ink according to this embodiment contains a coloring material other than the above-mentioned food dyes as food dyes, the total content of all food dyes is preferably in the range of 1.0% to 5.0% by mass, more preferably in the range of 1.0% to 4.0% by mass, and even more preferably in the range of 1.5% to 3.0% by mass, which can impart good visibility to the printed image and provide the inkjet ink with excellent printing stability, particularly intermittent resumability.

[0026] Examples of synthetic food dyes include tar-based dyes, natural dye derivatives, and natural synthetic dyes. Examples of tar-based 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, 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 No. 5 Aluminum Lake, Food Blue No. 1 Aluminum Lake, and Food Blue No. 2 Aluminum Lake. Examples of natural dye derivatives include norbixin potassium. Examples of natural synthetic dyes include β-carotene and riboflavin.

[0027] Examples of natural food dyes include anthocyanin dyes, carotenoid dyes, quinone dyes, chlorophyll dyes, flavonoid dyes, betaine dyes, monascus dyes, and other dyes derived from natural sources. Examples of anthocyanin dyes include red radish dye, red cabbage dye, red rice dye, elderberry dye, cowberry dye, gooseberry dye, cranberry dye, salmonberry dye, perilla dye, sweet blueberry dye, strawberry dye, dark sweet cherry dye, cherry dye, hibiscus dye, huckleberry dye, grape juice dye, grape skin dye, blackcurrant dye, blackberry dye, blueberry dye, plum dye, watermelon dye, boysenberry dye, mulberry dye, purple sweet potato dye, purple corn dye, purple yam dye, raspberry dye, redcurrant dye, loganberry dye, and other anthocyanin dyes. Examples of carotenoid pigments include annatto pigment, gardenia yellow, and other carotenoid pigments. Examples of quinone pigments include cochineal pigment, lithospermum root pigment, lac pigment, and other quinone pigments. Examples of flavonoid pigments include safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of betaine pigments include beet red pigment. Examples of monascus pigments include monascus pigment and monascus yellow pigment. Examples of pigments derived from other natural products include turmeric pigment, Clerodendron japonicum pigment, gardenia red pigment, and spirulina blue pigment.

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

[0029] When the adhesive has this configuration, adding it to the inkjet ink together with the solvent (water and ethanol) imparts appropriate viscosity (fluidity) to the inkjet ink and increases its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to adhere to the surface of the printed material. As a result, the inkjet ink according to this embodiment can improve the visibility of the printed image and also improve the ink fixability (transfer resistance) of the printed image. If the average molecular weight of polyethylene glycol is less than 280, the fluidity of the inkjet ink may be too high, and sufficient affinity (bonding) with the tablet surface substance may not be obtained. If the average molecular weight of polyethylene glycol is more than 420, the fluidity of the inkjet ink may be too low, and sufficient affinity (bonding) with the tablet surface substance may not be obtained.

[0030] Furthermore, in the inkjet ink according to this embodiment, two or more types of adhesives having different average molecular weights may be used in combination. In the inkjet ink according to this embodiment, for example, polyethylene glycol (PEG400) having an average molecular weight in the range of 380 to 420 and polyethylene glycol (PEG300) having an average molecular weight in the range of 285 to 315 may be used in combination. Polyethylene glycols having different average molecular weights are easily dissolved in different types of solvents. In other words, in the inkjet ink according to this embodiment, two or more types of adhesives having different average molecular weights may be used in combination. When polyethylene glycols such as those described above are used, their solubilities in water and ethanol, which are used as solvents, differ. Therefore, in this embodiment, by using two or more polyethylene glycols with different average molecular weights as the adhesive, the maximum solubility (total solubility) in a solvent containing water and ethanol can be increased compared to when only one type of polyethylene glycol is used as the adhesive. As a result, this configuration imparts appropriate viscosity (fluidity) to the inkjet ink, increasing its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to be fixed to the surface of the printed material. As a result, the inkjet ink according to this embodiment can improve the visibility of printed images and also improve the ink fixability (transfer resistance) of printed images.

[0031] In the inkjet ink according to this embodiment, the blending ratio of the adhesive is preferably in the range of 1.0% by mass to 7.0% by mass, more preferably in the range of 1.0% by mass to 4.2% by mass, and even more preferably in the range of 2.8% by mass to 4.2% by mass.

[0032] With this configuration, the adhesive can more reliably exert its ink fixing effect, reliably improving the ink fixability (transfer resistance) of the inkjet ink. In addition, the inkjet ink according to this embodiment is provided with appropriate viscosity (fluidity), which can impart high printing stability, particularly intermittent resumability.

[0033] On the other hand, if the blending ratio of the adhesive is less than 1.0 mass%, the ink fixing effect is reduced, and it may be difficult to obtain ink fixability (transfer resistance). Also, if the blending ratio of the adhesive is more than 7.0 mass%, the ink viscosity increases and the adhesive's dissolution stability deteriorates, which may cause clogging of the inkjet head nozzles during printing and reduce printing stability, especially intermittent restartability.

[0034] Furthermore, when the adhesive contains two or more types of adhesives with different average molecular weights, if the total blending ratio of the adhesives is less than 1.0 mass%, the ink fixing effect is reduced and it may be difficult to obtain ink fixability (transfer resistance). Furthermore, if the total blending ratio of the adhesives is more than 7.0 mass%, the ink viscosity increases and the adhesive dissolution stability deteriorates, which may cause clogging of the inkjet head nozzles during printing and reduce printing stability, especially intermittent restartability.

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

[0036] Furthermore, when the adhesive contains two or more types of adhesives with different average molecular weights, the blending ratio of the adhesive with the smaller average molecular weight may be higher than the blending ratio of the adhesive with the larger average molecular weight. For example, the blending ratio of the adhesive with the smaller average molecular weight is preferably in the range of 1.1 to 2.0 times the blending ratio of the adhesive with the larger average molecular weight, more preferably in the range of 1.1 to 1.5 times, and even more preferably in the range of 1.1 to 1.3 times.

[0037] Furthermore, when the adhesive contains two or more types of adhesives with different average molecular weights, the blending ratio of the adhesive with the higher average molecular weight may be higher than the blending ratio of the adhesive with the lower average molecular weight. For example, the blending ratio of the adhesive with the higher average molecular weight is preferably in the range of 1.1 to 2.0 times the blending ratio of the adhesive with the lower average molecular weight, more preferably in the range of 1.1 to 1.5 times, and even more preferably in the range of 1.1 to 1.3 times.

[0038] With this configuration, the adhesive agent can more reliably exert its ink fixing effect, and the fixability (transfer resistance) of the ink-jet ink can be reliably improved.

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

[0040] The inkjet ink according to this embodiment may further contain propylene glycol (PG) as a solvent. Propylene glycol functions as a humectant, preventing the ink from drying out in the inkjet nozzles and imparting high printing stability, particularly excellent intermittent restartability, to the ink. Furthermore, ethanol is highly volatile, which can improve the transfer resistance (drying property) of the inkjet ink.

[0041] Furthermore, although the blending ratio of each component of the above solvent in the inkjet ink according to this embodiment is not limited, the blending ratio of ethanol, i.e., the amount of ethanol added, is preferably in the range of 6.5% by mass to 11.5% by mass relative to the total mass of the ink. This configuration reliably improves the drying properties of the inkjet ink. As a result, the inkjet ink can be endowed with superior transfer resistance.

[0042] On the other hand, if the amount of ethanol added is less than 6.5% by mass, the drying of the printed surface on the tablet surface will be delayed, and when printed tablets come into contact with each other, undried ink may adhere to one tablet and cause smearing (poor transfer).On the other hand, if the amount of ethanol added is more than 11.5% by mass, the ink will dry out in the inkjet nozzle, causing clogging of the inkjet head nozzle during printing, and printing stability, particularly intermittent resumption, may be reduced.

[0043] Furthermore, in the inkjet ink according to this embodiment, when propylene glycol is contained in the solvent, the blending ratio of the propylene glycol, i.e., the amount of propylene glycol added, is preferably in the range of 0% by mass to 28.0% by mass relative to the total mass of the ink. This configuration imparts appropriate viscosity (fluidity) to the inkjet ink, prevents the ink from drying out in the inkjet nozzles, and imparts high printing stability, particularly excellent intermittent resumability, to the ink.

[0044] Furthermore, the amount of propylene glycol added is more preferably 10% by mass or more, which imparts appropriate viscosity (fluidity) to the inkjet ink, further prevents the ink from drying out in the inkjet nozzle, and further imparts high printing stability, particularly excellent intermittent restartability, to the ink.

[0045] Furthermore, if the amount of propylene glycol added exceeds 28.0% by mass, the drying time of the printed surface on the tablet surface will be delayed, and when printed tablets come into contact with each other, the undried ink may adhere to the other tablet, causing smudges and other problems (poor transfer).

[0046] The inkjet ink according to this embodiment may further contain at least one of glycerin and isopropyl alcohol as a solvent. Specifically, the solvent may further contain at least one of glycerin and isopropyl alcohol. Alternatively, the solvent may further contain both glycerin and isopropyl alcohol. Glycerin functions as a humectant, similar to the above-mentioned propylene glycol. Furthermore, isopropyl alcohol, like the above-mentioned ethanol, is highly volatile and can improve the transfer resistance (drying property) of the ink-jet ink. By further adding glycerin and isopropyl alcohol to the solvent in addition to the above components, the light resistance of the ink-jet ink can be improved and performance corresponding to each component can be imparted to the ink-jet ink. Furthermore, by further including these components in the solvent, the ink-jet ink is given appropriate viscosity (fluidity) and its affinity (binding ability) with the tablet surface substance is further increased, thereby further improving the fixing effect of the ink containing the above-mentioned food dye.

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

[0048] (Leveling agent) The inkjet ink according to this embodiment may contain a leveling agent in addition to the above-mentioned dyes, solvents, or internal resins. The leveling agent that can be added to the inkjet ink according to this embodiment may be an edible, water-soluble surfactant. Examples of the leveling agent include polyglycerin fatty acid esters (e.g., Decaglycerin Distearate Q-182S and Decaglycerin Monolaurate Q-12S, both manufactured by Taiyo Kagaku Co., Ltd.), 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 Daiichi Kogyo Seiyaku Co., Ltd.), and polysorbates (Emersol S-120 series, manufactured by Kao Corporation).

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

[0050] [Printing method] The inkjet ink according to this embodiment is not particularly limited in terms of printing method, and can be printed using inkjet devices such as commercially available inkjet printers. Therefore, the inkjet ink according to this embodiment has a wide range of applications and is extremely useful. For example, the inkjet ink according to this embodiment can be printed using a drop-on-demand inkjet device that uses a piezoelectric element (piezoelectric ceramic) as an actuator, and can also be printed using other types of inkjet device.

[0051] Examples of drop-on-demand inkjet devices include devices that use a thermal inkjet system in which inkjet ink is ejected using the water vapor pressure generated by momentarily heating a minute heating element to a high temperature (200 to 300°C), and devices that use an actuator that uses electrostatic vibration. Examples of such an ink jet recording device include an electrostatic type device that ejects ink jet ink by moving a nozzle, and an ultrasonic type device that uses the cavitation phenomenon of ultrasonic waves. Furthermore, if the ink jet ink according to this embodiment has charging properties, it is also possible to use a device that employs a continuous ejection method.

[0052] 〔tablet〕 In this embodiment, the inkjet ink according to this embodiment may be printed or imaged on the surface of, for example, a tablet using the printing method described above. That is, the tablet according to this embodiment may have a printed portion, i.e., a printed image, printed using the inkjet ink according to this embodiment. The inkjet ink according to this embodiment can improve 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, for example. The following describes the configuration of a tablet having a printed image printed with the inkjet ink according to this embodiment.

[0053] The tablet according to this embodiment is, for example, a medical tablet. Here, the term "medical tablet" refers to, for example, plain tablets (plain tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, as well as film-coated tablets in which a water-soluble surface layer is formed on the outermost surface of the tablet.

[0054] Fig. 1 is a schematic cross-sectional view showing an example of a printed (lettered or image-printed) medical tablet (plain tablet). Fig. 1 shows, in cross-section, a printed matter 5 of a plain tablet in which a printed image 3 such as letters is printed on the upper surface of a base material 1 of the tablet.

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

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

[0057] The active ingredient contained in the medical tablet is not particularly limited, and examples thereof include, but are not limited to, substances effective in the prevention and treatment of various diseases (e.g., substances having sleep-inducing activity, tranquilizing activity, antibacterial activity, antihypertensive activity, antianginal activity, analgesic activity, anti-inflammatory activity, tranquilizing activity, antidiabetic activity, diuretic activity, anticholinergic activity, anti-hyperacidity activity, antiepileptic activity, ACE inhibitory activity, β-receptor antagonist or agonist activity, anesthetic activity, appetite suppressant activity, antiarrhythmic activity, antidepressant activity, anticoagulant activity, antidiarrheal activity, antihistamine activity, antimalarial activity, antitumor activity, immunosuppressant activity, antiparkinsonian activity, antipsychotic activity, antiplatelet activity, antihyperlipidemic activity, etc.), substances having a cleansing effect, fragrances, substances having a deodorizing effect, etc.

[0058] The tablet according to this embodiment can be formulated with an acceptable carrier for the intended use along with the active ingredient, if necessary. For example, a medical tablet can be formulated with a pharmaceutically acceptable carrier. As the pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as pharmaceutical ingredients can be used, and for example, excipients, lubricants, binders, disintegrants, thickeners, etc. can be formulated in appropriate amounts. In addition, additives such as preservatives, antioxidants, colorants, and sweeteners can also be used as necessary.

[0059] In this embodiment, medical tablets have been described as an example of tablets, but the present invention is not limited to this. There are no particular limitations on the printing target of the inkjet ink according to this embodiment. For example, the ink may be printed on the surface of various tablets, such as tablets to be administered to animals other than humans (pets, livestock, poultry, etc.), feed, fertilizer, detergent, tablet candy such as Ramune candy, and food supplements. Furthermore, the inkjet ink according to this embodiment is not particularly limited in size to be printed on, and can be applied to tablets of various sizes.

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

[0061] (2) In the inkjet ink according to this embodiment, the adhesive may be polyethylene glycol. This configuration imparts appropriate viscosity (fluidity) to the inkjet ink compared to conventional techniques, further increasing its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to adhere to the surface of the substrate. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and can also further improve the ink fixability (transfer resistance) of the printed image.

[0062] (3) In addition, the inkjet ink according to this embodiment may have an average molecular weight of polyethylene glycol in the range of 280 or more and 420 or less. This configuration imparts appropriate viscosity (fluidity) to the inkjet ink compared to conventional techniques, further increasing its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to adhere to the surface of the substrate. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and can also further improve the ink fixability (transfer resistance) of the printed image.

[0063] (4) The inkjet ink according to this embodiment may further contain propylene glycol as a humectant. With this configuration, compared to conventional techniques, it is possible to prevent the ink from drying out in the inkjet nozzles, and to impart high printing stability, particularly excellent intermittent restartability, to the ink.

[0064] (5) Furthermore, when the inkjet ink according to this embodiment contains a humectant, the food dye may be blended in an amount ranging from 1.0% to 5.0% by weight of the total inkjet ink for tablets, the adhesive may be blended in an amount ranging from 1.0% to 7.0% by weight of the total inkjet ink for tablets, and the humectant may be blended in an amount ranging from 0% to 28.0% by weight of the total inkjet ink for tablets.

[0065] This configuration imparts appropriate viscosity (fluidity) to the inkjet ink compared to conventional techniques, further enhancing its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to adhere to the surface of the substrate. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and further improve the ink fixability (transfer resistance) of the printed image. Furthermore, it can prevent the ink from drying out in the inkjet nozzle, thereby imparting high printing stability, particularly excellent intermittent restartability, to the ink.

[0066] (6) Furthermore, when the inkjet ink according to this embodiment does not contain a humectant, the dye is blended in a range of 1.0% to 5.0% by weight of the total inkjet ink for tablets, and the adhesive is blended in a range of 1.0% to 7.0% by weight of the total inkjet ink for tablets. It may be blended in a range of 0% or less.

[0067] This configuration imparts appropriate viscosity (fluidity) to the inkjet ink compared to conventional techniques, further increasing its affinity (binding ability) with the tablet surface substance, allowing the ink containing the food dye to adhere to the surface of the substrate. As a result, the inkjet ink according to this embodiment can further improve the visibility of the printed image and can also further improve the ink fixability (transfer resistance) of the printed image.

[0068] (7) The inkjet ink according to this embodiment contains at least one food dye selected from azo dyes, triphenylmethane dyes, and xanthene dyes. It's okay to be. With this configuration, the visibility of the printed image can be further improved compared to the prior art.

[0069] (8) In addition, 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 this configuration, the visibility of the printed image can be further improved compared to the prior art.

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

[0071] [Example] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0072] <Examples 1 to 33 and Comparative Examples 1 to 12> The procedures for preparing the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12 will be described below.

[0073] (Inkjet ink manufacturing) First, a printing ink was prepared. The inkjet ink contains a pigment (food dye), a solvent, an adhesive (coating agent), and a discoloration inhibitor in the amounts described below. The preparation procedure was as follows: first, the adhesive and the discoloration 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 according to this example was prepared. The various components will be specifically described below.

[0074] In this example, purified water (ion-exchanged water), propylene glycol (PG), and ethanol were used as solvents as needed. Specifically, propylene glycol (PG) and ethanol were added to purified water and stirred thoroughly to obtain a solvent (mixed solvent). Furthermore, an adhesive and a discoloration inhibitor were added to the solvent as needed, and the mixture was stirred for about an hour to obtain a transparent base liquid. Food dyes such as Blue No. 1, Red No. 3, Red No. 102, and Yellow No. 4 were added as needed to the transparent base liquid to obtain the inkjet inks of Examples 1 to 33 and Comparative Examples 1 to 12.

[0075] <Sample 1 (Comparative Example 1)> In Sample 1 (Comparative Example 1), the blending ratio of the dye Blue No. 1 to the entire inkjet ink 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 the adhesive polyvinylpyrrolidone (PVP) (molecular weight 45,000) was 1.0% by mass. Note that polyvinylpyrrolidone (PVP) used as the adhesive in this sample is solid at temperatures between 0°C and 50°C. In this way, an inkjet ink of Sample 1 (Comparative Example 1) was obtained.

[0076] <Sample 2 (Comparative Example 2)> The blending ratio of polyvinylpyrrolidone (PVP) (molecular weight 45,000) among the adhesives was set to 0.5% by mass relative to the total inkjet ink of Sample 2 (Comparative Example 2). The same procedure was followed as in Sample 1 (Comparative Example 1), except that the blending ratio of polyethylene glycol (PEG400) was set to 0.5 mass %. The polyethylene glycol (PEG400) used as the adhesive in this sample is liquid at temperatures ranging from 0°C to 50°C. In this way, an inkjet ink of Sample 2 (Comparative Example 2) was obtained.

[0077] <Sample 3 (Comparative Example 3)> The same procedures were carried out as for Sample 1 (Comparative Example 1), except that the adhesive was a sodium salt of carboxymethyl cellulose (CMC-Na). Note that the sodium salt of carboxymethyl cellulose (CMC-Na) used as the adhesive in this sample is solid at temperatures ranging from 0°C to 50°C. In this way, an inkjet ink of Sample 3 (Comparative Example 3) was obtained.

[0078] <Sample 4 (Comparative Example 4)> Sample 4 (Comparative Example 4) was the same as Sample 1 (Comparative Example 1), except that the blending ratio of the sodium salt of carboxymethyl cellulose (CMC-Na) among the adhesives was 0.5 mass% and the blending ratio of polyethylene glycol (PEG400) was 0.5 mass% relative to the total inkjet ink. In this way, an inkjet ink of Sample 4 (Comparative Example 4) was obtained.

[0079] <Sample 5 (Comparative Example 5)> Sample 5 (Comparative Example 5) was prepared in the same manner as Sample 1 (Comparative Example 1), except that the blending ratio of the adhesive polyvinyl alcohol-acrylic acid-methyl methacrylate copolymer (POVACOAT) to the total inkjet ink was 1.0 mass %. Note that the adhesive polyvinyl alcohol-acrylic acid-methyl methacrylate copolymer (POVACOAT) used in this sample is solid at temperatures between 0°C and 50°C. In this way, an inkjet ink of Sample 5 (Comparative Example 5) was obtained.

[0080] <Sample 6 (Example 1)> Sample 6 (Example 1) was the same as Sample 1 (Comparative Example 1), except that the blending ratio of polyethylene glycol (PEG400) as an adhesive was set to 1.0 mass % relative to the total inkjet ink. In this way, the inkjet ink of Sample 6 (Example 1) was obtained.

[0081] <Sample 7 (Example 2)> In the total inkjet ink of Sample 7 (Example 2), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 1.0% by mass, and the blending ratio of the discoloration inhibitor reduced isomaltulose (referred to as "isomalt" in the table) was 10.0% by mass. In this way, the inkjet ink of Sample 7 (Example 2) was obtained.

[0082] <Sample 8 (Example 3)> In the total inkjet ink of Sample 8 (Example 3), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 50.5% 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 the adhesive polyethylene glycol (PEG400) was 1.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 7.5% by mass. In this way, the inkjet ink of Sample 8 (Example 3) was obtained.

[0083] <Sample 9 (Example 4)> In the total inkjet ink of Sample 9 (Example 4), the blending ratio of the pigment Blue No. 1 was 1.5% 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, the blending ratio of the adhesive polyethylene glycol (PEG400) was 1.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, the inkjet ink of Sample 9 (Example 4) was obtained.

[0084] <Sample 10 (Example 5)> In the total inkjet ink of Sample 10 (Example 5), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 55.5% 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 the adhesive polyethylene glycol (PEG400) was 1.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 2.5% by mass. In this way, an inkjet ink of Sample 10 (Example 5) was obtained.

[0085] <Sample 11 (Example 6)> In the total inkjet ink of Sample 11 (Example 6), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 58.0% 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 the adhesive polyethylene glycol (PEG400) was 1.0% by mass. In this way, an inkjet ink of Sample 11 (Example 6) was obtained.

[0086] <Sample 12 (Comparative Example 6)> In the inkjet ink of Sample 12 (Comparative Example 6), the blending ratio of the pigment Blue No. 1 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, and the blending ratio of propylene glycol (PG) was 28.0% by mass. In this way, an inkjet ink of Sample 12 (Comparative Example 6) was obtained.

[0087] <Sample 13 (Comparative Example 7)> The blending ratio of the pigment Blue No. 1 to the entire inkjet ink of Sample 13 (Comparative Example 7) 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, and the blending ratio of propylene glycol (PG) was 28. The blending ratio of reduced isomaltulose, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample 13 (Comparative Example 7) was obtained.

[0088] <Sample 14 (Example 7)> In the total inkjet ink of Sample 14 (Example 7), the blending ratio of the pigment Blue No. 1 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 26.6% by mass, and the blending ratio of the adhesive polyethylene glycol (PEG400) was 1.4% by mass. In this way, an inkjet ink of Sample 14 (Example 7) was obtained.

[0089] <Sample 15 (Example 8)> In the total inkjet ink of Sample 15 (Example 8), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 1.4% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 15 (Example 8) was obtained.

[0090] <Sample 16 (Example 9)> In the inkjet ink of Sample 16 (Example 9), the blending ratio of the dye Blue No. 1 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. The polyethylene glycol (PEG300) used as an adhesive in this sample is liquid at temperatures ranging from 0°C to 50°C. In this way, an inkjet ink of Sample 16 (Example 9) was obtained.

[0091] <Sample 17 (Example 10)> In the total inkjet ink of Sample 17 (Example 10), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG300) was 2.8% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 17 (Example 10) was obtained.

[0092] <Sample 18 (Example 11)> In the total inkjet ink of Sample 18 (Example 11), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 2.8% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 18 (Example 11) was obtained.

[0093] <Sample 19 (Example 12)> For the entire inkjet ink of Sample 19 (Example 12), the pigment Blue No. 1 The blending ratio of the above 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) as an adhesive was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 19 (Example 12) was obtained.

[0094] <Sample 20 (Example 13)> In the total inkjet ink of Sample 20 (Example 13), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 20 (Example 13) was obtained.

[0095] <Sample 21 (Example 14)> In the total inkjet ink of Sample 21 (Example 14), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 7.0% by mass. In this way, an inkjet ink of Sample 21 (Example 14) was obtained.

[0096] <Sample 22 (Example 15)> In the total inkjet ink of Sample 22 (Example 15), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 7.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 22 (Example 15) was obtained.

[0097] <Sample 23 (Example 16)> In the total inkjet ink of Sample 23 (Example 16), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 14.0% by mass. In this way, an inkjet ink of Sample 23 (Example 16) was obtained.

[0098] <Sample 24 (Example 17)> In the total inkjet ink of Sample 24 (Example 17), the blending ratio of the pigment Blue No. 1 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 14.0% by mass, the blending ratio of the adhesive polyethylene glycol (PEG400) was 14.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 24 (Example 17) was obtained.

[0099] <Sample 25 (Comparative Example 8)> In Sample 25 (Comparative Example 8), the blending ratio of the dye Blue No. 1 to the entire inkjet ink 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 (PEG4000) as an adhesive was 4.2% by mass. The polyethylene glycol (PEG4000) used as an adhesive in this sample is solid at temperatures between 0°C and 50°C. In this way, an inkjet ink of Sample 25 (Comparative Example 8) was obtained.

[0100] <Sample 26 (Comparative Example 9)> In the inkjet ink of Sample 26 (Comparative Example 9), the blending ratio of the dye Blue No. 1 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 (PEG1540) as an adhesive was 4.2% by mass. The polyethylene glycol (PEG1540) used as an adhesive in this sample is solid at temperatures ranging from 0°C to 50°C. In this way, an inkjet ink of Sample 26 (Comparative Example 9) was obtained.

[0101] <Sample 27 (Example 18)> In the total inkjet ink of Sample 27 (Example 18), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass. In this way, an inkjet ink of Sample 27 (Example 18) was obtained.

[0102] <Sample 28 (Example 19)> In the total inkjet ink of Sample 28 (Example 19), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG300) was 4.2% by mass. In this way, an inkjet ink of Sample 28 (Example 19) was obtained.

[0103] <Sample 29 (Example 20)> In the total inkjet ink of Sample 29 (Example 20), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 29 (Example 20) was obtained.

[0104] <Sample 30 (Example 21)> In the total inkjet ink of Sample 30 (Example 21), the blending ratio of the pigment Blue No. 1 was 1.0 mass%, the blending ratio of purified water among the solvents was 59.5 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 23.8 mass%, the blending ratio of the adhesive polyethylene glycol (PEG400) was 4.2 mass%, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0 mass%. In this way, an inkjet ink of Sample 30 (Example 21) was obtained.

[0105] <Sample 31 (Example 22)> In the total inkjet ink of Sample 31 (Example 22), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 31 (Example 22) was obtained.

[0106] <Sample 32 (Example 23)> In the total inkjet ink of Sample 32 (Example 23), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 32 (Example 23) was obtained.

[0107] <Sample 33 (Example 24)> In the total inkjet ink of Sample 33 (Example 24), the blending ratio of the pigment Blue No. 1 was 4.0% by mass, the blending ratio of purified water among the solvents was 56.5% 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 33 (Example 24) was obtained.

[0108] <Sample 34 (Example 25)> In the total inkjet ink of Sample 34 (Example 25), the blending ratio of the pigment Blue No. 1 was 5.0% by mass, the blending ratio of purified water among the solvents was 55.5% 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 34 (Example 25) was obtained.

[0109] <Sample 35 (Example 26)> In the total inkjet ink of Sample 35 (Example 26), the blending ratio of the pigment Blue No. 1 was 6.0% by mass, the blending ratio of purified water among the solvents was 54.5% 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 35 (Example 26) was obtained.

[0110] <Sample 36 (Comparative Example 10)> In the inkjet ink of Sample 36 (Comparative Example 10), the blending ratio of Blue No. 1 among the pigments was 0.04 mass %, the blending ratio of Red No. 3 among the solvents was 2.5 mass %, and The blending ratio of purified water 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, and the blending ratio of tripotassium citrate (referred to as "potassium 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. In this way, an inkjet ink of Sample 36 (Comparative Example 10) was obtained.

[0111] <Sample 37 (Comparative Example 11)> In the entire inkjet ink of Sample 37 (Comparative Example 11), the blending ratio of Blue No. 1 among the pigments 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 discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample 37 (Comparative Example 11) was obtained.

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

[0113] <Sample 39 (Example 28)> In the entire inkjet ink of Sample 39 (Example 28), the blending ratio of Blue No. 1 among the pigments 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 23.8% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, the blending ratio of tripotassium citrate among the discoloration inhibitors was 5.0% by mass, and the blending ratio of reduced isomaltulose was 0.7% by mass. In this way, an inkjet ink of Sample 39 (Example 28) was obtained.

[0114] <Sample 40 (Example 29)> In the entire inkjet ink of Sample 40 (Example 29), the blending ratio of Blue No. 1 among the pigments 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 25.2% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 2.8% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 40 (Example 29) was obtained.

[0115] <Sample 41 (Example 30)> In the entire inkjet ink of Sample 41 (Example 30), the blending ratio of Blue No. 1 among the pigments 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 23.8% by mass, the blending ratio of polyethylene glycol (PEG400) as an adhesive was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 41 (Example 30) was obtained.

[0116] <Sample 42 (Comparative Example 12)> In the total inkjet ink of Sample 42 (Comparative Example 12), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 42 (Comparative Example 12) was obtained.

[0117] <Sample 43 (Example 31)> In the total inkjet ink of Sample 43 (Example 31), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 43 (Example 31) was obtained.

[0118] <Sample 44 (Example 32)> In the total inkjet ink of Sample 44 (Example 32), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 44 (Example 32) was obtained.

[0119] <Sample 45 (Example 33)> In the total inkjet ink of Sample 45 (Example 33), the blending ratio of the pigment Blue No. 1 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 the adhesive polyethylene glycol (PEG400) was 4.2% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 5.0% by mass. In this way, an inkjet ink of Sample 45 (Example 33) was obtained.

[0120] Each of the inks from Examples 1 to 33 and Comparative Examples 1 to 12 was passed through a membrane filter to remove solid foreign matter from the liquid. Specifically, each ink was passed through a 5.0 μm membrane filter (cellulose acetate membrane) once and then through a 0.8 μm membrane filter (cellulose acetate membrane) once to obtain purified ink.

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

[0122] (Printing stability: initial printability and continuous printability) The inkjet head used was a piezoelectric ceramic-driven drop-on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (the direction in which the recording medium, such as a tablet, is transported), and a total of 2,656 nozzles. Using the inkjet head, a test pattern was printed immediately after nozzle maintenance. The print status of the test pattern was then used to check the readability of the printed image due to the occurrence of non-ejection areas. The evaluation criteria were as follows:

[0123] In this evaluation, "initial printability" refers to the printability immediately after printing begins, and "continuous printability" refers to the printability when a test pattern is printed after ink has been continuously ejected from the head for 30 minutes.

[0124] ○: When the gaps or bends in the lines are less than 5% of the total △: When the gaps or bends in the lines are less than 20% of the total ×: When the gaps or bends in the lines exceed 20% of the total If the initial printability and continuous printability were evaluated as "good" or "fair," there was no problem in use and the sheet was deemed to have passed.

[0125] (Printing stability: intermittent restartability) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a print resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (the direction in which tablets or other recording media are transported), and a total of 1,280 nozzles, the head was left to stand for a specified period of time (15 to 60 minutes) without flushing, and then a test pattern was printed with a print drop volume of 6 pL per drop, confirming that all nozzles were ejecting without any non-ejection. In Tables 1 to 4 below, the time during which ink could be ejected was measured as an evaluation result of intermittent printing performance (intermittent resumability and ejection stability). The evaluation criteria are as follows:

[0126] 〇: 30 minutes or more △: 20 minutes or more but less than 30 minutes ×: Less than 20 minutes If the result of the intermittent restartability (discharge stability) test was evaluated as "○" or "△", there was no problem in use and the ink was deemed to have passed.

[0127] (Transferability: Pressing test) Images were printed on the tablets listed below using the inkjet inks of the examples and comparative examples with a printing drop volume of 6 pL per drop using a piezoelectric ceramic-driven drop-on-demand inkjet head having a printing resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (direction in which the tablet or other recording medium is transported). The head had a total of 1,280 nozzles.

[0128] The tablets were dried with hot air for 5 seconds within 60 seconds of printing, and a pressure test was conducted 60 seconds after printing. In this pressure test, a tablet attached to a digital force gauge was contacted with the printed tablet at a pressure of 9-10 N for 0.9-1.0 seconds to confirm that the printed ink did not transfer. In Tables 1-4, the density of the transferred ink was visually observed as an evaluation result of transfer resistance (drying property). The evaluation criteria are as follows:

[0129] ◎: No ink transfer ○: When the ink transfer is very slight and difficult to visually confirm △: When ink transfer is slight and visual confirmation is possible (easy) ×: When the ink is transferred too darkly If the transferability (transfer resistance) was evaluated as "◎", "◯", or "△", there was no problem in use and the sample was deemed to have passed.

[0130] The compositions and evaluation results of the inkjet inks of the examples and comparative examples are shown in Tables 1 to 4. In Tables 1 to 4, "blank" indicates that the corresponding substance was not used. In addition, the units in Tables 1 to 4 are all "% by mass."

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3]

[0134] [Table 4]

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

[0136] As described above, an inkjet ink for tablets containing a food dye, an adhesive, and water and ethanol as solvents, and containing only an adhesive whose viscosity is 1000 mPa·s or less when the temperature of the adhesive is in the range of 0°C to 50°C, can be used as an inkjet ink with high printing stability and high ink fixation (transfer resistance). It is possible to provide a tablet printed product having a printed portion printed with inkjet ink.

[0137] The scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that achieve equivalent effects to the object of the present invention. Furthermore, the scope of the present invention is not limited to the combination of inventive features defined by the claims, but can be defined by any desired combination of specific features from among all the respective disclosed features.

[0138] Furthermore, for example, the present invention can have the following configuration. (1) The composition contains an edible dye, an adhesive, and water and ethanol as a solvent, An inkjet ink for tablets, comprising 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 within the range of 280 or more and 420 or less. (4) The ink-jet ink for tablets according to any one of the above (1) to (3), further comprising propylene glycol as a humectant. (5) the dye is blended in an amount of 1.0% to 5.0% by mass of the entire ink-jet ink for tablets, the adhesive is blended in an amount of 1.0% to 7.0% by mass of the entire inkjet ink for tablets, The inkjet ink for tablets according to (4) above, wherein the wetting agent is blended in an amount of more than 0% but not more than 28.0% by mass of the entire inkjet ink for tablets. (6) the dye is blended in an amount of 1.0% to 5.0% by mass of the entire ink-jet ink for tablets, The inkjet ink for tablets according to any one of (1) to (4) above, wherein the adhesive is blended in an amount of 1.0% to 7.0% by mass of the entire inkjet ink for tablets. (7) The ink for tablets according to any one of the above (1) to (6), wherein the dye is at least one selected from azo dyes, triphenylmethane dyes, and xanthene dyes. Jet ink. (8) the azo dye is Red No. 102 or Yellow No. 4, The triphenylmethane dye is Blue No. 1, The ink-jet ink for tablets according to (7) above, wherein the xanthene dye is Red No. 3. (9) A printed tablet product having a printed portion printed using the inkjet ink for tablets according to any one of (1) to (8) above. [Explanation of symbols]

[0139] 1. Tablet base material 3 Printed images 5. Printed plain tablets 7 Film coating layer 9. Film-coated tablet printouts 11 Plain tablet print image (solid image) 13 Film-coated tablet print image (two-dimensional barcode)

Claims

1. The adhesive contains an edible dye, an adhesive, water and ethanol as solvents, and a wetting agent; The humectant includes propylene glycol, The adhesive contains only one type of liquid adhesive, polyethylene glycol, 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 an amount of 1.0% or more and 14.0% or less by mass of the entire ink-jet ink for tablets, the ethanol is blended in an amount of 6.5% or more and 20.0% or less by mass of the entire inkjet ink for tablets, The dye includes at least one selected from an azo dye, a triphenylmethane dye, and a xanthene dye, the azo dye is Red No. 102 or Yellow No. 4, When the triphenylmethane dye is Blue No. 1, the dye further contains reduced isomaltulose as a discoloration inhibitor; When the xanthene dye is Red No. 3, the ink-jet ink for tablets further comprises tripotassium citrate as a discoloration inhibitor.

2. 2. The ink-jet ink for tablets according to claim 1, comprising only the edible dye, the adhesive, water and ethanol as the solvent, and the humectant.

3. the dye is blended in an amount of 1.0% to 5.0% by mass of the entire ink-jet ink for tablets, the adhesive is blended in an amount of 1.0% to 7.0% by mass of the entire inkjet ink for tablets, The ink-jet ink for tablets according to claim 1, wherein the humectant is blended in an amount of more than 0% and not more than 28.0% by mass of the entire ink-jet ink for tablets.

4. the dye is blended in an amount of 1.0% to 5.0% by mass of the entire ink-jet ink for tablets, The ink-jet ink for tablets according to claim 1, wherein the adhesive is blended in an amount of 1.0% to 7.0% by mass of the entire ink-jet ink for tablets.

5. the triphenylmethane dye is Blue No. 1, 2. The ink-jet ink for tablets according to claim 1, wherein the xanthene dye is Red No.

3.

6. the polyethylene glycol is blended in an amount of 1.0% or more and 14.0% or less by mass of the entire ink-jet ink for tablets, 2. The ink-jet ink for tablets according to claim 1, wherein the propylene glycol is blended in an amount ranging from 14.0% to 28.0% by mass of the entire ink-jet ink for tablets.

7. 7. The ink-jet ink for tablets according to claim 1, wherein the reduced isomaltulose is blended in an amount ranging from 0.7% to 10.0% by mass of the entire ink-jet ink for tablets.

8. The composition contains only the edible dye, the adhesive, water and ethanol as the solvent, the wetting agent, and the discoloration inhibitor; the dye is blended in an amount of 1.0% to 5.0% by mass of the entire ink-jet ink for tablets, the polyethylene glycol is blended in an amount of 1.0% or more and 7.0% or less by mass of the entire ink-jet ink for tablets, the propylene glycol is blended in an amount of 14.0% or more and 28.0% or less by mass of the entire ink-jet ink for tablets, The dyes include only Blue No. 1 and Red No. 3, The Blue No. 1 contains reduced isomaltulose as a discoloration inhibitor, The composition contains tripotassium citrate as a fading inhibitor for Red No. 3, 2. The ink-jet ink for tablets according to claim 1, wherein the reduced isomaltulose is blended in an amount ranging from 0.7% to 10.0% by mass of the entire ink-jet ink for tablets.

9. The Red No. 102 is blended in an amount of 1.4% by mass relative to the total mass of the ink-jet ink for tablets, or 7. The ink-jet ink for tablets according to claim 1, wherein the Yellow No. 4 is blended in an amount of 0.4% by mass relative to the total mass of the ink-jet ink for tablets.

10. The Red No. 102 is blended in an amount of 1.4% by mass relative to the total mass of the inkjet ink for tablets, 7. The ink-jet ink for tablets according to claim 1, wherein the Yellow No. 4 is blended in an amount of 0.4% by mass relative to the total mass of the ink-jet ink for tablets.

11. A printed product for a tablet comprising a printed portion printed using the inkjet ink for tablets according to any one of claims 1 to 6.

Images