Ink, method for producing printed tablets using the same, and tablet printing device

Abstract

To provide an ink suitable for printing onto an alkaline tablet, and a printed tablet producing method and a tablet printing device using the same.SOLUTION: An ink according to one embodiment is used for inkjet printing to print information for identifying a predetermined color on an alkaline tablet. The ink contains water, ethanol, a water-soluble high-boiling organic solvent, and a dye that shows a color different from the predetermined color before printed onto the alkaline tablet and changes into the predetermined color after printed onto the alkaline tablet.SELECTED DRAWING: None

Description

[Technical field]

[0001] An embodiment of the present invention relates to an ink, a method for producing a printed tablet using the ink, and a tablet printing device. [Background technology]

[0002] By printing identification information such as letters or symbols on tablets, the identification of the tablets is improved, and this helps to prevent dispensing errors by pharmacists and users from accidentally ingesting the tablets.

[0003] As a printing method for tablets, there is inkjet printing, which can print on tablets without contact, and can therefore be suitably used for tablets that are likely to disintegrate, such as orally disintegrating tablets (OD tablets).

[0004] In such inkjet printing, ink containing a dye (dye ink) may be used. With dye ink, printed characters and the like tend to be darker in color than ink containing a pigment, and the visibility of identification information is improved. In addition, since the pigment is dispersed in a solvent, ink containing a pigment is poorly ejected from the nozzles of an inkjet head, which can cause ejection failures and result in printing failures. On the other hand, since the dye is dissolved in a solvent in dye ink, ejection from the nozzles of an inkjet head is easily ensured, and printing failures can be suppressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-236279 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ink suitable for printing on alkaline tablets, a method for producing printed tablets using the ink, and a tablet printing device. [Means for solving the problem]

[0007] The ink according to an embodiment of the present invention is an inkjet ink for printing identification information of a predetermined color on an alkaline tablet, and includes water, ethanol, a water-soluble high-boiling-point organic solvent, and a dye that exhibits a color different from the predetermined color before printing on the alkaline tablet and changes to the predetermined color after printing on the alkaline tablet. the predetermined color is blue, the colorant includes Food Green No. 3, the content of the colorant is 0.1 to 10 weight percent, and the content of Food Green No. 3 is 0.5 to 8.0 weight percent; It is characterized by:

[0008] A tablet manufacturing method according to an embodiment of the present invention is characterized in that the ink according to the above embodiment is supplied to a print head that ejects ink from a nozzle, and identification information is printed on an alkaline tablet using the ink using the print head.

[0009] A tablet printing device according to an embodiment of the present invention has a transport device that transports alkaline tablets, and a print head that prints by ejecting ink from a nozzle onto the alkaline tablets transported by the transport device, and is characterized in that the print head prints identification information by ejecting the ink according to the above embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In inkjet printing, ink filled in the inkjet head is discharged from an opening in the nozzle at the tip of the inkjet head. If the ink dries and adheres inside or around the nozzle opening, causing the shape of the opening to deform or become clogged, this results in poor discharge. In addition, if the ink has high viscosity, it cannot be discharged normally from the nozzle, resulting in poor discharge. Droplets of ink discharged from the nozzle of the inkjet head land on the surface of the tablet to be printed, and letters, symbols, etc. are printed in pointillism by combining the printing dots (points) formed by these droplets. At this time, if there is poor discharge, the printing dots are not formed in the pattern that will become the letters or symbols, and the printing will look faint or will not look like the desired letters or symbols, resulting in poor printing.

[0011] Furthermore, if the ink that has landed on the surface of the tablet does not dry quickly, the ink may peel off during transportation after printing, or may adhere to other tablets or transportation devices, causing stains. Therefore, the inkjet ink used for tablet printing needs to have both the ability to be ejected from the nozzle and the ability to dry after printing.

[0012] There are tablets (hereinafter simply referred to as "alkaline tablets") whose surfaces (at least the areas to be printed on) are alkaline because they contain alkaline ingredients or are coated with alkaline components. It has been found that when printing is performed on alkaline tablets using dye ink, the printed characters, etc., discolor or bleed over time, depending on the dye.

[0013] In particular, when an alkaline tablet is printed with an ink containing edible blue No. 1 (Brilliant Blue FCF), which is a commonly used blue dye, and stored in an environment with a temperature of 40 degrees and a humidity of 75%, the printed identification information turns light purple in 1 to 2 days and bleeds. In other words, the color changes to a different color from the color immediately after printing or the desired color (prescribed color), so if a corporate logo or illustration containing blue is printed, the impression will change. In addition, when characters are printed, the resulting bleed makes the characters unclear and reduces the identification of the tablet.

[0014] In addition, for example, purple ink was created by mixing Food Red No. 3, which is a commonly used red dye, and Food Blue No. 1, which is a commonly used blue dye, and this was printed on alkaline tablets. However, just like blue ink, when stored in an environment with a temperature of 40 degrees and a humidity of 75%, the printed identification information turned red in 1-2 days, the two mixed dyes separated, causing spots, and bleeding.

[0015] For example, orange ink was created by mixing Food Red No. 3, which is a commonly used red dye, and Food Yellow No. 4, which is a commonly used yellow dye, and this was printed on alkaline tablets. However, like the other colors mentioned above, when stored in an environment with a temperature of 40 degrees and a humidity of 75%, the printed identification information turned yellow within 1 to 2 days, the two mixed dyes separated, causing spots, and bleeding.

[0016] Therefore, the inventor of the present application has invented an ink that can print the predetermined color when printing on an alkaline tablet by blending a dye that exhibits a different color (the predetermined color of the printed identification information) into the ink. For example, Edible Green No. 3 is used as the dye of an ink whose predetermined color is blue (or a color with a bluish tint). Edible Green No. 3 is a dye that is generally used as a green coloring agent, for example, in food. However, the inventor of the present application has focused on the fact that Edible Green No. 3 exhibits a blue color under alkaline conditions, and has invented an ink that exhibits a blue color on alkaline tablets by blending Edible Green No. 3.

[0017] Furthermore, cochineal pigment was applied to the alkaline tablet as an ink pigment with a specific purple color. Cochineal pigment is a pigment generally used as a red (maroon) coloring agent for food, for example. However, the inventor of the present application noticed that cochineal pigment turns purple under alkaline conditions, and invented an ink that turns purple on alkaline tablets by blending cochineal pigment.

[0018] In addition, Edible Red No. 102 was used as a pigment for an ink having a specific color of orange. Edible Red No. 102 is a pigment that is generally used as a red coloring agent for, for example, food. However, the inventor of the present application noticed that Edible Red No. 102 exhibits an orange color under alkaline conditions, and invented an ink that exhibits an orange color on an alkaline tablet by blending Edible Red No. 102.

[0019] It should be noted that "a pigment that exhibits a color different from a specified color" is not limited to the color of the pigment when it is in powder form, but also includes the color of the pigment when it is dissolved in water and then other additives are added to complete the ink, which is different from the specified color.

[0020] [ink] The ink according to this embodiment will be described. The ink according to this embodiment is an inkjet ink, and contains at least water, ethanol, and a water-soluble high-boiling organic solvent, in addition to any one of food colorings such as Food Green No. 3, cochineal coloring, and Food Red No. 102. In addition, emulsifiers, flavorings, preservatives, and the like may be blended as necessary. It is preferable that all of these ink compositions are edible.

[0021] (dye) The ink of this embodiment contains at least Food Green No. 3 (Fast Green FCF) as a pigment when the specified color is blue, contains at least cochineal pigment as a pigment when the specified color is purple, and contains at least Food Red No. 102 (New Coccine) as a pigment when the specified color is orange.

[0022] The content of the dye is preferably 0.1 to 10 weight percent, more preferably 0.5 to 8 weight percent, based on the total ink composition. If the content of the dye is less than 0.1 weight percent, the printed color is light and visibility is poor. If the content of the dye is more than 10 weight percent, the ink viscosity increases, causing the ink to be ejected improperly, resulting in poor printing. It has been confirmed that the dye with the above content can always obtain a desired color, regardless of the pH value of the alkaline tablet that is the printing target.

[0023] (ethanol) Ethanol is preferably fermented ethyl alcohol or sugarcane alcohol. The content of ethanol is preferably 5 to 60 weight percent, more preferably 10 to 40 weight percent, based on the total composition of the ink. If the content of ethanol is less than 5 weight percent, the ink dries poorly. For example, it takes more than 3 seconds to dry after printing, so the ink peels off during transportation after printing, or adheres to other tablets or transportation devices, causing stains. In addition, the surface tension of the ink increases, making the printed ink more likely to be repelled by the surface of the tablet. In other words, the ink does not spread wet on the surface of the tablet, so it does not dry easily, and since the contact area with the tablet surface is small, the adhesion is small, so that it peels off when rubbed, for example, even after 24 hours. If the content of ethanol is more than 60 weight percent, the ink dries and adheres to the inside or around the opening of the inkjet nozzle, blocking the opening, causing ejection failure and deviation in the flying direction of the ejected ink, resulting in poor printing.

[0024] (Water-soluble high boiling point organic solvent) The water-soluble high-boiling organic solvent is used to prevent the nozzle of the inkjet head from drying. As the water-soluble high-boiling organic solvent, for example, one or more of propylene glycol and glycerin can be selected. The content of the water-soluble high-boiling organic solvent is preferably 1 to 60 weight percent, more preferably 2 to 55 weight percent, based on the total ink composition. If the water-soluble high-boiling organic solvent is less than 1 weight percent, printing defects occur due to drying of the ink in the inkjet nozzle. On the other hand, if it is more than 60 weight percent, the ink viscosity increases, preventing normal ejection of the ink, resulting in printing defects.

[0025] (emulsifier) The emulsifier may be selected from one or more water-soluble emulsifiers selected from, for example, lecithin, glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. The emulsifier is not necessarily added, but when added, the content of the emulsifier is preferably 0.01 to 5 weight percent, more preferably 0.1 to 2 weight percent, based on the total ink composition. If the content is less than 0.01 weight percent, the surface tension of the ink increases, and an appropriate meniscus state does not occur at the nozzle opening, resulting in printing defects such as ink not being ejected from the nozzle or ink not landing at a specified position even if ejected. If the content is more than 5 weight percent, the ink thickens and precipitates occur over time, causing nozzle clogging, again resulting in printing defects.

[0026] (Ink manufacturing) Next, the present embodiment will be specifically described with reference to examples and comparative examples shown in Table 1. However, these examples are merely examples, and the present invention is not limited to these examples.

[0027] In Examples 1 to 5 and Comparative Examples 1 to 5, the compositions shown in Table 1 were prepared in the blending ratios shown in Table 1. The blending ratios shown in Table 1 are all expressed in weight percent. Examples 1 to 3 are inks containing Food Green No. 3 when the specified color is blue (a color containing a bluish hue, such as dark blue and blue-green). Comparative Examples 1 to 3 are inks containing a pigment that is widely used as a blue dye as a dye. Example 4 is ink containing cochineal pigment when the specified color is purple. Comparative Example 4 is ink containing Food Blue No. 1 and Food Red No. 3. Example 5 is ink containing Food Red No. 102 when the specified color is orange. Comparative Example 5 is ink containing Food Red No. 3 and Food Yellow No. 4.

[0028] The preparation procedure was as follows: First, all ingredients except for the pigments shown in Table 1 were dissolved by stirring while heating to 50°C. After each ingredient was dissolved, the pigments shown in Table 1 were mixed and further stirred at 50°C for 1 hour. The mixture was then left to stand for 1 hour, cooled to room temperature, and filtered to prepare the ink.

[0029] The dye to be mixed may be in the form of a powder, or may be dissolved in a liquid such as water to form a solution, or may be dispersed in a paste. Ultimately, it is sufficient that the dye is dissolved or mixed uniformly.

[0030] [Table 1]

[0031] (Ink evaluation) The prepared inks of Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated for ejection from the nozzle using an inkjet head. Furthermore, characters were printed on the tablets to be printed, and the light resistance and temporal stability of the print were evaluated (the methods for each evaluation are described below). In each evaluation, OD tablets, which are a type of alkaline tablet and contain magnesium oxide as a main component, were used as the printing subject. The results are shown in Table 1.

[0032] It should be noted that Comparative Example 3 was excluded from the targets of each measurement and evaluation because filtration was not possible.

[0033] <Evaluation of ejection from nozzle> The ejection properties from the nozzles were evaluated by filling the ink into an inkjet head, leaving it for 15 minutes, and then conducting a printing test to visually check for the presence or absence of printing defects.

[0034] ◯: Each printing dot is formed in the specified position.

[0035] ×: Print dots are missing and / or each print dot does not land in the specified position.

[0036] <Evaluation of light resistance of print> The light resistance of the print was evaluated by printing on the tablets, exposing them to light at 1000 lux for 50 days without packaging, and visually checking whether the print had faded.

[0037] A: No fading of the print was observed.

[0038] ×: The print has faded.

[0039] <Evaluation of printing stability over time> The stability of the print over time was evaluated by storing the printed tablets in an environment of 40°C and 75% RH for two weeks and visually checking for bleeding of the letters and any change in color compared to immediately after printing.

[0040] ○: There was no bleeding or discoloration.

[0041] ×: The color changed to a color different from the desired color and / or the print bled and became difficult to read.

[0042] (result) As can be seen from the experimental results of Examples 1 to 5 shown in Table 1, the inks containing any of Food Green No. 3, cochineal color, and Food Red No. 102 as the coloring matter had good nozzle ejection properties. Furthermore, when used to print on alkaline tablets, the inks had excellent light resistance and stability over time. The results are described in more detail below.

[0043] <Examples 1 to 3> In printing on alkaline tablets, Example 1 is an ink that is colored blue, Example 2 is a blue-green, and Example 3 is a dark blue. Example 1 and Example 3 are inks that change the amount of Food Green No. 3, and Example 2 contains Food Red No. 102 and Food Yellow No. 4 in addition to Food Green No. 3. When printing was performed using each of the inks of Examples 1 to 3, each printed dot was formed at a predetermined position on the surface of the tablet. In the light resistance evaluation, the printed characters on the printed tablets did not change color from the color immediately after printing. In the evaluation of stability over time, the printed characters could be read well without bleeding. Furthermore, there was no discoloration over time, and the blue color was maintained.

[0044] <Comparative Example 1> Comparative Example 1 is an ink that exhibits a blue color immediately after printing on an alkaline tablet. The pigment contains gardenia blue pigment. Natural pigments such as gardenia blue pigment need to be blended in large amounts to obtain sufficient darkness for printing. In the ink of Comparative Example 1, a sufficient amount of gardenia blue pigment was blended to make the print visible, resulting in high ink viscosity and poor ejection from the nozzle. In addition, in the light resistance evaluation, the print faded and was almost completely lost. In the evaluation of stability over time, no bleeding or discoloration of the print was observed.

[0045] <Comparative Example 2> Comparative Example 2 is an ink that, when printed on an alkaline tablet, is blue immediately after printing. It contains Food Blue No. 1 as a coloring matter. When a tablet was printed using the ink of Comparative Example 2, each printed dot was formed at a predetermined position on the surface of the tablet. In a light resistance evaluation, no fading occurred. However, in a time stability evaluation, the print turned pale purple in about 1 to 2 days. Furthermore, the print bleeds, making it difficult to read the print.

[0046] <Comparative Example 3> Comparative Example 3 contains Food Blue No. 2 as a coloring matter. Food Blue No. 2 is one of the dyes commonly used as a blue coloring matter. However, in Comparative Example 3, Food Blue No. 2 has poor solubility, and even when made into ink, it could not be filtered.

[0047] <Example 4> In printing on alkaline tablets, Example 4 is an ink that turns purple. When printing was performed using the ink of Example 4, each printed dot was formed at a predetermined position on the surface of the tablet. In the light resistance evaluation, the printed characters on the printed tablets did not change color from the color immediately after printing. In the evaluation of stability over time, the printed characters were easily read without bleeding. Furthermore, there was no discoloration over time, and the purple color was maintained.

[0048] <Comparative Example 4> Comparative Example 4 is an ink that is purple immediately after printing on alkaline tablets. The pigments include Food Blue No. 1 and Food Red No. 3. When tablets are printed with ink containing a mixture of these two pigments, each printed dot is formed at a specified position on the surface of the tablet. In the light resistance evaluation, no fading occurred. However, in the evaluation of stability over time, the print gradually began to separate into two colors, and in some cases the print turned red or became mottled within 1 to 2 days.

[0049] <Example 5> In printing on alkaline tablets, Example 5 is an ink that turns orange. When printing was performed using the ink of Example 5, each printed dot was formed at a predetermined position on the surface of the tablet. In the light resistance evaluation, the printed characters on the printed tablets did not change color from the color immediately after printing. In the evaluation of stability over time, the printed characters were easily read without bleeding. Furthermore, there was no discoloration over time, and the orange color was maintained.

[0050] <Comparative Example 5> Comparative Example 5 is an ink that shows orange color immediately after printing on alkaline tablets. The dyes include Food Red No. 3 and Food Yellow No. 4. When a tablet was printed with an ink containing a mixture of these two dyes, each printed dot was formed at a predetermined position on the surface of the tablet. In the light resistance evaluation, the print faded. Furthermore, in the evaluation of stability over time, the print gradually began to separate into two colors, and in some cases the print turned yellow or became mottled within 1 to 2 days.

[0051] (summary) From the above-mentioned results, when printing is performed by the inkjet method, ink containing any one of Food Green No. 3, cochineal coloring, and Food Red No. 102 can stabilize the ejection from the nozzle and suppress the occurrence of printing defects. In addition, by printing on an alkaline tablet using ink containing any one of Food Green No. 3, cochineal coloring, and Food Red No. 102, it is possible to make the alkaline tablet appear in a predetermined color (blue or a color with a bluish tint in the case of Food Green No. 3, purple in the case of cochineal coloring, and orange in the case of Food Red No. 102). In other words, ink containing any one of Food Green No. 3, cochineal coloring, and Food Red No. 102 can print identification information of a predetermined color on an alkaline tablet. Furthermore, this ink has high light resistance and stability over time, and can suppress discoloration of the printed identification information. In addition, it can also suppress bleeding of the print. Therefore, even after printing, the identification information can be easily recognized even after the tablet is stored, and dispensing errors and accidental ingestion can be prevented.

[0052] [Tablet printing device] A tablet printing device can be used to print the identification information on the tablets. The tablet printing device has a conveying device and an inkjet print head. The conveying device is, for example, a suction conveying device that conveys tablets while suctioning and holding them. The print head is disposed so as to face the conveying surface of the conveying device, and ejects ink from a nozzle toward the tablets passing under the print head to print the identification information on the tablets. By supplying ink containing the above-mentioned dye to the print head of this tablet printing device and printing on the alkaline tablets being conveyed, the identification information can be printed in a predetermined color on the alkaline tablets.

[0053] [Other embodiments] In the above-described embodiment, the predetermined color is blue, purple, or orange, but it is not limited thereto and may be other colors. For example, when the predetermined color is purple, lac pigment can be used in addition to cochineal pigment. When the predetermined color is light orange, safflower yellow can be used. When the predetermined color is reddish brown, turmeric pigment can be used. Lac pigment is a pigment used as a red coloring agent for food, for example, and safflower yellow and turmeric pigment are pigments used as yellow coloring agents.

[0054] The ink of the above-described embodiment can be mixed with other dyes to obtain a desired color. The other dyes can be one or more selected from conventionally known synthetic food dyes and natural food dyes.

[0055] Examples of synthetic food dyes include tar-based dyes, natural dye derivatives, natural synthetic dyes, titanium dioxide, etc. 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 Yellow No. 5 Aluminum Lake, Food Blue No. 2 Aluminum Lake, etc. As explained in Comparative Example 3, Food Blue No. 2 has poor solubility, but can be used in small amounts. As explained in Comparative Example 4, Food Red No. 3 is used in combination with Food Blue No. 1 to prepare purple ink, but color separation is observed, but it can be used in combination with other dyes. Examples of natural pigment derivatives include copper chlorophyll, sodium copper chlorophyllin, and potassium norbixin, and examples of natural synthetic pigments include β-carotene and riboflavin.

[0056] Examples of natural food dyes include plant charcoal pigments, anthocyanin pigments, carotenoid pigments, quinone pigments, flavonoid pigments, betaine pigments, monascus pigments, and other pigments derived from natural products. Examples of anthocyanin pigments include red radish pigments, red cabbage pigments, red rice pigments, elderberry pigments, cowberry pigments, gooseberry pigments, cranberry pigments, salmonberry pigments, perilla pigments, sweet blueberry pigments, strawberry pigments, dark sweet cherry pigments, cherry pigments, hibiscus pigments, huckleberry pigments, grape juice pigments, grape skin pigments, blackcurrant pigments, blackberry pigments, blueberry pigments, plum pigments, white wortberry pigments, boysenberry pigments, mulberry pigments, purple sweet potato pigments, purple corn pigments, purple yam pigments, raspberry pigments, redcurrant pigments, loganberry pigments, and other anthocyanin pigments. Carotenoid pigments include annatto pigment, gardenia yellow, and other carotenoid pigments. Quinone pigments include cochineal pigment, lithospermum pigment, lac pigment, and other quinone pigments. Flavonoid pigments include safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Betaine pigments include beet red pigment. Monascus pigments include monascus pigment and monascus yellow pigment. Other pigments derived from natural products include turmeric pigment, clover pigment, gardenia red pigment, spirulina blue pigment, and the like.

[0057] The ink may contain additives such as flavorings, preservatives (bacteriostatic agents), antifoaming agents, and surfactants, as necessary. Of course, if the printing subject is medicine or food, these should also be edible. In addition, when mixing the ink components, pre-treatments such as heating or post-treatments can be performed.

[0058] For stirring in preparing the ink, a commonly used stirrer such as a magnetic stirrer or a propeller stirrer can be used.

[0059] The ink may also contain so-called pigments, such as vegetable charcoal pigments, titanium dioxide, and aluminum lake. To prepare an ink containing a pigment, it is necessary to carry out a pigment dispersion process. This dispersion process is not particularly limited as long as it is carried out using a commonly used dispersing machine. Specific examples include a ball mill, a roll mill, a sand mill, and a bead mill.

[0060] The method for filtering the ink is not particularly limited, and centrifugal filtration, filter filtration, etc. can be used.

[0061] The above-mentioned tablets can include tablets used for medicine, food, cleaning, industrial or aromatic purposes, as long as at least the printing target portion is alkaline. In addition to the above-mentioned bare tablets (plain tablets) and film-coated tablets (film-coated tablets), tablets can also include sugar-coated tablets, enteric tablets, gelatin-coated tablets, multi-layer tablets, dry-coated tablets, and various capsule tablets such as hard capsules and soft capsules. Furthermore, tablets can have various shapes such as disks, lenses, triangles, and ellipses. In addition, when the tablet to be printed is for medicine or food, the composition of the ink used is preferably edible, but if this is not the case, the composition may be inedible.

[0062] Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This new embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

Claims

1. An inkjet ink for printing identification information of a predetermined color on an alkaline tablet, comprising: Water, Ethanol, A water-soluble high-boiling organic solvent; a dye that exhibits a color different from the predetermined color before being printed on the alkaline tablet and changes to the predetermined color after being printed on the alkaline tablet; Including, the predetermined color is blue; The colours include Food Green No. 3, The ink is characterized in that the content of the pigment is 0.1 to 10 weight percent, and the content of Food Green No. 3 is 0.5 to 8.0 weight percent.

2. 2. The ink according to claim 1, wherein the ethanol content is from 5 to 60 percent by weight.

3. 3. The ink according to claim 1, wherein the water-soluble high-boiling point organic solvent is either propylene glycol or glycerin, or both.

4. 4. The ink according to claim 1, wherein the content of the water-soluble high-boiling point organic solvent is 1 to 60 weight percent.

5. 5. The ink according to claim 1, wherein the alkaline tablet is a tablet containing magnesium oxide as a main component.

6. Supplying the ink according to any one of claims 1 to 5 to a print head which ejects ink from nozzles; A method for producing printed tablets, comprising using the print head to print identification information on the alkaline tablet with the ink.

7. A conveying device for conveying the alkaline tablets; a print head that prints on the alkaline tablets transported by the transport device by ejecting ink from a nozzle; having 6. A tablet printing device, comprising: a print head that prints identification information by ejecting the ink according to claim 1.

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