TWI825795B - Ink, method for manufacturing printed tablets using the same, and tablet printing device - Google Patents

Abstract

The present invention provides an ink suitable for printing alkaline tablets, a method for manufacturing printed tablets using the ink, and a tablet printing device. The ink of the embodiment is an inkjet ink for printing identification information on alkaline tablets in blue or a color including blue, and contains at least Edible Blue No. 1 and shellac.

Description

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

Embodiments of the present invention relate to an ink, a method for manufacturing printed tablets using the ink, and a tablet printing device.

Printing identification information such as characters or marks on tablets improves the tablet's visibility, thereby preventing pharmacists from making medication errors or users from accidentally ingesting the tablets.

An example of a printing method for tablets is inkjet printing. Inkjet printing allows tablets to be printed in a non-contact manner, so it is suitable for tablets with high disintegration potential such as OD (Orally Disintegrating) tablets (orally disintegrating tablets). For printing.

In such inkjet printing, ink containing dye (dye ink) may be used. According to the dye ink, compared with the ink containing the pigment, the printed text and the like are more likely to develop in a deeper color, and the visual recognition of the identification information becomes better. In addition, since the ink containing a pigment is in a state where the pigment is dispersed in a solvent, the ejection performance from the nozzle of the inkjet head is poor, which may cause ejection failure and result in printing failure. On the other hand, in dye ink, since the dye is dissolved in the solvent, ejection properties from the nozzles of the inkjet head are easily ensured, and printing defects can be suppressed. [Prior art documents] [Patent Document]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2011-236279

[Problem to be solved by the invention]

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

The ink according to the embodiment of the present invention is an inkjet ink used for printing identification information on alkaline tablets, and contains at least a pigment containing edible blue No. 1, shellac, water, and ethanol.

A method of manufacturing a tablet according to an embodiment of the present invention is characterized by supplying the ink to a print head that ejects ink from a nozzle, and using the print head to print identification using the ink of the embodiment on an alkaline tablet. information.

A tablet printing device according to an embodiment of the present invention is characterized by having: a conveying device that conveys alkaline tablets; and a print head that ejects ink from a nozzle to the alkaline tablet conveyed by the conveying device. To perform printing, the print head ejects the ink of the embodiment.

In inkjet printing, ink filled in an inkjet head is ejected from an opening located at a nozzle at the front end of the inkjet head. If the ink dries and adheres to the opening of the nozzle or around the opening, and the shape of the opening is deformed or clogged, it may lead to poor ejection. In addition, if the viscosity of the ink is high, it will not be ejected normally from the nozzle, resulting in poor ejection. On the surface of the tablet to be printed, droplets of ink ejected from the nozzles of the inkjet head land, and small printing dots (dots) (dots) formed by the landing droplets are combined to form dots. Draw to print words or symbols, etc. At this time, if there is an ejection failure, printing dots will not be formed in the pattern of characters or symbols, and the printing will look blurry, or the desired characters or symbols will not be visible, resulting in printing defects.

Furthermore, if it is difficult to dry the ink that has landed on the tablet surface, the ink may peel off during transportation after printing, or may adhere to other tablets, transportation equipment, etc., causing contamination. Therefore, as characteristics of an inkjet ink used for tablet printing, it is necessary to have both ejection properties from a nozzle and drying properties after printing.

Among tablets, there are tablets that contain alkaline raw materials or are coated with alkaline components so that the surface (at least the printed object portion) shows alkalinity (hereinafter, simply referred to as "alkaline tablets"). It was found that when dye ink is used to print alkaline tablets, the printed characters and the like may discolor or bleed over time depending on the dye.

Especially among blue inks, for example, when printing alkaline tablets using ink containing edible blue No. 1 (brilliant blue (FCF)), which is commonly used as a blue dye, the temperature is 40 degrees and the humidity is 75. When stored in a %RH environment, the printed identification information will change color to lavender within 1 to 2 days, causing bleeding. That is, since the color changes to a color different from the color immediately after printing or the desired color (prescribed color), for example, when a company logo or illustration containing blue is printed, the impression will change. In addition, when characters are printed, the characters become blurred due to the bleeding that occurs, and the visibility of the tablets decreases.

Therefore, the inventors of the present application invented an ink that can appropriately print identification information on alkaline tablets even when edible blue No. 1 is used as a pigment.

[Ink] The ink of this embodiment will be described. The ink of this embodiment is an inkjet ink, and is particularly a blue ink suitable for printing alkaline tablets. The ink contains at least edible blue No. 1 as a pigment and at least shellac as a resin. In addition, if necessary, emulsifiers, flavorings, preservatives, etc. can also be prepared. When preparing the ink, it is preferable to use an edible composition such as a composition approved by the Japanese Pharmacopoeia or the Food Additive Standard as each composition.

(pigment) The ink of this embodiment contains at least Food Blue No. 1 (Brilliant Blue FCF) as a pigment. In addition, it is more preferable to contain Gardenia Blue pigment together with Edible Blue No. 1.

The ink of this embodiment may be only Edible Blue No. 1, or only Edible Blue No. 1 and Gardenia Blue pigment, and further, by using not only Edible Blue No. 1 or Gardenia Blue pigment but also other The pigment can also be adjusted to blue or a desired color including blue. As other pigments, one or more types of pigments may be selected from conventionally known synthetic food pigments and natural food pigments. In addition, the color including blue is, for example, a color including blue as a color component, such as green or purple.

Examples of synthetic food pigments include tar-based pigments, natural pigment derivatives, natural synthetic pigments, titanium dioxide, etc. Examples of tar-based pigments include: Edible Red No. 2, Edible Red No. 3, Edible Red No. 40, Edible Red No. 102, Edible Red No. 104, Edible Red No. 105, Edible Red No. 106, Edible Yellow No. 4, Edible Yellow No. 5, Edible Blue No. 2, Edible Red No. 2 Aluminum Lake, Edible Red No. 3 Aluminum Lake, Edible red No. 40 aluminum lake, edible yellow No. 4 aluminum lake, edible yellow No. 5 aluminum lake, edible blue No. 2 aluminum lake, etc. Examples of natural pigment derivatives include copper chlorophyll and sodium copper chlorophyll (sodium). copper-chlorophyllin), potassium norbixin, etc. Examples of natural synthetic pigments include β-carotene, riboflavin, etc.

Examples of natural food pigments include plant carbon pigments, anthocyanin pigments, carotenoid pigments, quinone pigments, flavonoid pigments, betaine pigments, and monascus. Pigments and other pigments derived from natural products. Examples of anthocyanin pigments include: carrot pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, and cranberry. Pigment, salmon berry pigment, perilla pigment, thimbleberry pigment, strawberry pigment, dark sweet cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, Grape juice pigment, grape peel pigment, black currant pigment, blackberry pigment, blueberry pigment, plum pigment, whortleberry pigment, boysenberry pigment, mulberry pigment , purple sweet potato pigment, purple corn pigment, purple potato pigment, raspberry pigment, red currant pigment, loganberry pigment, and other anthocyanin pigments. Examples of carotenoid pigments include annatto pigments, gardenia yellow pigments, and other carotenoid pigments. Examples of quinone pigments include cochineal pigments, purple root pigments, shellac pigments, and other quinone pigments. Examples of flavonoid pigments include safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of betaine-based pigments include betalain pigments. Examples of red yeast rice pigments include red yeast rice pigments and red yeast rice yellow pigments. Examples of other pigments derived from natural products include curcumin, gardenia red pigment, spirulina blue pigment, and the like.

The content of the pigment is preferably 0.1% by weight to 10% by weight, and more preferably 0.5% by weight to 8% by weight, based on the entire ink composition. If the content of the pigment is less than 0.1% by weight, the printed color will be light and the visual recognition will be poor. In addition, if the content exceeds 10% by weight, the ink will not be ejected normally due to an increase in the viscosity of the ink, resulting in poor printing.

(resin) By blending a resin component into the ink, the adhesion of the ink to the tablet can be improved, and at the same time, after printing on the tablet, it is dried to form a film, thereby achieving scratch resistance. In the ink of this embodiment, shellac is used as the resin. Shellac is a resin obtained by refining the resinous substance secreted by lac insects. It is a mixture of various resin esters, waxes, pigments, etc. When blending into ink, it is preferable to use white shellac in which shellac has been bleached, or refined shellac in which pigments or waxes have been removed. In addition, by blending shellac into the ink, the viscosity of the ink can be increased and the viscosity can be adjusted to a viscosity suitable for ejection from the nozzle using an inkjet head.

The content of shellac is preferably 0.5% by weight to 10% by weight, more preferably 1% by weight to 8% by weight, based on the entire ink composition. If the content of shellac is less than 0.5% by weight, when alkaline tablets are printed and stored in an environment with a temperature of 40 degrees and a humidity of 75% RH, the printed identification information will change color within 1 to 2 days. It is lavender and bleeds. In addition, if the content exceeds 10% by weight, the ink will not be ejected normally due to an increase in the viscosity of the ink, resulting in poor printing.

(pH adjuster) It is known that shellac is soluble in alkaline aqueous solutions in addition to alcohols. By making the ink alkaline, the shellac can be maintained in a dissolved state without precipitating. As the pH adjuster, those approved as food additives are preferred. In order to obtain water resistance after printing ink containing shellac, it is preferable to use a component that volatilizes when the ink dries, and for example, ammonium carbonate or ammonium bicarbonate can be used. The pH of the ink is preferably 6.5 to 10.

(ethanol) Ethanol is preferably naturally brewed fermented ethyl alcohol or sugarcane alcohol. The content of ethanol is preferably 5% to 60% by weight, and more preferably 10% to 40% by weight relative to the entire ink composition. If the ethanol content is less than 5% by weight, the drying properties of the ink are poor. For example, since drying takes more than 3 seconds after printing, the ink may peel off during transportation after printing, or may adhere to other tablets or during transportation. Contamination may occur due to equipment etc. In addition, the surface tension of the ink becomes high, and the printed ink easily bounces to the surface of the tablet. That is, since it does not wet and spread on the surface of the tablet, it is difficult to dry, and the contact area with the tablet surface is small, so the adhesion becomes small, and the tablet may peel off even if it is wiped after 24 hours, for example. In addition, if it exceeds 60% by weight, the ink will dry and adhere to the opening of the inkjet nozzle or around the opening, clogging the opening, resulting in ejection failure or deviation of the flying direction of the ejected ink, resulting in printing bad.

(Water-soluble high boiling point organic solvent) Water-soluble high-boiling point organic solvents are used to prevent the nozzles of the inkjet heads from drying out. As the water-soluble high-boiling point organic solvent, for example, one or more types may be selected from propylene glycol and glycerin. The content of the water-soluble high-boiling organic solvent is preferably 1 to 60% by weight, and more preferably 2 to 55% by weight relative to the entire ink composition. If the water-soluble high-boiling point organic solvent is less than 1% by weight, the ink in the inkjet nozzle dries, resulting in poor printing. In addition, if the content exceeds 60% by weight, the ink will not be ejected normally due to an increase in the viscosity of the ink, resulting in poor printing.

(emulsifier) For example, the emulsifier may be selected from a substance that is more water-soluble than lecithin, glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, or polyoxyethylene sorbitan fatty acid ester. Two or more types. The emulsifier does not necessarily need to be blended, but when blended, the content of the emulsifier is preferably 0.01% to 5% by weight, and more preferably 0.1% to 2% by weight relative to the entire ink composition. If the content is less than 0.01% by weight, the surface tension of the ink becomes large and the nozzle opening may not be in an appropriate meniscus state. Therefore, the ink will not be ejected from the nozzle, or even if it is ejected, it will not land on the ink. Specify the position, resulting in poor printing. In addition, if the content exceeds 5% by weight, the ink may thicken, or precipitates may be generated over time, causing clogging of the nozzles, resulting in printing defects.

(Manufacture of ink) Next, this embodiment will be specifically described using the Examples and Comparative Examples shown in Table 1. However, these Examples are examples and are not limited to these Examples.

Examples 1 to 3 and Comparative Examples 1 and 2 were prepared using the blending ratios shown in Table 1 for each composition shown in Table 1. In addition, the compounding proportions shown in Table 1 are expressed as weight percentages relative to the entire ink composition. Examples 1 to 3 are inks containing edible blue No. 1 and shellac. Comparative Example 1 is an ink containing edible blue No. 1 as a pigment (excluding shellac), and Comparative Example 2 is an ink containing gardenia blue pigment as a pigment.

In addition, Comparative Example 1 does not contain shellac, so by increasing the proportion of propylene glycol, the viscosity can be adjusted to an appropriate viscosity when printing with an inkjet head. Regarding Comparative Example 2, since the gardenia blue pigment is dissolved, the proportion of purified water is higher and the proportion of ethanol is lower than in other Examples or Comparative Examples.

The modulation operation is described below. First, all the components except the pigment shown in Table 1 were heated to 50° C. and stirred to dissolve them. After each component was dissolved, the dyes shown in Table 1 were mixed and further stirred at 50° C. for 1 hour. Thereafter, the mixture was left to stand for 1 hour, cooled to room temperature, and then filtered to prepare an ink.

In addition, the mixed pigment may be maintained in a powder state, or may be in the form of a solution dissolved in a liquid such as water or a paste dispersed in a liquid such as water. Ultimately, as long as the pigment is evenly dissolved or mixed.

[Table 1] Composition Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 pigment Edible Blue No. 1 2.0 2.0 2.0 2.0 - gardenia blue pigment - 2.0 1.0 - 10.0 Resin Shellac 7.0 7.0 7.0 - - pH adjuster ammonium carbonate 0.8 0.8 0.8 - - water purified water 39.2 47.2 38.7 32.5 79.0 organic solvent ethanol 25.0 20.0 25.0 10.0 5.0 glycerin - - - - 2.0 propylene glycol 25.0 20.0 25.0 55.0 - emulsifier Glyceryl fatty acid ester - - 0.5 0.5 - Sucrose fatty acid ester - 1.0 - - - Polyoxyethylene sorbitan fatty acid ester 1.0 - - - 4.0 total 100.0 100.0 100.0 100.0 100.0 Evaluation characteristics Ejection properties from the nozzle 〇 〇 〇 〇 × Lightfastness of printing 〇 〇 〇 〇 × Stability of printing over time △ 〇 〇 × 〇

(Evaluation of ink) Regarding the prepared inks of Examples 1 to 3 and Comparative Examples 1 and 2, the ejection properties from the nozzles were evaluated using an inkjet head. Furthermore, with respect to printed characters on tablets as printed objects, the light fastness of the printing and the stability over time of the printing were evaluated (each evaluation method will be described later). In each evaluation, OD tablets containing magnesium oxide as a main component, which are a type of alkaline tablets, were used as printing objects. The results are shown in Table 1.

<Evaluation of ejection properties from the nozzle> Regarding the ejection performance from the nozzle, the inkjet head was filled with ink and left for 15 minutes, and then a printing test was performed to visually confirm whether there were any printing defects. 〇: Each printed dot can be formed at a specified position. ×: There are defects in the printed dots, or/and/or each printed dot does not land at the specified position.

＜Evaluation of light resistance of printing＞ The light fastness of printing is determined by exposing the tablets to 1000 lux for 50 days without packaging and visually confirming whether the printing has faded. 〇: No fading of printing was found. ×: Printing is faded.

＜Evaluation of printing stability over time＞ Regarding the stability of printing over time, the printed tablets were stored for two weeks in an environment of 40°C and 75% RH, and the presence of bleeding of the text and color changes was visually confirmed by comparing the tablets immediately after printing. 〇: No bleeding and no discoloration. △: The color changes slightly to a color different from the desired color. or/and) color bleeding is found to the extent that there is no problem with the visual legibility of the printed text. ×: The color changes to a color different from the desired color. Or/and the printed text bleeds, making it difficult to read.

(result) As can be seen from the experimental results of Examples 1 to 3 shown in Table 1, the ink using Edible Blue No. 1 as the pigment and mixed with shellac as the resin is effective in printing alkaline tablets. When printing, it is an ink with excellent light resistance and moisture resistance. Furthermore, an ink containing not only Edible Blue No. 1 but also gardenia blue pigment as a pigment is particularly preferred. The results are explained in more detail below.

<Example 1> The ink of Example 1 contains Edible Blue No. 1 as a pigment and shellac as a resin. The ink of Example 1 was filled into the inkjet head and printed. As a result, each printed dot was formed at a predetermined position. In the light fastness evaluation, there was no change in the color ratio of the characters printed on the alkaline tablets from those immediately after printing. In the evaluation of the stability over time, the blue color became slightly lighter and a slight color bleeding was observed, but this was to a level where there was no problem in visual recognition.

<Example 2> The ink of Example 2 contains not only Edible Blue No. 1 but also gardenia blue pigment as a pigment, and shellac as a resin. The ink of Example 2 was filled into the inkjet head and printed. As a result, each printed dot was formed at a predetermined position. In the light fastness evaluation, there was no change in the color ratio of the characters printed on the alkaline tablets from those immediately after printing. In the evaluation of the stability over time, no discoloration or bleeding over time was found, and the printed characters could be read well.

<Example 3> Like Example 2, the ink of Example 3 contains not only Edible Blue No. 1 but also gardenia blue pigment as a pigment. The ink of Example 3 was filled into the inkjet head and printed. As a result, each printed dot was formed at a predetermined position. In the light fastness evaluation, there was no change in the color ratio of the characters printed on the alkaline tablets from those immediately after printing. In the evaluation of the stability over time, no discoloration or bleeding over time was found, and the printed characters could be read well.

＜Comparative example 1＞ The ink of Comparative Example 1 contains Edible Blue No. 1 as a pigment and does not contain a resin component. The ink of Comparative Example 1 was filled into the inkjet head and printed. As a result, each printed dot was formed at a predetermined position. In the light fastness evaluation, there was no change in the color ratio of the characters printed on the alkaline tablets from those immediately after printing. However, in the time-lapse stability evaluation, the printed characters changed color to lavender in about 1 to 2 days. Furthermore, bleeding of printed characters occurs, making it difficult to read the printed characters.

＜Comparative example 2＞ The ink of Comparative Example 2 contains gardenia blue pigment as a pigment and does not contain a resin component. Natural pigments such as gardenia pigments need to be prepared in large quantities in order to obtain sufficient concentration for printing. In the ink of Comparative Example 1, an amount of gardenia pigment sufficient to visually recognize the printed characters was blended. As a result, the viscosity of the ink increased and the ejection properties from the nozzle deteriorated. In addition, in the composition shown in Comparative Example 2, the concentration of blue is also lighter than that in Example 1. In the light fastness evaluation, the printed characters faded and almost disappeared. In the evaluation of the stability over time, no bleeding or discoloration of the printed characters was found.

(summary) Based on the above results, when printing by inkjet method, the ink blended with Edible Blue No. 1 and shellac stabilizes the ejection performance from the nozzle, thereby suppressing the occurrence of printing defects. Furthermore, the ink has high light resistance and stability over time, and can suppress discoloration of the printed identification information. In addition, printing bleeding can be suppressed. Therefore, after printing, the identification information can be easily recognized even after the tablet is stored, thereby preventing medication errors or accidental ingestion.

Inks containing shellac are also superior in light resistance and stability over time compared to inks containing no resin component. The reason for this is that by blending shellac, the printed ink dries to form a film on the tablet, and the pigment of Edible Blue No. 1 is less susceptible to decomposition by alkali in alkaline tablets. In addition, since shellac is an acid-containing resin, it exerts a neutralizing effect with alkaline tablets, thereby minimizing the influence of alkali on pigments. Edible Blue No. 1 is a pigment that is widely used and has excellent color development. However, it is not suitable for use when printing alkaline tablets due to its low stability over time. On the other hand, by blending shellac, Edible Blue No. 1 can be applied to the printing of alkaline tablets.

In addition, in the past, among inkjet inks used for printing tablets, inks containing shellac were mostly inks with a high ethanol content (for example, about 60% by weight relative to the entire ink composition). ). If the ethanol content is high, it may cause printing defects as described above. If the dissolution of shellac in an alkaline aqueous solution is utilized, and the solvent of the ink is adjusted to be alkaline using, for example, the above-mentioned pH adjuster, it is possible to prepare ink in which shellac is dissolved even if the ethanol content is suppressed.

Furthermore, it is more preferable to mix not only Edible Blue No. 1 but also gardenia blue pigment as a pigment. By blending Edible Blue No. 1 and Gardenia Blue pigments, the stability over time of the ink can be further improved compared to the case where the pigment is Edible Blue No. 1 alone. Comparing the results of Example 1 with Example 2 and Example 3 also makes this clear. Comparing the results of Comparative Example 1 with Comparative Example 2 also shows that the ink containing gardenia blue pigment has excellent stability over time. . That is, it is thought that by blending not only Edible Blue No. 1 but also gardenia blue pigment, the stability over time can be compensated.

[Tablet printing device] When printing identification information on tablets, a tablet printing device can be used. The tablet printing device includes a conveyor and an inkjet printing head. The conveying device is, for example, a suction conveying device that conveys the tablets while suctioning and holding them. The print head is arranged to face the conveying surface of the conveying device, ejects ink from the nozzle toward the tablet passing under the print head, and prints identification information on the tablet. By supplying the above-mentioned ink containing at least Edible Blue No. 1 and shellac to the print head of the tablet printing device, and printing the conveyed alkaline tablets, the alkaline tablets can be printed. Print identification information in blue or colors including blue.

[Other embodiments] In the ink, additives such as spices, preservatives (bacteriostats), defoaming agents, and surfactants can also be mixed as needed. Of course, when the printed object is medicine, food, etc., it is only necessary to select edible substances. In addition, when mixing each composition of the ink, pre-processing or post-processing such as heating may be performed.

For stirring when preparing ink, a commonly used stirrer such as a magnetic stirrer or a propeller stirrer can be used.

In addition, so-called pigments such as vegetable carbon pigments, titanium dioxide, and aluminum lakes can also be blended into the ink. When preparing ink blended with pigments, pigment dispersion processing is required. The dispersion treatment is not particularly limited as long as it is a commonly used disperser. Specific examples include ball mills, roller mills, sand mills, bead mills, and the like.

There is no particular limitation on the filtration method for the ink, and centrifugal filtration, screening program filtration, etc. can be used.

The tablets may include tablets used for medical purposes, dietary purposes, cleaning purposes, industrial purposes, or aromatic purposes, as long as at least the portion to be printed is alkaline. In addition, as tablets, in addition to the above-mentioned bare tablets (uncoated tablets) or film-coated tablets (film-coated tablets), there are also sugar-coated tablets, enteric-coated tablets, gelatin-coated tablets, multi-layer tablets, and nucleated tablets. etc., various capsules such as hard capsules and soft capsules may also be included in the tablets. Furthermore, tablet shapes include various shapes such as disk shape, lens shape, triangle shape, and oval shape. In addition, when the tablet to be printed is for medical use or dietary use, the composition of the ink used is preferably edible, but of course, if this is not the case, it may be an inedible composition.

The embodiments of the present invention have been described above. However, the embodiments are merely examples and are not intended to limit the scope of the invention. The novel embodiment described above can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments or modifications thereof are included in the scope or gist of the invention, and are included in the invention described in the claims and their equivalent scope.

Claims (11)

An ink for inkjet printing for printing identification information of blue or colors including blue on alkaline tablets, characterized in that it contains: a combination of inks containing at least Edible Blue No. 1 The overall composition of the ink is 0.1% to 10% by weight of pigment; the total composition of the ink is 0.5% to 10% by weight of shellac; water; the total composition of the ink is 5% to 60% by weight Ethanol; and a water-soluble high-boiling point organic solvent in an amount of 1% to 60% by weight relative to the entire ink composition. The ink according to claim 1, wherein the water-soluble high-boiling point organic solvent is one or more selected from the group consisting of propylene glycol and glycerin. The ink according to claim 1, further comprising a gardenia blue pigment as the pigment. The ink according to claim 2, wherein the pigments are only the edible blue No. 1 and the gardenia blue pigment. The ink according to claim 1, wherein the shellac is a white shellac obtained by bleaching the shellac or a refined shellac obtained by removing pigments or waxes. The ink according to claim 1, further comprising a pH adjuster, The pH adjuster is ammonium carbonate or ammonium bicarbonate. The ink according to any one of claims 1 to 6, characterized in that the content of the pigment is 0.5% by weight to 8% by weight. The ink according to claim 1, further comprising an emulsifier selected from the group consisting of lecithin, glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, and propylene glycol fatty acid ester. , polyoxyethylene sorbitan fatty acid ester, one or more highly water-soluble substances, and the emulsifier is 0.01% to 5% by weight relative to the entire ink composition. The ink according to any one of claims 1 to 6 and 8, wherein the alkaline tablet is a tablet containing magnesium oxide as a main component. A method for manufacturing printed tablets, characterized in that the ink according to claim 1 is supplied to a printing head that ejects ink from a nozzle, and the printing head is used to print blue or blue color on an alkaline tablet using the ink. Identification information for colors including blue. A tablet printing device, characterized by having: a conveying device that conveys alkaline tablets; and a print head that performs printing by ejecting ink from a nozzle on the alkaline tablets conveyed by the conveying device, The print head prints identification information of blue or colors including blue by ejecting the ink described in claim 1.