CN115521660A

CN115521660A - Ink, method for producing printed tablet using same, and tablet printing apparatus

Info

Publication number: CN115521660A
Application number: CN202210702323.XA
Authority: CN
Inventors: 小林达美; 浅见夏希
Original assignee: Shibaura Mechatronics Corp
Current assignee: Storas Holding Co; Shibaura Mechatronics Corp
Priority date: 2021-06-24
Filing date: 2022-06-21
Publication date: 2022-12-27
Anticipated expiration: 2042-06-21
Also published as: JP2023061947A; CN115521660B; TW202317713A; JP2023003827A; TW202409217A; KR20230000422A; TWI825795B

Abstract

The invention provides an ink suitable for printing alkaline tablets, a method for manufacturing printed tablets using the same, and a tablet printing apparatus. The ink according to the embodiment is an ink for ink jet for printing identification information on an alkaline tablet in blue or a color including blue, and includes at least edible blue No. 1 and shellac.

Description

Ink, method for producing printed tablet using same, and tablet printing apparatus

Technical Field

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

Background

By printing identification information such as characters and symbols on the tablets, the tablet identification is improved, and the prevention of dispensing mistakes by a dispensing engineer, the prevention of eating mistakes by a user, and the like is achieved.

As a method of printing the tablet, inkjet printing is exemplified. Since the tablet can be printed in a non-contact manner by printing using an ink jet method, for example, a tablet having a high possibility of disintegration such as an OD (oral Disintegrating tablet) can be suitably printed.

In such printing by an inkjet method, an ink containing a dye (dye ink) is sometimes used. The dye ink is more likely to develop color in printed characters or the like deeper than ink containing pigment, and thus the visibility of identification information is improved. Further, since the ink containing the pigment is in a state in which the pigment is dispersed in the solvent, the ink is poor in ejection property from the nozzle of the inkjet head, and ejection failure may be caused, resulting in printing failure. On the other hand, in the dye ink, since the dye is dissolved in the solvent, the ejection property from the nozzle of the inkjet head is easily ensured, and the printing failure can be suppressed.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2011-236279

Disclosure of Invention

[ problems to be solved by the invention ]

The invention aims to provide an ink suitable for printing alkaline tablets, a method for manufacturing printed tablets by using the ink and a tablet printing device.

[ means for solving problems ]

An ink according to an embodiment of the present invention is an ink for ink jet for printing identification information on an alkaline tablet, and includes: at least comprises edible blue No. 1 pigment, shellac, water and ethanol.

In the method for producing a tablet according to an embodiment of the present invention, the ink is supplied to a print head that ejects the ink from a nozzle, and identification information is printed on the alkaline tablet with the ink according to the embodiment using the print head.

The tablet printing apparatus according to an embodiment of the present invention is characterized by comprising: a conveying device for conveying the alkaline tablets; and a printing head for performing printing by ejecting ink from nozzles to the alkaline tablet conveyed by the conveying device, wherein the printing head ejects the ink of the embodiment.

Detailed Description

In the ink jet printing, ink filled in an ink jet head is ejected from an opening located at a nozzle at the front end of the ink jet head. If the ink dries and adheres to the inside or periphery of the opening of the nozzle, and the shape of the opening is deformed or blocked, ejection failure may occur. Further, if the ink viscosity is high, the ink cannot be normally ejected from the nozzle, resulting in poor ejection. On the surface of a tablet to be printed, droplets of ink discharged from nozzles of an inkjet head land, and small printing dots (dots) formed by the landed droplets are combined to print characters, symbols, and the like by stippling. In this case, if there is a discharge failure, a print dot is not formed in the pattern of characters or symbols, the print looks blurred, or desired characters or symbols are not visible, resulting in a print failure.

Further, if the ink deposited on the surface of the tablet is hard to dry, the ink may peel off during transportation after printing or the like, or may adhere to another tablet, a transportation device, or the like, thereby causing contamination. Therefore, as the characteristics of an ink for ink jet used for tablet printing, it is necessary to have both ejection from a nozzle and drying after printing.

Some of the tablets contain an alkaline material or are coated with an alkaline component, and the surface (at least a portion to be printed) of the tablets exhibits alkalinity (hereinafter, simply referred to as "alkaline tablet"). It is known that when the alkaline tablet is printed using a dye ink, the printed characters or the like are discolored or bleeds with time depending on the dye.

In particular, in the blue ink, for example, when an alkaline tablet is printed with an ink containing edible blue No. 1 (brilliant blue FCF) which is generally widely used as a blue dye and stored in an environment of 40 degrees in temperature and 75% in humidity rh, the printed identification information changes to light purple within 1 to 2 days, and bleeding occurs. That is, since the color is changed to a color different from the color immediately after printing or a desired color (predetermined color), the impression is changed when, for example, a logo or illustration of a business including blue is printed. Further, when characters are printed, the characters become unclear due to the bleeding that occurs, and the visibility of the tablet is reduced.

Accordingly, the present inventors have invented an ink that can suitably print identification information on an alkaline tablet even when edible blue No. 1 is used as a coloring matter.

[ ink ]

The ink of the present embodiment will be explained. The ink of the present embodiment is an ink for inkjet, and particularly a blue ink suitable for printing on an alkaline tablet. The ink at least comprises edible blue No. 1 as a pigment and at least comprises shellac as a resin. Further, an emulsifier, a coloring agent, a preservative, and the like may be blended as necessary. In the production of the ink, it is preferable to use, as each composition, a composition which can be consumed, such as a composition approved by the japanese pharmacopoeia or food additive official books.

(pigments)

The ink of the present embodiment contains at least edible blue No. 1 (brilliant blue FCF) as a coloring matter. More preferably, the food additive further contains gardenia blue pigment in addition to the food additive blue No. 1.

The ink of the present embodiment may be edible blue No. 1 alone, or edible blue No. 1 and gardenia blue pigment alone, and further, by using not only edible blue No. 1 or gardenia blue pigment but also other pigments in combination, it is possible to adjust the color to a desired color, such as blue or including blue. The other coloring matter may be one or more selected from conventionally known synthetic edible coloring matters and natural edible coloring matters. The color including blue is, for example, a color including blue in a color component such as green or purple.

Examples of the synthetic edible pigment include tar-based pigments, natural pigment derivatives, natural synthetic pigments, and titanium dioxide, and examples of the 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., as natural pigment derivatives, copper chlorophyll, sodium copper chlorophyllin (sodium chlorophyllin), potassium norbixin (potassium norbixin), etc., as natural synthetic pigments, beta-carotene, riboflavin (riboflavin), etc., can be exemplified.

Examples of natural food colors include: plant carbon powder pigment, anthocyanin pigment, carotenoid pigment, quinone pigment, flavonoid (flavanoid) pigment, betaine pigment, monascus (monascus) pigment, and other pigments derived from natural substances. Examples of the anthocyanin-based coloring matter include: red radish pigment, red cabbage pigment, red rice pigment, elderberry (elderberry) pigment, cowberry fruit (cowberry) pigment, gooseberry (gooseberry) pigment, cranberry (cranberry) pigment, salmonberry (salmonon berry) pigment, perilla pigment, blackberry (thimbleberry) pigment, strawberry pigment, dark cherry pigment (dark cherry pigment), cherry pigment, hibiscus (hibiscus) pigment, american cowberry (huckleberry) pigment, grape fruit juice pigment, grape peel pigment, black currant (black currant) pigment, blackberry pigment, blueberry pigment, plum (plum) pigment, european cowberry (whitleberry) pigment, ebony berry (boysenberry) pigment, mulberry (mulberry) pigment, purple currant pigment, purple corn pigment, yam pigment, raspberry (raspberry) pigment, ruby (raspberry) pigment, sweet potato pigment, and other pigment. Examples of the carotenoid-based coloring matter include: annatto pigment, gardenia yellow pigment, and other carotenoid pigments. Examples of the quinone-based pigment include: cochineal pigment, radix Arnebiae pigment, lac pigment, and other quinone pigments. Examples of the flavonoid-based coloring matter include: safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of the betaine-based coloring matter include a betalain coloring matter. Examples of monascus pigments include monascus pigment and monascus yellow pigment. Examples of the other pigments derived from natural substances include curcumin, gardenia red pigment, spirulina blue pigment, and the like.

The content of the coloring matter is preferably 0.1 to 10% by weight, and more preferably 0.5 to 8% by weight, based on the whole ink composition. If the content of the coloring matter is less than 0.1% by weight, the printed color becomes light and the visibility becomes poor. If the amount is more than 10% by weight, the ink viscosity increases, and the ink cannot be normally ejected, resulting in poor printing.

(resin)

By blending a resin component in the ink, the adhesiveness of the ink to the tablet can be improved, and since the ink is printed on the tablet and then dried to form a coating film, the scratch resistance can be obtained. In the ink of the present embodiment, shellac is used as the resin. Shellac is a resin obtained by purifying a resinous substance secreted by shellac, and is a mixture of various resinates, waxes, pigments and the like. When the shellac is blended into an ink, it is preferable to use white shellac obtained by bleaching shellac or purified shellac obtained by removing pigments or waxes. Further, by blending shellac in the ink, the viscosity of the ink can be increased, and the viscosity can be adjusted to be suitable for ejection from the nozzle using the inkjet head.

The content of shellac is preferably 0.5 to 10 wt%, more preferably 1 to 8 wt%, based on the whole ink composition. When the shellac content is less than 0.5 wt%, when the alkaline tablet is printed and stored in an environment of 40 degrees in temperature and 75% rh, the printed identification information changes color to light purple within 1 to 2 days, and bleeding occurs. If the amount is more than 10% by weight, the ink viscosity increases, and the ink cannot be normally ejected, resulting in poor printing.

(pH adjusting agent)

It is known that shellac is dissolved in an alkaline aqueous solution in addition to alcohols, and that shellac can be maintained in a dissolved state without precipitation by making the ink alkaline. The pH adjuster is preferably a substance approved as a food additive. In order to obtain water resistance after printing of the ink containing shellac, a component that volatilizes when the ink is dried is preferred, and for example, ammonium carbonate or ammonium bicarbonate can be used. The pH of the ink is preferably 6.5 to 10.

(ethanol)

The ethanol is preferably fermented ethyl alcohol or policosanol (sugar alcohol) which is naturally brewed, or the like. The content of ethanol is preferably 5 to 60 wt%, more preferably 10 to 40 wt%, based on the entire ink composition. If the content of ethanol is less than 5% by weight, the drying property of the ink is poor, and for example, since it takes 3 seconds or more after printing to dry, the ink peels off during transportation after printing or the like, or adheres to another tablet, a transportation device, or the like, and stains. 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 the surface of the tablet is not wet and spread, it is difficult to dry the tablet, and since the contact area with the surface of the tablet is small, the adhesion is small, and the tablet peels off even after 24 hours of wiping, for example. If the amount is more than 60% by weight, the ink dries and adheres to the inside or around the opening of the ink jet nozzle, and the opening is closed, resulting in poor ejection or poor printing due to deviation in the flying direction of the ejected ink.

(Water-soluble high-boiling organic solvent)

The water-soluble high-boiling organic solvent is used for preventing the nozzle of the ink jet head from drying. The water-soluble high-boiling organic solvent may be at least one selected from propylene glycol and glycerin, for example. The content of the water-soluble high-boiling organic solvent is preferably 1 to 60 wt%, more preferably 2 to 55 wt%, based on the entire ink composition. If the water-soluble high-boiling organic solvent is less than 1% by weight, the ink in the inkjet nozzle dries, resulting in poor printing. If the amount is more than 60% by weight, the ink viscosity increases, and the ink cannot be normally ejected, resulting in poor printing.

(emulsifiers)

The emulsifier can be selected from one or more of lecithin, glycerin fatty acid ester, sucrose fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester, which have higher water solubility than the above-mentioned emulsifiers. The emulsifier may not necessarily be blended, but the content of the emulsifier in blending is preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, based on the whole composition of the ink. If the content is less than 0.01 wt%, the surface tension of the ink becomes large, and an appropriate meniscus state may not be formed at the nozzle opening, and therefore, the ink is not ejected from the nozzle, or the ink does not land on a predetermined position even if ejected, and a printing failure may occur. When the amount is more than 5% by weight, the ink may be thickened or precipitates may be formed with the lapse of time, so that the nozzles may be clogged, or a printing failure may occur.

(production of ink)

Next, the present embodiment will be specifically described with reference to examples and comparative examples shown in table 1. However, these examples are only examples and are not intended to limit the scope of the present invention.

Examples 1 to 3, comparative example 1 and comparative example 2 were prepared in the formulation ratios shown in table 1 for each composition shown in table 1. The formulation ratios shown in table 1 are each expressed by weight percentage of the entire composition of the ink. Examples 1 to 3 are inks containing edible blue color No. 1 and shellac. Comparative example 1 is an ink (containing no shellac) containing food blue No. 1 as a coloring agent, and comparative example 2 is an ink containing gardenia blue as a coloring agent.

In comparative example 1, since shellac was not contained, the viscosity was adjusted to an appropriate value when printing was performed by an inkjet head by increasing the proportion of propylene glycol. In comparative example 2, gardenia blue pigment was dissolved, and therefore, the proportion of purified water was high and the proportion of ethanol was low as compared with the other examples and comparative examples.

The operation of the modulation is as follows. First, all the components shown in table 1 except the dye were dissolved by heating to 50 ℃ and stirring. After the components were dissolved, the colorants shown in Table 1 were mixed and further stirred at 50 ℃ for 1 hour. Thereafter, the mixture was allowed to stand for 1 hour, cooled to room temperature, and then filtered to prepare an ink.

The mixed pigment may be in the form of a powder, 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. Finally, the pigments may be dissolved or mixed homogeneously.

[ Table 1]

(evaluation of ink)

The inks of examples 1 to 3, comparative example 1 and comparative example 2 thus prepared were evaluated for ejection from the nozzles using an inkjet head. Further, characters were printed on the tablets to be printed, and the light fastness of the print and the stability of the print over time were evaluated (each evaluation method will be described later). In each evaluation, an OD sheet containing magnesium oxide as a main component, which is one of the alkaline tablets, was used as a printing target. The results are shown in Table 1.

< evaluation of ejection from nozzle >

Regarding the ejection property from the nozzles, the inkjet head was filled with ink, left for 15 minutes, and then a printing test was performed to visually confirm the presence or absence of a printing failure.

Good component: each printed dot may be formed at a specified location.

X: the printed dots are defective, or (/ and) the printed dots are not landed at the predetermined positions.

< evaluation of light resistance of printed characters >

The light resistance of the print was such that after printing the tablets, they were exposed to light at 1000 lux (lux) for 50 days in an unpackaged state, and whether the print faded or not was visually confirmed.

Good: fading was not observed in the printed image.

X: the printed characters became faded.

< evaluation of printing stability with time >

Regarding the temporal stability of printing, the printed tablets were stored at 40 ℃ and 75% RH for two weeks, and the presence or absence of bleeding of characters and the presence or absence of color change were visually confirmed as compared with those immediately after printing.

Good: no color bleeding and no discoloration.

And (delta): slightly discolored to a color different from the desired color. Or (/ and) color bleeding to the extent that the visibility of the printed matter is not problematic.

X: the color change is a color different from the desired color. Or (/ and) print bleeding, which is difficult to read.

(results)

As is clear from the experimental results of examples 1 to 3 shown in table 1, the ink containing edible blue No. 1 as a coloring matter and shellac as a resin is excellent in the light fastness and the moisture resistance of printed matter when used for printing on alkaline tablets. Further, an ink prepared by blending not only edible blue No. 1 but also gardenia blue pigment as a pigment is particularly preferable. The results are described in more detail below.

< example 1 >

The ink of example 1 contained edible blue No. 1 as a pigment, and shellac as a resin. The ink of example 1 was filled in an ink jet head and printing was performed, so that each print dot was formed at a predetermined position. In the evaluation of light fastness, the color ratio of the print printed on the alkaline tablet was unchanged from that immediately after printing. In the evaluation of the stability over time, the blue color was slightly pale and slight bleeding was observed, but the color was not visually problematic.

< example 2 >

The ink of example 2 contains not only the food blue No. 1 but also gardenia blue pigment as a pigment, and shellac as a resin. The ink of example 2 was filled in an ink jet head and printing was performed, so that each print dot was formed at a predetermined position. In the evaluation of light fastness, the color ratio of the print printed on the alkaline tablet was unchanged from the color ratio immediately after printing. In the evaluation of the stability with time, no discoloration or bleeding was observed with time, and the print could be read well.

< example 3 >

The ink of example 3 also contained not only the food blue No. 1 but also gardenia blue pigment as a coloring matter, as in example 2. The ink of example 3 was filled in an ink jet head and printing was performed, so that each print dot was formed at a predetermined position. In the evaluation of light fastness, the color ratio of the print printed on the alkaline tablet was unchanged from the color ratio immediately after printing. In the evaluation of the stability with time, no discoloration or bleeding was observed with time, and the print could be read well.

< comparative example 1 >

The ink of comparative example 1 contains edible blue No. 1 as a coloring matter and does not contain a resin component. The ink of comparative example 1 was filled in an ink jet head and printing was performed, so that each print dot was formed at a predetermined position. In the evaluation of light fastness, the color ratio of the print printed on the alkaline tablet was unchanged from that immediately after printing. However, in the evaluation of the stability with time, the printed matter was discolored to pale purple in about 1 to 2 days. Further, bleeding of the print occurs, and the print becomes difficult to read.

< comparative example 2 >

The ink of comparative example 2 contains gardenia blue pigment as a coloring matter and does not contain a resin component. Natural pigments such as gardenia pigment are required to be blended in large amounts in order to obtain a sufficient concentration for printing. In the ink of comparative example 1, gardenia pigment was blended in an amount sufficient for visually recognizing printed characters, and as a result, the viscosity of the ink was increased and the ejection property from the nozzle was deteriorated. In the composition shown in comparative example 2, the blue color was also lighter in density than in example 1. In the evaluation of light fastness, fading of the printed matter occurred, and the printed matter almost disappeared. In the evaluation of the stability over time, no bleeding or discoloration of the printed matter was observed.

(Collection)

From the above results, when printing is performed by the ink jet method, the ejection property from the nozzle is stabilized by the ink containing the edible blue color No. 1 and the shellac, and the occurrence of printing defects can be suppressed. Further, the ink has high light resistance and high stability with time, and can suppress discoloration of printed identification information. In addition, bleeding of the print can be suppressed. Therefore, after printing, the identification information can be easily recognized even after the tablets are stored, and thus, dispensing errors or eating errors can be prevented.

The ink containing shellac is also excellent in light resistance and stability with time as compared with the ink containing no resin component. This is because the pigment of edible blue No. 1 is less susceptible to decomposition by alkali of the alkaline tablet or the like because shellac is blended and the printed ink is dried to form a coating film on the tablet. Further, since shellac is a resin having an acid, it is considered that shellac exerts a neutralizing effect with an alkaline tablet and thus the influence of alkali on pigment can be suppressed to a small extent. Edible blue No. 1 is a pigment which is generally widely used and also has excellent color development, but is not suitable for use when an alkaline tablet is printed because of its low stability with time. On the other hand, by blending shellac, edible blue No. 1 can be applied to printing of alkaline tablets.

In addition, in ink jet inks for printing on tablets, many of the inks containing shellac have been inks with a high ethanol content (for example, about 60 wt% based on the entire ink composition). If the content of ethanol is high, the printing failure may be caused as described above. If the shellac is dissolved in an alkaline aqueous solution and the solvent of the ink is adjusted to be alkaline using the pH adjuster, for example, an ink in which the shellac is dissolved can be prepared even if the content of ethanol is suppressed.

Further, it is more preferable to blend not only the edible blue No. 1 but also gardenia blue pigment as a coloring matter. By blending both the edible blue No. 1 and the gardenia blue pigment, the stability of the ink over time can be further improved as compared with the case where the pigment is the edible blue No. 1 alone. This is clear by comparing the results of example 1 with those of example 2 and example 3, and by comparing the results of comparative example 1 with those of comparative example 2, it is also found that the ink containing gardenia blue pigment is excellent in stability with time. That is, it is considered that the temporal stability can be compensated by blending not only the edible blue No. 1 but also the gardenia blue pigment.

[ tablet printing apparatus ]

When the identification information is printed on the tablet, a tablet printing apparatus may be used. The tablet printing apparatus includes a conveying device and an inkjet print head. The conveying device is, for example, a suction conveying device that conveys the tablets while holding the tablets by suction. The printing head is arranged to face the conveying surface of the conveying device, and ink is ejected from the nozzle toward the tablet passing below the printing head to print the identification information on the tablet. By supplying the ink prepared by blending at least the edible blue 1 and shellac described above to the print head of the tablet printing apparatus and printing the conveyed alkaline tablet, identification information of blue or a color including blue can be printed on the alkaline tablet.

[ other embodiments ]

Additives such as a perfume, a preservative (bacteriostatic agent), a defoaming agent, and a surfactant may be added to the ink as needed. Of course, when the printing object is a drug, a food, or the like, these may be selected as edible substances. In addition, when each composition of the ink is mixed, pretreatment such as heating or post-treatment may be performed.

For the stirring in the preparation of the 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, aluminum lakes, and the like may be blended in the ink. In the preparation of pigment-formulated inks, a pigment dispersion treatment is required. The dispersion treatment is not particularly limited as long as it is a commonly used dispersing machine. Specific examples thereof include a ball mill, a roll mill, a sand mill, and a bead mill.

The method of filtering the ink is not particularly limited, and centrifugal filtration, filter filtration, or the like can be used.

The tablet may be a tablet used for medical use, dietary use, cleaning use, industrial use, or aromatic use, as long as at least the portion to be printed is alkaline. As tablets, there are, for example, sugar-coated tablets, enteric-coated tablets, gelatin-coated tablets, multilayer tablets, core tablets and the like, in addition to the above-mentioned bare tablets (uncoated tablets) or film-coated tablets (film-coated tablets), and various capsule tablets such as hard capsules or soft capsules may be included in the tablets. Further, the shape of the tablet may be various shapes such as a disk shape, a lens shape, a triangular shape, and an oval shape. When the tablet to be printed is used for medical use or food and drink use, the ink used is preferably edible, but needless to say, it may be inedible.

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

Claims

1. An ink for ink jet printing for printing identification information on an alkaline tablet, comprising:

at least comprises edible blue No. 1 pigment;

shellac;

water; and

and (3) ethanol.

2. The ink according to claim 1, further comprising gardenia blue pigment as the pigment.

3. The ink according to claim 2, wherein the pigment is only the food blue No. 1 and the gardenia blue pigment.

4. The ink of claim 1, wherein the shellac is present in an amount of 0.5 to 10 wt.%.

5. The ink according to claim 1, further comprising a pH adjuster,

the pH regulator is ammonium carbonate or ammonium bicarbonate.

6. The ink according to any one of claims 1 to 5, wherein the content of the pigment is 0.1 to 10% by weight.

7. The ink according to any one of claims 1 to 5, wherein the alkaline tablet is a tablet containing magnesium oxide as a main component.

8. The ink according to claim 6, wherein the alkaline tablet is a tablet containing magnesium oxide as a main component.

9. A process for producing a printed tablet, characterized by supplying the ink according to any one of claims 1 to 8 to a printing head for ejecting the ink from a nozzle,

using the print head, identification information of blue or a color including blue is printed on the alkaline tablet with the ink.

10. A sheet printing apparatus, comprising:

a conveying device for conveying the alkaline tablets; and

a print head for printing by ejecting ink from nozzles onto the alkaline tablet conveyed by the conveying device,

the print head prints identification information of blue or a color including blue by ejecting the ink according to any one of claims 1 to 8.