Inkjet ink set for tablets, mixed inkjet ink for tablets and tablet prints

Abstract

An object of the present disclosure is to provide an inkjet ink set for tablets, a series of inkjet inks for tablets, a mixed inkjet ink for tablets, and tablet prints that maintain excellent printing stability, have excellent lightfastness regardless of the type of dye used in combination, and are capable of reproducing a wide color gamut. [Solution] The inkjet ink set for tablets according to this embodiment comprises a plurality of inkjet inks for tablets, each containing an edible dye and water and ethanol as a solvent, each containing a different type of dye, at least one of which contains reduced isomaltulose as a discoloration inhibitor, and the ratio (F / D) of the content F [wt%] of the discoloration inhibitor in the inkjet ink for tablets containing the discoloration inhibitor to the content D [wt%] of the dye is within the range of 0.2 or more and 30.0 or less.

Description

[Technical Field]

[0001] The present disclosure relates to an inkjet ink set for tablets. , tablets This invention relates to a mixed inkjet ink for pharmaceuticals and tablet prints. [Background technology]

[0002] Among inkjet inks for tablets (hereinafter also referred to simply as "inkjet inks"), which are inkjet inks for printing on tablets, there are some that are edible by using food dyes as coloring materials (see, for example, Patent Document 1). When printing on tablets using the inkjet ink, there is a demand for inks of various colors to improve visibility, distinguishability, and the like.

[0003] However, even if inkjet inks according to the prior art can reproduce a desired color tone by combining dyes, depending on the type of dyes combined, the lightfastness may be reduced even when an additive effective in improving lightfastness is added, and the printed image may be prone to discoloration. As a result, some inkjet inks according to the prior art have insufficient visibility, distinguishability, etc. Furthermore, with inkjet inks according to conventional technology, even when toning is performed by combining three types of dyes—blue, red, and yellow—some colors cannot be reproduced depending on the type of dye selected, making it difficult to print designs with excellent design. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6389506 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, there have been few inkjet inks according to conventional techniques that maintain excellent printing stability, have excellent lightfastness regardless of the type of dye combined, and are capable of reproducing a wide color gamut. The present inventors have found that in order to improve the above-mentioned performance of the inkjet ink, it is necessary to set the ratio of the content of the discoloration inhibitor to the content of the dye in the inkjet ink within a specific range.

[0006] The present disclosure has been made in consideration of these points, and aims to provide an inkjet ink set for tablets, a series of inkjet inks for tablets, a mixed inkjet ink for tablets, and tablet prints that are excellent in lightfastness regardless of the type of dyes combined, while maintaining excellent printing stability, and are capable of reproducing a wide color gamut. [Means for solving the problem]

[0007] In order to achieve the above object, an inkjet ink set for tablets according to one embodiment of the present disclosure comprises a plurality of inkjet inks for tablets, each containing an edible dye and water and ethanol as a solvent, each of which is different in type of dye, at least one of which contains reduced isomaltulose as a discoloration inhibitor, and the ratio (F / D) of the content F [wt%] of the discoloration inhibitor in the inkjet ink for tablets containing the discoloration inhibitor to the content D [wt%] of the dye is within the range of 0.2 or more and 30.0 or less.

[0008] In order to achieve the above object, an inkjet ink set for tablets according to one embodiment of the present disclosure comprises a first inkjet ink for tablets, a second inkjet ink for tablets, a third inkjet ink for tablets, and a fourth inkjet ink for tablets, wherein the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink each comprise an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor, and the first inkjet ink for tablets contains only Blue No. 1 as the dye, and the second inkjet ink for tablets contains only Blue No. 1 as the dye. The ink contains only Yellow No. 4 as the dye, the third ink-jet ink for tablets contains only Red No. 102 as the dye, and the fourth ink-jet ink for tablets contains only Red No. 106 as the dye, and in all of the first ink-jet ink for tablets, the second ink-jet ink for tablets, the third ink-jet ink for tablets, and the fourth ink-jet ink for tablets, the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is within the range of 2.0 or more and 30.0 or less, and the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is the same.

[0009] In order to achieve the above object, a series of inkjet inks for tablets according to one embodiment of the present disclosure comprises an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor, wherein the dye is only one of Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106, and the ratio (F / D) of the content F [wt%] of the discoloration inhibitor to the content D [wt%] of the dye is within the range of 2.0 or more and 30.0 or less.

[0010] In order to achieve the above object, a mixed inkjet ink for tablets according to one embodiment of the present disclosure contains the individual inkjet inks for tablets included in the inkjet ink set for tablets in any proportion.

[0011] In addition, in order to achieve the above object, a tablet printed matter according to one embodiment of the present disclosure has a printed portion printed using each of the tablet inkjet inks included in the tablet inkjet ink set.

[0012] In addition, in order to achieve the above object, a printed tablet product according to one embodiment of the present disclosure includes a printed portion printed using the above mixed inkjet ink for tablets. [Effects of the Invention]

[0013] According to one aspect of the present disclosure, it is possible to provide an inkjet ink set for tablets, a series of inkjet inks for tablets, a mixed inkjet ink for tablets, and tablet prints that are capable of maintaining excellent printing stability, exhibiting excellent lightfastness regardless of the types of dyes combined, and reproducing a wide color gamut, while maintaining excellent printing stability and regardless of the types of dyes combined. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are conceptual diagrams illustrating the permeability and lightfastness of an inkjet ink according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (plain tablet) according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (film-coated tablet) according to an embodiment of the present disclosure. [Figure 4] 1 is an example of a printed image of a tablet (plain tablet) according to an embodiment of the present disclosure. [Figure 5] 1 is an example of a printed image of a tablet (film-coated tablet) according to an embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates a color gamut reproducible by an inkjet ink according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] The inkjet ink set for tablets (hereinafter also simply referred to as "inkjet ink set") according to an embodiment of the present disclosure (hereinafter referred to as "the present embodiment") is capable of reproducing a wide color gamut and has excellent lightfastness regardless of the type of dyes used in combination, while maintaining excellent printing stability. Furthermore, the series of inkjet inks for tablets according to this embodiment (hereinafter also simply referred to as the "inkjet ink series") can maintain excellent printing stability, have excellent lightfastness regardless of the type of dye combined, and reproduce a wide color gamut. Furthermore, the mixed inkjet ink for tablets according to this embodiment (hereinafter also simply referred to as "mixed inkjet ink") has excellent lightfastness and can reproduce a wide color gamut, regardless of the type of dyes combined, while maintaining excellent printing stability.

[0016] A more preferred embodiment of the inkjet ink set according to this embodiment is a set (combination) of single-color inkjet inks that exhibit four colors: cyan, yellow, and two types of magenta (hereinafter, for convenience, also referred to as "first magenta" and "second magenta"). Each inkjet ink (each color) constituting the inkjet ink set contains an edible dye and water and ethanol as solvents. At least one of the inkjet inks (one color ink) constituting the inkjet ink set contains reduced isomaltulose as a fading inhibitor. The ratio (F / D) of the reduced isomaltulose content F [wt%] to the dye content D [wt%] in the inkjet ink containing reduced isomaltulose is in the range of 0.2 to 30.0.

[0017] Furthermore, it is preferable that the ratio (F / D) of the content F [wt %] of reduced isomaltulose to the content D [wt %] of dye in the inkjet ink containing reduced isomaltulose is in the range of 3.3 to 30.0. Furthermore, it is more preferable that the ratio (F / D) of the content F [wt%] of reduced isomaltulose to the content D [wt%] of dye in the inkjet ink containing reduced isomaltulose is in the range of 6.7 to 15.0. In this embodiment, the contents of water and ethanol, and reduced isomaltulose as a discoloration inhibitor in the inkjet ink may all be the same for each color. Furthermore, the components contained in the inkjet ink according to this embodiment other than the dye may all be the same for each color.

[0018] The inkjet ink series according to this embodiment contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a fading inhibitor. The inkjet ink series according to this embodiment contains only one of Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106 as the dye. The ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] in the inkjet ink series according to this embodiment is in the range of 2.0 to 30.0.

[0019] In this embodiment, the contents of water and ethanol, and reduced isomaltulose as a discoloration inhibitor in the inkjet ink may all be the same for each color. Furthermore, the components contained in the inkjet ink according to this embodiment other than the dye may all be the same for each color. The mixed inkjet ink according to this embodiment is an inkjet ink in which the color tone is adjusted by mixing the individual inkjet inks constituting the inkjet ink set described above in any desired ratio.

[0020] Furthermore, the present disclosure proposes and provides a new design concept for reproducing a wide color gamut in the technical field of inkjet inks containing edible dyes. This point will be explained below. Many conventional design concepts focus on the combination of the three pigments mentioned above - blue, red, and yellow - and expand the color gamut that can be reproduced by adjusting the amount of these pigments mixed.

[0021] In response to this, the present inventors have newly discovered that in order to reproduce a wider color gamut, it is important to use a combination of single-color inkjet inks that exhibit four colors, for example, cyan, yellow, and two types of magenta. In this way, the design concept of this disclosure is significantly different from conventional design concepts that focused only on adjusting the components of three-color dye inks, and instead expands the reproducible color gamut by adjusting the components while also focusing on the types and physical properties of the dyes to be combined.

[0022] The configurations of the inkjet ink sets, inkjet ink series, and inkjet ink mixtures of single colors according to the embodiments of the present invention will be described in detail below. Also, the configuration of a tablet (printed tablet) having a printed portion printed with inkjet inks constituting an inkjet ink set or inkjet ink series, or mixed inkjet inks, will be described in detail.

[0023] [Configuration of Inkjet Ink Set] The inkjet ink set according to this embodiment includes a plurality of inkjet inks each containing an edible dye (food colorant) and water and ethanol as solvents, each containing a different type of dye. Specifically, the inkjet ink set according to this embodiment includes a plurality of single-color inkjet inks each containing an edible dye and water and ethanol as solvents, each having a different color tone. Furthermore, at least one of the plurality of inkjet inks contains reduced isomaltulose as a fading inhibitor, and the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] in the inkjet ink containing the fading inhibitor is within the range of 0.2 to 30.0. With this configuration, excellent printing stability is maintained, and it is possible to achieve excellent lightfastness and reproduce a wide color gamut regardless of the type of dye used. The lightfastness of the single-color inkjet ink according to this embodiment will now be described with reference to FIG.

[0024] 1 is a conceptual diagram illustrating the relationship between ink adhesion and light resistance on the surface of a printed material (solid preparation). Here, for example, a tablet with a film-coated portion with few voids, i.e., a film-coated (FC) tablet, is used as the solid preparation. However, the present disclosure is not limited to this, and plain tablets or capsule tablets may also be used as the printed material. 1(a) to 1(c) are schematic cross-sectional views of a tablet (here, a film-coated tablet) in the thickness direction after printing inkjet inks A to C, each with a different composition, on the tablet and allowing a certain period of time to pass. In this example, inkjet ink A is an ink that uses edible dye 4 as the coloring material and water and ethanol as the solvent. An example of dye 4 is Blue No. 1.

[0025] Inkjet ink B is an ink obtained by adding a specific sugar as a fading inhibitor to inkjet ink A. Here, the sugar added to inkjet ink B as a fading inhibitor is, for example, maltose. Inkjet ink C is an ink obtained by adding reduced isomaltulose as a fading inhibitor to inkjet ink A. Specifically, Fig. 1(a) is a schematic cross-sectional view of a tablet in the thickness direction after ink-jet ink A containing dye 4 as a colorant and water and ethanol as a solvent is printed on the surface 1S of a tablet substrate 1 and a certain time (e.g., 140 hours) has elapsed. Fig. 1(b) is a schematic cross-sectional view of a tablet in the thickness direction after ink-jet ink B is printed on the surface 1S of a tablet substrate 1 and a certain time (e.g., 140 hours) has elapsed. Fig. 1(c) is a schematic cross-sectional view of a tablet in the thickness direction after ink-jet ink C is printed on the surface 1S of a tablet substrate 1 and a certain time (e.g., 140 hours) has elapsed.

[0026] First, the presence or absence of the addition of sugars as a discoloration inhibitor in inkjet inks and the permeability of dyes will be described using inkjet inks A and B as examples. Among the various coloring materials used in inkjet inks, for example, tar-based dyes used as food dyes can cause discoloration of characters and images printed on the surface of solid preparations. For example, among tar-based dyes, Blue No. 1 has caused discoloration of printed images due to penetration into solid preparations over time and photodecomposition. In response to this, a method is known in which sugars, which act as discoloration inhibitors, are added to inkjet inks to inhibit the penetration of dyes into solid preparations and prevent discoloration of printed images.

[0027] As shown in FIG. 1(a), when inkjet ink A, which does not contain sugars that function as fading inhibitors, is printed, dye 4 penetrates into the tablet substrate 1 after a certain time has passed since printing. Here, the penetration depth of dye 4 in inkjet ink A after the certain time has passed is defined as penetration depth X (μm). In contrast, as shown in FIG. 1(b), when inkjet ink B, which contains sugars that function as fading inhibitors, is printed, the penetration depth Y (μm) of inkjet ink B becomes smaller than the penetration depth X of inkjet ink A after a certain time has passed since printing (X>Y).

[0028] In inkjet ink B, the addition of a specific sugar that functions as a discoloration inhibitor increases the viscosity of the ink, thereby inhibiting the penetration of dye 4 into the tablet substrate 1. Therefore, when inkjet ink B is printed, dye 4 remains near the surface 1S within the tablet substrate 1 even after a certain time has passed since printing. In other words, inkjet inks containing a specific sugar that functions as a discoloration inhibitor can inhibit discoloration of printed images due to the penetration of dyes (e.g., Blue No. 1) compared to inks that do not contain a sugar that functions as a discoloration inhibitor.

[0029] As described above, the inkjet ink according to this embodiment adheres to the surface of a substrate by selecting the type and amount of the added discoloration inhibitor and solvent, thereby sufficiently suppressing light-induced discoloration of the printed image and improving lightfastness. The inventors have discovered that adhering the ink to the surface of a substrate (e.g., a tablet) is effective in suppressing light-induced discoloration of the printed image. In this example, by adhering the ink to the surface 1S of the tablet, the dye 4 adheres to the surface 1S, and as a result, the dye 4 can remain at a high concentration on the surface 1S.

[0030] When the concentration of dye 4 on the surface 1S of the tablet substrate 1 is high, for example, the proportion of dye 4 on the surface 1S that undergoes photodiscoloration due to photodecomposition is reduced. In other words, even if some of the dye 4 undergoes photodiscoloration, the impact is limited, and a decrease in the visibility (readability) of the printed image is suppressed. This maintains the visibility of the printed image as a whole, and as a result, photodiscoloration of the printed image can be sufficiently suppressed. Therefore, the lightfastness of the inkjet ink can be improved. The inventors have also discovered that certain sugars, such as maltose and reduced isomaltulose, function as fixing agents that fix ink containing a dye as a colorant to the surface of a printed substrate.

[0031] Specifically, the inkjet ink according to this embodiment contains a food dye as a colorant, reduced isomaltulose, a sugar that functions as a discoloration inhibitor, and water and ethanol that function as solvents. Furthermore, the ratio (F / D) of the reduced isomaltulose content F [wt%] to the food dye content D [wt%] is within the range of 0.2 to 30.0. This configuration allows the ink containing the dye used as a colorant to adhere to the surface of the printed material, allowing the dye to remain on the surface at a high concentration. This allows the inkjet ink according to this embodiment to adequately suppress light-induced discoloration of printed images and improve lightfastness.

[0032] As shown in FIG. 1( c), when inkjet ink C, which is a more preferred embodiment of the inkjet ink according to this embodiment, is printed on the surface 1S of a tablet substrate 1, dye 4 (here, Blue No. 1) in the ink is fixed to the surface 1S. Specifically, when inkjet ink C is printed, the penetration depth Z (μm) of dye 4 after a certain time has elapsed since printing is further reduced compared to the penetration depth Y of dye 4 in inkjet ink B containing a specific sugar (Y>Z). For example, the penetration depth Z of dye 4 in inkjet ink C is reduced to approximately 50% of the penetration depth Y of dye 4 in inkjet ink B. In other words, inkjet ink C can further suppress the penetration of dye 4. As a result, dye 4 remains at a high concentration on the surface 1S, suppressing the decrease in visibility of the printed image as described above. As a result, when inkjet ink C is used, light discoloration of the printed image is sufficiently suppressed, and inkjet ink C can improve lightfastness.

[0033] On the other hand, although inkjet ink B can cause dye 4 to remain near the surface 1S inside the base material 1 of the tablet, it does not sufficiently suppress the penetration of dye 4 compared to inkjet ink C, and is unable to fix the ink to the surface 1S. In other words, since the concentration of dye 4 remaining on the surface 1S is low with inkjet ink B, it is unable to suppress light discoloration of the printed image compared to inkjet ink C, and tends to be inferior to inkjet ink C in that it is difficult to improve (improve) lightfastness. In this way, the inkjet ink according to this embodiment contains reduced isomaltulose as a discoloration inhibitor, which significantly inhibits the penetration of the dye into the interior of the printed substrate and fixes the ink to the surface of the printed substrate. As a result, the inkjet ink according to this embodiment can inhibit discoloration due to light in the printed image, improving lightfastness, and further inhibiting discoloration of the printed image due to the penetration of the dye into the interior of the printed substrate.

[0034] Furthermore, as shown in FIG. 1(c), the inkjet ink C can be adhered to the surface 1S of the tablet substrate 1 in a slightly raised manner. As a result, when the inkjet ink C is printed, for example, the print appears to stand out thickly on the surface 1S. Therefore, compared to inkjet inks A and B, for example, the inkjet ink C can improve the visibility of the printed image at the time of printing. In other words, the inkjet ink according to this embodiment not only reduces the decrease in visibility due to light discoloration of the printed image, but also imparts good visibility to the printed image at the time of printing.

[0035] The light resistance of the inkjet ink according to this embodiment will be described in detail below. The inkjet ink according to this embodiment may have a color difference ΔE of 20 or less according to JIS Z 8781 before and after a lightfastness test. Here, the lightfastness test is, for example, a test in which a printed image printed using the inkjet ink according to this embodiment is compared for color difference ΔE (compliant with JIS Z 8781), which indicates the amount of change in chromaticity and optical color density, before and after irradiation with visible light. Specifically, the color difference ΔE is measured before and after irradiation of the printed image with a cumulative visible light of 1.2 million lux, and the values ​​are compared. For example, a xenon weather meter (Toyo Seiki Seisakusho Ci4000) is used for visible light irradiation. The printed image used in the lightfastness test is, for example, a solid print on a tablet (e.g., a film-coated tablet) that is the printing target.

[0036] Sufficient lightfastness required for forming printed images on medical tablets, etc., often refers to a color difference ΔE of 20 or less between printed images before and after exposure to visible light in a lightfastness test in which visible light is irradiated at 1.2 million lux. The inventors and others have determined that a color difference ΔE of 20 or less is the criterion for sufficient lightfastness based on opinion tests conducted by the present inventors and involving various medical professionals. When the color difference ΔE exceeds 20, it is recognized that the visibility of the printed image (e.g., the readability of the printed characters) is reduced. In other words, if the color difference ΔE before and after exposure to visible light is 20 or less, it can be said that the inkjet ink has sufficient suppression of light-induced discoloration and excellent lightfastness. Note that this number is larger than the standard color difference ΔE of 3 to 6 for general commercial printed materials. However, this number was obtained because tablets are not usually compared before and after exposure to light, and it is assumed that the printed image on the tablet surface will naturally fade.

[0037] The reason why reduced isomaltulose is used as a fixing agent in the inkjet ink according to this embodiment is that if a fixing agent other than reduced isomaltulose (for example, maltose) is added, the dye on the tablet surface is not sufficiently fixed to the surface of the printed substrate, and when the above-mentioned lightfastness test is performed on a solid printed image, the color difference ΔE may exceed 20. By adding reduced isomaltulose as a fixing agent, the dye on the tablet surface is sufficiently fixed to the surface of the printed substrate, so that the color difference ΔE before and after the lightfastness test falls below 20, and excellent lightfastness is imparted to the inkjet ink.

[0038] Hereinafter, each component constituting the inkjet ink set and inkjet ink series according to this embodiment will be described. (colorant) As described above, each of the inkjet inks (each color) constituting the inkjet ink set according to this embodiment and each of the inkjet inks (each color) constituting the inkjet ink series according to this embodiment each contain a food dye (an edible dye). The content of the food dye is preferably in the range of 0.5% by mass or more and 5.0% by mass or less, based on the total mass of the ink. This configuration can impart good visibility to the printed image and high intermittent resumability (i.e., excellent print quality). Furthermore, when the content of the food dye is within the above range, the addition of reduced isomaltulose, which serves as a fixing agent (fading inhibitor), ensures that the food dye remains at a high concentration on the surface of the printed material, thereby suppressing light-induced discoloration of the printed image and improving the lightfastness of the individual inkjet inks according to this embodiment.

[0039] On the other hand, if the food dye content is less than 0.5% by mass, the overall print color tends to be lighter and the visibility of the printed image tends to decrease.Furthermore, if the food dye content is less than 0.5% by mass, the lightfastness may decrease or may not be exhibited even if reduced isomaltulose, which is a fixing agent (fading inhibitor), is added. Furthermore, if the content of food dye exceeds 5.0% by mass, the dissolution stability of the coloring material will deteriorate, causing the pigment in the ink to precipitate or sediment as a solid, which may cause the nozzles of the inkjet head to clog during printing, resulting in a decrease in so-called print quality (especially intermittent restartability). The lower limit of the food dye content in each inkjet ink is preferably 1.0% by mass or more, and more preferably 1.5% by mass or more, relative to the total mass of the ink, and the upper limit of the food dye content in each inkjet ink is preferably 4.0% by mass or less, and more preferably 3.0% by mass or less, relative to the total mass of the ink.

[0040] Furthermore, each inkjet ink preferably contains only one food dye selected from, for example, azo dyes, triphenylmethane dyes, and xanthene dyes. Examples of azo dyes include Red No. 102 (New Coccine, CAS number: 2611-82-7, E number: E124) and Yellow No. 4 (Tartrazine, CAS number: 1934-21-0, E number: E102). Furthermore, examples of triphenylmethane dyes include Blue No. 1 (Brilliant Blue FCF, CAS number: 3844-45-9, E number: E133). Furthermore, examples of xanthene dyes include Red No. 106 (Acid Red 52, CAS number: 3520-42-1). Each inkjet ink (each color) constituting the inkjet ink series according to this embodiment contains only one food dye selected from Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106.

[0041] Specifically, among the inkjet inks constituting the inkjet ink set according to this embodiment, the cyan ink (first inkjet ink for tablets) may be in a form containing only Blue No. 1. Furthermore, in a form containing only Blue No. 1 as the food dye, it is preferable that the amount of Blue No. 1 added to the entire inkjet ink is in the range of 0.5% by mass to 5.0% by mass. Furthermore, among the inkjet inks constituting the inkjet ink set according to this embodiment, the yellow ink (second inkjet ink for tablets) may be in a form containing only Yellow No. 4. Furthermore, in a form containing only Yellow No. 4 as the food dye, it is preferable that the amount of Yellow No. 4 added to the entire inkjet ink is in the range of 0.5% by mass to 5.0% by mass.

[0042] Furthermore, among the inkjet inks constituting the inkjet ink set according to this embodiment, the first magenta ink (third inkjet ink for tablets) may be in a form containing only Red No. 102. Furthermore, in a form containing only Red No. 102 as the food dye, it is preferable that the amount of Red No. 102 added to the entire inkjet ink is in the range of 0.5% by mass to 5.0% by mass. Furthermore, of the inkjet inks constituting the inkjet ink set according to this embodiment, the second magenta ink (fourth inkjet ink for tablets) may be in a form containing only Red No. 106. Furthermore, in a form containing only Red No. 106 as the food dye, it is preferable that the amount of Red No. 106 added to the entire inkjet ink is in the range of 0.5% by mass to 5.0% by mass.

[0043] Furthermore, in all of the cyan ink, yellow ink, first magenta ink, and second magenta ink, the ratio (F / D) of the content F [wt%] of the reduced isomaltulose, which is a fading inhibitor, to the content D [wt%] of each of the above-mentioned dyes may be within the range of 0.2 or more and 30.0 or less, and the ratio (F / D) of the content F [wt%] of the reduced isomaltulose, which is a fading inhibitor, to the content D [wt%] of each of the above-mentioned dyes may be the same. It should be noted that the colorants that can be added to the individual inkjet inks according to this embodiment are not limited to the food dyes described above. In addition to the food dyes described above, the individual inkjet inks according to this embodiment can also be added with, for example, a colorant appropriately selected from conventionally known synthetic food colorants and natural food colorants.

[0044] Examples of synthetic food dyes include tar-based dyes, natural dye derivatives, and natural synthetic dyes. Examples of tar-based dyes include Food Blue No. 1, Food Red No. 2, Food Red No. 3, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow No. 4, Food Yellow No. 5, Food Blue No. 2, Food Red No. 2 Aluminum Lake, Food Red No. 3 Aluminum Lake, Food Red No. 40 Aluminum Lake, Food Yellow No. 4 Aluminum Lake, Food No. 5 Aluminum Lake, Food Blue No. 1 Aluminum Lake, and Food Blue No. 2 Aluminum Lake. Examples of natural dye derivatives include norbixin potassium. Examples of natural synthetic dyes include β-carotene and riboflavin.

[0045] Examples of natural food dyes include anthocyanin dyes, carotenoid dyes, quinone dyes, chlorophyll dyes, flavonoid dyes, betaine dyes, monascus dyes, and other dyes derived from natural sources. Examples of anthocyanin dyes include red radish dye, red cabbage dye, red rice dye, elderberry dye, cowberry dye, gooseberry dye, cranberry dye, salmonberry dye, perilla dye, sweet blueberry dye, strawberry dye, dark sweet cherry dye, cherry dye, hibiscus dye, huckleberry dye, grape juice dye, grape skin dye, blackcurrant dye, blackberry dye, blueberry dye, plum dye, watermelon dye, boysenberry dye, mulberry dye, purple sweet potato dye, purple corn dye, purple yam dye, raspberry dye, redcurrant dye, loganberry dye, and other anthocyanin dyes. Examples of carotenoid pigments include annatto pigment, gardenia yellow, and other carotenoid pigments. Examples of quinone pigments include cochineal pigment, lithospermum root pigment, lac pigment, and other quinone pigments. Examples of flavonoid pigments include safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of betaine pigments include beet red pigment. Examples of monascus pigments include monascus pigment and monascus yellow pigment. Examples of pigments derived from other natural products include turmeric pigment, Clerodendron japonicum pigment, gardenia red pigment, and spirulina blue pigment.

[0046] (adhesive) As described above, at least one inkjet ink in the inkjet ink set according to this embodiment contains a fixing agent for fixing the ink containing the food dye to the surface of a substrate. In the inkjet ink according to this embodiment, this fixing agent functions as a discoloration inhibitor. Specifically, the fixing agent contained in the inkjet ink according to this embodiment is reduced isomaltulose. When the fixing agent is reduced isomaltulose, it can be added to the inkjet ink together with a solvent having the component composition described below to fix the ink containing the food dye to the surface of a substrate. This allows the inkjet ink according to this embodiment to sufficiently suppress photodiscoloration of printed images and improve lightfastness. Furthermore, reduced isomaltulose used as a fixing agent in this embodiment also has the function of suppressing decomposition (photodecomposition) of the inkjet ink due to light irradiation. Therefore, it is also possible to suppress the occurrence of photodiscoloration itself.

[0047] It is preferable that all of the inkjet inks constituting the inkjet ink set according to this embodiment contain reduced isomaltulose used as a fixing agent, and it is even more preferable that the content of reduced isomaltulose is the same. Furthermore, it is preferable that the ratio (F / D) of the reduced isomaltulose content F [wt%] to the food dye content D [wt%] be the same for all of the inkjet inks that make up the inkjet ink set according to this embodiment.

[0048] It is also preferable that all of the inkjet inks constituting the inkjet ink series according to this embodiment contain reduced isomaltulose, which is used as a fixing agent, and it is even more preferable that the content of reduced isomaltulose is the same. Furthermore, it is preferable that the ratio (F / D) of the reduced isomaltulose content F [wt%] to the food dye content D [wt%] be within the range of 0.2 or more and 30.0 or less, and be the same for all of the inkjet inks that make up the inkjet ink series according to this embodiment.

[0049] The blending ratio of reduced isomaltulose, which is the fixing agent in the inkjet ink according to this embodiment, that is, the content (mass) of reduced isomaltulose, is preferably within the range of 1.0 mass % to 15.0 mass % relative to the mass of the entire ink. If the blending ratio of reduced isomaltulose is less than 1.0% by mass of the total ink, the ink may not adhere well, and therefore, if the blending ratio of reduced isomaltulose is less than 1.0% by mass of the total ink, the lightfastness may be reduced or may not be exhibited at all.

[0050] Furthermore, if the proportion of reduced isomaltulose exceeds 15.0% by mass of the total ink, the ink viscosity may increase and the solubility stability of the reduced isomaltulose may deteriorate, causing the reduced isomaltulose in the ink to precipitate or sediment as a solid, which may cause the nozzles of the inkjet head to clog during printing and reduce intermittent restartability. The lower limit of the content of reduced isomaltulose is preferably 5.0% by mass or more, and even more preferably 7.5% by mass or more, relative to the total mass of the ink, and the upper limit of the content of reduced isomaltulose is preferably 12.5% ​​by mass or less, and even more preferably 10.0% by mass or less, relative to the total mass of the ink.

[0051] (solvent) The inkjet ink according to this embodiment contains, in addition to the food dye and reduced isomaltulose, a solvent (dispersion medium) for dissolving (dispersing) the food dye and reduced isomaltulose. The inkjet ink according to this embodiment contains water (e.g., purified water) and ethanol as solvents. Generally, reduced isomaltulose has the property of being difficult to dissolve in alcohols. Therefore, in this embodiment, the inclusion of ethanol in the solvent reduces the solubility of the reduced isomaltulose used as a fixing agent in the solvent. Therefore, in this embodiment, by adding a solvent containing the above-mentioned alcohol (ethanol) together with reduced isomaltulose as a fixing agent to the inkjet ink, the ink fixing effect is reliably exhibited, allowing the food dye contained in the ink to remain at a higher concentration on the surface of the printed object (e.g., a tablet). As a result, the inkjet ink according to this embodiment can sufficiently suppress light discoloration of printed images and improve lightfastness. Furthermore, since ethanol is highly volatile, it can improve the transfer resistance (drying property) of the inkjet ink.

[0052] While the blending ratio of each component of the above solvent in the inkjet ink according to this embodiment is not limited, the blending ratio of ethanol, i.e., the amount of ethanol added, is preferably in the range of 1.0% by mass to 10.0% by mass of the total mass of the ink. This ensures a reduction in the solubility of reduced isomaltulose in the solvent, further improving the fixation effect of the ink containing food dyes. This allows the inkjet ink to have better lightfastness.

[0053] If the amount of ethanol added is less than 1.0% by mass, the effect of reducing the solubility of reduced isomaltulose in the solvent may be reduced. If the amount of ethanol added exceeds 10.0% by mass, reduced isomaltulose may precipitate, resulting in a reduction in the ink fixing effect. In addition, the ink may dry out in the inkjet nozzle, causing clogging of the inkjet head nozzle during printing and reducing intermittent restartability. The lower limit of the amount of ethanol added is preferably 2.5% by mass or more, and more preferably 4.0% by mass or more, relative to the total mass of the ink, and the upper limit of the amount of ethanol added is preferably 8.0% by mass or less, and more preferably 7.0% by mass or less, relative to the total mass of the ink.

[0054] Furthermore, at least one inkjet ink of the inkjet ink set according to this embodiment may contain propylene glycol as a solvent, which functions as a humectant, preventing the ink from drying out in the inkjet nozzles and providing the ink with sufficient intermittent resumability. When the solvent contains propylene glycol, the blending ratio of the propylene glycol, i.e., the amount of propylene glycol added, is preferably within the range of 40.0% by mass or less relative to the total mass of the ink. This configuration allows printing without impairing the drying properties of the ink, and further improves the fixing effect of ink containing food dyes. This allows the inkjet ink to have better lightfastness. Furthermore, if the amount of propylene glycol added exceeds 40.0% by mass, the drying time of the printed surface on the tablet surface will be delayed, and when printed tablets come into contact with each other, the undried ink may adhere to the other tablet, causing smudges and other problems (poor transfer).

[0055] It is also preferable that all of the inkjet inks constituting the inkjet ink set according to this embodiment contain propylene glycol as a solvent, and it is even more preferable that the amount of propylene glycol added is greater than the amount of ethanol added as a solvent. It is also preferable that all of the inkjet inks constituting the inkjet ink series according to this embodiment contain propylene glycol as a solvent, and it is even more preferable that the amount of propylene glycol added is greater than the amount of ethanol added as a solvent.

[0056] The inkjet ink according to this embodiment may further contain at least one of glycerin and isopropyl alcohol as a solvent. Specifically, the solvent may further contain either glycerin or isopropyl alcohol, or may further contain both glycerin and isopropyl alcohol. Glycerin functions as a humectant, similar to the above-mentioned propylene glycol. Furthermore, isopropyl alcohol, like the above-mentioned ethanol, is highly volatile and can therefore improve the transfer resistance (drying property) of the inkjet ink.

[0057] (internal resin) The inkjet ink according to this embodiment may contain an internal resin in addition to the dyes and solvents described above. The internal resin that can be added to the inkjet ink according to this embodiment may be an edible, water-soluble resin-like substance in the form of a powder, paste, or flake, and may be a substance that can form a coating on the surface of a tablet by drying after printing. Examples of the internal resin include polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), high-molecular-weight polyethylene glycols (PEGs) such as polyethylene glycol 4000 / polyethylene glycol 1540, shellac resin, methacrylic acid copolymer (product name: Eudragit S100), maltodextrin, and erythritol.

[0058] (Leveling agent) The inkjet ink according to this embodiment may contain a leveling agent in addition to the above-mentioned dyes, solvents, or internal resins. The leveling agent that can be added to the inkjet ink according to this embodiment may be an edible, water-soluble surfactant. Examples of the leveling agent include polyglycerin fatty acid esters (e.g., Decaglycerin Distearate Q-182S and Decaglycerin Monolaurate Q-12S, both manufactured by Taiyo Kagaku Co., Ltd.), sorbitan fatty acid esters (e.g., NIKKOL SL-10, manufactured by Nikko Chemicals Co., Ltd.), sucrose fatty acid esters (e.g., DK Ester F-110, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and polysorbates (Emersol S-120 series, manufactured by Kao Corporation).

[0059] [Printing method] The inkjet ink according to this embodiment is not particularly limited in terms of printing method, and can be printed using inkjet devices such as commercially available inkjet printers. Therefore, the inkjet ink according to this embodiment has a wide range of applications and is extremely useful. For example, the inkjet ink according to this embodiment can be printed using a drop-on-demand inkjet device that uses a piezoelectric element (piezoelectric ceramic) as an actuator, and can also be printed using other types of inkjet device.

[0060] Examples of drop-on-demand inkjet devices include devices that employ a thermal inkjet system in which inkjet ink is ejected using the water vapor pressure generated by momentarily raising the temperature of a micro-heating element (200 to 300°C), electrostatic type devices that eject inkjet ink by electrostatically vibrating an actuator, and ultrasonic type devices that utilize the cavitation phenomenon of ultrasonic waves. Furthermore, if the inkjet ink according to this embodiment has charging properties, it is also possible to use a device that employs a continuous ejection system.

[0061] More specifically, in this embodiment, the inkjet inks of each color, such as cyan, yellow, first magenta, and second magenta, constituting the inkjet ink set according to this embodiment may be printed using the inkjet device described above to obtain a printed product (tablet print) of a desired color tone. In other words, in this embodiment, the inkjet inks of each single color constituting the inkjet ink set according to this embodiment may be printed in any desired ratio and mixed to obtain a printed product (tablet print) of a desired color tone.

[0062] In addition, in this embodiment, the inkjet inks of each color, such as cyan, yellow, first magenta, and second magenta, constituting the inkjet ink set according to this embodiment may be mixed in any ratio to achieve a desired color tone, and then the toned inkjet inks (i.e., mixed inkjet inks) may be printed using the inkjet device described above to obtain a printed matter (tablet printed matter) of the desired color tone. The printed matter (tablet printed matter) according to this embodiment printed in this manner can have a wider reproducible color gamut than the printed matter (tablet printed matter) printed using inkjet ink according to the prior art. This point will be explained below with reference to the drawings.

[0063] FIG. 6 shows the color gamut that can be reproduced using the inkjet inks that make up the inkjet ink set according to this embodiment. As shown in FIG. 6, by using an inkjet ink set comprising cyan containing Blue No. 1, yellow containing Yellow No. 4, and a second magenta containing Red No. 106, which is a preferred embodiment of the inkjet ink set according to this embodiment, it is possible to effectively reproduce the color tones of the "first extended color gamut X," a color gamut that was difficult to reproduce using inkjet inks according to conventional technology.

[0064] Furthermore, as shown in Figure 6, by using an inkjet ink set that is a preferred embodiment of the inkjet ink set according to this embodiment, which is composed of cyan containing Blue No. 1, yellow containing Yellow No. 4, and first magenta containing Red No. 102, it is possible to effectively reproduce the color tones of the "second expanded color gamut Y," a color gamut that was difficult to reproduce using inkjet inks according to conventional technology. In FIG. 6, the color gamut that can be reproduced even with inkjet ink according to conventional technology is indicated as "conventional color gamut Z."

[0065] 〔tablet〕 In this embodiment, the inkjet ink according to this embodiment may be printed or imaged on the surface of, for example, a tablet using the printing method described above. In other words, the tablet according to this embodiment may have a printed portion, i.e., a printed image, printed using the inkjet ink according to this embodiment. The inkjet ink according to this embodiment can improve the light resistance of a printed image applied using an inkjet printing method to the surface of a medical tablet, for example. The following describes the configuration of a tablet having a printed image printed with the inkjet ink according to this embodiment. The tablet according to this embodiment is, for example, a medical tablet. Here, the term "medical tablet" refers to, for example, plain tablets (plain tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, as well as film-coated tablets in which a water-soluble surface layer is formed on the outermost surface of the tablet.

[0066] Fig. 2 is a schematic cross-sectional view showing an example of a printed (lettered or image-printed) medical tablet (plain tablet). Fig. 2 shows, in cross-section, a printed matter 5 of a plain tablet in which a printed image 3 such as letters is printed on the upper surface of a base material 1 of the tablet. Fig. 3 is a schematic cross-sectional view showing an example of a medical tablet (film-coated tablet) on which printing (printing of letters, images) has been performed. Fig. 3 shows, in cross-section, a film-coated tablet printed matter 9 in which a printed image 3 such as letters is printed on the upper surface of a substrate 1 of a tablet on the surface of which a film coating layer 7 has been formed. In this embodiment, as shown in FIG. 4, a solid image may be printed as the plain tablet print image 11, and as shown in FIG. 5, a two-dimensional barcode may be printed as the film-coated tablet print image 13.

[0067] The active ingredient contained in the medical tablet is not particularly limited, and examples thereof include, but are not limited to, substances effective in the prevention and treatment of various diseases (e.g., substances having sleep-inducing activity, tranquilizing activity, antibacterial activity, antihypertensive activity, antianginal activity, analgesic activity, anti-inflammatory activity, tranquilizing activity, antidiabetic activity, diuretic activity, anticholinergic activity, anti-hyperacidity activity, antiepileptic activity, ACE inhibitory activity, β-receptor antagonist or agonist activity, anesthetic activity, appetite suppressant activity, antiarrhythmic activity, antidepressant activity, anticoagulant activity, antidiarrheal activity, antihistamine activity, antimalarial activity, antitumor activity, immunosuppressant activity, antiparkinsonian activity, antipsychotic activity, antiplatelet activity, antihyperlipidemic activity, etc.), substances having a cleansing effect, fragrances, substances having a deodorizing effect, etc.

[0068] The tablet according to this embodiment can be formulated with an acceptable carrier for the intended use along with the active ingredient, if necessary. For example, a medical tablet can be formulated with a pharmaceutically acceptable carrier. As the pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as pharmaceutical ingredients can be used, and for example, excipients, lubricants, binders, disintegrants, thickeners, etc. can be formulated in appropriate amounts. In addition, additives such as preservatives, antioxidants, colorants, and sweeteners can also be used as necessary.

[0069] In this embodiment, medical tablets have been described as an example of tablets, but the present disclosure is not limited to this. There are no particular limitations on the objects to be printed with the inkjet ink according to this embodiment, and printing may be performed on the surface of various tablets, such as tablets to be administered to animals other than humans (pets, livestock, poultry, etc.), feed, fertilizer, cleaning agents, tablet candies such as Ramune candy, and food supplements. Furthermore, there are no particular limitations on the size of the objects to be printed with the inkjet ink according to this embodiment, and the inkjet ink according to this embodiment can be applied to tablets of various sizes.

[0070] (Effects of this embodiment) (1) The inkjet ink set according to this embodiment comprises a plurality of inkjet inks each containing an edible dye and water and ethanol as a solvent, each containing a different type of dye, at least one of which contains reduced isomaltulose as a fading inhibitor, and the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] in the inkjet ink containing the fading inhibitor is in the range of 0.2 or more and 30.0 or less. With this configuration, compared to conventional techniques, excellent printing stability is maintained, lightfastness is excellent regardless of the type of dyes combined, and a wide color gamut can be reproduced.

[0071] (2) In the inkjet ink set according to this embodiment, at least one of the plurality of inkjet inks for tablets may contain propylene glycol as a humectant. With this configuration, printing stability can be further improved.

[0072] (3) Furthermore, the inkjet ink set according to this embodiment may have a discoloration inhibitor content in the range of 1.0 wt % to 15.0 wt %. With this configuration, light resistance can be further improved.

[0073] (4) Furthermore, the inkjet ink set according to this embodiment may have a dye content in the range of 0.5 wt % to 5.0 wt %, and an ethanol content in the range of 1.0 wt % to 10.0 wt %. With this configuration, it is possible to further improve print quality (particularly intermittent restartability) without impairing the light resistance-improving effect of the discoloration inhibitor.

[0074] (5) Furthermore, each of the inkjet inks constituting the inkjet ink set according to this embodiment may contain only one dye selected from the group consisting of azo dyes, triphenylmethane dyes, and xanthene dyes. With this configuration, a wide color gamut can be easily reproduced.

[0075] (6) In addition, in the inkjet ink set according to this embodiment, the azo dye to be added may be Red No. 102 or Yellow No. 4, the triphenylmethane dye to be added may be Blue No. 1, and the xanthene dye to be added may be Red No. 106. With this configuration, a wide color gamut can be easily reproduced.

[0076] (7) Furthermore, all of the inkjet inks constituting the inkjet ink set according to this embodiment may contain a fading inhibitor, and the content F [wt%] of the fading inhibitor may be the same in all of the inkjet inks, or the ratio (F / D) of the content F [wt%] of the fading inhibitor to the dye content D [wt%] may be the same in all of the inkjet inks. With this configuration, when printing is performed using the inkjet ink set according to this embodiment, the content of the fading inhibitor F remains constant regardless of the printing method, whether the inks of the ink set are mixed in any desired ratio beforehand or any desired color is expressed by overprinting the same location on the substrate. This makes it possible to easily reproduce a wide color gamut, and the lightfastness-improving effect of the fading inhibitor is also exhibited within that color gamut.

[0077] (8) Furthermore, the inkjet ink set according to this embodiment includes a cyan ink, a yellow ink, a first magenta ink, and a second magenta ink, each of which contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor, and the cyan ink contains only Blue No. 1 as a dye, and the yellow ink contains only Yellow No. 4 as a dye, and The first magenta ink contains only Red No. 102 as a dye, and the second magenta ink contains only Red No. 106 as a dye, and in all of the cyan ink, yellow ink, first magenta ink, and second magenta ink, the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] is within the range of 2.0 or more and 30.0 or less, and the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] may be the same. With this configuration, compared to conventional techniques, excellent printing stability is maintained, lightfastness is excellent regardless of the type of dyes combined, and a wide color gamut can be reproduced.

[0078] (9) Furthermore, in the inkjet ink set according to this embodiment, the content of Blue No. 1 in the cyan ink may be in the range of 0.5 wt% to 5.0 wt%, the content of Yellow No. 4 in the yellow ink may be in the range of 0.5 wt% to 5.0 wt%, the content of Red No. 102 in the first magenta ink may be in the range of 0.5 wt% to 5.0 wt%, and the content of Red No. 106 in the second magenta ink may be in the range of 0.5 wt% to 5.0 wt%. With this configuration, sufficient visibility can be maintained and a wide color gamut can be easily reproduced.

[0079] (10) Furthermore, the cyan ink, yellow ink, first magenta ink, and second magenta ink constituting the inkjet ink set according to this embodiment may each further contain propylene glycol as a humectant. Such a configuration improves printing stability and makes it easier to reproduce a wide color gamut.

[0080] (11) Furthermore, the inkjet ink series according to this embodiment contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor, and the dye is only one of Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106, and the ratio (F / D) of the discoloration inhibitor content F [wt%] to the dye content D [wt%] is within the range of 2.0 to 30.0. With this configuration, compared to conventional techniques, excellent printing stability is maintained, lightfastness is excellent regardless of the type of dyes combined, and a wide color gamut can be reproduced.

[0081] (12) Furthermore, the mixed inkjet ink according to this embodiment contains the individual inkjet inks contained in the inkjet ink set described above in any desired ratio. With this configuration, compared to conventional techniques, excellent printing stability is maintained, lightfastness is excellent regardless of the type of dyes combined, and a wide color gamut can be reproduced.

[0082] (13) The tablet according to this embodiment has a printed portion printed using each of the inkjet inks for tablets included in the inkjet ink set described above. Compared to the prior art, this configuration can sufficiently suppress light discoloration of the printed image 3, etc. printed directly on the surface of the tablet, etc., and can sufficiently improve the light resistance of the printed image 3. Furthermore, it can also impart edibility to the printed image portion printed on the surface of the tablet.

[0083] (14) The tablet according to this embodiment has a printed portion printed using the mixed inkjet ink described above. Compared to the prior art, this configuration can sufficiently suppress light discoloration of the printed image 3, etc. printed directly on the surface of the tablet, etc., and can sufficiently improve the light resistance of the printed image 3. Furthermore, it can also impart edibility to the printed image portion printed on the surface of the tablet.

[0084] [Example] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way. <Examples 1 to 44 and Comparative Examples 1 to 11> The procedures for preparing the inkjet inks in Examples 1 to 44 and Comparative Examples 1 to 11 will be described below.

[0085] (Inkjet ink manufacturing) First, a printing ink was prepared. The inkjet ink contains a pigment (food dye), a solvent, and a discoloration inhibitor in the amounts described below. The preparation procedure was as follows: first, the discoloration inhibitor was added to the solvent to obtain a transparent base liquid; then, the pigment was added to the transparent base liquid. In this way, the ink according to this example was prepared. The various components will be specifically described below. In this example, purified water (ion-exchanged water), propylene glycol (PG), and ethanol were used as solvents as needed. Specifically, propylene glycol (PG) and ethanol were added to purified water and stirred thoroughly to obtain a solvent (mixed solvent). A discoloration inhibitor was added to the solvent as needed, and the mixture was stirred for about an hour to obtain a transparent base liquid. Food dyes such as Blue No. 1, Red No. 3, Red No. 102, and Yellow No. 4 were added as needed to the transparent base liquid to obtain the inkjet inks of Examples 1 to 44 and Comparative Examples 1 to 11.

[0086] <Sample #1 (Comparative Example 1)> In the inkjet ink of Sample #1 (Comparative Example 1), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, and the blending ratio of propylene glycol (PG) was 28.0% by mass. The inkjet ink of Sample #1 (Comparative Example 1) does not contain any of the fading inhibitors, reduced isomaltulose or tripotassium citrate. In this way, an inkjet ink of Sample #1 (Comparative Example 1) was obtained.

[0087] <Sample #2 (Comparative Example 2)> In the inkjet ink of Sample #2 (Comparative Example 2), the blending ratio of the pigment Red No. 3 was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, and the blending ratio of propylene glycol (PG) was 28.0% by mass. The inkjet ink of Sample #2 (Comparative Example 2) does not contain any of the fading inhibitors, reduced isomaltulose or tripotassium citrate. In this way, an inkjet ink of Sample #2 (Comparative Example 2) was obtained.

[0088] <Sample #3 (Comparative Example 3)> In the inkjet ink of Sample #3 (Comparative Example 3), the blending ratio of the pigment Red No. 102 was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, and the blending ratio of propylene glycol (PG) was 28.0% by mass. The inkjet ink of Sample #3 (Comparative Example 3) does not contain any of the fading inhibitors, reduced isomaltulose or tripotassium citrate. In this way, an inkjet ink of Sample #3 (Comparative Example 3) was obtained.

[0089] <Sample #4 (Comparative Example 4)> In the inkjet ink of Sample #4 (Comparative Example 4), the blending ratio of the pigment Red No. 106 was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, and the blending ratio of propylene glycol (PG) was 28.0% by mass. The inkjet ink of Sample #4 (Comparative Example 4) does not contain any of the fading inhibitors, reduced isomaltulose or tripotassium citrate. In this way, an inkjet ink of Sample #4 (Comparative Example 4) was obtained.

[0090] <Sample #5 (Comparative Example 5)> In the inkjet ink of Sample #5 (Comparative Example 5), the blending ratio of the pigment Yellow No. 4 was 1.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, and the blending ratio of propylene glycol (PG) was 28.0% by mass. The inkjet ink of Sample #5 (Comparative Example 5) does not contain any of the fading inhibitors, reduced isomaltulose or tripotassium citrate. In this way, an inkjet ink of Sample #5 (Comparative Example 5) was obtained.

[0091] <Sample #6 (Example 1)> In the total inkjet ink of Sample #6 (Example 1), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 54.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #6 (Example 1) was obtained.

[0092] <Sample #7 (Comparative Example 6)> In the inkjet ink of Sample #7 (Comparative Example 6), the blending ratio of the pigment Red No. 3 was 1.5% by mass, the blending ratio of purified water among the solvents was 54.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #7 (Comparative Example 6) was obtained.

[0093] <Sample #8 (Example 2)> In the total inkjet ink of Sample #8 (Example 2), the blending ratio of the pigment Red No. 102 was 1.5% by mass, the blending ratio of purified water among the solvents was 35.5% by mass, the blending ratio of ethanol was 25.0% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #8 (Example 2) was obtained.

[0094] <Sample #9 (Example 3)> In the total inkjet ink of Sample #9 (Example 3), the blending ratio of the pigment Red No. 106 was 1.5% by mass, the blending ratio of purified water among the solvents was 54.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #9 (Example 3) was obtained.

[0095] <Sample #10 (Example 4)> In the total inkjet ink of Sample #10 (Example 4), the blending ratio of the pigment Yellow No. 4 was 1.5% by mass, the blending ratio of purified water among the solvents was 54.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #10 (Example 4) was obtained.

[0096] <Sample #11 (Comparative Example 7)> In the inkjet ink of Sample #11 (Comparative Example 7), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of tripotassium citrate, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample #11 (Comparative Example 7) was obtained.

[0097] <Sample #12 (Comparative Example 8)> In the inkjet ink of Sample #12 (Comparative Example 8), the blending ratio of the pigment Red No. 3 was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of tripotassium citrate, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample #12 (Comparative Example 8) was obtained.

[0098] <Sample #13 (Comparative Example 9)> In the inkjet ink of Sample #13 (Comparative Example 9), the blending ratio of the pigment Red No. 102 was 1.5% by mass, the blending ratio of purified water among the solvents was 40.5% by mass, the blending ratio of ethanol was 25.0% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of tripotassium citrate, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample #13 (Comparative Example 9) was obtained.

[0099] <Sample #14 (Comparative Example 10)> In the inkjet ink of Sample #14 (Comparative Example 10), the blending ratio of the pigment Red No. 106 was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of tripotassium citrate, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample #14 (Comparative Example 10) was obtained.

[0100] <Sample #15 (Comparative Example 11)> In the inkjet ink of Sample #15 (Comparative Example 11), the blending ratio of the pigment Yellow No. 4 was 1.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of tripotassium citrate, a discoloration inhibitor, was 5.0% by mass. In this way, an inkjet ink of Sample #15 (Comparative Example 11) was obtained.

[0101] <Sample #16 (Example 5)> In the total inkjet ink of Sample #16 (Example 5), the blending ratio of the pigment Blue No. 1 was 0.5% by mass, the blending ratio of purified water among the solvents was 64.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 1.0% by mass. In this way, the inkjet ink of Sample #16 (Example 5) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #16 (Example 5) was 2.0.

[0102] <Sample #17 (Example 6)> In the total inkjet ink of Sample #17 (Example 6), the blending ratio of the pigment Blue No. 1 was 0.5% by mass, the blending ratio of purified water among the solvents was 60.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 5.0% by mass. In this way, the inkjet ink of Sample #17 (Example 6) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #17 (Example 6) was 10.0.

[0103] <Sample #18 (Example 7)> In the total inkjet ink of Sample #18 (Example 7), the blending ratio of the pigment Blue No. 1 was 0.5% by mass, the blending ratio of purified water among the solvents was 55.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #18 (Example 7) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #18 (Example 7) was 20.0.

[0104] <Sample #19 (Example 8)> In the total inkjet ink of Sample #19 (Example 8), the blending ratio of the pigment Blue No. 1 was 0.5% by mass, the blending ratio of purified water among the solvents was 50.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 15.0% by mass. In this way, the inkjet ink of Sample #19 (Example 8) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #19 (Example 8) was 30.0.

[0105] <Sample #20 (Example 9)> In the total inkjet ink of Sample #20 (Example 9), the blending ratio of the pigment Blue No. 1 was 1.0% by mass, the blending ratio of purified water among the solvents was 63.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 1.0% by mass. In this way, the inkjet ink of Sample #20 (Example 9) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #20 (Example 9) was 1.0.

[0106] <Sample #21 (Example 10)> In the inkjet ink of Sample #21 (Example 10), the blending ratio of the pigment Blue No. 1 was 1.0% by mass, the blending ratio of purified water among the solvents was 59.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 5.0% by mass. In this way, the inkjet ink of Sample #21 (Example 10) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #21 (Example 10) was 5.0.

[0107] <Sample #22 (Example 11)> In the total inkjet ink of Sample #22 (Example 11), the blending ratio of the pigment Blue No. 1 was 1.0 mass%, the blending ratio of purified water among the solvents was 54.5 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0 mass%. In this way, the inkjet ink of Sample #22 (Example 11) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #22 (Example 11) was 10.0.

[0108] <Sample #23 (Example 12)> In the inkjet ink of Sample #23 (Example 12), the blending ratio of the pigment Blue No. 1 was 1.0% by mass, the blending ratio of purified water among the solvents was 49.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 15.0% by mass. In this way, the inkjet ink of Sample #23 (Example 12) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #23 (Example 12) was 15.0.

[0109] <Sample #24 (Example 13)> In the inkjet ink of Sample #24 (Example 13), the blending ratio of the dye Blue No. 1 was 3.0% by mass, the blending ratio of purified water among the solvents was 61.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 1.0% by mass. In this way, an inkjet ink of Sample #24 (Example 13) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #24 (Example 13) was 0.3.

[0110] <Sample #25 (Example 14)> In the total inkjet ink of Sample #25 (Example 14), the blending ratio of the pigment Blue No. 1 was 3.0% by mass, the blending ratio of purified water among the solvents was 39.0% by mass, the blending ratio of ethanol was 25.0% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 5.0% by mass. In this way, an ink-jet ink of Sample #25 (Example 14) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #25 (Example 14) was 1.7.

[0111] <Sample #26 (Example 15)> In the inkjet ink of Sample #26 (Example 15), the blending ratio of the pigment Blue No. 1 was 3.0% by mass, the blending ratio of purified water among the solvents was 52.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, the inkjet ink of Sample #26 (Example 15) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #26 (Example 15) was 3.3.

[0112] <Sample #27 (Example 16)> In the total inkjet ink of Sample #27 (Example 16), the blending ratio of the pigment Blue No. 1 was 3.0% by mass, the blending ratio of purified water among the solvents was 47.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 15.0% by mass. In this way, the inkjet ink of Sample #27 (Example 16) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #27 (Example 16) was 5.0.

[0113] <Sample #28 (Example 17)> In the total inkjet ink of Sample #28 (Example 17), the blending ratio of the pigment Blue No. 1 was 5.0% by mass, the blending ratio of purified water among the solvents was 59.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 1.0% by mass. In this way, an inkjet ink of Sample #28 (Example 17) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #28 (Example 17) was 0.2.

[0114] <Sample #29 (Example 18)> In the total inkjet ink of Sample #29 (Example 18), the blending ratio of the pigment Blue No. 1 was 5.0% by mass, the blending ratio of purified water among the solvents was 55.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 5.0% by mass. In this way, the inkjet ink of Sample #29 (Example 18) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #29 (Example 18) was 1.0.

[0115] <Sample #30 (Example 19)> In the total inkjet ink of Sample #30 (Example 19), the blending ratio of the pigment Blue No. 1 was 5.0% by mass, the blending ratio of purified water among the solvents was 50.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 10.0% by mass. In this way, an inkjet ink of Sample #30 (Example 19) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #30 (Example 19) was 2.0.

[0116] <Sample #31 (Example 20)> In the total inkjet ink of Sample #31 (Example 20), the blending ratio of the pigment Blue No. 1 was 5.0% by mass, the blending ratio of purified water among the solvents was 45.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 15.0% by mass. In this way, an ink-jet ink of Sample #31 (Example 20) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #31 (Example 20) was 3.0.

[0117] <Sample #32 (Example 21)> In the total inkjet ink of Sample #32 (Example 21), the blending ratio of the pigment Blue No. 1 was 1.5% by mass, the blending ratio of purified water among the solvents was 51.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #32 (Example 21) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #32 (Example 21) was 8.3.

[0118] <Sample #33 (Example 22)> In the entire inkjet ink of Sample #33 (Example 22), the blending ratio of Blue No. 1 among the pigments was 1.0 mass%, the blending ratio of Red No. 102 was 0.5 mass%, the blending ratio of purified water among the solvents was 52.0 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5 mass%. In this way, an ink-jet ink of Sample #33 (Example 22) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #33 (Example 22) was 8.3.

[0119] <Sample #34 (Example 23)> In the entire inkjet ink of Sample #34 (Example 23), the blending ratio of Blue No. 1 among the pigments was 0.75% by mass, the blending ratio of Red No. 102 was 0.75% by mass, the blending ratio of purified water among the solvents was 52.3% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #34 (Example 23) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #34 (Example 23) was 8.3.

[0120] <Sample #35 (Example 24)> In the entire inkjet ink of Sample #35 (Example 24), the blending ratio of Blue No. 1 among the pigments was 0.5% by mass, the blending ratio of Red No. 102 was 1.0% by mass, the blending ratio of purified water among the solvents was 52.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #35 (Example 24) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #35 (Example 24) was 8.3.

[0121] <Sample #36 (Example 25)> In the entire inkjet ink of Sample #36 (Example 25), the blending ratio of Blue No. 1 among the pigments was 1.0 mass%, the blending ratio of Red No. 106 was 0.5 mass%, the blending ratio of purified water among the solvents was 52.0 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5 mass%. In this way, an ink-jet ink of Sample #36 (Example 25) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #36 (Example 25) was 8.3.

[0122] <Sample #37 (Example 26)> In the entire inkjet ink of Sample #37 (Example 26), the blending ratio of Blue No. 1 among the pigments was 0.75% by mass, the blending ratio of Red No. 106 was 0.75% by mass, the blending ratio of purified water among the solvents was 52.3% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an inkjet ink of Sample #37 (Example 26) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #37 (Example 26) was 8.3.

[0123] <Sample #38 (Example 27)> In the entire inkjet ink of Sample #38 (Example 27), the blending ratio of Blue No. 1 among the pigments was 0.5% by mass, the blending ratio of Red No. 106 was 1.0% by mass, the blending ratio of purified water among the solvents was 52.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an inkjet ink of Sample #38 (Example 27) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #38 (Example 27) was 8.3.

[0124] <Sample #39 (Example 28)> In the total inkjet ink for Sample #39 (Example 28), the blending ratio of Blue No. 1 among the pigments was 1.0% by mass, the blending ratio of Yellow No. 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 52.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an inkjet ink of Sample #39 (Example 28) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #39 (Example 28) was 8.3.

[0125] <Sample #40 (Example 29)> In the total inkjet ink of Sample #40 (Example 29), the blending ratio of Blue No. 1 among the pigments was 0.75% by mass, the blending ratio of Yellow No. 4 was 0.75% by mass, the blending ratio of purified water among the solvents was 52.3% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #40 (Example 29) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #40 (Example 29) was 8.3.

[0126] <Sample #41 (Example 30)> In the total inkjet ink of Sample #41 (Example 30), the blending ratio of Blue No. 1 among the pigments was 0.5% by mass, the blending ratio of Yellow No. 4 was 1.0% by mass, the blending ratio of purified water among the solvents was 34.0% by mass, the blending ratio of ethanol was 25.0% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #41 (Example 30) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #41 (Example 30) was 8.3.

[0127] <Sample #42 (Example 31)> In the inkjet ink of Sample #42 (Example 31), the blending ratio of the pigment Red No. 102 was 1.5% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #42 (Example 31) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #42 (Example 31) was 8.3.

[0128] <Sample #43 (Example 32)> In the entire inkjet ink of Sample #43 (Example 32), the blending ratio of Red No. 102 among the pigments was 1.0 mass%, the blending ratio of Red No. 106 was 0.5 mass%, the blending ratio of purified water among the solvents was 53.0 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5 mass%. In this way, the inkjet ink of Sample #43 (Example 32) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #43 (Example 32) was 8.3.

[0129] <Sample #44 (Example 33)> In the entire inkjet ink of Sample #44 (Example 33), the blending ratio of Red No. 102 among the pigments was 0.75% by mass, the blending ratio of Red No. 106 was 0.75% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #44 (Example 33) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #44 (Example 33) was 8.3.

[0130] <Sample #45 (Example 34)> In the entire inkjet ink of Sample #45 (Example 34), the blending ratio of Red No. 102 among the pigments was 0.5% by mass, the blending ratio of Red No. 106 was 1.0% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #45 (Example 34) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #45 (Example 34) was 8.3.

[0131] <Sample #46 (Example 35)> In the entire inkjet ink of Sample #46 (Example 35), the blending ratio of Red No. 102 among the pigments was 1.0 mass%, the blending ratio of Yellow No. 4 was 0.5 mass%, the blending ratio of purified water among the solvents was 53.0 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5 mass%. In this way, the inkjet ink of Sample #46 (Example 35) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #46 (Example 35) was 8.3.

[0132] <Sample #47 (Example 36)> In the entire inkjet ink of Sample #47 (Example 36), the blending ratio of Red No. 102 among the pigments was 0.75% by mass, the blending ratio of Yellow No. 4 was 0.75% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #47 (Example 36) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #47 (Example 36) was 8.3.

[0133] <Sample #48 (Example 37)> In the entire inkjet ink of Sample #48 (Example 37), the blending ratio of Red No. 102 among the pigments was 0.5% by mass, the blending ratio of Yellow No. 4 was 1.0% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #48 (Example 37) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #48 (Example 37) was 8.3.

[0134] <Sample #49 (Example 38)> In the total inkjet ink of Sample #49 (Example 38), the blending ratio of the pigment Red No. 106 was 1.5% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #49 (Example 38) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #49 (Example 38) was 8.3.

[0135] <Sample #50 (Example 39)> In the entire inkjet ink of Sample #50 (Example 39), the blending ratio of Red No. 102 among the pigments was 1.0 mass%, the blending ratio of Yellow No. 4 was 0.5 mass%, the blending ratio of purified water among the solvents was 53.0 mass%, the blending ratio of ethanol was 6.5 mass%, the blending ratio of propylene glycol (PG) was 28.0 mass%, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5 mass%. In this way, an inkjet ink of Sample #50 (Example 39) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #50 (Example 39) was 8.3.

[0136] <Sample #51 (Example 40)> In the entire inkjet ink of Sample #51 (Example 40), the blending ratio of Red No. 106 among the pigments was 0.75% by mass, the blending ratio of Yellow No. 4 was 0.75% by mass, the blending ratio of purified water among the solvents was 34.5% by mass, the blending ratio of ethanol was 25.0% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an ink-jet ink of Sample #51 (Example 40) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #51 (Example 40) was 8.3.

[0137] <Sample #52 (Example 41)> In the entire inkjet ink of Sample #52 (Example 41), the blending ratio of Red No. 106 among the pigments was 0.5% by mass, the blending ratio of Yellow No. 4 was 1.0% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, the inkjet ink of Sample #52 (Example 41) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #52 (Example 41) was 8.3.

[0138] <Sample #53 (Example 42)> In the total inkjet ink of Sample #53 (Example 42), the blending ratio of the pigment Yellow No. 4 was 1.5% by mass, the blending ratio of purified water among the solvents was 53.0% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose as a discoloration inhibitor was 12.5% ​​by mass. In this way, an inkjet ink of Sample #53 (Example 42) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #53 (Example 42) was 8.3.

[0139] <Sample #54 (Example 43)> In the total inkjet ink of Sample #54 (Example 43), the blending ratio of Blue No. 1 among the pigments was 0.5% by mass, the blending ratio of Red No. 102 was 0.5% by mass, the blending ratio of Yellow No. 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 52.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an inkjet ink of Sample #54 (Example 43) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #54 (Example 43) was 8.3.

[0140] <Sample #55 (Example 44)> In the entire inkjet ink of Sample #55 (Example 44), the blending ratio of Blue No. 1 among the pigments was 0.5% by mass, the blending ratio of Red No. 106 was 0.5% by mass, the blending ratio of Yellow No. 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 52.5% by mass, the blending ratio of ethanol was 6.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and the blending ratio of reduced isomaltulose, which is a discoloration inhibitor, was 12.5% ​​by mass. In this way, an inkjet ink of Sample #55 (Example 44) was obtained. The mass ratio of reduced isomaltulose to dye in the inkjet ink of Sample #55 (Example 44) was 8.3.

[0141] The evaluation items and evaluation methods used in this example will be described below. (Printing stability: initial printability and continuous printability) The inkjet head used was a piezoelectric ceramic-driven drop-on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (the direction in which the recording medium, such as a tablet, is transported), and a total of 2,656 nozzles. Using the inkjet head, a test pattern was printed immediately after nozzle maintenance. The print status of the test pattern was then used to check the readability of the printed image due to the occurrence of non-ejection areas. The evaluation criteria were as follows: In this evaluation, "initial printability" refers to the printability immediately after the start of printing, and "continuous printability" refers to the printability 30 minutes after the start of printing. ○: When the gaps or bends in the lines are less than 5% of the total △: When the gaps or bends in the lines are less than 20% of the total ×: When the gaps or bends in the lines exceed 20% of the total If the initial printability and continuous printability were evaluated as "good" or "fair," there was no problem in use and the sheet was deemed to have passed.

[0142] (Printing stability: intermittent restartability) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a print resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (the direction in which tablets or other recording media are transported), and a total of 1,280 nozzles, the head was left to stand for a specified period of time (15 to 60 minutes) without flushing, and then a test pattern was printed with a print drop volume of 6 pL per drop, confirming that all nozzles were ejecting without any non-ejection. In Tables 1 to 4 below, the time during which ink could be ejected was measured as an evaluation result of intermittent printing performance (intermittent resumability and ejection stability). The evaluation criteria are as follows: 〇: 15 minutes or more but less than 30 minutes △: 5 minutes or more but less than 15 minutes ×: Less than 5 minutes If the result of the intermittent restartability (discharge stability) test was evaluated as "○" or "△", there was no problem in use and the ink was deemed to have passed.

[0143] (Lightfastness) The tablet prints of each Example and Comparative Example, whose chromaticity and optical color density had been measured, were irradiated with a cumulative 1.2 million lux of visible light using a photostability tester (Nagano Science LT-200A-14WC). The chromaticity and optical color density of the tablet prints irradiated with visible light were measured using a spectrophotometer, and the color difference ΔE (based on JIS Z 8781), which indicates the change in chromaticity and optical color density before and after visible light irradiation, was compared. Regarding the change in color before and after visible light irradiation, as described above, the inventors have concluded that if the color difference ΔE according to JIS Z 8781 is 20 or less (ΔE≦20), light discoloration is sufficiently suppressed and the ink has excellent lightfastness. Furthermore, they have concluded that if the color difference ΔE is 20 or less (ΔE≦20), the ink also has excellent readability. Therefore, if ΔE≦20, the inkjet ink is deemed to have excellent lightfastness and readability and is rated as passing in this evaluation. The evaluation criteria in the table are as follows: ◎:ΔE≦10 ○:ΔE≦15 △: ΔE≦20 ×:ΔE>20

[0144] (Initial color tone) Tablet prints were prepared by printing a round solid image with the ink of each example and each comparative example, and the chromaticity and optical color density were measured using an X-rite spectrodensitometer "eXact2" (L*a*b* color system). The viewing angle was set to 2° and the light source was D50. The obtained L*, a*, and b* values ​​are listed in the table.

[0145] [Table 1]

[0146] [Table 2]

[0147] [Table 3]

[0148] [Table 4]

[0149] As shown in Tables 1 to 4, when the inkjet inks of Samples 6, 8 to 10, and 16 to 55 corresponding to Examples 1 to 44 are used alone (i.e., when the inkjet inks are not overprinted on the same location on the substrate), excellent lightfastness can be obtained while maintaining excellent printing stability (particularly initial printability, continuous printability, and intermittent reprintability). More specifically, the inkjet ink according to this embodiment can achieve excellent lightfastness while maintaining excellent printing stability (particularly initial printability, continuous printability, and intermittent restartability) even when it contains only one type of dye. Furthermore, with the inkjet ink according to this embodiment, even when multiple types of dyes are contained, excellent lightfastness can be obtained while maintaining excellent printing stability (particularly initial printability, continuous printability, and intermittent restartability).

[0150] Furthermore, with the inkjet inks of Samples 6, 8 to 10, and 16 to 55 corresponding to Examples 1 to 44, even when the inkjet inks are overprinted and toned on the same location on a substrate, excellent lightfastness can be obtained while maintaining excellent printing stability (particularly initial printability, continuous printability, and intermittent reprintability). Furthermore, as shown in Tables 1 to 4, by printing each of the inkjet inks of Samples 6, 8 to 10, and 16 to 55 corresponding to Examples 1 to 44 on the same location on a substrate, a wider color gamut can be reproduced compared to when inkjet inks according to conventional technology are used.

[0151] For example, the color tone specified by "Yellow 4: Red 102 = 2:1" shown in Figure 6 means a color tone obtained by overprinting an inkjet ink containing only Yellow No. 4 and an inkjet ink containing only Red No. 102 at a mass ratio of 2:1 on the same location on a substrate to achieve color matching, or a color tone obtained by pre-mixing inkjet inks containing only two types of pigments, Yellow No. 4 and Red No. 102, at a mass ratio of 2:1 on the same location on a substrate without overprinting them.

[0152] More specifically, the color tone identified by "Yellow 4: Red 102 = 2:1" shown in Figure 6 means a color tone obtained by overprinting the inkjet ink of Sample #10 (Example 4), which is an inkjet ink containing only Yellow No. 4, and the inkjet ink of Sample #8 (Example 2), which is an inkjet ink containing only Red No. 102, in a mass ratio of 2:1 on the same location on a printed substrate to achieve a toned color, or a color tone obtained by overprinting the inkjet ink of Sample #48 (Example 37), which is an inkjet ink containing only two types of pigments, Yellow No. 4 and Red No. 102, and which was obtained by pre-mixing the two pigments in a mass ratio of 2:1, on the same location on a printed substrate without overprinting it.

[0153] Furthermore, the color tone identified by "Red 106:Red 102 = 1:2" shown in Figure 6 means a color tone obtained by overprinting the inkjet ink of Sample #9 (Example 3), which is an inkjet ink containing only Red No. 106, and the inkjet ink of Sample #8 (Example 2), which is an inkjet ink containing only Red No. 102, at a mass ratio of 1:2 on the same location on a printed substrate to achieve color matching, or a color tone obtained by overprinting the inkjet ink of Sample #43 (Example 32), which is an inkjet ink containing only two types of pigments, Red No. 106 and Red No. 102, and which was obtained by pre-mixing the two pigments at a mass ratio of 1:2, on the same location on a printed substrate without overprinting it.

[0154] Furthermore, the color tone identified by "Red 106:Blue 1 = 2:1" shown in Figure 6 means a color tone obtained by overprinting the inkjet ink of Sample #9 (Example 3), which is an inkjet ink containing only Red No. 106, and the inkjet ink of Sample #6 (Example 1), which is an inkjet ink containing only Blue No. 1, at a mass ratio of 2:1 on the same location on a printed substrate to achieve color matching, or a color tone obtained by overprinting the inkjet ink of Sample #38 (Example 27), which is an inkjet ink containing only two types of pigments, Red No. 106 and Blue No. 1, and which was obtained by pre-mixing the two pigments at a mass ratio of 2:1, on the same location on a printed substrate without overprinting it.

[0155] As described above, the inkjet ink according to the present embodiment can reproduce a wider color gamut than inkjet inks according to conventional techniques. Furthermore, the inkjet ink according to the present embodiment has excellent lightfastness while maintaining excellent printing stability, regardless of the type of dyes used in combination.

[0156] As described above, the inkjet ink set of this embodiment comprises a plurality of inkjet inks containing an edible dye and water and ethanol as solvents, each containing different types of dye, at least one of which contains reduced isomaltulose as a fading inhibitor, and the ratio (F / D) of the fading inhibitor content F [wt%] in the inkjet ink containing the fading inhibitor to the dye content D [wt%] is within the range of 0.2 or more and 30.0 or less, so that each inkjet ink maintains excellent printing stability, has excellent light resistance regardless of the type of dye combined, and can reproduce a wide color gamut.

[0157] The present invention also includes a first ink-jet ink, a second ink-jet ink, a third ink-jet ink, and a fourth ink-jet ink, each of which contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a fading inhibitor, and the first ink-jet ink contains only Blue No. 1 as the dye, the second ink-jet ink contains only Yellow No. 4 as the dye, and the third ink-jet ink contains only Red No. 102 as the dye, and the fourth ink-jet ink contains only Yellow No. 4 as the dye. In the inkjet ink set of this embodiment, in which the first inkjet ink, the second inkjet ink, the third inkjet ink, and the fourth inkjet ink all contain only Red No. 106 as the dye, and the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] is within the range of 0.2 or more and 30.0 or less, and the ratio (F / D) of the fading inhibitor content F [wt%] to the dye content D [wt%] is the same, each inkjet ink maintains excellent printing stability, has excellent light resistance regardless of the type of dye combined, and can reproduce a wide color gamut.

[0158] In addition, in the inkjet ink series of this embodiment, which contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor, and the dye is only one of Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106, and the ratio (F / D) of the discoloration inhibitor content F [wt%] to the dye content D [wt%] is within the range of 0.2 or more and 30.0 or less, each inkjet ink maintains excellent printing stability, has excellent light resistance regardless of the type of pigment combined, and can reproduce a wide color gamut.

[0159] The scope of the present disclosure is not limited to the exemplary embodiments shown and described, but also includes all embodiments that achieve equivalent effects to those intended by the present disclosure. Furthermore, the scope of the present disclosure is not limited to the combinations of disclosed features defined by the claims, but may be defined by any desired combination of specific features from among all the respective disclosed features.

[0160] Furthermore, for example, the present invention can have the following configuration. (1) a plurality of ink-jet inks for tablets, each containing an edible dye and water and ethanol as a solvent, the dyes being different from one another; at least one of the plurality of ink-jet inks for tablets contains reduced isomaltulose as a discoloration inhibitor; An inkjet ink set for tablets, wherein the ratio (F / D) of the content F [wt%] of the fading inhibitor in the inkjet ink for tablets containing the fading inhibitor to the content D [wt%] of the dye is within the range of 0.2 or more and 30.0 or less. (2) The inkjet ink set for tablets according to (1) above, wherein at least one of the plurality of inkjet inks for tablets contains propylene glycol as a wetting agent. (3) The inkjet ink set for tablets according to (1) or (2) above, wherein the content of the discoloration inhibitor is within the range of 1.0 wt% or more and 15.0 wt% or less. (4) The content of the dye is in the range of 0.5 wt% to 5.0 wt%, The inkjet ink set for tablets according to any one of (1) to (3) above, wherein the ethanol content is within the range of 1.0 wt% or more and 10.0 wt% or less. (5) The inkjet ink set for tablets according to any one of (1) to (4) above, wherein each of the plurality of inkjet inks for tablets contains only one dye selected from azo dyes, triphenylmethane dyes, and xanthene dyes. (6) the azo dye is Red No. 102 or Yellow No. 4, The triphenylmethane dye is Blue No. 1, The inkjet ink set for tablets according to (5) above, wherein the xanthene dye is Red No. 106. (7) all of the inkjet inks for tablets included in the inkjet ink set for tablets contain the fading inhibitor, The content F [wt%] of the fading inhibitor is the same in all of the ink-jet inks for tablets, or The inkjet ink set for tablets according to any one of (1) to (6) above, wherein the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is the same for all of the inkjet inks for tablets. (8) a first tablet ink-jet ink, a second tablet ink-jet ink, a third tablet ink-jet ink, and a fourth tablet ink-jet ink; the first ink-jet ink for tablets, the second ink-jet ink for tablets, the third ink-jet ink for tablets, and the fourth ink-jet ink for tablets each contain an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor; the first ink-jet ink for tablets contains only Blue No. 1 as the dye; the second ink-jet ink for tablets contains only Yellow No. 4 as the dye; the third ink-jet ink for tablets contains only Red No. 102 as the dye; the fourth ink-jet ink for tablets contains only Red No. 106 as the dye; An inkjet ink set for tablets, wherein the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is the same for all of the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets, each within the range of 2.0 or more and 30.0 or less, and the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is the same for all of the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets. (9) the content of Blue No. 1 in the first ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, the content of Yellow No. 4 in the second ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, the content of Red No. 102 in the third ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, The inkjet ink set for tablets according to (8) above, wherein the content of Red No. 106 in the fourth inkjet ink for tablets is in the range of 0.5 wt% or more and 5.0 wt% or less. (10) The inkjet ink set for tablets according to (8) or (9) above, wherein the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets each further contain propylene glycol as a humectant. (11) The composition contains an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor; The dye is only one of Red No. 102, Yellow No. 4, Blue No. 1, and Red No. 106, A series of inkjet inks for tablets, in which the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is in the range of 2.0 or more and 30.0 or less. (12) A mixed inkjet ink for tablets, comprising the individual inkjet inks for tablets contained in the inkjet ink set for tablets according to any one of (1) to (10) above, in any proportion. (13) A printed tablet product comprising a printed portion printed using an individual inkjet ink for tablets included in the inkjet ink set for tablets according to any one of (1) to (10) above. (14) A printed tablet product comprising a printed portion printed using the mixed inkjet ink for tablets described in (12) above. [Explanation of symbols]

[0161] 1. Tablet base material 3 Printed images 5. Printed plain tablets 7 Film coating layer 9. Film-coated tablet printouts 11 Plain tablet print image (solid image) 13 Film-coated tablet print image (two-dimensional barcode) X 1st Extended Color Gamut Y 2nd Extended Color Gamut Z conventional color gamut

Claims

1. a first tablet ink-jet ink, a second tablet ink-jet ink, a third tablet ink-jet ink, and a fourth tablet ink-jet ink; the first ink-jet ink for tablets, the second ink-jet ink for tablets, the third ink-jet ink for tablets, and the fourth ink-jet ink for tablets each contain an edible dye, water and ethanol as solvents, and reduced isomaltulose as a discoloration inhibitor; the first ink-jet ink for tablets contains only Blue No. 1 as the dye; the second ink-jet ink for tablets contains only Yellow No. 4 as the dye; the third ink-jet ink for tablets contains only Red No. 102 as the dye; the fourth ink-jet ink for tablets contains only Red No. 106 as the dye; In all of the first ink-jet ink for tablets, the second ink-jet ink for tablets, the third ink-jet ink for tablets, and the fourth ink-jet ink for tablets, the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is within a range of 2.0 or more and 30.0 or less, and the ratio (F / D) of the content F [wt%] of the fading inhibitor to the content D [wt%] of the dye is the same, the first tablet-use ink-jet ink, the second tablet-use ink-jet ink, the third tablet-use ink-jet ink, and the fourth tablet-use ink-jet ink each further comprise propylene glycol as a humectant; The first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets are inkjet ink sets for tablets, each of which has an added amount of propylene glycol greater than an added amount of ethanol added as the solvent.

2. 2. The inkjet ink set for tablets according to claim 1, wherein in all of the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets, the ratio (F / D) of the content F [wt %] of the discoloration inhibitor to the content D [wt %] of the dye is within the range of 8.3 to 30.

0.

3. 2. The inkjet ink set for tablets according to claim 1, wherein in all of the first inkjet ink for tablets, the second inkjet ink for tablets, the third inkjet ink for tablets, and the fourth inkjet ink for tablets, the ratio (F / D) of the content F [wt %] of the discoloration inhibitor to the content D [wt %] of the dye is within the range of 10.0 or more and 30.0 or less.

4. the content of Blue No. 1 in the first ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, the content of Yellow No. 4 in the second ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, the content of Red No. 102 in the third ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less, The ink-jet ink set for tablets according to claim 1 , wherein the content of Red No. 106 in the fourth ink-jet ink for tablets is in the range of 0.5 wt % or more and 5.0 wt % or less.

5. The inkjet ink set for tablets according to claim 1 , wherein all of the inkjet inks for tablets are inkjet inks for tablets for printing without thinning printing.

6. A mixed inkjet ink for tablets, comprising the individual inkjet inks for tablets included in the inkjet ink set for tablets according to any one of claims 1 to 5 in any proportion.

7. A printed tablet product comprising a printed portion printed using an individual inkjet ink for tablets included in the inkjet ink set for tablets according to any one of claims 1 to 5.

8. A printed tablet product comprising a printed portion printed using the mixed inkjet ink for tablets according to claim 6.

Images