Inkjet ink and tablet printed matter

Abstract

To provide an inkjet ink excellent in light resistance by suppressing light discoloration and color fading of a printed image, and a tablet printed matter provided with a printed part printed with the inkjet ink.SOLUTION: An inkjet ink pertaining to the present embodiment includes: Blue No.1 as a food color; and water and ethanol as solvents, wherein a blending ratio of trehalose is 7.5 mass% or more and 20.0 mass% or less to a total mass of the inkjet ink when including only trehalose as a sticking agent, a blending ratio of trehalose is 2.5 mass% or more and 15.0 mass% or less to a total mass of the inkjet ink, and a blending ratio of reduced isomaltulose is 10.0 mass% or less to a total mass of the inkjet ink when including trehalose and reduced isomaltulose as sticking agents.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to inkjet ink and tablet prints.

Background Art

[0002] Some inkjet inks for inkjet printing (hereinafter, also simply referred to as "inkjet ink") have edibility by using food dyes such as tar-based dyes as coloring materials. Conventionally, some inkjet inks have discoloration in which the color tone (color shade) of the coloring material changes in printed characters, images, etc. due to deterioration of the coloring material, or fading due to a decrease in the chroma of the coloring material. For example, when the light resistance of inkjet ink is insufficient, the coloring material may be decomposed (photodecomposed) by the action of light, resulting in discoloration and fading (photo-discoloration and fading). Such discoloration and fading are recognized as a decrease in visibility in printed characters, images, etc. (hereinafter, collectively referred to as "printed images").

[0003] In order to suppress such discoloration and fading of printed images, technology development has been promoted, and various methods for suppressing discoloration and fading have been proposed (for example, Patent Document 1). However, with conventional methods, the photo-discoloration and fading of printed images cannot be sufficiently suppressed, and the light resistance of inkjet ink cannot be improved. For example, in the case of Food Blue No. 1 among food dyes, the light resistance of inkjet ink may be improved by including reduced isomaltulose in the inkjet ink. Reduced isomaltulose is a substance classified as a disaccharide, but among the same disaccharides, reduced isomaltulose has relatively low solubility in water. Therefore, it may be difficult to sufficiently increase the addable ratio (upper limit of the content) of reduced isomaltulose in inkjet ink.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The inventor has found that in order to further improve the light resistance of inkjet ink, it is necessary to add a more soluble light resistance inhibitor to the inkjet ink. In view of such points, the present invention has been made, and an object thereof is to provide an inkjet ink that sufficiently suppresses light fading of a printed image and has improved light resistance, and a tablet printed matter including a printed portion printed with the inkjet ink. MEANS FOR SOLVING THE PROBLEMS

[0006] In order to achieve the above object, an inkjet ink according to an aspect of the present invention contains Blue No. 1 as an edible dye, contains only trehalose as a fixing agent, contains water and ethanol as solvents, and the blending ratio of the trehalose is in the range of 7.5% by mass or more and 20.0% by mass or less with respect to the total mass of the inkjet ink. Further, in order to achieve the above object, an inkjet ink according to an aspect of the present invention contains Blue No. 1 as an edible dye, contains trehalose and reduced isomaltulose as fixing agents, contains water and ethanol as solvents, the blending ratio of the trehalose is in the range of 2.5% by mass or more and 15.0% by mass or less with respect to the total mass of the inkjet ink, and the blending ratio of the reduced isomaltulose is 10.0% by mass or less with respect to the total mass of the inkjet ink.

[0007] Further, in order to achieve the above object, a tablet printed matter according to an aspect of the present invention is characterized by including a printed portion printed with the above inkjet ink. EFFECTS OF THE INVENTION

[0008] According to one aspect of the present invention, it is possible to sufficiently suppress the light-induced fading of a printed image and improve the light resistance of an inkjet ink.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] The inkjet ink according to an embodiment of the present invention (hereinafter referred to as "the present embodiment") relates to an inkjet ink that can sufficiently suppress the light-induced fading of, for example, a printed image applied by an inkjet printing method on the surface of a medical tablet and improve the light resistance. Hereinafter, the configuration of the inkjet ink according to the embodiment of the present invention and a tablet including a printed portion printed with the inkjet ink will be described in detail.

[0011] 〔Configuration of Inkjet Ink〕 The inkjet ink according to this embodiment is an edible inkjet ink, which contains Food Blue No. 1 (hereinafter simply referred to as "Blue No. 1") as an edible dye (edible pigment). Further, the inkjet ink according to this embodiment contains a saccharide having a relatively high solubility in water as a fixing agent for fixing the ink on the surface of the object to be printed (for example, a solid preparation). Specifically, in this embodiment, trehalose (a disaccharide) having a solubility of 69 g in 100 ml of water at 20°C is used as the fixing agent. Further, the inkjet ink according to this embodiment contains trehalose in the range of 7.5% by mass or more and 20.0% by mass or less based on the total mass of the inkjet ink. Further, the inkjet ink according to this embodiment contains water and ethanol as solvents.

[0012] Further, in this embodiment, trehalose and reduced isomaltulose (a disaccharide) having a solubility of 38 g in 100 ml of water at 20°C are used as the fixing agent. Further, the inkjet ink according to this embodiment contains trehalose in the range of 2.5% by mass or more and 15.0% by mass or less based on the total mass of the inkjet ink. Further, the inkjet ink according to this embodiment contains reduced isomaltulose in the range of 10.0% by mass or less based on the total mass of the inkjet ink. Further, the inkjet ink according to this embodiment contains water and ethanol as solvents. According to such a configuration, it is possible to sufficiently suppress the light fading of the printed image and improve the light resistance of the inkjet ink. Hereinafter, this point will be described with reference to FIG. 1.

[0013] FIG. 1 is a conceptual diagram for explaining the relationship between the fixing of the ink on the surface of the object to be printed (solid preparation) and the light resistance. Here, as the solid preparation, for example, a tablet provided with a film-coated portion having few voids, that is, a film-coated tablet is used. Note that the present invention is not limited to this, and a plain tablet or a capsule tablet may be used as the object to be printed.

[0014] Figs. 1(a) to 1(c) are schematic cross-sectional views in the thickness direction of tablets (here, film-coated tablets) printed with inkjet inks A to C having different compositions and allowed to stand for a certain period of time. In this example, the inkjet ink A is an ink using a specific dye 4 as a coloring material and water as a solvent. Here, the specific dye 4 only needs to contain Brilliant Blue No. 1. Further, the inkjet ink B is an ink obtained by adding a predetermined saccharide to the inkjet ink A. Here, the saccharide added to the inkjet ink B is a saccharide having a relatively low solubility in water and not corresponding to the fixing agent in the present embodiment (for example, reduced isomaltooligosaccharide). Further, the inkjet ink C is an ink obtained by adding a disaccharide (that is, trehalose) having a relatively high solubility in water and corresponding to the fixing agent in the present embodiment to the inkjet ink A, and further adding ethanol to water as a solvent.

[0015] Specifically, Fig. 1(a) is a schematic cross-sectional view in the thickness direction of a tablet in a state where an inkjet ink A containing a specific dye 4 as a coloring material and water as a solvent is printed on the surface 1S of the substrate 1 of the tablet and a certain period of time (for example, 140 hours) has elapsed. Further, Fig. 1(b) is a schematic cross-sectional view in the thickness direction of a tablet in a state where the inkjet ink B is printed on the surface 1S of the substrate 1 of the tablet and a certain period of time (for example, 140 hours) has elapsed. Further, Fig. 1(c) is a schematic cross-sectional view in the thickness direction of a tablet in a state where the inkjet ink C is printed on the surface 1S of the substrate 1 of the tablet and a certain period of time (for example, 140 hours) has elapsed.

[0016] First, the presence or absence of addition of saccharides in the inkjet ink and the penetrability of the dye will be described taking the inkjet inks A and B as examples. Among various colorants used in inkjet inks, for example, in the case of tar-based pigments used as food dyes, discoloration may occur in printed characters, images, etc. on the surface of solid preparations. For example, in the case of Food Blue No. 1 among tar-based pigments, discoloration of the printed image occurred due to penetration into the solid preparation over time and photodegradation. On the other hand, a method is known in which by adding saccharides to the inkjet ink, penetration of the dye into the solid preparation is suppressed and discoloration of the printed image is suppressed.

[0017] As shown in Fig. 1(a), when printing with inkjet ink A that does not contain saccharides, after a certain time has elapsed since printing, a specific dye 4 penetrates into the inside of the base material 1 of the tablet. Here, let the penetration depth of the specific dye 4 in the inkjet ink A after the elapse of the certain time be the penetration depth X (μm). On the other hand, as shown in Fig. 1(b), when printing with inkjet ink B that contains saccharides, after a certain time has elapsed since printing, the penetration depth Y (μm) of the inkjet ink B is smaller than the penetration depth X of the inkjet ink A (X > Y).

[0018] In inkjet ink B, the addition of a predetermined saccharide causes an increase in the viscosity of the ink, etc., and penetration of the specific dye 4 into the inside of the base material 1 of the tablet is suppressed. Therefore, when printing with inkjet ink B, even after a certain time has elapsed since printing, the specific dye 4 remains near the surface 1S in the base material 1 of the tablet. That is, an inkjet ink containing a predetermined saccharide can suppress discoloration of the printed image due to penetration of the dye (for example, Food Blue No. 1) compared to the case where no saccharide is added. On the other hand, in the inkjet ink B to which a predetermined saccharide is added, discoloration of the printed image due to light irradiation (photo-discoloration) cannot be sufficiently suppressed.

[0019] In contrast, the inkjet ink according to this embodiment selects the types and physical properties of the saccharides and solvents to be added, so that the ink adheres to the surface of the object to be printed, sufficiently suppressing the light fading of the printed image and improving the light resistance. The inventors of the present invention have found that in order to suppress the light fading of the printed image, it is effective to fix the ink on the surface of the object to be printed (for example, a tablet). In this example, when the ink adheres to the surface 1S of the tablet, the specific dye 4) adheres to the surface 1S, and as a result, the specific dye 4 can remain on the surface 1S at a high concentration.

[0020] When the concentration of the specific dye 4 is high on the surface 1S of the base material 1 of the tablet, for example, the ratio of the coloring material that causes light fading due to photodegradation among the specific dyes 4 on the surface 1S is reduced. That is, even if light fading occurs in a part of the specific dye 4, the influence is limited, and a decrease in the visibility (readability) of the printed image is suppressed. As a result, the visibility of the entire printed image is maintained, and as a result, the light fading of the printed image can be sufficiently suppressed. Therefore, the light resistance of the inkjet ink can be improved. And the inventors of the present invention have discovered that among saccharides, disaccharides function as a fixing agent for fixing an ink containing Food Blue No. 1 as a coloring material to the surface of the object to be printed. Furthermore, regarding the above-mentioned disaccharide used as a fixing agent, the inventors have discovered that by using a substance having a relatively high solubility in a solvent, the addition amount of the disaccharide in the inkjet ink can be increased, and the fixing effect of the ink can be surely exhibited.

[0021] Specifically, the inkjet ink according to this embodiment contains Food Blue No. 1 as a coloring material and an edible dye, contains only trehalose as a fixing agent, and contains water and ethanol as solvents. Also, the blending ratio of trehalose is in the range of 7.5% by mass or more and 20.0% by mass or less with respect to the total mass of the inkjet ink. In addition, the inkjet ink according to the present embodiment contains Food Blue No. 1 as a coloring material and a colorant, contains trehalose and reduced isomaltulose as fixing agents, and contains water and ethanol as solvents. Further, the blending ratio of trehalose is in the range of 2.5% by mass or more and 15.0% by mass or less with respect to the total mass of the inkjet ink, and the blending ratio of reduced isomaltulose is 10.0% by mass or less with respect to the total mass of the inkjet ink. According to such a configuration, it is possible to fix an ink containing a specific tar-based dye (in this example, Food Blue No. 1) used as a coloring material on the surface of the object to be printed, and to leave the specific tar-based dye on the surface at a high concentration. Thereby, the inkjet ink according to the present embodiment can sufficiently suppress the light fading of the printed image and improve the light resistance.

[0022] As shown in FIG. 1(c), when an inkjet ink C corresponding to the inkjet ink according to the present embodiment is printed on the surface 1S of the base material 1 of the tablet, a specific dye 4 (here, Food Blue No. 1) in the ink is fixed on the surface 1S. Specifically, when the inkjet ink C is printed, the penetration depth Z (μm) of the specific dye 4 after a certain time has elapsed since printing is further reduced than the penetration depth Y of the specific dye 4 in the inkjet ink B containing a predetermined saccharide (Y>Z). For example, the penetration depth Z of the specific dye 4 in the inkjet ink C is reduced to about 50% of the penetration depth Y of the specific dye 4 in the inkjet ink B. That is, the inkjet ink C can further suppress the penetration of the specific dye 4. Therefore, the specific dye 4 remains on the surface 1S at a high concentration, and the decrease in the visibility of the printed image is suppressed as described above. Thereby, the light fading of the printed image is sufficiently suppressed, and the inkjet ink C can improve the light resistance.

[0023] On the one hand, although the inkjet ink B can leave the specific dye 4 near the surface 1S inside the base material 1 of the tablet, the suppression of the penetration of the specific dye 4 is not sufficient, and the ink cannot be fixed on the surface 1S. That is, in the inkjet ink B, since the concentration of the specific dye 4 remaining on the surface 1S is low, the photo-fading of the printed image cannot be sufficiently suppressed, and the light resistance is not improved.

[0024] Thus, the inkjet ink according to this embodiment adds the above-mentioned disaccharides (trehalose only, or a mixture of trehalose and reduced isomaltulose) as a fixing agent, and further sets the solvent to the above-mentioned component composition (a mixed solvent of water and ethanol), thereby greatly suppressing the penetration of a specific tar-based dye (Blue No. 1) into the printed material and fixing the ink on the surface of the printed material. Thereby, the inkjet ink according to this embodiment can suppress the photo-fading of the printed image and improve the light resistance, and further can also suppress the discoloration of the printed image due to the penetration of the specific tar-based dye into the printed material.

[0025] Also, as shown in FIG. 1(c), the inkjet ink C can be fixed on the surface 1S of the base material 1 of the tablet so as to slightly bulge. Thereby, for example, when the inkjet ink C is printed, it is recognized that the printing is dark and prominent on the surface 1S. Therefore, for example, compared with the inkjet inks A and B, the inkjet ink C can improve the visibility during printing of the printed image. That is, in the inkjet ink according to this embodiment, in addition to reducing the decrease in visibility due to the photo-fading of the printed image, good visibility can be imparted to the printed image at the time of printing.

[0026] Hereinafter, the details of the light resistance in the inkjet ink according to this embodiment will be described. The inkjet ink according to this embodiment only needs to have a color difference ΔE in JIS Z 8781 of 25 or less before and after the lightfastness test. Here, the lightfastness test is a test for comparing the color difference ΔE (conforming to JIS Z 8781), which indicates the amount of change in chromaticity and optical color density before and after irradiation with visible light, for a printed image printed using the inkjet ink according to this embodiment. Specifically, the color difference ΔE is measured before and after irradiating the printed image with 1.2 million lux of cumulative visible light, and the values are compared. For the irradiation with visible light, for example, a light stability test apparatus (Nagano Science LT-120A-WD) is used. Also, the printed image in the lightfastness test is, for example, one printed solidly on a tablet (for example, a film-coated tablet) that is the object to be printed.

[0027] Sufficient lightfastness necessary for forming a printed image on medical tablets, etc. often refers to a case where the color difference ΔE of the printed image before and after irradiation with visible light is 25 or less in a lightfastness test in which 1.2 million lux of visible light is irradiated under normal humidity (60% RH in the test machine installation room). Setting the color difference ΔE of 25 or less as the criterion for sufficient lightfastness was derived from the results of an opinion test conducted by the inventors together with various medical personnel. When the color difference ΔE exceeds 25, the visibility of the printed image (for example, the readability of the printing) begins to be recognized as deteriorating. That is, if the color difference ΔE before and after irradiation with visible light is 25 or less, it can be said that the inkjet ink is excellent in lightfastness with sufficient suppression of light fading and discoloration. Although it is a larger number than the standard of 3 to 6 for the color difference ΔE in general commercial printed matter, usually, the tablets before and after exposure are not compared, and since it is assumed that the printed image on the tablet surface naturally fades, this number could be obtained.

[0028] In the inkjet ink according to this embodiment, the reason for using a disaccharide (for example, trehalose with a solubility of 69 g in 100 ml of water at 20°C) having a relatively high solubility in 100 ml of water at 20°C as a fixing agent and using the solvent having the above composition is that when only a saccharide having a relatively low solubility in 100 ml of water at 20°C (for example, reduced isomaltulose with a solubility of 38 g in 100 ml of water at 20°C) is added, or when the solvent does not have the above composition, a specific tar-based dye on the tablet surface, that is, Blue No. 1, is not sufficiently fixed to the surface of the printed material, and the color difference ΔE exceeds 25 when the above lightfastness test is performed on the solid printed image. By adding a disaccharide having a relatively high solubility in water as a fixing agent and increasing the solubility of the disaccharide in the solvent by using a solvent that satisfies the above composition, the color difference ΔE becomes less than 25 before and after the lightfastness test, and the inkjet ink is imparted with excellent lightfastness.

[0029] Hereinafter, each component constituting the inkjet ink according to this embodiment will be described. (Colorant) As described above, the inkjet ink according to this embodiment contains at least Blue No. 1 as an edible dye. Blue No. 1 is an edible tar-based dye and is also called Brilliant Blue FCF. In the inkjet ink according to this embodiment, when only trehalose is included as a fixing agent, the blending ratio of the edible dye containing the specific tar-based dye (Blue No. 1), that is, the total content of the edible dye, is preferably in the range of 1.0% by mass or more and 15.0% by mass or less with respect to the mass of the entire ink.

[0030] Further, in the inkjet ink according to this embodiment, when trehalose and reduced isomaltulose are included as a fixing agent, the blending ratio of the edible dye containing the specific tar-based dye (Blue No. 1), that is, the total content of the edible dye, is preferably in the range of 1.0% by mass or more and 15.0% by mass or less with respect to the mass of the entire ink. With such a configuration, it is possible to impart good visibility to the printed image and high intermittent restartability. Also, if the total content of the edible dye is within the above range, by adding the above fixing agent, the specific tar-based dye can be surely left on the surface of the printed matter at a high concentration, suppressing the light fading of the printed image, and improving the lightfastness of the inkjet ink according to the present embodiment.

[0031] On the other hand, in an inkjet ink containing only trehalose as a fixing agent, when the total content of the edible dye is less than 1.0% by mass, the entire printed color tends to become lighter and the visibility of the printed image tends to decrease. Also, when the content exceeds 15.0% by mass, the deterioration of the dissolution stability of the colorant causes the pigment in the ink to precipitate or settle as a solid, which may cause nozzle clogging of the inkjet head during printing, that is, the so-called printing restartability (intermittent restartability) may decrease. Also, in an inkjet ink containing trehalose and reduced isomaltulose as a fixing agent, when the total content of the edible dye is less than 1.0% by mass, the entire printed color tends to become lighter and the visibility of the printed image tends to decrease. Also, when the content exceeds 15.0% by mass, the deterioration of the dissolution stability of the colorant causes the pigment in the ink to precipitate or settle as a solid, which may cause nozzle clogging of the inkjet head during printing, that is, the so-called printing restartability (intermittent restartability) may decrease.

[0032] In addition, the inkjet ink according to the present embodiment may contain the above-specified tar-based dye, that is, a dye (colorant) other than Food Blue No. 1. There is no particular limitation on the dye other than Food Blue No. 1 as long as it is edible. Dyes that can be added to the inkjet ink according to the present embodiment can be appropriately selected and added, for example, from conventionally known synthetic food dyes and natural food dyes. Further, when the inkjet ink according to the present embodiment contains a colorant other than the above-specified tar-based dye as an edible dye, the total content of the edible dye is preferably in the range of 1.0% by mass or more and 15.0% by mass or less when only trehalose is contained as a fixing agent, and is preferably in the range of 1.0% by mass or more and 15.0% by mass or less when trehalose and reduced isomaltulose are contained as a fixing agent. Thereby, while improving the light resistance of the inkjet ink, good visibility can be imparted to the printed image, and sufficient intermittent restartability can be imparted to the inkjet ink.

[0033] Examples of synthetic food dyes include tar-based dyes, natural pigment derivatives, natural synthetic dyes, etc. Examples of tar-based dyes include Food Red No. 2, Food Red No. 3, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow No. 4, Food Yellow No. 5, Food Blue No. 2, Food Red No. 2 Aluminum Lake, Food Red No. 3 Aluminum Lake, Food Red No. 40 Aluminum Lake, Food Yellow No. 4 Aluminum Lake, Food No. 5 Aluminum Lake, Food Blue No. 1 Aluminum Lake, Food Blue No. 2 Aluminum Lake, etc. Examples of natural pigment derivatives include potassium norbixin, etc. Examples of natural synthetic dyes include β-carotene, riboflavin, etc.

[0034] Examples of natural food colorants include, for example, anthocyanin pigments, carotenoid pigments, quinone pigments, chlorophyll pigments, flavonoid pigments, betaine pigments, Monascus pigments, and pigments derived from other natural products. Examples of anthocyanin pigments include, for example, red radish pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, cranberry pigment, salmonberry pigment, perilla pigment, sweet blueberry pigment, strawberry pigment, dark sweet cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, grape juice pigment, grape skin pigment, blackcurrant pigment, blackberry pigment, blueberry pigment, plum pigment, whortleberry pigment, boysenberry pigment, mulberry pigment, purple sweet potato pigment, purple corn pigment, purple yam pigment, raspberry pigment, redcurrant pigment, loganberry pigment, and other anthocyanin pigments. Examples of carotenoid pigments include, for example, annatto pigment, gardenia yellow pigment, and other carotenoid pigments. Examples of quinone pigments include, for example, cochineal pigment, shikonin pigment, lac pigment, and other quinone pigments. Examples of flavonoid pigments include, for example, safflower yellow pigment, turmeric pigment, onion pigment, and other flavonoid pigments. Examples of betaine pigments include, for example, beet red pigment. Examples of Monascus pigments include, for example, red kojic pigment, red kojic yellow pigment. Examples of pigments derived from other natural products include, for example, turmeric pigment, safflower pigment, gardenia red pigment, spirulina blue pigment, etc.

[0035] (Fixing agent) As described above, the inkjet ink according to this embodiment contains a fixing agent for fixing ink containing a specific tar-based dye (Blue No. 1) on the surface of an object to be printed. Specifically, the fixing agent contained in the inkjet ink according to this embodiment is trehalose. Trehalose is a disaccharide with a solubility of 69 g in 100 ml of water at 20°C. Since trehalose has a higher solubility in 100 ml of water at 20°C than other disaccharides, the amount of trehalose added to a solvent containing water can be increased. Therefore, with the inkjet ink having the above configuration, high light resistance (ΔE ≤ 25) can be achieved even under normal humidity.

[0036] Also, in the inkjet ink according to this embodiment, trehalose and reduced isomaltulose may be used in combination as the fixing agent. Reduced isomaltulose is a disaccharide with a solubility of 38 g in 100 ml of water at 20°C. Also, trehalose and reduced isomaltulose have different types of solvents in which they are easily dissolved. That is, in the inkjet ink according to this embodiment, the solubilities in water and ethanol used as solvents are different. Therefore, in this embodiment, by using trehalose and reduced isomaltulose in combination as the fixing agent, the maximum dissolution amount (total dissolution amount) in a solvent containing water and ethanol can be increased compared to the case where only trehalose is used as the fixing agent. As a result, with this configuration, high light resistance (ΔE ≤ 25) can be achieved even under normal humidity.

[0037] If the fixing agent has such a composition, by adding it to the inkjet ink together with the solvents of the above component composition (water and ethanol), the ink containing the specific tar-based dye can be fixed on the surface of the printed material. As a result, the inkjet ink according to the present embodiment can sufficiently suppress the light-induced fading of the printed image and improve the lightfastness. Further, the disaccharide (only trehalose or a mixture of trehalose and reducing isomaltulose) used as the fixing agent in the present embodiment also has a function of suppressing the decomposition (photodegradation) of the inkjet ink by light irradiation. Therefore, the occurrence of light-induced fading itself can also be suppressed.

[0038] In the inkjet ink according to the present embodiment, when only trehalose is included as the fixing agent, the blending ratio of trehalose is preferably in the range of 7.5% by mass or more and 20.0% by mass or less, more preferably in the range of 7.5% by mass or more and 18.0% by mass or less, and even more preferably in the range of 7.5% by mass or more and 16.0% by mass or less with respect to the mass of the entire ink.

[0039] Further, in the inkjet ink according to the present embodiment, when trehalose and reducing isomaltulose are included as the fixing agent, the blending ratio of trehalose is preferably in the range of 2.5% by mass or more and 15.0% by mass or less, more preferably in the range of 5.0% by mass or more and 15.0% by mass or less, and even more preferably in the range of 7.5% by mass or more and 15.0% by mass or less with respect to the mass of the entire ink. Also, the blending ratio of reducing isomaltulose is preferably 10.0% by mass or less, more preferably in the range of 8.0% by mass or more and 10.0% by mass or less with respect to the mass of the entire ink. With such a configuration, the fixing effect of the ink by the disaccharide can be more surely exhibited, and the lightfastness of the inkjet ink can be surely improved. Further, high intermittent restartability can be imparted to the inkjet ink according to the present embodiment.

[0040] On the other hand, when only trehalose is included as the fixing agent, if the blending ratio of the fixing agent is less than 7.5% by mass, the fixing effect of the ink may be reduced and it may be difficult to obtain light resistance. Also, when the blending ratio of the fixing agent (trehalose) exceeds 20% by mass, the viscosity of the ink increases and the dissolution stability of the fixing agent deteriorates, causing the fixing agent in the ink to precipitate or deposit as a solid, which may cause nozzle clogging of the inkjet head during printing and reduce the ejection stability.

[0041] Also, when trehalose and reduced isomaltulose are included as the fixing agent, if the blending ratio of trehalose is less than 2.5% by mass, the fixing effect of the ink may be reduced and it may be difficult to obtain light resistance. Also, when the blending ratio of trehalose exceeds 15.0% by mass, the viscosity of the ink increases and the dissolution stability of the fixing agent deteriorates, causing the fixing agent in the ink to precipitate or deposit as a solid, which may cause nozzle clogging of the inkjet head during printing and reduce the ejection stability. Also, when trehalose and reduced isomaltulose are included as the fixing agent, if the blending ratio of reduced isomaltulose exceeds 10.0% by mass, the viscosity of the ink increases and the dissolution stability of the fixing agent deteriorates, causing the fixing agent in the ink to precipitate or deposit as a solid, which may cause nozzle clogging of the inkjet head during printing and reduce the ejection stability.

[0042] In addition, in the inkjet ink according to the present embodiment, when trehalose and reduced isomaltulose are included as the fixing agent, it is sufficient that the total blending ratio of trehalose and reduced isomaltulose is 7.5% by mass or more. With such a configuration, the fixing effect of the inkjet ink according to the present embodiment can be more reliably exhibited, and the light resistance of the inkjet ink can be reliably improved. Also, the blending ratio of trehalose may be larger than the blending ratio of reduced isomaltulose. With such a configuration, the fixing effect of the ink by the above disaccharide can be more surely exhibited, and the light resistance of the inkjet ink can be surely improved.

[0043] Further, in the inkjet ink according to the present embodiment, when containing trehalose and reducing isomaltulose as a fixing agent, the blending ratio of reducing isomaltulose may be larger than the blending ratio of trehalose. With such a configuration, the fixing effect of the ink by the above disaccharide can be more surely exhibited, and the light resistance of the inkjet ink can be surely improved.

[0044] (Solvent) The inkjet ink according to the present embodiment contains a solvent (dispersion medium) for dissolving (dispersing) the specific tar-based dye (Blue No. 1) and the fixing agent in addition to the specific tar-based dye and the fixing agent. The inkjet ink according to the present embodiment may contain water (for example, purified water) and ethanol as the solvent.

[0045] Sugars generally have a property of being difficult to dissolve in alcohols. For this reason, in the present embodiment, the solubility of the above disaccharide used as a fixing agent in the solvent is moderately reduced by including ethanol in the solvent. Therefore, by adding a solvent containing the above alcohols (ethanol) together with the above disaccharide (only trehalose or a mixture of trehalose and reducing isomaltulose) as a fixing agent to the inkjet ink, the fixing effect of the ink can be surely exhibited, and the specific tar-based dye (in this example, Blue No. 1) contained in the ink can be left on the surface of the object to be printed (for example, a tablet) at a higher concentration. Thereby, the inkjet ink according to the present embodiment can sufficiently suppress the light fading of the printed image and improve the light resistance.

[0046] In addition, the inkjet ink according to this embodiment may further contain propylene glycol (PG) as a solvent. Propylene glycol functions as a wetting agent, can prevent the drying of the ink at the inkjet nozzle, and can impart sufficient intermittent restartability to the ink. Further, since ethanol has high volatility, the transfer resistance (drying property) of the inkjet ink can be improved. Also, in the inkjet ink according to this embodiment, the blending ratio of each component of the above solvent is not limited, but the blending ratio of ethanol, that is, the addition amount of ethanol, is preferably in the range of 11.5% by mass or more and 40% by mass or less with respect to the mass of the entire ink. With such a configuration, the solubility of the fixing agent in the solvent is surely reduced, and the fixing effect of the ink containing the specific tar-based dye is further improved. Therefore, excellent light resistance can be imparted to the inkjet ink.

[0047] On the other hand, when the addition amount of ethanol is less than 11.5% by mass, the delay in drying of the printed surface on the tablet surface increases, and when the printed tablets come into contact with each other, the undried ink may adhere to the other tablet and cause a problem (transfer defect) such as dirt. On the other hand, when the addition amount of ethanol exceeds 40% by mass, drying of the ink at the inkjet nozzle occurs, which may cause nozzle clogging of the inkjet head during printing and reduce the intermittent restartability.

[0048] In addition, in the inkjet ink according to the present embodiment, when propylene glycol is contained in the solvent, the blending ratio of the propylene glycol, that is, the addition amount of propylene glycol, is preferably in the range of 0% by mass or more and 40% by mass or less with respect to the mass of the entire ink. With such a configuration, the solubility of the fixing agent in the solvent is surely decreased, and the fixing effect of the ink containing the specific tar-based dye is further improved. Therefore, excellent light resistance can be imparted to the inkjet ink. Further, the addition amount of propylene glycol is more preferably 10% by mass or more. Thereby, the solubility of the fixing agent in the solvent is more surely decreased, and the fixing effect of the ink containing the specific tar-based dye is further improved, so that further excellent light resistance can be imparted to the inkjet ink. When the addition amount of propylene glycol exceeds 28% by mass, the drying of the printed surface on the tablet surface is delayed, and when the printed tablets come into contact with each other, the unfixed ink may adhere to the other tablet and cause a problem (transfer defect) such as dirt.

[0049] In addition, the inkjet ink according to the present embodiment may further contain at least one of glycerin or isopropyl alcohol as a solvent. Specifically, in the above solvent, either one of glycerin or isopropyl alcohol may be further contained, or both glycerin and isopropyl alcohol may be further contained. Glycerin functions as a wetting agent in the same manner as the above-mentioned propylene glycol. In addition, since isopropyl alcohol has high volatility in the same manner as the above-mentioned ethanol, the transfer resistance (drying property) of the inkjet ink can be improved. By further adding glycerin and isopropyl alcohol to the solvent in addition to the above components, the light resistance of the inkjet ink can be further improved, and the performance according to each component can be imparted to the inkjet ink. Further, by further containing these components in the solvent, the solubility of the fixing agent in the solvent is more surely decreased, and the fixing effect of the ink containing the specific tar-based dye can be further improved.

[0050] (Internal additive resin) In addition to the above-described dyes and solvents, the inkjet ink according to this embodiment may contain an internal additive resin. The internal additive resin that can be added to the inkjet ink according to this embodiment is an edible and water-soluble powder, paste, or flaky resin-like substance, and any substance that can form a film on the tablet surface by drying after printing may be used. Examples of the above internal additive resin include polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), polyvinyl pyrrolidone (PVP), high molecular weight polyethylene glycol (PEG) such as polyethylene glycol 4000 / polyethylene glycol 1540, shellac resin, methacrylic acid copolymer (product name: Eudragit S100), maltodextrin, erythritol, and the like.

[0051] (Leveling agent) In addition to the above-described dyes, solvents, or internal additive resins, the inkjet ink according to this embodiment may contain a leveling agent. The leveling agent that can be added to the inkjet ink according to this embodiment is an edible and water-soluble surfactant. Examples of the above leveling agent include polyglycerol fatty acid ester (e.g., Decaglycerin distearate Q-182S, Decaglycerin monolaurate Q-12S manufactured by Sun Chemical Corporation), sorbitan fatty acid ester (e.g., NIKKOL SL-10 manufactured by Nikko Chemicals Co., Ltd.), sucrose fatty acid ester (e.g., DK ester F-110 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), polysorbate (Emulsol S-120 series manufactured by Kao Corporation), and the like.

[0052] 〔Printing method〕 The inkjet ink according to this embodiment is not particularly limited with respect to the printing method, and printing can be performed using an inkjet device such as a commercially available inkjet printer. Therefore, the inkjet ink according to this embodiment has a wide range of applications and is very useful. For example, the inkjet ink according to this embodiment can be printed with a so-called drop-on-demand inkjet device using a piezo element (piezoelectric ceramics) as an actuator, and can also be printed with other types of inkjet devices.

[0053] Examples of drop-on-demand inkjet devices include devices that employ a thermal inkjet method in which inkjet ink is ejected by the water vapor pressure generated by instantaneously heating a microheating element to a high temperature (200 to 300°C), electrostatic type devices in which the actuator is electrostatically vibrated to eject the inkjet ink, and devices that employ an ultrasonic method that utilizes the cavitation phenomenon of ultrasonic waves. Further, if the inkjet ink according to this embodiment has chargeability, it is also possible to use a device that employs a continuous injection type (continuous method).

[0054] 〔Tablets〕 In this embodiment, the inkjet ink according to this embodiment may be used to print or draw on the surface of, for example, a tablet using the above-described printing method. That is, the tablet according to this embodiment only needs to have a printed portion printed using the inkjet ink according to this embodiment, that is, a printed image. If it is the inkjet ink according to this embodiment, for example, the light resistance of a printed image (for example, printed image 3) applied to the surface of a medical tablet using the inkjet printing method can be improved. Hereinafter, the configuration of a tablet having a printed image printed with the inkjet ink according to the embodiment will be described. The tablet according to this embodiment is, for example, a medical tablet. Here, the "medical tablet" includes, for example, plain tablets (naked tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, etc., and also includes film-coated tablets in which a water-soluble surface layer is formed on the outermost surface of the tablet.

[0055] FIG. 2 is a schematic cross-sectional view showing an example of a medical tablet (plain tablet) on which printing (letterpress printing, printing) has been performed. FIG. 2 shows, in a cross-sectional view, a plain tablet print 5 on which a printed image 3 such as letters is printed on the upper surface of the 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 (letterpress printing, printing) has been performed. FIG. 3 shows, in a cross-sectional view, a film-coated tablet print 9 on which a printed image 3 such as letters is printed on the upper surface of the base material 1 of the tablet having a film coat layer 7 formed on the surface. In addition, in the present embodiment, as shown in FIG. 4, a solid image may be printed as the plain tablet printed image 11, and as shown in FIG. 5, a two-dimensional barcode may be printed as the film-coated tablet printed image 13.

[0056] The active ingredient contained in the medical tablet is not particularly limited. For example, substances effective for the prevention and treatment of various diseases (for example, substances having a sleep-inducing action, a tranquilizer activity, an antibacterial activity, an antihypertensive action, an antianginal activity, an analgesic action, an anti-inflammatory activity, a psychotropic action, a diabetes treatment activity, a diuretic action, an anticholinergic activity, an anti-hyperacidity action, an antiepileptic action, an ACE inhibitory activity, a β-receptor antagonist or agonist activity, an anesthetic action, an appetite suppressant action, an antiarrhythmic action, an antidepressant action, an anticoagulant activity, an antidiarrheal action, an antihistamine activity, an antimalarial action, an antitumor activity, an immunosuppressive activity, an antiparkinsonian action, an antipsychotic action, an antiplatelet activity, an antihyperlipidemic action, etc.), substances having a cleaning action, fragrances, substances having a deodorizing action, etc., but are not limited thereto.

[0057] The tablet according to the present embodiment can be blended with a carrier acceptable for its use together with the active ingredient as necessary. For example, in the case of a medical tablet, a pharmaceutically acceptable carrier can be blended. As the pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as formulation materials are used. For example, excipients, lubricants, binders, disintegrants, thickeners, etc. are appropriately blended in appropriate amounts. Further, additives such as preservatives, antioxidants, colorants, sweeteners, etc. can also be used as necessary.

[0058] In this embodiment, a medical tablet has been described as an example, but the present invention is not limited thereto. The printing target of the inkjet ink according to this embodiment is not particularly limited. For example, it may be printed on the surfaces of various tablets such as tablets to be administered to animals other than humans (pets, livestock, poultry, etc.), feeds, fertilizers, detergents, tablet confections such as ramune candies, and foods such as supplements. Further, the inkjet ink according to this embodiment is not particularly limited with respect to the size of the printing target, and is applicable to tablets of various sizes.

[0059] (Effect of this embodiment) (1) The inkjet ink according to this embodiment contains Brilliant Blue FCF as a food dye, contains only trehalose as a fixing agent, contains water and ethanol as solvents, and the blending ratio of trehalose is in the range of 7.5% by mass or more and 20.0% by mass or less with respect to the total mass of the inkjet ink. With such a configuration, compared with the prior art, it is possible to sufficiently suppress the light fading and discoloration of a printed image using a specific colorant, and to impart excellent light resistance to the inkjet ink.

[0060] (2) The inkjet ink according to this embodiment contains Brilliant Blue FCF as a food dye, contains trehalose and reduced isomaltulose as fixing agents, contains water and ethanol as solvents, the blending ratio of trehalose is in the range of 2.5% by mass or more and 15.0% by mass or less with respect to the total mass of the inkjet ink, and the blending ratio of reduced isomaltulose is 10.0% by mass or less with respect to the total mass of the inkjet ink. With such a configuration, compared with the prior art, it is possible to sufficiently suppress the light fading and discoloration of a printed image using a specific colorant, and to impart excellent light resistance to the inkjet ink.

[0061] (3) Further, when the inkjet ink according to this embodiment contains only trehalose as a fixing agent, the blending ratio of Brilliant Blue FCF may be in the range of 1.0% by mass or more and 15.0% by mass or less with respect to the total mass of the inkjet ink. With such a configuration, compared with the prior art, it is possible to impart excellent light resistance to the inkjet ink while imparting high visibility and intermittent restartability to the inkjet ink.

[0062] (4) Further, when the inkjet ink according to the present embodiment contains trehalose and reducing isomaltulose as a fixing agent, the blending ratio of Blue No. 1 may be in the range of 1.0% by mass or more and 15.0% by mass or less with respect to the total mass of the inkjet ink. With such a configuration, compared with the prior art, it is possible to impart excellent light resistance to the inkjet ink while imparting high visibility and intermittent restartability to the inkjet ink.

[0063] (5) The tablet printed matter according to the present embodiment includes a printed image (an example of a printed portion) 3 printed with the above-described inkjet ink. With such a configuration, compared with the prior art, it is possible to sufficiently suppress light fading in the printed image 3 or the like directly printed on the surface of the tablet or the like, and sufficiently improve the light resistance of the printed image 3. Furthermore, it is possible to impart edibility to the printed image portion printed on the surface of the tablet.

[0064] [Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples. <Examples 1 to 63 and Comparative Examples 1 to 4> Hereinafter, the preparation procedures of the inkjet inks of Examples 1 to 63 and Comparative Examples 1 to 4 will be described.

[0065] (Manufacture of Inkjet Ink) First, printing ink was prepared. The inkjet ink contains components of a dye (colorant), a solvent, and a fixing agent (fading inhibitor). As the preparation order, first, the fixing agent was added to the solvent to obtain a transparent base liquid. Next, a food dye was added to the transparent base liquid. Thus, the ink according to the present embodiment was prepared. Hereinafter, various components will be specifically described. In this example, purified water (ion-exchanged water), propylene glycol, and ethanol were each used as solvents as needed. Specifically, propylene glycol and ethanol were added to purified water, and the mixture was stirred well to obtain a solvent (mixed solvent). Further, trehalose and reduced isomaltose were added as fixing agents (fading inhibitors) to the above-mentioned solvent as needed, and the mixture was stirred for about 1 hour to obtain a transparent base liquid. To the above-mentioned transparent base liquid, Food Blue No. 1, which is an edible dye, and Red No. 3, Red No. 102, and Yellow No. 4 were added as coloring materials as needed to obtain the inkjet inks of Examples 1 to 63 and Comparative Examples 1 to 4.

[0066] <Sample 1 (Comparative Example 1)> With respect to the entire inkjet ink of Sample 1 (Comparative Example 1), the blending ratio of Food Blue No. 1 as a coloring material was 1.5% by mass, the blending ratio of purified water in the solvent was 49.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of reduced isomaltose as a fixing agent (fading inhibitor) was 10.0% by mass. Thus, the inkjet ink of Sample 1 (Comparative Example 1) was obtained.

[0067] <Sample 2 (Example 1)> With respect to the entire inkjet ink of Sample 2 (Example 1), the blending ratio of Food Blue No. 1 as a coloring material was 1.5% by mass, the blending ratio of purified water in the solvent was 51.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 2.5% by mass, and the blending ratio of reduced isomaltose was 5.0% by mass. Thus, the inkjet ink of Sample 2 (Example 1) was obtained.

[0068] <Sample 3 (Example 2)> For the entire inkjet ink of Sample 3 (Example 2), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 50.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 3 (Example 2) was obtained.

[0069] <Sample 4 (Example 3)> For the entire inkjet ink of Sample 4 (Example 3), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 48.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 8.0% by mass. Thus, the inkjet ink of Sample 4 (Example 3) was obtained.

[0070] <Sample 5 (Example 4)> For the entire inkjet ink of Sample 5 (Example 4), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 46.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 5 (Example 4) was obtained.

[0071] <Sample 6 (Example 5)> For the entire inkjet ink of Sample 6 (Example 5), the blending ratio of C.I. Acid Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 44.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 5.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 6 (Example 5) was obtained.

[0072] <Sample 7 (Example 6)> For the entire inkjet ink of Sample 7 (Example 6), the blending ratio of C.I. Acid Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 41.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 7.5% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 7 (Example 6) was obtained.

[0073] <Sample 8 (Example 7)> For the entire inkjet ink of Sample 8 (Example 7), the blending ratio of C.I. Acid Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 39.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 8 (Example 7) was obtained.

[0074] <Sample 9 (Example 8)> For the entire inkjet ink of Sample 9 (Example 8), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 36.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 13.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 9 (Example 8) was obtained.

[0075] <Sample 10 (Example 9)> For the entire inkjet ink of Sample 10 (Example 9), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of C.I. Red 3 was 0.5% by mass, the blending ratio of C.I. Red 102 was 0.5% by mass, the blending ratio of C.I. Yellow 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 34.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 13.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 10 (Example 9) was obtained.

[0076] <Sample 11 (Example 10)> For the entire inkjet ink of Sample 11 (Example 10), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 35.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 14.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 11 (Example 10) was obtained.

[0077] <Sample 12 (Example 11)> For the entire inkjet ink of Sample 12 (Example 11), the blending ratio of Blue No. 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 34.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 12 (Example 11) was obtained.

[0078] <Sample 13 (Comparative Example 2)> For the entire inkjet ink of Sample 13 (Comparative Example 2), the blending ratio of Blue No. 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 32.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 17.0% by mass, and the blending ratio of reduced isomaltulose was 10.0% by mass. Thus, the inkjet ink of Sample 13 (Comparative Example 2) was obtained.

[0079] <Sample 14 (Comparative Example 3)> For the entire inkjet ink of Sample 14 (Comparative Example 3), the blending ratio of Blue No. 1 as a coloring material 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 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 5.0% by mass. Thus, the inkjet ink of Sample 14 (Comparative Example 3) was obtained.

[0080] <Sample 15 (Example 12)> For the entire inkjet ink of Sample 15 (Example 12), the blending ratio of Blue No. 1 as a coloring material was 5.0% by mass, the blending ratio of purified water among the solvents was 48.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 7.5% by mass. Thus, the inkjet ink of Sample 15 (Example 12) was obtained.

[0081] <Sample 16 (Example 13)> For the entire inkjet ink of Sample 16 (Example 13), the blending ratio of Blue No. 1 as a coloring material 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 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass. Thus, the inkjet ink of Sample 16 (Example 13) was obtained.

[0082] <Sample 17 (Example 14)> For the entire inkjet ink of Sample 17 (Example 14), the blending ratio of Blue No. 1 as a coloring material was 3.0% by mass, the blending ratio of purified water among the solvents was 45.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 12.0% by mass. Thus, the inkjet ink of Sample 17 (Example 14) was obtained.

[0083] <Sample 18 (Example 15)> For the entire inkjet ink of Sample 18 (Example 15), the blending ratio of C.I. Blue 1 as a coloring material was 3.0% by mass, the blending ratio of purified water among the solvents was 42.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass. Thus, the inkjet ink of Sample 18 (Example 15) was obtained.

[0084] <Sample 19 (Example 16)> For the entire inkjet ink of Sample 19 (Example 16), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 43.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 19 (Example 16) was obtained.

[0085] <Sample 20 (Example 17)> For the entire inkjet ink of Sample 20 (Example 17), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 41.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 18.0% by mass. Thus, the inkjet ink of Sample 20 (Example 17) was obtained.

[0086] <Sample 21 (Example 18)> For the entire inkjet ink of Sample 21 (Example 18), the mixing ratio of Pigment Blue 1 as a coloring material was 1.5% by mass, the mixing ratio of Pigment Red 3 was 0.5% by mass, the mixing ratio of Pigment Red 102 was 0.5% by mass, the mixing ratio of Pigment Yellow 4 was 0.5% by mass, the mixing ratio of purified water among the solvents was 39.5% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further, the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 18.0% by mass. Thus, the inkjet ink of Sample 21 (Example 18) was obtained.

[0087] <Sample 22 (Example 19)> For the entire inkjet ink of Sample 22 (Example 19), the mixing ratio of Pigment Blue 1 as a coloring material was 1.5% by mass, the mixing ratio of purified water among the solvents was 39.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further, the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 20.0% by mass. Thus, the inkjet ink of Sample 22 (Example 19) was obtained.

[0088] <Sample 23 (Comparative Example 4)> For the entire inkjet ink of Sample 23 (Comparative Example 4), the mixing ratio of Pigment Blue 1 as a coloring material was 1.5% by mass, the mixing ratio of purified water among the solvents was 37.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further, the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 22.0% by mass. Thus, the inkjet ink of Sample 23 (Comparative Example 4) was obtained.

[0089] <Sample 24 (Example 20)> For the entire inkjet ink of Sample 24 (Example 20), the blending ratio of Blue No. 1 as a coloring material was 0.7% by mass, the blending ratio of purified water among the solvents was 35.8% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 24 (Example 20) was obtained.

[0090] <Sample 25 (Example 21)> For the entire inkjet ink of Sample 25 (Example 21), the blending ratio of Blue No. 1 as a coloring material was 1.0% by mass, the blending ratio of purified water among the solvents was 35.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 25 (Example 21) was obtained.

[0091] <Sample 26 (Example 22)> For the entire inkjet ink of Sample 26 (Example 22), the blending ratio of Blue No. 1 as a coloring material was 1.2% by mass, the blending ratio of purified water among the solvents was 35.3% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 26 (Example 22) was obtained.

[0092] <Sample 27 (Example 23)> For the entire inkjet ink of Sample 27 (Example 23), the blending ratio of Blue No. 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 40.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 27 (Example 23) was obtained.

[0093] <Sample 28 (Example 24)> For the entire inkjet ink of Sample 28 (Example 24), the blending ratio of Blue No. 1 as a coloring material was 2.0% by mass, the blending ratio of purified water among the solvents was 39.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 28 (Example 24) was obtained.

[0094] <Sample 29 (Example 25)> For the entire inkjet ink of Sample 29 (Example 25), the blending ratio of Blue No. 1 as a coloring material was 2.0% by mass, the blending ratio of Red No. 3 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 38.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further, the blending ratio of trehalose as a fixing agent (anti-fading agent) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 29 (Example 25) was obtained.

[0095] <Sample 30 (Example 26)> For the entire inkjet ink of Sample 30 (Example 26), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 38.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 30 (Example 26) was obtained.

[0096] <Sample 31 (Example 27)> For the entire inkjet ink of Sample 31 (Example 27), the blending ratio of Blue No. 1 as a coloring material was 4.5% by mass, the blending ratio of purified water among the solvents was 42.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 5.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 31 (Example 27) was obtained.

[0097] <Sample 32 (Example 28)> For the entire inkjet ink of Sample 32 (Example 28), the blending ratio of Blue No. 1 as a coloring material was 5.0% by mass, the blending ratio of purified water among the solvents was 41.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 5.0% by mass, and the blending ratio of reduced isomaltulose was 9.0% by mass. Thus, the inkjet ink of Sample 32 (Example 28) was obtained.

[0098] <Sample 33 (Example 29)> For the entire inkjet ink of Sample 33 (Example 29), the blending ratio of C.I. Blue 1 as a coloring material was 10.0% by mass, the blending ratio of purified water among the solvents was 43.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 5.0% by mass. Thus, the inkjet ink of Sample 33 (Example 29) was obtained.

[0099] <Sample 34 (Example 30)> For the entire inkjet ink of Sample 34 (Example 30), the blending ratio of C.I. Blue 1 as a coloring material was 15.0% by mass, the blending ratio of purified water among the solvents was 38.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 5.0% by mass. Thus, the inkjet ink of Sample 34 (Example 30) was obtained.

[0100] <Sample 35 (Example 31)> For the entire inkjet ink of Sample 35 (Example 31), the blending ratio of C.I. Blue 1 as a coloring material was 17.0% by mass, the blending ratio of purified water among the solvents was 36.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 2.5% by mass, and the blending ratio of reduced isomaltulose was 5.0% by mass. Thus, the inkjet ink of Sample 35 (Example 31) was obtained.

[0101] <Sample 36 (Example 32)> For the entire inkjet ink of Sample 36 (Example 32), the mixing ratio of C.I. Blue 1 as a coloring material was 0.7% by mass, the mixing ratio of purified water among the solvents was 39.8% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 20.0% by mass. Thus, the inkjet ink of Sample 36 (Example 32) was obtained.

[0102] <Sample 37 (Example 33)> For the entire inkjet ink of Sample 37 (Example 33), the mixing ratio of C.I. Blue 1 as a coloring material was 1.0% by mass, the mixing ratio of purified water among the solvents was 39.5% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 20.0% by mass. Thus, the inkjet ink of Sample 37 (Example 33) was obtained.

[0103] <Sample 38 (Example 34)> For the entire inkjet ink of Sample 38 (Example 34), the mixing ratio of C.I. Blue 1 as a coloring material was 1.2% by mass, the mixing ratio of purified water among the solvents was 39.3% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 28.0% by mass, and further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 20.0% by mass. Thus, the inkjet ink of Sample 38 (Example 34) was obtained.

[0104] <Sample 39 (Example 35)> For the entire inkjet ink of Sample 39 (Example 35), the blending ratio of C.I. Blue 1 as a coloring material was 1.5% by mass, the blending ratio of purified water among the solvents was 39.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 20.0% by mass. Thus, the inkjet ink of Sample 39 (Example 35) was obtained.

[0105] <Sample 40 (Example 36)> For the entire inkjet ink of Sample 40 (Example 36), the blending ratio of C.I. Blue 1 as a coloring material was 2.0% by mass, the blending ratio of purified water among the solvents was 38.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 20.0% by mass. Thus, the inkjet ink of Sample 40 (Example 36) was obtained.

[0106] <Sample 41 (Example 37)> For the entire inkjet ink of Sample 41 (Example 37), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 41.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (anti-fading agent) was 16.0% by mass. Thus, the inkjet ink of Sample 41 (Example 37) was obtained.

[0107] <Sample 42 (Example 38)> For the entire inkjet ink of Sample 42 (Example 38), the blending ratio of C.I. Blue 1 as a coloring material was 4.5% by mass, the blending ratio of purified water among the solvents was 40.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 42 (Example 38) was obtained.

[0108] <Sample 43 (Example 39)> For the entire inkjet ink of Sample 43 (Example 39), the blending ratio of C.I. Blue 1 as a coloring material was 4.5% by mass, the blending ratio of C.I. Red 3 was 0.5% by mass, the blending ratio of C.I. Red 102 was 0.5% by mass, the blending ratio of C.I. Yellow 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 39.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass. Thus, the inkjet ink of Sample 43 (Example 39) was obtained.

[0109] <Sample 44 (Example 40)> For the entire inkjet ink of Sample 44 (Example 40), the blending ratio of C.I. Blue 1 as a coloring material was 5.0% by mass, the blending ratio of purified water among the solvents was 40.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 15.0% by mass. Thus, the inkjet ink of Sample 44 (Example 40) was obtained.

[0110] <Sample 45 (Example 41)> For the entire inkjet ink of Sample 45 (Example 41), the blending ratio of C.I. Blue 1 as a coloring material was 10.0% by mass, the blending ratio of purified water among the solvents was 40.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass. Thus, the inkjet ink of Sample 45 (Example 41) was obtained.

[0111] <Sample 46 (Example 42)> For the entire inkjet ink of Sample 46 (Example 42), the blending ratio of C.I. Blue 1 as a coloring material was 15.0% by mass, the blending ratio of purified water among the solvents was 37.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 8.0% by mass. Thus, the inkjet ink of Sample 46 (Example 42) was obtained.

[0112] <Sample 47 (Example 43)> For the entire inkjet ink of Sample 47 (Example 43), the blending ratio of C.I. Blue 1 as a coloring material was 17.0% by mass, the blending ratio of purified water among the solvents was 35.5% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 8.0% by mass. Thus, the inkjet ink of Sample 47 (Example 43) was obtained.

[0113] <Sample 48 (Example 44)> For the entire inkjet ink of Sample 48 (Example 44), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 48 (Example 44) was obtained.

[0114] <Sample 49 (Example 45)> For the entire inkjet ink of Sample 49 (Example 45), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 50.5% by mass, the blending ratio of ethanol was 20.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 49 (Example 45) was obtained.

[0115] <Sample 50 (Example 46)> For the entire inkjet ink of Sample 50 (Example 46), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of Red No. 3 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 49.0% by mass, the blending ratio of ethanol was 20.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 50 (Example 46) was obtained.

[0116] <Sample 51 (Example 47)> For the entire inkjet ink of Sample 51 (Example 47), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 40.5% by mass, the blending ratio of ethanol was 30.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 51 (Example 47) was obtained.

[0117] <Sample 52 (Example 48)> For the entire inkjet ink of Sample 52 (Example 48), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 30.5% by mass, the blending ratio of ethanol was 40.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 52 (Example 48) was obtained.

[0118] <Sample 53 (Example 49)> For the entire inkjet ink of Sample 53 (Example 49), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 69.0% by mass, the blending ratio of ethanol was 11.5% by mass, further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 53 (Example 49) was obtained.

[0119] <Sample 54 (Example 50)> For the entire inkjet ink of Sample 54 (Example 50), the mixing ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the mixing ratio of C.I. Red 3 was 0.5% by mass, the mixing ratio of C.I. Red 102 was 0.5% by mass, the mixing ratio of C.I. Yellow 4 was 0.5% by mass, the mixing ratio of purified water among the solvents was 67.5% by mass, the mixing ratio of ethanol was 11.5% by mass, further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the mixing ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 54 (Example 50) was obtained.

[0120] <Sample 55 (Example 51)> For the entire inkjet ink of Sample 55 (Example 51), the mixing ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the mixing ratio of purified water among the solvents was 59.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 10.0% by mass, further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the mixing ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 55 (Example 51) was obtained.

[0121] <Sample 56 (Example 52)> For the entire inkjet ink of Sample 56 (Example 52), the mixing ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the mixing ratio of purified water among the solvents was 49.0% by mass, the mixing ratio of ethanol was 11.5% by mass, the mixing ratio of propylene glycol (PG) was 20.0% by mass, further the mixing ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the mixing ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 56 (Example 52) was obtained.

[0122] <Sample 57 (Example 53)> For the entire inkjet ink of Sample 57 (Example 53), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 41.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 10.0% by mass, and the blending ratio of reduced isomaltulose was 6.0% by mass. Thus, the inkjet ink of Sample 57 (Example 53) was obtained.

[0123] <Sample 58 (Example 54)> For the entire inkjet ink of Sample 58 (Example 54), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 58 (Example 54) was obtained.

[0124] <Sample 59 (Example 55)> For the entire inkjet ink of Sample 59 (Example 55), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 50.5% by mass, the blending ratio of ethanol was 20.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further, the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 59 (Example 55) was obtained.

[0125] <Sample 60 (Example 56)> For the entire inkjet ink of Sample 60 (Example 56), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of C.I. Red 3 was 0.5% by mass, the blending ratio of C.I. Red 102 was 0.5% by mass, the blending ratio of C.I. Yellow 4 was 0.5% by mass, the blending ratio of purified water among the solvents was 49.0% by mass, the blending ratio of ethanol was 20.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 60 (Example 56) was obtained.

[0126] <Sample 61 (Example 57)> For the entire inkjet ink of Sample 61 (Example 57), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 40.5% by mass, the blending ratio of ethanol was 30.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 61 (Example 57) was obtained.

[0127] <Sample 62 (Example 58)> For the entire inkjet ink of Sample 62 (Example 58), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 30.5% by mass, the blending ratio of ethanol was 40.0% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 62 (Example 58) was obtained.

[0128] <Sample 63 (Example 59)> For the entire inkjet ink of Sample 63 (Example 59), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 69.0% by mass, the blending ratio of ethanol was 11.5% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 63 (Example 59) was obtained.

[0129] <Sample 64 (Example 60)> For the entire inkjet ink of Sample 64 (Example 60), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of Red No. 3 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 67.5% by mass, the blending ratio of ethanol was 11.5% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 64 (Example 60) was obtained.

[0130] <Sample 65 (Example 61)> For the entire inkjet ink of Sample 65 (Example 61), the blending ratio of Blue No. 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 59.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 10.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 65 (Example 61) was obtained.

[0131] <Sample 66 (Example 62)> For the entire inkjet ink of Sample 66 (Example 62), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 49.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 20.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 66 (Example 62) was obtained.

[0132] <Sample 67 (Example 63)> For the entire inkjet ink of Sample 67 (Example 63), the blending ratio of C.I. Blue 1 as a coloring material was 3.5% by mass, the blending ratio of purified water among the solvents was 41.0% by mass, the blending ratio of ethanol was 11.5% by mass, the blending ratio of propylene glycol (PG) was 28.0% by mass, and further the blending ratio of trehalose as a fixing agent (fading inhibitor) was 16.0% by mass. Thus, the inkjet ink of Sample 67 (Example 63) was obtained.

[0133] Each of the inks of the aforementioned Examples 1 to 63 and Comparative Examples 1 to 4 was passed through a membrane filter to remove solid foreign matters in the liquid. Specifically, the purified inks were obtained by passing through a membrane filter (cellulose acetate membrane) with a pore size of 5.0 μm once and then passing through a membrane filter (cellulose acetate membrane) with a pore size of 0.8 μm once.

[0134] <Evaluation> Regarding the purified inks using the inks of the above Examples and Comparative Examples, the lightfastness (ΔE, readability) and printability were evaluated by the following method. The evaluation results are shown in Tables 1 to 6 described later together with the ink compositions of the above Examples and Comparative Examples.

[0135] (Lightfastness test) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of the recording medium such as tablets), and a total of 2,656 nozzles, the purified inks of Examples 1 to 63 and Comparative Examples 1 to 4 were each printed on the following tablets as images with a printing drop volume of 6 pl per drop. The tablets to be printed were test film-coated tablets (base: modified starch, coating agent: a mixture of 70% hydroxypropylmethylcellulose and 30% titanium oxide, diameter: 6.5 mm). The printed image was a solid circular image (diameter 4.0 mm). Thereby, film-coated tablet prints were obtained. The light resistance test was conducted in an environment where the ambient humidity of the tester was set to 60% RH (25°C).

[0136] For the film-coated tablet prints of each Example and each Comparative Example for which the chromaticity and optical color density were measured, visible light of a cumulative 1.2 million lux was irradiated using a light stability test apparatus (Nagano Science LT-120A-WD). The chromaticity and optical color density of the film-coated tablet prints irradiated with visible light were measured with a spectrophotometer, and the color difference ΔE (conforming to JIS Z 8781), which indicates the change amount of the chromaticity and optical color density before and after the irradiation with visible light, was compared. The comparison results are shown in Tables 1 to 6. As described above, regarding the change in color tone before and after the irradiation with visible light, as described above, the inventors have derived that if the color difference ΔE in JIS Z 8781 is 25 or less (ΔE ≦ 25), the light fading is sufficiently suppressed and it has excellent light resistance. Also, it has been derived that if the color difference ΔE is 25 or less (ΔE ≦ 25), it also has excellent readability. Therefore, if ΔE ≦ 25, it was considered that the inkjet ink has excellent light resistance and readability, and it was judged as passing in this evaluation. The evaluation criteria for readability are as follows. ◎: ΔE ≦ 15 〇: ΔE ≦ 20 △: ΔE ≦ 25 ×: ΔE > 25

[0137] (Printability: Initial ejection) For the inkjet head, a piezoelectric ceramic-driven drop-on-demand type inkjet head with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of the recording medium such as tablets), and a total of 2,656 nozzles was used. Using the above inkjet head, a test pattern was printed immediately after nozzle maintenance was performed. Then, from the printing status of the test pattern, the readability of the printed image due to the occurrence of non-ejection areas was confirmed. The evaluation criteria are as follows. 〇: No non-ejection △: Readability exists ×: No readability In addition, if the evaluation of the initial ejection property is "〇" or "△", since there are no problems in use, it was judged as qualified.

[0138] The compositions and evaluation results of the inkjet inks of each example and each comparative example are shown in Tables 1 to 6. In Tables 1 to 6, the "blank" parts indicate that the substance is not used. Also, all units in Tables 1 to 6 are "mass%".

[0139]

Table 1

[0140]

Table 2

[0141]

Table 3

[0142]

Table 4

[0143]

Table 5

[0144]

Table 6

[0145] As shown in Tables 1 to 6, in the film-coated tablet prints of Examples 1 to 63, as a result of the lightfastness test, the color difference ΔE before and after irradiation with visible light was all 25 or less (ΔE ≦ 25). Specifically, in the film-coated tablet prints of Examples 1 to 63, the color difference ΔE before and after irradiation with visible light was in the range of 2.2 to 24.6, and all were less than 25. That is, it was found that the inkjet inks of Examples 1 to 63 sufficiently suppressed the light-induced fading of the printed image and were imparted with excellent lightfastness. On the other hand, as shown in Tables 1 to 6, in the film-coated tablet prints of Comparative Examples 1 to 4, as a result of the lightfastness test, the color difference ΔE before and after irradiation with visible light was a value exceeding 25 (ΔE > 25) or could not be measured. That is, it was found that the inkjet inks of Comparative Examples 1 to 4 could not sufficiently suppress the light-induced fading of the printed image and had insufficient lightfastness.

[0146] From the results of the above lightfastness test, it was found that an inkjet ink containing Blue No. 1 as a food dye, only trehalose as a fixing agent, water and ethanol as solvents, and the blending ratio of trehalose being in the range of 7.5% by mass or more and 20.0% by mass or less based on the total mass of the inkjet ink could sufficiently suppress the light-induced fading of the printed image and was imparted with excellent lightfastness. Also, from the results of the above lightfastness test, it was found that an inkjet ink containing Blue No. 1 as a food dye, trehalose and reduced isomaltulose as fixing agents, water and ethanol as solvents, the blending ratio of trehalose being in the range of 2.5% by mass or more and 15.0% by mass or less based on the total mass of the inkjet ink, and the blending ratio of reduced isomaltulose being 10.0% by mass or less based on the total mass of the inkjet ink could sufficiently suppress the light-induced fading of the printed image and was imparted with excellent lightfastness.

[0147] Furthermore, as shown in Tables 1 to 6, in the inkjet inks of Examples 1 to 63, the evaluation results of printability (initial ejection) were all "△" or higher, and it was found that they had sufficient printability (initial ejection) along with excellent light resistance.

[0148] The scope of the present invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that bring about equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention is not limited to the combination of the features of the invention defined by the claims, but may be defined by any desired combination of the specific features among all the disclosed individual features.

Explanation of Reference Numerals

[0149] 1 Substrate of tablet 1S Surface 3 Printed image 4 Specific dye 5 Printed matter of plain tablet 7 Film coat layer 9 Printed matter of film-coated tablet 11 Printed image of plain tablet (solid image) 13 Printed image of film-coated tablet (two-dimensional barcode)

Claims

Claim 1 containing Brilliant Blue No. 1 as a food dye, containing only trehalose as a fixing agent, containing water and ethanol as solvents, The inkjet ink is characterized in that the blending ratio of the trehalose is in the range of 7.5% by mass or more and 20.0% by mass or less based on the total mass of the inkjet ink. Claim 2 containing Brilliant Blue No. 1 as a food dye, containing trehalose and reduced isomaltulose as fixing agents, containing water and ethanol as solvents, The blending ratio of the trehalose is in the range of 2.5% by mass or more and 15.0% by mass or less based on the total mass of the inkjet ink, The inkjet ink is characterized in that the blending ratio of the reduced isomaltulose is 10.0% by mass or less based on the total mass of the inkjet ink. Claim 3 The inkjet ink according to claim 1, wherein the blending ratio of the Brilliant Blue No. 1 is in the range of 1.0% by mass or more and 15.0% by mass or less based on the total mass of the inkjet ink. Claim 4 The inkjet ink according to claim 2, wherein the blending ratio of the Brilliant Blue No. 1 is in the range of 1.0% by mass or more and 15.0% by mass or less based on the total mass of the inkjet ink. Claim 5 A tablet printed matter provided with a printed portion printed with the inkjet ink according to any one of claims 1 to 4.

Images