Inkjet ink and printed tablet

Abstract

To provide an inkjet ink having drying properties, lightfastness, and discharge stability, and a printed tablet including a printed part printed with the inkjet ink.SOLUTION: An ink according to this embodiment contains: Red No. 102; reduced isomaltulose; and, as a solvent, water, monohydric alcohol, and a wetting agent. The monohydric alcohol includes at least one of ethanol, NPA, and IPA. The wetting agent includes at least one of glycerol and PG. The compounding ratio of the Red No. 102 is in the range of 0.5 mass% or more and 3.0 mass% or less based on the total mass of the inkjet ink. The compounding ratio of the monohydric alcohol is in the range of 30 mass% or more and 60 mass% or less based on the total mass of the inkjet ink. The compounding ratio of the wetting agent is in the range of 0.05 mass% or more and 10 mass% or less based on the total mass of the inkjet ink.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to ink-jet inks and tablet prints. [Background technology]

[0002] 2. Description of the Related Art Some inkjet printing inks (hereinafter simply referred to as "inkjet inks" or "inks") are edible by using food dyes such as tar-based pigments as coloring materials. Conventionally, some inkjet inks have been subject to discoloration, in which the colorant's hue (tone) changes in printed characters and images, or discoloration due to a decrease in saturation of the colorant, due to degradation of the colorant. For example, if the inkjet ink lacks light resistance, discoloration (photodiscoloration) may occur due to the decomposition (photodecomposition) of the colorant by the action of light. Such discoloration is recognized as a decrease in the visibility of printed characters and images (hereinafter collectively referred to as "printed images").

[0003] Techniques for suppressing discoloration of such printed images have been developed, and various methods for suppressing discoloration have been proposed (for example, Patent Document 1). In addition, when printing letters or images on tablets, etc., inkjet inks containing food dyes with color development properties may be used to improve visibility. However, some food dyes contained in such inks are subject to significant discoloration and fading due to exposure to light.

[0004] In addition, in recent years, there has been an increasing demand for inkjet inks with excellent drying properties. If the content of drying solvents such as alcohol (lower alcohol) contained in the inkjet ink is increased in order to improve the drying properties of the inkjet ink, the drying of the ink surface in the nozzle of the inkjet printer is accelerated, which deteriorates the ejection properties of the inkjet ink and causes precipitation of the coloring material. In particular, inkjet inks containing Food Red No. 102 tend to have poor ejection properties.

[0005] Furthermore, in conventional techniques, when printing characters or images on tablets or the like, in order to obtain good printing characteristics such as high landing accuracy of ink droplets, a viscosity adjuster may be added to the inkjet ink or the like to adjust the viscosity of the inkjet ink or the like. As a viscosity adjuster for adjusting the viscosity of ink-jet ink or the like, for example, a non-volatile liquid such as glycerin, or a thickener such as sodium alginate or hydroxypropylmethylcellulose may be used.

[0006] However, when a non-volatile liquid such as glycerin is used as the viscosity adjuster, the drying properties of the ink-jet ink or the like may decrease. Furthermore, when a thickener such as sodium alginate or hydroxypropylmethylcellulose is used as the viscosity adjuster, if the solvent contained in the inkjet ink or the like is a quick-drying solvent (a solvent containing a lower alcohol and water), the solubility of the thickener in the quick-drying solvent may decrease, and the ejection stability of the ink or the like may decrease. Furthermore, when a thickener such as sodium alginate or hydroxypropylmethylcellulose is used as the viscosity adjuster, drying on the nozzle liquid surface may be promoted, and the ejection stability of the ink or the like may decrease. Thus, in many of the ink-jet inks and the like according to the conventional technology, there is a trade-off between drying property, light fastness, and ejection stability. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6389506 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of these points, and aims to provide an ink (ink-jet ink) that has drying properties, light resistance, and ejection stability, and a tablet (tablet printed matter) that has a printed portion printed with the ink (ink-jet ink). [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, an ink (inkjet ink) according to one embodiment of the present invention contains Red No. 102, reduced isomaltulose, water as a solvent, a monohydric alcohol, and a humectant, wherein the monohydric alcohol includes at least one of ethanol, NPA, and IPA, and the humectant includes at least one of glycerin and PG, and is characterized in that the blending ratio of Red No. 102 is within the range of 0.5% by mass or more and 3.0% by mass or less with respect to the total mass of the inkjet ink, the blending ratio of the monohydric alcohol is within the range of 30% by mass or more and 60% by mass or less with respect to the total mass of the inkjet ink, and the blending ratio of the humectant is within the range of 0.05% by mass or more and 10% by mass or less with respect to the total mass of the inkjet ink.

[0010] In addition, in order to achieve the above-mentioned object, a tablet (printed tablet) according to one embodiment of the present invention is characterized in that it has a printed portion printed using the above-mentioned ink (inkjet ink). Effect of the Invention

[0011] According to one aspect of the present invention, it is possible to provide an inkjet ink having drying properties, light resistance, and ejection stability, and a tablet printed matter having a printed portion printed with the inkjet ink. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a conceptual diagram illustrating the permeability and light resistance of an ink-jet ink according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (plain tablet) according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic cross-sectional view showing an example of a tablet (film-coated tablet) according to an embodiment of the present invention. [Figure 4] 1 is an example of a printed image of a tablet (plain tablet) according to an embodiment of the present invention. [Diagram 5] 1 is an example of a printed image of a tablet (film-coated tablet) according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The inkjet ink (ink) according to an embodiment of the present invention (hereinafter referred to as "the present embodiment") is an inkjet ink containing a viscosity modifier, and relates to an inkjet ink that can sufficiently suppress light discoloration of images printed by inkjet printing on the surface of medical tablets, maintain light resistance, and has excellent ejection stability (intermittent resumability) and excellent drying properties, and a tablet print having a printed part printed with the inkjet ink. The configuration of the inkjet ink according to the embodiment of the present invention and the tablet print having a printed part printed with the inkjet ink will be described in detail below.

[0014] [Constitution of Inkjet Ink] The inkjet ink of this embodiment is an edible inkjet ink, and contains Edible Red No. 102 (hereinafter simply referred to as "Red No. 102"), which is an edible dye (food colorant), reduced isomaltulose, water as a solvent, a monohydric alcohol, and a humectant, wherein the monohydric alcohol includes at least one of ethanol, NPA, and IPA, and the humectant includes at least one of glycerin and PG, the blending ratio of Red No. 102 is within the range of 0.5% by mass or more and 3.0% by mass or less with respect to the total mass of the inkjet ink, the blending ratio of the monohydric alcohol is within the range of 30% by mass or more and 60% by mass or less with respect to the total mass of the inkjet ink, and the blending ratio of the humectant is within the range of 0.05% by mass or more and 10% by mass or less with respect to the total mass of the inkjet ink.

[0015] The reduced isomaltulose used in this embodiment is a substance that functions as a viscosity adjuster that adjusts the viscosity of the inkjet ink. In addition, this reduced isomaltulose is a substance that also has the fixing property (ink fixing property) that fixes the ink to the surface of the printed material (e.g., a solid preparation). According to the above-mentioned configuration, it is possible to sufficiently suppress discoloration due to light of the printed image, maintain the light resistance of the inkjet ink, and provide excellent ejection stability and excellent drying properties. Hereinafter, the mechanism related to the improvement of the light resistance will be described with reference to FIG. 1. After that, the mechanism related to the improvement of the ejection stability will be described.

[0016] FIG. 1 is a conceptual diagram for explaining the relationship between ink adhesion and light resistance on the surface of a printed material (solid preparation). Here, for example, a tablet with a film-coated portion with few voids, that is, a film-coated (FC) tablet, is used as the solid preparation. Note that the present invention is not limited to this, and plain tablets or capsule tablets may be used as the printed material.

[0017] 1(a) to 1(c) are schematic cross-sectional views in the thickness direction of a tablet (here, a film-coated tablet) after printing inkjet inks A to C having different compositions on the tablet for a certain period of time. In this example, inkjet ink A is an ink using a specific dye 4 as a coloring material, and a mixture containing water as a solvent, a monohydric alcohol which is at least one of ethanol, normal propyl alcohol (NPA), and isopropyl alcohol (IPA), and a wetting agent which is at least one of glycerin and propylene glycol (PG). An example of the specific dye 4 is Red No. 102.

[0018] Inkjet ink B is an ink obtained by adding a specific viscosity modifier to inkjet ink A. The viscosity modifier added to inkjet ink B is a viscosity modifier (e.g., maltose) that has a relatively high solubility in water and a relatively low ink fixation property. Inkjet ink C is an ink obtained by adding reduced isomaltulose, a viscosity modifier with a relatively high ink fixation property, to inkjet ink A.

[0019] Specifically, FIG. 1(a) is a schematic cross-sectional view in the thickness direction of a tablet in a state where an ink-jet ink A containing a mixture containing a specific dye 4 as a coloring material, water as a solvent, a monohydric alcohol which is at least one of ethanol, normal propyl alcohol (NPA) and isopropyl alcohol (IPA), and a wetting agent which is at least one of glycerin and propylene glycol (PG) is printed on the surface 1S of a tablet substrate 1 and a certain time (for example, 140 hours) has elapsed. FIG. 1(b) is a schematic cross-sectional view in the thickness direction of a tablet in a state where an ink-jet ink B is printed on the surface 1S of a tablet substrate 1 and a certain time (for example, 140 hours) has elapsed. FIG. 1(c) is a schematic cross-sectional view in the thickness direction of a tablet in a state where an ink-jet ink C is printed on the surface 1S of a tablet substrate 1 and a certain time (for example, 140 hours) has elapsed.

[0020] First, the presence or absence of a viscosity modifier in the inkjet ink and the permeability of the dye will be described using inkjet inks A and B as examples. Among various coloring materials used in inkjet inks, for example, tar-based dyes used as food dyes can cause discoloration of characters and images printed on the surface of solid preparations. For example, among tar-based dyes, Red No. 102 has caused discoloration of printed images due to penetration into solid preparations over time and photodecomposition. In response to this, the addition of a viscosity modifier to the inkjet ink can suppress the penetration of the dye into the solid preparation and the discoloration of printed images.

[0021] As shown in FIG. 1(a), when inkjet ink A that does not contain a viscosity modifier is printed, the specific dye 4 penetrates into the base material 1 of the tablet after a certain time has passed since printing. Here, the penetration depth of the specific dye 4 in the inkjet ink A after the certain time has passed is defined as penetration depth X (μm). In contrast, as shown in FIG. 1(b), when inkjet ink B that contains a viscosity modifier (e.g., maltose) with relatively low ink fixing property is printed, the penetration depth Y (μm) of the inkjet ink B becomes smaller than the penetration depth X of the inkjet ink A after a certain time has passed since printing (X>Y).

[0022] In the inkjet ink B, the addition of a specific viscosity modifier increases the viscosity of the ink, suppressing the penetration of the specific dye 4 into the tablet substrate 1. Therefore, when the inkjet ink B is printed, the specific dye 4 remains in the vicinity of the surface 1S in the tablet substrate 1 even after a certain time has passed since printing. In other words, the inkjet ink containing a specific viscosity modifier can suppress discoloration of the printed image due to the penetration of the dye (i.e., Red No. 102) compared to the inkjet ink without the viscosity modifier. On the other hand, the inkjet ink B with the specific viscosity modifier added may not be able to sufficiently suppress discoloration of the printed image due to light irradiation (light discoloration).

[0023] In contrast, the inkjet ink according to the present embodiment is made to adhere to the surface of a substrate by selecting the type and physical properties of the added viscosity modifier (i.e., reduced isomaltulose, which is a viscosity modifier with relatively high ink adhesion) and the solvent, thereby sufficiently suppressing discoloration due to light of the printed image and improving light resistance. The present inventors have found that adhering the ink to the surface of a substrate (e.g., a tablet) is effective in suppressing discoloration due to light of the printed image. In this example, the ink adheres to the surface 1S of the tablet, so that the specific dye 4 adheres to the surface 1S, and as a result, the specific dye 4 can remain at a high concentration on the surface 1S.

[0024] When the concentration of the specific dye 4 on the surface 1S of the tablet substrate 1 is high, for example, the ratio of coloring material that undergoes photodiscoloration due to photodecomposition among the specific dye 4 on the surface 1S is reduced. In other words, even if a part of the specific dye 4 undergoes photodiscoloration, the effect is limited, and the decrease in visibility (readability) of the printed image is suppressed. This maintains the visibility of the entire printed image, and as a result, photodiscoloration of the printed image can be sufficiently suppressed. Therefore, the light resistance of the inkjet ink can be improved. The present inventors have discovered that reduced isomaltulose, which has a relatively low solubility in water among viscosity modifiers, functions as a fixing agent that fixes ink containing Red No. 102 as a coloring material to the surface of a printed material.

[0025] Specifically, the inkjet ink according to this embodiment contains Red No. 102 as an edible dye, which is a coloring material, and contains reduced isomaltulose, which has a solubility of less than 39 g in 100 ml of water at 20° C., as a viscosity adjuster. With this configuration, ink containing a specific tar-based dye used as a coloring material (Red No. 102 in this example) can be fixed to the surface of a printed material, and the specific tar-based dye can be left on the surface at a high concentration. As a result, the inkjet ink according to this embodiment can sufficiently suppress light discoloration of printed images and improve light resistance.

[0026] As shown in FIG. 1(c), when the inkjet ink C corresponding to the inkjet ink according to this embodiment is printed on the surface 1S of the tablet substrate 1, the specific dye 4 (here, Red No. 102) in the ink is fixed to 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 sugar (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. In other words, the inkjet ink C can further suppress the penetration of the specific dye 4. Therefore, the specific dye 4 remains at a high concentration on the surface 1S, and the decrease in visibility of the printed image is suppressed as described above. As a result, the light discoloration of the printed image is sufficiently suppressed, and the inkjet ink C can improve the light resistance.

[0027] On the other hand, while the inkjet ink B can cause the specific dye 4 to remain near the surface 1S inside the base material 1 of the tablet, it does not sufficiently suppress the penetration of the specific dye 4 and is therefore unable to fix the ink onto the surface 1S. In other words, since the concentration of the specific dye 4 remaining on the surface 1S in the inkjet ink B is low, it is unable to sufficiently suppress discoloration due to light in the printed image and light resistance is not improved.

[0028] In this way, the inkjet ink according to this embodiment contains reduced isomaltulose as a viscosity modifier with ink fixing properties, which significantly suppresses the penetration of a specific tar-based dye (Red No. 102) into the interior of the printed material, thereby fixing the ink to the surface of the printed material. As a result, the inkjet ink according to this embodiment can improve light resistance by suppressing light discoloration of the printed image, and can also suppress discoloration of the printed image due to the penetration of the specific tar-based dye into the interior of the printed material.

[0029] Also, as shown in FIG. 1(c), the inkjet ink C can be fixed to the surface 1S of the tablet substrate 1 in a slightly raised manner. As a result, when the inkjet ink C is printed, for example, the print is recognized as being dark and raised on the surface 1S. Therefore, compared to the inkjet inks A and B, for example, the inkjet ink C can improve the visibility of the printed image when printed. In other words, the inkjet ink according to this embodiment can reduce the decrease in visibility due to discoloration due to light of the printed image, and can impart good visibility to the printed image at the time of printing.

[0030] The light fastness of the inkjet ink according to this embodiment will be described in detail below. The inkjet ink according to the present embodiment may have a color difference ΔE of 20 or less in JIS Z 8781 before and after the light fastness test. Here, the light fastness test is, for example, a test for comparing the color difference ΔE (based on JIS Z 8781) indicating 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 the present embodiment. Specifically, the color difference ΔE is measured before and after irradiation with a cumulative visible light of 1.2 million lux on the printed image, and the values ​​are compared. For example, a light stability tester (Nagano Science LT-120A-WD) is used for the irradiation with visible light. The printed image in the light fastness test is, for example, a solid print on a tablet (e.g., a film-coated tablet) that is the printing target.

[0031] The light resistance necessary and sufficient for forming a printed image on a medical tablet or the like often means that the color difference ΔE of the printed image before and after irradiation with visible light is 20 or less in a light resistance test in which visible light of 1.2 million lux is irradiated. The inventors derived the color difference ΔE of 20 or less as the criterion for sufficient light resistance as a result of an opinion test conducted by the inventors and various medical professionals, and it is recognized that the visibility of the printed image (e.g., the readability of the printed characters) is reduced when the color difference ΔE exceeds 20. In other words, if the color difference ΔE before and after irradiation with visible light is 20 or less, it can be said that the inkjet ink has excellent light resistance because the light discoloration is sufficiently suppressed. Note that this number is larger than the standard of color difference ΔE of 3 to 6 in general commercial printed matter, but this number was obtained because it is assumed that the printed image on the surface of the tablet will naturally fade without comparing the tablets before and after exposure to light.

[0032] Each component constituting the inkjet ink according to this embodiment will be described below. (Colorant) As described above, the inkjet ink according to this embodiment contains the food dye Red No. 102. Red No. 102 is an edible tar-based colorant, and is also called New Coccine.

[0033] In the inkjet ink according to the present embodiment, the blending ratio of Red No. 102, i.e., the content of Red No. 102, is within a range of 0.5% by mass to 3.0% by mass 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 excellent ejection stability (i.e., excellent intermittent restartability). Furthermore, if the content of Red No. 102 is within the above range, the addition of reduced isomaltulose, which is a viscosity modifier with relatively high ink fixation property, ensures that Red No. 102 remains at a high concentration on the surface of the printed matter, suppressing light discoloration in the printed image and reliably improving the light resistance of the inkjet ink according to the present embodiment.

[0034] In contrast, if the content of Red No. 102 is less than 0.5% by mass, the overall printed color tends to become lighter and the visibility of the printed image tends to decrease. Furthermore, if the content of Red No. 102 is less than 0.5% by mass, the light resistance of the printed tablet may decrease or may not be exhibited during storage.

[0035] Furthermore, if the content of Red No. 102 exceeds 3.0% by mass, the dissolution stability of the colorant will deteriorate, causing the pigment in the ink to precipitate or deposit as a solid, which may clog the nozzles of the inkjet head during printing and reduce ejection stability. The content of Red No. 102 is more preferably in the range of 1.0% by mass to 2.5% by mass, and even more preferably in the range of 1.0% by mass to 1.6% by mass, based on the total mass of the ink. With this composition, it is possible to impart better visibility to the printed image and to impart more excellent ejection stability.

[0036] The inkjet ink according to the present embodiment may contain the above-mentioned specific tar-based dye, that is, a dye (coloring material) other than Red No. 102. The dye other than Red No. 102 is not particularly limited as long as it is edible. The dye that can be added to the inkjet ink according to the present embodiment may be appropriately selected from conventionally known synthetic food dyes and natural food dyes and added. When the inkjet ink according to the present embodiment contains a coloring material other than Red No. 102 as an edible dye, the total content of the edible dyes other than Red No. 102 is preferably within a range of 0.6% by mass or less, more preferably within a range of 0.4% by mass or less, and even more preferably within a range of 0.3% by mass or less, based on the mass of the entire ink. If the total content of the edible dyes other than Red No. 102 is within the above range, the light fastness of the inkjet ink can be improved, good visibility can be imparted to the printed image, and sufficient ejection stability can be imparted to the inkjet ink.

[0037] Examples of synthetic food dyes include tar-based dyes, natural dye derivatives, and natural synthetic dyes. Examples of tar-based dyes include Food Red No. 2, Food Red No. 3, Food Red No. 40, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow No. 4, Food Yellow No. 5, Food Blue No. 1, Food Blue No. 2, Food Red No. 2 Aluminum Lake, Food Red No. 3 Aluminum Lake, Food Red No. 40 Aluminum Lake, Food Yellow No. 4 Aluminum Lake, Food No. 5 Aluminum Lake, Food Blue No. 1 Aluminum Lake, and Food Blue No. 2 Aluminum Lake. Examples of natural dye derivatives include norbixin potassium. Examples of natural synthetic dyes include β-carotene and riboflavin.

[0038] Examples of natural food dyes include anthocyanin dyes, carotenoid dyes, quinone dyes, chlorophyll dyes, flavonoid dyes, betaine dyes, monascus dyes, and other dyes derived from natural products. Examples of anthocyanin dyes include red radish dyes, red cabbage dyes, red rice dyes, elderberry dyes, cowberry dyes, gooseberry dyes, cranberry dyes, salmonberry dyes, perilla dyes, sweet blueberry dyes, strawberry dyes, dark sweet cherry dyes, cherry dyes, hibiscus dyes, huckleberry dyes, grape juice dyes, grape skin dyes, blackcurrant dyes, blackberry dyes, blueberry dyes, plum dyes, white wortberry dyes, boysenberry dyes, mulberry dyes, purple sweet potato dyes, purple corn dyes, purple yam dyes, raspberry dyes, redcurrant dyes, loganberry dyes, and other anthocyanin dyes. Examples of carotenoid pigments include annatto pigment, gardenia yellow, and other carotenoid pigments. Examples of quinone pigments include cochineal pigment, lithospermum pigment, lac pigment, and other quinone pigments. Examples of flavonoid pigments include safflower yellow, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of betaine pigments include beet red pigment. Examples of monascus pigments include red koji pigment and red koji yellow. Examples of pigments derived from other natural products include turmeric pigment, clover pigment, gardenia red pigment, spirulina blue pigment, and the like.

[0039] (Viscosity modifier) As described above, the inkjet ink according to this embodiment contains a viscosity modifier having an ink fixing property that fixes the ink containing a specific tar-based colorant (Red No. 102) to the surface of the printed material. Specifically, the viscosity modifier contained in the inkjet ink according to this embodiment is reduced isomaltulose, and the solubility of reduced isomaltulose in 100 ml of water at 20° C. is 38 g. If the viscosity modifier has this composition, the ink containing Red No. 102 can be sufficiently fixed to the surface of the printed material. As a result, the inkjet ink according to this embodiment can sufficiently suppress the photo-induced discoloration of the printed image and improve the light resistance. In addition, reduced isomaltulose used as a viscosity modifier in this embodiment also has a function of suppressing the decomposition (photodecomposition) of the inkjet ink by irradiation with light. Therefore, the occurrence of photo-induced discoloration itself can be suppressed.

[0040] Furthermore, by adding reduced isomaltulose as a viscosity adjusting agent to the inkjet ink, it becomes easier to adjust the viscosity of the inkjet ink, and the ejection stability can be improved.

[0041] The blending ratio of reduced isomaltulose in the inkjet ink according to this embodiment, i.e., the content of reduced isomaltulose, is preferably within the range of 3.0% by mass to 8.5% by mass relative to the total mass of the ink. With this configuration, the ink fixing effect of reduced isomaltulose is more reliably exhibited, and the lightfastness of the inkjet ink can be reliably improved. In addition, high ejection stability can be imparted to the inkjet ink according to this embodiment.

[0042] On the other hand, if the blending ratio of reduced isomaltulose is less than 3.0% by mass, the ink adhesion effect is reduced and light resistance may decrease. Also, if the blending ratio of reduced isomaltulose is less than 3.0% by mass, the ink viscosity may be insufficient, so that the ejected ink droplets may not land at the intended position (i.e., the landing accuracy of the ink droplets may decrease). Also, if the blending ratio of reduced isomaltulose is more than 8.5% by mass, the ink viscosity increases and reduced isomaltulose precipitates on the nozzle surface, which may cause nozzle clogging of the inkjet head during printing and decrease ejection stability.

[0043] The blending ratio of reduced isomaltulose is preferably in the range of 4.0% by mass to 8.0% by mass of the total ink, and more preferably in the range of 5.0% by mass to 8.0% by mass of the total ink. With such a composition, the ink fixing effect of reduced isomaltulose can be more reliably exhibited, and the lightfastness of the inkjet ink can be reliably improved. Furthermore, the inkjet ink according to this embodiment can be provided with even higher ejection stability.

[0044] The viscosity of the inkjet ink according to this embodiment, i.e., the viscosity of the inkjet ink to which reduced isomaltulose has been added as a viscosity modifier, is preferably within the range of 1.0 mPa·s to 7.0 mPa·s. With this configuration, it is possible to impart an appropriate viscosity to the ink, so that the ejected ink droplets can land at the intended positions (i.e., the landing accuracy of the ink droplets can be improved).

[0045] In contrast, if the viscosity of the inkjet ink is less than 1.0 mPa s, the ink viscosity is too low and the ejected ink droplets may not land at the intended position (i.e., the landing accuracy of the ink droplets may decrease).If the viscosity of the inkjet ink is more than 7.0 mPa s, the ink viscosity is too high and the ink droplets may be difficult to eject.

[0046] The viscosity of the inkjet ink is more preferably in the range of 2.0 mPa·s to 6.0 mPa·s, even more preferably in the range of 2.0 mPa·s to 5.0 mPa·s, and most preferably in the range of 2.5 mPa·s to 3.5 mPa·s. With this configuration, the landing accuracy of the ink droplets can be further improved.

[0047] (Viscosity measurement method) The viscosity of the ink may be measured, for example, using a rotational viscometer at a measurement temperature of 25°C. In this embodiment, the viscosity of the ink is a value measured at a measurement temperature of 25° C. using a rotational viscometer.

[0048] Furthermore, the ratio of the mass of reduced isomaltulose to the mass of Red No. 102 in the inkjet ink according to this embodiment (reduced isomaltulose / Red No. 102) is preferably in the range of 2.3 to 6.5, more preferably in the range of 3.1 to 6.1, and even more preferably in the range of 3.8 to 6.1. With this configuration, the ink fixing effect of reduced isomaltulose can be more reliably exhibited, and the lightfastness of the inkjet ink can be reliably improved. Furthermore, high ejection stability can be imparted to the inkjet ink according to this embodiment.

[0049] On the other hand, if the ratio (reduced isomaltulose / Red No. 102) is less than 2.3, the ink adhesion effect may be reduced. Also, if the ratio (reduced isomaltulose / Red No. 102) is less than 2.3, the light resistance of the printed tablet may decrease or may not be exhibited during storage. Also, if the ratio (reduced isomaltulose / Red No. 102) is less than 2.3, the viscosity of the ink may be insufficient, and the ejected ink droplets may not land at the intended position (i.e., the landing accuracy of the ink droplets may decrease).

[0050] Furthermore, if the above ratio (reduced isomaltulose / Red No. 102) exceeds 6.5, the ink viscosity will increase and reduced isomaltulose will precipitate on the nozzle surface, which may cause the nozzles of the inkjet head to clog during printing and reduce ejection stability. As described above, by setting the amount of reduced isomaltulose added to the ink-jet ink within a specific numerical range, it is possible to improve both the light fastness and the ejection stability.

[0051] The mechanism for improving the ejection stability will be described below. Reduced isomaltulose added to inkjet ink forms a film on the ink interface of the nozzle surface of an inkjet device such as an inkjet printer, and also has the function of preventing solvent evaporation. In addition, the film has the property of easily collapsing and redissolving during the ink ejection operation by the piezo of the inkjet device. Therefore, by adding reduced isomaltulose to the inkjet ink, the change in the physical properties of the ink near the nozzle surface of the inkjet device is suppressed, and stable ejection is possible. As a result, the ejection stability of the inkjet ink containing reduced isomaltulose is improved.

[0052] (solvent) The inkjet ink according to this embodiment contains, in addition to the specific tar-based colorant (Red No. 102) and the viscosity modifier (reduced isomaltulose), a solvent (dispersion medium) for dissolving (dispersing) the specific tar-based colorant and the viscosity modifier. The inkjet ink according to this embodiment contains, as a solvent, water (e.g., purified water), a monohydric alcohol which is at least one of ethanol, normal propyl alcohol (NPA), and isopropyl alcohol (IPA), and a wetting agent which is at least one of glycerin and propylene glycol (PG).

[0053] Generally, reduced isomaltulose has a property of being difficult to dissolve in alcohols. Therefore, in this embodiment, the solvent contains at least one monohydric alcohol selected from ethanol, normal propyl alcohol, and isopropyl alcohol, and at least one wetting agent (polyhydric alcohol) selected from glycerin and propylene glycol, thereby decreasing the solubility of reduced isomaltulose in the solvent. As a result, in the inkjet ink according to this embodiment, the ink fixing effect of reduced isomaltulose is further improved, and the above-mentioned specific tar-based dye (in this example, Red No. 102) contained in the ink can be left at a higher concentration on the surface of the printed material (e.g., a tablet). Therefore, the lightfastness of the inkjet ink according to this embodiment can be further improved.

[0054] Glycerin and propylene glycol also function as wetting agents, preventing the ink from drying in the inkjet nozzles and providing sufficient ejection stability to the ink. Ethanol, normal propyl alcohol, and isopropyl alcohol are particularly volatile, and therefore can improve the transfer resistance (drying property) of the inkjet ink. By adding the above-mentioned alcohols to the solvent in addition to water, the light resistance of the inkjet ink can be further improved and the inkjet ink can be provided with performance according to each component.

[0055] In the inkjet ink according to this embodiment, the blending ratio of the monohydric alcohol described above, i.e., the content of the monohydric alcohol, is within a range of 30% by mass to 60% by mass with respect to the mass of the entire ink. With this configuration, it is possible to impart excellent drying properties to the ink. Furthermore, if the content of the monohydric alcohol is within the above range, it is possible to impart appropriate viscosity to the ink, so that the ejected ink droplets can be landed at the intended position (i.e., the landing accuracy of the ink droplets can be improved).

[0056] In contrast, if the content of monohydric alcohol is less than 30% by mass, the drying properties of the ink tend to decrease.

[0057] Furthermore, if the content of monohydric alcohol exceeds 60% by mass, drying of the liquid surface in the nozzle is accelerated, and the nozzle of the inkjet head is clogged during printing, which may reduce ejection stability. The content of the monohydric alcohol is more preferably in the range of 35% by mass to 55% by mass, and even more preferably in the range of 35% by mass to 50% by mass, based on the total mass of the ink. With this configuration, the drying property of the ink can be reliably maintained and excellent ejection stability can be imparted.

[0058] In addition, the blending ratio of each component of the above-mentioned solvent in the inkjet ink according to the present embodiment is not limited, but the blending ratio of the above-mentioned wetting agent, i.e., the amount of the wetting agent added, is in the range of 0.05% by mass to 10% by mass with respect to the total mass of the ink. With such a configuration, the solubility of reduced isomaltulose in the solvent is reliably reduced, and the fixing effect of the ink containing the above-mentioned specific tar-based dye is further improved. Therefore, it is possible to impart superior light resistance to the inkjet ink. Furthermore, with the above configuration, it is possible to prevent the liquid surface in the nozzle from drying, thereby improving the ejection stability.

[0059] On the other hand, if the amount of the wetting agent is less than 0.05% by mass, the effect of reducing the solubility of reduced isomaltulose in the solvent decreases, and the fixing effect may decrease. Also, if the amount of the wetting agent is less than 0.05% by mass, the drying of the liquid surface in the nozzle may be accelerated, and the ejection stability may decrease.

[0060] Furthermore, if the amount of humectant added exceeds 10% by mass, the proportion of monohydric alcohol in the ink as a whole decreases relatively, which increases the delay in drying of the printed surface on the tablet surface and can cause problems (poor transfer) such as wet ink adhering to one tablet and causing stains when printed tablets come into contact with each other. The blending ratio of the humectant, i.e., the amount of the humectant added, is preferably in the range of 0.05% by mass to 6% by mass, and more preferably in the range of 0.05% by mass to 4% by mass, with respect to the total mass of the ink. With this configuration, the drying property of the ink can be reliably maintained and excellent ejection stability can be imparted.

[0061] (Internal resin) The inkjet ink according to the present embodiment may contain an internal resin in addition to the above-mentioned dyes and solvents. The internal resin that can be added to the inkjet ink according to the present embodiment may be an edible, water-soluble powder, paste, or flake-like resin-like substance that can form a film on the tablet surface by drying after printing. Examples of the internal resin include polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), high molecular weight polyethylene glycols (PEGs) such as polyethylene glycol 4000 / polyethylene glycol 1540, shellac resin, methacrylic acid copolymer (product name: Eudragit S100), maltodextrin, erythritol, and the like.

[0062] (Leveling agent) The inkjet ink according to the present embodiment may contain a leveling agent in addition to the above-mentioned dyes, solvents, or internally added resins. The leveling agent that can be added to the inkjet ink according to the present embodiment may be an edible and water-soluble surfactant. Examples of the leveling agent include polyglycerin fatty acid esters (e.g., Decaglycerin Distearate Q-182S and Decaglycerin Monolaurate Q-12S, both manufactured by Taiyo Kagaku Co., Ltd.), sorbitan fatty acid esters (e.g., NIKKOL SL-10, manufactured by Nikko Chemicals Co., Ltd.), sucrose fatty acid esters (e.g., DK Ester F-110, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and polysorbates (Emersol S-120 series, manufactured by Kao Corporation).

[0063] [Printing method] The inkjet ink according to the present embodiment is not particularly limited in terms of the printing method, and can be printed using an inkjet device such as a commercially available inkjet printer. Therefore, the inkjet ink according to the present embodiment has a wide range of applications and is very useful. For example, the inkjet ink according to the present embodiment can be printed using a so-called drop-on-demand type inkjet device that uses a piezoelectric element (piezoelectric ceramics) as an actuator, and can also be printed using other types of inkjet devices. 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 momentarily heating a micro-heating element to a high temperature (200 to 300°C), electrostatic type devices that eject inkjet ink by electrostatically vibrating an actuator, devices that employ an ultrasonic method that utilizes the cavitation phenomenon of ultrasonic waves, etc. In addition, if the inkjet ink according to this embodiment has charging properties, it is also possible to use a device that employs a continuous ejection method.

[0064] 〔tablet〕 In this embodiment, the inkjet ink according to this embodiment may be printed or printed on the surface of a tablet, for example, using the printing method described above. In other words, the tablet according to this embodiment may have a printed portion, i.e., a printed image, printed using the inkjet ink according to this embodiment. The inkjet ink according to this embodiment can improve the light resistance of a printed image applied to the surface of a medical tablet using an inkjet printing method, for example. The configuration of a tablet having a printed image printed with the inkjet ink according to this embodiment will be described below.

[0065] The tablet according to the present embodiment is, for example, a medical tablet. Here, the term "medical tablet" refers to, for example, plain tablets (plain tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, as well as film-coated tablets in which a water-soluble surface layer is formed on the outermost surface of the tablet.

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

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

[0068] The tablet according to the present embodiment can be mixed with a carrier acceptable for its use together with the active ingredient as necessary. For example, if it is a medical tablet, a medicament acceptable carrier can be mixed. As the medicament acceptable carrier, various organic or inorganic carrier substances commonly used as pharmaceutical materials are used, and for example, excipients, lubricants, binders, disintegrants, thickeners, etc. are appropriately mixed in appropriate amounts. In addition, additives such as preservatives, antioxidants, colorants, and sweeteners can be used as necessary.

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

[0070] (Effects of this embodiment) (1) The inkjet ink of this embodiment contains Red No. 102, reduced isomaltulose, water as a solvent, a monohydric alcohol, and a humectant, the monohydric alcohol includes at least one of ethanol, NPA, and IPA, the humectant includes at least one of glycerin and PG, the blending ratio of Red No. 102 is within the range of 0.5% by mass to 3.0% by mass of the total inkjet ink, the blending ratio of the monohydric alcohol is within the range of 30% by mass to 60% by mass of the total inkjet ink, and the blending ratio of the humectant is within the range of 0.05% by mass to 10% by mass of the total inkjet ink. With this configuration, it is possible to provide drying properties, light resistance, and ejection stability.

[0071] (2) The amount of reduced isomaltulose blended in the inkjet ink according to this embodiment may be within a range of 3.0% by mass or more and 8.5% by mass or less with respect to the mass of the entire inkjet ink. With this configuration, it is possible to further improve the light resistance and the ejection stability.

[0072] (3) The viscosity of the inkjet ink according to this embodiment may be within the range of 1.0 mPa·s to 7.0 mPa·s. With this configuration, it is possible to impart appropriate viscosity to the ink, so that the ejected ink droplets can land at the intended positions (that is, the landing accuracy of the ink droplets can be improved).

[0073] (4) The tablet according to this embodiment has a printed image (an example of a printed portion) 3 printed with the above-mentioned inkjet ink. With this configuration, it is possible to sufficiently suppress light discoloration of the printed image 3 etc. printed directly on the surface of the tablet, and to 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.

[0074] [Example] <Example 1> The procedure for preparing the inkjet ink according to Example 1 will be described below. (Inkjet ink manufacturing) First, a printing ink was prepared. The inkjet ink contains the following components: a dye (coloring material), a solvent, a wetting agent, and a viscosity modifier (reduced isomaltulose). The preparation was carried out in the following order: first, a wetting agent and a viscosity modifier (reduced isomaltulose) were added to a solvent to obtain a transparent base liquid. Next, the dye was added to the transparent base liquid. In this way, the ink according to this embodiment was prepared. The various components will be specifically described below.

[0075] In Examples 1 to 30 and Comparative Examples 1 to 12, purified water (ion-exchanged water), ethanol, normal propyl alcohol (NPA: 1-propanol), and isopropyl alcohol (IPA: 2-propanol) were used as solvents as necessary. In addition, in Examples 1 to 30 and Comparative Examples 1 to 12, glycerin and PG (propylene glycol) were used as moisturizing agents as necessary.

[0076] In this example, at least one of ethanol, NPA, and IPA, and at least one of glycerin and PG were added to purified water and thoroughly stirred to obtain a solvent (mixed solvent). Reduced isomaltulose was added to the solvent as a viscosity modifier, and the mixture was stirred for about 1 hour to obtain a transparent base liquid. Food dyes Red No. 102, Red No. 3, Yellow No. 4, and Blue No. 1 were added as colorants to the transparent base liquid to obtain the inkjet ink of Example 1. With respect to the entire inkjet ink of Example 1, the blending ratio of the colorant Red No. 102 was 0.50% by mass, the blending ratio of Red No. 3 was 0.03% by mass, the blending ratio of Yellow No. 4 was 0.03% by mass, the blending ratio of Blue No. 1 was 0.03% by mass, the blending ratio of purified water among the solvents was 52.96% by mass, the blending ratio of ethanol was 40.0% by mass, the blending ratio of propylene glycol (PG) was 0.1% by mass, and the blending ratio of reduced isomaltulose as a viscosity adjuster was 6.35% by mass. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 in the ink-jet ink of Example 1 (mass of reduced isomaltulose / mass of Red No. 102) was adjusted to 12.7.

[0077] <Example 2> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.0 mass%, the blending ratio of Red No. 3 was 0.06 mass%, the blending ratio of Yellow No. 4 was 0.06 mass%, the blending ratio of Blue No. 1 was 0.06 mass%, and the blending ratio of purified water was 52.37 mass%. Except for this, the inkjet ink of Example 2 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 2 was adjusted to 6.4.

[0078] <Example 3> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, and the blending ratio of purified water was 52.00% by mass. Except for this, the inkjet ink of Example 3 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 3 was adjusted to 4.8.

[0079] <Example 4> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.60% by mass, the blending ratio of Red No. 3 was 0.10% by mass, the blending ratio of Yellow No. 4 was 0.10% by mass, the blending ratio of Blue No. 1 was 0.10% by mass, and the blending ratio of purified water was 51.65% by mass. Except for this, the inkjet ink of Example 4 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 4 was adjusted to 4.0.

[0080] <Example 5> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 2.50% by mass, the blending ratio of Red No. 3 was 0.15% by mass, the blending ratio of Yellow No. 4 was 0.15% by mass, the blending ratio of Blue No. 1 was 0.15% by mass, and the blending ratio of purified water was 50.60% by mass. Except for this, the inkjet ink of Example 5 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 5 was adjusted to 2.5.

[0081] <Example 6> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 3.00% by mass, the blending ratio of Red No. 3 was 0.18% by mass, the blending ratio of Yellow No. 4 was 0.18% by mass, the blending ratio of Blue No. 1 was 0.18% by mass, and the blending ratio of purified water was 50.01% by mass. Except for this, the inkjet ink of Example 6 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 6 was adjusted to 2.1.

[0082] <Example 7> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 62.00% by mass, and the blending ratio of ethanol was 30.0% by mass. Except for this, the inkjet ink of Example 7 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 7 was adjusted to 4.8.

[0083] <Example 8> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 57.00% by mass, and the blending ratio of ethanol was 35.0% by mass. Except for this, the inkjet ink of Example 8 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 8 was adjusted to 4.8.

[0084] <Example 9> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 42.00% by mass, and the blending ratio of ethanol was 50.0% by mass. Except for this, the inkjet ink of Example 9 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 9 was adjusted to 4.8.

[0085] <Example 10> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 37.00% by mass, and the blending ratio of ethanol was 55.0% by mass. Except for this, the inkjet ink of Example 10 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 10 was adjusted to 4.8.

[0086] <Example 11> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 32.00% by mass, and the blending ratio of ethanol was 60.0% by mass. Except for this, the inkjet ink of Example 11 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 11 was adjusted to 4.8.

[0087] <Example 12> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, and the blending ratio of NPA instead of ethanol was 40.0% by mass. Otherwise, the inkjet ink of Example 12 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 12 was adjusted to 4.8.

[0088] <Example 13> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, and the blending ratio of IPA instead of ethanol was 40.0% by mass. Otherwise, the inkjet ink of Example 13 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 13 was adjusted to 4.8.

[0089] <Example 14> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, the blending ratio of ethanol was 35.0% by mass, and the blending ratio of NPA was 5.0% by mass. Otherwise, the inkjet ink of Example 14 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 14 was adjusted to 4.8.

[0090] <Example 15> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, the blending ratio of ethanol was 35.0% by mass, and the blending ratio of IPA was 5.0% by mass. Except for this, the inkjet ink of Example 15 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 15 was adjusted to 4.8.

[0091] <Example 16> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.05% by mass, and the blending ratio of PG was 0.05% by mass. Except for this, the inkjet ink of Example 16 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 16 was adjusted to 4.8.

[0092] <Example 17> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 48.10% by mass, and the blending ratio of PG was 4.00% by mass. Except for this, the inkjet ink of Example 17 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 17 was adjusted to 4.8.

[0093] <Example 18> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 46.10% by mass, and the blending ratio of PG was 6.00% by mass. Except for this, the inkjet ink of Example 18 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 18 was adjusted to 4.8.

[0094] <Example 19> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 42.10% by mass, and the blending ratio of PG was 10.00% by mass. Except for this, the inkjet ink of Example 19 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Example 19 was adjusted to 4.8.

[0095] <Example 20> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, and the blending ratio of glycerin instead of PG was 0.10% by mass. Otherwise, the inkjet ink of Example 20 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 20 was adjusted to 4.8.

[0096] <Example 21> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 55.85% by mass, and the blending ratio of reduced isomaltulose was 2.50% by mass. Except for this, the inkjet ink of Example 21 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 21 was adjusted to 1.9.

[0097] <Example 22> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 55.35% by mass, and the blending ratio of reduced isomaltulose was 3.00% by mass. Except for this, the inkjet ink of Example 22 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 22 was adjusted to 2.3.

[0098] <Example 23> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 54.35% by mass, and the blending ratio of reduced isomaltulose was 4.00% by mass. Except for this, the inkjet ink of Example 23 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 23 was adjusted to 3.1.

[0099] <Example 24> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 53.35% by mass, and the blending ratio of reduced isomaltulose was 5.00% by mass. Except for this, the inkjet ink of Example 24 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 24 was adjusted to 3.8.

[0100] <Example 25> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 51.35% by mass, and the blending ratio of reduced isomaltulose was 7.00% by mass. Except for this, the inkjet ink of Example 25 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 25 was adjusted to 5.3.

[0101] <Example 26> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 50.35% by mass, and the blending ratio of reduced isomaltulose was 8.00% by mass. Except for this, the inkjet ink of Example 26 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 26 was adjusted to 6.1.

[0102] <Example 27> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 49.85% by mass, and the blending ratio of reduced isomaltulose was 8.50% by mass. Except for this, the inkjet ink of Example 27 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 27 was adjusted to 6.5.

[0103] <Example 28> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, Red No. 3 was 0.08% by mass, Yellow No. 4 was 0.08% by mass, Blue No. 1 was 0.08% by mass, purified water was 40.35% by mass, and reduced isomaltulose was 18.00% by mass. Except for this, the inkjet ink of Example 28 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 28 was adjusted to 13.7.

[0104] <Example 29> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 3.00% by mass, the blending ratio of Red No. 3 was 0.18% by mass, the blending ratio of Yellow No. 4 was 0.18% by mass, the blending ratio of Blue No. 1 was 0.18% by mass, the blending ratio of purified water was 27.86% by mass, the blending ratio of ethanol was 60.00% by mass, and the blending ratio of reduced isomaltulose was 8.50% by mass. Except for this, the inkjet ink of Example 29 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 29 was adjusted to 2.8.

[0105] <Example 30> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 0.50% by mass, the blending ratio of Red No. 3 was 0.03% by mass, the blending ratio of Yellow No. 4 was 0.03% by mass, the blending ratio of Blue No. 1 was 0.03% by mass, the blending ratio of purified water was 56.41% by mass, the blending ratio of ethanol was 30.00% by mass, the blending ratio of PG was 10.00% by mass, and the blending ratio of reduced isomaltulose was 3.00% by mass. Otherwise, the inkjet ink of Example 30 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 30 was adjusted to 6.0.

[0106] <Example 31> In this example, the blending ratio of Red No. 102 was 0.50 mass% and the blending ratio of purified water was 53.05 mass% relative to the total mass of the inkjet ink. Except for this, the inkjet ink of Example 31 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 31 was adjusted to 12.7.

[0107] <Example 32> In this example, the blending ratio of Red No. 102 was 1.00 mass% and the blending ratio of purified water was 52.55 mass% with respect to the entire inkjet ink. Except for that, the inkjet ink of Example 32 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 32 was adjusted to 6.4.

[0108] <Example 33> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31 mass %, and the blending ratio of purified water was 52.24 mass %. Except for that, the inkjet ink of Example 33 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 33 was adjusted to 4.8.

[0109] <Example 34> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.60 mass %, and the blending ratio of purified water was 51.95 mass %. Except for that, the inkjet ink of Example 34 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 34 was adjusted to 4.0.

[0110] <Example 35> In this example, the blending ratio of Red No. 102 was 2.50 mass% and the blending ratio of purified water was 51.05 mass% with respect to the entire inkjet ink. Except for that, the inkjet ink of Example 35 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 35 was adjusted to 2.5.

[0111] <Example 36> In this example, the blending ratio of Red No. 102 was 3.00 mass% and the blending ratio of purified water was 50.55 mass% relative to the total mass of the inkjet ink. Except for this, the inkjet ink of Example 36 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 36 was adjusted to 2.1.

[0112] <Example 37> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31 mass%, the blending ratio of purified water was 57.24 mass%, and the blending ratio of ethanol was 35.00 mass%. Except for that, the inkjet ink of Example 37 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 37 was adjusted to 4.8.

[0113] <Example 38> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of purified water was 42.24% by mass, and the blending ratio of ethanol was 50.00% by mass. Except for this, the inkjet ink of Example 38 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 38 was adjusted to 4.8.

[0114] <Example 39> In this example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31 mass %, the blending ratio of purified water was 52.29 mass %, and the blending ratio of PG was 0.05 mass %. Except for that, the inkjet ink of Example 39 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 39 was adjusted to 4.8.

[0115] <Example 40> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 48.34% by mass, and the blending ratio of PG was 4.00% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 40 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 40 was adjusted to 4.8.

[0116] <Example 41> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 53.59% by mass, and the blending ratio of reduced isomaltulose was 5.00% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 41 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 41 was adjusted to 3.8.

[0117] <Example 42> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 50.59% by mass, and the blending ratio of reduced isomaltulose was 8.00% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 42 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 42 was adjusted to 6.1.

[0118] <Example 43> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 56.09% by mass, and the blending ratio of reduced isomaltulose was 2.50% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 43 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 43 was adjusted to 1.9.

[0119] <Example 44> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 55.59% by mass, and the blending ratio of reduced isomaltulose was 3.00% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 44 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 44 was adjusted to 2.3.

[0120] <Example 45> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 50.09% by mass, and the blending ratio of reduced isomaltulose was 8.50% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 45 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 45 was adjusted to 6.5.

[0121] <Example 46> In this example, the blending ratio of Red No. 102 was 1.31% by mass, the blending ratio of purified water was 48.59% by mass, and the blending ratio of reduced isomaltulose was 10.00% by mass, based on the total mass of the inkjet ink. Except for this, the inkjet ink of Example 46 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the ink-jet ink of Example 46 was adjusted to 7.6.

[0122] <Comparative Example 1> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 0.30% by mass, the blending ratio of Red No. 3 was 0.02% by mass, the blending ratio of Yellow No. 4 was 0.02% by mass, the blending ratio of Blue No. 1 was 0.02% by mass, and the blending ratio of purified water was 53.19% by mass. Except for this, the inkjet ink of Comparative Example 1 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 1 was adjusted to 21.2.

[0123] <Comparative Example 2> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 5.00 mass%, the blending ratio of Red No. 3 was 0.31 mass%, the blending ratio of Yellow No. 4 was 0.31 mass%, the blending ratio of Blue No. 1 was 0.31 mass%, and the blending ratio of purified water was 47.62 mass%. Except for that, the inkjet ink of Comparative Example 2 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 2 was adjusted to 1.3.

[0124] <Comparative Example 3> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 67.00% by mass, and the blending ratio of ethanol was 25.00% by mass. Except for this, the inkjet ink of Comparative Example 3 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 3 was adjusted to 4.8.

[0125] <Comparative Example 4> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 27.00% by mass, and the blending ratio of ethanol was 65.00% by mass. Except for this, the inkjet ink of Comparative Example 4 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 4 was adjusted to 4.8.

[0126] <Comparative Example 5> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.09% by mass, the blending ratio of ethanol was 40.00% by mass, and the blending ratio of PG was 0.01% by mass. Except for this, the inkjet ink of Comparative Example 5 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 5 was adjusted to 4.8.

[0127] <Comparative Example 6> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 37.10% by mass, and the blending ratio of PG was 15.00% by mass. Except for this, the inkjet ink of Comparative Example 6 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 6 was adjusted to 4.8.

[0128] <Comparative Example 7> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, and the blending ratio of cellobiose instead of reduced isomaltulose was 6.35% by mass. Except for this, the inkjet ink of Comparative Example 7 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 7 was adjusted to 0.0.

[0129] <Comparative Example 8> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 52.00% by mass, and the blending ratio of galactose instead of reduced isomaltulose was 6.35% by mass. Except for this, the inkjet ink of Comparative Example 8 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 8 was adjusted to 0.0.

[0130] <Comparative Example 9> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 54.35% by mass, and the blending ratio of gum arabic instead of reduced isomaltulose was 4.00% by mass. Except for this, the inkjet ink of Comparative Example 9 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 9 was adjusted to 0.0.

[0131] <Comparative Example 10> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 57.85% by mass, and the blending ratio of sodium alginate instead of reduced isomaltulose was 0.50% by mass. Except for this, the inkjet ink of Comparative Example 10 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 10 was adjusted to 0.0.

[0132] <Comparative Example 11> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 1.31% by mass, the blending ratio of Red No. 3 was 0.08% by mass, the blending ratio of Yellow No. 4 was 0.08% by mass, the blending ratio of Blue No. 1 was 0.08% by mass, the blending ratio of purified water was 57.85% by mass, and the blending ratio of hydroxypropyl methylcellulose instead of reduced isomaltulose was 0.50% by mass. Otherwise, the inkjet ink of Comparative Example 11 was obtained in the same manner as in Example 1. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 11 was adjusted to 0.0.

[0133] <Comparative Example 12> In this comparative example, the blending ratio of Red No. 102 was 6.00% by mass, the blending ratio of Red No. 3 was 0.37% by mass, the blending ratio of Yellow No. 4 was 0.37% by mass, the blending ratio of Blue No. 1 was 0.37% by mass, the blending ratio of purified water was 68.39% by mass, the blending ratio of polyethylene glycol instead of PG was 7.50% by mass, the blending ratio of polyglycerol fatty acid esters instead of PG was 2.00% by mass, and the blending ratio of reduced isomaltulose was 15.00% by mass, based on the entire inkjet ink. Except for this, the inkjet ink of Comparative Example 12 was obtained in the same manner as in Example 1. In addition, ethanol was not added in this comparative example. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 12 was adjusted to 2.5.

[0134] <Comparative Example 13> In this comparative example, the blending ratio of Red No. 102 was 0.30 mass% and the blending ratio of purified water was 53.25 mass% relative to the total inkjet ink. Except for that, the inkjet ink of Comparative Example 13 was obtained in the same manner as in Example 1. In this comparative example, no coloring material other than Red No. 102 was added. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 13 was adjusted to 21.2.

[0135] <Comparative Example 14> In this comparative example, the blending ratio of Red No. 102 to the entire inkjet ink was 5.00 mass %, and the blending ratio of purified water was 48.55 mass %. Except for that, the inkjet ink of Comparative Example 14 was obtained in the same manner as in Example 1. In this comparative example, no coloring material other than Red No. 102 was added. In this manner, the mass ratio of reduced isomaltulose to Red No. 102 (mass of reduced isomaltulose / mass of Red No. 102) in the inkjet ink of Comparative Example 14 was adjusted to 1.3.

[0136] Each of the inks of the above-mentioned Examples 1 to 46 and Comparative Examples 1 to 14 was passed through a membrane filter to remove solid foreign matter in the liquid. Specifically, each of the inks was passed once through a membrane filter (cellulose acetate membrane) having a diameter of 5.0 μm, and then once through a membrane filter (cellulose acetate membrane) having a diameter of 0.8 μm to obtain a purified ink.

[0137] <Evaluation> The inks of the above examples and comparative examples were evaluated for solubility, viscosity, readability, initial ejection, fine line reproducibility, intermittent restartability, tablet drying property, and light resistance by the following methods. The evaluation results are shown in Tables 1 to 4. In Tables 1 to 4, the "blank" indicates that the substance was not used. In addition, sodium alginate used as a viscosity modifier in Comparative Example 10 had low solubility in the solvent used in Comparative Example 10. Therefore, the viscosity, readability, initial ejection, fine line reproducibility, intermittent restartability, tablet drying property, and light resistance of the ink of Comparative Example 10 were not evaluable, and are indicated by "-" in Table 4.

[0138] (Solubility test) After adding pigments (coloring materials) and various additives to the solvent, the mixture was stirred for one hour at room temperature and humidity. The samples in which the pigments and other solutes had dissolved were then stored under low temperature conditions (below 5°C) for one week to verify their solubility. ○: After stirring for 1 hour at room temperature and humidity, all solutes are dissolved. No precipitates are formed when stored at low temperature (5℃ or less). △: After stirring for 1 hour at room temperature and humidity, all solutes are dissolved. Precipitation occurs when stored at low temperature (5℃ or less). ×: Partially insoluble even after stirring for 1 hour at room temperature and humidity If the solubility test was evaluated as "○" or "△", there was no problem in use and the product was deemed to have passed the test.

[0139] (viscosity measurement) The viscosity of the ink in each of the Examples and Comparative Examples was measured using a rotational viscometer under the measurement conditions of a measurement temperature of 25°C. ◎ :2.5mPa·s≦Viscosity≦3.5mPa·s 〇 :2.0mPa·s≦Viscosity<2.5mPa·s 〇 :3.5mPa·s<Viscosity≦5.0mPa·s △ :5.0mPa·s<Viscosity≦6.0mPa·s △-:1.0mPa·s≦Viscosity<2.0mPa·s △-:6.0mPa・s<Viscosity≦7.0mPa・s ×: Viscosity<1.0mPa·s × :7.0mPa·s<viscosity If the viscosity was rated as "◎", "◯", "△" or "△-", there was no problem in use and the product was deemed to have passed the test.

[0140] (readability) Readability was evaluated based on optical density (OD value). The evaluation criteria for readability are as follows: ◎:0.3 <OD ○:0.2 <OD≦0.3 △:0.15 <OD≦0.2 ×:OD≦0.15 In addition, if the readability was rated as "◎", "○", or "△", there was no problem with use and the item was deemed to have passed.

[0141] (Initial discharge) The inkjet head used was a piezoelectric ceramic-driven drop-on-demand type inkjet head with a print resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the direction in which recording media such as tablets are transported), and a total of 1,280 nozzles. Using the inkjet head, a test pattern was printed immediately after nozzle maintenance was performed. Then, the print status of the test pattern was used to confirm the readability of the printed image due to the occurrence of non-ejection areas. The evaluation criteria are as follows. ◎: No non-ejection ○: Readable ×: No readability If the initial discharge property was evaluated as "◎" or "◯", there was no problem in use and the sample was deemed to have passed the test.

[0142] (Fine line reproducibility) The inkjet head used was a piezoelectric ceramic-driven drop-on-demand type inkjet head with a print resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the direction in which recording media such as tablets are transported), and a total of 1,280 nozzles. Using the inkjet head, a test pattern was printed immediately after nozzle maintenance was performed. Then, the reproducibility of the printed image of a 1-dot thin line was confirmed from the printing status of the test pattern. The evaluation criteria are as follows. ○: Reproduces the printed image exactly △: Some position deviation occurs from the print image. ×: Overall position deviation from the print image occurs If the fine line limit was "○" or "△", there was no problem in use and the product was deemed to have passed.

[0143] (Intermittent restartability (discharge stability) test) Using a piezoelectric ceramic-driven drop-on-demand inkjet head with a print resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (direction of transport of recording media such as tablets), and a total of 1,280 nozzles, a test pattern was printed with a print drop volume of 6 pl per drop after leaving it for a specified time (15 to 60 minutes) without flushing, and it was confirmed that ink could be ejected from all nozzles without any non-ejection. In addition, in Tables 1 to 4 below, the time during which the ink could be left to eject was measured as an evaluation result of intermittent printability (intermittent resumability and ejection stability). The evaluation criteria are as follows. ◎: 30 minutes or more but less than 60 minutes ○: 15 minutes or more but less than 30 minutes △: 5 minutes or more but less than 15 minutes ×: Less than 5 minutes If the result of the intermittent restartability (discharge stability) test was rated as "◎", "◯", or "△", there was no problem in use and the test was deemed to have passed.

[0144] (Tablet drying (transfer resistance) test) Images were printed on the tablets listed below using the inkjet inks of the examples and comparative examples 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 direction in which the tablet or other recording medium is transported), and a total of 1,280 nozzles, with a printing drop volume of 10 pl per drop. Ten seconds after printing, the printed tablet was contacted with a white copy paper attached to a digital force gauge at a pressure of 4 to 5 N for 0.4 to 0.5 seconds to confirm that the printed ink did not transfer. In Tables 1 to 4, the transfer resistance (drying property) was evaluated by visually observing the density of the transferred ink. The evaluation criteria are as follows. ◎: No ink transfer ○: Ink transfer is very slight and difficult to visually confirm ×: Ink is transferred too darkly If the tablet drying property (transfer resistance) was rated as "◎" or "◯", there was no problem in use and the tablet was deemed to have passed the test.

[0145] (Light resistance 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 (direction of transport of recording media such as tablets), and a total of 1,280 nozzles, images were printed on the following tablets with the refined inks of Examples 1 to 46 and Comparative Examples 1 to 14 above at a print drop volume of 6 pl per drop. The refined inks of Examples 1 to 46 and Comparative Examples 1 to 14 above were used (printed) in a normal humidity environment (60% RH) and light resistance tests were performed in a normal humidity environment (50% RH). The tablets to be printed were test film-coated tablets (base: modified starch, coating agent: mixture of 70% hydroxypropyl methylcellulose and 30% titanium oxide, diameter: 6.5 mm). The printed image was a circular solid image (diameter 4.0 mm). This resulted in a film-coated tablet print.

[0146] The film-coated tablet prints of each Example and Comparative Example, in which the chromaticity and optical color density were measured, were irradiated with a cumulative visible light of 1.2 million lux using a light stability tester (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 (based on JIS Z 8781), which indicates the amount of change in chromaticity and optical color density before and after irradiation with visible light, was compared. The results of the comparison are shown in Tables 1 to 4. As described above, with regard to the change in color before and after irradiation with visible light, as described above, the inventors have derived that if the color difference ΔE in JIS Z 8781 is 20 or less (ΔE≦20), light discoloration is sufficiently suppressed and the ink has excellent light resistance. Therefore, if ΔE≦20, the inkjet ink is deemed to have excellent light resistance and is considered to pass in this evaluation, and if ΔE≦13, the inkjet ink is deemed to have very excellent light resistance and is considered to be better in this evaluation. ◎:ΔE≦13 ○:13<ΔE≦15 △:15<ΔE≦20 ×:20<ΔE If the light resistance test was evaluated as "◎", "◯", or "△", there was no problem in use and the product was deemed to have passed the test.

[0147] [Table 1]

[0148] [Table 2]

[0149] [Table 3]

[0150] [Table 4]

[0151] As shown in Tables 1 to 4, the intermittent resumability evaluation results for the inkjet inks of Examples 1 to 46 were all rated as "△" or better, indicating that the inkjet inks had sufficient intermittent resumability. Furthermore, as shown in Tables 1 to 4, the evaluation results for tablet drying property for the inkjet inks of Examples 1 to 46 were all rated as "good" or better, indicating that the inkjet inks had sufficient tablet drying property. Furthermore, as shown in Tables 1 to 4, the lightfastness evaluation results for the inkjet inks of Examples 1 to 46 were all rated as "△" or better, indicating that the inkjet inks had sufficient lightfastness.

[0152] As described above, an inkjet ink containing Red No. 102, reduced isomaltulose, water as a solvent, a monohydric alcohol, and a humectant, wherein the monohydric alcohol contains at least one of ethanol, NPA, and IPA, the humectant contains at least one of glycerin and PG, the blending ratio of Red No. 102 is within the range of 0.5% by mass to 3.0% by mass with respect to the total mass of the inkjet ink, the blending ratio of the monohydric alcohol is within the range of 30% by mass to 60% by mass with respect to the total mass of the inkjet ink, and the blending ratio of the humectant is within the range of 0.05% by mass to 10% by mass with respect to the total mass of the inkjet ink, can provide an inkjet ink that has drying properties (tablet drying properties), light resistance, and ejection stability (intermittent resumability), and a tablet printed product that has a printed portion printed with the inkjet ink.

[0153] Furthermore, for example, the present invention can have the following configuration. (1) It contains Red No. 102, reduced isomaltulose, water as a solvent, a monohydric alcohol, and a wetting agent, The monohydric alcohol includes at least one of ethanol, NPA, and IPA, The humectant includes at least one of glycerin and PG, the blending ratio of the Red No. 102 is within a range of 0.5% by mass or more and 3.0% by mass or less with respect to the mass of the entire inkjet ink, the blending ratio of the monohydric alcohol is within a range of 30% by mass or more and 60% by mass or less with respect to the total mass of the inkjet ink, The ink-jet ink has a blending ratio of the wetting agent in the range of 0.05% by mass to 10% by mass based on the total mass of the ink-jet ink. (2) The ink-jet ink according to (1) above, wherein the amount of the reduced isomaltulose is within the range of 3.0% by mass or more and 8.5% by mass or less with respect to the total mass of the ink-jet ink. (3) The ink-jet ink according to (1) or (2) above, wherein the viscosity of the ink-jet ink is within the range of 1.0 mPa·s to 7.0 mPa·s. (4) A printed item on a tablet, comprising a printed portion printed using the ink-jet ink according to any one of (1) to (3) above.

[0154] The scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that achieve equivalent effects to the object of the present invention. Moreover, the scope of the present invention is not limited to the combination of inventive features defined by the claims, but may be defined by any desired combination of specific features among all the respective disclosed features. [Explanation of symbols]

[0155] 1 Tablet base material 1S surface 3 Print image 4 Specific dyes 5 Plain tablet printout 7 Film Coating Layer 9 Film-coated tablet printouts 11 Plain tablet print image (solid image) 13 Film-coated tablet print image (2D barcode)

Claims

1. It contains Red No. 102, reduced isomaltulose, water as a solvent, a monohydric alcohol, and a wetting agent, The monohydric alcohol includes at least one of ethanol, NPA, and IPA, The humectant includes at least one of glycerin and PG, the blending ratio of Red No. 102 is within the range of 0.5% by mass or more and 3.0% by mass or less with respect to the mass of the entire inkjet ink, the blending ratio of the monohydric alcohol is within the range of 30% by mass or more and 60% by mass or less with respect to the mass of the entire ink-jet ink, The ink-jet ink has a blending ratio of the wetting agent in the range of 0.05% by mass to 10% by mass based on the total mass of the ink-jet ink.

2. 2. The ink-jet ink according to claim 1, wherein the amount of the reduced isomaltulose is within a range of 3.0% by mass to 8.5% by mass based on the total mass of the ink-jet ink.

3. 3. The ink-jet ink according to claim 2, wherein the viscosity of the ink-jet ink is in the range of 1.0 mPa.s to 7.0 mPa.s.

4. A printed matter for a tablet, comprising a printed part printed using the ink-jet ink according to any one of claims 1 to 3.

Images