JP7420176B2 - Inkjet ink, tablets, printing machines and tablet manufacturing methods - Google Patents

Description

The present invention relates to inkjet inks, tablets, printing machines, and methods for manufacturing tablets.

Inkjet printing inks (hereinafter also simply referred to as "inkjet inks") include those that are edible (edible inkjet inks). When solid preparations such as tablets and capsules are to be printed, as the edible inkjet ink, for example, a water-soluble ink using a water-soluble edible dye as a coloring material is used (for example, Patent Document 1).
Conventionally, in order to protect printed images formed with water-soluble inks, there has been a technology to print an overcoat inkjet ink (hereinafter also simply referred to as "overcoat ink") on the printed image to form an overcoat layer. known (for example, Patent Documents 2 and 3). Here, protection of the printed image refers to preventing transfer of the printed image by, for example, improving dryness, scratch resistance, etc. of the printed image.

For example, in Cited Document 3, in order to improve the scratch resistance of a printed image and prevent bleeding or transfer of the printed image, a coating liquid (overcoat ink) containing a water-insoluble material (for example, shellac resin) is used to overcoat the printed image. A technique for forming a coat layer is disclosed.

Japanese Patent Application Publication No. 2006-169301 International Publication No. 2018/168733 Japanese Patent Application Publication No. 2020-19906

The overcoat layer is formed by printing an overcoat ink on the printed image after forming the printed image using a pre-printed ink (for example, a water-soluble ink) for forming the printed image. Overcoat ink ejected from an inkjet head in a printing machine may adhere to an inkjet head that ejects preprint ink. Here, if the pre-print ink is a water-soluble ink and a coating liquid made of a water-insoluble material is used as the overcoat ink, the overcoat ink attached to the inkjet head of the pre-print ink will be transferred to the water-soluble pre-print ink. It may solidify without dissolving, or the coating agent may precipitate. For this reason, there is a possibility that the inkjet head for the pre-printed ink may become clogged and the ejection stability of the pre-printed ink may deteriorate. In other words, there is a risk that the ejection stability of inkjet ink in the printing machine may deteriorate.
In addition, if a coating liquid made of a material insoluble in organic solvents (e.g. alcohol) is used as overcoat ink, if the solvent of the preprint ink contains an organic solvent, the overcoat ink attached to the inkjet head of the preprint ink will be removed. Coagulation or precipitation of the coating agent may occur without being dissolved in the water-soluble preprinting ink. Further, the coating liquid becomes an overcoat ink that uses water as a main solvent in order to dissolve the coating agent. Therefore, even if the overcoat ink is printed over the pre-printed ink, the overcoat ink will not stick to the printed image, resulting in poor drying properties and a risk of reducing the protective effect of the printed image.

The present invention has been made in view of these points, and provides an inkjet ink that can protect printed images and improve the ejection stability of water-soluble preprint ink, and a printed area printed with the inkjet ink. An object of the present invention is to provide a tablet comprising a tablet, a printing machine capable of printing the inkjet ink, and a method for manufacturing the tablet.

In order to achieve the above object, an inkjet ink according to one aspect of the present invention is an overcoat ink containing a coating agent that is soluble in both water and alcohol, and the alcohol is is propyl alcohol , and the coating agent has a solubility in a solvent at 25° C. in which the mass ratio of the alcohol to water (the alcohol: water) is 1:1, and the solubility is 0.5% by mass or more, Contains at least one of methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose, and polyvinyl acetal diethylamino acetate, and contains water and water as a solvent. , the alcohols are isopropyl alcohol and normal propyl alcohol , and the content of the coating agent is lower than that of the solvent, and the solvent has a lower content of the alcohol than the water content. It is characterized in that the ratio is 19 (the alcohol: water = 19:1) .

Further, in order to achieve the above object, a tablet according to one aspect of the present invention is characterized by including a printed part printed using the above inkjet ink.

Further, in order to achieve the above object, a printing machine according to one aspect of the present invention is a printing machine capable of printing at least two or more types of inkjet inks on a printing base material, and which is capable of printing at least two or more types of inkjet inks on a printing base material. includes at least a first inkjet ink, which is the above-mentioned inkjet ink, and a second inkjet ink containing water as a main solvent and at least one coloring material, and the second inkjet ink is applied to the printing substrate. After printing the ink, the first inkjet ink can be printed in an overlapping manner.

In addition, in order to achieve the above object, a method for manufacturing a tablet according to one embodiment of the present invention includes printing a first inkjet ink that is an overcoat ink containing a coating agent that is soluble in both water and alcohol. The alcohols are isopropyl alcohol and normal propyl alcohol , and the first inkjet ink has a mass ratio of the alcohols to water at 25°C (the alcohols methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer. , a coating agent containing at least one of hydroxypropyl cellulose, ethyl cellulose, and polyvinyl acetal diethylamino acetate, water as a solvent , and isopropyl alcohol and n-propyl alcohol as the alcohols, and the solvent and In comparison, the content ratio of the coating agent is low, and the ratio of the content of the alcohol to the content of water in the solvent is 19 (the alcohol: water = 19:1). It is characterized by

According to one aspect of the present invention, it is possible to protect a printed image and improve the ejection stability of preprint ink used for forming a printed image.

1 is a diagram schematically showing a configuration example of a printing press according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing an example of a tablet (uncoated tablet) according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing an example of a tablet (film-coated tablet) according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a top view which shows the structural example of the tablet (uncoated tablet) based on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a configuration example of a tablet (film-coated tablet) according to an embodiment of the present invention.

The inkjet ink according to the embodiment of the present invention is, for example, an overcoat ink (first (an example of an inkjet ink). Hereinafter, an overcoat ink according to an embodiment of the present invention, a tablet having a printing part printed with the overcoat ink, a configuration of a printing machine that prints the inkjet ink, and a method for manufacturing the tablet will be described in detail.

[Ink set]
In this embodiment, an ink set including at least a combination of a water-soluble ink and an overcoat ink is used. This ink set is used in an inkjet printer (an example of a printing machine) that prints on a base material (for example, a solid preparation) using an inkjet method. A printed image is formed using a water-soluble ink on a printing substrate (for example, a solid preparation) to be printed. In this embodiment, an overcoat layer is formed by further printing an overcoat ink on the printed image. Thereby, the printed image can be protected and transferred, etc., and the printed image can be fixed to the base material.

As described above, the overcoat ink and the water-soluble ink (an example of the second inkjet ink) according to the present embodiment are both inkjet inks, that is, ink compositions used in inkjet printers. Further, both the overcoat ink and the water-soluble ink according to this embodiment are edible. The edibility of the overcoat ink and the water-soluble ink is imparted, for example, by using materials that meet the standards of pharmaceutical additives stipulated by the Pharmaceutical Affairs Law, the Japanese Pharmacopoeia, or the Food Additives Standards.

[Composition of water-soluble ink]
Hereinafter, the structure of a water-soluble ink for forming a printed image on a printing substrate will be explained.
In this embodiment, the water-soluble ink is a water-soluble inkjet ink that uses water as a main solvent and contains at least one coloring material. Here, the water-soluble ink refers to an inkjet ink in which a coloring material is dissolved or dispersed in water, which is a main solvent, and is stabilized.
The coloring material contained in the water-soluble ink is not particularly limited as long as it is edible. The colorant that can be added to the inkjet ink according to the present embodiment can be appropriately selected from conventionally known synthetic food colorants and natural food colorants.

Examples of synthetic food dyes include tar-based dyes, natural dye derivatives, and natural synthetic dyes. Examples of tar-based pigments include Food Red No. 2 (Amaranth, FDA Name: FD&C Red No. 2, Color Index Name: Acid Red 27, CAS Number: 915-67-3), Food Red No. 40 (Allura Red AC, FDA Name: FD & C Red No. 40, Color Index Name: Food Red 40, CAS Number: 25956-17-6), Food Red No. 102 (New Coccine, Color Index Name: Acid Red 18, CAS Number : 2611-82-7), Food Red No. 104 (Phloxine, FDA Name: D&C Red No. 28, Color Index Name: Acid Red 92, CAS Number: 18472-87-2), Food Red No. 105 (Rose bengal, Color Index Name: Acid Red 94, CAS Number: 632-69-9), Food Red No. 106 (Acid Red, Color Index Name: Acid Red 52, CAS Number: 3520-42-1) ), Food Yellow No. 4 (Tartrazine , FDA Name: FD&C Yellow No.5, Color Index Name: Acid Yellow 23, CAS Number: 1934-21-0), Sunset Yellow FCF, FDA Name: FD&C Yellow No.6, Color Index Name: Food Yellow 3, CAS Number: 2783-94-0), Brilliant Blue FCF, FDA Name: FD & C Blue No. 1, Color Index N ame: Food Blue 2, CAS Number: 3844 -45-9), Food Red No. 2 (Indigo Carmine, FDA Name: FD & C Blue No. 2, Color Index Name: Acid Blue 74, CAS Number: 860-22-0), Food Red No. 2 Aluminum Lake ( FD&C Red No. 2 Aluminum Lake), Food Red No. 3 Aluminum Lake (FD & C Red No. 3 Aluminum Lake), Food Red No. 40 Aluminum Lake (FD & C Red No. 40 Aluminum Lake), Food Yellow No. 4 Aluminum Lake (FD & C Yellow No. 5 Aluminum Lake), Edible No. 5 Aluminum Lake (FD & C Yellow No. 6 Aluminum Lake), Edible Blue No. 1 Aluminum Lake (FD & C Blue No. 1 Aluminum Lake), Edible Blue No. 2 Aluminum Lake (FD & C Blue No. 2 Aluminum Lake) and the like.
Examples of natural pigment derivatives include norbixin potassium. Examples of natural synthetic pigments include β-carotene and riboflavin.

The above-mentioned "Color Index Name" was established by the American Association of Textile Chemists and Colorists. Moreover, the above-mentioned "FDA Name" is one established by the US FDA (Food and Drug Administration). In addition, in this embodiment, each usable pigment (each substance) was specified using CAS Number, but the present invention is not limited to this. For example, although the substance has the same name as the dye (substance) described in this embodiment, it is assigned a different CAS Number because it is a substance containing geometric isomers, stereoisomers, isotopic elements, or salts thereof. Of course, dyes (substances) that have been used can also be used in this embodiment. In addition, if there are no isomers or the like, or if usable dyes (substances) are specified (limited), the substance (compound) of the CAS Number described in this embodiment can be used itself.

Further, examples of natural food pigments include anthocyanin pigments, carotenoid pigments, quinone pigments, chlorophyll pigments, flavonoid pigments, betaine pigments, monascus pigments, and pigments originating from other natural products. Examples of anthocyanin pigments include red radish pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, cranberry pigment, salmonberry pigment, perilla pigment, swim blueberry pigment, strawberry pigment, and dark sweet. Cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, grape juice pigment, grape skin pigment, black currant pigment, blackberry pigment, blueberry pigment, plum pigment, whirlberry pigment, boysenberry pigment, mulberry pigment, purple sweet potato pigment , purple corn pigment, purple yam pigment, raspberry pigment, red currant pigment, loganberry pigment, and other anthocyanin pigments. Examples of carotenoid pigments include annatto pigment, gardenia yellow pigment, and other carotenoid pigments. Examples of quinone dyes include cochineal dyes, chicon dyes, lac dyes, and other quinone dyes. Examples of flavonoid pigments include safflower yellow pigment, safflower pigment, onion pigment, and other flavonoid pigments. Examples of betaine dyes include beet red dyes. Examples of monascus pigments include mosscus pigment and mosscus yellow pigment. Examples of pigments originating from other natural products include turmeric pigment, sedge pigment, gardenia red pigment, and spirulina blue pigment.

(carbon)
Further, in this embodiment, the water-soluble ink may contain carbon.
The carbon contained in the water-soluble ink is not particularly limited, and examples include medicinal charcoal, Bincho charcoal, vegetable charcoal powder pigment such as bamboo charcoal, orally ingestible carbon, or industrial petroleum-derived carbon black. It is. Among these carbons, those that can be taken orally are particularly preferred. When using orally ingestible carbon, the inkjet ink according to this embodiment can be used for direct printing on the surface of tablets, direct printing on foods, and packaging that comes into direct contact with pharmaceuticals and foods.

(solvent)
In this embodiment, the water-soluble ink contains a solvent for dispersing the above-mentioned coloring material (edible dye or carbon). Water-soluble ink contains water as a main solvent and an alcohol solvent as a drying solvent. The main solvent and drying solvent will be explained below.
The main solvent contained in the inkjet ink according to this embodiment is water, for example, purified water. In addition, the above-mentioned "main solvent" means the component having the largest mass ratio in the entire solvent. In this embodiment, the proportion of water as the main solvent contained in the water-soluble ink is, for example, 50% by mass or more of the entire inkjet ink.

In this embodiment, the drying solvent contained in the water-soluble ink is an alcohol solvent. As the alcohol solvent, for example, an alcohol solvent containing at least one of ethanol, isopropyl alcohol (IPA), and normal propyl alcohol (NPA) can be used. The concentration of the alcohol solvent may be 35 parts by mass or less based on the entire inkjet ink. Note that when the concentration of the alcohol solvent exceeds 35 parts by mass based on the entire inkjet ink, the drying properties of the ink tend to be excessive and the intermittent restartability tends to decrease. Further, the lower limit of the concentration of the alcohol solvent is not particularly limited, but is, for example, 0.001 parts by mass or more based on the entire inkjet ink. Within the above numerical range, the deterioration in intermittent restartability can be reduced.

(dispersant)
In this embodiment, the water-soluble ink may contain a dispersant in addition to the above-mentioned coloring material (food dye, carbon) and solvent. For example, when the water-soluble ink contains carbon as a coloring material, it preferably contains a dispersant that increases the dispersibility of carbon. The dispersant may be any dispersant as long as it can improve the dispersibility of carbon and is edible. As the dispersant, for example, a sucrose fatty acid ester having an HLB value in the range of 11 or more and 20 or less can be used. The content of the sucrose fatty acid ester may be within the range of 48% by mass or more and 100% by mass or less based on the above-mentioned carbon. Note that if the content of the sucrose fatty acid ester as a dispersant is less than 48% by mass based on the above-mentioned carbon, the dispersion stability of the carbon tends to decrease. Furthermore, if the content of the sucrose fatty acid ester as a dispersant exceeds 100% by mass based on the above-mentioned carbon, drying properties tend to decrease.

(wetting agent)
In this embodiment, the water-soluble ink may contain a wetting agent in addition to the above-mentioned coloring material, solvent, and dispersant, and the content thereof is 0.001 parts by mass or more based on the mass of the entire inkjet ink. It may be within the range of 40 parts by mass or less. With such a configuration, it is possible to prevent the water-soluble ink from drying in the nozzle (inkjet nozzle) in the inkjet head, and to provide the ink with sufficient intermittent restartability. Note that if the content of the wetting agent is less than 0.001 parts by mass based on the entire inkjet ink, the water-soluble ink tends to dry out and printing restartability tends to decrease. Furthermore, if the content of the wetting agent exceeds 40 parts by mass based on the total mass of the water-soluble ink, the drying properties of the ink may be reduced. For this reason, the overcoat ink printed on the printed image may become wet and the protective effect of the printed image may be reduced.

Specific examples of the wetting agent according to this embodiment include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, 2-ethyl-1 , 3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycol with a number average molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, glycerin, mesoerythritol, penta Examples include erythritol, 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. Among these wetting agents, particularly preferred are wetting agents containing at least one of propylene glycol and glycerin. With such a configuration, in the present embodiment, it is possible to impart sufficient drying properties to the water-soluble ink, and it is possible to further reduce a decrease in printing restartability.
Further, the wetting agents according to this embodiment may be used alone or in combination of two or more.

(binder)
In this embodiment, the water-soluble ink may contain a binder in addition to the above-mentioned coloring material (food dye, carbon), solvent, dispersant, and wetting agent. In the present embodiment, the binder that can be added to the water-soluble ink is not particularly limited as long as it is a binder that is generally added to inkjet inks, and includes, for example, polysaccharides. Further, it is more preferable that the polysaccharide contained in the binder according to the present embodiment has a weight average molecular weight within the range of 1,000 or more and 10,000 or less. With such a configuration, sufficient drying properties can be imparted to the water-soluble ink, and deterioration in print restartability can be further reduced. Note that if the weight average molecular weight of the polysaccharide that is the binder is less than 1,000, it tends to be difficult to impart sufficient drying properties to the water-soluble ink. Furthermore, if the weight average molecular weight of the polysaccharide used as the binder exceeds 10,000, printing restartability tends to decrease.

Further, the content of the binder according to the present embodiment is preferably 0.01% by mass or more and 10% by mass or less based on the total mass of the water-soluble ink. When the content of the binder is within the above range, the viscosity of the ink is such that inkjet printing can be performed suitably.
Examples of the binder according to this embodiment include maltodextrin, erythritol, PVP (polyvinylpyrrolidone), dextran, polydextrose, starch substances such as corn and wheat, cellulose substances such as carboxymethylcellulose and hydroxymethylcellulose, sodium alginate, Examples include polysaccharides such as gum arabic, locust bean gum, tranquil gum, guar gum, and tamarind seed.

(Leveling agent)
In this embodiment, the water-soluble ink may contain a leveling agent in addition to the above-mentioned pigment, solvent, or binder. In this embodiment, the leveling agent that can be added to the water-soluble ink may be an edible and water-soluble surfactant. Examples of the leveling agent include polyglycerin fatty acid esters (e.g., decaglycerin distearate Q-182S manufactured by Taiyo Kagaku Co., Ltd., decaglyceryl monolaurate Q-12S manufactured by the same company), sorbitan fatty acid esters (e.g. NIKKOL SL-10, manufactured by Nikko Chemicals Co., Ltd.) ), sucrose fatty acid ester (eg, DK Ester F-110 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), polysorbate (Emazol S-120 series manufactured by Kao Corporation), and the like.

[Composition of overcoat ink]
Next, the structure of an overcoat ink for forming an overcoat layer on a printed image on a printing substrate (for example, a solid formulation) will be explained.
The overcoat ink according to this embodiment contains a coating agent that is soluble in both water and alcohol. The coating agent improves the drying properties of the printed image when forming the overcoat layer using the overcoat ink. This prevents the print image formed with the water-soluble ink from being transferred and protects the print image.

Furthermore, the overcoat ink according to the present embodiment includes a coating agent that is soluble in both water and alcohol, thereby improving the ejection stability of the water-soluble ink. The water-soluble ink may contain an alcohol solvent as a drying solvent as described above. Since the overcoat ink according to this embodiment has a structure in which the coating agent is soluble in both water and alcohol, it is also soluble in water-soluble ink containing an alcohol solvent. Therefore, for example, when forming an overcoat layer, the overcoat ink that adheres to the inkjet head that discharges the water-soluble ink will be dissolved in the water-soluble ink. Therefore, it is possible to suppress the coagulation of the overcoat ink adhering to the inkjet head, and it is possible to improve the ejection stability of the water-soluble ink, such as printing restartability (intermittent restartability) and continuous printing performance. Intermittent restartability indicates the ejection stability when inkjet ink that has been retained in the inkjet head for a long time is ejected, and continuous printability indicates the ejection stability when the inkjet ink is continuously ejected from the inkjet head.
In this way, the overcoat ink according to the present embodiment can protect the printed image and improve the ejection stability of the water-soluble ink.

(Coating agent)
The overcoat ink according to this embodiment contains a coating agent as a binder. As described above, the coating agent contained in the overcoat ink according to the present embodiment has the property of being "soluble in both water and alcohol." Specifically, the coating agent used in the overcoat ink according to the present embodiment has a solubility in ethanol at 25°C of 1% by mass or more, a solubility in isopropyl alcohol at 25°C of 1% by mass or more, and a solubility in ethanol at 25°C of 1% by mass or more. The solubility in normal propyl alcohol is preferably 1% by mass or more.
As will be described in detail later, these alcohols (ethanol, isopropyl alcohol, and normal propyl alcohol) are used as a solvent for the overcoat ink according to this embodiment. Therefore, in this embodiment, the coating agent is configured to satisfy the above-mentioned solubility condition with respect to the above-mentioned alcohols, so that undissolved substances (insoluble matter) of the coating agent are reduced during the production of the overcoat ink. It is possible to suppress the generation and ensure the solubility of the coating agent. Further, the solubility of the coating agent in the above-mentioned alcohols may be 25% or less. Thereby, generation of undissolved coating agent (insoluble matter) can be more reliably suppressed.

The coating agent in the overcoat ink is a mixed solvent of an alcohol solvent (at least one of ethanol, isopropyl alcohol, and normal propyl alcohol) and water at a mass ratio of 1:1 (alcohol solvent: water) at 25°C. It is preferable that the solubility in the compound is 0.5% by mass or more. As a result, when a coating agent is added to a mixed solvent of an alcohol solvent and water, no undissolved substances (insoluble matter) are generated, and the undissolved coating agent is prevented from forming when manufacturing an overcoat ink using a mixed solvent. The solubility of the coating agent can be ensured by suppressing this. Further, the solubility of the coating agent in the above-mentioned mixed solvent may be 25% or less.

Furthermore, water, ethanol, isopropyl alcohol, and normal propyl alcohol are materials used as solvents in water-soluble inks, as described above. In other words, in this embodiment, the coating agent is configured to satisfy the above-mentioned solubility condition in an alcohol or a mixed solvent of water and alcohol, so that the overcoat ink is a solvent for the water-soluble ink. dissolve in Therefore, when the overcoat ink is scattered, the overcoat ink is prevented from coagulating in the inkjet head that discharges the water-soluble ink, and undissolved coating agent (precipitation) is suppressed, further improving the discharge stability of the water-soluble ink. can do.

Further, the coating agents contained in the overcoat ink according to the present embodiment include methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, and ethyl cellulose. and polyvinyl acetal diethylamino acetate.
These coating agents satisfy the solubility conditions in water and alcohol solvents (ethanol, isopropyl alcohol, and normal propyl alcohol), and can improve the ejection stability of water-soluble ink.
In the overcoat ink according to this embodiment, at least one of these may be used as a coating agent, or a mixture of two or more may be used.

Furthermore, as the coating agent in the overcoat ink according to the present embodiment, it is preferable to use at least one of methacrylic acid copolymer L and ammonioalkyl methacrylate copolymer. Further, from the viewpoint of protecting printed images formed with water-soluble ink, it is more preferable to use an ammonioalkyl methacrylate copolymer having excellent drying properties. As a result, the drying properties of the printed image are further improved, and transfer of the printed image can be more reliably prevented.

Moreover, it is preferable that the content of the above-mentioned coating agent is within the range of 1% by mass or more and 25% by mass or less with respect to the entire overcoat ink according to the present embodiment.
By setting the content of the coating agent within the range of 1% by mass or more and 25% by mass or less, it is possible to protect the printed image by improving the drying properties of the printed image, and to improve the ejection stability of the overcoat ink and water-soluble ink. This can be done more reliably.
Here, from the viewpoint of improving discharge stability, the content of the coating agent is preferably 10% or less, more preferably 2.5% by mass or less. By setting the content of the coating agent to 10% or less, precipitation of the coating agent due to drying of the overcoat ink can be suppressed, and ejection stability such as intermittent restartability and continuous printability can be further improved. Further, by controlling the content of the coating agent to 2.5% by mass or less, the ejection stability can be further improved.
Further, from the viewpoint of reducing the amount of overcoat ink used during printing, it is preferable that the content of the coating agent exceeds 10% by mass. In this case, printability (ejection stability) tends to be slightly lower than when the coating agent content is 10% by mass or less, but it is possible to keep the amount of overcoat ink used during printing to a small amount. Therefore, it is possible to reduce printing costs and improve printing speed. Furthermore, drying properties can also be improved.

(solvent)
In addition to the above-mentioned coating agent, the overcoat ink according to the present embodiment contains a solvent (dispersion medium) for dissolving (dispersing) the coating agent. The overcoat ink according to the present embodiment may contain at least one type of alcohol among water (for example, purified water), ethanol, isopropyl alcohol, and normal propyl alcohol as a solvent. For example, as the solvent for the overcoat ink according to the present embodiment, any one of water (for example, purified water), ethanol, isopropyl alcohol, and normal propyl alcohol may be used alone, or two or more types may be mixed. It may also be used.

Further, the overcoat ink according to the present embodiment may contain water and any one type of alcohol among ethanol, isopropyl alcohol, and normal propyl alcohol as a solvent. In this case, the content of water in the solvent is within the range of 3% by mass or more and 10% by mass or less based on the mass of the entire solvent, and the content of water in the solvent is at least one of ethanol, isopropyl alcohol, and normal propyl alcohol. The content may be in the range of 90% by mass or more and 97% by mass or less based on the mass of the entire solvent. When the water content and the alcohol solvent content in the solvent are within the above-mentioned ranges, the overcoat ink is provided with a good balance of drying properties and ejection stability. As a result, a printed image formed with water-soluble ink can be more reliably protected, and the ejection stability of the water-soluble ink can be improved more reliably.

Further, in the solvent in the overcoat ink according to the present embodiment, the ratio of the alcohol solvent content to the water content is 1.2 or more and 19 or less (alcohol solvent: water = 1.2:1 or more and 19:1 or less). ) is preferably within the range. This provides the overcoat ink with a better balance of drying properties and ejection stability, and as a result, print images formed with water-soluble ink are more reliably protected, and the water-soluble ink is Discharge stability can be further improved reliably.

The above-mentioned coating agent used in the overcoat ink tends to be more soluble in an alcohol solvent than in water. Therefore, by containing more alcohol solvent than water in the solvent of the overcoat ink, it is possible to suppress undissolved coating agent (precipitation) in the overcoat ink. Furthermore, from the viewpoint of protecting printed images, overcoat inks are required to dry faster than water-soluble inks. For this reason, it is preferable that the solvent in the overcoat ink according to this embodiment has a ratio of alcohol solvent content to water content within the above-mentioned range, and contains a large amount of an alcohol solvent with excellent drying properties. .
In addition, since the above-mentioned coating agent has compatibility with water, it is preferable to use a mixed solvent containing a small amount of water in addition to the alcohol solvent as the solvent for dissolving the coating agent, compared to the case of using an alcohol solvent alone. is preferred. Therefore, the solvent in the overcoat ink according to the present embodiment is a mixed solvent in which the ratio of the alcohol solvent content to the water content is 9 to 19 (alcohol solvent: water = 9:1 to 19:1). It is more preferable that This makes it possible to reliably provide the overcoat ink with a better balance between drying properties and ejection stability, and prevents coagulation of the overcoat ink and precipitation of the coating agent in the inkjet head that ejects water-soluble ink. This can be suppressed more reliably.

In addition, the alcohol solvents used in overcoat ink, such as ethanol, isopropyl alcohol, and normal propyl alcohol, can cause cloudiness when used alone, so it is preferable that the solvent in overcoat ink be a mixed solvent with water. .

The overcoat ink according to this embodiment is preferably colorless and has light transmittance. Thereby, it is possible to suppress a decrease in visibility when a printed image is observed through the overcoat layer. Note that the present invention is not limited to this, and the overcoat ink may be colored and have light transmittance as long as it does not adversely affect the visibility of the printed image.

(Ultraviolet luminescent agent)
The overcoat ink according to the present embodiment may contain an ultraviolet light emitting agent (hereinafter also referred to as "UV light emitting agent") in addition to the above-mentioned coating agent and solvent.
As described above, the overcoat ink according to this embodiment is preferably colorless and has light transmittance. Therefore, it is difficult for a visible light camera sensitive to the visible light region to recognize an overcoat layer formed on a printed substrate (for example, a solid preparation).
By adding a UV luminescent agent to the overcoat ink, the overcoat layer can be recognized using ultraviolet illumination and an ultraviolet camera equipped with a sensor sensitive to ultraviolet light. As a result, a test (UV test) is performed to confirm the state of formation of the overcoat layer on the printing substrate (for example, whether the overcoat layer is able to coat the printed image), and the solid formulation on which the printed image has been formed is tested. (For example, tablets) can be evaluated for quality related to the printed part.

The overcoat ink according to the present embodiment uses riboflavin, which has a solubility (at a temperature of 25°C) of 0.05% or more in the above-mentioned solvent (at least one of water, ethanol, isopropyl alcohol, and normal propyl alcohol) as a UV luminescent agent. It is preferable to include the following.
Thereby, it is possible to suppress the undissolved UV luminescent agent during the production of the overcoat ink and ensure the solubility of the UV luminescent agent in the solvent.

Further, in the overcoat ink according to the present embodiment, the content of the UV luminescent agent (in this example, riboflavins) is within the range of 0.001% by mass or more and 1.0% by mass or less of the total mass of the overcoat ink. It is preferable that there be.
When the content of the UV luminescent agent is within the above range, the overcoat layer can be recognized by a UV camera during UV inspection, and the ejection stability of the overcoat ink can be improved.
Further, in the overcoat ink according to the present embodiment, the riboflavin used as the UV luminescent agent is preferably riboflavin butyrate, sodium riboflavin phosphate, or a mixture thereof.
The above-mentioned riboflavins emit strong light when irradiated with ultraviolet light, and even when added in a very small amount, the light emission can be confirmed with a UV camera. Further, by using the above-mentioned riboflavins, the drying properties and transparency of the overcoat ink can be maintained.

Further, the overcoat ink according to the present embodiment may contain the same binder and leveling agent as the water-soluble ink described above, in addition to the above-mentioned coating agent, solvent, and UV luminescent agent.

〔Printer〕
Next, a printing press according to the present embodiment will be described using FIG. 1. FIG. 1 is a diagram schematically showing a part of a printing press 50 according to this embodiment.
The printing machine 50 according to the present embodiment is a printing machine capable of printing at least two or more types of inkjet inks. The two or more types of inkjet inks that can be printed in the printing machine 50 include an overcoat ink that includes a coating agent that is soluble in both water and alcohol, and a water-soluble ink that uses water as a main solvent and contains at least one coloring material. It is sufficient that at least ink is included. That is, the printing press 50 can perform printing using an ink set that includes at least a combination of the above-described water-soluble ink and overcoat ink.

Further, the printing press 50 according to the present embodiment can print the overcoat ink according to the present embodiment on the printing substrate 15 after printing the water-soluble ink. Thereby, the printing press 50 according to the present embodiment can protect images printed with water-soluble ink and improve the ejection stability of the water-soluble ink. Hereinafter, printing with water-soluble ink may be referred to as "pre-printing", and printing with overcoat ink after printing with water-soluble ink may be referred to as "post-printing".

As shown in FIG. 1, a printing press 50 according to this embodiment includes an inkjet head 51. The inkjet head 51 is configured to be able to eject overcoat ink after ejecting water-soluble ink. Specifically, the inkjet heads 51 include a preprinting inkjet head (an example of a second inkjet head) 51a that ejects water-soluble ink, and a postprinting inkjet head (an example of a first inkjet head) 51b that ejects overcoat ink. It consists of

The printing press 50 is configured such that the printing substrate 15 conveyed on the conveyor 52 passes below the preprinting inkjet head 51a faster than the postprinting inkjet head 51b. In other words, the printing press 50 according to the present embodiment is configured to eject water-soluble ink from the pre-printing inkjet head 51a and then eject overcoat ink from the post-printing inkjet head 51b.
Thereby, the printing press 50 can pre-print the water-soluble ink on the printing substrate 15 and post-print the overcoat ink according to the present embodiment on the printed image formed by the pre-printing. . In this way, the printing press 50 according to the present embodiment is configured to be able to execute an inline process in which preprinting processing and postprinting processing are performed within one printing press.

As shown in FIG. 1, in the printing press 50 according to the present embodiment, the time from the end of post-print pre-printing processing to the start of post-printing processing by the inline process (post-printing start time) is 0.1 seconds or more. Preferably, it is within a period of .0 seconds or less. At this time, the printing speed may be within a range of 200 mm/s or more and 2000 mm/s. Thereby, it is possible to protect the printed image by quickly forming an overcoat layer on the printed image while suppressing the occurrence of bleeding in the printed image formed with the water-soluble ink. Further, in order to keep the post-printing start time within the above range, the pre-printing inkjet head 51a and the post-printing inkjet head 51b are provided at a close distance. For example, the distance between the pre-printing inkjet head 51a and the post-printing inkjet head 51b may be within a range of 40 mm or more and 200 mm or less in terms of the distance between the centers of the inkjet heads.

In this way, in the printing press 50 according to the present embodiment, since the preprint inkjet head 51a and the postprint inkjet head 51b are close to each other, the postprint inkjet head 51a and the postprint inkjet head 51b are close to each other. The overcoat ink ejected from the head 51b may scatter in the form of mist and adhere to the preprinting inkjet head 51a. Even in this case, the overcoat ink according to the present embodiment can be dissolved in the water-soluble ink because it includes a coating agent that is soluble in both water and alcohol as described above. Therefore, coagulation of the overcoat ink adhering to the inkjet head 51a and precipitation of the coating agent are suppressed, and the ejection stability of the water-soluble ink from the inkjet head 51a can be improved.

Note that in the present invention, the configuration of the printing press 50 is not limited to this. For example, the printing press 50 may have one inkjet head. In this case, two systems of nozzles may be arranged in one inkjet, and one nozzle may eject water-soluble ink for preprinting, and the other nozzle may eject overcoat ink for postprinting. . In other words, the printing machine 50 performs preprinting on the printing substrate 15 by ejecting water-soluble ink from one nozzle, and then ejects overcoat ink from the other nozzle onto the printing substrate 15. It is sufficient to perform post-printing.
In this way, when the inkjet head has two systems of nozzles, the printing press 50 only needs to include one or more inkjet heads. Thereby, two types of inkjet inks (in this example, a water-soluble ink and an overcoat ink) can be ejected from one inkjet head to perform printing using the two types of inkjet inks.

Furthermore, the printing press 50 according to the present embodiment includes a waste liquid mechanism 53 that is a mechanism for recovering inkjet ink ejected without a printing substrate due to nozzle maintenance of the inkjet head 51 or the like. The waste liquid mechanism 53 may be configured as a tray that stores the ejected inkjet ink, or discharges the ejected inkjet ink to a waste liquid storage section provided at a predetermined position of the printing machine 50 or to the outside of the printing machine 50. It may also be configured as piping for. In addition, the tray and piping used as the waste liquid mechanism 53 have an inlet where inkjet ink flows into two systems, one for water-based ink and one for overcoat ink, which are integrated into one system internally. Good too.

In the waste liquid mechanism 53, the discharged water-soluble ink and overcoat ink are mixed. Conventional overcoat inks that use water-insoluble coating agents can coagulate in the waste system when mixed with water-soluble inks; It was necessary to provide a waste liquid mechanism for ink. This has led to problems such as a complicated structure of the printing press, an increase in manufacturing costs, and an increase in the size of the printing press.
On the other hand, since the overcoat ink according to the present embodiment dissolves in the water-soluble ink as described above, coagulation and precipitation of the coating agent do not occur even when mixed with the water-soluble ink. Therefore, the waste liquid mechanisms can be integrated and a common waste liquid mechanism 53 can be used for the water-soluble ink and the overcoat ink. Thereby, the printing press 50 according to the present embodiment can simplify the structure of the printing press, reduce manufacturing costs, and further suppress an increase in the size of the printing press.

Further, the printing machine 50 according to the present embodiment only needs to be capable of printing overcoat ink and water-soluble ink that are inkjet inks, and for example, an inkjet device such as an inkjet printer can be used. Therefore, the overcoat ink and water-soluble ink according to this embodiment have a wide range of applications and are very useful. Further, for example, the printing machine 50 according to the present embodiment may be a so-called drop-on-demand type inkjet device that uses a piezo element (piezoelectric ceramic) as an actuator, or an inkjet device of another type.

Drop-on-demand inkjet devices include, for example, devices that employ a thermal inkjet method that ejects inkjet ink using water vapor pressure generated by momentarily raising a microheating element to a high temperature (200 to 300°C), and actuators. Examples include electrostatic type devices that eject inkjet ink by electrostatic vibration, and devices that employ an ultrasonic method that utilizes the cavitation phenomenon of ultrasonic waves. Further, if the inkjet ink (in this example, water-soluble ink and overcoat ink) used in the printing machine 50 according to the present embodiment has charging performance, an apparatus adopting a continuous injection type (continuous method) can be used. It is also possible to use

〔tablet〕
In this embodiment, a tablet may be used as the printing substrate. Specifically, the overcoat ink according to this embodiment may be printed, for example, on the surface of a tablet using the printing machine 50. That is, the tablet according to the present embodiment only needs to include a printed portion printed using the overcoat ink according to the present embodiment, that is, a printed portion including at least an overcoat layer (for example, overcoat layer 23). In addition, if the overcoat layer is the overcoat ink according to this embodiment, the overcoat layer protects a printed image (for example, printed image 3) applied to the surface of a medical tablet using an inkjet printing method, and It is possible to suppress coagulation of the overcoat ink adhering to the inkjet head 51a and precipitation of the coating agent, thereby improving the ejection stability of the water-soluble ink. Hereinafter, the structure of a tablet including an overcoat layer printed with an overcoat ink and a printed image formed with a water-soluble ink according to the present embodiment will be described.
The tablet according to this embodiment is, for example, a medical tablet. Here, "medical tablets" include, for example, plain tablets (naked 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. This includes tablets, etc.

FIG. 2 is a schematic cross-sectional view showing an example of a printed medical tablet. In FIG. 2, in a cross-sectional view, a printed image 3 such as characters is printed on the upper surface of the base material 1 of a tablet 100, which is a plain tablet, and an uncoated tablet printed matter 5 in which an overcoat layer 23 is further provided on the printed image 3 is shown. It is shown.
FIG. 3 is a schematic cross-sectional view showing an example of a printed medical tablet. In FIG. 3, in cross-sectional view, a printed image 3 such as characters is printed on the upper surface of a tablet base material 1 on which a film coat layer 7 is formed on the surface of a tablet 200, which is a film-coated tablet, and furthermore, a printed image 3 such as characters is printed on the printed image 3. A film-coated tablet print 9 is shown comprising a print 30 provided with an overcoat layer 23 .

As described above, the printed image 3 is formed with water-soluble ink, and the overcoat layer 23 is formed with the overcoat ink according to this embodiment. In other words, the tablets 100 and 200 according to the present embodiment have a printed image 3 formed of a water-soluble ink containing water as a main solvent and at least one coloring material, and an overcoat ink overlaid on the printed image 3. The printing part 30 has an overcoat layer 23 formed by printing.
As a result, the tablets 100, 200 according to the present embodiment can protect the printed image 3, suppress coagulation of the overcoat ink attached to the inkjet head 51a and precipitation of the coating agent, and stabilize the ejection of water-soluble ink. can improve sex.

4 is a plan view showing an example of the structure of the tablet 100, and FIG. 5 is a plan view showing an example of the structure of the tablet 200. As shown in FIGS. 4 and 5, in the tablets 100, 200 according to this embodiment, the overcoat layer 23 is formed to cover the printed image 3 formed with water-soluble ink. Thereby, the overcoat layer 23 can improve the dryness, scratch resistance, etc. of the printed image 3, prevent transfer of the printed image 3, and protect the printed image 3.
Note that in FIGS. 2 to 5, the overcoat layer 23 is illustrated by diagonal hatching for easy understanding, but as described above, the overcoat ink according to this embodiment has light transmittance. Therefore, the overcoat layer 23 is not actually visible under visible light. Therefore, it is possible to suppress a decrease in visibility when the printed image 3 is observed through the overcoat layer 23.
In the present invention, the print image 3 is not limited to characters, and a solid image may be printed. Furthermore, a two-dimensional barcode may be printed as the print image 3 on the tablet 200, which is a film-coated tablet, for example.

The active ingredient contained in the medical tablet is not particularly limited. For example, substances that are effective in preventing and treating various diseases (e.g., sleep-inducing activity, tranquilizer activity, antibacterial activity, antihypertensive activity, anti-anginal activity, analgesic activity, anti-inflammatory activity, tranquilizing effect, anti-diabetic activity, diuretic effect) , anticholinergic activity, antiacidity, antiepileptic activity, ACE inhibitory activity, β-receptor antagonist or agonist activity, anesthetic activity, appetite suppressant activity, antiarrhythmic activity, antidepressant activity, anticoagulant activity, antidiarrheal activity , substances with antihistamine activity, antimalarial activity, antitumor activity, immunosuppressive activity, antiparkinsonian activity, antipsychotic activity, antiplatelet activity, antihyperlipidemia activity, etc.), substances with cleansing activity, fragrances , substances with deodorizing effects, etc., but are not limited thereto.

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

Although this embodiment has been described using a medical tablet as an example of the tablet, the present invention is not limited to this. The objects to be printed with the overcoat ink and the water-soluble ink according to the present embodiment are not particularly limited, and include, for example, tablets to be administered to animals other than humans (pets, livestock, poultry, etc.), feed, fertilizer, cleaning agents, ramune sweets, etc. It may be printed on the surface of various tablets such as food such as candy tablets and supplements. Further, the overcoat ink and water-soluble ink according to the present embodiment are not particularly limited in the size of the printing target, and can be applied to tablets of various sizes.

(Method for manufacturing tablets)
The method for manufacturing tablets (for example, tablets 100 and 200) according to the present embodiment includes at least a printing step of printing an overcoat ink according to the present embodiment containing a coating agent that is soluble in both water and alcohol. Bye. In addition, the printing process includes a preprinting process in which a water-soluble ink containing water as the main solvent and at least one coloring material is printed to form the printed image 3, and a print formed in the preprinting process. It is preferable to include a post-printing step of printing an overcoat ink on the image 3 in an overlapping manner.
According to the tablet manufacturing method according to the present embodiment, the formation of the overcoat layer 23 protects the printed image 3 printed on the tablet, and prevents coagulation of the overcoat ink attached to the inkjet head 51a and precipitation of the coating agent. The ejection stability of the water-soluble ink can be improved by suppressing this.
Moreover, the printing process in the method for manufacturing the tablets 100, 200 may be performed using the printing machine 50 according to the present embodiment described above.

(Effects of this embodiment)
(1) The overcoat ink, which is the inkjet ink according to this embodiment, contains a coating agent that is soluble in both water and alcohol.
With such a configuration, it is possible to protect the printed image, and it is also possible to improve the ejection stability of the water-soluble ink used as the pre-printing ink compared to the conventional technology.

(2) Furthermore, the coating agent contained in the overcoat ink, which is the inkjet ink according to the present embodiment, has a solubility in ethanol of 1% by mass, a solubility in isopropyl alcohol of 1%, and a solubility in normal propyl alcohol. It is 1%.
With such a configuration, even when the solvent in the overcoat ink according to the present embodiment is a mixed solvent composed of water and alcohol, the occurrence of undissolved coating agent (precipitation) is suppressed, and , the ejection stability of the water-soluble ink used as the pre-printing ink can be improved.

(3) Furthermore, the coating agents contained in the inkjet ink according to the present embodiment include methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, It is sufficient that it contains at least one of ethyl cellulose and polyvinyl acetal diethylamino acetate.
With such a configuration, the solubility conditions of the coating agent in each of water and alcohol solvents (ethanol, isopropyl alcohol, and n-propyl alcohol) are satisfied, and compared to the conventional technology, the water-soluble ink that is the preprint ink is The ejection stability can be improved.

(4) Furthermore, the content of the coating agent in the overcoat ink, which is the inkjet ink according to the present embodiment, is within the range of 1% by mass or more and 25% by mass or less based on the entire inkjet ink (overcoat ink). Good too.
With such a configuration, it is possible to reliably achieve both the protection of the printed image by improving the drying properties of the printed image and the improvement in the ejection stability of the water-soluble ink that is the overcoat ink and the preprint ink.
(5) Furthermore, the overcoat ink, which is the inkjet ink according to the present embodiment, may contain at least one type of alcohol among water, ethanol, isopropyl alcohol, and normal propyl alcohol as a solvent.
With such a configuration, as compared with the conventional technology, it is possible to improve the ejection stability of the water-soluble ink used as the preprint ink and to improve the ejection stability of the overcoat ink.
(6) Further, the overcoat ink, which is the inkjet ink according to the present embodiment, contains water and alcohol (at least one of ethanol, isopropyl alcohol, and normal propyl alcohol) as a solvent, and in the solvent, water The ratio of the alcohol content to the alcohol content may be within the range of 9 or more and 19 or less (alcohol:water = 9:1 or more and 19:1 or less).
With such a configuration, a good balance between drying properties and ejection stability can be imparted to the overcoat ink, and the coagulation of the overcoat ink and precipitation of the coating agent in the inkjet head that ejects the water-soluble ink can be prevented. This can be suppressed more reliably.
(7) Furthermore, the overcoat ink, which is the inkjet ink according to the present embodiment, contains water and alcohol (at least one of ethanol, isopropyl alcohol, and normal propyl alcohol) as a solvent, and the water content is is within the range of 3% by mass or more and 10% by mass or less based on the mass of the entire solvent, and the content of the alcohol is within the range of 90% by mass or more and 97% by mass or less based on the mass of the entire solvent. There may be.
With such a configuration, it is possible to more reliably protect the printed image formed with the water-soluble ink, and to more reliably improve the ejection stability of the water-soluble ink that is the pre-printed ink.

(8) Furthermore, the overcoat ink, which is the inkjet ink according to the present embodiment, may contain riboflavins having a solubility in the solvent of 0.05% by mass or more.
With such a configuration, the quality of the printed portion of the tablet according to the present embodiment can be evaluated by performing a UV inspection.
(9) Furthermore, the riboflavin contained in the overcoat ink, which is the inkjet ink according to the present embodiment, is riboflavin butyrate, sodium riboflavin phosphate, or a mixture of the riboflavin butyrate and the sodium riboflavin phosphate. There may be.
With such a configuration, the light emission is strong when irradiated with ultraviolet illumination, and the light emission can be confirmed with a UV camera even when a very small amount is added. Further, by using the above-mentioned riboflavins, the drying properties and transparency of the overcoat ink can be maintained.

(10) Furthermore, the tablets 100, 200 according to the present embodiment include a printed portion 30 printed with overcoat ink, which is the inkjet ink of (1) to (9) described above.
With such a configuration, it is possible to protect the printed image 3 in the printing unit 30 and improve the ejection stability of the water-soluble ink, which is the pre-printed ink, compared to the conventional technology.
(11) Furthermore, the printing unit 30 in the tablets 100, 200 according to the present embodiment has a printed image 3 formed with a water-soluble ink that is an inkjet ink containing water as a main solvent and at least one coloring material; It may also have an overcoat layer 23 formed by overprinting an overcoat ink, which is an inkjet ink, on the printed image 3.
According to the tablet according to this embodiment, the printed image 3 is reliably protected by the overcoat layer 23.

(12) Furthermore, the printing machine 50 according to the present embodiment is a printing machine capable of printing at least two or more types of inkjet inks on the printing substrate 15, and the two or more types of inkjet inks include the above-mentioned inkjet inks. The overcoat ink, which is the inkjet ink of (1) to (9), and the water-soluble ink, which is an inkjet ink containing water as a main solvent and at least one kind of coloring material, are included, and are applied to the printing substrate 15. Therefore, it is possible to print an overcoat ink after printing a water-soluble ink.
With such a configuration, it is possible to protect the printed image, and it is also possible to improve the ejection stability of the water-soluble ink used as the pre-printing ink compared to the conventional technology.
(13) Furthermore, the printing press 50 according to the present embodiment includes an inkjet head 51 that can eject overcoat ink after ejecting water-soluble ink.
With such a configuration, the printed image can be reliably protected, and the ejection stability of the water-soluble ink used as the pre-printing ink can be further improved compared to the conventional technology.
(14) Furthermore, the printing machine 50 according to the present embodiment includes a post-printing inkjet head 51b that ejects overcoat ink and a pre-printing inkjet head 51a that ejects water-soluble ink. After ejecting the water-soluble ink, the overcoat ink may be ejected from the post-printing inkjet head 51b.
With such a configuration, the printed image 3 can be reliably protected, and the ejection stability of the water-soluble ink used as the pre-printing ink can be more reliably improved compared to the conventional technology. .

(15) Furthermore, the method for manufacturing the tablets 100, 200 according to the present embodiment includes at least a printing step of printing an overcoat that is an inkjet ink containing a coating agent that is soluble in both water and alcohol.
With such a configuration, it is possible to protect the printed image, and it is also possible to improve the ejection stability of the water-soluble ink used as the pre-printing ink compared to the conventional technology.
(16) Furthermore, the printing process in the method for manufacturing tablets 100, 200 according to the present embodiment includes printing a water-soluble ink containing water as a main solvent and at least one coloring material to form a printed image 3. The printing process may include a preprinting process and a postprinting process in which overcoat ink is printed in an overlapping manner on the print image 3 formed in the preprinting process.
With such a configuration, the printed image 3 can be reliably protected, and the ejection stability of the water-soluble ink used as the pre-printing ink can be more reliably improved compared to the conventional technology. .

[Example]
EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by the Examples in any way.
(Manufacture of water-soluble ink)
Hereinafter, a procedure for preparing a water-soluble ink used as a preprint ink in Examples and Comparative Examples will be described.
As shown in Table 1 below, four types of water-soluble inks were prepared: two types of dye inks (dye inks 1 and 2) and two types of pigment inks (pigment inks 1 and 2). Each water-soluble ink contains the following components: coloring material, organic solvent, water, and additives (dispersant, binder). As for the order of preparation, first, water and an organic solvent were mixed to obtain a mixed solvent. Next, a coloring material was added to the mixed solvent, and then additives were added as needed. Finally, this liquid mixture was placed in a dispersion machine such as a paint shaker, and was atomized and dispersed for a specified period of time. In this way, a water-soluble inkjet ink was prepared as the pre-printing ink according to this example. Hereinafter, various components will be specifically explained.

Purified water (ion-exchanged water) was used as the water constituting the water-soluble ink.
As the coloring material, Blue No. 1 was used for the dye ink, and bamboo charcoal (carbon) was used for the pigment ink. Ethanol, propylene glycol, and glycerin were used as organic solvents.
As additives, sucrose fatty acid ester (DK Ester SS, Daiichi Kogyo Seiyaku Co., Ltd.) was used as a dispersant, and reduced isomaltulose was used as a binder.
Note that solid foreign matter in the liquid was removed by passing each of the water-soluble inks described above through a membrane filter. Specifically, purified ink was obtained by passing through a membrane filter (cellulose acetate membrane) having a diameter of 5.0 μm once, and then passing through a membrane filter (cellulose acetate membrane) having a diameter of 0.8 μm once.
The composition of each water-soluble ink (dye ink 1, 2 and pigment ink 1, 2) was as shown in Table 1. Note that "-" in Table 1 indicates that the relevant substance was not used.

Hereinafter, procedures for preparing overcoat inks in Examples and Comparative Examples will be explained.
(Manufacture of overcoat ink)
The overcoat ink contains the following components: a coating agent, a drying solvent, water, and a UV luminescent agent. As for the order of preparation, first, a solvent was obtained. As the solvent, water and dry solvents (ethanol, isopropyl alcohol (IPA), normal propyl alcohol (NPA)) were used alone or in combination. Next, a coating agent was added to the solvent, and further a UV luminescent agent was added as needed. Finally, this liquid mixture was placed in a dispersion machine such as a paint shaker, and was atomized and dispersed for a specified period of time. In this way, an overcoat ink, which is an inkjet ink according to this example, was prepared.

Note that solid foreign matter in the liquid was removed by passing each of the above-mentioned overcoat inks through a membrane filter. Specifically, purified ink was obtained by passing through a membrane filter (cellulose acetate membrane) having a diameter of 5.0 μm once, and then passing through a membrane filter (cellulose acetate membrane) having a diameter of 0.8 μm once.
The compositions of Examples 1 to 143 and Comparative Examples 1 and 2 are as shown in Tables 2 to 8 below. Note that "-" in the "overcoat ink composition" column in Tables 2 to 8 indicates that the substance was not used.

<Evaluation>
The purified inks obtained using the overcoat inks of the above Examples and Comparative Examples were evaluated for ejection stability, printed image transfer resistance evaluation, and UV emission performance using the following methods. The evaluation results are shown in Tables 2 to 8 together with the ink compositions of each of the above Examples and Comparative Examples. Note that "-" in the "Evaluation" column in Tables 2 to 8 indicates that the ink was not used or the evaluation was not performed.

<Discharge stability evaluation>
As shown in Tables 2 to 8, in this evaluation, dyes 1 and 2 and pigments 1 and 2 were used as preprinting inks, respectively, as water-soluble inks. For example, in Examples 9 to 52, during each evaluation, preprint printing was performed using each of four types of water-soluble inks, dyes 1 and 2 and pigments 1 and 2, and postprint printing was performed using overcoat ink. That is, each of the four types of water-soluble inks was printed in combination with an overcoat ink.
(1) Continuous printing performance evaluation The inkjet head for pre-printing is a piezoelectric ceramic-driven drop with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (transfer direction of recording media such as tablets), and a total number of nozzles of 2,656. An on-demand inkjet head was used. In addition, the inkjet and head for post-printing had the same configuration. After flushing for a specified period of time (5 to 30 minutes), use the inkjet head to continuously print a test pattern with a printing drop amount of 6 pl per drop, and check whether or not all nozzles are able to eject without any non-ejection amount. It was confirmed. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. Further, the printing speed was 300 mm/s, and the time from the end of the pre-printing process to the start of the post-printing process was 0.5 seconds.
In addition, in Tables 2 to 8, the continuous printing time during which ink could be ejected was measured as the evaluation result of continuous printability. The evaluation criteria are as follows.
◎: Continuous printing time is 30 minutes or more 〇+: Continuous printing time is 20 minutes or more and less than 30 minutes 〇: Continuous printing time is 10 minutes or more and less than 20 minutes △: Continuous printing time is 5 minutes or more and less than 10 minutes ×: Continuous printing Time less than 5 minutes

(2) Evaluation of intermittent restartability The inkjet head for pre-printing has a piezoelectric ceramic drive with a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (transfer direction of recording media such as tablets), and a total number of nozzles of 2,656. A drop-on-demand inkjet head was used. In addition, the inkjet and head for post-printing had the same configuration. After the ink was left in the inkjet head without flushing for a specified period of time (5 to 30 minutes), a test pattern was printed using the inkjet head at a printing drop amount of 6 pl per drop. Then, based on the printing status of the test pattern, it was confirmed whether ink could be ejected from all the nozzles without an amount of ejection failure. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. Further, the printing speed was 300 mm/s, and the time from the end of the pre-printing process to the start of the post-printing process was 0.5 seconds.
In addition, in Tables 2 to 8, as an evaluation result of intermittent restartability, the standing time during which ink could be ejected was measured. The evaluation criteria are as follows.
◎ : Leaving time for which ink can be ejected is 30 minutes or more 〇+: Leaving time for which ink can be ejected is 20 minutes or more and less than 30 minutes 〇 : Leaving time for which ink can be ejected is 10 minutes or more and less than 20 minutes △ :Leaving time for which ink can be ejected is 5 minutes or more and less than 10 minutes × :Leaving time for which ink can be ejected is less than 5 minutes

<Evaluation of printed image transfer resistance>
(1) Evaluation of drying properties by transfer test The following two types of tablets 1 and 2 were printed at a printing resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (the conveyance direction of recording media such as tablets), and a total number of nozzles of 2,656. Using a drop-on-demand inkjet head driven by a piezoelectric ceramic, each image was printed (preprinted) with a water-soluble ink (dye ink 1 in Table 1) at a printing drop amount of 10 pl per drop. Furthermore, using a drop-on-demand inkjet head similar to that used for printing water-soluble inks, overcoat inks according to each example and each comparative example were printed on each of tablets 1 and 2 on the image (post-printing). )did. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. Further, the printing speed was 300 mm/s, and the time from the end of the pre-printing process to the start of the post-printing process was 0.5 seconds.
In addition, as samples for comparison, Tablets 1 and 2 were separately prepared on which only a water-soluble ink (dye ink 1) was printed.
・Tablet 1 (film coated tablet)
Tablet types that have a coating layer formed on the surface of the tablet by adding polyethylene glycol, titanium oxide pigment, etc. to hydroxypropyl cellulose, hydroxypropyl methyl cellulose, etc. - Tablet 2 (difficult to print tablets)
Tablet types with a coating layer formed on the surface of the tablet by adding polyethylene glycol, titanium oxide pigment, etc. to polyvinyl alcohol.

After 10 seconds of printing, the tablets printed with the water-soluble ink (dye ink 1) and the overcoat inks according to each example and each comparative example were attached to a digital force gauge, and the tablets were applied with a pressure of 2 to 3 N for 0.5 seconds. Contact was made for 4 to 0.5 seconds to check whether the printed ink was transferred. Similarly, a tablet affixed to a digital force gauge is brought into contact with a tablet printed only with water-soluble ink for 0.4 to 0.5 seconds at a pressure of 2 to 3 N, and whether or not the printed ink is transferred is checked. It was confirmed.
In addition, in Tables 2 to 8, the density of the transferred ink was visually observed as the drying evaluation result. The evaluation criteria are as follows.
◎: When there is no transfer of the water-soluble ink ○+: When the transfer of the water-soluble ink is so slight that it is difficult to visually confirm it 〇: When the transferred water-soluble ink is pale in color but can be easily confirmed visually △ : The color of the transferred water-soluble ink is lighter when compared with water-soluble ink alone, but the water-soluble ink is transferred with a darker color. ×: When the water-soluble ink is transferred with a darker color than with water-soluble ink alone.

<UV emission performance evaluation>
The overcoat inks of Examples 39 to 52, Examples 83 to 96, and Examples 127 to 140 to which a UV luminescent agent was added were evaluated for UV luminescence performance as follows.
(1) Solubility evaluation When producing the overcoat ink according to each of the above-mentioned examples in which a UV luminescent agent was added, it was visually checked whether there was any undissolved UV luminescent agent in the solvent after dispersion treatment using a dispersion machine. I judged it. The evaluation criteria are as follows.
〇: No undissolved material was visually confirmed. ×: Undissolved material was visually confirmed.

(2) Evaluation of luminescence amount The overcoat ink according to each of the above examples to which a UV luminescent agent was added was diluted 33 times, and was measured using a fluorometer "RF5300-PC manufactured by Shimadzu Corporation" under the following conditions. Fluorescence photometry was performed to confirm the amount of light emitted during ultraviolet irradiation.
The excitation wavelength was 445 nm, and the fluorescence wavelength was measured from 400 nm to 700 nm.
Further, the scanning speed was set to Fast, and the sampling interval was set to 1.0 nm.
The band width was set to 1.5 nm for both excitation and fluorescence, the sensitivity was set to High, and the response was set to Auto, and the amount of light emission was measured.
The evaluation criteria are as follows.
◎: Luminescence amount 50 or more ○: Luminescence amount 20 or more and less than 50 △: Luminescence amount 10 or more and less than 20 There is no problem.

Tables 2 to 8 show the compositions and evaluation results of the overcoat inks of each Example and Comparative Example.

(Discharge stability evaluation results)
As shown in Tables 2 to 8, the overcoat inks and water-soluble inks of Examples 1 to 143 were evaluated for ejection stability evaluation (continuous printability evaluation, intermittent printability evaluation) and printed image transfer resistance (drying property). All evaluation results were ``△'' or higher (pass).
Specifically, in Examples 1 to 143, since the continuous printability evaluation and the intermittent printability evaluation of preprint ink (water-soluble ink) were all passed, preprint printing with water-soluble ink and overcoat ink When post-printing is performed using water-soluble ink, the coagulation of the overcoat ink that adheres to the inkjet head and the precipitation of the coating agent are suppressed, and the ejection stability of the water-soluble ink is improved. Do you get it. In other words, it was found that the overcoat inks of Examples 1 to 143 can improve the ejection stability of water-soluble inks. Similarly, the after-printing inks (overcoat inks) of Examples 1 to 143 passed all evaluations of continuous printability and intermittent printability, and the overcoat inks themselves of Examples 1 to 140 had stable ejection properties. It was found that the performance was improved.
Furthermore, all of the results of the print image transfer resistance evaluation (drying property) were passed, so the overcoat inks of Examples 1 to 143 had excellent drying properties, and the printed images formed with water-soluble inks were I found out that it can be protected.
In other words, it was found that the overcoat inks of Examples 1 to 143 were able to protect printed images and improve the ejection stability of water-soluble preprint inks.

On the other hand, as shown in Table 8, the overcoat inks and water-soluble inks of Comparative Examples 1 and 2 showed the results of ejection stability evaluation (continuous printability evaluation, intermittent printability evaluation) or printed image transfer resistance evaluation. contained "x" (fail).
Specifically, the overcoat ink and water-soluble ink of Comparative Example 1 were evaluated as "x" in both the ejection stability evaluation and the printed image transfer resistance (drying property) evaluation, and the water-soluble ink and overcoat ink were evaluated as "x". Ejection stability was insufficient, and printed images were not sufficiently protected. In addition, the overcoat ink and water-soluble ink of Comparative Example 2 had a printed image transfer resistance evaluation of "x" and lacked drying properties. Not protected.

From the results of the above ejection stability evaluation and print image transfer resistance evaluation, we found that overcoat inks containing a coating agent that is soluble in both water and alcohol can protect printed images and maintain the ejection stability of water-soluble inks. was found to be sufficiently improved.

(Evaluation results of UV emission performance)
In addition, as shown in Tables 4, 6, and 8, from the results of the UV emission performance evaluation in Examples 39 to 50, Examples 83 to 94, and Examples 127 to 138, water, ethanol, All overcoat inks containing riboflavins (riboflavin butyrate or sodium riboflavin phosphate) having a solubility in at least one of isopropyl alcohol and normal propyl alcohol of 0.001% or more have a solubility of "△" ( (passed) and above. In particular, Examples 41 to 44, Examples 47 to 50, Examples 85 to 88, Examples 91 to 94, in which the amount of riboflavin added is 0.01% by mass or more based on the total mass of the overcoat ink, The overcoat inks according to Examples 129 to 132 and Examples 135 to 138 had a luminescence amount of 50 or more (◎), and were found to have particularly high UV luminescence performance.
On the other hand, the overcoat inks according to Examples 51, 52, 95, 96, 139, and 140 containing a UV luminescent agent (riboflavin) that does not satisfy the above-mentioned solubility conditions have no evaluation of solubility or luminescence amount. The result was "x", indicating that the UV emission performance was lower than that of the overcoat ink according to the above-mentioned example, which contained 0.001% or more of riboflavins that satisfied the above-mentioned solubility.

The scope of the invention is not limited to the exemplary embodiments shown and described, but also includes all embodiments giving equivalent effect to the object of the invention. Moreover, the scope of the invention is not limited to the combinations of inventive features defined by the claims, but may be defined by any desired combinations of specific features of each and every disclosed feature.

1 Base material 3 Printed image 5 Plain tablet printed material 7 Film coat layer 9 Film coated tablet printed material 15 Printing substrate 23 Overcoat layer 30 Printing section 50 Printing machine 51, 51a, 51b Inkjet head 52 Conveyor 53 Waste liquid mechanism 100, 200 Tablet

Claims (14)

It is an overcoat ink containing a coating agent that dissolves in both water and alcohol.
The alcohols are isopropyl alcohol and normal propyl alcohol ,
The coating agent has a solubility of 0.5% by mass or more in a solvent in which the mass ratio of the alcohol to water (the alcohol: water) is 1:1 at 25°C, and has a solubility of 0.5% by mass or more in a solvent at 25° C. Containing at least one of acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose, and polyvinyl acetal diethylamino acetate,
Containing water as a solvent and isopropyl alcohol and normal propyl alcohol as the alcohols,
The content of the coating agent is lower than that of the solvent,
In the solvent, the ratio of the alcohol content to the water content is 19 (the alcohol: water = 19:1).
An inkjet ink characterized by: The inkjet ink according to claim 1 , wherein the coating agent has a solubility in isopropyl alcohol of 1% by mass or more and a solubility in normal propyl alcohol of 1% by mass or more. The inkjet ink according to claim 1 or 2, wherein the coating agent is polyvinyl acetal diethylaminoacetate. The inkjet ink according to any one of claims 1 to 3, wherein the content of the coating agent is within a range of 1% by mass or more and 25% by mass or less based on the entire inkjet ink. The solvent includes water and the alcohol,
The water content is within the range of 3% by mass or more and 10% by mass or less based on the mass of the entire solvent,
The inkjet ink according to any one of claims 1 to 4, wherein the content of the alcohol is within a range of 90% by mass or more and 97% by mass or less based on the mass of the entire solvent. The inkjet ink according to any one of claims 1 to 5 , comprising riboflavins having a solubility in the solvent of 0.05% by mass or more. The inkjet ink according to claim 6 , wherein the riboflavin is a riboflavin butyrate, a sodium riboflavin phosphate, or a mixture of the riboflavin butyrate and the sodium riboflavin phosphate. A tablet comprising a printed portion printed using a first inkjet ink that is the inkjet ink according to any one of claims 1 to 7. The printing section is
a printed image formed with a second inkjet ink containing water as a main solvent and at least one coloring material;
The tablet according to claim 8 , further comprising an overcoat layer formed by overprinting the first inkjet ink on the printed image. A printing machine capable of printing at least two or more types of inkjet inks on a printing substrate,
The two or more types of inkjet inks include a first inkjet ink that is the inkjet ink according to any one of claims 1 to 7 , and a second inkjet ink containing water as a main solvent and at least one coloring material. Contains at least two inkjet inks;
A printing machine characterized in that it is possible to print the first inkjet ink on the printing substrate in an overlapping manner after printing the second inkjet ink. The printing machine according to claim 10 , further comprising an inkjet head capable of ejecting the first inkjet ink after ejecting the second inkjet ink. a first inkjet head that discharges the first inkjet ink;
a second inkjet head that ejects the second inkjet ink,
The printing machine according to claim 10 , wherein the first inkjet ink is ejected from the first inkjet head after the second inkjet ink is ejected from the second inkjet head. at least a printing step of printing a first inkjet ink that is an overcoat ink containing a coating agent that is soluble in both water and alcohol;
The alcohols are isopropyl alcohol and normal propyl alcohol ,
The first inkjet ink is
As the coating agent, a methacrylic acid copolymer L having a solubility in a solvent having a mass ratio of the alcohol to water (the alcohol: water) of 1:1 at 25° C. is 0.5% by mass or more, A coating agent containing at least one of methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose, and polyvinyl acetal diethylamino acetate,
Containing water as a solvent and isopropyl alcohol and normal propyl alcohol as the alcohols,
The content of the coating agent is lower than that of the solvent,
In the solvent, the ratio of the alcohol content to the water content is 19 (the alcohol: water = 19:1).
A method for manufacturing a tablet, characterized by: The printing process includes:
a preprinting step of printing a second inkjet ink containing water as a main solvent and at least one coloring material to form a predetermined printed image;
The method for manufacturing a tablet according to claim 13 , further comprising a post-printing step of printing the first inkjet ink in an overlapping manner on the printed image formed in the pre-printing step.

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