JP6993278B2 - Aqueous ink precursor composition for latent images, a method for producing the same, and an aqueous ink composition for latent images. - Google Patents

Description

The present invention relates to a water-based ink precursor composition for latent images, a method for producing the same, and a water-based ink composition for latent images. The present invention relates to a water-based ink precursor composition for a latent image capable of printing a latent image that can be formed, a method for producing the same, and a water-based ink composition for a latent image.

In recent years, there has been growing concern about the widespread use of counterfeit pharmaceutical products (counterfeit drugs). Counterfeit products not only worsen the profits of authorized manufacturers, but also pose a health hazard to consumers who purchase them without knowing that they are counterfeit products. Therefore, it is necessary to prevent counterfeit pharmaceutical products from being put on the market.

On the other hand, for pharmaceutical products such as tablets and capsules, product information is directly printed by stamp printing, stamp printing, inkjet printing, etc., so that the user can visually confirm the product information of the pharmaceutical product. For example, as an edible inkjet ink composition that can be directly printed on a tablet having an orally disintegrating property, Patent Document 1 uses a squid ink dye composed of particles having a particle size of 10 nm or more and 1 μm or less as an edible dye. It has been disclosed. Further, Patent Document 2 discloses that the synthetic dye aluminum lake is used as an edible dye in the edible inkjet ink composition. Further, Patent Document 3 discloses that a water-soluble ink composed only of a dye-based food coloring is used for printing an image on the surface of a solid preparation.

However, when product information is printed on tablets or the like using these edible inkjet ink compositions, the product information can be visually recognized by anyone, so that the counterfeiter prints the same product information on the counterfeit product. It is possible to do. As a result, printing product information using conventional edible inkjet ink compositions facilitates the manufacture of counterfeit products. Further, in known optical reading methods such as OCR, OMR, barcodes and two-dimensional codes, since the code is visible as a printed image line, the risk of decoding and falsification is expected, and measures to prevent counterfeiting and falsification are expected. Insufficient to use as. On the other hand, the product information includes information that can be visually recognized by general users.

Japanese Unexamined Patent Publication No. 2015-81315 Japanese Unexamined Patent Publication No. 2012-11824 Japanese Unexamined Patent Publication No. 2015-3883

The present invention has been made in view of the above problems, and an object thereof is a water-based ink for latent images that is difficult to visually recognize under visible light irradiation and can print a latent image that is visualized by ultraviolet irradiation. It is an object of the present invention to provide a precursor composition, a method for producing the same, and an aqueous ink composition for a latent image.

The aqueous ink precursor composition for latent images according to the present invention is an aqueous ink precursor composition for latent images having light transmission in the visible light region in order to solve the above-mentioned problems, and is edible. A wax and / or oil that contains at least an invisible color material having light transmission in the visible light region and a solvent, and the invisible color material has light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm. It is characterized by being.

Since the aqueous ink precursor composition for latent images having the above configuration (hereinafter, may be referred to as “precursor composition”) has light transmission in the visible light region, the precursor composition thereof. When an image is printed using the water-based ink composition containing the above, it is possible to print a latent image that is difficult to visually recognize under visible light. On the other hand, since the precursor composition having the above constitution contains a wax and / or an oil which has light transmission in the visible light region and exhibits light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm, it is a latent image. When light containing ultraviolet rays in the wavelength range is irradiated, the latent image can be visualized by the contrast with the region where the ultraviolet rays are not absorbed as a result of the light absorption of the ultraviolet rays in the latent image. ..

In the above configuration, the content of the invisible color material is in the range of 0.01% by mass or more and 30% by mass or less with respect to the total mass of the aqueous ink precursor composition for latent images. preferable. By setting the content of the invisible color material to 0.01% by mass or more, when the latent image of the water-based ink using the precursor composition is visualized by ultraviolet irradiation, it is a region where ultraviolet rays are not absorbed. Visibility can be maintained by contrast. On the other hand, by setting the content of the invisible color material to 30% by mass or less, it is possible to maintain the light transmission in the visible light region and prevent the latent image from being visually recognized under visible light.

Further, in the above configuration, the invisible color material may be dissolved in the solvent and exist. When the invisible color material is dissolved in the precursor composition, the precursor composition can be applied to water-based inks such as stamp printing.

On the other hand, in the above configuration, a dispersant for dispersing the invisible color material is further contained, and the content of the dispersant is 1 mass with respect to the total mass of the aqueous ink precursor composition for latent image. It may be in the range of% or more and 10% by mass or less, and the invisible color material may consist of a dispersion dispersed in the solvent using the solvent as a dispersion medium. By containing a dispersant that disperses the invisible color material and allowing the invisible color material to exist in the state of a dispersed dispersion, a precursor composition applicable to water-based inks used for printing such as an inkjet method can be obtained. Can be done. By setting the content of the dispersant to 1% by mass or more, the dispersibility of the invisible coloring material can be maintained. On the other hand, by setting the content of the dispersant to 10% by mass or less, it is possible to suppress a decrease in the dispersion stability of the invisible color material due to the excessive presence of the dispersant.

Further, in the above configuration, the content of the invisible color material is in the range of 0.1% by mass or more and less than 10% by mass with respect to the total mass of the aqueous ink precursor composition for latent images. Is preferable. As a result, the particle size (D50) of the invisible color material can be reduced to 300 nm or less, the particle size (D99) can be reduced to 800 nm or less, and the dispersibility and ejection stability can be improved.

Further, in the above configuration, the average primary particle diameter of the invisible color material before dispersion is 50 μm or less, the D50 of the invisible color material dispersed in the solvent is 300 nm or less, and the D99 is 800 nm. The following is preferable. By setting the average primary particle diameter of the invisible color material before dispersion to 50 μm or less, coarse particles in the precursor composition of the invisible color material can be reduced, and sedimentation of the invisible color material can be prevented. Further, when printing by an inkjet method, it is possible to suppress clogging of an aqueous ink composition containing a precursor composition with an inkjet nozzle. Further, by setting D50 of the dispersed invisible color material to 300 nm or less and D99 to 800 nm or less, separation and sedimentation of the invisible color material can be prevented, and dispersion stability can be maintained.

In the above configuration, it is preferable that the invisible coloring material is at least one selected from the group consisting of vegetable wax, animal wax, vegetable oil and animal oil.

Further, the method for producing an aqueous ink precursor composition for latent images of the present invention is a method for producing an aqueous ink precursor composition for latent images having light transmission in the visible light region in order to solve the above-mentioned problems. The invisible color material is edible and includes at least a mixing step of mixing an invisible color material having light transmission in the visible light region and a solvent, and the invisible color material includes ultraviolet rays in the wavelength range of 100 nm to 400 nm. It is characterized by using a wax and / or an oil having light absorption.

According to the above configuration, by using a wax and / or oil that exhibits light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm as an invisible color material having light transmission in the visible light region, it is possible to use under visible light. It is difficult to visually recognize, and when irradiated with light containing the ultraviolet rays, it enables the formation of a latent image that can be visualized by the contrast with the region where the ultraviolet rays are not absorbed. A precursor composition for image ink can be produced.

In the above configuration, in the mixing of the invisible color material in the mixing step, the content of the invisible color material is 0.01 mass with respect to the total mass of the aqueous ink precursor composition for latent image. It is preferable to carry out the process so as to be within the range of% or more and 30% by mass or less. By setting the content of the invisible color material to 0.01% by mass or more, the contrast with the region where the ultraviolet rays are not absorbed when the latent image by the aqueous ink using the precursor composition is visualized by the ultraviolet irradiation. It is possible to obtain a precursor composition capable of maintaining good visibility according to the above. On the other hand, by reducing the content of the invisible color material to 30% by mass or less, the precursor composition that can maintain the light transmission in the visible light region and prevent the latent image from being visually recognized under visible light. You can get things.

In the above configuration, in the mixing step, the dispersant for dispersing the invisible color material is in the range of 1% by mass to 10% by mass with respect to the total mass of the aqueous ink precursor composition for latent images. As described above, it is a step of mixing the invisible color material with the solvent in an arbitrary order, and further, the invisible color material after mixing with the solvent is dispersed in the solvent to disperse the invisible color material. It may include a dispersion step of making a body. According to the above configuration, by adding a dispersant that disperses the invisible color material, it is possible to produce a dispersion in which the invisible color material is well dispersed. As a result, a precursor composition applicable to an aqueous ink for inkjet can be produced. By setting the content of the dispersant to 1% by mass or more, a precursor composition in which the dispersibility of the invisible coloring material is maintained can be obtained. On the other hand, by setting the content of the dispersant to 10% by mass or less, a precursor composition in which the deterioration of the dispersion stability of the invisible color material due to the excessive presence of the dispersant is suppressed can be obtained.

Further, in the above configuration, in the mixing of the invisible color material in the mixing step, the content of the invisible color material is 0. It is preferably performed so as to be within the range of 1% by mass or more and less than 10% by mass. Thereby, the particle size (D50) of the invisible color material can be reduced to 300 nm or less and the particle size (D99) can be reduced to 800 nm or less, and a precursor composition having good dispersibility and ejection stability can be obtained.

In the above configuration, in the dispersion step, the invisible color material having an average primary particle diameter of 50 μm or less before dispersion has a D50 of 300 nm or less and a D99 of 800 nm or less. In addition, it is preferable that the step is to disperse in the solvent. By setting the average primary particle diameter of the invisible color material before dispersion to 50 μm or less, coarse particles in the precursor composition of the invisible color material can be reduced, and sedimentation of the invisible color material can be prevented. Further, when printing by an inkjet method, it is possible to suppress clogging of an aqueous ink composition containing a precursor composition with an inkjet nozzle. Further, by setting the D50 of the dispersed invisible color material to 300 nm or less and the D99 to 800 nm or less, separation and sedimentation of the invisible color material can be prevented, and a precursor composition in which the dispersion stability is well maintained can be obtained. Obtainable.

In the above configuration, the mixing of the dispersant in the mixing step is preferably performed with respect to the solvent having a liquid temperature in the range of 40 ° C. to 50 ° C. Thereby, for example, even if the dispersant is in a solid state at room temperature, the solubility of the dispersant in the solvent can be improved by setting the liquid temperature of the solvent to 40 ° C. or higher. As a result, the dispersion time of the invisible color material can be shortened.

In the above configuration, it is preferable that the invisible coloring material is at least one selected from the group consisting of vegetable wax, animal wax, vegetable oil and animal oil.

Further, the aqueous ink composition for a latent image of the present invention is characterized by containing the aqueous ink precursor composition for a latent image in order to solve the above-mentioned problems.

According to the above configuration, by containing a precursor composition having light transmission in the visible light region, it is possible to provide an aqueous ink composition that is difficult to see under visible light. Further, since the precursor composition contains a wax and / or an oil that exhibits light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm, when the latent image is irradiated with light containing ultraviolet rays in the wavelength range, the latent image is irradiated with light. As a result of light absorption of ultraviolet rays in the latent image, it is possible to provide an aqueous ink composition capable of revealing the latent image by contrast with a region where ultraviolet rays are not absorbed.

Further, the printed matter of the solid preparation of the present invention is a printed matter of the solid preparation in which an ink layer having light transmission in the visible light region is provided on the solid preparation in order to solve the above-mentioned problems, and the ink layer is described. Is composed of a dry film of a water-based ink for latent images, and the water-based ink is characterized by containing the water-based ink composition.

According to the above configuration, since the ink layer provided on the solid-state preparation has light transmission in the visible light region, it is possible to make it difficult to see in the visible light region. Therefore, when the product information or the like is printed as a latent image on the ink layer, it is difficult to visually recognize the product information in the visible light region, and it is possible to prevent the manufacture of a counterfeit product on which the product information is printed. Further, since the ink layer contains wax and / or oil that absorbs ultraviolet rays having a wavelength range of 100 nm to 400 nm as an invisible color material, the ultraviolet rays can be emitted in the printed matter of the solid preparation having the above constitution. By irradiating the contained light, the ink layer can absorb the ultraviolet light. Thereby, under the irradiation of light including ultraviolet rays, the latent image can be visualized by the contrast with the region where the ultraviolet rays are not absorbed. As a result, the product information printed on the ink layer containing the latent image can be confirmed under irradiation with light including ultraviolet rays, the occurrence of dispensing errors and the like can be suppressed, and the authenticity of the product can also be confirmed.

The aqueous ink precursor composition for latent images of the present invention contains a wax and / or an oil that has light transmittance in the visible light region and absorbs ultraviolet rays having a wavelength range of 100 nm to 400 nm. Therefore, when the water-based ink precursor composition for latent images of the present invention is used in the water-based ink composition, it is difficult to visually recognize it in the visible light region, and it is under irradiation with light containing ultraviolet rays in the wavelength range. Then, it is possible to form a latent image that can be visualized by contrast with a region where ultraviolet rays are not absorbed. Thereby, for example, when the water-based ink composition containing the water-based ink precursor composition for latent image of the present invention is used for printing product information or the like on a solid preparation, it is possible to prevent the production of counterfeit products. It will be possible. In addition, when dispensing etc. is performed by confirming product information, or when it is desired to confirm the authenticity of the product, a printed image can be easily visualized by irradiating light containing ultraviolet rays in the wavelength range of at least 100 nm to 400 nm. It has the effect of being able to be transformed.

(Aqueous ink precursor composition for latent image)
A water-based ink precursor composition for latent images (hereinafter, referred to as “precursor composition”) according to the present embodiment will be described below.

The precursor composition of the present embodiment is a composition containing at least an invisible coloring material and a solvent. The precursor composition may be a composition of a dispersion in which the invisible color material is dispersed in a solvent as a dispersion medium, or may be a composition in which the invisible color material is dissolved in a solvent and exists. .. In addition, the precursor composition can be made edible by using a material conforming to the standards of the Pharmaceutical Affairs Law, the Japanese Pharmacopoeia, or the official standard of food additives.

In the present specification, the "latent image" is difficult to distinguish in an environment irradiated with visible light (wavelength range larger than 400 nm and 760 nm or less), and is a manifest image under specific conditions. It means the image to be converted. In addition, "edible" means a substance approved for oral administration as a drug or a pharmaceutical additive, and / or a substance approved as a food or a food additive.

The precursor composition of the present embodiment has light transmission in the visible light region (greater than 400 nm and 760 nm or less). Thereby, when the ink layer is formed by using the aqueous ink composition containing the precursor composition, the light transmission of the ink layer to visible light can be imparted. The light transmittance of the precursor composition may be colorless or may be colored. The details of light transmission will be described later.

The invisible color material is a component having light transmittance in the visible light region and light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm. The invisible color material is specifically a wax and / or an oil. Examples of the wax include animal wax and vegetable wax. Examples of animal wax include beeswax and the like. Examples of the vegetable wax include carnauba wax, rice wax, shea butter and the like. Examples of the oil include animal oil and vegetable oil. Examples of animal oils include lard and horse oil. Examples of vegetable oils include coconut oil and the like. Further, as the invisible color material of the present embodiment, a commercially available product can be used, and examples of the commercially available beeswax, coconut oil and shea butter include those manufactured by Sankei Sangyo Co., Ltd. Examples of commercially available carnauba wax include those manufactured by Toa Kasei Co., Ltd., Nippon Seiro Co., Ltd., and Hiroyuki Kato Co., Ltd. Further, examples of commercially available rice wax include rice wax S-100, rice wax R-100, rice wax R-110 (all manufactured by Sankei Sangyo Co., Ltd.) and the like.

When the precursor composition is a composition composed of a dispersion of an invisible color material, it is preferable to use carnauba wax, beeswax or the like as the invisible color material. When the invisible coloring material is present in the precursor composition dissolved in a solvent, it is preferable to use beeswax, rice wax, shea butter, coconut oil or the like as the invisible coloring material.

The content of the invisible coloring material is preferably 0.01% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 12% by mass or less, based on the total mass of the precursor composition. It is particularly preferable that it is 0.5% by mass or more and 8% by mass or less. By setting the content of the invisible color material to 0.01% by mass or more, when the latent image of the water-based ink using the precursor composition is visualized by ultraviolet irradiation, it is a region where ultraviolet rays are not absorbed. Visibility can be maintained by contrast. On the other hand, by setting the content of the invisible color material to 30% by mass or less, it is possible to maintain the light transmission in the visible light region and prevent the latent image from being visually recognized under visible light.

When the precursor composition is a composition composed of a dispersion of the invisible color material, the content of the invisible color material is further 0.1% by mass or more and 10% by mass with respect to the total mass of the precursor composition. It is preferably less than, and more preferably 0.1% by mass or more and 8% by mass or less. By setting the content of the dispersed invisible color material to less than 10% by mass, the particle size (D50) of the invisible color material can be reduced to 300 nm or less and the particle size (D99) can be reduced to 800 nm or less, which is good. Dispersibility and discharge stability can be maintained. Further, in the case of a precursor composition in which the invisible color material is dissolved in a solvent, the content of the invisible color material is preferably set so that the insoluble matter does not precipitate within the above numerical range.

When the precursor composition is a composition composed of a dispersion of an invisible color material, the average primary particle size (volume average particle size) of the invisible color material is preferably 50 μm or less, more preferably 30 μm or less, and particularly preferably 20 μm or less. .. When the average primary particle size of the invisible color material is 50 μm or less, coarse particles in the precursor composition of the invisible color material can be reduced, and sedimentation of the invisible color material can be prevented. Further, when printing by an inkjet method, it is possible to suppress clogging of an aqueous ink composition containing a precursor composition with an inkjet nozzle.

The average primary particle size means the arithmetic mean diameter obtained by observing the invisible color material in a solvent together with a dispersant with an SEM (scanning electron microscope) or TEM (transmission electron microscope). .. Further, in the present embodiment, an invisible color material having a monodisperse particle size distribution is used, but the present embodiment is not limited to this, and an invisible color material having a wide particle size distribution may be used. good. Further, two or more kinds of invisible color materials having a monodisperse particle size distribution may be mixed and used.

Further, when the precursor composition is a composition composed of a dispersion of an invisible color material, the particle size (D50) of the invisible color material in the dispersed state is 50% in the integrated particle size distribution in the volume-based integrated particle size distribution. Immediately after the preparation of the precursor composition and after a certain period of time, the range of 50 nm to 300 nm is preferable, and the range of 70 nm to 150 nm is more preferable. By setting D50 to 50 nm or more, it is possible to prevent a decrease in the dispersion stability of the invisible color material and a decrease in the ejection stability from the nozzle head when printing by an inkjet method, and it is possible to prevent a decrease in the print density. On the other hand, by setting D50 to 300 nm or less, separation and sedimentation of the invisible color material can be prevented, and dispersion stability can be maintained. In the present specification, the "inkjet method" means a method in which an aqueous ink composition is ejected as droplets from a fine inkjet head, and the droplets are fixed on a solid preparation to form an image.

Further, the particle size (D99) of the invisible color material in the dispersed state at the integrated particle size of 99% in the volume-based integrated particle size distribution is 100 nm or more immediately after the preparation of the precursor composition and after a certain period of time. The range of 800 nm is preferable, and the range of 200 nm to 600 nm is more preferable. By setting D99 to 100 nm or more, it is possible to prevent a decrease in the dispersion stability of the invisible color material and a decrease in the ejection stability from the nozzle head when printing by an inkjet method, and it is possible to prevent a decrease in the print density. On the other hand, by setting D99 to 800 nm or less, it is possible to prevent deterioration of discharge stability.

When a plurality of invisible color materials are contained in the precursor composition, D50 and D99 of the respective invisible color materials may be included in the above numerical range. The values of D50 and D99 of the lake pigment are values measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.).

When the precursor composition is a composition composed of a dispersion of an invisible color material, it is preferable that the precursor composition contains a dispersant for satisfactorily dispersing the invisible color material. .. The dispersant improves the dispersibility of the invisible color material in the solvent as the dispersion medium. The dispersant is not particularly limited as long as it can improve the dispersibility of the invisible color material and has edible properties. Examples of such a dispersant include surfactants. Examples of the surfactant include glycerin monoesters such as decaglycerin monoester, hexaglycerin monoester and tetraglycerin monoester, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether and polyoxyethylene. Examples thereof include polyoxyethylene acrylic ethers such as stearyl ether and polyoxyethylene behenyl ether. In addition to the surfactant, the dispersant includes sodium polyacrylate, polyvinylpyrrolidone, polysaccharide, gelatin, collagen, polyvinyl alcohol, polyvinyl alcohol derivative, aminoalkyl methacrylate copolymer, methacrylic acid copolymer, and ammonioalkyl methacrylate copolymer. , Ethyl acrylate / methyl methacrylate copolymer, vinyl acetate and the like may be used.

The content of the dispersant is preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 6% by mass or less, and 2% by mass with respect to the total mass of the precursor composition. It is particularly preferable that it is% or more and 4% by mass or less. By setting the content of the dispersant to 1% by mass or more, the dispersibility of the invisible coloring material can be maintained. On the other hand, by setting the content of the dispersant to 10% by mass or less, it is possible to suppress a decrease in the dispersion stability of the invisible color material due to the excessive presence of the dispersant.

The solvent contained in the precursor composition is not particularly limited as long as it meets the standards of the Pharmaceutical Affairs Law and the like. When the precursor composition is a composition composed of a dispersion of an invisible coloring material, examples of the solvent include water and a mixed solution of water and a water-soluble organic solvent. As the water, it is preferable to use pure water such as ion-exchanged water, ultra-filtered water, reverse osmosis water, distilled water, or ultrapure water from which ionic impurities have been removed. In particular, water sterilized by irradiation with ultraviolet rays or addition of hydrogen peroxide is suitable because it can prevent the growth of mold and bacteria for a long period of time. Further, in the case of a mixed solution of water and a water-soluble organic solvent, the water-soluble organic solvent is not particularly limited as long as it meets the standards of the Pharmaceutical Affairs Law and the like. Specific examples thereof include ethyl alcohol, n-butyl alcohol, isobutyl alcohol, n-propyl alcohol, isopropyl alcohol, acetone, propylene glycol, polyethylene glycol, glycerin and the like.

When the precursor composition is a composition containing a dissolved invisible color material, the solvent is not particularly limited as long as it meets the standards of the Pharmaceutical Affairs Law and the like and dissolves the invisible color material. Examples of such a solvent include organic solvents such as ethyl alcohol capable of dissolving carnauba wax and the like.

The content of the solvent is not particularly limited and can be appropriately set as needed. When a mixed solution of water and a water-soluble organic solvent is used as the solvent, the blending amount of the water-soluble organic solvent is not particularly limited and can be appropriately set as necessary.

It is preferable that the precursor composition of the present embodiment does not contain a visible color material such as a pigment or a dye that can be visually recognized under visible light. When such a visible color material is contained, it becomes difficult to form a latent image that is difficult to see under visible light. In addition, when printing by the inkjet method, the flight property and stability of ink droplets may be deteriorated.

The method for producing the precursor composition of the present embodiment includes at least a mixing step of mixing the invisible colorant and the solvent. In the mixing step, the mixing method and the order of addition of the invisible color material, the solvent and other additives to be blended as necessary are not particularly limited. For example, when preparing a precursor composition composed of a dispersion of an invisible color material, the invisible color material, a solvent as a dispersion medium, and a dispersant as an additive may be mixed at once.

Further, when mixing the dispersant, it is preferable to heat the solvent so that the liquid temperature is in the range of 40 ° C. to 50 ° C. For example, even if the surfactant as a dispersant is in a solid state at room temperature, the solubility of the surfactant in the solvent can be improved by setting the liquid temperature of the solvent to 40 ° C. or higher. As a result, the dispersion time of the invisible color material can be shortened in the dispersion step described later. The "normal temperature" means that the temperature is in the temperature range of 5 ° C to 35 ° C.

When the precursor composition is a composition composed of a dispersion of an invisible color material, it comprises a dispersion step of dispersing the invisible color material after mixing with a solvent in the solvent to prepare a dispersion of the invisible color material. Is preferable.

The disperser used in the dispersion treatment of the invisible color material is not particularly limited as long as it is a generally used disperser. Specific examples thereof include ball mills, roll mills, sand mills, bead mills, paint shakers, nanomizers and the like.

The dispersion time in the dispersion step can be appropriately set according to the type of the disperser used, and is not particularly limited, but the D50 of the invisible color material is in the range of 50 nm to 300 nm. It is preferable to set it, and further, in addition to the condition of D50, it is more preferable to set D99 of the invisible color material to be in the range of 100 nm to 800 nm. By setting the dispersion time so that the D50 of the invisible color material is 300 nm or less, it is possible to reduce the residual large amount of coarse particles of the invisible color material and prevent the dispersion stability and the storage stability from being lowered. be able to. On the other hand, by setting the dispersion time so that the D50 of the invisible color material is 50 nm or more, it is possible to prevent the dispersion stability and the storage stability of the invisible color material from deteriorating. Further, when the water-based ink composition containing the precursor composition of the present embodiment is used for printing by the inkjet method, it is possible to prevent the ejection stability from the inkjet nozzle from being lowered. Further, it is possible to suppress a decrease in print density.

Further, the precursor composition of the present embodiment is a conventional aqueous ink jet composition as long as the wax and / or oil as an invisible color material is not decomposed or the precursor composition is modified. It can be stored in the same manner as the ink composition. For example, it is preferable to store the precursor composition in a closed container and suppress the flow of air to the outside of the closed container. This makes it possible to prevent denaturation of the precursor composition. Further, the storage temperature of the precursor composition under normal pressure is also within a range that can prevent denaturation of the precursor composition or precipitation of insoluble components of the dissolved invisible color material. It is preferable to set it.

(Aqueous ink composition for latent image)
The water-based ink composition for latent images of the present embodiment (hereinafter referred to as "water-based ink composition") is a composition containing at least a precursor composition and whose main solvent is water. Further, the water-based ink composition of the present embodiment has edible properties and is suitably used for printing by an inkjet method, stamp printing, or the like.

The content of the precursor composition is preferably in the range of 1% by mass to 60% by mass, more preferably in the range of 10% by mass to 30% by mass in terms of the invisible color material content with respect to the total mass of the water-based ink composition. By setting the content of the precursor composition to 1% by mass or more, it is possible to maintain visibility by contrast with a region where ultraviolet rays are not absorbed when the latent image is visualized by irradiation with ultraviolet rays. On the other hand, by setting the content of the precursor composition to 60% by mass or less, it is possible to maintain the light transmission in the visible light region and prevent the latent image from being visually recognized under visible light. ..

In the aqueous ink composition of the present embodiment, water or the like can be contained as a solvent, as described in the precursor composition.

Further, in the water-based ink composition of the present embodiment, other additives may be blended. Examples of other additives include surface tension regulators, wetting agents, water-soluble resins, organic amines, surfactants, pH regulators, chelating agents, preservatives, viscosity regulators, defoamers and the like. When the aqueous ink composition of the present embodiment is used for printing on the surface of a solid product (details will be described later) such as a food product or a pharmaceutical product, these other additives are pharmaceutical products specified by the Pharmaceutical Affairs Law. It is preferable that the product conforms to the standards of the Japanese Pharmacy and Food Additives Official Form. The contents of these additives are not particularly limited except for the surface tension adjusting agent and the wetting agent, and can be appropriately set as necessary (the contents of the surface tension adjusting agent and the wetting agent are set respectively). It will be described later.).

The surface tension adjusting agent is not particularly limited as long as it conforms to the standards of the Pharmaceutical Affairs Law and the like, and specific examples thereof include glycerin fatty acid ester and the like. Examples of the glycerin fatty acid ester include decaglyceryl caprylate, decaglyceryl laurate having an HLB of 15 or less, decaglyceryl oleate having an HLB of less than 13, hexaglycerin lauric acid ester, hexaglycerin oleate ester, and tetra condensed linolenate. Examples thereof include glycerin ester and fatty acid ester palm palm. These may be used alone or in combination of two or more.

As the caprylic acid decaglyceryl, a commercially available product can be used, and as such a commercially available product, for example, Ryoto (registered trademark) polyglycerate CE19D (trade name, manufactured by Mitsubishi Chemical Foods Co., Ltd., HLB value) 15), SY Glister MCA750 (trade name, manufactured by Sakamoto Pharmaceutical Co., Ltd., HLB value 16) and the like.

The HLB value is an HLB value obtained by the Griffin method, and means a value obtained by the following formula.
HLB value = 20 × (sum of formulas of hydrophilic groups / molecular weight)
The HLB value is in the range of 0 to 20, and the larger the HLB value, the stronger the hydrophilicity, and the smaller the HLB value, the stronger the hydrophobicity.

As the decaglyceryl laurate, those having an HLB of 15 or less can be used. If the HLB is decaglyceryl laurate exceeding 15, the ejection stability is lowered, such as fading due to clogging of the nozzle of the inkjet head. The lower limit of HLB is preferably 10 or more from the viewpoint of solubility in an aqueous solvent. Further, as the decaglyceryl laurate having an HLB of 15 or less, a commercially available product can be used, and as such a commercially available product, for example, NIKKOL (registered trademark) DECAGLYN 1-L (trade name, Nikko Chemicals Co., Ltd.) Co., Ltd., HLB value 14.5), SY Glister ML-750 (trade name, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., HLB value 14.8) and the like.

As the decaglyceryl oleate, one having an HLB of less than 13 can be used. When the HLB is 13 or more, the ejection stability is lowered, such as blurring due to clogging of the nozzle of the inkjet head. The lower limit of HLB is preferably 10 or more from the viewpoint of solubility in an aqueous solvent. Further, as the decaglyceryl oleate having an HLB of less than 13, a commercially available product can be used, and as such a commercially available product, for example, NIKKOL (registered trademark) DECAGLYN 1-OV (trade name, Nikko Chemicals Co., Ltd.) HLB value 12) manufactured by SY Glister MO-7S (trade name, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., HLB value 12.9) and the like.

As the lauric acid hexaglycerin ester, a commercially available product can be used, and as such a commercially available product, for example, NIKKOL (registered trademark) HEXAGLYN 1-L (trade name, manufactured by Nikko Chemicals Co., Ltd., HLB value) 14.5), SY Glister ML-500 (trade name, manufactured by Sakamoto Pharmaceutical Co., Ltd., HLB value 13.5) and the like.

As the oleic acid hexaglycerin ester, a commercially available product can be used, and as such a commercially available product, for example, SY Glyster MO-5S (trade name, manufactured by Sakamoto Pharmaceutical Co., Ltd., HLB value 11.6). ) Etc. can be mentioned.

As the condensed linolenic acid tetraglycerin ester, a commercially available product can be used, and examples of such a commercially available product include SY Glister CR-310 (trade name, manufactured by Sakamoto Pharmaceutical Co., Ltd.). ..

As the fatty acid ester coconut palm, a commercially available product can be used, and examples of such a commercially available product include tirabazole W-01 (trade name, manufactured by Taiyo Kagaku Co., Ltd.).

The content of the surface tension adjusting agent is preferably in the range of 0.1% by mass to 5% by mass and in the range of 1% by mass to 2% by mass with respect to the total mass of the aqueous ink composition. Is more preferable. When the content of the surface tension adjusting agent is 0.1% by mass or more, when printing is performed by the inkjet method, it is possible to prevent ejection defects due to poor meniscus formation in the nozzles of the inkjet head and to prevent ejection defects of the nozzles. It is possible to prevent clogging from occurring. As a result, the discharge stability can be improved. On the other hand, when the content of the surface tension adjusting agent is 5% by mass or less, it is possible to prevent adverse effects on discharge due to the insoluble content of the surface tension adjusting agent and poor emulsification.

The wetting agent is not particularly limited as long as it conforms to the standards of the Pharmaceutical Affairs Law and the like, and specific examples thereof include propylene glycol and glycerin.

The amount of the wetting agent added is preferably 1% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, based on the total mass of the aqueous ink composition. By setting the content of the wetting agent to 1% by mass or more, clogging in the vicinity of the nozzle of the inkjet head can be prevented, and the ejection performance can be further improved. On the other hand, by setting the content of the wetting agent to 50% by mass or less, the viscosity of the aqueous ink composition can be appropriately controlled.

When the water-based ink composition of the present embodiment is used for printing by an inkjet method, the viscosity of the water-based ink composition is 2 mPa · s or more at the time of ejection from the inkjet nozzle in consideration of ejection stability from the inkjet nozzle. 7 mPa · s is preferable, and 3 mPa · s to 5 mPa · s is more preferable. By setting the viscosity of the water-based ink composition within the above numerical range, it is possible to suppress the occurrence of clogging in the inkjet nozzle, maintain good ejection stability, and suppress deterioration of flight performance. The viscosity of the water-based ink composition is obtained, for example, by measuring with a viscometer (trade name: VISCOMATE MODEL VM-10A, manufactured by SEKONIC Corporation) under the condition of a measuring temperature of 25 ° C.

The water-based ink composition of the present embodiment is contained at least in the latent image water-based ink which is the final product, and can also be used as the latent image water-based ink itself.

The water-based ink composition of the present embodiment can be produced by mixing the above-mentioned components by an appropriate method. That is, for example, an additive or the like is separately added to the dispersion liquid of the precursor composition, and the mixture is further diluted with water. Then, the mixture is sufficiently stirred, and if necessary, filtration is performed to remove coarse particles and foreign substances that cause clogging. Thereby, the water-based ink composition according to the present embodiment can be obtained.

The mixing method of each material is not particularly limited, and for example, the materials are sequentially added to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer to perform stirring and mixing. The filtration method is not particularly limited, and for example, centrifugal filtration, filter filtration, or the like can be adopted.

When the precursor composition is a composition containing a dissolved invisible color material, the invisible color material and the solvent are mixed in the method for producing an aqueous ink composition containing such a precursor composition. In the mixing step to be carried out, each of the above-mentioned components may be mixed at once by an appropriate method for production. As a result, the efficiency of the manufacturing process can be improved.

The water-based ink composition of the present embodiment can be suitably used for, for example, a water-based ink for latent images. When the precursor composition is a composition composed of a dispersion of an invisible color material, the water-based ink composition can provide a water-based ink for latent images suitable for printing by an inkjet method. As a result, non-contact printing by the inkjet method is possible even for tablets having poor surface smoothness such as uncoated tablets and OD tablets. Further, when the precursor composition is a composition containing a dissolved invisible color material, the water-based ink composition can provide a water-based ink for latent images suitable for printing by a stamp method. Further, since the water-based ink composition of the present embodiment uses a material conforming to the standards of the Pharmaceutical Affairs Law and the like, it has edible properties and enables direct printing on the tablet surface of supplements and the like. Further, since the aqueous ink composition of the present embodiment contains a wax and / or an oil which has light transmission in the visible light region and exhibits light absorption to ultraviolet rays in the wavelength range of 100 nm to 400 nm. A latent image that is difficult to see under visible light and can be visualized under irradiation with light containing ultraviolet rays in the wavelength range of 100 nm to 400 nm can be directly printed on the surface of a solid preparation such as a drug or a supplement.

(Printed matter of solid product)
The printed matter of the solid pharmaceutical product of the present embodiment has a latent image on at least a part of the surface. Here, the term "solid preparation" as used herein means to include a food preparation and a pharmaceutical preparation, and the form thereof includes, for example, an OD (orally disintegrating) tablet, an uncoated tablet, and an FC (film-coated) tablet. , Tablets such as sugar-coated tablets or capsules. The solid preparation may be used for pharmaceutical products or may be used for food products. Examples of tablets for food use include health foods such as tablets and supplements. Among the solid preparations, the tablets are in a solid state at room temperature, and for example, those produced by compressing and / or molding a tablet material containing an active ingredient into a certain shape are preferable. The shape of the tablet is not particularly limited, and any shape can be adopted. Further, the tablet may be a tablet for pharmaceutical use or a tablet for food use. Examples of tablets for food use include health foods such as tablets and supplements.

The latent image consists of an ink layer formed by using a water-based ink for a latent image. The ink layer is composed of a dry film of the above-mentioned water-based ink for latent images. As will be described later, the dry film can be formed by printing directly on the surface of the solid preparation using, for example, an inkjet method using a water-based ink for latent images.

The ink layer has light transmission in the visible light region (greater than 400 nm and 760 nm or less). This makes it difficult to visually recognize the ink layer under visible light irradiation. Here, the term "light transmission" as used herein means the property of transmitting at least a part of incident visible light. In particular, the light transmittance in the ink layer means, for example, that the transmittance of visible light having a wavelength range larger than 400 nm and 760 nm or less is 50% for an ink layer having a thickness of 2 μm as compared with the case where the ink layer is not present. It means that it is preferably 70% or more, and more preferably 90% or more. Further, the light transparency includes not only the case where the ink layer is colorless but also the case where the ink layer is colored.

Further, the ink layer contains an invisible color material that absorbs ultraviolet rays in the wavelength range of 100 nm to 400 nm, whereby the ink layer absorbs the ultraviolet rays when irradiated with the ultraviolet rays. As a result, a contrast is generated between the region where the ink layer is not formed and the region does not absorb ultraviolet light, and the latent image formed by the ink layer can be visualized.

The thickness of the ink layer (after dry coating) is not particularly limited, and is appropriately set in consideration of the composition and printing speed of the latent image water-based ink, the fixing property of the latent image water-based ink droplets, the drying speed, and the like. be able to.

A visible image composed of a visible ink layer may be formed on the surface of the solid preparation. The visible ink layer is an ink layer that can be visually recognized under visible light irradiation. Further, the visible ink layer is preferably made of a dry film of a water-based ink for visible images. As the water-based ink for visible images, conventionally known water-based inks containing pigments and dyes as visible color materials can be used. The dry film of the water-based ink for visible images can be formed by printing directly on the surface of the solid preparation using the water-based ink for visible images, for example, by an inkjet method or the like.

The ink layer and the visible ink layer can be provided in different regions on the surface of the solid product. For example, when the solid preparation is a disk-shaped or lens-shaped tablet, an ink layer may be provided on one surface and a visible ink layer may be provided on the other surface. By making the print areas of the ink layer and the visible ink layer different from each other, it is possible to prevent the latent image visualized by the light absorption of the irradiated ultraviolet light and the visible image from being visually recognized in duplicate, and the visibility is improved. It is possible to suppress the decrease in the amount of ink.

Further, the ink layer and the visible ink layer may be laminated on the surface of the solid preparation in a state of at least partially overlapping. This makes it possible to record more information on the surface of the solid product even when the area of the printable area is small. When laminating the ink layer and the visible ink layer in a state where at least a part thereof overlaps, it is preferable that the ink layer is laminated on the visible ink layer. This makes it possible to irradiate the entire area of the ink layer with ultraviolet rays when irradiating with ultraviolet rays. As a result, the latent image can be visualized in a good state. Further, since the ink layer has light transmission in the visible light region, it is possible to suppress a decrease in visibility of a visible image under visible light irradiation.

(How to use water-based ink for latent image)
The method of using the latent image water-based ink of the present embodiment includes a printing step of printing on the surface of a solid preparation using the latent image water-based ink containing the above-mentioned water-based ink composition, and visualizing the printed image by irradiation with ultraviolet rays. It includes at least a visualization step of (visualization).

The printing step is a step of forming an ink layer on the surface of the solid preparation by printing by an inkjet method or stamp printing. In the case of the inkjet method, water-based ink is ejected as ink droplets onto the solid pharmaceutical product from a fine nozzle, and the ink droplets are adhered to the surface of the solid pharmaceutical product. The discharge method is not particularly limited, and for example, a known method such as a continuous injection type (charge control type, spray type, etc.), an on-demand type (piezo method, thermal method, electrostatic suction method, etc.) can be adopted. .. Printing conditions such as the amount of ink droplets ejected and the printing speed are not particularly limited, and can be appropriately set as necessary.

Further, in the printing step, a drying process for drying the water-based ink adhering to the surface of the solid preparation may be performed. The drying method is not particularly limited, and in addition to hot air drying, natural drying and the like can be performed. The drying temperature is not particularly limited as long as it is lower than the melting point of the invisible coloring material, and can be appropriately set. Further, the drying time is not particularly limited, and can be appropriately set according to the amount of ink droplets ejected (in the case of stamp printing, the amount of water-based ink applied), the type of water-based ink composition, and the like. When it is desired to allow the water-based ink adhered to the surface of the solid pharmaceutical product to permeate the surface layer portion of the solid pharmaceutical product, it is preferable to omit the drying treatment.

The visualization step is a step of irradiating the ink layer printed in the printing step with light containing at least ultraviolet rays (irradiation light) to visualize the latent image and enable visualization of the latent image.

The irradiation light is not particularly limited as long as it contains at least ultraviolet rays having a wavelength range of 100 nm to 400 nm. Therefore, in the visualization step, for example, it is possible to visualize the latent image by using the ultraviolet rays in the wavelength range in the presence of light in the visible light region in the room. Most of the invisible coloring materials used in this embodiment have a maximum absorption wavelength in the range of 280 nm to 380 nm. Therefore, it is more preferable that the light used for the visualization of the latent image includes ultraviolet rays in the range of 280 nm to 380 nm. As a result, the absorption of ultraviolet rays by the invisible color material can be maximized, and the light intensity of the fluorescence emitted by the invisible color material can be further increased.

Further, for the irradiation light, it is not necessary to block light other than ultraviolet rays in the range of 100 nm to 400 nm by using, for example, a filter or the like. A light emitter that emits light including an ultraviolet region, which is generally sold, simultaneously irradiates light in the visible light region in addition to the ultraviolet region. Therefore, when an attempt is made to block light other than ultraviolet rays in the wavelength range by using a filter or the like, the ultraviolet rays are also blocked by the filter, and as a result, the integrated light amount of the ultraviolet rays irradiated to the ink layer is also reduced. May be done. As a result, the light intensity of the fluorescence emitted by the ink layer may decrease.

Further, the wavelength range of the ultraviolet rays included in the irradiation light can be appropriately set according to the type of the invisible color material. Further, the integrated light amount (mJ / cm ² ) of the irradiation light can be appropriately set according to the type of the invisible color material, the content in the ink layer, and the like.

The latent image visualization step may include an observation step of observing the visualized latent image. The observation method is not particularly limited, and an imaging means such as a camera may be used in addition to visual inspection. The imaging means is not particularly limited, and can be appropriately selected depending on the type of the invisible color material, the solid preparation, and the like.

Hereinafter, preferred embodiments of the present invention will be described in detail exemplary. However, the materials, contents, etc. described in the following examples are not limited to those of the present invention unless otherwise specified. In addition, each material of the water-based ink precursor composition for latent images and the water-based ink composition for latent images conforms to the standards of the Pharmaceutical Affairs Law, the Japanese Pharmacopoeia, or the official standard of food additives. be.

(Preparation of water-based inks A to C for latent images)
First, a water-based ink precursor composition for a latent image was prepared. That is, carnauba wax as an invisible color material (manufactured by Toa Kasei Co., Ltd.), POE (20) stearyl ether as a dispersant (trade name; NIKKOL (registered trademark) BS-20, manufactured by Nikko Chemical Co., Ltd.), and a dispersion medium. The ion-exchanged water was placed in a container and dispersed in a disperser (paint shaker, manufactured by Asada Iron Works Co., Ltd.) at room temperature for 72 hours (dispersion time). Further, at the time of dispersion, 190 g of zirconia beads (average particle size 0.8 mm) were mixed. As a result, a water-based ink precursor composition for latent images was prepared.

Next, for the aqueous ink precursor composition for latent images, decaglyceryl monocaprylate as a surface tension adjuster (trade name: SY Glister MCA750, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., HLB value 16), as a wetting agent. Propylene glycol and ion-exchanged water were added to prepare the mixture so as to have the blending ratio shown in Table 1, and the mixture was stirred with a disper. As a result, water-based ink compositions A to C for latent images, each of which was composed of a dispersion in which an invisible color material was dispersed, were prepared.

(Preparation of water-based ink D for latent image)
In the water-based ink composition D for latent images, the invisible color material was changed to rice wax (manufactured by Sankei Sangyo Co., Ltd.), and each composition was further prepared so as to have the blending ratio shown in Table 2. Other than that, the latent image water-based ink composition D was prepared in the same manner as the latent image water-based ink composition A.

(Preparation of water-based ink E for latent image)
In the water-based ink composition E for latent images, the invisible color material was changed to shea butter (manufactured by Sankei Sangyo Co., Ltd.), and each composition was further prepared so as to have the blending ratio shown in Table 2. Other than that, the latent image water-based ink composition E was prepared in the same manner as the latent image water-based ink composition A.

(Preparation of water-based ink F for latent image)
In the water-based ink composition F for latent images, the invisible color material was changed to coconut oil (manufactured by Sankei Sangyo Co., Ltd.), and each composition was further prepared so as to have the blending ratio shown in Table 2. Other than that, the latent image water-based ink composition F was prepared in the same manner as the latent image water-based ink composition A.

(Preparation of water-based ink G for latent image)
In the water-based ink composition G for latent images, the invisible color material was changed to beeswax (manufactured by Sankei Sangyo Co., Ltd.), and each composition was further prepared so as to have the blending ratio shown in Table 2. Other than that, the latent image water-based ink composition G was prepared in the same manner as the latent image water-based ink composition A.

(Examples 1 to 18)
Using the latent image water-based inks A to C of the latent image water-based ink compositions A to C, the latent image was printed on the uncoated tablet by an inkjet recording method (printing step). Printing was performed only on one side of the unprinted lock, and the printed area and the non-printed area had a checkered pattern. The printing method was a single-pass (one-pass) method using an inkjet printer (KC 600 dpi head, medium-speed printing jig). The printing conditions were such that the mass per droplet was 7 ng and the appropriate amount of the liquid was 7 pl. Further, after printing, the printed image surface was dried by natural drying for 24 hours.

Next, the uncoated lock on which the latent image was printed was irradiated with ultraviolet rays while changing the wavelength for each example (visualization step), and the latent image was visualized and imaged. As the irradiation means, a xenon light source (trade name; MAX-303) manufactured by Asahi Spectral Co., Ltd. shown in Table 3 was used. The wavelength of the ultraviolet rays to be irradiated was changed by using the mirror module attached to the xenon light source and various UV bandpass filters (optical filters) in combination. As shown in Tables 5 to 7, the wavelengths of the ultraviolet rays were 320 nm, 340 nm, 350 nm, 360 nm, 370 nm, and 380 nm. The light intensity of the xenon light source was set to about 5000 μW / cm2.

The ultraviolet camera shown in Table 4 was used as the imaging means used for imaging. The imaging was performed in a dark room where outside light other than the xenon light source did not enter.

(Examples 19 to 24)
In Examples 19 to 24, the latent image was printed on the uncoated tablet by stamp printing using the latent image water-based ink composed of the latent image water-based ink composition D (printing step). Printing was performed on only one side of the uncoated lock. After printing, the printed image surface was dried by natural drying for 24 hours.

Next, in the same manner as in Example 1, the uncoated lock on which the latent image is printed is irradiated with ultraviolet rays while changing the wavelength for each example (visualization step), and the latent image is visualized and imaged. went.

(Examples 25 to 30)
In Examples 25 to 30, as the latent image water-based ink, an ink composed of the latent image water-based ink composition E was used. Other than that, a latent image was printed on one side of the uncoated lock in the same manner as in Example 19, and the latent image was further visualized.

(Examples 31 to 36)
In Examples 31 to 36, as the latent image water-based ink, those made of the latent image water-based ink composition F were used. Other than that, a latent image was printed on one side of the uncoated lock in the same manner as in Example 19, and the latent image was further visualized.

(Examples 37 to 42)
In Examples 37 to 42, as the latent image water-based ink, those made of the latent image water-based ink composition G were used. Other than that, a latent image was printed on one side of the uncoated lock in the same manner as in Example 19, and the latent image was further visualized.

(Evaluation of ejection stability (flying property) of water-based ink for latent images)
The ink layer printed on each of the uncoated tablets of Examples 1 to 18 is irradiated with ultraviolet rays having wavelengths of 320 nm, 340 nm, 350 nm, 360 nm, 370 nm, and 380 nm, and the invisible color material contained in the ink layer absorbs the ultraviolet rays. Then, the presence or absence of printing defects in the ink layer was inspected. UV irradiation and inspection were performed in the dark. The results are shown in Tables 5 to 7.

The evaluation criteria for discharge stability (flying property) are as follows.
◯: Nozzle chipping and fading are not observed, and ejection stability is good. Δ: At least one of nozzle chipping or fading occurs partially ×: At least one of nozzle chipping or fading occurs in large numbers What is nozzle chipping? It means that the coating liquid (droplet) is not discharged from the nozzle where the clogging has occurred. Blurring means blurring of an image in the early stages of printing.

(Visibility of the latent image that has been visualized)
The visibility of the visualized latent image under ultraviolet irradiation was evaluated based on the following criteria. The results are shown in Tables 5 to 11.
○: Good visibility of latent image △: Visible latent image ×: Difficult to see latent image

(Result 1)
As shown in Table 5, in Examples 1 to 6 in which carnauba wax having a content of 0.1% by mass was used as the invisible color material, the ejection stability (flying property) from the inkjet nozzle was excellent. It was also possible to visually recognize the latent image visualized by ultraviolet irradiation. Further, as shown in Table 6, in Examples 7 to 12 in which the carnauba wax having a content of 6% by mass was used as the invisible color material, the ejection stability (flying property) from the inkjet nozzle was lowered, but the flying property was lowered. The latent image under ultraviolet irradiation could also be visualized by the contrast with the non-printed area that does not absorb ultraviolet light, and the visibility was good. Further, as shown in Table 7, in Examples 13 to 18 in which carnauba wax having a content of 8% by mass was used as the invisible coloring material, the ejection stability (flying property) from the inkjet nozzle was lowered, but the flying property was lowered. The visibility of the latent image visualized by ultraviolet irradiation was also good. It was found that the water-based ink for latent images containing carnauba wax has higher light absorption as the ultraviolet rays having a wavelength closer to 320 nm, and the visualization is extremely good.

Further, as shown in Tables 8 to 11, even when printing by stamp printing using rice wax, shea butter, coconut oil and beeswax as invisible coloring materials, the latent image visualized under ultraviolet irradiation is obtained. It was confirmed that the visibility was good.

(Example 43)
Carnauba wax (manufactured by Toa Kasei Co., Ltd.) 5 g as an invisible color material, decaglyceryl monocaprylate as a dispersant (trade name: SY Glister MCA750, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., HLB value 16) 2 g, and as a dispersion medium. 53 g of pure water was placed in a container and dispersed in a disperser (paint shaker, manufactured by Asada Iron Works Co., Ltd.) at room temperature for 24 hours (dispersion time). Further, at the time of dispersion, 130 g of zirconia beads (average particle size 0.8 mm) were mixed. As a result, an aqueous ink precursor composition for latent images composed of a dispersion in which an invisible color material was dispersed was prepared.

(Examples 44 to 47)
In Examples 44 to 47, the contents of decaglyceryl monocaprylate and pure water were changed to the values shown in Table 12. Other than that, the aqueous ink precursor composition for latent images according to this example was prepared in the same manner as in Example 43.

(Example 48)
In this embodiment, 1 g of POE (20) stearyl ether (trade name; NIKKOL (registered trademark) BS-20, manufactured by Nikko Chemical Co., Ltd.) is used as a dispersant, and ion-exchanged water is contained as a dispersion medium. The amount was changed to 54 g. The dispersion time was 96 hours. Other than that, the aqueous ink precursor composition for latent images according to this example was prepared in the same manner as in Example 43.

(Examples 49 to 52)
In Examples 49 to 52, the contents of POE (20) stearyl ether and pure water were changed to the values shown in Table 13. Other than that, the aqueous ink precursor composition for latent images according to this example was prepared in the same manner as in Example 48.

(Measurement of average primary particle size, D50 and D99 of invisible color material, and evaluation of dispersibility)
The average primary particle diameters, D50 and D99, of the invisible color material were measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.).

The dispersibility of the invisible color material was evaluated according to the following evaluation criteria. The results are shown in Tables 11 and 12.
⊚: D50 is 200 nm or less and D99 is 500 nm or less ◯: D50 is larger than 200 nm and 300 nm or less, and D99 is larger than 500 nm and 800 nm or less Δ: D50 is larger than 300 nm and 400 nm or less, and D99 is larger than 800 nm and 1000 nm or less ×: D50 is greater than 400 nm and D99 is greater than 1000 nm

(Result 2)
As can be seen from Tables 11 and 12, when the content of carnauba wax is less than 10% by mass and the content of the surfactant as a dispersant is 10% by mass or less, the dispersibility of the invisible coloring material becomes It was confirmed that it was good and the values of D50 and D99 could be reduced.

Claims (16)

A water-based ink precursor composition for latent images having light transmission in the visible light region.
It contains at least an invisible color material that is edible and has light transmission in the visible light region, and a solvent.
A water-based ink precursor composition for latent images, wherein the invisible color material is a wax and / or oil having light absorption with ultraviolet rays in the wavelength range of 100 nm to 400 nm. The water-based latent image according to claim 1, wherein the content of the invisible color material is in the range of 0.01% by mass or more and 30% by mass or less with respect to the total mass of the aqueous ink precursor composition for latent images. Ink precursor composition. The aqueous ink precursor composition for a latent image according to claim 1 or 2, wherein the invisible color material is dissolved in the solvent and exists. Further containing a dispersant for dispersing the invisible color material,
The content of the dispersant is in the range of 1% by mass or more and 10% by mass or less with respect to the total mass of the aqueous ink precursor composition for latent images.
The aqueous ink precursor composition for a latent image according to claim 1 or 2, wherein the invisible color material comprises a dispersion dispersed in the solvent using the solvent as a dispersion medium. The water-based latent image according to claim 4, wherein the content of the invisible color material is in the range of 0.1% by mass or more and less than 10% by mass with respect to the total mass of the aqueous ink precursor composition for latent images. Ink precursor composition. The average primary particle size of the invisible color material before dispersion is 50 μm or less.
The aqueous ink precursor composition for a latent image according to claim 4 or 5, wherein the invisible color material dispersed in the solvent has a D50 of 300 nm or less and a D99 of 800 nm or less. The water-based ink precursor for latent images according to any one of claims 1 to 6, wherein the invisible coloring material is at least one selected from the group consisting of vegetable wax, animal wax, vegetable oil and animal oil. Body composition. A method for producing an aqueous ink precursor composition for a latent image having light transmission in the visible light region.
It comprises at least a mixing step of mixing an invisible color material which is edible and has light transmission in the visible light region and a solvent.
A method for producing an aqueous ink precursor composition for a latent image, which uses a wax and / or oil having light absorption against ultraviolet rays in the wavelength range of 100 nm to 400 nm as the invisible color material. In the mixing of the invisible color material in the mixing step, the content of the invisible color material is 0.01% by mass or more and 30% by mass or less with respect to the total mass of the aqueous ink precursor composition for latent image. The method for producing an aqueous ink precursor composition for a latent image according to claim 8, which is carried out so as to be within the range. In the mixing step, the invisible color is such that the dispersant for dispersing the invisible color material is in the range of 1% by mass or more and 10% by mass or less with respect to the total mass of the aqueous ink precursor composition for latent images. It is a step of mixing the material with the solvent in any order.
The water-based ink precursor for latent images according to claim 8 or 9, further comprising a dispersion step of dispersing the invisible color material after mixing with the solvent in the solvent to prepare a dispersion of the invisible color material. Method for producing body composition. In the mixing of the invisible color material in the mixing step, the content of the invisible color material is 0.1% by mass or more and less than 10% by mass with respect to the total mass of the aqueous ink precursor composition for latent image. The method for producing an aqueous ink precursor composition for a latent image according to claim 10, which is performed so as to be within the range. In the dispersion step, the invisible color material having an average primary particle diameter of 50 μm or less before dispersion is dispersed in the solvent so that the D50 of the invisible color material is 300 nm or less and the D99 is in the range of 800 nm or less. The method for producing an aqueous ink precursor composition for an latent image according to claim 10 or 11, which is a step of making the ink precursor composition. The aqueous ink precursor for latent images according to any one of claims 10 to 12, wherein the mixing of the dispersant in the mixing step is performed with respect to the solvent having a liquid temperature in the range of 40 ° C. to 50 ° C. Method for producing the composition. The water-based ink precursor for latent images according to any one of claims 8 to 13, wherein the invisible coloring material is at least one selected from the group consisting of vegetable wax, animal wax, vegetable oil and animal oil. Method for producing body composition. A water-based ink composition for a latent image, which comprises the water-based ink precursor composition for a latent image according to any one of claims 1 to 7. A printed matter of a solid preparation in which an ink layer having light transmission in the visible light region is provided on the solid preparation.
The ink layer is composed of a dry film of a water-based ink for latent images.
The latent image water-based ink is a printed matter of a solid preparation containing the latent image water-based ink composition according to claim 15.