WO2016063891A1 - Pigment composition, and aqueous ink composition for inkjet printing - Google Patents

Abstract

Provided are a pigment composition and an aqueous ink composition for inkjet printing that are edible, have excellent dispersibility, and enable direct inkjet printing on pharmaceutical or food-related tablets or the like. The pigment composition is characterized by containing carbon black and a polyoxyethylene alkyl ether having at least 31 carbon atoms but fewer than 118 carbon atoms. The aqueous ink composition for inkjet printing is characterized by being edible and containing the pigment composition.

Description

Pigment composition and water-based ink composition for inkjet

The present invention relates to a pigment composition and an aqueous inkjet ink composition, and more specifically, an edible pigment that is excellent in dispersibility and can be directly printed on a tablet such as a pharmaceutical or food by an inkjet method. The present invention relates to a composition and an aqueous inkjet ink composition.

For foods such as tablet medicines and supplements, product information is displayed not only on the package but also on the tablet body, thereby improving their discrimination and preventing dispensing errors and accidental ingestion. Tablets with a coated surface can be printed by a contact method such as gravure printing, so information with high discrimination is displayed on the one hand, but uncoated or OD (orally disintegrating) tablets with poor surface smoothness are in contact. Printing by the method is difficult. Therefore, for these tablets, a marking method that can display only simple characters has become the mainstream. As a result, in the pharmaceutical industry in particular, there is an increasing need for a new printing method capable of displaying highly discriminating information even for uncoated tablets, OD tablets and the like.

As such a printing method, for example, inkjet printing using a water-based ink composition using a dye can be cited (see Patent Document 1 below). However, when printing on a pharmaceutical tablet or the like using the aqueous ink composition, there is a problem that a printed image is blurred and inferior in light resistance. As one method for solving such a problem, it is conceivable to use a pigment instead of a dye or the like, thereby improving the light resistance and eliminating the bleeding problem.

Here, in order to use a pigment in the water-based ink composition, high dispersibility is required in order to ensure good aggregation stability and sedimentation stability. Therefore, in a water-based ink composition using a pigment, it is necessary to blend a pigment dispersant. However, since compounds that can be used as pharmaceutical additives are limited by the Pharmaceutical Affairs Law, aqueous ink compositions that exhibit good pigment dispersibility and that meet the standards for pharmaceutical additives stipulated by the Pharmaceutical Affairs Law have been developed. The current situation is not.

JP 2011-236279 A

The present invention has been made in view of the above-mentioned problems, and an object thereof is an edible pigment that is excellent in dispersibility and can be directly printed by an ink jet method on tablets such as pharmaceuticals and foods. The object is to provide a composition and an aqueous ink composition for inkjet.

The inventors of the present application have studied the pigment composition and the water-based ink composition for inkjet in order to solve the above problems, and found that the above problems can be solved by adopting the following constitution. It came to complete.

That is, the pigment composition according to the present invention is characterized by containing carbon black and a polyoxyethylene alkyl ether having 31 or more and less than 118 carbon atoms in order to solve the above-mentioned problems.

According to the above configuration, since a pigment made of carbon black is used instead of a dye, when the pigment composition of the present invention is used, for example, in an aqueous inkjet ink composition, an ink composition using a dye. Compared with, light resistance can be improved. In addition, as a carbon black pigment dispersant, a polyoxyethylene alkyl ether having a carbon number of 31 or more and less than 118 that conforms to the pharmaceutical additives defined in the Pharmaceutical Affairs Law and the standards of the 16th Japanese Pharmacopoeia is used. This makes it possible to print on tablets such as pharmaceuticals using an ink jet method while maintaining the properties. Moreover, since it is excellent also in light resistance as above-mentioned, generation | occurrence | production of the blur of a printed image can also be prevented.

In the above configuration, the content ratio of the carbon black and the polyoxyethylene alkyl ether is preferably 1: 0.2 to 1: 4 on a mass basis. When the content ratio is 1: 0.2 or more, a decrease in dispersibility can be prevented. On the other hand, when the content ratio is 1: 4 or less, for example, when used in an aqueous inkjet ink composition, it is possible to prevent a decrease in ejection stability due to nozzle clogging.

Further, in the above configuration, the number of ethylene oxide groups in the polyoxyethylene alkyl ether is preferably 10 or more and less than 50. Thereby, the dispersibility of carbon black can be further improved.

In the above configuration, it is preferable that the average dispersed particle diameter D50 of the dispersed carbon black is 85 nm to 140 nm. By setting the average dispersed particle diameter D50 to 50 nm or more, light resistance and dispersibility can be improved. On the other hand, carbon black sedimentation can be prevented by setting the average dispersed particle diameter D50 to 300 nm or less.

The aqueous ink composition for inkjet according to the present invention is characterized by containing the pigment composition described above and having edible properties in order to solve the above-mentioned problems.

In the pigment composition, a polyoxyethylene alkyl ether having a carbon number of 31 or more and less than 118 that conforms to the standard of the 16th Japanese Pharmacopoeia and the pharmaceutical additive defined by the Pharmaceutical Affairs Law is used as the pigment dispersant. The ink-jet aqueous ink composition containing the composition can be used as an ink material that is printed by an inkjet method on tablets of pharmaceuticals, foods, and the like. In the pigment composition, since a pigment made of carbon black is used instead of a dye, for example, even if printing is performed on a tablet surface of a pharmaceutical product or the like by an inkjet method, the printed image is excellent in light resistance, and The occurrence of bleeding can be prevented. In addition, edible means that it consists only of the substance recognized as oral administration as a pharmaceutical or a pharmaceutical additive, and / or the substance recognized as a food or a food additive.

In order to solve the above-mentioned problem, the solid preparation according to the present invention is a solid preparation comprising a tablet or a capsule, and having a dry film of an aqueous inkjet ink on the surface. It consists of the water-based ink composition for inkjet.

According to the above configuration, since the inkjet aqueous ink composition containing the pigment dispersant and the polyoxyethylene alkyl ether having 31 to 118 carbon atoms is used as the inkjet aqueous ink, inkjet recording with the inkjet aqueous ink is performed. Even if it is directly printed by the method, it is possible to realize a printed image that is excellent in light resistance and prevents bleeding. Thereby, it is possible to display product information on the solid preparation main body, and it is possible to provide a solid preparation that can improve identification and prevent dispensing mistakes and accidental ingestion. The solid preparation of the present invention is meant to include food preparations and pharmaceutical preparations.

According to the present invention, the number of carbon atoms that conforms to the standards of pharmaceutical additives defined in the Pharmaceutical Affairs Law and the 16th Japanese Pharmacopoeia and that imparts good dispersibility to pigments made of carbon black is 31 or more and less than 118. Since the polyoxyethylene alkyl ether is contained, it is possible to provide a pigment composition and an ink-jet aqueous ink composition that enable printing on tablets of pharmaceuticals, foods, and the like by an inkjet method. Further, an aqueous ink composition for ink jet using a pigment made of carbon black is superior in light resistance to that using a dye or the like, and can prevent bleeding of a printed image.

(Pigment composition)
The pigment composition according to the present embodiment is a composition containing at least a pigment made of carbon black and a polyoxyethylene alkyl ether having 31 to 118 carbon atoms.

Examples of the carbon black include channel black, furnace black, acetylene black, and thermal black. Moreover, it is also possible to use a commercial item as carbon black of this Embodiment, As such a commercial item, # 900, # 970, # 100, # 2200, # 2300, # 2350, # 2600, MA-7, MA-8, MA-100, MA-11, MCF88, # 45L, # 50, # 10, # 33, # 40, # 4000, # 52, CF9, etc. (trade names are all Mitsubishi) Chemical Co., Ltd.), Niteron, HTC (trade names, all manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), Asahi # 55, Asahi # 51, Asahi # 50U, Asahi # 50, Asahi # 35, Asahi # 15, Asahi Thermal (product) Name, all manufactured by Asahi Carbon Co., Ltd.), Raven700, 5750, 5250, 5000, 3500, 1255 (trade names, all manufactured by Columbia), REGAL400R, 330R, 660R, ogulL, Monarch 700, 800, 880, 900, 1000, 1100, 1300, Monarch 1400 (trade names, all manufactured by Cabot Corporation), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170 (product names, any Also manufactured by Degussa), PRINTEX35, U, V, 140U, 140V (trade names, all manufactured by Degussa), SpecialＳBlack6, 5, 4A, 4 (product names, all manufactured by Degussa), TOKABLACK # 8500, # 8300, # 7550, # 7400, # 7350, # 7240, # 7100, # 7050, # 5500, # 4500, # 4400, # 4300 (trade names, all manufactured by Tokai Carbon Co., Ltd.) and the like. These pigments can be used alone or in admixture of two or more as required. However, when the pigment composition of the present embodiment is used for printing on the surface of tablets such as pharmaceuticals and supplements, carbon black may be a pharmaceutical additive specified by the Pharmaceutical Affairs Law or a food additive specified by the Food Sanitation Law. preferable.

The average primary particle size of the carbon black is preferably 10 nm to 40 nm. In addition, an average primary particle diameter means the arithmetic average particle diameter calculated | required by observing the said carbon black particle before making it disperse | distribute in a solvent with a dispersing agent with an electron microscope.

The carbon black content has a direct effect on the image density, and when printing on a water-based ink composition, which will be described later, when printing on a tablet or the like, it has an effect on the printing density. Therefore, it may be set appropriately in consideration of these points. Usually, the range of 0.5% by mass to 20% by mass is preferable with respect to the total mass of the pigment composition, more preferably within the range of 1% by mass to 15% by mass, and particularly preferably within the range of 1% by mass to 3% by mass. preferable. By setting the carbon black content to 0.5% by mass or more, a decrease in image density can be suppressed. On the other hand, by setting the carbon black content to 20% by mass or less, it is possible to prevent a decrease in gloss, nozzle clogging, and a decrease in ejection stability.

The average dispersed particle diameter D50 of the carbon black in a dispersed state is preferably in the range of 50 nm to 200 nm, and more preferably in the range of 85 nm to 140 nm. The cumulative 99% value (D99) of the particle size distribution of the carbon black is preferably in the range of 100 nm to 500 nm. By setting the D50 to 50 nm or more, it is possible to prevent the dispersion stability, light resistance and ejection stability from deteriorating and to prevent the printing density from being lowered. On the other hand, by setting the D50 to 200 nm or less, separation and sedimentation of the carbon black can be prevented and dispersion stability can be maintained. The average dispersed particle diameter D50 or D99 of carbon black is a value measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.).

The polyoxyethylene alkyl ether is represented by the general formula R—O— (CH ₂ —CH ₂ —O) _n —H (where R represents an alkyl group and n represents the number of ethylene oxide groups). The pigment dispersant has a total carbon number of 31 or more and less than 118. By adding a polyoxyethylene alkyl ether having a total carbon number of 31 or more and less than 118, the dispersibility of carbon black can be improved. In addition, polyoxyethylene alkyl ethers conform to the pharmaceutical additives and the 16th Japanese Pharmacopoeia standards specified by the Pharmaceutical Affairs Law. Therefore, the polyoxyethylene alkyl ether can be suitably used for printing on tablets or the like of drugs or foods.

The number n of ethylene oxide groups in the general formula is preferably 10 or more and less than 50. When n is 10 or more, a hydrophilic function can be imparted and the dispersibility of carbon black can be improved. In addition, carbon number of the alkyl group R in the said general formula can be suitably determined according to the total carbon number of polyoxyethylene alkyl ether, and the number of ethylene oxide groups.

The content ratio of the carbon black and the polyoxyethylene alkyl ether is preferably 1: 0.2 to 1: 4 on a mass basis. When the content ratio is 1: 0.2 or more, it is possible to prevent a decrease in dispersibility of carbon black. On the other hand, when the content ratio is 1: 4 or less, for example, when used in an aqueous inkjet ink composition, it is possible to prevent a decrease in ejection stability due to adhesion of a nozzle plate.

In the pigment composition according to the present embodiment, a dispersion medium for dispersing carbon black is included. Examples of the dispersion medium include water, and more specifically, pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water, or those obtained by removing ionic impurities such as ultrapure water. . In particular, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented over a long period of time. Moreover, it is not specifically limited as content of a dispersion medium, It can set as needed suitably.

Further, as the dispersion medium, a mixed solution of water and a water-soluble organic solvent may be used. The water-soluble organic solvent is not particularly limited, and specifically, for example, alcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-propyl alcohol, isopropyl alcohol; Amides such as dimethylformamide and dimethylacetamide; Ketones such as acetone and methyl ethyl ketone; Tetrahydrofuran, dioxane, ethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether, triethylene glycol mono Ethers such as ethyl ether; ethylene glycol, propylene glycol, butylene glycol , Diethylene glycol, dipropylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, polyethylene glycol, polypropylene glycol, glycerin, diglycerin, polyglycerin and other polyhydric alcohols; N-methylpyrrolidone 1,3-dimethyl-2-imidazolidinone and the like. You may use these individually by 1 type or in mixture of 2 or more types. Among the water-soluble organic solvents listed above, in the present embodiment, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, n-propyl alcohol, isopropyl alcohol, acetone, propylene glycol, polyethylene glycol, glycerin Is preferred. Furthermore, the blending amount when a water-soluble organic solvent is used as the dispersion medium is not particularly limited, and can be appropriately set as necessary.

In the method for producing the pigment composition of the present embodiment, the mixing method and the order of addition of carbon black, polyoxyethylene alkyl ether, dispersion medium, and other additives blended as necessary are not particularly limited. For example, carbon black, polyoxyethylene alkyl ether, water as a dispersion medium, and the like may be mixed at a time, and the mixed solution may be subjected to a dispersion treatment using an ordinary disperser. The dispersion time at this time is not particularly limited, but is preferably set so that the average dispersed particle diameter of the pigment is within the above numerical range. For example, when a paint shaker is used, it is preferably in the range of 2 hours to 48 hours, more preferably in the range of 6 hours to 20 hours, depending on the mass of the pigment composition. By setting the dispersion time to 2 hours or longer, the large amount of coarse particles of carbon black is reduced, and the adsorption of polyoxyethylene alkyl ether on the carbon black surface becomes insufficient, resulting in dispersion stability and storage stability. It is possible to prevent the performance from deteriorating. On the other hand, by reducing the dispersion time to 48 hours or less, the occurrence of many pigment fine particles having an average dispersed particle diameter smaller than the above numerical range is reduced, and dispersion stability, storage stability, and ejection stability are further reduced. A decrease can be prevented. In addition, a decrease in printing density can be suppressed. In addition, it does not specifically limit as a disperser used in the case of the dispersion process of a pigment, What is generally used can be used. Specific examples include a ball mill, a roll mill, a sand mill, a bead mill, a paint shaker, and a nanomizer.

The pigment composition of the present embodiment has a form of a pigment dispersion for preparing the water-based ink composition in addition to a form of a water-based ink composition for inkjet (details will be described later) as a final product. It is included.

(Water-based ink composition for inkjet)
The aqueous inkjet ink composition (hereinafter referred to as “aqueous ink composition”) according to the present embodiment is an aqueous ink containing at least the pigment composition and having a main solvent of water. Further, the water-based ink composition of the present embodiment has edible properties and is suitably used for inkjet recording. Furthermore, since a pigment is used as a coloring material, the water-based ink composition is superior in terms of color developability, light resistance, water resistance and the like as compared with an ink composition using a dye.

The content of the pigment composition is preferably in the range of 0.5% by mass to 20% by mass in terms of solid content, more preferably in the range of 1% by mass to 15% by mass with respect to the total mass of the aqueous ink composition. By making the content of the pigment composition 0.5% by mass or more, the coloring power can be improved. On the other hand, dispersibility can be improved by making the content of the pigment composition 20% by mass or less.

The water-based ink composition according to the present embodiment contains water (water as a main solvent). As the water, it is preferable to use water from which ionic impurities such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water have been removed. In particular, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented over a long period of time. Moreover, it does not specifically limit as content of water, It can set suitably as needed.

In the water-based ink composition of the present embodiment, other additives may be blended. However, when used as an ink-jet ink for tablets of pharmaceuticals, etc., it must comply with the pharmaceutical additives defined in the Pharmaceutical Affairs Law, etc., and the standards of the 16th Japanese Pharmacopoeia, or the food additives. preferable. Examples of the additive include a surface tension adjusting agent, a wetting agent, a water-soluble resin, an organic amine, a surfactant, a pH adjusting agent, a chelating agent, an antiseptic, a viscosity adjusting agent, and an antifoaming agent. The content of these additives is not particularly limited, and can be appropriately set as necessary.

Among the additives, as the surface tension adjuster, those that comply with the standards of pharmaceutical additives and the 16th Japanese Pharmacopoeia, or food additives defined by the Food Sanitation Law, and a water-based ink composition There is no particular limitation as long as the surface tension can be adjusted. Specifically, for example, caprylic acid degaglycerin ester, capric acid decaglycerin ester, lauric acid decaglycerin ester, oleic acid decaglycerin ester, lauric acid hexaglycerin ester, oleic acid hexaglycerin ester, condensed linolenic acid tetraglycerin ester , Fatty acid ester palm palm, capric acid decaglycerin ester, lauric acid decaglycerin ester, myristic acid decaglycerin ester, stearic acid decaglycerin ester, oleic acid decaglycerin ester, myristic acid hexaglycerin ester, glycerin fatty acid ester mixture, stearic acid glycerin Ester (self-emulsifying type), pyroglutamic acid POE, polyethylene glycol monolaurate (10EO), monoole Polyethylene glycolate (6EO), polyoxyethylene coconut oil fatty acid sorbitan (20EO), polyoxyethylene sorbitan monostearate (20EO), polyoxyethylene sorbitan monooleate (20EO), polyoxyethylene sorbitan monopalmitate (20EO) ), POE (4.2) lauryl ether, POE (9) lauryl ether, and the like. You may use these individually by 1 type or in mixture of 2 or more types.

Among these surface tension modifiers, caprylic acid decaglycerin ester (trade name; Ryoto polyglycerin CE19D, manufactured by Mitsubishi Chemical Foods), caprylic acid decaglycerin ester ( Product name: SY glyceric MCA750, Sakamoto Yakuhin Kogyo), lauric acid decaglycerin ester (trade name; NIKKOL DECAGLYN 1-L, manufactured by Nikko Chemicals Co., Ltd.), lauric acid decaglycerin ester (trade name: SY glycerase ML-750, Sakamoto Yakuhin Kogyo Co., Ltd.), oleic acid decaglycerin ester (trade name; NIKKOL DECAGLYN 1-OV, manufactured by Nikko Chemicals Co., Ltd.), oleic acid decaglycerin ester (brand name: SY Glister MO-7S, Sakamoto Yakuhin Kogyo) (Made by Co., Ltd.) Acid hexaglycerin ester (trade name: NIKKOL HEXAGLYN 1-L, manufactured by Nikko Chemicals Co., Ltd.), lauric acid hexaglycerin ester (trade name: SY Glyster ML-500, manufactured by Sakamoto Pharmaceutical Co., Ltd.), hexaoleic acid Glycerin ester (trade name: SY Glister MO-5S, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), condensed linolenic acid tetraglycerin ester (product name: SY Glister CR-310, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), fatty acid ester palm palm It is preferable to use a commercially available product such as (trade name: Tirabazole W-01, manufactured by Taiyo Kagaku Co., Ltd.).

The content of the surface tension adjusting agent is preferably in the range of 0.2% by mass to 10% by mass, and more preferably in the range of 1% by mass to 4% by mass with respect to the total mass of the aqueous ink composition. By setting the content of the surface tension adjusting agent to 0.2% by mass or more, it is possible to suppress a decrease in discharge performance. On the other hand, storage stability can be ensured by setting the content of the surface tension adjusting agent to 10% by mass or less.

Of the additives, examples of the wetting agent include the water-soluble organic solvents described above. The content of the wetting agent is preferably in the range of 3% by mass to 50% by mass and more preferably in the range of 10% by mass to 40% by mass with respect to the total mass of the aqueous ink composition. By setting the content of the wetting agent to 3% by mass or more, clogging in the vicinity of the nozzle of the inkjet head can be prevented, and the discharge performance can be 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.

The water-based ink composition of the present embodiment can be produced by mixing the aforementioned components by an appropriate method. That is, for example, the additive is separately added to the dispersion of the pigment composition, and further diluted with water. Thereafter, the mixture is sufficiently stirred, and if necessary, filtration is performed to remove coarse particles and foreign matters that cause clogging. Thereby, the water-based ink composition which concerns on this 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 disper, a homomixer, a mechanical stirrer, a magnetic stirrer, and the like and stirred. Moreover, it does not specifically limit as a filtration method, For example, centrifugal filtration, filter filtration, etc. are employable.

The water-based ink composition of the present embodiment can be applied to ink and paint. In addition, since the water-based ink composition of the present embodiment is excellent in dispersibility of carbon black as a pigment, it can be suitably used for inkjet ink. In particular, the water-based ink composition of the present embodiment includes carbon black and a pigment dispersant that meet the pharmaceutical additives defined by the Pharmaceutical Affairs Law and the like, and the standards of the 16th Japanese Pharmacopoeia or fall under food additives. Therefore, it is edible and can be printed directly on the surface of tablets such as pharmaceuticals and supplements. In addition, non-contact printing by an inkjet method is possible even for tablets with poor surface smoothness such as uncoated tablets and OD tablets. Furthermore, since the water-based ink composition is excellent in light resistance, the occurrence of bleeding can be prevented even if it is directly printed on the surface of a tablet such as a pharmaceutical or a supplement.

(Solid preparation)
The solid preparation of the present embodiment is composed of a tablet or a capsule, and the surface of the solid agent is directly printed by an inkjet recording method using an inkjet aqueous ink composed of the aqueous ink composition. is there. As described above, the water-based ink composition is excellent in the dispersibility of carbon black, which is a pigment, and there is no occurrence of bleeding in the printed image, so that a good printed image can be obtained. Various information for improving the performance can be printed. As a result, dispensing errors and accidental ingestion can be prevented.

Tablets are solid at normal temperature, and for example, tablets produced by compressing and / or molding a tablet material containing an active ingredient into a certain shape are preferable. The capsule is preferably prepared by filling a powder, granule, liquid or the like in a capsule made of gelatin, cellulose derivative or the like, or encapsulating with a capsule base. The shape of a tablet and a capsule is not specifically limited, Arbitrary shapes can be employ | adopted. Tablets and capsules may be used for pharmaceuticals or foods. Examples of tablets for food use include health foods such as tablet confectionery and supplements.

The ink jet recording method for the surface of the solid preparation is not particularly limited. Specifically, for example, the water-based ink composition can be discharged as droplets from a fine nozzle, and the droplets can be attached to the surface of the solid preparation. 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 type, thermal type, electrostatic suction type, etc.) can be employed. .

Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. However, materials, contents, and the like described in the following examples are not intended to limit the scope of the present invention only to those unless otherwise specified. In addition, each of the materials described in the following Examples and Comparative Examples are those that conform to the pharmaceutical additives defined in the Pharmaceutical Affairs Law and the standards of the 16th Japanese Pharmacopoeia, or correspond to food additives. is there.

(Examples 1 to 36)
The pigment compositions of Examples 1 to 36 were prepared with the blending compositions shown in Tables 1 to 3 below. Moreover, the pigment composition of each Example was prepared by the following operation. That is, each material shown in Tables 1 to 3 was put in a container and dispersed with a paint shaker (manufactured by Asada Tekko Co., Ltd.) at room temperature for 7 hours (dispersion time). This obtained the pigment composition of each Example.

(Comparative Examples 1 to 7)
The pigment compositions of Comparative Examples 1 to 6 were prepared with the composition shown in Table 4 below. Moreover, the pigment composition of each comparative example was prepared by the following operation. That is, each material shown in Table 4 was put in a container and dispersed with a disperser at room temperature for 7 hours (dispersion time). This obtained the pigment composition of each comparative example.

(Examples 37 to 42)
Water-based ink compositions of Examples 37 to 42 were prepared with the composition shown in Table 5 below. Moreover, the water-based ink composition of each Example was prepared by the following operation. First, a pigment composition was prepared by the same procedure as in Example 1, and then a surface tension adjusting agent, a wetting agent and water were added and mixed so that the blending composition shown in Table 5 below was obtained. 37-42 aqueous ink compositions were obtained. The numerical values in Table 5 below are all expressed in mass%.

(Comparative Examples 8 and 9)
The pigment compositions of Comparative Examples 8 and 9 were prepared with the composition shown in Table 6 below. Moreover, the pigment composition of each comparative example was prepared by the following operation. That is, each material shown in Table 6 was put in a container and dispersed with a disperser at room temperature for 7 hours (dispersion time). As a result, pigment compositions of Comparative Examples 8 and 9 were obtained. The numerical values in Table 6 below are all expressed in mass%.

(Examples 43 to 58)
Water-based ink compositions of Examples 43 to 58 were prepared with the composition shown in Table 7 and Table 8 below. Moreover, the water-based ink composition of each Example was prepared by the following operation. First, a pigment composition was prepared by the same procedure as in Example 1, and then a surface tension adjusting agent, a wetting agent and water were added and mixed so as to have the composition shown in Table 7 and Table 8 below. The aqueous ink compositions of Examples 43 to 58 were obtained. The numerical values in the following Tables 7 and 8 are all expressed in mass%.

(Examples 59 to 77)
In Examples 59 to 77, first, a pigment composition having the composition shown in Table 9 below and a carbon black concentration of 25% by mass was prepared. The pigment composition was prepared by placing each material in a container and dispersing it at room temperature for 16 hours (dispersion time) with a disperser. Furthermore, using the obtained pigment composition, aqueous ink compositions were prepared with the blending compositions shown in Table 10 and Table 11 below. The water-based ink composition was prepared by placing each material in a container and stirring with a disper for 20 minutes. In the blending composition shown in Table 10, the surface tension when the surface tension modifier was not added was 43.0 mN / m.

(Measurement of average dispersed particle size of pigment)
The average dispersed particle diameter D50 or D99 of the pigments in the aqueous ink compositions of Examples and Comparative Examples was measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.). The results are shown in Tables 1 to 8.

(Evaluation of missing nozzles and fading)
Matt paper (trade name: Superfine paper, manufactured by Epson Corporation) was prepared as a recording medium, and printing was performed using the aqueous ink compositions prepared in Examples 42 to 57. Printing was performed by a single pass (one pass) method using an inkjet printer (printing jig with KC 600 dpi head).

Evaluation of nozzle omission and fading was performed by checking whether nozzle omission or fading was observed in the printed image when the ink jet printer was stopped after discharging the aqueous ink composition from the head and then printing was performed again. . The results are shown in Table 7, Table 8 and Table 11. ○ in each table means a case where no nozzle omission or fading was observed. X means a case where nozzle missing or fading occurs during printing. The term “nozzle missing” means that an ink droplet made of a water-based ink composition is not ejected from a nozzle where clogging has occurred. Fading means fading of an image at the initial stage of printing. Further, 1 min, 5 min, and 15 min in Tables 7 and 8 represent time intervals (open time) until the water-based ink composition is first ejected from the head and then stopped and then printed again.

(Measurement of surface tension of water-based ink composition)
The surface tension of each of the aqueous ink compositions of Examples 42 to 75 was measured at room temperature using a surface tension meter (trade name: DY-500, manufactured by Kyowa Interface Science Co., Ltd.). The results are shown in Table 11 above.

(result)
As can be seen from the experimental results of Examples 1 to 36 shown in Tables 1 to 3, the number n of ethylene oxide groups is 10 or more and less than 50 and the total number of carbon atoms is 31 or more and 118 for various pigments made of carbon black. Less polyoxyethylene alkyl ether as a pigment dispersant, and when the content ratio of polyoxyethylene alkyl ether to carbon black is 0.2 or more on a mass basis, the average dispersed particle diameter D50 of carbon black And it was confirmed that the value of D99 can be made small and a pigment composition excellent in dispersibility can be produced.

On the other hand, as can be seen from the experimental results of Comparative Examples 1 to 7 shown in Table 4, polyoxyethylene alkyl ether was used as the dispersant, and the content ratio of polyoxyethylene alkyl ether to carbon black was 0.3 by mass. Even in the above case, when the total carbon number of the polyoxyethylene alkyl ether is 30 or less or 118 or more, and the number n of ethylene oxide groups is less than 10 or 50 or more, carbon black is not dispersed, Even when dispersed, it was confirmed that the average dispersed particle diameters D50 and D99 of carbon black were large.

Further, as can be seen from the experimental results of Examples 37 to 42 shown in Table 5, the average dispersed particle diameters D50 and D99 of carbon black can be reduced also in the aqueous ink composition to which the surface tension modifier is added. It was confirmed that an aqueous ink composition having excellent dispersibility can be produced. On the other hand, in Comparative Examples 8 and 9 shown in Table 6, carbon black could not be dispersed.

Further, in Examples 43 to 58 shown in Tables 7 and 8, each water-based ink composition exhibits excellent dispersibility, and in the printed image, no nozzle omission or blurring occurs, and excellent ejection performance is exhibited. It was confirmed.

Further, as can be seen from the experimental results shown in Table 11, it was confirmed that when the surface tension adjusting agents shown in Examples 59 to 69 were used, extremely good ejection performance was exhibited.

Claims (6)

1. A pigment composition containing carbon black and a polyoxyethylene alkyl ether having 31 or more and less than 118 carbon atoms.
2. The pigment composition according to claim 1 or 2, wherein the number of ethylene oxide groups in the polyoxyethylene alkyl ether is 10 or more and less than 50.
3. 2. The pigment composition according to claim 1, wherein the content ratio of the carbon black and the polyoxyethylene alkyl ether is 1: 0.2 to 1: 4 on a mass basis.
4. The pigment composition according to any one of claims 1 to 3, wherein the dispersed carbon black has an average dispersed particle diameter D50 of 85 nm to 140 nm.
5. An aqueous inkjet ink composition comprising the pigment composition according to any one of claims 1 to 4 and having edible properties.
6. A solid preparation comprising a tablet or a capsule and having a dry film of an aqueous inkjet ink on its surface,
   The solid formulation which the said water-based ink for inkjets consists of the water-based ink composition for inkjets of Claim 5.