JP2019199571A - Aqueous inkjet ink - Google Patents

Abstract

To provide an aqueous inkjet ink that can suppress the amount of generation of VOCs from a recorded image and paper deformation.SOLUTION: An aqueous inkjet ink has a colorant and water, and further has a water-soluble organic solvent, wherein the water-soluble organic solvent has a boiling point of 300°C or more and a 23°C viscosity of 20 mPa s or less, and wherein an aqueous solution containing the water-soluble organic solvent of 80 mass% or more and less than 100 mass% has a 23°C viscosity of 20 mPa s or less.SELECTED DRAWING: None

Description

  Embodiments of the invention relate to aqueous inkjet inks.

Ink jet inks used in the ink jet recording method are roughly classified into aqueous inks and non-aqueous inks. Since the water-based ink contains water as a solvent, the recording medium may absorb moisture in the ink and cause paper deformation such as curling and cockling, which causes the printed matter to come into contact with the inkjet head, etc. There is a possibility of affecting the transportability of the recording medium.

Further, in recent years, ink jet recording methods are increasingly required to perform printing at high speed. Under these demands, line head type ink jet printers are becoming popular as ink jet printers capable of high-speed printing. However, when the speed is increased, the problems caused by the deformation of the paper as described above are likely to occur.

In recent years, VOC (Vola), an organic compound that is volatile and becomes gaseous in the atmosphere.
Tile Organic Compounds) is concerned about the impact on human health.

Patent Documents 1 and 2 propose a technique for suppressing paper deformation for ink jet ink.
Patent Document 3 proposes a method for suppressing the occurrence of VOC.

JP 2005-220296 A Japanese Patent Laying-Open No. 2015-67678 JP 2014-200197 A

In Patent Documents 1 and 2, a technique for suppressing paper deformation is proposed for ink-jet ink, but a low-boiling solvent may be used and VOC may be generated.
Patent Document 3 proposes a method for suppressing the occurrence of VOC, but the suppression of sheet deformation has not been studied.

An object of the present invention is to provide a water-based inkjet ink that can reduce the amount of VOC generated from a recorded image and deformation of the paper.

According to one embodiment of the present invention, there is provided a water-soluble organic solvent containing a colorant and water, having a boiling point of 300 ° C. or higher and a viscosity at 23 ° C. of 20 mPa · s or lower,
There is provided an aqueous inkjet ink further comprising a water-soluble organic solvent having a viscosity at 23 ° C. of 20% by mass or more and less than 100% by mass of an aqueous solution having a viscosity of 20 mPa · s or less.
According to another embodiment of the present invention, there is provided an aqueous inkjet ink comprising a coloring material and water, and further comprising at least one water-soluble organic solvent selected from the group consisting of bisethoxydiglycol succinate and benzyldiglycol. Is done.

According to the embodiment of the present invention, it is possible to provide a water-based inkjet ink capable of reducing the amount of VOC generated from a recorded image and the deformation of the paper.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

An aqueous inkjet ink according to an embodiment of the present invention (hereinafter sometimes referred to as “ink”) includes a coloring material and water, has a boiling point of 300 ° C. or higher, and a viscosity at 23 ° C. of 20 mPa · s.
a water-soluble organic solvent having a viscosity at 23 ° C. of 20 mPa · s or less of an aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent (hereinafter referred to as “
And water-soluble organic solvent A ”).

The water-soluble organic solvent A will be described.
The boiling point of the water-soluble organic solvent A is from the viewpoint of reducing the amount of VOC generated from the recorded image.
It is 300 ° C or higher.

The viscosity of the water-soluble organic solvent A at 23 ° C. is preferably 20 mPa · s or less, more preferably 19 mPa · s or less, and even more preferably 18 mPa · s or less, from the viewpoint of reducing paper deformation.
The viscosity at 23 ° C. of an aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent A is preferably 20 mPa · s or less, more preferably 19 mPa · s or less, and more preferably 18 mPa · s, from the viewpoint of reducing paper deformation. The following is more preferable.
Here, the aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent A is a mixture of the water-soluble organic solvent A and water, and is water-soluble with respect to the total amount of the water-soluble organic solvent A and water. It is an aqueous solution in which the proportion of the organic solvent A is 80% by mass or more and less than 100% by mass. In addition, the viscosity at 23 ° C. of an aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent A is within a predetermined range means that the water-soluble organic solvent is a mixture of the water-soluble organic solvent A and water. In the aqueous solution of A, the amount of the water-soluble organic solvent A is 2% of the aqueous solution over the entire range of 80% by mass or more and less than 100% by mass.
It means that the viscosity at 3 ° C. is within a predetermined range.

Further, the viscosity at 23 ° C. of the water-soluble organic solvent A and 80% by mass or more of the water-soluble organic solvent A 1
When the viscosity at 23 ° C. of an aqueous solution of less than 00% by mass is 20 mPa · s or less, the viscosity is relatively low, so that the ink can easily have a low viscosity without containing a large amount of water.
Thereby, the amount of water contained in the ink can be reduced. This is also considered to be advantageous in reducing sheet deformation.

The viscosity of the water-soluble organic solvent A at 23 ° C. is preferably higher than the viscosity of the aqueous solution of the water-soluble organic solvent A that is 80% by mass or more and less than 100% by mass.

The viscosity at 23 ° C. of the water-soluble organic solvent A is preferably 10 mPa · s or more, preferably 11 mPa · s or more, and more preferably 12 mPa · s or more.
The viscosity of an aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent A is 10 mPa ·
s or more is preferable, 11 mPa · s or more is preferable, and 12 mPa · s or more is more preferable.

If the printed material is sandwiched between clear files using polypropylene (PP) as a main component, the clear file may be deformed so as to wave as time passes. When the viscosity of the water-soluble organic solvent A at 23 ° C. and the viscosity of the aqueous solution of the water-soluble organic solvent A of 80% by mass or more and less than 100% by mass is 10 mPa · s or more, the water-soluble organic solvent A is contained in clear file polypropylene. There is a tendency that it is difficult to enter, and there is also a tendency that it is difficult to generate a clear file deformation.

The number of hydroxyl groups in one molecule of the water-soluble organic solvent A is preferably 1 or less from the viewpoint of reducing deformation of the paper. That the number of hydroxyl groups in one molecule is 1 or less, for example, the number of hydroxyl groups in one molecule may be 1 or 0.

As one of the causes that the paper absorbs moisture in the ink and causes deformation of the paper, it is conceivable that water enters hydrogen bonds between cellulose molecules of the paper and breaks hydrogen bonds between cellulose molecules. In addition, it is considered that a water-soluble organic solvent having a hydroxyl group may enter hydrogen bonds between cellulose molecules like water and break hydrogen bonds between cellulose molecules. When the number of hydroxyl groups in one molecule is 1 or less, it is considered that the water-soluble organic solvent tends not to enter between the cellulose molecules of the paper and tends to break hydrogen bonds. When the number of hydroxyl groups in one molecule is 1 or less,
Water-soluble organic solvents tend to be relatively difficult to retain water, and even when the volatility is relatively low, the influence of water retained by the water-soluble organic solvent remaining on the paper is small. For this reason, when the number of hydroxyl groups in one molecule of the water-soluble organic solvent A is 1 or less, it is considered that the deformation of the paper can be further reduced, but the above theory is not restrictive.

Specific examples of the water-soluble organic solvent A include bisethoxydiglycol succinate and benzyldiglycol.

  The water-soluble organic solvent A can be used alone or in combination of two or more.

The content of the water-soluble organic solvent A in the ink is preferably 40% by mass or more, preferably 50% by mass or more, and more preferably 55% by mass or more based on the total amount of the ink. Water-soluble organic solvent A
Is preferably 85% by mass or less, more preferably 80% by mass or less, and still more preferably 75% by mass or less based on the total amount of the ink.

The ratio of the content of the water-soluble organic solvent A and water in the ink is not particularly limited, but from the viewpoint of further reducing paper deformation, the content of the water-soluble organic solvent A in the ink is the content of water in the ink. 1.0 times or more by mass ratio with respect to the amount is preferable, 1.2 times or more is more preferable, 1.4
More than double is more preferable. Further, the content of the water-soluble organic solvent A in the ink is preferably 10 times or less, more preferably 5 times or less, for example, 4 times or less, relative to the content of water in the ink.

In addition to the water-soluble organic solvent A, other water-soluble organic solvents may be added to the ink as long as the effects of the present invention are not impaired. Other water-soluble organic solvents can be appropriately selected from organic compounds that are liquid at room temperature and are soluble in water.

The content of the water-soluble organic solvent A in the ink is 6 with respect to the total amount of the water-soluble organic solvent in the ink.
It is preferably 0% by mass or more, more preferably 70% by mass or more,
More preferably, it is at least mass%. The content of the water-soluble organic solvent A in the ink may be 100% by mass of the total amount of the water-soluble organic solvent in the ink.

Explain about water.
As water, it is preferable to use pure water such as ion-exchanged water or distilled water, or ultrapure water.
The water content in the ink is not particularly limited. The content of water in the ink is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less from the viewpoint of further reducing paper deformation. The water content in the ink may be, for example, 10% by mass or more, 15% by mass or more, or 20% by mass or more.

The color material will be described.
As the color material, pigments and dyes can be used alone or in combination.

Examples of the pigment include organic pigments such as azo, phthalocyanine, dye, condensed polycyclic, nitro, and nitroso (brilliant carmine 6B, lake red C, watching red, disazo yellow, hanza yellow, phthalocyanine blue, Phthalocyanine green, alkali blue, aniline black, etc.); metals such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese, nickel, metal oxides and sulfides, and ocher, ultramarine, bitumen, etc. Carbon blacks such as inorganic pigments, furnace carbon black, lamp black, acetylene black and channel black can be used.

When a pigment is contained in the ink, a pigment dispersant can be added to stably disperse the pigment in the ink. Examples of pigment dispersants include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, Activators such as oxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivative, vinyl naphthalene derivative, acrylic acid, acrylic acid derivative A block copolymer composed of two or more monomers selected from maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives, random copolymers and salts thereof. It can gel.

A self-dispersing pigment may be used as the pigment. The self-dispersing pigment is preferably a pigment having an ionic hydrophilic functional group introduced on the pigment surface, and the pigment particles are electrostatically repulsive by charging the pigment surface anionic or cationic. Can be stably dispersed in water. Anionic functional groups include sulfonic acid groups, carboxy groups,
A carbonyl group, a hydroxy group, a phosphonic acid group, a phosphoric acid group and the like are preferable. As the cationic functional group, a quaternary ammonium group, a quaternary phosphonium group and the like are preferable.

These hydrophilic functional groups may be directly bonded to the pigment surface or may be bonded via other atomic groups. Examples of other atomic groups include, but are not limited to, an alkylene group, a phenylene group, and a naphthylene group. Examples of the treatment method for the pigment surface include diazotization treatment, sulfonation treatment, hypochlorous acid treatment, humic acid treatment, and vacuum plasma treatment.
In addition, for example, a self-dispersing pigment having a quaternary ammonium ion as a counter ion is also preferable. For example, a self-dispersing pigment having an anionic group and having a quaternary ammonium ion as a counter ion can be preferably used. Quaternary ammonium ions include tetramethylammonium ions, tetraethylammonium ions,
Tetrapropylammonium ion and tetrabutylammonium ion are preferred, tetrapropylammonium ion and tetrabutylammonium ion are more preferred,
Tetrabutylammonium ions are particularly preferred.

Examples of commercially available self-dispersing pigments include CAB-O-JET300 and CAB manufactured by Cabot Corporation.
-O-JET400, BONJET BLACK CW- manufactured by Orient Chemical Industry Co., Ltd.
1, CW-1S, CW-2, Aqua-Black 162 manufactured by Tokai Carbon Co., Ltd.
Etc. can be illustrated. Further, for example, those obtained by converting counter ions of these commercially available self-dispersing pigments into quaternary ammonium ions may be used.

As dyes, basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes,
Examples include mordant dyes, reactive dyes, vat dyes, sulfur dyes, and the like, and among these, water-soluble dyes are preferable. More specifically, examples of the dye include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane dyes.

These pigments and dyes may be used alone or in appropriate combination.

The content of the coloring material (coloring material solid content) in the ink is preferably about 0.1 to 25% by mass, more preferably 1 to 20% by mass, further preferably 3 to 15% by mass, 15 mass% is further more preferable.

If necessary, the ink may contain various additives usually used in the art as long as the object of the present invention is not impaired.

Specifically, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or a polymer, silicone, fluorine, as a pigment dispersant, an antifoaming agent, a surface tension reducing agent, etc. System surfactants can be included in the ink.
Although it does not specifically limit as surfactant, For example, acetylene glycol type surfactant, polyoxyethylene alkylphenol, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester etc. are preferable. Examples of acetylene glycol surfactants include Surfynol 465 and Surfynol 104 (Air Product).
ts and Chemical), Olfine STG, Olfine E1010 (Nisshin Chemical Industry Co., Ltd.).

In order to adjust the storage stability of the ink, an electrolyte can be blended in the ink. Examples of the electrolyte include sodium sulfate, potassium hydrogen phosphate, sodium citrate, potassium tartrate, sodium borate and the like, and two or more kinds may be used in combination.

In order to adjust the pH of the ink, a known pH adjusting agent may be added. Sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonium hydroxide, triethanolamine and the like can be used as a pH adjuster or as a thickening aid for ink.

By blending an antioxidant, it is possible to prevent the ink components from being oxidized and improve the storage stability of the ink. As the antioxidant, for example, L-ascorbic acid, sodium L-ascorbate, sodium isoascorbate, potassium sulfite, sodium sulfite, sodium thiosulfate, sodium dithionite, sodium pyrosulfite and the like can be used.

By blending a preservative, the ink can be prevented from being spoiled and the storage stability can be improved. Examples of preservatives include 5-chloro-2-methyl-4-isothiazoline-3
Isothiazolone preservatives such as -one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one; Triazine preservatives such as 3,5-tris (2-hydroxyethyl) -s-triazine; pyridine / quinoline preservatives such as 2-pyridinethiol sodium-1-oxide and 8-oxyquinoline; sodium dimethyldithiocarbamate Dithiocarbamate preservatives of 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitro-1,3-propanediol, 2,2-dibromo-2-nitroethanol, 1,2-dibromo Organic bromine preservatives such as -2,4-dicyanobutane; methyl p-hydroxybenzoate, p-hydroxy Ethyl benzoate, potassium sorbate, sodium dehydroacetate, can be used salicylic acid.

The ink can be adjusted by mixing each component in a lump or divided and dispersing the mixture appropriately using a disperser.

The viscosity range of the ink is preferably 1 to 30 mPa · s at 23 ° C., although its suitability range varies depending on the nozzle diameter of the discharge head, the discharge environment, and the like.

An ink jet recording method or a printed material manufacturing method according to an embodiment will be described.
This inkjet recording method or printed matter manufacturing method includes applying the above-described ink to a recording medium by an inkjet recording method.
As the ink jet recording method, any method such as a thermal ink jet method, a piezo ink jet method, and an electrostatic suction method may be used.For example, the ink according to the present embodiment is ejected from an ink jet head based on a digital signal, The ejected ink droplets are allowed to adhere to the recording medium.

The recording medium is not particularly limited, and may be plain paper, reprinted paper, high-quality plain paper, inkjet (I
J) Paper, IJ matte paper, coated paper with an ink absorbing solution coated on a recording medium, fine coated paper with a thinner ink absorbing layer than coated paper, glossy paper (photo glossy paper), special paper, cloth, etc. Can be used.

According to this inkjet recording method or printed matter manufacturing method, paper deformation such as curling can be reduced, so that paper transportability is good and high-speed printing can be handled. For this reason, the ink according to the present embodiment can be preferably used in a line head type ink jet printer equipped with a line head.

Embodiments of the present invention include the following, but the present invention is not limited to the following embodiments.
<1> Including coloring material and water,
Viscosity at 23 ° C. of a water-soluble organic solvent having a boiling point of 300 ° C. or higher and a viscosity at 23 ° C. of 20 mPa · s or less, of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent. Further includes a water-soluble organic solvent having a viscosity of 20 mPa · s or less,
Water-based inkjet ink.
<2> The viscosity of the water-soluble organic solvent at 23 ° C. is 10 mPa · s or more, and the viscosity of the aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent is 10 mP.
The aqueous inkjet ink according to <1>, which is a · s or more.
<3> The number of hydroxyl groups in one molecule of the water-soluble organic solvent is 0 or 1, <1> or <2
> The water-based inkjet ink of description.
<4> Including coloring material and water,
Further comprising at least one water-soluble organic solvent selected from the group consisting of bisethoxydiglycol succinate and benzyldiglycol,
Water-based inkjet ink.
<5> The water-based inkjet ink according to any one of <1> to <4>, wherein the water content is 50% by mass or less based on the total amount of the water-based inkjet ink.
<6> The content of the water-soluble organic solvent is 40 with respect to the total amount of the water-based inkjet ink.
The water-based inkjet ink according to any one of <1> to <5>, which is at least% by mass.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

<Preparation of ink>
Tables 1 and 2 show ink formulations of Examples and Comparative Examples. The raw materials shown in Table 1 and Table 2
Mix in the proportions shown in the table, stir for 10 minutes at a rotational speed of 60 rpm using a three-one motor, and after stirring, filter through a membrane filter with a pore size of 0.8 μm to obtain the inks of the examples and comparative examples. It was.
The pigment A and the pigment B shown in Table 1 and Table 2 are dispersion liquids containing water, and the dye B is a liquid containing water. In Tables 1 and 2, the amounts of “pigment” and “dye” both indicate the amount of pigment or dye solids. In Tables 1 and 2, the amount of “water” is the water content of the entire ink including the water of pigment A, pigment B, and dye B.

  The materials used are shown below.

1. Pigment / Pigment A: Self-dispersing carbon black dispersion “Cab-O-JET300” manufactured by Cabot Corporation
(Trade name) "is treated with an ion exchange resin (trade name: Amberlite, manufactured by Sigma-Aldrich) on which tetrabutylammonium ions are adsorbed, and sodium ions contained in the dispersion as counter ions are converted into tetra ions. It was converted to butylammonium ion to give pigment A. The pigment solid content is 15% by mass.
Pigment B: Self-dispersing carbon black dispersion “Cab-O-JET400” manufactured by Cabot Corporation
(Trade name) "is treated with an ion exchange resin (trade name: Amberlite, manufactured by Sigma-Aldrich) on which tetrabutylammonium ions are adsorbed, and sodium ions contained in the dispersion as counter ions are converted into tetra ions. Pigment B was obtained by converting into butylammonium ions. The pigment solid content is 15% by mass.

2. Dye / Dye A: “Food Black 2” manufactured by Daiwa Kasei Co., Ltd., 100% by mass of dye solid content
Dye B: “WATER BLACK 256-L” manufactured by Orient Chemical Co., Ltd., dye solid content: 14% by mass

3. Organic solvent / benzyl diglycol: Nippon Emulsifier Co., Ltd., boiling point 302 ° C., number of hydroxyl groups in one molecule 1
-Bisethoxydiglycol succinate: “High Aquastar DCS” manufactured by Higher Alcohol Industry Co., Ltd., boiling point 330 ° C., number of hydroxyl groups in one molecule 0
Triethylene glycol monomethyl ether: manufactured by Kanto Chemical Co., Inc., boiling point 245 ° C., 1
Number of hydroxyl groups in molecule 1
Polyethylene glycol dimethyl ether: manufactured by Toho Chemical Industry Co., Ltd., boiling point 264-2
94 ° C, number of hydroxyl groups in one molecule 0
Diethylene glycol: Wako Pure Chemical Industries, Ltd., boiling point 244 ° C., number of hydroxyl groups in one molecule 2
Triethylene glycol: manufactured by Kanto Chemical Co., Inc., boiling point 285 ° C., number of hydroxyl groups in one molecule 2
Tetraethylene glycol: manufactured by Kanto Chemical Co., Inc., boiling point 327 ° C., number of hydroxyl groups in one molecule 2
4). Water / ion exchange water

<Viscosity of water-soluble organic solvent and its aqueous solution>
The viscosity at 23 ° C. of the water-soluble organic solvent used for preparation of each ink was measured. Further, each water-soluble organic solvent and water were mixed to prepare aqueous solutions having a water-soluble organic solvent concentration of 90% by mass and 80% by mass, respectively, and the viscosity at 23 ° C. was measured. For the measurement of viscosity, a rheometer “AR-G2” (cone angle 2 °, diameter 40 mm) manufactured by TA Instruments was used.
The results are shown in Tables 1 and 2. In the table, “100% by mass” represents each water-soluble organic solvent, “90% by mass”
And “80 mass%” represent an aqueous solution containing 90 mass% and 80 mass% of each water-soluble organic solvent, respectively.

<Evaluation>
Each ink was evaluated as follows. The results are shown in Tables 1 and 2.
1. Ink Viscosity The viscosity of each ink at 23 ° C. is measured with a rheometer “AR-” manufactured by TA Instruments.
It was measured using “G2” (cone angle 2 °, diameter 40 mm).

2. VOC
Shimadzu Corporation for water-soluble organic solvents (benzyl diglycol, bisethoxydiglycol succinate, triethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, diethylene glycol, triethylene glycol and tetraethylene glycol) used in the production of each ink Analysis by a gas chromatograph was performed by “TD-20” manufactured by the manufacturer, and it was examined whether or not a peak was detected between n-hexane and n-hexadecane, which was an index of VOC. As a result, among these organic solvents, a peak was detected between n-hexane and n-hexadecane in diethylene glycol, triethylene glycol monomethyl ether and polyethylene glycol dimethyl ether, but in other water-soluble organic solvents, n-hexane was used. No peak was detected between n and hexadecane.
In Tables 1 and 2, A is used when an organic solvent in which a peak is detected between n-hexane and n-hexadecane is used, and an organic solvent in which a peak is detected between n-hexane and n-hexadecane is used. The case where it is defined as C.

3. Deformation of paper As a recording medium, plain paper cut to 50 mm x 100 mm ("Riso Kagaku Kogyo Co., Ltd."
Using an ideal paper thin mouth ”), a wire bar P0.08H5S (manufactured by OSG Products System Co., Ltd.) is set on a printing tester K202 control coater (manufactured by Matsuo Sangyo Co., Ltd.), and each ink is used at a speed of 10. Each was coated on a recording medium. The ink-coated surface was placed on a horizontal surface, and the amount of deformation of the paper 10 seconds after ink coating was measured.
The deformation amount of the sheet is obtained by measuring the maximum height from the horizontal plane of the portion of the sheet that is left on the horizontal plane with the ink coating surface facing upward and the sheet is deformed and lifted. Based on the absolute value of the amount of deformation of the paper, both the negative curl that deforms into a convex shape so that the ink coating surface becomes convex and the plus curl that deforms into a concave shape so that the ink coating surface becomes concave. The deformation was evaluated according to the following evaluation criteria.
A: Absolute value of paper deformation amount is less than 10 mm B: Absolute value of paper deformation amount is 10 mm or more and less than 15 mm C: Absolute value of paper deformation amount is 15 mm or more

4). Clear File Deformation Using plain paper (Ideal Paper Co., Ltd. “Ideal Paper Thin”) as the recording medium and wire bar P0.08H5S (manufactured by OSG Products System Co., Ltd.), ink is applied to the entire recording medium. As a result, a printed matter was obtained. The obtained printed matter was sandwiched between clear files made of polypropylene and left in a room temperature environment for one week. The deformation of the clear file after being left for one week was evaluated visually. A case where no deformation was observed was designated as A, and a case where deformation was observed was designated as C.

In any of Examples 1 to 10, the absolute value of the deformation amount of the paper was less than 10 mm.
Moreover, the water-soluble organic solvent used in Examples 1 to 10 did not detect a peak between n-hexane and n-hexadecane, which was an index of VOC.

Claims (6)

Including coloring material and water,
Viscosity at 23 ° C. of a water-soluble organic solvent having a boiling point of 300 ° C. or higher and a viscosity at 23 ° C. of 20 mPa · s or less, of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent. Further includes a water-soluble organic solvent having a viscosity of 20 mPa · s or less,
Water-based inkjet ink. The viscosity of the water-soluble organic solvent at 23 ° C. is 10 mPa · s or more, and the viscosity of the aqueous solution of 80% by mass or more and less than 100% by mass of the water-soluble organic solvent is 10 mPa · s.
The aqueous inkjet ink according to claim 1, which is as described above. The aqueous inkjet ink according to claim 1 or 2, wherein the number of hydroxyl groups in one molecule of the water-soluble organic solvent is 0 or 1. Including coloring material and water,
Further comprising at least one water-soluble organic solvent selected from the group consisting of bisethoxydiglycol succinate and benzyldiglycol,
Water-based inkjet ink. The water content is 50% by mass or less based on the total amount of the water-based inkjet ink.
The water-based inkjet ink of any one of Claims 1-4. The content of the water-soluble organic solvent is 40% by mass with respect to the total amount of the water-based inkjet ink.
The aqueous inkjet ink according to any one of claims 1 to 5, which is as described above.