JP2013188958A - Inkjet recording method and inkset for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet ink recording method for preventing color unevenness or void as well as feathering and color bleeding to form a clear image without any influence of a recording medium, and to provide an inkset for inkjet recording available in the recording method.SOLUTION: In an inkjet recording method, a receiving solution adheres on a printing surface of a recording medium, and an inkjet ink adheres to a receiving solution adhesion part, for printing. The receiving solution contains at least a divalent metallic salt. The inkjet ink contains at least pigment, resin, surfactant and an aqueous solvent. In the inkjet recording method, each of the receiving solution and inkjet ink has a surface tension of 32mN/m or less, and a difference between the surface tensions of the receiving solution and inkjet ink is 5mN/m or less.

Description

  The present invention relates to an ink jet recording method and an ink set for ink jet recording.

In the printing field, ink-jet printing methods have been developed and widely used.
When printing using an ink jet printer, the ink droplets ejected from the print head land on the printing paper, and then penetrate and fix to form dots, and an image is formed by collecting a large number of these dots. This dot formation process is important for forming a clear image.

As the recording medium, various materials such as polyester resin and vinyl chloride resin are used in addition to non-coated paper, coated paper, and cloth.
Non-coated paper is a hydrophilic substance in which a large number of hydroxyl groups of cellulose are present, and has a property that it is easily compatible with water. When water-based ink is used for such a hydrophilic recording medium, since the ink easily penetrates into the recording medium, bleeding called feathering is likely to occur along the fibers of the recording medium, and the coloring material is recorded on the recording medium. Since the color material density on the surface of the recording medium is low, a clear image cannot be obtained, and the blurring is further increased, there is a problem in that the color material is seen through.

  The coated paper is coated with a solution (coating solution) in which pigment and binder mainly composed of kaolin or calcium carbonate having a particle system of about 0.1 to 0.3 μm are dispersed in water. In other words, the coating layer is formed on the surface and smoothed, and a binder such as synthetic latex used for fixing the pigment fills the gaps between the pigment particles to make the surface hydrophobic. Examples of the coated paper include coated paper and art paper, and are used for printed materials that require high reproducibility such as calendars, posters, and magazine color pages. In recent years, printing lots are becoming more and more small, and as an alternative to conventional offset printing, inkjet printing, which is on-demand printing that is easy to handle high-speed printing, has attracted attention. Printing on inkjet paper using inkjet ink is expected.

When a recording medium having a hydrophobic surface, such as coated paper, is used as the recording medium, water-based ink hardly penetrates into the recording medium, and feathering that occurs in a hydrophilic recording medium such as the above-mentioned non-coated paper Hard to occur.
On the other hand, the water-based ink landed on the hydrophobic recording medium by the ink jet method has a problem that the dots are not sufficiently spread and the dot diameter is small. When the dot diameter is small, the coloring material cannot be uniformly applied to the surface of the recording medium, and thus printing unevenness may occur or an excessive gap may be formed between dots, resulting in white spots. In addition, since the water-based ink droplets remain on the surface of the recording medium, the coloring material is difficult to be fixed, uneven color mixing occurs in the boundary area of different colors, and bleeding called color bleeding is likely to occur. There was a problem.

  As described above, the generation mechanism of the problem of feathering and back-through in a hydrophilic recording medium such as non-coated paper and the problem of color bleeding in a recording medium having a hydrophobic surface such as coated paper are There is a need for an ink jet recording method that is completely different and that does not cause bleeding problems regardless of the recording medium.

Up to now, dyes have often been used as coloring materials in water-based inkjet inks. However, since the dye is dissolved in the ink, the non-coated paper, which is called high-quality paper or plain paper, has high absorbency and spreads as the water and solvent are absorbed by the paper fiber. It was difficult to obtain a clear printed matter.
Therefore, recording paper called special paper has been proposed in which a layer containing a component that absorbs and fixes ink is applied in advance to the surface of the recording medium (for example, Patent Documents 1, 2, 3, 4, 5). ). In addition, other techniques such as a technique for insolubilizing an anionic dye dissolved in an ink with a cationic substance such as an amine or a metal ion (for example, Patent Documents 6, 7, 8, and 9), Techniques (for example, Patent Documents 10, 11, and 12) for fixing dyes or pigments by aggregating resin components contained therein with polyallylamine derivatives, cationic oligomers, or metal ions have been proposed. These techniques were for uncoated paper with high absorbency, called plain paper or fine paper.

Ink-jet ink (for example, Patent Documents 13 and 14) using a technique for improving the fixing property by using calcium carbonate contained in a paper material has also been proposed. Color bleeding that occurs when printing on paper and feathering that occurs when printing on uncoated paper such as high-quality paper and medium-quality paper cannot be sufficiently suppressed, and a clearer image is desired to be printed. It was rare.

JP-A-57-069054 JP-A-1-63185 Japanese Patent Laid-Open No. 6-143797 JP 2000-168228 A JP 2009-178912 A JP 63-299970 A JP-A-5-202328 JP-A-8-080664 JP 2001-162920 A Japanese Patent Laid-Open No. 08-193175 Japanese Patent Laid-Open No. 08-197840 Japanese Patent Laid-Open No. 11-034478 Special table 2009-513802 Special table 2009-515007

  The present invention has been made in view of the above circumstances, and is an ink jet that is free from color unevenness and white spots without being affected by a recording medium, can suppress feathering and color bleeding, and can provide a clear image. It is an object of the present invention to provide an ink recording method, and an ink set for ink jet recording that can suppress blur due to feathering or color bleeding without color unevenness or white spots, and can obtain a clear image.

An ink jet recording method according to the present invention is an ink jet recording method in which a receiving solution is attached to a printing surface of a recording medium, and ink jet ink is attached to the receiving solution attaching portion for printing.
The receiving solution is a receiving solution containing a divalent or higher metal salt,
The inkjet ink is an inkjet ink containing at least a pigment, a resin, a surfactant and an aqueous solvent,
The receiving solution and the inkjet ink have a surface tension of 32 mN / m or less, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less.

The ink set for ink jet recording according to the present invention also includes a receiving solution and an ink jet used for an ink jet recording method in which a receiving solution is attached to a printing surface of a recording medium and ink is attached to the receiving solution attaching portion by an ink jet method. An ink set combining inks,
The receiving solution is a receiving solution containing a divalent or higher metal salt,
The inkjet ink is an inkjet ink containing at least a pigment, a resin, a surfactant and an aqueous solvent,
The receiving solution and the inkjet ink have a surface tension of 32 mN / m or less, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less.

  In the inkjet recording method and the inkjet recording ink set of the present invention, the divalent or higher valent metal salt is selected from the group consisting of calcium salts, magnesium salts, nickel salts, aluminum salts, boron salts, and zinc salts. A metal salt of a seed or more is preferable from the viewpoint of suppressing feathering and color bleeding without causing color unevenness or white spots.

  In the ink jet recording method of the present invention, the method for adhering the receiving solution to the recording medium is preferably a spray method, a coater method, an ink jet method, a gravure method or a flexo method.

  In the ink jet recording method and the ink set for ink jet recording of the present invention, it is preferable that the pigment is a self-dispersing pigment from the viewpoint of preventing feathering and color bleeding without causing color unevenness and white spots.

  In the ink jet recording method and the ink set for ink jet recording of the present invention, the pigment is preferably a self-dispersing pigment from the viewpoint of suppressing feathering and color bleeding without causing color unevenness and white spots, More preferably, the self-dispersing pigment is a pigment in which a phosphorus-containing group having at least one P—O or P═O bond is bonded to the surface.

  Further, in the ink jet recording method and the ink set for ink jet recording of the present invention, the pigment is dispersed by a dispersant from the viewpoint of suppressing feathering and color bleeding without causing color unevenness and white spots. Preferably, the dispersant includes a polymer dispersant.

According to the present invention, there is no color unevenness or white spot without being affected by a recording medium, feathering and color bleeding can be suppressed, and a clear image can be obtained. It is possible to provide an ink set for ink-jet recording that does not have white spots, can suppress bleeding due to feathering or color bleeding, and can obtain a clear image.
In particular, according to the present invention, even when coated paper is used as the recording medium, a clear image can be obtained with no color unevenness or white spots and with suppressed color bleeding.

6 is an enlarged photograph of a printed matter printed using the inkjet ink set for inkjet recording of Example 6. FIG. 6 is an enlarged photograph of a printed matter printed using the inkjet ink set for inkjet recording of Comparative Example 4. 20 is an enlarged photograph of a printed matter printed using the inkjet ink set for inkjet recording of Comparative Example 19.

Hereinafter, the ink jet recording method according to the present invention and the ink set for ink jet recording according to the present invention will be described in detail.
In the present invention, (meth) acrylic acid represents methacrylic acid and / or acrylic acid.

[Inkjet recording method]
An ink jet recording method according to the present invention is an ink jet recording method in which a receiving solution is attached to a printing surface of a recording medium, and ink jet ink is attached to the receiving solution attaching portion for printing.
The receiving solution is a receiving solution containing a divalent or higher metal salt,
The inkjet ink is an inkjet ink containing at least a pigment, a resin, a surfactant and an aqueous solvent,
The receiving solution and the inkjet ink have a surface tension of 32 mN / m or less, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less.
According to the present invention, it is possible to obtain a clear image that is not affected by the recording medium, has no color unevenness or white spots, and is suppressed in feathering and color bleeding.
In particular, according to the present invention, even when coated paper having a hydrophobic surface is used as a recording medium, a clear image can be obtained with no color unevenness or white spots and with suppressed color bleeding. .

The action of exerting the above-described effects by the ink jet recording method of the present invention is estimated as follows although not yet understood.
When a hydrophilic recording medium such as non-coated paper is used, since the water-based ink easily penetrates into the recording medium, the coloring material does not stay on the surface of the recording medium, and the coloring material concentration on the surface of the recording medium is lowered. However, since it tends to spread along the fiber of the paper, there is a problem that feathering is likely to occur and a clear image cannot be obtained. In the present invention, by applying a receiving solution containing a divalent or higher metal salt to the printing surface of the recording medium in advance, the pigment in the water-based ink adhered by the ink jet method interacts with the divalent or higher metal salt. It is presumed that the dispersion state changes due to the action and the toner is fixed on the surface of the recording medium. Thereby, it is estimated that an image in which feathering is suppressed can be obtained.

When the above method is applied to a hydrophobic recording medium, the ink does not easily penetrate and feathering does not easily occur. However, the dot diameter is small and the printing surface is not sufficiently filled with ink, so printing unevenness and white There is a problem that omission is likely to occur. In the present invention, by setting the surface tension of the receiving solution and the inkjet ink to 32 mN / m or less, the wettability of the receiving solution with respect to the substrate surface is improved, and the receiving solution is sufficiently applied to the substrate surface. By spreading quickly and improving the wettability of the inkjet ink to increase the dot diameter of the inkjet ink, printing unevenness and white spots are eliminated, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less By using the ink set, it is presumed that the receiving solution and the ink jet ink are immediately mixed to rapidly change the dispersion state of the pigment, and the ink is fixed without causing color bleeding.
As described above, according to the ink jet recording method of the present invention, it is estimated that, regardless of the type of recording medium, feathering and color bleeding can be suppressed, and a clear image free from printing unevenness and white spots can be obtained. The

<Recording medium>
In the inkjet recording method of the present invention, the recording medium is not particularly limited, and can be suitably used regardless of whether it is hydrophilic or hydrophobic. Examples of the recording medium include non-coated paper such as modified paper, medium-quality paper, and high-quality paper; coated paper such as coated paper, art paper, and cast paper; and fabrics such as cotton, synthetic fabric, silk, hemp, and non-woven fabric A plastic film such as a polyester-based resin, a polypropylene-based resin, a vinyl chloride resin, or a polyimide resin; metal, metal-deposited paper, glass, synthetic rubber, natural rubber, leather, and the like. The coated paper includes not only a paper coated with an absorbent base such as pulp paper but also a paper provided with a coating layer on the printing surface of a non-absorbent base such as a plastic film.
In particular, the inkjet recording method of the present invention can be suitably used for coated paper having a hydrophobic surface and low ink permeability, and there is no color unevenness even when the recording medium is coated paper. A clear image in which color bleeding is suppressed can be obtained.

<Accepted solution>
In the present invention, the “accepting solution” refers to a pretreatment applied to a printing surface before the inkjet ink is applied to the printing surface of the recording medium in order to improve printing quality when printing is performed by the inkjet recording method. Ink.
The receiving solution used in the ink jet recording method of the present invention contains at least a divalent or higher metal salt, and may further contain other components as necessary. By containing a metal salt having a valence of 2 or more, it can interact with the pigment, suppress feathering and color bleeding, and obtain a clear image without printing unevenness or white spots.
The receiving solution of the present invention is not particularly limited as long as it contains a divalent or higher valent metal salt, but usually contains a solvent. The receiving solution may further contain other components as necessary. Hereinafter, each component contained in the receiving solution of the present invention will be described.

(1) Divalent or higher metal salt In the present invention, the bivalent or higher metal salt improves the fixability of the ink on the recording medium.
The divalent or higher metal salt is not particularly limited as long as it is a divalent or higher metal salt composed of a polyvalent metal ion and an anion bonded to the polyvalent metal ion. Organic acid metal salts may also be used. Among these, calcium salt, magnesium salt, nickel salt, aluminum salt, boron salt, and the like that interact with pigments, suppress feathering and color bleeding, and can obtain clear images without printing unevenness and white spots. It is preferably at least one selected from the group consisting of zinc salts. Bivalent or higher metal salts may be used singly or in combination of two or more.

  Specific examples of the inorganic metal salt include, but are not limited to, calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium nitrate, magnesium nitrate, and magnesium sulfate. Among these inorganic metal salts, generally, chlorides or nitrates having high solubility in water are more preferable. Further, among these inorganic metal salts, calcium chloride or magnesium chloride is more preferable, and calcium chloride is particularly preferable from the viewpoint that the solubility in water and the interaction with the components in the inkjet ink described later are efficient and occur quickly.

  Specific examples of organic acid metal salts include calcium salts, magnesium salts, nickel salts, zinc salts, and the like of organic acids such as pantothenic acid, propionic acid, ascorbic acid, acetic acid, and lactic acid. It is not limited. Among these organic acid metal salts, calcium salts of pantothenic acid, propionic acid, and acetic acid are more preferable from the viewpoint of solubility in water and interaction with components in the inkjet ink described later.

  The solubility of the divalent or higher metal salt in water is preferably 0.1 mol / liter or higher. When the solubility of the divalent or higher metal salt in water is 0.1 mol / liter or higher, the fixability is further improved by the interaction between the metal ions and the pigment surface described later.

  The content of the divalent or higher metal salt in the receiving solution is not particularly limited. Among them, from the viewpoint of fixability, the concentration of the divalent or higher metal salt is preferably 0.005 to 2.0 mol / liter, more preferably 0.01 to 1.0 mol / liter, Even more preferably, it is 0.1 to 0.5 mol / liter. If it is more than the said lower limit, a feathering and color bleeding can fully be suppressed. On the other hand, when the above upper limit is exceeded, the metal salt may be precipitated during storage of the receiving solution.

(2) Solvent The receiving solution usually contains a solvent. The type of solvent in the receiving solution is not particularly limited. Among these, an aqueous solvent is preferable. In the present invention, “aqueous solvent” refers to water, water-soluble organic solvents, and mixtures thereof. Further, a solvent capable of forming a state in which the divalent or higher valent metal salt is on the surface of the recording medium when the receiving solution is attached to the recording medium is preferable.
Examples of the water-soluble organic solvent include 1 carbon atom such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol. Alkyl alcohols of ˜5; monohydric alcohols such as 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-n-butanol; 1-dimethylformamide, dimethylacetamide, 3-methoxypropanamide, 3-butoxypropanamide, N, N-dimethyl-3-methoxypropanamide, N, N-dibutyl-3-methoxypropanamide, N, N-dibutyl- 3-Butoxypropanami Amides such as N, N-dimethyl-3-butoxypropanamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Oxyethylene or oxypropylene such as polyethylene glycol and polypropylene glycol Copolymer; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,2-butanediol, 1,3-butane Diol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyldiol Diols such as lu-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol; glycerin, trimethylolethane, trimethylolpropane, 1,2,6 -Triols such as hexanetriol: tetrahydric alcohols such as mesoerythritol and pentaerythritol; ethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, diethylene glycol monomethyl (or ethyl) , Isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, triethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl) ether, propylene glycol monomethyl Monoalkyl ethers such as (or ethyl, isopropyl, n-butyl, isobutyl) ether, dipropylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl) ether; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, Dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether and dipropylene glycol diethyl ether ; Alkanolamines such as ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine; N-methyl Examples thereof include nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; cyclic compounds such as γ-butyrolactone and sulfolane. These water and water-soluble organic solvents can be used alone or as a mixture.
When the receiving solution is attached to the recording medium by the inkjet method, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, propylene glycol, dipropylene glycol, tripropylene glycol, glycerin, triglyceride A high boiling organic solvent such as ethanolamine can be used. When a paper substrate is used as the recording medium, it is preferable to use water and a water-soluble organic solvent in combination from the viewpoint of suppressing curling and cockling (waving) of the substrate.

(3) Other components In this invention, the receiving solution may contain the other component further as needed. As other components, for example, in addition to a surfactant for adjusting the surface tension, a resin described later can be used. As the surfactant, the same surfactant as that in the inkjet ink described later can be used.

  Examples of the resin contained in the receiving solution include a resin having a hydrophilic group and a cationic or nonionic resin emulsion. When such a resin is used, for example, it suppresses the formation of lumps during the storage of the receiving liquid of a divalent or higher valent metal salt such as calcium chloride, and it does not occur when applied to a recording medium. Adhesion of a metal salt having low adhesion to the absorber can be improved.

The surface tension of the receiving solution is 32 mN / m or less from the viewpoint of sufficient wettability of the receiving solution with respect to the printing surface of the recording medium. Especially, it is preferable that it is 30 mN / m or less, and it is more preferable that it is 28 mN / m or less from the point which can suppress a color nonuniformity and a white spot and can obtain a clear image. On the other hand, when the receiving solution is adhered to the substrate surface by the ink jet method, the surface tension of the receiving solution is preferably 20 mN / m or more from the viewpoint of improving the ejection stability of the ink from the ejection head.
The surface tension of the receiving solution can be adjusted by appropriately selecting the solvent and the surfactant.
The surface tension in the present invention is a value measured by the Wilhelmy method (Kyowa Interface Science model: CBVP-Z) at a measurement temperature of 25 ° C.

<Inkjet ink>
The ink-jet ink used in the ink-jet recording method of the present invention contains at least a pigment, a resin, a surfactant, and an aqueous solvent, and may contain other components as necessary.
Hereinafter, each component contained in the inkjet ink of the present invention will be described.

(1) Pigment In the present invention, the pigment is not particularly limited, and pigments conventionally used in inkjet inks, such as barium sulfate, iron oxide, zinc oxide, barium carbonate, barium sulfate, silica, clay, talc, titanium oxide, Examples thereof include inorganic pigments such as calcium carbonate, synthetic mica, and alumina, or organic pigments. These may be used alone or in combination of two or more. Specific organic pigments include, for example, insoluble azo pigments, soluble azo pigments, derivatives from dyes, phthalocyanine organic pigments, quinacridone organic pigments, perylene organic pigments, dioxazine organic pigments, nickel azo pigments, isoindolinones. Organic pigments, pyranthrone organic pigments, thioindigo organic pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments, isoindoline organic pigments, quinacridone solid solution pigments, perylene solid solution pigments, etc. Examples of solid solution pigments and other pigments include carbon black.
When organic pigments are exemplified by color index (CI) numbers, C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 117, 120, 125, 128, 129, 130, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, 213, 214
C. I. Pigment Red 5, 7, 9, 12, 48, 49, 52, 53, 57, 97, 112, 122, 123, 149, 168, 177, 180, 184, 192, 202, 206, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254,
C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71,
C. I. Pigment violet 19, 23, 29, 30, 37, 40, 50,
C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 16, 22, 60, 64,
C. I. Pigment Green 7, 36, 58
C. I. Pigment brown 23, 25, 26, and the like.

  Specific examples of the inorganic pigment include titanium oxide, barium sulfate, calcium carbonate, zinc white, lead sulfate, yellow lead, zinc yellow, red bean (red iron (III) oxide), cadmium red, ultramarine blue, bitumen, and oxidation. Examples include chrome green, cobalt green, amber, titanium black, synthetic iron black, and inorganic solid solution pigments.

  In the present invention, a self-dispersing pigment can be used as the pigment from the viewpoint of fixing to the surface of the recording medium. The self-dispersing pigment refers to a pigment in which a hydrophilic group is directly modified on the pigment surface. As the hydrophilic group used in the self-dispersing pigment, a carbonyl group, a carboxyl group, a hydroxyl group, a sulfonyl group, a sulfone are used because they have a strong interaction with the divalent metal salt of the receiving solution and are excellent in pigment fixing property. Acid groups, phosphorus-containing groups and the like are preferable. Among them, it is preferable to use a self-dispersing pigment having a phosphorus-containing group having at least one P—O or P═O bond.

Examples of the phosphorus-containing group include a phosphonic acid group, a phosphinic acid group, a phosphinic acid group, a phosphite group, a phosphate group, a diphosphate group, a triphosphate group, and a pyrophosphate group. It may be an ester or a salt. Among them, the phosphorus-containing group is preferably a phosphonic acid group, a partial ester of a phosphonic acid group, or a phosphonate, and preferably includes two or more phosphonic acid groups, a partial ester of a phosphonic acid group, or a phosphonate. . The “partial ester” means that the phosphonic acid group is a partial phosphonic acid ester group having —PO ₃ RH or a salt thereof. Here, R is an aryl, alkaryl, aralkyl or alkyl group.

Examples of the phosphorus-containing group having a P—O or P═O bond include the phosphorus-containing groups described in the following (i) to (viii), but the phosphorus-containing group of the present invention is exemplified in these examples. It is not limited.
(I) When the phosphorus-containing group includes at least two phosphonic acid groups or salts thereof, one or both of these phosphonic acid groups may be a partial phosphonic acid ester group. One of these phosphonic acid groups may be a phosphonic acid ester having the formula —PO ₃ R ₂ , and the other may be a partial phosphonic acid ester group, a phosphonic acid group, or a salt thereof. Among these, at least one of these phosphonic acid groups is preferably phosphonic acid, a partial ester thereof, or a salt thereof. The “salt thereof” means that the phosphonic acid group has a cation counter ion and is partially or completely ionized.
Where the functional group comprises at least two phosphonic acid groups, one or both of these phosphonic acid groups may be in either a partially ionized form or a fully ionized form. Among them, the functional group comprises at least two phosphonic acid groups, either or both of these phosphonic acid has the formula ^{_{-PO 3 H 2, -PO 3 H}} - M + ( monobasic salt), or _-PO ^{3 2-M} It is preferred to have ²⁺ (dibasic salt). Here, M ⁺ is a cation such as Na ⁺ , K ⁺ , Li ⁺ , or NR ₄ ⁺ . R may be the same or different and represents hydrogen or an organic group (such as a substituted or unsubstituted aryl and / or alkyl group).

(Ii) When the phosphorus-containing group includes at least two phosphonic acid groups, examples of the functional group include a group including at least one geminal bisphosphonic acid group, a partial ester thereof, or a salt thereof. That is, the functional group includes a group including at least two phosphonic acid groups directly bonded to the same carbon atom, a partial ester thereof or a salt thereof. Such groups are sometimes referred to as 1,1-diphosphonic acid groups, partial esters thereof or salts thereof.
Such phosphorus-containing groups, e.g., groups having the formula _{-CQ (PO 3 H 2) 2} , include groups containing a partial ester or a salt thereof. Q is bonded to the geminal position, and H, R, OR, SR or NR ₂ (wherein R may be the same or different, and H, C1 to C18 (C1 to C18 are carbon atoms) The number is 1 to 18. The same shall apply hereinafter.) Saturated or unsaturated branched or unbranched alkyl group, C1 to C18 saturated or unsaturated branched or non- A branched acyl group, an aralkyl group, an alkaryl group, or an aryl group. Q is, for example, H, R, OR, SR or NR ₂ (wherein R may be the same or different and is H, a C1-C6 alkyl group or an aryl group), and H , OH or NH ₂ is preferred. Furthermore, examples of the pre-functional group include a group having the formula — (CH ₂ ) _n —CQ (PO ₃ H ₂ ) ₂ , a group including a partial ester thereof, or a salt thereof. Here, Q is as described above.
n is 0 to 9, preferably 0 to 3, and more preferably 0 or 1.

(Iii) Examples of the functional group include a group having the formula —X— (CH ₂ ) _n —CQ (PO ₃ H ₂ ) ₂ , a partial ester thereof, or a group containing a salt thereof. Here, Q and n are as described above. X is an arylene group, a heteroarylene group. An alkylene group, a vinylidene group, an alkalilene group, an aralkylene group, a cyclic group or a heterocyclic group; X is preferably an arylene group such as a phenylene group, a naphthalene group or a biphenylene group (which may be further substituted with any group such as one or more alkyl groups or aryl groups). When X is an alkylene group, X may be a substituted or unsubstituted alkylene group (branched or unbranched, and one or more groups (such as aromatic groups)). And may be substituted.). Moreover, as X, C1-C12 groups, such as a methylene group, ethylene group, a propylene group, or a butylene group, are illustrated. X is preferably bonded directly to the pigment. This means that there are no other atoms or groups between the pigment and X.

X may be further substituted with one or more organic groups. Examples of such an organic group include R ′, OR ′, COR ′, COOR ′, OCOR ′, carboxylate, halogen, CN, NR ′ ₂ , SO ₃ H, sulfonate, sulfate, NR ′ (COR ′ ), CONR ′ ₂ , imide, NO ₂ , phosphate, phosphonate, N═NR ′, SOR ′, NR′SO ₂ R ′ and SO ₂ NR ′ ₂ . Where R ′ may be the same or different and is independently hydrogen, branched or unbranched C1-C20 substituted or unsubstituted saturated or unsaturated hydrocarbon (eg, alkyl, Alkenyl, alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkaryl or substituted or unsubstituted aralkyl).

(Iv) Examples of the functional group include a group having the formula —X—Sp— (CH ₂ ) n —CQ (PO ₃ H ₂ ) ₂ , a partial ester thereof, or a group containing a salt thereof. Here, X, Q, and n are as described above. Sp is a spacer group (a connecting body between two groups). Sp includes a bond or a linking group. The linking group, for _{example, -CO 2 -, - O 2} C -, - CO -, - OSO 2 -, - SO 3 -, - SO 2 -, - SO 2 C 2 H 4 O -, - SO 2 _{C 2 H 4 S -, -} SO 2 C 2 H 4 NR "-, - O -, - S -, - NR" -, - NR "CO -, - CONR" -, NR "CO 2 -, - O _{2 CNR "-, - NR"} CONR ", - N (COR") CO -, - CON (COR ") -, - NR" COCH (CH 2 CO 2 R ") - and its cyclic imide, -NR" _{COCH 2 CH (CO 2 R "} ) - and its cyclic _{imide, -CH (CH 2 CO 2 R} ") CONR "- and its cyclic _{imide, -CH (CO 2 R")} CH 2 CONR "- and Its cyclic imide (including phthalimide and maleimide), sulfonamide group (-S ₂ NR "- and -NR" SO ₂ -. Containing group), an arylene group, and alkylene group. R ″ may be the same or different and represents hydrogen or an organic group (such as a substituted or unsubstituted aryl or alkyl group). As shown in the structure of the above formula, at least two A group containing a phosphonic acid group or a salt thereof is bonded to X through a spacer group Sp. Sp is —CO ₂ —, —O ₂ C—, —O—, —NR ″ —, —NR ″ CO— or _{-CONR "-, - SO 2 NR} " -, - SO 2 CH 2 CH 2 NR "-, - SO 2 CH 2 CH 2 O- or _-SO 2 _CH 2 _CH 2 S- (wherein, R" is H Or a C1-C6 alkyl group).

(V) When the functional group includes at least two phosphonic acid groups, the functional group includes at least one group having the formula —N — [(CH ₂ ) _m (PO ₃ H ₂ )] ₂ , a portion thereof Mention may be made of groups containing esters or salts thereof. Here, m may be the same or different and is 1 to 9, preferably 1 to 3, and more preferably 1 or 2. Further, when the functional group includes at least two phosphonic acid groups, the functional group includes at least one group having the formula — (CH ₂ ) _n —N — [(CH ₂ ) _m (PO ₃ H ₂ )] _2. And a group containing a partial ester or a salt thereof. Here, n is 0-9 (for example, 1-9), and it is preferable that it is 0-3 (for example, 1-3). m is as described above. When the functional group includes at least two phosphonic acid groups, the functional group includes at least one formula —X— (CH ₂ ) _n —N — [(CH ₂ ) _m (PO ₃ H ₂ )] ₂ . And a group containing a partial group thereof, a partial ester thereof or a salt thereof. Here, X, m, and n are as described above. X is preferably an arylene group. Further, when the functional group includes at least two phosphonic acid groups, the functional group includes at least one formula —X—Sp— (CH ₂ ) _n —N — [(CH ₂ ) _m (PO ₃ H ₂ )]. _And a group containing ₂ or a group containing a partial ester or a salt thereof. Here, X, m, n, and Sp are as described above.

(Vi) when the functional group includes at least two phosphonic acid groups, the functional group includes at least one group having the formula —CR═C (PO ₃ H ₂ ) ₂ , a group including a partial ester thereof or a salt thereof. Can be mentioned. R is H, a saturated or unsaturated branched or unbranched alkyl group of C1 to C18, a saturated or unsaturated branched or unbranched acyl group of C1 to C18, an aralkyl group, an alkaryl group. Group or aryl group. R is preferably H, a C1-C6 alkyl group or an aryl group.
(Vii) Further, when the functional group contains at least two phosphonic acid groups, the functional group may be a group containing more than two phosphonic acid groups, partial esters thereof or salts thereof. Examples of such a functional group include a group having the formula —X— [CQ (PO ₃ H ₂ ) ₂ ] _p , a group containing a partial ester thereof, or a salt thereof. X and Q are as described above. X is an arylene group or heteroarylene group. An alkylene group, an alkali-ylene group or an aralkylene group is preferred. p is 1 to 4, preferably 2.

(Viii) When the functional group includes at least two phosphonic acid groups, the functional group may be a group including at least one vicinal bisphosphonic acid group, a partial ester thereof, or a salt thereof. In this case, it means that these groups are adjacent to each other. Such functional groups include, for example, groups containing two phosphonic acid groups bonded to adjacent carbon atoms, partial esters thereof or salts thereof. Such groups are referred to as 1,2-diphosphonic acid groups, partial esters thereof or salts thereof. Examples of the group containing two phosphonic acid groups, a partial ester thereof or a salt thereof include an aromatic group and an alkyl group. Examples of the vicinal bisphosphonic acid group include a vicinal alkyl group or a vicinal aryl diphosphonic acid group, a partial ester thereof, or a salt thereof. Specifically, examples of the functional group include a group having the formula —C ₆ H ₃ — (PO ₃ H ₂ ) ₂ , a partial ester thereof, or a group containing a salt thereof. Here, the acids, esters or bases are ortho to one another.

The self-dispersing pigment can be obtained by introducing the hydrophilic group into the organic pigment or the inorganic pigment by a conventionally known method.
A method for introducing a phosphorus-containing group having a P—O or P═O bond into a pigment is described, for example, in US Pat. Nos. 5,554,739, 5,707,432, and 5,837. , 045 and the like.

The average dispersed particle diameter of the pigment is not particularly limited as long as the desired color development is possible. Although different depending on the type of pigment used, the median diameter (D50) is preferably in the range of 5 to 200 nm from the viewpoint of good dispersibility and dispersion stability of the pigment and obtaining sufficient coloring power. More preferably, it is 150 nm. If the median diameter is not more than the above upper limit, nozzle clogging of the ink jet head is unlikely to occur, a highly reproducible and homogeneous image can be obtained, and the resulting printed matter can be of high quality. When the median diameter is not more than the above lower limit value, the light resistance may be lowered.
In the present invention, the average dispersed particle diameter of the pigment is measured at a measurement temperature of 25 ° C. using a concentrated particle size analyzer (manufactured by Otsuka Electronics Co., Ltd., model: FPAR-1000).

  In the present invention, the pigment content may be appropriately adjusted. Although depending on the type of pigment, the content of the pigment in the entire inkjet ink is preferably 0.05 to 20% by mass, more preferably 0.1 to 10% by mass from the viewpoint of achieving both dispersibility and coloring power. .

(2) Resin The resin used for the inkjet ink suppresses the penetration of the pigment into the recording medium and promotes the fixing of the pigment to the surface of the recording medium. As the resin, a resin emulsion is preferable from the viewpoint of excellent fixability and excellent water resistance of printed matter.
In the present invention, the resin emulsion means an aqueous dispersion in which the continuous phase is water and the dispersed particles are resin fine particles. The above resin emulsion generally has a property of thickening and aggregating when water, which is a continuous phase, is reduced by evaporation or penetration, and has the effect of suppressing the penetration of pigment into the printing paper and promoting the fixing to the paper. Have.
The resin emulsion can be produced by, for example, mixing water, a monomer, an emulsifier, and a polymerization initiator to cause an emulsion polymerization reaction and neutralizing the reaction after the reaction. As the emulsifier, a normal polymer surfactant may be used, or a reactive emulsifier having an unsaturated bond may be used. The resin emulsion can also be obtained by mixing resin fine particles with water together with a surfactant without causing an emulsion polymerization reaction. For example, it can be obtained by adding (meth) acrylic acid ester or resin fine particles comprising styrene and (meth) acrylic acid ester and a surfactant to water and mixing them. In this case, the mixing ratio (weight ratio) of the resin component and the surfactant is usually preferably about 10: 1 to 5: 1, and if the amount of the surfactant used is less than the range, it is difficult to form an emulsion. On the other hand, outside the above range, the water resistance and penetrability of the ink may decrease, which is not preferable.
Specific examples of the resin component constituting the resin emulsion include, for example, (meth) acrylic resin, styrene resin, polyester resin, vinyl resin, polyethylene resin, urethane resin, silicone (silicon) resin, acrylamide resin, epoxy resin, (meta ) A resin containing an acid group such as acrylic acid or a mixed form thereof is preferable. In particular, it is preferable that the resin fine particles contain a (meth) acrylic resin. These resins are not particularly limited in the form of copolymerization, and can be, for example, block copolymers, random copolymers, and the like.
These resin components are preferably polymers having both a hydrophilic part and a hydrophobic part, and the average particle diameter is not particularly limited as long as an emulsion can be formed, but is preferably 500 nm or less, more preferably 200 nm or less, 100 nm or less is more preferable. When the particle size of the resin component constituting the resin emulsion is larger than 500 nm and the difference from the pigment particle size becomes large, the resin particles formed from the resin and emulsion particles come into contact with each other when forming dots by being ejected from the inkjet ink. As a result, the pigment particles are present in the gaps, and a sea-island structure is formed, which may impair the fixability of the pigment.

(I) Emulsifier, polymerization initiator, chain transfer agent The emulsifier and polymerization initiator used in the emulsion polymerization will be described.
As the emulsifier, for example, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant can be used. A reactive surfactant can also be used.
As polymerization initiators, potassium persulfate, ammonium persulfate, hydrogen persulfate, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, peracetic acid, cumene hydroperoxide, t-butylhydroxyperoxide, paramentanehydroxy A peroxide or the like can be used.
Examples of chain transfer agents for polymerization include t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, xanthogens dimethylxanthogen disulfide, diisobutylxanthogen disulfide, dipentene, indene, 1,4-cyclohexadiene, dihydrofuran. , Xanthene and the like can be used.

(Ii) Monomer component (ii-1) Monomer The monomer used in the emulsion polymerization is preferably an unsaturated vinyl monomer. Specific examples of unsaturated vinyl monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide monomers, halogenated monomers generally used in emulsion polymerization. Examples include monomers, olefin monomers, and diene monomers.
Specific examples thereof include acrylic esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, and n-butyl methacrylate; Vinyl esters such as vinyl acetate; Vinyl cyanides such as acrylonitrile and methacrylonitrile; Halogenated monomers such as vinylidene chloride and vinyl chloride; Styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, etc. Aromatic vinyl monomers; olefins such as ethylene, propylene and isopropylene; dienes such as butadiene and chloroprene; vinyl ether, vinyl ketone and vinyl Vinyl monomers such as pyrrolidone and the like. For the monomer having no carboxyl group, the use of an unsaturated vinyl monomer having a carboxyl group is essential, but preferred examples thereof include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, The use of methacrylic acid is preferred.

(Ii-2) Crosslinkable monomer In addition, the resin fine particles forming the resin emulsion can have a structure crosslinked by a crosslinkable monomer having two or more polymerizable double bonds. Examples of the crosslinkable monomer having two or more polymerizable double bonds include diacrylate compounds such as polyethylene glycol diacrylate, triethylene glycol diacrylate, and 1,3 monobutylene glycol diacrylate; trimethylolpropane triacrylate , Triacrylate compounds such as trimethylol ethane triacrylate, tetramethylol methane triacrylate; dimethacrylate compounds such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate; trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, etc. A trimethacrylate compound; divinylbenzene.
Furthermore, printing stability can be further improved by adding an acrylamide or a hydroxyl group-containing monomer in addition to the monomer. Specific examples of acrylamides include acrylamide and N, N-dimethylacrylamide. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxyethyl methacrylate, and these can be used as one kind or a mixture of two or more kinds.

(Iii) Neutralizing agent As the neutralizing agent to be used after completion of the emulsion polymerization reaction, an acid or a base can be used depending on the type of the salt-forming group. Examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, acetic acid, propionic acid, lactic acid, and succinic acid. Examples include organic acids such as glycolic acid, gluconic acid, and glyceric acid. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide, 2-amino-2-methyl-1-propanol and the like.
The degree of neutralization is not particularly limited. Among these, the pH of the resin emulsion is preferably 7 to 10, but the concentration of the ionic component needs to be adjusted so that the conductivity of the resin emulsion does not increase.

(Iv) Molecular weight of the resin emulsion The molecular weight of the resin emulsion is preferably 1,000 to 1,000,000. The content of the resin emulsion in the inkjet ink is not particularly limited, but the solid content of the resin emulsion is, for example, about 0.05 to 20% by mass with respect to the total amount of the inkjet ink. Can do.

(V) Conductivity of Resin Emulsion When using a pigment as a coloring material in the inkjet ink of the present invention, particularly when using the self-dispersing pigment, the conductivity of a 1% by weight aqueous solution of the resin emulsion. By being low, the reactivity of a resin emulsion and a surface treatment pigment can be made low, and the storage stability of an inkjet ink can be improved. The “resin emulsion having a solid content of 1% by mass” refers to a solution obtained by dissolving or dispersing the resin emulsion in water so that the solid content concentration is 1% by mass.
The electrical conductivity of the 1% by weight aqueous solution of the resin emulsion can be adjusted by, for example, the type of resin component, monomer type, reaction mechanism, type of emulsifier, presence or absence of addition of an emulsifier, type of neutralizing agent, and the like.
The low conductivity of a 1% by weight aqueous solution of the resin emulsion is considered to indicate that the resin emulsion itself has a small amount of ionic groups and counter ions of the ionic groups in the ink. . Moreover, it is thought that the low electrical conductivity of 1 mass% solid content aqueous solution of a resin emulsion shows that there exist few amounts in the ink of impurities, such as an ionic substance derived from manufacture of a resin emulsion. Moreover, it is thought that the low electrical conductivity of 1 mass% solid content aqueous solution of a resin emulsion shows that the polarity of a resin component is low or an acid value is low.

The electrical conductivity of a 1% by mass aqueous solution of the resin emulsion is preferably 300 μS / cm or less, more preferably 200 μS / cm or less, and even more preferably 150 μS / cm or less. If the conductivity is high, the ionic group and its counter ion or ionic impurity in the resin emulsion may affect the dispersion stability of the surface-treated pigment. Thus, since the influence on the dispersibility of the surface-treated pigment is suppressed by reducing the ions in the resin emulsion, the lower the electrical conductivity of the aqueous solution with a solid content of 1% by mass of the resin emulsion, the better. It is about 20 μS / cm. If the conductivity is too low, it is difficult to disperse the resin emulsion or to produce a resin emulsion with stable quality.
As a method for measuring the conductivity, first, the resin emulsion is diluted with ion exchange water to adjust the solid content to 1% by mass, and then a conductivity meter (Eutech Instruments, model: EC Testr 11+) is used. The method of measuring the electrical conductivity of an aqueous solution having a solid content of 1% by mass of the resin emulsion is adopted.

(3) Surfactant The surfactant in the inkjet ink is used for improving the ejection stability of the ink in the inkjet system and adjusting the surface tension of the inkjet ink. The surfactant is not particularly limited, but is an anionic surfactant, a nonionic surfactant, a silicone (silicone) surfactant, a fluorine-based interface because of excellent surface tension adjustment. An activator, an acetylene glycol surfactant and the like are preferably used. Specific examples include Emar, Latem, Perex, Neoperex, and Demol (all anionic surfactants; manufactured by Kao Corporation), Sannole, Lipolane, Lipon, Lipar (all anionic surfactants; Lion shares) Company), Neugen, Epan, Sorgen (all nonionic surfactants; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Emulgen, Amit, Emazole (all nonionic surfactants; manufactured by Kao Corporation), NAROACTY , Emalmin, Sannonic (all nonionic surfactants; manufactured by Sanyo Chemical Industries, Ltd.), Surfynol 104, 82, 465, 485, TG, 2502, Dynol 604, Dynol 607 (all are acetylene glycol surfactants Agent; manufactured by Air Products), Olfine E1004 E1010, PD004, EXP4300 (all are acetylene glycol surfactants; manufactured by Nissin Chemical Industry Co., Ltd.), MegaFac (fluorine surfactants; manufactured by DIC Corporation), Surflon (fluorine surfactants; AGC Seimi) Chemical Company), BYK302, 306, 307, 331, 333, 345, 347, 348, 349, 3455 (all are silicone (silicone) surfactants; manufactured by BYK Chemie), KP-110, 112, 323, 341 6004 (both are silicone (silicone) surfactants; manufactured by Shin-Etsu Chemical Co., Ltd.). The content of the surfactant is appropriately adjusted according to the content of the water-soluble organic solvent or other surfactant. The content of the surfactant is preferably about 0.01 to 3.0% by mass and more preferably within the range of 0.1 to 2.0% by mass with respect to the total amount of the inkjet ink.

(4) Aqueous solvent Examples of the aqueous solvent used in the inkjet ink include water and a water-soluble organic solvent. The water-soluble organic solvent can be the same as the water-soluble organic solvent exemplified in the receiving solution. Water and water-soluble organic solvents can be used alone or as a mixture.
Among them, it is preferable to use a high-boiling organic solvent such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, propylene glycol, dipropylene glycol, tripropylene glycol, glycerin, and triethanolamine. When a paper base material is used as the recording medium, it is preferable to use water and a water-soluble organic solvent together from the viewpoint of suppressing curling and cockling (waving) of the base material.

These water-soluble organic solvents can be used alone or as a mixture. Moreover, as water, it is preferable to use deionized water instead of the general water containing various ions. When the inkjet ink contains water, the content of water is not particularly limited, but can be, for example, about 20 to 80% by mass, and 30 to 50% by mass with respect to the total amount of the inkjet ink. % Is preferable.

(5) Other components In the present invention, the inkjet ink may further contain other components as necessary. Examples of other components include a dispersant, a penetrating agent, a wetting agent, an antiseptic, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, an antifoaming agent, and an oxygen scavenger.

(5-1) Dispersant In the present invention, a pigment dispersant can be used to disperse the pigment. In the present invention, the pigment dispersant is not particularly limited. For example, surfactants such as cationic, anionic, nonionic, amphoteric, silicone (silicon), and fluorine can be used. Among the surfactants, polymer surfactants (polymer dispersants) as exemplified below are preferable.

Examples of the polymer dispersant include a polyester-based, polyacryl-based, polyurethane-based, polyamine-based, and polycaptolactone-based main chain, such as amino group, carboxy group, sulfo group, and hydroxy group in the side chain. Examples thereof include a dispersant having a polar group. Examples of such polymer dispersants include (co) polymers of unsaturated carboxylic acid esters such as polyacrylic acid esters; aromatic vinyl compounds such as styrene and α-methylstyrene and unsaturated acrylates and the like. Copolymers of carboxylic acid esters; (partial) amine salts, (partial) ammonium salts and (partial) alkylamine salts of (co) polymers of unsaturated carboxylic acids such as polyacrylic acid; hydroxyl group-containing polyacrylic acid esters (Co) polymers of hydroxyl group-containing unsaturated carboxylic acid esters such as, and their knitted articles; polyurethanes; unsaturated polyamides; polysiloxanes; long-chain polyaminoamide phosphates; polyethyleneimine derivatives (poly (lower alkyleneimine) ) And free carboxyl group-containing polyesters to obtain amides and their bases); poly A lylamine derivative (obtained by reacting polyallylamine with one or more compounds selected from three compounds of polyester, polyamide or ester / amide co-condensate (polyesteramide) having a free carboxyl group) Reaction product) and the like. Among them, (co) polymers of unsaturated carboxylic acid esters are preferable from the viewpoint of suppressing feathering and color bleeding.
As specific examples, “SMA1440” manufactured by SARTOMER (styrene-maleic acid-maleic acid ester polymer dispersant weight average molecular weight 7,000, acid value 185 mg KOH / g), “Joncrill 682” manufactured by BASF Japan (styrene- Acrylic acid polymer dispersing agent weight average molecular weight 1,700, acid value 238 mgKOH / g), “RY72” (styrene-acrylic acid-acrylic acid ester polymer dispersing agent weight average molecular weight 14,800, acid, manufactured by Gifu Shellac Co., Ltd. Value 170 mgKOH / g).

  In the present invention, the above pigment dispersants can be used singly or in combination of two or more. In the present invention, when a pigment dispersant is used, its content is not particularly limited. Although depending on the type of pigment, the pigment dispersant is usually 3 to 80% by mass with respect to 100% by mass of the pigment, and 5 to 60% by mass is preferable from the viewpoint of dispersibility and dispersion stability, and 10 to 50%. The mass% is more preferable.

(5-2) Penetrant The inkjet ink of the present invention may further contain a penetrant. In the present invention, the penetrant is not particularly limited, and any of the aqueous solvents having permeability can be used. Examples of the penetrant include 1,2-alkyl diol, glycol ether, acetylene glycol surfactant, acetylene alcohol surfactant, and the like. Specific examples of 1,2-alkyldiol include 1,2-hexanediol, 1,2-pentanediol, and the like. Specific examples of the glycol ether include diethylene glycol monobutyl ether and diethylene glycol monopentyl ether. Examples include diethylene glycol monohexyl ether, 3-methoxy-3-methyl-1-butanol, and the like can be used alone or in combination of two or more.
When the penetrant is used, the amount of penetrant added is preferably 1 to 15% by mass and more preferably 1 to 10% by mass with respect to the total amount of the ink-jet ink.

(5-3) Wetting agent The inkjet ink of the present invention may further contain a wetting agent. The wetting agent is not particularly limited, but is preferably a water-soluble organic solvent having a boiling point of 180 ° C. or higher and water absorption and water retention. Examples of preferable wetting agents include glycerin, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,3-butanediol, and the like. When using the said wetting agent, the addition amount is preferably in the range of 5 to 50% by mass, more preferably in the range of 5 to 35% by mass with respect to the total amount of the inkjet ink.
The inkjet ink of the present invention can also use a tertiary amine as a wetting agent. Examples of the tertiary amine include trimethylamine, triethylamine, triethanolamine and the like. When a tertiary amine is used as the wetting agent, the amount added is preferably in the range of about 0.3 to 3.0% by mass, more preferably 0.5 to 1.0% by mass with respect to the total amount of the inkjet ink. % Range.
In this invention, a wetting agent can be used individually by 1 type or in combination of 2 or more types.

  The solid content in the inkjet ink is preferably in the range of 0.1 to 30% by mass with respect to the entire inkjet ink. In addition, solid content represents components other than the aqueous solvent in inkjet ink.

<Method for preparing inkjet ink>
The method for preparing the inkjet ink is not particularly limited. For example, a method in which a self-dispersing pigment is added to an aqueous solvent and dispersed, followed by addition of a resin, a surfactant, and other components as necessary, and a pigment and a dispersant are added to an aqueous solvent for dispersion. After adding the resin, surfactant and other components as necessary, the pigment is dispersed in the aqueous solvent after adding the pigment, resin, surfactant and other components as necessary. And a method of preparing it.

The surface tension of the inkjet ink is 32 mN / m or less. Especially, it is preferable that it is 30 mN / m or less, and it is more preferable that it is 28 mN / m or less from the point which can suppress a color nonuniformity and a white spot. On the other hand, the surface tension of the inkjet ink is preferably 20 mN / m or more from the viewpoint of improving the ejection stability of the ink from the ejection head.
Furthermore, by using the receiving solution, feathering can be suppressed and a clear image can be obtained.
Further, the difference between the surface tension of the inkjet ink and the surface tension of the receiving solution is 5 mN / m or less. Especially, it is preferable that it is 3 mN / m or less from the point which can suppress color bleeding and can obtain a clear image.
The surface tension of the inkjet ink can be adjusted by appropriately selecting the solvent and the surfactant.

[Printing method using ink set for inkjet recording]
The ink set for inkjet recording according to the present invention includes a receiving solution and an inkjet ink used in an inkjet recording method in which a receiving solution is attached to a printing surface of a recording medium and ink is attached to the receiving solution attaching portion by an inkjet method for printing. It is a combination.
By using the inkjet set for inkjet recording of the present invention, there is no color unevenness regardless of the recording medium, feathering and color bleeding can be suppressed, and a clear image can be obtained.

Method for Adhering Receiving Solution to Recording Medium The method for adhering the receiving solution to the recording medium is not particularly limited as long as it is a method capable of adhering only to the portion to be printed or the front surface of the printing surface, and a conventionally known method can be used. it can. Among them, it is preferable to use a spray method, a coater method, an ink jet method, a gravure method, or a flexo method, and it is particularly preferable to apply by an ink jet method. According to the ink jet method, it is possible to change a printed image without changing the plate, and it is possible to easily change application to an arbitrary place or application to the entire surface.
From the viewpoint of interaction with the pigment, the receiving solution is preferably applied so that the amount of the divalent or higher valent metal salt attached to the recording medium is 20 to 2000 μmol / cm ² .
The timing of adhering the receiving solution to the recording medium is not particularly limited as long as it is before printing. The receiving solution may be applied to the recording medium in advance and dried before use, or may be applied immediately before printing. When a hydrophobic substrate such as coated paper is used as the recording medium, it is preferable to apply the receiving solution immediately before printing from the viewpoint of improving color unevenness and white spots and suppressing color bleeding.
By applying immediately before printing, there are many receiving solutions on the surface of the substrate, so that the reaction with the pigment occurs more quickly, and the effect of the receiving solution is more easily expressed. Also in this respect, it is preferable to apply the receiving liquid by the ink jet method.

Method for printing with ink-jet ink attached The ink-jet ink is printed on the receiving solution adhering portion of the recording medium by ink-jet printing. In the present invention, it is preferable that the ink is attached before the receiving solution is completely dried from the viewpoint of preventing color unevenness and white spots and suppressing feathering and color bleeding. For this reason, when using the ink set of this invention, the process and time which dry the receiving solution adhering to the printing surface can be reduced, and it can use suitably also for mass printing and high-speed printing.
The inkjet ink of the present invention can be applied to any inkjet recording apparatus such as a piezo system, a thermal system, and an electrostatic system, but among them, aggregates hardly occur and discharge stability is excellent. It is preferably used for an inkjet recording apparatus. A piezo-type recording head uses a piezoelectric vibrator as a pressure generating element, and discharges ink droplets by pressurizing and depressurizing a pressure chamber by deformation of the piezoelectric vibrator.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In the examples, “part” represents “part by mass”.

(Production Examples 1 to 11) Preparation of Accepting Solution In order to obtain the composition shown in Table 1 below, the metal salt and the resin were added to the solvent and dissolved, and water was added to make the total amount 100 parts by mass. A to K were prepared. The surface tensions of the obtained receiving solutions A to K were measured by the Wilhelmy method at 25 ° C.
The abbreviations in the table are as follows.
E1010: Acetylene glycol surfactant Olfin E1010 manufactured by Nissin Chemical Industry Co., Ltd.
BYK348: Silicone surfactant BYK348 manufactured by Big Chemie
D607: Acetylene glycol surfactant Dynol 607 manufactured by Air Products
PG: Propylene glycol GLY: Glycerol 1,3-PD: 1,3-propanediol DEG: Diethylene glycol

(Production Example 12) Preparation of pigment dispersion A (black)
Using procedures similar to those shown in Kieczykowski et al., J. Org. Chem., 1995, Vol. 60, P.8310-831, and US Pat. No. 4,922,007, [2- (4-Aminophenyl) -1-hydroxyethane-1,1-diyl] bisphosphonic acid-sodium salt was prepared. First, a 500 mL three-necked flask was equipped with a condenser with a gas outlet at the top of the condenser, a thermometer and dry nitrogen inlet, and a 100 mL pressure equalizing addition funnel. To this flask was initially added 32 g phosphorous acid (380 mmol) and 160 mL methanesulfonic acid (solvent). To this stirred mixture, 57.4 g of aminophenylacetic acid (380 mmol) was added in portions. The stirred mixture was heated to 65 ° C. for 1-2 hours to completely dissolve the solids. The entire system was flushed with dry nitrogen and the temperature was reduced to 40 ° C. after all of the solids had dissolved. To this heated solution 70 mL of PCl ₃ (800 mmol) was slowly added through an addition funnel. HCl gas generated by the reaction was discharged through a gas outlet. After the addition was complete, the reaction mixture was stirred for 2 hours and heated at 40 ° C. The temperature was then raised to 65-70 ° C. and the mixture was stirred overnight. The resulting clear brown solution was cooled to room temperature and quenched by addition into a 600 g ice / water mixture.
This aqueous mixture was placed in a 1 L beaker and heated to 90-95 ° C. for 4 hours (the top of the beaker was covered with a glass plate). The mixture was then cooled to room temperature and the pH of the mixture was adjusted to 4-5 with 50% NaOH solution. The mixture is cooled in an ice bath to 5 ° C. for 2 hours, then the resulting solid is collected by suction filtration, washed with 1 L of cold deionized water, dried at 60 ° C. overnight, white or off-white color Of a solid product (yield: 48 g, yield: 39%). ¹ H-NMR data (D ₂ O / NaOH) of the obtained solid product was as follows. That is, 7.3 (2H, d), 6.76 (2H, d), 3.2 (2H, t). The ¹³ C-NMR data (D ₂ O / NaOH) of the obtained solid product were 141, 130, 128, 112, and 73, respectively.

  20 g of carbon black (Black Pearls (registered trademark) 700 carbon black (manufactured by Cabot)), 20 mmol of the above solid product, 20 mmol of nitric acid, and 200 mL of deionized water were mixed at room temperature with a Silverson mixer (6000 rpm). Mixed. After 30 minutes, sodium nitrite (20 mmol) dissolved in a small amount of water was slowly added into the mixture. The temperature reached 60 ° C. by mixing and was allowed to proceed for 1 hour. As a result, self-dispersed pigments (including pigments in which at least two phosphonic acid groups or salts thereof are bonded) in which the solid product is modified to carbon black were generated. The pH is adjusted to 8-9 with NaOH solution, and after 30 minutes, the dispersion with the self-dispersing pigment is diafiltered with a spectrum membrane using 20 parts by volume of deionized water, The mixture was concentrated to a solid content of 15% by mass to obtain pigment dispersion A (black).

(Production Examples 13 to 15) Preparation of Pigment Dispersion A (Blue), Pigment Dispersion A (Yellow), and Pigment Dispersion A (Red) In Production Example 12, C.I. I. Pigment blue 15: 4 (PB15: 4), C.I. I. Pigment red 122 (PR122), C.I. I. Pigment Dispersion A (Blue), Pigment Dispersion A (Yellow), and Pigment Dispersion A (Red) were obtained in the same manner as in Production Example 12 except that CI Pigment Yellow 74 (PY74) was used.

(Production Example 16) Preparation of Pigment Dispersion B (Black) To 80.1 g of ion-exchanged water, styrene-acrylic acid polymer dispersant (“Joncrill 682” manufactured by BASF Japan Ltd., weight average molecular weight 1,700, acid value 238mgKOH / g) 3.0g and triethanolamine 1.8g, 15g of carbon black and 0.1g of anti-foaming agent ("Surfinol 104E" manufactured by Air Products) are added and paint using zirconia beads. Dispersion was carried out using a shaker to obtain pigment dispersion B (black).

(Production Examples 17 to 19) Preparation of Pigment Dispersion B (Blue), Pigment Dispersion B (Yellow), and Pigment Dispersion B (Red) In Production Example 16, instead of carbon black, PB15: 4, PR122, Pigment dispersion B (blue), pigment dispersion B (yellow), and pigment dispersion B (red) were obtained in the same manner as in Production Example 16 except that PY74 and PY74 were used.

Production Example 20 Preparation of Resin Emulsion A resin emulsion was prepared by the following method. The average particle size of the obtained resin emulsion was measured at 25 ° C. using a concentrated particle size analyzer (manufactured by Otsuka Electronics Co., Ltd., model: FPAR-1000).
After sufficiently replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, a reactive surfactant (trade name: Latemul PD-, manufactured by Kao Corporation) 104) 0.75 g, potassium persulfate 0.04 g, acrylic acid 3 g and pure water 150 g were charged and stirred at 25 ° C. and mixed. A pre-emulsion was prepared by adding dropwise a mixture of 22.5 g of styrene, 60 g of methyl methacrylate, 30 g of ethyl methacrylate, and 34.5 g of 2-ethylhexyl acrylate. Also, after sufficiently replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, a reactive surfactant (trade name: Latemul manufactured by Kao Corporation) PD-104) 3 g, potassium persulfate 0.01 g and pure water 200 g were stirred and mixed at 70 ° C. Thereafter, the prepared pre-emulsion was dropped into the flask over 3 hours. The mixture was further heated and aged at 70 ° C. for 3 hours and then cooled, adjusted to pH 8 with an aqueous ammonia solution, filtered through # 150 mesh (manufactured by Japanese woven fabric), and 500 g of resin emulsion (solid content 30% by mass) was obtained. Obtained. The average particle diameter of the obtained resin emulsion was 90 nm.
Moreover, the electrical conductivity of the 1 mass% solid content aqueous solution of the resin emulsion was 69.2 μS / cm.

(Production Example 21) Preparation of inkjet ink (hereinafter sometimes simply referred to as ink) According to the composition described in the row of ink A (black) in Table 2 below, the pigment dispersion, resin emulsion, surfactant and solvent were added. After mixing, water was further added to bring the total amount to 100 parts by mass to obtain ink A (black).
In the preparation of the ink A (black), instead of the pigment dispersion A (black), the pigment dispersion A (blue), the pigment dispersion A (red), and the pigment dispersion A (yellow) were used. Except for the above, ink A (blue), ink A (red), and ink A (yellow) were obtained in the same manner as in the preparation of ink A (black). Hereinafter, the ink A (black), the ink A (blue), the ink A (red), and the ink A (yellow) may be simply referred to as “ink A”. The same applies to ink B and the following.

(Production Examples 22 to 30) Preparation of Ink B to Ink J Ink B to Ink J were obtained in the same manner as in Production Example 21 according to the composition described in each row of Table 2 above.

  The surface tension of the obtained inks A to J was measured by the Wilhelmy method at 25 ° C. Table 2 shows the surface tensions of ink A (black) to ink J (black). The surface tension of the ink did not depend on the type of pigment. That is, the surface tension of ink A (blue), ink A (red), and ink A (yellow) was the same as that of ink A (black), and the same was true for inks B to J.

Example 1
As a recording medium, coated paper (manufactured by Oji Paper Co., Ltd., mirror coat platinum) was used. The receiving solution B was attached to the printing surface of the coated paper by an inkjet method (manufactured by Konica Minolta, model number: KM512, droplet amount 10 pL, resolution 720 dpi). Next, a pattern in which different colors of inks (black, blue, red, yellow) belonging to the ink B are adjacent to each other is formed on the receiving solution adhering portion by an ink jet method (droplet amount: 10 pL, resolution: 720 dpi). Printed.

(Examples 2 to 19)
In Example 1, printing was performed in the same manner as in Example 1 except that the combination of the receiving solution and the ink was changed to that shown in Table 3.

(Comparative Examples 1-26)
In Example 1, printing was performed in the same manner as in Example 1 except that the combination of the receiving solution and the ink was changed to that shown in Table 3.

(Example 20)
In Example 15, printing was performed in the same manner as in Example 15 except that the recording medium was changed to a non-absorbent (manufactured by Toyobo Cosmo Shine A8300).

(Comparative Example 27)
In Example 20, printing was performed in the same manner as in Example 20 except that the receiving solution was not used.

[Evaluation method]
The solid filling and bleeding of the printed materials obtained in Examples 1 to 20 and Comparative Examples 1 to 27 were evaluated visually. The results are shown in Tables 3-4.

(1) Solid filling evaluation criteria A: Printing unevenness and white spots were not observed, and it was determined that the printing surface was sufficiently filled with ink (the dot diameter was sufficiently widened).
B: There was slight printing unevenness, but the printed surface was buried.
C: The base material surface was slightly exposed (white spots), and the printing surface was not sufficiently filled.
D: The base material surface was remarkably exposed and the printing surface was not sufficiently filled.
If the solid filling evaluation is A or B evaluation, it is within the practical range.

(2) Smudge (color bleed) evaluation criteria A: Smudge was not observed and the image was clear.
B: Slight blur was observed, but the image was clear.
C: Smudge was observed and a clear image was not obtained.
D: Significant blur was observed.
If the blur (color bleed) evaluation is A or B evaluation, it is within the practical range.

[Summary of results of Examples 1 to 20 and Comparative Examples 1 to 27]
According to the inkjet recording methods of Examples 1 to 20, the surface tension of the receiving solution and the inkjet ink is 32 mN / m or less, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less. As a result, it was revealed that even when coated paper or a non-absorbent material was used, a clear image with good solid filling was obtained. As an example, FIG. 1 shows an enlarged photograph of a portion where the printed matter obtained in Example 6 is adjacent to yellow and black. As shown in the photograph of FIG. 1, the printed matter obtained in Example 6 had a clear image without blurring or white spots.
In Comparative Examples 1 and 6, the evaluation of the solid filling was bad, but the evaluation of the color bleed was good because there was no difference in surface tension or it was very small.
In Comparative Examples 1, 6, 9, 10, 12, 13, 15, 18, 20-23, 25, and 26 using the ink A, F, or I having a surface tension of more than 32 mN / m, the printing surface is buried. Insufficient color unevenness occurred.
In Comparative Examples 4, 5, 7, 8, 11, 13, 15, and 16, where the difference in surface tension between the receiving solution and the ink-jet ink exceeds 5 mN / m, color bleeding is recognized and a clear image cannot be obtained. It was. As an example, FIG. 2 shows an enlarged photograph of a portion of the printed matter obtained in Comparative Example 4 where yellow and black are adjacent to each other. On the other hand, even when the surface tension difference exceeds 5 mN / m, Comparative Examples 3, 10, 12, 14, 17, 20-22, 25, and 26 in which the color bleed was evaluated as A or B were poorly filled and printed. The filling of the surface was insufficient.
In Comparative Examples 18, 19 and 27 in which the receiving solution was not used, the evaluation of solid filling and the evaluation of color bleed were poor. Similarly, in Comparative Examples 23 and 24 using the receiving solution I having no divalent metal salt, the evaluation of solid filling and the evaluation of color bleed were also poor. As an example, FIG. 3 shows an enlarged photograph of a portion of the printed matter obtained in Comparative Example 19 where yellow and black are adjacent to each other.

(Example 21)
In Example 2, printing was performed in the same manner as in Example 2 except that non-coated paper (Oji Paper, OK fine paper) was used as the recording medium.

(Example 22)
In Example 9, printing was performed in the same manner as in Example 9, except that non-coated paper (Oji Paper, OK fine paper) was used as the recording medium.

(Example 23)
In Example 10, printing was performed in the same manner as in Example 10 except that non-coated paper (Oji Paper, OK fine paper) was used as the recording medium.

(Comparative Example 28)
In Comparative Example 7, printing was performed in the same manner as in Comparative Example 7, except that non-coated paper (Oji Paper, OK fine paper) was used as the recording medium.

(Comparative Example 29)
In Comparative Example 1, printing was performed in the same manner as in Comparative Example 1, except that non-coated paper (Oji Paper, OK fine paper) was used as the recording medium.

(Comparative Example 30)
In Example 21, printing was performed in the same manner as in Example 21 except that the receiving solution was not used and ink D was used.

[Evaluation method]
The bleeding of the printed matter obtained in Examples 21 to 23 and Comparative Examples 28 to 30 was evaluated visually. The results are shown in Table 5.
(1) Blur (feathering) evaluation criteria A: No blur was observed and the image was clear.
B: Slight bleeding along the fiber was observed.
C: Bleeding along the fibers was observed.
D: Remarkably blurring was observed.
If the blur (feathering) evaluation is A evaluation, it is within the practical range.

[Summary of results of Examples 21 to 23 and Comparative Examples 28 to 30]
According to the ink jet recording method of Examples 21 to 23, the surface tension of the receiving solution and the ink jet ink is 32 mN / m or less, and the difference in surface tension between the receiving solution and the ink jet ink is 5 mN / m or less. As a result, it was revealed that a clear image could be obtained even when non-coated paper was used.
In Comparative Example 29 in which printing was performed on uncoated paper using a receiving solution and ink having a surface tension exceeding 32 mN / m, the result of feathering was good. On the other hand, from the result of Comparative Example 1 in which printing was performed on coated paper using the same receiving solution and ink as those printed on non-coated paper in Comparative Example 29, the case of coated paper (Comparative Example 1 ), When the surface tension of the receiving solution or ink exceeded 32 mN / m, solid filling was poor.
In Example 21 in which the receiving solution and the ink were combined and printed on the non-coated paper so that the difference in surface tension was 5 mN / m or less, the feathering was good. In Example 21, the non-coated liquid In Example 2 in which printing was performed on the coated paper using the same receiving solution and ink as those printed on, solid embedding and color bleed were good. On the other hand, Comparative Example 28, in which the difference in surface tension between the receiving solution and the ink exceeded 5 mN / m and printed on non-coated paper, had good feathering. In Comparative Example 7 in which printing was performed on the coated paper using the same receiving solution and ink as those printed in No. 3, the bleeding was observed and the color bleed was poorly evaluated.
Similarly, in Examples 22 and 23 in which printing was performed on uncoated paper by combining the receiving solution and the ink so that the surface tension difference was 5 mN / m or less, the feathering was good. In Examples 9 and 10 where printing was performed on coated paper using the same receiving solution and ink as those printed on the non-coating liquid in 22 and 23, solid filling and color bleeding were good. In contrast, Comparative Example 29, in which the difference in surface tension between the receiving solution and the ink exceeded 5 mN / m and printed on non-coated paper, had good feathering. In Comparative Example 1 in which printing was performed on the coated paper using the same receiving solution and ink as those printed on the coating liquid, the evaluation of solid filling was poor.
Therefore, even in the case of an ink jet recording method that does not cause color unevenness, white spots, and blurring in the case of non-coated paper, color unevenness, white spots, and blurring problems occur in the case of coated paper. It became clear that there was something.

  According to the ink jet recording method of the present invention, not only when non-coated paper is used as a recording medium, but also when coated paper or non-absorbent material is used, there is no color unevenness or white spots, and the image is clear. It became clear that a correct image was obtained.

Claims (13)

An ink jet recording method for printing by attaching a receiving solution to a printing surface of a recording medium and attaching an ink jet ink to the receiving solution adhering portion,
The receiving solution is a receiving solution containing a divalent or higher metal salt,
The inkjet ink is an inkjet ink containing at least a pigment, a resin, a surfactant and an aqueous solvent,
An inkjet recording method, wherein the surface tension of the receiving solution and the inkjet ink is 32 mN / m or less, and the difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less.   The divalent or higher valent metal salt is at least one metal salt selected from the group consisting of calcium salt, magnesium salt, nickel salt, aluminum salt, boron salt and zinc salt. The ink jet recording method described in 1.   The ink jet recording method according to claim 1 or 2, wherein the method of adhering the receiving solution to the recording medium is a spray method, a coater method, an ink jet method, a gravure method, or a flexo method.   The inkjet recording method according to claim 1, wherein the pigment is a self-dispersing pigment.   The inkjet recording method according to claim 4, wherein the self-dispersing pigment is a pigment in which a phosphorus-containing group having at least one P—O or P═O bond is bonded to the surface.   The ink jet recording method according to claim 1, wherein the pigment is dispersed by a dispersant.   The inkjet recording method according to claim 6, wherein the dispersant contains a polymer dispersant. An ink set in which a receiving solution is attached to a printing surface of a recording medium, and the receiving solution and an inkjet ink are combined for use in an inkjet recording method for printing by attaching an ink to the receiving solution attaching portion by an inkjet method,
The receiving solution is a receiving solution containing a divalent or higher metal salt,
The inkjet ink is an inkjet ink containing at least a pigment, a resin, a surfactant and an aqueous solvent,
An ink set for inkjet recording, wherein the receiving solution and the inkjet ink have a surface tension of 32 mN / m or less, and a difference in surface tension between the receiving solution and the inkjet ink is 5 mN / m or less.   9. The divalent or higher metal salt is at least one metal salt selected from the group consisting of calcium salt, magnesium salt, nickel salt, aluminum salt, boron salt and zinc salt. The ink set for inkjet recording as described in 2.   The ink set for inkjet recording according to claim 8 or 9, wherein the pigment is a self-dispersing pigment. 11. The ink set for inkjet recording according to claim 10, wherein the self-dispersing pigment is a pigment in which a phosphorus-containing group having at least one P-O or P = O bond is bonded to the surface.   The ink set for inkjet recording according to claim 8 or 9, wherein the pigment is dispersed by a dispersant.   The ink set for inkjet recording according to claim 12, wherein the dispersant includes a polymer dispersant.