JP5801075B2 - Ink composition, ink set, and image forming method - Google Patents

Description

  The present invention relates to an ink composition and an ink set, and an image forming method using them.

  The ink jet recording method is a method of performing recording by ejecting droplet-shaped ink from a large number of nozzles formed on an ink jet recording head toward a recording medium and fixing the ink to the recording medium. Inks used for ink-jet recording are generally water-based and contain at least a coloring component and an organic solvent. However, an ink containing a pigment as a coloring component is proposed for the purpose of improving image storage stability. Has been.

  Furthermore, various recording media have been developed for ink jet recording, and there is a demand for inks that can form high-quality images regardless of the recording medium. For example, an aqueous ink containing a self-dispersing pigment having a hydrophilic group on the surface has been studied, and it is said that the image density is high and the storage stability is excellent (see, for example, Patent Documents 1 and 2).

  On the other hand, as a technique for quickly fixing ink to a recording medium in order to obtain a high-resolution and high-quality image, a treatment liquid (also referred to as a fixing liquid or a reaction liquid) containing a compound that promotes aggregation of the ink is used. It has been studied.

JP 2002-201388 A JP 2002-003756 A

The ink adheres to the ink jet recording head and dries to form a fixed substance, which may cause ejection abnormalities such as an abnormal ink ejection amount or an abnormal ejection direction. In particular, when the ink and the treatment liquid are combined, the fixed matter that is misted, mixed, and aggregated around the head adheres to the head, and discharge abnormality is likely to occur. Therefore, the ink is required to be easily removed (excellent in maintainability) even if a fixed matter is generated on the head surface.
Moreover, the dispersibility of a pigment may fall with the passage of time in the ink containing a pigment. In order to obtain a high-quality image, the ink is required to have excellent temporal stability.

The present invention has been made in view of the above, and an object thereof is to provide an ink composition and an ink set that are excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed, and to achieve the object. Is an issue.
Another object of the present invention is to provide an image forming method that is excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed, and an object thereof is to achieve the object.

<1> A self-dispersing pigment in which a carboxylic acid group is bonded to the surface of the pigment directly or through another atomic group, a tertiary amine, a water-soluble organic solvent, and water, A solvent having an SP value of 27.5 or less and a polar solvent which is at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone have a mass ratio of 12: 1 to 12: 8, an ink composition in which 50 to 90 mol% of the carboxylic acid groups on the surface of the self-dispersing pigment are neutralized with the tertiary amine.
<2> The ink composition according to <1>, wherein the tertiary amine is at least one of triethylamine and triethanolamine.
<3> The solvent having an SP value of 27.5 or less is at least one selected from dipropylene glycol, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monobutyl ether. The ink composition according to <1> or <2>, which is a seed.
< 4 > The ink according to any one of <1> to < 3 >, wherein the pigment constituting the self-dispersing pigment includes at least one selected from a magenta pigment, a cyan pigment, a yellow pigment, and a black pigment. Composition.
< 5 > The pigment constituting the self-dispersing pigment includes any one of <1> to < 4 >, including at least one selected from Pigment Yellow 74, Pigment Red 122, and Pigment Blue 15: 3. Ink composition.
< 6 > The ink composition according to any one of <1> to < 5 >, a treatment liquid containing a cationic polymer and aggregating components in the ink composition when in contact with the ink composition; An ink set.
< 7 > The ink set according to < 6 >, wherein the cationic polymer includes at least one polyguanidine.
< 8 > An image forming method including an ink application step of applying the ink composition according to any one of <1> to < 5 > to a recording medium by an inkjet method.
< 9 > Using the ink set according to < 6 > or < 7 >, an ink application step of applying the ink composition in the ink set to a recording medium by an inkjet method, and a treatment liquid in the ink set as a recording medium An image forming method comprising a treatment liquid application step of applying.

According to the present invention, it is possible to provide an ink composition and an ink set that are excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed.
Further, according to the present invention, it is possible to provide an image forming method that is excellent in maintainability and excellent in abrasion resistance of an image formed after the ink has elapsed.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to this, A various deformation | transformation can be implemented within the range of the meaning.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

In the present specification, the ink fixed product refers to a thickened product and a solidified product obtained by removing at least a part of a solvent from an ink composition or a mixture of an ink composition and a treatment liquid.
In this specification, maintenance includes maintaining a recording head that discharges an ink composition and its discharge performance at or near the intended state (maintenance), and cleaning the recording head ( Cleaning) and maintaining and maintaining a better condition.

<Ink composition>
The ink composition of the present invention contains a self-dispersing pigment in which a carboxylic acid group is bonded to the surface of the pigment directly or through another atomic group, a tertiary amine, a water-soluble organic solvent, and water. 50 to 90 mol% of the carboxylic acid groups on the surface of the dispersed pigment are neutralized with the tertiary amine.
With this configuration, the ink composition is excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed. In addition, the ink composition is less likely to cause adhesion and deposition of the fixed ink on the recording head.
The ink composition is less likely to cause adhesion and accumulation of a fixed ink to a recording head, and has excellent maintainability, so that when an image is formed using the ink composition, an image failure such as white spots may occur. Generation | occurrence | production can be suppressed and high-resolution image formation can be implement | achieved.

The ink composition is used not only for forming a single-color image but also for forming a multicolor image (for example, a full-color image), and can form an image by selecting one or more desired colors. When forming a full color image, the ink composition can be used as a magenta color ink, a cyan color ink, and a yellow color ink. Further, in order to adjust the color tone, it may be used as a black color tone ink.
In addition, ink compositions having red (R), green (G), blue (B), and white (W) tones other than yellow (Y), magenta (M), and cyan (C), and so-called printing fields. It can also be used as an ink composition having a special color.
The ink composition of each color tone can be prepared by changing the hue of the self-dispersing pigment.

(Self-dispersing pigment)
The ink composition contains at least one kind of self-dispersing pigment having a carboxylic acid group on the surface of the pigment as a colorant. The self-dispersing pigment has a carboxylic acid group on the surface of the pigment, so that the pigment can be dispersed or dissolved in an aqueous medium constituting the ink. In addition, the self-dispersing pigment has a carboxylic acid group on the surface of the pigment, thereby suppressing adhesion / deposition of the ink adhering matter and excellent removability (maintenance) of the adhering / depositing ink. It is possible to realize high-resolution image formation by suppressing the occurrence of image failure such as omission. Furthermore, the self-dispersing pigment has excellent rub resistance of an image by having a carboxylic acid group on the surface of the pigment.
In addition to the self-dispersing pigment, the ink composition may contain pigments, dyes, and the like as long as the effects of the present invention are not impaired.

The self-dispersing pigment is a pigment in which a carboxylic acid group (hereinafter also referred to as a dispersibility-imparting group) is bonded to the surface of the pigment directly or indirectly through another atomic group. The self-dispersing pigment exhibits at least one of water dispersibility and water solubility in the absence of an additional dispersant for dispersing the pigment.
Since the ink containing the self-dispersing pigment as a colorant does not need to contain an additional dispersant for dispersing the pigment, there is almost no foaming due to a decrease in the defoaming property caused by the dispersant, and stable ejection. It is easy to prepare ink with excellent properties.

  Examples of other atomic groups for indirectly bonding a carboxylic acid group to the surface of the pigment constituting the self-dispersing pigment include, for example, a linear or unsubstituted alkylene group having 1 to 12 carbon atoms, substituted or unsubstituted And a substituted or unsubstituted naphthylene group. Here, examples of the substituent which may be bonded to the phenylene group or the naphthylene group include a linear or branched alkyl group having 1 to 6 carbon atoms.

The self-dispersing pigment can be produced, for example, by hydrophilizing the pigment by surface oxidation treatment. The carboxylic acid group (—COOH) and the salt thereof, which are the dispersibility-imparting group, are obtained by subjecting the pigment as a raw material to a physical treatment or a chemical treatment, so that the active species having the dispersibility-imparting group or the dispersibility-imparting group Is attached (grafted) to the pigment surface and applied to the pigment.
Examples of the physical treatment include vacuum plasma treatment. In addition, as the chemical treatment, for example, a wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water, or a method in which p-aminobenzoic acid is bonded to the pigment surface to bond a carboxylic acid group via a phenylene group Etc. can be exemplified.
In the present invention, preferred examples include self-dispersing pigments that are surface-treated by oxidation treatment with hypohalous acid and / or hypohalite, or oxidation treatment with ozone.

For example, when a dispersibility-imparting group is imparted to the surface of carbon black, examples of the method for introducing —COOH include a method of oxidizing commercially available carbon black with sodium hypochlorite.
Also, for example, as a method of bonding —Ar—COOH (wherein Ar represents an arylene group) to the carbon black surface, a diazonium salt obtained by allowing nitrous acid to act on NH ₂ —Ar—COOH is bonded to the carbon black surface. The method of letting it be mentioned. Of course, the present invention is not limited to this.

  Commercially available products may be used as the self-dispersing pigment, and specific examples include Cabojet 300 (trade name; modified pigment by carboxylic acid group, manufactured by Cabot Corporation).

The self-dispersing pigments may be used alone or in combination of two or more.
The content of the self-dispersing pigment in the ink composition is preferably 1 to 25% by mass with respect to the total mass of the ink composition from the viewpoints of color density, granularity, ink stability, and ejection reliability. 5 to 20% by mass is more preferable.

[Pigment]
There is no restriction | limiting in particular as a pigment which comprises the said self-dispersion type pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient.
Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable.
Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of dye chelates include basic dye chelates and acidic dye chelates. Specific examples of the organic pigment that can be used in the present invention include pigments described in paragraph numbers 0142 to 0145 of JP-A-2007-100071.

  Examples of inorganic pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable. Examples of carbon black include those produced by known methods such as a contact method, a furnace method, and a thermal method.

  The pigment constituting the self-dispersing pigment is not particularly limited, but preferably contains at least one selected from a magenta pigment, a cyan pigment, a yellow pigment and a black pigment. From the viewpoint of color tone, Pigment Yellow 74 is preferable as the yellow pigment, Pigment Red 122 is preferable as the magenta pigment, Pigment Blue 15: 3 is preferable as the cyan pigment, and these pigments constituting the self-dispersing pigment are It is preferable to contain at least one selected from

~ Degree of neutralization of carboxylic acid group ~
In the self-dispersing pigment, 50 to 90 mol% of carboxylic acid groups on the surface thereof are neutralized with a tertiary amine. When the neutralization degree of the carboxylic acid group is less than 50 mol%, the solubility of the ink fixed substance in the maintenance liquid and the image rubbing resistance before and after ink aging may be poor. If the neutralization degree of the carboxylic acid group is more than 90 mol%, the solubility of the fixed ink in the maintenance liquid and the image abrasion resistance before and after the ink aging may be poor.
Here, the degree of neutralization of the carboxylic acid group is a value obtained by neutralization titration. Neutralization titration is performed using hydrochloric acid adjusted to 0.1 mol / L by diluting a self-dispersing pigment to a pigment concentration of 5% by mass using a water-soluble organic solvent described later. Perform Japanese titration. At this time, titration is started after setting the initial pH to 12 or more with NaOH, and the titration is terminated when the pH becomes 2 or less. The degree of neutralization is defined by setting the acid amount from the first inflection point of the obtained titration curve to complete neutralization as 100% neutralization.

  The neutralization degree of the carboxylic acid group is preferably 60 to 85 mol%, more preferably 70 to 80 mol%, from the viewpoint of dispersion stability.

(Tertiary amine)
The ink composition contains a tertiary amine as a neutralizing agent for carboxylic acid groups on the surface of the self-dispersing pigment. The tertiary amine is used to neutralize 50 to 90 mol% of the carboxylic acid group, and the self-dispersing pigment forms a stable emulsified state or dispersed state in an aqueous solvent.

  The tertiary amine used in the present invention includes trimethylamine, triethylamine, tripropylamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl- Examples include 1-propanol, N-methyldiethanolamine, N-ethyldiethanolanine, and triisopropanolamine. Among these, triethylamine and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing pigment.

  The content of the tertiary amine in the ink composition is an amount that neutralizes 50 to 90 mol% of the carboxylic acid groups on the surface of the self-dispersing pigment. The content of the tertiary amine in the ink composition is preferably an amount that neutralizes 60 to 85 mol% of the carboxylic acid group, and more preferably an amount that neutralizes 70 to 80 mol% of the carboxylic acid group.

(Water-soluble organic solvent)
The ink composition contains at least one water-soluble organic solvent as a solvent for the ink composition. In the present invention, the water-soluble organic solvent means an organic solvent that dissolves 5 g or more in 100 g of water.
By containing the water-soluble organic solvent, it is possible to obtain the effect of preventing drying, wetting or penetration of the ink composition. To prevent drying, the ink composition adheres and dries at the ink discharge port of the ejection nozzle to form an aggregate and is used as a drying inhibitor to prevent clogging. A water-soluble organic solvent having a vapor pressure lower than that of water is used. preferable. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

Examples of the water-soluble organic solvent include alkanediols (polyhydric alcohols) such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol; sugar alcohols; ethanol, methanol Alkyl alcohols having 1 to 4 carbon atoms, such as butanol, propanol, isopropanol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol monobutyl ether (ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether), ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl Ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether ,Propylene glycol No ethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-t-butyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol Examples include glycol ethers such as mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, and tripropylene glycol monomethyl ether.

For the purpose of preventing drying and wetting, polyhydric alcohols are useful. For example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2 , 3-butanediol and the like.
For the purpose of promoting penetration, polyol compounds are preferred, and aliphatic diols are preferred. Examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, -Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol and the like. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

The water-soluble organic solvent may be used alone or in combination of two or more.
The content of the water-soluble organic solvent is preferably 1 to 60% by mass, more preferably 5 to 40% by mass, based on the total mass of the ink composition.

  The water-soluble organic solvent preferably contains at least one of a solvent having a SP value of 27.5 or less and a polar solvent from the viewpoint of the temporal stability of the ink. More preferably, both are included.

[Solvent with SP value of 27.5 or less]
The ink composition preferably contains at least one solvent having an SP value of 27.5 or less as the water-soluble organic solvent from the viewpoint of the temporal stability of the ink.
The SP value (solubility parameter) of the solvent referred to in the present invention is a value represented by the square root of the molecular cohesive energy. F. It can be calculated by the method described in Fedors, Polymer Engineering Science, 14, p147 to p154 (1974), and this numerical value is adopted in the present invention.

  Specific examples of preferred compounds as the solvent having an SP value of 27.5 or less and their SP values (in parentheses) are shown below. Of course, the present invention is not limited to this.

・ Diethylene glycol monoethyl ether (22.4)
・ Diethylene glycol monobutyl ether (21.5)
・ Triethylene glycol monomethyl ether (22.1)
・ Triethylene glycol monoethyl ether (21.7)
・ Triethylene glycol monobutyl ether (21.1)
・ Dipropylene glycol monomethyl ether (21.3)
・ Dipropylene glycol monobutyl ether (20.5)
Dipropylene glycol (27.2)
・ Tripropylene glycol monomethyl ether (20.4)

_{· NC 4 H 9 O (AO} ) 4 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) (20.1)
_{· NC 4 H 9 O (AO} ) 10 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) (18.8)
HO (A′O) ₄₀ −H (A′O = EO or PO, the ratio is EO: PO = 1: 3) (18.7)
HO (A ″ O) ₅₅ −H (A ″ O = EO or PO, the ratio is EO: PO = 5: 6) (18.8)
HO (PO) ₃ -H (24.7)
・ HO (PO) _7- H (21.2)
・ 1,2-Hexanediol (27.4)
In the above, EO and PO represent an ethyleneoxy group and a propyleneoxy group.

  Among the alkylene oxide adducts of glycerin described below, a solvent having an SP value of 27.5 or less is also suitable. The alkylene oxide adduct of glycerin is preferably a compound represented by the following structural formula (1).

  In the structural formula (1), l, m, and n each independently represent an integer of 1 or more and satisfy the relationship of 3 ≦ l + m + n ≦ 15. When the value of l + m + n is 3 or more, the curl suppressing force is good, and when it is 15 or less, the ink ejection property is good. Especially, l + m + n has the preferable range of 3-12, and the range of 3-10 is more preferable.

AO in the structural formula (1) represents an ethyleneoxy group and / or a propyleneoxy group, and among them, a propyleneoxy group is preferable. Each AO of (AO) _l , (AO) _m , and (AO) _{n in} the structural formula (1) may be the same or different.

  Specific examples of the compound represented by the structural formula (1) are shown below. However, the present invention is not limited to these. The numerical value in parentheses represents the SP value.

  A commercially available product may be used as the alkylene oxide adduct of glycerin. As a commercial item, for example, as a polyoxypropylated glycerin (ether of polypropylene glycol and glycerin), Sannix GP-250 (SP value 26.4), Sannix GP-400 (SP value 23.2) (and above) And Sanyo Chemical Industries, Ltd.).

  Examples of the solvent having an SP value of 27.5 or less include dipropylene glycol, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dipropylene glycol monomethyl ether and dipropylene glycol monobutyl ether from the viewpoint of stability over time. At least one selected from is preferred.

The content of the solvent having an SP value of 27.5 or less in the total water-soluble organic solvent in the ink composition is preferably 50% by mass or more from the viewpoint of improving the solubility of the fixed ink in the maintenance liquid. More preferably, it is more preferably 70% by mass or more.
The solvent having an SP value of 27.5 or less is more preferably a solvent having an SP value of 24 or less, more preferably a solvent having an SP value of 22 or less, from the viewpoint of improving the solubility of the fixed ink in the maintenance liquid. preferable.
A solvent having an SP value of 27.5 or less may be used alone or in combination of two or more.

[Polar solvent]
The ink composition preferably contains at least one polar solvent as the water-soluble organic solvent from the viewpoint of the temporal stability of the ink.
In the present invention, the polar solvent is a solvent having a dipole moment of 0.5 or more or a dielectric constant of 3.0 or more, such as —OH, —SH,> C═O, —COOH, —NH—R, etc. It has a structure with a group.

  Examples of the polar solvent include formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2 -Oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone and the like. Among these, at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone is preferable.

  The content of the polar solvent in the total water-soluble organic solvent in the ink composition is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and 10 to 30% by mass from the viewpoint of ink stability over time. % Is more preferable. The polar solvent may be used alone or in combination of two or more.

  In the ink composition, the mixing ratio of the solvent having the SP value of 27.5 or less and the polar solvent is preferably the former: latter [mass ratio] of 1: 1 to 50: 1, and 12: 1 to 12. : 8 is more preferable.

(water)
The ink composition contains water. Although there is no restriction | limiting in particular in content of water, Preferably it is 10-99 mass%, More preferably, it is 30-80 mass%, More preferably, it is 50-70 mass%.

(Resin particles)
The ink composition preferably contains at least one resin particle. By including the resin particles, fixability and abrasion resistance of the formed image are improved.

  Resin particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, and benzoguanamine resins. A phenol resin, a silicone resin, an epoxy resin, a urethane resin, a paraffin resin, a fluorine resin, or the like can be used. Among these, acrylic resins, acrylic-styrene resins, styrene resins, crosslinked acrylic resins, and crosslinked styrene resins are preferable as the resin particles.

The weight average molecular weight of the resin particles is preferably in the range of 3000 to 200,000, more preferably in the range of 5000 to 150,000, and still more preferably in the range of 10,000 to 100,000 from the viewpoint of stabilizing self-dispersibility.
The average particle diameter of the resin particles is preferably in the range of 10 nm to 1 μm in terms of volume average particle diameter, more preferably in the range of 10 to 200 nm, still more preferably in the range of 10 to 100 nm, and particularly preferably in the range of 10 to 50 nm. When the volume average particle size is 10 nm or more, the production suitability is improved, and when it is 1 μm or less, the storage stability is improved.
The particle size distribution of the resin particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Further, two or more kinds of resin particles having a monodispersed particle size distribution may be mixed and used.
The average particle size of the resin particles is obtained by measuring the particle size distribution by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

The resin particles can be used alone or in combination of two or more.
The content of the resin particles in the ink composition is preferably 0.5 to 20% by mass, more preferably 2 to 20% by mass, and still more preferably 3 to 15% by mass with respect to the total mass of the ink composition.

(Surfactant)
The ink composition preferably contains at least one surfactant. The surfactant is used as a surface tension adjusting agent. As the surface tension modifier, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively, and an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic interface Either an activator or a betaine surfactant can be used. Further, a dispersant (polymer dispersant) may be used as a surfactant.
In the present invention, a nonionic surfactant is preferable from the viewpoint of suppression of droplet ejection interference of the ink composition, and among them, an acetylene glycol derivative is more preferable.

When a surfactant (surface tension adjusting agent) is contained in the ink composition, the surfactant has a surface tension of 20 to 60 mN / m from the viewpoint of satisfactorily discharging the ink composition by an inkjet method. It is preferable to contain the quantity of the range which can be adjusted, More preferably, it is 20-45 mN / m from the point of surface tension, More preferably, it is 25-40 mN / m.
The surface tension of the ink composition is measured under conditions of 25 ° C. by the plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Orphine (Nissin Chemical Industry Co., Ltd.) and SURFYNOLS (Air Products & Chemicals), which are acetylene-based polyoxyethylene oxide surfactants, are also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

Further, pages 37 to 38 of JP-A-59-157636 and Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
In addition, fluorine (fluorinated alkyl-based) surfactants, silicone-based surfactants and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also included. Scratch resistance can also be improved.

  These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

(Other ingredients)
In addition to the above components, the ink composition may contain various additives as necessary. Examples of the various additives include, for example, ultraviolet absorbers, antifading agents, antifungal agents, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, and dispersions. Known additives such as stabilizers, chelating agents, solid wetting agents and the like can be mentioned.

  Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.

  As the anti-fading agent, various organic and metal complex anti-fading agents can be used. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, and metal complexes. There are nickel complex, zinc complex and the like.

Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one, sodium sorbate, pentachloro Examples include phenol sodium.
The antifungal agent preferably has a content in the ink composition of 0.02 to 1.00% by mass.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Examples of the antioxidant include phenolic antioxidants (including hindered phenolic antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.

  Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.

  Examples of the solid wetting agent include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose and other sugars; sugar alcohols; hyaluronic acids; Examples include ureas.

~ Physical properties of ink composition ~
The pH of the ink composition is preferably 7 to 10 and more preferably 7.5 to 9 from the viewpoint of the aggregation rate of the ink composition. As the pH of the ink composition, a value measured at 25 ° C. using a pH meter WM-50EG manufactured by Toa DDK Co., Ltd. is adopted.
The surface tension of the ink composition is preferably 20 mN / m to 60 mN / m. More preferably, it is 20mN-45mN / m, More preferably, it is 25mN / m-40mN / m. The surface tension of the ink composition employs a value measured at 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).
The viscosity of the ink composition is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, and further preferably 2.5 mPa · s or more and less than 10 mPa · s. It is. As the viscosity of the ink composition, a value measured at 25 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) is adopted.

<Ink set>
The ink set of the present invention contains a self-dispersing pigment in which a carboxylic acid group is bonded to the surface of the pigment directly or through another atomic group, a tertiary amine, a water-soluble organic solvent, and water. An ink composition in which 50 to 90 mol% of the carboxylic acid groups on the surface of the type pigment are neutralized with the tertiary amine, and a cationic polymer in the ink composition when contacted with the ink composition. And a treatment liquid for aggregating the components.
The ink set having such a configuration is excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed.

[Treatment solution]
The treatment liquid contains at least one kind of cationic polymer that aggregates the components in the ink composition, particularly the self-dispersing pigment, when coming into contact with the ink composition. By containing a cationic polymer in the treatment liquid, the formation speed of aggregates due to contact with the ink composition is effectively improved, so that white spots of the image are suppressed and the scratch resistance of the image is reduced. improves.

(Cationic polymer)
The cationic polymer is not particularly limited as long as it aggregates the self-dispersing pigment. For example, poly (vinyl pyridine) salt, polyalkylaminoethyl acrylate, polyalkylaminoethyl methacrylate, poly (vinyl imidazole), polyethyleneimine, polyguanidine (eg, polybiguanide, polyguanide), polyallylamine, or other quaternary polyamines And polyamines. Examples of the polybiguanide which is a polyguanidine include hexamethylene biguanide polymer, and examples of the polyguanide include hexamethylene guanide polymer, or Vantocil (registered trademark, manufactured by Avicia).
Among these, it is preferable to contain at least one polyguanidine from the viewpoint of scratch resistance and maintenance.
A cationic polymer may be used individually by 1 type, and may use 2 or more types together.

The weight average molecular weight of the cationic polymer is preferably smaller in terms of the viscosity of the treatment liquid. When the treatment liquid is applied to the recording medium by an inkjet method, 500 to 500,000 is preferable, 700 to 200,000 is more preferable, and 1,000 to 100,000 is still more preferable.
When the weight average molecular weight is 500 or more, it is advantageous from the viewpoint of aggregation speed, and when it is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, this is not the case when the treatment liquid is applied to the recording medium by a method other than inkjet.

1-35 mass% is preferable with respect to the total mass of a process liquid, and, as for content of the said cationic polymer, 5-25 mass% is more preferable.
The amount of the cationic polymer applied to the recording medium is not particularly limited as long as it is an amount sufficient to stabilize the ink composition. However, since the ink composition can be easily fixed, 0.5 g / m ² to 4.0 g / m ² is preferable, and 0.9 g / m ^{2 to} 3.75 g / m ² is more preferable.

(Other ingredients)
The treatment liquid may contain a fixing agent that can agglomerate the ink composition other than the cationic polymer. As the fixing agent, an acidic compound or a polyvalent metal compound may be added as long as the effects of the present invention are not impaired.

  The treatment liquid may generally contain a water-soluble organic solvent, and may further contain other various additives. The details of the water-soluble organic solvent and other various additives are the same as those in the ink composition.

1.0-10.0 are preferable and, as for pH of the said processing liquid, 2.0-9.0 are more preferable. As the pH of the treatment liquid, a value measured at 25 ° C. using a pH meter WM-50EG manufactured by Toa DDK Co., Ltd. is adopted.
The surface tension of the treatment liquid is preferably 20 mN / m to 60 mN / m from the viewpoint of the aggregation rate of the ink composition. More preferably, it is 25mN-50mN / m, More preferably, it is 25mN / m-45mN / m. As the surface tension of the treatment liquid, a value measured at 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) is adopted.
The viscosity of the treatment liquid is preferably 1 to 30 mPa · s, more preferably 1 to 20 mPa · s, still more preferably 2 to 15 mPa · s, and particularly preferably 2 to 10 mPa · s from the viewpoint of the aggregation rate of the ink composition. preferable. As the viscosity of the treatment liquid, a value measured at 25 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) is adopted.

<Image forming method>
[Image Forming Method According to First Aspect]
The image forming method of the present invention according to the first aspect includes an ink application step of applying the above-described ink composition to a recording medium by an inkjet method. The image forming method may further include other steps as necessary.
By using the ink composition described above, the image forming method is excellent in maintainability and excellent in the abrasion resistance of an image formed after the ink has elapsed.

(Ink application process)
In the ink application step, the ink composition is applied to a recording medium by an inkjet method. The constitution and preferred embodiments of the ink composition used in this step are as described above.

There is no restriction | limiting in particular in the inkjet method which discharges an ink composition from an inkjet head. Known methods, for example, charge control method that ejects ink using electrostatic attraction force, drop-on-demand method (pressure pulse method) that uses vibration pressure of piezo element, electric signal is converted into acoustic beam and ink is irradiated The acoustic ink jet method that ejects ink using radiation pressure, and the thermal ink jet (bubble jet (registered trademark)) method that uses ink to form bubbles by heating the ink, Also good.
The inkjet method uses a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method used is included.
As the ink jet head (hereinafter also referred to as “head”), a known one can be applied, and for example, a continuous type or a dot on demand type can be used.

(Ink drying process)
The image forming method may include an ink drying step for drying and removing an ink solvent (for example, water, a water-soluble organic solvent, etc.) in the ink composition applied on the recording medium, if necessary. . The ink drying step is not particularly limited as long as at least a part of the ink solvent can be removed, and a commonly used method can be applied.

(Immobilization process)
The image forming method preferably further includes an immobilization step of immobilizing the image formed in the ink application step on a recording medium. The fixing step is preferably a heat and pressure fixing step for melting and fixing resin particles that may be contained in the ink composition. The heat and pressure fixing step is not particularly limited as long as it is a method capable of melting and fixing the resin particles contained in the ink composition, and can be appropriately selected according to the purpose.
For example, the heat and pressure fixing process described in Japanese Patent Application Laid-Open No. 2004-174981 can be applied to the present invention.

[Image Forming Method According to Second Aspect]
The image forming method of the present invention according to the second aspect uses the ink set described above, an ink applying step of applying an ink composition in the ink set to a recording medium by an ink jet method, and the ink set And a treatment liquid application step for applying the treatment liquid to the recording medium. The image forming method may further include other steps as necessary.
By using the above-described ink set, the image forming method is excellent in maintainability and excellent in abrasion resistance of an image formed after the ink has elapsed.

  In the image forming method, either the treatment liquid application process or the ink application process may be performed in advance. In the present invention, an embodiment in which an ink application process is provided after the treatment liquid application process is preferable. Specifically, an embodiment in which a treatment liquid is applied on a recording medium in advance before applying the ink composition, and the ink composition is applied so as to come into contact with the treatment liquid applied on the recording medium. . Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

  The ink application process in the image forming method according to the second aspect is the same as the ink application process in the image formation method according to the first aspect, and the preferred aspects are also the same. Moreover, you may provide the said ink drying process and the said fixing process as needed.

(Processing liquid application process)
In the treatment liquid application step, a treatment liquid containing a cationic polymer that is a component for aggregating the components in the ink composition is applied to the recording medium. The configuration and preferred embodiments of the treatment liquid used in this step are as described above.

For applying the treatment liquid onto the recording medium, a known liquid application method can be used without any particular limitation. For example, an arbitrary method such as a coating method, an ink jet method, or an immersion method can be selected.
The area to which the treatment liquid is applied is a partial application that is applied to the entire area of the recording medium, even if it is applied to the entire recording medium. May be. In the present invention, from the viewpoint of uniformizing the application amount of the treatment liquid, it is preferable to apply the entire surface to the entire recording medium by application using an application roller or the like.

The application amount of the treatment liquid is not particularly limited as long as the ink composition can be aggregated. For example, the application amount of the aggregation agent is preferably 0.5 g / m ^{2 to} 4.0 g / m ^{2, and} preferably 0.9 g / m ^2. m ^{2 to} 3.75 g / m ² is more preferable.

[recoding media]
Examples of the recording medium used in the image forming method of the present invention include known image receiving materials, that is, plain paper, resin-coated paper, ink jet paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics and the like.

In the image forming method of the present invention, it is preferable to use a coated paper used for general offset printing or the like as a recording medium. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated.
These general printing papers are liable to cause quality problems such as image bleeding and abrasion resistance in image formation by an inkjet method using ordinary water-based ink. According to the image forming method of the present invention, it is possible to prevent image bleeding and density unevenness and to form an image having good abrasion resistance.

  The coated paper can be obtained and used on the market. For example, coated paper (A2, B2) such as “OK Top Coat +” manufactured by Oji Paper Co., “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd. A1).

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

[Preparation of pigment dispersion 1]
10 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 ml / 100 g and 3.41 g of p-aminobenzoic acid were mixed well with 72 g of water, and then 1.62 g of nitric acid was added dropwise thereto at 70 ° C. Stir. Several minutes later, a solution of 1.07 g of sodium nitrite dissolved in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was Toyo Filter Paper No. 2 (manufactured by Advantis), the pigment particles were sufficiently washed with water and dried in an oven at 90 ° C. To 23.9 g of this pigment, 7.2 g of triethylamine and water (amount for adjusting the pigment concentration to a predetermined concentration) were mixed to obtain a pigment dispersion 1 having a pigment concentration of 10% by mass. As shown in the following formula, the self-dispersing pigment contained in the pigment dispersion 1 has a carboxylate group bonded to the surface via a phenylene group and is anionicly charged.

[Preparation of pigment dispersion 2]
In the preparation of pigment dispersion 1, triethylamine was changed to triethanolamine to prepare pigment dispersion 2.

[Preparation of pigment dispersion 3]
In preparing the pigment dispersion 1, the pigment dispersion 3 was prepared by changing the carbon black to the magenta pigment pigment red 122.

[Preparation of pigment dispersion 4]
In preparing the pigment dispersion 1, the pigment dispersion 4 was prepared by changing carbon black to magenta pigment pigment 122 and changing triethylamine to triethanolamine.

[Preparation of pigment dispersion 5]
In preparing the pigment dispersion 1, the pigment dispersion 5 was prepared by changing the carbon black to yellow pigment pigment yellow 74.

[Preparation of pigment dispersion 6]
In preparing the pigment dispersion 1, pigment dispersion 6 was prepared by changing the carbon black to cyan pigment pigment blue 15: 3.

[Preparation of pigment dispersion 7]
(Resin-coated pigment dispersion)
10 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 ml / 100 g, 4 g of benzyl methacrylate / methacrylic acid (= 90/10 [mass ratio]) copolymer, 20 g of methyl ethyl ketone, and 1 N aqueous NaOH solution 4 2 g and 100.8 parts of ion-exchanged water were mixed and dispersed in a bead mill using 0.1 mmφ zirconia beads for 2 to 6 hours. Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed. Thus, a pigment dispersion 7 containing resin-coated carbon black particles having a carbon black concentration of 10.2% by mass was obtained.

[Preparation of pigment dispersion 8]
In the preparation of pigment dispersion 1, triethylamine was changed to sodium hydroxide to prepare pigment dispersion 8.

[Preparation of Pigment Dispersion 9]
In the preparation of pigment dispersion 1, triethylamine was replaced with potassium hydroxide to prepare pigment dispersion 9.

[Preparation of pigment dispersion 10]
In the preparation of pigment dispersion 1, triethylamine was changed to diethylamine to prepare pigment dispersion 10.

[Preparation of Pigment Dispersion 11]
In the preparation of pigment dispersion 2, pigment dispersion 11 was prepared by changing the amount of triethanolamine added to 10.6 g.

[Preparation of Pigment Dispersion 12]
In the preparation of pigment dispersion 2, pigment dispersion 12 was prepared by changing the amount of triethanolamine added to 10.6 g.

[Preparation of Latex Liquid PL-1]
To 120 g of water, latemul ASK (manufactured by Kao Corporation, carboxylate-based emulsifier) 19.8 g, 5 mol / L aqueous sodium hydroxide solution 6 g, and 2,2′-azobis (2-amidinopropane) dihydrochloride 3 g was added and dissolved uniformly. The mixture was heated to 70 ° C., and a monomer mixture of 25.9 g of styrene, 26.3 g of butyl acrylate, and 5.1 g of acrylic acid was added over 2 hours under a nitrogen stream. Then, it heated at 70 degreeC for 2 hours and 80 degreeC for 3 hours. After cooling to room temperature, a 1 mol / L aqueous sodium hydroxide solution was added with stirring so that the pH was around 9, and latex solution PL-1 was obtained. The solid content of the latex liquid PL-1 was 33% by mass. The resin particles contained had a volume average particle size of 115 nm. The particle diameter of the resin particles was measured by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

[Preparation of Treatment Solution 1]
Each material was mixed with the following composition, and the processing liquid 1 was prepared. The pH of the treatment liquid 1 at 25 ° C. was 4.5 when measured using a pH meter WM-50EG manufactured by Toa DKK Co., Ltd.
"composition"
-Polyguanidine-4.0 parts-Trimethylolpropane-10.0 parts-Olphine E1010-1.0 parts-2-Ethyl-1,3-hexanediol-2.0 parts- Sodium dehydroacetate: 0.2 parts ・ Ion-exchanged water: Remaining amount of 100 parts

[Preparation of treatment liquid 2]
In the preparation of the treatment liquid 1, polyguanidine was changed to polyethyleneimine to prepare a treatment liquid 2. The pH (25 ° C.) of the treatment liquid 2 was 2.4.

[Preparation of treatment liquid 3]
In the preparation of the treatment liquid 1, polyguanidine was changed to polydiallylamine hydrochloride to prepare a treatment liquid 3. The pH (25 ° C.) of the treatment liquid 3 was 5.6.

<Example 1>
[Preparation of water-based ink]
Each material was mixed with the following composition, and it filtered with the PVDF 5 micrometer filter (Millipore SV, Millex SV, diameter 25mm) with the plastic disposable syringe, and prepared the water-based ink. The pH of this water-based ink at 25 ° C. was 8.9 when measured using a pH meter WM-50EG manufactured by Toa DKK.
"composition"
・ Pigment dispersion 1 ・ ・ ・ 38.2 parts ・ Latex liquid PL-01 ・ ・ ・ 8 parts ・ Triethylene glycol monobutyl ether ・ ・ ・ 20 parts ・ 2-pyrrolidone ・ ・ ・ 10 parts ・ Orphine E1010 ・ ・ ・ 1 (Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant)
・ Ion-exchanged water ... 22.8 parts

  The neutralization degree of the carboxylic acid group on the surface of the self-dispersing pigment contained in the aqueous ink obtained above was determined by neutralization titration. Neutralization titration uses a water-soluble organic solvent in the “composition” of the water-based ink (in the above case, a mixed solution in which triethylene glycol monobutyl ether and 2-pyrrolidone are mixed at a ratio [mass ratio] of 20:10). The pigment dispersion 1 was diluted to a pigment concentration of 5% by mass, and neutralization titration was performed using hydrochloric acid adjusted to 0.1 mol / L using the same water-soluble organic solvent. At this time, titration was started after the initial pH was set to 12 or more with NaOH, and the titration was terminated when the pH became 2 or less. The degree of neutralization was determined by setting the acid amount from the first inflection point of the obtained titration curve to complete neutralization as 100% neutralization.

[Evaluation of water-based ink and ink set]
The aqueous ink obtained above and the treatment liquid 1 were combined to produce an ink set. The following evaluation was performed using only water-based ink (referred to as a one-component system) and an ink set (referred to as a two-component system). The evaluation results are shown in Table 1.

(Clear white)
As an ink jet recording apparatus, an ink jet apparatus provided with a prototype print head (piezo element) of 600 dpi and 256 nozzles was prepared, and an ink set was loaded. FX-L paper (Fuji Xerox Co., Ltd.) was used as the recording medium.
The treatment liquid and the water-based ink were ejected from different heads on FX-L paper for 60 minutes in the order of water-based ink only in the case of the one-liquid system and in the order of treatment liquid → water-based ink in the case of the two-liquid system. Thereafter, as a maintenance work, the print head was pressurized with a pressure of 15 KPa for 10 seconds, and then wiped with a clean wiper FF-390c (manufactured by Kuraray Co., Ltd.). Thereafter, the discharge was further continued for 5 minutes, and the image (5 cm × 5 cm) recorded on the FX-L paper after 5 minutes was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: No white spots were observed.
B: Occurrence of white spots was 1 to 2 places.
C: There were 3 to 10 white spots.
D: The occurrence of white spots was 11 to 20 places.
E: Occurrence of white spots exceeded 20 points, and there was a problem in practical use.

(Ink rub resistance before aging)
An ink jet device equipped with a GELJET GX5000 printer head (full line head manufactured by Ricoh) was prepared, and an ink set was loaded. Tokishi Art Double Sided N (manufactured by Mitsubishi Paper Industries Co., Ltd.) is fixed as a recording medium on a stage that can move in a predetermined linear direction at 500 mm / second, and the treatment liquid 1 is discharged onto the stage at 5 pL per 50 μm square. And dried at 50 ° C. for 2 seconds. However, in the case of one liquid system, the process liquid discharge process was omitted.
Thereafter, the GELJET GX5000 printer head is fixedly arranged so that the direction of the line head in which the nozzles are arranged (main scanning direction) is inclined by 75.7 ° with respect to the direction orthogonal to the moving direction of the stage (sub scanning direction). Then, while moving the recording medium at a constant speed in the sub-scanning direction, the ink droplet amount is 3.5 pL, the discharge frequency is 24 kHz, the discharge method is a line method under a discharge condition of 1200 dpi × 600 dpi, and a solid image is printed to obtain an evaluation sample. It was. Immediately after printing, it was dried at 60 ° C. for 5 seconds.
Wrapped unprinted special diamond art double-sided N cut to 10mm x 50mm around paperweight (weight 470g, size 15mm x 30mm x 120mm) (area of contact between unprinted special diamond art double-sided N and evaluation sample is 150mm ² ), And the evaluation sample was rubbed 3 times (corresponding to a load of 260 kg / m ² ). The marking screen after rubbing was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Image peeling on the printed surface was not visible at all.
B: The peeling of the image on the printed surface was about 1 to 2 places and was hardly found with the naked eye.
C: Slight peeling of the image on the printed surface was observed, but there was no practical problem.
D: The peeling of the image on the printing surface was easily visually recognized.
E: Level at which image peeling on the printed surface can be visually recognized and has a practical problem.

(Ink rub resistance after time)
The aqueous ink was aged at 60 ° C. for 7 days, and the ink rub resistance after aging was evaluated in the same manner as the ink rub resistance before aging.

<Example 2>
In Example 1, except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 2, triethylene glycol monobutyl ether was changed to diethylene glycol monobutyl ether, and 2-pyrrolidone was changed to N-methyl-2-pyrrolidone. A water-based ink was prepared in the same manner as in Example 1. The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 3>
A water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 3 in Example 1. The pH (25 ° C.) of this water-based ink was 8.2. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 4>
In Example 1, a water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 5 and triethylene glycol monobutyl ether was changed to dipropylene glycol monobutyl ether. . The pH (25 ° C.) of this water-based ink was 8.5. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 5>
In Example 1, the pigment dispersion 1 contained in the aqueous ink was changed to the pigment dispersion 6, triethylene glycol monobutyl ether was changed to dipropylene glycol monobutyl ether, and 2-pyrrolidone was changed to N-methyl-2-pyrrolidone. A water-based ink was prepared in the same manner as in Example 1 except for the above. The pH (25 ° C.) of this water-based ink was 8.3. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 6>
In Example 1, the water-based ink was prepared in the same manner as in Example 1 except that triethylene glycol monobutyl ether contained in the water-based ink was changed to dipropylene glycol monobutyl ether and 2-pyrrolidone was changed to N-methyl-2-pyrrolidone. Prepared. The pH (25 ° C.) of this water-based ink was 8.5. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 7>
In Example 1, a water-based ink was prepared in the same manner as in Example 1, except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 2 and triethylene glycol monobutyl ether was changed to dipropylene glycol monomethyl ether. . The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 8>
A water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 2 and triethylene glycol monobutyl ether was changed to dipropylene glycol. The pH (25 ° C.) of this water-based ink was 8.7. Then, evaluation was performed in the same manner as in Example 1 in which an ink set was prepared by combining with the treatment liquid 1. The evaluation results are shown in Table 1.

< Reference Example 9>
A water-based ink was prepared in the same manner as in Example 1 except that triethylene glycol monobutyl ether contained in the water-based ink was changed to ethylene glycol. The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

< Reference Example 10>
A water-based ink was prepared in the same manner as in Example 1, except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 4 and 2-pyrrolidone was changed to dimethyl sulfoxide. The pH (25 ° C.) of this water-based ink was 8.2. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Example 11>
Each material was mixed with the following composition, and it filtered with the PVDF 5 micrometer filter (Millipore SV, Millex SV, diameter 25mm) with the plastic disposable syringe, and prepared the water-based ink. The pH of this water-based ink at 25 ° C. was 8.5 when measured using a pH meter WM-50EG manufactured by Toa DKK. Then, an ink set was prepared by combining with the treatment liquid 2 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.
"composition"
・ Cabojet300 ... 38.2 parts (manufactured by Cabot, surface modified pigment, containing carboxylic acid group)
・ Latex fluid PL-01 ・ ・ ・ 8 parts ・ Dipropylene glycol ・ ・ ・ 15 parts ・ 2-Pyrrolidone ・ ・ ・ 5 parts ・ Triethylamine ・ ・ ・ 10 parts ・ Orphine E1010 ・ ・ ・ 1 part (Nisshin Chemical Industry ( Co., Ltd., acetylene glycol surfactant)
・ Ion-exchanged water ... 22.8 parts

<Comparative Example 1>
Each material was mixed with the following composition, and it filtered with the PVDF 5 micrometer filter (Millipore SV, Millex SV, diameter 25mm) with the plastic disposable syringe, and prepared the water-based ink. The pH of this water-based ink at 25 ° C. was 8.5 when measured using a pH meter WM-50EG manufactured by Toa DKK. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.
"composition"
・ Pigment dispersion 7 (resin-coated pigment dispersion) 38.2 parts ・ Latex liquid PL-01 8 parts ・ Dipropylene glycol monobutyl ether 15 parts ・ 2-pyrrolidone 5 parts・ Triethanolamine: 10 parts ・ Orphine E1010: 1 part (Nisshin Chemical Industry Co., Ltd., acetylene glycol surfactant)
・ Ion-exchanged water ... 22.8 parts

<Comparative Example 2>
In Example 11, Cabojet 300 contained in the water-based ink was changed to Cabojet 200 (manufactured by Cabot, surface modified pigment, sulfonic acid group-containing), and dipropylene glycol was changed to triethylene glycol monobutyl ether. A water-based ink was prepared as described above. The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 3 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative Example 3>
A water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 8 and triethylene glycol monobutyl ether was changed to dipropylene glycol. The pH (25 ° C.) of this water-based ink was 8.2. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative Example 4>
A water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 9 and triethylene glycol monobutyl ether was changed to dipropylene glycol. The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative Example 5>
A water-based ink was prepared in the same manner as in Example 1 except that the pigment dispersion 1 contained in the water-based ink was changed to the pigment dispersion 10 in Example 1. The pH (25 ° C.) of this water-based ink was 8.4. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative Example 6>
A water-based ink was prepared in the same manner as in Example 7, except that the pigment dispersion 2 contained in the water-based ink was changed to the pigment dispersion 11 in Example 7. The pH (25 ° C.) of this water-based ink was 8.3. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

<Comparative Example 7>
A water-based ink was prepared in the same manner as in Example 2 except that the pigment dispersion 2 contained in the water-based ink was changed to the pigment dispersion 12 in Example 2. The pH (25 ° C.) of this water-based ink was 8.45. Then, an ink set was prepared by combining with the treatment liquid 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 11, abnormal discharge due to adhesion of an ink fixed matter derived from the ink composition to the head is prevented, and occurrence of whiteout failure in a recorded image is prevented. I was able to suppress it. In addition, the ink adhering matter generated by mixing the ink composition and the treatment liquid can be easily removed, thereby facilitating maintenance.
On the other hand, in Comparative Examples 1 to 7, ink ejection abnormality could not be prevented and the occurrence of white spot failure could not be suppressed.

  As shown in Table 1, in Examples 1 to 11, ink rub resistance before and after ink aging was good. On the other hand, in Comparative Examples 1 to 7, ink rub resistance before and after ink aging was poor.

Claims (9)

A self-dispersing pigment having a carboxylic acid group bonded to the surface of the pigment directly or through another atomic group, a tertiary amine, a water-soluble organic solvent, and water;
The water-soluble organic solvent includes a solvent having an SP value of 27.5 or less and a polar solvent that is at least one selected from 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. In a ratio of 12: 1 to 12: 8,
An ink composition in which 50 to 90 mol% of carboxylic acid groups on the surface of the self-dispersing pigment are neutralized with the tertiary amine.   The ink composition according to claim 1, wherein the tertiary amine is at least one of triethylamine and triethanolamine.   The solvent having an SP value of 27.5 or less is at least one selected from dipropylene glycol, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monobutyl ether. The ink composition according to claim 1 or 2. The ink composition according to any one of claims 1 to 3 , wherein the pigment constituting the self-dispersing pigment includes at least one selected from a magenta pigment, a cyan pigment, a yellow pigment, and a black pigment. The ink composition according to any one of claims 1 to 4 , wherein the pigment constituting the self-dispersing pigment includes at least one selected from Pigment Yellow 74, Pigment Red 122, and Pigment Blue 15: 3. object. An ink comprising the ink composition according to any one of claims 1 to 5 and a treatment liquid containing a cationic polymer and aggregating components in the ink composition when contacted with the ink composition. set. The ink set according to claim 6 , wherein the cationic polymer includes at least one polyguanidine. An image forming method comprising an ink application step of applying the ink composition according to any one of claims 1 to 5 to a recording medium by an inkjet method. An ink application process using the ink set according to claim 6 or 7 , applying an ink composition in the ink set to a recording medium by an inkjet method, and applying a treatment liquid in the ink set to the recording medium An image forming method comprising a liquid application step.