# Patent

## Title
Image recording method

## Abstract

An image recording method includes applying an ink containing a pigment and polymer particles to a region of a recording medium, and applying a liquid composition capable of destabilizing the dispersion of the pigment in the ink to the recording medium so as to cover at least part of the region of the recording medium. The liquid composition contains 6.0% by mass or more of at least one surfactant selected from the group consisting of the compounds expressed by General Formula (1) and the compounds expressed by General Formula (2) relative to the total mass of the liquid composition. The content of the polymer particles in the ink is 1.0% by mass or more relative to the total mass of the ink.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording method.
2. Description of the Related Art
For recording an image, two-liquid reaction systems have been studied which use an ink and a liquid composition containing a reaction agent capable of destabilizing the dispersion of the pigment in the ink. Among such two-liquid reaction systems, a system using an ink containing polymer particles has been studied (Japanese Patent Laid-Open Nos. 7-32721, 2010-31267, 2010-46918, and 2011-178033).
On the other hand, an image recording method (single-liquid reaction system) not using a liquid composition has been studied for recording high-density, high-quality images (Japanese Patent Laid-Open No. 2012-92317). This method takes advantage of the nature of the ink itself to react. Japanese Patent Laid-Open No. 2012-92317 discloses an image recording method using an ink containing a pigment, polymer particles, and a block copolymer having an ethylene oxide structure and a propylene oxide structure. This block copolymer gelates at a specific temperature (gelation temperature) or more. This patent document describes that the ink aggregates rapidly by being applied to a recording medium heated to the gelation temperature or more.
In the studies of the present inventors, however, the image recording methods using the two-liquid reaction systems of the above-cited patent documents did not provide high-quality images when recording was performed at such a high speed as to meet recent demand. Also, in the above-cited single-liquid reaction system, the apparatus for this method tends to become large because the recording medium must be heated.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides an image recording method using a two-liquid reaction system that can provide high-quality images without heating the recording medium.
According to an aspect of the invention, an image recording method is provided which includes applying an ink containing a pigment and polymer particles to a region of a recording medium, and applying a liquid composition capable of destabilizing the dispersion of the pigment in the ink to the recording medium so as to cover at least part of the region of the recording medium. The liquid composition contains 6.0% by mass or more of at least one surfactant selected from the group consisting of the compounds expressed by general formula (1) and the compounds expressed by general formula (2) relative to the total mass of the liquid composition. The content of the polymer particles in the ink is 1.0% by mass or more relative to the total mass of the ink.




where l and n are numerals with “l+n” being 3 or more and 45 or less, and m represents a numeral of 16 or more and 57 or less.




where p and r are numerals with “p+r” being 25 or more and 50 or less, and q represents a numeral of 8 or more and 25 or less.
Further features of the present invention will become apparent from the following description of exemplary embodiments.


DESCRIPTION OF THE EMBODIMENTS
The present invention will be further described using exemplary embodiments.
The present inventors investigated why the known two-liquid reaction systems did not provide high-quality images when recording was performed at such a high speed as to meet recent demand. The results are as below.
Known image recording methods using a two-liquid reaction system are designed to increase the reactivity between the ink and the liquid composition and thus to prevent blotting or bleeding effectively. More specifically, the constituents and their contents of the ink and the liquid composition are controlled so that the pigment can aggregate rapidly when the ink and the liquid composition come into contact with each other. In a high-speed recording, the time interval between the applications of the ink and the liquid composition is very small, and accordingly, the ink and the liquid composition may be mixed in a state in which they are both liquid. The inventors found that if the reactivity between the ink and the liquid composition are excessively high, a phenomenon (image migration) occurs when they are mixed, in which the pigment aggregates to decrease in volume and the volume-decreased aggregate moves from the region where the ink and the liquid composition have been applied and is fixed to a region different from the desired region.
The present inventors have studied a method for reducing the phenomenon of image migration and reached the concept of the invention. More specifically, in an embodiment of the invention, the liquid composition used in combination with an ink containing a pigment and polymer particles contains 5% by mass or more of at least one surfactant selected from the group consisting of the compounds expressed by General Formula (1) and the compounds expressed by General Formula (2).




In General Formula (1), l and n are numerals with “l+n” being 3 or more and 45 or less, and m represents a numeral of 16 or more and 57 or less.





In General Formula (2), p and r are numerals with “p+r” being 25 or more and 50 or less, and q represents a numeral of 8 or more and 25 or less.

The following mechanism of the combination of the ink and the liquid composition produces an advantageous effect.
Although the surfactants expressed by General Formula (1) or (2) have a hydrophilic ethylene oxide structure (CH2CH2O) and a less hydrophilic propylene oxide structure (CH2CH(CH3)O), thus acting as a surfactant, the function of these surfactants is weaker than typical surfactants. Therefore, when a surfactant of General Formula (1) or (2) is present with a pigment or polymer particles, the surfactant is likely to adsorb the surfaces of the pigment particles or polymer particles rather than is oriented to the gas-liquid interface. When the ink and the liquid composition are mixed, therefore, aggregation reaction of the pigment and polymer particles of the ink occurs with the surfactant of general formula (1) or (2) adsorbed to the surfaces of the pigment and polymer particles. At this time, while the aggregation reaction itself occurs rapidly, the volume of the aggregate is unlikely to decrease because the surfactant is confined among the pigment and polymer particles. Probably, image migration is thus suppressed.
The studies of the present inventors teach that when the content of the surfactant, or at least one surfactant selected from the group consisting of the compounds of General Formulas (1) and (2), in the liquid composition is 6.0% by mass or more while the content of the polymer particles in the ink is 1.0% by mass or more, image migration can be suppressed effectively. If the surfactant content is less than 6.0% by mass, or if the polymer particles content in the ink is less than 1.0%, the aggregate decreases in volume and results in image migration.
As in such a mechanism, the constituents and their contents of the ink and liquid composition interact synergetically with each other and thus produce an effect advantageous in solving the issue described above.
Image Recording Method
The image recording method according to an embodiment of the invention includes Step (A) of applying the ink to a region of a recording medium, and Step (B) of applying the liquid composition to the recording medium so as to cover at least part of the region to which the ink is applied.
In the present embodiment, the ink may be applied by an ink jet recording method that includes the step of discharging the ink from an ink jet recording head according to recording signals. In particular, an ink jet recording method is advantageous in which the ink is discharged through ejection openings of a recording head by thermal energy applied to the ink. The liquid composition is applied to the recording medium by, for example, an ink jet method or a coating method. Exemplary techniques for the coating method include roller coating, bar coating, and spray coating. The term “recording” mentioned herein includes the operation of recording on a recording medium such as glossy paper or plain paper, and the operation of printing on an impermeable recording medium such as a glass or plastic sheet or a plastic film.
In the present embodiment, Step (A) may be performed before Step (B), or Step (B) may be performed before Step (A). Also, if the same step is performed twice or more, the two steps may be performed, for example, in this order: Step (A), Step (B), and Step (A); or Step (B), Step (A) and Step (B). In particular, the operation of performing Step (A) after Step (B) is advantageous in enhancing image quality.
Set of Ink Jet Ink and Liquid Composition
The ink used in the present embodiment in combination with the liquid composition is not particularly limited, and may be a cyan ink, a magenta ink, a yellow ink, or a black ink. An image recording method of the present embodiment and a set of an ink and a liquid composition used in the image recording method will now be described. In the following description, “(meth)acrylic acid” refers to acrylic acid and methacrylic acid, and “(meth)acrylate” refers to acrylate and methacrylate.
Ink
The ink used in the image recording method of the present embodiment contains a pigment and polymer particles.
Resin Particles
The polymer particles mentioned herein refer to a polymer having particle sizes dispersed in a solvent. In the present embodiment, the particle size of the polymer particles is preferably 10 nm or more and 1,000 nm or less, and more preferably 100 nm or more and 500 nm or less, in terms of volume median particle size (D50). The median particle size D50 of the polymer particles can be measured as below. The dispersion of the polymer particles is diluted to 50 times (on a volume basis) with pure water and subjected to measurement with UPA-EX150 (manufacture by Nikkiso) under the conditions: SetZero of 30 s; number of measurements of 3; measurement time of 180 s; and refractive index of 1.5.
Preferably, the polymer particles have a polystyrene-equivalent weight average molecular weight of 1,000 or more and 2,000,000 or more, measured by gel permeation chromatography (GPC).
The content of the polymer particles in the ink is 1.0% by mass or more relative to the total mass of the ink. Preferably, the polymer particle content in the ink is 1.0% by mass or more and 50.0% by mass or less, such as 2.0% by mass or more and 40.0% by mass or less, relative to the total mass of the ink.
In addition, the mass ratio of the polymer particles to the pigment in the ink is preferably 0.2 or more and 20 or less.
Any polymer particles may be used in the ink of the present embodiment as long as under the above-mentioned condition. For producing the polymer particles, any monomers can be used, as long as capable of being polymerized by emulsion polymerization, suspension polymerization, dispersion polymerization, or the like. Exemplary polymer particles, different in monomer, include particles of acrylic polymer, vinyl acetate polymer, ester, ethylene, urethane polymer, synthetic rubber, vinyl chloride polymer, vinylidene chloride polymer, and olefin polymer. Among these, acrylic polymer particles and urethane polymer particles are advantageous.
The polymer particles may be made of an anionic polymer. Anionic polymer particles can react with a reaction agent in the liquid composition, described later, to facilitate the aggregation of the polymer particles.
For acrylic polymer particles, exemplary monomers include α,β-unsaturated carboxylic acids and salts thereof, such as (meth)acrylic acid, maleic acid, crotonic acid, angelic acid, itaconic acid, and fumaric acid; α,β-unsaturated carboxylic acid esters, such as ethyl (meth)acrylate, methyl (meth)acrylate, butyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, monobutyl maleate, and dimethyl itaconate; α,β-unsaturated carboxylic acid alkylamides, such as (meth)acrylamide, dimethyl(meth)acrylamide, N,N-dimethylethyl(meth)acrylamide, N,N-dimethylpropyl(meth)acrylamide, isopropyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acryloyl morpholine, maleic acid monoamide, and crotonic acid methylamide; aryl group-containing α,β-ethylenic unsaturated compounds, such as styrene, α-methylstyrene, phenylvinyl acetate, benzyl (meth)acrylate, and 2-phenoxyethyl (meth)acrylate; and esters of polyfunctional alcohols, such as ethylene glycol diacrylate and polypropylene glycol dimethacrylate. The polymer particles may be made of a homopolymer produced by polymerizing one of these monomers, or a copolymer produced by polymerizing two or more of these monomers. If the polymer particles are made of a copolymer, the copolymer may be a random copolymer or a block copolymer. In particular, polymer particles made of a copolymer of a hydrophilic monomer and a hydrophobic monomer are advantageous. The hydrophilic monomer may be an α,β-unsaturated carboxylic acid or a salt thereof, and the hydrophobic monomer may be an α,β-unsaturated carboxylic acid ester or an α,β-ethylenic unsaturated compound having an aryl group.
Urethane polymer particles are produced by a reaction of a polyisocyanate compound, which has two or more isocyanate groups, and a polyol compound, which has two or more hydroxy groups. In the present embodiment, any of the urethane polymer particles produced by a reaction of a known polyisocyanate compound and a known polyol compound can be used as long as the particle size is within the above-mentioned range.
In structure, the polymer particles may have a single layer structure or a multilayer structure such as a core-shell structure. In the present embodiment, multilayer particles are advantageous. Resin particles having a core-shell structure are particularly advantageous. In polymer particles having a core-shell structure, the core portions and the shell portions have definitely different functions from each other. Resin particles having such a core-shell structure are advantageous in imparting more functions to the ink than polymer particles having a single-layer structure.
Pigment
In the present embodiment, any known pigments may be used as the pigment. The pigment content in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, more preferably 1.0% by mass or more and 10.0% by mass or less, relative to the total mass of the ink.
The pigment may be of polymer-dispersed type that is dispersed with a polymer dispersant (polymer-dispersed pigment using a polymer dispersant, microencapsulated pigment including polymer particles whose surfaces are coated with a polymer, or polymer-bonded pigment including polymer particles having organic groups of a polymer chemically bonded to the surfaces thereof), or may be of self-dispersing type whose particles have hydrophilic groups at the surfaces thereof (self-dispersing pigment). Two or more pigments different in state of dispersion may be used in combination. Exemplary pigments include carbon black and organic pigments. The pigment may be composed of a single pigment or may contain two or more pigments. If the pigment is of polymer dispersed type, a polymer is used as a dispersant. The molecule of the polymer used as the dispersant desirably has a hydrophilic site and a hydrophobic site. Examples of such a polymer include acrylic polymer produced by polymerization using a monomer having a carboxy group, such as acrylic acid or methacrylic acid, and urethane polymer produced by polymerization using a diol having an anionic group, such as dimethylolpropionic acid.
The polymer used as a dispersant has an acid value, preferably, 50 mg KOH/g or more and 550 mg KOH/g or less. The polystyrene-equivalent weight average molecular weight (Mw), measured by gel permeation chromatography (GPC), of the polymer dispersant is preferably 1,000 or more and 50,000 or less.
The polymer dispersant content in the ink may be 0.1% by mass or more and 10.0% by mass or less, preferably 0.2% by mass or more and 4.0% by mass or less. The mass ratio of the polymer dispersant to the pigment is preferably 0.1 or more and 3.0 or less.
Aqueous Medium
The ink may contain water or an aqueous medium that is a mixture of water and a water-soluble organic solvent. If the ink contains an aqueous medium, the water-soluble organic solvent content is preferably 3.0% by mass or more and 50.0% by mass or less relative to the total mass of the ink. Any conventionally used water-soluble organic solvents can be used as the water-soluble organic solvent. Exemplary water-soluble organic solvents include alcohols, glycols, alkylene glycols containing an alkylene group having a carbon number of 2 to 6, polyethylene glycols, nitrogen-containing compounds, and sulfur-containing compounds. These water-soluble organic solvents may be used singly or in combination as required. If the ink contains water, the water is desirably deionized water (ion exchanged water). In this instance, the water content is preferably 50.0% by mass or more and 95.0% by mass or less relative to the total mass of the ink.
Other Constituents
The ink may further contain a water-soluble organic compound that is solid at room temperature, such as trimethylolpropane, trimethylolethane or any other polyhydric alcohol, or urea, ethyleneurea or any other urea derivative, if necessary. Furthermore, the ink may optionally contain other additives, such as a surfactant, a pH adjuster, a corrosion inhibitor, a preservative, an antifungal agent, an antioxidant, an antireductant, an evaporation promoter, a chelating agent, and a polymer other than the above-described polymer particles.
Liquid Composition
The liquid composition is desirably colorless, milky-white or white so as not to affect images recorded with the ink. Accordingly, the absorbance of the liquid composition for wavelengths of visible light of 400 nm or more and 800 nm or less is desirably such that the ratio of the highest absorbance to the lowest absorbance (highest absorbance/lowest absorbance) is 1.0 or more and 2.0 or less. This suggests that the absorbance spectrum of the liquid composition has substantially no peak in the visible region. Even if a peak is exhibited, the intensity of the peak is very low. In addition, the liquid composition desirably does not contain a coloring material. The absorbance of the liquid composition can be obtained by measuring the liquid composition as it is using Hitachi Double Beam Spectrophotometer U-2900 (manufactured by Hitachi High-Technologies). For measuring the absorbance, the liquid composition may be diluted. The highest absorbance and the lowest absorbance are both proportional to dilution rate, and the ratio of the highest absorbance to the lowest absorbance is independent of the dilution rate.
Surfactants Expressed by General Formula (1) or (2)
Surfactants expressed by General Formula (1) or (2) are block copolymers having an ethylene oxide structure and a propylene oxide structure.




In General Formula (1), l and n are numerals with “l+n” being 3 or more and 45 or less, and m represents a numeral of 16 or more and 57 or less.





In General Formula (2), p and r are numerals with “p+r” being 25 or more and 50 or less, and q represents a numeral of 8 or more and 25 or less.

In the present embodiment, the surfactants expressed by General Formula (1) are more advantageous, and it is more advantageous that l+n is 3 or more and 15 or less and m is 16 or more and 31 or less.
In the present embodiment, the content of the surfactant of General Formula (1) or (2) (surfactant content) in the liquid composition is 6.0% by mass or more relative to the total mass of the liquid composition. Preferably, the surfactant content is 20% by mass or more, more preferably 30% by mass or more. Furthermore, the surfactant content is 70% by mass or less from the viewpoint of the reactivity between the ink and the liquid composition. Hence, the surfactant content in the liquid composition is preferably 20% by mass or more and 70% by mass or less relative to the total mass of the liquid composition.
Also, in the image recording method of the present embodiment, the ink and the liquid composition may be applied to a recording medium such that the proportion of the amount of the surfactant of the liquid composition applied to the recording medium is 4 parts by mass or more and 160 parts by mass or less, preferably 15 parts by mass or more and 140 parts by mass or less, relative to the amount of the polymer particles of the ink applied to the recording medium.
Reaction Agent
The liquid composition used in the present embodiment may contain a reaction agent that will destabilize the dispersion of the pigment in the ink. The reaction agent may be selected from known materials and is, advantageously, at least one material selected from the group consisting of organic acids and polyvalent metal ions. A plurality of compounds may be used as the reaction agent.
Examples of the polyvalent metal ions include divalent metal ions, such as Ca2+, Cu2+, Ni2+, Mg2+, Sr2+, Ba2+, and Zn2+; and trivalent metal ions, such as Fe3+, Cr3+, Y3+, and Al3+. Polyvalent metal ions can be added in a hydroxide form or a chloride salt form to the liquid composition, and may be produced by dissociation. The polyvalent ion content is preferably 3% by mass or more and 90% by mass or less relative to the total mass of the liquid composition.
Examples of the organic acids include oxalic acid, polyacrylic acid, formic acid, acetic acid, propionic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, levulinic acid, succinic acid, glutaric acid, glutamic acid, fumaric acid, citric acid, tartaric acid, lactic acid, pyrrolidonecarboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumalic acid, thiophenecarboxylic acid, nicotinic acid, oxysuccinic acid, and dioxysuccinic acid. The organic acid content is preferably 3% by mass or more and 99% by mass or less relative to the total mass of the liquid composition.
Aqueous Medium
The liquid composition of the present embodiment may contain water or an aqueous medium that is a mixture of water and a water-soluble organic solvent. If the liquid composition contains a water-soluble organic solvent, the water-soluble organic solvent content is preferably 3.0% by mass or more and 50.0% by mass or less relative to the total mass of the liquid composition. Any conventionally used water-soluble organic solvents can be used as the water-soluble organic solvent. Exemplary water-soluble organic solvents include alcohols, glycols, alkylene glycols containing an alkylene group having a carbon number of 2 to 6, polyethylene glycols, nitrogen-containing compounds, and sulfur-containing compounds. These water-soluble organic solvents may be used singly or in combination as required. If the liquid composition contains water, the water is desirably deionized water (ion exchanged water). In this instance, the water content is preferably 50.0% by mass or more and 95.0% by mass or less relative to the total mass of the liquid composition.
Other Constituents
The liquid composition may further contain a water-soluble organic compound that is solid at room temperature, such as trimethylolpropane, trimethylolethane or any other polyhydric alcohol, or urea, ethyleneurea or any other urea derivative, if necessary. Furthermore, the liquid composition may optionally contain other additives, such as a surfactant other than the surfactants expressed by General Formula (1) or (2), a pH adjuster, a corrosion inhibitor, a preservative, an antifungal agent, an antioxidant, an antireductant, an evaporation promoter, a chelating agent, and a polymer.
EXAMPLES
The invention will be further described in detail with reference to Examples and Comparative Examples. However, the invention is not limited to the following Examples. In the following Examples, “part(s)” is on a mass basis unless otherwise specified.
Preparation of Inks
Preparation of Pigment Dispersions
Preparation of Black Pigment Dispersion
A batch type vertical sand mill (manufactured by Aimex) was charged with a mixture of 10 parts of carbon black (product name: Monarch 1100, produced by Cabot), 15 parts of a polymer solution (containing 20.0% by mass of styrene-ethyl acrylate-acrylic acid copolymer (acid value: 150, weight average molecular weight: 8,000) in water, neutralized with an aqueous solution of potassium hydroxide), and 75 parts of pure water, and the materials were dispersed in each other with 200 parts of zirconia beads of 0.3 mm in diameter for 5 hours while being cooled with water. The resulting dispersion liquid was centrifuged to remove coarse particles, and thus a black pigment dispersion containing 10.0% by mass of pigment was prepared.
Preparation of Cyan Pigment Dispersion
A cyan pigment dispersion containing 10.0% by mass of a pigment was prepared in the same manner as in the preparation of the black pigment dispersion, except that C. I. Pigment Blue 15:3 was used as the pigment instead of carbon black.
Preparation of Magenta Pigment Dispersion
A magenta pigment dispersion containing 10.0% by mass of a pigment was prepared in the same manner as in the preparation of black pigment dispersion, except that C. I. Pigment Red 122 was used as the pigment instead of carbon black.
Preparation of Resin Particle Dispersion
The mixture of 18 parts of ethyl methacrylate, 2 parts of 2,2′-azobis-(2-methylbutyronitrile), and 2 parts of n-hexadecane was stirred for 0.5 hour. The mixture was dropped to 78 parts of 6% aqueous solution of styrene-butyl acrylate-acrylic acid copolymer (acid value: 130 mg KOH/g, weight average molecular weight: 7,000), followed by stirring for 0.5 hour. Then, the resulting mixture was subjected to supersonic wave irradiation for 3 hours. Subsequently, the mixture was subjected to a polymerization reaction for 4 hours in a nitrogen atmosphere at 80° C., followed by cooling at room temperature. The reaction product was filtered to yield a polymer particle dispersion with a polymer content of 40.0% by mass. The polymer particles in the dispersion had a weight average molecular weight of 250,000, and an average particle size (D50) of 200 nm.
Surfactants
Surfactants shown in Tables 1 and 2 were used. In the column of product name in the Tables, Pluronics are products of Adeka. Also, Newpol PE-78 is a surfactant produced by Sanyokasei.







TABLE 1







Surfactants Expressed by General Formula (1)












   General Formula (1)












Ethylene oxide structure
Propylene oxide structure


Surfactant No.
Product name
l + n
m













Surfactant 1-1
Pluronic L31
3.0
16.4


Surfactant 1-2
Pluronic L34
14.0
16.4


Surfactant 1-3
Pluronic L61
5.3
30.2


Surfactant 1-4
Pluronic P84
43.9
38.8


Surfactant 1-5
Pluronic P103
37.1
56.0


Surfactant 1-6
Pluronic L101
12.1
56.0


Surfactant 1-7
Pluronic P85
53.0
38.8


Surfactant 1-8
Pluronic P123
40.5
66.4


Surfactant 1-9
Pluronic L23
6.0
12.4


Surfactant 1-10
Newpol PE-78
150.0
35.0
















TABLE 2







Surfactants Expressed by General Formula (2)












   General Formula (2)












Ethylene oxide structure
Propylene oxide structure


Surfactant No.
Product name
q
p + r













Surfactant 2-1
Pluronic 25R-2
16.6
47.4


Surfactant 2-2
Pluronic 17R-2
16.6
30.2









Preparation of Inks

Preparation of Black Inks

The above-prepared polymer particle dispersion and pigment dispersion were mixed with the following materials. The “balance” of ion exchanged water is an amount in which the sum of the constituents of the ink becomes 100.0% by mass.
Pigment dispersion (pigment content: 10.0% by mass): 30.0% by mass
Resin particle dispersion (polymer content: 30.0% by mass): X (% by mass) in Table 3.
Glycerin: 10.0% by mass
Acetylenol E 100 (surfactant, produced by Kawaken Fine Chemical): 1.0% by mass
Ion-exchanged water: balance
These materials were sufficiently dispersed in each other, and the resulting mixture was subjected to pressure filtration through a microfilter having a pore size of 3.0 μm (manufactured by Fujifilm). Thus Black Inks 1 to 6 were prepared.







TABLE 3







Black ink Preparation Conditions









Polymer particle dispersion










Black ink

Content
Polymer particle


No.
Type
X
solid content













Black ink 1
Polymer particle dispersion 1
16.7
5.0


Black ink 2
Polymer particle dispersion 1
33.2
10.0


Black ink 3
Polymer particle dispersion 2
16.7
5.0


Black ink 4
—
0
0


Black ink 5
Polymer particle dispersion 1
3.3
1.0


Black ink 6
Polymer particle dispersion 1
2.0
0.6









Preparation of Cyan Inks and Magenta Inks

Cyan Inks 1 to 6 and Magenta Inks 1 to 6 were prepared in the same manner as the Black Inks described above, except that the cyan pigment dispersion or the magenta pigment dispersion was used instead of the black pigment dispersion.
Preparation of Liquid Compositions
The following materials were sufficiently mixed, and the resulting mixture was subjected to pressure filtration through a microfilter having a pore size of 3.0 μm (manufactured by Fujifilm). Thus liquid compositions were prepared. The “balance” of ion exchanged water is an amount in which the sum of the constituents of the liquid composition becomes 100.0% by mass.
Reagent (see Table 4): Y (% by mass) in Table 4
Potassium hydroxide (neutralizer): 3.0% by mass
Surfactant (see Table 4): Z (% by mass) in Table 4
Acetylenol E 100 (surfactant, produced by Kawaken Fine Chemical): 1.0% by mass
Ion-exchanged water: balance







TABLE 4







Liquid composition preparation conditions











Surfactant expressed




by General Formula



Reagent
(1) or (2)











Liquid

Con-

Con-


composition

tent

tent


No.
Compound
Y
Type
Z














Liquid composition 1
Glutaric acid
21.0
Surfactant 1-1
40.0


Liquid composition 2
Glutaric acid
21.0
Surfactant 1-2
40.0


Liquid composition 3
Glutaric acid
21.0
Surfactant 1-3
40.0


Liquid composition 4
Glutaric acid
21.0
Surfactant 1-4
40.0


Liquid composition 5
Glutaric acid
21.0
Surfactant 1-5
40.0


Liquid composition 6
Glutaric acid
21.0
Surfactant 1-6
40.0


Liquid composition 7
Glutaric acid
21.0
Surfactant 2-1
40.0


Liquid composition 8
Glutaric acid
21.0
Surfactant 2-2
40.0


Liquid composition 9
Glutaric acid
21.0
Surfactant 1-1
5.0


Liquid composition 10
Glutaric acid
21.0
Surfactant 1-1
20.0


Liquid composition 11
Glutaric acid
21.0
Surfactant 1-1
70.0


Liquid composition 12
Glutaric acid
21.0
Surfactant 1-1
75.0


Liquid composition 13
Levulinic acid
42.0
Surfactant 1-1
40.0


Liquid composition 14
Malonic acid
21.0
Surfactant 1-1
40.0


Liquid composition 15
Calcium
21.0
Surfactant 1-1
40.0



chloride


Liquid composition 16
Glutaric acid
21.0
—
0


Liquid composition 17
Glutaric acid
21.0
Surfactant 1-7
40.0


Liquid composition 18
Glutaric acid
21.0
Surfactant 1-8
40.0


Liquid composition 19
Glutaric acid
21.0
Surfactant 1-9
40.0


Liquid composition 20
Glutaric acid
21.0
Surfactant 1-10
40.0


Liquid composition 21
Glutaric acid
21.0
Surfactant 1-1
3.0


Liquid composition 22
Glutaric acid
21.0
Surfactant 1-1
6.0









Evaluation of Images

The ink cartridges charged with the inks prepared above were mounted on an image recording apparatus. In the image recording apparatus used for the evaluation, the recording duty of 100% was a condition where one droplet of 3.0 ng of ink is applied to a unit region of 1/1,200 inch× 1/1,200 inch at a resolution of 1,200 dpi×1,200 dpi. Images were recorded in a manner described below, and the quality of the images was evaluated by examining the variation in dot size and the occurrence of image migration. Examination processes and Evaluation criteria were as follows: When either the variation in dot size (diameter) or the occurrence of image migration was rated as C or D, the image quality was judged to be low and unacceptable. The results are shown in Table 5.
Variation in Dot Size
First, each liquid composition was applied to a recording medium (Pearl Coat, manufactured by Mitsubishi Paper Mills) with a coating roller at an application rate of 1.0 g/m2, using the above-described image recording apparatus. Then, a cyan ink was discharged onto the resulting recording medium from an ink jet recording head, thus recording an image (5 cm×5 cm solid pattern) with a recording duty of 100%. Furthermore, a black ink was applied to the region where the solid pattern of the cyan ink was recorded and a region of the recording medium where the solid pattern was not recorded. The dot size (diameter) d1 of the black ink in the region of the cyan solid pattern and the dot size (diameter) d2 of the black ink in the region where the cyan solid patter was not printed were measured, and the dot size ratio (=100×|d1−d2|/d1) was calculated. The results were rated according to the following criteria:
AA: Dot size ratio was less than 5.
A: Dot size ratio was 5 or more and less than 10.
B: Dot size ratio was 10 or more and less than 15.
C: Dot size ratio was 15 or more and less than 20.
D: Dot size ratio was 20 or more.
Occurrence of Image Migration
First, each liquid composition was applied to a recording medium (Pearl Coat, manufactured by Mitsubishi Paper Mills) with a coating roller at an application rate of 1.0 g/m2, using the above-described image recording apparatus. Then, a black ink, a cyan ink and a magenta ink were discharged onto the recording medium having the coating of the liquid composition from an ink jet recording head, thus recording an image (5 cm×5 cm solid pattern) with a recording duty of 300% (100% for each ink). The resulting image was checked for missing color through a microscope. If image migration occurs, a missing color is observed in the solid pattern. The rating criteria were as follows:
A: No missing color was observed.
B: Missing color was observed, but was at an acceptable level.
C: Marked missing color was observed.







TABLE 5







Evaluation of Ink-Liquid Composition Combinations









Evaluation














Black
Cyan
Magenta
Liquid
Dot size
Image


Example No.
ink No.
ink No.
ink No.
composition No.
Variation
migration





Example 1
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 1


Example 2
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 2


Example 3
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 3


Example 4
Black
Cyan
Magenta
Liquid
B
A



ink 1
ink 1
ink 1
composition 4


Example 5
Black
Cyan
Magenta
Liquid
B
A



ink 1
ink 1
ink 1
composition 5


Example 6
Black
Cyan
Magenta
Liquid
B
A



ink 1
ink 1
ink 1
composition 6


Example 7
Black
Cyan
Magenta
Liquid
A
B



ink 1
ink 1
ink 1
composition 7


Example 8
Black
Cyan
Magenta
Liquid
A
B



ink 1
ink 1
ink 1
composition 8


Example 9
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 10


Example 10
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 11


Example 11
Black
Cyan
Magenta
Liquid
B
A



ink 1
ink 1
ink 1
composition 12


Example 12
Black
Cyan
Magenta
Liquid
A
A



ink 2
ink 2
ink 2
composition 1


Example 13
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 13


Example 14
Black
Cyan
Magenta
Liquid
A
A



ink 1
ink 1
ink 1
composition 14


Example 15
Black
Cyan
Magenta
Liquid
A
B



ink 1
ink 1
ink 1
composition 15


Example 16
Black
Cyan
Magenta
Liquid
A
A



ink 3
ink 3
ink 3
composition 1


Example 17
Black
Cyan
Magenta
Liquid
A
B



ink 5
ink 5
ink 5
composition 1


Example 18
Black
Cyan
Magenta
Liquid
B
A



ink 1
ink 1
ink 1
composition 22


Comparative
Black
Cyan
Magenta
Liquid
D
C


Example 1
ink 4
ink 4
ink 4
composition 1


Comparative
Black
Cyan
Magenta
Liquid
D
C


Example 2
ink 1
ink 1
ink 1
composition 16


Comparative
Black
Cyan
Magenta
Liquid
C
B


Example 3
ink 1
ink 1
ink 1
composition 17


Comparative
Black
Cyan
Magenta
Liquid
D
C


Example 4
ink 1
ink 1
ink 1
composition 18


Comparative
Black
Cyan
Magenta
Liquid
C
C


Example 5
ink 1
ink 1
ink 1
composition 19


Comparative
Black
Cyan
Magenta
Liquid
D
B


Example 6
ink 1
ink 1
ink 1
composition 20


Comparative
Black
Cyan
Magenta
Liquid
D
B


Example 7
ink 1
ink 1
ink 1
composition 21


Comparative
Black
Cyan
Magenta
Liquid
D
B


Example 8
ink 6
ink 6
ink 6
composition 1


Comparative
Black
Cyan
Magenta
Liquid
C
A


Example 9
ink 1
ink 1
ink 1
composition 9









While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2013-162390, filed Aug. 5, 2013, which is hereby incorporated by reference herein in its entirety.

## Claims

1. An image recording method comprising:
applying an ink comprising a pigment and a polymer particle to a region of a recording medium; and
applying a liquid composition capable of destabilizing the dispersion of the pigment dispersed in the ink to the recording medium so as to cover at least part of the region of the recording medium;

wherein the content of the polymer particle is 1.0% by mass or more relative to the total mass of the ink, and
wherein the liquid composition comprises at least one surfactant selected from the group consisting of the compounds expressed by General Formula (1) and the compounds expressed by General Formula (2) with a content of 6.0% by mass or more relative to the total mass of the liquid composition:



wherein “l+n” is 3 or more and 45 or less, and m is 16 or more and 57 or less, and




wherein “p+r” is 25 or more and 50 or less, and q is 8 or more and 25 or less.

2. The image recording method according to claim 1, wherein the content of the surfactant in the liquid composition is 20% by mass or more and 70% by mass or less relative to the total mass of the liquid composition.

3. The image recording method according to claim 1, wherein the polymer particle in the ink is an anionic polymer particle.

4. The image recording method according to claim 1, wherein the proportion of the amount of the surfactant applied to the recording medium is 4 parts by mass or more and 160 parts by mass or less relative to 100 parts by mass of the polymer particles applied to the recording medium.

5. The image recording method according to claim 1, wherein the content of the surfactant in the liquid composition is 20% by mass or more relative to the total mass of the liquid composition.

6. The image recording method according to claim 1, wherein the content of the surfactant in the liquid composition is 30% by mass or more relative to the total mass of the liquid composition.

7. The image recording method according to claim 1, wherein the liquid composition comprises a reaction agent for destabilizing the dispersion of the pigment in the ink.

8. The image recording method according to claim 7, wherein the reaction agent is selected from the group consisting of organic acids and polyvalent metal ions.

9. The image recording method according to claim 1, wherein the recording medium is a paper such as glossy paper or plain paper or an impermeable recording medium such as a glass or plastic sheet or a plastic film.