JP2011207985A - Ink set and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set excellent in the sharpness of an image, and capable of forming an image that has excellent light resistance.SOLUTION: The ink set includes: an ink composition that contains a pigment, polymer particles, and a phosphoric acid ester surfactant; and a treatment liquid that contains a cationic polymer that has a nitrogen atom in a main chain.

Description

The present invention relates to an ink set and an image forming method.

  In recent years, paints and inks (hereinafter also referred to as “inks”) are becoming water-based due to increasing needs such as resource protection, environmental protection, and improvement of work stability. The quality required for water-based paints and water-based inks is fluidity, storage stability, gloss of film, vividness, coloring power and the like, similar to oil-based paints and oil-based inks. However, since most pigments are remarkably inferior in suitability for pigment dispersibility and the like as compared with an oily vehicle with respect to an aqueous vehicle, satisfactory quality cannot be obtained by a normal dispersion method. Until now, the use of various additives such as aqueous pigment dispersion resins and surfactants has been studied, but all the above-mentioned suitability is satisfied, and it is comparable to existing high-quality oil-based paints or oil-based inks. No water-based paint or water-based ink has been obtained.

In order to solve such problems, in particular, in order to improve the image quality and light fastness of inkjet printing, printing an inkjet image using an ink containing a pigment and latex and a fixing agent composition containing a cationic polymer. A system for this purpose is disclosed (for example, see Patent Document 1).
Also, a method of recording an image using a recording liquid and a treatment liquid containing a cationic compound is disclosed on the assumption that the recording liquid does not show through and there is no color boundary blurring at a high concentration (see, for example, Patent Document 2). ).

JP 2004-130799 A JP 2002-79739 A

However, it has been difficult to say that the image recording methods described in Patent Documents 1 and 2 are satisfactory in terms of light resistance and image sharpness.
INDUSTRIAL APPLICABILITY The present invention is capable of forming an ink set that is excellent in image sharpness and capable of forming an image having good light resistance, and an image having excellent light resistance while being excellent in image sharpness. It is an object to provide an image forming method.

<1> An ink set comprising: an ink composition containing a pigment, polymer particles, and a phosphate ester-based surfactant; and a treatment liquid containing a cationic polymer having a nitrogen atom in the main chain.
<2> The ink set according to <1>, wherein the treatment liquid further includes a phosphate ester-based surfactant.
<3> The ink set according to <1> or <2>, wherein the treatment liquid further includes an acetylene glycol surfactant.
<4> The ink set according to any one of <1> to <3>, wherein the nitrogen atom of the cationic polymer is a nitrogen atom derived from a secondary amine or a tertiary amine constituting the cationic polymer.
<5> The ink set according to any one of <1> to <4>, wherein a surface tension of the ink composition is 31 mN / m or more and 45 mN / m or less.
<6> The ink set according to any one of <1> to <5>, wherein the ink composition further includes an acetylene glycol surfactant.
<7> A phase inversion having a dispersion step of mixing and dispersing a pigment, a polymer dispersant, water, and an organic solvent as the pigment, and a solvent removal step of removing at least one part of the organic solvent and water after the dispersion. The ink set according to any one of <1> to <6>, comprising a pigment dispersion obtained by an emulsification method.
<8> An ink application step in which the ink set according to any one of <1> to <7> is used, and an ink composition in the ink set is applied to a recording medium;
A treatment liquid application step of applying a treatment liquid in the ink set to a recording medium;
An image forming method comprising:
<9> The image forming method according to <8>, wherein the recording medium is a coated paper having a base paper and a coating layer containing an inorganic pigment.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in the sharpness of an image, the ink set which can form the image which has favorable light resistance can be provided.
Further, according to the present invention, it is possible to provide an image forming method capable of forming an image having excellent image sharpness and excellent light resistance.

[Ink set]
The ink set of the present invention includes an ink composition containing a pigment, polymer particles, and a phosphate ester surfactant, and a cationic polymer having a nitrogen atom in the polymer main chain, and agglomerates the components in the ink composition. And a treatment liquid to be configured.
The ink set of the present invention uses a treatment liquid together with the ink composition. In particular, the ink composition contains a phosphate ester surfactant, and the treatment liquid aggregates dispersed particles such as pigments in the ink composition. By including at least one cationic polymer as an aggregating component capable of forming an aggregate, the inkjet recording can be performed at high speed, and the density and sharpness (for example, fine lines and fine parts) Reproducibility) and an image with excellent light resistance.

<Ink composition>
The ink composition according to the invention is preferably configured to include a pigment, polymer particles, and a phosphate ester surfactant, and further includes an acetylene glycol surfactant. Moreover, it is comprised including other components as needed.

(Pigment)
There is no restriction | limiting in particular as a pigment in this invention, A conventionally well-known organic and inorganic pigment can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, basic Examples include dye lakes such as dye-type lakes and acid dye-type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. Any pigment not described in the color index can be used as long as it can be dispersed in the aqueous phase. Furthermore, it is of course possible to use a pigment whose surface is treated with a surfactant, a resin dispersant (polymer dispersant) or the like, or graft carbon. Among the pigments, it is particularly preferable to use an azo pigment, a phthalocyanine pigment, an anthraquinone pigment, a quinacridone pigment, or a carbon black pigment. Specific examples include pigments described in JP2007-100071A.

~ Polymer dispersant ~
In the ink composition of the present invention, the pigment is preferably dispersed in an aqueous solvent as pigment particles containing the pigment. The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant is preferably dispersed with a water-insoluble polymer dispersant (hereinafter sometimes simply referred to as “dispersant”). The water-insoluble polymer is not particularly limited as long as the pigment can be dispersed, and a conventionally known water-insoluble polymer dispersant can be used. The water-insoluble polymer dispersant can be constituted by including, for example, both a hydrophobic structural unit and a hydrophilic structural unit.

Examples of the monomer constituting the hydrophobic structural unit include styrene monomers, alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like.
Moreover, as a monomer which comprises the said hydrophilic structural unit, if it is a monomer containing a hydrophilic group, there will be no restriction | limiting in particular. Examples of the hydrophilic group include a nonionic group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. In addition, a nonionic group is synonymous with the nonionic group in the below-mentioned self-dispersing polymer.
From the viewpoint of dispersion stability, the hydrophilic structural unit in the present invention preferably contains at least a carboxyl group, and preferably includes a nonionic group and a carboxyl group.

Specific examples of the polymer dispersant include styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic. Examples include acid copolymers, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymers, and styrene-maleic acid copolymers.
Here, “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  The polymer dispersant is preferably a vinyl polymer containing a carboxyl group from the viewpoint of dispersion stability of the pigment, and has a structural unit derived from at least an aromatic group-containing monomer as a hydrophobic structural unit, and is hydrophilic. A vinyl polymer having a structural unit containing a carboxyl group as the structural unit is more preferable.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, and still more preferably 5,000 to 80, from the viewpoint of dispersion stability of the pigment. 1,000, particularly preferably 10,000 to 60,000.

  The content of the polymer dispersant in the pigment particles to be dispersed is preferably 5 to 200% by mass of the polymer dispersant with respect to the pigment from the viewpoint of dispersibility of the pigment, ink colorability, and dispersion stability. 10-100 mass% is more preferable, and 20-80 mass% is especially preferable.

The pigment particles may contain other additives such as other dispersants and surfactants in addition to the water-insoluble polymer dispersant. For example, a conventionally known water-soluble low-molecular dispersant, water-soluble polymer, or the like can be used. The content of the dispersant other than the water-insoluble polymer dispersant can be used within the range of the content of the polymer dispersant.
Moreover, a basic substance (neutralizing agent) can be added to the pigment particles as necessary.

As the basic substance, a neutralizing agent (organic base, inorganic alkali) can be used. For the purpose of neutralizing the dispersant, the basic substance is preferably added so that the composition containing the dispersant has a pH of 7 to 11, more preferably 8 to 10.
As content of a basic substance, it is preferable that it is 50-150 mol% with respect to 100 mol% of ionic groups of a dispersing agent, it is more preferable that it is 70-120 mol%, and it is 80-100 mol%. It is particularly preferred.
Specific examples of the basic substance are the same as those in the self-dispersing polymer particles described above.

  The pigment particles can be obtained as a pigment particle dispersion by dispersing a mixture containing, for example, a pigment, a polymer dispersant, and, if necessary, a solvent (preferably an organic solvent) with a dispersing machine.

The pigment particle dispersion contains a pigment, a dispersant, an organic solvent for dissolving or dispersing the dispersant, and a basic substance, and after mixing a solution containing water as a main component (mixing / hydration step), It is preferable to produce by removing the organic solvent (solvent removal step).
According to this method for producing a pigment particle dispersion, the pigment particle dispersion in which the pigment particles are finely dispersed and excellent in storage stability can be produced.

  The organic solvent in the method for producing a pigment particle dispersion is preferably one that can dissolve or disperse the polymer dispersant, and in addition, preferably has a certain degree of affinity for water. Specifically, the solubility in water at 20 ° C. is preferably 10% by mass or more and 50% by mass or less.

More specifically, the pigment particle dispersion can be produced by a production method including the following steps (1) and (2), but is not limited thereto.
Step (1): A step of dispersing a mixture containing a pigment, a polymer dispersant, an organic solvent for dissolving and dispersing the polymer dispersant, a basic substance, and water. Step (2): Dispersion Removing at least a portion of the organic solvent from the mixture after treatment;

In the step (1), first, the polymer dispersant is dissolved or dispersed in an organic solvent to obtain a mixture thereof (mixing step). Next, a pigment, a solution containing a basic substance and containing water as a main component, water and, if necessary, a surfactant or the like are added to the mixture and mixed and dispersed to obtain an oil-in-water pigment. A particle dispersion is obtained.
There is no limitation in the addition amount (degree of neutralization) of the basic substance. Usually, it is preferable that the liquid property of the pigment particle dispersion finally obtained is a liquid property close to neutrality, for example, pH (25 ° C.) is 4.5 to 10. The pH can also be determined by the degree of neutralization according to the dispersant.

  The pigment, the dispersant, and other additives used in the method for producing the pigment particle dispersion have the same meanings as those described in the above-mentioned pigment particle section, and preferred examples are also the same.

Preferable examples of the organic solvent used in the present invention include alcohol solvents, ketone solvents, and ether solvents. Among these, examples of alcohol solvents include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, and diacetone alcohol. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable.
These organic solvents may be used alone or in combination.

In the production of the pigment particle dispersion, a strong shearing force is applied using a two-roll, a three-roll, a ball mill, a tron mill, a disper, a kneader, a kneader, a homogenizer, a blender, a single screw or a twin screw extruder. The kneading and dispersing process can be carried out.
For details on kneading and dispersing, see T.W. C. “Paint Flow and Pigment Dispersion” by Patton (published by John Wiley and Sons, 1964) and the like.
If necessary, use a vertical or horizontal sand grinder, pin mill, slit mill, ultrasonic disperser, etc. to finely disperse with beads made of glass with a particle diameter of 0.01 to 1 mm, zirconia, etc. Can be obtained.

  In the method for producing the pigment particle dispersion, the removal of the organic solvent is not particularly limited, and can be removed by a known method such as vacuum distillation.

  The pigment particles in the pigment particle dispersion thus obtained maintain a good dispersion state, and the obtained pigment particle dispersion has excellent stability over time.

In the present invention, the average particle diameter of the pigment particles is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because an average particle diameter is 10 nm or more.
The particle size distribution of the pigment particles is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Further, two or more kinds of pigment particles having a monodisperse particle size distribution may be mixed and used.
The average particle size and particle size distribution of the pigment particles can be employed as measured using a dynamic light scattering method.

In the ink composition of the present invention, the pigment particles may be used alone or in combination of two or more.
The pigment particle content is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and more preferably 1.5 to 15% with respect to the ink composition from the viewpoint of image density. % By mass is more preferable, and 1.5 to 10% by mass is particularly preferable.

<Thickener>
The ink composition of the present invention preferably contains at least one thickener.
The thickener is preferably a water-soluble polymer thickener, and can be used without particular limitation as long as it is a compound in which the viscosity of the aqueous solution is higher than that of water in the aqueous solution in which it is dissolved.

  The thickener preferably has a solubility in 100 g of water (25 ° C.) of 1 g or more. Moreover, as the molecular weight, it is preferable that it is 3000-100000 as a weight average molecular weight, It is more preferable that it is 4000-50000, It is still more preferable that it is 1500-40000.

  Examples of the thickener may include vinyl polymers, polyether polymers, polysaccharide polymers, polyacrylic polymers, pyrrolidone polymers, and cellulose polymers.

  Specific examples of the thickener include gelatins, polyvinyl alcohols, various modified polyvinyl alcohols, polyvinylpyrrolidones, vinyl formals and derivatives thereof, polyoxyalkylene glycols, polyacrylamide, polydimethylacrylamide, poly Dimethylamino acrylate, polyacrylic acid soda, acrylic acid methacrylic acid copolymer salt, polymethacrylic acid soda, acrylic acid vinyl alcohol copolymer salt-containing polymer, starch, oxidized starch, carboxyl starch, dialdehyde starch, Dextrin, sodium alginate, gum arabic, casein, pullulan, dextran, cellulose or derivatives thereof (for example, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropyl Natural polymers such as cellulose) or derivatives thereof, polyethylene glycol, polypropylene glycol, polyvinyl ether, polyglycerin, maleic acid alkyl vinyl ether copolymer, maleic acid N-vinyl pyrrole copolymer, styrene maleic anhydride copolymer, polyethylene Examples include synthetic polymers such as imines.

  Among them, from the viewpoint of ejection stability, polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyalkylene glycols, gelatins, vinyl formals and derivatives thereof, polymers containing an acrylic group of vinyl acrylate copolymer salt, starch, dextrin, Natural polymers such as gum arabic, casein, pullulan, dextran, cellulose or derivatives thereof (for example, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, etc.) or derivatives thereof are preferred. Furthermore, polyvinyl alcohol, polyvinyl pyrrolidone, and polyoxyalkylene glycols are more preferable.

The polyoxyalkylene glycols may contain a single oxyalkylene group or may contain two or more oxyalkylene groups. When the polyoxyalkylene glycol contains two or more oxyalkylene groups, it may be a random polymer or a block polymer.
In the present invention, from the viewpoint of ejection stability, it is preferably at least one of polyoxyethylene glycol and polyoxyethylene polyoxypropylene block polymer.

  The average degree of polymerization of the polyvinyl alcohol is preferably from 100 to 3500, more preferably from 120 to 2000, from the viewpoints of curling suppression and ejection stability. The degree of saponification is preferably 50 mol% or more, more preferably 70 mol% or more, from the viewpoint of ink dispersion stability.

  The thickener preferably has a weight average molecular weight of 3000 to 100,000, and is preferably at least one selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyethylene glycol, and polyoxyethylene polyoxypropylene block polymer. The average molecular weight is 4000 to 50000, and it is more preferably at least one selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyoxyethylene glycol, and polyoxyethylene polyoxypropylene block polymer.

Moreover, it is also preferable that the thickener in this invention contains a basic group or an acidic group.
Examples of the basic group include an amino group and a quaternary ammonium group which may have a substituent. Of these, amino groups are preferred from the viewpoint of ink dispersion stability.
Examples of the acidic group include a carboxyl group, a phosphoric acid group, a phosphonic acid group, a sulfonic acid group, and a sulfonamide group. Of these, a carboxyl group and a sulfonic acid group are preferable from the viewpoint of ink dispersion stability.

The thickener having a basic group in the present invention has at least one basic functional group. Among them, the amine value is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and further preferably 40 mgKOH / g or more.
The thickener having an acidic group has at least one acidic functional group. Especially, it is preferable that an acid value is 10 mgKOH / g or more, It is more preferable that it is 20 mgKOH / g or more, It is still more preferable that it is 40 mgKOH / g or more.
Here, the amine value indicates the total amount of 1, 2, and tertiary amines that are basic groups, and mg of KOH equivalent to hydrochloric acid required to neutralize all basic groups in 1 g of a sample. It is expressed in numbers. Moreover, an acid value is the mg number of KOH required in order to neutralize all the acidic groups contained in 1g of samples.

In the present invention, when the thickener contains a basic group, from the viewpoint of ink dispersion stability, the pH of the ink composition is preferably 7.5 or more, and is 8.0 to 9.0. Is more preferable.
In the present invention, when the thickener contains an acidic group, the pH of the ink composition is preferably 6.5 or less, and preferably 5.0 to 6.0 from the viewpoint of ink dispersion stability. It is more preferable.

In this invention, a thickener may be used individually by 1 type and may use 2 or more types together.
The content of the thickener in the ink composition can be appropriately selected according to the type of the thickener. For example, it can be 0.01-20 mass%. Among these, from the viewpoint of ejection stability, it is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 2% by mass.

(Surfactant)
The ink composition in the present invention is configured to contain at least one phosphate ester surfactant, and it is more preferable to use an acetylene glycol surfactant in combination.

-Phosphate-based surfactant-
By including a phosphate ester surfactant in the ink composition, the light resistance of the image is improved, and an image having excellent sharpness without color boundary blurring can be obtained. Furthermore, by containing an acetylene glycol surfactant in the ink composition, the light resistance and sharpness of the image are further improved.

  About the addition effect of the phosphate ester type | system | group surfactant in this invention, it estimates as follows. That is, by adding a phosphate ester-based surfactant to the ink composition, the cohesiveness of the ink composition is improved, and the ink composition can be applied to the recording medium with small droplets. Aggregates formed by aggregating the components in the applied ink composition at a high speed by the aggregating action of the treatment liquid are less susceptible to external influences during storage. As a result, the sharpness and light resistance of the image are remarkably improved.

  As the phosphate ester-based surfactant in the present invention, any one known as a kind of anionic surfactant can be used. For example, any of phosphoric acid monoesters, diesters, triesters and the like represented by the following structural formula can be used. In the following structural formula, n represents an average added mole number of ethylene oxide of 0 to 10, R represents an alkyl group having 8 to 30 carbon atoms, or an alkylphenyl group having 8 to 30 carbon atoms, and among them, from the viewpoint of sharpness, n is preferably an average addition mole number of ethylene oxide of 3 to 10, R is preferably an alkyl group having 10 to 20 carbon atoms or an alkylphenyl group having 12 to 22 carbon atoms, and n is an average addition mole of ethylene oxide of 6 It is more preferable that R is an alkyl group having 12 to 18 carbon atoms or an alkylphenyl group having 14 to 20 carbon atoms.

  In addition, the phosphoric acid ester surfactant in the present invention is effective in terms of sharpness as a monoester or diester surfactant of phosphoric acid.

The phosphate ester surfactant may be a phosphate ester surfactant obtained by synthesis or a commercially available phosphate ester surfactant.
Specifically as a commercial item, phosphanol RD-720, ML-220, RD-510Y, RS-410, RS-610, RS-710, RL-210, RL-310, RB-410, RE -410, RE-510, RE-610, PA-600, PM-410, RM-510, RM-710, LP-700 and other trade names (Toho Chemical Industry Co., Ltd.), Nikkor DLP-10, DDP- 6 (manufactured by Nikko Chemicals Co., Ltd.).

The phosphate ester surfactant is preferably used in an amount of 0.2 to 5% by mass, more preferably 1 to 3% by mass, based on the total mass of the ink composition from the viewpoint of improving the sharpness of the image.
Among the above addition amounts, in order to eject ink droplets favorably by inkjet, the amount of adjusting the surface tension of the ink composition of the present invention to 31 to 60 mN / m is preferable, more preferably 31 to 50 mN / m, still more preferably. Is an amount that can be adjusted to 31 to 45 mN / m.
In the present invention, the surface tension of the ink composition is measured at 25 ° C. using a plate method.

-Acetylene glycol surfactant-
The ink composition according to the invention preferably contains at least one acetylene glycol-based surfactant together with the phosphate ester-based surfactant.
By using the phosphate ester surfactant and the acetylene glycol surfactant in combination, the sharpness and light resistance of the image can be further improved.

  Examples of the acetylene glycol surfactant in the present invention include compounds represented by the following general formula (I).

In general formula (I), 1 ≦ m + n ≦ 15, R ¹ , R ² , R ³ , and R ⁴ are each independently a linear or branched alkyl group.
In the general formula (I), m and n may be the same or different and are a number satisfying m + n = 1 to 15, preferably a number satisfying m + n = 3 to 11. R ¹ , R ² , R ³ and R ⁴ may be the same or different and each is a linear or branched alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.

The acetylene glycol surfactant may be an acetylene glycol surfactant obtained by synthesis or a commercially available acetylene glycol surfactant.
Commercially available acetylene glycol surfactants include, for example, Olphine (registered trademark) E1010, Orphine (registered trademark) E1004 manufactured by Nissin Chemical Industry Co., Ltd., Surfynol (registered trademark) 420, 440 manufactured by Air Products & Chemicals, Inc. 465, 485, and acetylenol (registered trademark) E40 and acetylenol (registered trademark) E100 manufactured by Kawaken Fine Chemical Co., Ltd.

  The addition amount of the acetylene glycol surfactant (a) is 1/10 to 5/1 in terms of mass ratio with respect to the phosphate ester surfactant (p) from the viewpoint of improving the sharpness of the image. Preferably, 1/4 to 4/1 is more preferable.

~ Other surfactants ~
In the ink composition of the present invention, other surfactants other than those described above may be added as long as the effects of the present invention are not impaired. The surface tension of the ink composition can be adjusted by adding a surfactant.

  Examples of other surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like as surface tension adjusting agents.

Specific examples of other surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonates in hydrocarbons. Anionic surfactants such as formalin condensate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, Nonionic surfactants such as polyoxyethylene alkylamines, glycerin fatty acid esters, and oxyethyleneoxypropylene block copolymers are preferred. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.
Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
Further, fluorine (fluorinated alkyl type) surfactants, silicone type surfactants and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are disclosed. By using, the abrasion resistance can 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.

(Polymer particles)
The ink composition of the invention includes at least one polymer particle including at least one structural unit derived from a hydrophilic monomer and at least one structural unit derived from a hydrophobic monomer.
By adding the polymer particles to the ink composition, an image having scratch resistance and press blocking resistance can be formed. In particular, even under high-temperature and high-humidity conditions, it is possible to form an image having excellent discharge recovery and having good blocking resistance.

  The polymer particles are preferably self-dispersing polymer particles (self-dispersing polymer particles) having a glass transition temperature Tg of 100 ° C. or higher.

-Self-dispersing polymer particles-
The ink composition of the present invention preferably contains at least one self-dispersing polymer particle.
Among the self-dispersing polymer particles, a volume average particle size of 0.1 to 10 nm is preferable from the viewpoint of improving scratch resistance.

  The measured Tg obtained by actual measurement is applied as the glass transition temperature (Tg) of the self-dispersing polymer. Specifically, the measurement Tg means a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology.

However, when measurement is difficult due to polymer decomposition or the like, calculation Tg calculated by the following calculation formula is applied.
Calculation Tg is calculated by the following formula (1).
1 / Tg = Σ (Xi / Tgi) (1)
Here, it is assumed that n types of monomer components from i = 1 to n are copolymerized in the polymer to be calculated. Xi is the weight fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. The homopolymer glass transition temperature value (Tgi) of each monomer is the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

Self-dispersing polymer particles can be dispersed in an aqueous medium due to the functional groups of the polymer itself (especially acidic groups or salts thereof) when dispersed by phase inversion emulsification in the absence of a surfactant. It refers to water-insoluble polymer particles.
Here, the dispersed state means both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in a liquid state in an aqueous medium, and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. It includes the state of.
The self-dispersing polymer is preferably a self-dispersing polymer that can be in a dispersed state in which a water-insoluble polymer is dispersed in a solid state from the viewpoint of ink fixing properties when contained in the ink composition.

  Examples of a method for preparing an emulsified or dispersed state of the self-dispersing polymer, that is, an aqueous dispersion of the self-dispersing polymer include a phase inversion emulsification method. As the phase inversion emulsification method, for example, a self-dispersing polymer is dissolved or dispersed in a solvent (for example, a hydrophilic organic solvent) and then poured into water as it is without adding a surfactant. Examples include a method of obtaining an aqueous dispersion in an emulsified or dispersed state after stirring and mixing in a state in which a salt-forming group (for example, an acidic group) of the polymer is neutralized and removing the solvent.

  The stable emulsification or dispersion state in the self-dispersing polymer means a solution in which 30 g of a water-insoluble polymer is dissolved in 70 g of an organic solvent (for example, methyl ethyl ketone), and neutralization capable of neutralizing 100% of the salt-forming group of the water-insoluble polymer. Agent (sodium hydroxide if the salt-forming group is anionic, acetic acid if it is cationic) and 200 g of water were mixed and stirred (apparatus: stirring device with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C.). Thereafter, even after the organic solvent is removed from the mixed solution, the emulsified or dispersed state is stably present at 25 ° C. for at least one week, and the occurrence of precipitation cannot be visually confirmed.

The stability of the emulsified or dispersed state in the self-dispersing polymer can also be confirmed by an accelerated sedimentation test by centrifugation. The stability of the sedimentation acceleration test by centrifugation is, for example, adjusted by adjusting the aqueous dispersion of polymer particles obtained by the above method to a solid concentration of 25% by mass, and then centrifuging at 12,000 rpm for 1 hour. It can be evaluated by measuring the solid content concentration of the supernatant after separation.
If the ratio of the solid content concentration after centrifugation to the solid content concentration before centrifugation is large (a value close to 1), the sedimentation of the polymer particles by centrifugation does not occur, that is, the aqueous dispersion of polymer particles Means more stable. In the present invention, the ratio of the solid content concentration before and after centrifugation is preferably 0.8 or more, more preferably 0.9 or more, and particularly preferably 0.95 or more.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when neutralized with sodium hydroxide or acetic acid according to the kind of the salt-forming group of the water-insoluble polymer.

The self-dispersing polymer preferably has a water-soluble component content that is water-soluble when in a dispersed state of 10% by mass or less, more preferably 8% by mass or less, and 6% by mass or less. More preferably. When the water-soluble component is 10% by mass or less, swelling of the polymer particles and fusion between the polymer particles can be effectively suppressed, and a more stable dispersion state can be maintained. In addition, an increase in the viscosity of the ink composition can be suppressed. For example, when the ink composition is applied to an ink jet method, the ejection stability becomes better.
Here, the water-soluble component is a compound contained in the self-dispersing polymer and is a compound that dissolves in water when the self-dispersing polymer is in a dispersed state. The water-soluble component is a water-soluble compound that is by-produced or mixed when the self-dispersing polymer is produced.

  The self-dispersing polymer contains at least one hydrophilic constituent unit derived from a hydrophilic monomer and at least one hydrophobic constituent unit derived from a hydrophobic monomer. The main chain skeleton of the self-dispersing polymer is not particularly limited, but from the viewpoint of dispersion stability of polymer particles, a vinyl polymer is preferable, and a (meth) acrylic polymer is preferable. Here, the (meth) acrylic polymer means a polymer containing at least one of a structural unit derived from a methacrylic acid derivative and a structural unit derived from an acrylic acid derivative.

(Hydrophilic structural unit)
The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer (hydrophilic monomer). Even if it is derived from one kind of hydrophilic group-containing monomer, two or more hydrophilic units are used. It may be derived from a functional group-containing monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
From the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state, at least one of the hydrophilic groups is preferably a dissociable group, and preferably an anionic dissociable group. More preferred. Examples of the anionic dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Among these, a carboxyl group is particularly preferable from the viewpoint of fixability when an ink composition is formed.

The hydrophilic group-containing monomer is preferably a dissociable group-containing monomer from the viewpoint of self-dispersibility, and is preferably a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond.
Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. It is done. Specific examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate.
Among the dissociable group-containing monomers, from the viewpoint of dispersion stability and ejection stability, unsaturated carboxylic acid monomers are preferable, and at least one of acrylic acid and methacrylic acid is more preferable.

Examples of the monomer having a nonionic hydrophilic group include 2-methoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, 2- (2-methoxyethoxy) ethyl methacrylate, ethoxytriethylene glycol methacrylate, and methoxypolyethylene. Ethylenically unsaturated monomers containing (poly) ethyleneoxy groups or polypropyleneoxy groups such as glycol (molecular weight 200 to 1000) monomethacrylate, polyethylene glycol (molecular weight 200 to 1000) monomethacrylate, hydroxymethyl (meth) acrylate, 2 -Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate Rate, ethylenically unsaturated monomer having a hydroxyl group such as hydroxymethyl (meth) acrylate.
In addition, as a monomer having a nonionic hydrophilic group, an ethylenically unsaturated monomer having a terminal alkyl ether is more stable in terms of particle stability and content of water-soluble components than an ethylenically unsaturated monomer having a terminal hydroxyl group. It is preferable from the viewpoint.

As the hydrophilic structural unit, an embodiment containing only a hydrophilic structural unit having an anionic dissociable group, a hydrophilic structural unit having an anionic dissociative group, and a hydrophilic having a nonionic hydrophilic group It is preferable that it is either of the aspects containing both a structural unit.
In addition, an embodiment containing two or more hydrophilic structural units having an anionic dissociative group, a hydrophilic structural unit having an anionic dissociative group, and two hydrophilic structural units having a nonionic hydrophilic group are provided. It is also preferable that more than one species be used in combination.

The content of the hydrophilic structural unit in the self-dispersing polymer is preferably 25% by mass or less, more preferably 1 to 25% by mass, and more preferably 2 to 23% by mass from the viewpoints of viscosity and stability over time. % Is more preferable, and 4 to 20% by mass is particularly preferable.
Moreover, when it has 2 or more types of hydrophilic structural units, it is preferable that the total content rate of a hydrophilic structural unit exists in the said range.

The content of the hydrophilic structural unit having an anionic dissociative group in the self-dispersing polymer is preferably in a range where the acid value is in a suitable range described later.
In addition, the content of the structural unit having a nonionic hydrophilic group is preferably 0 to 25% by mass, more preferably 0 to 20% by mass, from the viewpoint of ejection stability and temporal stability. Particularly preferred is 0 to 15% by mass.

When the self-dispersing polymer has an anionic dissociable group, the acid value (mgKOH / g) is determined from the viewpoint of self-dispersibility, the content of water-soluble components, and the fixing property when an ink composition is constituted. From 50 mgKOH / g to 75 mgKOH / g, preferably from 52 mgKOH / g to 75 mgKOH / g, more preferably from 55 mgKOH / g to 72 mgKOH / g. Particularly preferred is 60 mg KOH / g or more and 70 mg KOH / g or less.
When the acid value is 50 mgKOH / g or more, the ejection responsiveness and ejection recovery property of the ink composition using the polymer are improved, and when the acid value is 75 mgKOH / g or less, the viscosity is increased and the anti-blocking property is improved. It tends to improve.

(Hydrophobic building block)
The hydrophobic structural unit is not particularly limited as long as it is derived from a hydrophobic group-containing monomer (hydrophobic monomer). Even if it is derived from one type of hydrophobic group-containing monomer, two or more types of hydrophobic structural units are used. It may be derived from a functional group-containing monomer. The hydrophobic group is not particularly limited and may be any of a chain aliphatic group, a cyclic aliphatic group, and an aromatic group.
From the viewpoint of blocking resistance, abrasion resistance, and dispersion stability, at least one of the hydrophobic monomers is preferably a cyclic aliphatic group-containing monomer, and a cyclic aliphatic group-containing (meth) acrylate (hereinafter, “ More preferably, it may be referred to as “alicyclic (meth) acrylate”.

-Alicyclic (meth) acrylate-
The alicyclic (meth) acrylate includes a structural site derived from (meth) acrylic acid and a structural site derived from alcohol, and the structural site derived from alcohol is unsubstituted or substituted. It has a structure containing at least one hydrogen group. The alicyclic hydrocarbon group may be a structural part derived from alcohol itself or may be bonded to a structural part derived from alcohol via a linking group.
The “alicyclic (meth) acrylate” means methacrylate or acrylate having an alicyclic hydrocarbon group.

The alicyclic hydrocarbon group is not particularly limited as long as it contains a cyclic non-aromatic hydrocarbon group, and is a monocyclic hydrocarbon group, a bicyclic hydrocarbon group, a tricyclic or more polycyclic group. A hydrocarbon group is mentioned.
Examples of the alicyclic hydrocarbon group include a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, a cycloalkenyl group, a bicyclohexyl group, a norbornyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantyl group. , Decahydronaphthalenyl group, perhydrofluorenyl group, tricyclo [5.2.1.02,6] decanyl group, and bicyclo [4.3.0] nonane.

The alicyclic hydrocarbon group may further have a substituent. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, a hydroxyl group, a primary amino group, a secondary amino group, a tertiary amino group, an alkyl or arylcarbonyl group, and a cyano group. Is mentioned.
The alicyclic hydrocarbon group may further form a condensed ring.
As an alicyclic hydrocarbon group, it is preferable that carbon number of an alicyclic hydrocarbon group part is 5-20 from a viscosity or a soluble viewpoint.

  Examples of the linking group that connects the alicyclic hydrocarbon group and the structural portion derived from alcohol include alkyl groups, alkenyl groups, alkylene groups, aralkyl groups, alkoxy groups, mono- or oligoethylene groups having 1 to 20 carbon atoms. Preferable examples include a cholic group, a mono- or oligopropylene glycol group, and the like.

Specific examples of the alicyclic (meth) acrylate are shown below, but the present invention is not limited thereto.
Monocyclic (meth) acrylates include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, and cyclononyl. Examples thereof include cycloalkyl (meth) acrylates having 3 to 10 carbon atoms in the cycloalkyl group such as (meth) acrylate and cyclodecyl (meth) acrylate.
Examples of the bicyclic (meth) acrylate include isobornyl (meth) acrylate and norbornyl (meth) acrylate.
Examples of the tricyclic (meth) acrylate include adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.
These can be used alone or in admixture of two or more.

  Among these, at least one kind of bicyclic (meth) acrylate or tricyclic or higher polycyclic (meth) acrylate is used from the viewpoints of dispersion stability, fixing property and blocking resistance of the self-dispersing polymer particles. Preferably, it is at least one selected from isobornyl (meth) acrylate, adamantyl (meth) acrylate, and dicyclopentanyl (meth) acrylate.

The content of the structural unit derived from the alicyclic (meth) acrylate contained in the self-dispersing polymer particles is as follows: in the aqueous medium due to the stability of the self-dispersing state and the hydrophobic interaction between the alicyclic hydrocarbon groups From the viewpoint of stabilization of the particle shape and reduction in the amount of water-soluble components due to appropriate hydrophobicity of the particles, the content is preferably 20% by mass or more and 90% by mass or less, and preferably 40% by mass or more and 90% by mass or less. More preferred. Particularly preferred is 50 mass% or more and 80 mass% or less.
Fixing property and blocking can be improved by making the structural unit derived from the alicyclic (meth) acrylate 20% by mass or more. On the other hand, the stability of the polymer particles is improved when the structural unit derived from the alicyclic (meth) acrylate is 90% by mass or less.

  In addition to the structural unit derived from the said alicyclic (meth) acrylate as a hydrophobic structural unit, a self-dispersing polymer can be comprised further including other structural units as needed. The monomer that forms the other structural unit is not particularly limited as long as it is a monomer copolymerizable with the alicyclic (meth) acrylate and the above-described hydrophilic group-containing monomer, and a known monomer may be used. it can.

Specific examples of the monomer that forms the other structural unit (hereinafter sometimes referred to as “other copolymerizable monomer”) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and isopropyl (meth) acrylate. Alkyl (meth) acrylates such as n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; Aromatic ring-containing (meth) acrylates such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; styrenes such as styrene, α-methylstyrene and chlorostyrene; dialkylaminoalkyls such as dimethylaminoethyl (meth) acrylate (Meth) acrylate; N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxyalkyl (meth) acrylamide such as N-hydroxybutyl (meth) acrylamide; N-methoxymethyl (meth) acrylamide N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N- (n-, iso ) (Meth) acrylamide such as N-alkoxyalkyl (meth) acrylamide such as butoxyethyl (meth) acrylamide.

  Among these, from the viewpoint of the flexibility of the polymer skeleton and the ease of controlling the glass transition temperature (Tg) and the viewpoint of the dispersion stability of the self-dispersing polymer, it contains a chain alkyl group having 1 to 8 carbon atoms (meth). It is preferably at least one acrylate, more preferably a (meth) acrylate having a chain alkyl group having 1 to 4 carbon atoms, and particularly preferably methyl (meth) acrylate or ethyl (meth) acrylate. . Here, the chain alkyl group refers to an alkyl group having a straight chain or a branched chain.

Moreover, the (meth) acrylate containing an aromatic group can also be used preferably.
When an aromatic-containing (meth) acrylate is included as another copolymerizable monomer, the structural unit derived from the aromatic-containing (meth) acrylate is 40% by weight or less from the viewpoint of dispersion stability of the self-dispersing polymer particles. It is preferably 30% by weight or less, more preferably 20% by weight or less.

In addition, when a styrene monomer is used as another copolymerizable monomer, the structural unit derived from the styrene monomer is preferably 20% by mass or less from the viewpoint of stability when the self-dispersing polymer particles are obtained. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less, The aspect which does not contain the structural unit derived from a styrene-type monomer is especially preferable.
Here, the styrene monomer refers to styrene, substituted styrene (α-methylstyrene, chlorostyrene, etc.), and a styrene macromer having a polystyrene structural unit.

Other copolymerizable monomers may be used singly or in combination of two or more.
However, when it contains another structural unit, it is preferable that the content is 10-80 mass%, More preferably, it is 15-75 mass%, Most preferably, it is 20-70 mass%. When using the monomer which forms another structural unit in combination of 2 or more types, it is preferable that the total content is the said range.

From the viewpoint of dispersion stability, the self-dispersing polymer is preferably a polymer obtained by polymerizing at least three types of alicyclic (meth) acrylate, other copolymerizable monomer, and hydrophilic group-containing monomer. , An alicyclic (meth) acrylate, a linear or branched alkyl group-containing (meth) acrylate having 1 to 8 carbon atoms, and a polymer obtained by polymerizing at least three kinds of hydrophilic group-containing monomers. It is more preferable.
In the present invention, from the viewpoint of dispersion stability, substitution with a large hydrophobicity derived from a (meth) acrylate having a linear or branched alkyl group having 9 or more carbon atoms, an aromatic group-containing macromonomer, or the like The content of the structural unit having a group is preferably substantially not contained, and more preferably not contained at all.

  The self-dispersing polymer may be a random copolymer in which each constituent unit is irregularly introduced, or a block copolymer that is regularly introduced. Each constitutional unit may be synthesized in any order of introduction, and the same constitutional component may be used twice or more, but is preferably a random copolymer in terms of versatility and manufacturability. .

The molecular weight range of the self-dispersing polymer is preferably 3000 to 200,000, more preferably 10,000 to 200,000, and still more preferably 30000 to 150,000 in terms of weight average molecular weight. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.
The weight average molecular weight can be measured by gel permeation chromatography (GPC).

The self-dispersing polymer preferably has an acid value of 50 to 75 mgKOH / g, more preferably 52 to 75 mgKOH / g, from the viewpoints of viscosity adjustment of the ink composition, ejection response, and ejection recovery. It is more preferable that it is 55-72 mgKOH / g, and it is especially preferable that it is 60-70 mgKOH / g.
When the acid value is 50 mgKOH / g or more, the ejection response and ejection recovery properties of the ink composition using the polymer are improved, and when the acid value is 75 mgKOH / g or less, the viscosity tends to increase.
In the present invention, the acid value is determined by the method described in JIS standard (JIS K 0070: 1992).

The self-dispersing polymer has a degree of neutralization of preferably 40 to 60%, more preferably 45 to 55%, and more preferably 47 to 53% from the viewpoints of viscosity adjustment, discharge response, and discharge recovery. It is particularly preferred.
When the degree of neutralization is 40% or more, the effect of increasing the viscosity and the effect of improving the discharge response are obtained, and when it is 60% or less, the discharge recovery property is improved.
Further, when the degree of neutralization is 40% or less, or 60% or more, there is a problem that the self-dispersing polymer cannot be stably produced.
In the present invention, the degree of neutralization refers to the mol% of alkali added when the dissociable group contained in the self-dispersing polymer chain is 100 mol% during the production of the self-dispersing polymer.

  The self-dispersing polymer is preferably a combination of the acid value and the neutralization degree when the acid value is 52 to 75 mgKOH / g and the neutralization degree is 45 to 55%, and the acid value is 55 to 72 mgKOH / g. The degree is more preferably 45 to 55%, and the acid value is more preferably 55 to 65 mgKOH / g and the neutralization degree is 47 to 53%.

The self-dispersing polymer has a structure derived from an alicyclic (meth) acrylate derived from an alicyclic (meth) acrylate as a copolymerization ratio of 20% by mass to 90% by mass, and a structure derived from a dissociable group-containing monomer. And at least one type of structure derived from (meth) acrylate containing a chain alkyl group having 1 to 8 carbon atoms, the acid value is 20 to 120, and the total content of hydrophilic structural units is It is preferably 25% by mass or less and a vinyl polymer having a weight average molecular weight of 3000 to 200,000.
Moreover, it contains a chain alkyl group having 1 to 4 carbon atoms and a structure derived from a bicyclic or tricyclic or higher polycyclic (meth) acrylate as a copolymerization ratio of 20% by mass or more and less than 90% by mass. A structure derived from (meth) acrylate as a copolymerization ratio of 10% by mass to less than 80% by mass, and a structure derived from a carboxyl group-containing monomer in an acid value of 50 to 75 mgKOH / g, A vinyl polymer having a total content of 25% by mass or less and a weight average molecular weight of 10,000 to 200,000 is more preferable.
Furthermore, a structure derived from a bicyclic or tricyclic or higher polycyclic (meth) acrylate having a copolymerization ratio of 40% by mass or more and less than 80% by mass, at least methyl (meth) acrylate or ethyl (meth) acrylate A structure derived from a copolymerization ratio of 20% by mass to less than 60% by mass, a structure derived from acrylic acid or methacrylic acid in an acid value of 50 to 75 mgKOH / g, and a total content of hydrophilic structural units. The vinyl polymer is particularly preferably 25% by mass or less and having a weight average molecular weight of 30,000 to 150,000.

  Hereinafter, as specific examples of the self-dispersing polymer, exemplary compounds are listed, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymerization component.

Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (20/72/8), glass transition temperature: 180 ° C., I / O value: 0.44, acid value: 52.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40/52/8), glass transition temperature: 160 ° C., I / O value: 0.50, acid value: 52.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (38/52/10), glass transition temperature: 160 ° C., I / O value: 0.523, acid value: 65.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (42/52/6), glass transition temperature: 161 ° C., I / O value: 0.469, acid value: 39.1
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (36.5 / 52 / 11.5), glass transition temperature: 160 ° C., I / O value: 0.538, acid value: 74.8
Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (36/52/12), glass transition temperature: 160 ° C., I / O value: 0.543, acid value: 78.1
Methyl methacrylate / isobornyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/62/10/8), glass transition temperature: 170 ° C., I / O value: 0.44, acid value: 52 .1
Methyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (20/72/8), glass transition temperature: 160 ° C., I / O value: 0.47, acid value: 52.1 Cyclopentanyl methacrylate / methacrylic acid copolymer (18/72/10), glass transition temperature: 161 ° C., I / O value: 0.47, acid value: 65.1

In the calculation of the I / O value, the following numerical values were used as the I / O values of the monomers constituting each polymer.
Methyl methacrylate: 0.60, isobornyl methacrylate: 0.29, dicyclopentanyl methacrylate: 0.32, methacrylic acid: 0.47

There is no restriction | limiting in particular as a manufacturing method of a self-dispersing polymer, It can manufacture by copolymerizing a monomer mixture by a well-known polymerization method. Among these polymerization methods, from the viewpoint of droplet ejection stability when used as an ink composition, polymerization in an organic medium is more preferable, and solution polymerization is particularly preferable.
In the method for producing a self-dispersing polymer, the water-insoluble polymer is produced by copolymerizing a monomer mixture and, if necessary, a mixture containing an organic solvent and a radical polymerization initiator in an inert gas atmosphere. can do.

There is no restriction | limiting in particular as a manufacturing method of the aqueous dispersion of self-dispersing polymer particles, It can be set as the aqueous dispersion of self-dispersing polymer particles by a well-known method. The step of obtaining the self-dispersing polymer as an aqueous dispersion is preferably a phase inversion emulsification method including the following step (1) and step (2).
Step (1): A step of stirring a mixture containing a water-insoluble polymer, an organic solvent, a neutralizing agent, and an aqueous medium to obtain a dispersion.
Step (2): A step of removing at least a part of the organic solvent from the dispersion.

The step (1) is preferably a treatment in which the water-insoluble polymer is first dissolved in an organic solvent, and then a neutralizer and an aqueous medium are gradually added, mixed and stirred to obtain a dispersion. Thus, by adding a neutralizing agent and an aqueous medium to a water-insoluble polymer solution dissolved in an organic solvent, a self-dispersing polymer having a particle size with higher storage stability without requiring strong shearing force. Particles can be obtained.
There is no restriction | limiting in particular in the stirring method of this mixture, Dispersing machines, such as a generally used mixing stirring apparatus and an ultrasonic disperser, a high-pressure homogenizer, can be used as needed.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents.
Examples of the alcohol solvent include isopropyl alcohol, n-butanol, t-butanol, ethanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether and dioxane. Among these organic solvents, ketone solvents such as methyl ethyl ketone and alcohol solvents such as isopropyl alcohol are preferable.
It is also preferable to use isopropyl alcohol and methyl ethyl ketone in combination. By using the solvent in combination, it is possible to obtain self-dispersing polymer particles having a fine particle size with high dispersion stability without aggregation and sedimentation and fusion between particles. This can be considered, for example, because the polarity change during the phase inversion from the oil system to the water system becomes mild.

  The neutralizing agent is used so that a part or all of the dissociable group is neutralized and the self-dispersing polymer forms a stable emulsified or dispersed state in water. When the self-dispersing polymer has an anionic dissociative group as a dissociable group, examples of the neutralizing agent used include basic compounds such as organic amine compounds, ammonia, and alkali metal hydroxides. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolamine, monoisopropanolamine, diisopropanol Examples include amines and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing polymer particles of the present invention in water.

  In the step (2), the aqueous dispersion of the self-dispersing polymer particles is obtained by distilling off the organic solvent from the dispersion obtained in the step (1) by a conventional method such as distillation under reduced pressure and inversion into an aqueous system. You can get things. The organic solvent in the obtained aqueous dispersion has been substantially removed, and the amount of the organic solvent is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

The volume average particle size (hereinafter, also simply referred to as “average particle size”) of the self-dispersing polymer particles needs to be 0.1 to 10 nm. If it is less than 0.1, the viscosity increases too much and the discharge recovery property deteriorates, and if it exceeds 10 nm, the thickening effect becomes poor.
Among the above average particle diameter ranges, 0.5 to 8 nm is preferable, 1 to 7 nm is more preferable, and 1 to 5 nm is even more preferable in terms of thickening and discharge properties (discharge response and discharge recovery properties). . Especially preferably, it is 1-4 nm.
An average particle size of 0.1 nm or more is preferable in terms of further improving the production suitability and ejection recovery property, and an average particle size of 10 nm or less improves storage stability and the ink thickening effect. Further, by giving the self-dispersibility a thickening effect, it is possible to improve the discharge response by reducing the amount of the thickener added as a result.
Further, the particle size distribution of the self-dispersing polymer 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 water-insoluble particles may be mixed and used.
The average particle size and particle size distribution of the self-dispersing polymer particles can be measured using, for example, a light scattering method.

In the ink composition of the present invention, the self-dispersing polymer particles are preferably present in a form containing substantially no pigment.
The self-dispersing polymer particles of the present invention are excellent in self-dispersibility, and the stability when dispersed alone is very high. However, for example, since the function as a so-called dispersant for stably dispersing the pigment is not high, if the self-dispersing polymer in the present invention is present in the ink composition in a form containing the pigment, as a result, the entire ink composition The stability of the may be greatly reduced.

The ink composition of the present invention may contain one kind of polymer particles or two or more kinds of polymer particles.
Further, the content of the polymer particles in the ink composition of the present invention is preferably 1 to 30% by mass, and 2 to 20% by mass with respect to the ink composition from the viewpoint of glossiness of the image. It is more preferable that the content is 2 to 10% by mass.
In addition, the content ratio of pigment particles to polymer particles (pigment particles / polymer particles) in the ink composition of the present invention is 1 / 0.5 to 1/10 from the viewpoint of image scratch resistance and the like. Preferably, it is 1/1 to 1/4.

(Hydrophilic organic solvent)
The ink composition of the present invention preferably contains at least one hydrophilic organic solvent, and more preferably contains at least two hydrophilic organic solvents.
As the hydrophilic organic solvent (the first hydrophilic organic solvent which is one of two or more hydrophilic organic solvents), the I / O value is preferably 0.70 or more and less than 1.00. . When the I / O value is less than 1.00, the compatibility with the self-dispersing polymer particles is improved, the fixability of the formed image is more effectively improved, and the abrasion resistance of the image is further improved. To do. Further, when the I / O value is 0.70 or more, the stability of the ink composition is improved.

  The I / O value is a value that treats the polarity of various organic compounds, also called inorganic values / organic values, in an organic concept, and is one of functional group contribution methods for setting parameters for each functional group. It is.

  The I / O value is described in detail in an organic conceptual diagram (written by Yoshio Koda, Sankyo Publishing (1984)). The concept of the I / O value is that the properties of a compound are divided into an organic group that represents covalent bonding and an inorganic group that represents ionic bonding, and all organic compounds are orthogonal coordinates named organic axes and inorganic axes. Each of the above points is shown.

The inorganic value is obtained by quantifying the magnitude of the influence on the boiling point of various substituents and bonds of an organic compound, based on the hydroxyl group.
Specifically, when the distance between the boiling point curve of a straight chain alcohol and the boiling point curve of a straight chain paraffin is about 100 ° C., the influence of one hydroxyl group is set to 100 as a numerical value. A value obtained by quantifying the influence of various substituents or various bonds on the boiling point based on this numerical value is the inorganic value of the substituent that the organic compound has.
For example, the inorganic value of the —COOH group is 150, and the inorganic value of the double bond is 2. Therefore, the inorganic value of a certain kind of organic compound means the sum of inorganic values such as various substituents and bonds of the compound.
The organic value is determined based on the influence of the methylene group in the molecule as a unit and the boiling point of the carbon atom representing the methylene group.
That is, since the average value of the boiling point increase due to the addition of one carbon in the vicinity of 5 to 10 carbon atoms of the linear saturated hydrocarbon compound is 20 ° C., the organic value of one carbon atom is set to 20 on the basis of this. A value obtained by quantifying the influence on the boiling point of various substituents and bonds based on this is the organic value. For example, the organic value of a nitro group (—NO ₂ ) is 70.
An I / O value closer to 0 indicates a non-polar (hydrophobic or organic) organic compound, and a larger value indicates a polar (hydrophilic or inorganic) organic compound. Indicate

  In the present invention, the I / O value of the hydrophilic organic solvent means that obtained by the following method. Based on the organicity (O value) and inorganicity (I value) described in Yoshio Koda, Organic Conceptual Diagram-Fundamentals and Applications (1984), p. 13, etc. I / O value of hydrophilic organic solvents ( = I value / O value) is calculated.

The content of the hydrophilic organic solvent (the first hydrophilic organic solvent) in the ink composition of the present invention is preferably 0.1 to 20% by mass from the viewpoint of image fixability and ink stability. 1 to 16% by mass is more preferable, and 2 to 12% by mass is even more preferable.
Further, the hydrophilic organic solvent preferably contains 1 to 16% by mass of a hydrophilic organic solvent selected from an I / O value of 0.70 or more and less than 1.00, and an I / O value of 0.70 or more and 0.90. It is more preferable that 2-12 mass% of hydrophilic organic solvents chosen from less than are included.

The ink composition of the present invention has an I / O value of 1.00 to 1 separately from the above (in addition to the first hydrophilic organic solvent when two or more hydrophilic organic solvents are included). It is preferable to further include at least one of other hydrophilic organic solvents (the second hydrophilic organic solvent which is the other when two or more are included) of 50 or less.
When the I / O value is 1.00 or more, the stability of the ink composition is more effectively improved. Moreover, it can suppress that the fixability of the image formed by I / O value being 1.50 or less falls.

Specific examples of the first hydrophilic organic solvent having an I / O value of 0.70 or more and less than 1.00 include glycol ethers, and propylene glycol ethers or ethylene glycol ethers are preferable, and more preferable. Is propylene glycol ether, specifically, triprolene glycol monomethyl ether (I / O value: 0.80), triprolene glycol monoethyl ether (I / O value: 0.73), triprolene glycol monobutyl ether ( I / O value: 0.61), diprolene glycol monoethyl ether (I / O value: 0.78), diprolene glycol monobutyl ether (I / O value: 0.70), prolene glycol monobutyl ether (I / O value: 0.88).
Among these, from the viewpoints of image fixability and ink stability, triprolene glycol monomethyl ether (I / O value: 0.80) is preferable.

  Specific examples of the second hydrophilic organic solvent having an I / O value of 1.0 or more and 1.5 or less include propylene glycol monomethyl ether (I / O value: 1.50), propylene glycol monoethyl ether (I / O value: 1.20), diethylene glycol monobutyl ether (I / O value: 1.40), triethylene glycol monobutyl ether (I / O value: 1.20), 2,2-diethyl-1,3 -Propanediol (I / O value: 1.43), 2-methyl-2-propyl-1,3-propanediol (I / O value: 1.43), 2,4-dimethyl-2,4-pentane Diol (I / O value: 1.43), 2,5-dimethyl-2,5-hexanediol (I / O value: 1.25), tripropylene glycol (I / O value: 1.33), Sun Knicks GP 50 (I / O value: 1.30, manufactured by Sanyo Chemical Industries, Ltd.), and the like. Of these, SANNIX GP250 is preferable from the viewpoint of image fixability and ink stability.

The content of the other hydrophilic organic solvent (the second hydrophilic organic solvent) is preferably 0.1 to 20% by mass from the viewpoint of image fixability and ink stability. It is more preferable that it is mass%, and it is still more preferable that it is 2-12 mass%.
Further, the second hydrophilic organic solvent preferably contains 1 to 16% by weight of a hydrophilic organic solvent selected from an I / O value of 1.00 to 1.50, and an I / O value of 1.20 or more. It is more preferable that 2-12 mass% of hydrophilic organic solvents chosen from 1.40 or less are included.

  Further, when two or more hydrophilic organic solvents are contained, the content ratio of the second hydrophilic organic solvent to the first hydrophilic organic solvent in the ink composition of the present invention (second hydrophilic organic solvent: first The hydrophilic organic solvent) is preferably from 1:10 to 10: 1, more preferably from 1: 4 to 4: 1, from the viewpoint of image fixability and ink stability. More preferably, it is 2: 1.

  The ink composition of the present invention may further contain other hydrophilic organic solvent in addition to the first hydrophilic organic solvent and the second hydrophilic organic solvent. As other hydrophilic organic solvents, polyhydric alcohols are useful for the purpose of drying inhibitors and wetting agents. For example, glycerin (I / O value: 5.00), ethylene glycol (I / O value: 2.00), diethylene glycol (I / O value: 5.00), triethylene glycol (I / O value: 3.43), propylene glycol (I / O value: 2.50), dipropylene glycol (I / O) O value: 2.00), 1,3-butanediol (I / O value: 2.50), 2,3-butanediol (I / O value: 2.50), 1,4-butanediol (I / O value: 2.50), 3-methyl-1,3-butanediol (I / O value: 2.00), 1,5-pentanediol (I / O value: 2.00), tetraethylene glycol (I / O value: 2.91), 1,6-hexane All (I / O value: 1.67), 2-methyl-2,4-pentanediol (I / O value: 1.67), polyethylene glycol (I / O value depends on the number of ethylene chain repeats), 1 2,4-butanetriol (I / O value: 3.75), 1,2,6-hexanetriol (I / O value: 2.50), and the like. These may be used individually by 1 type and may use 2 or more types together.

  For the purpose of the penetrant, a polyol compound is preferable. Examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol (I / O value: 1.67), 3,3- Dimethyl-1,2-butanediol (I / O value: 1.67), 5-hexene-1,2-diol, 2-ethyl-1,3-hexanediol (I / O value: 2.00), 2,2,4-trimethyl-1,3-pentanediol (I / O value: 1.88) can be mentioned as a preferred example.

  As content rate of another hydrophilic organic solvent, it can be 16 mass% or less, for example, it is preferable that it is 12 mass% or less, and it is more preferable that it is 8% or less.

  The ink composition of the present invention preferably contains two or more hydrophilic organic solvents, and the content is preferably 1% by mass or more and 60% by mass or less from the viewpoint of stability and dischargeability, and 5% by mass. The content is more preferably 40% by mass or less and particularly preferably 10% by mass or more and 30% by mass or less.

  The amount of water used in the present invention is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, more preferably 30% from the viewpoint of ensuring stability and ejection reliability in the ink composition. It is not less than 80% by mass and more preferably not less than 50% by mass and not more than 70% by mass.

(Solid wetting agent)
The ink composition of the present invention preferably contains at least one solid wetting agent.
The ink composition preferably contains a solid wetting agent in that the wiping property is improved.
Here, the solid wetting agent in the present invention means a water-soluble compound having a water retention function and solid at 25 ° C.

  As the solid wetting agent that can be used in the present invention, those generally used in aqueous ink compositions can be used as they are, and more specifically, sugars, sugar alcohols, hyaluronic acids, trimethylolpropane, Polyhydric alcohols such as 1,2,6-hexanetriol, urea and urea derivatives.

  Examples of the urea derivative include a compound in which hydrogen on nitrogen of urea is substituted with an alkyl group or alkanol, thiourea, a compound in which hydrogen on nitrogen of thiourea is substituted with an alkyl group or alkanol, and the like. Specific examples include N, N-dimethylurea, thiourea, ethyleneurea, hydroxyethylurea, hydroxybutylurea, ethylenethiourea, and diethylthiourea.

Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Specifically, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, Examples thereof include aldonic acid, glucitol, (sorbit), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature, such as alginic acid, α-cyclodextrin, and cellulose. Examples of derivatives of these saccharides include the reducing sugars (eg, sugar alcohols) and oxidized sugars (eg, aldonic acid, uronic acid, amino acids, thio sugars, etc.) of the aforementioned saccharides. Particularly preferred are sugar alcohols, and specific examples include maltitol, sorbitol, xylitol and the like. As the hyaluronate, a commercially available sodium hyaluronate 1% aqueous solution (molecular weight 350,000) can be used.
Among these, urea and urea derivatives have a high moisturizing function and can be more suitably used as the solid wetting agent of the present invention.

  The content of the solid wetting agent in the ink composition of the present invention is preferably 5% by mass or more, more preferably 5 to 30% by mass, and further preferably 5 to 20% by mass from the viewpoint of improving wiping properties.

There is no particular limitation on the combination of the content of the solid wetting agent in the ink composition of the present invention and the content of the polymer particles in the ink composition of the present invention. The following combinations are preferable from the viewpoint of achieving both effectively.
That is, a combination in which the content of the solid wetting agent is 5% by mass or more and the content of the polymer particles is 5% by mass or more is preferable, and the content of the solid wetting agent is 5 to 20% by mass. A combination in which the content of the particles is 5 to 20% by mass is more preferable, and a combination in which the content of the solid wetting agent is 5 to 10% by mass and the content of the polymer particles is 5 to 10% by mass is particularly preferable. .
Further, the ratio of the content of the solid wetting agent to the total amount of solid content in the ink composition (the mass of the solid wetting agent / the mass of the total solid content) is preferably 0.3 or more, and 0.4-2. It is more preferably 0, and most preferably 0.5 to 1.5.

(Other additives)
The ink composition of the present invention may contain other additives as necessary in addition to the above components.
Other additives in the present invention include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, antifoaming agents, viscosity adjusters, dispersants, Well-known additives, such as a dispersion stabilizer, a rust preventive agent, and a chelating agent, are mentioned. These various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared. Specific examples include other additives described in paragraph numbers [0153] to [0162] of JP-A-2007-100071.

The viscosity of the ink composition of the present invention is preferably 4, 5 mPa · s to 6.5 mPa · s from the viewpoint of droplet ejection stability and agglomeration speed when ink is applied by an ink jet method. 6 mPa · s is more preferable.
In addition, when the ink composition is applied by a method other than the inkjet method, the range of 1 to 40 mPa · s is preferable, and the range of 5 to 20 mPa · s is more preferable.
As the viscosity of the ink composition, a value measured at 25 ° C. using an E-type viscometer (manufactured by Toki Sangyo) is adopted.

<Processing liquid>
The treatment liquid contains at least one cationic polymer containing a nitrogen atom in the main chain (hereinafter also simply referred to as a cationic polymer) as an aggregating component capable of forming an aggregate upon contact with the ink composition. To do.
Aggregation of pigments and the like stably dispersed in the ink composition is promoted by mixing the ink composition ejected onto the recording medium by the inkjet method and the treatment liquid containing the cationic polymer. .

(Cationic polymer containing nitrogen atom in the main chain)
As the cationic polymer containing a nitrogen atom in the main chain in the present invention, a polymer having a secondary to tertiary amino group or a quaternary ammonium base is preferably used.
Examples of the cationic polymer include a homopolymer of a monomer having a secondary to tertiary amino group and a salt thereof, or a quaternary ammonium base (cationic monomer), and the cationic monomer and other monomers. (Hereinafter referred to as “non-cationic monomer”) is preferably obtained as a copolymer or a condensation polymer. Particularly preferred are polyethyleneimine, polybiguanide, and / or polyguanide, and the nitrogen atom of the main chain is preferably constituted as a secondary amine or a tertiary amine.
The weight average molecular weight of the cationic polymer is preferably about 1000 to 50000. In addition, the said cationic polymer may be used individually by 1 type, and may use 2 or more types together. As a content rate of the cationic polymer in a processing liquid, it is preferable that it is 5-80 mass% with respect to the total mass of a processing liquid from a viewpoint of the aggregation effect, and it is more preferable that it is 5-30 mass%. More preferably, it is 5-15 mass%.

  The treatment liquid may contain at least one acidic compound as an aggregation component. As the acidic compound, a compound having a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group, or a salt thereof (for example, a polyvalent metal salt) may be used. it can. Among these, from the viewpoint of the aggregation rate of the ink composition, a compound having a phosphate group or a carboxyl group is more preferable, and a compound having a carboxyl group is still more preferable.

  The compound having a carboxyl group includes polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid. , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts), etc. It is preferable to be selected from among These compounds may be used alone or in combination of two or more.

  Further, the treatment liquid may contain a polyvalent metal salt or polyallylamine as an aggregating component other than the above, and this addition can improve the high-speed aggregating property. Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and cations from Group 13 of the periodic table. (For example, aluminum), salts of lanthanides (for example, neodymium), polyallylamine, and polyallylamine derivatives. As the metal salt, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

  The content of the metal salt in the treatment liquid is preferably 1 to 10% by mass, more preferably 1.5 to 7% by mass, and still more preferably 2 to 6% by mass from the viewpoint of the aggregation effect. It is.

  The aggregating components can be used alone or in combination of two or more.

(Surfactant)
The treatment liquid in the present invention preferably contains at least one phosphate ester surfactant in addition to the cationic polymer, and more preferably comprises an acetylene surfactant.
When the treatment liquid contains the phosphate ester surfactant, it can contact the components in the ink composition and aggregate dispersed particles such as pigments at high speed to form an aggregate. Furthermore, the aggregation effect is further enhanced by containing an acetylene surfactant.

  As the phosphate ester surfactant and the acetylene surfactant that can be used in the treatment liquid, those described in the section of the ink composition can be selected, and preferred examples are also the same.

  From the viewpoint of improving the sharpness of the image, it is preferable that the phosphate ester-based surfactant has an appropriate content such that the following surface tension is obtained. Especially, it is preferable to use 0.2-5 mass% with respect to the total mass of a process liquid, and 1-3 mass% is more preferable.

The treatment liquid can generate aggregates by changing the pH of the ink composition. At this time, the pH (25 ° C. ± 1 ° C.) of the treatment liquid is preferably 1 to 6, more preferably 1.2 to 5, more preferably 1.5 from the viewpoint of the aggregation rate of the ink composition. More preferably, it is ~ 4. In this case, the pH (25 ± 1 ° C.) of the ink composition used in the ejection step is preferably 7.5 to 9.5 (more preferably 8.0 to 9.0).
Among these, in the present invention, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ± 1 ° C.) of the ink composition is 7.5 or more, and the pH of the treatment liquid (25 ± 1 ° C) is preferably 1.5 to 3.
The viscosity of the treatment liquid is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, still more preferably in the range of 2 to 15 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The range of 10 mPa · s is particularly preferable. The viscosity is measured under a condition of 20 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

  The surface tension of the treatment liquid is preferably 20 to 60 mN / m, more preferably 20 to 45 mN / m, and more preferably 25 to 40 mN / m from the viewpoint of the aggregation rate of the ink composition. More preferably. The surface tension is measured under conditions of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

(Other ingredients)
The treatment liquid in the present invention can generally contain a hydrophilic organic solvent in addition to the aggregating component, and can be constituted using other various additives within the range not impairing the effects of the present invention. it can. The details of the hydrophilic organic solvent are the same as those in the ink composition described above.

  Examples of the other additives include drying inhibitors (wetting agents), antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, antifoaming agents, viscosity modifiers, and dispersions. Known additives such as an agent, a dispersion stabilizer, a rust preventive agent, and a chelating agent can be mentioned, and those listed as specific examples of other additives contained in the ink composition described above can be applied.

[Image forming method]
The image forming method of the present invention includes an ink application step of applying the ink composition in the ink set of the present invention to a recording medium, and a treatment liquid that forms an aggregate upon contact with the components in the ink composition on the recording medium. A treatment liquid application step to be applied, and other steps as necessary.

Hereafter, each process which comprises the image forming method of this invention is demonstrated.
-Ink application process-
In the ink application process, the ink composition of the present invention described above is applied to a recording medium by an ink jet method. In this step, the ink composition can be selectively applied onto the recording medium, and a desired visible image can be formed. Details of each component in the ink composition of the present invention and details such as preferred embodiments are as described above.

  Specifically, the image formation using the ink jet method is performed by supplying energy to a desired recording medium, that is, plain paper, resin-coated paper, such as JP-A-8-169172 and JP-A-8-27693. JP-A-2-276670, JP-A-7-276789, JP-A-9-323475, JP-A-62-238783, JP-A-10-153789, JP-A-10-217473, JP-A-10-235995. No. 10-337947, No. 10-217597, No. 10-337947, etc. Inkjet exclusive paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics, etc. This can be done by discharging. As a preferred image forming method of the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, an electric method An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink with ink and ejects the ink using radiation pressure, and a thermal ink jet (bubble jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used.
The ink jet method includes a method of ejecting many 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 using is included.

In addition, an ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
There are no particular restrictions on the ink nozzles used when recording by the ink jet method, and they can be appropriately selected according to the purpose.

  As an inkjet head, a short serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line system, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system. The image forming method of the present invention can be applied to any of these, but generally, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image scratch resistance is great.

  Furthermore, in the ink application process in the present invention, in the case of the line method, not only one type of ink composition is used but also two or more types of ink compositions are used, and an ink composition (nth color ( n ≧ 1), for example, the second color), and the ink composition (n + 1th color, for example, the third color) to be ejected subsequently is preferably set to 1 second or less for the ejection (droplet ejection) interval to perform recording. be able to. In the present invention, an ejection interval of 1 second or less in the line method prevents bleeding and color mixing between ink droplets, and has excellent scratch resistance under high-speed recording higher than that of the prior art, and occurrence of blocking. A suppressed image can be obtained. In addition, an image having excellent hue and drawability (reproducibility of fine lines and fine portions in the image) can be obtained.

  The amount of ink droplets ejected from the inkjet head is preferably 0.5 to 6 pl (picoliter), more preferably 1 to 5 pl, and still more preferably 2 to 4 pl from the viewpoint of obtaining a high-definition image. .

-Treatment liquid application process-
In the treatment liquid application step, the treatment liquid in the present invention, which can form an aggregate by contact with the ink composition, is applied to the recording medium, and the treatment liquid is contacted with the ink composition to form an image. In this case, dispersed particles such as polymer particles and pigment in the ink composition are aggregated, and the image is fixed on the recording medium. The details and preferred embodiments of each component in the treatment liquid are as described above.

  The treatment liquid can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method. As a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, or the like can be used. The details of the inkjet method are as described above.

  The treatment liquid application step may be provided either before or after the ink application step using the ink composition.

  In the present invention, an embodiment in which the ink application step is provided after the treatment liquid is applied in the treatment liquid application step is preferable. That is, before applying the ink composition to the recording medium, a processing liquid for aggregating the pigment in the ink composition is applied in advance, and the recording liquid is brought into contact with the processing liquid applied on the recording medium. An embodiment in which an ink composition is applied to form an image is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The amount of the treatment liquid applied is not particularly limited as long as the ink composition can be aggregated. Preferably, the amount of the aggregation component (for example, cationic polymer) applied is 0.1 g / m ² or more. can do. Especially, the quantity from which the provision amount of an aggregation component will be 0.1-1.0 g / m < ² > is preferable, More preferably, it is 0.2-0.8 g / m < ² >. When the amount of the aggregating component is 0.1 g / m ² or more, the agglomeration reaction proceeds favorably, and when it is 1.0 g / m ² or less, the glossiness is not excessively increased.

  In the present invention, an ink application step is provided after the treatment liquid application step, and the treatment liquid on the recording medium is heated and dried after the treatment liquid is applied on the recording medium and before the ink composition is applied. It is preferable to further provide a heat drying step. By heating and drying the treatment liquid in advance before the ink application step, ink colorability such as bleeding prevention is improved, and a visible image with good color density and hue can be recorded.

  Heating and drying can be performed by known heating means such as a heater, air blowing means using air blowing such as a dryer, or a combination of these. As the heating method, for example, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the recording medium, a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, or an infrared heater was used. The heating method etc. are mentioned, You may heat combining these two or more.

[Heat fixing process]
The image forming method of the present invention preferably has a heating and fixing step of heating and fixing an ink image formed by applying the ink composition by bringing the heating surface into contact with the ink image after the ink applying step. By performing the heat fixing process, the image on the recording medium is fixed, and the resistance against image abrasion can be further improved.

Heating is preferably performed at a temperature equal to or higher than the minimum film-forming temperature (MFT) of the polymer particles in the image. By heating to MFT or higher, the polymer particles become a film and the image is enhanced. The heating temperature is preferably in the temperature range of MFT or higher. Specifically, the heating temperature is preferably in the range of 40 to 80 ° C, more preferably in the range of 50 ° C to 75 ° C, and still more preferably in the range of 55 ° C to 70 ° C.
The minimum film forming temperature (MFT) of the polymer particles is controlled by the Tg of the polymer and the type and amount of the ink solvent. Generally, the lower the Tg, the lower the I / O value of the ink solvent, the lower the amount of the ink solvent. The greater the number, the lower the MFT.

  The pressure at the time of pressurizing with heating is preferably in the range of 0.1 to 3.0 MPa, more preferably in the range of 0.1 to 1.0 MPa, and still more preferably 0.1 in terms of surface smoothing. It is the range of -0.5MPa.

  The method of heating is not particularly limited, but a non-contact drying method such as a method of heating with a heating element such as a nichrome wire heater, a method of supplying warm air or hot air, a method of heating with a halogen lamp, an infrared lamp, etc. Preferably, it can be mentioned. The heating and pressing method is not particularly limited. For example, a method of pressing a hot plate against the image forming surface of a recording medium, a pair of heating and pressing rollers, a pair of heating and pressing belts, or a recording medium Using a heating and pressing device equipped with a heating and pressing belt arranged on the image recording surface side and a holding roller arranged on the opposite side, heat fixing by bringing them into contact, such as a method of passing a pair of rollers, etc. The method of performing is mentioned suitably.

  In the case of heating and pressing, a preferable nip time is 1 to 10 seconds, more preferably 2 to 1 second, and further preferably 4 to 100 milliseconds. Moreover, a preferable nip width is 0.1 mm to 100 mm, more preferably 0.5 mm to 50 mm, and still more preferably 1 to 10 mm.

  The heat and pressure roller may be a metal metal roller, or a metal core bar provided with a coating layer made of an elastic body and, if necessary, a surface layer (also referred to as a release layer). Good. The latter metal core can be formed of, for example, a cylindrical body made of iron, aluminum, SUS, or the like, and the surface of the metal core is preferably at least partially covered with a coating layer. The coating layer is particularly preferably formed of a silicone resin or fluororesin having releasability. Further, it is preferable that a heating element is built in one core metal of the heat and pressure roller, and heat treatment and pressure treatment are performed simultaneously or necessary by passing a recording medium between the rollers. Accordingly, the recording medium may be sandwiched and heated using two heating rollers. As the heating element, for example, a halogen lamp heater, a ceramic heater, a nichrome wire or the like is preferable.

  As a belt base material constituting the heat and pressure belt used in the heat and pressure apparatus, seamless nickel brass is preferable, and the thickness of the base material is preferably 10 to 100 μm. Further, as the material of the belt base material, aluminum, iron, polyethylene or the like can be used in addition to nickel. When silicone resin or fluororesin is provided, the thickness of the layer formed using these resins is preferably 1 to 50 μm, more preferably 10 to 30 μm.

  Further, in order to realize the pressure (nip pressure), for example, an elastic member such as a spring having tension so that a desired nip pressure can be obtained in consideration of the nip gap at both ends of a roller such as a heat and pressure roller. Select and install.

  The conveyance speed of the recording medium when using a heat and pressure roller or a heat and pressure belt is preferably in the range of 200 to 700 mm / second, more preferably 300 to 650 mm / second, and still more preferably 400 to 600 mm / second. It is.

-Recording media-
The image forming method of the present invention records an image on a recording medium.
The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in absorption and drying of ink in image recording by a general ink jet method using water-based ink, and pigment movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. According to the image forming method of the present invention, it is possible to record a high quality image excellent in color density and hue by suppressing pigment movement.

  As the recording medium, commercially available media can be used. For example, “OK Prince fine quality” manufactured by Oji Paper Co., Ltd., “Shiorai” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries ( Fine coated paper such as “New NPI fine quality” manufactured by Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Lightweight coated paper (A3) such as “OK Coat L” manufactured by Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. ) Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. Is mentioned. It is also possible to use various photographic papers for ink jet recording.

Among the above, from the viewpoint of obtaining a high-quality image having a large effect of suppressing pigment movement and better color density and hue than before, preferably, the water absorption coefficient Ka is 0.05 to 0.5 mL. / M ² · ms ^1/2 recording medium, more preferably 0.1 to 0.4 mL / m ² · ms ^1/2 recording medium, still more preferably 0.2 to 0.3 mL / m. It is a recording medium of ² · ms ^1/2 .

  The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI paper pulp test method No. 51: 2000 (issued by Japan Paper Pulp Technology Association). Specifically, the absorption coefficient Ka is an automatic scanning absorption meter. It is calculated from the difference in the amount of water transferred between the contact time of 100 ms and the contact time of 900 ms using KM500Win (manufactured by Kumagai Riki Co., Ltd.).

  Among the recording media, so-called coated paper used for general offset printing is preferable. 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. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, it is preferable to use a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate. More specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

  The recorded matter recorded on the recording medium by the image forming method of the present invention is excellent in light resistance, sharpness and scratch resistance even when recording at high speed.

  The present invention will be described more specifically with reference to the following examples. The scope of the present invention is not limited to the specific examples shown below. Unless otherwise specified, “part” and “%” are based on mass.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), and three columns are connected in series using TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, and TSKgeL SuperHZ2000 (all are trade names of Tosoh Corporation). , THF (tetrahydrofuran) was used as an eluent. The conditions were as follows: the sample concentration was 0.35% by mass, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and the RI detector was used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It produced from eight samples of "A-2500", "A-1000", and "n-propylbenzene".

[Example 1]
<Preparation of inkjet ink>
-Preparation of self-dispersing polymer particles-
In a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 560.0 g of methyl ethyl ketone was charged and the temperature was raised to 87 ° C. While maintaining the reflux state in the reaction vessel (hereinafter referred to as reflux until the end of the reaction), 220.4 g of methyl methacrylate, 301.6 g of isobornyl methacrylate, 58.0 g of methacrylic acid, 108 g of methyl ethyl ketone, and “V-601” (Wako Pure) A mixed solution consisting of 2.32 g (manufactured by Yakuhin Co., Ltd.) was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, the mixture was stirred for 1 hour, and (1) a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added, followed by stirring for 2 hours. Subsequently, the step (1) was repeated four times, and a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added, and stirring was continued for 3 hours. After completion of the polymerization reaction, the temperature of the solution was lowered to 65 ° C., and 163.0 g of isopropanol was added and allowed to cool. The weight average molecular weight (Mw) of the obtained copolymer was 63000, and the acid value was 65.1 (mgKOH / g).

Next, 317.3 g of the obtained polymerization solution (solid content concentration 41.0%) was weighed, 46.4 g of isopropanol, 1.65 g of a 20% maleic anhydride aqueous solution (based on the water-soluble acidic compound and copolymer). 40.77 g of 2 mol / L NaOH aqueous solution was added, and the temperature in the reaction vessel was raised to 70 ° C. Next, 380 g of distilled water was added dropwise at a rate of 10 ml / min to disperse in water (dispersing step).
Thereafter, under reduced pressure, the temperature in the reaction vessel was kept at 70 ° C. for 1.5 hours, and 287.0 g of isopropanol, methyl ethyl ketone and distilled water were distilled off in total (solvent removal step), and Proxel GXL (S) (Arch Chemicals, Inc.) 0.278 g (manufactured by Japan Co., Ltd.) (440 ppm as benzoisothiazolin-3-one with respect to the solid content of the polymer) was added. Thereafter, filtration was carried out with a 1 μm filter, and the filtrate was recovered to obtain an aqueous dispersion of self-dispersing polymer particles B-01 having a solid concentration of 26.5%. The obtained self-dispersing polymer particles were diluted with ion-exchanged water and measured for physical properties of a 25.0% liquid. As a result, pH 7.8, electric conductivity 461 mS / m, viscosity 14.8 mPa · s, volume average particle diameter It was 2.8 nm.

<Measurement of volume average particle diameter Mv>
The obtained aqueous dispersion of self-dispersing polymer particles is appropriately diluted to a concentration suitable for measurement (loading index is in the range of 0.1 to 10), and ultrafine particle size distribution analyzer Nanotrac UPA-EX150 (Nikkiso Co., Ltd.) The volume average particle diameter of each aqueous dispersion was measured under the same measurement conditions by the dynamic light scattering method. That is, the measurement was performed under the conditions of particle permeability: transmission, particle refractive index: 1.51, particle shape: non-spherical, density: 1.2 g / cm ³ , solvent: water, cell temperature: 18-25 ° C.

~ Synthesis of resin dispersant P-1 ~
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. A solution in which 50 g of ethyl methacrylate, 11 g of methacrylic acid, and 39 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, and the temperature was raised to 78 ° C. and heated for 4 hours. MEK was added to the obtained reaction solution, and phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid (copolymerization ratio [mass% ratio] = 50/39/11) copolymer (resin dispersant P-1) 36.8% Of MEK was obtained.
The composition of the obtained resin dispersant P-1 was confirmed by 1H-NMR, and the weight average molecular weight (Mw) determined by GPC was 49400. Furthermore, when the acid value of this polymer was determined by the method described in JIS standard (JIS K 0070: 1992), it was 71.7 mgKOH / g. Moreover, it was 94 degreeC when Tg was measured.

~ Synthesis of resin dispersant P-2 ~
Resin dispersant P-1 was carried out in the same manner except that the monomer% of the copolymerization component was changed, and phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid (copolymerization ratio [mass% ratio] = 50/20 / 30) A 37.2 mass% MEK solution was obtained.
The weight average molecular weight (Mw) of the obtained resin dispersion P-2 was 47600.

-Synthesis of resin dispersant P-3-
To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 240 g of methyl ethyl ketone, N- (4-vinylbenzyl) -10H-acridine-9-one and N- (3-vinylbenzyl) -10H-acridine-9-one ( 1/1 = wt / wt) 30 g, methacrylic acid 20 g, and ethyl methacrylate 150 g were added and heated to 75 ° C. in a nitrogen atmosphere. To this, 16 g of methyl ethyl ketone was added to dimethyl-2,2′-azobisisobutyrate. A solution in which 2.44 g of rate was dissolved was added.
After stirring for 2 hours while maintaining the same temperature, a solution of 1.0 g of dimethyl-2,2′-azobisisobutyrate dissolved in 2 g of methyl ethyl ketone was added and reacted for another 2 hours, and then 2 g of methyl ethyl ketone. A solution in which 1.0 g of dimethyl-2,2′-azobisisobutyrate was dissolved was added, heated to 80 ° C. and heated for 4 hours.
Methyl ethyl ketone (MEK) was added to the obtained reaction solution, and resin dispersants P-3 (N- (4-vinylbenzyl) -10H-acridin-9-one and N- (3-vinylbenzyl) were added. ) A MEK solution of -10H-acridin-9-one (1/1 = wt / wt) / ethyl methacrylate / methacrylic acid (copolymerization ratio [mass ratio] = 15/75/10) copolymer) Obtained.

A part of the obtained solution was heat-dried under reduced pressure to obtain non-volatile content, which was 36.8%.
The composition of the obtained resin dispersant P-3 was confirmed by 1H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44200.

(Preparation of yellow pigment dispersion Y1)
Pigment Yellow 74 (Fast Yellow FG, manufactured by Sanyo Color Co., Ltd.) as a pigment, 42 g of phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid copolymer (resin dispersant P-1) in solid content, 108 g of methyl ethyl ketone, As a pH adjuster, 47.2 g of 1 mol / L sodium hydroxide (degree of neutralization with respect to methacrylic acid 88 mol%) and 369.5 g of ion-exchanged water were predispersed with a disper, and further a disperser (manufactured by Microfluidics) , Microfluidizer M-140K, 150 MPa). Furthermore, it filtered with the filter of 1 micrometer of pore diameters, and collect | recovered filtrates.
Subsequently, after removing methyl ethyl ketone from the obtained dispersion at 56 ° C. under reduced pressure and further removing 1 part of water, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), It was used and centrifuged at 8000 rpm for 30 minutes, and the supernatant other than the precipitate was collected.
Subsequently, the obtained dispersion (supernatant) was heated at 70 ° C. for 4 hours, and then 80 ppm of 2-methyl-4-isothiazolin-3-one as a preservative, 5-chloro-2-methyl-isothiazoline-3. -40 ppm of 2-one, 10 ppm of 2-bromo-2-nitropropane-1, 30 ppm of 4,4-dimethyloxazolidine-3-ol, 80 ppm of 1,2-benzisothiazolin-3-one, 2-n-octyl- 4-isothiazolin-3-one was added to a concentration of 30 ppm. Filtration was performed and the filtrate was recovered.
Thereafter, the pigment concentration was determined from the absorbance spectrum to obtain a yellow pigment dispersion Y1 (dispersion of resin-coated pigment particles) having a pigment concentration of 15%. The obtained dispersion had a particle size of 91 nm, pH 8.6, and viscosity 3.2.

(Preparation of yellow pigment dispersion Y2)
CI Pigment Yellow 74 (Fast Yellow FG) 100 g, Resin Dispersant P-2 42 g in solid content, 1 mol / L sodium hydroxide 129 g as a pH adjuster (neutralization degree to methacrylic acid 88 mol%), ion exchange The mixture was mixed with 395.5 g of water and dispersed with a bead mill using 0.1 mmφ zirconia beads for 4 hours. Further, the mixture was filtered through a filter having a pore diameter of 1 μm to prepare a yellow pigment dispersion Y2 having a pigment concentration of 15%.

-Preparation of yellow ink (Y-01)-
Using the yellow pigment dispersion obtained above and the self-dispersing polymer particles B-01, each component was mixed so as to have the following ink composition. This was packed in a plastic disposable syringe and filtered with a PVDF 5 μm filter (Millex-SV, diameter 25 mm, manufactured by Millipore) to prepare cyan ink (ink composition) (Y-01).

-Yellow ink composition (Y-01)-
-Yellow pigment (Pigment Yellow 74): 4.0%
-Resin dispersant P-1 (solid content): 1.7%
-Self-dispersing polymer particle B-01 (solid content): 7%
・ Sanix GP250: 8%
(Sanyo Chemical Industries, Ltd., hydrophilic organic solvent)
Tripropylene glycol monomethyl ether (TPGmME): 8%
(Nippon Emulsifier MFTG, hydrophilic organic solvent)
・ Urea: 5%
(Nissan Chemical Industry Co., Ltd., solid wetting agent)
New Pole PE-108: 0.15%
(Thickener made by Sanyo Chemical Industries, Ltd.)
・ Nikkor DLP-10: 1%
(Nikko Chemicals Co., Ltd., R = C ₁₂ H ₂₅ diester compound of the structural formula in the present invention, n = 10)
・ Orphine E1010: 1%
(Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant)
Ethylene oxide average 10 mol adduct)
-Ion exchange water: remainder The surface tension of the yellow ink was 36 mN / m.

-Preparation of yellow ink (Y-02)-
In the preparation of yellow ink (Y-01), instead of Nikkor DLP-10, Phosphanol RD-720 (manufactured by Toho Chemical Industry Co., Ltd., structural formula R = C ₁₈ H ₃₇ , n = 7, mono) A yellow ink (Y-02) was prepared in the same manner as the yellow ink (Y-01) except that the ester compound: diester compound = 1: 1) was used.

-Preparation of yellow ink (Y-03)-
In the preparation of yellow ink (Y-01), instead of Nikkor DLP-10, Nikkor DDP-6 (manufactured by Nikko Chemicals Co., Ltd., R = C ₁₂ H _{25 to} C ₁₅ H ₃₁ diester compound of the structural formula in the present invention, A yellow ink (Y-03) was prepared in the same manner as the yellow ink (Y-01) except that n = 6) was used.

-Preparation of yellow inks (Y-04) to (Y-8)-
A yellow ink was prepared in the same manner as the yellow ink (Y-01) except that the amount of Olfine E1010 added was changed as shown in Table 1 in the preparation of the yellow ink (Y-01).

-Preparation of yellow inks (Y-09) to (Y-10)-
A yellow ink was prepared in the same manner as the yellow ink (Y-01) except that the surfactant shown in Table 1 was used in place of Olfine E1010 in the preparation of the yellow ink (Y-01).

-Preparation of yellow inks (Y-11) to (Y-14)-
In the preparation of the yellow ink (Y-01), the yellow ink was prepared in the same manner as the yellow ink (Y-01), except that the types and amounts of other surfactants listed in Table 1 were used instead of Olfine E1010. Prepared.

-Preparation of yellow ink (Y-15)-
A yellow ink was prepared in the same manner as the yellow ink (Y-01) except that the amount of Nikkor DLP-10 was changed as shown in Table 1 in the preparation of the yellow ink (Y-01).

-Preparation of yellow ink (Y-16)-
In preparing yellow ink (Y-01), an ink having a surface tension of 36 mN / m was prepared in the same manner as yellow ink (Y-01), except that yellow pigment dispersion Y2 was used instead of yellow pigment dispersion Y1. did.

-Preparation of yellow ink (Y-17)-
In the preparation of the yellow ink (Y-01), an ink having a surface tension of 36 mN / m was prepared in the same manner as the yellow ink (Y-01) except that phosphanol RB-410 was not used.

-Preparation of Cyan Pigment Dispersion C-
Pigment Blue 15: 3 as pigment (phthalocyanine blue A220 wet cake (pigment solid content 33.5%), manufactured by Dainichi Seika Co., Ltd.) as pigment solid content 100 g, and the above phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid 45 g of an acid copolymer (resin dispersant P-1) in solid content, 140 g of methyl ethyl ketone, and 50.6 g of a 1 mol / L sodium hydroxide aqueous solution as a pH adjuster (degree of neutralization with respect to methacrylic acid of 88 mol%) 331 g of ion-exchanged water was predispersed with a disper and further subjected to 8 passes with a disperser (manufactured by Microfluidics, Microfluidizer M-140K, 150 MPa).
Subsequently, after removing methyl ethyl ketone from the obtained dispersion at 56 ° C. under reduced pressure and further removing 1 part of water, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), It was used and centrifuged at 8000 rpm for 30 minutes, and the supernatant other than the precipitate was collected.
Subsequently, the obtained dispersion (supernatant) was heated at 70 ° C. for 4 hours, and then 80 ppm of 2-methyl-4-isothiazolin-3-one as a preservative, 5-chloro-2-methyl-isothiazoline-3. -40 ppm of 2-one, 10 ppm of 2-bromo-2-nitropropane-1, 30 ppm of 4,4-dimethyloxazolidine-3-ol, 80 ppm of 1,2-benzisothiazolin-3-one, 2-n-octyl- 4-isothiazolin-3-one was added to 30 ppm. Filtration was performed to obtain a dispersion of resin-coated pigment particles (cyan pigment dispersion C) having a recovered pigment concentration of 15%.

-Preparation of black pigment dispersion K-
As a pigment, carbon black (# 2600, manufactured by Mitsubishi Chemical Corporation) 100 g, phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid copolymer (resin dispersant P-1) 57 g in solid content, methyl ethyl ketone 155.8 g, pH adjustment As an agent, 10.8 mol of 1 mol / L sodium hydroxide (degree of neutralization with respect to methacrylic acid 110 mol%) and 491 g of ion-exchanged water were predispersed with a disper, and further dispersed with 0.1 mmφ zirconia beads with a bead mill disperser. . After dispersion, the mixture was filtered with a filter having a pore size of 1 μm, and the filtrate was recovered. Thereafter, a dispersion of resin-coated pigment particles having a pigment concentration of 15% (black pigment dispersion K) was obtained in the same manner as cyan pigment dispersion C.

-Preparation of magenta pigment dispersion M-
CI Pigment Red 122 (Chrophtal Jet Magenta DMQ (manufactured by Ciba Japan; magenta pigment) 100 g, 30 g of the above-mentioned resin dispersant P-2 in solid content, 133 g of methyl ethyl ketone, 27.2 g of 1 mol / L NaOH aqueous solution ( The neutralization degree with respect to methacrylic acid 78 mol%) and 424 g of ion-exchanged water were mixed, predispersed by disper mixing, and further subjected to a 10-pass treatment with a disperser (Microfluidizer M-140K, 150 MPa).
Thereafter, a dispersion of resin-coated pigment particles having a pigment concentration of 15% (magenta pigment dispersion M) was obtained in the same manner as cyan pigment dispersion C.

-Preparation of cyan ink (C-01)-
Using the cyan pigment dispersion C obtained above and the self-dispersing polymer particles B-01, each component was mixed so as to have the following ink composition. This was packed in a plastic disposable syringe and filtered through a PVDF 5 μm filter (Millex-SV, diameter 25 mm, manufactured by Millipore) to prepare cyan ink (ink composition) C-01.

-Cyan ink composition (C-1)-
-Cyan pigment (Pigment Blue 15: 3): 2.5%
-Resin dispersant P-1 (solid content): 1.125%
-Self-dispersing polymer particle B-01 (solid content): 8.5%
・ Sanix GP250: 8%
(Sanyo Chemical Industries, Ltd., hydrophilic organic solvent, I / O value 1.30)
Tripropylene glycol monomethyl ether (TPGmME): 8%
(MFTG manufactured by Nippon Emulsifier Co., Ltd., hydrophilic organic solvent, I / O value 0.80)
・ Urea: 5%
(Nissan Chemical Industry Co., Ltd., solid wetting agent)
New Pole PE-108: 0.15%
(Thickener made by Sanyo Chemical Industries, Ltd.)
・ Nikkor DLP-10: 1%
(Nikko Chemicals Co., Ltd., R = C ₁₂ H ₂₅ diester compound of the structural formula in the present invention, n = 10)
・ Orphine E1010: 1%
(Surfactant manufactured by Nissin Chemical Industry Co., Ltd.)
-Ion-exchanged water: The remaining surface tension of the ink composition was 36 mN / m.

-Preparation of cyan inks (C-02) to (C-17)-
In the same manner as in the preparation of the yellow ink (Y-1), the cyan ink is changed in the same manner as the types and amounts of the surfactants shown in Table 1 used in the yellow inks (Y-02) to (Y-17). Cyan inks (C-02) to (C-17) were prepared in the same manner except that the preparation of (C-01) was changed.

―Preparation of magenta ink―
Using the magenta pigment dispersion M obtained above, magenta ink (ink composition) M-01 was prepared in the same manner as cyan ink C-01, except that each component was mixed so as to have the following ink composition. Prepared.

-Magenta ink (M-01) composition-
-Magenta pigment (Pigment Red 122): 5.0%
-Resin dispersant P-2 (solid content): 1.5%
-Self-dispersing polymer particle B-01 (solid content): 7.25%
・ Sanix GP250: 10%
(Sanyo Chemical Industries, Ltd., hydrophilic organic solvent, I / O value 1.30)
Tripropylene glycol monomethyl ether (TPGmME): 6%
(MFTG manufactured by Nippon Emulsifier Co., Ltd., hydrophilic organic solvent, I / O value 0.80)
・ Urea: 5%
(Nissan Chemical Industry Co., Ltd., solid wetting agent)
New Pole PE-108: 0.05%
(Thickener made by Sanyo Chemical Industries, Ltd.)
・ Nikkor DLP-10: 1%
(Nikko Chemicals Co., Ltd., R = C ₁₂ H ₂₅ diester compound of the structural formula in the present invention, n = 10)
・ Orphine E1010: 1%
(Surfactant manufactured by Nissin Chemical Industry Co., Ltd.)
-Ion-exchanged water: The remaining surface tension of the ink composition was 36 mN / m.

-Preparation of magenta inks (M-02) to (M-17)-
In the same manner as in the preparation of the yellow ink (Y-1), the magenta ink is changed in the same manner as the types and amounts of the surfactants shown in Table 1 used in the yellow inks (Y-02) to (Y-17). Magenta inks (M-02) to (M-17) were prepared in the same manner except that the preparation of (M-01) was changed.

~ Preparation of black ink ~
Using the black pigment dispersion K obtained above, the black ink (ink composition) K-01 was prepared in the same manner as the cyan ink C-01 except that each component was mixed so as to have the following ink composition. Prepared.

-Black ink (K-01) composition-
・ Carbon black: 4.0%
-Resin dispersant P-1 (solid content): 2.3%
-Self-dispersing polymer particle B-01 (solid content): 5.2%
・ Sanix GP250: 10%
(Sanyo Chemical Industries, Ltd., hydrophilic organic solvent, I / O value 1.30)
Tripropylene glycol monomethyl ether (TPGmME): 6%
(MFTG manufactured by Nippon Emulsifier Co., Ltd., hydrophilic organic solvent, I / O value 0.80)
・ Urea: 5%
(Nissan Chemical Industry Co., Ltd., solid wetting agent)
New Pole PE-108: 0.3%
(Thickener made by Sanyo Chemical Industries, Ltd.)
・ Nikkor DLP-10: 1%
(Nikko Chemicals Co., Ltd., R = C ₁₂ H ₂₅ diester compound of the structural formula in the present invention, n = 10)
・ Orphine E1010: 1%
(Surfactant manufactured by Nissin Chemical Industry Co., Ltd.)
-Ion-exchanged water: remainder The surface tension of the ink composition was 36 mN / m.

-Preparation of black inks (K-02) to (K-17)-
In the same manner as in the preparation of the yellow ink (Y-1), the black ink was changed in the same manner as the types and amounts of the surfactants shown in Table 1 used in the yellow inks (Y-02) to (Y-17). Black inks (K-02) to (K-17) were prepared in the same manner except that the preparation of (K-01) was changed.

<Preparation of treatment solution>
A treatment liquid was prepared as follows.

-Treatment liquid (T-01)-
Each component was mixed so as to have the following treatment liquid composition to prepare a treatment liquid.

<Composition of treatment liquid>
Cationic polymer 1 (see below): 5%
4-methylmorpholine-N-oxide: 18%
・ Ethylhydroxypropanediol: 8%
・ Nikkor DLP-10: 1%
(Nikko Chemicals Co., Ltd., R = C ₁₂ H ₂₅ diester compound of the structural formula in the present invention, n = 10)
・ Water: remainder ・ Methanesulfonic acid: Adjust to pH 4

-Preparation of treatment liquids (T-02) to (T-12)-
In the preparation of the treatment liquid (T-01), the treatment liquid was changed in the same manner as the treatment liquid (T-01) except that the type and amount of the surfactant and the kind of the cationic polymer were changed as shown in Table 1. Prepared.

Details of the components used in the aqueous ink composition and the treatment liquid are shown below.
・ Orphine E1004 (ethylene oxide average 4 mol adduct of acetylene glycol, manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant)
・ Surfinol 485 (85% by mass of acetylene glycol ethylene oxide adduct, manufactured by AirProducts & ChemicaLs, acetylene glycol surfactant)
・ Surfinol 82 (acetylene diol, manufactured by AirProducts & ChemicaLs, acetylene alcohol surfactant)
・ Zonyl FSN (manufactured by DuPont, fluorosurfactant)
・ Sodium di (2-ethylhexyl) sulfosuccinate (anionic surfactant)
-Poemin SP-006 (polyethyleneimine, manufactured by Nippon Shokubai Co., Ltd.)
・ Emulgen LS-110 (manufactured by Kao Corporation)

<Image Forming Method and Evaluation 1>
(Image forming method)
A GELJET GX5000 printer head manufactured by Ricoh Co., Ltd. was prepared, and the storage tank connected thereto was refilled with the yellow ink (Y-01) obtained above. As a recording medium, a special diamond art double-sided N (Mitsubishi Paper Co., Ltd.) having a basis weight of 104.7 g / m ² is fixed on a stage movable in a predetermined linear direction at 500 mm / second, and the stage temperature is 30 ° C. Then, the treatment liquid (T-01) obtained above was applied with a bar coater to a thickness of about 1.2 μm and dried at 50 ° C. for 2 seconds immediately after the application.
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 degrees 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, an ink droplet amount of 4.8 pL, an ejection frequency of 24 kHz, a resolution of 1200 dpi × 1200 dpi was ejected by the line method, and a solid image having a yellow density of 0.7 was printed. .
Immediately after printing, the sample is dried with a dryer at 60 ° C. for 3 seconds, passed through a pair of fixing rollers heated to 60 ° C., and subjected to a fixing process with a nip pressure of 0.25 MPa and a nip width of 4 mm to obtain an evaluation sample. It was.

  In the same manner as described above, an evaluation sample was prepared with a combination of the yellow ink and the treatment liquid shown in Table 1, and the light resistance of each evaluation sample was evaluated. The evaluation results are shown in Table 2.

(Light resistance evaluation)
The sample for evaluation obtained as described above was irradiated for 20 days using a xenon weather meter (manufactured by Suga Test Instruments Co., Ltd.) under outdoor direct exposure equivalent conditions (9.9 klux), and then the optical density OD before irradiation. With respect to a solid image having a value of 0.7, a dye residual ratio [(post-irradiation density / pre-irradiation density) × 100%] was determined, and light resistance was evaluated according to the following evaluation criteria.
~Evaluation criteria~
A: The residual ratio of the dye was 80% or more.
○: The pigment residual ratio was 70% or more and less than 80%.
X: The pigment residual ratio was less than 70%.

  As is clear from Table 1, all of the ink compositions having the constitution of the present invention were excellent in light resistance.

[Example 2]
<Preparation of ink set>
The ink composition and the treatment liquid obtained above were combined as shown in Table 2 to prepare an ink set.

<Image Forming Method and Evaluation 2>
(Sharpness evaluation)
Sharpness is the same as that used in the (light resistance evaluation), using the same conditions as in the inkjet recording device, and using a yellow ink, magenta ink, cyan ink, and black ink set as the ink. Printed on “Saturation Photo Finishing Pro”. The obtained images were viewed by 20 inspectors, the sharpness was evaluated in the following three stages, and the average of the 20 inspectors was taken as the evaluation result.
~Evaluation criteria~
◎: Slightly superior to very excellent ○: Standard ×: Slightly inferior to very inferior

  Similarly, landscape image samples were prepared using combinations of the ink composition and the treatment liquid shown in Table 2, and the sharpness of each sample was evaluated. The evaluation results are shown in Table 2.

  As is apparent from Table 2, the examples having the constitution of the present invention had good results in both light resistance and sharpness of the image.

Claims (9)

  An ink set comprising: an ink composition containing a pigment, polymer particles, and a phosphate ester-based surfactant; and a treatment liquid containing a cationic polymer having a nitrogen atom in the main chain.   The ink set according to claim 1, wherein the treatment liquid further contains a phosphate ester surfactant.   The ink set according to claim 1, wherein the treatment liquid further contains an acetylene glycol surfactant.   The ink set according to any one of claims 1 to 3, wherein a nitrogen atom of the cationic polymer is a nitrogen atom derived from a secondary amine or a tertiary amine constituting the cationic polymer.   The ink set according to any one of claims 1 to 4, wherein a surface tension of the ink composition is 31 mN / m or more and 45 mN / m or less.   The ink set according to any one of claims 1 to 5, wherein the ink composition further contains an acetylene glycol surfactant.   As the pigment, by a phase inversion emulsification method having a dispersion step of mixing and dispersing a pigment, a polymer dispersant, water and an organic solvent, and a solvent removal step of removing at least one part of the organic solvent and water after the dispersion. The ink set according to any one of claims 1 to 6, comprising the obtained pigment dispersion. An ink application step in which the ink set according to any one of claims 1 to 7 is used, and an ink composition in the ink set is applied to a recording medium;
A treatment liquid application step of applying a treatment liquid in the ink set to a recording medium;
An image forming method comprising:   The image forming method according to claim 8, wherein the recording medium is a coated paper having a base paper and a coating layer containing an inorganic pigment.