JP5676406B2 - Ink set and image forming method - Google Patents

Description

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

Recording methods using the inkjet method are widely used because high-quality images can be recorded on a wide variety of recording media by ejecting ink droplets from a large number of nozzle holes provided in the inkjet head. Has been.
In image recording by an ink jet method, an image recording method may be used in which an image is formed by bringing an ink composition (pigment ink) containing a pigment into contact with a treatment liquid that aggregates components in the pigment ink. Such a combination of pigment ink and treatment liquid is also called an ink set.

For example, an ink composition containing a colorant, resin particles, a water-soluble organic solvent, and water as an ink set capable of suppressing the occurrence of ink bleeding and color mixing in an image while suppressing the occurrence of curling and cockle due to recording And a treatment liquid containing a flocculant that aggregates the components in the ink composition and a water-soluble polymer that does not cause aggregation of the components in the ink composition are known (for example, patents) Reference 1).
An ink set having a pigment ink and a treatment liquid (treatment liquid) containing a polyvalent organic acid and at least one of polyphosphoric acid and metaphosphoric acid as an ink set capable of forming a homogeneous image with uniform dot diameters Is known (see, for example, Patent Document 2).
In addition, as an ink jet recording method in which a high quality image can be obtained by forming an ink jet recorded product excellent in quick-drying by a two-component supply method on plain paper, a polyvalent metal salt and 3-methoxy-3-methyl-1 A step of adhering a colorless pretreatment liquid containing butanol and water to plain paper and pretreating, and at least one of the plainpaper after the pretreatment containing pigment and water and reacting with the polyvalent metal salt; An ink jet recording method including a step of forming an image by ejecting a seed ink composition is known (for example, see Patent Document 3).

JP 2010-23339 A JP 2010-188661 A JP 2009-202596 A

According to the study of the present inventors, in an ink set including an ink composition containing a pigment and water and a treatment liquid containing an organic acidic compound and water, the treatment liquid further contains a water-soluble polymer compound (water-soluble polymer). As a result, it became clear that the roughness of the image can be suppressed.
However, the processing liquid containing the water-soluble polymer compound (water-soluble polymer) easily generates bubbles, and when an image is formed using an ink set containing the processing liquid, the processing liquid caused by the bubbles in the processing liquid It has also been found that uneven coating may occur.
The present invention has been made in view of the above, and it is an object of the present invention to provide an ink set and an image forming method capable of suppressing unevenness in the application of a treatment liquid and forming an image with reduced roughness. This is the issue.

  Specific means for achieving the above object are as follows.

<1> Water-soluble polymer compound and organic acidic compound comprising an ink composition containing a pigment and water, a hydrophilic structural unit having an ionic group which is a sulfonic acid group or a salt thereof, and a hydrophobic structural unit , Silicone oil, and a treatment liquid containing water.
<2> The ink set according to <1>, wherein the silicone oil is dispersed in the treatment liquid using a surfactant .
<3 > The ink according to <1> or <2> , wherein the water-soluble polymer compound includes a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B). set.

[In General Formula (A), R ^a1 represents a hydrogen atom or a methyl group.
In general formula (A), L ^a1 contains a single bond, —COO—, or —CONR ^a3 — (R ^a3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In General Formula (A), L ^a2 represents a single bond or a divalent linking group having 1 to 30 carbon atoms that may include at least one of an ether bond, a thioether bond, and an ester bond.
In the general formula (A), A ^a represents an ionic group which is a sulfonic acid group or a salt thereof . ]

[In general formula (B), ^Rb1 represents a hydrogen atom or a methyl group.
In general formula (B), L ^b1 contains a single bond, —COO—, or —CONR ^b3 — (R ^b3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In general formula (B), R ^b2 represents a hydrogen atom or a monovalent group having 1 to 30 carbon atoms that may contain at least one of an ether bond, a thioether bond, and an ester bond.
However, when R ^b2 is a hydrogen atom, L ^b1 is a single bond. ]

<4 > The ink set according to any one of <1> to < 3 >, wherein the content of the silicone oil is 500 ppm or less with respect to the total amount of the treatment liquid.
< 5 > The content of the silicone oil according to any one of <1> to < 4 >, in which the content of the water-soluble polymer compound is 0.1% by mass to 20.0% by mass with respect to the total amount of the water-soluble polymer compound. Ink set.
< 6 > R ^b2 is a linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, an aliphatic hydrocarbon group having 3 to 12 carbon atoms having a branched structure, or an aliphatic hydrocarbon group having 3 to 12 carbon atoms having a ring structure. The ink set according to any one of < 3 > to < 5 >, which is a group hydrocarbon group, an aralkyl group having 7 to 12 carbon atoms, or an aryloxyalkyl group having 7 to 12 carbon atoms.
< 7 > Any one of < 3 > to < 6 >, wherein the content of the structural unit represented by the general formula (A) is 10% by mass to 50% by mass with respect to the total amount of the water-soluble polymer compound. The ink set according to one.
< 8 > The ink set according to any one of <1> to < 7 >, wherein the water-soluble polymer compound has a weight average molecular weight of 20,000 to 80,000.
<9> is the ^{R a1} represents a hydrogen atom, wherein ^{L a1} is -COO- or -CONH-, wherein ^{L a2} is an alkylene group having 1 to 12 carbon atoms, prior Symbol ^{R b1} is a hydrogen atom or methyl The L ^b1 is —COO—, and the R ^b2 is a linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, a branched hydrocarbon structure having 3 to 12 carbon atoms, Any one of < 3 > to < 8 >, which is a C3-C12 aliphatic hydrocarbon group having a ring structure, a C7-C12 aralkyl group, or a C7-C12 aryloxyalkyl group The ink set described in 1.
< 10 > The ink set according to any one of <1> to < 9 >, wherein the organic acidic compound includes a compound represented by the following general formula (I).

_{C n H 2n + 2-m} (COOH) m ... general formula (I)
[In General Formula (I), n represents an integer of 2 or more, and m represents an integer of 3 or more. ]

< 11 > A treatment liquid application step in which the ink set according to any one of <1> to < 10 > is used, and the treatment liquid is applied onto a recording medium, and the treatment applied onto the recording medium. And an ink application process for applying the ink composition onto the liquid.
< 12 > The image forming method according to < 11 >, further comprising a heat fixing step of heat fixing the image formed by the treatment liquid application step and the ink application step.

  According to the present invention, it is possible to provide an ink set and an image forming method capable of suppressing the uneven application of the treatment liquid and forming an image with reduced roughness.

  The ink set and image forming method of the present invention will be described in detail below.

≪Ink set≫
The ink set of the present invention includes an ink composition containing a pigment and water (hereinafter also simply referred to as “ink”), a water-soluble polymer compound, an organic acidic compound, silicone oil, and a treatment liquid containing water, including.

In recent years, by using an ink composition containing a pigment and water and a treatment liquid containing an organic acidic compound and water, the components (pigments, etc.) in the ink composition are aggregated by the organic acidic compound in the treatment liquid. An image is formed.
As a result of studies by the present inventors, it has been clarified that the roughness of the image tends to be suppressed by further adding a water-soluble polymer compound to the treatment liquid containing the organic acidic compound.
However, the processing liquid containing the water-soluble polymer compound easily generates bubbles, and when an image is formed using an ink set containing the processing liquid, uneven application of the processing liquid due to the bubbles in the processing liquid occurs. It was also found that there was a case. Furthermore, even when an antifoaming agent (specifically, an antifoaming agent other than silicone oil) is included in the treatment liquid in an attempt to reduce bubbles, the application unevenness of the treatment liquid due to foam cannot always be improved. It was also found that there is.
Therefore, the present inventor can suppress uneven application of the treatment liquid due to the bubbles in the treatment liquid by adding a silicone oil as a defoaming agent to the treatment liquid containing the water-soluble polymer compound. The inventors have obtained knowledge that the roughness of the image can be reduced, and have completed the present invention based on this knowledge.

That is, when the ink set has the configuration of the present invention, it is possible to suppress uneven application of the treatment liquid and to suppress the roughness of the formed image.
Hereinafter, the treatment liquid and the ink composition in the ink set of the present invention will be described.

<Processing liquid>
The treatment liquid in the present invention contains a water-soluble polymer compound, an organic acidic compound, and silicone oil, and other components as necessary.
The treatment liquid is a liquid for aggregating components (pigments and the like) in the ink composition with the organic acidic compound. By using a treatment liquid in addition to an ink composition containing a pigment, ink jet recording can be speeded up, and even with high speed recording, images with high density and high resolution (for example, reproducibility of fine lines and fine parts) are excellent. Is obtained.

(Silicone oil)
The treatment liquid contains at least one silicone oil.
Thereby, the application | coating nonuniformity of the process liquid resulting from the bubble in a process liquid can be suppressed.
In general, an antifoaming agent is sometimes used to suppress bubbles in the liquid. However, in the present invention, even if an antifoaming agent other than silicone oil is used, the above-described application unevenness suppressing effect cannot be obtained.

There is no restriction | limiting in particular as said silicone oil, The silicone oil (The modified silicone oil, such as hydrophilic silicone oil is included in the concept of this silicone oil) used suitably as an active ingredient of a well-known silicone antifoamer is selected suitably Can be used.
The silicone oil is not particularly limited, and examples thereof include organopolysiloxanes such as dimethylpolysiloxane and modified organopolysiloxanes such as polyoxyalkylene-modified organopolysiloxane. These may be used individually by 1 type and may use 2 or more types together.
Moreover, as said silicone oil, the silicone oil described in Japanese Patent Publication No. 07-090128 and the silicone oil described in patent 3976113 can also be used, for example.
Moreover, as said silicone oil, the silicone oil whose viscosity in 25 degreeC is 100-100,000 mm < ² > / s is preferable from a defoaming viewpoint.

As the form in which the silicone oil is contained in the treatment liquid, the silicone oil is dispersed in the treatment liquid from the viewpoint of further suppressing the generation of bubbles in the treatment liquid and suppressing coating unevenness due to the bubbles. The form is preferred.
Among these, a form in which the silicone oil is dispersed in the treatment liquid by a surfactant (that is, a form in which the silicone oil is emulsified and dispersed in the treatment liquid) is more preferable.
As a specific method for obtaining a form in which the silicone oil is dispersed in the treatment liquid by a surfactant, a method using an emulsion type silicone antifoaming agent, which will be described later, is preferable when producing the treatment liquid. is there.
The surfactant for dispersing the silicone oil is not particularly limited, and can be appropriately selected from surfactants capable of emulsifying and dispersing silicone oil in a treatment liquid containing water.
A nonionic surfactant is suitable as the surfactant for dispersing the silicone oil.
As the surfactant for dispersing the silicone oil, specifically, for example, a surfactant exemplified as a surface tension adjusting agent described later can be used.

As a method for containing the silicone oil in the treatment liquid, a method for adding a known silicone antifoaming agent to the treatment liquid is suitable.
Here, the silicone antifoaming agent is an antifoaming agent containing silicone oil as an active ingredient.
Examples of the form of the silicone antifoaming agent include various forms such as an oil type silicone antifoaming agent, a compound type silicone antifoaming agent, an emulsion type silicone antifoaming agent, and a self-emulsifying type silicone antifoaming agent.
The oil-type silicone antifoaming agent refers to silicone oil itself (including modified silicone oil such as hydrophilic silicone oil). The hydrophilic silicone oil is also called “hydrophilic oil type silicone antifoaming agent”.
The compound-type silicone antifoaming agent is a form in which particles such as silica and alumina are dispersed in an oil-type silicone antifoaming agent to improve antifoaming properties.
The emulsion type silicone antifoaming agent is a form in which the compound type silicone antifoaming agent is made into an O / W type emulsion by an emulsifier (surfactant) to increase the dispersibility in water.
The self-emulsifying type silicone antifoaming agent contains silicone oil and silica, and forms a O / W type emulsion easily when diluted with water.

As the silicone antifoaming agent, a compound type silicone antifoaming agent, an emulsion type silicone antifoaming agent, and a self-emulsifying type silicone antifoaming agent containing silica particles having excellent antifoaming properties are preferable.
Among these, an emulsion type silicone antifoaming agent is preferable in that the effect of suppressing coating unevenness is particularly remarkable.

As said silicone antifoamer, the following commercial item can be used, for example.
Examples of the commercially available products include KS-508, KS-531, KS-537, KS-604, KM-72, KM-72F, KM-90, KM-98 (manufactured by Shin-Etsu Chemical Co., Ltd.), SF -8427, SF-8428, SH-3749, SH-8400, FZ-2101, FZ-2104, FZ-2118, FZ-2203, FZ-2207 (above, manufactured by Toray Dow Corning Co., Ltd.), BYK-345 BYK-346, BYK-348 (manufactured by Big Chemie Japan Co., Ltd.), TSA-739, TSA-7341, TSA-732, TSA-732A, TSA-772, TSA-730, TSA-770, TSA- 775, YMA 6509, TSA-737, TSA-737F, YSA-6406, TSA-780 (above, momentary performance Performance Materials Japan made a joint company), and the like.

The content of the silicone oil in the processing liquid is not particularly limited, but from the viewpoint of further suppressing the decrease in surface tension of the processing liquid due to the addition of silicone oil and further suppressing the roughness of the image, The total amount is preferably 1500 ppm or less, more preferably 1000 ppm or less, and particularly preferably 500 ppm or less. The content of the silicone oil is preferably 30.0% by mass or less, more preferably 20.0% by mass or less, and particularly preferably 10.0% by mass or less with respect to the total amount of the water-soluble polymer compound.
The lower limit of the content of the silicone oil in the treatment liquid is not particularly limited, but from the viewpoint of further suppressing uneven application of the treatment liquid, the lower limit of the content is 5 ppm relative to the total amount of the treatment liquid. Is preferable, 10 ppm is more preferable, and 50 ppm is particularly preferable. The lower limit of the content is preferably 0.1% by mass, more preferably 0.2% by mass, and particularly preferably 1.0% by mass with respect to the total amount of the water-soluble polymer compound.
In the present invention, “ppm” is based on mass.

(Water-soluble polymer compound)
The treatment liquid in the present invention contains at least one water-soluble polymer compound.
Thereby, the aggregation rate at the time of aggregating the components in the ink composition with the organic acidic compound can be suppressed to some extent, and the ink droplets applied to the recording medium can be expanded to a desired size. Thereby, the roughness of the image due to insufficient spreading of the ink can be suppressed.
Here, “water-soluble” means that it can be dissolved in water at a certain concentration or higher, and any substance that can be dissolved (desirably uniformly) in an aqueous processing solution may be used. Specifically, the solubility in water at 25 ° C. is preferably 5% by mass or more, and more preferably 10% by mass or more.

As described above, when the treatment liquid contains a water-soluble polymer compound, bubbles tend to be generated in the treatment liquid, and uneven application of the treatment liquid due to the bubbles tends to occur.
Therefore, in the present invention, by adding silicone oil to the treatment liquid containing a water-soluble polymer compound, it is possible to suppress uneven application of the treatment liquid due to bubbles in the treatment liquid while suppressing roughness of the image.

The water-soluble polymer compound is not particularly limited, and known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, and polyethylene glycol can be used.
Moreover, as the water-soluble polymer compound, a specific polymer compound described later is also suitable.

  Although there is no limitation in particular in the weight average molecular weight of the said water-soluble high molecular compound, For example, it can be set to 10000-100,000, Preferably it is 20000-80000, More preferably, it is 30000-80000.

In addition, the content of the water-soluble polymer compound in the treatment liquid in the present invention is not particularly limited, but is preferably 0.1% by mass to 10% by mass, and preferably 0.1% by mass to 4 mass% is more preferable, 0.1 mass%-2 mass% is still more preferable, and 0.1 mass%-1 mass% is especially preferable.
When the content is 0.1% by mass or more, the spreading of ink droplets can be further promoted, and when the content is 10% by mass or less, thickening of the treatment liquid can be further suppressed. Moreover, if the said content is 10 mass% or less, the application | coating nonuniformity of the process liquid resulting from the bubble in a process liquid can be suppressed more.

(Specific polymer compound)
Examples of the water-soluble polymer compound contained in the treatment liquid include a polymer compound containing a hydrophilic structural unit having an ionic group (preferably an anionic group) (hereinafter also referred to as “specific polymer compound”). preferable. Thereby, the spreading of the ink droplets applied to the recording medium can be further promoted, and the roughness of the image is further suppressed.
The reason why the above effect can be obtained by the specific polymer compound is presumed as follows.
The specific polymer compound retains affinity with a solvent (for example, water) in the treatment liquid by the action of the ionic group in the side chain portion. On the other hand, in the treatment liquid applied on the recording medium, the polymer compound is mainly near the surface of the treatment liquid (on the side away from the recording medium) by the action of the main chain portion and the side chain portion excluding the ionic group. ). When the ink composition is applied to the treatment liquid on the recording medium in this state, the specific polymer compound present near the surface of the treatment liquid hinders the penetration of the treatment liquid into the ink composition to some extent. It is considered that the aggregation rate of the ink composition by the organic acidic compound is suppressed to some extent, and the spread of the ink droplets is promoted.

As described above, the specific polymer compound is likely to be present in the vicinity of the surface of the treatment liquid, and thereby exhibits a high effect in suppressing the roughness of the image.
However, on the other hand, it was found that when the specific polymer compound was used as the water-soluble polymer compound, bubbles were more likely to occur in the treatment liquid, and uneven application of the treatment liquid due to the bubbles was more likely to occur.
Therefore, when the specific polymer compound is used as the water-soluble polymer compound, the effect of suppressing the coating unevenness of the treatment liquid by the silicone oil is more remarkably exhibited.

Examples of the ionic group in the specific polymer compound include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a boronic acid group, an amino group, an ammonium group, and salts thereof. Among them, preferred is a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a salt thereof, more preferred is a carboxyl group, a sulfonic acid group, or a salt thereof, and still more preferred is a sulfonic acid group or a salt thereof. Salt.
The content of the structural unit having an ionic group (preferably an anionic group) in the water-soluble polymer compound can be, for example, 10 to 100% by mass in the total mass of the water-soluble polymer compound. It is preferably 10 to 90% by mass, more preferably 10 to 70% by mass, further preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass.

The specific polymer compound more preferably includes a hydrophilic structural unit having an ionic group (preferably an anionic group, particularly preferably a sulfonic acid group) and a hydrophobic structural unit.
By including the hydrophobic structural unit, the specific polymer compound is more likely to be present on the surface of the treatment liquid, so that the spread of the ink droplets applied to the recording medium is further promoted, and the roughness of the image is further suppressed.

Thus, when the specific polymer compound includes a hydrophilic structural unit having an ionic group (preferably an anionic group, particularly preferably a sulfonic acid group) and a hydrophobic structural unit, the specific polymer compound Is more likely to exist in the vicinity of the surface of the treatment liquid, so that a more excellent roughness suppressing effect can be obtained.
However, on the other hand, bubbles are more likely to be generated in the processing liquid, and uneven application of the processing liquid due to the bubbles is more likely to occur.
Accordingly, when the specific polymer compound containing a hydrophilic structural unit having an ionic group (preferably an anionic group, particularly preferably a sulfonic acid group) and a hydrophobic structural unit is used as the specific polymer compound. In this case, the effect of suppressing application unevenness by silicone oil is more remarkably exhibited.

  The content of the hydrophobic structural unit in the specific polymer compound can be, for example, 10 to 90% by mass in the total mass of the specific polymer compound, and is preferably 30 to 90% by mass, More preferably, it is 90 mass%, and it is especially preferable that it is 60-80 mass%.

  In the specific polymer compound, the hydrophilic structural unit having an ionic group (preferably an anionic group, particularly preferably a sulfonic acid group) is preferably a structural unit represented by the following general formula (A), which is hydrophobic. As the structural unit, a structural unit represented by the general formula (B) described later is preferable.

-Structural unit represented by formula (A)-
First, the structural unit represented by the general formula (A), which is a preferred example of the hydrophilic structural unit in the specific polymer compound, will be described.

In general formula (A), R ^a1 represents a hydrogen atom or a methyl group.
In general formula (A), L ^a1 contains a single bond, —COO—, or —CONR ^a3 — (R ^a3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In General Formula (A), L ^a2 represents a single bond or a divalent linking group having 1 to 30 carbon atoms that may include at least one of an ether bond, a thioether bond, and an ester bond.
In the general formula ^(A), A ^a represents an ionic group.

R ^a1 is preferably a hydrogen atom.
The L ^a1 is preferably —COO— or CONR ^a3 —, more preferably —COO— or CONH—, and particularly preferably —CONH—.

In R ^a3 , the monovalent group having 1 to 30 carbon atoms that may include at least one of an ether bond, a thioether bond, and an ester bond includes a monovalent hydrocarbon group having 1 to 30 carbon atoms, Alternatively, a monovalent group having 1 to 30 carbon atoms configured by connecting at least one of an ether bond, a thioether bond, and an ester bond and at least one hydrocarbon group can be given.
Examples of the hydrocarbon group for R ^a3 include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group composed of a combination thereof.

Here, the group which consists of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and these combinations in this invention is demonstrated.
In the present invention, the aliphatic hydrocarbon group is not limited to a linear hydrocarbon group, and may have at least one of a ring structure (alicyclic structure) and a branched structure.
In the present invention, the group consisting of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a combination thereof may be unsubstituted or substituted with a substituent. Examples of the substituent include an alkoxy group, a hydroxy group, a halogen atom, and the like.

  Specific examples of the aliphatic hydrocarbon group in the present invention include an alkyl group, an alkenyl group, and an alkynyl group. These may have a branched structure or may have a cyclic structure. Moreover, these may be substituted by the substituent.

  As said alkyl group, a methyl group, an ethyl group, a propyl group, and a butyl group are mentioned as an unsubstituted alkyl group. Examples of the substituted alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group substituted with a methoxy group, a hydroxy group, a chlorine atom, a bromine atom, a fluorine atom, and the like.

Specific examples of the aromatic hydrocarbon group (that is, aryl group) in the present invention are derived from a phenyl group, a condensed aromatic compound having 8 or more carbon atoms, or an aromatic ring compound in which a heterocycle is condensed. And a monovalent group.
The condensed aromatic ring compound having 8 or more carbon atoms is an aromatic ring in which two or more benzene rings are condensed and / or an alicyclic carbonization in which at least one aromatic ring and the aromatic ring are condensed. It is an aromatic compound having 8 or more carbon atoms composed of hydrogen.
Specific examples of the condensed aromatic compound having 8 or more carbon atoms include naphthalene, anthracene, fluorene, phenanthrene, acenaphthene, and the like.

  Examples of the group consisting of a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group in the present invention include an aralkyl group and an alkylaryl group. These may have a branched structure or may have an alicyclic structure. Moreover, these may be substituted by the substituent.

  In the present invention, the “monovalent group formed by linking at least one of an ether bond, a thioether bond, and an ester bond and at least one hydrocarbon group” includes an alkoxy group, an alkylthio group, Alkylcarbonyloxy group, alkyloxycarbonyl group, aryloxy group, arylthio group, arylcarbonyloxy group, aryloxycarbonyl group, alkyloxyaryl group, aryloxyalkyl group, alkylthioaryl group, arylthioalkyl group, alkylcarbonyloxyaryl Group, arylcarbonyloxyalkyl group, alkyloxycarbonylaryl group, aryloxycarbonylalkyl group, and the like.

In R ^a3 , the number of carbon atoms of the aliphatic hydrocarbon group is preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, particularly preferably 1 to 3, and most preferably 1.
In R ^a3 , the aromatic hydrocarbon group preferably has 6 to 16 carbon atoms, more preferably 6 to 14 carbon atoms, still more preferably 6 to 10 carbon atoms, and particularly preferably 6 carbon atoms.
In R ^a3 , the hydrocarbon group composed of a combination of the aliphatic hydrocarbon group and the aromatic hydrocarbon group preferably has 7 to 28, more preferably 7 to 15, still more preferably 7 to 12, ~ 9 is particularly preferred.

As R ^a3 , preferably, at least one of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an ether bond, a thioether bond, and an ester bond is linked to at least one hydrocarbon group. And a monovalent group having 1 to 12 carbon atoms, more preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 12 carbon atoms, and particularly preferably a hydrogen atom.

In the L ^a2, ether bond, a divalent linking group thioether bond, and an ester bond of at least one kind of carbon atoms which may contain 1 to 30, a divalent hydrocarbon group having 1 to 30 carbon atoms Or a divalent group having 1 to 30 carbon atoms formed by linking at least one of an ether bond, a thioether bond, and an ester bond and at least one of a hydrocarbon group.
Examples of the hydrocarbon group in ^La2 include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group composed of a combination thereof.

Specific examples of the aliphatic hydrocarbon group for L ^a2 include an alkylene group, an alkenylene group, and an alkynylene group, which may have a branched structure or an alicyclic structure.
Examples of the group consisting of a combination of the aliphatic hydrocarbon group and an aromatic hydrocarbon group for L ^a2 (arylene), may have a branched structure or may have an alicyclic structure, Examples include an arylene alkylene group and an alkylene arylene group.
In the L ^a2 The "ether bond, a thioether bond, and at least one ester bond divalent group composed at least one is connected hydrocarbon group", the aforementioned "ether bond, a thioether bond And a divalent group obtained by removing one hydrogen atom from the group exemplified as “a monovalent group formed by linking at least one kind of ester bond and at least one kind of hydrocarbon group”.

In ^La2 , the aliphatic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 3 to 4 carbon atoms.
In the ^{L a2,} the number of carbon atoms of the aromatic hydrocarbon group preferably has 6 to 16, preferably 6 to 14 and more, more preferably 6 to 10, 6 is particularly preferred.
In ^La2 , the hydrocarbon group composed of a combination of the aliphatic hydrocarbon group and the aromatic hydrocarbon group preferably has 7 to 28, more preferably 7 to 15, more preferably 7 to 12, and 7 ~ 9 is particularly preferred.

As L ^a2 , preferably, a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or at least one of an ether bond, a thioether bond or an ester bond and at least one hydrocarbon group are linked. It is a group having 1 to 12 carbon atoms, more preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 12 carbon atoms, and still more preferably an aliphatic hydrocarbon group having 1 to 12 carbon atoms. In particular, an alkylene group having 1 to 12 carbon atoms is preferable.

Examples of the ionic group represented by A ^a include a cationic group and an anionic group, and among these, an anionic group is preferable.
Here, the cationic group represents a group dissociable into a cation or a group dissociated into a cation, and the anionic group represents a group capable of dissociating into an anion or a group dissociated into an anion. .
Specific examples of A ^a include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a boronic acid group, an amino group, an ammonium group, or a salt thereof. Among these, from the viewpoint of moderate acidity, a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a salt thereof is preferable, and a carboxyl group, a sulfonic acid group, or a salt thereof is more preferable. Is a sulfonic acid group or a salt thereof.

The structural unit represented by the general formula (A) is a structural unit derived from a monomer having an ionic group (that is, a structural unit formed by polymerization of a monomer having an ionic group). It may be a structural unit formed by introducing an ionic group after the (trunk polymer) is formed. In the present invention, from the viewpoint of production efficiency and stability, a structural unit derived from a monomer having an ionic group is preferable.
As the monomer having an ionic group, a commonly used monomer can be used without particular limitation.

Specific examples of the monomer having an anionic group as the ionic group include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2- And methacryloyloxymethyl succinic acid.
Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. .
Examples of the monomer having a phosphate group include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2 -Acryloyloxyethyl phosphate and the like.
The monomer which has an anionic group can be used individually by 1 type or in mixture of 2 or more types.

  Specific examples of the monomer having a cationic group as the ionic group may include monomers described in “Polymer Handbook 4th Edition John Wiley & Sons”, etc. A mixture of seeds or more can be used.

  The content of the structural unit represented by the general formula (A) can be, for example, 10 to 100% by mass, preferably 10 to 90% by mass, based on the total mass of the specific polymer compound. It is more preferably 10 to 70% by mass, further preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass.

Examples of the combination of the groups in formula (A), from the viewpoint of providing the effect of the invention more effectively, the ^{R a1} represents a hydrogen atom, is said ^{L a1} is -COO- or -CONH-, wherein ^{L a2} is an alkylene group having 1 to 12 carbon atoms, wherein preferably the combination ^{a a} is a sulfonic acid group or a salt thereof, wherein ^{L a1} is a -CONH-, wherein ^{L a2} is 3-4 carbon atoms A combination in which A ^a is a sulfonic acid group or a salt thereof, a combination in which L ^a2 is an alkylene group having 4 carbon atoms, and the A ^a is a sulfonic acid group or a salt thereof. Particularly preferred.

  Hereinafter, although the specific example of a structural unit represented by the said general formula (A) is shown, this invention is not limited to the following specific examples. In the following specific examples, the carboxyl group, sulfonic acid group, and phosphoric acid group may be in the form of a salt.

-Structural unit represented by formula (B)-
Next, the structural unit represented by the general formula (B), which is a preferred example of the hydrophobic structural unit in the specific polymer compound, will be described.

In general formula (B), ^Rb1 represents a hydrogen atom or a methyl group.
In general formula (B), L ^b1 contains a single bond, —COO—, or —CONR ^b3 — (R ^b3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In general formula (B), R ^b2 represents a hydrogen atom or a monovalent group having 1 to 30 carbon atoms that may contain at least one of an ether bond, a thioether bond, and an ester bond.
However, when R ^b2 is a hydrogen atom, L ^b1 is a single bond.

R ^b1 is preferably a methyl group.
The L ^b1 is preferably —COO— or CONR ^a3 —, more preferably —COO— or CONH—, and particularly preferably —COO—.

In R ^b3 , the monovalent group having 1 to 30 carbon atoms that may contain at least one of an ether bond, a thioether bond, and an ester bond includes a monovalent hydrocarbon group having 1 to 30 carbon atoms, Alternatively, a monovalent group having 1 to 30 carbon atoms configured by connecting at least one of an ether bond, a thioether bond, and an ester bond and at least one hydrocarbon group can be given.
In the R ^b3 , examples of the hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group composed of a combination thereof.
Here, examples of the group consisting of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a combination thereof are as described above.

In ^Rb3 , the aliphatic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 3, and most preferably 1.
In the ^{R b3,} the number of carbon atoms of the aromatic hydrocarbon group is preferably 6 to 16, more preferably 6 to 14, more preferably 6 to 10, 6 is particularly preferred.
In ^Rb3 , the hydrocarbon group composed of a combination of the aliphatic hydrocarbon group and the aromatic hydrocarbon group preferably has 7 to 28, more preferably 7 to 15, still more preferably 7 to 12, and 7 ~ 9 is particularly preferred.

As R ^b3 , preferably, a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or at least one of an ether bond, a thioether bond or an ester bond and at least one hydrocarbon group are linked. It is a monovalent group having 1 to 12 carbon atoms, more preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 12 carbon atoms, and particularly preferably a hydrogen atom.

In R ^b2 , the monovalent group having 1 to 30 carbon atoms which may contain at least one of an ether bond, a thioether bond, and an ester bond is a monovalent hydrocarbon having 1 to 30 carbon atoms. And a monovalent group having 1 to 30 carbon atoms formed by linking at least one of a group, an ether bond, a thioether bond, and an ester bond and at least one of a hydrocarbon group.
In R ^b2 , examples of the hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group composed of a combination thereof.
Here, examples of the group consisting of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a combination thereof are as described above.

In ^Rb2 , the number of carbon atoms of the aliphatic hydrocarbon group is preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, and preferably 1 to 4 when it does not include a ring structure and a branched structure. Is particularly preferred. 3-12 are preferable, as for carbon number of the said aliphatic hydrocarbon group, when a ring structure is included, 6-12 are more preferable, and 6-10 are especially preferable. 3-12 are preferable, as for carbon number of the said aliphatic hydrocarbon group, when containing a branched structure, 6-12 are more preferable, and 6-10 are especially preferable.
In R ^b2 , the aromatic hydrocarbon group preferably has 6 to 16 carbon atoms, more preferably 6 to 14 carbon atoms, still more preferably 6 to 10 carbon atoms, and particularly preferably 6 carbon atoms.
In R ^b2 , the number of carbon atoms of the group consisting of the aliphatic hydrocarbon group and the aromatic hydrocarbon group is preferably 7 to 28, more preferably 7 to 15, further preferably 7 to 12, and 7 to 9 Is particularly preferred.

R ^b2 is preferably an aliphatic hydrocarbon group (that is, a linear or branched aliphatic hydrocarbon group or an aliphatic hydrocarbon group having an alicyclic structure); an aliphatic hydrocarbon group and an aromatic hydrocarbon A group composed of a combination with a group (preferably an aralkyl group); a monovalent group composed of at least one of an ether bond, a thioether bond or an ester bond and at least one aliphatic hydrocarbon group linked (preferably Is an aryloxy group); a monovalent group (preferably an aryloxyalkyl group) formed by linking an aliphatic hydrocarbon group and an aromatic hydrocarbon group to at least one of an ether bond, a thioether bond or an ester bond ;

R ^b2 is more preferably an aliphatic hydrocarbon group (that is, a linear or branched aliphatic hydrocarbon group or an aliphatic hydrocarbon group having a ring structure); an aliphatic hydrocarbon group and an aromatic hydrocarbon A group composed of a combination with a group (preferably an aralkyl group); a monovalent group constituted by connecting an aliphatic hydrocarbon group and an aromatic hydrocarbon group by at least one of an ether bond, a thioether bond or an ester bond (Preferably an aryloxyalkyl group);
It is.

R ^b2 is more preferably a group consisting of a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group (preferably an aralkyl group); an aliphatic hydrocarbon represented by at least one of an ether bond, a thioether bond or an ester bond. A monovalent group (preferably an aryloxyalkyl group) constituted by connecting a group and an aromatic hydrocarbon group.

R ^b2 is particularly preferably a group consisting of a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group (preferably an aralkyl group).

In addition, as a more specific form of R ^b2 , from the viewpoint of more effectively achieving the effect of the present invention, a straight-chain aliphatic hydrocarbon group having 1 to 12 carbon atoms and 3 carbon atoms having a branched structure. An aliphatic hydrocarbon group having 12 to 12 carbon atoms, an aliphatic hydrocarbon group having 3 to 12 carbon atoms having a ring structure, an aralkyl group having 7 to 12 carbon atoms, or an aryloxyalkyl group having 7 to 12 carbon atoms, and a branched structure An aliphatic hydrocarbon group having 3 to 12 carbon atoms, an aliphatic hydrocarbon group having 3 to 12 carbon atoms having a ring structure, an aralkyl group having 7 to 12 carbon atoms, or an aryloxyalkyl group having 7 to 12 carbon atoms Are more preferable, an aralkyl group having 7 to 12 carbon atoms or an aryloxyalkyl group having 7 to 12 carbon atoms is more preferable, and an aralkyl group having 7 to 12 carbon atoms is particularly preferable.

Moreover, as a combination of each group in the said general formula (B), said ^Rb1 is a hydrogen atom or a methyl group, said ^Lb1 is -COO-, and said ^Rb2 is linear C1-C1. 12 aliphatic hydrocarbon groups, C3-C12 aliphatic hydrocarbon groups having a branched structure, C3-C12 aliphatic hydrocarbon groups having a ring structure, C7-C12 aralkyl groups, or A combination that is an aryloxyalkyl group having 7 to 12 carbon atoms is preferable, the R ^b1 is a methyl group, and the R ^b2 has a branched hydrocarbon structure having 3 to 12 carbon atoms and a ring structure. More preferred is a combination of an aliphatic hydrocarbon group having 3 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, or an aryloxyalkyl group having 7 to 12 carbon atoms, wherein R ^b1 is a methyl group, and R ^{b A combination in which 2} is an aralkyl group having 7 to 12 carbon atoms or an aryloxyalkyl group having 7 to 12 carbon atoms is particularly preferable.

The structural unit represented by the general formula (B) is preferably a structural unit derived from the following monomer.
That is, as the monomer constituting the structural unit represented by the general formula (B), specifically, styrene, α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) Acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, tert-octyl (meth) acrylate, stearyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-bromoethyl (meth) acrylate, 4-chlorobutyl (meth) Acrylate, cyanoethyl (meth) acrylate, 2-acetoxyethyl (meth) acrylate, benzyl (meth) acrylate, chlorobenzyl (meth) acrylate, methoxybenzyl (meth) acrylate, 2-chlorocyclohexyl (meth) acrylate, cyclohexyl (meth) Acrylate, norbornyl (meth) acrylate, isobornyl (meth) acrylate, furfuryl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, phenyl (meth) acrylate, cresyl (meth) acrylate, naphthyl (meth) acrylate, 2-phenoxyethyl (Meth) acrylate, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate 2,2-dimethyl-3-hydroxypropyl (meth) acrylate, triethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, 2-methoxyethyl (meth) acrylate, 3-methoxybutyl (meth) ) Acrylate, 2-ethoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, 2-iso-propoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) ) Acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2- (3-phenylpropyloxy) ethyl (meth) acrylate, 2-acetoxyethyl METAKU Rate, 2-acetoacetoxyethyl methacrylate, allyl methacrylate, glycidyl methacrylate, 1-bromo-2-methoxyethyl acrylate, 1,1-dichloro-2-ethoxyethyl acrylate, 2,2,2-tetrafluoroethyl acrylate, 1H, 1H, 2H, 2H-perfluorodecyl acrylate, and the like.
Here, (meth) acrylate refers to acrylate or methacrylate.

  In order for the specific polymer compound to be present in the vicinity of the surface of the treatment liquid applied on the recording medium, it is preferable that the fluidity is low when the treatment liquid is heated and dried. For this reason, as the specific polymer compound, one having a high glass transition temperature generally correlated with the softening temperature of the polymer compound is preferable. From that viewpoint, as the monomer that forms the structural unit represented by the general formula (B), methacrylate is preferable to acrylate.

  When the specific polymer compound includes one or more structural units represented by the general formula (B), the total content is, for example, 10 to 90% by mass in the total mass of the specific polymer compound. It is preferably 30 to 90% by mass, more preferably 50 to 90% by mass, and particularly preferably 60 to 80% by mass.

  The specific polymer compound preferably includes at least one of the structural units represented by the general formula (B) in addition to the structural unit represented by the general formula (A). From the viewpoint that it is easy to control “hydrophilicity” and “property existing near the surface of the treatment liquid” by adjusting the composition ratio of the structural units, the structural unit represented by the general formula (A) and It is particularly preferable to include three or more structural units selected from the group consisting of the structural units represented by the general formula (B).

The specific polymer compound in the present invention contains a structural unit represented by the general formula (A) and other structural units other than the structural unit represented by the general formula (B) as necessary. Also good.
As other structural units, for example, among structural units derived from known vinyl monomers, structural units other than the structural unit represented by the general formula (A) and the structural unit represented by the general formula (B) Can be used.

  Although there is no limitation in particular in the weight average molecular weight of the said specific high molecular compound, For example, it can be set to 10000-100,000, Preferably it is 20000-80000, More preferably, it is 30000-80000.

Further, the content of the specific polymer compound in the treatment liquid in the present invention is not particularly limited, but is preferably 0.1% by mass to 10% by mass, and preferably 0.1% by mass to 4 mass% is more preferable, 0.1 mass%-2 mass% is still more preferable, and 0.1 mass%-1 mass% is especially preferable.
When the content is 0.1% by mass or more, the spreading of ink droplets can be further promoted, and when the content is 10% by mass or less, thickening of the treatment liquid can be further suppressed. Moreover, if the said content is 10 mass% or less, the application | coating nonuniformity of the process liquid resulting from the bubble in a process liquid can be suppressed more.

The specific polymer compound is a monomer (preferably for forming a structural unit represented by the general formula (A) by various polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Can be further synthesized by a known synthesis method in which a monomer component containing a monomer for forming the structural unit represented by formula (B) is homopolymerized or copolymerized.
The polymerization reaction can be performed by a known operation such as a batch system, a semi-continuous system, or a continuous system. The polymerization initiation method includes a method using a polymerization initiator, a method of irradiating light or radiation, and the like. These polymerization methods and polymerization initiation methods are, for example, the revised version of Tsuruta Junji “Polymer Synthesis Method” (published by Nikkan Kogyo Shimbun, 1971), Takatsu Otsu, Masato Kinoshita, “Experimental Methods for Polymer Synthesis” It is described in pp. 47-154 published in 1972.
Among the above polymerization methods, a solution polymerization method using a polymerization initiator (for example, a radical polymerization initiator) is particularly preferable. Solvents used in the solution polymerization method include, for example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, benzene, toluene, acetonitrile, A single organic solvent such as methylene chloride, chloroform, dichloroethane, methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol, or a mixture of two or more thereof may be used, or a mixed solvent with water may be used.
The polymerization temperature can be set in relation to the molecular weight of the polymer to be produced, the type of initiator, and the like. Usually, the polymerization temperature is about 0 ° C. to 100 ° C., but the polymerization is preferably performed in the range of 50 to 100 ° C. The reaction time is preferably about 1 to 30 hours. The obtained polymer may be subjected to purification such as reprecipitation.

  Hereinafter, exemplary compounds (A-1 to A-29) of the specific polymer compound are shown, but the present invention is not limited to these. In the following structure, Me is a methyl group, Et is an ethyl group, nBu is a normal butyl group, and tBu is a tertiary butyl group.

In the exemplary compounds A-1 to A-29, a, b, c, and d indicate the content ratio (% by mass) of each structural unit. The sum of a, b, c, and d is 100.
In exemplary compounds A-1 to A-29, a combination in which the a is 0 to 73, the b is 0 to 90, the c is 10 to 90, and the d is 0 to 90 is preferable. is there.
Specific combinations of a / b / c / d in exemplary compounds A-1 to A-29 include 5/5/90/0, 33/33/34/0, 17/50/33/0, 50 / 17/33/0, 40/10/30/0, 56/17/27/0, 60/13/27/0, 70/3/27/0, 90/0/10/0, 73/0 / 27/0, 50/0/50/0, 20/0/80/0, 5/0/90/0, 0/90/10/0, 0/77/23/0, 0/50/50 / 0, 0/20/80/0, 40/30/27/3, 34/30/27/9, 18/40/27/15.

(Organic acidic compounds)
The treatment liquid contains at least one organic acidic compound.
Thereby, components (pigments etc.) in the ink composition can be aggregated.
As the organic acidic compound, at least one polyvalent organic acid can be used.
The polyvalent organic acid is preferably a compound containing two or more carboxyl groups in one molecule.
Examples of the polyvalent organic acid include tartaric acid, phthalic acid, 4-methylphthalic acid, DL-malic acid, malonic acid, glutaric acid, dimethylmalonic acid and maleic acid as compounds containing two carboxyl groups in one molecule. It is done. Of these, DL-malic acid, malonic acid, glutaric acid, dimethylmalonic acid and maleic acid are preferred.

Further, as the polyvalent organic acid, a compound represented by the following general formula (I) is also suitable as a compound containing three or more carboxyl groups in one molecule.
When the organic acidic compound contains a compound represented by the following general formula (I), the cohesiveness is further improved, and the movement of the ink droplets applied on the recording medium is further suppressed. As a result, the roughness of the image due to the movement of the ink droplets is further suppressed.

_{C n H 2n + 2-m} (COOH) m ... general formula (I)
[In General Formula (I), n represents an integer of 2 or more, and m represents an integer of 3 or more. ]

In the general formula (I), n is preferably an integer of 3 to 5. When n is 3 or more, the roughness of the image is further suppressed. When n is 5 or less, the scratch resistance of the image (the physical strength of the image; the same applies hereinafter) is further improved.
Moreover, in the said general formula (I), it is preferable that the said m is an integer of 3-5. When m is 3 or more, the movement of the ink droplet is further suppressed. When m is 5 or less, the abrasion resistance of the image is further improved.

  Specific examples of the compound represented by the general formula (I) include 1,2,3-propanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, Etc.

  When the organic acidic compound includes the compound represented by the general formula (I), the organic acidic compound is added to the compound represented by the general formula (I), in addition to the above-mentioned “two carboxyls in one molecule”. It is preferable to include a “compound containing a group”.

  Moreover, when the organic acidic compound in this invention contains the compound represented by the said general formula (I), the content does not have limitation in particular, 5 mass%-30 mass% with respect to the whole quantity of an organic acidic compound. It is preferable that When the content is 5% by mass or more, the roughness of the image can be further suppressed, and when the content is 30% by mass or less, the abrasion resistance of the image is further improved.

  In addition, when the organic acidic compound in the present invention contains the compound represented by the general formula (I), the content is not particularly limited, but the content is 0.5 mass relative to the total amount of the treatment liquid. % To 25% by mass is preferable, 0.5% to 20% by mass is more preferable, 0.5% to 15% by mass is further preferable, and 0.5% to 10% by mass is particularly preferable. When the content is 0.5% by mass or more, the roughness of the image can be further suppressed, and when the content is 25% by mass or less, the abrasion resistance of the image is further improved.

  In the present invention, the content of the total organic acidic compound contained in the treatment liquid is not particularly limited, but from the viewpoint of suppressing the cohesiveness of the ink and the roughness of the image, the content is relative to the total amount of the treatment liquid. 0.5 mass% to 25 mass% is preferable, 5 to 25 mass% is more preferable, and 10 to 20 mass% is particularly preferable.

(Phosphoric acid, phosphoric acid compound)
The treatment liquid in the present invention may contain at least one of phosphoric acid and a phosphoric acid compound as an inorganic acid. Thereby, uneven gloss of the image is suppressed. It is considered that uneven glossiness of an image is caused by a reaction between a component (for example, calcium carbonate) in a recording medium and an organic acidic compound in a processing liquid.
As the phosphoric acid compound, for example, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, or a salt thereof can be used.

  In the treatment liquid of the present invention, the content of the organic acidic compound with respect to the total of the organic acidic compound and the phosphoric acid and the phosphoric acid compound is not particularly limited, but is preferably 60% by mass to 90% by mass. . When the content is 60% by mass or more, the roughness of the image is further suppressed. Further, when the content is 90% by mass or less, uneven glossiness of the image is further suppressed, and the abrasion resistance of the image is further improved.

(water)
The treatment liquid in the present invention contains water.
Although there is no restriction | limiting in particular in content of water, The range of 10-99 mass% is preferable, More preferably, it is 50-90 mass%, More preferably, it is 60-80 mass%.

(Organic solvent)
The treatment liquid in the present invention preferably contains at least one selected from organic solvents.
The organic solvent is preferably an organic solvent that dissolves 5 g or more in 100 g of water at 20 ° C. (hereinafter also referred to as “water-soluble organic solvent”).
As the water-soluble organic solvent, the same water-soluble organic solvents as those contained in the ink described later can be used. Among these, from the viewpoint of curling suppression, polyalkylene glycol or a derivative thereof is preferable. Diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, polyoxypropylene More preferably, it is at least one selected from oxyethylene polyoxypropylene glycol.
The content of the organic solvent in the treatment liquid is not particularly limited, but from the viewpoint of curling suppression, it is preferably 1 to 30% by mass, and preferably 5 to 15% by mass with respect to the entire treatment liquid. More preferred.

(Nitrogen-containing heterocyclic compounds and organic mercapto compounds)
The treatment liquid in the present invention may contain at least one selected from nitrogen-containing heterocyclic compounds and organic mercapto compounds. Thereby, the abrasion resistance of the image and the transportability of the recording medium are improved. Among these, it is preferable to contain a nitrogen-containing heterocyclic compound.

-Nitrogen-containing heterocyclic compound-
The structure of the nitrogen-containing heterocyclic compound is preferably a nitrogen-containing 5-membered ring structure or a 6-membered ring structure, and particularly preferably a nitrogen-containing 5-membered ring structure.

Among the nitrogen-containing 5-membered ring structure or the nitrogen-containing 6-membered ring structure, a 5- or 6-membered heterocyclic structure preferably containing at least one kind of carbon atom, nitrogen atom, oxygen atom, sulfur atom and selenium atom Is preferred. This hetero ring may be condensed with a carbon aromatic ring or a hetero aromatic ring.
Examples of the heterocycle include a tetrazole ring, a triazole ring, an imidazole ring, a thiadiazole ring, an oxadiazole ring, a selenadiazole ring, an oxazole ring, a thiazole ring, a benzoxazole ring, a benzthiazole ring, a benzimidazole ring, a pyrimidine ring, and a tria ring. Examples thereof include a zaindene ring, a tetraazaindene ring, a pentaazaindene ring, and the like.

  These rings may have a substituent, and the substituent is a nitro group, a halogen atom (for example, chlorine atom, bromine atom), a mercapto group, a cyano group, or a substituted or unsubstituted alkyl group (for example, methyl group). , Ethyl, propyl, t-butyl, cyanoethyl groups), aryl groups (for example, phenyl, 4-methanesulfonamidophenyl, 4-methylphenyl, 3,4-dichlorophenyl, naphthyl groups), alkenyl groups ( For example, allyl group), aralkyl group (for example, benzyl, 4-methylbenzyl, phenethyl groups), sulfonyl group (for example, methanesulfonyl, ethanesulfonyl, p-toluenesulfonyl groups), carbamoyl group (for example, unsubstituted carbamoyl, methyl) Carbamoyl, phenylcarbamoyl groups), sulfamoyl groups (eg Sulfamoyl, methylsulfamoyl, phenylsulfamoyl groups), carbonamido groups (eg acetamido, benzamide groups), sulfonamido groups (eg methanesulfonamide, benzenesulfonamide, p-toluenesulfonamide groups) ), Acyloxy groups (for example, acetyloxy and benzoyloxy groups), sulfonyloxy groups (for example, methanesulfonyloxy), ureido groups (for example, unsubstituted ureido, methylureido, ethylureido, and phenylureido groups), acyl groups ( For example, acetyl, benzoyl groups), oxycarbonyl groups (for example, methoxycarbonyl, phenoxycarbonyl groups), oxycarbonylamino groups (for example, methoxycarbonylamino, phenoxycarbonylamino, 2-ethylhexyl) Each group sill butyloxycarbonylamino), optionally substituted with hydroxyl group and the like. Multiple substituents may be substituted on one ring.

Specific examples of preferable nitrogen-containing heterocyclic compounds include the following.
That is, imidazole, benzimidazole, benzoindazole, benzotriazole, tetrazole, benzoxazole, benzothiazole, pyridine, quinoline, pyrimidine, piperidine, piperazine, quinoxaline, morpholine and the like, and these include the alkyl group and carboxyl group described above. And may have a substituent such as a sulfo group.

Preferred nitrogen-containing 6-membered ring compounds are compounds having a triazine ring, a pyrimidine ring, a pyridine ring, a pyrroline ring, a piperidine ring, a pyridazine ring or a pyrazine ring, and among them, a compound having a triazine ring or a pyrimidine ring is preferable. These nitrogen-containing 6-membered ring compounds may have a substituent. In this case, the substituent is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and more preferably 1 to 6 carbon atoms. Are 1 to 3 alkoxy groups, hydroxyl groups, carboxyl groups, mercapto groups, 1 to 6 carbon atoms, more preferably 1 to 3 alkoxyalkyl groups, 1 to 6 carbon atoms, more preferably 1 to 3 hydroxyalkyl groups. Can be mentioned.
Specific examples of preferable nitrogen-containing 6-membered ring compounds include triazine, methyltriazine, dimethyltriazine, hydroxyethyltriazine ring, pyrimidine, 4-methylpyrimidine, pyridine and pyrroline.

-Organic mercapto compounds-
Examples of the organic mercapto compound include alkyl mercapto compounds, aryl mercapto compounds, and heterocyclic mercapto compounds.
Examples of the alkyl mercapto compound include cysteine and thiomalic acid, examples of the aryl mercapto compound include thiosalicylic acid, and examples of the heterocyclic mercapto compound include 2-phenyl-1-mercaptotetrazole, 2-mercaptobenzimidazole, Examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptopyrimidine, 2,4-dimercaptopyrimidine, 2-mercaptopyridine, and the like. These include substituents such as an alkyl group, a carboxyl group, and a sulfo group. May be included.

  Among the nitrogen-containing heterocyclic compounds and the organic mercapto compounds, benzotriazole, 5-methylbenzotriazole, 5-aminobenzotriazole, 5-chlorobenzotriazole, tetrazole, 5-aminotetrazole, 5-methyltetrazole, 5-phenyl Tetrazole is particularly preferred and benzotriazole is most preferred.

The nitrogen-containing heterocyclic compound and the organic mercapto compound can be used alone or in combination.
The content (total content) of the nitrogen-containing heterocyclic compound and the organic mercapto compound in the treatment liquid is not particularly limited, but is 0.1 to 5.0% by mass with respect to the total amount of the treatment liquid. Is preferable, and it is more preferable that it is 0.1-3.0 mass%.

(Surfactant)
The treatment liquid in the present invention may contain at least one surfactant. The surfactant can be used as a surface tension adjusting agent. Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.
Among these, a nonionic surfactant or an anionic surfactant is preferable from the viewpoint of the aggregation rate of the ink composition.

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

  Although there is no restriction | limiting in particular as content of surfactant in the said processing liquid, It is preferable that it is content that the surface tension of a processing liquid will be 40 mN / m or more, and it will be 40-60 mN / m. The content is more preferable, and the content is more preferably 42 to 50 mN / m.

(Other aggregation components)
The treatment liquid in the present invention can contain other aggregating components in addition to the above-mentioned organic acidic compound, as long as the effects of the present invention are not impaired. Examples of other flocculants include polyvalent metal salts and polyallylamine.
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 polyvalent metal salt in the treatment liquid can be, for example, 1 to 10% by mass.

-Other additives-
The treatment liquid in the present invention can be configured to contain other additives in addition to the above components.
Other additives include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, viscosity adjusters, dispersion stabilizers, rust preventives, chelating agents. And the like, and known additives. In addition, an antifoaming agent other than the silicone oil may be included as long as the effects of the present invention are not hindered.
Further, the treatment liquid in the present invention does not substantially contain a colorant such as a pigment. Specifically, the content of the colorant is less than 1% by mass (more preferably 0.5% by mass or less) with respect to the total amount of the treatment liquid. And more preferably 0.1% by mass or less).

There is no restriction | limiting in particular as surface tension of the said process liquid, For example, it can be 40 mN / m or more. Among these, from the viewpoint of suppressing the occurrence of curling in the recording medium, it is more preferably 40 to 60 mN / m, more preferably 42 to 50 mN / m, and further preferably 42 to 47 mN / m.
The surface tension of the treatment liquid can be adjusted, for example, by adding a surfactant. Further, the surface tension of the treatment liquid is measured under conditions of 25 ° C. by a plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

In addition, the treatment liquid in the present invention preferably has a pH (25 ° C. ± 1 ° C.) of 3.5 or less, more preferably 0.5 to 2.5, from the viewpoint of the aggregation rate of the ink composition. More preferably, it is 0.5 to 2.0.
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, and still more preferably in the range of 2 to 15 mPa · s, from the viewpoint of the aggregation rate of the ink composition. A range of 2 to 10 mPa · s is particularly preferable. In addition, a viscosity is measured on 25 degreeC conditions using VISCOMETER TV-22 (product made from TOKI SANGYO CO.LTD).

<Ink composition>
The ink composition in the present invention contains a pigment.
The ink composition contains a pigment dispersant (polymer dispersant), resin particles, an organic solvent, a neutralizer, water, and other components as necessary.

(Pigment)
The ink composition in the present invention contains at least one pigment.
The type of the pigment is not particularly limited, and conventionally known organic and inorganic pigments 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. Further, any pigment that is not described in the color index can be used as long as it is dispersible in the aqueous phase. Further, pigments whose surface is treated with a surfactant, a polymer dispersant, or the like, or graft carbon can also be used.
Of these pigments, azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, and carbon black pigments are particularly preferable.

~ Dispersant ~
In the ink composition according to the invention, a form in which the pigment is dispersed by a dispersant is preferable.
Among these forms, a form in which the pigment is dispersed with a polymer dispersant, that is, a form in which at least a part of the pigment is coated with the polymer dispersant is particularly preferable. Hereinafter, the pigment at least partially coated with the polymer dispersant is also referred to as “resin-coated pigment”.

The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be a water-soluble polymer dispersant or a water-insoluble polymer dispersant.
As the low molecular surfactant type dispersant, the surfactant type dispersant described in paragraphs 0016 to 0020 of JP 2010-188661 A can be used.

Among the polymer dispersants, hydrophilic polymer compounds can be used as the water-soluble polymer dispersant.
As the water-soluble polymer dispersant, for example, natural hydrophilic polymer compounds described in paragraphs 0021 to 0022 of JP 2010-188661 A can be used.

As the water-soluble polymer dispersant, a synthetic hydrophilic polymer compound may be used.
Examples of the synthetic hydrophilic polymer compound include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, acrylic resins such as polyacrylamide, polyacrylic acid or alkali metal salts thereof, and water-soluble styrene acrylic resins. Water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic acid resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium, amino group, etc. Examples thereof include polymer compounds having a cationic functional group salt in the side chain.

  Among these, from the viewpoint of pigment dispersion stability and aggregation, a polymer compound containing a carboxyl group is preferable. For example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic resin, and a water-soluble vinyl naphthalene. High molecular compounds containing a carboxyl group such as an acrylic resin and a water-soluble vinyl naphthalene maleic resin are particularly preferred.

Among the polymer dispersants, as the water-insoluble dispersant, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include a meth) acrylate- (meth) acrylic acid copolymer and a styrene-maleic acid copolymer.
The styrene- (meth) acrylic acid copolymer, the (meth) acrylic acid ester- (meth) acrylic acid copolymer, the polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, the styrene-maleic acid. The acid copolymer may be a binary copolymer or a ternary or higher copolymer.
Of these, (meth) acrylic acid ester- (meth) acrylic acid copolymer is preferable as the polymer dispersant, and benzyl (meth) acrylate- (meth) acrylic acid-methyl (meth) acrylate ternary copolymer Coalescence is particularly preferred.
Here, (meth) acrylic acid refers to acrylic acid or methacrylic acid, and (meth) acrylate refers to acrylate or methacrylate.

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

  The acid value of the polymer dispersant is not particularly limited, but from the viewpoint of cohesiveness, the acid value of the polymer dispersant is larger than the acid value of resin particles (preferably self-dispersing resin particles) described later. It is preferable.

  In the ink composition of the present invention, the mass ratio of pigment to dispersant (pigment: dispersant) is preferably in the range of 1: 0.06 to 1: 3, and 1: 0.125 to 1: 2. More preferably, it is 1: 0.125 to 1: 1.5.

The average particle diameter of the pigment (in the case of a resin-coated pigment, the average particle diameter of the resin-coated pigment; hereinafter the same) is preferably 10 to 200 nm, more preferably 10 to 150 nm, and even more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. The particle size distribution of the pigment is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.
The average particle size and particle size distribution of the pigment are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is.

In the present invention, the content of the pigment in the ink composition is preferably from 1 to 25 mass%, more preferably from 2 to 20 mass%, based on the total amount of the ink composition, from the viewpoint of image density. 2-10 mass% is especially preferable.
You may use a pigment individually by 1 type or in combination of 2 or more types.

(Resin particles)
The ink composition in the present invention can contain resin particles as necessary.
The resin particles preferably have a function of fixing the ink composition by destabilizing and agglomerating to increase the viscosity of the ink when it comes into contact with a treatment liquid described later or a dried region thereof. Such resin particles are preferably dispersed in at least one of water and an organic solvent.

Resin particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, and benzoguanamine resins. A phenol resin, a silicone resin, an epoxy resin, a urethane resin, a paraffin resin, a fluorine resin, or a latex thereof can be used. Preferred examples include acrylic resins, acrylic-styrene resins, styrene resins, cross-linked acrylic resins, and cross-linked styrene resins.
The resin particles can also be used in the form of latex.

The weight average molecular weight of the resin particles is preferably 10,000 or more and 200,000 or less, more preferably 20,000 or more and 200,000 or less.
The average particle size of the resin particles is preferably in the range of 1 nm to 1 μm, more preferably in the range of 1 nm to 200 nm, still more preferably in the range of 1 nm to 100 nm, and particularly preferably in the range of 1 nm to 50 nm.
The glass transition temperature Tg of the resin particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.

It is preferable to use self-dispersing resin particles (self-dispersing resin particles) as the resin particles.
Here, the self-dispersing resin is dispersed in an aqueous medium by a functional group (particularly an acidic group or a salt thereof) of the polymer itself when dispersed by the phase inversion emulsification method in the absence of a surfactant. A water-insoluble polymer that can be in a state.
Here, the dispersed state refers to an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in an aqueous medium. It includes both states.
As the self-dispersing resin particles, the self-dispersing resin particles described in paragraphs 0090 to 0121 of JP2010-64480A and paragraphs 0130 to 0167 of JP2011-068805A can be used. .

  The molecular weight of the water-insoluble polymer constituting the self-dispersing resin particles is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. Further preferred. 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 is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is 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 is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The water-insoluble polymer constituting the self-dispersing resin particles is a structural unit derived from an aromatic group-containing (meth) acrylate monomer (preferably a structure derived from phenoxyethyl (meth) acrylate) from the viewpoint of controlling hydrophilicity / hydrophobicity of the polymer. It is preferable that 15-80 mass% of the total mass of a self-dispersing polymer particle is included as a copolymerization ratio for the unit and / or the structural unit derived from benzyl (meth) acrylate.
In addition, the water-insoluble polymer is derived from a carboxyl group-containing monomer having a copolymerization ratio of 15 to 80% by mass of a structural unit derived from an aromatic group-containing (meth) acrylate monomer from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. It is preferable to include a structural unit and a structural unit derived from an alkyl group-containing monomer (preferably a structural unit derived from an alkyl ester of (meth) acrylic acid), and a structural unit derived from phenoxyethyl (meth) acrylate and / Or a structural unit derived from benzyl (meth) acrylate as a copolymerization ratio of 15 to 80% by mass, a structural unit derived from a carboxyl group-containing monomer, and a structural unit derived from an alkyl group-containing monomer (preferably (meta ) A structural unit derived from an alkyl ester of 1 to 4 carbon atoms of acrylic acid) More preferably, the acid value is 25 to 100, the weight average molecular weight is preferably 3000 to 200,000, the acid value is 25 to 95, and the weight average molecular weight is 5000 to 15. More preferably, it is 10,000.

The content of the resin particles (for example, self-dispersing resin particles) is preferably 0.1 to 20% by mass and more preferably 0.1 to 10% by mass with respect to the total mass of the ink composition.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a resin microparticle, What has a wide particle size distribution or a thing with a monodispersed particle size distribution may be sufficient. Two or more kinds of resin particles having a monodispersed particle size distribution may be mixed and used.

(water)
The ink composition in the present invention contains water.
Although there is no restriction | limiting in particular in content of water, The range of 10-99 mass% is preferable with respect to the whole quantity of an ink composition, More preferably, it is 30-80 mass%, More preferably, it is 50-80 mass%. .

(Organic solvent)
The ink composition in the invention may further contain at least one organic solvent (preferably a water-soluble organic solvent) as necessary.
The water-soluble organic solvent can obtain an effect of preventing drying, wetting or promoting penetration. In order to prevent drying, the ink adheres to and drys at the ink discharge port of the ejection nozzle and is used as an anti-drying agent to prevent clogging. For drying prevention and wetting, the vapor pressure is lower than that of water. A water-soluble organic solvent is preferred. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

  Examples of water-soluble organic solvents include, for example, alkanediols (polyhydric alcohols) such as glycerin, ethylene glycol, and propylene glycol; sugar alcohols; those having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol Alkyl alcohols; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl Ether, diethylene glycol mono-iso-propyl ether, ethylene glycol -N-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono T-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, Dipropylene glycol mono-iso-propyl ether, tripropylene glycol monomethyl ester Glycol ethers such as such as ether and the like. These can be used individually by 1 type or in combination of 2 or more types.

(Surfactant)
The ink composition in the invention preferably contains at least one surfactant.
Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like. From the viewpoint of the aggregation rate, an anionic surfactant or a nonionic surfactant is preferable.

The surfactant is preferably a nonionic surfactant, more preferably an acetylene glycol-based surfactant, from the viewpoint of more effectively achieving the effects of the present invention.
Examples of acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7. -Alkylene oxide adduct of diol etc. can be mentioned, It is preferable that it is at least 1 sort (s) chosen from this. Examples of commercially available products of these compounds include E series such as Olphine E1010 manufactured by Nissin Chemical Industry Co., Ltd.

  The surfactant preferably contains an amount capable of adjusting the surface tension of the ink composition to 25 mN / m or more and 40 mN / m or less in order to eject ink droplets favorably by the ink jet method. Among them, the content of the surfactant is preferably an amount capable of adjusting the surface tension to 27 to 37 mN / m.

  These surfactants can also be used as an antifoaming agent. As the surfactant, fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

(Other additives)
The ink composition in the invention may further contain other additives in addition to the above components. Other additives include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, antifoaming agents, viscosity modifiers, dispersion stabilizers, and rust inhibitors. Known additives such as agents and chelating agents are included. These various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared.

  As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. From the viewpoint of improving the storage stability of the ink composition, the pH adjuster is preferably added so that the pH of the ink composition is 6 to 10, and more preferably added so that the pH is 7 to 10. .

The viscosity of the ink composition in the present invention is preferably in the range of 1 to 30 mPa · s, and preferably in the range of 1 to 20 mPa, from the viewpoint of ejection stability when ejected by an ink jet method and the aggregation rate when using the treatment liquid described below. -The range of s is more preferable, the range of 2-15 mPa * s is further more preferable, and the range of 2-10 mPa * s is especially preferable.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under conditions of 25 ° C. of the ink composition.

  The ink composition in the present invention includes a pigment coated with a polymer dispersant having a carboxyl group, and resin particles, and has a solid content of 7 to 10% by mass, and a solid content other than the pigment relative to the pigment. The content ratio is preferably 0.8 to 1.6, and includes a pigment coated with an acrylic polymer and self-dispersing resin particles, and has a solid content of 7 to 9% by mass. It is more preferable that the content ratio of solids other than the pigment is 1.0 to 1.4.

Although the ink set of the present invention has been described above, the ink set of the present invention has a specific configuration as long as it includes a combination of at least one of the ink compositions and at least one of the treatment liquids. There is no particular limitation.
A preferred configuration of the ink set of the present invention is a combination of the cyan ink as the ink composition, the magenta ink as the ink composition, the yellow ink as the ink composition, and the treatment liquid. A black ink that is the ink composition, a cyan ink that is the ink composition, a cyan ink that is the ink composition, a magenta ink that is the ink composition, A configuration (four-color configuration) composed of a combination of a yellow ink, which is an ink composition, and the treatment liquid may be mentioned.
However, the ink set of the present invention may be a one-color or two-color ink set composed of one or two kinds of ink compositions and a treatment liquid, if necessary.
The ink set of the present invention has other ink compositions such as at least one selected from light cyan ink, light magenta ink, and light yellow ink, if necessary, in addition to the ink composition described above. May be. As the other ink compositions described above, known ink compositions can be used without any particular limitation.
Further, the ink set of the present invention may contain two or more kinds of treatment liquids as necessary. When the ink set of the present invention includes two or more ink compositions, at least one of the ink compositions may be an ink composition containing a pigment and water. Further, when the ink set of the present invention contains two or more kinds of treatment liquids, at least one of the treatment liquids is a treatment liquid containing a water-soluble polymer compound, an organic acidic compound, silicone oil, and water. Good.
The ink set of the present invention is suitably used in the following image forming method of the present invention.

<Image forming method>
In the image forming method of the present invention, the ink set of the present invention described above is used, and a treatment liquid coating step for coating the treatment liquid on a recording medium, and the treatment liquid coated on the recording medium on the treatment liquid. An ink application step of applying an ink composition.
With the image forming method having such a configuration, it is possible to suppress unevenness in application of the treatment liquid due to bubbles and to form an image with reduced roughness.

(Processing liquid application process)
The treatment liquid application step is a step of applying the treatment liquid to a recording medium.
This treatment liquid coating step is provided before the ink application step using the ink composition.
That is, in the image forming method of the present invention, a treatment liquid for aggregating components (such as pigments) in the ink composition is applied to the recording medium in advance before the ink composition is applied (droplet ejection). Then, the ink composition is ejected to form an image so as to come into contact with the treatment liquid applied on the recording medium.
Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

  The treatment liquid can be applied by a known application method using a bar coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like.

  In the present invention, it is preferable to heat-dry the treatment liquid on the recording medium after the treatment liquid is applied on the recording medium and before the ink composition is applied. Thereby, ink coloring properties such as bleeding prevention are improved, and a visible image having a good color density and hue can be recorded.

Heating and drying can be performed by a known heating means such as a heater, a blowing means using blowing air 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.

(Ink application process)
In the ink application step, the above-described ink composition is applied (droplet ejected) onto the treatment liquid of the recording medium coated with the treatment liquid by an inkjet method.
In this step, the ink composition can be applied on the recording medium, and a desired visible image can be formed. The details of the ink composition are as described above.

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. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
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 single 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 in which recording elements are arranged corresponding to the entire area of one side of the recording medium. There is a line system using a head. 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.

The ink application step is preferably started within 10 seconds after the treatment liquid coating step, and more preferably within 0.1 seconds to 10 seconds. Thereby, an image can be recorded at high speed.
In the image forming method of the present invention, by using the ink set described above, even when an image is recorded at high speed, landing interference can be suppressed and a high-definition image can be formed.
Here, “starts within 10 seconds after the treatment liquid application step” means that the time from the end of application / drying of the treatment liquid to the first ink droplet landing on the recording medium is within 10 seconds. Means.

Further, in the ink application step, from the viewpoint of high-definition printing, it is preferable that the amount of ink droplets to be applied (droplet ejection) is 1.5 to 3.0 pL, preferably 1.5 to 2.5 pL. More preferably.
The amount of ink droplets can be adjusted by appropriately selecting the ejection conditions in the ink jet method according to the ink composition to be ejected.

(Heat fixing process)
In the present invention, it is preferable to further provide a heat fixing step of heat fixing the image (ink) formed by the treatment liquid applying step and the ink applying step.
By such heat fixing, the image on the recording medium is fixed, and the scratch resistance of the image is further improved.

The heating is preferably performed at a temperature equal to or higher than the minimum film-forming temperature (MFT) of the resin particles in the image. By heating to MFT or higher, the particles become a film and the image is enhanced.
When pressurizing with heating, the pressure during pressurization 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 in terms of surface smoothing. It is in the range of 0.1 to 0.5 MPa.

The heating method 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 or the like is suitable. Can be listed.
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 mm to 10 mm.

  As the heating and pressing roller, a metal metal roller, or a coating layer made of an elastic body and a surface layer (also referred to as a release layer) as necessary around a metal cored bar is provided. But you can. 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 200 to 700 mm / second, more preferably 300 to 650 mm / second, and still more preferably 400 to 600 mm / second. .

(recoding media)
In the image forming method of the present invention, an image is formed on a recording medium as described above.
Although there is no restriction | limiting in particular in a recording medium, The general printing paper mainly used for a cellulose used for general offset printing etc. can be used.

As the recording medium, so-called coated paper is suitable.
The coated paper is provided with a coating layer (also referred to as a coating layer) containing an inorganic pigment or the like on the surface of high-quality paper, neutral paper or the like, which is generally not surface-treated, mainly composed of cellulose as a support. Is. Although the coated paper tends to cause uneven glossiness in the image area, when the processing liquid contains phosphoric acid or a phosphoric acid compound, the occurrence of uneven glossiness in the image area can be effectively suppressed. . Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is preferable.

  Although there is no restriction | limiting in particular as an inorganic pigment contained in the said coating layer, From a viewpoint from which the effect of gloss nonuniformity suppression by making phosphoric acid or a phosphoric acid compound contain in the said processing liquid is exhibited more notably, a silica and a carion Clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, aluminum oxide, aluminum hydroxide, pseudoboehmite, calcium carbonate, satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, and diatomaceous earth At least one selected from the above is preferable, and calcium carbonate, silica, and carion are more preferable. In particular, when calcium carbonate is contained in the coat layer, the effect of suppressing gloss unevenness by phosphoric acid or a phosphoric acid compound is particularly remarkable.

  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 these, from the viewpoint of obtaining a high-quality image having a large color material movement suppression effect and better color density and hue than before, the water absorption coefficient Ka is preferably 0.05 to 0.5. a recording medium mL ^/ m 2 ^{· ms 1/2,} more preferably recording medium 0.1~0.4mL ^/ m 2 ^{· ms 1/2,} more preferably 0.2-0.3 ml / It is a recording medium of m 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.).

  In the present invention, the application amount of the treatment liquid and the application amount of ink are preferably adjusted as necessary. For example, the coating amount of the treatment liquid may be changed in order to adjust the physical properties such as the viscoelasticity of the aggregate formed by mixing the treatment liquid and the ink according to the recording medium.

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 “ppm” are based on mass.
In Table 2, the ink set No. The “present invention” in the 13 remarks column shall be read as “reference example”.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). Unless otherwise specified, GPC uses HLC-8020 GPC (manufactured by Tosoh Corporation), and uses three columns, TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm), THF (tetrahydrofuran) was used as an eluent. The conditions were as follows: the sample concentration was 0.45 mass%, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and an IR 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".

<Preparation of water-soluble polymer compound (water-soluble polymer)>
Water-soluble polymer compounds (water-soluble polymers 1 to 10) used as components in the treatment liquid were prepared as follows.

(Synthesis of water-soluble polymer 1)
The structure of the water-soluble polymer 1 is shown below.
In the water-soluble polymer 1 shown below, the number on the lower right of each structural unit represents a mass ratio (mass%), and Mw represents a weight average molecular weight. The same applies to the structural formulas of the subsequent polymers.

Water-soluble polymer 1 was synthesized as follows.
In a 200 ml three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 30.0 g of isopropyl alcohol was charged, and the temperature was raised to 65 ° C. in a nitrogen atmosphere.
Next, methyl methacrylate (hereinafter also referred to as “MMA”) (30.0 g), ethyl acrylate (hereinafter also referred to as “EA”) (6.5 g), acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as “AMPS”). (Also referred to as “13.5 g”), isopropyl alcohol (30 g), water (15 g), and “V-601” (a polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) (2.97 g (0.0129 mol)). ); 3 mol% with respect to the total number of moles of monomers (0.430 mol)) was dropped at a constant speed so that the dropping was completed in 2 hours.
After completion of the dropwise addition, the mixture was stirred for 2 hours, and then “V-601” (1.5 mol% (1.48 g) based on the total number of moles of monomers) and isopropyl alcohol (3.0 g) were added and stirred for 2 hours. went.
The obtained polymer solution was neutralized with an aqueous solution of acrylamide-2-methylpropanesulfonic acid and an equimolar number of sodium hydroxide, and isopropyl alcohol was distilled off by concentration under reduced pressure, so that the total amount of the polymer solution became 310 g. Water was added to obtain a polymer aqueous solution containing 16% by mass of water-soluble polymer 1.
The weight average molecular weight (Mw) of the obtained water-soluble polymer 1 was 45000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), and the columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)). Met.

(Preparation of water-soluble polymer 2)
As the water-soluble polymer 2, a commercially available polyvinyl alcohol (PVA235 manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 3500) was prepared.

(Synthesis of water-soluble polymers 3 to 10)
In the synthesis of the water-soluble polymer 1, the following water-soluble polymers 3 to 10 were synthesized in the same manner as the synthesis of the water-soluble polymer 1 except that the monomer species and ratio were changed.
In the following structure, Me is a methyl group, Et is an ethyl group, nBu is a normal butyl group, and tBu is a tertiary butyl group.
In Tables 2 and 3 below, focusing on the monomer component of the water-soluble polymer, the water-soluble polymer 3 is “MMA / AMPS”, the water-soluble polymer 4 is “MMA / SPA (K)”, and the water-soluble polymer. 5 is “MMA / BMA / AMPS”, water-soluble polymer 6 is “MMA / TBMA / AMPS”, water-soluble polymer 7 is “MMA / IBOMA / AMPS”, and water-soluble polymer 8 is “MMA / CHMA / AMPS”. ", The water-soluble polymer 9 is represented as" MMA / BzMA / AMPS ", and the water-soluble polymer 10 is represented as" MMA / PEMA / AMPS ".

<Synthesis of Polymer Dispersant P-1>
According to the following scheme, a polymer dispersant P-1 was synthesized as shown below.

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. in a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and 60 g of benzyl methacrylate. Then, a solution in which 10 g of methacrylic acid and 30 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, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated resin was dried to obtain 96 g of a polymer dispersant P-1. In addition, the number of each structural unit of the polymer dispersant P-1 shown above represents a mass ratio.
The composition of the obtained resin was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44,600. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

<Preparation of pigment dispersion>
(Preparation of cyan dispersion)
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.), which is a cyan pigment, 5 parts of the polymer dispersant P-1, 42 parts of methyl ethyl ketone, and 1N aqueous NaOH solution 5.5 Part and 87.2 parts of ion-exchanged water were mixed and dispersed with a bead mill for 2 to 6 hours using 0.1 mmφ zirconia beads.
After removing methyl ethyl ketone at 55 ° C. under reduced pressure and further removing a part of the water under reduced pressure, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), using a 50 mL centrifuge tube, Centrifugation was performed at 8000 rpm for 30 minutes, and the supernatant liquid other than the precipitate was collected. Thereafter, the pigment concentration was determined from the absorbance spectrum, and a dispersion (cyan dispersion C) of resin-coated pigment particles (pigment coated with a polymer dispersant) having a pigment concentration of 10.2% by mass was obtained. The average particle size of the obtained Cyan Dispersion C was 105 nm.

(Preparation of magenta dispersion)
In the preparation of the cyan dispersion, the same procedure as in the preparation of the cyan dispersion was used, except that Pigment Red 122, which is a magenta pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.). Thus, a dispersion (magenta dispersion M) of resin-coated pigment particles (pigment coated with a polymer dispersant) was prepared. The average particle size of the obtained magenta dispersion M was 85 nm.

(Preparation of yellow dispersion)
Resin-coated pigment was prepared in the same manner as in the preparation of the cyan dispersion, except that Pigment Yellow 74, which is a yellow pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.) A dispersion (yellow dispersion Y) of particles (pigment coated with polymer dispersant) was prepared. The average particle size of the obtained yellow dispersion Y was 82 nm.

(Preparation of black dispersion)
In the preparation of the cyan dispersion liquid, except that carbon black (NIPEX 160-IQ manufactured by Degussa), which is a black pigment, was used instead of Pigment Blue 15: 3 (Phthalocyanine Blue A220, manufactured by Dainichi Seika Co., Ltd.) A dispersion (black dispersion K) of resin-coated pigment particles (pigment coated with a polymer dispersant) was prepared by the method described above. The average particle size of the obtained black dispersion K was 130 nm.

<Preparation of self-dispersing resin particles>
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. While maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) A mixed solution consisting of 44 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.72 g of “V-601” and 36.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C. and stirring was further continued for 2 hours. The weight average molecular weight (Mw) of the obtained copolymer was 64000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 38.9 (mgKOH / g).
Next, 668.3 g of the polymerization solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 913. 7 g was distilled off to obtain an aqueous dispersion (emulsion) of self-dispersing resin fine particles (B-01) having a solid content concentration of 28.0%.

<Preparation of ink>
Using the pigment dispersions (cyan dispersion C, magenta dispersion M, yellow dispersion Y, black dispersion K) and self-dispersing resin particles B-01 obtained above, the ink compositions shown in Table 1 below are used. Ingredients were mixed so that each ink composition (magenta ink composition M1, black ink composition K1, cyan ink composition C1, yellow ink composition Y1) was prepared.
Each prepared ink composition is filtered with a plastic disposable syringe through a PVDF 5 μm filter (Millex SV manufactured by Millipore, diameter 25 mm), and the completed ink (magenta ink M1, black ink K1, cyan ink C1, yellow ink Y1) and did.
About each completed ink, pH was measured using Toa DKK Co., Ltd. pH meter WM-50EG. Moreover, surface tension was measured by Kyowa Interface Science Co., Ltd. FASE Automatic Surface Tensionmeter CBVP-Z.
The results are shown in Table 1.

<Description of Table 1>
・ New Pole GP-250: Organic solvent manufactured by Sanyo Chemical Co., Ltd. ・ Orphine E1010: Nonionic surfactant manufactured by Nissin Chemical Industry Co., Ltd.

<Preparation of treatment liquids 1 to 23>
Treatment liquids 1 to 23 (treatment liquids Nos. 1 to 23) shown in Table 2 and Table 3 below were produced.
Hereinafter, the preparation of the treatment liquid 7 will be mainly described.

(Preparation of treatment liquid 7)
Each component was mixed so that it might become the following composition, and the processing liquid 7 was produced.
-Composition of treatment liquid 7-
・ Diethylene glycol monoethyl ether: 4% by mass
・ Tripropylene glycol monomethyl ether: 4% by mass
Organic acid compound (malonic acid) 17.2% by mass
・ Inorganic acidic compound (phosphoric acid) 4.3% by mass
・ Water-soluble polymer 1 0.5 mass%
・ Benzotriazole: 1% by mass
・ Antifoamer (Momentive Performance Materials Japan TSA-739 (15%); emulsion type silicone antifoam)
... 100ppm as the amount of silicone oil
・ Ion-exchanged water: Total remaining amount of 100% by mass

(Preparation of treatment liquid 1)
In the production of the treatment liquid 7, a treatment liquid 1 was produced in the same manner as in the production of the treatment liquid 7 except that no antifoaming agent was used.

(Preparation of treatment liquids 2-6 and 8-23)
In the preparation of the treatment liquid 7, except that the type of organic acidic compound, the kind of water-soluble polymer, the kind and amount of antifoaming agent (content in the treatment liquid) are as shown in Table 2 and Table 3 below. In the same manner as the treatment liquid 7, treatment liquids 2 to 6 and 8 to 23 were produced.
In the treatment liquid 14, malonic acid and malic acid (mass ratio [malonic acid / malic acid] = 50/50, total content 17.2% by mass) were used as the organic acidic compound.
In the treatment liquids 15 to 23, malonic acid, malic acid, and propanetricarboxylic acid (mass ratio [malonic acid / malic acid / propanetricarboxylic acid] = 42.5 / 42.5 / 15, total content as organic acidic compounds 17.2 mass%) was used.

<Ink set>
A combination of each of the completed inks (magenta ink M1, black ink K1, cyan ink C1, yellow ink Y1) and any one of the treatment liquids 1 to 23 were combined to prepare ink sets 1 to 23. The correspondence between the treatment liquid number and the ink set number is as shown in Tables 2 and 3 below.

<Image formation>
Images were formed under the following conditions using A4 size Tokuhishi Art (Mitsubishi Paper) as the recording medium and using ink sets 1 to 23 shown in Tables 2 and 3 below.
In the image formation described below, ink droplet ejection was started within 10 seconds after the treatment liquid application step.

(Processing liquid application process)
Immediately before the ink application to the recording medium, the treatment liquid was applied to the surface of the recording medium using a coating bar so that the coating amount was 1.7 g / m ² .

Next, the treatment liquid applied on the recording medium was dried under the following conditions.
~ Drying conditions for treatment liquid (blow drying) ~
Wind speed: 15m / s
Temperature and heating method: A contact type flat heater is used from the back side of the recording medium (the surface on which the processing liquid is not applied) so that the surface temperature of the recording medium (the temperature on the side on which the processing liquid is applied) is 60 ° C. Heated.
Air blowing area: 450mm (drying time 0.7 seconds)

(Ink application process)
Four-color single-pass image formation was performed on the recording medium provided with the treatment liquid under the following conditions.
Specifically, an image was formed by applying (dropping) ink of each color under the following conditions onto the processing liquid of the recording medium to which the processing liquid was applied.
Head: A head in which 1,200 dpi / 20 inch width piezo full line heads were arranged for four colors was used.
Discharged droplet amount: 2.4 pL.
Drive frequency: 30 kHz (recording medium conveyance speed 635 mm / sec).

Next, the ink applied on the recording medium was dried under the following conditions.
~ Drying conditions for ink (fan drying) ~
Wind speed: 15m / s
Temperature: The recording medium was heated with a contact type flat heater from the back surface (the surface to which ink was not applied) so that the surface temperature of the recording medium (the temperature to which ink was applied) was 60 ° C.
Air blowing area: 640 mm (drying time 1 second)

(Heat fixing process)
The image formed by applying the ink was heat-fixed using a silicon rubber roller (hardness 50 °, nip width 5 mm) under the following conditions.
Thereby, a sample having an image formed on the recording medium was obtained.
-Heat fixing conditions-
Roller temperature: 90 ° C
Pressure: 0.8 MPa

<Evaluation>
(Roughness evaluation of images)
In the ink application step, magenta ink is applied in a solid form on the treatment liquid to form a magenta solid image, and the dot area ratio of cyan ink is 50% to 80% on the obtained magenta solid image. In this way, a secondary color image was obtained.
The obtained secondary color image was subjected to the heat fixing process described above.
The secondary color image after heat fixing was visually observed and the roughness of the image was evaluated according to the following criteria.
-Evaluation criteria-
5: Roughness was not seen on the whole and was uniform.
4: Slightly fine roughness was observed, but the entire surface was almost uniform.
3: Although a fine roughness was seen, it was a level with no problem in practical use.
2: There was much roughness and it was conspicuous even visually and was a level which becomes a problem in practical use.
1: A lot of roughness with strong shading occurred, and it was a level that was not uniform.

(Evaluation of coating unevenness of treatment liquid)
In the same manner as the image roughness evaluation, secondary color images were continuously formed on 100 recording media.
The secondary color image was visually observed for each of the 100 recording media on which the secondary color images were formed, and it was confirmed whether or not there was uneven application of the treatment liquid due to bubbles in the treatment liquid.
The probability of occurrence of uneven coating on 100 recording media on which secondary color images were formed was determined, and the uneven coating of the treatment liquid was evaluated according to the following criteria.
-Evaluation criteria-
5: Occurrence probability of coating unevenness in 100 recording media was 0%.
4: The probability of occurrence of coating unevenness in 100 recording media was 1% or more and 4% or less.
3: The probability of occurrence of coating unevenness in 100 recording media was 5% or more and 9% or less.
2: The probability of occurrence of coating unevenness in 100 recording media was 10% or more and 19% or less.
1: Occurrence probability of coating unevenness in 100 recording media was 20% or more and 39% or less.
0: The probability of occurrence of coating unevenness in 100 recording media was 40% or more.

<Explanation of Table 2 and Table 3>
-The quantity of a water-soluble polymer shows content (mass%) with respect to the whole quantity of a process liquid.
-The quantity of a silicone antifoamer shows content (mass%) with respect to the process liquid whole quantity of the silicone oil contained in each silicone antifoamer.
KS-537 is a self-emulsifying silicone antifoaming agent manufactured by Shin-Etsu Chemical Co., Ltd.
KS-604 is a hydrophilic oil-type silicone antifoaming agent manufactured by Shin-Etsu Chemical Co., Ltd.
KM-72F is a hydrophilic emulsion type silicone antifoaming agent manufactured by Shin-Etsu Chemical Co., Ltd.
-TSA-739 is an emulsion type silicone antifoaming agent manufactured by Momentive Performance Materials Japan GK.
Olfin AF104 is an acetylene glycol antifoaming agent manufactured by Nissin Chemical Industry Co., Ltd. The amount of Olfin AF104 indicates the content (% by mass) of the active ingredient contained in Olfin AF104 with respect to the total amount of the treatment liquid.
-BYK-012 is a non-silicone antifoaming agent (containing polymer) manufactured by Big Chemie Japan. The amount of BYK-012 indicates the content (% by mass) of the active ingredient contained in BYK-012 with respect to the total amount of the treatment liquid.

  As shown in Table 2 and Table 3, in the ink sets 4 to 23 including the treatment liquids 4 to 23 containing a water-soluble polymer compound (water-soluble polymer), an organic acidic compound, and a silicone antifoaming agent, The coating unevenness was suppressed, and the roughness of the image was suppressed.

Furthermore, from the results of the ink sets 4 to 7, by using an emulsion type silicone defoamer as a silicone defoamer, the silicone oil is dispersed (emulsified and dispersed) with a surfactant in the treatment liquid. It was found that the coating unevenness can be remarkably suppressed and the roughness of the image can be suppressed.
Further, based on the results of ink sets 9 and 13 to 23, by using water-soluble polymers 1 and 3 to 10 containing a hydrophobic structural unit and a hydrophilic structural unit having a sulfonic acid group as the water-soluble polymer, an image was obtained. It was found that the roughness can be further suppressed.
Furthermore, it was found from the results of ink sets 7 to 12 that the roughness of the image can be further suppressed by setting the content of the silicone oil to 500 ppm or less.
Furthermore, from the results of ink sets 14 to 23, it was found that image roughness can be further suppressed by using propanetricarboxylic acid as the organic acidic compound.

  The evaluation result of the secondary color image using magenta ink and cyan ink has been described above, but the same applies to a halftone dot image (black single color image) having a halftone dot area ratio of 50% to 80% formed using black ink. As a result of the evaluation, an evaluation result similar to the evaluation result of the secondary color image was obtained.

Claims (12)

An ink composition containing a pigment and water;
A treatment liquid containing a hydrophilic structural unit having an ionic group which is a sulfonic acid group or a salt thereof and a hydrophobic structural unit, a water-soluble polymer compound, an organic acidic compound, silicone oil, and water; ,
Ink set containing.   The ink set according to claim 1, wherein the silicone oil is dispersed in the treatment liquid by a surfactant. The ink set according to claim 1, wherein the water-soluble polymer compound includes a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B).

[In General Formula (A), R ^a1 represents a hydrogen atom or a methyl group.
In general formula (A), L ^a1 contains a single bond, —COO—, or —CONR ^a3 — (R ^a3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In General Formula (A), L ^a2 represents a single bond or a divalent linking group having 1 to 30 carbon atoms that may include at least one of an ether bond, a thioether bond, and an ester bond.
In the general formula (A), A ^a represents an ionic group which is a sulfonic acid group or a salt thereof . ]

[In general formula (B), ^Rb1 represents a hydrogen atom or a methyl group.
In general formula (B), L ^b1 contains a single bond, —COO—, or —CONR ^b3 — (R ^b3 contains a hydrogen atom, or at least one of an ether bond, a thioether bond, and an ester bond. Represents a monovalent group having 1 to 30 carbon atoms.
In general formula (B), R ^b2 represents a hydrogen atom or a monovalent group having 1 to 30 carbon atoms that may contain at least one of an ether bond, a thioether bond, and an ester bond.
However, when R ^b2 is a hydrogen atom, L ^b1 is a single bond. ] The ink set according to any one of claims 1 to 3 , wherein a content of the silicone oil is 500 ppm or less with respect to a total amount of the treatment liquid. The ink set according to any one of claims 1 to 4 , wherein a content of the silicone oil is 0.1% by mass to 20.0% by mass with respect to a total amount of the water-soluble polymer compound. R ^b2 is a linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, an aliphatic hydrocarbon group having 3 to 12 carbon atoms having a branched structure, or an aliphatic hydrocarbon having 3 to 12 carbon atoms having a ring structure. The ink set according to any one of claims 3 to 5 , which is a group, an aralkyl group having 7 to 12 carbon atoms, or an aryloxyalkyl group having 7 to 12 carbon atoms. The content of the structural unit represented by formula (A) is, relative to the total amount of the water-soluble polymer compound, in any one of claims 3 to 6 is 10% by mass to 50% The ink set described. The ink set according to any one of claims 1 to 7 , wherein the water-soluble polymer compound has a weight average molecular weight of 20,000 to 80,000. R ^a1 is a hydrogen atom, L ^a1 is —COO— or —CONH—, L ^a2 is an alkylene group having 1 to 12 carbon atoms ,
The R ^b1 is a hydrogen atom or a methyl group, the L ^b1 is —COO—, the R ^b2 is a linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, a branched carbon structure having 3 to 3 carbon atoms. 12 aliphatic hydrocarbon group, aliphatic hydrocarbon group having 3 to 12 carbon atoms having a ring structure, an aralkyl group having 7 to 12 carbon atoms, or claims 3 to an aryloxyalkyl group having 7 to 12 carbon atoms The ink set according to claim 8 . The ink set according to any one of claims 1 to 9 , wherein the organic acidic compound contains a compound represented by the following general formula (I).
_{C n H 2n + 2-m} (COOH) m ... general formula (I)
[In General Formula (I), n represents an integer of 2 or more, and m represents an integer of 3 or more. ] The ink set according to any one of claims 1 to 10 , is used,
A treatment liquid application step of applying the treatment liquid onto a recording medium;
An ink application step of applying the ink composition onto the treatment liquid applied on the recording medium;
An image forming method comprising: The image forming method according to claim 11 , further comprising a heat fixing step of heat fixing the image formed by the treatment liquid applying step and the ink applying step.