JP2016193980A - Ink composition for inkjet, ink set and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an ink composition for inkjet capable of forming an image excellent in abrasion resistance and blocking resistance and suppressing wear deterioration of a liquid repellent film provided in an inkjet head; an ink set and an image forming method.SOLUTION: There are provided an ink composition for inkjet which comprises wax particles A having a volume-average particle diameter of 20 nm or more and 60 nm or less and a melting point of 110°C or more, wax particles B having a volume-average particle diameter of 100 nm or more and less than 200 nm and a melting point of 70°C or less, a water-soluble solvent and water, wherein the mass ratio of the content of the wax particles B to the wax particles A is 0.1-5.0; and an ink set and an image forming method using the ink composition for inkjet.SELECTED DRAWING: None

Description

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

  As an ink-jet ink composition (hereinafter also simply referred to as “ink composition”) used in an image forming method by an ink-jet method, in addition to a solvent-based ink composition using a solvent as a solvent, it is suitable for the global environment and working environment. From the point of consideration, water-based ink compositions using water as a solvent are known.

As an ink composition, an ink composition containing a wax is known.
For example, the ink composition having excellent color developability, gloss and scratch resistance of the recorded image includes at least water, a pigment coated with a water-insoluble polymer, and at least two kinds of waxes having different average particle diameters. Ink compositions are known (see, for example, Patent Document 1).
In addition, as an ink composition that gives a recorded material having excellent abrasion resistance, does not deteriorate in abrasion resistance even at high temperature recording, and has excellent recording stability, a pigment, first wax particles, and second wax particles And the first wax particles have a melting point of 120 ° C. or higher and 170 ° C. or lower, the second wax particles have a melting point of 70 ° C. or higher and lower than 120 ° C., and the resin emulsion has a melting point of 50 ° C. The glass wax has a glass transition point of 150 ° C. or lower, the first wax particles include one or more wax particles selected from the group consisting of polyethylene wax particles or polypropylene wax particles, and the second wax particles include polyethylene wax particles. An ink composition containing at least one wax particle selected from the group is known (see, for example, Patent Document 2).
An ink containing a coloring material, water, and wax particles containing at least two kinds of waxes as an ink composition capable of forming an image having excellent storage stability and excellent blocking resistance immediately after image formation A composition is known (see, for example, Patent Document 3).

JP 2007-277290 A JP 2014-162812 A JP 2012-25911 A

However, images formed using the ink compositions of Patent Documents 1 and 2 may be inferior in blocking resistance.
Further, there are cases where it is required to further improve the abrasion resistance of an image formed using the ink composition described in Patent Document 3.

Incidentally, image formation by the ink jet method is performed by discharging an ink composition from an ink discharge surface (nozzle surface) of an ink jet head toward a recording medium. In general, a liquid repellent film having a property of repelling an ink composition is provided on an ink discharge surface (nozzle surface) of the inkjet head. When image formation by the ink jet method is repeatedly performed, the ink composition adheres to the liquid repellent film, and this adhesion may reduce the dischargeability of the ink composition. For this reason, an operation of wiping the ink composition adhering to the liquid repellent film with a nonwoven fabric or the like (hereinafter also referred to as “wiping operation”) is performed.
However, when the ink composition of Patent Document 1 or 2 is used, the liquid repellent film is worn by the wiping operation, and the liquid repellency of the ink discharge surface of the ink jet head is reduced by this wear (hereinafter referred to as this phenomenon). This phenomenon may be referred to as “abrasion degradation of the liquid repellent film”.

This invention is made | formed in view of the above, and makes it a subject to achieve the following objectives.
That is, an object of the present invention is to provide an inkjet ink composition, an ink set, and an image forming method capable of forming an image excellent in abrasion resistance and blocking resistance and suppressing wear deterioration of the liquid repellent film of the inkjet head. Is to provide.

Specific means for solving the problems are as follows.
<1> Wax particles A having a volume average particle diameter of 20 nm or more and 60 nm or less and a melting point of 110 ° C. or more, wax particles B having a volume average particle diameter of 100 nm or more and less than 200 nm and a melting point of 70 ° C. or less, water-soluble An ink-jet ink composition comprising an ionic solvent and water, wherein the mass ratio of the wax particles B to the wax particles A is 0.1 to 5.0.
<2> The inkjet ink composition according to <1>, wherein the wax constituting the wax particles A is polyethylene wax or polypropylene wax.
<3> The ink composition for inkjet according to <1> or <2>, wherein the wax constituting the wax particles B is an acrylic wax.
<4> The inkjet ink composition according to any one of <1> to <3>, wherein the wax constituting the wax particle A is a polyethylene wax, and the wax constituting the wax particle B is an acrylic wax.
<5> The inkjet ink composition according to any one of <1> to <4>, wherein the wax particles A have a melting point of 120 ° C. or higher.
<6> The inkjet ink composition according to any one of <1> to <5>, wherein the content ratio of the wax particles B to the wax particles A is 0.2 to 2.0.
<7> The inkjet ink composition according to any one of <1> to <6>, wherein the content ratio of the wax particles B to the wax particles A is 0.3 to 1.0.
<8> In any one of <1> to <7>, the total content of the wax particles A and the wax particles B is 1.0% by mass to 10% by mass with respect to the total amount of the inkjet ink composition. The ink-jet ink composition as described.
<9> The ink composition for inkjet according to any one of <1> to <8>, further containing carbon black.
<10> The ink composition for inkjet according to any one of <1> to <9>, further containing resin particles.
<11> The inkjet ink composition according to any one of <1> to <10>,
A treatment liquid containing an acid that agglomerates the components in the inkjet ink composition;
Ink set containing.
<12> An ink application step of forming an image by applying the ink-jet ink composition according to any one of <1> to <10> on the recording medium by an ink-jet method;
A treatment liquid application step for applying a treatment liquid containing an acid that agglomerates the components in the inkjet ink composition onto the recording medium; and
A drying step of drying the image after the ink application step and the treatment liquid application step;
An image forming method comprising:

  According to the present invention, an ink composition for ink jet, an ink set, and image formation capable of forming an image excellent in abrasion resistance and blocking resistance and suppressing wear deterioration of a liquid repellent film provided on an ink jet head. A method is provided.

It is a schematic block diagram which shows the structural example of the inkjet recording device used for implementation of image formation.

Hereinafter, the ink composition for inkjet according to the present invention, an ink set using the same, and an image forming method will be described in detail.
In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the present specification, “(meth) acrylic acid” is a concept including both acrylic acid and methacrylic acid, and “(meth) acrylate” is a concept including both acrylate and methacrylate.
In the present specification, “wax particles” mean particles made of wax, and the melting point of the wax particles means the melting point of the wax constituting the wax particles. For example, “wax particles having a melting point of 110 ° C. or higher” means particles made of wax having a melting point of 110 ° C. or higher.
In the present specification, “particle diameter” and “particle diameter” both mean volume average particle diameter unless otherwise specified.

[Inkjet ink composition]
The ink-jet ink composition of the present invention (hereinafter also simply referred to as “ink composition” or “ink”) has a volume average particle diameter of 20 nm to 60 nm and a melting point of 110 ° C. It contains wax particles B having an average particle diameter of 100 nm or more and less than 200 nm and a melting point of 70 ° C. or less, a water-soluble solvent, and water, and the contained mass ratio of the wax particles B to the wax particles A is 0.1. -5.0.

According to the ink composition of the present invention, it is possible to form an image excellent in abrasion resistance and blocking resistance, and to reduce wear and tear of a liquid repellent film provided on an inkjet head (hereinafter also simply referred to as “head”). Can be suppressed.
The reason why this effect is achieved is assumed as follows.
The ink composition of the present invention comprises:
Wax particles A having a high melting point (specifically, a melting point of 110 ° C. or more; the same shall apply hereinafter) and a small particle size (specifically, a volume average particle diameter of 60 nm or less; the same shall apply hereinafter);
Wax particles B having a low melting point (specifically, a melting point of 70 ° C. or lower; the same applies hereinafter) and a large particle size (specifically, a volume average particle size of 100 nm or higher; the same applies hereinafter);
Is included.
In the ink composition of the present invention, it is considered that the wax particles A contribute to improving the abrasion resistance of the image, and the wax particles B contribute to improving the blocking resistance of the image and suppressing wear deterioration of the liquid repellent film. .

Hereinafter, first, the reason for presuming that the effect of improving the scratch resistance and blocking resistance is obtained will be described.
In image formation by the ink jet method, an ink composition is applied on a recording medium to form an image, and then the image is dried at a high temperature (for example, 60 ° C. or higher, preferably 65 ° C. or higher, particularly preferably 70 ° C. or higher). Is done.
In the image formation, it is considered that the wax particles A having a high melting point and a small particle diameter do not melt even during the drying because of the high melting point, and remain in the surface state of the image while maintaining the particle state. Thereby, a minute convex portion derived from the wax particles A is generated on the surface of the image after drying, and it is considered that the abrasion resistance of the image is improved by the minute convex portion. Specifically, when rubbing an image, it is considered that rubbing of the entire surface of the image is mainly suppressed by rubbing the apex of the convex portion, and consequently damage of the entire image due to the rubbing is suppressed.
On the other hand, in the above image formation, the wax particle B having a low melting point and a large particle diameter maintains a particle state in the ink composition before being applied to the recording medium due to the large particle diameter. The melting point is considered to melt at the time of drying. Thereby, it is considered that a film derived from the wax particles B is formed on the surface portion of the image after drying. It is thought that this coating contributes to suppression of blocking (that is, improvement of blocking resistance).

Next, the reason for presuming the effect of suppressing the wear deterioration of the liquid repellent film will be described.
Since the wax particles A are relatively hard particles having a high melting point, it is considered that the wax particles A have a property of polishing the liquid repellent film (that is, causing wear deterioration) during the wiping operation of the ink composition on the liquid repellent film. .
However, the ink composition of the present invention contains not only wax particles A having a property of polishing a liquid repellent film but also wax particles B. The wax particle B is a relatively soft particle having a low melting point and a particle having a large particle size. For this reason, it is considered that the polishing action of the liquid repellent film by the wax particles A is mitigated by the wax particles B acting like a cushion during the wiping operation of the ink composition on the liquid repellent film.
Thus, according to the ink composition of the present invention, it is considered that the abrasion deterioration of the liquid repellent film due to the wax particles A is suppressed by the wax particles B. Further, it is considered that the wear deterioration of the liquid repellent film is suppressed by the wax particles B even when the component that causes wear deterioration of the liquid repellent film is included in addition to the wax particles A.

The effects of the wax particles A (the effect of improving the abrasion resistance of the image) and the effects of the wax particles B (the effect of improving the anti-blocking property of the image and the effect of suppressing the wear deterioration of the liquid repellent film) are as follows. It is effectively exhibited when the content ratio of the particles B (hereinafter, the content ratio [wax particles B / wax particles A]) is 0.1 to 5.0.
Specifically, when the content mass ratio [wax particle B / wax particle A] is 0.1 or more, the effect of the wax particle B is exhibited.
Moreover, the effect by wax particle A is exhibited because content mass ratio [wax particle B / wax particle A] is 5.0 or less.

The wax particles A contained in the ink composition of the present invention may be one type or two or more types. Further, the wax particles B contained in the ink composition of the present invention may be one type or two or more types.
In the present specification, the “containing mass ratio [wax particles B / wax particles A]” is the ratio [the content of the wax particles B with respect to the total amount of the ink composition (the total content when there are two or more types) / the ink composition. Content of wax particles A relative to the total amount (in the case of 2 or more types, the total content)].

The ink composition of the present invention is a water-based ink composition containing water and a water-soluble solvent.
Therefore, the above-mentioned “wear deterioration of the liquid repellent film” means wear deterioration of the liquid repellent film (for example, a liquid repellent film containing a fluorine compound) used in the water-based ink composition.
In the ink composition of the present invention, the water-soluble solvent contributes to securing ejection properties from the head, securing the storage stability of the ink composition, suppressing deformation of the recording medium due to water, and the like.

Incidentally, an ink composition containing two or more kinds of wax particles has been conventionally known.
For example, the ink composition described in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2007-277290) includes at least two types of waxes having different average particle diameters. However, in Patent Document 1, no consideration is given to the relationship between the particle diameter and the melting point of the wax particles. In particular, Patent Document 1 does not describe low-melting-point wax particles (wax particles B) referred to in this specification. Therefore, the image formed using the ink composition of patent document 1 may be inferior to blocking resistance. Furthermore, when the ink composition of Patent Document 1 is used, the liquid-repellent film may be worn out.
In addition, the ink composition described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-162812) has a melting point of 120 ° C. or higher and 170 ° C. or lower, first wax particles that are polyethylene wax particles or polypropylene wax particles, and a melting point. And second wax particles which are 70 ° C. or higher and lower than 120 ° C. and are polyethylene wax particles. However, Patent Document 2 does not consider any relationship between the particle diameter and the melting point of the wax particles. In particular, Patent Document 2 does not describe the low melting point wax particles (wax particles B) referred to in the present specification. Therefore, an image formed using the ink composition of Patent Document 2 may be inferior in blocking resistance, similarly to an image formed using the ink composition of Patent Document 1. Further, when the ink composition of Patent Document 2 is used, wear deterioration of the liquid repellent film may occur as in the case of using the ink composition of Patent Document 1.
The ink composition described in Patent Document 3 (Japanese Patent Laid-Open No. 2012-25911) also contains two or more types of wax particles. However, Patent Document 3 does not describe high melting point wax particles (wax particles A) referred to in the present specification. For this reason, it may be required to further improve the abrasion resistance of an image using the ink composition described in Patent Document 3.

  In contrast to the above-mentioned Patent Documents 1 to 3, the present invention not only uses two or more kinds of wax particles, but also improves the abrasion resistance by using two or more kinds of wax particles that specify a particle diameter and a melting point. The present inventors have found out that the problems of improving blocking resistance and suppressing wear deterioration of the liquid repellent film can be solved.

  Furthermore, the ink composition of the present invention is excellent in dischargeability from the inkjet head because the volume average particle diameter of the wax particles A is 60 nm or less and the volume average particle diameter of the wax particles B is less than 200 nm. .

  Further, the ink composition of the present invention is excellent in gloss of the formed image because the volume average particle diameter of the wax particles B is 60 nm or less and the melting point of the wax particles B is 70 ° C. or less. This is because the volume average particle diameter of the wax particles B is 60 nm or less and the melting point of the wax particles B is 70 ° C. or less, so that the size of the convex portion on the surface of the formed image is limited to some extent. This is probably because of this.

Next, the effect of the wax particles A will be described more specifically.
When the volume average particle diameter of the wax particles A is 20 nm or more, the effect of improving the abrasion resistance of the image is exhibited.
Further, the volume average particle diameter of the wax particles A being 60 nm or less is advantageous in terms of suppressing wear deterioration of the liquid repellent film. Further, the volume average particle diameter of the wax particles A being 60 nm or less is advantageous in terms of glossiness of the image and dischargeability of the ink composition.
Furthermore, when the melting point of the wax particles A is 110 ° C. or higher, the abrasion resistance of the image is improved as described above. The melting point of the wax particles A is preferably 120 ° C. or higher and more preferably 125 ° C. or higher from the viewpoint of further improving the abrasion resistance of the image.
The upper limit of the melting point of the wax particles A is not particularly limited, but from the viewpoint of the productivity of the wax particles A (that is, the ease of production of the wax particles A), the melting point of the wax particles A is 160 ° C. or less. Is preferable, 150 ° C. or lower is more preferable, and 145 ° C. or lower is further preferable.

Next, the effect of the wax particles B will be described more specifically.
When the volume average particle diameter of the wax particles B is 100 nm or more, the anti-blocking property of the image is improved, and wear deterioration of the liquid repellent film is suppressed.
Moreover, when the volume average particle diameter of the wax particles B is less than 200 nm, the blocking resistance of the image is improved. Furthermore, when the volume average particle diameter of the wax particles B is less than 200 nm, the dischargeability of the ink composition and the glossiness of the image are maintained.
Furthermore, when the melting point of the wax particles B is 70 ° C. or less, the blocking resistance of the image is improved. Further, the ink ejection properties and the glossiness of the image are maintained.
The lower limit of the melting point of the wax particles B is not particularly limited, but from the viewpoint of the productivity of the wax particles B (that is, the ease of production of the wax particles B), the melting point of the wax particles B is 0 ° C. or higher. It is preferable.

In the present specification, the volume average particle diameter of the wax particles A and the volume average particle diameter of the wax particles B are both the particle size distribution measuring device using light scattering (for example, Microtrack UPA (manufactured by Nikkiso Co., Ltd.) (Registered trademark) EX150) means a value measured.
In the present specification, the melting point of the wax particles A and the melting point of the wax particles B are both differential scanning calorimetry (DSC) (for example, differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Co., Ltd.). ) It means the temperature of the endothermic peak top in DSC measurement using EXSTAR 6220).

  Next, the preferable aspect of this invention is demonstrated.

  In the present invention, the wax constituting the wax particle A is preferably a polyethylene wax or a polypropylene wax in that the melting point is higher (that is, the effect of the wax particle A is more effectively exhibited). More preferred.

  In addition, the wax constituting the wax particle B is preferably an acrylic wax or a urethane wax, more preferably an acrylic wax in that the melting point is lower (that is, the effect of the wax particle B is more effective). .

  Further, from the viewpoint that the effect of the wax particle A and the effect of the wax particle B are more effectively exhibited, the wax constituting the wax particle A is a polyethylene wax, and the wax constituting the wax particle B is an acrylic wax. More preferably it is.

Further, as described above, the containing mass ratio of the wax particles B to the wax particles A (containing mass ratio [wax particles B / wax particles A]) is 0.1 to 5.0.
From the viewpoint that the effect of the wax particle A and the effect of the wax particle B are more effectively exhibited, the content mass ratio [wax particle B / wax particle A] is preferably 0.2 to 2.0, more preferably. Is 0.3 to 1.5, more preferably 0.3 to 1.0, still more preferably 0.3 to 0.9, and particularly preferably 0.3 to 0.8.

  Further, from the viewpoint that the effect of the wax particle A and the effect of the wax particle B are more effectively exhibited, the volume average particle diameter ratio of the wax A to the wax B [the volume average particle diameter of the wax A / the volume average particle of the wax B The diameter] is preferably 0.10 to 0.60, more preferably 0.15 to 0.45, and still more preferably 0.17 to 0.30.

Moreover, there is no restriction | limiting in particular in the sum total content of the wax particle A and the wax particle B in the inkjet ink composition.
From the viewpoint that the effect of the wax particles A and the effect of the wax particles B are more effectively exhibited, the total content of the wax particles A and the wax particles B is preferably 1.0 with respect to the total amount of the ink composition for inkjet. The content is 10% by mass to 10% by mass, more preferably 1.5% by mass to 6.0% by mass, and particularly preferably 2.0% by mass to 5.0% by mass.
Here, needless to say, the total content of the wax particles A and the wax particles B is the content of the wax particles A (the total content in the case of two or more types) and the content of the wax particles B ( In the case of two or more types, the total content).

The ink composition of the present invention preferably further contains resin particles.
Thereby, the abrasion resistance of the image is further improved.
The resin particles are preferably resin particles that aggregate with an acid.

Here, the distinction between “wax particles” and “resin particles” in the present specification will be described.
The “wax particles” in the present specification means organic particles having a melting point of 170 ° C. or less.
On the other hand, “resin particles” in the present specification means organic particles having no melting point or having a melting point higher than 170 ° C.

From the viewpoint of dispersion stability, the resin particles are preferably self-dispersing polymer particles, and more preferably self-dispersing polymer particles having a carboxyl group.
A preferred range of the self-dispersing polymer particles will be described later.

  Next, each component that can be contained in the ink composition of the present invention will be described.

<Wax particles A>
The ink composition of the present invention contains wax particles A.
As described above, the wax particles A have a volume average particle diameter of 20 nm or more and 60 nm or less and a melting point of 110 ° C. or more.
The volume average particle diameter of the wax particles A is preferably 30 nm or more and 50 nm or less from the viewpoint that the effect of the wax particles A is more effectively exhibited.
The preferable melting point of the wax particles A is as described above.

The wax constituting the wax particle A may be a natural wax or a synthetic wax.
The following wax is illustrated as a wax which comprises the wax particle A.
Examples of natural waxes include petroleum wax, plant wax, and animal and plant wax.
Examples of petroleum wax include paraffin wax, microcrystalline wax, petrolatum, and the like.
Examples of plant waxes include carnauba wax, candelilla wax, rice wax, and wood wax.
Examples of animal plant waxes include lanolin, beeswax and the like.

Synthetic waxes include synthetic hydrocarbon waxes, modified waxes, resin waxes, and the like.
Examples of the synthetic hydrocarbon wax include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, and the like.
Examples of the modified wax include paraffin wax derivatives, montan wax derivatives, microcrystalline wax derivatives, fatty acid amide wax derivatives, and the like.
Examples of the resin wax include acrylic wax and urethane wax.

  As described above, the wax constituting the wax particle A is preferably polyethylene wax or polypropylene wax, and more preferably polyethylene wax.

Wax particles A (and wax particles B described later) are preferably produced in the form of an aqueous dispersion of wax particles (in particular, an emulsion).
The ink composition of the present invention is preferably prepared using an aqueous dispersion of wax particles.
Generally, as a method for producing an aqueous dispersion of wax particles,
A wet pulverization method in which an aqueous dispersion is obtained by adding a surfactant or a dispersant and pulverizing the oil phase in a water phase by mechanical force such as a colloid mill;
An emulsification method in which an aqueous phase having a temperature equal to or higher than the melting temperature of the oil phase is emulsified and dispersed with a high shear force by using a homogenizer or the like, and then cooled to obtain an aqueous dispersion.
Examples include the method described in “Emulsification / Solubilization Technology” (Susumu Tsuji, Engineering Books Co., Ltd., 1976, P92-104), the method described in JP-A-2002-18254, and the like. .
In preparing the ink composition of the present invention, each of an aqueous dispersion in which wax particles A are dispersed and an aqueous dispersion in which wax particles B are dispersed may be used. Alternatively, an aqueous dispersion in which both wax particles A and wax particles B are dispersed may be used.

A commercially available product may be used as the wax particles A.
As a commercial product of the aqueous dispersion of wax particles A,
AQUACER (registered trademark) 552 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles made of oxidized polyethylene wax),
AQUACER (registered trademark) 515 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles made of oxidized polyethylene wax),
AQUACER (registered trademark) 537 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles comprising a modified wax),
Hitech E9015 (manufactured by Toho Chemical Co., Ltd., an aqueous dispersion of wax particles made of polyethylene wax), and the like.

<Wax particles B>
The ink composition of the present invention contains wax particles B.
As described above, the wax particle B is a wax particle having a volume average particle diameter of 100 nm or more and less than 200 nm and a melting point of 70 ° C. or less.
The volume average particle diameter of the wax particles B is preferably 110 nm or more and 190 nm or less, more preferably 120 nm or more and 190 nm or less, and further preferably 150 nm or more, from the viewpoint that the effect of the wax particles B is more effectively exhibited. It is 190 nm or less, More preferably, it is 160 nm or more and 180 nm or less.
The melting point of the wax particles B is preferably 0 ° C. or higher and 70 ° C. or lower, more preferably 0 ° C. or higher and 65 ° C. or lower, more preferably 20 from the point that the effect of the wax particles B is more effectively exhibited. It is 30 degreeC or more and 60 degrees C or less, More preferably, it is 30 degreeC or more and 60 degrees C or less,
More preferably, it is 40 degreeC or more and 60 degrees C or less.

As the wax constituting the wax particle A, the wax constituting the wax particle B may be a natural wax or a synthetic wax.
Examples of the wax constituting the wax particle B include the same waxes as exemplified as the wax constituting the wax particle A.

  As described above, the wax constituting the wax particle B is preferably an acrylic wax or a urethane wax, and more preferably an acrylic wax.

A commercially available product may be used as the wax particles B.
As a commercially available product of the aqueous dispersion of wax particles B, ST200 (manufactured by Nippon Shokubai Co., Ltd., aqueous dispersion of wax particles made of acrylic wax) can be mentioned.

  The preferable range of the content (total content and content ratio) of the wax particles A and the wax particles B in the ink composition of the present invention is as described above.

The ink composition of the present invention may contain other wax particles other than the wax particles A and the wax particles B.
The other wax particles are wax particles in which at least one of the melting point and the volume average particle diameter is not included in the range of the wax particles A and the range of the wax particles B.
The wax constituting the other wax particles may be a natural wax or a synthetic wax. Examples of the wax (material) that constitutes the other wax particles include those exemplified as the wax that constitutes the wax particle A.
Other aqueous dispersions of wax particles include:
Cerozole (registered trademark) 524 (manufactured by Chukyo Yushi Co., Ltd., an aqueous dispersion of wax particles made of carnauba wax, volume average particle diameter 65 nm, melting point 83 ° C.),
Nopcoat PEM17 (manufactured by San Nopco, aqueous dispersion of wax particles made of polyethylene wax, volume average particle size 50 nm, melting point 103 ° C.),
Chemipearl (registered trademark) W4005 (manufactured by Mitsui Chemicals, Inc., aqueous dispersion of wax particles made of polyethylene wax, volume average particle diameter 400 nm, melting point 110 ° C.),
AQUACER (registered trademark) 531 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles made of a mixture of paraffin wax and hydrocarbon wax, volume average particle diameter 175 nm, melting point 130 ° C.),
Hitech E6314 (manufactured by Toho Chemical Co., Ltd., an aqueous dispersion of wax particles made of polyethylene wax), and the like.
Of these, Cerozol (registered trademark) 524 is particularly preferable.

In the ink composition of the present invention, the ratio of the total amount of wax particles A and wax particles B in the total amount of wax particles (the total amount of wax particles A, wax particles B, and other wax particles that may be included) is: 50 mass% or more is preferable, 70 mass% or more is more preferable, 80 mass% or more is further more preferable, and 90 mass% or more is still more preferable.
When the proportion is 50% by mass or more, the effect of the present invention (the effect of the wax particles A and the wax particles B) is more effectively achieved.

<Water>
The ink composition of the present invention contains water.
Although there is no restriction | limiting in particular in content of water, Content of water can be 50 mass% or more with respect to the whole quantity of an ink composition, for example.
The content of the water is preferably 50% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 75% by mass or less, and further preferably 50% by mass or more and 70% by mass with respect to the total amount of the ink composition. % Or less.

<Water-soluble solvent>
The ink composition of the present invention contains a water-soluble solvent.
Thereby, the ejection property from the head and the storage stability are ensured, and the deformation of the recording medium due to water is suppressed.

  In the present specification, “water-soluble” refers to the property of being soluble in water at a certain concentration or more. “Water-soluble” preferably has a property of dissolving 5 g or more (more preferably 10 g or more) in 100 g of water at 25 ° C.

As the water-soluble solvent, known ones can be used without particular limitation.
Examples of the water-soluble solvent include glycols such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and dipropylene glycol. 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1, In addition to polyhydric alcohols such as alkanediols such as 2-pentanediol and 4-methyl-1,2-pentanediol, saccharides, sugar alcohols, and hyaluronic acids described in paragraph 0116 of JP2011-42150A , Alkyl having 1 to 4 carbon atoms Alcohols, glycol ethers, 2-pyrrolidone, N- methyl-2-pyrrolidone. One or more of these solvents can be appropriately selected and used. Polyhydric alcohols are also useful as drying inhibitors and wetting agents, and examples include the examples described in paragraph 0117 of JP-A-2011-42150. Moreover, a polyol compound is preferable as a penetrant, and examples of the aliphatic diol include those described in paragraph 0117 of JP2011-42150A.
As other water-soluble solvents, for example, water-soluble solvents described in paragraphs 0176 to 0179 of JP2011-46872A, and paragraphs 0063 to 0074 of JP2013-18846A are described. It is also possible to appropriately select from the water-soluble solvents that are present.

The content of the water-soluble solvent in the ink composition of the present invention (the total content in the case of two or more) is preferably 2% by mass to 20% by mass with respect to the total amount of the ink composition.
When the total content is 2% by mass or more, the ejectability from the head and the storage stability are further improved, and deformation of the recording medium due to water is further suppressed.
The total content is more preferably 3% by mass to 20% by mass and further preferably 5% by mass to 18% by mass with respect to the total amount of the ink composition.

The ink composition of the present invention includes a solvent A represented by the following structural formula (I), ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, and methylpropylene as a water-soluble solvent. It is more preferable to contain at least one solvent B selected from triglycol. With such a composition, good abrasion resistance is obtained, and curling and stacker blocking of the recording medium after image formation is suppressed.
Here, stacker blocking means that recording media on which images are formed are stacked, and the front surface (the surface on which the image is formed) of the recording media and the back surface of another recording medium (the image is formed). This refers to a phenomenon in which an image formed on a recording medium is destroyed by contact with a non-contact surface. The destruction of the image occurs, for example, when the image is transferred to the back surface of the recording medium or between the recording media.
Stacker blocking is described in, for example, Japanese Patent Application Laid-Open No. 2011-088323.
When the ink composition of the present invention contains the solvent A and the solvent B, the content of the solvent A with respect to the total amount of the ink composition is 1.0% by mass to 10.0% by mass, and the content of the solvent B with respect to the total amount of the ink composition The amount (mass basis) is preferably 0.05 to 20.0 times the content (mass basis) of the solvent A with respect to the total amount of the ink composition.

  In the present specification, the content (mass basis) of the solvent B with respect to the total amount of the ink composition is a times to b times (for example, 0.05 times to 20 times) the content (mass basis) of the solvent A with respect to the total amount of the ink composition. (The ratio [mass of solvent B / mass of solvent A] is a to b (for example, 0.05 to 20.0)).

  The ratio [mass of solvent B / mass of solvent A] is preferably 0.1 to 15.0, and more preferably 0.2 to 10.0.

  When the ink composition of the present invention includes the solvent A and the solvent B, the total content of the solvent A and the solvent B is 2.0% by mass to 30.0% by mass with respect to the total amount of the ink composition. It is preferably 3.0% by mass to 20.0% by mass, more preferably 5.0% by mass to 15.0% by mass.

  Further, when the ink composition of the present invention includes the solvent A and the solvent B, the content of the solvent B is preferably 0.5% by mass to 20.0% by mass with respect to the total amount of the ink composition. It is more preferable that it is 0.0 mass%-15.0 mass%, and it is still more preferable that it is 2.0 mass%-10.0 mass%.

(Solvent A)
The solvent A is at least one selected from compounds represented by the following structural formula (I). The solvent A may be a single (single component) solvent selected from the compounds represented by the following structural formula (I), or may be selected from the compounds represented by the following structural formula (I). It may be a mixed solvent composed of two or more kinds.

In Structural Formula (I), l, m, and n each independently represent an integer of 0 or more and satisfy l + m + n = 0-15. Especially, l + m + n has the preferable range of 3-12, and the range of 3-10 is more preferable. In Structural Formula (I), AO represents an ethyleneoxy group or a propyleneoxy group. Of these, a propyleneoxy group is preferable. When l + m + n ≧ 2, two or more AOs may be the same or different.
As the compound represented by the structural formula (I), glycerin or an alkylene oxide adduct of glycerin is preferable.

  Examples of the compound represented by the structural formula (I) are shown below. However, the present invention is not limited to these. Hereinafter, the numbers in parentheses represent SP values.

_{· NC 4 H 9 O (AO} ) 4 -H
(AO = EO or PO (EO: PO = 1: 1), SP value = 20.1)
_{· NC 4 H 9 O (AO} ) 10 -H
(AO = EO or PO (EO: PO = 1: 1), SP value = 18.8)
・ HO (A'O) ₄₀ -H
(A′O = EO or PO (EO: PO = 1: 3), SP value = 18.7)
・ HO (A''O) ₅₅ -H
(A ″ O = EO or PO (EO: PO = 5: 6), SP value = 18.8)
・ HO (PO) ₃ −H (SP value = 24.7)
HO (PO) ₇ -H (SP value = 21.2)
1,2-hexanediol (SP value = 27.4)
In addition, EO and PO represent an ethyleneoxy group and a propyleneoxy group, respectively.

  As the alkylene oxide adduct of glycerin, a commercially available product may be used. For example, as polyoxypropylated glycerin (ether of polypropylene glycol and glycerin), Sannix (registered trademark) GP-250 (average molecular weight 250), GP-400 (average molecular weight 400), GP-600 (average molecular weight) 600) [manufactured by Sanyo Chemical Industries, Ltd.], REOCON (registered trademark) GP-250 (average molecular weight 250), GP-300 (average molecular weight 300, GP-400 (average molecular weight 400), GP- 700 (average molecular weight 700) [manufactured by Lion Corporation], polypropylene triol glycol triol type (average molecular weight 300, average molecular weight 700) [manufactured by Wako Pure Chemical Industries, Ltd.] and the like.

(Solvent B)
The solvent B is at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol (for example, PEG-200 described later), pentaethylene glycol, propylene glycol, and methylpropylene triglycol (MFTG). It is a seed. The solvent B preferably contains at least one of triethylene glycol and tetraethylene glycol.
The solvent B may be a single (single component) solvent or a mixed solvent of two or more.

As the solvent B, commercially available products may be used.
For example, PEG-200 (average molecular weight 200), PEG-300 (average molecular weight 300), PEG-400 (average molecular weight 400) [manufactured by Sanyo Chemical Industries, Ltd.], PEG # 200 (average molecular weight 200), PEG # 300 (average molecular weight 300), PEG # 400 (average molecular weight 400) (manufactured by Lion Corporation), PEG # 200 (average molecular weight 200), PEG # 300 (average molecular weight 300), PEG # 400 (average molecular weight) 400) [manufactured by NOF Corporation], PEG200 (average molecular weight 200), PEG300 (average molecular weight 300), PEG400 (average molecular weight 400) [above, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], and the like. .

<Resin particles>
The ink composition of the present invention preferably contains at least one resin particle. Thereby, the abrasion resistance of the image is further improved.
In particular, when the ink composition of the present invention contains resin particles and an image is formed by applying the ink composition to a recording medium together with a treatment liquid described later, the abrasion resistance of the image is further improved. To do.
That is, when the resin particles come into contact with a recording medium (particularly, a treatment liquid or a region where the processing liquid is dried in the recording medium), the resin particles are dispersed and destabilized in the ink composition to aggregate and thicken. Has the function of immobilizing the composition. Thereby, the abrasion resistance of the image is further improved. Furthermore, the adhesion of the ink composition to the recording medium is further improved.

As described above, unlike the wax particles described above, the resin particles mean organic particles having no melting point or having a melting point higher than 170 ° C. The resin particles preferably have a glass transition temperature (Tg).
The resin particles are distinguished from pigments (resin-coated pigments) coated with a resin, which will be described later, in that they are particles made of resin.

As the resin particles, for example, resin particles formed of a resin selected from a thermoplastic resin and a thermosetting resin can be used.
These resins may be further modified resins.
Examples of the resin used for forming the resin particles include acrylic resin, epoxy resin, urethane resin, polyether resin, polyamide resin, unsaturated polyester resin, phenol resin, silicone resin, fluorine resin, and polyvinyl resin (eg, vinyl chloride). , Vinyl acetate, polyvinyl alcohol, or polyvinyl butyral), alkyd resin, polyester resin (eg, phthalic acid resin, etc.), amino material (eg, melamine resin, melamine formaldehyde resin, aminoalkyd co-condensation resin, urea resin, urea resin) Etc.).
The resin forming the resin particles may be a copolymer containing two or more structural units constituting the resin exemplified above, or may be a mixture of two or more resins. In addition, the resin particles themselves may be composite resin particles in which two or more resins are laminated like a core / shell, for example, as well as a mixture of two or more resins.
When resin particles are used in the ink composition, only one type may be used, or two or more types may be used in combination.

  Among the above, as the resin particles, acrylic resin, urethane resin, polyether resin, polyester resin, and polyolefin resin particles are preferable. From the viewpoint of stability and film quality of the formed film (image), acrylic resin particles Or the particle | grains of a urethane resin are still more preferable.

  In addition, in this specification, an acrylic resin means resin containing the structural unit derived from (meth) acrylic acid. The acrylic resin may contain structural units other than the structural unit derived from (meth) acrylic acid.

The glass transition temperature (Tg) of the resin particles is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and still more preferably 100 ° C. or higher.
The upper limit of the glass transition temperature of the resin particles is preferably 250 ° C, and more preferably 230 ° C.
The glass transition temperature of the resin particles is preferably in the range of 40 ° C. or higher and 250 ° C. or lower, more preferably in the range of 50 ° C. or higher and 230 ° C. or lower, and particularly preferably in the range of 100 ° C. or higher and 230 ° C. or lower.
For example, when an image is formed by applying the ink composition onto a recording medium together with a treatment liquid described later, the resin particles are contained in the ink composition when contacting the treatment liquid or a region where the treatment liquid is dried. The ink composition has a function of fixing the ink composition by destabilizing and agglomerating and thickening.
Thereby, the abrasion resistance of the image is further improved. Furthermore, image unevenness is further suppressed. Furthermore, the adhesion of the ink composition to the recording medium and the scratch resistance of the image are further improved.

  The glass transition temperature of the resin particles can be appropriately controlled by a commonly used method. For example, the glass transition temperature of the resin particles can be controlled within a desired range by appropriately selecting the type of monomer (polymerizable compound) constituting the resin particles, the composition ratio thereof, the molecular weight of the polymer constituting the resin particles, and the like. Can do.

In this specification, the measurement Tg obtained by actual measurement is applied to the glass transition temperature of the resin particles.
Specifically, the measurement Tg means a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by Hitachi High-Tech Science Co., Ltd. However, when measurement is difficult due to polymer decomposition or the like, calculation Tg calculated by the following calculation formula is applied. The calculation Tg is calculated by the following equation (1).
1 / Tg = Σ (Xi / Tgi) (1)
Here, it is assumed that n types of monomer components from i = 1 to n are copolymerized in the polymer to be calculated. Xi is the weight fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. The homopolymer glass transition temperature value (Tgi) of each monomer employs the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

The resin particles are preferably resin particles obtained by a phase inversion emulsification method, and the following self-dispersing polymer particles (self-dispersing polymer particles) are more preferable.
Here, the self-dispersing polymer refers to a functional group (particularly, an acidic group such as a carboxyl group or a salt thereof) that the polymer itself has when dispersed by a phase inversion emulsification method in the absence of a surfactant. A water-insoluble polymer that can be dispersed in an aqueous medium.
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.
“Water-insoluble” means that the amount dissolved in 100 parts by mass of water (25 ° C.) is 5.0 parts by mass or less.

  As the phase inversion emulsification method, for example, a polymer is dissolved or dispersed in a solvent (for example, a water-soluble solvent) and then poured into water as it is without adding a surfactant. For example, a method of obtaining an aqueous dispersion in an emulsified or dispersed state after stirring and mixing in a state in which an acidic group such as a carboxyl group) is neutralized and removing the solvent.

  The self-dispersing polymer particles are selected from the self-dispersing polymer particles described in paragraphs 0090 to 0121 of JP2010-64480A or paragraphs 0130 to 0167 of JP2011-068805A. be able to. In particular, it is preferable to select and use those having a glass transition temperature of 100 ° C. or higher from the self-dispersing polymer particles described in the above publication.

As described above, the self-dispersing polymer particles are preferably self-dispersing polymer particles having a carboxyl group.
A more preferable form of the self-dispersing polymer particles having a carboxyl group is a form made of a polymer containing a structural unit derived from an unsaturated carboxylic acid (preferably (meth) acrylic acid).

A more preferable form of the self-dispersing polymer particles having a carboxyl group is
A structural unit having an alicyclic group;
A structural unit having an alkyl group;
A structural unit derived from an unsaturated carboxylic acid (preferably (meth) acrylic acid);
It is the form which consists of a polymer containing.
The content of the structural unit having an alicyclic group in the polymer (total content when two or more types are present) is preferably 3% by mass to 95% by mass with respect to the total amount of the polymer, and 5% by mass. -75 mass% is more preferable, and 10 mass%-50 mass% is still more preferable.
The content of the structural unit having an alkyl group in the polymer (the total content when two or more types are present) is preferably 5% by mass to 90% by mass with respect to the total amount of the polymer, and 10% by mass to 85%. % By mass is more preferable, 20% by mass to 80% by mass is further preferable, 30% by mass to 75% by mass is further preferable, and 40% by mass to 75% by mass is further preferable.
The content of the structural unit derived from the unsaturated carboxylic acid (preferably (meth) acrylic acid) in the polymer (total content when two or more are present) is 2% by mass to the total amount of the polymer. 30 mass% is preferable, 5 mass%-20 mass% is more preferable, 5 mass%-15 mass% is still more preferable.

Moreover, as a form of the self-dispersing polymer particle having a carboxyl group, the structural unit having an alicyclic group in the above-mentioned “further preferred form of the self-dispersing polymer particle having a carboxyl group” has an aromatic group. A form changed to a structural unit or a form containing a structural unit having an aromatic group in addition to a structural unit having an alicyclic group is also preferred.
In any form, the total content of the structural unit having an alicyclic group and the structural unit having an aromatic group is preferably 3% by mass to 95% by mass with respect to the total amount of the polymer, and 5% by mass to 75% by mass. % Is more preferable, and 10% by mass to 50% by mass is still more preferable.

The structural unit having an alicyclic group is preferably a structural unit derived from an alicyclic (meth) acrylate.
Alicyclic (meth) acrylates include monocyclic (meth) acrylates, bicyclic (meth) acrylates, and tricyclic (meth) acrylates.
Monocyclic (meth) acrylates include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, and cyclononyl. Examples thereof include cycloalkyl (meth) acrylates having 3 to 10 carbon atoms in the cycloalkyl group such as (meth) acrylate and cyclodecyl (meth) acrylate.
Examples of the bicyclic (meth) acrylate include isobornyl (meth) acrylate and norbornyl (meth) acrylate.
Examples of the tricyclic (meth) acrylate include adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.
These can be used alone or in admixture of two or more.
Among these, from the viewpoints of fixing property, blocking resistance, and dispersion stability of the self-dispersing polymer particles, bicyclic (meth) acrylate or tricyclic or higher polycyclic (meth) acrylate is preferable, and isobornyl ( More preferred are meth) acrylate, adamantyl (meth) acrylate, or dicyclopentanyl (meth) acrylate.

The structural unit having an aromatic group is preferably a structural unit derived from an aromatic group-containing monomer.
Examples of the aromatic group-containing monomer include aromatic group-containing (meth) acrylate monomers (for example, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, etc.), styrene monomers, and the like. It is done.
Of these, aromatic group-containing (meth) acrylate monomers are preferred from the viewpoint of the balance between the hydrophilicity and hydrophobicity of the polymer chain and the ink fixing property, and phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, or phenyl (meth) is preferred. An acrylate is more preferable, and phenoxyethyl (meth) acrylate or benzyl (meth) acrylate is more preferable.

The structural unit having an alkyl group is preferably a structural unit derived from an alkyl group-containing monomer.
Examples of the alkyl group-containing monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t -Alkyl (meth) acrylates such as butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate Ethylenically unsaturated monomers having a hydroxyl group such as 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, and hydroxyhexyl (meth) acrylate; dimethylaminoethyl Dialkylaminoalkyl (meth) acrylates such as meth) acrylate; N-hydroxyalkyl (meth) acrylamides such as N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide And (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as N- (n-, iso) butoxyethyl (meth) acrylamide.
Among them, alkyl (meth) acrylate is preferable, alkyl (meth) acrylate having 1 to 4 carbon atoms in the alkyl group is more preferable, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, or Butyl (meth) acrylate is more preferred, and methyl (meth) acrylate is more preferred.

Specific examples of the self-dispersing polymer particles are listed below as exemplary compounds P-1 to P-5, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymerization component.
P-1: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (70/20/10)
P-2: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (48/42/10)
P-3: Methyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (65/25/10)
P-4: Isopropyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (50/40/10)
P-5: butyl methacrylate / dicyclopentanyl methacrylate / methacrylic acid copolymer (60/30/10)

As described above, urethane resin is also preferable as the resin particle.
Examples of the urethane resin include a urethane resin obtained by reacting a diol compound and a diisocyanate compound.
For details of the diol compound and the diisocyanate compound, reference can be made, for example, to the descriptions in paragraph numbers [0031] to [0036] of JP-A No. 2001-247787. Among these, it is preferable to use a polyester urethane resin or a polyether urethane resin having an ester bond in the main chain structure.

  Regarding the urethane resin, the description in paragraphs 0128 to 0136 of JP2013-227498A can be appropriately referred to.

The weight average molecular weight of the polymer constituting the resin particles (preferably self-dispersing polymer particles; the same shall apply hereinafter) is preferably 3000 to 200,000, more preferably 5000 to 150,000, and 10,000 to 100,000. More preferably.
When the weight average molecular weight is 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.

Here, the weight average molecular weight of the polymer constituting the resin particles means a value measured by gel permeation chromatography (GPC).
The above GPC uses HLC-8020 GPC (manufactured by Tosoh Corporation), and uses TSKgel (registered trademark) and Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns. This is performed using THF (tetrahydrofuran) as a liquid.
GPC is performed using a RI detector with a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection amount of 10 μl, and a measurement temperature of 40 ° C.
The calibration curve is “Standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A -2500 "," A-1000 ", and" n-propylbenzene ".

  The polymer constituting the resin particles is preferably a polymer having an acid value of 100 mgKOH / g or less from the viewpoints of self-dispersibility and aggregation rate when the treatment liquid comes into contact, and the acid value is 25 mgKOH / g to 100 mgKOH / g of polymer is more preferred.

  The volume average particle diameter of the resin particles is preferably in the range of 1 nm to 200 nm, more preferably in the range of 1 nm to 150 nm, still more preferably in the range of 1 nm to 100 nm, and particularly preferably in the range of 1 nm to 10 nm. Manufacturability is improved when the volume average particle diameter is 1 nm or more. Moreover, storage stability improves that a volume average particle diameter is 200 nm or less. Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more kinds of polymer particles may be mixed and used.

  Here, the volume average particle diameter of the resin particles refers to a value obtained by the same method as the volume average particle diameter of the wax particles A and the wax particles B described above.

The content of the resin particles (preferably self-dispersing polymer particles) in the ink composition (the total content in the case of two or more types) is not particularly limited, but is 0. 0 relative to the total amount of the ink composition. 3 mass%-10.0 mass% are preferable, 0.5 mass%-7.0 mass% are more preferable, 1.0 mass%-5.0 mass% are still more preferable.
When the content is 0.3% by mass or more, the abrasion resistance of the image can be further improved, and image unevenness can be further suppressed.
When the content is 10.0% by mass or less, the ink ejection property can be further improved, and it is advantageous in that the generation of precipitates in a low temperature environment is suppressed.

<Color material>
The ink composition of the present invention can contain at least one colorant.
However, the ink composition of the present invention may be a colorless and transparent ink (sometimes referred to as “clear ink” or the like). In this case, the ink composition of the present invention contains a coloring material. It does not have to be.

  When the ink composition of the present invention contains a color material, the color material contained is a resin coating having a structure in which at least a part of the surface of the pigment is coated with a resin (hereinafter also referred to as “coating resin”). Pigments are preferred. Thereby, the dispersion stability of the ink composition is improved, and the quality of the formed image is improved.

(Pigment)
There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient.
Further, as the pigment, a black pigment (for example, carbon black), a magenta pigment, a cyan pigment, and a yellow pigment may be used.
The pigment is preferably a pigment that is almost insoluble or hardly soluble in water from the viewpoint of ink colorability.

Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.
Among these, carbon black is more preferable as the pigment.

In addition, since carbon black is a hard particle, an ink composition containing carbon black generally tends to wear and degrade the liquid repellent film during the wiping operation on the liquid repellent film.
However, as described above, the ink composition of the present invention contains wax particles B that function as a cushion during the wiping operation of the ink composition on the liquid repellent film. For this reason, even when the ink composition of the present invention contains carbon black, wear deterioration of the liquid repellent film due to the carbon black is suppressed by the action of the wax particles B. In other words, when the ink composition of the present invention contains carbon black, the improvement effect (the effect of suppressing wear deterioration of the liquid repellent film) by the wax particles B is more remarkably exhibited (that is, by the wax particles B). The improvement will be greater).

  When a pigment is used, the average particle diameter of the pigment is preferably small from the viewpoint of transparency and color reproducibility, but is preferably large from the viewpoint of light resistance. From the viewpoint of achieving both of these, the average particle size is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 120 nm. Further, the particle size distribution of the pigment is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more pigments having a monodispersed particle size distribution may be mixed and used.

You may use a pigment individually by 1 type or in combination of 2 or more types.
The content of the pigment in the ink composition is preferably 1% by mass to 20% by mass and more preferably 2% by mass to 10% by mass with respect to the ink composition from the viewpoint of image density.

(Coating resin)
As the coating resin in the resin-coated pigment, a dispersant is preferable.
The dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant.
The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  As the low molecular surfactant type dispersant, for example, known low molecular surfactant type dispersants described in paragraphs 0047 to 0052 of JP2011-178029A can be used.

  Among polymer dispersants, water-soluble dispersants include hydrophilic polymer compounds. For example, natural hydrophilic polymer compounds include plant polymers such as gum arabic, tragacanth gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, seaweeds such as alginic acid, carrageenan and agar. Examples include molecules, animal polymers such as gelatin, casein, albumin and collagen, and microorganism polymers such as xanthene gum and dextran.

In addition, in hydrophilic polymer compounds modified from natural products, fiber polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch such as sodium starch glycolate and sodium starch phosphate And seaweed polymers such as sodium alginate, propylene glycol alginate, and the like.
Further, synthetic hydrophilic polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid or alkali metal salts thereof, water-soluble styrene acrylic resins, and the like. Acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium and amino And a polymer compound having a salt of a cationic functional group such as a group in the side chain, a natural polymer compound such as shellac, and the like.

  Among these, water-soluble dispersants introduced with carboxyl groups are hydrophilic polymers such as homopolymers of acrylic acid, methacrylic acid, styrene acrylic acid, and copolymers with monomers having other hydrophilic groups. Preferred as a compound.

Among the polymer dispersants, as the water-insoluble dispersant, a polymer having both a hydrophobic portion and a hydrophilic portion can be used. The hydrophilic structural unit is preferably a structural unit having an acidic group, and more preferably a structural unit having a carboxyl group. Examples of the water-insoluble resin include styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer. Examples thereof include a polymer, a polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, a vinyl acetate-maleic acid copolymer, and a styrene-maleic acid copolymer.
More specifically, for example, the water-insoluble resins described in JP-A-2005-41994, JP-A-2006-238991, JP-A-2009-084494, JP-A-2009-191134, and the like are preferably used in the present invention. Can be used.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000. 000 to 40,000.

  In addition, the weight average molecular weight of a polymer dispersing agent refers to the value calculated | required by the method similar to the weight average molecular weight of the above-mentioned resin particle.

  The polymer dispersant preferably contains a polymer having a carboxyl group from the viewpoints of self-dispersibility and aggregation rate when the treatment liquid comes into contact. The polymer dispersant has a carboxyl group and has an acid value of 130 mgKOH / g or less. It is preferable that the polymer has an acid value of 25 mgKOH / g to 120 mgKOH / g. In particular, when the ink composition of the present invention is used with a treatment liquid that aggregates the components in the ink composition, a polymer dispersant having a carboxyl group and an acid value of 25 mgKOH / g to 100 mgKOH / g is effective. It is. The processing liquid will be described later.

  The mixing mass ratio (p: s) between the pigment (p) and the dispersant (s) is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 2. Preferably, it is 1: 0.125 to 1: 1.5.

  The content of the coating resin for coating the pigment with respect to the total mass of the ink composition is preferably 0.5% by mass to 3.0% by mass, more preferably 1.0% by mass to 2.8% by mass, and 1.2% by mass. % To 2.5% by mass is more preferable.

  The mass ratio of the coating resin and the inorganic salt (coating resin / inorganic salt) is preferably 10 to 250, more preferably 15 to 200, and more preferably 30 to 150, from the viewpoints of ink viscosity reduction and image surface roughness suppression. Is more preferable.

  The volume average particle size (secondary particle size) of the resin-coated pigment (pigment in a dispersed state) is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 100 nm. When the volume average particle diameter is 200 nm or less, the color reproducibility is good, and the droplet ejection characteristics when droplets are ejected by the ink jet method are good. When the volume average particle diameter is 10 nm or more, light resistance is improved. Further, the particle size distribution of the color material 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 monodispersed particle size distribution may be mixed and used. Here, the volume average particle diameter of the pigment in the dispersed state indicates the average particle diameter in the ink state, but the same applies to the so-called concentrated ink dispersion in the previous stage before the ink is formed.

  Here, the volume average particle diameter of the resin-coated pigment refers to a value obtained by the same method as the volume average particle diameter of the wax particles A and the wax particles B described above.

Moreover, it is preferable that resin which coat | covers the pigment in a resin coating pigment is bridge | crosslinked with the crosslinking agent.
That is, the resin-coated pigment is preferably a resin-coated pigment in which at least a part of the surface of the pigment is coated with a resin crosslinked with a crosslinking agent.
Regarding the resin-coated pigment in which at least a part of the surface of the pigment is coated with a resin crosslinked with a crosslinking agent, paragraphs 0029 to 0048, paragraphs 0110 to 0118, and paragraphs 0111 to 0129 of JP2012-162655A. In addition, the description in paragraphs 0035 to 0071 of JP2013-47311A can be appropriately referred to.

The crosslinking agent is not particularly limited as long as it is a compound having two or more sites that react with a resin, but preferably has two or more epoxy groups from the viewpoint of excellent reactivity with a carboxy group. (A bifunctional or higher functional epoxy compound).
Specific examples of the crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, Examples include trimethylolpropane triglycidyl ether, and polyethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether are preferable.

  A commercial item can also be used as a crosslinking agent. As a commercial item, DENACOL (trademark) EX-321, EX-821, EX-830, EX-850, EX-851 (made by Nagase ChemteX Corporation) etc. can be used, for example.

  The molar ratio of the crosslinking site of the crosslinking agent (for example, epoxy group) and the crosslinked site of the resin (for example, carboxy group) is preferably 1: 1 to 1:10 from the viewpoint of the crosslinking reaction rate and the dispersion stability after crosslinking. 1: 1 to 1: 5 is more preferable, and 1: 1 to 1: 1.5 is most preferable.

  Further, as the resin-coated pigment, a resin-coated pigment having a structure in which at least a part of the pigment surface is coated with a water-insoluble resin by a method for producing a pigment dispersion described in JP-A-10-140065 can be used. .

<Surfactant>
The ink composition of the present invention can contain at least one surfactant as required. The surfactant can be used as a surface tension adjusting agent, for example.
As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant Either a surfactant or a betaine surfactant can be used. Furthermore, the above-described polymer dispersant may be used as a surfactant.

The surfactant is preferably a nonionic surfactant from the viewpoint of suppressing ink droplet ejection interference, and more preferably an acetylene glycol derivative (acetylene glycol-based surfactant).
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.
As the surfactant other than the acetylene glycol surfactant, a fluorine surfactant is preferable. Examples of the fluorine surfactant include an anionic surfactant, a nonionic surfactant, and a betaine surfactant, and among these, an anionic surfactant is more preferable. Examples of the anionic surfactant include Capstone FS-63, Capstone FS-61 (manufactured by DuPont), Footgent 100, Footent 110, Footent 150 (manufactured by Neos Co., Ltd.), CHEMGUARD S-760P (Chemguard) Inc.).

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

  When the ink composition of the present invention contains a surfactant, the specific amount of the surfactant is not particularly limited, but is preferably 0.1% by mass or more, more preferably based on the total amount of the ink composition. It is 0.1 mass%-10 mass%, More preferably, it is 0.2 mass%-3 mass%.

<Urea>
The ink composition of the present invention can contain urea.
Since urea has a high moisturizing function, it can effectively suppress undesirable drying or coagulation of the ink as a solid wetting agent.
Furthermore, the ink composition of the present invention contains the above-described colloidal silica and urea, so that the maintainability (wiping workability) of the ink jet head and the like is more effectively improved.

  The content of urea in the ink composition of the present invention is preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less from the viewpoint of improving maintenance properties (wiping workability). 3 mass% or more and 10 mass% or less are still more preferable.

  When the ink composition of the present invention contains urea and colloidal silica, which will be described later, the ratio of urea content and colloidal silica content is not particularly limited, but the urea content ratio relative to colloidal silica (Urea / colloidal silica) is preferably 5 to 1000, more preferably 10 to 500, and still more preferably 20 to 200.

In addition, when the ink composition of the present invention contains urea and colloidal silica, the combination of the urea content and the colloidal silica content is not particularly limited, but the wiping property and image fixing property are more effective. From the viewpoint of achieving both, the following combinations are preferable.
That is, a combination in which the urea content is 1.0 mass% or more and the colloidal silica content is 0.01 mass% or more is preferable, and the urea content is 1.0 mass% to 20 mass%. More preferred is a combination in which the colloidal silica content is 0.02% by mass to 0.5% by mass, the urea content is 3.0% by mass to 10% by mass, and the colloidal silica content. Is particularly preferably a combination of 0.03% by mass to 0.2% by mass.

<Colloidal silica>
The ink composition of the present invention may contain colloidal silica as necessary.
Thereby, the stability at the time of continuous discharge of ink can be improved more.
Colloidal silica is a colloid composed of fine particles of inorganic oxide containing silicon having an average particle size of several hundred nm or less. Colloidal silica contains silicon dioxide (including hydrates thereof) as a main component, and may contain aluminate (sodium aluminate, potassium aluminate, etc.) as a minor component.
In addition, colloidal silica may contain inorganic salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide, and organic salts such as tetramethylammonium hydroxide. These inorganic salts and organic salts act, for example, as colloid stabilizers.
About colloidal silica, the description of Paragraphs 0043-0050 of JP, 2011-202117, A can be referred to suitably, for example.
Further, the ink composition of the present invention may contain an alkali metal silicate salt instead of or in addition to colloidal silica, if necessary. Regarding the alkali metal silicate, the description in paragraphs 0052 to 0056 of JP-A-2011-202117 can be appropriately referred to.

  When the ink composition of the present invention contains colloidal silica, the content of colloidal silica is preferably 0.0001% by mass to 10% by mass, and 0.01% by mass to 3% by mass with respect to the total amount of the ink composition. More preferably, 0.02 mass% to 0.5 mass% is further more preferable, and 0.03 mass% to 0.3 mass% is particularly preferable.

<Water-soluble polymer compound>
The ink composition of the present invention may contain at least one water-soluble polymer compound as necessary.
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.
Further, as the water-soluble polymer compound, a specific polymer compound that may be contained in a treatment liquid described later, or a water-soluble polymer compound described in paragraphs 0026 to 0080 of JP2013-001854A is also suitable. is there.

  When the ink composition of the present invention contains a water-soluble polymer compound, the content of the water-soluble polymer compound is preferably 0.0001% by mass to 10% by mass, and 0.01% by mass with respect to the total amount of the ink composition. % To 3% by mass is more preferable, 0.02% to 0.5% by mass is more preferable, and 0.03% to 0.3% by mass is particularly preferable.

<Antifoaming agent>
The ink composition of the present invention may contain at least one antifoaming agent as necessary.
Examples of the antifoaming agent include silicone compounds (silicone defoaming agents) and pluronic compounds (pluronic defoaming agents). Among these, silicone antifoaming agents are preferable.
As the silicone-based antifoaming agent, a silicone-based antifoaming agent having a polysiloxane structure is preferable.

A commercial item can be used as an antifoamer.
Examples of commercially available products include BYK-012, 017, 021, 022, 024, 025, 038, 094 (above, manufactured by Big Chemie Japan Co., Ltd.), KS-537, KS-604, KM-72F (above, Shin-Etsu Chemical). Kogyo Co., Ltd.), TSA-739 (Momentive Performance Materials Japan GK), Olfin AF104 (Nisshin Chemical Co., Ltd.), and the like.
Among these, BYK-017, 021, 022, 024, 025, 094, KS-537, KS-604, KM-72F, and TSA-739, which are silicone-based antifoaming agents, are preferable. In view of this, BYK-024 is most preferred.

  When the ink composition of the present invention contains an antifoaming agent, the content of the antifoaming agent is preferably 0.0001% by mass to 1% by mass, and 0.001% by mass to 0.00% by mass with respect to the total amount of the ink composition. 1% by mass is more preferable.

<Inorganic salt>
The ink composition of the present invention may contain at least one inorganic salt as required.
Thereby, surface alignment of the formed image is suppressed.
Here, the surface area is rough because the high and low density portions of the ink composition are unevenly distributed in the middle area (halftone area) between the bright area (highlight) and dark area (shadow) of the image. A phenomenon that appears to be.
“Surface alignment” is not a phenomenon caused by insufficient local agglomeration of ink compositions such as conventional “bleeding” or “streak”, but non-aggregation due to non-uniform distribution of processing liquid on the recording medium. It is a phenomenon caused by

As the inorganic salt, hydrochloride or nitrate is preferable.
Of these, monovalent salts are preferable, alkali metal salts are more preferable, and lithium chloride, lithium nitrate, potassium chloride, or potassium nitrate is more preferable from the viewpoint of excellent ink viscosity reduction and surface roughness suppression.
An inorganic salt can be used individually or in combination of 2 or more types.
When the ink composition of the present invention contains an inorganic salt, the content of the inorganic salt in the ink composition (the total content in the case of two or more types) is not particularly limited, but the total amount of the ink composition On the other hand, 0.01 mass%-0.1 mass% are preferable, 0.02 mass%-0.1 mass% are more preferable, 0.03 mass%-0.1 mass% are especially preferable.

<Other ingredients>
The ink composition of the present invention may contain other components as necessary in addition to the above components.
Examples of other components include solid wetting agents, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusting agents, viscosity adjusting agents, rust preventing agents, chelating agents, and the like. And known additives.

The ink composition of the present invention may be an active energy ray (for example, ultraviolet ray) curable ink composition containing at least one polymerizable compound.
In this case, it is preferable that the ink composition (at least one of the ink composition and the treatment liquid when a treatment liquid described later is used) further contains a polymerization initiator.
Examples of the polymerizable compound include polymerizations described in paragraphs 0128 to 0144 of 2011-184628, paragraphs 0019 to 0034 of JP2011-178896A, paragraphs 0065 to 0086 of JP2015-25076, and the like. Compounds (for example, bifunctional or higher functional (meth) acrylamide compounds).
Examples of the polymerization initiator are described in paragraphs 0186 to 0190 of JP2011-184628A, paragraphs 0126 to 0130 of JP2011-178896A, or paragraphs 0041 to 0064 of JP2015-25076A. A well-known polymerization initiator is mentioned.

<Preferred physical properties of ink composition>
The physical properties of the ink composition of the present invention are not particularly limited, but the following physical properties are preferable.
The ink composition of the present invention preferably has a pH of 7.5 or more at 25 ° C. (± 1 ° C.) from the viewpoints of aggregation rate and dispersion stability of the composition.
The pH (25 ° C. ± 1 ° C.) of the ink composition is preferably pH 7.5 to 13, and more preferably 7.5 to 10.

The viscosity of the ink composition of the present invention is preferably in the range of 0.5 mPa · s to 10 mPa · s, more preferably in the range of 1 mPa · s to 7 mPa · s, from the viewpoint of the aggregation rate.
The viscosity is measured under a condition of 30 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

  The surface tension of the ink composition of the present invention at 25 ° C. (± 1 ° C.) is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and more preferably 25 mN / m to 45 mN / m. More preferably, it is m. When the surface tension of the ink composition is within the range, the occurrence of curling in the recording medium is advantageously suppressed. The surface tension is measured at 25 ° C. by a plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

[Ink set]
The ink set of the present embodiment includes the above-described ink jet ink composition of the present invention and a treatment liquid containing an acid that aggregates the components in the ink jet ink composition (hereinafter also referred to as “acidic compound”). Including.
The ink set may contain only one type of the ink jet ink composition of the present invention described above, or may contain two or more types (for example, two or more colors).
Moreover, the ink set may contain only 1 type of process liquid, and may contain 2 or more types.

<Processing liquid>
The treatment liquid contains at least one acidic compound.

(Acidic compounds)
Examples of the acidic compound include acidic substances that can lower the pH of the ink composition.
As the acidic compound, either an organic acidic compound or an inorganic acidic compound may be used, and two or more organic acidic compounds and inorganic acidic compounds may be used in combination.

-Organic acidic compounds-
Examples of the organic acidic compound include an organic compound having an acidic group.
Examples of acidic groups include phosphoric acid groups, phosphonic acid groups, phosphinic acid groups, sulfuric acid groups, sulfonic acid groups, sulfinic acid groups, and carboxy groups. In the invention, the acidic group is preferably a phosphoric acid group or a carboxy group, more preferably a carboxy group, from the viewpoint of the aggregation rate of the ink composition.

  Organic compounds having a carboxy group (organic carboxylic acid) are polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid. Acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, Nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts) are preferred. These compounds may be used alone or in combination of two or more.

  The organic carboxylic acid is preferably a divalent or higher carboxylic acid (hereinafter also referred to as polyvalent carboxylic acid) from the viewpoint of the aggregation rate of the ink composition, and malonic acid, malic acid, maleic acid, and succinic acid. , Glutaric acid, fumaric acid, tartaric acid, 4-methylphthalic acid, and citric acid are more preferable, and malonic acid, malic acid, tartaric acid, and citric acid are more preferable.

The organic acidic compound preferably has a low pKa.
As a result, the surface charge of particles such as pigments and polymer particles in the ink composition dispersed and stabilized with a weakly acidic functional group such as a carboxy group is reduced by contacting with an organic acidic compound having a lower pKa, and dispersed. Stability can be reduced.

  The organic acidic compound contained in the treatment liquid preferably has a low pKa, a high solubility in water, and a valence of 2 or more, and a functional group that stabilizes the particles in the ink composition (for example, More preferably, it is a divalent or trivalent acidic substance having a high buffer capacity in a pH range lower than the pKa of a carboxy group or the like.

-Inorganic acidic compounds-
Examples of the inorganic acidic compound include phosphoric acid, nitric acid, nitrous acid, sulfuric acid, hydrochloric acid and the like, but are not particularly limited thereto. As the inorganic acidic compound, phosphoric acid is most preferable from the viewpoint of suppressing the occurrence of uneven glossiness in the image area and the ink aggregation rate.

Phosphoric acid has a low water solubility (25 ° C.) of 0.0018 g / 100 g of water when a calcium salt (calcium phosphate) is used. Therefore, when the inorganic acidic compound contained in the treatment liquid is phosphoric acid, the calcium salt is not dissolved but is fixed, and the effect of suppressing the occurrence of uneven gloss on the surface of the image area is excellent.
In particular, when a recording medium having a coating layer containing calcium carbonate is used as the recording medium, phosphoric acid is advantageous as the inorganic acidic compound contained in the treatment liquid.

The total amount of acidic compounds contained in the treatment liquid is not particularly limited, but is preferably 5% by mass to 40% by mass with respect to the total amount of the treatment liquid from the viewpoint of the aggregation rate of the ink composition, and is 10% by mass. More preferably, it is -30 mass%.
In the case where an organic acidic compound and an inorganic acidic compound are used in combination as the acidic compound, the content ratio of the organic acidic compound and the inorganic acidic compound is determined from the viewpoint of suppressing aggregation unevenness and gloss unevenness. The content of is preferably 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 15 mol% to 35 mol%.

In addition to the acidic compound, the treatment liquid may use other aggregating components such as a polyvalent metal salt and a cationic polymer as necessary.
As for the polyvalent metal salt and the cationic polymer, for example, the polyvalent metal salt and the cationic polymer described in paragraphs 0155 to 0156 of JP2011-042150A can be used.

(Water-soluble polymer compound)
The treatment liquid preferably contains at least one water-soluble polymer compound.
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.
As the water-soluble polymer compound, a specific polymer compound described later and water-soluble polymer compounds described in paragraphs 0026 to 0080 of JP2013-001854A are also suitable.

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

The content of the water-soluble polymer compound in the treatment liquid is not particularly limited, but is preferably 0.1% by mass to 10% by mass, and 0.1% by mass to 4% by mass with respect to the total amount of the treatment liquid. Is more preferable, 0.1% by mass to 2% by mass is further preferable, and 0.1% by mass to 1% by mass is further preferable.
If the content is 0.1% by mass or more, spreading of the ink droplets can be further promoted, and if the content is 10% by mass or less, the thickening of the treatment liquid can be further suppressed. Moreover, if 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.

As the water-soluble polymer compound, a polymer compound containing a hydrophilic structural unit having an ionic group (preferably an anionic group) (hereinafter also referred to as “specific polymer compound”) is preferable. Thereby, the spread of the ink droplets applied to the recording medium can be further promoted, and the roughness of the image is further suppressed.
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 hydrophilic structural unit having an ionic group (preferably an anionic group) is preferably a structural unit derived from a (meth) acrylamide compound having an ionic group (preferably an anionic group).
The content of the hydrophilic structural unit having an ionic group (preferably an anionic group) in the water-soluble polymer compound is, for example, 10% by mass to 100% by mass in the total mass of the water-soluble polymer compound. It is preferably 10% by mass to 90% by mass, more preferably 10% by mass to 70% by mass, still more preferably 10% by mass to 50% by mass, and further preferably 20% by mass to 40% by mass. More preferably, it is mass%.

The specific polymer compound includes at least one hydrophobic structural unit in addition to at least one hydrophilic structural unit having the above-described ionic group (preferably an anionic group, particularly preferably a sulfonic acid group). Is more preferable. 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.
As the hydrophobic structural unit, a structural unit derived from (meth) acrylic acid ester (preferably, alkyl ester having 1 to 4 carbon atoms of (meth) acrylic acid) is preferable.

  Content of the hydrophobic structural unit in a specific polymer compound can be made into 10 mass%-90 mass% in the total mass of a specific polymer compound, for example, It is preferable that it is 30 mass%-90 mass%. 50 mass% to 90 mass% is more preferable, and 60 mass% to 80 mass% is still more preferable.

(water)
The treatment liquid preferably contains water.
The content of water is preferably 50% by mass to 90% by mass and more preferably 60% by mass to 80% by mass with respect to the total mass of the treatment liquid.

(Water-soluble solvent)
The treatment liquid preferably contains at least one water-soluble solvent.
Specifically, as the water-soluble solvent, a water-soluble solvent that can be contained in the ink composition of the present invention can be used in the treatment liquid as well.
Among them, 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, and More preferably, it is at least one selected from polyoxyethylene polyoxypropylene glycol.

  As content in the processing liquid of a water-soluble solvent, it is preferable that it is 3 mass%-20 mass% with respect to the whole processing liquid from viewpoints, such as applicability | paintability, and it is more preferable that it is 5 mass%-15 mass%. preferable.

-Surfactant-
The treatment liquid 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.

  As the surfactant, JP-A-59-157636, pages 37-38 and Research Disclosure No. The compounds listed as surfactants in 308119 (1989) are also included. Further, fluorine (fluorinated alkyl) -based surfactants and silicone-based surfactants 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 a processing liquid, It is preferable that it is content so that the surface tension of a processing liquid will be 50 mN / m or less, and it will become 20 mN / m-50 mN / m. The content is more preferable, and the content is more preferably 30 mN / m to 45 mN / m.

(Other additives)
The treatment liquid may contain other additives other than those described above as necessary.
Other additives that can be contained in the treatment liquid are the same as other additives that can be contained in the ink composition described above.

(Physical properties of processing solution)
The treatment liquid preferably has a pH of 0.1 to 0.5 at 25 ° C. (± 1 ° C.) from the viewpoint of the aggregation rate of the ink composition.
When the pH of the treatment liquid is 0.1 or more, the roughness of the recording medium is further reduced and the adhesion of the image area is further improved.
When the pH of the treatment liquid is 0.5 or less, the aggregation rate is further improved, the coalescence of dots (ink dots) by the ink composition on the recording medium is further suppressed, and the roughness of the image is further reduced.
The pH (25 ° C. ± 1 ° C.) of the treatment liquid is more preferably 0.2 to 0.4.

  The viscosity of the treatment liquid is preferably in the range of 0.5 mPa · s to 10 mPa · s, more preferably in the range of 1 mPa · s to 5 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The viscosity is measured under a condition of 25 ° C. using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

  The surface tension at 25 ° C. (± 1 ° C.) of the treatment liquid is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and 30 mN / m to 45 mN / m. Is more preferable. When the surface tension of the treatment liquid is within the range, the occurrence of curling in the recording medium is suppressed, which is advantageous. The surface tension of the treatment liquid is measured by a plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

(Image forming method)
The image forming method of the present embodiment includes an ink applying step of forming an image by applying the above-described ink jet ink composition of the present invention on a recording medium by an ink jet method,
A treatment liquid application step of applying a treatment liquid containing an acid for aggregating the components in the inkjet ink composition onto the recording medium;
A drying step of drying the image after the ink application step and the treatment liquid application step;
Have

As the recording medium, commercially available media can be used. For example, “OK Prince Quality” manufactured by Oji Paper Co., Ltd., “Shiraoi (registered trademark)” manufactured by Nippon Paper Industries Co., Ltd., Japan High quality paper (A) such as “New NPI (registered trademark) fine quality” manufactured by Paper Industries Co., Ltd., “OK Everlight (registered trademark) coat” manufactured by Oji Paper Co., Ltd., “Aurora” manufactured by Nippon Paper Industries Co., Ltd. Lightly coated paper (A3) such as “OK” L manufactured by Oji Paper Co., Ltd., “Aurora L” manufactured by Nippon Paper Industries Co., Ltd .; “Coated paper manufactured by Oji Paper Co., Ltd.” Coated paper (A2, B2) such as “OK Top Coat (registered trademark) +”, “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd .; “OK Kanto (registered trademark) +” manufactured by Oji Paper Co., Ltd. and Mitsubishi Paper Industries Art paper (A1) such as “Tokuhishi Art” manufactured by Co., Ltd .; “Nyu” manufactured by Oji Paper Co., Ltd. Age (registered trademark), OK Topcoat (registered trademark) mat, Nippon Paper Industries 'Ulite (registered trademark), Mitsubishi Paper Industries' New V mat, Chuetsu Pulp & Paper Co., Ltd. ) Matte paper (A2) such as “Thunderbird mat coat N”; “Ibest (registered trademark)” manufactured by Nippon Daishowa Paperboard Co., Ltd., “Perfect W” manufactured by Hokuetsu Kishu Paper Co., Ltd., Oji Paper ( “Bon Ivory (registered trademark) +” manufactured by Oji Paper Co., Ltd., “OK Plow” manufactured by Oji Paper Co., Ltd., “F1 Card” manufactured by Nippon Daishowa Paper Co., Ltd., “No” manufactured by Hokuetsu Kishu Paper Co., Ltd. "Back W", "Hi Lucky (registered trademark)" manufactured by Hokuetsu Kishu Paper Co., Ltd., "OK L Card" manufactured by Oji Paper Co., Ltd., "Pearl Deluxe (registered trademark)" manufactured by Mitsubishi Paper Industries, Ltd., Oji “PC Green 100” manufactured by Paper Manufacturing Co., Ltd., Hokuetsu Kishu Paper Co., Ltd. "NewDV" of Hokuetsu Paper Mills Co., Ltd. "Marikoto (registered trademark)", thick paper such as "UF-coating" manufactured by Oji Paper Co., and the like.
In addition, as a recording medium, it is also possible to use various types of photographic paper for inkjet recording.

<Ink application process>
The ink application step is a step of applying the above-described ink composition to a recording medium by an ink jet method.
In this step, the ink composition can be selectively applied onto the recording medium, and a desired visible image can be formed. The details of the ink composition, such as details and preferred embodiments of the ink composition, are as described above in the description of the ink composition.

  In the image formation by the ink jet method, by applying energy, the above-described ink composition is ejected onto a desired recording medium to form an image. As a preferred inkjet method for this embodiment, the method described in paragraph numbers 0093 to 0105 of JP-A No. 2003-306623 can be applied.

  The inkjet method is not particularly limited, and is a known method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, An acoustic ink jet system that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, and a thermal ink jet that forms bubbles by heating the ink and uses the generated pressure (bubble jet (registered) Trademark)) method or the like. 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.

  As an inkjet head, a short serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line method, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction crossing 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 embodiment can be applied to any of these, but in general, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image abrasion resistance is great.

  The amount of ink droplets ejected from the inkjet head is preferably 1 pl (picoliter) to 10 pl, more preferably 1.5 pl to 6 pl, from the viewpoint of obtaining a high-definition image. In addition, from the viewpoint of improving the unevenness of the image and the continuous gradation, it is also effective to discharge different amounts of liquids in combination, and even in such a case, the present embodiment can be suitably used.

Ink jet heads usually have a liquid repellent film on the surface from which ink is ejected (ink ejection surface).
As the inkjet head, an inkjet head including a nozzle plate in which a plurality of ejection holes are two-dimensionally arranged and a liquid repellent film is provided on the ejection hole forming surface (ink ejection surface) is preferable.
As the nozzle plate and the inkjet head, the nozzle plates described in paragraphs 0206 to 0214 and FIGS. 3 and 4 of JP2013-223958A can be used.

The liquid repellent film is preferably a liquid repellent film containing a fluorine compound.
As the fluorine compound, a compound having a fluorinated alkyl group is preferable.
Examples of the liquid repellent film containing a fluorine compound include the liquid repellent films described in paragraphs 0192 to 0205 of JP2013-223958A.

The liquid repellent film is particularly preferably a liquid repellent film formed using a fluorinated alkylsilane compound (preferably by chemical vapor deposition).
As the fluorinated alkylsilane compound, a fluorinated alkylsilane compound represented by the following general formula (F) can be suitably used. The fluorinated alkylsilane compound represented by the following general formula (F) is a silane coupling compound.
_{C n F 2n + 1 -C m} H 2m -Si-X 3 ... Formula (F)
In general formula (F), n represents an integer of 1 or more, and m represents 0 or an integer of 1 or more. X represents an alkoxy group, an amino group, or a halogen atom. A part of X may be substituted with an alkyl group.

Examples of the fluorinated alkylsilane compound represented by the general formula (F) include C ₈ F ₁₇ C ₂ H ₄ SiCl ₃ (“1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane” and “FDTS”). ), Fluoroalkyltrichlorosilanes such as CF ₃ (CF ₂ ) ₈ C ₂ H ₄ SiCl ₃ ; CF ₃ (CF ₂ ) ₈ C ₂ H ₄ Si (OCH ₃ ) ₃ , ₃ , ₃ , _3- Fluoroalkylalkoxysilanes such as trifluoropropyltrimethoxysilane, tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane, heptadecafluoro-1,1,2,2-tetrahydrodecyltrimethoxysilane; etc. Can be mentioned.

As the fluorinated alkylsilane compound represented by the general formula (F), n is an integer of 1 to 14 and m is 0 or 1 to 5 in terms of liquid repellency and durability of the liquid repellent film. A compound in which X is an alkoxy group or a halogen atom is preferable, and n is an integer of 1 to 12, m is an integer of 0 to 3, and X is an alkoxy group or a halogen atom. Is preferred.
As the fluorinated alkylsilane compound represented by the general formula (F), C ₈ F ₁₇ C ₂ H ₄ SiCl ₃ is most preferable.

  Although there is no restriction | limiting in particular as thickness of a liquid repellent film, The range of 0.2-30 nm is preferable, and the range of 0.4-20 nm is more preferable. Even if the thickness of the liquid repellent film exceeds 30 nm, there is no particular problem, but if it is 30 nm or less, it is advantageous in terms of film uniformity, and if it is 0.2 nm or more, the liquid repellency is good.

As the liquid repellent film containing a fluorine compound, for example, a monomolecular film of a fluorinated alkylsilane compound (SAM (Self-Assembled Monolayer) film) or a laminated film of a fluorinated alkylsilane compound is preferable.
Here, the laminated film of the fluorinated alkylsilane compound includes not only a film in which the fluorinated alkylsilane compound is stacked without being polymerized but also a polymerized film of the fluorinated alkylsilane compound.
As the liquid repellent film containing a fluorine compound, a monomolecular film (SAM film) of a fluorinated alkylsilane compound is particularly preferable.

<Processing liquid application process>
The image forming method of the present embodiment includes a treatment liquid application step for applying the treatment liquid to the recording medium.
In the treatment liquid application step, a treatment liquid containing an acidic compound that aggregates the components in the ink composition is applied to the recording medium, and the treatment liquid is brought into contact with the ink composition to form an image. In this case, the dispersed particles including the resin particles in the ink composition are aggregated, and the image is fixed on the recording medium. The treatment liquid contains at least an aggregating component, and details and preferred embodiments of each component are as described above.

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

The treatment liquid application step may be provided either before or after the ink application step using the ink composition.
In the present embodiment, an aspect in which an ink application process is provided after the treatment liquid application process is preferable.
Specifically, before applying the ink composition onto the recording medium, a treatment liquid is applied in advance to agglomerate the components (the above-mentioned dispersed particles) in the ink composition, and then applied onto the recording medium. An embodiment in which an ink composition is applied so as to come into contact with the treated liquid and imaged is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The application amount of the treatment liquid is not particularly limited as long as the ink composition can be aggregated. However, it is preferable that the application amount of the aggregation component is 0.1 g / m ² or more. The amount of the applied aggregating component is 0.2g ^{/ m 2} ~2.0g ^/ m 2 is preferred. When the application amount of the aggregating component is 0.1 g / m ² or more, good high-speed aggregating property can be maintained according to various usage forms of the ink composition. Moreover, it is preferable that the application amount of the aggregating component is 2.0 g / m ² or less because it does not affect the surface properties (gloss change, etc.) of the applied recording medium.

  In this embodiment, an ink application step is provided after the treatment liquid application step, and the treatment liquid on the recording medium is heated after the treatment liquid is applied on the recording medium and before the ink composition is applied. It is preferable to dry. As a result, the effect of preventing bleeding and improving the ink colorability can be obtained, and as a result, a visible image with good color density and hue can be recorded. The preferred embodiment of the means and method for heat-drying the treatment liquid is the same as the means and method for heat-drying the image in the preferred embodiment of the drying step described later.

<Drying process>
The drying process in the present embodiment is a process of drying the image after the ink application process and the treatment liquid application process.
In this step, it is preferable to heat dry the image.
Examples of means for heating and drying the image include known heating means such as a heater, known blower means such as a dryer, and a combination of these.
Examples of a method for heating and drying an image include a method of applying heat with a heater or the like from the side opposite to the image forming surface of the recording medium, a method of applying warm air or hot air to the image forming surface of the recording medium, and a recording medium And a method of applying heat with an infrared heater from the opposite side to the image forming surface, a method combining a plurality of these, and the like.

The heating temperature during image drying is preferably 60 ° C. or higher, more preferably 65 ° C. or higher, and particularly preferably 70 ° C. or higher.
Although there is no restriction | limiting in particular in the upper limit of heating temperature, As an upper limit, 100 degreeC is mentioned, for example, 90 degreeC is preferable.
There is no particular limitation on the time for heating and drying the image, but it is preferably 3 seconds to 60 seconds, more preferably 5 seconds to 30 seconds, and particularly preferably 5 seconds to 20 seconds.

<Inkjet recording apparatus>
The image forming apparatus that can be used in the image forming method of the present embodiment is not particularly limited, and is described in JP 2010-830221 A, JP 2009-234221 A, JP 10-175315 A, or the like. A known image forming apparatus can be used.

Hereinafter, an example of an image forming apparatus that can be used in the image forming method of the present embodiment will be described with reference to FIG.
Next, an example of an ink jet recording apparatus suitable for carrying out the image forming method of the present embodiment will be specifically described with reference to FIG.
FIG. 1 is a schematic configuration diagram illustrating a configuration example of the entire inkjet recording apparatus.

  As shown in FIG. 1, the ink jet recording apparatus includes an anilox roller 20 and a coating roller 22 in contact with the anilox roller 20 as roller materials for coating the processing liquid sequentially in the recording medium conveyance direction (arrow direction in the figure). The provided treatment liquid application unit 12, the treatment liquid drying zone 13 provided with a heating means (not shown) for drying the applied treatment liquid, the ink ejection unit 14 that ejects various ink compositions, and the ejected ink An ink drying zone 15 for drying the composition is provided.

  The recording medium supplied to the ink jet recording apparatus includes a processing liquid application unit 12, a processing liquid drying zone 13, and an ink discharging unit by a conveying roller from a paper feeding unit that feeds the recording medium from a case loaded with the recording medium. 14 and the ink drying zone 15 are sent in order and collected in the collecting unit. In addition to the method using a conveyance roller, the conveyance may be performed by a drum conveyance method using a drum-shaped member, a belt conveyance method, a stage conveyance method using a stage, or the like.

  Among the plurality of transport rollers, at least one roller may be a driving roller to which the power of a motor (not shown) is transmitted. By rotating a driving roller rotated by a motor at a constant speed, the recording medium is conveyed in a predetermined direction by a predetermined conveyance amount.

The treatment liquid application unit 12 is provided with an anilox roller 20 that is arranged by immersing a part in a storage dish in which the treatment liquid is stored, and an application roller 22 that is in contact with the anilox roller 20. The anilox roller 20 is a roller material for supplying a predetermined amount of processing liquid to the application roller 22 disposed to face the recording surface of the recording medium. The treatment liquid is uniformly applied onto the recording medium by the application roller 22 supplied with an appropriate amount from the anilox roller 20.
The application roller 22 is configured to be able to convey a recording medium in a pair with the opposing roller 24, and the recording medium passes between the application roller 22 and the opposing roller 24 and is sent to the treatment liquid drying zone 13.

  A treatment liquid drying zone 13 is disposed downstream of the treatment liquid application unit 12 in the recording medium conveyance direction. The treatment liquid drying zone 13 can be configured by using a known heating means such as a heater, an air blowing means using air blowing such as a dryer, or a combination of these. The heating means is a method of installing a heating element such as a heater on the side opposite to the treatment liquid application surface of the recording medium (for example, below the conveyance mechanism that carries the recording medium when conveying the recording medium automatically), Examples include a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, a heating method using an infrared heater, and the like.

Also, since the surface temperature of the recording medium varies depending on the type (material, thickness, etc.) of the recording medium and the environmental temperature, the surface temperature of the recording medium measured by the measuring unit that measures the surface temperature of the recording medium and the measuring unit It is preferable to apply the treatment liquid while providing a control mechanism that feeds back the value to the heating control unit. As a measurement part which measures the surface temperature of a recording medium, a contact or non-contact thermometer is preferable.
Further, the solvent may be removed using a solvent removal roller or the like. As another embodiment, a method of removing excess solvent from the recording medium with an air knife is also used.

  The ink discharge unit 14 is disposed downstream of the treatment liquid drying zone 13 in the recording medium conveyance direction. The ink discharge section 14 includes a recording head (ink discharge head) 30K connected to each of the ink storage sections that store black (K), cyan (C), magenta (M), and yellow (Y) color inks. 30C, 30M, and 30Y are arranged. Each ink storage section (not shown) stores an ink composition containing a pigment corresponding to each hue, resin particles, a water-soluble solvent, and water. The heads 30K, 30C, 30M, and 30Y are supplied. Further, as shown in FIG. 1, a recording head 30A for spot color ink discharge is provided on the downstream side in the transport direction of the ink discharge heads 30K, 30C, 30M, and 30Y so that spot color ink can be discharged as needed. 30B can be further provided.

  The ink ejection heads 30K, 30C, 30M, and 30Y each eject ink corresponding to an image from ejection nozzles arranged to face the recording surface of the recording medium. Thus, each color ink is applied on the recording surface of the recording medium, and a color image is recorded.

  The ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30B are all full in which a large number of discharge ports (nozzles) are arranged over the maximum recording width (maximum recording width) of an image recorded on the recording medium. It is a line head. Compared to the serial type in which recording is performed while reciprocating a short shuttle head in the width direction of the recording medium (direction perpendicular to the conveying direction on the recording medium conveying surface), it is possible to record an image on the recording medium at a higher speed. it can. In the present embodiment, either a serial type recording or a method capable of relatively high speed recording, for example, a single pass method of forming one line by one scan may be employed. According to the image recording method of the embodiment, a high-quality image with high reproducibility can be obtained even with the single pass method.

Here, the ink ejection heads 30K, 30C, 30M, 30Y, 30A, and 30B all have the same structure.
Although not shown, these ink ejection heads include a nozzle plate. The nozzle plate is provided with two-dimensionally arranged ejection holes.
A film liquid film containing a fluorine compound is provided on the ink ejection surface of the nozzle plate.

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

  The ink drying zone 15 is disposed downstream of the ink discharge unit 14 in the recording medium conveyance direction. The ink drying zone 15 can be configured in the same manner as the treatment liquid drying zone 13.

  Further, in the ink jet recording apparatus, a heating unit that performs a heat treatment on the recording medium can be arranged in a conveyance path from the paper feeding unit to the stacking unit. For example, the temperature of the recording medium is raised to a desired temperature by disposing a heating unit at a desired position such as the upstream side of the treatment liquid drying zone 13 or between the ink discharge unit 14 and the ink drying zone 15. Thus, drying and fixing can be effectively performed.

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

<Synthesis of water-soluble polymer dispersant Q-1>
A monomer supply composition was prepared by mixing methacrylic acid (172 parts), benzyl methacrylate (828 parts), and isopropanol (375 parts). In addition, an initiator supply composition was prepared by mixing 2,2-azobis (2-methylbutyronitrile) (22.05 parts) and isopropanol (187.5 parts).
Next, isopropanol (187.5 parts) was heated to 80 ° C. under a nitrogen atmosphere, and the mixture of the monomer supply composition and the initiator supply composition was dropped therein over 2 hours. After the completion of dropping, the mixture was further maintained at 80 ° C. for 4 hours, and then cooled to 25 ° C.
After cooling, the solvent was removed under reduced pressure to obtain a water-soluble polymer dispersant Q-1 having a weight average molecular weight of about 30,000 and an acid value of 112 mgKOH / g.

<Preparation of Cyan Pigment Dispersion C-1>
After neutralizing 0.8 equivalent of the amount of methacrylic acid in the water-soluble polymer dispersant Q-1 (150 parts) obtained above with an aqueous potassium hydroxide solution, the water-soluble polymer dispersant concentration is 25 masses. % Was further adjusted by adding ion-exchanged water to obtain a water-soluble polymer dispersant aqueous solution.
This water-soluble polymer dispersant aqueous solution (124 parts), Pigment Blue 15: 3 (cyan pigment) (48 parts), water (75 parts) and dipropylene glycol (30 parts) are mixed, and a bead mill ( A dispersion of polymer-coated cyan pigment particles having a pigment concentration of 15% by mass (uncrosslinked dispersion C-1) was obtained by dispersing with a bead diameter of 0.1 mmφ and zirconia beads) until a desired volume average particle size was obtained.
To this uncrosslinked dispersion C-1 (136 parts), DENACOL (registered trademark) EX-321 (manufactured by Nagase ChemteX Corporation, crosslinking agent) (1.3 parts) and boric acid aqueous solution (boric acid concentration: 4 mass%) (14.3 parts), and after reacting at 50 ° C. for 6 and a half hours, the mixture was cooled to 25 ° C. to obtain a crosslinked dispersion C-1.
Next, ion-exchanged water was added to the obtained crosslinked dispersion C-1, and a stirring type ultra holder (manufactured by ADVANTEC Co., Ltd.) and an ultrafiltration filter (manufactured by ADVANTEC Co., Ltd., molecular weight cut off 50,000, Q0500076E ultra). Filter) and purifying the dispersion so that the dipropylene glycol concentration in the dispersion is 0.1% by mass or less, and then concentrating until the pigment concentration is 15% by mass. Dispersion C-1 was obtained.
The color material contained in the cyan pigment dispersion C-1 is covered with at least a part of the surface of Pigment Blue 15: 3 (cyan pigment) by the water-soluble polymer dispersant Q-1 crosslinked by a crosslinking agent. It is a resin-coated pigment.

<Preparation of Magenta Pigment Dispersion M-1>
In the preparation of the cyan pigment dispersion C-1, the same procedure as in the preparation of the cyan pigment dispersion C-1 was performed except that Pigment Red 122 (magenta pigment) was used instead of Pigment Blue 15: 3 (cyan pigment). As a result, a magenta pigment dispersion M-1 was obtained.

<Preparation of Yellow Pigment Dispersion Y-1>
Preparation of cyan pigment dispersion C-1 was the same as that of cyan pigment dispersion C-1, except that Pigment Yellow 74 (yellow pigment) was used instead of Pigment Blue 15: 3 (cyan pigment). As a result, a yellow pigment dispersion Y-1 was obtained.

<Preparation of Black Pigment Dispersion K-1>
In the preparation of cyan pigment dispersion C-1, except that carbon black MA-100 (black pigment) was used instead of pigment blue 15: 3 (cyan pigment), preparation of cyan pigment dispersion C-1 Similarly, a black pigment dispersion K-1 was obtained.

<Synthesis of self-dispersing polymer particles P-1 (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. Thereafter, while maintaining the temperature in the flask at 75 ° C., 72.0 g of isobornyl methacrylate, 252.0 g of methyl methacrylate, 36.0 g of methacrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) A mixed solution consisting of 1.44 g of a polymerization initiator, compound name: (dimethyl 2,2′-azobis (2-methylpropionate)) was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion, a solution composed of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added thereto, stirred at 75 ° C. for 2 hours, and further a solution composed of 0.72 g of “V-601” and 36.0 g of isopropanol. The mixture was further stirred for 2 hours at 75 ° C. Thereafter, the temperature was raised to 85 ° C., and the stirring was continued for another 2 hours. A polymer solution of a tacrylate / methacrylic acid (= 20/70/10 [mass ratio]) copolymer was obtained.
The weight average molecular weight (Mw) measured in the same manner as above was 60000 (calculated in terms of polystyrene by gel permeation chromatography (GPC)) and the acid value was 64.9 mgKOH / g. It was.

  Next, 668.3 g of the obtained polymer solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added thereto, 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, and then the reaction vessel internal temperature was 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure. Kept. Thereafter, the inside of the reaction vessel is evacuated, and 913.7 g of isopropanol, methyl ethyl ketone, and distilled water are distilled off in total. ) Was obtained.

It was 145 degreeC when the glass transition temperature (Tg) of the said self-dispersing polymer particle P-1 was measured with the following method.
-Measurement of glass transition temperature (Tg)-
An aqueous dispersion of self-dispersing polymer particles having a solid content of 0.5 g was dried under reduced pressure at 50 ° C. for 4 hours to obtain a polymer solid content. Tg of the obtained polymer solid content was measured with a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by Hitachi High-Tech Science Co., Ltd. Specifically, 5 mg of the polymer solid content is sealed in an aluminum pan, and the temperature change according to the following temperature profile is applied to the polymer solid content in a nitrogen atmosphere, and Tg is obtained based on the measurement data at the second temperature increase. It was. In addition, the melting point was not observed within the range of the following temperature profile.
-Temperature profile in Tg measurement of resin particles-
30 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 220 ° C. (temperature rising at 20 ° C./min)
220 ° C to -50 ° C (cooling at 50 ° C / min)
−50 ° C. → 220 ° C. (temperature rising at 20 ° C./min)

<Synthesis of water-soluble polymer compound (water-soluble polymer)>
A water-soluble polymer compound (water-soluble polymer 1) used as a component in the treatment liquid was synthesized.
This synthesis was performed according to paragraphs 0200 to 0204 and 0229 of JP2013-001854A.
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.

[Experimental Example 1]
As Experimental Example 1, a black ink was prepared, the stability of the prepared black ink at high temperature with time was evaluated, and the abrasion resistance, blocking property, glossiness, and ejection of an image formed using the prepared black ink were evaluated. Sex was evaluated. Details will be described below.
In Experimental Example 1, black inks having test numbers 1 to 19 shown in Table 1 were prepared and evaluated using each black ink.
Details will be described below.

<Preparation of black ink>
Components of the following composition were mixed and coarse particles were removed through a membrane filter (pore size 0.5 μm) to obtain a black ink (ink composition).
The physical properties of the produced black ink were a viscosity of 5.0 mPa · s (30 ° C.), a surface tension of 36.0 mN / m (25 ° C.), and a pH of 8.5 (25 ° C.).
Here, the viscosity, the surface tension, and the pH are respectively VISCOMETER TV-22.
It was measured using TOKI SANGYO CO. LTD, Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.), and pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.).

-Black ink composition-
Black pigment dispersion K-1: 15.0% by mass
-Magenta pigment dispersion M-1: 4.0% by mass
Cyan pigment dispersion C-1: 4.0% by mass
・ Sanix (registered trademark) GP250 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent)
... 8.0% by mass
・ PEG-200 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent): 2.5% by mass
・ Propylene glycol (made by ADEKA, water-soluble solvent): 1.5% by mass
・ MFTG (manufactured by Nippon Emulsifier Co., Ltd., water-soluble solvent) ... 2.0% by mass
・ Orphine (registered trademark) E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 0.3% by mass
Olfin (registered trademark) E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 1.0% by mass
Self-dispersing polymer particle P-1 (resin particle): 8.0% by mass
・ PVP K-15 (manufactured by ISB Japan Co., Ltd.)… 0.2% by mass
・ Urea: 5.0% by mass
・ Wax particles A (described in Table 1) (described in Table 1)
・ Wax particles B (described in Table 1) ... (described in Table 1)
・ Lithium chloride (inorganic salt): 0.01% by mass
・ Snowtex (registered trademark) XS (Nissan Chemical Co., Ltd., colloidal silica)
... 0.3% by mass
・ CAPSTONE (registered trademark) FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
-BYK (registered trademark) -024 (Bic Chemie Japan Co., Ltd., antifoaming agent)
… 0.01% by mass
・ Ion-exchanged water: Total remaining amount of 100% by mass

<Preparation of treatment solution>
The component of the following composition was mixed and the processing liquid was obtained.
The physical properties of the prepared treatment liquid were a viscosity of 2.9 mPa · s (25 ° C.), a surface tension of 41.0 mN / m (25 ° C.), and a pH of 0.7 (25 ° C.).
Here, the viscosity, the surface tension, and the pH are respectively VISCOMETER TV-22.
It was measured using TOKI SANGYO CO. LTD, Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.), and pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.).

-Composition of treatment liquid-
・ TPGmME (Tripropylene glycol monomethyl ether) 4.8% by mass
・ DEGmBE (diethylene glycol monobutyl ether) 4.8% by mass
・ Malonic acid: 9.0% by mass
・ Malic acid: 8.0% by mass
・ Propanetricarboxylic acid: 2.5% by mass
・ 85% by mass aqueous solution of phosphoric acid 6.0% by mass
・ The aforementioned water-soluble polymer 1 0.5 mass%
・ Antifoamer (Momentive Performance Materials Japan TSA-739 (15%); emulsion type silicone antifoam)
… 0.01% by mass as silicone oil
・ Benzotriazole: 1.0% by mass
・ Ion-exchanged water: Total remaining amount of 100% by mass

<Image formation>
A GELJET (registered trademark) GX5000 printer head manufactured by Ricoh Co., Ltd. was prepared.
This printer head is a line head in which 96 nozzles are arranged.
This printer head was fixedly arranged in an ink jet recording apparatus having the same configuration as the ink jet recording apparatus shown in FIG.
The arrangement at this time was such that the direction in which the 96 nozzles were aligned was inclined by 75.7 ° with respect to the direction orthogonal to the moving direction of the stage of the inkjet apparatus.

A liquid repellent film containing a fluorine compound is provided on the ink ejection surface of the line head. The liquid repellent film containing a fluorine compound is a monomolecular film (SAM film) of C ₈ F ₁₇ C ₂ H ₄ SiCl ₃ .

  An OK top coat (manufactured by Oji Paper Co., Ltd.) was prepared as a recording medium, and the following treatment liquid application process, ink application process, and drying process were sequentially performed to form (record) an image on the recording medium.

(Processing liquid application process)
An OK topcoat as a recording medium is fixed on the stage of the ink jet recording apparatus, and then the stage on which the recording medium is fixed is moved in a linear direction at a constant speed of 500 mm / sec. It apply | coated so that it might become about 1.5 g / m < ² >.
At the place where the application of the treatment liquid is completed, the drying of the treatment liquid is started at 50 ° C. using a dryer 1.5 seconds after the completion of the application of the treatment liquid to this place. After 3.5 seconds from the end of drying. The drying time at this time is 2 seconds.

(Ink application process)
The black ink prepared above from the printer head is applied to the surface of the recording medium to which the processing liquid has been applied while moving the recording medium after drying the processing liquid at a constant speed of a stage speed of 50 mm / sec. And 40% dot image of 100 mm × 150 mm was printed. The black ink discharge was started within 2 seconds from the end of drying of the treatment liquid.
The black ink ejection conditions were an ink droplet amount of 3.5 pL, an ejection frequency of 24 kHz, and a resolution of 1200 dpi × 1200 dpi (dot per inch).
The black ink used was deaerated through a deaeration filter and temperature-controlled at 30 ° C.

(Drying process)
The halftone dot image immediately after printing was dried at 70 ° C. for 10 seconds.

<Measurement of volume average particle diameter of wax particles>
The volume average particle diameter of each of the wax particles A and the wax particles B used for the preparation of the black ink is measured by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). did.
The results are shown in Table 1.

<Measurement of melting point of wax particles>
The melting points of the wax particles A and the wax particles B used for the preparation of the black ink were measured as follows. The results are shown in Table 1.
A water dispersion of 0.5 g of wax particles A in terms of solid content was dried under reduced pressure at 50 ° C. for 4 hours to obtain wax particles A (solid content). The melting point of the obtained wax particles A was measured using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by Hitachi High-Tech Science Co., Ltd.
5 mg of wax particles A (solid content) were sealed in an aluminum pan, and the temperature change according to the following temperature profile was performed on the wax particles A (solid content) in a nitrogen atmosphere. In the following temperature profile, the DSC peak top (endothermic peak) at the second temperature rise was defined as the melting point of the wax particles A.
The melting point of the wax particle B was also measured in the same manner as the measurement of the melting point of the wax particle A.

-Temperature profile for melting point measurement of wax particles-
30 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 220 ° C. (temperature rising at 20 ° C./min)
220 ° C to -50 ° C (cooling at 50 ° C / min)
−50 ° C. → 220 ° C. (temperature rising at 20 ° C./min)

<Evaluation of abrasion resistance of image>
A 100% solid image was formed as a recorded image in the same manner as in <Image formation> (including the drying step) except that a 100% solid image was formed instead of a 40% halftone dot image.
An unrecorded recording medium (the same recording medium used for recording) is superimposed on a 100% solid image after drying (hereinafter also referred to as “recorded image”), and 500 reciprocations are applied with a load of 5 kg / m ^2. The rubbing operation was performed.
After this operation, scratches on the recorded image and the degree of ink transfer to the recording medium that was not recorded were visually observed, and the abrasion resistance of the image was evaluated according to the following evaluation criteria.
The results are shown in Table 1.
In the following evaluation criteria, if it is A, B or C, it is within a practical allowable range.

-Evaluation criteria for image abrasion resistance-
A: No scratches are observed in the recorded image, and there is no transfer of ink to a recording medium that is not recorded, so that the image has excellent abrasion resistance.
B: Scratches are hardly observed in the recorded image, but slight transfer of ink to the recording medium not recorded is recognized. The rubbing resistance of the image is at a level that causes no problem in practice.
C: Slight scratches are observed in the recorded image, and ink transfer to a recording medium that is not recorded is also slightly observed, but the scratch resistance of the image is practically acceptable.
D: The scratch of the recorded image is recognized, and the transfer of the ink to the recording medium which is not recorded is clearly seen, and the abrasion resistance of the image is out of the practical allowable range.
E: The scratch of the recorded image is remarkable, and the transfer of the ink to the recording medium that is not recorded is also remarkable, and the image has extremely poor abrasion resistance.

<Evaluation of blocking resistance of image>
The following blocking resistance evaluation was performed assuming blocking (that is, adhesion between images) due to pressure applied during cutting of a printed material (recording medium on which an image was formed).
First, a 100% solid image was formed as a recorded image in the same manner as in <Image formation> (including the drying step) except that a 100% solid image was formed instead of a 40% halftone dot image.
Next, the recording medium on which the recorded image was formed was cut into a size of 2 cm × 2 cm to obtain an evaluation sample. Two evaluation samples were produced.
Next, the two evaluation samples were overlapped so that the recorded images were in contact with each other, then a load of 1000 N in a direction in which the two evaluation samples were pressed against each other was applied for 10 seconds, and then the evaluation samples were peeled off.
Next, the recorded images of each of the two evaluation samples are observed, the presence or absence of traces of the recorded images and the degree of the adhered traces are visually observed, and the blocking resistance of the images is evaluated according to the following evaluation criteria. did.
The results are shown in Table 1.

-Evaluation criteria for image blocking resistance-
A: Traces of the recorded images adhering to each other are not observed, and the blocking resistance of the images is very excellent.
B: Traces of the recorded images adhering to each other are observed in a range of more than 0% and less than 3% with respect to the total area of the recorded images, but the blocking resistance of the images is at a level that causes no problem in practice.
C: Traces of the recorded images adhered to each other in a range of 3% to less than 10% with respect to the total area of the recorded images, but the blocking resistance of the images is within a practically acceptable range.
D: Traces of the recorded images adhering to each other are observed in a range of 10% or more and less than 50% with respect to the total area of the recorded images, and the blocking resistance of the images is outside the practically acceptable range.
E: Traces of the recorded images adhering to each other are observed in a range of 50% or more with respect to the total area of the recorded images, and the blocking resistance of the images is extremely poor.

<Glossiness evaluation of image>
In the above <image formation> (including the drying process), a solid image having 10 levels of density was recorded as a recorded image in the same manner except that a solid image having 10 levels instead of a 40% halftone image was formed. Each was formed.
The glossiness of each solid image was visually observed, and the glossiness of the image was evaluated according to the following evaluation criteria.
The results are shown in Table 1.
In the following evaluation criteria, if it is A, B or C, it is within a practical allowable range.

-Evaluation criteria for glossiness of images-
A: There is no problem in glossiness in solid images of all densities.
B: A slight decrease in glossiness of the solid image is observed depending on the density, but the glossiness of the image is at a level that causes no problem in practical use.
C: The glossiness of the solid image is clearly seen depending on the density, but the glossiness of the image is practically acceptable.
D: In a solid image having a density of one level, the glossiness is greatly reduced, and the glossiness of the image is outside the allowable range for practical use.
E: In a solid image having two or more levels of density, the glossiness is greatly reduced, and the glossiness of the image is very poor.

<Ink ejection performance>
A 100% solid image was formed as a recorded image in the same manner as in <Image formation> (including the drying step) except that a 100% solid image was formed instead of a 40% halftone dot image. This solid image was formed continuously at a rate of 2700 sheets per hour for 30 minutes. Subsequently, an image composed of a parallel line pattern (length: 1 cm) of 75 dpi × 2400 dpi was formed.
The position of the center of the line width of the obtained parallel line pattern was measured using a general-purpose image processing apparatus DA-6000, and the standard deviation σ of the deviation from the position of the center of the theoretical line width was calculated. Based on the obtained standard deviation σ, the ink ejection properties were evaluated according to the following evaluation criteria.
The results are shown in Table 1.

-Evaluation criteria-
A: σ <1 μm, and there is no problem with the ink ejection properties.
B: 1 μm ≦ σ <3 μm, and there is no problem in ink ejection.
C: 3 μm ≦ σ <5 μm, and ink ejection properties are practically acceptable.
D: 5 μm ≦ σ <10 μm, and the ink ejectability is outside the allowable range for practical use.
E: 10 μm ≦ σ, and the ink ejection property is very poor.

<Evaluation of wear deterioration of liquid repellent film>
First, the contact angle (° C.) between the liquid repellent film of the head and water before the wear operation described later (before the test) was measured.
Next, a roller made of silicone rubber having a diameter of 40 mm was prepared, and a fabric (Toraysee (registered trademark) manufactured by Toray Industries, Inc.) was wound around the outer peripheral surface of the roller. Next, 2 ml of the black ink was soaked into the fabric wound around the roller. Next, the roller was pressed against the liquid repellent film of the head so that the cloth soaked with black ink and the liquid repellent film were in contact with each other, and the contact pressure between them was 40 kPa. In this state, the water-repellent film was reciprocated 3500 times at a speed of 50 reciprocations per minute, so that the liquid-repellent film was rubbed with the cloth soaked with black ink (this operation is hereinafter referred to as “abrasion operation”). ). The reciprocation of 3500 times in the wear operation was performed by adding 0.5 ml of black ink to the fabric every 50 reciprocations and newly replacing the fabric every 1000 reciprocations.
Next, the contact angle (° C.) between the liquid repellent film and water after the wear operation was measured.
From the above results, a decrease in the contact angle due to the wear operation (that is, a value obtained by subtracting the contact angle after the wear operation from the contact angle before the test) was calculated, and the wear deterioration of the liquid repellent film was evaluated according to the following evaluation criteria.
The results are shown in Table 1.
In the following evaluation criteria, if it is A, B or C, it is within a practical allowable range.

-Evaluation criteria for wear deterioration of liquid repellent film-
A: The decrease in the contact angle of the liquid repellent film by the wear operation was less than 10 °, and the wear deterioration of the liquid repellent film was significantly suppressed.
B: The decrease in the contact angle of the liquid repellent film by the wear operation was 10 ° or more and less than 15 °, and the wear deterioration of the liquid repellent film was suppressed.
C: The decrease in the contact angle of the liquid repellent film due to the wear operation was 15 ° or more and less than 25 °, and the effect of suppressing the wear deterioration of the liquid repellent film was within a practically acceptable range.
D: The decrease in the contact angle of the liquid repellent film due to the wear operation was 25 ° or more and less than 30 °, and the wear deterioration of the liquid repellent film could not be suppressed.
E: The contact angle of the liquid repellent film by the wear operation was 30 ° or more, and the wear deterioration of the liquid repellent film could not be suppressed.

-Description of Table 1-
The contents (mass%) of the wax particles A and the wax particles B are the amount of wax particles relative to the total amount of the ink composition. The amount of wax particles here is the amount of solids in the aqueous dispersion of wax particles.
・ Details of the wax particles are as follows.
A552 ... AQUACER (registered trademark) 552 (Aqueous dispersion of wax particles made of oxidized polyethylene wax, manufactured by Big Chemie Japan Co., Ltd.)
E9015 ... Hitech E9015 (manufactured by Toho Chemical Co., Ltd., aqueous dispersion of wax particles made of polyethylene wax)
A515 ... AQUACER (registered trademark) 515 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles made of oxidized polyethylene wax)
A537 ... AQUACER (registered trademark) 537 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles comprising a modified wax emulsion)
A531 ... AQUACER (registered trademark) 531 (manufactured by Big Chemie Japan Co., Ltd., an aqueous dispersion of wax particles made of a mixture of paraffin wax and hydrocarbon wax)
S524 ... Cerozole (registered trademark) 524 (manufactured by Chukyo Yushi Co., Ltd., aqueous dispersion of wax particles made of carnauba wax)
PEM17: Nopcoat PEM17 (manufactured by San Nopco, an aqueous dispersion of wax particles made of polyethylene wax)
W4005 ... Chemipearl (registered trademark) W4005 (manufactured by Mitsui Chemicals, aqueous dispersion of wax particles made of polyethylene wax)
ST200 ... ST200 (manufactured by Nippon Shokubai Co., Ltd., an aqueous dispersion of wax particles made of acrylic wax)
E6314 ... Hitech E6314 (manufactured by Toho Chemical Industry Co., Ltd., aqueous dispersion of wax particles made of polyethylene wax)
In Table 1, for the comparative example, those not corresponding to the wax particles A may be described in the column of “wax particles A” for convenience, and those not corresponding to the wax particles B are also referred to as “wax particles B” for convenience. It may be described in the column.

  As shown in Table 1, wax particles A having a volume average particle size of 20 nm or more and 60 nm or less and a melting point of 110 ° C. or more, and wax particles having a volume average particle size of 100 nm or more and less than 200 nm and a melting point of 70 ° C. or less. In Examples (Experiment Nos. 1 to 10) using an ink composition containing B and a mass ratio of [wax particles B / wax particles A] of 0.1 to 5.0, the image was rubbed. And the anti-blocking property of the image, and the deterioration of wear of the liquid repellent film was suppressed. In the examples (Experiment Nos. 1 to 10), the glossiness of the image and the ink dischargeability were also excellent.

In contrast to the above examples, in Experiment No. 11 (Comparative Example) using wax particles having a volume average particle diameter of more than 60 nm in place of the wax particles A, wear deterioration of the liquid repellent film is significant, The glossiness of the image and the ink discharge performance also decreased.
Further, in Experiment Nos. 12 and 13 (comparative examples) using wax particles having a melting point exceeding 70 ° C. in place of the wax particles B, the blocking resistance of the image was lowered.
In addition, in Experiment Nos. 14 and 15 (both were comparative examples) using wax particles having a melting point of less than 110 ° C. in place of the wax particles A, the abrasion resistance of the image was lowered.
In addition, in Experiment No. 16 (Comparative Example) using wax particles having a volume average particle diameter of significantly larger than 60 nm and 400 nm in place of the wax particles A, wear deterioration of the liquid repellent film is significant, The glossiness of the image and the ink discharge performance also decreased. In this experiment number 16 (comparative example), the abrasion resistance of the image also decreased. The reason why the abrasion resistance of the image is lowered is considered to be that a large convex portion derived from the 400 nm wax particles remained on the image surface. More specifically, it is considered that the convex portion dropped out due to the rubbing operation described above, and the image was damaged.
Further, in Experiment No. 17 (Comparative Example) in which only the wax particles B were used without using the wax particles A, the abrasion resistance of the image was extremely poor.
Further, in Experiment No. 18 (Comparative Example) in which only the wax particles A were used without using the wax particles B, the anti-blocking property of the image was lowered, and the wear deterioration of the liquid repellent film was remarkable.
Further, in Experiment No. 19 (Comparative Example) using wax particles having a melting point of more than 70 ° C. and a volume average particle diameter of less than 100 nm in place of the wax particles B, the blocking resistance of the image is lowered, and the liquid repellency is decreased. The wear deterioration of the film was remarkable.

Further, in the examples, it was confirmed from the comparison between the results of Experiment No. 4 and the results of other Experiment Nos. That the wax particles A have a melting point of 120 ° C. or more, particularly excellent in image abrasion resistance. .
Further, among the examples, the content mass ratio [wax particle B / wax particle A] is 0.3 to 2. based on the comparison between the results of Experiment Nos. 5, 9, and 10 and the results of other experiment numbers. It was confirmed that the image was particularly excellent in both abrasion resistance and blocking resistance of the image.

[Experimental example 2]
Magenta ink, cyan ink, and yellow ink having the following respective compositions were produced, and the same evaluation as in Experiment No. 7 of Experimental Example 1 was performed using each ink.
As a result, it was confirmed that an evaluation result (Table 1) equivalent to Experiment No. 7 in Experiment Example 1 was obtained for each ink.

-Magenta ink composition-
-Magenta pigment dispersion M-1: 40.0% by mass
・ Sanix (registered trademark) GP250 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent)
... 6.0 mass%
・ PEG-200 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent): 2.5% by mass
・ Propylene glycol (made by ADEKA, water-soluble solvent): 7.0% by mass
・ MFTG (manufactured by Nippon Emulsifier Co., Ltd., water-soluble solvent) ... 2.0% by mass
・ Orphine (registered trademark) E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 0.3% by mass
Olfin (registered trademark) E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 1.0% by mass
-Self-dispersing polymer particles P-1 (resin particles): 5.0% by mass
・ PVP K-15 (manufactured by ISB Japan Co., Ltd.)… 0.2% by mass
・ Urea: 5.0% by mass
AQUACER (registered trademark) 552 (an aqueous dispersion of wax particles (wax particles A) made of oxidized polyethylene wax manufactured by Big Chemie Japan Co., Ltd.)
... (as solid content) 2.0% by mass
ST200 (manufactured by Nippon Shokubai Co., Ltd., an aqueous dispersion of wax particles (wax particles B) made of acrylic wax) (1.0% by mass)
・ Snowtex (registered trademark) XS (Nissan Chemical Co., Ltd., colloidal silica)
... 0.3% by mass
・ CAPSTONE (registered trademark) FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
-BYK (registered trademark) -024 (Bic Chemie Japan Co., Ltd., antifoaming agent)
… 0.01% by mass
・ Ion-exchanged water: Total remaining amount of 100% by mass

-Composition of cyan ink-
Cyan pigment dispersion C-1 20.0% by mass
・ Sanix (registered trademark) GP250 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent)
... 6.0 mass%
・ PEG-200 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent): 3.5% by mass
・ Propylene glycol (made by ADEKA, water-soluble solvent)… 6.0% by mass
・ MFTG (manufactured by Nippon Emulsifier Co., Ltd., water-soluble solvent) ... 2.0% by mass
・ Orphine (registered trademark) E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 0.3% by mass
Olfin (registered trademark) E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 1.0% by mass
・ Self-dispersing polymer particles P-1 (resin particles): 9.0% by mass
・ PVP K-15 (manufactured by ISB Japan Co., Ltd.)… 0.2% by mass
・ Urea: 5.0% by mass
AQUACER (registered trademark) 552 (an aqueous dispersion of wax particles (wax particles A) made of oxidized polyethylene wax manufactured by Big Chemie Japan Co., Ltd.)
... (as solid content) 2.0% by mass
ST200 (manufactured by Nippon Shokubai Co., Ltd., an aqueous dispersion of wax particles (wax particles B) made of acrylic wax) (1.0% by mass)
-Potassium nitrate (inorganic salt): 0.05% by mass
・ Snowtex (registered trademark) XS (Nissan Chemical Co., Ltd., colloidal silica)
... 0.3% by mass
・ CAPSTONE (registered trademark) FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
-BYK (registered trademark) -024 (Bic Chemie Japan Co., Ltd., antifoaming agent)
… 0.01% by mass
・ Ion-exchanged water: Total remaining amount of 100% by mass

-Composition of yellow ink-
Yellow pigment dispersion Y-1 30.0% by mass
・ Sanix (registered trademark) GP250 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent)
... 7.0% by mass
・ PEG-200 (manufactured by Sanyo Chemical Industries, Ltd., water-soluble solvent): 2.5% by mass
・ Propylene glycol (made by ADEKA, water-soluble solvent): 5.0% by mass
・ MFTG (manufactured by Nippon Emulsifier Co., Ltd., water-soluble solvent) ... 2.0% by mass
・ Orphine (registered trademark) E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 0.3% by mass
Olfin (registered trademark) E1020 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant)
... 1.0% by mass
Self-dispersing polymer particle P-1 (resin particle): 8.0% by mass
・ PVP K-15 (manufactured by ISB Japan Co., Ltd.)… 0.2% by mass
・ Urea: 5.0% by mass
AQUACER (registered trademark) 552 (an aqueous dispersion of wax particles (wax particles A) made of oxidized polyethylene wax manufactured by Big Chemie Japan Co., Ltd.)
... (as solid content) 2.0% by mass
ST200 (manufactured by Nippon Shokubai Co., Ltd., an aqueous dispersion of wax particles (wax particles B) made of acrylic wax) (1.0% by mass)
-Potassium nitrate (inorganic salt): 0.05% by mass
・ Snowtex (registered trademark) XS (Nissan Chemical Co., Ltd., colloidal silica)
... 0.3% by mass
・ CAPSTONE (registered trademark) FS-63 (manufactured by Dupont, surfactant): 0.01% by mass
-BYK (registered trademark) -024 (Bic Chemie Japan Co., Ltd., antifoaming agent)
… 0.01% by mass
・ Ion-exchanged water: Total remaining amount of 100% by mass

DESCRIPTION OF SYMBOLS 12 ... Processing liquid provision part 13 ... Processing liquid drying zone 14 ... Ink discharge part 15 ... Ink drying zone 30K, 30C, 30M, 30Y ... Ink discharge head

Claims (12)

  Wax particles A having a volume average particle diameter of 20 nm or more and 60 nm or less and a melting point of 110 ° C. or more, wax particles B having a volume average particle diameter of 100 nm or more and less than 200 nm and a melting point of 70 ° C. or less, a water-soluble solvent, Ink-jet ink composition containing water, and the mass ratio of the wax particles B to the wax particles A is 0.1 to 5.0.   The ink composition for inkjet according to claim 1, wherein the wax constituting the wax particles A is polyethylene wax or polypropylene wax.   The ink composition for inkjet according to claim 1 or 2, wherein the wax constituting the wax particles B is an acrylic wax.   The inkjet ink composition according to any one of claims 1 to 3, wherein the wax constituting the wax particles A is polyethylene wax, and the wax constituting the wax particles B is acrylic wax.   The ink composition for inkjet according to any one of claims 1 to 4, wherein the wax particles A have a melting point of 120 ° C or higher.   The ink composition for inkjet according to any one of claims 1 to 5, wherein the content ratio of the wax particles B to the wax particles A is 0.2 to 2.0.   The ink composition for inkjet according to any one of claims 1 to 6, wherein the content ratio of the wax particles B to the wax particles A is 0.3 to 1.0.   The total content of the wax particles A and the wax particles B is 1.0% by mass to 10% by mass with respect to the total amount of the inkjet ink composition. Ink-jet ink composition.   Furthermore, the ink composition for inkjets of any one of Claims 1-8 containing carbon black.   Furthermore, the ink composition for inkjets of any one of Claims 1-9 containing a resin particle. The inkjet ink composition according to any one of claims 1 to 10, and
A treatment liquid containing an acid for aggregating components in the inkjet ink composition;
Ink set containing. An ink application step of forming an image on the recording medium by applying the ink composition for ink jet according to any one of claims 1 to 10 by an ink jet method;
A treatment liquid application step of applying a treatment liquid containing an acid for aggregating the components in the inkjet ink composition on the recording medium;
A drying step of drying the image after the ink application step and the treatment liquid application step;
An image forming method comprising: