JP2016194007A - Ink composition for ink jet recording, ink set, and ink jet recording method - Google Patents

Abstract

An ink composition for ink-jet recording, an ink set, and an ink-jet recording method capable of suppressing the occurrence of curling and cockle of a paper medium, obtaining an image having high image density and excellent film quality.
A water-soluble organic solvent is contained in an amount of 20% by mass or more and 40% by mass or less based on the total mass of a colorant, water, and an ink composition, and the water-soluble organic solvent has a surface tension at 25 ° C. of 40 mN /%. a first water-soluble organic solvent having a molecular weight of 150 or less and a second water-soluble organic solvent having a molecular weight of 200 or more, and a total content of the first water-soluble organic solvent The total amount of the amount Y1 and the total content Y2 of the second water-soluble organic solvent is 70% or more of the total amount of the water-soluble organic solvent on a mass basis, and the relationship of 1.5 ≦ Y1 / Y2 ≦ 4.0 is satisfied. An ink composition for ink jet recording, an ink set, and an ink jet recording method are provided.
[Selection figure] None

Description

  The present invention relates to an ink composition for ink jet recording, an ink set, and an ink jet recording method.

  Various methods have been proposed as methods for recording images. In recent years, inkjet technology has been widely used from the viewpoint of simple recording on various media. For example, application in the commercial printing field is expected.

  Also in inks for recording images, water-based inks using water as a solvent have been widely used in consideration of the environment. Water-based inks using water as a solvent tend to be slower to dry and tend to impair the original properties of paper than inks that use solvents with relatively low boiling points such as organic solvents. Such a tendency has a larger influence as the paper medium is thinner, and appears with a deformation such as a curl or wavy cockle in which the base material is rounded on one side.

  As a method for preventing deformation of a substrate such as curl, a technique of adding an anti-curl agent or the like is generally known. However, a satisfactory effect may not always be exhibited depending on the amount of ink ejected or the type of recording medium. Reducing the amount of ink droplets to be ejected is also effective in preventing deformation of the substrate, but not only the type of image is limited, but the effect of preventing deformation is small depending on the type of recording medium.

In other technologies related to the above, for example, a water-based inkjet ink containing a specific alkylacrylamide together with water has been proposed as an ink used for printing on plain paper. It is said that curling is prevented and high-quality image recording is possible (see, for example, Patent Document 1).
In addition, as a water-based ink containing water as a solvent, an ink having a composition containing water and an organic solvent in a ratio of about 6: 1 in the total amount of ink is disclosed (for example, see Patent Document 2).

JP 2014-198829 A JP 2014-65845 A

  It has been known that water is a factor that destroys and deforms paper tissue. However, when recording an image using water-based ink, there is a technique for avoiding deformation such as curling that appears on a paper medium. Not established. In particular, when an image is recorded on a thin paper medium, the deformation tends to occur more and more, and the degree of deformation increases. For this reason, if it is attempted to prevent deformation by reducing the amount of ink droplets, problems such as the inability to reproduce a desired hue are likely to occur.

  On the other hand, among the above-described conventional technologies, Patent Document 1 contains a specific alkylacrylamide as a solvent component together with water, and is expected to be effective in preventing curling that occurs during recording. Curling due to volatilization cannot be prevented. Moreover, in patent document 2, since there is too much quantity of the water contained compared with the quantity of the organic solvent, it is easy to produce the wavy-shaped cockle whose period is shorter than curl.

  As described above, the water-based ink containing water as a main solvent contains a large amount of water, and thus is likely to be deformed due to swelling of the paper medium, destruction of the fiber structure, and the like. For this reason, in order to use water-based ink, which is increasing from the viewpoint of environmental considerations, as a recording material for paper media without problems, it is necessary to establish a technology that can fundamentally suppress paper deformation such as curling. Desired.

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 an ink composition and an ink set for ink-jet recording that can suppress the occurrence of curling and cockle of a paper medium, have a high image density, and have an excellent film quality while being an aqueous composition. Another object of the present invention is to provide an ink jet recording method capable of obtaining an image having low curl and crackle, high image density and excellent film quality when an image is recorded using an ink and paper medium prepared in an aqueous system.

Specific means for solving the problems include the following aspects.
<1> A water-soluble organic solvent containing 20% by mass to 40% by mass with respect to the total mass of the colorant, water, and the ink composition, and the water-soluble organic solvent has a surface tension at 25 ° C. of 40 mN / m. And a first water-soluble organic solvent having a molecular weight of 150 or less and a second water-soluble organic solvent having a molecular weight of 200 or more, and the total content of the first water-soluble organic solvent The total amount of Y1 and the total content Y2 of the second water-soluble organic solvent is 70% or more of the total amount of the water-soluble organic solvent on a mass basis, and satisfies the relationship 1.5 ≦ Y1 / Y2 ≦ 4.0. An ink composition for ink jet recording.
<2> The ink composition for inkjet recording according to <1>, wherein the second water-soluble organic solvent has a molecular weight of 200 or more and 400 or less.
<3> The ink composition for inkjet recording according to <1> or <2>, further including resin particles having a glass transition temperature Tg of 40 ° C. or higher and a volume average particle diameter of 30 nm or higher.
<4> The water-soluble organic solvent of 80% by mass or more of the total amount of the water-soluble organic solvent contained in the ink composition is any one of <1> to <3>, wherein the number of hydroxyl groups contained in the molecule is 2 or more. It is an ink composition for inkjet recording as described in one.
<5> The solubility parameter of 70 mass% or more water-soluble organic solvent of the total amount of water-soluble organic solvent contained in the ink composition, ^{21 MPa} is ^1/2 or more ^{30 MPa 1/2} or less <1> to <4> The ink composition for ink-jet recording according to any one of the above.
<6> The inkjet according to any one of <1> to <5>, wherein the absolute value of the difference between the molecular weight of the first water-soluble organic solvent and the molecular weight of the second water-soluble organic solvent is 90 or more. It is a recording ink composition.
<7> As the second water-soluble organic solvent, at least one water-soluble organic solvent selected from the solvent group represented by the following structural formula (S) or the following structural formula (S2), dialkylene glycol monoalkyl ether, and The ink composition for inkjet recording according to any one of <1> to <6>, comprising at least one water-soluble organic solvent selected from the group consisting of trialkylene glycol monoalkyl ethers.
In the following structural formula (S) or structural formula (S2), t, u, and v each independently represent an integer of 1 or more, and satisfy t + u + v = 3 to 15. p, q, r, and s each independently represent an integer of 1 or more and satisfy p + q + r + s = 4-40. AO represents at least one of ethyleneoxy and propyleneoxy.

  <8> The ink composition for ink jet recording according to any one of <3> to <7>, wherein the resin particles have at least one selected from structural units represented by the following general formula 1 or general formula 2. It is a thing.

In formula, R < ¹ > and R < ² > represents a hydrogen atom or a C1-C4 alkyl group each independently. A ¹ represents an oxygen atom or NR ³ , and R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A ² represents a single bond, —COO—, or —CONH—. L ¹ represents an alkylene group having 6 to 22 carbon atoms. L ² represents a divalent linking group having 6 to 23 carbon atoms. M ¹ and M ² each independently represent a hydrogen ion, an alkali metal ion, or an ammonium ion.
<9> An ink having the ink composition for ink jet recording according to any one of <1> to <8>, and a treatment liquid containing a compound that aggregates at least a colorant in the ink composition for ink jet recording. Is a set.
<10> An ink jet recording method comprising an ink application step of applying the ink composition for ink jet recording according to any one of <1> to <8> on a paper medium having a thickness of 0.11 mm or less by an ink jet method. It is.
<11> Furthermore, a treatment liquid is applied on a paper medium having a thickness of 0.11 mm or less before or after the ink application step, and a treatment liquid containing a compound that aggregates at least the colorant in the ink composition for inkjet recording is applied. It is the inkjet recording method as described in <10> which has a process.
The <12> ink application step is the ink jet recording method according to <10> or <11>, wherein the solid image is formed by applying an ink composition for ink jet recording with an ink application amount of 10 g / m ² or less. .
<13> The ink jet recording method according to any one of <10> to <12>, wherein the paper medium is a coated paper having a coating layer on a paper substrate.

According to the present invention, there are provided an ink composition and an ink set for ink jet recording that can suppress the occurrence of curling and cockle of a paper medium, have a high image density, and have an excellent film quality while having an aqueous composition. The
In addition, according to the present invention, there is provided an ink jet recording method capable of obtaining an image having less curl and cockle, high image density, and excellent film quality when an image is recorded using an ink and paper medium prepared in an aqueous system. Provided.

It is a schematic diagram of the recording paper used for the evaluation of cockle. FIG. 6 is a diagram schematically showing the state of recording sheet cuckling when the vertical axis represents the position z in the height direction of the recording paper ridge and the horizontal axis represents the horizontal position x of the recording paper.

  Hereinafter, the ink composition for ink jet recording of the present invention, the ink set using the ink composition, and the ink jet recording method will be described in detail.

  In this specification, a numerical range using “to” indicates a range including the numerical values described before and after “to” as a minimum value and a maximum value, respectively.

“Curl” refers to a phenomenon in which a difference in shrinkage occurs between one side and the other side of a paper medium, and the paper medium curls and deforms to either side. “Cuckling” is also called cockling or undulation, and refers to a phenomenon in which fine wrinkles occur on the surface of a paper medium when recorded on the paper medium.
The “solid image” in this specification means a surface image formed by applying an ink composition at a specific halftone dot ratio (density).

<Ink composition for inkjet recording>
The ink composition for ink-jet recording of the present invention (hereinafter also simply referred to as “ink composition” or “ink”) is 20% by mass or more and 40% by mass with respect to the total mass of the colorant, water, and ink composition. It contains the following water-soluble organic solvents, preferably resin particles, and may contain surfactants and other additives as necessary.
The water-soluble organic solvent in the ink composition of the present invention has a first water-soluble organic solvent having a surface tension at 25 ° C. of 40 mN / m or less and a molecular weight of 150 or less, and a molecular weight of 200 or more. The content (mass) Y1 of the first water-soluble organic solvent and the content (mass) Y2 of the second water-soluble organic solvent include at least two of the second water-soluble organic solvent. The following conditions (1) and (2) are satisfied.
Total amount (mass) of Y1 + Y2 ≧ 70 mass% of the total amount of the water-soluble organic solvent (1)
1.5 ≦ Y1 / Y2 ≦ 4.0 (2)

  The ink composition for ink jet recording of the present invention may be used for image recording by using the ink alone at the time of image recording, or may be used in an ink set using ink and a treatment liquid described later. It may be provided for.

There has been a demand for an ink composition that is capable of forming an image having a water-based composition, curling and curling of a paper medium, high image density, and excellent film quality. It was difficult to obtain a satisfactory ink composition.
Since cockle is generated by the water applied to the paper medium by the ink, it is conceivable to reduce the amount of water contained in the ink in order to suppress the cockle. Only increasing the amount of solvent tends to impair the image quality.
Depending on the type of water-soluble organic solvent used, curling is likely to occur.
In addition, if the amount of ink applied to the paper medium is reduced to suppress cockle, it is difficult to obtain a high image density, and the performance of ink that can maintain a high image density by spreading on the paper medium even with a small amount of ink applied Is required.
Therefore, the present inventors have studied the combination of the type of water-soluble organic solvent (especially molecular weight and surface tension) and the content of the water-soluble organic solvent in the ink, and thereby the occurrence of curling and cockle of the paper medium. It has been found that an ink composition that can be suppressed and can form an image having high image density and excellent film quality and that satisfies all the required performances can be obtained.

  Hereinafter, each component of the ink composition for inkjet recording of the present invention will be described.

-Water-soluble organic solvent-
The ink composition for inkjet recording of the present invention contains a water-soluble organic solvent together with water. In the present invention, an appropriate amount of a water-soluble organic solvent is contained, and an appropriate type is selected to control the spread of ink at the time of droplet landing and the influence on deformation due to the difference in the molecular weight of the solvent. Therefore, curling and cockle are prevented from occurring when an image is recorded on a paper medium, in particular, a relatively thin paper medium having a thickness of 0.11 mm or less.

  The term “water-soluble” means that when the target organic solvent is dissolved in 100 g of water at 25 ° C., the dissolved amount is 100 g or more.

Specifically, the content of the water-soluble organic solvent with respect to the total mass of the ink composition is in the range of 20% by mass to 40% by mass. When the content of the water-soluble organic solvent is 20% by mass or more, the content ratio of the organic solvent does not decrease too much as compared with the content of water, which is the main solvent, so that significant cockle generation can be suppressed. In addition, when the content of the water-soluble organic solvent is 40% by mass or less, the organic solvent hardly remains in the film, so that the film quality is kept good, and scratches due to scratching or coloration on the scraped object are observed. It becomes difficult to occur.
As content of the water-soluble organic solvent contained in an ink composition, the range of 25 mass% or more and 40 mass% or less is more preferable, and the range of 30 mass% or more and 40 mass% or less is more preferable.

The ink composition of the present invention contains at least two water-soluble organic solvents. Specifically, in the ink composition of the present invention, the first water-soluble organic solvent having a surface tension of 40 mN / m or less and a molecular weight of 150 or less, and a molecular weight of 200 or more. You may contain 2 or more types of at least 1 type of 2 water-soluble organic solvents. The ink composition of the present invention includes a first water-soluble organic solvent having a surface tension of 40 mN / m or less and a molecular weight of 150 or less, and a second water-soluble organic solvent having a molecular weight of 200 or more. And may contain two types. Furthermore, the ink composition of the present invention contains three or more water-soluble organic solvents including the first water-soluble organic solvent, the second water-soluble organic solvent, and the third water-soluble organic solvent. May be.
By containing at least the first water-soluble organic solvent and the second water-soluble organic solvent, it is possible to achieve a balance between the spread of the deposited ink and the amount of water applied to the paper and the film quality. Thereby, the deformation | transformation by the curl and cockle at the time of recording an image on a paper medium can be suppressed.

-First water-soluble organic solvent-
The first water-soluble organic solvent is a water-soluble organic solvent having a surface tension at 25 ° C. of 40 mN / m or less and a molecular weight of 150 or less. By containing the first water-soluble organic solvent, when an aqueous ink composition is applied to a paper medium and an image is recorded, the film quality, image quality, and cockle of the image are improved. “Water-soluble” is as described above.

When the surface tension (25 ° C.) of the first water-soluble organic solvent is 40 mN / m or less, the ink droplets (dots) are likely to spread when the ink composition is deposited on the paper medium. Therefore, a vivid image with a good color density can be obtained while reducing the amount of ink ejected in accordance with the spread of dots.
If the surface tension is too low, the spread of the deposited dots becomes too large, and the color density is likely to be lowered or mixed with different color inks. Therefore, the surface tension (25 ° C.) of the first water-soluble organic solvent is preferably 20 mN / m or more. Especially, as surface tension (25 degreeC) of a 1st water-soluble organic solvent, the range of 25 mN / m or more and 35 mN / m or less is more preferable.

  The surface tension is a value measured in an environment at a temperature of 25 ° C. using a surface tension meter (Automatic Surface Tensiometer CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

The first water-soluble organic solvent is an organic solvent having a molecular weight of 150 or less. When the molecular weight exceeds 150, the difference from the molecular weight of the second water-soluble organic solvent described later becomes small. By setting the molecular weight of the first water-soluble organic solvent to 150 or less, the effect of using two kinds of the first water-soluble organic solvent and the second water-soluble organic solvent in combination appears remarkably. Excellent film quality.
The molecular weight of the first water-soluble organic solvent is preferably 150 or less, more preferably 120 or less, from the viewpoint of excellent permeability to paper media. In addition, the molecular weight of the first water-soluble organic solvent is desirably 100 or more from the viewpoint of ejection stability.

  The molecular weight of the first water-soluble organic solvent is determined by arithmetic calculation after specifying the molecular structure by mass spectrometry.

(Also referred to as SP value.) Solubility parameter of the first water-soluble organic solvent as is preferably in the range of ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less. Among them, from the viewpoint of ejection stability, SP value is preferably ^{21 MPa 1/2} or more ^{28 MPa 1/2} or less of the range, ^{21 MPa 1/2} or more ^{26 MPa 1/2} or less of the range are preferred. The method for obtaining the SP value will be described later.

  Specific examples of the first water-soluble organic solvent include the following water-soluble organic solvents. The first water-soluble organic solvent may be used alone or in combination of two or more.

  The total content of the first water-soluble organic solvent in the ink composition can be appropriately selected within a range that satisfies the conditions (1) and (2) described below. Specifically, the ink composition Is preferably in the range of 10% to 35%, more preferably in the range of 15% to 30%.

-Second water-soluble organic solvent-
The second water-soluble organic solvent is a water-soluble organic solvent having a molecular weight of 200 or more. By containing the second water-soluble organic solvent, when an aqueous ink composition is applied to a paper medium and image recording is performed, the occurrence of curling over time can be suppressed. “Water-soluble” is as described above.

  The second water-soluble organic solvent is an organic solvent having a molecular weight of 200 or more. When the molecular weight is less than 200, the difference from the molecular weight of the first water-soluble organic solvent described above becomes small. By setting the molecular weight of the second water-soluble organic solvent to 200 or more, the effect of using both the first water-soluble organic solvent and the second water-soluble organic solvent in combination, that is, water volatilizes over time. The effect of suppressing the phenomenon of curling gradually appears. Further, the molecular weight of the second water-soluble organic solvent being 200 or more contributes to the improvement of the film quality of the image.

  The molecular weight of the second water-soluble organic solvent is preferably in the range of 200 to 400. When the molecular weight of the second water-soluble organic solvent is 400 or less, curling is effectively suppressed, the film quality of the image is kept good, and the generation of scratches or color images during rubbing is not significantly impaired. Furthermore, the molecular weight of the second water-soluble organic solvent is preferably 200 or more and 300 or less, and preferably 200 or more and 250 or less, from the viewpoint of preventing curling and remaining in the image to balance the film quality of the image and the suppression of water volatilization. Further preferred.

  The absolute value of the difference between the molecular weight of the first water-soluble organic solvent and the molecular weight of the second water-soluble organic solvent is 90 or more from the viewpoint of maintaining good image quality and suppressing curling. It is preferable that it is 100 or more.

  The molecular weight of the second water-soluble organic solvent is obtained by arithmetic calculation after specifying the molecular structure by mass spectrometry.

(Also referred to as SP value.) Solubility parameter of the second water-soluble organic solvent as is preferably in the range of ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less. When the SP value is 21 MPa ^1/2 or more, deformation of the paper medium can be effectively suppressed while maintaining ejection stability. Further, when the SP value is 30 MPa ^1/2 or less, the effect of suppressing the deformation of the paper medium is excellent. Among them, from the viewpoint of ejection stability, SP value is preferably ^{21 MPa 1/2} or more ^{28 MPa 1/2} or less of the range, ^{21 MPa 1/2} or more ^{26 MPa 1/2} or less of the range are preferred. The method for obtaining the SP value will be described later.

  Specific examples of the second water-soluble organic solvent include the following water-soluble organic solvents. You may use a 2nd water-soluble organic solvent individually by 1 type or in combination of 2 or more types.

  Specific examples of the second water-soluble organic solvent include an organic solvent (an alkylene oxide adduct of glycerin) represented by the following structural formula (S).

In the structural formula (S), t, u, and v each independently represent an integer of 1 or more, and satisfy t + u + v = 3-15.
When the value of t + u + v is 3 or more, a good curl suppressing force is exhibited. Further, when the value of t + u + v is 15 or less, good dischargeability can be obtained. Especially, t + u + v has the preferable range of 3-12, and the range of 3-10 is more preferable.

AO represents at least one of ethyleneoxy (EO) and propyleneoxy (PO), and propyleneoxy is particularly preferable. Each AO in (AO) _t , (AO) _u , and (AO) _v may be the same or different.

  Specific examples of the organic solvent represented by the structural formula (S) are shown below. However, the present invention is not limited to the following specific examples. In addition, the description of “POP (3) glyceryl ether” in the compound means glyceryl ether in which a total of three propyleneoxy groups are bonded to glycerin, and the same applies to other descriptions.

  Further, specific examples of the second water-soluble organic solvent include organic solvents represented by the following structural formula (S2).

  In the structural formula (S2), p, q, r, and s each independently represent an integer of 1 or more and satisfy p + q + r + s = 4-40. The value of p + q + r + s is preferably 4-20, more preferably 4-16, and particularly preferably 4-12. AO has the same meaning as AO in formula (S), and is preferably propyleneoxy.

As the organic solvent represented by the structural formula (S) or the structural formula (S2), commercially available products may be used. For example, polyoxypropylated glycerin (polypropylene glycol and glycerin and As an ether), Sanniks GP-250, Sanniks GP-400, Sanniks GP-600, etc. (all of which are manufactured by Sanyo Chemical Industries, Ltd.), SCP-400 (POP (4) diglyceryl ether, p + q + r + s) = 4, AO = propyleneoxy), SCE-450 (POE (6) polyglyceryl ether, p + q + r + s = 6, AO = ethyleneoxy), SCE-750 (POE (13) polyglyceryl ether, p + q + r + s = 13, AO = ethyleneoxy) Etc. (all of which are manufactured by Sakamoto Pharmaceutical Co., Ltd.).
In the above, the description “POP (4) diglyceryl ether” means diglyceryl ether in which a total of four propyleneoxy bonds to diglycerin, and the description “POE (6) polyglyceryl ether” , Means a polyglyceryl ether having a total of 6 ethyleneoxy bonded to polyglycerin, and the same applies to other descriptions.

Specific examples of the second water-soluble organic solvent include, in addition to the organic solvent represented by the structural formula (S) or the structural formula (S2), from the viewpoint of curling suppression in paper media, Solvents (i) to (vii) can also be mentioned as suitable organic solvents. In the chemical formula, EO represents ethyleneoxy and PO represents propyleneoxy.
_{(I) n-C 4 H} 9 O (AO) 4 -H (AO = EO or PO, EO: PO = 1: 1) (SP value: 20)
_{(Ii) n-C 4 H} 9 O (AO) 10 -H (AO = EO or PO, EO: PO = 1: 1) (SP value: 19)
(Iii) HO (AO) ₄₀ -H (AO = EO or PO, EO: PO = 1: 3) (SP value: 19)
(Iv) HO (AO) ₅₅ -H (AO = EO or PO, EO: PO = 5: 6) (SP value: 19)
(V) HO (PO) _3- H (SP value: 25)
(Vi) HO (PO) ₇ -H (SP value: 21)
(Vii) 1,2-hexanediol (SP value 27)

The organic solvent represented by the above structural formula (S) or structural formula (S2), from the viewpoint of image quality, SP value of ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less of the alkylene glycol alkyl ether (preferably di It is preferably contained in combination with an alkylene glycol monoalkyl ether or a trialkylene glycol monoalkyl ether (preferably the carbon number of the alkyl moiety is 1 to 4 each). In other words, as the second water-soluble organic solvent, at least one water-soluble organic solvent selected from the solvent group represented by Structural Formula (S) or Structural Formula (S2), dialkylene glycol monoalkyl ether and It is preferable to contain at least one water-soluble organic solvent selected from the group consisting of alkylene glycol monoalkyl ethers, and contains a combination of an organic solvent represented by structural formula (S) and a trialkylene glycol monoalkyl ether It is particularly preferable to do this.
Examples of dialkylene glycol monoalkyl ether or trialkylene glycol monoalkyl ether include diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tripropylene glycol monomethyl ether , Etc.
In this case, mixing ratio of the organic solvent represented by the structural formula (S) or structural formula (S2) (a), the SP value ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less of the alkylene glycol alkyl ether (b), For the same reason as above, (a: b) is preferably in the range of 1: 5 to 5: 1, and more preferably in the range of 1: 2.5 to 2.5: 1.

You may use a 2nd water-soluble organic solvent individually by 1 type or in combination of 2 or more types.
The total content of the second water-soluble organic solvent in the ink composition can be appropriately selected within a range that satisfies the conditions (1) and (2) described later. Specifically, the ink composition Is preferably in the range of 5% to 15%, and more preferably in the range of 8% to 12%.

The total amount (mass) of the total content Y1 of the first water-soluble organic solvent and the total content Y2 of the second water-soluble organic solvent is as shown in the following condition (1). Adjust to a range of 70% by weight or more of the total amount of solvent.
Total amount (mass) of Y1 + Y2 ≧ 70 mass% of the total amount of the water-soluble organic solvent (1)
Since the total amount of Y1 + Y2 is 70% by mass or more of the total amount of the water-soluble organic solvent, as described above, the color density is good, the spread of the deposited ink, the amount of water applied to the paper, the film quality, Can be balanced. As a result, deformation due to curling and cockle when an image is recorded on a paper medium can be effectively suppressed. Especially, the total amount of Y1 + Y2 has the preferable range of 85 mass% or more of the total amount of the water-soluble organic solvent.

Further, the ratio of the total content Y1 of the first water-soluble organic solvent to the total content Y2 of the second water-soluble organic solvent is adjusted to a range satisfying the relationship of the following condition (2) on a mass basis.
1.5 ≦ Y1 / Y2 ≦ 4.0 (2)
By satisfying the condition (2), it is possible to suppress deformation due to cockle and curl while maintaining good image density and film quality. In particular, when 1.5 ≦ Y1 / Y2 is satisfied, the film quality of the image becomes better, and when Y1 / Y2 ≦ 4.0 is satisfied, deformation due to curling is further suppressed.
Especially, as ratio of Y1 / Y2, 1.5 or more and 3.5 or less are preferred, and 2.0 or more and 3.5 or less are more preferred.

  The ink composition for inkjet recording of the present invention further contains a third water-soluble organic solvent other than the first water-soluble organic solvent and the second water-soluble organic solvent as long as the effects of the present invention are not impaired. You may go out.

The water-soluble organic solvent contained in the ink composition of the present invention is preferably an organic solvent having a hydroxyl group in the molecule. By having a hydroxyl group, the ejection stability when ejecting the ink composition is excellent. Among these, from the viewpoint of ejection stability when ejecting the ink composition, the ink composition of the present invention preferably contains a water-soluble organic solvent having 2 or more hydroxyl groups, and further has 2 or more hydroxyl groups. The content of the water-soluble organic solvent is preferably 80% by mass or more based on the total amount of the water-soluble organic solvent.
The content of the water-soluble organic solvent having 2 or more hydroxyl groups is more preferably 85% by mass or more based on the total amount of the water-soluble organic solvent.

Water-soluble organic solvent contained in the ink composition of the present invention, the solubility (also referred to as SP value.) Parameter is preferably in the range of ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less. When the SP value is 21 MPa ^1/2 or more, the ejection stability when ejecting the ink composition is excellent. Further, when the SP value is 30 MPa ^1/2 or less, the ejection stability when ejecting the ink composition is excellent.
Of these, 70 from the same viewpoint as above, the ink composition of the present invention, SP value of water-soluble organic solvent in the range of ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less, relative to the total amount of the water-soluble organic solvent It is preferably contained in an amount of at least mass%, more preferably at least 85 mass% based on the total amount of the water-soluble organic solvent.

The solubility parameter (SP value) is a value [unit: MPa ^1/2 ] obtained by the Okitsu method. The Okitsu method is one of the well-known methods for calculating the SP value. 29, no. 6 (1993) 249-259.

-Colorant-
The ink composition for inkjet recording of the present invention contains at least one colorant. The colorant is not particularly limited, and can be arbitrarily selected from known colorants such as pigments and water-soluble dyes. Among these, it is more preferable to include a pigment from the viewpoint of excellent weather resistance and rich color reproducibility.
The ink composition may contain one colorant alone or in combination of two or more.

There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, a well-known organic pigment and an inorganic pigment are mentioned.
Examples of organic pigments and inorganic pigments include yellow pigments (yellow pigments), red pigments, magenta pigments, blue pigments, cyan pigments, green pigments, orange pigments, purple pigments, brown pigments, black pigments, and white pigments. .

  Regarding colorants such as pigments, paragraphs [0180] to [0188] of JP-A No. 2014-040529 can be appropriately referred to.

  Examples of the pigment include commercially available pigment dispersions and surface-treated pigments. For example, a resin-coated pigment in which all or part of the surface of the pigment is coated with a water-insoluble resin is used from the viewpoints of dispersion stability and ejection reliability of the ink composition, and abrasion resistance and light resistance of the formed image. Therefore, it is preferable.

  The resin-coated pigment can be produced by a conventional physical or chemical method using a water-insoluble resin, a pigment or the like. For example, as described in JP-A-9-151342, JP-A-10-140065, JP-A-11-209672, JP-A-11-172180, JP-A-10-25440, or JP-A-11-43636. It can be manufactured by a method. Specific examples of the method for producing a resin-coated pigment include phase inversion emulsification methods and acid precipitation methods described in JP-A-9-151342 and JP-A-10-140065. Among these, From the viewpoint of dispersion stability, the phase inversion emulsification method is preferred.

The phase inversion emulsification method is basically a self-dispersion (phase inversion emulsification) method in which a mixed melt of a water-insoluble resin having self-dispersibility or solubility and a pigment is dispersed in water. The mixed melt may contain a curing agent or a polymer compound. Here, the “mixed melt” refers to a mixed state that is not dissolved, a state that is dissolved and mixed, or a state that includes both of these states.
Specific methods of the “phase inversion emulsification method” are disclosed in JP-A-10-140065, JP-A-2009-212251 (particularly, paragraphs [0074] to [0082]), JP-A-2011-195684 (particularly, , Paragraphs [0042] to [0052]) can be appropriately referred to.

In the resin-coated pigment, the water-insoluble resin for coating the pigment preferably includes at least one structural unit having an acidic group, and preferably includes other structural units as necessary.
The water-insoluble resin can be stably present in the ink composition, reduces adhesion or accumulation of aggregates, and facilitates removal of the adhered aggregates, so that at least one hydrophilic structural unit is present. It is preferable to include a seed and at least one hydrophobic structural unit, and it is more preferable that an acidic group is included in at least one hydrophilic structural unit.
Here, the “water-insoluble resin” means a resin having a dissolution amount of 5 g or less with respect to 100 g of water at 25 ° C. The “dissolution amount” is a dissolution amount when the acidic group of the water-insoluble resin is neutralized 100% with sodium hydroxide.

The hydrophilic structural unit in the water-insoluble resin is not particularly limited as long as it contains at least one kind of hydrophilic functional group, and may contain an ionic hydrophilic group or a nonionic hydrophilic group. It may contain a group.
The hydrophilic structural unit is preferably a hydrophilic structural unit having an acidic group, and the hydrophilic structural unit having an acidic group may be a structural unit derived from an acidic group-containing monomer or an acidic group. An acidic group may be introduced into a structural unit that does not have (polymer chain after polymerization) by a polymer reaction.

  The acidic group is not particularly limited, and examples thereof include a carboxy group, a phosphoric acid group, and a sulfonic acid group from the viewpoint of stability in an emulsified or dispersed state. Among these, from the viewpoint of dispersion stability when the ink composition is configured, the acidic group is preferably a carboxy group.

  It is preferable that the water-insoluble resin includes a structural unit having an acidic group and further includes at least one hydrophobic structural unit. The hydrophobic structural unit is not particularly limited as long as it is a structural unit containing a hydrophobic functional group. For example, it is preferable that at least one structural unit having an aromatic ring is contained.

  The content of the colorant in the ink composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, and more preferably 1.5% by mass with respect to the total mass of the ink composition. % Or more is more preferable. When the content of the colorant is 0.5% by mass or more, the optical density of the image is further improved. Further, the upper limit of the content of the colorant is not particularly limited. For example, the content of the colorant in the ink composition is preferably 9% by mass or less, more preferably 7% by mass or less, and more preferably 5% by mass or less with respect to the total mass of the ink composition. More preferably it is.

-Water-
The ink composition for ink jet recording of the present invention contains water.
Examples of water include ion-exchanged water and distilled water, and it is preferable to use water that does not contain ionic impurities.
The content of water in the ink composition is not particularly limited and can be appropriately set according to the purpose. For example, from the viewpoint of dispersion stability and ejection properties, the water content is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 60% by mass, with respect to the total amount of the ink composition. % Or less, and more preferably 45% by mass or more and 55% by mass or less.

-Resin particles-
The ink composition of the present invention preferably contains at least one kind of resin particles. When resin particles are contained, the strength of the image is improved and the scratch resistance is improved. In addition, since the ink droplets spread on the paper medium after landing, the desired color can be reduced while reducing the amount of ink ejected. A density image can be recorded without being deformed by curl and cockle. This is particularly effective when an image is recorded using a treatment liquid containing a compound (aggregating compound) that aggregates at least the colorant in the ink. That is, the ink viscosity after agglomeration with the treatment liquid is kept soft, and the ink droplets (dots) after landing are prevented from spreading and the dots from becoming too small, so the amount of ink ejected can be reduced. Thereby, the occurrence of curling and cockle when an image is recorded on a paper medium can be more effectively suppressed.

  Examples of resin particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, cross-linked cross-linked acrylic resins, and cross-linked cross-links. Particles such as styrene resin, benzoguanamine resin, phenol resin, silicone resin, epoxy resin, urethane resin, paraffin resin, and fluorine resin can be used. Among these, acrylic resin particles, acrylic-styrene resin particles, styrene resin particles, cross-linked cross-linked acrylic resin particles, and cross-linked cross-linked styrene resin particles are preferable as the resin particles.

  The resin particles may be used, for example, in the form of latex that is a dispersion in which resin particles are dispersed in water.

  The ink composition of the present invention preferably contains at least resin particles having a structural unit represented by the following general formula 1 or 2 as resin particles. The resin forming the resin particles may have a structure having the structural unit represented by the general formula 1 and not having the structural unit represented by the general formula 2, and having the structural unit represented by the general formula 2. And the structure which does not have the structural unit represented by General formula 1 may be sufficient. Moreover, the structure which has both the structural unit represented by General formula 1 and the structural unit represented by General formula 2 may be sufficient.

  As the resin particles in the present invention, the resin preferably has at least one selected from structural units represented by the following general formula 1 or general formula 2, and the structural unit represented by general formula 1 It is more preferable to have.

In General Formula 1, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ¹ is preferably a hydrogen atom or a methyl group, more preferably a methyl group.

A ¹ represents an oxygen atom or NR ³ . R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The A ^1, preferably NR ^3, NH being more preferred.

L ¹ represents an alkylene group having 6 to 22 carbon atoms. The alkylene group represented by L ¹ may be linear or branched, and is preferably linear from the viewpoint of ejection stability and resin particle stability. L ¹ is preferably an alkylene group having 8 to 22 carbon atoms, more preferably an alkylene group having 8 to 18 carbon atoms, still more preferably an alkylene group having 8 to 16 carbon atoms, still more preferably 8 to 8 carbon atoms. 14 alkylene group, more preferably an alkylene group having 10 to 12 carbon atoms, and particularly preferably an alkylene group having 11 carbon atoms.

M ¹ represents a hydrogen ion, an alkali metal ion, or an ammonium ion. From the viewpoint of ejection stability and resin particle stability, M ¹ is preferably an alkali metal ion, more preferably a sodium ion or a potassium ion, and even more preferably a potassium ion.

In the general formula 2, ^{R 2} and ^{M 2} in the general formula 1 ^{R 1} and ^{M 1} and have the same meanings, the same preferred form also respectively.
A ² represents a single bond, —COO—, or —CONH—, and preferably a single bond.

L ² represents a divalent linking group having 6 to 23 carbon atoms. The divalent linking group represented by L ² is not particularly limited, and from the viewpoint of synthesis, —C (═O) NR ⁴ — (CH ₂ ) _n — or —C (═O) O— ( CH ₂ ) _n — is preferred, and —C (═O) NR ⁴ — (CH ₂ ) _n — is more preferred. Wherein, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, a hydrogen atom is preferable. Moreover, n represents the integer of 5-22, 6-18 are preferable, 7-15 are more preferable, 8-14 are more preferable, 10-12 are especially preferable, and 11 is the most preferable.

  The total content of the structural unit represented by the general formula 1 or 2 in the resin forming the resin particles is 0.5% by mass or more and 30% from the viewpoint of image quality, dischargeability, and resin particle stability. The range of mass% or less is preferable. In other words, in the resin forming the resin particles, when the structural unit represented by the general formula 1 is not included, the content of the structural unit represented by the general formula 2 is in the above range, and is represented by the general formula 2. In the above range, the structural unit represented by general formula 1 and the structural unit represented by general formula 2 are preferred. When both are included, the total content of both structural units is preferably in the above range. Furthermore, the total content of the structural units represented by the general formula 1 or 2 in the resin forming the resin particles is more preferably in the range of 1% by mass to 20% by mass for the same reason as described above. Preferably, 1% by mass to 5% by mass is more preferable.

  Other structural units other than the structural unit represented by the general formula 1 or 2 in the resin forming the resin particles (hereinafter simply referred to as “other structural units”) are not particularly limited. It can be selected appropriately. Preferable examples of other structural units include the structural units described in JP-A Nos. 2001-181549 and 2002-88294.

  Specific examples of the other structural unit include (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms (preferably 1 to 15 and more preferably 1 to 12), an aromatic ring-containing (meth) acrylate, Examples include structural units derived from monomers selected from alicyclic (meth) acrylates, styrene compounds, alkyl (meth) acrylamides, and (meth) acrylonitrile.

As (meth) acrylic acid alkyl ester, as specific examples of alkyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl Alkyl (meth) acrylates such as (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, and ethylhexyl (meth) acrylate; hydroxymethyl (meth) acrylate, 2-hydroxyethyl ( Hydroxy such as (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate, etc. Alkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, alkylaminoalkyl (meth) acrylates such as t- butyl aminoethyl (meth) acrylate; and the like.
Examples of the aromatic ring-containing (meth) acrylate include benzyl (meth) acrylate and phenoxyethyl (meth) acrylate.
Cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclononyl as alicyclic (meth) acrylate (Meth) acrylate, cyclodecyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, etc. It is done.
Examples of the styrene compound include styrene, α-methylstyrene, chlorostyrene, and the like.
Examples of the alkyl (meth) acrylamide include N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxyalkyl (meth) acrylamide such as N-hydroxybutyl (meth) acrylamide; N-methoxymethyl ( (Meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N- (n N-alkoxyalkyl (meth) acrylamides such as-, iso) butoxyethyl (meth) acrylamide, and the like.
The resin forming the resin particles may have two or more of the above structural units as other structural units.
Among the above, it is preferable that the other structural unit includes a structural unit derived from a (meth) acrylic acid alkyl ester and a structural unit derived from a monomer selected from styrene compounds.

Among these, the resin forming the resin particles is a structural unit derived from an alkyl (meth) acrylate having 2 to 15 (preferably 4 to 12, more preferably 4 to 10) carbon atoms of an alkyl group as another structural unit. (Hereinafter referred to as “structural unit (i)”). 5 mass% or more and 90 mass% or less are preferable, as for the content rate in the resin of the resin particle of structural unit (i), 10 mass% or more and 70 mass% or less are more preferable, and 20 mass% or more and 55 mass% or less are more preferable. 25 mass% or more and 50 mass% or less are more preferable, and 30 mass% or more and 45 mass% or less are especially preferable.
Moreover, it is also preferable that resin which forms the resin particle has a structural unit derived from methyl (meth) acrylate as another structural unit. In this case, the content of the resin particles of the structural unit derived from methyl (meth) acrylate in the resin is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 85% by mass or less, and 20% by mass. 80 mass% or less is more preferable, 30 mass% or more and 70 mass% or less is further more preferable, and 40 mass% or more and 60 mass% or less is especially preferable.
Especially, it is preferable that resin which forms a resin particle has a structural unit derived from methyl (meth) acrylate which has structural unit (i) as another structural unit. By having a structural unit derived from methyl (meth) acrylate, the yield when resin particles are prepared can be improved, and the glass transition temperature (Tg) of the resin particles can be adjusted to an appropriate range. is there. This improves the film quality of the recorded image.

The resin particles can be prepared by an emulsion polymerization method or a phase inversion emulsification method.
The emulsion polymerization method is a method of preparing resin particles by polymerizing an emulsion prepared by adding a monomer, a polymerization initiator, an emulsifier, and a chain transfer agent, if necessary, in an aqueous medium (for example, water). is there. When the emulsion polymerization method is applied to the preparation of resin particles, the monomer that derives the structural unit represented by the general formula 1 and the monomer that derives the structural unit represented by the general formula 2 also function as an emulsifier. To do. Therefore, it is not necessary to separately mix an emulsifier other than the monomer that leads to the structural unit represented by General Formula 1 or General Formula 2, but as long as it does not deteriorate the ejection properties and image quality when an ink is prepared, A known emulsifier may be added separately.
The emulsion polymerization method is suitable for preparing resin particles having a volume average particle diameter of 30 nm or more.

The phase inversion emulsification method is a method in which a water-insoluble polymer, an organic solvent, and, if necessary, a neutralizing agent are mixed in an aqueous medium (for example, water) to obtain a dispersion through a step of stirring, In this method, the organic solvent is distilled off from the dispersion by a conventional method, and the phase is changed to an aqueous dispersion. In the obtained aqueous dispersion, the organic solvent is substantially removed, and the amount of the organic solvent in the dispersion is preferably 0.2% by mass or less, more preferably 0.1% by mass or less. It is.
In this case, the resin of the resin particles is preferably a resin having at least one of a structural unit having an aromatic group and a structural unit having an alicyclic group. An alicyclic group is synonymous with a cyclic aliphatic group. The structural unit having an aromatic group is preferably a structural unit derived from a (meth) acrylate monomer having an aromatic group, such as phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, etc. The structural unit derived from is mentioned. The structural unit having an alicyclic group is preferably a structural unit derived from a bicyclic or tricyclic or higher alicyclic (meth) acrylate having an alicyclic group, such as isobornyl (meth) acrylate and adamantyl. Examples thereof include structural units derived from (meth) acrylate, dicyclopentanyl (meth) acrylate, and the like.
Among them, a preferred embodiment of the resin particles (for example, self-dispersing resin particles) is a structural unit derived from an alicyclic (meth) acrylate (preferably a bicyclic or tricyclic or higher polycyclic (meth) acrylate). 20% by mass or more and 90% by mass or less and 25% by mass of a structural unit derived from a dissociable group-containing monomer (preferably an anionic dissociable group, more preferably a carboxyl group, a phosphoric acid group, a sulfonic acid group, etc.) And at least one structural unit derived from a (meth) acrylate having a linear alkyl group having 1 to 8 carbon atoms, and an acid value of 20 mgKOH / g to 120 mgKOH / g (more preferably 25 mgKOH / g to 100 mg KOH / g), and the weight average molecular weight is 3,000 to 200,000 (preferably 10,000 to 200,000). Are embodiments a vinyl polymer.

The resin particles in the present invention are preferably self-dispersing resin particles.
Self-dispersing resin particles refer to particles made of a water-insoluble resin that can be dispersed in an aqueous medium by a functional group (particularly, an acidic group or a salt of an acidic group) that the resin itself has. The dispersed state refers to both an emulsified state (emulsion) in which a water-insoluble resin is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble resin is dispersed in a solid state in an aqueous medium. It includes the state of.
“Water-insoluble” means that the amount dissolved in 100 parts by mass of water (25 ° C.) is 5.0 parts by mass or less.

The weight average molecular weight of the resin of the resin particles is preferably in the range of 100,000 to 1,000,000, and more preferably in the range of 200,000 to 600,000.
The resin weight average molecular weight (Mw) of the resin particles is a value obtained as a polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions. The calibration curve is “Standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “ It is prepared from 8 samples of “A-2500”, “A-1000”, and “n-propylbenzene”.
~conditions~
Measurement device: High-speed GPC HLC-8020 GPC (manufactured by Tosoh Corporation)
Detector: differential refractometer (RI) RI-8020 (manufactured by Tosoh Corporation)
Column: TSKgeL Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) is used. Column temperature: 40 ° C.
・ Eluent: Tetrahydrofuran (THF)
Sample concentration: 0.45% by mass
・ Injection volume: 10 μL
・ Flow rate: 0.35 mL / min

The volume average particle diameter of the resin particles is preferably 30 nm or more, more preferably in the range of 30 nm to 1 μm, still more preferably in the range of 30 nm to 300 nm, and particularly preferably in the range of 30 nm to 150 nm. When the volume average particle diameter of the resin particles is 30 nm or more, the viscosity decreases due to aggregation when the ink droplets land, and the ink droplets easily spread. Further, the color density and film quality of the recorded image are further improved.
There is no restriction | limiting in particular in the adjustment method of a volume average particle diameter, For example, according to an emulsion polymerization method, a particle diameter can be easily adjusted to 30 nm or more.
Further, the particle size distribution of the resin particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more types of resin particles having a monodispersed particle size distribution may be mixed and used.

  The volume average particle size and particle size distribution are values measured by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

The glass transition temperature (Tg) of the resin particles is preferably 40 ° C. or higher, and more preferably 50 ° C. or higher. Tg is preferably 80 ° C. or lower. When Tg is 40 ° C. or higher, it is difficult to form a film due to the resin particles in the ink jet head, and thus it is easy to maintain good ejection stability. Further, the film quality of the image can be kept strong, and scratches and color images on the object to be scratched hardly occur during rubbing. When the Tg is 80 ° C. or lower, an ink having good film forming properties is easily obtained, and the film quality of the image is excellent.
Especially, as Tg, the range of 40 to 60 degreeC is more preferable.

The measured measurement Tg is applied to the glass transition temperature of the resin particles. Specifically, the measurement Tg is a value measured by a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nano Technology. As a measurement condition, a sample amount of 5 mg is sealed in an aluminum pan, and the DSC peak top value of the measurement data at the second temperature rise is applied in a nitrogen atmosphere with the following temperature profile.
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)

  Among the above, the resin particles are preferably resin particles having a glass transition temperature Tg of 40 ° C. or higher and a volume average particle diameter of 30 nm or higher from the viewpoint of deformation of the paper medium, ejection stability, and film quality. .

  The content of the resin particles in the ink composition for inkjet recording is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less based on the total amount of the ink composition. The ink composition may not contain resin particles. However, from the viewpoint of recording an image having a desired color density without curling and deformation due to curl while reducing the amount of ink ejected, the resin particles are not included. It is preferably contained (contained in a range of more than 0% by mass with respect to the total amount of the ink composition), more preferably the content of the resin particles is 0.1% by mass or more, and still more preferably the content of the resin particles Is 1% by mass or more.

-Other additives-
The ink composition for inkjet recording of the present invention may contain other additives as necessary in addition to the components described above. Other additives include, for example, surfactants, hydrophilic organic solvents different from the water-soluble organic solvents described above, colloidal silica, urea, anti-fading agents, emulsion stabilizers, wax agents, penetration enhancers, UV absorption Examples include known additives such as additives, antiseptics, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, viscosity modifiers, dispersion stabilizers, rust preventives, and chelating agents.
The additive may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared. For details of other additives, reference can be made to the descriptions in paragraphs [0153] to [0162] of JP-A-2007-100071 as appropriate.

(Surfactant)
The ink composition may contain at least one surfactant. By using the surfactant, the surface tension of the ink can be adjusted more effectively.
The surfactant is not particularly limited, and can be appropriately selected from known surfactants. As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be effectively used. Anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants Either a surfactant or a betaine surfactant can be used.

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 surfactant). Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,4,7,9-tetramethyl-5-decyne-4,7. -Alkylene oxide adduct of diol etc. can be mentioned. Commercial products may be used, and examples of commercially available products include Olfin (registered trademark) E series such as Olfin (registered trademark) E1010 and E1020.
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 them, an anionic surfactant is more preferable. Examples of the anionic surfactant include Capstone (registered trademark) FS-63, FS-61 (above, manufactured by Dupont), and Footgent (registered trademark) 100, 110, 150 (over, manufactured by Neos Co., Ltd.). ), CHEMGUARD S-760P (manufactured by Chemguard Inc.), and the like.

  When the ink composition contains a surfactant, the content of the surfactant is preferably, for example, in the range of 0.1% by mass to 10% by mass with respect to the total mass of the ink composition.

(Hydrophilic organic solvent)
The ink composition may contain a hydrophilic organic solvent other than the first water-soluble organic solvent and the second water-soluble organic solvent described above. When a hydrophilic organic solvent is contained, nozzle clogging that may occur due to drying of the ink at the ink discharge port can be effectively prevented when the ink composition is discharged by an ink jet method to record an image.
In order to prevent drying, a hydrophilic organic solvent having a vapor pressure lower than that of water is preferable.
Specific examples of hydrophilic organic solvents suitable for preventing drying include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, methylpropylene triglycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propane. Polyhydric alcohol compounds represented by diol, 1,2,6-hexanetriol, acetylene glycol derivatives, glycerin, trimethylolpropane, etc., 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2- Examples thereof include heterocyclic compounds such as imidazolidinone and N-ethylmorpholine, sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 3-sulfolene, polyfunctional compounds such as diacetone alcohol and diethanolamine, and urea derivatives. Of these, polyhydric alcohol compounds such as glycerin, propylene glycol, and methylpropylene triglycol are preferable.

(Colloidal silica)
The ink composition can contain colloidal silica. When the ink composition contains colloidal silica, the nozzle discharge surface (for example, the surface of the liquid repellent film that may be provided on the nozzle discharge side) when the ink composition is repeatedly discharged is more effective. Can be suppressed. Such an effect becomes more prominent when a nozzle (for example, a silicon nozzle plate) in which silicon is applied to the surface of a plate on which ejection holes are arranged is used as a nozzle (for example, a nozzle plate).
Colloidal silica is a colloid composed of fine particles of inorganic oxide containing silicon having a volume average particle diameter of several hundred nm or less. Silicon dioxide (including silicon dioxide hydrate) may be included as a main component, and aluminate may be included as a minor component. Examples of the aluminate that may be contained as a minor component include sodium aluminate and potassium aluminate.
As the colloidal silica, for example, known colloidal silica described in paragraphs [0014] to [0022] of JP2011-195684A can be used.

(urea)
The ink composition may contain urea. Urea can be used as a solid wetting agent because it has an excellent moisturizing function. When the ink composition contains urea, drying and coagulation are more effectively suppressed.

~ Physical properties of ink composition ~
(viscosity)
When an ink composition is applied to a paper medium by an ink jet method, the viscosity of the ink composition is 1 mPa · s or more and 30 mPa · s from the viewpoint of ejection stability and agglomeration rate of a colorant or the like when in contact with the treatment liquid. Is preferably 1 mPa · s or more and 20 mPa · s or less, more preferably 3 mPa · s or more and 15 mPa · s or less, and particularly preferably 8 mPa · s or more and 12 mPa · s or less. preferable.
The viscosity of the ink composition is a value measured by adjusting the ink composition at a temperature of 25 ° C. using a viscometer (VISCOMETER TV-22, manufactured by TOKI SANGYO CO. LTD).

(surface tension)
When an ink composition is applied to a paper medium by an inkjet method, the surface tension of the ink composition is preferably 20 mN / m or more and 60 mN / m or less, and preferably 20 mN / m or more and 45 mN / m from the viewpoint of ejection stability. m or less is more preferable, and 25 mN / m or more and 40 mN / m or less is still more preferable.
The surface tension of the ink composition is a value measured under an environment at a temperature of 25 ° C. using a surface tension meter (Automatic Surface Tensiometer CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

(PH)
The ink composition for inkjet recording of the present invention is preferably prepared to be alkaline. Although details of the ink jet recording method will be described later, as a preferable form in the case of recording an image using a treatment liquid, the ink composition is prepared to be alkaline from the viewpoint of aggregating property such as a colorant in the ink composition. And it is the form by which the process liquid is prepared acidic.
The pH of the ink composition is preferably in the range of 7.5 or more and 10 or less, and preferably in the range of 8 or more and 9 or less, from the viewpoint of the ink stability and the aggregation rate of the colorant or the like in the ink composition. More preferred. The pH of the ink composition is a value measured by adjusting the ink composition to a temperature of 25 ° C. using a pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.).
The pH of the ink composition can be appropriately adjusted using an acidic compound or a basic compound. As an acidic compound or a basic compound, the compound used normally can be especially used without a restriction | limiting.

  The ink composition for ink-jet recording of the present invention contains at least a colorant, water, a first water-soluble organic solvent, and a second water-soluble organic solvent, and contains the water-soluble organic solvent with respect to the total mass of the ink composition. It can prepare by adjusting so that quantity may become the range of 20 mass% or more and 40 mass% or less. At this time, in the water-soluble organic solvent of 20% by mass or more and 40% by mass or less, the total content Y1 of the first water-soluble organic solvent and the total content Y2 of the second water-soluble organic solvent are the conditions described above. Meet (1) and condition (2). The colorant is mixed with a water-insoluble resin in advance to prepare a resin-coated colorant (for example, a resin-coated pigment) in which at least a part of the surface is coated with the water-insoluble resin. And a water-soluble organic solvent may be mixed.

<Ink set>
The ink set of the present invention has the ink composition for ink jet recording of the present invention described above and a treatment liquid containing a compound that aggregates at least the colorant in the ink composition for ink jet recording. Since the ink set of the present invention uses the ink composition for ink jet recording described above, the deformation of the paper medium (recording medium) during image recording, that is, the occurrence of curling and cockle is suppressed.

  The details of the ink composition for inkjet recording in the ink set are as described above, and the preferred embodiments are also the same.

[Treatment solution]
The treatment liquid in the ink set includes a compound that aggregates at least the colorant in the ink composition for inkjet recording (hereinafter, also referred to as “aggregating compound”), and an organic solvent, an aqueous solvent, and various types as necessary. Additives and the like may be included.

-Aggregating compounds-
The aggregating compound is a compound that forms an aggregate by aggregating components in the ink composition (hereinafter also referred to as an aggregating component) when the treatment liquid and the ink composition come into contact with each other. By contact between the treatment liquid containing the aggregating compound and the ink composition, the aggregation reaction of the colorant stably dispersed in the ink composition and, in some cases, the aggregating component such as resin particles is promoted. The treatment liquid may contain aggregating compounds alone or in combination of two or more.

For example, the treatment liquid may be prepared as a liquid composition capable of generating an aggregate by changing the pH of the ink composition. In this case, the treatment liquid is preferably prepared as an acidic liquid.
Specifically, the pH (25 ° C.) of the treatment liquid is preferably 1 or more and 6 or less, more preferably 1.2 or more and 5 or less, from the viewpoint of the aggregation rate of the ink composition. More preferably, it is 5 or more and 4 or less. In this case, the pH (25 ° C.) of the ink composition is preferably 7.5 or more and 12 or less, more preferably 8 or more and 11 or less.

Examples of the aggregating compound include at least one acidic compound.
Examples of the acidic compound include a compound having at least one group selected from a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, and a carboxyl group, or a salt thereof (for example, Polyvalent metal salts). Among these, as the acidic compound, from the viewpoint of the aggregation rate of the ink composition, a compound having at least one group selected from a phosphate group and a carboxyl group is more preferable, and a compound having a carboxyl group is still more preferable.
Examples of the compound having a carboxyl group include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, pyrrolidone carboxylic acid, and pyrone. Preference is given to compounds such as 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).

The treatment liquid may contain these compounds alone or in combination of two or more.
When the treatment liquid contains an acidic compound, the content of the acidic compound in the treatment liquid is preferably in the range of 5% by mass to 95% by mass with respect to the total mass of the treatment liquid from the viewpoint of the aggregation effect. A range of from mass% to 80 mass% is more preferred.

  Further, the treatment liquid may contain a polyvalent metal salt or a cationic polymer described in paragraphs [0155] and [0156] of JP2011-042150A as an aggregating compound other than the acidic compound. .

-Organic solvent-
The treatment liquid preferably contains an organic solvent.
As the organic solvent, those similar to the water-soluble organic solvent contained in the ink composition described above can be used, and polyalkylene glycol or polyalkylene glycol derivatives are preferable from the viewpoint of curling suppression. Specific examples include diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, polyoxyethylene polyoxypropylene glycol and the like.
The content of the organic solvent in the treatment liquid is not particularly limited, and is preferably 1% by mass or more and 30% by mass or less, and preferably 5% by mass or more and 15% by mass or less with respect to the entire treatment liquid from the viewpoint of curling suppression. A range is more preferred.

-Aqueous solvent-
The treatment liquid preferably further contains an aqueous solvent (for example, water) in addition to the aggregating compound (preferably an acidic compound). Although there is no restriction | limiting in particular in content of an aqueous solvent, The range of 10 mass% or more and 99 mass% or less is preferable, More preferably, it is the range of 50 mass% or more and 90 mass% or less.

-Other additives-
The treatment liquid may contain other additives in addition to the above components. Other additives include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, surfactants, antifoaming agents, viscosity modifiers, and dispersion stabilizers. Well-known additives, such as an agent, a rust preventive agent, and a chelating agent, are mentioned.

The viscosity of the treatment liquid is preferably 1 mPa · s or more and 30 mPa · s or less, more preferably 1 mPa · s or more and 20 mPa · s or less, from the viewpoint of the aggregation rate of the ink composition, and 2 mPa · s or more and 15 mPa · s or less. The range of s or less is more preferable, and the range of 2 mPa · s or more and 10 mPa · s or less is particularly preferable. In addition, the viscosity of a process liquid is a value measured on 25 degreeC conditions using a viscometer (VISCOMETER TV-22, the product made by TOKI SANGYO CO.LTD).
The surface tension of the treatment liquid is preferably in the range of 20 mN / m to 60 mN / m, more preferably in the range of 20 mN / m to 45 mN / m, and more preferably 25 mN / m from the viewpoint of the aggregation rate of the ink composition. The range of 40 mN / m or less is more preferable. The surface tension is a value measured under conditions of 25 ° C. using a surface tension meter (Automatic Surface Tensiometer CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

<Inkjet recording method>
The ink jet recording method of the present invention has an ink application step of applying the ink composition for ink jet recording of the present invention described above on a paper medium having a thickness of 0.11 mm or less by an ink jet method. It is possible to record an image while suppressing deformation of the recording medium.
The ink jet recording method of the present invention may record an image using one or two or more of the ink compositions for ink jet recording described above alone. In addition, an image may be recorded using a treatment liquid containing at least a compound that aggregates a colorant (an aggregating compound that aggregates components in the ink composition for ink jet recording) together with the ink composition for ink jet recording described above. Good. In this case, it is preferable to have a treatment liquid application process for applying the treatment liquid before or after the ink application process, and it is more preferable to have a treatment liquid application process before the ink application process.

[Ink application process]
In the ink application step, the ink composition for ink jet recording of the present invention described above is applied to a paper medium having a thickness of 0.11 mm or less by the ink jet method.

  Application of the ink composition to the paper medium is performed by ejection using an inkjet method. Examples of a method for ejecting an ink composition by an inkjet method and applying the ink composition to a paper medium include, for example, paragraphs [0093] to [0105] of JP-A No. 2003-306623 and JP-A No. 2014-0473302. The methods described in paragraphs [0172] to [0187] can be referred to as appropriate.

The amount of ink applied to the paper medium in the ink application process is not particularly limited and may be appropriately selected depending on the type of image to be recorded, color density or size, or type of paper medium. In the ink jet recording method of the present invention, an image with good color tone can be easily obtained with a small amount of ink, and curling or cuckling of the paper medium when the image is recorded hardly occurs, so that various ink application amounts can be selected. For example, in the case of recording a solid image, a solid image with little deformation due to cockle is recorded by applying an ink composition for inkjet recording with an ink application amount of 10 g / m ² or less (particularly preferably less than 8 g / m ² ). can do.

  The type of the paper medium is not particularly limited, and a relatively thin paper medium having a thickness of 0.11 mm or less is used. In this step, since an image is recorded with the ink composition of the present invention described above, an image having a high color density and a good film quality can be obtained while curling and cockle of the paper medium are suppressed.

  As the paper medium, for example, a general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, which is used for plain paper, general offset printing, and the like can be used. JP-A-8-169172, JP-A-8-27693, JP-A-2-276670, JP-A-7-276789, JP-A-9-323475, JP-A-62-238783 Ink jet paper described in JP-A-10-153898, JP-A-10-217473, JP-A-10-235995, JP-A-10-217597, JP-A-10-337947, etc. Also good.

  As the paper medium, commercially available products that are generally marketed may be used. For example, “OK Prince Quality” manufactured by Oji Paper Co., Ltd., “Shiraoi” manufactured by Nippon Paper Industries Co., Ltd., Nippon Paper Industries Co., Ltd. Fine paper (A) such as “New NPI Fine” manufactured by Oji Paper Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., and Oji Paper Co., Ltd. Lightweight coated paper (A3) such as “OK Top Coat Mat” and “OK Top Coat” manufactured by Nippon Paper Industries Co., Ltd., “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd., etc. Coated paper (A2, B2), “OK Kanfuji +” manufactured by Oji Paper Co., Ltd., art paper (A1) such as “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd., and the like.

Further, as a paper medium, the water absorption coefficient Ka is 0.05 mL / m ² · ms ^1/2 from the viewpoint of obtaining a high-quality image having a greater color density and hue than before, and having a large effect of suppressing the movement of the colorant. preferably ^{2 ~0.5mL /} m ^{2 · ms 1/2} of the paper ^{medium, 0.1mL / m 2 · ms 1/2} ~0.4mL / m 2 · ms 1/2 of the paper medium, more preferably, 0 A paper medium of ² mL / m ² · ms ^{1/2 to} 0.3 mL / m ² · ms ^1/2 is more preferable.
The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI paper pulp test method No. 51: 2000 (issued by Japan Paper Pulp Technology Association). Specifically, the absorption coefficient Ka is calculated from the difference in the amount of water transferred between the contact time of 100 ms and the contact time of 900 ms using an automatic scanning liquid absorption meter KM500Win (manufactured by Kumagai Riki Co., Ltd.).

As a paper medium, what is called coated paper used for general offset printing etc. is preferable. The coated paper has a coating layer (coat layer) formed by applying a coating material on a paper substrate mainly composed of cellulose (for example, high-quality paper, neutral paper, etc., which is generally not surface-treated). It is what you have. When ink-jet recording is performed using ordinary water-based ink, the coated paper has concerns about not only image color density and film quality (scratch resistance, color fastness), but also deformation due to curling and cockle after recording. Cheap. However, in the ink jet recording method of the present invention, deformation due to curling and cockle is suppressed. In addition, an image excellent in color density and film quality (abrasion resistance, color transfer resistance) of the image can be obtained.
As the paper medium, it is particularly preferable to use a coated paper having a base paper and a coated layer containing at least one of kaolin and calcium bicarbonate, more preferably art paper, coated paper, lightweight coated paper, or fine coated paper. preferable.

[Processing liquid application process]
The ink jet recording method of the present invention comprises a compound (aggregating compound) that aggregates at least a colorant in an ink composition for ink jet recording on a paper medium having a thickness of 0.11 mm or less before or after the ink application step described above. It is preferable to have the process liquid provision process which provides the process liquid containing). Examples of the component (aggregation component) in the ink composition that causes aggregation upon contact with the treatment liquid include a colorant (particularly a pigment), and further includes particles such as resin particles when particles such as resin particles are included. Is also included in the aggregating component.

  By contacting the treatment liquid applied to the paper medium and the ink composition, the colorant, which is an aggregating component in the ink composition, and, in some cases, resin particles and the like are aggregated, and the image is fixed on the paper medium. . In the ink jet recording method of the present invention, by having the treatment liquid application step, it is possible to speed up image recording, and an image with high color density and resolution can be obtained even when the speed is increased.

  Application of the treatment liquid to the paper medium can be performed by applying a known method such as a coating method, an inkjet method, or an immersion method. Examples of the coating method include known coating methods 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, and the like.

The amount of the treatment liquid applied to the paper medium is not particularly limited as long as it is an amount capable of aggregating the aggregating component in the ink composition, and the amount of the aggregating compound applied amount is 0.1 g / m ² or more. ^preferably, more preferably in an amount to be ^{0.1g / m 2 ~1.0g / m 2} , the amount to be 0.2g / ^{m 2} ~0.8g / m 2 is more preferable. When the amount of the aggregating compound applied is 0.1 g / m ² or more, the aggregation reaction proceeds well. Further, it is preferable that the amount of the aggregating compound applied is 1.0 g / m ² or less in that the glossiness of the image does not become too high.

[Drying process]
In the case where the treatment liquid application step is included before the ink application step, a drying step of drying the treatment liquid on the paper medium from the time when the treatment liquid is applied on the paper medium to the time when the ink composition is applied is further provided. It is preferable to have. By drying the treatment liquid prior to the ink application step, the colorant is easily fixed, such as preventing bleeding of the image, and a visible image having a good color density and hue is easily obtained. Moreover, the aspect which has the heat drying process which heat-drys the process liquid on a medium is also suitable.

  Drying or heat drying of the treatment liquid applied on the paper medium can be performed by a known heating means such as a heater, a blowing means using blowing air such as a dryer, or a combination of the heating means and the blowing means. As a heating method, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the paper medium, a method of applying warm air or hot air to the treatment liquid application surface of the paper medium, a method of heating using an infrared heater Etc., and a plurality of methods may be combined and heated.

The treatment liquid used in the treatment liquid application step preferably contains an aggregating compound that forms an aggregate by aggregating the aggregating components in the ink composition when in contact with the ink composition. By contact between the treatment liquid containing the aggregating compound and the ink composition, the aggregation reaction of the colorant stably dispersed in the ink composition and, in some cases, the aggregating component such as resin particles is promoted. The treatment liquid may contain aggregating compounds alone or in combination of two or more.
Details of the treatment liquid are as described above.

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

In addition, in a present Example, the weight average molecular weight (Mw) was measured as a polystyrene conversion value by the gel permeation chromatography (GPC) of the conditions shown below.
<Condition>
Measurement device: High-speed GPC HLC-8020 GPC (manufactured by Tosoh Corporation)
Detector: differential refractometer (RI) RI-8020 (manufactured by Tosoh Corporation)
Column: TSKgeL Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) is used. Column temperature: 40 ° C.
・ Eluent: Tetrahydrofuran (THF)
Sample concentration: 0.45% by mass
・ Injection volume: 10 μL
・ Flow rate: 0.35 mL / min

The surface tension of the water-soluble organic solvent was measured using a surface tension meter (Automatic Surface Tensiometer CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).
The SP value (unit: MPa ^1/2 ) of the water-soluble organic solvent was determined by the Okitsu method.

Example 1
<Preparation of ink>
-Synthesis of water-insoluble polymer P1-
To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. To this, 50 g of methyl ethyl ketone was added with 0.85 g of dimethyl-2,2′-azobisisobutyrate and phenoxy. A solution in which 50 g of ethyl methacrylate, 13 g of methacrylic acid, and 37 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution prepared by dissolving 0.42 g of dimethyl-2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in an excess amount of hexane, the precipitated resin was dried, and phenoxyethyl methacrylate / methyl methacrylate / methacrylic acid (copolymerization ratio [mass ratio] = 50/37/13) 96.5 g of a polymer (water-insoluble polymer P1) was obtained.
The composition of the obtained water-insoluble polymer P1 was confirmed by a proton nuclear magnetic resonance ( ¹ H-NMR) method, and the weight average molecular weight (Mw) determined by the above method (GPC) was 49400. Furthermore, the acid value of the water-insoluble polymer P1 obtained by the method specified in Japanese Industrial Standard (JIS K 0070: 1992) was 84.8 mgKOH / g.

-Preparation of black pigment dispersion K1-
After mixing 10 parts of carbon black (black pigment), 4.6 parts of water-insoluble polymer P1, 18 parts of methyl ethyl ketone, and 8.0 parts of 1 mol / liter sodium hydroxide aqueous solution, kneading with a roll mill for 2-8 hours The kneaded product was dispersed in 60 parts of ion-exchanged water. Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed. After cooling to room temperature, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Manufacturing Co., Ltd.), a 50 mL centrifuge was used, and centrifugation was performed at 10,000 rpm for 30 minutes, and the supernatant liquid other than the precipitate was collected.
The supernatant liquid was measured for volume average particle diameter by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.), and found to be 91 nm. Thereafter, the pigment concentration was determined from the absorbance spectrum, and ion-exchanged water was added to obtain a black pigment dispersion K1 as a dispersion of resin-coated pigment particles having a pigment concentration of 14% by mass.

-Production of resin particle S1-
In a 1 liter three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, water (250 g), 12-methacrylamide decanoic acid (1.84 g), potassium bicarbonate (0.68 g) and isopropanol (20 g) was charged and heated to 85 ° C. under a nitrogen stream. A mixed solution consisting of V-501 (radical polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd.) (0.57 g), potassium hydrogen carbonate (0.43 g) and water (9 g) was added thereto and stirred for 10 minutes. Next, a monomer solution composed of methyl methacrylate (60 g) and 2-ethylhexyl methacrylate (40 g) was dropped into the three-necked flask at a constant speed so that dripping was completed in 3 hours, and V-501 (0.28 g) was further added. ), Potassium hydrogen carbonate (0.21 g) and water (6 g) were added in two portions, immediately after the start of dropping of the monomer solution and 1.5 hours after the start of dropping. After completion of the dropwise addition of the monomer solution, the mixture was stirred for 1 hour, a mixed solution consisting of V-501 (0.28 g), potassium hydrogen carbonate (0.21 g) and water (6 g) was added, and the mixture was further stirred for 3 hours. The obtained reaction mixture was filtered using a mesh filter having a lattice width of 50 μm to obtain an aqueous dispersion of resin particles S1. The resin particle S1 has the structural unit represented by the general formula 1 described above, the structural unit (i) described above, and the structural unit derived from methyl methacrylate, and a specific structural formula is shown below.
The obtained aqueous dispersion of resin particles S1 had a pH of 7.5, a solid content concentration of 25% by mass, and a volume average particle diameter of 121 nm. Moreover, the resin weight average molecular weight (Mw) of resin of resin particle S1 was 200,000, and Tg was 70 degreeC.

The volume average particle size of the resin particles S1 was measured by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It carried out similarly about the volume average particle diameter of the following resin particle S2-S3.
Moreover, the glass transition temperature (Tg) of resin particle S1 was measured with the following method. It carried out similarly about Tg of the following resin particles S2-S3.

<Measurement of glass transition temperature (Tg)>
A dispersion of 0.5 g of the self-dispersing resin particles S1 with a solid content was dried under reduced pressure at 50 ° C. for 4 hours to obtain a polymer solid content. The glass transition temperature (Tg) was measured with a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology, Inc. using the obtained polymer solid content. The measurement condition was that a sample amount of 5 mg was sealed in an aluminum pan, and the DSC peak top value of the measurement data at the second temperature increase was defined as Tg under the following temperature profile in a nitrogen atmosphere.
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)

  In the structural formula of the resin particle S1 below, the numbers given to the respective structural units represent the mass ratio (% by mass) in the resin. In addition, “*” shown in each structural unit represents a connecting site in the resin. The same applies to the structural formulas of the following resin particles S2 to S3.

-Production of resin particle S2-
In a 2 liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 293.0 g of methyl ethyl ketone was charged and heated to 80 ° C. in a nitrogen atmosphere. Thereafter, while maintaining the temperature in the flask at 80 ° C. (hereinafter refluxed until the end of the reaction), 60 g of isobornyl methacrylate, 210 g of methyl methacrylate, 30 g of methacrylic acid, 48 g of methyl ethyl ketone, and “V-601” (radical polymerization initiator, A mixed solution consisting of 1.31 g (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise at a constant speed so that the addition was completed in 2 hours.

A solution consisting of 0.66 g of “V-601” and 5 g of methyl ethyl ketone is added to the solution after completion of the dropwise addition, followed by stirring at 80 ° C. for 2 hours, and then a solution consisting of 0.66 g of “V-601” and 5 g of methyl ethyl ketone is added. , And stirred at 80 ° C. for 2 hours. Thereafter, the temperature in the reaction vessel was raised to 85 ° C., and the stirring was further continued for 2 hours to obtain an isobornyl methacrylate / methyl methacrylate / methacrylic acid (= 20/70/10 [mass ratio]) copolymer polymer. A solution was obtained.
The weight average molecular weight (Mw) measured by the said method (GPC; polystyrene conversion value) of the obtained copolymer was 58,000. The acid value of the copolymer was 65 mgKOH / g. The acid value was measured by the method described in Japanese Industrial Standard (JIS K 0070 (1992)).

Next, 588.2 g of the obtained polymer solution was weighed, 165 g of isopropanol and 140.1 ml of 1 mol / liter sodium hydroxide aqueous solution were added to this polymer solution, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of pure water was added dropwise to the reaction vessel at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was kept at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure. Subsequently, the pressure in the reaction vessel is reduced, isopropanol, methyl ethyl ketone, and distilled water pure water are distilled off, and pure water is added so that the solid content concentration (resin particle concentration) is 23.0% by mass. An aqueous dispersion of dispersible resin particles (self-dispersing resin particles) S2 was obtained.
The obtained aqueous dispersion of resin particles S2 had a pH of 7.4, a solid content concentration of 23.0% by mass, and a volume average particle size of 3 nm. Moreover, the weight average molecular weight (Mw) of resin particle S2 in the obtained aqueous dispersion was 60,000, and Tg was 143 degreeC.

-Production of resin particle S3-
In the production of the resin particle S1, the following structural formula is shown in the same manner as the production of the resin particle S1, except that the type and amount of the monomer used are changed to the type and amount of the monomer that leads to the following structural unit. An aqueous dispersion of resin particles S3 was obtained.
The obtained aqueous dispersion of resin particles S3 had a pH of 8.4, a solid content concentration of 25% by mass, and a volume average particle diameter of 350 nm. Moreover, the resin weight average molecular weight (Mw) of resin particle S3 was 300,000, and Tg was 3 degreeC.

-Preparation of ink K1-
Using the aqueous dispersion of the black pigment dispersion K1 and the resin particles S1 prepared above, a mixed liquid having the following composition was prepared, and coarse particles were removed through a membrane filter (pore size 0.5 μm) to obtain a black ink. Ink K1, which is a composition, was obtained.
When the pH of the obtained ink K1 was measured at 25 ° C. using a pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.), the pH value was 8.3. Moreover, when surface tension was measured at 25 degreeC using FASE Automatic Surface Tensionmeter CBVP-Z (made by Kyowa Interface Science Co., Ltd.), surface tension was 30 mN / m.

<Composition of ink K1>
・ Carbon black (black pigment): 4% by mass
-Resin particle S1 ... 10 mass%
・ Hexylene glycol: 25% by mass
(First water-soluble organic solvent, surface tension = 33 mN / m (25 ° C.), molecular weight = 118, hydroxyl group number = 2, SP value = 24 MPa ^1/2 ; manufactured by Wako Pure Chemical Industries, Ltd.)
・ Sanix GP250 ・ ・ ・ 8% by mass
(Second water-soluble organic solvent, molecular weight: 250, number of hydroxyl groups = 3, SP value = 26 MPa ^1/2 ; manufactured by Sanyo Chemical Industries, Ltd.)
・ Diethylene glycol monobutyl ether: 4% by mass
(Third water-soluble organic solvent, number of hydroxyl groups = 1, SP value = 22 MPa ^1/2 , manufactured by Wako Pure Chemical Industries, Ltd.)
・ Ion-exchanged water: 49% by mass

<Preparation of treatment solution>
Each component in the following composition was mixed to prepare a treatment liquid. About the obtained processing liquid, when pH was measured at 25 degreeC using pH meter WM-50EG (made by Toa DDK Co., Ltd.), pH value was 1.10. Moreover, when surface tension was measured at 25 degreeC using FASE Automatic Surface Tension meter CBVP-Z (made by Kyowa Interface Science Co., Ltd.), surface tension was 41.3 mN / m.

<Composition of treatment liquid>
Malonic acid (acidic compound (aggregating compound)) ... 11.25% by mass
DL-malic acid (acidic compound (aggregating compound)) 14.5% by mass
・ Diethylene glycol monobutyl ether: 4.0% by mass
(DEGmBE; water-soluble organic solvent manufactured by Wako Pure Chemical Industries, Ltd.)
・ Tripropylene glycol monomethyl ether: 4.0% by mass
(TPGmME; water-soluble organic solvent manufactured by Wako Pure Chemical Industries, Ltd.)
・ Ion-exchanged water: Amount that is 100% by mass as a whole

<Image recording>
An ink jet head provided with a silicon nozzle plate was prepared, and the ink composition prepared above was accommodated in a storage tank connected to the ink jet head. A liquid repellent film formed using a fluorinated alkylsilane compound is provided in advance on the surface of the silicon nozzle plate.
In addition, the following two types of coated paper were used for the recording paper. The coated paper used as the recording paper was fixed on a stage movable in a predetermined linear direction at 500 mm / second, and the stage temperature was kept at 30 ° C.
<Paper type>
OK top coat mat (basis weight: 104.7 g / m ² , paper thickness: 0.09 mm, manufactured by Oji Paper Co., Ltd.)
OK top coat (basis weight 84 g / m ² , paper thickness: 0.07 mm, manufactured by Oji Paper Co., Ltd.)

-Treatment liquid application process-
The treatment liquid prepared above was applied to the retained recording paper with a bar coater so as to have a thickness of about 1.2 μm (1.5 g / m ² ). Immediately after application, the treatment liquid on the paper piece was dried at 50 ° C. for 2 seconds.

-Ink application process-
After that, the inkjet head is fixedly arranged so that the direction of the line head in which the nozzles are aligned is inclined by 75.7 degrees with respect to the direction orthogonal to the moving direction of the stage, and the recording paper is moved at a constant speed in the moving direction of the stage. However, the ink droplet amount is 8 g / m ² , the discharge frequency is 25.5 kHz, and the discharge condition is 1200 dpi × 1200 dpi. An image having a length in the direction perpendicular to 140 mm (direction perpendicular to the paper grain direction) was recorded. A solid image without a pattern is formed in an area of the image to which ink has been applied.
In addition, dpi means “dot per inch”.

<Evaluation>
The following evaluation was performed on the discharge properties of the recorded image and ink. The evaluation results are shown in Table 6 below.

-1. Image density
A solid image was recorded on an OK top coat mat (basis weight: 104.7 g / m ² , paper thickness: 0.09 mm, manufactured by Oji Paper Co., Ltd.) and measured using Gretag Macbeth (manufactured by X-Rite). The visual density was determined by coloring and evaluated according to the following evaluation criteria.
The practically acceptable range is rank 5 to rank 3, more preferably rank 4 or higher, and most preferably rank 5.
<Evaluation criteria>
5: Visual density is 2.2 or more.
4: The visual density is 2.0 or more and less than 2.2.
3: The visual density is 1.8 or more and less than 2.0.
2: The visual density is 1.6 or more and less than 1.8.
1: Visual density is less than 1.6.

-2. Film quality (abrasion resistance)
An OK top coat mat (basis weight: 104.7 g / m ² , paper thickness: 0.09 mm, manufactured by Oji Paper Co., Ltd.), on which no image was recorded, was placed on top of the solid image. A 200 g load was applied to 10 cm ² on the OK top coat mat and rubbed 10 times with a stroke of 20 mm. Thereafter, the degree of color transfer to the OK top coat mat placed on the image was visually observed, and the film quality was evaluated according to the following evaluation criteria.
<Evaluation criteria>
6: No color transfer is observed in the area of the rubbing surface.
5: A slight color transfer is observed in less than 5% of the area of the rubbing surface, but there is no problem.
4: A slight color transfer is observed in 5% or more and less than 10% of the area of the rubbing surface, but there is no problem.
3: A slight color transfer was observed in 10% or more of the area of the rubbing surface, which is of concern for practical use.
2: Clear color transfer is observed in less than 10% of the area of the rubbing surface, which is problematic in practical use.
1: Clear color transfer is observed in 10% or more of the area of the rubbing surface, which is very problematic in practice.
The practically acceptable range is rank 6 to rank 3, more preferably rank 4 or higher, more preferably rank 5 or higher, and most preferably rank 6.

-3. Carl
A solid image was recorded on an area of 25 cm × 20 cm OK top coat (basis weight 84 g / m ² , paper thickness: 0.07 mm, manufactured by Oji Paper Co., Ltd.). After recording, the recorded matter was left in an environment of a temperature of 23 ° C. and a relative humidity of 55% for 7 days. The recorded matter after standing was placed on a horizontal plane, and the heights of the four corners floating from the horizontal plane from the horizontal plane were measured, and the average value of the four heights was calculated. Based on the average value, it evaluated according to the following evaluation criteria.
<Evaluation criteria>
5: The average value is 0.5 mm or less.
4: The average value is 0.5 mm or more and less than 2.0 mm.
3: The average value is 2.0 mm or more and less than 5.0 mm.
2: The average value is 5.0 mm or more and less than 10 mm.
1: The average value is 10 mm or more.
The practically acceptable range is rank 5 to rank 3, more preferably rank 4 or higher, and most preferably rank 5.

-4. Cockle
Using an OK topcoat mat (basis weight: 104.7 g / m ² , paper thickness: 0.09 mm, manufactured by Oji Paper Co., Ltd.), the ink K1 prepared above was used with an ink droplet amount of 1.2 pL and an ejection frequency. Under a discharge condition of 24 kHz, resolution 1200 dpi × 1200 dpi (dot per inch), stage speed 508 mm / s, the line is discharged to the center of the coated surface of the recording paper coated with the treatment liquid in a 2 cm × 10 cm size solid An image (black 100% solid image) was recorded. Ink was ejected so that the deposited ink droplets (dots) overlapped, and immediately after recording the intended solid image, it was dried at 80 ° C. for 10 seconds. Thereafter, the degree of wavy deformation that occurred in the solid image region was observed.
A specific description will be given with reference to FIGS.
FIG. 1 shows a state in which a rectangular solid image 52 having a length (x direction) 140 mm × width (y direction) 50 mm is recorded on a 150 mm square recording paper 54. In the recording paper shown in FIG. 1, the grain direction (paper making direction) of the recording paper is the width direction (y direction) of the rectangular solid image. In this embodiment, the cuckling on the straight line 56 in the direction (x direction) perpendicular to the grain direction (y direction) of the recording paper 54 in FIG. 1 was measured. When the cut surface in the case where the recording sheet is cut in two along the straight line 56 in the x direction is observed as the curve shown in FIG. FIG. 2 is a graph schematically showing the shape of the cut surface of the recording paper 54 when the recording paper 54 is cut along a straight line 56 with the x direction and the z direction as direction displacements. 1 and 2, the x direction indicates the same direction, the x direction is a direction orthogonal to the grain direction (y direction) of the recording paper 54, and the z direction is a solid surface of the recording paper 54. The height of wrinkles (waves) in the image 52 is represented.
2 uses the obtained ink to create the image shown in FIG. 2 and within 2 minutes after drying, the height Z of the recording paper 54 on the straight line 56 (displacement in the z direction of the recording paper 54). Profile) was measured with a laser displacement meter (Laser displacement meter LK-080 manufactured by Keyence Co., Ltd.), and the amount of cockle was determined from the following, which was used as an index representing the degree of cockle. The same operation was repeated three times to produce three identical images, the amount of cockle was measured for each image, and the average value of the amount of cockle was used in accordance with the following evaluation criteria.
The practically acceptable range is rank 5 to rank 3, more preferably rank 4 or higher, and most preferably rank 5.
Amount of cockle = (L′−L) / L
Here, L represents the measurement length (150 mm), L ′ is the path integral length of the displacement profile, and was calculated from the formula “L ′ = Σ√ (Δxi2 + Δzi2)”. Δxi and Δzi in the equation are parameters represented in FIG.
<Evaluation criteria>
5: The amount of cockle is less than 0.17%.
4: The amount of cockle is 0.17% or more and less than 0.20%.
3: The amount of cockle is 0.20% or more and less than 0.23%.
2: The amount of cockle is 0.23% or more and less than 0.26%.
1: The amount of cockle is 0.26% or more.

-5. Discharge stability
A solid image was continuously recorded for 30 minutes at a recording speed of 2700 sheets per hour using ink K1, and then a parallel line pattern sample (length 1 cm) of a line image of 75 dpi × 2400 dpi was created. Using the general-purpose image processing device DA-6000, the center position of the line width of the parallel line pattern is measured, the standard deviation σ of the distance (deviation amount) deviated from the theoretical center position is calculated, and ejection is performed according to the following criteria. Stability was evaluated.
The practically acceptable range is rank 6 to rank 3, more preferably rank 4 or higher, more preferably rank 5 or higher, and most preferably rank 6.
<Evaluation criteria>
6: The standard deviation σ is σ <1 μm, and there is no problem at all.
5: Standard deviation σ is 1 μm ≦ σ <2 μm, no problem 4: Standard deviation σ is 2 μm ≦ σ <3.5 μm, no problem.
3: The standard deviation σ is 3.5 μm ≦ σ <5 μm, which is practically acceptable.
2: The standard deviation σ is 5 μm ≦ σ <10 μm, which is practically unacceptable.
1: The standard deviation σ is 10 μm ≦ σ, which may impede practical use.

(Example 2)
In Example 1, images were recorded and evaluated in the same manner as in Example 1 except that the amount of ink droplets applied to the recording paper was changed as shown in Table 3. The evaluation results are shown in Table 6.

(Examples 3-4, Comparative Examples 1-3)
In Example 1, except that the content of the water-soluble organic solvent in the ink was changed as shown in Table 3, an ink was prepared and an image was recorded and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.

(Comparative Examples 4-6)
In Example 1, except that the type of the water-soluble organic solvent in the ink was changed as shown in Table 3, ink was prepared and an image was recorded and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.

(Examples 5-6)
In Example 1, except that the type (namely, molecular weight) of the second water-soluble organic solvent was changed as shown in Table 4, an ink was prepared and an image was recorded in the same manner as in Example 1. evaluated. The evaluation results are shown in Table 6.

(Examples 7-8, Comparative Examples 7-9)
In Example 1, except that the content of the water-soluble organic solvent in the ink was changed as shown in Table 4, an ink was prepared and an image was recorded and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.

(Examples 9 to 10)
In Example 1, an ink was prepared and an image was recorded and evaluated in the same manner as in Example 1 except that the resin particle S1 was replaced with the resin particle S2 or the resin particle S3. The evaluation results are shown in Table 6.

(Examples 11 to 20)
In Example 1, an ink is prepared in the same manner as in Example 1 except that the type of the first water-soluble organic solvent or the second water-soluble organic solvent in the ink is changed as shown in Table 5. Along with this, images were recorded and evaluated. The evaluation results are shown in Table 6.

(Example 21)
In Example 1, images were recorded and evaluated in the same manner as in Example 1 except that the ink droplet amount in the ink application process was changed from 8 g / m ² to 7.5 g / m ² . The evaluation results are shown in Table 6.

(Example 22)
In Example 1, an image was recorded in the same manner as in Example 1 except that the second water-soluble organic solvent was not used and two kinds of second water-soluble organic solvents were used in combination as shown in Table 5. And evaluated. The evaluation results are shown in Table 6.

The notation “-” shown in the table indicates that it is not contained.
In Tables 3 to 5, details of the organic solvent are shown below.
GP-250: Sannix GP-250 (organic solvent represented by structural formula (S) (t + u + v = 3, AO = propyleneoxy), molecular weight 250), manufactured by Sanyo Chemical Industries, Ltd. GP-400: Sun Nix GP-400 (organic solvent represented by structural formula (S) (t + u + v = 6, AO = propyleneoxy), molecular weight 400), manufactured by Sanyo Chemical Industries, Ltd. SCE-450: diglycerin ethylene oxide adduct ( Solvent represented by structural formula (S2) (p + q + r + s = 6, AO = ethyleneoxy), molecular weight 450), manufactured by Sakamoto Pharmaceutical Co., Ltd.

As shown in Table 6, with the inks of the examples, an image having excellent image color density and film quality and excellent quality in which the occurrence of curling and cockle was suppressed was obtained.
As shown in Examples 1 to ² and 21, when the ink droplet amount is suppressed to 10 g / m ² , the occurrence of curling and cockle can be further suppressed. The image color density and film quality were excellent.
When Examples 1, 4 to 5 and Comparative Examples 1 to 3 were compared, when the content of the water-soluble organic solvent was less than 20% by mass (Comparative Examples 2 to 3), the cockle was remarkably deteriorated and curl was also generated. . Further, when the content of the water-soluble organic solvent exceeded 40% by mass (Comparative Example 1), a large amount of the organic solvent was likely to remain in the image, and the film quality of the image was remarkably deteriorated. From these examples, it can be seen that the total amount of the water-soluble organic solvent affects the balance between the film quality of the image and the deformation of the paper medium.
In Comparative Examples 4 to 5, the first water-soluble organic solvent was not contained, and the color density and film quality of the image were significantly reduced. On the other hand, in Example 11 where the surface tension of the first water-soluble organic solvent is 40 mN / m, the color density of the image is maintained. By maintaining the surface tension at 40 mN / m or less to ensure the spread of dots, an image with a good color density can be reproduced even if the amount of ink droplets is reduced. Further, as in Comparative Example 6, curling could not be suppressed even when a predetermined amount was maintained using a third water-soluble organic solvent instead of the second water-soluble organic solvent.
As represented by Examples 5 to 6, the molecular weight of the second water-soluble organic solvent is preferably in the range of 400 or less from the viewpoint of maintaining good image film quality.
Further, as is clear from Examples 8 to 9 and Comparative Examples 8 to 9, it is important to appropriately select Y1 / Y2 values in terms of improving the film quality of the image and suppressing the occurrence of curling. is there.
As shown in Example 22, the film quality of the image could be further improved by using two kinds of the second water-soluble organic solvent in addition to the first water-soluble organic solvent.

(Example 23)
In Example 1, a solid image was formed and evaluated in the same manner as in Example 1 except that the treatment liquid was not used and the ink K1 was directly applied to the piece of paper in the ink application step 2 shown below.

  As a result, in the same manner as in the above example using the treatment liquid, it was possible to obtain an image with good film quality and color density while suppressing the occurrence of curling and cockle.

-Ink application step 2-
A piece of A5 size paper (recording paper) was fixed on a stage movable in a predetermined linear direction at 500 mm / second, and the stage temperature was kept at 30 ° C. The inkjet head is fixedly arranged so that the direction of the line head in which the nozzles are aligned is inclined by 75.7 degrees with respect to the direction orthogonal to the moving direction of the stage, and the recording paper is moved at a constant speed in the moving direction of the stage. As an ejection condition with an ink droplet amount of 8 g / m ² and an ejection frequency of 25.5 kHz and a resolution of 1200 dpi × 1200 dpi, a line method and a direction (x in FIG. 1) orthogonal to the paper grain direction (y direction in FIG. 1) Direction), a solid image having a width (y direction) of 50 mm and a length (x direction) of 140 mm was created.

52... Solid image 54... Recording sheet 56.

Claims (13)

Including 20% by weight or more and 40% by weight or less of a water-soluble organic solvent based on the total weight of the colorant, water, and ink composition;
The water-soluble organic solvent has a first water-soluble organic solvent having a surface tension at 25 ° C. of 40 mN / m or less and a molecular weight of 150 or less, and a second water-soluble organic solvent having a molecular weight of 200 or more. A total content Y1 of the first water-soluble organic solvent and a total content Y2 of the second water-soluble organic solvent is 70% of the total amount of the water-soluble organic solvent on a mass basis. An ink composition for ink jet recording satisfying the relationship of 1.5 ≦ Y1 / Y2 ≦ 4.0.   The ink composition for ink jet recording according to claim 1, wherein the second water-soluble organic solvent has a molecular weight of 200 or more and 400 or less.   Furthermore, the ink composition for inkjet recording of Claim 1 or Claim 2 containing the resin particle whose glass transition temperature Tg is 40 degreeC or more and whose volume average particle diameter is 30 nm or more.   The number of hydroxyl groups contained in the molecule of the water-soluble organic solvent of 80% by mass or more of the total amount of the water-soluble organic solvent contained in the ink composition is 2 or more. The ink composition for inkjet recording as described. Solubility parameter of 70 mass% or more water-soluble organic solvent of the total amount of water-soluble organic solvent contained in the ink composition any one of claims 1 to 4 is ^{21 MPa 1/2} or more ^{30 MPa 1/2} or less 2. An ink composition for ink jet recording according to item 1.   The inkjet recording according to any one of claims 1 to 5, wherein an absolute value of a difference between a molecular weight of the first water-soluble organic solvent and a molecular weight of the second water-soluble organic solvent is 90 or more. Ink composition. As the second water-soluble organic solvent, at least one water-soluble organic solvent selected from the solvent group represented by the following structural formula (S) or the following structural formula (S2), dialkylene glycol monoalkyl ether and trialkylene The ink composition for inkjet recording according to any one of claims 1 to 6, comprising at least one water-soluble organic solvent selected from the group consisting of glycol monoalkyl ethers.

In the structural formula (S), t, u, and v each independently represent an integer of 1 or more, and satisfy t + u + v = 3-15. AO represents at least one of ethyleneoxy and propyleneoxy.

In the structural formula (S2), p, q, r, and s each independently represent an integer of 1 or more and satisfy p + q + r + s = 4-40. AO represents at least one of ethyleneoxy and propyleneoxy. The ink composition for ink jet recording according to any one of claims 3 to 7, wherein the resin particles have at least one selected from structural units represented by the following general formula 1 or general formula 2.

In formula, R < ¹ > and R < ² > represents a hydrogen atom or a C1-C4 alkyl group each independently. A ¹ represents an oxygen atom or NR ³ , and R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A ² represents a single bond, —COO—, or —CONH—. L ¹ represents an alkylene group having 6 to 22 carbon atoms. L ² represents a divalent linking group having 6 to 23 carbon atoms. M ¹ and M ² each independently represent a hydrogen ion, an alkali metal ion, or an ammonium ion. The ink composition for inkjet recording according to any one of claims 1 to 8,
A treatment liquid containing a compound that aggregates at least the colorant in the ink composition for inkjet recording;
An ink set.   An ink jet recording method comprising an ink application step of applying the ink composition for ink jet recording according to any one of claims 1 to 8 on a paper medium having a thickness of 0.11 mm or less by an ink jet method.   Further, a treatment liquid application step of applying a treatment liquid containing a compound that aggregates at least the colorant in the ink composition for ink jet recording onto the paper medium having a thickness of 0.11 mm or less before or after the ink application step. The inkjet recording method according to claim 10, comprising: The ink jet recording method according to claim 10 or 11, wherein the ink application step forms a solid image by applying the ink composition for ink jet recording with an ink application amount of 10 g / m ² or less.   The inkjet recording method according to any one of claims 10 to 12, wherein the paper medium is a coated paper having a coating layer on a paper substrate.