JP5819341B2 - Curable composition, curable composition set, and image forming method - Google Patents

Description

  The present invention relates to a curable composition, a curable composition set, and an image forming method.

As a composition (for example, ink) used for image formation, in addition to a solvent-based composition using a solvent as a solvent, a water-based composition using water as a solvent from the point of consideration of the global environment and working environment. Attention has been paid.
In addition, a polymerizable compound or a polymerization initiator is included in the composition to obtain a curable composition, and by curing the curable composition, scratch resistance such as scratches (hereinafter also referred to as “scratch resistance”) is high. Techniques for forming images are being studied.

For example, it is excellent in curability and scratch resistance, and when used as an inkjet ink, as an ultraviolet curable ink excellent in ink ejection properties, water, a water-soluble solvent, a compound having an ethylenically unsaturated group, and a specific photoinitiator An ultraviolet curable ink containing a benzophenone compound or a specific thioxanthone compound is known (for example, see Patent Document 1).
In particular, an ultraviolet curable ink-jet curable composition suitable for printing on so-called low-absorption and absorbent media such as printing paper, high-quality paper, plain paper, etc. and having sufficient curability and capable of high-speed printing. As a coloring material, water, a photopolymerizable initiator, an ultraviolet curable resin, and a water-soluble organic solvent, and the water-soluble organic solvent is a 3- to 10-membered heterocyclic compound, A heterocyclic compound containing a specific structure in the ring structure, wherein the photopolymerization initiator absorbs in a wavelength region of 380 nm or more, and a first photopolymerization initiator having absorption in a wavelength region of less than 380 nm. An inkjet curable composition comprising at least two types of second photopolymerization initiators is known (see, for example, Patent Document 2).
In addition, as a photo-curable coating composition having antistatic properties, sufficient scratch resistance and transparency as a hard coat, and excellent durability that also has waterproof properties, a quaternary ammonium base in the molecule. An antistatic copolymer (A) having three or more compounds (B) having three or more ethylenically unsaturated groups, a photopolymerization initiator (c-1) having a solubility in water of 0.2 g / L or less And a photopolymerization initiator (C) containing a photopolymerization initiator (c-2) having a solubility in water of 1.0 g / L or more, and a solvent (D) containing an alcohol (d-1) Coating compositions are known (see, for example, Patent Document 3).
Moreover, although it is a technique related to a solvent-based composition rather than an aqueous composition, it is an ultraviolet curable ink jet recording curable composition that is excellent in ejection stability and print film performance such as abrasion resistance and scratch resistance of printed matter. As an example, an ultraviolet curable ink jet recording curable composition containing an ultraviolet curable compound, a photopolymerization initiator, and methylphenyl silicone oil is known (for example, see Patent Document 4).

JP 2008-280427 A JP 2010-229181 A JP 2011-225797 A JP 2011-111522 A

  Generally, in a curable composition containing a polymerizable compound and a polymerization initiator, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- is used as the polymerization initiator. 1-one (hereinafter also referred to as “polymerization initiator Ia”) may be used. A commercially available product of this polymerization initiator (polymerization initiator Ia) is Irgacure 2959 (trade name) (manufactured by BASF Japan Ltd.).

However, in the curable composition containing the polymerization initiator Ia described above and containing water as a solvent (aqueous curable composition), the precipitate (described above) caused by the polymerization initiator Ia described above in a low temperature environment. The polymerization initiator Ia itself may contain precipitates). Even when the water-based curable composition further contains a water-soluble solvent, precipitates may still be generated in a low-temperature environment.
Here, the low temperature environment includes storage in a low temperature environment, transportation in a low temperature environment, use in a low temperature environment, and the like.

  On the other hand, when an image is formed using an aqueous composition containing a polymerizable compound and a polymerization initiator, it is required to maintain high abrasion resistance of the formed image.

  The present invention has been made in view of the above, and a curable composition, a curable composition set, and an image forming method capable of forming an image excellent in abrasion resistance with generation of precipitates in a low-temperature environment being suppressed. It is an object to provide this and to achieve this purpose.

Specific means for achieving the object are as follows.
<1> Water, a water-soluble solvent, a polymerizable compound, and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1- as a polymerization initiator Ia ON and 2-hydroxy-2-methyl-1-phenyl-propan-1-one as the polymerization initiator Ib, and the total content of the polymerization initiator Ia and the polymerization initiator Ib is curable. 0.8% by mass to 10.0% by mass with respect to the total amount of the composition, and the content ratio of the polymerization initiator Ib to the polymerization initiator Ia is 0.2 times to 1.5 times on a mass basis. The content of water is 50% by mass or more with respect to the total amount of the curable composition, and the content of the water-soluble solvent is 2% by mass to 20% by mass with respect to the total amount of the curable composition . It is a composition.
<2> The curable composition according to <1>, wherein the total content is 1.0% by mass to 7.0% by mass.
<3> The curable composition according to <1> or <2>, wherein the content ratio is 0.3 to 0.9 times on a mass basis.
<4> Furthermore, it is a curable composition as described in any one of <1>-<3> containing a coloring material.
<5> The curable composition according to any one of <1> to <4>, which is a curable composition for inkjet.
<6> The water-soluble solvent includes at least one selected from the group consisting of a compound represented by the following general formula (A) and a compound represented by the following general formula (B) <1> to <5>. It is a curable composition as described in any one of these.

[In General Formula (A), R ^A1 represents a linear or branched alkyl group having 1 to 6 carbon atoms. R ^A2 and R ^A3 each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.
In General Formula (B), W represents a divalent linking group that forms a heterocyclic ring with the carbon atom and nitrogen atom in General Formula (B). ]

<7> The curable composition according to any one of <1> to <6>, wherein the water-soluble solvent includes 3-n-butoxy-N, N-dimethylpropionamide.
<8> The curable composition according to any one of <1> to <7>, wherein the water-soluble solvent contains 2-pyrrolidone.

<9> The curable composition according to any one of <1> to <8>, wherein at least one of the polymerizable compounds is a (meth) acrylamide compound represented by the following general formula (1). .

[In General Formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms. However, R ² does not have a structure in which an oxygen atom and a nitrogen atom bonded to both ends of R ² are bonded to the same carbon atom of R ² . R ³ represents a divalent linking group. k represents 2 or 3. x, y, and z each independently represent an integer of 0 to 6, and x + y + z satisfies 0 to 18. ]

<10> The curable composition according to <9>, further including a (meth) acrylamide compound represented by the following general formula (2).

[In General Formula (2), R ¹⁰ represents a hydrogen atom or a methyl group, R ¹¹ represents a hydrogen atom, a methyl group or an ethyl group, and R ¹² represents a substituted or unsubstituted alkyl group. R ¹¹ and R ¹² may combine with each other to form a 5- to 8-membered ring, and the 5- to 8-membered ring further contains at least one selected from —O—, —S—, and —NR ^b —. You may go out. R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]

<11> Furthermore, it is a curable composition as described in any one of <1>-<10> containing the polymer particle whose glass transition temperature is 90 degreeC or more.
<12> Curing comprising the curable composition according to any one of <1> to <11> and a treatment liquid containing an aggregating component that forms an aggregate when contacted with the curable composition. It is a sex composition set.
<13> The curable composition set according to <12> is used, and a treatment liquid application step for applying the treatment liquid to a recording medium, and an image obtained by applying the curable composition to a recording medium by an inkjet method. And an image forming process for forming the image.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the precipitate in a low-temperature environment is suppressed, and the curable composition which can form the image excellent in abrasion resistance, a curable composition set, and an image forming method can be provided. .

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

Hereinafter, the curable composition of the present invention, and the curable composition set and image forming method using the same will be described in detail.
In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.

≪Curable composition≫
The curable composition of the present invention comprises water, a water-soluble solvent, a polymerizable compound, and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl- as the polymerization initiator Ia. 1-propan-1-one and 2-hydroxy-2-methyl-1-phenyl-propan-1-one as the polymerization initiator Ib, and the total of the polymerization initiator Ia and the polymerization initiator Ib The content is 0.8% by mass to 10.0% by mass with respect to the total amount of the curable composition, and the content ratio of the polymerization initiator Ib to the polymerization initiator Ia is 0.2 times to 1 on a mass basis. .5 times.
The curable composition of this invention may contain the other component as needed.

Hereinafter, the content ratio of the polymerization initiator Ib to the polymerization initiator Ia on a mass basis, that is, the mass ratio [the content of the polymerization initiator Ib / the content of the polymerization initiator Ia] is referred to as “mass ratio [polymerization initiator Ib / polymerization initiator Ia] ”.
Further, the fact that the content ratio of the polymerization initiator Ib to the polymerization initiator Ia is X times on a mass basis may be referred to as “mass ratio [polymerization initiator Ib / polymerization initiator Ia] is X”. .

  That is, the curable composition of the present invention contains water, a water-soluble solvent, a polymerizable compound, a polymerization initiator Ia, and a polymerization initiator Ib, and the total content of the polymerization initiator Ia and the polymerization initiator Ib is 0.8 mass% to 10.0 mass%, and the mass ratio [polymerization initiator Ib / polymerization initiator Ia] is 0.2 to 1.5.

In general, in a curable composition containing a polymerizable compound and a polymerization initiator, the polymerization initiator Ia is used as a polymerization initiator excellent in sensitivity to active energy rays (for example, ultraviolet rays) (hereinafter also simply referred to as “sensitivity”). May be used. As a commercial item of this polymerization initiator Ia, Irgacure 2959 (trade name) (manufactured by BASF Japan Ltd.) can be mentioned.
However, in a curable composition (water-based curable composition) containing this polymerization initiator Ia and containing water as a solvent, a precipitate (polymerization initiator Ia) caused by the polymerization initiator Ia in a low temperature environment. In some cases, including precipitates that are themselves). Even when the water-based curable composition further contains a water-soluble solvent, precipitates may still be generated in a low-temperature environment.
On the other hand, when an image is formed using an aqueous curable composition containing a polymerizable compound and a polymerization initiator, it is required to maintain high image abrasion resistance.

Regarding the above points, in the curable composition of the present invention, as a polymerization initiator, a polymerization initiator Ia and a polymerization initiator Ib having a structure similar to that of the polymerization initiator Ia are used in combination, and the mass ratio [polymerization initiator Ib / polymerization initiator Ia] is 0.2 to 1.5, and the total content of polymerization initiator Ia and polymerization initiator Ib is 0.8% by mass to 10.0% with respect to the total amount of the curable composition By setting the mass%, it is possible to suppress the generation of precipitates in a low temperature environment and to form an image having excellent abrasion resistance.
When the mass ratio [polymerization initiator Ib / polymerization initiator Ia] is less than 0.2, precipitates are generated in a low temperature environment.
On the other hand, when the mass ratio [polymerization initiator Ib / polymerization initiator Ia] exceeds 1.5, the abrasion resistance of the image decreases.
In the present invention, the mass ratio [polymerization initiator Ib / polymerization initiator Ia] is 0 from the viewpoint of achieving both the suppression of the generation of precipitates in a low temperature environment and the improvement of image abrasion resistance at a higher level. 0.3 to 1.2 is preferable, 0.3 to 0.9 is more preferable, and 0.4 to 0.9 is particularly preferable.

Further, when the total content of the polymerization initiator Ia and the polymerization initiator Ib is less than 0.8% by mass, the sensitivity is insufficient, and the abrasion resistance of the image is lowered.
On the other hand, when the total content of the polymerization initiator Ia and the polymerization initiator Ib exceeds 10.0% by mass, precipitates are generated in a low temperature environment. Further, when the total content exceeds 10.0% by mass, the total amount of nonvolatile components increases, and the image abrasion resistance decreases.
In the present invention, the total content of the polymerization initiator Ia and the polymerization initiator Ib is 1 from the viewpoint of achieving both the suppression of the generation of precipitates in a low temperature environment and the improvement of the abrasion resistance of the image at a higher level. 0.0 mass% to 7.0 mass% is preferable, 1.0 mass% to 5.0 mass% is more preferable, and 1.5 mass% to 4.5 mass% is particularly preferable.

As described above, the curable composition of the present invention is a composition used for image formation.
A particularly preferred form of image formation is a form in which an image is formed by applying the curable composition of the present invention onto a recording medium by an ink jet method. Hereinafter, the curable composition used for image formation in this form may be referred to as “ink-jet curable composition” or “ink”.
Ink jet curable compositions (inks) may be required to have excellent ejection properties from ink jet nozzles (hereinafter also referred to as “ejection stability”).
In the following description, the term “ejection property” (or “ejection stability”) simply refers to ejection property (or ejection stability) from an inkjet nozzle.

  Hereinafter, each component of the curable composition of this invention is demonstrated.

<Polymerization initiator>
The curable composition of the present invention has 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (polymerization initiator Ia) as a polymerization initiator. And 2-hydroxy-2-methyl-1-phenyl-propan-1-one (polymerization initiator Ib).
As a commercial item of the polymerization initiator Ia, as described above, Irgacure 2959 (trade name) (manufactured by BASF Japan Ltd.) can be mentioned.
As a commercial item of the polymerization initiator Ib, Darocur 1173 (trade name) (manufactured by BASF Japan Ltd.) can be mentioned.
The mass ratio [polymerization initiator Ib / polymerization initiator Ia] and the total content of the polymerization initiator Ia and the polymerization initiator Ib are as described above.

In the present invention, the content of the polymerization initiator Ia is not particularly limited as long as the total content and the mass ratio [polymerization initiator Ib / polymerization initiator Ia] are within the above-described ranges.
However, from the following viewpoints, the content of the polymerization initiator Ia is preferably 0.6% by mass or more, more preferably 0.7% by mass or more, and 1.0% by mass or more with respect to the total amount of the curable composition. More preferred is 1.5% by mass or more.
When the content of the polymerization initiator Ia is 0.6% by mass or more, the abrasion resistance of the image is further improved. In general, as the content of the polymerization initiator Ia increases, there is a tendency that precipitates are likely to be generated in a low temperature environment. However, in the curable composition of the present invention, as described above, Generation of precipitates can be suppressed.
On the other hand, the content of the polymerization initiator Ia is preferably 6.0% by mass or less, and more preferably 5.0% by mass or less, from the viewpoint of suppressing the generation of precipitates in a low temperature environment.

The curable composition of the present invention may appropriately contain a polymerization initiator other than the polymerization initiator Ia and the polymerization initiator Ib.
Other polymerization initiators may be selected as appropriate from compounds that can initiate a polymerization reaction with active energy rays. ) Can be used. For example, a photoinitiator or the like can be used.
Examples of other polymerization initiators include hydroxyalkylphenone initiators, acetophenone initiators, benzophenone initiators, benzoin initiators, benzoin ether initiators, aminoalkylphenone initiators, xanthone initiators, Examples include oxime initiators.
For example, examples of the hydroxyalkylphenone initiator include 1-hydroxycyclohexyl phenyl ketone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, and JP-A No. 2000-186242. Compound examples (29) to (33).
Examples of acetophenone-based initiators include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, and the like.
Examples of the benzophenone initiator include benzophenone, 2-chlorobenzophenone, p, p′-dichlorobenzophene, p, p′-bisdiethylaminobenzophenone, Michler's ketone, and the like.
Examples of the benzoin initiator and benzoin ether initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n-butyl ether and the like.

As described above, the curable composition of the present invention may contain at least one polymerization initiator other than the polymerization initiator Ia and the polymerization initiator Ib.
However, from the viewpoint of more effectively achieving the effects of the present invention, the total content of the polymerization initiator Ia and the polymerization initiator Ib is 80% by mass or more with respect to the total amount of the polymerization initiator contained in the curable composition. It is preferably 90% by mass or more, more preferably 95% by mass or more, particularly preferably 97% by mass or more, and 100% by mass (that is, curability). It is most preferable that the composition does not contain any other polymerization initiator other than the polymerization initiator Ia and the polymerization initiator Ib).

When the curable composition of the present invention contains at least one polymerization initiator other than the polymerization initiator Ia and the polymerization initiator Ib as the polymerization initiator, the total content of the polymerization initiator (the polymerization initiator Ia The total content of the polymerization initiator Ib and other polymerization initiators) is preferably 0.8% by mass to 10.0% by mass, and 1.0% by mass to 7.% by mass with respect to the total amount of the curable composition. 0 mass% is more preferable, 1.0 mass%-5.0 mass% is more preferable, and 1.5 mass%-4.5 mass% is especially preferable.
When the total content is 0.8% by mass or more, the abrasion resistance of the image is further improved.
Generation | occurrence | production of the precipitate in a low-temperature environment can be suppressed more as the said total content is 10.0 mass% or less. Furthermore, the total amount of non-volatile components can be reduced, thereby further improving the abrasion resistance of the image.

<Water>
The curable composition of the present invention contains water.
The content of water in the curable composition is not particularly limited, but the content can be 50% by mass or more.
In the curable composition having a water content of 50% by mass or more, precipitates resulting from the polymerization initiator Ia tend to be generated.
However, as described above, the curable composition of the present invention can suppress the generation of precipitates even in a low temperature environment.
Therefore, the curable composition of the present invention can contain 50% by mass or more of water.
The preferable content of water in the curable composition is preferably 50% by mass to 80% by mass, more preferably 50% by mass to 75% by mass, and still more preferably 60% by mass with respect to the total amount of the curable composition. It is mass%-70 mass%.

<Water-soluble solvent>
The curable composition of the present invention contains at least one water-soluble solvent.
As the water-soluble solvent, known ones can be used without particular limitation.
The water-soluble solvent is selected from the group consisting of a compound represented by the following general formula (A) and a compound represented by the following general formula (B) from the viewpoint of further suppressing the generation of precipitates in a low temperature environment. It is preferable that it is at least one kind.

In general formula (A), R ^A1 represents a linear or branched alkyl group having 1 to 6 carbon atoms. R ^A2 and R ^A3 each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.
In General Formula (B), W represents an atomic group that forms a heterocyclic ring together with the carbon atom and the nitrogen atom in General Formula (B).

(Compound represented by formula (A))
Hereinafter, the compound represented by the general formula (A), which is an example of the water-soluble solvent, will be described.
The compound represented by the general formula (A) is a β-alkoxypropionamide compound as described above.
In the curable composition, the compound represented by the general formula (A) can improve the compatibility between the polymerization initiator and water while maintaining the solubility of the polymerization initiator.
For this reason, when a curable composition contains the compound represented by general formula (A), even if a curable composition is set | placed in a low temperature environment, a polymerization initiator becomes difficult to precipitate. In addition, since this compound has a small environmental load and little odor, the curable composition is easy to handle.

In the general formula (A), the linear or branched alkyl group having 1 to 6 carbon atoms represented by R ^A1 is methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, tert-butyl. Group, n-pentyl group, n-hexyl group and the like.
In the general formula (A), examples of the linear or branched alkyl group having 1 to 6 carbon atoms represented by R ^A2 and R ^A3 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, Examples thereof include a tert-butyl group.

Among them, the alkyl group represented by R ^A1 preferably has 3 to 6 carbon atoms, and is a propyl group, isopropyl group, n-butyl group, tert-butyl group, n-pentyl group, and n-hexyl group. Is more preferable.
The alkyl group represented by R ^A2 or R ^A3 preferably has 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group.

  Although the exemplary compounds A-1 to A-33 of the compound represented by the general formula (A) are shown below, the compound represented by the general formula (A) is not limited thereto.

A-1: 3-methoxy-N, N-dimethylpropionamide A-2: 3-n-butoxy-N, N-dimethylpropionamide A-3: 3-ethoxy-N, N-diethylpropionamide A-4 : 3-methoxy-N, N-diethylpropionamide A-5: 3-methoxy-N, N-monomethylmonoethylpropionamide A-6: 3-methoxy-N, N-di-n-propylpropionamide A- 7: 3-methoxy-N, N-di-n-butylpropionamide A-8: 3-methoxy-N, N-di-n-butylpropionamide A-9: 3-ethoxy-N, N-dimethylpropion Amide A-10: 3-Ethoxy-N, N-monomethylmonoethylpropionamide A-11: 3-Ethoxy-N, N-di-n-propylpropionamide A-12: 3 Ethoxy-N, N-di-n-butylpropionamide A-13: 3-n-butoxy-N, N-diethylpropionamide A-14: 3-n-butoxy-N, N-monomethylmonoethylpropionamide A -15: 3-n-butoxy-N, N-di-n-propylpropionamide A-16: 3-n-butoxy-N, N-di-n-butylpropionamide A-17: 3-n-propoxy -N, N-dimethylpropionamide A-18: 3-n-propoxy-N, N-diethylpropionamide A-19: 3-n-propoxy-N, N-monomethylmonoethylpropionamide A-20: 3- n-propoxy-N, N-di-n-propylpropionamide A-21: 3-n-propoxy-N, N-di-n-butylpropionamide A-22: 3- so-propoxy-N, N-dimethylpropionamide A-23: 3-iso-propoxy-N, N-diethylpropionamide A-24: 3-1 so-propoxy-N, N-monomethylmonoethylpropionamide A-25 : 3-iso-propoxy-N, N-di-n-propylpropionamide A-26: 3-iso-propoxy-N, N-di-n-butylpropionamide A-27: 3-tert-butoxy-N , N-dimethylpropionamide A-28: 3-tert-butoxy-N, N-diethylpropionamide A-29: 3-tert-butoxy-N, N-monomethylmonoethylpropionamide A-30: 3-tert- Butoxy-N, N-di-n-propylpropionamide A-31: 3-tert-butoxy-N, N- Di-n-butylpropionamide A-32: 3-hexyloxy-N, N-dimethylpropionamide A-33: 3-hexyloxy-N, N-diethylpropionamide

The compound represented by general formula (A) may be used individually by 1 type, and may use 2 or more types together.
A specific method for producing the compound represented by the general formula (A) can be produced, for example, based on a synthesis method described in JP2009-185079A or International Publication No. 2008/102615. Moreover, the compound represented by general formula (A) may use a commercial item, for example, can be obtained as "Examide" by Idemitsu Kosan Co., Ltd.

  As the compound represented by the general formula (A), 3-n-butoxy-N, N-dimethylpropionamide (Exemplified Compound A-2 above) is most preferable.

(Compound represented by formula (B))
Next, the compound represented by General Formula (B), which is an example of a water-soluble solvent, will be described.
The compound represented by general formula (B) is a heterocyclic compound as the said structure.
The compound represented by the general formula (B) can also enhance the compatibility of the polymerization initiator and water while maintaining the solubility of the polymerization initiator in the curable composition.

In General Formula (B), W represents an atomic group that forms a heterocyclic ring together with the carbon atom and the nitrogen atom in General Formula (B).
W is preferably an alkylene group.
This alkylene group may be unsubstituted or substituted with a substituent. Examples of the substituent include an alkyl group (preferably a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms), a hydroxy group, a hydroxyalkyl group (preferably a hydroxyalkyl group having 1 to 6 carbon atoms). ) Is preferred.
The preferable range of the number of carbon atoms of the alkylene group (including the number of carbon atoms of the substituent when it has a substituent) is 1 to 10.
Moreover, the number of heterocycles in the general formula (B) is preferably 3-6.
Specific examples of the compound represented by the general formula (B) include 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, 1-butyl-2- Examples include pyrrolidone, 1-pentyl-2-pyrrolidone, 1-hexyl-2-pyrrolidone, 1-hydroxyethyl-2-pyrrolidone, 1-cyclohexyl-2-pyrrolidone and the like, particularly in terms of solubility of the polymerization initiator, 2-pyrrolidone is preferred.

When the curable composition of the present invention contains at least one selected from the group consisting of the compound represented by the general formula (A) and the compound represented by the general formula (B) as the water-soluble solvent,
The total content of the compound represented by the general formula (A) and the compound represented by the general formula (B) is preferably 2% by mass to 20% by mass with respect to the total amount of the curable composition.
The solubility to the curable composition of a polymerization initiator can be improved more because the said total content is 2 mass% or more.
Moreover, since a polymeric compound can fully be contained in a curable composition because the said total content is 20 mass% or less, sclerosis | hardenability of a curable composition can be improved.
The total content is more preferably 3% by mass to 18% by mass, further preferably 5% by mass to 15% by mass, and more preferably 8% by mass to 12% by mass with respect to the total amount of the curable composition. It is particularly preferred that

  Among the above, among the compound represented by the general formula (A) and the compound represented by the general formula (B), the viscosity of the curable composition is lowered, and the dischargeability of the curable composition is further improved. The compound represented by general formula (B) is especially preferable at the point which can be performed.

As the water-soluble solvent in the present invention, other water-soluble solvents other than the compound represented by the general formula (A) and the compound represented by the general formula (B) may be used.
Further, as the water-soluble solvent, at least one selected from the group consisting of the compound represented by the general formula (A) and the compound represented by the general formula (B) and another water-soluble solvent are used in combination. You can also.

Examples of other water-soluble solvents include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, and dipropylene glycol. Glycols, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, In addition to polyhydric alcohols such as alkanediols such as 1,2-pentanediol and 4-methyl-1,2-pentanediol, saccharides and sugar alcohols described in paragraph 0116 of JP2011-42150A, Hyaluronic acid having 1 to 4 carbon atoms Le kill alcohols, glycol ethers, and the like. These solvents can be used singly or in combination of two or more. Polyhydric alcohols are also useful as drying inhibitors and wetting agents, and examples include the examples described in paragraph 0117 of JP-A-2011-42150. Moreover, a polyol compound is preferable as a penetrant, and examples of the aliphatic diol include those described in paragraph 0117 of JP2011-42150A.
As other water-soluble solvents, for example, water-soluble solvents described in paragraphs 0176 to 0179 of JP2011-46872A, and paragraphs 0063 to 0074 of JP2013-18846A are described. It is also possible to appropriately select from the water-soluble solvents that are present.

When the curable composition of the present invention contains a water-soluble solvent, the content of the water-soluble solvent (the total content in the case of two or more) is 2% by mass to the total amount of the curable composition. It is preferably 20% by mass.
The solubility to the curable composition of a polymerization initiator can be improved more because the said total content is 2 mass% or more.
Moreover, since a polymeric compound can fully be contained in a curable composition because the said total content is 20 mass% or less, sclerosis | hardenability of a curable composition can be improved.
The total content is more preferably 3% by mass to 18% by mass, further preferably 5% by mass to 15% by mass, and more preferably 8% by mass to 12% by mass with respect to the total amount of the curable composition. It is particularly preferred that

<Polymerizable compound>
The curable composition of the present invention contains at least one polymerizable compound.
When the curable composition of the present invention is applied on a recording medium, it is cured by polymerization of the polymerizable compound contained in the curable composition. Thereby, the image formed using the curable composition of this invention is strengthened.

The polymerizable compound is preferably a water-soluble polymerizable compound.
Here, “water-soluble” means that it can be dissolved in water at a certain concentration or more. Specifically, the solubility in water at 25 ° C. is preferably 5% by mass or more, and more preferably 10% by mass or more. The water-soluble polymerizable compound is preferably one that can be dissolved (desirably uniformly) in the aqueous curable composition. Further, the solubility may be increased by adding a water-soluble solvent to be described later, and it may be dissolved (desirably uniformly) in the curable composition.

The polymerizable compound is not particularly limited, and may be a monofunctional polymerizable compound or a polyfunctional polymerizable compound.
A polyfunctional polymerizable compound is preferable in that it has high polymerizability and polymerization efficiency when the image is cured by irradiation with active energy rays, and can improve the abrasion resistance and scratch resistance of the formed image.

Moreover, as a polymeric compound, a (meth) acrylamide compound is preferable.
The “(meth) acrylamide compound” means at least one of a methacrylamide compound and an acrylamide compound. The (meth) acrylamide compound is a compound that has a (meth) acrylamide structure in the molecule and is polymerized when irradiated with active energy rays.

From the above points, polyfunctional (meth) acrylamide compounds are preferred.
Among polyfunctional (meth) acrylamide compounds, a (meth) acrylamide compound represented by the following general formula (1) (hereinafter simply represented by “general formula (1)” in that it has high polymerization ability and curing ability. Are also particularly preferred.
This compound has four acrylamide groups or methacrylamide groups as polymerizable groups in the molecule. In addition, this compound exhibits curability based on a polymerization reaction due to application of energy such as active energy rays such as α rays, γ rays, X rays, ultraviolet rays, visible rays, infrared rays, and electron beams, and heat. The compound represented by the general formula (1) exhibits water solubility and dissolves well in water-soluble solvents such as water and alcohol.

((Meth) acrylamide compound represented by general formula (1))
In the curable composition of the present invention, as described above, at least one of the polymerizable compounds is preferably a (meth) acrylamide compound represented by the following general formula (1).

In general formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms. However, R ² does not have a structure in which an oxygen atom and a nitrogen atom bonded to both ends of R ² are bonded to the same carbon atom of R ² . R ³ represents a divalent linking group. k represents 2 or 3. x, y, and z each independently represent an integer of 0 to 6, and x + y + z satisfies 0 to 18.

In general formula (1), R ¹ represents a hydrogen atom or a methyl group. Several R < ¹ > may mutually be same or different. R ¹ is preferably a hydrogen atom.

In the general formula (1), R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms. A plurality of R ² may be the same as or different from each other. R ² is preferably an alkylene group having 3 to 4 carbon atoms, more preferably an alkylene group having 3 carbon atoms, and particularly preferably a linear alkylene group having 3 carbon atoms. The alkylene group for R ² may further have a substituent, and examples of the substituent include an aryl group and an alkoxy group.
However, R ² does not have a structure in which an oxygen atom and a nitrogen atom bonded to both ends of R ² are bonded to the same carbon atom of R ² . R ² is a linear or branched alkylene group linking an oxygen atom and a nitrogen atom of the (meth) acrylamide group. When the alkylene group has a branched structure, the oxygen atom at both ends and the nitrogen of the (meth) acrylamide group It is also conceivable to take an —O—C—N— structure (hemaminal structure) in which an atom is bonded to the same carbon atom in an alkylene group. However, the compound represented by the general formula (1) does not include a compound having such a structure. Thereby, decomposition | disassembly in a position is suppressed to the carbon atom of a -O-C-N- structure, and the storage stability of a curable composition can be improved more.

In general formula (1), R ³ represents a divalent linking group. Examples of the divalent linking group for R ³ include an alkylene group, an arylene group, a heterocyclic group, or a group composed of a combination thereof, and an alkylene group is preferable. When the divalent linking group includes an alkylene group, the alkylene group may further include at least one group selected from —O—, —S—, and —NR ^a —. R ^a represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

When R ³ contains an alkylene group, examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, and a nonylene group. The number of carbon atoms of the alkylene group of R ³ is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1.
The alkylene group for R ³ may further contain at least one selected from —O—, —S—, and —NR ^a —. Examples of the alkylene group containing —O— include —C— ₂ H ₄ —O—C ₂ H ₄ —, —C ₃ H ₆ —O—C ₃ H ₆ — and the like can be mentioned.
The alkylene group for R ³ may further have a substituent, and examples of the substituent include an aryl group and an alkoxy group.

When R ³ includes an arylene group, examples of the arylene group include a phenylene group and a naphthylene group. The number of carbon atoms of the arylene group of R ³ is preferably 6 to 14, and is 6 to 10 More preferably, 6 is particularly preferable.
The arylene group for R ³ may further have a substituent, and examples of the substituent include an alkyl group and an alkoxy group.

When R ³ contains a heterocyclic group, the heterocyclic group is preferably a 5-membered or 6-membered ring, which may be further condensed. Further, it may be an aromatic heterocyclic ring or a non-aromatic heterocyclic ring. Specific examples of the heterocyclic group when R ³ includes a heterocyclic group include pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, cinnoline, phthalazine, quinoxaline, pyrrole, indole, furan, benzofuran, and thiophene. , Benzothiophene, pyrazole, imidazole, benzimidazole, triazole, oxazole, benzoxazole, thiazole, benzothiazole, isothiazole, benzisothiazole, thiadiazole, isoxazole, benzisoxazole, pyrrolidine, piperidine, piperazine, imidazolidine, thiazoline, etc. Is mentioned. Of these, an aromatic heterocyclic group is preferable, and pyridine, pyrazine, pyrimidine, pyridazine, triazine, pyrazole, imidazole, benzimidazole, triazole, thiazole, benzothiazole, isothiazole, benzisothiazole, and thiadiazole are preferable. In addition, although the heterocyclic group shown above is illustrated in a form in which the substitution position is omitted, the substitution position is not limited. For example, in the case of pyridine, substitution is made at the 2-position, 3-position, and 4-position. It is possible to include all of these substitutions. The heterocyclic group may further have a substituent, and examples of the substituent include an alkyl group, an aryl group, and an alkoxy group.

In general formula (1), k represents 2 or 3. Several k may mutually be same or different. C _k H _2k may have a linear structure or a branched structure.

  In general formula (1), x, y, and z each independently represent an integer of 0 to 6, preferably an integer of 0 to 5, and more preferably an integer of 0 to 3. x + y + z satisfies 0-18, is preferably 0-15, and is more preferably 0-9.

  Specific examples (polymerizable compounds a to f) of the compound represented by the general formula (1) are shown below, but the compound represented by the general formula (1) is not limited thereto.

  Although there is no restriction | limiting in particular in the synthesis | combining method of the compound represented by General formula (1), For example, it can synthesize | combine by the method described in Unexamined-Japanese-Patent No. 2013-18846 Paragraph 0028-0033 and Paragraph 0123-0139.

When the curable composition of the present invention contains the compound represented by the general formula (1) described above, the curable composition may contain only one type of the compound represented by the general formula (1). And you may contain 2 or more types.
When the curable composition of the present invention contains the compound represented by the general formula (1) described above, the content of the compound represented by the general formula (1) is based on the total amount of the curable composition. 0.1-45 mass% is preferable, 1-30 mass% is more preferable, and 2-20 mass% is especially preferable. When the content of the compound represented by the general formula (1) is within the above range, the curability and storage stability of the curable composition are further improved.

((Meth) acrylamide compound represented by general formula (2))
The curable composition of the present invention contains at least one (meth) acrylamide compound represented by the following general formula (2) (hereinafter also referred to as “compound represented by the general formula (2)”). Can do. Thereby, the flexibility of an image can be improved more.
In the curable composition of this invention, it is also preferable to use together the compound represented by General formula (1) mentioned above, and the compound represented by following General formula (2), for example.

In General Formula (2), R ¹⁰ represents a hydrogen atom or a methyl group, R ¹¹ represents a hydrogen atom, a methyl group, or an ethyl group, and R ¹² represents a substituted or unsubstituted alkyl group. R ¹¹ and R ¹² may combine with each other to form a 5- to 8-membered ring, and the 5- to 8-membered ring further contains at least one selected from —O—, —S—, and —NR ^b —. You may go out. R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In the general formula (2), R ¹⁰ represents a hydrogen atom or a methyl group, a hydrogen atom is preferable.
R ¹¹ represents a hydrogen atom, a methyl group or an ethyl group, preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.
R ¹² represents a substituted or unsubstituted alkyl group. As the alkyl group for R ¹² , a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group) is preferable, and the number of carbon atoms is 2 An alkyl group having ˜4 is more preferable, and an alkyl group having 2 or 3 carbon atoms is particularly preferable.

The alkyl group of R ¹² is preferably further substituted, and examples of the substituent include an acyl group, a hydroxyl group, a tertiary amino group, a quaternary ammonium group, and a sulfo group. Among these, R ¹² preferably has an acyl group, a hydroxyl group, or a dialkylamino group as a substituent, and more preferably has a hydroxyl group.

When R ¹² has an acyl group as a substituent, the acyl group is represented by —CO—R ′ (R ′ is an alkyl group), preferably an acyl group having 2 to 4 carbon atoms, and having 2 or 3 carbon atoms. Are more preferable, and an acyl group having 2 carbon atoms is particularly preferable. Specific examples of the acyl group include —COCH ₃ .
When R ¹² has a tertiary amino group as a substituent, the tertiary amino group is represented by —NR ″ ₂ (R ″ is a substituent). R ″ is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an alkyl group having 1 or 2 carbon atoms. Two R ″ may be the same as or different from each other. Specific examples of the tertiary amino group include a dimethylamino group and a diethylamino group.
When R ¹² has a quaternary ammonium group as a substituent, the quaternary ammonium group is represented by —N ⁺ R ′ ″ ₃ (R ′ ″ is a substituent). R ′ ″ is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an alkyl group having 1 or 2 carbon atoms. Three R ′ ″ may be the same as or different from each other. Specific examples of the quaternary ammonium group include a trimethylammonium group and a triethylammonium group. Further, examples of the counter anion of the quaternary ammonium group include halide ions such as chloride ions, bromide ions, and iodide ions, and sulfate ions.
If R ¹² has a sulfo group as a substituent, the sulfo group, sulfo group _(-SO 3 H) and salts thereof - including _(-SO ^{3 X +).} In the case of a salt, examples of the cation (X ⁺ ) include Li ⁺ , Na ⁺ , K ⁺ , ammonium cation and tetramethylammonium cation.

In the general formula (2), R ¹¹ and R ¹² may be bonded to each other to form a 5- to 8-membered ring. And at least one selected from —NR ^b —.
The ring structure formed by combining R ¹¹ and R ¹² with each other is preferably a 5- to 6-membered ring. The ring formed by combining R ¹¹ and R ¹² with each other preferably further contains at least one selected from —O—, —S—, and —NR ^b —, and includes —O—. Is more preferable.
R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

Specific examples of the compound represented by the general formula (2) include the following exemplary compounds (C-1) to (C-13), but the compound represented by the general formula (2) is limited to these. It is not something.
(C-1): Diacetone acrylamide (manufactured by Nippon Kasei Co., Ltd.)
(C-2): Hydroxyethylacrylamide (manufactured by Kojinsha)
(C-3): Hydroxypropylacrylamide (manufactured by Fluka)
(C-4): N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propenamide (manufactured by Aldrich)
(C-5): N- (2-dimethylaminoethyl) acrylamide (manufactured by Aldrich)
(C-6): Dimethylaminopropylacrylamide (manufactured by Kojinsha)
(C-7): 2- (acryloyloxy) -N, N, N-trimethylethaneaminium chloride (manufactured by Kojin Co., Ltd.)
(C-8): (3-acrylamidopropyl) trimethylammonium chloride (manufactured by Kojin Co., Ltd.)
(C-9): 2-acrylamido-2-methylpropanesulfonic acid (manufactured by Toa Gosei Co., Ltd.)
(C-10): N- [1,1-dimethyl-2- (sodiooxysulfonyl) ethyl] acrylamide (manufactured by Aldrich)
(C-11): N, N-dimethylacrylamide (manufactured by Kojinsha)
(C-12): N, N-diethylacrylamide (manufactured by Kojinsha)
(C-13): 4-acryloylmorpholine (manufactured by Kojin Co., Ltd.)

When the curable composition of the present invention contains the compound represented by the general formula (2) described above, the curable composition may contain only one type of the compound represented by the general formula (2). And you may contain 2 or more types.
When the curable composition of the present invention contains the compound represented by the above general formula (2), the preferred range of the content of the compound represented by the general formula (2) is the above general formula (1). It is the same as that of the preferable range of content of the compound represented by these.

In the curable composition of this invention, it is also preferable to use together the compound represented by General formula (1), and the compound represented by following General formula (2) as above-mentioned.
In this case, the content ratio (mass ratio [compound represented by general formula (1): compound represented by general formula (2))] is preferably 10:90 to 90:10, and 30:70 to 70:30 is more preferable, and 40:60 to 60:40 is particularly preferable.
It is preferable that the content ratio of both be in the above range since excellent performance can be exhibited in all of the curability, storage stability, ejection recovery property, and image flexibility of the curable composition.

Examples of the polymerizable compound in the present invention also include other polymerizable compounds other than the compound represented by the general formula (1) and the compound represented by the general formula (2).
In the present invention, the compound represented by the general formula (1) (and the compound represented by the general formula (2) as necessary) and other polymerizable compounds may be used in combination. Of course.
Examples of other polymerizable compounds include nonionic polymerizable monomers and cationic polymerizable monomers described in paragraphs 0149 to 0169 of JP-A-2011-46872.

  The content of the polymerizable compound in the curable composition of the present invention (the total content in the case of two or more) is preferably 0.1 to 45% by mass with respect to the total amount of the curable composition, 1-30 mass% is more preferable, and 2-20 mass% is still more preferable. When the content of the polymerizable compound is within the above range, the curability and storage stability of the curable composition are further improved.

In the curable composition of the present invention, the total content of the compound represented by the general formula (1) and the compound represented by the general formula (2) is contained in the curable composition. The total content is preferably 50% by mass or more (more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more).
In this embodiment, the generation of precipitates in a low temperature environment is further suppressed, and the image abrasion resistance is further improved.

<Color material>
The curable composition of the present invention may contain at least one coloring material.
The color material is not particularly limited, and may be a pigment or a dye.

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

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

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

-Dispersant-
When the curable composition of the present invention contains a coloring material, it can further contain at least one dispersant.
For example, when a pigment is used in the curable composition of the present invention, the pigment is preferably dispersed by a dispersant.
The pigment dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

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

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

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

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

  Among the polymer dispersants, as the water-insoluble dispersant, a polymer having both a hydrophobic portion and a hydrophilic portion can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include (meth) acrylate- (meth) acrylic acid copolymers, vinyl acetate-maleic acid copolymers, and styrene-maleic acid copolymers.

The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000. 000 to 40,000.
In addition, the weight average molecular weight of a polymer dispersing agent is measured similarly to the weight average molecular weight of the polymer which comprises the polymer particle mentioned later.

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

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

The curable composition of the present invention preferably contains a pigment and a dispersant, and preferably contains an organic pigment and a polymer dispersant (preferably a polymer dispersant containing a carboxyl group) from the viewpoints of image light resistance and quality. It is more preferable.
Further, the curable composition preferably contains a polymer-coated pigment in which at least a part of the pigment surface is coated with a polymer dispersant. Furthermore, the curable composition particularly preferably contains a polymer-coated pigment in which at least a part of the pigment surface is coated with a polymer dispersant having a carboxyl group. Furthermore, the curable composition particularly preferably contains a water-insoluble polymer-coated pigment in which at least a part of the pigment surface is coated with a polymer dispersant having a carboxyl group, from the viewpoint of aggregation.

The average particle size of the pigment in the dispersed state (for example, the average particle size of the polymer-coated pigment) is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, and the droplet ejection characteristics when droplets are ejected by the ink jet method are good. When the average particle size is 10 nm or more, light resistance is improved. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodispersed particle size distribution may be mixed and used. Here, the average particle diameter of the pigment in the dispersed state indicates the average particle diameter in the ink state, but the same applies to the so-called concentrated ink dispersion in the previous stage before the ink is formed.
The average particle size of the pigment in the dispersed state is determined in the same manner as the average particle size and particle size distribution of the polymer particles described later.

You may use a pigment individually by 1 type or in combination of 2 or more types.
As content in the curable composition of a pigment, 1 mass%-20 mass% are preferable with respect to a curable composition from a viewpoint of image density, and 2 mass%-10 mass% are more preferable.

(dye)
As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably.
Moreover, when using dye, what hold | maintained dye to the water-insoluble support | carrier may be used. The carrier holding the dye (water-insoluble colored particles) can be used as an aqueous dispersion using a dispersant. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.

<Polymer particles>
The curable composition of the present invention preferably contains at least one polymer particle from the viewpoint of further improving the abrasion resistance of the image.
The polymer particles are particles made of a polymer that is present separately from the pigment, unlike a polymer dispersant (a polymer dispersant that covers at least a part of the pigment) described later.
For example, when an image is formed by applying a curable composition onto a recording medium together with a treatment liquid described later, the polymer particles are brought into contact with the treatment liquid or a region where the treatment liquid has been dried. It has the function of fixing the curable composition by destabilizing and agglomerating and thickening in the product. Thereby, the abrasion resistance of the image is further improved. Furthermore, the adhesion of the curable composition to the recording medium is further improved.

On the other hand, generally, a composition containing the above-described polymerization initiator Ia, polymer particles, and water tends to generate precipitates in a low-temperature environment.
However, the curable composition of the present invention includes polymer particles by specifying the mass ratio [polymerization initiator Ib / polymerization initiator Ia] and the total content of the polymerization initiator Ia and the polymerization initiator Ib. Even if it is a case, generation | occurrence | production of the precipitate in a low-temperature environment can be suppressed.

The polymer particles are preferably polymer particles having a glass transition temperature of 90 ° C. or higher (hereinafter also referred to as “specific polymer particles”).
When the glass transition temperature of the polymer particles is 90 ° C. or higher, the abrasion resistance of the image is further improved.
The glass transition temperature is more preferably 100 ° C. or higher.
The glass transition temperature of the polymer particles is preferably 250 ° C. or lower, and more preferably 230 ° C. or lower. When the glass transition temperature of the polymer particles is 250 ° C. or lower, the polymer particles are fused in the drying process, and the image strength and abrasion resistance are further improved.

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

In the present invention, the measured Tg obtained by actual measurement is applied as the glass transition temperature (Tg) of the polymer particles.
Specifically, the measurement Tg means a value measured under normal measurement conditions using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology. However, when measurement is difficult due to polymer decomposition or the like, calculation Tg calculated by the following calculation formula is applied. The calculation Tg is calculated by the following equation (1).
1 / Tg = Σ (X _i / Tg _i ) (1)
Here, it is assumed that n types of monomer components from i = 1 to n are copolymerized in the polymer to be calculated. X _i is the weight fraction of the i-th monomer (ΣX _i = 1), and Tg _i is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. The homopolymer glass transition temperature value (Tg _i ) of each monomer is the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immersutt (Wiley-Interscience, 1989)).

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

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

  Examples of the self-dispersing polymer particles include, among the self-dispersing polymer particles described in paragraphs 0090 to 0121 of JP2010-64480A and paragraphs 0130 to 0167 of JP2011-066805A, glass. Those having a transition temperature of 90 ° C. or higher can be selected and used.

The polymer constituting the specific polymer particles (specific polymer; the same shall apply hereinafter) preferably has at least one of a structural unit having an aromatic group and a structural unit having an alicyclic group. Here, the alicyclic group is synonymous with the cyclic aliphatic group.
Thereby, the strength of the formed image can be further improved (for example, scratch resistance and blocking resistance).
In the present specification, the structural unit contained in the specific polymer may be referred to as “constituent component”.

(Structural unit having an aromatic group)
Examples of the structural unit having an aromatic group include a structural unit having a phenyl group, a structural unit having a benzyl group, a structural unit having a phenoxy group, and a structural unit having a phenethyl group. A structural unit and a structural unit having a phenoxy group (preferably a structural unit having a phenoxyethyl group) are preferred.

The structural unit having an aromatic group is preferably a structural unit derived from a monomer having an aromatic group (hereinafter also referred to as “aromatic group-containing monomer”).
The aromatic group-containing monomer is preferably a monomer having an aromatic group derived from an aromatic hydrocarbon and an ethylenically unsaturated bond. The aromatic group-containing monomers may be used singly or in combination of two or more.

Examples of the aromatic group-containing monomer include aromatic group-containing (meth) acrylate monomers (for example, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, etc.), styrene monomers, and the like. Can be mentioned. Of these, aromatic group-containing (meth) acrylate monomers are preferred from the viewpoint of the balance between hydrophilicity and hydrophobicity of polymer chains and fixing properties, and phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate. At least one selected from the above is more preferable, and phenoxyethyl (meth) acrylate and benzyl (meth) acrylate are more preferable.
“(Meth) acrylate” means acrylate or methacrylate.

(Structural unit having an alicyclic group)
The structural unit having an alicyclic group is preferably a structural unit derived from a monomer having an alicyclic group (hereinafter also referred to as “alicyclic group-containing monomer”).
The alicyclic group-containing monomer is preferably a monomer having an alicyclic group and an ethylenically unsaturated bond, and a (meth) acrylate having an alicyclic group (hereinafter referred to as “alicyclic (meth) acrylate”. Are also preferred).
The alicyclic (meth) acrylate includes a structural site derived from (meth) acrylic acid and a structural site derived from alcohol, and the structural site derived from alcohol is unsubstituted or substituted. It has a structure containing at least one hydrogen group. The alicyclic hydrocarbon group may be a structural part derived from alcohol itself or may be bonded to a structural part derived from alcohol via a linking group.

The alicyclic hydrocarbon group is not particularly limited as long as it contains a cyclic non-aromatic hydrocarbon group, and is a monocyclic hydrocarbon group, a bicyclic hydrocarbon group, a tricyclic or more polycyclic group. A hydrocarbon group is mentioned. Examples of the alicyclic hydrocarbon group include a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, a cycloalkenyl group, a bicyclohexyl group, a norbornyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantyl group. , Decahydronaphthalenyl group, perhydrofluorenyl group, tricyclo [5.2.1.0 ^2,6 ] decanyl group, and bicyclo [4.3.0] nonane.
The alicyclic hydrocarbon group may further have a substituent. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkoxy group, a hydroxyl group, a primary amino group, a secondary amino group, a tertiary amino group, an alkyl or arylcarbonyl group, and a cyano group. Is mentioned. Further, the alicyclic hydrocarbon group may further form a condensed ring. As an alicyclic hydrocarbon group in this invention, it is preferable that the carbon atom number of an alicyclic hydrocarbon group part is 5-20 from a viscosity or a soluble viewpoint.

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

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

  In the polymer constituting the specific polymer particle in the present invention, the total content of the structural unit having the aromatic group and the structural unit having the alicyclic group is 3% by mass to 95% by mass. preferable. When the total content is within this range, the stability of the self-emulsification or dispersion state can be improved, and further the increase in the viscosity of the curable composition can be suppressed.

  Moreover, when the removability (maintenance property) of the curable composition from a nozzle and the re-discharge property after removal are also considered, it is more preferable that the said specific polymer particle has a structural unit which has an aromatic group.

In a more preferred embodiment of the specific polymer particle, the polymer constituting the specific polymer particle includes a structural unit having the aromatic group, and the content of the structural unit having the aromatic group is 3 with respect to the total amount of the polymer. It is the form which is mass%-45 mass% (more preferably 3-40 mass%, especially preferably 5-30 mass%).
With this form, it becomes easier to adjust the glass transition temperature of the specific polymer particles to 90 ° C. or higher.

(Hydrophilic structural unit)
The polymer constituting the specific polymer particles preferably includes a hydrophilic constituent unit from the viewpoint of dispersibility in the curable composition (self-dispersibility in the case of self-dispersing polymer particles).
The hydrophilic structural unit is preferably a structural unit derived from a monomer having a hydrophilic group (hereinafter also referred to as “hydrophilic group-containing monomer”).
In this case, the hydrophilic structural unit may be derived from one type of hydrophilic group-containing monomer or may be derived from two or more types of hydrophilic group-containing monomers.
The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
The hydrophilic group is preferably a dissociable group and more preferably an anionic dissociable group from the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state. Examples of the dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Among these, a carboxyl group is preferable from the viewpoint of fixability when a curable composition is formed.

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

Specific examples of the unsaturated carboxylic acid monomer include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconate, and the like. Is mentioned.
Specific examples of the unsaturated phosphoric acid monomer include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, and dibutyl-2. -Acryloyloxyethyl phosphate and the like.
Among the dissociable group-containing monomers, an unsaturated carboxylic acid monomer is preferable and (meth) acrylic acid is more preferable from the viewpoints of dispersion stability and ejection stability.

  The content of the hydrophilic structural unit in the polymer constituting the specific polymer particle is not particularly limited, but from the viewpoint of dispersion stability, the content is 2% by mass with respect to the total amount of the specific polymer particle. -30 mass% is preferable, 5 mass%-20 mass% is more preferable, and 5 mass%-15 mass% is especially preferable.

(Structural unit having an alkyl group)
The polymer constituting the specific polymer particles preferably includes a structural unit having an alkyl group from the viewpoint of flexibility of the polymer skeleton and easy control of the glass transition temperature (Tg).
As for the carbon atom number of the alkyl group in the structural unit which has an alkyl group, 1-4 are preferable.
The structural unit having an alkyl group is preferably a structural unit derived from a monomer having an alkyl group (hereinafter also referred to as “alkyl group-containing monomer”).

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

  The content of the structural unit having an alkyl group in the polymer constituting the specific polymer particle is not particularly limited, but from the viewpoint of dispersion stability, the content is 5 mass with respect to the total amount of the specific polymer particle. % To 90% by weight, more preferably 30% to 90% by weight, still more preferably 40% to 90% by weight, particularly preferably 50% to 90% by weight, and most preferably 60% to 85% by weight. preferable.

  The polymer which comprises the said specific polymer particle may contain structural units other than the structural unit mentioned above as needed.

From the viewpoints of easily adjusting the glass transition temperature to 90 ° C. or more and maintaining good dispersion stability, preferred forms of the copolymerization ratio of the polymer constituting the specific polymer particles are as follows.
That is, the preferable form seen from the above viewpoint is that the polymer constituting the specific polymer particle is 3% by mass to 45% by mass in terms of a copolymerization ratio of the structural unit having the aromatic group (preferably benzyl group or phenoxy group). More preferably 3 to 40% by mass, particularly preferably 5 to 30% by mass) and a hydrophilic structural unit as a copolymerization ratio of 2 to 30% by mass (more preferably 5 to 20% by mass, particularly preferably). Is 5% by mass to 15% by mass) and 5% by mass to 90% by mass (more preferably 30% by mass to 90% by mass, and still more preferably 50% by mass to 90% by mass) with the structural unit having an alkyl group as a copolymerization ratio. %, Particularly preferably 60% by mass to 85% by mass).
A more preferable form of the specific polymer particle is 3% by mass to 45% by mass (more preferably) with at least one of a structural unit derived from benzyl (meth) acrylate or a structural unit derived from phenoxyethyl (meth) acrylate as a copolymerization ratio. 3 to 40% by mass, particularly preferably 5 to 30% by mass) and a structural unit derived from (meth) acrylic acid as a copolymerization ratio of 2 to 30% by mass (more preferably 5 to 20% by mass). , Particularly preferably 5% by mass to 15% by mass) and 40% by mass to 90% by mass (more preferably 50% by mass to 90% by mass), particularly preferably a structural unit derived from an alkyl (meth) acrylate. Is 60% by mass to 85% by mass).

  The molecular weight range of the polymer constituting the specific polymer particles is preferably 3000 to 200,000 in terms of weight average molecular weight, more preferably 5000 to 150,000, and still more preferably 10,000 to 100,000. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.

  In addition, the weight average molecular weight of the polymer which comprises specific polymer particles is measured by a gel permeation chromatograph (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns, and THF (tetrahydrofuran) as an eluent. ) Is used. As conditions, the sample concentration is 0.45% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The average particle diameter of the specific polymer particles (especially self-dispersing polymer particles) in the present invention is preferably in the range of 10 to 400 nm in terms of volume average particle diameter, more preferably in the range of 10 to 200 nm, and still more preferably in the range of 10 to 100 nm. Especially preferably, it is the range of 10-50 nm. Manufacturability is improved when the volume average particle diameter is 10 nm or more. Moreover, storage stability improves that a volume average particle diameter is 400 nm or less. The particle size distribution of the polymer particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Further, two or more kinds of the polymer particles may be mixed and used.
The average particle size and particle size distribution of the specific polymer particles are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is required.

When the curable composition of the present invention contains polymer particles (preferably specific polymer particles), there is no particular limitation on the content of the polymer particles (the total content when there are two or more types; the same applies hereinafter). However, 0.1% by mass to 10.0% by mass is preferable, 0.2% by mass to 7.0% by mass is more preferable, and 0.2% by mass to 7.0% by mass with respect to the total amount of the curable composition. % Is more preferable, and 0.5% by mass to 5.0% by mass is particularly preferable.
When the content is 0.1% by mass or more, the abrasion resistance of the image can be further improved.
Generation | occurrence | production of the precipitate in a low-temperature environment can be suppressed more as the said content is 10.0 mass% or less. Moreover, the discharge property of a curable composition can be improved more.

  When the curable composition of the present invention contains polymer particles (preferably specific polymer particles), the ratio between the content of the polymer particles and the content of the polymerization initiator Ia (mass ratio [polymer particle / polymerization initiator Ia]) is preferably 0.05 to 10.0, and particularly preferably 0.1 to 5.0.

<Wax particles>
The curable composition in the present invention can contain at least one wax particle. Thereby, abrasion resistance can be improved more.

  As wax particles, for example, plant waxes such as carnauba wax, candeli wax, beeswax, rice wax, lanolin, petroleum waxes such as animal wax, paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, petrolatum, Particles of natural wax or synthetic wax such as montan wax, mineral wax such as ozokerite, synthetic wax such as carbon wax, Hoechst wax, polyolefin wax, stearamide, α-olefin / maleic anhydride copolymer, etc. A mixed particle etc. are mentioned.

The wax is preferably added in the form of a dispersion. For example, the wax can be contained in the curable composition as a dispersion such as an emulsion. As a solvent in the case of a dispersion, water is preferable, but it is not limited thereto. For example, a commonly used organic solvent can be appropriately selected and used during dispersion. Regarding the organic solvent, reference can be made to the description of paragraph number [0027] of JP-A-2006-91780.
Wax particles can be used singly or as a mixture of plural kinds.

  As the wax particles, commercially available products may be used. Examples of commercially available products include Nopcoat PEM17 (manufactured by Sannopco), Chemipearl W4005 (manufactured by Mitsui Chemicals), AQUACER 515, AQUACER 593 (all of which are manufactured by Big Chemie Japan).

  Among the above, preferable waxes are carnauba wax and polyolefin wax, and carnauba wax is particularly preferable from the viewpoint of abrasion resistance.

  When the curable composition in the present invention contains polymer particles and wax particles, the content ratio of the polymer particles to the wax particles is in the range of polymer particles: wax particles = 1: 5 to 5: 1 (solid content ratio). ) Is preferable. When the content ratio is within this range, the image has excellent abrasion resistance.

<Surfactant>
The curable composition in this invention can contain at least 1 type of surfactant as needed. The surfactant can be used as a surface tension adjusting agent, for example.
As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactants, cationic surfactants, amphoteric surfactants, nonions Either a surfactant or a betaine surfactant can be used. Further, the above water-soluble polymer (polymer dispersing agent) may be used as a surfactant.

In the present invention, from the viewpoint of suppression of droplet ejection interference, a nonionic surfactant is preferable, and among them, an acetylene glycol derivative (acetylene glycol surfactant) is more preferable.
Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4, An alkylene oxide adduct of 7-diol can be used, and at least one selected from these is preferable. Examples of commercially available products of these compounds include E series such as Olphine E1010 manufactured by Nissin Chemical Industry Co., Ltd.

  When the surfactant (surface tension modifier) is contained in the curable composition, the surfactant has a surface tension of 20 to 20 from the viewpoint of favorably discharging the curable composition by an ink jet method. It is preferable to contain the quantity of the range which can be adjusted to 60 mN / m, More preferably, it is 20-45 mN / m from the point of surface tension, More preferably, it is 25-40 mN / m.

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

<Water-soluble polymer compound>
The curable composition in the present invention preferably contains at least one water-soluble polymer compound as required. The water-soluble polymer compound is not particularly limited, and known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, and polyethylene glycol can be used.
Further, as the water-soluble polymer compound, a specific polymer compound that may be contained in a treatment liquid described later, or a water-soluble polymer compound described in paragraphs 0026 to 0080 of JP2013-001854A is also suitable. is there.

<Antifoaming agent>
The curable composition of this invention may contain at least 1 type of antifoamer as needed.
Examples of the antifoaming agent include silicone compounds (silicone defoaming agents) and pluronic compounds (pluronic defoaming agents). Among these, silicone antifoaming agents are preferable.
As the silicone-based antifoaming agent, a silicone-based antifoaming agent having a polysiloxane structure is preferable.

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

  When the curable composition of this invention contains an antifoamer, 0.0001 mass%-1 mass% are preferable with respect to the curable composition whole quantity, and 0.001 mass%-content of an antifoamer is preferable. 0.1 mass% is more preferable.

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

  When the curable composition of this invention contains colloidal silica, 0.0001 mass%-10 mass% are preferable with respect to the whole quantity of a curable composition, and 0.01 mass%-3 mass are preferable. % Is more preferable, 0.02% by mass to 0.5% by mass is still more preferable, and 0.03% by mass to 0.3% by mass is particularly preferable.

<PH adjuster>
The curable composition of this invention may contain at least 1 type of pH adjusters as needed.
The pH adjuster is not particularly limited as long as it can adjust the pH to a desired value without adversely affecting the prepared curable composition, and can be appropriately selected according to the purpose. For example, alcohol amines (for example, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, etc.), alkali metal hydroxides (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide) Etc.), ammonium hydroxide (for example, ammonium hydroxide, quaternary ammonium hydroxide, etc.), phosphonium hydroxide, alkali metal carbonate and the like.
When the curable composition of the present invention contains a pH adjuster, the content of the pH adjuster is such that the pH of the curable composition is 5 to 10 (more preferably 8.0 to 9.5). preferable.

<Other ingredients>
The curable composition of this invention may contain another component as needed.
Other components include, for example, polymerization inhibitors, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, viscosity modifiers, and dispersion stabilizers. And known additives such as rust preventives and chelating agents.

In order to suppress bleeding by acid aggregation and obtain a high resolution, the curable composition of the present invention is preferably basic, and is preferably in the vicinity of neutrality in terms of high temperature aging stability of the curable composition.
Specifically, the liquidity (pH) of the curable composition is preferably pH 5 to pH 10. Further, the curable composition is more preferably pH 8.0 to pH 9.5. Moreover,
From the viewpoint of suppressing the load on the member used for image formation, the curable composition preferably has a pH of less than 9.5.

≪Curable composition set≫
The curable composition set of the present invention forms an aggregate when it comes into contact with the curable composition of the present invention described above (preferably the curable composition for inkjet. The same shall apply hereinafter) and the curable composition. And a treatment liquid containing an aggregating component.
Since the curable composition of the present invention is used in the curable composition set of the present invention, it is possible to suppress the generation of precipitates in a low temperature environment and to form an image having excellent abrasion resistance.
In particular, the curable composition set of the present invention has a treatment liquid, whereby the abrasion resistance of the image is further improved.

<Processing liquid>
Hereinafter, the treatment liquid will be described in detail.
When the treatment liquid applied to the recording medium comes into contact with the curable composition, the dispersed particles (such as pigments and polymer particles) in the curable composition are aggregated to fix the image on the recording medium. The treatment liquid contains at least an aggregating component for aggregating the components in the curable composition, may further contain a polymerization initiator, and may be constituted using other components as necessary. In addition, by using the treatment liquid together with the curable composition, it is possible to speed up ink jet recording, and an image with excellent density and resolution can be obtained (for example, reproducibility of fine lines and fine parts) even at high speed recording. .

(Aggregating component)
The treatment liquid contains at least one aggregation component.
The aggregation component may be a compound capable of changing the pH of the curable composition, a polyvalent metal salt, or a cationic polymer having a quaternary or tertiary amine such as polyallylamines. May be. In the present invention, from the viewpoint of cohesiveness of the curable composition, a compound capable of changing the pH of the curable composition is preferable, and a compound capable of lowering the pH of the curable composition is more preferable.

Examples of the compound capable of lowering the pH of the curable composition include acidic substances.
Examples of acidic substances include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, and tartaric acid. , Lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, or salts thereof Etc. are preferable.
An acidic substance may be used individually by 1 type, and may use 2 or more types together.

When the treatment liquid in the present invention contains an acidic substance, the pH (25 ° C.) of the treatment liquid is preferably 6 or less, more preferably 4 or less. Especially, pH (25 degreeC) has the preferable range of 1-4, Especially preferably, pH is 1-3. At this time, the pH (25 ° C.) of the curable composition is preferably 7.5 or more (more preferably 8.0 or more).
Among these, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ° C.) of the curable composition is 8.0 or more, and the pH (25 ° C.) of the treatment liquid is 0.5-4. Is preferred.

  Among them, the aggregation component in the present invention is preferably an acidic substance having high water solubility, preferably an organic acid, more preferably a divalent or higher valent organic acid in terms of enhancing the aggregation property and fixing the entire ink. Above-mentioned trivalent or less acidic substances are particularly preferred. The organic acid having a valence of 2 or more is preferably an organic acid having a first pKa of 3.5 or less, more preferably 3.0 or less. Specific examples include phosphoric acid, oxalic acid, malonic acid, citric acid and the like.

  As for the polyvalent metal salt and the cationic polymer, for example, the polyvalent metal salt and the cationic polymer described in paragraphs 0155 to 0156 of JP2011-042150A can be used.

The aggregating components can be used singly or in combination of two or more.
As content in the processing liquid of the aggregation component which aggregates a curable composition, 1-50 mass% is preferable, More preferably, it is 3-45 mass%, More preferably, it is the range of 5-40 mass%. .

(Water-soluble polymer compound)
The treatment liquid preferably contains at least one water-soluble polymer compound.
The water-soluble polymer compound is not particularly limited, and known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, and polyethylene glycol can be used.
As the water-soluble polymer compound, a specific polymer compound described later and water-soluble polymer compounds described in paragraphs 0026 to 0080 of JP2013-001854A are also suitable.

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

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

As the water-soluble polymer compound, a polymer compound containing a hydrophilic structural unit having an ionic group (preferably an anionic group) (hereinafter also referred to as “specific polymer compound”) is preferable. Thereby, the spreading of the ink droplets applied to the recording medium can be further promoted, and the roughness of the image is further suppressed.
Examples of the ionic group in the specific polymer compound include a carboxyl group, a sulfonic acid group, a phosphoric acid group, a boronic acid group, an amino group, an ammonium group, and salts thereof. Among them, preferred is a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a salt thereof, more preferred is a carboxyl group, a sulfonic acid group, or a salt thereof, and still more preferred is a sulfonic acid group or a salt thereof. It is salt.
The hydrophilic structural unit having an ionic group (preferably an anionic group) is preferably a structural unit derived from a (meth) acrylamide compound having an ionic group (preferably an anionic group).
The content of the hydrophilic structural unit having an ionic group (preferably an anionic group) in the water-soluble polymer compound is, for example, 10 to 100% by mass in the total mass of the water-soluble polymer compound. It is preferably 10 to 90% by mass, more preferably 10 to 70% by mass, further preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass.

The specific polymer compound includes at least one hydrophobic structural unit in addition to at least one hydrophilic structural unit having the ionic group (preferably anionic group, particularly preferably sulfonic acid group). More preferably. By including the hydrophobic structural unit, the specific polymer compound is more likely to be present on the surface of the treatment liquid, so that the spreading of the droplets of the curable composition applied to the recording medium is further promoted, and the roughness of the image is reduced. It is further suppressed.
As the hydrophobic structural unit, a structural unit derived from (meth) acrylic acid ester (preferably, alkyl ester having 1 to 4 carbon atoms of (meth) acrylic acid) is preferable.

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

(water)
The treatment liquid can be configured to contain water.
Although there is no restriction | limiting in particular in content of water, The range of 10-99 mass% is preferable, More preferably, it is 50-90 mass%, More preferably, it is 60-80 mass%.

(Organic solvent)
The treatment liquid preferably contains at least one selected from organic solvents.
As said organic solvent, the thing similar to the water-soluble solvent contained in the said curable composition can be used. Among these, from the viewpoint of curling suppression, polyalkylene glycol or a derivative thereof is preferable. Diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, polyoxypropylene More preferably, it is at least one selected from oxyethylene polyoxypropylene glycol.
The content of the organic solvent in the treatment liquid is not particularly limited, but from the viewpoint of curling suppression, it is preferably 1 to 30% by mass, and preferably 5 to 15% by mass with respect to the entire treatment liquid. More preferred.

(Defoamer)
The treatment liquid may contain at least one antifoaming agent as necessary.
Examples of the antifoaming agent that can be contained in the treatment liquid include the same antifoaming agents that can be contained in the curable composition.
When the processing liquid contains an antifoaming agent, the content of the antifoaming agent is preferably 0.0001% by mass to 1% by mass, and 0.001% by mass to 0.1% by mass with respect to the total amount of the processing liquid. More preferred.

(Polymerization initiator)
The treatment liquid can contain at least one polymerization initiator that starts polymerization of the polymerizable compound in the curable composition with active energy rays, in addition to the curable composition described above. A polymerization initiator can be used individually by 1 type or in mixture of 2 or more types or with a sensitizer.
As in the case of the curable composition, the polymerization initiator used in the treatment liquid can be appropriately selected from compounds that can initiate the polymerization reaction of the polymerizable compound with active energy rays. As an example of a polymerization initiator, the polymerization initiator (for example, photoinitiator etc.) which generate | occur | produces active species (a radical, an acid, a base, etc.) with a radiation or light, or an electron beam is mentioned.
Details of the polymerization initiator and the like are as described in the section of the curable composition.

  Further, the processing liquid may further contain other additives as other components within a range not impairing the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, anti-foaming agents. Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, an antirust agent, a chelating agent, are mentioned.

≪Image formation method≫
The image forming method of the present invention includes an applying step of applying the above-described curable composition of the present invention to a recording medium by an inkjet method to form an image.
Since the curable composition of the present invention is used in the image forming method of the present invention, fine images with good abrasion resistance are formed under various temperature environments including low temperature environments.

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

  In the image formation by the ink jet method, by applying energy, the curable composition described above is discharged onto a desired recording medium to form a colored image. As a preferable inkjet method for the present invention, the method described in paragraphs 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, An acoustic ink jet system that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, and a thermal ink jet that forms bubbles by heating the ink and uses the generated pressure (bubble jet (registered) Trademark)) method or the like. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
The inkjet method uses a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method used is included.

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

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

<Processing liquid application process>
The image forming method of the present invention preferably further includes a treatment liquid application step of applying a treatment liquid containing an aggregating component that forms an aggregate when contacted with the curable composition to a recording medium.
Thereby, the abrasion resistance of the image is further improved, and the image unevenness is further reduced.

  In the treatment liquid application step, a treatment liquid containing an aggregating component that aggregates the components in the curable composition is applied to the recording medium, and the treatment liquid is brought into contact with the curable composition to form an image. In this case, dispersed particles including polymer particles in the curable composition are aggregated, and the image is fixed on the recording medium. The treatment liquid contains at least an aggregating component, and details and preferred embodiments of each component are as described above.

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

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

The application amount of the treatment liquid is not particularly limited as long as the curable composition can be aggregated. However, it is preferable that the application amount of the aggregation component is 0.1 g / m ² or more. Especially, the quantity from which the provision amount of an aggregation component will be 0.2-0.7 g / m < ² > is preferable. When the application amount of the aggregating component is 0.1 g / m ² or more, good high-speed aggregating property can be maintained according to various usage forms of the curable composition. Moreover, it is preferable that the application amount of the aggregating component is 0.7 g / m ² or less from the viewpoint of not affecting the surface properties of the applied recording medium (change in gloss, etc.).

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

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

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

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

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper is liable to cause quality problems such as glossiness and scratch resistance of the image in normal aqueous inkjet image formation. However, in the image forming method of the present invention, gloss unevenness is suppressed and glossiness and resistance to abrasion are reduced. An image having good rubbing properties can be obtained. In particular, a coated paper having a base paper and a coating layer containing an inorganic pigment is preferably used, and a coated paper having a base paper and a coating layer containing at least one of kaolin and calcium bicarbonate is more preferably used. Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

<Inkjet recording apparatus>
The image forming apparatus that can be used in the image forming method of the present invention is not particularly limited, and is publicly known as described in JP 2010-830221 A, JP 2009-234221 A, JP 10-175315 A, and the like. The image forming apparatus can be used.
The image forming apparatus preferably includes an active energy ray (for example, ultraviolet ray) irradiation unit. For the configuration of other means including the active energy ray irradiation means, for example, a known configuration described in JP 2011-184628 A can be referred to as appropriate.

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

  As shown in FIG. 1, the ink jet recording apparatus includes a processing liquid application unit 12 including a processing liquid discharge head 12S that sequentially discharges a processing liquid in the recording medium conveyance direction (the arrow direction in the figure); A treatment liquid drying zone 13 provided with heating means (not shown) for drying the applied treatment liquid, an ink discharge section 14 for discharging various inks, and an ink drying zone 15 for drying the discharged ink are provided. Has been. Further, an ultraviolet irradiation unit 16 including an ultraviolet irradiation lamp 16S is disposed on the downstream side of the ink drying zone 15 in the conveyance direction of the recording medium.

  The recording medium supplied to the ink jet recording apparatus includes a processing liquid application unit 12, a processing liquid drying zone 13, and an ink discharging unit by a conveying roller from a paper feeding unit that feeds the recording medium from a case loaded with the recording medium. 14, the ink drying zone 15, and the ultraviolet irradiation unit 16 are sequentially sent and accumulated in the accumulation unit. In addition to the method using a conveyance roller, the conveyance may be performed by a drum conveyance method using a drum-shaped member, a belt conveyance method, a stage conveyance method using a stage, or the like.

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

  The treatment liquid application unit 12 is provided with a treatment liquid discharge head 12S connected to a storage tank that stores the treatment liquid. The treatment liquid ejection head 12S can eject the treatment liquid from ejection nozzles arranged to face the recording surface of the recording medium, and can apply the treatment liquid on the recording medium. The treatment liquid application unit 12 is not limited to a method of discharging from a nozzle-shaped head, and an application method using an application roller can also be adopted. In this coating method, the treatment liquid can be easily applied to almost the entire surface including the image area where the ink droplets land on the recording medium by the ink discharge unit 14 disposed on the downstream side. In order to make the thickness of the processing liquid on the recording medium constant, for example, an air knife or a member having a sharp corner is provided with a gap corresponding to the specified amount of the processing liquid provided between the recording medium and the recording medium. You may provide the method of doing.

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

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

  The ink discharge unit 14 is disposed downstream of the treatment liquid drying zone 13 in the recording medium conveyance direction. The ink discharge section 14 includes a recording head (ink discharge head) 30K connected to each of the ink storage sections that store ink of each color of black (K), cyan (C), magenta (M), and yellow (Y). , 30C, 30M, 30Y are arranged. Ink storage units (not shown) store inks corresponding to the respective hues, and are supplied to the respective ink ejection heads 30K, 30C, 30M, and 30Y as necessary for image recording. Yes. Further, as shown in FIG. 1, a recording head 30A for spot color ink discharge is provided on the downstream side in the transport direction of the ink discharge heads 30K, 30C, 30M, and 30Y so that spot color ink can be discharged as needed. 30B can be further provided.

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

  Each of the treatment liquid ejection head 12S and the ink ejection heads 30K, 30C, 30M, 30Y, 30A, and 30B has a large number of ejection openings over the maximum recording width (maximum recording width) of an image recorded on the recording medium. It is a full line head in which (nozzles) are arranged. Compared to the serial type in which recording is performed while reciprocating a short shuttle head in the width direction of the recording medium (direction perpendicular to the conveying direction on the recording medium conveying surface), it is possible to record an image on the recording medium at a higher speed. it can. In the present invention, either a serial type recording or a system capable of relatively high speed recording, for example, a single pass system in which one line is formed by one scan may be employed. According to this image recording method, a high-quality image with high reproducibility can be obtained even with the single pass method.

  Here, the treatment liquid discharge head 12S and the ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30B all have the same structure.

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

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

The ultraviolet irradiation unit 16 is arranged further downstream in the recording medium conveyance direction of the ink drying zone 15, and is irradiated with ultraviolet rays by an ultraviolet irradiation lamp 16S provided in the ultraviolet irradiation unit 16, and in the image after image drying. The monomer component is polymerized and cured. The ultraviolet irradiation lamp 16S irradiates the entire recording surface with a lamp disposed opposite to the recording surface of the recording medium, so that the entire image can be cured. The ultraviolet irradiation unit 16 is not limited to the ultraviolet irradiation lamp 16S, and a halogen lamp, a high-pressure mercury lamp, a laser, an LED, an electron beam irradiation device, or the like can also be employed.
The ultraviolet irradiation unit 16 may be installed either before or after the ink drying zone 15, or may be installed both before and after the ink drying zone 15.

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

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” and “%” are based on mass.
In the following examples, ink was prepared as a curable composition, and various evaluations were performed.

<Preparation of Polymer Dispersant 1 Solution>
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 5 parts of Bremer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2 -0.05 part of mercaptoethanol and 24 parts of methyl ethyl ketone were added to prepare a mixed solution. Meanwhile, in a dropping funnel, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 9 parts of Blenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid 2-mercaptoethanol (0.13 parts), methyl ethyl ketone (56 parts), and 2,2′-azobis (2,4-dimethylvaleronitrile) (1.2 parts) were added to prepare a mixed solution.
Thereafter, the mixed solution in the reaction vessel was heated to 75 ° C. with stirring in a nitrogen atmosphere, and the mixed solution in the dropping funnel was gradually dropped over 1 hour. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise over 3 hours. Aged at 80 ° C. for 2 hours to obtain a polymer dispersant 1 solution.

  For a part of the obtained polymer dispersant 1 solution, the weight average molecular weight measured by the measurement method described above was 25,000 in terms of polystyrene. The acid value of the polymer determined by the method described in JIS standard (JIS K0070: 1992) was 99 mgKOH / g.

<Preparation of pigment dispersion M>
5.0 g of the obtained polymer dispersant 1 solution in terms of solid content, 10.0 g of magenta pigment (Pigment Red 122, manufactured by Dainichi Seika Co., Ltd.), 40.0 g of methyl ethyl ketone, 1 mol / L (liters; the same applies hereinafter) 8.0 g of sodium hydroxide and 82.0 g of ion-exchanged water were supplied to a vessel together with 300 g of 0.1 mm zirconia beads and dispersed at 1000 rpm for 6 hours using a ready mill disperser (manufactured by Imex). The obtained dispersion was concentrated under reduced pressure using an evaporator until methyl ethyl ketone could be sufficiently distilled off, and further concentrated until the pigment concentration became 10% to prepare a pigment dispersion M of a polymer-coated magenta pigment.
The volume average particle size (secondary particles) of the obtained pigment dispersion M was measured using a dynamic light scattering method using a Microtrac particle size distribution analyzer (trade name Version 10.1.2-211BH, manufactured by Nikkiso Co., Ltd.). Was 84 nm.

<Preparation of pigment dispersion Y>
In the preparation of the pigment dispersion M, the same procedure as in the preparation of the pigment dispersion M was performed except that Irgalite Yellow GS (Pigment Yellow 74, manufactured by BASF Japan) was used instead of Pigment Red 122 used as the pigment. A pigment dispersion Y of polymer-coated yellow pigment was obtained. The volume average particle diameter (secondary particles) of the pigment dispersion Y measured in the same manner as in the pigment dispersion M was 75 nm.

<Preparation of pigment dispersion K>
In the preparation of the pigment dispersion M, the same procedure as in the preparation of the pigment dispersion M was performed except that carbon black MA-100 (manufactured by Mitsubishi Chemical Corporation; black pigment) was used instead of Pigment Red 122 used as the pigment. Thus, a pigment dispersion K of the polymer-coated black pigment was obtained. The volume average particle diameter (secondary particles) of the pigment dispersion K measured in the same manner as in the pigment dispersion M was 80 nm.

<Preparation of pigment dispersion C>
As pigment dispersion C, CABO-JET250C (Pigment Blue 15: 4 (PB15: 4); cyan pigment dispersion manufactured by CABOT Co., Ltd.) was prepared. The pigment dispersion C is a pigment dispersion of a polymer-coated cyan pigment in which PB15: 4 is coated with a polymer. The volume average particle diameter (secondary particles) of pigment dispersion C measured in the same manner as pigment dispersion M was 110 nm.

<Synthesis of polymerizable compound>
A polymerizable compound a, which is an exemplary compound of the (meth) acrylamide compound represented by the general formula (1), was synthesized.
This synthesis was performed according to the method described in paragraphs 0123 to 0128 of JP2013-18846A.

<Synthesis of self-dispersing polymer particles P-1 (polymer particles)>
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. Thereafter, while maintaining the temperature in the flask at 75 ° C., 151.2 g of benzyl methacrylate, 172.8 g of methyl methacrylate, 36.0 g of methacrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) 1 .44 g of the mixed solution was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution composed of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added thereto, stirred at 75 ° C. for 2 hours, and further a solution composed of 0.72 g of “V-601” and 36.0 g of isopropanol. And stirred at 75 ° C. for 2 hours. Thereafter, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours to obtain a polymer solution of a benzyl methacrylate / methyl methacrylate / methacrylic acid (= 42/48/10 [mass ratio]) copolymer.
The weight average molecular weight (Mw) measured in the same manner as described above of the obtained copolymer was 58000 (calculated in terms of polystyrene by gel permeation chromatography (GPC)), and the acid value was 32.6 mgKOH / g. It was.

  Next, 668.3 g of the obtained polymer solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added thereto, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water, and then the reaction vessel internal temperature was 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure. Kept. Thereafter, the pressure in the reaction vessel is reduced, and 913.7 g of isopropanol, methyl ethyl ketone, and distilled water are distilled off in total, and the self-dispersing polymer particles P-1 (polymer particles) having a solid content concentration (polymer particle concentration) of 28.0% by mass ) Was obtained.

Among the constituents (structural units) of the self-dispersing polymer particles P-1, constituents derived from benzyl methacrylate (structural units), constituents derived from methyl methacrylate (structural units), and constituents derived from methacrylic acid Hereinafter, (structural unit) is also referred to as “component A”, “component B”, and “component C”, respectively.
In addition, the mass ratio of the constituent component A, the constituent component B, and the constituent component C [the mass of the constituent component A / the mass of the constituent component B / the mass of the constituent component C] is hereinafter referred to as the mass ratio of the constituent components [A / B / C].

It was 90 degreeC when the glass transition temperature (Tg) of the said self-dispersing polymer particle P-1 was measured with the following method.
-Measurement of glass transition temperature (Tg)-
An aqueous dispersion of self-dispersing polymer particles having a solid content of 0.5 g was dried under reduced pressure at 50 ° C. for 4 hours to obtain a polymer solid content. Using the obtained polymer solid content, Tg was measured with a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nanotechnology. 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. → 120 ° C. (temperature rising at 20 ° C./min)
120 ° C to -50 ° C (cooled at 50 ° C / min)
−50 ° C. → 120 ° C. (temperature rising at 20 ° C./min)

The self-dispersing polymer particles P-1 are polymer particles used for the preparation of the following ink 5 and the like.
In the synthesis of the self-dispersing polymer particles P-1, the type of component A and the mass ratio of each component [component A / component B / component C]) were changed as shown in Table 5 below. Except for the above, self-dispersing polymer particles used in the inks 51 to 57 were synthesized in the same manner as the self-dispersing polymer particles P-1.

<Synthesis of water-soluble polymer compound (water-soluble polymer)>
A water-soluble polymer compound (water-soluble polymer 1) used as a component in the treatment liquid was synthesized. This synthesis was performed according to paragraphs 0200 to 0204 and 0229 of JP2013-001854A.
The structure of the water-soluble polymer 1 is shown below.
In the water-soluble polymer 1 shown below, the number on the lower right of each structural unit represents a mass ratio (mass%), and Mw represents a weight average molecular weight.

[Experimental Example 1]
As Experimental Example 1, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (polymerization initiator Ia) in the ink (curable composition) ) And 2-hydroxy-2-methyl-1-phenyl-propan-1-one (polymerization initiator Ib), an experiment on the content ratio (mass ratio [polymerization initiator Ib / polymerization initiator Ia]) went.
Hereinafter, the details will be described with a focus on the experiment on the ink 5 in Table 1.

<Preparation and Evaluation of Ink 5>
(Preparation of ink 5)
Components of the following composition were mixed, and coarse particles were removed through a membrane filter (pore size: 0.5 μm) to obtain ink 5 (curable composition) as a black ink.
The pH of the prepared ink 5 was 8.8.
-Composition of ink 5-
-Pigment dispersion K 20.0% by mass
-Pigment dispersion M: 4.2% by mass
-Pigment dispersion C: 4.2% by mass
Hydroxyethyl acrylamide (manufactured by Hayato Co., Ltd.) (specific example of compound represented by general formula (2)): 7.0% by mass
Polymerizable compound a (specific example of compound represented by general formula (1)): 8.0% by mass
・ Polymerization initiator Ia (BASF Japan (manufactured by “Irgacure 2959”))
... 2.0% by mass
・ Polymerization initiator Ib (BASF Japan (manufactured by DAROCURE 1173))
... 1.0% by mass
3-n-butoxy-N, N-dimethylpropionamide (Exemplary Compound A-2 of the compound represented by Formula (A)): 5.0% by mass
・ 2-Pyrrolidone (specific example of the compound represented by formula (B)): 2.0% by mass
・ Glycerin: 1.0% by mass
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1.0% by mass
-Self-dispersing polymer particles P-1: 1.2% by mass
・ Snowtex XS (Nissan Chemical Co., Ltd., colloidal silica): 0.3% by mass
-BYK-024 (Bic Chemie Japan Co., Ltd., antifoaming agent) ... 0.01% by mass
・ Triethanolamine: 0.2% by mass
・ Ion-exchanged water: Remaining amount when 100% by mass as a whole

<Evaluation of precipitate after low-temperature storage>
100 ml of ink 5 was placed in 200 ml polybin and stored for 7 days under low temperature conditions (low temperature storage). The bottom of the polybin after low-temperature storage was visually observed, and the precipitate after low-temperature storage (precipitate after storing the ink at low temperature) was evaluated according to the following evaluation criteria.
This evaluation was performed for two low temperature conditions of + 5 ° C. and −5 ° C., respectively.
The evaluation results are shown in Table 1 below.

-Evaluation criteria for deposits after low temperature storage-
A: No deposits are observed even after storage for 7 days under low temperature conditions.
B: Only a small amount of precipitate is observed after storage for 7 days under low temperature conditions (the ink is completely filtered through a microfilter, and there is a slight amount of precipitate on the filter and / or on the wall surface of the polybin). It is a level that can be confirmed).
C: Many powdery deposits are observed after storage for 7 days under low temperature conditions.
D: Many large crystalline precipitates are observed after storage for 7 days under low temperature conditions.

<Image formation and evaluation>
A GELJET GX5000 printer head manufactured by Ricoh Co., Ltd. was prepared.
This printer head is a line head in which 96 nozzles are arranged.
This printer head was fixedly arranged in an ink jet recording apparatus having the same configuration as the ink jet recording apparatus shown in FIG.
The arrangement at this time was such that the direction in which the 96 nozzles were aligned was inclined by 75.7 ° with respect to the direction orthogonal to the moving direction of the stage of the inkjet apparatus.
The storage tank connected to the printer head was filled with the supernatant of ink 5 stored at −5 ° C. for 7 days.

The processing liquid was prepared by mixing components having the following composition.
-Composition of treatment liquid-
・ Diethylene glycol monoethyl ether: 5.0% by mass
・ Tripropylene glycol monomethyl ether: 5.0% by mass
-Malonic acid: 8.0% by mass
・ Malic acid: 8.0% by mass
・ Phosphoric acid 85%… 5.0% by mass
・ The aforementioned water-soluble polymer 1 0.5 mass%
・ Antifoamer (Momentive Performance Materials Japan TSA-739 (15%); emulsion type silicone antifoam)
… 0.01% by mass as silicone oil
・ Ion-exchanged water: Remaining amount of 100% by mass

  The pH (25 ° C.) of the treatment liquid was 1.0. The pH was measured while adjusting the temperature to 25 ° C. with a pH meter WM-50EG manufactured by Toa DKK.

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

-Treatment liquid application process-
An OK top coat was fixed on a stage movable in a linear direction at 500 mm / second, and each of the treatment liquids obtained above was applied thereto with a wire bar coater so as to be about 1.7 g / m ² .
-Drying process-
At the place where the application of the treatment liquid is completed, drying of the recording medium is started under the condition of 50 ° C. using a dryer after 1.5 seconds from the end of the application of the treatment liquid to the place. The drying was finished 3.5 seconds after the end of the application of the. The drying time at this time is 2 seconds.
-Granting process-
Within 2 seconds after the drying step, ink ejection was started by the following method.

--- Drip ejection method--
While moving the recording medium at a constant speed in the moving direction of the stage, the ink 5 is ejected from the printer head under the ejection conditions of an ink droplet amount of 3.5 pL, an ejection frequency of 24 kHz, a resolution of 1200 dpi × 1200 dpi, and a stage speed of 50 mm / s. It was ejected by the line method, and a solid image was printed. The ink 5 was degassed through a degassing filter and temperature-controlled at 30 ° C.
The solid image immediately after printing was dried at 60 ° C. for 3 seconds, and the solid image after curing was irradiated with UV (ultraviolet rays) to cure the solid image.

Irradiation of the above UV (ultraviolet light) is performed by using a metal halide lamp (maximum irradiation wavelength: 365 nm) manufactured by Eye Graphics Co., Ltd., and controlling the light source power and the conveyance speed to achieve an illuminance of 1.5 W / cm ² (integrated irradiation). (Amount: 0.75 J / cm ² )

(Evaluation of image abrasion resistance)
Immediately after recording a 100% solid image having a width of about 6 mm on the recording medium, the same recording as that used for recording was performed on the recorded solid image (hereinafter also referred to as “recorded image”). The operation was carried out by rubbing 10 reciprocations with a load of 150 kg / m ² over the medium. After this operation, the scratches on the recorded image and the degree of ink transfer to the recording medium not recorded were visually observed, and the abrasion resistance of the image was evaluated according to the following evaluation criteria.
The evaluation results are shown in Table 1 below.

-Evaluation criteria for image abrasion resistance-
A: There was no transfer of ink to a recording medium that was not recorded.
B: Scratches are hardly observed in the recorded image, but a slight transfer of ink to the recording medium not recorded is recognized.
C: Slight scratches on the recorded image are recognized, and the ink is transferred to a recording medium that is not recorded.
D: The scratch of the recorded image is remarkable, and the transfer of the ink to the recording medium not recorded is also remarkable.

<Preparation and Evaluation of Inks 1-4 and 6-16>
Inks 1 to 4 and 6 to 16 were respectively prepared in the same manner as the preparation of ink 5 except that the type of self-dispersing polymer particles and the type of polymerization initiator were changed as shown in Table 1 below. Each of these inks was evaluated in the same manner as ink 5.
The evaluation results are shown in Table 1 below.

-Description of Table 1-
• Irgacure 2959 is 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (polymerization initiator Ia).
Darocur 1173 is 2-hydroxy-2-methyl-1-phenyl-propan-1-one (polymerization initiator Ib).
The “mass ratio of Darocur 1173 to Irgacure 2959” corresponds to the content ratio of the polymerization initiator Ib to the polymerization initiator Ia on the mass basis (the aforementioned mass ratio [polymerization initiator Ib / polymerization initiator Ia]). .

As shown in Table 1, in the ink of the present invention in which the mass ratio of Darocur 1173 to Irgacure 2959 is 0.2 to 1.5, the generation of precipitates after low-temperature storage is suppressed, and the image has excellent abrasion resistance. It was.
On the other hand, in the inks 1 and 2 (both were comparative examples) having a mass ratio of less than 0.2, the generation of precipitates after low-temperature storage was significant. With these inks, the abrasion resistance of the image was also significantly reduced. The reason for this is considered to be that image formation was performed using the supernatant liquid of the ink stored for 7 days under the condition of −5 ° C. in the evaluation of the abrasion resistance of the image. That is, the deposition of the polymerization initiator by this storage reduces the substantial content of the polymerization initiator in the ink (supernatant liquid) used for image formation, thereby reducing the curability of the image. Possible cause.
In addition, in the inks 10 and 11 (both are comparative examples) having a mass ratio of more than 1.5, the abrasion resistance of the image was significantly reduced. The reason for this is considered to be that when the ratio of the polymerization initiator Ib is increased, the polymerization initiator Ib remains in the image area as in the case where the solvent is increased, and as a result, the film strength is decreased.

[Experimental example 2]
As Experimental Example 2, an experiment related to the type of polymerization initiator was performed.
Specifically, in the ink 5 of Experimental Example 1, an ink was prepared in the same manner as the ink 5 except that the type of the polymerization initiator was changed as shown in Table 2 below, and the same evaluation as the ink 5 was performed. .
The evaluation results are shown in Table 2 below.

-Description of Table 2-
Irgacure 184: Alkylphenone polymerization initiator (compound name: 1-hydroxy-cyclohexyl-phenyl-ketone) manufactured by BASF Japan Ltd.
Irgacure 819: Acylphosphine oxide polymerization initiator (compound name: bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide) manufactured by BASF Japan Ltd.
Irgacure 127: Alkylphenone-based polymerization initiator (compound name: 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} manufactured by BASF Japan Ltd. -2-methyl-propan-1-one)
Irgacure 907: Alkylphenone polymerization initiator (compound name: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one) manufactured by BASF Japan Ltd.
Darocur TPO: Acylphosphine oxide polymerization initiator (compound name: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) manufactured by BASF Japan Ltd.

  As shown in Table 2, in the ink of the comparative example using a combination other than the combination of Irgacure 2959 (polymerization initiator Ia) and Darocur 1173 (polymerization initiator Ib) as a polymerization initiator, precipitates were observed during low-temperature storage. Occurred, and the abrasion resistance of the image was significantly reduced.

[Experimental Example 3]
As Experimental Example 3, an experiment related to the type of water-soluble solvent was performed.
Specifically, in the ink 5 of Experimental Example 1, an ink was prepared in the same manner as the ink 5 except that the type of the water-soluble solvent was changed as shown in Table 3 below, and the same evaluation as the ink 5 was performed. .
The evaluation results are shown in Table 3 below.
In Table 3 below, 3-n-butoxy-N, N-dimethylpropionamide in Ink 5 was designated as “Solvent Type 1”, and 2-pyrrolidone in Ink 5 was designated as “Solvent Type 2”.
The contents of the solvent type 1 and the solvent type 2 are common to the inks except for the inks 31 and 32. In inks 31 and 32, the amount of solvent type 1 was the total amount of solvent type 1 and solvent type 2 in ink 5.

-Description of Table 3-
S-1: 3-n-butoxy-N, N-dimethylpropionamide (Exemplary Compound A-2 of the compound represented by Formula (A))
S-2: 3-n-propoxy-N, N-dimethylpropionamide (Exemplary Compound A-17 of the compound represented by Formula (A))
S-3: 3-methoxy-N, N-dimethylpropionamide (Exemplary Compound A-1 of the compound represented by Formula (A))
S-4: 2-pyrrolidone (specific example of the compound represented by the general formula (B))
S-5: 1-hydroxyethyl-2-pyrrolidone (specific example of compound represented by formula (B))
S-6: 1-ethyl-2-pyrrolidone (specific example of compound represented by general formula (B))
S-7: 1-cyclohexyl-2-pyrrolidone (specific example of the compound represented by the general formula (B))
S-8: Sannix GP250 (manufactured by Sanyo Chemical Industries, Ltd .; polyoxypropylated glycerin water-soluble solvent)
・ S-9: Dipropylene glycol

  As shown in Table 3, as a water-soluble solvent, the ink (ink 5, ink 31 to 39) containing the compound represented by the general formula (A) or the compound represented by the general formula (B) is stored at a low temperature. The generation of subsequent precipitates was remarkably suppressed.

[Experimental Example 4]
As Experimental Example 4, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (polymerization initiator Ia) and 2-hydroxy- in the ink were used. Experiments on the total content with 2-methyl-1-phenyl-propan-1-one (polymerization initiator Ib) were performed.
Specifically, in the ink 5 of Experimental Example 1, the “ink ratio of Darocur 1173 to Irgacure 2959” was fixed at 0.5, and the total amount of these was changed as shown in Table 4 below. Ink was prepared in the same manner as described above, and the same evaluation as in ink 5 was performed.
The evaluation results are shown in Table 4 below.

As shown in Table 4, when the total amount of Irgacure 2959 and Darocur 1173 is 0.8 mass% to 10.0 mass% (preferably 1.0 mass% to 7.0 mass%), it is stored at low temperature. It was confirmed that the generation of subsequent precipitates was suppressed.
On the other hand, with the ink 43 (comparative example) having a total amount of less than 0.8% by mass, the abrasion resistance of the image was lowered.
Further, in the ink 47 (comparative example) in which the total amount exceeds 10.0% by mass, the generation of precipitates after low-temperature storage was significant.

[Experimental Example 5]
As Experimental Example 5, an experiment relating to the glass transition temperature of polymer particles contained in the ink was performed.
Specifically, in the ink 5 of Experimental Example 1, an ink was prepared in the same manner as the ink 5 except that the type of the self-dispersing polymer particles was changed as shown in Table 5 below. went.
The evaluation results are shown in Table 5 below.

  As shown in Table 5, it was confirmed that when the glass transition temperature of the polymer particles is 90 ° C. or higher, the abrasion resistance of the image is remarkably improved.

[Experimental Example 6]
The following inks were prepared, and the prepared inks were evaluated in the same manner as the ink 5 of Experimental Example 1. As in the case of the ink 5, the generation of precipitates after low-temperature storage was suppressed, and the image was rub-resistant. It was excellent.

-Composition of ink of Experimental Example 6-
-Pigment dispersion K 20.0% by mass
-Pigment dispersion M: 4.2% by mass
-Pigment dispersion C: 4.2% by mass
Diacetone acrylamide (manufactured by Nippon Kasei Co., Ltd.) (specific example of compound represented by general formula (2)): 7.0% by mass
Polymerizable compound a (specific example of compound represented by general formula (1)): 8.0% by mass
・ Polymerization initiator Ia (BASF Japan (manufactured by “Irgacure 2959”))
... 1.5% by mass
・ Polymerization initiator Ib (BASF Japan (manufactured by DAROCURE 1173))
... 1.0% by mass
・ The following compound X (polymerization initiator): 0.5% by mass
・ 2-Pyrrolidone (specific example of compound represented by formula (B)): 8.0% by mass
・ Glycerin: 2.0% by mass
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., surfactant): 1.0% by mass
-Self-dispersing polymer particles P-1: 1.2% by mass
・ Snowtex XS (Nissan Chemical Co., Ltd., colloidal silica): 0.3% by mass
・ Ion-exchanged water: Remaining amount when 100% by mass as a whole

[Experimental Example 7]
As Experimental Example 7, the following magenta ink, cyan ink, and yellow ink were prepared, and the same experiment as in Experimental Example 1 was performed using these inks.
Here, the magenta ink was prepared in the same manner as the ink 5 except that only the pigment dispersion M was used as the pigment dispersion.
Cyan ink was prepared in the same manner as ink 5 except that only pigment dispersion C was used as the pigment dispersion.
The yellow ink was prepared in the same manner as ink 5 except that only pigment dispersion Y was used as the pigment dispersion.
As a result, in any of the inks, the same effects as those of the ink 5 in Experimental Example 1 were obtained with respect to the suppression of the generation of precipitates after storage at low temperature and the improvement of the abrasion resistance of the image.

DESCRIPTION OF SYMBOLS 12 ... Treatment liquid provision part 12S ... Treatment liquid discharge head 13 ... Treatment liquid drying zone 14 ... Ink discharge part 15 ... Ink drying zone 16 ... Ultraviolet irradiation part 16S ... Ultraviolet irradiation lamps 30K, 30C, 30M, 30Y ... Ink ejection head

Claims (13)

Water, a water-soluble solvent, a polymerizable compound, and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one as a polymerization initiator Ia; 2-hydroxy-2-methyl-1-phenyl-propan-1-one as a polymerization initiator Ib,
The total content of the polymerization initiator Ia and the polymerization initiator Ib is 0.8% by mass to 10.0% by mass with respect to the total amount of the curable composition,
The content ratio of the polymerization initiator Ib against polymerization initiator Ia is Ri 0.2 times to 1.5 Baidea a mass basis,
The water content is 50% by mass or more based on the total amount of the curable composition,
The curable composition whose content of the said water-soluble solvent is 2 mass%-20 mass% with respect to curable composition whole quantity .   The curable composition according to claim 1, wherein the total content is 1.0% by mass to 7.0% by mass.   The curable composition according to claim 1 or 2, wherein the content ratio is 0.3 to 0.9 times on a mass basis.   Furthermore, the curable composition of any one of Claims 1-3 containing a coloring material.   It is a curable composition for inkjets, The curable composition of any one of Claims 1-4. The water-soluble solvent includes at least one selected from the group consisting of a compound represented by the following general formula (A) and a compound represented by the following general formula (B). The curable composition according to item 1.

[In General Formula (A), R ^A1 represents a linear or branched alkyl group having 1 to 6 carbon atoms. R ^A2 and R ^A3 each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.
In General Formula (B), W represents a divalent linking group that forms a heterocyclic ring with the carbon atom and nitrogen atom in General Formula (B). ]   The curable composition according to any one of claims 1 to 6, wherein the water-soluble solvent contains 3-n-butoxy-N, N-dimethylpropionamide.   The curable composition according to any one of claims 1 to 7, wherein the water-soluble solvent contains 2-pyrrolidone. The curable composition according to any one of claims 1 to 8, wherein at least one of the polymerizable compounds is a (meth) acrylamide compound represented by the following general formula (1).

[In General Formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms. However, R ² does not have a structure in which an oxygen atom and a nitrogen atom bonded to both ends of R ² are bonded to the same carbon atom of R ² . R ³ represents a divalent linking group. k represents 2 or 3. x, y, and z each independently represent an integer of 0 to 6, and x + y + z satisfies 0 to 18. ] Furthermore, the curable composition of Claim 9 containing the (meth) acrylamide compound represented by following General formula (2).

[In General Formula (2), R ¹⁰ represents a hydrogen atom or a methyl group, R ¹¹ represents a hydrogen atom, a methyl group or an ethyl group, and R ¹² represents a substituted or unsubstituted alkyl group. R ¹¹ and R ¹² may combine with each other to form a 5- to 8-membered ring, and the 5- to 8-membered ring further contains at least one selected from —O—, —S—, and —NR ^b —. You may go out. R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]   Furthermore, the curable composition of any one of Claims 1-10 containing the polymer particle whose glass transition temperature is 90 degreeC or more. The curable composition according to any one of claims 1 to 11,
A treatment liquid comprising an aggregating component that forms an aggregate when contacted with the curable composition;
A curable composition set having: A curable composition set according to claim 12 is used,
A treatment liquid application step of applying the treatment liquid to a recording medium;
An application step of applying the curable composition to a recording medium by an inkjet method to form an image;
An image forming method comprising: