JP7023202B2 - A method for producing a resin dispersion for water-based inkjet ink, an ink composition for water-based inkjet ink, and a resin dispersion for water-based inkjet ink. - Google Patents

Description

The present invention relates to a resin dispersion for water-based inkjet ink, an ink composition for water-based inkjet ink, and a method for producing a resin dispersion for water-based inkjet ink.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are recording methods such as an electrophotographic method, a sublimation type and melt type thermal transfer method, and an inkjet method.
Since the inkjet recording method does not require a printing plate and ejects ink only to the image forming portion to form an image directly on the recording medium, the ink can be used efficiently and the running cost is low. Further, in the inkjet recording method, the printing device is relatively low in cost as compared with the conventional printing machine, can be miniaturized, and has less noise. As described above, the inkjet recording method has various advantages over other image recording methods.

The water-based inkjet ink (hereinafter, also simply referred to as “ink”) generally contains a colorant such as a pigment and a hydrophilic solvent, and further, in order to impart abrasion resistance and the like to the formed image portion. Contains binder resin. As this binder resin, resin fine particles capable of achieving low viscosity even with a high solid content concentration are often used from the viewpoint of enhancing characteristics such as ink storage stability and ejection stability.
For example, Patent Document 1 describes a monomer mixture containing a styrene monomer, a (meth) acrylic acid alkyl ester monomer having a specific alkyl chain length, a carboxy group-containing monomer, an alkoxysilyl group-containing monomer, and a surfactant monomer in specific amounts. Described is a resin dispersion for an aqueous inkjet ink, which comprises resin particles having an average particle diameter of 30 to 100 nm obtained by emulsion polymerization of the above, and an aqueous medium. According to Patent Document 1, by using this resin dispersion, it is possible to achieve both ink physical characteristics such as storage stability and ejection property and coating film physical properties such as gloss, abrasion resistance, water resistance and solvent resistance. Will be done.
Further, in Patent Document 2, an aqueous ink composition containing at least an aqueous medium and a specific amount of resin fine particles composed of a resin having a specific structure has excellent ejection stability, and after ejection, a treatment agent is applied on the recording medium. It is described that the agglomeration is quick due to the action of the water-based ink composition, and the color density of the image portion formed by this water-based ink composition is enhanced.

Japanese Patent No. 6115694 International Publication No. 2016/159504

When the water-based ink contains coarse particles (aggregates of pigments, aggregates of resin fine particles, etc.), when this water-based ink is applied to an inkjet recording method, the coarse particles clog the head and the desired ejection stability is achieved. Cannot be obtained. Therefore, the dispersion of the resin fine particles to be blended in the water-based ink is usually subjected to a filtration treatment to remove coarse particles before use.
For the preparation of the resin fine particles used for the water-based ink, an emulsification polymerization method which has a small number of steps and is advantageous in terms of cost is often adopted. In one form of this emulsion polymerization method, a polymerization-reactive emulsifier is used as an emulsifier (surfactant). In this case, the emulsifier itself is also added as a monomer by the polymerization reaction and incorporated into the polymer to obtain a reaction solution (resin dispersion) in which the target polymer exists as a finely divided dispersoid. However, in emulsion polymerization using a polymerization-reactive emulsifier as an emulsifier, the amount of the polymerization-reactive emulsifier used is limited. Therefore, the resin fine particles formed in the emulsion polymerization reaction solution generally tend to aggregate, and the reaction solution is inferior in filterability. Further, even when an aqueous inkjet ink is prepared by using this reaction liquid as a resin dispersion, the ink tends to be inferior in storage stability, ejection property and the like.

Therefore, the present invention is a resin dispersion for water-based inkjet ink in which a resin composed of a polymer having a polymerization-reactive emulsifying component as a component is dispersed in an aqueous medium, and water-based inkjet is used as a source of resin fine particles. It is an object of the present invention to provide a resin dispersion capable of making the obtained water-based inkjet ink excellent in storage stability and ejection property by blending with ink. Another object of the present invention is to provide a water-based inkjet ink composition containing resin fine particles, having excellent storage stability and excellent ejection properties. Further, the present invention is a method for producing a resin dispersion for an aqueous inkjet ink, which comprises obtaining an aqueous resin dispersion by emulsion polymerization using a polymerization-reactive emulsifier as an emulsifier and filtering the aqueous resin dispersion by emulsion polymerization. The above-mentioned aqueous resin dispersion obtained has excellent filterability, and by blending the filtered aqueous resin dispersion into the aqueous inkjet ink as a source of resin fine particles, the aqueous inkjet has excellent storage stability and ejection property. An object of the present invention is to provide a method for producing a resin dispersion capable of obtaining ink.

As a result of diligent studies in view of the above problems, the present inventors have obtained a monomer having a specific structure as a part of the raw material monomer in the preparation of resin fine particles for aqueous inkjet ink by emulsion polymerization using a polymerization-reactive emulsifier as an emulsifier. By using it, the aqueous resin dispersion, which is a reaction solution containing the polymer after emulsion polymerization, exhibits excellent filterability, and the aqueous inkjet ink containing the aqueous resin dispersion after the filtration treatment is stable in storage. We have found that it has excellent properties and excellent ejection properties.
The present invention has been further studied based on these findings and has been completed.

一般式（１）中、
Ｒは水素原子又は炭素数１～４のアルキル基を示し、
Ｌは炭素数１～１０のアルキレン基を示し、
ｎは２以上の整数であり、
＊はポリマー中に組み込まれる連結部位を示す。
但し、上記樹脂微粒子が、表面に電荷を有する芯物質がポリマーを主成分とする壁材によって被覆したカプセル化物である形態を除く。
〔２〕
上記ポリマー中の重合反応性乳化剤成分の含有量が１～１０質量％である、〔１〕に記載の水性インクジェットインク用樹脂分散体。
〔３〕
上記ポリマーが、イオン性基を有さず且つ芳香族環構造を有する構成成分を有する、〔１〕又は〔２〕に記載の水性インクジェットインク用樹脂分散体。
〔４〕
上記重合反応性乳化剤成分がカルボキシ基の塩及びスルホ基の塩から選ばれる構造を有する、〔１〕～〔３〕のいずれかに記載の水性インクジェットインク用樹脂分散体。
〔５〕
上記重合反応性乳化剤成分を導く重合反応性乳化剤のＨＬＢ値が１５以下である、〔１〕～〔４〕のいずれかに記載の水性インクジェットインク用樹脂分散体。
〔６〕
上記重合反応性乳化剤成分が炭素数６以上のアルキル基を有する、〔１〕～〔５〕のいずれかに記載の水性インクジェットインク用樹脂分散体。
〔７〕
上記ポリマー中、上記重合反応性乳化剤成分の含有量Ｘと上記一般式（１）で表される構成成分の含有量Ｚとの比が、質量比でＸ：Ｚ＝３：１～１００：１を満たす、〔１〕～〔６〕のいずれかに記載の水性インクジェットインク用樹脂分散体。
〔８〕
上記重合反応性乳化剤成分の少なくとも一部が下記一般式（Ｉ）で表される、〔１〕～〔７〕のいずれかに記載の水性インクジェットインク用樹脂分散体。

一般式（Ｉ）中、
Ｒ^１は水素原子又は炭素数１～４のアルキル基を示し、
Ａ^１は－Ｏ－又は－ＮＲ^３－を示し、
Ｒ^３は水素原子又は炭素数１～４のアルキル基を示し、
Ｌ^１は炭素数６～２２のアルキレン基を示し、
Ｍ^１は水素原子、アルカリ金属イオン又はアンモニウムイオンを示す。
＊はポリマー中に組み込まれる連結部位を示す。
〔９〕
樹脂微粒子と、水性媒体とを含有する水性インクジェット用インク組成物であって、
上記樹脂微粒子を構成するポリマーが、重合反応性乳化剤成分と、下記一般式（１）で表される構成成分とを有し、上記ポリマー中の上記一般式（１）で表される構成成分の含有量が０．１～１５質量％である、水性インクジェット用インク組成物。

一般式（１）中、
Ｒは水素原子又は炭素数１～４のアルキル基を示し、
Ｌは炭素数１～１０のアルキレン基を示し、
ｎは２以上の整数であり、
＊はポリマー中に組み込まれる連結部位を示す。
但し、上記樹脂微粒子が、表面に電荷を有する芯物質がポリマーを主成分とする壁材によって被覆したカプセル化物である形態を除く。
〔１０〕
上記水性インクジェット用インク組成物が着色剤を含有する、〔９〕に記載の水性インクジェット用インク組成物。
〔１１〕
上記ポリマー中の重合反応性乳化剤成分の含有量が１～１０質量％である、〔９〕又は〔１０〕に記載の水性インクジェット用インク組成物。
〔１２〕
上記ポリマーが、イオン性基を有さず且つ芳香族環構造を有する構成成分を有する、〔９〕～〔１１〕のいずれかに記載の水性インクジェット用インク組成物。
〔１３〕
上記重合反応性乳化剤成分がカルボキシ基の塩及びスルホ基の塩の少なくともいずれかの構造を有する、〔９〕～〔１２〕のいずれかに記載の水性インクジェット用インク組成物。
〔１４〕
上記重合反応性乳化剤成分を導く重合反応性乳化剤のＨＬＢ値が１５以下である、〔９〕～〔１３〕のいずれかに記載の水性インクジェット用インク組成物。
〔１５〕
上記重合反応性乳化剤成分が炭素数６以上のアルキレン基を有する、〔９〕～〔１４〕のいずれかに記載の水性インクジェット用インク組成物。
〔１６〕
上記ポリマー中、上記重合反応性乳化剤成分の含有量Ｘと上記一般式（１）で表される構成成分の含有量Ｚとの比が、質量比でＸ：Ｚ＝３：１～１００：１を満たす、〔９〕～〔１５〕のいずれかに記載の水性インクジェット用インク組成物。
〔１７〕
上記重合反応性乳化剤成分の少なくとも一部が下記一般式（Ｉ）で表される、〔９〕～〔１６〕のいずれかに記載の水性インクジェット用インク組成物。

一般式（Ｉ）中、
Ｒ^１は水素原子又は炭素数１～４のアルキル基を示し、
Ａ^１は－Ｏ－又は－ＮＲ^３－を示し、
Ｒ^３は水素原子又は炭素数１～４のアルキル基を示し、
Ｌ^１は炭素数６～２２のアルキレン基を示し、
Ｍ^１は水素原子、アルカリ金属イオン又はアンモニウムイオンを示す。
＊はポリマー中に組み込まれる連結部位を示す。
〔１８〕
乳化重合によりモノマーを重合して水性媒体中に樹脂微粒子が分散してなる水性樹脂分散体を得て、この水性樹脂分散体をろ過処理することを含む水性インクジェットインク用樹脂分散体の製造方法であって、
乳化剤として重合反応性乳化剤を用い、かつ、全モノマーに占める下記一般式（１ａ）で表されるモノマーの割合を０．１～１５質量％として上記乳化重合を行う、水性インクジェットインク用樹脂分散体の製造方法。

式（１ａ）中、
Ｒは水素原子又は炭素数１～４のアルキル基を示し、
Ｌは炭素数１～１０のアルキレン基を示し、
ｎは２以上の整数である。
但し、前記樹脂微粒子が、表面に電荷を有する芯物質がポリマーを主成分とする壁材によって被覆したカプセル化物である形態を除く。
That is, the above problem of the present invention is solved by the following means.
[1]
A resin dispersion for an aqueous inkjet ink containing resin fine particles and an aqueous medium, wherein the polymer constituting the resin fine particles contains a polymerization-reactive emulsifier component as a constituent component and a constituent component represented by the following general formula (1). A resin dispersion for an aqueous inkjet ink, wherein the content of the component represented by the general formula (1) in the polymer is 0.1 to 15% by mass.

In general formula (1),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 10 carbon atoms.
n is an integer greater than or equal to 2
* Indicates the connection site incorporated into the polymer.
However, the above-mentioned resin fine particles exclude the form in which the core substance having an electric charge on the surface is an encapsulated material coated with a wall material containing a polymer as a main component.
[2]
The resin dispersion for water-based inkjet ink according to [1], wherein the content of the polymerization-reactive emulsifier component in the polymer is 1 to 10% by mass.
[3]
The resin dispersion for an aqueous inkjet ink according to [1] or [2], wherein the polymer has a component having no ionic group and having an aromatic ring structure.
[4]
The resin dispersion for an aqueous inkjet ink according to any one of [1] to [3], wherein the polymerization-reactive emulsifier component has a structure selected from a carboxy group salt and a sulfo group salt.
[5]
The resin dispersion for water-based inkjet ink according to any one of [1] to [4], wherein the HLB value of the polymerization-reactive emulsifier that leads to the polymerization-reactive emulsifier component is 15 or less.
[6]
The resin dispersion for an aqueous inkjet ink according to any one of [1] to [5], wherein the polymerization-reactive emulsifier component has an alkyl group having 6 or more carbon atoms.
[7]
In the polymer, the ratio of the content X of the polymerization-reactive emulsifier component to the content Z of the component represented by the general formula (1) is X: Z = 3: 1 to 100: 1 in mass ratio. The resin dispersion for an aqueous inkjet ink according to any one of [1] to [6], which satisfies the above conditions.
[8]
The resin dispersion for water-based inkjet ink according to any one of [1] to [7], wherein at least a part of the polymerization-reactive emulsifier component is represented by the following general formula (I).

In general formula (I),
R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
A ¹ indicates -O- or -NR ^3- , and
R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L ¹ represents an alkylene group having 6 to 22 carbon atoms.
M ¹ represents a hydrogen atom, an alkali metal ion or an ammonium ion.
* Indicates the connection site incorporated into the polymer.
[9]
A water-based inkjet ink composition containing resin fine particles and a water-based medium.
The polymer constituting the resin fine particles has a polymerization-reactive emulsifier component and a component represented by the following general formula (1), and the component represented by the general formula (1) in the polymer. A water-based inkjet ink composition having a content of 0.1 to 15% by mass.

In general formula (1),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 10 carbon atoms.
n is an integer greater than or equal to 2
* Indicates the connection site incorporated into the polymer.
However, the above-mentioned resin fine particles exclude the form in which the core substance having an electric charge on the surface is an encapsulated material coated with a wall material containing a polymer as a main component.
[10]
The water-based inkjet ink composition according to [9], wherein the water-based inkjet ink composition contains a colorant.
[11]
The water-based inkjet ink composition according to [9] or [10], wherein the content of the polymerization-reactive emulsifier component in the polymer is 1 to 10% by mass.
[12]
The water-based inkjet ink composition according to any one of [9] to [11], wherein the polymer has a component having no ionic group and having an aromatic ring structure.
[13]
The water-based inkjet ink composition according to any one of [9] to [12], wherein the polymerization-reactive emulsifier component has at least one structure of a carboxy group salt and a sulfo group salt.
[14]
The water-based inkjet ink composition according to any one of [9] to [13], wherein the HLB value of the polymerization-reactive emulsifier that leads to the polymerization-reactive emulsifier component is 15 or less.
[15]
The water-based inkjet ink composition according to any one of [9] to [14], wherein the polymerization-reactive emulsifier component has an alkylene group having 6 or more carbon atoms.
[16]
In the polymer, the ratio of the content X of the polymerization-reactive emulsifying component to the content Z of the component represented by the general formula (1) is X: Z = 3: 1 to 100: 1 in mass ratio. The water-based inkjet ink composition according to any one of [9] to [15], which satisfies the above conditions.
[17]
The water-based inkjet ink composition according to any one of [9] to [16], wherein at least a part of the polymerization-reactive emulsifier component is represented by the following general formula (I).

In general formula (I),
R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
A ¹ indicates -O- or -NR ^3- , and
R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L ¹ represents an alkylene group having 6 to 22 carbon atoms.
M ¹ represents a hydrogen atom, an alkali metal ion or an ammonium ion.
* Indicates the connection site incorporated into the polymer.
[18]
A method for producing a resin dispersion for an aqueous inkjet ink, which comprises polymerizing a monomer by emulsion polymerization to obtain an aqueous resin dispersion in which resin fine particles are dispersed in an aqueous medium, and filtering the aqueous resin dispersion. There,
A resin dispersion for aqueous inkjet ink, in which a polymerization-reactive emulsifier is used as an emulsifier and the emulsion polymerization is carried out with the proportion of the monomer represented by the following general formula (1a) in the total monomers being 0.1 to 15% by mass. Manufacturing method.

In equation (1a),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 10 carbon atoms.
n is an integer of 2 or more.
However, the form in which the resin fine particles are encapsulated in which the core substance having an electric charge on the surface is coated with a wall material containing a polymer as a main component is excluded.

In the present specification, unless otherwise specified, when there are a plurality of substituents, linking groups, repeating units, etc. (hereinafter referred to as substituents, etc.) indicated by a specific reference numeral, or a plurality of substituents, etc. are simultaneously or selected. When defined uniformly, the substituents and the like may be the same or different from each other. This also applies to the regulation of the number of substituents and the like.
In the present specification, the "group" of each group described as an example of each substituent and a linking group is used to include both an unsubstituted form and a form having a substituent, unless otherwise specified. For example, "alkyl group" means an alkyl group which may have a substituent.
In the present invention, when the number of carbon atoms of a certain group is specified, the number of carbon atoms means the number of carbon atoms of the entire group. That is, when this group is in the form of further having a substituent, it means the total number of carbon atoms including this substituent.
As used herein, the term "(meth) acrylate" is used to include both acrylate and methacrylate. This also applies to "(meth) acrylic acid", "(meth) acrylamide", and "(meth) acryloyl".
The numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.

The resin dispersion for water-based inkjet ink of the present invention is excellent in storage stability and ejection property of the water-based inkjet ink obtained by blending it with water-based inkjet ink as a source of resin fine particles of water-based inkjet ink. Can be. The water-based inkjet ink composition of the present invention is excellent in storage stability and ejection property.
The method for producing a resin dispersion for an aqueous inkjet ink of the present invention comprises obtaining an aqueous resin dispersion by emulsion polymerization using a polymerization-reactive emulsifier as an emulsifier and filtering it, and is obtained by the above emulsion polymerization. The filterability of the aqueous resin dispersion can be improved, and the aqueous resin dispersion after filtration can be blended with the aqueous inkjet ink as a source of resin fine particles to store the obtained aqueous inkjet ink with excellent storage stability. In addition, it can be excellent in ejection property.

A preferred embodiment of the present invention will be described.

[Resin dispersion for water-based inkjet ink]
The resin dispersion for water-based inkjet ink of the present invention (hereinafter, also referred to as “resin dispersion of the present invention”) is composed of an aqueous medium and a polymer having specific constituents dispersed in the aqueous medium. It contains at least the obtained resin fine particles and is suitably used as a source of the resin fine particles to be blended in the water-based inkjet ink.

<Aqueous medium>
The aqueous medium used for the resin dispersion of the present invention contains at least water, and if necessary, contains at least one of water-soluble organic solvents. The content of the aqueous medium in the resin dispersion of the present invention is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more. The content of the aqueous medium in the resin dispersion of the present invention is usually 98% by mass or less, more preferably 95% by mass or less.
As the water used for the resin dispersion of the present invention, it is preferable to use water that does not contain ionic impurities such as ion-exchanged water and distilled water. The proportion of water in the aqueous medium constituting the resin dispersion is appropriately selected according to the intended purpose, and is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 80% by mass or more, and 90% by mass. Mass% is particularly preferred. It is also preferable that all of the aqueous media constituting the resin dispersion are water.
The type of the water-soluble organic solvent that can be used for the resin dispersion of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an aqueous medium that can be used in an ink composition for an aqueous inkjet described later can be mentioned.

<Resin fine particles>
In the resin fine particles contained in the resin dispersion of the present invention, the polymer constituting the resin fine particles has a polymerization-reactive emulsifier component as a constituent component, and also has a constituent component represented by the general formula (1) described later. The above polymer may have one kind of polymerization reactive emulsifier component or two or more kinds. In addition, the above polymer has one or more of the constituents represented by the general formula (1). The above polymer usually has a component other than the polymerization-reactive emulsifier component and a component other than the component represented by the general formula (1).

(Polymerization reactive emulsifier component)
The above-mentioned polymerization-reactive emulsifier component is a component derived from the polymerization-reactive emulsifier, which is incorporated into the polymer by the polymerization reaction between the polymerization-reactive emulsifiers or the polymerization reaction between the polymerization-reactive emulsifier and another monomer. The polymerization-reactive emulsifier that leads to the polymerization-reactive emulsifier component is a monomer having a polymerizable group and having a surface-active group (that is, having both a hydrophilic group and a hydrophobic group). The polymerization-reactive emulsifier preferably has a carbon-carbon double bond (ethylenically unsaturated bond) or a carbon-carbon triple bond as a polymerizable group, and more preferably has a carbon-carbon double bond. Examples of the polymerizable group include a vinyl group, a vinylidene group, a propenyl group, an isopropenyl group, a (meth) acryloyl group, and an isobutylidene group.

Polymerization-reactive emulsifiers are classified into anionic, cationic, and nonionic, depending on the type of hydrophilic group of the polymerization-reactive emulsifier. The polymerization-reactive emulsifier used in the present invention is preferably anionic. Among them, the polymerization-reactive emulsifier used in the present invention preferably has at least one structure of a carboxy group salt or a sulfo group salt as a hydrophilic group.
The polymerization-reactive emulsifier used in the present invention preferably has an HLB value of 15 or less from the viewpoint of storage stability. The HLB value of the polymerization-reactive emulsifier is preferably 6 or more. The HLB value is a value determined by the Griffin method (WC Griffin, J.Soc.Cosmetic.Chemists., 1949, vol.1, p.311).

The polymerization-reactive emulsifier used in the present invention preferably has an alkyl group having 6 or more carbon atoms as a hydrophobic group from the viewpoint of ink ejection stability. This alkyl group may be linear or branched. The alkyl group preferably has 6 to 22 carbon atoms, more preferably 8 to 18 carbon atoms. The alkyl group having 6 or more carbon atoms which can be possessed by the polymerization reactive emulsifier used in the present invention may be unsubstituted or having a substituent. When it has a substituent, the substituent is preferably an ionic group, and examples of the ionic group include a carboxy group or a salt thereof, a sulfo group or a salt thereof, a phosphoric acid group or a salt thereof, and the like. The ionic group that can be possessed by an alkyl group having 6 or more carbon atoms is more preferably a carboxy group or a salt thereof.

In the resin fine particles contained in the resin dispersion of the present invention, at least a part of the polymerization-reactive emulsifier component which is a component of the polymer constituting the resin fine particles is represented by the following general formula (I) or (II). It is preferable, and it is more preferable that it is represented by the following general formula (I). It is preferable that all of the polymerization-reactive emulsifier components in the polymer are represented by the general formula (I) or (II), and all of the polymerization-reactive emulsifier components in the polymer are represented by the general formula (I). It is more preferable to be.

In the general formula (I), R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ¹ is preferably a hydrogen atom or methyl, more preferably methyl.

A ¹ indicates -O- or -NR ^3- , and R ³ indicates a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A ¹ is preferably -NR ^3- , more preferably -NH-.

L ¹ represents an alkylene group having 6 to 22 carbon atoms. This alkylene group may be linear or may have a branch, and is preferably linear from the viewpoint of ejection stability and stability of the resin fine particles. L ¹ is preferably an alkylene group having 8 to 22 carbon atoms, more preferably 8 to 18 carbon atoms, still more preferably 8 to 16 carbon atoms, still more preferably 8 to 14 carbon atoms, still more preferably 10 to 12 carbon atoms. L ¹ is particularly preferably an alkylene group having 11 carbon atoms.

M ¹ represents a hydrogen atom, an alkali metal ion or an ammonium ion. From the viewpoint of ejection stability and stability of the resin fine particles, alkali metal ion is ^more preferable, sodium ion or potassium ion is more preferable, and potassium ion is further preferable.

In the general formula (II), R ² and M ² have the same meaning as R ¹ and M ¹ , respectively, and the preferred forms are also the same.
A ² indicates a single bond, -COO- or CONH-, and a single bond is preferable.
L ² represents a divalent linking group having 6 to 23 carbon atoms. The divalent linking group is not particularly limited, and from a synthetic point of view, -C (= O) NR ^4- (CH ₂ ) _n- or -C (= O) O- (CH ₂ ) _n -is used. Preferably —C (= O) NR ⁴ − (CH ₂ ) _n − is even more preferred. Here, R ⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and a hydrogen atom is preferable. Further, n is an integer of 5 to 22, with 6 to 18 being more preferred, 7 to 15 being even more preferred, 8 to 14 being even more preferred, 10 to 12 being even more preferred, and 11 being particularly preferred.
* Indicates the connection site incorporated into the polymer.

The resin fine particles contained in the resin dispersion of the present invention are obtained by setting the content of the polymerization-reactive emulsifying component (content in 100% by mass of the polymer) in the polymer constituting the resin fine particles to 1% by mass or more. It is possible to effectively prevent a decrease in the solid content concentration of the resin dispersion. The content of the polymerization-reactive emulsifier component in the polymer constituting the resin fine particles is preferably 1 to 10% by mass, more preferably 2 to 9% by mass, still more preferably 3 to 9% by mass, and 4 to 8%. Mass% is particularly preferred.

(Constituents represented by the general formula (1))
In the resin fine particles contained in the resin dispersion of the present invention, the polymer constituting the resin fine particles has one or more constituents represented by the following general formula (1).

In the general formula (1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The alkyl group that can be taken as R may be linear or may have a branch. The number of carbon atoms of this alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably methyl. R is preferably a hydrogen atom or methyl.

L represents an alkylene group having 1 to 10 carbon atoms. The alkylene group preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms. Among them, L is preferably an ethylene group or a propylene group, and an ethylene group is particularly preferable.

n is an integer of 2 or more, preferably 2 to 50, more preferably 2 to 30, still more preferably 2 to 10, further preferably 2 to 5, and particularly preferably 2 or 3.

The polymer constituting the resin fine particles contained in the resin dispersion of the present invention contains at least one of a diethylene glycol monomethacrylate component and a triethylene glycol monomethacrylate component as a component represented by the general formula (1). Is preferable. The constituent component represented by the general formula (1) contained in the polymer is preferably a diethylene glycol monomethacrylate component and / or a triethylene glycol monomethacrylate component.

By having the resin fine particles contained in the resin dispersion of the present invention having the constituent component represented by the general formula (1) as the constituent component of the polymer constituting the resin fine particle, the dispersed state of the resin fine particle can be stabilized. can. That is, the dispersed state of the resin fine particles dispersed in the aqueous medium can be highly stabilized by the action of the polymerization-reactive emulsifier component. Although the reason is not clear, the constituent component represented by the general formula (1) acts as a nonionic emulsifier (surfactant) on the resin fine particles in a complex manner together with the polymerization-reactive emulsifier component to disperse the resin fine particles. It is considered to contribute to stabilization.

The resin fine particles contained in the resin dispersion of the present invention have a content of the constituent component represented by the general formula (1) in the polymer constituting the resin fine particles (content in 100% by mass of the polymer) of 0.1. It is ~ 15% by mass, more preferably 0.1 to 10% by mass, preferably 0.1 to 5% by mass, and preferably 0.1 to 3% by mass.

The resin fine particles contained in the resin dispersion of the present invention have the above-mentioned content X of the polymerization-reactive emulsifier component and the above-mentioned general in the polymer constituting the resin fine particles from the viewpoint of suppressing the amount of aggregates during emulsion polymerization. It is preferable that the ratio of the constituent component represented by the formula (1) to the content Z satisfies X: Z = 3: 1 to 100: 1 in terms of mass ratio, and X: Z = 3: 1 to 80: 1. It is more preferable to satisfy.

(Constituents having no ionic group and having an aromatic ring structure)
The resin fine particles contained in the resin dispersion of the present invention are constituents in which the polymer constituting the resin fine particles does not have an ionic group and has an aromatic ring structure (hereinafter, "non-ionic having an aromatic ring structure"). It is preferable to have one or more of the constituents). The aromatic ring structure may be an aromatic hydrocarbon ring structure or an aromatic heterocyclic structure, and an aromatic hydrocarbon ring structure is preferable. The aromatic ring structure may be a monocyclic structure or a condensed ring structure, and a monocyclic structure is preferable.
The ionic group refers to a group capable of producing an ion in an aqueous medium (for example, a carboxy group or a salt thereof, a sulfo group or a salt thereof, a phosphoric acid group or a salt thereof, etc.). The monomer leading to the nonionic constituent having an aromatic ring structure does not function as the above-mentioned polymerization-reactive emulsifier in emulsion polymerization.
Examples of nonionic constituents having an aromatic ring structure include styrene component, phenyl (meth) acrylate component, benzyl (meth) acrylate component, N-phenyl (meth) acrylamide component, phenoxyethyl (meth) acrylate component, and the like. Examples thereof include α-methylstyrene component, p-methylstyrene component, vinyltoluene component, chlorostyrene component, divinylbenzene component and the like, and one or more of these can be used. The nonionic constituent having an aromatic ring structure is more preferably a styrene component, a phenyl (meth) acrylate component, a benzyl (meth) acrylate component, an N-phenyl (meth) acrylamide component, a phenoxyethyl (meth) acrylate component, and the like. And one or more of the α-methylstyrene component, more preferably one or two of the styrene component, the phenyl (meth) acrylate component, the benzyl (meth) acrylate component, and the N-phenyl (meth) acrylamide component. That is all.
The resin fine particles contained in the resin dispersion of the present invention have a content of nonionic constituents having an aromatic ring structure (content in 100% by mass of the polymer) of 15% by mass in the polymer constituting the resin fine particles. The above is preferable. In the above polymer, the content of the nonionic component having an aromatic ring structure is more preferably 15 to 60% by mass, further preferably 15 to 50% by mass.

(Alkyl (meth) acrylate component)
As for the resin fine particles contained in the resin dispersion of the present invention, it is preferable that the polymer constituting the resin fine particles has an alkyl (meth) acrylate component. The alkyl group of the alkyl (meth) acrylate component may be linear or may have a branch. The alkyl group of the alkyl (meth) acrylate component is an unsubstituted alkyl group. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and even more preferably 1 to 10 carbon atoms. When the polymer constituting the resin fine particles has an alkyl (meth) acrylate component, it is preferable that at least a part of the alkyl (meth) acrylate component is methyl (meth) acrylate.
The resin fine particles contained in the resin dispersion of the present invention have an alkyl (meth) acrylate component content (content in 100% by mass of the polymer) of 20% by mass or more in the polymer constituting the resin fine particles. preferable. The content of the alkyl (meth) acrylate component in the polymer is more preferably 30 to 80% by mass, further preferably 40 to 80% by mass, and particularly preferably 45 to 80% by mass.

(Other components)
In the resin fine particles contained in the resin dispersion of the present invention, the polymer constituting the resin fine particles may have other constituent components in addition to the above-mentioned constituent components. The other constituents are not particularly limited and can be appropriately incorporated into the polymer as long as the effects of the present invention are not impaired. Examples of other components include a component having an aliphatic ring, a (meth) acrylamide component, and a hydroxyalkyl (meth) acrylate component (the hydroxyalkyl group preferably has 2 to 10 carbon atoms, more preferably 2 to 10 carbon atoms). 6. More preferably, 2 to 4), a (meth) acrylate component containing a glycidyl group, a (meth) acrylate component having two or more ethylenically unsaturated bonds, a (meth) acrylate component containing an alkoxysilyl group, and the like. It can be mentioned, but it is not limited to these. The aliphatic ring of the constituent component having the aliphatic ring preferably has a ring-constituting atom number of 3 to 20, more preferably 4 to 15, and even more preferably 5 to 12. The aliphatic ring may have a hetero atom (preferably an oxygen atom, a sulfur atom, a nitrogen atom, etc.) as a ring-constituting atom.
Among the polymers constituting the resin fine particles, the content of "other constituents" (content in 100% by mass of the polymer) is preferably 0 to 35% by mass, more preferably 0 to 30% by mass.

The weight average molecular weight (Mw) of the polymer constituting the resin fine particles used in the present invention is preferably 80,000 or more, more preferably 80,000 to 1,000,000, still more preferably 100,000 to 800,000, and 100,000 to 50. 10,000 is more preferable, and 100,000 to 300,000 is particularly preferable. By setting the weight average molecular weight to 80,000 or more, the cohesiveness, the color density of the image, and the mechanical characteristics of the obtained film can be further improved. The weight average molecular weight is measured using a gel permeation chromatograph (GPC) by the method described in Examples described later.
The polymer constituting the resin fine particles used in the present invention may be a block copolymer or a random copolymer.

The particle size of the resin fine particles contained in the resin dispersion of the present invention is preferably 1 to 400 nm, more preferably 5 to 300 nm, and further preferably 20 to 200 nm from the viewpoint of ink ejection property. It is more preferably 20 to 100 nm, and even more preferably 20 to 70 nm.
The particle size of the resin fine particles is the primary particle size and the volume average particle size.
The content of the resin fine particles contained in the resin dispersion of the present invention is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, still more preferably 10 to 35% by mass.

The resin dispersion of the present invention can be prepared by an emulsion polymerization method using a polymerization-reactive emulsifier as an emulsifier. That is, the monomers corresponding to the above-mentioned constituent components are mixed at a predetermined ratio and polymerized by an emulsion polymerization method to obtain an aqueous resin dispersion in which resin fine particles are dispersed in an aqueous medium, and this aqueous resin dispersion is obtained. By filtering, the resin dispersion of the present invention can be obtained.
The emulsion polymerization method is a method for preparing resin fine particles by polymerizing an emulsion prepared by adding a monomer, a polymerization initiator, an emulsifier, and a chain transfer agent as necessary in an aqueous medium (for example, water). Is. When this emulsion polymerization method is applied to the preparation of the resin fine particles used in the present invention, the above-mentioned polymerization-reactive emulsifier functions as an emulsifier while being a monomer. Therefore, when the emulsification polymerization method is applied to the preparation of the resin fine particles used in the present invention, it is not necessary to separately mix an emulsifier other than the polymerization-reactive emulsifier. A known emulsifier may be added separately as long as it does not reduce the discharge property and the cohesive property.

The above-mentioned polymerization initiator is not particularly limited, and is not particularly limited, and is an inorganic persulfate (for example, potassium persulfate, sodium persulfate, ammonium persulfate, etc.) and an azo-based initiator (for example, 2,2'-azobis (2-amidinopropane). ) Dihydrochloride, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 4,4'-azobis (4-cyanovaleric acid), etc.), organic peroxide ( For example, peroxypivalic acid-t-butyl, t-butylhydroperoxide, dipoxalic acid peroxide, etc.) or salts thereof can be used. These can be used alone or in combination of two or more. Of these, it is preferable to use an azo-based initiator or an organic peroxide.
The amount of the polymerization initiator used in the present invention is usually 0.01 to 5 parts by mass, preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of all the monomers.

As the chain transfer agent, known compounds such as carbon tetrahalogenates, dimers of styrenes, dimers of (meth) acrylic acid esters, mercaptans, and sulfides can be used. Among them, styrene dimers and mercaptans described in JP-A-5-17510 can be preferably used.

[Aqueous Inkjet Ink Composition]
The water-based inkjet ink composition of the present invention (hereinafter, also referred to as “ink composition of the present invention”) contains at least resin fine particles and an aqueous medium. In addition, the water-based ink composition of the present invention usually contains a colorant. When the water-based ink composition does not contain a colorant, it can be used as a clear ink, and when it contains a colorant, it can be used for color image forming applications.

<Aqueous medium>
The aqueous medium used in the ink composition of the present invention contains at least water and, if necessary, at least one water-soluble organic solvent. The content of the aqueous medium in the ink composition of the present invention is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more. The content of the aqueous medium in the ink composition of the present invention is usually 98% by mass or less, more preferably 95% by mass or less.
As the water used in the present invention, it is preferable to use water that does not contain ionic impurities such as ion-exchanged water and distilled water. The proportion of water in the aqueous medium constituting the ink composition is appropriately selected depending on the intended purpose, and is preferably 30 to 99% by mass, more preferably 40 to 95% by mass, and even more preferably 50. It is ~ 95% by mass, particularly preferably 60 to 90% by mass.

<Water-soluble organic solvent>
The aqueous medium in the present invention preferably contains at least one of the water-soluble organic solvents. By containing a water-soluble organic solvent, the effects of preventing drying, wetting or promoting penetration can be obtained. Here, the term “prevention of drying” means to prevent ink from adhering to the ink ejection port of the injection nozzle and drying to form aggregates and clogging. A water-soluble organic solvent having a lower vapor pressure than water is preferable for preventing drying and wetting. Further, the water-soluble organic solvent can be used as a penetration accelerator for enhancing ink permeability into paper.

Examples of water-soluble organic solvents include alkanediols (polyhydric alcohols) such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol; sugar alcohols; ethanol, methanol, etc. Alkyl alcohols with 1 to 4 carbon atoms such as butanol, propanol and isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono -N-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol mono Ethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, di Examples thereof include glycol ethers such as propylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, and tripropylene glycol monomethyl ether. .. These can be used alone or in combination of two or more.

Polyhydric alcohols are useful for the purpose of drying prevention and wetting, for example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2 , 3-Butanediol and the like. These may be used alone or in combination of two or more.

For the purpose of promoting permeation, a polyol compound is preferable, and an aliphatic diol is preferable. Examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, and 2, -Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol and the like can be mentioned. Among these, 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol can be mentioned as preferable examples.

Further, as the water-soluble organic solvent in the present invention, it is preferable to contain at least one compound represented by the following structural formula (S).

In the structural formula (S), t, u, and v each independently represent an integer of 1 or more, satisfy t + u + v = 3 to 15, and t + u + v is preferably in the range of 3 to 12, and more preferably in the range of 3 to 10. preferable. When the value of t + u + v is 3 or more, a good curl suppressing force is shown, and when it is 15 or less, a good ejection property is obtained. In the structural formula (S), AO represents at least one of an ethyleneoxy group (EO) and a propyleneoxy group (PO), and a propyleneoxy group is preferable. Each AO in the above (AO) _t , (AO) _u , and (AO) _v may be the same or different.
Hereinafter, examples of the compound represented by the structural formula (S) will be shown. However, the present invention is not limited to this. In the exemplified compound, the description of "POP (3) glyceryl ether" means that it is a glyceryl ether in which a total of three propyleneoxy groups are bonded to glycerin, and the same applies to other descriptions.

Further, the water-soluble organic solvent in the present invention is preferably the water-soluble organic solvents (i) to (vii) exemplified below.
(I) n-C ₄ H ₉ O (AO) ₄ -H (AO = EO or PO, the ratio is EO: PO = 1: 1)
(Ii) n-C ₄ H ₉ O (AO) ₁₀ -H (AO = EO or PO, the ratio is EO: PO = 1: 1)
(Iii) HO (AO) ₄₀ -H (AO = EO or PO, ratio is EO: PO = 1: 3)
(Iv) HO (AO) ₅₅ -H (AO = EO or PO, ratio is EO: PO = 5: 6)
(V) HO (PO) ₃ -H
(Vi) HO (PO) ₇ -H
(Vii) 1,2-Hexanediol

The total content of the compound represented by the structural formula (S) and the above-exemplified compounds (i) to (vii) in the all-water-soluble organic solvent contained in the ink composition of the present invention is 3% by mass or more in total. Is preferable, 4% by mass or more is more preferable, and 5% by mass or more is further preferable.

In the present invention, the water-soluble organic solvent may be used alone or in combination of two or more.
The content of the water-soluble organic solvent in the ink composition is preferably 1 to 60% by mass, more preferably 5 to 40% by mass, and further preferably 7 to 30% by mass.

<Resin fine particles>
The structure of the resin fine particles contained in the ink composition of the present invention is the same as the resin fine particles contained in the resin dispersion of the present invention described above. That is, the resin dispersion of the present invention can be suitably used as a source of resin fine particles in the ink composition of the present invention.
In the ink composition of the present invention, the content of the resin fine particles is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, still more preferably 3 to 15% by mass.

<Colorant>
The ink composition of the present invention can be used not only for forming a monochromatic image but also for forming a multicolor image (for example, a full-color image), and it is possible to select and form a desired one color or two or more colors. can. When forming a full-color image, the ink composition can be used, for example, as a magenta color tone ink, a cyan color tone ink, and a yellow color tone ink. Further, it may be further used as a black color tone ink.

Further, the ink composition of the present invention contains red (R), green (G), blue (B), and white (B) other than yellow (Y), magenta (M), cyan (C), and black (K) tones. It can be used as an ink composition having a color tone of W), a so-called special color ink composition in the printing field, or the like.

In the ink composition of the present invention, known dyes, pigments and the like can be used as the colorant without particular limitation. From the viewpoint of the colorability of the formed image, a colorant that is almost insoluble or sparingly soluble in water is preferable. Specific examples thereof include various pigments, disperse dyes, oil-soluble dyes, and dyes forming J-aggregates. Further, considering the light resistance, the pigment is more preferable. The content of the colorant in the ink composition of the present invention is preferably 1 to 20% by mass, more preferably 1 to 10% by mass.

The type of pigment used in the ink composition of the present invention is not particularly limited, and ordinary organic or inorganic pigments can be used.
Examples of the organic pigment include an azo pigment, a polycyclic pigment, a dye chelate, a nitro pigment, a nitroso pigment, and an aniline black. Among these, azo pigments or polycyclic pigments are preferable.
Examples of the azo pigment include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.
Examples of the polycyclic pigment include phthalocyanine pigment, perylene pigment, perinone pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, indigo pigment, thioindigo pigment, isoindolinone pigment, and quinophthalone pigment.
Examples of the dye chelate include a basic dye type chelate and an acid dye type chelate.

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.

Specific examples of the pigment that can be used in the present invention include the pigments described in paragraphs 0142 to 0145 of JP-A-2007-170571.

The volume average particle size of the pigment in the ink composition of the present invention is preferably 10 to 200 nm, more preferably 10 to 150 nm, still more preferably 10 to 100 nm. When the volume average particle size is 200 nm or less, the color reproducibility is good, and in the case of the inkjet method, the drip characteristics are good. Further, when the volume average particle size is 10 nm or more, the light resistance becomes good. The volume average particle size of the pigment in the ink composition can be measured by a known measuring method. Specifically, it can be measured by a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction / scattering method, or a dynamic light scattering method.
The particle size distribution of the pigment in the ink composition of the present invention is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Further, two or more kinds of colorants having a monodisperse particle size distribution may be mixed and used.
The volume average particle size of the pigment can be measured by the same method as the above-mentioned measurement of the volume average particle size of the resin fine particles.

(Dispersant)
When the ink composition of the present invention contains a pigment, as the pigment, colored particles in which the pigment is dispersed in an aqueous medium by a dispersant (hereinafter, simply referred to as “colored particles”) are prepared, and this is referred to as an aqueous ink composition. It is preferable to use it as a raw material for.
The dispersant may be a polymer dispersant or a small molecule surfactant-type dispersant. Further, the polymer dispersant may be either a water-soluble polymer dispersant or a water-insoluble polymer dispersant.

As the small molecule surfactant-type dispersant, for example, the known low-molecular-weight surfactant-type dispersants described in paragraphs 0047 to 0052 of JP-A-2011-178029 can be used.

Among the above polymer dispersants, examples of the water-soluble dispersant include hydrophilic polymer compounds. For example, natural hydrophilic polymer compounds include vegetable polymers such as Arabic gum, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, and quince seed starch, and seaweed-based high polymers such as alginic acid, carrageenan, and agar. Examples thereof include animal macromolecules such as molecules, gelatin, casein, albumin and collagen, and microbial macromolecules such as xanthengum and dextran.

In addition, as hydrophilic polymer compounds modified from natural products, fibrous polymers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and carboxymethyl cellulose, starch such as sodium starch glycolate and sodium starch phosphate ester Examples thereof include based polymers, seaweed polymers such as sodium alginate and propylene glycol alginate.
Further, examples of the synthetic hydrophilic polymer compound include vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyvinylmethyl ether, non-crosslinked polyacrylamide, polyacrylic acid or an alkali metal salt thereof, and water-soluble styrene acrylic resin. Acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic acid resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium and amino Examples thereof include a polymer compound having a salt of a cationic functional group such as a group in a side chain, a natural polymer compound such as cellac, and the like.

Among these, a hydrophilic polymer compound having a carboxy group introduced, such as a homopolymer of acrylic acid or methacrylic acid, a copolymer of acrylic acid or methacrylic acid and another monomer, is preferable.

The water-insoluble polymer dispersant is a water-insoluble polymer and is not particularly limited as long as the pigment can be dispersed, and conventionally known water-insoluble polymer dispersants can be used. The water-insoluble polymer dispersant can be configured, for example, to contain both hydrophobic and hydrophilic structural units.

Here, examples of the monomer leading to the hydrophobic structural unit include styrene-based monomers, alkyl (meth) acrylates, aromatic group-containing (meth) acrylates, and the like.
Further, the monomer for deriving the hydrophilic structural unit is not particularly limited as long as it is a monomer containing a hydrophilic group. Examples of the hydrophilic group include a nonionic group, a carboxy group, a sulfonic acid group, a phosphoric acid group and the like. Examples of the nonionic group include a hydroxyl group, an amide group (without substitution of a nitrogen atom), a group derived from an alkylene oxide polymer (for example, polyethylene oxide, polypropylene oxide, etc.), a group derived from a sugar alcohol, and the like.
From the viewpoint of dispersion stability, the hydrophilic structural unit preferably contains at least a carboxy group, and preferably has a form containing both a nonionic group and a carboxyl group.

Specific examples of the water-insoluble polymer dispersant include styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, and (meth) acrylic acid ester- (meth). ) Acrylic acid copolymer, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, styrene-maleic acid copolymer and the like can be mentioned.

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

The weight average molecular weight of the water-insoluble polymer dispersant is preferably 3000 to 200,000, more preferably 5,000 to 100,000, still more preferably 5,000 to 80,000, and particularly preferably 10,000 to 60,000 from the viewpoint of dispersion stability of the pigment. ..

The content of the dispersant in the colored particles is preferably 10 to 90 parts by mass, preferably 20 to 70 parts by mass with respect to 100 parts by mass of the pigment, from the viewpoint of the dispersibility of the pigment, the colorability of the ink, and the dispersion stability. Parts by mass are more preferable, and parts by mass of 30 to 50 are particularly preferable.
When the content of the dispersant in the colored particles is within the above range, the pigment is coated with an appropriate amount of the dispersant, and it tends to be easy to obtain colored particles having a small particle size and excellent stability over time, which is preferable.

The colored particles can be obtained by dispersing a mixture containing, for example, a pigment, a dispersant, and if necessary, a solvent (preferably an organic solvent) by a disperser.
More specifically, for example, after a step (mixing / hydration step) of adding an aqueous solution containing a basic substance to a mixture of a pigment, a dispersant, and an organic solvent that dissolves or disperses the dispersant, the organic solvent is used. It can be produced as a dispersion by providing a step (solvent removing step) excluding the above. As a result, the pigment is finely dispersed, and a dispersion of colored particles having excellent storage stability can be produced.

The organic solvent needs to be able to dissolve or disperse the dispersant, but in addition, it preferably has a certain affinity for water. Specifically, those having a solubility in water of 10 to 50% by mass or less at 20 ° C. are preferable.
Preferred examples of the organic solvent include a water-soluble organic solvent. Of these, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable. The organic solvent may be used alone or in combination of two or more.

The basic substance is used to neutralize anionic groups (preferably carboxyl groups) that a polymer may have. The degree of neutralization of the anionic group is not particularly limited. Usually, it is preferable that the final obtained dispersion of colored particles has a liquid property of, for example, a pH of 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the polymer.

The method for removing the organic solvent in the production step of the colored particle dispersion is not particularly limited, and the organic solvent can be removed by a known method such as vacuum distillation.

In the ink composition of the present invention, the colored particles may be used alone or in combination of two or more.

<Surfactant>
The ink composition of the present invention may contain a surfactant as a surface tension adjusting agent.
As the surfactant, any of anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant and betaine-based surfactant can be used.

Specific examples of the anionic surfactant include sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium stearate, potassium oleate, and sodium dioctyl. Sodium sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylate sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, sodium dialkyl sulfosuccinate, sodium stearate, sodium oleate, t-octylphenoxyethoxypolyethoxyethyl Examples thereof include sodium sulfate and the like, and one or more of these can be selected.

Specific examples of the nonionic surfactant include acetylene diol derivatives such as an ethylene oxide adduct of acetylene diol, polyoxyethylene lauryl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleylphenyl ether, and polyoxyethylene nonyl. Examples thereof include phenyl ether, oxyethylene / oxypropylene block copolymer, t-octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol and the like, and one or more of these can be selected.

Examples of the cationic surfactant include tetraalkylammonium salt, alkylamine salt, benzalkonium salt, alkylpyridium salt, imidazolium salt and the like, and specific examples thereof include dihydroxyethylstearylamine and 2-heptadecenyl. -Hydroxyethyl imidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stealamidemethylpyridium chloride and the like can be mentioned.
Among these surfactants, nonionic surfactants are preferable, and acetylene diol derivatives are more preferable, from the viewpoint of stability.

When the ink composition of the present invention is used in an inkjet recording method, it is preferable to adjust the amount of the surfactant so that the surface tension of the water-based ink composition is 20 to 60 mN / m from the viewpoint of ink ejection property. The amount is preferably 20 to 45 mN / m, and more preferably 25 to 40 mN / m.
The surface tension of the ink composition of the present invention is measured at a temperature of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).
The content of the surfactant in the ink composition of the present invention is preferably an amount that can keep the water-based ink composition within the range of the surface tension. More specifically, the content of the surfactant in the ink composition is preferably 0.1% by mass or more, more preferably 0.1 to 10% by mass, still more preferably 0.2 to 3% by mass. Is.

<Other ingredients>
The ink composition of the present invention further comprises, if necessary, an anti-drying agent (swelling agent), an anti-coloring agent, a penetration accelerator, an ultraviolet absorber, an antiseptic, a rust inhibitor, an antifoaming agent, a clay adjusting agent, and a pH. Additives such as a preparation agent and a chelating agent may be mixed. The mixing method is not particularly limited, and a commonly used mixing method can be appropriately selected to obtain the water-based ink composition of the present invention.

<Physical characteristics of ink composition>
The viscosity of the ink composition of the present invention at 30 ° C. is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, still more preferably 2. It is 0.5 mPa · s or more and less than 10 mPa · s.
The viscosity of the ink composition of the present invention is measured using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) at a temperature of 30 ° C.

The pH of the ink composition of the present invention is preferably 6 to 11 at 25 ° C. from the viewpoint of dispersion stability. In the case of the ink set described later, it is preferable that the ink composition aggregates at high speed by contact with the treatment agent, so that the pH at 25 ° C. is more preferably 7 to 10, and even more preferably 7 to 9.

It is preferable that the ink composition of the present invention is ejected to a recording medium containing a treatment agent, and then the ink composition and the treatment agent come into contact with each other to form an aggregate of a colorant or resin fine particles.

<Treatment agent>
The treatment agent contains a component (aggregation-inducing component) capable of forming an aggregate containing a pigment in the aqueous ink composition by contacting with the ink composition of the present invention. Examples of the aggregation-inducing component include a component selected from an acidic compound, a polyvalent metal salt and a cationic polymer, and the aggregation component is preferably an acidic compound. The treatment agent may contain other components in addition to the aggregation-inducing component, if necessary.
The treatment agent constituting the ink set of the present invention is usually in the form of an aqueous solution.

(Acid compound)
The acidic compound can agglomerate (immobilize) the components in the water-based ink composition by coming into contact with the water-based ink composition on the recording medium, and functions as an immobilizing agent. For example, if the water-based ink composition is dropped on the recording medium in a state where the treatment agent containing the acidic compound is applied to the recording medium (preferably coated paper), the components in the water-based ink composition are aggregated. It can be immobilized on a recording medium.

Examples of acidic compounds include sulfuric acid, hydrochloric acid, nitrate, 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 tartrate acid. , Lactic acid, sulfonic acid, orthoric acid, metaphosphate, pyrrolidone carboxylic acid, pyron carboxylic acid, pyrrol carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumarin acid, thiophene carboxylic acid, nicotinic acid, oxalic acid, acetic acid, benzoic acid Can be mentioned. From the viewpoint of both suppression of volatilization and solubility in a solvent, the acidic compound is preferably an acid having a molecular weight of 35 or more and 1000 or less, more preferably an acid having a molecular weight of 50 or more and 500 or less, and particularly preferably an acid having a molecular weight of 50 or more and 200 or less. Further, as pKa (in _H2O , 25 ° C.), an acid of -10 or more and 7 or less is preferable, an acid of 1 or more and 7 or less is more preferable, and an acid of 1 or more is more preferable, from the viewpoint of achieving both ink bleeding prevention and photocurability. Acids of 5 or less are particularly preferred.
pKa is a value calculated by Advanced Chemistry Technology (ACD / Labs) Software V11.02 (1994-2014 ACD / Labs), or a literature value (for example, described in J. Phys. Chem. A 2011, 115, 6641-6645). Values can be used.

Among these, acidic compounds having high water solubility are preferable. Further, from the viewpoint of reacting with the ink composition to immobilize the entire ink, a trivalent or lower acidic compound is preferable, and a divalent or trivalent acidic compound is particularly preferable.
As the treatment agent, one type of acidic compound may be used alone, or two or more types may be used in combination.

When the treatment agent is an aqueous solution containing an acidic compound, the pH (25 ° C.) of the treatment agent is preferably 0.1 to 6.8, more preferably 0.1 to 6.0, and 0. It is more preferably 1.1 to 5.0.

When the treatment agent contains an acidic compound as an agglomerating component, the content of the acidic compound in the treatment agent is preferably 40% by mass or less, more preferably 15 to 40% by mass, still more preferably 15 to 35% by mass, and 20 to 20 to 30% by mass is particularly preferable. By setting the content of the acidic compound in the treatment agent to 15 to 40% by mass, the components in the aqueous ink composition can be more efficiently immobilized.

When the treatment agent contains an acidic compound as an aggregation-inducing component, the amount of the treatment agent applied to the recording medium is not particularly limited as long as it is sufficient to aggregate the ink composition, but the ink composition can be easily immobilized. From the above viewpoint, it is preferable to add the treatment agent so that the amount of the acidic compound applied is 0.5 g / m ² to 4.0 g / m ² , and 0.9 g / m ² to 3.75 g / m ² It is preferable to add a treatment agent so as to be.

(Multivalent metal salt)
As the treatment agent, a form containing one or more of polyvalent metal salts as an aggregation-inducing component is also preferable. By containing a polyvalent metal salt as an aggregation-inducing component, high-speed aggregation can be improved. Examples of the polyvalent metal salt include a salt of the second group of alkaline earth metals (for example, magnesium and calcium) in the periodic table, a salt of a transition metal of the third group of the periodic table (for example, lantern), and the thirteenth of the periodic table. Salts of cations (eg, aluminum) from the genus, salts of lanthanides (eg, neodym) can be mentioned. Suitable metal salts include carboxylates (formic acid, acetic acid, benzoate, etc.), nitrates, chlorides, and thiocyanates. Among them, a calcium salt or magnesium salt of a carboxylic acid (artic acid, acetic acid, benzoate, etc.), a calcium salt or magnesium salt of nitrate, calcium chloride, magnesium chloride, and a calcium salt or magnesium salt of thiocyan acid are preferable.

When the treatment agent contains a polyvalent metal salt as an aggregation-inducing component, the content of the polyvalent metal salt in the treatment agent is preferably 1 to 10% by mass, more preferably 1.5, from the viewpoint of the aggregation-inducing effect. It is in the range of about 7% by mass, more preferably 2 to 6% by mass.

Further, as the treatment agent, it is also preferable to contain one kind or two or more kinds of cationic polymers as the aggregation-inducing component. The cationic polymer is a homopolymer of a cationic monomer having a primary to tertiary amino group or a quaternary ammonium base as a cationic group, and the co-weight of the cationic monomer and the non-cationic monomer. Those obtained as coalesced or shrunk polymers are preferred. As the cationic polymer, either a water-soluble polymer or a water-dispersible latex particle may be used.
Preferred specific examples of the cationic polymer include poly (vinylpyridine) salt, polyalkylaminoethyl acrylate, polyalkylaminoethyl methacrylate, poly (vinylimidazole), polyethyleneimine, polybiguanide, polyguanide, or polyallylamine and its derivatives. Cationic polymers can be mentioned.

As the weight average molecular weight of the cationic polymer, it is preferable that the molecular weight is small from the viewpoint of the viscosity of the treating agent. When the treatment agent is applied to the recording medium by an inkjet method, the range of 1,000 to 500,000 is preferable, the range of 1,500 to 200,000 is more preferable, and the range of 2,000 to 100,000 is more preferable. Is the range of. When the weight average molecular weight is 1000 or more, it is advantageous in terms of aggregation rate, and when it is 500,000 or less, it is advantageous in terms of discharge reliability. However, this does not apply when the treatment agent is applied to the recording medium by a method other than inkjet.

When the treatment agent contains a cationic polymer as an aggregation-inducing component, the content of the cationic polymer in the treatment agent is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, from the viewpoint of the aggregation-inducing effect. It is more preferably in the range of 2 to 20% by mass.

<Image formation method>
An image forming method using the ink composition of the present invention will be described.
The above image forming method is preferable.
A treatment agent application step of applying the above treatment agent onto a recording medium, and
The process includes an ink application step of applying the ink composition of the present invention containing a colorant on a recording medium after the treatment agent application step by an inkjet method to form an image.

(recoding media)
The recording medium is not particularly limited, and may be a penetrating recording medium which is a paper medium, or a low-permeability recording medium typified by coated paper (coated paper), and is non-penetrating of plastic, metal, glass and the like. It is also preferable that it is a recording medium. The water-based ink composition of the present invention can be quickly dried even when an image portion is formed on a low-permeability or non-permeable recording medium, and a desired image is formed at high speed and with high accuracy. be able to.
In the present invention, the "low permeability recording medium" means a recording medium having a water absorption coefficient Ka of 0.05 to 0.5 mL / m ² · ms ^1/2 . Further, in the present invention, the "impermeable recording medium" means a recording medium having a water absorption coefficient Ka of less than 0.05 mL / m ² · ms ^1/2 .
The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI Pulp and Paper Test Method No. 51: 2000 (Published by Japan Technical Association of the Pulp and Paper), and specifically, the automatic scanning liquid absorption meter KM500Win (Kumaya Riki). It is calculated from the difference in the amount of water transfer between the contact time of 100 ms and the contact time of 900 ms.

The non-permeable base material is not particularly limited, but a resin base material is preferable. The resin base material is not particularly limited, and examples thereof include a base material obtained by molding a thermoplastic resin into a sheet shape. The resin base material preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

The resin base material may be a transparent resin base material, a colored resin base material, or at least a part thereof may be subjected to metal vapor deposition treatment or the like.
The shape of the resin base material is not particularly limited. The resin base material is usually a sheet-shaped resin base material, and is more preferably a sheet-shaped resin base material on which rolls can be formed by winding from the viewpoint of productivity of the recording medium.
The thickness of the resin base material is preferably 10 μm to 200 μm, more preferably 10 μm to 100 μm.

The resin base material may be surface-treated from the viewpoint of improving the surface energy.
Examples of the surface treatment include, but are not limited to, corona treatment, plasma treatment, frame treatment, heat treatment, wear treatment, light irradiation treatment (UV treatment), flame treatment, and the like.
The corona treatment can be performed using, for example, a corona master (manufactured by Shinko Electric Meter Co., Ltd., PS-10S) or the like.
The conditions for the corona treatment may be appropriately selected depending on the type of the resin base material, the composition of the ink, and the like. As an example, the following processing conditions can be mentioned.
-Processing voltage: 10 to 15.6 kV
-Processing speed: 30 to 100 mm / s

(Treatment agent application process)
In the treatment agent application step, the treatment agent contained in the ink set is applied onto the recording medium. The treatment agent is usually applied onto a recording medium in the form of an aqueous solution. A known liquid application method can be used without particular limitation for applying the treatment agent to the recording medium, and any method such as spray coating, coating with a coating roller, application by an inkjet method, or immersion can be selected. can.
Specifically, for example, a size press method typified by a horizontal size press method, a roll coater method, a calendar size press method, etc .; a size press method typified by an air knife coater method, etc .; a typified by an air knife coater method, etc. Knife coater method; Transfer roll coater method such as gate roll coater method, Direct roll coater method, Reverse roll coater method, Roll coater method represented by squeeze roll coater method; Bill blade coater method, Short duel coater method; Two Blade coater method represented by stream coater method; bar coater method represented by rod bar coater method; bar coater method represented by rod bar coater method; cast coater method; gravure coater method; curtain coater method; Die coater method; brush coater method; transfer method and the like can be mentioned.
Further, a method of controlling the coating amount by using a coating device provided with a liquid amount limiting member, such as the coating device described in Japanese Patent Application Laid-Open No. 10-230201, may be used.

The region to which the treatment agent is applied may be a full-scale application applied to the entire recording medium, or a partial application to a region to which the ink is applied in the ink application step. From the viewpoint of uniformly adjusting the amount of the treatment liquid applied, uniformly recording fine lines and fine image parts, and suppressing density unevenness such as image unevenness, the image forming surface of the recording medium is coated with a coating roller or the like. It is preferable to give the whole surface.

As a method of controlling the amount of the treatment agent to be applied within the above range, for example, a method using an Anilox roller can be mentioned. Anilox rollers are rollers that have a pyramid-shaped, diagonal line, or hexagonal shape, etc., by processing the surface of the roller on which ceramic is sprayed with a laser. The treatment liquid enters the recessed portion on the surface of the roller, and when it comes into contact with the paper surface, it is transferred and coated with the coating amount controlled by the recess of the Anilox roller.

(Ink application process)
In the ink applying step, the ink composition of the present invention is applied onto a recording medium by an inkjet method.
In the image formation by the inkjet method, the water-based ink composition is ejected onto the recording medium by supplying energy to form a colored image. As a preferred inkjet recording method for the present invention, the method described in paragraphs 093 to 0105 of JP-A-2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method for ejecting ink by using electrostatic attraction, a drop-on-demand method (pressure pulse method) using the vibration pressure of a piezo element, and the like. Either an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink to eject the ink using radiation pressure, or a thermal inkjet method that heats the ink to form bubbles and uses the generated pressure. You may.
Further, the inkjet head used in the inkjet method may be an on-demand method or a continuous method. Further, the ink nozzle or the like used when recording by the above-mentioned inkjet method is not particularly limited, and can be appropriately selected depending on the purpose.
The inkjet method includes a method called photo ink, in which a large number of low-density inks are ejected in a small volume, a method in which multiple inks having substantially the same hue but different densities are used to improve image quality, and colorless and transparent inks. The method used is included.

In addition, as an inkjet method, a shuttle method that uses a short serial head and scans the head in the width direction of the recording medium for recording, 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 method using. In the line method, the image can be recorded on the entire surface of the recording medium by scanning the recording medium in the direction orthogonal to the arrangement direction of the recording elements, and a transport system such as a carriage that scans the short head becomes unnecessary. Further, since the movement of the carriage and the complicated scanning control between the recording medium and the recording medium are not required and only the recording medium is moved, the recording speed can be increased as compared with the shuttle method.

The order in which the treatment agent application step and the ink application step are performed is not particularly limited, and from the viewpoint of image quality, it is preferable that the ink application step is performed after the treatment agent application step. That is, the ink applying step is preferably a step of applying the ink composition of the present invention on the recording medium to which the treatment agent is applied.

When the ink application step is carried out by an inkjet method, the amount of droplets of the water-based ink composition ejected by the inkjet method is preferably 1.5 to 3.0 pL from the viewpoint of forming a high-definition print. It is more preferable that it is 5 to 2.5 pL. The amount of droplets of the water-based ink composition to be ejected can be adjusted by appropriately adjusting the ejection conditions.

<Ink drying process>
If necessary, the above image forming method may include an ink drying step of drying and removing a solvent (for example, water, the above-mentioned aqueous medium, etc.) in the ink composition applied onto the recording medium. The ink drying step is not particularly limited as long as at least a part of the ink solvent can be removed, and a commonly used method can be applied.

<Heat fixing process>
If necessary, the image forming method preferably includes a heat fixing step after the ink drying step. By performing the heat fixing treatment, the image on the recording medium is fixed, and the resistance to scratching of the image can be further improved. As the heat fixing step, for example, the heat fixing step described in paragraphs [0112] to [0120] of JP2010-221415A can be adopted.

<Ink removal process>
The image forming method may include, if necessary, an ink removing step of removing the ink composition (for example, the solid ink solidified by drying) adhering to the inkjet recording head with a maintenance liquid. As for the details of the maintenance liquid and the ink removing step, the maintenance liquid and the ink removing step described in International Publication No. 2013/180074 can be preferably applied.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "parts" and "%" are based on mass.

[Preparation Example 1] Preparation of Aqueous Resin Dispersion <Preparation of Resin Dispersion B-01>
A 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube was charged with water (932 g), 12-methacrylamide dodecanoic acid (2.02 g), and potassium hydrogen carbonate (0.75 g). Then, the temperature was raised to 80 ° C. under a nitrogen stream. A mixed solution consisting of potassium persulfate (radical polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd.) (0.28 g), potassium hydrogen carbonate (0.21 g) and water (18.2 g) was added thereto, and the mixture was stirred for 10 minutes. Next, in the above three-necked flask, a monomer solution consisting of methyl methacrylate (206.0 g), benzyl methacrylate (60.0 g), styrene (60.0 g) and n-butyl acrylate (14.0 g), and 12-methacrylamide. Dodecanoic acid (23.25 g), potassium hydrogen carbonate (8.62 g), 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Chemical, trade name Acrylate HISS (high purity), 58.6 g) and diethylene glycol monomethacrylate (1.4 g). An aqueous monomer solution consisting of water (160 g) and water (160 g) was added dropwise at a constant velocity so that the addition could be completed in 8 hours. At that time, a mixed solution consisting of potassium persulfate (0.36 g), potassium hydrogen carbonate (0.29 g) and water (31.9 g) was added to the monomer solution and the monomer aqueous solution immediately after the start of dropping and from the start of dropping 1. It was added in 4 portions after 2 and 3 hours. After the dropping of the monomer solution and the monomer aqueous solution was completed, the mixture was stirred for 1 hour. The obtained reaction mixture was filtered through a mesh having a mesh of 70 μm to obtain a resin dispersion B-01 in which the resin fine particles were dispersed in an aqueous medium. The obtained resin dispersion B-01 has a pH of 8.5, a solid content concentration of 25% by mass, and a volume average particle size of the resin fine particles in the resin dispersion B-01 of 42 nm (volume average particle size is Microtrac UPA EX-). The weight average molecular weight (Mw) of the polymer constituting the resin fine particles was 140,000, and the glass transition temperature (Tg) was 97 ° C. (measured at 150 (manufactured by Nikkiso Co., Ltd.)).

<Preparation of resin dispersions B-02 to B-21>
Resin dispersions B-02 to B-21 were obtained in the same manner as in the preparation of the resin dispersion B-01, except that the combination of the monomers used was changed as shown in the table below.
In the preparation of the resin dispersions B-10 and B-11, diethylene glycol monomethacrylate was dissolved in isopropyl alcohol and then added to the aqueous monomer solution. Further, in the preparation of the resin dispersions B-14 and B-15, Orfin E1020 (manufactured by Nissin Chemical Co., Ltd.) was added as an auxiliary emulsifier to the aqueous monomer solution. Further, the resin dispersions B-01, B-08 and B-09 have the same ratio as the monomers used, but the particle size of the resin fine particles is different. This particle size was controlled by the amount of 12-methacrylamide dodecanoic acid initially charged in a 2 liter three-necked flask.

[Test Example 1] Evaluation of Filtrationability Each resin dispersion prepared above (both have a solid content concentration of 25%) is pressure-filtered at 0.08 MPa using a 30 μm filter (manufactured by Advancedc), and 230 g or more. A filtrate (a liquid that passed through a 30 μm filter) was obtained. This filtrate was pressure-filtered at a constant pressure of 0.08 MPa using a 1 μm filter (manufactured by Advantec). The mass of the filtrate that passed through the filter was measured until the change in the mass of the filtrate disappeared (until the filtration became impossible). The mass of this filtrate was applied to the following evaluation criteria, and the filterability of the resin dispersion was evaluated.
<Filtability evaluation criteria>
A: Mass of filtrate is 200 g or more B: Mass of filtrate is 130 g or more and less than 200 g C: Mass of filtrate is 80 g or more and less than 130 g D: Mass of filtrate is less than 80 g The results are shown in the table below.

[Preparation Example 2] Preparation of water-based ink composition <Preparation of black ink K-01>
(Synthesis of water-insoluble polymer dispersant)
In the reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei), 5 parts of Plenmer PP-500 (manufactured by NOF), 5 parts of methacrylic acid, 0.05 of 2-mercaptoethanol. A mixed solution of 24 parts of methyl ethyl ketone was prepared.
On the other hand, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toagosei), 9 parts of Plemmer PP-500 (manufactured by Nippon Yushi), 10 parts of methacrylic acid, 0.13 parts of 2-mercaptoethanol, A mixed solution consisting of 56 parts of methyl ethyl ketone and 1.2 parts of 2,2'-azobis (2,4-dimethylvaleronitrile) was prepared and placed in a dropping funnel.

Then, under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 75 ° C. while stirring, and the mixed solution in the dropping funnel was gradually added dropwise over 1 hour. After 2 hours have passed from the completion of the dropping, 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, and the solution was further added at 75 ° C. for 2 hours. Further, the mixture was aged at 80 ° C. for 2 hours to obtain a methyl ethyl ketone solution of a water-insoluble polymer dispersant.

A part of the obtained water-insoluble polymer dispersant solution was isolated by removing the solvent, the obtained solid content was diluted to 0.1% with tetrahydrofuran, and the weight average molecular weight was measured by GPC. As a result, the isolated solid content had a weight average molecular weight of 25,000.

(Preparation of black pigment dispersion liquid)
5.0 g of the obtained water-insoluble polymer dispersant solution in terms of solid content, 10.0 g of pigment dispersion CAB-O-JETTM 200 (carbon black, manufactured by CABOT), 40.0 g of methyl ethyl ketone, 1 mol / L sodium hydroxide 8.0 g, 82.0 g of ion-exchanged water, and 300 g of 0.1 mm zirconia beads were supplied to the vessel and dispersed at 1000 rpm for 6 hours with a ready mill disperser (manufactured by IMEX). The obtained dispersion was concentrated under reduced pressure with an evaporator until the methyl ethyl ketone was sufficiently distilled off. The pigment concentration was adjusted to 10% to obtain a black pigment dispersion liquid BK-01 as a dispersion liquid of colored particles made of a pigment whose surface was coated with a water-insoluble polymer dispersant.

The black pigment dispersion liquid BK-01 and the resin dispersion B-01 prepared above (in the evaluation of the filterability, pressure-filtered using a 1 μm filter were used. Other black inks described below. The same applies to the preparation of the above), water and a water-soluble organic solvent were mixed so as to have the following composition, and the ink composition was prepared. After the liquid preparation, coarse particles were removed with a 1 μm filter to prepare black ink K-01, which is an aqueous ink composition.
The ink composition of the black ink K-01 is as follows.
・ Black pigment dispersion BK-01 (solid content equivalent) 4.5%
・ Resin dispersion B-01 (solid content equivalent) 6%
・ Orfin E1010 (manufactured by Nissin Chemical Co., Ltd.) 1%
・ Propylene glycol 22%
・ Diethylene glycol monohexyl ether 2%
・ Amount of water that makes the total water 100%

<Preparation of black ink K-02-21>
In the preparation of the black ink K-01, the water-based ink composition was used in the same manner as in the preparation of the black ink K-01, except that the resin dispersion used was changed to B-02 to B-21 shown in the table below. Certain black inks K-02-21 were prepared respectively. That is, the black inks K-02 to K-21 each contain the resin dispersions B-02 to B-21 having the same numbering.

[Test Example 2] Evaluation of ejection performance Each black ink prepared above is ejected by a line method under the ejection conditions of a fixed Ricoh GELJET GX5000 printer head with a resolution of 1200 x 1200 dpi and a droplet volume of 3.5 pL. did. After confirming that the filled ink was ejected from all 96 nozzles at the start of ejection, the ink was continuously ejected for 45 minutes as it was. Then, after the end of continuous ejection for 45 minutes, the number of nozzles that could be ejected to the end (the number of ejection nozzles after the end of continuous ejection for 45 minutes) was counted. The number of ejection nozzles after the end of continuous ejection for 45 minutes was applied to the following evaluation criteria, and the ejection property of the ink composition was evaluated.
<Dischargeability evaluation criteria>
A: The number of discharge nozzles after the end of continuous discharge for 45 minutes is 94 or more B: The number of discharge nozzles after the end of continuous discharge for 45 minutes is 92 or 93 C: The number of discharge nozzles after the end of continuous discharge for 45 minutes is 90 or 91 D: The number of ejection nozzles after 45 minutes of continuous ejection is 89 or less. The results are shown in the table below.

[Test Example 3] Evaluation of storage stability Each black ink prepared above was placed in a polyethylene terephthalate container, sealed tightly, and stored in a constant temperature bath at 50 ° C. for 14 days. The viscosity and spectral absorption after storage were measured, and the storage stability was evaluated based on the viscosity before storage and the rate of change of the viscosity after storage and the spectral absorption with respect to the spectral absorption.
The viscosity was measured with an R100 type viscometer (manufactured by Toki Sangyo Co., Ltd.) under the conditions of 25 ° C. and a cone rotation speed of 20 to 100 rpm.
Spectral absorption was measured using V-570 (manufactured by JASCO Corporation) as an apparatus and using a quartz cell. Specifically, the ink was diluted 1500 times with ultrapure water, and ultrapure water was used as a control to compare the change in absorbance at 600 nm.
The rate of change in viscosity and spectral absorption was calculated by the following formula, and the storage stability was evaluated based on the following evaluation criteria.
Rate of change (%) = 100 x {[(measured value after storage)-(measured value before storage)] absolute value} / (measured value before storage)
<Storage stability evaluation criteria>
A: Rate of change in both viscosity and spectroscopic absorption is less than 10% B: Rate of change in either viscosity or spectroscopic absorption is 10% or more C: Rate of change in both viscosity and spectroscopic absorption is 10% or more Shown in the table below.

The abbreviations in the above table are as follows.
MMA: Methyl Methacrylate BzMA: Benzyl Methacrylate St: Styrene nBA: n-Butyl Acrylate IBOMA: Isoboronyl Methacrylate 2EHMA: 2-Ethylhexyl Methacrylate DEFMA: Diethylene Glycol Monomethacrylate (monomer for deriving the constituents of the general formula (1))
MADA: 12-methacrylamide dodecanoic acid (HLB: 7.9, in the form of a potassium salt in the resin dispersion)
JS-20: Anionic polymerization reactive emulsifier having the following structure (HLB: 7.9)

RS3000: Anionic polymerization reactive emulsifier having the following structure (HLB: 18.4)

NE-10: Nonionic polymerization-reactive emulsifier having the following structure (HLB: 13.7)

As shown in the above table, when the content of the constituent component of the general formula (1) is smaller than that specified in the present invention, the obtained resin dispersion tends to aggregate and is inferior in filterability, and these resin dispersions are used. The water-based ink used was inferior in both ejection property and storage stability (Comparative Examples 1 and 2).
On the contrary, when the content of the constituent component of the general formula (1) is larger than that specified in the present invention, the filterability of the obtained resin dispersion is slightly improved, but the aqueous solution using this resin dispersion is used. The ink was inferior in both ejection property and storage stability (Comparative Example 3).
On the other hand, all the resin dispersions satisfying the provisions of the present invention were excellent in filterability, and the water-based ink using these resin dispersions was excellent in both ejection property and storage stability (Example 1). ~ 18).

Claims (20)

A resin dispersion for an aqueous inkjet ink containing resin fine particles and an aqueous medium, wherein the polymer constituting the resin fine particles contains a polymerization-reactive emulsifier component as a constituent component and a constituent component represented by the following general formula (1). And an alkyl (meth) acrylate component having an alkyl group having 1 to 15 carbon atoms .
In the polymer , the content of the polymerization-reactive emulsifier component is 0.5 to 11.0% by mass, the content of the component represented by the general formula (1) is 0.1 to 15% by mass , and the alkyl. A resin dispersion for an aqueous inkjet ink having a (meth) acrylate component content of 30 to 80% by mass .
However, the form in which the resin fine particles are encapsulated in which the core substance having an electric charge on the surface is coated with a wall material containing a polymer as a main component is excluded.

In general formula (1),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 3 carbon atoms.
n is an integer of 2 to 5 ,
* Indicates the connection site incorporated into the polymer. The resin dispersion for an aqueous inkjet ink according to claim 1 , wherein the polymer has a component having no ionic group and having an aromatic ring structure. The resin dispersion for an aqueous inkjet ink according to claim 2, wherein the content of the constituent component having no ionic group and having an aromatic ring structure in the polymer is 60% by mass or less. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 3, wherein the polymerization-reactive emulsifier component contains an anionic and / or nonionic polymerization-reactive emulsifier component. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 4 , wherein the polymerization-reactive emulsifier component has a structure selected from a carboxy group salt and a sulfo group salt. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 5 , wherein the HLB value of the polymerization-reactive emulsifier that leads to the polymerization-reactive emulsifier component is 15 or less. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 6 , wherein the polymerization-reactive emulsifier component has an alkyl group having 6 or more carbon atoms. In the polymer, the ratio of the content X of the polymerization-reactive emulsifier component to the content Z of the component represented by the general formula (1) is X: Z = 3: 1 to 100: 1 in mass ratio. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 7 , which satisfies the above conditions. The resin dispersion for an aqueous inkjet ink according to any one of claims 1 to 8 , wherein at least a part of the polymerization-reactive emulsifier component is represented by the following general formula (I).

In general formula (I),
R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
A ¹ indicates -O- or -NR ^3- , and
R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L ¹ represents an alkylene group having 6 to 22 carbon atoms.
M ¹ represents a hydrogen atom, an alkali metal ion or an ammonium ion.
* Indicates the connection site incorporated into the polymer. A water-based inkjet ink composition containing resin fine particles and a water-based medium.
The polymer constituting the resin fine particles has a polymerization-reactive emulsifier component, a component represented by the following general formula (1), and an alkyl (meth) acrylate component having an alkyl group having 1 to 15 carbon atoms. ,
In the polymer , the content of the polymerization-reactive emulsifier component is 0.5 to 11.0% by mass, the content of the component represented by the general formula (1) is 0.1 to 15% by mass , and the alkyl. A water-based inkjet ink composition having a (meth) acrylate component content of 30 to 80% by mass .
However, the form in which the resin fine particles are encapsulated in which the core substance having an electric charge on the surface is coated with a wall material containing a polymer as a main component is excluded.

In general formula (1),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 3 carbon atoms.
n is an integer of 2 to 5 ,
* Indicates the connection site incorporated into the polymer. The water-based inkjet ink composition according to claim 10 , wherein the water-based inkjet ink composition contains a colorant. The water-based inkjet ink composition according to claim 10 or 11 , wherein the polymer has a component having no ionic group and having an aromatic ring structure. The water-based inkjet ink composition according to claim 12, wherein the content of the component having no ionic group and having an aromatic ring structure in the polymer is 60% by mass or less. The water-based inkjet ink composition according to any one of claims 10 to 13, wherein the polymerization-reactive emulsifier component contains an anionic and / or nonionic polymerization-reactive emulsifier component. The water-based inkjet ink composition according to any one of claims 10 to 14 , wherein the polymerization-reactive emulsifier component has at least one structure of a carboxy group salt and a sulfo group salt. The water-based inkjet ink composition according to any one of claims 10 to 15 , wherein the HLB value of the polymerization-reactive emulsifier that leads to the polymerization-reactive emulsifier component is 15 or less. The water-based inkjet ink composition according to any one of claims 10 to 16 , wherein the polymerization-reactive emulsifier component has an alkylene group having 6 or more carbon atoms. In the polymer, the ratio of the content X of the polymerization-reactive emulsifying component to the content Z of the component represented by the general formula (1) is X: Z = 3: 1 to 100: 1 in mass ratio. The water-based inkjet ink composition according to any one of claims 10 to 17 , which satisfies the above conditions. The water-based inkjet ink composition according to any one of claims 10 to 18 , wherein at least a part of the polymerization-reactive emulsifier component is represented by the following general formula (I).

In general formula (I),
R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
A ¹ indicates -O- or -NR ^3- , and
R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L ¹ represents an alkylene group having 6 to 22 carbon atoms.
M ¹ represents a hydrogen atom, an alkali metal ion or an ammonium ion.
* Indicates the connection site incorporated into the polymer. A method for producing a resin dispersion for an aqueous inkjet ink, which comprises polymerizing a monomer by emulsion polymerization to obtain an aqueous resin dispersion in which resin fine particles are dispersed in an aqueous medium, and filtering the aqueous resin dispersion. There,
A polymerization-reactive emulsifier is used as the emulsifier, and the ratio of the polymerization-reactive emulsifier to all the monomers is 0.5 to 11.0% by mass, and the ratio of the monomer represented by the following general formula (1a) is 0. A method for producing a resin dispersion for an aqueous inkjet ink, wherein the emulsion polymerization is carried out with the proportion of an alkyl (meth) acrylate monomer having 1 to 15% by mass and an alkyl group having 1 to 15 carbon atoms being 30 to 80% by mass .
However, the form in which the resin fine particles are encapsulated in which the core substance having an electric charge on the surface is coated with a wall material containing a polymer as a main component is excluded.

In equation (1a),
R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
L represents an alkylene group having 1 to 3 carbon atoms.
n is an integer of 2 to 5 .